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W H Zhang

Publications and source records attributed to W H Zhang.

At least 37 records · Page 2Linked to original sources
PubMed2000

[The regulation of NO on sleep-wakefulness in rats].

AIM AND METHODS: The effects of an inhibitor of nitric oxide synthase L-NAME and a precursor of NO(L-arginine) on sleep-wakefulness in rats were examined. RESULTS: 1. The time of waking was increased(P < 0.01) and the time of SWS was decreased(P < 0.01) during the first two hours after injection intracerebroventricularly(i.c.v.) of L-NAME 1 mg, this effect was showed across the 4 h recording period(P < 0.05). The i.c.v. injection of L-NAME 0.2 mg had no significant effect. 2. The time of waking was su-ppressed during the third and fourth hours after i.c.v. injection of L-arginine 300 micrograms(P < 0.05). At the same time the increase of SWS was observed (P < 0.01). 3. There was no change on W, SWS, PS when L-NAME 1 mg was given after administration of L-arginine. CONCLUSION: The excitatory effect of L-NAME on wakefulness is mediated by inhibition of NOS. This effect could be antagonized by L-arginine. It suggests that NO is involved in regulation of sleep-wakefulness.

Animals↗
PubMed2000

[Effect of interleukin 2 on the expression of estrogen receptors in the anterior pituitary of rats].

Using primary serum-free cell culture combined with immunocytochemistry and semi-quantified RT-PCR methods, we observe the modulation of estrogen receptor alpha (ERalpha) and beta (ERbeta) by interleukin-2 (IL-2) in rat anterior pituitary. The results show that IL-2 up-regulates the level of ERalpha protein and the expression of ERalpha mRNA, but down-regulates those of ERbeta. The density per cell of ERalpha-immunoreactive (ir) cells increases from 48.740 4.567 to 81.188+/-6.619, whereas that of ERbeta -ir cells decreases from 102.560+/-6.250 to 72.718+/-7.623 after rhIL-2 (10 microgram/L) incubation for 48 h. In parallel with these changes, the ratio of ERalpha/ beta -actin mRNA increases from 0.1511 to 0.4334, and ERbeta /beta -actin mRNA declines from 0.3822 to 0.1528. It is likely that IL-2 has direct regulatory effect on ER in anterior pituitary.

Animals↗
PubMed2000

[Interleukin-2 stimulates the proliferation of cultured RC-4B/C pituitary adenoma cell line].

The aim of the present study was to investigate whether interleukin-2 (IL-2) is involved in the proliferation control of the cultured RC-4B/C cell, which is a derived pituitary adenoma cell line of the rat. The level of cell proliferation was estimated by assessing (3)H-thymidine ((3)H-TdR) incorporation rate. IL-2 (10 1000 U/ml) significantly stimulated (3)H-TdR incorporation into the cell line in a dose-dependent manner. Specific PTK inhibitor tyrphostin (1 micromol/L) suppressed RC-4B/C cell proliferation and blocked the effect of IL-2 on RC-4B/C cells. After the PKA signaling pathway was inhibited by specific PKA inhibitor H-9 (1 micromol/L), the proliferation rate of RC-4B/C cells increased significantly. H-9 also enhanced the stimulation of IL-2 on RC-4B/C cell growth. Anti-estrogen tamoxifen (1 micromol/L) had no significant effect on the action of IL-2 on the proliferation of RC-4B/C cells. In conclusion, it is suggested that IL-2 modulates the proliferation of the cultured RC-4B/C pituitary adenoma cell line, and the action is closely related with the PTK and PKA signaling pathway.

Adenoma↗
PubMed2000

[Studies on the effect of column temperature on gel permeation chromatography].

By experiments, we found that the effect of temperature on column efficiency increased with the increase of relative molecular mass. The elution volume was relevant to the temperature, while the selectivity was not. Besides, the resolution for macromolecules was improved significantly by increasing temperature while not for small molecules. Further, the same results were obtained at different temperatures in certain range.

Chromatography, Gel↗
PubMed2000

[Ultrastructural observation of E. coli K12 treated with antibacterial peptide CM4].

