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Biomedical subjects

M Cunningham

Publications and source records attributed to M Cunningham.

At least 19 recordsLinked to original sources
PubMed1992

Determination of the sequence of an expressible cDNA clone encoding ERp60/calregulin by the use of a novel nested set method.

An analysis of the N-terminal sequence of the luminal endoplasmic reticulum protein, ERp60, showed that it was identical to the well-characterized Ca2+-binding protein, calregulin. A full-length, expressible cDNA clone encoding this protein was isolated from a mouse fibroblast cDNA library. A novel nested set strategy for the production of overlapping fragments for DNA sequencing was used to determine the complete nucleotide (nt) sequence of both strands of the ERp60 clone. This method utilizes a series of nonspecific deletion primers in conjunction with a specific site primer to generate the nested set fragments. This procedure possesses several advantages over other nested set techniques, since it does not require (i) the re-cloning of the DNA insert into other vectors, (ii) any prior knowledge of the restriction sites of the nt sequence, or (iii) the transformation and analysis of bacterial subclones. ERp60 has a 17-amino acid (aa) signal sequence and the mature protein contains 399 aa with a calculated M(r) of 46,347.

Amino Acid Sequence↗
PubMed1992

Innovative approach to genetic counseling services for the deaf population.

Genetic service providers have stressed the importance of genetic counseling that is nondirective and specific to the personal needs of consultants. Successful genetic counseling for deaf persons often requires special provisions for complex family histories, syndromic conditions, and diversity in communication methods and cultural orientation. The Gallaudet University Genetic Services Center (GSC) was established in 1984 to provide genetic education and counseling services to the deaf community. The GSC staff developed and implemented a standardized system of data collection (family and medical history), clinical evaluation by consultant clinical geneticists, and counseling in sign language. In addition to clinical services, an in-depth educational program for professionals and consumers was developed and carried out. During a 6-year period, over 220 educational presentations were made and 659 deaf persons were seen for genetic evaluation and counseling. Most of these persons were self-referred. Sign language was the preferred means of communication of more than 90% of these individuals. A genetic cause of deafness was diagnosed in over 50% of the deaf consultants and was confirmed by segregation analysis, which had results similar to those reported for other studies of students in schools for the deaf. Special materials and strategies were developed in order to provide genetic services that were sensitive to the cultural and linguistic differences of the deaf population. These included written and visual materials that contained culturally neutral terminology and training of all staff members in sign language and the culture of the deaf.

Adolescent↗
PubMed1992

Regulation of glycoprotein IIb-IIIa receptor function studied with platelets permeabilized by the pore-forming complement proteins C5b-9.

Recent evidence suggests that the cytoplasmic domains of platelet glycoprotein (GP) IIb-IIIa are involved in the agonist-initiated transformation of this integrin into a receptor for fibrinogen. To identify intracellular reactions that regulate the receptor function of GP IIb-IIIa, membrane-impermeable agonists and antagonists were introduced into the platelet by permeabilizing the plasma membrane with the pore-forming complement proteins C5b-9. Platelet responses were then analyzed by flow cytometry. Non-lytic concentrations of C5b-9 caused permeabilization of the platelet plasma membrane, as determined by uptake of a water-soluble fluorescent tracer dye. The complement pores were large enough to permit the entry of fluorescein isothiocyanate (FITC)-labeled oligopeptides in a size-dependent manner. Under conditions of low external Ca2+, C5b-9 treatment per se did not activate GP IIb-IIIa, as measured by binding of the activation-dependent antibody FITC-PAC1. However, FITC-PAC1 binding to C5b-9-permeabilized platelets was stimulated by a thrombin receptor agonist acting at the cell surface and by guanosine 5'-O-(thiotriphosphate), a membrane-impermeable activator of G proteins. Permeabilization also permitted the entry of cyclic AMP and the peptide, RFARKGALRQKNV, a pseudo-substrate inhibitor of protein kinase C. Each of these inhibited agonist-induced FITC-PAC1 binding to permeabilized platelets but not to intact platelets. Agonist-induced GP IIb-IIIa activation in permeabilized platelets was also inhibited by tyrphostin-23, a protein tyrosine kinase inhibitor. Thus, C5b-9 can be used to permeabilize the plasma membrane to permit the selective entry of small peptides and other bioactive compounds into permeabilized platelets. Results obtained with these platelets indicate that GP IIb-IIIa receptor function is regulated by a network of signaling reactions involving G proteins, serine/threonine kinases, and tyrosine kinases.

Amino Acid Sequence↗
PubMed1992

Regulation of perfluorooctanoic acid--induced peroxisomal enzyme activities and hepatocellular growth by adrenal hormones.

