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Biomedical subjects

R Halliday

Publications and source records attributed to R Halliday.

At least 37 records · Page 2Linked to original sources
PubMed1983

Hyperactive children's event-related potentials fail to support underarousal and maturational-lag theories.

Hyperactivity in children has been attributed to underarousal, maturational lag, and both. Using event-related potentials (ERPs) and EEG spectra, we compared hyperactive children with age-matched normal controls. Neither underarousal nor maturational lag explained our findings, and we concluded that these explanations are now too simple to be useful. We found a number of differences in EEGs and ERPs between hyperactive subjects and controls. The best single measure was EEG power from 14 to 25 Hz, which was consistent with previous reports. Hyperactive children had lower beta power than normal controls.

Age Factors↗
PubMed1983

A comparison of methods for measuring event-related potentials.

Visual event-related potentials (ERPs) were recorded from 21 hyperactive children under 2 attention conditions and 4 doses of stimulant drug (methylphenidate). This data base was used to evaluate several methods of EP component measurement. These methods were (1) conventional visual peak and trough selection; (2) automatic feature extraction based on peaks; (3) automatic features extraction based on segments; (4) gross amplitude measures; (5) principal components analysis on normalized data and latency-adjusted data. No one method emerged as the best overall. Rather it is the case that different methods are best suited to different purposes, and criteria for choosing methods are outlined.

Brain↗
PubMed1983

Visual evoked potential changes induced by methylphenidate in hyperactive children: dose/response effects.

Visual event related potentials (ERP) were recorded from 21 hyperactive children aged 7-13 years under two attention conditions at 4 levels of methylphenidate dose (placebo, low, medium and high). ERP measures were very sensitive to age (under or over 10 years) and attention condition, but less sensitive to drug dose. There appeared to be two classes of drug dose effect on ERP amplitude, those that changed monotonically with dose and those from which dose interacted with attention non-monotonically. Drug effect on ERP amplitude may also depend on age so that opposite effects may occur in young and old children. No latency measures showed a dose effect. It appears that methylphenidate can speed reaction times without shortening ERP latency. This suggests the drug acts more on response-related processes than on stimulus evaluation.

Attention Deficit Disorder with Hyperactivity↗
PubMed1982

Lateralized loss of biting attack-patterned reflexes following induction of contralateral sensory neglect in the cat: a possible role for the striatum in centrally elicited aggressive behaviour.

A syndrome of "contralateral sensory neglect' was induced by hypothalamic knife cuts in 6 of 10 cats in which quiet biting attack behaviour could be elicited by lateral hypothalamic stimulation. The contralateral sensory neglect in the 6 affected cats was accompanied by a loss on the "neglected' side of the body of the patterned reflexes which mediate positioning of the head to bite and the jaw-opening component of biting. As a result, when these cats were stimulated in the lateral hypothalamus, although they continued to approach and even make tactile contact with the rat, they generally failed to bite it. Analysis of the histological and behavioural data suggested that damage to the nigrostriatal and/or striato/pallidonigral fibre systems provided the likely basis for both the induction of the contralateral sensory neglect and the lateralized patterned reflex loss. It was suggested, with respect to these specific patterned reflex components of the attack, that an important contribution may be made by the striatum.

Animals↗
PubMed1982

The effect of attentional effort on visual evoked potential N1 latency.

The latency of the visual evoked potential N1 component evoked by nontarget stimuli increases with an increased attention to nontarget stimuli. The latency increase seems related to a general effort at processing, rather than any early filtering. This phenomenon is illustrated in one study of hyperactive children and another of normal young adults. The literature of this phenomenon is reviewed, and various explanations are considered. It does not appear to be a result of a slow negative wave, but rather a genuine effect of one aspect of attention on N1.

Adolescent↗
PubMed1982

A screening method for measuring somatomedin B protein binding in serum from children with growth retardation.

A simple method which uses 100 microliter serum has been developed to measure the binding of somatomedin B (SMB) to protein in serum from normal children, adults, and patients with growth hormone deficiency. 125I-labelled SMB was used as binding ligand. The correlation between the binding of label by the proposed procedure and by an immunoelectrophoretic technique was acceptable (r = 0.73; P less than 0.02). The mean percentage of label bound to protein in serum from patients with deficiencies of growth hormone or other trophic hormones was significantly (P less than 0.001) lower than that for controls. The physicochemical characteristics of a specific binding-protein suggested that a protein with low capacity (160 pmol/l) and low Ka (4.37 X 10(6) l/mol was present in serum, in addition to a high concentration of alpha globulin(s) which also bound 125I SMB.

Adolescent↗
PubMed1981

Anterior hypothalamic knife cut eliminates a specific component of the predatory behavior elicited by electrical stimulation of the posterior hypothalamus or ventral midbrain in the cat.

Following unilateral transection of the medial forebrain bundle (MFB) within the anterior hypothalamic-preoptic region of cats, the biting attack upon a rat elicited by ipsilateral posterior hypothalamic or ventral midbrain stimulation is eliminated, although the cat continues to approach from 2.8 metres away to within several centimetres of the rat. In contrast, both the approach to and biting attack upon a rat elicited by contralateral posterior hypothalamic and ventral midbrain stimulation are unchanged. The results suggest that specific agents (biting, approach) of the elicited behaviour may be mediated by neural effects which proceed along anatomically distinct components of the ascending as well as the descending MFB.

Animals↗
PubMed1980

The relatioship between serum immunoglobulin levels and specific antibody production in cows.

