Narrative skills in deaf children who use spoken English: Dissociations between macro and microstructural devices.

Previous research has highlighted that deaf children acquiring spoken English have difficulties in narrative development relative to their hearing peers both in terms of macro-structure and with micro-structural devices. The majority of previous research focused on narrative tasks designed for hearing children that depend on good receptive language skills. The current study compared narratives of 6 to 11-year-old deaf children who use spoken English (N=59) with matched for age and non-verbal intelligence hearing peers. To examine the role of general language abilities, single word vocabulary was also assessed. Narratives were elicited by the retelling of a story presented non-verbally in video format. Results showed that deaf and hearing children had equivalent macro-structure skills, but the deaf group showed poorer performance on micro-structural components. Furthermore, the deaf group gave less detailed responses to inferencing probe questions indicating poorer understanding of the story's underlying message. For deaf children, micro-level devices most strongly correlated with the vocabulary measure. These findings suggest that deaf children, despite spoken language delays, are able to convey the main elements of content and structure in narrative but have greater difficulty in using grammatical devices more dependent on finer linguistic and pragmatic skills.

The impact of developmental visuospatial learning difficulties on British Sign Language.

There has been substantial research interest in recent years in the relationship between the development of language and cognition, especially where dissociations can be seen between them. Williams syndrome, a rare congenital disorder characterized by a fractionation of higher cortical functions, with relatively preserved language but marked difficulties with visuospatial constructive cognition, has been extensively studied. The case of Heather, who is remarkably similar to the characteristic phenotype of Williams syndrome in physical appearance and cognitive abilities, but who is also congenitally deaf and a user of British Sign Language, provides the first opportunity to explore the consequences of specific visuospatial learning difficulties on the linguistic system when the language used is visuospatial. Heather shows a pattern of impaired drawing ability and visual form discrimination, but preserved ability to discriminate faces. She has a large vocabulary in British Sign Language, and overall presents a picture of relative competence in British Sign Language grammar. However, she shows specific deficits in those areas of British Sign Language which directly rely on spatial representations for linguistic purposes. A number of theories as to the nature of her impairments and those found in Williams syndrome are discussed, using models of the relationship between language and visuospatial cognition based on data from this unique case.

A tribological study of retrieved hip prostheses.

One hundred Charnley cemented acetabular cups, 78 of which had the associated femoral stems, were obtained after revision surgery. Patient characteristics, which were obtained from hospital records, and roentgenographs showed that component loosening was the most common cause of failure. Examination of the acetabular cups revealed six categories of damage: socket erosion, rim wear, cement ingress, cratering, discoloration, and articulating surface scoring. Damage to the femoral stems was characterized by stem fracture and roughening of the femoral head. The latter was predominantly caused by the roentgenographic contrast medium within the acrylic cement scratching the articulating surface. The amount of wear, in terms of the penetration of the femoral head into the acetabular cup, could be measured in 87 cases. The mean penetration was 1.69 mm and the mean penetration rate was 0.21 mm per year with a range from less than 0.005 mm to 0.6 mm per year. It was shown that within this group, a high penetration rate precludes a long service life. It is therefore likely that reducing the rate of wear would improve the performance of the artificial hip joint.

Neuropeptide Y is a vasoconstrictor of human coronary arteries.

Neuropeptide Y (NPY) is a 36-amino-acid polypeptide which coexists with catecholamines in many adrenergic and noradrenergic neurons. It has been demonstrated to exert pressor effects in the perfused guinea pig heart and to constrict large cerebral and coronary blood vessels in animal studies. To determine if NPY might be a human coronary vasoconstrictor, the authors studied its effect on postmortem human coronary arteries. Proximal epicardial coronary rings were studied in a superfusion apparatus in Krebs-Ringer bicarbonate buffer (37 degrees C, pH 7.4) presaturated with 95% O2-5% CO2. Concentration-response curves were obtained using NPY in 0.1% bovine serum albumin in buffer and the responses were compared to those obtained in the presence of alpha 1, beta, and cyclooxygenase antagonists. A dose-related constrictor effect was obtained with NPY, which was significantly more potent than noradrenaline, constriction often being seen at 10(-12) M concentration. A vasorelaxant effect was seen in nonatherosclerotic vessels at higher concentrations. The vasoconstriction produced by noradrenaline was potentiated by subthreshold concentrations of NPY. The vasoconstrictor effect of NPY was not inhibited by prazosin (10(-6) M), and the vasodilatory effect was not inhibited by propranolol (10(-5) M). Indomethacin (3 X 10(-6) M) did not alter either vasoconstriction or vasorelaxation. The authors conclude that NPY is a potent constrictor of the human coronary artery at concentrations that may be achievable in vivo; it may thus be a contributor to sympathetic enhancement of coronary artery tone.

