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Biomedical subjects

W K Yu

Publications and source records attributed to W K Yu.

At least 19 recordsLinked to original sources
PubMed2006

Prenatal ethanol exposure alters the effects of gonadectomy on hypothalamic-pituitary-adrenal activity in male rats.

Prenatal ethanol exposure has marked effects on development of the hypothalamic-pituitary-adrenal (HPA) and -gonadal (HPG) axes. In adulthood, ethanol-treated rats show altered gonadal hormone responses and reproductive function, and increased HPA responsiveness to stressors. Importantly, prenatal ethanol differentially alters stress responsiveness in adult males and females, raising the possibility that the gonadal hormones play a role in mediating prenatal ethanol effects on HPA function. To examine a possible testicular influence on HPA activity in males, we compared the effects of gonadectomy on HPA stress responses of adult male offspring from ethanol, pair-fed (PF) and ad libitum-fed control dams. Intact ethanol-treated rats showed increased adrenocorticotrophic hormone (ACTH) but blunted testosterone and luteinising hormone (LH) responses to restraint stress, and no stress-induced elevation in arginine vasopressin (AVP) mRNA levels compared to those observed in PF and/or control rats. Gonadectomy: (i) significantly increased ACTH responses to stress in control but not ethanol-treated and PF males; (ii) eliminated differences among groups in plasma ACTH and AVP mRNA levels; and (iii) altered LH and gonadotrophin-releasing hormone responses in ethanol-treated males. Taken together, these findings suggest that central regulation of both the HPA and HPG axes are altered by prenatal ethanol exposure, with normal testicular influences on HPA function markedly reduced in ethanol-treated animals. A decreased sensitivity to inhibitory effects of androgens could contribute to the HPA hyperresponsiveness typically observed in ethanol-treated males.

Adrenocorticotropic Hormone↗
PubMed2001

Prevalence of Helicobacter pylori in gastric cancer in a South-East Asian population by 14C-urea breath test.

BACKGROUND: Helicobacter pylori is believed to play an important role in the aetiology of gastric cancer. There is a great variability in seropositivity and histological frequency of H. pylori in gastric cancer. The present prospective study investigates the prevalence of H. pylori infection in gastric cancer patients using 14C-urea breath testing. METHODS: Patients with endoscopic biopsy-proven gastric cancer were fasted for 6 h prior to ingesting 18.5 x 104 Bq of 14C-urea cocktail orally. Breath samples were collected after 20 min by asking them to blow into a hyamine solution and measurements were read in a scintillation counter. RESULTS: Fifty out of 51 patients (98%) with gastric cancer were positive on the 14C-urea breath test compared to 29 patients (61%) who were positive on histology. There was no association between sex, age or tumour site, stage, differentiation, Lauren type and H. pylori status. The test was negative in one patient with cardial tumour in which histology of the resected specimen was also negative for the bacteria. CONCLUSIONS: Active H. pylori infection is highly prevalent in gastric cancer in a South-East Asian population. The 14C-urea breath test is a highly sensitive method for detecting the presence of H. pylori even in gastric adenocarcinoma irrespective of the stage.

Adenocarcinoma↗
PubMed2001

Effects of prenatal ethanol exposure on hypothalamic-pituitary-adrenal regulation after adrenalectomy and corticosterone replacement.

