High Resolution Proton NMR Spectroscopy of Multiple Sclerosis Lesions

Abstract: Tissue from postmortem multiple sclerosis and normal control brains was extracted with perchloric acid and analysed using proton NMR spectroscopy. The content of N -acetyl-derived groups (the sum of N -acetylaspartate, acetate, and N -acetylaspartylglutamate) was decreased in multiple sclerosis plaques compared with normal control white matter (mean, 4.36 vs. 6.64 µmol/g wet weight). In normal appearing white matter adjacent to plaques a corresponding decrease was seen, with no change in white matter distant from plaques. A decrease in the content of total creatine was observed in multiple sclerosis plaques in comparison with normal control white matter (mean, 4.64 vs. 6.56 µmol/g wet weight), which correlated strongly with the decrease in N -acetyl-derived groups. No changes in other metabolites such as total choline or myo -inositol were seen. The decreases in content of N -acetyl-derived groups are in agreement with observations from in vivo proton NMR spectroscopy in multiple sclerosis patients. The decrease in total creatine is in contrast to most of the observations made in vivo where total creatine is assumed to be unchanged and metabolite levels are often expressed as a total creatine ratio. The use of a total creatine ratio in vivo could lead to an underestimation of reductions in N -acetylaspartate and an apparent increase in other metabolites in the multiple sclerosis lesion.     

The utility of wing morphometrics for assigning type specimens to cryptic bumblebee species

Since the beginning of taxonomy, species have been described based on morphology, but the advent of using semio-chemicals and genetics has led to the discovery of cryptic species (i.e. morphologically similar species). When a new cryptic species is described, earlier type specimens have to be re-evaluated, although this process can be challenging as only nondestructive methods ought to be used in order to preserve the integrity of the type specimens. Methods should allow comparison with recently collected specimens clustered based on chemical, ethological and/or genetic traits with old specimens (i.e. type specimens) where only morphological traits are available. Here we develop a method based on geometric morphometric analyses of wing shape for a taxonomically challenging group of bumblebees, the subgenus Alpinobombus Skorikov. We consider nine monophyletic taxa (including several cryptic species) to assess the accuracy of this method to discriminate the taxa based on their wing shape and then to attribute type specimens using a leave-one-out cross-validation procedure. We show that, for these bees, wing shape is taxon-specific, except for two sister taxa for which the species status is still debated. Moreover, for most of the taxa, type specimens were correctly attributed with high posterior probabilities of attribution, except for a few type specimens corresponding to the same two sister taxa where taxa delimitation based on wing shape was previously the subject of discussion. Our study highlights the potential of geometric morphometric analyses to help in the re-attribution of type specimens when the existence of cryptic species is revealed.     

Climatic seasonality, resource bottlenecks, and abundance of rainforest birds: implications for global climate change

We demonstrate that within-year climatic variability, particularly rainfall seasonality, is the most significant variable explaining spatial patterns of bird abundance in Australian tropical rainforest. The likely mechanism causing this pattern is a resource bottleneck (insects, nectar, and fruit) during the dry season that limits the population size of many species. The patterns support both the diversity–climatic–stability hypothesis and the species–energy hypothesis but clearly show that seasonality in energy availability may be a more significant factor than annual totals or means. An index of dry season severity is proposed that quantifies the combined effect of the degree of dryness and the duration of the dry season. We suggest that the predicted increases in seasonality due to global climate change could produce significant declines in bird abundance, further exacerbating the impacts of decreased range size, increased fragmentation, and decreased population size likely to occur as a result of increasing temperature. We suggest that increasing climatic seasonality due to global climate change has the potential to have significant negative impacts on tropical biodiversity.     

Administration of IL-7 to normal mice stimulates B-lymphopoiesis and peripheral lymphadenopathy.

