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Biomedical subjects

A Cheung

Publications and source records attributed to A Cheung.

At least 55 records · Page 3Linked to original sources
PubMed1997

The role of aspiration and contrast-enhanced arthrography in evaluating the uncemented hip arthroplasty.

OBJECTIVE: The purpose of this study was to determine the value of aspiration and contrast-enhanced arthrography in evaluating uncemented total hip arthroplasty components. A retrospective study was performed to determine the sensitivity, specificity, and accuracy of these procedures. MATERIALS AND METHODS: Preoperative aspiration of the hip joint and contrast-enhanced arthrography were performed by a skeletal radiologist in 33 hips with uncemented components before exploration or revision. In one patient, the hip aspiration yielded grossly purulent fluid and arthrography was not performed. Twenty-one uncemented acetabular components and 29 uncemented femoral components were evaluated by arthrography. The aspiration of the hip provided fluid for culture in 33 hips; in one hip, no fluid could be obtained. RESULTS: A preoperative diagnosis of infection based on growth on solid media was made in five hips (15%). An additional infection was determined to be present in the hip in which no fluid was obtained when purulent fluid was found at operation. On the basis of the operative findings, contrast-enhanced arthrography of the 21 acetabular components had a sensitivity of 50%, a specificity of 77%, and an accuracy of 68%. Arthrography of the 29 femoral components had a sensitivity of 63%, a specificity of 64%, and an accuracy of 63%. CONCLUSION: Aspiration of the hip joint before revision of uncemented hip arthroplasties was valuable because the diagnosis of infection was made preoperatively in five of six hips. However, contrast-enhanced arthrography was not valuable, with a low sensitivity and specificity for both uncemented acetabular and uncemented femoral components. Only a preoperative aspiration of the hip joint is recommended before revision of uncemented components.

Cementation↗
PubMed1996

Calcium blockage in pulmonary hypertension and hypoxic vasoconstriction.

Both extracellular and intracellular calcium (Ca2+) play important roles in hypoxic pulmonary vasoconstriction (HPV) and the vasoconstrictor responses to endogenous pulmonary vasoconstrictor substances, as evidenced by the effect of calcium-channel blockers on these vasoconstrictor responses and the measurement of changes in Ca2+ flux or intracellular Ca2+ concentrations in isolated cells. The more vasoselective the calcium-channel blocker, the greater its effect on pulmonary vasoconstriction. However, these drugs are not selective for the pulmonary vascular bed and are not as potent as pulmonary vasodilators when compared with other vasodilator drugs, including prostaglandin E1, isoproterenol, prostacyclin, or nitroglycerin. Moreover, the primary effect of vasoselective calcium-channel blockers on pulmonary vascular resistance is secondary to the effects of these agents on systemic vascular resistance and cardiac output. Although there is improvement in oxygen delivery, exercise tolerance, and survival in patients with primary pulmonary hypertension who respond to calcium-channel blockers, the response of individual patients to these drugs is difficult to predict because the extent of reversible versus irreversible changes in the pulmonary vasculature is not known. The use of these drugs in patients with chronic hypoxia-induced pulmonary vasoconstriction may be associated with a worsening of ventilation-perfusion mismatching secondary to inhibition of HPV.

Animals↗
PubMed1995

Induction of tissue factor on monocytes by adhesion to endothelial cells.

Activated monocytes express tissue factor (TF), a protein that is important in the pathogenesis of thrombotic disorders. We sought to characterize an adhesion-dependent pathway for monocyte activation. In this study, we showed that adhesion of monocytes to cytokine-activated endothelial cells (EC) increased (approximately 5- to 10-fold) monocyte procoagulant activity (PCA). The PCA was attributed to TF because it was dependent on the coagulation factors VII and X, but not VIII, and was completely blocked by an anti-TF mAb. Direct cell-cell contact between monocytes and EC was required. The induction of TF was rapid, peaked at 30 min, and persisted for 4 h. Northern analysis revealed a rapid (approximately 30 min) increase in TF mRNA following adhesion, distinct from that induced by LPS (approximately 2-4 h). Four-hour TNF-treated EC supported TF expression, but 0.5- and 24-h TNF-treated EC had no effect. An anti-E-selectin mAb (H18/7) exerted partial inhibition, whereas anti-VCAM-1, ICAM-1, and CD11/CD18 mAbs had no inhibition. Synthetic Lewis X (Le(x)) oligosaccharide partially blocked TF induction, whereas sialyl-Le(x) (sLex) oligosaccharide had no effect. Cross-linking Le(x) on monocytes, but not sLex, significantly increased (approximately 10-fold) the TF expression. Le(x) cross-linking induced TF in 30 min and lasted for 4 h. All seventeen anti-Le(x) mAbs induced significant amount of TF generation, and epitope mapping revealed a single binding epitope on Le(x). These findings indicate that adhesion of monocytes to activated EC induces TF generation, and also suggest that Le(x) may represent an important signaling molecule on monocytes.

