Ernest Schoffeniels

Pheromones are involved in the control of sexual behaviour in birds.

high degree. The high degree of acidification and the carbon assimilation of this crop plant as evidenced from the present investigation provide the physiological basis for its known survival under a semiarid tropical environment. The fact that the CAM behavior has been observed for the first time in this field crop should lead to further survey of other tropical crops. This investigation was partly supported by the Indian Council of Agricultural Research, New Delhi. Thanks are due to Prof. Dr. M. Kluge, Darmstadt, for his helpful comments. Received September 28, 1978

Sex differences in the chemical composition of uropygial gland waxes in domestic ducks

Abstract Sexual differences in the chemical composition of the uropygial gland waxes in domestic ducks have been detected before the nesting period. 3-Hydroxy fatty acids containing diester waxes and significant differences in the composition of the fatty acid and alcohol moieties of the monoester waxes occur during February–June only in the female preen wax. Males as well as ducklings, however, show constant wax patterns. Moreover, no significant influence on wax composition of testosterone or estradiol, respectively in male or female ducklings could be verified.

Determination of Thiamin and Its Phosphate Esters in Cultured Neurons and Astrocytes Using an Ion-Pair Reversed-Phase High-Performance Liquid Chromatographic Method

A sensitive method, based on fluorescence detection, for the determination of thiamin derivatives after precolumn derivatization is described. The separation is achieved on a PRP-1 column using ion-pair reversed-phase HPLC. This method is especially well adapted to the detection of thiamin triphosphate in complex mixtures such as tissue extracts. The detection limit for TTP is 50 fmol. The contents of thiamin derivatives were determined in primary cultures of rat cerebellar granule neurons and cerebral astrocytes. The amount of TTP is about five times higher in neurons than in astrocytes. Thus in rat brain TTP seems to be essentially associated with neurons and the intracellular concentration is estimated to be about 0.2 microM. Our results suggest the existence, in nerve cells, of specific regulatory mechanisms not related to the blood-brain barrier and responsible for the maintenance of thiamin homeostasis in brain.

Thiamine triphosphate activates an anion channel of large unit conductance in neuroblastoma cells

In neuroblastoma cells, the intracellular thiamine triphosphate (TTP) concentration was found to be about 0.5 μm, which is several times above the amount of cultured neurons or glial cells. In inside-out patches, addition of TTP (1 or 10) μm to the bath activated an anion channel of large unit conductance (350–400 pS) in symmetrical 150 mm NaCl solution. The activation occurred after a delay of about 4 min and was not reversed when TTP was washed out. A possible explanation is that the channel has been irreversibly phosphorylated by TTP. The channel open probability (Po) shows a bell-shaped behavior as a function of pipette potential (Vp). Po is maximal for −25 mV<Vp<10 mV and steeply decreases outside this potential range. From reversal potentials, permeability ratios of PCl/ PNa = 20 and PCl/Pgluconate = 3 were estimated. ATP (5 mm) at the cytoplasmic side of the channel decreased the mean single channel conductance by about 50%, but thiamine derivatives did not affect unit conductance; 4,4′ -diisothiocyanostilbene-2,2′-disulfonic acid (0.1 mm) increased the flickering of the channel between the open and closed state, finally leading to its closure. Addition of oxythiamine (1 mm), a thiamine antimetabolite, to the pipette filling solution potentiates the time-dependent inactivation of the channel at Vp=−20 mV but had the opposite effect at +30 mV. This finding corresponds to a shift of Po towards more negative resting membrane potentials. These observations agree with our previous results showing a modulation of chloride permeability by thiamine derivatives in membrane vesicles from rat brain.

The cationic composition of incubated cerebral cortex slices.

Abstract— 1. A new type of cutting table is described. It makes use of the elastic properties of a nylon thread, 0·08 mm thick, in which longitudinal vibrations greatly increase its ability to cut through soft tissue. Two slices of cerebral cortex may thus be obtained within 3–4 min after the death of an animal.

Metabolism of thiamine triphosphate in rat brain : correlation with chloride permeability

Abstract: Our results show that a net synthesis of thiamine triphosphate (TTP) can be demonstrated in vitro using rat brain extracts. The total homogenate was preincubated with thiamine or its diphosphate derivative (TDP), centrifuged, and washed twice. With TDP (1 mM) as substrate, a 10‐fold increase in TTP content was observed in this fraction (nuclear fraction, membrane vesicles). A smaller, but significant, increase was observed in the P2 fraction (mitochondrial/synaptosomal fraction). In view of the low TTP content of our fractions, it was carefully assessed that authentic TTP was being formed. Incorporation of radioactivity from [β‐32P]TDP and [γ‐32P]ATP in TTP suggests that these two compounds are its precursors. Furthermore, TTP synthesis was inhibited by ADP and relatively low concentrations of Zn2+. These results suggest that TTP synthesis is catalyzed by an ATP:TDP transphosphorylase rather than by the cytoplasmic adenylate kinase that may be present in the vesicles. After osmotic lysis of the vesicles at alkaline pH, TTP was recovered in protein‐bound form. Concomitantly, a soluble thiamine triphosphatase, with alkaline pH optimum, was also released from the vesicles. No net synthesis could be obtained in the cytosolic fraction or in detergent‐solubilized systems. Like TTP synthesis, chloride permeability of the vesicles was increased when the homogenate had been incubated with thiamine and particularly with TDP. Our results suggest a regulatory role of TTP on chloride permeability, but the target remains to be characterized.

