An Extraordinary Example of Photokarren in a Sandstone Cave, Cueva Charles Brewer, Chimantá Plateau, Venezuela: Biogeomorphology on a Small Scale

A distinctive suite of small-scale erosional forms that are oriented towards the light occur close to the entrance of Cueva Charles Brewer, a large cave in a sandstone tepui, in SE Venezuela. These are the third example of photokarren ever studied in the world, the other two being from Borneo and Ireland. They are the only photokarren ever described from sandstone, and the only example from a non-carbonate environment. The host rock is a poorly-lithified unit of the Precambrian quartz arenite of the Roraima Supergroup. The forms are all oriented towards the light at 30° regardless of rock surface orientation. The primary (negative) erosional form is the tube. Coalescence of tubes results in the positive remnant forms of rods, pinnacles, and cones. The final stage is a bumpy, wavy surface of degraded cones. The size of the features varies with erosion rate, and details of the form vary with development stage. The main population averages 4.4 cm in depth, with 55% of the surface eroded. This is divided into 10% tubes, 70% rods, 10% cones, 5% linear valley and 5% wavy lowland. The micro-ecosystem includes many bacteria, diatoms, red algae, green algae, liverworts, and oribatid mites, but, surprisingly, no cyanobacteria. The presence of a surface biofilm inside the forms but not on the remnant rock surface and, in the non-degraded forms, the direct relationship of biomass with depth suggests that biological activity is the dominant control on development. In addition, direct bacterial corrosion was noted. These same features occur to varying extents in the photokarren of Borneo and Ireland, and the model for development that we present provides a unifying theory for all photokarren. (This study also includes the first published petrographic analysis of uppermost unit of the Mataui Formation)

Consumo voluntario y digestibilidad de nutrientes de heno de gramíneas y leguminosas tropicales suplementadas con ensilaje de residuos de pescadería

