Contribution of Xpert® MTB/RIF to tuberculosis case finding among pregnant women in Botswana

Setting

Seven health facilities with antenatal care (ANC) clinics in two districts near Gaborone, Botswana.

Objectives

To determine 1) the prevalence of tuberculosis (TB) and HIV-TB co-infection in pregnancy, and 2) the sensitivities of symptomatic TB screening and Xpert testing against gold standard culture.

Design

This was a cross-sectional study. Pregnant women were randomly enrolled and screened using TB symptoms. HIV status was determined from ANC clinics' client records. Two sputum specimens were collected from all clients and each was tested using Xpert^® and culture for Mycobacterium tuberculosis.

Results

Of 407 cases, eight had one or more TB symptoms, and all tested negative with Xpert^® and culture. Another two (0.5%, 95%CI 0.08-1.96) asymptomatic clients tested positive with both tests. The adjusted TB prevalence was higher than that of the general population (0.6% vs. 0.24%; P < 0.001). The prevalence of TB among HIV-positive and HIV-negative clients was 1/69 (1.45%, 95%CI 0.29-2.61) and 1/336 (0.3%, 95%CI 0.23-0.83), respectively (Fisher's exact test P = 0.312). Xpert^® demonstrated a 100% sensitivity and 100% specificity, while symptom screening had 0.0% sensitivity and 98% specificity.

Conclusions

TB prevalence among pregnant women was high and TB symptom screening had limited ability to detect TB. An alternative TB screening algorithm for pregnant women is urgently needed irrespective of TB symptoms.

Reconceptualizing sex, brain and psychopathology: interaction, interaction, interaction

In recent years there has been a growing recognition of the influence of sex on brain structure and function, and in relation, on the susceptibility, prevalence and response to treatment of psychiatric disorders. Most theories and descriptions of the effects of sex on the brain are dominated by an analogy to the current interpretation of the effects of sex on the reproductive system, according to which sex is a divergence system that exerts a unitary, overriding and serial effect on the form of other systems. We shortly summarize different lines of evidence that contradict aspects of this analogy. The new view that emerges from these data is of sex as a complex system whose different components interact with one another and with other systems to affect body and brain. The paradigm shift that this understanding calls for is from thinking of sex in terms of sexual dimorphism and sex differences, to thinking of sex in terms of its interactions with other factors and processes. Our review of data obtained from animal models of psychopathology clearly reveals the need for such a paradigmatic shift, because in the field of animal behaviour whether a sex difference exists and its direction depend on the interaction of many factors including, species, strain, age, specific test employed and a multitude of environmental factors. We conclude by explaining how the new conceptualization can account for sex differences in psychopathology.

A biomedical educational intervention to change explanatory models of psychosis among community health workers in South India

BACKGROUND

Community health workers in developing countries commonly hold indigenous beliefs about mental illness which differ markedly from biomedical models.

AIM

To test the effect of a biomedical intervention on explanatory models (EMs) of community health workers.

METHODS

Indigenous beliefs about chronic psychosis were elicited from community health workers. The Short Explanatory Model Interview formed the basis of the interview. Half the workers were taught about the biomedical model after discussing their EMs of chronic psychosis. The others did not receive education. The beliefs of all community health workers were reassessed 2 weeks after the initial assessment.

RESULTS

A variety of indigenous beliefs, which contradicted the biomedical model, were elicited at the baseline evaluation. Seeking biomedical help at follow up was significantly related to receiving education about the biomedical aspects of chronic psychosis (OR 17.2; 95% CI: 18.75, 15.65; p<0.001). This remained statistically significant (OR 9.7; 95% CI: 82.28, 1.14; p<0.04) after using logistic regression to adjust for baseline variables.

CONCLUSION

The high prevalence of non-medical beliefs among community health workers suggests the need to elicit and discuss beliefs before imparting knowledge about biomedical models of mental disorders. Biomedical educational intervention can change EMs of mental illness among health workers.

