Zur ?kologie jamaikanischer Kolibriarten

Zusammenfassung Auf Jamaika brüten 4 Kolibriarten, wobei die beiden congenerischen ArtenTrochilus polytmus undTrochilus scitulus allopatrisch leben. Jede Art weist jeweils eine eindeutige Präferenz bezüglich Meereshöhe und Vegetationshöhe auf.T. polytmus undT. scitulus stimmen in diesen beiden Parametern ihrer ökologischen Nische überein. Da sich beide Arten auch gewichtsmäßig entsprechen, nehmen sie in der nektarivoren Nahrungsgemeinschaft homologe Planstellen ein.Bei den auf Jamaika untersuchten ornithophilen Blütenpflanzen wurden Zuckerkonzentrationen von 15–22% gemessen, bei einigen auch von Insekten frequentierten Pflanzenarten solche bis 44%. Der Verlauf der Nektarsekretionsrate pro Stunde in Abhängigkeit von der Tageszeit entsprach bei Pflanzen, die ausschließlich von Kolibris bestäubt wurden, dem täglichen Aktivitätsrhythmus der Kolibris. Blütenpflanzen, die sowohl von Kolibris als auch von Insekten besucht wurden, zeigten hingegen eine weitgehend konstante stündliche Nektarproduktionsrate am Tage.Artspezifisch unterschiedliche Blütenpflanzen wurden als Nahrungsquelle ausgewählt. Diese nahrungsökologische Separation ist darauf zurückzuführen, daß die Kolibriarten aufgrund ihrer Gewichtsunterschiede jeweils nur bei bestimmten ornithophilen Blütenpflanzenarten einen Nettoenergiegewinn erzielen können (z. B. Nettoenergiegewinn bei der Nahrungsaufnahme im Schwirrflug aus einer Blüte vonAsclepias currassavica vonMellisuga minima: 0.308 cal,Anthracothorax mango: — 0.661 cal).

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On the ecology of Jamaican hummingbirds

Summary On Jamaica 4 hummingbird species are resident. The congeneric speciesTrochilus polytmus andTrochilus scitulus are geographically separated (allospecies). Relative abundance depending on altitude and on height of vegetation (proportional occurence of each species in mist-netted samples s. Fig. 1,2) indicate a species-specific preference in both parameters.T. polytmus andT. scitulus correspond in both ecological parameters as well as in morphological characteristics. It is argued that both species occupy homologous niches in their range of distribution.Nectar of all studied ornithophilic plant species varied in sugar concentration from 15% to 22%. Flowering plants visited by insects and hummingbirds reached a sugar concentration in nectar of 44% (s. Tab. 1). The rate of daily nectar production per hour in plant species solely visited by hummingbirds varied according to the daily rhythm of activity of the birds (s. Fig. 3 B). Plant species visited by hummingbirds and insects showed little daily variation in nectar production per hour (s. Fig. 3 A).To gain energy benefits Jamaican hummingbirds selected flowering plants according to their weight-specific energy requirements (s. Tab. 3, 4).

     

The α-keto acids of branched-chain amino acids: Simplified derivatization for physiological samples and complete separation as quinoxalinols by packed column gas chromatography

By use of a relatively new mixed stationary phase, complete separation of the branched-chain α-keto acids as O-trimethylsilyl-quinoxalinol derivatives is achieved within 10 min by packed column gas chromatography. Precise quantification of less than 5 nmol of α-keto acids in biological samples is possible. In small aqueous samples the α-keto acids are directly derivatized without prior purification. Plasma need only be deproteinized by perchlorate and neutralized before derivatization. Average relative precision for determination of the three main branched-chain α-keto acids is ± 5.8%.     

Potentiation of the in vitro cytotoxic response to syngeneic lymphoma cells by soluble products of tuberculin-sensitive lymphoid cells stimulated with PPD

Spleen cells from rats immunized with the syngeneic (C58NT)D Gross virus induced lymphoma have previously been shown to differentiate into cytotoxic effector cells following restimulation with tumor cells in vitro. Previous work has also demonstrated that the addition of PPD-primed syngeneic spleen cells and PPD to cultures of (C58NT)D-primed spleen cells will potentiate the in vitro cytotoxic response to tumor antigens. In the studies presented here, the potentiating effect was found to be mediated by a soluble factor(s) released by nonadherent cells from BCG-primed rats. The release of this immunopotentiating factor(IPF) required the presence of PPD and varied with the concentration of PPD added. IPF was produced by BCG-primed spleen, lymph node, and thymus cells. Maximal production of IPF in PPD-stimulated cultures was obtained after 6–12 hr of incubation. Supernatants obtained after 30 hr of incubation lacked apparent IPF activity when tested initially, but activity was recovered after mild heat treatment. Recovery of IPF activity after heat exposure is best explained by the presence of a heat-labile inhibitor. IPF itself is stable to heat treatment to 56 °C for 40 min. IPF was also shown to be capable of enhancing immune responses to histocompatibility antigens in vitro.     

