Biomedical subjects

G J King

Publications and source records attributed to G J King.

At least 19 recordsLinked to original sources

PubMed2003

Effect of distraction rate and consolidation period on bone density following mandibular osteodistraction in rats.

The high cost of large animal protocols has limited the study of distraction osteogenesis (DO) in the craniofacial region. This study was designed to characterise a rat model for DO with regard to distraction rate and consolidation period. Unilateral mandibular distraction was performed on 129 male Sprague-Dawley rats using an osteotomy from the sigmoid notch to the inferior border of mandible. After a 3-day latency, 12 groups of 8-9 rats underwent distraction for 5 days at four different rates (0, 0.2, 0.4, 0.6mm per day), with three different post-osteotomy sacrifice times (10, 24, and 38 days) and four final predicted distraction lengths (0, 1, 2, and 3mm). Another four groups of rats (N=8 per group) were sacrificed 6 days post-osteotomy, resulting in distraction for 3 days with a predicted distraction length of 0, 0.6, 1.2, 1.8mm. Changes in mandibular morphology were measured from radiographs of disarticluated hemimandibles. The bone density of the regenerate and control sites was measured using microdensitometry calibrated with an epoxy stepwedge. Distraction linearly increased mandibular length, distraction gap width and the area of the distraction gap (P<0.00005). Mandibular length increased by 0.394 mm per distraction rate. Gap width and area increased by 0.67 and 5.8mm(2) per distraction rate, respectively. The increase in length represents only 39.4% of what was predicted, suggesting that compensatory alteration in condylar or mandibular morphology may have occurred. This speculation was further supported by the finding that mandibular length, measured without the condylar landmark, was 53.8% of predicted. During DO and early consolidation, the measures of bone density in the regenerates decreased compared to control for all groups. Thereafter, bone density in the regenerates generally increased in all groups until day 24 (P<0.01), obtaining levels that were comparable to the unoperated side. At both rostral and caudal sites adjacent to the osteotomies, measures of bone density were enhanced over control in all groups, with the rostral site also showing significant increases over time in the sham and the highest distraction groups (P<0.008 and P<0.014). We conclude that this rat model for mandibular distraction osteogenesis provides bone density changes that are consistent with those reported using larger animal protocols.

Analysis of Variance↗

PubMed2002

A set of simple-sequence repeat (SSR) markers covering the Prunus genome.

A set of 109 microsatellite primer pairs recently developed for peach and cherry have been studied in the almond x peach F(2) progeny previously used to construct a saturated Prunus map containing mainly restriction fragment length polymorphism markers. All but one gave amplification products, and 87 (80%) segregated in the progeny and detected 96 loci. The resulting Prunus map contains a total of 342 markers covering a total distance of 522 cM. The approximate position of nine additional simple sequence repeats (SSRs) was established by comparison with other almond and peach maps. SSRs were placed in all the eight linkage groups of this map, and their distribution was relatively even, providing a genome-wide coverage with an average density of 5.4 cM/SSR. Twenty-four single-locus SSRs, highly polymorphic in peach, and each falling within 24 evenly spaced approximately 25-cM regions covering the whole Prunus genome, are proposed as a 'genotyping set' useful as a reference for fingerprinting, pedigree and genetic analysis of this species.

Chromosome Mapping↗

PubMed2002

A longitudinal evaluation of pulpal pain during orthodontic tooth movement.

