Search PubMed⌕ Search

Biomedical subjects

C Hudson

Publications and source records attributed to C Hudson.

At least 55 records · Page 3Linked to original sources
PubMed1994

Fatigue effects during a single session of automated static threshold perimetry.

PURPOSE: To determine using a routine clinical program the time course of the fatigue effect in both eyes at a given examination, the influence of rest periods during the examination, and the differences in the fatigue effect between persons with ocular hypertension and age-matched normal subjects. METHODS: Perimetry was undertaken for both eyes of 20 normal persons and 20 persons with ocular hypertension using Program G1X (Interzeag AG, Schlieren, Switzerland) of the Octopus 1-2-3 perimeter. Global mean defect and loss variance were calculated for each of the eight individual stages and global SF was calculated for stages 5 to 8. The superoinferior and nasotemporal hemifield indices and those for within and beyond 17 degrees eccentricity were calculated separately to investigate the locus of the fatigue effect. RESULTS: Group mean mean defect and loss variance deteriorated over stages (P < 0.001) and between eyes for both groups (P < 0.001; P < 0.004). The deterioration in the mean defect was more marked peripherally (P < 0.001) and inferiorly with age and group (P < 0.001) whereas the localized loss was more pronounced peripherally (P < 0.001), superiorly (P < 0.010) and nasally (P < 0.001). A 1-minute break during the examination of a given eye and a 3-minute break between eyes was insufficient to overcome the fatigue effect. The performance of the two groups was almost indistinguishable. CONCLUSIONS: The deterioration in the visual field indices mean defect and loss variance challenges the currently accepted ideal length of a perimetric examination with the conventional algorithms. Confidence limits for the definition of abnormality with these algorithms should reflect the presence of the fatigue effect and be different for the second eye.

Aged↗
PubMed1993

Evaluation of FASTPAC: a new strategy for threshold estimation with the Humphrey Field Analyser.

A new strategy for threshold estimation, FASTPAC, has been introduced for the Humphrey Field Analyser with the aim of improving the efficiency of visual field examination without loss of accuracy. FASTPAC was compared to the standard 4-2 double staircase strategy in 98 normal volunteers (age 23-83 years). One eye of each subject was examined with both strategies on two visits using Program 30-2. The order of strategy was randomised. FASTPAC examination time was 43% faster than the standard algorithm, but the mean sensitivities were similar. Short-term fluctuation was 24% higher with FASTPAC (P < 0.001). Most parameters were adversely affected by increasing age. FASTPAC offers a valid alternative to the standard strategy in the examination of suspected normal fields and should always be considered as an alternative to the threshold-related screening strategies. The performance of the algorithm in the identification of field loss and in areas of reduced sensitivity awaits further study.

Adult↗
PubMed1993

An investigation of awareness of antenatal protocols.

Previous audit at the Homerton Hospital had revealed a poor level of compliance with established antenatal protocols mandated by risk factors detected at the booking visit. Medical staff were questioned as to their awareness of five of the most important protocols and their response was analysed by a new scoring system. The scores were generally low though consultants scored more highly than junior staff. Scores were related to the length of obstetric experience and duration of work in the obstetric unit but were not related to frequency of the use of the protocol manual nor to the last time that reference was made to the manual. To improve compliance within the unit, the following recommendations were made: (1) regular revision of protocols to incorporate the current views of senior clinicians and (2) improved dissemination of information. The scoring system described here should prove to be a simple and effective method for the assessment of protocols within any unit.

Awareness↗
PubMed1993

Maximizing the dynamic range of the humphrey field analyzer for blue-on-yellow perimetry.

