Selective Vulnerability of Spinal and Cortical Motor Neuron Subpopulations in delta7 SMA Mice

Loss of the survival motor neuron gene (SMN1) is responsible for spinal muscular atrophy (SMA), the most common inherited cause of infant mortality. Even though the SMA phenotype is traditionally considered as related to spinal motor neuron loss, it remains debated whether the specific targeting of motor neurons could represent the best therapeutic option for the disease. We here investigated, using stereological quantification methods, the spinal cord and cerebral motor cortex of ∆7 SMA mice during development, to verify extent and selectivity of motor neuron loss. We found progressive post-natal loss of spinal motor neurons, already at pre-symptomatic stages, and a higher vulnerability of motor neurons innervating proximal and axial muscles. Larger motor neurons decreased in the course of disease, either for selective loss or specific developmental impairment. We also found a selective reduction of layer V pyramidal neurons associated with layer V gliosis in the cerebral motor cortex. Our data indicate that in the ∆7 SMA model SMN loss is critical for the spinal cord, particularly for specific motor neuron pools. Neuronal loss, however, is not selective for lower motor neurons. These data further suggest that SMA pathogenesis is likely more complex than previously anticipated. The better knowledge of SMA models might be instrumental in shaping better therapeutic options for affected patients.     

Organization of the murine immunoglobulin VH complex in the inbred strains.

Deletion mapping analyses have been employed to order the heavy chain variable region (VH) gene families in three inbred murine strains. These nine VH gene families have been positioned with respect to the J558 and 3660 VH families in A/J (Ighe) as follows: 3609-J558-(J606,VGAM3-8,S107)-3660-(X24,Q52,7183 )-DH. Maps generated with respect to J558 in the BALB/c (Igha) and C57BL/6 (Ighb) strains are consistent with these results. The organization of the VH complex produced by deletion mapping is quite different from the accepted map generated by other methods, particularly in that J558 is more DH distal and 3660 is more DH proximal than previously thought. The order presented here is compatible with VH rearrangement frequencies suggesting preferential utilization of DH-proximal VH gene segments. Our data also indicate that interspersion of some VH family members may be a common feature of the murine VH complex since the 3609 VH family is interdigitated in the three strains and a Q52 VH gene segment is interspersed in C57BL/6.     

Characterization, localization, and biosynthesis of acetylcholinesterase in K 562 cells

K 562 cell acetylcholinesterase (AChE), identifiable by active site labeling with radioactive diisopropylfluorophosphate (DFP), showed a Mr around 55,000 in both a crude lysate and a purified sample. The K 562 AChE was reactive with one polyclonal and two monoclonal antibodies produced against human erythrocyte AChE. Subcellular localization, investigated by assay on cell fractions, showed that AChE is membrane bound and that it is located on the cell surface as well as on microsomal and Golgi membranes. Biosynthesis of new enzyme molecules, after inactivation of the constitutive AChE with the irreversible inhibitor DFP, allowed us to follow the kinetics of reappearance in the intracellular compartment and at the cell surface (4 and 8 h, respectively).     

Human hydatidosis in Sardinia. Epidemiologic study of the cases operated on from 1974 to 1981

A retrospective survey of surgical cases to obtain baseline data on hydatid disease in Sardinia from 1974 to 1981 revealed an annual mean rate of 11.1/100.000 population. However, real prevalence is obviously higher, since infection is not always synonymous with disease and surgical incidence should be regarded as the figure that counts. Information on sex, age, residence, occupation, cyst location, number of re-operations was collected to assess the public health impact to hydatidosis within the island. The obtained results indicate that not all population is at equal risk, being hydatid disease most prevalent in rural areas and particularly in the districts where sheep-breeding is highly diffused (annual mean rate greater than 20/100.000 population). The highest rate was observed in farmers and shepherds (34.2/100.000) respect to retired (14.1/100.000), housewives (10.9/100.000), employed in services (8.9/100.000) and students (8.3/100.000). Over 55% of the cysts were found in the liver, about 30% in the lung and 15% in other sites. A correlation between age and cyst location and between profession and cyst location was shown. Pulmonary cysts were prevalent in children and young people, hepatic in grown-up people, whereas nearly the same hepatic and pulmonary frequency was observed in shepherds. Comparisons between previous surveyed periods were done and results were discussed, suggesting the need of a continuous and well-planned control programme.     

Primary structural variation among serologically indistinguishable DS antigens: the MB3-bearing molecule in DR4 cells differs from the MB3-bearing molecule in DR5 cells

HLA-DS molecules bearing the MB3 supertypic specificity have been isolated from two DR4 and two DR5 homozygous cell lines by using the monoclonal antibody IVD12 . Limited amino-terminal amino acid sequence analysis of these molecules demonstrates polymorphism of the HLA-DS subregion. Although the distribution of amino-terminal tyrosine residues in the alpha-chains of all IVD12 -reactive molecules was identical, amino-terminal amino acid sequence differences existed between DS beta-chains isolated from these two groups of cell lines bearing different DR specificities. These studies indicate that two DS molecules bearing the same serologic determinant ( MB3 ), although similar to one another, may be structurally distinct.     

Nucleotide sequence of a human monoclonal anti-idiotypic antibody specific for a rabies virus-neutralizing monoclonal idiotypic antibody reveals extensive somatic variability suggestive of an antigen-driven immune response

We previously described the isolation and characterization of a human monoclonal anti-idiotypic antibody (Ab2) isolated from EBV-transformed human PBL after immunization with rabies vaccine. The present study concerns the molecular characteristics of the Ab2 and the germ-line elements that gave rise to it. The H chain of this antibody derives from the small VHV family of human V region gene segments. Parallel studies on the germ-line VHV gene isolated from the same individual revealed that the expressed molecule contains 19 nucleotide differences in the VH gene segment. The D segment of Ab2 could have arisen by a D to D fusion; the J segment is a JH6. Extensive somatic variation evident in the H chain variable region of this naturally arising monoclonal anti-idiotypic antibody suggests that this Ab2, the product of a CD5+ B cells, was the consequence of an Ag-driven immune response.     

VH sequence of a human anti-Sm autoantibody. Evidence that autoantibodies can be unmutated copies of germline genes

The utilization of germline genes for the synthesis of autoantibodies has been suspected for many years based on the presence of cross-reactive idiotypes among patients as well as in some healthy first-degree relatives of patients with several autoimmune diseases including SLE. One such system of idiotypes involves anti-Sm antibodies, which are highly specific for SLE. To definitively establish the utilization of germline genes in the Sm system, we produced human-human B cell hybridomas from a patient with SLE who had circulating anti-Sm antibodies. One stable hybridoma designated 4B4 secretes an IgM-kappa mAb that binds Sm and shares idiotypic determinants with other anti-Sm antibodies. A second anti-Sm antibody (3C3), isolated from the same patient was also studied. Oligo(dT) priming was used to produce cDNA corresponding to full length IgM. Sequence analysis revealed that the VH gene segment (1-96) of 4B4 is identical to a VH sequence previously detected in a fetal liver cDNA library by Schroeder and his co-workers as well as a germline VH recently described by Berman and his associates. The identity of a lupus mAb and sequences derived from unrelated individuals provides strong evidence that this autoantibody is a direct copy of a germline gene.