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H Yang

Publications and source records attributed to H Yang.

At least 883 records · Page 49Linked to original sources
PubMed1993

A three-dimensional anatomical model of the human patello-femoral joint, for the determination of patello-femoral motions and contact characteristics.

The object of this study is to develop a three-dimensional mathematical model of the patello-femoral joint, which is modelled as two rigid bodies representing a moving patella and a fixed femur. Two-point contact was assumed between the femur and patella at the medial and lateral sides and in the analysis, the femoral and patellar articular surfaces were mathematically represented using Coons' bicubic surface patches. Model equations include six equilibrium equations and eleven constraints: six contact conditions, four geometric compatibility conditions, and the condition of a rigid patellar ligament; the model required the solution of a system of 17 nonlinear equations in 17 unknowns, its response describing the six-degrees-of-freedom patellar motions and the forces acting on the patella. Patellar motions are described by six motion parameters representing the translations and rotations of the patella with respect to the femur. The forces acting on the patella include the medial and lateral component of patello-femoral contact and the patellar ligament force, all of which were represented as ratios to the quadriceps tendon force. The model response also includes the locations of the medial and lateral contact points on the femur and the patella. A graphical display of its response was produced in order to visualize better the motion of the components of the extensor mechanism. Model calculations show good agreement with experimental results available from the literature. The patella was found to move distally and posteriorly on the femoral condyles as the knee was flexed from full extension. Results indicate that the relative orientation of the patellar ligament with respect to the patella remains unchanged during this motion. The model also predicts a patellar flexion which always lagged knee flexion. Our calculations show that as the angle of knee flexion increased, the lateral contact point moved distally on the femur without moving significantly either medially or laterally. The medial contact point also moved distally on the femur but moved medially from full extension to about 40 degrees of knee flexion, then laterally as the knee flexion angle increased. The lateral contact point on the patella did not change significantly in the medial and lateral direction as the knee was flexed; however, this point moved proximally toward the basis of the patella with knee flexion. The medial contact point also moved proximally on the patella with knee flexion, and in a similar manner the medial contact point on the patella moved distally with flexion from full extension to about 40 degrees of flexion.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗
PubMed1993

A unified functional/anatomic substrate for circus movement atrial flutter: activation and refractory patterns in the canine right atrial enlargement model.

OBJECTIVES: This study was designed to test the concept of a functional/anatomic interaction in a canine model of reentry based on right atrial enlargement and to elucidate the electrophysiologic basis for functional conduction block. BACKGROUND: The monotonic feature of atrial flutter suggests a uniform substrate for the arrhythmia. Atrial flutter in the sterile pericarditis model is due to single-loop circus movement around a functional or a functional/anatomic obstacle near the atrioventricular (AV) ring. Sustained circus movement requires a critical interaction of a functional arc of block, a natural obstacle, the AV ring and a zone of slow conduction. The location of the inferior vena cava predisposes the lower right atrium to single-loop reentry. METHODS: In 11 dogs with right atrial enlargement, 127 bipolar epicardial electrograms were obtained during atrial flutter. For correlation of activation and refractory maps, the effective refractory period under each electrode was determined using the extrastimulus technique. RESULTS: Atrial flutter was due to single-loop reentry around functional arcs of block near the AV ring (n = 2) or around functional/anatomic obstacles (n = 8) involving the inferior vena cava. A slow zone was located between the arc and the AV ring and between the inferior vena cava and AV ring, respectively. During initiation, the arc joined the AV ring, forcing activation to proceed around the free end of the arc before breaking through the arc near the AV ring. Arrhythmia termination required the arc of block to rejoin the AV ring. Inducibility of sustained atrial flutter was associated with a marked spatial dispersion of refractoriness. The configuration of the functional arc of block was critically dependent on the spatial pattern of refractoriness. CONCLUSIONS: Atrial flutter requires a similar functional or functional/anatomic substrate independent of the underlying etiology. The spatial distribution of refractoriness in enlarged canine atria provides an adequate substrate for the development of functional conduction block.

Animals↗
PubMed1993

Monoclonal antibody to rat alpha-CGRP: production, characterization, and in vivo immunoneutralization activity.

