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J Townsend

Publications and source records attributed to J Townsend.

At least 37 records · Page 2Linked to original sources
PubMed2001

A comparision of linear-array and mechanical-sector cranial ultrasound scanning techniques to predict neurodevelopmental outcome at 8 years in preterm newborn infants.

Two methods of neonatal cranial ultrasound (US) scanning, linear-array and mechanical-sector, were compared for their accuracy in predicting neurodevelopmental outcome in a cohort of 854, of whom 782 (92%) infants, all born less than 33 weeks of gestation and cared for on the Neonatal Intensive Care Unit at University College Hospital, London between 1979 and 1988, were included in the analysis. A total of 205 infants were studied by linear-array and 577 infants by mechanical-sector scan. Ultrasound findings were grouped into three risk categories on the basis of the US diagnosis. Outcome was assessed at 8 years of age. The probability estimates for neurologically disabling and nondisabling impairments, extra education and mean IQ were compared for the two US methods. There was no significant difference between the two methods in the accuracy of prediction of neurodevelopmental outcome.

Brain Diseases↗
PubMed2001

Neurodevelopmental status at 1 year predicts neuropsychiatric outcome at 14-15 years of age in very preterm infants.

BACKGROUND: Neurodevelopmental and behavioural problems have been repeatedly reported in very preterm survivors, often showing themselves later in childhood as poor school performance. Early identification of problems would mean that appropriate remedial therapy can be implemented. We have previously shown that neurodevelopmental status at 1 year was predictive of outcome at 8 years in a cohort of preterm infants. The aim of this paper was to see if neurodevelopmental outcome in adolescence could be predicted by assessment by 1 year in the same cohort of preterm infants. STUDY DESIGN: Prospective cohort study. SUBJECTS: 150 adolescents, born before 33 weeks gestation. OUTCOME MEASURES: Neurological examination, developmental quotient, vision and hearing by 1 year. At 14-15 years, neurological examination, school performance questionnaire, Schonnell test of reading age, a premorbid adjustment score, Rutter behavioural score and for those born from 1981, cognitive tests (WISC-R). RESULTS: A highly significant relationship existed between neurological status by 1 year and the need for extra educational provision, overall neurodevelopmental status, cognitive function in those that had their IQs measured and premorbid adjustment score of prepsychotic symptoms in adolescence. However, status at 1 year was not predictive of adolescent reading age or behavioural score. CONCLUSIONS: Neurodevelopmental assessment at 1 year is predictive of school performance and outcome in the adolescent period.

Adolescent↗
PubMed2001

Event-related brain response abnormalities in autism: evidence for impaired cerebello-frontal spatial attention networks.

Although under some conditions the attention-related late positive event-related potential (ERP) response (LPC) is apparently normal in autism during visual processing, the LPC elicited by visuospatial processing may be compromised. Results from this study provide evidence for abnormalities in autism in two components of the LPC generated during spatial processing. The early frontal distribution of the LPC which may reflect attention orienting was delayed or missing in autistic subjects during conditions in which attention was to peripheral visual fields. The later parietal distribution of the LPC which may be associated with context updating was smaller in amplitude in autistic subjects regardless of attention location. Both abnormalities suggest disruption of function in spatial attention networks in autism. Evidence that the cerebellar abnormalities in autism may underlie these deficits comes from: (1) similar results in ERP responses and spatial attention deficits in patients with cerebellar lesions; (2) brain-behavior correlations in normally functioning individuals associating the size of the posterior cerebellar vermis and the latency of the frontal LPC; and (3) a previously reported complementary correlation between the size of the posterior vermal lobules and spatial orienting speed. Although the scalp-recorded LPC is thought to be cortically generated, it may be modulated by subcortical neural activity. The cerebellum may serve as a modulating influence by affecting the task-related antecedent attentional process. The electrophysiological abnormalities reported here index spatial attention deficits in autism that may reflect cerebellar influence on both frontal and parietal spatial attention function.

Adolescent↗
PubMed2001

The equine hypophysis: a gland for all seasons.

