Appearance of lymphocyte surface markers and functional responses in neonatal and young rabbit spleens

We examined spleen cells from newborn to 1-month-old rabbits for easily detectable surface immunoglobulin, complement receptors, and for in vitro proliferative responsiveness to anti-immunoglobulin antisera and several mitogens. From birth through the first month of life about 15% of the cells from rabbit spleens had easily detectable surface immunoglobulin while about 45% had C3 receptors. In adults as many as 77% of the spleen cells had easily detectable surface Ig but the proportion with C3 receptors remained about 45%. The proliferative response to anti-allotype antisera was present at birth, and was at adult levels by 1 month of age. The proliferative response to pokeweed mitogen was low when cells were obtained during the first week of life but was comparable in magnitude to the response of adult cells by 2 weeks of age. In vitro responsiveness to concanavalin A was present at low levels at birth and increased sharply during the first week. We did not observe significant stimulation of spleen cells from neonatal to 4-week-old rabbits by lipopolysaccharide from Salmonella typhosa. Our data suggest that lymphocyte surface markers and functional responses appear asynchronously in spleen cells of developing rabbits.     

Calycadenia hooveri (Asteraceae), a new tarweed from California

In accord with its cytological and morphological distinctiveness and its geographical disjunction, the Sierran element ofC. pauciflora A. Gray is described as a new species,C. hooveri. Its chromosome number ofn = 7 is documented for the first time. Evidence from cytogenetic analysis of synthetic hybrids is presented to support the conclusion thatC. hooveri is more closely related toC. villosa DC. than toC. pauciflora. Characteristics of ligule morphology and the distribution of the peculiar saucer-shaped glands on the peduncular and receptacular bracts of these species also support the new interpretation.     

Chromosome numbers in some North American species of the genus Cirsium. III. Western United States,Mexico, and Guatemala

New data are presented on chromosome numbers for 36 species, two varieties, and two hybrids ofCirsium (Compositae). These include first reports forC. rhothophilum (2n = 34),C. andrewsii (2n = 32),C. crassicaule (2n = 32),C. quercetorum (2n= 32, 112),C. pascuarense (2n= 32),C. douglasii var.canescens (2n = 30, 34),C. hydrophilum (2n = 32),C. neomexicanum (2n = 30),C. cymosum (2n = 30, 34),C. acantholepis (2n= 34),C. radians (2n = 34), C.grahami (2n = 32),C. nigriceps (2n = 36),C. andersonii (2n= 32, 64),C. anartiolepis (2n = 34), andC. subcoriaceum (2n= 34). The published data on chromosome numbers of Eurasian and AmericanCirsium are summarized. In Eurasia, speciation has taken place primarily at the diploid level but is occasionally reinforced by polyploidy. The ancestral base number of 17 has been preserved in almost all species, and there is little evidence that reduction in chromosome number has played a significant role in speciation. In America speciation has proceeded exclusively at the diploid level, but the ancestral genome of 17 chromosomes has been retained in only about half of the species examined. In the remaining species, restructuring of the genome has occurred resulting in a reduction in number from 17 to 9 in extreme cases. Polyploidy, when seen, is of no significance. It is suggested that all species with greatly reduced numbers may represent products of a single reduction series.     

A critique of the utility of the prediction of protein secondary structure

The Chou-Fasman predictive algorithm for determining the secondary structure of proteins from the primary sequence is reviewed. Many examples of its use are presented which illustrate its wide applicability, such as predicting (a) regions with the potential for conformational change, (b) sequences which are capable of assuming several conformations in different environments, (c) effects of single amino acid mutations, (d) amino acid replacements in synthesis of peptides to bring about a change in conformation, (e) guide to the synthesis of polypeptides with definitive secondary structure,e.g. signal sequences, (f) conformational homologues from varying sequences and (g) the amino acid requirements for amphiphilicα-helical peptides.     

The utility of microsatellite DNA markers for the evaluation of area-wide integrated pest management using SIT for the fruit fly, Bactrocera dorsalis (Hendel), control programs in Thailand

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a key pest that causes reduction of the crop yield within the international fruit market. Fruit flies have been suppressed by two Area-Wide Integrated Pest Management programs in Thailand using Sterile Insect Technique (AW-IPM-SIT) since the late 1980s and the early 2000s. The projects’ planning and evaluation usually rely on information from pest status, distribution, and fruit infestation. However, the collected data sometimes does not provide enough detail to answer management queries and public concerns, such as the long term sterilization efficacy of the released fruit fly, skepticism about insect migration or gene flow across the buffer zone, and the re-colonisation possibility of the fruit fly population within the core area. Established microsatellite DNA markers were used to generate population genetic data for the analysis of the fruit fly sampling from several control areas, and non-target areas, as well as the mass-rearing facility. The results suggested limited gene flow (m < 0.100) across the buffer zones between the flies in the control areas and flies captured outside. In addition, no genetic admixture was revealed from the mass-reared colony flies from the flies within the control area, which supports the effectiveness of SIT. The control pests were suppressed to low density and showed weak bottleneck footprints although they still acquired a high degree of genetic variation. Potential pest resurgence from fragmented micro-habitats in mixed fruit orchards rather than pest incursion across the buffer zone has been proposed. Therefore, a suitable pest control effort, such as the SIT program, should concentrate on the hidden refuges within the target area.     

Upward shift of alpine plants increases floristic similarity of mountain summits

Question: Does the upward shift of species and accompanied increase in species richness, induced by climate change, lead to homogenization of Alpine summit vegetation? Location: Bernina region of the Swiss Alps. Methods: Based on a data set from previous literature we expand the analysis from species richness to beta‐diversity and spatial heterogeneity. Species compositions of mountain summits are compared using a two‐component heterogeneity concept including the mean and the variance of Sørensen similarities calculated between the summits. Non‐metric multidimensional scaling is applied to explore developments of single summits in detail. Results: Both heterogeneity components (mean dissimilarity and variance) decrease over time, indicating a trend towards more homogeneous vegetation among Alpine summits. However, the development on single summits is not strictly unidirectional. Conclusions: The upward shift of plant species leads to homogenization of alpine summit regions. Thus, increasing alpha‐diversity is accompanied by decreasing beta‐diversity. Beta‐diversity demands higher recognition by scientists as well as nature conservationists as it detects changes which cannot be described using species richness alone.     

Flux of reduced chemical constituents (Fe2+, Mn2+, NH inf4 sup+ and CH4) and sediment oxygen demand in Lake Erie

Sediment pore water concentrations of Fe²⁺, Mn²⁺, NH _inf4 ^sup+ and CH₄ were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4 mM m⁻² day⁻¹ (0.3 g m⁻² day⁻¹). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe²⁺ and CH₄. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe²⁺ and Mn²⁺ to as high as 26% for NH _inf4 ^sup+ , and 30% for CH₄. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this station.