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PubMed1984

Brain monoaminergic control of male reproductive behavior. I. Serotonin and the post-ejaculatory refractory period.

The present experiment was performed to examine the role of serotonergic mechanisms in the control of copulation and the post-ejaculatory refractory period in the male rat. Disruption of central serotonergic systems in two separate groups of animals was achieved by: (1) selective electrolytic lesions of the midbrain raphe nuclei, or (2) localized intraventricular or intracerebral injection of a specific serotonergic neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT). A third group of animals was tested for sexual behavior following intraperitoneal injection of p-chlorophenylalanine (PCPA), an inhibitor of serotonin synthesis. Both electrolytic and neurochemical lesions localized in the dorsal raphe nucleus produced a highly significant shortening of the ejaculatory latency, and the post-ejaculatory refractory period. Disruption of serotonergic mechanisms following intraventricular injection of 5,7-DHT or systemic administration of PCPA also caused a significant reduction in the length of the refractory period. These results support the hypothesis that central serotonergic systems are normally inhibitory to certain facets of male copulatory behavior and suggest the existence of a serotonergic control system which normally exerts an inhibitory influence over the resumption of mating following ejaculation.

5,7-Dihydroxytryptamine↗
PubMed1984

Brain monoaminergic control of male reproductive behavior. II. Dopamine and the post-ejaculatory refractory period.

This study was designed to examine the role of central dopaminergic mechanisms in the control of copulation and the subsequent post-ejaculatory refractory period in the male rat. Disruption of central dopaminergic pathways was achieved in two separate groups of animals by: (1) selective electrolytic lesions of the substantia nigra (the major locus for dopamine cell bodies in the brain); or (2) localized intracerebral injection of 6-hydroxydopamine, a specific neurotoxin for catecholaminergic pathways. A third group of animals was tested for sexual behavior following administration of the dopamine receptor blocker pimozide. Both electrolytic and neurochemical lesions localized in the substantia nigra produced a significant increase in the length of the post-ejaculatory refractory period. Dopamine receptor blockade following administration of pimozide also caused a significant increase in refractory period duration. These results support the hypothesis that central dopaminergic pathways are involved in the motivational or arousal component of copulation and may be integral to the maintenance of a normal post-ejaculatory refractory period.

Amygdala↗
PubMed1984

Brain monoaminergic control of male reproductive behavior. III. Norepinephrine and the post-ejaculatory refractory period.

The present study was performed to examine the role of brain norepinephrine in the control of copulation and the post-ejaculatory refractory period in the male rat. Disruption of central noradrenergic systems was achieved by (1) selective electrolytic lesion of noradrenergic cell bodies in the locus coeruleus or (2) administration of specific inhibitors of norepinephrine synthesis, sodium diethyldithiocarbamate (DDC) or 1-phenyl-3-(2-thiazolyl)-2 thiourea (U-14, 624). Electrolytic lesions of the locus coeruleus produced a significant increase in the duration of the post-ejaculatory refractory period and its concomitant 22-kHz ultrasonic vocalization. Administration of norepinephrine synthesis inhibitors significantly increased both mount and intromission latencies and caused a dramatic increase in the length of the post-ejaculatory refractory period. These findings support the hypothesis that norepinephrine-containing neural pathways are involved in the control of sexual arousal and suggest that a functional noradrenergic system is essential to the integrity of normal masculine copulatory behavior.

Animals↗
PubMed1987

Kinetoplast DNA of Trypanosoma evansi.

We show here that the kinetoplast DNA (kDNA) networks from six Trypanosoma evansi strains differ from those of T. brucei by their lack of maxi-circles and absence of mini-circle sequence heterogeneity. The lack of maxi-circles is sufficient to account for the inability of T. evansi to multiply in tsetse flies, since this requires functional mitochondria containing maxi-circle gene products. Judged by restriction enzyme analysis, five of the six T. evansi strains contain mini-circles that differ less than 4% in sequence. This type A mini-circle is found in strains from East Africa, West Africa and South America. Another strain from East Africa contains a very different mini-circle (type B), which shows about the same degree of hybridization to type A mini-circles as to a mini-circle from T. brucei. We propose that the pronounced sequence heterogeneity of the mini-circles of T. brucei has arisen by recombination of strains that had diverged for long periods of time in reproductive isolation. We further propose that the homogeneous mini-circles of T. evansi (and T. equiperdum) reflect the inability of species to mate. This proposal implies that mini-circle heterogeneity indicates (infrequent) genetic exchange and that all kinetoplastid flagellates with heterogeneous mini-circles exchange DNA.