The intrahypophysial mechanisms involved in the control of gonadotrophin secretion remain unclear. In the horse, a divergent pattern of gonadotrophins is observed at different stages of the reproductive cycle in response to a single secretagogue (gonadotrophin-releasing hormone), and dramatic changes in fertility take place throughout the year in response to photoperiod. This species thus provides a useful model to investigate the regulation of fertility directly at the level of the hypophysis. A series of studies were undertaken to examine the cytological arrangements and heterogeneity of gonadotrophin storage in the pars distalis (PD) and pars tuberalis (PT) of the hypophysis of male and female horses. Specifically, the seasonal and gonadal effects on distribution, density and hormonal identity of gonadotrophs, the existence of gonadotroph-lactotroph associations and the expression of prolactin receptors (PRL-R) as possible morphological bases for the differential control of gonadotrophin secretion were investigated. It became apparent that both isolated and clustered gonadotrophs are normally distributed around the pars intermedia and surrounding capillaries in the PD, and in the caudal ventral region of the PT. In the PD, no effects of season or of reproductive state on the density or number of gonadotrophs could be detected in either male or female animals. In contrast, a fivefold increase in gonadotroph density was observed in the PT during the sexually active stage. In males, robust gonadal effects were detected on the gonadotroph population; orchidectomy significantly reduced both the number and proportion of gonadotrophs, in relation to other hypophysial cell types, in both the PD and PT regions. Luteinizing hormone (LH) monohormonal, follicle-stimulating hormone (FSH) monohormonal and bihormonal gonadotrophs were identified in the PD and PT of male and female horses. Interestingly, in males, the relative proportions of gonadotroph subtypes and the LH/FSH monohormonal gonadotroph ratio were not affected by either season or the presence of the gonads. In contrast, a larger proportion of monohormonal gonadotrophs was clearly observed in sexually active females. Specific gonadotroph-lactotroph associations and expression of PRL-R in cells other than gonadotrophs were detected in the PD throughout the annual reproductive cycle. In addition to a stimulatory gonadal effect on lactotroph density, a substantial gonadal-independent effect of season was apparent on this variable. The findings have revealed important seasonal and gonadal effects on the cytological configuration of the equine hypophysis, which may provide the morphological basis for the intrahypophysial control of fertility.

Animals↗
PubMed2001

Prolactin actions in the sheep testis: a test of the priming hypothesis.

This study investigated whether prolactin (PRL) plays a priming role in the testis during the nonmating season and thereby facilitates gonadal reactivation. Sexually inactive Soay rams under long days were treated as follows: 1) group C (control) received vehicle, 2) group B received bromocriptine to suppress PRL secretion, 3) group B + PRL received bromocriptine + ovine PRL to reinstate physiological levels of PRL (n = 5/group). Treatments were for 10 wk. The photoperiod was then switched to short days to reactivate the reproductive axis. Testis diameter and sex skin coloration were recorded, and routine blood samples were collected to measure concentrations of FSH, inhibin A, and testosterone (T). At the end of the treatments, blood samples were collected every 10 min for 10 h to monitor LH pulses and the T-response to exogenous LH, and a testis biopsy was collected to assess spermatogenic activity (bromodeoxyuridine [BrDU] method) and expression of PRL receptor (reverse transcription-polymerase chain reaction and immunocytochemistry). There were no significant differences between groups in spermatogenesis (BrDU index) or steroidogenesis (T-response), and no difference in the time taken to achieve full testicular redevelopment under short days. Testis diameter and inhibin A were marginally increased in group B + PRL. Overall, this thorough experiment provides minimal support for the priming hypothesis.

Animals↗
PubMed2001

Hungry for tobacco: an analysis of the economic impact of tobacco consumption on the poor in Bangladesh.

OBJECTIVE: To investigate the extent of tobacco expenditures in Bangladesh and to compare those costs with potential investment in food and other essential items. DESIGN: Review of available statistics and calculations based thereon. RESULTS: Expenditure on tobacco, particularly cigarettes, represents a major burden for impoverished Bangladeshis. The poorest (household income of less than $24/month) are twice as likely to smoke as the wealthiest (household income of more than $118/month). Average male cigarette smokers spend more than twice as much on cigarettes as per capita expenditure on clothing, housing, health and education combined. The typical poor smoker could easily add over 500 calories to the diet of one or two children with his or her daily tobacco expenditure. An estimated 10.5 million people currently malnourished could have an adequate diet if money on tobacco were spent on food instead. The lives of 350 children could be saved each day. CONCLUSION: Tobacco expenditures exacerbate the effects of poverty and cause significant deterioration in living standards among the poor. This aspect of tobacco use has been largely neglected by those working in poverty and tobacco control. Strong tobacco control measures could have immediate impact on the health of the poor by decreasing tobacco expenditures and thus significantly increasing the resources of the poor. Addressing the issue of tobacco and poverty together could make tobacco control a higher priority for poor countries.

