Deuterolysis of amino acid precursors: evidence for hydrogen cyanide polymers as protein ancestors

Deuterolysis experiments suggest that hydrogen cyanide polymers rather than aminoacetonitriles are major precursors of alpha-amino acids obtained from spark reactions and other studies on chemical evolution. These results are consistent with the hypothesis that the original heteropolypeptides on the earth were synthesized spontaneously from hydrogen cyanide and water without the intervening formation of alpha-amino acids.

Heteropolypeptides from poly-alpha-cyanoglycine and hydrogen cyanide: a model for the origin of proteins

Poly-alpha-cyanoglycine, a homopolymer synthesized from the N-carboxyanhydride of alpha-cyanoglycine, is converted by cumulative reaction of hydrogen cyanide to heteropolypeptides that can be hydrolyzed to protein amino acids, including glycine, alanine, valine, aspartic acid, and glutamic acid. These results are consistent with the hypothesis that the original heteropolypeptides on the earth arose spontaneously from hydrogen cyanide and water without the intervening formation of alpha-amino acids.

Absence of an apolipoprotein E epsilon4 allele is associated with increased parietal regional cerebral blood flow asymmetry in Alzheimer disease

BACKGROUND

The apolipoprotein E (Apo E) epsilon4 allele has been associated with parietal metabolic abnormalities and asymmetries in asymptomatic subjects at risk for Alzheimer disease (AD). However, previous research has shown minimal effect of the epsilon4 allele on regional cerebral blood flow (rCBF) and metabolism in patients with probable AD.

OBJECTIVE

To determine whether the Apo E epsilon4 allele is associated with parietal rCBF abnormalities and asymmetries in patients with probable AD.

PATIENTS AND METHODS

Thirty patients with AD with the epsilon4 allele (epsilon4+ AD), 22 patients with AD without the epsilon4 allele (epsilon4- AD), and 14 healthy control subjects underwent single-photon emission computed tomography (SPECT) scanning with 740 MBq technetium Tc 99m hexamethylpropyleneamine oxime. Ratios of parietal-unaffected regions and a left-right parietal asymmetry index were compared between both patient groups.

RESULTS

The group with epsilon4- AD was younger (P = .005, Student t test) and had an earlier age of onset (P = .005) than the group with epsilon4+ AD. Analysis of covariance revealed no significant difference in the parietal rCBF ratio, controlling for age of onset and Mini-Mental State Examination score (F(1,48) = 0.06; P = .81). However, contrary to hypothesis, significantly greater parietal rCBF asymmetry was seen in patients with epsilon4- AD (mean +/- SD, 9.7% +/- 5.5%) than those with epsilon4+ AD (6.3% +/- 4.7%; F(1,50) = 5.89; P = .02; analysis of variance). When number of epsilon4 allele copies was considered, this effect appeared to accrue primarily from a difference between patients with 0 and with 2 epsilon4 allele copies. An exploratory analysis of multiple cortical structures suggested that this asymmetry extended to additional regions (superior temporal) and to combined association cortex.

CONCLUSIONS

Greater parietal rCBF asymmetry is involved in epsilon4- AD than in epsilon4+ AD. Lack of the epsilon4 allele may be associated with other (as yet undiscovered) genetic or environmental risk factors, which confer greater neuropathological asymmetry.

Gap junction blockers decrease defibrillation thresholds without changes in ventricular refractoriness in isolated rabbit hearts

BACKGROUND

The maintenance and termination of reentry arrhythmias are determined by tissue properties such as refractoriness and conduction velocity. Although the effects of Na(+) and K(+) channel block on electrophysiological properties and defibrillation threshold (DFT) have been studied, little is known about the effect of gap junction blockers on defibrillation and tissue electrophysiological properties.

