Showing papers by "Memorial University of Newfoundland published in 1983"
451 citations
322 citations
TL;DR: There appears to be a low level of maturational hormone present when the fish resumes ovarian development after spawning, but it is sufficient to establish vitellogenin production by the liver.
Abstract: Publisher Summary This chapter discusses the yolk formation of teleost fishes The process of vitellogenesis in teleosts has been shown to be similar to that operating in other oviparous vertebrates The contribution of autosynthetic processes (endogenous vitellogenesis) to the yolk mass in the teleost ovary, relative to exogenous yolk acquired by incorporation of vitellogenin, has not been estimated Exogenous vitellogenesis can be considered to consist of two phases The first phase involves the induction of hepatic vitellogenin production under stimulation of ovarian estrogen During the second phase vitellogenin is taken up from the blood stream and incorporated into ovarian yolk proteins In salmonids maturational gonadotropin occurs at high levels in plasma around spawning time but is near the lower limit of the radioimmunoassay during the phase of active incorporation of vitellogenin There appears to be a small increase in maturational gonadotropin coincident with an increase in estradiol in trout plasma early in vitellogenesis, and antibody to maturational gonadotropin inhibits ovarian growth immediately prior to the rapid and massive increase in the ovarian weight Therefore, there appears to be a low level of maturational hormone present when the fish resumes ovarian development after spawning, but it is sufficient to establish vitellogenin production by the liver
273 citations
TL;DR: A nomenclature is proposed designating not only the migration pattern of the C4 variants in agarose gels but also the heterogeneity of theC4 chains observed in SDS-PAGE, which resulted in a total of 11 variants in the population studied.
216 citations
TL;DR: At 39% of the potentiated sites norepinephrine application resulted in long-lasting potentiation (LLP), suggesting a role for NE inLong-term hippocampal plasticity.
170 citations
TL;DR: It is indicated that 17 alpha, 20 beta-diOHprog is the major steroid responsible for oocyte maturation in amago salmon, produced as the follicular mediator of gonadotropin.
162 citations
TL;DR: In the case of the Musandam Peninsula, the authors of as mentioned in this paper show that the shelf edge of the Zagros fold was formed by fragmentation and rifting of a vast east-facing carbonate platform, resulting in the establishment of a shelf edge and small ocean basin.
Abstract: The northernmost extremity of the Oman Mountains, the Musandam Peninsula, is composed of an allochthonous sequence of Permian to middle Cretaceous shelf carbonates. These are separated from ophiolitic rocks to the south by a northeast-southwest-trending belt known as the Dibba zone. This structurally complex belt is composed of allochthonous slope- and basin-facies sediments, Haybi volcanic rocks, “Oman Exotic” limestones, sub-ophiolitic metamorphic rocks, and ultra-mafic slices. Lithofacies correlation confirms that fragmentation and rifting of a vast east-facing carbonate platform occurred in Middle to Late Triassic time, resulting in the establishment of a shelf edge and small ocean basin. This margin was typified from northwest to southeast by ooid-skeletal lime sand shoals or small bioherms on the shelf edge, a bypass foreslope of well-laminated periplatform ooze, and basin-margin accumulations of carbonate turbidites or debris flows. The shelf edge now coincides with the northern boundary of the Dibba zone and appears to have remained stationary from Middle Triassic to Late Jurassic time. Periods of arrested carbonate sedimentation on the platform either because of exposure (Late Triassic and middle Cretaceous) or because of drowning (Late Jurassic) are represented in the basin by starved sedimentation and deposition of radiolarian cherts. A spectacular platform margin collapse occurred in the middle and Late Cretaceous, as represented by massive conglomerates, with clasts as young as Albian, above an unconformity that progressively removed all of the Lower Cretaceous. The Tethyan basinal and ophiolitic rocks of the Dibba zone were emplaced from the east-southeast during the Turonian to lower Maastrichtian. After emplacement of these allochthonous units, compressional deformation in the mid-Tertiary resulted in large-scale, open, “whaleback” folds with wavelengths as much as 15 km, generally with north-south axes. In places, these folds, which affect the complete shelf and allochthonous sequences, are overturned toward the west, and thrusting has caused previously lower tectonic units of the Late Cretaceous stacking order to be thrust over previously higher tectonic units, thus reversing the Late Cretaceous tectonostratigraphy. The maximum amount of translation on the later thrusts is in excess of 5 km on the Hagab thrust, where the complete shelf carbonate sequence of the Musandam Mountains has been thrust west-northwest over the previously higher Hawasina and Haybi thrust sheets. The Tertiary folding and thrusting can be correlated in time and space with the Zagros fold belt of southwestern Iran.
