Cutting edge: a new tool to evaluate human pre-erythrocytic malaria vaccines: rodent parasites bearing a hybrid Plasmodium falciparum circumsporozoite protein

Malaria vaccines containing the Plasmodium falciparum Circumsporozoite protein repeat domain are undergoing human trials. There is no simple method to evaluate the effect of vaccine-induced responses on P. falciparum sporozoite infectivity. Unlike the rodent malaria Plasmodium berghei, P. falciparum sporozoites do not infect common laboratory animals and only develop in vitro in human hepatocyte cultures. We generated a recombinant P. berghei parasite bearing P. falciparum Circumsporozoite protein repeats. These hybrid sporozoites are fully infective in vivo and in vitro. Monoclonal and polyclonal Abs to P. falciparum repeats neutralize hybrid parasite infectivity, and mice immunized with a P. falciparum vaccine are protected against challenge with hybrid sporozoites.     

Low frequency noise enhances cortisol among noise sensitive subjects during work performance

Salivary free cortisol concentration, rated stress and annoyance were determined in 32 subjects before, during and after carrying out a battery of performance tasks for 2 hours during exposure to ventilation noise, with dominant low frequencies (low frequency noise) or a flat frequency spectrum (reference noise). Both noises had a level of 40 dBA. All subjects were studied on two occasions and were exposed to both noises in strict rotation. Subjects were categorised as high- or low-sensitive to noise in general and low frequency noise in particular on the basis of questionnaires. Cortisol concentrations during the task were not significantly modulated by the noises or related to noise sensitivity alone. The normal circadian decline in cortisol concentration was however significantly attenuated in subjects high-sensitive to noise in general, when they were exposed to the low frequency noise. This noise was rated as more annoying and more disruptive to working capacity than the reference noise. The study showed physiological evidence of increased stress related to noise sensitivity and noise exposure during work. This is the first study to demonstrate an effect of moderate levels of noise on neuroendocrine activity. The impact of long-term exposure to moderate noise levels, and particularly low frequency noise, in the workplace deserves further investigation.     

Primary sequence determinants responsible for site-selective dephosphorylation of the PDGF beta-receptor by the receptor-like protein tyrosine phosphatase DEP-1

Site-selective dephosphorylation of receptor tyrosine kinases contributes to receptor regulation. The receptor-like protein tyrosine phosphatase DEP-1 site-selectively dephosphorylates the PDGF beta-receptor. DEP-1 dephosphorylation of original and chimeric phospho-peptides spanning the preferred pY1021 and the less preferred pY857 and pY562 sites was analyzed. Double substitutions of basic residues at -4 and +3 of pY857 and pY562 peptides improved affinity. Substitutions of single amino acids indicated preference for an acidic residue at position -1 and a preference against a basic residue at position +3. DEP-1 site-selective dephosphorylation of PDGF beta-receptor is thus determined by the primary sequence surrounding phosphorylation sites and involves interactions with residues spanning at least between positions -1 and +3.     

Genetic diversity amongst landraces of rye (Secale cereale L.) from northern Europe

Genetic variation and diversity were estimated for three improved varieties and 18 landraces of Secale cereale, originating from the northern Europe. This material was compared with eight improved varieties and 16 landraces from Sweden, which were analysed before. The analysis used starch gel electrophoresis with the enzymes ACO, GPI, MDH, PGD and PGM and resulted in one fixed locus and seven polymorphic loci. Most of the genetic diversity was found within the accessions and it was very small between accessions. The results show that the landraces from Germany and Norway have a low genetic variation compared to the other landraces in this study. This can possibly be explained with a small original sample size of some accessions. However, in the dendrogram these accessions are well separated. The landraces from Sweden and Finland showed a high genetic variation, which is almost the same for all these accessions. In the dendrogram all of the Finnish landraces and 11 of the Swedish ones were grouped together with a very small diversity index; they can almost be considered as part of the same accession. This is probably due to the fact that a high number of Finnish immigrants arrived in Sweden during the 17th century bringing their own rye material. The early Finnish rye landraces may have the same original source. The data also show that landraces as well as improved varieties have a high heterozygosity but they are separated in the dendrogram into different clusters. The currently used varieties show a large genetic distance variation, different from that in the landraces.     