BACKGROUND: Previous studies have demonstrated that rats prenatally exposed to ethanol (E) exhibit hypothalamic-pituitary-adrenal (HPA) hyperresponsiveness, demonstrated by increased and/or prolonged elevations of adrenocorticotropin (ACTH) and/or corticosterone (CORT) after stress. This study investigated possible mechanisms of HPA hyperresponsiveness in E rats by manipulating CORT feedback regulation of HPA activity via adrenalectomy (ADX) with or without CORT replacement. METHODS: Male Sprague-Dawley rat offspring from prenatal E, pair-fed (PF) and ad libitum-fed control (C) groups were tested at 90 to 120 days of age. Rats were either sham-operated or underwent ADX, with or without CORT replacement. CORT (25 microg/ml) was replaced via the drinking water to achieve basal plasma CORT levels and maintain a phasic CORT signal. Seven days after surgery, animals were decapitated at the diurnal peak either under basal conditions or after a 15-min restraint stress, and trunk blood was collected. RESULTS: After ADX, loss of the CORT feedback signal resulted in increased plasma ACTH in all groups compared with those in sham animals. In addition, under basal conditions, ADX E rats had significantly greater plasma ACTH levels than both PF and C rats. However, no differences were seen in ADX rats after stress. CORT replacement after ADX was partially effective in normalizing ACTH levels under both basal and stress conditions, with no differences among E, PF, and C animals. CONCLUSIONS: These results suggest that E males may exhibit enhanced stimulatory inputs to the hypothalamus, increased pituitary sensitivity to secretagogues, or both, which may be revealed after ADX. In contrast, E animals seem similar to controls in their ability to use an exogenous CORT signal to regulate HPA activity.

Adrenal Glands↗
PubMed2000

Influence of respiration and portal pressure on transabdominal duplex Doppler ultrasound measurement of portal blood flow: a porcine model for experimental studies.

Transabdominal duplex Doppler ultrasonography (TDDU) is commonly used for measuring hepatic blood flow (HBF) in clinical practice. Flow velocity and the cross-sectional area (CSA) of vessels are obtained separately and used to compute blood flow. Respiration and changes in portal pressure are known to cause variations in the CSA of the portal vein, but the impact of these parameters on TDDU measurement of portal blood flow is unclear. Eight Yorkshire pigs (20.7-25.1 kg) were used for the study. TDDU determination of portal blood flow was carried out using CSA of the portal vein obtained at inspiration (maximal) and at expiration (minimal) for computation, and the differences obtained were compared. Determination of HBF was carried out simultaneously on the same animals using diisopropyliminodiacetic acid (DISIDA) clearance. A physiological increase in portal pressure was then created by 50% hepatectomy and TDDU measurement similarly carried out on the second postoperative day. Computing portal blood flow in the intact liver using maximal and minimal CSA gave rise to a mean difference of 7.0 ml kg(-1) min(-1) (P < 0.001). A significant correlation was obtained between HBF and portal flow computed from maximal CSA (Pearson's correlation = 0.85, P < 0.033). The respiratory index of the portal vein (maximal CSA/minimal CSA) decreased from 1.5 to 1.2 after hepatectomy, which also caused a 90% increase in portal pressure. Respiration and portal pressure thus significantly impact on TDDU determination of HBF, and in this porcine model, computation using maximal CS more accurately reflects HBF.

Animals↗
PubMed2000

Changes in prostaglandin and nitric oxide levels in the hyperdynamic circulation following liver resection.

BACKGROUND AND AIMS: Significant changes in hepatic haemodynamics occur after major hepatectomy, but the pathogenesis of this phenomenon is unclear. This study investigates the serum profile of prostaglandin and nitric oxide in the hepatic and systemic circulation before and after hepatectomy and the temporal relationship of these to changes in the hepatic blood flow. METHODS: Blood samples were collected from the internal jugular, portal and hepatic veins of six Yorkshire pigs (17-25 kg) before, immediately after and 48 h after partial hepatectomy. RESULTS: Serum levels of prostacyclin I2 (PGI2) and prostaglandin E2 (PGE2) from the systemic circulation, the portal circulation and from the hepatic veins were found to differ considerably even before hepatectomy. After the hepatectomy was performed, there was a significant rise in PGI2 levels in the systemic circulation (P=0.027). Hepatic blood flow and cardiac output were measured before hepatectomy, 24 and 48 h after hepatectomy in another six pigs. A significant increase in hepatic blood flow (P=0.029) occurred after the hepatectomy and this was accompanied by a concomitant increase in the cardiac output (P=0.042). The increase in PGI2 concentration in the systemic circulation after hepatectomy appears to accompany the development of hyperdynamic hepatic and systemic circulations. No significant change was found in circulating PGE2 levels in the systemic, portal and hepatic veins at the three collection intervals (i.e. pre, post and 48 h after hepatectomy). The PGE2 levels in the hepatic vein, however, were significantly higher from than in the portal vein (P=0.028). No significant changes were observed in the level of nitric oxide. CONCLUSION: This study demonstrates an increase in the total hepatic blood flow after hepatectomy together with a threefold increase in prostacyclin in the systemic circulation. The liver was identified as the main source of circulatory prostaglandin.

