Plasmodium falciparum: in vitro activity of sulfadoxine and dapsone in field isolates from Kenya: point mutations in dihydropteroate synthase may not be the only determinants in sulfa resistance

We have determined the relationship between point mutations in the gene that encodes the sulfa target, dihydropteroate synthase (DHPS) and the chemosensitivity profile to sulfadoxine and dapsone in 67 isolates from Kilifi, Kenya. We assessed the presence of mutations at codons 436, 437, 540, 581, and 613 of dhps. The results showed that the dhps genotype had a strong influence on the sensitivity to sulfadoxine and dapsone, but that the correlation was far from perfect. Eleven isolates carried a wild-type dhps allele, but were resistant to sulfadoxine (IC(50) values >10 microg/ml), and 4/28 isolates were classed as sensitive to sulfadoxine (IC(50) values <10 microg/ml), but carried a triple mutant (436/437/613) allele of dhps. These data show that in low folate medium in vitro, the dhps genotype alone did not account completely for sulfadoxine or dapsone resistance; other factors such as the utilisation of exogenous folate must also be considered.     

Temperature effects and genotype-temperature interactions on sex determination in the European sea bass (Dicentrarchus labrax L.)

The effect of temperature on sex-ratios in 27 families of sea bass reared in the same tank from the fertilization stage onward was investigated. An excess of males (68%) was found in the groups that were reared at high temperature (mean +/- standard deviation: 20+/-1 degrees C) until they reached the mean size of 8.1 cm (Standard Length, 149 days post-fertilization [p.f.]). Masculinization was higher (89% of males) in the groups maintained at low temperature (13 degrees C), from fertilization to a mean length of 6.5 cm (346 days p.f.). Shifts from high to low temperature at 8.1cm and from low to high temperature at 6.5 cm had no consequence on the sex-ratio. The percentage of males showing intratesticular oocytes was higher at low temperature (63%) than at high temperature (36%), suggesting that these males may be sensitive fish that have been masculinized by environmental factors. Fish sampled in the groups reared at high (2,200 fish) and low (500 fish) temperature were genotyped on three microsatellite loci. This allowed them to be assigned to the breeders used in the crossing design, thus permitting an analysis of parental influence on sex-ratios. In groups reared at high temperature, both parents had a significant additive effect on the percentage of females, and the interaction between sire and dam was not significant. Genotype temperature interactions were also detected and their existence suggests the interesting possibility of selecting nonsensitive genotypes in breeding programs.     

Hereditary spastic paraplegia SPG13 is associated with a mutation in the gene encoding the mitochondrial chaperonin Hsp60

SPG13, an autosomal dominant form of pure hereditary spastic paraplegia, was recently mapped to chromosome 2q24-34 in a French family. Here we present genetic data indicating that SPG13 is associated with a mutation, in the gene encoding the human mitochondrial chaperonin Hsp60, that results in the V72I substitution. A complementation assay showed that wild-type HSP60 (also known as "HSPD1"), but not HSP60 (V72I), together with the co-chaperonin HSP10 (also known as "HSPE1"), can support growth of Escherichia coli cells in which the homologous chromosomal groESgroEL chaperonin genes have been deleted. Taken together, our data strongly indicate that the V72I variation is the first disease-causing mutation that has been identified in HSP60.     

Engrailed homeoprotein secretion is a regulated process

Chicken Engrailed 2 homeoprotein is transported between cells in culture. This intercellular transfer is based on unconventional secretion and internalisation mechanisms: Engrailed 2 has access to vesicles but lacks a signal sequence for secretion and is internalised by a non-endocytic process. We show that phosphorylation of a serine-rich domain within Engrailed 2 by the protein kinase CK2 specifically inhibits Engrailed 2 secretion. The availability of the serine-rich domain to CK2 is highly increased when it is displaced from its normal position to the C terminus of Engrailed 2, leading to a constitutive blockage of Engrailed 2 intercellular transfer. This indicates that intercellular transfer of Engrailed 2 is a highly regulated process.     

In vitro self-assembled HCV core virus-like particles induce a strong antibody immune response in sheep.

The in vitro self-assembly properties of the entire hepatitis C virus core protein (HCcAg) obtained from Pichia pastoris cells and the induction of specific antibody immune response were studied. HCcAg was purified as a low-molecular-weight species by electroelution under denaturing conditions for confirmation of its self-assembly properties. After renaturalization, electron microscopy showed that HCcAg assembled into spherical particles of 30 nm. HCcAg also showed homogeneity and was specifically recognized by serum from a chronic HCV carrier patient. The data indicated that in vitro assembly of HCcAg, into virus-like particles resembling HCV nucleocapsid particles at a mature stage, is an intrinsic quality of this protein. Finally, HCcAg generated a strong antibody immune response in sheep, suggesting its usefulness for stimulating the host immune response against HCV.     

