Cardiopathic effects of dichloroacetate in the fetal Long-Evans rat.

Dichloroacetic acid (DCA) is a by-product of the chlorine disinfection of water and may occur in treated water at levels exceeding 100 micrograms/L. Previous studies revealed teratogenic effects, particularly heart malformations, at high doses (900-2,400 mg/kg given on days 6-15 of pregnancy). In a series of three studies, groups of 7-10 Long-Evans rats were dosed with 1,900 mg/kg of DCA on days 6-8, 9-11, or 12-15; with 2,400 mg/kg on days 10, 11, 12, or 13; and with 3,500 mg/kg on days 9, 10, 11, 12, or 13, in an attempt to determine the most sensitive period and further characterize the heart defect. In a fourth study, six dams were treated with 1,900 mg/kg of DCA days 6-15 of pregnancy, and 56 fetuses were harvested for light microscopy of the heart. Eight control fetuses from four litters were also examined. No heart malformations were seen in the groups treated with 1,900 mg/kg DCA days 6-8 but were present in the group treated on days 9-11 and 12-15, with the higher incidence occurring on days 12-15. Single doses of 2,400 mg/kg DCA given on days 10, 11, 12, or 13 resulted in a much lower incidence of cardiac malformations, which occurred only on days 10 and 12. The high dose of DCA (3,500 mg/kg) did not increase the incidence of heart defects but showed that dosing on day 9 as well as on days 10 and 12 would produce the defect. The defects seen were characterized as high interventricular septal defects (H-IVSD). Light microscopy showed that the defect was caudal to the semilunar valves, with the anterior right wall of the aorta communicating with the right ventricle. Another aspect of the defect is at the level of the semilunar valves, with the right cusp or sinus of Valsalva in communication with the right ventricle. The defects are discussed more fully and methods for further study suggested.     

Sub-compartmentation of the 'cytosolic' glucose 6-phosphate pool in cultured rat hepatocytes

[14C]Glucose release either from endogenous 14C-prelabelled glycogen or from added 14C-labelled glucose 6-phosphate was measured in filipin-treated, permeabilized hepatocytes in 48 h culture. [14C]Glucose output from prelabelled glycogen was not altered by the addition of 5 mM glucose 6-phosphate to the incubation medium. Conversely, [14C]glucose release from 5 mM labelled glucose 6-phosphate was not influenced by different glycogen concentrations in the cells. Moreover, in the permeabilized cells the anion transport inhibitor DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) inhibited only the liberation of [14C]glucose from labelled glucose 6-phosphate but not from glycogen. It is therefore concluded that there exist at least 2 separate, mutually non-accessible glucose 6-phosphate pools in cultured rat hepatocytes, one linked to glycogenolysis and the other to gluconeogenesis.     

Effects of nucleotides and divalent cations on phospholipase activity in Saccharomyces cerevisiae

Divalent cations activate the lysophospholipase and transacylase reactions catalyzed by the same enzymes in the yeast Saccharomyces cerevisiae. The activation was observed at neutral pH, but not at the pH optimum of lysophospholipase/transacylase, near 3.5. Adenine nucleotides, especially AMP and ADP, are strong inhibitors of the same group of enzymes. Half maximal inhibition by AMP was found at a concentration of about 20 M. The inhibition by nucleotides in low concentrations is enhanced by divalent cations.     

Membrane responses to large hyperpolarizations in trabecles and single cells of frog atrium

Atrial trabeculae (studied in voltage-clamping conditions and in the presence of 0.5 mmol/l BaCl2 to abolish gK1) responded to 1 s hyperpolarizations to beyond approximately E = -140 mV (from HP of about E = -80 mV) with an inwardly directed current increasing with time. Quite similar results were obtained with enzymatically dissociated frog atrial cells studied in whole cell voltage clamp with a patch-clamp pipette. This behaviour could be accounted for by assuming the presence of an "if" current at this quite negative range of potentials or by the fact that the cell membrane may undergo reversible electropermeabilization when its potential is brought to values negative to about -140 mV (St?mpfli 1958). When a brief (1 ms) and large (150 mV) hyperpolarization was applied 1 s before the test pulse, an inwardly directed current increasing with time was elicited by test pulses to beyond approximately E = -120 mV. This current was neither abolished in the presence of 1 mmol/l CsCl nor greatly reduced in the absence of Na+ ions, unlike "if" (Di Francesco 1981). We conclude that this current having a time course similar to that of "if" is of different nature and we argue that it might be accounted for by electropermeabilization of the membrane (reversible within about 2.5 min) due to the electrical shock represented by a brief and large hyperpolarization.     

