Evidence for central neuropeptidergic control of rumination in sheep

Effects of intracerebroventricular (ICV) vs. intravenous (IV) administration of tetragastrin, pentagastrin, CCK₈ and gastrin 17 on rumination were investigated in conscious sheep. Administered at 26 pmoles/kg ICV both tetra and pentagastrin induced a premature short (15–27 min) period of rumination only $\text{24±7}$ and $\text{23±9}$ min after food distribution in place of $\text{112±44}$ min in controls. Similar but less pronounced effects were observed for ICV administration of an equimolar dose of gastrin 17 whereas CCK₈ did not promote an early peciod of rumination despite its anorectic effects. Administered intravenously tetra and pentagastrin but not gastrin 17 caused early rumination only for 10 times higher doses. It is concluded that gastrin 17 and its C-terminal tetrapeptide may play a physiological role in the central control of rumination in sheep.     

Proglumide: Selective antagonism of the rumination but not gastric motor effects induced by pentagastrin in sheep

The effect of intravenous (IV) vs intracerebroventricular (ICV) administrations of pentagastrin on gastro-intestinal motility and rumination were investigated by electromyography in sheep ; these effects were compared to those obtained after a previous IV or ICV injection of proglumide. When ICV administered at a dose of 20 ng.kg^?1, pentagastrin did not significantly affect the frequency of reticular and abomasal spiking activity but elicited a 13 to 37 min period of rumination after a delay of 23 ± 7 min. In contrast, when IV infused at a rate of 20 ng.kg^?1.h^?1 during 20 min, pentagastrin inhibited significantly the frequency of reticular and abomasal contractions for 30 to 40 min but did not induce rumination. Proglumide ICV administered (0.8 mg/kg^?1) abolished the rumination induced by central injection of pentagastrin whereas a 10 times higher dose administered systematically (8 mg.kg^?1 IV) did not block these effects. Both of ICV and IV administrations of proglumide at respectively 0.8 and 8 mg.kg^?1 were unable to antagonize the inhibitory effects of pentagastrin on reticulum and abomasum motility.     

Absorption of Escherichiacoli endotoxin from the small intestines of mature non-pregnant gilts

The small intestines of 31 mature crossbred gilts were infused with $\text{Escherichia}$$\text{coli}$ endotoxin through permanent jejunostomies. A total of 86 infusions were done. The endotoxin was absorbed after 4 infusions. Evidence of absorption included variations in body temperatures, decline in white blood cell counts, detection of the endotoxin in circulating blood plasma samples by a limulus amebocyte lysate gelation test, and abnormal clinical signs. $\text{E.}$$\text{coli}$ endotoxin placed in the small intestines of normal, healthy, mature gilts does not readily cause illness.     

Pentagastrin-stimulated gastric acid secretion by the isolated perfused rat stomach

The purpose of this present study was to develop a method for stimulation of acid secretion by the isolated perfused rat stomach. Rat stomachs were perfused $\text{in}$$\text{situ}$ via the abdominal aorta and celiac axis with Krebs-Ringer bicarbonate buffer in the presence or absence of 10% ovine erythrocytes. The gastric lumen was perfused with distilled water and gastric contents were collected at frequent intervals through a catheter at the pylorus. Sixty minute gastric acid output in response to various concentrations of pentagastrin was determined by titration of gastric contents with 0.01 N NaOH to pH 7.0. During arterial perfusion with Krebs-Ringer bicarbonate buffer in the absence of ovine erythrocytes gastric acid output was 2.50±0.58 SEM μEq H⁺/h, which did not increase in response to perfusion with Krebs-Ringer bicarbonate buffer containing pentagastrin. However, inclusion of 10% ovine erythrocytes in the arterial perfusate resulted in substantial stimulation of gastric acid by pentagastrin: maximal acid output, achieved with a pentagastrin dose of 0.6 μg/kg/h, was 23.5±3.73 μEq H⁺/h (p<0.01). The results of the present study demonstrate the capacity of the isolated vascularly perfused rat stomach to secrete acid and provide a model for studying interactions of gastrointestinal regulatory peptides and their physiologic roles in the regulation of gastric acid secretion.     

