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S Lees

Publications and source records attributed to S Lees.

At least 37 records · Page 2Linked to original sources
PubMed1990

The design of a stress-management programme for nursing personnel.

This study identifies the stressors and coping strategies of nursing staff (students, trained staff and those who had left the profession before qualification) in a variety of ward specialisms. The research instruments included an open-ended interview concerning pre-nursing experience, perceived stressors and satisfactions, and ways of coping, and psychometric tests of self-esteem, assertion, ways of coping and personality. The five most frequently cited stressors were understaffing, conflict with nurses, dealing with death and dying, overwork and conflict with doctors. Experience of stressors was related to role and seniority of respondents, with different aspects of the same stressor differentially affecting nurses at different levels of experience. Coping strategies also depended on experience. Trained staff showed more use of problem-focused ways of coping, whilst students and leavers relied more on emotion-focused strategies to deal with stressful situations. These differences were related to personality characteristics of respondents and to self-esteem as well as to situational characteristics of the stressful episode. Social support was important in times of work-related stress, with students in particular making good use of peer group support. Respondents were generally lacking in assertiveness and high in anxiety. Although self-esteem was generally high, leavers scored markedly less than other subject groups in the areas of personal and social self-esteem. Leavers had little prior knowledge or experience of nursing before entering training and knew few nurses or doctors: consequently, nursing failed to meet their expectations. Stress was identified as the major cause of attrition and the sources of stress are identified. This study informed a major programme of stress-management training for student nurses which began in 1988 at the North Wales School of Nursing and which is currently under evaluation. It includes relaxation therapy, assertiveness training, and on-going group discussions which foster peer-group support and which explore the stressors and coping strategies relevant to different stages of training and ward specialisms.

Adaptation, Psychological↗
PubMed1990

Studies of compact hard tissues and collagen by means of Brillouin light scattering.

A measure of the elastic properties of tissue can be found from the propagation of sound in the tissue. Longitudinal sonic velocities were measured for mineralized turkey leg tendon (density 1.50 g/cc), deer antler (1.77 g/cc) and cow tibia (2.05 g/cc) in the 10 GHz frequency regime by means of Brillouin light scattering using a nine pass Fabry-Perot interferometer. Wet, air dried, mineralized and demineralized specimens were tested. Sonic velocity in each tissue increased with mineral content and decreased when the tissue was wet. All wet values are higher than for wet rat tail tendon collagen, axially and radially, but with considerably less anisotropy. The results are interpreted to indicate that bone matrix collagen is more highly crosslinked than tail tendon collagen. The loss of anisotropy is taken to correspond to a much higher crosslinking density between adjacent collagen molecules in mineralized tissue compared to rat tail tendon. The axial sonic velocity of dried rat tail tendon is almost that for low density dried mineralized tissue and greater than the radial sonic velocity of these tissues, but the radial sonic velocity for dried rat tail tendon is much lower, again corresponding to less crosslinking in this tissue. Longitudinal modulus, K, is defined as the tissue density times the square of the velocity. The compliance, 1/K, was found to be a linear function of density for each of the four conditions. It suggests that a Reuss formalism describes the elastic properties. Since the difference between the compliance for wet and dry tissue is also a linear function of density, the effect of water on the compliance is additive. The axial sonic velocity for cow bone is essentially constant over a frequency range spanning 10 orders. Presumably the axial sonic velocity is controlled by the continuity of the collagen fibers lying along the bone axis. The radial velocity decreases by 30% over this frequency range, probably due to the many levels of structure observed in long bone like osteons, Haversian canals and blood vessels, as well as internal surfaces like cement lines and between lamellae. The sonic anisotropy of hard tissues decreases considerably with increasing frequency. While rat tail tendon collagen is very anisotropic both sonically and optically, hard tissues whether wet, dry, mineralized or demineralized show much less anisotropy. The optical index of refraction, both axially and radially, was found by Brillouin scattering for the air dried demineralized tissues. A close match was found between optical and sonic anisotropy for all the demineralized tissues.

Animals↗
PubMed1990

BAPN dose dependence of mature crosslinking in bone matrix collagen of rabbit compact bone: corresponding variation of sonic velocity and equatorial diffraction spacing.

