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Biomedical subjects

J Larsen

Publications and source records attributed to J Larsen.

At least 127 records · Page 7Linked to original sources
PubMed1989

The influence of growth phase and culture conditions of Tetrahymena on effects of cadmium.

The batch culture system is used in the majority of toxicity studies employing protozoa and other cell cultures, although it is known that metal toxicity may vary depending on the age and therefore on the physiological state of the culture. The ciliate Tetrahymena was exposed to cadmium during short-term incubations at different stages of the growth cycle. In cultures with cells proliferating at a high rate (log phase cells) the toxicity of cadmium was found to increase with increasing initial cell density. However, in the subsequent stationary growth phase with decreased rate of cell proliferation, the sensitivity against cadmium again decreases. Thus the effect of a given concentration of cadmium depends on the initial cell density of the culture. This effect of cadmium may be explained either by changes in the chemical composition of the culture medium during the growth cycle or by a changed cellular metabolism. Furthermore, it is shown that the cadmium concentration of the medium decreases during prolonged exposure when the cells are grown in batch cultures. Some of the problems associated with the toxicity bioassay performed in a static system may be overcome by using a continuous flow system. In such a system, Tetrahymena can be kept under optimal growth conditions with a generation time of less than 3 h, and any cell density may be maintained for extended periods of time. Furthermore, the cadmium concentration of the medium remained constant during prolonged exposure when maintaining a cell density of about 50 x 10(3) cells/ml. This illustrates the great advantage of using a continuous flow system in such investigations, where for example, long-term adaptations of the organism to a metal may be studied under constant conditions.

Animals↗
PubMed1989

Management behaviour of one community health nurse supervisor.

Mintzberg's theoretical framework of management, which examines the roles and functions of a manager in relation to effective communication, is used to analyse observational data of managerial conflict within a community health setting. In this setting the manager failed to establish sound interpersonal relations with her peers or with the clinic nurses. This led to a poor information base from which she could make decisions. The result was that the group became stressed and developed signs of disintegration.

Communication↗
PubMed1989

Atrial natriuretic factor during exercise in male endurance athletes: effect of training.

Nine male endurance runners were evaluated with bicycle exercise testing before a training break of 3 weeks duration, and 0, 2 and 4 weeks after resumption of training to assess the effects of training on resting and exercise plasma atrial natriuretic factor (ANF) measured at 50% and 100% of predetermined maximal workload. Maximal oxygen uptake and lean body mass (LBM) were calculated at each time point. Maximal oxygen uptake decreased during training break, but rose 4 weeks after resumption of training (P less than 0.01). LBM was unchanged after inactivity, but rose after resumption of training (P less than 0.01). Plasma ANF at rest did not change throughout the experiment. ANF levels rose after training break at maximal workload (P less than 0.05), and decreased 4 weeks after resumption of training, but only at submaximal workload (P less than 0.05). No correlations between systolic blood pressure, mean blood pressure or heart rate and ANF could be demonstrated. These results indicate that the haemodynamic changes associated with endurance training are reflected in plasma ANF levels during exercise, but not at rest. The full adaptation of ANF release to training probably requires more time than the 4 weeks reported for the haemodynamic adjustments.

Adult↗
PubMed1989

High levels of oral yeasts in early HIV-1 infection.

Ten human immunodeficiency virus-1 (HIV-1) infected homosexual or bisexual individuals (ages 24-45) with no history of opportunistic infection were examined, by culture, for the presence of yeasts in whole saliva and on oral mucosa. All were HIV-1 antibody-positive men, non-smokers, non-denture wearers, and taking no medication. The mean salivary level of yeast was four logs higher in the HIV-1 infected group compared to a control group of normal, unmedicated, non-smoking men (ages 20-41) who denied any risk behavior for HIV-1 infection. Identification of the yeast in these HIV-1 positive individuals established that Candida albicans was the predominant species found in whole saliva and on buccal mucosa and tongue. Distinct hyphae were observed with only one mucosal sample. No significant correlation was found between whole saliva yeast concentration and the T4/T8 lymphocyte ratios or absolute number of T4 cells. No correlation was observed between oral yeast concentration and anti-C. albicans IgA titers. The high level of oral yeast in these individuals prior to the development of opportunistic infections is consistent with the suggestion that oral defense mechanisms are compromised in individuals following HIV-1 infection.

