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Biomedical subjects

D Walker

Publications and source records attributed to D Walker.

At least 325 records · Page 18Linked to original sources
PubMed1986

CRF-induced seizures and behavior: interaction with amygdala kindling.

Intracerebroventricular (i.c.v.) administration of ovine corticotropin-releasing factor (CRF) in doses varying from 10 to 100 micrograms has been reported to produce the late onset of seizures that resemble those observed during electrical kindling of the amygdala. We assessed the effects of repeated CRF administration on seizure development and on subsequent electrical kindling of the amygdala. Rats were administered vehicle or CRF (100 micrograms in 10 microliter of sterile water, i.c.v.) once daily for 5 consecutive days and were rated for seizures and aggressive behavior. On days 1 or 2, all animals receiving CRF developed major motor seizures of late onset (1-5 h post-injection), accompanied by spiking in the amygdala. By day 5, however, no rats had seizures, suggesting the development of tolerance. Defensive biting attacks were also observed following latencies of several hours and tolerance appeared to develop to these as well. After the CRF regimen, treated rats developed amygdala-kindled seizures following electrical stimulation approximately twice as fast as vehicle-injected controls (P less than 0.03). In a second experiment, rats were electrically kindled or sham-kindled prior to receiving i.c.v. CRF (100 micrograms). Kindled animals were significantly less sensitive to the seizure-inducing effects of CRF (P less than 0.03), but were more intensely aggressive than sham-kindled animals or naive rats receiving CRF for the first time.

Amygdala↗
PubMed1986

Voltage-dependent increase in ionized cytoplasmic calcium in the L6H9 muscle cell line detected with quin2.

The concentration of free Ca2+ ions in the cytoplasm ([Ca2+]i) is a key parameter in the function of muscle cells. This study describes the effect of membrane depolarization on [Ca2+]i in differentiating cells of the L6H9 line of rat skeletal muscle. [Ca2+]i was assessed using the fluorescent indicator quin2. In the presence of 1 mM extracellular Ca2+, [Ca2+]i averaged 250 nM. Replacement of extracellular Na+ with K+ resulted in cellular depolarization from -64 to -20 mV, measured with a fluorescent oxonol indicator. Depolarized cells showed a significant increase in [Ca2+]i, from 250 to 390 nM. The increase was prevented by nifedipine (5 microM) and was in great part dependent on the presence of extracellular Ca2+. A residual significant increase in [Ca2+]i was observed upon depolarization in Ca2+-free medium; this rise may be attributed to Ca2+ release from intracellular organelles. In the presence of extracellular Ca2+, replacement of extracellular Na+ by N-methylglucamine+ did not depolarize the cells, yet resulted in a significant increase in [Ca2+]i. This rise may be ascribed to inhibition or reversal of Na+/Ca2+ exchange activity due to the absence of extracellular Na+. The data are consistent with the presence of voltage-sensitive Ca2+ channels and Na+/Ca2+ antiporters at the cell surface, and of mechanisms of voltage-sensitive Ca2+ release from intracellular organelles.

Animals↗
PubMed1986

The child with arthritis in the school setting.

The school experience is a crucial one for the child with arthritis. In school, these children face obstacles common to all chronically ill children and certain problems unique to a child with arthritis. The school environment for these children has changed drastically in the last two decades with the new civil rights legislation on the state and federal levels. Today there is a better chance of a child with arthritis having a relatively problem-free school experience than ever before. The pediatrician can be a source of information, advice, support, and help with any school problems that the child and parent cannot solve. Most minor problems, such as medication at school, physical education problems, an extra set of books, and extra time between classes, may be solved by an informal telephone call or a letter. More severe problems, such as prolonged and frequent absences, multiple modifications of the school environment, and contesting of school placement, may require the use of more formal channels, including the IEP process and parent advocacy groups. When chronic problems exist in the school system, the pediatrician may choose to work for needed changes that improve the school situation of these and other chronically ill children. The pediatrician also may serve as a valued adviser and educator to the school system in the difficult task of educating these special children.

Absenteeism↗
PubMed1986

Behavioral interventions for childhood nocturnal enuresis: the differential effect of bladder capacity on treatment progress and outcome.

