Primary productivity studies during early years of West Point Reservoir, Alabama-Georgia

SUMMARY. 1. Phytoplankton density (organisms ml^?1), standing crop (chlorophyll a mg m^?2) and primary productivity (mg C m^?2 d^?1) were measured during years 2 (1976) to 5 (1979) after impoundment on West Point Lake. 2. West Point waters had low alkalinity (<0.4 meq 1^–1) and low conductivity (<75 μs cm^?1 at 20°C) but N and P concentrations typically exceeded those considered apt to cause nuisance blooms of algae. Abiogenic turbidity was normally higher in the upstream areas of the reservoir than in the downstream areas and was several times higher in winter-spring than in summer-autumn due to increased rains and runoff. 3. Primary productivity varied greatly both temporally and spatially. A mean value of 684 mg C m^?2 d^?1 was well within the mesotrophic range and did not approach the highly eutrophic state predicted. Productivity increased from a low of 550 mg C m^?2 d^?1 in 1976 to high of 763 mg Cm^?2d^?1 in 1979. 4. Observed variation in both chlorophyll a and primary productivity was more predictable in the cool (December-March) than in the warm (June-September) season and with plant nutrient data than without it. With plant nutrient data in the cool season 84% and 86% of the variation (R²) in chlorophyll a and productivity, respectively, were accounted for by the regression equations. During the warm season, with plant nutrient data, regression equations accounted for 44% and 68% of the variation in chlorophyll a and productivity, respectively. Higher R² values in cool seasons resulted from the overriding influence of abiogenic turbidity on phytoplankton communities.     

Enzymes of Carbohydrate Metabolism in Leishmania donovani Amastigotes1

A method for the isolation of Leishmania donovani amastigotes from infected hamster spleen and liver tissues is described. Over 85% of the isolated amastigotes were viable as judged by acridine orange-ethidium bromide staining and in vitro transformation to the promastigote form. A comprehensive survey of the enzymes of carbohydrate metabolism in L. donovani amastigotes and promastigotes was conducted. Amastigotes and promastigotes possess all of the enzymes of the Embden-Meyerhof pathway, hexose monophosphate shunt, and tricarboxylic acid cycle. Cell-free extracts of both forms show pyruvate dehydrogenase activity which permits entry of pyruvate into the tricarboxylic acid cycle. Both forms demonstrate an active glutamate dehydrogenase, thus linking amino acid metabolism with carbohydrate metabolism. Pyruvate carboxylase, the enzyme responsible for replenishment of C₄ acids by heterotrophic CO₂ fixation into pyruvate, was also demonstrable in the tissue and insect forms. In general, activities of promastigote enzymes are higher than the amastigote enzymes. Differences between the vertebrate (amastigote) and invertebrate (promastigote) forms in their potential to utilize carbohydrates as substrates would appear to be quantitative rather than qualitative.     

In Vitro Excystation of Caryospora simplex (Apicomplexa: Eimeriorina)1

In vitro excystation of sporozoites of the heteroxenous coccidian Caryospora simplex Léger, 1904 (Apicomplexa: Eimeriorina) is described. Sporocysts freed mechanically from oocysts released a maximum of 51% of their sporozoites within 45 min at 25°C and a maximum of 74% within 20 min at 37°C when incubated in a 0.25% (w/v) trypsin–0.75% (w/v) sodium taurocholate (bile salt) excystation solution. At emergence from sporocysts, sporozoites were weakly motile then became highly active after about 2 min in excystation solution. Sporozoites within sporocysts exposed to bile salt only became highly motile within 25 min at 25°C and within 15 min at 37°C but did not excyst. When exposed only to trypsin at the above temperatures, the Stieda body dissolved; the substieda body remained intact, and the sporozoites exhibited only limited motility within sporocysts; only a few excysted. Intact, sporulated oocysts incubated at 25° or 37°C in 0.02 M cysteine-HC1 and a 50% CO₂ atmosphere for 18 h had no morphologic changes in the oocyst wall. Further incubation of these intact oocysts in excystation solution for 30 min at 37°C caused neither motility of sporozoites within sporocysts nor excystation. Grinding oocysts for 30 sec in a motor-driven, teflon-coated tissue grinder caused motility of some sporozoites within sporocysts but did not result in excystation.     