Role of the orbital cortex and of the serotonergic system in a rat model of obsessive compulsive disorder

The serotonergic system and the orbitofrontal cortex have been consistently implicated in the pathophysiology of obsessive compulsive disorder. Yet, the relations between these two systems and the ways they interact in producing obsessions and compulsions are poorly understood. The present study tested the hypothesis that pathology of the orbitofrontal cortex leads to a dysregulation of the serotonergic system which is manifested in compulsive behavior, using a new rat model of this disorder. In the model, 'compulsive' behavior is induced by attenuating a signal indicating that a lever-press response was effective in producing food. We found that lesion to the rat orbital cortex led to a selective increase in compulsive lever-pressing that was prevented by the serotonin re-uptake inhibitor, paroxetine, and was paralleled by an increase in the density of the striatal serotonin transporter, assessed using high affinity [3H]imipramine binding. These results suggest that the serotonergic system is involved in orbital lesion-induced compulsivity, and provide a possible account for the observed association between obsessions and compulsions and dysfunction of the orbitofrontal cortex and of the serotonergic system in obsessive compulsive disorder.

'Compulsive' lever-pressing in rats is attenuated by the serotonin re-uptake inhibitors paroxetine and fluvoxamine but not by the tricyclic antidepressant desipramine or the anxiolytic diazepam

Rats undergoing extinction of lever-pressing for food after the attenuation of an external feedback for this behavior, exhibit excessive lever-pressing unaccompanied by an attempt to collect a reward, which may be analogous to the excessive and unreasonable behavior seen in obsessive-compulsive disorder (OCD). Given that one of the most salient features of OCD is its selective response to treatment with serotonin re-uptake inhibitors (SRIs), the present study compared the effects of the SRIs paroxetine and fluvoxamine on compulsive lever-pressing, with those of the tricyclic antidepressant, desipramine, and the benzodiazepine, diazepam, which are not effective in the treatment of OCD. Paroxetine (1-15 mg/kg) and fluvoxamine (10-20 mg/kg) dose-dependently reduced the number of compulsive lever-presses and the number of lever-presses followed by an attempt to collect a reward; desipramine (5-15 mg/kg) dose-dependently reduced only the number of lever-presses followed by an attempt to collect a reward; diazepam (2-10 mg/kg) did not affect either type of lever-pressing, except for the highest dose (10 mg/kg), which almost completely abolished lever-press responding. When administered in an extinction session not preceded by signal attenuation, paroxetine, fluvoxamine and desipramine affected only the number of lever-presses followed by an attempt to collect a reward, whereas diazepam (4-8 mg/kg) decreased both types of lever-presses. The present findings strengthen the suggestion that compulsive lever-pressing may serve to model compulsive behavior in OCD, and lends the model predictive validity.

Explanatory models of psychosis among community health workers in South India

OBJECTIVE

To examine commonly held indigenous beliefs about mental illness, which often differ markedly from the biomedical models, among community health workers in rural South India.

METHOD

Indigenous beliefs about chronic psychosis were elicited from community health workers. The Short Explanatory Model Interview formed the basis of the interview.

RESULTS

A variety of indigenous beliefs, which contradicted the biomedical model, were elicited. A significant proportion of health workers did not recognize chronic psychosis as a disease condition, believing that it was caused by black magic, evil spirits and poverty, and felt that doctors could not help.

CONCLUSION

The results of the study suggest that training programmes should elicit and discuss local beliefs prior to the teaching of the biomedical model of mental disorders.

