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Biomedical subjects

M Wittner

Publications and source records attributed to M Wittner.

At least 19 recordsLinked to original sources
PubMed2006

Early rehabilitation model shows positive effects on neural degeneration and recovery from neuromotor deficits following traumatic brain injury.

This study used an experimental early rehabilitation model combining an enriched environment, multisensory (visual, acoustic and olfactory) stimulation and motor training after traumatic brain injury (via fluid-percussion model) to simulate early multisensory rehabilitation. This therapy will be used by brain injured patients to improve neural plasticity and to restore brain integration functions. Motor dysfunction was evaluated using a composite neuroscore test. Direct structural effects of traumatic brain injury were examined using Fluoro-Jade staining, which allows identification of degenerating neural cell bodies and processes. Animals in the rehabilitation model group performed significantly better when tested for neuromotor function than the animals in standard housing in the 7-day and 15-day interval after injury (7d: p=0.005; 15d: p<0.05). Statistical analysis revealed significantly lower numbers of Fluoro-Jade positive cells (degenerating neurons) in the rehabilitation model group (n=5: mean 13.4) compared to the standard housing group (n=6: mean 123.8) (p<0.005). It appears that the housing of animals in the rehabilitation model led to a clear functional increase in neuromotor functions and to reduced neural loss compared with the animal group in standard housing.

Animals↗
PubMed2005

Transient hypobaric hypoxia improves spatial orientation in young rats.

To achieve a better understanding of learning and declarative memory under mild transient stress, we investigated the effect of brief hypobaric hypoxia on spatial orientation in rats. Young male Wistar rats aged 30 days were exposed for 60 min to hypobaric hypoxia, simulating an altitude of 7,000 m (23,000 ft) either shortly prior to attempting or after mastering an allothetic navigation task in the Morris water maze with a submerged platform. The post-hypoxic group performed significantly better in the navigation task than the control animals (the mean difference in escape latencies was 11 seconds; P=0.0033, two-way ANOVA with repeated measures, group x session). The experimental group also achieved a remarkably higher search efficiency (calculated as a percentage of successful trials per session), especially during the first four days following hypoxic stress (P=0.0018). During the subsequent training, the post-hypoxic group performed better than the control animals, whilst the efficiency levels of both groups progressively converged. Spatial memory retention and recall of well-trained rats were not affected by the transient hypobaric hypoxia. These results indicate that brief hypobaric hypoxia enhances rats' spatial orientation. Our findings are consistent with several studies, which also suggested that mild transient stress improves learning.

Adaptation, Physiological↗
PubMed2001

The role of endothelin in the pathogenesis of Chagas' disease.

Infection with Trypanosoma cruzi causes a generalised vasculitis of several vascular beds. This vasculopathy is manifested by vasospasm, reduced blood flow, focal ischaemia, platelet thrombi, increased platelet aggregation and elevated plasma levels of thromboxane A(2) and endothelin-1. In the myocardium of infected mice, myonecrosis and a vasculitis of the aorta, coronary artery, smaller myocardial vessels and the endocardial endothelium are observed. Immunohistochemistry studies employing anti-endothelin-1 antibody revealed increased expression of endothelin-1, most intense in the endocardial and vascular endothelium. Elevated levels of mRNA for prepro endothelin-1, endothelin converting enzyme and endothelin-1 were observed in the infected myocardium. When T. cruzi-infected mice were treated with phosphoramidon, an inhibitor of endothelin converting enzyme, there was a decrease in heart size and severity of pathology. Mitogen-activated protein kinases and the transcription factor activator-protein-1 regulate the expression of endothelin-1. Therefore, we examined the activation of mitogen-activated protein kinases in the myocardium by T. cruzi. Western blot demonstrated an extracellular signal regulated kinase. In addition, the activator-protein-1 DNA binding activity, as determined by electrophoretic mobility shift assay, was increased. Increased expression of cyclins A and cyclin D1 was observed in the myocardium, and immunohistochemistry studies revealed that interstitial cells and vascular and endocardial endothelial cells stained intensely with antibodies to these cyclins. These data demonstrate that T. cruzi infection of the myocardium activates extracellular signal regulated kinase, activator-protein-1, endothelin-1, and cyclins. The activation of these pathways is likely to contribute to the pathogenesis of chagasic heart disease. These experimental observations suggest that the vasculature plays a role in the pathogenesis of chagasic cardiomyopathy. Additionally, the identification of these pathways provides possible targets for therapeutic interventions to ameliorate or prevent the development of cardiomyopathy during T. cruzi infection.

Animals↗
PubMed2001

Fas-FasL interaction modulates nitric oxide production in Trypanosoma cruzi-infected mice.

