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H Yang

Publications and source records attributed to H Yang.

At least 829 records · Page 46Linked to original sources
PubMed1994

A new kind of immobilized lipase in organic solvent and its structure model.

In this paper, we used Ca-alginate gel beads coated with polyetheneimine and glutaraldehyde to adsorb Expansum penicillium lipase. The immobilized lipase catalyzed esterification of 1-dodecanol with dodecanoic acid in benzene. The results show that when the concentration of Ca-alginate, polyetheneimine (PEI) and glutaraldehyde is 1%, 6% and 1%, respectively, the activity of the immobilized lipase and the amount of adsorbed protein are the highest. The immobilized lipase is better than the SDS-immobilized lipase. The activity of the immobilized lipase connected by glutaraldehyde is higher than the activity of that without glutaraldehyde. The initial rate of the immobilized lipase and lyophilized lipase powder is 5.9 x 10(2) nmol/min.mgpr and 2.8 x 10(1) nmol/min.mgpr, respectively. After the immobilized lipase catalyzed the esterification reaction at 37 degrees C for about 12 hours, 93.3% of 1-dodecanol was converted to ester, but for lyophilized lipase powder, only 17.5% converted. Based on all above results, we have presumed and explained the structure of this kind of immobilized lipase.

Alginates↗
PubMed1994

Raphe pallidus stimulation increases gastric contractility via TRH projections to the dorsal vagal complex in rats.

The role of thyrotropin releasing hormone (TRH) in the dorsal vagal complex (DVC) in mediating the enhanced gastric contractility induced by glutamate (100 pmol) microinjected into the raphe pallidus (Rpa) was investigated in urethane-anesthetized rats acutely implanted with miniature strain gauge force transducers on the corpus of the stomach. Glutamate-induced stimulation of gastric contractility was dose-dependently inhibited by bilateral microinjection into the DVC of TRH antibody (0.17, 0.85 or 1.7 micrograms/100 nl/site) but not by vehicle. TRH antibody microinjected into the dorsal medullary reticular field had no effect. These data indicate that activation of Rpa neurons by glutamate increases gastric motor function through TRH release in the DVC.

Animals↗
PubMed1994

Inhibition of nuclear hormone receptor activity by calreticulin.

We have shown that a polypeptide of M(r) 60,000 (60K) that shares N-terminal homology with a calcium-binding protein, calreticulin, can bind to an amino-acid sequence motif, KXGFFKR, found in the cytoplasmic domains of all integrin alpha-subunits. The homologous amino-acid sequence, KXFFKR (where X is either G, A or V), is also present in the DNA-binding domain of all known members of the steroid hormone receptor family; amino acids in this sequence make direct contact with nucleotides in their DNA-responsive elements and are crucial for DNA binding. Here we show that both the 60K protein (p60), purified on a KLGFFKR-Sepharose affinity matrix, and recombinant calreticulin can inhibit the binding of androgen receptor to its hormone-responsive DNA element in a KXFFKR-sequence-specific manner. Calreticulin can also inhibit androgen receptor and retinoic acid receptor transcriptional activities in vivo, as well as retinoic acid-induced neuronal differentiation. Our results indicate that calreticulin can act as an important modulator of the regulation of gene transcription by nuclear hormone receptors.

Amino Acid Sequence↗
PubMed1994

Feasibility of agarose microbeads with xenogeneic islets as a bioartificial pancreas.

A bioartificial pancreas, that is, transplantation of islets of Langerhans (islets) which are enclosed in a semipermeable membrane, has been proposed as a treatment for type I diabetes. The islets are immuno-isolated from the host by the semipermeable membrane preventing rejection while maintaining control of glucose metabolism for an extended period. The purpose of the current research is to evaluate the feasibility of preparing agarose microbeads with xenogeneic hamster islets as a bioartificial pancreas in streptozotocin induced diabetic mice. In the recipients with a low level of anti-hamster antibodies, the combination of encapsulation of hamster islets in 5% agarose microbeads and in vitro culture of them prolonged xenograft survivals. Four of 6 recipients were still normoglycemic at 100 days after implantation. However, the same procedure was not effective in the recipients which were sensitized in advance by transplantation of free hamster islets and thus had high levels of anti-hamster antibodies. The average normoglycemic period was 32 days. Antibodies permeated through the microbeads and activated complement on the cell surfaces. The network of agarose microbeads was rendered dense by increasing the concentration of agarose to restrict the diffusion of antibodies. Graft survivals were prolonged with increasing concentrations of agarose. As an analysis using diffusion equations predicted, the survivals were inversely proportional to the diffusion coefficient of IgG in each agarose gel. Islet xenotransplantation was enabled by the combination of the microbeads with a concentration of agarose higher than 7.5% and in vitro culture even in recipients having a high level of preformed antibodies.

