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This study compares the peak serum growth hormone (GH) concentration during slow wave sleep with the serum GH responses to insulin-induced hypoglycaemia and intravenous arginine infusion in 23 children referred because of short stature (20) or precocious puberty (3). Peak serum GH concentration during sleep correlated significantly with peak GH response to insulin hypoglycaemia (r = 0.64, p less than 0.01) and arginine infusion (r = 0.57, p less than 0.01). 3 children had subnormal (less than 15 mU/l) peak serum GH concentrations during sleep but normal responses to either insulin-induced hypoglycaemia or intravenous arginine infusion. 1 child had a normal peak serum GH response to sleep but subnormal responses to insulin and arginine. Sleep studies of GH secretion may be indicated when the GH responses to pharmacological stimuli are inconsistent with the observed growth pattern.

We have examined the anatomy and fibre type composition of the human adductor pollicis in muscles taken post mortem. Histochemical staining of muscle fibres showed that type I fibres predominated in all cases with a mean occurrence of 80%. This composition is similar to that of the soleus muscle and unlike that of the quadriceps which has approximately equal proportions of the two fibre types. Comparing the contractile characteristics, however, the adductor pollicis has similar properties to the quadriceps and both are quite distinct from those of the slowly contracting soleus muscle. The lack of correlation between fibre composition, as revealed by histochemical staining, and contractile properties in these muscles must mean that fibres of the same type from different muscles do not necessarily have the same contractile speed. The results also suggest that the type I fibres of the human adductor pollicis are faster than those of both the soleus and quadriceps muscles.

A feasibility study in the use of membranes for the recovery of L-asparaginase from the fermentation stage has been undertaken. In the cell harvesting stage 100 l of broth (0.55% dry weight approx) of Erwinia carotovora is concentrated to 3.2 l by a I m2 prototype cross flow microfiltration unit in just over 4 hours. Cell disruption was carried out by raising the cell suspension to pH 11.5 to release the enzyme, which is stable in alkali, for a short period. After neutralisation by acetic acid addition, the enzyme is separated from the cell debris by filtration with 0.45 μm Asypor membranes. A preliminary economic analysis shows that the membrane process can compete favourably with the conventional process, which employs high speed centrifuges.

The use of cross flow microfiltration for the separation of aryl acylamide amidohydrolase (amidase) from cell lysate has been investigated. The transmembrane pressure, the feed velocity and the membrane configuration were all found to have significant influence on the transmission of the enzyme through the membrane. Other factors which affect flux and transmission severely are the physical and biochemical properties of the lysate which control the rate of fouling. These, however, are as yet not well characterised. It has been shown that a large amount of amidase is adsorbed to the cell debris which results in a poor enzyme yield. In some cases the apparent membrane transmission of enzyme reaches 154%; this was ascribed to the desorption of the enzyme in a shear field. A model is offered to account for the mechanism of enzyme transmission enhancement.

Ultrastructural studies were undertaken on sections of skeletal muscle from normal pigs and pigs with splayleg from herds with high or low incidence of the disease. Studies were also made of the growth of the muscle from 1 to 7 days after birth. No consistent qualitative differences between the muscles from normal and affected pigs were detected. During the first week of post-natal life, muscle cell cross-sectional areas, intracellular lipid and motor endplate size and complexity increased. Concurrently, the degree of myofibrillar hypoplasia and the area of the extramyofibrillar space (EMS) were reduced. The EMS was occupied by a granular material with a sub-structure of electrondense particles 3 to 7 nm in diameter and was considered to be predominantly glycogen. Evidence is presented that muscle cells were being formed in the early post-natal period. No significant degenerative changes were found in muscle cells from any pig.

SUMMARY Cross-sections of semitendinosus muscle from Landrace pigs with splayleg and from unaffected litter-mates were examined with a Quantimet 720 image analyzer to determine the extent and distribution of myofibrillar hypoplasia (MFH). MFH was not uniformly distributed, so that measurement of a large number of muscle samples was necessary. Even though the extent of MFH was found to be the same in the two groups of pigs there was a very highly significant difference between the arrangement of the myofibrils within the fascicles of affected and unaffected animals.

Light microscopical studies were undertaken on 1 μm thick araldite sections of skeletal muscle from normal pigs and pigs with splayleg from herds with high or low incidence of the disease. The progressive clinical improvement occurring during the first week of life was accompanied by an increase in muscle cell cross-sectional area, a reduction in the degree of myofibrillar hypoplasia and an increase in intracellular lipid. Similar changes occurred in normal pig muscle. Clinical splayleg occurred without significant abnormality in either the extrafusal muscle cells or in the intrafusal cells of neuromuscular spindles. Thus, light microscopical study of sections of skeletal muscle is not generally useful to determine whether or not a pig had splayleg. At present this can only be determined consistently by clinical observation.