Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied salt and water absorption in isolated rabbit superficial proximal straight tubules perfused and bathed with solutions providing oppositely directed transepithelial anion gradients similar to those which might obtain in vivo. The perfusing solution contained 138.6 mM Cl- 3.8 mM HCO-3 (pH 6.6) while the bathing solution contained 113.6 mM Cl- and 25 mM HCO-3 (pH 7.4); the system was bubbled with 95% O2-5% CO2. At 37 degrees C, net volume absorption (Jv nl min-1 mm-1) was 0.32 +/- 0.03 (SEM); Ve, the transepithelial voltage (millivolts; lumen to bath), was +3.1 +/- 0.2. At 21 degrees C, Ve rose to +3.7 +/- 0.1 and Jv fell to 0.13 +/- 0.01 (significantly different from zero at P less than 0.001); in the presence of 10(-4)M ouabain at 37 degrees C, Ve rose to +3.8 +/- 0.1 and Jv fell to 0.16 +/- 0.01 (P less than 0.001 with respect to zero). In paired experiments, the ouabain- and temperature-insensitive moieties of Jv and Ve became zero when transepithelial anion concentration gradients were abolished. Titrametric determinations net chloride flux at 21 degrees C or at 37 degrees C with 10(-4) M ouabain showed that chloride was the sole anion in an isotonic absorbate. And, combined electrical and tracer flux data indicated that the tubular epithelium was approximately 18 times more permeable to Cl- than to HCO-3. We interpret these results to indicate that, in these tubules, NaCl absorption depends in part on transepithelial anion concentration gradients similar to those generated in vivo and in vitro by active Na+ absorption associated with absorption to anions other than chloride. A quantitative analysis of passive solute and solvent flows in lateral intercellular spaces indicated that fluid absorption occurred across junctional complexes when the osmolality of the lateral intercellular spaces was equal to or slightly less than that of the perfusing and bathing solutions; the driving force for volume flow under these conditions depended on the fact that sigmaHCO3 exceeded sigmaCl.
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PMID:A component of fluid absorption linked to passive ion flows in the superficial pars recta. 118 77

The aim of this study was to examine the effect of an inotropic intervention on regional myocardial function in the presence of a significant stenosis in a coronary artery. During 0.5% halothane anesthesia, intravenous dobutamine (2.5 and 5 micrograms.kg-1.min-1) was administered to eight pigs. A critical constriction was applied to the left anterior descending (LAD) coronary artery and regional myocardial function was determined with the end-systolic pressure-length relationship in the area of distribution of the LAD and left circumflex coronary artery. Infusion of dobutamine was associated with an increase in the end-systolic pressure-length relationship in the left circumflex coronary artery region from 31.81 +/- 7.87 to 81.03 +/- 21.43 mm Hg.mm-1 (X +/- SEM, P = 0.005), whereas function in the LAD coronary artery region did not change significantly (21.78 +/- 3.97 to 21.97 +/- 6.91 mm Hg.mm-1, P = 0.124). Regional stroke work in the left circumflex coronary artery distribution area increased from 124.38 +/- 24.04 to 222.00 +/- 37.83 mm Hg.mm during the administration of 5 micrograms.kg-1.min-1 dobutamine (P = 0.0125). In the LAD coronary artery area, regional stroke work remained at baseline values. Once the constriction was released, the end-systolic pressure-length relationship in the LAD artery segment increased from 21.97 +/- 2.45 to 35.36 +/- 4.55 mm Hg.mm-1 (P = 0.121). These results suggest that hibernation develops in the myocardial segment supplied by a stenotic coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional myocardial function in the presence of coronary artery stenosis and inotropic intervention: a case for myocardial hibernation? 240 Jan 15

Unidirectional fluxes of L-35S-cystine and intracellular 35S activity were measured in isolated perfused segments of rabbit proximal straight tubule. The absorptive (lumen-to-both) flux of L-35S-cysteine showed a tendency toward saturation within the concentration limits imposed by the low solubility of cystine (0.3 mmol . l-1). In contrast, for the bath-to-lumen fluxes, there was a linear relation between the bathing solution concentration of L-35S-cystine and the rate of 35S appearance in the lumen. Nonlinear fitting of both sets of unidirectional flux data gave a maximal cystine transport rate (Jmax) of 1.45 +/- 0.27 (SEM) pmol min-1 mm-1, a Michaelis constant (Km) of 0.20 +/- 0.07 mmol . l-1, and an apparent permeability coefficient of 0.27 +/- 0.11 pmol min-1 mm-1 (mmol . l-1)-1 (approximately 0.06 micrometer/s). The 35S concentration in the cell exceeded that in the lumen by almost 60-fold during the lumen-to-bath flux, and exceeded the bathing solution concentration by 4.7-fold during the bath-to-lumen flux. Thus cystine was accumulated by the cells across either membrane, but over 77% of the intracellular activity was in the form of cysteine. Although the presence of luminal L-lysine or cycloleucine inhibited the absorptive flux of cystine, neither amino acid affected the bath-to-lumen flux.
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PMID:Transport of L-cystine in isolated perfused proximal straight tubules. 643 21

