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Biomedical subjects

R Foster

Publications and source records attributed to R Foster.

At least 37 records · Page 2Linked to original sources
PubMed1989

Calcium phosphate-mediated transfection alters metallothionein gene expression in response to Cd2+ and Zn2+.

The level of expression of a transfected metallothionein (MT)-IGcat fusion gene in response to cadmium differed from that of the endogenous MT-IG gene. Atomic absorption analysis indicated that the total cellular content of cadmium and zinc increased upon calcium phosphate-mediated transfection. Thus, changes in the influx/efflux of metals may regulate the level of MT gene expression.

Cadmium↗
PubMed1988

Structure and expression of the human metallothionein-IG gene. Differential promoter activity of two linked metallothionein-I genes in response to heavy metals.

The human metallothionein (MT)-IG gene (hMT-IG) is tandemly linked in a head-to-head fashion with the hMT-IF gene. The hMT-IG gene encodes a MT-I polypeptide and has a tripartite structure. The 5'-flanking region of the hMT-IG gene has a TATAA box, four GC motifs, and at least four metal responsive elements. The 3'-untranslated region has a variation of the polyadenylation signal, AATTAA, and the 3'-flanking region a YGTGTTYY RNA processing signal. This gene is expressed in hepatoma-derived cell lines (Hep G2 and Hep3B2) in response to the heavy metals (cadmium, copper, and zinc) but not to the glucocorticoid analogue dexamethasone. In contrast, the lymphoblastoid cell line (Wi-L2) does not express the hMT-IG gene. These results suggest that the hMT-IG gene is regulated differentially and in a cell type-specific manner. Transient expression studies of the chloramphenicol acetyltransferase (CAT) gene under the transcriptional control of either the hMT-IG or hMT-IF promoter in Hep G2 cells has demonstrated that both promoters contain all the necessary cis-acting elements to elicit a similar pattern of heavy metal inducibility. However, the hMT-IG promoter in all instances is five times more active than the hMT-IF promoter. The differences in promoter activity of these genes could possibly be due to inherent differences in their basal level regulatory sequences. The expression of MT-IGcat in transfected Wi-L2 cells demonstrates that the hMT-IG promoter is not cell type-specific.

Base Sequence↗
PubMed1988

Expression of heat stress proteins by human periodontal ligament cells.

The purpose of the present report was to document the stress response produced by physical and chemical abuses to human periodontal ligament cells, and to review some of the known functions of stress response proteins produced as a result of such treatments. For these studies human PDL cells were exposed to sublethal challenges of 43 degrees C heat, sodium arsenite and the amino acid analog L-azetidine-2-carboxylic acid (AZC). The cells were labelled with [35S]-methionine and the proteins produced were examined by autofluorography of SDS-PAGE gels. Heat challenges were shown to induce hsps with an apparent mol. wts. of 90K, 68-72K, 41-47K, and 36 K. Arsenite-treated cells produced similar hsps including a 30k protein not produced by other forms of stress. AZC treatment resulted in the production of apparent functionless hsps with apparent molecular weights of 90,000, 72,000, 68,000 and 36,000. The function of these proteins and their possible role in periodontal disease is discussed.

Arsenic↗
PubMed1987

Structure and expression of the human metallothionein genes.

The human metallothioneins are represented by a multigene family consisting of about 14 members. A number of MT-like genes have been isolated from a human genomic library and in this report, four MT genes have been characterized. Our results show that two of these genes represent the MT-I and MT-II processed genes. The other two genes (MT-IF and MT-IG) are functional members of the MT-I gene family. The amino acid sequence encoded by the MT-IF and MT-IG genes differ from the amino acid sequences of the published MT-I proteins at few positions. The 5'-flanking region of these genes contain metal responsive elements. Our studies show that the MT-IF and MT-IG genes are differentially regulated in two human hepatoma cell lines, HepG2 and Hep3B2, and a human lymphoblastoid cell line, WI-L2 in response to the heavy metals cadmium, zinc and copper, and glucocorticoids. In addition, these genes also show cell-type specific expression.

Amino Acid Sequence↗
PubMed1987

A review of clinical experience with oxamniquine.

