Investigations on integration of mossy fiber inputs to Purkyně cells in the anterior lobe

Summary The 275 Purkyn cells identified by the criteria of the previous paper have been investigated with respect to their role as units integrating the input to the anterior lobe from various limb nerves. The discharges from single Purkyn cells have been studied in lightly anesthetized (pentothal) or in decerebrate unanesthetized cats, there being averaging usually of 128 responses in the form of post-stimulus time histograms and cumulative frequency distributions.Single Purkyn cells exhibited a wide variation in their responses to the diverse inputs from the various afferent nerves. Attention was focussed on excitatory and inhibitory responses evoked by mossy fibers with a short latency, usually 10–15 msec for hindlimb afferents. With most Purkyn cells these responses were predominantly evoked from cutaneous nerves, low threshold fibers being particularly effective. A few Purkyn cells were preponderantly excited by afferent volleys from muscle nerves, but there was a large group with a mixed input from cutaneous and muscle nerves. Graded strengths of stimulation of muscle nerves showed that sometimes group I volleys were prepotent, but other Purkyn cells were selectively excited by group II volleys. Though sometimes the afferent volleys from antagonistic muscles had a reciprocal action on a Purkyn cell, as on a motoneurone, it was more common to find similar actions. Also convergence of inputs from forelimb and hindlirnb nerves, both cutaneous and muscular, was not uncommon, particularly in marginal areas between hindlimb and forelimb zones. A special design feature is the convergence onto a Purkyn cell of mossy fiber and climbing fiber inputs evoked by the same afferent volley. This convergence was of particular interest along the parasagittal strip of hindlimb climbing fiber distribution in lobule V.It was not possible to translate the observations into some map of the cerebellar cortex on which are marked the territorial distributions from the various limb afferent nerves. Rather, there was an ill-defined patchy character, closely adjacent Purkyn cells often receiving very different subsets of the total input from the various limb nerves. The unitary integrations accomplished by the individual Purkyn cells are further integrated when their axons converge onto and inhibit the neurones of the cerebellar nuclei, and this integration by convergence would occur in each successive relay on the output pathways from the cerebellum.It is pointed out that the experimental findings on the integrative action of the individual Purkyn cells provide basic information for attempts to construct models simulating cerebellar performance and control.Post-Doctoral Fellow NINDS (1F2NB40, 545101 NSRB).Post-Doctoral Fellow UHF Grant No. FTF-3-UB-70.     

Predicting development of sustained unresponsiveness to milk oral immunotherapy using epitope-specific antibody binding profiles

1. Download high-res image (260KB)
2. Download full-size image

     

Significance of PBMC response of rheumatic fever patients and control individuals to immunodominant streptococcal M5 protein epitopes

β-hemolytic streptococcal infection in developing countries still causes thousands of cases of Rheumatic Fever (RF). Molecular mimicry between streptococcal M protein (strep M) and heart components has been proposed as the triggering factor leading to autoimmunity in individuals with genetic susceptibility, which is linked to different HLA-DR alleles in different populations. In our hands, RF was significantly associated to HLA-DR7/53. Previous work in our lab has shown that heart-infiltrating T cells that simultaneously recognize strep M and heart proteins. Further, such T cells predominantly recognized the 81-103 strep M5 epitope. In this work, we analysed the proliferative response of peripheral blood mononuclear cells of 99 RF patients and 40 normal controls. Eighty-nine of the RF patients were HLA-typed. As among heart-infiltrating T cells, the 81-103 strep M5 protein epitope is the most frequently recognized epitope among RF PBMC (35.4%), against a 7.5% frequency of proliferation among normal controls (p=0.0018, chi square). However, the 81-103 epitope was as frequently recognized by HLA-DR7,53 positive as by negative individuals (45.2% vs 54.8%, respectively). Taken together, the results suggest that the 81-103 strep M5 epitope may be the immunodominant epitope, “promiscuously” recognized by T cells in a genetically diverse population. The demonstration that molecular mimicry is targeted to a discrete immunodominant “promiscuous” epitope in strep M5 may allow the development of a safe anti-streptococcal synthetic vaccine devoid of such epitopes.     

Neuropeptide Y in the female reproductive tract of the rat. Distribution of nerve fibres and motor effects

The spontaneous firing of single neurones in the region of the lateral reticular nucleus was the subject of a pharmacological study employing microiontophoretic and systemic application of adrenoceptor agonists and antagonists. Both iontophoretic noradrenaline and systemic clonidine depressed neuronal firing. The depressions were consistently reversed by the alpha-2 antagonist RX781094. Other adrenergic antagonists, prazosin and sotalol, were ineffective. The results suggest the existence of alpha-2 receptors in this region of the brain.     

Molecular pathology of NEU1 gene in sialidosis

Lysosomal sialidase (EC 3.2.1.18) has a dual physiological function; it participates in intralysosomal catabolism of sialylated glycoconjugates and is involved in cellular immune response. Mutations in the sialidase gene NEU1, located on chromosome 6p21.3, result in autosomal recessive disorder, sialidosis, which is characterized by the progressive lysosomal storage of sialylated glycopeptides and oligosaccharides. Sialidosis type I is a milder, late-onset, normosomatic form of the disorder. Type I patients develop visual defects, myoclonus syndrome, cherry-red macular spots, ataxia, hyperreflexia, and seizures. The severe early-onset form, sialidosis type II, is also associated with dysostosis multiplex, Hurler-like phenotype, mental retardation, and hepatosplenomegaly. We summarize information on the 34 unique mutations determined so far in the sialidase gene, including four novel missense and one novel nonsense mutations found in two Czech and two French sialidosis patients. The analysis of sialidase mutations in sialidosis revealed considerable molecular heterogeneity, reflecting the diversity of clinical phenotypes that make molecular diagnosis difficult. The majority of sialidosis patients have had missense mutations, many of which have been expressed; their effects on activity, stability, intracellular localization, and supramolecular organization of sialidase were studied. A structural model of sialidase allowed us to localize mutations in the sialidase molecule and to predict their impact on the tertiary structure and biochemical properties of the enzyme.     

