Biomedical subjects

H Shen

Publications and source records attributed to H Shen.

At least 163 records · Page 9Linked to original sources

PubMed1999

Detection of peptides by precolumn derivatization with biuret reagent and preconcentration on capillary liquid chromatography columns with electrochemical detection.

The separation and detection of biuret complexes of neuropeptides by capillary liquid chromatography with electrochemical detection was explored. Capillaries of 25-micron inner diameter packed with base-resistant, polymer-based reversed-phase particles were used for separation, and C-fiber electrodes were used for detection. Detection at the C-fiber electrode was found to have some differences in relative sensitivity for peptides compared to glassy carbon electrodes used previously. On-column preconcentration of preformed complexes allowed up to 1-microL samples to be injected with minimal band broadening resulting in a 100-fold improvement in concentration detection limit with no effect on mass detection limit. Concentration detection limits ranged from 5 to 59 pM, depending upon the peptide, corresponding to 5-59 amol injected. The low concentration detection limit was possible because of minimal baseline disturbances, minimal formation of unwanted products, and high efficiency of complex formation associated with biuret derivatization. The method was applied to determination of vasopressin and bradykinin in dialysates collected with 5-min sampling frequency from the rat supraoptic nucleus.

Animals↗

PubMed1999

Expression of neurotrophin mRNAs in the dorsal root ganglion after spinal nerve injury.

Neurotrophins have specificity toward distinct subpopulations of dorsal root ganglion (DRG) neurons with different neurotrophin receptors. It has been suggested that neurotrophins also play important roles in mature DRG neurons after injury. In the present study, we examined the expression of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3) mRNAs in the DRG after a peripheral nerve injury. The data showed that following a spinal nerve ligation, the level of NGF mRNA increased 4 times over the normal level and was maintained at a high level for a period of 3 weeks. The induction of BDNF mRNA was brief (lasting less than 3 days) and lesser in quantity ( approximately 1. 7 times increase) compared to NGF expression. The expression of NT-3 mRNA was not detected either in normal or nerve injured rats. Results suggest that different neurotrophins play different functional roles in the DRG after spinal nerve injury.

Animals↗

PubMed1999

Tolerization of adult mice to immunodominant proteins before monoclonal antibody production.

Generating monoclonal antibodies (mAbs) against one polypeptide chain of a heterodimeric protein can be difficult when the other chain is more immunogenic. To influence the immune response in favor of the less immunogenic protein, we rendered adult mice tolerant to the immunodominant protein using a procedure based on the phenomenon of high zone tolerance. We then immunized the tolerized mice with a heterodimeric protein containing the immunogenic protein and produced hybridomas in the usual way. Screening the hybridomas for reactivity against the immunodominant protein and against the heterodimer revealed that this tolerization procedure can result in an increase of hybridomas producing mAbs against the protein of interest by up to 90-fold. This method should be of general utility for the production of mAbs against weakly antigenic proteins in mixtures of antigens.

Animals↗

PubMed1999

2-Tetradecylglycidic acid, an inhibitor of carnitine palmitoyltransferase-1, induces myocardial hypertrophy via the AT1 receptor.

Activation of the antiogensin II, type 1 (AT1) receptor mediates the myocardial response to numerous hypertrophic stimuli. This study tested the hypothesis that 2-tetradecylglycidic acid (TDGA), an oxirane carboxylate inhibitor of mitochondrial carnitine plamitoyltransferase-1, induces myocardial hypertrophy via the AT1 receptor system. Male Sprague-Dawley rats treated with 10 mg TDGA/kg/day for 7 days had a heart wet weight:body weight ratio of 3. 58+/-0.16 mg/g compared with a ratio of 2.79+/-0.07 for rats treated with vehicle (P<0.05). The plasma level of antiogensin II was 117. 75+/-17.39 pg/ml in rats treated with 10 mg TDGA/kg/day compared with 54.0+/-11.38 pg/ml for rats treated with vehicle (P<0.05). The plasma level of angiotensin I in these two groups of rats was not different statistically. Rats treated with TDGA and given drinking water containing 1 mg losartan/ml had a heart wet weight:body weight ratio of 2.84+/-0.05 mg/g. This value was not statistically different from the value measured in rats given drinking water containing 1 mg losartan/ml and treated with vehicle alone. No significant difference in the heart wet weight:dry weight ratio occurred among these groups of rats. Finally, treating rats with TDGA or giving rats drinking water that contained 1 mg losartan/ml altered neither their heart rate nor their mean arterial blood pressure when compared with untreated rats. This data, therefore, suggests that oxirane carboxylates induce myocardial hypertrophy by activating the AT1 receptor independent of changes in systemic hemodynamics.