A comparison of drug effects in latent inhibition and the forced swim test differentiates between the typical antipsychotic haloperidol, the atypical antipsychotics clozapine and olanzapine, and the antidepressants imipramine and paroxetine

Current animal models of antipsychotic activity that have the capacity to dissociate between typical and atypical antipsychotic drugs (APDs) have two drawbacks: they require previous administration of a psychotomimetic drug, and they achieve the dissociation by demonstrating effectiveness of atypical but not typical APDs, thus losing specificity and selectivity for APDs. The present experiments were designed to solve these problems by using two non-pharmacological tests: latent inhibition (LI), in which potentiation of the deleterious effects of non-reinforced stimulus pre-exposure on its subsequent conditioning served as a behavioral index for a common action of typical and atypical APDs (antipsychotic), and the forced swim test (FST), in which reduction of immobility served as a behavioral index for a dissimilar action of these drugs (antidepressant). The typical APD haloperidol (0.1 mg/kg), the atypical APDs clozapine (2.5 mg/kg) and olanzapine (0.6 mg/kg), and the antidepressants imipramine (10 mg/kg) and paroxetine (7.0 mg/kg), produced distinct patterns of action in the two tests: haloperidol potentiated LI and increased immobility in the FST, clozapine and olanzapine potentiated LI and decreased immobility in the FST, and imipramine and paroxetine decreased immobility in the FST and did not potentiate LI. Thus, the comparison of drug effects in LI and FST enabled a discrimination between typical and atypical APDs without losing selectivity for APDs.

Enhancement of excessive lever-pressing after post-training signal attenuation in rats by repeated administration of the D1 antagonist SCH 23390 or the D2 agonist quinpirole, but not the D1 agonist SKF 38393 or the D2 antagonist haloperidol

The authors have recently shown that attenuation of an external response feedback leads to excessive lever-pressing that is not associated with attempts to collect reward, and they have suggested that this may be an analogue to "unreasonable" excessive behavior characteristic of obsessive-compulsive disorder. The present study shows that repeated administration of SCH 23390 or quinpirole, but not SKF 38393 or haloperidol, enhances this behavioral pattern. On the basis of data regarding the enduring effects of chronic treatment with dopaminergic agents, these results suggest that overstimulation of striatal D1 receptors underlies enhanced response to signal attenuation. These results may link the hypothesis that obsessions and compulsions result from a deficient response feedback mechanism with findings implicating dopaminergic abnormalities in the production of obsessions and compulsions.

Enhancement of excessive lever-pressing after post-training signal attenuation in rats by repeated administration of the D1 antagonist SCH 23390 or the D2 agonist quinpirole, but not the D1 agonist SKF 38393 or the D2 antagonist haloperidol

The authors have recently shown that attenuation of an external response feedback leads to excessive lever-pressing that is not associated with attempts to collect reward, and they have suggested that this may be an analogue to "unreasonable" excessive behavior characteristic of obsessive-compulsive disorder. The present study shows that repeated administration of SCH 23390 or quinpirole, but not SKF 38393 or haloperidol, enhances this behavioral pattern. On the basis of data regarding the enduring effects of chronic treatment with dopaminergic agents, these results suggest that overstimulation of striatal D1 receptors underlies enhanced response to signal attenuation. These results may link the hypothesis that obsessions and compulsions result from a deficient response feedback mechanism with findings implicating dopaminergic abnormalities in the production of obsessions and compulsions.

Acute mania and hemichorea

A 61-year-old man suddenly became euphoric and talkative. Later the same day, he developed hemichoreic movements of the left limbs. The patient fulfilled the DSM-IV criteria for a manic episode by abnormally and persistently elevated mood, decreased need for sleep, high distractibility, pressured speech, increased goal-directed activity, and hypersexuality. The mood changes persisted for several weeks. Magnetic resonance imaging of the brain showed a right thalamic infarction. The co-occurrence of hemichorea and mania caused by focal thalamic lesion is very rare. It may be explained by dysfunction in basal ganglia thalamocortical circuitry.

Excessive lever pressing following post-training signal attenuation in rats: A possible animal model of obsessive compulsive disorder?

