The kinetics of in vitro reoxidation and reduction of the inter heavy--light chain disulfide bond in an unusual murine immunoglobulin G myeloma protein lacking inter-heavy chain disulfide bonds

After 5 years of subcutaneous transfer in Balb/C mice, our MOPC 173 myeloma tumour line (originally an IgG2a,κ H2L2-producer) exclusively synthesized an unusual IgG2b,κ protein lacking inter-heavy (H) chain disulfide bonds. This protein was designated MOPC 173B. On sodium dodecyl sulfate – polyacrylamide gel electrophoresis, it migrated with an apparent molecular weight of 77 000; following complete reduction and alkylation, the mobilities of its constituent H and light (L) chains were found to differ slightly from those of MOPC 173 H2L2. MOPC 173B was serologically identical to another typical IgG2b,κ myeloma protein, MOPC 195, and peptide mapping studies showed that it possessed only the inter H–L disulfide bond characteristic of typical IgG2b,κ proteins. In a nondissociating solvent, the sedimentation coefficient of the protein was 6.3S even at concentrations as low as 0.2 mg/ml, indicating that noncovalent interactions existed between two half-molecule subunits. Since this unusual IgG myeloma protein contained only a single category of interchain disulfide bridge, the inter H–L bond, it was an ideal model system for characterization of the kinetics of formation and reduction of interchain disulfide bonds. The kinetics of the glutathione-catalyzed reoxidation of the inter H–L disulfide bridge in MOPC 173B followed an apparent second-order rate equation. In contrast, reduction of its inter H–L bridge under anaerobic conditions with dithioerythritol in excess, was strictly a first-order process and not a simple reversal of the reoxidation. These studies provide the basis for the more complex mathematical models that describe the reoxidation and reduction of typical immunoglobulin molecules.

Glucose effect on respiration: possible mechanism for capacitation in guinea pig spermatozoa

Guinea pig sperm respiration was determined in minimal capacitation medium (MCM) with different energy sources. The ZO2 observed for spermatozoa suspended in media containing pyruvate and lactate was 35.7 +/- 5.9, pyruvate alone, 27.9 +/- 3.8 and D-glucose alone 3.4 +/- 1.1. When D-glucose was added to spermatozoa rapidly respiring in media containing pyruvate as the only exogenous energy source, an immediate suppression in respiration was observed. Further reduction was caused by continued addition of D-glucose. Fructose and mannose also produced a suppression in respiratory rate. However, lactose, fucose, sucrose, L-glucose, and galactose did not alter the respiratory rate. The suppression of respiration by metabolizable sugars is paralleled by a suppression of acrosome reaction in guinea pig spermatozoa. The possibility that suppression of respiration is the mechanism for retardation of capacitation and the subsequent acrosome reaction by D-glucose and other metabolizable sugars is suggested.

Effects of Aureomycin on bile acids in rats

Primary BA's secreted into the duodenum are extensively altered by bacteria in the large intestine. Such changes are not found in GF animals. As a result, GF rats reabsorb BA much more efficiently than do CV controls, and BA and cholesterol pools are higher in GF than CV rats. This indicates the importance of the intestinal flora in the homeostasis of cholesterol metabolism. Antibiotics can affect the extent to which BA's are altered by bacteria. In some cases, the antibiotic treatment also affects cholesterol levels in serum or liver. We have found that treatment of CV rats for only 5 days with low levels of Aureomycin (0.85 micron) led to a predominance of omega-MC over HDC in the feces at 10 days after withdrawal of the antibiotic. This reduced the usual HDC/omega-MC ratio from approximately 2.0 to 0.9 or less. These rats were also found to have liver cholesterol levels modestly elevated over those of controls. In other experiments the decrease in hyodeoxycholate/omega-muricholate ratio was found to persist for at least 90 days after discontinuation of treatment. Later experiments carried out with Aureomycin and with penicillin revealed the possible existence of a resistance factor to Aureomycin. A significant lowering of the hyodeoxycholate/omega-muricholate ratio was now found only with antibiotic concentrations 10 to 100 times greater than those used previously. Possible implications of the persistence of antibiotic effects, as measured by changes in fecal BA's, include effects on vitamin metabolism, colon cancer, and cholesterol metabolism.

Effect of autoclaving of a lactose-containing diet on cholesterol and bile acid metabolism of conventional and germ-free rats

Feeding of lactose in amounts comparable to the adult human intake in developed countries (6% of diet, and in later studies 10%) had no major effect on cholesterol and bile acid metabolism of germ-free and conventional rats. However, when lactose-containing casein-starch diets were sterilized by autoclaving, changes in intestinal and/or fecal bile acids were found. Both germ-free and conventional rats demonstrated some increase in intestinal beta-muricholic acid concentrations ascribable to the mere presence of lactose in the diet. Autoclaving of the diet produced additional changes, especially in the fecal bile acid pattern of conventional rats. Here the ratio between the beta-muricholic-derived secondary bile acids hyodeoxycholic and omega-muricholic acids changed from the usual 5:3 to approximately 1:10, with omega-muricholic acid becoming the major fecal bile acid. These changes point to a notable effect of lactose-derived products, formed during steam-sterilization, on the microbial modification of intestinal bile acids in the lower gut. Similar changes have been observed after oral administration of aureomycin and other, unrelated antibiotics that inhibit growth of gram positive organisms.

