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Biomedical subjects

L Chow

Publications and source records attributed to L Chow.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effect of heating human sera at a temperature necessary to deactivate human immunodeficiency virus on measurement of free phenytoin, free valproic acid, and free carbamazepine concentrations.

Minimizing the risk for infection to laboratory staff from a contaminated blood sample is a major safety goal in the clinical laboratory. One dangerous pathogen, the human immunodeficiency virus (HIV), can be deactivated by heating sera at 56 degrees C for 30 minutes. The authors previously reported that if serum was subjected to those conditions, the concentrations of the nine most commonly monitored drugs were not altered, whereas phenytoin and carbamazepine concentrations were reduced slightly. Monitoring free phenytoin, free valproic acid, and free carbamazepine concentrations is strongly recommended for patients with uremia, liver disease, and hypoalbuminemia. Because drug protein binding can be affected by temperature, the authors investigated the effect on free drug concentrations of sera heated to levels necessary for deactivation of the HIV virus. They measured total and free drug concentrations in serum pools prepared from patients receiving phenytoin, valproic acid, and carbamazepine. Serum pools were heated at 56 degrees C for 30 minutes and then brought to room temperature. The total and free drug concentrations were measured immediately after heating and then at 20- and 45-minute intervals. The concentrations of free phenytoin and free valproic acid were significantly higher after heat treatment. However, after equilibration of sera at room temperature for 20 minutes, the free concentrations of phenytoin were comparable to preheating values, although total phenytoin concentrations (Serum Separator Tubes) were reduced slightly. In contrast, free valproic acid concentrations did not return to the original levels even after 45 minutes. Free carbamazepine concentrations did not change even immediately after heating. However, total carbamazepine concentrations were reduced slightly when sera were heated in serum separator tubes (SST Tubes).

Anticonvulsants↗
PubMed1998

Assessment of chemosensitivity in patients with osteogenic sarcoma using the doxorubicin binding assay.

BACKGROUND AND OBJECTIVES: Assessment of chemosensitivity in patients with osteosarcoma may help identify those with resistance to chemotherapy. In this study, we investigated the clinical value of the doxorubicin binding assay in its ability to identify patients with drug resistance. METHODS: We tested tumor tissue samples obtained at biopsy of 24 patients with high-grade osteosarcoma aged 9-61 years (mean 19.2) for sensitivity to doxorubicin, using the doxorubicin binding assay. Tumor excision was performed in these patients after neoadjuvant chemotherapy. Chemotherapy response was judged on the basis of tumor necrosis achieved and was compared with doxorubicin sensitivity in each of these patients. RESULTS: Doxorubicin sensitivity was good in 15 and poor in 9 of 24 patients studied. In patients with good sensitivity (n = 15), 9 (60%) exhibited a good response to chemotherapy while response was poor in 6. In patients with poor sensitivity (n = 9), response to chemotherapy was poor in all 9 (100%) patients and 7 (77.8%) of these patients developed metastatic disease within a mean period of 5.2 months, resulting in two deaths. The results were statistically significant at P = 0.0193. CONCLUSIONS: Doxorubicin binding assay may be useful in identifying patients with inherent resistance to chemotherapy. As the outcome of patients showing resistance to doxorubicin is poor, innovative strategies may need to be developed for this group of patients.

Adolescent↗
PubMed1998

The nuclear receptor transcription factor, retinoid-related orphan receptor beta, regulates retinal progenitor proliferation.

We examined the role of retinoid-related orphan receptor (ROR)beta, a member of the nuclear receptor family of transcription factors, in retinal neurogenesis. In situ hybridization studies showed that RORbeta is expressed in retinal progenitor cells in the embryonic rat retina. Further studies demonstrated that RORbeta colocalizes with Chx10, a transcription factor thought to influence retinal progenitor proliferation (Burmeister, M., Novak, J., Liang, M-Y., Basu, S., Ploder, L., Hawes, N.L. Vidgen, D., Hoover, F., Goldman, D. , Kalnins, V.I., Roderick, T.H., Taylor, B.A., Hankin, M.H. and McInnes, R.R., 1996. Ocular retardation mouse caused by Chx10 homeobox null allele: impaired retinal progenitor proliferation and bipolar cell differentiation. Nature Genetics 12, 376-383). Northern analysis reveals that RORbeta expression is dramatically decreased in the ocular retardationJ mutant, which possesses a defect in the Chx10 gene. Overexpression of RORbeta in retinal progenitors by biolistic transfection results in an increase in the number of large cell clones. These data support a role for RORbeta in regulating retinal progenitor proliferation, possibly via the Chx10 gene.

