Asymmetry of the phospholipid bilayer of rat liver endoplasmic reticulum

The phospholipids of intact microsomal membranes were hydrolysed 50% by phospholipase C of Clostridium welchii, without loss of the secretory protein contents of the vesicle, which are therefore not permeable to the phospholipase. Phospholipids extracted from microsomes and dispersed by sonication were hydrolysed rapidly by phospholipase C-Cl. welchii with the exception of phosphatidylinositol. Assuming that only the phospholipids of the outside of the bilayer of the microsomal membrane are hydrolysed in intact vesicles, the composition of this leaflet was calculated as 84% phosphatidylcholine, 8% phosphatidylethanolamine, 9% sphingomyelin and 4% phosphatidylserine, and that of the inner leaflet 28% phosphatidylcholine, 37% phosphatidylethanolamine, 6% phosphatidylserine and 5% sphingomyelin. Microsomal vesicles were opened and their contents released in part by incubation with deoxycholate (0.098%) lysophosphatidylcholine (0.005%) or treatment with the French pressure cell. Under these conditions, hydrolysis of the phospholipids by phospholipase C-Cl. welchii was increased and this was mainly due to increased hydrolysis of those phospholipids assigned to the inner leaflet of the bilayer, phosphatidylethanolamine and phosphatidylserine. Phospholipase A₂ of bee venom and phospholipase C of Bacillus cereus caused rapid loss of vesicle contents and complete hydrolysis of the membrane phospholipids, with the exception of sphingomyelin which is not hydrolysed by the former enzyme.     

Identification of 5,6,7,8-tetrahydropterin and 5,6,7,8-tetrahydrobiopterin in Drosophila melanogaster

Using reversed-phase high-performance liquid chromatography with electrochemical detection we have demonstrated the occurrence of 5,6,7,8-tetrahydropterin and 5,6,7,8-tetrahydrobiopterin in Drosophila melanogaster. The former is the first time that has been detected in vivo. The identification has been based on the retention times, hydrodinamic voltagrams and the differential concentration in three strains of Drosophila melanogaster. Compared to the wild type, the Punch2 mutant has diminished levels of both pteridines, whereas Henna-recessive3 lacks completely tetrahydropterin and has increased levels of tetrahydrobiopterin, as expected according to their biochemical lesions.     

Microbial characteristics of sandy soils exposed to diazinon under laboratory conditions

Changes in microbiological characteristics in response to diazinon, applied at three different dosages of 7, 35 and 700 mg kg^?1 soil, were studied in pots filled with sandy soils of different texture. The insecticide dosages corresponded to the maximum predicted environmental concentration (PEC) in field conditions and five or hundred times this rate, respectively. To ascertain these changes, activities of selected soil enzymes, numbers of some microbial populations and bacterial community structure (r/K-strategists) were determined. Acid phosphatase activity and concentrations of ammonium ions either increased or were unaffected by the diazinon dosages. In contrast, nitrate ions, alkaline phosphatase, urease and especially dehydrogenase activities decreased in both soils treated with the higher dosages of the insecticide. The diazinon treatments increased the numbers of culturable bacteria and fungi; however, N-fixing bacteria and nitrifiers (but not denitrifiers) were decreased in both soils. When the high concentration of diazinon (100-times PEC) was added to the loamy sand soil (LS), simulating an undiluted chemical spill, the bacterial community structure shifted towards domination of K-strategists over time. However, r-strategists dominated in the community exposed to the same dosage of the insecticide in the sandy loam soil (SL). Generally, SL soil characteristics were more suitable for microbial activity and growth than those of LS soil were. The results indicate that except a situation of undiluted spill diazinon seems to be a non-hazardous chemical for the culturable soil microorganisms when applied at recommended concentrations.     