This study aimed at developing a rat model of obsessive compulsive disorder based on the hypothesis that a deficient response feedback mechanism underlies obsessions and compulsions. Rats were trained to lever press for food, whose delivery was signaled by the presentation of a compound stimulus (light+tone). Subsequently, the classical contingency between the stimulus and food was extinguished (signal attenuation). Experiment 1 showed that this manipulation resulted in increased lever pressing during a subsequent extinction test, which was highly correlated with an increase in the number of trials on which the rat did not attempt to collect the food reward. This behavioral pattern was not evident in an extinction test not preceded by signal attenuation (Experiment 2), suggesting that the latter is a crucial factor in the development of this behavioral pattern. Excessive lever pressing was attenuated by the selective serotonin re-uptake inhibitor, fluoxetine (10 mg/kg; Experiment 3), but not by the anxiolytic drug, diazepam (2 mg/kg; Experiment 4). Based on these results we propose that post-training signal attenuation may provide a rat model of obsessive compulsive disorder.

Open interconnected model of basal ganglia-thalamocortical circuitry and its relevance to the clinical syndrome of Huntington's disease

The early stages of Huntington's disease (HD) present with motor, cognitive, and emotional symptoms. Correspondingly, current models implicate dysfunction of the motor, associative, and limbic basal ganglia-thalamocortical circuits. Available data, however, indicate that in the early stages of the disease, striatal damage is mainly restricted to the associative striatum. Based on an open interconnected model of basal ganglia-thalamocortical organization, we provide a detailed account of the mechanisms by which associative striatal pathology may lead to the complex pattern of motor, cognitive, and emotional symptoms of early HD. According to this account, the degeneration of a direct and several indirect pathways arising from the associative striatum leads to impaired functioning of: (1) the motor circuit, resulting in chorea and bradykinesia, (2) the associative circuit, resulting in abnormal eye movements, "frontal-like" cognitive deficits and "cognitive disinhibition," and (3) the limbic circuit, resulting in affective and psychiatric symptoms. When relevant, this analysis is aided by comparing the symptomatology of HD patients to that of patients with mild to moderate Parkinson's disease, since in the latter there is similar dysfunction of direct pathways but opposite dysfunction of indirect pathways. Finally, we suggest a potential novel treatment of HD and provide supportive evidence from a rat model of the disease.

The connections of the dopaminergic system with the striatum in rats and primates: an analysis with respect to the functional and compartmental organization of the striatum

This Commentary compares the connections of the dopaminergic system with the striatum in rats and primates with respect to two levels of striatal organization: a tripartite functional (motor, associative and limbic) subdivision and a compartmental (patch/striosome-matrix) subdivision. The topography of other basal ganglia projections to the dopaminergic system with respect to their tripartite functional subdivision is also reviewed. This examination indicates that, in rats and primates, the following observations can be made. (1) The limbic striatum reciprocates its dopaminergic input and in addition innervates most of the dopaminergic neurons projecting to the associative and motor striatum, whereas the motor and associative striatum reciprocate only part of their dopaminergic input. Therefore, the connections of the three striatal subregions with the dopaminergic system are asymmetrical, but the direction of asymmetry differs between the limbic versus the motor and associative striatum. (2) The limbic striatum provides the main striatal input to dopamine cell bodies and proximal dendrites, with some contribution from a subset of neurons in the associative and motor striatum (patch neurons in rats; an unspecified group of neurons in primates), while striatal input to the ventrally extending dopamine dendrites arises mainly from a subset of neurons in the associative and motor striatum (matrix neurons in rats; an unspecified group of neurons in primates). (3) Projections from functionally corresponding subdivisions of the striatum, pallidum and subthalamic nucleus to the dopaminergic system overlap, but the specific targets (dopamine cells, dopamine dendrites, GABA cells) of these projections differ. Major differences include the following. (1) In rats, neurons projecting to the motor and associative striatum reside in distinct regions, while in primates they are arranged in interdigitating clusters. (2) In rats, the terminal fields of projections arising from the motor and associative striatum are largely segregated, while in primates they are not. (3) In rats, patch- and matrix-projecting dopamine cells are organized in spatially, morphologically, histochemically and hodologically distinct ventral and dorsal tiers, while in primates there is no (bi)division of the dopaminergic system that results in two areas which have all the characteristics of the two tiers in rats. Based on the anatomical data and known dopamine cell physiology, we forward an hypothesis regarding the influence of the basal ganglia on dopamine cell activity which captures at least part of the complex interplay taking place within the substantia nigra between projections arising from the different basal ganglia nuclei. Finally, we incorporate the striatal connections with the dopaminergic system into an open-interconnected scheme of basal ganglia-thalamocortical circuitry.

