Abstract: The relative importance of various energy sources to the early mammalian embryo has received little attention. In the past, media used to cultivate rabbit embryos in vitro have in most cases contained 50% or more serum (Austin, 1961). This makes the determination of the compounds supplying energy impossible. In contrast, mouse embryos from the eight-cell stage to the blastocyst have been cultivated in relatively simple salt solutions supplemented with protein and glucose (Hammond, 1949; Whitten, 1956). In 1957 Whitten reported that the energy for development of eight-cell mouse ova to blastocysts could be supplied by glucose or mannose, but could not be supplied by fructose, galactose, maltose, or lactose. Similarly, energy could be supplied by lactate, pyruvate or malate, but could not be supplied by acetate, propionate, citrate, glycerol or glycine. Unfortunately, details of the exact experimenttal procedures were not presented. Whitten (1957) was also able to obtain the development of some late two-cell mouse ova into blastocysts in a medium containing lactate. The recent development of a method to cultivate early cleavage stages of the mouse ovum completely in vitro and the ability of the method to produce quantitative results, allows critical examination of possible energy sources of early mammalian embryos (Brinster, 1963). A number of possible energy sources were examined for their ability to support the development of two-cell mouse embryos in vitro.

Abstract: Several thousand two-cell mouse ova were cultivated in vitro, and the effect on development of changing the osmolarity and hydrogen ion concentration of the medium was examined. Statistical experimental design techniques were employed throughout the experiments in order to make the most efficient use of the material available. The two-cell ova were cultivated for three days, and the percentage which developed into normal blastocysts was used as a measure of the treatment effect. Changing the osmolarity of the medium had a marked effect on the number of blastocysts developing from two-cell mouse ova. Blastocysts developed in media with osmolarities ranging between 0.2002 and 0.3542 osmols. The optimum osmolarity for the development of two-cell mouse ova into blastocysts was 0.2760 osmols. The hydrogen ion concentration of the culture medium also had an effect on the development of two-cell mouse ova into blastocysts. Although blastocysts developed in media with pH's ranging from 5.87 to 7.78, the optimum pH appeared to be near 6.82.

Abstract: The annual fat body cycle in the lizard Uta stansburiana is associated with reproduction In females fat bodies decline in late winter and early spring when deutoplasm is deposited in the ovarian follicles Males have a similar fat cycle, but fat bodies are much smaller Ovariectomy eliminated rapid lipid mobilization from the fat bodies which occurs in sham operated controls Fat body removal from early estrus females induces high incidence of follicular atresia and retards the rate of yolk deposition Follicular growth is delayed or inhibited if fat bodies are excised from preestrus animals The amount of extractable lipid in the pre-estrus fat body is nearly equivalent to the lipid in a typical egg clutch The adaptive value of the fat bodies is apparently associated with the formation of the first egg clutch which in accordance with population studies is the most important clutch

Abstract: Previous studies of the spontaneous cyclic motility of the chick embryo were extended to incubation day 17. The activity and inactivity phases of the cycle were recorded on a polygraph, for a 15-minute observation period. The percentage of time spent in activity rises steadily from less than 10% at the beginning of motility at three and one-half days to 80% at day 13. This peak is maintained up to day 17; subsequently, motility declines. The mean duration of activity phases increases and that of the inactivity phases decreases until the high plateau is reached, though both values change independently of each other. In order to study the effect of the brain on spontaneous motility, spinal embryos were obtained by extirpation of part of the cervical cord in two-day embryos. The spinal embryos retain their capacity for cyclic motility. However, the activity is reduced by approximately 10–20% at all stages between the eighth and the seventeenth day. The brain influence asserts itself in a lengthening of the duration of the activity phases and in a shortening of the inactivity phases. An inhibitory effect was not observed at any stage.

