Isolation and characterization of collagen messenger RNA*.

Chick embryo collagen-synthesizing polysomes were isolated by differential centrifugation. RNA extracted from these particles was chromatographed in oligo(dT)-cellulose solumns and the mRNA thus obtained characterized as collagen mRNA by its electrophoetical mobility in acrylamide gels (equivalent to 1.05 x 10-6 daltons) and its effect upon a cell-free system derived from Krebs ascites tumor cells. The incorporation of 3H-proline was markedly dependent upon rabbit reticulocyte initiation factors and inhibited by initiation inhibitors such as aurintricaboxilate and pyrocatechol violet. The incorporation product was characterized as collagen by its lack of tryptophan, digestibility by purified bacterial collagenase, and by its co-chromatography with unlabled chick collagen in Sephadex G-200 and CM-cellulose columns.     

Cortical cell fluxes and transport to the stele in excised root segments of Allium cepa L.

Summary From compartmental analysis of radioisotope elution measurements, concentrations and fluxes of Mg²⁺ were estimated for cortical cells in root segments of onion, Allium cepa L., relative to a complete nutrient solution containing 0.25 mM Mg²⁺. Five compartments for Mg²⁺ in the cortex were found and, in order of increasing rates of exchange, identified with the vacuoles and the cytoplasm of the cortical parenchyma, the Donnan free space, the water free space, and the superficial film of solution on the segments. With the Ussing-Teorell flux ratio equation as the criterion, it was concluded that Mg²⁺ entered the cytoplasm passively and was actively pumped back across the plasmalemma. Mg²⁺ concentration in the vacuole could be estimated only as lying between wide limits (1.3 to 14.3 eq ml^-1), but whatever the concentration within this range, it was concluded that Mg²⁺ was passively distributed across the tonoplast. Net flux was zero and the vacuolar concentration commensurate with this was found to be 6.6 eq ml^-1. The transported fraction of total efflux, appearing at the segment cut ends, was estimated separately. Magnesium was found to be transported almost exclusively in the basipetal direction.     

A note on the screening of dried shrimps, shrimp paste and raw groundnut kernels for aflatoxin-producing Aspergillus flavus

All of 33 samples of dried shrimps, shrimp paste, peanut butter and raw groundnut kernels were contaminated with fungi. Aspergillus and Penicillium spp. were the predominant types in dried shrimps and raw groundnut kernels but no Aspergillus spp. were present in peanut butter or shrimp paste samples. Among 81 Aspergillus isolates obtained from dried shrimps and raw groundnut kernels, 10 were A. flavus/A. parasiticus, of which five were potential aflatoxin-producing A. flavus strains. No aflatoxins were detected in the food samples although some were visibly mouldy and some had high mould counts. The occurrence of aflatoxin-producing strains of A. flavus in dried shrimps and raw groundnut kernels warrants further investigation of these foods and their products as potentially significant sources of aflatoxins.     

Characterization of primary amino acid sequence of human complement control protein factor I from an analysis of cDNA clones.

A cDNA clone of the mRNA coding for the human complement system control protein Factor I has been isolated. The predicted amino acid sequence obtained from the DNA sequence demonstrates a protein consisting of a heavy chain (Mr 35,400) linked to a light chain (Mr 27,600), both of which contain three sites for N-linked glycosylation. The light chain has clear homology with other serine proteinases, most notably in the region of the catalytically active and structurally important amino acids and shares some of the features characteristic of the plasminogen activators. The heavy chain has a clear 'mosaic' nature typical of the plasma serine proteinases; in particular it contains class A and class B LDL (low-density lipoprotein) receptor repeats with conserved cysteine residues similar to those found in other complement proteins.     

Coliphage counts: are they necessary to maintain drinking-water safety?

Summary Samples of drinking water collected from three different sources in Singapore University were tested for total coliforms, fecal coliforms and coliphage. Five samples from each site were tested with and without dechlorination procedures. Results showed that nine of the samples were positive for coliphage while being negative for total and fecal coliforms, and another nine samples were positive for all three parameters. In no instance was total coliform and fecal coliform counts found without coliphage also being found. The presence of coliphage in these waters indicates that other viruses might be present.

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Resumen Se efectuaron recuentos de coliformes totales, coliformes fecales y colifagos de muestras de agua potable recogidas de tres lugares distintos de la Universidad de Singapur. Se analizaron cinco muestras de cada sitio, con y sin proceso de desclorinización. Nueve de los recuentos efectuados dieron positivo para colifagos mientras que coliformes totales fecales eran negativos, nueve muestras más dieron recuentos positivos para los tres parámetros. No se observó en ningún caso un recuento que dando positivo para coliformes totales y fecales no diera colifagos positivo. La presencia de colifagos en estas aguas indica la posible existencia de otros virus.

