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Biomedical subjects

S Katz

Publications and source records attributed to S Katz.

At least 307 records · Page 17Linked to original sources
PubMed1986

Na-K-C1 cotransport and Na pump in red cells of young blacks and blood pressure response to salt loading.

The functional operation of Na and K fluxes, mediated by the furosemide-sensitive (FS) Na-K-C1 cotransport and the ouabain-sensitive Na pump, was studied in a representative young (18-22 years) black population. Cation fluxes (mumol/L cell X hour = FU) were studied prior to salt loading; results were compared with the blood pressure response to chronic oral salt loading. All subjects (n = 26) took 10 g/day NaC1 plus their usual diets for 14 days. A mean arterial blood pressure increase higher than 5 mmHg was considered a sodium-sensitive (SS) response; a response lower than 5 mmHg was considered sodium-insensitive (SI). The Km for Nac to stimulate FS Na efflux was significantly greater in SS (SS = 13.8 +/- 1.39 mmol/L cells, n = 15; SI = 8.5 +/- 0.8 mmol/L cells, n = 11; p less than 0.001). Inward cotransport of Na and K was also studied at constant Nac (13 mmol/L cells) and incubation of 140 mM Na and 4 mM K. No significant differences were found in the Vmax of outward FS Na and K efflux, FS86 Rb, Na influx, net Na movement (efflux minus influx), and the Na/K ratio of inward cotransport. Several parameters of the ouabain-sensitive Na pump (Vmax of the Na efflux, Rb influx, Na/K coupling ratio (2.2), and fresh Nac) were found to be similar in both groups. The results indicate that in young blacks, the Na sensitivity of the blood pressure may be associated with lower affinity for internal Na of the outward Na-K-C1 cotransport system.

Adolescent↗
PubMed1986

Sodium sensitivity, growth and family history of hypertension in young blacks.

The response to chronic oral sodium loading was studied in young adult (18-23 years) blacks. A representative sample of participants (n=40) from previous longitudinal studies had growth measures at age 6-7 years and 11-16 years. Blood pressure, weight and stress-induced reactivity were measured before and after 14 days of 10 g NaCl daily added to the usual diet. A sodium-sensitive response (SS) was an increase in mean arterial pressure (MAP) greater than or equal to 5 mmHg. A sodium-insensitive response (S) was an increase in MAP less than or equal to 5 mmHg. Family history of hypertension (FH+) was determined by self-report. Fifty-three per cent were SS. There were no difference in age-related BP, weight or height between SS and SI in childhood or adolescence. Those with a family history of hypertension had a greater BP response to stress and greater weight change with sodium load. The group which was both SS and FH+ had the highest weight and MAP stress response after sodium load. These results indicate that sodium sensitivity is high among blacks, but does not correlate with childhood growth variables. Sodium sensitivity and FH+ combined produce the greatest stress-induced BP response.

Adolescent↗
PubMed1986

Free perforation in Crohn's disease: a report of 33 cases and review of literature.

Thirty-three patients with free perforation in Crohn's disease are described. There are 14 males and 19 females in this series with ages ranging from 14 to 79 years. The sites of perforation were 22 of the ileum, nine colonic, one jejunal, and one gastroduodenal. Toxic megacolon coexisted in two. Reperforation occurred in three. Free perforation was the presenting sign of the disease in three. Steroid therapy coexisted in 16 patients but in five was administered for less than 10 days before perforation. Obstruction coexisted in only three patients. There were two deaths. Twenty-two patients were treated with resection and diversion, nine patients with resection and drainage, and two with plication only. No relationship between steroid therapy, duration of disease, toxic dilatation, or obstruction with perforation could be established. Resection of the perforated disease segment is necessary when possible. In contradistinction to previous literature, free perforation in Crohn's disease is not as unusual as heretofore believed.

Adolescent↗
PubMed1986

Congenital aplasia of the deep veins of lower extremities in children: the role of ascending functional phlebography.

Eighty-two children with vascular diseases underwent phlebography. Congenital aplasia of the deep venous system of the lower extremities was diagnosed in 10 children. With ascending functional phlebography, three anatomic variations with different degrees of venous dysfunction were defined: aplasia of the femoral vein with collateral drainage into the common femoral vein, aplasia of the femoral vein with drainage into the internal iliac vein, and total aplasia with drainage into the axillary vein. The phlebographic findings correlated with the symptoms. Patients with type a aplasia had no clinical and radiologic signs of venous insufficiency. Patients with types b and c aplasia had severe venous insufficiency that necessitated supportive treatment. Palliative surgical procedures such as hemorrhoidectomy, clitoridectomy, and excision of bleeding vascular nevi were performed. Ligation or excision of the dilated superficial veins (usually the main channels for venous drainage from the extremity) is absolutely contraindicated. Ascending functional phlebography is therefore essential for correct diagnosis and planning of future therapy.

Adolescent↗
PubMed1985

Bacterial clearance in the intact and regenerating liver.

