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Biomedical subjects

J Duke

Publications and source records attributed to J Duke.

At least 19 recordsLinked to original sources
PubMed2003

Apoptosis staining in cultured pseudoachondroplasia chondrocytes.

Pseudoachondroplasia (PSACH) is a skeletal dysplasia caused by a mutation in cartilage oligomeric matrix protein (COMP), a glycoprotein of normal cartilage matrix. PSACH chondrocytes have a distinctive phenotype with enlarged rER cisternae containing COMP, aggrecan, type IX collagen, and chaperone proteins. Ultrastructural studies suggested that this accumulation compromises cell function, hastening cell death, and consequently reducing the number of cells in the growth plate contributing to linear bone growth. Using the alginate bead system, we cultured control and PSACH chondrocytes for twenty weeks and one year to determine the effect of the mutation on size and number of cartilage nodules; and the presence of apoptotic cell death (TUNEL assay). At 20 weeks, beads containing PSACH or control chondrocytes did not differ in size and number of cartilage nodules or number of TUNEL-positive cells. After one year, nodule number, size and percent cartilage per bead were significantly less in PSACH nodules, and the number of cells staining positive for apoptosis was significantly greater than in controls (71.8% vs. 44.6%). The increase in apoptosis in PSACH nodules correlates with a decrease in growth of cartilage, supporting our hypothesis that death of damaged cells contributes to the growth plate defects in PSACH.

Achondroplasia↗
PubMed2002

Analysis of thirteen populations of black cohosh for formononetin.

Black cohosh (Actaea racemosa L. syn. Cimicifuga racemosa (L.) Nutt.), a North American perennial plant, is a promising natural alternative to hormone replacement therapy for treating menopausal symptoms, but the mechanism of action is not understood. The clinical actions of this plant have been attributed to the isoflavonone formononetin since 1985, when its presence was reported in a black cohosh extract. Others have since looked for formononetin, but have not detected it. We looked for formononetin in extracts of black cohosh roots and rhizomes collected in thirteen locations in the eastern United States, including Maryland, New Jersey, New York, North Carolina, Pennsylvania, Virginia, and Tennessee. The rhizome samples were extracted using 80% methanol, and the extracts were partially purified using solid-phase extraction to concentrate any isoflavonoids that might be present. We tested for formononetin in these partially purified samples using thin-layer chromatography and high-performance liquid chromatography with a photodiode array detector and a mass spectrometer. Formononetin was not detected in any of the thirteen plant populations examined. Remifemin, a German product now on the United States market, and CimiPure, a commercially available black cohosh rhizome extract, were also analyzed. We did not detect formononetin, or ononin (formononetin-7-glucoside), in any sample tested by the above-mentioned chemical analyses. Therefore, the clinically observed estrogen-like actions of black cohosh, such as reduction of hot flashes, are likely due to a compound, or combination of compounds, other than formononetin.

Chromatography, High Pressure Liquid↗
PubMed1999

Crystallization and preliminary X-ray diffraction data of the complex of recombinant tick anticoagulant peptide (rTAP) and bovine factor Xa.

The complex of bovine factor Xa and recombinant tick anticoagulant peptide (rTAP) was crystallized in two different crystal forms using polyethylene glycol as a precipitant. Form I belongs to space group P42212 with unit-cell dimensions a = b = 133.1, c = 68.8 A. It contains one complex per asymmetric unit and diffracts to 3.0 A resolution. Form II belongs to P41212 (or P43212) with dimensions a = b = 126.5, c = 146.7 A; it contains two complexes per asymmetric unit and diffracts to 2.5 A. The crystals of both forms consist of factor Xa (MW = 45.3 kDa) and rTAP (MW = 6.7 kDa).

Animals↗
PubMed1998

Unexpected binding mode of tick anticoagulant peptide complexed to bovine factor Xa.

