Biomedical subjects
Publications and source records attributed to J L Smart.
Type C botulism in turkeys has been confirmed on several production sites by demonstrating the presence of toxin in sera from affected birds. Only male turkeys were affected, mortalities being up to 30 per cent. No source of toxin was found. Possible modes of intoxication are discussed.
Developing rats of 2 outbred stocks were either well-nourished or undernourished by underfeeding their mothers throughout pregnancy and lactation. All rats were well-fed from 25 days of age. Starting at 110 days male rats were observed first in an open field and then in a social situation; finally their motor performance was tested on a revolving drum. The social behavior test comprised pairing male rats of the same stock, 1 well-fed control with 1 previously undernourished rat. Analysis of variance of the results of the open-field and social behavior tests revealed main effects of Nutrition and of Stock for several measures of behavior in each test. There were also Nutrition X Stock interactions for 2 measures from the open field and 1 from the social situation. Motor performance was not impaired by early life undernutrition. The evidence of Nutrition X Stock interactions, together with that from analyses of the effects of nutrition performed separately for the 2 stocks, as if each stock had been investigated in a separate study, indicates that genotypic differences may be one of the reasons for the discordance often found between the conclusions of different early life malnutrition studies.
In the rat, brain growth is most vulnerable to undernutrition during the suckling period. Undernutrition at that stage also produces lasting effects on behaviour and it is often assumed that these are due to disturbances of brain growth. The proposal that this may not necessarily be so was explored by testing the behaviour of rats which had been undernourished at later stages of life and which, therefore, would be expected to show little or no deficit in brain growth. Rats were undernourished either immediately after weaning (25-67 days) or in adulthood (80-134 days) and were tested 3-4 months later on variable interval and variable ratio schedules of reinforcement with food as the reward. Their behaviour on these schedules was similar to that of rats undernourished during the suckling period: both groups responded or tended to respond at a higher rate than controls. Hence, it is possible that undernutrition at any stage in life may make animals more responsive to food when deprived subsequently. A cognitive mechanism for this change in behaviour is suggested.
The present study examines the applicability of Fishbein and Ajzen's theory of reasoned action to the prediction and understanding of how primiparous and multiparous mothers intended to feed their infants and how they actually fed these infants during the 6 weeks following delivery. Measures of attitudes to behavior, subjective norms, and behavioral intentions were taken during the last trimester of pregnancy. Behavior was assessed by self-report 6 weeks postpartum. In most respects the findings supported the theory of reasoned action. However, attitudes to behavior were found to make an independent and significant contribution to the prediction of infant-feeding behavior, and the previous behavior of multiparous mothers explained an independent and significant proportion of variation in their behavioral intentions. The relative importance of the attitudinal and normative components of the theoretical model tended to vary according to whether the mothers had direct experience of the criterion behavior. Further analysis revealed that mothers who breast-fed during the 6-week postpartum period differed from those who bottle-fed exclusively during this period on a number of behavioral beliefs, outcome evaluations, and normative beliefs, and on one measure of motivation to comply. The implications of these findings for the theory of reasoned action are discussed.
In order to exclude the possibility of differences in maternal care which are known to result from typical methods of undernutrition during the suckling period, rat pups were reared artificially on different planes of nutrition away from their mothers. Artificial rearing was accomplished by fitting infant rats with a gastric cannula through which a milk substitute was infused intermittently. Rats were fed thus from 4 to 21 d on a high (ARHI) or a low (ARLO; 44% of ARHI level) plane of nutrition. Underfeeding of the ARLO group was continued till 25 d, after which all rats were given a good-quality pelleted diet qd lib. Compared with mother-reared (MR) litter-mates, ARHI rats showed advanced eye-opening and, at 21 and 25 d, they resisted restraint more strongly. Growth in body-weight of ARHI and MR rats was similar but, when autopsied at 32 weeks, the ARHI rats were shorter (nose-rump length) and had lighter gastrocnemius muscles, adrenals and brains, but heavier epididymal-fat pads. ARLO rats had deficits at 32 weeks compared with ARHI rats in whole body, kidney and epididymal-fat-pad weights, and in tibia length. In a second experiment, ARHI and MR rats were killed at 21 d. All the differences found at 32 weeks were already present at 21 d. In addition, the ARHI pups had enlarged livers and intestines but shorter tibias. The milk substitute, which is one commonly used in such studies, has a low protein and high carbohydrate content compared with rats' milk. This difference probably caused the abnormal organ growth of ARHI rats.
