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Biomedical subjects

M Ritter

Publications and source records attributed to M Ritter.

At least 181 records · Page 10Linked to original sources
PubMed1990

Determination of cell membrane resistance in cultured renal epithelioid (MDCK) cells: effects of cadmium and mercury ions.

Previous studies have indicated that the cell membrane of Madin Darby Canine Kidney (MDCK) cells is hyperpolarized by a number of hormones and trace elements, in parallel with an enhancement of potassium selectivity. Without knowledge of the cell membrane resistance (Rm), however, any translation of potassium selectivity into potassium conductance remains equivocal. The present study was performed to determine the Rm of MDCK cells by cellular cable analysis. To this end, three microelectrodes were impaled into three different cells of a cell cluster; current was injected via one microelectrode and the corresponding voltage deflections measured by the other two microelectrodes. In order to extract the required specific resistances, the experimental data were analysed mathematically in terms of an electrodynamical model derived from Maxwell's equations. As a result, a mean Rm of 2.0 +/- 0.2 k omega cm2 and an intercellular coupling resistance (Rc) of 6.1 +/- 0.8 M omega were obtained at a mean potential difference across the cell membrane of -47.0 +/- 0.6 mV. An increase of the extracellular K+ concentration from 5.4 to 20 mmol/l depolarized the cell membrane by 16.2 +/- 0.5 mV and decreased Rm by 30.6 +/- 3.0%; 1 mmol/l barium depolarized the cell membrane by 20.1 +/- 1.1 mV and increased Rm by 75.9 +/- 14.3%. Omission of extracellular bicarbonate and carbon dioxide at constant extracellular pH caused a transient hyperpolarization (up to -60.4 +/- 1.4 mV), a decrease of Rm (by 75 +/- 4.5%) and a decrease of Rc (by 23.1 +/- 8.4%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Surfactant protein A concentrations in tracheal aspirate fluid from infants requiring extracorporeal membrane oxygenation.

To understand the lung abnormalities leading to respiratory failure in infants, we measured 35,000-dalton surfactant protein A concentrations in tracheal aspirate fluid collected daily from 25 infants receiving extracorporeal membrane oxygenation (ECMO). Surfactant protein A concentrations were standardized per milligrams of total protein present in the aspirate. Among the 23 survivors with complete data, the surfactant protein A concentration increased significantly with time (p less than 0.0001). Concurrent increases in lung compliance (p less than 0.0001) and radiographic scores (p less than 0.0001) were also observed. This increase in surfactant protein A content may reflect lung recovery from barotrauma and oxygen toxic effects or be a response to the primary pulmonary disease process. The two infants who did not survive extracorporeal membrane oxygenation failed to demonstrate these trends.

Body Fluids↗
PubMed1990

Quantification of aortic regurgitation with amplitude-weighted mean flow velocity from continuous wave Doppler spectra.

Aortic regurgitant fraction (RFao) was quantified by estimating the ratio of the forward blood flow through the aortic (Qao) and pulmonary (Qp) valve: RFao = 100(Qao - Qp)/Qao. Aortic and pulmonary flow were measured by the systolic time integrals of the amplitude-weighted mean velocity from continuous wave Doppler spectra recorded over the aortic and pulmonary valves. Thus, measurements are independent of the left and right ventricular outflow tract area. In 20 normal subjects, aortic regurgitant fraction ranged between -2.9% and +12.0% (mean +4.3%), the physiologic value being +2%. In 20 patients with pure aortic regurgitation, aortic regurgitant fraction obtained by Doppler spectra (y) was compared with that calculated from biplane left ventriculography and cardiac output determined with the Fick method (x). The correlation was r = 0.94, (SEE = 5.4%, which is 10.6% of the angiography-Fick mean value). The regression line was y = 0.87x + 6.6 (mean y = 51.2%, mean x = 51.1%). It is concluded that determination of aortic regurgitant fraction in pure aortic regurgitation by using the amplitude-weighted mean velocity from continuous wave Doppler spectra is accurate and allows easy noninvasive evaluation of the regurgitant fraction in routine clinical applications.

Adult↗
PubMed1990

Collagenous gastroduodenitis on collagenous colitis.

