Utilization of the exotic cladoceran Daphnia lumholtzi by juvenile fishes in an Illinois River floodplain lake

Daphnia lumholtzi comprises a substantial component of the zooplankton community during mid‐ to late‐summer in Lake Chautauqua, a floodplain lake along the Illinois River near Havana, Illinois. In order to quantify the utilization of D. lumholtzi by juvenile fishes, diet analyses were conducted for seven juvenile fish species collected from Lake Chautauqua during the 2001 annual drawdown period. Freshwater drum Aplodinotus grunniens and emerald shiner Notropis atherinoides demonstrated negative selectivity for D. lumholtzi relative to native zooplankton species whereas four species of fish (bluegill Lepomis macrochirus, white bass Morone chrysops, white crappie Pomoxis annularis and black crappie Pomoxis nigromaculatus) consumed substantial amounts of D. lumholtzi. Although selectivity values for D. lumholtzi varied among these fish species, positive selection for D. lumholtzi increased similarly among larger size classes of each fish species, and corresponded with ontogenetic shifts in diet. Mean body length of D. lumholtzi consumed by 20–69 mm L_T juvenile fishes ranged from 0·75 to 0·99 mm with a calculated total length range of 2·0–2·6 mm. Results from this study provide evidence that high abundances of D. lumholtzi in mid‐ to late‐summer provide an additional food source for several juvenile fish species during a time when abundances of large native cladoceran species (i.e. Daphnia) are low, and juvenile fishes are searching for larger prey associated with ontogenetic shifts from zooplankton to macroinvertebrates and fishes. Because zooplankton production is typically lower in rivers than in lakes, survivorship of juvenile fishes produced in floodplain lakes may be higher in riverine systems if they are not reliant on zooplankton as a primary food resource. Therefore, high abundances of D. lumholtzi may benefit juvenile fishes in managed floodplain lakes, such as Lake Chautauqua, by increasing growth and facilitating the transition from zooplanktivory to insectivory or piscivory.     

A light and electron microscopic study of the pre- and postnatal development and secretory differentiation of the pars tuberalis of the rat hypophysis

Summary The development of the pars tuberalis was studied in the rat fetus from 13 days of gestation to 6 weeks after birth. After the closure of Rathke's pouch, the pars tuberalis anlage is clearly distinguishable from the anlagen of the partes intermedia and distalis. It comprises the entire basal portion of the adenohypophysial anlage; the limit between the anlagen of the pars tuberalis and the pars distalis is defined by Atwell's recess, i.e. the pathway taken by the hypophysial vessels coming from the vascular plexus of the median eminence.At 14 days the pars tuberalis cells are characterized by the presence of glycogen which persists in the adult. Their secretory differentiation (elaboration of granules with a diameter of 100–120 nm) is obvious at 15 days of gestation. It therefore, clearly precedes that of the other hypophysial cell types. Its functional differentiation takes place well before its adhesion to the primary vascular plexus of the portal system. Cystic formations appear just before birth in the pars tuberalis, much later than those of the pars distalis.These observations on the development of the pars tuberalis, together with previous observations on the adult PT in various species, showing that the specific glandular cells of the pars tuberalis are cytologically different from all known adenohypophysial cell types, seem to indicate a specific endocrine function of this lobe.     

Selective Staining of Neurosecretory Material in Semithin Epoxy Sections by Gomori's Aldehyde Fuchsin

The epoxy resin was removed from semithin (1 μm) sections by immersing them for 30 sec in sodium methoxide (Mayor et al., J. Biophys. Biochem. Cytol., 9: 909-10, 1961) and then processed as follows: (1) left for 1-3 hr at 60 C in a mixture of formalin, 25 ml; glacial acetic acid, 5 ml; CrO₃, 3 gm; and distilled water, 75 ml: (2) oxidized 10 min in a 1:1:6 v/v mixture of 2.5% KMnO₄, 5% H₂SO₄ and distilled water: (3) bleached in 1% oxalic acid, and (4) stained for 15 min in aldehyde fuchsin, 0.125% in 70% alcohol, or in a 1% aqueous solution of toluidine blue. The neurosecretory material is selectively stained.     

Sur l'existence de cellules de type ≪corticotrope≫ dans la pars intermedia de l'hypophyse du rat

Résumé Nos observations démontrent l'existence de deux types de cellules glandulaires dans la pars intermedia de l'hypophyse du rat: des cellules propres, à M.S.H., dont les grains de sécrétion sont détruits par la fixation osmiée et relativement bien conservés par la fixation au glutaraldéhyde; des cellules à petits grains denses, osmio-résistants, qui s'apparentent morphologiquement aux éléments corticotropes de l'antéhypophyse. L'existence bien connue d'A.C.T.H. ou, plus précisément, d'un facteur A.C.T.H.-like dans le lobe neuro-intermédiaire nous fait considérer comme très vraisemblable la nature corticotrope de ce deuxième type cellulaire de la pars intermedia.

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On the existence of cells of the Corticotrophic type in the intermediate lobe of the rat hypophysisAn electronmicroscopic study

Summary Two types of glandular cells have been shown to occur in the intermediate lobe of the rat hypophysis: 1) M.S.H. producing cells whose secretory granules are destroyed by osmium fixation and relatively well preserved by glutaraldehyde fixation, 2) cells with small dense osmium resistant granules being morphologically similar to the corticotrophic cells of the anterior lobe. The well known occurrence of A.C.T.H. or, more precisely, of an A.C.T.H.-like factor in the neuro-intermediate lobe makes the corticotrophic nature of this second cell type very likely.

