Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion

We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.     

Microhabitat segregation and cannibalism in an endangered freshwater isopod, Thermosphaeroma thermophilum

Intraspecific microhabitat segregation is expected to arise when there are age- or sex-specific differences in predation risk. The degree to which conspecific predation (cannibalism) can generate this risk, however, is poorly understood. In this paper, we examine microhabitat use, cannibalism, and individual responses to the presence of conspecifics in Thermosphaeroma thermophilum, an endangered isopod crustacean species that is endemic to a single, thermal spring in Socorro, N.M. USA. In samples from the natural habitat, juveniles (mancas) were found mainly on vegetation, whereas adults were found predominantly on bottom sediments. Females were found on vegetation more often than males. In laboratory containers without refuges, males cannibalized females, males and females cannibalized mancas, and mancas cannibalized each other, even in the presence of alternative food. When placed in containers provided with refuges, mancas actively avoided adults. We suggest, therefore, that cannibalism in T. thermophilum generates age-, size-, and sex-specific predation risks which are responsible for microhabitat segregation between mancas and adults, and between males and females. Since interspecific predation in the spring is negligible, cannibalism appears to play a significant role in population regulation and behavioral evolution in this species. We recommend, given the current “endangered” status of this species, that microhabitat heterogeneity be maintained in its native spring because it provides refuges from cannibalism and may support a larger and more viable natural population. Received: 28 June 1996 / Accepted: 24 February 1997     

ATP-Binding Proteins on the External Surface of Synaptic Plasma Membranes: Identification by Photoaffinity Labeling

Abstract: 8-Azidoadenosine triphosphate labeled in the α or γ position with ³²P was used as a photoaffinity reagent for identifying ATP binding sites on the external surface of intact rat brain synaptosomes. As revealed by autoradiography of sodium dodecyl sulfate-polyacrylamide gel electrophoretic patterns, UV irradiation of intact synaptosomes in the presence of the above radioactive compounds at 5–10 µ M resulted in the formation of several major radioactive conjugates with approximate molecular masses of 29, 45/46, 58, and 93 kDa. Minor bands of 20, 39, 52/54, 82/84, 120, and 140 kDa were also consistently labeled in these experiments. The possibility that labeling of these proteins was due to the presence of contaminating subcellular particles or intrasynaptosomal proteins was excluded. The major 8-azidoadenosine [α-³²P]triphosphate-labeled protein complex of ∼45/46 kDa was resolved into several subbands that are labeled differently depending on the type of divalent cations added to the photoaffinity reaction. In the presence of magnesium only, the major labeled band appeared at 45 kDa. With calcium, two additional subbands (43 and 46 kDa) could be distinguished. In the presence of 1 m M EDTA, a band at 44 kDa was labeled within this ATP-binding complex. The labeling pattern of the subbands of this 45/46-kDa complex is consistent with these bands being extracellular ATP-binding proteins on the surface of the synaptosome.     

Ecto-ATPase of Mammalian Synaptosomes: Identification and Enzymic Characterization

Intact synaptosomes isolated from mammalian brain tissues (rat, mouse, gerbil, and human) have an ATP hydrolyzing enzyme activity on their external surface. The synaptosomal ecto-ATPase(s) possesses characteristics consistent with those that have been described for ecto-ATPases of various other cell types. The enzyme has a high affinity for ATP (the apparent Km values are in the range of 2-5 X 10(-5) M), and is apparently stimulated equally well by either Mg2+ or Ca2+ in the absence of any other cations. The apparent activation constant for both divalent cations is approximately 4 X 10(-4) M in all mammalian brain tissues studied. The involvement of a non-specific phosphatase in the hydrolysis of externally added ATP is excluded. ATP hydrolysis is maximal in the pH range 7.4-7.8 for both divalent cation-dependent ATPase activities. Dicyclohexylcarbodiimide, 2,4-dinitrophenol, trifluoperazine, chlorpromazine, and p-chloromercuribenzoate (50 microM) inhibit the ecto-ATPase, whereas ouabain (1 mM) and oligomycin (3.5 micrograms X mg-1 protein) show little or no inhibition of this enzyme activity. Inhibitor data suggest that the Mg2+- and Ca2+-dependent ecto-ATPase may represent two different enzymes on the surface of synaptosomes.     

Interactions of sera from patients with autoimmune diseases with cDNA expressed fragment of topoisomerase I and monoclonal antibodies against enzyme

The interaction of sera from 34 patients with different autoimmune diseases with the expressed fusion protein cloned in lambda gt11 vector (topoisomerase I--beta galactosidase) and monoclonal antibodies against enzyme was studied. It was demonstrated that 100% of Scl cases possessed positive activity against fusion protein. It was shown that this test is not absolutely specific for Scl, i. e. 57.1% of Sle and 84.6% of RA demonstrated positive activity against "topoisomerase test". Autoimmune sera had the positive activity against monoclonal antibodies for topoisomerase I. This activity was shown to be due to the presence of antiidiotypic antibodies against topoisomerase in the autoimmune sera.     

Use of ureidopenicillins for selection of plasmid vector transformants in Pseudomonas aeruginosa and Pseudomonas putida.

Broad-host-range plasmids coding for beta-lactamase were successfully selected after transformation of Pseudomonas strains. Transformants of both Pseudomonas aeruginosa and Pseudomonas putida containing plasmid pRO1614 were isolated in media containing low concentrations of piperacillin. These strains were also susceptible to other ureidopenicillins. Similar selections of transformants with carbenicillin, ampicillin, or ticarcillin required high concentrations of antibiotics and yielded backgrounds of spontaneous resistant mutants.     

Metal contamination and human health risk associated with the consumption of Labeo rosae from the Olifants River system,South Africa

The Olifants River, a tributary of the Limpopo River system, is one of the most polluted rivers in South Africa. In May 2011 the concentrations of metals in fish muscle tissue from two impoundments, Loskop and Flag Boshielo dams, on the Olifants River were measured and a human health risk assessment conducted to investigate whether it was safe to consume Labeo rosae from these impoundments. Labeo rosae is one of the most common pan fish in these impoundments and is readily available to rural communities. Metals are accumulating in the muscle tissue of L. rosae even although the fish populations appear to be healthy. At Loskop Dam all L. rosae analysed exceeded the recommended hazard quotient (HQ) of 1 for antimony, and less than 50% exceeded that for lead. At Flag Boshielo Dam, the recommended HQ was exceeded for lead in less than 50% of L. rosae analysed, and more than 50% exceeded that for antimony. The weekly consumption of 150?g of L. rosae muscle tissue from these impoundments may pose an unacceptable health risk to rural communities.