We report on a case of collagenous gastroduodenitis with concomitant collagenous colitis in a 75-year-old woman with watery diarrhea of approximately six months' standing. The step biopsy material obtained from the colon revealed continuous collagenous colitis with thickening of the basal membrane to 30 microns. The biopsies taken from the stomach and duodenum also revealed a band-like deposition of collagen in the duodenum (bulb and proximal portion of the descending portion) along the basal membrane of the lining epithelium, associated with partial atrophy of the villi. In the stomach, this band of collagen was located, parallel to the mucosal surface, at the level of the floor of the foveolae.

Aged↗
PubMed1990

Doppler-echocardiographic findings in a patient with persisting right ventricular sinusoids.

The Doppler-echocardiographic features of persisting right ventricular myocardial sinusoids are presented. An 18-year-old patient with persisting right ventricular sinusoids had undergone comissurotomy for critical pulmonary artery stenosis at the age of 12 months. Follow-up catheterization at the age of 17 years revealed no signs of residual pulmonary artery stenosis, outflow tract obstruction or pulmonary hypertension. No shunt could be documented. High systolic velocity jets within the myocardial sinusoids were recorded by means of continuous-wave Doppler. Pulmonary artery blood flow velocity was recorded mainly consequent to atrial contraction and was reduced during right ventricular ejection period, thus reflecting impaired systolic and diastolic right ventricular function.

Echocardiography, Doppler↗
PubMed1990

[Approach of relations to trauma patients in intensive care units].

Because of medical sciences and techniques progresses, Intensive Care Units receive more and more difficult patients. Treatment and care have to respect people human dignity. Person contains body and mind, which are inseparable, as relation and care are. For us, nurses, patients global care have to harmonize technical quality of care and human dimension.

France↗
PubMed1990

[Diffuse eosinophilic gastroenteropathy].

Eosinophilic gastroenterocolitis is a very rare disease of the gastrointestinal tract. As a result, frequently the diagnosis is missed and/or symptoms get misinterpreted. Histological examination and blood analysis however support the finding of the correct diagnosis in most cases. We report here the case of a 47 year old female patient with diffuse gastroenterocolitis and we will comment the diagnostic problems.

Colitis↗
PubMed1989

Nifedipine for high altitude pulmonary oedema.

In a laboratory at 4559 m six subjects with high altitude pulmonary oedema (HAPO) characterised by clinical signs, severe hypoxaemia, widened alveolar-arterial oxygen gradient, pulmonary hypertension, and alveolar oedema on chest radiography were treated with nifedipine. Despite continued exercise at the same altitude this treatment, without supplementary oxygen, resulted in clinical improvement, better oxygenation, reduction of alveolar arterial oxygen gradient and pulmonary artery pressure, and progressive clearing of alveolar oedema. Nifedipine offers a potential emergency treatment for HAPO when descent or evacuation is impossible and oxygen is not available. The findings also suggest that hypoxic pulmonary hypertension is essential in the pathogenesis of HAPO.

Acute Disease↗
PubMed1989

Complex lymphoid and epithelial thymic tumours in Thy1-myc transgenic mice.

T-lymphocyte development takes place mainly in the thymus, where stromal cells of epithelial and haemopoietic origin are involved in inductive and selective mechanisms, which enable specific lymphocyte populations to migrate to the periphery and establish a network of immune responses. Experiments with intact animals have clarified the precursor-product relationships between thymocyte subpopulations, but the molecular mechanisms of cell interactions in the thymus are difficult to study in vivo. In an attempt to expand thymic cell populations in vivo and maintain them in vitro for such studies, we directed high levels of expression of the murine c-myc proto-oncogene in transgenic mice by inserting it into the mouse Thy-1 transcriptional unit. Such mice develop thymic tumours which contain proliferating thymocytes and, interestingly, expanded populations of epithelial cells. Both cell types can be maintained in vitro.

Animals↗
PubMed1989

A simple method for multiple fluid exchange.