Aggression and Mating Success in Three Species of Drosophila1

Three closely related species of Drosophila: D. virilis, D. americana, and D. novamexicana, are known to differ in levels of male-male aggression. Through direct observation in the laboratory, we attempted to determine and characterize the relationships between intrasexual aggression and mating success in males of each of these species. Our results indicated that the most important determinant of male mating success was not the amount of aggression performed by a male, but rather the amount of aggression directed towards him.     

Anatomical dissemination of circumsporozoite protein in wild Afrotropical Anopheles affects malaria sporozoite rate determination by ELISA

The head, thorax, wings, legs and abdomen of 320 wild-caught Anopheles gambiae Giles sensu lato and 115 An.funestus Giles were tested by an enzyme-linked immunosorbent assay (ELISA) for Plasmodium falciparum Welch to determine how anatomical dissemination of circumsporozoite (CS) protein could affect the estimation of malaria sporozoite rates by ELISA. Of fifty-three Anopheles with CS protein detected in any body part, positive reactions were observed for 58.5% of heads, 67.0% of thoraces, 39.6% of wings, 52.8% of legs and 60.4% of abdomens. Mean absorbance values (range 0-2.00) were highest in thorax samples (1.17), followed by heads (0.80), abdomens (0.67), wings (0.48) and legs (0.46). Circumsporozoite protein was present in the wings or legs, but not in the head or thorax, in 11.3% (6/53) of the infected Anopheles. The ELISA infection rate of 12.8% (41/320) for An.gambiae would have increased to 14.7% (47/320) by inclusion of six mosquitoes with CS protein in wings or legs alone. The slight overestimation of the proportion of infective mosquitoes due to disseminated CS protein would have little effect on estimates of relative infection rates by ELISA for field-collected Anopheles, with abdomens removed prior to testing. However, the widespread dissemination of CS protein indicates that sporozoite load estimates by ELISA, for mosquitoes without abdomens, may not provide adequate measurements of the numbers of sporozoites in the salivary glands. Operationally, careful processing of mosquito samples for the determination of infectivity rates by ELISA is necessary to prevent the mixing of wings or legs among samples representing individual mosquitoes.     

Is foraging in the desert ant,Messor pergandei (Hymenoptera: Formiceidae), limited by water?

Abstract.

• 1 The seed-harvesting ant Messor (Veromessor) prrgandei (Mayr) is a common inhabitant of southwestern deserts of the U.S.A. Foragers vary in size from less than 1 mg to more than 10 mg in body mass and may travel over 80 m on a single foraging trip. Their small size, long foraging range, and hot, arid habitat suggest that water stress may limit foraging activity. We examined intercolony and interindividual variation in water loss of M.pergandei foragers under several different situations in the field.
• 2 Colonies differed significantly in minimum critical water content (W_c) of individual foragers (water content below which foragers are incapable of normal locomotion). In one colony small workers had disproportionately higher W_c than larger workers; in the other colony W_c was isometric with body size.
• 3 Groups of workers confined in the field approached W_c only after normal foraging stopped and substrate temperatures exceeded 45°C, while water content of individual foragers did not approach the W_c during normal foraging periods. Moreover, seed load and distance travelled did not negatively affect forager water content, as measured on return to the nest: indeed, our results suggest that forager hydration level may influence load selection and/or foraging distance. We conclude that, under normal circumstances, foraging in M.pergandei is not water-limited.