Crosslinking density in demineralized bone matrix collagen was found to depend on the beta-aminopropionitrile (BAPN) dose level for compact bone from rabbit femurs. The dependence was demonstrated for the hydroxypyridinium (HP) concentration, a mature crosslink. A more consistent dependence on BAPN dosage was observed for the fraction of the demineralized bone matrix insoluble in 0.5 M acetic acid (AIF) corresponding to the remaining crosslinked collagen. The average HP concentration in 21 week old controls was 0.24 moles HP/mole collagen which decreased to 0.13 +/- 0.04 for the same age rabbits dosed with 1 gm BAPN/kg/day for 13 wks. The comparable mean AIF values were 0.91 for controls and 0.75 for maximum dose level. Most of the effect of BAPN on crosslinking was observed at the lower dosages below 0.2 g/kg/day. On the other hand, overt osteolathyritic symptoms are seen only for BAPN dosages greater than 0.2 g/kg/day. The mean sonic plesio-velocity was previously found to decrease from 3.4 to 3.03 km/sec as the BAPN dosage was increased. A similar close relationship was discovered for the equatorial diffraction spacing in fully mineralized bone which increased from 1.235 for normal rabbit bone to 1.28 nm for maximum dose. Most of the effect on these physical properties is exhibited at the highest BAPN dosage after much of the decrease in mature crosslinking density has been observed and when the further decrease in mature crosslinking density proceeds very slowly with increased drug dosage. These observations suggest that osteolathyrism does not become manifest until practically all mature crosslinking that can be affected has been inhibited. The mineralization process apparently can be maintained in the newly laid collagen even in the presence of severe osteolathyritic conditions. Intermolecular crosslinking in bone collagen appears to play an important role in the development of bone properties whether by direct or indirect processes. Much of the effects on bone properties occur at the higher BAPN dosages where overt osteolathyrism is observed and where there seem to be only small changes in crosslinking density.

Acetates↗
PubMed1988

The locus of mineral crystallites in bone.

The organic content of mineralized tissues has been found to decrease with increasing tissue density, from about 60% of the mineral weight in light bone like deer antler to 1 to 2% in hyperdense bone like porpoise petrosal. The ratio of the weight of mineral that can fill the collagen hole zones to the total mineral content can be no greater than 20% for deer antler and decreases to less than 5% for hyperdense bone. Moreover, the dimensions of hydroxyapatite crystallites have been determined by various investigators to be larger than the intermolecular spacing of collagen molecules. Such crystallites can only be fitted within the collagen fibril if collagen molecules are packed differently from the accepted models. Electron micrographs of fish dentin, at a very early stage of mineralization, show the needle-like crystallites lying in dense strips between collagen fibrils and practically no crystallites within the fibrils. A similar pattern of dense strips of crystallites between fibrils can be identified in examples from more advanced stages of mineralization, taken from fish dentin, cat dentin and cow tibia, even though some of the needle-like crystallites are superimposed on the fibril banded pattern. In every instance there are regions of the fibrils where there are no visible needle-like crystallites. Examination of the work of others shows a similar distribution of the mineral component, except that none exactly resemble the micrograph of the earliest stage of fish dentin provided in this report. The collagen banding is observed to be in spatial phase over many fibrils. The needle-like crystallites may be observed to be bunched in phase with the collagen banding and with the same spatial periodicity. The bunching is most obvious in the least densely mineralized specimens. This observation can account for the x-ray and neutron diffraction patterns which shown the axial period of the mineral to be like that of the collagen axial macroperiod and to be in phase with the hole zones of collagen fibrils. These prior studies were interpreted to show that the crystallites must be within the hole zones. Our images are interpreted to show that most of the mineral is outside of the collagen fibrils in the extrafibrillar volume. The interpretation is in agreement with neutron diffraction studies of various mineralized tissues as well as with earlier diffraction studies of mineralized turkey leg tendon and with the calculations of the amount of mineral that can be contained within the collagen of mineralized tissue.

Animals↗
PubMed1987

The variation of sonic plesio-velocity in dose dependent lathyritic rabbit femurs.

It has been hypothesized that the origin of the increased elastic modulus of mineralized bone compared with the demineralized bone matrix is in the higher crosslinking density of the collagen in bone. Osteolathyrism is ascribed to an inhibition of crosslinking of the collagen by the lathyrogen and should be accompanied by a decrease in the elastic modulus of the bone. Dose dependent osteolathyrism was induced by varying the amount of BAPN ingested per day by young New Zealand white rabbits until they were mature. The femurs exhibited dose dependent properties, including wet bone density and sonic plesio-velocity in the radial direction. It was found that there is no minimum critical dose. Even though no overt osteolathyritic stigmata could be observed, both the sonic properties and the wet bone density could be affected at any dose level. The sonic plesio-velocity and the longitudinal elastic modulus decreased with BAPN dose level, most rapidly at the lower dose levels and then less so at higher dosages. Since BAPN acts to inhibit the crosslinking density, it appears that the elastic moduli of bone are dependent on the crosslinking density.

Aminopropionitrile↗
PubMed1987

Considerations regarding the structure of the mammalian mineralized osteoid from viewpoint of the generalized packing model.

