Biomedical subjects
Publications and source records attributed to L Rome.
Physicians caring for patients with community-acquired pneumonia are often faced with the dilemma of how to approach a patient with slowly resolving or even nonresolving pneumonia. When the radiograph has failed to resolve by 50% in 2 weeks or completely in 4 weeks, the pneumonia should be considered to be nonresolving or slowly resolving. The causes of a nonresolving pneumonia and an approach to the work-up are presented.
The major vault protein (MVP) is the predominant constituent of ubiquitous, evolutionarily conserved large cytoplasmic ribonucleoprotein particles of unknown function. Vaults are multimeric protein complexes with several copies of an untranslated RNA. Double labeling employing laser-assisted confocal microscopy and indirect immunofluorescence demonstrates partial colocalization of vaults with cytoskeletal elements in Chinese hamster ovary (CHO) and nerve growth factor (NGF)-treated neuronlike PC12 cells. Transfection of CHO and PC12 cells with a cDNA encoding the rat major vault protein containing a vesicular stomatitis virus glycoprotein epitope tag demonstrates that the recombinant protein is sorted into vault particles and targeted like endogenous MVPs. In neuritic extensions of differentiated PC12 cells, there is an almost complete overlap of the distribution of microtubules and vaults. A pronounced colocalization of vaults with filamentous actin can be seen in the tips of neurites. Moreover, in NGF-treated PC12 cells the location of vaults partially coincides with vesicular markers. Within the terminal tips of neurites vaults are located near secretory organelles. Our observations suggest that the vault particles are transported along cytoskeletal-based cellular tracks.
Advanced autosomal dominant polycystic kidney disease (ADPKD) is characterized morphologically by massive cyst enlargement, moderate interstitial infiltration with mononuclear cells, and extensive fibrosis. In patients affected by a common genotype (PKD1), it has been suggested that the progressive decline in renal function that transpires over a highly variable time course may be due to endogenous or exogenous epigenetic factors. We have postulated that a neutral lipid, discovered in human cyst fluid and stimulating the rates of transepithelial fluid secretion and cellular proliferation of renal epithelial cells in vitro may have a potential role in cyst growth and the progressive decline of kidney function. In this study, we used thin-layer chromatography (TLC) and high-performance TLC (HPTLC) to determine whether lipid extracts of human cyst fluid stimulated monocyte chemotaxis in vitro. Monocyte chemotactic activity, determined by the transmembrane migration of murine RAW 264.7 cells, was stimulated (delta 26.0 +/- 1.5 optical density units) by a lipid fraction less polar than sphingosine but more polar by TLC and HPTLC than 1-monooleoylglycerol. A high level of secretagogue activity was detected in this fraction (delta 0.336 +/- 0.022 microliter/cm2 1 hr) and to a lesser extent (delta 0.253 +/- 0.022 microliter/cm2/hr) in a neighboring fraction that encompassed the 1-monooleoylglycerol standard. Cyst fluid with undetectable secretagogue activity had a monocyte chemotactic-activity level only 18% as great as fluids with high levels of secretagogue activity. The secretagogue and chemotactic activities in TLC-HPTLC fractions were resistant to treatment with KOH, but both were diminished by HCl, borohydride, or periodate. Rat proximal tubule cultures incubated with oleate complexed with albumin elaborated secretagogue and chemotactic activities in the conditioned medium, with TLC-HPTLC mobility characteristics similar to the biologically active cyst fluid lipids. On the basis of these studies, we conclude that human cyst fluids harbor potent secretagogue and chemotactic lipids that may have a role in determining the functional course of ADPKD. On the basis of preliminary chemical characterizations, we suggest that the secretatogue and monocyte chemotactic activities of cyst fluid may reflect the action of lipid molecules of similar structure, the source of which may be renal epithelial cells.
Renal correction of chloride-depletion alkalosis (CDA) by chloride replacement results in bicarbonate secretion in the cortical collecting duct (CD) and urinary bicarbonate excretion. To assess the participation of the more distal segments of the CD, we determined net total CO2 transport in the outer medullary (OMCD), initial (IMCDi) and terminal (IMCDt) inner medullary CD segments obtained from Sprague-Dawley rats with normal acid-base balance (NML) or with CDA produced by peritoneal dialysis. Tubules were bathed and perfused with isotonic solutions containing Cl 110 mM and HCO, 25 mM. Net total CO2 transport was decreased in all segments: OMCD 22.1 +/- 4.2 to 9.2 +/- 2.0; IMCDi 38.1 +/- 4.6 to 9.3 +/- 1.7; IMCDt 6.7 +/- 1.2 to -0.5 +/- 0.4 pmol/min/mm tubule length. Perfusion rates, tubule lengths, and transepithelial voltages did not differ between groups in any segment. These data show that all CD segments beyond the cortical segment decrease bicarbonate reabsorption during CDA. This permits the bicarbonate secreted by the cortical CD to be excreted, and is likely an important mechanism for the correction of CDA.
