Biomedical subjects

R J Pietras

Publications and source records attributed to R J Pietras.

At least 55 records · Page 3Linked to original sources

PubMed1975

Surface modifications evoked by antidiuretic hormone in isolated epithelial cells: evidence from lectin probes.

Epithelial cells (80-90% "granular" type) were isolated from urinary bladders of Bufo marinus and Rana catesbiana. The inhibitory effect of alpha-methyl-D-mannoside on fluorescein-labeled concanavalin A (Con A) binding to these cells indicates that they possess specific binding sites for Con A. The lectin also mediates adsorption of erythrocytes to these cells. Both Con A binding and Con A-mediated hemadsorption to epithelial cells are depressed at 4 degrees C, as compared with cells maintained at 22 degrees C. Elevation of temperature to 37 degrees C, however, enhances hemadsorption independently of alterations in lectin binding. Treatment of cells with antidiuretic hormone (ADH) at 22 degrees C followed by 15 min of incubation at 22 degrees or 37 degrees C before exposure of cells to Con A promotes increments in Con A-mediated hemadsorption, but not in lectin binding, at 22 degrees or 37 degrees C. These hormonal effects are not significant when hemadsorption is assayed at 4 degrees C. Treatment of cells with another octapeptide, angiotensin, elicits a small, but significant, increment in hemadsorption to epithelial cells which is likewise uninfluenced by quantitative changes in lectin binding. Collectively, these data and other independent observations suggest that treatment with octapeptide hormones acts to enhance the redistribution and aggregation of lectin-binding proteins in the membranes of granular epithelial cells from amphibian urinary bladder. Such changes, in turn, may contribute to the alterations in membrane transport properties which characterize the hormonal response.

Angiotensin II↗

PubMed1975

The membrane action of antidiuretic hormone (ADH) on toad urinary bladder.

Radioactive tracer and electrical techniques were used to study the transport of nonelectrolytes and sodium, respectively, across toad urinary bladders in the presence and absence of ADH. The permeability of lipophilic molecules was roughly proportional to bulk phase oil/water partition coefficients both in the presence and absence of hormone; i.e., ADH elicited a general nonselective increase in the permeation of all nine solutes tested. The branched nonelectrolyte, isobutyramide, was less permeable than its straight-chain isomer, n-butyramide, in control tissues. ADH reduced the discrimination between these structural isomers. Hydrophilic solutes permeated more rapidly than expected. In the presence of hormone, there was no change in the permeation of large hydrophilic solutes considered to move via an extracellular pathway, but there was a marked increase in the permeability of water and other small hydrophilic solutes. Collectively, these results suggest that ADH acts to increase the motional freedom or fluidity of lipids in the cell membrane which is considered to be the preferred pathway for the permeation of lipophilic and small hydrophilic molecules. At concentrations of cAMP and ADH which elicit equivalent increments in the shortcircuit current, the effects of these agents on nonelectrolyte transport and membrane electrical conductance are divergent. Such observations suggest that some membrane effects of ADH may not be directly dependent upon cAMP. ADH in the mucosal solution increased the permeability of the toad bladder when the surface charge on the outer surface of the apical membrane was screened with the polyvalent cation, La-3+. These experiments emphasize that interaction of ADH with membranes of toad urinary bladder may account for at least some effects of this hormone.

Alcohols↗

PubMed1975

Pulmonary arterial oxygen saturation during treadmill exercise. A discriminative index of functional class.

Six patients in functional class II and 11 in functional class III underwent graded treadmill exercise, with severe fatigue as their limiting symptom. During exercise, none of the patients developed chest pain, or significant arrhythmia. Our data suggest that at a treadmill workload of 2 mph and 7 per cent slope, with an oxygen consumption four times that at rest, measurement of the pulmonary arterial oxygen saturation permits clear separation of functional class II from functional class III. Although there was a significant difference in the heart rate response, mean pulmonary arterial pressure, and percentage change in pulmonary arterial end-diastolic pressure, considerable overlap occurred. The use of pulmonary arterial oxygen saturation may prove to be of value in instances in which the functional cardiac status is not reasonably clear from the clinical interview or routine exercise testing. It requires less than maximal effort on the part of the patient, and provides an objective end point to distinguish between two important groups of patients.

