Spectrofluorometric assay of gentamicin in serum.

A spectrofluorometric method has been developed for the assay of gentamicin in serum. The fluorogen of this reaction is the Zn2+ chelate of N-pyridoxylidene gentamicin. The ratio of gentamicin to Zin is 1.0. Interfering compounds in serum are removed by chromatography on Bio-Rex 70. Recovery of added gentamicin is between 90 and 100%. Determination of gentamicin levels in patient sera correlate well with those done by bioassay. This assay is relatively fast (about 1 h), and requires 1.0 ml of serum. It also can be applied to the determination of other deoxystreptamine antibiotics such as kanamycin and tobramycin.

Determination of the gamma G/gamma A ratio in homozygous beta-thalassemic patients among a Lebanese population.

The gamma G/gamma A ratio was determined on 50 cord blood samples from normal newborns and in 28 beta-thalassemia homozygotes among the Lebanese population, using electrophoresis on acrylamide-bisacrylamide gels containing Triton X-100, urea, and 2-mercapto-ethanol. 2-Mercapto-ethanol was found to be the most effective reducer, giving good resolution and a clean background. As the concentration of Triton X-100 was critical in this study, a concentration of 500 microliters of Triton X-100/25 ml of reaction mixture was found to be optimal. In our 50 cord blood samples, the mean total Hb was 20 g/dl, with a range of 12-26. The mean fetal Hb (HbF) level was 64%, and the range 50-90%. The mean value for gamma G/gamma G + gamma A was 0.75. All beta-homozygotes had an elevated HbF, ranging from 7.7-99.3%, and their mean gamma G/gamma G + gamma A was 0.64. Only two out of 28 had gamma G/gamma G + gamma A ratio of 0.5; in the rest it was 0.60 or greater. This may be due to the greater resistance of erythrocytes with higher HbF and higher gamma G/gamma A destruction.

Isolated adipic aciduria.

Adipic acid can appear, in combination with other dicarboxylic acids, in the urine of patients in a number of underlying metabolic diseases. A child with seizures and mental retardation of unknown etiology who was found to have elevated isolated adipic aciduria on investigation for metabolic diseases is reported. A dietary artifact was suspected, and the adipic aciduria resolved after the child was kept on a specific restricted diet for 3 days. This is the third report of isolated adipic aciduria secondary to food. Findings confirm the previous reports of dietary origin of isolated adipic aciduria and should alert clinicians to such artifact before committing patients to unnecessary treatments.

Serum lipids and lipoprotein profile in a selected group of normal Lebanese subjects.

Serum triglycerides, total cholesterol, LDL, VLDL and HDL cholesterol levels were determined in a group of 442 apparently healthy Lebanese subjects after a 12 hr fast. Age-dependent increase was noted for total cholesterol, LDL cholesterol and triglycerides. On the other hand, VLDL and HDL cholesterol levels were age-independent. In addition, sex differences were noted for HDL cholesterol only. Our findings for total cholesterol and triglycerides are comparable with values reported by other authors, while values for LDL and VLDL are significantly different.

Hyperlipoproteinemia with albumin-lipid complex: a novel type of hyperlipoproteinemia associated with insulin-resistant diabetes mellitus.

We describe a new phenotype of hyperlipoproteinemia in two members of a family with a high degree of consanguinity. Both have a history of uncontrolled diabetes mellitus without ketoacidosis, and a family history of coronary artery disease at a relatively early age. A high degree of insulin resistance was found. The abnormal lipoprotein(s) has alpha-lipoprotein mobility on cellulose acetate electrophoresis and has a relative density of less than 1.006 as determined by ultracentrifugation of serum collected after a short fast. The fraction isolated by ultracentrifugation contains about half of the serum cholesterol and triglycerides and most of the phospholipids; the major protein component is albumin. Immunoelectrophoresis showed low concentrations of beta-lipoproteins in both sera, and two abnormal precipitin bands against monospecific antiserum to antilipoprotein A; a third member of the family showed only one abnormal precipitin band against the same antibody. We tentatively propose an abnormal gene(s) as the underlying mechanism. The insulin-resistant diabetes mellitus, probably inherited separately, may aggravate the hyperlipidemia.

Receptors of prostaglandin E1 in the plasma membrane of normal liver. Effect of membrane fluidity on PGE1 binding.

