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Biomedical subjects

R Heller

Publications and source records attributed to R Heller.

At least 127 records · Page 7Linked to original sources
PubMed1993

Nitric oxide synthesis is impaired in glutathione-depleted human umbilical vein endothelial cells.

Human endothelial cells cultured from umbilical vein (HUVEC) were tested for their ability to synthesize nitric oxide (NO), which has been identified as an endothelium-derived relaxing factor. The synthesis of this free radical (detected as citrulline, which is produced stoichiometrically with NO from arginine) in HUVEC is Ca2+ dependent, is increased sevenfold by the calcium ionophore ionomycin, and accounts for most basal and ionomycin-induced guanosine 3',5'-cyclic monophosphate (cGMP) production. Loading of cells with reduced glutathione (GSH), but not with N-(2-mercaptopropionyl)- glycine (MPG), led to increased citrulline production, both basally and after ionomycin stimulation. When the cells were depleted of GSH by incubation with 1-chloro-2,4-dinitrobenzene (CDNB), citrulline synthesis and cGMP production were inhibited in a concentration-dependent way. CDNB was not cytotoxic and did not inhibit cGMP increase elicited by sodium nitroprusside; cell loading with GSH (but not with MPG) relieved the block of citrulline synthesis. These results suggest that GSH is necessary in HUVEC for NO synthesis rather than for the NO effect on guanylate cyclase.

Calcium↗
PubMed1992

Human endothelial cells are target for platelet-activating factor. II. Platelet-activating factor induces platelet-activating factor synthesis in human umbilical vein endothelial cells.

Platelet-activating factor (PAF), a phospholipid mediator with broad and potent biologic activities, is synthesized by several inflammatory cells including endothelial cells (EC). PAF is also an effective stimulating agent for EC leading to increased cell permeability and adhesivity. We examined the synthesis of PAF in human umbilical cord vein EC after stimulation of EC with PAF or with its nonmetabolizable analog 1-O-alkyl-2-N-methyl-carbamyl-sn-glycero-3-phosphocholine (C-PAF). PAF (1 to 100 nM) induced a dose- and time-dependent increase of PAF synthesis as detected by [3H]acetate incorporation into PAF fraction. Stimulation of PAF synthesis occurred via activation of the "remodeling pathway" as the 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine (lyso-PAF):acetyl-CoA acetyltransferase was dose-dependently increased after PAF treatment. The de novo pathway of PAF synthesis was not activated under these conditions. C-PAF was able to mimic the effect of authentic PAF on [3H] acetate incorporation. The inactive metabolite lyso-PAF (100 nM) had no influence on PAF synthesis in EC. CV-3988, BN 52021, and WEB 2086, potent and specific antagonists of PAF suppressed PAF effects on the remodeling pathway completely. The PAF- and C-PAF-induced [3H]PAF remained 93% cell-associated and was not degraded up to 10 min after stimulation. Characterization of the [3H]acetate-labeled material co-migrating with authentic PAF revealed that a significant proportion (approximately 57%) was actually 1-acyl-2-acetyl-sn-glycero-3-phosphocholine. PAF-induced PAF synthesis might be an important mechanism for amplifying original PAF signals and potentiating adhesive interactions of circulating cells with the endothelium.

Acetates↗
PubMed1992

Nitrovasodilators inhibit thrombin-induced platelet-activating factor synthesis in human endothelial cells.

In response to inflammatory agents such as thrombin, cultured endothelial cells produce platelet-activating factor (PAF), which has been linked with most inflammatory and immune processes, and is a potent coronary constrictor. Sodium nitroprusside (SNP) and SIN-1 (3-morpholinosydnonimine), which spontaneously release the free radical nitric oxide (NO), cause direct relaxation of blood vessels and inhibition of platelet aggregation by activating soluble guanylate cyclase. In the present study we report that in human umbilical vein endothelial cells (HUVEC) these compounds stimulate the production of cGMP and inhibit thrombin-induced PAF synthesis in a concentration-dependent manner. 8-bromo-cGMP, a permeant non-hydrolysable analogue of cGMP, mimics the inhibitory effect of NO-generating vasodilators. PAF synthesis requires phospholipase A2-mediated hydrolysis of membrane precursors to lyso-PAF, which is in turn converted into PAF by an acetyltransferase. The thrombin-elicited activation of both enzymes is inhibited in a dose-dependent way in HUVEC pretreated with SNP and SIN-1. The inhibitory effect of SNP and SIN-1 on the thrombin-mediated PAF synthesis suggests a new mechanism of action whereby the endogenous NO can affect vascular tone and endothelium-dependent intercellular adhesion. Moreover, PAF production in endothelial cells appears to be an important target for the pharmacological action of nitrovasodilators.