Fimbria-fornix cut affects spontaneous activity, two-way avoidance and delayed non matching to sample, but not latent inhibition

Latent inhibition (LI) consists of a decrement in conditioning to a stimulus as a result of its prior nonreinforced preexposure. Based on evidence pointing to the involvement of the hippocampus and the nucleus accumbens (NAC) in LI disruption, it has been proposed that LI depends on the integrity of the subicular input to the NAC. Since fibers originating in the subiculum and destined for the NAC run through the fimbria-fornix, we assessed the effects of fimbria-fornix lesion, made using a knife cut, on LI. In addition, we assessed the effects of the fimbria-fornix cut in three tests known to be sensitive to lesions to the hippocampal region, namely, spontaneous activity, two-way active avoidance and delayed-non-matching-to-sample. In accord with previously documented effects of lesions to the hippocampus and related structures, the fimbria-fornix cut increased spontaneous activity (Experiment 1), facilitated the acquisition of two-way active avoidance (Experiment 3), and produced a delay-dependent deficit in the delayed-non-match-to-sample task (Experiment 4), demonstrating that it disrupted hippocampal functioning. In contrast, LI remained unaffected by the fimbria-fornix cut (Experiment 2), indicating that disruption of subicular input to the NAC is not responsible for the attenuation of LI following non-selective hippocampal lesions. The implications of these results for the neural circuitry of LI are discussed.

Electrolytic lesion of globus pallidus ameliorates the behavioral and neurodegenerative effects of quinolinic acid lesion of the striatum: a potential novel treatment in a rat model of Huntington's disease

Bilateral electrolytic pallidal lesion ameliorated the deleterious effects of bilateral quinolinic acid (QA) lesion to the striatum on post-surgery weight, activity level, and performance in a water maze task, and reduced the extent of striatal damage. Given that the neurodegenerative and behavioral effects of QA striatal lesion are thought to mimic those seen in Huntington's disease, these results may point to a potential novel treatment for this disease.

Effects of electrolytic lesions of the medial prefrontal cortex or its subfields on 4-arm baited, 8-arm radial maze, two-way active avoidance and conditioned fear tasks in the rat

The present study tested the effects of electrolytic lesions in two mPFC subregions, the dorsal anterior cingulate area (dACA) and prelimbic cortex, as well as the effects of a larger medial prefrontal cortex (mPFC) lesion which included both subregions, on 4-arm baited, 4-arm unbaited, 8-arm radial maze task and its reversal (Experiments 1 and 4), two-way active avoidance (Experiments 2 and 5) and conditioned emotional response (Experiments 3 and 6). Rats with large or small lesions of the mPFC learned the location of the 4 baited arms in the training and reversal stages of the radial maze task similarly to sham rats, indicating that these lesions did not affect animals' capacity to process and remember spatial information. dACA and mPFC lesions produced a transient deficit in the acquisition of the radial maze task, suggestive of an involvement of these regions in mnemonic processes. However, in view of the normal performance of these groups by the end of training and during reversal, this deficit is better interpreted as stemming from a difficulty to learn the memory-based strategy used to solve the task. Only mPFC lesion led to better avoidance performance at the beginning of training and tended to increase response during the presentation of a stimulus previously paired with shock, compared to sham rats. Both effects can be taken as an indication of reduced emotionality following mPFC lesion. The results are discussed in relation to known behavioral functions of the mPFC and the suggested functional specialization within this region.