Pentagastrin and adenosine 3',5'-cyclic monophosphate stimulated secretion of somatostatin from perfused rat gastric mucosa.

Immunoreactive somatostatin is secreted by rat gastric mucosa perifused $\text{in vitro}$. Somatostatin release is stimulated by pentagastrin and cyclic AMP with theophylline. These results suggest that gastric mucosal somatostatin may have a paracrine action as feedback inhibitor of gastrin secretion.     

Escherichiacoli endotoxin absorption from the ewe's uterus and peritoneal cavity

An experiment was conducted to assess the effects of estrogen or parturition on absorption of endotoxin from the ovine uterus. Twelve cycling ewes were assigned to one of four treatment groups (three ewes/group): Group I, no estrogen (NE) + intrauterine infusion of sterile saline (IUS); Group II, NE + intrauterine infusion of 100 mg endotoxin - Lipopolysaccharide W./$\text{E.}$$\text{coli}$ 0127:B8, Difco Laboratories, Detroit, MI (IUE); Group III, 3 days pretreatment with estradiol-17β (50 μg/da, E) + IUS; and Group IV, E + IUE. In addition, the uteri of three early postpartum ewes were infused with 100 mg endotoxin (Group V). Rectal temperatures (RT) and jugular blood samples were obtained at ?40, ?20, 0 (infusion), 20, 40, 60, 80, 100, 120, 180, and 240 minutes. The blood samples were analyzed for total white blood cell counts (WBC) and Limulus Amebocyte Lysate Assays (LAL). There were no alterations in RT, WBC, or LAL observed in Groups I–V. These results indicated that neither prior treatment with estradiol in cycling ewes nor parturition affected absorption of $\text{E.}$$\text{coli}$ endotoxin from the ovine uterus.A second study was conducted to characterize the changes in RT, WBC, and LAL during endotoxemia in cycling ewes. Three ewes received intraperitoneal infusions of 100 mg endotoxin and three ewes received intraperitoneal infusions of sterile saline. Evidence that endotoxin was absorbed from the peritoneal cavity was a decrease (P<0.10) in WBC and positive LAL in endotoxin-infused ewes. WBC and LAL did not change in saline-infused ewes. No changes in RT were observed in either group.     

Site of action for β-endorphin-induced changes in plasma luteinizing hormone and prolactin in the ovariectomized rat

A number of sites have been hypothesized as loci at which opioid substances act to alter the secretion of luteinizing hormone (LH) and prolactin (PRL) (1–8). The aim of the present study was to determine the site(s) at which the opioid peptide β-endorphin (β-END) acts to influence plasma LH and PRL levels in the ovariectomized (OVX) rat. β-END, administered into the third ventricle of conscious OVX rats fitted with jugular catheters, significantly decreased plasma LH in doses ? 50 ng and increased PRL levels at all doses administered (10, 50, 100 and 250 ng) in a dose dependent fashion. To identify possible central nervous system sites of action, 250 ng β-END was unilaterally infused into various brain sites. Plasma LH was significantly decreased and plasma PRL significantly increased by infusions into the ventromedial hypothalamic area, the anterior hypothalamic area, and the preoptic-septal area. There was no significant effect of β-END infusions into the lateral hypothalamic area, amygdala, midbrain central gray, or caudate nucleus. When hemipituitaries of OVX rats were incubated $\text{in}$$\text{vitro}$ with β-END (10^?7M to 10^?5M), there was no suppression of basal or LHRH-induced LH release, nor was there any alteration of basal PRL release. It is concluded that β-END acts at a medial hypothalamic and/or preoptic-septal site and not the pituitary, to alter secretion of LH and PRL.     