Adolescent↗
PubMed2001

Prenatal, perinatal, and neonatal factors in autism, pervasive developmental disorder-not otherwise specified, and the general population.

OBJECTIVES: To examine various pre-, peri-, and neonatal factors in autistic participants and in pervasive developmental disorder-not otherwise specified (PDD-NOS) participants and to compare the incidence of each factor to that of the normal population. METHODS: Seventy-four participants (66 males, 8 females) were diagnosed with autism at 2.5 through 4 years of age using the most accurate and up-to-date methods, including the Diagnostic and Statistical Manual of Mental Disorders and the Autism Diagnostic Interview-Revised. At age 5, all participants were reevaluated using the Diagnostic and Statistical Manual of Mental Disorders, the Autism Diagnostic Interview-Revised, the Childhood Autism Rating Scale, and the Autism Diagnostic Observation Schedule-Revised, resulting in 61 autistic and 13 PDD-NOS participants. Twenty-eight pre-, peri-, and neonatal factors were examined in these 2 groups using both medical records and parental interviews. Incidences were compared with those of the US population as reported in the Report of Final Natality Statistics, 1995. This grand scale population group was used to closely approximate comparison to a normal, unbiased population. Results were analyzed using the binomial probability test, with a P value of <.05, constituting a significant difference in incidence. A Bonferroni correction was applied to the data to adjust for the number of factors investigated. RESULTS: Although most of the factors showed comparable incidences between the index and control groups, several factors showed statistically significant differences. Following the Bonferroni correction, the autism group was found to have a significantly higher incidence of uterine bleeding, a lower incidence of maternal vaginal infection, and less maternal use of contraceptives during conception when compared with the general population. Similarly, the PDD-NOS group showed a higher incidence of hyperbilirubinemia when compared with the general population. CONCLUSIONS: The results of this study support previous findings suggesting a consistent association of unfavorable events in pregnancy, delivery, and the neonatal phase and the pervasive developmental disorders. However, interpretation of the meaningfulness of these results is difficult, as the specific complications that carried the highest risk of autism and PDD-NOS represented various forms of pathologic processes with no presently apparent unifying feature. Additional studies are needed to corroborate and strengthen these associations, as well as to determine the possibility of an underlying unifying pathological process. This study's analysis of obstetric and neonatal complications in combination with the use of participants diagnosed at an early age provides some interesting concepts to consider. Perhaps future research will confirm certain pre-, peri-, and neonatal associations that could be used to generate a high-risk historical profile with which to use in conjunction with currently employed diagnostic tools. This may, in turn, help to determine the reliability of a diagnosis of autism in younger children, leading to earlier intervention and assistance for an improved outcome in long-term functionality and quality of life.

Apgar Score↗
PubMed2001

Making faces: creating three-dimensional parameterized models of facial expression.

Previous studies of the perceptual processing and dynamics of emotional expression in faces have been limited by the lack of realistic yet controlled stimuli. The present work offers researchers a method for creating such stimuli for exploring these phenomena. We describe the creation of the stimuli and a series of experiments testing the validity of these stimuli with respect to emotional expressions in humans. Participants evaluated synthesized facial images and standardized photographs of six basic emotional expressions for intensity and accuracy of perceived emotion. Comparisons of these measures were qualitatively similar for synthesized and photographed faces. A manipulation of the magnitude of the synthesized expressions yielded a significant effect on the perceived intensity of expression. In a subsequent multidimensional scaling study, no systematic differences were uncovered in the derived configurations of the synthesized expressions and the photographs. These results are discussed in the context of possible future research applications.

Emotions↗
PubMed2000

Removal of eye activity artifacts from visual event-related potentials in normal and clinical subjects.

