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H M Chan

Publications and source records attributed to H M Chan.

67 records · Page 4Linked to original sources
PubMed1992

Heterogeneity of antibodies to metallothionein isomers and development of a simple enzyme-linked immunosorbent assay.

A competitive enzyme-linked immunosorbent assay (ELISA) for the measurement of metallothionein (MT) in tissues and body fluids has been developed. The ELISA employs the IgG fraction of a rabbit antiserum to rat liver Cd-MT-2 polymer, a biotinylated secondary antibody, and peroxidase conjugated avidin. With a 1:4000 dilution of the immunoglobulins, typical standard curves (logit-log regression) provide a linear range of 0.1-100 ng for MT-2 and 10-1000 ng for MT-1. Fifty percent inhibition is accomplished with 15 ng and 250 ng for MT-2 and MT-1, respectively. Rat liver MT-1 and MT-2 containing different metals (Ag, Cu, and Zn) inhibited the antibodies as effectively as CdMT. However, the antibodies exhibited greater affinity for both Apo-MT isoforms. Previously reported discrepancies between results obtained by metal binding assays (e.g., Ag-hem binding) and radioimmunoassay for MT levels in tissues have been largely resolved. By addition of 1% Tween 20 to samples, the ELISA routinely estimated the total MT in samples of rat, mouse, and human liver and kidney at 88% of the value obtained by the silver-hem binding assay. Specific antibodies to MT-2 were purified from our antiserum by affinity purification using CH-Sepharose 4B coupled with rat liver MT-1. Estimation of MT in samples using purified MT-2 antibodies provided slightly lower values (72%) for MT in tissues as compared to the Ag-hem method. The predominant form of MT in tissues of control animals was found to be MT-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Quantification of metallothionein isoforms using an enzyme-linked immunosorbent assay (ELISA) with two specific antisera.

The specificity of three populations of antibodies to the two metallothionein (MT) isoforms has been characterized using a competitive enzyme-linked immunosorbent assay (ELISA). A polyclonal sheep anti-MT-1 antibody (PAb 1) showed higher affinity to MT-1 than to MT-2 with I50 (concentrations required to achieve 50% inhibition) being 18 and 480 ng for MT-1 and MT-2, respectively. Conversely, a polyclonal rabbit anti-MT-2 antibody (PAb 2) showed higher affinity to MT-2 than to MT-1 (I50 being 250 and 15 ng for MT-1 and MT-2, respectively). A third antibody (PAb 3), isolated by removal of anti-MT-1 antibodies in PAB 2 by immunoaffinity purification, showed no cross-reactivity with MT-1. This result suggests that there are two populations of antibodies which cross-react specifically with the MT isoforms. Rat tissue MT concentrations were quantified by ELISA using the three different antibodies and silver-saturation method. The sum of MT isoform concentrations (ELISA estimation using antibodies PAb 1 and PAb 3) were not significantly different (p < 0.05) from the total MT concentrations obtained by silver-saturation method. Therefore, the ELISA can be used to estimate the relative quantities of the two MT isoforms in rat tissues. The predominant isoform in rat tissues was MT-2 and the proportion of MT-1 increased with induced synthesis of MT by metal injection.

Animals↗
PubMed1992

Protective roles of metallothionein and glutathione in hepatotoxicity of cadmium.

The protective roles of metallothionein (MT) and glutathione (GSH) in acute hepatotoxicity of cadmium (Cd) were investigated in an in vitro system. Liver slices were incubated in a buffer containing cadmium chloride (20-50 ppm) at 37 degrees C for 3 h. Viability of the slices was monitored by measuring intra-cellular potassium (K) content and GSH concentrations. A dose-dependent decrease of intracellular K content of GSH concentrations was observed. Pre-induction of MT (100-fold increase) by injection of zinc sulphate (30 mg Zn/kg body weight) showed protection against decrease in both intracellular K and GSH concentrations in liver slices. Decrease of hepatic GSH (90%) by an injection of buthionine sulfoximine (BSO)(4 mmol/kg body weight) to the rats further enhanced the Cd toxicity in the liver slices. This enhanced toxicity resulting from BSO treatment can be totally overvome by induction of MT by Zn pre-treatment. The cellular uptake of Cd remained unaltered in all experiments. These results demonstrate that hepatic toxicity of Cd may be due to its binding to intracellular sulfhydryl groups and both intracellular GSH and MT levels may provide protection against cytotoxicity of Cd in liver. Moreover, even at low GSH levels, MT could partially protect the hepatic cells from Cd cytotoxicity.

Animals↗
PubMed1992

Pneumatosis cystoides intestinalis arising in jejunal diverticular disease: report of a case and a suggestion to its pathogenesis.

The occurrence of pneumatosis cystoides intestinalis (PCI) in the gastrointestinal tract is rare. Among the cases already documented in the English language literature, the association of PCI with jejunal diverticulosis has only been mentioned once or twice. We herein report a case of a 63-year-old woman who had both entities concurrently in a segment of the jejunum. What is important to note is the relationship of PCI to the diverticulosis and its possible pathogenesis. Through histological examination and review of related articles, we are convinced that a mechanical theory plays a pivotal role when both diseases occur in the same segment of intestine and are compounded by obstruction or impaired peristalsis. This finding, when properly applied to PCI in other settings, helps to resolve the pathogenesis of PCI and other related gas-filled cysts.

