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Biomedical subjects

J L Hess

Publications and source records attributed to J L Hess.

At least 55 records · Page 3Linked to original sources
PubMed1992

Calcium efflux in rat lens: Na/Ca-exchange related to cataract induced by selenite.

Sodium gradient-dependent 45Ca2+ transport occurred across the lens membrane both in the direction of Ca2+ uptake by inside-out vesicles and Ca2+ efflux after Ca2+ loading of right-side-out vesicles. Using the calcium ionophore, A23187, greater than 90% of the Na+ gradient-dependent Ca2+ uptake was estimated to be free Ca2+. A normal Na+ gradient was also required to maintain calcium homeostasis in the intact lens. The Na+ gradient contributed to Ca2+ efflux from lenses pre-loaded in medium containing 15 mM CaCl2. Therefore, a Na/Ca-exchange functions to control Ca efflux in rat lens, in addition to the Ca-ATPase. In the preweanling rat mature nuclear cataracts occurred by 96 h after subcutaneous injection of sodium selenite (30 nmol/g animal wt). A 3-5 fold increase of Ca2+ accompanied cataract formation. The loss of Ca2+ homeostasis can be detected by 48 h after treatment selenite treatment. At this time the initial rate of Na+ gradient-dependent Ca2+ uptake was 30% lower in lens vesicles from selenite-treated rats compared to controls. No significant reduction of Na+,K(+)-ATPase activity was detected. Altered Na/Ca-exchange may contribute directly to the loss of Ca2+ homeostasis that leads to nuclear cataract.

Animals↗
PubMed1992

Deferoxamine effect on selenite-induced cataract formation in rats.

A single subcutaneous dose of 30 nmol of sodium selenite per gram of body weight in 13-day-old rats resulted in posterior subcapsular cataract (PSC) after 24 hr and bilateral nuclear cataracts at 72-96 hr. Within 24 hr of treatment, a 60% decrease in lens glutathione was seen. A loss of calcium homeostasis observed by 48 hr resulted in increased lens calcium (4 mumol/g dry weight), which accompanied nuclear opacification. The iron chelator, deferoxamine (DF), was evaluated as a potential protective agent against these selenite-induced changes. Three doses each consisting of 1.1 mumol DF/g body weight were administered during the initial 24 hr of selenite exposure. Within 96 hr, all lenses from animals treated only with DF remained transparent, but 50% of these lenses showed cortical cataract at 3 wk postinjection. Concurrent administration of DF and selenite protected 80% of rats against PSC after 48 hr and 25% against nuclear cataract after 96 hr. No elevation in lens calcium occurred in the protected lenses. An additional 20% of animals were not protected fully but showed substantially less nuclear opacity than with selenite alone. They had a significant but moderate increase in lens calcium. After 3 wk (animal age, 35-40 d), cataract appeared in these "protected" lenses involving both the nucleus and cortex and loss of ion homeostasis. The glutathione content remained lower in lenses from animals treated with both selenite and DF compared with those from selenite-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Rapid deterioration of lens fibers in GSH-depleted mouse pups.

Lens opacities developed within 48-72 hr in mice that received a series of eight injections of L-buthionine sulfoximine, a specific inhibitor of glutathione (GSH) biosynthesis, on postnatal days 8 and 9. Initial histopathologic features consisted of swollen fibers in the central anterior cortex and displacement of cell nuclei from the bow region to the posterior cortex. These aberrations suggest early fiber cell membrane and/or cytoskeletal dysfunction. A massive wave of fiber cell lysis then engulfed the entire lens cortex and nucleus within 24 hr and left only epithelial cells intact, suggesting a concerted mechanism of cataract generation. The acellular core of the mature cataract seen on postnatal day 16 consisted of a granular matrix in which pycnotic and fragmented cell nuclei were located near the terminus of the lens epithelium. The epithelium displayed increased mitotic activity and meridional row disorganization. During the next two weeks, rapid regeneration of lens fibers, displacement of the acellular necrotic cytoplasm to the center and rear of the lens, and vacuole formation were observed. As new fibers were differentiated, partial regeneration of the bow was seen. However, the cataract was irreversible.

