Anatomy of the arteries of the head in the domestic fowl

The anatomy of the cephalic arterial system in the fowl was studied in 24 specimens by means of latex-injected preparations and by dissection. Branches of the external carotid artery supply the extracranial regions. The vertebral arteries unite with the occipitals and have no major communications with the encephalic system. Blood can reach the brain directly from the internal carotid artery and indirectly by way of the extensive cerebral-extracranial anastomoses; especially prominent are those to the palatine and sphenomaxillary arteries from the maxillary and facial branches of the external carotid artery. A large external ophthalmic artery supplies the temporal rete and eye musculature, and an internal ophthalmic artery links the rete and the cerebral vessels. The circle of Willis is incomplete both anteriorly and posteriorly; the anterior cerebral arteries do not unite and the basilar artery is generally asymmetrical in origin. The basilar artery tapers caudally and is continued as the ventral spinal artery.     

Substrate specificities in class A beta-lactamases: preference for penams vs. cephems. The role of residue 237

Site saturation mutagenesis has been carried out at Ala-237 in RTEM-1 beta-lactamase to assess the role of this site in modulating differences in specificity of beta-lactamases for penams vs. cephems as substrates. (An Ala-237 Thr mutation had previously been shown to increase activity on cephems by about 30-80%.) Screening of all 19 possible mutants on penams and cephems revealed the even more active Ala-237 Asn mutant. Detailed kinetic analysis shows that this mutant has about four times the activity toward cephalothin and cephalosporin C as the wild-type enzyme. Both mutations reduce the activity toward penams to about 10% that of RTEM-1 beta-lactamase and lower by about 5 degrees C the temperature at which the enzyme denatures. Functional properties of the other mutants have also been surveyed. The most interesting aspect of these results is that two quite disparate amino acids, threonine and asparagine, when introduced for Ala-237, cause such similar changes in enzyme specificity while more similar residues do not alter the catalytic properties of the enzyme to such a significant degree.     

Fermentation of potato mash,potato mash/maltrin mixtures,maltrin and wheat starch usingZymomonas mobilis

Summary Potato mash, potato mash/maltrin mixtures, maltrin and wheat starch have been fermented with 95 to 98% conversion efficiencies. Highest ethanol yields obtained were 13.5% (v/v) in 24 h. The addition of 20% backset (= thin stillage) or change of pre-culture conditions did not affect the process.

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Fermentation de purée de pommes de terre seule et en mélange avec la maltrine, de maltrine seule et d'amidon de froment par Zymomonas mobilis

Résumé On fermente la purée de pommes de terre seule et en mélange avec la maltrine ainsi que l'amidon de froment jusqu'à 95 à 98% d'efficacité de conversion. Les rendements les plus élevés en éthanol sont de 13.5% (v/v) en 24 h. Le recyclage de 20% de résidu fluide de fermentation ou le changement des conditions de préculture n'affectent pas le processus.

     

A comparison of within-plant karyological heterogeneity between agamospermous and sexualTaraxacum (Compositae) as assessed by the nucleolar organiser chromosome

Morphological variation for the NOR chromosome was studied for four half-siblings of a sexual outbreedingTaraxacum, for three siblings of the obligate agamospermT. pseudohamatum, and for two individuals of the agamospermT. brachyglossum. No rearrangement was detected for the 113 chromosomes of sexuals, or for 41 chromosomes of two agamospermous individuals. In the other three agamospermous individuals, 3/16, 5/50, and 5/20 chromosomes showed evidence of chromosomal rearrangement. The majority of rearrangement events (10/13) occurred to the satellite rather than to the body of the NOR-chromosome. It is considered that such high levels of somatic chromosomal rearrangement in agamospermousTaraxacum may be the result of activity by transposable genetic elements. This recombination may be of selective advantage to asexual plants which cannot generate genetic variability through the sexual process.     

Rapid recovery of Echinococcus granulosus following 'successful' albendazole therapy in a gerbil model

Peritoneal Echinococcus granulosus in gerbils was treated with albendazole. Both early and late infections were studied; response to albendazole therapy and the ability of the parasite to recover after treatment was found to depend on dose and length of therapy. Even after treatment at 50 mg/kg for 2 months late infections retained the ability to recover over 3 months.     

Boron deficiency in cultured pine cells : quantitative studies of the interaction with ca and mg

A pronounced interaction between calcium, magnesium, and boron was found in growth studies with Pinus radiata cell cultures. Quantitative isoactivity data for the interaction was analyzed in terms of selected simple and plausible theoretical models. The data was found to be consistent with a model in which a critical acceptor molecule is activated only by binding both Ca and B at separate sites; Mg competitively displaces Ca to inactivate the acceptor. It was found that B is, surprisingly, not bound strongly (K_diss = 450 ± 80 micromolar) and that the affinity for Ca is two orders of magnitude stronger than for Mg. Therefore only a small proportion of the acceptor will be boronated under natural conditions. Moderate levels of mannitol were found to aggravate B deficiency due to its effective removal by direct chemical complexation. At higher concentrations of mannitol (or other sugars), where osmotic contribution is significant, little B was needed to overcome growth inhibition—a result consistent with B having a primary role in cell wall biosynthesis.