Oxamniquine has now been in general use for 11 years for the treatment of schistosomiasis mansoni. Dosage varies with the geographical origin of the parasites due to different susceptibilities of local strains, and the appropriate regimen can be expected to cure over 80% of patients and reduce egg excretion in others by over 90%. The drug has been used safely in all stages of the disease. Some late-stage and complicated forms have shown clinical improvement, and prognosis has been improved in all by the removal of the causative organisms. Toleration is usually good with side effects limited to a mild, transient dizziness. Neuropsychiatric disturbances have been recorded in a small number of patients, and care should be taken in treating subjects with a history of such disorders. Nevertheless, these effects have not limited use of the drug which has been used widely for the field treatment of several million people in rural communities. These schemes have led to reductions in incidence, prevalence and the occurrence of hepatosplenic involvement.

Central Nervous System Diseases↗
PubMed1987

Retroperitoneal fibrosis and nonmalignant ileal carcinoid.

The carcinoid syndrome and fibrosis are unusual but identifiable disease processes. We report a rare case of retroperitoneal fibrosis associated with an ileal carcinoid in the absence of metastatic disease. The literature is reviewed.

Carcinoid Tumor↗
PubMed1987

Osmotic significance of glycerol accumulation in exponentially growing yeasts.

Natural-abundance 13C-nuclear magnetic resonance spectroscopy has shown glycerol to be the major osmotically significant low-molecular-weight solute in exponentially growing, salt-stressed cells of the yeasts Saccharomyces cerevisiae, Zygosaccharomyces rouxii, and Debaromyces hansenii. Measurement of the intracellular nonosmotic volume (i.e., the fraction of the cell that is osmotically unresponsive) by using the Boyle-van't Hoff relationship (for nonturgid cells, the osmotic volume is directly proportional to the reciprocal of the external osmotic pressure) showed that the nonosmotic volume represented up to 53% of the total cell volume; the highest values were recorded in media with maximum added NaCl. Determinations of intracellular glycerol levels with respect to cell osmotic volumes showed that increases in intracellular glycerol may counterbalance up to 95% of the external osmotic pressure due to added NaCl. The lack of other organic osmotica in 13C-nuclear magnetic resonance spectra indicates that inorganic ions may constitute the remaining component of intracellular osmotic pressure.

Glycerol↗
PubMed1986

A cytokinin mutant derived from cultured tobacco cells.

Tissues cultured from the leaf lamina of wild-type Nicotiana tabacum L. cv. "Havana 425" plants require an exogenous source of cytokinin for rapid growth. In contrast, leaf tissues of plants heterozygous or homozygous for the partially dominant, monogenic habituated leaf (H1-1) trait, exhibit a cytokinin-autotrophic phenotype in culture. Here we show that the H1 trait can arise in culture. Cytokinin autotrophic variants were obtained by culturing wild-type tissues of leaf lamina successively on media containing reduced concentrations of the cytokinin, kinetin. Plants regenerated from clones of these variants exhibited the H1 phenotype, which segregated in breeding tests as expected for a dominant, monogenic trait. This trait, designated H1-2, is inherited at a different locus than the H1-1 trait described earlier. Our results show that cytokinin mutants can arise in cell culture and that at least two genes regulate the cytokinin requirement of cultured tobacco tissues.

Cell Division↗
PubMed1986

Transdetermination of plant cells.

Tissues derived from the leaf lamina of Nicotiana tabacum L. cv. Havana 425 plants require cytokinin for continuous proliferation in culture, whereas tissues derived from the cortex of the stem are cytokinin autotrophic. Both phenotypes persist when the two types of cells are cloned, indicating that leaf- and cortex-derived cells are determined to express different cytokinin requirements in culture. We showed that cultures derived from leaf and cortex tissues of plants regenerated from cloned leaf and cortex cells exhibit the cytokinin requirement of comparable tissues of seed-grown plants. This provides direct evidence that plant cells can undergo transdetermination and that this process has an epigenetic basis.

Cell Differentiation↗
PubMed1986

Structure, organization, and regulation of human metallothionein IF gene: differential and cell-type-specific expression in response to heavy metals and glucocorticoids.

