Sexual dimorphism in healthy aging and mild cognitive impairment: a DTI study

Previous PET and MRI studies have indicated that the degree to which pathology translates into clinical symptoms is strongly dependent on sex with women more likely to express pathology as a diagnosis of AD, whereas men are more resistant to clinical symptoms in the face of the same degree of pathology. Here we use DTI to investigate the difference between male and female white matter tracts in healthy older participants (24 women, 16 men) and participants with mild cognitive impairment (21 women, 12 men). Differences between control and MCI participants were found in fractional anisotropy (FA), radial diffusion (DR), axial diffusion (DA) and mean diffusion (MD). A significant main effect of sex was also reported for FA, MD and DR indices, with male control and male MCI participants having significantly more microstructural damage than their female counterparts. There was no sex by diagnosis interaction. Male MCIs also had significantly less normalised grey matter (GM) volume than female MCIs. However, in terms of absolute brain volume, male controls had significantly more brain volume than female controls. Normalised GM and WM volumes were found to decrease significantly with age with no age by sex interaction. Overall, these data suggest that the same degree of cognitive impairment is associated with greater structural damage in men compared with women.     

Mapping the ligand-binding site on the C5a receptor: arginine74 of C5a contacts aspartate282 of the C5a receptor.

The interaction between the anaphylatoxin C5a and its receptor involves two distinct sites. One site is formed by acidic residues at the receptor N-terminus and contributes to only ligand binding. The second site, responsible for activation, is less well defined. In this study, we demonstrate that the receptor residue D(282), near the extracellular face of transmembrane domain VII, is a component of the second ligand-binding site. Mutation of D(282) to A decreases the sensitivity of the receptor to activation by intact C5a but not by its less potent metabolite, C5adR(74), which lacks the C-terminal arginine(74). The mutation of the R(74) residue of C5a to A causes a 60-fold decrease in wild-type receptor sensitivity, but only a 2-fold decrease for the receptor mutated at D(282). In contrast, the mutation of R(74) to D makes C5a completely inactive on both wild-type and A(282) C5a receptors. The mutation of D(282) to R partly restores the response to C5a[D(74)], which is a more effective ligand than C5a at the mutant receptor. A peptide mimic of the C5a activation domain with a C-terminal R potently activates the wild type but is only a weak agonist at the mutant D(282)R-C5a receptor. Conversely, a peptide with D at the C-terminus is a more effective activator of D(282)R than wild-type C5a receptors. These data indicate that the R(74) side chain of C5a makes an interaction with receptor D(282) that is responsible for the higher potency of intact C5a versus that of C5adR(74).     

Turkey liver xanthine dehydrogenase. Relation between nicotinamide-adenine dinucleotide oxidoreductase activity and the content of functional enzyme.

The turkey liver xanthine dehydrogenase-catalysed oxidation of NADH by Methylene Blue, by ferricyanide or by O2 is not dependent on the integrity of the active-centre persulphide groups. By contrast, the NADH-dichlorophenol-indophenol oxidoreductase and NADH-trinitrobenzenesulphonate oxidoreductase activities are directly proportional to the content of functional enzyme. These findings help to identify the sites of egress of electrons to oxidizing substrates.     

Cloning and characterization of the calreticulin gene from Ricinus communis L.

A full-length cDNA encoding a calreticulin-like protein was isolated by immune-screening a germinating castor bean endosperm cDNA library with antisera raised to the total lumenal fraction of purified plant endoplasmic reticulum. The calcium-binding properties of the recombinant protein were characterized and shown to be essentially identical to those reported for the mammalian calreticulin. Calcium overlays and immune blot analysis confirmed the endoplasmic lumenal identity of this reticuloplasmin. Probing protein blots of endoplasmic reticulum subfractions with radio-iodinated calreticulin showed specific associations with various polypeptides including one identified as the abundant reticuloplasmin protein disulfide isomerase.Characterization of the corresponding genomic clones revealed that calreticulin is encoded by a single gene of 3 kb in castor. The full genomic sequence reveals the presence of 12 introns, 12 translated exons, and one exon containing the last three amino acids of the translated sequence and the 3-untranslated region of the gene. Northern blot analysis of RNA isolated from various organ tissues showed a basal constitutive level of expression throughout the plant, but more abundant mRNA being detected in tissues active in secretion. This was confirmed by analysis of transgenic tobacco plants containing 1.8 kb of 5-untranslated genomic sequence fused to the -glucuronidase reporter gene (GUS) showed a more localized pattern of expression. Activity being localized to the vasculature (phloem, root hairs and root tip) in vegetative tissue, and being strongly expressed in the floral organs including the developing and germinating seed.     

