Structure of vancomycin and its complex with acetyl-D-alanyl-D-alanine

Vancomycin, a broad-spectrum antibiotic, inhibits the growth of cell walls by complex formation with peptides terminating in D-alanyl-D-alanine. The structure of vancomycin was determined by X-ray analysis of the degradation product CDP-I. A model of the complex is proposed based on this study and spectroscopic data.

Malignant disease in childhood: the problems in general practice

The role of the family doctor with regard to malignant disease in childhood, can be summarized as follows: To act appropriately so that early diagnosis, which to an important degree determines the prognosis, is not delayed by a justifiably low index of suspicion. To assist the family, including the siblings, to cope with the severe emotional stress inherpent in the diagnosis of a malignancy in a child. To recognize the extreme danger of chicken pox and measles when contracted during chemotherapy, for cytotoxic drugs are also immune-suppressants, and appropriate immune globulins can be life-saving. To arrange for and cooperate in the support necessary when a child is nursed at home in the terminal stages.

An evaluation of Potts' aortopulmonary shunt for palliation of cyanotic heart disease

The results of 28 Potts' aortopulmonary shunts created for the relief of cyanotic heart disease are reviewed in this study. The shunt gave excellent symptomatic relief, but the incidence of immediate and late complications is high. Regular follow-up of patients is mandatory to detect evidence of increasing pulmonary vascular disease and to under take corrective surgery whenever feasible before its occurrence. Although Potts' anastomosis has been largely replaced by alternative shunt procedures, there may still be a place for its application in selected situations. Only a few problems were encountered at the time of closure of the shunt in 11 patients during corrective surgery using a transpulmonary technique and hypothermia with circulatory arrest.

Radioligand receptor assay for 25-hydroxyvitamin D2/D3 and 1 alpha, 25-dihydroxyvitamin D2/D3

A competitive protein binding assay for measurement of the plasma concentration of 1 alpha, 25-dihydroxyvitamin D3 [1alpha, 25-(OH)2D3] has been extended to include the immediate precursor of this hormone, 25-hydroxyvitamin D3 (25-OHD3). In addition, the assay system is capable of measuring the two metabolic products of ergocalciferol, namely. 25-hydroxyvitamin D2 (25-OHD2) and 1alpha, 25-dihydroxyvitamin D2 [1alpha, 25-(OH)2D2]. The target tissue assay system consists of a high affinity cytosol receptor protein that binds the vitamin D metabolites and a limited number of acceptor sites on the nuclear chromatin. By utilizing a series of chromatographic purification steps, a single plasma sample can be assayed for any of the four vitamin D metabolites either individually or combined. Therefore, the assay procedure allows for both the quantitative and qualitative assessment of the total active vitamin D level in a given plasma sample. To show that the binding assay was capable of measuring 1alpha, 25-(OH)2D2 as well as 1alpha, 25 (OH)2D3, two groups of rats were raised. One group, supplemented with vitamin D3, produced assayable material that represented 1alpha, 25-(OH)2D3. The other group, fed only vitamin D2 in the diet, yielded plasma containing only 1alpha, 25-(OH)2D2 as the hormonal form of the vitamin. The circulating concentrations of the two active sterols were nearly identical (15 ng/100 ml) in both groups, indicating that the competitive binding assay can be used to measure both hormonal forms in plasma. In a separate experiment, 1alpha, 25-(OH)2D2 was generated in an in vitro kidney homogenate system using 25-OHD2 as substrate. Comparison of this sterol with 1alpha, 25-(OH)2D3 in the assay system showed very similar binding curves; the D2 form was slightly less efficient (77%). Comparison of the respective 25-hydroxy forms (25-OHD2 vs. 25-OHD3) at concentrations 500-fold that of 1alpha, 25-(OH)2D3, again suggested that the binding of the D2 metabolite was slightly less efficient (71%). Finally, the assay was employed to measure the total active vitamin D metabolite pools in the plasma of normal subjects and patients with varying degrees of hypervitaminosis D. The normal plasma levels of 25-OHD and 1alpha, 25-(OH)2D measured in Tucson adults were 25-40 ng/ml and 2.1-4.5 ng/100 ml, respectively. Both sterols were predominately (greater than 90%) in the form of vitamin D3 metabolites in this environment. Typical cases of hypervitaminosis D exhibited approximately a 15-fold increase in the plasma 25-OHD concentration, and a dramatic changeover to virtually all metabolites existing in the form of D2 vitamins. In contrast, the circulating concentration of 1alpha, 25-(OH)2D was not substantially enhanced in vitamin D-intoxicated patients. We therefore conclude that hypervitaminosis D is not a result of abnormal plasma levels of 1alpha, 25-(OH)2D but may be cuased by an excessive circulating concentration of 25-OHD.