Animals↗
PubMed1994

T1 discrimination contributions to proton magnetization transfer in heterogeneous biological systems.

Water proton spin-lattice relaxation times are commonly used as a guide in establishing the off-resonance irradiation time as well as the repetition time of the magnetization transfer experiment. T1 discrimination effects occur if the motionally restricted spin bath longitudinal magnetization does not reach thermal equilibrium. In this study we developed the formalism necessary for the evaluation of T1 discrimination contributions to proton magnetization transfer arising from the use of a short repetition time relative to the spin-lattice relaxation time of the motionally restricted spin bath. The results of computer simulation indicate that T1 discrimination contributions occur when the repetition time is small relative to the spin-lattice relaxation time of the motionally restricted spin bath, and when the off-resonance irradiation is weak and far off-resonance. For somewhat longer repetition times, T1 discrimination contributions become important only when the cross relaxation rate is small, and the fractional amount of motionally restricted component large. The occurrence of T1 discrimination effects results in distortion of water proton intensity ratio dispersion curves thereby resulting in the estimation of erroneous magnetization transfer parameters, whereas in magnetization transfer contrast enhanced imaging, such contributions are manifested by a decrease in image contrast.

Animals↗
PubMed1994

Relaxation-matrix formalism for rotating-frame spin-lattice proton NMR relaxation and magnetization transfer in the presence of an off-resonance irradiation field.

The derivation of a generalized relaxation matrix equation for the off-resonance rotating-frame spin-lattice experiment, representing N macromolecular components, is presented. The applicability of the derived formalism was demonstrated using water proton off-resonance rotating-frame spin-lattice relaxation data obtained for calf lens cortical and nuclear homogenates, a tissue system characterized by the presence of both mobile and solid-like protein domains, whose relative amounts vary in a protein-concentration-dependent manner. Protein concentration and temperature were utilized as variables in the magnetization-transfer experiments. Curve fitting to obtain the relevant magnetization-transfer parameters was accomplished by simulated annealing and the method of steepest descents. In all cases, the best fit, as reflected by the smallest root-mean-square deviation, was obtained by assuming the presence of three components representing bulk-water and mobile and solid-like macromolecular components, characterized by Lorentzian (water and mobile protein) and Gaussian proton resonance lineshapes (solid-like protein). A two-component relaxation model gave unsatisfactory fits. Dilution of nuclear homogenate resulted in physically realistic changes in the derived magnetization-transfer parameters, which included a decrease in the fraction of solid-like protein, in agreement with previously published 13C NMR studies. Changes in magnetization-transfer parameters occurred as a result of the cold cataract phase transition in nuclear homogenate. The utility and limitations of the derived formalism are discussed.

Animals↗
PubMed1994

Modified Jeener solid-echo pulse sequences for the measurement of the proton dipolar spin-lattice relaxation time (T1D) of tissue solid-like macromolecular components.

Modified Jeener solid-echo pulse sequences are proposed for the measurement of the proton dipolar spin-lattice relaxation time, T1D, of motionally restricted (solid-like) components in the presence of mobile molecular species, such as encountered in biological tissue. A phase-cycled composite-pulse sequence was used for detection of the dipolar signal and cancellation of the Zeeman signal. A homospoil gradient pulse was added to the Jeener echo pulse sequence to enhance dephasing of the transverse magnetization components of mobile species, thereby aiding in elimination of the Zeeman signal during dipolar signal acquisition. A modified Jeener echo sequence incorporating water suppression is also proposed as a means to further depress the Zeeman signal arising from mobile components. The modified Jeener echo sequences were successfully used for the measurement of proton T1D values of solid 2,6-dimethylphenol and Sephadex gels of differing degrees of cross linking and hydration.

Cross-Linking Reagents↗
PubMed1994

EDU pretreatment decreases polymorphonuclear leukocyte migration into rat lung airways.

