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SUMMARY
A high concentration of alkaline phosphatase occurs in the vessels of the hypothalamus and neurohypophysis of the macaque, and a low concentration in the cytoplasm of neurones of the supraoptic and paraventricular nuclei. These neurones contain a high concentration of acid phosphatase, and also both true and pseudo-cholinesterase. The neurohypophysis contains only pseudo-cholinesterase in a predominantly perivascular distribution.
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SUMMARY
The pars distalis, pars intermedia and infundibular process make up, respectively, 61, 5 and 34% of the volume of the pituitary gland of normal mature female rhesus monkeys. The pars distalis is relatively smaller in immature animals, and larger during pregnancy.
Section of the pituitary stalk is followed by a significant increase in the volume of the pars intermedia; the infundibular process always decreases in volume, while the pars distalis shrinks to a lesser and more variable extent.
Histological changes in the pars intermedia suggest that cellular hypertrophy, infiltration of atypical cells, and cyst formation all contribute to the increase in volume, and that the changes are at any rate partly degenerative in nature.
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The regional distribution of types of cell in the pars distalis of the ferret's pituitary gland has been described. Seasonal variations in cytology, and the effect of thyroidectomy and gonadectomy have been studied.
The gonadotrophic cells contain coarse PAS-positive granules, and are distributed widely throughout the gland. In anoestrous animals they are poorly granulated, and become almost totally degranulated after ovariectomy. PAS-positive cells which also stain with Alcian blue appear to be thyrotrophic in function, and become degranulated after thyroidectomy. They occur throughout most of the gland, but especially in ventral and rostro-lateral regions.
Pregnancy, or treatment of ovariectomized animals with oestrogen, is followed by the appearance of numerous cells equivalent to the 'carminophils' of the cat.
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SUMMARY
1. The pituitary stalk was divided transpalatally in a series of female ferrets.
2. The lesion was followed by infarction of a variable amount of tissue in the antero-superior region of the pars distalis, up to a maximum of 30% of its volume. Later fibrosis and incomplete regeneration of glandular tissue occurred.
3. There was no significant hypertrophy of the pars intermedia, but its cells showed an increase in cytoplasmic ribonucleic acid after division of the stalk.
4. The neural process appeared normal for several days after operation, but after the 4th day atrophied rapidly.
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SUMMARY
Six distinct types of cell can be distinguished in the pars distalis of the pituitary gland of the female ferret after staining by performic acid-Alcian blue followed by periodic acid-Schiff (PAS)-orange G. The first of these types contains coarsely granular PAS-positive material; the second contains granules which stain with Alcian blue, with or without PAS-positive material; while the third contains finely granular or diffuse PAS-positive material. The fourth type of cell, apparently equivalent to the 'carminophil' of other species, stains deep orange due to a combination of staining with orange G and a weakly positive PAS reaction. The fifth type is the ordinary acidophil, and the sixth the chromophobe.
The pars tuberalis is extensive, and may be compact or lobulated. The pars intermedia contains two types of cell, but shows no obvious secretory characteristics. The neural process consists of a central zone which resembles the stalk in structure, and a peripheral, more vascular zone which contains the bulk of the neurosecretory material. A nucleus of small nerve cells lies in the junctional region where the stalk joins the main neural process.
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Search for other papers by R. L. HOLMES in
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Hypertrophy of the remaining gonad after unilateral ovariectomy was first described by Carmichael & Marshall (1908) in the rabbit, and it is generally accepted that such hypertrophy is dependent on the presence of the anterior pituitary gland. The experiments reported here were made in an attempt to gain some information on the rate of progress of the hypertrophy in the rhesus monkey, and to compare the effect of unilateral ovariectomy alone with that of unilateral ovariectomy combined with hypophysectomy.
Young mature female rhesus macaques, weighing about 5 kg., were used. One ovary was removed, and on the next day either a sham (group A) or a real hypophysectomy (group B) was performed parapharyngeally (Smith, 1954). Animals were killed 1, 2 or 3 months after operation. The remaining ovary, the adrenals and thyroid glands were weighed, and later examined histologically. The completeness of hypophysectomy in animals of group B was ascertained
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Search for other papers by R. L. HOLMES in
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1. Infant rats were given doses of l-triiodothyronine (T3) alone and combined with growth hormone during different periods of development. The effects of these treatments on the growth of the body and on the size and structure of the pituitary and thyroid glands have been examined.
2. At the dose levels given, the growth of the body and of the thyroid and pituitary glands was impaired. This impairment persisted in rats treated during the first 24 days of life and in animals in which treatment was confined to the 2–4th days long after injections had been discontinued and well into adult life. It did not persist in rats in which treatment was begun after the 14th day of age.