OBJECTIVES: To examine the longitudinal changes in pulpal sensitivity to electrical stimulation and the relationship to pulpal sensitivity as measured by electrical stimulation and subjective reports of tooth pain after archwire insertion. DESIGN: Non-randomized, prospective trial, with matched controls. SETTING AND SAMPLE POPULATION: Regional Clinical Dental Research Center at the University of Washington School of Dentistry. Eighteen adult subjects of age 13-37 years. Nine experimental subjects planned for orthodontic treatment. Nine control subjects matched for gender and age who did not have orthodontic treatment. EXPERIMENTAL VARIABLE: Fixed orthodontic appliances and initial archwire placement in experimental subjects compared with 'no treatment' control subjects. OUTCOME MEASURE: Subjective assessments of orthodontic tooth pain were made using visual analogue scales. Electrically evoked detection and pain thresholds were determined using a computer-controlled tooth stimulator. Data were gathered at five time points: after bracket placement (baseline), 1 h after placement of initial archwires, 1 day after archwire placement, 1 week after archwire placement, and 1 month after archwire placement. Comparable time intervals were used for the 'no treatment' control subjects. RESULTS: Subjective ratings of treatment-evoked tooth pain in the experimental group were the greatest at the post-archwire day 1 observation and progressively decreased for the remaining observations. Control subjects reported little pain at any of these observation times. The detection and pain threshold changes from baseline showed no statistical differences over time or between groups. While not statistically significant, a trend was noted where reports of greater orthodontic tooth pain were associated with increased sensitivity to electrical stimulation (i.e. lower detection and pain thresholds). CONCLUSION: Orthodontic patients experience significant pain and discomfort 1 day after initial archwire placement (i.e. activation). Future research should investigate whether self-reports of treatment-evoked tooth pain intensity are associated with pulpal sensitivity.

Adolescent↗

PubMed2002

Ultrastructural observations on the platelets of the Arabian tahr (Hemitragus jayakari).

The ultrastructure of platelets was studied in specimens of peripheral blood from 18 healthy adult Arabian tahrs (Hemitragus jayakari). The platelets were characterized by their extreme polymorphism. The number of alpha granules, typically one to six per cell, was considerably less than that reported for most animal platelets. Similar to humans, the platelets of the Arabian tahr had nucleoids within the alpha granules. However, nucleoids were not a consistent finding. One or more electron-dense granules, most commonly contained within clear vesicles, was commonly observed. A unique feature was the lack of an open canalicular system, which is considered a hallmark feature of this cell type in most mammalian and reptilian platelets.

Animals↗

PubMed2002

Ultrastructural changes in caprine lungs infected with Mycoplasma capricolum subspecies capripneumonia.

Ultrastructural examination of the lungs from goats with natural infections with Mycoplasma capricolum subspecies capripneumonia, the causative agent of contagious caprine pleuropneumonia, revealed extensive hyperplasia of type II pneumocytes. Typically, these type II cells contained abundant numbers of osmiophilic lamellar bodies that had lost most of their characteristic lamellar ultrastructure. These findings were absent in healthy control goats.

Animals↗

PubMed2001

Chrysanthemyl diphosphate synthase: isolation of the gene and characterization of the recombinant non-head-to-tail monoterpene synthase from Chrysanthemum cinerariaefolium.

Chrysanthemyl diphosphate synthase (CPPase) catalyzes the condensation of two molecules of dimethylallyl diphosphate to produce chrysanthemyl diphosphate (CPP), a monoterpene with a non-head-to-tail or irregular c1'-2-3 linkage between isoprenoid units. Irregular monoterpenes are common in Chrysanthemum cinerariaefolium and related members of the Asteraceae family. In C. cinerariaefolium, CPP is an intermediate in the biosynthesis of the pyrethrin ester insecticides. CPPase was purified from immature chrysanthemum flowers, and the N terminus of the protein was sequenced. A C. cinerariaefolium lambda cDNA library was screened by using degenerate oligonucleotide probes based on the amino acid sequence to identify a CPPase clone that encoded a 45-kDa preprotein. The first 50 aa of the ORF constitute a putative plastidial targeting sequence. Recombinant CPPase bearing an N-terminal polyhistidine affinity tag in place of the targeting sequence was purified to homogeneity from an overproducing Escherichia coli strain by Ni(2+) chromatography. Incubation of recombinant CPPase with dimethylallyl diphosphate produced CPP. The diphosphate ester was hydrolyzed by alkaline phosphatase, and the resulting monoterpene alcohol was analyzed by GC/MS to confirm its structure. The amino acid sequence of CPPase aligns closely with that of the chain elongation prenyltransferase farnesyl diphosphate synthase rather than squalene synthase or phytoene synthase, which catalyze c1'-2-3 cyclopropanation reactions similar to the CPPase reaction.

