Temporal genetic differentiation in cultured and natural beds of the brown mussel Perna perna (Mytilidae)

Perna perna is the most important cultivated mussel of Santa Catarina, Brazil, sustaining an important economic input for many local families. Natural stocks of P. perna are depleted by the extraction of adults and seeds for consumption and culture. The aim of the present study was to use the microsatellite locus pms-2 to study the variation of the genetic composition and diversity between natural and cultured stocks in samples of 2001 and 2005 from Penha, Santa Catarina. DNA was extracted from adductor muscle by Chelex/proteinase-K and phenol/chloroform protocols. Amplification by polymerase chain reaction was performed using specific primers for analyzing the pms-2 locus. Polymerase chain reaction products were submitted to vertical denatured 6% polyacrylamide gel electrophoresis and horizontal 2% agarose gel electrophoresis, and visualized by silver staining and ethidium bromide, respectively. Allele diversity and heterozygote deficiency were higher for samples of 2005 than for those of 2001. No significant genetic differentiation was found between natural and cultured stocks of 2001 by the chi(2) test, but G(2) (likelihood ratio) detected slight differences (I = 0.949; chi(2), P = 0.147; G(2), P = 0.046), while cultured and natural stocks of 2005 were very different (I = 0.798, P = 0.006). Between the years of 2001 and 2005, a large change in genetic composition was observed (I = 0.582; P < 0.001). Although nothing is known about natural changes in the genetic composition of this species with time, the results suggest a strong impact of human activities on natural stocks of P. perna, which is expected to be related to heavy extraction and farming.     

Leber congenital amaurosis and retinitis pigmentosa with Coats-like exudative vasculopathy are associated with mutations in the crumbs homologue 1 (CRB1) gene

Mutations in the crumbs homologue 1 (CRB1) gene cause a specific form of retinitis pigmentosa (RP) that is designated "RP12" and is characterized by a preserved para-arteriolar retinal pigment epithelium (PPRPE) and by severe loss of vision at age <20 years. Because of the early onset of disease in patients who have RP with PPRPE, we considered CRB1 to be a good candidate gene for Leber congenital amaurosis (LCA). Mutations were detected in 7 (13%) of 52 patients with LCA from the Netherlands, Germany, and the United States. In addition, CRB1 mutations were detected in five of nine patients who had RP with Coats-like exudative vasculopathy, a relatively rare complication of RP that may progress to partial or total retinal detachment. Given that four of five patients had developed the complication in one eye and that not all siblings with RP have the complication, CRB1 mutations should be considered an important risk factor for the Coats-like reaction, although its development may require additional genetic or environmental factors. Although no clear-cut genotype-phenotype correlation could be established, patients with LCA, which is the most severe retinal dystrophy, carry null alleles more frequently than do patients with RP. Our findings suggest that CRB1 mutations are a frequent cause of LCA and are strongly associated with the development of Coats-like exudative vasculopathy in patients with RP.     

Electric and magnetic fields of the closed depolarization front in the anisotropic myocardium

On the basis of the bidomain model of anisotropic myocardium, mathematical relationships for calculating the characteristics of the extracellular electric and magnetic fields outside a closed or open depolarization front were derived on the assumption that the generator and fields are axially symmetric with respect to the longitudinal direction of the fibres making up the excitable tissue. The spatial configuration of the fields was determined and quantitative estimates were obtained for the electric potential and magnetic induction caused solely by the macroscopic anisotropy of the myocardium tissue as a volume conductor.     

Rhythmical sporogenesis in Streptomyces colonies. A one-dimensional model

A one-dimensional model imitating the growth and zone formation of a colony of the radiant fungus streptomycete on a synthetic agar nutrient medium with pyruvate, glucose, or succinate as a limiting source of energy and carbon was considered. The key parameters were determined whose values depend on the composition of nutrient medium and environmental conditions.     

Coordinated expression of matrix Gla protein is required during endochondral ossification for chondrocyte survival

Matrix Gla protein (MGP) is a 14-kD extracellular matrix protein of the mineral-binding Gla protein family. Studies of MGP-deficient mice suggest that MGP is an inhibitor of extracellular matrix calcification in arteries and the epiphyseal growth plate. In the mammalian growth plate, MGP is expressed by proliferative and late hypertrophic chondrocytes, but not by the intervening chondrocytes. To investigate the functional significance of this biphasic expression pattern, we used the ATDC5 mouse chondrogenic cell line. We found that after induction of the cell line with insulin, the differentiating chondrocytes express MGP in a stage-specific biphasic manner as in vivo. Treatment of the ATDC5 cultures with MGP antiserum during the proliferative phase leads to their apoptosis before maturation, whereas treatment during the hypertrophic phase has no effect on chondrocyte viability or mineralization. After stable transfection of ATDC5 cells with inducible sense or antisense MGP cDNA constructs, we found that overexpression of MGP in maturing chondrocytes and underexpression of MGP in proliferative and hypertrophic chondrocytes induced apoptosis. However, overexpression of MGP during the hypertrophic phase has no effect on chondrocyte viability, but it does reduce mineralization. This work suggests that coordinated levels of MGP are required for chondrocyte differentiation and matrix mineralization.     

A new protein of human atrium

The partial amino acid sequence (23 amino acid residues) of a protein isolated from human atrium has been determined. The sequence homology shows that this protein belongs to the myosin 1 light chain family (an atrium-specific isoform).     

The effect of pH on biological activity of plant cytotoxin cauloside C

The effect of plant carboxyl-containing glycoside cauloside C upon eucaryotic cells has been studied. The glycoside interacts with cells as a pH-dependent cytotoxin and increases K+ leakage and Ca2+ uptake with strong action in acidic media Cell viability after glycoside action at acidic pH may be recovered by the shift of medium pH from 5.6 to 7.4. Directed transport of low molecular weight effectors such as cAMP and Ca2+ to human embryo fibroblasts under the action of cauloside C has been demonstrated. Calcium uptake is accompanied by about a twofold stimulation of fibroblast proliferation in serum-free medium. The manifestation of the effect depends on the strictly determined time of the 'open' state of the membrane permeability (2 min) and upon concentration of glycoside in the medium (1 ng/ml) Cauloside C-stimulated Ca-transport is not blocked by Ca-channel blockers such as verapamil, diltiasem, and nitrendipine (all at a concentration of 1 x 10(-6) M) but these blockers inhibit cauloside C-stimulated proliferation of fibroblasts. We conclude that stimulation of fibroblast proliferation is caused by activation of membrane associated Ca-channels at the expense of calcium, incorporated into cells with cauloside C. The use of cauloside C as a new biochemical tool for cell permeabilisation is suggested.