The structure of recombinant tick anticoagulant peptide (rTAP) complexed to bovine factor Xa at 3.0 A resolution reveals the structural basis for the specificity and the high affinity of rTAP. Three N-terminal residues, Tyr501, Asn502 and Arg503, play a critical role in the complex formation as suggested by earlier mutagenic studies and the ornithodorin-thrombin complex. Unexpectedly, the side-chain of Tyr501 is located in the S1 pocket, although factor Xa favors arginine as a P1 residue. Arg503 is located at the aryl binding pocket and forms a salt-bridge with Glu97 of factor Xa. The autolysis loop, which is disordered in the uninhibited factor Xa structure, is involved in the formation of the complex as a part of the secondary binding site. The C-terminal helix of rTAP interacts with factor Xa as a secondary binding determinant. The N-terminal residues of rTAP reorganize during the formation of the factor Xa-rTAP complex from the conformation found in the solution into an extended conformation. The presence of the secondary binding site confirms the proposed two-step kinetic mechanism based on the results of a mutagenesis study.

Animals↗
PubMed1996

Chondrogenesis in aggregates of embryonic limb cells grown in a rotating wall vessel.

Previous studies in this lab have shown that chondrogenesis is affected in growth plates of rats exposed to microgravity, and in micromass cultures of embryonic limb mesenchyme differentiating in space. In order to provide a three dimensional aspect not seen in the micromass system, and a tissue homogeneity not possible with explants of limb or limb elements, and to alleviate certain difficulties regarding crew time and stowage, we began culturing embryonic limb cells in Rotating Wall Vessels (RWV). First, these cells were attached to beads, and grown for up to 65 days in a type of RWV known as STLV at the Johnson Space Center. During this time, the cells and beads aggregated and the aggregates continued to increase in size, and differentiated into Alcian blue staining chondrocytes. Because our intent was to use these aggregates for implanting into bony defects in addition to their use in studies of chondrogenic regulation at 1g and microgravity, aggregates of these cells without beads were grown in the commercially available version of the STLV, and their ability to ossify when subcutaneously implanted assessed.

Animals↗
PubMed1995

Clinorotation inhibits chondrogenesis in micromass cultures of embryonic mouse limb cells.

Studies of the response of mammalian chondrocytes to gravitational changes in vivo, in organ culture, and in cell culture show that chondrogenesis is reduced in microgravity or by unloading, and increased by low levels of excess g. To investigate the cellular responses to microgravity using a ground based model, micromass cultures were exposed to simulated weightlessness on two clinostats. For rotation on the large clinostat, cultures were set up in Rose chambers, and cells were videotaped and photographed at several time periods after rotation began. For the smaller clinostat, cultures were set up in T-flasks, and two axes of rotation for clinostated cultures were used. Stationary controls [+1 g, -1 g (upside-down), and sideways] as well as rotation controls were employed. Rotation rate was 30 rpm for both clinostatted cultures and rotation controls. Chondrocyte differentiation was assessed by cartilage specific alcian blue staining. Significantly fewer alcian blue stained nodules were present in clinostatted cultures than in stationary controls or rotation controls. Nodules that did not stain with alcian blue, probably due to unsulfated matrix were present in all cultures. The number of nodules in sideways controls was greater than in any other culture (108% of +1 g controls), probably due to ongoing stimulus of the cell via cytoskeletal components. The results show that chondrocytes in culture respond to changes in the gravity vector in a predictable manner, and that carefully controlled clinostat studies can be useful adjuncts to and predictors for spaceflight experiments.

Animals↗
PubMed1994

Pregnancy and cirrhosis: management of hematemesis by Warren shunt during third trimester gestation.

Considerable pathophysiologic changes accompany cirrhosis. Elevation of portal venous pressure predisposes to esophageal varices and hematemesis. The physiologic changes associated with pregnancy may exacerbate these conditions. Medical management of cirrhosis-associated problems may fail, necessitating surgical intervention. The anesthetic management of a pregnant cirrhotic patient for a Warren shunt is complicated by concerns for pre-existing hepatic dysfunction and pregnancy-induced physiologic changes as well as fetal well-being. The management of such a case is reviewed and relevant pathophysiology discussed.

Journal Article↗
PubMed1992

Elbow flexion test in the normal population.

The elbow flexion test was investigated in 204 elbows in 102 normal volunteers. The effects of various wrist and shoulder positions were also studied. In 20 elbows in 15 persons (10%) flexion tests were positive with the wrist and shoulder in neutral position. In 27 elbows in 20 persons (13%) tests were positive with wrist extension and shoulder abduction.