Amino Acid Sequence↗

PubMed2001

Simulated active control produces repeatable motion pathways of the elbow in an in vitro testing system.

The purpose of this study was to determine if the repeatability and pattern of elbow kinematics are affected by changing the relative magnitudes of loads applied to muscles around the elbow in vitro. In eight cadaveric upper extremities, passive and three methods of simulated active elbow flexion were tested with the forearm maintained in both pronation and supination. Passive flexion involved moving the elbow manually through a full arc of motion. Simulated active flexion used a custom designed loading system to generate elbow motion by applying loads to various tendons via pneumatic actuators. Three different simulated active loading protocols, with loading ratios based on muscle activity and physiologic cross-sectional area, were tested. Testing was performed initially on an intact elbow, and then an unstable elbow model created by transection of the lateral collateral ligament (i.e. the radial and lateral ulnar collateral ligaments). An electromagnetic tracking device was used to measure rotation of the ulna relative to the humerus. Varus-valgus angulation and internal-external rotation were less repeatable during passive flexion than simulated active flexion, regardless of the loading ratio used, in both the intact (p<0.05) and unstable (p<0.05) elbows. Throughout the arc of flexion, the motion pathways were similar for the three simulated active motion protocols employed in this study (p>0.05). The pathways followed during passive motion were different from those generated with simulated active motion, especially in the unstable elbow with the forearm supinated (p<0.001). These results suggest that using simulated active motion rather than manual passive motion can improve the repeatability of elbow kinematics generated in the laboratory, and that a wide range of muscle loading ratios may produce similar kinematic output.

Aged↗

PubMed2001

Treatment of instability after total elbow arthroplasty.

Instability after total elbow arthroplasty can be due to incorrect component selection or position, inadequacy of the medial or lateral ligaments or triceps tendon, polyethylene wear, limb malalignment, or trauma. Patients with significant loss of bone structure, ligament deficiency, and tendon deficiency around the elbow are at increased risk of instability following total elbow arthroplasty.

Arthroplasty, Replacement↗

PubMed2001

Heterotopic ossification following elbow arthroscopy.

With advances in technique and skills, the indications for elbow arthroscopy continue to expand. The authors report a case of heterotopic ossification following arthroscopic debridement of the elbow. Surgeons need to be aware of this potential complication of elbow arthroscopy.

Arthroscopy↗

PubMed2001

The radioulnar ratio: a new method of quantifying distal radioulnar joint subluxation.

Computed tomography was used to image the distal radioulnar joint (DRUJ) for instability. Four methods were used to quantify subluxation of the DRUJ: the Mino criteria, the epicenter method, the congruency method, and a new method called the radioulnar ratio (RUR). Validity of the various methods was evaluated in clinical and laboratory situations. Rheumatoid patients with symptomatic DRUJ pathology had significantly more abnormal RUR values (100% vs 73% [epicenter method] and 88% [Mino criteria]). The RUR detected instability sooner in a progressive laboratory-induced instability model. The intraobserver and interobserver reliability of the RUR was high, with intraclass correlation coefficients of 0.89 and 0.87, respectively. The RUR demonstrated superior performance in the diagnosis of DRUJ subluxation.

Adult↗

PubMed2001

Ilizarov hybrid external fixation for fractures of the distal radius: Part I. Feasibility of transfixion wire placement.

The advantages of Ilizarov external fixation, allowing early motion of adjacent joints during fixation of periarticular fractures, have not yet been applied to distal radius fractures. A magnetic resonance imaging study of 10 normal volunteers evaluated the safety of passing percutaneous transfixion pins across the distal radius in 3 forearm positions. Even in the optimal forearm position, the safe zones between the transfixion pin, vessel, nerve, or tendon was small, suggesting that open placement would be required. A cadaver study in 8 specimens demonstrated that the pins could be placed with an open technique using an aiming device and that the pins could be placed without limiting forearm rotation. The proximity of vital structures to transfixion pins dictates open placement to safely apply Ilizarov fixation to distal radius fractures.

