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Biomedical subjects

Z Huang

Publications and source records attributed to Z Huang.

At least 487 records · Page 27Linked to original sources
PubMed1992

2-(2'-phosphoryloxyphenyl)-4(3H)-quinazolinone derivatives as fluorogenic precipitating substrates of phosphatases.

Characterization of 2-(2'-phosphoryloxyphenyl)-4(3H)-quinazolinone (PPQ) derivatives as fluorogenic precipitating substrates of phosphatases is reported in this work. Soluble and colorless PPQ derivatives can be specifically hydrolyzed by acid and alkaline phosphatases into insoluble products, 2-(2'-hydroxyphenyl)-4(3H)-quinazolinone (HPQ) derivatives which appear as fluorescent precipitates in water. The fluorescence and precipitation of HPQ depend on the concentration of its neutral phenolic form and therefore are related to the aqueous pH and PPQ concentration converted. Since HPQ formed from corresponding PPQ hydrolysis by phosphatases instantly precipitates and simultaneously fluoresces with a high photostability and large Stokes shift in water, PPQ can serve as a novel class of substrate dyes for detecting any immobilized phosphatase activities in situ, especially for applications of sensitive fluorescence histochemistry and cytochemistry. This is demonstrated by the alkaline phosphatase-aided visualization of static concanavalin A (Con A) receptors. By a linkage-amplification technique involving biotinylated Con A, streptavidin-alkaline phosphatase conjugate, and a PPQ substrate, the Con A receptors on the membrane of fixed NIH 3T3 cell were specifically viewed as dense, contrasting, durable, and cytologically resolved fluorescent stains under a conventional fluorescent microscope.

3T3 Cells↗
PubMed1992

Theoretical and experimental investigation of steady-state voltammetry for quasi-reversible heterogeneous electron transfer on a mercury oblate spheroidal microelectrode.

A mercury microelectrode formed by electroreduction of mercury on an inlaid gold microdisk is experimentally shown to be well modeled by oblate spheroidal geometry when the ratio of the semiminor axis to the semimajor axis of the protruding drop is less than 1. The validity of the geometry is established by comparison of the experimentally determined coefficient in the steady-state diffusion current equation with the theoretical value for oblate spheroidal geometry. Spherical cap geometry is also shown to be an equally valid geometric model; however, theoretical treatment for this system is more difficult. The theory of a quasi-reversible electrode process is developed and applied to the determination of the electrode parameters of the RuIII(NH3)6/RuII(NH3)6 electrode reaction on a mercury oblate spheroidal microelectrode. Results agree well with others found in the literature for the same process on a mercury electrode.

Electrons↗
PubMed1992

Ester and amide derivatives of E64c as inhibitors of platelet calpains.

Ester and amide derivatives of E64c, (+)-(2S,3S)-3-[[(S)-3-methyl-1- [(3-methylbutyl)carbamoyl]butyl]carbamoyl]-2-oxiranecarboxylic acid, an inhibitor of calpains, were synthesized and tested for ability to inhibit calpain in lysed cells, ability to enter intact cells, and ability to inhibit calpain in intact cells. The esters were from halogen-substituted alcohols and alcohols with increasing size. There were no appreciable differences in the inhibitory potency of any of the halogen-substituted esters from ethyl to trifluoroethyl, indicating that ease of hydrolysis of this class of ester is not important for activity. The only ester with impaired activity was the largest, Z-leucyl-norleucyl, which was about 5% as effective as the ethyl ester, E64d. Amides of amino acid esters also had impaired activity. To explore the possibility of targeting E64c derivatives to specific cells, esters and amides of E64c with 5-hydroxytryptamine were tested on the rationale that the active 5-hydroxytryptamine uptake mechanism of platelets might selectively concentrate the drug in platelets. Both the ester and amide inhibited calpain in lysed cells, but only the ester inhibited in intact cells. The 5-hydroxytryptamine ester showed no advantage over the ethyl ester in entering platelets.

Adult↗
PubMed1992

A sensitive competitive ELISA for 2,4-dinitrophenol using 3,6-fluorescein diphosphate as a fluorogenic substrate.

