Assay of Oxytocin by the Milk-Ejection Response in the Anesthetized Lactating Guinea Pig

Endocrinology ◽  
1962 ◽  
Vol 71 (2) ◽  
pp. 196-202 ◽  
Author(s):  
JOHN S. TINDAL ◽  
AKIRA YOKOYAMA
Keyword(s):  
Guinea Pig ◽  
Milk Ejection

PREFERENTIAL RELEASE OF OXYTOCIN FROM THE NEUROHYPOPHYSIS AFTER ELECTRICAL STIMULATION OF THE AFFERENT PATH OF THE MILK-EJECTION REFLEX IN THE BRAIN OF THE GUINEA-PIG

1968 ◽  
Vol 40 (2) ◽  
pp. 205-214 ◽  
Author(s):  
J. S. TINDAL ◽  
G. S. KNAGGS ◽  
A. TURVEY
Keyword(s):  
Blood Pressure ◽  
Electrical Stimulation ◽  
Guinea Pig ◽  
Arterial Blood Pressure ◽  
Pituitary Stalk ◽  
Milk Ejection ◽  
Arterial Blood ◽  
Milk Ejection Reflex ◽  
The Brain ◽  
Stimulation Of

SUMMARY Discrete portions of the afferent path of the milk-ejection reflex have been explored in the brain of the lactating guinea-pig. Both intramammary pressure and arterial blood pressure were recorded to detect release of oxytocin and vasopressin. It was found that the milk-ejection responses which occurred after electrical stimulation of the pathway in the midbrain and hypothalamus were caused by the release of oxytocin without detectable release of vasopressin. A mixture of oxytocin and vasopressin, in the ratio of approximately 3:1, was released only after electrical stimulation of the rostral tuberal region of the hypothalamus adjacent to the pituitary stalk. It is concluded that the afferent path in the brain of the guinea-pig studied is concerned with the preferential release of oxytocin from the neurohypophysis and that it is the pathway of the milk-ejection reflex.

THE AFFERENT PATH OF THE MILK-EJECTION REFLEX IN THE BRAIN OF THE GUINEA-PIG

1967 ◽  
Vol 38 (3) ◽  
pp. 337-349 ◽  
Author(s):  
J. S. TINDAL ◽  
G. S. KNAGGS ◽  
A. TURVEY
Keyword(s):  
Guinea Pig ◽  
Medial Geniculate Body ◽  
Pituitary Stalk ◽  
Medial Lemniscus ◽  
Milk Ejection ◽  
Major Pathway ◽  
Ventral Thalamus ◽  
Medial Geniculate ◽  
Milk Ejection Reflex ◽  
The Brain

SUMMARY The afferent path of the milk-ejection reflex has been studied in the brain of the lactating guinea-pig in light pentobarbitone anaesthesia. Square-wave pulses were applied between an indifferent electrode in the scalp and a monopolar electrode inserted stereotaxically in the brain. The brain was transected at the mid-cerebellar level to eliminate activation of the sympathetico-adrenal system, and milk-ejection pressure was monitored to detect release of neurohypophysial hormone(s). The afferent path of the reflex in the caudal midbrain was very compact and lay in the lateral tegmentum. More rostrally, milk-ejection responses were obtained from the tectum and mesencephalic central grey, but the major pathway remained in the lateral tegmentum and passed forward to lie ventromedial to the medial geniculate body, after which it divided into two components which we have termed the dorsal and ventral paths. The dorsal path traversed dorsomedially across the brainstem to reach the parafascicular thalamic nucleus, the extreme rostral central grey and the periventricular region at the meso-diencephalic boundary, and then continued forward to reach the pituitary stalk and the medial and dorsal hypothalamus. The ventral path traversed ventromedially to enter the subthalamus and then the lateral hypothalamus, in which it passed both to the rostral basal diencephalon and to the pituitary stalk. In the diencephalon, milk-ejection responses were obtained after stimulation of part of the ventral thalamus, the lateral, dorsal and anterior hypothalamic areas, the dorsomedial, ventromedial, arcuate, supraoptic and paraventricular nuclei, and the pituitary stalk. It is suggested from these findings that in the guinea-pig the suckling stimulus ascends by the spinothalamic system, and continues rostrally to relay with the medial and ventral thalamus, the dorsal longitudinal fasciculus and the medial forebrain bundle. Other ascending pathways in the medial lemniscus and mammillary peduncle may also be involved, but appear to be of only minor significance.

