Replication and meta-analysis of common variants identifies a genome-wide significant locus in migraine.

BACKGROUND AND PURPOSE: Genetic factors contribute to the aetiology of the prevalent form of migraine without aura (MO) and migraine with typical aura (MTA). Due to the complex inheritance of MO and MTA, the genetic background is still not fully established. In a population-based genome-wide association study by Chasman et al. (Nat Genet 2011: 43: 695-698), three common variants were found to confer risk of migraine at a genome-wide significant level (P < 5 × 10(-8) ). We aimed to evaluate the top association single nucleotide polymorphisms (SNPs) from the discovery set by Chasman et al. in a primarily clinic-based Danish and Icelandic cohort. METHODS: The top association SNPs were assessed in 2523 cases and 38,170 controls, and a meta-analysis was performed, combining the discovery set with all the follow-up studies. Finally the confirmed SNPs were assessed in a genotype-phenotype analysis. RESULTS: Two out of three SNPs that showed genome-wide significant associations in the previous study: rs10166942 (near TRPM8) and rs11172113 (in LRP1) were significantly associated with migraine in the present study. The meta-analysis confirmed the previous three genome-wide significant associated SNPs (rs2651899, rs10166942 and rs11172113) to confer risk of migraine. In addition, the C-allele of rs2078371 (near TSPAN-2) also reached genome-wide significance for association with migraine [OR = 1.14; CI = (1.09-1.20); P = 2.55 × 10(-8) ]. CONCLUSION: TSPAN-2 encodes an integral membrane protein involved in oligodendrogenesis. This new finding supports the plausible implication of neuroglia in the pathophysiology of MO and MTA.

AR intragenic deletions linked to androgen receptor splice variant expression and activity in models of prostate cancer progression.

Reactivation of the androgen receptor (AR) during androgen depletion therapy (ADT) underlies castration-resistant prostate cancer (CRPCa). Alternative splicing of the AR gene and synthesis of constitutively active COOH-terminally truncated AR variants lacking the AR ligand-binding domain has emerged as an important mechanism of ADT resistance in CRPCa. In a previous study, we demonstrated that altered AR splicing in CRPCa 22Rv1 cells was linked to a 35-kb intragenic tandem duplication of AR exon 3 and flanking sequences. In this study, we demonstrate that complex patterns of AR gene copy number imbalances occur in PCa cell lines, xenografts and clinical specimens. To investigate whether these copy number imbalances reflect AR gene rearrangements that could be linked to splicing disruptions, we carried out a detailed analysis of AR gene structure in the LuCaP 86.2 and CWR-R1 models of CRPCa. By deletion-spanning PCR, we discovered a 8579-bp deletion of AR exons 5, 6 and 7 in the LuCaP 86.2 xenograft, which provides a rational explanation for synthesis of the truncated AR v567es AR variant in this model. Similarly, targeted resequencing of the AR gene in CWR-R1 cells led to the discovery of a 48-kb deletion in AR intron 1. This intragenic deletion marked a specific CWR-R1 cell population with enhanced expression of the truncated AR-V7/AR3 variant, a high level of androgen-independent AR transcriptional activity and rapid androgen independent growth. Together, these data demonstrate that structural alterations in the AR gene are linked to stable gain-of-function splicing alterations in CRPCa.

A genotype-phenotype analysis of the 8q22.1 variant in migraine with aura.

BACKGROUND AND PURPOSE: Although the genetics of familial hemiplegic migraine are being unraveled, this is not the case for the prevalent types of migraine. However, a recent genome wide association study (GWAS) reported an association of the single nucleotide polymorphism (SNP) rs1835740 and migraine. The aim of this study is to evaluate the association of clinical characteristics in migraine with aura (MA) with the newly discovered minor allele A of rs1835740 at 8q22.1. METHODS: Participants were recruited from the Danish Headache Center and from specialist practices during the periods 1999-2002 and 2005-2006, and diagnosed according to the International Classification of Headache Disorders (ICHD-II) using a validated physician-conducted semi-structured interview. A large number of clinical characteristics were systematically determined. Caucasians of Danish ancestry diagnosed with MA and successfully genotyped for the SNP rs1835740 were included. Patients with hemiplegic migraine were excluded. Blood samples were collected for extraction of genomic DNA and genotyped for the common susceptibility variant rs1835740. RESULTS: Six hundred and ninety one successfully genotyped MA patients with substantial description of their clinical characteristics were included. Two hundred and fifty one were heterozygous and 40 were homozygote for the variant marker. Carriers of the rs1835740 variant showed a non-significant tendency towards having a higher frequency of aura symptoms and a non-significant tendency towards milder migraine headache characteristics and fewer accompanying symptoms. These tendencies were not increased in homozygote carriers. CONCLUSION: None of the clinical characteristics of MA were significantly influenced by the common susceptibility variant on 8q22.1.

