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Biomedical subjects

J Reinhard

Publications and source records attributed to J Reinhard.

33 records · Page 2Linked to original sources
PubMed1999

Nongastric H+,K+-ATPase: cell biologic and functional properties.

Several members of the H+,K+-ATPase family of ion pumps participate in renal K transport. This class of P-type ATPases includes the gastric H+,K+-ATPase as well as a number of nongastric H+,K+-ATPase isoforms. Physiological studies suggest that these enzymes operate predominantly at the apical surfaces of tubule epithelial cells. Although much has been learned about the pattern of H+,K+-ATPase isoform expression and its response to stress, the functional and cell biologic attributes of these pumps remain largely unelucidated. We have studied the properties of renal H+,K+-ATPases both in vitro and in situ. Our analysis of ion fluxes driven by a nongastric H+,K+-ATPase isoform suggests that it exchanges Na (rather than H) for K under normal circumstances. Thus, the individual H+,K+-ATPase isoforms may make diverse contributions to renal cation transport. We find that the activities of renal H+,K+-ATPases in situ are regulated by endocytosis, which is mediated by an endocytosis signal in the cytoplasmic tail of the gastric H+,K+-ATPase beta-subunit. Transgenic mice expressing a version of this protein in which the signal has been disabled show constitutively active renal K resorption. The identities of the H+,K+-ATPase isoforms that are normally subject to endocytic regulation and the nature of the participating epithelial cell machinery have yet to be established.

Animals↗
PubMed1998

Suppression of inflammatory neurotoxins by highly active antiretroviral therapy in human immunodeficiency virus-associated dementia.

A human immunodeficiency virus type 1 (HIV)-seropositive, antiretroviral-naive patient presented with significant cognitive dysfunction. Neuropsychologic, neuroradiologic, immunologic, and virologic studies confirmed HIV-associated dementia (HAD). After 12 weeks of highly active antiretroviral therapy (HAART) with ibuprofen, dramatic improvements were demonstrated in neurologic function and were sustained for > 1 year. HIV-1 RNA in cerebrospinal fluid (CSF) decreased from 10(5) to 10(4) copies/mL after 4 weeks. After 20 weeks of therapy, plasma viremia decreased from 10(6) copies/mL to undetectable (< 96 copies/mL). Assays of neurotoxins (tumor necrosis factor-alpha, quinolinic acid, and nitric oxide) in plasma and CSF were considerably elevated at presentation and significantly decreased after therapy. Baseline plasma and CSF demonstrated neurotoxic activities in vitro, which also reduced markedly. These data, taken together, support the notion that HAD is a reversible metabolic encephalopathy fueled by viral replication. HAART used with nonsteroidal antiinflammatory agents leads to the suppression of inflammatory neurotoxins and can markedly improve neurologic function in HAD.

AIDS Dementia Complex↗
PubMed1998

The vertical field border in hemianopia and its significance for fixation and reading.

PURPOSE: The existence of macular sparing, a central seeing area of several degrees within the hemianopic field defect, has been controversial for a long time, because inaccurate fixation during perimetry can produce ambiguous results. The visual field border in hemianopia was studied to examine whether a vertical strip of hemifield overlap described in monkeys exists in humans and whether additional macular sparing could be found. METHODS: Vertical triplets of dots were scanned on the retinas of eight patients (13 eyes) with hemianopia at different eccentricity from the vertical meridian during strict simultaneous fixation control using a scanning laser ophthalmoscope (SLO). Additionally, eye movements were measured by SLO and by an infrared reflection system while subjects read texts. RESULTS: Macular sparing of 2 degrees to 5 degrees and absence of sparing were observed. The presence and amount of sparing influenced fixation behavior, reading performance, and reliability of conventional perimetry. The smaller the macular sparing, the less stable the fixation. In the absence of sparing, either central unstable fixation with frequent saccades toward the hemianopic side or eccentric fixation occurred, resulting in a shift of the field defect toward the hemianopic side. A vertical strip of sometimes partial perception was found in 12 eyes at 0.5 degrees from the midline. CONCLUSIONS: Macular sparing and a slight vertical strip of hemifield overlap exists in humans. Adaptive strategies like eccentric fixation and predictive saccades improve reading performance and can augment rehabilitation.

