Retinal photoreceptor fine structure in the velvet cichlid (Astronotus ocellatus).

Summary The structure and arrangement of the retinal photoreceptors of the velvet cichlid fish (Astronotus ocellatus) have been studied by light and electron microscopy. Rods, single cones and double (twin) cones are present. In the light-adapted state, rods are very tall cells that reach deep into the retinal epithelial (RPE) layer. The long outer segment is composed of discs of uniform diameter displaying one or two incisures. The rod inner segment shows a distal ellipsoid of mitochondria, and then narrows dramatically in the myoid region. Rod nuclei are electron dense and located deep in the outer nuclear layer. Rod synaptic spherules are small and show two to three invaginated synaptic sites as well as superficial synapses. Single cones are similar to the individual members of a double cone and all display a short tapering outer segment, a large ellipsoid of mitochondria and a myoid rich in rough endoplasmic reticulum, polysomes, Golgi zones and autophagic vacuoles. Double cones have extensive subsurface cisternae along their entire contiguous surfaces. Cone nuclei are large and vesicular and located close to or through the external limiting membrane. The synaptic pedicles of cones are larger, more electron lucent, and display more invaginated (ribbon) synapses as well as conventional (superficial) synaptic sites than do the rod spherules. Rod photoreceptors certainly undergo retinomotor movements and it is probable that cones do as well. In the light-adapted state the cone photoreceptors are arranged in a repeating square mosaic pattern with one single cone surrounded by four double (twin) cones.     

CORRELATION OF IMMUNOLOGICAL SURFACE ANTIGENS WITH SURVIVAL IN DIFFUSE LARGE CELL LYMPHOMA

The prognostic value of immunophenotyping lymphomas with a panel of monoclonal antibodies (Mab) to various lymphoid antigens was assessed by studying 47 cases of diffuse large cell lymphoma. Cell suspensions were analysed by flow cytometry after labelling by indirect immunofluorescence. Thirty-eight cases were demonstrated to be of B cell and nine of T cell phenotype. Univariate analysis demonstrated that survival was significantly longer in patients expressing higher levels of HLA-DR (p=0·01) and normal levels of CD8 (p=0·04) but was not significantly associated with any of the other antigens. Our results support the possible value of HLA-DR in determining the prognosis of patients with diffuse large cell lymphoma.     

Laboratory diagnosis of variant Creutzfeldt-Jakob disease

The neuropathological and biochemical features of 33 cases of variant Creutzfeldt-Jakob disease (vCJD) diagnosed up to the end of 1998 are analysed in relation to the 646 cases of suspected CJD referred to the CJD Surveillance Unit laboratory from 1990 to 1998. Morphological studies of the central nervous system, lymphoid tissues and other organs were accompanied by immunocytochemistry; Western blot analysis of PrPRES was performed on frozen brain tissue. The findings were analysed in relation to clinical and genetic data. The pathology of vCJD showed morphological and immunocytochemical characteristics distinct from other cases of CJD. PrP accumulation was widespread in lymphoid tissues in vCJD, but was not identified in other non-neural tissues. PrPRES accumulation in vCJD brain tissue showed a uniform glycotype pattern distinct from sporadic CJD. All analysed cases of vCJD were methionine homozygotes at codon 129 of the PrP gene. No evidence currently exists to suggest that cases of CJD diagnosed in individuals who are MV or VV at codon 129 of the PrP gene represent 'human bovine spongiform encaphalopathy (BSE)'. Continued surveillance is required to further investigate this possibility, with the need to investigate autopsy tissues from suspected cases by histological and biochemical techniques.     

Prion protein accumulation and neuroprotection in hypoxic brain damage

The function of the normal conformational isoform of prion protein, PrP(C), remains unclear although lines of research have suggested a role in the cellular response to oxidative stress. Here we investigate the expression of PrP(C) in hypoxic brain tissues to examine whether PrP(C) is in part regulated by neuronal stress. Cases of adult cerebral ischemia and perinatal hypoxic-ischemic injury in humans were compared with control tissues. PrP(C) immunoreactivity accumulates within neuronal processes in the penumbra of hypoxic damage in adult brain, and within neuronal soma in cases of perinatal hypoxic-ischemic injury, and in situ hybridization analysis suggests an up-regulation of PrP mRNA during hypoxia. Rodents also showed an accumulation of PrP(C) in neuronal soma within the penumbra of ischemic lesions. Furthermore, the infarct size in PrP-null mice was significantly greater than in the wild type, supporting the proposed role for PrP(C) in the neuroprotective adaptive cellular response to hypoxic injury.     

