N2O ionization and dissociation dynamics in intense femtosecond laser radiation, probed by systematic pulse length variation from 7 to 500 fs.

We have made a series of measurements, as a function of pulse duration, of ionization and fragmentation of the asymmetric molecule N2O in intense femtosecond laser radiation. The pulse length was varied from 7 fs to 500 fs with intensity ranging from 4 × 10(15) to 2.5 × 10(14) W∕cm(2). Time and position sensitive detection allows us to observe all fragments in coincidence. By representing the final dissociation geometry with Dalitz plots, we can identify the underlying breakup dynamics. We observe for the first time that there are two stepwise dissociation pathways for N2O(3+): (1) N2O(3+) → N(+) + NO(2+) → N(+) + N(+) + O(+) and (2) N2O(3+) → N2 (2+) + O(+) → N(+) + N(+) + O(+) as well as one for N2O(4+) → N(2+) + NO(2+) → N(2+) + N(+) + O(+). The N2 (2+) stepwise channel is suppressed for longer pulse length, a phenomenon which we attribute to the influence which the structure of the 3+ potential has on the dissociating wave packet propagation. Finally, by observing the total kinetic energy released for each channel as a function of pulse duration, we show the increasing importance of charge resonance enhanced ionization for channels higher than 3+.

Evidence for prejunctional GABAB receptors mediating inhibition of ovarian follicle contraction induced by nerve stimulation.

The motor effects of gamma-aminobutyric acid (GABA) on the bovine ovarian follicle were studied in vitro using strips from follicle walls. Electrical field stimulation of nerves in the preparation, secured by tetrodotoxin blockade, caused a contraction that was almost totally abolished by phentolamine and only slightly affected by atropine. This mainly adrenergic neurogenic response was inhibited by GABA in a dose-dependent way. The GABAA-receptor antagonists, bicuculline and picrotoxin, did not affect the GABA action whereas the GABAB-receptor antagonist, homotaurine, significantly inhibited the GABA effect. The GABAA-receptor agonist, muscimol, did not affect the contractile response while the GABAB-receptor agonist, baclofen, imitated the action of GABA. On the other hand, GABA had no direct contractile or relaxing effect on the follicle strips nor did it interfere with the contractile response induced by noradrenaline or acetylcholine. The findings suggest that activation of prejunctional GABAB receptors inhibits transmitter release from mainly adrenergic nerves associated with the follicle, thereby affecting nerve-mediated tension in the follicle wall.

Extracellular and intracellular calcium sources mediating contractile responses of smooth muscle in bovine ovarian follicle and ovarian artery.

The relative importance of extracellular and intracellular calcium sources mediating smooth muscle contraction in ovarian follicle and ovarian artery was assessed in experiments on the influence of nifedipine, D-600, amrinone, diethylstilbestrol (DES), lanthanum and/or calcium removal on contractions induced by K+ depolarization, by noradrenaline, histamine and acetylcholine. The K+-induced response was biphasic in the ovarian artery but not in the ovarian follicle. The K+-induced contraction in both preparations was greatly inhibited by nifedipine (1 microM), D-600 (10 microM) and lanthanum (2 mM). Although both phases of the responses in the ovarian artery appeared to be completely dependent on extracellular calcium, phase I was significantly more sensitive to nifedipine than phase II. Incubation in calcium-free medium for 15 min almost abolished the K+-induced contraction. Noradrenaline- and histamine-induced contractions of ovarian follicle were essentially unaffected by nifedipine (1 microM) and D-600 (10 microM) whereas the noradrenaline-induced contraction in ovarian artery was inhibited significantly by D-600 (1 and 10 microM) but not nifedipine (1 microM). In calcium-free medium containing EGTA (1 mM) the responses of ovarian follicle to noradrenaline and histamine were reduced by 26 and 22% respectively. When preparations were stimulated with noradrenaline more than one in calcium-free medium, the contraction decreased progressively compared to time-matched controls. The response was 34% of the control after 50 min in calcium-free medium containing EGTA. In the ovarian artery the response obtained (6% of control) was significantly smaller (P less than 0.05) than that in the follicle.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuronal localization of pancreatic polypeptide (PP) and vasoactive intestinal peptide (VIP) immunoreactivity in the earthworm (Lumbricus terrestris).

