Outcomes after mitral valve repair: A single-center 16-year experience

OBJECTIVE

To evaluate outcomes after mitral valve repair.

METHODS

Between May 1999 and June 2015, 446 patients underwent mitral valve repair. Isolated mitral valve annuloplasty was excluded. A total of 398 (89%) had degenerative valve disease. Mean follow-up was 5.5 ± 3.8 years. Postoperative echocardiograms were obtained in 334 patients (75%) at a mean of 24.3 ± 13.7 months.

RESULTS

Survival was 97%, 96%, 95%, and 94% at 1, 3, 5, and 10 years. Risk factor analysis showed age >60 years and nondegenerative etiology predict death (hazard ratio, 2.91; 95% confidence interval, 1.06-8.02, P = .038; and hazard ratio, 1.87; 95% confidence interval, 1.16-3.02, P = .010, respectively). Considering competing risks due to mortality, the cumulative incidence of reoperation was 2.8%, 4.2%, 5.1%, and 9.6% at 1, 3, 5, and 10 years. Competing risk proportional hazard survival regression identified nondegenerative etiology and previous cardiac surgery as predictors of reoperation, and posterior repair was protective (all P < .05). Cumulative incidence of progression of mitral regurgitation (2 or more grades) with mortality as a competing risk was 4.7%, 10.5%, 21.0%, and 35.8% at 1, 3, 5, and 10 years. Patients with previous sternotomy, repair or coronary artery bypass grafting, and concurrent tricuspid valve procedure or isolated anterior leaflet repair were more likely to develop progression of mitral regurgitation (all P < .05), and posterior leaflet repair was protective (P = .038). On multivariate analysis diabetes, previous coronary artery bypass grafting and concurrent tricuspid valve intervention predicted MR progression.

CONCLUSIONS

Mitral valve repair has excellent outcomes. Our results demonstrate failures appear to occur less in those who undergo posterior leaflet repair.

Arsenite accumulation in the mouse eye

Elevated arsenic (As) concentrations in drinking water are a major worldwide public health concern. Exposure to As is associated with carcinogenesis, skin lesions, cardiovascular disease, cognitive deficits, and other disorders. However, little is known regarding chronic As-mediated effects on the eye. Oxidative stress is believed to be an important factor in As-related pathology and is also implicated in certain eye diseases such as cataract. Thus, elevated exposure to arsenic could potentially be a contributing factor for ocular pathology. A pilot study was therefore initiated to determine whether As could be detected in eye tissue of mice exposed to sodium arsenite in drinking water. Total As concentrations were determined by inductively coupled plasma-mass spectroscopy in whole eyes, lens, liver, heart, lung, kidneys, spleen, brain, and hair from mice given 0, 10, 50, or 250 ppm sodium arsenite in their drinking water for 4 wk or 0, 10 or 50 ppm for 6 mo. Dose-dependent increases in As concentration were observed in all organs and tissues. Surprisingly, As concentrations in the eye and lens were significantly higher than those in liver, lung, heart, spleen, and brain and similar to that found in kidneys. The relatively high concentration in the eye, and the lens in particular, suggests As exposure may be a contributing factor in cataract formation in parts of the world where As in drinking water is endemic.

Ro ribonucleoproteins contribute to the resistance of Deinococcus radiodurans to ultraviolet irradiation

The genome of the radiation-resistant eubacterium Deinococcus radiodurans contains an ortholog of an RNA-binding protein known as the Ro 60-kD autoantigen. This protein, which was previously identified only in higher eukaryotes, is normally bound to small RNAs known as Y RNAs. We show that the Ro protein ortholog Rsr contributes to the resistance of D. radiodurans to UV irradiation. Rsr binds several small RNAs, encoded upstream of rsr, that accumulate following UV irradiation. One of these RNAs resembles a Y RNA. These results suggest that Ro RNPs could similarly contribute to the recovery of higher cells following UV irradiation.