3. There were no obvious structural changes in the thyroid gland apart from its reduced size. All treatments were followed by pituitary changes characterized by a severe reduction, both in relative and absolute amount, of acidophilic tissue. There was only minor restoration of these changes after discontinuation of the hormone treatment except in rats injected after the 14th day in which recovery was complete. Changes in the amount of mucoid tissue (PAS-positive cells) were variable and generally of doubtful statistical significance. Non-secretory tissue was unaffected.
4. Administration of growth hormone in combination with T3 for the first 24 days of life did not give rise to effects which were noticeably different from those of giving T3 alone over the same period.
5. Possible explanations for these findings and the interrelationship between the pituitary changes and impaired growth are discussed.
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Search for other papers by ANITA M. MANDL in
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Prolonged treatment with norethynodrel at a dose level sufficient to cause sterility did not consistently lead to blocking of ovulation. The ovaries of some of the animals were devoid of corpora lutea, while those of others contained variable numbers at different stages of development and regression. None of the treated animals, however, possessed as many corpora lutea as did their oil-injected controls.
The treatment also induced a variable degree of follicular inhibition. Typical and regular oestrous cycles were abolished.
The incidence of corpora lutea formed during the period of injection was slightly greater in animals housed with males than in those kept isolated. Although coitus was not followed by a period of pseudopregnancy, as judged by vaginal smears, most of the mated animals possessed corpora lutea resembling those of pseudopregnancy.
The pituitary gland of the norethynodrel-treated animals was heavier than that of their controls, due largely to an increase in the volume of tissue occupied by chromophobe cells. The proportion of basophil cells was lower, while that of eosinophil cells remained unchanged.
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An attempt was made to separate the pituitary gland from the hypothalamus in eight mature female rhesus monkeys by placing a piece of polythene film between the cut ends of the pituitary stalk. One animal died shortly after operation. In two it was established that the stalk had not been divided, and normal menstrual cycles continued. In a fourth, normal cycles also continued in spite of extensive damage to the stalk.
Amenorrhoea set in in three of the monkeys despite variable degrees of regeneration of hypothalamo-hypophysial vascular connexions. One animal underwent two phases of uterine bleeding in spite of complete structural and vascular separation of the pituitary gland from the hypothalamus.
The neural process was found to be atrophic in each of the seven surviving animals, and all developed diabetes insipidus. The severity of the polyuria could be correlated with the amount of damage to the median eminence rather than to the stalk.
Search for other papers by Anna G Holmes in
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Search for other papers by Jose L Mesa in
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Diabetes and Metabolism Division, School of Medical Sciences, St Vincent's Institute and Department of Medicine, CSIRO Molecular and Health Technologies, Department of Physiology, Cellular and Molecular Metabolism Laboratory, Baker Heart Research Institute, PO Box 6492, St Kilda Road Central, Melbourne, Victoria 8008, Australia
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Diabetes and Metabolism Division, School of Medical Sciences, St Vincent's Institute and Department of Medicine, CSIRO Molecular and Health Technologies, Department of Physiology, Cellular and Molecular Metabolism Laboratory, Baker Heart Research Institute, PO Box 6492, St Kilda Road Central, Melbourne, Victoria 8008, Australia
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Chronic elevations in interleukin (IL)-6 have been associated with insulin resistance, but acute IL-6 administration can enhance insulin sensitivity. Our aim was to exogenously administer IL-6 to rats to elicit either chronic or repeated acute elevations in systemic IL-6. We hypothesized that a continuous elevation of IL-6 would inhibit glucose tolerance and insulin sensitivity while acute intermittent elevations would improve it. Male Wistar rats were treated for 14d with recombinant human IL-6 (2.4 μg/day) or saline administered either by miniosmotic pump (continuous IL-6) or via twice-daily injection (intermittent IL-6). Glucose and insulin tolerance tests were performed following 14-d treatment and 24 h later rats were administered a bolus of insulin (150 mU/g) or saline intraperitoneally. Approximately, 10 min after insulin injection soleus, gastrocnemius and liver were excised and rapidly frozen in liquid nitrogen for subsequent metabolic measures. Irrespective of the mode of delivery, IL-6 treatment increased basal insulin sensitivity, as measured by the homeostatic model assessment of insulin resistance, and enhanced glucose clearance during an i.p. glucose tolerance test. IL-6 increased circulating fatty acids, but did not increase triglyceride accumulation in either skeletal muscle or liver, while it increased the protein expression of both PPARα and UCP2 in skeletal muscle, suggesting that IL-6 can enhance fat oxidation via mitochondrial uncoupling. These data demonstrate that, irrespective of the mode of delivery, IL-6 administration over 2 weeks enhances glucose tolerance. Our results do not support the notion that prolonged chronically elevated IL-6 impairs insulin action in vivo.