Blood Coagulation↗
PubMed1995

Tuberculosis surveillance practices in long-term care institutions.

OBJECTIVES: To identify the tuberculosis (TB) skin-testing practices of long-term care facilities for the elderly in Toronto, Ontario. DESIGN: A telephone survey using a 25-item questionnaire. SETTING: Twenty-nine nursing homes (NHs) and 26 Homes for the Aged (HFAs) in metropolitan Toronto. RESULTS: Thirty-one percent of facilities (17 of 55) had no formal tuberculin skin-testing program, including 52% of NHs (15 of 29) versus 8% of HFAs (2 of 26; P = 0.001). Ninety-two percent of HFAs (24 of 26), compared with 45% of NHs (13 of 29), obtained preadmission or admission skin-test status of residents (P = 0.0005). Annual testing was performed at 46% of HFAs (12 of 26) and 27% of NHs (8 of 29; P = 0.28). Of facilities that carried out any skin testing, 64% of HFAs (16 of 25) versus 32% of NHs (6 of 19) measured induration to establish test positivity (P = 0.068). Fifty-two percent of HFAs (13 of 25), compared with 21% of NHs (4 of 19), recorded the actual size of induration in the patient record (P = 0.085). Only 28% of HFAs (7 of 25) and 21% of NHs (4 of 19) correctly defined a positive tuberculin skin test. CONCLUSIONS: TB surveillance practices in long-term care institutions in Toronto are inadequate and often yield results that do not predict the risk of infection and cannot be used to investigate outbreaks. Tuberculin skin-testing practices were better at HFAs, which are subject to provincial legislation regarding TB surveillance, than at NHs, which are not subject to this legislation. Staff at HFAs and NHs require education regarding tuberculin skin-testing policies and procedures.

Homes for the Aged↗
PubMed1994

Feedback regulation of glucose-dependent insulinotropic polypeptide (GIP) secretion by insulin in conscious rats.

Feedback regulation of glucose-dependent insulinotropic polypeptide (GIP) was studied in a conscious rat model. Male Wistar rats were preconditioned to partial restraint, the tail artery and vein were cannulated under local anesthesia. All animals received 1 g/kg oral glucose by gavage and were divided into 3 groups: One group ('euglycemic hyperinsulinemic', EH) underwent rapid induction of hyperinsulinemia by i.v. insulin infusion from 5 min prior to oral glucose until 120 min after (mean plasma insulin = 2285 +/- 108 pM +/- S.E.M., n = 5); a second group ('hyperglycemic hyperinsulinemic', HH) underwent rapid induction of both hyperinsulinemia and hyperglycemia (mean serum glucose = 12.9 +/- 0.4 mM +/- S.E.M., mean plasma insulin 3160 +/- 109 pM, n = 5). A third group ('control') underwent saline infusion alone (n = 5). Arterial blood was collected for GIP estimation at -10, 0, 10, 20, 30, 50, 70, 90 and 120 min after oral glucose. In the control group GIP rose by 96% from a mean basal concentration of 114 +/- 12 pM to a peak of 224 +/- 14 pM by 20 min, and returned to baseline within 70 min. In EH, the GIP rise was blunted and the peak (146 +/- 31 pM) occurred at 10 min, while in HH GIP peaked at 192 +/- 32 pM 10 min after oral glucose (a 92% increase over basal). Compared to controls, total area under the curve for GIP was less for EH (598 +/- 112 versus 971 +/- 94 pmol/l/h +/- S.E.M., P < 0.034). GIP response in HH was similar to the control group at 853 +/- 134 pmol/l/h.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Localized in vivo 31P NMR spectroscopy of skin flap metabolism.

