Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ultrastructural features of paraventricular (PVN) and supraoptic (SON) neurons and of their axons were studied in lactating and dehydrated rats. Under both conditions of stimulation, the PVN and SON neurons and their axons enlarge. The protein synthesizing apparatus of the neurons becomes activated, but the number of neurosecretory granules (NSG) is decreased. No differences are seen between the PVN and SON neurons during lactation or dehydration. The similarity and simultaneity of the response of the PVN and SON neurons to these two different stimuli is discussed in the light of the theory of nuclear and neuronal specialization for the production of only one hormone. After prolonged lactation of over 2 1/2 weeks' duration, neurons with extreme vacuolation of the rough endoplasmic reticulum (RER) appear in the PVN and SON; the vacuolated neurons appear earlier and predominantly in the PVN involving a maximum of 10-15% of all PVN neurons. Vacuolated neurons were never seen in either nucleus during dehydration of up to 6 days' duration. The vacuolation is suggested to represent an exhaustion phenomenon due to an intense, long-lasting stimulus for oxytocin synthesis. The predominant location of the vacuolated neurons in the PVN supports the theory that oxytocin is produced predominantly in the PVN. The decrease in the number of NSGs during these states of enhanced hormone secretion is considered to corroborate the proposed existence of an extragranular fast axoplasmic transport mechanism in PVN and SON neurons. The possible existence of a reuptake mechanism into NSGs, similar to that in the vesicles of monoaminergic nerve endings is discussed.
 ...
PMID:Ultrastructural studies on the hypothalamic neurosecretory neurons of the rat. III. Paraventricular and supraoptic neurons during lactation and dehydration. 5 8

Treatment of unanesthetized castrated adult male rats every 3 h for 48 h with either 5 microgram of arginine vasotocin (AVT) and/or 1 microgram luteinizing hormone-releasing hormone (LRH) caused a significant inhibition of plasma levels of luteinizing hormone (LH) and compared to castrated control rats receiving diluent only. However, the intravenous (iv) injection of 1 microgram of AVT into urethane-anesthetized male rats which had been castrated for 0, 24 or 48 h did not affect plasma levels of LH at 10, 20 or 60 min following injection compared to their respective diluent-treated castrated control rats. Similarly, the iv injection of either 100 ng, 1 microgram or 10 microgram AVT was unable to acutely affect plasma levels of LH in intact male rats. Following the iv injection of 2 doses of 50 ng LRH spaced 1 h apart in anesthetized castrated male rats, 2 peaks of equal magnitude in plasma LH were noted. Castrated rats treated with 2 injections spaced 1 h apart of LRH + AVT had significantly higher plasma levels of LH than did rats treated with LRH alone. In subsequent studies, both AVT and arginine vasopressin were observed to augment the plasma response of LH to an injection of LRH whereas oxytocin had no effect. A single injection of AVT + LRH significantly augmented the plasma titers of LH compared to levels observed in LRH-treated control rats as did a second injection 1 h later. The administration of cyproterone acetate sc for 2 days by itself had no effect on plasma LH but in conjunction with LRH caused a marked rise in plasma LH compared to intact rats treated with LRH alone. AVT in combination with LRH and cyproterone acetate caused a significant elevation in plasma LH at 60 min post-injection when compared to plasma levels of rats treated with LRH alone or the combination of LRH and cyproterone acetate. It is concluded that acute intravenous injections of AVT augment the LH-releasing activity of LRH; chronic treatment for 48 h, however, with LRH + AVT leads to a significant depression of plasma LH perhaps due to an exhaustion of the releasable pool of LH in the anterior pituitary.
 ...
PMID:Interaction of luteinizing hormone-releasing hormone, cyproterone acetate and arginine vasotocin on plasma levels of luteinizing hormone in intact and castrated adult male rats. 37 36

Neurosecretory terminals (neurosecretosomes, NSS) were isolated from rat neurohypophyses. High [K+]o or veratridine stimulated secretion of vasopressin and oxytocin by up to approximately 100-fold. Stimulated secretion was dependent on calcium and temperature, and could be elicited from NSS maintained in culture for 4 days. After overnight culture of the NSS, secretion was still inhibited by calcium channel blockers (cobalt, dihydropyridines, omega-conotoxin, D 600) and kappa opiates (dynorphin and U50488). Ionomycin evoked dose- and calcium-dependent hormone release, with a Hill coefficient for calcium of 1.74. High [K+]o enhanced the 5 microM ionomycin-induced secretion, apparently through calcium entry rather than depolarization, as the increase in secretion was abolished by 100 microM D 600. During prolonged depolarization the hormone secretion peaked within 2 min, then declined to near basal levels. Depolarization for 25 min without calcium neither activated secretion nor prevented subsequent secretion on readdition of calcium, suggesting that the decline in secretion was not due to membrane depolarization. Indeed, the rates of decline in secretion were similar for different levels of depolarization (0.070 +/- 0.003 and 0.081 +/- 0.003 min-1 for 25 and 45 mM [K+]o, respectively). Four minutes after the onset of continuous depolarization (45 mM [K+]o) in the presence of calcium, the declining secretion was still dependent on voltage-activated calcium influx through channels sensitive to D 600 and nitrendipine. The results presented here suggest that the decline in secretion during prolonged depolarizing stimuli may be due to exhaustion, inactivation, or desensitization of a calcium-triggered event.
 ...
PMID:Activation and inactivation of oxytocin and vasopressin release from isolated nerve endings (neurosecretosomes) of the rat neurohypophysis. 207

