Neutron diffraction studies of collagen in fully mineralized bone

Neutron diffraction measurements have been made of the equatorial and meridional spacings of collagen in fully mineralized mature bovine bone and demineralized bone collagen, in both wet and dry conditions. The collagen equatorial spacing in wet mineralized bovine bone is 1.24 nm, substantially lower than the 1.53 nm value observed in wet demineralized bovine bone collagen. Corresponding spacings for dry bone and demineralized bone collagen are 1.16 nm and 1.12 nm, respectively. The collagen meridional long spacing in mineralized bovine bone is 63.6 nm wet and 63.4 nm dry. These data indicate that collagen in fully mineralized bovine bone is considerably more closely packed than had been assumed previously, with a packing density similar to that of the relatively crystalline collagens such as wet rat tail tendon. The data also suggest that less space is available for mineral within the collagen fibrils in bovine bone than had previously been assumed, and that the major portion of the mineral in this bone must be located outside the fibrils.

Parameters influencing the sonic velocity in compact calcified tissues of various species

Compact calcified tissues from a wide variety of species were used in a study of the dependence of sonic plesio-velocity on physical parameters. A linear dependence of velocity on wet density has been found for each of three categories of wet mineralized tissue: compact long bone measured in the axial direction, compact long bone measured in the radial direction, and hyperpycnotic mineralized tissues. A similar linear dependency was found for dry calcified tissue using the dry density. In addition to these three parameters (density, orientation, and water content) two other factors were identified. The bone fibers in long bone matrix are ordered with respect to the bone axis and the anisotropy of long bone matches that of its matrix. There is no corresponding order to the fibers in hyperpycnotic tissue matrix. The fifth parameter is believed to be the porosity. Fish bone is much more porous than other compact bone from long bone and the sonic velocity in fish bone is much lower than for other bone. These parameters are not independent.

Ultrasonic measurements of deer antler, bovine tibia and tympanic bulla

Longitudinal sonic plesio-velocity, density and mineral volume fraction of the three bone types plus bovine bone matrix are reported. The axial sonic velocity in km/s and the mineral volume fraction for each is as follows: deer antler 3.08, 0.33; bovine tibia 3.89, 0.44; tympanic bulla 4.53, 0.85; bovine matrix 1.82. A brief discussion of the deer antler and tympanic bulla histology is included.

Density of a sample bovine cortical bone matrix and its solid constituent in various media

The density of a bovine cortical bone matrix sample was found in water, several ethanol-water solutions, and in dried state. Previously the density of the same mineralized bone was found fresh and when desiccated. The volume in each state was estimated from the dimensional changes axially, tangentially, and radially. Confirmation was found by determining the density of dried specimens upon immersion in xylene. The amount of imbibed xylene provided an estimate of the free pore volume in the dried matrix. The volume fraction of the solid constituent, S, in the wet matrix was found to be 0.57, from which the density of S in various solutions was calculated. Density of wet matrix in 0.15 M saline: 1.180 g/cc; for dried matrix, 1.246 g/cc. Density of wet S in saline: 1.33 g/cc; for dried S, 1.42 g/cc, which matches published values for collagen molecules. Dimensional changes between wet and dried state of matrix match published values for artificially cross-linked rat tail tendon fibers. Axially: 1.04, by area: 2.27; by volume: 2.62. Estimate of intrafibrillar volume, assuming 80% of mineral is within fibrils: 0.73 cc/g dry collagen.

A mixed packing model for bone collagen

A wide variety of physical properties, including sonic velocity, dimensional changes between wet and dried stages, anisotropy of the tissue properties, density, X-ray diffraction, differential microcalorimetry, dielectric constant, and composition (water, mineral, organic content) for the mineralized and demineralized tissue was used to develop a model for the superlattice structure of bone collagen. A mixed model is suggested where the collagen molecules are in register as in SLS type of aggregation within the microfibril, and the microfibrils are staggered in D unit steps according to the Hodge-Petruska scheme. A square packing model with 4 or more molecules per microfibril best fits the HP scheme with the effective molecular diameter of the wet collagen molecule, and allows for the regular array of axial gap filling microcrystallites of 5 nm or larger diameter. It is concluded that: 1. Macroscopic dimensional changes of adult bovine bone matrix closely match molecular dimensional changes of collagen superlattice. 2. Effective molecular diameter of dry collagen is 1.09 nm and that of wet bone collagen is 1.42-1.45 nm. 3. Water layer of the wet bone collagen molecule is 0.16 nm thick. 4. Water in the bone collagen molecule is distributed in 5 regimes much like in the tendon collagen molecule. 5. "Hidden" water, 0.10 g water per dry collagen of regimes I and II, is within the triple helix. 6. "External" water incorporated in the collagen molecule provides transition between the highly structured collagen molecule and the intermolecular medium. 7. Water incorporated in the mineralized bone collagen molecule is less than in demineralized bone matrix. 8. For adult bovine cortical bone, 25% by volume is water, 32% dry organic, 43% mineral; 28% by volume of the mineral is axial gap filling, 58% radial intrafibrillar, and 14% radial extrafibrillar.

