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Biomedical subjects

D D Wu

Publications and source records attributed to D D Wu.

27 records · Page 2Linked to original sources
PubMed1991

Morphologic and morphometric changes in synovial membrane associated with mechanically induced osteoarthrosis.

We sought to determine whether synovial leukocytic inflammation is a primary event in mechanically induced osteoarthrosis. Repetitive impulse loading (50 ms duration at 60 Hz for 40 minutes each day) was applied to the right hindlimbs of 24 New Zealand white rabbits for 3, 6, or 9 weeks. The synovial membrane from the medial suprapatellar area was examined qualitatively using transmission electron microscopy and quantitatively using light microscopic morphometry. The results indicate that synovial inflammation is not a primary event in this mechanically induced osteoarthrosis, but synovial hyperplasia occurs prior to histologically evident cartilage destruction at 6-9 weeks.

Animals↗
PubMed1990

Bone and cartilage changes following experimental varus or valgus tibial angulation.

The purpose of this work was to determine whether subchondral bone changes are an integral part of the development of osteoarthrosis of the knee following experimentally created tibial angulation. Thirty degree varus or valgus proximal tibial osteotomies were created in female New Zealand white rabbits. Bone and cartilage changes were assessed grossly, radiologically, and histologically. Thirty-four weeks following osteotomy, severe cartilage changes, including osteophytes, fibrillation, derangement of cell columns, and cloning, were evident on the overloaded condyle, accompanied by increased subchondral bone density. The pattern of cartilage deterioration was different from that found in other experimental, mechanically induced arthroses. We conclude that osteoarthrosis is a final common pathway for mechanically induced joint failure, and that progressive cartilage change is associated with increased subchondral bone density.

Animals↗
PubMed1990

Regional patterns of bone loss and altered bone remodeling in response to calcium deprivation in laboratory rabbits.

This study explores the effects of a calcium-deficient diet on patterns of bone remodeling, and examines regional differences in the amount of bone lost. Skeletally mature female rabbits (n = 6) were fed a calcium-deficient diet (0.10% Ca2+ and 0.50% P) for 14 weeks. A separate group of rabbits (n = 4) were fed a maintenance diet (1.2% Ca2+ and 0.45% P). Bone mineral content, serum calcium, and serum phosphorus were measured each week during the experimental period. Following sacrifice, the L3 vertebra, femoral head, proximal tibial metaphysis, and tibial midshaft were analyzed histomorphometrically. Rabbits had 20% less vertebral bone after only 14 weeks of a calcium-deficient diet. As in human postmenopausal osteoporosis, bone loss in calcium-deficient rabbits occurs in the trabecular bone of the lumbar spine before that in the trabecular bone of the lower extremity. Calcium-deficient diets alone do not lead to increased osteoid volume or thickness. Because bone loss is relatively rapid and because the pattern of loss is similar in some respects to that found in humans, adult rabbits may provide an attractive model of calcium deficiency osteoporosis in a skeletally mature mammal in which remodeling is predominant over modeling.

Animals↗
PubMed1989

The scid mouse as a model to identify and quantify myeloid and lymphoid stem cells.

Scid mice are excellent recipients for studying the characteristics of stem cells. Sublethal irradiation not only enhances engraftment of stem cells but enables one to graft limiting numbers of cells without compromising the survival of the recipient. This enables one to estimate the frequency of stem cells by limiting dilution analysis. Compared to fresh bone marrow, LTBMC are slightly enriched for stem cells capable of reconstituting lymphoid function in scid recipients. The stem cells have self-renewal ability since bone marrow from cured primary scid recipients can cure secondary recipients. Our results indicate that lymphoid reconstitution following engraftment with LTBMC occurs from a lymphoid-restricted stem cell; similar restricted stem cells also exist in normal bone marrow.

Animals↗
PubMed1989

The effects of altered strain environments on bone tissue kinetics.

This study defines the alteration in bone tissue kinetics responsible for the "adaptive remodeling" response to altered strain environments. Adult beagle dogs were separated into three experimental groups: ulnar osteotomy, ulnar osteotomy with fracture fixation plate spanning the gap and sham surgery. Four sets of double fluorochrome labels were administered. Prior to sacrifice at 1, 3, and 6 months, strains were measured through rosette strain gages on the cranial and caudal surfaces of the intact radius. Histomorphometric analysis indicated that the increased bone mass in response to elevated strain results from increased activation frequency of modeling with more sites undergoing formation processes than resorption processes on periosteal and endocortical surfaces. Increased remodeling activation did not lead to increased bone mass. There was no evidence that elevated strain changes the individual vigor of osteoclasts or osteoblasts, or that the sigma period was altered by elevated strain.

