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Biomedical subjects

Y Hu

Publications and source records attributed to Y Hu.

At least 469 records · Page 26Linked to original sources
PubMed1997

[Screening of thermophilic superoxide dismatase producing strain and some properties of the enzyme].

A thermophilic SOD producing strain was obtained from the bacteria preserved in our lab. Its content of SOD was 8774u/g fresh cells. The strain can tolerate 0.4% H2O2 and 70 degrees C, and it has outstanding culture characteristics. It was identified as Bacillus stearothermophilus, called B.S 211-15. Crude SOD was extracted from B.S 211-15, the recovery of total activity was 69.5%, the specific activity was 1793u/mg protein. The enzyme showed fine heat stability, pH stability and good proteinase resistance. The SOD activity didn't decrease after being kept in room temperature for 2 months. The results of inhibition reactions indicated that this enzyme was Fe-SOD.

Geobacillus stearothermophilus↗
PubMed1997

[The intelligence test of the patients with chronic renal insufficiency].

Thirty patients with chronic renal insufficiency (CRF) and twenty-six normal subjects were tested with Wechsler Adult Intelligence Scal (WALS). The verbal intelligence quotients (VIQ), performance intelligence quotients (PIQ), and full intelligence quotients (FIQ) of the patients were lower than those of the normal group (P < 0.01). Among them the mild and moderate intelligence damages were accounted 13.33%. Further analysis indicates that uremic posionous materials damage on the cerebral function was dose dependant. But the disease course was independant with the intelligence damage (P > 0.05). The results suggest that the plasma concentrations of uremia poisonous materials (BuN, Scr, etc.) in CRF patients should be lowered as early as possible in order to keep the normal function of the cerebrum.

Adult↗
PubMed1996

Loss of Rb activates both p53-dependent and independent cell death pathways in the developing mouse nervous system.

Extensive apoptosis occurs in the nervous system of mouse embryos homozygous mutant for a targeted disruption of the retinoblastoma (Rb) gene. This cell death is present in both the central (CNS) and peripheral nervous systems (PNS) and is associated with abnormal S phase entry of normally post-mitotic neurons. Aberrant proliferation in the CNS correlates with increased free E2F DNA binding activity and increased expression of cyclin E, an E2F target gene and critical cell cycle regulator. Cell death in the CNS is accompanied by increased levels of the p53 tumor suppressor gene product and increased expression of the p53 target gene, p21Waf-1/Cip-1. However, induction of p53 is not observed in the PNS of Rb-mutant embryos, nor does loss of p53 function inhibit cell death in the PNS. Surprisingly, p21Waf-1/Cip-1 is induced in the sensory ganglia of Rb-mutant embryos in a p53-independent manner. Although loss of p53 gene function prevents cell death in the CNS of Rb-mutant embryos, it does not restore normal proliferative control.

Animals↗
PubMed1996

Use of a subcutaneous glucose sensor to detect decreases in glucose concentration prior to observation in blood.

The development of a hypoglycemic alarm system using a subcutaneous glucose sensor implies that a decrease in blood glucose is rapidly followed by a decrease in the signal generated by the sensor. In a first set of experiments the linearity and the kinetics of the response of sensors implanted in the subcutaneous tissue of normal rats were investigated during a progressive increase in plasma glucose concentration: the sensitivities determined between 5 and 10 mM and between 10 and 15 mM were not significantly different, and a 5-10 min delay in the sensor's response was observed. In a second set of experiments, performed in diabetic rats, the kinetics of the decrease in subcutaneous glucose concentration following insulin administration was monitored during a decrease in plasma glucose level, from 15 to 3 mmol/L. During the 20 first min following insulin administration, the sensor monitored glucose concentration in subcutaneous tissue with no lag time. Subsequently, the decrease in the estimation of subcutaneous glucose concentration preceded that of plasma glucose. This phenomenon was not observed when the same sensors were investigated in vitro during a similar decrease in glucose concentration and may be due to a mechanism occurring in vivo, such as the effect of insulin on glucose transfer from the interstitial space to the cells surrounding the sensor. It reinforces the interest of the use of implantable glucose sensors as a part of a hypoglycemic alarm.

Scintillation Counting↗
PubMed1996

Identification of a novel hypothalamic neuropeptide Y receptor associated with feeding behavior.

