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Biomedical subjects

L Henderson

Publications and source records attributed to L Henderson.

At least 19 recordsLinked to original sources
PubMed1995

Oculomotor function in amyotrophic lateral sclerosis: evidence for frontal impairment.

Saccadic eye movements, fixation, and smooth pursuit were recorded in 17 subjects with amyotrophic lateral sclerosis (ALS) and 11 age-matched controls using a magnetic scleral search coil. Reflexive, remembered and antisaccades, and smooth pursuit at four target velocities were studied. Subjects with ALS showed significantly elevated error rates (distractibility) and latency in the antisaccade and remembered saccade paradigms but no abnormality of reflexive saccades. The frequency of small saccades that intruded on steady fixation (square-wave jerks) was also increased in ALS subjects. Peak velocity gain of smooth pursuit and performance on the Wisconsin Card Sort Test did not differ significantly between the two groups. These findings are consistent with prefrontal dysfunction in ALS and provide an independent source of support for the thesis that the pathology of this condition invades frontal cortex.

Adult↗
PubMed1995

The internal control of action and Parkinson's disease: a kinematic analysis of visually-guided and memory-guided prehension movements.

This paper reports two experiments which examined the effects of Parkinson's disease (PD) upon the sensorimotor mechanisms used to control prehension movements. Transport and grasp kinematics for visually-guided and memory-guided prehension movements were examined in healthy control subjects and compared against those of patients with idiopathic PD. Two research questions were addressed: (1) Are patients with PD particularly susceptible to distraction by non-relevant objects? (2) Are patients with PD especially reliant on external feedback when executing goal-directed actions? The results indicated that the patient group were no more susceptible to distraction by non-relevant objects than the control group. In contrast, the patients with PD were shown to be significantly impaired when executing memory-guided reaches. Furthermore, the deficits exhibited by the PD group on memory-guided reaches were confined solely to those markers associated with the transport component of the prehension movement. That is, while both controls and patients with PD widened their grip aperture on memory-guided trials, the magnitude of this adjustment was comparable across the two groups. The implications of these findings for theories of visuomotor processing in sufferers of PD and the control of prehension movements more generally are discussed.

Aged↗
PubMed1995

Serial reaction time learning and Parkinson's disease: evidence for a procedural learning deficit.

This paper presents evidence in support of a serial reaction time (SRT) deficit associated with Parkinson's disease, and related to the acquisition or execution of serial-order information. Eleven patients with idiopathic Parkinson's disease, and 10 age-matched but otherwise healthy control subjects, were compared on a variant of the SRT task introduced by Nissen and Bullemer (Cognit. Psychol. 19, 1-32, 1987). The results of this study clearly demonstrate that PD patients produce a quite different pattern of RT performance to that of control subjects. Such a pattern of results may reflect either: (1) a deficit in the patients' ability to learn the temporal order information provided by a repeating sequence of target locations in the SRT task; or (2) a deficit in the patients' ability to express temporal order information provided by the repeating sequence of target locations in the SRT task.

Aged↗
PubMed1995

A Project Alpha program for smaller chapters.

Smaller chapters cannot easily adapt to their groups the projects of larger chapters or programs at the national level. To address this problem, the Coosa Valley chapter of AORN, Rome, Ga, developed a program that offers perioperative experience to nursing students at a local college. Members of the chapter act as preceptors for the students and educate them before the students' preceptorships in the OR. This education seems to relieve some of the intimidation and fear related to the OR, and students in the program are more willing to participate in the program.

Curriculum↗
PubMed1995

Saccadic abnormalities in psychotic patients. I. Neuroleptic-free psychotic patients.

