Obstetric practice and outcome of pregnancy in Cardiff residents 1965-73.

Trends in management and outcome of pregnancy in Cardiff residents from 1965 to 1973 were reviewed. The mean age and parity of parturients fell. Hospital delivery became almost universal, monitoring the fetus during pregnancy was introduced, and induction and acceleration of labour became commonplace. These developments were not associated with any striking change in either the total perinatal death rate or the timing or cause of perinatal death. Possibly a real change in perinatal mortality between 1965 and 1973 was masked by random fluctuation of small numbers, or possibly factors peculiar to the Cardiff population prevented a decrease in perinatal mortality that would otherwise have resulted from improved medical care. Only by large-scale randomised trials can the true value of induction and other medical developments be assessed.     

Follow-up study of small-for-dates babies.

A group of small-for-dates full-term babies whose intra-uterine growth was followed by serial ultrasonic cephalometry were examined at a mean age of 4 years. Those children whose skull growth had begun to slow in utero before 34 weeks'' menstrual age were more likely to have a height and weight less than the 10th centile. When the onset of growth failure had occurred before 26 weeks there was a lower developmental quotient at follow-up using the Griffiths extended scales. Prolonged slow growth in utero therefore seems to be followed by slow growth and development after birth.     

Avian mitochondrial glutamine metabolism.

Intact avian liver mitochondria were shown to synthesize glutamine from glutamate in the absence of exogenous ATP and ammonia. With L-[U-14C]glutamate as the substrate, there was an approximate 1:1 stoichiometry between glutamate deaminated (as measured by the release of 14CO2 due to alpha-keto-[14C]glutarate oxidation) and glutamate amidated. With L-[15N]glutamate as the substrate, the isolated glutamine was shown by low and high resolution mass spectrometry of its phenylisothiocyanate derivative to contain 15N in both the alpha-amino and amide groups. Thus, for each mole of glutamate taken up, approximately 0.5 mol is deaminated and the other 0.5 mol serves as a substrate for glutamine synthetase previously localized in these mitochondria (Vorhaben, J. E., and Campbell, J. W. (1972) J. Biol. Chem. 247,2763). The permeability of L-glutamine to intact avian liver mitochondria was studied by a rapid centrifugation technique. Efflux as well as influx of L-glutamine were both rapid and appeared to occur by a passive, energy-independent process. These results indicate that the mitochondrial glutamine synthetase present in uricotelic species represents the primary ammonia detoxication reaction in that ammonia released intramitochondrially during amino acid catabolism is converted to glutamine for efflux to the cytosol where it may serve as a substrate for purine (uric acid) biosynthesis.     

Immune serum-mediated cytotoxicity against Trypanosoma rhodesiense.

The metabolic integrity of Trypanosoma rhodesiense can be assessed in vitro by the extent of incorporation of radiolabeled leucine into trichloroacetic acid precipitable material or into material retained after filtration on a glass fiber filter. Incorporation is an approximately linear function of time, and the rate of incorporation is linearly dependent on cell concentration in the presence of normal rat serum. Incorporation is completely prevented if the organisms are reacted wiith fresh serum from animals immunized with gamma-irradiated parasites; the degree of inhibition is a function of the dose of immune serum used. This serum-mediated cytotoxic activity is abrogated by heating the serum, but can be fully restored by addition of fresh rat or guinea pig serum to the heated immune serum. The serum activity arises promptly after one to four immunizing doses of irradiated parasites, falls to lower levels by 1 month, but persists for at least 2(1/2) months, and is unaffected by challenge with viable trypanosomes.     

Purification, properties and kinetics of sheep and human renin substrates.

Sheep plasma renin substrate was purified 1,200-fold by using nephrectomised sheep plasma, followed by DEAE-Sephadex chromatography and gel filtration. The purified substrate contained 8 mu-g angiotensin II/mg protein and had an estimated molecular weight of 52,000. The kinetic characteristics of the purified substrate were identical both to those of unpurified nephrectomised sheep plasma and to normal sheep plasma substrates. At pH 7.5, K-m of the human renin-sheep substrate reaction was 0.29 mu-M and for sheep renin-sheep substrate, 2.0 mu-M. Sheep substrate was susceptible to peptic digestion with generation of pepsitensin. Human renin substrate was less readily purified. DEAE-Sephadex chromatography of plasma from pregnant women at 36-40 weeks' gestation produced a 70-fold increase in purity (0.9 mu-g angiotensin II/mg protein). No further increase was achieved with gel filtration. Human renin substrate behaved as a larger (mol. wt. 82,000) more anionic protein than sheep substrate and was resistant to the proteolytic actions of both pepsin and sheep renin. K-m for the human renin-human substrate reaction was high and could not be accurately determined (range 3-8 mu-M, mean 5.7 mu-M). The presence of human substrate in a human renin-sheep substrate system did not alter the measured initial velocity. In both sheep and man, the normal concentration of renin substrate is considerably less than K-m and must therefore be considered a determinant of angiotensin production rate in vivo.     

Comparative aspects of the calcium-sensitive photoproteins aequorin and obelin

1. The calcium-dependency of the process of light emission has been investigated for the photoproteins aequorin and obelin.2. The experimental curves of light production, expressed as a percentage of the maximal rate of utilisation, versus pCa are accurately predicted by the cooperative action of at least 2Ca²⁺ for aequorin and at least 3Ca²⁺ for obelin.3. At low total monovalent cation concentrations, a pH change from 6.8 to 7.1 shifts the light production vs pCa curve by approx. 0.2 pCa units to the right for aequorin, while that for obelin is shifted by some 0.37 pCa units.4. Other monovalent cations, such as Na⁺ are able to compete with Ca²⁺ for the active sites of aequorin and also shift the light production vs pCa curve to the right. There is no apparent change in the calcium stoichiometry for light production under these conditions.5. The same calcium stoichiometry for light emission was also obtained for aequorin or obelin in the presence of either unbuffered Ca²⁺ solutions or of calcium/EGTA buffers.