Stimulatory effect of endogenous orexin A on gastric emptying and acid secretion independent of gastrin

Orexin A (OXA) increases food intake and inhibits fasting small bowel motility in rats. The aim of this study was to examine the effect of exogenous OXA and endogenous OXA on gastric emptying, acid secretion, glucose metabolism and distribution of orexin immunoreactivity in the stomach. Rats equipped with a gastric fistula were subjected to intravenous (IV) infusion of OXA or the selective orexin-1 receptor (OX1R) antagonist SB-334867-A during saline or pentagastrin infusion. Gastric emptying was studied with a liquid non-nutrient or nutrient, using 51Cr as radioactive marker. Gastric retention was measured after a 20-min infusion of OXA or SB-334867-A. Plasma concentrations of OXA, insulin, glucagon, glucose and gastrin were studied. Immunohistochemistry against OXA, OX1R and gastrin in gastric tissue was performed. OXA alone had no effect on either acid secretion or gastric emptying. SB-334867-A inhibited both basal and pentagastrin-induced gastric acid secretion and increased gastric retention of the liquid nutrient, but not PEG 4000. Plasma gastrin levels were unchanged by IV OXA or SB-334867-A. Plasma OXA levels decreased after intake of the nutrient meal and infusion of the OX1R antagonist. Only weak effects were seen on plasma glucose and insulin by OXA. Immunoreactivity to OXA and OX1R were found in the mucosa, myenteric cells bodies and varicose nerve fibers in ganglia and circular muscle of the stomach. In conclusion, endogenous OXA influences gastric emptying of a nutrient liquid and gastric acid secretion independent of gastrin. This indicates a role for endogenous OXA, not only in metabolic homeostasis, but also in the pre-absorptive processing of nutrients in the gut.     

Errors in medication history at hospital admission: prevalence and predicting factors

Background

Data on adverse drug reactions (ADRs) related to antiretroviral (ARV) use in public health practice are few indicating the need for ART safety surveillance in clinical care.

Objectives

To evaluate the incidence, type and risk factors associated with adverse drug reactions (ADRs) among patients on antiretroviral drugs (ARV).

Methods

Patients initiated on ARVs between May 2006 and May 2009 were evaluated in a retrospective cohort analysis in three health facilities in Nigeria. Regimens prescribed include nucleoside backbone of zidovudine (AZT)/lamivudine (3TC), stavudine (d4T)/3TC, or tenofovir (TDF)/3TC in combination with either nevirapine (NVP) or efavirenz (EFV). Generalized Estimating Equation (GEE) model was used to identify risk factors associated with occurrence of ADR.

Results

2650 patients were followed-up for 2456 person-years and reported 114 ADRs (incidence rate = 4.6/100 person-years).There were more females 1706(64%) and 73(64%) of the ADRs were reported by women. Overall, 61(54%) of ADRs were reported by patients on AZT with 54(47%) of these occurring in patients on AZT/NVP. The commonest ADRs reported were pain 25(30%) and skinrash 10(18%). Most ADRs were grade 1(39%) with only 1% being life threatening (grade 4). Adjusted GEE analysis showed that ADR was less likely to occur in patients on longer duration of ART compared to the first six months on treatment; 6-12 months AOR 0.38(95% CI:0.16-0.91) and 12-24 months AOR 0.34(95% CI:0.16-0.73) respectively. Compared to patients on TDF, ADR was less likely to occur in patients on d4T and AZT AOR 0.18(95% CI 0.05-0.64) and AOR 0.24(95% CI:0.7-0.9) respectively. Age, gender and CD4 count were not significantly associated with ADRs.

Conclusion

ADRs are more likely to occur within the first six months on treatment. Close monitoring within this period is required to prevent occurrence of severe ADR and improve ART adherence. Further research on the tolerability of tenofovir in this environment is recommended.     

Long-term gene therapy causes transgene-specific changes in the morphology of regenerating retinal ganglion cells

Recombinant adeno-associated viral (rAAV) vectors can be used to introduce neurotrophic genes into injured CNS neurons, promoting survival and axonal regeneration. Gene therapy holds much promise for the treatment of neurotrauma and neurodegenerative diseases; however, neurotrophic factors are known to alter dendritic architecture, and thus we set out to determine whether such transgenes also change the morphology of transduced neurons. We compared changes in dendritic morphology of regenerating adult rat retinal ganglion cells (RGCs) after long-term transduction with rAAV2 encoding: (i) green fluorescent protein (GFP), or (ii) bi-cistronic vectors encoding GFP and ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF) or growth-associated protein-43 (GAP43). To enhance regeneration, rats received an autologous peripheral nerve graft onto the cut optic nerve of each rAAV2 injected eye. After 5-8 months, RGCs with regenerated axons were retrogradely labeled with fluorogold (FG). Live retinal wholemounts were prepared and GFP positive (transduced) or GFP negative (non-transduced) RGCs injected iontophoretically with 2% lucifer yellow. Dendritic morphology was analyzed using Neurolucida software. Significant changes in dendritic architecture were found, in both transduced and non-transduced populations. Multivariate analysis revealed that transgenic BDNF increased dendritic field area whereas GAP43 increased dendritic complexity. CNTF decreased complexity but only in a subset of RGCs. Sholl analysis showed changes in dendritic branching in rAAV2-BDNF-GFP and rAAV2-CNTF-GFP groups and the proportion of FG positive RGCs with aberrant morphology tripled in these groups compared to controls. RGCs in all transgene groups displayed abnormal stratification. Thus in addition to promoting cell survival and axonal regeneration, vector-mediated expression of neurotrophic factors has measurable, gene-specific effects on the morphology of injured adult neurons. Such changes will likely alter the functional properties of neurons and may need to be considered when designing vector-based protocols for the treatment of neurotrauma and neurodegeneration.     