Neuropeptide Y (NPY) plays important roles in the central control of appetite and energy balance, but the receptor subtype responsible for this function has not been cloned. Here we report the cloning by expression of a novel NPY receptor subtype from a rat hypothalamus cDNA library. The novel receptor, referred to as the NPY Y5 receptor, has a transcript of approximately 2.6 kilobases with an open reading frame of 1335 base pairs that encodes a 445-amino acid protein. The amino acid sequence deduced from the rat Y5 cDNA clone shows only 30-33% identity to other NPY receptors, including Y1, Y2, and Y4/PP1. Using the rat Y5 receptor cDNA probe, the human homologue was obtained by low stringency hybridization. The human Y5 amino acid sequence has 88% identity to the rat Y5 receptor. Importantly, pharmacological analysis shows that the rat and human Y5 receptors have high affinity for the peptides that elicit feeding (e.g. NPY, PYY, (2-36)NPY, and (LP)NPY) and low affinity for nonstimulating peptides (e.g. (13-36)NPY and rat PP), suggesting that it is the NPY feeding receptor subtype.

Amino Acid Sequence↗
PubMed1996

Crystal structure of glycine N-methyltransferase from rat liver.

Glycine N-methyltransferase (GNMT) from rat liver is a tetrameric enzyme with 292 amino acid residues in each identical subunit and catalyzes the S-adenosylmethionine (AdoMet) dependent methylation of glycine to form sarcosine. The crystal structure of GNMT complexed with AdoMet and acetate, a competitive inhibitor of glycine, has been determined at 2.2 A resolution. The subunit of GNMT forms a spherical shape with an extended N-terminal region which corks the entrance of active site of the adjacent subunit. The active site is located in the near center of the spherical subunit. As a result, the AdoMet and acetate in the active site are completely surrounded by amino acid residues. Careful examination of the structure reveals several characteristics of GNMT. (1) Although the structure of the AdoMet binding domain of the GNMT is very similar to those of other methyltransferases recently determined by X-ray diffraction method, an additional domain found only in GNMT encloses the active site to form a molecular basket, and consequently the structure of GNMT looks quite different from those of other methyltransferases. (2) This unique molecular structure can explain why GNMT can capture folate and polycyclic aromatic hydrocarbons. (3) The unique N-terminal conformation and the subunit structure can explain why GNMT exhibits positive cooperativity in binding AdoMet. From the structural features of GNMT, we propose that the enzyme might be able to capture yet unidentified molecules in the cytosol and thus participates in various biological processes including detoxification of polycyclic aromatic hydrocarbons. In the active site, acetate binds near the S-CH3 moiety of AdoMet. Simple modeling indicates that the amino group of the substrate glycine can be placed close to the methyl group of AdoMet within 3.0 A and form a hydrogen bond with the carboxyl group of Glu15 of the adjacent subunit. On the basis of the ternary complex structure, the mechanism of the methyl transfer in GNMT has been proposed.

Amino Acid Sequence↗
PubMed1996

RNA structural features responsible for potato spindle tuber viroid pathogenicity.

The native structure of potato spindle tuber viroid (PSTVd) contains a series of short double helices and small internal loops that are organized into five structural domains. Nucleotides within the pathogenicity domain are known to play a critical role in modulating PSTVd symptom expression, and it has been suggested that disruption of a comparatively unstable "premelting region" within the pathogenicity domain may be required for disease induction. We have used a combination of quantitative bioassays, temperature gradient gel electrophoresis of circularized RNA transcripts, and thermodynamic calculations to compare the biological and structural properties of 12 representative PSTVd sequence variants. Certain mutations appeared to act indirectly, downregulating pathogenicity by suppressing the rate of PSTVd replication/accumulation. The effects of other mutations appeared to be more direct, but there was no consistent correlation between symptom severity and melting temperature. Taking into account the three-dimensional shape of RNA helices, comparison of the optimal secondary structures for these variants point to major differences in the geometry of their pathogenicity domains; i.e., variants producing intermediate symptoms possess a linear arrangement of three consecutive helices, whereas for variants producing mild or severe symptoms this domain is bent in opposing directions. Such alterations in RNA structure together with concomitant alterations in RNA-protein interaction(s) may be the primary cause of viroid pathogenicity.

Base Sequence↗
PubMed1996

Assessment of chromatographic peak purity by means of artificial neural networks.

An improved chemometric approach is proposed for assessing chromatographic peak purity by means of artificial neural networks. A non-linear transformation function with a back-propagation algorithm was used to describe and predict the chromatographic data. The Mann-Whitney U-test was used for the concluding the purity of the chromatographic peak. Simulation data and practical analytical data for both pure and mixture samples were analysed with satisfactory results. A prior knowledge of the impurity and the related compound is unnecessary when a slight difference between their chromatogram and spectrum exists. The performance on simulated data sets by this approach was compared with the results from principal component analysis.

