Major histocompatibility complex class II-restricted presentation of secreted and endoplasmic reticulum resident antigens requires the invariant chains and is sensitive to lysosomotropic agents

We have tested the involvement of the invariant chains (Ii) p31 and p41 in the presentation of peptides derived from hen egg lysozyme (HEL) constructs targeted to different intracellular compartments within transfected fibroblasts. The endogenous HEL constructs were either present in the cytosol (HELc), secreted (HELs), or linked to the mammalian (KDEL C-terminal sequence that causes retention of HEL in the endoplasmic reticulum (ER)/pre-Golgi recycling compartment (HELr). Using Ii-negative antigen-presenting cells, the presentation of HELr to a HEL 46-61 specific T cell hybridoma was far less efficient than the presentation of the HELs. High levels of Ii expression enhanced drastically the presentation of the HEL 46-61 determinant derived from both HELr and HELs. HELr and HELs presentation was fully sensitive to lysosomotropic agents such as chloroquine, indicating that the formation of complexes between major histocompatibility complex (MHC) class II molecules and determinants derived from endogenous antigens entering the secretory pathway is taking place in an acidic compartment. The degradation and dissociation of Ii might be a prerequisite for the efficient presentation of endogenously derived determinants by MHC class II molecules, as for the presentation of most exogenous antigens. All our results are compatible with the notion that endogenous molecules being translocated into the lumen of the ER could be presented by class II molecules through a processing pathway involving an acidic compartment in which Ii chains dissociate from class II molecules.     

Projections from the paratrigeminal nucleus and the medullary and spinal dorsal horns to the peribrachial area in the cat

The projections from the medullary and spinal dorsal horns to the dorsolateral pons were investigated in the cat utilizing both the retrograde and anterograde transport of a wheat germ agglutinin-horseradish peroxidase complex and the retrograde transport of the fluorescent dyes Fast Blue and Nuclear Yellow. After injections of wheat germ agglutinin-horseradish peroxidase into the area surrounding the brachium conjunctivum, numerous neurons were labeled ipsilaterally near levels of the obex in the paratrigeminal nucleus. Such neurons were located in connected pockets of neuropil located within the spinal trigeminal tract and along its medial edge. Most of the neurons labeled in the dorsal horns after such injections were found in lamina I. Those found in the medullary dorsal horn were mostly ipsilateral to the injection while those in the spinal dorsal horn were found bilaterally. Some labeled neurons were also found in lamina V of both the medullary and spinal dorsal horns bilaterally. When the injection was centered in either the medial parabrachial nucleus or the Kolliker-Fuse nucleus, a greater number of neurons were labeled ipsilaterally in lamina V of the medullary dorsal horn. Since neurons in lamina I of the medullary dorsal horn also project to the medial thalamus, fluorescent dyes were used to determine if the same neuron might project to both targets. Fast Blue was first injected into either the peribrachial area or the medial thalamus. After an appropriate period, Nuclear Yellow was injected into that target not injected first with Fast Blue. The injection of Nuclear Yellow was always placed on the side of the brain opposite to the first injection. Both dyes were transported retrogradely and were found in neurons located in lamina I of the medullary dorsal horn. However, no double-labeled neurons were seen. In general those labeled after injections of the medial thalamus were more superficial than those labeled after injections of the dorsolateral pons. The anterograde transport of wheat germ agglutinin-horseradish peroxidase was used to determine the termination of the projections from neurons in the medulary dorsal horn and the cervical spinal cord to the peribrachial area. After injections into these areas a moderate to sparse labeling of the lateral parabrachial nucleus and the Kolliker-Fuse nucleus was seen. It was mostly ipsilateral in cases with injections of the medullary dorsal horn but was bilateral following injections into the cervical enlargement.(ABSTRACT TRUNCATED AT 400 WORDS)     

Major histocompatibility complex class I molecules are required for the development of insulitis in non-obese diabetic mice

An early step in the development of autoimmune diabetes is lymphocyte infiltration into the islets of Langerhans of the pancreas, or insulitis. The infiltrate contains both CD4⁺ and CD8⁺ T cells and both are required for progression to diabetes in non-obese diabetic (NOD) mice. It has been thought that the CD4⁺ lymphocytes are the initiators of the disease, the islet invaders, while CD8⁺ cells are the effectors, the islet destroyers. We question this interpretation because NOD mice lacking MHC class I molecules, hence CD8⁺ T cells, do not display even insulitis when expected.     