Diverticulum↗
PubMed1992

Mondor's disease of the breast--three cases report.

Mondor's disease is a rare and relatively little known clinical entity. Clinical features include sudden development of localized pain in the breast, followed by visible and papable, tender, cordlike, branching cutaneous grooves. It involves superficial thrombophlebitis of the thoracoepigastric or lateral thoracic vein occurring mostly in middle-age women. The etiology of Mondor's disease is unknown, and it may be related to trauma, operation, infection, bandaging, or tight clothes. The mammogram of most cases showed no abnormality, but the ultrasonography revealed hyperechoic cordlike pattern in the lesions. The symptomatic treatment is required and surgery will be indicated when it is associated with malignancy or severe painful cord due to pain and traction. It usually resolves over a period of 2 to 8 weeks. We report three cases of Mondor's disease and that we believe to be the first reported cases in Taiwan.

Adult↗
PubMed1990

Left paraduodenal hernia complicating pregnancy--a case report.

A pregnant woman with intestinal obstruction due to left paraduodenal hernia is described. To the authors' knowledge, this paper represents the first case of left paraduodenal hernia complicating pregnancy. Paraduodenal hernia is a congenital anomaly where the small intestine is trapped. The enlarging uterus distorts the hernial sac, and converts a partial obstruction into a complete one. The pathogenesis and management of this rare case is discussed.

Adult↗
PubMed1990

[Colon and rectal trauma].

From July 1982 to June 1989, 64 patients with trauma involving a colon and rectum operated on at the Kaohsiung Medical College Hospital were retrospectively reviewed. Their ages ranged from 14 to 90 years (mean 43.6 +/- 17.6 years); 48 were male, 16 female. Thirty-four (53.1%) had penetrating injuries, 30 (46.9%) had blunt injuries. Twenty-six (86.7%) blunt injuries and 7 (20.6%) penetrating injuries involved various associated injuries. There was a significantly greater number of associated organ injury in cases of blunt trauma. The most common organ injured concomitantly was the small intestine. The severity of injury and general condition were quantified for each patient using the intraoperative grading system proposed by Flint et al, and revealed that it was independent of the colorectal site, but related to the mode of trauma. After an assessment of the grade of injury, 42 patients underwent colostomies, 14 primary closures, 2 resections and anastomoses and 6 exteriorized repairs In the primary closure group, there was no mortality but 2 suture leakages which reoperated to colostomies. In three patients (50%) of the exteriorized repair group with fecal leakage developed at the repair site, the exteriorized loops were coverted into colostomies without complication. The most common complications were wound infection and abdominal abscess. The mortality (14.1%) and morbidity (45.3%) were not related to the location of the injured bowel but were influenced by the grade of colorectal trauma, associated organ injury and the mode of trauma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Evaluation of galactography for nipple discharge.

Galactography is useful in the evaluation of spontaneous discharge from the nipple of a nonlactating breast. Without galactography, surgeons have relied on either masectomy or excision of the major duct system responsible for the discharge. From January 1989 to May 1996, 106 galactograms were performed with monofilament polypropylene suture guiding for duct cannulation in 105 cases. The discharge duct was identified by pre-operative galactography, followed by a selective excision of ductal-lobular unit. In all tissue specimens, the cause of the pathologic secretion was found histologically; most often, it was intraductal papilloma (42.6%). In 35.6% of the specimens, findings with a prospective significance (papillomatosis, hyperplasia, carcinoma) were discovered and further operative treatment was initiated. The color of the discharge allowed no prediction of the histological findings. The accuracy of galactography was 88.4%, 84.6%, and 77.4% in papilloma, cancer, and other benign lesions, respectively. It is better than physical examination and other tests. Galactography represents a useful test in the diagnostic workup of secretory breasts.

Adolescent↗
PubMedDate not supplied

A database for environmental contaminants in traditional foods in northern and Arctic Canada: development and applications.

The potential health effects of environmental contaminants in traditional food has become a concern among northern communities because of the presence of environmental contaminants in the Arctic ecosystem. Exposure assessments are needed but they require comprehensive dietary information and contaminant data. Over the last 10 years, there has been considerable effort to monitor the level of contaminants in fish and wildlife collected from different regions in northern and Arctic Canada. The development of a database and its application for dietary contaminant exposure assessment are described. We conducted an extensive literature review on levels of environmental contaminants in northern and Arctic Canada. The ranges of levels of four contaminants of major concern (chlordane, mercury, polychlorinated biphenyls and toxaphene) in 81 species of marine mammals, terrestrial mammals, birds, fish and plants are summarized. These data represent 69% of the 117 species of fish, wildlife and plants mentioned in our dietary interviews conducted in the northern communities. A significant percentage of the foods had contaminant levels exceeding the guidelines used by Health Canada for market food consumed by the 'southern' populations. Mathematic modelling of the distributions of the data showed that contaminant levels in most food groups are log-normally distributed and have a typical coefficient of variation of about 100%. Examples are presented to demonstrate the use of the data for contaminant exposure assessment. Average contaminant exposure levels estimated using the database for two communities are comparable to those obtained previously using community specific data. With the current knowledge of environmental contaminant levels in the northern traditional food system, it may be feasible to conduct preliminary risk assessment of dietary exposure of environmental contaminants when some diet information for a community is available. Further sampling and analysis may be needed only for confirmation purposes.