During acute Trypanosoma cruzi infection in mice, many leucocytes undergo apoptosis. Although apoptosis has been ascribed to increased levels of nitric oxide (NO) and Fas-FasL interaction, the importance of this phenomenon in modulating the host response against T. cruzi is unknown. Herein, the role of NO- and Fas-FasL-induced apoptosis in modulating the immune response to T. cruzi was evaluated using mice deficient in Fas expression (MRL/MpJ-Fas lpr) and inducible nitric oxide synthase (iNOS) knockout mice (iNOS-/-). The results showed that besides decreasing apoptosis induction after infection, impairment of the Fas-FasL interaction resulted in decreased NO production, as a consequence of enhanced T helper 2 (Th2) cytokine production. Differently, blockage of NO-induced apoptosis resulted in uncontrolled cytokine production, rather than a biased Th2 cytokine pattern. Together, these results suggested that Fas and FasL-induced apoptosis could be implied in modulation of the immune response against T. cruzi by interfering with cytokine and NO production during the acute phase of the infection.

Acute Disease↗
PubMed2001

Evidence supporting a role for KCl cotransporter in the thick ascending limb of Henle's loop.

BACKGROUND: A basolateral Ba(2+)-sensitive KCl cotransporter has previously been proposed as participating in basolateral K+ recycling and transepithelial NaCl reabsorption in the thick ascending limb of Henle's loop (TAL). The aim of the present study was to answer the question as to whether this cotransporter plays a role in transepithelial K+ reabsorption and whether dietary Mg(2+) deficiency, known to regulate the KCl cotransporter in erythrocytes, also regulates KCl transport in the TAL. METHODS: The effects of a low-Mg(2+) diet were investigated on urinary and plasma K+ concentration in control mice and Mg(2+)-deficient mice. Transepithelial Na+, Cl- and K+ net fluxes (J(Na), J(Cl), J(K)), determined in isolated perfused TALs with electron probe analysis or cation-exchange high-performance liquid chromatography (HPLC) and electrophysiological parameters (V(te), R(te)), were measured in both animal groups. Expression of transcripts for the KCl cotransporter and its possible regulation by low-Mg(2+) were studied by RT-PCR in microdissected mouse cortical TAL (CTAL) and medullary TAL (MTAL) segments. RESULTS: In isolated perfused CTALs, basolateral Ba(2+) and amiloride induced a large K+ net secretion towards the tubular lumen, paralleled by a 50% decrease in transepithelial NaCl reabsorption. KCC1 transcripts were found in the mouse CTAL and MTAL. A low-Mg(2+) diet led to diminished urinary K+ excretion, lowered plasma K+ concentration and up-regulation of KCC1 transcripts in the TAL. For low-Mg(2+) diet, this upregulation was associated with increased transepithelial K+ reabsorption in the in vitro-perfused CTAL. CONCLUSIONS: Our study provides evidence that the KCl cotransporter, which is functionally expressed in the TAL, plays an important role in transepithelial K+ reabsorption. Direct inhibition of this transporter by Ba(2+) and its indirect inhibition by amiloride lead to a strong transepithelial K+ secretion and diminished NaCl reabsorption in the TAL. Up-regulation of KCC1 mRNA by dietary Mg(2+) restriction is associated with an increased K+ reabsorption in the in vitro perfused CTAL.

Acetonitriles↗
PubMed2001

Initial characterization of CST1, a Toxoplasma gondii cyst wall glycoprotein.

Toxoplasma gondii is an important protozoan pathogen of humans that can cause encephalitis in immunocompromised individuals such as those with AIDS. This encephalitis is due to reactivation of latent infection in T. gondii-seropositive patients. Latent organisms survive within tissue cysts, which are specialized parasitophorous vacuoles containing bradyzoites. The cyst wall of this structure is produced by modification of the parasitophorous vacuole by the parasite and is important in cyst survival. The components of the cyst wall have been poorly characterized. By using immunofluorescence and immunoelectron microscopy, we have identified a monoclonal antibody (MAb 93.18) that reacts with the cyst wall. This antibody recognizes a 116-kDa glycoprotein, which we have termed CST1, containing sugar residues that bind Dolichos biflorans lectin (DBA). CST1 is distinct from T. gondii antigen labeled with succinyl Triticum vulgare lectin (S-WGA) and represents the major DBA-binding component in T. gondii. The carbohydrate components of the tissue cyst, such as CST1, are probably important in both providing stability and facilitating persistence in its host. As is seen in the carbohydrate capsules of fungi, glycoproteins in the T. gondii cyst wall may protect cysts from the immune response of the host. Further characterization of the formation of the cyst wall and its components should lead to insights into the mechanism of tissue cyst persistence and may suggest novel therapeutic approaches to eliminate tissue cysts of this organism.