Genetic variation in three species of Hordeum,and the selection of accessions for the Barley Core Collection

Starch gel electrophoresis of isozymes was used to investigate the level and distribution of genetic variation in accessions of three wild, diploid Hordeum species. Allelic variation was assessed for seven isozyme loci and used in the statistical analysis of 18 accessions of Hordeum brachyantherum subsp. californicum, 29 accessions of H. murinum subsp. glaucum and 11 accessions of H. pusillum. A major purpose with this study was to evaluate the selection of accessions for the international Barley Core Collection, complementing existing passport data. Allelic variation was found in all three species. The variation was mainly between accessions, as most accessions were fixed for certain alleles. Since all three species are self-pollinated, this was anticipated. The fact that the accessions have undergone one or several regeneration cycles from a rather limited number of individuals, after being collected, likely also have reduced the variation. The accessions were clustered by subjecting the genetic distances between them to UPGMA statistical treatment. The clusters in the dendrograms displayed for H. brachyantherum subsp. californicum and H. pusillum distinct patterns related to the geographical origin of the accessions. The accessions of H. murinum subsp. glaucum were less variable than the other two, and did not reveal such a clear pattern. By comparing the already made, geographically based, selection of accessions with the results from this study, it was evident that the selection had worked fairly well for H. brachyantherum subsp. californicum, but less so for the other two species.     

A single nucleotide polymorphism in the promoter region of the human gene for osteoprotegerin is related to vascular morphology and function

Osteoprotegerin (OPG) is a secreted member of the tumor necrosis factor receptor family, and has previously been shown to regulate bone mass by inhibiting osteoclast differentiation and activation. Recent evidence indicates that OPG also plays a role in the vascular system, since ablation of the OPG gene in mice results in calcification of the aorta and renal arteries, and association has been found between serum levels of OPG and cardiovascular mortality. This study presents a novel single nucleotide polymorphism, a T/C transition located 129 bp upstream the TATA-box of the human OPG gene, detected by sequence analysis. The OPG genotype was determined by restriction fragment length polymorphism in a cohort consisting of 59 healthy subjects. The intima-media thickness (IMT) in the common carotid artery and maximal post-ischemic forearm blood flow (FBF) were investigated. Subjects with the CC genotype showed a significantly increased IMT (p<0.05) and a concommitantly reduced maximal FBF (p<0.01) as compared to those with the T allele. Thus, our results show that the polymorphism in the promoter region of OPG is associated with both vascular morphology and function in apparently healthy subjects.     

Effects of digestive status on the reptilian gut

Reptiles, including the Burmese python, Python molurus bivittatus, that feed at infrequent intervals show a prominent increase in gastrointestinal mass, metabolism and brush border transport rates after feeding. Current knowledge and theories around these phenomena, as well as studies on the innervation of the reptilian gut, are summarised in this review. Little is known about the putative changes in the nervous and humoral control systems of the gut, and it is not known whether feeding affects innervation and motility of the stomach and intestine. Using immunohistochemistry, we have investigated possible up/down regulation of several neurotransmitters in specimens that had been fasted for a minimum of 3 weeks and specimens that had ingested a large meal 2 days before the experiments were conducted. There were no major changes in the innervation by nerves containing calcitonin gene-related peptide (CGRP), galanin, nitric oxide synthase (NOS), pituitary adenylate cyclase-activating polypeptide (PACAP), somatostatin (SOM), substance P/neurokinin A (SP/NKA), or vasoactive intestinal polypeptide (VIP)-like immunoreactivity. Nor did we find any differences in the effect of substance P (stomach and intestine), galanin (intestine), or bradykinin (intestine) on motility in strip preparations from the gut wall. A significant increase in dry weight of the intestine was obtained 48 h after feeding. We conclude that although there are considerable changes in gut thickness and absorptive properties after feeding, the smooth muscle and its control appear little affected.     

Potential applications and pitfalls of Bayesian inference of phylogeny

Only recently has Bayesian inference of phylogeny been proposed. The method is now a practical alternative to the other methods; indeed, the method appears to possess advantages over the other methods in terms of ability to use complex models of evolution, ease of interpretation of the results, and computational efficiency. However, the method should be used cautiously. The results of a Bayesian analysis should be examined with respect to the sensitivity of the results to the priors used and the reliability of the Markov chain Monte Carlo approximation of the probabilities of trees.     

The redox state of glutathione, cysteine and homocysteine in the extracellular fluid in the skin

Glutathione, the most abundant low-molecular weight thiol in the skin, has been shown to protect the skin from both photobiological and chemical injury. The thiols, glutathione in particular, have also been shown to be crucially involved in defence against contact allergens. Since the levels of extracellular thiol concentrations are important determinants of intracellular thiol status, we have compared the normal concentrations and the redox status of the main low-molecular weight thiol components in the extracellular fluid at the dermo-epidermal junction with the corresponding plasma levels. In their sulfhydryl form, all three thiols, i.e. glutathione, cysteine and homocysteine, were more abundant in experimental skin blister fluid than in plasma, as were the free disulfides of glutathione and homocysteine, whereas the free disulfides of cysteine were about the same in blister fluid and in plasma. Protein mixed disulfide levels were higher in plasma than in blister fluid. The present results provide information concerning the extracellular defence in the skin.