Animals↗
PubMedDate not supplied

Ontogenic changes in hepatic metallothionein isoforms in prenatal and newborn rats.

The relative quantities of the two metallothionein isoforms (MT-1 and MT-2) in prenatal and newborn rat livers have been quantified using a competitive enzyme-linked immunosorbent assay with two specific polyclonal antisera. Both MT isoforms were detected in fetal liver on gestation day 16 and their levels continued to increase into the neonatal period. A concomitant increase was observed in plasma MT levels in the pregnant rats. The level of MT-2 was higher (75%) than that of MT-1 in the liver of both prenatal and neonatal rats. Both hepatic MT isoforms showed a significant correlation (P < 0.05) with the hepatic Zn level. Immunohistochemical localization of MT isoforms showed no apparent difference in intracellular distribution. Both MT isoforms were mainly cytoplasmic in fetal rat liver. Intense intranuclear staining was observed in newborn rat liver when the total MT concentration reached a maximum of over 1 mg MT/g tissue. The nuclear MT staining decreased with age, and at day 7, approximately equal concentrations of MT were found in nucleus and cytoplasm. When the newborn rats (1 day old) were injected with Zn (10 mg/kg), both MT isoforms were induced on days 2 and 7. Injection of Cd (1 mg/kg) increased the hepatic MT levels only on day 7. The level of MT-2 remained higher than that of MT-1 in all cases. These results suggest that both MT isoforms play a similar role in the metabolism of Zn during early development and the relative abundance of the MT isoforms may be a species-specific phenomenon.

Aging↗
PubMedDate not supplied

Assessment of dietary exposure to trace metals in Baffin Inuit food.

Chronic metal toxicity is a concern in the Canadian Arctic because of the findings of high metal levels in wildlife animals and the fact that traditional food constitutes a major component of the diet of indigenous peoples. We examined exposure to trace metals through traditional food resources for Inuit living in the community of Qikiqtarjuaq on Baffin Island in the eastern Arctic. Mercury, cadmium, and lead were determined in local food resources as normally prepared and eaten. Elevated concentrations of mercury ( > 50 micrograms/100 g) were found in ringed seal liver, narwhal mattak, beluga meat, and beluga mattak, and relatively high concentrations of cadmium and lead ( > 100 micrograms/100 g) were found in ringed seal liver, mussels, and kelp. Quantified dietary recalls taken seasonally reflected normal consumption patterns of these food resources by adult men and women ( > 20 years old) and children (3-12 years old). Based on traditional food consumption, the average daily intake levels of total mercury for both adults (65 micrograms for women and 97 micrograms for men) and children (38 micrograms) were higher than the Canadian average value (16 micrograms). The average weekly intake of mercury for all age groups exceeded the intake guidelines (5.0 micrograms/kg/day) established by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives and Contaminants. The primary foods that contributed to metal intake for the Baffin Inuit were ringed seal meat, caribou meat, and kelp. We review the superior nutritional benefits and potential health risks of traditional food items and implications for monitoring metal contents of food, clinical symptoms, and food use.

Adult↗
PubMedDate not supplied

Population exposure to radioactivity from consumption of caribou among the Dene/Métis of Denendeh (western Northwest Territories, Canada).

There has been long-standing concern with exposure to radioactivity through the consumption of caribou, particularly in indigenous populations in the western Northwest Territories, Canada, who are traditionally high consumers. We conducted a dietary survey in this region in 1994 to estimate population exposure levels. Dietary information was collected from 1012 individuals in sixteen communities (1012 days of 24-hour dietary recalls, 1012 food frequency questionnaires) and radionuclide levels in caribou flesh, liver and kidneys were measured. Monte Carlo statistical methods were employed to integrate these data sets and estimate the distribution of radiation exposure for people in five regions (Gwich'in, Sahtú, Dogrib, Deh-Cho, South Slave). The exposure levels were highest in the South Slave region and in older males (40+ years), and lowest in the Gwich'in region and in younger females (20-40 years). Median exposure level ranged from 0.95 to 5.31 mSv per year (mean of medians = 2.96 mSv/y). In each group the 95th percentile of exposure was 2-3 times greater than the median. These exposure levels are comparable to exposure levels in Alaskan Eskimos and Marshall Island residents, and are much higher than European or American urban populations. Caribou meat is a very nutritious food. We conclude that, although there is some radiation exposure from consuming caribou, the associated health risks are low and are outweighed by the physical, social and cultural benefits derived from hunting and eating caribou.

Adult↗