Abstract: Isocitrate dehydrogenase (IDH) exists in mammalian tissues as three enzymes, one specific for NAD and two specific for NADP. The two NADP isozymes differ in electrophoretic mobility, immunological characteristics, and tissue and subcellular location. ONe is found mainly in the mitochondrial fraction and one in the supernatant fraction of tissue homogenates. Two allelic forms of the supernatant NADP isocitrate dehydrogenase have been described in inbred strains of mice. In a heterozygote containing both alleles, three forms of the supernatant NADP-IDH are generated in a ratio of 1:2:1. This implies that the supernatant enzyme is a dimer. The mitochondrial form is not affected by the gene, indicating separate genetic control. Liver mitochondria contain both the supernatant and the mitochondrial isozymes. Thus at least one protein found in the mitochondria is encoded in a nuclear gene.

Abstract: There has been considerable discussion as to whether the developing mouse ova requires an exogenous protein supply. A series of experiments were performed to determine the effect of various fixed-nitrogen sources on the development in vitro of two-cell mouse ova into blastocysts. It was found that two-cell mouse ova would not develop into blastocysts in medium that did not contain a fixed-nitrogen source. Crystalline bovine serum albumin (BSA) at 1 mg/ml or, alternatively, the constituent amino acids of BSA could supply this requirement for fixed-nitrogen. In the presence of single amino acids at 10−3M or 8 × 10−3M, only an occasional two-cell ova developed into a blastocyst. Single amino acids were omitted from the medium containing the constituent amino acids of BSA in an attempt to demonstrate an essential amino acid requirement of two-cell mouse ova. The omission of no single amino acid from the medium, completely prevented the development of some two-cell ova into blastocysts. The only amino acid whose omission resulted in a significant decrease in development was cystine. In the medium where amino acids were used in place of BSA, a non-protein polymer was used to replace the physical properties of albumin. The non-protein polymers which appeared best were Polyvinylpyrrolidone (MW = 150,000), Acacia, Dextran, and Ficoll.

Abstract: Mitochondria of rat sperm tail middle-piece remain associated with the flagellum after penetration of the egg by the spermatozoon and during the time of the first cleavage. During two- to four-cell stages the middle-piece mitochondria gradually swell while they separate in large clusters from the axial filament. The swelling of the male mitochondrial elements becomes more extreme during the cleavage divisions, and they finally seem to disintegrate. Thus all mitochondria found in the developing rat embryo may originate from the egg.

Abstract: By means of a rapid microelectrophoretic technique suitable for single-fly analysis, two types of alcohol dehydrogenase (ADH) isozyme patterns were found, each true breeding in homozygous stocks. A cross of these two types produces offspring with a third type of ADH pattern, containing hybrid ADH molecules in addition to the parental forms. Various strains were analyzed and found to contain flies of the three ADH types in various proportions indicating different gene frequencies. When octanol was used as a substrate instead of ethanol, an additional isozyme system was found, for which some strains are polymorphic also. The results obtained thus far are consistent with the assumption that ADH in Drosophila is a dimer.

Abstract: Inductive tissue interaction involved in lens differentiation in the mouse embryo has been studied using millipore filter culture methods. The entire eye rudiment (nine day embryo) comprising optic vesicle, surrounding mesenchyme and overlying ectoderm differentiated in vitro into lens and retina, essentially as in normal development. Individual tissue components of trypsin-separated lens primordia lost their structural organization when cultured alone, but lens epithelium in combination with mesenchyme was maintained as a vesicle without obvious lens fiber formation. Tissue recombination experiments show that differentiation of lens fibers in the presumptive lens ectoderm as well as in the lens placode depends on the inductive influence of optic cup. This influence can pass through a millipore filter barrier of 25 μ thickness and 0.45 μ porosity. Differentiation of lens fibers in the anterior lens epithelium of later embryos was also dependent on the inductive action of neural retina, suggesting the presence of continued inductive interaction in lens formation. The initial influence of optic vesicle on the presumptive lens ectoderm seems to be critical and of short duration, leading to the formation of a placode which has acquired stabilized lens forming property. Continued realization of this property depends on further inductive action.