Adult↗

PubMed2001

Ilizarov hybrid external fixation for fractures of the distal radius: Part II. Internal fixation versus Ilizarov hybrid external fixation: Stability as assessed by cadaveric simulated motion testing.

The in vitro stability of an Ilizarov hybrid external fixator was compared with that of a dorsal 3.5-mm AO T-plate in 8 unpaired, fresh-frozen upper extremities. A specially designed testing device that used computer-controlled pneumatic actuators was used to simulate active finger, wrist, and forearm motions by applying loads to relevant tendons. A comminuted extra-articular distal radius fracture was modelled using a dorsally based wedge osteotomy. Fracture stability was assessed using an electromagnetic tracking device to measure motion across the fracture site after randomized application of the plate and the hybrid fixator. During simulated finger and wrist motions with the forearm pronated or supinated, motion of the distal fragment with the hybrid fixator applied was comparable to or statistically less than with the AO plate applied. During simulated forearm rotation, the stability provided by the 2 fixation types was similar, although the plate allowed statistically less radial-ulnar deviation of the fragment. In this model of a 2-part extra-articular distal radius fracture, the clinically meaningful stability of the Ilizarov hybrid external fixator was comparable to that of the dorsal AO plate.

Aged↗

PubMed2001

The effect of flexor tendon repair bulk on tendon gliding during simulated active motion: an in vitro comparison of two-strand and six-strand techniques.

The gliding function of 2-strand (Tajima) and 6-strand (Savage) techniques of flexor tendon repair were compared in an in vitro biomechanical model. Stainless steel beads were inserted directly into the metacarpals, phalanges, and flexor digitorum profundus tendons of 22 human cadaver specimens. The FDP tendons were loaded from 5 to 25 N using a pneumatic actuator. The angular rotation and tendon excursion of the cadaver specimens were measured radiographically. The gliding function of the repairs was compared with core suture only, core suture plus epitenon repair, and sheath repair. There was no significant difference in angular rotation or linear excursion between the 2-strand and 6-strand techniques of flexor tendon repair. The addition of the epitendinous suture to the core suture improved the angular rotation and linear excursion for the 2-strand technique. Although the 6-strand repair tended to increase the repair site bulk more than the conventional 2-strand technique, the gliding function of the repair techniques was equivalent.

Aged↗

PubMed2001

An anthropometric study of the radial head: implications in the design of a prosthesis.

The dimensions of the native radial head were measured in 28 cadaveric upper extremities and radiographs of the contralateral elbows of 40 patients who had received a radial head replacement. The mean difference between the maximum and minimum radial head diameters was 1.7 +/- 0.7 mm (range, 0.12-3.27 mm). This variability suggests that although the native radial head is not circular, it does not have a consistently elliptic shape. The native radial head also is variably offset from the axis of the neck (4.2 +/- 2.5 mm), suggesting that a radial head hemiarthroplasty that precisely replicates normal anatomy would be difficult to achieve. There was a poor correlation between the radial head diameter and the medullary canal of the radial neck, suggesting that a modular implant system should be considered.

Aged↗

PubMed2001

A biomechanical analysis of intrascaphoid compression using the 3.00 mm Synthes cannulated screw and threaded washer: an in vitro cadaveric study.

This study evaluated the compressive capabilities of the 3.0 mm Synthes cannulated screw and threaded washer. A transverse osteotomy was performed at the waist of eight cadaveric scaphoids and a custom-designed load cell was inserted before internal fixion with a 3.0 mm cannulated screw and threaded washer. The mean intrascaphoid compression achieved was 108 (SD, 60) N. This compressive force is comparable to that produced by standard cortical screws.

Aged↗

PubMed2001

Osteoclast clearance from periodontal tissues during orthodontic tooth movement.

