Molecular heterogeneity underlying the G6PD Mediterranean phenotype

Summary As part of a study aiming to define the molecular basis of glucose-6-phosphate dehydrogenase (G6PD) deficiency, we analysed a sample from a Portugese boy with a family history of favism. Although the biochemical properties of red-cell G6PD from this subject were similar to those of the common variant G6PD Mediterranean, the corresponding mutation (563 CT) was not present. Instead, polymerase chain reaction (PCR) amplification and sequencing of the entire gene detected a CT transition at nucleotide 592 in exon VI, changing an arginine residue to a cysteine residue only 10 amino acids downstream from the Mediterranean mutation. Single-strand conformation polymorphism analysis of a PCR-amplified DNA fragment spanning exons VI and VII of the G6PD gene has detected the same mutation, confirmed by sequencing, in a G6PD-deficient patient from Southern Italy. We name this new variant G6PD Coimbra.     

Application of automated DNA sizing technology for genotyping microsatellite loci.

Highly polymorphic microsatellite loci offer great promise for gene mapping studies, but fulfillment of this potential will require substantial improvements in methods for accurate and efficient genotyping. Here, we report a genotyping method based on fluorescently labeled PCR primers and size characterization of PCR products using an automated DNA fragment analyzer. We capitalize on the availability of three distinct fluorescent dyes to label uniquely loci that overlap in size, and this innovation increases by threefold the number of loci that can be analyzed simultaneously. We label size standards with a fourth dye and combine these with the microsatellite PCR products in each gel lane. Computer programs provide very rapid and accurate sizing of microsatellite alleles and efficient data management. In addition, fluorescence signals are linear over a much greater range of intensity than conventional autoradiography. This facilitates multiplexing of loci (since signal intensities often vary greatly) and helps distinguish major peaks from artifacts, thereby improving genotyping accuracy.     

Failure to kindle seizures after repeated intracerebral administration of arginine vasopressin

In an attempt to kindle seizures with arginine-vasopressin (AVP), we injected AVP into the amygdala or hippocampus of rats. Although behavioral and electrographic alterations were sometimes observed, seizures failed to develop, even in rats that had previously been kindled with electrical stimulation. This and previous failures to kindle seizures by intraventricular injections of AVP call into question the possibility of AVP kindling.     

Chromosome size polymorphisms in Plasmodium falciparum can involve deletions and are frequent in natural parasite populations

A comparison of independent cultured isolates of Plasmodium falciparum revealed that while chromosome number was constant, the sizes of analogous chromosomes varied widely. We show here that chromosome size polymorphisms are not generated during differentiation of the asexual blood stages, as the molecular karyotype of a cloned parasite line is constant through this part of the life cycle. Experiments using whole P. falciparum chromosomes as hybridization probes to examine polymorphisms within two independent parasite populations indicate that the polymorphisms observed here are not the consequence of large-scale interchromosomal exchanges, and imply that deletions/duplications represent one mode of generating chromosome length polymorphisms. Although the deletions probably involve repetitive DNA, we show here that structural genes for P. falciparum antigens can also be lost. Furthermore, these dramatic size polymorphisms occur not only in cultured lines of P. falciparum, but with surprising frequency in natural malarial infections.     

The effect of papain upon proline and sodium transport of rat renal brush-border membrane vesicles

Treatment of renal brush-border membrane vesicles with papain resulted in the removal of the activity of maltase, gamma-glutamyl transpeptidase and leucine aminopeptidase by 85, 50 and 75%, respectively. Stripping of these membrane enzyme activities constituted about 2% of the total membrane proteins and resulted in a widespread diminution in the ability of a variety of amino acids and sugars to be taken up by the membrane vesicles which remained osmotically responsive. Kinetic analysis of the uptake of proline, which was shown previously to be transported by both sodium-dependent and sodium-independent systems, revealed that the Vmax for the sodium-dependent system and Km for the sodium-independent system were halved, but other parameters were not affected indicating that the papain treatment altered sodium-gradient-stimulated entry and the affinity of the sodium-gradient-independent system for proline. Experiments on sodium entry and efflux demonstrate a marked enhancement of flux, so that equilibration of the sodium gradient occurred about 5-times more rapidly than in untreated vesicles. This occurred without any change in the osmotic properties of the vesicle with regard to sodium or amino acid uptake. Studies of fluorescence polarization suggest that incubation with papain does not alter the lipid domains of the membrane.     

Inhibitors from Carob (Ceratonia siliqua L.) I. Nature of the Interaction With Gibberellic Acid on Shoot Growth

Concentrated whole extracts of the immature fruit of carob and 3 fractions derived from this extract have been shown to inhibit the gibberellic acid induced growth of pea seedlings. The inhibition can be completely reversed by increasing the amount of gibberellic acid. The inhibitors do not reduce the endogenous growth of seedlings but only that induced by gibberellic acid. One of the fractions is a newly separated one not previously reported.     

Urethane anesthesia blocks the development and expression of kindled seizures

The effect of anesthetic and subanesthetic doses of urethane on the development of amygdala kindled seizures and on the expression of previously kindled seizures was studied in hooded rats. An anesthetic dose of urethane (1.5 g/kg) almost completely eliminated evoked afterdischarge and completely eliminated convulsive behavior in both groups. It also eliminated the seizure response to pentylenetetrazol. Subanesthetic doses of urethane (0.25 and 0.5 g/kg) strongly attenuated the expression of previously kindled seizures. These results suggest that urethane may not be an appropriate anesthetic for the study of epileptiform phenomena.