Biomedical subjects

J Lewin

Publications and source records attributed to J Lewin.

At least 73 records · Page 4Linked to original sources

PubMed1983

Ultrastructural assessment of cryopreserved hepatocytes after prolonged ectopic transplantation.

Isolated adult rat hepatocytes were cryopreserved by cooling, in the presence of dimethyl sulfoxide, to low subzero temperatures and they were stored for 14 days at -196 C. The cells were then recovered and transplanted into the splenic pulp of the original donor animal. A similar transplant procedure was performed with hepatocytes which had not been cryopreserved. Ultrastructural assessment was made 1 month after transplantation. In general fewer hepatocytes survived ectopic transplantation after cryopreservation, but the surviving cells were ultrastructurally similar to ectopically transplanted cells not subjected to cryopreservation. Thus, the reduced metabolic activity measured previously in transplants of cryopreserved hepatocytes is likely to result from a smaller number of competent cells rather than from hepatocytes which have survived in an extensively damaged or abnormal state.

Animals↗

PubMed1982

Screw fixation in bone of guinea pigs sensitized to nickel and cobalt.

A screw was inserted transversely through the distal femora and proximal tibiae of guinea pigs sensitized to either Ni or Co. An equal number of nonsensitized animals were treated in the same way. The animals with Ni allergy received an ASIF stainless steel screw and the animals with Co allergy a Howmedica Vitallium screw. After 6 weeks no obvious differences were observed in the histological picture around the femur screws that could be ascribed to metal sensitivity. The mechanical strength of the bone adjacent to the tibial screws was tested by measuring maximum torque during continuous tightening of the screws at a rate of 2 revolution/second. No significant differences in maximum torque resistance were found between sensitized and nonsensitized animals. The results indicate that sensitivity to Ni or Co does not compromise the mechanical fixation between metal and bone during the early period after the implantation.

Animals↗

PubMed1982

Measurements by filter elution of DNA single- and double-strand breaks in rat hepatocytes: effects of nitrosamines and gamma-irradiation.

This work presents a filter elution method for measuring DNA single- and double-strand breaks in primary rat hepatocytes without radioactive labeling of DNA. We have studied the effects of a series of nitrosamines and of gamma-irradiation on DNA single- and double-strand break induction. The repair of DNA single-strand breaks in the hepatocytes was measured after treatment with 60Co, 1-methyl-1-nitrosourea, and N-nitrosodimethylamine. The hepatocytes were isolated by ethylene glycol-bis(beta-aminoethyl ether)-N,N'-tetra acetic acid-collagenase perfusion and had a mean viability of 91 +/- 4% (S.D.). The isolated cells were treated for varying lengths of time with nitrosamines in suspension culture in L-15 medium containing 10% fetal bovine serum. After treatment, the cells were chilled, loaded onto 2 micrometers polycarbonate filters, and lysed in a 2% sodium dodecyl sulfate-proteinase K solution, pH 9.6. The DNA was eluted from the filter at either native or denaturing pH with fractions collected every 3 hr. The quantity of DNA in each fraction was determined by measuring the fluorescent product formed between it and diaminobenzoic acid after ethanol-sodium acetate precipitation and trapping of the DNA on 0.2-micrometer polycarbonate filters. The results show that the carcinogens, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodipropylamine, N-nitrosodibutylamine, and 1-nitrosopiperidine all made dose- and time-related increases in the number of single-strand breaks in rat hepatocytes. N-Nitrosodiphenylamine produced small numbers of single-strand breaks. No double-strand breaks were formed by any of the nitrosamines. Single-strand breaks induced by N-nitrosodimethylamine were repaired very slowly relative to repair of either gamma-ray of 1-methyl-1-nitrosourea-induced single-strand breaks. This system has many advantages for studying carcinogen metabolism and DNA damage in hepatocytes, one of the major target cells for many carcinogens.-

Animals↗

PubMed1981

Ultrastructural features in chronic non-A, non-B (NANB) hepatitis: A controlled blind study.

Liver biopsies from 12 patients with chronic Non-A, Non-B (NANB) hepatitis, 7 with hepatitis B surface antigen (HBsAg) positive chronic liver disease, 1 HBsAg positive normal carrier, and 4 patients with non-viral liver disease, were examined by electron microscopy for cytoplasmic and nuclear changes. Aggregates of particles measuring 20-35 nm in diameter were noted in the nuclei of 8 of 12 patients with NANB chronic hepatitis, but not in the other groups. The tubular changes seen in the endoplasmic reticulum (ER) of chimpanzees with NANB hepatitis were not noted in biopsies from any of our patients.

Cell Nucleus↗

PubMed1979

Acute haemorrhagic cystitis and glomerulonephritis.

Two patients presented with macroscopic haematuria and dysuria. Cytoscopic examination showed haemorrhagic cystitis. The findings of casts in the urine and of impaired renal function led to renal biopsies. These showed glomerulonephritis with deposits of IgA in the mesangium. No evidence of viral infection was found. A third patient diagnosed on biopsy 9 years previously as having focal glomerulonephritis developed gross haematuria and dysuria. Cystoscopy revealed haemorrhagic cystitis, and deposits of immunoglobulins were present in the bladder wall. It is suggested that haemorrhagic cystitis may occur as part of a syndrome with glomerulonephritis and may be due to an immunological mechanism.

Adolescent↗

PubMed1975

Heterotrophic nutrition of the marine pennate diatom Navicula pavillardi Hustedt.

Navicula pavillardi Hustedt, a marine, littoral, pennate diatom, can grow in the dark on glutamate or on the complex organic supplements tryptone or yeast extract. Growth on glutamate in the dark took place without an initial lag phase, whereas growth on tryptone began only after a 2-day lag phase that could be abolished by the simultaneous presence of glucose. Lactate inhibited growth in the dark on glutamate, but not photoautotrophic growth. Relatively low concentrations of glutamine inhibited photoautotrophic growth. The observed doubling time for heterotrophic growth on glutamate or tryptone was about 70 h, compared with a doubling time of 24 h under optimal photoautotrophic conditions. Glucose did not decrease the doubling time in the dark on tryptone. The assimilation efficiency for glutamate was 41%. The estimated necessary uptake rate for glutamate to account for the observed heterotrophic doubling time on glutamate was close to those measured with isotope techniques. The kinetic parameters for glutamate uptake, which followed Michelis-Menten kinetics, were Ks = 0.018 mM, and Vmax = 7.0 X 10(-10) mumol per cell per minute. Although several amino acids served as sole nitrogen sources for photoautotrophic growth and were demonstrated by the use of isotope techniques to enter the cells, they could not be used as substrates for growth in the dark. Glucose was not taken up to a significant extent except by cells grown in the presence of tryptone. Lactate was taken up only by dark-grown cells. Results of preliminary studies on the metabolic fate of several uniformly labeled amino acids are presented.

Acetates↗

PubMed1973