Animals↗
PubMed1997

Blockade of angiotensin converting enzyme but not of angiotensin AT1 receptors improves glucose tolerance.

This study compared the effect of benazepril, an angiotensin converting enzyme inhibitor to valsartan, an angiotensin AT1 receptor antagonist, on glucose tolerance in the conscious, spontaneously hypertensive rat. Intraperitoneal infusion of benazepril or valsartan at 1, 3 and 10 mg/kg per day produced equivalent dose-related reductions in systolic blood pressure for 12 weeks. Body weight gain during the treatment period was significantly reduced by infusion rates of benazepril. In contrast, only the highest infusion rate of valsartan significantly affected body weight gain. At the end of the 12-week treatment period, neither benazepril nor valsartan significantly affected glucose disposal during intravenous glucose tolerance tests. The insulin response to glucose challenge was unaffected by valsartan whereas following the highest infusion rate of benazepril the plasma levels were significantly reduced. The results demonstrate that benazepril but not valsartan reduces the insulin required to dispose of a glucose load.

Angiotensin Receptor Antagonists↗
PubMed1997

Tumor necrosis factor-alpha contributes to apoptosis in hippocampal neurons during experimental group B streptococcal meningitis.

To evaluate the role of tumor necrosis factor-alpha (TNF-alpha) in neuronal injury in experimental group B streptococcal meningitis, infected neonatal rats were treated with a monoclonal antibody against TNF-alpha (20 mg/kg intraperitoneally) or saline given at the time of infection. Histopathology after 24 h showed necrosis in the cortex and apoptosis in the hippocampal dentate gyrus. Treated animals had significantly less hippocampal injury than did controls (P < .001) but had similar cortical injury and cerebrospinal fluid (CSF) inflammation. The antibody was then administered directly intracisternally (170 microg) to test whether higher CSF concentrations reduced inflammation or cortical injury. Again, hippocampal apoptosis was significantly reduced (P < .01), while cortical injury and inflammation were not. Thus, TNF-alpha played a critical role in neuronal apoptosis in the hippocampus, while it was not essential for the development of inflammation and cortical injury in this model.

Animals↗
PubMed1997

Thoracoscopic vagotomy for recurrent ulcer after previous gastric operation.

BACKGROUND: Recurrent peptic ulcer after previous gastric operation is a difficult surgical problem and abdominal re-operation is associated with significant morbidity, mortality and recurrence rate. METHODS: The authors report on five patients with recurrent ulcers who, after previous gastric operation, were treated with thoracoscopic vagotomy. RESULTS: All patients tolerated the procedure well without complications, and the median hospital stay was 5 days. Endoscopy confirmed healing of the ulcers in all patients. Pre-operative and postoperative gastric acid studies showed a significant postoperative reduction in both basal and maximal acid output (P < 0.05). In a follow-up period of 18-33 months, one patient had a recurrent ulcer presenting with bleeding. Gastric biopsy revealed presence of Helicobacter pylori and repeated gastroscopy after a course of H. pylori eradication treatment showed a healed ulcer. The other four patients were asymptomatic. CONCLUSIONS: We conclude that thoracoscopic vagotomy is a simple and safe procedure for the treatment of recurrent ulcers after previous gastric operation, but the long-term results need further assessment.

Adult↗
PubMed1997

[Detection of neutralizing antibodies to Japanese encephalitis virus by enzyme-linked immunosorbent assay (ELISA)].

Competitive ELISA was used for the detection of neutralizing antibody to JE. Based on the principle that human serum JE antibody competed with JE monoclonal antibody (MAb) for JE antigen, it was found that 3 JE MAbs (E3-3, NPF-5 and NNN-5) were suitable for competitive ELISA for the detection of JE neutralizing antibody. The sensitivity of cometitive ELISA for 29 JE confirmed serum specimens with titer of plaque reduction neutralization test (PRNT) was checked to be 82.1% (23/28). The specificity of E3-3 MAb to JE used in competitive ELISA was 100%. Correlation coefficient of JE confirmed cases of 57 hemagglutination inhibition (HI) titers in 1995 and 37 PRNT titers in 1994 compared with competitive ELISA were 0.744 and 0.732, respectively. Compared the competitive ELISA titers of 154 sera of healthy people with PRNT titers, the results showed that 70% of the sera could be detected by competitive ELISA which saved a lot of time and manpower.