The relative magnitudes of mineral, organic and water contents of dense mammalian bone are calculated by a new theory based on recent findings: (1) The neutron diffraction studies of mineralized tissues with different densities demonstrated an inverse relationship between wet density and the equatorial diffraction spacing of the collagen. (2) The neutron studies showed there was very little mineral within the collagen fibrils. (3) A generalized packing model for collagen has been advanced to show how the equatorial spacing can be varied depending on tissue type, water content, and mineral content. (4) The water content of collagen fibrils when calculated from the generalized packing model matches the experimentally determined values for rat tail tendon fibers, bone matrix, and fully mineralized bone. A computational model was developed based on the generalized packing model. It provides a unifying approach to explain many features of mineralized fibrous collagenous tissues. The results are presented as estimates of the mineralized collagen fibril density, the volume fraction of collagen in bone, the density of the extrafibrillar space, the fraction of the e.f. space occupied by mineral and the ratio of mineral within collagen to total mineral content, each expressed as a function of wet bone density. A useful data base, available from previous studies, related mineral, organic and water weight fractions to wet bone density, for a density range from 1.7 g/cc for deer antler to 2.7 g/cc for porpoise petrosal. A second order polynomial was found for each weight fraction component, with bone density as the input variable, with a standard deviation less than 2% of total bone weight. This permits the bone properties to be related to a single variable, the wet bone density. It is seen that compacting the collagen fibrils as well as reducing the organic component weight fraction are two important factors determining the structure of the mineralized osteoid. It was concluded that voids and pore spaces may occupy at least 5% of the bone volume.

Animals↗
PubMed1987

Vapor pressure isotherms, composition and density of hyperdense bones of horse, whale and porpoise.

Water adsorption studies of three types of hyperdense bone show vapor pressure isotherms and enthalpy to be different from that for pure apatitic mineral. The mineral content of these bones varied from 80 to 98%, much greater than for the better known cortical bone. The high mineral content of all these bones and the variation of mineral content from one type of bone to the next make it possible to evaluate the contribution of the mineral component in bone to water adsorption. Both water content and the fractional shrinkage when dried decrease with increasing mineral content of the bone and increase with the organic component. The total water content of hyperdense bone is much less than the maximum water adsorbed by the equivalent pure mineral powder or by anorganic bone. It was concluded that: (1) Very little water appears to be adsorbed by the mineral in hyperdense bone; (2) It is likely that the mineral crystallites are coated with noncollagenous organic matter; (3) Water is taken up by organic matter both intra- and extrafibrillar; and (4) the enthalpy associated with the adsorption of water by HAP is higher than for hyperdense bone at all corresponding vapor pressures.

Adsorption↗
PubMed1986

Equatorial diffraction spacing as a function of water content in fully mineralized cow bone determined by neutron diffraction.

Variation of the equatorial diffraction spacing of soft type I collagen tissues with water content using X-rays has been known for many years. Recently, a generalized model for collagen molecule packing within fibrils was deduced from this information for different collagenous tissues. It is now known that the eq. diff. sp. of mineralized tissues can be less than for soft tissues and is inversely dependent on the wet density. A determination of the eq. dif. sp. dependence on water content using neutron diffraction of fully mineralized cow bone was undertaken for comparison. Specimens with various partial water content between 0 and 100% were tested. Data show collagen molecules pack more closely together as water content decreases, just as for soft tissues.

Animals↗
PubMed1985

Major histocompatibility complex restriction fragment length polymorphisms define three diabetogenic haplotypes in BB and BBN rats.

Class I and II major histocompatibility complex (MHC) probes can be used to subdivide diabetes-prone BB rats and their BBN control strain, coderived from the same outbred colony by selection against diabetes. Class II probes (A-alpha in particular) distinguish four restriction fragment length polymorphisms (RFLP), termed 1a, 1b, 2a, and 2b, in the BBN population, only one of which (2a) is found in BB rats. The degree of class II RFLP in the population studied is RT1.B-alpha greater than or equal to RT1.B-beta greater than RT1.D-alpha greater than or equal to RT1.D-beta, suggesting that intra-class II region dynamics may be different in rats compared with mice. A class I probe (S16) absolutely distinguished BB from BBN rats, since all BB rats exhibit an RFLP pattern termed 2a0, while 2a BBN rats can be subdivided into 2a1 and 2a2 forms. Serologic evaluation has shown that 2a0, 2a1, and 2a2 rats express RT1.AuBu, 1a rats express RT1.AaDa, and 1b rats express neither RT1a nor RT1u at the loci tested. A breeding study was carried out to determine the diabetogenicity of the MHC-defined RFLP's. As expected, the BB-derived 2a0 is diabetogenic. The BBN-derived 2a1 and 2a2 RFLPs are also diabetogenic, while 1a and 1b rats do not carry MHC-linked diabetogenic genes. The MHC-linked diabetes gene acts in a functionally recessive manner, since there is a 10-fold higher incidence in homozygotes than in heterozygotes. Analysis of the RFLP patterns leads us to hypothesize that the 2a1 RFLP results from a crossover between 1a and 2a0 MHCs and that the diabetogenic MHC-linked gene is on the class II side of Qa and T1. The availability of three diabetogenic MHC haplotypes should help localize the MHC-linked diabetogenic gene of rats.

Animals↗
PubMed1985

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.

Achilles Tendon↗
PubMed1983

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.

Acoustics↗
PubMed1982

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.

Animals↗
PubMed1981

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.

Animals↗
PubMed1981

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.

Animals↗
PubMed1981

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.

Animals↗
PubMed1980

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.

Administrative Personnel↗