Adult↗

PubMed1975

Frequency response of fluid-filled catheter-micromanometer systems used for measurement of left ventricular pressure.

The resonant frequencies of five commonly used fluid-filled catheters connected to a solidstate microdisplacement pressure gauge were 18 to 33 per cent higher than those obtained with a conventional manometer. Four catheters had a flat amplitude response to 26 Hz. or more at the 20 per cent amplitude distortion level. The dynamic response characteristic of certain fluid-filled catheters used with microdisplacement pressure gauges allows one to record high fidelity left ventricular pressure curves.

Amplifiers, Electronic↗

PubMed1975

Effects of atrial pacing site on atrial and atrioventricular nodal function.

The effects of the site used for atrial pacing on atrial and atrioventricular nodal conduction were assesed in 16 patients. In 13 patients, three atrial pacing sites were used: high right atrium, low lateral right atrium, and midcoronary sinus. Two recording sites were used: low septal right atrium, including His electrogram, and high right atrium. Stimulus (S) to high right atrium interval was longest with coronary sinus pacing (76 plus or minus 7 ms) (P less than 0.001), and shortes with high right atrial pacing (41 plus or minus 3 ms) (P less than 0.05). There was no significant difference in stimulus to low septal right atrium from all three pacing sites. Atrial functional and effective refractory periods were not significantly different. Mean low septal right atrium to His was significantly shorter from the coronary sinus (93 plus or minus 8 ms) (P less than 0.001), as compared to high right atrium (139 plus or minus 16 ms), and low lateral right atrium (129 plus or minus 13 ms) pacing. AV nodal functional and effective refractory periods, and the paced rate producing AV nodal Wenckebach were not significantly different when comparing the three sites. Left atrial appendage and high right atrium were similarly compared in three additional patients, and no significant differences were found in conduction times and refractory periods.

Adult↗

PubMed1975

Demonstration of sustained sinus and atrial re-entry as a mechanism of paroxysmal supraventricular tachycardia.

Electrophysiological studies in five patients with documented (4) or suspected (1) paroxysmal supraventricular tachycardia (PSVT), suggested sinus or atrial reentrance (SR or AR). Two of the patients had preexcitation, three had evidence of atrial enlargement, and all had organic heart disease. The following observations supported a diagnosis of SR and AR; 1) induction of sustained PSVT with atrial extrastimulus technique allowing definition of an echo zone; 2) induction of sustained PSVT during constant rapid atrial pacing at a rate less than that producing A-V nodal Wenckebach periods, or producing normalization of QRS complex in patients with pre-excitation: 3) P waves preceding each QRS during PSVT with an A-H interval appropriate for the rate of the PSVT; 4) antegrade P wave morphology during PSVT, a normal high to low sequence of right atrial activation (SR), or P wave morphology and atrial activation sequence different from sinus (AR); 5) lack of correlation of PSVT induction with critical A-H interval. The rates of induced sustained PSVT ranged from 114 to 143 beats/min, and were similar to those observed during spontaneous episodes of PSVT in the four patients. PSVT could be terminated with critically timed extra-stimuli or carotid massage. In conclusion, SR and AR appear to be mechanisms of spontaneous PSVT in man. Rates of SR and AR PSVT tend to be relatively slow.

Adolescent↗

PubMed1975

Steroid hormone-responsive, isolated endometrial cells.