Trigger factors in migraine with aura.

The aim of the present study was to identify trigger factors in migraine with aura (MA). A total of 629 MA patients representative of the Danish population were sent a questionnaire listing 16 trigger factors thought to be relevant as well as space for free text. Distinction was made between attacks with or without aura within each patient. The questionnaire was returned by 522 patients of whom 347 had current MA attacks. In total 80% with current attacks (278/347) indicated that at least one factor triggered their migraine, and 67% (187/278) in this group indicated that they were aware of at least one factor often or always giving rise to an attack of MA. Forty-one per cent (113/278) had co-occurring attacks of migraine without aura (MO). Stress (following stress), bright light, intense emotional influences, stress (during stress) and sleeping too much or too little were the trigger factors mentioned by most. Attack frequency had little impact on the number of trigger factors. Women reported more trigger factors than men. Patients having attacks of both MA and MO reported more trigger factors for MO attacks than for MA attacks. In conclusion, 80% of patients with MA reported trigger factors and two-thirds of these reported at least one trigger factor often or always triggering an attack of MA. Patients should be educated to avoid these factors.

Efficacy and safety of tonabersat, a gap-junction modulator, in the acute treatment of migraine: a double-blind, parallel-group, randomized study.

The ability of tonabersat to relieve the symptoms of migraine attacks with or without aura was evaluated in a randomized, double-blind, placebo-controlled, multicentre, parallel-group study. Patients received 20 or 40 mg of tonabersat, or 50 mg of sumatriptan (positive control), or placebo at the onset of a moderate or severe attack. Headache intensity, relief and recurrence were recorded for 24 h after dosing. On the basis of primary or secondary efficacy measures, tonabersat did not provide a clinically or statistically significant advantage over placebo. Tonabersat generally was well tolerated and had no effect on vital signs, electrocardiogram recordings or laboratory values. The lack of efficacy may be a function of the slow absorption of tonabersat. As a consequence of slow absorption, daily administration of tonabersat as prophylaxis for migraine attacks is under investigation in ongoing studies.

Oxygen dependence of tyrosine hydroxylase.

The effects of dioxygen on tyrosine hydroxylase (TH) activity was studied, measuring the formation of DOPA from tyrosine, (3)H(2)O from 3,5-(3)H-tyrosine, or by direct oxygraphic determination of oxygen consumption. A high enzyme activity was observed during the initial 1-2 min of the reactions, followed by a decline in activity, possibly related to a turnover dependent substoichiometrical oxidation of enzyme bound Fe(II) to the inactive Fe(III) state. During the initial reaction phase, apparent K (m)-values of 29-45 microM for dioxygen were determined for all human TH isoforms, i.e. 2-40 times higher than previously reported for TH isolated from animal tissues. After 8 min incubation, the K (m) (O(2))-values had declined to an average of 20 +/- 4 microM. Thus, TH activity may be severely limited by oxygen availability even at moderate hypoxic conditions, and the enzyme is rapidly and turnover dependent inactivated at the experimental conditions commonly employed to measure in vitro activities.

[Should iron preparations be available only by prescription?]. / Bør jernpreparater reseptbelegges?

Many persons associate fatigue and lassitude with iron deficiency and take extra iron "to be on the safe side". This is an unfortunate practice, as the early symptoms of iron deficiency anaemia and of hereditary iron overload (homozygous primary haemochromatosis) are similar. Primary haemochromatosis is considerably more prevalent than earlier believed. As many as 5 per 1,000 of the Norwegian population may have two mutated genes for haemochromatosis, while up to 15% may be carriers of a single mutated gene, and for these an extra intake of iron may be hazardous. The condition is highly underdiagnosed. In Norway at present, iron preparations of 60-100 mg are sold over the counter in pharmacies without prescription and often by self-service. However, no one should use iron tablets until iron deficiency and its cause has been ascertained. To avoid uncritical use of iron, iron preparations should be available only by doctor's prescription. Prolonged abuse of iron tablets may result in secondary haemochromatosis.

Reduced autonomic activity during stepwise exposure to high altitude.

