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Biomedical subjects

Z Cai

Publications and source records attributed to Z Cai.

At least 199 records · Page 11Linked to original sources
PubMed1993

Cytolytic activity of intestinal intraepithelial lymphocytes in germ-free mice is strain dependent and determined by T cells expressing gamma delta T-cell antigen receptors.

We have compared the cytolytic activities and the cellular compositions of the intestinal intraepithelial lymphocyte (i-IEL) populations in three different combinations of conventional (CV) and germ-free (GF) mice. Cytolytic activity of i-IELs expressing gamma delta T-cell antigen receptors (TCRs) is strain dependent in CV mice (high vs. low), and this strain-dependent variability is unaltered in the GF condition. Although absolute numbers of gamma delta i-IELs are slightly decreased, the composition of CD8 alpha alpha+ and CD4-CD8- subsets and the usage of TCR gamma- and delta-chain variable gene segments by gamma delta i-IELs remain the same in GF mice. By contrast, cytolytic activity of alpha beta TCR-expressing i-IELs is uniformly high in CV mice but attenuated sharply in the GF condition. A conspicuous decrease in the total numbers of alpha beta i-IELs is also noted, and CD8 alpha beta+ and CD4+CD8+ subsets are reduced, whereas the CD8 alpha alpha+ subset is expanded in GF mice. These results indicate that microbial deprivation preferentially influences the alpha beta i-IEL population to decrease and become noncytolytic but has little effect on the pool size or characteristics of gamma delta i-IELs. Consequently, cytolytic activity of freshly isolated i-IELs from GF mice is determined by T cells expressing gamma delta TCRs and is found to be strain dependent.

Animals↗
PubMed1993

Differential expression of H-2K and H-2D in the central nervous system of mice infected with Theiler's virus.

A model of demyelination induced by Theiler's murine encephalomyelitis virus (TMEV) was used to study differential regulation of class I MHC gene products in the brain and spinal cord of resistant (B10) and susceptible (B10.Q and B10.RBQ) mice. Allelic polymorphisms in the H-2D region, but not the H-2K region, play a primary role in determining susceptibility to late demyelinating disease. However, even though significant structural diversity distinguishes class I alleles, there are no discernible K or D-specific patterns of structural diversity within the peptide binding domains of these glycoproteins. Our hypothesis was that D region association of susceptibility to demyelination was related to differences in the expression of the K and D Ag in the central nervous system (CNS) after TMEV infection. Using allele-specific mAb and an immunoperoxidase technique, we demonstrated transient but equivalent increases in K and D Ag expression in the brain and spinal cord of resistant mice beginning 7 days after TMEV infection, which returned to baseline by 90 days. However, when genetically susceptible animals were examined, a significantly greater increase in D expression relative to K expression was seen in the brain and spinal cord at all post-infection observation periods. Immunosuppression of genetically resistant animals before TMEV infection, which results in viral persistence, was accompanied by equivalent increases in both the K and D Ag. Depletion of CD8+ T cells, but not CD4+ T cells, in susceptible mice ablated class I expression in the CNS in response to TMEV infection, implying that CD8+ cells contribute to the differential regulation of K and D Ag in the CNS. These findings are consistent with the hypothesis that differences in gene regulation may account for different roles of the K and D loci play in determining resistance and susceptibility to TMEV-induced demyelinating disease.

Animals↗
PubMed1993

Acute, chronic and differential effects of several anesthetic barbiturates on glutamate receptor activation in neuronal culture.