Nerve fibres and cell bodies displaying vasoactive intestinal polypeptide (VIP) or pancreatic polypeptide (PP) immunoreactivity were demonstrated in ganglia of the earthworm (Lumbricus terrestris). VIP cell bodies were found in the most anterior ganglion of the ventral nerve cord, the subpharyngeal ganglion. Immunoreactive nerves were seen running in the center of the cord until about the 10th segment. PP cell bodies were found in the cerebral ganglion where VIP was lacking, in the subpharyngeal ganglion and in more posteriorly located ganglia of the ventral nerve cord. PP nerve fibres could be followed below the 10th segment of the cord.

Contraction of the ovarian follicle induced by local stimulation of its sympathetic nerves.

Strips of bovine ovarian follicle wall, known to contain smooth muscle cells innervated by adrenergic nerves, were dissected out and exposed to transmural electrical stimulation in an organ bath. A frequency-dependent contractile response was obtained with a maximum at 8-16 Hz. The response was abolished in the presence of tetrodotoxin and inhibited by bretylium, phentolamine and reserpine. Thus, stimulation of the sympathetic nerves in the ovarian follicle releases sufficient amounts of norepinephrine to produce a contraction of its wall, an effect mediated by alpha-adrenergic receptors.

Electron microscopic and pharmacologic evidence for a functional adrenergic innervation of the smooth musculature in the human fallopian tube.

Triple fixation for electron microscopy of the isthmic region of the human Fallopian tube distinguished adrenergic nerve terminals through their content of synaptic vesicles with a diameter of 50-60 nm. Non-vascular adrenergic nerves were found both outside and within smooth muscle bundles. Adrenergic varicosities, partly devoid of their Schwann cell ensheathing, frequently approached the smooth muscle cells within a distance of about 200 nm, and sometimes as close as 60-100 nm. These close contacts often occupied a considerable area of the naked varicosity. Electrical field stimulation of adrenergic nerves in the isthmic smooth muscle preparations in vitro induced an alpha-receptor mediated, frequency-dependent contractile response. The results show that the sympathetic nerves in the human Fallopian tube are able to exert a motor control of its smooth musculature, and may thus be involved in local functions essential for the normal fertilization process.

Myometrial norepinephrine in human pregnancy. Elevated levels in various disorders leading to cesarean section.

Myometrial norepinephrine was measured consecutively with high-performance liquid chromatography in women who delivered by cesarean section. The previously recorded marked reduction in tissue norepinephrine at the end of normal pregnancy was confirmed. When cesarean section was performed because of abruptio placentae/hemorrhage, impending asphyxia, dystocia or preeclampsia, the norepinephrine concentrations were six to ten times higher than in normal pregnancy. When an emergency cesarean section was carried out for premature breech presentation, transverse position of the fetus or prolapse of the umbilical cord (following an otherwise-normal pregnancy), the reduced norepinephrine values were not significantly different from those measured in a control group of women who underwent elective cesarean section. It is possible that the abnormally elevated levels of myometrial norepinephrine are part of the primary pathophysiologic condition associated with sympathetic overactivity, resulting in disturbed myometrial circulation and/or motor activity.

Lack of correlation between maternal body weight or weight gain and stillbirth in twin pregnancy.

OBJECTIVE: To study differences in maternal weight and weight gain for 48 twin-pregnant women with at least one stillbirth, versus 96 control mothers where both twin pairs survived the perinatal period. MATERIAL AND METHODS: In all, 48 twin gestations with one or both twins dead before or during birth (cases), in a defined region with 12 hospitals in southern Sweden between 1973 and 1989, were identified by using information stored at the Medical Birth Registry, the National Board of Health and Welfare, Stockholm. For each case pregnancy, two control twin pregnancies were selected; matching criteria were same parity and delivery unit, and similar year of delivery (+/- 1 year) and maternal age (+/- 5 years). RESULTS: Case and control women had a similar number of maternal body weight measurements during pregnancy, 8.9 vs. 8.0 (t = 1.5, p > 0.05). No significant difference between cases and controls was found regarding maternal weight (mean +/- SEM) at 12 weeks of gestation (68.0 +/- 1.4 vs. 68.1 +/- 0.9 kg; t = 0.2, p > 0.05), or in weight gain/pregnancy week (0.59 +/- 0.28 vs. 0.61 +/- 0.19 kg; t = 0.8; p > 0.05). CONCLUSION: The results of this study indicate that repeated body weight measurements of the twin-pregnant woman are of very limited value in the identification of a twin-pregnant woman later to face stillbirth.