Addition of estradiol-17beta in vitro to suspensions of isolated endometrial cells resulted in significant effects on glucose, water and electrolyte metabolism. Cells were prepared from uterine tissues of ovariectomized rats. In part, the procedures involved incubation with collagenase in Ca2+-, Mg2+-free, phosphate-buffered mammalian Ringer's solution, followed by restoration of divalent cations before gentle scraping of the endometrium from the underlying smoothmuscle. Cells were then disaggregated, washed, separated from coarse and fine debris, and incubated in an enriched medium for 2 h before the start of all experiments. Cellular integrity was established by measurement of electrolyte contents and by dye exclusion methods. Substantial production of 14CO2 from glucose-U-14C by the cell suspensions provided further evidence of cell viability. Estradiol-17beta, 10-9M, elicited significant increments in sodium and water contents within 2 h. Addition of estradiol-17beta, but not the alpha-epimer, also resulted in a significant increase in the yield of 14CO2 as early as 1.5 h, peaking at 2 h. The responses were dose-dependent between 10-10M through 10-8M. The stimulatory effect of estradiol-17beta at 10-9M was abolished in the presence of 3 times 10-6M cortisol or by cellular homogenization. Epithelial cells isolated from rat urinary bladder responded significantly to 6 times 10-9M aldosterone but not to estradiol-17beta, demonstrating specificity of the target site. These data lend further support to the suggestion that a primary action of estrogen in its target cell involves specific changes in the ionic and biochemical profile of the cytoplasm which may ultimately be communicated to the nucleus.

Aldosterone↗

PubMed1975

Surface modifications evoked by estradiol and diethylstilbestrol in isolated endometrial cells: evidence from lectin probes and extracellular release of lysosomal protease.

Endometrial cells were isolated from the uteri of ovariectomized rats. The inhibitory effect of alpha-methyl-D-mannoside on fluorescein-labeled concanavalin A (Con A) binding to these cells indicates that they possess specific binding sites for Con A. The lectin also mediates adsorption of homologous erythrocytes to these cells. Both Con A binding and Con A-mediated hemadsorption to endometrial cells are depressed at 4 C compared with these functions in cells maintained at 22 C. Gross elevations in lectin-mediated hemadsorption to endometrial cells are evident following prior exposure to 1 X 10(-9)M concentrations of diethylstilbestrol (DES) or estradiol-17beta, but not to the physiologically inactive 17 alpha-epimer, at 22 C. The enhancement of hemagglutinability cannot be attributed to a corresponding increase in lectin binding at 22 C. Although estrogen treatment elicited significant increments in Con A binding as early as 5 min after addition of estrogen to cell suspensions, the increment in agglutination attributable to hormone treatment consistently ranged from 1.5-3 times greater than the increase in lectin binding. These estrogenic effects were reduced by incubation of the endometrial cells at 4 C or when cortisol, 3 X 10(-6)M, was present with estradiol-17beta. In parallel experiments, treatment with DES and estradiol-17beta, but not estradiol-17 alpha, also enhanced the release of cathepsin B 1 and acid phosphatase from uterine segments into the particle-free extracellular media in which the tissues had been incubated for 30-60 min. The marked increment in the extracellular activity of the lysosomal hydrolases induced by estrogen treatment was suppressed in cells incubated at 4 C or when cortisol was present concomitantly. These and related data suggest the hypothesis that acute increments in lysosomal hydrolase activity may contribute to cell surface alterations which have been described in both normal and aberrant processes of cell growth.

Acid Phosphatase↗

PubMed1975

New manifestations of dual A-V nodal pathways.

Electrophysiological studies with extrastimulus technique demonstrated evidence of dual A-V pathways in two patients with paroxysmal supraventricular tachycardia (PSVT). In case one, the second P of paced Wenckebach sequences was followed by two conducted QRS complexes without an intervening P wave. The A-H of the first and second QRS were consistent with the fast and slow pathway conduction times. The second QRS was followed by an atrial echo and PSVT, suggesting that the first pathway was available for retrograde propagation following the second QRS. In case two, PSVT was induced with atrial extrastimulus, followed by development of A-V dissociation. The two cases suggest the following conclusions: (1) dual A-V nodal pathways may allow the occurrence of double antegrade conduction of one P; (2) the atria are not necessary for A-V nodal circus movements in "dual pathway" A-V nodal reentrant PSVT.

Animals↗

PubMed1974