Animals↗
PubMed1990

Purification, characterization, and immunological properties for two isoforms of glutathione reductase from eastern white pine needles.

Glutathione reductase (EC 1.6.4.2) was purified from Eastern white pine (Pinus strobus L.) needles. The purification steps included affinity chromatography using 2', 5'-ADP-Sepharose, FPLC-anion-exchange, FPLC-hydrophobic interaction, and FPLC-gel filtration. Separation of proteins by FPLC-anion-exchange resulted in the recovery of two distinct isoforms of glutathione reductase (GR(A) and GR(B)). Purified GR(A) had a specific activity of 1.81 microkatals per milligram of protein and GR(B) had a specific activity of 6.08 microkatals per milligram of protein. GR(A) accounted for 17% of the total units of glutathione reductase recovered after anion-exchange separation and GR(B) accounted for 83%. The native molecular mass for GR(A) was 103 to 104 kilodaltons and for GR(B) was 88 to 95 kilodaltons. Both isoforms of glutathione reductase were dimers composed of identical subunit molecular masses which were 53 to 54 kilodaltons for GR(A) and 57 kilodaltons for GR(B). The pH optimum for GR(A) was 7.25 to 7.75 and for GR(B) was 7.25. At 25 degrees C the K(m) for GSSG was 15.3 and 39.8 micromolar for GR(A) and GR(B), respectively. For NADPH, the K(m) was 3.7 and 8.8 micromolar for GR(A) and GR(B), respectively. Antibody produced from purified GR(B) was reactive with both native and denatured GR(B), but was cross-reactive with only native GR(A).

Journal Article↗
PubMed1990

DNA damage, repair, and replication in selenite-induced cataract in rat lens.

DNA synthesis was evaluated in vitro by measuring incorporation of 3H-thymidine in rat lens following systemic delivery of a cataractogenic dose of selenite. Among early metabolic changes observed in the lenses of rats receiving a single dose of 30 nmol Na2SeO3/g body weight was a 30% decrease in DNA replication in lens epithelium occurring between 6 and 12 h after administration of the selenite. This change was followed by an 80% increase in replication by 24 h. Thymidine incorporation in DNA remained elevated compared to controls through 96 h. Unscheduled DNA synthesis was found to be approximately 10% of the total DNA formed, but there was a 30% and 70% increase of this putative DNA repair in the lenses from selenite-treated animals at 6 and 24 h after the injection. Using the alkaline unwinding assay, the proportion of single-strand DNA in lenses from selenite-treated animals increased after 24 h. This estimate of DNA damage was greater in lenses after 96 h. Each component of DNA metabolism: damage, repair, and replication, was affected by the occurrence of selenite stress in lens. These changes both preceded and accompanied nuclear cataract formation.

Animals↗
PubMed1989

Sequences in the visna virus long terminal repeat that control transcriptional activity and respond to viral trans-activation: involvement of AP-1 sites in basal activity and trans-activation.

Visna virus is a pathogenic lentivirus of sheep whose gene expression is developmentally regulated in cells of the monocyte-macrophage lineage. Gene expression directed by the visna virus long terminal repeat (LTR) is increased in infected cells by a virus-encoded trans-acting protein. trans-Activation is mediated in part by increases in the steady-state level of mRNA. Deletion and linker-scanner mutants were constructed to locate sequences in the LTR that regulate transcription and are responsive to viral trans-activation. The activities of these mutants were tested by using them to drive transcription of the bacterial gene for chloramphenicol acetyltransferase in transient expression assays. Three regions located between-140 and the cap site were found to be important for basal transcriptional activity, and the importance of each region was found to be dependent on the cell type. Sequences responsive to viral trans-activation were found to be the same sequences required for basal transcriptional activity. The visna virus LTR contains six sequences that are homologous to the recognition site for cellular transcriptional factor AP-1 and a single sequence homologous to the recognition site for transcriptional factor AP-4. Both of these classes of binding sites appear to be important for regulating the basal level of transcription of visna virus. The AP-1-binding site most proximal to the TATA box was found to be one target for viral trans-activation. The visna virus promoter was found to be activated by serum; this serum response has also been mapped to the AP-1-related sequences in the LTR.

