Blastocystis hominis in hospital employees

Several reports have appeared that either support or deny the importance of the protozoan Blastocystis hominis as an intestinal pathogen in humans. In this report, we describe the clinical characteristics of B. hominis and its response to therapy in hospital employees found to have the parasite on routine screening of stools. During the study, 49 patients with B. hominis were identified, and 413 stools were examined from these patients. Twenty-nine patients were asymptomatic (59%), and 20 had symptoms of bloating, flatulence, soft/loose stools, or constipation. Of these 20 patients, 10 had symptoms that correlated with the presence or absence of B. hominis, four had symptoms that were independent of B. homonis, and six had other intestinal parasites that could account for their symptoms. Nineteen percent of patients without treatment had eradication of B. hominis from stool on follow-up examination. Metronidazole did not increase this rate. Iodoquinol treatment eradicated the organism in 41% of patients (p less than 0.05), and resulted in the reduction or eradication of the parasite in 62%, as determined by follow-up examination.

Gap junction distribution is altered between cardiac myocytes infected with Trypanosoma cruzi

Conduction disturbances frequently accompany both acute and chronic Chagas' disease. To explore the possibility that changes in gap junction distribution or abundance might play a role in these disturbances, we have investigated intercellular communication between rat neonatal cardiac myocytes in cultures infected with Trypanosoma cruzi. Contractile activity of infected cells was characterized by regional asynchrony within the culture as well as by irregular contraction patterns. Junctional conductance between infected cell pairs was found to be significantly lower than in uninfected cell pairs, and the rapidity and extent of intercellular transfer of the dye lucifer yellow was markedly reduced between infected cells. Immunocytochemical studies demonstrated that the parasitic infection significantly decreased connexin43 expression at junctional membrane regions, correlating with the detected functional uncoupling. These findings of reduced gap junction abundance and function in trypanosome-infected cells may provide important insight into the pathogenesis of the cardiac arrhythmias that attend Chagas' disease.

Pyrimethamine concentrations in serum during treatment of acute murine experimental toxoplasmosis

Central nervous system toxoplasmosis is a major opportunistic infection in patients with acquired immunodeficiency syndrome. The standard therapy for this infection is pyrimethamine (PYR) and sulfonamides. To assess in vivo if PYR alone could adequately treat toxoplasmosis, a murine model of acute toxoplasmosis was used. The CD1 strain of mice was infected intraperitoneally with 10(4) parasites of the RH strain of Toxoplasma gondii. Pyrimethamine was administered in mouse chow at concentrations of 0, 0.03125, 0.0625, 0.125, 0.25, or 1.0 mg of PYR/g of food, which provides the following daily PYR dosages: 0, 6.25, 12.5, 25, 50, and 200 mg/kg/day. No sulfonamides were administered. Serum PYR levels proved more accurate than mg of PYR/g of food in predicting survival. Mice with serum PYR levels greater than or equal to 500 ng/ml (2 microM) survived and had no parasites present on peritoneal lavage. Mice with serum PYR levels less than 100 ng/ml (0.4 microM) had a 100% mortality rate and the average parasite count was 3 x 10(7) organisms in the lavage fluid. At a PYR level of 370 ng/ml, six of 11 mice survived and the lavage fluid contained 2.5 x 10(5) organisms. Previously, using 3H-uracil in an in vitro assay, PYR at a concentration of 500 ng/ml was shown to be as effective in inhibiting Toxoplasma growth as the combination of PYR (100 ng/ml) and sulfonamides 25 micrograms/ml). These data suggest the potential usefulness of PYR for monotherapy of toxoplasmosis and are consistent with previously described in vitro assays.

Trypanosoma cruzi: stage expression of calmodulin-binding proteins

The subcellular distribution of calmodulin-binding proteins in three life stages of Trypanosoma cruzi was analyzed by a [125I]calmodulin gel overlay procedure under conditions where proteolysis was kept to a minimum. It was found that T. cruzi contains a complex profile of calcium-dependent calmodulin-binding proteins and that several of these polypeptides were differentially expressed at specific stages of development. The majority of these stage-specific polypeptides was found in the particulate fractions of the replicative stages of the parasite, i.e., epimastigote and amastigote. These studies suggest that calcium and calmodulin may play an important central role in the growth and differentiation of this parasite. We have also assessed the calmodulin content of the various life stages by immunoblot analysis. These studies identified a 14-kDa immunoreactive peptide present at equivalent levels in epi-, trypo-, and amastigote stages (extracellular).