Adaptation, Physiological↗
PubMed1988

The use of pre-operative scan prior to neck exploration for primary hyperparathyroidism.

A group of patients with diagnosed primary hyperparathyroidism (PHP) in Auckland between 1982 and 1986 is reviewed. Of the 119 patients, 55 had pre-operative scanning, 36 had no scanning prior to surgery and 29 were managed conservatively. Of the 52 patients who had pre-operative localization with ultrasound scanning, only 27 (52%) had their adenoma correctly predicted upon neck exploration. Of the 14 patients investigated with thallium-201 and technetium-99m (T1/Tc) subtraction scanning, 10 (71%) had their adenoma positively identified in the predicted locations, whereas the cause of the parathyroid pathology was correctly identified in 33 of the 36 patients (92%) who had surgery alone with no pre-operative scanning. In 11 patients both ultrasound and T1/Tc subtraction scanning were employed. In eight patients the results of the two scanning modalities agreed, and in seven of these eight patients the adenoma was correctly predicted (six single adenomas and one with double adenoma). In the three patients in whom the results of the two modalities differed, the T1/Tc subtraction scanning correctly predicted the site of the adenoma in two patients and in the third patient (with a small 223 mg adenoma) both modalities were incorrect. Of the six patients with histologically proven parathyroid hyperplasia, only three had pre-operative localization with ultrasound alone, and all three had incorrect predictions (one false positive for adenoma, and two false negative scans). Overall the results cast doubt over the usefulness of pre-operative scanning as a routine investigation prior to initial neck exploration for primary hyperparathyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1987

High efficiency gene transfer and expression in normal murine B lymphocytes.

The introduction of new genetic information into hematopoietic cells offers a new approach for investigating the molecular events controlling differentiation. Retrovirus vectors have been used to transfer new genes with high efficiency into murine hematopoietic cells, primarily of the myeloid lineage. In this report, we show that vectors carrying the dominant, selectable gene for neomycin resistance (neo gene) can successfully infect normal murine B lymphocytes (CFU-B). The infected CFU-B formed colonies in vitro in high concentrations (750 micrograms/ml) of G418, a neomycin analogue. That B lymphocytes contained the neo gene was confirmed by the findings that the putative B cell colonies growing in G418 contained antibody-producing cells and that the cells responding to the B cell mitogen, LPS, were resistant to G418. Infection of normal spleen cells with different vectors containing a variety of transcriptional regulatory sequences resulted in 7-40% of the CFU-B becoming G418 resistant. Introduction of the immunoglobulin heavy chain enhancer into NEO vectors appeared to augment the expression of the neo gene, since the level of G418 resistance was higher in B cells infected with a NEO vector containing the enhancer than in cells infected with a vector lacking the enhancer.

Animals↗
PubMedDate not supplied

Bone streaming potentials and currents depend on anatomical structure and loading orientation.

Bone streaming potentials (SPs) and streaming currents (SCs) may be a remodeling signal to cells, and might also be used to probe bone pore structure and fluid flows. For SPs or SCs to serve as either a remodeling signal or as a probe for pore structure, they must depend on bone structure. This study was undertaken to address two related questions. First, will differences in Haversian and laminar bone structure and fluid flow direction produce measurable differences in SP and SC? Second, do differences in SP or SC relate to differences in macroscopic bone impedance or large pore structure? SPs and SCs were measured across Haversian and laminar bone specimens with fluid flow driven in different directions by sinusoidal four-point bending. Data were grouped by bone type and flow direction (Haversian tissue, laminar tissue with radial flow, and laminar tissue with tangential flow) and flow direction alone (tangential and radial). SPs were larger for Haversian tissue and for laminar tissue with radial flow than for laminar tissue with tangential flow. SP and SC magnitude, and impedance were larger for radial than tangential flow. No difference in SC magnitude, SP or SC kinetics, or macroscopic bone impedance was observed between Haversian tissue, laminar tissue with radial flow, and laminar tissue with tangential flow. Thus, since laminar tissue with tangential flow had more vascular connections in the direction of fluid flow, SP was smallest for greatest vascular connectivity. The relation between SP or SC and impedance was inconclusive.

Analysis of Variance↗