THE AFFERENT PATHWAY OF THE MILK-EJECTION REFLEX IN THE MID-BRAIN OF THE GOAT

1972 ◽  
Vol 52 (2) ◽  
pp. 333-341 ◽  
Author(s):  
G. S. KNAGGS ◽  
A. S. McNEILLY ◽  
J. S. TINDAL
Keyword(s):  
Guinea Pig ◽  
Afferent Pathway ◽  
Milk Ejection ◽  
Spinothalamic Tract ◽  
Blood Samples ◽  
Indifferent Electrode ◽  
Oxytocin Release ◽  
Milk Ejection Reflex ◽  
Fuller’S Earth ◽  
Stimulation Of

SUMMARY The position of the pathway for the release of oxytocin in the mid-brain was ascertained by exploration of a transverse stereotaxic plane (A4) in 23 anaesthetized goats. Electrical stimulation was applied between a monopolar electrode and an indifferent electrode in the scalp. Oxytocin release was monitored by simultaneous collection of blood samples during stimulation from a catheter in a jugular vein. The blood samples were extracted by the Sephadex G-25 or fuller's earth method and assayed for oxytocin content on the lactating guinea-pig preparation. Oxytocin release occurred occasionally after stimulation of certain sites in the tectum, central grey and reticular formation. Regular releases of oxytocin, however, were only obtained after stimulation of a pathway which was compact and lay in the lateral tegmentum of the mid-brain in association with the spinothalamic tract. The position of this pathway corresponds to that described previously for the afferent pathway of the milk-ejection reflex in the mid-brain of the guinea-pig and rabbit. In these three species therefore, the impulses concerned in oxytocin release appear to ascend through the mid-brain in the spinothalamic tract.

LEVELS OF OXYTOCIN IN THE JUGULAR VEIN BLOOD OF GOATS DURING PARTURITION

1965 ◽  
Vol 33 (2) ◽  
pp. 301-315 ◽  
Author(s):  
S. J. FOLLEY ◽  
G. S. KNAGGS
Keyword(s):  
Guinea Pig ◽  
Blood Plasma ◽  
Half Life ◽  
Jugular Vein ◽  
Gel Filtration ◽  
Induction Of Labour ◽  
Milk Ejection ◽  
Second Stage ◽  
Second Stage Of Labour ◽  
Considerable Portion

SUMMARY Oxytocin has been assayed in the jugular vein blood of goats during parturition; for comparison a few measurements were also made during pregnancy. The hormone was extracted from blood plasma by gel filtration, followed by lyophilization and then assayed in the lactating guinea-pig by the increase in intramammary pressure after intra-arterial injection. No oxytocin could be detected in the blood during pregnancy and it was found in only one of eight goats studied during the first stage of labour. The hormone was present in appreciable quantities in blood taken during the second stage of labour, and in general, the concentration rose to a maximum when the head presented. In cases of twin births oxytocin was usually present in the blood during the birth of the second kid but at a concentration lower than during delivery of the first. After expulsion of the kid the blood oxytocin titre diminished rapidly, suggesting that secretion of oxytocin ceased as soon as the kid was born. In three experiments the total release of oxytocin during a considerable portion (2·7–11·0 min.) of the second stage labour was estimated as 223–726 m-u. The results are consistent with the view that oxytocin is not essential for the induction of labour. Rather the hormone is released in response to stimuli arising from distension of the vagina and vulva, and by virtue of its contractile effect on the uterus assists parturition. The half-life of intravenously injected oxytocin in the lactating goat was found to be 1 min. 22 sec. After storage of lyophilized blood extracts at −15° for 5 months milk-ejection activity had declined by only 27%.