Spleen cells from a Robertsonian mouse immunized with rat alpha-CGRP were fused with FOX-NY cells to induce hybridoma cells. Antibody activities were screened by radioimmunoassay, and hybridomas producing high affinity antibodies were cloned by limiting dilutions. Ascites were produced from the highest affinity clone in pristine-primed Balb/c mice. Ascites fluid contained approximately 20 mg/ml IgG which was of subclass IgG2a as determined by immunodiffusion analysis. The titer of this IgG2a antibody titled #4901, was 1:2,000,000 and the ID50 for rat alpha-CGRP, rat beta-CGRP and human alpha-CGRP were 350, 4000, and 4500 pg/ml respectively. Protein A purified CGRP antibody #4901 (5-10 mg/kg) completely abolished the portal release of somatostatin and the inhibition of gastric acid secretion induced by intravenous infusion of rat alpha CGRP (15-20 micrograms/kg/h) in anesthetized rats. The unpurified antibody (25 mg/kg) also prevented the fall in mean arterial blood pressure and the increase in heart rate caused by intravenous injection of rat alpha-CGRP. Immunohistochemistry showed that CGRP monoclonal antibody stains nerve fibers and endocrine-like cells in the pancreas, and neuronal elements in the gastrointestinal tract. These results show that CGRP monoclonal antibody #4901, which is relatively specific for rat alpha-CGRP, is useful for in vivo immunoneutralization of CGRP and is also an excellent reagent for immunohistochemical localization of alpha- and beta-CGRP in mammals.

Amino Acid Sequence↗
PubMed1993

Total parenteral nutrition containing medium- vs. long-chain triglyceride emulsions elevates plasma cholesterol concentrations in rats.

Male Fischer 344 rats (235-246 g) were fed for 6-14 d by intravenous or intragastric infusion with total parenteral nutrition (TPN) solutions providing 40 or 65% of nonprotein energy as fat from long-chain triglyceride (LCT) or a 3:1 admixture of medium-chain triglyceride (MCT) and LCT emulsions. In three separate experiments, plasma cholesterol concentrations were significantly greater (24-32%) with intravenous infusion of TPN solutions containing MCT-LCT rather than LCT. Plasma cholesterol concentrations in rats were not significantly different with intragastric infusion of TPN solutions containing MCT-LCT rather than LCT. Hepatic total lipid and triglyceride concentrations were not significantly different. Hepatic total cholesterol and esterified cholesterol concentrations were significantly lower in animals given 65% of energy from MCT-LCT rather than LCT emulsions (main effects, two-way ANOVA). The concentration of individual hepatic acyl-CoA esters reflected the fatty acid profiles of the lipid emulsions infused. Total hepatic acyl-CoA concentrations suggested differences in utilization of acyl-CoA esters with intravenous infusion of MCT-LCT rather than LCT and were consistent with rapid oxidation of MCT. These data demonstrate that MCT-LCT elevates plasma cholesterol concentrations compared with LCT emulsions with intravenous, but not with intragastric, infusion of TPN solutions in rats.

3-Hydroxybutyric Acid↗
PubMed1993

The sex-determining region Y (SRY) gene is mapped to p12-p13 of the Y chromosome in pig (Sus scrofa domestica) by in situ hybridization.

The sex-determining region Y is a gene located in the distal portion of the short arm of human (SRY) and mouse (Sry) Y chromosomes and considered to be the best candidate for the testis determining factor (TDF/Tdy). The gene is believed to be the key factor in sex differentiation in mammals and is conserved across mammalian species. We report herein that the SRY/Sry gene has been assigned to p12-p13 on the short arm of the Y chromosome in pig by in situ hybridization. The result confirms interspecies conservation of this chromosomal segment in the evolution of mammalian chromosomes, and suggests further use of this gene probe in genomic studies in another mammals. The assignment of the Sry gene is the second physical gene mapping data available for the Y chromosome in pigs. Such data can be used in the effort of constructing the pig gene map and for further establishment of a comparison of sex chromosome morphology in different mammalian species concerning sex-specific and pseudoautosomal regions.

Animals↗
PubMed1993

Preparation and reactivities of anti-porcine CD44 monoclonal antibodies.

Five monoclonal antibodies (MoAbs) were raised against porcine soluble CD44. The MoAbs recognized the same antigen on the surface of porcine lymphocytes as was recognized by anti-human CD44 MoAb Hermes-1, but identified five different epitopes. They bound to most porcine leucocytes but not to red cells. The epitopes were susceptible to treatment with papain or bromelain, whereas trypsinization of porcine leucocytes only reduced the antigen density. The epitopes seem to be co-expressed among various lymphoid tissues. The MoAbs also cross-reacted to various degrees with leucocytes of humans, dogs, sheep, cattle, goats and horses, suggesting that the corresponding epitopes are differentially conserved among species.

Animals↗
PubMed1993

Ability of Pseudomonas pseudomallei malleobactin to acquire transferrin-bound, lactoferrin-bound, and cell-derived iron.

