Differential Protein Synthesis During the Life Cycle of the Protozoan Parasite Trypanosoma brucei1

Two-dimensional polyacrylamide gel electrophoresis has been used to analyze changes in protein content and protein synthesis in three stages of the life cycle of the protozoan parasite Trypanosoma brucei. The stages examined were slender and stumpy mammalian bloodstream forms and procyclic forms, which are analogous to the tsetse fly midgut stage. Two-dimensional gels of ³⁵S-methionine-labeled proteins were examined by autoradiography to analyze newly synthesized protein, and gels were stained with ammoniacal silver to analyze proteins present. Several stage-specific molecules were noted. The most obvious was the variant surface glycoprotein, which was only present in bloodstream forms. Some other proteins were also bloodstream form specific; they had molecular weights of 120,000 and 38,000. Proteins of 52,000, 46,000, 25–30,000, and 16,000 daltons were present both in stumpy forms and procyclics but not in slender-form trypanosomes. Several proteins (molecular weights of 50–70,000, 43,000, 40,000, 26–24,000, 20–25,000, and 15,000) were present only in one of the three stages. One protein, a molecule of about 18,000 daltons present in both slender and stumpy parasites, did not appear to be synthesized in the stumpy stage. In vitro translation products of mRNA purified from the three stages were also examined. The abundance of mRNA encoding a protein of about 40,000 daltons appeared to be greater in slender than in stumpy parasites although the stumpy forms contained more of the protein and synthesized it at a higher rate.     

Symposium on “Protozoan Ecology”: The Role of Protozoa in Litters and Soils1

Soil is the focus of organic matter turnover in terrestrial ecosystems and is an interstitial mosaic of microsites composed of particle aggregates and pore spaces, where transformation, decomposition, mineralization, and humification of organic matter takes place. Microorganisms and animals are scattered discontinuously in these microsites. Microarthropods and larger fauna increase the rate and amount of mineralization by comminution of organic matter and by redistribution of microsites through movements of earthworms and large arthropods; however, mineralization and return of nutrients to plants occurs in the community of bacteria, fungi, protozoa, and nematodes living in the water films covering aggregates and filling pore spaces. Protozoa, especially small amoebae, are important bacterial grazers because they can enter tiny spaces unavailable to nematodes. The latter graze bacteria, fungi, and protozoa. Protozoan and nematode predation increase the amounts of soluble nutrients and decrease the competitive abilities of bacteria, thus making these nutrients more available to plants. Protozoa enhance nutrient recycling out of proportion to their biomass.     

GROWTH, MORTALITY, AND FEEDING RATES OF THE SNAIL HELIX ASPERSA AT DIFFERENT POPULATION DENSITIES IN THE LABORATORY, AND THE DEPRESSION OF ACTIVITY OF HELICID SNAILS BY OTHER INDIVIDUALS, OR THEIR MUCUS

When reared at high densities, young Helix aspersa show lessshell growth, even if waste products are removed. They alsofeed less, and show increased mortality. It is suggested thatthese effects are linked to reduced activity. Juveniles showreduced activity in the presence of adults or their mucus. Mucusof adult Cepaca nemoralis also depresses the activity of bothadult and young Helix and Cepaea. ^* Present Address: Unit Zoologi, Universiti Kebangsaan Malaysia,Jalan Pantai Baru, Kuala Lumpur, West Malaysia. (Received 12 May 1981;     

Carbon Dioxide as the Initial Stimulus for Excystation of Eimeria tenella Oocysts*

SYNOPSIS. The stimulus necessary to initiate in vitro excystation of the chicken coccidium Eimeria tenella was provided by exposure of intact sporulated oocysts to an atmosphere of carbon dioxide. This stimulus produced a thinning and indentation at the micropylar region and oocysts became permeable to trypsin and bile. Sporozoites became active and began to escape from sporocysts into the oocyst cavity and then to the outside thru the altered micropyle after incubation in the enzyme-bile mixture. Activation of sporozoites when CO₂-pretreated oocysts were incubated in trypsin and bile, was used as the criterion to determine the number of oocysts responding to the initial stimulus. Thus, activation of sporozoites within intact oocysts was an indirect measurement of the number of oocysts stimulated during CO₂-pretreatment. Approximately 90% of the oocysts contained active sporozoites after 18 hr of pretreatment with carbon dioxide and 8 hr incubation in trypsin and bile at 38 or 41 C, respectively. Pretreatment of oocysts with air, N₂, O₂, or He resulted in 8% or less activation during incubation in trypsin and bile. Approximately 83% of the oocysts responded to the stimulus during 8 hr CO₂-pretreatment at 41 C, whereas at 38 C, 16 hr of pretreatment were required for a similar response. The stimulus did not elicit a response from oocysts held at 23 C during the pretreatment gasphase. No significant difference occurred in number of oocysts containing active sporozoites after sufficient CO₂-pretreatment for maximum stimulation of oocysts and incubation in trypsin and bile at 38 or 41 C.     

