The relationship between subjective sleep disturbance and attenuated psychotic symptoms after accounting for anxiety and depressive symptoms

BACKGROUND AND HYPOTHESES

Sleep disturbances are increasingly recognized as cooccurring with psychotic symptoms. The potential importance of this relationship is complicated when considering the effects of anxiety and depressive symptoms which commonly present in early-stage illness states. This study aimed to investigate the relationship between self-reported sleep disturbance on the development of attenuated psychotic symptoms (APS) cross-sectionally and longitudinally while adjusting for roles of anxiety and depressive symptoms.

DESIGN

Eight-hundred and two help-seeking young people aged 12 to 25 years who engaged with our Australian early intervention services were included in the study (the "Transitions" cohort). Cross sectional mediation and cross-lagged longitudinal (12-month) mediation models were developed with outcomes being different APS domains.

RESULTS

Only baseline excessive daytime sleepiness predicted later APS when accounting for previous APS, anxiety and depressive symptomatology. Cross sectionally, self-reported sleep disturbance showed both direct and indirect predictive relationships with all APS domains. Partial mediation through anxiety and depression was shown for unusual thought content, perceptual abnormalities, and disorganised speech, while full mediation through depression was shown for non-bizarre ideas.

CONCLUSIONS

The specificity of the relationship between self-reported sleep disturbance on APS highlights the potential for different roles in mechanistic models of psychotic symptom expression. This further indicates the need for further experimental research to illuminate potential causal pathways. Future research should continue to use continuous, symptom level approaches across a range of timeframes to more accurately model the complex dynamics present in the sleep-psychosis relationship.

Hybrid photocathode based on a Ni molecular catalyst and Sb2Se3 for solar H2 production

We report a H₂ evolving hybrid photocathode based on Sb₂Se₃ and a precious metal free molecular catalyst. Through the use of a high surface area TiO₂ scaffold, we successfully increased the Ni molecular catalyst loading from 7.08 ± 0.43 to 45.76 ± 0.81 nmol cm^-2, achieving photocurrents of 1.3 mA cm^-2 at 0 V vs. RHE, which is 81-fold higher than the device without the TiO₂ mesoporous layer.

Routes to increase performance for antimony selenide solar cells using inorganic hole transport layers

Simple compound antimony selenide (Sb₂Se₃) is a promising emergent light absorber for photovoltaic applications benefiting from its outstanding photoelectric properties. Antimony selenide thin film solar cells however, are limited by low open circuit voltage due to carrier recombination at the metallic back contact interface. In this work, solar cell capacitance simulator (SCAPS) is used to interpret the effect of hole transport layers (HTL), i.e., transition metal oxides NiO and MoO_x thin films on Sb₂Se₃ device characteristics. This reveals the critical role of NiO and MoO_x in altering the energy band alignment and increasing device performance by the introduction of a high energy barrier to electrons at the rear absorber/metal interface. Close-space sublimation (CSS) and thermal evaporation (TE) techniques are applied to deposit Sb₂Se₃ layers in both substrate and superstrate thin film solar cells with NiO and MoO_x HTLs incorporated into the device structure. The effect of the HTLs on Sb₂Se₃ crystallinity and solar cell performance is comprehensively studied. In superstrate device configuration, CSS-based Sb₂Se₃ solar cells with NiO HTL showed average improvements in open circuit voltage, short circuit current density and power conversion efficiency of 12%, 41%, and 42%, respectively, over the standard devices. Similarly, using a NiO HTL in TE-based Sb₂Se₃ devices improved open circuit voltage, short circuit current density and power conversion efficiency by 39%, 68%, and 92%, respectively.

Has improved treatment contributed to the declining rate of transition to psychosis in ultra-high-risk cohorts?

BACKGROUND

The factors contributing to declining psychotic disorder transition rates in ultra-high-risk populations remain unclear. We examined the contribution of longitudinal changes in standard clinical treatment ('treatment as usual') to this decline.