The ability of malleobactin to mobilize iron from transferrin and lactoferrin was examined in an equilibrium dialysis assay in the absence of bacteria. Malleobactin was capable of removing iron from both transferrin and lactoferrin at pH values of 7.4, 6.0, and 5.0. However, the levels of iron mobilization were greater for transferrin than for lactoferrin at all the pH values used in the assay. The ability of Pseudomonas pseudomallei to acquire iron from 30% iron-saturated transferrin and K562 human erythroleukemic cells was compared in parallel cultures as described previously (J. H. Brock, P. H. Williams, J. Liceaga, and K. G. Woldridge, Infect. Immun. 59:3185-3190, 1991). P. pseudomallei U7 tended to acquire iron from transferrin. In contrast, P. aeruginosa PAO and P. cepacia Pc275C acquired iron from both sources. P. cepacia H1721, which does not produce detectable siderophores, but can utilize malleobactin, pyochelin, and azurechelin as iron sources, was used in a similar experiment. Addition of malleobactin resulted in iron uptake only from transferrin, whereas pyochelin and azurechelin promoted iron uptake from both sources. When the siderophores were incubated with K562 cells alone, malleobactin was less efficient at removing iron from cells than pyochelin and azurechelin. It was also determined that malleobactin was less effective in binding to or entering cells than pyochelin and azurechelin. These results suggest that malleobactin can acquire iron more effectively from host proteins than from cellular sources. Pyochelin and azurechelin can acquire cell-derived iron in addition to iron bound to host proteins.

Burkholderia pseudomallei↗
PubMed1993

Familial empirical risks for inflammatory bowel disease: differences between Jews and non-Jews.

The Jewish population has an increased frequency of inflammatory bowel disease compared with their non-Jewish neighbours. Genetic factors have been implicated in the aetiology of this disorder and may contribute to ethnic differences. This study determined the familial empirical risks for inflammatory bowel disease in the first degree relatives of inflammatory bowel disease probands (for both Jews and non-Jews) for the purpose of accurate genetic counselling and genetic analysis. A total of 527 inflammatory bowel disease patients from Southern California (291 Jews and 236 non-Jews) were questioned about inflammatory bowel disease in their first degree relatives (a total of 2493 individuals). Since inflammatory bowel disease has a variable and late age of onset, age specific incidence data were used to estimate the life time risks and to make valid comparisons between the different groups. In the first degree relatives of non-Jewish probands, the life time risks for inflammatory bowel disease were 5.2% and 1.6% when probands had Crohn's disease and ulcerative colitis respectively. These values were consistently lower than the corresponding risks for relatives of Jewish patients -7.8% and 4.5% for Crohn's disease and ulcerative colitis probands respectively (p value for comparison between Jews and non-Jews: 0.028; between ulcerative colitis and Crohn's disease: 0.005). These data provide the requisite basis for genetic counselling for these disorders in the white American population. In addition, these different empirical risks for relatives of Jewish and non-Jewish probands allow rejection of single Mendelian gene models for inflammatory bowel disease, but are consistent with several alternative genetic models.

Adolescent↗
PubMed1993

TRH in dorsal vagal complex mediates acid response to excitation of raphe pallidus neurons in rats.

The role of thyrotropin-releasing hormone (TRH) in the dorsal vagal complex (DVC) in the acid response to excitation of raphe pallidus neurons was investigated in urethan-anesthetized rats with gastric fistula. Kainic acid (0.19 microgram/30 nl) microinjected into the raphe pallidus stimulated gastric acid secretion. The response was prevented by vagotomy. A specific polyclonal TRH antibody, 8964, was raised and characterized (50% inhibitory dose for TRH was 80 pg/ml at an antibody final dilution of 1:10(5)). The TRH antibody injected intracisternally blocked the acid response to intracisternal TRH, but not that of the TRH analogue RX-77368. The TRH antibody (0.33, 0.65, or 1.3 micrograms.100 nl-1.site-1) microinjected bilaterally into the DVC prevented dose dependently by 31, 60, and 76%, respectively, the increase in acid secretion induced by kainic acid injected into the raphe pallidus. The TRH antibody (1.3 microgram/site) microinjected into medullary sites outside of the DVC had no effect. These data indicate that excitation of raphe pallidus neurons induces a vagal-dependent stimulation of gastric acid secretion that is mediated by endogenous TRH in the DVC. TRH neurons in the raphe pallidus projecting to the DVC may have a physiological relevance in the vagal regulation of gastric function.

Animals↗
PubMed1993

Vagal regulation of gastric function involves thyrotropin-releasing hormone in the medullary raphe nuclei and dorsal vagal complex.

