LHRH receptors and LHRH receptor-bearing cells in pituitaries of streptozocin diabetic male rats.

Streptozocin (STZ)-diabetic rats have low hypothalamic luteotropic hormone-releasing hormone (LHRH) secretion and various alterations of gonadotrope cells, among which low luteotropic hormone (LH) secretion. Possible causes for the gonadotrope disorders may be low hypothalamic LHRH secretion alone or combined with reduced (a) number of LHRH receptor sites, or (b) receptor to ligand affinity, or (c) of LHRH receptor-bearing cells. To clarify this question we determined by saturation and competition binding Bmax, KD and KA of the LHRH receptor sites and counted the receptor-bearing cells in pituitary glands of control and STZ-diabetic adult male rats. We found a single receptor class, the Bmax was strongly reduced in diabetic animals whereas both KD and KA were similar in the two groups. The number of LHRH receptor-bearing cells in diabetic animals was increased. Therefore a reduced number of receptor sites per gonadotrope cell occurs in our model. Since in the STZ-diabetic male rats the number of gonadotropes is increased, a higher number of receptor-bearing cells was observed. We conclude that the reduced LH secretion from the diabetic pituitary gland might be due to a reduced number of LHRH receptor sites in the pituitary gland. The increased number of receptor-bearing cells might partially compensate for this change.

LH, FSH, PRL and ACTH cells in pituitary glands of cows with ovarian cysts.

We investigated morphometrically and densitometrically LH, FSH, PRL, and ACTH cells in pituitary glands in cows with follicular cysts and normal animals. Three groups were considered: cows in diestrus, cows in periestrus and cows with follicular cysts. The periestrous group was obtained by merging pro- and metaestrous groups, since the two did not differ when evaluated separately. The attribution to groups was confirmed by plasma progesterone measurements and by postmortem examination of the ovaries. After immunocytochemical labeling the pituitary cells were counted, and their area and total immunoreactivity were measured. The results suggest hypofunction of the LH cells (P < 0.05) and hyperfunction of the ACTH cells (P < 0.05) from the cows of the follicular cyst group. The FSH and PRL cells were similar in the three groups. These changes are consistent with the reduced LH release reported by most authors in cows with follicular cysts and should be relevant to the pathogenesis of the bovine follicular cysts. The subnormal activity of LH cells might be secondary to the activation of the ACTH cells.

Hypoglycemia in a dog with a leiomyoma of the gastric wall producing an insulin-like growth factor II-like peptide.

A 12-year-old mixed-breed male dog was referred to the Clinica Medica Veterinaria of Bologna University for recurrent episodes of seizures due to hypoglycemia with abnormally low plasma insulin levels (18 pmol/l). Resection of a large leiomyoma (780 g) of the gastric wall resulted in a permanent resolution of the hypoglycemic episodes. Insulin-like growth factors I and II (IGF-I and -II) were measured by RIA in serum before and after surgery and in tumor tissue. Results were compared to the serum concentration of 54 normal and to the tissue concentration observed in eight non-hypoglycemic dog gastric wall extracts. Before surgery, circulating immunoreactive IGF-I was 0.92 nmol/l, which is significantly lower than the control values (16.92 +/- 8.44 nmol/l, range 3.53-35.03), while IGF-II was 152 nmol/l, which is significantly higher than the control values (42.21 +/- 3.75, range 31.99-50.74). After surgery, IGF-I increased to 6.80 nmol/l while IGF-II decreased to 45.52 nmol/l. Tumor tissue IGF-II concentration was higher than normal (5.66 nmol/kg tissue as compared to a range in normal gastric wall tissue of 1.14-3.72 nmol/kg), while IGF-I was 0.08 nmol/kg tissue, which is close to the lowest normal value (range in controls, 0.08-1.18 nmol/kg). Partial characterization of IGF-II immunoreactivity extracted from tissue evidenced a molecular weight similar to that of mature IGF-II, thus excluding that peptide released by the tumor is a precursor molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

The reduction of circulating growth hormone and prolactin in streptozocin-induced diabetic male rats is possibly caused by hypothalamic rather than pituitary changes.