Two experiments were conducted to determine the effect of supplementation with tilapia fish silage (FS) prepared in laboratory scale silos with addition of cane molasses, on intake and digestibility of tropical grass hay (GH) (Digitaria eriantha, 80%, and Urochloa maximum, 20%), and rhizome perennial peanut hay (RPPH) (Arachis glabrata). In Experiment I, GH was the basal diet and treatments were Control or T1 = GH, and GH supplemented daily with FS at 0.45% (T2) and 0.90% (T3) of the animal body weight (BW). In Experiment II, the basal diet was RPPH and treatments were Control or T1 = RPPH;T2 = RPPH supplemented daily with FS at 0.225% BW; and T3 = RPPH with 0.45% BW. In both experiments nine adult intact rams were used. The animals were fed for eight days of adaptation and six days of data collection in each period. Both experiments used a 3 X 3 Latin Square design. In experiment I dry matter (DM) intake and digestibility of GH increased (P less than 0.05) with FS supplementation, which also increased crude protein (CP) intake. CP digestibility increased (P < 0.05) at each level of supplementation compared to that of the control, but T2 and T3 did not differ significantly. Neutral detergent fiber (NDF) intake was higher (P < 0.05) in T1 than in T3 but similar in T1 and T2. Fiber digestibility was not affected (P greater than 0.05) by the treatments. It was concluded that supplementation of a GH basal diet with FS at 0.90% of BW is the best alternative. In Experiment II, DM digestibility of T3 differed (P less than 0.05) from that in T1 but in T2 did not differ from DM digestibility either in T1 or T3. Intake of DM, CP and fiber were similar in all treatments (P greater than 0.05). Crude protein digestibility was similar at both levels of supplementation and superior (P < 0.05) to that of the control, but fiber digestibility was not affected (P > 0.05). It is concluded that daily supplementation with FS for sheep fed a basal diet of RPPH should be limited to 0.225% of BW. Upon comparing both experiments, voluntary intake of DM, NDF and CP from RPPH was higher than from GH.The legume also showed a higher (P < 0.05) digestibility of DM and CP.Se realizaron dos experimentos con el objetivo de determinar el efecto de la suplementación con ensilaje de residuos de pescado tilapia (EP) preparado en silos de laboratorio con la adición de melaza de caña sobre el consumo voluntario y la digestibilidad de nutrientes, de heno de gramíneas tropicales (HG) (Digitaria eriantha, 80% y Urochloa maximun, 20%) y de heno de maní rizoma perenne (HMRP) (Arachis glabrata). En el ensayo experimental I se evaluaron tres tratamientos (T1 o Control = HG;T2= HG + EP a 0.45% del peso vivo (PV); T3= HG + EP a 0.90% del PV diariamente), mientras que en el ensayo experimental II se evaluaron los tratamientos (T1 o Control = HMRP; T2= HMRP + EP a 0.225% del PV; T3= HMRP + EP a 0.45% del PV diariamente). En ambos ensayos se utilizaron nueve carneros enteros distribuidos según un diseño de cuadrado latino 3X3. Los animales se sometieron a una etapa de adaptación a las dietas de ocho días y a un periodo de recolección de datos de seis días durante cada periodo. En el ensayo I, la suplementación con EP a carneros alimentados con HG aumentó linealmente (P < 0.05) el consumo voluntario y la digestibilidad de materia seca (MS) y también (P < 0.05) el consumo de proteína bruta (PB). En la digestibilidad de la PB hubo diferencias (P < 0.05) entre el control y los tratamientos con suplementación, pero T2 fue similar a T3 (P > 0.05). Por otro lado, la suplementación con EP no afectó (P > 0.05) la digestibilidad de la fibra detergente neutro (FDN), pero enT3 se redujo (P < 0.05) su consumo. Se concluyó que la suplementación de HG con EP al 0.90% del PV se presenta como la mejor alternativa. En el ensayo II, la suplementación con EP al 0.45% del PV aumentó (P< 0.05) la digestibilidad de la MS, mientras el aumento casi tan grande obtenido con EP al 0.225% del PV no alcanzó significación a P = 0.05 en carneros alimentados con HMRP. Sin embargo, la suplementación con EP no aumentó (P > 0.05) el consumo de MS, de PB ni de FDN. En cuanto a la digestibilidad de la PB se observaron diferencias entre el control y los demás tratamientos pero la de T2 fue similar a la de T3. La suplementación con EP no afectó la digestibilidad de la fibra (P > 0.05). Por lo tanto, en carneros alimentados con la leguminosa el menor nivel de suplementación es recomendable. Al comparar los tratamientos control de los dos ensayos, el consumo voluntario de MS, FDN y PB en forma de HMRP fue mayor que con HG. La leguminosa también presentó una mayor (P < 0.05) digestibilidad de la MS y PB

Naturally-acquired and vaccine-induced human monoclonal antibodies to plasmodium vivax Duffy binding protein inhibit invasion of Plasmodium knowlesi (pvdbpor) transgenic parasites

The Duffy antigen receptor for chemokines (DARC) expressed on erythrocytes is central to Plasmodium vivax (Pv) invasion of reticulocytes. Pv expresses a Duffy binding protein (PvDBP) on merozoites, a DARC ligand, and their protein-protein interaction is central to vivax blood stage malaria. Here we compared the functional activity of humAbs derived from naturally exposed and vaccinated individuals for the first time using easily cultured P. knowlesi (Pk) that had been genetically modified to replace its endogenous PkDBP orthologue with PvDBP to create a transgenic parasite, PkPvDBPOR. This transgenic parasite requires DARC to invade human erythrocytes but is not reticulocyte restricted. Using this model, we evaluated the invasion inhibition potential of 12 humAbs (9 naturally acquired; 3 vaccine-induced) targeting PvDBP individually and in combinations using growth inhibition assays (GIAs). The PvDBP-specific humAbs demonstrated 70-100% inhibition of PkPvDBPOR invasion with the IC50 values ranging from 51 to 338 μg/mL for the 9 naturally acquired (NA) humAbs and 33 to 99 μg/ml for the 3 vaccine-induced (VI) humAbs. To evaluate antagonistic, additive, or synergistic effects, six pairwise combinations were performed using select humAbs. Of these combinations tested, one NA/NA (099100/094083) combination demonstrated relatively strong additive inhibition between 10-100 μg/mL; all combinations of NA and VI humAbs showed additive inhibition at concentrations below 25 μg/mL and antagonism at higher concentrations. None of the humAb combinations showed synergy. This PkPvDBPOR model system enables efficient assessment of NA and VI humAbs individually and in combination

