Durhamycin, a Pentaene Antifungal Antibiotic from Streptomyces durhamensis sp. n

Durhamycin, derived from a previously undescribed soil isolate, is an apparently new antibiotic active against many of the fungi pathogenic for man and animals. Cultural and morphological characteristics and biochemical reactions of Streptomyces durhamensis are detailed. Methods of extraction of the antibiotic, physicochemical properties, antimicrobial spectrum, and results of mouse toxicity and protection tests are given.     

Motor unit territories supplied by primary branches of the phrenic nerve

Recent studies have demonstrated that, under certain circumstances, the diaphragm does not contract as a homogeneous unit. These observations suggest that motor units may not be randomly distributed throughout the muscle but confined to localized subvolumes. In the present study, electromyographic (EMG) and glycogen depletion methods were combined to investigate the organization of motor units supplied by the primary branches of the phrenic nerve in the cat. Four primary branches are generally present, one branch to the crus and three branches to the sternocostal region. The gross motor-unit territory of each of the four phrenic primary branches was determined by stimulating each nerve separately, while recording from nine EMG electrodes distributed over the hemidiaphragm. Stimulation of the crural branch evoked activity in the ipsilateral crus, whereas stimulation of each of the remaining branches evoked activity in discrete but overlapping areas of the sternocostal diaphragm. A more precise analysis of the distribution and borders of the motor territories was obtained by mapping regions depleted of muscle glycogen due to stimulation of each primary branch for 90 min. Glycogen depletion results closely matched the EMG findings of a localized distribution of motor units served by single primary branches. Stimulation of the crural branch typically caused depletion of the ipsilateral crus, whereas the sternocostal branches each served a striplike compartment. In the majority of cases, the borders of the sternocostal compartments were relatively abrupt and consisted of a 1- to 2-mm transition zone of depleted and nondepleted fibers. These studies demonstrate that motor unit territories of the primary branches of the phrenic nerve are highly delineated. This compartmentalization provides the central nervous system with the potential for a more precise regional motor control of costal and crural diaphragm than previously suspected.     

Development of the pulmonary vasculature in newborn lambs: structure-function relationships

Our objectives were 1) to describe the quantitative light microscopy and ultrastructure of newborn lamb lungs and 2) to correlate hemodynamic changes during normoxia and hypoxia with the morphology. By light microscopy, we measured the percent muscle thickness (%MT) and peripheral muscularization of pulmonary arteries and veins from 25 lambs aged less than 24 h, 2-4 days, 2 wk, and 1 mo. At the same ages, lungs were isolated and perfused in situ and, after cyclooxygenase blockade with indomethacin, total, arterial (delta Pa), middle (delta Pm), and venous pressure gradients at inspired O2 fractions of 0.28 (mild hyperoxia) and 0.04 (hypoxia) were determined with inflow-outflow occlusion. During mild hyperoxia, delta Pa and delta Pm fell significantly between 2-4 days and 2 wk, whereas during hypoxia, only delta Pm fell. The %MT of all arteries (less than 50 to greater than 1,000 microns diam) decreased, and peripheral muscularization of less than 100-microns-diam arteries fell between less than 4 days and greater than 2 wk. Our data suggest that 1) the %MT of arteries determines normoxic pulmonary vascular resistance, because only arterial and middle segment resistance fell, 2) peripheral muscularization is a major determinant of hypoxic pulmonary vasoconstriction, because we observed a fall with age in peripheral muscularization of less than 100-micron-diam arteries and in delta Pm with hypoxia, and 3) the arterial limit of the middle segment defined by inflow-outflow occlusion lies in 100- to 1,000-microns-diam arteries.     

Estimating the rate of plasmid transfer: an end-point method

We describe a method for determining the rate parameter of conjugative plasmid transfer that is based on single estimates of donor, recipient and transconjugant densities and the growth rate in exponential phase of the mating culture. The formula for estimating the plasmid transfer rate, gamma, was derived from a mathematical model describing cell growth and plasmid transfer in batch culture. Computer simulations were used to explore the sensitivity of this method to the realities of bacterial life, such as growth rate differences, plasmid segregation and transitory derepression of pilus synthesis. As predicted by the theory, mating experiments with the plasmid R1 in Escherichia coli K12 demonstrated that the estimate gamma is unaffected by cell density, donor:recipient ratio and mating time. Unlike previous techniques, our method allows us to investigate the effect of environmental factors on plasmid transfer rates when these factors also influence population growth rates. To illustrate this, we examined the effect of temperature on the rate of plasmid transfer.     

