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BMJ 2010; 340 doi: https://doi.org/10.1136/bmj.b5686 (Published 05 January 2010) Cite this as: BMJ 2010;340:b5686

S6k1 is an ageing gene common to yeast, flies, worms, and mice

Clinical trials of antiageing drugs are still things of the future, but translational science is closing in.

In mice, deletion of the S6k1 gene (which encodes ribosomal protein S6 kinase 1) prolongs life, improves sensitivity to insulin in old age, and protects from degeneration of motor, bone, and immune functions, although not from cancer. Similar effects have previously been shown in yeast, flies, and worms.

S6k1 might alter energy metabolism by altering the activity of mRNA and AMP kinase in the conserved target of rapamycin (TOR) pathway, much like fasting, which is thought to prolong life through a similar mechanism. The TOR pathway, along with the insulin and insulin-like growth factor 1 signalling pathway, has a major role in modulating longevity across the species studied so far.

Metformin and sirolimus (rapamycin)—two human drugs that target the TOR pathway—have been shown to prolong life in mice, although the effect of metformin was reserved for females. This sex specific effect warrants further study, as do the long term effects of these drugs and the differences in the ageing process between human and other species.

Catheter ablation helps prevent ventricular tachycardia after myocardial infarction

Implantable cardioverter defibrillators save lives by preventing sudden cardiac death in people with ventricular tachycardia after myocardial infarction. The shocks are painful, however, and do not avert all deaths. An open label multicentre randomised trial of 110 participants tested whether adding early catheter ablation to the procedure improves outcomes compared with implantable cardioverter defibrillators alone. All participants had stable ventricular tachycardia, a history of myocardial infarction, and a reduced left ventricular ejection fraction of 50% or less. They were aged 18-80 years and were followed up for a mean of 22.5 months.

The time to first recurrence of ventricular tachycardia or ventricular fibrillation was longer in the ablation group than in the control group (median 18.6 months v 5.9 months). Nearly half (47%) of the patients in the ablation group survived to two years free of ventricular tachycardia or ventricular fibrillation, compared with less than a third (29%) of the control group. Ablation related complications occurred in two patients (transient ischaemic ST segment elevation and a transient cerebral ischaemic event with aphasia and tiredness), but no deaths were recorded within 30 days of the procedure.

The authors of a linked comment (p 4) stress that the procedure cannot as yet be recommended for routine use because evidence of a positive effect on survival, hospital admissions, or quality of life is lacking.

H1N1 transmissibility is low in households but higher in schools

In the United States, an investigation of 216 people with 2009 pandemic influenza A (H1N1) and their 600 household members showed that only 78 (13%) of the household contacts developed an acute respiratory illness. The majority (72%) of the households remained free of acute respiratory illness other than the index patient, whereas one or more than one person aside from the index patient developed an acute respiratory infection in 21% and 6% of households, respectively.

Contacts aged 18 years or younger were twice as likely to get infected as people aged 19-50 years, and people older than 50 years were the least susceptible. The mean incubation period was 2.6 days (Bayesian 95% credible interval 2.2 to 3.5).

In a secondary school in New York City that suffered an outbreak of H1N1 flu in April 2009, 35% of students and 10% of staff reported having had an influenza-like illness. No cases of severe illness were detected. The median incubation period was estimated at 1.4 days (95% confidence interval 1.0 to 1.8).

The authors estimated that the number of incident cases of flu-like illness doubled every 1.3 days, indicating that each case infected an estimated 3.3 other students or staff (95% CI 3.0 to 3.6). The probability of household transmission in this study was 14%.

Tarantulas can cause ophthalmia nodosa

A recent case report describes a 29 year old man who presented with a red, watery, and photophobic right eye with reduced visual acuity. His symptoms had lasted for three weeks despite treatment with antibiotic ointment for a suspected conjunctivitis.

Examination with a low power slit lamp was initially consistent with viral keratoconjunctivitis. On higher magnification, however, fine hair-like projections were found at varying depths within the cornea, as well as on the retina. The diagnosis was hence made of ophthalmia nodosa—the inflammatory response of the eye to insect or vegetable material. The only effective treatment for this condition is long term use of a topical steroid.

As soon as the findings were conveyed to the patient, he remembered an incident from three weeks earlier: while he was cleaning his terrarium his pet, a Chilean Rose tarantula, closed in on him and released “a mist of hairs” that hit his face. This defence mechanism, meant to protect from predators, makes use of urticating hairs that grow on the spider’s back. Should the spider feel endangered, it will rub its back legs against its abdomen and so release the hairs up into the air.

Lovers of the exotic pet may want to protect their eyes when handling the spider.

Notes

Cite this as: BMJ 2010;340:b5686

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