Algorithms↗
PubMed1996

Sos1 rapidly associates with Grb2 and is hypophosphorylated when complexed with the EGF receptor after EGF stimulation.

The Son of sevenless (Sos) protein, a guanine nucleotide exchange factor for ras proteins, appears to play a central role in signalling between protein tyrosine kinase receptors and ras. The C-terminal region of Sos binds an adaptor protein, Grb2, which in turn binds to activated receptors including the EGF receptor (EGFR). Although the Sos protein is rapidly phosphorylated following cytokine stimulation, there is no evidence that this alters the enzymatic activity of Sos for ras proteins. Therefore, we investigated whether the ability of Sos1 to form complexes with Grb2 and with the EGF receptor (EGFR) changes following EGF stimulation, as a possible mechanism for regulating Sos activity. In contrast to earlier findings, we find that both the association and dissociation of Sos1 with Grb2 is responsive to EGF. Whilst the association of Sos1 and Grb2 following EGF stimulation is not cell type specific, we find that it is dependent on cell density and that the response to EGF differs to that induced by NGF. We find that following EGF stimulation, the Sos1 protein associated with the EGFR is markedly less phosphorylated than the majority of the Sos1 within the cell and there was reduced binding of Grb2 with phosphorylated Sos1 protein in a direct binding assay. A time course analysis showed that Sos1 dissociates from the EGFR more rapidly than does Grb2 following EGF stimulation. Collectively our findings are consistent with the notion that the phosphorylation of Sos1 affects its ability to complex with the EGFR and Grb2.

3T3 Cells↗
PubMed1996

Role of the variable domain in modulating potato spindle tuber viroid replication.

Potato spindle tuber viroid (PSTVd) is believed to undergo a series of specific structural transitions during replication. The variable domain of PSTVd is known to contain sequences that are important for replication/accumulation as well as one of three "premelting regions" which control breakdown of the native structure in vitro. We have examined the structural and biological effects of five single and two double nucleotide substitutions within premelting region 3 in an effort to isolate temperature-sensitive mutations affecting PSTVd replication or pathogenesis. None of these mutants replicated as rapidly as the wild type, and a variety of spontaneous sequence changes were detected in their progeny. Higher temperatures were able to partially overcome the inhibition of replication associated with a more stable secondary structure, but no well-defined temperature-sensitive PSTVd mutants were identified. Selective pressures arising from the interaction of assay temperature and structural stability in vivo appear capable of moving PSTVd populations between peaks of relatively high fitness. Depending on the exact nature and location of the mutation, selection may occur at the level of either the plus or the minus strand.

Base Sequence↗
PubMed1996

The COOH-terminal domain of Drosophila TRP channels confers thapsigargin sensitivity.

Previous studies have shown that the Drosophila cation channels designated Trp and Trpl can be functionally expressed in Sf9 insect cells using baculovirus expression vectors. The trp gene encodes a Ca2+-permeable channel that is activated by thapsigargin, blocked by low micromolar Gd3+, and is relatively selective for Ca2+ versus Na+ and Ba2+. In contrast, trpl encodes a Ca2+-permeable cation channel that is constitutively active, not affected by thapsigargin, blocked by high micromolar Gd3+, and non-selective with respect to Ca2+, Na+, and Ba2+. The region of lowest sequence identity between Trp and Trpl occurs in the COOH-terminal domain. To test the hypothesis that this region is responsible for the differential sensitivity of these channels to thapsigargin, chimeric constructs of Trp and Trpl were created in which the COOH-terminal tail region of each protein was exchanged. The Trp construct with the Trpl COOH-tail was constitutively active, insensitive to thapsigargin, but retained selectivity for Ca2+ over Na+ and Ba2+. In contrast, the Trpl construct with the Trp COOH-tail was not constitutively active, could be activated by thapsigargin, but remained non-selective with respect to Ca2+, Ba2+, and Na+. These results suggest that the COOH-terminal domain of Trpl plays an important role in determining constitutive activity, whereas the COOH-terminal region of Trp contains the structural features necessary for activation by thapsigargin.

Amino Acid Sequence↗
PubMed1996

Disturbed immunoendocrine communication via the hypothalamo-pituitary-adrenal axis in murine lupus.

