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Biomedical subjects

J Cardinal

Publications and source records attributed to J Cardinal.

At least 55 records · Page 3Linked to original sources
PubMed1986

Total parenteral nutrition during pregnancy.

Parenteral hyperalimentation or total parenteral nutrition has become an established therapy for patients with a wide variety of conditions that preclude oral feeding. Because pregnancy is an infrequent event in poorly nourished women with acute or chronic illness, total parenteral nutrition has not been widely used for pregnant patients. Some obstetricians believe that total parenteral nutrition entails risks in excess of its potential benefit to pregnancy and demands skills and knowledge that are either not available or are in limited supply. Sufficient favorable clinical experience has accumulated over the past 15 years so that total parenteral nutrition can be recommended in the management of malnutrition during pregnancy. The purpose of this report is to review the authors' experience and the literature about total parenteral nutrition during pregnancy.

Adult↗
PubMed1984

Luminal and peritubular ionic substitutions and intracellular potential of the rabbit proximal convoluted tubule.

Transepithelial (psi T) and basolateral (psi BL) potential difference was measured in rabbit proximal convoluted tubules perfused in vitro. In control solution without protein, the mean psi BL was -54 +/- 2.2 mV (n = 57). Luminal substitution of K by Na had no effect. Complete luminal substitution of glucose and alanine, 110 mM substitution of Na or NaCl produced transient hyperpolarizations of psi BL of 14, 10, and 13 mV, respectively, with a return close to the control value within 4-8 min in all cases. Returning to control solution produced similar time-course transient depolarizations of psi BL of 17, 11, and 16 mV, respectively, again with a return to the control value in 4-10 min. Omission of glucose and alanine in the perfusate produced a decrease in cell volume of 14% that was maximal in 4 min with a complete recovery in the post-control period. A 110 mM luminal or peritubular substitution of Cl by cyclamate produced no significant effect on psi BL after taking into account the large psi T generated by the diffusion of Cl across the paracellular pathway. On the other hand, complete peritubular substitution of K by Na and 110 mM substitution of Na or NaCl produced sustained but reversible depolarizations of psi BL of 37.5, 10.2, and 20.4 mV, respectively. The transient nature of the hyperpolarization following luminal substitution of glucose, alanine, or Na can be interpreted in terms of changes in the intracellular sodium activity that would affect the Na-K-ATPase pump. Similarly, the sustained depolarization seen after a peritubular substitution of K and Na would also be compatible with a decrease in the basolateral ionic pump activity.

Alanine↗
PubMed1984

Transepithelial and cell membrane electrical resistances of the rabbit proximal convoluted tubule.

A technique using double-barreled perfusion pipettes and intracellular microelectrodes was developed to measure transepithelial, apical, and basolateral membrane electrical resistances in isolated rabbit proximal convoluted tubules (PCT). This technique has been tested successfully with respect to cable analysis: the transepithelial resistance (RT) did not change with tubule length and the measured core resistance of the lumen (RC) varied according to prediction with lumen diameter and perfusate resistivity. In control solutions, a linear I-V relationship was observed at the entry of the tubule for current varying from -300 to +300 nA. The mean RT was 1,050 +/- 70 omega X cm (n = 33) (a specific resistance of 8.2 omega X cm2). Bath proteins and large variations in transtubular hydrostatic pressure had no significant effect on RT, whereas RT was not systematically related to transepithelial PD or to the sodium-to-chloride permeability ratio (n = 22). Perfusate substitution of 50 mM NaCl by mannitol increased RT by 21% (n = 7) but the same maneuver in the peritubular solution had no significant effect after a 5-min equilibration period. The ratio of apical to basolateral cell membrane resistance (RA/RBL) determined with intracellular microelectrodes was 3.1 +/- 0.3 (n = 27) in control solutions and increased within 1 min by 36% (n = 8) when glucose and alanine were replaced by mannitol in the perfusate solution. Using simultaneous initial changes in transepithelial and basolateral potential differences when glucose and alanine were removed, the individual values of RA and RBL were determined. Mean RBL was 4,900 +/- 990 omega X cm (39 +/- 1.3 omega X cm2) and mean RA was 15,000 +/- 4,300 omega X cm (118 +/- 33 omega X cm2).