162 citations
TL;DR: A shift in the allocation of resources from growth to reproduction is seen as an appropriate response to a depletion of the food supply in an environment in which the duration of adverse conditions cannot be predicted, yet the urchin may retain the capacity to restore the normal energy balance should conditions improve.
Abstract: Gamete production, somatic growth and reproductive effort were measured in sea urchins maintained on a mixture of kelp and mussel flesh at three ration levels. Urchins on low ration were able to maintain an output of gametes half that of urchins fed ad libitum. This was achieved at the expense of somatic production, which was negative in the low ration groups. Despite the reduction in the output of gametes, reproductive effort was greater in the low ration urchins than in the well fed ones. The lipid content and the energy content were greater in eggs released by urchins fed ad libitum than in eggs produced by urchins at low ration.
137 citations
TL;DR: The facilitatory effects of 5HT and NE on excitability of motoneurons were readily blocked by antagonists and were, therefore, attributed to actions on separate 5 HT and NE receptors in the ventral horn.
122 citations
TL;DR: The ophiolite was emplaced southwards onto the Zanskar shelf edge during latest Cretaceous or earliest Tertiary times as mentioned in this paper. But deep-sea sedimentation ended abruptly with initial collision between the Indian plate and the Dras island arc.
Abstract: The Tibetan–Tethys zone of the Zanskar Himalaya shows a complete Mesozoic shelf carbonate sequence overlying metamorphic basement of the Central crystalline complex and Palaeozoic sedimentary rocks. Continental rifting in the Permian produced the alkaline and basaltic Panjal volcanic rocks and by Triassic time a small ocean basin was developed in the Indus-Tsangpo zone. Stable sedimentation continued until the Middle-Late Cretaceous when a thick sequence of tholeiitic to andesitic island arc lavas (Dras arc) were erupted in the basin above a N-dipping subduction zone. The Spontang ophiolite was emplaced southwards onto the Zanskar shelf edge during latest Cretaceous or earliest Tertiary times.Following emplacement of the Spontang ophiolite, deep-sea sedimentation ended abruptly with initial collision between the Indian plate and the Dras island arc. Emplacement of the massive Ladakh (Trans-Himalayan) batholith along the southern margin of Tibet in late Cretaceous-Eocene time occurred by crustal melting as a result of northward subduction of Mesozoic oceanic crust along the Indus subduction zone. Southward-directed thrusting in both Zanskar and Indus zones accompanied ocean closure during the late Cretaceous–Eocene. Late Tertiary compression caused intense folding, overturning and a phase of northward-directed thrusting along the Indus suture zone and the northern margin of the Tibetan–Tethys zone, resulting in a large amount of crustal shortening.
111 citations
TL;DR: Happiness, greater in rural than in institutionalized persons, remained stable for all groups, and the results show that, although predictor effectiveness may differ across subgroups, happiness remains stable in later years.
Abstract: The current investigation reports findings on the temporal stability of happiness as assessed by the Memorial University of Newfoundland Scale of Happiness (MUNSH), and the stability of the predictor/happiness relationships in three subgroups of persons over 64 years of age Respondents were interviewed twice, 18 months apart, on the MUNSH and on nine established correlates Separate multiple regression analyses were used to assess the predictor/happiness relationship for each phase The stability of happiness was evaluated by the inclusion of phase 1 MUNSH scores in the phase 2 predictor array For urban and institutional persons the main independent predictors of happiness in both phases were housing satisfaction, health, activities, and changes in life events For rural individuals only health and marital status remained consistent predictors for both phases Happiness, greater in rural than in institutionalized persons, remained stable for all groups, with an average of 86% of the accounted MUNSH 2 variance due to MUNSH 1 scores These results show that, although predictor effectiveness may differ across subgroups, happiness remains stable in later years
TL;DR: It can be concluded from these studies that the testosterone stimulus is sufficient to induce onset of sexual development in immature males but not females.