The conditions employed for blue-on-yellow perimetry (i.e. a blue stimulus filter and a high luminance yellow background) are in conflict with those that allow a maximum dynamic range. A modification is described for increasing the dynamic range of the Humphrey Field Analyzer (HFA) for blue-on-yellow perimetry. The position of the HFA stimulus bulb was lowered by reducing the length of both terminals. A concave mirror with a 28 mm radius of curvature was positioned behind the lowered stimulus bulb to give a filament image partly above and partly overlapping the original filament profile within the confines of the size V stimulus patch diameter. The modification achieved a 60% increase in the light output on the default 0 dB value of 10,000 apostilbs and, therefore, a useable dynamic range for blue-on-yellow perimetry of 2.94 log units. The effective increase in voltage supply to the stimulus bulb permitted a filament life of 260 operating hours. Furthermore, the modification ensured the correct calibration of the instrument.

Color↗
PubMed1993

An investigation of indoor air contamination in residences above dry cleaners.

An investigation of residences located above dry cleaning facilities was conducted to determine whether indoor and outdoor air concentrations of the dry cleaning solvent tetrachloroethene (perchloroethylene, PCE) were elevated compared to residences not near a dry cleaning facility. Data were also collected on the dry cleaners' operating conditions and equipment. Significantly elevated levels of PCE were found in the indoor air of each of six apartments located above dry cleaners compared to control residences for both day and night samples. The PCE concentrations in outdoor air near the dry cleaners were also significantly elevated compared to control locations and were lower than the concentrations measured indoors. The type of dry cleaning machine was significantly associated with the concentration of PCE found in the apartment above. A strong correlation was also found between the day and night PCE levels in the study apartments.

Air Pollutants, Occupational↗
PubMed1993

Medical audit: the problem of missing case-notes.

This paper reports the results of a case-note audit undertaken to detect the antenatal risk factors found at the initial booking visit, including the subsequent clinical action taken. From a total of 2,139 case-notes of women booked via an obstetric computer system, and delivered between March 1990 and March 1991, 136 (6.4%) were missing. The results showed that these 136 mothers experienced significantly worse delivery outcomes, ie higher incidence of perinatal death; preterm labour; a baby with a low Apgar score and low birth weight. There was also a higher incidence of perinatal death and babies with a low Apgar score for women booked manually compared with those booked via the computer system. These results show that many audit procedures may be the subject of substantial bias due to the problem of missing information. The extended use of a computer-based medical record system should help to resolve this problem, although hybrid information systems can themselves be biased.

Bias↗
PubMed1992

Assessment of physiologic statokinetic dissociation by automated perimetry.

The effects of age, stimulus size, meridian, and eccentricity on physiologic statokinetic dissociation were investigated in clinically normal subjects using the Humphrey field analyzer (HFA, model 640), an automated perimeter capable of both static and kinetic perimetry. The right eyes of 20 age-matched young and 20 age-matched elderly volunteers was examined along the 15 degrees and 195 degrees meridians with six Goldmann size I and five size III kinetic stimuli. These were chosen to produce a spread of discrete eccentricities. Kinetic sensitivity was determined seven times for each stimulus, and the mean stimulus locations were expressed in terms of their x and y coordinates. Static sensitivity for each stimulus size then was determined seven times at each of the corresponding locations using a custom threshold program. The area under each sensitivity gradient was determined using the trapezium rule. Group mean kinetic sensitivity was greater than group mean static sensitivity (P < 0.001), and this difference was largely independent of age, stimulus size, meridian, and eccentricity.

Adult↗
PubMed1991

Childhood leukaemia and poliomyelitis in relation to military encampments in England and Wales in the period of national military service, 1950-63.