Antibodies, Viral↗
PubMed1996

Near-infrared spectroscopy in experimental pneumococcal meningitis in the rabbit: cerebral hemodynamics and metabolism.

Near-infrared spectroscopy is a noninvasive technique which measures oxidized cytochrome aa3, oxygenated Hb, and deoxygenated Hb and calculates total Hb in tissue. This technique, in conjunction with measurement of cerebral blood flow, was used in rabbits with experimental bacterial meningitis to determine whether there was evidence for cerebral energy depletion and alterations in the cerebral vascular bed with infection. Rabbits with meningitis had a significant reduction in cerebral blood flow, cerebral oxidized cytochrome aa3 and a relative increase in the deoxygenated Hb fraction and a decrease in the oxygenated Hb fraction compared with uninfected controls. Total Hb was not significantly different between the two groups. These findings may help clarify the mechanism for some of the intracranial pathophysiologic abnormalities in meningitis.

Animals↗
PubMed1996

Detection of IgM antibody to Japanese encephalitis virus infection by enzyme-linked immunosorbent assay (ELISA).

BACKGROUND: Japanese encephalitis (JE) is an important infectious disease in Taiwan, with reported cases observed all the year around. Laboratory tests for JE consist mainly of hemagglutination inhibition (HI) test and neutralization test (NT). Commercialized enzyme-linked immunosorbent assay (ELISA) kits for detection of JE-IgM are still not available. Therefore an attempt has been made to develop a sensitive and rapid ELISA for detection of the IgM antibody to JE to serve as an indication of recent Japanese encephalitis virus infection. METHODS: Both positive and negative JE serum specimens, confirmed by HI test, were checked for IgM antibody to JE by ELISA. The optimum concentration of biotin-IgG and avidin horse-radish peroxidase conjugate used in MAC-ELISA were 1/2000 and 1/ 15000, respectively. RESULTS: From 1987 to 1989, 118 paired serum specimens of HI-confirmed JE patients were tested for JE-IgM by ELISA. The positive rate of JE-IgM was 65.7% (25/38), 73.9% (17/23), 93.5% (29/31) and 88.8% (8/9) for the consecutive first to fourth weeks after onset of the disease. The JE-IgM antibody of 17 serum specimens collected from the 5th to the 10th week after onset of the disease were 100% detected. In addition, among the 13 HI-confirmed JE cases occurring in 1994, 84.6% of the acute phase serum specimens demonstrated the JE-IgM antibody. CONCLUSIONS: About 65.7% of the JE-IgM of the acute serum specimens collected within one week after onset of the disease were detected. The JE-IgM positive rate elevated as the days from disease onset increased. Therefore the appearance of JE-IgM could be used as an indication of recent JEV infection to serve as a rapid laboratory diagnostic tool.

Adolescent↗
PubMed1995

Gastric acid secretion after blockade of angiotensin AT1 receptors in the Na(+)-depleted rat.

This study tested the hypothesis that angiotensin II acting through the angiotensin AT1 receptor plays an important role in the control of gastric acid secretion. Basal gastric acid secretion and gastric blood flow were lower in Na(+)-depleted animals, in which the renin-angiotensin system was activated, than in animals maintained on a normal Na+ diet. Intravenous infusion of pentagastrin at 0.6 microgram/kg/min increased gastric acid secretion to a greater extent in normal Na+ than in Na(+)-depleted animals. In addition to stimulating gastric acid secretion, pentagastrin increased gastric blood flow by proportionally the same amount in both normal and low Na+ animals. However, because basal gastric blood flow was considerably reduced in Na(+)-depleted animals, the increase produced by pentagastrin extended only to the levels observed in non-pentagastrin-treated normal Na+ animals. Lower gastric blood flow in response to pentagastrin may explain the smaller increase in gastric acid secretion observed in Na(+)-depleted animals. In Na(+)-depleted animals, the selective angiotensin AT1 receptor antagonist losartan did not affect basal gastric acid secretion or gastric blood flow, suggesting the involvement of mechanisms other than angiotensin II. Following blockade of angiotensin AT1 receptors, pentagastrin significantly increased gastric blood flow in Na(+)-depleted animals to levels observed with infusion of the pentapeptide in normal Na+ animals. The results suggested that the decrease in pentagastrin-stimulated acid secretion in Na(+)-depleted animals is mediated by angiotensin II acting through the angiotensin AT1 receptor, most probably through vascular mechanisms.

