Subsistence ecology and play among the okavango delta peoples of botswana

Children’s play is widely believed by educators and social scientists to have a training function that contributes to psychosocial development as well as the acquisition of skills related to adult competency in task performance. In this paper we examine these assumptions from the perspective of life-history theory using behavioral observation and household economic data collected among children in a community in the Okavango Delta of Botswana where people engage in mixed subsistence regimes of dry farming, foraging, and herding. We hypothesize that if play contributes to adult competency then time allocation to play will decrease as children approach adult levels of competence. This hypothesis generates the following predictions: (1) time allocated to play activities that develop specific productive skills should decline in relation to the proportion of adult competency achieved; (2) children will spend more time in forms of play that are related to skill development in tasks specific to the subsistence ecology in which that child participates or expects to participate; and (3) children will spend more time in forms of play that are related to skill development in tasks clearly related to the gender-specific productive role in the subsistence ecology in which that child participates or expects to participate. We contrast these expectations with the alternative hypothesis that if play is not preparatory for adult competence then time allocated to each play activity should diminish at the same rate. This latter hypothesis generates the following two predictions: (1) time allocation to play should be unaffected by subsistence regime and (2) patterns of time allocation to play should track patterns of growth and energy balance. Results from multiple regression analysis support earlier research in this community showing that trade-offs between immediate productivity and future returns were a primary determinant of children’s activity patterns. Children whose labor was in greater demand spent significantly less time playing. In addition, controlling for age and gender, children spent significantly more time in play activities related to tasks specific to their household subsistence economy. These results are consistent with the assertion that play is an important factor in the development of adult competency and highlight the important contributions of an evolutionary ecological perspective in understanding children’s developmental trajectories. John Bock is an associate professor of anthropology at Cal State Fullerton and Associate Editor of Human Nature. He received a Ph.D. in Anthropology (Human Evolutionary Ecology) from the University of New Mexico in 1995, and from 1995 to 1998 was an Andrew W. Mellon Foundation postdoctoral fellow in demography and epidemiology at the National Centre for Epidemiology and Population Health at Australian National University. His recent research has focused on the application of life-history theory to understanding the evolution of the primate and human juvenile period. Bock has been conducting research among the Okavango Delta peoples of Botswana since 1992, and his current research there is an examination of child development and family demography in relation to socioecology and the HIV/AIDS epidemic. Other research is focused on health disparities among minorities and indigenous peoples in Botswana and the United States related to differential access to health care. Sara E. Johnson is an assistant professor of anthropology at California State University, Fullerton. She received her Ph.D. in Anthropology (Human Evolutionary Ecology) from the University of New Mexico in 2001. She uses behavioral ecology and life-history theory to address her research interests in the evolution of primate and human growth; ecological variation and phenotypic plasticity in growth and development; ecological variation in life course trajectories, including fertility, health, morbidity, and mortality differentials; food acquisition and production related to nutrition; societal transformation and roles of the elderly among indigenous peoples; and women’s reproductive and productive roles in both traditional and nontraditional societies. Over the past 10 years she has conducted research on these issues in several different populations, including chacma baboons in the Okavango Delta of Botswana, two multiethnic communities of forager/agropastoralists in the Okavango Delta of Botswana, and among New Mexican men.     

Are we sure we know how to measure 8-oxo-7,8-dihydroguanine in DNA from human cells?

