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Biomedical subjects

F Ellendorff

Publications and source records attributed to F Ellendorff.

At least 37 records · Page 2Linked to original sources
PubMed1990

Opioid action on luteinizing hormone secretion in newborn pigs: paradoxical effect of naloxone.

German Landrace piglets, 6-7 days of age, received either saline (9 males, 8 females), 0.5 mg naloxone/kg body weight (7 males, 7 females), 2.0 mg naloxone/kg (7 males, 8 females) or 0.5 mg DADLE (potent leu-enkephalin analog)/kg (7 males, 7 females) through a catheter inserted into the jugular vein 2-4 days previously. Male or female piglets were allocated randomly, within litter, to the different experimental groups. Blood samples were withdrawn for a period of 240 min at 10-min intervals for the first 60 min following injection and at 20-min intervals for the rest of the test period. Piglets were separated from their mother via a detachable wall and were allowed to suckle every 50 min. DADLE failed to alter plasma levels of LH in both males and females. Naloxone induced a significant (P less than 0.01) decrease in LH concentrations in females 10 to 60 min after injection (saline: 2.3 +/- 0.2 ng/ml plasma (SEM); 0.5 mg naloxone/kg: 1.0 +/- 0.2 ng/ml plasma and 2 mg naloxone/kg 1.2 +/- 0.4 ng/ml plasma). In males low doses of naloxone reduced plasma LH levels 10 to 40 min after injection (saline: 2.0 +/- 0.3 ng/ml plasma and 0.5 ng naloxone/kg: 1.1 +/- 0.3 ng/ml), whereas a decrease in plasma LH levels occurred 80 to 140 min after injection of high doses of naloxone (saline: 2.1 +/- 0.2 ng/ml and 2 mg naloxone/kg: 1.0 +/- 0.2 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

In vitro characterization of secretion rates from silastic micropellets containing estradiol.

For local, controlled steroid hormone administration into tissues, such as the brain, we have prepared cylindric micropellets of 1 mm in length and 1 mm diameter. The micropellets are a mixture of silicone glue (silastic) and 0.1%, 1.0%, or 10% estradiol (E2). To evaluate in vivo E2 secretion rates, micropellets were implanted into the brains of 40 rats for either 1, 4, 8, or 12 weeks. In vitro 24 h E2 secretion rates of these implants were compared-after removal from the rat brain-with 24 h secretion rates of micropellets that had been incubated for the same periods of time in vitro only. In vitro release of E2 decreased steadily but asymptotically from the first day of incubation to the 3rd or 4th week, when an apparent steady state is achieved. With any E2 concentration the coefficient of variation for 24 h release rates rarely exceeded 15% within a group. The release rates increased nonlinearly with the concentration of E2 in the pellet. Subsequent to in vivo implantation the in vitro secretion of E2 was slightly higher than the in vitro secretion of micropellets incubated for the same period of time in vitro. Thus (1) the secretion rate from a pellet can be predicted rather exactly by the mixing ratio of silastic and E2 and (2) the secretion rate from the micropellet in vitro and in vivo appears to be rather similar. It is concluded that the method described is very useful for short-term (days) or long-term (weeks, albeit not constant) local exposure of defined tissues to steroid hormones.

Animals↗
PubMed1989

Spontaneous electromyographic activity throughout the cycle in the sow and its change by intrauterine oestrogen infusion during oestrus.

Two experiments were carried out to monitor influences on the uterine electromyographic activity (EMG) in cyclic gilts with chronic uterine EMG electrodes. In Exp. 1 the EMG was recorded continuously from Day -1 for 24 days and was evaluated for frequency, duration and amplitude. Progesterone and oestradiol in peripheral plasma were measured daily. As high amounts of oestrogens are characteristic for boar semen, in Exp. 2 the influence of seminal oestrogens on uterine contractions at Day 0 (first day of standing reflex) was investigated in gilts with chronic intrauterine catheters. They were infused with 10 ml saline (N = 4) or saline with physiological amounts of oestrogens (5 micrograms oestradiol + 2 micrograms oestrone + 4.5 micrograms oestrone sulphate; N = 4). Sham-treated gilts (infusion catheters, no infusion; N = 5) served as controls. The EMG was recorded for 2 h before and 9 h after infusion. In Exp. 1 the maximal amplitude (2040 +/- 98 microV) and duration (32 +/- 1.7 sec) but the lowest frequency (15.8 +/- 2.1 contractions/h) were found on Day 0. With decreasing oestrogen and increasing progesterone concentrations the frequency increased continuously until Day 5 (63.5 +/- 1.0 contractions/h) while the amplitude (183 +/- 13 microV) and duration (3.3 +/- 0.7 sec) decreased. During Days 6-13 the EMG activity was not detectable. The reverse pattern was found from the onset of luteolysis until the following Day 0. On Day 0 a significant correlation between oestradiol and the duration (r = 0.81; P less than 0.01; n = 10) but not the frequency was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Halothane anesthesia of several hours' duration in swine of the German Landrace breed, selected for resistance to malignant hyperthermia].