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Infant rats were either handled daily during the first 10 days of life or left undisturbed. Brains were examined, using quantitative histological methods, at 22 days postnatum and at 6 months postnatum. At 22 days the handled animals showed a deficit in glial cells in both the anterior limb of the anterior commissure and in the indusium griseum. The deficit in the former was in the oligodendrocyte fraction, whereas in the latter the deficit was in astrocytes. Myelination was unaffected, the percentage of myelinated axons, the diameter of myelinated and unmyelinated axons and the mean number of myelin lamellae being identical in handled and control groups. The numbers of mitotic figures in the subependymal layer were also similar in both groups. At 6 months of age the handled group contained more glial cells in both the rostral part of the anterior limb of the anterior commissure and the indusium griseum. In the former, the increase in glial cells was due to an increase in the number of oligodendrocytes in the handled group compared with controls; in the latter, the main increase was in astrocytes. The percentage of myelinated axons and the number of subependymal mitotic figures were both significantly higher in handled animals. It was concluded that infantile handling leads to an initial growth retardation associated with a long term increase in glial cell number. It was suggested that the initial retardation might be the result of glial cells remaining for a longer than normal time in the proliferative subependymal pool before migrating to the periphery. It was noted that the timing of the handling coincided with the period of normal rapid proliferation of oligodendrocytes in the anterior commissure and of astrocytes in the indusium griseum.
Rats were either undernourished from birth to 43 days and thereafter well fed (previously undernourished, PU) or well nourished throughout. When behaviour was tested in adulthood it was found that significant differences between the groups in rate of lever-pressing for food occurred when they were tested under a variable-interval 60-sec schedule of reinforcement, but not when reward was delivered according to a fixed-interval 60-sec or variable-ratio ten schedule. The results of a second experiment suggested that the rate difference might reduce or disappear with extended exposure to the schedule. The third experiment exposed rats to fixed-interval 60-sec and mixed fixed-interval 10-sec fixed-interval 110 sec schedules. Response rate differences between the PU and control groups occurred only under the mixed schedule, a result interpreted as showing that temporal irregularity of reward delivery plays some role in the genesis of more rapid operant responding in PU rats. When rats received a larger variable-ratio schedule, requiring 40 responses for reward, no significant rate differences between the groups were found over the whole experimental condition. It is suggested that schedules on which there are significant differences have some special characteristic, possibly sensitivity to differences in food motivation between the groups.
The spontaneous activity of cerebellar Purkinje cells was compared in 100- to 130-day-old rats undernourished during the suckling period (i.e. 0-21 days) and subsequently nutritionally rehabilitated (PU rats), with that in rats of the same strain and of similar age fed normally (age controls), and in normally fed rats of the same strain but approximately one month younger (weight controls). Simple spike activity of single cells was recorded with extracellular microelectrodes in pentothal-anaesthetized animals. The discharge patterns were assessed by on-line computer analysis of the interspike interval distributions with subsequent transformation of the data to enable the results to be evaluated by an analysis of variance. In addition, the distribution of the mean interval, the percentage of intervals less than 30 ms, the percentage of intervals greater than or equal to 150 ms, and the time spent in intervals greater than 150 ms, were compared for the PU rats and pooled controls by a nonparametric statistical test on the untransformed data. None of the results indicated that there were any significant differences between the simple spike activity of Purkinje cells from age- and weight- control rats nor between that in PU rats and the control groups. These results are discussed in relation to the previously reported deficits of granule cells in the cerebella of PU rats.
The hypothesis that a high concentration of fat in milk acts as a satiety signal for babies was tested by feeding neonates formula milks of different fat concentrations. Babies were tested on 2 consecutive days. On day 1 they were fed a high fat milk followed by a low fat milk, or vice versa, each for 2 min; and on day 2 the same procedure was followed but in the opposite order. Milk intake and 6 parameters of sucking behaviour were recorded. There was no indication that high fat milk acted as a cue to babies to slow or stop feeding. On the contrary babies appeared to feed more actively on the high fat milk, in that they sucked in longer bursts for it and spent a smaller proportion of the test period resting.
