Subunit characterization of lens intermediate filaments

The intermediate filaments from the bovine ocular lens can be fractionated into three 54000 dalton polypeptides (alpha, beta and gamma) which are present in equimolar quantities and differ from one another with respect to isoelectric point, two-dimensional peptide map pattern and total amino acid composition. The polypeptides, for which the name lentin is proposed, were purified from the 8 M urea extract of the water-insoluble residue of the cortical fiber cells by ion-exchange chromatography on DE- and CM-cellulose. The regeneration of native-appearance filaments from each purified fraction, or combinations thereof, definitively established the three polypeptides as the subunit species. Additionally, small diameter 'protofilaments' were regenerated when one or two fractions were utilized, but not when all three fractions were combined. This, together with the fact that the stoichiometric yield of the three species was invariably equimolar, suggests that alpha, beta, and gamma may be distinct entities not related by artifactual interconversion.

Mevinolin: a highly potent competitive inhibitor of hydroxymethylglutaryl-coenzyme A reductase and a cholesterol-lowering agent

Mevinolin, a fungal metabolite, was isolated from cultures of Aspergillus terreus. The structure and absolute configuration of mevinolini and its open acid form, mevinolinic acid, were determined by a combination of physical techniques. Mevinolin was shown to be 1,2,6,7,8,8a-hexahydro-beta, delta-dihydroxy-2,6-dimethyl-8-(2-methyl-1-oxobutoxy)-1-naphthalene-hepatanoic acid delta-lactone. Mevinolin in the hydroxy-acid form, mevinolinic acid, is a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase [mevalonate: NADP+ oxidoreductase (CoA-acylating), EC 1.1.1.34]; its Ki of 0.6 nM can be compared to 1.4 nM for the hydroxy acid form of the previously described related inhibitor, ML-236B (compactin, 6-demethylmevinolin). In the rat, orally administered sodium mevinolinate was an active inhibitor of cholesterol synthesis in an acute assay (50% inhibitory dose = 46 microgram/kg). Furthermore, it was shown that mevinolin was an orally active cholesterol-lowering agent in the dog. Treatment of dogs for 3 weeks with mevinolin at 8 mg/kg per day resulted in a 29.3 +/- 2.5% lowering of plasma cholesterol.

Studies on the relations of selenium and Keshan disease

Keshan disease is an endemic cardiomyopathy of unknown cause in The People's Republic of China that occurs most frequently in children under 15 years of age and women of child-bearing age. Studies of children 1-9 years old in Mianing County of Sichuan Province have indicated that Keshan disease is a selenium responsive condition. Incidence rates of 9.5-13.5/1000 in 1974-1975 were reduced to 1-2/1000 in children treated with a tablet weekly of 0.5-1 mg sodium selenite. During 1974-1977, only 21 cases of the disease occurred in 36,603 treated children, compared with 106 cases in 9430 untreated children, of whom 53 died and 5 still have insufficient heart function. Occurrence of the disease was invariably associated with a lower selenium content of cereals, and of hair (less than 0.12 ppm Se) in residents from affected, compared with non-affected, areas. The dose relationship between selenium and regional characteristics of Keshan disease suggests that it is probably a biogeochemical disease; other etiological factors have also been considered.

Significance of "high" acid phosphatase activity in the serum of normal children

Serum acid phosphatase activity in normal children (newborn to 18 years) is several fold that in normal adults. Activity is age-related but not sex-related. The isoenzyme pattern in children is similar to that in adults and contains no prostatic fraction. Quantitatively, most of the enzyme activity in the serum of children is tartrate-resistant and correlates well with heat-labile fractions of alkaline phosphatase activity in serum, suggesting that the source of the higher acid phosphatase activity in children is bone. Significant tartrate-resistant acid phosphatase activity was demonstrated in the giant cells in three patients with giant-cell tumors, but not in the "osteoblasts" in six patients with osteogenic sarcomas and many other normal or abnormal tissues. This work suggests that the higher enzyme activity in the serum of children represents a normal physiological phenomenon resulting from their greater osteoclastic activity.

Significance of "high" acid phosphatase activity in the serum of normal children

Serum acid phosphatase activity in normal children (newborn to 18 years) is several fold that in normal adults. Activity is age-related but not sex-related. The isoenzyme pattern in children is similar to that in adults and contains no prostatic fraction. Quantitatively, most of the enzyme activity in the serum of children is tartrate-resistant and correlates well with heat-labile fractions of alkaline phosphatase activity in serum, suggesting that the source of the higher acid phosphatase activity in children is bone. Significant tartrate-resistant acid phosphatase activity was demonstrated in the giant cells in three patients with giant-cell tumors, but not in the "osteoblasts" in six patients with osteogenic sarcomas and many other normal or abnormal tissues. This work suggests that the higher enzyme activity in the serum of children represents a normal physiological phenomenon resulting from their greater osteoclastic activity.