Corpus luteum regression induced by ultra-low pulses of prostaglandin F2α

In view of the pulsatile nature of PGF_2α secretion from the ovine uterus at the time of luteolysis, experiments were designed to examine the effect of pulsed infusions of PGF_2α on luteal function and to re-examine the minimal effective levels of PGF_2α required to induce luteolysis. To mimic physiological conditions, hour-long infusions of PGF_2α in increasing concentrations were given either 4 times in 19 h or 5 times in 25 h into the arterial supply of the autotransplanted ovary in conscious sheep on day 12 of an induced cycle. Blood flow and progesterone secretion rate from the ovary were used to monitor directly the luteolytic effect of administered PGF_2α. The concentration of LH in peripheral plasma was measured throughout each infusion experiment and the presence of a preovulatory peak of LH was used as an indicator of the permanence of luteal regression. Four pulses of PGF_2α in 19 h caused complete corpus luteum regression in only 1 of 4 animals whereas the addition of a fifth pulse (5 pulses in 25 h) caused permanent regression in 4 out of 4 animals. Infusion of 5 hour-long pulses of saline or PGF_2α at a rate of <0.04 μg/h did not induce permanent suppression of progesterone secretion. The average total effective dose of PGF_2α required to induced luteal regression when given as 5 pulses was 1/40th of the amount currently regarded as the minimal effective one when given by constant infusion into the ovarian artery. In another series of experiments the luteolytic effect of a single hour-long pulse of 0.1 μg/h PGF_2α given daily for either 3 or 4 days was investigated. A significant fall (ANOVA, F_0.01) in progesterone secretion rate, which reached a nadir at $\text{5.3 ± 2.2}\text{h (}\text{x}\text{±}\text{S.D.}\text{, n=15)}$, was followed by a recovery of progesterone secretion rate. Permanent luteal regression did not occur with this protracted regimen, suggesting that a relatively short pulse frequency of PGF_2α over a minimal period of 24 h is a necessary condition for physiological regression of the corpus luteum in sheep.     

Studies of the genetic and immunologic components of the maternal age effect

To assess the genetic component of the maternal age effect, the frequencies of aneuploid embryos derived from several inbred mouse strains were examined as a function of maternal age. Some of the strains were chosen to evaluate possible etiologic agents: CBA for premature reproductive aging and increased univalent frequency, and $\text{NZB}\text{J}$ and $\text{A}\text{J}$ for predisposition toward autoimmunity. The $\text{C3H}\text{HeJ}$ and $\text{C57BL}\text{6J}$ strains also were examined. Although there was considerable variation between strains, an increased frequency of aneuploid fetuses was observed in all strains as a function of maternal aging. The CBA strain revealed the greatest increase in frequency of aneuploid fetuses at a relatively early maternal age. The effect of autoimmunity was assessed by analyzing the frequency of aneuploid embryos derived from thymectomized $\text{A}\text{J}$ females. No significant difference in aneuploidy was found between thymectomized and control nonthymectomized animals.     

Parotid secretion and associated efferent activity inhibited by pentagastrin in sheep

The inhibition of parotid secretion by pentagastrin increased with dose for jugular and carotid injections (0.01-0.16 micrograms/kg) in acute preparations of 3 sheep anesthetized with sodium pentobarbital. The intracarotid effect exceeded that for the jugular both in magnitude across all doses and in slope relating % inhibition to ln dose (p less than 0.005). The greater depression from carotid injections indicated that the effect was mediated in the head in response to higher pentagastrin concentrations at any dose level. In other experiments, both secretion and associated efferent activity in the parotid nerve were depressed more by carotid than jugular injections of pentagastrin, secretion being reduced by 27.2 vs. 12.1% and efferent activity by 43.2 vs. 20.6% respectively (p less than 0.025). These results indicate that gastrin in the circulation may be able to inhibit parotid secretion in sheep by acting directly on the central nervous system.     

Serum principal iodothyronines and the influence of cold exposure associated with shearing in the sheep

The effect of cold exposure caused by shearing on serum thyroid hormone (TH) concentrations in sheep kept at an ambient temperature of 8.5°C was studied. While the deep body temperature fell to the lowest level 4 h after shearing the concentration of triiodothyronine (T₃) increased to a peak value at that time. Thyroxine (T₄) and metabolically inactive reverse triiodothyronine (rT₃) levels reached their peak value after 24 h. The $\text{T}{}_3\text{T}{}_4$ ratio reached a maximum at about 4 h and $\text{rT}{}_3\text{T}{}_4$ and $\text{rT}{}_3\text{T}{}_3$ ratios rose to maximum values about 24 h after shearing. This sequence of events suggest a biphasic response to cold—an immediate secretion of TH from the thyroid gland, followed by adaptive alteration in T₃ and rT₃ generation in the extrathyroidal tissues.     

