Search PubMed⌕ Search

Biomedical subjects

H Zeng

Publications and source records attributed to H Zeng.

At least 145 records · Page 8Linked to original sources
PubMed1996

The timSL mutant of the Drosophila rhythm gene timeless manifests allele-specific interactions with period gene mutants.

To identify new components of the Drosophila circadian clock, we screened chemically mutagenized flies for suppressors or enhancers of the long periods characteristic of the period (per) mutant allele perL. We isolated a novel mutant that maps to the rhythm gene timeless (tim). This novel allele, timSL, alters the temporal pattern of perL protein nuclear localization and restores temperature compensation to perL flies. timSL more generally manifests specific interactions with different per alleles. The identification of this first period-altering tim allele provides further evidence that TIM is a major component of the clock, and the allele-specific interactions with PER provide evidence that the PER/TIM heterodimer is a unit of circadian function. Although timSL fails to restore PER-L/TIM temperature insensitivity in yeast, it alters the TIM phosphorylation pattern during the late night. The effects on phosphorylation suggest that timSL functions as a partial bypass suppressor of perL and provide evidence that the TIM phosphorylation program contributes to the circadian timekeeping mechanism.

Alleles↗
PubMed1996

Identification of the primary metal ion-activation sites of the diphtheria tox repressor by X-ray crystallography and site-directed mutational analysis.

The diphtheria tox repressor, DtxR, is a 226 amino acid transition metal ion-activated regulatory protein that controls the expression of diphtheria toxin in toxigenic Corynebacterium diphtheriae. The previously solved three-dimensional DtxR structures have identified two potential metal ion binding sites which may play a role in the activation of DNA binding by the repressor. We have used both X-ray crystallographic and site-directed mutational analysis of DtxR(C102D)-Ni2+ complexes and DtxR to identify the metal ion-binding site which results in the activation of the repressor. We demonstrate that DtxR contains both a primary and an ancillary metal ion binding site. The primary site functions directly in the activation of DNA binding. In contrast, the ancillary site contributes weakly, if at all, to activation.

Bacterial Proteins↗
PubMed1996

Phototoxicity of some bromine-substituted rhodamine dyes: synthesis, photophysical properties and application as photosensitizers.

The synthesis of some bromine-substituted rhodamine derivatives viz., 4,5-dibromorhodamine methyl ester (dye 2) and 4,5-dibromorhodamine n-butyl ester (dye 3) are reported. These dyes were synthesized to promote a more efficient cancer cell photosensitizer for potential use in in vitro bone marrow purging in preparation for autologous bone marrow transplantation. Spectroscopic and photophysical characterization of these dyes together with rhodamine 123 (dye 1) are reported in water, methanol, ethanol and also in a microheterogeneous system, sodium dodecyl sulfate. The possible mechanism of photosensitization is characterized in terms of singlet oxygen efficiency of these dyes. Singlet oxygen quantum yields for bromine-substituted dyes are in the range of 0.3-0.5 depending on the solvent. For dye 1 no singlet oxygen production is found. The photodynamic actions of these dyes in different cell lines are tested. It was found that dye 2 and dye 3 are efficient photosensitizers and mediate eradication of K562, EM2, myeloid cell lines (CML) and the SMF-AI rhabdomyosarcoma line.

Animals↗
PubMed1996

Na-K-ATPase in lacrimal gland acinar cell endosomal system: correcting a case of mistaken identity.

Na-K-ATPase is associated with a variety of membrane populations in lacrimal acinar cells. Acinus-like structures formed by rabbit acinar cells in primary culture were incubated with horseradish peroxidase (HRP) to label basolateral and endosomal membranes and then analyzed by electron microscopy cytochemistry with the 3-3'-diaminobenzidine reaction or by fractionation and measurement of marker catalytic activities or immunoreactivities. HRP adsorbed to basolateral membranes at 4 degrees C. Fractionation showed it associated with low-density membranes enriched in acid phosphatase and TGN38 but containing only minor amounts of Na-K-ATPase. Cells internalized HRP to cytoplasmic vesicles, Golgi structures, and lysosomes at 37 degrees C. The major endosomal compartment revealed by fractionation coincided with major peaks of Na-K-ATPase and Rab6 and secondary peaks of galactosyltransferase and gamma-adaptin. Carbachol (10 microM) increased lysosomal and Golgi labeling. Thus most of the Na-K-ATPase is located in the basolateral membrane-oriented endosomal system, concentrated in a compartment possibly related to the trans-Golgi network. Constitutive and stimulation-accelerated traffic to and from this compartment may serve several exocrine cell functions.

Animals↗
PubMed1995

Structures of the apo- and the metal ion-activated forms of the diphtheria tox repressor from Corynebacterium diphtheriae.