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Résumé Des échantillons d'eau potable, récoltés en trois points différents de l'Université de Singapoure ont été analysés pour les coliformes totaux, les coliformes fécaux et les coliphages. Cinq échantillons de chaque site ont été testés avec et sans une procédure de déchloration. Les résultats montrent que 9 des échantillons étaient positifs pour les coliphages tout en étant négatifs pour les coliformes totaux et fécaux, tandis que 9 autres échantillons étaient positifs pour les 3 tests. En aucun cas, on n'a démontré de coliformes totaux et de coliformes fécaux sans trouver également des coliphages. La présence de coliphages dans ces eaux indiquent que d'autres virus peuvent bien être présents.

     

Tempo and mode of concerted evolution in the L1 repeat family of mice

A 300-bp DNA sequence has been determined for 30 (10 from each of three species of mice) random isolates of a subset of the long interspersed repeat family L1. From these data we conclude that members of the L1 family are evolving in concert at the DNA sequence level in Mus domesticus, Mus caroli, and Mus platythrix. The mechanism responsible for this phenomenon may be either duplicative transposition, gene conversion, or a combination of the two. The amount of intraspecies divergence averages 4.4%, although between species base substitutions accumulate at the rate of approximately 0.85%/Myr to a maximum divergence of 9.1% between M. platythrix and both M. domesticus and M. caroli. Parsimony analysis reveals that the M. platythrix L1 family has evolved into a distinct clade in the 10-12 Myr since M. platythrix last shared a common ancestor with M. domesticus and M. caroli. The parsimony tree also provides a means to derive the average half-life of L1 sequences in the genome. The rates of gain and loss of individual copies of L1 were estimated to be approximately equal, such that approximately one-half of them turn over every 3.3 Myr.      

Apparent suicidal inactivation of DNA polymerase by adenosine 2',3'-riboepoxide 5'-triphosphate.

Adenosine 2',3'-riboepoxide 5'-triphosphate (epoxyATP) has been found to be a suicidal inactivator of DNA polymerase I from Escherichia coli by the following criteria. Inactivation is complete, is first order in enzyme activity, and shows saturation kinetics with an apparent KD of 30 +/- 10 micron for epoxy ATP. This KD is comparable to the KM of the substrate dATP. The t1/2 for inactivation is 1.3 min. Inactivation requires Mg2+ and the complementary template. The enzyme is protected by dATP but not by an excess of template. Gel filtration of the reaction mixture after inactivation with [3H]epoxy ATP results in the comigration of E. coli DNA polymerase I, the tritium-labeled inactivator, and the DNA template. The stoichiometry of binding approaches 1 mol of [3H]epoxy nucleotide per mol of inactivated enzyme. These results are consistent with the hypothesis that epoxy ATP initially serves as a substrate for the polymerase reaction, elongating the DNA chain by a nucleotidyl unit, and subsequently alkylates an essential base at the primer terminus binding site of the enzyme. Epoxy ATP also inactivates human and viral DNA polymerases but not E. coli RNA polymerase or rabbit muscle pyruvate kinase. Hence epoxy ATP may be a specific suicide reagent for DNA polymerases.     

Behaviour of does and leverets of the European hare (Lepus europaem) whilst nursing

After birth in one particular place, the leverets of a litter dispersed after a few days. In the evening, the leverets were observed gathering at, or near, their birth place to await nursing. There the doe would arrive later, about one hour after sunset, to nurse the young gathered there. Individual recognition between leverets and their doe seemed of no importance, and meeting was dependent on time and place. The young were nursed for only a few minutes and their urine, excreted during nursing, was licked up by the doe, which finished nursing by jumping away from the young. The leverets dispersed again and kept apart from each other until they gathered again the next evening. Usually leverets are nursed for four weeks, but longer nursing periods were found in the last litters of the breeding season. The nursing behaviour is probably adapted to prevent discovery of leverets by predators.     

A Three-Dimensional Stereotaxic MRI Brain Atlas of the Cichlid Fish Oreochromis mossambicus

The African cichlid Oreochromis mossambicus (Mozambique tilapia) has been used as a model system in a wide range of behavioural and neurobiological studies. The increasing number of genetic tools available for this species, together with the emerging interest in its use for neurobiological studies, increased the need for an accurate hodological mapping of the tilapia brain to supplement the available histological data. The goal of our study was to elaborate a three-dimensional, high-resolution digital atlas using magnetic resonance imaging, supported by Nissl staining. Resulting images were viewed and analysed in all orientations (transverse, sagittal, and horizontal) and manually labelled to reveal structures in the olfactory bulb, telencephalon, diencephalon, optic tectum, and cerebellum. This high resolution tilapia brain atlas is expected to become a very useful tool for neuroscientists using this fish model and will certainly expand their use in future studies regarding the central nervous system.