Previous studies have suggested the presence of an H(+)-K(+)-ATPase in rat cortical and medullary intercalated cells with similar properties to the gastric proton pump. The purpose of this study was to determine the functional contribution of an H(+)-K(+)-adenosinetriphosphatase(ATPase) to total CO2 (tCO2) transport along the rat collecting duct. After baseline determination of tCO2 transport in isolated perfused collecting duct segments, Sch 28080 (10 microM) was added to either the perfusate or bath. When Sch 28080 was added to the perfusate, there was no effect in the cortical collecting duct (CCD, 20.8 +/- 6.7 vs. 25.3 + 3.0 pmol.mm-1.min-1), but a marked decrease in tCO2 absorption was effected in both the outer medullary (OMCD, 37.6 + 6.2 vs. 10.7 +/- 4.1 pmol.mm-1.min-1) and initial inner medullary collecting duct (IMCD1, 34.4 +/- 8.1 vs. 16.2 +/- 5.6 pmol.mm-1.min-1). In the CCD from rats with acute alkalosis in vivo, Sch 28080 added to the bath inhibited tCO2 secretion in the CCD (-17.1 +/- 4.4 vs 3.5 + 3.3 pmol.mm-1.min-1). These findings suggest that 1) H(+)-K(+)-ATPase is important in tCO2 absorption in the OMCD and IMCD1 and in tCO2 secretion in the CCD, 2) HCO3(-)-absorbing intercalated cells differ functionally in the cortex and medulla, 3) HCO3- secretion is not the reverse process of HCO3- absorption in the CCD, and 4) H(+)-K(+)-ATPase is important in distal acidification under normal and altered acid-base conditions.
Explore the source record for details and available documents.
The systemic and renal adaptations for the maintenance and correction of metabolic alkalosis generated by chloride depletion (CDA) are the focus of this review. The hypothesis that extracellular fluid (ECF) volume expansion is essential for the correction of CDA is refuted, while the concept that Cl- repletion is necessary and sufficient for correction is developed. Contraction of ECF volume probably can occur as a consequence of CDA. The principal mechanisms by which the kidney corrects CDA appear to reside primarily in the collecting duct, which is endowed with the anion exchange mechanisms and the capacity to effect the necessary changes in body anion composition. Although the remainder of the collecting duct is undoubtedly important in this response, the cortical segment appears to have the paramount role since it can either absorb or secrete HCO3-. Alterations in the delivery of Cl- or HCO3- to the collecting duct may also be important but changes in glomerular filtration rate appear to have a minor role. Major unanswered questions in the pathophysiology of CDA are the manner in which exogenous Cl- repletion is detected and the kidney is signaled to excrete HCO3- and the cellular mechanisms by which this is accomplished in the various nephron segments.
Chloride-depletion alkalosis (CDA) has been characterized by hypereninemia. To determine whether angiotensin II (ANG II) has an important role in its maintenance or correction, anesthetized alkalotic rats, chloride depleted by peritoneal dialysis, were infused with 5% dextrose and saralasin (1 microgram.kg-1.min-1) (SAR) or vehicle (SAR-C), 5% dextrose and pretreatment with enalapril (1-1.5 mg/kg) (ENP) or vehicle (ENP-C), or 80 mM Cl solution with ANG II (20 micrograms/min) (ANG) or vehicle (ANG-C). Rats infused with 5% dextrose showed no differences in the magnitude of the alkalosis, inulin clearance, or urinary total CO2 excretion; both SAR and ENP were associated with decreased blood pressure. In SAR, tCO2 delivery out of late proximal convoluted tubule did not differ from that in SAR-C. Rats infused with 80 mM Cl corrected CDA similarly (delta plasma [Cl] - ANG-C + 6 +/- 1, ANG + 5 +/- 1 mM; P = not significant). These data suggest that, although ANG II can importantly influence vascular tone and early proximal tubule bicarbonate reabsorption, it does not have an important role in the renal maintenance or correction of acute CDA.