The most commonly measured marker of oxidative DNA damage is 8-oxo-7,8-dihydroguanine (8-oxoGua) or its deoxyribonucleoside (8-oxodGuo). Published estimates of the concentration of 8-oxoGua/8-oxodGuo in DNA of normal human cells vary over a range of three orders of magnitude. Analysis by chromatographic methods (GC-MS, HPLC with electrochemical detection (ECD) or HPLC-MS/MS) is beset by the problem of adventitious oxidation of guanine during sample preparation. An alternative approach, based on the use of the DNA repair enzyme formamidopyrimidine DNA N-glycosylase (FPG) to make breaks in the DNA at sites of the oxidised base, gives much lower values. ESCODD, the European Standards Committee on Oxidative DNA Damage, has been testing the ability of different laboratories using a variety of methods to measure 8-oxoGua in standard samples of 8-oxodGuo, calf thymus DNA, pig liver, oligonucleotides, and HeLa cells, and in lymphocytes isolated from blood of volunteers. HPLC-ECD is capable of measuring 8-oxodGuo induced experimentally in calf thymus DNA or HeLa cells with high accuracy. However, there is no sign of consensus over the background level of this damage, suggesting that, even though standard extraction procedures were used, variable oxidation of Gua is still occurring. GC-MS failed to detect a dose response of induced 8-oxoGua and cannot be regarded as a reliable method for measuring low levels of damage. HPLC-MS/MS as yet has not proved capable of measuring low levels of oxidative DNA damage. FPG-based methods seem to be less prone to the artefact of additional oxidation. Although they can be used quantitatively, they require careful calibration and standardisation if they are to be used in human biomonitoring. The background level of DNA oxidation in normal human cells is likely to be around 0.3-4.2 8-oxoGua per 10(6) Gua. An effort should be made to develop alternative, validated methods for estimating oxidative DNA damage.     

Relationship of Vibrio Species Infection and Elevated Temperatures to Yellow Blotch/Band Disease in Caribbean Corals

The bacterial and temperature factors leading to yellow blotch/band disease (YBD), which affects the major reef-building Caribbean corals Montastrea spp., have been investigated. Groups of bacteria isolated from affected corals and inoculated onto healthy corals caused disease signs similar to those of YBD. The 16S rRNA genes from these bacteria were sequenced and found to correspond to four Vibrio spp. Elevating the water temperature notably increased the rate of spread of YBD on inoculated corals and induced greater coral mortality. YBD-infected corals held at elevated water temperatures had 50% lower zooxanthella densities, 80% lower division rates, and a 75% decrease in chlorophyll a and c₂ pigments compared with controls. Histological sections indicated that the algal pyrenoid was fragmented into separate segments, along with a reconfiguration and swelling of the zooxanthellae, as well as vacuolization. YBD does not appear to produce the same physiological response formerly observed in corals undergoing temperature-related bleaching. Evidence indicates that YBD affects primarily the symbiotic algae rather than coral tissue.     

Exopolysaccharide, pigment and protein production by the marine microalga Chroomonas sp. in semicontinuous cultures

The marine microalga Chroomonas sp. isolated from Venezuela was grown in semicontinuous culture in order to study the effect of renewal rate and nutrient concentration on alloxanthin, chlorophyll a, carotenoid, carbohydrate, exopolysaccharide, protein and cell productivity. Maximal cell productivity of 8.43 ± 1.8 and 8.81 ± 2.3 × 10⁹ cell l^–1 day^–1 were achieved with renewal rates of 30 and 40%. Maximal protein and chlorophyll productivity of 64.64 ± 2.3 and 2.72 ± 0.3 mg l^–1 day^–1 were obtained with renewal rate of 20 and 30%. Biochemical composition of Chroomonas sp. was influenced by renewal rate. Nutrient concentration seems not to affect cell, protein, chlorophyll and carotenoid productivity. However, carbohydrate and exopolysaccharide productivity of 7.56 ± 0.4 and 9.57 ± 1.2 mg l^–1 day^–1 were increased at 12 mM NaNO₃(P < 0.05). Also, alloxanthin and chlorophyll a production analysed by HPLC, were higher between 8 and 12 mM NaNO₃ at a renewal rate of 30%. Results demonstrated that a renewal rate of 30% and nutrient concentration at 8 mM NaNO₃ optimize the cell, protein, carbohydrate, chlorophyll a, and exopolysaccharide productivity in semicontinuous cultures of Chroomonas. This microalga, as biological source of commercially valuable compounds, shows high capacity for changing its productivity and biochemical composition in semicontinuous system on the basis of nutrient concentration and the renewal rate.     

