Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Stimulates Adenylyl Cyclase and Phospholipase C Activity in Rat Cerebellar Neuroblasts

Abstract: The presence of receptors for the novel neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) has been recently demonstrated in the external granule cell layer of the cerebellum, a germinative matrix that generates the majority of cerebellar interneurons. In the present study, we have taken advantage of the possibility of obtaining a culture preparation that is greatly enriched in immature cerebellar granule cells to investigate the effect of PACAP on the adenylyl cyclase and phospholipase C transduction pathways. The two molecular forms of PACAP, i.e., 27-(PACAP27) and 38-(PACAP38) amino-acid forms of PACAP, induced a dose-dependent stimulation of cyclic AMP production in granule cells. The potencies of PACAP27 and PACAP38 were similar (ED₅₀ = 0.12 ± 0.01 and 0.23 ± 0.07 n M , respectively), whereas vasoactive intestinal polypeptide (VIP) was ∼100 times less potent. PACAP27 and PACAP38 also induced a dose-dependent stimulation of polyphosphoinositide breakdown (ED₅₀ = 19.1 ± 6.3 and 13.4 ± 6.0 n M , respectively), whereas VIP had no effect on polyphosphoinositide metabolism. The effect of PACAP38 on inositol phosphate formation was significantly reduced by U-73122 and by pertussis toxin, indicating that activation of PACAP receptors causes stimulation of a phospholipase C through a pertussis toxin-sensitive G protein. In contrast, forskolin and dibutyryl cyclic AMP did not affect PACAP-induced stimulation of inositol phosphates. Taken together, the present results demonstrate that PACAP stimulates independently the adenylyl cyclase and the phospholipase C transduction pathways in immature cerebellar granule cells. These data favor the concept that PACAP may play important roles in the control of proliferation and/or differentiation of cerebellar neuroblasts.     

Circadian Locomotor Rhythms in Mice with Targeted Disruption of the Gene for the Carbon Monoxide Synthesizing Enzyme,Heme Oxygenase-2

Carbon monoxide (CO), generated in neurons by the enzyme heme oxygenase-2 (HO2), is postulated to be a gaseous signaling molecule in the mammalian brain. Because of the recent evidence suggesting an important role of another endogenously produced gas, nitric oxide (NO), in entrainment of circadian rhythms in mammals, we hypothesized that CO may also be involved in regulating these rhythms. Consistent with this idea, others have found a circadian rhythm of heme turnover and CO synthesis can be induced by bright light. Furthermore, HO2 is co-localized with guanylyl cyclase, the putative target of CO, throughout the brain, with high amounts of staining in the suprachiasmatic nucleus (SCN) of the hypothalamus. The goal of the present study was to evaluate the role of CO in photic entrainment in wild-type and HO2 deficient mice. HO2–/– mice did not display any abnormalities in circadian rhythmicity. Entrainment to a light–dark cycle, the ability to phase delay locomotor activity after a four hour phase shift in photoperiod, and the period of the free running rhythm (t) were similar between HO2–/– and wild-type mice. Taken together, these data suggest that CO does not play a major role in regulating circadian activity rhythms in mice.     

Photoperiod modulates the effects of norepinephrine on lymphocyte proliferation in Siberian hamsters

Siberian hamsters (Phodopus sungorus) rely on photoperiod to coordinate seasonally appropriate changes in physiology, including immune function. Immunity is regulated, in part, by the sympathetic nervous system (SNS), although the precise role of the SNS in regulating photoperiodic changes in immunity remains unspecified. The goal of the present study was to examine the contributions of norepinephrine (NE), the predominant neurotransmitter of the SNS, to photoperiodic changes in lymphocyte proliferation. In experiment 1, animals were maintained in long [16:8-h light-dark cycle (16:8 LD)] or short days (8:16 LD) for 10 wk, and splenic NE content was determined. In experiment 2, in vitro splenocyte proliferation in response to mitogenic stimulation (concanavalin A) was assessed in spleen cell suspensions taken from long- or short-day hamsters in which varying concentrations of NE were added to the cultures. In experiment 3, splenocyte proliferation was examined in the presence of NE and selective alpha- and beta-noradrenergic receptor antagonists (phenoxybenzamine and propranolol, respectively) in vitro. Short-day animals had increased splenic NE content compared with long-day animals. Long-day animals had higher proliferation compared with short-day animals independent of NE. NE (1 microM) further suppressed splenocyte proliferation in short but not long days. Last, NE-induced suppression of proliferation in short-day hamsters was blocked by propranolol but not phenoxybenzamine. The present results suggest that NE plays a role in photoperiodic changes in lymphocyte proliferation. Additionally, the data suggest that the effects of NE on proliferation are specific to activation of beta-adrenergic receptors located on splenic tissue. Collectively, these results provide further support that photoperiodic changes in immunity are influenced by changes in SNS activity.     

Reductions in total body fat decrease humoral immunity

Mounting an immune response requires substantial energy, and it is well known that marked reductions in energy availability (e.g. starvation) can suppress immune function, thus increasing disease susceptibility and compromising survival. We tested the hypothesis that moderate reductions in energy availability impair humoral immunity. Specifically, we examined the effects of partial lipectomy (LIPx) on humoral immunity in two seasonally breeding rodent species, prairie voles (Microtus ochrogaster) and Siberian hamsters (Phodopus sungorus). Animals received bilateral surgical removal of epididymal white adipose tissue (EWATx), inguinal white adipose tissue (IWATx) or sham surgeries and were injected with the antigen keyhole limpet haemocyanin (KLH) either four or 12 weeks after surgery. In prairie voles, serum anti-KLH immunoglobulin G (IgG) did not differ significantly at four weeks. At 12 weeks, serum IgG was significantly reduced in IWATx, but not EWATx animals, compared with sham-operated animals. In Siberian hamsters, both IWATx and EWATx animals reduced serum IgG at four weeks. At 12 weeks, EWATx hamsters displayed a significant compensatory increase in IWAT pad mass compared with sham-operated hamsters, and serum IgG no longer differed from sham-operated animals. There was no significant increase in EWAT in IWATx hamsters compared with sham animals and IgG remained significantly reduced in IWATx hamsters. These results suggest that reductions in energy availability can impair humoral immunity.     