Adult↗
PubMed1997

The rat myosin myr 5 is a GTPase-activating protein for Rho in vivo: essential role of arginine 1695.

myr 5 is an unconventional myosin (class IX) from rat that contains a Rho-family GTPase-activating protein (GAP) domain. Herein we addressed the specificity of the myr 5 GAP activity, the molecular mechanism by which GAPs activate GTP hydrolysis, the consequences of myr 5 overexpression in living cells, and its subcellular localization. The myr 5 GAP activity exhibits a high specificity for Rho. To achieve similar rates of GTPase activation for RhoA, Cdc42Hs, and Rac1, a 100-fold or 1000-fold higher concentration of recombinant myr 5 GAP domain was needed for Cdc42Hs or Rac1, respectively, as compared with RhoA. Cell lysates from Sf9 insect cells infected with recombinant baculovirus encoding myr 5 exhibited increased GAP activity for RhoA but not for Cdc42Hs or Rac1. Analysis of Rho-family GAP domain sequences for conserved arginine residues that might contribute to accelerate GTP hydrolysis revealed a single conserved arginine residue. Mutation of the corresponding arginine residue in the myr 5 GAP domain to a methionine (M1695) virtually abolished Rho-GAP activity. Expression of myr 5 in Sf9 insect cells induced the formation of numerous long thin processes containing occasional varicosities. Such morphological changes were dependent on the myr 5 Rho-GAP activity, because they were induced by expression the myr 5 tail or just the myr 5 Rho-GAP domain but not by expressing the myr 5 myosin domain. Expression of myr 5 in mammalian normal rat kidney (NRK) or HtTA-1 HeLa cells induced a loss of actin stress fibers and focal contacts with concomitant morphological changes and rounding up of the cells. Similar morphological changes were observed in HtTA-1 HeLa cells expressing just the myr 5 Rho-GAP domain but not in cells expressing myr 5 M1695. These morphological changes induced by myr 5 were inhibited by coexpression of RhoV14, which is defective in GTP hydrolysis, but not by RhoI117. myr 5 was localized in dynamic regions of the cell periphery, in the perinuclear region in the Golgi area, along stress fibers, and in the cytosol. These results demonstrate that myr 5 has in vitro and in vivo Rho-GAP activity. No evidence for a Rho effector function of the myr 5 myosin domain was obtained.

Actins↗
PubMed1996

Cloning and characterization of myr 6, an unconventional myosin of the dilute/myosin-V family.

We have isolated cDNAs encoding a second member of the dilute (myosin-V) unconventional myosin family in vertebrates, myr 6 (myosin from rat 6). Expression of myr 6 transcripts in the brain is much more limited than is the expression of dilute, with highest levels observed in choroid plexus and components of the limbic system. We have mapped the myr 6 locus to mouse chromosome 18 using an interspecific backcross. The 3' portion of the myr 6 cDNA sequence from rat is nearly identical to that of a previously published putative glutamic acid decarboxylase from mouse [Huang, W.M., Reed-Fourquet, L., Wu, E. & Wu, J.Y. (1990) Proc. Natl. Acad. Sci. USA 87, 8491-8495].

Amino Acid Sequence↗
PubMed1996

Human immunodeficiency virus encephalitis in SCID mice.

The human immunodeficiency virus (HIV) is neuroinvasive and commonly causes cognitive and motor deficits during the later stages of viral infection. (referred to as HIV dementia). The mechanism(s) for disease revolves around secretory products produced from immune-activated brain macrophages/microglia. Recently, we developed an animal model system for HIV dementia that contains xenografts of HIV-1-infected cells inoculated into brains of mice with severe combined immunodeficiency (SCID). This animal system was used to quantitatively evaluate HIV-induced neuropathology. Xenografts of HIV-1-infected human monocytes (placed into the putamen and cortex of SCID mice) remained viable for 5 weeks. HIV-1 p24 antigen expression in mouse brain was persistent. Progressive inflammatory responses (including astrogliosis and cytokine production), which began at 3 days, peaked at day 12. The range of astrocyte proliferative reactions exceeded the inoculation site by > 1000 microns. Brains with virus-infected monocytes showed a > or = 1.6-fold increase in glial fibrillary acidic protein (staining distribution and intensity) as compared with similarly inoculated brains with uninfected control monocytes. These findings paralleled the accumulation and activation of murine microglia (increased branching of cell processes, formation of microglial nodules, interleukin (IL)-1 beta and IL-6 expression). An inflammatory reaction of human monocytes (as defined by HLA-DR, IL-1 beta, IL-6, and tumor necrosis factor-alpha expression) and neuronal injury (apoptosis) also developed after virus-infected monocyte xenograft placement into mouse brain tissue. These data, taken together, demonstrate that this SCID mouse model of HIV-1 neuropathogenesis can reproduce key aspects of disease (virus-infected macrophages, astrocytosis, microglial activation, and neuronal damage). This model may serve as an important means for therapeutic development directed toward improving mental function in HIV-infected subjects with cognitive and motor dysfunction.

