Further experience with discriminant functions in differential diagnosis of hypercalcaemia

Further experience has been obtained in the use of discriminant functions in the differential diagnosis of hypercalcaemia from the study of 140 new patients. The discriminant functions described in an earlier paper were derived from the results for plasma inorganic phosphate, alkaline phosphatase, chloride, bicarbonate and urea obtained from hypercalcaemic patients on admission to hospital. They indicated the correct diagnosis in ninety-two of 103 new hypercalcaemic patients (89·3%) admitted to University College Hospital and in thirty-one of thirty-seven hypercalcaemic patients at two other hospitals.

Revised discriminant functions have been calculated including the erythrocyte sedimentation rate as a sixth variable. These revised functions have led to some improvement in diagnostic accuracy. The correct diagnosis was indicated in ninety-three of ninety-eight patients (94·9%) at University College Hospital and in thirty-three of the thirty-seven patients at the two other hospitals.

Complement activation in semi-solid medium: Insolubilization of properdin and the third component of complement (C3) in agar gels

Although the role of properdin in the alternative pathway of complement activation remains unclear, evidence has recently been obtained for the formation of complexes between properdin and other components, including C3. In this study such complexes have apparently been directly visualized. When normal human serum and properdin were allowed to diffuse toward each other in agar gel for 16 hr, a line of precipitation could be seen when stained with Coomassie brilliant blue. The reaction occured at pH 8.6 in 0.05 M Veronal buffer at room temperature but not under physiologic conditions of pH or tonicity. Like the alternative pathway, the reaction was Me++ dependent, occurred with C2- or C5-deficient or hypogammaglobulinemic serum, and did not occur with aged, 52 degrees C-inactivated, C3b inactivator-deficient, or C3-deficient serum. 125I-labeled C3 and properdin but not Factor B were incorporated in the precipitate. Eleven sera containing the C3 nephritic factor failed to produce a precipitate with properdin, but a line of precipitation occurred between seven of these sera and normal serum. This line showed identity with the line occurring between properdin and normal serum. The phenomenon appears to result from formation of insoluble complexes between proteins of the alternative pathway and agar.

Genetic polymorphism of properdin factor B in the rhesus: evidence for single subunit structure in primates

Properdin Factor B shows genetic polymorphism in the human and the polymorphic patterns in agarose gel electrophoresis suggest a tetrameric structure. Factor B polymorphism in the rhesus monkey has been demonstrated in the present study to be genetically determined and under the control of a single autosomal locus, rhesus Bf. Six codominant alleles, Bf-F, Bf-G-1, Bf-G-2, Bf-S-1, Bf-S-2 have been recognized and the first five have been shown to have gene frequencies of 0.307,0.160,0.016,0.377, and 0.139. The electrophoretic appearance of the polymorphic patterns does not suggest a tetrameric structure in the rhesus. Structural studies show purified human factor B to exist as a single subunit of molecular weight 94,000 daltons so that a tetrameric structure appears highly unlikely.

Iatrogenic osteomalacia and myopathy due to phosphate depletion

In a patient receiving regular dialysis prolonged hypophosphataemia due to aluminium hydroxide therapy resulted in osteomalacia and severe proximal myopathy. Both osteomalacia and myopathy responded to correction of hypophosphataemia without vitamin D therapy.

Genetic polymorphism in human glycine-rich beta-glycoprotein

Extensive polymorphism of glycine-rich beta-glycoprotein (GBG) was found in human sera. In all instances, GBG consisted of at least five components on electrophoresis. Patterns were such that they provided evidence for four alleles (at a locus designated Gb) which were expressed as autosomal codominant traits. Gb(S) and Gb(F) were found in all populations but with different frequencies, Gb(F1) was found in Negroes, and Gb(S1) was found in Caucasians. From electrophoretic studies of GBG, evidence was obtained that suggested that the GBG molecule was a tetramer consisting of A and B subunits in a proportion of about 1.6:1. The genetically controlled differences in GBG embodied in the Gb system indicated the presence of a third moiety of the molecule (C), possibly a polypeptide subunit. Electrophoretic studies of fragments from defined types of GBG suggested that GBG cleavage induced by complement or properdin activation in serum occurred through this C moiety, since two variants were detectable in one fragment and two were found in the other fragment. On comparison of fetal-maternal Gb types, approximately one-half the pairs showed differences. This indicated that GBG did not cross the placental barrier.

Glycine-Rich γ-Glycoprotein (GBG): Evidence for Relation to the Complement System and for Genetic Polymorphism in Man

Glycine-rich β-glycoprotein (GBG) is a 6.3S protein which occurs at a concentration of 9 to 47 mg/100 ml of normal serum. On storage of serum, particularly at 37°C, this protein fragments very slowly into glycine-rich γ-glycoprotein (GGG) which is 4.3S and glycine-rich α-glycoprotein (GAG) of similar size. Incubation of serum for 1 hr at 37°C with antigen-antibody precipitates or zymosan but not hydrazine results in virtually complete conversion of GBG but little appearance of GAG in the fluid phase. EDTA blocks GBG conversion by antigen-antibody or zymosan.

GBG is highly polymorphic when examined in various human sera and consists of at least five bands in all samples tested. Population and family studies indicate that this polymorphism is determined by two common genes, GbF and GbS, with frequencies of 0.50 and 0.44, 0.28 and 0.71, and 0.13 and 0.87 in Negroes, Caucasians and Orientals respectively, and two rare genes, GbF1 with a frequency of 0.06 in Negroes, and GbS1 with a frequency of 0.01 in Caucasians.

Effect of ethanol on magnesium excretion

The effect of ethanol on magnesium excretion was studied in three normal subjects. It was found that the ingestion of 2 ml ethanol/kg body weight produced a marked immediate increase in urinary magnesium excretion, but there was no significant effect on overall magnesium balance when this amount was taken daily for eight days.