THE PREPARATION AND PROPERTIES OF HIGHLY PURIFIED ASCORBIC ACID OXIDASE

1. A method is described for the preparation of a highly purified ascorbic acid oxidase containing 0.24 per cent copper. 2. Using comparable activity measurements, this oxidase is about one and a half times as active on a dry weight basis as the hitherto most highly purified preparation described by Lovett-Janison and Nelson. The latter contained 0.15 per cent copper. 3. The oxidase activity is proportional to the copper content and the proportionality factor is the same as that reported by Lovett-Janison and Nelson. 4. When dialyzed free of salt, the blue concentrated oxidase solutions precipitate a dark green-blue protein which carries the activity. This may be prevented by keeping the concentrated solutions about 0.1 M in Na₂HPO₄. 5. When highly diluted for activity measurements the oxidase rapidly loses activity (irreversibly) previous to the measurement, unless the dilution is made with a dilute inert protein (gelatin) solution. Therefore activity values obtained using such gelatin-stabilized dilute solutions of the oxidase run considerably higher than values obtained by the Lovett-Janison and Nelson technique. 6. The effect of pH and substrate concentration on the activity of the purified oxidase in the presence and absence of inert protein was studied.     

Heterocyclic zinc-binding groups for use in next-generation matrix metalloproteinase inhibitors: potency, toxicity, and reactivity

In an effort to improve the zinc-chelating portion of matrix metalloproteinase (MMP) inhibitors, we have developed a family of heterocyclic zinc-binding groups (ZBGs) as alternatives to the widely used hydroxamic acid moiety. Elaborating on findings from an earlier report, we performed in vitro inhibition assays with recombinant MMP-1, MMP-2, and in a cell culture assay using neonatal rat cardiac fibroblast cells. In both recombinant and cell culture assays, the new ZBGs were found to be effective inhibitors, typically 10–100-fold more potent than acetohydroxamic acid. The toxicity of these chelators was examined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt cytotoxicity assays, which demonstrate that most of these compounds are nontoxic at concentrations of almost 100 μM. To address the possible interaction of sulfur-containing ZBGs with biological reductants, the reactivity of these chelators with 5,5′-dithiobis(2-nitrobenzoic acid) was examined. Finally, thione ZBGs were shown to be effective inhibitors of cell invasion through an extracellular matrix membrane. The data presented herein suggest these heterocyclic ZBGs are potent, nontoxic, and biocompatible compounds that show promise for incorporation into a new family of MMP inhibitors.     

Records of Carulaspis juniperi (Homoptera: Diaspididae) in New Zealand

Abstract

Previous reports of Carulaspis visci (Schrank) in New Zealand are considered to be misidentifications of C. juniperi (Bouché), the juniper scale. The known hosts (Cupressaceae and Taxodiaceae), distribution (all South Island localities), and a record of a parasite (Aspidiotiphagus citrinus (Craw), Aphelinidae) of C. juniperi in New Zealand are given.     

Downward causes and appropriate abstractions: Alternative argument for Noble's position

In his article of this issue, Denis Noble argues that causation can occur at and between any scales – rather than levels – in nature. I agree with this conclusion, but do not find his reasoning fully persuasive. I offer an independent but related argument for his position, which focuses on the role of the process of abstraction in identifying and understanding a phenomenon. My aim is to give the reader another way to think about causal talk within the framework of Systems Biology.     

Molecular systematics of pinniped hookworms (Nematoda: Uncinaria): species delimitation,host associations and host-induced morphometric variation

Hookworms of the genus Uncinaria have been widely reported from juvenile pinnipeds, however investigations of their systematics has been limited, with only two species described, Uncinaria lucasi from northern fur seals (Callorhinus ursinus) and Uncinaria hamiltoni from South American sea lions (Otaria flavescens). Hookworms were sampled from these hosts and seven additional species including Steller sea lions (Eumetopias jubatus), California sea lions (Zalophus californianus), South American fur seals (Arctocephalus australis), Australian fur seals (Arctocephalus pusillus), New Zealand sea lions (Phocarctos hookeri), southern elephant seals (Mirounga leonina), and the Mediterranean monk seal (Monachus monachus). One hundred and thirteen individual hookworms, including an outgroup species, were sequenced for four genes representing two loci (nuclear ribosomal DNA and mitochondrial DNA). Phylogenetic analyses of these sequences recovered seven independent evolutionary lineages or species, including the described species and five undescribed species. The molecular evidence shows that U. lucasi parasitises both C. ursinus and E. jubatus, whereas U. hamiltoni parasitises O. flavescens and A. australis. The five undescribed hookworm species were each associated with single host species (Z. californianus, A. pusillus, P. hookeri, M. leonina and M. monachus). For parasites of otarids, patterns of Uncinaria host-sharing and phylogenetic relationships had a strong biogeographic component with separate clades of parasites from northern versus southern hemisphere hosts. Comparison of phylogenies for these hookworms and their hosts suggests that the association of U. lucasi with northern fur seals results from a host-switch from Steller sea lions. Morphometric data for U. lucasi shows marked host-associated size differences for both sexes, with U. lucasi individuals from E. jubatus significantly larger. This result suggests that adult growth of U. lucasi is reduced within the host species representing the more recent host–parasite association. Intraspecific host-induced size differences are inconsistent with the exclusive use of morphometrics to delimit and diagnose species of Uncinaria from pinnipeds.     

