Existence in fetal and adult rat of several forms of material reacting with anti-insulin antibody (IRI).

The double antibody procedure detects 3 peaks in the elution fractions of adult or fetal rat sera, after passage on Sephadex G50 or G100 columns. Peak A (apparent MW 6000) contains insulin monomer; peak B (apparent MW 10-12000) is tentatively attributed to proinsulin (or proinsulin like substances); peak C (apparent MW 50-100000) is similar to the so called "big big" insulin. During intravenously induced hyperglycemia, the 3 peaks show parallel increases, but, after the disappearance of peaks A and B in streptozotocin treated rats, peak C remains unaltered. Pancreatic extracts and secreta present a very minor and inconstant peak C, the bulk of their immunoreactive material belonging to peaks A and B. A companion paper further discusses the nature of peaks B and C materials.     

Three major forms of adenylate kinase from adult and fetal rat tissues.

The major enzymatic forms of adenylate kinase have been purified to homogeneity from fetal liver and adult brain of the rat. The two enzymes differ with respect to isoelectric points, Km (ATP), Km (AMP), and Ka (citrate). Antibody to adult liver adenylate kinase does not inhibit either enzyme, while entibody to adult skeletal muscle enzyme inhibits the brain enzyme but not the fetal liver enzyme. It is therefore probable that there are three major forms of adenylate kinases in fetal and adult rat tissues.     

Monoclonal antibodies reacting with multiple epitopes on the human insulin receptor.

Monoclonal antibodies for the human insulin receptor were produced following immunization of mice with IM-9 lymphocytes and/or purified placental receptor. Four separate fusions yielded 28 antibodies, all of which reacted with receptor from human placenta, liver and IM-9 cells. Some antibodies cross-reacted to varying degrees with receptor from rabbit, cow, pig and sheep, but none reacted with rat receptor. At least 10 distinct epitopes were recognized as indicated by species specificity and binding competition experiments. All of these epitopes appeared to be on extracellular domains of the receptor as shown by binding of antibodies to intact cells. In some cases the epitopes were further localized to alpha or beta subunits by immunoblotting. Several antibodies inhibited binding of 125I-insulin to the receptor, some had no effect on binding, and others enhanced the binding of 125I-insulin. It is concluded that these antibodies will be valuable probes of receptor structure and function.     

Studies on the different molecular forms of tyrosine aminotransferase from rat liver and hepatoma cells

In an attempt to clarify the significance of the separable forms of tyrosine aminotransferase, the enzyme from rat liver and from cultured hepatoma cells was studied by carboxymethyl-Sephadex chromatography. Our studies of the form conversion during the purification procedure of the enzyme, where all cellular components were quickly discarded, do not allow us to invoke a specific "converting factor", the existence of which in the particulate fraction has been suggested. Moreover the addition of serine protease inhibitors is not sufficient to prevent the classical conversion. More probably, several factors depending on the environmental conditions might influence different reactions which lead to a preferential conformation of the enzyme in vitro. The difference in the PO4- content of the various enzyme forms and the consecutive differences in negative charge may be the determining factor in the elution pattern of the three forms of the isolated soluble enzyme. This observation raises the possibility that phosphorylation might play a specific role in the regulation of tyrosine aminotransferase synthesis.     

Different rhodopsin monoclonal antibodies reveal different binding patterns on developing and adult rat retina

We used a battery of 10 monoclonal antibodies directed against different identified peptide sequences within the carboxyl, transmembrane loop, and amino terminal regions of rhodopsin to label retinas from early postnatal and adult rats. Intensity of label, age of initial appearance of staining, and distribution of label varied depending on the antibody. Most antibodies showed detectable labeling at postnatal day 1, and were eventually observed binding to the cell bodies and the inner and outer segments of the photoreceptors. One amino terminal and two carboxyl terminal antibodies, however, showed no detectable labeling until postnatal day 5 and were only transiently detectable in the cell body region. These patterns cannot be explained by accessibility of binding site, binding affinity, fixation artifact, or crossreactivity. The results indicate that physiological and experimental parameters can alter the apparent immunocytochemical localization of conformationally active molecules such as rhodopsin. The results also suggest that rhodopsin can undergo light-dependent conformational changes in several different compartments within rat retinal photoreceptors before the time of eye opening.     