AIDS Dementia Complex↗
PubMed1995

A novel type of myosin implicated in signalling by rho family GTPases.

A novel widely expressed type of myosin (fifth unconventional myosin from rat: myr 5) from rat tissues, defining a ninth class of myosins, was identified. The predicted amino acid sequence of myr 5 exhibits several features not found previously in myosins. The myosin head domain contains a unique N-terminal extension and an insertion of 120 amino acids at a postulated myosin-actin contact site. Nevertheless, myr 5 is able to bind actin filaments in an ATP-regulated manner. The head domain is followed by four putative light chain binding sites. The tail domain of myr 5 contains a region which coordinates two atoms of zinc followed by a region that stimulates GTP hydrolysis of members of the ras-related rho subfamily of small G-proteins. Myr 5 therefore provides the first direct link between rho GTPases which have been implicated in the regulation of actin organization and the actin cytoskeleton. It is also the first unconventional myosin for which a tail binding partner(s), namely members of the rho family, has been identified.

Actins↗
PubMed1995

A novel mammalian myosin I from rat with an SH3 domain localizes to Con A-inducible, F-actin-rich structures at cell-cell contacts.

In an effort to determine diversity and function of mammalian myosin I molecules, we report here the cloning and characterization of myr 3 (third unconventional myosin from rat), a novel mammalian myosin I from rat tissues that is related to myosin I molecules from protozoa. Like the protozoan myosin I molecules, myr 3 consists of a myosin head domain, a single light chain binding motif, and a tail region that includes a COOH-terminal SH3 domain. However, myr 3 lacks the regulatory phosphorylation site present in the head domain of protozoan myosin I molecules. Evidence was obtained that the COOH terminus of the tail domain is involved in regulating F-actin binding activity of the NH2-terminal head domain. The light chain of myr 3 was identified as the Ca(2+)-binding protein calmodulin. Northern blot and immunoblot analyses revealed that myr 3 is expressed in many tissues and cell lines. Immunofluorescence studies with anti-myr 3 antibodies in NRK cells demonstrated that myr 3 is localized in the cytoplasm and in elongated structures at regions of cell-cell contact. These elongated structures contained F-actin and alpha-actinin but were devoid of vinculin. Incubation of NRK cells with Con A stimulated the formation of myr 3-containing structures along cell-cell contacts. These results suggest for myr 3 a function mediated by cell-cell contact.

Actins↗
PubMed1995

Localization of the rat myosin I molecules myr 1 and myr 2 and in vivo targeting of their tail domains.

Myr 1 is a widely distributed mammalian myosin I molecule related to brush border myosin 1. A second widely distributed myosin I molecule similar to myr 1 and brush border myosin I, called myr 2, has now been identified. Specific antibodies and expression of epitope-tagged molecules were used to determine the subcellular localization of myr 1 and myr 2 in NRK cells. Myr 1 was detected at the plasma membrane and was particularly enriched in cell protrusions like lamellipodia, membrane ruffles and filopodia. In dividing cells myr 1 localized to the cleavage furrow. Myr 2 was localized in a discrete punctate pattern in resting cells and in cells undergoing cytokinesis. In subcellular fractionation experiments myr 1 and myr 2 were both partly soluble and partly associated with smooth membranes of medium density. The tail domains of myosin I molecules have been proposed to interact with a receptor and thereby determine the subcellular localization. To test this hypothesis we expressed the tail domains of myr 1 and myr 2 that lack the F-actin-binding myosin head domain in NRK cells. These tail domains also partly copurified with smooth membranes of medium density and immunolocalized similar to the respective endogenous myosin I; however, they exhibited a lower affinity for membranes and an increased diffuse cytosolic localization. These results suggest that the tail domains of myr 1 and myr 2 are sufficient for subcellular targeting but that their head domains also contribute significantly to maintaining a proper subcellular localization.