Acetyltransferases↗
PubMed1992

Spectrofluorometric assay for the quantitation of cell-tissue electrofusion.

Fluorometric assay for quantitating electrofusion, FAQE, was developed to measure the number of cells fused to intact tissue. The fluorescent vital dye hydroethidine is used in this method. The fluorescent intensity detected in the cell tissue hybrids is proportional to the number of individual cells fused. The number of cells fused was determined after fusion by lysing the epithelial layer with 0.2% sodium dodecyl sulfate and the supernatant fluids were measured in a spectrofluorometer and compared to established standard curves. The mean number of cells fused, in five separate experiments, was determined to be approximately 5000. All the experimental corneas had approximately the same number of fused cells with less than 10% variation. In addition, the technique was used to demonstrate an increase in the number of cells fused when multiple fusions were applied to the cell-tissue electrofusion system. These results demonstrate that FAQE can be utilized to quantitatively analyze the fusion yields.

Animals↗
PubMed1992

Characterization of a new compound, S35b, as a guanylate cyclase activator in human platelets.

The effects of S35b (4-methyl-3-phenyl sulfonylfuroxan), a new phenyl sulfonylfuroxan compound, were investigated on human platelets activated by different agonists. Platelet aggregation evoked by arachidonic acid (AA), collagen, ADP and thrombin was inhibited by the drug in a dose-dependent manner. S35b inhibited the AA-induced increase of cytosolic free Ca2+ ([Ca2+]i) and production of malondialdehyde. A primary action of the compound on cyclooxygenase is unlikely since: (1) U-46619 (15s-hydroxy-11,9-[epoxymethano]-prosta-5Z,13E-dienoic acid, a stable epoxymethano analog of prostaglandin H2) could not reverse the inhibitory effect of S35b on AA-induced aggregation and [Ca2+]i increase; (2) U-46619-induced aggregation and [Ca2+]i rise were inhibited by S35b; and (3) at high collagen concentrations platelet aggregation (which is unresponsive to aspirin under such conditions) was blocked by S35b as well. Thus the drug action is likely to be exerted at an early step of the platelet activation pathway. The elevation in the platelet cGMP level evoked by S35b in a time- and concentration-dependent manner can account for the inhibitory effect: increased cGMP levels could interfere, for instance, with G protein-phospholipase C coupling and subsequent phosphoinositide hydrolysis.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

Reduction of ischemic heart disease risk markers in the teenage children of heart attack patients.

BACKGROUND: Families of people with ischemic heart disease (IHD) are likely to share high levels of risk markers and to have similar lifestyle patterns. Teenage children in such families were the focus of a behavioral intervention program. METHODS: Families were randomly allocated to either an "early" or a "late" advice group. The late group and a third "control" group (consisting of families with no cardiovascular disease) received the intervention only after baseline measurements were repeated in all three groups at the end of 12 months. Pedigree analysis was used to compare changes across groups. RESULTS: The decrease in self-reported total fat intake was greater among teenagers in the early group (mean = -3.38, SE = 1.00) than among those in the late group (mean = -0.58, SE = 1.06), as was the decrease in saturated fat intake (mean = -2.46, SE = 0.56; mean = -0.54, SE = 0.60, respectively). These differences were statistically significant (P < 0.05). There were no differences between these groups for changes in total or high-density lipoprotein cholesterol levels. There was a statistically significant difference between the change in total cholesterol levels in the control group (mean = +0.08, SE = 0.07) and that in the late group (mean = -0.14, SE = 0.11). CONCLUSIONS: The intervention program appears to have made the teenagers aware of high-fat foods, as stated fat intake was significantly lowered, but it was not successful in decreasing blood cholesterol levels. Having a parent with IHD did, however, influence the teenagers' risk-related behavior, leading to a significant reduction in blood cholesterol levels.

