Biomedical subjects

E L Chan

Publications and source records attributed to E L Chan.

At least 37 records · Page 2Linked to original sources

PubMed1994

The effect of high protein and high salt intake for 4 months on calcium and hydroxyproline excretion in normal and oophorectomized rats.

The effect of feeding high protein (40%) and high salt intake (18 gm/L of sodium chloride in drinking water) for 4 months on the urinary excretion of calcium and hydroxyproline (OHP) in sham operated and oophorectomized (OX) rats was studied. OX rats had higher body weight and increased excretion of calcium and OHP. Feeding a high-salt diet caused an increase in the excretion of calcium, phosphate, and OHP. The high-protein diet had a similar effect. There was a significant interaction between the effects of salt and protein on calcium excretion. OX did not influence the effect of high salt or high protein intakes. It is concluded that high protein and/or high salt intake increases the excretion of calcium and OHP. The effect is seen even after 4 months of the diet. Oophorectomy did not cause any additional effect.

Analysis of Variance↗

PubMed1993

Effect of different amounts of sodium intake for 4 months on calcium metabolism in normal and oophorectomized rats.

The effects of different amounts of salt intake on urinary calcium and hydroxyproline (OHP) excretion were studied in oophorectomized (O) and sham-operated (S) rats on normal calcium diet. Groups of O and S rats were given either tap water or 2, 6, or 18 g/liter of NaCl to drink. Urinary excretion of sodium, calcium, and OHP was monitored at 0, 2, and 4 months. Urinary excretion of calcium and OHP increased with increasing salt intake (P < 0.001 by ANOVA) in S and O groups. Oophorectomy did not have any additional effect on calcium or OHP excretion. We conclude that increased salt intake causes increased excretion of calcium and OHP and oophorectomy does not further aggravate the loss.

Analysis of Variance↗

PubMed1993

The effect of high sodium intake on bone mineral content in rats fed a normal calcium or a low calcium diet.

The effect of high sodium intake on bone mineral content of rats fed a normal (0.6% Ca) or a low (0.02% Ca) calcium diet was studied. Rats on a normal calcium diet given 1.8% sodium chloride to drink showed persistent and significant hypercalciuria and subnormal bone mineral content. Total calcium content of femur was significantly lower after 4 months (p < 0.02) and 12 months (p < 0.001). In rats maintained on a low calcium diet (0.02% Ca), a high sodium diet for 8 weeks caused a significant loss of calcium in bone similar to that seen in animals fed a normal calcium diet for 4 months. We conclude that high sodium intake reduces bone mineral content, especially if the diet is low in calcium.

Animals↗

PubMed1993

Potassium intake and urinary calcium excretion in healthy subjects.

Potassium depletion increases and potassium supplementation decreases urinary calcium excretion. To determine whether these experimental observations have any significance in healthy free living subjects, we measured 24 h urinary calcium, sodium, potassium and serum parathyroid hormone (PTH) in 142 healthy young (aged 18-40 years) female Chinese subjects. Sodium excretion and potassium excretion were positively correlated with calcium excretion (r = 0.494, p < 0.0001 and r = 0.181, p = 0.031, respectively). However stepwise multiple regression analysis showed that only urinary sodium excretion contributed to the excretion of calcium. We conclude that in free living subjects potassium intake has little effect on calcium excretion.

Adolescent↗

PubMed1992

Serum intact parathyroid hormone levels in elderly Chinese females with hip fracture.

Serum intact parathyroid hormone (PTH), 25 hydroxyvitamin D(25OHD), 1,25 dihydroxyvitamin D (1,25(OH)2D), albumin, and ionized calcium were measured in 61 Chinese female patients with hip fracture and 61 control subjects. Hip fracture patients had low albumin, ionized calcium, and 250HD levels. Serum PTH and 1,25(OH)2D values were not different between the two groups. We conclude that although 250HD level in hip fracture patients is low, there is no evidence of secondary hyperparathyroidism, suggesting that the low 250HD levels may be a secondary phenomenon in response to the fracture.

Aged↗

PubMed1992

A rapid assay for the measurement of Na+,K(+)-ATPase inhibitors.

A rapid and automated assay for inhibitors of Na+, K(+)-ATPase was developed by determining the amount of inorganic phosphorus (Pi) released by Na+,K(+)-ATPase in a centrifugal analyzer. This method avoids long incubation, strong acids and centrifugation as in the conventional manual method. The coefficients of variation of intra- and inter-assay at ouabain concentration 0.5 mumol/L were 1.0 and 1.4%, respectively. The method is quick, reproducible and easy compared with current techniques.

