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Biomedical subjects

E Chow

Publications and source records attributed to E Chow.

At least 55 records · Page 3Linked to original sources
PubMed1998

Differential effects of anoxia and glutamate on cultured neocortical neurons.

That glutamate increases in the extracellular space of the brain during hypoxia or ischemia and that this amino acid, in high enough concentrations, kills neurons has led investigators to use glutamate and study the mechanisms underlying neuronal excitotoxicity as a model for acute cell death that occurs with low oxygen. However, there is some evidence that increased glutamate, on the one hand, and anoxia, on the other, may not be similar events. In this study we undertook experiments to determine whether glutamate, at various concentrations (20-500 microM), and anoxia induce similar changes in intracellular Ca2+ and in cell morphology as assessed by cell volume and eccentricity (degree of some ellipsoid shape). We found that glutamate was much more rapid in inducing a rise in Cai2+ and that the rise itself occurred at a faster rate than during anoxia. Anoxia produced more marked changes in cell volume and eccentricity. These results, which show major differences between glutamate and anoxia, indicate that while glutamate may play an important role in anoxic brain injury, glutamate excitotoxicity should not be used to mimic the effects of anoxia on nerve and brain function.

Adenosine Triphosphate↗
PubMed1998

Re-irradiation for locally recurrent nasopharyngeal carcinoma.

Since 1989, 17 patients have undergone re-irradiation for locally recurrent nasopharyngeal cancer (NPC). The dose currently administered externally is 39.6 Gy in 36 fractions (BID) followed by an intracavitary boost (15-20 Gy). Disease persisted in five out of five patients treated palliatively. Eleven of 12 patients treated with curative intent achieved local control.

Adult↗
PubMed1998

Evolving perspectives in contralateral breast cancer.

Despite extensive publications reviewing contralateral breast cancer (CBC), the role of screening and preventative measures for contralateral tumours is controversial and optimal clinical management remains undefined. This paper addresses the incidence, the predisposing factors, the prevention and the treatment of bilateral breast cancer based on a review of the literature. Risk factors for CBC include young age at primary breast cancer diagnosis, hereditary breast cancer (due to a germline mutation), familial breast cancer (one or more affected relatives), radiation exposure at a young age, lobular carcinoma in situ (LCIS), lobular invasive carcinoma and multicentricity. Retrospective studies suggest that contralateral mammographic surveillance results in the early detection of breast cancer, but no clear survival benefit has been demonstrated. Trials of adjuvant tamoxifen in breast cancer patients have shown a reduction in the incidence of CBC in both pre- and postmenopausal women. In addition, breast cancer patients treated with ovarian ablation and prednisone have significantly reduced CBC versus controls. In patients with primary breast cancer there is no evidence that contralateral breast biopsies or contralateral prophylactic mastectomy reduce mortality. Randomised, prospective trials to determine optimal surveillance, prevention and treatment strategies for the contralateral breast in breast cancer patients have not been conducted. Based on the published literature, contralateral breast surveillance in breast cancer patients reasonably includes breast self-examination, regular physical examinations and annual mammography. In women who have no evidence of distant metastasis at the time of CBC diagnosis, we recommend that the CBC be treated in the same manner as a first breast cancer, taking into account prior local and systemic therapy.

BRCA2 Protein↗
PubMed1997

Enhanced control by radiotherapy of cervical lymph node metastases arising from nasopharyngeal carcinoma compared with nodal metastases from other head and neck squamous cell carcinomas.

PURPOSE: To test the hypothesis that metastatic cervical lymph nodes arising from nasopharyngeal carcinoma (NPC) are more readily controlled with radiotherapy than comparable nodes from squamous cell carcinomas of other head and neck sites (SCC). METHODS AND MATERIALS: One hundred four NPC patients with metastatic cervical nodes (mean size of the largest node equals 4.1 cm) were randomly selected from radiation treatment files for two time periods, 1969-1976 and 1983-1988, when radiation alone was the first line treatment. Candidate controls were selected randomly from radiation treatment files of node positive squamous cell carcinomas arising from the oropharynx, hypopharynx, oral cavity or larynx who were also treated by radical radiation therapy as sole initial treatment in the 1970s and 1980s. Each NPC case was matched with a control using the size of the largest involved node as the matching criterion. The median follow-up of all 208 patients was 3 years (4.2 years in NPC cases and 1.4 years in the matched controls). For those who were alive at last follow-up, the median follow-up for both arms was 7.7 years (6.7 years in NPC cases and 10.2 years in the matched controls). Nodal control was evaluated by clinical neck examination in both arms. Nodal recurrence was defined as relapse or persistence of metastatic nodal disease from day 1 of radiotherapy treatment. RESULTS: Despite a similar mean delivered dose to involved neck nodes (52.9 Gy for the NPC group and 53.9 Gy for the matched controls), the SCC group had significantly worse nodal control with radiation when compared to the NPC group (p < 0.0001, relative risk 3.0, 95% [1.8, 5.1]). The 3-year nodal recurrence-free rate among NPC cases was 71 +/- 5%, compared to 43 +/- 5% among matched controls. CONCLUSION: The result of this study supports the hypothesis that metastatic cervical nodes from NPC are more readily controlled by irradiation than cervical nodes of similar size arising from other head and neck squamous cell carcinomas. Further study is required to explore the reasons for this apparent radiosensitivity.