The malignant hyperthermia syndrome is widely spread in pigs of the German Landrace. This has precluded the use of halothane anesthesia. The advent of homozygous halothane-negative strains stimulated us to test whether such animals were suitable for longduration halothane anesthesia. Nine sows of the German Landrace (n = 4, homozygous halothane-positive (H+); n = 5, homozygous halothane-negative (-)) were used. Anesthesia was induced by Azaperon/Metomidat-HCL followed by intubation and exposure to halothane. All 4 halothane-positive animals died within 45-90 min following the onset of halothane administration, while all 5 halothane-negative animals survived a 4-5 h deep anesthesia without problems. Thus, homozygous hylothane-positive strains of German Landrace pigs may be surgically anesthetized for long durations with halothane anesthesia.

Anesthesia↗
PubMed1988

Characteristics of milk ejection, associated intramammary pressure changes and oxytocin release in the mare.

The neuroendocrine reflex theory of milk ejection was investigated in the horse under natural suckling conditions. To this end 12 lactating mares were provided with acute jugular catheters and with intramammary pressure (IMP) recording catheters. The foal had free access to the contralateral mammary complex. Intramammary pressure could thus be recorded while blood was drawn simultaneously for oxytocin analysis from the undisturbed animal. Suckling periods associated with a characteristic increase in IMP lasted significantly longer than unsuccessful nursing attempts. Elements of successful sucklings involved physical stimulation of the mammary gland, a quiet phase and a sudden increase in IMP. Successful suckling took place at about 20-min intervals with a wide range from less than 5 min to greater than 100 min. Between 5 and 10 mU oxytocin i.v. were sufficient to evoke an increase in IMP identical in shape and duration to a naturally induced increase in IMP. Mean peak oxytocin levels reached 15.8 pmol/l plasma, with a maximal release of 39 pmol/l. In the majority of cases (greater than 80%) peak oxytocin release did not occur until after the increase in IMP; in some cases an oxytocin surge was not detectable at all, despite a milk ejection-associated increase in IMP. In three cases increase in IMP could be observed while the foals were away from the mother with no signs of any intention to suckle. The data indicate that in the horse some elements of the neuroendocrine reflex, such as tactile stimulation of the teat and a surge of oxytocin before an increase in IMP, are facultative and not essential for normal milk ejection.

Animals↗
PubMed1988

Fetal and postnatal oxytocin secretion in the pig before and after a prostaglandin challenge.

Maturation of oxytocin secretion was studied in anaesthetized male and female 80 (n = 42) and 105 (n = 35) days-old fetal pigs and in conscious unrestrained piglets 4 weeks post partum (n = 11). Blood samples were taken from the maternal jugular vein and simultaneously from the exteriorized umbilical artery of fetuses (n = 4/sow) kept in utero under acute experimental conditions. Four weeks-old piglets were catheterized chronically. After initial observation of basal oxytocin secretion PGF2 alpha (0.5 mg in fetal and 2.5 mg in postnatal pigs as an intramuscular injection) was used as a challenge for oxytocin release. In sham groups physiological saline was injected. After treatment blood was collected up to 25 min (fetuses 80 days), 35 min (fetuses 105 days) or 125 min (piglets). Sampling interval was 5 min (fetuses 80 d) or 10 min (other groups). Maternal oxytocin concentrations remained at a stable level throughout the experiment and were not altered by PGF2 alpha application to the fetus. In the fetus, preinjection baseline oxytocin levels were obtained for all age groups with no sex difference. PGF2 alpha resulted in a rise (P less than 0.001) of fetal and postnatal oxytocin release within 5 min. In the day 80 fetal group only 60% of the animals responded with an increase of oxytocin concentration while 100% of the animals responded in all other age groups. Oxytocin levels remained elevated for the rest of the observation period in all age groups. Again, no sex difference was detected. The data demonstrate that oxytocin secretion is present and could be stimulated in the fetal pig as early as day 80 of fetal life. Maturational changes expressed by an increase in the number of fetuses responding to a challenge of PGF2 alpha with a release of oxytocin become apparent between day 80 and 105 of pregnancy.

Animals↗
PubMed1987

Ontogenetic development of proenkephalin A and proenkephalin B messenger RNA in fetal pigs.