Outbreak of carbapenem-resistant Acinetobacter baumannii producing the OXA-23 enzyme in Curitiba,Brazil

Carbapenem-resistant Acinetobacter baumannii isolates were obtained from eight patients in two hospitals in Curitiba, Brazil. The isolates were multiresistant, belonged to a single strain, and produced the OXA-23 carbapenemase. Treatment options were limited, although the isolates were susceptible to polymyxin B in vitro. The strain contributed to the deaths of five patients.     

Afferent volleys in limb nerves influencing impulse discharges in cerebellar cortex I. In mossy fibers and granule cells

Summary This paper is the first of a series in which the processing of information in the cerebellum has been studied by investigating the effects that known inputs from limb nerves produce on the unitary spike potentials in the cerebellar cortex. These spikes have been recorded extracellularly at all depths along microelectrode tracks in the 5th, 4th and 3rd lobules of the anterior lobe in the lateral vermis or in the pars intermedia. These units have a background frequency of discharge, often very irregular, and computer averaging techniques have been employed in order to derive reliable information on the time course and intensity of the excitatory and/or inhibitory actions produced by the input against this background.Most of the spike responses recorded from the granular layer fall into two classes, one characteristic of impulses in mossy fibers, and the other of impulse discharges from granule cells. Both in the spontaneous background and in the response to afferent volleys in limb nerves the mossy fibers exhibit a performance in close accord with that described for the discharges up the spino-cerebellar tracts. The short latency of 6–9 msec for hindlimb stimuli and the high frequency burst response of 2–4 impulses are characteristic. The mossy fibers displayed a wide variety of responses to the wide range of testing inputs, there being various combinations of excitatory and inhibitory responses and also delayed excitatory actions, all of which must be assumed to be reflections of synaptic influences on the cells of origin of the mossy fibers in the spinal cord.Granule cells have a longer latency by several milliseconds, 9–20 msec for the hindlimb, and a slower frequency in their burst response which tended to be longer and more irregular. The small unitary spike potentials are more difficult to isolate. Also with repetitive stimulation granule cells are more readily depressed than are mossy fibers.Usually a granule cell exhibits a wider range of response to the various cutaneous and muscular afferents of a limb. Both mossy fibers and granule cells may display reciprocal responses to volleys from muscle nerves to antagonistic muscles. This attempt to define properties of the mossy fiber and granule cell spike potentials should help in their identification in future investigations.Post-Doctoral Fellow NINDS (1F2NB40,544101 NSRB).Post-Doctoral Fellow UHF Grant No. FTF-3-UB-70.     

Geminin regulates neuronal differentiation by antagonizing Brg1 activity

Precise control of cell proliferation and differentiation is critical for organogenesis. Geminin (Gem) has been proposed to link cell cycle exit and differentiation as a prodifferentiation factor and plays a role in neural cell fate acquisition. Here, we identified the SWI/SNF chromatin-remodeling protein Brg1 as an interacting partner of Gem. Brg1 has been implicated in cell cycle withdrawal and cellular differentiation. Surprisingly, we discovered that Gem antagonizes Brg1 activity during neurogenesis to maintain the undifferentiated cell state. Down-regulation of Gem expression normally precedes neuronal differentiation, and gain- and loss-of-function experiments in Xenopus embryos and mouse P19 cells demonstrated that Gem was essential to prevent premature neurogenesis. Misexpression of Gem also suppressed ectopic neurogenesis driven by Ngn and NeuroD. Gem's activity to block differentiation depended upon its ability to bind Brg1 and could be mediated by Gem's inhibition of proneural basic helix-loop-helix (bHLH)-Brg1 interactions required for bHLH target gene activation. Our data demonstrate a novel mechanism of Gem activity, through regulation of SWI/SNF chromatin-remodeling proteins, and indicate that Gem is an essential regulator of neurogenesis that can control the timing of neural progenitor differentiation and maintain the undifferentiated cell state.     

Monitoring gp43 antigenemia in Paracoccidioidomycosis patients during therapy

Paracoccidioidomycosis (PCM) is a systemic fungal disease that is particularly important among individuals living and working in rural areas of endemicity in Latin America. Detection of anti-Paracoccidioides brasiliensis antibodies is of limited value due to false-negative results. Detection of P. brasiliensis-gp43 circulating antigen is a practical approach for a specific diagnosis of the disease. In a previous study we described an inhibition enzyme-linked immunosorbent assay able to detect the 43-kDa P. brasiliensis antigen in sera of 100% of patients with the acute form of PCM and in 95.31 and 100% of patients with the chronic multifocal and unifocal forms of PCM. To investigate its potential application for the follow-up of PCM patients during treatment, antigen levels were monitored at regular intervals for up 8 to 12 months in serum samples from 23 patients. The results showed that treatment with itraconazole resulted in decreasing levels of circulating gp43 that were correlated with the reduction of anti-gp43 antibodies. It was also observed that by the end of 12 months of treatment gp43 levels were <5 microg/ml in all patients.