Active NaCl transport in the cortical thick ascending limb of Henle's loop of the mouse does not require the presence of bicarbonate

The aim of the present study was to investigate whether bicarbonate buffer (CO2 + HCO3-) is required to sustain maximal NaCl transport in the cortical thick ascending limb of Henle's loop (cTAL) of the mouse. Transepithelial Na+ and Cl- net fluxes (JNa, JCl, pmol min-1 mm-1), measured by electron microprobe analysis, were similar irrespective of the presence or absence of CO2 + HCO3- in luminal and bathing solutions (JNaCl with CO2 + HCO3- = 203 +/- 25 pmol min-1 mm-1; JNaCl without CO2 + HCO3- = 213 +/- 13 pmol min-1 mm-1, n = 14). Furthermore the transepithelial potential difference, Vte, the transepithelial resistance, Rte, and the basolateral membrane potential, Vbl, were unaffected by CO2 + HCO3-. In the absence of CO2 + HCO3-, Vte was +17.0 +/- 1.7 mV (n = 9) (lumen positive), Rte was 28 +/- 2 omega cm2 (n = 9) and Vbl was -76 +/- 4 mV (n = 6). In the presence of CO2 + HCO3-, Vte, Rte and Vbl were +15.9 +/- 1.5 mV, 29 +/- 1 omega cm2 and -73 +/- 5 mV, respectively. 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS; 0.1 mmol l-1) and amiloride (1 mmol l-1) added to the (CO2 + HCO3-)-containing lumen perfusate were without effect on Vte and Rte. Finally, the effect of furosemide (0.1 mmol l-1) on Vte and Vbl in the presence of CO2 + HCO3- was investigated. Furosemide reversibly decreased Vte from +13.7 +/- 1.1 mV to +1.7 +/- 0.7 mV (n = 6) and hyperpolarized Vbl from -70 +/- 1 to -89 +/- 3 mV (n = 5), suggesting passive distribution of Cl- across the basolateral membrane. In conclusion, these data suggest that active NaCl transport in the cTAL of the mouse does not require the presence of CO2 + HCO3-.

Trypanosoma cruzi: alteration of cAMP metabolism following infection of human endothelial cells

We have previously reported that Trypanosoma cruzi infection of endothelial cells results in alterations in the metabolism of Ca2+, inositol triphosphate (IP3), and prostacycline (PGI2). In this report, we demonstrate that infection also alters the metabolism of cAMP. Infection of endothelial cells does not significantly alter beta-adrenergic receptor density or affinity, adenylate cyclase activity, and whole-cell cAMP levels. However, incubation of infected endothelial cells with the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) resulted in less than a 60% increase in cell cAMP in contrast to the greater than a 100% increase observed in uninfected endothelial cells under otherwise identical reaction conditions. Infected endothelial cells demonstrated a twofold increase in phosphodiesterase activity when measured directly. Moreover, homogenates prepared from infected endothelial cells previously incubated with isoproterenol for 20 min showed little or no change in PDE activity. In contrast, homogenates prepared from uninfected endothelial cells treated under otherwise identical reaction conditions showed a 5.7-fold increase in PDE activity. In the presence of IBMX, isoproterenol-dependent stimulation of cAMP levels in infected endothelial cells reached a maximum level at 5 min of incubation, and thereafter rapidly declined. In contrast, cAMP levels in uninfected endothelial cells reached a maximum at 2 min of incubation, and thereafter remained elevated throughout the duration of the incubation. Infection-associated changes in isoproterenol dependent stimulation of cAMP accumulation appear to relate, in part, to changes in PDE activity.

Medical management of AIDS patients. Gastrointestinal manifestations

Gastrointestinal manifestations of AIDS are common. Opportunistic infections and tumors may affect any portion of the GI tract from oral cavity to anus. Esophageal involvement may result from Candida, CMV, HSV, HIV, and tumors. Biliary tract and pancreatic disease may cause abdominal pain. Diarrhea occurs in over 50% of AIDS patients and is multifactorial.