Animals↗

PubMed1992

Multicentre study on antibiotic susceptibilities of anaerobic bacteria to cefoperazone-sulbactam and other antimicrobial agents.

The antibiotic susceptibilities of 241 anaerobic bacteria recovered from six geographic sites in North America were tested by agar dilution to cefoperazone-sulbactam and other drugs. Of the 189 Bacteroides fragilis group isolates, only one was resistant to cefoperazone-sulbactam (0.5%) or ampicillin-sulbactam (0.5%), and none was resistant to ticarcillin-clavulanate or chloramphenicol. No resistance to cefoperazone-sulbactam was observed among the other Bacteroides spp., Clostridium spp., or Peptostreptococcus spp. Resistance to cefoperazone-sulbactam is not commonly observed against anaerobic bacteria recovered from different geographical sites across North America.

Anti-Bacterial Agents↗

PubMed1992

Age-related changes in bone density, serum parathyroid hormone, calcium absorption and other indices of bone metabolism in Chinese women.

OBJECTIVE: To study the age-related changes in bone density, serum parathyroid hormone, calcium absorption and other indices of calcium metabolism in Chinese women who habitually have a low calcium intake. DESIGN: Cross-sectional study. SUBJECTS: One hundred and fifty-six healthy Chinese women aged 20-83 years. None were on any medication or vitamin supplements. Subjects over the age of 60 years were all living in a hostel; younger subjects were nurses or subjects attending a family clinic for minor illnesses. MEASUREMENTS: Fasting blood and urine samples were collected for biochemical measurements and calcium absorption was measured using 45Ca by the method of Marshall and Nordin. Bone density was measured by dual energy X-ray densitometry (Norland X R20 X-ray bone densitometer) at the left hip and lumbar spine. Serum parathyroid hormone was measured by a chemiluminometric assay. RESULTS: Plasma ionized calcium concentration, alkaline phosphatase, bicarbonate, plasma creatinine and serum B2 microglobulin were significantly higher in the elderly than in the young, whereas plasma phosphate and the anion gap were higher in the young. Urinary excretion of calcium, phosphate and hydroxyproline were all higher in older women. Plasma parathyroid hormone concentration was positively correlated with age even after taking into account the decline in renal function (as indicated by the rise in B2 microglobulin (r = 0.506, P less than 0.001). Serum concentrations of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were not lower in the older women. Fractional calcium absorption from an oral load of radiolabelled calcium was significantly lower in the older women and 37% of the older women were below the 2.5 percentile found in the younger women. Bone density measured by dual energy X-ray densitometry was also significantly lower in the elderly. CONCLUSION: In Chinese women there is an increase in PTH and a decrease in calcium absorption with age in spite of the presence of normal vitamin D metabolites.

Absorption↗

PubMed1992

Interrelationships between urinary sodium, calcium, hydroxyproline and serum PTH in healthy subjects.

The effect of sodium intake on the excretion of calcium, hydroxyproline (OHP) and serum parathyroid hormone (PTH) was examined. When seven healthy males increased their sodium intake by 200 mmol/day, excretion of calcium increased by 1.70 mmol/day and that of OHP by 27%. Serum PTH, however, did not increase significantly. In a cross-sectional study of 334 healthy female subjects there were strong positive correlations between fasting urinary sodium/creatinine (Na/Cr) and calcium/creatinine (Ca/Cr) ratios (r = 0.573) and between Na/Cr and urinary OHP/Cr ratios (r = 0.246). Serum PTH was negatively correlated with Na/Cr ratio (r = -0.161). We conclude that an increase in dietary sodium causes calciuria and an increase in hydroxyproline excretion. The results do not support the hypothesis that this is mediated by PTH.

Adult↗

PubMed1992

Free triiodothyronine in sera of acutely ill general medical patients: a prognostic indicator?

We measured free triiodothyronine (FT3), thyrotropin (TSH), and C-reactive protein (CRP) in sera of 39 acutely ill medical patients who died within three months of admission and 39 age- and sex-matched control patients selected at random from a total of 294 acute medical admissions. Serum FT3 in nonsurvivors (1.91 +/- 1.51 pmol/L) was significantly lower than that in survivors (3.01 +/- 1.3 pmol/L, P less than 0.01) and the CRP in nonsurvivors (54.6 +/- 59.2 mg/L) was significantly higher than in survivors (43.6 +/- 59.5 mg/L, P less than 0.05). There was no difference in plasma TSH between the two groups. The estimated odds ratio relating death to a plasma FT3 value less than 1.0 pmol/L on admission was 17 (highly significant: P less than 0.001). We conclude that plasma FT3 may be a useful prognostic indicator in acutely ill patients.

