Biomedical subjects

X Huang

Publications and source records attributed to X Huang.

At least 523 records · Page 29Linked to original sources

PubMed1996

Serotonin modulates retinotectal and corticotectal convergence in the superior colliculus.

A dense serotonin (5-HT)-containing projection to the superficial layers of the superior colliculus (SC) has been demonstrated in diverse mammalian species, but how 5-HT may affect visual signals within these laminae is largely unknown. This study undertook to investigate the distribution of 2 types of 5-HT receptors in the SC and to ascertain their physiological effects on transmission of visual signals to the SC from the retinotectal and corticotectual pathways. Autoradiography of tissue sections exposed to [3H]-8-OH-DPAT (8-hydroxy-dipropylaminotetraline) or to [125I]cyanopindolol plus isoproterenol showed that 5-HT1A and 5-HT1B receptors, respectively, were present in the superficial SC layers. In unilaterally enucleated animals, binding of ligand to 5-HT1B receptors was greatly reduced on the deafferented (contralateral) side, which is consistent with the possibility that these receptors are located on preterminal axons. Binding to 5-HT1A receptors was unaltered by enucleation. In recordings of superficial layer neurons from SC slices, application of 5-HT during blockade of 5-HT1A receptors with spiperone reduced the amplitude of EPSPs evoked by stimulation of the optic tract. The 5-HT concentration for a 50% reduction in EPSP amplitude was 6 microM. Under these conditions, there were no significant alterations in either membrane potential or input resistance concurrent with 5-HT mediated reduction in EPSPs. During extracellular in vivo recordings, 5-HT, applied by iontophoresis or micropressure or by endogenous release produced by electrical stimulation of the dorsal raphé nucleus, strongly suppressed visual activity in SC neurons. The effectiveness of 5-HT application was significantly stronger on responses evoked by electrical stimulation of the optic chiasm (an average response decrement of 92.2%) than on these evoked in the same neurons by stimulation of visual cortex (an average response reduction of 32.3%). These results support the following conclusions. The 5-HT1B receptors are located preferentially on optic axon terminals and exert presynaptic inhibition of retinotectal inputs. Secondly, 5-HT1A receptors probably have a postsynaptic localization and may affect activity of SC neurons irrespective of the source of input. The combined effect of 5-HT at both subtypes would bias SC visual activity toward information received from the corticotectal pathway.

Animals↗

PubMed1996

Exogenous glutamate concentration regulates the metabolic fate of glutamate in astrocytes.

The metabolic fate of glutamate in astrocytes has been controversial since several studies reported > 80% of glutamate was metabolized to glutamine; however, other studies have shown that half of the glutamate was metabolized via the tricarboxylic acid (TCA) cycle and half converted to glutamine. Studies were initiated to determine the metabolic fate of increasing concentrations of [U-13C] glutamate in primary cultures of cerebral cortical astrocytes from rat brain. When astrocytes from rat brain were incubated with 0.1 mM [U-13C] glutamate 85% of the 13C metabolized was converted to glutamine. The formation of [1,2,3-13C3] glutamate demonstrated metabolism of the labeled glutamate via the TCA cycle. When astrocytes were incubated with 0.2-0.5 mM glutamate, 13C from glutamate was also incorporated into intracellular aspartate and into lactate that was released into the media. The amount of [13C] lactate was essentially unchanged within the range of 0.2-0.5 mM glutamate, whereas the amount of [13C] aspartate continued to increase in parallel with the increase in glutamate concentration. The amount of glutamate metabolized via the TCA cycle progressively increased from 15.3 to 42.7% as the extracellular glutamate concentration increased from 0.1 to 0.5 mM, suggesting that the concentration of glutamate is a major factor determining the metabolic fate of glutamate in astrocytes. Previous studies using glutamate concentrations from 0.01 to 0.5 mM and astrocytes from both rat and mouse brain are consistent with these findings.

Alanine↗

PubMed1996

Fast comparison of a DNA sequence with a protein sequence database.

We describe a computer program, named DNA-Protein Search (DPS), for comparing a megabase DNA sequence with a protein sequence database. The DPS program addresses the problems of frameshifts and introns in the DNA sequence. The DPS program was used to compare each of the following sequences with the Swiss-Prot database: the 1.8-megabase sequence of the Haemophilus influenzae Rd genome, the 0.58-megabase sequence of the Mycoplasma genitalium genome, and the 0.56-megabase sequence of Saccharomyces cerevisiae chromosome VIII. The comparisons found new regions that are similar to protein sequences. The sensitivity of DPS was evaluated using as test data the known coding regions of the three DNA sequences. The results demonstrate that the DPS program is a useful tool for finding the coding regions of the DNA sequence. The DPS program uses an order of magnitude less computer memory and is several times faster than the BLASTX program.

