In the frigid desert of the Antarctic dry valleys there are no visible life forms on the surface of the soil or rocks. Yet in certain rock types a narrow subsurface zone has a favorable microclimate and is colonized by microorganisms. Dominant are lichens of unusual organization. They survive not by physiological adaptation to lower temperatures, but by changing their mode of growth, being able to grow between the crystals of porous rocks. Their activity results in mobilization of iron compounds and in rock weatherning with a characteristic pattern of exfoliation. This simple ecosystem lacks both higher consumers and predators.

https://science.sciencemag.org/content/sci/215/4536/1045.full.pdf

Endolithic Microorganisms in the Antarctic Cold Desert

The existence of at least two stages in bladder carcinogenesis was evaluated in male Fischer rats using N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) fed for six weeks at a level of 0.2% of the diet as the initiator. Sodium saccharin and dl-tryptophan were fed at levels of 5 and 2% of the diet, respectively, as possible promoting chemicals, and they were fed either immediately after FANFT administration or after six weeks of FANFT plus six weeks of control diet. All surviving rats were killed at the end of two years. Both chemicals significantly increased the incidence of bladder tumors following FANFT feeding compared to six weeks of FANFT feeding followed by control diet, and the results were similar whether saccharin or tryptophan feeding was started immediately after FANFT feeding was concluded or after a six-week delay. Saccharin was considerably more potent as a promoting agent than was tryptophan, inducing higher incidences of bladder tumors and having a shorter latent period. Long-term administration of FANFT induced a 100% incidence of bladder cancer. Sequential epithelial changes were observed by scanning and transmission electron microscopy as well as by light microscopy. Pleomorphic microvilli were present on the superficial cells of all tumors examined and on the surface cells of hyperplastic bladder epithelium after six weeks of FANFT plus six weeks of saccharin, but not after six weeks of FANFT and six weeks of control diet. Rats fed only saccharin, tryptophan, or control diet did not have bladder tumors or pleomorphic microvilli on bladder epithelium. These data suggest that saccharin and tryptophan might act as tumor-promoting agents during bladder carcinogenesis.

https://cancerres.aacrjournals.org/content/canres/39/4/1207.full.pdf

Promoting Effect of Saccharin and dl-Tryptophan in Urinary Bladder Carcinogenesis

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the urinary tract of rats and mice. The standardized nomenclature of urinary tract lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for urinar...

Proliferative and Nonproliferative Lesions of the Rat and Mouse Urinary System

Lichen-forming fungi are a large, taxonomically diverse group of nutritional specialists which acquire fixed carbon from a population of minute green algal or cyanobacterial cells. Mycobionts of foliose or fruticose lichens differ from the rest of the fungi by expressing morphologically and anatomically complex symbiotic phenotypes. The extracellularly located photobiont cell population of these macrolichens is housed and controlled by the quantitatively predominant fungal partner which competes for space above ground, secures adequate illumination and facilitates gas exchange. This review summarizes data on the ontogeny, functional morphology, growth patterns and internal thalline differentiation of macrolichens. Contents Summary 659 I. Introduction 659 II. Establishment of the lichen symbiosis 662 III. Growth and cell turnover 669 IV. Outlook 674 Acknowledgements 674 References 674.

Developmental biology of lichens.

The concept that most transitional cell neoplasms of the urinary bladder exist as either nonaggressive lesions of low cytologic grade or aggressive anaplastic cancers is gradually gaining acceptance. The extent to which the biological potential of these neoplasms is revealed in their pathologic features is the subject of this article. Using guidelines developed in experimental models, a series of 400 transitional cell neoplasms selected for long-term follow-up were classified into the WHO system. The results indicate that (1) almost all transitional cell tumors can be grouped into low and high grades at initial presentation; (2) the low grade lesions (usually designated transitional cell carcinoma, Grade I) are benign and should be called papillomas rather than carcinomas; (3) the risk of progression is not a function of the number of recurrences for these noninvasive, low-grade, papillary tumors; (4) the high-grade neoplasms are aggressive whether papillary or nodular and account for greater than 93% of tumor-related deaths; (5) patients with high-grade lesions have a reduced life expectancy even if progression does not occur; (6) depth of invasion and growth pattern are limited as predictive factors compared with histologic grade; (7) histologic grading of the initial tumor tissue can be highly predictive of outcome.

