Genes for the biosynthesis of spinosyns: applications for yield improvement in Saccharopolyspora spinosa

Spinosyns A and D are the active ingredients in an insect control agent produced by fermentation of Saccharopolyspora spinosa. Spinosyns are macrolides with a 21-carbon, tetracyclic lactone backbone to which the deoxysugars forosamine and tri-O-methylrhamnose are attached. The spinosyn biosynthesis genes, except for the rhamnose genes, are located in a cluster that spans 74 kb of the S. spinosa genome. DNA sequence analysis, targeted gene disruptions and bioconversion studies identified five large genes encoding type I polyketide synthase subunits, and 14 genes involved in sugar biosynthesis, sugar attachment to the polyketide or cross-bridging of the polyketide. Four rhamnose biosynthetic genes, two of which are also necessary for forosamine biosynthesis, are located outside the spinosyn gene cluster. Duplication of the spinosyn genes linked to the polyketide synthase genes stimulated the final step in the biosynthesis — the conversion of the forosamine-less pseudoaglycones to endproducts. Duplication of genes involved in the early steps of deoxysugar biosynthesis increased spinosyn yield significantly. Journal of Industrial Microbiology & Biotechnology (2001) 27, 399–402. Received 31 May 2001/ Accepted in revised form 09 July 2001     

Effects of hypoxia on lung mechanics in the newborn cat

The present study was designed to investigate the effects of hypoxia on lung mechanics in the newborn cat and to determine if vagal efferent innervation to the airways is involved in the response. We studied 11 animals, aged 2-7 days, anesthetized with a mixture of chloralose-urethane administered intraperitoneally. A tracheal cannula was inserted just below the larynx and following paralysis (pancuronium bromide), mechanical ventilation was initiated. A pneumothorax was created by a midline thoracotomy and an end-expiratory load was applied to maintain functional residual capacity. Animals were placed in a flow plethysmograph from which measurements of transpulmonary pressure, flow, and volume, mean inspiratory resistance, and dynamic compliance of the lung were calculated. The experimental protocol consisted of a series of 8-min trials, each preceded by a controlled volume history. The hypoxia challenge was composed of 1 min of ventilation with 40% O2, followed by 5 min exposure to 10% O2 and 2 min of recovery. In the majority of animals (7 out of 11), hypoxia had no effect on lung mechanics compared with control trials. Four animals responded to hypoxia with an increase in resistance and a decrease in compliance. Resistance remained elevated throughout the hypoxia with an average maximal increase of 47.2 +/- 22.2% (SD). Dynamic compliance was significantly decreased at the 2nd, 3rd, and 4th min only of hypoxia. Bilateral vagotomy abolished the response in the four animals and hypoxia had no effect on mechanics postvagotomy. Our data suggest that in most cases changes in lung mechanics do not play a causal role in the biphasic ventilatory response to hypoxia seen in the newborn.     

The dynamics of quadrupedal locomotion

This paper presents a dynamical analysis of quadrupedal locomotion, with specific reference to an adult Nubian goat. Measurements of ground reaction forces and limb motion are used to assess variations in intersegmental forces, joint moments, and instantaneous power for three discernible gaits: walking, running, and jumping. In each case, inertial effects of the torso are shown to dominate to the extent that lower-extremity contributions may be considered negligible. Footforces generated by the forelimbs exceed those exerted by the hindlimbs; and, in general, ground reactions increase with speed. The shoulder and hip dominate mechanical energy production during walking, while the knee plays a more significant role in running. In both cases, however, the elbow absorbs energy, and by so doing functions primarily as a damping (control) element. As opposed to either walking or running, jumping requires total horizontal retardation of the body's center of mass. In this instance, generating the necessary vertical thrust amounts to energy absorption at all joints of the lower extremities.     

A glucuronyltransferase involved in glucuronoxylan synthesis in pea (Pisum sativum) epicotyls.

A particulate enzyme preparation made from epicotyls of 1-week-old etiolated pea (Pisum sativum) seedlings was shown to incorporate glucuronic acid from UDP-D-[U-14C]glucuronic acid into a hemicellulosic polysaccharide. Optimum conditions for the incorporation include the presence of Mn2+ ions at between 4 and 10 mmol/litre and a pH between 5 and 6. UDP-D-xylose at 1 mmol/litre allows incorporation to continue for at least 8 h. In its absence, the reaction stops within 30 min. Analysis of the product by partial and total acid hydrolysis, followed by paper chromatography or electrophoresis, indicates that the polysaccharide produced is a glucuronoxylan.     

