Pathogenesis of trimethyltin neuronal toxicity. Ultrastructural and cytochemical observations

The ultrastructural cytopathologic and cytochemical effects of trimethyltin (TMT) neurotoxicity were delineated in hippocampal and pyriform neurons of acutely intoxicated adult rats. TMT produced neuronal necrosis that preferentially involved hippocampal formation pyriform cortex. The first subcellular alterations were multifocal collection of dense-cored vesicles and tubules and membrane-delimited vacuoles in the cytoplasm of the perikaryon and proximal dendrite. Ultrastructural cytochemical examination revealed that the vesicles and tubules had acid phosphatase activity analagous to Golgi-associated endoplasmic reticulum (GERL). Shortly after the appearance of the GERL-like vesicles and tubules, autophagic vacuoles and polymorphic dense bodies accumulated in the neuronal cytoplasm. Some dense bodies appeared to arise from the dense-cored tubules. Neuronal necrosis was characterized by increased electron density of the cytoplasm and large, electron-dense intranuclear masses. Alterations of mitochondria and other organelles were not observed in the early stages of cell injury. No light- or electron-microscopic alterations were found in liver or kidney. Comparable subcellular alterations were observed in adult and neonatal rats chronically intoxicated with TMT. A series of other trialkyl and tricyclic tins and dimethyltin did not produce similar pathologic findings. The GERL-like accumulations are unique in neuronal cytopathology. These findings suggests that GERL and autophagy play an important role in the pathogenesis of TMT-induced neuronal injury.     

Effect of sulfate on carbon and electron flow during microbial methanogenesis in freshwater sediments

Rickettsiae of the spotted fever group were detected by haemocyte test in 8 (12%) of 51 partially engorged Dermacentor marginatus females collected in March/April 1975 in South Germany. Four strains of rickettsiae were isolated from ticks positive in haemocyte test. It was concluded with isolated strain BRD-1 and homologous immune guinea pig, hamster and mouse sera in CF cross reactions with antigens and immune sera against other members of the SF group, that the newly isolated strains are similar, almost undistinguishable from Rickettsia slovaca.     

Polyuridylic sequences and negative strands of Sindbis virus-specific RNAs: study by affinity chromatography on poly (A)-sepharose columns (author''s transl)

The experimental conditions of affinity chromatography on poly (A)-Sepharose columns have been determined. This method makes obvious the existence of polyuridylic acid sequences on the negative strands of Sinbis virus-spedific RNAs. The isolated RNAs are negative and positive strands hybrids. By polyacrylamide gel electrophoresis, it has been shown that the negative strands have the same length as the 26 S interjacent RNA at the 6th hour, and as the 42 S virion RNA at the 9th hour postinfection. The polyadenylic acid sequences of the virion RNA and of the replicative intermediate are therefore probably genetically coded.     

Histologic structures preserved for 21,300 years

Histologic examination of rehydrated tissue samples from late Pleistocene (Alaskan) mammal mummies demonstrates that the preservative effect of freezing and drying extends to remains 15,000 to 25,000 years old. Some muscle and liver tissue retained identifiable histologic structures. Most tissues were completely disintegrated and partly replaced by masses of bacteria, an indication of considerable postmortem decay before the remains were entombed beneath the permafrost zone.     

Ultrastructure and elemental composition of dormant and germinating Diplodia maydis spores

The ultrastructure of Diplodia maydis spores was studied in thin sections with a transmission electron microscope. Storage vacuoles were evenly distributed in the two cells. Some of the vacuoles that contained a dense osmiophilic sphere(s) were surrounded by a membrane, and had membranous aggregates around their periphery. The sport wall was composed of an electron-dense layer and an electron-translucent layer. An inner cytoplasmic membrane was present. Dormant and germinating spores were studied with scanning electron microscopy and also with a Si (Li) energy-dispersive X-ray analyzer. The dormant spore was ovate and usually two-celled with a central septum. Germination proceeded via a germ tube from the side of one end of the cell. Of several methods for preparation of specimens for X-ray analysis studied, freeze-dried spores mounted on carbon stubs and then further carbon coated gave the best results. X-ray analyses revealed that spore populations contained large amounts of Si, P, Cl, and K, smaller amounts of S and Ca, and trace amounts of Mg and Al. Analyses of single spores revealed high K and Cl and low P and Mg at one end of the cell with concomitant low K and Cl and high P and Mg in the central portion and other end of the cell. In two-celled germinating spores, high K and Cl occurred in the end of the nongerminating spore cell, whereas the germinating cell contained high P and Mg and low K and Cl. X-ray image maps revealed that K and Cl were located together at one end of the spore.     

Dose-rate dependence of heat radiosensitization

The dose rate dependence of heat radiosensitization was studied using rat astrocytoma cells in culture and a clinically relevant protocol of heat dose and heat radiation sequence. Cells were treated with a minimally toxic heat dose of 43 degrees C for 30 minutes, after which they were irradiated with varying doses of radiation at dose rates ranging from 0.567 to 300 cGy/min. This heat dose substantially reduced the extrapolation number (n), but had little effect on Do of the radiation survival curve at dose rates of 50 cGy/min or greater. At dose rates less than 10 cGy/min, 43 degrees C for 30 min had little effect on n and only for the lowest dose rate studied (0.567 cGy/min) was there a significant reduction in Do (60%). The thermal enhancement ratio did not vary inversely with radiation dose rate over the dose rate range studied but, instead, was maximal at the two dose rate extremes (0.567 and 300 cGy/min). These data demonstrate that a clinically relevant heat dose enhances very low dose rate, as well as high dose rate, ionizing radiation, but suggest that little benefit is to be gained from using dose rates intermediate between conventional radiotherapeutic high dose rates or dose rates representative of interstitial implants.     

Hepatic lipids in Reye-Johnson syndrome and in acute encephalopathy without fatty liver

The relationship between Reye-Johnson syndrome and acute encephalopathy without fatty liver was investigated by comparing the lipid composition of liver samples obtained from five patients with Reye-Johnson syndrome, two patients with acute encephalopathy, and five controls. The mean total hepatic triglyceride concentration was increased nearly sevenfold in Reye-Johnson syndrome and slightly decreased in acute encephalopathy when compared with the mean control value. The mean total hepatic free fatty acid concentration was increased nearly threefold in acute encephalopathy when compared with the mean value in Reye-Johnson syndrome. Total phospholipid content was decreased in the liver in Reye-Johnson syndrome, and this difference was caused mainly by a diminution of the hepatic lecithin fraction. The ratio of palmitic acid to oleic acid and hepatic free fatty acids was 2.5 in Reye-Johnson syndrome, 0.7 in acute encephalopathy, and 0.8 in controls. These results suggest that, despite clinical similarities and laboratory evidence of hepatic dysfunction in both Reye-Johnson syndrome and acute encephalopathy, different pathogenic mechanisms may be responsible for the liver abnormalities found in the two syndromes.