Les yeux des Cyclostomes fossiles et le problème de l'origine des MyxinoïdesJanvier, Philippe
doi: 10.1111/j.1463-6395.1975.tb00077.xpmid: N/A
Abstract The Eyes of the Fossil Cyclostomes and the Problem of the Origin of Myxinoids Studies on orbital cavities in various fossil Cyclostomes have yielded certain conclusions as concerns the organ of sight and the arrangement of the extrinsic ocular muscles in these ancient animals. Thus, evidence is offered that osteostracans possessed spheroidal eyeballs similar to those of present‐day petromyzontids; also, that heterostracans were equipped with conical eyeballs closely conforming to those encountered in the recent myxinoid Eptatretus burgeri. On the basis of the last‐mentioned resemblance, the shape of the prenasal sinus, the construction of the biting mechanism, the lack of a pineal foramen, the presence of a common external aperture for the ipsilateral gill‐slits, and the probable existence of a paired longitudinal row of mucous glands, it is further suggested that heterostracans and myxinoids are immediately related. Résumé La forme et la musculature des yeux des Cyclostomes fossiles peuvent être reconstituées à partir de l'étude de la cavité orbitaire. Il apparaît alors que l'organisation de l'ceil des Ostéostracés devait être très proche de celle de l'ceil des Pétromyzontides tandis que l'ceil cônique des Hétérostracés rappelle fortement celui du Myxinoïde Eptatretus burgeri. Ce caractère, joint à la structure du sinus prénasal, au type de mécanisme buccal, à l'absence de foramen pineal, à la présence d'un orifice branchial commun et à l'existence probable de rangées de glandes mucogénes, nous oblige à considérer les Hétérostracés comme les formes les plus proches des Myxinoïdes et, peut‐être, leurs ancêtres directs.
The Cerebral Neurosecretory System, Secretory End‐Foot System and Infracerebral Gland—a Probable Neuroendocrine Complex in Nephtys (Annelida; Polychaeta)Zahid, Z.R.; Golding, D. W.
doi: 10.1111/j.1463-6395.1975.tb00078.xpmid: N/A
Abstract The brain of Nephtys contains four neurosecretory cell types with distinctive cytoplasmic inclusions, a cells are located uniquely in a single pair of ganglionic nuclei and b cells are represented by a single pair of cells, whereas c cells and d cells have a scattered distribution. Their axons form two types of secretory release structure. First, possible axon collaterals synapse upon slender “dentritic twigs” in the core of the brain. Secondly, two tracts descend to the brain floor to form a “neurosecretory neuropile” (or storage and release complex) in contact with the inner surface of the brain capsule. Other neurosecretory fibres penetrate through the capsule, branch extensively, and terminate in contact with its ventral surface in close association with the “infracerebral gland”. The gland is derived from the pericapsular epithelium and exhibits signs of specialization for glandular function. In contrast to certain other polychaetes, it does not contain secretory neuron perikarya. The secretory end‐foot system is poorly developed. Its terminals are located adjacent to the neurosecretory neuropile, which they encircle. The cell bodies are probably represented by four e cells which, like the terminals, contain many mitochondria.
Immunohistochemical Localization of Growth Hormone and Prolactin in the Pituitary Gland of Acipenser güldenstaedti Brandt (Chondrostei)Hansen, Georg Nørgaard; Hansen, Bente Langvad
doi: 10.1111/j.1463-6395.1975.tb00079.xpmid: N/A
Abstract Prolactin (LTH) and growth hormone (GH) containing cells in A. güldenstaedti have been localized by means of anti‐ovine prolactin and anti‐bovine growth hormone respectively, coupled indirectly to peroxidase, and localized histochemically with hydrogen peroxide as substrate and 3,3′‐diaminobenzidine as capturing agent. The distribution of the anti‐prolactin positive cells has been demonstrated and correlated histologically with the acidophilic cells both in the rostral and proximal pars distalis. This cell type is elongated and arranged in follicles in the rostral pars distalis; in the proximal pars distalis they are smaller and oval, without any special orientation. Neither of the other cell types which are scattered among these acidophils contain prolactin. The anti‐bovine growth hormone positive cells are evenly distributed in the proximal pars distalis above the hypophysial cleft, and some are also found in the pars intermedia. The anti‐GH positive cells have been correlated histologically with the amphiphilic cells in the proximal pars distalis. These cells are arranged in cell cords in close contact with the secondary capillary plexus, near its origin from the primary capillary plexus covering the median eminence.
