Type I Antifreeze Proteins Enhance Ice Nucleation above Certain Concentrations

In this study, we examined the effects that antifreeze proteins have on the supercooling and ice-nucleating abilities of aqueous solutions. Very little information on such nucleation currently exists. Using an automated lag time apparatus and a new analysis, we show several dilution series of Type I antifreeze proteins. Our results indicate that, above a concentration of ∼8 mg/ml, ice nucleation is enhanced rather than hindered. We discuss this unexpected result and present a new hypothesis outlining three components of polar fish blood that we believe affect its solution properties in certain situations.     

MPTP, MPP+ and mitochondrial function

1-Methyl-4-phenylpyridinium (MPP+), the putative toxic metabolite of the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), inhibited NAD(H)-linked mitochondrial oxidation at the level of Complex I of the electron transport system. MPTP and MPP+ inhibited aerobic glycolysis in mouse striatal slices, as measured by increased lactate production; MPTP-induced effects were prevented by inhibition of monoamine oxidase B activity. Several neurotoxic analogs of MPTP also form pyridinium metabolites via MAO; these MPP+ analogs were all inhibitors of NAD(H)-linked oxidation by isolated mitochondria. 2'-Methyl-MPTP, a more potent neurotoxin in mice than MPTP, was also more potent than MPTP in inducing lactate accumulation in mouse brain striatal slices. Overall, the studies support the hypothesis that compromise of mitochondrial oxidative capacity is an important factor in the mechanisms underlying the toxicity of MPTP and similar compounds.     

The structure of toxic protein, the mistletoe lectin, at different pH: the study using intrinsic fluorescence method

The effects of pH on the conformation of mistletoe lectin I and its isolated A- and B-subunits has been investigated by using the methods of intrinsic fluorescence. By the denaturating action of guanidine hydrochloride and the influence of the quenchers (I-, Cs+, acrylamide) the structural stability of the native protein and its isolated subunits was estimated. Treatment of the protein with the denaturant and quenchers revealed its different structure at pH 7.0 and 4.0. At pH 4.0 tryptophan residues become more accessible to quenchers, positive charge of the surrounding area increases and the protein becomes more stable to the action of denaturant. The structure of the isolated A- and B-chains of mistletoe lectin I differs considerably from that of the whole protein: a) its stability to the action of guanidine hydrochloride is lower; b) it depends on the ionic strength of the solvent; c) it is characterized by increased accessibility of tryptophan residues to quenchers (for B-chain). Differences between the conformations of the isolated chains at pH 7.0 and 4.0 are marked more strongly; moreover, at pH 4.5 the B-chain undergoes structural transition. The possible relationship between structural peculiarities of mistletoe lectin I and the mechanism of its transmembrane transfer is discussed.     

A variable region gene subfamily encoding T cell receptor beta-chains is selectively conserved among mammals

Studies of murine T cell receptor genes indicate that the VT beta repertoire, in contrast to the large VT alpha, VH, and VK repertoires, is limited to approximately 21 genes. Large differences between the various VT beta sequences allow classification into distinct subfamilies consisting of one or few members. The VT beta sequence of a gene, RTB92, expressed in a rabbit T cell line is most closely related to a VT beta gene expressed in the human cell line Molt-4. Genomic blots with RTB92 VT beta region used as probe indicated conservation of related VT beta gene subfamilies in man and pig, but no related sequences were seen in rat, mouse, or hamster. The relationship among these VT beta genes mirrors similarities and differences in MHC genes of the compared species and suggests coordinate evolution of these functionally related gene families. The constant region of RTB92 was shown to be rabbit CT beta 2 by reference to genomic clones. Comparisons with constant region sequences of human and murine CT beta 1 and CT beta 2 chains reveal no similarities in amino acid or nucleic acid sequence in the coding region characteristic of the respective isotypes. Intraspecies homologies between CT beta 1 and CT beta 2 sequences were much greater than those between CT beta 1 or CT beta 2 from other species. By contrast, comparisons of JT beta and 3' untranslated region sequences showed significant interspecies conservation of sequences in the beta 1 and in the beta 2 regions.     

Localization of C4 genes within the HLA complex by molecular genotyping

Segregation of the complement component, C4, was analyzed in six families that each included an individual who inherited an HLA haplotype where a crossover event had occurred in the region between HLA-B and HLA-DR. Two cDNA clones corresponding to the C4 gene were utilized as probes in Southern blot analysis of DNA from members of each family. Restriction fragment length polymorphisms (RFLP) were observed and were assigned to haplotypes. In one family RFLP, hybridizing with the C4 probes, segregrated with HLA-B, and in four families RFLP segregated with HLA-DR; one family was not informative in this respect. These analyses have made it possible to localize the genes for C4 between HLA-B and HLA-DR by molecular genotyping and to characterize three different genomic configurations of C4 genes by limited restriction mapping.Abbreviations RFLP restriction fragment length polymorphisms - LCL lymphoblastoid cell lines     