Intramolecular cyclization of pentose and hexose dithioacetals

The intramolecular cyclization of O-tosyl derivatives of dithioacetals of d-ribose, d-arabinose, and d-glucose was investigated. p-Toluenesulfonylation of d-glucose diethyl dithioacetal gave 3,6-anhydro-d-glucose diethyl dithioacetal. Variously substituted 5-O-tosyl-d-glucose dibenzyl dithioacetals gave derivatives of either 2,5-anhydro-l-idose dibenzyl dithioacetal, benzyl 1,5-dithio-l-idopyranoside, or l-idose dibenzyl dithioacetal. Likewise, 4-O-tosyl-d-glucose dibenzyl dithioacetal derivatives gave benzyl 1,4-dithio-d-galactofuranoside derivatives.     

Inconsistency in the species concept for yeasts due to mutations during vegetative growth

Summary The generic classification of yeasts is based mainly on morphological characteristics whereas the definition of a species depends predominantly on physiological properties such as the utilization of carbon and nitrogen sources. Classification procedures are routinely done on agar slants, and in negative tests single colonies are often noticed. These colonies are spontaneous mutations and can be idetified as such after transfer onto adequate media and appropriate genetic tests. It is sometimes possible after selection steps to obtain a completely different species. This means that in many cases the classification depends only on single gene differences, where the differences in DNA base homology is almost certainly less than 1%. Since it is rather difficult to justify a new species on the basis of a single biochemical gene mutation, it is necessary in practice to perform at regular intervals an extended series of physiological tests in order to avoid confusion in nomenclature.     

Localization of corticotropin- and endorphin-related peptides in the intermediate lobe of the rat pituitary

Summary The question is examined whether -melanocyte stimulating hormone (-MSH), adrenocorticotropic hormone (ACTH), met-enkephalin and -endorphin are detectable by enzyme immunocytochemistry in the cells of the intermediate lobe (PI) of the rat pituitary. By applying antibodies against MSH, ACTH and -endorphin on light microscopic sections, intense immunostaining was found in all PI-cells. At the ultrastructural level, after treatment of consecutive serial sections with these three antibodies the immunoreactivity was localized in the same secretory granules. No specific metenkephalin immunoreactivity could be detected in the cells of the intermediate lobe.Supported by Deutsche Forschungsgemeinschaft SFB 87/B2     

Study of a possible structural relationship between thymopoietin and the facteur thymique serique

Background peptide chemistry, and the known 49-amino acid sequence of thymopoietin and the known 9-amino acid sequence of the facteur thymique serique (FTS) allowed the concept that Arg⁴⁹ of thymopoietin might be linked to Gln¹ of FTS in a new 58-amino acid peptide in tissue. Cleavage between Arg⁴⁹ and Gln⁵⁰ adjacent to the unique Lys⁴⁸-Arg⁴⁹ moiety could liberate thymopoietin and the [H-Gln¹]-FTS which could cyclize to FTS by the known reaction. In support of, rather than negating, this concept, synthetic FTS and the new dodecapeptide consisting of Val-Lys-Arg linked to the N-terminal of [H-Gln¹]-FTS showed comparable immune stimulating activity, $\text{in vivo}$; both peptides appeared more active than synthetic thymopoietin II.     

The phenoloxidases of the ascomycete Podospora anserina. Structural differences between laccases of high and low molecular weight.

In order to investigate the extent of the relationship between the three copper-containing glycoproteins, laccases I, II and III (Mr70000, 80000 and 390000 respectively) of Podospora anserina, the following experiments were carried out on laccases II and III: (a) determination of amino acid composition; (b) determination of N-terminal and C-terminal amino acid; (c) determination of sugar composition; (d) dissociation studies on native and denatured laccases and also after removal of copper from the enzymes; (e) digestion of the carbohydrate moieties with the aid of glycosylhydrolases. A comparison between the results of these experiments and data previously obtained with laccase I allows the following conclusions to be drawn. 1. Laccases II and III are not identical. 2. Neither of these low molecular weight laccases are as complete molecules subunits of the oligomeric laccase I. 3. The possibility of partial identity of amino acid sequences of laccases I and III can not be excluded. 4. Laccase II possibly consists of subunits of Mr37000 whereas laccase III does not. 5. Digestion of 50% of the carbohydrate content leads to complete loss of serological specificity (serological reaction and cross reaction). This finding is discussed with regard to the possible role of the carbohydrate moiety as antigenic determinants and thus as the reason for the immunological relationship. As a consequence, at least three independent structural genes for laccases must be assumed.