Study of a Caucasian Family with von Willebrand’s Disease in Association with Vascular Telangiectasia and Hemoglobinopathy

This family carries multihematological inherited disorders; namely, von Wille-brand’s, vascular telangiectasia and hemoglobinopathy. Family members were studied by quantifying the following: Factor VIII pro-coagulant activity, Factor VIII related antigen, Factor VIII inhibitors, platelet adhesion, platelet aggregation (with ristocetin, collagen and ADP), bleeding time, platelet count, partial thromboplastin time, prothrombin time, hemoglobin electrophoresis, hemoglobin finger-printing, sickling preparation and the presence of telangiectasia.

The affected members of this family with von Willebrand’s express their disease in a variable tendency to bleeding from almost clinically asymptomatic cases to cases with severe bleeding tendency.One member of this family had to have a hysterectomy at the age of 20 to control the abnormal uterine bleeding after conservative treatment failed. All affected members with von Willebrand’s disease had a normal platelet count, prolonged bleeding time, decreased Factor VIII pro-coagulant activity and related antigen, negative aggregation using the ristocetin co-factor for von Willebrand’s, defective platelet adhesiveness to glass beads, and normal platelet aggregation to collagen and ADP. Some members have vascular telangiectasia in the mucous membranes. An incidental finding was the presence of an abnormal hemoglobin S in some family members.

Supported in part by the Cumberland Chapter of the National Hemophilia Foundation.

Translation of rat liver fatty acid synthetase mRNA in a cell-free system derived from wheat germ

Total liver polysomes were isolated from rats that had fasted for 48 hr and that then had been re-fed a high-carbohydrate, fat-free diet for 20-24 hr. Indirect immunoprecipitation of the polysomes with purified antibody to rat liver fatty acid synthetase and deproteination on sodium dodecyl sulfate-containing sucrose gradients gave an RNA fraction which, when translated in a cell-free system derived from wheat germ, yielded a major polypeptide of apparent molecular weight 225,000 when the translation products were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The polypeptide was specifically precipitated with antibody against rat liver fatty acid synthetase and competed with unlabeled fatty acid synthetase for binding to the antibody. It was somewhat smaller than native fatty acid synthetase subunits (molecular weight 240,000). The peptide accounted for approximately 65% of the radioactive, antibody-precipitable product, the remainder being peptides in the molecular weight range 100,000-150,000. Synthesis of the polypeptide was optimized with respect to K(+), Mg(2+), and spermine concentrations. The quantity of fatty acid synthetase mRNA obtained by the above procedure and measured by translation was a function of the nutritional state of the animal. The relative activity in fasting rats compared to rats that were re-fed for 12 hr was 1:12. The data suggest that rat liver fatty acid synthetase is synthesized as intact subunits from a large mRNA molecule or molecules.

Effect of the anorectic drug, phenylpropanolamine, on blood glucose in rats

Phenylpropanolamine hydrochloride (PPA) is a widely used decongestant and anorectic drug. The present study investigated the hypoglycemic effects of intraperitoneal PPA on rats to test the possibility that it might derive some of its anorectic properties through effects on glucostatic mechanisms. PPA tended to lower blood glucose levels in normal rats; the glycemia reducing effect was larger and statistically significant in rats made hyperglycemic by prior treatment with streptozocin to cause diabetes. This is the first evidence that PPA migh possibly reduce feeding by increasing blood sugar utilization.

Apolipoprotein A-II content of human plasma high density lipoproteins measured by radioimmunoassay

A double antibody radioimmunoassay for human ApoA-II is reported. ApoA-II isolated from human plasma high density lipoprotein (HDL) by column chromatography migrated as a single band on polyacrylamide disc gel electrophoresis, had the appropriate amino acid composition, and provoked the production of monospecific antisera. (125)I-ApoA-II (iodinated by lactoperoxidase, purified by Sephadex G-75 chromatography) migrated with "cold" ApoA-II as a single band on disc gel electrophoresis in SDS. Its specific radioactivity was 5-12 mCi/ micro g. In assays, (0.05 M barbital buffer, 0.01% Triton X-100, pH 8.6) over 90% of (125)I-ApoA-II was bound by excess first antibody and over 95% was displaced by excess "cold" ApoA-II. Low density lipoprotein, very low density lipoprotein, ApoA-I, ApoC-II, and ApoC-III displaced no counts. Intraassay and interassay coefficients of variation for lipoprotein or plasma samples were 7 +/- 4 and 11 +/- 6%, respectively. As little as 1.0 ng of ApoA-II was detectable with a precision of 10%. ApoA-II made up 20-25% of the proteins of HDL (d 1.083-1.19), HDL(2) (d 1.083-1.124), and HDL(3) (d 1.124-1.19) on column chromatography. The ApoA-II contents of these HDL fractions were also 20-25% by radioimmunoassay. Similar results were obtained whether assays were carried out on intact or delipidated HDL samples. Thus, in contrast with ApoA-I (only 10% of which is detectable), all of the ApoA-II contents of intact HDL are detected with accuracy by this assay. Plasma levels of ApoA-II in young normolipemic subjects were approximately 40 mg/dl (n = 29). In these subjects, over 98% of ApoA-II was found in the d 1.063-1.21 density fractions.