Effect of octreotide on refractory AIDS-associated diarrhea. A prospective, multicenter clinical trial

OBJECTIVE

To determine the efficacy and safety of octreotide for treatment of refractory, profuse diarrhea in patients with the acquired immunodeficiency syndrome (AIDS).

DESIGN

A prospective, open-label study.

SETTING

Inpatient metabolic units of four university medical centers.

PATIENTS

Fifty-one patients infected with human immunodeficiency virus (HIV) who had uncontrolled diarrhea (greater than or equal to 500-mL liquid stool per day) despite treatment with maximally tolerable doses of antidiarrheal medications.

INTERVENTION

After initial baseline studies, patients received octreotide, 50 micrograms every 8 hours for 48 hours. If stool volume was not reduced to less than 250 mL/d, the dose of octreotide was increased stepwise to 100, 250, and 500 micrograms.

MAIN RESULTS

Fifty men and one woman (mean age, 36.3 +/- 1.1 years) entered and completed the 28-day protocol (14 days of inpatient therapy and 14 days of outpatient therapy). Stool frequency and volume decreased significantly (6.5 +/- 0.5 stools per day on day 0 compared with 3.8 +/- 0.3 stools per day on day 21 [P less than 0.001] and 1604 +/- 180 mL/d on day 0 compared with 1084 +/- 162 mL/d on day 14 [P less than 0.001], respectively). Twenty-one patients (41.2%) were considered to be partial or complete responders (reduction in daily stool volume by greater than or equal to 50% of initial collections or reduction to less than or equal to 250 mL/d). Of the 21 responders, 14 (67%) had no identifiable pathogens at initial screening compared with 9 of 30 (30%) nonresponders (P less than 0.01).

CONCLUSION

Patients with AIDS-associated refractory watery diarrhea, especially those without identifiable pathogens, may respond favorably to subcutaneously administered octreotide. This drug deserves further study in a randomized, placebo-controlled trial.

Vasopressin stimulation of NaCl transport in the medullary thick ascending limb of Henle's loop is decreased in aging mice

The maximal urinary osmolality that can be reached by the kidney is reduced with age. This may be due to impaired NaCl transport by the medullary thick ascending limb of Henle's loop, which is part of the renal concentrating mechanism and is modulated by antidiuretic hormone (ADH). We therefore tested in vitro a possible age-related change in the transport capacity and in the response of this nephron segment to ADH in young (1-2 months) and old (20-24 months) mice. The transepithelial potential difference (Vte) was significantly higher in young mice (+8.5 +/- 0.4 mV, n = 13) than in old ones (+6.6 +/- 0.5 mV, n = 17). Addition of 0.1 nmol.1-1 ADH to the bath solution significantly increased Vte by 5.2 +/- 0.5 mV in the young and by 3.1 +/- 0.6 mV in the old animals. Application of dibutyryl-cAMP (0.1 mmol.1-1) did not further increase the hormonal response in both groups. The ADH-mediated increase in the corresponding equivalent short-circuit current (ISC = Vte/Rte) was twice as great in young mice as in old, indicating that the stimulation of NaCl transport by ADH across the medullary thick ascending limb is significantly reduced with age. These results suggest that the previously reported age-related defect in the urinary concentrating ability of the kidney is partly due to a decreased response of the medullary thick ascending limb to ADH.

Stimulation of NaCl reabsorption by antidiuretic hormone in the cortical thick ascending limb of Henle's loop of the mouse

The effect of antidiuretic hormone (ADH) on transepithelial Na+ Cl-, Ca2+ and Mg2+ net fluxes (JNa, JCl, JMg, JCa) was investigated in isolated perfused cortical thick ascending limb segments (cTAL) of the mouse nephron, using the microperfusion technique and the electron microprobe analysis to determine the ionic composition of the collected tubular fluid. Simultaneously, the transepithelial potential difference (PDte) and the transepithelial resistance (Rte) were recorded. Prior to the flux measurements cTAL segments were perfused for one hour. During this equilibration period PDte decreased significantly from +19.9 +/- 1.6 to +14.9 +/- 1.1 mV and Rte increased from 30.6 +/- 3.5 omega cm2 to 38.8 +/- 2.4 omega cm2 (n = 7), reflecting a decline in NaCl transport. After ADH was added to the bath solution at 10(-10) mol.l-1, PDte increased from +14.4 +/- 1.1 to +18.0 +/- 1.5 mV, accompanied by a rise in JNa and JCl from 205 +/- 11 to 273 +/- 19 and from 216 +/- 12 to 283 +/- 21 pmol.min-1.mm-1 (n = 7), respectively. JCa and JMg also increased from 0.81 +/- 0.07 to 1.50 +/- 0.12 and from 0.43 +/- 0.11 to 0.76 +/- 0.08 pmol.min-1.mm-1 (n = 7), respectively. All these effects were fully reversible after withdrawal of the hormone. In conclusion our data indicate that ADH stimulates divalent cation transport and NaCl transport in the cortical thick ascending limb of Henle's loop of the mouse.

