Snake venomics of the lancehead pitviper Bothrops asper: geographic, individual, and ontogenetic variations

We report the comparative proteomic characterization of the venoms of adult and newborn specimens of the lancehead pitviper Bothrops asper from two geographically isolated populations from the Caribbean and the Pacific versants of Costa Rica. The crude venoms were fractionated by reverse-phase HPLC, followed by analysis of each chromatographic fraction by SDS-PAGE, N-terminal sequencing, MALDI-TOF mass fingerprinting, and collision-induced dissociation tandem mass spectrometry of tryptic peptides. The two B. asper populations, separated since the late Miocene or early Pliocene (8-5 mya) by the Guanacaste Mountain Range, Central Mountain Range, and Talamanca Mountain Range, contain both identical and different (iso)enzymes from the PLA 2, serine proteinase, and SVMP families. Using a similarity coefficient, we estimate that the similarity of venom proteins between the two B. asper populations may be around 52%. Compositional differences between venoms among different geographic regions may be due to evolutionary environmental pressure acting on isolated populations. To investigate venom variability among specimens from the two B. asper populations, the reverse-phase HPLC protein profiles of 15 venoms from Caribbean specimens and 11 venoms from snakes from Pacific regions were compared. Within each B. asper geographic populations, all major venom protein families appeared to be subjected to individual variations. The occurrence of intraspecific individual allopatric variability highlights the concept that a species, B. asper in our case, should be considered as a group of metapopulations. Analysis of pooled venoms of neonate specimens from Caribbean and Pacific regions with those of adult snakes from the same geographical habitat revealed prominent ontogenetic changes in both geographical populations. Major ontogenetic changes appear to be a shift from a PIII-SVMP-rich to a PI-SVMP-rich venom and the secretion in adults of a distinct set of PLA 2 molecules than in the neonates. In addition, the ontogenetic venom composition shift results in increasing venom complexity, indicating that the requirement for the venom to immobilize prey and initiate digestion may change with the size (age) of the snake. Besides ecological and taxonomical implications, the geographical venom variability reported here may have an impact in the treatment of bite victims and in the selection of specimens for antivenom production. The occurrence of intraspecies variability in the biochemical composition and symptomatology after envenomation by snakes from different geographical location and age has long been appreciated by herpetologist and toxinologists, though detailed comparative proteomic analysis are scarce. Our study represents the first detailed characterization of individual and ontogenetic venom protein profile variations in two geographical isolated B. asper populations, and highlights the necessity of using pooled venoms as a statistically representative venom for antivenom production.     

Widow and widower remarriage: an analysis in a rural 19th century Costa Rican population and a cross-cultural discussion

Although the topic of remarriage features saliently in the cultural anthropological literature, it is virtually absent in the biological anthropology journals. This is perplexing, given that remarriage affects the differential reproductive success of males and females in a community, and could well impact a community's population structure. In this paper, we research remarriage practices in a rural 19th century community in Costa Rica. Although we find support for the proposition that males are more likely to remarry than females, we find that widows who remarry are not all young and able to reproduce. Our findings support the cross-culturally-generated suggestion that a female's ability not to remarry is tied to her to ability to own property. Remarriage is a topic of interest to biological anthropologists from a cross-cultural and biocultural perspective.     

Macrophage colony stimulating factor (M-CSF) within cord blood sera may be partially responsible for the reduced proliferation of cord blood T cells

We show that there are differences in the soluble factors in cord blood (CB) and adult serum and that these differences play a role in T cell function. Thus, the mitogen and alloantigen-specific proliferative response of adult T cells was enhanced with increasing concentrations of adult serum and CB serum, but to a lesser extent with CB serum. In addition, proliferation of T cells induced by stimulation through the T cell receptor alone (via CD3 stimulation), could be enhanced with adult but not CB serum. However, CB serum enhanced the IL-2-specific proliferative response of pure T cells whereas adult serum did not. To determine whether there was an anti-inflammatory cytokine within CB serum which could induce these results, we assayed our serum samples for anti-inflammatory cytokines. IL-13 could not be detected in any serum sample, whereas IL-10 could be detected in adult but not CB serum (P < 0.002). However, there was a significant difference in the levels of macrophage colony stimulating factor (M-CSF) detected in adult and CB serum samples (P < 0.01). M-CSF was detected in 6/7 CB serum samples (mean +/- SD was 3.8 +/- 2.3 ng/ml) and 0/5 adult serum samples. Furthermore, anti-M-CSF antibody restored the reduced allo-response of T cells incubated in CB serum. Thus, M-CSF may act as a suppressor factor in CB serum. Whether this is sufficient to explain the lack of an allo-response by the foetus to the mother, or the reduced graft-versus-host disease when CB is used instead of bone marrow in stem cell transplantation, is yet to be determined.     

The influence of exogenous peptide on β2–microglobulin exchange in the HLA complex: analysis in real-time