Seasonal changes in adiposity: the roles of the photoperiod,melatonin and other hormones,and sympathetic nervous system

It appears advantageous for many non-human animals to store energy body fat extensively and efficiently because their food supply is more labile and less abundant than in their human counterparts. The level of adiposity in many of these species often shows predictable increases and decreases with changes in the season. These cyclic changes in seasonal adiposity in some species are triggered by changes in the photoperiod that are faithfully transduced into a biochemical signal through the nightly secretion of melatonin (MEL) via the pineal gland. Here, we focus primarily on the findings from the most commonly studied species showing seasonal changes in adiposity-Siberian and Syrian hamsters. The data to date are not compelling for a direct effect of MEL on white adipose tissue (WAT) and brown adipose tissue (BAT) despite some recent data to the contrary. Thus far, none of the possible hormonal intermediaries for the effects of MEL on seasonal adiposity appear likely as a mechanism by which MEL affects the photoperiodic control of body fat levels indirectly. We also provide evidence pointing toward the sympathetic nervous system as a likely mediator of the effects of MEL on short day-induced body fat decreases in Siberian hamsters through increases in sympathetic drive on WAT and BAT. We speculate that decreases in the SNS drive to these tissues may underlie the photoperiod-induced seasonal increases in body fat of species such as Syrian hamsters. Clearly, we need to deepen our understanding of seasonal adiposity, although, to our knowledge, this is the only form of environmentally induced changes in body fat where the key elements of its external trigger have been identified and can be traced to and through their transduction into a physiological stimulus that ultimately affects identified responses of white adipocyte physiology and cellularity. Finally, the comparative physiological approach to the study of seasonal adiposity seems likely to continue to yield significant insights into the mechanisms underlying this phenomenon and for understanding obesity and its reversal in general.     

Analysis of plastid DNA-like sequences within the nuclear genomes of higher plants

A wide-ranging examination of plastid (pt)DNA sequence homologies within higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion with methylation-sensitive restriction enzymes and Southern analysis was used to distinguish plastid and nuclear DNA in order to assess the extent of variability of promiscuous sequences within and between plant species. Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum (tobacco), and Chenopodium quinoa, showed homogenity of these sequences, while intraspecific sequence variation was observed among different cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum aestivum (wheat). Hypervariability of plastid sequence homologies was identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta vulgaris (beet), in which individual plants were shown to possess a unique spectrum of nuclear sequences with ptDNA homology. This hypervariability apparently extended to somatic variation in B. vulgaris. No sequences with ptDNA homology were identified by this method in the nuclear genome of Arabidopsis thaliana.      

Metabolic stress suppresses humoral immune function in long-day,but not short-day,Siberian hamsters (<Emphasis Type="Italic">Phodopus sungorus</Emphasis>)

Individuals of many species experience marked seasonal variation in environmental conditions and must adapt to potentially large fluctuations in energy availability and expenditure. Seasonal changes in immunity have likely evolved as an adaptive mechanism to cope with seasonal stressors. In addition, these changes may be constrained by seasonal fluctuations in energy availability. The goal of this study was to assess the role of energetic trade-offs associated with seasonal variation in immunity. In addition to body fat stores, metabolic fuels (e.g., glucose) may affect immune function in seasonally breeding rodents. In this study we experimentally reduced energy availability via injections of the metabolic inhibitor 2-deoxy-d-glucose (2-DG) in long- and short-day housed Siberian hamsters (Phodopus sungorus) and then examined antigen-specific antibody production. Metabolic stress decreased antibody response compared with control animals in long days. In contrast, no difference was observed between treatment groups in short days. These data suggest that reductions in energy availability suppress immunity and short days buffer organisms against glucoprivation-induced immunosuppression.     

Gonadal hormones modulate the display of submissive behavior in socially defeated female Syrian hamsters

There are striking differences in the behavioral response to social defeat between male and female Syrian hamsters. Whereas males exhibit a prolonged behavioral response to defeat (i.e., conditioned defeat), many females remain aggressive or show only a transient submissive response following defeat. The current study tested the hypothesis that sex steroids underlie this differential behavioral responsivity to social defeat. Female hamsters were ovariectomized and implanted with Silastic capsules containing estradiol (E(2)), testosterone (T), progesterone (P), dihydrotestosterone (DHT), or a blank capsule (no hormone replacement). After a 3-week recovery period, each subject was placed inside the home cage of a larger, more aggressive female for four 5-min defeat trials. The following day, each animal was tested for conditioned defeat by testing it in its own home cage in the presence of a smaller, non-aggressive intruder. Submissive, aggressive, social, and nonsocial behaviors were subsequently scored. Hamsters receiving E(2) or T displayed significantly lower levels of submissive behavior than did animals receiving P, DHT, or no hormone replacement. There were no significant differences in aggressive behavior among groups. These data suggest that gonadal hormones can influence submissive behavior in female hamsters. Collectively, these results suggest that the sex differences observed in conditioned defeat may, in part, be explained by sex differences in circulating gonadal hormones.