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Biomedical subjects

G Lum

Publications and source records attributed to G Lum.

At least 55 records · Page 3Linked to original sources

Sequential changes in serum glucose, triglycerides and cholesterol in aging of normal and alloxan-diabetic rats.

16-week-old Wistar, alloxan diabetic rats exhibited progressive elevations in levels of serum glucose, total triglycerides, cholesterol and creatinine over a period of 8 weeks; hyperglycemia preceded hyperlipidemia and hypercreatininemia and hypertriglyceridemia preceded hypercholesteremia. Age-matched control rats failed to develop any signs of hyperglycemia or hypercreatininemia, but did develop both hypercholesterolemia and hypertriglyceridemia at 24 weeks of age. This suggests that the progressive cardiovascular derangements (e.g., atherosclerosis, hypertension) noted in experimental diabetes mellitus and in the normal aging (and maturation) process may be brought about by distinctly different biochemical processes.

Aging↗

Vascular responsiveness and serum biochemical parameters in alloxan diabetes mellitus.

Responses of isolated aorta and portal vein (PV) to norepinephrine (NE), angiotensin II (AII), KCl, and CaCl2 were investigated in alloxan diabetic rats. Based on serum biochemical parameters (i.e., glucose, cholesterol, triglycerides, and creatinine) (alloxan, 150 mg/kg), diabetic rates were divided into three groups: 1) mildly diabetic at 1 week (only elevated glucose levels), 2) moderately diabetic at 4 wk (elevated glucose, triglycerides, and creatinine), and 3) severely diabetic at 8 wk (all serum biochemical parameters elevated). The sensitivity (i.e., ED50) of aortic smooth muscle from diabetic rats when compared to saline controls was 1) unchanged in mild diabetes; 2) decreased to KCl, AII, and CaCl2 in moderate diabetes; and 3) decreased to KCl, NE, and CaCl2 in severe diabetes. Ability of aortic smooth muscle to develop maximal contractions (i.e., contractility) to all these agonists was markedly diminished in severe diabetes. Spontaneous phasic contractions of PV from diabetic rats exhibited progressively greater tension as the disease advanced. Unlike aortas, contractility of PV to vasoactive agents was not affected at any stage of diabetes. PV sensitivity to AII in moderate diabetes and to Ca in severe diabetes was decreased when compared to saline controls. These differences in reactivity and contractility of aorta and PV in progressive stages of experimental diabetes could be due to alterations in calcium handling and its metabolism in arterial and venous smooth muscle cells in the diabetic state.

Angiotensin II↗

Preparation and stability of a liquid creatine kinase isoenzyme control from rabbit serum.

The MB isoenzyme of creatine kinase (CK) may be prepared in vitro from rabbit serum containing only the MM and BB isoenzymes, by means of a hybridization technique. The MM and BB dimers dissociate in 4 mol/L urea, which allows random recombination of M and B monomers. A liquid CK-isoenzyme control can be made from mixtures of rabbit sera obtained after hybridization and stabilized with glycerol and 25 mmol of 2-mercaptoethanol per liter. A liquid control stored at 4 degrees C showed good stability over a three-month period, declining to a mean residual activity of CK of approximately 90% after three weeks and a mean residual activity of MM, MB, and BB of 80--85% after six weeks. At 25 degrees C, CK activity of the liquid control declined to 75--80% after the fourth week. CK-BB at 25 degrees C was the least stable isoenzyme, declining to 75% after the third week and reaching 60% of activity after 12 weeks. CK-MB and CK-MM showed approximately 10--15% less stability at 25 degrees C than at 4 degrees C.

Animals↗

Amylase activity in serum and urine: comparison of results by the amyloclastic, dyed-starch, and nephelometric techniques.

We assayed serum and urine specimens for amylase activity by the nephelometric (I),dyed-starch (Amylochrome) (II), and mayloclastic (III) techniques. For serum, the correlation coefficients of the regression lines were: I vs. II, 0.978 (n = 106); I vs. III, 0.736 (n = 110); and II vs. III, 0.739 (n = 108). For urine, they were I vs. II, 0.938 (n = 49); and I vs. III, 0.752 (n = 46). Because calculation of the Kolmogorov-Smirnov statistic showed the distributions to be nongaussian, Spearman rank correlation coefficients were determined and showed that I and II correlated well but neither method correlated with III. The clinical data show that I and II gave above-normal activities in every case of pancreatitis, but III gave normal values in two of eight cases. In all cases, I and II were more sensitive, giving higher amylase activities (as compared with the upper limit of normal) than did III. The nephelometric procedure is most suitable for routine and emergency testing; the dyed-starch assay is equally sensitive and reliable, but less convenient. The amyloclastic procedure appears to be less reliable.

Adult↗

Chromatographic and electrophoretic separation of creatine kinase isoenzymes compared.

We compared two techniques for separating and evaluating serum creatine kinase isoenzymes--fluorometric agarose electrophoresis and Sephadex chromatography--in 50 patients, 25 of whom had confirmed acute myocardial infarction. In every case isoenzyme MB (heart isoenzyme) was detected with equal sensitivity by either procedure. Evidently, only the presence or absence of MB is clinically significant; none of the 25 patients without infarction had detectable MB activity in their serum. Columns connected to a continuous-flow sample line for analyses of the eluting stream without further modification produced satisfactory results.

