ULTRASTRUCTURAL CHARACTERISTICS OF NEPHROBLASTOMAS AND THEIR RELATION TO DNA PLOID

Fifty-one cases of nephroblastoma were pathologically studied by light and electron microscopy as well as microspectrophotometry. Under light and electron microscope, the tumor appeared to be carcinosarcoma structurally, consisting of epithelial, sarcomatous and undlfferentiated tumor cells. Their ultrastructural feature was similar to that of renal tubular epithelial cells and tibroblast. It could differentially be diagnosed from renal metoblastic tumors by electron microscopy when the tumor was mainly composed of sarcomatous cells. Microspectrophotometer measurement showed an Increased mean nuclear DNA content (DI>1. 04), belonging to aneuplold tumor, which together with polyploid cells, serving as one of the Important characteristics of malignant tumors. In addition, the poorer the tumor differentiation the higher was the DNA content of the tumor cells, suggesting that the measurement of nuclear DNA of tumor cells might also serve as one of signs to acertain the degree of differentiation and malignant of nephroblastomas with more preciseneas than general morphological examinations.

Effects of High Temperature Stress on Microscopic and Ultrastructural Characteristics of Mesophyll Cells in Flag Leaves of Rice

The microscopic and ultrastructural characteristics of mesophyll cells in flag leaves of two rice lines （a thermosensitive line 4628 and a thermo-resistant line 996） under high temperature stress （37℃ during 8：00-17：00 and 30℃ during 17：00-8：00） were investigated using an optical and a transmission electron microscopy. The membrane permeability and malondialdehyde content increased under the high temperature stress, and the increase of both variables was greater in the line 4628 than in the line 996. Under the high temperature stress, the line 996 showed tightly arranged mesophyll cells in flag leaves, fully developed vascular bundles and some closed stomata, whereas the line 4628 suffered from injury because of undeveloped vascular bundles, loosely arranged mesophyll cells and opened stomata. The mesophyll cells in flag leaves of the line 4628 were severely damaged under the high temperature stress, i.e. the chloroplast envelope became blurred, the grana thylakoid layer was arranged loosely and irregularly, the stroma layer disappeared, many osmiophilic granules appeared within the chloroplast, the outer membrane of mitochondria and the nucleus disintegrated and became blurred, the nucleolus disappeared, and much fibrillar-granular materials appeared within the nucleus. In contrast, the mesophyll cells in flag leaves of the line 996 maintained an intact ultrastructure under the high temperature stress. From these results, it is suggested that the ultrastructural modification of the cell membrane system is the primary plant response to high temperature stress and can be used as an index to evaluate the crop heat tolerance.

Characteristics of the Sertoli Cells of Salmonidae from Ohrid Lake during Spermatogenesis-Ultrastructural Analysis

Ultrastructual characteristics of Sertoli cells of Salmonidae from Ohrid Lake during the spermatogenetic cycle have been analysed. Sertoli cells being an integral part of the seminiferous lobules underwent considerable changes, which influenced their cytomorphological features. The degenerative changes of Sertoli cells were manifested by an extreme vacuolisation, mitochondria in degeneration with widened crysts and thickened matrix, desorganised ER, autophagosomes, ＂myeline-like＂ structures and lysed cytoplasmic regions. The above mentioned changes were followed by karyopycnisis, comlete degeneration and delamination of cells from the wall of the seminiferous lobules, lysis and detritus formations （Sertoli necrotic material） in the lumen of the lobules. The aim of this paper is special research of the ultrastructural characteristics, i.e. the changes on a level with testes which happen in the postspawning period in the two species of Teleostei of Ohrid Lake, Ohrid trout （Salmo letnica Kar.） and Ohrid belvica （Acantholingua ochridana Steind.）. The postspawning period is emphasized in Teleostei in this relatively short period, when one reproductive cycle finishes and the following has to start, on a level of testicular parenhyma very important histological changes are going on which give special histological identification, i. e. in the postspawning period there is a complete reorganization of the testes.

Toxicity effects of disinfection byproduct chloroacetic acid to Microcystis aeruginosa: Cytotoxicity and mechanisms

Chlorine-based disinfectants are widely used for disinfection in wastewater treatment.The mechanism of the effects of chlorinated disinfection by-products on cyanobacteria was unclear.Herein,the physiological effects of chloroacetic acid(CAA)on Microcystis aeruginosa(M.aeruginosa),including acute toxicity,oxidative stress,apoptosis,production of microcystin-LR(MC-LR),and the microcystin transportation-related gene mcyH transcript abundance have been investigated.CAA exposure resulted in a significant change in the cell ultrastructure,including thylakoid damage,disappearance of nucleoid,production of gas vacuoles,increase in starch granule,accumulation of lipid droplets,and disruption of cytoplasm membranes.Meanwhile,the apoptosis rate of M.aeruginosa increased with CAA concentration.The production of MC-LR was affected by CAA,and the transcript abundance of mcyH decreased.Our results suggested that CAA poses acute toxicity to M.aeruginosa,and it could cause oxidative damage,stimulate MC-LR production,and damage cell ultrastructure.This study may provide information about the minimum concentration of CAA in the water environment,which is safe for aquatic organisms,especially during the global coronavirus disease 2019 pandemic period.