The effect of antibacterial peptide CM4 of Bombyx mori against E. coli K12 was investigated using scanning electron microscopy(SEM) and transmission electron microscopy (TEM). The ultrastructural changes of E. coli K12 were observed by the challenge of the purified antibacterial peptide CM4. The results showed that the antibacterial peptide caused a series of pathological changes on E. coli. SEM and TEM revealed aggregates of bacteria and SEM revealed wrinkled bacterial surfaces in the early stage. Thereafter, plasmolysis was observed with irregular holes appearing in the two ends of bacteria and the cytoplasmic contents of the cells leaking out. Finally, bacteria became empty vesicles and disintegrated into small fragments subsequently. Comparatively, the bacterial membrane was normal and the bacterial structure remained intact in the control group.

Animals↗
PubMed1999

Sexually dimorphic expression of sst1 and sst2 somatostatin receptor subtypes in the arcuate nucleus and anterior pituitary of adult rats.

The pattern of growth hormone (GH) secretion and rate of somatic growth are markedly sexually dimorphic, but the underlying neuroendocrine mechanisms are far from clear. In the present study, we tested the hypothesis that the sexual dimorphism of GH secretion may be due to gender-related differences in the transduction of somatostatin's actions in brain and/or pituitary. To accomplish this, we compared the distributional pattern and level of expression of two somatostatin receptor subtypes, sst1 and sst2, in the brain and pituitary of adult male and female rats by in-situ hybridization using 35S-labelled antisense riboprobes. In the brain, the hybridization pattern and labelling density of sst1 and sst2 mRNA-expressing cells, as revealed by computer-assisted image analysis, in areas including the cerebral cortex, medial habenula (MHb) and ventromedial hypothalamic nucleus (VMN), were similar in male and female rats. In contrast, there was a marked sex-related difference in sst1 expression in the arcuate nucleus of the hypothalamus; both the number and labelling density of sst1 mRNA-expressing cells were two- to threefold greater in males than in females and this significant increase was homogenous throughout the rostrocaudal extent of the nucleus. No gender-related differences in arcuate sst2 mRNA levels were found. At the level of the anterior pituitary, the labelling density of sst2 mRNA in males was significantly higher than that of females. No sex-related difference in pituitary sst1 mRNA was observed. These results demonstrate a sexual dimorphism in the expression of two somatostatin receptor subtypes, sst1 and sst2, at the level of the arcuate nucleus and anterior pituitary, respectively. Such dimorphism suggests a differential involvement of sst1 and sst2 in GH regulation with respect to gender, and may imply roles for sst2 and sst1 in transducing somatostatin's actions on pituitary somatotrophs and GH-releasing hormone-containing arcuate neurones, respectively, to generate the lower basal and higher GH pulse levels characteristic of the male rat.

Animals↗
PubMed1998

Further evidence for hexagonal organization of HIV gag protein in prebudding assemblies and immature virus-like particles.

The fullerene-like model for the organization of HIV gag encoded precursor pr55gag was based on the study of prebudding assemblies at the plasma membrane of cells infected with a recombinant baculovirus expressing HIV-1 gag protein. The objective of the present study was to support the model by image processing of virus-like particles (VLP). In this work we used VLP purified by density gradient centrifugation, which caused partial or occasionally complete loss of the lipid bilayer in some VLP without the use of detergent. In addition more plasma membrane-associated pr55gag protein assemblies were processed. Image processing of negatively stained specimens revealed the presence of threefold symmetry and a hexagonal network of rings with a resolution of 29 A in VLP and better than 25 A in membrane associated assemblies. The center-to-center spacing of the rings was 67 A in VLP and 70 A in membrane assemblies. Patches of gag protein oligomers at the plasma membrane were usually round and varying in size, but some of them were triangular. Indication of triangular-shaped gag protein assemblies was also seen in partly dissociated VLP. Since the hexagonal network is formed by the uncleaved gag polyprotein, we conclude that the threefold symmetry applies to all domains including p24gag. The presence of threefold symmetry and the hexagonal network in VLP are consistent with the hypothesis that immature HIV particles possess icosahedral symmetry.

