Citations

Dopamine-β-hydroxylase activity is released into the blood with catecholamines from the adrenal medulla and sympathetic nerves. This enzyme activity has been measured in the blood of 317 normal children and 227 normal adults. A significant sibling-sibling correlation of serum dopamine-β-hydroxylase values was found in the 94 sibling pairs tested. Frequency distributions of serum enzyme values in both children and adults suggest the existence of two populations with regard to serum activity of this enzyme.

Dopamine-β-hydroxylase activity accumulated above a ligature on biopsy samples of normal human sural nerves incubated in vitro. The rate of accumulation indicated that this enzyme was transported distally at a velocity of 2 millimeters per hour. Axoplasmic transport of dopamine-β-hydroxylase was greatly reduced in sural nerves from a few patients with peripheral neuropathies.

In a rare myopathy muscle fibers contained myriad lipid-filled vacuoles. Homogenates of the patient's muscle oxidized fatty acids more slowly than normal (11 controls). Addition of carnitine increased the oxidation rate with the patient's muscle to the level attained by the controls with carnitine. In five separate muscle samples from the patient the mean carnitine level was less than 20 percent of that observed in 42 controls. Carnitine palmityl transferase and palmityl thiokinase levels in the patient's muscles were not depressed. The present case represents the first recognized instance of carnitine deficiency in human skeletal muscle.

Serum immunoreactive parathyroid hormone (IPTH) is normal in patients with X-linked hypophosphatemic rickets who are not treated with phosphate salts. Phosphate raises IPTH in these patients. Endogenous IPTH does not influence the existing defect in tubular reabsorption of phosphate in male patients.

The titers of antibodies to the benzylpenicilloyl antigenic determinant are increased with specific antiserum to immunoglobulin D, as shown by the enhancement method. This increase in titer is blocked by purified immunoglobulin D protein but not by immunoglobulins of the other four classes.

Two strains of mice (C-57 B1 and DBA) were given skin allografts from Swiss ICR/HA mice and were treated with varying doses of concanavalin A; the dosage ranged from only two injections of 25 micrograms during the experiment to daily doses of 1000 micrograms intraperitoneally. Immunosuppression was present at all dosages, the most prolonged and consistent effect being observed at 300 micrograms per day. Grafts survived for 14 to 21 days at this dosage compared to 4 to 9 days for controls.

In thin bundles of dog ventricular myocardium, a slow inward current (distinct from the sodium inward current) could be recorded under voltage-clamp conditions. This inward current was influenced by changes in external calcium concentration, but it was not dependent on external sodium concentration. Therefore, this current which contributes an appreciable amount of charge transfer during the plateau of the action potential, is carried by calcium ions. In sodium-free solution, the flow of calcium ions into the fiber is directly related to activation of contraction. In sodium-containing solution, however, calcium inward current serves primarily to fill up some intracellular stores from which calcium can be released by moderate depolarization.

Membrane currents were measured in thin bundles of dog ventricular myocardium under voltage-clamp conditions. A rather large initial inward current which had an equilibrium potential at about + 55 millivolts could be recorded. When the external sodium concentration was reduced, the equilibrium potential for this current was shifted by the amount predicted theoretically for a current carried solely by sodium ions. The size of the sodium inward current ( I Na ) was largely dependent on the preceding membrane potential. The I Na was completely inactivated if the membrane potential was as low as -45 millivolts. Sodium ions are the main carrier of charge during the rapid depolarization phase of the action potential.

Among the factors that can govern the relative rates of mitochondrial oxidation of isocitrate by means of the isocitrate dehydrogenases linked to diphospho- and triphosphopyridine nucleotides are the intramitochondrial concentrations of these nucleotides. Yeast mitochondria contain enzymes that can alter the ratio of these pyridine nucleotides by interconverting them. A diphosphopyridine nucleotide kinase catalyzes the formation of triphosphopyridine nucleotide from diphosphopyridine nucleotide and adenosine triphosphate; a phosphatase converts triphosphopyridine nucleotide to diphosphopyridine nucleotide. Both reactions are more active with the reduced forms of the pyridine nucleotide coenzymes. These studies suggest that the activity of the mitochondrial triphosphopyridine-nucleotide-linked isocitrate dehydrogenase may be regulated by a cyclic system of pyridine-nucleotide interconversions involving triphosphopyridine nucleotide synthesis and breakdown.

It has been demonstrated in man that mechanically induced shifts of the retinal image without change in total luminous flux evoke a parieto-occipital electrical response (lambda waves). The technique provides a simple method of quantifying responses in the visual system without complication by voluntary movements and their associated readiness potentials. The observation contradicts the view that lambda waves are directly concerned with mechanisms preventing blur during eye movement.