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Samoyed hereditary glomerulopathy (SHG) is an X-linked dominant disease characterized by proteinuria and renal failure in affected male dogs. Electron microscopic examination of glomerular capillary basement membranes (GCBM) shows widespread multilaminar splitting of the lamina densa, identical to that in Alport's syndrome. Anionic sites in GCBM of three affected males and five unaffected dogs were labeled using polyethyleneimine to determine whether proteinuria was associated with an alteration in their number. No significant differences were noted in the number of anionic sites in the lamina rara externa, whereas small but statistically significant increases were seen in the number of sites in the lamina rara interna of affected males. In the lamina densa, affected males showed a striking increase in anionic sites, particularly in regions of GCBM which were split. Thus, although proteinuria in some glomerular diseases has been attributed to a reduction in anionic sites in GCBM, this was not so in SHG.

Samoyed hereditary glomerulopathy (SHG) in dogs has been employed as a model for human hereditary nephritis (HN), since affected dogs and patients show splitting of glomerular capillary basement membranes by electron microscopy (EM) and absent staining of glomerular capillaries for Goodpasture antigen (GPA) by immunofluorescence (IF). EM and IF were used to examine basement membranes (BM) in skin, lung, choroid plexus, lens, retina, and inner ear in SHG. By EM, BM in these tissues appeared similar in affected male, carrier female, and unaffected dogs. By IF, GPA could be detected only in lens capsule, internal limiting membrane of retina and basilar membrane of inner ear of unaffected and carrier female dogs, but not in affected male dogs. However, eye abnormalities and hearing loss were not present in any dogs, in contrast to their frequent occurrence in human HN. Our findings on extra-renal BM in SHG suggest that GPA is not required to maintain normal vision or hearing in affected male dogs and permit a greater understanding of the pathogenesis of human HN.

Functional proteins coded by genes 46 and 47 are required for (i) continuation of deoxyribonucleic acid (DNA) synthesis in the late period of T4 infection and (ii) production of normal, late replicating DNA which contains strands with a sedimentation coefficient in alkaline sucrose greater than that of mature DNA (73S). Continued DNA synthesis in the late period in the absence of functional genes 46 or 47 can be achieved by inhibiting late protein synthesis either by using bacterio-phage with a second mutation in gene 55 or by adding chloramphenicol to the culture before the decline in the rate of DNA synthesis. However, when functional 46/47 proteins are absent throughout infection, no strands with a sedimentation coefficient greater than 73S(in alkaline sucrose) are produced. This is the case even when DNA synthesis is allowed to continue. DNA arrest is accompanied by conversion of rapidly sedimenting, replicating DNA to slower sedimenting forms. When 46/47 is absent from the beginning of infection, the conversion product has a smaller sedimentation coefficient than mature DNA both in neutral and alkaline sucrose. When DNA arrest occurs midway in infection by heat-inactivating the ts46 enzyme, the conversion product has a sedimentation coefficient (i) the same as mature DNA in both neutral (63S) and alkaline sucrose if capsid assembly is allowed to take place and (ii) close to 63Sin neutral sucrose but heterogenous and relatively greater (up to 100S) in alkaline sucrose if capsid assembly is inhibited. The structure of this DNA is unknown.