The effects of electrolytic lesion to the shell subterritory of the nucleus accumbens on delayed non-matching-to-sample and four-arm baited eight-arm radial-maze tasks

The effects of bilateral electrolytic lesions of the "shell" subterritory of the nucleus accumbens in the rat were examined on 2 tasks known to be sensitive to hippocampal damage. Experiment 1 tested the effects of shell lesion on delayed non-matching-to-sample (DNMS) task in a T-maze. The maze was rotated 180 degrees after the end of acquisition. Experiment 2 used a 4-arm baited, 4-arm unbaited, 8-arm radial-maze task and its reversal. Shell lesion led to impaired acquisition of DNMS in a T-maze and of 4-arm baited, 4-arm unbaited, 8-arm radial maze tasks, suggestive of mnemonic deficits. Following analysis of animals' choice pattern in both tasks, the deficit was interpreted as being largely due to an extensive use of response strategy. The results suggest that the inappropriate use of response strategy by shell animals was a result of their inability to switch from initial response strategy to a later, more appropriate, memory-dependent strategy.

Electrolytic lesions of the medial prefrontal cortex in rats disrupt performance on an analog of the Wisconsin Card Sorting Test, but do not disrupt latent inhibition: implications for animal models of schizophrenia

The effects of electrolytic lesions of the medial prefrontal cortex (mPFC) or its subregions were investigated on two cognitive tests that may have relevance to the behavioral impairments of patients with schizophrenia. One task consisted of a delayed non-match-to-sample and reversal of the non-match-to-sample rule, in a Skinner box. The reversal component simulated the essential feature of rule shifting of the Wisconsin Card Sorting Test (WCST), which is a commonly used test for assessing 'frontal-like' deficits in schizophrenia. The second was latent inhibition, in which repeated pre-exposure to a stimulus without consequence retards subsequent associations with that stimulus. Latent inhibition is impaired in acute schizophrenic patients, and its disruption in the rat has been suggested to constitute an animal model of schizophrenia. Expts. 1 and 2 tested the effects of lesions of the dorsal anterior cingulate cortex (dACA) and mPFC, respectively, on the WCST analog. Expt. 3 tested the effects of lesions of the dACA or infralimbic cortex, and Expt. 4 tested the effects of mPFC lesion, on latent inhibition. Lesions of mPFC subregions had no effect. mPFC lesion produced transient deficits in the performance of the DNMS task and impaired the reversal from the non-match-to-sample to the match-to-sample rule, but left the latent inhibition effect intact. Possible relevance of this behavioral profile of mPFC lesion to the 'frontal syndrome' is discussed.

The effects of electrolytic lesion to the shell subterritory of the nucleus accumbens on delayed non-matching-to-sample and four-arm baited eight-arm radial-maze tasks

The effects of bilateral electrolytic lesions of the "shell" subterritory of the nucleus accumbens in the rat were examined on 2 tasks known to be sensitive to hippocampal damage. Experiment 1 tested the effects of shell lesion on delayed non-matching-to-sample (DNMS) task in a T-maze. The maze was rotated 180 degrees after the end of acquisition. Experiment 2 used a 4-arm baited, 4-arm unbaited, 8-arm radial-maze task and its reversal. Shell lesion led to impaired acquisition of DNMS in a T-maze and of 4-arm baited, 4-arm unbaited, 8-arm radial maze tasks, suggestive of mnemonic deficits. Following analysis of animals' choice pattern in both tasks, the deficit was interpreted as being largely due to an extensive use of response strategy. The results suggest that the inappropriate use of response strategy by shell animals was a result of their inability to switch from initial response strategy to a later, more appropriate, memory-dependent strategy.

The connections of the primate subthalamic nucleus: indirect pathways and the open-interconnected scheme of basal ganglia-thalamocortical circuitry