Amino Acids↗
PubMed1983

Self-instructed relaxation: a therapeutic alternative.

A self-instructed relaxation program was compared with therapist-instructed relaxation and waiting list controls. Self-report anxiety measures ( IPAT and STAI ) and a psychophysiological stress profile (frontal EMG, GSR, heart rate, finger temperature monitored under relaxation and stressor conditions) were utilized pre- and posttreatment to determine efficacy. Self-monitored heart rate, respiration rate, and finger temperature were used to monitor home practice sessions. Subjects reported increased ability to relax and control stress; however, frontal EMG measured under stressor conditions was the only dependent measure to confirm this perception. No between-group differences on any other dependent measures were observed. Reliable changes on all self-monitored home practice measures were observed, suggesting that this procedure is a useful gauge of home practice.

Adolescent↗
PubMed1983

Liquid junctions and isolated proximal tubule transepithelial potentials.

Accurate evaluation of the unavoidable liquid junction potentials (LJP) involved whenever bath (B) and perfusate (P) solutions differ in ionic composition is of fundamental importance in the determination of proximal convoluted tubule (PCT) transepithelial potential, psi T, and its active and diffusion components, psi A and psi D. Therefore, a precise method of measuring these LJP, using Ag/AgCl electrodes, has been developed and successfully tested. The measured LJP, psi B-P, between artificial bath serum containing 6 g/100 ml albumin and ultrafiltrate-like perfusate is +2.6 mV. The average measured potential difference (PD) in rabbit PCT with these solutions was -3.0 mV, psi T thus being only -0.4 mV. Three maneuvers known to abolish psi A (hypothermia, 10(-4) ouabain, or K-free bath) brought the PD close to the reference potential, indicating that psi A congruent to PD and that psi D congruent to psi B-P. From dilution potentials, after correction for LJP (4.3 in the absence and 6.2 mV in the presence of proteins), PNa/PCl was calculated to be 0.9 for midcortical and 1.1 for juxtamedullary PCT in the absence of proteins and slightly lower in their presence. These values of LJP obtained with Ag/AgCl electrodes are between 30 and 100% larger than the ones measured using a saturated KCl bridge or the ones in previous studies, indicating that in these studies psi T as well as PNa/PCl has been overestimated.

Animals↗
PubMed1983

Fluidity of brush border and basolateral membranes from human kidney cortex.

The physical state of lipids in brush border and basolateral membrane vesicles prepared from normal human kidney cortex was investigated by fluorescence polarization and electron spin resonance. At physiologic temperature, lipids were significantly less ordered, i.e., more fluid, in basolateral than in brush border membranes. This difference was also observed using corresponding liposomes made from total lipid extracts. For both brush border and basolateral membranes, temperature-dependent experiments revealed the existence of a broad thermotropic transition extending approximately from 20 to 42 degrees C. These data are interpreted to indicate that plasma membranes from human kidney cortex function physiologically at the upper critical temperature of a transition that probably corresponds to a liquid crystalline-to-gel lipid phase separation.

Cell Fractionation↗
PubMed1982

Effect of maleate on membrane physical state of brush border and basolateral membranes of the dog kidney.

The effects of maleate on the physical state of isolated brush border and basolateral membranes from dog kidney cortex have been studied by fluorescence polarization and ESR methods. Anisotropy of 1,6-diphenyl-1.3.5.-hexatriene and hyperfine splitting (2T parallel) of 5-doxylstearic acid in brush border and basolateral membranes were not significantly modified by the addition of 10(-2) M maleate after 60-90 min treatment. These findings further support the view that maleic acid nephropathy is not due to a direct effect of maleate on tubular membranes per se.

Animals↗
PubMed1982

Membrane fluidity and enzyme activities in brush border and basolateral membranes of the dog kidney.