A competitive ELISA for sensitive detection of 2,4-dinitrophenol (DNP) was established. Certain amounts of bovine serum albumin conjugate of DNP were readily coated on a polystyrene microplate. Free DNP was then quantitated by its competition with the coated DNP for binding to anti-DNP (antibody)-alkaline phosphatase conjugate. The enzyme conjugate remaining on the plate surface as a result of the competition was detected by an enzymatic reaction with a fluorogenic substrate, 3,6-fluorescein diphosphate (FDP), or comparatively with a conventional chromogenic substrate, p-nitrophenyl phosphate (PNPP). The results showed that the ELISA with FDP at the optimal conditions of enzymatic reaction can detect as little as 10 fmol DNP, a detection limit of 50 times less than that with PNPP. The easy and sensitive DNP assay procedures in this work can be generalized to ELISAs for other antigens, particularly small antigens, haptens or drugs.

2,4-Dinitrophenol↗
PubMed1992

Recombinant synthesis, purification, and nucleotide binding characteristics of the first nucleotide binding domain of the cystic fibrosis gene product.

The majority of mutations which lead to clinical cystic fibrosis are located within the two predicted nucleotide binding domains of the cystic fibrosis gene product. We have used a prokaryotic expression system to synthesize and purify the first nucleotide binding domain (NBD-1, amino acids 426-588) with and without the most common mutation associated with the disease (the deletion of phenylalanine at position 508, delta F508). Both wild type and delta F508 NBD-1 bind ATP-agarose in a quantitatively comparable manner; this binding was inhibited by excess Na2ATP, trinitrophenol-ATP, or 8-azido-ATP. Irreversible NBD-1 labeling by an ATP analog was demonstrated using [32P]8-azido-ATP. This covalent labeling was inhibited by preincubation with Na2ATP, with half-maximal inhibition for Na2ATP occurring at approximately 5 mM for both the wild type and delta F508 nucleotide binding domain. These experiments are among the first to confirm the expectation that the cystic fibrosis transmembrane conductance regulator NBD-1 binds nucleotide. Since, under the conditions used in our study, NBD-1 without phenylalanine 508 displays very similar nucleotide binding characteristics to the wild type protein, our results support previous structural models which predict that the delta F508 mutation should not cause an alteration in ATP binding.

Adenosine Triphosphate↗
PubMed1992

Clinical trial on termination of early pregnancy with RU486 in combination with prostaglandin.

Termination of early pregnancy was performed in 1572 healthy women with RU486 (mifepristone, 600mg orally once), followed 36-60 hours later by administration of methyl ester of dl-15-methyl-PGF2 alpha (PG05, 1mg vaginal suppository). Complete abortion was accomplished in 91.2% (1433/1571), incomplete abortion in 4.8% (76/1571), and continued pregnancy in 3.9% (62/1571). The time elapsed between RU486 intake and complete expulsion was 2.4 +/- 1.3 days. Expulsion took place on the third day in 935 women (72%), and on the 4th day in 273 women (21.0%). Uterine bleeding occurred on the second or third day after RU486 intake in 1256 women (88.8%), and lasted 11.7 +/- 6.4 (SD) days, range 2-55 days. One subject had blood transfusion due to excessive bleeding. The main side effects were nausea/vomiting (22.3%), abdominal pain (10.2%), headache/dizziness (4.1%) and diarrhea (2.8%). Fatal side effects have not been reported in this study. About 73% of subjects with complete abortion assessed the treatment as good to excellent. Even in the failed cases, 25-42% of subjects considered the treatment as good. Further studies are needed to determine the optimal dose of the RU486 regimen. It should be emphasized that the treatment must be used under close medical supervision in order to monitor the uterine bleeding.

Abortion, Incomplete↗
PubMed1992

Specific lysis of targets expressing varicella-zoster virus gpI or gpIV by CD4+ human T-cell clones.