Effect of dietary lactose at levels comparable to human consumption on cholesterol and bile acid metabolism of conventional and germfree rats

In recent years, the use of milk products and the concomitant intake of lactose have been tentatively linked to the etiology of cardiovascular disease. An effect of lactose on the microbial modification of acid and neutral sterols has been suggested. In the present study lactose intake, ranging up to 30% of total diet increased beta-muricholic (beta-MC) but not cholic acid concentrations in conventional (CV) rat small intestine to the extent that at the 20% and 30% intake level, the intestinal cholic: beta-MC ratio approached that in germ-free (GF) rats. Total intestinal bile acid (BA) content increased by approximately 1/3, but remained at less than half the value found in GF rats. At lactose intake levels within a range corresponding to the consumption of dairy products often recommended for adult man (5% to 10%) only moderate changes in intestinal, and little change in fecal BA were found during and after the 3 months experimental period. Intestinal beta-MC was increased in the presence and in the absence of an intestinal microflora. Experiments with GF rats fed 10% lactose or 10% maltose indicated that this increase is evoked similarly by both carbohydrates. The slight increase in serum cholesterol levels seen with disaccharide feeding, which became evident only in the GF rats, was again not specific for lactose. No influence was found of lactose feeding on liver cholesterol values. Comparison of CV rats fed nonsterile and radiation-sterilized lactose-containing diets suggested that this mode of sterilization has only a minor influence on the resulting data. When GF experiments are to be incorporated, sterilazation of diet by irradiation with 3.5 to 4.0 X 10(6) Rad is preferable to autoclaving. The present data indicate that no major effect specifically related to a normal dietary intake of lactose on cholesterol and BA metabolism of the adult rat could be demonstrated for the duration of these experiments.

Rauwolfia derivatives and breast cancer

During the course of a collaborative study initiated in investigate the relationship of breast cancer and the use of hormones, it was possible to study the possible relationship of rauwolfia derivatives, mainly reserpine, to breast cancer. Interviews were administered to breast cancer patients admitted to five hospitals in the Baltimore metropolitan area. The study of reserpine use was conducted for a period of approximately one and a half years and information on reserpine use was obtained on 164 breast cancer cases. Each case was matched with a control with respect to age, color, hospital of admission, and admission date. An additional set of controls was drawn from women residing in the same neighborhood as the cases. Neither reserpine, methyldopa, nor thiazides were found to be significantly associated with breast cancer. The exclusion from the analysis of hospital controls with a diagnosis of hypertensive disease and their matched cases did not significantly alter the results. Those cases who used reserpine, used more for longer periods of time than did the controls, however this was judged inconclusive due to a considerable amount of missing data. After comparison of these results with previously reported studies, it did not appear that reserpine was strongly associated with breast cancer. However, because of methodological problems and differences between the studies, a possible small overall relationship could not be definitely excluded.

Analysis of bile acids in conventional and germfree rats

The well-known bile acid analysis technique used by us and others (Grundy, Ahrens, and Miettinen. 1965. J. Lipid Res. 6:397-410) does not allow for the detection of hyodeoxycholic acid, a product of quantitative importance in rodent feces. Using updated methodology, it was established that hyodeoxycholic acid and omega-muricholic acid, both apparent conversion products of beta-muricholic acid, occur in apppreciable amounts in intestinal contents and feces of conventional Wistar type Lobund rats. In conventional rats, these bile acids comprise about 50% of fecal bile acids; they are not found in intestinal contents or feces of germfree rats. Others have demonstrated that hyodeoxycholic acid if formed by combined action of gut flora and liver. A new method for the separation of conjugated and free bile acids in biological samples was developed. Results with this method confirmed the total conjugation of bile acids in the germfree rat, and the almost total deconjugation that takes place in the cecum of the conventional rat.

Primary structure of a deleted human lambda type immunoglobulin light chain containing carbohydrate: protein Sm lambda