Adolescent↗
PubMed1992

Platelet aggregation and coronary heart disease risk factor variation in Australian populations with different coronary heart disease mortality.

In a cross-sectional analytic study, we examined the differences in coronary heart disease (CHD) risk factors, including coagulation factors and platelet aggregation, among males from southern European countries and those of Anglo-Celtic descent who had widely different CHD standardized mortality ratios. The participants included 169 men aged 40 to 49 years, 27% of whom were born in southern European countries. The subjects had no history of heart disease and no other clinical conditions, or were not taking medications known to affect hemostasis. Data obtained included their medical history and CHD-related risk behaviors, blood pressure, height, weight, abdominal and pelvic circumference, and coagulation, fibrinolysis, platelet activity, lipids, and lipoproteins profiles. There were significant differences between the two groups in the prevalence of a positive family history, mean apolipoprotein A1 levels, and platelet aggregation responses to ADP. Other established risk factors, including coagulation factor levels, were not significantly different.

Adenosine Diphosphate↗
PubMed1992

Detection of occult lymph node metastases in malignant melanoma.

An accurate prediction of the prognosis of melanoma is dependent on the ability to determine the presence or absence of malignant cells in lymph nodes. Our laboratory has developed a method for screening lymph node sections for the presence of micrometastatic disease. The nodes obtained from regional lymphadenectomies are dissected free from surrounding tissue and divided into halves. One-half is subjected to routine histopathological evaluation and the other one-half is disrupted into a single cell suspension and placed into cell culture. Lymph nodes from 19 patients with malignant melanoma were evaluated by tissue culture. Tumor cells were isolated in 125 of the 173 nodes examined. In contrast, only 14 of these nodes were initially found positive for melanoma by routine pathological evaluation. All lymph nodes positive for melanoma by pathological evaluation were also culture positive. Examination by cell culture has led to an upgrade in the stage of disease in 58% of the histologically node-negative patients. In addition, 43% of the patients who were histologically node negative but culture positive have recurred, suggesting some clinical correlation. These results indicate that the tissue culture method for detecting micrometastatic lymph node disease may prove more reliable and sensitive than current techniques for determining the presence of occult melanoma.

Antigens, Neoplasm↗
PubMed1992

PC CLIN-SIM: a toolbook based clinical simulation environment.

The Departments of Computer Medicine, Health Care Sciences, Medicine, and Electrical Engineering & Computer Science at the George Washington University have joined forces to create a clinical simulation program. The purpose of this program is to provide experience in the management of complex patient populations (eg geriatrics). A number of simulation programs are available commercially, however none provide adequate geriatric content, or were deemed to lack functionality important to the developers. The immediate goal of this effort was to create a computer-based, core curriculum in geriatric medicine for medical and allied health students. The curriculum includes case simulations linked to a comprehensive reference database. The development objectives were to create an intuitive, friendly, consistent user interface which could serve as a shell for additional content areas. In order to increase fidelity, free text entry and time simulation were included.

Computer Graphics↗
PubMed1991

Stimulation of platelet-activating factor synthesis in human endothelial cells by activation of the de novo pathway. Phorbol 12-myristate 13-acetate activates 1-alkyl-2-lyso-sn-glycero-3-phosphate:acetyl-CoA acetyltransferase and dithiothreitol-insensitive 1-alkyl-2-acetyl-sn-glycerol:CDP-choline cholinephosphotransferase.

Human umbilical vein endothelial cells (HUVEC) produce platelet-activating factor (PAF) by a remodeling pathway involving a phospholipase A2 followed by an acetyl-CoA-dependent acetyltransferase which acetylates a lyso-PAF intermediate to form PAF and is stimulated by a variety of agents that generate inflammatory and allergic responses. A second route for PAF synthesis in mammalian tissues is a de novo pathway, which requires the participation of three enzymes: 1-alkyl-2-lyso-sn-glycero-3-phosphate (alkyllyso-GP): acetyl-CoA acetyltransferase, 1-alkyl-2-acetyl-sn-glycero-3-phosphate phosphohydrolase, and dithiothreitol (DDT)-insensitive 1-alkyl-2-acetyl-sn-glycerol (alkylacetyl-G):CDP-cholinecholinephosphotransferase. In the present study we show that protein kinase C activation by phorbol 12-myristate 13-acetate (PMA) induces PAF production in HUVEC by an increase of both alkyllyso-GP:acetyl-CoA acetyltransferase and DTT-insensitive alkylacetyl-G:CDP-choline choline-phosphotransferase. PAF synthesis, labeled precursors [( 3H]acetate and [methyl-3H]choline) incorporation, and both enzyme activities of the de novo pathway increase concomitantly in response to different doses of PMA. PMA does not activate the enzymes of the remodeling pathway. We conclude that both remodeling and the de novo pathway for PAF synthesis are present in HUVEC and might be alternatively activated depending on the conditions of cell stimulation.