Animals↗
PubMed2000

A non-invasive isotope dilution technique for quantifying hepatic blood flow using radiolabelled red blood cells.

Clinically significant changes in hepatic haemodynamics accompany the development of portal hypertension, hepatocellular carcinoma, liver metastases and liver cirrhoses, and after major liver resection. Hepatic blood flow parameters, such as hepatic arterial flow (HAF), hepatic portal flow (HPF), total hepatic blood flow (THBF) and hepatic perfusion index (HPI), are useful adjuncts to the diagnosis of liver pathology, the evaluation of disease progress and prognostication. Here, we describe a non-invasive method that combines the measurement of these parameters in a single study in real time. Red blood cells from eight pigs were labelled with 99Tc(m) using an in-vitro method and re-injected into the pigs. Data acquisition over the heart, lungs, liver and kidneys was started immediately and a blood sample was obtained 15 min post-injection. Hepatic arterial flow was determined from the ratio of the maximum gradients between the integrated time-activity curve of the left ventricle and the first-pass time-activity curve of the liver before the peak of the kidneys time-activity curve. The hepatic perfusion index was determined by comparing the slope of the liver time-activity curve before and after the kidney peak. Hepatic portal flow was determined from the hepatic arterial flow and the hepatic perfusion index, and total hepatic blood flow was determined as the sum of arterial and portal flow. The results were compared against those obtained from a clearance method using 99Tc(m)-DISIDA. The average hepatic perfusion index was 0.38, and the average hepatic arterial flow and hepatic portal flow were 168.3 +/- 52.9 and 274.6 +/- 60.1 ml x min(-1) respectively. The average total hepatic blood flow was 442.8 +/- 53.5 ml x min(-1), while the total hepatic flow determined by 99Tc(m)-DISIDA clearance was 419.7 +/- 62.6 ml x min(-1). No significant difference in total hepatic blood flow was found between the two methods. The results of this study show that it is possible to obtain all hepatic haemodynamics data in a single study using a non-invasive method.

Animals↗
PubMed1999

Five micro-curie urea breath test for the diagnosis of Helicobacter pylori infection: evaluation in a South-East Asian population.

BACKGROUND: Helicobacter pylori is an important pathogen responsible for significant morbidity and mortality. Its prevalence varies widely in different geographical locations and is especially high in parts of Asia. METHODS: A double-blind study was carried out to evaluate the use of the 5 microCi (185 KBq) [14C]-urea breath test ([14C]-UBT) in a South-East Asian population by validating its diagnostic accuracy against histology and the CLO test. RESULTS: The sensitivity and specificity of the [14C]-UBT was 100% when compared against the CLO test. When histology was used as the 'gold standard', the sensitivity and specificity were 100% and 97.2%, respectively. There was no overlap or indeterminate values between positive and negative results on the [14C]-UBT. CONCLUSIONS: Among South-East Asian populations where the prevalence of H. pylori infection is high, the high sensitivity of the 5 microCi [14C]-UBT makes it a very important test in the detection of H. pylori.

Adult↗
PubMed1999

AO fixateur interne in treating burst fractures of the thoracolumbar spine.

