The impact of reinforcement density on response differentiation in configural discrimination problems

Two human Pavlovian conditioning experiments investigated the impact of reinforcement density (the number of reinforced trials divided by the total number of trials) on discrimination learning. Experiment 1 used a negative patterning problem (A+, B+, AB-) and Experiment 2 used a positive patterning problem (A-, B-, AB+). In both experiments, reinforcement density varied across four levels. Response differentiation between reinforced and non-reinforced stimuli was linearly related to the decrease in reinforcement density. Responses to nonreinforced stimuli did not differ between the four groups in either experiment. In contrast to this, responses to reinforced stimuli were considerably more pronounced in conditions with lower reinforcement density. For negative patterning, this replicates and extends similar observations from other species. For positive patterning, this is a finding that has not yet been reported in other experiments. The results are in agreement with the comparator hypothesis (Miller & Matzel, 1988) and with Wagner's (1981) "standard operating procedures" (SOP) model.     

Arterial Embolization as a Treatment of Chronic Edema Following Free Cutaneous Flap Transfer to the Lower Limbs

Persisting chronic edema following postoperative free flap transfer is a common complication. We report 3 cases of successful treatment by selective arterial embolization of the feeding arterial branches without side effect. One session embolization is advocated as a first line treatment of this condition.     

Local cooling alters neural mechanisms producing changes in peripheral blood flow by spinal cord stimulation

This study was performed to investigate the respective role of sensory afferent and sympathetic fibers in peripheral vasodilatation induced by spinal cord stimulation at different hindpaw skin temperatures. Cooling the skin was used as a strategy to enhance sympathetic activity [Am. J. Physiol.: Heart Circ. Physiol. 263 (1992) H1197]. Cutaneous blood flow in the footpad of anesthetized rats was recorded using laser Doppler flowmetry. Local cooling (<25 degrees C) or moderate local cooling (25-28 degrees C) of the hindpaw was produced with a cooling copper coil. Spinal cord stimulation delivered at clinically relevant parameters and with 30%, 60%, and 90% of motor threshold induced the early phase of vasodilatation in the cooled and the moderately cooled hindpaw. In addition, spinal cord stimulation at 90% of motor threshold produced the late phase of vasodilatation only in the cooled hindpaw, which was possible to block by the autonomic ganglion-blocking agent, hexamethonium. The early responses to spinal cord stimulation in the moderately cooled hindpaw were not affected by hexamethonium. In contrast, both the early and the late phase responses were eliminated by CGRP (8-37), an antagonist of the calcitonin gene-related peptide receptor. After dorsal rhizotomy, spinal cord stimulation at 90% of motor threshold elicited hexamethonium-sensitive vasodilatation in the cooled hindpaw (late phase). These results suggest that spinal cord stimulation-induced vasodilatation in the cooled hindpaw (<25 degrees C) is mediated via both the sensory afferent (early phase of vasodilatation) and via suppression of the sympathetic efferent activity (late phase) although the threshold for vasodilatation via the sympathetic efferent fibers is higher than that via sensory nerves. In contrast, vasodilatation via sensory afferent fibers may predominate with moderate temperatures (25-28 degrees C). Thus, two complementary mechanisms for spinal cord stimulation-induced vasodilatation may exist depending on the basal sympathetic tone.     

Seasonal patterns of invasive pneumococcal disease

Pneumococcal infections increase each winter, a phenomenon that has not been well explained. We conducted population-based active surveillance for all cases of invasive pneumococcal disease in seven states; plotted annualized weekly rates by geographic location, age, and latitude; and assessed correlations by time-series analysis. In all geographic areas, invasive pneumococcal disease exhibited a distinct winter seasonality, including an increase among children in the fall preceding that for adults and a sharp spike in incidence among adults each year between December 24 and January 7. Pneumococcal disease correlated inversely with temperature (r -0.82 with a 1-week lag; p<0.0001), but paradoxically the coldest states had the lowest rates, and no threshold temperature could be identified. The pattern of disease correlated directly with the sinusoidal variations in photoperiod (r +0.85 with a 5-week lag; p<0.0001). Seemingly unrelated seasonal phenomena were also somewhat correlated. The reproducible seasonal patterns in varied geographic locations are consistent with the hypothesis that nationwide seasonal changes such as photoperiod-dependent variation in host susceptibility may underlie pneumococcal seasonality, but caution is indicated in assigning causality as a result of such correlations.     

