Acute and chronic exposure to ammonia and olfactory acuity for n-butanol in the pig

An associative learning method (using a food reward) was developed to measure pigs' olfactory acuity for n-butanol, a standard odourant in human olfactometry. The pig could press two operant paddles but it only received a food reward when it pressed the one over which n-butanol was released. Once each pig had reached a training criterion (10 consecutive roots on the correct paddle on each of two consecutive sessions) this method was used to assess the impact of acute and chronic exposure to an atmosphere containing approximately 40 parts per million (ppm) ammonia gas, compared to fresh air, on its ability to perceive different concentrations of n-butanol. These were presented using a staircase pattern, i.e. if the pig gained or failed to gain a food reward on two consecutive occasions the concentration was reduced or increased, respectively. Acute exposure for approximately 45min to about 40ppm ammonia had no effect (P>0.05) on the lowest detected concentration (LDC) of n-butanol in six pigs. The geometric mean LDC was 1.23 parts per trillion (ppt) in approximately 40ppm ammonia and 2.09ppt in fresh air. The LDC of three pigs increased, i.e. acuity fell, from 5.1 to 175.5ppt over 24 days of exposure to congruent with40ppm ammonia. Ammonia had no effect on one of the other pigs and the high variability in the LDC for the remaining two pigs produced no meaningful assessment of its impact. Subsequent removal to fresh air for a further 24 days led to partial recovery of acuity in one of the three pigs that had shown evidence of olfactory impairment but not in the other two. Collectively our findings suggest that chronic, but not acute, exposure to congruent with40ppm ammonia can interfere with olfactory perception in some pigs (50% of our sample) and that this loss of acuity is not necessarily reversible.     

Digital vascular imaging and selective renin sampling in evaluation of vascular anatomy in renal transplant recipients.

Sixty-five renal transplant recipients underwent digital vascular imaging of the graft and simultaneous selective venous sampling for plasma renin activity. Renal artery stenosis was found in seven patients but did not appear to be functionally important. Diffuse intrarenal arterial attenuation was found in seven patients and was associated with impaired graft function and perfusion; it may indicate chronic rejection. Lower pole hypoperfusion was found in nine patients without impaired graft function or perfusion; its clinical relevance is uncertain. Aneurysmal dilatation of the main renal artery was found in two patients. Severe hypertension was common in patients with these three major abnormalities, but a causal association between the abnormality and hypertension could rarely be inferred. It may be the abnormalities on digital vascular imaging, especially diffuse intrarenal arterial attenuation and lower pole hypoperfusion, are secondary to severe hypertension. Digital vascular imaging with simultaneous selective venous sampling for plasma renin activity is useful in evaluating the vascular anatomy of the grafted kidney and in assessing any abnormality found. The combined procedure was well tolerated by all patients with no complications and no incidence of acute tubular dysfunction or proteinuria after the investigation.     

Pathogenesis of developmental defects induced in the rat by amniotic sac puncture

The morphogenesis of developmental defects induced by aminotic sac puncture was studied at the gross and microscopic levels. In fetuses recovered from 15 min to 48 h after amniocentesis, a pattern of hemorrhagic lesions, excessive accumulation of interstitial fluid, followed by tissue necrosis and leading ultimately to the reduction of amputation of distal limb segments and morphological changes in the head, was observed. These changes were indicative of venous stasis, hypervolemia and embryonic oxygen deficiency. Intrauterine compression of the fetus and the obstruction of the fetomaternal circulation were considered to be the primary etiological factors in amniocentesis-induced anomalies which included hemorrhagic lesions, limb reductions and amputations, deformities of the head and abdominal regions, generalized edema and postural moulding.     

Differences in the Volume of Pharmaceutical Advertisements between Print General Medical Journals

Background

Pharmaceutical advertisements have been argued to provide revenue that medical journals require but they are intended to alter prescribing behaviour and they are known to include low quality information. We determined whether a difference exists in the current level of pharmaceutical advertising in print general medical journals, and we estimated the revenue generated from print pharmaceutical advertising.