Animals↗

PubMed1999

Changes in trkA expression in the dorsal root ganglion after peripheral nerve injury.

Most of the biological effects of nerve growth factor (NGF) are mediated by TrkA, the high affinity receptor for NGF. Previous studies have shown that NGF levels in the dorsal root ganglia (DRG) fluctuate following a peripheral nerve injury. The present study examined changes of TrkA immunoreactivity and trkA mRNA expression in the DRG after segmental nerve ligation. In the normal L5 DRG of the rat, there were, on average, 4700 TrkA-immunoreactive (TrkA-IR) neurons, representing 42% of the total neuronal population. Following L5 spinal nerve ligation, the number of TrkA-IR neurons in the L5 DRG slowly declined, reducing by 25% at 1 week and 35% at 3 weeks postoperation (PO). In contrast, trkA mRNA in these ganglia showed a significant decrease from 3 days to 3 weeks PO and was followed by a full recovery at 2 months PO. The early decrease of trkA mRNA is likely due to deprivation of target-derived NGF, which is caused by nerve ligation, and the recovery might be because substitute sources of NGF become available. Despite the decline in trkA mRNA in the ganglion, 3000 injured DRG neurons sustain TrkA immunoreactivity, suggesting that exogenous NGF can still influence these TrkA expressing neurons, even though they are isolated from the periphery. Accordingly, the effects of endogenous NGF should be as well manifested by local administration of NGF to the ganglion as to the stump of the damaged nerve.

Animals↗

PubMed1999

Influence of antiresorptive agent OST-766 on signal transduction pathways involved in parathyroid hormone action.

The effects of OST-766, an inhibitor of vacuolar H+-ATPase activity, on adenylyl cyclase and phospholipase C activity were explored in the osteoblast cell line ROS 17/2.8. In fresh homogenates of ROS 17/2.8 cells, OST-766 inhibited adenylyl cyclase activity (ACA) in response to guanine nucleotide and forskolin but had no effect on basal ACA. OST-766 enhanced the basal generation of IP2, but not that formed in response to Ca2+ or guanine nucleotides. In marked contrast, incubation of intact ROS 17/2.8 cells with OST-766 for at least 48 hours resulted in an increase in basal ACA as well as in response to PTH, guanine nucleotides and forskolin. Under similar conditions, the compound also increased IP1, IP2 and IP3 generation in response to guanine nucleotides and Ca2+. Levels of the guanine nucleotide binding proteins Gs and Gi were also increased in OST-766-treated cells. The results suggest that the actions of this H+-ATPase inhibitor include effects on osteoblasts through PTH-sensitive signal transduction pathways.

Adenylyl Cyclases↗

PubMed1999

Mortality among young immigrants to California: injury compared to disease deaths.

The authors "investigated adolescent and young adult immigrants' risk of death due to disease and injury.... The death certificates of 15- to 34-year-old California residents who died from 1989 through 1993 comprised the study population. Disease and injury deaths were identified using ICD-9 codes on the California Master Mortality data files. Frequencies and gender-standardized rates and risk ratios were calculated by nativity (U.S., non-U.S.) and by ethnicity and nativity." The results suggest that "young immigrants, at least in terms of mortality, do not constitute a burden in that they are at lower or similar risk of death than U.S.-born youth."

Americas↗

PubMed1999

Leukaemia disease genes: large-scale cloning and pathway predictions.

