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Biomedical subjects

Y Hu

Publications and source records attributed to Y Hu.

At least 613 records · Page 34Linked to original sources
PubMed1993

2-Aminopurine inhibits the double-stranded RNA-dependent protein kinase both in vitro and in vivo.

The autophosphorylation of interferon (IFN)-induced double-stranded RNA-dependent p68 protein kinase (PKR) and phosphorylation of the alpha-subunit of the translation initiation factor eIF-2 were inhibited by 10 mM 2-aminopurine in vitro. High concentrations of ATP overcame the inhibition. Kinetic studies indicated that 2-aminopurine is a competitive inhibitor with respect to ATP, suggesting that these two molecules bind the same site on the kinase. Treatment of HeLa cells with poly(I):poly(C) stimulated PKR autophosphorylation in vivo. The stimulated activity was inhibited by 10 mM 2-aminopurine to approximately the same extent as the in vitro inhibition.

2-Aminopurine↗
PubMed1993

Cloning of a xylanase gene from the ruminal fungus Neocallimastix patriciarum 27 and its expression in Escherichia coli.

An endo-beta-1,4-xylanase gene was cloned from Neocallimastix patriciarum 27 in the bacteriophage vector lambda gtWES lambda B and was subcloned into the plasmid vectors pUC18 and pUC19 in which xylanase activity was expressed in both orientations. The xylanase was located in the periplasmic space of the host, Escherichia coli HB101. The pH and temperature optima for periplasmic xylanase activity were 6.2 and 40 degrees C, respectively, and the Km for oat spelt xylan hydrolysis was 0.89 mg.mL-1. It also exhibited hydrolytic activity on carboxymethyl cellulose that was equivalent to 28% of the activity exhibited by the enzyme on xylan. It bound to crystalline cellulose, but lacked hydrolytic activity on amorphous cellulose. SDS-PAGE followed by zymogram analysis showed active bands of 68, 58, and 51 kDa. Isoelectric focusing in gels combined with zymogram analysis showed one band of xylanase activity with a pI of 3.6.

Animals↗
PubMed1993

Disturbed immuno-endocrine communication via the hypothalamo-pituitary-adrenal axis in autoimmune disease.

Previous studies in our laboratory demonstrated an altered immuno-endocrine feedback communication via the hypothalamo-pituitary-adrenal (HPA) axis, which may be an important modulatory factor in the development of spontaneous autoimmune thyroiditis in Obese strain (OS) chickens. These birds show a significantly lower, or even absent, increase in serum glucocorticoid levels in response to an intravenous injection of antigen or conditioned medium (CM) from mitogen-stimulated spleen cells known to contain glucocorticoid-increasing factors (GIFs), notably interleukin-1 (IL-1). The present study was aimed at investigating this feedback regulation in animal models with spontaneous systemic autoimmune diseases, such as the UCD-200 chicken, which serves as a model for human scleroderma, and various murine lupus models. In contrast to OS chickens, UCD-200 chickens displayed a nearly normal plasma corticosterone surge in response to CM, and IL-1 was again identified as the primary GIF in CM. Recombinant IL-1 also induced a drastic increase in plasma corticosterone levels in various strains of normal mice. A similar increase was observed in the bacterial lipopolysaccharide-resistant C3H/HeJ strain, thus excluding the possibility of bacterial endotoxin contamination. However, in young lupus-prone (NZB/W)F1 and MRL/MP-lpr mice, a significantly lower increase in plasma corticosterone levels was observed after injection of recombinant IL-1, suggesting a deficient immuno-endocrine communication via the HPA loop in this instance as well. Detailed studies to identify further cytokines with GIF activity in the avian and murine systems showed that both IL-6 and tumor necrosis factor-alpha could induce increased plasma corticosterone levels in mice, but not in chickens. IL-3, IL-8, transforming growth factor-beta, interferon-gamma and granulocyte-macrophage colony-stimulating factor were devoid of GIF activity in both chickens and mice.

Animals↗
PubMed1993

[Studies on the correlation of blood selenium and lung cancer. II. An analysis of serum selenium levels and influencing factors in patients with lung cancer].

This paper reports the serum selenium concentration in 100 cases of lung cancer patients and 100 healthy controls. The results showed that the serum selenium level in patients with lung cancer was significantly lower than that of controls. Serum selenium level in lung cancer patients was inversely related to the stage of cancer, the amount of tobacco abuse and the serum Cu level. It was positively correlated with patient's nutritional status and the serum albumin level. Serum selenium level was decreased with cancer progression and increased with disease remission. These results suggest that the lower serum selenium level in lung cancer patients was the result rather than the cause of cancer.

Adenocarcinoma↗
PubMed1993

[Studies on the mechanisms of resistance to trimethoprim in Salmonella typhimurium].