Abstract: The effects of 5-fluorodeoxyuridine, 5-fluorouridine, actinomycin D, and p-fluorophenylalanine on cell division and oral morphogenesis in both exponentially growing and synchronized Tetrahymena pyriformis GL were investigated. All of the inhibitors tested were capable of preventing and/or greatly delaying cell division in both growth situations. Associated with the block of cell division, there were pronounced effects on oral morphogenesis. Following addition of any one of the inhibitors to an exponetially growing culture, the proportion of cells with developing oral primordia (particularly primordia in the process of membranelle formation) declined sharply, and there appeared, after some time, primordia with oral membranelles in the process of resorption. In synchronized cultures, the effects of the inhibitors on specific developmental stages were followed with more precision. Development continued for about 30 minutes after addition, and then stopped in most of the cells. In cells which were undergoing membranelle formation (developmental stages 3 and 4) at the time when the inhibitor took effect, development was halted and oral primordia were resorbed. On the other hand, cells in which membranelle formation was complete or nearly so (stages 5 and 6) continued to develop and eventually divided. Stabilization occurred at late stage 4 with respect to all of the inhibitors considered in this study, as well as with high and low temperatures, considered earlier. At inhibitor concentrations just below those required to permanently block development in all cells, renewed development in some cells was observed several hours after addition of the agent. The oral structures formed during this period were always normal in both size and internal pattern. In this respect the effects of the chemical inhibitors differ from those of high temperature, which not only interferes in the maintenance of development, but also brings about abnormalities in spatial pattern. The following conclusions may be drawn from these studies: (a) both protein and template RNA synthesis must take place during the process of oral development in order to maintain further development; (b) the pattern and size of the oral structures that are formed is not affected by limitation in the supply of protein and RNA precursors.

Abstract: This is the first of a series of studies on protein synthesis and its control during the molt cycle of the land crab, Gecarcinus lateralis. Incorporation of valine-1-C14 and leucine-1-C14 into proteins of blood, epithelium, midgut gland, and muscle has been measured at each stage and found to reach a maximum rate in all tissues during the stages D0 through D2 of the premolt period. This period is not necessarily the period of maximum net synthesis of total protein in all tissues. Total muscle protein, in fact, is decreasing at this time: the high incorporation rate may reflect synthesis of degradative enzymes. In control experiments on possible rate limiting features in amino acid incorporation, the pool sizes of valine and leucine in plasma water were determined. These do not vary systematically with stages in the molt cycle; the relatively small fluctuations in these pools do not correlate with the larger fluctuations in incorporation rate. The sizes of these pools do not appear to be rate limiting. In conjunction with these measurements, the plasma water volume of Gecarcinus was found to be 22 ± 1.72 (S.D.) per cent of the body weight. It is also shown that the rate of penetration of amino acid from plasma water into intracellular water was not the rate limiting step in the incorporation of C14-leucine into muscle protein. (Muscle is the tissue with the lowest incorporation rates.) Leucine penetrates muscle readily and appears to be concentrated four-fold in muscle water relative to plasma water.

Abstract: Because information concerning the time relations of the cleavage stimulus should prove useful in characterizing both the stimulus and the nature of the response in the cell surface, methods were devised for determining how long the surface must be acted upon by the asters to produce a furrow and the duration of the latent period between the end of this stimulus period and appearance of the furrow. Eggs of the sand dollar Echinorachnius parma were used in experiments wherein unstimulated surface was brought close to the interastral zone of the mitotic apparatus for specified periods. Since this modification subjected the cell to physical stress or constraint, several different methods were used. As was anticipated, the times determined differed somewhat according to the method used. Exposure of the surface to the interastral zone for about one minute subsequently produces an active furrow. The latent period between the end of the stimulus period and the appearance of the furrow is about two and one-half minutes and the total time from the beginning of stimulation to appearance of the furrow is between two and three and one-half minutes. The mitotic apparatus can repeatedly elicit new furrows within the same cell despite visible loss of distinctness from frequent handling. This suggests that stimulation is accomplished by a fundamentally simple relationship between asters and surface. During the latent period the presumptive furrow area has greater ability to retain its contour despite inncreased tension at the surface than does non-furrow surface. The undiminished capacity for division that persists in cells subjected to frequent and extensive cytoplasmic shifting which accompanies relocation of the mitotic apparatus by pressure displacement implies that after stimulation, completion of the cleavage process is independent of any specific subsurface cytoplasmic configuration.

