Search PubMed⌕ Search

Biomedical subjects

T Williams

Publications and source records attributed to T Williams.

At least 307 records · Page 17Linked to original sources
PubMed1980

Physiology of Candida utilis yeast in zinc-limited chemostat culture.

Candida utilis NRRLY -900 was grown in aerobic continuous culture in a minimal salts medium with sucrose (1% w/v) as the carbon source. increasing the concentration of zinc in the medium from 2.3 microM results in an increase in the apparent critical dilution rate from 0.3 to 0.47h-1, and in the maximum biomass productivity form 1.5g dry weight per litre per hour (at D=0.33-1) to 2.56g per litre per hour (at D = 0.45-1). The maximum steady-state level of cell-associated zinc (at D = 0.4-1) is 4nmol Zn2+/mg dry weight, during carbon-limited growth, and about 9mumol Zn2+/mg dry weight when FeCI3 is omitted form the medium. At input zinc concentrations <20microM, the cellular zinc concentration decreases linearly in proportion to the input zinc concentration and at <4.5microM Zn2+ the culture becomes zinc-limited. Zinc-limitation results in a decrease iun the growth yield Ysurcosefrom 0.54 to 0.38 cells/g sucrose consumed, and Y0 from 22 to 13g cells/g-atom 02, suggesting an altered efficiency of energy metabolism. The composition of the culture biomass with respect to protein and RNA content is not affected by zinc limitation.

Aerobiosis↗
PubMed1980

Hyperaccumulation of zinc by zinc-depleted Candida utilis grown in chemostat culture.

The steady-state levels of zinc in Candida utilis yeast grown in continuous culture under conditions of zinc limitations are <1nmol Zn2+/mg dry weight of cells. Unlike carbon-limited cells, zinc-depleted cells from a zinc-limited chemostat possess the capacity to accumulate and store zinc at levels far in excess of the steady-state level of 4 nmol/mg dry biomass observed in carbon-limited chemostat cultures. Zinc uptake is energy-dependent and apparently undirectional since accumulated 65Zn neither exists from preloaded cells nor exchanges with cold Zn2+. The transport system exhibits a high affinity for Zn2+ (Km =.36micrM) with a Vmaxof 2.2 nmol per minute per milligram dry weight of cells. Growth during the period of the uptake assay is responsible for the apparent plateau level of 35 nmol Zn2+/mg dry weight of cells achieved after 20-30 min in the presence of 65Zn at pH 4.5 and 30 degrees C. Inhibition of growth during the uptake assay by cycloheximide results in a biphasic linear pattern of zinc accumulation where the cellular zinc is about 60 nmol/mg dry weight after 1 h. The enhanced level of accumulated zinc is not inhibtory to growth. Zinc-depleted C. utilis contains elevated amounts of polyphosphate and this anionic evidence does not allow discrimination between possible regulation of zinc homestasis either by inhibitions of zinc efflux through control of the membrane carrier or by control of the synthesis of a cytoplasmic zinc-sequestering macromolecule.

Biological Transport, Active↗
PubMed1980

Morphometric studies of the response of the luminal epithelium in the rat uterus to exogenous hormones.

The luminal epithelium of the uterus has been examined morphometrically in ovariectomized rats from 0--25 hours after a single injection of either 2.5 mg progesterone or 2.5 micrograms oestradiol subcutaneously. In each case, the epithelial cells were 50% taller at 25 hours than in controls. In progesterone series, this growth occurred between 6 and 25 hours: it was preceded by a significant increase in nuclear size and in the volume fraction of cytoplasm occupied by free ribosomes at 3 hours, and increases in the volume fractions of free ribosomes and RER at 6 hours. AT 25 hours, many smooth-surfaced vesicles appeared at the cell apex. In the oestradiol series, cell size decreased at 3 and 6 hours before increasing at 25 hours. Apical vesicles were reduced in number at all times after oestradiol: at 25 hours the nucleolus showed a fivefold increase in size, the RER had a greater volume fraction, and the lipid droplets were significantly reduced in number. The nature and timing of these results are consistent with the hypothesis that progesterone acts on these cells by a different mechanism to oestradiol, which does not involve DNA-directed RNA synthesis.

Animals↗
PubMed1979

Pulmonary haemorrhage and haemolytic anaemia due to trimellitic anhydride.

Two young men who had been exposed at work to epoxy resin powder containing trimellitic anhydride (TMA) presented with haemolytic anaemia and repeated haemoptyses. They did not return to work at the factory and the symptoms and the anaemia resolved spontaneously. Seven similar cases have lately been presented at meetings, so it seems that TMA, already known to cause respiratory syndromes such as asthma, can also lead to several extrapulmonary toxic effects, including haemoptyses and haemolytic anaemia. Studies on these patients' sera with TMA haptenised protein and cells pointed to an immunological mechanism.

Adolescent↗
PubMed1979

Dextran biosynthesis and dextransucrase production by continuous culture of Leuconostoc mesenteroides.

