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Biomedical subjects

M J Morgan

Publications and source records attributed to M J Morgan.

At least 199 records · Page 11Linked to original sources
PubMed1977

A method for the isolation of Chinese hamster cell variants with an altered ability to utilise carbohydrates.

Chinese hamster ovary cells (CHO-K1) are able to utilise only a few carbohydrates for growth such as glucose, mannose, fructose and galactose. They do not grow on ribose, lactose, sucrose, glycerol, lactate, pyruvate, citrate, succinate, fumarate or malate nor on glycogenic or ketogenic amino acids. After mutagenesis and selection in glucose free medium supplemented with various, individual, growth substrates, we have isolated single-cell derived clones which are now able to grow on one of the following energy source: ribose, lactose, sucrose or lactate.

Carbohydrate Metabolism↗
PubMed1977

Properties of carbohydrate utilising variants of Chinese hamster cells.

Variants of Chinese hamster ovary cells (CHO-K1) have been isolated which can grow on one of the following carbohydrates: lactose, sucrose, ribose or lactate. The ribose+ clones grow at the same rate on glucose as the parental cells whereas the others grow more slowly. With the exception of one ribose+ clone all excrete lactic acid while growing on glucose; none excrete significant amounts of lactic acid while growing on the alternative energy source. Wild-type cells and the variants accumulate radioactively labelled glucose and the corresponding radio-actively labelled alternative energy source to the same extent. The ribose+ variant that does not accumulate lactate while growing on glucose is also exceptional in its inability to utilise mannose.

Carbohydrate Metabolism↗
PubMed1977

Differential visual persistence between the two eyes: a model for the Fertsch-Pulfrich effect.

By presenting moving bars of different widths to the two eyes, an attempt was made to model the differential visual persistence produced by differential intensity filtering in the two eyes (the Fertsch-Pulfrich effect). If the phase of the two moving bars was controlled so that the thinner bar lined up with the leading edge of the wider bar, a clear depth effect was seen, which was the same as that produced by placing a filter in front of the eye seeing the wider bar. The depth effect was reversed, for example, from clockwise to anticlockwise, when the trailing edges of the targets were in alignment. These effects were additive to those produced by differential intensity filtering. When observers were permitted to control the phase relation between the two target bars in order to null the depth effect, they placed the thinner bar in alignment with the geometrical center of the wider bar. Widening the variable bar led to a reduction in its luminance, but this did not in itself seem to entail a Fertsch-Pulfrich effect. The classical latency explanation of the differential filtering effect is questioned, and a model involving spatial averaging of visual direction in conditions of differential persistence is proposed in its stead. Possible differences in the mechanisms of static and dynamic stereopsis are discussed.

Depth Perception↗
PubMed1976

Pigeons learn the concept of an "A".

Pigeons learned to discriminate between "A"S and "2"s in eighteen different typefaces. They subsequently showed excellent transfer to twenty-two typefaces that they had not previously seen; one pigeon was tested with handwritten letters and responded correctly to them also. Pigeons' responses to "A's and "2's with parts removed suggested that their performance was controlled by several features, none of which alone could be considered necessary or sufficient. A test in which birds were shown other letters of the alphabet supported this conclusion. It appears that the original discrimination was learned as what Ryle calls a "polymorphous concept".

Animals↗
PubMed1976

Pulfrich effect and the filling in of apparent motion.

In the stroboscopic version of the Pulfrich effect a filter is able to induce depth shifts in a target as if the latter were moving continuously, rather than merely occupying a series of discrete positions. This was examined in a further series of experiments, in which a visual alignment technique was used to measure the perceived visual direction of an apparently moving target in intervals between its presentations. Results showed that the target has approximately the visual direction that it would have if it were moving continuously. This "filling in" of apparent motion was shown to occur before the level of stereopsis. The possible influence of tracking eye movements is discussed.

Eye Movements↗
PubMed1976

The aftereffect of tracking eye movements.