Base Sequence↗
PubMed1989

Regulation of the visna virus long terminal repeat in macrophages involves cellular factors that bind sequences containing AP-1 sites.

Visna virus gene expression is highly restricted in monocytes but is induced by monocyte-macrophage differentiation in vivo. Deletion and linker-scanning mutants, gel shift assays, and DNase I footprinting were used to identify sequences in the visna virus long terminal repeat involved in the developmental regulation of gene expression in the U937 monocytic cell line. We found that an AP-1 and an AP-4 binding site were critical for basal activity and that the AP-1 site was required for phorbol ester-inducible gene expression. These results suggest that cellular factors that interact with AP-1 sites are involved in the developmental regulation of visna virus gene expression in macrophages.

Base Sequence↗
PubMed1987

Intracellular Localization of the Neurotoxin 2,4-Diaminobutyric Acid in Lathyrus sylvestris L. Leaf Tissue.

The intracellular distribution of the neurotoxin 2,4-diaminobutyric acid (DABA) in mature leaves of the perennial legume Lathyrus sylvestris L. var ;Lathco' (flatpea) was determined using subcellular fractions from mesophyll protoplasts. Chloroplasts contained about 15% of the cellular DABA. At least 75% of the DABA was vacuolar, based on the assumptions that each protoplast contained a single vacuole and that acid phosphatase occurred exclusively in the vacuole. DABA was not detectable in peroxisomal and mitochondrial fractions. Because the vacuole is not a major site of amino acid synthesis, this distribution implicates synthesis of DABA within chloroplasts with subsequent transport to and storage within the vacuoles of the mesophyll cells.

Journal Article↗
PubMed1987

Immune responses in the central nervous system.

Immune responses occurring within the central nervous system (CNS) have unique features attributable to the cellular and functional organization of the CNS and to the presence of the blood-brain barrier. Immune responses to viral infection of the CNS involve the participation of most immunologically important cells: T and B lymphocytes, monocytes, and natural killer cells. Normally, helper/inducer T lymphocytes are predominant in the cerebrospinal fluid (CSF) and in perivascular cuffs. After stimulation with antigen in tissue, these cells produce lymphokines, which stimulate mast cells to open capillary tight junctions, stimulate proliferation of lymphocytes, and attract monocytes and B lymphocytes. B lymphocytes mature into immunoglobulin-producing cells that secrete antibody locally which appears in the CSF. Cytotoxic/suppressor T lymphocytes, which damage antigen-containing cells, are predominant in immunopathologic reactions. In other situations the immune response targets normal CNS tissue rather than foreign antigens. Two general types of reactions may be seen: (1) vasculitis with destruction of vessel walls and infarction, and (2) perivascular inflammation with demyelination. The former is associated with immune complex deposition, and the cellular infiltrate includes polymorphonuclear leukocytes. The inflammation associated with perivenular demyelination is composed almost exclusively of mononuclear leukocytes. In the diseases for which pathogenetic mechanisms are understood, cells become sensitized to myelin constituents and induce local demyelinating lesions in which the damage is effected by macrophages. It is not clear whether macrophages are directed in this destructive effort by lymphokines or immunoglobulins or both.

Animals↗
PubMed1986

Cells with natural killer activity in the cerebrospinal fluid of normal mice and athymic nude mice with acute Sindbis virus encephalitis.

