A linkage study in seven breast cancer families.

Seven breast cancer families are examined for evidence of linkage to a site in the region of 17q12-q21, by using five markers. The families constitute a subset of a larger series of familial breast cancer; the seven families were selected because constitutional DNA was available on informative members, either from clinical samples or extracted from paraffin blocks. Two-point lod scores are reported. The maximum lod score, 0.8824, is obtained with marker NM23 at theta = 0. This is clearly not significant in itself; however, when taken in context with evidence from existing reports, it provides support for linkage to this region.     

mtDNA variation of aboriginal Siberians reveals distinct genetic affinities with Native Americans.

The mtDNA variation of 411 individuals from 10 aboriginal Siberian populations was analyzed in an effort to delineate the relationships between Siberian and Native American populations. All mtDNAs were characterized by PCR amplification and restriction analysis, and a subset of them was characterized by control region sequencing. The resulting data were then compiled with previous mtDNA data from Native Americans and Asians and were used for phylogenetic analyses and sequence divergence estimations. Aboriginal Siberian populations exhibited mtDNAs from three (A, C, and D) of the four haplogroups observed in Native Americans. However, none of the Siberian populations showed mtDNAs from the fourth haplogroup, group B. The presence of group B deletion haplotypes in East Asian and Native American populations but their absence in Siberians raises the possibility that haplogroup B could represent a migratory event distinct from the one(s) which brought group A, C, and D mtDNAs to the Americas. Our findings support the hypothesis that the first humans to move from Siberia to the Americas carried with them a limited number of founding mtDNAs and that the initial migration occurred between 17,000-34,000 years before present.     

Presence of anisotropic (birefringent) crystalline structures in embryonic and juvenile monogonont rotifers

A systematic survey for the presence of birefringent (anisotropic) structures in rotifers was undertaken. Several common features of rotifers exhibit anisotropism (e.g. trophi & muscles). However, unusual anisotropic crystalline structures (ACS) were found in late stage embryos (i.e. possessing eyespots and trophi, and showing movement). ACS were found in 18 of 26 species of monogonont rotifers (comprising 11 genera of 5 families). In Sinantherina socialis, ACS were present in the lower gut as compact, spherical masses of minute crystals that slowly broke apart and disappeared within 20 hours of hatching. Although several authors have described the existence of refractive bodies in rotifers, to my knowledge this is the first report of their birefringent properties.     

Climate change disrupts core habitats of marine species

Driven by climate change, marine biodiversity is undergoing a phase of rapid change that has proven to be even faster than changes observed in terrestrial ecosystems. Understanding how these changes in species composition will affect future marine life is crucial for conservation management, especially due to increasing demands for marine natural resources. Here, we analyse predictions of a multiparameter habitat suitability model covering the global projected ranges of >33,500 marine species from climate model projections under three CO₂ emission scenarios (RCP2.6, RCP4.5, RCP8.5) up to the year 2100. Our results show that the core habitat area will decline for many species, resulting in a net loss of 50% of the core habitat area for almost half of all marine species in 2100 under the high-emission scenario RCP8.5. As an additional consequence of the continuing distributional reorganization of marine life, gaps around the equator will appear for 8% (RCP2.6), 24% (RCP4.5), and 88% (RCP8.5) of marine species with cross-equatorial ranges. For many more species, continuous distributional ranges will be disrupted, thus reducing effective population size. In addition, high invasion rates in higher latitudes and polar regions will lead to substantial changes in the ecosystem and food web structure, particularly regarding the introduction of new predators. Overall, our study highlights that the degree of spatial and structural reorganization of marine life with ensued consequences for ecosystem functionality and conservation efforts will critically depend on the realized greenhouse gas emission pathway.     