There is convincing electrophysiological, neuroanatomical and functional data in support of an excitatory action of thyrotropin-releasing hormone (TRH) on the dorsal motor nucleus of the vagus neurons leading to stimulation of vagal outflow to the stomach and to a vagal cholinergic-dependent stimulation of gastric secretory and motor function and alterations of mucosal integrity in rats and cats. The raphe pallidus and obscurus have become important medullary nuclei regulating vagal function through their TRH and serotonin projections to the dorsal vagal complex. However, still little is known about the transmitters and conditions which influence the activity of these TRH-containing medullary raphe neurons. Existing knowledge points out a possible physiological role of TRH in mediating vagal reflex and the cephalic phase of digestion.

Animals↗
PubMed1993

Circus movement atrial flutter in the canine sterile pericarditis model. Cryothermal termination from the epicardial site of the slow zone of the reentrant circuit.

BACKGROUND: We have shown that atrial flutter (AF) in dogs with sterile pericarditis is commonly due to a single-loop reentrant circuit in the lower right atrium comprised of a functional or functional/anatomic obstacle and a slow zone of conduction (SZ) between the central obstacle and the atrioventricular (AV) ring. The goals of the present study were 1) to establish that the epicardial SZ is the critical component of circus movement AF and 2) to identify the optimal site within the epicardial SZ at which interruption of circus movement can be accomplished by ablative techniques. METHODS AND RESULTS: We analyzed the atrial activation patterns during epicardial cooling of the SZ with as N2O-cooled probe in eight dogs (five with clockwise [CW] reentrant circuit, one with counterclockwise [CCW] reentrant circuit, and two with both CW and CCW reentrant circuits around the same pathway). In all eight dogs, cooling (-5 to +5 degrees C for 5-20 seconds) the narrow isthmus at the inferoposterior part of the SZ between the central obstacle and the AV ring reversibly terminated the reentrant circuit, whereas cooling outside this area failed to terminate the reentrant circuit. The circus movement was not observed to continue along alternate pathways when conduction in this critical zone was interrupted. Both CW and CCW reentrant circuits could be terminated from the same site within the SZ. Cooling resulted in slowing of conduction in the SZ (55 +/- 15 msec) in both CW and CCW reentrant circuits. Cooling-induced termination of CW reentrant circuits was characteristically associated with oscillations of conduction in the cooled zone of the last three cycles before termination and conduction block occurred within the cooled zone. The last "manifest" reentrant cycle was associated with the longest conduction delay in the cooled zone. However, this delay was not necessarily reflected in the length of the last reentrant cycle because of compensatory acceleration of conduction in the rest of the pathway. On the other hand, in CCW reentrant circuits, conduction block occurred abruptly at the distal border of the SZ and without significant oscillations of conduction. CONCLUSIONS: The present study provides convincing evidence that single-loop circus movement in this model is critically dependent on an obligatory conduction in a SZ in the inferoposterior portion of the free right atrial wall between a functional obstacle and the AV ring. Because the atrial myocardium behaves electrophysiologically as a two-dimensional surface, the results of this study may help to guide the endocardial electrode catheter ablative technique for treatment of clinical AF.

Animals↗
PubMed1993

Ulcerative colitis: a genetically heterogeneous disorder defined by genetic (HLA class II) and subclinical (antineutrophil cytoplasmic antibodies) markers.

Newly described distinct associations of HLA class II genes with ulcerative colitis (UC) (DR2) and Crohn's disease (CD) (DR1/DQ5) provide strong evidence for genetic heterogeneity of susceptibility between these two forms of inflammatory bowel disease. A familial distribution of antineutrophil cytoplasmic antibodies (ANCAs, a subclinical marker of UC) in UC families has further implied the existence of heterogeneity within UC. To test the hypothesis that the heterogeneity within UC indicated by ANCAs has a genetic basis that resides within the HLA region, we studied 89 UC cases and an ethnically matched control group (n = 50). Serological and molecular typing techniques were applied to define HLA class II genes (DR, DQ). ANCAs were detected using an enzyme-linked immunosorbent assay, and positive values were confirmed by indirect immunofluorescence. We observed that ANCA-positive UC patients (n = 70) had a significantly increased frequency of DR2 compared with ANCA-negative controls (n = 46) (44% vs 22%, P = 0.01). In contrast, the frequency of DR2 in ANCA-negative UC cases (21%) was virtually identical to that in controls (22%, P = 0.9). Furthermore, the ANCA-negative UC patients had an increase in the DR4 allele compared with ANCA-positive UC (P = 0.004). Thus, with the combination of a subclinical marker (ANCAs) and molecular genetic markers, genetic heterogeneity has been demonstrated within UC: ANCA-positive UC associated with DR2, and ANCA-negative UC likely associated with DR4.