High-copy suppressor analysis reveals a physical interaction between Sec34p and Sec35p, a protein implicated in vesicle docking

A temperature-sensitive mutant, sec34-2, is defective in the late stages of endoplasmic reticulum (ER)-to-Golgi transport. A high-copy suppressor screen that uses the sec34-2 mutant has resulted in the identification of the SEC34 structural gene and a novel gene called GRP1. GRP1 encodes a previously unidentified hydrophilic yeast protein related to the mammalian Golgi protein golgin-160. Although GRP1 is not essential for growth, the grp1Delta mutation displays synthetic lethal interactions with several mutations that result in ER accumulation and a block in the late stages of ER-to-Golgi transport, but not with those that block the budding of vesicles from the ER. Our findings suggest that Grp1p may facilitate membrane traffic indirectly, possibly by maintaining Golgi function. In an effort to identify genes whose products physically interact with Sec34p, we also tested the ability of overexpressed SEC34 to suppress known secretory mutations that block vesicular traffic between the ER and the Golgi. This screen revealed that SEC34 specifically suppresses sec35-1. SEC34 encodes a hydrophilic protein of approximately 100 kDa. Like Sec35p, which has been implicated in the tethering of ER-derived vesicles to the Golgi, Sec34p is predominantly soluble. Sec34p and Sec35p stably associate with each other to form a multiprotein complex of approximately 480 kDa. These data indicate that Sec34p acts in conjunction with Sec35p to mediate a common step in vesicular traffic.

Human deltex is a conserved regulator of Notch signalling

A fundamental cell-fate control mechanism regulating multicellular development is defined by the Notch-signalling pathway. Developmental and genetic studies of wild type and activated Notch-receptor expression in diverse organisms suggest that Notch plays a general role in development by governing the ability of undifferentiated precursor cells to respond to specific signals. Notch signalling has been conserved throughout evolution and controls the differentiation of a broad spectrum of cell types during development. Genetic studies in Drosophila have led to the identification of several components of the Notch pathway. Two of the positive regulators of the pathway are encoded by the suppressor of hairless [Su(H)] and deltex (dx) genes. Drosophila dx encodes a ubiquitous, novel cytoplasmic protein of unknown biochemical function. We have cloned a human deltex homologue and characterized it in parallel with its Drosophila counterpart in biochemical assays to assess deltex function. Both human and Drosophila deltex bind to Notch across species and carry putative SH3-binding domains. Using the yeast interaction trap system, we find that Drosophila and human deltex bind to the human SH3-domain containing protein Grb2 (ref. 10). Results from two different reporter assays allow us for the first time to associate deltex with Notch-dependent transcriptional events. We present evidence linking deltex to the modulation of basic helix-loop-helix (bHLH) transcription factor activity.

Bet1p activates the v-SNARE Bos1p

Bet1p is a type II membrane protein that is required for vesicular transport between the endoplasmic reticulum and Golgi complex in the yeast Saccharomyces cerevisiae. A domain of Bet1p, that shows potential to be involved in a coiled-coil interaction, is homologous to a region of the neuronal protein SNAP-25. Here, we used in vitro binding studies to demonstrate that Bet1p plays a role in potentiating soluble NSF attachment protein receptor (SNARE) interactions. Mutational analysis points to the coiled-coil region as necessary for Bet1p function, and circular dichroism experiments support this theory. In vitro binding studies were also used to demonstrate that a direct interaction between Bet1p and Bos1p is required for the efficient interaction of the vesicle SNARE with its SNARE target. Genetic studies suggest that the interactions of Bet1p with Bos1p are regulated by the small GTP-binding protein Ypt1p.

Tracheal intubation without neuromuscular block in children

We have studied 80 healthy children, aged 2-14 yr, undergoing adenotonsillectomy in a double-blind, randomized design. Tracheal intubation facilitated by either suxamethonium 1.5 mg kg-1 or alfentanil 15 micrograms kg-1 was compared after induction of anaesthesia with propofol 3-4 mg kg-1. The quality of tracheal intubation was graded according to the ease of laryngoscopy, position of the vocal cords, coughing, jaw relaxation and movement of limbs. There were no significant differences in the overall assessment of intubating conditions between the two groups, and all children underwent successful tracheal intubation. Fewer patients coughed (P < 0.014) and limb movement was less common (P < 0.007) after tracheal intubation facilitated by suxamethonium. Alfentanil attenuated the haemodynamic responses to tracheal intubation.

