Aims: Preliminary studies have suggested that there is an increase in adipocytic tissue in osteoporotic (OP) bone, supporting in vitro evidence for a switch in differentiation of stromal cells from the osteoblastic to the adipocytic lineage. To investigate this the variation of the ratio of adipose tissue to haemopoietic/stromal tissue in OP bone was measured. Methods: The ratio of adipocytic to haemopoietic/stromal tissue (A/H) was measured by semi-automated image analysis in iliac crest biopsies from 127 patients with osteoporosis (84 female patients, 48 male patients; mean age, 55 years; range, 5-80). Fourteen patients with normal histomorphometric data (nine women; five men; mean age, 48 years; range 21-70) acted as controls. Results: The ratio of A/H was higher in OP bone than in the normal controls (OP mean 43.06% v normal mean 22.4%; p < 0.001). Multiple regression analysis showed that 98.5% of the variability in the A/H ratio was the result of age and several measures of bone formation, including cancellous wall thickness, osteoid volume, cancellous thickness, cortical wall thickness, cancellous apposition rate, and bone formation rate, together with cancellous separation (each significant at p < 0.001). Those with the greatest effect on the A/H ratio (in decreasing order) were cancellous apposition rate, osteoid volume, and age. Conclusions: Cancellous apposition rate, osteoid volume, and age were associated with the increase in the proportion of adipose tissue present in OP bone. Of these, cancellous apposition rate reflects osteoblast activity, indicating that the increase in the volume of adipose tissue in osteoporosis is associated with reduced bone formation, supporting the postulated switch in differentiation of stromal cells from the osteoblastic to the adipocytic pathway in osteoporosis.

When compared with other published series, the CD4 and CD8 values in healthy Indians were no different from those reported in the West. These observations have important clinical implications for the use of T-lymphocyte subset measurements in India, especially in the management of HIV infection. The normal ranges established by this study can be used as a reference for decisions made in clinical practice.

The coronavirus nucleocapsid (N) protein is a multifunctional viral gene product that encapsidates the RNA genome and also plays some as yet not fully defined role in viral RNA replication and/or transcription. A number of conserved negatively charged amino acids are located within domain III in the carboxy end of all coronavirus N proteins. Previous studies suggested that the negatively charged residues are involved in virus assembly by mediating interaction between the membrane (M) protein carboxy tail and nucleocapsids. To determine the importance of these negatively charged residues, a series of alanine and other charged-residue substitutions were introduced in place of those in the N gene within a mouse hepatitis coronavirus A59 infectious clone. Aspartic acid residues 440 and 441 were identified as functionally important. Viruses could not be isolated when both residues were replaced by positively charged amino acids. When either amino acid was replaced by a positively charged residue or both were changed to alanine, viruses were recovered that contained second-site changes within N, but not in the M or envelope protein. The compensatory role of the new changes was confirmed by the construction of new viruses. A few viruses were recovered that retained the D 441 -to-arginine change and no compensatory changes. These viruses exhibited a small-plaque phenotype and produced significantly less virus. Overall, results from our analysis of a large panel of plaque-purified recovered viruses indicate that the negatively charged residues at positions 440 and 441 are key residues that appear to be involved in virus assembly.Coronaviruses are enveloped RNA viruses that cause respiratory and enteric infections in humans and many domesticated animals. Members of the family Coronaviridae contain single-stranded, positive-sense genomes that range from approximately 27 to 31 kb in length. The viral genes are expressed through a discontinuous transcription mechanism that yields a nested set of subgenomic RNAs (39). Coronavirus virions contain at least three envelope proteins, membrane (M), spike (S), and envelope (E). The genomic RNA is encapsidated by the nucleocapsid (N) protein as a helical nucleocapsid (10, 26). The S protein is the viral receptor attachment protein that facilitates infection through fusion of viral and cellular membranes and is the major target of neutralizing antibodies during infection (15). The M protein is a major envelope component that plays an important role in virus assembly (11,21,31,33,46). The E protein is a minor component of the viral envelope that also plays a critical role in virus budding. Coexpression of the E and M proteins is sufficient for formation of virus-like particles (3,8,46). Deletion of the E gene from the mouse hepatitis coronavirus (MHV-CoV) genome results in severely crippled virus (23), whereas elimination of expression of the gene in porcine transmissible gastroenteritis coronavirus blocks virus assembly (9, 34). Recently, the severe acute respiratory syndrome coronavi...

The commonly used Cartesian and hybrid local grid refinements have the disadvantage that the base grid is always Cartesian, which makes it difficult to align along reservoir heterogeneities. Also, the locally orthogonal Voronoi and k-orthogonal perpendicular bisector (PEBI) grids are only useful for isotropie or limited anisotropic permeability distributions. The finite-difference approach proposed in this paper overcomes limitations of existing flexible gridding schemes in modeling fuIl, anisotropic and asymmetrie permeability tensors and permeability heterogeneity. The new scheme assumes uniform properties inside control-volumes and it can be used for control volumes formed around vertices of triangles in two-dimensions and tetrahedra in threedimensions. It can thus be used with Voronoi grids in twodimensions, and median (i.e. CVFE) and boundary adapting grids (BAG) in two-and three-dimensions. Applications ofVoronoi grids in three-dimensions are limited due to geometrical considerations. The proposed method can also be used with grids constructed to align along major reservoir heterogeneities, wells and streamlines. Several applications of this method for two-and three-dimensional problems are presented.

Background: This study was designed to flow cytometrically determine baseline and sequential values of CD4 and CD8 lymphocyte subsets in patients without the human immunodeficiency virus and with pulmonary tuberculosis (TB) and to correlate these values with those obtained from normal male blood donors and with the radiologic extent of disease and response to therapy.Methods: We studied 39 male patients without the human immunodeficiency virus and with sputum positive for pulmonary TB who had been admitted to Military Hospital (Cardiothoracic Center) in Pune, India. Clinical, laboratory, and radiologic evaluations of these patients were done. Hematologic parameters were assessed by an automated hematology cell counter (AcT*Diff, Coulter), and T-cell subsets (CD4 and CD8) were determined flow cytometrically (EPICS-XL, Coulter).Results: CD4 counts and percentages of CD4 were significantly lower, but CD8 values were normal, in patients with pulmonary TB when compared with values obtained in normal blood donors. The CD4/CD8 ratio was significantly lower in patients with TB. The CD4 counts normalized with antitubercular treatment. The radiologic extent of disease did not correlate well with the immune parameters studied.Conclusions: TB is a reversible cause of CD4 lymphocytopenia and is associated with normal numbers of CD8 cells. The radiologic extent of disease does not seem to determine the immune response.