A simple device for fluid exchange is described, which allows the exchange of an unlimited number of solutions at low (10-1000 nl/min) constant perfusion rate. The applicability of the system has been tested in microperfusion experiments of rat distal tubules. At a luminal perfusion rate of 40 nl/min, the lag time was some 20 sec and 80% fluid exchange time some 3 sec. Simple modification allows further reduction of the lag time. Under control conditions, the potential difference across the late distal tubule (PDte) approaches -19.4 +/- 2.5 mV (n = 27). Increase of luminal potassium concentration from 5.4 to 40 mmol/l hyperpolarizes PDte to -29.9 +/- 4.3 mV (n = 8). Amiloride (10 mumol/l) leads to a reversible depolarization to -3.2 +/- 1.0 mV (n = 19), barium (1 mmol/l) to a reversible hyperpolarization to -25.8 +/- 2.6 mV (n = 19). As expected, PDte is largely created by amiloride sensitive sodium channels and is partially blunted by barium sensitive potassium channels.

Amiloride↗
PubMed1989

Left ventricular pressure-length relation during exercise-induced ischemia.

The pressure-length relation in normal and ischemic segments was analyzed with use of left ventriculography and simultaneous micromanometry during supine exercise in 9 normal subjects and 12 patients with effort angina. Segmental analysis was done in the right anterior oblique projection using a long axis with three perpendicular, equidistant chords. The apical segment in the 12 patients with coronary artery disease represented the ischemic region. In 5 of the 12 patients with coronary artery disease, the basal segment that showed no exercise-induced deterioration in wall motion was used as an intrapatient control (nonischemic segment). In the 12 patients with coronary artery disease, left ventricular ejection fraction decreased (from 65% to 50%, p less than 0.001), end-diastolic pressure increased (from 24 to 40 mm Hg, p less than 0.001) and the lowest diastolic filling pressure increased (from 9 to 22 mm Hg, p less than 0.001) during exercise-induced ischemia. In normal subjects, ejection fraction increased (from 64% to 70%, p less than 0.01) with unchanged end-diastolic pressure, whereas the lowest diastolic filling pressure decreased during exercise (from 9 to 3 mm Hg, p less than 0.01). Global left ventricular diastolic pressure-volume curves showed an upward and rightward shift during exercise-induced ischemia. Regional pressure-length curves of both nonischemic (n = 5) and ischemic (n = 12) segments were shifted upward in early diastole, but moved to a higher portion of the rest pressure-length curve without an upward shift during mid- to end-diastole. In contrast, the apical segment in normal subjects showed a downward shift during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicycling↗
PubMed1989

Determination of the ratio of pulmonary blood flow to systemic blood flow by derivation of amplitude weighted mean velocity from continuous wave Doppler spectra.

Conventional Doppler echocardiographic techniques for the estimation of blood flow ratios depend on the precise measurement of the diameters of the aorta and the pulmonary artery and the mean blood flow velocities in these vessels. A simpler and quicker method is described, based on the calculation of the systolic time integrals of the amplitude weighted mean velocities from continuous wave Doppler spectra within the great arteries. In 30 controls the mean (2 SD) ratio of pulmonary to systemic blood flow averaged 0.952 (0.085). The results of the new technique showed a good agreement with those of quantitative dye dilution and oximetry in 16 patients with intracardiac left to right shunts.

Adolescent↗
PubMed1989

Quantification of mitral regurgitation with amplitude-weighted mean velocity from continuous wave Doppler spectra.

Amplitude-weighted mean velocity from continuous wave (CW) Doppler spectra was used to measure aortic flow (QAo) and left ventricular mitral inflow (QLVin). These flows were used to quantify mitral regurgitation fraction: RFm = (QLVin-QAo).QLVin-1.100(%).QLVin was calculated from the diastolic time integral of amplitude-weighted mean velocity that was derived from CW spectra with the transducer placed in the apical window and the CW beam directed toward the left ventricular inflow tract. QAo was obtained from the systolic time integral of amplitude-weighted mean velocity by using the same apical window and directing the CW beam toward the left ventricular outflow tract. In 20 normal subjects, RFm ranged between -6.2% and +8% (mean, -0.8%). In 25 patients with pure mitral regurgitation, RFm obtained by Doppler (y) was compared with RFm calculated from biplane left ventriculography and the Fick method (x). The correlation was r = 0.96, SEE = 6.1% of the mean or 12% of the angio-Fick mean; the regression line was y = 0.96x + 0.18; mean y = 49%, mean x = 51%. It is concluded that RFm can be determined accurately by using amplitude-weight mean velocities from CW Doppler spectra. The advantages of this method are its independence from the measurement of the left ventricular inflow or outflow tract area.

Adult↗
PubMed1989

Immunosuppression with cyclosporin A alters the thymic microenvironment.