When observers tracked moving stripes across a background either of stationary stripes, or of stripes moving in the opposite direction, they saw a clear motion aftereffect when the stripes stopped moving. The direction of this aftereffect was opposite to that of the previously tracked stripes, and was thus the same as the direction of the retinal movement of the non-tracked stripes. This aftereffect of tracking was shown not to depend upon slippage of the tracked contours on the retina during tracking, or upon the saccadic phase of optokinetic nystagmus. The effect showed storage over a period of time with the eyes shut. It appears that the effect is due to induced movement, and arises originally from stimulation of the retina by background contours in the tracking phase. This was shown by confining the view of the moving target to one eye, while permitting both eyes to be exposed to background stimulation during tracking. After such stimulation the magnitude of the aftereffect was equal in the two eyes.

Electroretinography↗
PubMed1976

The production and action of interferon in Chinese hamster cells.

The interferon system has been investigated in primary cell cultures established from Chinese hamster embryos and new born pups. Interferon synthesis was induced with Sindbis virus, ultraviolet inrradiated Newcastle disease virus (u.v.-NDV) and with polyriboinosine acid-polyribocytidylic acid complex [poly (rI). poly (rC)]. Only u.v.-NDV induced significant production of interferon, maximum amounts being produced in 'aged' cells. Its apparent mol. wt. was 25000. CHO-KI cells, an established line of Chinese hamster cells, did not synthesize interferon in response to viruses, but were sensitive to its action.

Animals↗
PubMed1975

The effects of psychomotor stimulants on stereotypy and locomotor activity in socially-deprived and control rats.

Using measures of locomotor activity and stereotypy, dose-response curves to several psychomotor stimulant drugs were obtained on rats reared in deprived or normal environments. At both 0.5 and 1.5 mg/kg d-amphetamine, the deprived rats exhibited more intense stereotyped behavior than the control rats. At 5.0 mg/kg, both groups showed maximum response. However, there was no significant difference between the two groups in locomotor response. A similar pattern of results was found for pipradrol, cocaine, and apomorphine. The findings show that different social and environmental experience can modify the response to dopaminergic stimulating agents. The results also suggest that stereotyped behavior should not be considered on the same continuum as locomotor activity. These two behaviors may be mediated by different mechanisms.

Amphetamine↗
PubMed1975

The development of intersession habituation and emergence in socially reared and isolated rats.

Male and female hooded rats were weaned at 17 days and then reared in isolation or in social groups. Intersession habituation of locomotor activity in the open field was tested at 15, 25, and 45 days. Contrary to some previous reports, the 15-day-old animals showed significant habituation. At 45 days, however, the isolates showed very little habituation compared to the social animals. The isolates showed a similar pattern of development in their emergence into the open field. Apparently, isolation does not result in an arresting of development, but rather in the formation of behavior patterns otherwise absent in normally reared rats.

Age Factors↗
PubMed1975

Apparent motion and the Pulfrich effect.

The Pulfrich pendulum effect, obtained by viewing a moving object with a filter over one eye, was examined with target stimuli in apparent, rather than continuous, motion. The filter-induced depth effect persisted until a certain degree of intermittency in the presentations of the target was reached, and then it broke down. The degree of intermittency that could be tolerated before the depth effect broke down increased with the density of the filter. It could be argued that the filter determined a shift in the pairing of successive inputs to the eyes, such that the target position in the unfiltered eye was fused with the preceding target position in the filtered eye. However, it appears that the shifted-pairing effect cannot account for the depth impression seen when the target intermittency is less than about 30 ms. Below this value of intermittency a filter can produce a depth effect even when the delay it introduces is small in comparison to the intermittency of the input. The depth effect seen with intermittencies less than 30 ms appears to be of the same magnitude as that obtained with stimuli in continuous motion. It is concluded that a filter can cause two different kinds of depth shift with apparently moving stimuli.

Depth Perception↗
PubMed1974

Effects of random reinforcement sequences.

Rats were exposed to a random sequence of reinforcement on two levers, such that there was no way to predict from the previous reinforcement which lever would deliver reinforcement next. The rats showed a tendency to repeat the choice that had just produced reinforcement, despite the absence of an overall contingency that differentially reinforced such repetition. However, this tendency decreased with continued exposure to the schedule. Runs of successive reinforcements on a lever increased the probability of pressing that lever, but only slightly, and only in the earlier phases of training. The more quickly a press was made after reinforcement the more likely it was to be on the lever that had delivered that reinforcement. Repetition of choice followed by reinforcement should be viewed as a naturally occurring behavior in the rat, but not necessarily as a behavior that will continue without differential reinforcement of repetition.

Journal Article↗