Sulphatide metabolism in brain.

Octanol-water partition coefficients (log P) were determined for a series of substituted psychotomimetic phenethylamine derivatives. A relationship was established between log P, steric bulk in the paraposition and the ability to stimulate serotonin (5-HT) receptors in an $\text{in vitro}$ sheep umbilical artery preparation. It appears that Log P values and $\text{in vitro}$ activity in this preparation.may be useful in predicting hallucinogenic potency in man.     

Ontogenetic changes in pacemaker activity in chick heart

Pacemaker activity of the isolated chick heart changed considerably during development. The spontaneous impulse frequency increased up to the 11th–15th incubation day. This period of acceleration was followed by a marked deceleration around the time of hatching. Both acceleration and deceleration appeared to be caused by changes intrinsic to the pacemaker. Deceleration was related to a decrease in rate of slow diastolic depolarization. The results were compared with well-known ontogenetic changes in heart rate $\text{in vivo}$. This comparison indicates that the deceleration of pacemaker firing around hatching is counteracted by the development of sympathetic cardiac reflexes $\text{in vivo}$.     

Temperature dependence of active K+ transport in cation dimorphic sheep erythrocytes

Arrhenius diagrams of K⁺ pump fluxes measured between 15°C and 41°C were discontinuous in high K⁺ but not in low K⁺ sheep red cells. Exposure of low K⁺ cells to anti-L caused a bimodal temperature response of K⁺ pump flux with a transition temperature, $\text{T}\text{c}$, similar to that found in high K⁺ cells but with comparatively higher activation energies above $\text{T}\text{c}$.     

Evidence for dosage compensation of an X-linked gene in the 6-day embryo of the mouse.

The time at which dosage compensation of an X-linked gene in the mouse is established has been estimated by measuring the activity levels of two glycolytic enzymes, phosphoglycerate kinase (EC 2.7.2.3) and triosephosphate isomerase (EC 5.3.1.1), during early development of embryos from $\text{X}\text{X}$ and $\text{X}\text{O}$ mice. During preimplantation development the level of phosphoglycerate kinase in embryos from $\text{X}\text{X}$ mice was constant for the first 48 hr of development (2.55–2.71 nmoles/hr/embryo) and then dropped to one-half the earlier level (1.44 nmoles/hr/embryo) by 72 hr of development. The general developmental profile of phosphoglycerate kinase was similar in embryos from $\text{X}\text{O}$ mice; however, the absolute level of enzyme activity was reduced to approximately 1.4 nmoles/hr/embryo during the first 48 hr of development and to 0.9 nmoles/hr/embryo by 72 hr of development. These differences in phosphoglycerate kinase levels between embryos from $\text{X}\text{X}$ and $\text{X}\text{O}$ mice disappeared between the blastocyst and egg cylinder stages (150 hr postplug) during which time the activity levels had increased to 183 and 193 nmoles/hr/egg cylinder for embryos from $\text{X}\text{O}$ and $\text{X}\text{X}$ mice, respectively.The activity level for triosephosphate isomerase in embryos from $\text{X}\text{X}$ and $\text{X}\text{O}$ mothers did not differ at any stage of development; this suggests that the gene coding for triosephosphate isomerase is autosomal. In addition the level of activity remained constant during preimplantation development (approximately 3 nmoles/hr/embryo) and then, like phosphoglycerate kinase, increased 100-fold between the blastocyst and egg cylinder stages.The frequency distribution of the activity ratio (triosephosphate isomerase to phosphoglycerate kinase) in the egg cylinder of individual embryos from both $\text{X}\text{X}$ and $\text{X}\text{O}$ mothers was determined in order to detect differences among $\text{X}\text{X}\text{,}\text{X}\text{O}$ and $\text{X}\text{Y}$ embryos. These frequency distributions were unimodal, and hence these results coupled with the gene dosage differences observed during preimplantation development indicate that dosage compensation for an X-linked gene has been established in the 6-day mouse embryo.     