Angiotensin I↗
PubMed1995

Improved glucose metabolism following blockade of angiotensin converting enzyme but not angiotensin AT1 receptors.

This study compared the effect of benazepril, an angiotensin converting enzyme inhibitor ([S-(R*,R*)]-3-[[1-(ethoxycarbonyl)-3-phenylpropyl]amino]-2,3,4,5- tetrahydro-2-oxo) to valsartan, an angiotensin AT1 receptor antagonist ((S)-N-valeryl-N-[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]-methyl-valin e) on glucose metabolism and plasma lipid levels in 11- to 12-week-old conscious spontaneously hypertensive rats. Intraperitoneal infusion of benazepril or valsartan at 1, 3 and 10 mg/kg/day produced dose-related reductions in systolic blood pressure after 12 weeks which were not significantly different from each other. During the infusion, valsartan-treated animals gained weight at the same rate as controls, but all infusion rates of benazepril significantly suppressed normal weight gain, despite both compounds having similar antihypertensive effects. At the end of the 12-week treatment period, benazepril (3 and 10 mg/kg/day) significantly increased glucose disposal but did not significantly affect insulin disposal in insulin/glucose tolerance tests. In contrast, none of the infusion rates of valsartan significantly affected glucose or insulin disposal. Finally, compared to controls benazepril and valsartan were without effect on the fasting basal plasma concentrations of glucose, insulin, triglycerides, total cholesterol and K+. The results demonstrate that angiotensin converting enzyme inhibition and angiotensin AT1 receptor antagonism have similar antihypertensive effects, but express differences on body weight gain and insulin-stimulated glucose disposal in the conscious spontaneously hypertensive rat.

Angiotensin Receptor Antagonists↗
PubMed1995

Metastatic cervical nodes in papillary carcinoma of the thyroid: ultrasound and histological correlation.

The ultrasound appearances and histological correlation of metastatic cervical lymph nodes in 20 patients with papillary carcinoma of the thyroid are presented. The majority of the malignant nodes were homogeneous (81.2%), hyperechoic (87.5%) compared to adjacent sternomastoid muscle and 68.7% showed peripheral punctate calcification on US and histology. Histology revealed that the peripheral echogenic foci seen within the nodes on US correlated with psammoma bodies which are characteristic for papillary carcinomas, highlighting the importance of recognizing peripheral punctate calcification in the cervical nodes as a useful sign for the diagnosis of metastatic papillary carcinoma of the thyroid.

Calcinosis↗
PubMed1994

Expression of the gap junction protein connexin-43 is increased in the human myometrium toward term and with the onset of labor.

OBJECTIVES: Our aim was to determine the temporal pattern of expression of transcripts encoding the myometrial gap junction protein connexin-43 in the human myometrium during late pregnancy and with the onset of labor. We also correlated these data with levels of total connexin-43 protein and the appearance of gap junctions within the myometrial cell membrane. STUDY DESIGN: Myometrial tissue was collected during cesarean section from 27 women between 37 and 41 weeks of gestation not in labor and from 7 women between 39 and 41 weeks during active labor. The levels of connexin-43 messenger ribonucleic acid and protein were estimated by Northern and Western analysis, respectively. The appearance of gap junctions between myometrial cells was assessed by immunofluorescence of histologic sections of myometrium from these women. RESULTS: Levels of connexin-43 messenger ribonucleic acid in myometrial tissue collected from women not in labor increased (p < 0.01) between 37 and 40 weeks' gestation with a further significant increase occurring during labor (p < 0.05). The level of connexin-43 protein decreased (p < 0.05) during late pregnancy and was not increased during labor although gap junctions (which were not present during pregnancy) did appear in the myometrial cell membrane during labor. CONCLUSIONS: These data suggest that the mechanisms responsible for the increased myometrial cell-cell communication necessary for the development of effective labor contractions likely involves regulation at the level of both messenger ribonucleic acid and gap junction formation in the cell membrane.

Animals↗
PubMed1992

Technical modification to laparoscopic appendectomy.

An alternative technique for laparoscopic appendectomy is described. The isolated appendix is exteriorized through the trocar wound, ligated, and resected. The cecum is then returned to the abdomen.

Appendectomy↗