Effects of MET-ENK, substance P and SRIF on the behavior of Hemichromis bimaculatus

Administration of 10 and 30 micrograms methionine-enkephalin (MET-ENK)/g bw (n = 10/dose) affected the propensity towards fighting in H. bimaculatus; 10 micrograms increased, while 30 micrograms decreased the aggressive behavior. MET-ENK also affected a number of behavior patterns displayed by the fish. Moreover, the "wet-dog-shakes" observed suggest that MET-ENK acts on opiate-receptors. Treatment with substance P (SP)/g bw (n = 10/dose) induced chafing movements in the fish slightly. It also decreased fighting and increased biting of the air stone, which is evidence that H. bimaculatus is still aggressive, directing its attacks to different objects. When 4, 8, 12 micrograms somatostatin (SRIF)/g bw (n = 10/dose) were injected, H. bimaculatus stopped fighting for several hours after the onset of treatment, depending on the dosage. Somatostatin reduces blood glucose concentration, causing a sudden stop of aggressive behavior, 0.04, 0.1, 0.6, 1.0 and 3.0 IU prolactin (PRL)/g bw (n = 5/dose) eventually decreased fighting and affected a number of behavior patterns displayed by the fish.     

Antagonistic regulation of the glucose/glucose 6-phosphate cycle by insulin and glucagon in cultured hepatocytes.

Flux through the glucose/glucose 6-phosphate cycle in cultured hepatocytes was measured with radiochemical techniques. Utilization of [2-3H]glucose was taken as a measure of glucokinase flux. Liberation of [14C]glucose from [U-14C]glycogen and from [U-14C]lactate, as well as the difference between the utilization of [2-3H]glucose and of [U-14C]glucose, were taken as measures of glucose-6-phosphatase flux. At constant 5 mM-glucose and 2 mM-lactate concentrations insulin increased glucokinase flux by 35%; it decreased glucose-6-phosphatase flux from glycogen by 50%, from lactate by 15% and reverse flux from external glucose by 65%, i.e. overall by 40%. Glucagon had essentially no effect on glucokinase flux; it enhanced glucose-6-phosphatase flux from glycogen by 700%, from lactate by 45% and reverse flux from external glucose by 20%, i.e. overall by 110%. At constant glucose concentrations cellular glucose 6-phosphate concentrations were essentially not altered by insulin, but were increased by glucagon by 230%. In conclusion, under basic conditions without added hormones the glucose/glucose 6-phosphate cycle showed only a minor net glucose uptake, of 0.03 mumol/min per g of hepatocytes; this flux was increased by insulin to a net glucose uptake of 0.21 mumol/min per g and reversed by glucagon to a net glucose release of 0.22 mumol/min per g. Since the glucose 6-phosphate concentrations after hormone treatment did not correlate with the glucose-6-phosphatase flux, it is suggested that the hormones influenced the enzyme activity directly.     

Germline integration of moloney murine leukemia virus at the Mov13 locus leads to recessive lethal mutation and early embryonic death

Thirteen mouse substrains genetically transmitting the exogenous Moloney murine leukemia virus (M-MuLV) at a single locus (Mov locus) have been derived previously. Experiments were performed to investigate whether homozygosity at the Mov loci would be compatible with normal development. Animals heterozygous at an Mov locus were mated, and the genotype of the offspring was analyzed. From parents heterozygous at the loci Mov1 to Mov12, respectively, homozygous offspring were obtained with the expected Mendelian frequency. In contrast, no homozygous offspring or embryos older than day 15 of gestation were obtained from parents heterozygous at the Mov13 locus. When pregnant Mov13 females at day 13 and day 14 of gestation were analyzed, approximately 25% of the embryos were degenerated. Genotyping revealed that these degenerated embryos were invariably homozygous and the normal appearing embryos were either heterozygous or negative for M-MuLV. These results suggest that integration of M-MuLV at the Mov13 locus leads to insertion mutagenesis, resulting in embryonic arrest between day 12 and day 13 of gestation. It is possible that the Mov13 locus represents a gene or gene complex involved in the early embryonic development of the mouse.     

Quantitative investigations on the effect of pentamethylenetetrazol on the supraoptic neurones in rabbit

Summary Quantitative investigations were made on the effect of convulsant doses of pentamethylenetetrazol (PMT) on the neurones of the supraoptic nucleus in rabbit. In contrast to results reported by other workers, the present investigation yielded statistical evidence for an increase in the number of Gomori-positive elements in the supraoptic nucleus following epileptic seizures induced by PMT. The factors that might be responsible for this phenomenon are discussed. It is pointed out that a satisfactory interpretation cannot be given on the basis of histological findings alone. The problem requires further investigation with other techniques, such as electron microscopy and biochemical methods.Dedicated to Professor Dr. Dr. h.c. H. Spatz on the occasion of his 80th birthday.     

Stereoisomeric flavour compounds XXXV: Chiral aroma compounds of sherry I. Optically pure stereoisomers of solerone and solerole

The enantioseparation of the sherry aroma components 5-oxo-4-hydroxyhexanoic acid γ-lactone (solerone) and 4,5-dihydroxyhexanoic acid γ-lactone (solerole) is achieved, using Chiraspher (Merck) as the chiral HPLC phase and the optical purity ascertained directly by HRGC with heptakis(3-O-acetyl-2,6-di-O-pentyl)-β-cyclodextrin (Lipodex D) as the chiral stationary phase. The absolute configurations of 4,5-dihydroxyhexanoic acid γ-lactones are assigned by ¹H-NMR spectral data of diastereomeric α-methoxy-α-trifluoromethylphenylacetic acid (MTPA) esters, according to Mosher's model. Sensory qualities of the isomers are given.