The presence of osteoclasts at locations of alveolar bone remodeling is antecedent to orthodontic tooth movement. Cell recruitment and clearance are the mechanisms by which osteoclast populations are regulated. Research in other tissues has revealed that many cells die after their functional lives are past by a process called apoptosis, or programmed cell death. The purpose of this study was to examine the role of apoptosis in osteoclast clearance at orthodontically treated sites as a function of time and location. Orthodontic appliances were placed on 96 rats of the Sprague-Dawley strain. The rats were assigned to either treatment or sham (control) groups and killed 1, 3, 5, and 7 days after appliance placement. Tissue samples were prepared for histochemical evaluation and quantification of morphologic features. Tartrate-resistant acid phosphatase (TRAP) and ApopTag (TdT-mediated dUTP-biotin nick 3' end labeling) stains were used to identify osteoclasts and committed preosteoclasts and to discriminate between apoptotic and nonapoptotic nuclei. Pyknotic nuclei and apoptotic bodies were also counted as a morphologic assessment of apoptosis. The percentages of TRAP/ApopTag-positive nuclei were measured in 4 different periodontal regions. There was a highly significant difference in the overall percentage of TRAP/ApopTag-positive nuclei between the control and the treatment groups at 3, 5, and 7 days (P <.001). Morphologic criteria were also statistically different at days 5 and 7 (P <.05). These data strongly suggested that osteoclasts recruited for orthodontic tooth movement are, at least in part, cleared by apoptosis.

Acid Phosphatase↗

PubMed2001

Osteoclast recruitment to sites of compression in orthodontic tooth movement.

Although it is widely acknowledged that osteoclasts are formed by the fusion of mononuclear cells of hematopoietic origin, it has been extremely difficult to understand how they originate after appliance activation. The purpose of this study was to quantify osteoclast recruitment at compression sites as a function of time following orthodontic force application. Appliances were placed in 96 rats. At day 0, the animals were randomized to either appliance activation or sham activation followed by the injection of 5-bromo-2'-deoxyuridine (BrdU). Thus, BrdU was incorporated into the nuclei of cells in S-phase, including hematopoietic stem cells. Groups of 10 to 13 rats were killed at 1, 3, 5, and 7 days after activation/sham, and the tissue samples were prepared. The numbers of BrdU-labeled cells positively stained with tartrate-resistant acid phosphatase (TRAP) were measured in the periodontium. A significant number of BrdU-positive preosteoclasts was observed in the periodontal ligament (PDL) and bone surface at day 3. The number of osteoclastic cells in the bone marrow also peaked at day 3; however, the highest percentage of cells in this location was observed at day 1. These data suggest that osteoclasts in the PDL originate by the fusion of recently recruited preosteoclasts from the marrow instead of from local PDL cells. Furthermore, the alveolar bone marrow plays a role in the formation of osteoclasts during orthodontic tooth movement.

Acid Phosphatase↗

PubMed2001

Muscle forces and pronation stabilize the lateral ligament deficient elbow.

The influence of muscle activity and forearm position on the stability of the lateral collateral ligament deficient elbow was investigated in vitro, using a custom testing apparatus to simulate active and passive elbow flexion. Rotation of the ulna relative to the humerus was measured before and after sectioning of the joint capsule, and the radial and lateral ulnar collateral ligaments from the lateral epicondyle. Gross instability was present after lateral collateral ligament transection during passive elbow flexion with the arm in the varus orientation. In the vertical orientation during passive elbow flexion, stability of the lateral collateral ligament deficient elbow was similar to the intact elbow with the forearm held in pronation, but not similar to the intact elbow when maintained in supination. This instability with the forearm supinated was reduced significantly when simulated active flexion was done. The stabilizing effect of muscle activity suggests physical therapy of the lateral collateral ligament deficient elbow should focus on active rather than passive mobilization, while avoiding shoulder abduction to minimize varus elbow stress. Passive mobilization should be done with the forearm maintained in pronation.

Collateral Ligaments↗