Retroviral insertional mutagenesis in BXH2 and AKXD recombinant inbred mice induces a high incidence of myeloid or B- and T-cell leukaemia and the proviral integration sites in the leukaemias provide powerful genetic tags for disease gene identification. Some of the disease genes identified by proviral tagging are also associated with human disease, validating this approach for human disease gene identification. Although many leukaemia disease genes have been identified over the years, many more remain to be cloned. Here we describe an inverse PCR (IPCR) method for proviral tagging that makes use of automated DNA sequencing and the genetic tools provided by the Mouse Genome Project, which increases the throughput for disease gene identification. We also use this IPCR method to clone and analyse more than 400 proviral integration sites from AKXD and BXH2 leukaemias and, in the process, identify more than 90 candidate disease genes. Some of these genes function in pathways already implicated in leukaemia, whereas others are likely to define new disease pathways. Our studies underscore the power of the mouse as a tool for gene discovery and functional genomics.

Animals↗

PubMed1999

Inverse agonist activities of beta-adrenoceptor antagonists in rat myocardium.

1. Negative inotropic effects of several beta-adrenoceptor (betaAR) antagonists on electrically-stimulated right atria, left atria, right ventricles and left ventricular papillary muscles from reserpine-treated rats were used as a measure of their inverse agonist activities. 2. Beta1AR antagonists acebutolol, atenolol and metoprolol, beta2AR antagonist ICI-181,551 and nonselective betaAR antagonists alprenolol, nadolol, propranolol and timolol produced negative inotropic effects, which were most marked on the right atria. 3. The nonselective betaAR antagonist pindolol did not exhibit inverse agonist activity but inhibited the negative inotropic activities of ICI-118,551, atenolol and propranolol. 4. The negative inotropic effects of lidocaine, nifedipine and pentobarbitone were similar on all the four myocardial preparations. 5. The positive inotropic efficacy of salbutamol on right and left atria but not on right ventricles and papillary muscles was comparable to that of isoprenaline. The antagonist activity of ICI-118,551 against isoprenaline was greater on right atria than on other cardiac regions. 6. Beta1AR proteins were expressed in all regions of the heart but of beta2AR were primarily localized in the right atrium. 7. It is concluded that beta2AR play a greater role in right atria than in other cardiac regions and almost all betaAR antagonists behave as inverse agonists.

Adrenergic beta-Agonists↗

PubMed1999

Lifetime severity index for cocaine use disorder (LSI-Cocaine): a predictor of treatment outcomes.

We developed a lifetime severity index for cocaine use disorder and examined its predictive validity of posttreatment outcome using data from the national Drug Abuse Treatment Outcome Study. The index, based on 28 items, considered frequency of use, recency, dependency, and attempt to quit. A higher value of the index, indicating greater severity, predicted a greater likelihood of relapse (the odds ratios were 5.7 for high severity and 4.4 for medium severity, relative to low severity) and shorter time to relapse. Similarly, the polytomous logistic analysis indicated that the index predicted levels of posttreatment cocaine use (odds ratios of daily use were 47.8 for the high severity and 18.8 for medium severity; the corresponding odds ratios of weekly use were 6.75 and 5.10 and for less-than-weekly use were 3.35 and 3.57). The index can be a useful measure for both clinical and research purposes.

Adult↗

PubMed1999

Rapid automated tracing and feature extraction from retinal fundus images using direct exploratory algorithms.

Algorithms are presented for rapid, automatic, robust, adaptive, and accurate tracing of retinal vasculature and analysis of intersections and crossovers. This method improves upon prior work in several ways: 1) automatic adaptation from frame to frame without manual initialization/adjustment, with few tunable parameters; 2) robust operation on image sequences exhibiting natural variability, poor and varying imaging conditions, including over/under-exposure, low contrast, and artifacts such as glare; 3) does not require the vasculature to be connected, so it can handle partial views; and 4) operation is efficient enough for use on unspecialized hardware, and amenable to deadline-driven computing, being able to produce a rapidly and monotonically improving sequence of usable partial results. Increased computation can be traded for superior tracing performance. Its efficiency comes from direct processing on gray-level data without any preprocessing, and from processing only a minimally necessary fraction of pixels in an exploratory manner, avoiding low-level image-wide operations such as thresholding, edge detection, and morphological processing. These properties make the algorithm suited to real-time, on-line (live) processing and is being applied to computer-assisted laser retinal surgery.