Travail dédié à la mémoire de Nicole Granboulan.     

Localisation ultimobranchiale et thyroidienne des cellules C (cellules à calcitonine) chez deux Columbidae: le pigeon et le tourtereau

Résumé Chez les deux Columbidae étudiés, les cellules C sont présentes à la fois dans les corps ultimobranchiaux et dans la thyroïde. Les corps ultimobranchiaux sont constitués de cordons renfermant des cellules glandulaires et des cellules bordantes. Dans certaines zones périphériques de la thyroïde, des cordons ultimobranchiaux typiques sont localisés dans les espaces interfolliculaires et sous-capsulaires. Des cellules C folliculaires basales analogues à celles de la thyroïde du mammifère sont rarement observées.Les caractères morphologiques des cellules C sont identiques quelle que soit leur localisation: ultimobranchiale, thyroidienne extrafolliculaire ou folliculaire basale. Les granules sécrétoires diffèrent légèrement par leur forme chez le pigeon et le tourtereau; leur diamètre moyen est plus variable d'une cellule à l'autre chez le pigeon.Des contacts neuroglandulaires existent au niveau des cordons glandulaires localisés dans les corps ultimobranchiaux et dans la thyroïde. Leur signification reste obscure.

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Ultimobranchial and thyroidian localization of C cells in two Columbidae: the pigeon and the turtle-doveAn electron microscopic study

Summary In the two Columbidae we studied, C cells are present both in the ultimobranchial bodies and in the thyroid. Ultimobranchial bodies consist of cords which are made up of glandular cells and limiting cells. In certain peripheral regions of the thyroid, typical ultimobranchial cords are situated in the interiollicular and infracapsular spaces. Basal follicular C cells similar to those of the mammalian thyroid are rarely observed.The morphological characteristics of the C cells are identical whatever their situation may be: ultimobranchial or thyroidian, be it extrafollicular or basal follicular. The secretory granules differ slightly by their shape in the pigeon and the turtle-dove; their medium diameter varies more from one cell to another in the pigeon.Neuroglandular contacts exist at the level of the glandular cords situated in the ultimobranchial body and in the thyroid. Their signification is not clearly understood.

     

Expression of the α-subunit of glycoprotein hormones in the pars tuberalis-specific glandular cells in rat,mouse and guinea-pig

The nature of the hormone(s) secreted by the pars tuberalis (PT) is still unknown. This pituitary lobe is mainly formed by specific glandular cells that differ in their ultrastructural features from the other adenohypophysial cell types. Data from the literature indicate the presence of thyroid-stimulating hormone immunoreactivity in the PT-specific cells of the rat and the Djungarian hamster but not of other species, including the mouse and guinea-pig. The PT also encloses variable numbers of pars distalis cells, essentially gonadotrophs that are mainly dispersed in its caudal area. We studied the expression of the glycoprotein hormone -subunit in the PT of the rat, mouse and guinea-pig by in situ hybridization and immunocytochemistry. In situ hybridization, using an oligonucleotide probe complementary to rat cDNA sequence 196–237 revealed the expression of the -subunit gene throughout the PT of the rat and the mouse; in the guinea-pig, the probe labelled no pituitary cells. Light-and electron-microscopic immunocytochemistry demonstrated -subunit immunoreactivity in the secretory granules of the PT-specific cells in the three species examined. These cells did not react with a specific antibody against the -subunit of luteinizing hormone, an antibody that labelled scattered gonadotrops. The present data suggest that hormone(s) produced by the PT-specific glandular cells are, at least partly, related to glycoprotein hormones.     

Sur la signification des vacuoles intraneuronales du noyau supra-optique de la souris en surcharge osmotique

Résumé La fixation osmiée et l'étude ultrastructurale permettent de préciser que les grosses vacuoles intraneuronales des cellules du N.S.O. de la Souris, qui apparaissent après une surcharge osmotique prolongée, ont un contenu lipidique.

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Summary Fixation with Palade's fluid and ultrastructural study reveal that after prolonged ingestion of hypertonic saline, the vacuoles in the Cells of the supraoptic nuclei of the Mouse contain lipid droplets.

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Dédié amicalement à Madame le Professeur Berta Scharrer, avec nos très respectueux hommages.

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Attachée de Recherches au C.N.R.S.

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Collaboratrice technique. Travail réalisé dans le cadre de la R.C.P. No 39 du C.N.R.S.     

Morphologie fine d'une differenciation glandulaire du recessus infundibulaire chez le rat

Resumé Dans le tiers postérieur du recessus infundibulaire du Rat existe une zone périventriculaire colorable par le P.A.S. dont l'étude ultrastructurale révèle les caractères glandulaires L'intervention possible de cette glande infundibulaire périventriculaire dans la régulation de certaines fonctions antéhypophysaires est discutée.

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Summary An alcohol-choroform insoluble periodic acid — Schiff reactive substance associated with the ependymal lining of the infundibular recess was demonstrated in the hypothalamus of the white rat.Electronmicroscopic studies revealed the glandular character of this zone. The possible role of this infundibular periventricular gland in the regulation of anterior pituitary functions is discussed.

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Dédié amicalement à M. le Professeur Dr. W. Bargmann pour son 60^ème anniversaire.

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Special fellow N.I.N.D.B.; U.S.P.H.S., bénéficiaire d'une subvention no B 0 3468 — U.S.P.H.S.

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Travail en partie réalisé dans le cadre de la R. C. P. 39 du C. N. R. S. Avec la collaboration technique de M^elles M. J. Klein, S. Veidt et G. Haller.