Amino Acid Sequence↗

PubMed1996

Methods for comparing a DNA sequence with a protein sequence.

We describe two methods for constructing an optimal global alignment of, and an optimal local alignment between, a DNA sequence and a protein sequence. The alignment model of the methods addresses the problems of frameshifts and introns in the DNA sequence. The methods require computer memory proportional to the sequence lengths, so they can rigorously process very huge sequences. The simplified versions of the methods were implemented as computer programs named NAP and LAP. The experimental results demonstrate that the programs are sensitive and powerful tools for finding genes by DNA-protein sequence homology.

Algorithms↗

PubMed1996

Effects of tetramethylpyrazine phosphate and sodium ferulate alone or in combination on hemodynamics in anesthetized dog.

Hemodynamic actions of intravenous (iv) administration of tetramethylpyrazine phosphate (TMPP) and sodium ferulate (SF) alone or in combination were studied in anesthetized dogs. When given alone, TMPP increased left ventricular systolic pressure (LVSP), peak positive first derivative of left ventricular pressure (+LVdp/dt), coronary blood flow (CBF) and heart rate (HR) while decreasing mean aortic pressure (mAoP). SF alone did not produce any significant hemodynamic changes. When the two were administered in combination, SF antagonized dose-dependently the hemodynamic actions of TMPP. Results of this study did not support the efficacy of combined treatment of Ligusticum wallichi and Angelica root, which contain TMPP and SF respectively.

Analysis of Variance↗

PubMed1996

New insights into the compartmentation of glutamate and glutamine in cultured rat brain astrocytes.

Studies from several groups have provided evidence that glutamate and glutamine are metabolized in different compartments in astrocytes. In the present study we measured the rates of 14CO2 production from U-[14C]glutamate and U-[14C]glutamine, and utilized both substrate competition experiments and the transaminase inhibitor aminooxyacetic acid (AOAA) to obtain more information about the compartmentation of these substrates in cultured rat brain astrocytes. The rates of oxidation of 1 mM glutamine and glutamate were 26.4 +/- 1.4 and 63.0 +/- 7.4 nmol/h/mg protein, respectively. The addition of 1 mM glutamate decreased the rate of oxidation of glutamine to 26.3% of the control rate, demonstrating that glutamate can effectively compete with the oxidation of glutamine by astrocytes. In contrast, the addition of 1 mM glutamine had little or no effect on the rate of oxidation of glutamate by astrocytes, demonstrating that the glutamate produced intracellularly from exogenous glutamine does not dilute the glutamate taken up from the media. The addition of 5 mM AOAA decreased the rate of 14CO2 production from glutamine to 29.2% of the control rate, consistent with earlier studies by our group. The addition of 5 mM AOAA decreased the rate of oxidation of concentrations of glutamate < or = 0.1 mM by approximately 50%, but decreased the oxidation of 0.5-1 mM glutamate by only approximately 20%, demonstrating that a substantial portion of glutamate enters the tricarboxylic acid (TCA) cycle via glutamate dehydrogenase (GDH) rather than transamination, and that as the concentration of glutamate increases the relative proportion entering the TCA cycle via GDH also increases. To determine if the presence of an amino group acceptor (i.e. a ketoacid) would increase the rate of metabolism of glutamate, pyruvate was added in some experiments. Addition of 1 mM pyruvate increased the rate of oxidation of glutamate, and the increase was inhibited by AOAA, consistent with enhanced entry of glutamate into the TCA cycle via transamination in the presence of pyruvate. Enzymatic studies showed that pyruvate increased the activity of mitochondrial aspartate aminotransferase (AAT). Overall, the data demonstrate that glutamate formed intracellularly from glutamine enters the TCA cycle primarily via transamination, but does not enter the same TCA cycle compartment as glutamate taken up from the extracellular milieu. In contrast, extracellular glutamate enters the TCA cycle in astrocytes via both transamination and GDH, and can compete with, or dilute, the oxidation of glutamate produced intracellularly from glutamine.

Aminooxyacetic Acid↗

PubMed1996

Polymorphism of the glycogen synthase gene in hypertensive and normotensive subjects.