We describe a human genomic clone containing the metallothionein (MT) IF and MT IG genes. Southern blot analysis and partial DNA sequence determinations show that these genes are organized in a head-to-head fashion and are located approximately 7.0 kilobases apart from each other. Sequence analysis shows that the MT IF gene contains three exons separated by two introns. All of the intron-exon junctions are defined by the GT-AG rule. The 5' flanking region shows the presence of a duplicated metal regulatory element (TGCGC CCGGCCC) important in heavy-metal induction of this gene and a sequence for its basal level expression (GCGGGGCGGGTGCAAAG). The 5' flanking region is also highly G + C rich (approximately 75%) and contains several GC boxes (GGGCGG), probably important in the binding of transcription factors. The TATAA box and the AATAAA sequence are represented by their variants, the TATCAA box and the AATTAA sequence, respectively. This gene is functional and inducible by heavy metals but not by dexamethasone in mouse LMTK- cells after its transfer on a plasmid containing the herpes simplex virus thymidine kinase gene. Further studies on various human cell lines show that this gene is not expressed in a splenic lymphoblastoid cell line (WI-L2) but is expressed in two hepatoma cell lines (Hep 3B2 and Hep G2) in response to cadmium, zinc, and copper. Dexamethasone appears to have no significant effect on its expression. The studies suggest that the MT IF gene shows cell-type-specific expression and is differentially regulated by heavy metals and glucocorticoids.

Amino Acid Sequence↗
PubMed1986

Evaluation of radioimmunoassay performance for staphylococcal enterotoxin in foods: application of external quality assessment survey.

An external quality assessment survey for staphylococcal enterotoxin A, B, and C2 determinations was performed in the collaborative study. Three analysts in two laboratories took part. Three types of food, cheese, salami, and pasta, were artificially contaminated with either one toxin only or all three toxins. A total of 378 analyses were performed. The group mean of the analytical values corresponded fairly well to the given enterotoxin concentrations. However, a considerable interlaboratory imprecision was found despite analyses being performed with the same reagents and methodology.

Cheese↗
PubMed1986

Renal transplantation in diabetes mellitus. Influence of preexisting vascular disease on outcome.

We reviewed the recommendations and outcomes for all patients with diabetes mellitus and end-stage renal disease referred to the Medical Center Hospital of Vermont from 1971 through December 1983. During this period, we recommended transplantation in 53 of 73 patients evaluated. Thirty-two transplants were performed in 30 patients. Of the 30 patients, 10 had clinical vascular disease prior to transplantation, i.e., claudication, amputation, active angina, myocardial infarction, or stroke. Seven of the 10 had only claudication or amputation. These 10 patients showed a clear excess in graft failure and mortality. One- and 2-year graft survival was 37 and 13%; patient survival was 48 and 24%. By comparison, the 20 patients without evident vascular disease had 1- and 2-year graft survival rates of 83 and 75% and patient survival rates of 85% at both 1 and 2 years. The incidence of cardiovascular death in the group with vascular disease was 45% at 1 year and 63% at 2 years, as compared with none in the group without vascular disease. The high graft loss and mortality in this group after transplantation should be a major consideration when therapeutic alternatives are considered in diabetics with end-stage renal disease.

Adult↗
PubMed1979

Patterns of ventilation in postoperative and acutely ill patients.

Acutely ill patients commonly increase minute ventilation (V) to varying degrees. The pattern of breathing utilized to increase V was analyzed in normal subjects and acutely ill surgical patients. V = tidal volume (VT) x frequency (f), or V = inspiratory flow x (TI/TTOT, inspiratory time/total cycle time). CO2 inhalation and exercise were used to induce supine hyperventilation in normal subjects. This was compared to hyperventilation in acutely ill surgical patients. Measurements were made of O2 consumption, CO2 production, V, VT, f, inspiratory flow, TI, and TTOT. With small increases in V (up to twice control), normal subjects increased inspiratory flow and TI/TTOT with both CO2 and exercise. CO2 inhalation increased VT with no change in f, while exercise increased both VT and f. When V increased beyond twice control, TI/TTOT remained constant and increases in inspiratory flow accounted for the entire increase in V. In acutely ill patients with increased V, average f was elevated and VT decreased, but there was no constant relationship of f and VT with increasing V. However, TI/TTOT was relatively constant at 0.40- 0.46; therefore, in order to increase V, inspiratory flow had to increase! Patients also showed a tendency to breathe at a relatively fixed VT while normal subjects did not show this phenomenon, even with increases of up to 3 times control V. Continuous, rapid analysis of gas exchange and breathing patterns holds promise for early detection of patients with V inappropriate to metabolic demands, and serves as a sensitive indicator of abnormal patterns used by acutely ill patients to increase V.

Acute Disease↗