Studies on the mechanism of castanospermine inhibition of alpha- and beta-glucosidases

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) is an indolizidine alkaloid that was isolated from the Australian plant, Castanospermum australe. This alkaloid was found to be a potent inhibitor of lysosomal alpha- and beta-glucosidases. In this report, the mechanism of inhibition of amyloglucosidase (an exo-1,4-alpha-glucosidase) and almond emulsin beta-glucosidase was examined. Castanospermine proved to be a competitive inhibitor of amyloglucosidase at both pH 4.5 and 6.0 when assayed with the p-nitrophenyl-alpha-D-glucoside. It was also a competitive inhibitor of almond emulsin beta-glucosidase at pH 6.5, but in this case previous studies had shown that inhibition was of the mixed type at pH 4.5 to 5.0. Th pH of the incubation mixture had a marked effect on the inhibition. Thus, in all cases, castanospermine was a much better inhibitor at pH 6.0 to 6.5 than it was at lower pH values. The pK for castanospermine was found to be 6.09, indicating that the alkaloid was probably more active in the unprotonated form. This was also suggested by the fact that the N-oxide of castanospermine, while still a competitive inhibitor, was 50 to 100 times less active than was castanospermine, and its activity was not markedly altered by pH. These results probably explain why castanospermine is a good inhibitor of the glycoprotein processing enzyme, glucosidase I, since this is a neutral enzyme.     

Risk of Infection with Leishmania spp. in the Canine Population in the Netherlands

The dog is the main reservoir of Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in humans in Southern Europe. In order to identify the risk of dogs from a Leishmania non-endemic area traveling to a Leishmania -endemic area becoming infected and the risk of transmitting infection to humans in non-endemic areas an investigation was performed, in which the results of a questionnaire were combined with the results of a serologic survey.     

Lymphocyte responses to influenza and tetanus toxoid in vitro following intensive exercise and carbohydrate ingestion on consecutive days.

The effect of carbohydrate (CHO) ingestion on antigen- (rather than mitogen-) stimulated T-cell responses to prolonged, intensive exercise may give a more realistic insight into the effect of CHO on T-cell functional capacity and subsequent infection risk. This study investigated the effect of CHO ingestion during prolonged, intensive exercise on influenza- and tetanus toxoid-stimulated T-cell cytokine mRNA expression and proliferation. Mitogen- [phytohemagglutinin (PHA)] stimulated proliferation was assessed for comparison. Responses were assessed following exercise on consecutive mornings to determine any carryover effect. Fifteen male games players performed two exercise trials in a double-blind, randomized, crossover design. Each trial comprised 90 min of intensive, intermittent running on consecutive mornings, with either CHO (6.4% wt/vol) or placebo (PLA) beverage ingestion before, during, and after each bout of exercise. Postexercise CD3(+) cell counts were higher in PLA than CHO on both days (P < 0.05). Antigen-stimulated T-cell cytokine mRNA expression was unaffected by exercise or CHO ingestion. Before exercise on day 2, T-cell proliferative responses to PHA, influenza, and tetanus toxoid were higher in CHO than PLA by 99, 80, and 58%, respectively (P < 0.01 for PHA, P < 0.05 for influenza and tetanus toxoid). At 1 h postexercise on day 2, PHA-induced proliferation was 70% higher in CHO than PLA (P < 0.05), yet there were no differences between trials for antigen-induced proliferative responses. Therefore, mitogen-induced T-cell proliferation following strenuous exercise and CHO does not necessarily reflect responses to specific antigens and, consequently, may not provide a good model for the situation in vivo.     