Effect of the alpha-amino group on peptide retention behaviour in reversed-phase chromatography. Determination of the pK(a) values of the alpha-amino group of 19 different N-terminal amino acid residues

We have examined the contribution of the alpha-amino group to retention behaviour for peptides in reversed-phase chromatography using two series of peptide analogues, one containing an N alpha-acetylated terminal and the other containing an alpha-amino group (non-acetylated). The effect of the alpha-amino group, at pH 2, on the hydrophobicity of the side-chain of the N-terminal residue was obtained by referencing the retention time of the acetylated or non-acetylated peptide to the retention time of a glycine analogue. It was shown that the presence of an alpha-amino group could decrease or increase the hydrophobicity of the side-chain of the N-terminal residue with respect to the hydrophobicity of the side-chain in the absence of an alpha-amino group. The effect was also shown to be sequence dependent, with respect to the N-terminal residue. Increasing pH was shown to increase retention time dramatically for the non-acetylated analogues, through the deprotonation of the alpha-amino group. By separating pairs of acetylated/non-acetylated analogues over the pH range 2-9, it was possible to determine the pK(a) of the alpha-amino group, where it was shown that the pK(a) was dependent on two probable factors: (1) the inherent hydrophobicity of the stationary phase; and (2) the amino acid substituted in the N-terminal position. Interestingly, the pK(a) values determined were very similar to that found in proteins. It was also possible to determine the pK(a) values of some of the substituted amino acids containing ionizable side-chains. This study shows that, in order to understand fully the retention behaviour of peptides containing an alpha-amino group in reversed-phase chromatography, one must incorporate an alpha-amino group contribution and its effect on the hydrophobicity of the side-chain of the N-terminal residue.

Dual-specificity protein kinases: will any hydroxyl do?

Protein kinases are classified by the target amino acid in their substrates. Those protein kinases that phosphorylate hydroxyamino acids comprise two groups, the protein-tyrosine and protein-serine/threonine kinases, which, until recently, had been thought to be mutually exclusive. However, several new protein kinases have been discovered that, by the criterion of primary structure, would be classified as protein-serine/threonine kinases but which, surprisingly, are able to phosphorylate tyrosine residues. Even more surprising, there are reports of protein kinases that are capable of phosphorylating both tyrosine and serine/threonine residues. We review and discuss recent developments concerning these 'dal-specificity' protein kinases.

The protein kinase family: conserved features and deduced phylogeny of the catalytic domains

In recent years, members of the protein kinase family have been discovered at an accelerated pace. Most were first described, not through the traditional biochemical approach of protein purification and enzyme assay, but as putative protein kinase amino acid sequences deduced from the nucleotide sequences of molecularly cloned genes or complementary DNAs. Phylogenetic mapping of the conserved protein kinase catalytic domains can serve as a useful first step in the functional characterization of these newly identified family members.

Some notes on reading: talkers, material and reading rate

The paper describes a method of estimating a person's reading rate from a small sample of his speech (in other words, a short sentence). Reading rate was obtained by measuring the speaking portion of a considerable amount of reading, and dividing it by the number of phonemes in the material (this is called the grand mean). Out of 108 sentences read by four talkers, 58 having 15 words or less were selected. The ratio of unstressed to stressed syllables, and the number of syllables per occurrence of terminal lengthening were calculated for each of the 58 sentences. Sentences with both of these values in the middle range were considered to have an average phoneme duration close to the grand mean. The prediction was compared to actual readings by four talkers, with 83 percent agreement. The Summary section contains instructions for applying our method of estimating a person's reading rate. Those who are interested should read the Summary section and the Appendix first.