Mirror apraxia affects the peripersonal mirror space. A combined lesion and cerebral activation study

Mirror apraxia is a condition in which patients with lesions of the posterior parietal cortex have deficits in reaching to objects presented through a mirror. The aim of the present study was to investigate possible mechanisms underlying this disorder. First, we addressed the question of whether mirror apraxia is exhibited to the same extent in peripersonal and in body space. Four patients with lesions of the posterior parietal lobe on either side and with marked mirror apraxia were required to reach for objects that were presented to them through a mirror and located either in body space (i.e. on the body surface) or in peripersonal space (i.e. in the reaching distance). Whereas reaching for objects located in body space was flawless in all patients, the performance deteriorated when the same objects were transferred to the peripersonal space. Although the objects were located only a few centimetres above the body surface, the patients reached towards the virtual object in the mirror. Based on these results we suggest that mirror apraxia may originate from a dissociation between the representations of body schema and peripersonal space and that objects located on the body surface become integrated into the body schema. In the second part of the study, using positron emission tomography study (PET), we studied the cerebral activation pattern during reaching to objects presented through a mirror in the peripersonal space in healthy subjects. The results show that increased neural activity in the anterior part of the intraparietal sulcus and in the dorsal premotor cortex was bound to the transformation of the target position from the mirror space to the real space. In contrast, the activity related to object localization in the mirror occurred at the parieto-occipital junction. Both mirror and arm transformation involved the medial posterior part of the superior parietal lobule, putatively area V6a. The results demonstrate that acting through a mirror is processed in a number of cortical areas of the dorsal stream.     

GABAergic interneurons are the targets of cannabinoid actions in the human hippocampus

Cannabinoids have been shown to disrupt memory processes in mammals including humans. Although the CB1 neuronal cannabinoid receptor was identified several years ago, neuronal network mechanisms mediating cannabinoid effects are still controversial in animals, and even more obscure in humans. In the present study, the localization of CB1 receptors was investigated at the cellular and subcellular levels in the human hippocampus, using control post mortem and epileptic lobectomy tissue. The latter tissue was also used for [³H]GABA release experiments, testing the predictions of the anatomical data. Detectable expression of CB1 was confined to interneurons, most of which were found to be cholecystokinin-containing basket cells. CB1-positive cell bodies showed immunostaining in their perinuclear cytoplasm, but not in their somadendritic plasmamembrane. CB1-immunoreactive axon terminals densely covered the entire hippocampus, forming symmetrical synapses characteristic of GABAergic boutons. Human temporal lobectomy samples were used in the release experiments, as they were similar to the controls regarding cellular and subcellular distribution of CB1 receptors. We found that the CB1 receptor agonist, WIN 55,212-2, strongly reduced [³H]GABA release, and this effect was fully prevented by the specific CB1 receptor antagonist SR 141716A.

This unique expression pattern and the presynaptic modulation of GABA release suggests a conserved role for CB1 receptors in controlling inhibitory networks of the hippocampus that are responsible for the generation and maintenance of fast and slow oscillatory patterns. Therefore, a likely mechanism by which cannabinoids may impair memory and associational processes is an alteration of the fine-tuning of synchronized, rhythmic population events.     

Synaptic GABAergic and glutamatergic mechanisms underlying alcohol sensitivity in mouse hippocampal neurons