Adult↗
PubMed1993

Hepatitis B control in China: knowledge and practices among village doctors.

OBJECTIVES: To guide development of a hepatitis B control program in China, we investigated village doctors' sterilization practices, injection use, vaccination levels, and knowledge and counseling skills. METHODS: The head doctor from each village health station in a rural county (n = 260) completed a self-administered questionnaire. RESULTS: Of the respondents, 94.2% reported adequate sterilization of needles; however, inadequate sterilization of syringes and acupuncture needles was common. Injections were found to be frequent and profitable. Of head doctors, 16.2% reported that most infants in their villages are vaccinated against hepatitis B. There was very high knowledge of modes of hepatitis B transmission, but it was not used to formulate advice for a hypothetical carrier. Knowledge of the consequences, prevalence, and use of condoms to prevent sexual transmission was lower. CONCLUSIONS: The sterilization of acupuncture needles, reuse of syringes, and frequent injections are practices that may transmit the hepatitis B virus. Research into issues of vaccine acceptance is needed to expand immunization. A review of treatment practices and better training in counseling for village doctors is suggested.

Acupuncture Therapy↗
PubMed1993

A new antibiotic, cypemycin. Taxonomy, fermentation, isolation and biological characteristics.

A new peptide antibiotic, cypemycin, with a molecular weight of 2,097 (M+H), was isolated from the culture broth of Streptomyces sp. OH-4156. The antibiotic possesses cytocidal activity against P388 leukemia cells in vitro at a concentration of 1.3 microgram/ml (IC50 values), and the antibiotic showed antimicrobial activities against Micrococcus luteus (MIC, 0.2 microgram/ml).

Amino Acid Sequence↗
PubMed1993

Color Doppler imaging in the diagnosis and follow-up of carotid cavernous sinus fistulas.

This report describes color doppler imaging (CDI) in the evaluation and follow-up of nine patients with carotid cavernous sinus fistulas. The orbits and carotid arteries were examined with CDI. In all cases, the diagnosis was confirmed by angiography. CDI clearly demonstrated the dilated superior ophthalmic veins (SOVs) with retrograde flow and low resistance arterial doppler waveform in all nine patients (10 eyes). After the study of quantitative hemodynamics, we found that direct carotid cavernous sinus fistulas showed a high-velocity blood flow in the abnormal SOVs in all seven patients and a very low resistance, high flow volume circulation in the involved internal carotid artery (ICA) in six patients that had been examined; however, two patients with dural cavernous sinus fistulas had a lower blood flow in the SOVs than direct fistulas and no significant hemodynamic changes were found between the ipsilateral ICA and the contralateral ICA. These results were helpful for the diagnosis and the differential diagnosis between direct fistulas and dural fistulas. CDI also provides a convenient way to track the natural history and response to treatment of these arteriovenous fistulas. CDI offer several advantages, namely noninvasive and can be performed easily, quickly, inexpensively and reproducibly.

Adolescent↗
PubMed1993

[Color Doppler imaging in the study of normal orbital vessels and its hemodynamics].

Color Doppler Imaging (CDI) is a recent development in ultrasonography, which can display simultaneously two dimensional images of structure and Doppler evaluation of blood flow. Using the technique, we examined 74 normal eyes. Orbital vessels including ophthalmic artery (OA), posterior ciliary arteries (PCA), center retinal artery (CRA) and central retinal vein (CRV) could be located to make Doppler spectrum analysis and quantification of hemodynamics. Blood velocity (Unit cm/s) in these vessels was obtained as following: the average peak systolic flow velocity for OA was 31.9 +/- 5.01; for PCA, 14.74 +/- 3.85 and for CRA, 11.5 +/- 2.45. The time-averaged maximum velocity for OA was 14.91 +/- 1.83 and for PCA, 8.09 +/- 2.00 and for CRA, 5.78 +/- 1.14. The end-diastolic velocity for OA was 9.04 +/- 1.15; for PCA, 5.46 +/- 1.61 and for CRA, 3.73 +/- 1.06. The resistivity indices for OA were 0.715 +/- 0.04 and for PCA, 0.63 +/- 0.04 and for CRA, 0.68 +/- 0.04. The blood velocities in these vessels significantly declined with increasing age of subjects (P < 0.05). CDI is a noninvasive, accurate and reproducible modality for the study of ocular and orbital hemodynamics.

Adolescent↗