Splenic histiocytosis in idiopathic thrombocytopenic purpura: A relative sphingomyelinase deficiency?

The case of a patient in whom idiopathic thrombocytopenic purpura (ITP) was associated with diffuse splenic histiocytosis is described; the patient's subsequent sphingomyelinase level was at the lower limits of the normal range. The patient's splenic lecithin:sphingomyelin ratio was not significantly different from that of 11 age-matched control subjects. It is postulated that the sporadic cases of splenic histiocytosis in patients with ITP are due to a relative, acquired sphingomyelinase deficiency.     

The effects of anticipated information on skin conductance and cardiac activity

This experiment examined electrodermal and cardiac activity within a two-stimulus anticipation paradigm. A warning stimulus informed subjects (N = 24) whether an imperative stimulus to follow would contain two or four letters (low or high information conditions) and whether this stimulus would be presented for 60 or 75 msec (short or long duration). The subject's task was to identify as many of the letters in the imperative stimulus as possible. Although the amount of information conveyed by the warning stimulus was identical throughout the experiment (2 bits), skin conductance responses during the warning stimulus-imperative stimulus interval were larger prior to the high information imperative stimulus than prior to the low. Cardiac activity was not affected by the experimental manipulations. The implications of these findings for theories of the orienting response are discussed, particularly with reference to the view that orienting reflects an activation of the information processing system.     

The impact of warning signal intensity on reaction time and components of the contingent negative variation.

Slow EEG potentials were recorded during performance of a simple reaction task in which warning signal intensity was varied from trial to trial under foreperiod durations of 1, 3 and 8 sec. As shown by speed of reaction, the warning signal had an activating effect which increased with its intensity and decreased with foreperiod duration. This effect was related to the amplitude of a slow potential which appears in the EEG shortly after presentation of the warning signal. This potential is interpreted as a component of the orienting response regulating sensitivity to subsequent stimulation, so that reaction time is affected through change in the effective intensity of the imperative signal.     

Gestational stress: effects on open-field behaviour and heart rate reactivity in rat offspring.

Home-cage heart rate (HR) and open-field defecation, ambulation, rearing and HR, were recorded in the offspring of mothers who had been exposed to stress during gestation. Compared with controls, experimental animals showed no significant differences in ambulation and rearing, while defecation was significantly lower. The only significant finding on HR was an increase from home-cage level to open-field level in the experimental group. The results confirmed previous findings that illumination level is a useful independent variable in gestational stress studies, and suggested that different types of HR measure yield a similar picture of the HR/defecation relationship, which appears to be a negative function. These conclusions were discussed in the light of other findings in this area, and traditional assumptions about the emotionality construct were questioned.     

Stimulus omission and recovery of the electrodermal and digital vasoconstrictive components of the orienting response.

Three experiments are reported which investigated Sokolov's (1968) hypothesis that, after a number of stimulus presentations, complete omission of a stimulus leads to increased responsiveness of the orienting response (OR). The skin conductance response (SCR) and finger pulse volume (FPV) response components of the OR were studied. In experiment 1 (N=60), the effect of number of pre-omission training trials on response recovery was investigated, while experiment 2 (N=120) investigated the effects of stimulus intensity (70 or 90 dB) and interstimulus interval (12 or 21 sec) on recovery to stimulus omission following a fixed number of training trials. In experiment 3 (N=40), an attempt was made to control for possible below-zero habituation effects by training each subject to a habituation criterion before stimulus omission. All experiments employed a 1000 Hz tone of 3 sec duration which was presented at a constant interstimulus interval. Although recovery of the SCR did occur under some conditions, the results were largely negative. Manipulation of the number of training trials, training stimulus intensity and interstimulus interval had little effect on response recovery. A consistent finding, however, was that subjects who displayed SCR recovery also displayed significantly more spontaneous fluctuations in skin conductance during the pre-stimulus period and required significantly more training trials to reach the criterion of habituation than did subjects displaying no recovery. Moreover, the SCRs displayed by 'labile' subjects on omission trials were significantly larger than those displayed on either the last training trial or during a control interval just prior to stimulus omission.     