Algorithms↗

PubMed1999

Skeletal muscle Na(+)-K(+)-ATPase and K+ homeostasis during exercise: effects of short-term training.

The objective of this study was to determine the effects of 10 consecutive days of moderate intensity training on 1) the concentration of middle gluteal muscle Na(+)-K(+)-ATPase as determined by vanadate-facilitated 3H[ouabain binding; and 2) plasma potassium regulation before, during and after exercise at 100% of the pre-training maximum rate of oxygen consumption (VO2max). Six mature, unfit Thoroughbred horses completed both incremental (for determination of VO2max) and high-intensity exercise protocols before (HI1) and after (HI2) training. There additional horses undertook no training or exercise tests and served as controls for determination of middle gluteal muscle Na(+)-K(+)-ATPase concentration. Training consisted of 10 consecutive days of running at 55% VO2max for 60 min per day (13-14 km/day). For each high intensity exercise protocol, horses completed a 10 min warm-up at 50% VO2max, followed by exercise at 100% of pre-training VO2max (6 degrees incline, mean speed 9.8 m/s) until fatigue. Training resulted in a 13.8% increase in resting plasma volume (pre: 20.9 +/- 0.8 l; post: 23.8 +/- 0.9 l; P = 0.03), and an 8.9% increase in VO2max (pre: 142 +/- 4 ml/kg/min; post: 155 +/- 4 ml/kg/min; P = 0.004) during HI. Peak values for plasma potassium concentration and content during exercise decreased by 13% (P = 0.02) and 7% (P = 0.0002), respectively, after training whereas training had no effect on increases in packed cell volume, plasma total solids, and erythrocyte K+ concentration and content during exercise. Following training, there was also a significant (23%) increase in Na(+)-K(+)-ATPase concentration in biopsies of middle gluteal muscle, as measured by vanadate-facilitated 3H[ouabain binding. We conclude that 10 days of moderate intensity exercise results in increases in skeletal muscle Na(+)-K(+)-ATPase and attenuation in the elevation in plasma K+ during high intensity exercise at the same absolute workload. The increase in middle gluteal muscle Na(+)-K(+)-ATPase concentration is consistent with decreases in K+ efflux from working muscle during exercise.

Animals↗

PubMed1999

Muscular and metabolic responses to moderate-intensity short-term training.

The objectives of this study were to determine the effects of 10 consecutive days of moderate-intensity training on 1) the muscular metabolic response to exercise at 100% of the pre-training maximum rate of oxygen consumption (VO2max); and 2) mitochondrial enzyme markers (citrate synthase, CS; succinate dehydrogenase, SDH; 3-hydroxy-acyl-CoA dehydrogenase, HAD) of oxidative capacity in middle gluteal muscle. Six mature, unfit Thoroughbred horses completed both incremental (for determination of VO2max) and high-intensity exercise protocols before (HI1) and after (HI2) training. Training consisted of 10 consecutive days of running at 55% VO2max for 60 min per day (13-14 km/day). For the HI, horses completed a 10 min warm-up, followed by exercise at 100% of pre-training VO2max (mean speed 9.8 m/s) until fatigue. Training resulted in an 8.9% increases in VO2max (Pre: 142 +/- 4 ml/kg bwt/min; Post: 155 +/- 4 ml/kg bwt/min) and a 24% increase in run time to fatigue during HI. Whereas VO2 during HI was not altered by training, peak values for VCO2 and R were significantly lower following training. Compared to HI1, there was a 45% reduction in the net rate of muscle glycogenolysis during HI2. Peak (end exercise) values for plasma and muscle lactate concentrations decreased by 22 and 23%, respectively, after training. Training also attenuated the exercise-associated increase in plasma norepinephrine, but there was no effect on plasma epinephrine concentrations. Maximal activities of CS, SDH, and HAD were unaltered by training. We conclude that 10 days of moderate-intensity exercise results in decreases in muscle glycogenolysis and anaerobic metabolism during high-intensity exercise at the same absolute workload. Furthermore, development of measurable increases in mitochondrial oxidative potential may not be required for expression of these metabolic adaptations in early training.