Animals↗
PubMed1995

Interaction between long-term potentiation and the action of a peptide transmitter.

The interaction between long-term potentiation (LTP) and the action of a peptide transmitter was examined with evoked field potential recording in the CA1 region of the hippocampus in anesthetized male rats. The peptide transmitter transiently reversed and opposed the effects of LTP, and LTP reversed the action of the peptide transmitter. Because the peptide transmitter is released and has action particularly during sexual behaviors, the results are interpreted to mean that any memory trace encoded by potentiating mechanisms in the rat hippocampus is probably not accessible in the 20-30-min period of time surrounding reproductive activity in male rats.

Afferent Pathways↗
PubMed2004

Lifespan extension by dietary restriction in female Drosophila melanogaster is not caused by a reduction in vitellogenesis or ovarian activity.

Dietary restriction (DR) extends lifespan in a wide range of organisms. DR also reduces daily and lifetime fecundity. The latter may be an evolutionary adaptation to survive periods of food shortage. Reproductive rate is often negatively correlated with lifespan, and a reduced cost of reproduction could be the mechanism by which DR extends lifespan. We tested this hypothesis in Drosophila melanogaster females, by directly suppressing different aspects of reproduction and measuring the effect on the response of lifespan and age-specific mortality to DR. DR resulted in lifespan extension in females kept with males, in females kept without males, in females with vitellogenesis blocked by the mutant ovoD1 and in females with no germline as a result of X-irradiation. Moreover, rapid (48 h) changes in age-specific mortality, previously seen in fertile females switched between full feeding and DR, were also seen in ovoD1 females. Furthermore, these rapid changes in age-specific mortality in cohorts of fertile wild type females were not accompanied by concurrent changes in egg-production. These results indicate either that reduced reproduction is not necessary for lifespan extension by DR in Drosophila females, or that the relevant aspects of reproduction act upstream of our interventions and were therefore not blocked in our experiments.

Animals↗
PubMed2004

Spatial heterogeneity and the persistence of infectious diseases.

The endemic persistence of infectious diseases can often not be understood without taking into account the relevant heterogeneities of host mixing. Here, we consider spatial heterogeneity, defined as 'patchiness' of the host population. After briefly reviewing how disease persistence is influenced by population size, reproduction number and infectious period, we explore its dependence on the level of spatial heterogeneity. Analysis and simulation of disease transmission in a symmetric meta-population suggest that disease persistence typically becomes worse as spatial heterogeneity increases, although local persistence optima can occur for infections with oscillatory population dynamics. We obtain insight into the dynamics that underlie the observed persistence patterns by studying the infection prevalence correlation between patches and by comparing full-model simulations to results obtained using simplified patch-level descriptions of the interplay between local extinctions and between-patch transmissions. The observed patterns are interpreted in terms of rescue effects for strong spatial heterogeneity and in terms of between-patch coherence and synchronization effects at intermediate and weak levels of heterogeneity.

Communicable Diseases↗
PubMed2005

Effect of temperature and humidity on reproductive performance of crossbred sows in Thailand.

This study investigated the influence of season, temperature, and humidity on the reproductive performance of sows under tropical conditions. Data were collected from 11 sow herds from January 2001 to June 2002. Temperature and humidity were recorded daily for each herd from January 2001 to February 2002. Semen used was collected from boars housed in conventional open-air stables (six herds) or in evaporative cooling stables (five herds). A total of 43,875 farrowing records were included in the statistical analysis. Fourteen-day moving averages of daily maximum temperature and minimum humidity were calculated and merged with each reproductive record. ANOVA was applied to the reproductive records. In addition to the fixed effects included in the statistical models (e.g. system, season, parity, temperature, and humidity), the random effect of herd within system was included. The total number of piglets born was analyzed in relation to the climate at previous weaning (NTB-w), at mating (NTB-m), and at farrowing (NTB-f). The housing system of the boars had no significant effect on any of the reproductive variables analyzed. Season (2-month periods) as well as parity number had a significant effect on all reproductive variables analyzed. Increased length of previous lactation had a significant and favorable effect (P < 0.001) on NTB-w, NTB-m, and weaning-to-first-service interval. There were indications that high temperature and humidity (recorded at the herd level) at previous weaning/mating or at farrowing had negative effects on litter size, but these negative influences were not consistent.