Immune reactions and mitogen stimulation of mammals and chickens lead to an increase of glucocorticoid (GC) plasma levels concomitant with the immune response. Interleukin (IL) 1, one of the most important glucocorticoid increasing factors produced by cells of the immune system, acts via the hypothalamo-pituitary-adrenal (HPA) axis. This pattern of immunoendocrine feedback communication is altered in autoimmune disease (AID) and represents a possible site of action for GC therapy. In the present study we investigated the role and possible underlying mechanisms of a disturbed immunoendocrine communication via the HPA axis in murine lupus. We analyzed the response to recombinant human (rhu) IL-1alpha in AID-prone mice [NZB, NZW, (NZB/NZW)F1, MRL/MP-lpr] in comparison to nonautoimmune, normal control mice (Swiss, C3H/HeJ, MRL/MP-+/+) at different levels of the HPA axis. To this end, we quantified the plasma levels of ACTH, corticosterone, and corticosterone-binding globulin (CBG) and determined various pathology parameters for autoimmunity. AID-prone mice produced nearly the same levels of plasma corticosterone after injection of rhu IL-1alpha as normal mice, but had baseline corticosterone levels consistently higher, thus resulting in significantly lower corticosterone increasing ratios. ACTH levels increased after rhu IL-1alpha injection, but there was no clearcut difference in the increasing ratios of AID-prone and normal strains. CBG levels showed no difference. As expected, there was a correlation of pathology parameters for autoimmunity and the altered immunomodulatory response to rhu IL-1alpha per group. On an individual basis, there was no such correlation. In conclusion, our results confirm the existence of a disturbed immunoendocrine communication in AID-prone mice. This disturbance clearly differs from individual to individual and also among different types of AID.

Animals↗
PubMed1996

Synaptic distribution of the AMPA-GluR2 subunit and its colocalization with calcium-binding proteins in rat cerebral cortex: an immunohistochemical study using a GluR2-specific monoclonal antibody.

Due to its role as the dominant AMPA receptor subunit in respect to regulation of calcium permeability, information on the neuronal localization of GluR2 is of particular importance, yet has been hampered by the lack of a GluR2-specific antibody. Monoclonal antibodies were raised against the putative N-terminal portion (amino acids 175--430) of GluR2, using the fusion protein linked to trpE as an antigen. Western blot analysis and immunocytochemistry of transiently transfected human embryonic kidney 293 cells unambiguously confirmed the specificity of monoclonal antibody 6C4 for GluR2, which did not recognize or cross-react with any other AMPA/Kainate GluR subunits expressed. 6C4 was used in immunohistochemical studies to characterize the regional, cellular, and subcellular distribution of the GluR2 subunit at the light and electron microscopic levels in rat hippocampus and somatosensory cortex and in colocalization studies with the three calcium-binding proteins: parvalbumin, calbindin, and calretinin. GluR2 was widely distributed in both pyramidal cells and interneurons. Asymmetric synapses were labeled on both spines and small dendritic shafts. In contrast to previous reports, our double labeling studies using monoclonal antibody 6C4 with polyclonal antisera against calcium-binding proteins demonstrated that 84--97% of parvalbumin and calbindin-immunoreactive and 45--66% of the calretinin-immunoreactive interneurons in CA1 and somatosensory cortex also contain GluR2. These data have important implications regarding heterogeneity in calcium permeability of AMPA receptors across cell types in neocortex and hippocampus, as well as for differential vulnerability to excitotoxic injury.

Animals↗
PubMed1996

Human papilloma virus, vulvar dystrophy, and vulvar carcinoma: differential expression of human papillomavirus and vulvar dystrophy in the presence and absence of squamous cell carcinoma of the vulva.

In situ hybridization (ISH) and polymerase chain reaction (PCR) for several common HPV types were performed on 41 cases of vulvar dystrophy, 19 of which were associated with previous or simultaneous invasive squamous cell carcinoma of the vulva. Three of the 19 cases (16%) of dystrophy associated with cancer were found to contain HPV-16/18 by PCR. In contrast, 12 of the 22 cases (55%) of dystrophy not associated with carcinoma contained HPV-16/18 by PCR (P < 0.01). A control group of 10 vulvar specimens without dystrophy or carcinoma was negative for all HPV types tested. ISH was negative for all HPV types in all 41 cases. The data confirm the association between vulvar carcinoma and hypertrophic/mixed dystrophy, and provide evidence for an association between HPV-16/18 and some cases of vulvar dystrophy. Cases of vulvar dystrophy not associated with HPV-16/18 may be at increased risk for the development of vulvar carcinoma.

Blotting, Southern↗