Non-ependymal cilia in the habenulae and the interpeduncular nucleus of the frog tadpole

Summary Cilia of the 9+2 pattern are found electron microscopically in nonependymal cells of the habenulae and the interpeduncular nucleus of the tadpole of Rana esculenta at an early stage of development (8 mm length, head to tip of tail). A comparison is made between these and the ependymal and sensory cilia in the same specimens. The cilia project into the neuropil emerging from a perikaryon rich in free ribosomes and displaying a prominent Golgi apparatus. These perikarya contain dense core vesicles. Synapses with vesicles of the clear spherical type have been observed along the ciliary shaft. On a purely morphologic basis the authors hypothesize that these cilia, at least in this early ontogenetic stage, may extend considerably the conducting surface of the cell and represent a sensory structure which could be stimulated by terminal processes belonging to distantly located cells. In addition, they could also be involved in the trophic exchange of material with the adjacent structures.     

Ontogeny of vasopressin and oxytocin in the fetal rat: Early vasopressinergic innervation of the fetal brain

The content and distribution of vasopressin and oxytocin were determined during fetal development in the rat brain and pituitary by means of radioimmunoassay and immunocytochemistry. The vasopressin content in the fetal brain showed a gradual rise from day 16 of pregnancy onwards, while pituitary vasopressin rapidly increased from fetal day 19 until birth. The oxytocin content in the fetal brain was considerably lower than the vasopressin content. A decrease in oxytocin content was seen between day 16 and day 18 while from day 18 of pregnancy onwards a slight increase was found. The pituitary oxytocin content starts to rise between day 17 and 18 of pregnancy, but at term the pituitary oxytocin content was only 1/20 of the vasopressin value. Immunocytochemistry revealed that vasopressin levels in the fetal rat brain were not only due to the presence of the classical hypothalamoneurohypophyseal system, but also to the early development of exohypothalamic fibers. Vasopressin containing cells were seen from fetal day 16 in the supraoptic nucleus, and from fetal day 18 in the paraventricular nucleus. The fiber outgrowth of these cells towards the pituitary and extrahypothalamic brain sites seems to be well synchronized, as on day 17 vasopressin containing fibers could be demonstrated in the olfactory bulb as well as in the median eminence. No positive staining for oxytocin could be obtained in the fetal rat, while during the entire fetal period no positive staining was found in cell bodies in the region of the suprachiasmatic nucleus. The early peptidergic innervation of the brain, which enabled the tracing of the source of some exohypothalamic fibers, might be related to several central processes among which brain development itself is included.     

Adrenergic control of hypothalamic function during osmotic stress in the mallard duck (Anas platyrhynchos)

Summary The role of the paraventricular nucleus (PVN) and biogenic amines (BA) in regulating the level of corticoids in the serum of osmotically stressed mallard ducks (Anas platyrhynchos) was analyzed employing three experimental approaches: 1) pharmacologic alteration of central BA levels, 2) microscopic evaluation of BA distribution, and 3) placement of electrolytic lesions into the PVN. Reserpine and -methyl-p-tyrosine (mpt), agents that decrease the amount of BA's in the central nervous system, produced a fivefold increase in the concentration of serum corticoids. Conversely, pargyline and amphetamine, agents that increase the functional pool of BA's, prevented the rise in serum corticoid concentration normally observed in birds challenged with an intraperitoneal injection of hypertonic saline. When the topographic distribution of BA's was analyzed in the brains of osmotically stressed and nonstressed ducks distinct changes in the intensity of catecholamine (CA) fluorescence were observed in only one location, the PVN of the hypothalamus. Additionally, electrolytic lesions stereotaxically placed in the PVN blocked the osmotic stress-induced rise in serum corticoid concentration. These data therefore indicate that the PVN in the mallard duck plays some role in regulating the observed stress-induced rise in serum corticoid concentration, and that this regulatory function is probably inhibited by catecholamines.This research was supported by research grant No. GB 33321 from the National Science Foundation. We wish to express our sincere thanks to Mr. Howard Funk, research director, Colorado Division of Wildlife, for the use of the State's animal facilitiesThis research was submitted as partial fulfillment for the degree of Doctor of Philosophy, Department of Physiology and Biophysics, Colorado State University, Ft. Collins, CO 80521     