Imbalanced secondary mucosal antioxidant response in inflammatory bowel disease

Intestinal mucosal damage in the inflammatory bowel diseases (IBD) Crohn's disease (CD) and ulcerative colitis (UC) involves reactive oxygen metabolites (ROMs). ROMs are neutralized by endogenous antioxidant enzymes in a carefully balanced two-step pathway. Superoxide dismutases (SODs) convert superoxide anion to hydrogen peroxide (H(2)O(2)), which is subsequently neutralized to water by catalase (CAT) or glutathione peroxidase (GPO). Remarkably changed expression levels of the three isoforms of SOD in paired non-inflamed and inflamed mucosae from CD and UC patients have been previously reported in comparison to normal control mucosa. Most notable was the strong up-regulation of Mn-SOD in inflamed epithelium. It was hypothesized that in order to provide optimal protection against ROM-mediated damage, these changes should be coordinately counterbalanced by an increased H(2)O(2)-neutralizing capacity. Therefore, the same tissue samples were used to assess the levels, activities, and/or localization of the most prominent mucosal H(2)O(2)-related antioxidants CAT, GPO, glutathione (GSH), myeloperoxidase (MPO), and metallothionein (MT). Quantitative measurements showed that in both CD and UC patients, intestinal inflammation was associated with increased activities of CAT, GPO, and MPO, whereas the mucosal GSH content was unaffected and the concentration of MT was decreased. Despite this overall increase in mucosal H(2)O(2)-metabolizing enzyme capacity, immunohistochemical analysis revealed a differentially disturbed antioxidant balance in IBD epithelium and lamina propria. In the lamina propria, the risk of direct H(2)O(2)-mediated damage seemed to be restrained by the increasing numbers of CAT- and MPO-positive monocytes/macrophages and neutrophils that infiltrated the inflamed areas. On the other hand, MPO overexpression might increase the lamina propria levels of hypochlorous acid, a stable ROM with multiple pro-inflammatory effects. In the epithelium, the number of cells that expressed CAT remained unchanged during inflammation and GPO was found in only a very low and constant number of epithelial cells. In addition, the inflamed epithelium displayed decreased expression of the hydroxyl radical (OH(*)) scavenger MT. In view of the high epithelial SOD levels in inflamed IBD epithelium, it is speculated that the efficient removal of excess H(2)O(2) is hampered in these cells, thereby increasing not only the risk of detrimental effects of H(2)O(2) directly, but also those of its extremely reactive derivatives such as OH(*). Taken together, the results suggest an imbalanced and inefficient endogenous antioxidant response in the intestinal mucosa of IBD patients, which may contribute to both the pathogenesis and the perpetuation of the inflammatory processes.     

Classes of neurons in relation to the laminar organization of the lateral geniculate nucleus in the tree shrew, Tupaia belangeri

We used the rapid Golgi and horseradish peroxidase (HRP) techniques to study the dendritic spread of relay neurons in functionally distinct laminae of the tree shrew dorsal lateral geniculate nucleus (LGNd). On the basis of their dendritic spread in relation to laminar and interlaminar zones, we describe three classes of relay neurons. Unilaminar neurons with multipolar radiate, bitufted, and intermediate types of dendrites. Dendrites of these neurons are confined to one lamina only, but also can have some of their segments in adjacent interlaminar zones. Multilaminar neurons with multipolar radiate, bitufted, and intermediate types of dendrites. Independent of the site of their cell bodies in a laminar or interlaminar zone, these neurons spread their dendrites over two or more laminae. Interlaminar neurons whose cell bodies and dendrites are confined to a single interlaminar zone. Unilaminar neurons are found in all the laminae. In the medial three laminae, they are more of the radiate type, whereas in laminae 4 and 5 their dendrites tend to be more of a tufted nature. Lamina 6 shows a preponderance of the elongated bitufted type. Multilaminar neurons, although less common as compared to the unilaminar, are also observed in all the laminae. Some neurons have their dendrites confined to an interlaminar zone. By retrograde transport of HRP injected into the visual cortex, we have shown that these neurons are, in fact, relay neurons. In addition to relay neurons, there are small interneurons with "axoniform" dendrites and an unmyelinated axon whose arborization is confined within the limits of the neuron's dendritic spread. Neurons of this type are not labeled with HRP injected into the visual cortex. We conclude that although each lamina is functionally specialized by input from ipsilateral or contralateral retina and by segregation of neurons responding to on or off stimuli, some multilaminar neurons can be found in each lamina. Thus, laminar as well as interlaminar zones contain a class of neurons that could provide a cross-talk between the functionally specialized laminae. Most relay neurons in all the laminae, however, confine their dendrites to their home lamina. Thus, the dendritic architecture of relay neurons allows for processing of information both within channels and between channels.     

Affinities of barbiturates for the GABA-receptor complex and A1 adenosine receptors: a possible explanation of their excitatory effects