Hypertension and non-insulin-dependent diabetes mellitus (NIDDM) are characterized by a strong genetic component and impaired ability to store glucose as glycogen in skeletal muscle. Impaired insulin activation and altered genetic control of muscle glycogen synthase, the rate-limiting enzyme for glucose storage in skeletal muscle, could provide an explanation for this insulin resistance. We examined whether there is an association between the glycogen synthase gene (Xba I polymorphism) and hypertension in 304 nondiabetic subjects. We examined glucose tolerance with an oral glucose tolerance test and glucose storage in skeletal muscle with the euglycemic insulin clamp technique in combination with indirect calorimetry. The Xba I A2 allele of the glycogen synthase gene was enriched in subjects with hypertension and a family history of NIDDM (48%) compared with normotensive subjects without a family history of NIDDM (6%, P < .0001). The presence of the A2 versus the A1 allele was associated with decreased rates of insulin-stimulated glucose storage in hypertensive subjects (11.2 +/- 2.3 versus 16.9 +/- 2.6 mumol/kg lean body mass per minute, P = .029) but not in normotensive subjects (28.0 +/- 4.6 versus 29.6 +/- 3.7 mumol/kg lean body mass per minute). In conclusion, Xba I polymorphism of the glycogen synthase gene identifies a subgroup of hypertensive subjects with a family history of NIDDM. The data suggest that a locus in the glycogen synthase gene region on chromosome 19 may serve as a "thrifty gene," increasing susceptibility for insulin resistance when exposed to other environmental or genetic factors.

Adult↗

PubMed1996

Immunocytochemical detection of regional protein changes in rat brain sections using computer-assisted image analysis.

We used several approaches to assess the reliability and sensitivity of computer-assisted densitometry to detect regional changes in tissue antigen content as a function of immunohistochemical staining density. We designed a model system to mimic variations in antigen concentration in postfixed, slide-mounted rat brain sections by varying the ratios of conjugated (biotinylated) to unconjugated secondary antibody. Antigen concentration was also varied in tissue discs made from mixing rat brain homogenate with increasing amounts of tissue embedding compound. The monoclonal antibody bd-17 to the beta2/3 subunit of the GABAA receptor was used as the primary antibody. Immunostaining density was visualized with diaminobenzidine (DAB). There was a significant, positive linear relationship (r = 0.97-0.99) between immunostaining intensity and antigen concentration. With this approach, changes in antigen content of less than 10%, as reflected in immunostaining intensity, were detectable in brain sections. The low degree of variability in measures of regional variation in immunostaining in sections from naive rats (n = 7) suggested that the method was suitable for quantitative analysis and indicated the reliability of the method. This systematic study of the utility of computer-assisted image analysis for semiquantitative immunohistochemical analysis found the method to be both reliable and sensitive.

Animals↗

PubMed1996

Control of islet intercellular adhesion molecule-1 expression by interferon-alpha and hypoxia.

The ability of interferon-alpha (IFN-alpha) to induce the adhesion molecules that characterize the islets of patients with type I diabetes has been investigated. We have found that all tested recombinant IFN-as will induce major histocompatibility complex (MHC) class I on arterial endothelial cells. Some but not all IFN-as will induce intercellular adhesion molecule-1 (ICAM-1). However, there is only a transient and modest increase in VCAM on arterial endothelial cells. IFN-alpha has very little effect on endothelial MHC class II expression but will induce these proteins on monocytes. Thus, there is a close concordance between the biological actions of IFN-alpha and the appearance of those adhesion molecules induced in the islets of patients with type I diabetes. IFN-alpha is also produced in normal human islets during short-term cultures, probably as a result of the ischemia present at the center of the islet. This induction of IFN-alpha by hypoxia may explain the previously reported spontaneous induction of ICAM-1 in human islets and may also be a contributing factor to the failure of islet grafts.

Arteries↗

PubMed1996

Genetic absence of gamma-interferon delays but does not prevent diabetes in NOD mice.

Cytokines, particularly interferons, may participate in the development of type I diabetes. This involvement could be from direct cytotoxic actions of the interferons on the pancreatic beta-cells or from an indirect influence on the number, activity, or type of inflammatory cells that invade the islets in type I diabetes. To examine directly the role of interferon (IFN)-gamma in a mouse model of type I diabetes, we have introduced an inactivating mutation in the IFN-gamma gene (ifg) into NOD mice. The genetic absence of IFN-gamma does not prevent either insulitis or diabetes in the NOD mice, but it does increase the time to onset. Although it might have been predicted that the absence of IFN-gamma in these mice would lead to an increase in expression of Th2 T-helper cell-related cytokines, we found instead a profound decrease in the expression of two of the characteristic Th2 cytokines, interleukin (IL)-4 and IL-10. We also demonstrate that the splenocytes taken from IFN-gamma-deficient diabetic mice are fully capable of transferring diabetes to naive recipients.

Aging↗

PubMed1996

Research into analgesia by inhaling analgesic.