We have used a rectangular surface coil and chemical shift imaging to conduct in vivo localized 31P NMR metabolic studies in a rat dorsal skin flap model. This approach permits regional comparisons without manipulation of either coil position or subject within the magnet bore. Both the PCr:Pi ratio (reflecting ischemia insult) and the PCr:ATP ratio (reflecting phosphagen reserves) decreased as functions of time and distance from the vascular pedicle. The maximum change was nearly 6-fold for the PCr:Pi ratio, and 3-fold for the PCr:ATP ratio. Signal contamination from subjacent muscle is constant and does not interfere with the metabolic evaluations of skin flaps. This technique may facilitate a better understanding of cutaneous metabolic derangements, such as burns and skin flaps used in reconstructive surgery, as well as studies of pharmacologic regimens developed for their treatment. It also holds potential for application in the study of congenital and neoplastic metabolic disorders of skin.

Adenosine Triphosphate↗
PubMed1994

Modified method for the performance of glucose insulin clamp studies in conscious rats.

A modified method for performance of insulin-glucose clamp studies in rats was developed via catheterization of the tail vessels, after preconditioning of animals to limited restraint. The procedure is performed in conscious animals under local anesthesia and employs a specially designed foam rubber jacket which allows the animal mobility of the limbs and forward vision. In addition, a table utilizing a belt system allows easy positioning of the animal in the left and right lateral and supine positions during surgery. After initial development of the procedure, its use in 123 animals is reported. Line placement was successfully achieved in all cases with insignificant blood loss or morbidity and zero mortality. We note that 11% of animals did not complete the subsequent insulin-glucose clamp study due to either one of the vascular cannulae leaving the vessel (one animal), venous rupture (12 animals), or cannula blockage unrelated to surgical technique (one animal). Studies on Wistar Kyoto, Spontaneously Hypertensive, and Sprague-Dawley rats showed a fall in catecholamines after animals were replaced in cages, with stabilization within 30 min. In comparison to traditional techniques, this method is, therefore, proposed as a less traumatic and rapid way of performing infusion studies in conscious rats with a high success rate and minimization of loss of animal life due to procedural problems.

Anesthesia↗
PubMed1994

Nutritional status of elderly patients during recovery from chest infection and the role of nutritional supplementation assessed by a prospective randomized single-blind trial.

We examined changes in the nutritional status of elderly patients with chest infection for a period of 3 months after discharge from hospital, including the effects of nutritional supplementation on well-being and functional status as well as on nutritional indices. Eighty-one subjects admitted to an acute medical ward aged 65 years and over with chest infection were recruited consecutively, and randomized to receive supplement (500 ml of Ensure liquid daily) for 1 month, or no supplement, on discharge. Assessment at baseline, 1, 2 and 3 months included a questionnaire to determine health, mental and functional status, and anthropometric measurements. Biochemical nutritional status was assessed at baseline, 1 and 3 months, and dietary intake (24 h recall method) at 1 and 3 months. During recovery, both supplement and non-supplement groups showed improvement in various measures of well-being and biochemical status. In addition, the former group showed improvement in more anthropometric measurements, in thiamine and pyridoxine status, while the non-supplement group showed a lower level of functional ability after 3 months. Various measures of well-being and biochemical status of the water-soluble vitamins were better in the supplement groups. We conclude that nutritional supplementation may have a role in helping elderly patients to recover from chest infections.

Aged↗
PubMed1994

Bis(maltolato)oxovanadium(IV) attenuates hyperinsulinemia and hypertension in spontaneously hypertensive rats.

We previously reported that bis(maltolato)oxovanadium(IV) (BMOV), an organic vanadium complex, decreased plasma insulin concentrations in nondiabetic rats without affecting plasma glucose levels (McNeill JH, Yuen VG, Hoveyda HR, Orvig C: Bis(maltolato)oxovanadium(IV) is a potent insulin mimic. J Med Chem 35:1489-1491, 1992). In this study, chronic oral BMOV treatment was started in 6-week-old spontaneously hypertensive (SH) rats and their Wistar-Kyoto (WKY) controls, and the effects of the drug on insulin sensitivity, plasma insulin, and blood pressure (BP) were studied. BMOV (0.35-0.45 mmol.kg-1.day-1) caused a sustained reduction in plasma insulin (198 +/- 6 vs. untreated 366 +/- 13.2 pM, P < 0.0001) and systolic BP (149 +/- 3 vs. untreated 184 +/- 3 mmHg, P < 0.0001) in SH rats. No changes were seen in WKY rats (plasma insulin: treated 228 +/- 4.8 vs. untreated 222.6 +/- 3.6 pM, P > 0.05; BP: treated 134 +/- 3 vs. untreated 134 +/- 5 mmHg, P > 0.05). At 13 weeks of age, euglycemic clamps were performed in fasted, conscious, mobile rats. During low-dose insulin infusions (14 pmol.kg-1.min-1) with concomitant somatostatin administration, neither hepatic glucose output nor total body glucose uptake differed between the untreated SH and WKY rats. Insulin sensitivity, expressed as steady-state glucose clearance per unit of plasma insulin, was higher in the untreated SH compared with the untreated WKY rats (2.1 +/- 0.2 vs. 1.2 +/- 0.1 ml.kg-1.h-1.pM-1, P < 0.002). BMOV further enhanced insulin sensitivity in SH rats (3.6 +/- 0.4, P < 0.002 vs. untreated SH rats).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Cervical human papilloma virus infection of women attending social hygiene clinics in Hong Kong.

