Research of the week
How viruses cause cancer
New Scientist 3 March 2007; 2,593: 12
It is known that human papilloma virus (HPV) causes at least 93 per cent of cancers of the cervix. The mechanism for this has been shown recently in human fibroblast cells which were infected with a retrovirus that caused the some cells to fuse together.
This resulted in wildly rearranged chromosomes. When the fibroblasts were implanted into mice, the fused cells produced tumours. It may be that other common viruses may be oncogenic by this mechanism of action.
Keeping dust mites at bay
Br J Gen Pract 2007; 57: 184–90
Inhaled corticosteroids are used commonly in the treatment of asthma. The amount of inhaled corticosteroid used should be the least needed to keep the condition under control, since high dosages may have systemic effects. This study looked at a lifestyle intervention that might reduce the need for these drugs.
House dust mites are known to produce an allergic response; in patients with asthma, contact with the allergen can provoke symptoms. Minimising contact with dust mites might then mean that a lower dose is needed.
This study looked at the benefits of using a mattress cover that is impermeable to dust mites. Inhaled corticosteroid use was triggered by a patient self-management plan based on peak expiratory flow rate measurements and symptoms. The study found that these special mattress covers minimised the drug’s use in only a few households with a particularly high house dust mite level.
Contraception for men
Contraception 2007; 75: 218–23
Testosterone gel, administered transdermally in combination with injections of depomedroxyprogesterone acetate every three months, results in effective suppression of spermatogenesis in 90 per cent of men.
Men’s attitudes regarding the daily self-administration of testosterone-gel and the impact of such a regimen on sexual function, however, are unknown. This study looked at the acceptability of this method and whether it affected sexual function.
It was found that 50 per cent of subjects were either satisfied or very satisfied with the testosterone-gel-based contraceptive regimen, and 45 per cent indicated they would use the regimen if it were commercially available. Sexual function was largely preserved during treatment; however, slight decreases were noted after the trial.
Danger with henna tattoos
Can Med Assoc J 2007; 176: 945–6
Dermatologists in Canada studied a series of patients who developed an allergic contact dermatitis to paraphenylendiamine (PPD) from hair dye. All reported similar cases of developing erythema, oedema and pruritus in some combination of their scalp, hairline, eyelids or cheeks, one to two days after having their hair dyed. All had previously had at least one black henna tattoo; four of them also reported having a previous local allergic reaction to a black henna tattoo.
It is rare to develop an allergic reaction to pure henna. Black henna tattoos usually contain an additive, as well as henna. PPD is known to be a potent skin sensitiser and to cause allergic contact dermatitis.
The reaction can take weeks to fully resolve and might require treatment with oral corticosteroids.
The authors recommend that GPs advise their patients to avoid black henna tattoos, since these tattoos can cause potent skin sensitisation to PPD that may lead to serious skin reactions with subsequent exposure.
The problem of being a second twin
BMJ online, doi:10.1136/bmj.39118.483819.55
Twin pregnancies are known to carry a greater risk to babies than single pregnancies. Studies in the past have produced variable results, some support the idea that the method of delivery does not affect outcome, others favouring advantages to twins born by caesarean section.
This retrospective study found that pre-term deliveries were no riskier for the second twin than for the first but that at term, a second twin had a risk of anoxia when delivered vaginally. This is related to the greater perinatal death rate of the second twin born at term.
Dr Merriman is a GP in Oxford and a member of our team who regularly reviews the journals