Biomedical subjects

John Close

Publications and source records attributed to John Close.

3 recordsLinked to original sources

PubMed2006

Nanostructured calcium phosphates (NanoCaPs) for non-viral gene delivery: influence of the synthesis parameters on transfection efficiency.

Calcium phosphate (CaP) based approaches remain an attractive option for delivering plasmid DNA (pDNA) into cultured cells. However, despite their appeal, current synthesis methodologies typically yield lower, less consistent transfection efficiencies when compared to viral approaches. Therefore, we report here a novel method to consistently synthesize efficient, nano-sized, mono-dispersed CaP-pDNA particles; accomplished by optimizing both the stoichiometry (Ca/P ratio) of the CaP particles as well as the mode in which the calcium and phosphate precursor solutions are mixed. Our results indicate that calcium and phosphate precursors when mixed in a controlled and regulated manner reproducibly result in nano-sized particles that consistently yield higher transfection efficiencies when compared to particles synthesized via manual mixing (a two-fold increase was observed). Also, maximum transfection efficiencies in both HeLa and MC3T3-E1 cells lines were obtained when a Ca/P ratio between 100 and 300 was used. Particles synthesized within this optimum Ca/P ratio range were between 25 and 50 nm. Our data suggests that these maximized transfection efficiencies were obtained because these particles not only effectively condensed (70% efficient) but also efficiently bound (90% efficient) the pDNA. In addition, X-ray diffraction and Fourier transform infrared spectroscopy analyses confirmed that all of the synthesized CaP structures exhibited the hydroxyapatite phase.

3T3 Cells↗

PubMed2005

Fiber-type differences in masseter muscle associated with different facial morphologies.

BACKGROUND: The influence of muscle forces and associated physiologic behaviors on dental and skeletal development is well recognized but difficult to quantify because of the limited understanding of the interrelationships between physiologic and other mechanisms during growth. METHODS: The purpose of this study was to characterize fiber-type composition of masseter muscle in 44 subjects during surgical correction of malocclusion. Four fiber types were identified after immunostaining of biopsy sections with myosin heavy chain-specific antibodies, and the average fiber diameter and percentage of muscle occupancy of the fiber types were determined in each of 6 subject groups (Class II or Class III and open bite, normal bite, or deepbite). A 2 x 3 x 4 analysis of variance was used to determine significant differences between mean areas for fiber types, vertical relationships, and sagittal relationships. RESULTS: There were significant differences in percentage of occupancy of fiber types in masseter muscle in bite groups with different vertical dimensions. Type I fiber occupancy increased in open bites, and conversely, type II fiber occupancy increased in deepbites. The association between sagittal jaw relationships and mean fiber area was less strong, but, in the Class III group, the average fiber area was significantly different between the open bite, normal bite, and deepbite subjects. In the Class III subjects, type I and I/II hybrid fiber areas were greatly increased in subjects with deepbite. CONCLUSIONS: Given the variation between subjects in fiber areas and fiber numbers, larger subject populations will be needed to demonstrate more significant associations between sagittal relationships and muscle composition. However, the robust influence of jaw-closing muscles on vertical dimension allowed us to conclude that vertical bite characteristics vary according to the fiber type composition of masseter muscle.

Adult↗

PubMed2004

The effects of Le Fort I osteotomies on velopharyngeal and speech functions in cleft patients.

PURPOSE: Orthognathic surgery alters or even worsens symptoms of velopharyngeal insufficiency in cleft patients. The goal of this study was to evaluate how advancing the maxilla would affect the speech and articulation disorders of these patients. PATIENTS AND METHODS: This was a retrospective study in which we compiled and evaluated the speech scores of 54 cleft lip and palate patients who underwent maxillary advancement between 1981 and 2001. Although 34 individuals underwent an isolated Le Fort I advancement, 20 patients had a combined Le Fort I advancement/mandibular setback operation. The following variables were recorded from both preoperative and postoperative speech evaluations: presence of a pharyngeal flap at the time of surgery, oronasal fistulas, nasality, 7 different articulation errors, velopharyngeal function assessment, and overall speech score. Preoperative and postoperative changes in the data were analyzed using the McNemar test and paired t test. RESULTS: A decrease in competent velopharyngeal function mechanisms was noted postoperatively (42% to 18%), increased borderline incompetence (9% to 22%), and complete velopharyngeal insufficiency (13% to 20%). Speech scores deteriorated significantly (P <.05), whereas articulation defects insignificantly (P =.146) improved after surgery (84% to 73%), with those related to the anterior dentition (P =.064) showing the greatest change (64% to 47%). The frequency of hyponasality decreased after surgery. The number of cases of mild to moderate hypernasality increased. CONCLUSION: This study confirms previous findings that patients with clefts of the lip and palate or palate alone are predisposed to velopharyngeal function alteration after maxillary advancement, particularly with borderline function preoperatively. However, the results show that surgical correction of skeletal relationships and occlusion may translate into improvements in certain aspects of speech disorders.

Adolescent↗