Study participants were fifty 5- to 13-year-old children (33 boys and 17 girls) with nocturnal enuresis of at least 3 months duration. All wet their beds at least twice per week, were of normal intelligence, and were without demonstrable organic cause for their enuresis. Each youngster's pretreatment maximum functional bladder capacity (MFBC) was used to classify the child as having small or large MFBC based on available norms. Youngsters were then randomly assigned to treatment with the urine alarm (UA) alone or with the urine alarm supplemented with retention control training (UA plus RCT). Of the 40 youngsters who completed treatment, 37 (92.5%) achieved the treatment goal of 14 consecutive dry nights. Two additional children became dry during follow-up, leaving only one child who failed to stop wetting. Sixteen children (41%) subsequently relapsed, but all who reentered treatment became dry. Because treatment outcome was uniformly excellent across all groups, treatment progress was evaluated by analyzing wetting frequency and arising at night to use the bathroom during treatment, as well as prechange and postchange in MFBC For both wetting frequency and arising at night, there was a significant interaction between bladder capacity and treatment. Small MFBC children treated with the UA plus RCT and large MFBC youngsters treated with the UA alone had the fewest wetting episodes and got up at night to use the bathroom less often; these youngsters took less time to be successfully treated. Prechanges and postchanges in MFBC indicated that RCT did not lead to consistent increases in bladder capacity in the sample studies. The 10 children who terminated treatment prematurely had lower self-esteem and more parent-reported conduct problems than the 40 children who completed treatment.

Adolescent↗
PubMed1986

Chemical and genetic comparison of the glucose and nucleoside transporters.

Glucose and nucleoside uptake into human red cells occurs through protein(s) which copurify in a complex, known as band 4.5 of relative mass (Mr) 66,000 to 50,000. The specific inhibitor of glucose transport, [3H]cytochalasin B, and the specific inhibitor of nucleoside transport, [3H]nitrobenzylthioribofuranosylpurine ([3H]NBMPR), incorporate covalently into component(s) of band 4.5 upon irradiation with ultraviolet light. Both photolabelled components are shown to be glycoproteins, since their migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is increased after treatment of photolabelled band 4.5 with endoglycosidase F. Peptide maps of the photolabelled components were compared. Red cell membranes were photolabelled with either [3H]cytochalasin B or [3H]NBMPR and subjected to SDS-PAGE. The region containing band 4.5 was cut and transferred to a second SDS-PAGE system and exposed to either papain or Staphylococcus aureus V8 protease. Papain (5 micrograms) completely cleaved band 4.5 and produced fragments of Mr 33,000, 26,000, 21,000, 15,000, and 12,500. Of these, the 21,000 fragment was the most conspicuous and it retained the label of [3H]cytochalasin B; the 33,000 fragment retained the label of [3H]NBMPR. The V8 protease (0.75 microgram) completely cleaved band 4.5 and produced fragments of Mr 35,000, 28,000, 22,000, 16,000, 13,500, and 9,000. The 28,000 fragment retained the label of [3H]cytochalasin B. The label of [3H]NBMPR was distributed along the gel in several regions comprising the 35,000, 28,000, and 16,000 fragments. Longer treatment with the V8 protease did not alter the position of the 28,000 [3H]cytochalasin B labelled peak, but completely abolished the [3H]NBMPR labelled peaks. Genetic segregation of the glucose and nucleoside transporters was determined in a lymphoma cell line. A mutant (14T- g) of S49 cells was selected which had lost the capacity to transport thymidine or to bind NBMPR. Uptake of either 2-deoxyglucose or 3-O-methylglucose, inhibitable by cytochalasin B, was not impaired in this mutant. It is concluded that the nucleoside and glucose transporters are glycoprotein components of band 4.5, which are differentiated by peptide map analysis. Further, a lymphoblast mutant was isolated which had lost the nucleoside transport function but retained the glucose transport function.

Carrier Proteins↗
PubMed1986

Changes in cytoplasmic free calcium caused by halothane. Role of the plasma membrane and intracellular Ca2+ stores.