Summary The effects of barbiturates on the GABA-receptor complex and the A₁ adenosine receptor were studied. At the GABA-receptor complex the barbiturates inhibited the binding of [³⁵S]t-butylbicyclophosphorothionate ([³⁵S]TBPT) and enhanced the binding of [³H]diazepam. Kinetic and saturation experiments showed that both effects were allosteric. Whereas all barbiturates caused complete inhibition of [³⁵S]TBPT binding, they showed varying degrees of maximal enhancement of [3H]diazepam binding; (±)methohexital was identified as the most efficacious compound for this enhancement. At the A₁ adenosine receptor all barbiturates inhibited the binding of [³H]N⁶-phenylisopropyladenosine ([³H]PIA) in a competitive manner. The comparison of the effects on [³H]diazepam and [³H]PIA binding showed that excitatory barbiturates interact preferentially with the A₁ adenosine receptor, and sedative/anaesthetic barbiturates with the GABA-receptor complex. It is speculated that the interaction with these two receptors might be the basis of the excitatory versus sedative/anaesthetic properties of barbiturates.Abbreviations GABA -aminobutyric acid - TBPT t-butylbicyclophosphorothionate 1073 - DMBB 5-(1,3-dimethyl)butyl-5-ethylbarbituric acid - MCB N-methyl-5-(1-cyclohexen-1-yl)-5-ethylbarbituric acid - MPPB N-methyl-5-phenyl-5-propylbarbituric acid - PIA N⁶-phenylisopropyladenosine Send offprint requests to M. J. Lohse at the above address     

Partial epilepsy in neurologically normal children: clinical syndromes and prognosis

A clinical and electroencephalographic study of 107 neurologically normal children with partial seizures was undertaken to verify the existence and determine the frequency of epileptic syndromes reported in selected populations. Sixty-three children had simple partial seizures, 39 had complex partial seizures, and 5 children were unclassifiable. The syndrome of benign partial epilepsy of children with rolandic spikes (BPEC, 38 cases) was clearly identified and its uniformly benign final prognosis was confirmed even if some of these children had at times severe or poorly controlled seizures. Among the children with simple partial seizures outside the BPEC (25 cases) and complex partial seizures (39 cases), no homogeneous clinical or electroclinical subgroup could be found. Two children with benign partial epilepsy and myoclonic-astatic seizures ("atypical benign partial epilepsy of childhood") and one child with "benign epilepsy with occipital spike-waves" were identified. 74% of children with epilepsy with complex partial seizures (ECP) had a 1-year seizure-free interval, and many children with epilepsy with simple partial seizures outside the BPEC group (ESP) had no more than two seizures. A benign course is thus not limited to the BPEC but is difficult to predict. Prospective studies are necessary to confirm the existence of well-defined benign syndromes among the idiopathic partial epilepsies of childhood, which appear quite rare outside the BPEC.     

Callosal projections from area SII to SI in monkeys: anatomical organization and comparison with association projections

The present research was aimed at ascertaining in the macaque monkey the reciprocity of the heterotopical callosal connections between SI and SII, with particular regard to the connectivity of the hand representation, and at comparing the topographical and laminar pattern of these callosal connections with those of association connections entertained by these areas. Horseradish peroxidase (HRP) was unilaterally injected into area SI in five monkeys. The sites of HRP delivery included the trunk and the hand zones preliminarily identified by recording multi-unit responses to peripheral stimulation by means of microelectrodes. Anterograde and retrograde labelling was studied in SII of both sides. The results showed the complete reciprocity of the heterotopical callosal connections between SI and SII. In the latter area both callosal axon terminals and neurones were found, which were labelled from either the trunk or the hand zone of contralateral SI. Labelling of callosal axon terminals occurred mainly in layer IV and in the lowermost part of layer III. Labelled callosal neurones were mainly in the lower half of layer III, whereas few occurred in infragranular layers. Topographically, the distribution of callosal terminals and cell bodies duplicated the distribution of association terminals and cell bodies labelled in SII on the side ipsilateral to HRP injection. The laminar pattern of termination of association fibres from SI was similar to that of callosal fibres. However, the distribution of association-projecting neurones in SII showed a striking difference from that of callosal-projecting neurones. Unlike the latter neurones, which were mainly located in supragranular layers, association cell bodies overwhelmingly dwelt in layers V and VI and were less numerous in layers II and III. This laminar pattern of association SII-SI cells corresponds to the "feed-backward" model and fits the laminar pattern of their axon terminations (Friedman: Brain Res. 273: 147-151, '83). The association and callosal inputs and outputs of area SII are discussed in relation to the function of the forward and backward type of reciprocal connections entertained with SI in the ipsilateral hemisphere and to the function of SII in the interhemispheric exchange of somatosensory information.     

Preoptic area unit activity during sleep and wakefulness in the cat

The spontaneous discharge of 86 preoptic area (POA) neurons was recorded extracellularly in chronically prepared cats during wakefulness (W), slow-wave sleep (SWS), and REM sleep. Of these, the percentage of units exhibiting maximal discharge rates in SWS and REM sleep (84%) was significantly greater than that of those exhibiting a maximal discharge rate in W (16%). Furthermore, those neurons that discharged rapidly in sleep (fast units) generally had a reduced discharge rate in W. Sixteen of the 86 units showed a strong tendency to discharge in bursts during SWS but not during W or REM sleep. The mean coefficient of variation and the mean discharge rate for these bursting cells in SWS were significantly greater than the corresponding values for the same cells in W and REM sleep, and for the nonbursting cells in SWS. Because POA stimulation is known to initiate behavioral and electrocortical signs of sleep, it is suggested that "fast units" in SWS with reduced discharge rates in W, may be "hypnogenic" cells.