Fever during anaesthesia

Fever occurs when pyrogenic stimulation activates thermal control centres. Fever is common during the perioperative period, but rare during anaesthesia. Although only a limited number of studies are available to explain how anaesthesia affects fever, general anaesthesia seems to inhibit fever by decreasing the thermoregulatory-response thresholds to cold. Opioids also inhibit fever; however, the effect is slightly less than that of general anaesthesia. In contrast, epidural anaesthesia does not affect fever. This suggests that hyperthermia, which is often associated with epidural infusions during labour or in the post-operative period, may be a true fever caused by inflammatory activation. Accordingly, this fever might be diminished in patients who receive opioids for pain treatment. Post-operative fever is a normal thermoregulatory response usually of non-infectious aetiology. Fever may be important in the host defence mechanisms and should not be routinely treated lest the associated risks exceed the benefits.     

Noradrenaline-induced lipolysis in adipose tissue is suppressed at hibernation temperatures in ground squirrels

Responsiveness of white adipose tissue (WAT) and brown adipose tissue (BAT) from hibernating and nonhibernating golden-mantled ground squirrels (Spermophilus lateralis) to the lipolytic action of the sympathetic neurotransmitter, noradrenaline, was tested in vitro at temperatures characteristic of deep torpor (5 degrees C) and euthermia (37 degrees C). Noradrenaline-stimulated lipolysis, as indicated by WAT glycerol release, of tissue from hibernating ground squirrels was six- to ten-fold greater at 37 degrees C than at 5 degrees C. Noradrenaline was ineffective in increasing lipolysis at 5 degrees C. Noradrenaline-stimulated lipolysis in BAT was similarly suppressed at 5 degrees C. Noradrenaline-stimulated lipolysis was little affected by temperature change below approximately 15 degrees C but strongly correlated with temperature above approximately 15 degrees C. Noradrenaline-induced lipolysis of WAT from nonhibernating and hibernating ground squirrels did not differ at an incubation temperature of 5 degrees C. We conclude that noradrenaline-stimulated WAT lipolytic activity is markedly suppressed at the low temperatures characteristic of deep torpor and that there is no 'hibernation-specific' adaptation of WAT to enhance its responsiveness to noradrenaline at low tissue temperatures. Temperature dependence of noradrenaline-stimulated lipolysis may in part account for the shift from lipid to carbohydrate metabolism during the earliest stage of arousal from deep torpor.     

Non-aromatic naphthalane preparation; preliminary clinical study in the treatment of psoriasis vulgaris

This study aimed to prove the similarity of the composition of non-aromatic Croatian naphthalane (NAN) with brown naphthalane (BN), which is used in the treatment of psoriasis vulgaris. The comparison of the compositions was performed by obtaining GC fingerprints, which were supported by GC-MS data. In spite of remarkable differences in general profiles of the GC chromatograms, lower and medium molecular weight components of NAN were found to be qualitatively the same as the saturated constituents of BN. Quantitatively, lower molecular weight components as well as all n-alkanes were comparatively lower in NAN. NAN, additionally, contained higher molecular weight components, among which there were saturated oligocyclic hydrocarbons (up to pentakishomohopanes), described as responsible for the curing effect of naphthalane. The composition characteristics of NAN including its non-aromatic character made it suitable for a clinical study. In the treatment, the efficacy was determined by means of comparison of Psoriasis Area Severity Indices, PASI, at the beginning and at the end of the therapy. Adult volunteer-patients, nine males and six females, applied NAN over the whole body, except the scalp, at the room temperature for 20 min and this was followed by the selective UVB radiation. After the 3-week therapy, all essential clinical manifestations as erythema, desquamation and infiltration were significantly reduced in 14 patients; in nine cases the improvement was 50–93%, while the state of five patients improved between 25 and 50%. In one case, there was no obvious change. No exacerbation occurred during the therapy period. No adverse effect on hematological or biochemical parameters was noticed.     