METHOD

An audit was conducted on 105 clinical files of patients who received standard care at a specialised ultra-high-risk service. The session notes of these files were quantified, allowing examination of treatment quantity, targets, psychotherapy, and medication. Differences in these aspects across patients' year of clinic entry were assessed. Variables with significant differences across years were examined using cox regression to assess their contribution to psychosis transition rates.

RESULTS

Findings were that, as a function of patients' year of clinic entry, there were increases in: patients' number of sessions, cognitive behavioural therapy (CBT), problem and solving therapy. There was a relationship between baseline year cohort and psychosis transition rate, with lower rates observed in more recent cohorts. When changes in treatment between cohorts were adjusted for, the relationship between baseline year cohort and transition rate disappeared. The relationship between baseline year and transition rate was attenuated most by increases in CBT.

CONCLUSION

Changes in standard treatment, particularly increases in CBT, may have contributed to the decline in psychosis risk observed in recent ultra-high-risk cohorts, although these variables do not fully explain this trend. Implications for clinical practice, prediction and intervention research are discussed. Future ultra-high-risk research should investigate the impact of other treatment factors, such as therapeutic alliance.

Identification of lead vacancy defects in lead halide perovskites

Perovskite photovoltaics advance rapidly, but questions remain regarding point defects: while experiments have detected the presence of electrically active defects no experimentally confirmed microscopic identifications have been reported. Here we identify lead monovacancy (VPb) defects in MAPbI3 (MA = CH3NH3+) using positron annihilation lifetime spectroscopy with the aid of density functional theory. Experiments on thin film and single crystal samples all exhibited dominant positron trapping to lead vacancy defects, and a minimum defect density of ~3 × 1015 cm-3 was determined. There was also evidence of trapping at the vacancy complex [Formula: see text] in a minority of samples, but no trapping to MA-ion vacancies was observed. Our experimental results support the predictions of other first-principles studies that deep level, hole trapping, [Formula: see text], point defects are one of the most stable defects in MAPbI3. This direct detection and identification of a deep level native defect in a halide perovskite, at technologically relevant concentrations, will enable further investigation of defect driven mechanisms.

How Oxygen Exposure Improves the Back Contact and Performance of Antimony Selenide Solar Cells

The improvement of antimony selenide solar cells by short-term air exposure is explained using complementary cell and material studies. We demonstrate that exposure to air yields a relative efficiency improvement of n-type Sb₂Se₃ solar cells of ca. 10% by oxidation of the back surface and a reduction in the back contact barrier height (measured by J-V-T) from 320 to 280 meV. X-ray photoelectron spectroscopy (XPS) measurements of the back surface reveal that during 5 days in air, Sb₂O₃ content at the sample surface increased by 27%, leaving a more Se-rich Sb₂Se₃ film along with a 4% increase in elemental Se. Conversely, exposure to 5 days of vacuum resulted in a loss of Se from the Sb₂Se₃ film, which increased the back contact barrier height to 370 meV. Inclusion of a thermally evaporated thin film of Sb₂O₃ and Se at the back of the Sb₂Se₃ absorber achieved a peak solar cell efficiency of 5.87%. These results demonstrate the importance of a Se-rich back surface for high-efficiency devices and the positive effects of an ultrathin antimony oxide layer. This study reveals a possible role of back contact etching in exposing a beneficial back surface and provides a route to increasing device efficiency.

Vacancy-Ordered Double Perovskite Cs2TeI6 Thin Films for Optoelectronics

Alternatives to lead- and tin-based perovskites for photovoltaics and optoelectronics are sought that do not suffer from the disadvantages of toxicity and low device efficiency of present-day materials. Here we report a study of the double perovskite Cs₂TeI₆, which we have synthesized in the thin film form for the first time. Exhaustive trials concluded that spin coating CsI and TeI₄ using an antisolvent method produced uniform films, confirmed as Cs₂TeI₆ by XRD with Rietveld analysis. They were stable up to 250 °C and had an optical band gap of ∼1.5 eV, absorption coefficients of ∼6 × 10⁴ cm^-1, carrier lifetimes of ∼2.6 ns (unpassivated 200 nm film), a work function of 4.95 eV, and a p-type surface conductivity. Vibrational modes probed by Raman and FTIR spectroscopy showed resonances qualitatively consistent with DFT Phonopy-calculated spectra, offering another route for phase confirmation. It was concluded that the material is a candidate for further study as a potential optoelectronic or photovoltaic material.

