Mitochondrial aspartate aminotransferase-independent function of the catalytic binding sites

The enzyme mitochondrial aspartate aminotransferase from beef liver is a dimer of identical subunits. The enzymatic activity of the resolved enzyme is restored upon addition of the cofactor pyridoxal 5-phosphate. The binding of 1 molecule of cofactor restores 50% of the original enzymatic activity, whereas the binding of a 2nd molecule of cofactor brings about more than 95% recovery of the catalytic activity. Following addition of 1 mol of pyridoxal-5-P per dimer, three forms of the enzyme may exist in solution: apoenzyme-2 pyridoxal 5'-phosphate, apoenzyme-1 pyridoxal 5'-phosphate, and apoenzyme. The enzyme species are separated by affinity chromatography and the following distribution was found: apoenzyme-2 pyridoxal 5'-phosphate/apoenzyme-1 pytidoxal 5'-phosphate/apoenzyme, 2/6/2. Similar distribution was observed after reduction with NaBH4 of the mixture containing apoenzyme and pyridoxal-5-P at a mixing ratio of 1:1. Fluorometric titrations conducted on samples of apoenzyme and apoenzyme-1 pyridoxal 5'-phosphate reveal that the enzyme species display identical affinity towards the inhibitor 4-pyridoxic-5-P (KD equals 1.1 times 10- minus 6 M). It is concluded that the binding of the cofactor to one of the catalytic sites does not affect the affinity of the second site for the inhibitor. These results, obtained by two independent methods, lend strong support to the hypothesis that the two subunits of the enzyme function independently.

Chorioamnionitis and colonization of the newborn infant with genital mycoplasmas

To study the role of Mycoplasma hominis and T-mycoplasmas (Ureaplasma urealyticum) in chorioamnionitis, we obtained culture from 249 puerperal women and their babies. The placentas were examined histologically. Infants whose placentas showed inflammation (chorioamnionitis) had cultures positive for T-mycoplasmas more frequently (37.5 per cent) than those with normal placentas (19.0 per cent) (P = 0.021). Colonization with M. hominis was found in 16.0 per cent of the babies and was not significantly associated with chorioamnionitis. Material colonization with mycoplasmas was more frequent (73.4 per cent) and was not correlated with placental inflammation. We conclude that a substantial proportion of cases of chorioamnionitis may be caused by prenatal infection with T-mycoplasmas. The fact that these organisms are not highly virulent could explain the frequent finding of inflammed placentas from otherwise normal pregnacies. No adverse clinical effects of the placental lesions or of mycoplasmal colonization could be detected in this small study.

Isolation of genital mycoplasmas from blood obtained shortly after vaginal delivery

Blood obtained from three hundred and twenty-seven women within a few minutes of vaginal delivery was cultured for genital mycoplasmas (Mycoplasma hominis and T mycoplasmas). Twenty-six (8%) of the women had genital mycoplasmas isolated from their blood. Ten women had blood-cultures which contained M. hominis. Fifteen women had blood-cultures which contained T mycoplasmas. Both M. hominis and T mycoplasmas were isolated from the blood of one woman. Only one of two hundred and seventy-three blood-cultures obtained 1 or more days after delivery contained mycoplasmas. The isolation of M. hominis, but not of T mycoplasmas, from the blood was associated with vaginal colonisation and a serological response to the homologous isolate. Two of ten women whose blood contained M. hominis gave birth to stillborn infants. In contrast, there were only four (1.3%) stillbirths among the infants born to the three hundred and one women whose blood did not contain mycoplasmas. This difference is statistically significant.

Comparison of spectinomycin hydrochloride and aqueous procaine penicillin G in the treatment of uncomplicated gonorrhea

Men and women with uncomplicated gonorrhea were randomly assigned to receive aqueous procaine penicillin G (2,400,000 U for men; 2,400,000 U daily for 2 days for women) or spectinomycin hydrochloride (2.0 g for men; 4.0 g for women). Among men who returned for post-treatment evaluation within 10 days, treatment failures were noted among 16 (20.3%) of 79 men who received penicillin and 8 (9.5%) of 84 men who received spectinomycin (P < 0.1). Similarly, 6 (13.3%) of 45 women who received penicillin and 3 (6.5%) of 46 women who received spectinomycin had positive endocervical cultures for Neisseria gonorrhoeae at the time of the post-treatment examination (P = not significant).

Three-tube method for screening stool cultures for Salmonella and Shigella

A three-tube method developed is described as a screening test for non-lactose-fermenting organisms isolated from stool cultures. To evaluate the method, 976 strains of gram-negative bacilli were tested. All strains of Salmonella and Shigella were correctly identified generically.

In vitro studies on the isolation of genital mycoplasmas from blood

A method is described for the isolation of genital mycoplasmas from clinical blood cultures.