The mechanisms of resistance to trimethoprim (TMP) in the clinical isolates of Salmonella typhimurium were studied. The experimental results indicated that the frequency of TMP resistance of 50 strains of Salmonella typhimurium was 76%. Seven of the resistant strains were highly resistant to TMP and four of them contained different plasmids which could transfer in the same species and between different ones, and could be eliminated with 8% of SDS. The results of comparing the activities and characteristics of dihydrofolate reductase (DHFR) in crude extracts from seven resistant strains and those from controls suggested that overproduction of the chromosomal DHFR was the resistance mechanisms in three plasmid-free strains and the levels of DHFR activity of the strains was increased during prolonged exposure to TMP in vitro. However resistance to TMP of the plasmid-containing strains resulted from production of plasmid-mediated TMP resistant type Ia DHFR and a new type DHFR which has not been reported up to now. The present work provided the theoretical basis for clinical use of TMP and attempts to suppress development and spread of duge resistance of pathogenic bacteria.

Salmonella typhimurium↗
PubMed1993

Intelligence function in children with acute lymphoblastic leukemia after treatment.

In order to evaluate the effects of chemotherapy and central nervous system prophylaxis on the intelligence function of children with acute lymphoblastic leukemia (ALL), 147 patients were divided into 2 groups according to their different treatment regimens. Group A included 75 patients with ALL who were diagnosed and treated from 1981 to 1986. Group B included 72 ALL patients diagnosed and treated from 1988 to 1990. A control group included 73 healthy children who shared the same education and environmental background with the patients. Chinese revisions of Wechsler measures of intelligence quotient were used to estimate verbal IQ, performance IQ and total IQ in the 3 groups. American-produced Systate software was used to analyze the data. Results showed that IQ distribution, verbal IQ, performance IQ and total IQ of group A were obviously lower than those in the control group. Verbal IQ and total IQ of group B were also reduced. Significant differences of verbal IQ and performance IQ as well as total IQ were also found between groups A and B. Multiple regression analysis showed negative correlations between IQ and cranial irradiation dosage, times of intrathecal MTX and time after irradiation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

[Molecular and clinical cytogenetic studies of a family with a 22p+ marker chromosome].

A male with gonadal dysgenesis and a 22p+ was observed. Molecular and Clinical Cytogenetic studies have been carried out on the members of the family. The results showed that there was a 22p+ marker chromosome transmitted from the maternal grandmother of the proband to 6 members of this family. Its short arm showed a homogeneously dull stained region in C-banded preparations and a narrow dark or light stained band in R-, G-banded preparations respectively. A large Ag-band or double NORs was also observed on p+. The chromosomal in situ hybridization with tritium labelled rRNA gene probe demonstrated that the distribution of the silver grains was along the entire p+ of the marker chromosome. The number of silver grains on the short arm of the p+ was 3.9 times as that of any other normal acrocentric chromosomes. Two cases of female with repeated spontaneous abortions and 2 cases of male with gonadal dysgenesis were found by family study. Our studies, combining with previous literatures suggested that these abnormalities were probably in association with p+ marker chromosome.

Adult↗
PubMed1992

An improved ELISA with linear sweep voltammetry detection.

An improved ELISA combined with linear sweep voltammetry detection of p-nitrophenol generated by an enzyme has been investigated in this study. p-nitrophenol, produced from alkaline phosphatase catalysing p-nitrophenyl phosphate, yielded an oxidative peak at 1.06 V (vs. Ag/AgCl) with a wax-impregnated tubular graphite anode. Without separation, the small three-electrode system was directly inserted in the well of an ELISA plate for detection. The detection limit for p-nitrophenol was 1 x 10(-6) M, lower than that obtained by measuring the absorbance of p-nitrophenol. The feasibility of utilizing linear sweep voltammetry as a detection scheme was demonstrated by determining metallothionein, granulocyte-colony stimulating factor and Xenopus laevis keratin using the above new system. The method was simple, reproducible and much more sensitive than traditional spectrophotometry.

Animals↗
PubMed1992

Electroretinographic oscillatory potentials in diabetic retinopathy. An analysis in the domains of time and frequency.

The oscillatory potentials of the electroretinogram in dark and light adaptation were evaluated by Fourier transform in 87 diabetics and 74 age-matched controls. The study consisted of four groups: normal control, no observable diabetic retinopathy, background diabetic retinopathy and proliferative diabetic retinopathy. A reduction in the amplitude of each oscillatory potential, the summed amplitudes, the area and the total power of the oscillatory potentials as well as delayed implicit time of each oscillatory potential peak in dark and light adaptation could be found in patients with background diabetic retinopathy and proliferative diabetic retinopathy. The amplitude of oscillatory potential 4 in dark adaptation and the total power of the oscillatory potentials in light adaptation seemed to be affected in patients with no observable diabetic retinopathy. The implicit time of oscillatory potential 2 in dark adaptation was valuable to distinguish between patients with no observable diabetic retinopathy and background diabetic retinopathy.

Adult↗
PubMed1992

Activity of primate putamen neurons is selective to the mode of voluntary movement: visually guided, self-initiated or memory-guided.

