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Biomedical subjects

J R Sladek

Publications and source records attributed to J R Sladek.

At least 91 records · Page 5Linked to original sources
PubMed1985

Altered catecholamine innervation of the supraoptic nucleus in the nephrogenic diabetes insipidus mouse.

Fluorescence histochemical and immunocytochemical techniques were used to investigate morphologic correlates of the relationship between catecholamine varicosities and vasopressin-containing perikarya in an animal model of vasopressin excess, the nephrogenic diabetes insipidus mouse. Our results show hypertrophy and increased immunoreactivity in vasopressin neurons in these mice were accompanied by a marked increase in the density and to some extent the fluorescence intensity of catecholamine varicosities within the supraoptic nucleus. These results further support the concept of functional interactions between catecholamine and vasopressin neurons and raise the possibility that the target neuron, or one of its products, perhaps vasopressin, either exerts a trophic influence on the catecholamine innervation pattern of the supraoptic nucleus or enhances catecholamine content in existing fibers and terminals.

Animals↗
PubMed1985

Neurological control of vasopressin release.

Vasopressin (VP)-containing neurons of the supraoptic and paraventricular nuclei are influenced by a number of diverse, chemically defined neural systems. Of these the anatomy and physiology of noradrenergic and cholinergic afferents are best understood. Norepinephrine (NE)-containing neurons of the caudal medulla heavily innervate VP neurons; NE has been shown to either inhibit or facilitate the release of VP under different experimental paradigms. Acetylcholine is a powerful stimulant of VP release. gamma-Aminobutyric acid also appears to inhibit release. Several other putative transmitters are localized within the supraoptic and paraventricular nuclei, which suggests that VP release is integrated by a wide variety of neural systems.

Acetylcholine↗
PubMed1984

Development of the catecholamine innervation of the supraoptic nucleus in the Brattleboro rat.

The ontogenetic development of the noradrenergic innervation of the supraoptic nucleus was studied in the Brattleboro rat at late postcoital and early postnatal ages. This genetic mutant offers a useful model for analysis of neuronal development because of the absence of a specific peptide component of identifiable target neurons and has been used presently to eliminate the possibility that such substances are essential for the establishment of normal connectivity during postnatal development. In this model, catecholamine varicosities were seen in juxtaposition to vasopressin-deficient perikarya during the initial phases of postnatal development, but these varicosities gradually decreased in number suggesting the possibility that the target neuron peptide, or some functional aspect of the neuron, may be necessary for the normal maintenance of this neuronal interaction.

Adrenergic Fibers↗
PubMed1984

Plasticity of catecholaminergic neurons in aged rat brain: reinnervation and functional recovery after axotomy.

Regenerative growth at the lesion site, reinnervation of a target nucleus and functional manifestations of recovery were studied in aged (20 and 30 months old) rats subjected to long-term transection of catecholaminergic (CA) fibers which contact and influence neurons of the supraoptic nucleus (SON). Small bilateral knife cuts were placed stereotaxically just caudal and medial to the SON. CA histofluorescence, induced by formaldehyde-glutaraldehyde (FAGLU) or aluminum-formaldehyde (ALFA) methods, was examined in hypothalamus at 2, 14, 21 and 60 days postsurgically. Water consumption, and urine volume and osmolality, were monitored presurgically, and through survival times. Subtotal CA denervation in the SON, and typical axonal transmitter "pile-up" at the lesion site, were evident two days after surgery. Among these degenerative profiles, which persisted for up to three weeks, fine-sized new fibers were apparent at the lesion, beginning between 2 and 14 days, and persisting throughout the period studied. At 21 days, and progressively thereafter, SON neurons were rimmed with fluorescent varicosites. Water consumption initially was depressed, but returned to presurgical mean levels by nine days. Urine volume returned to normal by 32 days. Urine osmolality showed a recovery by approximately three weeks. These functional parameters rebounded to levels higher than presurgical means among 20 month old, but not 30 month old, rats beyond 6 weeks survival, concurrent with a morphological hyperinnervation. The results reaffirm morphological regeneration, and support reinnervation and functional recovery, which extend considerably into the aging process.

Afferent Pathways↗
PubMed1983

Regeneration of central catecholamine fibers in young and aged rat brain.

Catecholamine histofluorescence patterns were examined in brains of young and aged rats, 1 to 14 days following neurosurgical transection of the medial forebrain bundle. At all ages examined, two phenomena were observed: degeneration of nerve fibers and vigorous regrowth of catecholamine-containing fibers in the lesion site. Regenerated catecholamine fibers invaded the area of scarred tissue. This invasion of the scarred area implies that the robust plasticity of catecholaminergic pathways, known to exist in young animals, persists in aged brain.

Aging↗
PubMed1982

Monoamine distribution in primate brain-IV. Indoleamine-containing perikarya in the brain stem of Macaca arctoides.

The histochemical fluorescence technique for the demonstration of monoamines in the central nervous system was employed to assess the distribution of serotonin-containing neurons within the brain stem of the immature and adult stump-tailed macaque (Macaca arctoides). Microspectrofluorometric analysis was performed in order to verify the existence of serotonin within perikarya which contained yellow histofluorescence. Serotonin-containing perikarya were found with raphe nuclei including nucleus raphe-pallidus, -obscurus, -points, -magnus, -dorsalis, and -centralis superioralis. Serotoninergic perikarya did not appear confined exclusively to the raphe, but were observed in the reticular formation and other brain stem nuclei including the locus coeruleus and nucleus subcoeruleus. Serotoninergic cells were not seen within the brain stem at superior collicular levels. The localization of serotoninergic perikarya in regions other than the raphe nuclei presents certain dissimilarities in relation reported in other mammalian species.