Differentiation of human adult and fetal intestinal alkaline phosphatases with monoclonal antibodies

Two forms of intestinal alkaline phosphatase have been recognized in humans. They are very similar in a number of biochemical and immunologic characteristics, but the exact genetic relationship between them remains unclear. To further study this problem, six monoclonal antibodies and a polyclonal rabbit antiserum to human fetal intestinal alkaline phosphatase have been produced. All of the monoclonal antibodies and the rabbit antiserum crossreact with adult intestinal alkaline phosphatase and with the intestinal-like alkaline phosphatase found in D98/AH-2 human tissue-culture cells. Four of the monoclonal antibodies and the rabbit antiserum crossreact with placental alkaline phosphatase, while none of the antibodies or the antiserum recognize liver or kidney alkaline phosphatase. Four of the monoclonal antibodies can distinguish between adult and fetal intestinal alkaline phosphatase in electrophoretic titration-binding studies, with the relative binding of adult enzyme being significantly greater than that of the fetal enzyme in each case. One of these antibodies, which also reacts with placental alkaline phosphatase, can distinguish the type 3 allelic variant of the placental enzyme from types 1 and 2. This indicates that the antibody detects a structural difference in the protein moiety of one of the allelic forms of the enzyme. These data suggest that adult and fetal intestinal alkaline phosphatases represent structurally distinct proteins, either encoded for by different genes or produced by differential processing of a common precursor molecule determined by a single gene.     

Studies on the conversion of multiple forms of tyrosine aminotransferase in rat liver.

Studies from several laboratories have demonstrated the existence of at least three separable forms of the hepatic enzyme, tyrosine aminotransferase. The significance of these separable forms of the enzyme isolated in vitro for the nature and regulation of the enzyme in vivo has been the subject of some controversy. The studies reported in this paper demonstrate the existence of a heat-labile, pH- and temperature-dependent, nondialyzable component associated predominantly with the lysosomal and mitochondrial fraction of rat liver which catalyzes the conversion of form II to forms III and IV of the enzyme. The activity of this conversion factor is not significantly affected by F^?, molybdate ions, or two inhibitors of proteases. On the other hand, the cyanate ion completely inhibits the conversion of form II to forms III and IV of tyrosine aminotransferase, as do iodoacetate and oxidized glutathione. p-Chloromercuribenzoate also markedly inhibits the conversion. Kinetic studies suggest that the shift from one form to another follows the pathway: II to III to IV. Titration of the available sulfhydryl groups of the three forms of the enzyme demonstrates that form II possesses between 16 and 17 titratable SH groups per mole, while forms III and IV possess 15 and 13 or 14, respectively. The possible catalytic mechanism by which the conversion of the multiple forms of tyrosine aminotransferase is accomplished is discussed.     

Monoclonal antibodies reacting with serogroup and serovar specific epitopes on different lipopolysaccharide subunits of Leptospira interrogans serovar pomona

Monoclonal antibodies with two kinds of specificities, produced against Leptospira interrogans serovar pomona, were studied by agglutination and immunoblotting. Antibodies reacted either exclusively with serovar pomona or with all members of the Pomona serogroup, but none of the antibodies reacted with representative serovars of other serogroups. Both antibodies recognized epitopes on purified lipopolysaccharide (LPS) from serovar pomona. In immunoblotting experiments the serogroup specific antibody recognized both the major LPS bands of 21 kDa and 26 kDa whereas the serovar specific antibodies reacted only with the 26 kDa band, thus localizing serovar specificity in the 26 kDa band and serogroup specific epitopes on at least two different LPS subunits.     

Monoclonal antibodies reacting with serogroup and serovar specific epitopes on different lipopolysaccharide subunits of Leptospira interrogans serovar pomona

Abstract Monoclonal antibodies with two kinds of specificities, produced against Leptospira interrogans serovar pomona , were studied by agglutination and immunoblotting. Antibodies reacted either exclusively with serovar pomona or with all members of the Pomona serogroup, but none of the antibodies reacted with representative serovars of other serogroups. Both antibodies recognized epitopes on purified lipopolysaccharide (LPS) from serovar pomona . In immunoblotting experiments the serogroup specific antibody recognized both the major LPS bands of 21 kDa and 26 kDa whereas the serovar specific antibodies reacted only with the 26 kDa band, thus localizing serovar specificity in the 26 kDa band and serogroup specific epitopes on at least two different LPS subunits.     

Functional correlation of fetal and adult forms of glycine receptors with developmental changes in inhibitory synaptic receptor channels.