Effect of dietary linoleate on synthesis and degradation of fatty acid synthetase from rat liver

The induction of fatty acid synthetase activity in rat liver is markedly reduced by feeding a diet containing a source of linoleate. Within 48 h after changing from a fat-free, high carbohydrate diet to one containing 15% by weight of safflower oil, the specific activity of rat liver fatty acid synthetase is approximately 2-fold lower than that from rats fed a fat-free diet througout. In contrast, feeding a diet containing 15% hydrogenated coconut oil, a source of saturated fatty acids, or 5% methyl oleate for the same length of time has little effect on the activity of the enzyme. The rate of synthesis of the enzyme is reduced by safflower oil feeding from the fat-free (control) level and after 48 h is approximately one-half that of the control. The rate of degradation of fatty acid synthetase is markedly increased in the safflower oil-fed animals over the control; the half-lives are 1.8 days and 3.8 days, respectively. It is suggested that polyunsaturated fatty acids, or a product derived from them, may directly or indirectly regulate the transcription or translation (or both) of fatty acid synthetase messenger RNA.

Dissociation and reassociation of immobilized porphobilinogen synthase: use of immobilized subunits for enzyme isolation

The dissociation and association of an immobilized preparation of the octameric enzyme porphobilinogen synthase [5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing), EC 4.2.1.24] is described. On treatment of the immobilized preparation with 4 M urea, four subunits per octamer are removed which can be reassociated into a soluble octameric enzyme. The tetrameric bound residual protein can also be reassembled into an octameric structure, with the same initial enzyme activity, by exposing the residual bound protein to a soluble pure enzyme preparation or to a crude liver extract in the presence of urea. The dissociation of the reconstituted bound enzyme releases subunits that again can be reassembled into a soluble octameric pure protein even when the crude liver preparation is used as the donor of the subunits. Thus, a pure enzyme can be isolated in a reassociation-dissociation cycle. The use of immobilized preparations of oligomeric proteins is considered for intra- and interspecies hybridization studies and for the ready preparation of purified enzyme preparations from different species and is suggested as a model for study of the formation of an oligomeric enzyme in the presence of other polypeptides.

Meningitis caused by Rhodotorula

A case of rhodotorula meningitis in a 21 year old male compromised with acute lymphoblastic leukemia is reported. The yeast was identified as Rhodotorula rubra (Demme) Lodder.

Structure of high density lipoprotein. The immunologic reactivities of the COOH- and NH2-terminal regions of apolipoprotein A-I

Only 5 to 10% of the apolipoprotein A-I (ApoA-I) of intact high density lipoprotein (HDL) is detectable by radioimmunoassay. In addition, when isolated ApoA-I is recombined with lipids in vitro, its immunologic reactivity is decreased by 30 to 95%. Thus, ApoA-I is less reactive immunologically in the presence of lipids. Our aim was to ascertain whether the COOH- or NH2-terminal regions of ApoA-I were equally reactive in intact HDL2. CNBr fragments of ApoA-I were produced by the method of Baker et al. (Baker, H.N., Jackson, R.L., and Gotto, A.M. (1973) Biochemistry 12, 3866-3871) and iodinated with lactoperoxidase. Double-antibody radioimmunoassays were set up using anti ApoA-I antisera and 125I-CNBr I (COOH-terminal region) or 125I-CNBr II (NH2-terminal). Both labels were bound by the antisera. Affinity columns were prepared by binding CNBr I or CNBr II to Sepharose 4B. Antibodies specific against CNBr I or CNBr II were isolated by means of these columns, suggesting that ApoA-I had at least two antigenic sites. In other assays using labeled fragments and anti ApoA-I antisera, 125I-CNBr I was displaced by CNBr I, ApoA-I , and HDL2 but not CNBr II. Conversely, 125I-CNBr II was displaced by CNBr II, ApoA-I, and HDL2 but not by CNBr I. Thus the assays were region-specific. The reactivities of isolated ApoA-I and the ApoA-I in intact HDL2-ApoA-I) were compared in these assays. On a molar basis, HDL2-ApoA-I was consistently more reactive (2- to 5-fold) in the 125I-CNBr I than in the 125I-CNBr II assays. The findings suggest (a) that the two terminal regions of ApoA-I are immunologically distinct, (b) that the two regions can be assayed independently of each other in intact HDL2, and (c) that the COOH-terminal region is more reactive immunologically than is the NH2-terminal. The results are compatible with a more "exposed" position for the COOH-terminal region on the surface of HDL2.