Adolescent↗
PubMed1996

Nontraumatic subcutaneous emphysema in association with rectal carcinoma.

Nontraumatic subcutaneous emphysema is a rare complication of colorectal cancer. To the authors' knowledge, only eight cases have been reported to date. The initiating event was free colonic perforation in seven of the patients and contained colosubcutaneous fistula in the eighth. In nontraumatic subcutaneous emphysema typical fecal flora is cultured, whereas in nontraumatic gas gangrene, a different clinical entity that has a fulminant course, the bacteria are generally clostridial. The authors report a case of nontraumatic subcutaneous emphysema associated with rectal carcinoma and describe the associated computed tomography findings.

Adenocarcinoma↗
PubMed1995

Isolated systolic and diastolic ventricular interactions in pacing-induced dilated cardiomyopathy and effects of volume loading and pericardium.

BACKGROUND: Interactions between the closely coupled right and left ventricles are known to play important roles as determinants of ventricular function, and the purpose of this study was to evaluate their effects in a model of heart failure. METHODS AND RESULTS: A dilated cardiomyopathy resulting in congestive heart failure (CHF) was produced in pigs by rapid ventricular pacing at 230 beats per minute for 1 week. Blood was rapidly withdrawn from the left ventricular (LV) apex into a prosthetic ventricle, and the instantaneous effects on the right ventricle were studied during volume loading and before and after pericardiectomy. The systolic interaction gain between the right and left ventricles (Gs) was calculated as the ratio of changes in mean systolic pressure during isolated systolic LV unloading. Diastolic ventricular interaction gain (Gd) was calculated as the ratio of changes in mean diastolic pressures during LV unloading in the last 150 ms of diastole. With the pericardium closed, all interaction gains were significantly increased during volume loading from a right ventricular end-diastolic pressure of 3 to 9 mm Hg: Gs from 0.045 +/- 0.014 to 0.063 +/- 0.020 mm Hg/mm Hg (normal pigs) and from 0.077 +/- 0.040 to 0.103 +/- 0.019 (CHF pigs) and Gs from 0.196 +/- 0.116 to 0.493 +/- 0.117 mm Hg/mm Hg (normal pigs) and from 0.174 +/- 0.101 to 0.341 +/- 0.165 (CHF pigs). When the pericardium was opened, Gd was significantly reduced to 0.145 +/- 0.071 and 0.129 +/- 0.026 mm Hg/mm Hg (normal and CHF pigs, respectively), but Gs showed no significant change (0.067 +/- 0.027 and 0.109 +/- 0.012 mm Hg/mm Hg for normal and CHF pigs, respectively), and both were also significantly increased during volume loading. Gs was significantly greater in CHF versus normal pigs under all conditions, but there were no differences in Gd between CHF and normal pigs. CONCLUSIONS: These results suggest that dilated cardiomyopathy increases systolic but not diastolic interactions, that the pericardium increases diastolic but not systolic ventricular interactions, and that volume loading with and without the pericardium opened increases both systolic and diastolic interactions.

Animals↗
PubMed1995

In vitro endotoxin penetration of coronally unsealed endodontically treated teeth.