https://acsjournals.onlinelibrary.wiley.com/doi/pdf/10.1002/1097-0142%2819871201%2960%3A11%3C2766%3A%3AAID-CNCR2820601129%3E3.0.CO%3B2-0

Transitional cell neoplasms of the urinary bladder. Can biologic potential be predicted from histologic grading

The nature of the lichen symbiosis is not clear. It is generally thought to be mutualistic but this concept is not supported by experimental evidence1. Early workers2,3 considered that .lichens represented algae parasitized by fungi—as evidence, they noted algal cells in a lichen thallus that were dead or penetrated by fungal haustoria. Others, however, cited the seemingly healthy and long-lasting nature of lichens as evidence of mutualism. As we report here, our observations of artificial syntheses of the mycobiont Cladonia cristatella (‘British soldiers’) with different algae suggest that the relationship in this lichen is one of controlled parasitism. The mycobiont formed squamules mostly with algae related to its natural phycobiont, an indication perhaps of a long period of co-evolution between the symbionts of this lichen.

Relationship between fungus and alga in the lichen Cladonia cristatella Tuck

N-[4-(5-Nitro-2-furyl)-2-thiazolyl]formamide (FANFT) fed to male and female Fischer rats at a dose of 0.2% of the diet induces lesions of the urinary bladder which progress from mild hyperplasia at 2 to 4 weeks, to moderate hyperplasia at 6 to 8 weeks, severe nodular and papillary hyperplasia at 10 to 14 weeks, and microinvasive carcinomas by 25 weeks as observed by light microscopy. Male Fischer rats fed FANFT for 2 to 4 weeks and then maintained on control diet show regression of the bladder lesions within 2 weeks to normal-appearing mucosa which persists through 50 weeks. Rats fed FANFT for 6 weeks show regression of the moderately hyperplastic epithelium to normal within 4 weeks after being placed on control diet which persists through 50 weeks. Rats fed FANFT for 8 to 10 weeks show regression of the hyperplastic bladder epithelium within 2 weeks of receiving control diet, but focal areas of mild hyperplasia are detectable through the 20th week of the experiment. By the 50th week the rats fed FANFT for 8 weeks all had moderate to marked hyperplasia, but the rats fed FANFT for 10 weeks had transitional cell tumors, one of which was invasive through the entire thickness of the bladder wall. The lesions present in rats fed FANFT for 12, 14, or 20 weeks continued to progress to invasive tumors (microinvasive or invasion of muscle) after the rats had been maintained on control diet through 50 weeks. Thus, the hyperplastic lesions developing through 6 weeks of FANFT administration appear to be reversible if FANFT is discontinued, but later lesions appear to be irreversible.

https://cancerres.aacrjournals.org/content/canres/36/7_Part_2/2508.full.pdf

Early lesions in experimental bladder cancer: experimental design and light microscopic findings.

Urinary bladder damage caused by surgical incision, freeze-ulceration, or formalin instillation in male Fischer 344 rats was studied by light and scanning electron microscopy. The first two methods resulted in focal ulceration of the urinary bladder; the last induced diffuse mucosal damage. With each method, the damage was followed by regenerative hyperplasia and repair, the bladder mucosa returning to normal in 3-4 weeks. Epithelial cells in the hyperplastic areas had ropy microridges and uniform short microvilli on their luminal surfaces as observed by scanning electron microscopy. When the hyperplasia was marked, with nodular and papillary formation, occasional epithelial cells had pleomorphic microvilli on their surfaces. Rats treated either by surgical incision or freeze-ulceration had normal bladders after a 2-year observation period. Combined with results from previous experiments, pleomorphic microvilli are not a marker of neoplasia or irreversibility but appear with marked or prolonged mucosal proliferation even if reversible.

Scanning electron microscopic examination of reversible hyperplasia of the rat urinary bladder.

In the early stages of cellular interaction between the symbionts of Lecidea albocaerulescens, the phycobiont produced an extracellular sheath which bound to it hyphae of the mycobiont. Such a sheath may be a means by which the symbionts recognize each other. Hyphae of the mycobiont formed flattened appressoria as they grew over the algal cells and in this way secured the autotrophic population necessary for the development of a lichen thallus.

Scanning electron microscope study of early lichen synthesis.

SEM on bladder cells.

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