A revision of Eriogonum (Polygonaceae) subgenus Pterogonum

This revision discusses the 10 species of Eriogonum assigned to the subgenus Pterogonum. Six of the species are essentially restricted to northern Mexico; two additional species, E. hemipterum and E. nealleyi, are found primarily in Texas; and the remaining two, E. hieracifolium and E. alatum, are the most widespread species of the subgenus being found mainly in the United States and just barely entering Mexico. The subgenus is characterized by the broad, often winged or ribbed achenes, and the generally erect habit of the stems of these perennial herbs. Three new species, E. fimbriatum, E. viscanum, and E. clivosum, are described. They are related to E. ciliatum and are found in the desert foothills of north central Mexico. Two new varieties of E. atrorubens are proposed. One, var. nemorosum, is restricted to the high mountains of the Sierra Madre Occidental in northern Durango and southern Chihuahua, while the second, var. auritulum, is a plant of the Sierra Madre Oriental of Coahuila and Nuevo León. The subgenus is divided into four sections, two of which, Peregrina and Astra, are new. Cytological information is given for nearly all taxa and shows the majority of species to have a haploid number of 20. Eriogonum atrorubens var. intonsum is a polyploid with n = 40, and E. greggii is the most unusual with a haploid number of 16. Each species is described in detail, discussed, and illustrated. Distribution maps are given noting the known locations for each taxon.     

Reversible uncoupling of inactivation in N-type calcium channels.

N-type calcium channels are thought to be expressed specifically in neuronal cells and to have a dominant role in the control of neurotransmitter release from sympathetic neurons. But their unitary properties are poorly understood and the separation of neuronal Ca2+ current into components carried by N-type or L-type Ca2+ channels is controversial. Here we show that individual N-type Ca2+ channels in sympathetic neurons can carry two kinetically distinct components of current, one that is rapidly transient and one that is long lasting. The mechanism that gives rise to these two components is unexpected for Ca2+ channels: a test depolarization elicits either a rapidly inactivating, single short burst with an average duration of 40 ms, or sustained, noninactivating channel activity lasting for over 1 s. The switching between inactivating and noninactivating activity is a slow process, the occurrence of each type of unitary kinetic behaviour remaining statistically correlated over several seconds. Variable coupling of inactivation in N-type Ca2+ channels could be an effective mechanism for the modulation of neuronal excitability and synaptic plasticity.     

Synthesis of L-4-amino-3-isoxazolidinone,the unnatural stereoisomer of cycloserine and its antibiotic activity

Zusammenfassung Eine direkte Synthese vonl- undd-Cycloserin ausl- undd-Serin wurde beschrieben. Die bakteriostatischen Effekte der drei Formen von Cycloserin (d-,l-unddl-) aufE. coli in synthetischem Medium wurden verglichen.     

Relation between stimulus intensity and neutrophil chemotactic response

Summary The effect of chemotactic peptides which lack chemokinetic activity has been investigated. The neutrophil response is proportional to the logarithm of the stimulus intensity, or alternatively a power function with an exponent of 0.3. Equal responses are obtained for equal ratios between the peptide concentration in the lower compartment and the threshold concentration. The significance of Weber-Fechner's law in leucocyte chemotaxis is discussed.We thank Miss B. Zanolari, Mrs M. Marti, Mrs Hauck and Mr Dietz for excellent technical assistance. This work was supported by the Swiss National Foundation for Scientific Research.     

Attainment of sexuality inEnchytraeus fragmentosus Bell under laboratory conditions

Zusammenfassung Es wurde früher beschrieben, dassEnchytraeus fragmentosus Bell (Oligochaeta) keine Sexualorgane besitzt und sich nur durch Fragmentation fortpflanzt. Jetzt wurden männliche und weibliche Sexualorgane entdeckt, die sich wahrscheinlich als Folge veränderter Zuchtbedingungen entwickeln.

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This investigation was partially supported by the Department of Health, Education and Welfare, Public Health Service, No. AM 08632-04.     

Interferometric radar measurements of water level changes on the Amazon flood plain

Measurements of water levels in the main channels of rivers, upland tributaries and floodplain lakes are necessary for understanding flooding hazards, methane production, sediment transport and nutrient exchange. But most remote river basins have only a few gauging stations and these tend to be restricted to large river channels. Although radar remote sensing techniques using interferometric phase measurements have the potential to greatly improve spatial sampling, the phase is temporally incoherent over open water and has therefore not been used to determine water levels. Here we use interferometric synthetic aperture radar (SAR) data, acquired over the central Amazon by the Space Shuttle imaging radar mission, to measure subtle water level changes in an area of flooded vegetation on the Amazon flood plain. The technique makes use of the fact that flooded forests and floodplain lakes with emergent shrubs permit radar double-bounce returns from water and vegetation surfaces, thus allowing coherence to be maintained. Our interferometric phase observations show decreases in water levels of 7-11 cm per day for tributaries and lakes within approximately 20 km of a main channel and 2-5 cm per day at distances of approximately 80 km. Proximal floodplain observations are in close agreement with main-channel gauge records, indicating a rapid response of the flood plain to decreases in river stage. With additional data from future satellite missions, the technique described here should provide direct observations important for understanding flood dynamics and hydrologic exchange between rivers and flood plains.