An experimental study on the effect of rigid fixation on the developing craniofacial skeleton

Rigid fixation of the craniofacial skeleton has proven of great value in adult orthognathic and traumatic reconstructive surgical procedures. This technique has gained increased acceptance in the surgical treatment of infants and young children with congenital malformations, despite the fact that its effects on subsequent craniofacial growth are unknown. To examine this question, an experimental model using 25 young kittens was developed to compare rigid fixation with conventional wire fixation, with and without osteotomy. Our findings demonstrate a regional restriction of growth in the developing craniofacial skeleton when both wire and plate and screw fixation are utilized in concert with osteotomy. Further, a compensatory growth was observed in individual animals when plate fixation was utilized that was not seen in the wire-treated group. This suggests that there is a dynamic growth interaction between restriction and compensation in this setting.     

Aesthetic augmentation of the posterior mandible

The posterior mandible begins just behind the mental nerve and second bicuspid bilaterally, extends to the posterior edge of the ramus, and then runs superiorly to the zygomatic arch. Augmentation of the posterior mandible is possible by use of a synthetic implant that is tailored individually to each patient's specific needs. Implant plant thickness varies from 4 to 8 mm, with an average thickness of 6 mm. Careful preoperative planning is done based on an aesthetic assessment of the amount of highlighting desired, thickness of the soft tissues, and the use of life-size photographs and cephalometric and Panorex x-rays. A pattern is cut, and the implant is carved to fit the patient. Insertion of the material after careful tailoring to the individual patient's own mandibular size and configuration requires a generous posterior lower buccal sulcus incision. Antibiotic irrigation and systemic antibiotics are essential, and careful closure in two layers completes the procedure. One implant in the series extruded in a patient who had had radiation therapy, and one patient required repositioning of the implant. Otherwise, in 22 patients there were no infections or permanent morbidity. The procedure seems to be a realistic and safe one for both the youthful and aging face, as demonstrated in patients in this series, with ages varying from 16 to 40 years.     

Calculation of effective diffusivities for biofilms and tissues.

In this study we describe a scheme for numerically calculating the effective diffusivity of cellular systems such as biofilms and tissues. This work extends previous studies in which we developed the macroscale representations of the transport equations for cellular systems based on the subcellular-scale transport and reaction processes. A finite-difference model is used to predict the effective diffusivity of a cellular system on the basis of the subcellular-scale geometry and transport parameters. The effective diffusivity is predicted for a complex three-dimensional structure that is based on laboratory observations of a biofilm, and these numerical predictions are compared with predictions from a simple analytical solution and with experimental data. Our results indicate that, under many practical circumstances, the simple analytical solution can be used to provide reasonable estimates of the effective diffusivity.     

Prostatic Contribution to Normal Serum Acid Phosphatase

Total and tartrate-labile serum acid phosphatase levels were compared in patients with and without prostates, and in 12 patients before and after cystoprostatectomy. Absence of the prostate seems to make no significant difference to the levels of serum acid phosphatase. There is no justification for referring to the tartrate-labile serum acid phosphatase as “prostatic acid phosphatase.” A substantial incidence of marginally raised levels of serum acid phosphatase in each group of patients suggests that the upper limit of normal for the total serum acid phosphatase should be taken as 5 K.A.u.     

Disassembly of the cytosolic chaperonin in mammalian cell extracts at intracellular levels of K+ and ATP.

The eukaryotic, cytoplasmic chaperonin, CCT, is essential for the biogenesis of actin- and tubulin-based cytoskeletal structures. CCT purifies as a doubly toroidal particle containing two eight-membered rings of approximately 60-kDa ATPase subunits, each encoded by an essential and highly conserved gene. However, immunofluorescence detection with subunit-specific antibodies has indicated that in cells CCT subunits do not always co-localize. We report here that CCT ATPase activity is highly dependent on K+ ion concentration and that in cell extracts, at physiological levels of K+ and ATP, there is considerable dissociation of CCT to a smaller oligomeric structure and free subunits. This dissociation is consequent to ATP hydrolysis and is readily reversed on removal of ATP. The ranking order for ease with which subunits can exit the chaperonin particle correlates well with the length of a loop structure, identified by homology modeling, in the intermediate domain of CCT subunits. K+-ATP-induced disassembly is not an intrinsic property of purified CCT over a 40-fold concentration range and requires the presence of additional factor(s) present in cell extracts.