The physical state of membrane lipids and relationships with the activity of Na+-K+-ATPase and alkaline phosphatase were studied in basolateral and brush border membranes of the dog kidney. Fluorescence polarization and electron spin resonance experiments demonstrate that basolateral membranes are much more fluid than brush border membranes. This can be accounted for by a difference in fluidity of the lipid part of the membranes. Broad (43-17 degrees C) thermotropic transitions are observed in liposomes made from total lipid extracts of brush border and basolateral membranes. Fluorescence data strongly suggest that thermotropic transitions also occur in intact membranes and that a change in membrane physical state may take place around the physiological temperature. A nonlinear Arrhenius plot for the Na+-K+-ATPase activity in basolateral membranes (breakpoint 21 degrees C) provides additional support for the existence of a lipid liquid leads to gel transition in antiluminal plasma membranes. A break in the Arrhenius plot of alkaline phosphatase activity is also observed but at a temperature significantly higher (26 degrees C) than that of the end of the thermotropic transition. "Room temperature" appears as a critical zone for lipid physical state and activities of both enzymes.

Alkaline Phosphatase↗
PubMed1982

Cell volume regulation in the proximal convoluted tubule.

To evaluate the effect of hyper- and hypotonicity on proximal convoluted tubule (PCT) cell volume, nonperfused PCT were studied in vitro with hypertonic solutions containing sodium chloride, urea, or mannitol (450 mosmol/kg H2O) and with hypotonic low sodium chloride solutions (160 mosmol/kg H2O). When the tubules were subjected to hypertonic peritubular solutions containing NaCl, cell volume immediately decreased by 15.5% and remained constant throughout the experimental period (60 min). With mannitol, the initial decrease was identical to that with NaCl (17.7%), but the PCT volume increased slightly during the experimental period. With urea, the decrease in cell volume was smaller (7%) and transient. In hypotonicity, the PCT swelled rapidly, but this swelling was followed by a rapid regulatory phase in which PCT volume nearly returned to control values after less than 10 min. With a potassium-free peritubular medium or 10(-3) M ouabain, the regulatory phase of hypotonicity completely disappeared, whereas the cells did not maintain their reduced volume in NaCl-induced hypertonicity. These results suggest that Na-K-ATPase plays an important role in the maintenance of a reduced cellular volume in hypertonicity and in the regulatory phase of hypotonicity, probably by an active extrusion of sodium and water from the cell.

Animals↗
PubMed1981

Control of membrane lipids in Mycoplasma gallisepticum: effect on lipid order.

Adaptation of Mycoplasma gallisepticum, a sterol-requiring Mycoplasma sp., to growth in a serum-free medium supplemented with cholesterol in decreasing concentrations and with various saturated or unsaturated fatty acids enabled us to control both the cholesterol levels and the membrane fatty acid composition. An estimate of the membrane physical state from fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene indicated that the membrane lipids of native M. gallisepticum were highly ordered. Elongation of the saturated fatty acid chains from 14 to 18 carbon atoms caused only a small increase in the membrane lipid ordering, whereas the introduction of a cis double bond reduced it significantly. Lipid-phase transitions were observed in low-cholesterol-adapted organisms, whose membrane lipids were still highly ordered at the growth temperature.

Cholesterol↗
PubMed1980

Influence of sodium intake on catecholamine release by angiotensin and renal nerve stimulation in dogs.

For 10 days, dogs were fed a normal salt diet containing 70 mequiv. Na+/day (NSD) followed by a high salt diet containing 170 mequiv. Na+/day (HSD) or 240 mequiv. Na+/day (VHSD), or the order was reversed. K+ in these diets was fixed at 40 mequiv./day. The different diets did not influence the basal level of serum catecholamines (CA). Intravenous angiotensin II (ATII) in subpressor doses produced, under NSD and HSD, an increase in serum CA accompanied by reductions in total renal blood flow as well as regional blood flow rates (microspheres), mostly in the deeper regions of the cortex. Under VHSD, ATII did not affect serum CA and barely decreased total renal blood flow, reducing regional blood flow rate in C3 and C4 only. The increase in renal vein serum CA produced by renal nerve stimulation was potentiated by ATII but under constant plasma levels of the latter, progressive increments of Na+ in the diet markedly exaggerated the liberation of CA following renal nerve stimulation and the hemodynamic response of the kidney. We conclude that the Na+ content in the diet markedly influences the increase in serum CA after renal nerve stimulation and greatly influences the response of that organ to renal nerve stimulation.

Angiotensin II↗