BACKGROUND: A burst fracture of the thoracolumbar junction is an unstable spinal fracture, which is caused by high-energy trauma. There are many methods of treatment, both surgical and nonsurgical, in dealing with spinal burst fractures. The Arbeitsgemeinschaft für Osteosynthesefragen (AO) Fixateur Interne (FI) system was introduced in 1985 for posterior spine surgery with a transpedicular screw system. METHODS: From April, 1989, through December, 1994, we encountered 42 patients with 42 acute burst fractures of the spine; 26 were male and 16 were female, with an average age of 41.2 years. One fracture occurred on T11, seven on T12, 16 on L1, 11 on L2, one on L3, four on L4 and two on L5. According to the Denis classification, there were eight type A, 23 type B, five type C, three type D and three type E fractures. All of these patients received posterior reduction without decompression, posterior short segmental fixation with AO FI instrumentation and posterior fusion. RESULTS: After follow-up for an average of 66.1 months, all fractures were found to have united with residual back pain in only six patients; five patients, including one with nonunion, had back pain without the necessity of medication, and the other one had occasional back pain that was well controlled by medication. The immediate postoperative Cobb's angle improved by an average of 14.2 degrees, and there was an average loss of 3.3 degrees at final follow-up. All patients were neurologically intact at final follow-up except two patients, who were Frankel D. Seven patients had complications during follow-up; one experienced nonunion; four experienced screw breakage, one had screw pullout, and the other experienced breakage of the connecting rod. CONCLUSIONS: From our retrospective study, the outcome of burst fracture of the spine treated with AO FI instrumentation system was satisfactory.

Adult↗
PubMed1999

Delayed cholestatic hepatitis due to methimazole.

We report on a 71-year-old man who presented to the medical department of Our Lady of Maryknoll Hospital with progressive cholestatic hepatitis. Tests for hepatitis viral markers gave negative results and ultrasonography revealed no dilated bile ducts. Endoscopic retrograde cholangiopancreatography showed a normal biliary tree. The patient had completed a 5-month course of methimazole to treat thyrotoxicosis a few weeks before the onset of the jaundice. Methimazole was suspected to be the cause of the cholestatic hepatitis; this diagnosis was supported by the results from a liver biopsy. The presentation of the patient was unusual by virtue of the delayed onset and prolonged course of cholestasis.

Journal Article↗
PubMed1999

[Biosynthesis of a single peptide chain containing human chorionic gonadotropin beta and C3D of complement].

In view of the strong immunity-enhancing function of HEL-C3d3 designed by Dr. Paul W. Dempsey, we made our efforts to produce a similar recombinant protein of hCG beta. With polymerase chain reaction, we introduced a Bam HI restriction site into the 3' terminal of hCG beta cDNA. The new cDNA and its terminal's correctness has been confirmed by sequencing. Then we have it covalently attached to the C3d3 cDNA at the pre-designed Bam HI/Bgl II site. Having the chimeric DNA correctly cloned into the protein nuclear polyhedrosis virus (AcNPV) expression vector pVL1393, we constructed the expression vector pVL1393-(hCG beta-C3d3). The insect cells were co-transfected with the expression vector and linearized nuclear polyhedrosis virus DNA, and recombinant viruses AcNPV-(hCG beta-C3d3) were screened out. Through anti-hCG beta immunoaffnity chromatography, the recombinant hCG beta-C3d3 chimera polypeptide was purified from culture supernatant of insect cells infected by the recombinant viruses. In RIA test, the expressed product competitively inhibits the binding of 125I-hCG beta to hCG beta-antibody. On SDS-PAGE and Western blot, the recombinant peptide hCG beta-C3d3 obviously appears to be with a molecular weight of 116KD. Therefore, we arrive at a conclusion that it has a normal immunogenic ability.

Animals↗
PubMed1997

Surgical treatment of seat belt type injury of the thoracolumbar spine.