Malignant hyperthermia is a muscle disease characterized by an abnormal response to anaesthetics, stress, and exercise. It is typified by muscle contracture and a dramatic elevation in body temperature. A defect in the regulation of the concentration of cytoplasmic free calcium, [Ca2]i, is thought to underlie this disease, but the actual [Ca2+]i was not measurable until recently. We have shown that the anaesthetic halothane increases [Ca2+]i in isolated lymphocytes from malignant hyperthermia-susceptible humans and pigs but not in the normal counterparts. In this report we extend these observations to a larger number of cases and analyze the molecular mechanisms responsible for the increase. The halothane-mediated rise in [Ca2+]i required external Ca2+ and was prevented by nifedipine, an inhibitor of the voltage-sensitive Ca2+ channels of the cell membrane. In addition, the effect of halothane on the releasable Ca2+ from intracellular stores was determined by measuring the size of the releasable pool before and after addition of the anaesthetic. After addition of halothane, about 73% of this Ca2+ pool was still available for release by the Ca2+ ionophore ionomycin in cells from normal humans and pigs. In contrast, only about 45% of the free Ca2+ in intracellular stores was left after treatment with halothane in cells from malignant hyperthermia-susceptible humans and swine. These results indicate that halothane acts both at the cell membrane and at intracellular organelles, and that this action results in a net increase in [Ca2+]i in malignant hyperthermia, but not in normal cells. The action at the cell membrane appears to be on the voltage-sensitive Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoquinolines↗
PubMed1986

Enhancement of the proliferation of human marrow erythroid (BFU-E) progenitor cells by prostaglandin E requires the participation of OKT8-positive T lymphocytes and is associated with the density expression of major histocompatibility complex class II antigens on BFU-E.

The relationship between major histocompatibility complex class II antigens (MHC class II, eg, HLA-DR, Ia), T lymphocytes, and the enhancement of erythroid colony formation from BFU-E by prostaglandin E was analyzed using normal bone marrow cells. In primary methylcellulose culture, the addition of prostaglandin E1 (PGE1) to unseparated buffy coat, low-density, or nonadherent low-density (NAL) marrow cells resulted in an enhancement of the total number of erythroid (BFU-E) colonies observed. Treatment of bone marrow cells with a monoclonal antihuman MHC class II antibody plus complement (C') resulted in a reduction of the total number of colonies by approximately 50% and abrogation of the enhancing effect of PGE1. Analysis of accessory cell requirements by depletion of both adherent cells and sheep erythrocyte rosetting lymphocytes (E+ cells) and reconstitution using C' or anti-MHC class II antibody plus C'-treated T cell-depleted NAL (NALT-) marrow cells and E+ cell populations treated with C' or anti-MHC class II antibody plus C' demonstrated a requirement for MHC class II antigen-T cells, but not adherent cells, and a requirement for MHC class II antigen + BFU-E in order to observe the enhancing effect of PGE1 on erythroid colony formation. Positive selection of BFU-E in NALT- bone marrow expressing differing density distributions of MHC class II antigens was accomplished with monoclonal anti-MHC class II antibodies and sorting with a fluorescence-activated cell sorter (FACS). Addition of E+ cells to the different populations of MHC class II antigen+ NALT- cells demonstrated that the PGE-enhancing effects on erythroid colony formation were directly related to increasing density distributions of MHC class II antigens on BFU-E. Colony formation by BFU-E expressing a low density distribution of MHC class II antigens or having no detectable MHC class II antigens, as determined by FACS analysis, was not enhanced by PGE1 in the presence of MHC class II antigen-positive or -negative T cells.

Alprostadil↗
PubMed1985

Synthesis in cell culture of the gapped linear duplex DNA of the slow virus visna.