Most of the previous research reporting abnormalities of rapid re-fixation eye movements (saccades) in patients with schizophrenia has used patients receiving neuroleptic medication. In this study non-neuroleptically medicated schizophrenics were compared with other psychiatric patients using a variety of saccadic paradigms to determine the specificity of saccadic dysfunction. The patient groups consisted of schizophrenics (N = 18), bipolar affectives (N = 18), anxiety neurotics (N = 10) and normal controls (N = 31), none of whom had received neuroleptic medication for the preceding 6 months. Four behavioural paradigms, reflexive, predictive, remembered and ANTI were used to elicit saccades. The primary abnormality in the schizophrenic group was a significantly increased rate of distractibility in the ANTI (saccades made towards the target rather than in an opposite direction) and REM (saccades made prior to the imperative cue) paradigms. The major neuropsychological variable predictive of these errors was Wisconsin card sort perseverative errors. These data, in conjunction with findings from previous neurological research, would seem to provide converging evidence towards dysfunction of prefrontal cortex in schizophrenia.

Adult↗
PubMed1995

Saccadic abnormalities in psychotic patients. II. The role of neuroleptic treatment.

The effects of dopamine-antagonistic neuroleptic (NL) medication on saccadic eye movements were compared in matched groups of 40 NL-treated and 18 NL-free schizophrenic patients and in 18 NL-treated and 14 NL-free bipolar affective patients. Manipulation of the saccadic paradigm yielded data on four types of saccade: those reflexively elicited by novel stimuli (REFLEX saccades), those directed towards the remembered location of a target now extinguished (REM) or towards the location where a predictably alternating target is expected to appear (PRED), or ANTI saccades, directed away from the stimulus to the mirror image location. Extensive psychiatric, neurological and neuropsychological assessments were also carried out on all subjects. The saccades of NL-treated patients, regardless of diagnosis, were less spatially accurate than those of NL-free patients, with a greater tendency to fall short of the target when generated towards the locus of a mentally represented target. This effect was greatest with a predictably alternating target, especially during periods when target visibility was withdrawn, only a temporal cue remaining. This pattern of impairment which is also found in early stages of Parkinson's disease is likely to be due to deficiency of striatal dopamine. Its best clinical predictors were disease duration, and Webster-Parkinsonism scores. Failure to suppress reflexive saccades to the stimulus in the REM and ANTI paradigms were more closely associated with schizophrenia than with NL treatment and were best predicted by negative symptoms and Wisconsin perseverative errors, both of which are widely regarded as indicators of frontal lobe dysfunction.

Adult↗
PubMed1995

Procedures for the detection of chemically induced aneuploidy: recommendations of a UK Environmental Mutagen Society working group.

The development of assays to detect numerical chromosome aberrations has not kept pace with that for assays used to detect other genotoxicity endpoints such as gene mutations and structural chromosome aberrations, even though the importance of aneuploidy in relation to heritable defects in germ cells and to carcinogenesis in somatic cells is acknowledged. Regulatory bodies at present have no formal requirements concerning aneuploidy detection and decisions are made on a case-by-case basis. The aim of this review is to indicate which assays are available for the detection of chemically induced aneuploidy and what aspects should be taken into account when testing for chemically induced aneuploidy using in vitro, in vivo somatic and in vivo germ cell assays without dictating exact protocols. Our recommendations concentrate on systems that, to date, have been most extensively used and we indicate where future developments may lie. It is important that the currently available and future tests for chemically induced aneuploidy should be adequately validated before being implemented into screening strategies or regulatory guidelines. This requirement has not yet been met and is confounded by the lack of a well defined reference database of animal and human chemical aneugens.

Aneuploidy↗
PubMed1994

Photomutagenicity assays in bacteria: factors affecting assay design and assessment of photomutagenic potential of para-aminobenzoic acid.

Photomutagenicity assays are required for regulatory submissions of some chemicals. As yet there are no well-validated protocols available for these assays. Critical factors which may contribute to the ability of a bacterial assay to detect photomutagens (e.g. dose of UV and test chemical, exposure conditions, light source, bacterial strains) were investigated using two known photomutagens, chlorpromazine and 8-methoxypsoralen. Salmonella typhimurium strains TA98, TA102 and TA1537 and Escherichia coli strains WP2 and WP2(pKM101) were used and differences in the responsiveness of these strains were observed with these substances. Both chemicals were detected using either UV exposure in suspension or on the agar plates. On the basis of these observations and on other results reported in the literature, recommendations are made on protocol aspects for assessing photomutagenic potential in routine screening tests. Using these recommendations the sunscreen para-aminobenzoic acid was tested in S.typhimurium strains TA98, TA100, TA1535, TA1537 and E. coli strains WP2 and WP2 (pKM101), using both plate irradiation and suspension exposure conditions. No evidence of mutagenic potential was detected.