A Systematic Review of the Screening Accuracy of the HIV Dementia Scale and International HIV Dementia Scale

Background

The HIV Dementia Scale (HDS) and International HIV Dementia Scale (IHDS) are brief tools that have been developed to screen for and aid diagnosis of HIV-associated dementia (HAD). They are increasingly being used in clinical practice for minor neurocognitive disorder (MND) as well as HAD, despite uncertainty about their accuracy.

Methods and Findings

A systematic review of the accuracy of the HDS and IHDS was conducted. Studies were assessed on Standards for Reporting Diagnostic Accuracy criteria. Pooled sensitivity, specificity, likelihood ratios (LR) and diagnostic odds ratios (DOR) were calculated for each scale as a test for HAD or MND. We retrieved 15 studies of the HDS, 10 of the IHDS, and 1 of both scales. Thirteen studies of the HDS were conducted in North America, and 7 of the IHDS studies were conducted in sub-Saharan Africa. Estimates of accuracy were highly heterogeneous between studies for the HDS but less so for the IHDS. Pooled DOR for the HDS was 7.52 (95% confidence interval 3.75–15.11), sensitivity and specificity for HAD were estimated at 68.1% and 77.9%, and sensitivity and specificity for MND were estimated at 42.0% and 91.2%. Pooled DOR for the IHDS was 3.49 (2.12–5.73), sensitivity and specificity for HAD were 74.3% and 54.7%, and sensitivity and specificity for MND were 64.3% and 66.0%.

Conclusion

Both scales were low in accuracy. The literature is limited by the lack of a gold standard, and variation in estimates of accuracy is likely to be due to differences in reference standard. There is a lack of studies comparing both scales, and they have been studied in different populations, but the IHDS may be less specific than the HDS. These rapid tests are not recommended for diagnostic use, and further research is required to inform their use in asymptomatic screening.     

Improved Glucose Control and Reduced Body Weight in Rodents with Dual Mechanism of Action Peptide Hybrids

Combination therapy is being increasingly used as a treatment paradigm for metabolic diseases such as diabetes and obesity. In the peptide therapeutics realm, recent work has highlighted the therapeutic potential of chimeric peptides that act on two distinct receptors, thereby harnessing parallel complementary mechanisms to induce additive or synergistic benefit compared to monotherapy. Here, we extend this hypothesis by linking a known anti-diabetic peptide with an anti-obesity peptide into a novel peptide hybrid, which we termed a phybrid. We report on the synthesis and biological activity of two such phybrids (AC164204 and AC164209), comprised of a glucagon-like peptide-1 receptor (GLP1-R) agonist, and exenatide analog, AC3082, covalently linked to a second generation amylin analog, davalintide. Both molecules acted as full agonists at their cognate receptors in vitro, albeit with reduced potency at the calcitonin receptor indicating slightly perturbed amylin agonism. In obese diabetic Lep^ob/Lep ^ob mice sustained infusion of AC164204 and AC164209 reduced glucose and glycated haemoglobin (Hb_A1c) equivalently but induced greater weight loss relative to exenatide administration alone. Weight loss was similar to that induced by combined administration of exenatide and davalintide. In diet-induced obese rats, both phybrids dose-dependently reduced food intake and body weight to a greater extent than exenatide or davalintide alone, and equal to co-infusion of exenatide and davalintide. Phybrid-mediated and exenatide + davalintide-mediated weight loss was associated with reduced adiposity and preservation of lean mass. These data are the first to provide in vivo proof-of-concept for multi-pathway targeting in metabolic disease via a peptide hybrid, demonstrating that this approach is as effective as co-administration of individual peptides.     

Antibody Levels to Persistent Pathogens and Incident Stroke in Mexican Americans

Background

Persistent pathogens have been proposed as risk factors for stroke; however, the evidence remains inconclusive. Mexican Americans have an increased risk of stroke especially at younger ages, as well as a higher prevalence of infections caused by several persistent pathogens.

Methodology/Principal

Findings Using data from the Sacramento Area Latino Study on Aging (n = 1621), the authors used discrete-time regression to examine associations between stroke risk and (1) immunoglobulin G antibody levels to Helicobacter pylori (H. pylori), Cytomegalovirus, Varicella Zoster Virus, Toxoplasma gondii and Herpes simplex virus 1, and (2) concurrent exposure to several pathogens (pathogen burden), defined as: (a) summed sero-positivity, (b) number of pathogens eliciting high antibody levels, and (c) average antibody level. Models were adjusted for socio-demographics and stroke risk factors. Antibody levels to H. pylori predicted incident stroke in fully adjusted models (Odds Ratio: 1.58; 95% Confidence Interval: 1.09, 2.28). No significant associations were found between stroke risk and antibody levels to the other four pathogens. No associations were found for pathogen burden and incident stroke in fully adjusted models.

Conclusions/Significance

Our results suggest that exposure to H. pylori may be a stroke risk factor in Mexican Americans and may contribute to ethnic differences in stroke risk given the increased prevalence of exposure to H. pylori in this population. Future studies are needed to confirm this association.