A model for the evaluation of mandibular bone response to implant materials

SUMMARY An in vivo animal (goat) mandibular bone model has been evaluated for the cortical and trabecular bone response to biomaterials with different elastic modulus and/or different surfaces. The effect of the elastic modulus on the bone formation was also studied. The difficulties encountered in orientation of the implants probably could have been surmounted if pre-operative radiographs has been available. It was also established that there is a large variance in the amount of trabecular and cortical bone in the mandible of the goat'one model'.     

Probing the structure of human growth hormone by limited proteolysis

Digestion of human growth hormone (hGH) with the Glu-specific protease from Staphylococcus aureus V8 was performed at 20-22°C or 37°C at a 1:20 ratio (by weight) at pH 7.8 with or without 0.2% SDS. There are 14 Glu-residues evenly distributed along the polypeptide chain of hGH as possible sites of proteolytic cleavage of V8-protease. The pattern of fragmentation of hGH was analyzed by electrophoresis and reversed-phase HPLC, and the identity of the proteolytic fragments isolated to homogeneity was established by their partial sequencing and amino acid analysis after acid hydrolysis. Kinetic analysis of the proteolytic digestion process allowed to establish that initial nicking of the protein occurs at Glu³³ and subsequently at Glu⁵⁶ and Glu⁶⁶. Much slower cleavages occur at G1u³⁰ and Glu¹⁸⁶. These cleavage sites are located at chain loops in the hGH molecule, and in particular outside the helical segments of the four-helix bundle of the crystal structure of hGH. Fragments 1-33 and 67-191 comprising entirely the N-terminal helix and the three C-terminal helices of hGH, respectively, were isolated to homogeneity in amounts useful for subsequent conformational and functional studies. The results of this study and of previous ones [Li, C.H. (1982) Mol. Cell. Biochem. 46 , 31-41] describing limited proteolysis of hGH by various proteases have been interpreted on the basis of the three-dimensional structure and dynamics of hGH. Overall, it is shown that proteolytic enzymes preferentially cleave hGH at exposed and flexible loops only, thus emphasizing the fact that proteases can be used as reliable probes of protein structure and dynamics. © Munksgaard 1995.     

Trisomy 18q-. Trisomy mapping of chromosome 18 revisited

Two patients with trisomy for 18p and the proximal segment of 18q (trisomy 18q –) are reported and compared with similar cases from the literature. The phenotype of trisomy 18q– resembles that of full trisomy 18 but differs mainly in the birdlike face, small mouth, more pronounced microretrognathia, minor skeletal dysplasia and inner organ malformations, and less severe vital prognosis.     

Experience with intracoronary streptokinase in 36 patients with acute evolving myocardial infarction

Acute angiography was performed in 36 consecutive patients withevolving myocardial infarction admitted within 3 h after onsetof symptoms. No fatal complication occurred. Angiography revealeda total occlusion in 32 patients (89%), a subtotal stenosisin three (8%), and a 90% stenosis in one patient (3%). Anteriorinfarction was exclusively related to left anterior descending,and inferior infarction to right coronary or circumflex obstruction.After identification of the ‘infarct-vessel’, nifedipine10 mg was administered sublingually. In no patient was anterogradeflow affected with this treatment. In 35 patients an attempt to lyse clot was made with intracoronarystreptokinase; an infusion of 2000–4000 U/min, precededby a bolus of 10 000–20 000 U was infused into the ‘infarct-vessel’. In 26 patients (74%) reperfusion was achieved, two combinedwith guidewire perforation. The mean duration of onset of symptomsto reperfusion was 3.6 h (range 1.8–5.6). The mean durationof lysis was 1.2 h (range 0.3–3), and the mean dosageof streptokinase was 200 000 U (50 000–400 000 U]. In25 out of 26 patients (96%) a high degree of obstruction remainedimmediately after lysis and at repeat angiography 6–8weeks after the acute event. Despite treatment with aspirin200 mg daily and nifedipine 30 mg daily four re-occlusions occurred.Coronary bypass surgery was performed electively in five patients. Thus, we conclude that in patients with evolving myocardialinfarction, the infarct-vessel can be recanalized in 74% ofpatients by intracoronary streptokinase. The true benefit ofthis treatment must await a controlled study.