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1. Male rats were undernourished either during the gestational and suckling periods or for a period of time immediately following weaning. Some rats were killed at the end of the period of undernutrition; others were nutritionally rehabilitated for lengthy periods of time before examination. Two muscles, the extensor digitorum longus (EDL) and soleus (SOL) were studied from each rat. Histochemically-stained transverse sections of these muscles were used to determine total number of fibres, the fibre cross-sectional areas and the relative frequency of the various fibre types. 2. All rats killed immediately following undernutrition showed significant deficits in body-weight, muscle weight and fibre cross-sectional area compared to age-matched controls. 3. Animals undernourished during gestation and suckling and then fed normally for 5 months showed persistent and significant deficits in body-weight, muscle weight, muscle weight and total fibre number. There were also significant deficits in mean fibre cross-sectional area of each fibre type except for red fibres in the EDL. No difference in the volume proportion of connective tissue was found. 4. Rats undernourished after weaning and then fed ad lib. for approximately 7 months had normal body-and muscle weights. Their muscles showed no significant differences in total fibre number, relative frequency of the various fibre types, fibre size or volume proportion of connective tissue. 5. These results indicate that, although the effects on rat skeletal muscle of a period of undernutrition after weaning can be rectified, undernutrition before weaning causes lasting deficits.
1. The contractile properties of soleus and extensor digitorum longus muscles from animals at 12 months of age whose mothers had been undernourished during pregnancy and lactation (PU rats) have been compared with those of muscles from ge-matched controls. 2. Body-weight and muscle wet weight of PU rats was significantly reduced. Muscle:body-weight values were, however, no different from controls. 3. No significant alterations in whole muscle speeds of contraction or relaxation could be detected when compared with those of age-matched controls. 4. Twitch and tetanic forces of both SOL and EDL were greater per unit weight of muscle in PU rats. Apart from SOL twitch these differences were significant. The tetanus:twitch values were, however, not different.
1. A detailed investigation was made of the motor performance of rats which had impaired cerebellar and muscular growth resulting from early-life undernutrition. 2. Developing rats were growth-retarded by underfeeding their mothers during pregnancy and lactation. They were fed ad lib. from 25 d of age. 3. Adult male previously-undernourished (PU) and well-fed control rats were given tests of motor behaviour commencing at 5 months of age. They were required to run backwards to maintain their position on a revolving drum. Aspects of the test situation were varied systematically: visual environment, interval between trials, test duration and drum speed. 4. PU rats had a 29% body-weight deficit compared with controls at 5 months. 5. There was nio evidence of impaired motor performance by the PU rats under any for the test conditions.
The possibility that maternal unilateral ovariectomy, which is said to enhance fetal growth, might also ameliorate the harmful of undernutrition was investigated. Maternal undernutrition throughout pregnancy and unilateral ovariectomy on day 13 of pregnancy were investigated separately and in combination in primigravid rats with respect to male and female placental and fetal growth. Undernutrition increased the number of fetal resorptions in the 3rd week of pregnancy and depressed placental and fetal weights in both sexes, although there was some relative sparing of fetal brain weight. Unilateral ovariectomy of well-nourished mothers on day 13 of pregnancy caused significant increments in placental weight, and fetal body and brain weight in both sexes, but not in fetal length. None of these effects were observed in underfed mothers; that is, unilateral ovariectomy was ineffective in ameliorating the consequences for the fetus of maternal undernutrition. In none of the groups was there a significant relationship between fetal body weight and the number of fetuses, although in the undernourished litters significant negative correlations between fetal body weight and total number of placentae (normal and supernumerary) were found.
The activity of pyrimidine-5'-nucleotidase (P5N) (EC 3.1.3.5) was assayed in microsamples of rat blood using high performance liquid chromotography (HPLC). The assay is based on the measurement of enzymatically formed uridine in erythrocyte hemolysates (10-50 microliter) and produces a linear activity curve from 5 to 1000 microM/g Hb/h. Acute (22 h) administration of lead acetate ip to rats induced a dose-dependent inhibition of P5N activity in erythrocyte samples.
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