Effect of organic acid on gastrointertinal motility of rat invitro

The quantity of organic acids ( lactic acid, acetic acid, propionic acid and butyric acid ) in the content of the gastrointestinal tract of germ-free and conventional rats and the $\text{in}$$\text{vitro}$ effects of the organic acid on the motility of the gastrointestinal tract of rats were investigated.Organic acids were detected only in the gastrointestinal contents of conventional rats but not in those of germ-free rats.Lactic acid detected in the stomach of rats stimulated the motility of both small and large bowel while acetic acid, propionic acid and butyric acid found in the cecum stimulated the motility of the large bowel but not of small bowel.     

Plasma membrane NADH dehydrogenase and Ca2+-dependent potassium transport in erythrocytes of several animal species

Ca²⁺-dependent K⁺ transport and plasma membrane NADH dehydrogenase activities have been studied in several ‘high-K⁺’ (human, rabbit and guinea pig) and ‘low-K⁺’ (dog, cat and sheep) erythrocytes. All the species except sheep showed Ca²⁺-dependent K⁺ transport. NADH-ferricyanide reductase was detected in all the species and showed positive correlation with the flavin contents of the membranes. NADH-cytochrome $\text{c}$ reductase was very low or absent in dog, sheep and guinea pig membranes. No correlation was found between NADH dehydrogenase and Ca²⁺-dependent K⁺ channel activities in the species studied. Nor were any of the above activities correlated with $\text{(}\text{Na}{}^{\mathrm{+}}\text{+}\text{K}{}^{\mathrm{+}}\text{)-}\text{ATPase}$ activity.     

Altered motility of myometrium from estrous ewes after the regulation of estrus with progestagen or prostaglandin

The $\text{in}$$\text{vitro}$ motility of strips of myometrium was studied in estrous ewes after administration of melengestrol acetate (MGA), medroxyprogesterone acetate (MAP) or prostaglandin F_2α (PG) to regulate estrus. Ewes were killed during estrus, 2 to 4 days after the end of progestagen or PG treatment. The contractions of strips of myometrium were recorded by kymograph and compared to contractions of control ewes.Muscle relaxation was indicated by an interval of tracing that was nearly horizontal and close to the baseline. A major contraction was indicated by a sharp upward movement of the tracing pen and an interval of tracing above the baseline.Treating ewes with MAP by intravaginal sponge lengthened contraction time. Feeding MGA or MAP tended to shorten relaxation time, and injecting PG tended to both lengthen contraction time and shorten relaxation time. As a result of these effects, the proportion of time that myometrium spent in contraction averaged 74% for 42 ewes treated with progestagen or prostaglandin and 56% for 24 control ewes. These results indicate that treatments that inhibit sperm transport when used to regulate estrus also affect the nature of myometrial contractions $\text{in}$$\text{vitro}$.     

Impairment of primary in vitro response of New Zealand mouse spleen cells to a thymic-dependent antigen.

New Zealand Black (NZB) and NZB by New Zealand White (NZW) F₁ hybrid ($\text{B}\text{W}$) mice develop clinical signs of autoimmune disease between 6 and 10 months of age but spleen cells from these strains have a greatly reduced in vitro response to sheep erythrocytes (SRBC) as early as 5–6 weeks of age. This hyporesponsiveness can be only partially restored with 2-mercaptoethanol, allogeneic macrophages or spleen cells, or allogeneic factor. The response of NZB and $\text{B}\text{W}$ spleen cells to the thymic independent antigen DNP-Ficoll is nearly normal. The reduced in vitro SRBC response was found to be attributable to splenic T and B cells rather than macrophages. Macrophages from NZB mice were found to function normally. The in vitro behavior of NZB lymphocytes is very similar to non-autoimmune mice infected with common murine viral pathogens. NZB and $\text{B}\text{W}$ mice may be making an active immune response as early as 5 weeks of age.