Ultrasound examination in twin pregnancy and late fetal death.

OBJECTIVE: To test the hypothesis that the (case) twin later to succumb in utero has biparietal diameter measurements (by ultrasound) different from those (control) twins surviving the perinatal period. MATERIAL AND METHODS: Information from the Medical Birth Registry, National Board of Health and Welfare, Stockholm, was used to identify all births in a defined population in southern Sweden with about 20,000 deliveries each year. In 3,019 twin pregnancies between 1973 and 1989, one or both twins were stillborn in 47 cases (gestational duration > or = 28 weeks, birthweight > or = 500 g). For each case pregnancy, two control pregnancies were selected, the matching criteria being: same delivery unit, same parity (0, I, II, III+), similar year of delivery (+/- 1 year) and maternal age (+/- 5 years). Data on ultrasound examinations were extracted from the original medical records. Screening in early second trimester started at one of the units as early as 1973 and at the latest of 12 units in 1982. RESULTS: There was no obvious difference between cases and controls in intra-pair discordant biparietal diameter (BPD) measured in early second trimester. Nor was there any evident difference in the rate of deviant BPD between cases and controls. In all, 8% of dead male and 24% of dead female fetuses were by definition small-for-gestational age (< -2 standard deviations). CONCLUSIONS: No significant difference was seen between cases and controls regarding deviating biparietal diameters. Abdominal diameter may be a better predictor of subsequent fetal death (not analysed in this study), though only about 15% of all dead twins were deemed small-for-gestational age.

Effects of oophorectomy, sympathetic denervation and sex steroids on uterine norepinephrine content and myometrial contractile response to norepinephrine in the guinea pig.

Studies were performed in guinea pigs to elucidate alterations in endogenous uterine norepinephrine (NE) levels and changes in the contractile response to exogenous NE following local sympathetic denervation, oophorectomy, or treatment with sex steroids. Both in intact and oophorectomized animals the myometrial NE concentration was reduced after sex steroid treatment (0.5 microgram 17-beta-estradiol, or 0.1 microgram estradiol plus 2 mg progesterone, during 2 weeks), mainly as a result of increased uterine weight. After surgical removal of the hypogastric nerves and section of the suspensory ligaments, a similar response to sex steroids was seen if the animals had previously been oophorectomized. The myometrial contractile activity induced by exogenous NE was measured in vitro. The EC50 values (NE concentration giving 50% of the maximal response) showed a similar pattern of variations after hormonal treatment and oophorectomy as did the concentration of endogenous NE. Thus, exposure to the steroids leading to a reduction of neuronal NE also caused an increased sensitivity of the myometrial smooth musculature to exogenous NE, and in the various experimental groups the two parameters showed a close and significant relationship. The underlying mechanism may induce a denervation supersensitivity to NE induced by exposure to estrogen and progesterone.

Involvement of local adrenergic receptors in the process of ovulation in gonadotrophin-primed immature rats.

Immature female rats were primed with 4 i.u. PMSG at 08:00 h of Day 26. This results in ovulation in the morning of Day 29. The number of ovulations was counted in terms of newly formed corpora lutea in the morning of Day 30. Various adrenergic drugs were delivered into the ovarian bursa bilaterally in the afternoon of Day 27 to study their effect on ovulation. A methyl cellulose gel solution was used as vehicle to minimize leakage from the bursa. Noradrenaline, terbutaline and 4-aminopyridine significantly enhanced the number of corpora lutea compared to control ovaries injected with gel vehicle alone. The effect of terbutaline was counteracted by propranolol. Phentolamine partly blocked the noradrenaline-induced enhancement and the antagonist alone significantly reduced the number of ovulations. The results indicate that stimulation of alpha-adrenergic receptors (probably via actions in the follicle wall) as well as beta-receptors (influencing steroid-producing cells) may interfere with the ovulation process.

Influence of adrenoreceptor agonists and antagonists on ovulation in the rabbit ovary perfused in vitro.