The effect of oxytocin on the ACTH, cortisol, GH and PRL response to physical exercise was investigated in 6 normal men. In addition, the possible involvement of endogenous opioids in the mediation of oxytocin action was evaluated. After fasting overnight, each subject was tested on four mornings at least 1 week apart. Exercise was performed on a bicycle ergometer. The workload was gradually increased at 3-min intervals until exhaustion and lasted about 20 min in all subjects. Tests were carried out under administration of oxytocin (2000 mIU as an iv bolus injection plus 32 mIU/min per 30 min) or naloxone (10 mg as an iv bolus injection) alone; furthermore, the effect of oxytocin together with naloxone (10 mg as an iv bolus injection) was evaluated. In the remaining test, normal saline was given instead of drugs. Plasma ACTH, cortisol, PRL and GH concentrations were significantly increased by physical exercise. Administration of oxytocin, naloxone or their combination was without effect on the PRL and GH rise elicited by exercise. In contrast, the exercise-induced ACTH and cortisol response was significantly raised by naloxone and reduced by oxytocin. When oxytocin was preceded by administration of naloxone, the ACTH and cortisol response to exercise was not reduced by oxytocin. These data show that oxytocin is capable of inhibiting the rise in ACTH and cortisol, but not in GH and PRL induced by physical exercise. Since naloxone abolished the inhibitory effect of oxytocin, oxytocin action on ACTH and cortisol secretion might be supposed to be mediated by an opioid pathway.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Oxytocin reduces exercise-induced ACTH and cortisol rise in man. 284 72

Research on successful breast feeding demonstrated the need for a supportive person who encourages the mother. A letdown reflex induced by the release of oxytocin can cause insufficient milk production, as can psychosocial factors (exhaustion, fear, stress). A South African organization formed mother support groups resulting in increased prevalence and duration of breast feeding. Work pressures, and sore nipples among women of low socioeconomic status cause early cessation of nursing. In 1984, a sister at the Retreat Midwife Obstetric Unit in Cape Town involved mothers in a short course with great success. After discharge they could contact a person for help and support to continue breast feeding. This program could serve as a model for other nurses. There is a need for breast feeding counselors, since women are increasingly involved in work while taking care of young children. Health services are unable to provide such postpartum assistance and encourage breast feeding.
 ...
PMID:Support networks for breastfeeding mothers. 369 10

The effect of intense muscular work (80% of maximal oxygen uptake) on responses of plasma hormones involved in electrolyte and water balance were measured in 14 male subjects. They were divided into three groups according to their maximal oxygen uptake and the duration of exercise performed until exhaustion: well trained subjects (group I), trained subjects (group II), and untrained subjects (group III). Pulmonary gas exchange, heart rate, rectal and skin temperature, and weight loss were measured as well as hematocrit and plasma and urine sodium and potassium concentrations. Rectal temperature increased significantly in all subjects after exhaustion. The variation of hematocrit was smallest and the weight loss greatest in the well-trained subjects. Plasma aldosterone, renin activity (PRA), vasopressin (AVP), and neurophysin (Np) displayed highly significant increases after exercise in all three groups: PRA was increased 4.5 times (p < 0.01), aldosterone 13 times (p < 0.05), Np 2.6 times (p pe 0.05), and AVP 4.8 times (p < 0.05). Nevertheless, there was no correlation between the changes in PRA and those in plasma aldosterone, nor between aldosterone and plasma sodium or potassium. At the urinary level, the only striking observation was that free water clearance tends to become positive after exercise. Our results provide evidence that this kind of exercise produces a highly significant increase in plasma levels of the hormones involved in electrolyte and water balance. They also indicate that it is among the well-trained subjects that sweat loss is highest though the hematocrit increase is the smallest; this suggests that water is shifted more efficiently from the extravascular compartment.
 ...
PMID:Plasma AVP, neurophysin, renin activity, and aldosterone during submaximal exercise performed until exhaustion in trained and untrained men. 699 37