This study was designed to examine the neuronal mechanisms of ethanol sensitivity by utilizing inbred short sleep (ISS) and inbred long sleep (ILS) mouse strains that display large differences in sensitivity to the behavioural effects of ethanol. Comparisons of whole-cell electrophysiological recordings from CA1 pyramidal neurons in hippocampal slices of ISS and ILS mice indicate that ethanol enhances GABA_A receptor-mediated inhibitory postsynaptic currents (GABA_A IPSCs) and reduces NMDA receptor-mediated excitatory postsynaptic currents (NMDA EPSCs) in a concentration- and strain-dependent manner. In ILS neurons, these receptor systems are significantly more sensitive to ethanol than those in ISS neurons. To further examine the underlying mechanisms of differential ethanol sensitivities in these mice, GABA_B activity and presynaptic and postsynaptic actions of ethanol were investigated. Inhibition of GABA_B receptor function enhances ethanol-mediated potentiation of distal GABA_A IPSCs in ILS but not ISS mice, and this blockade of GABA_B receptor function has no effect on the action of ethanol on NMDA EPSCs in either mouse strain. Thus, subregional differences in GABA_B activity may contribute to the differential ethanol sensitivity of ISS and ILS mice. Moreover, analysis of the effects of ethanol on paired-pulse stimulation, spontaneous IPSC events, and brief local GABA or glutamate application suggest that postsynaptic rather than presynaptic mechanisms underlie the differential ethanol sensitivity of these mice. Furthermore, these results provide essential information to focus better on appropriate target sites for more effective drug development for the treatment of alcohol abuse.     

Does erythrocyte infusion improve 3.2-km run performance at high altitude?

The purpose of this study was to determine whether there are differences in the effects of exercise training between those with a parental history of hypertension and those without such a history. A group of 39 middle-aged hypertensive women were submitted to a 4-month exercise training programme. On the basis of their family histories, 18 individuals were classified as those having a positive parental history of hypertension (group P) and 21 individuals as those without such a history (group N). Both groups participated in a supervised training programme with the intensity set at the level producing the threshold lactate concentration for 90–120?min twice a week, together with self-determined aerobic exercise three times a week. Vital age was estimated to determine the health-fitness status. At the end of the training, group N exhibited reductions in the systolic and diastolic blood pressures at rest (12.6/8.0?mmHg) and increases in the peak oxygen uptake [V˙O_2peak 21.1 (SD 5.2) vs 25.2 (SD 5.7) ml · kg^?1· min^?1] and oxygen uptake corresponding to lactate threshold [13.7 (SD 2.4) vs 17.0 (SD 2.0) ml?·?kg^?1?·?min^?1; P?P?V˙O_2peak (P?>?0.05). There were no changes in the blood lipid and haematocrit variables in either group. The vital age decreased by approximately 4 and 7?years (P?相似文献   

Niedrigdosierte IFN-α-Behandlung der Haarzelleukämie

Zusammenfassung 15 Patienten (36–71 Jahre) mit histologisch gesicherter Haarzelleukämie wurden mit einer niedrigdosierten IFN--Therapie behandelt. Die Patienten erhielten im ersten Behandlungsmonat täglich subcutan 1 Mio. I.E. IFN--2b, danach nur noch sucutan 3 × 1 Mio. I.E. pro Woche. Zwei der 15 Patienten waren bereits vor der IFN-Therapie chemotherapiert, 5 splenektomiert. Sämtliche Patienten wiesen eine behandlungsbedürftige Leukopenie, Thrombozytopenie oder Anämie auf.Die Therapie konnte problemlos durchgeführt werden. Nur 2 Patienten litten unter leichtem Fieber nach der ersten IFN-Gabe, ein Patient entwikkelte nach zwei Monaten Müdigkeit und Apathie geringen Ausmaßes. Von 15 auswertbaren Patienten zeigten zwei nach 9–18 Monaten Therapie eine komplette Remission mit Normalisierung des Knochenmarkes und der peripheren Blutbildparameter. Bei zehn Patienten konnte eine partielle Remission, bei einem Patienten eine minimale Remission nur mit Normalisierung der Thrombozyten erreicht werden. Zwei Patienten verbesserten sich unter einer dreimonatigen IFN-Therapie nicht: sie erhalten gegenwärtig 5 Mio. I.E. IFN- dreimal pro Woche. Die Ergebnisse zeigen trotz der kleinen Zahl bisher behandelten Patienten, daß die IFN-Therapie auch niedrigdosiert bei der Haarzelleukämie wirksam ist.

