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Biomedical subjects

H Tang

Publications and source records attributed to H Tang.

At least 235 records · Page 13Linked to original sources
PubMed1995

An animal study on transmission of hepatitis B virus through mosquitoes.

Three gena of mosquitoes were fed with human blood infected with hepatitis B virus (HBV) artificially. When blood in the stomach was completely digested, mosquitoes were used to bite monkeys Tupaia Belangeri. A month after biting, venous blood samples were taken from the monkeys to detect serum HBsAg, HBeAg, Anti-HBs and Anti-HBc. Among 29 test monkeys, 9 were HBV infective serum markers positive. In 4 of 16 test monkey liver biopsies, acute inflammatory changes were found with Hematoxylin-Eosine staining. In the hepatic cells, HBsAg and HBcAg were detected by immunohistochemical double-labeling assays, and HBV-DNA was also positive by in situ hybridization in monkey liver sections. These results provided an evidence for the possibility of transmission of HBV through mosquitoes and suggest its epidemiological significance in mosquito infested areas.

Animals↗
PubMed1994

Location, structure, and function of the target of a transcriptional activator protein.

We have isolated and characterized single-amino-acid substitution mutants of RNA polymerase alpha subunit defective in CAP-dependent transcription at the lac promoter but not defective in CAP-independent transcription. Our results establish that (1) amino acids 258-265 of alpha constitute an "activation target" essential for CAP-dependent transcription at the lac promoter but not essential for CAP-independent transcription, (2) amino acid 261 is the most critical amino acid of the activation target, (3) amino acid 261 is distinct from the determinants for alpha-DNA interaction, and (4) the activation target may fold as a surface amphipathic alpha-helix. We propose a model for transcriptional activation at the lac promoter that integrates these and other recent results regarding transcriptional activation and RNA polymerase structure and function.

Amino Acid Sequence↗
PubMed1994

c-fos antisense attenuates Fos expression in rat central neurons induced by hemorrhage.

Hemorrhage caused by withdrawing 3-4 cm3 of blood from adult rats over a period of 1-2 h induced the expression of Fos proteins, which were detected by immunocytochemical methods in neurons of the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei, area postrema, nucleus of the solitary tract (NTS), ventrolateral medulla (VLM) and in intermediolateral cell column (IML) of the spinal cord. Daily intraventricular (i.c.v.) injections of c-fos antisense (50 nmol 5 microliters -1) for 2 days prior to hemorrhage markedly attenuated the extent and intensity of Fos-immunoreactivity (FOS-IR) compared with that of rats injected with c-fos sense in the areas mentioned above. The results indicate the effectiveness of i.c.v. administration of c-fos antisense in blocking Fos expression in central neurons following hemorrhage.

Animals↗
PubMed1994

Domain organization of RNA polymerase alpha subunit: C-terminal 85 amino acids constitute a domain capable of dimerization and DNA binding.

Using limited proteolysis, we show that the Escherichia coli RNA polymerase alpha subunit consists of an N-terminal domain comprised of amino acids 8-241, a C-terminal domain comprised of amino acids 249-329, and an unstructured and/or flexible interdomain linker. We have carried out a detailed structural and functional analysis of an 85 amino acid proteolytic fragment corresponding to the C-terminal domain (alpha CTD-2). Our results establish that alpha CTD-2 has a defined secondary structure (approximately 40% alpha helix, approximately 0% beta sheet). Our results further establish that alpha CTD-2 is a dimer and that alpha CTD-2 exhibits sequence-specific DNA binding activity. Our results suggest a model for the mechanism of involvement of alpha in transcription activation by promoter upstream elements and upstream-binding activator proteins.

Amino Acid Sequence↗
PubMed1994

Dynamic magnetic resonance imaging of human Rolandic cortex.

Rolandic cortex was imaged with magnetic resonance (MR) in nine subjects while performing a motor activation task. Imaging was performed by a volumetric, T2-weighted pulse sequence in a conventional 1.5 Tesla scanner during both resting conditions and volitional toe flexion and extension of the dominant foot. Significant changes in MR signal intensity of 7.8 +/- 2.3% (mean +/- s.e.m.) were observed in the medial Rolandic cortex contralateral to the active foot. Changes were maximal in the vicinity of the central sulcus, but were also identified anteroposteriorly, across successive coronal planes. No significant changes were found in the ipsilateral Rolandic cortex or in other brain structures. Volumetric functional MRI strategies may provide an important non-invasive tool for assessment of cortical motor function.

Adolescent↗
PubMed1994

Vasoactive intestinal peptide inhibits interleukin (IL)-2 and IL-4 production in murine thymocytes activated via the TCR/CD3 complex.