Cryopyrin-induced interleukin 1beta secretion in monocytic cells: enhanced activity of disease-associated mutants and requirement for ASC

Several autoinflammatory disorders are associated with missense mutations within the nucleotide-binding oligomerization domain of cryopyrin. The mechanism by which cryopyrin mutations cause inflammatory disease remains elusive. To understand the molecular bases of these diseases, we generated constructs to express three common cryopyrin disease-associated mutations, R260W, D303N, and E637G, and compared their activity with that of the wild-type protein. All cryopyrin mutant proteins tested were found to induce potent NF-kappaB activity when compared with the wild-type protein. This activation was dependent on the expression of ASC, an adaptor protein previously suggested to mediate cryopyrin signaling. When the disease-associated mutants were expressed in monocytic THP-1 cells (which express endogenous ASC), each induced spontaneous IL-1beta secretion, whereas wild-type protein did not. In the absence of stimuli, wild-type cryopyrin was unable to bind to ASC, whereas the three mutants coimmunoprecipitated with ASC, suggesting a mechanism involved in the constitutive activation of mutant proteins. The induction of cryopyrin activity by enforced oligomerization in THP-1 cells resulted in ASC binding and the secretion of IL-1beta, an effect that was abolished by the inhibition of ASC expression with small interfering RNAs. Thus, cryopyrin-mediated IL-1beta secretion requires ASC in monocytic cells. Further, these results indicate that cryopyrin disease-associated mutants are constitutively active and able to induce NF-kappaB activation and IL-1beta secretion at least in part by an increased ability to interact with ASC.     

Effects of two biorational insecticides, spinosad and methoxyfenozide, on Spodoptera littoralis (Lepidoptera: Noctuidae) under laboratory conditions

The toxicity of two biorational insecticides, spinosad (Tracer) and methoxyfenozide (RH-2485), was tested against eggs, larvae, and pupae of the noctuid Spodoptera littoralis (Boisduval). In the first experiment, filter paper circles containing egg masses of two different age classes, young (<24 h old) and old (24-48 h old), were dipped in different concentrations of each insecticide diluted in either water or acetone. No ovicidal activity was recorded when insecticides were diluted in water. In contrast, when insecticides were diluted in acetone, both egg age classes generally showed a concentration-dependent response for both compounds. Mortality of larvae that hatched from both egg age classes was significantly increased, compared with control larvae, at all concentrations of both insecticides when diluted in water or acetone alike. The prevalence of mortality was similar with each insecticide. In the second experiment, third instars of S. littoralis were fed semisynthetic diet containing different concentrations of both insecticides. According to LC50 values, no significant differences were observed between spinosad (2.11 mg [AI]/kg diet) and methoxyfenozide (3.98 mg [AI]/kg diet) after 48 h of treatment, based on the overlap of 95% CL. Toxic effects on the mortality of pupae, adult emergence, and the prevalence of deformed adults after topical application on young pupae also were examined. Only methoxyfenozide caused pupal mortality and deformed adults. Our results suggest that spinosad and methoxyfenozide are potentially potent compounds for control of S. littoralis.     

BRL1 and BRL3 are novel brassinosteroid receptors that function in vascular differentiation in Arabidopsis

Plant steroid hormones, brassinosteroids (BRs), are perceived by the plasma membrane-localized leucine-rich-repeat-receptor kinase BRI1. Based on sequence similarity, we have identified three members of the BRI1 family, named BRL1, BRL2 and BRL3. BRL1 and BRL3, but not BRL2, encode functional BR receptors that bind brassinolide, the most active BR, with high affinity. In agreement, only BRL1 and BRL3 can rescue bri1 mutants when expressed under the control of the BRI1 promoter. While BRI1 is ubiquitously expressed in growing cells, the expression of BRL1 and BRL3 is restricted to non-overlapping subsets of vascular cells. Loss-of-function of brl1 causes abnormal phloem:xylem differentiation ratios and enhances the vascular defects of a weak bri1 mutant. bri1 brl1 brl3 triple mutants enhance bri1 dwarfism and also exhibit abnormal vascular differentiation. Thus, Arabidopsis contains a small number of BR receptors that have specific functions in cell growth and vascular differentiation.     

