Juan H. Tramezzani

A TECHNIQUE FOR LIGHT AND ELECTRON MICROSCOPIC IDENTIFICATION OF ADRENALIN- AND NORADRENALIN-STORING CELLS.

Fixation of adrenal glands with 6.5% glutaraldehyde in Millonig buffer at pH 7.2 for 1 or more hours results in a yellow color in noradrenalin-storing cells while adrenalin-containing cells remains uncolored. When frozen sections of adrenal gland fixed in glutaraldehyde are treated with an ammoniacal silver solution, silver is reduced by noradrenalin cells in less than 30 seconds. A deep brown or black color according to the silver solution used, appears in noradrenalin-containing cells while the adrenalin ones remain uncolored. Based on these facts a technique for light and electron microscopic localization of noradrenalin has been developed. The results permit the following interpretation of the glutaraldehyde silver reaction for noradrenalin-containing cells. The condensation of glutaraldehyde with noradrenalin forms a yellow azomethine. Whereas this compound is insoluble adrenalin will not combine with glutaraldehyde and remains soluble. During washing adrenalin therefore disappears from sections while the yellow glutaraldehyde-noradrenalin compound remains. The aldehyde group of this compound reduces ammoniacal silver solutions.

Four types of main cells in the carotid body of the cat

Four types of main cells were found in the carotid body of the cat. They were distinguished on the basis of the electron density of their cytoplasm as well as on the morphological features of the osmiophilic granules they contain; they were named types I, II, III, and IV. The localization of noradrenaline (norepineptrine), dopamine, 5-hydroxytryptamine, and adrenaline (epinephrine) in these cell types has been discussed.

Melanin-Concentrating Hormone Stimulates the Release of Luteinizing Hormone-Releasing Hormone and Gonadotropins in the Female Rat Acting at Both Median Eminence and Pituitary Levels

Abstract The purpose of this study was to investigate whether melanin-concentrating hormone (MCH) acts directly on the median eminence and on the anterior pituitary of female rats regulating LHRH and gonadotropin release. In addition, immunohistochemistry was used to examine the density and distribution of MCH-immunoreactive fibers in the median eminence of proestrous rats. MCH-immunoreactive fibers were found in both the internal and external layers of the median eminence and in close association with hypophysial portal vessels. In the first series of in vitro experiments, median eminences and anterior pituitaries were incubated in Krebs-Ringer bicarbonate buffer containing two MCH concentrations (10−10 and 10−8 M). The lowest MCH concentration (10−10 M) increased (P < 0.01) LHRH release only from proestrous median eminences. Anterior pituitaries incubated with both MCH concentrations also showed that 10−10 M MCH increased gonadotropin release only from proestrous pituitaries. In the second series of experiments, median eminences and pituitaries from proestrous rats were incubated with graded concentrations of MCH. MCH (10−10 and 10−9 M) increased (P < 0.01) LHRH release from the median eminence, and only 10−10 M MCH increased (P < 0.01) LH and FSH release from the anterior pituitary. The effect of MCH on the stimulation of both gonadotropins from proestrous pituitaries was similar to the effect produced by LHRH. Simultaneous incubation of pituitaries with MCH and LHRH did not modify LH but increased the FSH release induced by LHRH. The present results suggest that MCH could be involved in the regulation of preovulatory gonadotropin secretion.

Acute superior cervical ganglionectomy depresses the postcastration of gonadotropins in male rats

In male rats, superior cervical ganglionectomy (SCGx) delayed the rise of serum FSH and LH induced by orchidectomy by 24 h. SCGx resulted in a decrease of median eminence norepinephrine (NE) content 16 h after surgery and in an increase of medio-basal hypothalamic cAMP synthesis and receptor occupancy. These data indicate that NE release from degenerating terminals originating in the superior cervical ganglion neurons modifies the regulatory mechanisms controlling the rise of gonadotropins after orchidectomy in rats.

Separate distribution of adrenaline- and noradrenaline-secreting cells in the adrenal of snakes

Abstract The chromaffin tissue of Xenodon merremii is distinctly segregated into two portions: one taking the form of a ribbon placed longitudinally over the surface of the adrenal gland, and the other appearing intermingled with the adrenocortical tissue. The histochemical technique of Hillarp and Hokfelt [ J. Histochem. Cytochem. 3 , (1955)] demonstrated that the superficially placed ribbon of chromaffin tissue contains only noradrenaline-secreting cells, whereas the adrenaline-secreting cells are contained in chromaffin tissue intermingled with that of the cortex. Chemical assays and chromatography of extracts showed that the peripheral chromaffin tissue contains almost pure noradrenaline. The extracts of the central part of the gland contain adrenaline and about 14% of noradrenaline. Electron microscope studies were made of these two types of chromaffin tissue and clear differences were found between the adrenaline- and noradrenaline-secreting cells.

