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Biomedical subjects

I Russell

Publications and source records attributed to I Russell.

13 recordsLinked to original sources
PubMed1992

Thiamine secretion in yeast.

To isolate thiamine excretors and (or) overproducers, 188 cultures belonging to nine yeast and three fungal genera were screened. Nine excreted thiamine as determined by both the presence of cross-feeding zones on a thiamine-free agar medium seeded with a thiamine-requiring yeast strain and by the direct detection of excreted thiamine on agar plates. Several of these cultures produced several-fold more intracellular thiamine than the general culture population. Thiamine-requiring strains of Saccharomyces cerevisiae and S. uvarum (carlsbergensis) were identified and were tentatively assigned to 10 complementation groups.

Extracellular Space↗
PubMed1990

Expression and regulation of glucoamylase from the yeast Schwanniomyces castellii.

Expression of the 146-kilodalton (kDa) extracellular glucoamylase by the budding yeast Schwanniomyces castellii is induced by maltose and starch. By use of antiglucoamylase antisera, we found that this expression was regulated at the level of the mRNA, taking place within 30 min after exposure of yeast cells to the respective sugars. Polyacrylamide gel electrophoresis analysis of the in vitro-translated products of total RNA from maltose-treated cells established that the glucoamylase precursor was approximately 120 kDa in size. Stable glucoamylase transcript was not produced in cells exposed to glucose, 2-deoxyglucose, and heat shock. Cells exposed to these two sugars also degraded intracellular and extracellular glucoamylase. In the presence of sugars such as cellobiose, galactose, lactose, and xylose or in the absence of any carbohydrate, a low-level, constitutive-like expression of this preglucoamylase occurred. The nascent glucoamylase underwent at least two posttranslational modifications, resulting in a 138-kDa cell-associated form and the 146-kDa active form that was found free in the medium. These results suggest that glucoamylase expression is tightly regulated similarly to expression of the enzymes responsible for maltose metabolism in Saccharomyces yeasts.

Blotting, Western↗
PubMed1990

A study of ethanol tolerance in yeast.

The ethanol tolerance of yeast and other microorganisms has remained a controversial area despite the many years of study. The complex inhibition mechanism of ethanol and the lack of a universally accepted definition and method to measure ethanol tolerance have been prime reasons for the controversy. A number of factors such as plasma membrane composition, media composition, mode of substrate feeding, osmotic pressure, temperature, intracellular ethanol accumulation, and byproduct formation have been shown to influence the ethanol tolerance of yeast. Media composition was found to have a profound effect upon the ability of a yeast strain to ferment concentrated substrates (high osmotic pressure) and to ferment at higher temperatures. Supplementation with peptone-yeast extract, magnesium, or potassium salts has a significant and positive effect upon overall fermentation rates. An intracellular accumulation of ethanol was observed during the early stages of fermentation. As fermentation proceeds, the intracellular and extracellular ethanol concentrations become similar. In addition, increases in osmotic pressure are associated with increased intracellular accumulation of ethanol. However, it was observed that nutrient limitation, not increased intracellular accumulation of ethanol, is responsible to some extent for the decreases in growth and fermentation activity of yeast cells at higher osmotic pressure and temperature.

Biotechnology↗
PubMed1986

Prognostic significance of tumor grade in clinical trials of adjuvant therapy for breast cancer with axillary lymph node metastasis.

The prognostic significance of histologic tumor grade has been evaluated in 1537 women entered into the Ludwig Trials I-IV of adjuvant therapy for node-positive breast cancer. Tumor grade was determined on histologic review of primary tumor sections by two central review pathologists using a modification of the Bloom and Richardson grading system. The 5-year overall survival rates (+/- SE) were: Grade 1, 86% +/- 2; Grade 2, 70% +/- 2; and Grade 3, 57% +/- 2 (P less than 0.0001). This survival difference was seen in both premenopausal (P less than 0.0001) and postmenopausal (P less than 0.0001) women. Significant differences in disease-free survival (DFS) by tumor grade were also observed (P less than 0.0001). The tumor grade determined by the 75 contributing local clinic pathologists was also highly significant for predicting DFS and overall survival. Tumor grade remained a statistically significant prognostic factor for DFS (P less than 0.0001) and overall survival (P less than 0.0001) in multivariate analyses controlling for nodal status, tumor size, estrogen receptor status, menopausal status, age, peritumoral vessel invasion, and treatment assigned. In postmenopausal patients for whom adjuvant treatment was compared with no adjuvant therapy, the prognostic significance of tumor grade was modified by the effect of treatment. The presence of vessel invasion by primary tumor cells was a stronger predictor of early recurrence than was increasing tumor grade in postmenopausal patients who received no adjuvant therapy. The higher failure rates for patients with high-grade tumors was due to a larger number of failures in regional and visceral sites. Tumor grade can be determined by any pathologist and allows for selection of a subpopulation of breast cancer patients at high risk for early mortality.

Adult↗
PubMed1977

The identification, characterization, and mapping of a gene for flocculation in Saccharomyces sp.

Genetic studies of a flocculent haploid strain of Saccharomyces have revealed the flocculation to be dominant and controlled at a single gene locus. The flocculation character of both hybrids and haploids derived from such hybrids appears to be influenced by the repression or derepression status of the culture. Mapping studies of this flocculation gene have revealed that it is linked to ade 1 and therefore located on Chromosome I. Consequently, this is a different gene to the three flocculation genes studied by other laboratories because they have found such genes to be unlinked to ade 1. The flocculation gene being discussed in this paper has been designated FLO4. FLO4 has been located 32-33 cM from the Chromosome I centromere and 37 cM from ade 1 (i.e., FLO4 is on the opposite side of the centromere to ade 1).

Chromosome Mapping↗
PubMed1976

Inhibition by efferent nerve fibres: action on hair cells and afferent synaptic transmission in the lateral line canal organ of the burbot Lota lota.

1. Intracellular recordings were made from morphologically identified hair cells in the lateral line canal organs of the burbot Lota lota. 2. I.p.s.p.s were recorded from hair cells when the efferent fibres were excited by electrical stimulation of the lateral line nerve. The i.p.s.p.s were abolished when the fish was injected with immobilizing concentration of Flaxedil which is known to block the efferent synapses. 3. The i.p.s.p.s are accompanied by a decrease in the resistance of the hair cell membrane and an increase in the intracellular receptor potential. 4. Spontaneous and mechanically evoked e.p.s.p.s which were recorded intracellularly from the post-synaptic afferent nerve terminals were reduced in amplitude for the duration of the i.p.s.p.

Animals↗
PubMed1976

Deputising services in Denmark--some implications for Great Britain.

In Denmark charges for home visits were abolished in April 1973. This paper analyses how this change affected the number of consultations undertaken by the deputising service in one Danish town and how the increase in consultations was distributed in time and place in a sample of individual families. It also describes how, in comparison with the deputising services sponsored by the British Medical Association in Great Britain, the more widely-used Danish deputising services operate.

Comprehensive Health Care↗
PubMed1975

Matched controls in surveys of the use of general practice. Another use for research practice age-sex registers.

This paper describes how an age-sex register may be used as a sampling frame for the selection of matched controls in studies of the use of general practice. It discusses both the analysis of data collected in this way and the advantages and limitations of the method itself. The application of the method to a case-study suggests that patients who use hospital accident departments are also high users of general practice. Although care is needed in the interpretation of such results, it is concluded that matched controls can be used to ameliorate some of the problems of research in general practice.

Age Factors↗