Human monoclonal antibodies inhibit invasion of transgenic Plasmodium knowlesi expressing Plasmodium vivax Duffy binding protein

Background: Plasmodium vivax has been more resistant to various control measures than Plasmodium falciparum malaria because of its greater transmissibility and ability to produce latent parasite forms. Therefore, developing P. vivax vaccines and therapeutic monoclonal antibodies (humAbs) remains a high priority. The Duffy antigen receptor for chemokines (DARC) expressed on erythrocytes is central to P. vivax invasion of reticulocytes. P. vivax expresses a Duffy binding protein (PvDBP) on merozoites, a DARC ligand, and the DARC: PvDBP interaction is critical for P. vivax blood stage malaria. Therefore, PvDBP is a leading vaccine candidate for P. vivax and a target for therapeutic human monoclonal antibodies (humAbs). Methods: Here, the functional activity of humAbs derived from naturally exposed and vaccinated individuals are compared for the first time using easily cultured Plasmodium knowlesi (P. knowlesi) that had been genetically modified to replace its endogenous PkDBP orthologue with PvDBP to create a transgenic parasite, PkPvDBPOR. This transgenic parasite requires DARC to invade human erythrocytes but is not reticulocyte restricted. This model was used to evaluate the invasion inhibition potential of 12 humAbs (9 naturally acquired; 3 vaccine-induced) targeting PvDBP individually and in combinations using growth inhibition assays (GIAs). Results: The PvDBP-specific humAbs demonstrated 70–100% inhibition of PkPvDBPOR invasion with the IC50 values ranging from 51 to 338 µg/mL for the 9 naturally acquired (NA) humAbs and 33 to 99 µg/ml for the 3 vaccine-induced (VI) humAbs. To evaluate antagonistic, additive, or synergistic effects, six pairwise combinations were performed using select humAbs. Of these combinations tested, one NA/NA (099100/094083) combination demonstrated relatively strong additive inhibition between 10 and 100 µg/mL; all combinations of NA and VI humAbs showed additive inhibition at concentrations below 25 µg/mL and antagonism at higher concentrations. None of the humAb combinations showed synergy. Invasion inhibition efficacy by some mAbs shown with PkPvDBPOR was closely replicated using P. vivax clinical isolates. Conclusion: The PkPvDBPOR transgenic model is a robust surrogate of P. vivax to assess invasion and growth inhibition of human monoclonal Abs recognizing PvDBP individually and in combination. There was no synergistic interaction for growth inhibition with the humAbs tested here that target different epitopes or subdomains of PvDBP, suggesting little benefit in clinical trials using combinations of these humAbs

Estimativa de parâmetros genéticos visando o melhoramento cafeeiro.

Os programas de melhoramento de Coffea canephora, var. conilon, buscam a seleção de genótipos promissores, de forma sustentável e ecologicamente equilibrada. No entanto, para alcançar o sucesso, há necessidade de quantificar a variabilidade genética e a estimação de parâmetros. As plantas de C. canephora são diplóides, de fecundação cruzada, com tendência a originar lavouras com ampla variabilidade genética em relação à arquitetura da parte aérea, ao formato e tamanho dos grãos, à época e uniformidade de maturação dos frutos, suscetibilidade a pragas e doenças, tolerância à seca, ao vigor vegetativo e à capacidade produtiva