Acetates↗
PubMed1991

Protein kinase C and cyclic AMP modulate thrombin-induced platelet-activating factor synthesis in human endothelial cells.

Stimulation of human endothelial cells (EC) by thrombin elicits a rapid increase of intracellular free Ca2+ [(Ca2+]i), platelet-activating factor (PAF) production and 1-O-alkyl-2-lyso-sn-glycero-3- phosphocholine (lyso-PAF): acetyl-CoA acetyltransferase (EC 2.3.1.67) activity. The treatment of EC with thrombin leads to a 90% decrease in the cytosolic protein kinase C (PKC) activity; this dramatic decline is accompanied by an increase of the enzymatic activity in the particulate fraction. The role of PKC in thrombin-mediated PAF synthesis has been assessed: (1) by the blockade of PKC activity with partially selective inhibitors (palmitoyl-carnitine, sphingosine and H-7); (2) by chronic exposure of EC to phorbol 12-myristate 13-acetate (PMA), which results in down-regulation of PKC. In both cases, a strong inhibition of thrombin-induced PAF production is observed, suggesting obligatory requirement of PKC activity for PAF synthesis. It is suggested that PKC regulates EC phospholipase A2 (PLA2) activity as thrombin-induced arachidonic acid (AA) release is 90% inhibited in PKC-depleted cells. Brief exposure of EC to PMA strongly inhibits thrombin-induced [Ca2+]i rise, acetyltransferase activation and PAF production, suggesting that, in addition to the positive forward action, PKC provides a negative feedback control over membrane signalling pathways involved in the thrombin effect on EC. Forskolin and iloprost, two agents that increase the level of cellular cAMP in EC, are very effective in inhibiting thrombin-evoked cytosolic Ca2+ rise, acetyltransferase activation and PAF production; this suggests that endogenously generated prostacyclin (PGI2) may modulate the synthesis of PAF in human endothelial cells.

Acetyltransferases↗
PubMed1991

Detection of submicroscopic lymph node metastases in patients with melanoma.

A cell culture technique was developed to investigate submicroscopic lymph node metastases in patients with stage 1 or 2 malignant melanoma. Lymph nodes were isolated from standard dissections and bivalved. Half of the node was evaluated by routine histopathologic examination, while the other half was processed and placed into tissue culture. Three hundred twenty-three lymph nodes were collected from 41 patients. The cell culture technique identified 155 of 323 lymph nodes containing micrometastases, while only 20 of 323 lymph nodes tested positive with routine histochemical processing. Nine patients were upgraded from stage 1 or 2 to stage 3 disease after micrometastases were identified in lymph node cultures. Identification of melanoma was confirmed by cytologic examination, immunohistologic staining, and the presence of GD3 ganglioside and 250-kd glycoprotein melanoma-associated antigens. This study provides evidence that the culture of lymph nodes is a sensitive method for the detection of micrometastases. In addition, this procedure may change prognosis and identify candidates for adjuvant therapies.

Antibodies, Neoplasm↗
PubMed1991

Dubbo study of the elderly: sociological and cardiovascular risk factors at entry.

A prospective study of elderly Australians commenced in 1988 in Dubbo, NSW. Its goals are to identify predictors of mortality, hospitalisation and placement in long-term care, with special focus on risk factors for cardiovascular disease. The study population were non-institutionalised subjects, comprising 1237 males and 1568 females 60 years and over. This report describes the baseline findings: demographic, educational and economic data; tobacco and alcohol usage, self-medication and other habits; medical contacts and past diagnosis; prescribed medication and in study diagnosis; psychosocial variables, functional health and social support; blood lipid and lipoprotein data; blood pressure, spirometry and glucose data; heights and weights. Where comparison has been feasible, the findings in Dubbo closely resemble those obtained from the rest of Australia. The findings presented provide the basis for aetiological studies of future outcomes.

