Chemotherapy of experimental visceral leishmaniasis in the opossum

Visceral leishmaniasis is a severe chronic disease of people and animals. The disease is caused by several subspecies of a protozoal organism, Leishmania donovani. If not treated, visceral leishmaniasis is often fatal. The most commonly used chemotherapeutic agents to treat the disease are pentavalent antimonials, which can be toxic, must be administered by parenteral routes, and are sometimes ineffective. In this study, meglumine antimoniate, a pentavalent antimony, was compared with WR 6026, an 8-aminoquinoline derivative, as to antileishmanial efficacy. The results indicate that either of these 2 drugs are effective in the suppression of amastigotes in the liver and spleen of the opossum. Despite the marked parasite suppression in the liver and spleen of the infected opossums, the experimental disease was fatal in all of the infected opossums, regardless of the therapy.     

A recombination event that redefines the Huntington disease region

We report both a recombination event that places the Huntington disease gene proximal to the marker D4S98 and an extended linkage-disequilibrium study that uses this marker and confirms the existence of disequilibrium between it and the HD locus. We also report the cloning of other sequences in the region around D4S98, including a new polymorphic marker R10 and conserved sequences that identify a gene in the region of interest.     

1H and 51V NMR studies of the interaction of vanadate and 2-vanadio-3-phosphoglycerate with phosphoglycerate mutase.

The formation of complexes of vanadate with 2-phosphoglycerate and 3-phosphoglycerate have been studied using 51V nuclear magnetic resonance spectroscopy. Signals attributed to two 2,3-diphosphoglycerate analogues, 2-vanadio-3-phosphoglycerate and 2-phospho-3-vanadioglycerate, were detected but were not fully resolved from signals of inorganic vanadate and the anhydride formed between vanadate and the phosphate ester moieties of the individual phosphoglycerates. Equilibrium constants for formation of the two 2,3-bisphosphate analogues were estimated as 2.5 M-1 for 2-vanadio-3-phosphoglycerate and 0.2 M-1 for 2-phospho-3-vanadioglycerate. The results of the binding study are fully consistent with non-cooperativity in the binding of vanadiophosphoglycerate to the two active sites of phosphoglycerate mutase (PGM). 2-Vanadio-3-phosphoglycerate was found to bind to the dephospho form of phosphoglycerate mutase with a dissociation constant of about 1 x 10(-11) M at pH 7 and 7 x 10(-11) M at pH 8. Three signals attributed to histidine residues were observed in the 1H NMR spectrum of phosphoglycerate mutase. Two of these signals and also an additional signal, tentatively attributed to a tryptophan, underwent a chemical shift change when the vanadiophosphoglycerate complex was bound to the enzyme. The results obtained here are in accord with these vanadate-phosphoglycerate complexes being much more potent inhibitors of phosphoglycerate mutase than either monomeric or dimeric vanadate. The dissociation constant of 10(-11) M for 2-vanadio-3-phosphoglycerate is about 4 orders of magnitude smaller than the Km for PGM, a result in accordance with the vanadiophosphoglycerates being transition state analogues for the phosphorylation of PGM by 2,3-diphosphoglycerate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ethanol transport in Zymomonas mobilis measured by using in vivo nuclear magnetic resonance spin transfer.

For the first time, unidirectional rate constants of ethanol diffusion through the lipid membrane of a microorganism, the bacterium Zymomonas mobilis, were determined, thus replacing indirect inferences with direct kinetic data. The rate constants k1 (in to out) were 6.8 +/- 0.4s(-1) at 29 degrees C and 2.7 +/- 0.3s(-1) at 20 degrees C. They were determined by using 1H selective nuclear magnetic resonance spin magnetization transfer. The measurements were done on l-ml cell suspensions. No addition of radiotracers, withdrawing of aliquots, physical separation methods, or chemical manipulations were required. Until now, the rate constants of ethanol transport in microorganisms have been unknown because ethanol diffuses through the cytoplasmic membrane too quickly for radiolabel approaches. Net velocities of ethanol exchange were calculated from unidirectional rate constants and cytoplasmic volume, which was also determined with the same nuclear magnetic resonance experiments. The results (i) confirmed that ethanol would not be rate limiting during the conversion of glucose by Z. mobilis and (ii) indicated that ethanol can serve as an in vivo marker of cytoplasmic volume changes. This was verified by monitoring for the first time the changes of both cytoplasmic volume and extracytoplasmic and cytoplasmic concentrations of alpha and beta anomers of D-glucose in cell suspensions of a microorganism. These findings may open up new possibilities for kinetic studies of ethanol and sugar transport in Z. mobilis and other organisms.     

