Freshwater crayfish invasions in South Africa: past,present and potential future

Freshwater crayfish invasions have been studied around the world, but less so in Africa, a continent devoid of native freshwater crayfish. The present study reviews historical and current information on alien freshwater crayfish species introduced into South Africa and aims to indicate which areas are at risk from invasion. As is the case elsewhere, South Africans have shown a keen interest in both farming and keeping freshwater crayfish as pets, which has resulted in Cherax cainii, Cherax destructor, Cherax quadricarinatus and Procambarus clarkii being introduced to the country. There is evidence of successful establishment in the wild for C. quadricarinatus and P. clarkii in different parts of the country. Species distribution models suggest that the eastern part of the country and parts of the Eastern and Western Cape are at higher risk of invasion. At present, illegal translocations represent the most likely pathway of crayfish spread in South Africa. A continued risk of invasion by freshwater crayfish species in South Africa is highlighted, which reinforces the need for more research, as well as for strong mitigation measures, such as stronger policing of existing regulations, management or eradication where feasible and public education.     

The PagN protein of <Emphasis Type="Italic">Salmonella enterica</Emphasis> serovar Typhimurium is an adhesin and invasin

Background  

The pagN gene of Salmonella enterica serovar Typhimurium is a PhoP-regulated gene that is up-regulated during growth within macrophages and in vivo in murine models of infection. The PagN protein displays similarity to the Hek and Tia invasins/adhesins of Escherichia coli. Thus far no function has been ascribed to the PagN protein.     

Dimerization of Receptor Protein-Tyrosine Phosphatase alpha in living cells

Background  

Dimerization is an important regulatory mechanism of single membrane-spanning receptors. For instance, activation of receptor protein-tyrosine kinases (RPTKs) involves dimerization. Structural, functional and biochemical studies suggested that the enzymatic counterparts of RPTKs, the receptor protein-tyrosine phosphatases (RPTPs), are inhibited by dimerization, but whether RPTPs actually dimerize in living cells remained to be determined.     

Impaired capsaicin-induced decrease in heart rate and coronary flow in isolated heart of diabetic rats

The effect of capsaicin (0.1 microM) on heart rate and coronary flow was studied in Langendorff-perfused heart from streptozotocin-induced (50 mg/kg i.v.) diabetic rats where sensory neuropathy developed. In hearts from animals 4- and 8-week diabetes baseline heart rate and coronary flow decreased from 317.9 +/- 2.9 b.p.m. and 13.4 +/- 0.7 m/min to 255.1 +/- 12.7 and 219.8 +/- 2.8 b.p.m. and 8.9 +/- 0.6 and 10.0 +/- 0.1 ml/min (P<0.05), respectively. Capsaicin significantly decreased both variables in either normal or 4-week diabetic animals its effects, however, on coronary flow or heart rate were missing in preparations from 8-week diabetic rats. Endothelin-1 (0.1 nM), the putative mediator of the capsaicin effect, significantly decreased heart rate and coronary flow irrespective of the presence or absence of diabetes. In the femoral nerve of streptozotocin-treated animals conduction velocity involving both fast conducting A- and slow-conducting C-fibres was decreased proportional to the duration of the pre-existing diabetic state. It is concluded that in insulin deficient diabetes the diminished responses evoked by capsaicin on heart rate and coronary flow are signs of sensory neuropathy. This is related to a feeble endothelin release from sensory nerve endings without changes in post-receptor mechanisms mediating the endothelin effects.     

Clinical and immunopathological significance of chimerism in bone marrow and organ transplantations

Chimerism is an exceptional immunogenetic state, characterized by the survival and collaboration of cell populations originated from two different individuals. The prerequisites to induce chimerism are immunosuppression, myeloablation or severe immunodeficiency of the recipients on one side and donor originated immuno-hematopoietic cells in the graft on the other. Special immunogenetic conditions to establish chimerism are combined with bone marrow transplantation, transfusion and various kinds of solid organ grafting. There are various methods to detect the type of chimera state depending on the immunogenetic differences between the donor and recipient. The chimera state seems to be one of the leading factors to influence the course of the post-transplant period, the frequency and severity of graft-versus-host disease (GVHD), and the rate of relapse. However, the most important contribution of the chimeric state is the development of graft versus leukemia (GVL) effect. A new conditioning protocol (DBM/Ara-C/Cy) for allogeneic BMT in CML patients and its consequence on chimera state and GVL effect is demonstrated.     