4-Aminobenzoic Acid↗
PubMed1994

Visuospatial difficulties and clumsiness: on the interpretation of conjoined deficits.

Sixteen children with motor difficulties and 16 controls, matched on age, gender and verbal I.Q., were assessed on the Test Of Motor Impairment, various graphic tasks and a measure of visuospatial discrimination. Poor perceptual and motor performance tended to co-occur but contrary to the visuospatial deficit account of clumsiness these abilities were uncorrelated even when attention was restricted to the less proficient children. There was no tendency for the control group's superiority in graphic reproduction to diminish when visual feedback was withheld. Some suggestions are offered concerning more appropriate methods for framing and testing causal deficit hypotheses.

Aptitude↗
PubMed1994

Distribution of bradykinin B2 receptors in target cells of kinin action. Visualization of the receptor protein in A431 cells, neutrophils and kidney sections.

Peptides corresponding to sequences derived from predicted extra- and intracellular loops of the rat bradykinin receptor were analyzed for interspecies homology as well as for matches within the present dataset of protein sequences to provide a theoretical basis for the specific recognition of the native cognate protein by antibodies raised against these antigens. Application of polyclonal antibodies raised against the selected peptides allowed the immunocytochemical localization of the native receptor protein in cells of rat and human origin. The detection of the molecule was achieved by different immunohisto- and immunocytochemical methods in combination with light, fluorescence, confocal optical laser and electron microscopy. These results were compared to localization studies by autoradiography. Distribution and subcellular localization were determined in human neutrophils, human epithelial carcinoma cells (A431) and in rat kidney tissue.

Amino Acid Sequence↗
PubMed1994

Genotoxicity testing of pidotimod in vitro and in vivo.

The mutagenic potential of pidotimod ((R)-3-[(S)-(5-oxo-2- pyrrolidinyl)carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) was assessed in a series of five assays designed to measure gene mutation, chromosomal damage and primary DNA damage. All tests were carried out in accordance with appropriate EEC and OECD Guidelines. No indications of mutagenic potential were observed in any of the assays.

Animals↗
PubMed1993

Induction of micronuclei in rat bone marrow and peripheral blood following acute and subchronic administration of azathioprine.

The frequency of micronuclei was assessed in polychromatic erythrocytes of bone marrow and in polychromatic and normochromatic erythrocytes in peripheral blood of rats following exposure to azathioprine for 28 days. This was compared with the incidence of micronuclei in bone-marrow following exposure to a single dose of azathioprine. The incidence of micronuclei in bone-marrow polychromatic erythrocytes at the maximum tolerated dose (10 mg/kg) following exposure for 28 days was 29.5/1000. The incidence of micronucleated polychromatic erythrocytes in the peripheral blood at this dose was 4.4/1000. At the maximum tolerated dose in the single-dose study (40 mg/kg) the incidence obtained at 48 h post-treatment was 15.7/1000. This supports the view that the use of animals in a subchronic toxicity study is at least as sensitive for assessing in vivo clastogenic activity as an acute study and could reduce animal usage in toxicology assessments.

Animals↗
PubMed1992

Effect of dietary fat on the in vitro hepatotoxicity of paracetamol.

In the present study, we have examined the effect of dietary fat on paracetamol-induced liver injury in an in vitro rat liver slice model. Rats were fed, for 7-10 days, diets containing either butter or polyunsaturated vegetable margarine, two fat sources commonly consumed in the human diet. Liver slices were then exposed to paracetamol for 2 hr and further incubated for 4 hr without paracetamol. Cell damage in the slices was quantified at 6 hr by measuring leakage of lactate dehydrogenase, increase in water content and potassium loss. Covalent binding of radioactive paracetamol to liver and the membrane fatty acid composition of the liver were also measured. Liver slices from rats fed butter diets were significantly more sensitive to the toxic effects of paracetamol than those from margarine fed rats. The membrane lipid composition of the livers also reflected the differing fatty acid content of the two diets.