Actins↗
PubMed1993

Alpha interferon and hepatitis B and C. An integrated approach using practice guidelines.

Utilizing the techniques of total quality management, a team designed a clinical guideline for the use of alpha interferon as a treatment for patients with chronic hepatitis. The team included TEMINEX staff, a primary care physician, the plan's internal gastroenterologist, and its university-based consultant gastroenterologists. A synopsis of the available published research data and clinical opinion (a draft TEMINEX report) was used to focus discussions. The final TEMINEX report represented consensus on patient selection criteria and treatment regimens. All members of the team agreed to a review and approval process. Although quantitative data concerning the effects of guideline implementation are not yet available, it appears that the concerns of all members of the team have been satisfied. Patient selection criteria supported by the results of well-designed research are in place. Appropriate candidates for alpha-interferon therapy receive expedited treatment and the plan's internal monitoring processes are more efficient. Primary care physicians and consultant gastroenterologists feel that they made positive contributions both to the quality of care and to the consensus development process.

Health Maintenance Organizations↗
PubMed1992

Technology management information exchange (TEMINEX). Applied technology assessment for HMOs.

In an effort to obtain timely, comprehensive and valid information, The HMO Group medical directors have pooled resources to facilitate decision-making on the appropriate use of new or unfamiliar technologies. The HMO Group has responded to over 175 requests for information on topics such as organ transplants, testing and screening procedures, drugs and devices.

Health Maintenance Organizations↗
PubMed1981

Nonspecific esterase in human lymphocytes.

A substantial proportion of human peripheral lymphocytes exhibits esterase activity as demonstrated by cytochemical techniques using hexazotized pararosanilin as coupling agent and different alpha-naphthyl compounds, in particular alpha-naphthyl-acetate, as substrates. Esterase-positive lymphocytes showed one or several dots of the reaction product. Plasma cells and macrophages also exhibited marked esterase activity but with diffuse distribution of the reaction product throughout the cytoplasm. The substrate specificity, the time course and the pH optimum of the cytochemical reaction were determined. The results indicate that these lymphocyte esterases are identical with acid lipases. The number of esterase-positive cells reaches a plateau well below 100% (85% for blood lymphocytes) even with optimal staining procedures. The relation between esterase activity and other so-called lymphocyte markers such as sIg and the capacity to form spontaneous rosettes with sheep red blood cells was investigated in peripheral human blood lymphocytes. A fair correlation between rosette formation and esterase activity was found and most of the esterase-positive cells were sIg-negative. However, the fit was never complete. The results suggest that esterase activity is largely characteristic for small peripheral T cells. Almost all blast cells formed following stimulation with Con A or PHA were esterase-positive. Histochemical studies showed that the large majority of the thymocytes in the cortex lacked esterase activity. In lymph nodes, a low proportion of esterase-positive cells was found in the germinal centers, whereas most lymphocytes in the paracortical are were esterase-positive.

Adolescent↗
PubMed1976

Model to study long-term effects of propoxyphene napsylate (darvon-N) on narcotic-dependent mice.

Five different strains of mice were investigated for their suitability to serve as models for the study of long-term effects of propoxyphene napsylate (PN) on narcotic-dependent mice. The NIH/Swiss outbred strain proved to be most suitable because of its high liability to manifest physical dependence on morphine. Following removal of subcutaneously-implanted morphine pellets from the mice, the incidence of spontaneous withdrawal jumping was used as a quantifiable criterion of physical dependence. An orally administered suspension of PN suppressed the withdrawal jumping in a dose-dependent manner. However, chronic (daily) administration of PN at doses high enough to prevent withdrawal jumping was characterized by a high degree of toxicity.

Animals↗