The diphtheria tox repressor (DtxR) of Corynebacterium diphtheriae plays a critical role in the regulation of diphtheria toxin expression and the control of other iron-sensitive genes. The crystal structures of apo-DtxR and of the metal ion-activated form of the repressor have been solved and used to identify motifs involved in DNA and metal ion binding. Residues involved in binding of the activated repressor to the diphtheria tox operator, glutamine 43, arginine 47, and arginine 50, were located and confirmed by site-directed mutagenesis. Previous biochemical and genetic data can be explained in terms of these structures. Conformational differences between apo- and Ni-DtxR are discussed with regard to the mechanism of action of this repressor.

Amino Acid Sequence↗
PubMed1995

Phosphorylation of HS1, GAP-associated p190 and a novel GAP-associated p60 protein by cross-linking of Fc gamma RIIIA.

Human Fc gamma receptor IIIA (hFc gamma RIIIA) cDNA was introduced into mouse macrophage/monocyte cell line P388D1, and several stable cell clones expressing hFc gamma RIIIA were isolated. This facilitated the study of the biological function of Fc gamma RIIIA in monocytes/macrophages. The cloned cells showed the high phagocytic activity mediated by hFc gamma-RIIIA, while the original P388D1 cells did not. In order to examine the phosphorylation of proteins involved in hFc gamma RIIIA signal transduction, these receptors were stimulated by cross-linking. The cross-linking of hFc gamma RIIIA induced a rapid increase in tyrosine phosphorylation of several proteins, including PLC-gamma 1, Syk, HS1, and p21rasGAP-associated p190 and p60 proteins. Immunoblotting with a polyclonal antibody specific for the GAP-associated p62 protein, which was originally found in fibroblasts and is homologous with an RNA-binding protein, revealed that the p60 phosphorylated after cross-linking of hFc gamma RIIIA seemed to represent a novel GAP-associated protein unrelated to the known GAP-associated p62 protein, which was also present in the P388D1 cells.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Spectroscopic and microscopic characteristics of human skin autofluorescence emission.

To improve the understanding of human skin autofluorescence emission, the spectroscopic and microscopic characteristics of skin autofluorescence were studied using a combined fluorescence and reflectance spectroanalyzer and a fiber optic microspectrophotometer. The autofluorescence spectra of in vivo human skin were measured over a wide excitation wavelength range (350-470 nm). The excitation-emission matrices of in vivo skin were obtained. An excitation-emission maximum pair (380 nm, 470 nm) was identified. It was revealed that the most probable energy of skin autofluorescence emission photons increases monotonically and near linearly with increasing excitation photon energy. It was demonstrated that the diffuse reflectance, R, can be used as a first order approximation of the fluorescence distortion factor f to correct the measured in vivo autofluorescence spectra for the effect of tissue reabsorption and scattering. The microscopic in vitro autofluorescence properties of excised skin tissue sections were examined using 442 nm He-Cd laser light excitation as an example. It was demonstrated that the fluorophore distribution inside the skin tissue is not uniform and the shapes of the autofluorescence spectra of different anatomical skin layers vary. The result of this study confirms that the major skin fluorophores are located in the dermis and provides an excellent foundation for Monte Carlo modeling of in vivo autofluorescence measurements.

Fluorescent Dyes↗
PubMed1995

Lys91 and His90 of the alpha-subunit are crucial for receptor binding and hormone action of follicle-stimulating hormone (FSH) and play hormone-specific roles in FSH and human chorionic gonadotropin.

Glycoprotein hormones, FSH, LH, CG, and TSH, consist of a common alpha-subunit and a hormone-specific beta-subunit. Both subunits are thought to interact with the hormone receptors. Although several C-terminal residues of hCG alpha are known to contact the LH/CG receptor, little is known about the roles of individual C-terminal residues of FSH alpha. In this report, substitutions of various amino acids for the penultimate Lys91 and the upstream His90 of the alpha-subunit demonstrate that these two residues of FSH alpha are important for high affinity receptor binding and hormone action to induce cAMP production. In contrast, the same residues of hCG alpha are more important for cAMP induction than for high affinity receptor binding. Some substitutions significantly improved receptor binding of FSH and hCG, whereas others were detrimental. Some had the same effect on both hormones, and others impacted differently. Particularly, the substitution of Val for alpha Lys91 resulted in an improved receptor binding of and a loss of cAMP induction by FSH and hCG. On the other hand, the substitution of Arg or Pro for alpha His90 abolished receptor binding of FSH, but not of hCG. These results allowed us to generate an antagonist to FSH. Our results indicate that alpha His90 and alpha Lys91 play roles in receptor binding and cAMP induction of FSH and hCG in strikingly different ways. They will be useful to elucidate the underlying mechanisms for the interaction of FSH and hCG with their complementary receptors as well as for receptor activation.

Animals↗
PubMed1995

Role of the carboxy-terminal residues of the alpha-subunit in the expression and bioactivity of human thyroid-stimulating hormone.