Pretreatment with the heterocyclic compound EDU (N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N'-phenylurea) has previously been shown to reduce polymorphonuclear leukocyte (PMN) infiltration into the airways of ozone-exposed rats. The present study further examined the effects of 1 and 2 days EDU pretreatment on rat lung inflammatory responses by determining PMN infiltration in response to intratracheal instillation with the chemoattractant formyl-norleucine-leucine-phenylalanine (fNLP). Maximal recovery of PMNs by bronchoalveolar lavage was observed 4 hr after fNLP instillation with no alteration in the numbers of recoverable macrophages and lymphocytes. Although 1-day pretreatment with EDU did not affect PMN recovery from fNLP-instilled rat lungs, 2 days of EDU pretreatment prevented PMN infiltration as indicated by PMN recoveries that were similar to those obtained from saline-instilled lungs. Measurements of lung-marginated and interstitial pools of inflammatory cells using collagenase tissue digestion demonstrated no effect of 2 days EDU pretreatment. Although 2 days EDU pretreatment alone did not alter blood PMN content, lung permeability, and the lavage recoveries of inflammatory cells, blood PMN responses to chemotactic stimuli in vitro were impaired. In addition, EDU was shown to directly inhibit PMN chemotaxis and superoxide anion generation in vitro. These data demonstrated that EDU acts by interfering with PMN activation and migration rather than by decreasing PMN availability. EDU, by modulating the inflammatory response, represents a useful compound for preventing PMN-associated amplification of acute lung injuries.

Animals↗
PubMed1994

Recruitment in anaesthesia: results of two national surveys.

Two national surveys were conducted in order to understand better the dynamics of anaesthesia recruitment. The first survey documented undergraduate anaesthesia curricula in Canadian medical schools. Also documented was the number of students from each school entering anaesthesia at the first-year post-graduate level (PGY1) in 1993; the number was then correlated with the undergraduate anaesthesia exposure in that school. Although all medical schools offered anaesthesia electives, a wide variation existed in the annual total anaesthesia lecture time, the length of anaesthesia rotations and the level at which they occurred. There was no correlation between the number of students entering anaesthesia in 1993 and the aspects of anaesthesia exposure surveyed in the study. The second survey examined why anaesthesia residents choose the specialty. The reasons were grouped into five categories and residents were asked to select as many reasons as applicable. Respondents were also asked to indicate two or three principal reasons for choosing anaesthesia. Four reasons were found to be among both the most selected reasons and principal reasons for choosing anaesthesia: "Hands-on", "Time-off", "Physiology/Pharmacology", and "Immediate gratification". Five reasons were found to be among both the least selected reasons and principal reasons: "Research", "Role model", "Earning potential", "Technology", and "Pain management". It is concluded that anaesthesia recruitment is not related to the duration of undergraduate anaesthesia exposure but is influenced by technical, applied basic sciences and life-style factors.

Anesthesiology↗
PubMed1994

Effects of repeated challenges with exogenous oestradiol benzoate and progesterone on reproduction in prepubertal Hubei white and Meishan cross gilts.

Two experiments were carried out to investigate the effects of repeated challenges of oestradiol benzoate and progesterone on reproduction in prepubertal gilts. In experiment 1, 21 Large White cross (Meishan cross Landrace) prepubertal gilts were allocated to one of three treatments. Treatment A gilts were given oestradiol benzoate injections (15 micrograms kg-1 bodyweight) at 140 and 160 days old and daily injections of progesterone (20 mg day-1 per gilt) for four days, from day 12 after each oestradiol benzoate challenge. Treatment B gilts were given the same oestradiol benzoate and progesterone challenges but from 160 days onwards. Treatment C gilts were the controls and were given only oil injections. All the gilts were mated at their first oestrous period. In experiment 2, 45 prepubertal Hubei White gilts were allocated to the same treatments as used in experiment 1. The administration of oestradiol benzoate induced oestrus (52 of 64) and ovulation (51 of 64) in a high proportion of the gilts in both experiments. The proportions of gilts which had regular oestrous cycles (within 10 days after progesterone withdrawal) were 0.82 (18 of 22) and 0.16 (3 of 19) in treatments A and B, respectively (P < 0.001).

Animals↗
PubMed1994

Comparative studies of in vitro and in vivo function of three different shaped bioartificial pancreases made of agarose hydrogel.