Abstract: The influence of testosterone, luteinizing hormone releasing hormone (LHRH) agonist and combinations of these hormones on gonadotropic hormone (GtH) levels in the sexually immature trout was investigated. Both the steroid and releasing hormone preparations, testosterone in Silastic capsules and cholesterol-pelleted LHRH-A, were formulated for sustained release and long-term biological action following a single hormone implantation. Marked increases in pituitary GtH followed testosterone and/or testosterone and LHRH analogue treatment combined, but the low pituitary GtH level in controls remained unchanged after LHRH analogue administration alone. Plasma GtH titers increased with time after testosterone treatment, indicating a positive steroid feedback effect by androgen on GtH in the juvenile rainbow trout. When combined with testosterone treatment, LHRH analogue augmented plasma GtH levels compared to fish receiving testosterone treatment alone. In males the elevated plasma GtH levels were associated with testes stimulation and onset of spermatogenesis; in females, however, no significant stimulation of the ovaries was observed. It can be concluded from these studies that the testosterone stimulus is sufficient to induce onset of sexual development in immature males but not females. Whereas LHRH analogue releases GtH from the testosterone-primed trout pituitary, LHRH treatment alone under these conditions fails to stimulate the juvenile trout reproductive system.
TL;DR: Three other parsimonious tree construction problems are described and proved that they, too, are NP-complete.
TL;DR: The present study investigated seasonal changes in plasma 17α,20β-dihydroxy-4-pregnen-3-one levels in precociously mature and fully grown mature male amago salmon and in vitro 17β-diOHprog production by the testes of amago Salmon and rainbow trout in response to chum salmon gonadotropin.
TL;DR: Study of the spermatocrit indicated that this increase is associated with an advancement in the production of spermatozoa and is not just due to sperm dilution, and this increase in milt volume is related to an increase in plasma GtH.
01 Jan 1983
TL;DR: In this article, a character state tree on which the states of each character are convex is defined. (See Estabrook, this volume, for definition of convex and other introductory concepts.)
Abstract: Determining whether characters are compatible is easy if character state trees are hypothesized (see papers by Le Quesne and Estabrook, this volume). However, many interesting characters available to systematists do not readily suggest the evolutionary relationships among their states. Characters without character state trees are called qualitative characters. Assume we have a study collection S, of six taxa: a, b, c, d, e, and f. A short piece of homologous DNA has been sequenced for these taxa. At position one, a and b have A, c and d have C, and e and f have G. At position two, a, b, and c have T, d and e have A, and only f has C. These are two three-state characters where each state is a set of taxa. Call the first character K, which has states {a,b}, {c,d}, and {e,f}; and the second L, which has states {a,b,c}, {d,e}, and {f}. These characters are compatible if there exists a tree on which the states of each character are convex. (See Estabrook, this volume, for definition of convex and other introductory concepts.) Figure 1 shows such an undirected tree on which the states of each character are convex. These characters are, in fact, compatible. Fitch (1975) and Estabrook and Landrum (1975) independently discovered an algorithm for determining the compatibility of a pair of qualitative characters.
TL;DR: Introduction Anatomic Considerations Capillaries Salivary glands Pancreas Stomach Small intestine Colon Pathways for transcapillary exchange Interstitium Lymphatics Stomach small intestine Colon SalivARY glands pancreas Physiology of Capillary Fluid and Solute Exchange Capillaryfluid Exchange Lymph flow Capillary filtration coefficient Capillary pressure Interstitial fluid pressure Osmotic reflection coefficient Oncotic pressure gradient.
TL;DR: Property of the cell-free binding assay is presented and evidence for masking of acceptor sites and properties of the masking proteins are presented and novel regulations of the chick oviduct progesterone receptor are discussed.
Abstract: Publisher Summary The chemical nature of the nuclear binding sites for steroid receptors is a very important but very obscure aspect of the processes of steroid hormone action and gene regulation. The steroid receptor complexes represent the first intracellular gene regulator ever discovered in eukaryotes. The receptors are bound with high affinity and steroid specificity by steroid hormones. The complex in turn migrates and binds to the acceptor sites on the genome and alters the gene expression in a quantitative and qualitative fashion. The steroid–receptor complex then dissociates from the nuclear acceptor sites—the steroid is probably metabolized and secreted from the cell—and the free receptor is recycled back into the receptor–acceptor site pathway, to await another steroid. Thus, the nuclear acceptor sites represent the first intranuclear sites through which steroid receptors initiate regulation of gene expression. This chapter presents properties of the cell-free binding assay. It also presents evidence for masking of acceptor sites and properties of the masking proteins and discusses novel regulations of the chick oviduct progesterone receptor. The chapter also discusses the isolation and characterization of specific chromatin proteins that are involved in the nuclear acceptor sites for the progesterone receptor.