The glycoprotein hormones TSH, CG, LH, and FSH are heterodimers consisting of a hormone-specific beta-subunit and a common alpha-subunit. The aim of the present study was to investigate the role of the carboxy terminus of the common alpha-subunit (amino acids Tyr89-His90-Lys91-Ser92), which has been shown to be important for human (h) CG and hFSH, for the activity of hTSH. Successive truncations of the alpha-carboxy terminus by site-directed mutagenesis revealed a stepwise reduction of bioactivity occurring at residues alpha Ser92 and alpha His90 to 64% and 13%, respectively. This contrasts with previous findings for hCG and hFSH, where loss of bioactivity occurred in a single step with the deletion of alpha Lys91 but alpha Ser92 was not important. The decreased bioactivities of the hTSH alpha-truncation mutants were reflected by concomitant reductions of cAMP production, thyroid hormone synthesis and cell growth and were accompanied by a loss of receptor binding. Substitution of residues alpha Lys91 or alpha His90 with either a hydrophobic or a bulkier residues resulted in a reduction of receptor binding and signal transduction, indicating that the alpha-carboxy terminus of hTSH may interact with the TSH receptor in a tight contact area. Conversely, substitution of alpha His90 with smaller residues enhanced bioactivity. In addition, the integrity of the alpha-carboxy terminus was essential for hTSH expression. Thus, we showed common and different roles of the alpha-carboxy-terminal residues for the glycoprotein hormones. The unique role of alpha Ser92 in hTSH activity explains the evolutionary constraint to preserve the alpha-carboxy-terminal Ser92 in all glycoprotein hormones.

Amino Acid Sequence↗
PubMed1995

[A study on the effective way and dosage of intravas deferens injection of HFMC for male contraception].

To investigate the effective way and dosage of intravas deferens injection of HFMC for male contraception, Teflon tubes of 1 mm caliber were used to imitate intravas injection of HFMC. We injected HFMC first, then the precipitant; thus HFMC could adhere to the walls and blend with the precipitant to precipitate. Eight adult male rabbits, exposed reproductive ducts were injected with dyed HFMC in opposite directions (upward and downward), HFMC flowed out of the distal end of the vas easily when its volume was more than that of the vas. 14 adult rabbits were used for the comparison of sperm density and fertility index between upward and downward injections of HFMC, and between the dosage of HFMC (50 microliters and 100 microliters) injected upward. The results show that it is difficult to attain contraception by intravas injection of HFMC downward, but contraception is quite possible by intravas injection of HFMC upward providing the volume is enough. The result also suggest that HFMC should be injected into vas deferens upward first; its volume should be 3 time as much as the natural volume of the vas from the injecting point to the epididymal end. Then a little precipitant is injected into the vas.

Animals↗
PubMed1994

Constitutive overexpression of the Drosophila period protein inhibits period mRNA cycling.

The Drosophila period gene (per) is a likely component of a circadian pacemaker. per protein (PER) participates in the regulation of its own expression, at least in part at the transcriptional level. There is at present no direct evidence that the effect of PER on its own transcription is intracellular. Results presented in this paper show that (i) the circadian oscillations of both per mRNA and PER protein are quantitatively similar in eye photoreceptor cells and in brain; (ii) constitutive overexpression of PER only in photoreceptors R1-R6 represses endogenous per RNA cycling in these cells but not in other per-expressing cells; (iii) the overexpression construct has no effect on locomotor activity rhythms. These results indicate that the autoregulation of per expression is a direct, intracellular event and suggest that each per-expressing cell contains an autonomous oscillator of which the per feedback loop is a component.

Animals↗
PubMed1994

[Therapeutic effectiveness of zuzhongping on patients with arteriosclerostic cerebral infarction].

Forty-six patients with acute arteriosclerostic cerebral infarction were randomly divided into two groups: control group and treatment group. Each of them included 23 patients respectively. The patients in the control group were given Dextran-40 but the ones in the treatment group were given the mixture of Zuzhongping. The course of treatment was 3 weeks. It was found that there was a significant difference (P < 0.01) in the score percentage, before and after treatment of neurological defects, between the control group and the treatment group, and the former (29.70 +/- 33.52) was much lower than the latter (45.40 +/- 27.60). The total curative rate of the treatment group (87.0%, 20/23) was significantly higher than that of the control group (60.9%, 14/23). There was an obviously prolonged KPTT (kaolin partial thromboplastin time) value and a decreased Fb (fibrinogen) level in the treatment group. Before treatment they were 32.43 +/- 4.03 sec and 6.18 +/- 1.77 g/L respectively, but after treatment, 52.96 +/- 10.50 sec and 4.5 +/- 0.95 g/L respectively. The authors suggest that the significant therapeutic efficacy of Zuzhongping in the patients with acute arteriosclerostic cerebral infarction is related to its action of anticoagulation, modification of PGI2 and TXA2 level in the body, decreased blood Fb level, hyperglycemia, etc.

Aged↗