The current view of basal ganglia organization holds that functionally corresponding subregions of the frontal cortex, basal ganglia and thalamus form several parallel segregated basal ganglia-thalamocortical circuits. In addition, this view states that striatal output reaches the basal ganglia output nuclei (the substantia nigra pars reticulata (SNR) and the internal segment of the globus pallidus (GPi)) via a 'direct' pathway, and via an 'indirect pathway' which traverses the external segment of the globus pallidus (GPe) and the subthalamic nucleus (STN). However, the topographical relationships of GPe and STN, and their topographical relationships with the basal ganglia-thalamocortical circuits are still unclear. The present work reviewed primate data on the topographical organization of STN afferents from GPe, and STN efferents to the pallidum, striatum and SNR, and examined these data with respect to a tripartite (motor, associative and limbic) functional subdivision of the striatum and pallidum. This examination indicated the following. (1) On the basis of its efferent connections, the STN may be divided into a motor and an associative territories, as well as a smaller limbic territory, each projecting to corresponding areas in the pallidum and striatum. (2) Efferents from GPe are in a position to contact subthalamic cells projecting to GPi/SNR, thus providing anatomical support for the existence of indirect pathways. (3) Moreover, given the tripartite division of the striatum, pallidum, and STN, the available data indicate the existence of indirect pathways connecting functionally corresponding subregions of the striatum, pallidum, and STN, as well as indirect pathways connecting functionally non-corresponding subregions. On the basis of the above we suggested that there may be two types of indirect pathways, one which terminates in the same subregion in GPi/SNR as the direct pathway arising from the same striatal subregion, and another which terminates in a different GPi/SNR subregion than the direct pathway arising from the same striatal subregion. We termed the former a 'closed indirect pathway' and the latter an 'open indirect pathway'. The application of these concepts to the surveyed data suggested the existence of three closed indirect pathways, each connecting the corresponding functional (motor, associative, and limbic) regions of the striatum, pallidum, STN, and SNR, as well as of two open indirect pathways, one connecting the associative striatum to the motor subregions of the basal ganglia, and the other connecting the associative striatum to the limbic subregions of the basal ganglia. While the organization of the closed indirect pathways fits the closed segregated arrangement of basal ganglia-thalamocortical circuitry, the organization of the open indirect pathways fits the recently suggested open interconnected scheme of basal ganglia thalamocortical circuitry. The clinical implications of this scheme for Huntington's disease are discussed.

The organization of the basal ganglia-thalamocortical circuits: open interconnected rather than closed segregated

Anatomical findings in primates and rodents have led to a description of several parallel segregated basal ganglia-thalamocortical circuits leading from a distinct frontocortical area, via separate regions in the basal ganglia and the thalamus, back to the frontocortical area from which the circuit originates. One of the questions raised by the concept of parallelism is whether and how the different circuits interact. The present Commentary proposes that interaction is inherent in the neural architecture of the basal ganglia-thalamocortical circuits. This proposal is based on the re-examination of the data on the topographical organization of the frontocortical-basal ganglia connections which indicates that each circuit-engaged striatal region sends divergent projections to parts of both substantia nigra pars reticulata and the internal segment of the globus pallidus (each ventral striatal region sends divergent projections to parts of ventral pallidum, substantia nigra pars reticulata and globus pallidus), and this segregation is maintained at subsequent thalamic and frontocortical levels. This results in an asymmetry in the frontal cortex-basal ganglia relationships, so that while each frontocortical subfield innervates one striatal region, each striatal region influences the basal ganglia output to two frontocortical subfields. Because of this asymmetry, at least one of the frontocortical targets of a given circuit-engaged striatal region is not the source of its frontocortical input. Since this organization is inconsistent with an arrangement in closed segregated circuits we introduce the concept of a "split circuit". A split circuit emanates from one frontocortical area, but terminates in two frontocortical areas. Thus, a split circuit contains at least one "open" striato-fronto-cortical pathway, that leads from a circuit-engaged striatal region to a frontocortical area which is a source of a different circuit. In this manner split circuits are interconnected via their open pathways. The second striato-fronto-cortical pathway of a split circuit can be another open pathway, or it can re-enter the frontocortical area of origin, forming a closed circuit. On the basis of the available anatomical data we tentatively identified a motor, an associative, and a limbic split circuit, each containing a closed circuit and an open pathway. The motor split circuit contains a closed motor circuit that re-enters the motor and premotor cortical areas and an open motor pathway that terminates in the associative prefrontal cortex. The associative split circuit contains a closed associative circuit that re-enters the associative prefrontal cortex and an open associative pathway that terminates in the premotor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Selective ablation of rat brain tumors by boron neutron capture therapy

PURPOSE

Damage to the surrounding normal brain tissue limits the amount of radiation that can be delivered to intracranial tumors. Boron neutron capture therapy (BNCT) is a binary treatment that allows selective tumor irradiation. This study evaluates the damage imparted to the normal brain during BNCT or x-irradiation.