To gain further information on diabetes-related disorders in the somatotrophic and lactotrophic axes, we undertook a functional, morphometrical and densitometrical study of the arcuate nucleus (AN), median eminence (ME) and anterior pituitary gland of adult male rats one month after streptozocin-induced diabetes (STZ-D). The basal secretory activity of somatotrophs and lactotrophs was tested by the reverse haemolytic plaque assay (RHPA) and plasma GH and prolactin (PRL) levels were determined by RIA. The number of GH-releasing factor (GRF)-labelled axons and the amount of axonal tyrosine hydroxylase (TH)-immunoreactivity increased in STZ-D. There were no significant differences in any of the other densitometrical measurements performed on GRF-, somatostatin-, thyrotropin-releasing hormone- and TH-labelled ME axon cross-sections as well as those on tuberoinfundibular-dopaminergic neurones of the AN in STZ-D compared with control rats. Plasma GH and PRL levels and measurements on anterior pituitary GH- and PRL-labelled structures were decreased in STZ-D. However, the GH and PRL plaque areas were increased after RHPA implying that the secretory capacity of somatotrophs and lactotrophs was not impaired. Taken together, these results suggest that the accumulated GRF in the ME is due to reduced GRF release. This could account for the reduced amplitude and/or frequency of GH secretory pulses. The increased axonal TH-immunoreactivity may indicate an increased dopamine synthesis. If coupled to increased release this could, in turn, be partly responsible for the reduced plasma and anterior pituitary PRL concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Pituitary gland changes in canine hypoadrenocorticism: a functional and immunocytochemical study.

Pituitary gland changes were evaluated immunocytochemically in three dogs with primary hypoadrenocorticism (HAC) and one dog with secondary HAC and related to the clinical, endocrinological and pathological findings. In primary HAC, the adrenocorticotrophic hormone (ACTH) immunoreactivity was increased in the pars distalis of the pituitary gland and all cortical layers of the adrenal gland were severely atrophied. This increase would be expected to reflect a high level of ACTH synthesis in the corticotrophs due to a lack of negative cortisol feed-back. In contrast, in the dog with secondary HAC the ACTH immunoreactivity was decreased in the pituitary gland, the basal plasma ACTH concentration was low and the zona fasciculata and reticularis were atrophied, but the zona glomerulosa was well preserved. These findings are consistent with a diminished synthesis of ACTH. Thus, pituitary gland changes differ in primary and secondary HAC and are consistent with the clinical, endocrinological and histopathological findings.

Somatotropic dysfunction in growth hormone-releasing hormone-deprived neonatal rats: effect of growth hormone replacement therapy.

In a previous work, we reported that passive immunization with anti-growth hormone-releasing hormone (GHRH) antibodies (GHRH-Ab) in neonatal rats caused disruption of somatotropic function that was still present 60 d posttreatment. We studied the reversibility of this condition by growth hormone (GH) replacement therapy. Neonatal rats received GHRH-Ab (50 microL/rat, s.c.) or normal rabbit serum every second day from birth up to postnatal d 10 and received hGH (0.4 microgram/g body weight, s.c., b.i.d.) or vehicle in a 2 x 2 factorial design. Animals were studied on d 11 of age. In GHRH-Ab-treated rats, GH therapy 1) counteracted the reduced body weight and low plasma IGF-I levels; 2) failed to modify the reduced pituitary weight and GH content; 3) further reduced the low plasma GH levels; 4) partially restored the defective GH responsiveness to GHRH; 5) failed to modify the reduced hypothalamic somatostatin and increased GHRH gene expression in the hypothalamus; and 6) reverted the decreased pituitary somatostatin binding. Morphologic and morphometric evaluation of the pituitary gland from GHRH-AB+GH pups showed that the number of GH-labeled structures was lower than in normal rat serum-GH-treated pups, whereas the total GH immunoreactivity per unit surface, an index of intracellular hormone concentration, was slightly higher than in vehicle-GH or GHRH-Ab pups. As determined by electron microscopy, somatotropes from GHRH-Ab+GH pups had morphologic features of high cellular activity. It appears that in GHRH-deprived pups GH replacement therapy can normalize most but not all altered indices of the somatotropic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretory disorders in pituitary thyrotropes of streptozocin-diabetic male rats.

Pituitary cells transport secretory products from deep cytoplasmic portions towards the subplasmalemmal region (SPL) by two mechanisms: (a) the regulated, secretagogue-dependent and (b) the secretagogue-independent constitutive pathway. Since thyrotropin (TSH) secretion is impaired in diabetes, we studied both pathways in the thyrotropes of control and streptozocin (STZ)-treated male rats. By electron microscopy, we measured the nucleus and cytoplasm area and counted the secretory granules. In 4 selected SPL (500 nm deep) areas per cell we also counted the marginated secretory granules and measured their area. Moreover, after TSH indirect immunogold labelling we counted immunogold particles on (a) the secretory granules of the SPL and (b) the intergranular SPL cytoplasm. To check the background staining we also counted immunogold particles on nonthyrotropic cells. In diabetic compared with control thyrotropes we found: (a) cytoplasmic atrophy and increased number of secretory granules per cytoplasm unit area, (b) reduced number of secretory granules in the SPL (blunted regulated secretion), (c) larger secretory granules in the SPL (abnormal secretory granule maturation), (d) decreased immunogold labelling of secretory granules in the SPL (reduced TSH transported by each secretory granule towards the cell membrane) and (e) decreased immunogold labelling of the intergranular SPL cytoplasm (blunted constitutive secretion). Our data suggest reduced regulated and constitutive TSH secretion and may thus contribute to a better understanding of the hypothyroidism in STZ-diabetic rats.