Animals↗
PubMed1998

Detection of a trimeric human immunodeficiency virus type 1 Gag intermediate is dependent on sequences in the matrix protein, p17.

Previous studies have shown that single amino acid changes in the amino-terminal matrix (MA) domain, p17, of the human immunodeficiency virus type 1 Gag precursor Pr55, can abrogate virion particle assembly. In the three-dimensional structure of MA such mutations lie in a single helix spanning residues 54 to 68, suggesting a key role for this helix in the assembly process. The fundamental nature of this involvement, however, remains poorly understood. In the present study, the essential features of the MA helix required for virus assembly have been investigated through the analysis of a further 15 site-directed mutants. With previous mutants that failed to assemble, residues mapped as critical for assembly were all located on the hydrophobic face of the helix and had a key role in stabilizing the trimeric interface. This implies a role for the MA trimer in virus assembly. We support this interpretation by showing that purified MA is trimeric in solution and that mutations that prevent virus assembly also prevent trimerization. Trimerization in solution was also a property of a larger MA-capsid (CA) Gag molecule, while under the same conditions CA only was a monomer. These data suggest that Gag trimerization driven by the MA domain is an intermediate stage in normal virion assembly and that it relies, in turn, on an MA conformation dependent on the hydrophobic core of the molecule.

Animals↗
PubMed1998

Growth hormone-releasing hormone neurons in the arcuate nucleus express both Sst1 and Sst2 somatostatin receptor genes.

Several lines of evidence suggest that somatostatin (SRIF) regulates GH release through central control of hypothalamic GHRH neurons. A possible mechanism is through interaction with SRIF binding sites previously shown to be associated with a subpopulation of GHRH-containing neurons in the arcuate nucleus (Arc), although the molecular identity of these binding sites is not yet known. We performed dual chromogenic and autoradiographic in situ hybridization to determine whether GHRH neurons coexpress either the sst1 and/or sst2 SRIF receptor mRNAs. Computerized image analysis revealed that approximately 15% of GHRH-hybridizing neurons in the Arc expressed the sst1 receptor gene, whereas 15% coexpressed sst2 mRNA. These studies are the first to colocalize any SRIF receptor subtype in GHRH mRNA-containing neurons in brain. The results suggest that, in the Arc, SRIF may directly modulate GHRH release into the hypophyseal portal blood, and thereby influence GH secretion, through interaction with both sst1 and sst2 receptor subtypes.

Animals↗
PubMed1997

Effect of low oxygen concentration on the electrical properties of cortical cells of wheat roots.

Short-term effect of oxygen-deficiency on the membrane potential difference (PD), membrane resistance of cortical cells and electrical coupling between cortical cells was investigated using excised wheat roots. Hypoxia rapidly depolarised the membrane potential of the cortical cells by about 60 mV, while hypoxia had little effect on the membrane resistance of the cells. No significant change in membrane resistance by potassium channel blockers, TEA+ and verapamil, under hypoxia was observed. The electrical coupling ratio, which is a measure of plasmodesmatal resistance, between cortical cells of wheat roots was 5.9 % in aerated solution and was not affected by the low oxygen treatment, suggesting that solute transport through cytoplasmic annulus of plasmodesmata could not be affected. The possible involvement of the endoplasmic reticulum in intercellular transport of solute and water is discussed.

Calcium Channel Blockers↗
PubMed1997

[Effect of interleukin-2 on the proliferation of cultured rat anterior pituitary cells].

The present study was to investigate whether IL-2 is involved in the proliferation control of anterior pituitary (AP) cells. Primary culture of AP cells was obtained from either male or female Sprague-Dawley rats. The effects of IL-2 were assessed by 3H-thymidine incorporation rate. It was found that: (1) IL-2 (10-500 U/ml) significantly stimulated 3H-TdR incorporation into AP cells of female pregnant as well as none-pregnant rats, but inhibited 3H-TdR incorporation in the male rats. (2) The stimulatory effect of IL-2 was reversed in overiectomized rats, but could be restored when the overiectomized rats were treated with estradiol benzoate (5 micrograms/d per rat). (3) When the male rats were orchiectomized for 2 weeks, the inhibitory effects of IL-2 did not occur. The above data indicated that the proliferative effect of IL-2 on AP is a joint action of sex steroids hormones.

