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Forty nine patients (19 adults and 30 children) with oocysts of Cryptosporidium in their faeces had repeated stool specimens taken until oocysts could no longer be identified. They were found in the stools up to 35 days after the onset of symptoms in one patient, but most had stopped shedding them by 20 days. In 25 of the 49 patients in whom symptoms could be compared with the shedding of oocysts, 19 (76%) had symptoms corresponding to the shedding period while symptoms persisted in four (16%) after shedding had stopped. [ABSTRACT FROM PUBLISHER]

Semantic understanding of numbers and related concepts can be dissociated from rote knowledge of arithmetic facts. However, distinctions among different kinds of semantic representations related to numbers have not been fully explored. Working with numbers and arithmetic requires representing semantic information that is both analogue (e.g., the approximate magnitude of a number) and symbolic (e.g., what / means). In this article, the authors describe a patient (MC) who exhibits a dissociation between tasks that require symbolic number knowledge (e.g., knowledge of arithmetic symbols including numbers, knowledge of concepts related to numbers such as rounding) and tasks that require an analogue magnitude representation (e.g., comparing size or frequency). MC is impaired on a variety of tasks that require symbolic number knowledge, but her ability to represent and process analogue magnitude information is intact. Her deficit in symbolic number knowledge extends to a variety of concepts related to numbers (e.g., decimal points, Roman numerals, what a quartet is) but not to any other semantic categories that we have tested. These findings suggest that symbolic number knowledge is a functionally independent component of the number processing system, that it is category specific, and that it is anatomically and functionally distinct from magnitude representations., (Copyright 2001 Elsevier Science.)

We recently conducted a dose-response study of the effects of cocaine on several activity measures in the panel of BxD/Ty recombinant inbred mice. Animals were tested in an automated activity chamber over 2 days with i.p. saline on day 1 and i.p. cocaine on day 2, at one of four doses, 5, 15, 30 or 45 mg kg(-1). The monitor recorded total distance traveled, nosepokes in a holeboard, repeated movements and time spent by an individual in proximity to the centre of the apparatus. Dose-response curves for locomotor activation, i.e. the difference between cocaine and saline scores, showed that for all strains tested, scores increased 5-30 mg kg(-1). With few exceptions, locomotor activity at 45 mg kg(-1) was not significantly higher than that at 30 mg kg(-1). Repeated movement scores showed patterns similar to locomotor activity and nosepokes tended to be progressively inhibited by increasing doses of cocaine. Recombinant inbred strain mean distributions for all behaviours and at all doses exhibited continuous, rather than discrete variation, thus providing evidence of multiple-gene effects on cocaine-related behaviours. Quantitative trait loci (QTL) analysis pointed to several chromosomal locations associated with variations in cocaine-related behaviours and some are either identical or close to QTL reported by others. In separate groups of animals, densities of dopamine D1, and D2 receptors and dopamine uptake transporters were measured in the medial prefrontal cortex, caudate-putamen, nucleus accumbens and ventral midbrain. In all areas, all measures showed distributions consistent with polygenic influence and were associated with QTL. Of particular interest was our finding of a large segment on chromosome 15, which is related to dopamine receptor densities and cocaine-related behaviours.

Investigated were those aspects of motor planning and execution underlying movem ent dysfunction in patients with Parkinson's disease (PD). Specifically examined was the effect of disease severity on these processes. An experiment is reported that dissociates preprogramm ing processes from on-line programming processes in a simple motor task that varies in movement complexity. Dependent m easures included reaction time, movement time, as well as kinematic measures of peak velocity, peak acceleration, peak deceleration, and their respective time values, plus inter-trial variability and EMG activation. While PD patients as a whole were able to pre-program movem ents, inter-trial variability for these measures was increased for more severely affected PD patients. Nonetheless, evidence for on-line programm ing occurred for all PD patients in later intervals of more complex movements. Further, EMG impulses correspond with acceleration trace deviations. The data as a whole support the hypothesis that disrupted basal ganglia function influences the consistency of cortical activation and the selection of motor program com ponents.

