A defect in thyroglobulin synthesis in an inherited ovine goitre: possible neonatal respiratory distress syndrome.

A ram lamb with congenital goitre showed signs of respiratory distress at birth. All previously affected lambs from this flock bad been born dead or bad died soon after birth. The serum free-thyroxine level at 1 birth was low (9.8 pmol/l) but treatment with oral L-thyroxine resulted in an increase in thyroxine blood levels to above normal and regression of the goitre. Four weeks after withdrawal of thyroid supplementation and when the lamb was eight weeks old, the radio iodide uptake mechanism of the thyroid glands was shown to be intact but the iodide was not organified. Low normal peroxidase activity was demonstrated in fresh thyroid tissue but gel electrophoresis demonstrated an absence of normal thyroglobulin from extracts of the goitrous thyroid. This lamb and the other affected lambs of this flock have an inherited defect in thyroglobulin synthesis and it is likely that the respiratory distress was associated with the low levels of thyroid hormone affecting foetal lung development.

A reinvestigation of the purity, isoelectric points and some kinetic properties of the aldehyde dehydrogenases from sheep liver.

1. Cytoplasmic aldehyde dehydrogenase was shown to be free of contamination by the mitochondrial enzyme by isoelectric focusing. 2. Both enzymes showed multiple banding in activity stains. The cytoplasmic enzyme gave two very close bands pI = 5.22 +/- 0.03 whereas the mitochondrial enzyme showed seven bands, a pair at pI = 5.22 and five further bands of pI 5.48 +/- 0.09, 5.56 +/- 0.07, 5.65 +/- 0.06, 5.70 +/- 0.03 and 5.76 +/- 0.02. Possible origins of the isoenzymes are discussed. 3. Disulfiram in a fourfold excess reduced the activity of the cytoplasmic enzyme to 9% of the initial value. The residual activity represents the activity of the disulfiram-modified enzyme and is not due to mitochondrial contamination. This casts doubt on the role of an essential thiol group. 4. The mitochondrial enzyme shows a low amplitude (22%) burst in the production of 4-nitrophenoxide ion during the hydrolysis of 4-nitrophenyl acetate at pH 7.6. The burst rate constant was 7.3 +/- 1 s-1 and the steady-state rate constant was 0.2 s-1, values similar to those previously reported for the cytoplasmic enzyme. 5. The mitochondrial enzyme shows a burst in the release of protons during the oxidation of propionaldehyde at pH 7.6. The burst rate constant was 6 s-1 and the amplitude was equal to half the formal enzyme concentration. The significance of these results for the steady-state mechanism is discussed.

Tryptophan deficiency in pigs: changes in food intake and plasma levels of glucose, amino acids, insulin and growth hormone.

Pigs were fed alternately tryptophan deficient diet and the same diet supplemented with tryptophan. The deficient diet depressed food intake, caused changes in the pattern of plasma amino acids, increased plasma glucose levels and increased plasma urea levels per unit food intake. Plasma levels of insulin and growth hormone gave no indication that either hormone was involved in the suppression of food intake.

Rhythmic fluctuations in the urine composition of sheep: separation of feed-dependent from other rhythms.

The relative contribution of feed-induced and feed-independent changes to the pattern of electrolyte excretion have been determined in sheep maintained for extended schedules providing feeds at intervals of 24, 19, 4 and 1 hr. Power spectral analysis indicated that the pattern of electrolyte excretion was predominantly fixed by the feeding cycle. Frequent small feeds reduced the peak levels of excretion. However, feed-independent periodicities on hourly feeding regimes included a 24 hrs rhythm in urinary total solids, K, Cl and HCO3 and a 32 (or 64) hrs periodicity in a wide range of components. None of these occurred in all animals. It would appear that the sheep studied were not as closely influenced by normal 24 hrs environmental cycles as are human subjects. Furthermore, the sheep electrolyte rhythms were not correlated with the 24 hrs variation in adrenal steroid production.