A novel action of activin A: stimulation of insulin secretion in rat pancreatic islets

The present study was conducted to examine an action of activin A on insulin secretion from rat pancreatic islets. In a batch incubation system, activin A stimulated insulin secretion in a dose-dependent manner at concentrations higher than 1 nM. Furthermore, activin A greatly potentiated glucose-induced insulin release. When islets were perifused with 1 nM activin A, insulin secretion was barely affected in this system. However, the insulin response to 16.7 mM glucose was greatly enhanced. Both the first and second phases of insulin response were enhanced by 1 nM activin A. These results indicate that, in addition to its known actions on pituitary-gonadal and hematopoietic systems, activin A modulates the function of pancreatic islets and stimulates insulin secretion.     

Establishment of a new hereditary-cataract mouse (CSM) strain derived from SENCAR mouse

A mouse representing a new hereditary cataract strain was found in a mouse colony and a new line was established strain CSM. These mice were investigated genetically, histologically and biochemically. The results suggested that this cataract was apparently inherited through two recessive autosomal genes. Histologically the denucleation process of lens fibers was abnormal and small vacuoles appeared in the equatorial region of the lens cortex at 12 days. Biochemically, insoluble protein and sodium increased in the lens with age.     

Increased erythrocyte catalase activity in patients with hyperthyroidism

Levels of human erythrocyte catalase activity were determined in 38 patients with thyroidal dysfunction. In patients with hyperthyroidism, erythrocyte catalase activities were found to be higher than the levels of normal subjects (P less than 0.001). In hypothyroidism, erythrocyte catalase activities were of the same order as those of normal subjects. Significantly high positive correlation was found between erythrocytes catalase activity and the levels of thyroxine (r = 0.5794, n = 36, P less than 0.001), and slight positive correlation was detected between catalase activity and the levels of triiodothyronine (r = 0.3978, n = 33, P less than 0.05). A decreased erythrocyte catalase activity was observed when erythrocytes lysate was incubated with thyroid hormones. It was suggested that erythrocyte catalase activity had close relationship with thyroid state, however, direct effect of thyroid hormones were not observed on erythrocyte catalase assay system in vitro.     

Immunohistochemical studies of the serotonergic supraependymal plexus in the mammalian ventricular system, with special reference to the characteristic reticular ramification

Distributional and morphological features, especially characteristics of the ramification of serotonin-containing supraependymal fibers (SEF), were studied in the ventricular systems of mammals (mouse, rat, guinea pig, rabbit, cat, dog, monkey) by means of a modified peroxidase antiperoxidase technique, using antiserotonin antiserum prepared in our laboratory. SEF were present in all ventricular systems, except on the third ventricle floor and in the choroid plexus. The density of SEF was higher in the smaller species. In the rat, light- and scanning electron microscopical SEF were almost completely abolished 1 week after intraventricular administration of 5,6-dihydroxytryptamine. Ramification of SEF was complicated; the SEF formed a true network with frequent anastomosing. In the ventricular system of rats rendered hydrocephalic by kaolin administration, the mode of axonal branching in the supraependymal plexus could best be analyzed by the scanning electron microscope because the meshes of the plexus were spread out.     

Phosphorylation of carnitine palmitoyltransferase and activation by glucagon in isolated rat hepatocytes

Effects of glucagon and forskolin on the phosphorylation and changes of activity of carnitine palmitoyltransferase (CPT) have been studied in isolated rat hepatocytes using anti-CPT immunoglobulin. When the activity was determined in lysed hepatocytes after glucagon or forskolin treatment, it was found to be stimulated 30-80% mainly through increased affinity for palmitoyl-CoA. By SDS electrophoresis of the immunoprecipitates, CPT subunit (Mr 69000) was noted to be phosphorylated 4-5-fold with glucagon (1.2 X 10(-7) M) and forskolin (0.1 mM) over control. These results indicate that hepatic ketogenesis is regulated with glucagon by phosphorylation of CPT through cAMP-dependent protein kinase.     

Homeostatic Regulation of Membrane Potential by an Electrogenic Ion Pump against Change in the K+ Concentration of the Extra- and Intra-Organ Perfusion Solutions

The dependence of membrane potentials on changes in the extra-cellularK⁺ concentration [K⁺]_e was investigated in potato tuber sliceswith dripping perfusion, and in growing Vigna hypocotyl segmentswith pressurized intra-organ perfusion methods. Only under anoxiawere the membrane potential of potato tuber slices and the electricpotential difference between the parenchyma symplast and xylem(V_px) of Vigna hypocotyl segments depolarized markedly (46 mVand 42 mV/log[K⁺]_e unit, respectively) with increasing [K⁺]_eabove the critical values. The electric potential differencebetween the parenchyma symplast and organ surface (V_ps of thehypocotyl segments remained nearly unchanged up to 30 mEq [K⁺]_e.Under highly aerobic conditions the membrane potentials wererelatively independent of [K⁺]_e except at very high K⁺ concentrations.V_ps showed even hyperpolarization with the increasing KCl concentrationin the perfusion solution that is not in direct contact withthe surface membrane of the parenchyma symplast. The respiration-dependentelectrogenic components of the membrane potentials regularlyincreased with the increasing [K⁺]_e. A voltage-dependent homeostaticcontrol of membrane potential is discussed. (Received August 13, 1984; Accepted December 21, 1984)     