This article deals with analgesia by inhaling analgesic. According to Chinese medical theories, TCM analgesics were chosen from the literature and folk prescriptions screened and proved by analgesic tests on animals. A reasonable prescription was made up and the drug inhaled. Its analgesic effect was superior to that of dolantin injection (3 mg/kg body weight, intraperitoneal injection). Clinical trials showed its analgesic effect in 3-10 minutes and it lasted for more than 2 hours in over 70% of the cases for a total effective rate of 94.6%. The drug is absorbed quickly and acts directly on the nerve center. Its use is not addictive.

Administration, Inhalation↗

PubMed1996

[The changing trend of cesarean section rates in 35 years].

OBJECTIVE: To investigate the changing trend of cesarean section rates in 35 years. METHODS: Samples taken from 4 months (March, June, September, December) of a year every 5 years in 35 years (from 1959 to 1994) were analysed and a total of 1 667 cases were collected. RESULTS: Cesarean section rates increased since 1975 and particularly from 1980 to 1994. The causes of this trend may be related to following reasons. (1) Improvement of skill and safety of operation. (2) Change of indications of cesarean section. (3) Social factors. CONCLUSION: The decrease of perinatal mortality rate was not relevant only to the cesarean section rate, but dependent more on good perinatal care.

Cesarean Section↗

PubMed1996

Atomic force microscopic study on topological structures of pBR322 DNA.

Plasmid pBR322 DNA (0.5 mg/mL) isolated from Escherichia coli HB101 was suspended in Tris-HCI-EDTA (1 mol/L-0.1 mol/L, pH 8.5); then a drop of the above solution was deposited on freshly cleaved mica substrate. After adsorption for about 1 mm, the sample was stained with phosphotungstic acid. The residual solution was removed with a piece of filter paper. Afterwards the sample was imaged with a home-made atomic force microscope (AFM) in air. The AFM images of pBR322 DNA with a molecular resolution have been obtained. These images show that pBR322 DNA exists in several different topological structures: (i) relaxed circular DNA with a different diameter; (ii) supercondensed DNA with different particle sizes; (iii) dimeric catenane connected by one relaxed circular molecule and another close-compacted molecule which might be either supercoiled or intramolecular knotted form; (iv) oligomeric catenane with multiple irregular molecules in which DNA is interlocked into a complex oligomer; (v) possibly-existing intermediates formed from monomer to oligomer.

DNA, Bacterial↗

PubMed1996

Modulation of central nervous system metabolism by macromolecules: effects of albumin and histones on glucose oxidation by synaptosomes.

Since increasing evidence suggests that several proteins play a significant role in the regulation of glucose oxidation in the central nervous system, a series of experiments was designed to determine the specific proteins involved and to delineate their possible mode of action. In these studies, the rate of substrate oxidation by isolated synaptosomes in vitro was determined by measuring the production of [14C]carbon dioxide from labeled compounds in the presence and absence of the added protein. In the initial experiments, an examination of a broad selection of pure proteins revealed that only albumin (bovine serum albumin [BSA]) or histones (at concentrations of 100 micrograms/mL or less) exhibited an inhibitory effect of greater than 60% on the rate of glucose oxidation. Furthermore, isolated cell fractions P1 (nuclei and cellular debris), P2 (mitochondria, synaptosomes, and myelin), and other membrane proteins had little or no effect on the rate of [14C]carbon dioxide production from [6(14)C]glucose. When either BSA or histones were treated with trypsin, the inhibitory effects were eliminated. To determine whether these effects were related to changes in substrate transport, we measured the rate of glucose uptake by synaptosomes using [6(14)C]glucose, [1,2-3H]2-deoxyglucose, and [3H]3-O-methylglucose in the presence of 5% serum protein. These experiments revealed that the rate of glucose transport was not affected by serum proteins. Collectively, these results indicate that albumin and histones attenuate the rate of glucose oxidation by synaptosomes. The results also support the conclusion that the intact protein molecule is required for this inhibition, since treatment with trypsin abolished this effect. It can also be concluded that this effect is not at the site of transport and that the protein(s) are acting either directly at intercellular site(s) or indirectly via specific messengers.

Animals↗

PubMed1996

[The effect of long-term tamoxifen therapy on the occurrence of contralateral primary breast cancer].