Ovaries from sexually mature virgin rabbits were dissected free on both sides and cannulated in situ via that part of the aortic segment supplying the ovarian arteries. The ovaries were mounted in a closed, recirculating perfusion system for oxygenation in vitro. Ovulation was induced by human chorionic gonadotropin (hCG) given either i.v. (100 IU) or directly into the perfusion medium (20 IU). Follicular ruptures occurred in 42 out of a total of 54 ovaries. The in vivo route of hCG administration was found to be most efficient, with ovulations occurring after a mean of 11.5 h, which corresponds well with the incidence of ovulations in situ. The prostaglandin synthesis inhibitor, indomethacin, totally abolished the hCG-induced ovulations. beta-Adrenoreceptor stimulation in vitro with terbutaline or with noradrenaline in the presence of alpha-receptor blockade with phenoxybenzamine caused a significantly increased number of gonadotropin-induced ovulations. Phentolamine or phenoxybenzamine given alone reduced the number of ruptured follicles. Noradrenaline (in the absence of hCG) and clonidine augmented the incidence of ovulation. The results indicate that local adrenoreceptor mechanisms participate in the process of ovulation, both via alpha-adrenoreceptors (probably affecting the follicular smooth musculature) and beta-adrenoreceptors (possibly through some trophic or endocrine mechanism other than a mechanical factor).

Evidence for a role of prostaglandins in the adrenergic neuromuscular mechanism of the ovarian follicle wall.

Sympathetic nerves innervate smooth muscle cells in the theca externa of Graafian follicles and induce contraction of the follicle wall. The interaction of prostaglandins (PGs) with the function of this neuromuscular complex has been elucidated by the use of isolated strips from the protruding part of the wall of bovine ovarian follicles. PGF2 alpha contracts the strips, and it also potentiates the contractile response to electrical field stimulation of the nerves, but it has no effect on noradrenaline-induced contractions. PGE1 and PGE2 have direct relaxatory actions on the strip preparation (previously given an active contraction by carbamylcholine) and in high doses they, therefore, reduce the contractile response induced by noradrenaline. In low doses not affecting the noradrenaline response, PGE1 and PGE2 both decrease the amount of contraction induced by electric nerve stimulation, indicating an inhibitory action of the PGEs on the transmitter release. It is suggested that the role of PGs in the process of ovulation might, at least partly, be mediated by their interactions with smooth muscle cells and their sympathetic innervation in the wall of the Graafian follicle.

Characterization of histamine receptors mediating contraction and relaxation of the ovarian follicle wall.

Histamine is known to be present in ovarian tissue and may play a role in the ovulation process. The effect of histamine on the follicular smooth musculature was investigated using strips from the protruding part of mature bovine follicles, mounted in vitro for registration of isometric motor activity. Histamine contracted the preparation in a concentration-dependent manner. The response was inhibited competitively by the specific H1 receptor antagonist pyrilamine while the adrenergic alpha-receptor antagonist phentolamine had no clear-cut effect. A Schild plot revealed a pA2 value of 8.81, corresponding to a mean KB value (dissociation constant for receptor-antagonist complex) of (7.5 +/- 3.2) X 10(-9) M. After potassium depolarization and blockade of the contractile H1-receptors with pyrilamine, histamine induced a concentration-dependent relaxation of the follicle wall preparation. This response could be inhibited by the H2-receptor antagonist cimetidine (which also potentiated the contractile effect in the absence of pyrilamine). The pA2 value for the cimetidine-induced inhibition was 6.25, and KB was found to be (6.5 +/- 3.0) X 10(-7) M. The beta-receptor antagonist propranolol was effective only in very high concentrations. It is suggested that a possible role for histamine during follicle rupture is mediated via specific receptors in the follicular smooth musculature.

Intraovarian adrenergic nerves in the guinea-pig: development from fetal life to sexual maturity.

The development of the intraovarian adrenergic nervous system was investigated in the guinea-pig by use of chemical determination of catecholamines with high performance liquid chromatography (HPLC) and with the formaldehyde-induced fluorescence method for visualization of adrenergic nerves (Falck-Hillarp technique). Ovaries from fetuses (39-40, 45-50, 55-57, 60-63 days of gestation) and young animals (1, 2, 3, 7, 14, 30, 40-45 days of age) were included in the study. The noradrenaline concentration was low in the ovaries from the youngest fetuses but increased with age, reaching a maximum level at 2 days post partum. A marked decrease in noradrenaline concentration from the second to the third day of life was found as a consequence of the rapid increase in the ovarian weight during this time. A similar decrease in ovarian noradrenaline concentration after a period of rapid ovarian growth was noted at 30 days of age. Measurable amounts of adrenaline were found in the ovary only in the fetal stages; the highest concentration (0.73 microgram) was detected at 55-57 days of gestation.