Plasma vasopressin (AVP) and oxytocin (OXT) were determined by radioimmunoassay in healthy young men before, during and after a running exercise until exhaustion. In four of the five test subjects (one subject was underloaded) physical load resulted in a marked increase in plasma AVP with peak values of 11.7 to 57.8 pg/ml at exhaustion. Plasma OXT increased in three test subjects with peak values of 4.5 to 23.9 pg/ml. Within 1 h of recovery, both neuropeptides returned to basal plasma levels. The relationship between plasma AVP and osmolality (p less than 0.001) suggests that changes in osmolality play a dominant role in regulating the secretion of AVP. Besides peripheral effects, the increased levels of AVP and/or OXT during and immediately after the exercise, respectively, might induce a favourable action on the brain function. Determination of plasma AVP and OXT during a day-night cycle in the same test subjects reveals increased AVP levels from 02.00 to 08.00 h as compared to the other time periods chosen (18.00--24.00 h, p less than 0.001; 08.00--16.00 h, p = 0.031). In contrast, OXT does not differ between these time periods but decreased from 08.00 to 16.00 h (p less than 0.01). Accordingly, no correlation exists between both neuropeptides suggesting an independent secretion. It is unclear whether the circadian variations shown are able to influence the neuropeptide response to exercise.
 ...
PMID:Plasma vasopressin and oxytocin in response to exercise and during a day-night cycle in man. 712 45

Effects of smoking on a fetus include higher perinatal mortality rates, lower birth weight, and impaired mental and physical growth due to carbon monoxide and nicotine. Infants of smoking mothers have greater risk for uteroplacental insufficiency which can be detected by the RAD (fetal activity-acceleration determination). A study of 350 high-risk nonsmoking pregnant women and 128 smoking pregnant women showed that pre-eclampsia was significantly less in smoking women; however, there was a higher incidence of fetal nonactivity (20.8% versus 13.1% for nonsmokers). When nonreactive FAD was evaluated, and OCT (oxytocin challenge test) was performed with more positive OCT's encountered in the nonsmoking group. Cesarean sections were higher (21.9%) in smokers than nonsmokers (17.8%) and cesareans due to fetal distress were also higher in smokers (3.9%). There was a 254.1 gm mean birth weight difference for infants of smoking mothers. Sporatic progression from reactive to nonreactive FAD may be due to: 1) a mother smoking prior to an FAD which could stimulate activity; or 2) exhaustion in the morning after the fetus has been stimulated due to smoking for approximately 16 hours; therefore, depending on when the last cigarette was smoked, fetal reactivity or nonreactivity could result.
 ...
PMID:Diminished fetal reactivity with smoking. 735 4

1. In many mammals, severe dehydration is known to cause exhaustion of the vasopressin content of the neural lobe. Here, we have examined the physiological state of the neurohypophysis of the jerboa Jaculus orientalis, a rodent inhabitant of a semi-desert climate. 2. Isolated neurohypophyses and neurosecretory nerve endings were perfused in vitro and vasopressin and oxytocin release were determined by radioimmunoassay. 3. Electrical stimulation of the neurohypophysis with bursts of pulses mimicking the activity of hypersecreting neuroendocrine neurones induced similar increases of secretion in both control animals and animals dehydrated for up to 2 months. Neurohormone release was greatly potentiated when the bursts of pulses were separated by silent intervals. 4. Prolonged stimulation of neurohypophyses from both control and dehydrated animals induced a sustained increase of vasopressin release; in contrast, oxytocin release under similar conditions showed a biphasic secretory pattern consisting of a transient increase that subsequently decreased to a steady level whose amplitude was similar to that for vasopressin. 5. K(+)-induced secretion was largely inhibited by the Ca2+ channel blockers nicardipine and omega-conotoxin, suggesting that in this neurosecretory system both L- and N-type calcium channels play a major role in stimulus-secretion coupling. Depolarization of isolated nerve endings using a fast-flow perifusion system showed that there was no difference in the amplitude and the time course of the secretory response in dehydrated and hydrated animals. 6. The results demonstrate that, despite the climatic conditions in which the jerboas live, their neural lobes retain the capacity to release, upon depolarization of the plasma membrane of the nerve endings, large amounts of neurohormone. It is concluded that the neurohypophyseal peptidergic release system in the dehydrated jerboa functions adequately even under extreme environmental stress.
 ...
PMID:Stimulus-secretion coupling in the neurohypophysis of the jerboa Jaculus orientalis. 796 10

The aims of this study were to test the hypothesis that the substrates of xanthine oxidase (XO), xanthine and hypoxanthine, are consumed while the milk is stored in the gland between milkings, and to explore how XO activity responds to bacteria commonly associated with subclinical infections in the mammary gland. Freshly secreted milk was obtained following complete evacuation of the gland and induction of milk ejection with oxytocin. In bacteria-free fresh milk xanthine and hypoxanthine were converted to uric acid within 30 min (T1/2 approximately 10 min), which in turn provides electrons for formation of hydrogen peroxide and endows the alveolar lumen with passive protection against invading bacteria. On the other hand, the longer residence time of milk in the cistern compartment was not associated with oxidative stress as a result of XO idleness caused by exhaustion of its physiological fuels. The specific response of XO to bacteria species and the resulting bacteria-dependent nitrosative stress further demonstrates that it is part of the gland immune system.
 ...
PMID:Posttranslational ruling of xanthine oxidase activity in bovine milk by its substrates. 1788 77


1 2 Next >>