SUCKLING IN THE GUINEA-PIG: THE SIMULTANEOUS RELEASE OF OXYTOCIN AND NEUROPHYSIN

1981 ◽  
Vol 90 (2) ◽  
pp. 227-236 ◽  
Author(s):  
I.C.A.F. ROBINSON ◽  
C. N. WOOLF ◽  
J. A. PARSONS
Keyword(s):  
Weight Gain ◽  
Guinea Pig ◽  
Direct Evidence ◽  
Maternal Blood ◽  
Laboratory Model ◽  
Hormone Release ◽  
Rapid Rise ◽  
Milk Ejection ◽  
Blood Samples ◽  
Serial Samples

The release of oxytocin and neurophysin during suckling has been studied in conscious unrestrained guinea-pigs. After prior separation, mothers and litters were allowed to suckle for a period of 10 min, and the weight gain of the litter recorded as an index of milk transfer. Maternal blood samples were obtained without disturbance through previously implanted intravenous cannulae and neurophysin and oxytocin determined on unextracted plasma by specific and sensitive radioimmunoassays. In 82 out of 118 experiments the young gained weight during suckling (1·6±0·1 (s.e.m.) g/pup) and this was associated with large rises in both oxytocin and neurophysin concentrations in plasma (mean concentrations: oxytocin 65·4fmol/ml, neurophysin 360fmol/ml). Where serial samples were taken, oxytocin and neurophysin showed a rapid rise and fall in concentration closely associated with the occurrence of milk ejection as judged by the behaviour of the litter. The present results provide the first direct evidence of a spurt release of both oxytocin and neurophysin measured simultaneously during milk ejection. The conscious lactating guinea-pig thus provides a useful laboratory model in which to study hormone release during milk ejection.

Effect of Contraceptive Steroids on the Endometrium of Guinea Pig: SEM study

1977 ◽  
Vol 35 ◽  
pp. 668-669
Author(s):  
Mai M. Said ◽  
Ramesh K. Nayak ◽  
Randall E. McCoy
Keyword(s):  
Guinea Pig ◽  
Reproductive Tract ◽  
Three Dimensional ◽  
Female Reproductive Tract ◽  
Human Female ◽  
Surface Ultrastructure ◽  
Transmission Electron ◽  
Sem Study ◽  
Uterine Mucosa ◽  
Group 1

Burgos and Wislocki described changes in the mucosa of the guinea pig uterus, cervix and vagina during the estrous cycle investigated by transmission electron microscopy. More recently, Moghissi and Reame reported the effects of progestational agents on the human female reproductive tract. They found drooping and shortening of cilia in norgestrel and norethindrone- treated endometria. To the best of our knowledge, no studies concerning the effects of mestranol and norethindrone given concurrently on the three-dimensional surface features on the uterine mucosa of the guinea pig have been reported. The purpose of this study was to determine the effect of mestranol and norethindrone on surface ultrastructure of guinea pig uterus by SEM.Seventy eight animals were used in this study. They were allocated into two groups. Group 1 (20 animals) was injected intramuscularly 0.1 ml vegetable oil and served as controls.