Degenerative joint disease among populations in Wensleydale,England and Jamaica

The prevalence of rheumatic complaints has been compared in populations living in Jamaica and Wensleydale. The Jamaicans had fewer complaints and had less incapacity from musculo-skeletal disorders than the Wensleydale populations. Radiological evidence of disc degeneration, both cervical and lumbar, was more frequent and severs in the Jamaican population, but the symptoms were less frequent for each grade of severity in the Jamaicans.Generalized osteo-arthrosis was found with about the same frequency in the two areas but was seldom associated with Heberden's nodes in Jamaica. Symptoms were less frequent in relation to all sites of osteoarthrosis except the cervical spine. The mean air temperature is 14°C higher in Jamaica than in Wensleydale and the radiant heat is more than twice as great.It is estimated that a farmer in Jamaica receives 90 kcal cm^–2/year compared with 44 kcal cm^–2/year in Wensleydale. The cooling index was three times as great in Wensleydale as in Jamaica. It is suggested that the low prevalence of rheumatic complaints in Jamaicans is due to an influence of increased radiation and diminished cooling on pain threshold.

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Zusammenfassung Es wurde das Vorkommen rheumatischer Erkrankungen in Bevölkerungsgruppen in Jamaika und in Wensleydale untersucht. Die Gruppe in Jamaika hatte Fieberzustände und weniger Beschwerden im Muskel-Skelettbereich als die in England.Der radiologische Nachweis von Bandscheibendegenerationen brachte sowohl cervical wie lumbal bei der Population von Jamaika mehr und schwerere Fälle, aber die Symptome traten hier bei jedem Schweregrad seltener auf.Generalisierte Osteoarthrosen wurden in den beiden Gebieten gleich häufig gefunden, waren jedoch in Jamaika selten mit Heberdenschen Knoten gekoppelt. Die Symptome waren an allen Stellen des Auftretens der Osteoarthrose mit Ausnahme des Nackenwirbels weniger häufig. Die mittlere Lufttemperatur liegt in Jamaika um 14°C höher als in Wensleydale,die Strahlungswärme ist mehr als doppelt so hoch. Man schätzt, dass ein Farmer in Jamaika 90 kcal cm^–2/Jahr empfängt, verglichen mit 44 kcal cm^–2/Jahr in Wensleydale. Der Abkühlungsindex ist in Wensleydale dreimal so gross wie in Jamaika. Es wird angenommen,dass das geringe Vorkommen rheumatischer Beschwerden in Jamaika eine Folge des Einflusses der stärkeren Strahlung und geringeren Kühle auf die Schmerzschwelle ist.

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Resume On a comparé l'apparition de maux d'origine rhumatismale à la Jamaïque et à Wensleydale. Les Jamaïcains présentaient de la fièvre,mais moins de troubles squeleto-musculaires que les gens de Wensleydale. Des examens radiologiques ont montré davantage et de plus graves dégénérescences disquaires aussi bien cervicales que lombaires dans la population de la Jamaïque. Pourtant,les symptômes cliniques y furent moins fréquents pour chaque degré de gravité. La fréquence des ostéo-arthroses généralisées fut approximativement la même aux deux endroits. Cette affection était cependant rarement liée à des nodosités de Heberden à la Jamaïque.Les symptômes cliniques en furent partout moins fréquents sauf en ce qui concerne les vertèbres cervicales. La température est, à la Jamaïque, de 14°C supérieure à celle de Wensleydale et la chaleur de rayonnement y est plus que double. On estime qu'un paysan de la Jamaïque reçoit 90 kcal cm^–2/ans contre 44 kcal cm^–2/ans pour celui de Wensleydale. L'indice de réfrigération est par contre trois fois plus grand à Wensleydale qu'à la Jamaïque. On admet enfin que la plus faible fréquence des maux rhumatismaux dont se plaignent les Jamaïcains est due à une influence du plus intense rayonnement et de la plus faible réfrigération sur le seuil de réaction à la douleur.

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Presented at the Fourth Int.Biometeorological Congress, New Brunswick, N.Y., 26 August – 2 September 1966.     

Onchocerciasis control: Moving towards the millennium

The recognition of onchocerciasis as a major public health problem in the savanna belts of West Africa resulted in the establishment of the Onchocerciasis Control Programme (OCP) in 1974. Control was initially based on vector control by weekly larviciding. The OCP is now in transition towards its final phase in which repeated treatment with ivermectin, a safe and effective microfilaricide, is incorporated with vector control, or in certain circumstances is used alone. Ivermectin distribution hingeing on sustainable community systems is the basis of a new programme in endemic African countries outside the OCP and in the Americas. David Molyneux and John Davies describe the latest trends and developments related to onchocerciasis control.     