Methods

Six print general medical journals in Canada, the United States, and the United Kingdom were sampled between 2007 and 2012. The number of advertisements and other journal content in selected issues of the Canadian Medical Association Journal (CMAJ), Canadian Family Physician (CFP), Journal of the American Medical Association (JAMA), New England Journal of Medicine (NEJM), British Medical Journal (BMJ), and Lancet were determined. Revenue gained from pharmaceutical advertising was estimated using each journal''s 2013 advertising price list.

Findings

The two Canadian journals sampled (CMAJ, CFP) contained five times more advertisements than the two American journals (JAMA, NEJM), and two British journals (BMJ, Lancet) (p<0.0001). The estimated annual revenue from pharmaceutical advertisements ranged from £0.025 million (for Lancet) to £3.8 million (for JAMA). The cost savings due to revenue from pharmaceutical advertising to each individual subscriber ranged from £0.02 (for Lancet) to £3.56 (for CFP) per issue.

Conclusion

The volume of pharmaceutical advertisements differs between general medical journals, with the two Canadian journals sampled containing the most advertisements. International and temporal variations suggest that there is an opportunity for all general medical journals to reduce the number of pharmaceutical advertisements, explore other sources of revenue, and increase transparency regarding sources of revenue.     

Cellular retinoic acid binding protein I mediates rapid non-canonical activation of ERK1/2 by all-trans retinoic acid

All-trans retinoic acid (atRA), one of the active ingredients of vitamin A, exerts canonical activities to regulate gene expression mediated by nuclear RA receptors (RARs). AtRA could also elicit certain non-canonical activities including, mostly, rapid activation of extracellular signal regulated kinase 1/2 (ERK1/2); but the mechanism was unclear. In this study, we have found that cellular retinoic acid binding protein I (CRABPI) mediates the non-canonical, RAR- and membrane signal-independent activation of ERK1/2 by atRA in various cellular backgrounds. In the context of embryonic stem cells (ESCs), atRA/CRABPI-dependent ERK1/2 activation rapidly affects ESC cell cycle, specifically to expand the G1 phase. This is mediated by ERK stimulation resulting in dephosphorylation of nuclear p27, which elevates nuclear p27 protein levels to block G1 progression to S phase. This is the first study to identify CRABPI as the mediator for non-canonical activation of ERK1/2 by atRA, and demonstrate a new functional role for CRABPI in modulating ESC cell cycle progression.     

Backbone Flexibility of CDR3 and Immune Recognition of Antigens

Conformational entropy is an important component of protein–protein interactions; however, there is no reliable method for computing this parameter. We have developed a statistical measure of residual backbone entropy in folded proteins by using the ?–ψ distributions of the 20 amino acids in common secondary structures. The backbone entropy patterns of amino acids within helix, sheet or coil form clusters that recapitulate the branching and hydrogen bonding properties of the side chains in the secondary structure type. The same types of residues in coil and sheet have identical backbone entropies, while helix residues have much smaller conformational entropies. We estimated the backbone entropy change for immunoglobulin complementarity-determining regions (CDRs) from the crystal structures of 34 low-affinity T-cell receptors and 40 high-affinity Fabs as a result of the formation of protein complexes. Surprisingly, we discovered that the computed backbone entropy loss of only the CDR3, but not all CDRs, correlated significantly with the kinetic and affinity constants of the 74 selected complexes. Consequently, we propose a simple algorithm to introduce proline mutations that restrict the conformational flexibility of CDRs and enhance the kinetics and affinity of immunoglobulin interactions. Combining the proline mutations with rationally designed mutants from a previous study led to 2400-fold increase in the affinity of the A6 T-cell receptor for Tax-HLAA2. However, this mutational scheme failed to induce significant binding changes in the already-high-affinity C225–Fab/huEGFR interface. Our results will serve as a roadmap to formulate more effective target functions to design immune complexes with improved biological functions.