Varicella-zoster virus (VZV)-specific CD4-positive T cells are known to lyse targets expressing VZV antigen, but little is known of the glycoprotein specificity or phenotype of these cells. To test the ability of T cells to distinguish between gpI and gpIV (which share an antibody-defined epitope), we prepared clones from blood from four healthy individuals by limiting dilution. Among 68 T-cell clones from four donors which were VZV specific in tests of proliferation, 30 lysed autologous Epstein-Barr virus-transformed lymphoblasts which had been superinfected with a recombinant vaccinia virus which included the whole VZV gpI sequence. These clones were characterized as major histocompatibility complex class II restricted by inhibition of their cytotoxicity with HLA-DR and CD4 monoclonal antibodies. Twenty-one clones lysed targets expressing gpIV. Fifteen of these clones lysed targets expressing gpI and gpIV. Four clones with gpI-gpIV specificity were examined in detail, and their dual specificity was confirmed by cold target inhibition. These four clones failed to kill target cells infected with a mutant gpIV recombinant vaccinia virus from which amino acid residues 212 to 354 had been deleted. This region includes one of the two gpIV decapeptides which have 50% homology with amino acids 111 to 121 of gpI. Our data confirm that T-cell-receptor-associated structures are required for specific lysis of VZV targets and indicate that (i) gpI-specific CD4 cytotoxic T cells outnumber gpIV-specific T cells in blood and (ii) 50% of gpI-specific T-cell clones also lyse gpIV-expressing targets.

CD4-Positive T-Lymphocytes↗
PubMed1992

Dexamethasone acts locally to inhibit longitudinal bone growth in rabbits.

Excess glucocorticoid is a potent inhibitor of epiphysial growth. Several mechanisms have been suggested to explain this growth inhibition, including both direct local effects of glucocorticoid on the epiphysial growth plate and indirect systemic effects. Previous studies do not distinguish which of these proposed mechanisms is actually responsible for the growth suppression in vivo. To resolve this controversy, we developed a method for delivering glucocorticoid directly into the rabbit epiphysial growth plate and for accurately measuring the resulting epiphysial growth rate. Five-week-old male rabbits received a local infusion of dexamethasone phosphate (80 ng/microliters, 1 microliters/h) into one proximal tibial growth plate and an infusion of vehicle into the contralateral growth plate. Growth rate was determined by inserting metal pins into the bone immediately adjacent to the growth plate and measuring the change in distance between pins on serial radiographs. This method permitted growth rates to be measured over intervals as short as 3 days, with an error of approximately 5%. Local dexamethasone administration decreased proximal tibial growth rate by 77% compared with the contralateral vehicle-treated tibia (P less than 0.0001). We conclude that excess glucocorticoid causes a rapid potent inhibition of growth by a direct local action on the growth plate.

Animals↗
PubMed1992

L-arginine decreases infarct size caused by middle cerebral arterial occlusion in SHR.

L-Arginine, but not D-arginine, serves as a precursor for the synthesis of nitric oxide (NO), a potent dilator of cerebral blood vessels. We examined the effects of administering L-arginine (300 mg/kg ip) on the volume of infarction in two models of focal cerebral ischemia in spontaneously hypertensive rats (SHR). L-Arginine was administered before (16 and 3 h) and after (5 min and 2 h) vessel occlusion, and animals were killed 24 h later. L-Arginine treatment decreased infarct size in rats subjected to distal middle cerebral arterial (MCA) plus ipsilateral common carotid arterial (CCA) occlusion by 31% [147 +/- 12 (saline) vs. 101 +/- 9 mm3 (L-arginine), P < 0.05]. D-Arginine, administered according to the same dosage and protocol, was without effect. In the group subjected to proximal MCA occlusion, L-arginine decreased infarction size in the striatum by 28% [47 +/- 5 (saline) vs. 34 +/- 3 mm3 (L-arginine), P < 0.05] and neocortex by 11% [193 +/- 7 (saline) vs. 171 +/- 8 mm3 (L-arginine), P < 0.05]. Changes in blood pressure or other measured physiological parameters did not account for the observed differences. The possible use of L-arginine for the treatment of focal cerebral ischemia merits further investigation.

