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Biomedical subjects

H Richards

Publications and source records attributed to H Richards.

At least 19 recordsLinked to original sources
PubMed1999

Anger as a predictor of aggression among incarcerated adolescents.

This study examined the validity of trait anger as a predictor of aggressive behavior among juvenile offenders. Two standard self-report anger scales were administered to 65 recently incarcerated male adolescents. These youths were followed prospectively for physical and verbal aggression during 3 months of subsequent incarceration. Anger scores were not correlated with participant history of violent offending or staff ratings of anger. However, anger scores from both instruments were predictive of subsequent physical and verbal aggression. For example, the Trait Anger scale successfully classified 66% of juvenile offenders into high and low aggressive groups; receiver operating characteristic analysis obtained an effect size of .72. These results support the predictive validity of self-reported anger in identifying juvenile offenders at risk for institutional aggression.

Adolescent↗
PubMed1998

Hydrodynamic properties of hydrocephalus shunts.

Hydrodynamic properties of hydrocephalus shunts are not always properly characterized by the manufacturer. Therefore, the choice of the shunt should be made, by matching performance of the shunt to the disturbed profile of CSF circulation of a given patient. The aim of the present shunt evaluation study is to evaluates all types of shunts presently in use in the U.K. and make this information available to neurosurgeons. Ten most common models of valves have been tested to date: Medtronik PS Medical: Delta Valve, Flow Control Valves and Lumbo-Peritoneal Shunt, Heyer-Schulte: In-line, Low Profile and Pudenz Flushing Valve, Codman: Medos-Programmable, Hakim-Precision, Sophy Programmable Valve, Cordis Orbis-Sigma. Our results show the majority of valves have low hydrodynamic resistance (exception: PS Lumboperitoneal, Orbis-Sigma), which increase by 100-200% after connection of a long distal catheter. A few shunts with siphon-preventing mechanism (Delta, Hayer-Schulte Low Profile, Pudenz-Flushing) offer reasonable resistance to negative outlet pressures, however, these valves may be blocked by raised subcutaneous pressure. All programmable valves are susceptible to siphoning. Programmed settings may be changed by external magnetic field.

Cerebrospinal Fluid Pressure↗
PubMed1997

A computing system for the clinical and experimental investigation of cerebrovascular reactivity.

We present a computing system for the recording and on-line analysis of analogue signals derived from bedside cerebrovascular monitors in different pathophysiological conditions. These include arterial blood pressure and oxygen saturation, end-tidal carbon dioxide concentration, cerebral blood flow velocities using transcranial Doppler ultrasonography, and concentration changes in cerebral oxy- and deoxyhaemoglobin from near infrared spectroscopy. Configuration and analysis adopts arithmetic expressions of different signal processing functions, various statistical properties for each signal, frequency spectrum analysis using fast Fourier transformation, and correlation/cross-correlation. The software offers off-line analysis of non-invasive tests of cerebrovascular reactivity. Several examples of clinical assessment of cerebrovascular reactivity are presented, including cerebral haemodynamic stress tests which employ carbon dioxide, acetazolamide, the breath holding test, leg cuff inflation and deflation, and transient carotid artery compression. Application within the experimental setting with induced haemorrhagic hypotension can also be used.

Cardiovascular Diseases↗
PubMed1996

A feedback-controlled pump produces stable hypotension in anaesthetised rabbits.

A method is described for the reliable production of controlled hypotension in experimental animals. Reduction in arterial blood pressure was obtained in rabbits by withdrawing arterial blood using a computer-driven pump operating within a feedback control system. Arterial blood pressure, blood flow velocity in the basilar artery (measured using transcranial Doppler), and anterior cortical microcirculation (measured using laser Doppler) were monitored. The aim of the experiments was to compare stability of hypotension produced using arterial blood pressure or basilar flow velocity as feedback control variables. Basilar artery flow velocity provided the most stable profound hypotension and during reinfusion when animals were not autoregulating. However, arterial blood pressure provided the most accurate stepwise control in autoregulating animals.

Anesthesia↗
PubMed1996

Rating child psychiatric caseness from detailed case histories.

Novel operationalized criteria were used to rate detailed psychiatric case histories on 151 schoolchildren with hemiplegia. Ratings of psychiatric caseness or non-caseness were reliable and valid; the method may be widely applicable. Caseness was defined both narrowly (in terms of social incapacity for the child) and broadly (in terms of disruption to others and distress too). Both definitions could be applied reliably to children of normal intelligence but broadly defined caseness was more reliable for children with low intelligence. Barely half of the psychiatric cases met operationalized criteria for one or more DSM-IV or ICD-10 diagnosis. The others mostly had partial or mixed syndromes that could, with clinical judgement, be assigned to "not otherwise specified' diagnoses. Even with clinical judgement, however, a substantial minority of children with low intelligence had clinically significant but undiagnosable abnormalities in social relatedness.

Affective Symptoms↗
PubMed1996

Are only children different? A study of child psychiatric referrals. A research note.

For this study, 683 only children seen in a psychiatric clinic were compared with 2364 children from two-child families seen in the same clinic. From the age of 5 years, there were no differences between the two groups. Among the under-5s, a higher proportion of only children had problems which did not warrant a psychiatric diagnosis, and their parents were more often rated as being over-protective. Our findings suggest, however, that the parents of only children differ from other parents not in being more over-protective but in being more willing or able to seek medical advice.