An "in vitro" model for combined functional and morphological investigations on the rat pituitary gland.

We have developed an alternative model for combined "in vitro" functional and morphological studies on the rat pituitary gland. To test its use for biochemical investigations we studied some aspects of the secretion in pituitary thyrotrophs under basal conditions and after stimulation with TRH. After stabilisation of basal TSH release, the stimulation with TRH significantly increased the TSH secretion. To test the usefulness of our model for morphological investigations the tissue was processed for conventional and immunocytochemical light and electron microscopy at the end of the incubation. Different types of pituitary cell resulted to be well preserved. Our model allows combined biochemical and morphological studies on the pituitary gland and thus reduces the number of animal groups, eliminates the extrapolation of results from different groups and replaces the "in vivo" by an "in vitro" experiment.

Sexually dimorphic effects of aging on tuberoinfundibular dopaminergic neurons and lactotropes of rats.

The effect of aging on plasma prolactin (PRL) levels, hypothalamic tuberonifundibular dopaminergic (TIDA) neurons and pituitary lactotropes was evaluated in prolactinoma-free young (5-month-old) and old (23- to 24-month-old) Long-Evans rats of either sex. The young female rats were in diestrus, the old ones in recurrent pseudo-pregnancy. The tyrosine hydroxylase (TH)-labelled neurons in the arcuate nucleus (AN) and axons in the median eminence (ME) as well as the PRL-labelled lactotropes in the pituitary gland were studied by morphometry and densitometric immunohistochemistry. Further, we investigated the secretory function of isolated lactotropes by reverse hemolytic plaque assay (RHPA) and by cell culture in comparable animal groups. Compared with young animals, the plasma PRL levels of old rats of both sexes were similar or reduced. All morphometric and densitometric measurements of the AN neurons, ME axons (except number) and pituitary lactotropes were comparable in young and old female rats. In old male rats the AN and ME measurements were mostly decreased, while the lactotropes remained almost unchanged. The RHPA generally showed a reduced PRL release from lactotropes of old animals of both sexes. The PRL release from the cultured lactotropes, on the contrary, was greatly increased in old female rats and unchanged in old male rats. Our functional and morphological data suggest that the in vivo function of lactotropes in old prolactinoma-free female and male rats does not seem to be strongly influenced by the mildly reduced TIDA neuron activity, yet emphasize the differences of the aging process in the two sexes.

Normal circulating triiodothyronine concentrations are maintained despite severe hypothyroidism in growing pigs fed rapeseed presscake meal.

Experiments were designed to study effects of dietary rapeseed presscake meal on the thyroid and on the liver 5'-monodeiodinase activity in growing pigs. Animals were fed rapeseed presscake meal (15% in the ration) of 0-varieties (containing relatively high amounts of glucosinolates and goitrin) or a control diet (soybean meal instead of rapeseed presscake meal) without or with thyroxine added to feed. Food intake and average daily gain were comparable because pigs were pair-fed. Serum thiocyanate concentration was significantly greater in pigs fed rapeseed presscake meal. Pigs fed rapeseed presscake meal developed hypothyroidism. Serum free thyroxine concentrations in rapeseed presscake meal-fed pigs were significantly lower than in controls, normal in thyroxine-supplemented pigs fed rapeseed presscake meal and significantly above normal in thyroxine-supplemented controls. Serum free triiodothyronine concentrations were not significantly influenced by rapeseed presscake meal feeding or thyroxine supplementation. Liver weight and total DNA content in pigs fed rapeseed presscake meal were higher than in controls but were not significantly affected by thyroxine feeding. Hepatic 5'-monodeiodinase activity on a protein basis was lower in pigs fed rapeseed presscake meal and was not normalized by thyroxine supplementation. However, in whole liver, because of greater liver mass, 5'-monodeiodinase activity in pigs fed rapeseed presscake meal was similar to that in controls. The data indicate that serum free triiodothyronine concentrations in pigs fed rapeseed presscake meal could be maintained in the physiological range, probably because of enhanced triiodothyronine secretion and sufficient extrathyroidal thyroxine to triiodothyronine conversion.