Various kinds of bioartificial pancreas (BAP) have been developed in the past. There have been many disputes about the advantages and disadvantages of each BAP. However, little attention has been paid to the shape of the devices. In this study, three different shaped BAPs were made of the same material, agarose hydrogel. These are microbead-, rod- and disc-shaped BAPs, which are comparable to microcapsules, hollow fibre diffusion chambers and disc-shaped diffusion chambers, respectively, in shape. Their performances were studied by in vitro culture, mathematical simulations and in vivo implantation into diabetic animals. The islets in the BAPs could survive and release insulin for more than 100 d regardless of the BAP shape during in vitro culture. Numerical analyses showed that insulin release kinetics depended greatly on the thickness of the gel membrane but not on the shape of the agarose hydrogel. The microbead BAP normalized blood glucose levels of all five recipients for more than 100 d. Three of eight recipients of the rod BAP and only one of six recipients of the disc BAP demonstrated long normoglycaemia. These results suggest that the shape of the BAPs determines the in vivo functioning period of the BAPs and that the microbead is the most suitable shape for the BAP.

Animals↗
PubMed1994

Analyses of monoclonal antibodies reactive with porcine CD44 and CD45.

Twenty-six monoclonal antibodies (mAbs), assigned to the CD44/CD45 section of the First International Swine CD Workshop, were compared for their reactivity against a selected group of target cells by one- and two-color flow cytometric analysis. Based on staining and reactivity patterns the 26 mAbs were assigned to six groups, group F1 mAbs were designated CD44 mAbs; and groups F2 and F3 as CD45 mAbs. With the information available, a CD designation could not be given to the mAbs in groups F4, F5 or F6 consisting of four, three and four mAbs each, respectively. The reactivity of all six mAbs in group F1 (MAC35, 25-32, PORC24A, H22A, BAG40A, and BAT31A) was blocked by soluble porcine CD44. One mAb in this group (MAC325) reacted with a cell surface protein with a molecular weight of 80 kDa and was designated as CD44; the other five mAbs were designated as wCD44 because no molecular weight was known. Blocking experiments utilizing a cross reactive anti-human CD44 (mAb Z062) allowed the definition of the wCD44a epitope recognized by mAbs PORC24A and H22A. The group F2 mAbs (74-9-3; MAC323; K252.1E4; and 2A5) were designated as CD45 based on their broad reactivity pattern with lymphoid and myeloid cells and their ability to immunoprecipitate three polypeptides with an apparent molecular weight of 226, 210 and 190 kDa. The F3 mAbs (MAC327; MAC326; 3a56 and -a2) were designated as CD45R based on their restricted reactivity against lymphoid and myeloid target cells, and their ability to immunoprecipitate either two polypeptides with an apparent molecular weight of 226 and 210 kDa (mAbs MAC327 and MAC326) or a single polypeptide with an apparent molecular weight of 210 kDa (mAbs-a2 and 3a56). Sequential immunoprecipitation analyses confirmed the relatedness of the F2 and F3 group mAbs. The work conducted for this first workshop led to the definition of six mAbs specific for CD44, four mAbs specific for CD45, and four mAbs specific for CD45R which should prove to be very valuable reagents for the study of the porcine immune system.

Animals↗
PubMed1994

Up-regulation of cytokine production in alveolar macrophages by histogranin, a novel endogenous pentadecapeptide.

Recently, histogranin (HN), a newly found pentadecapeptide, was shown to enhance tumor necrosis factor (TNF) production by alveolar macrophages (AM). In this study, we have investigated whether HN was present in tissues rich with immune cells and further explored the effect of HN and [Ser1]HN on the production of TNF and other key cytokines. Relatively high levels of immunoreactive (ir)-HN were found in rat lung (14.9 pmol/g) and spleen (12.3 pmol/g), indicating its localization in close proximity to macrophages/monocytes and lymphocytes. Furthermore, HN and [Ser1]HN (10(-8)-10(-7) M) stimulated basal and lipopolysaccharide (LPS)-induced interleukin 1 (IL-1) mRNA expression and IL-1 release from rat AM. [Ser1]HN also stimulated basal and LPS-induced interleukin-6 (IL-6) release. Although HN did not affect the kinetics of cytokine production, the maximal enhancing effect of HN was seen at 3 h for TNF, 6 h for IL-1 and 18 h for IL-6. These data indicate that HN can up-regulate a cytokine cascade involving TNF, IL-1 and IL-6 and suggest a role for this endogenous peptide in immune regulation.