The purpose of the study was to evaluate the penetration of bacterial endotoxin (L.P.S.) through obturated root canals. Twenty-four single-rooted teeth were instrumented in a uniform manner. The root canals of 16 teeth were obturated with guttapercha and Roth's sealer and 8 teeth were similarly obturated but without sealer. The teeth were then divided into three groups. Group 1-Positive control (4 teeth). Teeth obturated without sealer were used. Sticky wax was softened in an open flame and painted over the external root surface except the apical 2 mm and coronal canal orifice which were left free of the sticky wax. Group 2-Negative control (4 teeth). Again teeth without sealer comprised the teeth in this group. However, in this group the sticky wax covered the apical area of the root and the canal orifice coronally, in addition to the rest of the root. Group 3-Experimental (16 teeth). The teeth obturated in conjunction with sealer were used. Otherwise the teeth were treated as in group 1. The coronal root half was then hermetically sealed from the apical root half so that LPS placed coronally could move only through the obturated canal space to the apical segment. One ml of water containing 100 micrograms/ml endotoxin was placed in the upper chambers and pyrogen-free water in the lower chambers. The upper and lower chambers were then tested for endotoxin at different time periods upto 21 days. The upper chambers tested positive for endotoxin at all test times for all teeth. All 4 positive control teeth showed endotoxin in the lower chambers by 24 hrs.(ABSTRACT TRUNCATED AT 250 WORDS)

Aggregatibacter actinomycetemcomitans↗
PubMed1993

Blood-feeding patterns of Aedes aegypti (Diptera: Culicidae) collected in a rural Thai village.

Aedes aegypti (L.) were collected by aspiration once each week from in and around houses in a rural village in Chachoengsao Province. Thailand, during May 1990 to June 1991. Of the 1,230 specimens analyzed with a sandwich ELISA, 73% reacted to one or more of the seven hosts which we tested. Eighty-eight percent (789/896) of all detectable meals were identified as being from a single host (human). Patent multiple meals (double and triple), of which one was always human, were detected in 7% (66/896) of the specimens. The probability of feeding on a human, either as a single host or in a patent mixed meal, was > 0.90 during 12 of the 14 mo of the study; this probability never dropped below 0.85. The probability of Ae. aegypti taking multiple blood meals during a single gonotrophic cycle varied widely from 0.0 to 1.0. The possibility is discussed, including epidemiological significance, that there are seasonal fluctuations in the frequency of multiple feeding by Ae. aegypti and that multiple feeding increases in concert with seasonal trends for dengue infections of humans in Thailand.

Aedes↗
PubMed1993

Left ventricular unloading decreases rate of isovolumic right ventricular pressure decline.

To determine whether direct ventricular interaction affects right ventricular (RV) relaxation, we compared the minimum rate of change of RV pressure (dP/dtmin) and the time constant, tau, of isovolumic RV pressure decline in open-chest, anesthetized pigs following a normal left ventricular (LV) contraction and an acutely unloaded LV contraction. Rapid removal of blood via the LV apex into a prosthetic ventricle during a single systole decreased the LV pressure-time integral 68.3% and peak systolic pressure 49.9% without changing RV end-diastolic conditions. Micromanometers measured ventricular chamber pressures during single RV isovolumic beats, which were produced by transient pulmonary artery occlusion in both the control and the LV-unloaded states. When the LV was unloaded, RV tau rose significantly from 41.7 +/- (SD) 7.1 to 49.8 +/- 9.4 ms, P < 0.005 (pericardium intact) and 42.9 +/- 10.8 to 51.8 +/- 13.9 ms, P < 0.005 (pericardium opened). Simultaneously, RV dP/dtmin decreased from -400.5 +/- 136.6 to -288.3 +/- 46.8 mmHg/s, P = 0.14 (pericardium intact), and -342.4 +/- 104.2 to -241.2 +/- 118.9 mmHg/s, P < 0.01 (pericardium opened). These data indicate that LV systolic unloading decreases the rate of RV relaxation. We conclude that RV relaxation is influenced by direct anatomic ventricular interaction.

Animals↗
PubMed1993

Pacing-induced dilated cardiomyopathy increases left-to-right ventricular systolic interaction.