Animals↗
PubMed2001

Chronic exposure to vasopressin upregulates ENaC and sodium transport in the rat renal collecting duct and lung.

Vasopressin is known to acutely stimulate sodium transport in the renal collecting duct. We investigated the long-term regulation by vasopressin of the epithelial sodium channel (ENaC) in the rat kidney. Five-day infusion of dDAVP (a V(2) receptor agonist) to Brattleboro rats lacking vasopressin induced a marked increase in beta- and gamma-subunit ENaC mRNA levels in the renal cortex (beta, 85%; gamma, 100%), with no change in alpha-ENaC mRNA. Expression of beta- and gamma-ENaC mRNAs was also enhanced in lung (beta, 49%; gamma, 33%) but not in distal colon (an organ devoid of V(2) receptors). Similar results were obtained in Sprague Dawley rats after either partial water restriction or dDAVP infusion for 5 days. Transepithelial voltage and transepithelial sodium and water net fluxes were measured in isolated perfused cortical collecting ducts of Brattleboro rats. Acute addition of 2x10(-10) mol/L dDAVP to the bath increased sodium and water fluxes in the same proportion, and to a far greater extent in dDAVP-infused than in control Brattleboro rats (change in Na(+) net flux, 337+/-30 versus 49+/-11 pmol. min(-1). mm(-1), respectively; P<0.001). These effects were abolished by amiloride. Extrarenal water losses, partly originating from the lung, were reduced by high plasma vasopressin level. This study shows that vasopressin increases sodium transport in the renal collecting duct and probably in the lung, through a differential transcriptional regulation of ENaC subunits. This effect is followed by isoosmotic water reabsorption and likely contributes to the process of water conservation. It could lead to less efficient sodium excretion, however, and thus participate in some forms of salt-sensitive hypertension.

Animals↗
PubMed2000

Cellular adaptation of the mouse cortical thick ascending limb of Henle's loop (CTAL) to dietary magnesium restriction: enhanced transepithelial Mg2+ and Ca2+ transport.

Mice aged 4 or 8 weeks were fed with a low-Mg2+ diet for 1, 2, 3 or 4 days. After 1 day of diet, the urinary excretion of Mg2+ and Ca2+ was strongly reduced in both animal groups (4 and 8 weeks), accompanied by a significant fall in plasma Mg2+ concentration and an increase in urinary volume. This profile persisted after 2, 3 or 4 days of dietary Mg2+ restriction. After 1 day of diet, transepithelial ion net fluxes of Na+, Cl-, Ca2+ and Mg2+ (JNa' JCI, JCl, JMg) measured in vitro from isolated perfused cortical thick ascending limbs (CTALs) of these animals remained unchanged. After 2 days of diet, measurements of J(Ca) and J(Mg) in isolated perfused CTALs showed that transepithelial Mg2+ and Ca2+ reabsorption were enhanced in CTALs from Mg(2+)-depleted, 8-week-old animals, whereas transepithelial Mg2+ and Ca2+ transport were not altered in 4-week-old mice. JNa and JCl and the transepithelial potential (PDte) were not modified in CTALs from either animal group. Our results suggest that a low-Mg2+ diet leads to urinary retention of Mg2+ and Ca2+ which is most likely due to increased Mg2+ and Ca2+ transport in the CTAL. Furthermore, in response to dietary Mg2+ restriction, the reabsorption of divalent cations in the CTAL of adult, but not of young, mice undergoes cellular adaptation.

Adaptation, Physiological↗
PubMed2000

Trypanosoma cruzi infection (Chagas' disease) of mice causes activation of the mitogen-activated protein kinase cascade and expression of endothelin-1 in the myocardium.

Chagas' disease, caused by the parasite Trypanosoma cruzi, is an important cause of heart disease. Previous studies from this laboratory revealed that microvascular spasm and myocardial ischemia were observed in infected mice. Infection of endothelial cells with this parasite increased the synthesis of biologically active endothelin-1 (ET-1). Therefore. in the myocardium of T. cruzi-infected mice, we examined ET-1 expression and the p42/44-mitogen activated protein kinase (MAPK)-AP-1 pathway that regulates the expression of ET-1. There was parasitism and myonecrosis in the myocardium of infected C57BL/6 mice. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed elevated mRNA expression of transcription factor AP-1 (c-jun and c-fos) and increased AP-1 DNA binding activity as determined by electrophoretic mobility shift assay (EMSA). Western blot analysis demonstrated an increase in the phosphorylated forms of extracellular signal-regulated kinase (ERK1/2). ET-1 mRNA was upregulated in the myocardium of infected mice. Immunohistochemical and immunoelectron microscopy using anti-ET-1 antibody detected increased expression in cardiac myocytes and endothelium of these mice. These data suggest that ET-1 contributes to chagasic cardiomyopathy and that the mechanism of the increased expression of ET-1 is a result of the activation of the MAPK pathway by T. cruzi infection.

