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H Zhou

Publications and source records attributed to H Zhou.

At least 631 records · Page 35Linked to original sources
PubMed1993

Effects of the age of donor or host tissue on astrocyte migration from intracerebral xenografts of corpus callosum.

Our previous studies in which neural tissue was transplanted into neonatal rat brains have demonstrated that the patterns of astrocyte migration are stereotypic and are mainly influenced by local factors in the host brain. Here we examine how these patterns are affected by the relative maturity of donor cells and recipient brains. In one group of animals, adult mouse corpus callosum was transplanted into the cortex or midbrain of neonatal rat brains; in a second group, corpus callosum from 2- to 3-day-old mice was placed in adult rats. The location of the grafts and the distribution of donor astrocytes were defined by using a monoclonal antibody (anti-M2) specific for mouse astrocytes. In marked contrast to previous studies involving transplantation into neonatal hosts, very few neonatal astrocytes placed into adult brains invaded the gray matter and these never migrated more than 250 microns from the graft. The migration in adult brains also failed to show targeted migration to regions such as the substantia nigra. In the second group, astrocytes from adult grafts implanted in neonatal hosts migrated in both gray and white matter of brains in patterns similar to those of neonatal cells placed in neonatal brains. These observations suggest that the astrocyte migration in the white and gray matter is guided by different cues and that the maturation of host brain environment, but not the age of donor cells, influences the pattern of cell migration.

Aging↗
PubMed1993

Serological analysis of barley stripe mosaic virus-encoded proteins in infected barley.

Polyclonal antisera raised against proteins or peptides corresponding to barley stripe mosaic virus (BSMV) open reading frames were used in immunoblot experiments to investigate the in vivo expression of BSMV-encoded proteins during infection of barley. Six of the seven putative gene products, whose functional roles have been defined in previous genetic studies, were detected at one or more stages of infection in barley tissue sampled at 4, 7, 10, and 14 days postinoculation (DPI). The alpha a, beta a, beta b, beta d, gamma a, and gamma b gene products were observed during the course of infection, but a protein corresponding to the beta c gene could not be identified. The 130-kDa alpha a and the 74-kDa gamma a proteins, which comprise the essential BSMV-encoded replicase components, differed in the time course of their expression and in their subcellular distribution. The highest concentration of the alpha a protein coincided with the appearance of leaf symptoms at 4 DPI and declined gradually as infection progressed. The alpha a protein was found primarily in the soluble protein fraction but some of the protein was also found in the membrane and cell wall fractions. In contrast, the gamma a protein peaked in concentration later at 7 to 10 DPI and was more abundant in membranous fractions. The cysteine-rich 17-kDa gamma b protein was located predominantly in the soluble fraction and its concentration remained relatively constant during the course of infection. The 25-kDa capsid protein (beta a) was present in the highest amounts in the soluble fraction at 4 DPI and it continued to increase in abundance throughout the sampling period. The transiently expressed 58-kDa beta b protein, which like beta c and beta d is required for systemic infection, was most abundant at the onset of symptoms, but declined precipitously in concentration as the infection progressed. Although larger amounts of beta b were present in the soluble fraction, the cell wall fraction contained a substantial portion estimated to be 30 to 40% of the protein. Affinity-purified antisera raised against a peptide corresponding to the hydrophobic 14-kDa beta d ORF revealed the presence of a BSMV-specific protein of the predicted size in membrane and cell-wall fractions. Like the beta b protein, the level of the beta d protein decreased dramatically as infection progressed, suggesting that the synthesis of these two proteins is coordinately expressed from the RNA beta subgenomic RNA.

Amino Acid Sequence↗
PubMed1993

Secretory monoclonal IgA antibody to human sperm produced by gastrointestinal immunization inhibits human sperm activity and mouse in vitro fertilization.