METHODS AND MATERIALS

The brains of rats with implanted 9L gliosarcomas were examined 1 year after tumor-curative doses of either 250 kV X rays or BNCT. Histopathologic techniques included hematoxylin and eosin staining, horseradish peroxidase perfusion, and electron microscopy.

RESULTS

Longterm X ray survivors showed extensive cortical atrophy, loss of neurons, and widespread leakage of the blood-brain barrier (BBB), particularly around the tumor scar. In contrast, the brains and the BBB of longterm BNCT survivors appeared relatively normal under both light- and electron-microscopic examination. Intact blood vessels were observed running directly through the avascular, collagenous tumor scar.

CONCLUSION

The selective therapeutic effect of BNCT is evident in comparison to x-irradiation. Both groups of animals showed no evidence of residual tumor at 1 year. However, with x-irradiation there is no therapeutic ratio and tumor eradication severely injures the remaining brain parenchyma. These observations indicate a substantial therapeutic gain for BNCT.

Mononuclear cell-bound CD23 is elevated in both atopic dermatitis and psoriasis

As patients with atopic dermatitis (AD) frequently have elevated serum IgE levels, the relation of this disease to CD23/Fc epsilon RII, a low affinity Fc receptor for IgE, and its soluble forms, sCD23, was studied. We examined the expression of CD23 on peripheral blood mononuclear cells (PBMC) as well as the serum IgE and sCD23 levels in 33 patients with AD and in 9 patients with psoriasis in comparison with 10 healthy donors. In AD patients, the numbers of CD23+ unfractionated PBMC and CD23+ small adherent cells were significantly elevated (P less than 0.05, resp. P less than 0.005). In psoriatic patients however, CD23 was also significantly elevated on PBMC (P less than 0.05) and on small adherent cells (P less than 0.05). There was no significant difference in the frequencies of CD23+ cells between AD and psoriasis patients. In all donors, CD23 could be detected only on B cells, but not on monocytes/macrophages. In AD patients who were examined twice, an increase or decrease of the clinical AD score was always accompanied by an increase or decrease, resp., of cell-bound CD23. The serum sCD23 level was not significantly increased in either group of patients. Our results suggest that CD23 should be considered as a nonspecific marker for B cell activation in the context of inflammation and not as a specific marker for AD.

Experimental cryptosporidiosis in fetal lambs

Fetal lambs were infected in utero with purified sporulated oocysts of Cryptosporidium parvum in order to study pathogenesis and host cellular response to the enteropathogen. Ileal loops (IL) of fetuses, 124-130 days of gestation, were inoculated with 1-4 x 10(6) oocysts usually via cannulae in the abdominal wall of the ewe. Oocysts, both free and phagocytosed, were observed in the IL content as early as day 1 post-inoculation (PI). The percentage of oocysts phagocytosed by the host's polymorphonuclear neutrophils (PMN's) and mononuclear cells remained high up to day 13, the last day of examination. Numerous parasites were observed at days 6, 7, and 12 PI in the microvilli of the ileum with hypercellularity of the lamina propria, which consisted of a mixed infiltration of PMN's, mononuclear cells, including lymphoid cells, and a few eosinophils. Cytolysis and extrusion of epithelial cells, often heavily parasitized by various stages of the parasite, as well as inflammatory cells, were prominent in luminal contents. Germinal centers were prominent in mesenteric lymph nodes draining the infected loops by day 12 PI. Depletion of lymphoid cells was already present in Peyer's patches by day 4 PI.