Acetaminophen↗
PubMed1992

The effect of presentation and mode of delivery on neonatal outcome in the second twin.

OBJECTIVE: The purpose of this study was to determine if cesarean delivery of the nonvertex second twin improved neonatal outcome. STUDY DESIGN: We examined the maternal and neonatal records from 457 sets of twins delivered from 1985 to 1990. We compared 1- and 5-minute Apgar scores, umbilical artery and vein blood pH values, duration of neonatal hospitalization, the incidence and length of ventilation, intraventricular hemorrhage, birth trauma, and mortality rate between vertex and nonvertex second twins delivered either vaginally or by cesarean section. RESULTS: The presentation and mode of delivery of the second twin was not associated with a significant difference in any of the outcome variables except for the 1-minute Apgar score, which was lower in the nonvertex group delivered vaginally. CONCLUSION: Our data do not support routine cesarean delivery for twins of any birth weight when the second twin is nonvertex.

Apgar Score↗
PubMed1992

Saccadic eye movements in Parkinson's disease: I. Delayed saccades.

The saccadic eye movements of nine patients with Parkinson's disease were compared to those of nine age-matched controls in two paradigms generating volitional saccades. In both paradigms, subjects had to make delayed saccades to peripheral LED targets: a peripheral target appeared 700 msec before a buzzer sounded, the buzzer being the signal to make a saccade to the target. In the first paradigm ("centre-off"), the fixation target was extinguished simultaneously with buzzer onset. In the second ("centre-remain") it was not extinguished until 1000 msec later. The results showed that for outward saccades in both paradigms, there was no difference between Parkinsonian patients and controls, but saccadic latencies were significantly shorter in the "centre-remain" paradigm. The initial outward saccades were indistinguishable from the normal, reflex saccades of the same subjects. However, saccades returning to the centre (a type of remembered target saccade) were hypometric and showed multistepping. Both effects were more pronounced in patients with Parkinson's disease. The significance of these findings in terms of current hypotheses about the nature of the Parkinsonian saccadic deficit is discussed.

Aged↗
PubMed1992

Saccadic eye movements in Parkinson's disease: II. Remembered saccades--towards a unified hypothesis?

Ten patients with mild to moderate Parkinson's disease were compared with ten age-matched normal controls in a series of saccadic paradigms in order to test various hypotheses relating to the origin of the Parkinsonian saccadic defect. The paradigms comprised a reflex saccade paradigm, a standard remembered saccade paradigm, a remembered saccade paradigm with delayed centre-offset, and a remembered saccade paradigm with a second target flash immediately prior to saccade execution. Finally, subjects executed both reflex and remembered saccades in a standard remembered paradigm (the "two-saccade" paradigm). As has been reported previously, Parkinsonian subjects demonstrated hypometria on all remembered saccade paradigms, particularly the "two-saccade" paradigm. There was, however, no significant difference between the first three remembered saccade paradigms. These studies serve to refute a simple attentional capture hypothesis, and a hypothesis that suggests that the abnormality of remembered saccades is due to concurrent reflex saccade suppression. On the basis of the results, further hypotheses are advanced in an attempt to explain all published work on Parkinsonian saccades.

Aged↗
PubMed1992

Reaction time and movement time in children with a Developmental Coordination Disorder.

The Test of Motor Impairment (TOMI) was used to select 12 children with a Developmental Coordination Disorder (DCD) and 12 age-matched controls. In an aiming task, movement latency, movement duration and its variability were significantly prolonged in the DCD group. In a coincidence timing version of the task, absolute timing error was significantly greater in the DCD group. The most robust chronometric effect for differentiating the two groups seemed to be the duration of movement when the target was small. Multiple regression showed that TOMI was a powerful indicator of movement duration.

Child↗