Adult↗
PubMed1989

Cerebral air embolism after transthoracic aspiration with a 0.6 mm (23 gauge) needle.

A 54 yr old man experienced weakness in his legs, ataxia and subsequent urinary retention after a percutaneous fine-needle aspiration of a tumor in the right lower lobe. Clinical neurological examination and electroencephalography revealed signs of a brain stem lesion, probably due to an air embolism to the basilar artery. The symptoms and signs gradually disappeared prior to, as well as after, hyperbaric oxygen treatment. We believe this to be the first case of air embolism after transthoracic puncture with a 23 gauge needle to be reported in medical literature.

Biopsy, Needle↗
PubMed1988

An analysis in human lymphomas of a J alpha region involved in a c-myc/J alpha translocation; relationship with TCR alpha, beta, and gamma rearrangements.

The D14S7 locus defines the breakpoint on chromosome 14 of a t (8;14) (q24;q11) present in the T-cell line KE37-R in which DI4S7 sequences translocate 3' to the c-myc oncogene. It has been shown previously that DI4S7 rearranges specifically in some but not all T cell clones and in the present study we investigated the frequency and specificity of its rearrangements in human fresh lymphoma samples. DI4S7 rearrangements were extremely specific since they were detected in 3 out of 5 T-cell lymphoma samples positive for TCR beta and gamma but not in 17 miscellaneous non-T lymphomas, 4 non neoplastic lymphnodes as well as unstimulated and activated polyclonal T-cells. Most of the rearrangements were in the form of deletions that appear to involve large pieces of DNA since the segments detected by a V alpha probe were also deleted. Rearrangement of DI4S7 and V alpha regions were detected in lymphomas with a cortical thymocyte phenotype, demonstrating that they appear quite early in the differentiation of T cells.

Chromosomes, Human, Pair 14↗
PubMed1988

Hemodynamic effects of intravenously administered magnesium on patients with ischemic heart disease.

Central hemodynamic parameters were registered by right-side heart catheterization before and after intravenous administration of 12 mmol magnesium chloride (MgCl) in 15 patients with chronic ischemic heart disease and heart failure, New York Heart Association classes II and III. Serum magnesium concentrations increased from 0.76 +/- 0.03 (mean +/- SD) to 1.54 +/- 0.05 mmol/l, which resulted in a reduction in mean arterial as well as pulmonary artery pressure by 10% (p less than 0.0001) and 7% (p less than 0.05), respectively. This reduction was caused by a marked decrease in systemic as well as pulmonary vascular resistance (from 1323 +/- 205 to 1132 +/- 158 dyn.s/cm5, p less than 0.001 and from 156 +/- 73 to 133 +/- 72 dyn.s/cm5 (p less than 0.05). Heart rate, cardiac index, stroke volume index, and stroke work index increased slightly, although these differences did not reach statistical significance. Right and left ventricular filling pressures were not influenced, which indicates that the dilatory effect of magnesium, at the dosages used in the present study, is pronounced only at the arterial side of the vascular bed. The observed hemodynamic effects of the magnesium infusions may be beneficial in the setting of an acute myocardial infarction by reducing left ventricular afterload, which, together with the antiarrhythmic effect of magnesium may contribute to the positive effect of magnesium infusions on mortality in patients with acute myocardial infarction.

Aged↗
PubMed1988

Atrial natriuretic peptide during exercise in patients with coronary heart disease before and after single dose atenolol and acebutolol.