BALB/c mice were immunized intragastrically with human sperm. Cells from the Peyer's patches and spleens of the immunized mice were for the preparation of hybridomas secreting antisperm monoclonal IgA (mcIgA). The specific ratio of IgA-secreting cells in Peyer's patches was much higher than that in spleen. The binding site on human sperm of 9 of 19 mcIgA was in the post-acrosomal region using an immunofluorescent assay. Two of eight selected mcIgA caused strong human sperm agglutination and three of them produced significant inhibition of mouse in vitro fertilization. No mcIgA tested caused obvious human sperm immobilization or inhibited mouse in vivo fertilization. In vitro assembly of selected mcIgA in ascites with mouse secretory component (SC) caused no significant changes in effects on sperm function and in vitro fertilization. By use of Western blotting, dimer or higher polymers were demonstrated in all selected mcIgAs and corresponding protein antigens in 6 of 8 selected mcIgAs. These results suggest that human sperm function may be inhibited and fertilization rate reduced by specific secretory IgA to human sperm and that secretory immunity to protein antigens of human sperm could be induced by intragastrointestinal immunization.

Animals↗
PubMed1993

Sudden death due presumably to internal use of methamphetamine.

A 26-year-old male was found naked and excited in the backyard of his neighbor's house. He was carried to a nearby hospital, and returned home with his family, but took a sudden turn for the worse and died. In a judicial autopsy, the ethanol concentration of blood was found to be 0.58 milligrams, and methamphetamine (MA) was detected in his blood by thin-layer chromatography. The concentration of MA in his blood was 4.38 mumol/dl, higher than the fatal level. The amount of MA in his stomach was 5.8 mg (34.58 mumol/100 g), indicating that he ingested MA by internal use. Among the autopsy cases of acute MA poisoning reported in Japan, hyperesthesia is known to last 1-3 h before death, whether the administration is by intravenous injection or orally. But the present case is quite unusual, as the death followed 6 h or more of hyperesthesia. This was attributed to the patient's combined intake of alcohol with MA, as it is known to decrease the mortality in mice.

Adult↗
PubMed1993

Homophilic adhesion between Ig superfamily carcinoembryonic antigen molecules involves double reciprocal bonds.

Both carcinoembryonic antigen (CEA) and neural cell adhesion molecule (NCAM) belong to the immunoglobulin supergene family and have been demonstrated to function as homotypic Ca(++)-independent intercellular adhesion molecules. CEA and NCAM cannot associate heterotypically indicating that they have different binding specificities. To define the domains of CEA involved in homotypic interaction, hybrid cDNAs consisting of various domains from CEA and NCAM were constructed and were transfected into a CHO-derived cell line; stable transfectant clones showing cell surface expression of CEA/NCAM chimeric-proteins were assessed for their adhesive properties by homotypic and heterotypic aggregation assays. The results indicate that all five of the Ig(C)-like domains of NCAM are required for intercellular adhesion while the COOH-terminal domain containing the fibronectin-like repeats is dispensable. The results also show that adhesion mediated by CEA involves binding between the Ig(V)-like amino-terminal domain and one of the Ig(C)-like internal repeat domains: thus while transfectants expressing constructs containing either the N domain or the internal domains alone were incapable of homotypic adhesion, they formed heterotypic aggregates when mixed. Furthermore, peptides consisting of both the N domain and the third internal repeat domain of CEA blocked CEA-mediated cell aggregation, thus providing direct evidence for the involvement of the two domains in adhesion. We therefore propose a novel model for interactions between immunoglobulin supergene family members in which especially strong binding is effected by double reciprocal interactions between the V-like domains and C-like domains of antiparallel CEA molecules on apposing cell surfaces.

Animals↗
PubMed1993

Effects of spatial filtering and lack of effects of visual imagery on pattern-contingent color aftereffects.

Checkerboards contain fundamental two-dimensional Fourier components oriented 45 degrees from the edges of individual checks. Previous studies have shown that contingent color aftereffects following adaptation to chromatic checkerboard stimuli were associated with the fundamental components rather than the edges. In the present experiments, we measured contingent color aftereffects, using the method of constant stimuli, after subjects adapted to unfiltered checkerboards and checkerboards with the fundamental Fourier components removed. The adaptation stimuli were magenta (or green) squares and green (or magenta) diamonds; the test stimuli were vertical or oblique sine-wave gratings with different saturations. After adaptation to unfiltered checkerboards, aftereffects contingent on the fundamental components were obtained. In contrast, after adaptation to filtered stimuli, aftereffects of smaller magnitude were found to be aligned with the edges. The data support the previous findings of spatial-frequency-contingent color aftereffects with checkerboard adaptation stimuli and indicate that the aftereffects can be associated with edges if the fundamental components of adaptation stimuli are removed by spatial filtering. We reexamined the possibility of color aftereffects induced by imagery of checkerboards. Contrary to the previous reports, no significant aftereffects were obtained.

