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Biomedical subjects

M Fox

Publications and source records attributed to M Fox.

At least 271 records · Page 15Linked to original sources
PubMed1976

The effect of dibromodulcitol on resting and dividing lymphoid cells.

The effect of dibromodulcitol (DBD) on the incorporation of labelled precursors into DNA and RNA fractions of PHA-stimulated human lymphocytes and of P388F lymphoma cells at various stages of their growth was studied. Both cell systems showed sensitivity to the drug within the concentration rage of 1-10 mug/ml. When DBD was added before phytohaemagglutinin (PHA), h.han RNA. In contrast, by adding DBD after PHA, RNA labelling was much more inhibited than DNA. In the latter case, the decrease in DNA labelling occurred only 24 h after drug treatment whereas RNA labelling was decreased 1 h after treatment. Levels of DBD which normally produced 30% inhibition in plating efficiency of P388F lymphoma cells affected uridine-5-T incorporation to a different extent at different stages of growth of the culture. Enhanced RNA labelling occurred in early exponential stage while at later stages of growth, RNA synthesis was depressed.

Adult↗
PubMed1976

The relative effectiveness of 6-thioguanine and 8-azaguanine in selecting resistant mutants from two V79 Chinese hamster cells in vitro.

The frequency of surviving colonies in two V79 cell lines exposed to either 6-thioguanine or 8-azaguanine was dependent on initial plating density. Different degrees of metabolic-co-operation were found to occur in the two cell lines and the loss of both spontaneous and added mutants occurred at a lower cell density when 6TG was used for selection than when 8 AZ was used in both cell lines. Both analogues were degraded on incubation in medium plus serum in the absence of added cells. Variation in serum batch had little effect on the rate of degradation or on the frequency of colonies recovered after treatment of V79 cell lines with 8AZ. The reasons for preferring 8AZ to 6TG as a selective agent are discussed.

Animals↗
PubMed1976

Biological and biochemical characterisation of purine analogue resistant clones of V79 Chinese hamster cells.

Purine analogue resistant clones have been selected from the closely related Chinese hamster lines V79A and V79S. Clones were of either spontaneous origin or induced by EMS or ultraviolet light. The majority of clones selected in 8-azaguanine showed stable cross resistance to 6-thioguanine. Clones derived from V79A and selected for 6-thioguanine resistance were cross resistant to 8-azaguanine: however a group of 6-thioguanine resistant mutants selected from V79S cells were 8-azaguanine sensitive. All clones except two were unable to grow in HAT medium. The two exceptions were 8-azaguanine resistant, showed partial sensitivity to 6-thioguanine, and also differed in other biochemical characteristics. HGPRT activity was measurable in extracts of all clones under standard conditions. In many clones, HGPRT activity increased as the hypoxanthine concentration was reduced. Whole cell uptake of [14C] hypoxanthine was low in all cases examined and was not modified by incubation in the presence of amethopterin. The heat sensitivity and electrophoretic mobility of HGPRT in extracts of some clones was compared to that in wild-type extracts. All clones tested except one, which was consistently HAT positive, showed enhanced heat sensitivity and reduced electrophoretic mobility. None of the mutants reverted spontaneously at detectable frequency but some could be induced to revert by EMS. The presence of measurable enzyme with altered properties in all clones suggests that these revertable drug resistant clones represent missense mutants.

Animals↗
PubMed1976

Factors affecting the growth of Chinese hamster cells in HAT selection media.

Factors affecting the efficiency of selection of "revertants" of salvage pathway mutants in media containing amethopterin have been examined. Our V79 Chinese hamster cell line was found to require a significantly higher level of thymidine for optimal growth in such media than has been reported for other cell lines. Hypoxanthine (but not glycine) was also required for reversal of amethopterin toxicity, but levels did not differ significantly from those reported elsewhere. Growth in HAT was also dependent on plating density and serum batch. Our modification (VHAT) was compared with published HAT recipies in back selection reconstruction experiments. A sharp fall in EOR (efficiency of recovery) of wild type cells from mixtures with mutants at plating densities greater than 3500 cells/cm2 (10(5) cells/6 cm dish) was observed for VHAT. EOR with other HAT recipes was lower still, and was affected also by the particular mutant used in the mixture. EMS induced "revertants" were isolated from three 8AZr mutants by plating in VHAT. All revertants were however amethopterin resistant, they were also 8AZ resistant and the mobility of residual HGPRT (as measured by polyacrylamide gel electrophoresis) was similar to that of their 8AZr parents i.e. dissimilar from that in wild type. The modal chromosome number of V79 wild type cells was 21. No significant deviation from this mode was detected in any of the mutant lines examined. The data indicate that the recovery of colonies in HAT from 8AZr mutants does not necessarily indicate that a back mutation in the structural gene for HGPRT has occurred. Thus, the frequency of HAT+ colonies cannot be taken as a direct indication of reversion frequencies.

Animals↗
PubMed1976

The rejection of islets of Langerhans following intrahepatic transplantation in the rat.