The habitat diversity and fish reproductive function of floodplain ecosystems

Synopsis Fish reproduction in floodplain ecosystems, based on relative abundance and total biomass of 0+ juveniles, was studied using the synchronic approach to typological analysis in conjunction with Point Abundance Sampling by modified electrofishing. In 3 different flood plains of the Upper Rhône River, 1015 point samples yielding 4573 juveniles (0+) from 21 species were collected from 48 ecosystems of various geomorphological origin. The results demonstrate the lotic-to-lentic succession of floodplain ecosystems to be a series of non-sequential reproductive zones, with spawning conditions being reflected by the specific composition and guild structure of the YOY fish assemblages. The habitat diversity and the fish reproductive potential of floodplain ecosystems are strongly influenced by geomorphological origin and by past and present hydrological conditions. The YOY assemblages of autogenically driven ecosystems (usually of anastomose or meander origin) tend to differ both in composition and in quantity from those found in allogenically driven ecosystems (generally of braided origin). Ecosystems of intermediate character, and fish reproduction thereof, occur as the result of either ecosystem rejuvenation or senescence: autogenically driven ecosystems by allogenic mechanisms, or allogenically driven ecosystems by anthropic and/or autogenic mechanisms, respectively. Because of co-occurrence of ecosystems at similar and at different successional status, the flood plain as an entity is seen as stable with respect to fish reproduction.     

Type XII collagen. A large multidomain molecule with partial homology to type IX collagen

Three overlapping cDNAs encoding alpha 1 (XII) collagen have been isolated and sequenced. The DNAs define five sequence domains within the chain. Three domains are nontriple-helical; two are relatively short triple-helical regions. The amino acid sequences of tryptic peptides derived from 16- and 10-kDa pepsin-resistant fragments isolated from tendon extracts are in full agreement with the deduced sequences of the triple-helical regions. Two of the five sequence domains in alpha 1 (XII), one triple-helical and one nontriple-helical, show a high degree of similarity to regions in type IX collagen chains. In addition, examination of seven exons in the alpha 1 (XII) gene shows that the gene is, in part, similar to the structure of type IX collagen genes. Therefore, collagen types IX and XII are partially homologous. The alpha 1 (XII) sequence data predict an asymmetric structure for type XII collagen molecules, fully consistent with the rotary shadowing images. These images show a triple-helical 75-nm tail attached through a central globule to three finger-like structures, each 60 nm long (Dublet, B., Oh, S., Sugrue, S. P., Gordon, M. K., Gerecke, D. R., Olsen, B. R., and van der Rest, M. (1989) J. Biol. Chem. 264, 13150-13156).     

Embodying illness,embodying cancer

Individuals and societies embody illnesses in different ways, in part determined by the way a person knows and lives his or her diagnosis and prognosis. Based on research in Northern Italy, on the experiences and meanings of cancer and on the practice of nondisclosure of the diagnosis, we find nondisclosure reflects a world divided - life/death, good/bad, mind/body — with the unwanted converted to other. The strong association of cancer with death, suffering, and hopelessness in much of Italy, coupled with the tremendous power attributed to naming and sentencing makes nondisclosure a major mechanism for keeping the condemned in this social world, and keeping death, decay, and suffering in the other. It is the social reality that is dominant here, such that informing a patient of cancer can be tantamount to social death.

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Résumé Les individus et les sociétés incorporent la maladie de façon différente, déterminée en partie de comment une personne connait et vit son diagnostic et prognostic. A partir de la recherche des experiences des significations du cancer et de la pratique de ne pas dire la diagnostic au Nord de l'Italie, on a remarqué que l'habitude de ne rien dire reflète un monde séparé entre la vie et la mort, entre le bon et le mal, entre l'esprit et le corps, de sorte que ce qui West pas voulu soit transfomé en l'autre. L'association forte du cancer à la mort, à la souffrance, au désespérance en toute l'Italie, unie au grand pouvoir donne au fait de dénommer et de donner une sentence, rend ne pas dire un méchanisme important pour garder le condamnd dans ce monde social et pour garder la mort, la décadence et la souffrance dans l'autre. C'est la réalité sociale qui est ici dominante, tel que le fait d'informer un patient de cancer soit comme une mort sociale.

