Triphenyltin as inductor of mitochondrial membrane permeability transition

The effect of triphenyltin on mitochondrial Ca²⁺ content was studied. It was found that this trialkyltin compound induces an increase in membrane permeability that leads to Ca²⁺ release, drop of the transmembrane potential, and efflux of matrix proteins. Interestingly, cyclosporin A was unable to inhibit triphenyltin-induced Ca²⁺ release. Based on these results it is proposed that the hyperpermeable state is produced by modification of 2.25 nmol of membrane thiol groups.     

A toxic dinoflagellate bloom and PSP production associated with upwelling in Golfo Nuevo,Patagonia, Argentina

In 1980 Paralytic Shellfish Poison (PSP) was detected for the first time in Patagonia (Argentina), and has been recurring since during spring and summer.Human intoxicantions were recorded during the 1987/88 sumer due to ingestion of mussles. In January, concentrations of 750 000 cell l^–1 were observed, decreasing to 3100 cells l^–1 twenty days later. At the same time, values of 66 150.Mouse Unit (MU) 100 g^–1 of meat were measured in Aulacomya ater (a bivalve mollusk). A decrease in the concentration of toxic plankton resulted in a concomitant decrease in MU values. The mean detoxification time was 7.6 days. However, mussels retained toxicity up to 50 days after the disappearance of cells.The upwelling of cold waters at the beginning of summer, could have been one of the causes that favoured a bloom of Alexandrium excavatum and of Prorocentrum micans. In March, an abundance of the diatom Skeletonema costatum coincided with high concentrations of silicate.     

Characterization of an improved reaction center preparation from the photosynthetic green sulfur bacterium Chlorobium containing the FeS centers FA and FB and a bound cytochrome subunit.

A photosynthetic reaction center complex was prepared from the green sulfur bacterium Chlorobium by solubilization of chlorosome-depleted membranes with lauryl maltoside, followed by anion-exchange chromatography and molecular sieve chromatography. The purified complex was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, optical spectroscopy, and EPR spectroscopy. The major bands migrated at apparent molecular masses of 50, 42, and 32 kDa (heme-staining) and additional weaker bands at 22, 15, and 12 kDa. The isolated reaction center complex contained about 40 bacteriochlorophyll alpha molecules per primary electron donor, P840, assayed by photooxidation. It was competent in stable low-temperature photoreduction of the FeS centers FA and FB. The spectra of these acceptors and their low-temperature photochemistry in the purified complex were the same as found in intact Chlorobium membranes and similar to what had been described for photosystem I from plants. Membrane-bound cytochrome c553 copurified with the reaction center complex. A ratio of about four hemes per P840 was determined. This result indicates that cytochrome c553 that is closely associated with the reaction center is a tetraheme cytochrome, as described for some purple bacteria.     

Complementation of the cs dis2-11 cell cycle mutant of Schizosaccharomyces pombe by a protein phosphatase from Arabidopsis thaliana.

The activities of type I protein phosphatases play a central role in eukaryotic cell cycle control. Here, we report the cloning and characterization from the flowering plant Arabidopsis thaliana of a cDNA clone named PP1-At which is highly homologous to protein phosphatase 1. The deduced amino acid sequence of PP1-At shows that the PP1-At protein is 318 amino acid residues long and has a molecular weight of 35,298 Da. The PP1-At protein has strong similarity to all other known protein phosphatase type 1 catalytic subunits. Approximately 62% of the amino acids are identical to type 1 protein phosphatases of rabbit, mouse, Saccharomyces cerevisiae and Schizosaccharomyces pombe. RNA blot analysis revealed a single mRNA species of approximately the same size as the cDNA isolated. The PP1-At-encoded mRNA of 1.3 kb is abundant in most vegetative Arabidopsis tissues, with the lowest level of expression in leaves. When transferred to the fission yeast S.pombe, the PP1-At-encoded protein can rescue a semidominant mutant, cold sensitive (cs) dis2-11, which under nonpermissive conditions is unable to complete chromosome disjunction.     