Analysis of short stature homeobox-containing gene (<Emphasis Type="Italic">SHOX</Emphasis>) and auxological phenotype in dyschondrosteosis and isolated Madelung deformity

Dyschondrosteosis (DCO; also called Léri-Weill syndrome) is a skeletal dysplasia characterised by disproportionate short stature because of mesomelic shortening of the limbs. Madelung deformity is a feature of DCO that is distinctive, variable in expressivity and frequently observed. Mutations of the SHOX (short stature homeobox-containing) gene have been previously described as causative in DCO. Isolated Madelung deformity (IMD) without the clinical characteristics of DCO has also been described in sporadic and a few familial cases but the genetic defect underlying IMD is unknown. In this study, we have examined 28 probands with DCO and seven probands with IMD for mutations in the SHOX gene by using polymorphic CA-repeat analysis, fluorescence in situ hybridisation (FISH), Southern blotting, direct sequencing and fibre-FISH analyses. This was combined with auxological examination of the probands and their family members. Evaluation of the auxological data showed a wide intra- and interfamilial phenotype variability in DCO. Out of 28 DCO probands, 22 (79%) were shown to have mutations in the SHOX gene. Sixteen unrelated DCO families had SHOX gene deletions. Four novel DCO-associated mutations were found in different families. In two additional DCO families, the previously described nonsense mutation (Arg195Stop) was detected. We conclude that mutations in the SHOX gene are the major factor in the pathogenesis of DCO. In a female proband with severe IMD and her unaffected sister, we detected an intrachromosomal duplication of the SHOX gene.     

Comparison of two methods used to analyse lipid peroxidation from Vaccinium myrtillus (L.) during snow removal, reacclimation and cold acclimation.

Malondialdehyde (MDA) concentration is a widely used method to analyse lipid peroxidation in biological material. In plant tissues, however, certain compounds (anthocyanins, carbohydrates) may interfere with measurements which may lead to an overestimation of the MDA levels. Two methods were compared for analysing lipid peroxidation, either uncorrected or corrected for interfering compounds. The comparison was performed in three separate experiments with respect to cold treatments (snow removal in winter, reacclimation in summer and cold acclimation in autumn) in bilberry (Vaccinium myrtillus L.). During winter and autumn the methods seem to measure different compounds, but during active growth in the summer the difference between the methods was less. This is obviously due to carbohydrates which act as cryoprotectants and increase in concentration during cold acclimation as well as due to the anthocyanins. It is thus suggested that the validity of the uncorrected method to measure MDA and thereby lipid peroxidation is best in plant tissue which is in an active growth state.     

Role of PDGF-B and PDGFR-beta in recruitment of vascular smooth muscle cells and pericytes during embryonic blood vessel formation in the mouse.

Development of a vascular system involves the assembly of two principal cell types - endothelial cells and vascular smooth muscle cells/pericytes (vSMC/PC) - into many different types of blood vessels. Most, if not all, vessels begin as endothelial tubes that subsequently acquire a vSMC/PC coating. We have previously shown that PDGF-B is critically involved in the recruitment of pericytes to brain capillaries and to the kidney glomerular capillary tuft. Here, we used desmin and alpha-smooth muscle actin (ASMA) as markers to analyze vSMC/PC development in PDGF-B-/- and PDGFR-beta-/- embryos. Both mutants showed a site-specific reduction of desmin-positive pericytes and ASMA-positive vSMC. We found that endothelial expression of PDGF-B was restricted to immature capillary endothelial cells and to the endothelium of growing arteries. BrdU labeling showed that PDGFR-beta-positive vSMC/PC progenitors normally proliferate at sites of endothelial PDGF-B expression. In PDGF-B-/- embryos, limb arterial vSMC showed a reduced BrdU-labeling index. This suggests a role of PDGF-B in vSMC/PC cell proliferation during vascular growth. Two modes of vSMC recruitment to newly formed vessels have previously been suggested: (1) de novo formation of vSMC by induction of undifferentiated perivascular mesenchymal cells, and (2) co-migration of vSMC from a preexisting pool of vSMC. Our data support both modes of vSMC/PC development and lead to a model in which PDGFR-beta-positive vSMC/PC progenitors initially form around certain vessels by PDGF-B-independent induction. Subsequent angiogenic sprouting and vessel enlargement involves PDGF-B-dependent vSMC/PC progenitor co-migration and proliferation, and/or PDGF-B-independent new induction of vSMC/PC, depending on tissue context.     

Tyrosinase exacerbates dopamine toxicity but is not genetically associated with Parkinson's disease

Tyrosinase is a key enzyme in the synthesis of melanin in skin and hair and has also been proposed to contribute to the formation of neuromelanin (NM). The presence of NM, which is biochemically similar to melanin in peripheral tissues, identifies groups of neurons susceptible in Parkinson's disease (PD). Whether tyrosinase is beneficial or detrimental to neurons is unclear; whilst the enzyme activity of tyrosinase generates dopamine-quinones and other oxidizing compounds, NM may form a sink for such radical species. In the present study, we demonstrated that tyrosinase is expressed at low levels in the human brain. We found that mRNA, protein and enzyme activity are all present but at barely detectable levels. In cell culture systems, expression of tyrosinase increases neuronal susceptibility to oxidizing conditions, including dopamine itself. We related these in vitro observations to the human disease by assessing whether there was any genetic association between the gene encoding tyrosinase and idiopathic PD. We found neither genotypic or haplotypic association with three polymorphic markers of the gene. This argues against a strong genetic association between tyrosinase and PD, although the observed contribution to cellular toxicity suggests that a biochemical association is likely.