Aged↗
PubMed1991

The Dubbo study of the health of elderly: correlates of coronary heart disease at study entry.

A prospective study of the health of elderly Australians recently commenced in Dubbo, NSW, the study population comprising 1,237 males and 1,568 females 60 years and older. The prevalence rates of coronary heart disease (CHD) and its associated risk factors have been examined in the baseline data. The age-standardized rate of CHD was 23.8/100 in males and 18.1/100 in females. The prevalence rate increased with age until 79 years in males, thereafter declining. The rate increased steadily with age in females. In a multiple logistic model, the following possible predictors of CHD were included: age, cigarette smoking, use of alcohol, exercise, religiosity, years of education, hypertension, diabetes, family history of CHD, body mass index, lipid and lipoprotein variables. The presence of CHD in males was significantly predicted by age, hypertension (odds ratio, OR = 1.40), family history (OR = 2.05), and high density lipoprotein (HDL) cholesterol (OR = 0.78). The significant predictors in females were age, years of education (OR = 0.82), hypertension (OR = 1.45), family history (OR = 1.77), serum triglycerides (OR = 1.30), and HDL cholesterol (OR = 0.73). Hypertension was found to be a stronger predictor of CHD in the younger age group (60-69 years), while diabetes was a predictor of CHD in older males (70-79 years). Our findings require confirmation in the prospective study now in progress.

Age Factors↗
PubMed1991

Randomized 4-week exercise program in patients with impaired left ventricular function.

BACKGROUND: This study was designed to determine the controlled effects of a short-term exercise rehabilitation program on patients with moderate-to-severe left ventricular dysfunction after a recent myocardial infarction. METHODS AND RESULTS: Thirty-nine male patients 51 +/- 8 years old with a large anterior myocardial infarction less than 10 weeks old were recruited for the study. The patients were randomly assigned to either one of two training or control groups on the basis of their resting ejection fraction: training, less than 30%; control, less than 30%; training, 31-50%; or control, 31-50%. Patients were evaluated for filling pressures, radionuclide ventriculography, heart volume, echocardiography, and work capacity. Patients who underwent training participated in an intensive 4-week in-hospital exercise program, whereas the control patients were restricted to a minimal activity program. Results indicated that there were no significant improvements in resting, submaximal, and maximal hemodynamic measurements as a result of the program. Mean work capacity and peak oxygen consumption improved significantly in the less-than-30% training group but was accompanied by a significant increase in mean pulmonary wedge pressure. Resting ejection fraction improved markedly in both less-than-30% training and control patients, but ejection fraction measures were not associated with work capacity. Training did not cause further deterioration in ventricular function. CONCLUSIONS: It was concluded that in the present study, exercise training had little or no effect on hemodynamic measurements and that the training effects achieved in patients with left ventricular dysfunction are most likely due to corrected impaired vasodilation, not necessarily to cardiac function. The importance of using a control group in this type of study and the wide interindividual variations in training responses are emphasized.

Exercise Therapy↗
PubMed1991

[Effect of hypercholesteremic sera on endothelial cell proliferation in vitro].

Human hypercholesterolemic serum increases proliferation of human umbilical endothelial cells in vitro. This might be due to an increased content of low molecular weight growth factors, which are released by blood cells, mainly thrombocytes. Hypercholesterolemia could increase endothelial cell turnover and expression of dysfunctional cells which may support atherogenic processes.

Cell Division↗
PubMed1990

Transfer of human membrane surface components by incorporating human cells into intact animal tissue by cell-tissue electrofusion in vivo.

Current animal models employed for the study of the obligate human pathogen Neisseria gonorrhoeae fail to utilize specific human gonococcal attachment receptors required to initiate pathogenesis in a clinically meaningful way. This communication presents evidence that suggests that cell-tissue electrofusion may be employed to create an animal model for this human specific pathogen. This new biotechnology was used to incorporate human membrane gonococcal receptors directly into epithelium of laboratory animals and subsequently infecting the histologically modified tissue with N. gonorrhoeae strain Pgh 3-2.

Animals↗