During their development in the thymus, T cells acquire interleukin (IL)-2 and IL-4 inducibility in a developmentally controlled manner. Although the role of IL-2 and IL-4 in T cell development is still unclear, several reports indicated that IL-2/IL-2R and IL-4/IL-4R interactions in the thymus could play an important role in T cell development. The presence of vasoactive intestinal peptide (VIP)-immunoreactive cells and nerve fibers in the thymus suggests the possible local release of the neuropeptide in the thymic microenvironment. VIP has been previously reported to inhibit IL-2 and IL-4 production, as well as the proliferation of mitogen- or antigen-stimulated peripheral T cells. Here we report on the effect of VIP on IL-2 and IL-4 production by and proliferation of murine thymocytes stimulated through the TCR/CD3 receptor. VIP inhibited both IL-2 and IL-4 production, as well as the proliferation of murine thymocytes in a dose-dependent and specific manner. Structurally related peptides such as secretin or glucagon had little or no inhibitory activity. The intact VIP molecule was required for the inhibitory effect, since amino- or carboxy-terminal fragments did not inhibit IL-2 production. The inhibitory effect of VIP was observed for VIP additions up to 12 h after the initiation of the cultures, and incubations longer than 3 h were required for maximum inhibitory effects. Through its downregulatory effect on IL-2 and IL-4 production, locally released VIP could potentially affect T cell development within the thymus.

Animals↗
PubMed1994

Localization of putative neural respiratory regions in the human by functional magnetic resonance imaging.

In humans, the location of brain regions responsible for mediating the ventilatory response to CO2 remains unknown. Most of the available knowledge has been derived from animal studies or from pathophysiological correlations in patients presenting altered control of breathing. Magnetic resonance imaging at a specific pulse sequence designed to assess changes in brain tissue microcirculation was performed in 11 healthy volunteers, during steady-state conditions, while breathing 100% O2 or 5% CO2-95% O2. In one subject, 10% CO2-90% O2 was employed to examine a dose-response effect. Significant changes in image signal intensity consistently occurred in ventral and dorsal regions of medullary structures as well as in the midline pons and ventral cerebellum. These responses appeared to be dose dependent and reproducible. Magnetic resonance imaging revealed patterns of activation in brain stem and cerebellar regions during hypercapnic ventilatory challenge. These areas may underlie mechanisms for mediating the response to chemoreceptor activation.

Adolescent↗
PubMed1994

[Changes of auditory brainstem response and auditory cortex response after exposure to intensive noise].

Auditory brainstem response and auditory cortex response were recorded repeatedly in 35 guinea pigs after exposure to intensive white noise (125 dB, 150 min.) for 62 d. the amplitude of evoked potential of acoustic nerve was decreased by 29% (P < 0.05), of the cochlear nuclei by 28% (P < 0.05). However, the amplitude of response of superior olives nuclei was increased by 21% (P < 0.05), of the inferior colliculi by 37% (P < 0.05), of the cortical evoked response by 131% (P < 0.001). The results indicate that the amplitudes of auditory evoked potential showed a centripital augmentation after exposure to intensive noise. The centripital augmentation was observed not only during the period of the temporary threshold shift (TTS) but also during that of the permanent threshold shift (PTS).

Animals↗
PubMed1994

[Detection of human papillomavirus in cervical tissues using polymerase chain reaction].

Detection of human papillomavirus (HPV) 16 and 18 infection by polymerase chain reaction (PCR) was carried out in patients with normal cervix 53 cases, Chronic cervicitis with cervical erosion 59 cases, cervical cancer 12 cases, atypical hyperplasia 3 cases and condyloma acuminatum 2 cases. Results showed that a significantly higher detective rate of HPV-16 and 18 DNA in cervical cancer than in normal cervix, and a higher but not statistically significant positive rate than that in cervical erosion. It indicates that some cases of chronic cervicitis with HPV infection might develop into cervical carcinoma. This finding may help in the early discovery and prevention of cervical cancer.

Base Sequence↗
PubMed1994

Differential induction of 5-HT1A-mediated responses in vivo by three chemically dissimilar 5-HT1A agonists.