The effect of cyclosporin A (CyA) immunosuppression on the murine thymic microenvironment and T lymphocyte development has been analysed using monoclonal antibodies to epithelial and lymphocyte subpopulations, macrophages and major histocompatibility complex (MHC) class II antigens in immunohistochemistry and flow cytometry. The major microenvironmental target for CyA-induced damage was the thymic medulla, where a reduction in all epithelial cell subsets, dendritic cells and macrophages was observed. In contrast, the thymic cortex appeared essentially normal. CyA had no detectable effect on the intensity of microenvironmental expression of MHC class II molecules in either cortex or medulla, although the number of MHC class II positive medullary cells was reduced after CyA treatment. CyA also had a differential effect on the thymic lymphocyte populations where there was little change in the Thy-1 bright, CD5 dull, CD4+, CD8+ cortical thymocytes but a depletion of the Thy-1 dull, CD5 bright, CD4 or CD8 single-positive medullary cells. This lymphocyte loss may be due partly to increased migration from thymus to spleen and other peripheral lymphoid organs, and partly to a block in the differentiation stage from cortical to medullary lymphocyte. The thymic microenvironment and lymphocyte subpopulations recover rapidly after cessation of CyA treatment, although there may be longer term functional defects resulting from the CyA-induced injury.

Animals↗
PubMed1988

Prevention of coronary vasoconstriction by diltiazem during dynamic exercise in patients with coronary artery disease.

Whether exercise-induced vasoconstriction of coronary artery stenoses is modified by the administration of calcium antagonists was examined in 14 patients with classic angina pectoris. In this group the effect of intracoronary diltiazem (2 to 3 mg) on luminal area was evaluated in normal and stenotic segments of epicardial coronary arteries during symptom-limited supine exercise. The luminal area of a normal and a stenotic coronary artery segment was determined by quantitative coronary arteriography with a computer-assisted system. Patients were studied at rest, 6 min after 2 to 3 mg of intracoronary diltiazem, during supine bicycle exercise (96 W) and 5 min after sublingual administration of 1.6 mg nitroglycerin. Heart rate, mean pulmonary and aortic pressure as well as the percent change of both normal and stenotic luminal area were determined. Intracoronary administration of diltiazem was associated with mild dilation of both normal (19%, p less than 0.01) and stenotic coronary luminal area (11%, p less than 0.05). During subsequent exercise, luminal area of the stenotic vessel segment increased by 23% (p less than 0.001) and that of the normal vessel segment by 24% (p less than 0.001), whereas in a previously reported control group, luminal area of the stenotic vessel segment decreased by 29% during exercise. After sublingual administration of nitroglycerin, the luminal area of both the normal and the stenotic vessel segment increased further by 19% (p less than 0.01) and 22% (p less than 0.01), respectively, compared with the values after intracoronary administration of diltiazem.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1988

Results of noncomparative studies of cefotetan in the treatment of obstetric and gynecologic infections.

In a multicenter trial involving 11 centers, 160 women were enrolled to evaluate the safety and effectiveness of 1 or 2 gm of cefotetan administered every 12 hours in the treatment of obstetric and gynecologic infections. The 133 evaluable patients generally were under 25 years of age, were nonwhite, and had hospital-acquired endometritis or pelvic inflammatory disease caused by both aerobic and anaerobic bacteria. Escherichia coli, Neisseria gonorrhoeae, group D streptococci, Bacteroides sp., and Peptococcus sp. were among the most frequently isolated pathogens. The patients were treated for a mean of 5.6 +/- 1.6 days and received a total dose of 19.27 gm. The signs and symptoms of infection were cleared or improved in 93% of the 133 patients evaluable for clinical response. Of the 116 evaluated bacteriologically, 95% had a satisfactory or presumed satisfactory response; only six patients (5%) were considered to be bacteriologic failures. Differences in the results of several clinical laboratory tests performed before and after treatment were statistically, but not clinically, significant (p less than 0.05). Safety was evaluated in the 158 patients who received cefotetan, and only four (3%) had adverse reactions considered related to the drug. Cefotetan was clearly effective and produced no untoward reactions in these women with obstetric and gynecologic infections caused by both aerobic and anaerobic organisms when administered at 1 or 2 gm every 12 hours.

Adult↗