Animals↗
PubMed1992

[Visual and computer evaluation of diazepam-induced EEG changes in epilepsy for localization of epileptogenic lesion].

Diazepam-induced EEG changes were analyzed both visually and by computer in epilepsy for localization of epileptogenic lesion. The results demonstrated that changes in beta spectral were diminished in 11/24 or 15/25 cases, but regionally increased in 3/24 or 3/25 patients overlying the epileptogenic lesion or area of EEG abnormalities. Diazepam-induced delta spectral power was usually increased (9/24), but occasionally focally reduced (3/24) over the lesion. The percentage of positive findings for localization was 38% with visual analysis and 46% with spectral analysis in beta spectral power, 38% in delta spectral power, and 67% with the analysis in combined beta with delta, and 83% with four independent tests. Spectral analysis was more sensitive than visual analysis, and it was a useful supplement to visual analysis, to general EEG evaluation, and to CT. Finally, the study emphasized that a localizing diagnosis to define the epileptogenic lesion should be based on the combination of a multitude of independent tests.

Adolescent↗
PubMed1992

Protective effects of berberine and phentolamine on myocardial reoxygenation damage.

The protective effects of berberine and phentolamine against anoxia and reoxygenation damage in isolated rat hearts have been investigated. Incorporation of berberine (24.5 mumol/L) in both anoxic and aerobic perfusion media resulted in a significant reduction of CPK release during the reoxygenation period, and the ultrastructural damage was reduced as compared with the control group; the myocytes in the berberine-treated group displayed mild intracellular edema, well-registered myofibrils without contracted bands, and swollen mitochondria with partially broken cristae but without dense bodies. Berberine did not inhibit calcium and sodium accumulation or magnesium and potassium loss. Treatment with phentolamine (6.6 mumol/L), an alpha-adrenoceptor antagonist, had similar effects, though the CPK release profile was shifted to the right and downwards. These results suggest that although berberine and phentolamine have some beneficial effects on myocardial reoxygenation injury, they may not abolish the injury. Therefore alpha-adrenoceptor stimulation may not be the major mechanism behind the injury.

Adrenergic alpha-Antagonists↗
PubMed1992

[Clinic-pathological study of 485 cases of postmenopausal bleeding].

Four hundred and eighty-five patients with postmenopausal bleeding (PMB) who underwent a curettage were studied retrospectively to evaluate the relationship of clinical cause and pathological findings. The results showed that nonorganic causes were the most common, benign causes were much commoner than malignant causes. Bleeding from the uterus was the most common in all PMB. Pathological examination revealed atrophic endometrium in 41.5%, proliferative and secretory endometrium only a few. Endometrial and cervical carcinoma were the most common among the malignant causes. PMB with an enlarged uterus, and women with advanced age have a statistically significant correlation with more serious pathology. It is suggested that the postmenopausal endometrium changes are regulated by ovarian and ectopic sex hormones, and endometritis or vascular diseases of the endometrium may be involved in the mechanism of bleeding.

Adult↗
PubMed1992

[Inhibition of fructus Corni on experimental inflammation].

Fructus Corni (FC) decoction inhibits the increase of peritoneal capillary permeability by ip 0.7% acetic acid in mice, the proliferation of granuloma formed by implanting cotton pellets in rats, the swelling of mouse pinnea with xylene and the edema of hind paw induced by injection of fresh egg white 0.1 ml in rats. FC decreases the contents of ascorbic acid in adrenal, but has no marked effect on the contents of prostaglandin E in inflammatory tissue of rats. These results indicate that the inhibitory effect of FC on the inflammatory process may be related to pituitary-adrenal axis.

Adrenal Glands↗
PubMed1992

A simple and sensitive enzyme-mediated assay of biotin.

Free biotin was quantitated by a competition by coating biotin-bovine serum albumin conjugate on a polystyrene microplate for binding to avidin-beta-galactosidase conjugate. The enzyme conjugate remaining on the plate surface as a result of the competition was detected by reaction with one of the following fluorogenic substrates, resorufin beta-D-galactoside and fluorescein di-beta-D-galactoside, in a fluorescence plate reader. Free biotin as little as 0.1 nmol can be routinely detected.