Random root movements in weightlessness

The dynamics of root growth was studied in weightlessness. In the absence of the gravitropic reference direction during weightlessness, root movements could be controlled by spontaneous growth processes, without any corrective growth induced by the gravitropic system. If truly random of nature, the bending behavior should follow socalled 'random walk' mathematics during weightlessness. Predictions from this hypothesis were critically tested.
In a Spacelab ESA-experiment, denoted RANDOM and carried out during the IML-2 Shuttle flight in July 1994, the growth of garden cress ( Lepidium sativum ) roots was followed by time lapse photography at 1-h intervals.
The growth pattern was recorded for about 20 h. Root growth was significantly smaller in weightlessness as compared to gravity (control) conditions.
It was found that the roots performed spontaneous movements in weightlessness. The average direction of deviation of the plants consistently stayed equal to zero, despite these spontaneous movements. The average squared deviation increased linearly with time as predicted theoretically (but only for 8–10 h).
Autocorrelation calculations showed that bendings of the roots, as determined from the 1-h photographs, were uncorrelated after about a 2-h interval.
It is concluded that random processes play an important role in root growth. Predictions from a random walk hypothesis as to the growth dynamics could explain parts of the growth patterns recorded. This test of the hypothesis required microgravity conditions as provided for in a space experiment.     

A comparison of the toxic and sub-lethal effects of fluvalinate and esfenvalerate on the twospotted spider mite (Acari: Tetranychidae)

There was no difference in the direct toxicity of fluvalinate and esfenvalerate to twospotted spider mite (TSSM), Tetranychus urticae Koch. adults. The residual toxicity LC₅₀ of esfenvalerate was lower. Neither pyrethroid was toxic (<10% mortality) to TSSM eggs or adults at their recommended field concentrations. Fluvalinate was twice as toxic (45% mortality) than esfenvalerate to TSSM larvae at 0.01 g.a.i L^-1. The toxicity of the pyrethroids to TSSM protonymphs and deutonymphs was similar (16–28% mortality at 0.1 g a.i. L^-1). Dispersal from the treated surface was the main response to both pyrethroids by TSSM protonymphs, deutonymphs and adults. Maximum run-off by TSSM adults from fluvalinate and esfenvalerate treated surfaces was found with 0.01 and 0.005 g a.i. L^-1 respectively. Spin-down from pyrethroid treated surfaces was positively correlated with concentration. Oviposition was negatively correlated with concentration. Fluvalinate caused greater reductions in oviposition than esfenvalerate. Both pyrethroids reduced TSSM development rate from larval, protonymph and deutonymph stages, but fluvalinate caused larger reductions. Both pyrethroids prevented mating: for ten days oviposition 93% and 98% of offspring were male for esfenvalerate and fluvalinate respectively at 0.1 g a.i. L^-1. These findings are discussed with respect to the incidence of pyrethroid induced mite outbreaks.     

Hand dominance and bilateral asymmetry in the structure of the second metacarpal

Bilateral asymmetry in the structure of the second metacarpal was examined in relation to functional hand dominance in a large, clinically nonselected, healthy population sample from the Baltimore Longitudinal Study of Aging. Bilateral bone measurements were made from anteroposterior hand radiographs of a total of 992 individuals, 609 males and 383 females, with an age range of 19–94 years. Hand dominance was determined on the basis of personal impression. Total width and medullary width at the midshaft of the second metacarpal were measured to 0.05 mm using a Helios caliper. These two measurements were used to derive cortical thickness, cortical bone area, periosteal (total) area, medullary area, percent cortical area, and the second moment of area in the mediolateral plane. In both right and left-handed individuals, statistically significant side differences were found in the calculated bone areas and the second moment of area, with the dominant hand being larger. Cortical thickness did not show significant side-related differences for either handedness. These results show that functional handedness leads to periosteal and endosteal expansion of the second metacarpal cortex on the dominant side, increasing bone strength without increasing cortical thickness. This is the first time this pattern of asymmetry has been reported in left-handers as well as right-handers. Our results argue for the primacy of environmental (mechanical) effects in determining bilateral asymmetry of limb bone structural properties. © 1994 Wiley-Liss, Inc.