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Biomedical subjects

K J Anderson

Publications and source records attributed to K J Anderson.

68 records · Page 4Linked to original sources
PubMed1982

Impulsivity, caffeine, and proofreading: a test of the Easterbrook hypothesis.

Easterbrook's (1959) suggestion that arousal is inversely related to the range of cue utilization has been frequently cited as an explanation for the curvilinear relationship between arousal and performance. There is very little empirical support for this position, however. As a test of the Easterbrook hypothesis, 60 undergraduates who varied in their impulsivity level were given caffeine or placebo and then asked to proofread several passages. Estimates of sensitivity were calculated using signal detection techniques. It was predicted that high arousal would reduce sensitivity to interword errors, which require a broad range of cue utilization, but that the observed levels of arousal would not affect sensitivity to intraword errors, which require a minimal range of cue utilization. A significant crossover interaction between impulsivity and drug for interword errors indicated that caffeine increased the error detection rate of the (less aroused) more impulsive subjects but lowered the error detection rate of the (more aroused) less impulsive subjects. The results of this study support the suggestion that arousal has direct effects on the capacity for simultaneous information processing, independent of its effects on performance speed.

Arousal↗
PubMed1981

Effect of heat on the anaphylactic-sensitising capacity of cows' milk, gots' milk, and various infant formulae fed to guinea-pigs.

Cows' milk--fresh, boiled, and processed in different ways for the domestic market, and various infant milk formulae--was investigated for its sensitising capacity in the guinea-pig after being fed for 37 days. The anaphylactic sensitising capacity was considerably reduced by heat-treatment. As heat becomes more intense and more prolonged so beta-lactoglobulin and casein become less sensitising. It should be stressed that these were results from experiments on guinea-pigs drinking milk. Should they be found to apply to the human infant too, it seems that it would not be impossible to manufacture a non-sensitising but fully nutritive milk product. The sensitising capacity of fresh and boiled goats' milk was examined too, and it was found that boiling reduced the sensitising capacity to an even greater extent than was the case with cows' milk.

Animals↗
PubMed1981

Fetal cardiac arrhythmia: antepartum diagnosis of a case of congenital atrial flutter.

A case of antepartum atrial tachyarrhythmia was detected in the 36th week of pregnancy. Cardiotocograph recordings done twice daily enabled close surveillance of the fetal condition after oxytoxin challenge testing had failed to show evidence of hypoxia. After a diagnosis of fetal cardiac arrhythmia had been made, elective caesarean section in the 40th week of pregnancy resulted in delivery of an infant in atrial flutter and cardiac failure. Both these problems were soon resolved by cardioversion and subsequent treatment with digoxin. Cardiac catheterisation showed no underlying cardiac abnormality. Increasing use of antenatal cardiotocography may show that intrauterine tachyarrhythmias are more common than had generally been believed.

Arrhythmias, Cardiac↗
PubMed1979

Anaphylactic sensitivity of guinea-pigs drinking different preparations of cows' milk and infant formulae.

Guinea-pigs have been given various preparations of cows' milk or infant formulae to drink in an investigation of the capacity of these milk preparations to stimulate per os anaphylactic sensitivity. The treatment, presumably heat, used to concentrate the 'Evaporated' whole cows' milks (three brands were tested) almost abolished their sensitizing capacity to beta lactoglobulin. The brand presumed to be most heated as judged by the degree of caramelization had also lost most of its sensitizing capacity to casein. Injected parenterally, the 'Evaporated' milk adequately sensitized to anaphylaxis. An infant formula, which in its spray dried form was only moderately sensitizing to both beta lactoglobulin and casein, lost most of this sensitizing capacity when processed to a liquid concentrate state. The manufacturing process for the liquid concentrate involved greater and more prolonged heating than required for the spray-dried form. The relevance of these findings in the guinea-pig to cows' milk protein intolerance in the infant and possibly also to cot death is discussed.

Anaphylaxis↗
PubMed1978

Refractoriness to anaphylactic shock after continuous feeding of cow's milk to guinea-pigs.

Further studies have been undertaken on the anaphylactic sensitization to cows' milk in guinea-pigs given cows' milk to drink instead of water. With continuous feeding over a prolonged period of time (over 70 days), about 70% of the guinea-pigs became refractory to intratracheal challenge of cows' milk and about 30% to intravenous challenge. Some guinea-pigs given cows' milk from the second day of life appeared not to undergo an early sensitization at all and may have been displaying a tolerance to anaphylactic sensitization. The degree to which this was shown may be genetic. The anaphylactic sensitivity, particularly as regards intravenous challenge, could be assessed by examining the sera for IgGl a antibodies to cows' milk by passive cutaneous anaphylaxis.

Anaphylaxis↗
PubMed1977

Quantitative aspects of phenyl substituted alcohol and ether bacteriostatic interaction with Escherichia coli B/5.

It is well established that compounds of the class phenylalkane alcohols and ethers exert their antimicrobial action on the bacterial envelope--probably on the membrane. However, the overall stoichiometry, the number of molecules bound vs those merely added per cell, and the kinds of equilibria involved (site binding vs equipartitioning) are not clear. This work examines antimicrobial action on E. coli B/5 with eight such compounds. Directly determined binding data, plate counting viabilities, radiorespirometry, and microcalorimetry of glucose utilization were evaluated. The compounds mostly bind by simply equipartitioning, up to some threshold level, short of kill. That level depends sharply on the number of alkane carbons in the phenyl alkane derivative, but not on the precise structure. Past the threshold, bacteriostatic action is sudden and complete, probably reflecting cooperative behaviour in the cell envelope. The amount of bound compound at the threshold level is only about 0.5 to 3% of the weight of the bacterial envelope hydrocarbon, when bacteriostasis occurs. There is an unexpectedly small dependence on cell concentration. The principal governors on where the monooxygen phenylalkanes kill cells seems to be merely their concentration or chemical potential, the number of aliphatic carbons, and the binding mechanism. Because of the cell concentration independence, the cells act as if they constituted a second phase, relative to the solution. Results from the microcalorimetric method for assay of bacteriostasis correlate well with those from plate counting or viability assays.

Calorimetry↗
PubMedDate not supplied

Age-related changes in [3H]MK-801 binding in the Fischer 344 rat brain.

In this study we tested the hypothesis that the efficacy of L-glutamate to stimulate [3H]MK-801 binding to the NMDA receptor/channel complex is altered as a function of aging. L-Glutamate, or related excitatory amino acid (EAA), is the endogenous neurotransmitter of the NMDA receptor/channel complex. These studies examined the efficacy and potency with which L-glutamate produces receptor activation, channel opening and subsequent MK-801 binding as a function of increasing age by comparing dose-response curves (EC50 and Emax) from 6-, 12-, and 24-month-old F-344 rats. The number of NMDA receptors, as determined by [3H]MK-801 binding in the presence of a saturating concentration of L-glutamate, was reduced in the inner frontal cortex, entorhinal cortex and the lateral striatum in aged rats when compared with young adults. When a range of L-glutamate concentrations were used, differences in Emax were noted in the same brain regions in addition to several others in aged and middle-aged animals when compared with young-adult animals. No changes in EC50 values were noted in any of the brain regions at either age when compared with young-adults.

Aging↗