The aim of this report was to investigate the neural processes of movement initiation and control in which the basal ganglia play an essential role. Single-neuron activity was recorded in the putamen of monkeys performing learned arm movements initiated in three different modes: sensorially guided, internally-timed self-initiated and memory guided. There were no significant differences in the magnitude and timing of both prime mover and supporting muscle activity between the three modes of movement. Over half of the task-related neurons showed strong activity in one of the three modes of movement initiation, but were only slightly activated in the other two modes. No clear preference for a particular movement mode was evident in the population of putamen neurons as a whole. These results are consistent with the hypothesis that there are heterogeneous groups of neurons in the putamen, and that each group of neurons participates in retrieving a different kind of information required for movement based on either external sensory events or on internally stored information.

Animals↗
PubMed1992

Functional changes in salivary glands of autoimmune disease-prone NOD mice.

Lymphocytic infiltration of the salivary glands in autoimmune diseases results in the human condition known as xerostomia. To date, an animal model for the autoimmune development of salivary gland dysfunction has yet to be described. With the autoimmune diabetes-prone nonobese diabetic (NOD) mouse strain, salivary flow rates and total saliva protein concentration in both male and female mice showed a progressive decline in the nondiabetic and diabetic states. Submandibular gland weight decreased from control mice with the progression to onset of diabetes in both sexes, whereas the weight of the parotid gland remained unchanged. The level of saliva amylase activity, when measured relative to unit volume, decreased in nondiabetic males but increased upon onset of diabetes to control values. When expressed relative to protein concentration in saliva, amylase activity was depressed for both sets of NOD mice but was higher upon diabetes onset than in the nondiabetic animals. In females a similar pattern was observed except that amylase activity expressed relative to unit volume was not significantly depressed in either set of NOD mice. The same observations were made for glandular amylase activity. The level of epidermal growth factor (a product of the ductal cells of the submandibular gland) was reduced over 500- and 18-fold for male and female diabetic mice, respectively. Sodium dodecyl sulfate polyacrylamide gels of total saliva showed changes in mobility as well as concentration of several proteins in the NOD mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Effects of a benz[e]indene on gamma-aminobutyric acid-gated chloride currents in cultured postnatal rat hippocampal neurons.

Benz[e]indenes (BIs) are tricyclic molecules that can be envisioned as steroids without an A-ring. Because certain steroids are known to alter gamma-aminobutyric acid (GABA) responses in central neurons, we examined the effects of a substituted BI resembling 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-OH-DHP) on GABA-gated chloride currents in cultured postnatal rat hippocampal neurons. The compound, BI-1, reversibly potentiated GABA currents at concentrations of > 10 nM, with an EC50 value of 0.2 microM. BI-1 increased the apparent affinity of GABA for its receptor, decreasing the GABA EC50 from 9 microM to 3 microM. BI-1 had no effect on the shape of the GABA current-voltage relationship and did not alter the GABA reversal potential. The effects of BI-1 were not altered by benzodiazepine or picrotoxin site antagonists. At concentrations up to 10 microM, where maximal effects on GABA currents were seen, BI-1 did not directly activate a membrane current. This contrasts with the effects of 3 alpha-OH-DHP, which activated chloride currents at concentrations that were subsaturating for GABA potentiation. These results suggest that the BIs may be useful for determining the mechanisms by which steroids potentiate GABA responses and directly gate chloride channels.

Animals↗
PubMed1992

[The effect of plasmids on the resistance of E. coli to phages].

The introduction of the ColV, I-K94 or R124 plasmid into Escherichia coli K12 resulted in resistance to certain phages. Derivatives of E. coli carrying the plasmid R124 and ColV, I-K94 were resistance to the phages T4, Mel comparing with the plasmid-free parent and the plasmid ColV, I-K94 conferred resistance to the phage Tull*. It suggested that an envelope change caused by the plasmids might be responsible for the resistance because most of the phages fell to absorb to the plasmid-bearing E. coli cells.

Bacteriophage T4↗
PubMed1992

Ultrastructural study of cerebral arteries in Moyamoya disease.

The cerebral arteries in seven cases of Moyamoya disease, demonstrated by angiography were observed by light, transmission and scanning electron microscopy. In two cases, the lumen of the terminal portion of the internal carotid artery was completely occluded by proliferated connective tissue. The characteristic pathologic change was extensive destruction of the smooth muscle cells and the elastica interna. Degeneration and necrosis of smooth muscle cells were obvious in the media. Many condensed organelles and other elements of cellular destruction were dispersed throughout the interstitium. The media was thinned. The proliferated smooth muscle cells in the intima showed the same destructive changes as in the media. The elastica interna was excessively infolded and was thickened or thinned, disrupted or disintegrated in some segments. Identical, but less severe and more localized changes were seen in three middle cerebral arteries (M2 and M5 segments) and two collateral arteries at the base of brain. These changes suggest that Moyamoya disease is a progressive disorder characterized by repeated destruction of smooth muscle cells occurRing over a long time period. The pathogenesis of these changes is discussed.

Cerebral Arteries↗