A wide variety of compounds, including hypolipidemic drugs, plasticizers and other industrial chemicals, have been found to cause liver enlargement and hepatic peroxisome proliferation by mechanisms that are unclear. Although thyroid and sex hormones have been shown to modulate the hepatic response to these chemicals, the role of adrenal hormones in these phenomena is not clear, and a few studies have produced conflicting data. Therefore this study was undertaken to investigate the role of adrenal hormones in hepatomegaly and peroxisomal enzyme induction caused by peroxisomal proliferators and to further delineate the interrelationship between these parameters. Because adrenalectomy alters hepatic drug metabolism, we have used the nonmetabolizable proliferator perfluorooctanoic acid. Our data show that hepatomegaly caused by perfluorooctanoic acid depends on corticosterone, the major glucocorticoid in rodents. Liver growth caused by perfluorooctanoic acid appears to be predominantly hypertrophic in nature, and DNA synthesis in response to perfluorooctanoic acid predominates in periportal regions of the liver lobule. Data also show that although induction of peroxisomal beta-oxidation by perfluorooctanoic acid is independent of adrenal hormones, induction of catalase is dependent on the presence of these hormones. This study supports the contention that induction of activities of various peroxisomal enzymes is controlled by different regulatory mechanisms.

Adrenal Cortex Hormones↗
PubMed1992

Characterisation of melarsen-resistant Trypanosoma brucei brucei with respect to cross-resistance to other drugs and trypanothione metabolism.

An arsenical resistant cloned line of Trypanosoma brucei brucei was derived from a parent sensitive clone by repeated selection in vivo with the pentavalent melaminophenyl arsenical, sodium melarsen. The melarsen-resistant line was tested in vivo in mice against a range of trypanocidal compounds and found to be cross-resistant to the trivalent arsenicals, melarsen oxide, melarsoprol and trimelarsen (33, 67 and 122-fold, respectively). A similar pattern of cross-resistance was found in vitro using a spectrophotometric lysis assay (greater than 200-fold resistance to melarsen oxide and greater than 20-fold resistance to both trimelarsen and melarsoprol). Both lines were equally sensitive to lysis by the lipophilic analogue phenylarsine oxide in vitro, suggesting that the melamine moiety is involved in the resistance mechanism. Although trypanothione has been reported to be the primary target for trivalent arsenical drugs [1], levels of trypanothione and glutathione were not significantly different between the resistant and sensitive lines. Statistically significant differences were found in the levels of trypanothione reductase (50% lower in the resistant clone) and dihydrolipoamide dehydrogenase (38% higher in the resistant clone). However, the Km for trypanothione disulphide, the Ki for the competitive inhibitor Mel T (the melarsen oxide adduct with trypanothione) and the pseudo-first order inactivation rates with melarsen oxide were the same for trypanothione reductase purified from both clones. The melarsen-resistant line also showed varying degrees of cross-resistance to the diamidines: stilbamidine (38-fold), berenil (31.5-fold), propamidine (5.7-fold) and pentamidine (1.5-fold). Cross-resistance correlates with the maximum interatomic distance between the amidine groups of these drugs and suggests that the diamidines and melaminophenyl arsenicals are recognised by the same transport system.

Animals↗
PubMed1992

Evaluation of methods for typing coagulase-negative staphylococci.

One hundred and forty-two coagulase-negative staphylococci (CNS) isolated from dialysate effluent or skin of patients receiving continuous ambulatory peritoneal dialysis (CAPD) were typed by extended antibiogram (16 antibiotics) and biotype (26 reactions). These isolates were then typed by supplementary methods to determine the most suitable typing method for an epidemiological study of antibiotic resistance. These included phage typing, reverse phage typing, plasmid typing, whole-cell protein typing by SDS-PAGE with analysis by densitometry, and immunoblotting. The percentage of isolates typed successfully by the supplementary methods were: phage typing 20%, reverse phage typing 0%, plasmid typing 66%, SDS-PAGE 100%, immunoblotting 100%. The discrimination of each method was: phage typing 20%, plasmid typing 37%, SDS-PAGE 69%, immunoblotting 57%. Reproducibility was 88% for phage typing and 97% for plasmid typing. The reproducibility of the whole-cell protein typing was 83% if the same extracts were used but only 43% when separate protein extracts were analysed on separate occasions. However, strain relatedness was highly reproducible. The determination of an antibiogram-biotype profile was not a sufficiently accurate typing method for an epidemiological study of antibiotic resistance. Whole-cell protein typing by SDS-PAGE or immunoblotting was technically demanding but was the most effective of the supplementary methods for detecting erroneous discrimination and false matching produced by antibiogram-biotype combinations.

Bacterial Proteins↗
PubMed1991

[The value of endoscopic sclerotherapy in the treatment of gastroduodenal hemorrhagic ulcers].