Animals↗
PubMed1994

Cold exposure elevates thyrotropin-releasing hormone gene expression in medullary raphe nuclei: relationship with vagally mediated gastric erosions.

The stimulation of thyrotropin release by cold is associated with an increase in thyrotropin-releasing hormone gene expression in the paraventricular nucleus of the hypothalamus. Cold exposure also stimulates autonomic outflow to viscera. There is evidence that caudal raphe nuclei are involved in autonomic regulation through thyrotropin-releasing hormone projections to the dorsal vagal complex and spinal cord. To determine whether cold modulates thyrotropin-releasing hormone gene expression in the caudal raphe nuclei, the effect of cold exposure on thyrotropin-releasing hormone messenger RNA levels in the rat lower brainstem was examined by quantitative Northern blot analysis and thyrotropin-releasing hormone messenger RNA was localized by in situ hybridization. The gastric responses to cold exposure were also assessed in sham or vagotomized rats with pylorus ligation. Thyrotropin-releasing hormone messenger RNA signal was detected in the RNA extracted from the medulla and hypothalamus but not from the amygdala, periaqueductal gray or cerebellum. Cold exposure (4 degrees C) for 1 or 3 h increased thyrotropin-releasing hormone messenger RNA levels in the medulla by 77 +/- 37 and 142 +/- 39% respectively. In situ hybridization histochemistry showed that the increase in silver grain density occurred exclusively in the raphe pallidus and raphe obscurus. Exposure to cold stress for 2 h stimulated gastric acid secretion and resulted in gastric lesion formation in sham but not vagotomized rats. There are established thyrotropin-releasing hormone projections from the raphe pallidus and obscurus to the dorsal vagal complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Comparison of the transport characteristics of D- and L-methionine in a human intestinal epithelial model (Caco-2) and in a perfused rat intestinal model.

Absorption mechanisms of L- and D-methionine (MET) in an in vitro cultured human intestinal epithelial cell model (Caco-2) and an in situ perfused rat intestinal model were investigated to determine if the kinetic characteristics of absorption are comparable in these two popular absorption models. The results indicate that the transport of L- and D-MET were concentration-dependent in both model systems, and displayed comparable Km values. The Km value for L-MET is 1.34 mM in the Caco-2 model and 3.6 mM in the perfused rat intestinal model, while the Km value for D-MET is 1.79 mM in the Caco-2 model and 2.87 mM in the perfused rat intestinal model. Although the Jmax values were not comparable because of significant methodology differences, the Jmax values for L-MET were always higher than that for D-MET. In addition, transport of L- and D-MET across the Caco-2 cell monolayers were also inhibited by 10 mM Phe and Lys while MeAIB, Pro and Glu were generally ineffective. Similar results were also observed with these inhibitors in the perfused rat intestinal model with the exception that a combination of Pro and Glu stimulated the uptake of L-MET. In conclusion, the transport characteristics of L- and D-MET are comparable in both model systems.

Animals↗
PubMed1994

Insulin-like growth factor-I (IGF-I) responses in rats maintained with intravenous or intragastric infusion of total parenteral nutrition solutions containing medium- or long-chain triglyceride emulsions.

Our objective was to determine how intravenous or intragastric feeding affects serum concentrations of insulin-like growth factor (IGF)-I and -II and IGF binding proteins (IGFBP), and hepatic abundance of IGF-I mRNA. Male Fischer 344 rats (235-246 g) were fed for 14 d by intravenous or intragastric infusion with total parenteral nutrition (TPN) solutions providing 65% of energy from long-chain triglyceride (LCT) or a 3:1 admixture of medium-chain triglyceride (MCT) and LCT emulsions (MCT/LCT). Twice as much TPN solution was required per gram of weight gain with MCT/LCT compared with LCT infusion (P < 0.0003). Serum IGF-I and -II concentrations and hepatic IGF-I mRNA abundance were not significantly different. Circulating concentrations of IGFBPs with molecular weights of 38,000-43,000 (IGFBP-3) were significantly greater with intravenous MCT/LCT than with intravenous LCT infusion. Our data demonstrate that reduced growth in rats given TPN containing MCT/LCT compared with LCT emulsions is not associated with reduced serum IGF-I concentrations or hepatic abundance of IGF-I mRNA, although serum IGFBPs are elevated.

Animals↗