Cell wall synthesis during growth and maturation of Nitella internodal cells

An improved ¹³C-density-labeling method was used to study cell wall synthesis in rapidly expanding, slowly expanding and recently mature internodes of Nitella translucens var axillaris (A.Br.) R.D.W. As cells matured, the rate of wall synthesis slowed and the deposition of cellulose microfibrils changed from a predominantly transverse direction in the primary wall of rapidly expanding internodes to a helicoidal array in the secondary wall of mature internodes. The secondary wall was characterized by relatively higher rates of cellulose synthesis and lower rates of pectin synthesis than the primary wall. The synthesis of xyloglucan also decreased markedly at the transition to secondary wall synthesis, while the synthesis of mannose-rich hemicellulose increased. Even though structural differences were striking between the primary and secondary walls of Nitella, compositional differences between the two types of wall were quantitative rather than qualitative. The authors appreciate the assistance of Martin Yousef with the electron microscopy.     

Brain S-Adenosylmethionine Levels Are Severely Decreased in Alzheimer's Disease

Abstract: S -Adenosylmethionine is an essential ubiquitous metabolite central to many biochemical pathways, including transmethylation and polyamine biosynthesis. Reduced CSF S -adenosylmethionine levels in Alzheimer's disease have been reported; however, no information is available regarding the status of S -adenosylmethionine or S -adenosylmethionine-dependent methylation in the brain of patients with this disorder. S -Adenosylmethionine concentrations were measured in postmortem brain of 11 patients with Alzheimer's disease. We found decreased levels of S -adenosylmethionine (−67 to −85%) and its demethylated product S -adenosylhomocysteine (−56 to −79%) in all brain areas examined (cerebral cortical subdivisions, hippocampus, and putamen) as compared with matched controls (n = 14). S -Adenosylmethionine and S -adenosylhomocysteine levels were normal in occipital cortex of patients with idiopathic Parkinson's disease (n = 10), suggesting that the decreased S -adenosylmethionine levels in Alzheimer's disease are not simply a consequence of a chronic, neurodegenerative condition. Reduced S -adenosylmethionine levels could be due to excessive utilization in polyamine biosynthesis. The severe reduction in levels of this essential biochemical substrate would be expected to compromise seriously metabolism and brain function in patients with Alzheimer's disease and may provide the basis for the observations of improved cognition in some Alzheimer's patients following S -adenosylmethionine therapy.     

Effects of high altitude exposure on components of blood and urine in mountaineers

Physiological correlations with impaired or umimpaired performance at high altitude were sought among 24 blood and urine parameters measured in 50 mountaineers and 21 observers before (preclimb) and after (postclimb) expeditions on Mt. McKinley. Values and per cent changes were compared for five degrees of impairment at high altitude. Average preclimb values were all near established normal levels and no correlations with subsequent involvement at high altitude were found. Postclimb samples contained more Hb, PCV, urea, LDH, and HBD and less bilirubin (P < 0.05). But no association was found between degrees of altitude impairment and preclimb/postclimb changes in any of the 24 blood and urine parameters. Additional results from samples collected at 4300 m showed "weaker" mountaineers excreted 1/4 as much Na in urine and had 50% more serum FFA concentration than stronger mountaineers.

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Zusammenfassung Bei 50 Bergsteigern und 21 Beobachtern wurden vor und nach einer Expedition zum Mt. McKinley (Alaska) für 24 Parameter im Blut und Harn die Beziehungen zur Abschwächung der Leistung in grosser Höhe untersucht. Zum Vergleich wurden 5 Grade von unbeeinflusster bis schwerer Schädigung in der Höhe verwendet. Die mittleren Werte vor dem Aufstieg lagen alle im Bereich der Normbreite. Beziehungen zu nachfolgenden Komplikationen in der Höhe bestanden nicht. Nach dem Aufstieg waren Hgb, Hämatokrit, Harnstoff, LDH, Hydroxybutyric Dehydrogenase erhöht und Bilirubin erniedrigt (P < 0, 05). Es liess sich jedoch für keinen Parameter eine Beziehung zwischen dem Ausmass der Höhenschädigung und den Veränderungen vor und nach dem Aufstieg nachweisen. Zusätzliche Ergebnisse von Proben, die in 4300 m Höhe gesammelt wurden, ergaben, dass schwache Bergsteiger ein Viertel soviel Na im Harn ausschieden und 50% mehr freie Fettsäuren im Blut aufwiesen als starke Bergsteiger.