Plasma atrial natriuretic peptide (ANP) was measured during dynamic exercise in 10 patients with coronary heart disease before and after single dose atenolol 50 mg and acebutolol 200 mg, respectively. Systolic blood pressure, heart rate and the rate-pressure product increased during exercise before and after beta-blockade, but levels were lower after beta-blockade. Plasma ANP levels at rest were unchanged after atenolol, but rose after acebutolol (p less than 0.01). During exercise plasma ANP increased significantly both before and after beta-blockade, but plasma ANP levels were higher after acebutolol at all workloads (p less than 0.05), whereas plasma ANP levels after atenolol were higher at 125 W exclusively (p less than 0.05). The augmented ANP levels during exercise after beta-blockade probably reflect catecholamine-stimulated ANP release, whereas the elevated plasma ANP levels after acebutolol at rest might be a beta-adrenoceptor-mediated ANP release due to the intrinsic sympathomimetic effect of acebutolol.

Acebutolol↗
PubMed1988

Changes in atrial natriuretic factor during preload reduction with nitroglycerin in patients with congestive heart failure.

Nine patients with congestive heart failure, New York Heart Association class II-III, were evaluated with right heart catheterization. Plasma atrial natriuretic factor (ANF) was determined in blood samples from the pulmonary artery simultaneously with recordings of right atrial, pulmonary arterial, pulmonary capillary wedge and systemic arterial pressures and heart rate during preload reduction with 0.5 mg nitroglycerin sublingually. Basal plasma ANF levels were higher in patients with congestive heart failure compared to normal controls, and correlated to right atrial, pulmonary arterial, and pulmonary capillary wedge pressures. After nitroglycerin all patients had reductions in right atrial, pulmonary arterial, and pulmonary capillary wedge pressures and a simultaneous decrease in plasma ANF concentrations, reaching lowest values after 10 min. Central pressures and plasma ANF rose to baseline values within 30 min. After nitroglycerin plasma ANF concentrations correlated to pulmonary arterial and pulmonary capillary wedge pressures, while changes in plasma ANF correlated to changes in right atrial and pulmonary arterial pressures. These results provide further evidence that ANF is released by a pressure-sensitive mechanism and demonstrates that ANF secretion in relation to central pressure variations is preserved in patients with congestive heart failure and that the response is rapid.

Adult↗
PubMed1988

Variation in the growth medium during the culture cycle of Tetrahymena: with special reference to ammonia (NH3), ammonium (NH4+), and pH1.

The ciliate Tetrahymena pyriformis was grown in a peptone medium without added glucose. The interrelationship between increasing cell density and pH of the growth medium was studied from mid-log to the stationary phase, i.e. from 50,000 to 1,000,000 cells/ml, by continuous registration of the pH of the growth medium. The present findings correlate with the known physiological, biochemical, and structural changes occurring in Tetrahymena as it passes through the culture cycle. The ammonia production of the cells and the buffer capacity of the growth medium were determined throughout the growth cycle. The results revealed that the ammonia excreted by the cells can explain the increase in pH of the medium from 6.8 to about 8.3 normally seen during the culture cycle. Moreover, neither the increased pH nor the raised level of ammonia were found to be the responsible factor for cessation of cell proliferation in the stationary growth phase although these factors may affect cell proliferation in concentrations well beyond the range found in normal cultures.

Ammonia↗
PubMed1988

Atrial natriuretic factor during exercise in patients with congestive heart failure.

In order to evaluate the potential relationship between atrial pressure development and release of atrial natriuretic factor (ANF), 33 patients with congestive heart failure were investigated with right-sided heart catheterization during supine graded bicycle exercise. Resting plasma ANF levels were higher in patients with heart failure as compared with normal controls, 75.1 +/- 45.6 pmol/l vs 12.3 +/- 6.2 pmol/l (mean +/- SD, N = 33 and N = 42, respectively) and correlated with right atrial, pulmonary arterial and pulmonary capillary wedge pressures. During exercise, central pressures rose steeply with a simultaneous increase in plasma ANF in all patients. Plasma ANF levels correlated with heart rate at a workload of 25 w, to pulmonary arterial and pulmonary capillary wedge pressure at 50 w, and to pulmonary capillary wedge pressure at 75 w. The increments in ANF levels between the different workloads during exercise did not correlate with the corresponding increments in pressure values. In congestive heart failure, the capability of ANF secretion in consequence to pressure stimuli is preserved, and left atrial pressure seems to be the major stimulus for ANF release during exercise.

Adult↗