Thiamine triphosphate and membrane-associated thiamine phosphatases in the electric organ of Electrophorus electricus

The main electric organ of Electrophorus electricus is particularly rich in thiamine triphosphate, which represents 87% of the total thiamine content in this tissue. The thiamine pyrophosphate concentration, however, is very low in the eel electric organ and skeletal muscle as compared with other eel or rat tissues. Furthermore, electroplax membranes contain a whole set of enzymes responsible for the dephosphorylation of thiamine tri‐, pyro‐, and monophos‐phate. Thiamine triphosphatase has a pH optimum of 6.8 and is dependent on Mg2+. The real substrate of the enzyme is probably a 1:1 complex of Mg2+ and thiamine triphosphate. Thiamine pyrophosphatase is activated by Ca2+. The apparent Km for thiamine triphosphate and Vmax are found to be, respectively, 1.76 mM and 5.95 nmol/mg of protein/min. Thiamine triphosphatase activity is inhibited at physiological K+ concentrations (up to 90 mM) and increasing Na+ concentrations (50% inhibition at 300 mM). ZnCl2 (10 mM) inhibits 90% of the enzyme activity. ATP and ITP are also strongly inhibitory. No significant effect of neurotoxins is seen. Membrane‐associated thiamine triphosphatase is affected differently by proteolytic enzymes and is partially inactivated by pretreatment with phospholipase C and neuraminidase. The physiological significance of thiamine triphosphatase is discussed in relation to a specific role of thiamine in the nervous system.

Action de la vératrine, de la cocaïne et de la stimulation électrique sur la synthèse et sur le pool des acides aminés de la chaîne nerveuse ventrale du homard

Resume 1. 1. The synthesis of amino acids from [ 14 G 6 ]glucose and [I- 14 C]pyruvate in the ventral nerve cord of the lobster ( Homarus vulgaris L.) has beeb studied under the following conditions: in the presence of veratrine sulfate (4 μM), cocaine hydrochloride (4 mM) and during electrical stimulation. Our results show that veratrine and electrical stimulation increase the turn-over rate of the following amino acids: alanine, glycine, glutamic acid and aspartic acid. Cocaine brings about a decrease in the turn-over rate of dicarboxylic acids (glutamic acid and aspartic acid) and an increase in the labelling of alanine and glycine. Our experimental conditions are without effect on the labelling of arginine and lysine. These results are discussed in the light of the various metabolic pathways envisaged in a previous paper. Veratrine and electrical stimulation seem to be without effect on the rate of pyruvate amination. On the contrary, they seem to affect the metabolic pathways involving hydroxypyruvate or the decarboxylation in C-1 of pyruvate. Moreover, it would appear that these experimental conditions increase the rate of entry of pyruvate into the Krebs cycle. Concerning the effects of cocaine, our results indicate that it inhibits the access of pyruvate to the Krebs cycle. 2. 2. Contrary to that observed with cocaine, veratrine sulfate and electrical stimulation affect the cationic composition of the nerve cord (increase in Na concentration, decrease in K concentration). 3. 3. The pool of intracellular free amino acids is unaffected by veratrine. Thus veratrine seems to increase the turn-over rate of various amino acids. This conclusion is substantiated by the fact that the ammoniac content increases after application of veratrine. Electrical stimulation leads to an increase in the total concentration of the pool of free amino acids. 4. 4. The results are discussed within the framework of the osmoregulatory phenomena in aquatic invertebrates. A hypothesis concerning the mechanisms used by euryhaline invertebrates to adjust the intracellular concentration to that of the internal medium is proposed.

Le transport actif d'acides aminés au niveau de l'épithélium intestinal isolé de la tortue grecque

Resume An experimental method is described, which permits the study, on an isolated portion of the intestinal epithelium, of the flux of ions as a dependent variable of different parameters: potential difference through the epithelium, short-circuiting current, influx (flux of ions from external to internal medium), outflux (flux of ions from internal to external medium), and so on. This method has the advantage of utilizing an epithelium which has been cleared of muscular tissue by dissection; it also offers the possibility of replacing solutions rapidly on both sides of the epithelium. The study of the flux of amino acids shows that glycine, l -alamine and l -histidine are actively transported through the small intestine, while l -glutamic acid behaves passively; l -glutamic acid, glycine and l -histidine move passively through the colon. The results obtained show also that the permeability to amino acids is always higher in the small intestine than in the colon. In addition, it has been shown that l -alanine inhibits pratly the influx of glycine through the small intestine.

Origine des potentiels bioélectriques de l'épithélium intestinal de la tortue grecque

Abstract Potential difference measured between the lumen and the serosal side of the intestinal epithelium varies according to the level considered, usually ranging about a few mV in the small intestine and ranging about 20–50 mV in the colon, for the species we studied. The comparative study of the fluxes of Na+ through the isolated epithelium of the small intestine and the colon of the Greek tortoise shows that in both tissues the is a net flux of Na+ from the lumen to the serosal side. The values of fluxes are more important in the small intestine than in the colon though net fluxes are very similar. 2,4-Dinitrophenol inhibits partially the influx and the outflux of Na+ in the small intestine. It inhibits only the influx in the colon. The potential difference accross the small intestine is dependent on the concentration of Na+ and K+ in the solutions bathing both sides of the epithelium. The potential difference measured accross the colon depends on the concentration of Na+ in the solution in contact with the mucosal side of the epithelium while it depends on concentrations in Na+ and K+ in the solution touching the serosal side. These results allow us to conclude that cellular membranes forming both sides of the small intestine are permeable to Na+ and K+ at one and the same time. In the case of the colon, cellular membranes forming the mucosal side of the epithelium are permeable to Na+, while cellular membranes forming the serosal side are permeable to Na+ and K+. These results show also that the permeability of the intestinal epithelium to K+ is variable and is always less important than the permeability to Na+.