Retromandibular transparotid approach compared with transmasseteric anterior parotid approach for the management of fractures of the mandibular condylar process: a prospective randomised study.

Fractures of the mandibular condyle lead to displacement of the condyle and loss of the height of the ramus. A retromandibular approach is the most commonly used for open reduction and internal fixation (ORIF) of such fractures. We aimed to compare the complications associated with a retromandibular transparotid approach with a retromandibular transmasseteric anterior parotid (TMAP) approach for their management. Thirty patients were randomly selected into two groups (15 in each): Group A comprised the retromandibular transparotid approach and Group B the retromandibular TMAP. The variables evaluated were: operating time, facial nerve injury, occurrence of Frey syndrome, and sialocoele at one week, four weeks, three months, and six months. The mean (SD) age in group A and B was 33.93 (17.97) years and 33.53 (16.15) years, respectively, and there were 28 men and two women. Mean (SD) exposure time in the transparotid approach was 26.93 (5.19) minutes and 25.4 (8.35) minutes in the TMAP approach. The incidence of facial nerve injury was 2/15 patients in the transparotid group and 3/15 in the TMAP group, all of which resolved within six months. The incidence of sialocoele was 2/15 in the transparotid group. The results did not show any significant difference in complications between the two approaches, but the retromandibular transparotid approach provided straight-line access in fractures of the condylar neck, with fewer incidences of nerve injury. The anterior parotid approach, on the other hand, provided easier access for fractures that were medially dislocated or of the condylar base but had an increased incidence of facial nerve injuries.

Expression of annexin VI in A431 carcinoma cells suppresses proliferation: a possible role for annexin VI in cell growth regulation.

Human A431 cells exhibit many characteristics typical of transformed cells, such as lack of contact inhibition and reduced growth factor requirement. We have used these cells as a model for the study of annexin VI function, since they do not normally express this protein. In this study we isolated two stably transfected clones, both of which were found to express annexin VI at physiological levels, and examined various growth parameters associated with the transformed phenotype. In low serum, normal A431 cells had doubling times similar to those observed in high serum. However, although the annexin VI transfectants grew only slightly more slowly than controls in high serum, their doubling time was significantly increased in low serum. Moreover, in low serum the annexin VI transfectants stopped proliferating after reaching confluence, indicating contact inhibition. Fluorescence activated cell sorting analysis revealed that the annexin VI+ cells were growth arrested in the G1 phase of the cell cycle when cultured in low serum, whereas annexin VI- clones exhibited the same proportion of mitotic cells in both low and high serum. Thus, expression of annexin VI in a heterologous cell line has a moderating influence on cell proliferation suggesting a possible role for annexin VI in cell growth regulation.

Endocytosis occurs independently of annexin VI in human A431 cells.

Annexin VI is one of a family of calcium-dependent phospholipid-binding proteins. Although the function of this protein is not known, various physiological roles have been proposed, including a role in the budding of clathrin-coated pits (Lin et al., 1992. Cell. 70:283-291.). In this study we have investigated a possible endocytotic role for annexin VI in intact cells, using the human squamous carcinoma cell line A431, and report that these cells do not express endogenous annexin VI, as judged by Western and Northern blotting and PCR/Southern blotting. To examine whether endocytosis might in some way be either facilitated or inhibited by the presence of annexin VI, a series of A431 clones were isolated in which annexin VI expression was achieved by stable transfection. These cells expressed annexin VI at similar levels to other human cell types. Using assays for endocytosis and recycling of the transferrin receptor, we report that each of these cellular processes occurs with identical kinetics in both transfected and wild-type A431 cells. In addition, purified annexin VI failed to support the scission of coated pits in permeabilized A431 cells. We conclude that annexin VI is not an essential component of the endocytic pathway, and that in A431 cells, annexin VI fails to exert any influence on internalization and recycling of the transferrin receptor.

A growth-dependent post-translational modification of annexin VI.

Annexin VI (p68, 67-kDa calelectrin) is a member of a family of Ca2+/phospholipid-binding proteins, that includes p35 (annexin I) and p36 (annexin II), the major cellular substrates for phosphorylation by the epidermal growth factor receptor and pp60v-src tyrosine kinase activities, respectively. We report here that like annexins I and II, annexin VI is phosphorylated in vivo, but that in contrast, annexin VI phosphorylation is associated with cell growth. In both Swiss 3T3 fibroblasts and human T-lymphoblasts the pattern of phosphorylation followed an almost identical profile. In particular, annexin VI was not phosphorylated in quiescent cells, but was phosphorylated on serine and to a lesser extent threonine, several hours following cell stimulation. Furthermore, annexin VI also incorporated phosphate in a growth-dependent manner, in a form other than a phosphoamino-acid. The phosphate was visualised following acid hydrolysis of immunoprecipitated annexin VI, as part of a complex having high mobility on 2-D thin-layer electrophoresis. The identity of this complex is not known. The results suggest that a post-translational modification other than direct protein phosphorylation may influence the activity of annexin VI and provide evidence linking cell growth with regulation of annexin VI function.