Animals↗
PubMed1982

Characterization of noradrenergic control of vasopressin release by the organ-cultured rat hypothalamo-neurohypophyseal system.

Evidence is presented indicating that norepinephrine (NE) inhibits vasopressin (VP) release from the rat hypothalamo-neurohypophyseal explant under some, but not all, conditions in vitro. NE at 10(-5) M inhibited basal VP release and inhibited acetylcholine-induced release in a concentration-dependent fashion. However, the induction of VP release caused by the addition of NaCl (sufficient to yield a 10 mosmol/kg H2O increase in culture medium osmolality) was not reduced by NE in concentrations as high as 10(-5) M. An alpha-adrenergic receptor mediation of the inhibition of VP release by NE was suggested by the ability of phentolamine and phenoxybenzamine, but not propranolol, to block this effect. In addition, phentolamine at 10(-4) M, but not equimolar amounts of propranolol, increased VP release when added alone on day 2 of culture, but not on days 3 or 4. Histofluorescence examination of additional explants revealed that endogenous catecholamine was still present on day 2 within varicosities in the supraoptic nucleus, but diminished by days 3 and 4, suggesting that endogenous NE could influence basal VP release. The results indicate that NE can inhibit spontaneous and cholinergically stimulated VP release from the hypothalamo-neurohypophyseal explant, but osmotic stimulation renders the explants insensitive to attenuation of VP release by NE.

Acetylcholine↗
PubMed1981

Supraoptic nucleus of the Brattleboro rat has an altered afferent noradrenergic input.

The distribution of fluorescent varicosities in the supraoptic nucleus of Brattleboro rats was compared to that in normal rats. The Brattleboro rat, which is characterized by a genetic absence of vasopressin, had fewer fluorescent varicosities in apposition to the vasopressin-deficient perikarya. The oxytocin-producing neurons in the same nucleus were hyperinnervated. These data suggest that the target neuron peptide (vasopressin) is necessary for the maintenance of normal noradrenergic innervation patterns.

Adrenergic Fibers↗
PubMed1981

A comparison of neuropeptide immunocytochemistry in fluid-fixed and freeze-dried brains.

Immunocytochemical staining of luteinizing hormone-releasing hormone (LHRH), somatostatin, and neurophysin was compared in rat brains fixed with 1) formalin, 2) Bouin's solution, 3) freeze-dried (FD), or 4) freeze-dried + paraformaldehyde vapor perfused (FDV). The distribution of LHRH fibers was similar in all preparations; however, beads of granular reaction product often appeared finer and more numerous in the median eminence of FD- and FDV brains. Positively stained LHRH perikarya were not observed in any of the preparations. In contrast, somatostatin-immunoreactive perikarya were present in the fluid-fixed and FD brains, although few were observed in FDV brains. Somatostatin-immunoreactive fibers were present in all preparations, but appeared most numerous in the median eminence of FD brains. Staining of neurophysin-containing perikarya and fibers was similar in all preparations. These observations suggest that the FD brain can provide a suitable tissue substrate for immunocytochemistry, demonstrating staining comparable to or surpassing that of more conventional preparations. However, staining of antigens in FD brain was not uniformly successful and may depend on stereochemical characteristics of each antigen as well as properties of the primary antisera used in the staining procedure.

Animals↗
PubMed1981

Age related changes in the endocrine hypothalamus: I. Tanycytes and the blood-brain-cerebrospinal fluid barrier.

The fine structural organization of the floor of the third cerebral ventricle (dorsum of the median eminence of the hypothalamus) of 2 normal adult mice Fisher 344 rats was compared and contrasted with that of 2 aged rats 30 months old. Closely juxtaposed tanycytes (specialized ependymal cells) of normal young adults in the lower walls and floor of the third ventricle. In contrast, tanycytes in aged rats demonstrated significant intracellular separations, with only fine cytoplasmic processes remaining to interlink them. The phenomenon of mechanical separation between tanycytes in aged animals is discussed with respect to a potential impairment in the integrity of the blood-brain-cerebrospinal fluid barrier.

Aging↗
PubMed1981

Aging of tuberoinfundibular (A-12) dopamine neurons in the C57Bl/6N male mouse.

C57Bl/6N male mice at 4, 12, 20, and 28 months of age were processed for formaldehyde-induced fluorescence, and tuberoinfundibular dopamine (A-12) neurons were examined for qualitative, age-related changes. A-12 perikarya were weakly fluorescent at all ages studied. In mice of 4 and 12 months of age, A-12 terminals formed a brightly fluorescent band that filled the external zone of the median eminence. The zone of A-12 terminal fluorescence within the median eminence was less extensive and reduced in fluorescence intensity in 20-month old mice; in 28-month old mice, only a thin rim of fluorescence remained at the ventral edge of the median eminence. The drop in fluorescence intensity of A-12 terminals within the median eminence of the aged C57Bl/6N male mouse paralleled the decrease in A-12 terminal fluorescence previously reported for the Fischer 344 male rat [26]; however, mouse A-12 perikarya did not exhibit the dramatic increase in fluorescence intensity seen in the rat. The possibility that the divergent aging patterns exhibited in A-12 neurons of these two species might be related to differential resilience of their reproductive axes is discussed.

Aging↗