Classification of cDNA array genes that have a highly significant discriminative power due to their unique distribution in four brain regions

Novel statistical methods were used to distinguish functionally distinct brain regions using their cDNA array gene expression profiles, and it was found that one of four specific factors is often associated with the most regionally discriminative genes. The gene expression profiles for the substantia nigra (SN), striatum (STR), parietal cortex (PC), and posterolateral cortical amygdaloid nucleus (PLCo) brain regions were determined from each brain region. An F-test identified 339 genes of the 1185 array genes as having a P < or = 0.01 and applied a gene ranking and selection method based on Soft Independent Modeling of Class Analogy (SIMCA) to obtain 59 of the most discriminative genes. Their discriminative power was validated in three steps. The most convincing step showed their ability to correctly predict the brain regional classifications for 18 "test" gene expression sets obtained from the four regions. A two-way Hierarchical Cluster Analysis organized the 59 genes in six clusters according to their expression differences in the brain regions. Expression patterns in the SN and STR regions greatly differed from each other and the PC and PLCo. The closer similarity in the gene expression patterns of the PC and PLCo was probably due to their functional similarity. The important factors in determining differences in the regional gene expression profiles in six clusters were (1) regional myelin/oligodendrocyte levels, (2) resident neuron types, (3) neurotransmitter innervation profiles, and (4) Ca++-dependent signaling and second messenger systems.     

The somatostatin analogue peptide TT-232 induces apoptosis and chromosome breakage in cultured human lymphocytes

Somatostatin receptors are supposed to be important in the regulation of apoptosis. In this study, we measured apoptosis occurring spontaneously, or induced by the synthetic somatostatin analogue, the peptide TT-232. We examined isolated human peripheral blood lymphocytes (PBL) from 32 nurses exposed bedside to cytostatic drugs, 12 chronic lymphoid leukaemia (CLL) patients prior to treatment, and 19 unexposed, healthy donors without anamnestic occupational exposure to genotoxic agents. Cells were stimulated by phytohaemagglutinin-P (PHA) and cultured for 69 h with or without 15 microg/ml TT-232, respectively. Cell kinetic parameters and apoptosis were determined by flow cytometry after staining with FITC-labeled anti-BrdU and propidium iodide (PI) and the results on spontaneous and peptide-induced apoptosis were compared with the obtained chromosome aberration frequencies (CA). The peptide TT-232 unexpectedly induced chromosome breakage in addition to apoptosis. The mean spontaneous apoptotic fractions were 6.65+/-0.89%, 6.46+/-0. 53%, and 3.07+/-0.57%, and the mean CA yields in the samples without TT-232 were 1.74+/-0.46%, 2.44+/-0.40%, and 4.50+/-1.05%, for healthy subjects, nurses, and CLL patients, respectively. A total of 15 microg/ml TT-232 treatment in healthy subjects increased the mean CA frequency (10.38+/-1.57%), as well as the apoptotic cell fraction (2.63+/-0.45 times higher than the corresponding untreated sample). In TT-232-treated PBLs of nurses, CA remained unchanged and the mean apoptotic cell fraction showed only a slight increase (1.24+/-0.11 times higher than the untreated). Among CLL patients, TT-232 treatment significantly increased both CA (up to 17.83+/-4.04%) and the ratio of apoptotic cells (21.78+/-11.00 times higher than the untreated). These results demonstrated significant differences in apoptosis sensitivity in controls, nurses and CLL donors, after 15 microg/ml TT-232 treatment. Data also indicate that the induced CA yields in CLL donors with high CA are in correlation with TT-232-induced apoptosis.     

Polyethyleneglycol-Based Resins as Solid Supports for the Synthesis of Difficult or Long Peptides

An evaluation of the polyethyleneglycol-based ChemMatrix^? resin as solid support for the synthesis of challenging peptide sequences is presented. Comparison with conventional polystyrene and polyethyleneglycol-polystyrene resins in several instances of typically difficult solid phase syntheses shows a consistently better performance of the ChemMatrix^? resin in terms of end product purity. Representative test sequences include a 15-residue antibiotic, a gp41 ectodomain hybrid sequence, a calcipressin fragment with an N-terminal Arg₁₁ extension, and two chemokines of 69- and 64-amino acid residues. Interestingly, a difference in only five amino-acids between the two chemokine sequences had a remarkable impact on synthetic results, which in the case of the 69-residue peptide required additional refinements (β-sheet-breaking pseudoproline dipeptides) for success. This paper is dedicated to the memory of Bruce Merrifield, a dear teacher, mentor and friend.     

The phylogenetic relationships among some Randia (Rubiaceae) taxa

Phylogenetic relationships among some Randia (Rubiaceae, Gardenieae) taxa were estimated based on sequence variation in the nuclear ribosomal internal transcribed spacers (ITS) and rps 16 intron (cpDNA). During the investigation of rpsl6 intron of 9 studied Central American Randia species, two well supported subclades were separated. Analysis of ITS data of 16 Randia species shows 3 major clades. A group of mainly lowland, South American Randia species is moderate supported (75%). Species from Mexico form a strongly supported (97%) clade, but the Central American and Mexican Randia species are low supported (58%). However the last two groups are well supported together (95%). The molecular delimination is well in line with the size of leaves combined with the texture of exocarp.