Molecular genotyping of human T-cell antigen receptor variable gene segments

The gene complex encoding the chain of the T-cell antigen receptor (Tcr) in man was previously reported to contain a restriction fragment length polymorphism (RFLP) involving a single Bgl II site adjacent to the second constant region gene. This RFLP allowed assignment of Tcr genotypes in certain human families. In the present study, two different RFLP in a V gene family were detected using the murine probe V8.1 in genomic DNA samples digested with the restriction endonucleases Hind III and Bam HI. Use of these RFLP to mark the V gene complex allowed complete haplotype assignment in four of seven families studied and provided support for linkage of the V gene complex to the constant region genes. Different combinations of the C and two V region markers can result in eight possible distinct haplotypes. The observation of all but one of the eight possible haplotypes in parents of the families studied suggests that recombination events occur between the C and V region and among members of the V region subfamily marked by the V8.1 probe. These markers can be used for mapping studies of the V gene complex in man and will allow an appraisal of possible associations between Tcr genes and disease susceptibility.Abbreviations used in this paper: Tcr T-cell antigen receptor - RFLP restriction fragment length polymorphism - C2 second Tcr constant region gene - V Variable - C constant - J joining - D diversity     

Exploring the legacy of African and Indigenous Caribbean admixture in Puerto Rico

Objectives

From an anthropological genetic perspective, little is known about the ethnogenesis of African descendants in Puerto Rico. Furthermore, historical interactions between Indigenous Caribbean and African descendant peoples that may be reflected in the ancestry of contemporary populations are understudied. Given this dearth of genetic research and the precedence for Afro-Indigenous interactions documented by historical, archeological, and other lines of evidence, we sought to assess the biogeographic origins of African descendant Puerto Ricans and to query the potential for Indigenous ancestry within this community.

Materials and Methods

Saliva samples were collected from 58 self-identified African descendant Puerto Ricans residing in Puerto Rico. We sequenced whole mitochondrial genomes and genotyped Y chromosome haplogroups for each male individual (n = 25). Summary statistics, comparative analyses, and network analysis were used to assess diversity and variation in haplogroup distribution between the sample and comparative populations.

Results

As indicated by mitochondrial haplogroups, 66% had African, 5% had European, and 29% had Indigenous American matrilines. Along the Y chromosome, 52% had African, 28% had Western European, 16% had Eurasian, and, notably, 4% had Indigenous American patrilines. Both mitochondrial and Y chromosome haplogroup frequencies were significantly different from several comparative populations.

Discussion

Biogeographic origins are consistent with historical accounts of African, Indigenous American, and European ancestry. However, this first report of Indigenous American paternal ancestry in Puerto Rico suggests distinctive features within African descendant communities on the island. Future studies expanding sampling and incorporating higher resolution genetic markers are necessary to more fully understand African descendant history in Puerto Rico.     

Henipaviruses and lyssaviruses target nucleolar treacle protein and regulate ribosomal RNA synthesis

The nucleolus is a common target of viruses and viral proteins, but for many viruses the functional outcomes and significance of this targeting remains unresolved. Recently, the first intranucleolar function of a protein of a cytoplasmically-replicating negative-sense RNA virus (NSV) was identified, with the finding that the matrix (M) protein of Hendra virus (HeV) (genus Henipavirus, family Paramyxoviridae) interacts with Treacle protein within nucleolar subcompartments and mimics a cellular mechanism of the nucleolar DNA-damage response (DDR) to suppress ribosomal RNA (rRNA) synthesis. Whether other viruses utilise this mechanism has not been examined. We report that sub-nucleolar Treacle targeting and modulation is conserved between M proteins of multiple Henipaviruses, including Nipah virus and other potentially zoonotic viruses. Furthermore, this function is also evident for P3 protein of rabies virus, the prototype virus of a different RNA virus family (Rhabdoviridae), with Treacle depletion in cells also found to impact virus production. These data indicate that unrelated proteins of viruses from different families have independently developed nucleolar/Treacle targeting function, but that modulation of Treacle has distinct effects on infection. Thus, subversion of Treacle may be an important process in infection by diverse NSVs, and so could provide novel targets for antiviral approaches with broad specificity.     

Effects of the egg incubation environment on turtle carapace development

Developing organisms are often exposed to fluctuating environments that destabilize tissue-scale processes and induce abnormal phenotypes. This might be common in species that lay eggs in the external environment and with little parental care, such as many reptiles. In turtles, morphological development has provided striking examples of abnormal phenotypic patterns, though the influence of the environment remains unclear. To this end, we compared fluctuating asymmetry, as a proxy for developmental instability, in turtle hatchlings incubated in controlled laboratory and unstable natural conditions. Wild and laboratory hatchlings featured similar proportions of supernumerary scales (scutes) on the dorsal shell (carapace). Such abnormal scutes likely elevated shape asymmetry, which was highest in natural nests. Moreover, we tested the hypothesis that hot and dry environments cause abnormal scute formation by subjecting eggs to a range of hydric and thermal laboratory incubation regimes. Shape asymmetry was similar in hatchlings incubated at five constant temperatures (26–30°C). A hot (30°C) and severely Dry substrate yielded smaller hatchlings but scutes were not overtly affected. Our study suggests that changing nest environments contribute to fluctuating asymmetry in egg-laying reptiles, while clarifying the conditions at which turtle shell development remains buffered from the external environment.