Open-loop and closed-loop postural control mechanisms in Parkinson's disease: increased mediolateral activity during quiet standing

Stabilogram-diffusion analysis was used to gain insights into how idiopathic Parkinson's disease (IPD) affects the postural control mechanisms involved in maintaining erect stance. Twenty-two subjects with IPD and twenty-four healthy elderly subjects were studied under eyes-open, quiet-standing conditions. The postural control mechanisms in the parkinsonian subjects, compared to the healthy elderly, were characterized by an increase in the effective stochastic activity in the mediolateral direction. Mediolateral posturographic measures were also associated with a history of falls and poor performance on clinical measures of balance. It is hypothesized that the increase in mediolateral activity in subjects with IPD may reflect an attempt to maintain potentially stabilizing movements during quiet standing in the face of impaired movement in the anteroposterior direction. This study supports the notion that mediolateral instability is an important posturographic marker of functional balance impairment in the elderly.

The amniotic fluid embolism syndrome: 10 years' experience at a major teaching hospital

A review of the syndrome of amniotic fluid embolism (AFE) was carried out over a 10 year period, 1984-1993, at the Royal Women's Hospital, Brisbane. There were 9 patients with AFE, of whom 2 died--this gave an incidence of fatal AFE of 3.37 per 100,000 pregnancies at the hospital, in comparison with an incidence of 1.03 per 100,000 pregnancies over a 27-year period in Australia. The study revealed no identifiable risk factors in the characteristics of the patient or her baby, labour and delivery. Three of the patients did not undergo labour and in 4 of the 6 who did, the duration was less than 12 hours. The AFE syndrome could present before, during or after delivery; the common features were shock and respiratory distress, with coagulopathy occurring in 5 patients. Current views of predisposing factors, pathogenesis, diagnosis and management are discussed.

Age-related changes in open-loop and closed-loop postural control mechanisms

In an earlier posturographic investigation (Collins and De Luca 1993) it was proposed that open-loop and closed-loop control mechanisms are involved in the regulation of undisturbed, upright stance. In this study, stabilogram-diffusion analysis was used to examine how the natural aging process affects the operational characteristics of these control mechanisms. Stabilogram-diffusion analysis leads to the extraction of repeatable center-of-pressure (COP) parameters that can be directly related to the steady-state behavior and functional interaction of the neuromuscular mechanisms underlying the maintenance of erect posture. Twenty-five healthy young males (aged 19-30 years) and twenty-five elderly males (aged 71-80 years) who were free of major gait and postural disorders were included in the study. An instrumented force platform was used to measure the time-varying displacements of the COP under each subject's feet during quiet standing. The COP trajectories were analyzed as one-dimensional and two-dimensional random walks, according to stabilogram-diffusion analysis. Using this technique, it was demonstrated cross-sectionally that healthy aging is associated with significant changes in the 'quasi-static' dynamics of the postural control system. (It was also shown that more traditional posturographic analyses, i.e., summary statistics, were not sensitive enough to detect these age-related differences.) It was found that the steady-state behavior of the open-loop postural control mechanisms in the elderly is more positively correlated and therefore perhaps more unstable, i.e., the output of the overall system has a greater tendency to move or drift away from a relative equilibrium point over the short term. In contrast with this result, it was also found that the steady-state behavior of the closed-loop postural control mechanisms in the elderly is more negatively correlated and therefore perhaps more stable, i.e., over the longer term, there is an increased probability that movements away from a relative equilibrium point will be offset by corrective adjustments back towards the equilibrium position. In addition, it was demonstrated that the elderly utilize open-loop control schemes for longer time intervals and correspondingly larger COP displacements during periods of undisturbed stance. This result suggests that in the elderly there is a greater delay, on average, before closed-loop feedback mechanisms are called into play. Finally, it was shown that there is an increased heterogeneity of postural control abilities in healthy older adults.

Choroid plexus cysts in the fetal brain

Choroid plexus cysts may be detected in the fetal choroid plexus on routine second trimester ultrasound scanning. The presence of these cysts is associated with trisomy 18 (Edward syndrome) in 3.47% of cases and with trisomy 21 (Down syndrome) in 0.46% of cases. The cysts themselves almost always disappear by 23 weeks and are thought to be a normal developmental variant. The world literature experience would indicate that the size of the choroid plexus cyst and the presence of bilateral cysts has no bearing on the magnitude of risk of chromosomal abnormality; 76% of babies with trisomy 18 also have other dysmorphic features which may be detectable by ultrasound. It is strongly advised that genetic counselling be undertaken and amniocentesis be considered when choroid plexus cysts are identified in the fetus.

An Instability in Neutron Stars at Birth

Calculations with a two-dimensional hydrodynamic simulation show that a generic Raleigh-Taylor-like instability occurs in the mantles of nascent neutron stars, that it is possibly violent, and that the standard spherically symmetric models of neutron star birth and supemova explosion may be inadequate. Whether this "convective" instability is pivotal to the supemova mechanism, pulsar magnetic fields, or a host of other important issues that attend stellar collapse remains to be seen, but its existence promises to modify all questions concerning this most energetic of astronomical phenomena.