Adult↗
PubMed1992

A suppressor of TBP mutations encodes an RNA polymerase III transcription factor with homology to TFIIB.

The TDS4 gene of S. cerevisiae was isolated as an allele-specific high copy suppressor of mutations within the basic region of the TATA-binding protein (TBP). The gene is essential for viability and encodes a 596 aa protein. The first 300 aa of the TDS4 protein exhibit significant sequence similarity to the RNA polymerase II transcription factor TFIIB. However, TDS4 is required for RNA polymerase III transcription in vivo and in vitro. Antibodies specific for TDS4 or TBP react with the TFIIIB complex, indicating that both proteins are components of the RNA polymerase III initiation complex. These findings suggest that the RNA polymerase II and III initiation mechanisms are extremely similar, and they explain how the TATA-binding protein can function in both systems.

Amino Acid Sequence↗
PubMed1992

Unmutated proto-src coding region is tumorigenic if expressed from the promoter of Rous sarcoma virus: implications for the gene-mutation hypothesis of cancer.

The transforming (onc) genes of oncogenic retroviruses share most or all of their coding sequences with normal cellular genes termed proto-onc genes. The viral genes differ from proto-onc genes in virus-specific promoters and in various point mutations and substitutions of cell-derived coding regions. In view of the structural similarities between viral oncogenes and cellular proto-onc genes, the hypothesis has been advanced that proto-onc genes become cellular cancer genes if they have suffered mutations. Indeed, point mutations and substitutions have been observed in the proto-onc genes of some cancers. However, the hypothesis has been difficult to prove because mutated proto-onc genes from tumors do not transform diploid cells. Moreover, owing to the popularity of this hypothesis, even viral oncogenes are thought to derive transforming function from mutations of this cell-derived coding region. A competing hypothesis proposes that enhanced expression from retroviral promoters is necessary and sufficient for oncogenic function of proto-onc genes. To distinguish between these hypotheses we have tested tumorigenicity of RpSV, a synthetic retrovirus with the normal proto-src coding region in a vector derived from Rous sarcoma virus (RSV). In addition, we have tested the role of RSV-specific src point mutations on the tumorigenicity of RpSV. It was found that RpSV with an unmutated proto-src coding region is tumorigenic in chickens and that tumorigenicity is enhanced by RSV-specific src point mutations. It is concluded that retroviral promoters are essential for the transforming function of viral oncogenes and that certain point mutations merely supplement their transforming function. Thus retroviral onc genes are not models for the hypothesis that mutated, but transcriptionally normal, proto-onc genes of certain tumors are cancer genes.

Animals↗
PubMed1992

Transcription factor IID mutants defective for interaction with transcription factor IIA.

Transcription factor IID (TFIID) recognizes the TATA element of promoters transcribed by RNA polymerase II (RNAPII) and serves as the base for subsequent association by other general transcription factors and RNAPII. The carboxyl-terminal domain of TFIID is highly conserved and contains an imperfect repetition of a 60-amino acid sequence. These repeats are separated by a region rich in basic amino acids. Mutagenesis of the lysines in this region resulted in a conditioned phenotype in vivo, and the mutant proteins were defective for interactions with transcription factor IIA in vitro. Binding of TFIID to DNA was unaffected. These results suggest that the basic domain of TFIID is important for protein-protein interactions.

Amino Acid Sequence↗
PubMed1992

Fatal bleeding from duodenal varices as a late complication of neonatal thrombosis of the inferior vena cava.

A 21-year-old man was hospitalized with repeated bleeding from the gastrointestinal tract, the cause of which could not be detected by gastroscopy, colonoscopy or arteriography. After the third surgical intervention he died of uncontrollable bleeding. At autopsy, marked and partly ulcerated duodenal varices were found to be the cause of the bleeding. They were part of a collateral circulation that had developed from chronic obstruction of the inferior vena cava, where thrombosis had arisen in association with neonatal renal vein thrombosis. There was consecutive renal infarction which had required a left nephrectomy on the 2nd day after birth.

Adult↗
PubMed1992

Inhibition of cellular autophagy in proximal tubular cells of the kidney in streptozotocin-diabetic and uninephrectomized rats.