Adolescent↗
PubMed1991

Fibrochondrogenesis in male twins at 24 weeks gestation.

Fibrochondrogenesis is a rare lethal chondrodysplasia. Only 5 cases have been reported. We report on a pair of affected twins diagnosed at 24 weeks of gestation. Occurrence in sibs and consanguinity in the parents in a previous report support autosomal recessive transmission.

Alkaline Phosphatase↗
PubMed1991

Vasoactive intestinal peptide and nerve regeneration.

The role of vasoactive intestinal peptide (V.I.P.) in nerve regeneration was investigated by assessing the changes in immunoreactive V.I.P. levels in rat sciatic nerves following injury and repair. 60 rats were divided into three surgical groups and one control group: In group I (primary repair), sciatic nerves were divided and immediately repaired; in group II (secondary repair), sciatic nerves were divided and repaired two weeks later; in group III (no repair), sciatic nerves were divided and not repaired; and in group IV (controls), sciatic nerves were exposed but not divided. Animals were sacrificed at three days and at weekly intervals. Their sciatic nerves were extracted and assayed for V.I.P. concentrations by a specific radioimmunoassay. The mean V.I.P. concentration varied between 22 and 46 pg./mg. protein in the control nerves and between 60 and 529 pg./mg. protein in all other groups. In the three surgical groups the levels were significantly higher in proximal than in distal stumps. Following nerve injury, there was an increase in V.I.P. concentration in the injured and repaired areas. This increase was greater in injured non-repaired areas and was highest in the first 48 hours, but continued during regeneration. The accumulation of V.I.P. in divided nerves occurred in response to nerve injury.

Animals↗
PubMed1991

Using comparative clinical information to understand practice patterns and affect organizational change.

The University Hospital Consortium is collecting clinical, administrative and financial data from its members to develop a Clinical Information Network. The value of this collective data lies in how comparative information about peer hospitals and physicians in the same specialty can be used to influence practice. The raw data from each hospital is analyzed, classified, normalized and stored in a data repository which is easily accessible. This data becomes information when it is presented in a variety of ways, and is supported by a knowledge-base of health care rules. The "drilling down" technique to progressive levels of detail serves the needs of all levels in the organization--executives, managers, and analysts. The system combines the power of a mainframe for the data repository with the ease of use of a PC-based workstation. With an open-ended approach, the users can ask a variety of questions of the data, as well as perform statistical analysis, create graphical presentations and generate explanations of the analysis techniques.

Artificial Intelligence↗
PubMed1988

Effect of chronic centrifugation on mouse breeding pairs and their offspring.

Fetuses of chronically centrifuged mice are smaller than 1g fetuses, and have reduced areas of long bone ossification. Fewer pregnancies occurred in centrifuged mice. In this study, exposure of chronically centrifuged females to male bedding 48 hours prior to mating induced estrus as determined by vaginal smears. Females were paired with males on the centrifuge or at 1g, and were sacrificed at 18 days gestation. Fetuses were weighed, measured, and stained with alizarin red and methylene blue. This new mating method increased centrifuge pregnancies, but not to control levels. There were no pregnancies at 3.5 g. Weights and crown rump lengths of centrifuged 18-day fetuses were less than those of controls, significantly so at 2.6 and 2.9g. There was no effect on litter size, number of resorptions per litter or male/female ratio. Bones of centrifuged fetuses were found to be smaller and shaped differently from controls. Effects were mitigated by matings with 1g males. Results confirm our previous reports of decreased fetal size and areas of ossification in hypergravity, and demonstrate a reliable method for providing timed-pregnant mice in hyper-g conditions.

Animals↗
PubMed1985

SEM visualization of glycosylated surface molecules using lectin-coated microspheres.

There are several techniques currently used to localize glycosylated surface molecules by scanning electron microscopy (Grinnell, 1980; Molday, 1976; Linthicum and Sell, 1975; Nicolson, 1974; Lo Buglio, et al, 1972). A simple and rapid method, using a modification of Grinnell's technique is reported here. Essentially, microspheres coated with Concavalin A are used to bind to glycosylated regions of the palatal shelf epithelium and are visualized in the scanning electron microscope (SEM).

Animals↗