Using solution hybridization analysis and Northern blotting with complementary RNA probes labelled to high specific activity, levels of proenkephalin A and B mRNA were analyzed throughout prenatal development in the hippocampus and striatum of fetal pigs. A differential time course for the appearance of these opioid precursor mRNAs was observed: in hippocampus, both mRNAs increased linearly throughout development with proenkephalin B mRNA increasing faster than proenkephalin A mRNA. In striatum, both mRNAs behaved similarly, increasing to a maximum level around mid-gestation and declining thereafter. The differences might be attributed to differential localization of the two precursor systems in the tissues and might be of functional relevance.

Animals↗
PubMed1987

Seminal oestrogens in the boar: origin and functions in the sow.

The boar produces considerable amounts of oestrogens in the Leydig-cells also occurring in semen. Very high oestrogen concentrations are measurable in the fluid of the tubuli, which contribute the main part of seminal oestrogens. Additionally, the accessory sex glands add 22% of the unconjugated oestrogens and 12% of conjugated oestrogens to the ejaculate. Concentrations vary considerably according to season and individuals. So far a maximum of 15.3 micrograms was measured in one ejaculate. Infusion of oestrogens (simulation of the oestrogen content of an ejaculate) at oestrus through a catheter into the uterus lumen leads to an increase of the myometrial contraction-frequency for 3 h. Additionally "inseminations" with oestradiol-17 beta (Oe 2), oestrone (Oe 1), and oestrone-sulfate (Oe 1-S) (naturally occurring in the ejaculate) in 10-micrograms amounts at oestrus may lead to an increase of PGF2 alpha concentrations in the uterine veins within a few minutes. This increase may be found after "insemination" with each of the three steroids but not after saline. A parallel rise of the "inseminated" oestrogen is measurable in the uterine vein plasma and may reach concentrations up to several thousand pg/ml. This rise also leads to significantly increased concentrations in peripheral plasma for about 30 min after the "insemination" of Oe 2 (increase of Oe 2 and Oe 1-S) and Oe 1 (Oe 1 and Oe 1-S). Consequences of seminal oestrogens for sperm transport and the timing of ovulation are discussed.

Animals↗
PubMed1987

Absence of nocturnal plasma melatonin surge under long and short artificial photoperiods in the domestic sow.

The circadian plasma melatonin profile of German Landrace sows was determined at 1-h intervals for 31 h after exposure to each of four different artificial photoperiods. Under 12L:12D, melatonin concentrations in four sows during the light phase ranged from 22 +/- 5.9 to 96 +/- 25.1 pg/ml (mean +/- SEM). During the dark phase (total dark) the individual concentrations increased two- to fivefold over the peak individual light phase values in three sows. This nocturnal surge was of 3.8 h duration and peaked at 190, 294, and 546 pg/ml at 0100 h, which was 5.5 h after the onset of dark. The surge was abolished in these animals after exposure to 16L:8D and could not be reinstated by the subsequent exposure to 8L:16D. During the latter two photoperiods the mean concentrations were consistently less than the maximum mean value of 30.8 +/- 10 pg/ml during the dark phase and 55 +/- 21.9 pg/ml during the light phase. All the sows displayed regular estrous cycles during the study, and the day of the estrous cycle on which the samples were obtained under each photoperiod was not significantly correlated with the presence or absence of the nocturnal surge. A separate experiment using different animals confirmed the nocturnal surge under 12L:12D. In two out of four cycling sows the peak concentrations during the dark phase (122 and 110 pg/ml at 0400 and 0500 h) were two- to sixfold higher than those of the light phase. Absence of the nocturnal surge under long and short daylengths may be a factor contributing to the decline in reproductive performance during the summer and winter months.

Animals↗
PubMed1986

Functional development of the prenatal brain. I. Recording of extracellular action potentials from the magnocellular system of the 18-day-old chicken embryo.

For the full understanding of the ontogeny of the electrical activity in the brain it is essential to record single unit activity of the fetus. However, investigations of the functional development of neuronal properties in mammals are largely limited by the inaccessibility of the prenatal brain. Therefore, we have designed a new method to record extracellular single unit activities of identified magnocellular neurones in the Nucleus paraventricularis of the chicken embryo after 18 days of incubation. One hundred and four magnocellular neurones were identified by antidromic stimulation from the neural lobe. In a high percentage of the neurones an A-B inflexion of the action potential could be observed similar to that frequently encountered in mammalian magnocellular neurones. The mean duration of the action potential was 2.8 ms with a range between less than 1 ms and 7 ms. This large range is probably due to developmental processes of the cell membrane and subsequent changes in the extra- und intracellular ion concentration. Fourty-six percent of the neurones generated spontaneous action potentials with a slow irregular firing pattern. The mean discharge frequency was estimated as approx. 1 Hz. In further 13% of the cells orthodromic action potentials could be observed only after the occurrence of several antidromic spikes. The data presented are the first recordings of single unit activity in the magnocellular system in the prenatal brain. They demonstrate that the chicken embryo may offer a suitable model to study the ontogeny of neuroendocrine systems in the fetal brain in-vivo.

