Taste systems of the petrosal ganglion of the rat glossopharyngeal nerve

Single unit recordings were taken from sensory ganglion cellsin the petrosal ganglion (PG) of the glossopharyngeal nerveof the rat. These taste units were examined with respect tospontaneous and evoked discharge patterns and responsivenessto a wide variety of chemical compounds, most of natural occurrence.Spontaneous activity patterns, with few exceptions, tended tobe extremely irregular with both bursting (clusters of 2–3spikes) and grouping (large groups of spikes as in evoked discharges).Most interspike interval histograms of spontaneous activitywere multimodal, similar to rat geniculate ganglion (GG) units.Evoked discharges usually displayed grouping of spikes, andlong latencies of onset and persistence of discharge after rinsewere sometimes seen. Little response was shown to nucleotidesor salts. Units responsive to amino acids tended to show largedischarge to only one or two amino acids; and the most responsiveamino acid usually varied from cell to cell. Units responsiveto alkaloids only responded to a few alkaloids with atropineand quinine being the most stimulatory. Units responsive toacids only discharged to a few of the acids tested and oftenacids of low pH elicited no discharge. Saccharin activated unitsresponsive to both sugar and alkaloids. A few units highly responsiveto both sugar and alkaloids were seen. The units were placedinto four clusters on the basis of chemicals activating themand certain neurophysiological characteristics: PG salt units,PG acid units and, tentatively, amino acid (sugar) units andX (alkaloid and alkaloid plus) units. The PG salt units didnot show the exclusive sensitivity to sodium and lithium compoundsas did the GG salt units. The PG acid units could also be differentiatedfrom the GG acid units. The petrosal amino acid and X units,on the other hand, could not be differentiated from similarunits in the rat GG.     

Effects of yohimbine and desipramine on cardiac noradrenaline release and ventricular arrhythmias during acute coronary artery occlusion and reperfusion in anesthetized dogs

Effects of yohimbine (YHMB, an alpha 2-antagonist) and desipramine (DMI, a neuronal uptake inhibitor) were compared on cardiac noradrenaline (NA) release either upon left ansa subclavia nerve stimulation during acute occlusion of the left anterior descending coronary artery (LAD) or upon subsequent LAD reperfusion without stimulation in anesthetized dogs. In control dogs, before LAD occlusion, coronary sinus (CS) NA output increased from 5.4 +/- 1.0 to 26.8 +/- 4.0 ng/min (p less than 0.05) upon stimulation (2 Hz, 30 s). The response to stimulation remained unchanged 25 min after LAD occlusion. During reperfusion 60 min after occlusion, the output of CS-NA and lactate increased from 6.1 +/- 0.8 to 51.3 +/- 19.4 ng/min (p less than 0.05) and from 2.7 +/- 0.5 to 6.7 +/- 1.3 mg/min (p less than 0.05), respectively. In dogs treated with YHMB, the stimulation-induced increase in NA output was potentiated at least fourfold (p less than 0.05) either before or during LAD occlusion, but not during reperfusion. In dogs receiving DMI, stimulation-induced CS-NA output was enhanced to a similar extent (approximately twofold, p less than 0.05) either before or during occlusion, while reperfusion-induced NA output was markedly potentiated by approximately ninefold (p less than 0.05). Maximum dP/dt of left ventricular pressure remained unchanged upon reperfusion in all groups. The total arrhythmic ratio in the drug-treated groups did not significantly differ from the ratio in control dogs upon either stimulation or reperfusion. The data suggest that an abrupt increase in NA output upon reperfusion may result from a washout of NA locally accumulated in the ischemic and (or) peri-ischemic region during the preceding occlusion period, and that NA thus released does not have substantial hemodynamic effects. The results indicate that in the presence of YHMB or DMI, the potentiated increase in NA release in response to either nerve stimulation during LAD occlusion or to reperfusion without stimulation did not aggravate ventricular arrhythmia, most probably owing to the antiarrhythmic properties of these substances.     