OBJECTIVE: To determine if any excess of childhood leukaemia was associated with the large and increasing numbers of national military servicemen in 1949 and 1950, particularly in rural districts. This would be a further test of the hypothesis that childhood leukaemia can originate in an infection, the transmission of which is facilitated by an increased number of unaccustomed contacts in the community. DESIGN: Rural and urban districts, aggregated by county, were ranked by proportion of servicemen, and five groups containing similar numbers of children were created. In addition, individual local authority districts were ranked and grouped in tenths. Mortality from childhood leukaemia 1950-3 was examined in these groups. Data on infectious diseases were also examined, as well as data on leukaemia in later periods. SETTING: England and Wales. SUBJECTS: Children aged under 15 years. RESULTS: In 1950-3 but not subsequently a significant excess of leukaemia in children under 15 was found in the fifth of county groupings with the highest proportions of servicemen. This was due mainly to a significant excess in children under 2 years (and especially in those under 1 year) in rural districts. It was confirmed among the tenth of local authority districts with the highest proportion of servicemen. These rural areas showed significantly more notifications of, and deaths from, poliomyelitis among children than the rural average. CONCLUSIONS: The findings support the infection hypothesis. That the excess of leukaemia was greatest in children under 1 year suggests transmission of infection among adults and thence to the fetus. The pattern of spread of poliomyelitis may also have been influenced by the presence of large numbers of servicemen.

England↗
PubMed1990

Evidence from population mixing in British New Towns 1946-85 of an infective basis for childhood leukaemia.

Mortality from leukaemia under age 25 was studied in British New Towns to test the hypothesis that leukaemia represents a rare response to a much commoner (but unrecognised) infection, the transmission of which is facilitated when large numbers of people come together. The density of children was higher in the rural, but lower in the overspill, New Towns than in the areas from which their incomers originated. Residents of the rural New Towns had greater diversity of origin than those of the overspill towns of London and Glasgow. These two factors would encourage a greater rise in the postulated underlying infection in the rural towns, and in these a significant excess of leukaemia at ages 0-4 was found in 1946-65. In both sets of towns there was a significant deficit in other age groups consistent with immunising effects of the relevant infection. There are parallels with feline leukaemia virus infection, in which contrasting leukaemogenic and immunising effects occur in different social settings owing mainly to differences in intensity of viral exposure.

Adolescent↗
PubMed1990

Systemic administration of MK-801 protects against N-methyl-D-aspartate- and quisqualate-mediated neurotoxicity in perinatal rats.

MK-801, a non-competitive antagonist of N-methyl-D-aspartate-type glutamate receptors, was tested for its ability to antagonize excitotoxic actions of N-methyl-D-aspartate or quisqualic acid injected into the brains of seven-day-old rats. Stereotaxic injection of N-methyl-D-aspartate (25 nmol/0.5 microliters) or quisqualic acid (100 nmol/1.0 microliter) into the corpus striatum under ether anesthesia consistently produced severe unilateral neuronal necrosis in the basal ganglia, dorsal hippocampus and overlying neocortex. The distribution of the damage corresponded to the topography of glutamate receptors in the vulnerable regions demonstrated by previous autoradiographic studies. N-Methyl-D-aspartate produced severe, confluent neuronal destruction while quisqualic acid typically caused more selective neuronal necrosis. Intraperitoneal administration of MK-801 (0.1-1.0 mg/kg) 30 min before N-methyl-D-aspartate injection had a prominent dose-dependent neuroprotective effects as assessed morphometrically by comparison of bilateral striatal, hippocampal and cerebral hemisphere cross-sectional areas five days later. A 1 mg/kg dose of MK-801 given as pre-treatment completely protected the infant brain. The same dose of MK-801 was also completely protective when administered 30 or 40 min after N-methyl-D-aspartate and afforded partial protection when given 2 h later. MK-801 pre-treatment also prevented the electrically confirmed behavioral seizures induced by N-methyl-D-aspartate. The drug significantly reduced striatal but not hippocampal or neocortical injury when given as two doses (1 mg/kg) 30 min prior to and immediately following quisqualic acid injection. The data indicate that systemic administration of MK-801 can prevent N-methyl-D-aspartate-induced neuronal injury in perinatal rat brain even when administered after the initial insult. MK-801 also partially antagonized quisqualic acid-mediated neurotoxicity, suggesting that quisqualic acid-induced toxicity is, in part, mediated through N-methyl-D-aspartate receptor activation. The sensitivity of the developing brain to the toxicity of N-methyl-D-aspartate provides a sensitive and reproducible in vivo model for exploring these issues and for screening prospective neuroprotective drugs that act at the N-methyl-D-aspartate receptor-channel complex.