Analysis of Variance↗
PubMedDate not supplied

Achieving safe motherhood: applying a life course and multiple determinants perinatal health framework in public health.

Safe motherhood has begun to be identified as a priority for the health of American women. We argue that safe motherhood can be achieved through application of a life course and multiple determinants framework. This framework, with its focus on the preconception period, poses a dilemma in that it links together periods of life and domains of activities that have traditionally not been linked with maternal health. The interests of women and children have often been juxtaposed in the making of policy. Further, the domains of women's health, maternal and child health, and family planning have often clashed over policy priorities and funds. This framework shows that the research literature now links them inextricably to better health outcomes, albeit indirectly; there are no intervention studies that have demonstrated the empirical efficacy of this approach. Thus, although this framework creates a strong rationale for the linkages described, it also demands attention to a set of implementation strategies that will overcome existing barriers. Through a focus on one maternal factor, obesity, we discuss how a range of strategies grounded in the framework can be undertaken to address maternal morbidity and mortality. We then examine selected strategies at each level of the multiple determinants life course framework and emphasize how public policies and public and private sector professional practice can be reexamined to improve outcomes for women in all time periods and aspects of reproductive potential, which in turn might enhance outcomes for their offspring, both at birth and beyond. Our intent is to influence how policy makers, public health professionals, clinicians, and researchers approach safe motherhood.

Female↗
PubMed2005

The relative importance of vasoactive intestinal peptide and peptide histidine isoleucine as physiological regulators of prolactin in the domestic turkey.

In mammals, prolactin (PRL) secretion is regulated by vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI). In birds, however, VIP is considered a PRL-releasing factor (PRF), while the role of PHI is unknown. The purpose of this study was to compare the effects of turkey PHI (tPHI) and turkey VIP (tVIP) on PRL secretion in vitro, and to study their physiological significance in vivo through active immunization against tPHI and tVIP. In vitro studies were conducted using pituitary cell cultures from female turkeys. In the in vivo study, female turkeys were immunized with keyhole limpet hemocyanin (KLH; control), synthetic tPHI conjugate (KLH-tPHI), or synthetic tVIP conjugate (KLH-tVIP). Both tVIP and tPHI stimulated PRL secretion from anterior pituitary cells in a dose response manner. However, tPHI was 100-fold less potent than tVIP in stimulating maximum PRL secretion in vitro. In addition, the highest dose (10(-4) M) of tPHI inhibited its own PRL-releasing activity as well as that of VIP-stimulated PRL release. Whereas, circulating PRL levels and nesting activity remained low and unchanged during the photo-induced reproductive cycle (i.e., experimental period) in tVIP-immunized birds, control and tPHI-immunized turkeys showed a significant increase in plasma PRL levels and in the incidence of incubation behavior over time following photostimulation. These findings, taken together with earlier results, indicate that VIP is the sole physiological PRF in the turkey (avian species).

Animals↗
PubMed1995

Effects of testosterone buciclate on testicular and epididymal sperm functions in bonnet monkeys (Macaca radiata)

The effects of testosterone buciclate (TB), a long-acting androgen ester given i.m. at four sites (20 mg/site) on days 1 and 91 of the study period (360 days), on reproductive and hormonal parameters were evaluated in five adult male bonnet monkeys; untreated animals (n = 5) acted as controls to monitor seasonal changes in these parameters. In control animals, testicular volume remained unchanged throughout the study; sperm count, motility and gel penetrability decreased while the percentage of spermatozoa showing retention of cytoplasmic droplet and coiled tail increased in June-July (days 210-240), preceded by reduction in serum testosterone (T) levels on days 120-150 (March-April). The TB-treated animals showed reduced testicular volume (days 90-270), suppressed sperm motility and gel penetrability (days 45-240 except on day 120), decreased sperm count (days 75-270), and an increased percentage of spermatozoa showing retention of cytoplasmic droplet and coiled tail (days 45-240 except on day 120). Even though serum T levels remained elevated until day 300, these levels were within the physiological range. The changes induced by TB were reversible. The suppression of testicular and epididymal functions by TB indicates that this long-acting androgen may have the potentiality to induce and maintain reversible sterility, but further evaluation needs to be carried out to develop an appropriate dosage regimen that would prevent return to normal functions in order to develop this long-acting androgen as a hormonal male contraceptive.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Overwintering strategy in Pyrrhocoris apterus (Heteroptera): the relations between life-cycle, chill tolerance and physiological adjustments.