Animals↗
PubMed2000

Identification of novel serine/threonine protein phosphatases in Trypanosoma cruzi: a potential role in control of cytokinesis and morphology.

We cloned two novel Trypanosoma cruzi proteins by using degenerate oligonucleotide primers prepared against conserved domains in mammalian serine/threonine protein phosphatases 1, 2A, and 2B. The isolated genes encoded proteins of 323 and 330 amino acids, respectively, that were more homologous to the catalytic subunit of human protein phosphatase 1 than to those of human protein phosphatase 2A or 2B. The proteins encoded by these genes have been tentatively designated TcPP1alpha and TcPP1beta. Northern blot analysis revealed the presence of a major 2.3-kb mRNA transcript hybridizing to each gene in both the epimastigote and metacyclic trypomastigote developmental stages. Southern blot analysis suggests that each protein phosphatase 1 gene is present as a single copy in the T. cruzi genome. The complete coding region for TcPP1beta was expressed in Escherichia coli by using a vector, pTACTAC, with the trp-lac hybrid promoter. The recombinant protein from the TcPP1beta construct displayed phosphatase activity toward phosphorylase a, and this activity was preferentially inhibited by calyculin A (50% inhibitory concentration [IC(50)], approximately 2 nM) over okadaic acid (IC(50), approximately 100 nM). Calyculin A, but not okadaic acid, had profound effects on the in vitro replication and morphology of T. cruzi epimastigotes. Low concentrations of calyculin A (1 to 10 nM) caused growth arrest. Electron microscopic studies of the calyculin A-treated epimastigotes revealed that the organisms underwent duplication of organelles, including the flagellum, kinetoplast, and nucleus, but were incapable of completing cell division. At concentrations higher than 10 nM, or upon prolonged incubation at lower concentrations, the epimastigotes lost their characteristic elongated spindle shape and had a more rounded morphology. Okadaic acid at concentrations up to 1 microM did not result in growth arrest or morphological alterations to T. cruzi epimastigotes. Calyculin A, but not okadaic acid, was also a potent inhibitor of the dephosphorylation of (32)P-labeled phosphorylase a by T. cruzi epimastigotes and metacyclic trypomastigote extracts. These inhibitor studies suggest that in T. cruzi, type 1 protein phosphatases are important for the completion of cell division and for the maintenance of cell shape.

Amino Acid Sequence↗
PubMed1999

Localization and activity of nitric oxide synthases in the gastrointestinal tract of Trypanosoma cruzi-infected mice.

Chagas' disease, caused by the protozoan parasite, Trypanosoma cruzi, is associated with gastrointestinal abnormalities. Since nitric oxide (NO) has been shown to be a factor influencing intestinal function we evaluated the distributions and activities of the NO synthase (NOS) isoforms, in the gut of mice infected with T. cruzi. Ca2+-dependent (NOS1/NOS3) activity was decreased, whereas Ca2+-independent (NOS2) activity was increased in infected mice. NOS2-immunoreactivity was demonstrated in cells within the muscle layers and epithelium in infected mice and NOS1 immunoreactivity was seen in nerve structures. These data indicate that alterations in the NO-system may be important in the pathogenesis of the gastrointestinal manifestations in Chagas' disease.

Animals↗
PubMed1999

A cluster of transfusion-associated babesiosis cases traced to a single asymptomatic donor.

CONTEXT: The risk of acquiring babesiosis by blood transfusion is largely unknown since in areas where it is endemic it is often an asymptomatic infection. OBJECTIVE: To investigate and treat a cluster of blood transfusion-associated babesiosis cases. DESIGN: Case series and epidemiologic investigation. SETTING: Urban inner-city hospital. PATIENTS: Six persons who received Babesia microti-infected blood components from a donor. MAIN OUTCOME MEASURE: Diagnosis and successful therapy of babesiosis following transfusion. RESULTS: Six individuals (1 adult, 1 child, and 4 neonates) were exposed to products from a single blood donation by an asymptomatic Babesia-infected donor. Three of the 6 exposed patients became parasitemic. Polymerase chain reaction testing, animal inoculation studies, and indirect immunofluorescent antibody testing were used to confirm the presence of Babesia microti in the donor's blood and to establish the presence of infection in 3 of the 6 recipients. The 3 infected recipients and 1 additional recipient were treated without incident. CONCLUSION: Physicians should consider babesiosis in the differential diagnosis of a febrile hemolytic disorder after blood transfusion. Prompt diagnosis is important since babesiosis is responsive to antibiotic therapy and, untreated, can be a fatal disease in certain risk groups.

Aged↗