Proliferation of lamellar whorls in arcuate neurons of the hypothalamus of male rats treated with estradiol benzoate or cyproterone acetate

Summary The arcuate nucleus of the hypothalamus (AH) of male rats which had been treated either with estradiol benzoate (E²B) or cyproterone acetate (CPA) was examined ultrastructurally for the presence of whorls of endoplasmic reticulum. The incidence of whorl containing neurons (WCN) was 2–4 times higher in the AH of animals treated for 2–3 weeks with E²B or for 2 weeks with CPA than in the AH of oil treated controls. CPA is a powerful anti-androgen while E²B acts both peripherally and centrally to limit testosterone production. These findings, together with previous evidence that whorls proliferate in AH of male rats deprived of androgen by morphine treatment or castration, suggest that steroid feedback (androgen alone or both androgen and estrogen) plays an important role in AH whorl proliferation. The possibility that WCN may be LH-RH containing neurons is suggested by the close correspondence between the number and location of WCN within AH as determined in this study and the distribution of LH-RH containing cells reported by others.The authors are indebted to Schering AG for supplying cyproterone acetate for this study. This work was supported by grants DA-00259, NS-09156 and MH-14677 from U.S.P.H.S.Research Scientist Development Award MH-38894Research Scientist Development Award MH-70180     

Fine structure of the spermatozoa of Chiton marginatus (mollusca: Amphineura), with special reference to nucleus maturation

The spermatozoon of Chiton marginatus is a long uniflagellate cell displaying structural features of “modified sperm.” The nucleus presents a conical shape with a long apical cylindrical extension. The chromatin is homogeneously dense. Scattered inside the condensed nucleus, a few nuclear lacunae are visible. The acrosomal complex is lacking. Some mitochondria are located in a laterofrontal structure side by side with the nucleus. The typical midpiece is absent. The cytoplasm forms a thin layer around the nucleus and the mitochondria. The proximal centriole is in a basal nuclear indent. The distal centriole serves to form the axoneme tail with the usual microtubular pattern. During nuclear maturation, the early spermatid nucleus is spherical and contains fine granular chromatin patches. The nuclear envelope shows a deposit of dense material at the base of the nucleus, forming a semicircular invagination occupied by a flocculent mass. In middle spermatid stage, the chromatin gets organized in filaments, coiled as a hank, attached over the inner surface of the basal thickening of the nuclear envelope. The nucleus starts to elongate anteroposteriorly. At the pointed apical portion of the spermatid, a group of microtubules is observed seeming to impose external pressure to the nucleus giving rise to the long apical nuclear point. The mitochondria have a basal position. Late spermatids have an elongated conical nucleus. The chromatin filaments are further condensed, and lacunae appear inside the nucleus. Some mitochondria migrate to a lateral position.     

Feeding induced by opiates injected into the paraventricular hypothalamus

Injection of morphine or d-ala-2-met-5-enkephalinamide (DALA) into the paraventricular nucleus of the hypothalamus (PVN) produced a dose dependent increase in feeding in rats. DALA increased feeding within 45 minutes; morphine within 90 minutes. Naloxone injected into the PVN diminished the effect. DALA increased water intake only when food was available, suggesting the primary effect was on feeding. In summary, an enkephalin analogue induced feeding, and an opiate receptor blocker attenuated it; therefore the PVN may contain opiate receptors that facilitate feeding.     

心房利钠肽样免疫反应神经元在大鼠中脑和脑桥中某些锥体外系神经核内的分布

采用PAP免疫组织化学方法对大鼠中脑和脑桥内心房利钠肽(ANP)样免疫反应神经元的分布进行了研究,结果显示阳性神经元除存在于其他作者报导过的导水管周围灰质、Edinger-Westphal核、中缝核、脚间核和蓝斑核外,还存在于属于锥体外系的红核、黑质和脑桥核内,因此,推测脑内的ANP可能在锥外系对躯体运动的调节中起着一种神经递质或神经调质的作用。这为脑内ANP可能具有与液体和电解质平衡以及心血管功能的调节无关的其它作用提供了部分形态学证据。     