Hyposialylation of integrins stimulates the activity of myeloid fibronectin receptors

Despite numerous reports suggesting that beta(1) integrin receptors undergo differential glycosylation, the potential role of N-linked carbohydrates in modulating integrin function has been largely ignored. In the present study, we find that beta(1) integrins are differentially glycosylated during phorbol ester (PMA)-stimulated differentiation of myeloid cells along the monocyte/macrophage lineage. PMA treatment of two myeloid cell lines, U937 and THP-1, induces a down-regulation in expression of the ST6Gal I sialyltransferase. Correspondingly, the beta(1) integrin subunit becomes hyposialylated, suggesting that the beta(1) integrin is a substrate for this enzyme. The expression of hyposialylated beta(1) integrin isoforms is temporally correlated with enhanced binding of myeloid cells to fibronectin, and, importantly, fibronectin binding is inhibited when the Golgi disrupter, brefeldin A, is used to block the expression of the hyposialylated form. Consistent with the observation that cells with hyposialylated integrins are more adhesive to fibronectin, we demonstrate that the enzymatic removal of sialic acid residues from purified alpha(5)beta(1) integrins stimulates fibronectin binding by these integrins. These data support the hypothesis that unsialylated beta(1) integrins are more adhesive to fibronectin, although desialylation of alpha(5) subunits could also contribute to increased fibronectin binding. Collectively our results suggest a novel mechanism for regulation of the beta(1) integrin family of cell adhesion receptors.     

Parkinson's disease: what have we learned from the genes responsible for familial forms?

Parkinson's disease is characterized by the progressive and selective loss of the dopaminergic neurons in the substantia nigra and the presence of ubiquitinated protein inclusions termed Lewy bodies. In the past six years, four genes involved in rare inherited forms of Parkinson's disease have been identified: mutations in the alpha-synuclein and ubiquitin carboxyterminal hydrolase L1 genes (UCH-L1) cause autosomal dominant forms, whereas mutations in the Parkin and DJ-1 genes are responsible for autosomal recessive forms of the disease. A toxic gain of function related to the ability of alpha-synuclein to assemble into insoluble amyloid fibrils may underlie neuronal cell death in parkinsonism due to alpha-synuclein gene mutations. In contrast, loss of protein function appears to be the cause of the disease in parkinsonism due to mutations in the genes encoding Parkin and UCH-L1, which are key enzymes of the ubiquitin-proteasome pathway. The presence of alpha-synuclein, Parkin and UCH-L1 in Lewy bodies suggests that dysfunction of pathways involved in protein folding and degradation is not only involved in the pathogenesis of familial Parkinson's disease, but could also play a role in the frequent sporadic form of the disease (idiopathic Parkinson's disease).     

Insulin resistance and its contribution to colon carcinogenesis

The insulin resistance-colon cancer hypothesis, stating that insulin resistance may be associated with the development of colorectal cancer, represents a significant advance in colon cancer, as it emphasizes the potential for this cancer to become a modifiable disease. The fact that the incidence of insulin resistance has been increasing in the United States and much of the rest of the Western world where colon cancer remains the second leading cause of cancer death makes the exploration of the interrelationship of these conditions a subject of high priority. Here, we review the salient features of insulin resistance, defined as impaired biological response to the action of insulin. Recent epidemiological studies, evaluating potential associations between colon cancer risk and diabetes mellitus, dietary intake and metabolic factors, and IGF levels in several clinical settings, provide strong support of the insulin resistance-colon cancer hypothesis (without establishing causality). Mechanistically, insulin resistance has been associated with hyperinsulinemia, increased levels of growth factors including IGF-1, and alterations in NF-kappaB and peroxisome proliferator-activated receptor signaling, which may promote colon cancer through their effects on colonocyte kinetics. It is a reasonable expectation that in the not too distant future, critical interventions to the already mapped molecular sequence of events, which link two apparently disparate entities, combined with lifestyle changes could abrogate the development of colon cancer.     

Molecular monitoring of the Leu-164 mutation of dihydrofolate reductase in a highly sulfadoxine/pyrimethamine-resistant area in Africa

Background

Procalcitonin (PCT) is closely correlated with parasite burden and clinical outcome in falciparum malaria. The role of PCT in tertian malaria has not previously been investigated.

Patients and methods

PCT serum levels in 37 patients with tertian malaria were analysed. Clinical and laboratory parameters were assessed and statistically correlated both to the initial PCT levels and during the course of the disease.

Results

PCT levels rose for one day after commencing treatment and declined thereafter. However, there was no significant correlation with parasite burden, clinical parameters, laboratory values, or the presence of semi-immunity. Before treatment, the majority of patients showed normal or slightly elevated PCT levels (< 2.5 ng/ml), but PCT was markedly elevated (4.8 – 47 ng/ml) in one third of the population. The two groups did not differ by any other of the assessed parameters. Thus, while the post-treatment course of PCT resembles falciparum malaria, the lack of correlation between disease severity and even high PCT levels in a large proportion of patients is intriguing.

Conclusions

There is a fundamental difference in the relationship of PCT with tertian malaria not seen in other infectious diseases in which elevated PCT levels have been observed. This suggests distinct pathophysiological pathways in malaria.