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K Barnard

Publications and source records attributed to K Barnard.

17 recordsLinked to original sources
PubMed1992

Learning and behavioral--emotional problems of children born preterm at second grade.

A longitudinal prospective study examined the question, "which child and family factors discriminate between children born preterm who are characterized by the presence or absence of learning or behavioral-emotional problems at second grade?" Assessments were completed during the child's hospital stay at birth, at 4, 8, and 24 months, and 8 years of age for 68 children born preterm and their mothers. Discriminant analyses identified the variables that statistically maximized the differentiation between two groups of children defined to exhibit or not exhibit school age problems. Three categories of discriminators were used in the analyses: infant status, family interactive quality, and family context. The three significant discriminators were variables from the family categories. The results of this study highlight the importance of understanding the presence or absence of school age problems from a multivariate model of development that takes into account the quality of the child's interactions within the family during early childhood and school age and the current stress levels in the family context.

Achievement↗
PubMed1991

Short and long range order in basement membrane type IV collagen revealed by enzymic and chemical extraction.

Oriented bovine lens capsules give X-ray diffraction patterns suggesting a considerable degree of order in the collagenous components, predominantly type IV collagen. Here we report the effects of preliminary treatment of lens capsules before orientation. Extraction with 4 M guanidinium hydrochloride or with heparinase/hyaluronidase reveals the same collagenous diffraction patterns previously seen after extraction with 1 M NaCl. There is a four-point pattern of d-spacing 3.9 nm, indicating liquid crystal cybotactic nematic organization, along with sharp streaked meridional reflections which index as orders of 21 nm. This suggests that the removal of basement membrane proteoglycans results in a reduction in diffuse scatter and clarification of the pattern. Extraction of the lens capsules with trypsin or dithiothreitol greatly reduces the intensity of the four-point pattern while leaving the meridional pattern unaffected. This strengthens the evidence that the 21 nm period has its origins in the collagen IV helix. Reduction in the four-point pattern could arise if disruption of non-helical NC1 domains or 7S overlap regions allows slippage of the collagen molecules on orientation, weakening the proposed 1 nm intermolecular stagger. Ultra-low angle diffraction patterns of extracted lens capsules show meridional reflections which index as a long-range axial repeat of approximately 95 nm. This is consistent with a model of microfibrils of type IV collagen in which the NC1 domains bind to the collagen helix at approximately 100 nm intervals, as has been previously suggested.

Animals↗
PubMed1989

Molecular organization of type IV collagen: polymer liquid crystal-like aspects.

A new X-ray diffraction pattern from type IV collagen is described, which can be interpreted on the basis of crystalline and liquid crystalline origins of the reflections. Bovine anterior lens capsules extracted with 1 M NaCl and oriented by extension of 60% under constant load gave medium angle X-ray diffraction patterns showing many of the characteristics typical of liquid crystals. Prominent features, apart from those wide angle features attributable to the collagen triple helix, are (1) a four-point pattern of broad reflections at d-spacing 3.9 nm, and layer line spacing near 5 nm. (2) A broad intense equatorial peak centred at 1.24 nm, indicative of liquid-like lateral molecular associations. (3) A set of five sharp, streaked meridional reflections (previously obscured by the broad peak near 5 nm in unextracted capsules). (4) A further six higher angle reflections of a diffuse, arced and broad appearance on the meridian. The sharp streaked meridional reflections emanate from a long-range periodicity of units 8-9 nm in diameter. These features form a self-consistent system if interpreted on the basis of a staggered liquid crystal-like array of collagen molecules, in which case the first five meridionals and remaining broad reflections, sampled on the meridian, can all be indexed as orders of 21 nm.

Collagen↗
PubMed1987

Chemistry of the collagen cross-links. Origin and partial characterization of a putative mature cross-link of collagen.

The conversion of the reducible divalent cross-links in collagen to non-reducible multivalent cross-links in mature collagen has resulted in the identification of several new amino acids as the putative mature cross-link. None of these compounds has completely satisfied the necessary criteria. We have now isolated an amino acid of high Mr, derived from lysine, that is only present in high-Mr peptides derived from mature collagen. Its increase with age of the tissue correlates with the decrease in the reducible cross-links, and it is present both in mature skin and bone, which are initially cross-linked through the aldimine and oxo-imine divalent cross-link respectively. We propose that this amino acid, as yet incompletely characterized and designated compound M, is a major cross-link of mature collagen.

Aging↗
PubMed1987

Basement membrane collagen--evidence for a novel molecular packing.

Type IV collagen is the major structural protein of basement membranes but very little is known about its molecular organisation in vivo. We have used X-ray diffraction of a thick basement membrane, bovine lens capsule, to provide information. Under constant load, lens capsule gave a collagen diffraction pattern of a similar quality to unstretched rat rail tendon. In addition there were clear meridional reflections which indexed as orders of 10 nm, and equatorial reflections at 2.1 and 3.8 nm. These results suggest the ordering of type IV collagen molecules in fibrils, with a 10 nm periodicity along the length of the fibrils.

Animals↗
PubMed1986

Labour relations in health services management.

'Labour relations' or 'industrial relations' refers to employer-employee relations which are both economic as in matters of pay and conditions, and managerial, i.e. the political relationships between management and employees, collectivized through trade unions and professional associations. This paper traces the development of managerial relationships as illustrated by experiences in the British National Health Service particularly over the past 20 years focusing on groups of actors--management (within which may be distinguished government and local managers), health professional workers and other workers--whose interactions need to be studied if managerial relations within health services are to be satisfactorily analysed. We conclude that, although until recently, developments in management have had little impact upon worker behaviour outside unskilled groups, changing economic and other circumstances could create the conditions in which stronger managerial control over professional workers might emerge.

Forecasting↗
PubMedDate not supplied

Three-dimensional structure of type IV collagen in the mammalian lens capsule.

The anterior lens capsule provides a thick, easily handled model system for the study of the organization of type IV collagen, the main component of basement membranes. We have used the technique of rapid freezing, deep-etch, and rotary replication to study the three-dimensional organization of the collagen skeleton in mammalian lens capsule after a variety of extraction procedures. In all cases the collagen appeared as a densely packed three-dimensional branching network of fine microfibrils. The organization of the microfibrils appears to show some regularity, with branch points approximately 40 nm apart. Most junctions are three-way and the network forms predominantly five-sided figures. This closely resembles the collagenous network described by Yurchenco and Ruben (1987, 1988) in human amniotic basement membrane and EHS tumor matrix, but extends their findings to another system for which X-ray diffraction data are available. The three-dimensional network is discussed in terms of molecular packing of type IV collagen in light of the information available from the diffraction data.

Animals↗
PubMedDate not supplied

The family and you.

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Family↗