Effect of Aging on Tyrosine Hydroxylase Protein Content and the Relative Number of Dopamine Nerve Terminals in Human Caudate

This study examined the effect of aging on the relative number of dopamine (DA) nerve terminals in human caudate nucleus, their content of tyrosine hydroxylase (TH) protein, and the relative abundance of TH monomers with different molecular weights. Preliminary studies on brain tissue cryopreservation, performed with rat striatum, indicated that intact synaptosomes can be prepared from fresh tissue slowly frozen in 0.32 M sucrose with 5% dimethyl sulfoxide and then thawed rapidly prior to synaptosome preparation. Synaptosomes were prepared in this manner from postmortem caudate nucleus tissue obtained from normal humans 1 month to 63 years of age. To determine the relative number of DA nerve terminals for each individual, dopaminergic synaptosomes were selectively labeled with a monoclonal antibody to TH and quantified by fluorescence-activated cell sorting. To determine the relative amount of TH protein for each individual, the concentration of TH protein in the same synaptosomal preparations was determined using immunoblots. Our results suggest that caudate TH levels plateau soon after birth and tend to remain relatively stable during aging, since no changes in either the relative number of TH-containing nerve terminals or the concentration of TH protein were found in subjects 15-63 years of age. In light of previous studies showing an age-related loss of DA cell bodies, these findings suggest that remaining DA neurons compensate to maintain caudate levels of TH protein and TH-containing nerve terminals. Immunoblot studies identified three forms of TH monomer (60.6, 61.7, and 65.1 kDa), indicating that mRNAs coding for high molecular mass forms of TH may be actively translated in human brain. No age-related differences in the relative abundance of these forms were found.     

Effect of Cholecystokinin Octapeptide on Endogenous Amino Acid Release from the Rat Ventromedial Nucleus of the Hypothalamus and Striatum

The sulphated octapeptide of cholecystokinin (CCK-8S) was found to cause a dose-dependent increase in the basal release of aspartate, glycine, and gamma-aminobutyric acid from the striatum and the ventromedial nucleus of the hypothalamus (VMH). No effect on amino acid release was observed after electrical (VMH) or potassium (striatum) stimulation. Experiments performed using the CCKB-selective antagonist L-365,260 and the CCKA-selective antagonist L-364,718 suggested that this action of CCK-8S was mediated via the CCKB receptor. The ability of CCK-8S to evoke amino acid release was not dependent on the presence of extracellular calcium, though the effect was abolished by tetrodotoxin. Inhibition of protein kinase activity by staurosporine prevented the excitatory effects of CCK-8S on amino acid release.     

Distribution of Preproatrial Natriuretic Peptide mRNA in Rat Brain Detected by In Situ Hybridization of DNA Oligonucleotides: Enrichment in Hypothalamic and Limbic Regions

The expression and distribution of mRNA encoding preproatrial natriuretic peptide (ppANP) in rat brain has been investigated by in situ hybridization of two 35S-labeled synthetic DNA oligonucleotides, based on a cDNA clone sequence that encodes rat ppANP. The highest relative concentrations of ppANP mRNA were detected in the medial preoptic hypothalamic nucleus ("anteroventral/third ventricle region") and the medial habenula. Moderate concentrations of ppANP mRNA were observed in the CA1 pyramidal cells of the hippocampus, the endopiriform nucleus, the arcuate nucleus, the zona incerta, and cells of the pontine tegmental and peduculopontine nuclei. Several of these regions, including the habenula and the hypothalamic areas, have previously been reported to contain atrial natriuretic peptide (ANP)-like immunoreactivity, but the expression of ppANP mRNA in CA1 pyramidal cells suggests the occurrence of differential translation of ppANP mRNA into protein product in different brain regions, or the existence of different immunological forms of the peptide. The abundance of ppANP mRNA in brain was relatively low in comparison with that previously reported for many other mRNA species encoding other brain neuropeptides. These results demonstrate that ANP gene expression occurs in discrete neuronal populations of the CNS and that studies of the regulation of this expression should now be possible using quantitative in situ hybridization.