Ultrastructure and Drug Metabolism in the Developing Guinea Pig

1973 ◽  
Vol 31 ◽  
pp. 538-539
Author(s):  
W. Kuenzig ◽  
M. Boublik ◽  
J.J. Kamm ◽  
J.J. Burns
Keyword(s):  
Guinea Pig ◽  
Metabolic Activity ◽  
Animal Species ◽  
Adult Animal ◽  
Smooth Endoplasmic Reticulum ◽  
Fetal Life ◽  
Mixed Function Oxidase ◽  
Cytochrome P 450 ◽  
Microsomal Mixed Function Oxidase ◽  
Mixed Function Oxidase Activity

Unlike a variety of other animal species, such as the rabbit, mouse or rat, the guinea pig has a relatively long gestation period and is a more fully developed animal at birth. Kuenzig et al. reported that drug metabolic activity which increases very slowly during fetal life, increases rapidly after birth. Hepatocytes of a 3-day old neonate metabolize drugs and reduce cytochrome P-450 at a rate comparable to that observed in the adult animal. Moreover the administration of drugs like phenobarbital to pregnant guinea pigs increases the microsomal mixed function oxidase activity already in the fetus.Drug metabolic activity is, generally, localized within the smooth endoplasmic reticulum (SER) of the hepatocyte.

Glycogen in guinea pig neutrophils: Ultrastructural study of neutrophils at the intradermal site of BCG injection

1983 ◽  
Vol 41 ◽  
pp. 726-727
Author(s):  
Corazon D. Bucana
Keyword(s):  
Bone Marrow ◽  
Guinea Pig ◽  
Electron Density ◽  
Peritoneal Cavity ◽  
Ultrastructural Study ◽  
Guinea Pigs ◽  
Random Distribution ◽  
Glycogen Content ◽  
Polymorphonuclear Neutrophils ◽  
Ultrastructural Studies

In the circulating blood of man and guinea pigs, glycogen occurs primarily in polymorphonuclear neutrophils and platelets. The amount of glycogen in neutrophils increases with time after the cells leave the bone marrow, and the distribution of glycogen in neutrophils changes from an apparently random distribution to large clumps when these cells move out of the circulation to the site of inflammation in the peritoneal cavity. The objective of this study was to further investigate changes in glycogen content and distribution in neutrophils. I chose an intradermal site because it allows study of neutrophils at various stages of extravasation.Initially, osmium ferrocyanide and osmium ferricyanide were used to fix glycogen in the neutrophils for ultrastructural studies. My findings confirmed previous reports that showed that glycogen is well preserved by both these fixatives and that osmium ferricyanide protects glycogen from solubilization by uranyl acetate.I found that osmium ferrocyanide similarly protected glycogen. My studies showed, however, that the electron density of mitochondria and other cytoplasmic organelles was lower in samples fixed with osmium ferrocyanide than in samples fixed with osmium ferricyanide.

Ultrastructural Studies on Genital Infection with the Chlamydial Agent of Guinea Pig Inclusion Conjunctivitis

1977 ◽  
Vol 35 ◽  
pp. 352-353
Author(s):  
B. L. Soloff ◽  
A. L. Barron ◽  
H. J. White ◽  
R. G. Rank
Keyword(s):  
Guinea Pig ◽  
Sexual Contact ◽  
Chlamydia Psittaci ◽  
Genital Infection ◽  
Major Site ◽  
Ultrastructural Studies ◽  
Tissue Specimens ◽  
Guinea Pig Model ◽  
Adequate Tissue ◽  
Genital Tissue

Chlamydial organisms (specifically C. trachomatis) have been implicated as a frequent cause of genital infection in the human (1). Study of the histo- pathological aspects of such infections has been impeded because of difficulties in obtaining adequate tissue specimens and the lack of a suitable experimental host. In 1964, Murray (2) isolated the causative agent of guinea pig inclusion conjunctivitis which possesses similarities to human inclusion conjunctivitis. This guinea pig organism was found to be a member of the Chlamydia psittaci subgroup and was designated as the Gp-ic agent. Male guinea pigs have been successfully infected with Gp-ic by intraurethral inoculation. Transmission of the infection to the female by sexual contact has been demonstrated (3). We are not aware of any ultrastructural studies to date concerning the development of this agent in genital tissue.Studies in our laboratory have established that, in our guinea pig model, the cervix is the major site of injection.

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