Evidence for Self-healing Benign Grain Boundaries and a Highly Defective Sb2Se3-CdS Interfacial Layer in Sb2Se3 Thin-Film Photovoltaics

The crystal structure of Sb₂Se₃ gives rise to unique properties that cannot otherwise be achieved with conventional thin-film photovoltaic materials, such as CdTe or Cu(In,Ga)Se₂. It has previously been proposed that grain boundaries can be made benign provided only the weak van der Waals forces between the (Sb₄Se₆)_n ribbons are disrupted. Here, it is shown that non-radiative recombination is suppressed even for grain boundaries cutting across the (Sb₄Se₆)_n ribbons. This is due to a remarkable self-healing process, whereby atoms at the grain boundary can relax to remove any electronic defect states within the band gap. Grain boundaries can, however, impede charge transport due to the fact that carriers have a higher mobility along the (Sb₄Se₆)_n ribbons. Because of the ribbon misorientation, certain grain boundaries can effectively block charge collection. Furthermore, it is shown that CdS is not a suitable emitter to partner Sb₂Se₃ due to Sb and Se interdiffusion. As a result, a highly defective Sb₂Se₃ interfacial layer is formed that potentially reduces device efficiency through interface recombination.

Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting

Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30 mA cm-2 at 0 V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10 h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production.

Basic symptoms in young people at ultra-high risk of psychosis: Association with clinical characteristics and outcomes

There has been limited research into the predictive value of basic symptoms and their relationship with other psychopathology in patients identified using the 'ultra high risk' (UHR) for psychosis approach. The current study investigated whether basic symptoms, specifically cognitive disturbances (COGDIS), were associated with a greater risk of transition to psychotic disorder and persistent attenuated psychotic symptoms (APS) at medium term follow-up (mean = 3.4 years) in UHR patients, as well as with general psychopathology at baseline. The sample included 304 UHR participants (mean age = 19.12 years) involved in an international multicenter trial of omega-3 fatty acids. UHR individuals who also met the COGDIS criteria (basic symptoms risk criteria) did not have a greater risk of transition than those who met the UHR criteria alone. However, meeting COGDIS risk criteria was associated with a greater likelihood of meeting the UHR attenuated psychotic symptoms risk group (i.e., having persistent attenuated psychotic symptoms) at 12-month follow-up (odds ratio = 1.85; 95% CI = 1.03, 3.32). Greater severity of cognitive basic symptoms was also independently associated with more severe general psychopathology at study entry. The findings do not support the notion that combined risk identification approaches (UHR and basic symptoms) aid in the identification of individuals at greatest risk of psychosis, although this interpretation is limited by the modest transition to psychosis rate (13%) and the time of follow up. However, the findings indicate that basic symptoms may be a clinically useful marker of more severe general psychopathology in UHR groups and risk for persistent attenuated psychotic symptoms.

The prognostic significance of attenuated psychotic symptoms in help-seeking youth

BACKGROUND

Recent findings suggest that attenuated psychotic symptoms (APS) might serve as a risk factor for general mental health impairment in help-seeking youth. The current study was designed to test this possibility by examining the prognostic significance of APS in a large cohort of help-seeking youth not selected for psychosis risk.

METHOD

465 youth aged 12-25 referred to general youth mental health services were grouped as either APS + or APS- based on whether or not they met 'ultra high risk' for psychosis APS risk criteria as assessed using the Comprehensive Assessment of At Risk Mental States (CAARMS). They completed clinical assessments at baseline and at 12-month follow-up, measuring a range of psychopathology (depression, anxiety, eating disorders, general psychological distress, substance abuse) and psychosocial functioning.

RESULTS

APS + had significantly poorer outcomes at 12-months on a range of clinical variables, even after adjusting for baseline scores and amount of treatment received. However, the APS + group showed greater improvement in functioning at follow-up compared to APS-.