3-Hydroxyacyl CoA Dehydrogenases↗

PubMed1999

Existing antilisterial immunity does not inhibit the development of a Listeria monocytogenes-specific primary cytotoxic T-lymphocyte response.

Infection of BALB/c mice with Listeria monocytogenes stimulates an antilisterial immune response evident by the appearance of H2-Kd-restricted CD8(+) cytotoxic T lymphocytes (CTLs) specific for the nanomer peptides amino acids (aa) 91 to 99 of listeriolysin O (LLO 91-99) and aa 217 to 225 of the p60 molecule (p60 217-225). We have introduced point mutations at anchor residues within LLO 91-99 (92F) or p60 217-225 (218F), and BALB/c mice infected with L. monocytogenes strains containing these point mutations do not develop CTLs specific for LLO 91-99 or p60 217-225, respectively. We have used these strains to test whether primary CTL responses against L. monocytogenes-derived determinants can be stimulated within an environment of existing antilisterial immunity. We found that the development of a primary L. monocytogenes-specific CTL response is not altered by existing immunity to L. monocytogenes. For example, primary immunization with the p60 218F strain of L. monocytogenes followed by a secondary immunization with wild-type L. monocytogenes results in stimulation of p60 217-225-specific CTLs at primary response levels and LLO 91-99-specific effectors at levels consistent with a memory CTL response. Similarly, primary immunization with the 92F strain of L. monocytogenes followed by a secondary immunization with wild-type L. monocytogenes results in stimulation of LLO 91-99-specific CTLs at primary response levels and p60 217-225-specific effectors at levels consistent with a memory CTL response. These results provide additional support for the use of L. monocytogenes as a recombinant vaccine vector and show that antivector immunity does not inhibit the development of a primary CTL response when the epitope is delivered by L. monocytogenes as the vaccine strain.

Amino Acid Substitution↗

PubMed1999

Cytotoxic T-lymphocyte epitopes fused to anthrax toxin induce protective antiviral immunity.

We have investigated the use of the protective antigen (PA) and lethal factor (LF) components of anthrax toxin as a system for in vivo delivery of cytotoxic T-lymphocyte (CTL) epitopes. During intoxication, PA directs the translocation of LF into the cytoplasm of mammalian cells. Here we demonstrate that antiviral immunity can be induced in BALB/c mice immunized with PA plus a fusion protein containing the N-terminal 255 amino acids of LF (LFn) and an epitope from the nucleoprotein (NP) of lymphocytic choriomeningitis virus. We also demonstrate that BALB/c mice immunized with a single LFn fusion protein containing NP and listeriolysin O protein epitopes in tandem mount a CTL response against both pathogens. Furthermore, we show that NP-specific CTL are primed in both BALB/c and C57BL/6 mice when the mice are immunized with a single fusion containing two epitopes, one presented by Ld and one presented by Db. The data presented here demonstrate the versatility of the anthrax toxin delivery system and indicate that this system may be used as a general approach to vaccinate outbred populations against a variety of pathogens.

Animals↗

PubMed1999

Intrinsic human immunodeficiency virus type 1 resistance of hematopoietic stem cells despite coreceptor expression.

Interactions of human immunodeficiency virus type 1 (HIV-1) with hematopoietic stem cells may define restrictions on immune reconstitution following effective antiretroviral therapy and affect stem cell gene therapy strategies for AIDS. In the present study, we demonstrated mRNA and cell surface expression of HIV-1 receptors CD4 and the chemokine receptors CCR-5 and CXCR-4 in fractionated cells representing multiple stages of hematopoietic development. Chemokine receptor function was documented in subsets of cells by calcium flux in response to a cognate ligand. Productive infection by HIV-1 via these receptors was observed with the notable exception of stem cells, in which case the presence of CD4, CXCR-4, and CCR-5, as documented by single-cell analysis for expression and function, was insufficient for infection. Neither productive infection, transgene expression, nor virus entry was detectable following exposure of stem cells to either wild-type HIV-1 or lentivirus constructs pseudotyped in HIV-1 envelopes of macrophage-tropic, T-cell-tropic, or dualtropic specificity. Successful entry into stem cells of a vesicular stomatitis virus G protein-pseudotyped HIV-1 construct demonstrated that the resistance to HIV-1 was mediated at the level of virus-cell membrane fusion and entry. These data define the hematopoietic stem cell as a sanctuary cell which is resistant to HIV-1 infection by a mechanism independent of receptor and coreceptor expression that suggests a novel means of cellular protection from HIV-1.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Localization of PEPT1 and PEPT2 proton-coupled oligopeptide transporter mRNA and protein in rat kidney.