Stimulation of poly(ADP-ribose) synthesis by free radicals in C3H10T1/2 cells: relationship with NAD metabolism and DNA breakage

We have studied the effect of H2O2 and O2- produced by xanthine and xanthine oxidase on NAD catabolism, poly(ADP-ribose) synthesis, and production of DNA single-strand breaks in C3H10T1/2 cells. The results show a correlation between the induction of DNA single-strand breaks, the decrease of NAD pool, and the accumulation of polymer. New techniques, based on affinity chromatography and reversed-phase high pressure liquid chromatography, have allowed an accurate determination of polymer contents and showed a 20-fold stimulation of polymer biosynthesis induced by active oxygen species. Inhibition experiments performed with 3-aminobenzamide have shown that the decrease in NAD levels after exposure of cells to active oxygen species was caused by stimulation of poly(ADP-ribosyl)ation and of another cellular process.     

Transitional changes in arachidonic acid metabolism by bovine embryos at different developmental stages

In order to determine the profile of arachidonic acid (AA) metabolites synthesized by bovine embryos during early developmental stages, embryos collected from superovulated beef cattle (days 6 through 17) were incubated with AA and its metabolites were analyzed by high performance liquid chromatography and radioimmunoassay (RIA). Embryos harvested and cultured before day 12 of the estrous cycle metabolized AA primarily to prostaglandin E2 (PGE2), whereas, those harvested on day 13 of the cycle metabolized AA to both PGE2 and PGF2 alpha. Furthermore, embryos collected after day 15 of the cycle metabolized AA to PGI2 in addition to PGE2 and PGF2 alpha. In view of the luteotropic properties that have been attributed to PGE2 and the vasodilatory effect of PGI2, this transitional change in prostaglandin synthesis during early stages of embryonic development may be a part of the mechanism by which the embryo exerts a luteotropic effect leading to maternal recognition of pregnancy and by which the conceptus begins preparing for subsequent implantation.     

13C NMR of the bases of three DNA oligonucleotide duplexes: assignment methods and structural features

Natural abundance 13C NMR spectra of three DNA oligomers have been obtained. Most of the base resonances are well resolved from one another. A combination of two independent methods was used in making assignments: a one-dimensional spectral comparison method and a two-dimensional proton-detected 1H-13C correlated experiment for the protonated carbons. There are large shielding changes (between 1.62 and -1.40 ppm) upon thermal dissociation of the duplex. The shapes of the chemical shift vs temperature curves are largely independent of sequence. The base carbon resonance frequencies are sensitive to hydrogen bonding, base stacking, sugar conformation, and changes in the glycosyl torsion angle.     

Neurophysiology of geniculate ganglion (facial nerve) taste systems: species comparisons

On the basis of various measures taken from geniculate gangliontaste neurons in four species, it was concluded that withineach species the neurons could be subdivided into distinct functionalgroups. In this report, the neural groups of different specieswere directly compared. Units from all four species were studiedwith a common test series of solutions in addition to otherstimuli. Since these stimuli were presented at the same concentrationsto all species, direct quantitative comparisons across specieswere possible for a wide range of chemical compounds. In addition,the neural groups were compared with respect to spontaneousand evoked activity measures, latency to electrical stimulation,and receptive field characteristics. These neurophysiologicaldata suggest a basic model of four distinct subgroups: acidunits, salt units, amino acid units, and X units.     

Genetic variation of recent Alu insertions in human populations

The Alu family of intersperesed repeats is comprised of ovr 500,000 members which may be divided into discrete subfamilies based upon mutations held in common between members. Distinct subfamilies of Alu sequences have amplified within the human genome in recent evolutionary history. Several individual Alu family members have amplified so recently in human evolution that they are variable as to presence and absence at specific loci within different human populations. Here, we report on the distribution of six polymorphic Alu insetions in a survey of 563 individuals from 14 human population groups across several continents. Our results indicate that these polymorphic Alu insertions probably have an African origin and that there is a much smaller amount of genetic variation between European populations than that found between other populations groups. Present address: Department of Pathology, Stanley S. Scott Cancer Center, Louisiana State University Medical Center, 1901 Perdido St., New Orleans, LA 70112 Correspondence to: M.A. Batzer     