Visna virus is a nontransforming retrovirus that causes slow infections in animals and a rapidly progressive-lytic infection in cell culture. The results of an analysis of the synthesis of viral DNA in cell culture are reported. Region- and strand-specific probes cloned in M13 have been used to define the dynamics of DNA synthesis and the major nucleic acid species formed. It is shown that (i) within the first hours of infection, a full-length copy of the viral RNA genome is synthesized by reverse transcription, (ii) early in infection a major species of DNA is formed that extends from a site near the center of the molecule to the 3' end, (iii) somewhat later a second major species of plus-strand DNA is generated that extends from the 5' end to the middle of the genome. As a consequence, most viral DNA molecules consist of a full-length minus strand, and two plus strands separated by a gap or nick in the center of the molecule (J. D. Harris, J. V. Scott, B. Traynor, M. Brahic, L. Stowring, P. Ventura, A. T. Haase, and R. Peluso (1981). Virology 113, 573-583). The implications of this viral DNA structure for one unusual aspect of the lentivirus life cycle, the production of viral RNA, and virions from extrachromosomal DNA are discussed (J. D. Harris, H. Blum, J. Scott, B. Traynor, P. Ventura, and A. T. Haase (1984). Proc. Natl. Acad. Sci. USA 81, 7212-7215).

Animals↗
PubMed1985

Alcohol dehydrogenase II and fructose-1,6-bisphosphatase appear to be co-regulated in wild-type yeast.

An activity gel assay for fructose-1,6-bisphosphatase (FBP), the enzyme catalyzing the final step in gluconeogenesis in yeast, has been developed which can be used in conjunction with spectrophotometric assays to show that it is tightly co-regulated with the inducible alcohol dehydrogenase, ADHII. Both enzymes are repressed coordinately in aerobically grown yeast by the addition of high levels of glucose or ethanol, and induced on minimal medium by the addition of yeast extract. A mutant deficient in FBP segregates independently of the ADHII structural gene locus. This phenomenon is of interest because of the discovery of Ciriacy [(1979) Mol. Gen. Genet. 176, 427-431] of mutants (ccr, or carbon catabolite repression) which repress both FBP and ADHII simultaneously, along with several other enzymes.

Alcohol Dehydrogenase↗
PubMed1985

Detection of two viral genomes in single cells by double-label hybridization in situ and color microradioautography.

Double labeling and color microradioautography were used in a new method of hybridization in situ to identify different genes in individual cells. The method is based on the unequal penetration of 3H and 35S into two layers of nuclear track emulsion separated by a thin barrier film. Hybridization of a 35S-labeled probe specific for one kind of gene results in silver grains over cells in both layers of emulsion; a 3H-labeled probe for a second gene provides grains only in the first layer of emulsion. Silver grains are converted to magenta-colored grains in the first layer and to cyan-colored grains in the second to facilitate enumeration of grains in each layer. This technique should be widely applicable in analyses of differential gene expression in single cells or in discrete populations of cells.

Autoradiography↗
PubMed1985

Natural history of restricted synthesis and expression of measles virus genes in subacute sclerosing panencephalitis.

Subacute sclerosing panencephalitis (SSPE) is a slow infection caused by measles virus in which several years separate recovery from typical acute measles and the development of a slowly progressive neurological disease. We have investigated replication of measles virus in brain tissue obtained after the onset of neurological disease and in the terminal phase. With a hybridization tomographic technique that combines in situ hybridization with macroradioautographic screening of large areas of tissue, we analyzed the spatial and temporal distribution of virus genes in vivo, using region- and strand-specific probes for the nucleocapsid and matrix genes. We show that early in the course of SSPE there is a global repression in the synthesis and expression of the genome. In the final stage of SSPE most infected cells still have depressed levels of plus- and minus-strand viral RNA and contain nucleocapsid protein but lack matrix protein. These findings provide further evidence for a unified view of slow infections of the nervous system, where the general constraints on virus gene expression provide an explanation for persistence of virus in the face of the host's immune response, and the slow evolution of pathological change. In the final phases of SSPE the more specific block in virus replication accounts for the cell-associated state of the virus and the difficulty in virus isolation.

Brain↗
PubMed1985

The value of haematological screening for AIDS in an at risk population.

The haematological variables measured by automated full blood count in matched homosexual and heterosexual men attending a clinic for sexually transmitted diseases (STD) were compared with those of normal controls and patients infected with the human T lymphotropic virus type III (HTLV-III). Homosexual and heterosexual men were statistically identical for all variables, but both differed noticeably from patients with clinical diagnoses of the acquired immune deficiency syndrome (AIDS) or AIDS related disease. A full blood count as a screening test for AIDS is only interpretable in the context of clinical assessment.

Acquired Immunodeficiency Syndrome↗