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Biomedical subjects

L H Hahn

Publications and source records attributed to L H Hahn.

6 recordsLinked to original sources

Major mandibular reconstruction with vascularized bone grafts: indications and selection of donor tissue.

Free vascularized bones have been shown by many specialists to exhibit specific capabilities of reconstructing a major mandibular defect and can solve problems that may be insoluble by other methods. Nevertheless, absolute indications for using vascularized bone for major mandibular reconstructions have not been sufficiently well delineated to convince people of always considering vascularized bone for major mandibular reconstructions as a first option. Based on our experience with 55 major mandibular reconstructions, we might delineate the absolute indications for using free vascularized bone for major mandibular reconstructions explicitly: 1) osteoradionecrosis of mandible or on irradiated tissue bed; 2) hemimandibular reconstruction with a free end facing the glenoid fossa; 3) long segment mandibular defect, especially across the symphysis; 4) inadequate skin or mucosal lining; 5) defects demanding sandwich reconstruction; 6) inability to obtain secure immobilization on the reconstructed unit; 7) failure of reconstruction by other methods; 8) near total mandibular reconstruction. Selection of donor tissue should be according to 1) the amount of tissue deficiencies, 2) composition of the defect, 3) design and placement of the flap, 4) irradiation on the recipient site or not, 5) which vessels to be used, 6) which flap has the appropriate vessel length 7) skin color and texture of the donor tissue, 8) how many osteotomies required to stimulate the curvature of the resected mandible 9) speed of bony union, 10) feasibility of future osseointegration. We have used three kinds of vascularized bones (iliac bone, fibula, scapula). Iliac bone was most frequently used, and has always been our first choice, since it can carry good quality bone, a large skin flap, and ample soft tissue. The fibula has the merit of being less bulky and good for simultaneous intraoral lining, but the contour is more rigid and the bony height is insufficient. The scapula bone is rarely used at present because of its relative inconvenience.

Adult↗

Identification and isolation of a collagen-binding fragment of the adhesive glycoprotein fibronectin.

We have identified and purified a polypeptide region containing the collagen-binding site of the adhesive glycoprotein fibronectin. Chicken cellular fibronectin isolated from cultured embryonic fibroblasts was permitted to bind to gelatin coupled to agarose beads and was then digested extensively with chymotrypsin. A prominent 40,000-dalton fragment of fibronectin consisting of a single polypeptide chain was detected by sodium dodecyl sulfate/polyacrylamide gel electrophoresis of material remaining bound to the gelatin-agarose. This fragment appeared within 10 min after the digestion was initiated and persisted for more than 20 hr. This proteolytic fragment was isolated in electrophoretically pure form and retained its affinity for collagen. Plasma fibronectins from chicken and human blood also contained collagen-binding proteolytic fragments of similar size. This finding suggest that the collagen-binding sites of cellular and plasma fibronectins are homologous.

Animals↗

Cigarette smoking and inorganic dust in human lungs.

Whole left lungs from 18 smokers and 16 nonsmokers were obtained at autopsy and studied to determine the severity of subclinical emphysema and elemental dust loads of aluminum and silicon. Lungs selected were from individuals with work histories in non-dusty occupations and were sex- and age-matched by decade. Whole lung Gough sections were studied and emphysema was graded on a 0 to 100 score. Concentrations of aluminum and silicon were determined in homogenized-lyophilized lung of all 34 cases by plasma emission spectrometry. In addition, histological sections from 9 pairs of age-matched smokers and nonsmokers were studied by light microscopy and scanning electron microscopy in concert with semiquantitative x-ray spectrometric analysis of aluminum and silicon content in specific anatomical regions. The results of these studies indicate that aluminum and silicon concentrations increase in smokers with increased cigarette smoking. As expected, severity of pulmonary emphysema was associated with heavy cigarette smoking.

Adult↗