Avidin↗
PubMed1992

A clinical trial of oat bran and niacin in the treatment of hyperlipidemia.

BACKGROUND: Previous studies have demonstrated the lipid-lowering potential of wax-matrix controlled-release forms of nicotinic acid, but questions have been raised about the risks associated with long-term use. This report describes a 38-week trial that was designed as a follow-up to a shorter 16-week clinical trial of wax-matrix controlled-release niacin. The present study also tested the hypothesis that niacin (1500 mg/d) and oat bran (56 g/d [2 oz/day]) may have a synergistic effect on improving serum lipid levels. METHODS: Ninety-eight subjects began the following protocol: oat bran alone (6 weeks), oat bran plus niacin (6 weeks), and niacin alone (32 weeks). Blood lipids, blood chemistries, nutritional variables, and side-effect profiles were monitored throughout the study. Sixty-nine (70%) subjects completed the trial taking the full dose of niacin (1500 mg/d); 8 subjects completed the trial taking a reduced dose of niacin (average 906 mg/d); 11 discontinued taking any niacin because of either intolerable side effects (n = 7) or liver enzyme abnormalities (n = 4). RESULTS: Generally, oat bran-niacin synergism was not found. Only 10% of subjects who completed the study showed greater than expected lipid improvement on combination therapy. From baseline to the end of the final phase, significant reductions (P less than .05) occurred for total cholesterol (-10%) and low-density lipoprotein cholesterol (-16%). High-density lipoprotein cholesterol rose significantly at the end of the oat bran plus niacin phase, but returned to near baseline by the end of the study. The liver enzymes alkaline phosphatase, lactate dehydrogenase, and aspartate aminotransferase all showed a tendency to rise throughout the study. CONCLUSIONS: The results of this 38-week trial suggest that the relatively inexpensive wax-matrix form of niacin is effective and reasonably well tolerated. Approximately 8% of subjects were unable to continue taking niacin because of side effects, and 4% discontinued taking niacin because of liver enzyme elevations. A small group of subjects (10%) experienced greater than expected lipid improvements (synergism) on combined oat-bran and niacin therapy. Liver function monitoring with long-term use of niacin is warranted.

Adult↗
PubMed1991

Diagnosis of genetic disease by primer-specified restriction map modification, with application to cystic fibrosis and retinitis pigmentosa.

Detection of small alterations or abnormalities in genomic DNA (eg, point mutations or small deletions) has become increasingly important in the diagnosis of genetic disease and polymorphism. When a mutation or polymorphism creates a new restriction endonuclease site, it can easily be identified by polymerase chain reaction (PCR) amplification of the DNA region of interest, followed by digestion with the restriction endonuclease. However, useful restriction sites are the exception, and a variety of specialised techniques have been developed to identify subtle DNA abnormalities. We have shown that where a DNA mutation does not create a useful novel restriction site, such a site can be introduced by PCR and specially chosen primers. The approach is simple and inexpensive and should be broadly applicable in the diagnosis of genetic polymorphism and mutation. The technique is illustrated here by the three base-pair deletion responsible for most cases of cystic fibrosis and by detection of the point mutation in the rhodopsin gene that has been associated with some cases of autosomal dominant retinitis pigmentosa.

Alleles↗
PubMed1991

Study on mutagenicity and identification of organic pollutants in wastewater of industrial area.

In this study, wastewater samples from three industrial wastewater channels and 12 related factories were collected. Nonvolatile organic chemicals were concentrated on H-103 resin and analysed by GC/MS/DS techniques. The mutagenicity of organic extracts from the samples was examined by using S. typhimurium assay (Ames test). The results of both Ames test and chemical analysis showed that the mutagenic compounds in the Loujia Channel mainly come from Dyestuff Factory, and that Pharmaceutical Factory is a main pollution source of mutagenic compounds for the Xindun Channel. Our experimental results also showed that it is necessary to examine the mutagenicity of industrial wastewater by using short term bioassay for evaluating long-term effect of industrial wastewater on human health.

Coloring Agents↗