Acute Disease↗

PubMed1991

Measurement of brown adipose tissue uncoupling protein by enzyme linked immunosorbent assay.

Antibody to uncoupling protein (UCP) purified from rat brown adipose tissue (BAT) was raised in rabbits and an enzyme linked immunosorbent assay was developed. The antiserum did not cross-react with other mitochondrial proteins from BAT and from other tissues but cross-reacted with UCP from hamster, guinea pig and mouse. The assay is capable of detecting 5 ng of UCP. Using this assay and a crude mitochondrial preparation, UCP content of BAT was shown to increase during cold adaptation.

Adaptation, Physiological↗

PubMed1989

Vasoactive properties of dihomo-gamma-linolenic acid and series one prostaglandins in a freshwater teleost, Channa maculata.

1. Prostaglandins A1, B1, E1 and F1 alpha (2-120 micrograms/kg), arachidonic acid and dihomo-gamma-linolenic acid (0.1-2 mg/kg) were injected intravenously into Channa maculata and changes in arterial blood pressure were recorded. 2. Injection of PGF1 alpha had no significant effect on arterial blood pressure. Injection of PGA1 and PGE1 was followed by dose-dependent hypotension whereas injection of PGB1 elicited significant dose-dependent increase in arterial blood pressure. 3. Both dihomo-gamma-linolenic acid and arachidonic acid were also depressor agents but dihomo-gamma-linolenic acid was more potent. 4. A single bolus intravenous injection of indomethacin (5 mg/kg) or 4 daily intraperitoneal injections (4 x 10 mg/kg) significantly lowered arterial blood pressure. One hour after pre-treatment of indomethacin, the vascular effects of both prostaglandin precursors were abolished. 5. It appears that the vascular effects of prostaglandins in Channa maculata are qualitatively different from those reported for mammals.

8,11,14-Eicosatrienoic Acid↗

PubMed1989

The effect of ouabain on metabolic rate in guinea-pigs: estimation of energy cost of sodium pump activity.

1. The effect of different doses of ouabain, an inhibitor of the sodium pump, or saline (9 g sodium chloride/1; the vehicle) on the metabolic rate of guinea-pigs weighing 500 g was measured by indirect calorimetry for 120 min. 2. Ouabain (0.02-0.07 nmol/g body-weight) decreased the oxygen consumption in a dose-related manner. When higher doses of ouabain (0.10 nmol/g body-weight or greater) were injected the animals were observed to shiver. Ouabain (0.07 nmol/g body-weight) reduced Na+,K+-ATPase (EC 3.6.1.3) activity of liver, kidney and skeletal muscle by 18.0 (SE 6.6), 21.5 (SE 6.0) and 21.9 (SE 6.8)% respectively. An Eadie-Hofstee plot of percentage decrease in O2 consumption v. percentage inhibition divided by dose of ouabain showed that maximal inhibition of O2 consumption was 39.4%. 3. It is concluded that Na pump activity contributed to about 40% of the resting O2 consumption.

Animals↗

PubMed1987

Determination of synergy by two methods with eight antimicrobial combinations against tobramycin-susceptible and tobramycin-resistant strains of Pseudomonas.

Eleven strains of tobramycin-susceptible Pseudomonas aeruginosa, 12 strains of tobramycin-resistant P. aeruginosa, and 11 strains of P. maltophilia were tested against tobramycin in combination with azlocillin, piperacillin, ceftazidime, and imipenem and against colistin in combination with azlocillin, piperacillin, ceftazidime, and imipenem by microdilution checkerboard and time-kill curve techniques. Synergistic or additive effects were demonstrated in the tobramycin-ceftazidime combination against tobramycin-resistant strains of P. aeruginosa and P. maltophilia, and with all tobramycin combinations against tobramycin-susceptible strains of P. aeruginosa using the checkerboard technique. Synergistic and additive effects were seen with the time-kill curve technique with colistin-ceftazidime, colistin-imipenem, and tobramycin-piperacillin combinations against tobramycin-susceptible P. aeruginosa and in the colistin-ceftazidime combination against tobramycin-resistant P. aeruginosa. Fractional inhibitory concentrations (FIC) and fractional bactericidal concentrations (FBC) from checkerboard studies were compared to the time-kill curve results and vice versa. The overall agreement with FIC was 39.4% and 40.9% and agreement with FBC was 40.9% and 43.9%. This limited study illustrates the lack of agreement between these techniques in demonstrating antimicrobial synergy against pseudomonads.

Azlocillin↗

PubMed1987

The effect of antibiotics on the cell morphology of Legionella pneumophila.