METHODS AND RESULTS

Triplicate DFTs (volts) were obtained before and 15 minutes after 4 micromol/L 16-doxyl-stearic acid (16-DSA, n=8), 1 mmol/L 1-heptanol (n=12) (both gap junction blockers), 3 microg/mL lidocaine (a sodium channel blocker) (n=8), and respective controls (n=27) in isolated perfused rabbit hearts. DFT decreased after 16-DSA (23+/-14%, P<0.01) and 1-heptanol (21+/-16%, P<0.01) but increased after lidocaine (26+/-28%, P<0.05). Ventricular fibrillation cycle length (VFCL) and QRS duration increased after all 3 agents, by 36+/-19% and 44+/-16% (16-DSA), 87+/-42% and 49+/-15% (heptanol), and 57+/-20% and 43+/-26% (lidocaine), respectively (all P<0.01). Spatially averaged temporal VFCL dispersion decreased significantly after all 3 agents, by 47+/-42% (16-DSA, P<0.05), 74+/-19% (1-heptanol, P<0.01), and 82+/-13% (lidocaine, P<0.01), respectively. Ventricular effective refractory period and monophasic action potential duration at 90% repolarization were unchanged after 16-DSA and 1-heptanol (P=NS) but increased after lidocaine (16+/-13%, P<0.01, and 6+/-5%, P=NS, respectively). There were no significant changes in DFT or any other electrophysiological variable in control hearts.

CONCLUSIONS

Electrical uncoupling by 16-DSA and 1-heptanol significantly lowers DFT and dispersion of VFCL without altering refractoriness; lidocaine, at doses resulting in similar slowing of conduction, increases DFT.

A retrospective comparison of infliximab versus adalimumab as induction and maintenance therapy for Crohn disease

BACKGROUND

In Australia, infliximab (IFX) and adalimumab (ADA) are available for the treatment of moderate-severe Crohn disease (CD) refractory to conventional therapies, with minimal local data comparing their efficacy.

AIM

The aim of this study was to compare clinical and biochemical outcomes at 3 and 12 months between patients receiving induction and maintenance therapy with IFX versus ADA.

METHODS

Retrospective single-centre audit of all patients commenced on IFX or ADA as their first anti-tumour necrosis factor agent between July 2007 and May 2012. Clinical and biochemical parameters were compared pre-commencement, 3 and 12 months post-commencement.

RESULTS

A total of 81 patients was included in the study; 63 IFX-treated and 18 ADA-treated. Significant Crohn disease activity index (CDAI) reductions were noted within both groups at 3 months (P < 0.001) and 12 months (P < 0.001). Similarly, significant reductions were noted in steroid doses within groups at 3 months (P < 0.05) and 12 months (P < 0.05), with notable reductions in C-reactive protein (CRP) at 3 months within groups (P < 0.05). Adverse events occurred in 14.3% of IFX and 11.1% of ADA patients. Comparing IFX with ADA, no difference was shown between groups in CDAI reductions at 3 months (P = 0.94) and 12 months (P = 0.95), steroid dosing at 3 months (P = 0.23) and 12 months (P = 0.81), and CRP reduction at 3 months (P = 0.33) and 12 months (P = 0.62). Fistula-related admissions were significantly reduced in IFX patients (100% reduction post-IFX vs 66.7% post-ADA) (P = 0.01).

CONCLUSION

Clinical and biochemical outcomes were similar in patients treated with IFX or ADA as induction and maintenance therapy for CD. However, significant reductions were noted in admissions relating to fistulising disease in IFX patients.

High prevalence of hepatitis C virus-ribonucleic acid positivity in anti-hepatitis C virus negative renal transplant patients

BACKGROUND

Hepatitis C virus (HCV) infection is common in renal transplant (RT) patients. Some of these patients remain anti-HCV negative despite presence of infection and these are identified by a positive HCV-ribonucleic acid (RNA) test.

METHODS

We studied 404 RT patients for prevalence of HCV-RNA positivity in anti-HCV negative patients. Serum was tested for presence of anti-HCV antibodies using a third generation HCV micro-ELISA (enzyme-linked immunosorbent assay) test, which utilises a combination of HCV structural and nonstructural antigens. The RNA was extracted from patient serum for HCV viral quantification using Quiagen Ql Amp Viral RNA mini extraction kit. The HCV-RNA viral load was performed on Corbet Rotor Gene 3000 thermocycler using Taqman principle.

RESULTS

About 308 patients were anti-HCV negative and 96 were anti-HCV positive, resulting in prevalence of overt HCV infection of 23.7%. A total of 130 anti-HCV negative patients tested positive for HCV-RNA making a prevalence of occult HCV infection of 42.2%. There was no significant difference in the rate of overt or occult HCV infection between males and females. Patients with HCV infection (whether overt or occult) had received more number of dialysis sessions (62.5 vs 32.2) and blood transfusions (2.78 vs 1.99) when compared to those without HCV infection (P=0.001). The mean duration on dialysis was also longer (8.15 months vs 4.53 months) in patients with HCV infection (P= 0.0001).