An epifluorometric method was used to quantify the bidirectional fluxes of fluorescein across the basolateral surfaces of nonperfused rabbit tubule segments in vitro. Proximal S2 segments, but not cortical collecting tubules or cortical thick ascending limbs, accumulated fluorescein to levels in cytoplasm over 100-fold greater than in the external medium. The rate of intracellular fluorescein accumulation was dependent on the concentration of the ligand in the external bath. The apparent Km was 10 microM and the Vmax was 623 x 10(-6) mol.min-1.l-1. Probenecid and ouabain inhibited fluorescein accumulation. We conclude that fluorescein is transported into the cytoplasm of proximal tubules by basolateral mechanisms that share features in common with the classical organic anion system. This fluorescent compound offers some unique advantages for the study of the organic anion transport system in intact cells.
This study sought to measure the net loss of intracellular K+, Na+, and Cl- that accompanied isosmotic cell volume regulation in hypotonic media and to determine if electrolyte loss depended on the rate at which the extracellular osmolality was reduced. Isolated nonperfused proximal S2 segments from rabbit kidney cortex were studied in vitro. Gradual lowering of osmolality from 295 to 150 mOsm/kg at a rate of 2 mOsm/kg/min did not cause an increase in tubule cell volume until the medium osmolality decreased below 190 mOsm/kg. By contrast, tubules rapidly bathed in low osmolality media exhibited classical osmometric swelling followed by incomplete volume regulatory decrease. Volume regulation associated with gradual and rapid lowering of osmolality was accompanied by the net loss of intracellular K+, Na+, and Cl- (measured by electron probe); however, the temporal pattern of electrolyte loss depended on the rate of osmotic change. With gradual lowering of osmolality, cell K+ content did not decrease significantly until osmolality was lowered below 200 mOsm/kg, whereas Cl- was lost at the 200 mOsm/kg level and below. With rapid lowering of osmolality, cell K+ content was strikingly decreased at the 200 mOsm/kg level, but Cl- did not change appreciably until osmolality was decreased to 150 mOsm/kg. Cell Na+ content decreased in hypo-osmotic media, but the magnitude was relatively small. During volume regulation that accompanied either gradual or rapid lowering of medium osmolality from 295 to 150 mOsm/kg, intracellular osmolal gap, the difference between medium osmolality and the sum of intracellular concentrations of K+, Na+, and Cl- decreased 87 and 58 mOsm/kg, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Nonperfused proximal S2 segments from rabbit kidney cortex have been shown to keep cell volume constant as medium osmolality is slowly raised but to shrink and not exhibit regulatory volume increase (RVI) if medium osmolality is abruptly elevated (J. Lohr and J. Grantham. J. Clin. Invest. 78: 1165-1172, 1986). In the current study, 0.5 mM butyrate in the medium 1) extended the range from 361 to 450 mosmol/kgH2O over which cells maintained volume constant as osmolality was gradually raised and 2) restored RVI after cell shrinkage when osmolality was rapidly raised from 295 to 400 mosmol/kgH2O. Volume regulation was associated with net increases in intracellular Na+ and Cl- but no change in K+ (measured by electron probe). The increments in Na+ and Cl- were insufficient to account for the total addition of osmolytes required for volume maintenance or restoration. The fraction of the expected increase in intracellular osmoles accounted for by the increase in [(K+)i + (Na+)i + (Cl-)i] was 52 and 21% for gradual and rapid osmotic changes, respectively. We conclude that butyrate enhances the capacity of S2 segments to regulate volume in hyperosmotic medium by promoting addition of Na+ and Cl- and by other undermined factors.
The purpose of these experiments was to determine oxygen consumption (VO2) in rats as a function of treadmill speed (10, 20, 30, 40, and 50 m . min-1) as they ran on the level and up and down a 16 degree (17.8%) incline. The slopes of the regression lines relating VO2 (ml O2 . kg-1 . min-1) to running speed (m . min-1) were linear for all three inclines. The regression slope for uphill runners (y = 1.25x + 47.7) was greater than the regression slopes for level (y = 0.88x + 41.2) (P less than 0.025) or downhill (y = 0.68x + 39.7) (P less than 0.005) runners, and the regression slope for level runners was greater than that for downhill runners (P less than 0.10). All VO2 measurements were submaximal. In conclusion, incline has a significant effect on the metabolism of rats running on a motor-driven treadmill.
A simple one-step procedure that eliminates the need to calibrate the O2 analyzer or measure the flow past the animal is described for calibrating an open-flow respirometry system. The technique is particularly useful for situations of high ambient humidity and for large or active animals where a mask is employed to capture expired gases. A measured N2 flow is used to calibrate the system. The equations describing the technique are given, and the accuracy of the method is discussed in detail. The errors associated with the technique are compared with those of more conventional procedures and are usually smaller.
Explore the source record for details and available documents.