Abstract: Dimensions of the longest intestinal microvilli were measured in normal mice from the 14 day embryo through weaning. Major changes are associated with birth and weaning. Microvilli increase in height and volume before birth and after birth increase in height but keep the same volume by decreasing in diameter. There is thus an increase in surface area associated with birth and with weaning. This correlates with the increases in alkaline phosphatase activity of mouse intestine at these times as described by Moog. Location of reaction product suggests that phosphatase is associated with the inner layer of the unit membrane. Attempts to reproduce the normal shape changes of microvilli by injecting 9 to 10 day old mice with cortisone failed. The microvilli increased in height but did not decrease in diameter.

Abstract: The life stages of Aurelia were raised under controlled conditions in a chemically defined salt solution. Scyphistomae have thrived for three years in this medium, budding and strobilating normally. Ephyrae developed into mature medusae within a four month period. A description of all the life stages of a known species of jellyfish was obtained for the first time. Laboratory cultured medusae underwent developmental changes very similar to medusae in nature. The development of new structures occurred in a chronological sequence which consistently appeared in this order: marginal veil and oral arms, circular canal, margin tentacles, marginal lappets and special sensory lappets, subgenital pits, eight-partition scalloping of the bell, ruffling of the oral arms, and sexual products. Gastric filaments, nematocysts and mesogloea continually increased in number and amount throughout development. Laboratory cultured medusae differed from those developing in nature in that they (1) reached a maximum growth of 55 mm at the time of sexual maturation, (2) did not develop as many tentacles at the bell margin, and (3) did not yield as many planulae. It was not possible to correlate closely either the age or size of the medusae with the development of any specific morphological structure. All medusae underwent spontaneous deterioration. The extrusion of gastric filaments along with the release of sexual products indicated that medusae may starve to death since gastric filaments are believed necessary for digestion of food. The flexibility and variety of growth systems occurring in Aurelia under controlled conditions provide new opportunities for the study of basic mechanisms involved in normal and abnormal growth.

Abstract: Histological studies, carbon, carmine and vital dye marking of in ovo and explanted blastoderms have provided evidence for the following: (1) The cellular precursors of all three primary germ layers in the unincubated blastoderm are topographically represented by a disc-shaped, epithelial-like and complete uppermost layer; and ring-shaped, incomplete and congruent middle and lowest layers below the uppermost layer. (2) There is a gradient in cell population density decreasing from posterior to anterior. (3) Centripetal extension of a sheet of lowest and adjacent middle layer cells, primarily from the posterior portion of the ring but also from all points on its circumference, results in closing of the ring and completion of the middle and lowest layers as coherent discs. (4) No movement (invagination or involution) of uppermost, surface areas as coherent sheets into either the middle or lowest layers could be demonstrated in any region, including the primitive streak. (5) Embryonic germ layers arise in situ by proliferation from the streak. (6) The streak in its morphology and function is more like a blastema than a blastopore. (7) As an elongated growth center, the streak has its origin from the marginal zone ring, itself a circular blastema with multiple streak- and embryo body-forming capacities.

Abstract: The isozymic forms of four dehydrogenases, separated by disc electrophoresis in acrylamide gels, have been studied during development and in adult organs in the cyprinodontiform fish, Oryzias latipes, the medaka. Xanthine dehydrogenase appears as a single molecular form at hatching, and in the adult fish is found only in the liver and gut. Glucose-6-phosphate dehydrogenase is a single enzyme in early development, just before hatching two new forms appear, and after hatching all three decrease in whole larval extracts. In adults, the enzymes were found only in brain, liver, and ovary. Malate dehydrogenase increases from a single molecular form in early stages to five or six after hatching. Each adult tissue has its characteristic assemblage of isozymes. The only lactate dehydrogenase detectable before hatching is isozyme 5, and four others appear abruptly at hatching. All adult organs have one to three LDH isozymes, but isozymes 1 and 2 were found only in the retina of the eye. The abrupt change from the single isozyme 5 to the full complement occurs also in eyes of the larvae taken pre- and post-hatching. Homogenates of pre-hatching embryos do not inhibit the electrophoretic separation or reactivity of isozymes 1, 2, 3, and 4 of post-hatching larvae. Presumably hatching triggers the appearance of the more rapidly migrating isozymes, especially strongly in the retina. On the basis of the structure of LDH isozymes in other organisms, it can be concluded that polypeptide A is present before hatching, but some restraint on the synthesis or activation of polypeptide B seems to be removed by hatching. The importance of hatching as a time of qualitative change in these four enzymes is correlated with increases in other metabolic activities at this time.