Equine pituitary adenoma: a functional and morphological study.

Clinico-pathological correlations in horses with pituitary adenomas are poorly understood. This paper describes the functional and morphological features of five cases of equine pituitary adenoma and of a case of multinodular pituitary hyperplasia. New findings reported include immunoreactivity for beta-lipotropin (beta-LPH), beta-melanocyte-stimulating hormone (beta-MSH), gamma 3-MSH, prolactin (PRL), and follicle-stimulating hormone (FSH) in neoplastic cells of the pituitary adenoma; and, in the multinodular hyperplasia, beta-LPH, beta-endorphin (beta-END), alpha-MSH, beta-MSH, gamma 3-MSH and FSH immunoreactivity. It is suggested that the equine pituitary syndrome does not correspond to human Cushing's disease, as generally accepted, but is related to the overproduction of several pro-opiomelanocortin (POMC)-derived peptides by the cells of the tumour or hyperplastic nodules.

Megaoesophagus in rats: a clinical, pathological and morphometrical study.

Megaoesophagus was observed in 82 Long-Evans rats aged 3-32 months. Clinically, the hair was coarse, the neck distended, the mouth opened, wetted by saliva and soiled by bedding material, and the respiration characterized by tachypnoea and inspiratory crackles. By radiography, after barium administration, the oesophagus was seen to be dilated and filled with impacted dry food in the precardial region. The size of the dilatation varied depending on the oesophageal region and reached a diameter of 12 mm in the most severe case. Histologically, the muscular layers of the dilated portions showed focal inflammation and single fibre necrosis. Each affected oesophagus had (1) an increased circumference and radius and a reduced number of myenteric ganglion cells in both the thoracic and abdominal portions, and (2) a decreased thickness of the muscular layers in the thoracic portion and at the level of the cardia. A simple geometrical model showed that the reduced ganglion cell number was not due to a change in shape of the dilated oesophagus. Since no sign of infectious disease was found in these animals, and rats of other strains kept at the same time under the same conditions were not affected, a hereditary aetiology is suggested.

[Hepatic necrosis caused by Clostridium perfringens in a dog]. / Nécrose hépatique due à Clostridium perfringens chez un chien.

A case of acute hepatic necrosis in a dog is clinically and pathologically described. The occurrence of Clostridium perfringens in the liver lesions was revealed by histological examination and bacteriological isolation. Based on these findings we conclude that Clostridium perfringens is the cause of the infarcts. The case is discussed on the base of the literature.

Immunohistochemistry of hepatic IGF-I in calf, pig, and rat.

The liver appears to be the major site of synthesis of somatomedin C or insulin-like growth factor I (IGF-I), yet, the intrahepatic histological localization of this polypeptide is not well known. For this reason we investigated immunohistochemically the liver of calves, pigs, and rats, fixed by perfusion or immersion with Karnovsky solution. In all three animal species the layer of hepatocytes bordering the liver capsule was labeled by anti-IGF-I. In the pig and rats all perivenous hepatocytes were intensively labeled whereas in calves only the periportal hepatocytes contained immunoreactive IGF-I. While preabsorption of the anti-IGF-I antiserum with the antigen abolished the immunoreaction, preabsorption with insulin or IGF-II did not. No labeling occurred when immersion-fixed liver tissue was used.

Tuberoinfundibular dopaminergic neurons and lactotropes in young and old female rats.

Aging in female rats is accompanied by several endocrine dysfunctions, such as reproductive decline associated with characteristic hyperprolactinemia, lactotrope hyperplasia, and functional impairment of hypothalamic tuberoinfundibular dopaminergic (TIDA) neurons. The aim of this morphometrical, immunocytochemical, and densitometrical study was to gain a better anatomical knowledge of TIDA neurons and axons as well as of lactotropes in old female rats with (A) or without (NA) pituitary adenomas, compared with young animals. At the hypothalamic level, we found that tyrosine hydroxylase (TH)-labeled neurons in the arcuate nucleus were comparable in young and old NA yet their size and TH-content were increased in A animals. Also the TH-labeled median eminence axons did not differ significantly between young and old NA but were more numerous in the old A rats. Independently from adenomas, both number of prolactin (PRL)-labeled structures and content of immunoreactive PRL were increased in pituitaries of old rats, the plasma PRL levels, however, were high only in A. Our findings support the documented lactotrope hypertrophy and hyperplasia in old female rats and suggest that TIDA-neuron changes only occur in hyperprolactinemic animals carrier of adenomas.