In the rat, activation of 5-hydroxytryptamine1A (5-HT1A) receptors causes hypothermia and the 5-HT syndrome. The effects of three chemically dissimilar 5-HT1A agonists administered s.c. [8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), gepirone, and (+)4-[n-5-(methoxychroman-3-yl)n-propylamino]butyl-8-azaspiro++ +[4,5] decane-7,adione ((+) S-20499)] on both of these responses were studied. The same maximal drop in body temperature (approximately 2.5 degrees C) was elicited by all three agonists, 8-OH-DPAT being the most potent (EC50 = 0.05 mg/kg), followed by gepirone (1.8 mg/kg) and (+) S-20499 (8 mg/kg). Both pindolol, a nonselective 5-HT1A receptor/beta adrenoceptor antagonist and n-t-butyl,-3-[1-[4-(2-methoxy)phenyl]piperazinyl]-1-phenylpropionamid e [(+) WAY 100135], a more selective 5-HT1A receptor antagonist, dose dependently attenuated the hypothermia induced by all three agonists. From these data, we inferred that all three agonists caused hypothermia via activation of 5-HT1A receptors. The syndrome was observed reliably in rats at doses of 2 to 4 mg/kg 8-OH-DPAT; doses up to 100 mg/kg of gepirone or (+) S-20499 did not produce the syndrome. In reserpine-pretreated animals, 8-OH-DPAT (maximal effect at 2-4 mg/kg) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) (5 mg/kg) induced forepaw treading, whereas gepirone (10 mg/kg) and (+) S-20499 (75 mg/kg) did not. (+) WAY 100135 competitively antagonized the forepaw treading caused by 8-OH-DPAT in reserpine-pretreated rats. This indicates that forepaw treading, like hypothermia, is mediated by activation of 5-HT1A receptors. Gepirone (5-10 mg/kg) attenuated the forepaw treading induced by either 8-OH-DPAT (4 mg/kg) or 5-MeODMT (5 mg/kg); by contrast, (+) S-20499, at doses up to 75 mg/kg, did not attenuate the forepaw treading induced by either 8-OH-DPAT or 5-MeODMT. The inability of (+) S-20499 either to induce the 5-HT syndrome or forepaw treading or to attenuate the forepaw treading induced by other agonists could be due to several factors, one of which is that different subtypes of the 5-HT1A receptor mediate hypothermia and the 5-HT syndrome.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Influence of cell cycle phase on radiation-induced cytotoxicity and DNA damage in human colon cancer (HT29) and Chinese hamster ovary cells.

We have previously shown that fluorodeoxyuridine (FdUrd) radiosensitizes HT29 human colon carcinoma cells. Since treatment with FdUrd arrests cells at the G1/S-phase interface, a condition associated with increased radiation sensitivity in some cells, it seemed possible that redistribution of cells in the phases of the cell cycle might account for FdUrd-mediated radiosensitization. To begin to test this, HT29 cells were separated by centrifugal elutriation according to cell cycle phase and assessed for radiosensitivity, using a clonogenic assay, and radiation-induced DNA damage, using pulsed-field gel electrophoresis. We found that all of the elutriated fractions (which contained cells enriched in G1, G1/early S, mid to late S or G2/M phase) had the same radiation sensitivity and expressed a similar extent of radiation-induced DNA damage. To determine if the techniques used in this study could detect differences between the radiation sensitivity of cells in different phases of the cell cycle, analogous experiments were carried out using Chinese hamster ovary (CHO) cells. In contrast with the results of experiments with HT29 cells, but in agreement with previous studies, CHO cells separated under the same conditions as were used for HT29 cells showed a marked dependence on cell age of both clonogenic survival and radiation-induced DNA damage. Thus, within the limitations of the purity of separation obtained using elutriation, the radiation sensitivity of HT29 cells does not vary substantially as a function of cell cycle phase. Therefore, it seems unlikely that cell cycle redistribution alone explains the radiation sensitivity produced by exposure to FdUrd.

Animals↗
PubMed1993

Cytokine mRNA expression during an in vitro response of human B lymphocytes: kinetics of B cell tumor necrosis factor alpha, interleukin (IL)6, IL-10, and transforming growth factor beta 1 mRNAs.

Expression of mRNA for eight cytokines was analyzed in an in vitro response-proliferation and Ig-secretion--of normal human B lymphocytes. This was made possible by the use of murine thymoma cells as helper cells in conjunction with human T cell supernatant, and the design of human DNA sequence-specific primers for RT-polymerase chain reaction. mRNAs for interleukin (IL)2 and IL-4, but also for IL-1 alpha and IL-1 beta remained undetectable during the whole culture period in highly purified B cells prepared by a three-step purification protocol. However, tumor necrosis factor alpha and IL-6 mRNAs peaked during days 1-3 after culture start and became undetectable after 5-6 d, shortly before bulk B cell proliferation started to decline. In contrast, transforming growth factor beta 1 mRNA, after a progressive increase during the first few days, and IL-10 mRNA, after a peak on days 1-3, remained detectable in immunoglobulin (Ig)-secreting cultures throughout the observation period of 22 d. Clonal analysis on 8-d cultures that had been seeded with single B cells by autocloning with the cell sorter, revealed that 85% of 77 B cell clones studied, expressed TGF-beta 1 mRNA, and only 19% IL-10 mRNA. These findings show a differentiation stage-related cytokine program during a B cell response, whereby (a) B cells can become activated without IL-1 alpha or IL-1 beta expression; (b) mRNA for positive (IL-10) and negative (TGF-beta 1) autoregulatory factors coexists in cell populations during the later phase of the response, although not necessarily in all B cell clones; and (c) normal Ig-secreting cells cease IL-6 expression in contrast to their malignant counterparts, myeloma cells.

Antigens, CD↗