TBCD Links Centriologenesis,Spindle Microtubule Dynamics,and Midbody Abscission in Human Cells

Microtubule-organizing centers recruit α- and β-tubulin polypeptides for microtubule nucleation. Tubulin synthesis is complex, requiring five specific cofactors, designated tubulin cofactors (TBCs) A–E, which contribute to various aspects of microtubule dynamics in vivo. Here, we show that tubulin cofactor D (TBCD) is concentrated at the centrosome and midbody, where it participates in centriologenesis, spindle organization, and cell abscission. TBCD exhibits a cell-cycle-specific pattern, localizing on the daughter centriole at G1 and on procentrioles by S, and disappearing from older centrioles at telophase as the protein is recruited to the midbody. Our data show that TBCD overexpression results in microtubule release from the centrosome and G1 arrest, whereas its depletion produces mitotic aberrations and incomplete microtubule retraction at the midbody during cytokinesis. TBCD is recruited to the centriole replication site at the onset of the centrosome duplication cycle. A role in centriologenesis is further supported in differentiating ciliated cells, where TBCD is organized into “centriolar rosettes”. These data suggest that TBCD participates in both canonical and de novo centriolar assembly pathways.     

Immunocytochemical detection of a murine leukemia virus-related nuclear antigen in mouse oocytes and early embryos.

The expression of murine leukemia virus (MuLV)-related antigens in oocytes and early embryos of Swiss mice was studied by the unlabeled antibody peroxidase-antiperoxidase method using an antiserum to the major core protein, p30, of AKR MuLV. This procedure resulted in an intense staining, at antibody dilutions up to 1:500, of the germinal vesicles of oocytes and the interphase nuclei of early embryos. Nuclear staining was restricted to a specific period of oocyte growth and embryo development. It developed gradually in oocytes having reached one third to one half the full-grown size and persisted until meiotic maturation. In early embryos, nuclear staining was present from the one-cell stage to the morula, but disappeared during transition from morula to blastocyst and was not seen in expanded blastocysts. Nuclear staining was abolished by absorption of the anti-p30 serum with detergent-disrupted virions of Gross(A), AKR, Kirsten and Moloney MuLV, and Kirsten MSV(MuLV), but not with the Friend and Rauscher strains of MuLV, the xenotropic BALB:virus 2, a mouse tropic and an amphotropic clone of wild mouse MuLV, or with FeLV and RSV. On the basis of these results, it is suggested that the nuclear antigen (termed germinal vesicle antigen) reacting with the anti-p30 serum is the product of a cellular gene having a normal function in early embryonic development, and that sequences related to this gene are incorporated into the genome of AKR-type MuLV.     

Cryptosporidiosis in the V Region Chile. III. Study of malnourished patients, 1985-1987

Frequency of infection by Cryptosporidium sp. in 1,039 faecal smears stained by Ziehl-Neelsen, obtained from undernourished patients of a Nutritional Recovery Center and an ambulatory undernourished center from the Fifth Region, Chile, were studied. All underwent a coproparasitological examination by the modified Telemann method. Thirty eight (3.7%) patients infected by the parasite were detected, with an overall frequency of 8.5% among patients of the Nutritional Recovery Center and 1.9% among the ambulatory patients; this difference was statistically significant. The highest percentage of positive results were detected among the younger milk feeding infants. Also the percentage of difference among these and the older milk feeding infants (3.7%) was statistically significant. Association of Cryptosporidium sp. and Giardia lamblia was observed in 6 ambulatory patients (2.3%).     

Other developments regarding the concept of energy in biological systems

In order to recognize the realizability of inputs with different physical natures through a component, Yoneda's Lemma is applied. The major utility of this Lemma is when the components produce only energy. From this, it is assumed that a new material input must exist which was not recognized in the original developments in biological systems representation. Moreover, simple transfers of energy, between objects, components, and among both objects and components are developed under the generic name; energetical evolution. Thus, energetical evolution appears as anew element in the abstract representation of biological systems. These new concepts are incorporated into a new abstract diagram and a newM _β category. This paper was made possible by a Fellowship from the Consejo Nacional de Investigaciones Científicas y Técnicas of the República Argentina.