Action Potentials↗
PubMed1986

Functional development of the prenatal brain. II. Ontogeny of the hypothalamo-neurohypophysial axis in the pre- and perinatal chicken brain.

The present paper investigates the ontogeny of connective patterns in the brain of the 17-, 17.5-, and 18-day-old chicken embryo and in the newborn chicken as well. From the onset of electrical activity, neurophysiological properties of neurones undergo significant changes during further development. Total duration of action potentials decreases (p less than 0.001) between day 17 of incubation and day one of life. The percentage of spontaneously active neurones increases significantly (p less than 0.01) from 20% on day 17 to 69% in the newborn chick. For the same time period mean conduction velocity of presumed non-myelinated fibers in the hypothalamo-neurohypophysial-tract increases by about 50%. On the other hand, mean constant latency decreases from 20 ms in the 17-day-old embryo to 15.5 ms in the newborn chick (p less than 0.001). Changes in threshold intensity to antidromic stimulation and the increasing number of identifiable neurones per embryo indicate that new cell populations may become excitable during development. The results show, that considerable maturational events take place in action potential properties of the magnocellular system during late embryonal and early postnatal life of the chicken.

Action Potentials↗
PubMed1986

Ontogeny of secretory patterns of LH release and effects of gonadectomy in the chronically catheterized pig fetus and neonate.

Two experiments were conducted to determine the ontogeny of secretory patterns of luteinizing hormone (LH) release and effects of gonadectomy on the characteristics of LH secretion in the chronically catheterized pig fetus and neonate. To study secretory patterns in intact animals, blood samples were collected from 44 pig fetuses and their mothers (Days 81, 99, 109 and 113 of gestation) as well as from 25 neonates (Days 4 and 8) every 15 min for 3 h (2 h on Day 81). The results indicate that the fetal adenohypophysis secretes occasional pulses of LH as early as Day 81 of fetal life. Fetal and maternal mean LH levels are low (0.25-0.50 ng/ml) at all gestational ages, with lowest values just before birth (Day 113 post coitum). Four-day-old neonates show a significant increase in pulse frequency (male and female) as well as pulse amplitude (female), relative to fetal values, leading to significant augmentations in mean LH levels. This is associated with reductions in both 17 beta-estradiol and progesterone. By 8 days of age significant sex differences in mean LH levels (males greater than females) appear. Testosterone/5 alpha-dihydrotestosterone levels (males) are low prenatally but are significantly increased after birth, possibly due to the stimulating effects of increasing LH levels. To study the gonadal control of LH secretion, forty-one 105-day-old fetuses and thirty-eight 4-day-old neonates were chronically catheterized and were either gonadectomized or remained as sham or control animals. Forty-eight and 96 h after surgery, blood samples were taken every 15 min for 3 h. No significant changes are detectable at 96 h in mean LH, pulse frequency and amplitude in female or male fetuses or in neonates. While significant reductions in testosterone levels are observed at 96 h in the male fetus and neonate, progesterone concentration is reduced only in the neonate. In the castrated female, on the other hand, neither fetus nor neonate display significant changes in circulating levels of progesterone and 17 beta-estradiol at 96 h. It is concluded that the pituitary of the pig is able to discharge LH with occasional pulses as early as Day 81 of fetal life; however, the pituitary remains suppressed until after birth, probably due to high circulating nongonadal steroids in the fetal compartment.

Animals↗
PubMed1986

Effect of haemorrhage on plasma lysine vasopressin and the cardiovascular responses to vasopressin in the pig fetus.