IFN-alpha enhances CD40 ligand-mediated activation of immature monocyte-derived dendritic cells

Type I IFN are immune modulatory cytokines that are secreted during early stages of infection. Type I IFN bridge the innate and the adaptive immune system in humans and mice. We compared the capacity of type I and II IFN to induce the functional maturation of monocyte-derived dendritic cells (MoDC). Extending our earlier observation that type I IFN promote DC maturation, we report that these cytokines also enhance DC differentiation by augmenting CD40 ligand (CD40L)-induced cytokine secretion by MoDC. Type I IFN alone were poor inducers of MoDC maturation as compared with other stimuli. They up-regulated the expression of HLA-DR, CD80, CD86, partially CCR7 but not CD83, partially reduced antigen-uptake function, increased the levels of IL-12p35 mRNA, and prolonged surface expression of peptide-MHC class I complexes for presentation to cytotoxic T lymphocytes, but did not induce migration towards CCL21 chemokine. However, type I IFN were potent co-factors for CD40L-mediated function. Here, they enhanced CD40L-mediated IL-6, IL-10 and IL-12p70 secretion. Furthermore, when combined with IL-1beta and/or IL-4, IFN-alpha2a type I IFN increased CD40L-mediated IL-12p70 production by 2- to 3-fold, and biased the IL-12 p40/p70 ratio towards the IFN-gamma inducing p70 heterodimer, this correlating with higher levels of IFN-gamma secretion by allogeneic T cell subsets and NK cells. Our results suggest that the rapid expression of CD40L, IFN and IL-1beta at sites of infection and inflammation can act in concert on immature DC, thereby linking innate and adaptive immune responses. In this way, type I IFN play a dual role as DC maturation factors and enhancers of CD40L-mediated DC activation.     

Sequential karyotypes in non-Hodgkin lymphoma: their nature and significance

The examination of sequential karyotypes in hematologic disorders has demonstrated that karyotypic changes are often associated with concurrent changes in clinical behavior. Acquired abnormalities that recur among different patients may also suggest genomic areas important to tumor progression. We therefore examined sequential karyotypes in 21 patients with non-Hodgkin lymphoma (NHL). Sixteen of the 21 karyotypes demonstrated changes, including the majority of 6 small lymphocytic, 11 follicular, and 4 intermediate and high-grade diffuse lymphomas. The t(14;18)(q32;q21) occurred in ten initial karyotypes was retained in all cases. The band most frequently affected by newly acquired abnormalities was 14q32 (n = 5); chromosomes 1 and 2 (n = 5, each), and the 17p arm (n = 4) were also commonly affected. The acquired deletion of all or part of 17p appeared to be associated with a poor prognosis. Histologic transformation and karyotypic change did not correlate. This study of sequential karyotypes in NHL 1) confirms the primary importance of the t(14;18), 2) suggests that the 14q32 band is involved frequently in both primary and secondary cytogenetic events, and 3) suggests other genomic regions of potential significance to progression.     

Neuropathological Diagnostic Criteria for Creutzfeldt-Jakob Disease (CJD) and Other Human Spongiform Encephalopathies (Prion Diseases)

Neuropathological diagnostic criteria for Creutzfeldt-Jakob disease (CJD) and other human transmissible spongiform encephalopathies (prion diseases) are proposed for the following disease entities: CJD - sporadic, iatrogenic (recognised risk) or familial (same disease in 1st degree relative): spongiform encephalopathy in cerebral and/or cerebellar cortex and/or subcortical grey matter; or encephalopathy with prion protein (PrP) immuno-reactivity (plaque and/or diffuse synaptic and/or patchy/perivacuolar types). Gerstmann-Sträussler-Scheinker disease (GSS) (in family with dominantly inherited progressive ataxia and/or dementia): encephalo(myelo)pathy with multicentric PrP plaques. Familial fatal insomnia (FFI) (in member of a family with PRNP178 mutation): thalamic degeneration, variable spongiform change in cerebrum. Kuru (in the Fore population). Without PrP data, the crucial feature is the spongiform change accompanied by neuronal loss and gliosis. This spongiform change is characterised by diffuse or focally clustered small round or oval vacuoles in the neuropil of the deep cortical layers, cerebellar cortex or subcortical grey matter, which might become confluent. Spongiform change should not be confused with non-specific spon-giosis. This includes status spongiosus (“spongiform state”), comprising irregular cavities in gliotic neuropil following extensive neuronal loss (including also lesions of “burnt-out” CJD), “spongy” changes in brain oedema and metabolic encephalopathies, and artefacts such as superficial cortical, perineuronal, or perivascular vacuolation; focal changes indistinguishable from spongiform change may occur in some cases of Alzheimer's and diffuse Lewy body diseases. Very rare cases might not be diagnosed by these criteria. Then confirmation must be sought by additional techniques such as PrP immunoblotting, preparations for electron microscopic examination of scrapie associated fibrils (SAF), molecular biologic studies, or experimental transmission.