Evidence of Tyrosine Kinase Activity in the Protozoan Parasite Trypanosoma brucei

ABSTRACT. Phosphorylation of proteins at tyrosine is an important mechanism for regulating cell growth and proliferation in metazoan organisms. In this report, we have demonstrated that Trypanosoma brucei , a protozoan parasite, possesses a tyrosine kinase that plays a role in regulation of proliferation of this protozoan. Genistein, a tyrosine kinase inhibitor, prevented multiplication of the parasite. An in vitro kinase assay demonstrated the presence of a kinase capable of phosphorylating an exogenous substrate at tyrosine, and genistein was able to reduce trypanosome-mediated phosphorylation of this substrate. An alkali digestion of ³²P-labeled trypanosome proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated several proteins phosphorylated at tyrosine. These results indicate that T. brucei has a tyrosine kinase that is involved in proliferation or growth regulation of the parasite and provide further evidence for the possibility of growth factor regulation and signal transduction in trypanosomes.     

Competition Between Insectivorous Lizards and Birds in Central Panama

The following evidence suggests that birds and lizards competefor their arthropod prey on islands in Lake Gatun, Panama: (1)there is extensive overlap between the diets of a representativebird and lizard, (2) at least one insectivorous lizard, Anolislimifrons, appears to be food-limited, (3) birds appear to havea major impact on arthropod abundances, (4) avian abundanceis negatively correlated with the physiological condition and,thus, with the fecundity of female A. limifrons, (5) bird andlizard population densities are negatively correlated. LakeGatun was formed in 1914. In the intervening years, a greatmany bird species have been lost from the smaller islands, butvery few lizard populations have gone extinct. Ninety-six percentof the between-site variation in avian abundances is accountedfor by the number of bird species present at a site. Sites withdepauperate avifaunas are characterized by low avian abundancesbecause the species present do not experience ecological release,and resources which are utilized by birds on species-rich sitesare not exploited by birds on species-poor sites. Thus, avianabundances are controlled by factors extrinsic to the bird-lizardinteraction, and lizards opportunistically increase their abundancesat sites with low avian abundances.     

Generic revision of the New World tribe Hoplophorionini (Hemiptera: Membracidae: Membracinae)

Abstract. The tribe Hoplophorionini Goding, 1926, includes 105 species of treehoppers in 10 genera. All are apparently subsocial and lack mutualism with honeydew-collecting hymenopterans. In many species, parental investment in offspring is unique because of a specialized kicking defence (described herein) and construction of extra-ovipositional punctures in the host tissue through which nymphs feed. The tribe occurs from Canada to Chile, with most generic diversity in Central America but most species diversity near the equator. Three genera, Stalotypa Metcalf, Ramosella, new genus and Stirpis, new genus, are endemic to the Greater Antilles but do not constitute a monophyletic group; the first two genera appear most closely related to Turrialbia, new genus, from Costa Rica. Host plant specializations and other biological attributes are summarized for genera and species. A phylogenetic analysis of 23 hoplophorionine species produced 9 minimal-length cladograms that were similar in many respects. Potnia Stål appears to have retained the greatest number of ancestral features. Aposematic teneral coloration of adults probably evolved once. The modification of the ancestral kicking behaviour by the first hoplophorionines appears to have released them from a constraint on pronotal form. Diagnoses are given for adults of all genera and, when possible, for immatures. A key is presented for the 10 genera; three are described as New Genera based on the cladistic analysis: Ramosella, Stirpis, and Turrialbia. Three New Species are described: Ramosella thalli, Stirpis jamaicensis, and Turrialbia felina. The genus Micropepla Sakakibara is considered a junior synonym of Ochropepla Stal, New Generic Synonymy. Umbonia terribilis Walker is moved from synonymy under Alchisme virescens (Fairmaire) to a New Synonymy under Umbonia reducta Walker. The subspecies Platycotis vittata vittata (Fabricius), P. vittata lineata (Fairmaire), and P. vittata quadrivittata (Say) are returned to synonymy with Platycotis vittata (Fabricius), Reinstated Specific Synonymies. Three species are Reinstated as valid: Alchisme obscura (Walker) and A. veruta (Fowler), both from synonymy under A. turrita (Germar); and Umbonia reducta Walker, from synonymy under U. crassicomis (Amyot & Serville). Five New Combinations are proposed: Alchisme antigua (Funkhouser), referred from Umbonia; A. sordida (Germar), referred from Platycotis; A. sagittata (Germar), elevated from subspecific rank under Platycotis vittata; Ochropepla mourei (Sakakibara), referred from Micropepla; and Ramosella dominicensis (Ramos), referred from Platycotis. Platycotis nigrorufa (Walker), P. cornuta Plummer, P. salvini (Fowler), and P. fuscata (Fowler) were previously unplaced to subgenus; the first is referred to Platycotis (Lophopelta Stal) and the others to Platycotis (Platycotis Stål). Microschaema nigrostrigata Buckton is moved from synonymy under Alchisme recurva (Stål) to a New Synonymy under Ennya dorsalis (Fairmaire) of the tribe Polyglyptini, subfamily Smiliinae. A checklist with critical synonymies and indexes to hoplophorionine taxa and host plant associations are provided. Lectotypes are designated for Centrotus vittatus Fabricius, Hoplophora lineata Fairmaire, Membracis venosa Germar, Potnia affinis Buckton, and Triquetra obtusa Fowler.     