To determine the renal localization of oligopeptide transporters, Northern blot analyses were performed and polyclonal antisera were generated against PEPT1 and PEPT2, the two cloned rat H+/peptide transporters. Under high-stringency conditions, a 3.0-kb mRNA transcript of rat PEPT1 was expressed primarily in superficial cortex, whereas a 3.5-kb mRNA transcript of PEPT2 was expressed primarily in deep cortex/outer stripe of outer medulla. PEPT1 antisera detected a specific band on immunoblots of renal and intestinal brush-border membrane vesicles (BBMV) with an apparent mobility of approximately 90 kDa. PEPT2 antisera detected a specific broad band of approximately 85 kDa in renal but not in intestinal BBMV. PEPT1 immunolocalization experiments showed detection of a brush border antigen in S1 segments of the proximal tubule and in the brush border of villi from all segments of the small intestine. In contrast, PEPT2 immunolocalization was primarily confined to the brush border of S3 segments of the proximal tubule. All other nephron segments in rat were negative for PEPT1 and PEPT2 staining. Overall, our results conclusively demonstrate that although PEPT1 is expressed in early regions of the proximal tubule (pars convoluta), PEPT2 is specific for the latter regions of proximal tubule (pars recta).

Animals↗

PubMed1999

Contribution of 20-HETE to vasodilator actions of nitric oxide in the cerebral microcirculation.

BACKGROUND AND PURPOSE: The present study examined the contributions of a rise in cGMP versus a fall in 20-HETE levels to the vasodilator response to nitric oxide (NO) in the cerebral circulation of the rat. METHODS: Intact rat middle cerebral and basilar arteries were bathed in physiological saline solution containing indomethacin (5 micromol/L) and baicalein (0.5 micromol/L) and pressurized at 90 mm Hg. Relaxations to sodium nitroprusside (SNP) were studied before and after addition of [1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one] (ODQ, a guanylyl cyclase blocker), 8R,9S, 11S-(-)-9-methoxy-carbamyl-8-methyl-2,3,9,10-tetrahydro-8, 11-epoxy-1H,8H,11H-2,7b,11a-trizadibenzo-(a,g)-cycloocta-(c, d, e)-trinden-1-one (KT5823, a protein kinase G blocker), and 20-hydroxyeicosatetraenoic acid (20-HETE). Cerebral blood flow was measured by using a laser Doppler flow probe over a thin cranial window in anesthetized rats, and the effects of intracerebroventricular infusion of 1-hexamine, 6-(2-hydroxy-1-methyl-2-nitrosohydrazino)N-methyl (MAHMA nonoate) and dibromododecenyl methylsulfimide (DDMS) were determined. RESULTS: SNP-induced dilation of serotonin-preconstricted (0.2 micromol/L) middle cerebral arteries (10(-7) to 10(-3) mol/L) was attenuated in arteries treated with ODQ (10 micromol/L) or KT5823 (1 micromol/L) by 52% and 27%, respectively. Preventing the NO-induced fall in intracellular 20-HETE, by adding 20-HETE (100 nmol/L) to the bath, reduced the dilation to SNP by 62%. Simultaneous administration of ODQ and 20-HETE markedly attenuated the SNP-induced dilation by 90%. In basilar arteries, ODQ (10 micromol/L) alone completely blocked the response to SNP. Infusion of MAHMA nonoate (10 nmol/min ICV) in anesthetized rats increased cerebral blood flow by 52% before and 8% after blockade of the endogenous production of 20-HETE with DDMS (50 pmol/min). CONCLUSIONS: These results suggest that NO dilates cerebral arteries through both cGMP-dependent and cGMP-independent pathways and that inhibition of 20-HETE formation contributes to the cerebral vasodilator response to NO both in vitro and in vivo.

Adenosine↗