Abstract: Investigations of the stage 16 to 19 chick embryo have been performed specifically in relation to the composition of cardiac jelly. Biochemical analysis has demonstrated the presence of a non-dialyzable sulfated mucopolysaccharide, containing hexosamine and uronic acid. This material can be complexed with cetylpyridinium chloride, and then exhibits differential salt solubility in accordance with known characteristics of acid mucopolysaccharides, suggesting that the chondroitin sulfates and heparin-like compounds are the major sulfated components. Histochemical and 35S-sulfate incorporation studies also support the interpretation that cardiac jelly contains a significant amount of sulfated acid mucopolysaccharide.

Abstract: Oogenesis in rabbits was investigated by examining the development of germ cells after birth. The transformation of oogonia to oocytes begins in the one day old animal. The appearance of the different stages of meiotic prophase was noted and their differential distribution in the germ cell population determined. The early stages of meiotic prophase develop within the first two weeks of life, however, they are transitory and have transformed into the “stationary” phase of prophase by the end of the third week of life, when all nuclei of oocytes are in diplotene. DNA synthesis in germ cells was studied with the aid of H3-thymidine, which was injected into animals within the first ten days of life. The number of labeled germ cells varies with the age of the animal at the time of injection. Injection between the day of birth and the age of four days results in the labeling of 20 to 35% of the germ cells. After this age the labeling index falls, reaching 3% in the ten day old animal. The synthesis of the oocyte DNA takes place in the premeiotic interphase and may extend into the early phase of prophase, i.e. leptotene.

Abstract: Various cell components such as yolk nucleus, loose basophilic substance, mitochondria and lipid bodies (L2) proliferate with the growth of previtellogenic oocytes in cat and dog, investigated with various histochemical techniques. The yolk nucleus and its fragments consist of RNA, protein and some lipoprotein. The loose basophilic substance reacts mainly for RNA and protein. The mitochondria show phospholipid and protein. The lipid bodies (L2) contain phospholipid. The sites of distribution of lipid bodies (L2) and vacuoles in the oocytes and granulosa suggest a nutrient transfer design. Some large vacuoles, which react negatively with the various techniques used, gradually accumulate in the central cytoplasm of large oocytes which abundantly store sudanophilic lipid yolk droplets of various sizes. These consist mainly of phospholipid and neutral fat (triglyceride); the latter increases in amount during atresia of oocytes. They are formed by the coalescence and condensation of small lipid granules whose precursors appear to be transported from outside the oocyte, as judged from the corresponding infiltration of lipids through the zona pellucida into the oocyte. The incoming lipids are physicochemically changed before they are converted into lipid yolk droplets. This change may be brought about by the peripheral cell organelles (mitochondria and yolk nucleus substance) and ground cytoplasm. The direct transformation of cell organelles into lipid yolk has been ruled out in the present material.

Abstract: Bipolar electrical recordings from the cerebral lobes of chick embryos and of freely moving chicks after hatching indicate that spontaneous electrical activity begins about the eleventh to thirteenth day of incubation, but electroencephalographic patterns characteristic of behavioral sleep or attention appear within six hours after hatching. High amplitude, slow waves, are characteristic of behavioral sleep; low amplitude, fast waves are characteristic of behavioral attention. During sleeping postures the electroencephalographic record shows brief cyclic episodes of lower voltage fast waves (paradoxical sleep) and these cycles appear more definitely as the chick grows older. When the act of waking from sleep is associated with the opening of only one eye, the lower voltage, fast waves may appear only in the contralateral lobe, while the ipsilateral lobe shows the high amplitude slow waves. In the less mature chicks, the electrical waves are slower, less regular, and of smaller amplitude, especially during sleep, furthermore the cyclic episodes of activated sleep are less distinct and the span of attention is more brief. Although chick embryos may move following tactile stimulation, the response is probably due to reflex arcs involving lower nervous centers since the cerebral lobes do not show the transition to lower voltage faster waves characteristic of attention. After hatching electroencephalographic patterns associated with sleeping postures show more conspicuous developmental changes than those associated with attention.