CONCLUSION

A direct test for HCV viraemia is important to accurately determine the epidemiology of HCV infection in RT patients who remain anti-HCV negative despite harbouring active HCV infection.

Intestinal laceration secondary to clamping of an occult omphalocele

An omphalocele is a congenital defect of the abdominal wall, through which intestines and other intraabdominal organs protrude outside the abdominal cavity. The defect in the abdominal wall is covered by a translucent sac composed of peritoneum internally and amniotic membrane externally, through which the viscera can be seen. Such an anomaly is obvious and easily recognized at birth when the defect in the abdominal wall is large, but a small defect, also designated as umbilical cord hernia, is often unnoticed and may, when the cord is clamped, result in an iatrogenic laceration of the gut. We report such an encounter to alert the physician and suggest a method to prevent the iatrogenic misadventure. A careful follow-up of the child, including developmental evaluation, is presented and compared with her healthy twin. A review of the relevant literature shows that the anomaly is not rare and that there is often a delay of several days in establishing the correct diagnosis, leading to a fatal outcome in some cases.

Cervical status as a predictor of preterm labour

A study was conducted on 140 pregnant women at and after 28 weeks of pregnancy for finding out the relationship of cervical length and position with onset of preterm labour. Incidence of preterm labour was significantly higher (p < 0.001) in women with central position of cervix (54.67%) than that with posterior position of cervix (10.77%). Onset of preterm delivery was closely related to cervical length of 2.5 cm or less irrespective of central (82.75%) or posterior (20%) position of cervix (p < 0.001).

A mechanism of action of phenylephrine on heart

Phenylephrine exerted a positive chronotropic and inotropic effect on isolated, spontaneously beating, atria of reserpinised rabbits. Addition of phenoxybenzamine and phentolamine resulted in a depression of control contractile amplitude. Practolol, however, was devoid of this effect. The positive inotropic response to phenylephrine was significantly antagonised by all the three blockers used, while positive chronotropic response was annulled by phentolamine and practolol, but not with phenoxybenzamine. It is, therefore, suggested that phenylephrine exerts its cardiostimulant effects through mediation of both alpha and beta-1 adrenoceptors. A probable mechanism of action could be, that phenylephrine acts on some specific chemical group, shared by alpha and beta1 receptors. This specific group is probably blocked by both alpha and betaceptor antagonists separately, so phenylephrine becomes ineffective in presence of these antagonists.

Mitosis in the haemocytes of Sarcophaga ruficornis (Diptera)

Among the haemocytes of Sarcophaga ruficornis, only the prohaemocytes divide. Injection of phytohaemagglutinin-P induces 100% prohaemocytes to undergo mitosis but does not induce mitosis in other cells. Mitotic stages other than the prophase are apparently very short lived.

P152 Poor sleep quality, individual experiences and increased risk of self-harm – A multi-method study

Introduction

The COVID-19 pandemic has caused significant psychological distress to many people across the globe. Poor sleep quality may be linked to poor mental health and increased suicide ideation. To contextualise the risk factors associated with self-harm or suicidal ideation during the COVID-19 pandemic, this cross-sectional study examined links between poor sleep quality, individual experiences and self-harm risk.

Methods

N=1544 (Mage=44.3y) from 63 countries completed an online survey in March-April 2020. Participants reported their pandemic experiences as free text responses, which were examined quantitatively for frequent word usage using Linguist Inquiry and Word Count software. Pittsburgh Sleep Quality Index assessed poor sleep quality (cut-off score >8). Item-9 of Patient Health Questionnaire-9 measured the risk of self-harm.

Results

Individuals with poor sleep quality (45%) used more negative emotional tone and had greater use of anxiety or money-related words in their comments than good sleepers (all ps<.05). Additionally, 19% of respondents (n=295) reported thoughts of self-harm at least several days a week (3.4% nearly every day). Logistic regression indicated that younger individuals, males, and those feeling isolated or less resilient had 1.2 to 1.5 times greater risk of self-harm (all ps<.001). Poor sleep quality was associated with a two-fold increased risk of self-harm (95%CI=1.5–2.7, p<.0001) after controlling for demographic variables.

Discussion

Poor sleep quality is linked to negative emotionality and increased risk of self-harm during the COVID-19 pandemic. Sleep is a modifiable factor; therefore interventions aimed at addressing sleep disturbances may improve resilience and reduce the risk of self-harm in vulnerable individuals.