Regional differences in glutaminase activation by phosphate and calcium in rat brain: Impairment in aged rats and implications for regional glutaminase isozymes

Regional regulation of glutaminase by phosphate and calcium was examined in the temporal cortex (TCX), striatum (STR) and hippocampus (HIPP) from adult and aged male F344 rats. Phosphate-dependent glutaminase activity in adult rats was significantly lower (35–43%) in the HIPP (100 and 150 mM) and STR (150 mM) compared to PAG activity in the TCX. Phosphate activation in aged rats was 50–60% lower in the HIPP at concentrations greater than 25 mM compared to the aged TCX or STR. PAG activity in the TCX and STR was unaffected by age, but was significantly reduced (30–50%) in the HIPP from aged rats at phosphate concentrations of 25 mM and greater when compared to adult rats. In adult rats at concentrations of CaCl₂ above 1 mM, PAG activity was significantly lower (60–75%) in the STR and HIPP when compared to the TCX. In aged rats, PAG activity (1 mM CaCl₂) in the HIPP was significantly less (50%) than STR PAG activity in aged rats. Diminished PAG activity was seen only in the TCX (2.5 mM; 32%), and the HIPP (0.5 mM; 25% and 1 mM; 38%) at higher calcium concentrations compared to adult. Phosphate-independent calcium activation of PAG occurred in the HIPP but not in either the TCX or the STR. Addition of phosphate resulted in a synergistic activation of PAG in the STR and TCX, but not in the HIPP. These findings suggest that PAG is regionally regulated by phosphate and calcium, and this regulation is impaired in aged rats. These data also support the hypothesis that isozymes of PAG exist with different regulatory properties.Abbreviation PAG Phosphate-activated glutaminase - L-glutamine amidohydrolase EC 3.5.1.2 - TCX temporal cortex - STR striatum - HIPP hippocampus - F344 Fischer-344 rat     

Breakdown of different peptides byPrevotella (Bacteroides) ruminicola and mixed microorganisms from the sheep rumen

Several di-, tri-, and oligopeptides were incubated individually in vitro with rumen fluid from two sheep receiving a mixed grass hay/concentrate diet and with washed cells ofPrevotella (formerlyBacteroides)ruminicola M384 andP. ruminicola B₁4. The rates of breakdown of most peptides were similar in the rumen fluid from the two sheep. Acidic and proline-containing peptides tended to be more slowly degraded than neutral or basic peptides. The dipeptide at the N-terminus of higher peptides was observed as an early product of hydrolysis, confirming that a dipeptidyl aminopeptidase type of activity was present. The relative rates of breakdown of dipeptides byP. ruminicola were different from that of rumen fluid, but the hydrolysis of higher peptides followed a similar pattern, and dipeptides from the N-terminus were detected as early products.     

Influence of 1,10-phenanthroline and its analogues, other chelators and transition metal ions on dipeptidase activity of the rumen bacterium, Prevotella ruminicola

Prevotella ruminicola plays a prominent role in the breakdown of peptides in the rumen, a process which contributes to excessive ammonia production and inefficient nitrogen retention in ruminants. Various metal ions and chelators were examined to assess how the metal ion-dependent dipeptidase activity of P. ruminicola M384 might be inhibited. Using sonicated extracts, Cu²⁺, Cr²⁺ and Hg²⁺ were most inhibitory, decreasing Ala₂ breakdown to 15, 15 and 5% of control activity, whereas Co²⁺, Mn²⁺ and Zn²⁺ stimulated activity by 189, 30 and 26%, respectively. The chelators, EDTA, EGTA, TPEN and 1,10-phenanthroline, were inhibitory, as were several phenanthroline analogues. Among the stereoisomers of 1,10-phenanthroline tested, derivatives methylated on C-2 and C-9 were less effective than the parent molecule, but 3,4,7,8-tetramethyl,10-phenanthroline (TMP) was more inhibitory. Titration of the most effective inhibitors showed that EDTA, TPEN and TMP had similar potency and were effective at 0.1 mmol l⁻¹ and above. Thus some metal ions and chelators are potent inhibitors of P. ruminicola dipeptidase, although they are unlikely to be sufficiently specific to peptide metabolism to be useful in vivo.