Sindbis virus causes an acute, nonfatal inflammatory encephalitis in weanling BALB/c mice. Mononuclear inflammatory cells are present in the cerebrospinal fluid (CSF) as well as in the parenchyma of the brain. Both aspects of this inflammatory response were eliminated by treatment with cyclophosphamide. Athymic nude (nu/nu) mice developed no inflammation in the brain, but did develop a CSF pleocytosis that peaked on day 2 after infection. The time course of the appearance of cells in the CSF was earlier in nu/nu mice than their heterozygote (nu/+) littermates. The pleocytosis in nu/nu mice reached a peak on day 2, whereas in nu/+ mice the peak was on day 4, as it is in normal BALB/c mice. To determine whether some of the CSF cells in nu/nu mice may be natural killer (NK) cells, NK activity was measured in a 4-hr assay by using a YAC-1 target cell. NK cell activity in the spleen and peripheral blood was induced by infection with Sindbis virus in nu/nu mice with a similar time course to that of nu/+ mice (peak 1 day after infection). CSF from nu/nu mice had NK activity present 2 days after infection that was greater than that present in either the peripheral blood or spleen. BALB/c and nu/+ mice had insufficient cells present for assay at day 2, but BALB/c mice had NK activity present in the CSF 3 and 5 days after infection that exceeded that in the peripheral blood or spleen. Brain interferon was detectable on day 1 in nu/nu mice, but not until day 2 in nu/+ mice even though the amounts of brain virus were the same in the two groups at all time points. It is concluded that cells with NK activity contribute to the CSF pleocytosis induced by acute Sindbis virus encephalitis.

Acute Disease↗
PubMed1986

Nucleotide sequence and transcriptional activity of the caprine arthritis-encephalitis virus long terminal repeat.

Caprine arthritis-encephalitis virus (CAEV) and visna virus are pathogenic lentiviruses of goats and sheep which share morphologic features and sequence homology with human T-cell lymphotropic virus type III (HTLV-III), the etiologic agent of the acquired immune deficiency syndrome. The nucleotide sequence of the CAEV long terminal repeat (LTR) was determined, and it was found to be 450 base pairs long, with U3, R, and U5 regions of 287, 85, and 78 base pairs, respectively. Portions of the CAEV LTR are closely homologous to analogous regions of visna virus. The CAEV LTR is not significantly homologous with the HTLV-III LTR; however, like HTLV-III, visna virus, and equine infectious anemia virus, CAEV uses tRNA lysine as a primer for reverse transcription. The transcriptional activity of the CAEV and visna virus LTRs was measured by a chloramphenicol acetyltransferase assay, and the activity of the visna virus LTR was generally higher in a variety of uninfected cell types. Infection of cells with visna virus markedly increased gene expression directed by either the CAEV or visna virus LTR, but in contrast, infection of cells with CAEV had little effect on the activity of either LTR. The lack of trans-activation by CAEV, a virus which causes debilitating arthritis and encephalitis in goats, suggests that trans-activation may not be a general property of pathogenic lentiviruses.

Acetyltransferases↗
PubMed1985

cis- and trans-acting transcriptional regulation of visna virus.

Visna virus is a pathogenic lentivirus of sheep that is related to human T-cell lymphotropic virus type III (HTLV-III), the probable etiologic agent of the acquired immune deficiency syndrome (AIDS). The transcriptional activity of visna virus promoter and enhancer sequences was studied by means of an assay based on the transient expression of the bacterial gene chloramphenicol acetyltransferase (CAT). The results suggest that the high level of expression of visna virus is due in part to cis-acting enhancer sequences that give the viral promoter a high level of transcriptional activity. In addition, the rate of transcription from the visna virus promoter situated in a plasmid expressing the CAT gene was much greater in infected than uninfected cells. This phenomenon of trans-acting transcriptional activation may involve either virally or cellularly encoded factors.

Acetyltransferases↗
PubMed1984

Exercise-thermoregulatory stress and increased plasma beta-endorphin/beta-lipotropin in humans.