     

Immunocytochemical Localization of Wheat Storage Proteins in Endosperm Cells 30 Days After Anthesis

Antisera against seven different wheat (Triticum aestivum L.)storage protein subfractions were characterized using (1) ELISAwith gliadins and low- and high-molecular weight glutenin subunitsand (2) electrophoresis (SDS-PAGE and acidic buffer PAGE) andimmunoblotting. The specificities of these antisera (polyclonalantibodies) and 13 monoclonal antibodies covered various patternsof reactivity with alpha-, beta-, gamma- and omega-gliadinsand low- and high-molecular weight glutenins. The antisera andantibodies were applied to ultrathin sections of wheat endospermtissue, from kernels fixed 30 d after anthesis, and were detectedby secondary antibodies tagged with either 5 or 15 nm gold particlesusing transmission electron microscopy. Labelling was denserwhen the small gold particles were used but irrespective ofgold particle size, labelling of polyclonal antisera predominatedwhen the endosperm cells were subjected to both mono- and polyclonalantibodies. Each of the antisera and monoclonal antibodies thatlabelled the protein bodies, labelled them more or less uniformly.This indicates that only one kind of protein body, containingall gliadin and glutenin subfractions, exists during this stageof grain development. Electron-dense globular inclusions foundin many protein bodies were not labelled. Label was also foundon protein-like material present in the lumen of the rough endoplasmicreticulum and on vesicles of the Golgi apparatus. Thus concentrationof storage proteins takes place both at the site of synthesis,the lumen of the rough endoplasmic reticulum, and at the siteof processing and transport, the vesicles of the Golgi apparatus.Fusions between these proteinaceous materials give rise to largerprotein bodies and ultimately to the protein matrix. Key words: Wheat, immunocytochemistry, protein bodies, rough endoplasmic reticulum, Golgi apparatus     

In Vitro Production of Lysine from 2,2'-Diaminopimelic Acid by Rumen Protozoa

Rumen protozoa can produce lysine from free 2,2'-diaminopimelic acid (DAP). However, the quantitative importance of this transformation has been disputed; lysine contents of protozoal incubation supernatants reported by Onodera & Kandatsu [12] and Masson & Ling [9] show a 26-fold difference. The in vitro experimental methods of both groups were compared to determine the causes of this difference. Lysine production was proportional to DAP concentration. Results with rumen protozoa from sheep or goats were similar. The incubation medium and deproteinizing procedure of the Welsh group gave a two-fold increase in lysine production compared with Japanese protocols. Omissions of rice starch from protozoal incubations slightly increased lysine production, whereas omissions of antibacterial agents resulted in varying, yet relatively small changes. The greatest cause of the difference was the number of rumen protozoa incubated. When this factor was taken into account, the difference in the maximum rates of lysine production between the Welsh and Japanese groups was only three-fold, namely 4.5 versus 15.0 nmol lysine/10⁵ protozoa/h. Adding other amino acids to the incubations suggested that DAP uptake by rumen protozoa may occur via transport system ASC. The importance of DAP metabolism by protozoa as a source of lysine for ruminant host animals is discussed.     

Temperature-induced Changes in the Synthesis of Unsaturated Fatty Acids by Acanthamoeba castellanii

ABSTRACT. Major fatty acid components of Acanthamoeba castellanii lipids extracted after growth at 30°C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15°C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30°C to 15°C, increased lipid unsaturation occurred over a period of 24 h; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15°C to 30°C gave negligible alterations in fatty acid composition over a similar period. At 15°C organisms rapidly use [1-¹⁴C] acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30°C indicate only de novo synthesis and Δ9-desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1-¹⁴C] oleate at 30°C was not accompanied by metabolic conversion over two hours, whereas at 15°C n-6 desaturation to linoleate was observed. Temperature shift of organisms from 15°C to 30°C in the presence of [1-¹⁴C] acetate revealed that over half of the fatty acids in newly-synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 h. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n-6 desaturation in the low temperature adaptation of Acanthamoeba castellanii .