 We used an optical biosensor to determine the relative binding affinity of peptides to purified HLA class I molecules. In this assay we monitor β₂–microglobulin (β₂m) exchange within the HLA-A2 molecule, whereby native β₂m in the complex is replaced by β₂m immobilized at the surface of the biosensor. Quantitative kinetic measurements permit us to obtain association rate (k_ass), dissociation rate (k_diss) and affinity constants (K_A) for the β₂m exchange reaction, alone, (control) and in the presence of exogenous peptide. We tested a panel of six peptides which had been designed and synthesized with an HLA-A2 binding motif, and had also been tested by the T2-cell binding assay, along with control peptides. The biosensor results demonstrate that exogenous peptide influences the dynamics of β₂m exchange in a sequence-specific manner. Five of six peptides increased the association rate, decreased the dissociation rate, and significantly increased the affinity (K_A=1.55–1.88×10⁹ M^–1) of HLA-A2 for immobilized β₂m compared with the control (K_A =1.14±0.04×10⁹ M^–1), demonstrating stabilization of the complex. One peptide was unable to stabilize the complex, as also shown in the T2 binding assay. However, analysis of peptide sequences demonstrated that the HLA-A2 secondary motif as well as primary motif residues are required for HLA-A2 stabilization. Further experiments demonstrated that β₂m exchange alone cannot stabilize the HLA class I complex at the cell surface until a peptide of sufficient binding affinity is bound. Hence kinetics equal to or below the control values in our biosensor assay probably represent an unstable complex in vivo. Unlike other methods described for the analysis of peptide stabilization, this approach is significantly faster, provides full kinetic analysis, and is simpler, since it requires no labeling of peptides. Furthermore, this may have important implications in the assessment of peptide vaccines. Received: 9 October 1997 / Revised: 20 January 1998     

Human skin-color sexual dimorphism: a test of the sexual selection hypothesis

Applied to skin color, the sexual selection hypothesis proposes that male preference for light-skinned females explains the presence of light skin in areas of low solar radiation. According to this proposal, in areas of high solar radiation, natural selection for dark skin overrides the universal preference of males for light females. But in areas in which natural selection ceases to act, sexual selection becomes more important, and causes human populations to become light-skinned, and females to be lighter than males. The sexual selection hypothesis proposes that human sexual dimorphism of skin color should be positively correlated with distance from the equator. We tested the prediction that sexual dimorphism should increase with increasing latitude, using adult-only data sets derived from measurements with standard reflectance spectrophotometric devices. Our analysis failed to support the prediction of a positive correlation between increasing distance from the equator and increased sexual dimorphism. We found no evidence in support of the sexual selection hypothesis.     

Fusarium Species from the Fusarium fujikuroi Species Complex Involved in Mixed Infections of Maize in Northern Sinaloa,Mexico

Fusarium species belonging to the Fusarium fujikuroi species complex (FFSC) are associated with maize in northern Mexico and cause Fusarium ear and root rot. In order to assess the diversity of FFSC fungal species involved in this destructive disease in Sinaloa, Mexico, a collection of 108 fungal isolates was obtained from maize plants in 2007–2011. DNA sequence analysis of the calmodulin and elongation factor 1α genes identified four species: Fusarium verticillioides, F. nygamai, F. andiyazi and F. thapsinum (comprising 79, 23, 4 and 2 isolates, respectively). Differential distribution of Fusarium species in maize organs was observed, that is F. verticillioides was the most frequently isolated species from maize seeds, while F. nygamai predominated on maize roots. Mixed infections with F. verticillioides/F. thapsinum and F. verticillioides/F. nygamai were detected in maize seeds and roots, respectively. Pathogenicity assay demonstrated the ability of the four species to infect maize seedlings and induce different levels of disease severity, reflecting variation in aggressiveness, plant height and root biomass. Isolates of F. verticillioides and F. nygamai were the most aggressive. These species were able to colonize all root tissues, from the epidermis to the vascular vessels, while infection by F. andiyazi and F. thapsinum was restricted to the epidermis and adjacent cortical cells. This is the first report of F. nygamai, F. andiyazi and F. thapsinum infecting maize in Mexico and co‐infecting with F. verticillioides. Mixed infections should be taken into consideration due to the production and/or accumulation of diverse mycotoxins in maize grain.     

Pseudodicentric 22;Y translocation transmitted through four generations of a large family without phenotypic repercussion

The most frequent Y-autosome translocations involve an acrocentric autosome and they are frequently familial with neither phenotypic nor reproductive repercussion. However, different Y-autosome translocations have been related to infertility, due to abnormal pairing of the X and Y chromosomes at meiosis and an abnormal XY-body formation or by the disruption of the AZFs (Azoospermic Factor). Rare forms of Y-autosome translocations are those resulting in an unbalanced 45-chromosome karyotype that includes a dicentric Y+autosome chromosome. We describe a new case of a familial pseudodicentric 22;Y that is carried by 19 male members of a large family without phenotypic repercussion. Cytogenetic analysis, fluorescence in situ hybridisation (FISH) and subtelomeric Multiplex Ligation-dependent Probe Amplification (MLPA) assay have been performed. All male members of the family showed the karyotype 45,X,psu dic(22;Y)(p11.2;qter).ish psu dic(22;Y) (SRY+,DYZ3+,D14/D22Z1+). In conclusion, the presence of the dicentric chromosome in the male members of the family reported does not seem to interfere with the correct progression of spermatogenesis.     

Characterization of the MICA polymorphism by sequence-specific oligonucleotide probing

 A large number of diseases occur in association with specific HLA-B or –C alleles. Recently a new gene, termed major histocompatibility complex class I chain-related gene A (MICA), has been identified in close proximity to HLA-B. The function of this gene is still unknown, but, it is structurally related to HLA class I genes, is polymorphic, and is potentially associated with several diseases. Some DNA-based techniques have previously been described to type for MICA including sequencing and single-strand conformational polymorphism. In this paper we describe the application of sequence-specific oligonucleotide probe based typing for the analysis of the MICA gene. We used a set of 30 oligonucleotide probes to screen for the polymorphisms in exons 2, 3, and 4, which account for the 16 known alleles. We report here the typing results of MICA for 103 B-cell lines that have been well characterized for HLA and describe the linkage disequilibrium between MICA and HLA-B. Unequivocal MICA typing was achieved for 85 of the 103 cells tested, 6 cells gave ambiguous MICA types, and a further 12 cells showed patterns consistent with them expressing at least one new MICA allele. Received: 16 September 1998 / Revised: 15 December 1998