Male and female C57BL/6 (B6) and DBA/2 (D2) mice were subjected to either acute or 5 days of repeated restraint in ventilated, 50 ml centrifuge tubes. Control animals were not disturbed. The acute restraint animals were killed immediately following 15, 30 or 60 min of restraint and blood collected for corticosterone (CORT) analysis. The results of the acute restraint procedure revealed a strain difference in time to peak CORT in plasma with D2 animals showing an earlier peak. The males of both strains evinced similar maximum response and similar to B6 females; however, the D2 females showed a 2-fold greater CORT response than did the B6 females. Repeated restraint consisted of 5 days of 12 h in the tubes. At the end of 5 days, the animals were weighted and adrenalectomized in preparation for determination of brain corticosteroid receptors. Upon sacrifice, brains, thymus, adrenals and blood were harvested, the last for corticosteroid binding globulin (CBG). Five days of repeated restraint produced body weight loss in both strains, with B6s less affected than D2s. Repeated restraint reduced the mass of the adrenals in the B6s only. Restraint also reduced the mass of the thymus in both strains and sexes, but to a greater extent in the B6s. Plasma CBG densities were also sensitive to restraint, but only in females, showing a restraint-related decrease. Repeated restraint had no effect on hippocampal glucocorticoid or mineralocorticoid receptors; however for the latter, we observed significant strain and sex effects with D2 having higher Bmax than B6 and females having higher Bmax than males. In the pituitary, glucocorticoid receptors (GR) were reduced by repeated restraint in males, but increased in females, especially in the B6. These findings lend preliminary evidence for involvement of sex and genetics as sources of individual differences in bioadaptation to stress.

Developmental differences in the biobehavioral consequences of immune activation in early life were investigated in two lines of mice selectively bred for high and low levels of inter-male aggressive behavior. At age 5 or 6 days, male mice were administered saline or 0.05 mg/kg gram-negative bacterial endotoxin (Escherichia coli, LPS, ip). There was a transient endotoxin-induced reduction in the growth rate of the neonates in the high-aggressive line. At age 45-50 days, the animals' behaviors were assessed in a dyadic task. Hypothalami and sera were harvested 20 min later. Rates of socially reactive behaviors to conspecific contact (i.e., kick, startle) were increased in the endotoxin-treated groups from both lines. For the high-aggressive line only, endotoxin treatment increased behavioral immobility, decreased attack frequency, and decreased levels of hypothalamic corticotrophin-releasing factor (CRF). The effects of endotoxin exposure in early life on socially reactive behaviors in later life were associated with endotoxin-induced individual differences in CRF levels in the high-aggressive line but not the low-aggressive line. The findings demonstrate long-term social developmental consequences of immune activation during the neonatal period.

Four experiments addressed the question of whether prior knowledge of an object's typical movement in the real world affects the representation of motion. Representational momentum (RM) is the tendency for the short-term memory representation of an object to undergo a transformation corresponding to the object's trajectory. Using the standard RM paradigm, the RM elicited by objects with different typical motions was compared. Results indicate that conceptual knowledge about an object's typical motion affects the magnitude of RM and, as such, the representation of motion.

Neuropsychological dissociations suggest the existence of a body schema, a representation of the spatial relations among body parts, not used for other spatial stimuli. Four experiments verify the psychological reality of the body schema in normal participants. In Experiments 1 and 2, proprioceptive information concerning one's own body position influences visual perception of others' body positions. Contrary to expectations, facilitation is observed rather than interference in the dual-performance task. Experiment 3 eliminates the possibility that the effect is due to a particular mnemonic strategy. In Experiment 4, this effect is shown to be specific to the perception of bodies, as opposed to other complex 3-dimensional forms.

Perceptual dependence--the existence of perceptual interactions between the component dimensions of the same stimulus--was investigated for shape and texture during haptic processing. The haptic system combines tactual and kinesthetic information. Previous research has demonstrated that haptic exploration influences the extent to which object properties are integrated. Conditions designed to promote and impede the integration of shape and texture were compared. Perceptual independence was assessed by the use of a speeded-classification paradigm and quantitative tests developed by Ashby and Maddox. Results indicate that shape and texture are perceptually dependent for both conditions. Hand-movement analysis show simultaneous exploration for both dimensions. The tendency to process dimensions dependently is discussed in terms of a limited-capacity model of haptic-information processing.

We investigated the effects of cocaine on multiple activity measures and cocaine self-selection in C57BL/6Ibg and DBA/2Ibg mice. Male mice were tested in an automated activity monitor at three doses of cocaine, 5, 15 and 30 mg kg-1. Activity measures included locomotion, rearings, stereotyped movements and wall-seeking. Testing was conducted on 2 days with saline injection, i.p. on day one and cocaine i.p. injected on day two. We also tested other mice of both strains for cocaine ingestion in a two-choice test, pairing tap water with 40 mg% cocaine HCl in tap water. Two separate groups of mice received 15 or 30 mg kg-1 of cocaine i.p., killed at 5 min and brain cocaine levels were determined by HPLC. Cocaine produced dose-related increases in locomotion in both strains, with a delay in initial activation noticed at 30 mg kg-1 in C57s but not in DBAs. In DBAs, cocaine suppressed rearings and increased stereotyped movements while having no consistent effect on either behaviour in C57s. At all doses, cocaine produced moderate increases in proximity to the wall in DBAs and 30 mg kg-1 produced pronounced wall-seeking in C57s. At 15 and 30 mg kg-1 DBAs tended to have higher levels of cocaine in whole brain than did C57s. Finally, C57s consumed significantly more cocaine than did the DBAs.