Six adult male volunteers of similar body composition and physical fitness were tested to determine plasma immunoreactive beta-endorphin/beta-lipotropin (beta-EN/beta-LPH) response under three exercise-thermoregulatory stress conditions. The experimental protocol consisted of 120 min of stationary upright cycling at 50% VO2max under neutral (24 degrees C, 50% rh)-euhydration (NE), hot (35 degrees C, 50% RH)-euhydration (HE), and hot-dehydration (HD) environmental conditions. beta-EN/beta-LPH was calculated by radioimmunoassay at -30-min, 0-min, and 15-min intervals thereafter. Change in plasma volume (delta PV) was measured to determine its effect on beta-EN/beta-LPH concentration. Preexercise beta-EN/beta-LPH levels averaged 23.7 +/- 2.6 pg X ml-1 in all conditions. The greatest beta-EN/beta-LPH response occurred at 105 min in HD conditions when levels rose to 43.2 +/- 6.9 pg X ml-1. Exercise in HD and HE conditions resulted in significantly (P less than 0.05) elevated beta-EN/beta-LPH above levels observed in NE. delta PV did not account for more than 10% of beta-EN/beta-LPH changes at any time interval. The beta-EN/beta-LPH response pattern closely paralleled rectal temperature changes in all conditions. These data suggest that conditions of increasing exercise thermoregulatory stress are associated with increasing peripheral beta-endorphin concentration.

Adult↗
PubMed1984

Lens calcium and selenite-induced cataract.

Subcutaneous injection of sodium selenite into young rats produces a nuclear cataract within 72 hours. A three-fold elevation in lens calcium and a two-fold increase in lens inorganic phosphate have been found to precede opacification. Scanning electron micrographs suggested weakened cell-to-cell adhesion in the cataractous nuclear zone.

Animals↗
PubMed1984

Cataract formation following limited amino acid intake during gestation and lactation.

Female rats were fed defined diets limiting in one or more of certain amino acids and with or without vitamin E throughout gestation and lactation. Deficits of tryptophan, phenylalanine/tyrosine, or methionine/cystine reduced the body weight of progeny to about 50% or less of normal but only low tryptophan was cataractogenic. When total dietary amino acids were 12.4%, a low (65 mg%) level of tryptophan resulted in 34% incidence of cataract if vitamin E was simultaneously withheld. Elevation of total amino acids to 24.8% while maintaining tryptophan at 65 mg% caused 70 or 90% incidence of nuclear lens opacities in the presence or absence, respectively, of vitamin E. Maternal dietary amino acid imbalance was also associated with a 50% decrease in lens insoluble (membrane) proteins in the progeny independent of dietary vitamin E or the occurrence of opacities.

Amino Acids↗
PubMed1982

Immunochemical features of a case of progressive rubella panencephalitis.

Progressive rubella panencephalitis (PRP), a slowly progressive and fatal central nervous system (CNS) disorder due to rubella virus, is characterized by high cerebrospinal fluid (CSF) levels of immunoglobulins, oligoclonal bands and high CSF:serum rubella antibody titre ratios. Sera, CSF and neutral extracts of brain, spleen, lymph node and kidney obtained at autopsy from a case were analysed for immunoglobulin isotype and content by enzyme linked immunosorbent assays. Comparable titres of rubella specific IgA and IgG were found in sera and CSF, but accounted for a disproportionate amount of the isotype specific immunoglobulins of CSF (0.19%, 14.0%) as compared to serum (0.02%, 0.69%). The percentage of isotype specific immunoglobulins were not increased in extracts of most visceral tissues compared to serum, however, rubella specific IgA and IgG were disproportionately increased in extracts from most regions of brain sampled (1-60-fold and 8-27-fold respectively). No rubella specific IgM could be conclusively demonstrated in any specimen. Immunoprecipitation studies showed that the IgG reacted with the major glycoproteins (gp62, gp47-56 complex) and non-glycosylated polypeptide (p38) of radiolabelled rubella virions and infected cell lysates. These studies support the conclusion that a major portion of the rubella specific antibody is produced within the CNS of patients with PRP.

Antibodies, Viral↗