Specificity of the glutaraldehyde silver technique for catecholamines and related compounds

SummaryStudies regarding the specificity of glutaraldehyde-silver technique showed that this technique, used as described previously is positive for noradrenalin, dopamine, melanin and lipofuscin. Adrenalin and 5-hydroxytryptamin storing cell produce negative results.Light microscopy does not reveal 5-hydroxytryptamin containing cells even following prolonged (30 minutes) silver treatment, but a fine silver precipitate appears under these conditions in 5-hydroxytryptamin containing granules when the material is observed under the electron microscopy.Dopamine is not revealed by light microscopy because the silver precipitate is very fine and scattered in the granule but it is easily seen by electron microscopy.

DIFFERENTIAL EFFECTS OF SUPERIOR AND INFERIOR SPERMATIC NERVES ON TESTOSTERONE SECRETION AND SPERMATIC BLOOD FLOW IN CATS

It has been postulated that testosterone secretion is partially regulated by signals from the spermatic nerves. To further examine this hypothesis in vivo, the superior (SSN) or the inferior (ISN) spermatic nerves were stimulated electrically (varying intensity, 25 Hz, 0.2 msec, 10 min) in anesthetized cats, determining the testosterone concentration and the blood flow in the spermatic vein. In some additional experiments arterial blood was sampled, and norepinephrine (NE) output was calculated. Stimulation of the SSN (25–35 V) increased the testosterone concentration in spermatic vein blood (P < 0.01 compared with prestimulation levels). The response varied among animals, reaching a 50–100% increase in some animals, whereas in others it ranged from almost undetectable to more than 10 ng/100 g·min. Under the same experimental conditions, the NE output increased from 135.4 ± 99 to 1614.2 ± 347 pg/ml (P < 0.01), and spermatic blood flow decreased from 24.1 ± 1.42 to 20.2 ± 1.65 ml/min·100 g (P < 0.05) durin...

The epiphysis cerebri of the Weddell seal: its remarkable size and glandular pattern

A morphologic study of the pineal of the Weddell seal (Leptonichotes weddelli) was carried out during a whole polar year. The gland of the Weddell seal, a nonmigratory antarctic pinniped, shows a remarkable size, 20–30 mm long. Its structural pattern differs from that of the rest of mammals. It presents a cortical and medullar region. A capsule covers the gland and has a pigmentary layer on its dorsal and distal portion. The cortical region contains pinealocytes, nerve fibers, and glial cells while the medulla has connective tissue, blood vessels, nerve fibers, and some glial cells. Pinealocytes that are present only in the cortical region showed a clear seasonal variation in their lipidic content.

Median Eminence Serotonin Involved in the Proestrus Gonadotropin Release

Numerous studies have suggested that serotonin (5-HT) is involved in the regulation of anterior pituitary hormone release. In the present study, the 5-HT concentrations of the median eminence and anterior pituitary lobe were measured during the estrous cycle and lactation in order to correlate changes in 5-HT levels with changes in serum luteinizing hormone, follicle-stimulating hormone, and prolactin. On the day of proestrus, median eminence 5-HT concentrations declined significantly between 14.00 and 16.30 h at the beginning of the gonadotropin and prolactin surges. No changes in 5-HT concentrations were found between the morning and afternoon on other days of the cycle. In the anterior pituitary, the levels of 5-HT did not change during the estrous cycle. 5-HT turnover rates were also estimated in the median eminence on proestrus and diestrus 1. The median eminence 5-HT synthesis rate increased in the afternoon of proestrus at 16.30 h. 5-HT was also measured in the anterior pituitary and the median eminence of lactating rats in four experimental situations: mothers with their litter until decapitation, mothers separated from their pups 4 h earlier, and mothers separated from their pups 4 h earlier, after which the pups were allowed to suckle for 5 or 30 min. In spite of the acute changes in circulating prolactin, 5-HT levels in the median eminence were not affected in any situation studied. These results suggest that 5-HT in the median eminence is involved in the control of gonadotropin release. The data further suggest that 5-HT does not act directly on the anterior pituitary to modulate gonadotropin or prolactin release.

Central connections of the toad neural lobe as shown by retrograde neuronal labeling: classical and new connections.

Iontophoretic deposit of horseradish peroxidase (HRP) in the hypophysial neural lobe (NL) of the toad labeled neurons in the classical neurosecretory preoptic magnocellular nucleus. Further, a number of labeled neurons appeared in the whole extension of the periventricular and medial preoptic nuclei. The latter were continuous dorsally with two other labeled areas known as the bed nucleus of the hippocampal commissure (which appears to be homologous to the subfornical organ in mammals) and the ventromedial thalamic area of Frontera. The possible functional role of many of these afferents to the neural lobe is unknown because all types of neurons were labeled in the projecting zones and, in addition, many are outside of the generally recognized neurosecretory groups.