Dishabituation of the electrodermal orienting response following decay of sensitization

This study tested one of the basic propositions of dual-process theory (Groves and Thompson, 1970) that ‘dishabituation’ results from an independent, superimposed process of excitation and not from disruption of the habituation process as proposed by Sokolov (1963). Skin conductance level (SCL) was employed as a measure of sensitization. On the basis of dual-process theory, it was hypothesized that if sensitization produced by the ‘dishabituating’ stimulus has decayed prior to re-presentation of the habituating stimulus, skin conductance response (SCR) amplitude to the habituating stimulus will not differ from that displayed by a control group which did not receive presentation of the ‘dishabituating’ stimulus. In experiment 1 (N = 10), subjects received 13 presentations of a 1000 Hz, 70 dB tone of 3 sec duration with inter-stimulus intervals of 40, 50 and 60 sec. Between trials 11 and 12, there was one presentation of a dishabituating (light) stimulus. Analysis of SCL indicated that an interval of 50 sec between trials 12 and 13 was sufficient to allow sensitization to decline to the pre-light level. The experimental conditions in experiment 2 (N = 32) were the same as in experiment 1 except that only half the subjects received presentation of the dishabituating stimulus. The results indicated that although there were no group differences in SCR amplitude on trials 1–11, experimental subjects displayed significantly larger responses on trial 13 than did control subjects. These results suggest that interpolation of a different stimulus in an habituation series does, in fact, disrupt the habituation process.     

Extraversion and the EEG: II. A test of Gale's hypothesis

The study sought to test A. Gale's hypothesis that only under moderately arousing conditions will introverts be shown to differ from extraverts in EEG defined arousal. Alpha activity was recorded for 45 subjects under each of six conditions, and extravert and introvert groups formed on the basis of subject's score on the E scale of the Eysenck Personality Questionnaire (EPQ). Contrary to the hypothesis, extraverts showed more prestimulus alpha activity than introverts under all conditions except opening and closing eyes on instruction where the reverse was the case. It is argued that the failure to confirm the hypothesis is not due to faults in design or execution of the study, and that future research may profit more from ignoring interactions of the sort demonstrated.     

Extraversion and the EEG: I. An evaluation of Gale's hypothesis

The hypothesis of A. Gale that extraverts differ from introverts in EEG defined arousal only under moderately arousing conditions is examined. It is argued that the hypothesis is not entirely internally consistent and lacks empirical support. A re-analysis of the literature on which it was based points to problems in the measurement of extraversion as a more significant source of confounding than variation in conditions of testing.     

Elevated sister chromatid exchange rate in lymphocytes of the European eel (Anguilla anguilla) with cauliflower tumor

Sister chromatid exchange (SCE) frequency and chromosomal aberration were studied in cultured lymphocytes from the European eel (Anguilla anguilla) with cauliflower tumors. SCE was significantly increased in the affected fishes compared with normal controls, whereas chromosomal aberration did not. In comparison to normal cells, the lymphocytes responding to phytohemagglutinin M (PHA-M) in cultures from tumorous eels showed no evidence of cell cycle retardation. A possible mechanism for elevation of SCE and the significance of this finding relation to the etiology were discussed.     

On the specificity of uptake by isolated Torpedo synaptic vesicles

Synaptic vesicles were isolated from the electric organ of Torpedo marmorata in highly purified form. Their uptake properties were examined using a large number of small organic molecules as substrates. Following incubation at 26°C for 1 h, it was found that concentrative accumulation, indicated by a vesicle:medium concentration ratio greater than unity, was achieved by all the choline analogues used and by four biogenic amines, but not by a variety of purine and pyrimidine bases and nucleosides. Amino acids penetrated poorly, as did sugars, and of organic anions, acetate but not citrate or thiocyanate, was almost excluded.Thus Torpedo vesicles are relatively impermeable to compounds which cannot utilize the ACh or ATP carriers, but show a very high rate of amine uptake, which may be linked to a pH gradient.     

Inhibition of angiotensin converting enzyme by substance P.

Substance P was found to inhibit angiotensin converting enzyme (ACE) activity of rat striatal homogenates with an I₅₀ of about 50 μM.     