To examine the significance of anti-catabolism in renal hypertrophy, cellular autophagy was investigated by electron microscopic morphometry in proximal tubular cells (PTCs) of the outer cortex of the rat kidney after the induction of diabetes mellitus by streptozotocin (STZ) and after unilateral nephrectomy. Adult male Sprague-Dawley rats were divided into three groups and killed by retrograde perfusion fixation, 1, 2 and 3 days after the induction of diabetes (group D; n = 24), after unilateral nephrectomy (group N; n = 24) and after combined treatment (group DN; n = 24). Untreated, age-matched litter mates served as controls (group C; n = 24). By comparison with these controls, the left kidney to initial body weight ratio was increased by 8, 23, and 15% in group D animals, by 8, 23, and 24% in group N animals, and by 10, 21, and 25% in group DN animals at the first, second and third day, respectively. Quantitative evaluation of large test areas showed that the volume and numerical densities of autophagic vacuoles (AVs) in PTCs were significantly lower in these hypertrophed kidneys than in the controls. The average reduction in AV volume density was about 65% in group D animals, about 50% in group N animals and about 75% in group DN animals. These data show that autophagic degradation of cytoplasmic components in PTCs is inhibited in renal hypertrophy independently of the growth stimulus, i.e. uninephrectomy or diabetes. Since insulin per se inhibits cellular autophagy in PTCs, the expected effect of insulin dificiency seems to be counteracted by as yet undefined stimuli that may be related to metabolic work load.

Animals↗
PubMed1992

Cellular autophagy in proximal tubules of early diabetic rats following insulin treatment and islet transplantation.

The influence of insulin treatment (group 1) and allogenic islet transplantation (group 2) on renal cellular autophagy were evaluated in adult Lewis rats in the early phase of streptozotocin-induced diabetes mellitus--a condition in which autophagy is inhibited and renal mass is increased. Three days after insulin treatment or islet transplantation (IT), the right kidney was resected and cortical tubular tissue was examined by quantitative electron microscopy. In group 1, the volume and numerical densities of autophagic vacuoles (AVs) increased by 70% and 80% respectively in the proximal tubular cells compared with saline-injected controls. The additive effect of unilateral nephrectomy (Ux) on cellular autophagy was investigated 1 or 2 days after Ux. Compared with the resected right kidney, the volume and numerical densities of AVs in the remnant left kidney decreased by 49% and 43% in the insulin-treated rats, and by 43% and 39% in the saline-injected diabetic animals. In group 2, the volume and numerical densities of AVs increased by 45% and 44% in parenchyma regressing from diabetic hypertrophy after IT, compared with sham-operated controls. After Ux, the volume and numerical densities of AVs decreased by 49% and 43% in IT rats, and by 41% and 53% in the still diabetic sham-operated animals. The data show that inhibition of cellular autophagy in the proximal tubules of the early diabetic kidney can be reversed by insulin replacement, despite the fact that insulin per se inhibits cellular autophagy in the nondiabetic kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Electrical impedance tomography. Solving anisotropic mixed boundary value problems by means of the boundary element method.

In a previous study we have shown that an anisotropic volume conduction problem involving the Neumann condition at the outer surface of a volume conductor can be solved by means of the boundary element method by applying an appropriate coordinate transformation (Zhou and van Oosterom 1991). In this paper we will show that this approach can also be applied to solve the anisotropic mixed boundary value condition problems studied in electrical impedance tomography (EIT). Results are presented of numerical computations, which were carried out for a volume conductor of irregular (torso) shape.

Electric Conductivity↗
PubMed1992

Computation of the potential distribution in a four-layer anisotropic concentric spherical volume conductor.

A method for solving the potential distribution in a multilayer anisotropic concentric spherical volume conductor, which has recently been described in the literature, has been tested and found to be numerically unstable. In this paper it is demonstrated how these numerical difficulties can be avoided. Moreover, the method is extended by lifting the previously imposed restriction on the innermost region to be isotropic. A convergence criterion for determining the required number of terms in the final series expansion is proposed. The influences of radial and tangential conductivity values of the skull and brain tissue on the dipole-induced potential are investigated.

Algorithms↗
PubMed1992

China POPIN.

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Asia↗