BACKGROUND: The right ventricle (RV) receives part of its systolic pumping force from the left ventricle through systolic ventricular interaction. The purpose of this study was to determine the effects of dilated cardiomyopathy on left ventricular to right ventricular (LV-to-RV) systolic interaction. METHODS AND RESULTS: Studies were performed in six normal pigs and in six pigs in which dilated cardiomyopathy resulting in congestive heart failure (CHF) was produced with rapid ventricular pacing at 230 beats per minute for 1 week. In all pigs, we rapidly withdrew blood from the LV apex into a prosthetic ventricle in a single beat, which reduced LV systolic pressure without changing RV or LV end-diastolic pressure, and the resultant instantaneous changes in RV systolic pressure and pulmonary artery flow were determined. The LV-to-RV mean systolic interaction gain was calculated as the change from a normal beat to the instantaneous unloaded beat in mean RV systolic pressure divided by the change in mean LV systolic pressure. Mean systolic pressure gain was approximately 2 1/2 times greater (P < .05) in the CHF animals (0.103 +/- 0.018 mm Hg/mm Hg) than in the normal pigs (0.04- +/- 0.011 mm Hg/mm Hg). CONCLUSIONS: These data demonstrate that left-to-right ventricular systolic interaction is significantly greater in dilated cardiomyopathy compared with the normal heart, indicating that the contribution of the left ventricle to RV systolic pressure generation has increased. This is consistent with decreased elastance of the interventricular septum resulting in increased coupling between the ventricles.

Animals↗
PubMed1993

The effect of the Relaxodont brain wave synchronizer on endodontic anxiety: evaluation by galvanic skin resistance, pulse rate, physical reactions, and questionnaire responses.

The effects of a brain wave synchronizer (BWS) on endodontic (root canal) anxiety was evaluated in the clinical practices of the senior author. The experimental groups were: (1) a verbal method (routine calming words by dentist) plus BWS (N = 10) and (2) verbal method plus BWS and alpha relaxation tape (N = 10). The control group was verbal method alone (N = 10). All three groups were evaluated during a complete endodontic treatment by the use of galvanic skin resistance (GSR), pulse rate (PR), physical responses, and pre- and post-treatment questionnaires. Recordings were made during the following periods: (1) start; (2) local anesthetic injection; (3) rubber dam application; (4) drilling; (5) x-ray taking; (6) instrumentation; (7) obturation; and (8) conclusion. Results showed that the experimental groups were significantly better than the control group in the reduction of endodontic anxiety. The findings reinforced the belief that local anesthetic injection is the most anxiety producing aspect of endodontic treatment.

Adult↗
PubMed1993

Toxicity of desoxycorticosterone pivalate given at high dosages to clinically normal beagles for six months.

Desoxycorticosterone pivalate was administered IM to juvenile Beagles at 0, 2.2, 6.6, or 11 mg/kg of body weight daily over a consecutive 3-day period every 28 days (equivalent to a cumulative monthly dosage of 0, 6.6, 19.8, or 33 mg/kg) for 6 months. Polyuria, polydipsia, and decreases in serum potassium and BUN concentrations were detected while the dogs were being treated. Transient increases in serum sodium concentrations also were detected. The treated males had significant decreases in body weight gain, resulting in an 18% decrease in body weight in the 11-mg/kg dosage group, compared with the controls. The weights of the adrenal glands, epididymides, and testes also were lower in the treated males. Organ weights for the 2.2, 6.6, and 11-mg/kg dosage groups were: 86, 79, and 69%, respectively, of the controls (adrenal glands); 80, 70, and 68%, respectively, of the controls (epididymides); and, 79, 75, and 67%, respectively, of the controls (testes). When normalized to body weight, these decreases in organ weight were still dosage-dependent, but the differences were less remarkable. In contrast, the relative weight (to body weight) of the kidneys (males and females) and of the thyroid and parathyroid glands (males) were higher dosage-dependently. All of the treatment-related effects, other than organ and body weight changes, appeared to be reversible following the cessation of treatment. On the basis of these results, it was concluded that treatment with desoxycorticosterone pivalate could be tolerated, even when given at dosage 15-fold the therapeutic dosage of 2.2 mg/kg every 25 days.

Adrenal Cortex Diseases↗
PubMed1993

Identification of blood meals in Aedes aegypti by antibody sandwich enzyme-linked immunosorbent assay.

A comparative study of 3 ELISA protocols was performed for host blood meal identification in Aedes aegypti. In the sandwich-B ELISA, which used a combination of heavy and heavy+light chain conjugates, specificity was improved to such a degree that conjugates no longer required cross-adsorption with heterologous sera. Using the sandwich-B assay, human blood meals in laboratory reared Ae. aegypti could be detected longer after feeding (100% at 32 h and 80% at 42 h) than with a direct assay (100% at 20 h). Efficacy of the sandwich-B and direct ELISAs in field analyses was studied in parallel) using 80 field collected mosquitoes from Thailand. The sandwich-B assay was superior (88% detection rate) to the direct assay (41% detection rate) and was thus selected as the method of choice for future field studies.

Aedes↗