Sources of pain related responses to posterior tibial nerve stimulation

Brain responses to posterior tibial nerve stimulation were examined in patients who suffered from a proven neuropathic (traumatic) pain. The aim of this study was to learn if these responses could be used for the assessment of persistent pain and its relief in chronic pain patients. Experiments were carried out in five patients, where usual strategies had failed and spinal cord stimulation was applied. It was found that the measured evoked responses, when these patients were in pain, showed additional waves at latencies at around 110 ms and 150 ms after stimulation of the posterior tibial nerve. The magnetic field and electrical potential distributions at these latencies were dipolar and the responses at 110 ms and 150 ms could be ascribed to two equivalent current dipoles situated in two distinct areas in the brain. In patients, who underwent spinal cord stimulation, the additional wave disappeared once the patient was in a pain free condition. For this group of patients the additional waves appear to be related to the perception of pain and this may offer an objective method to assess this kind of pain and study the effects of spinal cord stimulation. Although not mentioned here, similar results were found for median nerve stimulation

Out-of-Hospital Cardiac Arrest in the 1990s: A Population-Based Study in the Maastricht Area on Incidence, Characteristics and Survival

AbstractObjectives. We sought to describe the incidence, characteristics and survival of out-of-hospital sudden cardiac arrest (SCA) in the Maastricht area of The Netherlands.Background. Incidence and survival rates of out-of-hospital SCA in different communities are often based on the number of victims resuscitated by the emergency medical services. Our population-based study in the Maastricht area allows information on all victims of witnessed and unwitnessed SCA occurring outside the hospital.Methods. Incidence, patient characteristics and survival rates were determined by prospectively collecting information on all cases of SCA occurring in the age group 20 to 75 years between January 1, 1991 and December 31, 1994. Survival rates were related to the site of the event (at home vs. outside the home) and the presence or absence of a witness and rhythm at the time of the resuscitation attempt in out-of-hospital SCA.Results. Five hundred fifteen patients were included (72% men, 28% women). In 44% of men and 53% of women, SCA was most likely the first manifestation of heart disease. In patients known to have had a previous myocardial infarction (MI), the mean interval between the MI and SCA was 6.5 years, with >50% having a left ventricular ejection fraction >30%. The mean yearly incidence of SCA was 1 in 1,000 inhabitants. Of all deaths in the age groups studied, 18.5% were sudden. Nearly 80% of SCAs occurred at home. In 60% of all cases of SCA a witness was present. Cardiac resuscitation, which was attempted in 51% of all subjects, resulted overall in 32 (6%) of 515 patients being discharged alive from the hospital. Survival rates for witnessed SCA were 8% (16 of 208 subjects) at home and 18% (15 of 85 subjects) outside the home (95% confidence interval 1% to 18.8%).Conclusions. The majority of victims of SCA cannot be identified before the event. Sudden cardiac arrest usually occurs at home, and the survival of those with a witnessed SCA at home was low compared with that outside the home, indicating the necessity of optimizing out-of-hospital resuscitation, especially in the at-home situation

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Reinforcing stimulus properties of drugs

The reinforcing efficacy of psychoactive drugs can reliably be studied in experimental animals by using procedures for drug self-administration. This property of drugs is used to predict qualitatively and quantitatively their abuse potential in humans. External factors like the dose of the drug, the schedule of drug availability and stimulus control are critically important in initiation, maintenance and cessation of self-administering behaviour. Drug-induced changes in the organism, including tolerance and physical dependence, may contribute more or less to the behaviour associated with drug use and consequently change the pattern of drug intake. Concerning the internal factors involved in the process by which a given drug consequence gains control over behaviour, it is suggested that addictive drugs may mimic the action of endogenous substances which are implicated in the physiological mechanisms underlying reinforcement. Neuropeptides e.g. those related to vasopressin, which are involved in the adaptation of the individual to his environment, may modulate the consequences of drug self-administration by interfering with the complex interaction of addictive drugs with brain homeostatic mechanisms. It is postulated that derangements in neuropeptide systems may be critical factors in the development of addictive behaviour