CONCLUSION

Attenuated psychotic symptoms are a prognostic indicator of persistent transdiagnostic mental health problems and reduced response to treatment in help-seeking youth over the short term. Hence, it is critical to screen and assess attenuated psychotic symptoms at the primary and secondary mental health services level, especially given that these subclinical symptoms are rarely voluntarily reported.

Stability and Performance of CsPbI2Br Thin Films and Solar Cell Devices

In this manuscript, the inorganic perovskite CsPbI₂Br is investigated as a photovoltaic material that offers higher stability than the organic-inorganic hybrid perovskite materials. It is demonstrated that CsPbI₂Br does not irreversibly degrade to its component salts as in the case of methylammonium lead iodide but instead is induced (by water vapor) to transform from its metastable brown cubic (1.92 eV band gap) phase to a yellow phase having a higher band gap (2.85 eV). This is easily reversed by heating to 350 °C in a dry environment. Similarly, exposure of unencapsulated photovoltaic devices to water vapor causes current (J_SC) loss as the absorber transforms to its more transparent (yellow) form, but this is also reversible by moderate heating, with over 100% recovery of the original device performance. NMR and thermal analysis show that the high band gap yellow phase does not contain detectable levels of water, implying that water induces the transformation but is not incorporated as a major component. Performances of devices with best efficiencies of 9.08% (V_OC = 1.05 V, J_SC = 12.7 mA cm^-2 and FF = 68.4%) using a device structure comprising glass/ITO/c-TiO₂/CsPbI₂Br/Spiro-OMeTAD/Au are presented, and further results demonstrating the dependence of the performance on the preparation temperature of the solution processed CsPbI₂Br films are shown. We conclude that encapsulation of CsPbI₂Br to exclude water vapor should be sufficient to stabilize the cubic brown phase, making the material of interest for use in practical PV devices.

In-depth analysis of chloride treatments for thin-film CdTe solar cells

CdTe thin-film solar cells are now the main industrially established alternative to silicon-based photovoltaics. These cells remain reliant on the so-called chloride activation step in order to achieve high conversion efficiencies. Here, by comparison of effective and ineffective chloride treatments, we show the main role of the chloride process to be the modification of grain boundaries through chlorine accumulation, which leads an increase in the carrier lifetime. It is also demonstrated that while improvements in fill factor and short circuit current may be achieved through use of the ineffective chlorides, or indeed simple air annealing, voltage improvement is linked directly to chlorine incorporation at the grain boundaries. This suggests that focus on improved or more controlled grain boundary treatments may provide a route to achieving higher cell voltages and thus efficiencies.

Dispersion relation data for methylammonium lead triiodide perovskite deposited on a (100) silicon wafer using a two-step vapour-phase reaction process

Ellipsometry was used to measure the amplitude ratio and phase difference of light undergoing a phase shift as it interacts with a thin film of organic–inorganic hybrid perovskite CH₃NH₃PbI₃ (MAPI) deposited onto a (100) silicon wafer. The refractive index and extinction coefficient was extracted from a multi-oscillator model fit to the ellipsometry data, as a function of wavelength, from 300 to 1500 nm.

Molecular bridging of silicon nanogaps

The highly doped electrodes of a vertical silicon nanogap device have been bridged by a 5.85 nm long molecular wire, which was synthesized in situ by grafting 4-ethynylbenzaldehyde via C-Si links to the top and bottom electrodes and thereafter by coupling an amino-terminated fluorene unit to the aldehyde groups of the activated electrode surfaces. The number of bridging molecules is constrained by relying on surface roughness to match the 5.85 nm length with an electrode gap that is nominally 1 nm wider and may be controlled by varying the reaction time: the device current increases from ≤1 pA at 1 V following the initial grafting step to 10-100 nA at 1 V when reacted for 5-15 min with the amino-terminated linker and 10 μA when reacted for 16-53 h. It is the first time that both ends of a molecular wire have been directly grafted to silicon electrodes, and these molecule-induced changes are reversible. The bridges detach when the device is rinsed with dilute acid solution, which breaks the imine links of the in situ formed wire and causes the current to revert to the subpicoampere leakage value of the 4-ethynylbenzaldehyde-grafted nanogap structure.

