Life in a dark biosphere: a review of circadian physiology in "arrhythmic" environments

Most of the life with which humans interact is exposed to highly rhythmic and extremely predictable changes in illumination that occur with the daily events of sunrise and sunset. However, while the influence of the sun feels omnipotent to surface dwellers such as ourselves, life on earth is dominated, in terms of biomass, by organisms isolated from the direct effects of the sun. A limited understanding of what life is like away from the sun can be inferred from our knowledge of physiology and ecology in the light biosphere, but a full understanding can only be gained by studying animals from the dark biosphere, both in the laboratory and in their natural habitats. One of the least understood aspects of life in the dark biosphere is the rhythmicity of physiology and what it means to live in an environment of low or no rhythmicity. Here we describe methods that may be used to understand rhythmic physiology in the dark and summarise some of the studies of rhythmic physiology in "arrhythmic" environments, such as the poles, deep sea and caves. We review what can be understood about the adaptive value of rhythmic physiology on the Earth's surface from studies of animals from arrhythmic environments and what role a circadian clock may play in the dark.

Comparing Zonisamide With Sodium Valproate in the Management of Migraine Headaches: Double-Blind Randomized Clinical Trial of Efficacy and Safety

Background

Migraine is one of the most debilitating medical conditions and has a high socioeconomic burden. As conventional therapeutic methods do not entirely alleviate the symptoms, new alternatives are being considered.

Objectives

This study evaluates the efficacy and safety of zonisamide compared with sodium valproate in the management of migraine headaches.

Patients and Methods

In the current double-blind, parallel, randomized, controlled trial, 96 patients with a migraine diagnosis based on the international headache society (HIS) criteria were selected. They were divided randomly into two groups; the case group was given zonisamide, and sodium valproate was given to a control group. In addition to the side effects of the drugs, the severity, duration, and frequency of migraine attacks were evaluated at baseline and at three months.

Results

The 96 selected patients were divided randomly into two treatment groups (zonisamide n = 48, sodium valproate n = 48). Seven patients were excluded from analysis because of early dropout, leaving 89 (n = 45; n = 44) patients for analysis. While using zonisamide, six (13%) patients complained of fatigue, and two (4%) patients encountered noticeable appetite and weight loss. In the control group, five (11%) patients reported dizziness, and four (9%) patients faced obvious appetite and weight gain. Both drugs were considerably efficient in reducing further attacks. There was no statistically significant correlation between frequency or severity of migraine attacks and the drug used for treatment in three months of follow-up.

Conclusions

Both medications are effective in reducing migraine attacks. It will be important to consider the drugs’ adverse effects and availability and patients’ medical and socioeconomic condition to select the appropriate treatment.

Computer-aided detection of temporal clusters of organisms reported to the Communicable Disease Surveillance Centre

This article describes a computer system developed to assist in the identification of temporal clusters among the several hundred different organisms reported each week to the PHLS Communicable Disease Surveillance Centre. A threshold value is calculated for each organism on the basis of past reports. Organisms in excess of their threshold are identified for further investigation. The calculation of the thresholds allows for past outbreaks, long-term trends, and scatter in the data.