The Kupffer cells in the liver play an important role in reticuloendothelial system (RES) function by clearing particulate matter and bacteria from the blood stream. While hepatocyte regeneration and function have been extensively studied following partial hepatectomy, little information is available concerning RES function in the regenerating liver. This study investigates hepatic RES function by evaluating bacterial clearance (live E. coli) in the intact and regenerating liver. Thirty-four young male Sprague Dawley rats were studied. Twenty-two animals underwent a standard 70% partial hepatectomy using ligature technique and 12 had a sham operation. Both groups of rats received 10(9) organism of S35 labeled E coli, intravenously at 24 hours, 72 hours, 2 1/2 weeks, and 6 weeks postoperatively. Rats were killed 10 minutes following injection and liver, lung, spleen, and kidney harvested, fixed, and radioactivity was determined using a scintillation spectrometer interfaced with a micro-computer counting the S35 radiolabel. The total organ count of trapped bacteria in liver in partially hepatectomized rats was lower than intact controls at 24 hours (22.0% v 46.4%, P less than .01), but was similar at 72 hours, 2 1/2 weeks, and 6 weeks. Partial hepatectomy increased the amount of bacterial trapping in the lung at 24 hours (11.3% v 1.7%, P less than .01) and 72 hours (10.1% v 1.7%, P less than .05) and returned to normal at 2 1/2 weeks and 6 weeks. Splenic activity was increased following hepatectomy at 2 1/2 weeks. Renal clearance was increased at 72 hours and 2 1/2 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Two-dimensional echocardiographic monitoring during percutaneous endomyocardial biopsy.

The use of two-dimensional echocardiography in four successive views was assessed to determine the optimal view for localizing a transvenous percutaneous bioptome in 23 consecutive patients undergoing right ventricular endomyocardial biopsy. The biopsy catheter tip was viewed in 21 (91%) of the 23 patients. The apical four chamber view allowed visualization of the bioptome head in 19 patients (83%), the subcostal view in 8 (34%) and the long-axis view in 4 (17%). The parasternal short-axis view was not helpful in any patient. Biplane fluoroscopy was not reliable in localizing the bioptome head against the interventricular septum and did not identify inadvertent septal perforation in one patient. Echocardiography also can be used to immediately identify possible complications.

Adult↗
PubMed1985

Characterization of trypsin stimulation of cardiac adenylate cyclase.

The activity of adenylate cyclase present in a purified dog heart sarcolemmal preparation in the presence of magnesium as cosubstrate is biphasically influenced by increasing concentrations of trypsin: Stimulation at low concentrations (0.5 to 1 microgram/mL) is followed by inhibition at higher concentrations. In the presence of manganese in place of magnesium, the stimulation phase is abolished but the inhibition is still observed at the same trypsin concentrations. The trypsin stimulatory effect does not occur when trypsin is preincubated with cardiac membranes prior to the addition of ATP. When trypsin is added with ATP, the stimulation is expressed by an increase in the Maximal Velocity (Vmax) rather than a decrease in the Michaelis constant (Km). The stimulatory effect of trypsin on AC activity is rapid, linear and irreversible. GTP, Gpp(NH)p and adrenaline stimulatory curves are shifted to the left in the presence of trypsin. These results suggest that protease stimulation of cardiac AC involves the GTP-binding protein (N) activity, but the exact mechanism remains to be determined.

Adenylyl Cyclases↗
PubMed1985

Characterization of calmodulin-dependent and cyclic-AMP-dependent protein kinase stimulation of cardiac sarcoplasmic reticulum calcium transport.

The mechanism by which calmodulin stimulates Ca2+ transport in cardiac microsomal preparations enriched in sarcoplasmic reticulum (SR) was investigated. Under incubation conditions in which the majority of the phosphoprotein formed was Ca2+-dependent and no phospholamban phosphorylation was observed (10 degrees C, 15-sec incubations in the presence of 2 microM ATP), calmodulin was found to have no effect on the steady-state level of the acylphosphate phosphorylation site of Ca2+-ATPase. A significant stimulation of Mg2+, Ca2+-ATPase activity by calmodulin and a 3-fold increase in the turnover of the Ca2+ pump were, however, observed. As the ATP concentration in the incubation media was elevated (20 and 200 microM ATP), a significant degree of phosphoprotein formed was observed to be cyclic AMP (cAMP)-dependent. The degree of Ca2+-dependent phosphorylation remained constant. Under these conditions, calmodulin had no effect on the degree of phosphoprotein formed. However, when the experiments were conducted at 30 degrees C for 5 min in the presence of 500 microM ATP, a significant amount of the phosphoprotein formed was calcium-calmodulin-dependent and was additive to phosphoprotein formation observed in the presence of cAMP-dependent protein kinase. The ratio of calcium-calmodulin-dependent to cAMP-dependent phosphorylation was 1:1. K+ (110 mM) decreased the levels of phosphorylation observed in the presence of calcium and calmodulin, but had less of an effect on the levels observed in the presence of cAMP-dependent protein kinase. Autoradiographic analysis of SR membranes labeled with [32P]-ATP revealed two protein bands (24,500 and 40,000 daltons) phosphorylated in the presence of added calcium and calmodulin that were not observed in the absence of either of these additions to the reaction media. These results suggest that calmodulin stimulates Ca2+ transport by a direct effect on the Mg2+, Ca2+-ATPase. An indirect effect on Ca2+ transport via a calcium-calmodulin-dependent protein kinase, though, cannot be ruled out.

Adenosine Triphosphatases↗