Interleukin-1beta reduces temperature sensitivity but elevates thermal thresholds in different populations of warm-sensitive hypothalamic neurons in rat brain slices.

Extracellularly recorded firing rates of neurons in slices of the preoptic area and anterior hypothalamus (PO/AH) of the rat were determined during thermal stimulation. Human recombinant interleukin-1beta (20 ng/ml) did not influence temperature-insensitive neurons, but reduced the firing rate and thermosensitivity in linear warm-sensitive neurons, and shifted the thermal thresholds of activation in threshold warm- and cold-sensitive neurons by 1.1-2.3 degrees C to hyperthermic temperatures. The data support the suggestion that endogenous pyrogens may act on different populations of thermosensitive PO/AH neurons to induce fever. The shift of the thermal thresholds of activation of threshold warm- and cold-sensitive neurons in combination with the otherwise maintained temperature sensitivity of these neurons appears to play a major part for the controlled shift of body temperature and the maintenance of the elevated body temperature during cytokine-induced fever.

Influence of bombesin on neuronal hypothalamic thermosensitivity during the early postnatal period in the Muscovy duck (Cairina moschata).

The influence of bombesin (1 microg/0.1 ml artificial cerebrospinal fluid) on neuronal thermosensitivity of the preoptic area of the anterior hypothalamus in brain slices of 5- (n = 7 neurons) and 10-day-old (n = 36 neurons) Muscovy ducks (Cairina moschata) was investigated. Similar to adult mammals, most of the neurons investigated increased the firing rate (FR) after bombesin application. Changes in FR were not related to changes in thermal coefficient (TC). The neurons react to bombesin also under synaptic blockade. The bombesin-induced effect on TC (increase or decrease in nearly the same number of neurons, e.g. nine neurons increased and ten decreased TC in 10-day-old ducklings) in the postnatal bird neurons investigated was different from the results described in adult mammals, where the main reaction to bombesin was an increase of TC in warm-sensitive and temperature-insensitive-neurons and a transformation of temperature-insensitive-neurons into warm-sensitive ones. This may be related to the assumption that during early ontogeny, body functions react to exogenous and endogenous factors nonspecifically. It is to speculate, that later, probably at the end of embryonic development or during the early postnatal period, the reactivity of these functions changes qualitatively, so that the reaction of an individual function to different factors becomes specific (ultimately adaptive).

The psychosocial aftermath of the Chernobyl disaster in an area of relatively low contamination.

INTRODUCTION: There has been relatively little attention paid to the mid- and long-term effects of large-scale disasters, particularly their effects on children and young people. At the present time, the impact of the Chernobyl catastrophe on the daily lives of the affected population may include one of strong psychological stress due to uncertainty about ultimate health outcomes. Persons in the Chernobyl region in specific areas of low contamination may be affected similarly. This investigation assesses radiation concerns and attitudes about health and government information, nine years after the disaster, in a group of adults and adolescents residing in a relatively uncontaminated village in the Chernobyl area. METHODS: Questionnaires were administered to 94 adults and 50 adolescents. Items assessed beliefs about extent of radiation exposure, health concerns regarding oneself and family members, past and current preoccupation about the disaster, and trust in the accuracy of government information about health effects. RESULTS: Considerable uncertainty was demonstrated in both adults and adolescents about the extent of their and their families exposure to radiation. Marked distrust of past and current government information about health effects was evident. A large proportion of subjects reported that they still thought frequently about the Chernobyl accident. They worried about health problems related to radiation exposure whenever they or their family members exhibited physical symptoms or complaints, and they urged family members to go to a medical clinic for evaluation to assess these symptoms. CONCLUSIONS: The extent of long-term concerns about the personal and family health effects of the Chernobyl disaster in this population residing in a relatively uncontaminated village is striking: the psychological impact on adolescents is considerable. The stress generated is maintained by the realistic uncertainty about the ultimate health consequences to the overall population as a result of radiation exposure and distrust in government information about contamination levels in this particular village. The level of stress and its effects on physical and mental health may increase over time if there is a rise in morbidity in the area. The continuing health needs of the extremely large population affected by the Chernobyl disaster need to be addressed.

First and second phases of biphasic fever: two sequential stages of the sickness syndrome?

We hypothesized that the systemic inflammatory response undergoes two consecutive stages, each characterized by different nonspecific sickness patterns. To test this hypothesis, we studied thermal, nociceptive, and motor responses to lipopolysaccharide (LPS) in 43 unanesthetized, habituated, and lightly restrained male Wistar rats previously implanted with a catheter in the jugular vein. Escherichia coli LPS was injected intravenously in a dose of 0, 0.1, 1, 10, 100, or 1,000 micrograms/kg. Colonic temperature (Tc) was measured with a thermocouple. Changes in nociception were assessed by tail flick latency (TFL) to a noxious heat stimulus. Motor activity was evaluated using an observation-based activity score (AS). The two lowest doses were apyrogenic. The next dose induced a monophasic fever with a maximal Tc rise of 0.9 +/- 0.2 degrees C at 108 +/- 11 min post-LPS. The next two higher doses caused biphasic fevers with the first and second peaks of 0.7 +/- 0.1 and 1.4 +/- 0.1 degrees C (10 micrograms/kg) and 0.7 +/- 0.1 and 1.4 +/- 0.2 degrees C (100 micrograms/kg) occurring at 60 +/- 6 and 165 +/- 17 min and at 45 +/- 3 and 141 +/- 6 min, respectively. The highest dose of LPS resulted in a Tc fall (nadir, -0.6 +/- 0.1 degree C at 83 +/- 6 min). Two different sickness patterns were exhibited. The first (high Tc, low TFL and high AS) occurred during the monophasic fever and the first (early) phase of the biphasic fevers, and it was termed the early phase syndrome. The second pattern (high or low Tc, high TFL, and low AS) developed during the second (late) phase of the biphasic fevers and LPS-hypothermia (endotoxin shock), and it was termed the late phase syndrome. Occurring at different stages of the systemic inflammatory response and developing through different coping patterns [fight/flight (energy expenditure) vs. depression/withdrawal (energy conservation)], the two syndromes represent two different types of adaptation to infection and have different biological significance. Viewing sickness as a dynamic entity is justified clinically. Such a dynamic approach to the problem resolves several contradictions in the current concept of sickness.

Interaction between the effects of centrally administered arecoline and leucocyte pyrogen on the activity of posterior hypothalamic neurons in the rabbit.

In experiments with urethane-anesthetized rabbits, the alteration in the activity of posterior hypothalamic neurons resulting from intracerebroventricular injection of leucocyte pyrogen was attenuated by subsequent administration of arecoline. Atropine failed to alter the neuronal response to leucocyte pyrogen but abolished the effect of arecoline. The neuronal response to arecoline was reversed in the absence of leucocyte pyrogen.

The effects of intracerebroventricular cycloheximide on protein synthesis and fever in rabbits.

Cycloheximide (40 micrograms) intracerebroventricularly (i.c.v.) had no effect on thermoregulation against cold, but reduced fever due to an i.c.v. injection of leucocyte pyrogen (LP) by 25%, and reduced incorporation of radioactive leucine into hypothalamic protein by 94%.