Animals↗
PubMed1990

Fatal post-splenectomy sepsis in a Papua New Guinean highlander.

A fatal case of overwhelming post-splenectomy sepsis (OPSS) occurring 5 years after splenectomy for trauma in a Papua New Guinean highlander is presented. The diagnosis of pneumococcal infection was made from a peripheral blood smear. The finding of OPSS in Papua New Guinea is cited as additional evidence in favour of a policy of conservative management, where possible, of ruptured spleen.

Adult↗
PubMed1989

Abnormal thyroid hormone and thyrotropin levels in homozygous sickle cell disease.

Male patients with SS disease had significantly lower T3 and higher TSH levels than a comparison group. Stimulation with TRH in 10 male sibling pairs showed highly significant increases in T3 and TSH in both patients and sibling controls although the increase in TSH was significantly greater in SS disease. The interpretation of these findings is unclear although the thyroid indices indicate an abnormal pituitary-thyroid axis most consistent with a modest primary thyroid failure.

Adolescent↗
PubMed1988

Anomalous motoric lateralization and schizophrenia: clinical implications.

Sixty-five schizophrenic subjects (46 men and 19 women) were tested for motor preference and compared to age and sex-matched controls. There were significantly more nondextrals among the schizophrenic women. Both male and female nondextral schizophrenics were hospitalized more frequently and for longer periods than dextral schizophrenics.

Adolescent↗
PubMed1987

Effects of postnatal hypoxia-ischemia on cholinergic neurons in the developing rat forebrain: choline acetyltransferase immunocytochemistry.

We studied the effect of early postnatal hypoxia-ischemia on cholinergic neurons in the developing rat forebrain using immunohistochemistry for choline acetyltransferase (ChAT). In 7-day-old rat pups, hypoxia-ischemia was induced in one cerebral hemisphere by combining unilateral carotid ligation with exposure to 8% oxygen for 2.5 h. This procedure caused brain injury in the hemisphere ipsilateral to ligation, most prominent in the corpus striatum, hippocampus and overlying cortex. In animals sacrificed 2-3 weeks after the insult, at approximately 3 weeks of age, the density of cholinergic cell bodies was slightly higher in the lesioned rostral caudate-putamen than the opposite side (+12%, P less than 0.05). In the more caudal portion of caudate-putamen, this effect was greater. In contrast, the size of the cholinergic perikarya in the injured striatum was significantly reduced. Cholinergic neurons in the septum (Ch1, Ch2), globus pallidus and nucleus basalis (Ch4) were relatively unaffected. Considered together with previously reported neurochemical data, these observations suggest that the immature cholinergic neurons are less vulnerable to death from hypoxia-ischemia than other components of the striatum. However, differentiation of surviving cholinergic perikarya and possibly their axonodendritic processes may be disrupted by the early insult.

Age Factors↗
PubMed1987

Evidence for transient perinatal glutamatergic innervation of globus pallidus.

There is no known glutamatergic innervation of globus pallidus (GP) in adult mammals, but we report that during postnatal development of the GP there are large, transient increases in both presynaptic high-affinity glutamate uptake and postsynaptic Na+-independent glutamate receptor binding. These glutamatergic markers increase rapidly in rat GP after birth and then decrease to adult levels over a period of weeks. A similar developmental pattern of pallidal glutamate binding was found in human brains. In contrast, binding in rat caudate-putamen (CPu) increases after birth, reaches a peak, and remains constant into adulthood. The results suggest that a glutamatergic pathway transiently innervates the globus pallidus during the perinatal period. Because glutamate is an excitotoxin, this pathway may account, in part, for the basal ganglia damage seen in some forms of cerebral palsy after perinatal hypoxia/ischemia.

Adult↗