Climatic limitation of the southern distribution of the common blossom bat Syconycteris australis in New South Wales

Abstract This study investigates the importance of climate as a factor influencing the southern distributional limit of the common blossom bat (Syconycteris australis). Using the climatic predictive model BIOCLIM and 73 locality records, 5. australis was predicted to have a coastal distribution in eastern Australia, where winter temperatures are relatively warm and moist conditions prevail throughout the year. The actual southern limit of S. australis, determined by mist-netting suitable habitats, was found to be at Booti-Booti (32°19'S 152°3l'E) on the mid-north coast of New South Wales. BIOCLIM predicted the southerly limit of 5. australis to be 150–200km further south of their actual limit. Booti-Booti was occupied at relatively low levels of abundance year round, while the abundance of S. australis at a site 50 km to the north was much greater, fluctuating with changes in Banksia flower numbers. Seasonal range extensions beyond Booti-Booti were not detected, despite the availability of apparently suitable habitat at Myall Lakes only 20–35 km further south. Metabolic costs of S. australis at Booti-Booti were estimated to exceed basal metabolic rate (BMR) by 4.5 times, well above the physiologically predicted limit of 2.5 times BMR. These results, together with the lack of range extensions and the close correspondence of BIOCLIM'S predicted southern limit of S. australis with their actual limit, suggest that the bat's southern distribution is limited by cold, wet winters and dry summers.     

Genetic diversity in the Eurasian otter, Lutra lutra, in Scotland. Evidence from microsatellite polymorphism

The relationship between microsatellite diversity and geographical fragmentation and isolation was studied in Scottish populations of the Eurasian otter, Lutra lutra. The geographic range of the study encompassed isolated archipelagos, islands adjacent to the Scottish mainland and both fragmented and continuous mainland populations. Tissue samples of 496 individuals from across Scotland were assayed for polymorphism at ten microsatellites. The isolation of populations on Shetland, and to a lesser degree on Orkney, was associated with reduced levels of microsatellite diversity. Most of the remaining island and fragmented mainland populations contained levels of microsatellite diversity similar to the high levels observed in die continuous mainland populations. Unexpectedly, both island and continuous mainland populations showed similar rates of departures from mutation-drift equilibrium. Such departures could have arisen from a variety of local demographic processes besides population bottlenecks. Gene flow appeared to be a major factor maintaining microsatellite diversity in all of these populations except the one on Shedand.     

Acriflavin Induction of Dyskinetoplasy in Leptomonas karyophilus*

SYNOPSIS. Acriflavin concentrations of 0.025 μg/ml and higher were Lo Leptomonas karyophilus in NNN medium to which no ribohad been added, and did not bring about the production of dys plastic forms. Upon addition of 0.4 μg/ml of riboflavin, contions of acriflavin up to 10.0 μg/ml allowed growth and rein the production of up to 86% dyskinetoplastic forms. Under conditions, increasing concentrations of acriflavin decreased the growth rate while increasing the rate of production of dyskinetoplastic forms. The number of dyskinetoplastic forms increased with time while the number of kinetoplastic forms remained approximately constant or decreased due to death. At a concentration of 1.0 μg/ml acriflavin and 0.4 μg/ml riboflavin, growth was primarily due to the production of dyskinetoplastic forms.