BACKGROUND: Seat belt type injury of thoracolumbar spine is an uncommon injury characterized by disruption of the posterior elements of the spine. The fracture has long been treated conservatively, but progressive kyphotic deformity developed frequently. METHODS: From January, 1991 through December, 1992, 10 cases of seat belt type injury of the thoracolumbar spine were encountered at our hospital with an incidence of 8% in overall spinal fractures. Of these patients, eight patients were male and two were female, average age 30.7 years old. The causes included motor-vehicle accident in five patients, fall from height in four, and stricken by a falling electric pole in one. None of the victims of motor vehicle accidents wore seat belt. All of them received open reduction, posterior internal fixation and posterior fusion. RESULTS: After follow-up for an average of 42.2 months, the average kyphotic angulation was 5.7 degrees. Back pain and function of these patients were all rated good. None of them suffered from neurologic deficit. One patient with breakage of transpedicular screws was encountered during follow-up, but there was no complaint. CONCLUSIONS: In treating seat belt type injuries of spinal column, benefits of operation outweigh the risks. Besides, the clinical result is satisfactory and more aggressive surgical approach should be encouraged.

Accidents, Traffic↗
PubMed1995

Evidence for lipoxygenase-catalyzed bioactivation of phenytoin to a teratogenic reactive intermediate: in vitro studies using linoleic acid-dependent soybean lipoxygenase, and in vivo studies using pregnant CD-1 mice.

Teratogenicity of the anticonvulsant drug phenytoin and structurally related compounds has been postulated to result in part from its cooxidative bioactivation to an embryotoxic reactive intermediate by the hydroperoxidase component of arachidonic acid-dependent prostaglandin H synthase (PHS). However, lipoxygenases (LPOs) could constitute a competing, arachidonate-dependent bioactivating system. The teratologic importance of LPO alone and together with PHS was evaluated in vitro and in vivo. To evaluate directly the potential role of LPO in phenytoin bioactivation, in vitro incubation conditions measuring the linoleic acid-dependent, soybean LPO-catalyzed covalent binding of phenytoin to protein, believed to constitute teratologic initiation, were optimized for substrate concentration, enzyme activity, incubation time, inhibitor vehicle, and inhibitor concentration. Under optimal conditions, 4.24 nM [3H]phenytoin, 100,000 units of soybean LPO (Type 1B, Sigma Chemical Co.), and 5 mg bovine serum albumin, with or without 5 mM linoleic acid, were adjusted with 100 mM Tris-HCl buffer (pH 9) to a 1-ml final volume and incubated at 37 degrees C for 60 min. Addition of linoleic acid substrate to the incubation medium enhanced the covalent binding of phenytoin by over threefold (p < 0.05). Linoleic acid-dependent covalent binding of phenytoin was inhibited in a concentration-dependent fashion by the selective and nonselective LPO/PHS inhibitors indomethacin, nordihydroguaiaretic acid, quercetin, BW755C, and 5,8,11,14-eicosatetraynoic acid (ETYA) and by the hydroperoxidase inhibitor methimazole (p < 0.05). In vivo, on Gestational Days 12 and 13, pregnant CD-1 mice were treated with the irreversible dual PHS/LPO inhibitor ETYA (0, 0.5, 5, 50, 100, and 125 mg/kg ip) or its vehicle, 2 hr before a teratogenic dose of phenytoin (65 mg/kg ip). Dams were killed on Day 19 and the fetuses were delivered by Caesarian section. ETYA pretreatment produced a dose-related decrease in phenytoin teratogenicity, with maximal reductions by 50 mg/kg of ETYA in the incidence of phenytoin-induced fetal cleft palates (1.8 +/- 1.8% vs 26.8 +/- 3%) (% +/- SE; p < 0.00001) and resorptions (22.5 +/- 5% vs 60 +/- 2%) (p < 0.05). Higher ETYA doses were embryotoxic. The reduction in phenytoin teratogenicity by the dual PHS/LPO inhibitor ETYA was considerably greater than that previously reported for acetylsalicylic acid, which inhibits only PHS.(ABSTRACT TRUNCATED AT 250 WORDS)

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1995

Surgical treatment of extensive discovertebral destruction in ankylosing spondylitis: a report of two cases.