Some properties of the organic matrix of a bovine cortical bone sample in various media

Dimensional stability of a demineralized bovine cortical bone sample was found in all media whether EDTA, saline or ethanol and water solutions or even 100% ethanol. A 6% volume shrinkage was observed, in strong contrast to the reported swelling for tail tendon fiber collagen. Sonic velocity was strongly dependent on the state and the medium, varying by a factor greater than 2. The medium appears to contribute strongly to the observed velocity suggesting that the Reuss formalism is applicable with the solid collagen skeleton as one component and the liquid in the pores as the second. Sonic anisotropy was noted although the intensity varied. The radial to axial velocity was greatest (0.93) in saline and least in 100% ethanol (0.80) indicating that the rigidity of the tissue influenced the character of sonic propagation. Two sets of intermolecular linkages are inferred. One set, in common with tendon collagen, controls the elastic properties. A second set in bone collagen maintains dimensional stability.

Developing effective institutional managers in the 1980s--part 2: some new directions

In the earlier paper (published in the March 1980 issue of the Journal of Advanced Nursing) two dominant themes were developed. One was that the organizational behaviour of nurse managers could be traced to the social defence system learned during early nursing, the other was that many of the assumptions which underpin much of the current thinking on nurse management training can do little either to help them unlearn these early behaviours or to prepare them to take more innovative action in their respective roles. Part 2 analyses some implications of this. The initial discussion examines the purpose of management training and what it is intended to achieve, which embraces the issues of the transfer of course learning back to the workplace and the greater involvement of line managers in the development of their staff. By redefining nursing in terms of open-system boundary management, some new directions are suggested which management trainers may find useful in clarifying and redefining their own task, as well as enabling nurse managers to be more innovative and effective within the constraints of their organizational situations. The implications go beyond just nursing and nurse management training. They are concerned with the wider range of institutions whose task is the throughput of people, and which tend to be managed by groups of professionals.

Developing effective institutional managers in the 1980s--Part 1: a current analysis

Two dominant themes are developed in this two part paper. One is that the organizational behaviour of nurse managers has its origins in the social defence system learned during early nursing; the other is that many of the assumptions which underpin current thinking on management training can do little either to help unlearn these early behaviours or to enable managers to be more innovative in their roles. In part one management training is examined in some detail from the three perspectives of the institution, the management trainers and the nurse managers, and in particular the widely differing assumptions and expectations which each have about the management training process. The social defence system of nursing is then analysed and tentative evidence is offered to illustrate how nurse managers transfer this system to managerial positions, with dysfunctional consequences. Although primarily concerned with nurse management training, there are implications for managers and management trainers in a much wider range of institutions and professions.

Modification of etching patterns in bovine dental enamel

It is presumed that the etching pattern is controlled by the residual organic content of dental enamel. Pretreatment with 1.ON NaOH sould remove the organic material and modify the etching pattern. SEM studies and other tests for physical and chemical properties show that the predicted modification of the etching pattern, when the tooth surface is pretreated with NaOH solution, occurs apparently without other changes or properties.

Radioimmunoassay kits for thyroid hormones

Characteristics of the T4 and T3 radioimmunoassay kits that are commercially available in the UK are described. Useful comparative data and criticism are given about many of these kits. Some unacceptable variation in accuracy is demonstrated.

Serum triiodothyronine determination in clinical use

Two radioimmunassays for the determination of serum triiodothyronine (T3) were developed. The assay of T3 in unextracted serum had several advantages over the assay on extracted serum and was chosen for the routine determination of T3 in serum from 117 patients requiring assessment of their thyroid status. In 53 subjects considered retrospectively not to have thyroid dysfunction nor to have been on steroid contraceptives or therapy, the pooled mean serum T3 concentration was 1-92 (actual range 0-88-2-62) nmol/l. A significant inverse relationship was observed between the serum T3 level and the age of the subject. Serum total T3 levels discriminate clearly between hypo-,eu- and hyperthyroid patients and provide a rather more sensitive index of hyperthyroid function than total serum T4. In the face of normal serum T4 the T3 level was depressed in five patients with marked hypoproteinaemia and elevated in two patients taking heroin.

Dental enamel: detection of surface changes by ultrasound

Evidence indicates that the tooth surface differs in structure from the enamel immediately beneath it, and particularly that the enamel rod type structure is minimal in the true natural surface. Furthermore, the rod ends appear to disappear with age after the eruption of the tooth. The thickness of the surface layer may be as much as 25 micrometers. Studies of caries incidence show a peak in the attack curve 2 to 4 years after eruption and a decline thereafter for all teeth. This information indicates that the mechanical structure of the tooth surface should be carefully studied. A highly useful means appears to be ultrasound since the specific acoustic impedance of highly mineralized tissue like enamel is strongly dependent on fraction volume mineralization and since non-destructive test techniques can be based on ultrasonics. An experimental demonstration of ultrasonic detection in vitro of tooth surface demineralization is given.

Looking into teeth with ultrasound

Ultrasound is readily conducted across a boundary when the specific acoustic impedances of the two media are about equal. The specific acoustic impedance of dental enamel is about that of aluminum. A longitudinal sonic pulse, less than 250 nanoseconds in duration, conducted to the tooth through an aluminum rod, has positively detected the enamel-dentin junction as well as the dentin-pulp interface.