The specific detection of IgA in immune complexes

An assay to detect IgA in circulating immune complexes (IC) using low avidity goat IgM antibody against human polyclonal IgA is described. The binding of this antibody to IgA coupled to Sepharose 6B is inhibited by IgA-containing IC. The specificity and sensitivity of this anti-IgA inhibition assay (a-IgA-InhA), was evaluated with aggregated purified immunoglobulins, sera of patients with Henoch-Schönlein purpura and normal human sera. Aggregated immunoglobulins of the IgA class, but not monomeric IgA, were reactive. Sucrose density ultracentrifugation showed that large IgA constituents (> 19S) were found only in the sera of patients with Henoch-Schönlen purpura. Both these sera and normal human serum contained smaller IgA components (between 7S and 19S), probably small polymers of IgA, which were reactive in this assay and interfered with detection of IgA-containing IC. Redissolved precipitates obtained from normal serum with polyethylene glycol showed reduced reactivity in the test, whereas the inhibitory activity of IgA-containing IC in sera of patients with Henoch-Schönlein purpura was retained in the precipitates. Precipitation of sera with polyethylene glycol allowed detection of smaller quantities of IgA-containing IC in patients with Henoch-Schölein purpura.     

Labelling of dying neurones by peroxidase injected intravascularly in chick embryos

Three lines of evidence indicate that intravascularly injected horseradish peroxidase labels dying neurones selectively in the developing isthmo-optic nucleus: (i) in unoperated embryos, labelled neurones are found only during the period of normal neuronal death; (ii) some of the labelled neurones are manifestly necrotic (iii) an intraocular injection of colchicine causes essentially all the isthmo-optic neurones to degenerate, and then they almost all take up peroxidase. However, deafferenting the developing isthmo-optic nucleus by a tectal lesion increases the loss of neurones whilst scarcely affecting the number labelled; this implies that the neurones which die because of the deafferentiation either do not take up the peroxidase or are phagocytozed exceptionally rapidly.     

Structural features of very fast sedimenting DNA formed by gene 49 defective T4

Very fast sedimenting DNA (VFS DNA) of T4 phage, which is formed by infection with a mutant in gene 49, was examined by electron microscopy after mild treatment with DNase I. It showed Y-shaped, branched strands in addition to linear strands. Each branch contained a single-stranded interruption about 60 nucleotides long at its proximal end. The average number of branches per T4 DNA unit was close to the average number of sites susceptible to gene 49 nuclease. Both numbers were consistently changed by the addition of a secondary mutation in a gene involving recombination.     

Striatal cholinergic activity during morphine-induced catalepsy in the rat: development of tolerance

Morphine hydrochloride (10 mg/kg,i.p.) induced marked catalepsy in rats, which was associated with significantly enhanced striatal acetylcholine levels and reduced cholinesterase activity. Rapid tolerance to morphine-induced catalepsy was noted after twice daily administrations, the tolerance being discernible after the third injection and was complete after the eleventh injection. With the development of tolerance, morphine-induced effects on striatal acetylcholine and cholinesterase were progressively reversed, confirming striatal cholinergic involvement in morphine-induced catalepsy in the rat.     

Measurement of the evoked cardiac response: The problem of prestimulus variability

This paper discusses the problem of prestimulus variability in cardiac activity and its implications for the measurement of evoked cardiac responses (ECRs). Two methods which have been proposed to reduce error arising from respiratory sinus arrhythmia (SA) were reviewed critically. The first approach attempts to control only for the error associated with the sampling of the prestimulus level. This is considered inappropriate since it does not take into account the continuation of SA into the poststimulus period. The second approach reviewed was time series analysis which provides an elegant statistical solution of the problem. Unfortunately, the application of time series analysis has not yet been evaluated for adult cardiac data. A third approach which utilizes an adjustment for SA by employing the actual prestimulus values of an SA cycle was proposed. The application of this technique in the case of a pseudostimulus demonstrated that correction for SA results in significantly smaller ‘responses’ with less variance than does a conventional procedure which does not take prestimulus variability into account.