Prostaglandin E1 binding to isolated liver plasma membrane as a function of PGE1 concentration showed saturability of the binding sites at PGE1 concentration of 2.5 X 10(-4) M. Scatchard analysis revealed heterogeneous population of binding sites with a binding capacity of 470 and 990 nmol/mg protein for the higher and lower affinity binding sites respectively. PGE1 binding to liver plasma membrane was progressively and significantly decreased (P less than 0.01) as the incubation temperature was reduced to 22 degrees and 4 degrees C. Procaine at 1 X 10(-3) M concentration showed a significant decrease (P less than 0.01) in the binding capacity of the liver plasma membrane. Colchicine plus cytochalasin-B inhibited PGE1 binding significantly (P less than 0.01) but their inhibition is not equivalent to that of procaine.

Dopamine receptors in normal and diabetic liver plasma membrane.

Dopamine binding to liver plasma membrane isolated from diabetic livers was significantly reduced (P less than 0.01) as compared to dopamine binding to the normal membrane. Diabetic membranes exhibited a significant decrease (P less than 0.01) in specific dopamine binding as compared to the normal membranes; whereas no significant change (P less than 0.5) was noticed in the nonspecific binding patterns. The dopamine binding capacity of both membranes is temperature dependent. Procaine at different concentrations inhibited significantly (P less than 0.01) dopamine binding to normal and diabetic membranes. Treatment of the normal and diabetic membranes with insulin showed a 33% decrease in the binding capacity of the normal and 42% decrease in the binding capacity of the diabetic membrane.

Effect of enzymatic digestion on phenylalanine transport across the small intestine.

Phenylalanine accumulation in mucosal strips isolated from rat small intestine was significantly inhibited (P less than 0.01) after preincubation with trypsin, chymotrypsin, phospholipase D and neuraminidase. Unidirectional phenylalanine influx across the small intestine was significantly reduced (P less than 0.01) when the mucosal strips were preincubated with the above mentioned enzymes. Intestinal cell water and volume were not significantly changed (P greater than 0.6) when the intestinal tissues were preincubated with these enzymes.

Cysteamine-induced duodenal ulcer: effects on calcium absorption across rat duodenum.

The effect of cysteamine-induced duodenal ulcers on calcium transport across rat duodenum was investigated. Intracellular calcium accumulation measured after 24 hr and 3 days of cysteamine injection showed a significant increase (P less than 0.001) in the duodenal strips isolated after 3 days with no change noticed in those isolated after 24 hr, although the morphological changes in both were very similar. The relationship between increasing calcium concentration in the incubation medium and intracellular calcium concentration is a saturable process that conforms to the Michaelis-Menten type of kinetics. The average maximal flux (Vmax) increased from 8.93 nmole/hr-gdw in normal to 12.5 nmole/hr-gdw in 3-day-ulcerated rats, with no apparent change in the Michaelis constant (Kt) (0.8 mM). Unidirectional influx of calcium across the mucosal membrane was significantly increased (P less than 0.001) in 3-day-ulcerated duodenum suggesting that the increase in calcium transport could be due to the activation of the active step at the mucosal border.

Enzymatic inhibition of lysine transport across the small intestine in vivo.

1. Trypsin, at different concentrations, significantly inhibited lysine absorption (P less than 0.05) in a dose-dependent pattern. 2. Maximum inhibition equivalent to 35% below control value was reached with 10 micrograms/ml (100 BAEE units) trypsin with a non-reversible inhibitory effect. 3. Chymotrypsin at 10 micrograms/ml produced a significant decrease (P less than 0.05) of lysine absorption although it did not exceed 5%. Perfusion of both enzymes did not show an additive inhibitory effect. 4. Lysine absorption showed a 39% decrease with 10 micrograms/ml trypsin and 1 X 10(-4) M ouabain, whereas ouabain alone produced 34% inhibition. 5. Lysine absorption showed a 71% decrease with 10 micrograms/ml trypsin in a sodium-free medium, and 70% inhibition with Na-free medium alone. 6. The inhibition of lysine absorption after trypsin treatment could be due to inhibition of the active component of lysine transport.

Cytoskeletal control of calcium absorption across the rat small intestine.

1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat small intestine was investigated. The results obtained show the following: 2. Colchicine and cytochalasin-B at different concentrations inhibited significantly (P less than 0.001) calcium accumulation in rat intestinal cells, whereas procaine at different concentrations increased significantly (P less than 0.001) calcium accumulation in the rat small intestine. 3. Unidirectional influx of calcium across the rat small intestine was significantly inhibited (P less than 0.01) in the presence of colchicine and cytochalasin-B in the preincubation medium. Procaine, on the other hand, caused a significant increase (P less than 0.01) in the unidirectional influx of calcium across the rat intestinal cells. 4. The cell water content was not altered in the presence of the different drugs indicating that the changes in calcium transport across the rat intestinal cells are not due to alterations in the structure of the cell membrane.