Clustering of mutations in the biotin-binding region of holocarboxylase synthetase in biotin-responsive multiple carboxylase deficiency

Holocarboxylase synthetase (HCS) catalyses the biotinylation of the four biotin-dependent carboxylases found in humans. A deficiency in HCS results in biotin-responsive multiple carboxylase deficiency (MCD). We have identified six different point mutations in the HCS gene in nine patients with MCD. Two of the mutations are frequent among the MCD patients analyzed. Four of the mutations cluster in the putative biotin- binding domain as deduced from the corresponding Escherichia coli enzyme and consistent with an explanation for biotin-responsiveness based on altered affinity for biotin. The two others may define an additional domain involved in biotin-binding or biotin-mediated stabilization of the protein.      

Increased degradation and alteered tissue distribution of cartilage oligomeric matrix protein in human rheumatoid and osteoarthritic cartilage

We investigated the degradation and tissue distribution of cartilage oligomeric matrix protein in normal, osteoarthritic, and rheumatoid arthritic articular cartilage of the human knee. Cartilage was subjected to sequential extractions with buffers containing neutral salt, with EDTA, and finally with guanidine/HCl and then was analyzed by Western blotting with a polyclonal antiserum to human cartilage oligomeric matrix protein. Western blots of the nine neutral salt extracts from normal cartilage revealed mostly intact pentameric molecules of cartilage oligomeric matrix protein, in contrast to the 13 osteoarthritic and five rheumatoid arthritic cartilage samples that demonstrated marked degradation of cartilage oligomeric matrix protein as noted by a predominance of reduction-sensitive bands at approximately 150 kDa and nonreduction-sensitive bands in the 67–94 kDa range. The EDTA and guanidine/HCl extracts from all groups were similar and showed mostly intact molecules of cartilage oligomeric matrix protein, with smaller amounts of degraded cartilage oligomeric matrix protein identical to those resolved by the Western blots of the neutral salt extracts. Western blots of matched pairs of synovial fluid and cartilage extracts demonstrated cartilage oligomeric matrix protein fragments of the same molecular mass. Competitive enzyme-linked immunosorbent assay revealed significantly less cartilage oligomeric matrix protein in rheumatoid articular cartilage than in either normal or osteoarthritic cartilage. In contrast to normal cartilage, where cartilage oligomeric matrix protein was predominately localized to the interterritorial matrix throughout all zones of the matrix, with increased staining in the deeper cartilaginous zones, the most intense staining in osteoarthritic cartilage was in the superficial zones of fibrillated cartilage, with little to no immunostaining in the midzones and relatively poor staining in the deeper cartilaginous zones. This distribution was the inverse of that for proteoglycans, as demonstrated by toluidine blue staining, where proteoglycans were depleted primarily from the superficial fibrillated cartilage. In mild to moderately affected rheumatoid cartilage, the tissue distribution of cartilage oligomeric matrix protein was similar to the distribution of proteoglycans, with relatively uniform staining of the interterritorial and territorial matrices. In more severely affected rheumatoid cartilage, the superficial zones demonstrated punctate immunostaining for cartilage oligomeric matrix protein in the interterritorial and territorial matrices, and staining was restricted to the territorial matrix in the deep cartilaginous zones. It is evident from this study that (a) noncollagenous proteins such as cartilage oligomeric matrix protein are greatly affected in arthritis. (b) degradation fragments released from the matrix into the synovial fluid reflect the processes occurring within the matrix, and (c) different zones of the articular cartilage are susceptible to degradation of cartilage oligomeric matrix protein in the different disease processes.     

Pseudoaneurysms complicating organ transplantation: roles of CT, duplex sonography, and angiography

In a retrospective study of proved pseudoaneurysms (PAs) in 15 patients with transplanted organs (11 liver, three kidney, one pancreas), the results of computed tomography (CT), duplex sonography, and angiography were reviewed. Of the 15 cases of PA, eight occurred at the arterial anastomosis and seven were nonanastomotic. Three of the eight anastomotic PAs were caused by infection. Of the seven nonanastomotic PAs, four were caused by percutaneous biopsy, two were caused by infection, and one was of undetermined cause. In nine (60%) of the 15 patients the PAs were incidentally detected at imaging studies performed for other reasons. Diagnosis requires a high degree of suspicion. CT was performed in nine cases and duplex sonography in ten. The diagnosis of PA was made with CT in six (67%) patients and with duplex sonography in five (50%). CT and duplex sonography could not enable diagnosis when the PA was small, when the arterial anastomosis was not included in the field of study, or when enhancement with intravenously administered contract material was suboptimal. Angiography depicted the PAs in all 15 patients. In three liver transplant recipients with gastrointestinal tract bleeding, the causative PAs were detected only with angiography.     

Spacing of cytochrome oxidase blobs in visual cortex of normal and strabismic monkeys

Some models of visual cortical development are based on the assumption that the tangential organization of V1 is not determined prior to visual experience. In these models, correlated binocular activity is a key element in the formation of visual cortical columns, and when the degree of interocular correlation is reduced the models predict an increase in column spacing. To examine this prediction we measured the spacing of columns, as defined by cytochrome oxidase (CO) blobs, in the visual cortex of monkeys whose binocular vision was either normal or disrupted by a strabismus. The spatial distribution of blobs was examined in seven normal and five strabismic macaques. Tangential sections through the upper layers of the visual cortex were stained to reveal the two-dimensional (2D) pattern of CO blobs. Each blob was localized and their center-to-center spacing, packing arrangement and density were calculated using 2D nearest-neighbor spatial analyses. The mean center-to-center spacing of blobs (590 microm for normally reared and 598 microm for strabismic macaques) and the mean density of blobs (3.67 blobs/mm2 for normally reared and 3.45 blobs/mm2 for strabismic macaques) were not significantly different. In addition, the 2D packing arrangement of the blobs was not affected by strabismus. While it is clear that neural activity plays a key role in the elaboration and refinement of ocular dominance cortical modules, we conclude that it does not determine the spatial period of the pattern of CO blobs. This suggests that aspects of the neural circuitry underlying the columnar architecture of the visual cortex are established prenatally and its fundamental periodicity is not modifiable by experience.