The Pituitary Gland of the Roach Leuciscus rutilusBåge, Gertrud; Ekengren, Bo; Fernholm, Bo; Fridberg, Gunnar
doi: 10.1111/j.1463-6395.1975.tb00080.xpmid: N/A
Abstract Two endocrine cell types, PbH+ and PAS+ cells, were recognized in the pars intermedia (PI) of the roach, Leuciscus rutilus, by light and electron microscopy. They can be distinguished by the appearance of their secretory granules. The PAS+ cells stain with toluidine blue in semithin sections as opposed to the PbH+ cells. After 5 days' treatment with metopirone the PbH+ cells are highly activated whereas the PAS+ cells show no response. The PbH+ cells are assumed to produce MSH. In roaches adapted to diluted sea water (10%) the transfer to fresh water for 1—1 1/2 hours or reserpine injections for the same period had no notable effect on neither cell type. Three kinds of axons innervate the PI. Two of these, which have granules averaging 111 nm and 151 nm in diameter, originate in the nucleus preopticus (NPO). The third type of axons has granules of an average size of 74 nm and is probably aminergic. The glia cells in this part of the neurohypophysis (NH) are granular pituicytes, which are innervated by all three axon types. The border between the NH and the PI is composed of a double basement membrane from which a network extends into the NH. This network, the basement membrane and the capillaries are the main sites for the terminations of the axons although nerve fibers also invade the endocrine tissue. Only axon type 3 was observed to synapse frequently with the PbH+ cells.
Premigratory Changes in the Hypothalamo‐Hypophysial Neurosecretory System in the Red‐winged Blackbird ( Agelaius phoeniceus) *Hawkes, Michael P. G.; George, J. C.
doi: 10.1111/j.1463-6395.1975.tb00082.xpmid: N/A
Abstract 1 The hypothalamo‐hypophysial neurosecretory system in the Red‐winged Blackbird (Agelaius phoeniceus) has been studied with special reference to changes during the period prior to fall migration. 2 In September the supraoptic and paraventricular cells were found to be considerably larger with substantial amounts of aldehyde fuchsin positive neurosecretory material (NSM) accumulating in the perikaryon. Large amounts of the NSM were found also in the anterior median eminence and pars nervosa. 3 Towards migration time (November), the cells in the hypothalamic nuclei contained very little NSM. A marked decline in the amount of NSM was also seen in the anterior median eminence and probably in the pars nervosa too. 4 The release of NSM toward migration time has been discussed as an important event in the sequence of events that control and regulate migratory activity.
Lethal Temperatures in Ammocoetes of Four Species of LampreysPotter, I. C.; Beamish, F. W. H.
doi: 10.1111/j.1463-6395.1975.tb00084.xpmid: N/A
Abstract An investigation has been made of the resistance time and upper lethal temperature of ammocoetes of four species of lampreys provided with a substrate into which they could readily burrow. In general, ammocoetes burrowed after transfer from the acclimation to the experimental temperature baths and later came out of the substrate only in lethal temperatures. A relationship was observed between the resistance time and the time taken to emerge, with the resistance time increasing exponentially with decreasing experimental temperature. In Ichthyomyzon fossor, landlocked Petromyzon marinus, Lampetra (Lethenteron) Lamottenii and in Lampetra (Lampetra) planeri from two different times of the year, the incipient lethal levels over a two week experimental period for larvae acclimated to 15° G were respectively 30.5, 30, 29.5, 28.5 and 28° C. Values for P. marinus acclimated to 5 and 25° C were respectively 29.5 and 31° C, whereas in L. planeri they were 28 and 29° C in April/May and 27 and 29° C in July/August. Extrapolation of the results for the three acclimation temperatures yielded ultimate incipient lethal levels of 31.4° G in P. marinus and 29.2 and 29.4° C for L. planeri examined in the spring and summer respectively.