Characteristics of angiotensin II-, K+- and ACTH-induced calcium influx in adrenal glomerulosa cells. Evidence that angiotensin II, K+, and ACTH may open a common calcium channel

The characteristics of angiotensin II-, K+-, and adrenocorticotropin (ACTH)-induced calcium influx were studied in isolated adrenal glomerulosa cells. Basal calcium influx rate is 0.64 +/- 0.09 nmol/min/mg of protein. Addition of angiotensin II (1 nM) causes a rapid 230% increase in calcium influx rate. This angiotensin II-induced calcium influx is sustained and is rapidly reversed by angiotensin II antagonist, [Sar1,Ala8]angiotensin II. Addition of either K+ or ACTH (1 nM) causes a 340 or 160% increase, respectively, in the rate of calcium influx. The effect of either angiotensin II, K+, or ACTH on calcium influx is dependent on extracellular calcium. The apparent Km for calcium is 0.46, 0.35, and 0.32 mM, respectively. When the extracellular concentration of K+ is 2 mM, neither angiotensin II nor ACTH stimulates calcium influx. Conversely, when extracellular K+ is increased to 6 mM, both angiotensin II and ACTH cause a greater stimulation of calcium influx than at 4 mM K+. When extracellular K+ is increased to 10 mM, calcium influx is 360% of the basal influx seen at 4 mM K+, and neither angiotensin II nor ACTH further stimulates the influx rate. Nitrendipine (1 microM) blocks both angiotensin II- and K+-induced calcium influx completely. In contrast, 10 microM nitrendipine does not completely block ACTH-induced calcium influx. The calcium channel agonist, BAY K 8644, also stimulates calcium influx; 10 nM BAY K 8644 leads to a rate of calcium influx which is 185% of basal. This BAY K 8644-induced increase in calcium influx and that caused by either angiotensin II or ACTH are additive. In contrast, BAY K 8644 has more than an additive effect on the calcium influx when paired with 6 mM K+. These results suggest that angiotensin II, K+, and ACTH stimulate calcium influx via a common calcium channel but act by different mechanisms to alter its function.     

Congenital absence of flexor pollicis longus without hypoplasia of thenar muscles

A 7-year-old girl who was unable to flex her left thumb at the interphalangeal joint proved to have an extremely hypoplastic flexor pollicis longus with normal thenar muscles, which is very rare. The flexor digitorum superficialis of the ring finger was transferred to the inserting portion of the flexor pollicis longus tendon with good results. The patient's cooperation seems to be a factor determining the prognosis.     

Glycolipid composition of ascitic fluids from patients with cancer

The glycolipid composition of ascitic fluids from nine patients with cancer and one pleural effusion from a hepatoma patient was studied. Glucosylceramide, lactosylceramide, globotriaosylceramide, and globotetraosylceramide were found in all samples and also in normal human serum. These glycolipids accounted for more than 90% of the neutral glycolipid fraction and the composition in ascitic fluids was similar to that in normal human serum. From ascitic fluids, several minor glycolipids, which could not be detected in normal human serum, were isolated and characterized by exoglycosidase treatment. Lactoneotetraosylceramide was found in eight samples of ascitic fluids, and globopentaosylceramide was detected in two samples from hepatoma and one from pancreatic cancer. A fucolipid which was converted to lactoneotetraosylceramide by alpha-L-fucosidase treatment was recognized in two samples from hepatoma patients. In the ganglioside fraction, GM3 was the predominant component both in normal human serum and in ascitic fluid. The GM2 content in ascitic fluids was much higher than that in normal human serum. From these results, lactoneotetraosylceramide and GM2 are possible candidates as cancer markers, because they seemed to be derived from cancer tissues by shedding.     

Radioimmunoassay of urinary 3 beta-hydroxy-5-cholenoyl glycine in hepatobiliary disease

A radioimmunoassay for 3 beta-hydroxy-5-cholenoyl glycine in human urine has been developed. The antiserum was elicited with the antigen in which the steroid hapten is linked to a bovine serum albumin through the C-19 position. The [125I]-tyrosine derivative of the hapten was used as radioligand. The standard curves were linear ranging from 10 to 320 ng/mL. The cross-reactivities with other bile acids were not detectable and below 0.3% with cholesterol. Sample preparation includes extraction of 3 beta-hydroxy-5-cholenoyl glycine from urine and solvolysis of the sulfates--main form present in urine. Urinary excretion of 3 beta-hydroxy-5-cholenoyl glycine was 0.373 +/- 0.133 mumol/day in healthy adults. Urinary excretion of 3 beta-hydroxy-5-cholenoyl glycine increased in chronic liver dysfunction, hepatoma and obstructive jaundice in this order.