External wear of the polyethylene socket in cemented total hip arthroplasty.

We examined 59 cemented high density polyethylene sockets removed at revision hip arthroplasty. Of these 19 showed areas of wear between the outside of the socket and the acetabular bone. This was associated with lack of acrylic cement in those areas and was also related to the depth of the wear on the articulating surface of the socket. It is suggested that, in some cases, changes at the bone-cement junction are secondary to socket loosening and abrasion against the bone of the acetabulum, rather than to particles migrating from the metal-polyethylene interface. It is therefore important that impingement of the neck of the femoral stem on the edge of the cup be avoided and that, when the socket is inserted, it is not in direct contact with the bone.

Silane crosslinked polyethylene for prosthetic applications. II. Creep and wear behaviour and a preliminary moulding test.

Creep and wear tests have been carried out on a high density polyethylene crosslinked using a silane. A comparison of the results with those obtained for ultra high molecular weight polyethylene (RCH 1000) indicates the superiority of the crosslinked material. It can be injection moulded without difficulty. It is our conclusion that silane crosslinked polyethylene is an exciting prospect in the field of prosthetic materials.

Silane cross-linked polyethylene for prosthetic applications. Part I. Certain physical and mechanical properties related to the nature of the material.

Certain physical and mechanical tests have been conducted and scanning electron microscopy carried out in order to characterize a high density polyethylene cross-linked using vinyl trimethoxysilane. It is suggested that this cross-linked polyethylene could be an alternative to high molecular weight polyethylene for prosthetic applications.

Materials for internal prostheses: the present position and possible future developments.

In this paper we consider solid phase forming as a method of manufacturing acetabular cups. Static and cyclic creep tests have been carried out on Charnley cups and indicate that creep, rather than wear, plays the major role in the penetration of the socket by the femoral ball, at least in the first few years. We have investigated a new type of cross-linked polyethylene and found it to be extremely good from both a wear and creep viewpoint, particularly under high loads and at high sliding velocities.

The characteristics of acetabular cups worn in the human body.

In laboratory tests, the ultra-high molecular weight polyethylene used for the acetabular cups of Charnley hip prostheses has a very low wear rate against steel. In the body radiographic measurements indicate that the polyethylene wears more rapidly. In order to investigate this higher wear rate, the sockets of acetabular cups removed at post-mortem have been examined using optical and electron microscopy. It has been shown that a socket wears predominantly on its superior part and that this is a direct consequence of the orientation of the cup in the body and the direction of loading of the hip. In the worn region the femoral head in effect bores out a new socket for itself, a process which is visible with the naked eye after approximately eight years. Electron microscopy shows that the predominant wear mechanism is adhesion, but after about eight years the appearance of surface cracks suggests that surface fatigue is taking place in addition to this. Laboratory wear tests have shown that pure surface fatigue is not sufficient to account for the high clinical wear rate. Other deformation processes are suggested and discussed with regard to the higher clinical wear rate.

Regional cortical blood flow at craniotomy.

Regional cortical blood flow was monitored at craniotomy in 32 patients with a thermal diffusion flow probe in an attempt to assess the effects of surgical conditions on flow. Changes in flow due to vascular manipulation, retraction, hypotension, and hyperventilation were readily apparent. Eleven patients with supratentorial tumors had intermittent measurements of cerebral blood flow; the expected differences in blood flow with halothane anesthesia and hyperventilation were observed. Fourteen patients with aneurysms were monitored continuously and demonstrated a reduction in flow during hypotension; in two of these cases, the reduction was to disastrously low levels. Flow reduction occurred secondary to branch occlusion by the aneurysm clip in a patient with three middle cerebral artery aneurysms and was corrected by changing the clip position. Direct measurement of regional flow may be of value in estimating the safety of temporary clips and the degree of hypotension that can be tolerated.

Cortical blood flow in controlled hypotension as measured by thermal diffusion.

A thermal diffusion flow probe which gave a continuous, dynamic, quantitative record of cortical blood flow (CBF) was used to assess CBF in experimental animals with controlled hypotension. Acute hypotension was produced by trimethaphan camsylate, halothane, and sodium nitroprusside. Halothane produced less reduction in CBF per drop in blood pressure than the other two agents.