Incidence of intestinal parasitic disease in an acquired immunodeficiency syndrome day-care center

In June, 1986, the Bronx Municipal Hospital Center opened an acquired immunodeficiency syndrome day-care center to provide a quality educational experience for children infected with the human immunodeficiency virus. A major concern was the possibility of increasing secondary infections among these immunocompromised children by placing them in a group environment. One particular worry was intestinal parasitic disease, a serious public health problem in day-care centers throughout the United States. To minimize the risk of parasitic infections, scrupulous hygienic and monitoring procedures were instituted at the acquired immunodeficiency syndrome day-care center. This study reports the incidence of intestinal parasitic disease at the acquired immunodeficiency syndrome day-care center during its first 40 months of operation, encompassing 669 child-months of enrollment, with 131 stool specimens examined for ova and parasites. There were 2 cases of parasitic infection: Entamoeba histolytica in an asymptomatic 6-year-old and Giardia intestinalis in a 7-year-old with diarrhea. In neither case was there any secondary spread. None of the 15 children in diapers had a positive specimen, and we found no Cryptosporidium. Our experience suggests that with appropriate precautions human immunodeficiency virus-infected children can participate in a group day-care program without excessive risk for parasitic disease. Strict adherence to hygienic procedures may also decrease the risk of intestinal parasitic disease among healthy children attending day-care centers.

Myocardial beta-adrenergic adenylate cyclase complex in a canine model of chagasic cardiomyopathy

Infection of beagles with an opossum-derived strain of Trypanosoma cruzi (Tc-O) results in features of early and chronic chagasic cardiomyopathy, that is, increases in PR interval, atrioventricular block, and frequent ventricular premature contractions, ventricular tachycardia, and decreased left ventricular ejection fraction. These signs are not observed in animals infected with a canine strain of T. cruzi (Tc-D). To understand the biochemical basis for these early cardiac effects, we examined the beta-adrenergic adenylate cyclase complex in myocardial membranes prepared from animals infected with either of the two strains. In animals infected with Tc-O (symptomatic), the maximum velocity (Vmax) decreased and concentration of agonist resulting in 50% of Vmax (Kact) increased for isoproterenol-dependent adenylate cyclase activity; in animals infected with Tc-D (asymptomatic), Vmax and Kact for isoproterenol were unchanged from control, uninfected animals. beta-Receptor density decreased by 20% in symptomatic animals with no change in affinity, whereas no differences were observed between uninfected and infected asymptomatic animals. A complex pattern of changes was apparent in the guanine nucleotide binding protein, Gs, in the setting of infection. Alterations in cholera toxin-dependent ADP-ribosylation patterns as well as immunochemical detection with anti-G alpha s antisera suggested a change in the biochemical nature of the Gs species and not necessarily a physical loss of this protein. Reconstitution of adenylate cyclase activity in cyc- membranes demonstrated a decrease in hormone-sensitive Gs activity in membranes prepared from symptomatic animals without a change in activity demonstrable in the presence of Gpp(NH)p. Collectively, the results suggest that the depression in beta-adrenergic adenylate cyclase activity associated with symptomatic infection of beagles with T. cruzi occurs primarily as a result of changes in the Gs protein complex, most likely resulting in an uncoupling of the beta-adrenergic receptor from the Gs protein.