Normal mice were injected with IL-7 (500 ng, twice daily) for various periods of time up to 6 days and the cellularity and phenotypic composition of the thymus, spleen, lymph node, and bone marrow was assessed. After 6 days of treatment, significant increases in the cellularity of the spleen, lymph node, and bone marrow were observed which returned to the normal range within 6 days after cessation of treatment. After 3 days of IL-7 treatment, increased numbers of B220+/surface(s) IgM- bone marrow cells were observed. After 6 days of treatment, these numbers were still further increased and a significant population of B220+/sIgM- cells were observed in the spleen. The numbers of c mu+/sIgM- cells were also increased in the IL-7-treated mice. Analysis of the expression of B220 and BP-1 on the sIgM- bone marrow cells revealed that the B220+/BP-1+ population was dramatically increased after IL-7 treatment and the size of the B220+/BP-1- population did not differ from control mice. The pre-B cell numbers declined rapidly after the cessation of IL-7 treatment. After 6 days of IL-7 treatment, a twofold increase in the number of B cells in the spleen and lymph node was observed. The B cell numbers declined to normal values within 6 days after the cessation of IL-7 administration. In the spleens of the IL-7-treated mice, there was a significant increase in the number of B cells with an immature phenotype (e.g., sIgMhi/sIgDlo, decreased levels of Ia and FcR expression). The numbers of CD8+ and CD4+ T cells were also increased in the lymph node and spleen of the IL-7-treated mice. These numbers declined to normal levels after the cessation of IL-7 treatment.     

Receptor and G protein-mediated responses to thrombin in HEL cells.

Thrombin is believed to activate platelets via cell surface receptors coupled to G proteins. In order to better understand this process, we have examined the interaction of thrombin with HEL cells, a leukemic cell line that has served as a useful model for studies of platelet structure and function. In HEL cells, as in platelets, thrombin stimulated inositol trisphosphate (IP3) formation and suppressed cAMP synthesis. Both events were inhibited by pertussis toxin with 50% inhibition occurring at a toxin concentration that ADP-ribosylated 50% of the Gi alpha subunits present in HEL cells. IP3 formation was also stimulated by a second serine protease, trypsin. The trypsin response was identical to the thrombin response in time course, magnitude, and pertussis toxin sensitivity, suggesting that a similar mechanism is involved. Agonist-induced changes in the cytosolic-free Ca2+ concentration were used to test this hypothesis. Both proteases caused a transient increase in intracellular calcium [Ca2+]i that could be inhibited with D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone thrombin. Exposure to either protease desensitized HEL cells against subsequent increases in [Ca2+]i and IP3 caused by the other, although responses to other agonists were retained. This loss of responsiveness persisted despite repeated washing of the cells and the addition of hirudin. Complete recovery occurred after 20 h and could be prevented with cycloheximide. These observations suggest that 1) HEL cell thrombin receptors, like those on platelets, are coupled to phospholipase C and adenylylcyclase by pertussis toxin-sensitive G proteins, 2) the G proteins involved are equally accessible to pertussis toxin in situ, 3) when access is limited to the outside of the cell the response mechanisms for thrombin and trypsin are similar, if not identical, despite the broader substrate specificity of trypsin, 4) both proteases cause persistent changes that may involve proteolysis of their receptors or associated proteins, and 5) desensitization of the thrombin response occurs at a step no later than the activation of phospholipase C and requires protein synthesis for recovery.     

Inv(10)(p11.2q21.2), a variant chromosome

We present 33 families in which a pericentric inversion of chromosome 10 is segregating. In addition, we summarise the data on 32 families in which an apparently identical inv(10) has been reported in the literature. Ascertainment was through prenatal diagnosis or with a normal phenotype in 21/33 families. In the other 12 families, probands were ascertained through a wide variety of referral reasons but in all but one case (a stillbirth), studies of the family showed that the reason for referral was unrelated to the chromosome abnormality. There has been, to our knowledge, no recorded instance of a recombinant chromosome 10 arising from this inversion and no excess of infertility or spontaneous abortion among carriers of either sex. We propose that inv(10)(p11.2q21.2) can be regarded as a variant analogous to the pericentric inversion of chromosome 2(p11q13). We conclude that prenatal chromosome analysis is not justified for inv(10) carriers. In addition, family investigation of carrier status is not warranted in view of the unnecessary concern this may cause parents and other family members. Received: 7 July 1997 / Accepted: 4 August 1997