Diol sulfonamides: A potent and novel class of inhibitors of human renin

The syntheses and pharmacological activity of a series of diol sulfonamides which function as inhibitors of human renin are described. The most potent compound in this series, compound 20 (SQ 33,800), is a subnanomolar inhibitor of human renin (IC₅₀ = 0.35 × 10⁻⁹ M).     

Synthesis of ribosomal and transfer ribonucleic acids in yeast during a nutritional shift-up.

The growth rate of Saccharomyces cerevisiae was increased by adding a mixture of amino acids to cultures containing proline as the sole nitrogen source. The transition from balanced growth in the basal medium (doubling time 4 h) to balanced growth in the enriched medium (doubling time 2 h) took about 2-5 h. The rate of RNA accumulation increased soon after the enrichment to almost its final value. This increase began after a short lag of 10 to 15 min, therefore synthesis of new RNA polymerase molecules may be required before stable RNA production can increase. The different stable RNA species were not stimulated at different times after the enrichment, but all increased continuosly throughout the transition. The rRNA species accumulated in a co-ordinate fashion at a rate faster than the rate of tRNA accumulation.     

An epidemiologic study of sacroiliac fusion in some human skeletal remains

A case-control study was undertaken to generate some hypotheses concerning the etiology of sacroiliac fusion in a group of skeletons dating from the 18th and 19th centuries. Forty-one skeletons with fusion of the sacroiliac joint were compared with eighty-two adult skeletons without the condition. The sacroiliac joints were most frequently fused with bridging osteophytes and no preference for site or side of fusion could be detected. Except where there were other features in the skeleton suggestive of a sero-negative arthropathy, radiography demonstrated that there was no intra-articular ankylosis. We were able to confirm earlier observations that the condition is more prevalent in males and in older age-groups. The study also showed a significant association between sacroiliac fusion and the presence of diffuse idiopathic skeletal hyperostosis (DISH) and osteoarthritis of the spine but not for osteoarthritis at any other site. There was a highly significant association between sacroiliac fusion and the phenomenon that we refer to as "bone forming." We devised a series of bone-former scores and were able to show a significant excess of cases with high scores compared with the controls. This association persisted when allowance had been made for potential confounding factors such as DISH, osteoarthritis of the spine, and age.     

Effect of growth rate on the amounts of ribosomal and transfer ribonucleic acids in yeast.

The steady-state growth rate of Saccharomyces cerevisiae was varied by growing the cells in different media. The total amount of ribonucleic acid (RNA) per cell was found to decrease as a nonlinear function of decreasing growh rate. The RNA from cells growing in different media was analyzed by polyacrylamide gel electrophoresis. Although the amounts of both ribosomal RNA and transfer RNA decreased with decreasing growth rate, the ratio of ribosomal to transfer RNA was not constant. As the growth rate was reduced the ribosomal RNA fraction decreased slightly, whereas the transfer RNA fraction increased slightly. Thus the levels of ribosomal and transfer RNA were regulated to similar yet different extents. The levels of the different ribosomal RNA species were more closely coordinated. At all growth rates the ribosomal RNAs (including 5S RNA) were present in equimolar amounts. The rate of protein synthesis in yeast cells also decreased with decreasing growth rate. The low rates of protein synthesis did not appear to be due to limiting numbers of ribosomes or transfer RNA molecules.     

Segregation in the African wintering ranges of English and Swiss Swallow Hirundo rustica populations: a stable isotope study

Capsule Stable isotope analysis of Swallow feathers, grown in Africa, revealed significant differences between populations breeding in Switzerland and England.

Aims To investigate the extent to which Swallow populations breeding in Switzerland and England are separated on their African wintering grounds.

Methods Swallows were caught at breeding colonies, biometric measurements were taken and feathers, grown in Africa, were collected. Feathers were combusted in a Carlo Erba C/N/S analyser and the δ¹³C and δ¹⁵N signatures were measured using a mass spectrometer.

Results The δ¹³C signatures of Swiss birds were significantly more depleted than those of birds from England. The δ¹⁵N signatures did not differ between the two populations.

Conclusion Birds from Switzerland and England probably winter in geographically distinct parts of Africa. The Swiss birds probably feed on prey that are more reliant on C₃ vegetation, from woodlands, than the prey of English birds, which are more reliant on C₄ vegetation, from grasslands.