Legionella pneumophila, in Buffered Yeast Extract broth, was treated for 5 h at 37 degrees C with rosaramicin, erythromycin, cefotaxime, dibekacin, penicillin, methicillin, cefoxitin, cephalothin, ticarcillin, carbenicillin or polymyxin B at near-MIC levels and above. Electronmicroscopy demonstrated morphological changes to the bacteria in some, but not all, of the antibiotic-treated suspensions. Penicillin, at 1000 micrograms/ml (40 X MIC) but not less, produced smooth bubble-like structures on cell surfaces; methicillin produced rough bubble-like structures at 100 micrograms/ml (MIC) but not at 1000 micrograms/ml. In each case, these structures resembled spheroplasts. Polymyxin B induced small-bleb formation on the bacterial cell surfaces at all concentrations tested (MIC-10 X MIC). The other eight antibiotics did not induce any morphological changes at any concentration tested.

Anti-Bacterial Agents↗

PubMed1985

The comparative in vitro susceptibility of cefazolin-resistant organisms to six cephalosporins, four penicillins, and three aminoglycosides.

One thousand thirty-seven cefazolin-resistant, gram-negative clinical isolates including members of the family Enterobacteriaceae, pseudomonads, and other nonfermenters were tested against a variety of newer antimicrobial agents by microdilution. Most of the Enterobacteriaceae were resistant to the second-generation cephalosporins, but highly susceptible to the third-generation agents and the broad-spectrum penicillins, 90% of the strains being inhibited at attainable serum concentrations. Cefoperazone and the penicillins had good activity against the Pseudomonas species, but the aminoglycosides remained the most active agents against all the gram-negative bacilli tested except Pseudomonas maltophilia.

Aminoglycosides↗

PubMed1984

Abdominal aortic aneurysm in high-risk patients. Outcome of selective management based on size and expansion rate.

Low mortality rates for elective surgical treatment of abdominal aortic aneurysms justify an aggressive approach in most patients. However, in high-risk patients with small aneurysms and no symptoms, the decision to operate remains a delicate balance of risk and benefit. Our observations include 99 high-risk patients with asymptomatic abdominal aortic aneurysms initially measuring 3 to 6 cm in the largest transverse diameter, who have been followed 1 to 9 years (average 2.4 years) with serial echographic measurements. Elective operations were performed for aneurysmal enlargement greater than 6 cm or symptom development. An additional 11 patients with aneurysms initially greater than 6 cm, whose initial evaluation did not result in elective surgery, were also followed. Serial data documented a mean expansion rate of 0.4 cm/year for aneurysms smaller than 6 cm. Forty-one of these 99 high-risk patients with small aneurysms eventually underwent an elective resection with two deaths (4.9%). Thirty-four patients (34%) died from causes unrelated to their unoperated aneurysms, and 21 patients (21%) are alive without symptoms. Three of the 99 patients suffered aneurysm rupture and emergency operation with two deaths. Thus, of the 99 high-risk patients with small aneurysms, four have died of elective aneurysm surgery or rupture (4%). A protocol of re-echo (or computerized tomography) examination at 3-month intervals appears to define which of these high-risk patients require elective aneurysm surgery, and has limited rupture to less than 5%. Improved criteria may emerge from recent advances in high-resolution computerized tomography.

Aorta, Abdominal↗

PubMed1984

Inferior vena cava bypass: experimental evaluation of externally supported grafts and initial clinical application.

Inferior vena caval obstruction is an unusual but important clinical problem for which adequate treatment previously has not been available. Recently, a polytetrafluoroethylene (PTFE) graft with external rigid spiral supports was developed that appeared particularly applicable to the venous system. In 18 dogs a 15 cm length of Impraflex was placed from the proximal right common iliac vein to the inferior vena cava (IVC) at the level of the renal veins after IVC and right iliac vein interruption. End-to-end and end-to-side iliac vein anastomoses were alternated, with and without distal femoral arteriovenous (AV) fistulas (AVFs). At 2 months, with a distal AV fistula, 11 of 12 (92%) grafts were patent, angiograms demonstrated no evidence of intraluminal clot, and there was no hind limb edema. Following AVF ligation 2 months after graft insertion, 10 grafts remained patent, but five developed some intraluminal thrombus and one of them progressed to complete occlusion. Four months after fistula ligation (6 months after graft insertion) 9 of 12 grafts (75%) remained patent. All six grafts without distal AVF were occluded within 1 week. This procedure was performed on one severely symptomatic patient who had IVC occlusion, and currently the patient shows marked improvement. Thus IVC bypass is possible when an externally supported PTFE prosthesis is complemented by a temporary AVF.

Adult↗