Successful management of intractable cryptosporidial diarrhea with intravenous octreotide, a somatostatin analogue

A 38-year-old man with AIDS and intractable large-volume diarrhea due to a cryptosporidial infection was successfully treated with intravenous octreotide, a somatostatin analogue. The volume of diarrhea, 10-12 liters with 8-13 movements per day, was reduced to three to four semi-formed to formed stools per day when the patient was treated with 400 micrograms intravenous octreotide daily. The patient's intravenous hyperalimentation was discontinued and he returned to oral feeding. He quickly regained his normal weight and has now resumed his normal activities. For those patients who cannot tolerate subcutaneous administration, intravenous octreotide therapy may not only be life-saving but may also markedly increase the quality of life. Roxithromycin, a macrolide antibiotic, was also administered to this patient with cryptosporidiosis but efficacy was not demonstrated.

Consequences of differential effects of ADH and other peptide hormones on thick ascending limb of mammalian kidney

Several hormones stimulate the adenylate cyclase system of the thick ascending limb (TAL). There are, however, some species differences concerning the cyclase sensitivity and the hormonal response in this nephron segment. In the mouse, antidiuretic hormone (ADH), parathyroid hormone, glucagon, calcitonin, and isoproterenol stimulate Na+, Cl-, Mg2+, and Ca2+ transports in the cortical TAL, whereas ADH, glucagon, and isoproterenol stimulate NaCl transport only in the medullary TAL. Many of these effects are different from those previously described for the corresponding segments of the rabbit nephron. The close similarity of the cyclase responsiveness to hormones of the mouse and rat TALs makes it possible to interpret the micropuncture data obtained in vivo in the rat superficial (S) and juxtamedullary (JM) nephrons, in the light of the in vitro data obtained in the mouse. Long-term treatment of Brattleboro rats with ADH also elicits differential effects along the TAL. Their consequences on the function of the S and JM nephrons are also examined. There are several indications supporting the view that the newly described hormonal effects in the mouse and rat are of physiological relevance.

Resolution of Cryptosporidium infection in an AIDS patient after improvement of nutritional and immune status with octreotide

An AIDS patient with severe large volume diarrhea and malnutrition due to cryptosporidial infection is presented. The patient, who was not receiving zidovudine, was treated with octreotide with resolution of diarrhea leading to improvement in nutritional status, immune functions, and subsequently, resolution of the Cryptosporidium infection. This case points out the need for adequate nutrition in AIDS patients and highlights the relationship of nutrition and the immune system.

Sensitive and specific detection of toxoplasma DNA in an experimental murine model: use of Toxoplasma gondii-specific cDNA and the polymerase chain reaction

Toxoplasma gondii, an apicomplexan parasite of mammals and birds, is well recognized as a cause of encephalitis in AIDS patients and as a cause of congenital infections. The polymerase chain reaction (PCR) and toxoplasma cDNA clones were used to diagnose T. gondii infection in an acute murine model of toxoplasmosis. Diagnosis of tissue infection by Southern blot hybridization with cDNA clones of T. gondii was possible within 5 days of infection. This technique could detect as few as 10,000 organisms. Specific T. gondii gene amplification by PCR using the primers 5'CACACGGTTGTATGTCGGTTTCGCT3' and 5'TCAAGGAGCTCAATGTTACAGCCT3' followed by oligonucleotide hybridization using 5'GCGGTCATTCTCACACCGACGGAGAACCACTTCACTCTCA3' allowed detection of T. gondii in the tissue of mice by day 2 after infection and in the blood of mice by day 5 after infection with RH strain T. gondii. This technique could detect as few as 10 organisms. Thus, these techniques may be useful in the diagnosis of toxoplasmosis.

How do loop diuretics act?

In the thick ascending limb of the loop of Henle, NaCl reabsorption is mediated by a Na+/2Cl-/K+ cotransport system, present in the luminal membrane of this nephron segment. Loop diuretics such as furosemide (frusemide), piretanide, bumetanide and torasemide bind reversibly to this carrier protein, thus reducing or abolishing NaCl reabsorption. This leads to a decrease in interstitial hypertonicity and thus to a reduced water reabsorption. In nephron segments other than the thick ascending limb, loop diuretics have no quantitative importance with respect to their saluretic and diuretic activities. Loop diuretics also reduce Ca++ and Mg++ reabsorption in the thick ascending limb in a way which is still not clear. Furthermore, these drugs increase the urinary K+ excretion by enhancing distal tubular K+ secretion and reducing K+ reabsorption in the loop of Henle. Finally, by reduction of active NaCl transport, loop diuretics drastically reduce the substrate requirement and oxygen dependence of the thick ascending limb cells. This renders these cells, which are characterised by high transport rates and only limited substrate reserves, less vulnerable in acute renal failure.