Seasonal dynamics of ecophysiological parameters are described which are relevant to overwintering in field-collected adults of a Czech population of the red firebug, Pyrrhocoris apterus. Five life-cycle phases were distinguished using the duration of pre-oviposition period as a criterion: reproductive activity (spring-early summer), intensification of reproductive diapause (RD) (peak of summer), maintenance of RD (late summer-early autumn), termination of RD (late autumn-early winter), and low temperature quiescence (LTQ) (winter). The supercooling capacity and chill tolerance (c.t.) increased simultaneously with the termination of RD and all three processes were triggered/conditioned by autumnal decrease in ambient temperatures. Maximum supercooling capacity and c.t. 'outlived' the end of diapause and persisted throughout the LTQ state. The limits of c.t. were estimated as -15 degrees C/1-2 weeks for 50% survival. Ribitol, sorbitol, arabinitol, and mannitol were accumulated in the winter-sampled insects. Relatively low concentrations of polyols (dominating ribitol reached ca. 1% FW) indicate that they do not function as colligative cryoprotectants. However, because their seasonal occurrence coincided with the highest c.t., their non-colligative cryoprotectant effects would merit further study. Although the overwintering microhabitat of P. apterus is buffered, the temperatures may fall to -13 degrees C during exceptionally cold winters and thus, the parameters of c.t. seem to be just appropriately tuned to the local overwintering conditions.

Journal Article↗
PubMed2004

Resumption of postpartum ovarian cyclicity in high-producing Holstein cows.

The objective of this study was to investigate the resumption of ovarian cyclicity postpartum in high-producing dairy cows in commercial dairy farms under subtropical conditions. The cows were kept in a free-stall or tie-stall barn. Milk samples were collected from cows twice weekly, and progesterone in the skim milk was assayed by double-antibody ELISA. Cows were examined rectally and vaginoscopically at 2-week intervals after calving. Body condition score (BCS) and body weights were taken before and after calving. A cow was considered to have resumed ovarian cyclicity on the day of ovulation if followed by regular ovarian cycles. Thirty seven percent (n=20/54) of the cows had normal resumption of ovarian cyclicity (resumption within 45 days after calving), and 63% (n=34/54) had delayed resumption (resumption did not occur until >45 days after calving). Delayed resumption Type I (one or more ovarian cycles with luteal phase >20 days, i.e. prolonged luteal phase; 31.5%) and delayed resumption Type II (first ovulation did not occur until > or =45 days after calving, i.e. delayed first ovulation; 24.1%) were the most common types of delayed resumptions. Almost half (46.3%) of the cows did not resume their ovarian cyclicity until >65 days postpartum. Cows with delayed resumption Type I had a higher incidence of abnormal cervico-vaginal discharge (64.7%) and incomplete uterine involution (94.1%) compared to cows with normal resumption (P<0.01). The BCS of cows with delayed resumption Type II were lower than those of normal resumption cows at 5 weeks and later in the postpartum period (P<0.05). Approximately two-thirds of high-producing cows had delayed resumption of ovarian cyclicity postpartum. Prolonged luteal phase and delayed first ovulation were two important ovarian dysfunctions that delayed postpartum resumption of cyclicity in high-producing dairy cows.

Animals↗
PubMed2003

Evaluation of seasonal variations of semen freezability in Leccese ram.