Characterization of GP120 binding to CD4 and an assay that measures ability of sera to inhibit this binding

There is evidence that the initial interaction between HIV-1 and the host that is essential for infection is the specific binding of the viral envelope glycoprotein, gp120, to the CD4 molecule found on certain T cells and monocytes. Most individuals infected with HIV develop antibodies against the gp120 protein. Although in vitro treatment of CD4+ T cells with mAb to a specific epitope of the CD4 molecule (T4a) blocks virus binding, syncytia formation, and infectivity, it is unclear if antibodies to gp120 from an infected individual that can inhibit the binding of gp120 to CD4 is in any way related to the clinical course of disease. Our present study characterizes the binding of 125I-labeled rgp120 to CD4+ cells, and describes an assay system that measures a potentially relevant form of immunity to HIV infection, i.e., the blocking of HIV binding to CD4+ cells. Optimal binding conditions included a 2-h incubation at 22 degrees C, 4 x 10(6) CD4+ cells, and 1 nM gp120. The dissociation constant (KD) for gp120 binding to cell surface CD4 was 5 nM, and was inhibited by soluble CD4 and by mAb to T4a but not to T3 or T4. For the binding inhibition assay, negative controls included healthy seronegatives, seronegatives with connective tissue diseases, patients with HTLV-1 disease, and patients infected with HIV-2. In studying over 100 sera, the assay was highly sensitive (98%) and specific (100%). The majority of HIV+ sera could inhibit binding at dilutions of 1/100 to 1/1000. No correlation was noted between binding inhibition (BI) titer in this assay and clinical stage of HIV infection. In addition, there was no correlation between BI titer and HIV neutralizing activity. The BI titer was correlated with the titer of anti-gp160 (r = 0.63) and the titer of anti-gp120 (r = 0.52) antibodies determined by Western blot dilution. As with neutralizing antibodies and other forms of immune response to HIV, it is unclear what role antibody blocking of HIV binding to CD4+ cells may play in active immunity to HIV in infected individuals. This activity may prove to have some value in protection against initial HIV infection and, thus, the assay may be of use in monitoring vaccine trials.

Characterization of GP120 binding to CD4 and an assay that measures ability of sera to inhibit this binding

There is evidence that the initial interaction between HIV-1 and the host that is essential for infection is the specific binding of the viral envelope glycoprotein, gp120, to the CD4 molecule found on certain T cells and monocytes. Most individuals infected with HIV develop antibodies against the gp120 protein. Although in vitro treatment of CD4+ T cells with mAb to a specific epitope of the CD4 molecule (T4a) blocks virus binding, syncytia formation, and infectivity, it is unclear if antibodies to gp120 from an infected individual that can inhibit the binding of gp120 to CD4 is in any way related to the clinical course of disease. Our present study characterizes the binding of 125I-labeled rgp120 to CD4+ cells, and describes an assay system that measures a potentially relevant form of immunity to HIV infection, i.e., the blocking of HIV binding to CD4+ cells. Optimal binding conditions included a 2-h incubation at 22 degrees C, 4 x 10(6) CD4+ cells, and 1 nM gp120. The dissociation constant (KD) for gp120 binding to cell surface CD4 was 5 nM, and was inhibited by soluble CD4 and by mAb to T4a but not to T3 or T4. For the binding inhibition assay, negative controls included healthy seronegatives, seronegatives with connective tissue diseases, patients with HTLV-1 disease, and patients infected with HIV-2. In studying over 100 sera, the assay was highly sensitive (98%) and specific (100%). The majority of HIV+ sera could inhibit binding at dilutions of 1/100 to 1/1000. No correlation was noted between binding inhibition (BI) titer in this assay and clinical stage of HIV infection. In addition, there was no correlation between BI titer and HIV neutralizing activity. The BI titer was correlated with the titer of anti-gp160 (r = 0.63) and the titer of anti-gp120 (r = 0.52) antibodies determined by Western blot dilution. As with neutralizing antibodies and other forms of immune response to HIV, it is unclear what role antibody blocking of HIV binding to CD4+ cells may play in active immunity to HIV in infected individuals. This activity may prove to have some value in protection against initial HIV infection and, thus, the assay may be of use in monitoring vaccine trials.

Anterior nongranulomatous uveitis: a seasonal variation

A review of 348 consecutive cases of nontraumatic uveitis seen in the Wills Eye Hospital emergency room between Jan 1, 1981, and Dec 31, 1981, was conducted. Patients who presented with an initial episode of anterior nongranulomatous uveitis, without obvious etiology by history or clinical examination, were further evaluated for epidemiologic clues suggestive of a pathogenesis. This group consisted of 121 patients. A statistical analysis for seasonal variation suggested an increased occurrence during the summer months (p .01).

Patient-centred nursing care in a multi-racial society: the relevance of ethnographic perspectives in nursing curricula

The aim of the paper is to demonstrate the importance of including cultural dimensions as a fundamental component of nursing curricula and to provide some indications as to how this may be achieved. The concept of 'institutionalized racism' is examined, with reference to the absence of the cultural dimension in nursing education, and it is suggested that nurses, as members of a 'caring profession', should be in the forefront in promoting mutual cultural understanding. The argument for promoting cultural awareness is developed in the context of individualized nursing care and the nursing process. The needs of ethnic minority learners are considered along with their potential role, and that of tutors, in breaking down barriers to the acceptance of cultural diversity. Some possible reasons for the failure to include ethnographic perspectives in nurse education programmes are postulated, and finally suggestions as to how this curriculum deficit may be rectified are made. The paper concludes that British nurse educators should ensure that the needs of learners and patients are better provided for in the future by directing more attention to ethnographic perspectives relating to learning and the provision of nursing care.