Mortality in upper GI tract bleeding has not been affected by the introduction of diagnostic fibre optic endoscopy. Recently, however, several modes of treatment delivered through the endoscope have been shown to be effective in improving the outcome of bleeding ulcers. We have retrospectively evaluated the course of 58 patients who underwent endoscopic treatment of a bleeding ulcer. Hemostasis was initially obtained in 93% of patients. 19 (34%) had a relapse of hemorrhage and 15 of these underwent emergency operation. 5 patients (8.6%) died; one of these deaths was due to a complication of endoscopic treatment. Definitive hemostasis was obtained in 41 patients (71%). Endoscopic sclerotherapy of bleeding gastroduodenal ulcers is effective, simple, and cheap, and should be considered in all patients presenting a high risk of relapse.

Adolescent↗
PubMed1991

[Constipation and incontinence: significance of colonic transit time, anorectal manometry and defecography].

Constipation and fecal incontinence are frequent motives of gastroenterological consultation. An etiological diagnosis can often be suspected from the history and can be confirmed by functional testing. We here report our experience with the measurement of colonic transit time (TTC), anorectal manometry (MAR) and defecography (D). Whilst TTC was unhelpful, MAR revealed abdomino-pelvic asynchrony (anismus) in 60 constipated patients and 7 (47%) of 15 incontinent patients. Perineal descent was suspected in 25 constipated patients and confirmed by defecography, which also revealed associated static pelvic disorders. Our experience confirms the role of functional exploration in the investigation of constipation and fecal incontinence and permits a more precise therapeutic approach.

Adult↗
PubMed1991

Genetic counseling of the deaf. Medical and cultural considerations.

Genetic counseling is a communication process where information is provided in a nondirective way. Genetic counseling emphasizes informed decision making and provision of medical, psychological, and social support; genetic counseling is not advice giving. Individuals who are members of the deaf community (culturally deaf) present unique challenges to the ability of genetic counselors to be nondirective. In contrast to the medical model which considers deafness to be a pathological condition, many deaf people do not consider themselves to be handicapped but define themselves as being part of a distinct cultural group with its own language, customs, and beliefs. Cultural and linguistic factors have a strong influence on the success of genetic counseling with deaf people. Strategies for effective genetic counseling to deaf people include the recognition that perception of "risk" is very subjective and that some deaf individuals may prefer to have deaf children. Other considerations for successful service provision include the use of appropriate questionnaires or history-taking tools, the use of qualified interpreters, and the revision of counseling materials and terminology to eliminate cultural bias. Nondirective counseling is also very dependent on the educational background and level of understanding of the consultants. There is a desperate need for education within the deaf community about genetics, particularly the less well educated, and a need for training of genetic counselors who have an appreciation of the linguistic and cultural differences of the deaf. Additionally, as with any other cultural, racial, or ethnic group, it would be very appropriate for deaf persons to be trained as genetic counselors to provide genetic counseling to deaf people. Unfortunately, there are at present no culturally deaf genetic counselors in the United States. Genetic counseling for deaf couples can also be complicated by complex family trees with mating between several deaf people and by the potential presence of other complicating features that may be associated with syndromic types of deafness. This requires careful history taking by trained geneticists and often long, complex explanations to families when the mode of inheritance cannot be confirmed. Even though deaf people most often do not pursue genetic counseling because of concerns for reproductive outcome, there is great enthusiasm among members of the deaf community about genetic services when they are provided in a manner that is sensitive to their linguistic and cultural differences. Genetic counseling for culturally deaf people can have great personal benefits for these individuals, can increase general knowledge regarding hereditary types of deafness and can help in developing strategies for providing appropriate genetic counseling for individuals with all degrees of hearing loss.

Adult↗
PubMed1991

Acetaldehyde increases procollagen type I and fibronectin gene transcription in cultured rat fat-storing cells through a protein synthesis-dependent mechanism.

