Heat shock protein and high-dose aspirin: effects on random skin flap survival in a rat model.

The heat shock response is known to have a protective effect against flap ischemia. It has been shown that heat shock protein (hsp) expression can be augmented in vivo with the administration of high-dose aspirin before heat treatment. The authors hypothesized that administration of aspirin before hsp induction through heat stress would enhance further the protective effects of the heat shock response against skin flap ischemia. They used a random dorsal skin flap model in 32 rats divided into four groups (N = 8 each): control, heat shock, aspirin plus heat shock, and aspirin. Before surgery, rats in the two heat shock groups were placed in a 45 degrees C water bath until core body temperature measured 42 degrees C, and they were maintained at 42 degrees C for 15 minutes. Rats in the two aspirin groups received a single oral dose of aspirin (100 mg per kilogram) 1 hour before heat bath or surgery. Immunohistochemistry confirmed hsp expression in the two heat groups. Skin flap survival was improved significantly (p < 0.05) in the heat shock (55%), aspirin plus heat shock (58%), and aspirin (60%) groups when compared with controls (45%). Contrary to their hypothesis, aspirin combined with hsp induction did not offer greater protection from ischemia than hsp induction alone (p > 0.05). However, high-dose aspirin administration alone did improve skin flap survival when compared with controls. Future studies are needed to investigate further the role of pharmacological therapy combined with hsp induction in improving skin flap survival and to delineate the dose-response relationship between aspirin and hsp.     

Permanent-temporary pacemakers in the management of patients with conduction abnormalities after transcatheter aortic valve replacement

Background

Damage to the cardiac conduction system requiring permanent pacemaker (PPM) implantation is a known adverse outcome of transcatheter aortic valve replacement (TAVR). A permanent-temporary pacemaker (PTPM) is a device that involves an active-fixation lead attached to an external pulse generator taped to the skin. We reviewed the utility of PTPMs as a temporary bridge measure after TAVR in patients with conduction abnormalities that do not meet conventional criteria for PPM placement.

Methods

Between January 01, 2013 and December 31, 2015, we analyzed 67 patients who received PTPM after TAVR. Baseline demographics, comorbidities, type and size of the valve, pre-TAVR electrocardiograms (ECGs), post-TAVR ECGs at 1 day, 1 month, and 6 months, and pacemaker interrogation results were reviewed for each patient if available.

Results

The mean age of patients was 80.5?±?9.1 years. PTPM were placed for 2.3?±?2.4 days. Among these patients, 44.8% (n?=?30) received a PPM prior to discharge. Male gender (OR 2.84, 95% CI 1.05–7.69, p?=?0.05) and an increase in QRS duration post-TAVR (p?=?0.01) were associated with PPM placement. Pacemaker interrogation data of 11 patients with PPM revealed that 27% (n?=?3) had <?1% V-pacing requirements and <?10% A-pacing requirements.

Conclusions

In post-TAVR patients who develop conduction abnormalities that do not meet conventional PPM implantation indications, PTPM safely provides a time period for further assessment and may prevent unnecessary PPM implantation. Male gender and an increase in QRS duration post-TAVR are associated with PPM implantation. Additionally, some patients may recover from their conduction disturbances and demonstrate low pacemaker utilization.

     

Relation of aortic wall thickness and distensibility to cardiovascular risk factors (from the Multi-Ethnic Study of Atherosclerosis [MESA])

To determine the relation between aortic wall thickness (WT) and aortic distensibility (AD) with traditional cardiovascular risk factors in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort, 1,053 participants in MESA who underwent cardiac magnetic resonance imaging were consecutively selected for the measurement of aortic WT and AD. Double inversion-recovery fast spin-echo images of the thoracic aorta were obtained to measure average and maximum WT. AD was measured at the same level using a gradient-echo cine sequence. Average and maximum WT were positively correlated with increasing age, and AD was inversely related to age (p <0.01). Compared with normotensive participants, those with hypertension had significantly greater mean average WT (2.45 vs 2.23 mm, p <0.01) and maximum WT (3.61 vs 3.41 mm, p <0.01) and lower AD (0.15 vs 0.2 mm Hg(-1), p <0.01). In multiple regression analysis, older age and hypertension were significantly associated with higher mean average WT, while older age, male gender, and higher blood pressure were associated with higher mean maximum WT. AD was inversely related to older age, hypertension, current smoking, African American ethnicity, and lower high-density lipoprotein cholesterol level. In conclusion, in the MESA cohort, older age and higher blood pressure were associated with higher aortic WT and lower AD. Decreased AD was further associated with current smoking, African American ethnicity, and higher high-density lipoprotein cholesterol level.     

Novel coding,translation, and gene expression of a replicating covalently closed circular RNA of 220 nt

The highly structured (64% GC) covalently closed circular (CCC) RNA (220 nt) of the virusoid associated with rice yellow mottle virus codes for a 16-kDa highly basic protein using novel modalities for coding, translation, and gene expression. This CCC RNA is the smallest among all known viroids and virusoids and the only one that codes proteins. Its sequence possesses an internal ribosome entry site and is directly translated through two (or three) completely overlapping ORFs (shifting to a new reading frame at the end of each round). The initiation and termination codons overlap UGAUGA (underline highlights the initiation codon AUG within the combined initiation-termination sequence). Termination codons can be ignored to obtain larger read-through proteins. This circular RNA with no noncoding sequences is a unique natural supercompact “nanogenome.”Viroids and virusoids (viroid-like satellite RNAs) are typically small (220–450 nt) covalently closed circular (CCC) RNAs with no coding capacity (i.e., no genetic information) (1–3) and are the smallest replicating circular RNA pathogens (3, 4). Because of their circular nature, they usually replicate through a rolling circle model to produce larger concatemers (4, 5) which are then processed into monomeric forms with a self-splicing hammerhead ribozyme (virusoids and viroids in the Avsunviroidae family) (6, 7) or by cellular enzymes (8). We have previously reported (9) the characterization and nucleotide sequence of the smallest circular virusoid (220 nt), that of the rice yellow mottle virus (sobemovirus) (RYMV). Like other known virusoids, the small circular satellite of RYMV (scRYMV) depends on a helper virus RYMV for replication and packaging (9, 10).In silico translation of scRYMV revealed the presence of an unusual ORF capable of initiating translation from the AUG in the sequence UGAUGA of the 220-nt circular RNA by internal ribosome binding site (IRBS). As 220 is not an integer multiple of 3, after the first round of translation, the same circular sequence (or possibly the linear head-to-tail concatemers generated in vivo during rolling-circle replication) would be read in a different frame register. After the second round of translation, termination at the same initiation–termination sequence UGAUGA would result in the production of a highly basic 16-kDa protein with the N- and C-terminal halves of the protein encoded by the same 220-nt sequence but read in two distinct, totally overlapping frames. This virusoid could also suppress the leaky tandem termination codons (UGAUGA) to read the same sequence in a third frame and produce a new (18 kDa) read-through protein with an 18-aa C-terminal extension ended by a UAG codon. However, even the latter UAG termination codon may occasionally be ignored to generate longer proteins.In this report, we present evidence demonstrating that the putative ORF(s) deduced from the 220-nt circular RNA sequence as described above are indeed operational.Although this scRYMV RNA is classified as a virusoid, we report here that this virusoid is the only one so far found to encode for a protein. Modalities of initiation of translation (e.g., overlapped initiation and termination codons), the distinct N- and C-terminal halves of the 16-kDa protein translated from the same 220-nt circular sequence and the generation of read-through proteins were examined. We discuss the evolutionary implications of the genetic information and biological functions densely packed into a 220-nt nanogenome.