The experiment was carried out in Southern Italy (41 degrees N latitude) to examine the effects of seasonal variations of semen freezability in Leccese ram. Semen from five rams, collected every 2 weeks for a whole year, was frozen in straws, using a system based on Tris-fructose egg yolk as extender to constitute semen doses of 100x10(6) spermatozoa. Post-thaw survival and acrosomal status of cells were assessed by dual staining by Hoechst 33258 and FITC-PSA. Three different forms of fluorescence distribution were displayed indicating sperm without acrosome (unstained cells), sperm with damaged acrosome (cells with incomplete fluorescence over the head), sperm with widespread fluorescence (cells completely fluorescent). Motility and kinetic rating at thawing and after 1 and 3h incubation (37 degrees C) were also assessed. Semen frozen in summer and autumn, corresponding to the breeding season, showed the highest (P<0.01) post-thaw survival of spermatozoa (41.7%) and the lowest (P<0.01) incidence of spermatozoa with damaged acrosome. The positive influence of the summer-autumn period was expressed also on motility and kinetic rating of spermatozoa at thawing. The integrity of the acrosomal membrane was positively correlated (P<0.01) with sperm viability before processing (r=0.32) and after thawing (r=0.51). In conclusion, the results show that season exerts a significant influence on semen freezability in Leccese ram, with the best performance occurring the summer and autumn period, corresponding to the reproductive season in temperate zones.

Acrosome↗
PubMed2000

Seasonal effects on puberty and reproductive characteristics of female Chios sheep and Damascus goats born in autumn or in February.

Ten Chios ewe lambs and 10 Damascus she-kids born in October-November and similar numbers born in February along with eight multiparous females from each species, were used to examine pubertal events and reproductive seasonality. Reproductive activity was monitored by determining serum progesterone concentrations once a week for 12 months. The mean date of onset of ovulation (puberty) in autumn-born Chios females (7 August) was earlier (p<0.05) than in February-born ones (11 September) though the onset of regular cyclicity was not significantly different between the two groups (30 August and 19 September, respectively). The age and live weight at puberty in autumn-born females was higher (p<0.01) than in February-born ones, the respective values being 43.3 weeks and 50.1kg, versus 29.9 weeks and 42.0kg. All animals, irrespective of time of birth, started ovulating after the summer equinox. Multiparous Chios ewes had reproductive cycles covering most time of the year with acyclic periods during spring and summer. In ewe lambs, about half of the animals ceased cycling during the second half of winter and in spring, while the rest continued cycling. The total number of cycles detected over the experimental period was lower (p<0.05) for February-born (n=9.4) compared with autumn-born females (n=13.7) and adult ewes (n=17.1). In Damascus she-kids born in autumn or in February, onset of puberty was at the same time in the following autumn, the respective mean date for the two groups being 1 November and 27 October. For autumn-born animals, age (48.4 weeks) and live weight (53.8kg) at puberty were higher (p<0.01) than for those born in February (37.3 weeks, 42.9kg). Reproductive cycles in adult goats started in the second half of September and continued until the end of March. Most young goats (75%) had their last seasonal cycle in February and the rest in March. The total number of cycles was higher (p<0.01) in adult (n=8.1) than in young goats born either in autumn (n=6.3) or in February (n=5.7). It is concluded that reproductive development and puberty in Chios female sheep are mostly under seasonal influences though age and body weight are also contributing factors. This breed has a long reproductive season with some animals cycling throughout the year. The Damascus female goat is strictly seasonal with distinct periods of reproductive cyclicity and inactivity. Puberty attainment of Damascus females born in autumn or in February is at the same time the following autumn.

Journal Article↗
PubMed2005

Molecular characterization and evolutionary study of spider tubuliform (eggcase) silk protein.

As a result of hundreds of millions of years of evolution, orb-web-weaving spiders have developed the use of seven different silks produced by different abdominal glands for various functions. Tubuliform silk (eggcase silk) is unique among these spider silks due to its high serine and very low glycine content. In addition, tubuliform silk is the only silk produced just during a short period of time, the reproductive season, in the spider's life. To understand the molecular characteristics of the proteins composing this silk, we constructed tubuliform-gland-specific cDNA libraries from three different spider families, Nephila clavipes, Argiope aurantia, and Araneus gemmoides. Sequencing of tubuliform silk cDNAs reveals the repetitive architecture of its coding sequence and novel amino acid motifs. The inferred protein, tubuliform spidroin 1 (TuSp1), contains highly homogenized repeats in all three spiders. Amino acid composition comparison of the predicted tubuliform silk protein sequence to tubuliform silk indicates that TuSp1 is the major component of tubuliform silk. Repeat unit alignment of TuSp1 among three spider species shows high sequence conservation among tubuliform silk protein orthologue groups. Sequence comparison among TuSp1 repetitive units within species suggests intragenic concerted evolution, presumably through gene conversion and unequal crossover events. Comparative analysis demonstrates that TuSp1 represents a new orthologue in the spider silk gene family.

Amino Acid Sequence↗