From January 1 1985 to December 31 1990, 874 cases of female primary breast cancer were treated in the Department of Surgery at Beijing Institute for Cancer Research. Of these, 21 patients suffered from contralateral primary breast cancer after surgery. These patients were divided into two groups, 523 patients received adjuvant tamoxifen therapy (20mg daily) for 2 to 5 years as the treated group. There were 351 patients without tamoxifen therapy as the control group. The medium follow-up of the treated and the control group was 7.8 years and 7.0 years, respectively. The incidence of contralateral primary breast cancer in the treated group was 1.5% (8/523), and that in the control group was 3.7% (13/351, P < 0.05). This result suggests that tamoxifen is useful to reduce the risk of contralateral primary breast cancer.

Adult↗

PubMed1996

[The influence of HX- I on rabbit thyroid allografts].

We studied the anti-rejection effect of HX- I, a preparation of traditional Chinese herbs, on rabbit thyroid allografts. The transplantations were performed on 28 rabbits after total thyroidectomies. The grafting sites were in their pretrachial muscles. These animals were divided into four groups, namely, Group I: homografts: Group I: allografts without medication; Group II: allografts with dexamethason (0.25 mg/(kg.d) intramuscularly), and Group IV: allografts with HX-I water solution, (5g/(kg.d), peros). The medication lasted 28 days. Blood samples were drawn every week postoperatively. Serum T3 and T4 were tested by RIA. The grafts were removed for histopathological evaluation on the 28th day postoperatively. The histopathology of rejection and survival were scored and classified. On the 7th and 14th days, serum T3 and T4 levels were almost the same between groups. On the 21st and 28th days, the T3 and T4 levels were higher in Groups I and IV than those in Group II (P < 0.05). The histopathological findings were; in Group I, damaged follicles with much lymphocytes infiltration and fibrosis, and 6 cases being rejected; in Group II, two deaths and three cases with damaged thyroid tissue and much lymphocytes infiltration; in Group IV, three cases with damaged thyroid tissue and four intact grafts. Our results indicate that HX-I and dexamethason both can inhibit rejection in thyroid allografts in rabbits, but dexamethason has more side effects HX-I has many components and the machanism of its early anti-rejection effect is worthy of further study.

Animals↗

PubMed1996

Detoxicating enzymes of Entamoeba histolytica and their detoxifying roles.

OBJECTIVE: To investigate the Entamoeba histolytica living in the low oxygen concentration colon of the host and how does it survive in the circumstance after invading the tissues with high oxygen concentration while obtaining oxygen without being damaged by the toxins. MATERIAL AND METHODS: E. histolytica cultured for 48 hours was collected, centrifuged, rinsed, ultrasonically shattered and again centrifuged, and the activities of superoxide dismutase and the catalase in the supernatant were determined. The catalase and peroxidase were identified by the electron microscopic enzyme cytochemical reaction technique. RESULTS: E. histolytica contained 122.42 +/- 15.47 U/mgpr of superoxide dismutase, 126.05 +/- 17.04 K/mgpr of catalase and peroxidase, and all of them are detoxifying enzymes. Catalase and peroxidase were located within microsomes and lysosome-like organelles respectively. CONCLUSIONS: E. histolytica contains the detoxifying enzymes as superoxide dismutase, catalase and peroxidase, that may prevent the aerobic metabolism from being poisoned by the activated oxygen free radical (superoxide anion radical and hydrogen peroxide) produced in this process, suggesting that the detoxifying function of these enzymes play an important defensive role in the survival of E. histolytica.

Animals↗

PubMed1996

Recombinant human granulocyte colony-stimulating factor after allogeneic bone marrow transplantation.

OBJECTIVE: To examine the effect of rhG-CSF on allogeneic bone marrow transplantation. PATIENTS AND METHODS: One hundred and twenty patients with acute or chronic leukemia received HLA-A.B.DR identical and MLC negative sibling donor allo-BMT. Among them, 58 cases of were treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF), while the other 62 cases of the 120 patients were treated as control. RESULTS: Clinical results showed that the time taken to reach an absolute neutrophil count > 0.5 x 10(9)/L was significantly faster in patients who received rhG-CSF compared with control patients (16.24 +/- 0.25 vs 25.20 +/- 0.16 days. P < 0.001), with significantly less early fever days in patients received rhG-CSF (1.17 +/- 1.10 vs 4.01 +/- 0.37 P < 0.001). We did not observe any increase in acute GVHD and relapse in myeloid leukemia patients. But 7 of 16 patients with ALL relapsed after allo-BMT in rhG-CSF group, while only 3 of 11 patients with ALL relapsed after allo-BMT in control grant (P > 0.05). This phenomenon has not been reported up to now. CONCLUSIONS: rhG-CSF can promote engraftment and reduce early fever days after BMT. rhG-CSF has not any effect on a GVHD. The effect of rhG-CSF on leukemia relapse needs to be further studied.

Adolescent↗