Stress and HPA-axis functioning in young people at ultra high risk for psychosis

It is thought that hypothalamic-pituitary-adrenal (HPA) axis functioning mediates between the experience of stress and development of psychotic symptoms. This study aimed to evaluate this model in a cohort of young people at ultra high risk (UHR) of psychosis. Information about the experience of psychological symptoms and recent stressful experiences was obtained from 23 young people who met UHR criteria. Plasma samples were taken to assess cortisol and glucocorticoid receptor numbers, and an MRI scan was also performed. Plasma cortisol levels were significantly and positively correlated with the experience of 'hassles' but not with the experience of stressful life events. Significant positive associations were also found between plasma cortisol levels and level of depression and anxiety. No significant relationships were found between plasma cortisol level and global psychopathology, psychotic symptomatology, functioning or pituitary and hippocampal volumes. These results suggest that the number of hassles experienced by young people at UHR of psychosis could be an important factor in raising their cortisol levels, which might, in turn, affect the severity of depressive and anxiety symptoms. No other relationships were found between plasma cortisol levels and the experience of psychotic symptoms, functioning or hippocampal and pituitary volumes. These results indicate possible impairment in HPA-axis functioning in the early stages of psychotic illness, but further investigation of the relationships between these parameters is required.

HPA axis functioning associated with transition to psychosis: combined DEX/CRH test

We investigated functioning of the hypothalamic-pituitary-adrenal (HPA) axis in 12 young people at ultra high risk for developing psychosis, using the combined dexamethasone corticotrophin releasing hormone (DEX/CRH) test. Over a two year period, three of the 12 participants developed an acute psychosis. Descriptive analysis of the data indicated that contrary to expectations, participants who did not make the transition to psychosis had on average higher cortisol levels at the latter stages of the test, as well as a greater severity of depression and anxiety symptoms, than participants who subsequently developed psychosis. These preliminary results suggest that dysregulated HPA-axis functioning in individuals at high risk for psychosis may be associated more with comorbid depression symptoms than factors specifically related to the process of emerging psychosis illness.

Neuroimaging and emerging psychotic disorders: the Melbourne ultra-high risk studies

Although the underlying neurobiology of emerging psychotic disorders is not well understood, evidence from structural imaging and other studies support the notion that schizophrenia arises as a consequence of both an 'early neurodevelopmental' disturbance, as well as 'late neurodevelopmental' changes occurring during the initial stages of a psychotic illness, including around the time of transition to illness. In line with this, our longitudinal MRI findings in individuals at ultra-high risk for developing a psychotic illness show that there are excessive neuroanatomical changes in those who convert to psychosis. These aberrant changes are observed most prominently in medial temporal and prefrontal lobe regions. In a further series of longitudinal studies in first-episode psychosis, we have identified changes in prefrontal regions that indicate an accelerated loss of grey matter in patients compared to healthy control subjects. We suggest that the available evidence is consistent with the presence of subtle regionally and temporally specific neurobiological changes through the course of psychosis (Pantelis et al., 2005), including: (1) evidence for early (pre- and peri-natal) neurodevelopmental anomalies, (2) evidence for progressive grey matter loss involving medial temporal and orbital prefrontal regions around the time of transition to illness, and (3) evidence of late (post-pubertal) neurodevelopmental changes soon after the onset of psychosis, involving an acceleration of normal brain maturational processes, associated with significant loss of grey matter in dorsal prefrontal regions. The pathological processes underlying such changes remain unclear and may reflect anomalies in genetic and/or other endogenous mechanisms responsible for brain maturation, the adverse effects of intense or prolonged stress, or other environmental factors. These findings suggest that early markers of impending illness may prove difficult to define, and that brain changes in psychosis may better be conceptualized as anomalous trajectories of brain development. Further, active changes during transition to illness may present the potential to intervene and ameliorate these changes with potential benefit clinically.