Several studies have shown increased sympathetic activity during acute exposure to hypobaric hypoxia. In a recent field study we found reduced plasma catecholamines during the first days after a stepwise ascent to high altitude. In the present study 14 subjects were exposed to a simulated ascent in a hypobaric chamber to test the hypothesis of a temporary reduction in autonomic activity. The altitude was increased stepwise to 4500 m over 3 days. Heart rate variability (HRV) was assessed continuously in seven subjects. Baroreceptor reflex sensitivity (BRS) was determined in eight subjects with the 'Transfer Function' method at baseline, at 4500 m and after returning to baseline. Resting plasma catecholamines and cardiovascular- and plasma catecholamine- responses to cold pressor- (CPT) and mental stress-test (MST) were assessed daily in all and 12 subjects, respectively. Data are mean +/- SEM. Compared with baseline at 4500 m there were lower total power (TP) (35 457 +/- 26 302 vs. 15 001 +/- 11 176 ms2), low frequency (LF) power (3112 +/- 809 vs. 1741 +/- 604 ms2), high frequency (HF) power (1466 +/- 520 vs. 459 +/- 189 ms2) and HF normalized units (46 +/- 0.007 vs. 44 +/- 0.006%), P < or = 0.001. Baroreceptor reflex sensitivity decreased (15.6 +/- 2.1 vs. 9.5 +/- 2.6 ms mmHg(-1), P = 0.015). Resting noradrenaline (NA) decreased (522 +/- 98 vs. 357 +/- 60 pmol L(-1), P = 0.027). The increase in systolic blood pressure (SBP) and NA during mental stress was less pronounced (21 +/- 4 vs. 10 +/- 2% and 25 +/- 9 vs. -2 +/- 8%, respectively, P < 0.05). The increase in SBP during cold pressor test decreased (16 +/- 3 vs. 1 +/- 6%, P = 0.03). Diastolic blood pressure, HR and adrenaline displayed similar tendencies. We conclude that a transient reduction in parasympathetic and sympathetic activity was demonstrated during stepwise exposure to high altitude.

[Thomas H.Huxley--the naval doctor who became Darwin's bulldog]. / Thomas H. Huxley--marinelegen som ble Darwins bulldogg.

Thomas H. Huxley (1825-1895) was an English physician and biologist who had a deep impact on the Victorian age. More than any other at his time he introduced scientifically based values. As a member of London's school board he brought science into the curriculum, encouraging school-children to ask questions and to make their own observations. Huxley came from a lower middle class family with little money. By sheer determination and hard work he managed to get a medical education at Charing Cross Hospital Medical School. He then obtained a posting on H.M.S. Rattlesnake, which gave him a chance to explore the southern seas and to study marine species. The results were published by the Royal Society of which Huxley became a member at the age of 26, and later its president. After several years of uncertainty he secured a position at the Royal School of Mines, which he transformed into the Imperial College of Science. He was a prolific scientist with wide interests, doing valuable work in paleontology, taxonomy and ethnology. Huxley wrote numerous essays on philosophy and scientific subjects. He coined the word agnostic to explain his attitude to Christian dogma. His style was clear and direct, and his essays still read very well. However, Huxley is now mostly, perhaps unfairly, remembered for his defence of Darwin's theory of evolution. In his book Evidence as to man's place in nature, Huxley, in contrast to Darwin, deals with the evolution of humans, mainly based on comparative anatomy. Huxley advocated a firmly held belief that scientific truths will have a liberating effect on the minds of men. His lectures on scientific subjects attracted large audiences of people who had not had the benefit of a higher education.

[Dr Alexander M. Kellas and the first Mount Everest expedition]. / Dr. Alexander M. Kellas og den første Mount Everest-ekspedisjon.

In 1921 the government of Tibet gave permission for a British party to attempt Mount Everest from the northern Tibetan side. Little was known about the physiological and medical problems associated with ascents to extreme altitudes. The person who knew most about these topics was Dr. Alexander Kellas, lecturer in medical chemistry at the Middlesex Hospital Medical School. He had made a number of expeditions to the Sikkim Himal and the Tibetan border before the first world war, and had become increasingly interested in the problems caused by altitude. He was invited to join the Everest expedition but died on the approach march at Kampa Dzong on the Tibetan plateau, within sight of the mountain. Before he went on the expedition Kellas wrote an article entitled A consideration of the possibility of ascending Mt. Everest. This paper was never published, but the manuscript exists in the archives of the Royal Geographical Society and the Alpine Club in London. As Kellas saw it, the main issue was whether sufficient adaptation could occur to allow a climber to ascend from a camp at about 7,700 m to the summit (8,848 m) in one day without supplementary oxygen. His conclusion was that this was possible and, in fact, the first such ascent by Habeler and Messner in 1978 started from a camp at 7,900 m. Kellas calculated the pressure on the summit to be 251 mmHg, a more accurate figure than estimates based on the "Standard Atmosphere" Kellas estimated maximum oxygen uptake at the summit to be 970 ml/min, and the current value is thought to be about 1,070 ml/min. His estimates of the climbing rate near the summit closely parallels the rate of Habeler and Messner. Kellas had a talent for asking the right questions. He applied his considerable knowledge of physiology to the topic of high altitude, and his suggestions and recommendations were of consistently high quality. He deserves to be better known, both for his geographical surveys and for his pioneer work on high altitude medicine and acclimatisation. The 1921 expedition, after many failed attempts, discovered a possible route to the top of Mount Everest, which was used on all the summit attempts between the two world wars. The route went from Kharta, over the pass Lhakpa La, across East Rongbuk glacier and up via the north col.