Retinal Pathology of Pediatric Cerebral Malaria in Malawi

Introduction

The causes of coma and death in cerebral malaria remain unknown. Malarial retinopathy has been identified as an important clinical sign in the diagnosis and prognosis of cerebral malaria. As part of a larger autopsy study to determine causes of death in children with coma presenting to hospital in Blantyre, Malawi, who were fully evaluated clinically prior to death, we examined the histopathology of eyes of patients who died and underwent autopsy.

Methodology/Principal Findings

Children with coma were admitted to the pediatric research ward, classified according to clinical definitions as having cerebral malaria or another cause of coma, evaluated and treated. The eyes were examined by direct and indirect ophthalmoscopy. If a child died and permission was given, a standardized autopsy was carried out. The patient was then assigned an actual cause of death according to the autopsy findings. The eyes were examined pathologically for hemorrhages, cystoid macular edema, parasite sequestration and thrombi. They were stained immunohistochemically for fibrin and CD61 to identify the components of thrombi, β-amyloid precursor protein to detect axonal damage, for fibrinogen to identify vascular leakage and for glial fibrillary acidic protein to detect gliosis. Sixty-four eyes from 64 patients were examined: 35 with cerebral malaria and 29 with comas of other causes. Cerebral malaria was distinguished by sequestration of parasitized erythrocytes, the presence and severity of retinal hemorrhages, the presence of cystoid macular edema, the occurrence and number of fibrin-platelet thrombi, the presence and amount of axonal damage and vascular leakage.

Conclusions/Significance

We found significant differences in retinal histopathology between patients who died of cerebral malaria and those with other diagnoses. These histopathological findings offer insights into the etiology of malarial retinopathy and provide a pathological basis for recently described retinal capillary non-perfusion in children with malarial retinopathy. Because of the similarities between the retina and the brain it also suggests mechanisms that may contribute to coma and death in cerebral malaria.     

The Diagnostic and Prognostic Accuracy of Five Markers of Serious Bacterial Infection in Malawian Children with Signs of Severe Infection

Background

Early recognition and prompt and appropriate antibiotic treatment can significantly reduce mortality from serious bacterial infections (SBI). The aim of this study was to evaluate the utility of five markers of infection: C-reactive protein (CRP), procalcitonin (PCT), soluble triggering receptor expressed on myeloid cells-1 (sTREM-1), CD163 and high mobility group box-1 (HMGB1), as markers of SBI in severely ill Malawian children.

Methodology and Principal Findings

Children presenting with a signs of meningitis (n = 282) or pneumonia (n = 95), were prospectively recruited. Plasma samples were taken on admission for CRP, PCT, sTREM-1 CD163 and HMGB1 and the performance characteristics of each test to diagnose SBI and to predict mortality were determined. Of 377 children, 279 (74%) had SBI and 83 (22%) died. Plasma CRP, PCT, CD163 and HMGB1 and were higher in HIV-infected children than in HIV-uninfected children (p<0.01). In HIV-infected children, CRP and PCT were higher in children with SBI compared to those with no detectable bacterial infection (p<0.0005), and PCT and CD163 were higher in non-survivors (p = 0.001, p = 0.05 respectively). In HIV-uninfected children, CRP and PCT were also higher in children with SBI compared to those with no detectable bacterial infection (p<0.0005), and CD163 was higher in non-survivors (p = 0.05). The best predictors of SBI were CRP and PCT, and areas under the curve (AUCs) were 0.81 (95% CI 0.73–0.89) and 0.86 (95% CI 0.79–0.92) respectively. The best marker for predicting death was PCT, AUC 0.61 (95% CI 0.50–0.71).

Conclusions

Admission PCT and CRP are useful markers of invasive bacterial infection in severely ill African children. The study of these markers using rapid tests in a less selected cohort would be important in this setting.