Extensive discovertebral destruction in ankylosing spondylitis is rare and difficult in diagnosis and management. We present two such cases who were treated with anterior decompression, autogenous strut iliac bone graft and fixed with anterior locking plate system (ALPS) instrumentation. After operation the patients' symptoms improved and the spinal deformities were corrected. Our experiences in these two patients emphasize the importance of early recognition, early detection and aggressive surgical treatment in the lesion.

Adult↗
PubMed1990

Cyclic fatigue-crack propagation, stress-corrosion, and fracture-toughness behavior in pyrolytic carbon-coated graphite for prosthetic heart valve applications.

Fracture-mechanics tests were performed to characterize the cyclic fatigue, stress-corrosion cracking, and fracture-toughness behavior of a pyrolytic carbon-coated graphite composite material used in the manufacture of cardiac valve prostheses. Testing was carried out using compact tension C(T) samples containing "atomically" sharp precracks, both in room-temperature air and principally in a simulated physiological environment of 37 degrees C Ringer's lactate solution. Under sustained (monotonic) loads, the composite exhibited resistance-curve behavior, with a fracture toughness (KIc) between 1.1 and 1.9 MPa square root of m, and subcritical stress-corrosion crack velocities (da/dt) which were a function of the stress intensity K raised to the 74th power (over the range approximately 10(-9) to over 10(-5) m/s). More importantly, contrary to common perception, under cyclic loading conditions the composite was found to display true (cyclic) fatigue failure in both environments; fatigue-crack growth rates (da/dN) were seen to be a function of the 19th power of the stress-intensity range delta K (over the range approximately 10(-11) to over 10(-8) m/cycle). As subcritical crack velocities under cyclic loading were found to be many orders of magnitude faster than those measured under equivalent monotonic loads and to occur at typically 45% lower stress-intensity levels, cyclic fatigue in pyrolytic carbon-coated graphite is reasoned to be a vital consideration in the design and life-prediction procedures of prosthetic devices manufactured from this material.

Biocompatible Materials↗
PubMed1989

The biodistribution of [75Se]bis-[beta-(N,N,N-trimethylamino)ethyl]selenide diiodide in adult guinea pigs.

The biodistribution of [75Se]BISTAES was studied in guinea pigs. A higher concentration of radioactivity was observed in articular cartilage than in other tissues or organs. A minimal amount of radioactivity was found in the blood, muscle and bone. The compound was excreted rapidly in urine. The target to background ratios were encouraging. [75Se]BISTAES has potential as an articular cartilage imaging agent and further studies in osteoarthritic animals are merited.

Animals↗
PubMed1988

Biodistribution of bis-[beta-(N,N,N-trimethylamino)ethyl]selenide-75Se diiodide, a potential articular cartilage imaging agent.

In an effort to develop a specific radiodiagnostic agent for articular cartilage imaging, we have investigated the biodistribution of bis[beta-(N,N,N-trimethylamino)ethyl]-selenide-75Se diiodide (75Se BISTAES) in rabbits. At an intravenous dose of 5 mg/kg, the greatest localization of the compound occurred in articular cartilage 15 min after injection. The compound was excreted rapidly in the urine. The results suggest that 75Se BISTAES has potential clinical use as an articular cartilage imaging agent.

Animals↗
PubMed1984

Economics and extended longevity: a case study.

Preventive and therapeutic advances have brought life expectancy in the United States to well over 70 years and have shifted mortality causes from acute to chronic diseases, the determinants of which are genetics, lifestyle, the environment, and aging itself. Plausible approaches to chronic disease prevention are likely to increase longevity further, with some foreseeable effects on demographic and economic projections. Primarily, longevity advances would swell forecasts of population size, and would thus have to be met by production advances in order to maintain or improve living standards. This study, a restricted example, considers the probable demographic and economic consequences of a limited prevention program in the context of the Ford Motor Company, based on actual experience and certain expectations up to the year 2000. According to the results, prevention would reduce outlays for life insurance, disability, and health care, but would also generate the higher costs of extending pension plans. Undoubtedly, prevention will continue to be highly ranked in society's pursuit of happiness, and society must prepare to meet its effects with appropriate social and economic policies.

Aged↗