Polyglycerophosphatide metabolism in Escherichia coli

When Escherichia coli B cells were labelled with [14-C] glycerol and chased, there was a marked sparing of the phosphatidyl moiety compared to the nonacylated glycerol moiety of phosphatidylglycerol. When energy-depleted cells were restored to an energy-rich medium there resulted a conversion of 32-P-labelled cardiolipin to phosphatidylglycerol, a lack of phosphatidic acid accumulation and no loss in total polyglycerophosphatide counts. In cell-free extracts, phosphatidic acid produced from 32-P-labelled cardiolipin by the action of Escherichia coli phosphalipase D, was readily recycled to form poly-glycerophosphatide. In the presence of glycerol, such extracts displayed traansphosphatidylase activity by degrading cardiolipin to phosphatidyglycerol mainly. The results as a whole indicate that the enzyme synthesizing cardiolipin together with cardiolipin-hydrolyzing phospholipase D constitute a cycle which is normally involved in the turnover of polyglycerophosphatides in Escherichia coli.

Coordinate variation in lengths of deoxyribonucleic acid molecules and head lengths in morphological variants of bacteriophage T4

We have investigated three classes of small bacteriophage T4 particles which differ from normal T4 particles in length of their deoxyribonucleic acid (DNA), in head length, in protein content, and in density. The different particles contain DNA molecules measuring 0.90, 0.77, or 0.67, respectively, of the normal T4 length. An additional class of viable particles contains DNA molecules of 1.1 unit length. These discrete differences in DNA length correspond to discrete differences in length (but not width) of the respective heads and are roughly proportional to the resulting differences in head volumes. The measured relative dimensions of the different heads fit best the relative dimensions predicted by a quasi-icosahedral model in which the smallest T4 head corresponds to an icosahedron with a triangulation number T = 21. The mid-portion of this structure is thought to be elongated by adding successive rows of gene 23 protein hexamers, the normal T4 head having three added rows. Different mutants produce small particles of the three classes in varying proportions, but no mutant produces exclusively particles of a single class. Particles of each class, with indistinguishable DNA content, show additional minor differences in protein content, as measured by differences in buoyant density and in the relative ratio of (32)P to (35)S.

The insulin response to glucose in patients with non-diabetic glycosuria

Glucose tolerance tests (GTT) were performed and plasma insulin levels measured by immunoassay in eighty-nine subjects previously found to have non-diabetic glycosuria (fifty-six with renal glycosuria and thirty-three with lag curves). The time-interval between the two tests varied from 6 months to 13 years.

Ten patients had developed chemical diabetes but only three had symptoms. Two had initially renal glycosuria and eight lag curves. This significantly different incidence may have been due to an excess of older patients in the lag-curve group.

The mean insulin response was higher in those with diabetes than in those in whom the second test was normal. The individual insulin responses were abnormal by our criteria in twenty-six subjects including six of the ten diabetics. In twenty-four subjects plasma insulin levels had been measured during the initial GTT. The insulin response had been abnormal in thirteen of these, four of whom were diabetic at follow up. In contrast only one of the eleven subjects with an initially normal insulin response had developed diabetes.

It is suggested that an abnormal insulin response to glucose may be an indication of potential diabetes.