An internal molecular deletion occurring in a human lambda type immunoglobulin light (L)-chain (Sm lambda) has been defined by sequence analysis. The Sm protein was isolated from the urine of a patient with a plasma cell dyscrasia involving the synthesis of an IgG molecule with both deleted gamma and lambda subunits. The Sm lambda polypeptide chain has an approximate molecular weight of 15,000 and contains 135 amino-acid residues. The constant (C) region is fully intact, comprising 105 residues, whereas the variable region (V) has only 30 residues. The V-region segment represents residues 1 through 30 of normal lambda chains and possesses considerable homology (87%) to lambda chains of subgroup II. Since lambdaII proteins normally contain 216 amino-acid residues, the defect represents an intramolecular deletion of 81 residues, which is entirely confined to the carboxyterminal three-quarters segment of the V-region, with a resumption of normal synthesis at a glutaminyl residue at position 110, the initiation point of the C-region. Carbohydrate is attached to an Asx residue at position 25, in the first hypervariable region, associated with the sequence triplet Asx-Ser-Ser, which is postulated to be a common recognition site for glycosylation of immunoglobulins. The carbohydrate moiety is a complex oligosaccharide with a branched chain structure containing sialic acid, fucose, mannose, N-acetylglucosamine, and galactose. These structural studies and other findings suggest that restricted areas in the DNA of immunoglobulin genes, such as the hinge regions of heavy (H) and light (L) chains and the hypervariable regions, are particularly susceptible to breakage and reunion. We postulate that the genetic defect of protein Sm could have originated from a somatic mutational event in the plasmacyte precursor during or after the integration of the V and C genes. These studies provide additional support for the hypothesis and two distinct structural genes encode a single immunoglobulin polypeptide chain.

Thyrotropin increases prostaglandin levels in isolated thyroid cells

We have shown that two unrelated prostaglandin antagonists block both thyrotropin (TSH) and prostaglandins E (PGE(1), PGE(2)) stimulation of thyroidal adenyl cyclase activation and cyclic 3',5'-adenosine monophosphate (cAMP) formation, suggesting that prostaglandins play an important role in regulating thyroid function. To further explore this postulate, we measured prostaglandin content by radioimmunoassay in homogeneous bovine thyroid cell preparations in the presence and absence of TSH. Antibodies to albumin-conjugated PGE(1) and PGF(2alpha) showed specificity for prostaglandins E and F, respectively, but reacted, albeit far less effectively, with heterologous prostaglandins. A double antibody system was used to separate free from antibody-bound PGE(1)-(3)H and PGF(2alpha)-(3)H. Thyroid cells were extracted with ethanol/ethyl acetate and the various prostaglandins separated on silicic acid columns. Recoveries of added PGE(1)-(3)H and PGF(2alpha)-(3)H through the extraction and separation procedures ranged from 50-80%. The sensitivity of the method was 10-50 pg. Basal thyroid cell content of PGE(1) and PGF(2alpha) "equivalents" varied between cell preparations (range = 2-6 ng/0.2 ml cell suspension) but, in each instance, remained constant during 5-30-min incubations at 37 degrees C. TSH, 10-100 mU/ml, increased the levels of cell PGE(1) and PGF(2alpha) "equivalents" 30-80% above basal during 5-15-min incubations. The stimulatory effect was specific for TSH, no increase in PGE(1) or PGF(2alpha) "equivalent" levels being seen with luteinizing hormone (LH), human growth hormone (HGH), adrenocorticotropic hormone (ACTH), or glucagon. These data support the thesis that prostaglandins may mediate TSH effects on thyroid.

Thermal analysis of polyanion metachromasy: temperature effects on stained cells, tissues and models

Metachromasy of toluidine blue-stained materials was examined at 5-95°C visually and 30-70°C microspectrophotometrically. Cells and tissues provided sites of acid mucopolysaccharides and nucleic acids, which were also prepared as films and droplets. As in similar studies of aqueous solutions, metachromatic ratios were inverse, linear, reversible functions of temperature, with the possible exception of deoxyribonucleic acid. An aqueous mounting medium (gelatin) supported maximum excursions of metachromasy during heating and cooling, although reversible loss of metachromasy occurs to lesser degrees in conventional media. Removal or denaturation of cartilage matrix protein merely increased over-all metachromasy; slopes of thermal plots were unchanged. All evidence suggests that metachromasy is not a fundamentally different phenomenon in solutions and solid systems. Temperature studies emphasize the role of structured water in metachromasy, interaction of water and other solvents and particularly solvent dielectric constant in relation to dye-dye interaction. The limited literature on temperature and biologic staining is reviewed.

Thermal analysis of polyanion metachromasy: effect of temperature on metachromatic solutions of nucleic acids and acid mucopolysaccharides

Spectra of toluidine blue with acid mucopolysaccharides and nucleic acids were recorded over the temperature range 10-70°C. Metachromatic ratios were inverse, linear functions of temperature. Intercepts and slopes of the thermal plots distinguished acid mucopolysaccharides from nucleic acids. Acid mucopolysaccharide reactions were thermally reversible. Nucleic acid reactions were not strictly reversible; such behavior was not attributable to thermal denaturation. An explanation for the unusual γ-peak of ribonucleic acid-toluidine blue metachromasy is offered in terms of terminal phosphate groups of ribonucleic acid. Solution data in which the polyanion-dye ratio was approximately 1, representing typical "metachromasy," were subjected to thermodynamic analysis. These data did not fit a common equation deriving equilibrium constants spectrophotometrically by variation of reactant concentrations. This failure supported the view of metachromasy as a phenomenon primarily involving dye-dye interaction. Another equation based only on temperature variation yielded a value of –4 kcal/mole for the chondroitin sulfate-toluidine blue complex, in good agreement with similar published values obtained both in solutions and stained materials.