The acute and chronic effects of several anesthetic barbiturates, in therapeutic concentrations, on the excitatory amino acid (EAA)-induced elevation of intracellular calcium levels ([Ca2+]i) were examined in neuronal tissue culture. The ultrashort-acting barbiturate, thiamylal, was effective in blocking elevations of [Ca2+]i induced by kainate, N-methyl-D-aspartate (NMDA), and quisqualate or by membrane depolarization with 40 mM KCl. The structurally similar barbiturate, secobarbital which differs from thiamylal only by having an oxygen in place of a sulfur, was able to block elevations induced by the above EAAs but was less effective than thiamylal and did not significantly reduce [Ca2+]i that resulted from membrane depolarization with KCl. Pentobarbital, while differing from secobarbital by only a methyl group, was without effect on either the NMDA- or 40 mM KCl-induced elevations of [Ca2+]i. By contrast, cyproheptadine, a compound that has been shown to block Ca2+ channels, has a different profile from the above barbiturates in that cyproheptadine is more effective in blocking elevation of [Ca2+]i induced by membrane depolarization with KCl while the barbiturates are more effective in reducing [Ca2+]i induced by EAAs. An anticonvulsant barbiturate, phenobarbital, did not reduced elevations of [Ca2+]i induced by any EAA tested or by membrane depolarization with KCl. When cells were treated chronically with thiamylal for 4 days, 2-6 h after the abrupt drug withdrawal there was a hyperresponsiveness to the elevations of [Ca2+]i induced by both kainate and NMDA but not by quisqualate. A similar hyperresponsiveness was not seen after the chronic treatment with phenobarbital.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Resiliency to amplification of carbon tetrachloride hepatotoxicity by chlordecone during postnatal development in rats.

The interactive hepatotoxicity of CCl4 and chlordecone, at an individually nontoxic dosage, was studied in neonatal and young developing rats. The well-documented amplification of CCl4 (100 microL/kg) hepatotoxicity and lethality by prior dietary exposure to chlordecone (10 ppm, for 15 d) was absent in neonatal and developing rats through 35 d of age. The chlordecone-potentiated hepatotoxicity and lethality of CCl4 was partially expressed in 45-d-old rats and fully expressed in 60-d-old rats. Although hepatic microsomal cytochrome P-450 content in 2- or 5-d-old rats was significantly lower than that in older age groups, the cytochrome P-450 content was not significantly different between 35-, 45-, and 60-d-old chlordecone-treated rats. During postnatal development, the ongoing hepatocellular proliferation declined in a biphasic manner, more rapidly up to 20 d and slowly thereafter, as indicated by 3H-thymidine incorporation in hepatic nuclear DNA. This pattern of postnatal liver proliferation and growth was not altered by exposure to chlordecone. In vivo metabolism of CCl4, in terms of 14CO2 production derived from 14CCl4 and 14CCl4 metabolites bound to hepatic tissue, was not significantly different between 35-, 45-, and 60-d-old chlordecone-treated rats, whereas CCl4-stimulated hepatocellular regeneration in 35-d-old chlordecone-treated rats was significantly higher than in 45- or 60-d-old chlordecone-treated rats, as indicated by 3H-thymidine incorporation into hepatic DNA and histomorphometric analysis. These data suggest that the absence of potentiation of CCl4 toxicity by chlordecone in postnatally developing rats is well correlated with the presence of ongoing and stimulatable hepatocellular regenerative activity.

Age Factors↗
PubMed1993

[The Chinese demographic challenge].

Recent official vital statistics data from China are used to emphasize the seriousness of the demographic situation in China, and to highlight the continued pressure on limited resources exerted by a growing population that is struggling to achieve socioeconomic development. The authors conclude that "the pessimistic scenarios of evolution of Chinese vital factors justify the pursuit, or even the intensification, of the birth control programme. New educational programmes should focus on the necessity to develop new solidarities, to achieve a [reasonable] vital growth at least during the next five decades, which could lead to a better balanced...development of the economy." (SUMMARY IN ENG)

Asia↗
PubMed1993

The cloning and sequencing of coat protein gene from beet necrotic yellow vein virus.

The beet necrotic yellow vein virus (BNYVV) isolate NM was isolated from sugarbeet infected with rhizomania in Inner Mongolia of China. The cDNA of BNYVV coat protein (CP) gene was amplified from the extracted RNA of BNYVV isolate NM by using the polymerase chain reaction (PCR) and cloned into pGEM-7zf(+). Its complete nucleotide sequence was determined by means of Sanger's dideoxy-mediated chain-termination method. The result shows that CP gene of BNYVV isolate has 567 nucleotides. It shares 98.8% and 96.7% identity with the CP gene of isolate F13 (report in reference [1]) in terms of amino acid and nucleotide sequence, respectively.