Adolescent↗
PubMed1996

Retrograde percutaneous gastrostomy and gastrojejunostomy in 505 children: a 4 1/2-year experience.

PURPOSE: To evaluate a technique of retrograde insertion of gastrostomy and gastrojejunostomy tubes with radiologic guidance in children. MATERIALS AND METHODS: During a 4 1/2-year period, 511 patients underwent attempted insertion of gastrostomy or gastrojejunostomy tubes. Patients' ages ranged from premature to 18.6 years (mean age, 3.8 years), and weight range was 0.8-86.0 kg (mean weight, 12 kg). The charts of 453 patients were reviewed. RESULTS: Placement was unsuccessful in six patients because of colonic interposition (n = 2), microgastria (n = 2), or hepatosplenomegaly (n = 2). Initial placement was a gastrostomy tube in 436 patients and a gastrojejunostomy tube in 69 patients. Sixty-eight gastrostomy tubes were converted to gastrojejunostomy tubes. Early complications (< 30 days) included skin infection (n = 11), stoma irritation (n = 20), and tube dislodgment (n = 6). Late complications included stoma irritation (n = 29), skin infection (n = 23), tube leakage (n = 14), and discomfort during feeding (n = 15). Two complications necessitated surgery: extragastric misplacement and small-bowel transgression. There were no tube-related deaths. CONCLUSION: Percutaneous retrograde placement of gastrostomy or gastrojejunostomy tubes safely and effectively provides long-term nutrition for children. A team approach is essential to provide service to this cumulative population.

Adolescent↗
PubMed1995

Child and adolescent psychiatric presentations of second-generation Afro-Caribbeans in Britain.

BACKGROUND: A clinical sample was used to investigate whether second-generation Afro-Caribbean children differed from other British-born children in their psychiatric presentation or vulnerability to risk factors. METHOD: Second-generation Afro-Caribbean patients (n = 292) were compared with a predominantly white group of patients (n = 1311) who lived in the same inner-city area and attended the same child psychiatric clinic between 1973 and 1989. Data on psychiatric presentation and background factors were systematically recorded at the time of the initial clinical assessment. RESULTS: Afro-Caribbean patients were exposed to more socio-economic disadvantage but less family dysfunction. The ratio of emotional to conduct disorders was lower among Afro-Caribbean than among the comparison patients--an effect that was not evidently due to demographic factors or diagnostic bias. Most risk factors for emotional or conduct disorders had comparable effects on Afro-Caribbean and comparison patients. Psychotic and autistic disorders were disproportionately common among the Afro-Caribbean patients. CONCLUSIONS: Second-generation Afro-Caribbean children differ somewhat from other British-born children in their psychiatric presentation--a difference that has persisted over the 1970s and 1980s and that deserves more investigation than it has received to date.

Acculturation↗
PubMed1994

Frequency-dependent properties of cerebral blood transport--an experimental study in anaesthetized rabbits.

Carotid arterial blood pressure and blood flow velocity in the basilar artery were studied in nine New Zealand rabbits under general anaesthesia. The cerebrovascular impedances for mean and maximal flow velocity were defined as the ratios of the respiratory and pulse waveforms of arterial blood pressure and blood flow velocities. The absolute values of these impedances were expressed and analysed as functions of frequency. Both functions decreased as frequency increased, demonstrating that a pulsatile blood movement need a lower energy expenditure than a continuous one. A minimum absolute value of impedance for flow velocity mean was found near 2.5-4 Hz in each rabbit. The impedance for mean flow velocity could be modelled by a second-order circuit, whereas the distribution of impedance for the maximal velocity had a more uniform character and could be approximated by a first-order model. A method of assessment of changes in cerebrovascular resistance using frequency properties of calculated impedance was proposed.

Animals↗
PubMed1994

Assessment of cerebral autoregulation with ultrasound and laser Doppler wave forms--an experimental study in anesthetized rabbits.

The aim of the study was to correlate changes in transcranial Doppler blood flow velocity wave form in the basilar artery with cortical red blood cell flux measured with a laser Doppler flowmeter during hemorrhage-induced hypotension in anesthetized and ventilated New Zealand rabbits. Although systolic flow velocity and flux exhibited an autoregulatory threshold at 45 mm Hg, diastolic flow velocity started to fall when mean arterial blood pressure fell below 65 mm Hg. The difference between the mean arterial blood pressure at which diastolic blood flow velocity decreases and the pressure at which mean flux decreases is the difference between systolic and diastolic blood pressure. The increasing divergence between systolic and diastolic flow velocities was reflected in an increase in the amplitude of blood flow velocity pulsations and pulsatility indices. An increase in flux pulsatile wave form was noted as cerebral resistive vessels dilated with hypotension.

Animals↗
PubMed1993

Identification of the minimal replicon of the streptomycete plasmid pIJ101.

The minimal replicon of pIJ101 was defined to a 2.0-kb BalI-SacII fragment containing the rep ORF and a non-coding region of DNA, but not orf56 (pQR435). This non-coding region of DNA was found to be crucial for plasmid replication in Streptomyces lividans and may contain either the origin of replication or the rep promoter (or both). A 1.4-kb NotI-SacII fragment containing only the rep ORF produced a 54-kDa protein in vitro when expressed from the lacZ promoter. pQR435 was structurally unstable in S. lividans and accumulated single-stranded (ss)DNA. The insertion of the site for second-strand initiation (ssi) into pQR435 did not prevent the plasmid from rearranging or from accumulating ssDNA.

DNA Replication↗