OBJECTIVE: To find the prevalence of HPV infection in women attending a sexually transmitted disease clinic in Hong Kong. METHOD: Cervical HPV infection was identified by cervical cytology and DNA filter in-situ-hybridization (Virapap) techniques in 207 women attending a social hygiene clinic. Other risk factors for cervical cancer were assessed and any association with HPV infection was sought. Statistical analysis was carried out using the chi 2-test. RESULT: The prevalence of HPV infection in the 207 Chinese women was 8.2% by cervical smear and 12.6% by DNA filter in-situ-hybridization. Risk factors for cervical cancer were not significantly associated with HPV infection in this group, 95% of whom were prostitutes. CONCLUSION: The prevalence of HPV infection in this group at high risk for cervical cancer is higher than in low-risk pregnant women, however the prevalence of HPV infection in Hong Kong is at the low end of the range of figures quoted for Caucasians. The cause of such a low prevalence is yet to be determined.

Adolescent↗
PubMed1992

Hyperglycemia and the rate of lactic acid accumulation during cerebral ischemia in developing animals: in vivo proton MRS study.

During cerebral ischemia, hyperglycemia has a deleterious effect upon the adult brain but not the neonatal brain. This phenomenon may be related to the fact that hyperglycemia in adult animals subjected to cerebral ischemia raises the ischemic accumulation of lactate by as much as 10-fold. The purpose of this study was to determine whether hyperglycemia during cerebral ischemia produces a similar increase in the rate of lactic acid accumulation in developing animals. Data from in vivo proton magnetic resonance spectroscopic experiments showed that blood glucose concentration did not affect the rate of lactic acid accumulation during cerebral ischemia in either the neonatal dog or juvenile rabbit. The lack of increase in the ischemic rate of lactic acid accumulation during hyperglycemia in the developing animal contrasts sharply with the marked effect of blood glucose concentration upon the rate of lactic acid accumulation in the adult animal. Differences in the total amount of lactic acid formed and the rate at which it is accumulated may contribute, in part, to the greater tolerance of the young animal to cerebral ischemia.

Aging↗
PubMed1991

Primary mixed neuroendocrine and mucinous carcinoma of the ovary.

A rare case of mixed carcinoma of ovary with a predominant malignant neuroendocrine and a lesser mucinous tumor component is described. Extensive areas of enteric-type epithelium containing endocrine cells were present in both the mucinous borderline tumor element and in the small foci of mucinous adenocarcinoma. Transition from the mucinous tumor to the malignant neuroendocrine component provides evidence for the derivation of some neuroendocrine or carcinoid tumors direct from mucinous tumors without necessarily being a component of a teratoma. Contrary to reported examples of mucinous carcinoid, the overgrowth and spread of the neuroendocrine component characterised the aggressive and lethal nature of this tumor.

Adenocarcinoma, Mucinous↗
PubMed1991

Biliary cystadenoma and cystadenocarcinoma: some unusual features.

Biliary cystadenoma and cystadenocarcinoma are rare tumours which have a good prognosis after complete surgical removal. Correct pre-operative diagnosis depends on the imaging characteristics of the tumours. We have observed some unusual features including multifocal tumours with attachment to other abdominal organs, tumour presenting as cholangitic abscess, and distant metastasis after apparently complete resection by hemihepatectomy.

Adult↗
PubMed1990

Measurement of neuropeptides in the brain and spinal cord of Wobbler mouse: a model for motoneuron disease.

The Wobbler mouse (wr) exhibits the loss of motoneurons especially in the cervical spinal cord, and thus has been studied as a model for human motoneuron diseases. Wobbler mice selected at various ages and stages during the disease process show increased levels of thyrotropin releasing hormone and substance P in spinal cord and brainstem (medulla). Enkephalins (methionine and leucine) also increase in the spinal cord and brainstem. Somatostatin increases in hypothalamus, perhaps accounting partly for the small size of this mutant mouse via its effect on growth hormone.

Aging↗