SCENEDESMUS WALL ORNAMENTATION. I. SCENEDESMUS PARISIENSIS CULTURES1

Four strains of Scenedesmus parisiensis Chodat were studied in xenic and axenic culture in 3 media as well as in cultures incubated in sterile vessels in nature. Organized coenobia are usually produced but these may have merely short spines, spines and serrate edges, or lack wall ornamentation. Because the serrate edge is either not formed or cannot be readily detected in most cases, it is not a satisfactory morphological feature for delimiting this species. In laboratory studies it is noted that S. parisiensis might be confused with S. denticulatus rather than S. brasilien-sis. Inasmuch as both xenic and axenic cultures of the -f strains produced similar results, S. parisiensis can be readily characterized.     

Immunotoxins up to the present day

Immunotoxins consist of monoclonal or polyclonal antibodies conjugated to bacterial or plant toxins. The toxins used are typically of the A-B type in which a toxic A chain is coupled to a B chain responsible for cell binding and facilitation of A chain entry into the cytosol. Two broad strategies have been followed: coupling intact toxins, or A chains alone, to antibodies. This review examines current progress inin vitro andin vivo research, including recent clinical studies, concentrating principally on ricin or ricin A chain conjugates. The future role of conjugates using membrane-acting toxins, immunolysins, is also discussed.     

The characterisation of liposomes with covalently attached proteins

The problem of characterising liposomes with covalently attached proteins has been analysed theoretically in terms of a normal weight distribution of liposome diameters. The polydispersity of protein conjugation is considered in terms of the width (standard deviation) of the liposome size distribution. It is shown that the weight-average number of proteins per liposome is a convenient parameter to use to define the protein content of proteoliposomes. Two types of proteoliposome have been prepared (small unilamellar vesicles and reverse phase evaporation vesicles) in which wheat germ agglutinin is covalently coupled to the liposomal surface. The liposomes cover a range of weight average diameter from 65 to 240 nm and of polydispersity (weight to number average diameter (dw/dn) from 2.6 to 11.4. The liposomes have been characterised by chemical analysis and photon correlation spectroscopy and the results are discussed in terms of the theoretical consequences of an equivalent normal weight distribution of diameters.     

The evolution of human chromosome 21: evidence from in situ hybridization in marsupials and a monotreme.

We have mapped five human chromosome 21 (HSA 21) markers in marsupials and a monotreme, two major groups of mammals that diverged from eutherians 130-150 and 150-170 million years before present (MYrBP), respectively. We have found that these genes map to two distinct autosomal sites, one containing SOD1/CBR/BCEI and the other containing ETS2/INFAR, in the marsupials Macropus eugenii and Sminthopsis macroura (which belong to orders that diverged 40-80 MYrBP), as well as in the monotreme Ornithorhynchus anatinus (the platypus). Since marsupials and monotremes diverged independently from eutherians, these data suggest that HSA 21 genes were originally located in two separate autosomal blocks. In another Sminthopsis species, SOD1 is linked to TRF (a marker on HSA 3q), suggesting that the ancestral SOD1/CBR/BCEI region also included HSA 3 markers. We suggest that these blocks became fused early in the eutherian evolution to form a HSA 3/21 chromosome, which has remained intact in artiodactyls, but has been independently disrupted in both the primate and rodent lineages.     

Corticotropin releasing factor stimulates growth hormone secretion in neonatal rats

Corticotropin releasing factor (CRF) both stimulates ACTH secretion from the pituitary and inhibits secretion of growth hormone (GH) in adult rats through actions in the CNS. The purpose of the present study was to evaluate these pituitary and central actions of CRF in neonatal rats, in which the hypothalamo- pituitary adrenal (HPA) axis is relatively hypo-functional. The results of this study show that central or peripheral administration of CRF evokes a marked dose-related rise in serum corticosterone in 6-day old rats. The same doses of CRF stimulate, rather than inhibit GH secretion. These results suggest that CRF has unique central actions early in ontogeny.     

Chromosome aberrations (CA), sister-chromatid exchanges (SCE) and mitogen-induced blastogenesis in cultured peripheral lymphocytes from 48 control individuals sampled 8 times over 2 years

Confidence in the measurement of positive effects determined by monitoring of environmentally or occupationally exposed individuals can be enhanced by a knowledge of the normal variability in these endpoints in the general population. Confounding effects can be determined and study interpretation improved by correlation of this variability with various lifestyle factors such as sex and age of donor, smoking and drinking habits, viral infections, exposure to diagnostic X-rays, etc.

8 blood samples were taken from each of 24 male and 24 female volunteers over a period of 2 years. Questionnaires pertaining to lifestyle were completed at the time of each sampling. Whole blood was cultured and slides prepared for CA or SCE analysis. Separated mononuclear cells were cultured with a range of phytohaemagglutinin concentrations and the maximum level of mitogen-induced blastogenesis was determined by measurement of [³H]thymidine uptake.

There was a significant effect of both year and season of sampling for all 3 endpoints. No significant effects in any of the 3 endpoints were found with respect to sex or age of donor nor any of the other lifestyle factors, although SCE frequency and mitogen-induced blastogenesis were nearly always higher in females than males. These results point to the need for concurrent sampling of controls with exposed populations.     

Morphological and cytoskeletal changes in epithelial cells occur immediately upon interaction with Salmonella typhimurium grown under low-oxygen conditions

Salmonella typhimurium grown under oxygen-limiting conditions were found to enter into, elicit actin filament rearrangement in, and effect morphological changes upon HEp-2 cells within 15 min after infection. Video microscopy revealed that host cell morphological changes associated with entry began within 1 min of productive adherence. Polarized Caco-2 cell morphology was affected 40 s after infection with low-oxygen-grown S. typhimurium. Stationary-phase S. typhimurium did not elicit these phenomena within this time-period even when adherence was enhanced with the afimbial adhesin, AFA-I. Thus, environmental cues regulate S. typhimurium invasion factors, allowing for immediate entry into host cells. Additionally, actin filament rearrangement and morphological changes in the eukaryotic host cell are essential for entry and occur within minutes of infection.     

A YAC contig across the fragile X site defines the region of fragility.

The fragile X syndrome is a common cause of mental retardation and is associated with a fragile site at Xq27.3 (FRAXA). Recently, evidence has been presented for the role of methylation and genomic imprinting in the expression of the disease. We have identified a site of methylation in patients by long range restriction mapping of the region. In this paper we present a YAC contig of this area, localise the CpG sequences which are methylated, and show by in situ hybridisation that the site of fragility lies within this region.