The effect of haemorrhage on plasma lysine vasopressin concentrations and the cardiovascular effects of intravenous injections of synthetic lysine vasopressin were studied in twenty-four chronically catheterized pig fetuses aged between 81 and 114 d gestation (term = 114 +/- 1 d). Removal of 15-20% of the estimated blood volume reduced mean arterial blood pressure and elevated plasma vasopressin concentrations above the mean basal value of 2.2 +/- 0.3 muu./ml. The vasopressin concentration in plasma of fetuses younger than 104 d was insignificantly affected at 30 and 60 min after the bleed, whereas the corresponding values in older fetuses were raised by 12.7 +/- 7.2 muu./ml (d.f. = 7) and 16.0 +/- 6.0 muu./ml (d.f. = 7) respectively. The pituitary concentration of vasopressin was also greater towards the end of gestation. Plasma osmolality was unaffected by fetal blood loss. Maternal concentrations of vasopressin did not change from the basal values of 1.0 +/- 0.1 muu./ml (d.f. = 16). Injection of vasopressin raised fetal blood pressure and decreased heart rate. These results demonstrate that lysine vasopressin is present in the circulation of the pig fetus at 81 d (0.72 gestation), and that near term fetuses respond to haemorrhage more rapidly, and to a greater degree than younger fetuses.

Animals↗
PubMed1985

Antidromic responses in the paraventricular magnocellular neurons of the rat hypothalamus: latency variations correlated with the firing rate.

Magnocellular neurosecretory cells were antidromically identified in the hypothalamic paraventricular nucleus (PVN) of urethane-anesthetized, ovariectomized female rats following electrical stimulation of the neurohypophysis. Seventy-one cells with a tonic pattern of spontaneous discharge were distinguished and used to examine the relationships between the measures of antidromic spike latency, activation threshold and discharge rate. The discharge rate was artificially modulated by either microiontophoresis of glutamate or antidromic stimulation of the neurohypophysis. In all the PVN cells with tonic activity, the latency lengthened and the threshold increased as a function of the discharge rate. Activation of individual cells by microiontophoresis of glutamate was effective, as was simultaneous activation of many PVN cells by antidromic stimulus. Similar relationships between the discharge rate and the parameters of antidromic activation were seen in 3 cells, when their rates varied spontaneously over a wide range without manipulation. These data suggest that the excitability of axons of presumed oxytocinergic cells in the PVN-neurohypophyseal system are influenced by their prior activity, probably through metabolic changes in individual axons.

Animals↗
PubMed1985

Prospects and limitations of the rosette inhibition test to detect activity of early pregnancy factor in the pig.

After preincubation of lymphocytes in serum of non-pregnant pigs and using a standard anti-pig-lymphocyte serum the upper limit of the 99.9% confidence interval of rosette inhibition titres (RIT) for pig serum was calculated to be 11.4 and all titres greater than 12 were defined as a proof of early pregnancy factor (EPF)-activity. The reproducibility of the RITs with serum samples of pregnant pigs was considered satisfactory (interassay coefficient of variation 23.8%), whereas their reproducibility was considered good with sera taken from non-pregnant animals (interassay coefficient of variation 6.5%). Problems of the test were particularly evident due to the absence of increased RITs after previous incubation of lymphocytes in serum of pregnant pigs. Therefore, all EPF-negative samples were reanalyzed up to two times; pregnancy was then correctly diagnosed for 88.7% of sows. There were 8.6% false positive results (N = 70) and 12.2% false negative results (N = 205). During the first half of pregnancy RITs displayed periodic fluctuations which resembled the physiological cycle interval of the pig. Between Weeks 5 and 9 of pregnancy greater numbers of EPF-negative sows were detected. Subsequently, a continuous increase of mean RITs occurred, which then declined gradually from Day 80 of pregnancy. Similar changes were observed for progesterone values in the dialysed serum samples. However, highest progesterone concentrations always followed elevated RITs with a delay of 1.5-4 days. A subthreshold cyclicity of ovarian and luteal function probably persists despite pregnancy.

Animals↗
PubMed1985

Detection of activity similar to that of early pregnancy factor after mating sows with a vasectomized boar.

Incubation of normal pig lymphocytes in serum samples collected from 10 sows immediately before, and at daily intervals after mating with a vasectomized boar significantly elevated the rosette inhibition titre (RIT) of a standard antilymphocyte serum in 6 animals on the first but not on the 2nd and 3rd day after copulation. Infusion of seminal plasma without mating into 5 sows induced an obvious, but not statistically significant, transient rise of titres in 3 pigs. Neither sodium chloride infusion (N = 5), nor sham copulation with diverted penis (N = 5) influenced serum RITs. Porcine seminal plasma showed an inherent rosette-inhibiting property. A depression of rosette formation was evident in a concentration-dependent fashion up to a dilution of 1 in 320. Similarly, preincubation of lymphocytes in serial dilutions of seminal plasma in a non-pregnancy serum sample led to an amplification of the rosette inhibiting capacity of the antilymphocyte serum. Non-specific activation of the eggs to release a signal which induces the production of early pregnancy factor (EPF) or the resorption of seminal plasma components into the blood circulation are considered as possible explanations for the EPF-like activity after mating with a vasectomized boar.

Animals↗