Effects of early undernutrition on hippocampal development and function.

The possibility of a "hippocampal syndrome' was investigated in mature animals whose mothers had received a period of undernutrition during pregnancy and throughout lactation. Spontaneous alternation behaviour was abolished, and performance was found to be at chance level. Significant depletions in cell numbers were found throughout the hippocampal region; however, hippocampal theta rhythm remained and threshold levels for theta driving appeared normal. It was concluded that the behavioural differences observed did no arise from some simple deficit in the circuitry controlling hippocampal theta rhythm and that it was more likely due to an impairment at the synaptic level. The similarity of these, and other recent behavioural observations, to those of animals with hippocampal damage may provide a reasonable basis for investigating a number of learning deficits induced by early undernutrition.

Deficits in spatial memory performance induced by early undernutrition.

Recent studies have shown that rats have a remarkable ability to keep track of their spatial location. Explanations stress the involvement of a form of short-term (working) memory in which the hippocampus appears to play a major role. The hippocampus appears to be vulnerable to early undernutrition and preliminary investigations indicate that Areas CA3 and CA4 suffer the most. Ninety-day-old rats, previously undernourished prenatally and throughout lactation, were tested in an 8- and, then, a 16-arm radial maze. Significant differences were observed between the experimental and control groups on both tests, especially in the 16-arm maze. Error distributions were also significantly different with experimental animals tending to perseverate in 1 area of the maze. Differences were also observed in the time taken to make the choices and in exploratory behavior. We conclude that early undernutrition affected the spatial learning ability of the animals and that this may be due to the distortions observed in the normal growth pattern of the hippocampus.

Sex-related differences in the response of fast and slow muscle fibres to early undernutrition.

Early undernutrition of male and female rats was effected by limiting the mothers' food supply by 40% during pregnancy and lactation. The rats were killed at the age of 20 weeks and physiologically fast and slow skeletal muscles were prepared for histochemical demonstration of muscle fibre types. In the fast extensor digitorum longus (EDL) and the slow soleus (SOL) significant decreases in muscle weight were seen only in male experimental animals. Decreases in muscle fibre type cross-sectional area were found in the EDL in both males and females. In SOL, both fibre types showed evidence of fibre hypertrophy, and this was statistically significant in male animals. No changes were seen in the proportions present of the fibre types in either of the muscles.

The effects of pre- and perinatal undernutrition on the succinic dehydrogenase content of muscle fibres from fast and slow rat muscles.

Male rats were subjected to early undernutrition by limiting the mothers' food supply by 50% during pregnancy and lactation. At age 36 weeks, quantitative cytochemical determinations of succinic dehydrogenase activity were made in muscle fibres from the anterior tibialis and soleus muscles. Marked decreases were found in the former muscle but relatively little decrease was seen in the latter. This response of the muscles to early undernutrition was discussed with reference to other studies on pre and post-natal starvation.

Effects of pre and perinatal malnutrition on muscle fibres from fast and slow rat muscles.

Pre and perinatal malnutrition of rats was effected by means of limiting the mothers' food intake by 50% during pregnancy and lactation. Male offspring were sacrificed at 36 weeks of age and the anterior tibialis (ANTIB) and soleus (SOL) muscles were prepared for histochemical demonstration of Type I, IIA and IIB muslce fibre types using myosin ATPase and succinic dehydrogenase activity. Muscle weights and mean muscle fibre area determinations showed greater decreases in ANTIB than SOL, SOL muscle fibre areas being relatively unaffected by the undernutrition regimen. The proportions present of the muscle fibre types differed in ANTIB and to a small extent on SOL. In the former muscle, some decreases in area in certain of the fibres were associated with increases in the percentages present, showing a tendency to maintain the physiological cross-sectional area of the muscle.

Myofibril content of histochemical fibre types in rat skeletal muscle.

A modification of the histochemical method for myosin ATPase was used to determine the myofibril complement, mean myofibril size and myofibrillar packing of defined muscle fibre types in rat skeletal muscle. Fast muscle fibres (Types IIA and IIB) were found to have smaller myofibrils and a lower packing density than slower (Type I) fibres. These findings were discussed with respect to their relevance in estimations of muscle strength from histological and histochemical preparations of muscle cross-sections.

Cell wall characteristics of Pseudomonas aeruginosa and its carbenicillin-induced L-form.

L-forms of Pseudomonas aeruginosa were induced and cultured on a medium supplemented with carbenicillin. Morphological studies of the passaged variant revealed the presence of a triple-layered cell wall similar to that found in the parent species. Furthermore, the L-form was found to be more susceptible to gentamicin, kanamycin, tetracycline and colistin sulphate. Chemical analysis of the lipopolysaccharide fraction showed a difference in phosphorus content, and changes in cell wall envelope fatty acid content were also exhibited. It is suggested that these differences may influence the transport of certain antibiotics through the cell wall.

Structural changes of erythrocyte membranes in muscllar dystrophy.

Erythrocytes from dystrophic hamsters and patients with Duchenne muscular dystrophy were examined for structural changes using light microscopical methods. The effects of specimen preparation were also investigated. The proportions present of echinocytes were significantly greater in dystrophic hamsters and humans when compared with their respective controls. In the dystrophic hamsters, the progression of the myopathy caused a significant increase in erythrocyte membrane deformations. With dystrophic patients, age-related changes were seen, but these were not statistically significant. These findings were discussed with relation to specimen preparation and the use of haematological techniques in the detection of carriers of muscular dystrophy.

Work-induced hypertrophy in exercised normal muscles of different ages and the reversibility of hypertrophy after cessation of exercise.

1. Groups of male hamsters of different ages were subjected to a weight-lifting exercise regimen, and the biceps brachii, soleus and extensor digitorum longus (EDL) muscles examined for structural changes occurring in response to the increased workload. In addition, two groups of adult hamsters were left to recover from the exercise stimulus for 5 and 15 weeks respectively.2. All the exercised muscles exhibited muscle fibre hypertrophy, and the extent of the hypertrophy was greater in the younger animals. In all age groups, the biceps brachii and EDL showed more hypertrophy than did the soleus. There was no significant increase in fibre number after exercise.3. In both groups allowed to recover from the exercise stimulus, the fibre dimensions reverted back to those of the control muscles; this appeared to be complete after 15 weeks recovery.4. Electron microscopical studies of fibres from exercised and control biceps brachii revealed no significant changes with exercise in the proportions present of myofibrillar, mitochondrial and tubular components within muscle fibres of the same size.