Functional maturation of the nicotinic acetylcholine receptor is executed by its gamma-to-epsilon subunit switching. The glycine receptor also has fetal (alpha 2) and adult (alpha 1) isoforms. However, whether subunit switching is responsible for developmental changes in glycine receptor function is not known. We recorded single-channel currents from homomeric glycine receptors expressed in Xenopus oocytes with cRNAs encoding the alpha 2 or alpha 1 subunits and compared them with those recorded from native glycine receptors in rat spinal neurons at various ontogenic periods. The mean channel life times of the alpha 1 and mature glycine receptors were equally short, whereas both the alpha 2 and fetal receptors showed a significantly longer open time. Consistent with these results, the decay time of the glycinergic inhibitory postsynaptic currents (IPSCs) in spinal neurons became shorter during postnatal development. We conclude that developmental switching of alpha subunits may accelerate the kinetics of IPSCs.     

Glutamine-dependent asparagine synthetase in fetal, adult and neoplastic rat tissues.

Three enzyme reactions related to asparagine synthesis were studied in rat tissues: formation of aspartylhydroxamate, either from aspartate or by transfer from asparagine, and actual synthesis of asparagine from aspartate. Actual asparagine synthesis occurred at one-thousandth the rate of the other two reactions. Optimal conditions for quantitative assay of asparagine synthesis were determined in fetal liver extract, which is a rich source of the enzyme. Demonstrable activity in liver fell 6 days after birth to 20% of the fetal value and decreased slowly thereafter to the low adult value. Adult pancreas was the most active tissue found. The asparagine synthetase of fetal liver extracts was significantly inhibited when combined with adult liver or tumor extracts. The inhibitor fractionated with ammonium sulfate in close association with the asparagine synthetase. Therefore, demonstrable activities of asparagine synthetase in tissue extracts, measured in the presence of this inhibitor, do not necessarily parallel the concentrations of the enzyme present.     

Effect of CrATP on the association of the reacting forms of yeast hexokinase.

Reacting enzyme sedimentation studies have been performed with yeast hexokinase isozymes A and B in the presence and absence of chromium ATP at pH 6.75. Preincubation of either isozyme with CrATP causes a shift in the monomer-dimer equilibrium toward the monomeric form. The results are consistent with the observed increase in inhibition caused by CrATP (Danenberg, K.D., and Cleland, W.W. (1975) Biochemistry 14, 28-39) being due to a conformational change in the protein which causes a decrease in the association constant for the monomer.     

Morquio's disease type A: Absence of material cross reacting with antibodies against N-acetylgalactosamine-6-sulfate sulfatase

Summary An antiserum was raised in guinea pigs against purified normal human N-acetylgalactosamine-6-sulfate sulfatase, the enzyme affected in Morquio's disease type A. The antiserum precipitated most of N-acetylgalactosamine-6-sulfate sulfatase from a concentrate of normal human urine. The antigen-antibody complex was enzymatically active. Urine concentrates from five patients with Morquio's disease type A did not contain material competing with the normal enzyme for binding to soluble or Sepharose-bound antibodies. No precipitin arc was obtained on immunodiffusion of antiserum and urine from the single patient investigated by this method. From the sensitivity of the indirect immunoassay it was concluded that the urine of the five patients contained less than 5% of the normal amount of cross-reacting material.     

Phosphatidate phosphatase: activity and properties in fetal and adult rat lung.

The purpose of this work is to compare the properties of phosphatidate phosphatase (L-alpha-phosphatidate phosphohydrolase, EC 3.1.3.4) in fetal and adult rat lung and to establish the developmental profile of activity measured under optimal conditions. The maximal pH of 6.0--7.0 and the inhibition by fluoride, Ca2+ and detergents were simialr for both adult and fetal. Phosphatidate phosphohydrolase activity was located in both mitochondria and microsomes. The localizations of marker enzymes indicated that the activity in these subfractions was not a result of cross contaminations. Very low activity was detected in the supernatant fraction and no Mg2+ requirement was demonstrable. The activity in the particulate fraction was about 50% of the adult from 18 day gestation until birth. Following birth, the activity rapidly increased to adult levels. Dipalmitoyl, dioleoyl and diacyl glycerol 3-phosphates are all utilized well as substrates. 1,2-dipalmitoyl-sn-glycerol 3-phosphate was hydrolyzed faster under maximal conditions. The velocity-substrate curves tended to be sigmoidal, particularly when 1,2-dipalmitoyl-sn-glycerol 3-phosphate was the substrate. Estimated apparent Km values of 0.02--0.03 mM were obtained for fetal and adult preparations.