Early-onset of symptoms predicts conversion to non-affective psychosis in ultra-high risk individuals

OBJECTIVE

We examined if age of onset of psychiatric symptoms and/or sex predict conversion to non-affective or affective psychosis in individuals considered to be at ultra-high risk for schizophrenia.

METHOD

Participants (n=86) were offered treatment and monthly follow-up until transition to psychosis, or for 12 months if they did not meet exit criteria for psychotic disorder. Individuals without transition to psychosis at 12-month were reassessed approximately 3 years after the end of the treatment phase. Ultra-high risk was defined by the presence of subthreshold and/or self-limiting psychotic symptoms and/or having a family history of psychotic disorder combined with functional decline. Cox regressions after adjustment for treatment interventions were applied to investigate associations between age of onset, sex, and other baseline measures with progression to psychotic outcomes.

RESULTS

Early age of onset of psychiatric symptoms, in particular onset before age 18 was the only tested variable that significantly predicted non-affective psychosis. Independent significant predictors of affective psychosis were poor functioning, female sex and the presence of a combination of intake criteria (family history of psychosis plus drop in functioning, and attenuated and/or brief limited psychotic symptoms) at baseline.

CONCLUSIONS

Age of onset of psychiatric symptoms is the single most important factor associated with conversion to non-affective psychosis in ultra-high risk individuals.

Spatial working memory ability is a marker of risk-for-psychosis

BACKGROUND

Working memory has been identified as a core cognitive deficit in schizophrenia that is associated with negative symptoms, but it is unclear whether it is impaired prior to onset of psychosis in symptomatic patients.

METHOD

Thirty-eight young people at ultra high-risk (UHR) of developing psychosis (of whom nine later became psychotic) were compared with 49 healthy controls on tests of spatial working memory (SWM) and delayed matching-to-sample (DMTS).

RESULTS

Both SWM and DMTS performance was significantly poorer in the UHR groups. Those who later became psychotic generally performed more poorly than those who did not, although this did not reach significance for any measure. A significant association between SWM errors and negative symptoms was seen in the later-psychotic group only (P = 0.02).

CONCLUSIONS

Spatial working memory abilities are impaired in those at high-risk for psychosis. The relationship between working memory and negative symptoms may be useful as a predictive tool.

Identification of young people at risk of psychosis: validation of Personal Assessment and Crisis Evaluation Clinic intake criteria

OBJECTIVE

To describe the development and validation of the criteria used at the Personal Assessment and Crisis Evaluation (PACE) Clinic to identify young people at 'ultra-high' risk of developing a psychotic disorder within a short follow-up period.

METHOD

The PACE Clinic criteria initially grew out of clinical observations and retrospective research describing the prodromal phase of first-episode psychosis. Early prospective research refined the criteria into the three intake groups for the Clinic. These criteria combine putative state and trait risk factors for psychosis. Whether or not a person meets criteria for one or more of these groups can usually be determined by a thorough psychological assessment interview. Two early studies are described that assess the validity of this screening protocol.

RESULTS

The transition rate to acute psychosis of the 'ultra-high' risk group identified in the second study was 41%.

CONCLUSIONS

These results suggest that it is possible to accurately identify young people at imminent risk of psychosis. The PACE criteria have now been adopted (or adapted) by a number of other clinical research programs both in Australia (i.e. Psychological Assistance Service in Newcastle) and other programs in the United States and elsewhere. This research may lead the way to the development of preventive interventions for the ultra-high risk group.

Prediction of psychosis. A step towards indicated prevention of schizophrenia

BACKGROUND

The identification of people at high risk of becoming psychotic within the near future creates opportunities for early intervention prior to the onset of psychosis to prevent or minimise later ill-health. The present study combines current knowledge about risk factors for schizophrenia with our knowledge of psychotic prodromes in an attempt to identify a group particularly vulnerable to impending psychosis. We wanted to identify people with high likelihood of transition to psychosis within a follow-up period of 12 months, and to determine the rate of transition to psychosis in this group.

