The hypnogenic effects of delta sleep-inducing peptide (DSIP) analogs: a comparative study in rabbits and rats]

Hypnogenic effects of 3 DSIP analogs with a higher stability against aminopeptidase activity have been studied in rabbits and rats using intraventricular administration (injections and infusions). An analog (D-Ala-2) DSIP augmented slow wave and paradoxical sleep within the 5th, 8th and 11th hours of the recording period. An analog (D-Val-2) DSIP made the same within the 8th and 10th hours, and hexapeptide (D-Ala-2) DSIP (1-6) increased sleep during the 1st, 3rd, and 5th hours. Both nonapeptides augmented sleep in rabbits as well as in rats, though hexapeptide produced this effect in rabbits only, that might be related to some difference in distribution and colocalization of endogenous DSIP-like peptide in the pituitary of two rodent species. It may be suggested that hypnogenic activity of DSIP analogs is determined by the structure of administrated molecule, being mediated by such hormones as GRF and CLIP.     

The facilitation of defensive reactions during food consumption in the snail helix: the participation of glucose and gastrin/cholecystokinin-like peptide]

Molecular and cellular mechanisms of the interrelations between the feeding and defense behaviour were studied in a snail Helix lucorum. The dynamics of defense reactions was investigated in snails with different levels of feeding motivation. Defense reactions were suppressed in hungry snails, while 15-20 min after the beginning of food intake they were facilitated. The facilitation depended on a duration of starvation. Injection of 0.5 ml of 5 mM glucose solution (up to the glucose level in the haemolymph of a food satiated snail, 1.6-2.0 mM) or injections of 20-30 ng of synthetic analogues of the gastrointestinal peptides (pentagastrin of octapeptide cholecystokinin, CCK-8) facilitated the defense reaction in a hungry snail. Parameters of the facilitation were similar to those in the period of food intake. Activity of the command neurons of defense behaviour (L-PPL1) after the carrot juice application to the lip of a semi-intact preparation from a hungry snail was glucose-dependent. Similar glucose-dependent changes of L-PPL1 activity were found after CCK-8, but not FMRFamide application during the perfusion with 0.5 mM glucose. L-PPL1, but not L-PPa2-3 neurons were most sensitive to glucose and CCK-8 level changes in the Ringer solution. Adaptive significance of the behavioural phenomena as well as glucose and gastrin/CCK-like peptide participation in these processes are discussed.     

The effect of the removal of the epiphysis on the antidepressive properties of paradoxical sleep deprivation in rats]

After REM sleep deprivation antidepressant shifts in forced swimming with increase of time of immobility and decrease of rhythmical index of depression were observed. Pinealectomy did not remove, but attenuated these behavioural changes.     

Responses of medullary and spinal cord neurons to simulataneous stimulation of two locomotor points

Responses of neurons in the medulla and cervical segments of the spinal cord to simultaneous repetitive stimulation (50 pps) of two locomotor points (LP) that exceed the threshold for evoking walking by one to two times were investigated in mesencephalic cats. In most cases a neuron responsed to stimulation of only one LP. Stimulation of a second LP usually enhanced the firing index of that response, if it was low. Or it decreased the firing index if it was high, and it had no effect if the firing index was about 0.1. Some of the neurons responded to stimulation of one LP by increasing the baseline activity, though the pulses were not locked to individual stimuli. The effect of stimulation of the second LP on this increase in activity depended on the size of the increase. Data were also obtained on the convergence of effects on single neurons from the ipsi- and contralateral LPs of the midbrain and medulla. Possible mechanisms of the summation of subthreshold excitation of a pair of LPs during the initiation of locomotion are discussed.Institute of Information Transmission Problems, Russian Academy of Sciences, Moscow. Translated from Neirofiziologiya, Vol. 24, No. 4, pp. 471–481, July–August, 1992.     

Pregnancy and ovulation detection in bison (Bison bison) assessed by means of urinary and fecal steroids.