An experimental program was devised to determine whether the canine anterior cruciate ligament (ACL), with an apparent helical twist of its component fiber bundles, could support a torque during axial loading to failure. At the point of first significant failure, the anterior cruciate was found to develop an average maximum torque of 122 +/- 26 N-mm (mean +/- SEM) for the nine tension-torsion tests performed. A nearly linear axial force-torque curve was also observed where the average slope of all tests was 5.2 +/- 0.2 mm-1 (mean +/- SEM). The experimental axial force data was then used to determine material parameters in the constitutive equation for the fascicle and underlying bone. A nonlinear ligament model based on this response was found to reproduce the axial force data adequately and to reasonably predict the observed ligament torque over the entire subfailure loading range. The presence of a ligament torque during axial loading has implications in the design and selection of a ligament substitute. Such a substitute has already been examined in the canine in another study. The results also suggest more refined experiments which could relate the mechanical properties of a ligament to its detailed macrostructure and insertion site geometries.
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PMID:Tension-torsion characteristics of the canine anterior cruciate ligament--Part II: Experimental observations. 686 58

Previous studies have demonstrated that prostaglandin E2 (PGE2) inhibits arginine vasopressin-(AVP)dependent adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in microdissected rat outer medullary collecting tubules (OMCD), by a mechanism unrelated to the inhibition of cAMP synthesis. The potential role of the activation of protein kinase C (PKC) to explain the negative regulation elicited by PGE2 was investigated in this study. Single OMCD samples were pre-incubated (10 min, 30 degrees C) in the presence or absence of either activators of PKC, phorbol 12-myristate 13-acetate (PMA), 1-oleoyl-2-acetyl-glycerol (OAG), dioctanoylglycerol (DOG) or an inhibitor of PKC, staurosporine (SSP). These compounds were present also with the agonists tested during the incubation period (4 min, 35 degrees C). In contrast to PGE2, activators of PKC did not decrease AVP-dependent cAMP accumulation (mean +/- SEM): 1 nM AVP = 47.1 +/- 6.8 fmol.mm-1 x 4 min-1; AVP+0.3 microM PGE2 = 20.1 +/- 2.7, P < 0.01 versus AVP; AVP + 10 nM PMA = 42.0 +/- 4.7, NS versus AVP; AVP + 50 micrograms/ml OAG = 44.1 +/- 4.8. NS versus AVP, N = 5 experiments. However, 10 nM PMA prevented PGE2-induced inhibition: AVP + PGE2 = 44.2 +/- 3.5% of the response to AVP and 90.3 +/- 3.2% without and with PMA respectively, N = 16. Similar results were obtained with either 50 micrograms/ml OAG or 25 micrograms/ml DOG (AVP + PGE2 + OAG = 92.9 +/- 6.6% of the response to AVP, N = 8; AVP + PGE2 + DOG = 94.1 +/- 5.3%, N = 7).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The activation of protein kinase C prevents PGE2-induced inhibition of AVP-dependent cAMP accumulation in the rat outer medullary collecting tubule. 790 84

We examined the actions of potentially natriuretic autacoids in the isolated perfused cortical collecting duct (CCD) dissected from inbred Dahl (Rapp strain) salt-sensitive rats (SS). Atrial natriuretic peptide (ANP, 10 nM), bradykinin (BK, 10 nM), and clonidine (1 microM) were studied to determine their effects on the lumen-to-bath flux of 22Na+ (J1-->b, pmol min-1 mm-1), hydraulic conductivity (Pf, micron/s), and transepithelial voltage (VT, mV). ANP and BK have been shown by others to significantly reduce net Na+ reabsorption and hydraulic conductivity in the Sprague-Dawley (SD) rat CCD, but previous results from our laboratory showed no ANP or BK effect in the SD CCD. In the present study, we were also unable to observe any effect of either ANP or BK in the SS rat CCD. However, in the presence of AVP, clonidine (a partial alpha 2-adrenergic receptor agonist) significantly reduced J1-->b and Pf from 139 +/- 6 (SEM) to 88 +/- 7 and from 959 +/- 176 to 490 +/- 73, respectively. In addition, clonidine significantly depolarized VT from -14.5 +/- 2.8 to -11.2 +/- 1.8. However, unlike its effects in the SD rat CCD, yohimbine (300 nM, an alpha 2-adrenergic receptor antagonist) did not significantly reverse the effects of clonidine on J1-->b, Pf or VT in the SS rat CCD.
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PMID:Clonidine, but not bradykinin or ANP, inhibits Na+ and water transport in Dahl SS rat CCD. 835 63