METHOD

Various state and trait risk factors for psychosis were used alone and in combination to operationally define a putatively high-risk group. Operationalised criteria for onset of psychosis were established. The individuals were assessed monthly on measures of psychopathology for six months.

RESULTS

Eight out of 20 people made the transition to frank psychosis within a six-month follow-up period. Follow-up of this group is still in progress, and the 12 month transition rate might prove to be higher still.

CONCLUSIONS

We have demonstrated that it is possible to identify individuals with a high likelihood of onset of psychosis within a brief follow-up period. This lays the foundation for early treatment in an attempt to prevent, delay or minimise the severity of first onset of schizophrenia.

Glucocorticoids and progestins signal the initiation and enhance the rate of myelin formation

Dexamethasone and progesterone have been found to accelerate the time of initiation and enhance the rate of myelin synthesis in Schwann cell/neuronal cocultures. The expression of mRNA for cytochrome P450scc (converts cholesterol to pregnenolone), 3beta-hydroxysteroid dehydrogenase (converts pregnenolone to progesterone), and the progesterone receptor were detected and markedly induced during peak myelin formation in the cocultures. The mRNA for the glucocorticoid receptor was detected, but was found to be constituitively expressed. In addition, the specific activity of 3beta-hydroxysteroid dehydrogenase was measured and found to increase by 10-fold. The mRNA for cytochrome P450scc and 3beta-hydroxysteroid dehydrogenase also were found to be induced during the differentiation of O-2A precursor cells to oligodendrocytes. Fibroblast growth factor and platelet-derived growth factor were found to have proliferative effects on Schwann cells, but they had no effect on the initiation or the rate of myelin formation. These results demonstrate that myelin-forming cells have inducible enzymes responsible for steroid biosynthesis and suggest a critical role for endogenous steroid hormones in signaling the initiation and enhancing the rate of myelin formation.

Distributions of total skin surface area to body weight ratios for use in dermal exposure assessments

Surface area to body weight ratios were calculated for three age groups of the population using direct measurement data reported in the scientific literature. A strong negative correlation was observed between these ratios and age, and ratios did not differ as a function of sex. Distribution data for surface area to body weight ratios are presented for three age groups. Because of the strong correlation between these two factors, the use of these distributions in human exposure/risk assessments using point estimation techniques and/or Monte Carlo simulations may be more appropriate than treating surface area and body weight as independent variables.

Replacement and care compliance in a planned replacement contact lens program

Three-hundred and seven contact lens wearers in a planned replacement program were evaluated to determine compliance with scheduled replacement, yearly evaluation, and lens care. Patients studied were wearing soft lenses and replaced them every 6 months or less but were not using disposable lenses. Those involved were in this program for more than 24 months. The results show a 97.1 percent compliance with lens replacement and a 94.7 percent compliance with scheduled annual visits. The 32.4 percent lens care compliance rate for a single solution system was lower than expected.

Evaluation of criteria for the acceptance of bioanalytical data

Results from bioanalytical analyses for registration of a new drug entity are used to define its pharmacokinetics and bioavailability/bioequivalence. Whilst analytical data may be derived from the application of a validated method, it is essential to apply mathematical criteria to its acceptance, in order that the analyst can be assured that the assay is performing within defined limits and to its validated specification. Parameters evaluated for acceptability are the batch calibration curve, the minimum quantifiable concentration and the quality control (QC) sample acceptability. Specifically, six QC samples per analytical batch are used, two samples at each of three concentrations. The rationale for the definition of these criteria is evaluated together with a consideration of their applications and limitations. The relevance and use of Shewhart and Cusum plots to monitor assay performance is illustrated.