Modulation of host cell metabolism by Trypanosoma cruzi

Chagas disease, caused by the hemoflagellate Trypanosoma cruzi, is a complicated and devastating disease. It is hypothesized that an important target of infection may be the endothelial cell and that both the acute and chronic forms of the disease involve abnormalities in the microcirculation. Stephen Morris and colleagues suggest that endothelial cell dysfunction occurs as a consequence of amastigote-associated interference in host cell metabolism.

Light microscopic diagnosis of human microsporidiosis and variable response to octreotide

Microsporida are protozoan parasites that have recently been identified as a cause of human disease in immunocompromised patients. Because of their small size, they have been recognized primarily by electron microscopy. This has limited the study of their prevalence, incidence, and association with large-volume diarrhea. The present report describes two cases of Enterocytozoon bieneusi infection of the small intestine in patients with intractable diarrhea in whom the diagnosis was made by light microscopy and confirmed by electron microscopy. Both patients were treated with octreotide, and one had a good response.

Disseminated strongyloidiasis with central nervous system involvement diagnosed antemortem in a patient with acquired immunodeficiency syndrome and Burkitts lymphoma

A 45-year-old man presented with central nervous system involvement as the initial manifestation of disseminated infection with Strongyloides stercoralis. Several concurrent clinical factors contributed to this event, all related to the patient's immunosuppression, including high-grade lymphoma, corticosteroid therapy, and acquired immunodeficiency syndrome. This is only the third case of CNS involvement in disseminated strongyloidiasis diagnosed antemortem.

Pathophysiological insights into the cardiomyopathy of Chagas' disease

The evidence gained from both human and animal studies of chronic chagasic cardiomyopathy suggests that the disease occurs as a consequence of several discrete and progressive pathophysiological processes occurring after infection, the ultimate expression of which depends on a host of unidentified factors. Collectively, the infection-associated events compromise microvasculature function and result in hypoperfusion, with consequences indistinguishable from those observed in other, nonparasitological cardiomyopathic diseases secondary to hypoperfusion. Therefore, chronic chagasic cardiomyopathy may share similar pathophysiological abnormalities with other chronic congestive cardiomyopathic states.

Extracellular matrix derived from Trypanosoma cruzi infected endothelial cells directs phenotypic expression

Infection of confluent human umbilical vein endothelial cells by the parasite Trypanosoma cruzi results in the appearance of an altered heparan sulfate proteoglycan (HSPG) isolated from the extracellular matrix of infected endothelial cells (ECMi). HSPG from ECMi differed from HSPG obtained from the extracellular matrix of uninfected endothelial cells (ECMu) by virtue of an 8-10-fold increase in sulfation and a different elution pattern using DEAE Sepharose chromatography. Analysis of the HSPG that binds to acidic fibroblast growth factor (aFGF) revealed that infection increased the proportion of HSPG that binds to aFGF by 35%. Heparitinase and alkaline borohydride treatment of aFGF-binding HSPG and chromatographic resolution on Sepharose CL4B column revealed an infection-associated 10-fold increase in sulfation of the GAG side chain with no significant change in the migration of the core protein. In addition, the aFGF binding HSPG isolated from ECMi demonstrated a markedly attenuated synergistic mitogenic activity with aFGF in a cell proliferation assay. All of the infection associated changes in HSPG could be demonstrated in HSPG obtained from uninfected endothelial cell cultures grown on ECMi. Hence, the ECMi is associated with signals capable of modulating the ECM associated metabolism of uninfected endothelial cells. This facility of ECMi was also shown to extend to patterns of Gs protein synthesis as revealed by Western blot analysis. The observation that the ECM produced by infected endothelial cells can direct the synthetic patterns of uninfected endothelial cells in a manner uniquely observed in infected endothelial cells suggests a plausible pathway by which infection of only a few cells can ultimately result in the coordinate responses of neighboring uninfected cells.

