Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system. While its etiology is not well understood, genetic factors are clearly involved. Until recently, most genetic studies in MS have been association studies using the case-control design testing specific candidate genes and studying only sporadic cases. The only consistently replicated finding has been an association with the HLA-DR2 allele within the major histocompatibility complex (MHC) on chromosome 6. Using the genetic linkage design, however, evidence for and against linkage of the MHC to MS has been found, fostering suggestions that sporadic and familial MS have different etiologies. Most recently, two of four genomic screens demonstrated linkage to the MHC, although specific allelic associations were not tested. Here, a dataset of 98 multiplex families was studied to test for an association to the HLA-DR2 allele in familial MS and to determine if genetic linkage to the MHC was due solely to such an association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta) in the MHC demonstrated strong genetic linkage (parametric lod scores of 4.60, 2.20 and 1.24, respectively) and a specific association with the HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results by HLA-DR2 status showed that the linkage results were limited to families segregating HLA-DR2 alleles. These results demonstrate that genetic linkage to the MHC can be explained by the HLA-DR2 allelic association. They also indicate that sporadic and familial MS share a common genetic susceptibility. In addition, preliminary calculations suggest that the MHC explains between 17 and 62% of the genetic etiology of MS. This heterogeneity is also supported by the minority of families showing no linkage or association with loci within the MHC.      

Factors influencing Cryptosporidium testing in Connecticut.

To describe patterns of testing for Cryptosporidium oocysts in stool samples, Connecticut laboratories were surveyed. Different detection methods were used. Most laboratories examined stools specifically for Cryptosporidium only on physician request. The rate of positive tests varted widely (0 to 28%). Higher rates of positivity were associated with the use of monoclonal antibody methods, the use of two or more staining procedures, and testing of stool specimens in addition to those requested by physicians.     

The inferior alveolar artery in its bony course

Based on the dissection of 30 hemi-mandibles, the authors report a study of the inferior alveolar artery in its intraosseous course. On morphologic considerations they propose a classification of the collaterals into two groups: the principal collaterals destined for the teeth and the bony alveolar tissue and the secondary collaterals destined for the sheath and the nerve as well as the bony tissue around the canal. Loss of the teeth and absorption of the alveolar bone modify the caliber of the inferior alveolar arterial axis, the distribution of its collaterals and possibly its mode of termination. These facts suggest a consideration of the vascularization of the mandible in terms of four sectors. They arrive at practical conclusions that may be drawn from this study in stomatology.     

Passive transfer of flt-3L-derived dendritic cells delays diabetes development in NOD mice and associates with early production of interleukin (IL)-4 and IL-10 in the spleen of recipient mice

CD11c+/CD11b+dendritic cells (DC) with high levels of major histocompatibility complex (MHC) class II and co-stimulatory molecules have been derived from spleen cells cultured with granulocyte-macrophage colony stimulating factor (GM-CSF) + flt-3L + interleukin (IL)-6 (flt-3L-DC). Investigating in vivo the function of DC in non-obese diabetic mice (NOD), we showed that a single injection of this in vitro-derived subset of DC prevents the development of diabetes into prediabetic female mice. In contrast, DC derived from bone marrow cells cultured with GM-CSF + IL-4 [bone marrow (BM)-DC] induced no protection. Moreover, protection against diabetes following injection of flt-3L-DC was associated with IL-4 and IL-10 production in the spleen and the pancreatic lymph nodes of recipient mice, indicating that this DC population is able to polarize the immune response towards a Th2 pathway. As we shown previously, NOD BM-DC exhibit an enhanced capacity to produce IL-12p70 in response to lipopolysaccharide (LPS) and anti-CD40 stimulation compared to BM-DC from control mice. In contrast, NOD flt-3L-DC, as their control mouse counterpart, produced no IL-12p70 to these stimuli. Our findings show that a subset of DC, characterized by a mature phenotype and the absence of IL-12p70 production can be derived from NOD mouse spleen favouring IL-4 and IL-10 regulatory responses and protection from diabetes development.     

A fish encephalitis virus that differs from other nodaviruses by its capsid protein processing

Summary.  RNA2, the short segment of the genome of Dicenthrarchus labrax encephalitis virus (DIEV), a fish nodavirus causing seabass encephalitis, was cloned. Sequence analysis revealed that DIEV RNA2 contains a single open reading frame (ORF), which carries the catalytic D-75 residue but lacks the site for autocatalytic proteolysis, the process yielding the two capsid proteins of insect nodaviruses. Nevertheless, SDS-PAGE analysis of mature virions revealed a 43–45 kDa protein doublet. In order to determine the mechanism of synthesis of the two capsid proteins in DIEV, wild type and mutagenized forms of RNA2 were expressed in cell-free translation extracts and in transfected cells. Results showed that, despite the presence of the catalytic D-75 residue, the DIEV capsid protein doublet did not result from the assembly-dependent autocatalytic cleavage of a protein precursor. Moreover, our data show that, although suggested by sequence analysis, the DIEV capsid protein doublet results from neither an alternative initiation codon usage nor from a −1 ribosomal frameshift. Results of cell-free translation experiments demonstrate that the capsid protein doublet neither results of the proteolytic cleavage of a precursor nor of a degradation process. Kinetics of capsid protein synthesis in cell-free translation programmed with RNA2 revealed, instead, that the two capsid proteins are cosynthesized. Together these data strongly suggest that the DIEV capsid protein doublet results from cotranslational modification(s) of the ORF-encoded protein. Accepted July 31, 1997 Received May 26, 1997     

Adolescent cocaine and injection stress effects on the estrous cycle

Chronic cocaine exposure during critical periods of development induces short- and long-term effects. During the pubertal period, the hypothalamic–pituitary–gonadal (HPG) axis undergoes many dynamic changes. The present study investigated whether chronic periadolescent cocaine alters reproductive maturity in the rat. Sixty female Long–Evans hooded rats were randomly assigned to one of three conditions (20 mg cocaine/kg/day, saline injected and uninjected), for dosing from postnatal day 21 (P21) through P60. Several indicators of reproductive maturation and functioning were assessed during and following treatment. Cocaine exposure had no effect on the onset of puberty or on the date of first ovulation. The number of proestrus–estrus transitions was significantly lower in cocaine-exposed females compared to uninjected females, but not compared to saline-injected controls. This reduction was observed during exposure to cocaine, as well as after the cessation of injections. During the dosing period, cocaine-exposed rats also exhibited a greater number of cycles that had no clear P–E transition than did UN subjects; this effect disappeared once injections stopped. These alterations suggest immediate, and possibly persisting, alterations in the control of ovulation after chronic cocaine exposure throughout adolescence. Interestingly, during the injection period, the saline-injected females had a significantly greater number of diestrus days compared to uninjected and cocaine-injected animals, as well as a lower proportion of regular 4- and 5-day cycles. These differences disappeared once injections stopped. These results suggest a stress-induced irregularity of the estrous cycle, possibly attenuated by cocaine and recoverable after exposure. The present findings indicate that the HPG axis is susceptible to short-term, and possibly to long-term, alterations induced by cocaine exposure throughout the adolescent period.