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Resume On a mesuré 24 paramètre du sang et de l'urine de 50 alpinistes et 21 observateurs avant et après l'ascension du Mont McKinley (Canada). On a établi ensuite la corrélation physiologique existant entre ces paramètres et une diminution éventuelle des performances. Les valeurs absolues et le taux de modification ont été comparés à 5 degrés de diminution des capacités physiques à haute altitude. Les valeurs moyennes des analyses faites avant l'ascension ont toutes été voisines du niveau normal et on n'a pas constaté de corrélation avec les performances individuelles subséquentes. Les échantillons recueillis après l'ascension contenaient davantage de Hb, PCV, urée, LDH, et HBD, mais moins de bilirubine (P < 0, 05). On n'a cependant trouvé aucune relation entre le degré de diminution des performances et les modifications d'aucun des 24 paramètres retenus du sang ou de l'urine avant et après l'ascension. Des échantillons prélevés à 4300 m d'altitude ont montré que les alpinistes peu aguerris ne sécrétaient que le 1/4 du Na par l'urine, mais avaient 50% d'acides gras libres de plus dans le sang que les montagnards les plus résistants.

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Work supported by Themis Contract No DADA 17-68-C-8018     

Effects of age and streptozotocin-induced diabetes on biogenic amines in rat tail artery

The changes in amine concentrations in different segments of the rat tail artery have been investigated at different ages and after different durations of streptozotocin-induced diabetes. There was a significant positive slope to the relationship between amine concentrations and age in proximal portion of the normal tail artery, and a significant additional increase in amine concentrations following induction of diabetes. The peak of the latter response occurred between 10 and 20 weeks following the induction of diabetes. There was also a significant dependence on the length of the post-ganglionic neurones, which may be related to the failure of axonal transport of some of the essential enzymes or transporters for these biogenic amines. This model of altered catecholamine metabolism and handling requires further investigation so that alterations in the mechanisms involved in processing of these amines in diabetic autonomic neuropathy may be elucidated.     

Use of stable isotopes to measure the metabolic activity of the human intestinal microbiota

The human intestinal microbiota is a complex biological system comprising a vast repertoire of microbes with considerable metabolic activity relevant to both bacterial growth and host health. Greater strides have been made in the analysis of microbial diversity than in the measurement of functional activity, particularly in vivo. Stable isotope probing offers a new approach by coupling measurements of metabolic activity with microbial identification. Using a low-enrichment labeling strategy in vitro, this study has identified metabolically active bacterial groups via magnetic-bead capture methodology and stable isotope ratio analysis. Using five probes (EUB338, Bac303, Bif164, EREC482, and Clep866), changes in the activities of key intestinal microbial groups were successfully measured by exploiting tracers of de novo RNA synthesis. Perturbation of the nutrient source with oligofructose generated changes in the activity of bifidobacteria as expected, but also in the Bacteroides-Prevotella group, the Eubacterium rectale-Clostridium coccoides group, and the Clostridium leptum subgroup. Changes in activity were also observed in response to the medium type. This study suggests that changes in the functional activity of the gut microbiota can be assessed using tracers of de novo nucleic acid synthesis combined with measurement of low isotopic enrichment in 16S rRNA. Such tracers potentially limit substrate bias because they are universally available to bacteria. This low-enrichment labeling approach does not depend on the commercial availability of specific labeled substrates and can be easily translated to in vivo probing experiments of the functional activity of the microbiota in the human gut.     

Development of multiple-locus variable-number tandem-repeat analysis for rapid genotyping of Ehrlichia ruminantium and its application to infected Amblyomma variegatum collected in heartwater endemic areas in Uganda

The rickettsial bacterium Ehrlichia ruminantium is the causative agent of heartwater, a serious tick-borne disease in ruminants. The genetic diversity of organisms in the field will have implications for cross-protective capacities of any vaccine developed, and for an effective vaccine design strategy proper genotyping and understanding of existing genetic diversity in the field is necessary. We searched for variable-number tandem-repeat (VNTR) loci for use in a multi-locus VNTR analysis (MLVA). Sequencing analysis of 30 potential VNTRs using a panel of 17 reference strains from geographically diverse origins identified 12 VNTRs with allelic profiles differing between strains. Application of MLVA to 38 E. ruminantium-infected Amblyomma variegatum collected from indigenous cattle in 6 different districts of Uganda identified 21 MLVA types. The discriminatory power of MLVA was greater than that of map1 PCR-restriction fragment length polymorphism analysis, with which only 6 genotypes were obtained. The high discriminatory power as well as cost- effective performance of MLVA provide the potential for this technique to be applied in the future with respect to optimizing vaccine trials by identifying local strain diversity, and also raise the possibility of exploring the association between E. ruminantium genotypes and phenotypes such as pathological outcome in the ruminant host.