Antibody responses were measured, by the Farr ammonium sulphate technique, to two unrelated antigens-human serum albumin and sperm whale myoglobin. Differences between cows in their mean responses to both antigens were highly significant (P less than 0.001) but there were no differences between Jerseys and Friesians. Preinoculation IgG1, IgG2 and IgM levels were correlated with subsequent specific antibody production. The most significant relationship was between total immunoglobulin (IgG1 plus IgG2 plus IgM) and specific antibody production (r=0.76, P less than 0.01). But there was a negative correlation between the total Ig levels and the relative avidities of the antibodies produced (r=-0.65). These data suggest that in antibody production there is a balance between quality and quantity; cows with normally high serum immunoglobulin concentrations generally produce more antibody in response to challenge but this increase only compensates for the relatively lower avidity of their antibody for the antigen.

Animals↗
PubMed1979

The absorption of immunoglobulin from colostrum by bottle-fed lambs.

Factors affecting the absorption of immunoglobulin from colostrum by new born lambs were studied. Merino, Scottish Blackface, Cheviot, Southdown, Border Leicester, Finnish Landrace and Finnish Landrace x Dorset Horn lambs were removed from their mothers before sucking and bottle-fed with measured amounts of colostrum, either from individual ewes, or from pools of colostrum, some of which had been frozen for up to two years. Afterwards the lambs were fostered onto other ewes or reared on milk substitute. Their serum IgG1 concentrations before and after colostrum intake, were compared with IgG1 concentrations in conventionally reared lambs. The concentrations in lambs given a single feed of 150 to 200 g 1 hour after birth, or 30 g/kg at 1 hour and 7 hours compared favourably with those in control lambs. Lambs fed 50 to 100 g at 1 hour had a high proportion of very low concentrations and lambs fed 30 g/kg at 1 h, or at 1 and 24 h had low mean concentrations but no very low individual concentrations. The concentrations after a feed at 1 hour were positively correlated with the total amounts of IgG1 in the colostrum and negatively correlated with the birth weights. Only very small amounts were absorbed at 24 hours. Absorption was more efficient in males than in females and in Cheviots than in other breeds. It was unaffected by the age of the colostrum. Similar proportions of bottle-fed and control lambs died before 6 months of age, but relatively more bottle-fed lambs died from respiratory infections. The IgG1 concentrations and growth rates of the bottle-fed lambs were not significantly correlated.

Absorption↗
PubMed1978

Time shift evoked potentials (TSEPs): method and basic results.

A simple technique for generating averaged evoked potentials to auditory signals that appear to move in space is described. Shifts in the apparent location of the signal were created by digitally delaying the output of a white noise generator with a minicomputer. The two channels were reconverted to two analog signals and presented binaurally through headphones. Shifts inthe apparent location of the signal produced a time shifted evoked potential (TSEP) that was not present during monaural control runs. TSEP amplitudes were largest near the vertex and varied as a function of the presentation format.

Acoustic Stimulation↗
PubMed1978

The effects of passive antibodies to egg albumin on active immunity in lambs to Brucella abortus and egg albumin.

The long-term effects of colostrum on active immunity to two unrelated antigens are described. Lambs were fed with pooled colostrum--to equalise passive immunity--with or without added antibodies to egg albumin (Ea). There were significant breed differences in the response both to Brucella abortus measured at one month of age, and to Ea, measured at three months of age, although there was no significant correlation between the responses to the two antigens, either within or between breeds. Surprisingly, whereas antibodies to Ea caused a four-fold reduction in antibody production to B abortus, they did not affect the overall mean response to Ea. But the timing of the response to Ea was significantly affected, suggesting that the low persisting concentrations of antibody had caused qualitative changes in the response.

Animals↗
PubMed1978

Effects of energy intake during late pregnancy and of genotype on immunoglobulin transfer to calves in suckler herds.

Blue-Grey (Shorthorn x Galloway) and Hereford x Friesian cows were given levels of feeding, during the last 12 weeks of pregnancy, varying between 75.2 per cent and 171.5 per cent of the maintenance requirements in one experiment and between 65 per cent and 125 per cent of the maintenance requirements in a second experiment. The concentrations of the immunoglobulin classes IgG1, IgG2 and IgM, in their colostrum and in their calves' serum were measured. The IG1 and IgM, but not the IgG2, concentrations were significantly higher in the Blue-Grey than in the Hereford x Friesian colostrum and serum. The relative concentrations of the three classes in the serum were almost identical to those in the colostrum, suggesting that absorption by the calves was non-selective. The amounts of immunoglobulin transferred to the calves were not affected by the cows' levels of feeding in the first year, but there was a small increase in transfer with increasing levels of feeding during the second year. Cows that transferred large amounts to their calves in the first year tended to do so in the second year. The milk intake and growth of the calves during the first 42 days were significantly correlated with their immunoglobulin concentrations.

Animals↗
PubMed1978

Variation in immunoglobulin transfer from ewes to lambs.

The IgG1 concentrations in two-day-old lambs were significantly correlated with litter size, date of lambing, length of gestation and age of the dam. When these and other effects were allowed for significant breed differences were found, the concentrations being relatively high in Finnish Landrace, Welsh Mountain and Soay lambs, and relatively low in Border Leicester, Oxford Down and Southdown lambs. The concentrations in crossbred lambs were related to those in the parent breeds. The effects of the various factors on the yields of colostrum and total IgG1 by ewes were similar to their effects on the lamb serum concentrations. The yields were highly correlated with milk production. The heritabilities for IgG1 concentration in lambs and for total IgG1 production by ewes were estimated at 0.10 and 0.45, respectively.

Animals↗