The objective of this study was to elucidate the structure of cancellous bone and its age-related changes at different skeletal sites. Therefore, the lumbar spine, iliac crest, femur, and calcaneus of 12 age- and sex-matched skeletal healthy autopsy cases (6 females, 6 males, aged 28-84 years, mean 54 years) were removed. The following analysis includes an evaluation of the trabecular bone volume (BV/TV, %) and the trabecular interconnection (TBPf, mm-1) as well as a qualitative investigation of the structure of trabecular bone. BV/TV shows the following mean values: lumbar spine, 8.3% (+/- 0.8%); iliac crest, 11.5% (+/- 1.6%); intertrochanteric, 10.2% (+/- 1.2%); femoral neck, 15.8% (+/- 1.6%); and calcaneus, 15.4% (+/- 2.0%). There are significant differences between the BV/TV of the femoral neck and that of the lumbar spine as well as between that of the calcaneus and the lumbar spine (p < 0.01). However, a positive correlation can be seen between the bone mass of the spine and that of all other investigated sites (r = 0.67 to r = 0.80; pr < 0.1). The trabecular interconnection of the lumbar spine (2.7 mm-1, SEM +/- 0.2 mm-1) and the femoral neck (0.3 mm-1, SEM +/- 0.3 mm-1) differs significantly. Only these two sites show a significant positive correlation of TBPf (r = 0.60; pr < 0.1). Age-dependent alteration of the spine and the femoral neck in bone mass and bone structure is nearly the same. The trabecular microarchitecture of the iliac crest varies systematically. A region 4-10 cm behind and 1-3 cm below the anterior superior iliac spine turns out to be the most suitable biopsy site because of its closest relation to the lumbar bone mass. However, drawing information about the trabecular interconnection within the lumbar spine by measurement of the iliac crest at any site seems to be impossible. The horizontal specimens reveal a vertical running tubular spongiosa pattern that is arranged in concentric rings starting from the dorsal shell like a honeycomb. The comparison of TBPf in horizontal and vertical planes and its age-related changes indicates the age-related bone loss to be predominantly a loss of horizontal trabeculae. Thus, the presented data provide further information about the skeletal distribution and heterogeneity of the trabecular microarchitecture.
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PMID:Heterogeneity of the skeleton: comparison of the trabecular microarchitecture of the spine, the iliac crest, the femur, and the calcaneus. 877 Jun 95

On the basis of our report that a glycolipoprotein fraction (GLP) extracted from Leptospira interrogans contains a potent inhibitor of renal Na,K-ATPase, we proposed that GLP-induced inhibition of Na,K-ATPase might be the primary cellular defect in the physiopathology of leptospirosis. The present study was designed to test this hypothesis by determining whether or not 1). GLP inhibits all the isoforms of Na,K-ATPase which are expressed in the tissues affected by leptospirosis, 2) Na,K-ATPase from leptospirosis-resistant species, such as the rat, is sensitive to GLP, 3) GLP inhibits Na,K-ATPase from intact cells, and 4) GLP inhibits ouabain-sensitive H,K-ATPase. The results indicate that in the rabbit, a leptospirosis-sensitive species, GLP inhibits with similar efficiency (apparent IC50: 120-220 micrograms protein GLP/ml) all isoforms of Na,K-ATPase known to be expressed in target tissues for the disease. Na,K-ATPase from rat kidney displays a sensitivity to GLP similar to that of the rabbit kidney enzyme (apparent IC50: 25-80 and 50-150 micrograms protein GLP/ml for rat and rabbit, respectively), indicating that resistance to the disease does not result from the resistance of Na,K-ATPase to GLP. GLP also reduces ouabain-sensitive rubidium uptake in rat thick ascending limbs (pmol mm-1 min-1 +/- SEM; control: 23.8 +/- 1.8; GLP, 88 micrograms protein/ml: 8.2 +/- 0.9), demonstrating that it is active in intact cells. Finally, GLP had no demonstrable effect on renal H,K-ATPase activity, even on the ouabain-sensitive form, indicating that the active principle of GLP is more specific for Na,K-ATPase than ouabain itself. Although the hypothesis remains to be demonstrated in vivo, the present findings are compatible with the putative role of GLP-induced inhibition of Na,K-ATPase as an initial mechanism in the physiopathology of leptospirosis.
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PMID:Na,K-ATPase: a molecular target for Leptospira interrogans endotoxin. 923 7