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Low dose alpha-interferon (rIFN- 2b) in hairy cell leukemia

Summary Fifteen patients (36–71 years old) with histologically proven hairy-cell leukemia were treated with a low dose of IFN-. The treatment consisted of 1 million I.U. given daily subcutaneously. After 1 month the dose was reduced in all patients 1 million I.U. thrice weekly. Four of the 15 patients have been splenectomized, with two patients receiving chemotherapy prior to the IFN treatment. All patients exhibited at least one cytopenia.The IFN treatment was well tolerated. Only two of the 15 patients experienced mild fever after the first injection, one patient had apathia and mild somnolence after 2 months of therapy. At present 15 patients can be evaluated: 6–18 months after start of therapy two patients showed a complete response with normalization of both peripheral blood and bone marrow, 10 patients experienced a partial response, while one patient showed a slight response with improvement of the thrombocyte count only. Two patients showed no improvement after 3 months of therapy; these patients are presently being treated with 5 million I.U. IFN- thrice weekly. In spite of the low number of patients these data strongly indicate that IFN--2 is effective in hairy-cell leukemia at this low dose.

     

Stapedectomy: fenestration versus partial or complete footplate removal

The introduction of stapes surgery in the 1950s has brought about numerous changes to the field. The designed changes in the prosthesis as well composition of the prosthesis has influenced stapes surgery. The introduction of microdrills and lasers has also had some dramatic influences in the field. Stapes surgery can be divided into large fenestra technique or small fenestra technique. There are various proponents to each technique, with reported excellent results for each technique. The long-term hearing results are comparable with each technique. This article reviews the long-term results for large fenestra and small fenestra surgery.     

Cholinergic innervation of mossy cells in the rat fascia dentata

Hilar mossy cells are the main cells of origin of the commissural/associational projection to the inner molecular layer of the rat fascia dentata. In order to analyze the cholinergic innervation of hilar mossy cells, a light and electron microscopic double‐labeling technique was used. Immunolabeling for calcitonin gene‐related peptide (CGRP) was employed to identify mossy cells and immunocytochemistry for choline acetyltransferase (ChAT) was used to label cholinergic septohippocampal fibers. Cholinergic boutons were abundant around mossy cell somata and on their proximal dendrites. Electron microscopy confirmed that many of these boutons formed synapses with the CGRP‐positive mossy cells. These data demonstrate a direct innervation of hilar mossy cells by cholinergic septohippocampal afferents. This connectivity could contribute to the electrophysiological behavior of mossy cells during theta oscillations. Hippocampus 1999;9:314–320. © 1999 Wiley‐Liss, Inc.     

Association of occupational and non-occupational risk factors with the prevalence of self-reported carpal tunnel syndrome in a national survey of the working population

To compare the association of occupational versus personal, nonoccupational risk factors with the prevalence of carpal tunnel syndrome (CTS), data from the 1988 National Health Interview Survey, Occupational Health Supplement, were analyzed. When both occupational factors (bending/twisting of the hands/wrists [B/T] and use of hand-held vibrating tools) and personal nonoccupational factors (gender, race, age, body mass index [BMI], smoking, education, and family income) were included in a multivariate logistic regression model, adjusted odds ratios (AORs) of these factors for reporting medically called CTS (MC-CTS) were: exposure to B/T, 5.5; exposure to vibration, 1.9; white race, 16.7; female gender, 2.3; BMI ≥25, 2.0; history of cigarette smoking, 1.6; age ≥40, 1.2; education >12 years, 1.2; and annual family income ≥$20,000, 1.5. Although both occupational and nonoccupational factors are associated with reporting of CTS, repetitive bending/twisting of the hands/wrists and use of vibrating tools remain important risk factors for work-related carpal tunnel syndrome. Am. J. Ind. Med. 32:550–556, 1997. © 1997 Wiley-Liss, Inc.