Amino Acid Sequence↗
PubMed1992

Amitriptyline, desipramine, cyproheptadine and carbamazepine, in concentrations used therapeutically, reduce kainate- and N-methyl-D-aspartate-induced intracellular Ca2+ levels in neuronal culture.

The glutamate receptor agonists, kainate and N-methyl-D-aspartate (NMDA) result in the elevation of intracellular calcium levels ([Ca2+]i) in primary cultures of cerebellar granule neurons. Several tricyclic antidepressants (TCAs), amitriptyline (0.5-1 microM), desipramine (1 microM) and doxepine (1 microM) partially prevent this elevation induced by both of these excitatory amino acids (EAAs), but not elevations of [Ca2+]i induced by another EAA, quisqualate. Evidence suggests that this EAA-tricyclic interaction may involve voltage-dependent Ca2+ channels since amitriptyline also partially blocks the elevation of [Ca2+]i induced by membrane depolarization with 40 mM KCl. However, the blockade is not reversed in high concentrations of extracellular Ca2+ ([Ca2+]o) as would be predicted by a direct interaction with Ca2+ channels. Cyproheptadine (0.5-1 microM), a serotonin antagonist that is structurally similar to amitriptyline, causes similar effects as reported above for the TCAs; however, ketanserine (10 microM), also a serotonin antagonist but without the tricyclic nucleus, is less effective in this regard. Carbamazepine, an anticonvulsant with a tricyclic nucleus, produces similar effects as the above three compounds only in higher, yet therapeutic, concentrations (50 microM). Neither 5-hydroxytryptamine nor norepinephrine (100 microM, each) had effects on the EAA-induced elevation of [Ca2+]i. This is the first report to show an interaction of tricyclic antidepressants with the function of glutamate receptors in concentrations which are consistent with therapeutic dosages.

Amitriptyline↗
PubMed1992

Structural and functional analysis of three D/L-like class I molecules from H-2v: indications of an ancestral family of D/L genes.

Three cDNA with D region gene features have been identified from the H-2v haplotype. Provisionally, the sequences have been designated as D/Lv1, D/Lv2, and D/Lv3. The coding segments for the antigen binding domain (ABD) of all three D/Lv genes were engineered into a class I genomic expression vector and expressed in L cells. FACS analysis of the three D/Lv-Ld gene transfectants revealed that the D/Lv1 molecules were recognized by both monoclonal antibodies (mAbs) 141 and 142, and the D/Lv2 molecules were recognized by mAb 143. In addition to the D/Lv1 molecules, the mAb 141 also recognized the D/Lv3 molecules. Both the D/Lv1-Ld and D/Lv2-Ld transfectants were killed efficiently by H-2Dv region-specific alloreactive CTL. The D/Lv3 gene is the first identified D region gene other than D and L that is transcribed abundantly in spleen and the D/Lv3 RNA is present as two alternatively spliced forms. Structural analysis of the D/Lv3 hybrid molecules showed that it was susceptible to proteolysis and thermolabile at 37 degrees C, suggesting D/Lv3 is a transcribed pseudogene. A parsimony tree analysis of three D/Lv sequences with a set of class I gene sequences revealed that the H-2v sequences clustered with D region genes. The presence of a third gene with D/L-like features in H-2v, yet structurally different from the known D/L alleles, raises the possibility that the current D/L genes evolved from a family of D/L-like genes, some of which are no longer represented among many of the mouse major histocompatibility complex haplotypes. The observation that D region alleles cluster into subgroups suggests that the alleles are not all related to each other by linear descent through a single locus. We propose that current alleles are derived from more than one ancestral locus in a manner similar to the origin of the gamma 2 a immunoglobulin constant region alleles.