Buffer capacity of cotton cells and effects of extracellular pH on growth and somatic embryogenesis in cotton cell suspensions

Summary This research was designed to: a) characterize the normal pH changes that occur when cotton cell are grown in culture; b) determine if cotton cells can regulate the pH of their extracellular medium; and c) explore the effects of starting pH on cellular differentiation in culture, including formation of somatic embryos. When an aliquot of cotton cell suspension culture (Gossypium hirsutum L. cv Coker 312) was inoculated into fresh Murashige and Skoog (MS) medium at pH 4.5, the pH stabilized near 5.5 during the log phase of growth and then rose to pH 7.25. Cotton cells actively adjust medium with initial pH between 3 and 8 to near pH 5.5 in the early culture period. By acid/base titration, it has been shown that living cotton cells increase the buffer capacity of water and MS medium. Therefore, the metabolic activity of living cells accounts for the adjustment and stabilization of pH during the log phase of growth. The starting pH of the culture medium affects longterm viability, growth, and differentiation of the cells; pH 3 to 5 is best for cell viability, pH 3 to 4 enhances cell elongation; and pH 4, 7, or 8 stimulates somatic embryogenesis. Cultured cotton cells and the pH of their extracellular medium are in a complex, interactive relationship. This study was supported by the Texas Advanced Technology Program and the USDA-ARS. The journal no. for this paper is T-4-280, The College of Agriculture, Texas Tech University.     

Photosynthetic reaction centres: variations on a common structural theme?

From their hybrid properties, the reaction centres of green sulphur bacteria and heliobacteria seem to be the missing links between the two branches of the reaction centre family, typified by higher plant photosystem I and the purple bacterial reaction centre. This suggests that all of the diverse types of photosynthetic reaction centres have closer structural resemblances than was previously thought.     

HLA-DQα allele and genotype frequencies in various human populations determined by using enzymatic amplification and oligonucleotide probes

Allele and genotype frequencies at the HLA-DQ alpha locus have been determined by the use of polymerase chain reaction (PCR) amplification and nonradioactive oligonucleotide probes. The probes define six alleles and 21 genotypes in a dot-blot format. A total of over 1,400 individuals from 11 populations has been typed by two different laboratories using this method. In contrast to some variable-number-of-tandem-repeat markers that have been used for identity determination, DQ alpha genotype frequencies do not deviate significantly from Hardy-Weinberg equilibrium in all populations studied. The distribution of alleles varies significantly between most of these populations. In Caucasians, the allele frequencies range from 4.3% to 28.5%. In this population, the power of discrimination is .94, and, for paternity determination, the power of exclusion is .642. These population data will allow the use of the HLA-DQ alpha marker in paternity determination, the analysis of individual identity in forensic samples, and anthropological studies.     

Seasonal changes in the prepuce of adult Fallow deer (Dama dama) and its probable function as a scent organ

The penis sheath of adult Fallow deer, which is an integral part of the abdominal skin, extends from the scrotum to the preputial orifice. Marked seasonal changes occur in the prepuce. In the non-rutting animal, the outer region of the prepuce, which is similar in structure to normal skin, passes through a transition zone characterized by a corrugated epidermis and multi-lobed sebaceous glands, before becoming the inner-sheath lining. Just before the rut, hypertrophy of the epidermis of the transition zone occurs with the formation of keratinous villi-like processes. The sebaceous glands enlarge and lipid production is increased. At the beginning of the rut, the transition zone everts and becomes located on the outer periphery of the prepuce, which now has the appearance of a dark brown, coarse, short-haired brush. At this stage, the animal and its voided urine develop a characteristic pungent odour whereas urine aspirated from the bladder is relatively odourless. After the rut, the prepuce returns to normal, the keratinous papillae being shed. It is suggested that the strong smelling rutting odour of male Fallow deer helps to synchronize oestrus in the females. The gross hyperkeratosis and associated epidermal hypertrophy of the prepuce produces a sponge-like mass which may help in scent production and dispersal.     

Apparent “in situ” clone of cytogenetically marked ataxia-telangiectasia lymphocytes

Summary Six adjacent metaphases, each with the same cytogenetic aberration of a group D chromosome, most probably a No. 14, were observed in a field of a slide from a 96-hour culture of lymphocytes from an individual with ataxia-telangiectasia (AT). None of the 304 orther metaphases examined from this or other simultaneous cultures of this individual showed such an aberration. It seems most likely that an in situ marked clone has been observed and this supports interpretation of consistent cytogenetic abnormalities in those with AT as having clonal origin. The method of slide preparation employed which involves placing, rather than dropping, the cell suspension on the slide may facilitate detection of in situ clones.