50 Abstracts of Bone & Tooth Society & Anatomical Society Meeting

X-RAYMICROTOMOGRAPHYOFBONE J.C. Elliott’ and SD. Dove? l Department of Biochemistry, The London Hospital Medical College, Turner Street, London, El 2AD 2Department of Biophysics, University of London King’s College, 26-29 Drury Lane, London, WC2B 5RL

X-ray tomography (also known as “computerized axial tomo- graphy, ” “transaxial tomography,” and “reconstruction from sections”) is now a well-established technique used in medical radiography for obtaining a section through the body of the x-ray absorption with a resolution of about 2 mm. The authors have recently described a microscopic version of this system (J. Microscop.l26:211, 1982) which has now been used to study an irregularly shaped rod of bone (maximum diameter about 1 mm) cut from a piece of human femur. Fifty- five projections of the x-ray absorption at angular intervals of 3.33’ were measured. Each projection consisted of 128 points at 11 m intervals and the absorption at each of these points was determined with a 15 m diameter beam of MoK x-rays counted for 15 sec. The total observation time was about 30 hours. The calculated reconstruction of the bone showed clearly several haversian canals. The method should be capable of giving quantitative information on the mineral density on a scale of about 15-20 m.

COMPARATlVECRYSTALCHEMlSTRYOFMARlNEVERTEBRATE TOOTHSURFACES J.G. Clement Department of Dental Anatomy, London Hospital Medical College, London, El 2AD

The name of the highly mineralized outer layer of shark teeth has been the subject of long-standing controversy. It has variously been called “enamel” because of its high degree of mineralization, supposed ectodermal origin, and noncol- lagenous organic matrix, or “modified dentine”. In this study it is called “enameloid” after the convention proposed by Poole (Structural and Chemical Organization of Teeth. 1967, p, 525, Academic Press). Samples of enameloid ground from shark teeth were subjected to x-ray diffraction and infrared spectroscopic analysis, Samples of whale enamels and human enamel obtained in the same way were also investigated for comparison. The x-ray diffraction patterns of all marine samples were similar to the apatitic pattern for human enamel. The sharpness of the lines enabled accurate measurement and the subsequent calculation of lattice dimensions. All shark samples were shown to have lattice constants with shorter a-axis dimensions than for whale or human samples, Infrared spectra for all shark samples were similar but differed markedly from those for whale and man. The most obvious difference was the absence of the hydroxyl stretching peak at 3565 cm-’ from all shark samples. This, together with the x-ray diffraction data, is consistent with a high degree of substitution of fluoride for hydroxyl ions in shark enameloid crystals. In the infrared spectra, splitting of the carbonate peak around 870 cm-’ was observed in whale and human samples but not in any shark sample. The relative intensities of carbonate in plane stretching peaks at 1420 cm-’ and 1450 cm-’ were very similar in human and whale samples but reversed in the shark samples. A third car- bonate peak was observed around 1545 cm-’ in mammalian samples only. These results suggested the carbonate ions in shark enameloid may occupy different

crystal sites to those in whale and human enamel. In conclusion, it seems that taxonomic affinities have a greater value in predicting the crystal chemistry of skeletal tissues than do habitat or diet.

SURFACEFEATURESOFHYDRATEDARTICULARCARTILAGE ANALYZEDBYX-RAYMICROPROBE P. O’Conner’, J.F.S. Middletot?, K. Oates*, D.L. Gardner’, and CR. Orford’ l Department of Histopathology, University of Manchester, Ml3 9PT 2Department of Biological Sciences, University of Lancaster, LA1 4YQ

Tertiary (3O) undulations are a characteristic surface feature of free, nonloaded, mammalian, hyaline articular cartilage. Measurements of their size, shape, and distribution in fixed tissue suggest that they represent underlying chondrocytes. Fixation and dehydration introduce problems of solute and ion redistribution. These difficultiescan be minimized by analyzing frozen hydrated tissue and low temperature scanning electron microscopy confirms the presence of rounded prominences on hydrated tissue surfaces.’ The present study extends this technique and uses x-ray microprobe to analyze 3” undulations and to compare them with adjacent surface areas and midzone chondrocytes2 Dog femoral condylar cartilage blocks were quench-frozen in slushy nitrogen (63K); some specimens were cleaved at 30° in an ultracryomicrotome to expose midzone (zone Ill) cartilage. Each specimen was coated in the front chamber of a modified JEOL JSM 50A SEM with a20 nm layer of aluminium before being placed on the low temperature stage (81 K). 1 pm* areas of 3O elevations, adjacent tissue and midzone chondrocytes, previously selected from secondary electron or backscattered electron images, were examined by SEM and analyzed using a Kevex energy dispersive x-ray detector and a Link Systems 860-500 series computer. X-ray spectra revealed significant differences between elevations and adjacent areas for all elements detected: Elevations and midzone chondrocytes had higher phosphorous and potassium but lower sodium, sulfur, chlorine, and calcium counts than adjacent tissue. These elemental differences closely resemble those obtained when cellular and extracellular tissues are compared. The data reinforce the evidence that 3O elevations overlie superficial chondrocytes.

Gardner D.L., O’Connor I? and Oates K.: Low temperature scanning electron microscopy of dog and guinea-pig hyaline articular cartilage. J.Anat. 132 :267-282, 1981.

Middleton J ES., Oates K., O’Connor P and Gardner D.L.: Articular cartilage surface features examined in bulk frozen specimens by X-ray microprobe analysis. (In preparation.)

EFFECTOFLlPOPOLYSACCHARlDESFROMPLADUEBACTERlA ON BONERESORPTIONINTISSUECULTURE R. Hopps and Y. Ino Departments of Oral Pathology and Oral Microbiology, London Hospital Medical College

Lipopolysaccharides (LPS) from Actinobacillus actino- mycetemcomitans, Capnocytophaga ochracea, and Bacferoides gingivalis, organisms thought to be important in the pathogenesis of destructive periodontal disease, were extracted from freeze-dried cells by a hot phenol-water