Abstract: During recent years techniques have been evolved which permit the development of embryonic mouse cleavage stages in vitro. These methods are now sufficiently reliable for use in quantitative experiments such as the mapping of concentration-response surfaces to discover the interaction of effects produced by various components of the medium. In studies on the development of mouse embryos in vitro conducted in our laboratory, a series of specialized biometrical problems has arisen. In the present paper, the theoretical basis for analyzing the responses of two-cell mouse ova in vitro is discussed. The responses are quantal in nature and are transformed before statistical treatment. The application of the angular and probit transformation to this data is illustrated. In certain cases, allowances must be made for a control portion of embryos failing to develop. The analyses are illustrated by two examples, one concerned with the determination of optimum conditions, and the other with the estimation of the median effective dose of a metabolic inhibitor.

Abstract: Autoradiographs of Tetrahymena cells labeled with 3H-thymidine for long periods of time indicate incorporation into acid-insoluble, DNase sensitive material in the cytoplasm. Results of electron microscope autoradiography show that 73% of the cytoplasmic silver grains occurred over mitochondria profiles, 92% of the grains were located over or within 0.5 μ of mitochondria while 97% of the silver grains were over or within 1.0 μ of mitochondria. Tests to determine loss or gain of radioactivity during cell growth and division show that approximately one-half of the label in each cell is transmitted to each daughter cell during division. The results demonstrate that mitochondria of Tetrahymena pyriformis contain a stable DNA-like material.

Abstract: The present work analyzes the mechanism of activation of the prothoracic glands in larvae and pupae of saturniid moths, and examines changes which occur in the prothoracic glands during the larval-pupal and pupal-adult transformation. The prothoracic glands of Samia cynthia ricini and Antheraea polyphemus synthesize DNA in the fourth instar. DNA synthesis occurred to a lesser extent in the fifth instar and in prepupae, but was not found in diapausing pupae or developing adults. Injury to diapausing pupae did not stimulate DNA synthesis in the prothoracic glands. The prothoracic glands of pupae of A. polyphemus injected with juvenile hormone extract did not synthesize DNA, nor did the prothoracic glands of pupae of Samia cynthia walkeri after transplantation into larvae. Apparently the prothoracic glands lose their ability to synthesize DNA during the larval-pupal transformation. The prothoracic glands of larvae of S. cynthia ricini synthesized RNA at a high rate throughout the fourth larval instar. In A. Polyphemus the rate of RNA synthesis in the prothoracic glands of developing adults was several times greater than the rate of RNA synthesis in diapausing pupae. The injection of juvenile hormone extract into pupae of A. polyphemus caused a marked increase in the rate of RNA synthesis. Changes in the rate of RNA synthesis were correlated with cytological changes in developing adults and in pupae injected with juvenile hormone extract. Prothoracic gland cells were found in adult S. cynthia ricini. Some of the cells were degenerating while the others appeared inactive. The relationship of RNA synthesis to activation and secretion, and the significance and control of DNA synthesis in the prothoracic glands are considered. Preliminary work on protein synthesis on the prothoracic glands and their activation in vitro is evaluated.

Abstract: The spermatozoa of Ascidia nigra contain only one mitochondrion. Phase contrast and electron microscopical evidence is presented showing that the spermatozoon loses its mitochondrion before it enters the perivitelline space. Thus, in these organisms, the paternal mitochondrion plays no role in the development of the zygote and cannot contribute mitochondrial DNA to the genetic repertory of the zygote.