     

Validation of age readings from otoliths of juvenile roundnose grenadier, Coryphaenoides rupestris, a deep-water macrourid fish

Validation of the ageing of deep-water fish is difficult and there are only a few instances where the rings on the otoliths have been shown to be laid down annually. Roundnose grenadier have been fished commercially in the North Atlantic since the 1960s and the adult fish have frequently been aged by counting the rings in otoliths or scales. All the ageing was done on the assumption that the rings in the otoliths or scales were annual. Between 1975 and 1992, the Scottish Association for Marine Science carried out seasonal trawling surveys in the Rockall Trough using a fine-meshed trawl, and collected otoliths from a wide size range of roundnose grenadier. An examination of the growing edge of otoliths from juvenile fish from these collections suggests that the rings in the otoliths are laid down annually. The broader, opaque zones which represent the growth phase were dominant between September and March. The thinner, hyaline zones were dominant between April and July. The apparent delay in the growth phase compared with most shallow-water species is discussed in relation to the availability of mesopelagic prey.     

Differentiation trees,a junk DNA molecular clock,and the evolution of neoteny in salamanders

Obligate neotenic salamanders die if forced to metamorphose. We suggest that this can be explained by assuming: 1) their “excess” DNA is “junk” DNA; 2) the “adult” specifying portion of the DNA becomes junk DNA and is available for repeated duplication. This suggests a “new” junk DNA molecular clock. We obtain remarkable agreement in “predicting” the amount of DNA per nucleus in present day non-obligate neotene salamanders from this molecular clock. These observatons are consistent with the idea that the development of these animals is describable in terms of differentiation trees whose branches (gene cascades) corresponding to adult somatic tissues accumulate deleterious mutations over evolutionary time. We show that the amount of DNA per nucleus increases linearly with the phylogenetic age of salamander families. The lack of constraints by natural selection, on unused adult branches, may account for the large amount of so-called “junk DNA” in obligate neotenic salamanders. The effects of this excess DNA, via increased cell size, suggest a positive feedback, ecophysiological explanation for such junk DNA: adaptation to cool water environments is enhanced by the lower metabolism associated with more DNA, larger cells and slower developmental time.     

Carbohydrate fermentation by three species of polycentric ruminal fungi from cattle and water buffalo in tropical Australia

Fructose, glucose and xylose were the only monosaccharides to be fermented by the polycentric fungi, Orpinomyces joyonii (three cattle isolates) and O. intercalaris (two cattle isolates) and Anaeromyces spp. (four cattle isolates and two water buffalo isolates). Both Orpinomyces spp. utilised a similar range of oligosaccharides and polysaccharides by fermenting cellobiose, gentiobiose, lactose, maltose, sucrose, cellulose, glycogen, starch and xylan. In contrast, there was considerable variation in carbohydrate fermentation amongst Anaeromyces spp., with only cellobiose, gentiobiose and cellulose being fermented by all strains. Formate, acetate and ethanol were the major fermentation end-products formed from glucose by all polycentric fungi. In addition, Anaeromyces spp. produced considerable amounts of lactate, although only small amounts were formed by Orpinomyces spp. This difference was explained by the low specific activity for lactate dehydrogenase in Orpinomyces spp. Several Anaeromyces spp. also produced malate as a significant end-product of glucose fermentation. Fermentation of specifically-labelled Z14C]glucose molecules by polycentric fungi showed that hexose was catabolised by both polycentric and monocentric fungi via the glycolysis pathway with end-products being derived from the following carbon atoms: lactate and malate (C1-C3; C4-C6), acetate and ethanol (C1-C2; C5-C6), CO2 and formate (C3; C4). The results were compared to those obtained for monocentric and polycentric fungi isolated from temperate climate ruminants.