Animals↗
PubMed1996

Gag-Gag interactions in the C-terminal domain of human immunodeficiency virus type 1 p24 capsid antigen are essential for Gag particle assembly.

Seven internal deletions within the p24 domain of the human immunodeficiency virus type 1 Gag precursor have been assessed for their effect on Gag particle formation following their expression using recombinant baculoviruses. In addition, each deleted molecule was assessed for its ability to bind soluble p24 antigen in vitro. The mutants fell into three different phenotypic groups: (i) three mutants that had no effect on either p24 binding or Gag particle assembly, (ii) three mutants that abolished both features and (iii) one mutant that bound p24 in vitro but failed to assemble particles. Mutations that abolished both in vitro p24 binding and particle assembly mapped to the C terminus of p24 confirming this region as critical for virion assembly. We suggest the division of virion assembly into at least two distinct phases and suggest a model in which the critical sequences mapped to date are combined with available structural information.

Animals↗
PubMed1996

[Involvement of the nerve fiber elements in the anterior pituitary in the regulation of ACTH secretion].

While peptidergic nerve fibers have been immunoreactively identified in the adenohypophysis of mammals, the function of these fibers in the regulation of hormone secretion remain unknown. The present work was undertaken to investigate possible modulating effects of these fibers on the secretion of ACTH in the anterior pituitary. Electrical field stimulation (EFS) was applied to excite the nerve terminals in anterior pituitary quarters of male rats under static incubation, and the ACTH level was determined by radioimmunoassay. It was found that the ACTH release from the anterior pituitary was significantly enhanced by EFS (30 mA, 0.5 ms and 10 Hz), which could be significantly decreased by adding TTX or veratridine into the incubation medium. However, TTX failed to inhibit AVP-induced ACTH secretion. Since the dispersed cultured anterior pituitary cells did not respond to the same EFS, it was suggested that there might exist dual modulatory mechanisms on the anterior pituitary hormone secretion.

Adrenocorticotropic Hormone↗
PubMed1995

A molecular determinant of human immunodeficiency virus particle assembly located in matrix antigen p17.

We report single-point mutations that are located in the matrix protein domain of the gag gene of human immunodeficiency virus type 1 and that prevent Gag particle formation. We show that mutations of p17 that abolish human immunodeficiency virus particle assembly also prevent the dimerization of p17 protein, as measured directly by a protein-protein binding assay. In the three-dimensional structure of p17, mutations that abolish dimerization are located in a single alpha helix that forms part of a fingerlike projection from one side of the molecule. Peptides derived from this region of p17 also reduce the level of p17 dimer when they are added to p17-expressing cells and compete for p17 self-association when present in protein-protein binding assays. We propose that the dimerization of the Gag precursor that occurs by the interdigitation of alpha helices on adjacent matrix molecules is a key stage in virion assembly and that the prevention of such an interaction is the molecular basis of particle misassembly.

Base Sequence↗
PubMed1995

[Regulatory effect of ventral tegmental area on sleep-wakefulness in rats].

Experiments were performed on 31 male SD rats. The results were as follows: (1) The time of waking was increased during the second and third hours after microinjection of 3.3 and 6.6 nmol bromocriptine into bilateral VTA (P < 0.01), but the 1.33 nmol group was without significant effect. (2) The time of waking was decreased during the second and third hours after microinjection of 2 and 4 nmol SCH23390 into VTA (P < 0.01 and P < 0.05 respectively), while 3.4 nmol sulpiride group was without effect. (3) One week after administration of kainic acid (0.3 microgram), the rats presented less time of waking in the day (P < 0.05), while sleep-wakefulness cycle at night showed no change. The results suggest that bromocriptine could increase wakefulness by activating VTA DA neurons via D1 receptor and that the DA neurons might exert a tonic effect for maintaining the wakefulness at the daytime.

Animals↗