OBJECTIVES: Electrical potentials produced by blinks and eye movements present serious problems for electroencephalographic (EEG) and event-related potential (ERP) data interpretation and analysis, particularly for analysis of data from some clinical populations. Often, all epochs contaminated by large eye artifacts are rejected as unusable, though this may prove unacceptable when blinks and eye movements occur frequently. METHODS: Frontal channels are often used as reference signals to regress out eye artifacts, but inevitably portions of relevant EEG signals also appearing in EOG channels are thereby eliminated or mixed into other scalp channels. A generally applicable adaptive method for removing artifacts from EEG records based on blind source separation by independent component analysis (ICA) (Neural Computation 7 (1995) 1129; Neural Computation 10(8) (1998) 2103; Neural Computation 11(2) (1999) 606) overcomes these limitations. RESULTS: Results on EEG data collected from 28 normal controls and 22 clinical subjects performing a visual selective attention task show that ICA can be used to effectively detect, separate and remove ocular artifacts from even strongly contaminated EEG recordings. The results compare favorably to those obtained using rejection or regression methods. CONCLUSIONS: The ICA method can preserve ERP contributions from all of the recorded trials and all the recorded data channels, even when none of the single trials are artifact-free.

Adult↗
PubMed2000

Nurse practitioners in primary care.

OBJECTIVES: Recent policy emphasizing the role of primary care has increased the workload of general practitioners (GPs) while simultaneously placing nurse practitioners (NPs) as key providers in the delivery of health care. There is need to examine the latter's work practices. The purpose of this article is to explore the role and practice of NPs in general practice. METHODS DESIGN: Thirty-six semi-structured interviews with GPs, NPs, receptionists and patients were analysed. SETTING: Four general practices in south-east England. MAIN OUTCOME MEASURES: Data from semi-structured interviews relating to allocation, prescribing and referral practices of NPs in primary care. RESULTS: These include the differences in presenting problems of patients seen by GPs and NPs, prescribing and referral practice and legal issues of the nurse practitioner. A wide range of practice is reported. CONCLUSION: This study highlights the variation in how patients are allocated for NP consultation and in NP autonomy, prescribing and referral, which raises issues for clinical governance of protocols and risk management.

Attitude of Health Personnel↗
PubMed2000

Normal brain development and aging: quantitative analysis at in vivo MR imaging in healthy volunteers.

PURPOSE: To quantitate neuroanatomic parameters in healthy volunteers and to compare the values with normative values from postmortem studies. MATERIALS AND METHODS: Magnetic resonance (MR) images of 116 volunteers aged 19 months to 80 years were analyzed with semiautomated procedures validated by means of comparison with manual tracings. Volumes measured included intracranial space, whole brain, gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF). Results were compared with values from previous postmortem studies. RESULTS: Whole brain and intracranial space grew by 25%-27% between early childhood (mean age, 26 months; age range, 19-33 months) and adolescence (mean age, 14 years; age range, 12-15 years); thereafter, whole-brain volume decreased such that volunteers (age range, 71-80 years) had volumes similar to those of young children. GM increased 13% from early to later (6-9 years) childhood. Thereafter, GM increased more slowly and reached a plateau in the 4th decade; it decreased by 13% in the oldest volunteers. The GM-WM ratio decreased exponentially from early childhood through the 4th decade; thereafter, it gradually declined. In vivo patterns of change in the intracranial space, whole brain, and GM-WM ratio agreed with published postmortem data. CONCLUSION: MR images accurately depict normal patterns of age-related change in intracranial space, whole brain, GM, WM, and CSF. These quantitative MR imaging data can be used in research studies and clinical settings for the detection of abnormalities in fundamental neuroanatomic parameters.

Adolescent↗
PubMed2000

Employee retaliation: the neglected consequence of poor leader-member exchange relations.

Although the beneficial effects of high-quality leader-member exchange (LMX) relationships have been well-documented in the leadership literature, much less is known about the potentially damaging effects of poor exchange relationships. Using 150 intact leader-member dyads, the authors investigated the relationship between LMX and supervisors' reports of employee retaliation behavior, performance, and citizenship. Results indicated that performance and citizenship were positively related to LMX. More important, LMX was negatively correlated with retaliation behavior. Supervisors reported that subordinates in poor exchange relationships were more likely to engage in retaliation against the organization than subordinates in high-quality relationships. The lack of a high-quality exchange relationship was, therefore, not just associated with the absence of positive consequences but also led to reports of potentially disruptive behaviors.

Adult↗
PubMed1999

Functionally independent components of early event-related potentials in a visual spatial attention task.