Effects of parathyroid hormone and calcitonin on Na+, Cl-, K+, Mg2+ and Ca2+ transport in cortical and medullary thick ascending limbs of mouse kidney

The effect of parathyroid hormone (PTH) on transepithelial Na+, Cl-, K+, Ca2+ and Mg2+ transport was investigated in isolated perfused cortical thick ascending limbs (cTAL) and that of human calcitonin (hCT) was tested in both cortical and medullary thick ascending limbs (mTAL) of the mouse nephron. The transepithelial ion net fluxes (Jx) were determined by electron probe analysis of the perfused and collected fluids. Simultaneously, the transepithelial voltage (PDte) and resistance (Rte) were recorded. In cTAL segments, PTH and hCT significantly stimulated the reabsorption of Na+, Cl-, Ca2+ and Mg2+, hCT generated a net K+ secretion towards the lumen and PTH tended to exert the same effect. Neither PDte nor Rte were significantly altered by either PTH or hCT. However, in the post-experimental period a significant decrease in PDte was noted. Time control experiments carried out under similar conditions revealed a significant decrease in PDte with time, which could have masked the hormonal response. In mTAL segments, Mg2+ and Ca2+ transport was close to zero, hCT did not exert any detectable effect on either PDte or Jcl-, JNa+, JK+, JMg2+ and JCa2+ in these segments. In conclusion, our data demonstrate that PTH and hCT stimulate NaCl reabsorption as well as Mg2+ and Ca2+ reabsorption in the cTAL segment of the mouse. These data are in agreement with and extend data obtained in vivo in the rat.

Enhanced platelet adherence and aggregation in Chagas' disease: a potential pathogenic mechanism for cardiomyopathy

Spasm and thrombosis of the coronary microcirculation has been implicated in the pathogenesis of the cardiomyopathy of Chagas' disease. We demonstrate that increases in platelet adherence and aggregation accompany Trypanosoma cruzi infection and may contribute to the observed microvascular pathology. Scanning electron microscopy and radiolabeled platelets studies revealed that platelet adherence to T. cruzi-infected human endothelial cells was significantly increased when compared to controls (P = 0.024). In in vitro experiments, we determined the influence of infection on prostacyclin production, a marker of endothelial cell perturbation. The basal levels of 6-keto-prostaglandin F1 alpha was significantly greater in the supernatant of infected endothelial cells than in those of uninfected endothelial cells (P less than 0.05). The influence of infection was assessed on platelet aggregation at days 5 and 12 post-infection in A/J mice. Platelets from T. cruzi-infected mice were 2-6-fold more sensitive to aggregation induced by adenosine diphosphate and sodium arachidonate than controls. Thromboxane B2 levels in the plasma of infected mice were greater than controls. These data support the hypothesis that heightened platelet reactivity and endothelial cell dysfunction are associated with acute Chagas' disease and may cause coronary microvascular spasm and/or occlusion.

Effects of antidiuretic hormone, parathyroid hormone and glucagon on transepithelial voltage and resistance of the cortical and medullary thick ascending limb of Henle's loop of the mouse nephron

The effect of antidiuretic hormone (arginine vasopressin, AVP, 10(-10) mol.l-1), parathyroid hormone (PTH, 10(-8) mol.l-1) and glucagon (10(-8) mol.l-1) on the transepithelial potential difference (PDte) and the transepithelial resistance (Rte) were tested in in vitro perfused cortical (cTAL) and medullary (mTAL) thick ascending limbs of Henle's loop of the mouse nephron. When compared with mTAL segments (PDte: 8.5 +/- 0.4 mV, n = 16), cTAL segments displayed a high PDte of 15.7 +/- 0.9 mV (n = 11) at the beginning of perfusion experiments which reached a value of 9.4 +/- 0.6 mV (n = 11) after 38 +/- 4 min perfusion. Simultaneously Rte increased significantly from 24 +/- 3 to 28 +/- 1 omega cm2 (n = 11). When PTH, AVP or glucagon were added to the bath solution, PDte increased with PTH from 10.3 +/- 0.8 to 15.2 +/- 0.8 mV (n = 13), with AVP from 10.2 +/- 0.5 to 15.0 +/- 0.7 mV (n = 24) and with glucagon from 11.3 +/- 1.9 to 15.3 +/- 2.1 mV (n = 8). At the same time Rte decreased from 30 +/- 3 to 23 +/- 2 omega cm2, from 28 +/- 1 to 23 +/- 1 omega cm2 and from 23 +/- 2 to 18 +/- 2 omega cm2, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)