Standing stock and production of Ecklonia radiata (C.Ag.): J. Agardh

The monthly productivity, standing stock, plant size and density of Ecklonia radiata (C.Ag.) J. Agardh is presented for a 2-yr period. Annual production was 20.7 kg wet wt · m^?2 with maximum growth of 0.9% per day in spring (October–December) and minimum growth of 0.2% per day in late summer. (March–April). A close negative correlation was found between spring and summer growth and water temperature. Maximum biomass (18 kg wet wt · m ^?2) did not coincide with maximum growth but occurred in late summer. Minimum biomass (6 kg wet wt · m ^?2) occurred in winter. An estimate of erosion of plant material from the kelp bed was made from these data and a hypothesis concerning the ultimate destination of eroded and removed kelp plants was formulated.     

Altered aggregational properties in a genetic variant of human glucose 6-phosphate dehydrogenase

The Tel Hashomer variant of human G6PD migrates as two prominent components during electrophoresis in several gel systems in which red cell G6PD from other males migrates predominantly as a single band. Since human males normally have but one X-chromosome, the extra band of this variant seemed an exception to earlier biochemical and genetic observations suggesting that human red cell G6PD is determined by a locus on the X chromosome. Results of the present studies indicate that the Tel Hashomer variant is unusually susceptible to the formation of a complex which has a higher molecular weight than normal G6PD and which represents the slow electrophoretic component. The conditions of formation and disruption of this complex in crude and purified Tel Hashomer preparations suggest that it results from the formation of disulfide bridges between molecules of Tel Hashomer G6PD.Supported by U.S. Public Health Service Research Grants AM-11065 and FR-5406 and Research Career Development Award 5 K3 AM 7992.     

Fifteen-year experience with screening for phenylketonuria with an automated fluorometric method.

An automated fluorometric method, rather than the Guthrie test, has been used in North Carolina for neonatal screening for phenylketonuria (PKU). Although there is no testing law, 97% of newborn infants are screened. Twelve children with PkU, not referred for dietary management, were born before the screening program was established, were born elsewhere, or were successfully identified at birth but not referred for treatment. None was missed because of laboratory error or because of the lack of a testing law. Positive skewing was noted among initial blood phenylalanine levels of 49 infants with PKU and severe hyperphenylalaninemia. Log transformations caused the values to be normally distributed and permitted the calculation of tolerance and confidence limits. These provided estimates of the percentage of phenylketonuric infants whose initial blood levels might fall below any given cutoff value.     

Revisiting the use of Iprodione and Trichoderma in the integrated management of onion white rot

The biocontrol properties of Trichoderma species are well documented, but their effectiveness in antagonism of the problematic Sclerotium cepivorum, the causal agent of white rot in Allium species, appears limited with reports of significant control only relating to deliberately-mutated strains of Trichoderma. Our previous studies have indicated the possibility of using selected naturally-occurring strains of the antagonist in the suppression of other diseases; now in vitro and controlled environment in vivo studies have indicated that a degree of control of Onion White Rot is possible, and that the selected antagonist strains can be used in integrated treatments with Iprodione to good effect. The possible value of such treatments is considered in light of other approaches to the suppression of this continuing problem.     

Productivity and species richness across an environmental gradient in a fire-dependent ecosystem

The fire-dependent longleaf pine-wiregrass (Pinus palustris Mill.-Aristida beyrichiana Trin. & Rupr.) savannas of the southeastern United States provide a unique opportunity to examine the relationship between productivity and species richness in a natural ecosystem because of the extremely high number of species and their range across a wide ecological amplitude (sandhills to edges of wetlands). We used a natural gradient to examine how plant species richness and plant community structure vary with standing crop biomass (which in this system is proportional to annual net productivity) as a function of soil moisture and nitrogen mineralization rates in a frequently burned longleaf pine-wiregrass savanna. Highest ground cover biomass and highest species richness were found at the same position along the gradient, the wet-mesic sites. Relative differences in species richness among site types were independent of scale, ranging from 0.01 m(2) to 100 m(2). Nitrogen availability was negatively correlated with species richness. Dominance of wiregrass (in terms of biomass) was consistent across the gradient and not correlated with species richness. Regardless of site type, the community structure of the savannas was characterized by many perennial species with infrequent occurrences, a factor in the low temporal heterogeneity (percent similarity between seasons and years) and high within-site spatial heterogeneity (percent dissimilarity of vegetation composition). The coexistence of numerous species is likely due to the high frequency of fire that removes competing hardwood vegetation and litter and to the suite of fire-adapted perennial species that, once established, are able to persist. Our results suggest that soil moisture is an important factor regulating both the number of species present and community production within the defined gradient of this study.     

Steroidogenic correlates of pregnancy in the rock hyrax (Procavia capensis)

In pregnant rock hyraxes isolated leucocytes metabolise both [3H]pregnenolone and [3H]progesterone while whole blood, erythrocytes and an erythrocyte/leucocyte mixture only metabolised [3H]progesterone. Plasma displayed no tendency to metabolically convert any one of these two steroids. In whole blood [3H]progesterone appears to be converted to 5alpha-pregnane-3,20-dione and a compound with chromatographic properties similar to that of 5alpha-pregnan-3alpha-ol-20-one. 5Alpha-pregnane-3,20-dione exhibited a high relative binding affinity for the uterine progesterone eceptor (94%), but 5alpha-pregnan-3alpha-ol-20-one displayed very little affinity for the same receptor (0.4%). 5Alpha-pregnane-3,20-dione may therefore aid in the maintenance of pregnancy. Corpora lutea metabolised progesterone to 17alpha-hydroxyprogesterone, a compound exhibiting no progestational function because of its low relative binding affinity for the uterine progesterone receptor (2%). Progesterone appears to be the main product of the corpus luteum. However, 5alpha-pregnane-3,20-dione circulated at concentrations approximately 8.5 times higher than progesterone, probably due to the metabolic conversion of progesterone to 5alpha-pregnane-3,20-dione by the blood. We conclude that in the hyrax progesterone, produced by the corpora lutea, enters the circulation, where it is reduced to 5alpha-pregnanes. 5Alpha-pregane-3,20-dione may then be transported to the uterus where it binds to the progesterone receptor to assist in the maintenance of pregnancy. This mechanism appears to be analogous to that of the African elephant which is phylogenetically related to the hyrax, except that in the elephant the 5alpha-reduced metabolites are produced by luteal tissue and not the blood.     

CD8 T cells are sufficient to mediate allorecognition and allograft rejection

Different T cell subsets may play different roles in allorecognition and allograft rejection. It has been suggested that CD8 T cells can only initiate rejection with help from CD4 T cells. Since CD8 T cells may have different requirements for allorecognition and for costimulation, it is important to clarify the role of CD8 cells in rejection. We examined the role of CD8 cells in allorecognition using a TCR transgenic mouse transplantation model. In our study, CD8 cells were able to recognize alloantigens and reject allografts in the absence of help from CD4 T cells. Furthermore our study provides a model to study the mechanisms of CD8-mediated allograft rejection. It may be important in the future, to consider that CD8 T cells may need to be targeted independently of CD4 T cells in strategies used to prevent rejection and induce tolerance.     

A web server to locate periodicities in a sequence

Summary : FT is a tool written in C++, which implements the Fourier analysis method to locate periodicities in aminoacid or DNA sequences. It is provided for free public use on a WWW server with a Java interface. Availability : The server address is http://o2.db. uoa.gr/FT Contact : shamodr@atlas.uoa.gr