Sulfated beef insulin treatment elicits CD8+ T cells that may abrogate immunologic insulin resistance in type I diabetes.

The in vitro responses of T cells from 13 insulin-nonresistant and 1 immunologically insulin-resistant (IIR) type I diabetes patients to sulfated beef insulin (SBI) were analyzed. Insulin A-loop specific CD4+ T cells from these patients did not respond to SBI. After 1 yr of treatment with SBI the IIR patient's T cell and antibody responses to beef, pork, and human insulin progressed from very high to nondetectable levels. This occurred in parallel to the appearance of her insulin-specific CD8+ T cells, which inhibited the response of her A-loop-specific CD4+ T cells to insulin. A transient increase in her CD8+ anti-insulin antibody activity coincided with a relative lack of her CD8+ T cell activity. CD8+ T cells that regulate T cell responsiveness to insulin are probably present but difficult to detect in most type I diabetes patients. These T cells were identified in only 2 of 13 insulin-nonresistant patients who presented with lipoatrophy and insulin allergy, respectively, and who possessed high-titered, anti-insulin antibodies. Our data demonstrate that CD8+ T cells play an important role in controlling peripheral tolerance to insulin and may abrogate IIR in a diabetic patient treated with SBI.     

Mouse thymic epithelial cell lines interact with and select a CD3lowCD4+CD8+ thymocyte subset through an LFA-1-dependent adhesion--de-adhesion mechanism

Differentiation of bone-marrow-derived precursor cells into mature mouse T lymphocytes occurs in the thymus and involves sequential interactions with MHC-positive hemopoietic and epithelial stromal cells. To study the in vitro molecular mechanisms at play during the lympho-epithelial cell adhesion, we derived thymic stromal cell lines which were shown to possess cytokeratin filaments and tight junctions. These mouse thymic epithelial (MTE) cell lines did not express the classical hemopoietic stromal cell surface markers (i.e. LFA-1, Mac-1, and CD45) but expressed ICAM-1, NCAM, J11d, CD44, and MHC molecules. A quantitative cell adhesion assay was used to evaluate the interaction of various lymphoid cell subsets with MTE cells. Two cell interaction patterns could be defined: first, a rapid adhesion of a fraction of CD4+CD8+ and of a few CD4-CD8- immature thymocytes to MTE cells was observed at 4 degrees C. The CD8 molecule was shown to be partially involved in this initial contact. The strength of adhesion between MTE cells and distinct thymocyte subsets was evaluated and found to be maximal with neonatal thymocytes. Second, a temperature-dependent adhesion step characterized by a rapid and active stabilization of the interaction of MTE cells with 20% of CD4+CD8+CD3low thymocytes was seen, followed by a more progressive de-adhesion step. This active process of engagement was highly LFA-1-dependent, involved the CD4 and CD8 molecules, and required protein kinase C activation and cytoskeletal integrity. The results are consistent with the involvement of LFA-1 in a transient and regulated cell adhesion under the control of the TCR-CD3 complex that progressively appears on maturing cells. This phenomenon might contribute to the selection of a subset of immature thymocytes by epithelial cells occurring during the process of maturation of these cells.     

Anatomical atlas of the baboon''s brain in the orbito-meatal plane used in experimental positron emission tomography

An anatomical atlas has been constructed of the brain of the baboon (Papio papio) in the orbito-meatal plane (OM-plane) which is frequently used in experimental positron emission tomography (PET) investigations. The atlas comprises 12 photographic reproductions of histological brain sections separated by 2.5 mm intervals, and covers telencephalic to pontine brain stem levels. The anatomical atlas was used in analysis of some PET scan images obtained after administration of either a benzodiazepine (BZ) antagonist, (11C)-Ro 15-1788, or a dopamine D2 receptor antagonist, (76Br)-bromospiperone. Since PET camera detects radiation emitted from a slice of tissue of 15 mm thickness, each PET image corresponds to the tissue represented on six levels of the anatomical atlas. In optimal conditions, the PET image shows a pattern of receptor labelling reminiscent of anatomical structures in the atlas. Sometimes, however, the superimposition of different labelled structures yields a PET image which lacks any apparent resemblance with individual anatomical structures. In these cases, the analysis of the PET scan must rely on the anatomical atlas, as well as available data on the distribution of specific binding sites.     

Effects of localized, chronic GABA infusions into different cortical areas of the photosensitive baboon, Papio papio

The effects of chronic (7 days) intracortical GABA infusions were investigated in both naturally photosensitive and non-photosensitive baboons. Bilateral and unilateral infusions into motor and occipital regions blocked photosensitivity, while premotor and prefrontal cortex infusions had no effect on the electro-clinical manifestations of this type of reflex epilepsy; the monkeys with prefrontal GABA infusions, however, showed selective attention deficits, detected with the delayed response test. In all cases a GABA withdrawal syndrome, appearing as epileptogenic spontaneous activity localized to the infused sites, was found at the cessation of GABA application. We conclude that GABAergic systems localized at discrete cortical areas play an important role in photosensitivity and in the modulation of cognitive processes in the monkey.     

Temporo-spatial pattern of subcortical spike activity in kindling epilepsy. A statistical approach.

Recording electrodes were implanted stereotaxically in limbic and thalamic structures and the mesencephalic reticular formation in twelve cats. The animals were submitted to daily stimulation of the left amygdaloid nucleus following the technique for the kindling procedure, always combined with 5 h 30 min post-stimulation monitoring. After about 18 days, generalized convulsive activity was established. The following results concerning the quantitative evolution of spontaneously occurring interictal spikes were obtained. Amygdaloid nuclei, the hippocampus and the thalamic nucleus ventralis lateralis (VL) demonstrated an increase of discharge activity during the kindling procedure, following by a significant decrease after convulsions had been elicited. Thalamic nucleus centrum medianum (CM) was the only recording site investigated where the amount of interictal discharge increased and remained at a high level even after generalized convulsions had been established. Fourier analysis of slow oscillations in discharge generation yielded two main types of significant periodicity. A 165 min oscillation could be detected in all structures tested except reticular formation, which developed a 110 min cycle shared only with the thalamic CM. Significant correlations in spike activity were obtained from various structures. Stimulated amygdala seemed to have alternating relations with thalamic CM and VL, whereas stimultaneous oscillations excisted between MRF and CM. The occurrence of high voltage spikes in both contralateral and ipsilateral amygdalae was shown to be significantly correlated.     

A study of the action of valproic acid on the kindling effect.

The effect of an antiepileptic drug, valproic acid (VPA), on an experimental form of epilepsy, the kindling phenomenon, is described. In cat, 50 mg/kg i.p. per day is sufficient to block the progressive establishment of generalized seizures produced normally by repetitive electrical stimulation of the amygdala. However, a focal afterdischarge persists during the entire treatment. Higher doses (75-150 mg/kg) are necessary to protect the animal against the generalized tonic-clonic seizure when the kindling phenomenon is established. These effects and the action of barbiturates, which was also tested, seem to attribute to VPA a complex role in the mechanism of this action.