A study of the haptic integration of texture, shape, and hardness of nonplanar solid objects is reported. In experiment 1 the relative discriminability of the objects along each dimension was assessed. While levels of texture and shape were equally discriminable, hardness discriminations proved considerably more difficult. The extent of dimensional integration in a speeded classification task when both dimensions could be extracted from the same local patch was investigated in experiments 2 and 3. In experiment 2 subjects were initially encouraged to attend to a nontargeted dimension covarying with a targeted one. The nontargeted dimension was subsequently held constant (withdrawn). In experiment 3 dimensional variation was introduced which was uncorrelated with the targeted property during the course of categorization and hence discouraged subjects from attending to the nontargeted property. The results of these two studies converged in showing evidence of bidirectional dimensional integration between texture and shape and unidirectional integration when hardness was the targeted dimension. The failure to integrate hardness into categorization based on texture or shape was attributed to the difficulty of hardness discriminations. Integration effects in experiment 3 were not consistently smaller than those in experiment 2, which suggests a strong involuntary component to dimensional integration. The results of an analysis of the accompanying hand movements are interpreted in terms of constraints on dimensional integration. Implications for visual, cross-modal, and two-handed codimensional processing are also discussed.

Three studies investigate the role of size information in haptic classification of custom-made planar objects when size covaries with hardness, texture, or planar contour. The haptic exploratory procedure (Lederman & Klatzky, 1987) associated with size extraction is also sufficient for encoding shape, which should promote their integration. Experiment 1 showed substantial facilitation of classification by redundant size and shape cues, indicating the coprocessing of size and shape. Experiments 2 and 3 used a withdrawal paradigm: Classification trials began with two redundant properties, and one was then held constant (withdrawn). Experiment 2 showed that when size and shape were redundant, withdrawal of either impaired responses, whereas when size was redundant with texture or hardness, only size withdrawal had an effect. Experiment 3 demonstrated that this size weighting was not restricted to a single procedure for exploration. Size appears to be highly weighted in haptic classification and potentially integrated with other properties having compatible methods of extraction.

Human herpesviruses have been associated with numerous diseases throughout history (Table 3), but their ability to induce latent and recurrent infections, alongwith their oncogenic capabilities, is only beginning to be understood. Accordingly, our ability to deal with the diseases induced by herpesviruses is severely limited by our lack of information concerning the basic processes of virus-host cell interactions and systemic host factors; especially immune factors that are involved in the disease process.

During the two years 1986 and 1987 83 cases of cryptosporidiosis were identified by the finding of oocysts in the faecal samples submitted to a single microbiology laboratory. There were 58 children and 25 adults. Cryptosporidiosis was the commonest cause of gastrointestinal infection identified in children and the third commonest overall. Spring and autumn peaks were identified. The main symptoms were diarrhoea (median 10 days), vomiting (median seven days), abdominal pain (median seven days) and fever (median three days). A variety of other less common symptoms were noted including reactive arthritis. Three cases occurred during late pregnancy and the puerperium. Contact tracing supported both person-to-person transmission and an animal origin for cases within the group. Cryptosporidiosis is shown to be an important cause of traveller's diarrhoea. The incubation period was from two to 11 days.

The etiology of cancer resembles that of many other diseases in that multiple factors may be required. Because of this, the role or viruses in the etiology of human cancers is especially difficult to assess. When animal tumor systems were used as models, the roles of various predisposing characteristics in virus oncogenesis were elucidated. Extrapolation of these findings to the human diseases suggests the importance of genetics, age, hormones, immune competence, and stress in determining susceptibility to tumor development in individuals infected with an oncogenic virus. The importance of cofactors in induction of those human tumors most strongly associated with virus infection, including Burkitt's lymphoma, nasopharyngeal carcinoma, cerviccal carcinoma, acute myelogenous leukemia, and breast cancer, is reviewed. Understanding of the role of these cofactors in virus carcinogenesis may lead to disease prevention through elimination of one or more of the cofactors.