Pancreatic acinar tissue and islets of Langerhans have been isolated using a collagenase technique from Agus rats and transplanted separately into the liver of diabetic and nondiabetic isogeneic Agus and allogenic PVG/C rats. Livers were removed on days 1, 2, 4, 7 and 14 and examined histologically. Transplanted isogeneic islets showed no evidence of cellular infiltration and the beta cells appeared fully granulated. Transplanted allogeneic islets in non-diabetic recipients were surrounded by a mononuclear cellular infiltrate on day 2 and this became maximal by day 4. Although initially fully granulated, beta cells became degranulated on day 7 and by day 14 only small fragments of islet tissue remained. In allogeneic diabetic recipients the cellular infiltrate appeared less dense; beta cells appeared incompletely granulated from days 1 to 4 and a transient fatty degeneration occurred in the hepatic parenchuma around islets.

Animals↗
PubMed1976

Single dose fast neutron RBE for pulmonary and esophageal damage in mice.

Mice whose thoraxes were exposed to cyclotron neutrons or x rays died from esophagus damage 10 to 70 days after exposure, and from pulmonary damage 70 days to 6 months after exposure. The single exposure RBE for esophagus lethality was 1.9 at at a neutron dose of 1,475 rads and 1.6 for pulmonary lethality at a neutron dose of 950 rads. The significance of these values for neutron radiotherapy of the thorax is discussed.

Animals↗
PubMed1975

Effect of methyl methanesulphonate (MMS) and methylene dimethanesulphonate (MDMS) on the template activity of DNA isolated from MDMS-sensitive and -resistant Yoshida cells.

Both methylene dimethanesulphonate (MDMS) and methyl methanesulphonate (MMS) cause the template activity of Yoshida cell DNA to decrease in a dose-dependent manner. The MDMS-resistant subline of Yoshida tumour is less sensitive in terms of DNA template activity than the MDMS-sensitive subline towards both agents. Although the difference in sensitivity is not reflected in the survival data after each agent, it does suggest that the DNA from each cell line differs in its capacity to function as an efficient template.

Animals↗
PubMed1975

Factors affecting the quantitation of dose-response curves for mutation induction in V79 Chinese hamster cells after exposure to chemical and physical mutagens.

Using four common mutagens, ethyl methanesulphonate (EMS), methyl methanesulphonate (mms), uv, and X-irradiation, the relationship between dose of mutagen, cellular lethality and frequency of 8-azaguanine resistant colonies in V79 Chinese hamster cells has been examined. Several factors affecting the recovery of mutants including inter and intra-clone metabolic co-operation have been quantitated and their influence on survival response curves examined. Induced mutant frequencies were assayed by two methods in situ, and after replating. After exposure to X-rays, MMS and UV a significantly higher frequency of mutants was observed in replated experiments as compared with the in situ situation, at all survival levels assayed. With EMS, an increment on replating was observed only at high survival levels. The replating data suggest that two types of azgr colonies are produced, i.e. those which contain only azgr cells and those which, due to damage segregation, contain a mixture of azgr and azg8 cells. These mixed colonies appear to be lost by metabolic co-operation when mutation frequencies are assayed in silu. The proportion of mixed to homogeneous colonies differs with different mutagens. Taking into account such factors, EMS and UV irradiation were similarly mutagenic at a given survival level, but at equitoxic doses, fewer mutants were recovered after exposure of V79 cells to MMS and X-rays.

Cell Division↗
PubMed1975

Idiopathic chronic urinary retention in the female.

The clinical features in 14 female patients with chronic urinary retention unassociated with extrinsic or obvious intrinsic obstruction or neurological disease are described. Management, results and histological findings are presented and discussed in relation to the clinical findings.

Adolescent↗
PubMed1975

Transplantation of interstitial cells of the testis: effect of implant site, graft mass and ischaemia.

Autotransplantation of testicular tissue was performed in inbred mice to subcutaneous trunk, ear lobe and intraperitoneal sites. The results were assessed after 3 months by determining the weights of seminal vesicle and penis and by the histological appearances of the grafts and seminal vesicles. Intraperitoneal implantation produced maximal effects and as little as 5 mg of testicular tissue could be grafted with demonstrable androgenic action on the host. Spermatogenic tissue atrophied in all cases but interstitial cells were shown to survive and function 3 months after subcutaneous grafting following 48 hours ischaemia in 3 degrees C, 12 hours at 21 degrees C and 3 hours at 37 degrees C.

Animals↗
PubMed1975

Pancreatic ischaemia; sensitivity and reversibility of the changes.

In the rat, pancreatic clamping producing warm ischaemic times ranging from 5 to 90 min gives rise to changes similar to those of an haemorrhagic pancreatitis. The severity of the changes is proportional to the time of ischaemia. After 1 to 1 1/2 h clamping 95 per cent of the glandular changes are reversible, and at 2 months the pancreas appears normal apart from localized areas of fibrosis. The islets of Langerhans remain morphologically normal even after 90 min ischaemia. The implications for islet cell transplantation are discussed.

Adipose Tissue↗