Chromatography, Gel↗

Angular deformity of the lower extremity in children with renal osteodystrophy.

We have treated 15 children with end-stage renal disease (ESRD), renal osteodystrophy, and genu valgum in the last 22 years. In a retrospective review, we determined that periods of metabolic instability, best characterized as an alkaline phosphatase of 500 U for at least 10 months, were associated with progression of deformity. Histomorphometric bone biopsy provided information that proved essential for effective evaluation and treatment in this group. Complications of corrective osteotomy were related to perioperative metabolic instability. A surgical treatment protocol is described, emphasizing preoperative assessment by histomorphometric bone biopsy and multimodal medical management to maintain metabolic stability perioperatively.

Adolescent↗

Use of C-terminal parathyroid assays in a large metropolitan hospital.

The use of C-terminal parathyroid (C-PTH) assays, performed at a commercial laboratory, was evaluated for one year at Charity Hospital, New Orleans. Of 72 patients, the most frequent diagnosis was primary hyperparathyroidism (1 degree HPT) (n = 17, 24 percent), followed by malignancy (n = 15, 21 percent), chronic renal disease (n = 10, 14 percent), and thiazide diuretics (n = 5, 7 percent). In the 1 degree HPT group, all were hypercalcemic (mean serum calcium, 11.6 ml per dL) and had elevated C-PTH. Patients with malignancy had higher mean serum calcium levels than patients with 1 degree HPT. Three patients with malignancy had elevated C-PTH; two had suspected coexisting 1 degree HPT and neoplasm; and one had suspected pseudohyperparathyroidism. Patients with chronic renal disease undergoing dialysis treatment had the highest C-PTH recorded (all had elevated C-PTH) but only 50 percent were hypocalcemic. Three of the five patients on thiazide diuretics had increased C-PTH, indicating that the withdrawal of this drug may unmask underlying hyperparathyroidism. Appropriate reasons for ordering C-PTH include evaluation of hypercalcemia (n = 32, 44 percent) or hypocalcemia (n = 12, 17 percent); indicated clinical reasons not included in the hyper- or hypocalcemic groups, including chronic renal disease in patients undergoing dialysis or transplant (n = 5, 7 percent); in suspected 1 degree HPT, (n = 5, 7 percent); and in patients with renal stones (n = 2, 3 percent) or on thiazide diuretics (n = 2, 3 percent). Based on laboratory and clinical criteria, C-PTH assay was appropriately used in 81 percent of the patients surveyed (58/72).

Calcium↗

Should the transfusion trigger and hemoglobin low critical limit be identical?

At this medical center, the transfusion trigger and the hemoglobin low critical limit are identical (< 8.0 g/dL), but should they be the same? To answer this question, over one year all hemoglobin results < 8.0 g/dL (n = 421) were reviewed, physician awareness of and response to various hemoglobin levels were evaluated, and the effect of adopting a lower hemoglobin critical limit assessed. Patients were divided into three groups: (1) 7.5-7.9 g/dL (n = 81); (2) 7.0-7.4 g/dL (n = 53); and (3) < 7.0 g/dL (n = 59). Seventy (86 percent), 47 (89 percent), and 52 (88 percent) patients were transfused in Groups 1, 2, and 3; transfused units, mean (sd), were 2.0 (0.8), 2.3 (1.1), and 2.8 (1.7), respectively. Post transfusion hemoglobin increase, mean (sd) was 2.1 (1.0), 2.4 (1.0), and 3.1 (1.5) g/dL for Groups 1, 2, and 3, indicating an inverse correlation between severity of anemia and number of transfused units and post-transfusion hemoglobin increase. Physicians were aware of anemia for all patients in Groups 1 and 2, but three patients in Group 3, not clinically anemic, had erroneous results (improperly collected specimens). Physicians randomly surveyed (n = 20) indicated that the hemoglobin critical limit could be lowered without adverse clinical consequence. A lower hemoglobin critical limit of 7.5 and < 7.0 g/dL would lead to a 52 percent and 77 percent decrease in phone calls for physician notification. The medical center has now lowered the critical limit for hemoglobin to < 7.0 g/dL. The transfusion trigger and the low critical limit for hemoglobin are distinct entities, need not be identical, and represent a balance between the need for transfusion response and the need to be aware of a highly abnormal lab result.

Anemia↗

Carbon monoxide in firemen before and after exposure to smoke.

A statistically significant difference was found between the mean baseline carboxyhemoglobin of non-smoking firemen (COHb 2.53, sd = 1.05, n = 32) and smoking firemen (COHb 5.54, sd = 2.61, n = 26). A consistent increase in mean COHb levels after exposure to smoke was seen in both non-smoking (4.41 sd = 2.95, n = 7) and smoking men (8.74, sd = 5.66, n = 11), but the mean increase in these two groups was statistically significant only at the 90 percent level (t = 1.85, df = 16, p less than 0.1).

Adult↗