In vitro collagen fibril assembly: thermodynamic studies

The in vitro fibril assembly of calf skin collagen was examined as a function of ionic strength and temperature. In a 0.03 M NaPi, pH 7.0, buffer, fibril assembly required a minimum critical concentration of collagen. At nearly physiological ionic strengths and temperatures, the critical concentration was less than 1 microgram/mL and required a very sensitive method for measurement. Raising the ionic strength of the buffer resulted first in higher and then lower critical concentrations. Raising the temperature led to lower critical concentrations. A van't Hoff plot of the fibril growth constant calculated from the critical concentration gave positive enthalpy changes and positive heat capacity changes which indicate that the fibril growth is driven by both hydrophobic and ionic inter-collagen interactions. Sedimentation equilibrium studies showed the collagen to be monomeric at subcritical concentrations. Differential scanning microcalorimetric studies showed only one very sharp heat absorption peak for the fibril assembly which coincided with the appearance of solution turbidity. Within experimental error, the enthalpy changes of the fibril assembly measured with the microcalorimeter were of the same magnitude as the van't Hoff enthalpy changes. These results are discussed in light of a cooperative nucleation-growth mechanism of collagen fibril assembly proposed earlier.

The radiosensitivity of embryos of domestic chickens and black-headed gulls

Eggs of domestic chickens and black-headed gulls were continuously exposed to gamma-rays during incubation, using dose rates ranging from 0.004 to 0.08 Gy h-1 for 20 days. Acute-dose experiments were also conducted, and eggs were irradiated on day 10 of incubation with doses of between 1.92 and 28.8 Gy. Hatchability and numbers reaching full-term developed were affected only after chronic doses of 9.6 Gy and acute doses of 4.8 Gy or higher. Maximum embryo mortality occurred around days 10-11 of incubation and just before hatching, in all experiments. An increase in foot and limb deformities was observed above acute and chronic doses of 9.6 Gy.

Counting processes in deaf children's arithmetic

Ten profoundly deaf children and 10 hearing controls matched for arithmetical achievement were given integer additions to classify as right or wrong. Hearing children perform this task by using covert counting strategies which have been assumed to be subvocal. In view of deaf children's poor spoken language abilities it was expected that the deaf group would make little or no use of such covert counting strategies and would rely more on alternative methods such as recalling learned number facts from long-term memory. The results failed to confirm this expectation and showed that classification times for the deaf were generally consistent with the same counting model as for the hearing. There was no difference between the groups in responses to correct sums involving ties or to incorrect sums, potential indicators of the use of associative retrieval. It is suggested that the covert counting processes of both deaf and hearing children in integer addition do not involve subvocalization. Alternative possibilities and general implications of this result for the education of the deaf are discussed.

Intraocular lenses: an update

The use of intraocular lenses has been rapidly increasing in recent years. Improved designs and newer surgical techniques have reduced already low complication rates making implantation of an intraocular lens the procedure of choice for both patients and practitioners. Trends in lens design and a review of the most recent literature is offered for the practitioner.

Evaluation of the binocularity of 147 unilateral and bilateral pseudophakic patients

Tests of binocular functions were performed on a group of 147 patients with unilaterally or bilaterally implanted intraocular lenses. The quality of the binocular vision achieved was significantly better than that of unilateral aphakic patients wearing contact lenses. Compared to the normal population, the stereoscopic threshold in the pseudophakic population was found to be slightly poorer. Visual acuity, anisometropia, lens fixation, and vertical deviation were analyzed in relation to stereopsis.

Intraocular lenses and their follow-up in the optometric office

A broad overview of intraocular lens implantation is presented for the optometrist. Included in this overview is a review of the most recent literature comparing complication rates for lens implants versus standard cataract surgery. A proportion of the paper addresses itself to the pre and post-operative optometric management of the pseudophakic patient. This paper is presented to give the optometrist a basic understanding of the expanding field of intraocular lens implantation as well as a reference list which will serve as a starting point for further review.

Evaluation of 225 consecutive intraocular-lens implants

A retrospective study of the first 225 intraocular lens implants (IOL) performed by a single surgeon was conducted for this report. In complication rate and visual acuity assessed 4.5 months postoperatively, these patients (pseudophakes) compared very closely with 2 populations of aphakic patients who had had phacoemulsification surgery without lens implantation by the same surgeon. The majority of pseudophakes were left with moderate to low refractive errors. Patient satisfaction was found to be high. It appears that implantation of iris and capsular fixated intraocular lenses is a comparatively safe and in many cases advantageous procedure.