Sexually mature bison (Bison bison) cows were tested for both pregnancy and ovulation by means of urinary steroid metabolites and fecal steroids. The accuracy of pregnancy diagnosis was determined among 18 bison cows, in approximately the third month of gestation, by means of urinary pregnanediol-3 delta-glucuronide (PdG), urinary estrone conjugates (E1C), and fecal total estrogens (TE). Urinary PdG was 100% accurate, urinary E1C was 89% accurate, and fecal TE was 100% accurate in predicting pregnancy. Fecal progesterone (P4) and TE, as well as urinary E1C and PdG concentrations all increased from conception (August) through January, but significant differences were not apparent until November. During the rutting season ovulation was detected by increases in either urinary PdG or fecal P4 concentrations. Both pregnancy and ovulation were detected in uncaptured bison with reasonable accuracy by means of urinary and fecal steroids or their metabolites.     

Pause transfer: a topogenic sequence in apolipoprotein B mediates stopping and restarting of translocation.

Previously, we described the stepwise translocation of a large amino-terminal fragment of apolipoprotein B (apo B15) in which the nascent secretory chain translocates through a series of distinct, nonintegrated transmembrane intermediates with large domains exposed to the cytoplasm. Thus, apo B15 appears to stop and restart translocation at several points. We have identified a sequence of amino acids in apo B15 that confers this behavior on a heterologous chimeric protein. In addition, we dissect pausing into two distinct steps, stopping and restarting, thereby trapping otherwise transient intermediates. Finally, we demonstrate the function of a second "pause transfer" sequence over 200 amino acids downstream in apo B15 that restarts translocation posttranslationally, suggesting that multiple pause transfer sequences are involved in the biogenesis of apolipoprotein B.     

Identification and population dynamics of bacteria in leaf spots of soybean

The qualitative and quantitative composition of bacterial flora occurring inside the leaf spots of field grown soybeans was studied during the growing seasons (June to October) of 1989 and 1990. As a rule these leaf spots (necrotic lesions with chlorotic haloes) were caused by Pseudomonas syringae pv. glycinea. This pathogenic bacterium was predominantly found during the whole season in the symptomatic leaf tissue. Other species, mainly Erwinia herbicola, were also found in the same habitat. The population sizes of P. s. pv. glycinea increased from the beginning of symptom occurrence until July, stabilized until September, and then decreased a little. In general, the size of saprophytic populations was orders of magnitude lower than that of the pathogenic populations. The number of different bacterial genera per sample increased up to four genera per leaf spot by the end of the season. No significant influence of the occurring saprophytes on the population dynamics of the pathogen in planta could be observed. Send offprint requests to: Dr. Beate Völksch, Friedrich Schiller University Jena, Biological Faculty, Institute of Microbiology, Pbilosophenweg 12, D/0-6900 Jena, Germany.     

Gramicidin channels: a new mechanism for transmembrane transfer of ions (from high resolution x-ray structural studies of the antibiotic)]