Amiloride does not alter NaCl avoidance in Fischer-344 rats

Fischer-344 (F-344) rats differ from other common rat strains in that they fail to show any preference for NaCl at any concentration in two- bottle preference tests. Because 100 microM amiloride partially blocks the NaCl-evoked chorda tympani (CT) response in electrophysiological studies, we tested NaCl preference (0.068-0.273 M) in F-344 rats with and without 100 microM amiloride solution as the solvent. A third group was tested with unadulterated NaCl solutions following CT transection. Amiloride had no significant effect on the NaCl preference-aversion function, whereas CT transection significantly reduced NaCl avoidance. These results suggest that the amiloride-sensitive component of the NaCl response is not necessary for F-344 rats to display avoidance of NaCl, but the entire CT input is.      

Vaccination with SARS-CoV-2 variants of concern protects mice from challenge with wild-type virus

Vaccines against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) have been highly efficient in protecting against Coronavirus Disease 2019 (COVID-19). However, the emergence of viral variants that are more transmissible and, in some cases, escape from neutralizing antibody responses has raised concerns. Here, we evaluated recombinant protein spike antigens derived from wild-type SARS-CoV-2 and from variants B.1.1.7, B.1.351, and P.1 for their immunogenicity and protective effect in vivo against challenge with wild-type SARS-CoV-2 in the mouse model. All proteins induced high neutralizing antibodies against the respective viruses but also induced high cross-neutralizing antibody responses. The decline in neutralizing titers between variants was moderate, with B.1.1.7-vaccinated animals having a maximum fold reduction of 4.8 against B.1.351 virus. P.1 induced the most cross-reactive antibody responses but was also the least immunogenic in terms of homologous neutralization titers. However, all antigens protected from challenge with wild-type SARS-CoV-2 in a mouse model.

This study explores the immune response induced by wild type and variant SARS-CoV-2 spike proteins, and the protection that these immune responses provide against challenge with wild type virus in the mouse model.     

Molecular biodiversity of cassava begomoviruses in Tanzania: evolution of cassava geminiviruses in Africa and evidence for East Africa being a center of diversity of cassava geminiviruses

Cassava is infected by numerous geminiviruses in Africa and India that cause devastating losses to poor farmers. We here describe the molecular diversity of seven representative cassava mosaic geminiviruses (CMGs) infecting cassava from multiple locations in Tanzania. We report for the first time the presence of two isolates in East Africa: (EACMCV-[TZ1] and EACMCV-[TZ7]) of the species East African cassava mosaic Cameroon virus, originally described in West Africa. The complete nucleotide sequence of EACMCV-[TZ1] DNA-A and DNA-B components shared a high overall sequence identity to EACMCV-[CM] components (92% and 84%). The EACMCV-[TZ1] and -[TZ7] genomic components have recombinations in the same genome regions reported in EACMCV-[CM], but they also have additional recombinations in both components. Evidence from sequence analysis suggests that the two strains have the same ancient origin and are not recent introductions. EACMCV-[TZ1] occurred widely in the southern part of the country. Four other CMG isolates were identified: two were close to the EACMV-Kenya strain (named EACMV-[KE/TZT] and EACMV-[KE/TZM] with 96% sequence identity); one isolate, TZ10, had 98% homology to EACMV-UG2Svr and was named EACMV-UG2 [TZ10]; and finally one isolate was 95% identical to EACMV-[TZ] and named EACMV-[TZ/YV]. One isolate of African cassava mosaic virus with 97% sequence identity with other isolates of ACMV was named ACMV-[TZ]. It represents the first ACMV isolate from Tanzania to be sequenced. The molecular variability of CMGs was also evaluated using partial B component nucleotide sequences of 13 EACMV isolates from Tanzania. Using the sequences of all CMGs currently available, we have shown the presence of a number of putative recombination fragments that are more prominent in all components of EACMV than in ACMV. This new knowledge about the molecular CMG diversity in East Africa, and in Tanzania in particular, has led us to hypothesize about the probable importance of this part of Africa as a source of diversity and evolutionary change both during the early stages of the relationship between CMGs and cassava and in more recent times. The existence of multiple CMG isolates with high DNA genome diversity in Tanzania and the molecular forces behind this diversity pose a threat to cassava production throughout the African continent.