Leuconostoc mesenteroides NRRL B-512(F) was grown in continuous culture under conditions of energy-limited growth. The extracellular enzyme dextransucrase (sucrose: 1,6-alpha-D-glucan 6-alpha-glucosyltransferase EC 2.4.1.5), was not detected in glucose- or maltose-limited cultures. Under conditions of sucrose-limited growth, the enzyme activity of the cell-free culture supernatant increased with increasing dilution rate only after the critical concentration of enzyme inducer (sucrose) in the chemostat had been achieved. The appearance of fructose in the effluent of the sucrose-limited chemostat at higher dilution rates indicated that sucrose was being diverted to dextran biosynthesis. The competition between bacteria and extracellular enzyme for the common substrate sucrose represents an inefficiency in the system of enzyme production. Dextransucrase was isolated from the cell-free culture supernatant by ammonium sulfate precipitation and DEAE-cellulose chromatography. The enzyme preparation exhibited both dextran biosynthetic activity and an invertase-like activity. The biosynthetic efficiency was increased by decreasing the temperature from 30 to 10 degrees C. The enzyme was irreversibly denatured by prolonged incubation in the absence of Ca2+.

Dextrans↗
PubMed1979

Ventricular fluid levels of chloramphenicol in infants.

Investigation of two infants suggested that peak ventricular fluid levels of chloramphenicol after intravenous administration were achieved after 3 h. The penetration of chloramphenicol into ventricular fluid may be unpredictable. In one patient, the peak ventricular fluid level was 57.5% of the peak serum level, and it was only 22.5% in the other patient. This observation may explain some of the past treatment failures when chloramphenicol was utilized in patients with gram-negative ventriculitis and meningitis.

Brain Diseases↗
PubMed1979

Phase II study demonstrating failure of both a five-drug continuous-therapy regimen and a two-drug pulse-therapy regimen in the treatment of metastatic neuroblastoma: Southwest Oncology Group Study 822.

Twenty-six children greater than 1 year of age with previously untreated stage IV neuroblastoma were randomized to receive either a five-drug regimen (prednisone, cyclophosphamide, actinomycin D, vincristine, and daunorubicin) or a two-drug regimen (cyclophosphamide and vincristine). Complete response rates were 6% and 9% for the five-drug and the two-drug regimens respectively. Partial response rates were 13% and 27% for the five-drug and the two-drug regimens respectively. The mean duration of the seven responses was 9 months, and all 26 patients had died within 2 years. Neither regimen was effective for long-term disease control in these children with neuroblastoma.

Antineoplastic Agents↗
PubMed1978

The role of phosphoenolpyruvate carboxykinase in amino acid metabolism in muscle.

Starvation or feeding rats on a high-protein diet, valine or isoleucine, but not leucine, increases the activity of muscle phosphoenolpyruvate carboxykinase, but has no effect on NADP+-linked malate dehydrogenase. This suggests that muscle phosphoenolpyruvate carboxykinase is involved in oxidation or conversion of some amino acids to alanine.

Amino Acids↗
PubMed1978

Enterobacter aerogenes primary bacteremia in pediatric patients.

Enterobacter aerogenes bacteremia associated with the infusion of contaminated admixed intravenous (IV) fluid occurred in seven patients in a pediatric hospital over a five-day period. Clinical illness was characterized by spiking fever in all patients. The temporal clustering of cases allowed for rapid recognition of the problem. The primary control measure was the prompt replacement of the IV fluids, although IV antibiotics were also administered. Hospital pharmacy practices for admixing IV solutions should follow published recommendations to minimize this source of potential contamination of fluids.

Child↗
PubMed1977

Effect of citrate on the activities of 6-phosphofructokinase from nervous and muscle tissues from different animals and its relationships to the regulation of glycolysis.

1. Citrate inhibits the activities of phosphofructokinase from muscles and nervous tissues from different animals across the Animal Kingdom except for the insects. The enzymes from the flight muscle of nine different insects and the cerebral ganglion of the locust were investigated: no inhibition by citrate was observed. Inhibition was observed with the enzymes from both aerobic (e.g. pectoral muscle of pigeon) and anaerobic (e.g. fish muscle, pectoral muscle of the game birds) muscles. It is suggested that this inhibition is of physiological importance in decreasing the rate of glucose utilization in skeletal muscle of animals during starvation and/or prolonged exercise. 2. The rates of glucose utilization by the sartorius and gastrocnemius muscles of the frog were markedly decreased by ketone bodies. The latter elevated the glucose 6-phosphate and citrate contents of the gastrocnemius muscle, indicating that citrate inhibition of phosphofructokinase could be, in part, responsible for the decreased rate of glycolysis. 3. These findings provide evidence that the concept of the glucose-fatty acid-ketone-body cycle involves both aerobic and anaerobic skeletal muscle and nervous tissue from a wide range of animals except the insects. In the latter the concept of the cycle may not be applicable.

Adenosine Triphosphate↗
PubMed1977

The consultation process and its effects on therapeutic outcome.

There is little in the literature dealing with consultation from the point of view of patient care. Since one of the major elements in the definition of family practice deals with the synthesizing role and the responsiblity of the family physician to help guide patients through the complex health-care system, it is entirely appropriate to take a critical look at the consultation process. This will allow more appropriate teaching of the family practice resident, so that he may use consultation and referral in a more productive manner in the future. This paper defines and discusses six common problems in the consultation process. Classification of pitfalls in the consutative process can serve as a starting point from which a more critical and systematic study of the consultation can be made, to the end of making the consultant and the referring physician both more skilled and more comfortable with their coordinated tasks.

Adult↗