Abstract: The maintenance of Aurelia aurita polyps in this laboratory has made possible the study of strobilation under well controlled laboratory conditions for the first time. The development of pulsing, statocysts and gastric filaments during normal strobilation occurring in artificial sea water at constant temperature was observed. Comparisons made of intact strobilae and segments cut from strobilae revealed that isolated segments of strobilae differentiated at a rate comparable to segments of intact strobilae. Furthermore, segments and pieces of segments which appeared morphologically to be polyp tissue and which exhibit no differentiation of structure were already “programmed” to become medusa tissue. Since isolated completed segments developed into ephyrae without further contributions of cells or substances from the parent it was postulated that segments of intact strobilae are, likewise, independent in their development once segments are completed. Studies of atypical strobilation resulting from simple environmental change emphasized that mechanisms that regulate segmentation are different from and probably independent of those that regulate metamorphosis of the segments into ephyrae. A discussion of the major processes involved in strobilation is presented and a close analogy to the metamorphosis of higher animals is drawn. The value of this primitive form of metamorphosis for studies of mechanisms involved in growth and differentiation is demonstrated.

Abstract: Prelactating mammary tissues from five mammalian species (laboratory rat, guinea pig, hamster, rabbit, dog) were maintained in organ culture in the presence of insulin, corticoids and ovine prolactin (mammotropin — MH) and/or bovine growth hormone (somatotropin — STH). MH stimulated secretion in all but one species; however, any apparent secretory effect of STH could be accounted for by contamination with MH. Accordingly, these mammals did not demonstrate the interchangeability of MH and STH established for some mouse strains. There are species differences in mammary sensitivity to MH: dog and rabbit are most sensitive, hamster and rat are less sensitive, and guinea pig was unresponsive. No difference in response between Long-Evans and Sprague-Dawley rats was detected. Mammary tissues from the dog, guinea pig and rabbit showed some ability to survive in the unsupplemented synthetic medium “199” whereas tissues from the other two species showed little or no viability. Supplementation of the medium with insulin results in improvement in survival of mammary tissues from all species. The further addition of corticosteroid (aldosterone, cortisol or corticosterone) leads to greater augmentation of survival in tissues from all five species, with some indication that the gluco-corticoid principally characteristic of the species concerned was more effective than the others.

Abstract: Dissociated monolayer cell cultures of chick embryonic spinal ganglia were set up on collagen-coated coverslips and incubated in 5% CO2 atmosphere at 38°C. Neurons were maintained in good condition for approximately three weeks and showed regeneration of nerve fibers as well as recovery from chromatolysis to normal Nissl pattern. Synthesis and transport of nucleic acids and protein in neurons and in spindle cells were studied with tritiated precursors by means of autoradiography. Less than 3% (10 of 318) of nerve cells from 12-day-old chick embryo spinal ganglia showed tritiated thymidine incorporation, whereas 27% (511 of 1880) of spindle cells from the same source incorporated tritiated thymidine. Thus, under our cultural conditions most neurons did not synthesize DNA. Both neurons and spindle cells incorporated tritiated uridine. Newly synthesized RNA appeared in the nucleus, and after several hours it was distributed over the perikaryon of neurons and the cytoplasm of spindle cells. The label was never found in nerve fibers, even after prolonged tritiated uridine treatment. A conclusion is thus made that RNA is absent in the nerve fibers. In neurons, protein was synthesized only in the perikaryon. Nerve fibers did not show protein synthesis. Newly synthesized protein was transported from perikaryon distally along nerve fibers at a rate of approximately 10 mm per day.

Abstract: Thyroidectomy of adult Spotted munia (Uroloncha punctulata) leads to the gonads remaining permanently in full breeding condition and is responsible for an early increase in testis size and activity in juvenile birds. These effects may be due to (i) general disturbances in metabolism or (ii) continuous secretion of gonadotropic hormones from the hypopyhsis or (iii) to both of these processes.

Abstract: Animals whose interstitial cells have been selectively destroyed by nitrogen mustard continue to form new buds for nine days after mustard treatment. Buds present on parent animals at the time of mustard teatment continued to develop at the same rate as control animals; however, in most cases they failed to detach as quickly as control forms. Extensive histological examination revealed a lack of mitoses in gastrodermal digestive cells after nitrogen mustard treatment. Divisions continued in epidermal epithelio-muscular cells for as long as 20 days. It is suggested that cell divisions in the epidermis are necessary for the initiation of the budding process and that under the present conditions the gastrodermal cells are pulled along passively into the bud outgrowth.