Alleles↗
PubMed1992

Selective effects of cyanide (100 microM) on the excitatory amino acid-induced elevation of intracellular calcium levels in neuronal culture.

The effect of low concentrations of cyanide on the excitatory amino acid-induced elevations of intracellular calcium levels ([Ca2+]i) was studied in cerebellar granule cells using ratio fluorometry with fura-2. Glutamate, kainate, N-methyl-D-aspartate (NMDA), quisqualate (50 microM, each) and membrane depolarization by 40 mM KCl caused elevations of [Ca2+]i which were 10-, 10-, 3-, 2.3-, 10-fold over baseline levels, respectively. Cyanide, 100 microM, greatly augmented the increases in [Ca2+]i induced by glutamate, kainate and NMDA but not those induced by quisqualate or KCl. In the absence of these excitatory amino acids, cyanide had no significant effect in concentrations up to 400 microM. Elevations of [Ca2+]i induced by quisqualate and KCl were not significantly augmented by higher concentrations of cyanide (400 microM). Selective antagonists could block the effect of cyanide+the respective agonist; however, the calcium channel blockers, lanthanum and diltiazem lowered both NMDA- and kainate-induced elevations of [Ca2+]i, yet neither blocked increases in calcium when 100 microM cyanide was added. Collectively, these data support an interaction of cyanide with the excitatory amino acid receptor.

Amino Acids↗
PubMed1991

Hepatotoxicity and lethality of halomethanes in Mongolian gerbils pretreated with chlordecone, phenobarbital or mirex.

The hepatotoxic and lethal effects of CBrCl3, CCl4 and CHCl3 were investigated in gerbils with or without prior exposure to dietary chlordecone (CD), phenobarbital (PB) and mirex (MX) at 10, 225 and 10 ppm, respectively, for 15 days. Gerbils were quite sensitive to these halomethanes (48 h LD50: 20, 80 and 400 microliters/kg, respectively). CD, known to potentiate hepatotoxic and lethal effects of halomethanes in rats, failed to potentiate the toxic effects of any of these three halomethanes in gerbils. PB and MX were also ineffective. Since stimulation of early hepatocellular regeneration has been shown to be responsible for the recovery from the toxicity of a low dose of CCl4, liver cell regeneration and tissue repair were studied in gerbils after CCl4 administration. The objectives of these studies were to investigate the possible reasons for the high sensitivity of gerbils to halomethane toxicity and to investigate the mechanism for their refractoriness to CD-potentiated halomethane toxicity. A low and a high dose of CCl4 (15 and 80 microliters/kg, i.p. respectively) were used to study the time-course of liver injury in gerbils pretreated with or without CD. The low dose of CCl4 stimulated cellular regeneration as indicated by the increase of 3H-thymidine (3H-T) incorporation in hepatic nuclear DNA. The cellular regeneration and tissue repair activities resulted in complete recovery from the limited liver injury in both CD-pretreated and control gerbils. In contrast to rats, however, the process of cell division in gerbils occurred much later, 2 days after CCl4 administration. Evidence from histomorphometric studies was consistent with serum enzyme and 3H-T incorporation data.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Determination of eucalyptole in eucalyptus oil by gas chromatography].

This paper reports the determination of eucalyptole in eucalyptus oil by gas chromatography. The results were similar to the specifications in the Chinese Pharmacopoeia. The method is simple, rapid, accurate and sensitive and requires only small amount of samples. The coefficient of variation is less than or equal to 0.52%.

Chromatography, Gas↗
PubMed1989

Scanning electron microscopic observation on the surface ultrastructure of leucocytes in CSF.

Using scanning electron microscope (SEM), The CSF leucocytes from 3 healthy subjects and 12 patients with various NS diseases were observed. The findings were used to compare with those by optical microscope (OM) and those of human peripheral blood cells by SEM. Five types of CSF cells with particular surface structures, are emphasized in relation to both optical microscopic findings and the involved diseases.

Cell Membrane↗