Transferable antibiotic resistance elements in Haemophilus influenzae share a common evolutionary origin with a diverse family of syntenic genomic islands

Transferable antibiotic resistance in Haemophilus influenzae was first detected in the early 1970s. After this, resistance spread rapidly worldwide and was shown to be transferred by a large 40- to 60-kb conjugative element. Bioinformatics analysis of the complete sequence of a typical H. influenzae conjugative resistance element, ICEHin1056, revealed the shared evolutionary origin of this element. ICEHin1056 has homology to 20 contiguous sequences in the National Center for Biotechnology Information database. Systematic comparison of these homologous sequences resulted in identification of a conserved syntenic genomic island consisting of up to 33 core genes in 16 beta- and gamma-Proteobacteria. These diverse genomic islands shared a common evolutionary origin, insert into tRNA genes, and have diverged widely, with G+C contents ranging from 40 to 70% and amino acid homologies as low as 20 to 25% for shared core genes. These core genes are likely to account for the conjugative transfer of the genomic islands and may even encode autonomous replication. Accessory gene clusters were nestled among the core genes and encode the following diverse major attributes: antibiotic, metal, and antiseptic resistance; degradation of chemicals; type IV secretion systems; two-component signaling systems; Vi antigen capsule synthesis; toxin production; and a wide range of metabolic functions. These related genomic islands include the following well-characterized structures: SPI-7, found in Salmonella enterica serovar Typhi; PAP1 or pKLC102, found in Pseudomonas aeruginosa; and the clc element, found in Pseudomonas sp. strain B13. This is the first report of a diverse family of related syntenic genomic islands with a deep evolutionary origin, and our findings challenge the view that genomic islands consist only of independently evolving modules.     

Preliminary studies of the 2D crystallization of Omp1 of Serratia marcescens: observation by atomic force microscopy in native membranes environment and reconstituted in proteolipid sheets

In this work the porin Omp1 of Serratia marcescens was expressed in a porin deficient mutant (Escherichia coli UH302) and its functionality studied following the accumulation of ciprofloxacin in bacteria. The protein was extracted, purified and reconstituted in proteoliposomes of different composition (lipopolysaccharide (LPS), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and, 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)). Maximum extraction of the detergent was achieved applying different steps of dialysis and centrifugation. Proteolipid sheets with different composition were spread onto mica and observed by atomic force microscopy. Two-dimensional crystal of Omp1 was not observed in any case due to low resolution achieved. Judging from the images features POPC is the most suitable phospholipid to enhance 2D lattice formation for Omp1.     

Identification and molecular characterization of Mnk1b, a splice variant of human MAP kinase-interacting kinase Mnk1

In this paper, we report the identification and molecular characterization of a splice variant of human Mnk1 which has been named as Mnk1b. Human Mnk1b mRNA is homologous to human Mnk1 mRNA but lacking a region corresponding to exon 19, which causes a change in the reading frame generating a stop codon. The resulting protein lacks the last 89 amino acids at the C-terminal region that are replaced by 12 amino acids with an entirely new sequence. The C-terminal end in Mnk1 corresponds to the extracellular signal-regulated kinase (ERK1/2) binding site. Although Mnk1b lacks this domain and, consequently, is not phosphorylated by ERK1/2, it is able, however, to phosphorylate eIF4E in vitro and in vivo in a mitogen-activated protein kinases-independent manner. This result suggests that Mnk1b may play a key role in regulating protein translation in the absence of stimuli. Interestingly, a significant population of cells shows Mnk1b within the nucleus whereas Mnk1 is always detected in the cytoplasm. This fact may be explained because Mnk1b maintains the nuclear localization signal (NLS) but lacks the nuclear export sequence (NES).