[Infectious hemorrhagic disease of rabbits in the Bern pathology institute (1988-90): seasonal and regional distribution and histopathological findings]. / Infektiöse hämorrhagische Krankheit der Kaninchen im Berner Sektionsgut (1988-1990): Zeitliche und regionale Verteilung sowie histopathologische Befunde.

Between 1988 and 1990 we have investigated 45 cases of the rabbit viral haemorrhagic disease (VHD) at our institute in order to ascertain: 1) both monthly and regional distribution of the disease: 2) the histopathological patterns of the disease. The VHD cases were particularly frequent between October and January and between May and August. They occurred in 7 cantons. The panlobular hepatocytic necrosis was observed in 80% of the cases, whereas in the remaining 20% the necrosis occurred in the periportal region. In 80% of the animals the spleen blood vessels were dilated with perivascular fibrin accumulation indicative of hyperpermeability. In two cases haemoglobin cages were observed in the kidney tubules.

Reduced number and LH content of marginated secretory granules in pituitary gonadotropes of streptozocin-induced diabetic male rats.

The transport of secretory granules towards the subplasmalemmal (SPL) region of the luteinizing-hormone (LH) gonadotrope is controlled by the LH-releasing-hormone-dependent pathway. The SPL granules contain the most readily releasable LH. To test the effect of diabetes on both the number and LH content of marginated granules, we studied by indirect immunogold-labelling pituitaries from control and streptozocin (STZ)-treated male rats. On electron micrographs we measured the areas of the gonadotrope nucleus and cytoplasm, counted all secretory granules, and counted and measured secretory granules in selected SPL regions. Furthermore, we counted gold particles (IG) on (a) the secretory granules of the SPL regions, (b) the intergranular SPL cytoplasm and (c) the region outside the cell. Finally, in order to evaluate possible diabetes-related changes of the pituicyte cytoskeleton, we measured by densitometry actin, tubulin, vimentin, and desmin in immunocytochemically stained pituitary sections. In diabetic compared with control cells of the studied pituitary region, we observed: (a) cytoplasmic atrophy; (b) the number of secretory granules per unit area increased in the total cytoplasm, and decreased in the SPL cytoplasm (lowered regulated secretion); (c) decreased IG labelling in the SPL granules (reduced amount of hormone transported by each granule towards the cell membrane); (d) decreased IG labelling in the integranular SPL cytoplasm (reduced constitutive secretion), and (e) strongly increased actin and desmin, yet unchanged tubulin and vimentin immunoreactivity. Our data indicate that both regulated and constitutive secretion are possibly reduced in gonadotropes of diabetic male rats. The cytoskeletal alterations may also contribute to the reduced regulated secretion.

A clinico-pathological study of canine Cushing's disease caused by a pituitary carcinoma.

Knowledge of clinico-pathological correlations in canine Cushing's disease is rather poor. Therefore we describe, clinically and pathologically, a case of pituitary tumour-dependent Cushing's disease in an 8-year old female cocker spaniel. Based on our results, the tumour was defined as a non-dexamethasone-suppressive, corticotrophic adenocarcinoma characterized by some new findings such as intracerebral metastases of anti-ACTH-labelled tumour cells and combined alpha-, beta- and gamma 3-MSH immunoreactivity in the tumour.

Functional and morphological changes in the hypothalamo-pituitary-gonadal axis of aged female rats.

Age-related functional and morphological alterations in the hypothalamo-pituitary-gonadal axis were investigated in old recurrently pseudopregnant (RPP) female rats, and these alterations were compared with those in young diestrous rats. LHRH in the median eminence (ME) and mediobasal hypothalamus (MBH) as well as plasma FSH, LH, and progesterone were measured by RIA. LHRH in the lateral ME (LME) and pituitary FSH and LH were evaluated by morphometry and densitometrical immunocytochemistry. Furthermore, by light microscopy, we classified and counted the number of ovarian follicles and corpora lutea. LHRH concentrations in the ME and MBH were similar in old and young rats, whereas in old rats, plasma FSH was markedly increased, LH was moderately increased, and plasma progesterone was unchanged. The number and the total area and immunoreactivity of LHRH-labeled axon cross sections in the LME were reduced in old rats. The number of nucleated FSH-labeled cells and total FSH area and immunoreactivity were almost twice in old compared with young animals. The measurements of LH-labeled cells were not different between the two groups. In old rats, the numbers of ovarian follicles and corpora lutea were reduced and that of atretic follicles increased. In conclusion, age-related morphological impairments of LHRH axons associated with an increased number of FSH gonadotropes and higher plasma FSH in our old RPP rats suggest hypothalamic and pituitary disturbances, which may largely contribute to the complex hormonal disarrangement responsible for the decline of reproductive functions in old female rats.