The crystal structure of the membrane-active antibiotic-cyclopeptide gramicidin S complex with urea was determined by the X-ray structure analysis. The gramicidin S molecule possesses an antiparallel beta-structure, its slightly twisted 30-membered cycle has a roughly rectangular form about 4.8 x 13.6 A in size, with the lesser side being formed by the main chain atoms of Phe and Pro residues. The maximum size of the molecule is 22.9 A. A characteristic feature of the molecule is the position of the extended side chains of the Orn residues on one side of the molecular cycle in the form of peculiar "legs--tentacles". One of these legs is "fastened" by the intramolecular H-bond to O atom of the nearer Phe4 residue, the other being free. The distance between the terminal NE atoms of the Orn residues is 5.7 A. The side chains of the Phe and Orn2 residues have trans-orientation, those of the Val, Orn7, Leu residues gauche-orientation. For Val1 and Leu3 side chains statistical disorder of the terminal C atoms is realized. The pyrrolidine rings of the Pro residues adopt Cs-C beta-exo conformation. There are one urea and 20 water molecules per one antibiotic molecule in the structure. The positions of three water molecules are fully occupied, the others with the probability of 0.56-0.20. One of the "water" positions is occupied on 2/3 by water, and on 1/3 by the O atom of the alcohol. There is a complicated system of intra- and intermolecular H-bonds in the structure, with and without the participation of water, alcohol and urea molecules. The gramicidin S molecules, collecting around 3(1) axis according to the left-handed double helix, form the channels whose outside hydrophobic surface is built of the side uncharged radicals, the inside surface being built of the main chain atoms, mainly of the O and N atoms and of the ornithine "tails" with uncharged NE atoms at the termini. The outer diameter of the channel is 29-43 A, inner (without ornithine "tails") is about 12.7 A. At the expense of the change of these "tails" conformation, the inner diameter of the channel filled with water molecules may change from 3.4 up to 6.3 A. Thus, the ions and particles of a rather large size may pass through the channel. The gramicidin channels are discovered and described for the first time. The channels in the crystal structure are close-packed under the hexagonal law.(ABSTRACT TRUNCATED AT 400 WORDS)     

Synthesis and cytotoxic properties of anomeric 5-substituted 3'-azido-2',3'-dideoxyuridines]

Glycosylation of trimethylsilyl derivatives of 5-benzyloxymethyl- and 5-hydroxymethyluracil with 3-azido-2,3-dideoxy-5-O-benzoyl-D-ribofuranosyl chloride (prepared from ethyl 3-azido-2,3-dideoxy-5-O-benzoyl-D-ribofuranoside) and subsequent deacylation gave in both cases a mixture of anomeric 3'-azido-2',3'-dideoxy-5-benzyloxymethyl-or 5-hydroxymethyluridines. The anomers were separated by preparative TLC and their structures were studied by UV, IR and 1H-NMR spectroscopy. It is shown that 1-(3-azido-2,3-dideoxy-alpha-D-ribofuranosyl)-5-benzyloxymethyluracil has cytotoxic activity in vitro: in 10(-5)-10(-4) M concentrations it inhibits the thymidine incorporation into DNA of CaOv cells on 78.6-95.2%.     

Depolymerization of cortical microtubules is not a primary cause of chilling injury in corn (Zea mays L. cv Black Mexican Sweet) suspension culture cells

Cold-induced depolymerization of cortical microtubules were examined in suspension culture cells of corn (Zea mays L. cv Black Mexican Sweet) at various stages of chilling. In an attempt to determine whether microtubule depolymerization contributes to chilling injury, experiments were carried out with and without abscisic acid (ABA) pretreatment, since ABA reduces the severity of chilling injury in these cells. Microtubule depolymerization was detectable after 1 h at 4°C and became more extensive as the chilling was prolonged. There was little chilling injury after 1 d at 4°C in either ABA-treated or non-ABA-treated cells. After 3 d at 4°C, there was about 26% injury for ABA-treated and 40% injury for non-ABA-treated cells, as evaluated by 2,3,5-triphenyl-tetrazolium chloride reduction and by regrowth. After 1d at 4°C, less than 10% of cells retained full arrays of microtubules in both ABA-treated and non-ABA-treated cells, the remainder having either partial arrays or no microtubules. After 3d at 4°C, about 90% of cells showed complete or almost complete depolymerization of microtubules in both ABA-treated and non-ABA-treated cells. ABA did not stabilize the cortical microtubules against cold-induced depolymerization. In about 66% of ABA-treated cells and 57% of non-ABA-treated cells that had been held at 4°C for 3d, repolymerization of cortical microtubules occurred after 3h at 28°C. These results argue against the hypothesis that depolymerization of cortical microtubules is a primary cause of chilling injury.