Spatial visual attention modulates the first negative-going deflection in the human averaged event-related potential (ERP) in response to visual target and non-target stimuli (the N1 complex). Here we demonstrate a decomposition of N1 into functionally independent subcomponents with functionally distinct relations to task and stimulus conditions. ERPs were collected from 20 subjects in response to visual target and non-target stimuli presented at five attended and non-attended screen locations. Independent component analysis, a new method for blind source separation, was trained simultaneously on 500 ms grand average responses from all 25 stimulus-attention conditions and decomposed the non-target N1 complexes into five spatially fixed, temporally independent and physiologically plausible components. Activity of an early, laterally symmetrical component pair (N1aR and N1aL) was evoked by the left and right visual field stimuli, respectively. Component N1aR peaked ca. 9 ms earlier than N1aL. Central stimuli evoked both components with the same peak latency difference, producing a bilateral scalp distribution. The amplitudes of these components were no reliably augmented by spatial attention. Stimuli in the right visual field evoked activity in a spatio-temporally overlapping bilateral component (N1b) that peaked at ca. 180 ms and was strongly enhanced by attention. Stimuli presented at unattended locations evoked a fourth component (P2a) peaking near 240 ms. A fifth component (P3f) was evoked only by targets presented in either visual field. The distinct response patterns of these components across the array of stimulus and attention conditions suggest that they reflect activity in functionally independent brain systems involved in processing attended and unattended visuospatial events.

Adolescent↗
PubMed1999

Spatial attention deficits in patients with acquired or developmental cerebellar abnormality.

Recent imaging and clinical studies have challenged the concept that the functional role of the cerebellum is exclusively in the motor domain. We present evidence of slowed covert orienting of visuospatial attention in patients with developmental cerebellar abnormality (patients with autism, a disorder in which at least 90% of all postmortem cases reported to date have Purkinje neuron loss), and in patients with cerebellar damage acquired from tumor or stroke. In spatial cuing tasks, normal control subjects across a wide age range were able to orient attention within 100 msec of an attention-directing cue. Patients with cerebellar damage showed little evidence of having oriented attention after 100 msec but did show the effects of attention orienting after 800-1200 msec. These effects were demonstrated in a task in which results were independent of the motor response. In this task, smaller cerebellar vermal lobules VI-VII (from magnetic resonance imaging) were associated with greater attention-orienting deficits. Although eye movements may also be disrupted in patients with cerebellar damage, abnormal gaze shifting cannot explain the timing and nature of the attention-orienting deficits reported here. These data may be consistent with evidence from animal models that suggest damage to the cerebellum disrupts both the spatial encoding of a location for an attentional shift and the subsequent gaze shift. These data are also consistent with a model of cerebellar function in which the cerebellum supports a broad spectrum of brain systems involved in both nonmotor and motor function.

Adolescent↗
PubMed1999

Functionally independent components of the late positive event-related potential during visual spatial attention.

Human event-related potentials (ERPs) were recorded from 10 subjects presented with visual target and nontarget stimuli at five screen locations and responding to targets presented at one of the locations. The late positive response complexes of 25-75 ERP average waveforms from the two task conditions were simultaneously analyzed with Independent Component Analysis, a new computational method for blindly separating linearly mixed signals. Three spatially fixed, temporally independent, behaviorally relevant, and physiologically plausible components were identified without reference to peaks in single-channel waveforms. A novel frontoparietal component (P3f) began at approximately 140 msec and peaked, in faster responders, at the onset of the motor command. The scalp distribution of P3f appeared consistent with brain regions activated during spatial orienting in functional imaging experiments. A longer-latency large component (P3b), positive over parietal cortex, was followed by a postmotor potential (Pmp) component that peaked 200 msec after the button press and reversed polarity near the central sulcus. A fourth component associated with a left frontocentral nontarget positivity (Pnt) was evoked primarily by target-like distractors presented in the attended location. When no distractors were presented, responses of five faster-responding subjects contained largest P3f and smallest Pmp components; when distractors were included, a Pmp component appeared only in responses of the five slower-responding subjects. Direct relationships between component amplitudes, latencies, and behavioral responses, plus similarities between component scalp distributions and regional activations reported in functional brain imaging experiments suggest that P3f, Pmp, and Pnt measure the time course and strength of functionally distinct brain processes.

Adult↗