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Biomedical subjects

H Bohr

Publications and source records attributed to H Bohr.

At least 37 records · Page 2Linked to original sources
PubMed1990

Analysis of the secondary structure of the human immunodeficiency virus (HIV) proteins p17, gp120, and gp41 by computer modeling based on neural network methods.

A neural network computer program, trained to predict secondary structure of proteins by exposing it to matching sets of primary and secondary structures from a database, was used to analyze the human immunodeficiency virus (HIV) proteins p17, gp120, and gp41 from their amino acid sequences. The results are compared to those obtained by the Chou-Fasman analysis. Two alpha-helical sequences corresponding to the putative fusigenic domain and to the transmembrane domain of gp41 could be predicted, as well as a possible binding site between p17 and gp41. On the basis of the secondary structure predictions, a three-dimensional model of p17 was constructed. This model was found to represent a stable conformation by an analysis using an energy-minimization program. The model predicts that p17 is attached to the membrane only by the acylated N-terminus, in analogy with the N-terminus of the gag protein of other retroviruses and also with the src oncogene protein p60src. The intracellular C-terminal part of gp41 may act as a receptor by electrostatic interaction with p17.

Algorithms↗
PubMed1988

Protein secondary structure and homology by neural networks. The alpha-helices in rhodopsin.

Neural networks provide a basis for semiempirical studies of pattern matching between the primary and secondary structures of proteins. Networks of the perceptron class have been trained to classify the amino-acid residues into two categories for each of three types of secondary feature: alpha-helix or not, beta-sheet or not, and random coil or not. The explicit prediction for the helices in rhodopsin is compared with both electron microscopy results and those of the Chou-Fasman method. A new measure of homology between proteins is provided by the network approach, which thereby leads to quantification of the differences between the primary structures of proteins.

Amino Acid Sequence↗
PubMed1988

Different trends of age-related diminution of bone mineral content in the lumbar spine, femoral neck, and femoral shaft in women.

The bone mineral content (BMC) was measured by dual photon absorptiometry of 153Gd simultaneously in the lumbar spine, femoral neck, and femoral shaft in a cross-sectional study of 113 healthy women aged 20-89 years. The measurements suggest differences in the patterns of bone mineral decrease at the three sites of the skeleton in relation to age. The lumbar spine BMC decreases mainly during the usual time of menopause, whereas BMC decreases linearly in the femoral neck from young adulthood to old age. The femoral shaft BMC is nearly unaltered until the seventh decade, and thereafter BMC declines significantly. In each of the three age groups selected according to the usual time for menopause there was significant correlations between BMC of the scanning sites and nearly identical variance of BMC with age, suggesting homogeneity in the female population with regard to rate of bone diminution.

Adult↗
PubMed1988

Bone mineral content of the lumbar spine and lower extremities years after spinal cord lesion.

Bone mineral content (BMC) was measured by dual photon absorptiometry in the lumbar spine, femoral neck and shaft, and proximal tibia in 26 individuals with spinal cord lesions sustained 2 to 25 years previously. In average BMC of the lumbar spine was within the range of normal values. BMC of the femoral neck and shaft was in average 25% lower than the normal values, and for the proximal tibia more than 50% lower than the normal value. Participants with cervical lesions had lower BMC values in the femoral bones than those with thoracic lesions. Neither presence of spasticity nor daily use of long leg braces influenced the BMC significantly. Participants with previous lower extremity fractures had lower BMC values in the long bones compared with participants without fractures. The preservation of the BMC of the lumbar spine may be due to maintenance of load on the spine while sitting in a wheelchair.

Adolescent↗
PubMed1985

Bone mineral content of the femoral neck and shaft: relation between cortical and trabecular bone.

Bone mineral content (BMC) of the femoral neck and shaft was determined with dual photon absorptiometry, using 153Gd. Comparison of BMC with the amount of hydroxyapatite (HA) of in vitro specimen showed correlation coefficients of 0.992 and 0.996 for the femoral neck and shaft respectively. In the femoral neck the amount of cortical bone in a bone section varies from 16% ash weight in the proximal part to 71% in the distal part. Corresponding to the site of BMC measurements, the cortical bone constitutes 57% in the femoral neck and 95% in the femoral shaft. The precision error of measurements of BMC in vivo, expressed as the coefficient of variation for repeated determinations, was 1.4% for the femoral neck and 1.3% for the femoral shaft. In the femoral neck it is possible to distinguish between structures consisting mainly of cortical bone and structures containing mostly trabecular bone. While the cortical bone value decreases only slowly with age in normal women, corresponding to BMC of the femoral shaft, the trabecular bone value decreases rapidly even compared with BMC of the femoral neck. Despite the significant correlation between the values for cortical and trabecular bone a distinction seems essential from a clinical point of view.

Adult↗
PubMed1983

Bone mineral content of femoral bone and the lumbar spine measured in women with fracture of the femoral neck by dual photon absorptiometry.

The bone mineral content (BMC) in the lumbar spine, femoral neck, and femoral shaft in 46 women ranging in age from 60 to 89 years with fractures of the femoral neck was measured by dual photon absorptiometry and compared with that of 38 healthy women in the same age group. For BMC of the lumbar spine and femoral neck there was no significant difference between the fracture group and the control group, whereas BMC of the femoral shaft was significantly reduced in the fracture group. No significant difference was found between BMC values for the 18 transcervical and 28 pertrochanteric fractures. Radiographic evidence of osteoporosis with compression fractures of vertebrae could be demonstrated in ten of the patients with femoral neck fractures. There was a significant correlation between BMC of the axial and peripheral skeleton in the patients with fractures. The Singh Index was significantly correlated with BMC of the lumbar spine but not with that of the femoral neck or shaft. It is concluded that the high incidence of femoral neck fracture with increasing age might be explained in part by a reduction in BMC, primarily cortical bone mineral, but it is likely that other factors that reduce the strength of bone or increase the tendency in older persons to fall are also of importance.

Aged↗
PubMed1976

Experimental osteoarthritis in the rabbit knee joint.

The development of arthrotic-like changes following the resection of the cruciate ligaments in the knee joint of rabbits has been studied at intervals from 2 weeks to 10 months in 35 animals. Signs of cartilage degeneration were followed by changes in the subchondral bone, where formation of osteophytes and condensation took place. An increased vascular supply was demonstrated by microangiographic and scintigraphic investigations. The uptake of 18F and 99mTc-polyphosphate reached a maximal value about 2 months after the operation and then diminished despite further development of arthrotic changes.

Animals↗
PubMed1976

Comparison of 18F and 99mTc-polyphosphate in orthopedic bone scintigraphy.

To compare 99mTc-polyphosphate and 18F for use in orthopedics, 79 patients were examined with both. Fifty cases were suitable for analysis. While the extraskeletal uptake of 18F was found to be negligible, 99mTc-polyphosphate may accumulate considerably in pathologic soft tissue, e.g., in soft-tissue tumors and in inflamed synovial tissue. This soft-tissue Tc accumulation may obscure the osseus uptake, notably in the examination of joint regions, commonly the regions of interest in orthopedics. After simultaneous administration of both agents, quantitative measurements were performed on specimens of bone and synovial tissue from diseased joints in human patients and in rabbits. The uptake of 99mTc-polyphosphate in synovial tissue was shown to be about seven times that of 18F, while their uptakes in bone were equal. In short, 99mTc-polyphosphate, a valuable tracer in general, is hardly the agent of choice in orthopedics.

Adult↗