TL;DR: Pelleted LHRH implants could prove useful in advancing spawning time in order to meet schedules of smolt production or assist in synchronizing the spawning time of salmonid brood stock reared or held in salt water.
TL;DR: It was determined that a hyperinnervation of jeJunal vessels in the hypertensive rats is present from 2 weeks of age onwards, before significant elevation of blood pressure and medial hypertrophy of jejunal arteries occurs.
Abstract: The catecholaminergic innervation of jejunal arteries was examined during development in normotensive and hypertensive rats. It was determined that a hyperinnervation of jejunal vessels in the hypertensive rats is present from 2 weeks of age onwards, before significant elevation of blood pressure and medial hypertrophy of jejunal arteries occurs. It is concluded that this hyperinnervation may be causally related to the medial hypertrophy in arteries of hypertensive animals.
TL;DR: In this article, 40Ar39Ar incremental-release ages have been determined for 15 hornblende and 20 biotite concentrates separated from rocks collected across the garnet and kyanite zones of Grenvillian metamorphism in southwestern Labrador.
TL;DR: This chapter discusses the isolation, biochemistry, and function of teleost gonadotropins, which manifest distinctive chromatographic, compositional, immunological, and biological characteristics.
Abstract: Publisher Summary This chapter discusses the isolation, biochemistry, and function of teleost gonadotropins Methods of purification include solvent fractionation, affinity chromatography, gel filtration, and ion-exchange chromatography Reports on purification of a single gonadotropin from various teleost species appear to be in contrast to the discovery of vitellogenic hormone and maturational hormone The difference stems from the use of or lack of affinity chromatography (Con A-Sepharose) as one of the purification procedures and the fact that most workers did not monitor vitellogenic activity during the course of purification The gonadotropins that were isolated, as judged from the spectrum of biological activities, correspond to maturational hormones Maturational gonadotropin levels in plasma do not appear to correlate well with the reproductive processes Substantial evidence has been collected for the existence of two gonadotropins, vitellogenic hormone, and maturational hormone in teleost The two hormones manifest distinctive chromatographic, compositional, immunological, and biological characteristics Antiserum to each of these two hormones produces inhibitory effects on those aspects of fish reproduction, which are consistent with the biological activities of the hormone
TL;DR: In infants in whom atopic eczema subsequently developed, numbers of T8-positive cells were reduced, the T4/T8 ratio was raised, and functional suppressing activity was lower than normal.
TL;DR: Oil exposure had no effect on levels of total plasmatic androgens or estradiol in male and female flounder during gonadal recrudescence, and Aryl hydrocarbon hydroxylase activity increased in liver and kidney of both species.
TL;DR: Level of Facteur thymique serique, mitogenic response of lymphocytes to optimal concentration of phytohemagglutinin and number of antibody producing splenocytes to sheep red blood cells were estimated in animals fed ad libitum, copper deficient and pair-fed control rats.
TL;DR: The steps involved in the conversion of nonlipid precursors into lipid are illustrated and have been the subject of a number of recent reviews.
Abstract: The steps involved in the conversion of nonlipid precursors into lipid are illustrated in Fig. 1 a. These steps may be conveniently divided into four parts:
1.
Generation of cytoplasmic acetyl-CoA.
2.
Conversion of acetyl-CoA to fatty acyl-CoA, predominantly palmitoylCoA.
3.
Incorporation of fatty acyl-CoA into triglyceride.
4.
Generation of NADPH for fatty acid synthesis by fatty acid synthetase.
Lipid synthesis and its regulation have been the subject of a number of recent reviews (Geelen et al.,1980; Freedland and Szepesi, 1971; Numa, 1974; Numa and Yamashita, 1974; Romsos and Leveille, 1974; Volpe and Vagelos, 1976). Readers who desire a more detailed treatment than presented below are advised to consult one or more of these reviews.
TL;DR: This paper presents a meta-anatomy of Lymphedema, a simple but effective treatment for central giant cell granuloma, which has shown promise in patients with weak immune systems.
TL;DR: Palmaria, Membranoptera, and Phycodrys show similar patterns of seasonal changes in epiphyte biomass with a peak in September and a decline in winter and Ptilota, which in the British Isles is considered to be a species of northern distribution, shows an earlier peak biomass and a correspondingly earlier decline in abundance.
TL;DR: Several bacterial isolates from raw milk produced proteases which were heat-resistant, being able to retain partial activity even after heat-treatment at 120°C for 10 min, and tentatively assigned to genus Pseudomonas, and were used in the present investigation.