Acid-base regulation during hypothermia. a brief review.

Acid-base physiology has mainly focused on mechanisms that maintain normal, extracellular pH at a constant temperature. Usually it is the arterial blood which is considered. As reliable pH meters became generally available in the 1950s it was observed that an arterial pH of about 7.39-7.42 was maintained remarkably constant in normal man and in mammals in general. This moderate degree of blood alkalosis is maintained by chemical buffering, by appropriate adjustment of the lung ventilation and by the kidneys. To measure pH intracellularly was more difficult, but not impossible, and over some time it became apparent that intracellular fluid was close to neutrality. pH values around 6.8 was found. This is a favorable state for retention of metabolites inside the cells. From an analysis by Davis (1) of the ionization constants of several hundred watersoluble biosynthetic intermediates one may argue that the ideal intracellular pH would occur near the neutrality of water where most of these compounds are ionized and thus captured within the cells, with little tendency to escape across the cell membrane. Apparently, if cells are to defend their neutrality and also to eliminate their acid metabolites and CO2, there must be a considerable transmembrane H+ gradient: The hydrogen ion concentration at neutrality is 160 nmol/L (pH 6.8) and that of blood 40 nmol/l (pH 7.4).

[Chaos and fractals. Are these of interest to medical science?]. / Om kaos og fraktaler. Er dette av interesse for medisinske fag?

Biological systems are governed by nonlinear dynamics and often appear to be random, because the available information, though accurate, is usually incomplete. It is important to be aware of the fact that nonlinear deterministic systems can behave unpredictably in the long term. Traditional reductionism is unable to provide an adequate understanding of such systems. A more global description and explanation of forms, features and functions is required. Chaos theory and fractal geometry are of value in this respect. This article is an introduction to this relatively new field of science and mathematics.

Endothelin-1-induced increases in microvascular permeability in isolated, perfused rat lungs requires leukocytes and plasma.

Effect of endothelin-1 (ET-1) (10(-8) M) on pulmonary microvascular permeability was examined in isolated rat lungs perfused with blood or various blood components. Microvascular permeability was assessed by measuring fluid filtration rate (FFR) in lungs pretreated with papaverine in order to prevent changes in vascular smooth muscle tone. ET-1 significantly increased FFR (131.0 +/- 10.1 mg/min, P < 0.01) after perfusion with blood for 60 min. In lungs perfused with leukocytes resuspended in plasma, ET-1 increased FFR significantly both 30 min (40.4 +/- 11.4 mg/min, P < 0.01) and 60 min (97.4 +/- 14.5 mg/min, P < 0.01) after it was added to the perfusate. Heat inactivation (56 degrees C; 1 hr) of plasma did not attenuate this effect of ET-1 (94.4 +/- 25.1 mg/min, P < 0.01). When lungs were perfused with leukocytes resuspended in Krebs Ringer albumin instead of plasma, or with plasma only, ET-1 did not cause any change in FFR. In conclusion, ET-1 increases microvascular permeability in isolated blood-perfused rat lungs. The effect is critically dependent on the presence of leukocytes and plasma components other than complement.

Effects of exercise and CO2 inhalation on the breathing pattern in man.

Conflicting opinions exist concerning the breathing pattern in man during resting and stimulated ventilation. Some but not all investigators have reported the existence of an abrupt change, a 'breakpoint', in the relation between mean tidal volume and mean inspiratory time. Different opinions exist as to whether the slope and the intercept for the relation between mean minute ventilation and mean tidal volume are identical regardless of the mode of stimulating the ventilation. We have studied 10 subjects, at rest and during graded stimulation of ventilation by CO2 inhalation and exercise. No breakpoint was observed in the relations between (1) mean tidal volume and mean inspiratory time and (2) mean tidal volume and mean expiratory time, even if a wide range of tidal volumes was achieved in our subjects. Carbon dioxide inhalation (normoxic or hyperoxic) and exercise gave different regression lines for the relation between mean minute ventilation and mean tidal volume in 8 out of 10 subjects with a larger slope during exercise. At exercise inspiratory time decreased with any increase in tidal volume, while during CO2 breathing no consistent change in inspiratory time was seen. Mean inspiratory flow was linearly related to exercise load and apparently also to arterial carbon dioxide pressure. We conclude that CO2 breathing gives a breathing pattern which is different from that obtained with exercise in the majority of normal subjects. Furthermore, we could not confirm the existence of breakpoints in relations describing the breathing pattern of normal man.