Overexpression of P-glycoprotein in heat-and/or drug-resistant hepatoma variants

We have earlier isolated a glucocorticoid-resistant, dedifferentiated rat hepatoma variant, the clone 2, which exhibited deficient stress activation of the major stress-inducible heat-shock protein hsp68.Multidrug-resistant variants were isolated from clone 2 cells using increasing concentrations of colchicine. The induction deficiency of hsp68 was maintained in the colchicine-resistant clone 2 cells grown for several months in the presence of 1 g/ml colchicine (termed ashighly multidrug-resistant variant) indicating that this heat-shock protein is not involved in the multidrug resistance. No alteration of the protein synthesis pattern was observed except the strong increase of the P-glycoprotein, which correlated with high level of corresponding mRNA. Stableheat-resistant variants of clone 2 were also isolated, which showed increaseddrug resistance to several drugs, i.e. they becamemoderately multidrug-resistant. This moderate multidrug resistance of the heat-resistant variants was further increased by stepwise selection with colchicine (highly multidrug-resistant heat-resistant variants). The levels of P-glycoprotein mRNA and protein were elevated both in the heat-resistant, non drug selected, moderately drug-resistant and in heatresistant, colchicine selected, highly drug-resistant variants. Decreased retention of antitumor drugs was observed in all multidrug-resistant variants indicating that P-glycoprotein was functional. Verapamil increased doxorubicin retention and cytotoxicity significantly. Our results showing that severely stressed hepatoma cells overexpressed the multidrug resistance gene(s) raise the possibility that the P-glycoprotein may participate in protection against enviromental stress such as heat.Abbreviations hsp heat-shock protein - MDR multidrug resistance - P-gp P-glycoprotein     

Gene rearrangements in Chlamydomonas chloroplast DNAs are accounted for by inversions and by the expansion/contraction of the inverted repeat

To gain insight into the mutational events responsible for the extensive variation of chloroplast DNA (cpDNA) within the green algal genus Chlamydomonas, we have investigated the chloroplast gene organization of Chlamydomonas pitschmannii, a close relative of the interfertile species C. eugametos and C. moewusii whose cpDNAs have been well characterized. At 187 kb, the circular cpDNA of C. pitschmannii is the smallest Chlamydomonas cpDNA yet reported; it is 56 and 105 kb smaller than those of its C. eugametos and C. moewusii counterparts, respectively. Despite this substantial size difference, the arrangement of 77 genes on the C. pitschmannii cpDNA displays only three noticeable differences from the organization of the corresponding genes on the collinear C. eugametos and C. moewusii cpDNAs. These changes in gene order are accounted for by the expansion/contraction of the inverted repeat and one or two inversions in a single-copy region. In land plant cpDNAs, these kinds of events are also responsible for gene rearrangements. The large size difference between the C. pitschmannii and C. eugametos/C. moewusii cpDNAs is mainly attributed to multiple events of deletions/additions as opposed to the usually observed expansion/contraction of the inverted repeat in land plant cpDNAs. We also found that the mitochondrial genome of C. pitschmannii is a circular DNA molecule of 16.5 kb which is 5.5 and 7.5 kb smaller than its C. moewusii and C. eugametos counterparts, respectively.     

Urinary prostaglandin and kallikrein excretion are not flow dependent in the rat

To study the relationship between urine flow, urinary prostaglandin (PG) and kallikrein excretion in the rat high urine flow was induced in hydropenic Long-Evans rats by either hypotonic volume expansion or with manniitol or with furosemide. PGE, excretion remained unchanged during hypotonic volume expansion (134.5 ± 29.7 before and 153.0 ± 48.9 pg/min after) while it decreased significantly with mannitol (from 166.3 ± 32.4 to 45.2 ± 8.2 pg/min, p<0.01) and with furosemide (from 170.0 ± 20.4 to 29.5 ± 5.3 pg/min, p<0.001). PGF_2α excretion rates were slightly reduced following all three interventions. Urinary kallikrein excretion remained unchanged in all three groups of animals. It is concluded that, in contrast to human and dogs in the rat urine flow and urinary PG excretion are not interlinked.