We previously reported that acetaldehyde increases the production of type I collagen in cultured rat fat-storing cells. We studied the regulation of this effect by determining the expression of procollagen type I, fibronectin and transforming growth factor-beta 1 messenger RNAs in passage 1 and 2 cultures of fat-storing cells exposed to acetaldehyde for up to 24 hr. By 6 hr, acetaldehyde increased the steady-state levels of alpha 1 procollagen type I messenger RNA 3.2-fold and of fibronectin messenger RNA 2.8-fold above control values. At 24 hr, messenger RNA levels remained elevated. In contrast, transforming growth factor-beta 1 messenger RNA steady-state levels remained unaltered by 6 hr, but increased 1.5-fold by 24 hr. Cycloheximide (0.3 mmol/L) completely inhibited the acetaldehyde effect when added at zero time but was less effective when added at 15 min. The effect of acetaldehyde was not modified when cells were cultured in the presence of the acetaldehyde dehydrogenase inhibitor cyanamide (100 mumol/L). Fat-storing cells were also cultured in the presence of lactate (5, 15 and 25 mmol/L) for 6 hr. At none of these concentrations was any effect seen on either alpha 1(I) procollagen or fibronectin messenger RNAs. In the presence of methylene blue, a scavenger of reducing equivalents, the effect of acetaldehyde on alpha 1(I) procollagen and fibronectin gene expression was totally inhibited. Transcription run-on assay showed that acetaldehyde increased both procollagen type I and fibronectin transcriptional activity threefold and 2.5-fold, respectively. We conclude that acetaldehyde increases alpha 1(I) procollagen and fibronectin gene expression through enhanced transcription by a mechanism dependent on newly synthesized proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1991

Carbohydrate and oxygen metabolism during hepatocellular proliferation: a study in perfused livers from mirex-treated rats.

Liver regeneration after partial hepatectomy is accompanied by altered hepatic intermediary metabolism. Because the organochlorine compound mirex also causes liver cell growth, the purpose of this study was to investigate hepatic carbohydrate and oxygen metabolism in perfused livers from mirex-treated rats and to localize cell proliferation in this model. Pretreatment with mirex (100 mg/kg, intragastrically) increased liver/body weight ratios and DNA synthesis in livers of fed rats, effects that were markedly diminished in livers of fasted rats. This finding shows that liver growth caused by mirex, as is the case after partial hepatectomy, is hindered when animals are deprived of food. Furthermore, perfused livers from mirex-treated rats had depleted glycogen stores but significantly elevated oxygen uptake compared with livers from control rats. Increases in oxygen uptake and hepatocellular proliferation were observed mostly in periportal regions of the liver lobule. In regenerating livers, most DNA synthesis was reported to also occur in these regions of the liver lobule. Taken together, these data show that liver cell growth caused by mirex is accompanied by changes in hepatic intermediary metabolism and sublobular proliferation similar to those observed after partial hepatectomy.

Animals↗
PubMed1990

Role of calcium and calpain in complement-induced vesiculation of the platelet plasma membrane and in the exposure of the platelet factor Va receptor.

The role of calcium and intracellular calpains in the expression of platelet prothrombinase activity was investigated. Incubation of gel-filtered platelets with complement proteins C5b-9 resulted in alpha-granule and dense granule secretion and exposure of membrane binding sites for coagulation factors Va and Xa. This was accompanied by the release of microparticles from the cell surface that incorporated plasma membrane glycoproteins GP Ib, IIb, and IIIa and the alpha-granule membrane protein GMP-140. Generation of these membrane microparticles was dependent on the presence of extracellular calcium and was accompanied by proteolytic degradation of the cytoskeletal proteins, actin binding protein (ABP), talin, and myosin heavy chain. Microparticle formation was also detected when unstirred platelets were activated by thrombin plus collagen, although proteolysis of ABP, talin, or myosin was not observed. Preincorporation of the calpain inhibitor leupeptin into the platelet cytosol completely blocked C5b-9-induced proteolysis of ABP, talin, and myosin. However, inhibition of this calpain-mediated proteolysis had no effect on platelet secretion, the generation of microparticles, the exposure of membrane sites for factors Va and Xa, or the expression of prothrombinase activity. Furthermore, the microparticles that formed in the presence of leupeptin contained intact ABP, talin, and myosin heavy chain. Prior depletion of ATP with metabolic inhibitors eliminated all platelet responses to thrombin plus collagen, but did not affect C5b-9-induced microparticle formation or exposure of binding sites for factor Va on the microparticles. These data indicate that the formation of microparticles and the expression of platelet prothrombinase activity in response to C5b-9 are dependent upon an influx of calcium into the platelet cytosol, but do not require metabolic energy or calpain-mediated proteolysis of cytoskeletal proteins.

Adenosine Triphosphate↗
PubMed1990

Mechanisms regulating cell number and type in the mammalian central nervous system.

In the developing brain, neurons are derived from multipotential precursor cells in a precise sequence, where the time when a neuron becomes postmitotic is closely linked to the differentiated function of the neuron. Work from our group (1) identifies the Nes+ neuronal precursor state, (2) defines growth factors that regulate the proliferation of Nes+ precursor cells and their differentiation into neurons, and (3) establishes immortal cell lines that may be useful models for the terminal differentiation of Nes+ cells into neurons and astrocytes. These results suggest that the basic technical requirements are now in place to define the signals that control the transition from a precursor cell to a postmitotic neuron in the mammalian CNS. Control of this terminal differentiation is a key step in generating the large numbers and types of cells in the CNS.

Animals↗