Laser doppler flowmetry in combined needle acupuncture and moxibustion: a pilot study in healthy adults

Laser Doppler flowmetry (LDF) (DRT 4/Moor Instruments Ltd, Devon, UK) was used in this pilot study for monitoring the effects of an invariable acupuncture pattern on microcirculation of the skin before, during, and after combined needle acupuncture and moxibustion in 12 healthy volunteers (mean age 35.2±4.4 years, range 26–41 years, four female and eight male). According to the standards of traditional Chinese medicine (TCM), this acupuncture pattern is assumed to be unspecific and non-therapeutic. Flux decreased during the treatment period (p<0.05) compared to the control phase before combined needle acupuncture and moxibustion. After the removal of the needles, flux did not return to the initial control value. No significant differences between mean arterial blood pressure, heart rate, skin temperature or gender were detected. A prediction of individual incidences and kinds of acupuncture effects in our healthy volunteers was not possible. Modern monitoring techniques like LDF could be a method to separate responders from non-responders to acupuncture in peripheral microcirculatory disorders. Further studies on patients with peripheral microcirculatory disorders are necessary in order to demonstrate the value of LDF in detecting responders/non-responders in combination with therapeutic acupuncture patterns according to TCM. Paper received 13 September 2000; accepted after revision 2 October 2000.     

Influence of caffeine, cold and exercise on multiple choice reaction time

RATIONALE: The effects of caffeine on psychomotor performance have been evaluated under resting conditions and in a thermoneutral environment. Our hypothesis was that these effects could be modified by factors enhancing the level of alertness, such as exercise and cold exposure. OBJECTIVE: The purpose of this study was to follow up changes in the multiple choice reaction time (RT) during exercise at room and low ambient temperatures after caffeine or placebo administered in a double blind manner. METHODS: Nine soccer players performed multistage, incremental exercise until volitional exhaustion on a bicycle ergometer at 22 degrees C or 4 degrees C, 1 h after ingestion of coffee with caffeine (CAF) or without it (PL). Immediately before exercise and at the end of each workload, RT and blood lactate (LA) were measured. Oxygen uptake (VO2) and heart rate (HR) were recorded continuously. Blood LA threshold and the workload associated with the shortest RT were determined. RESULTS: During exercise at 22 degrees C, RT was significantly shorter in CAF than in the PL test, while at 4 degrees C there were no differences in RT between CAF and PL trials. Cold exposure did not affect RT either at rest or during exercise. Neither caffeine nor cold exposure influenced the maximal VO2, the maximal HR and LA threshold. CONCLUSION: In the thermoneutral environment, caffeine ingestion improved psychomotor performance during exercise, whilst at low ambient temperature this effect was blunted. These findings suggest that the stimulating action of caffeine depends on the level and source of arousal.     

Anaphylaxis to the 23-valent pneumococcal vaccine in child: a case-control study based on immediate responses in skin tests and specific IgE determination

Injections of the 23-valent pneumococcal vaccine are usually well tolerated. Skin tests (prick and intradermal) and a self-made RAST with pneumococcal vaccine and phenol were performed in a child reporting a severe anaphylactic reaction induced by a 23-valent pneumococcal vaccine, and in ten control children, including one child with a well-tolerated vaccination, and nine non-vaccinated children. Skin tests and RAST with the vaccine were positive in the child reporting anaphylaxis, and negative in nine of the control children. Intradermal test with the vaccine was slightly positive in a non-vaccinated child with negative RAST. Skin tests and RAST with phenol were negative in all the children. These results suggest that immediate responses in skin tests and specific IgE determination have a good diagnostic value in children reporting severe reactions suggestive of IgE-dependent hypersensitivity to pneumococcal vaccine.