Cornelius F. Strittmatter

Appearance of biochemical components related to acetylcholine metabolism during the embryonic development of chick brain

Abstract The normal pattern of appearance of acetylcholinesterase, acetylcholine, choline acetylase, acetothiokinase and choline during the development of chick embryo brain has been determined. During the early period of development, no dramatic changes occur in the concentration of these components of the acetylcholine metabolizing system. During the period from 13 days to hatching, when nervous function is initiated in the major portions of the chick brain, marked increases occur in the concentrations of acetylcholinesterase, choline acetylase, choline and protein and the acetylcholine concentration increases slightly. The concentration of acetothiokinase remains constant throughout the course of embryonic development. The possible interrelations of these changes are discussed.

Oxidative enzyme components of avian liver microsomes. Changes during embryonic development and the effects of phenobarbital administration

Abstract Changes in the levels of oxidative enzyme activities and hemoproteins in chicken liver microsomes were studied during late embryonic and post-hatching development and following administration of phenobarbital at several developmental stages. 1. 1. During the developmental period studied, the oxidative N-demethylation and NADPH-cytochrome c reductase activities increased markedly and in parallel fashion, while oxidative O-demethylation and cytochrome b5 increased only slightly and at a different developmental stage, and the cytochrome P-450 level did not increase. Phenobarbital treatment caused marked increases in the cytochrome P-450 level and N-demethylation activity at each developmental stage, but only minor changes in cytochrome b5 level, O-demethylation activity or capacity for electron transport from NADH or NADPH to cytochrome c or to oxygen. 2. 2. Spectroscopic studies with microsome suspensions indicate that the avian liver microsomal cytochrome P-450 is similar to the mammalian hemoprotein in its spectral properties and lability. 3. 3. The characteristics of the avian microsomal mixed-function oxidase system are considered in the light of the developmental and induced changes in the levels of oxidative components.

Differentiation of electron transport systems in mitochondria and microsomes during embryonic development

Abstract Activities of various particulate-linked oxidative enzyme activities and of cytochrome components were examined in well-defined mitochondrial and microsomal fractions obtained from 24-hr. chick embryos and from heart and liver of chick embryos and chicks. Changes in relative as well as absolute levels of these components are considered in terms of the differentiation of organized electron transport chains in different tissues and within a given tissue in the course of embryonic development.

COMPARATIVE STUDIES IN THE CHARACTERIZATION OF MONOAMINE OXIDASES.

Summary Fractionation of rat liver homogenates suggests a dual intracellular localization of monoamine oxidase, with the major portion in the mitochondria and a smaller but significant portion sedimenting with the microsomal fraction. Comparative studies on substrate specificities and Michaelis constants of monoamine oxidase preparations from liver, kidney and heart of rat and guinea pig indicate marked tissue differences in monoamine oxidases. Multiple substrate studies and other data support the view that each tissue contains a single, distinctive major monoamine oxidase.

Developmental and hormone-induced changes in chicken intestinal disaccharidases.

Abstract Changes in specific activity levels, on tissue wet wt. and protein bases, were determined for avian jejunal disaccharidases in the developing chick embryo and chick. Maltase (α- d -glucoside glucohydrolase, EC 3.2.1.20) and sucrase (β- d -fructofuranoside fructohydrolase, EC 3.2.1.26) showed similar but not identical patterns of change, with marked increases of specific activity on either basis about the time of hatching, while lactase (β- d -galactoside galactohydrolase, EC 3.2.1.23) showed no increase on a protein basis. The pH-activity profile of chick jejunal maltase was significantly different from that of the embryo enzyme; no such difference was observed for sucrase or lactase. The specific activity levels of all three enzymes showed significant but quantitatively different elevations in late embryos obtained from eggs injected with hydrocortisone at 14 days of development, compared to levels in control embryos of the same developmental stages. Jejunal lactase levels were also increased modestly by hydrocortisone administration to newly hatched chicks. No significant changes in disaccharidase levels were produced by disaccharide administration to embryos or by high disaccharide diets in chicks.

Hexose monophosphate shunt dehydrogenases in the developing frog

Abstract 1. 1. Total activities and specific activities of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6-PGD) were measured at various stages in the early development of the frog Rana pipiens , and in individual tissues of tadpoles and adult frogs. 2. 2. Total activities and specific activities of both enzymes were low in frog eggs and embryos, but increased markedly during larval development. The ratio of G6PD/6-PGD activities also increased from 1·0 to 3·5 during larval development. 3. 3. Differences were also found in the specific activities and the ratio of the two activities among individual tadpole tissues and between tissues of the tadpoles and adult frogs.

The zinc-stimulated acid and neutral p-nitrophenyl phosphatase activities of chick liver and duodenum.

Abstract 1. 1.|Some properties of the soluble Zn2+-stimulated p-nitrophenyl phosphatases active at acid and neutral pH have been studied with (NH4)2SO4-precipitated preparations from the soluble cytoplasm fraction of homogenates from chick liver, duodenum and metanephros. Analogous Zn2+-stimulated phosphatase activity was not found in the particulate fraction from these tissues or in any fraction from homogenates of chick brain or heart muscle. 2. 2.|The pH optima of these soluble, Zn2+-stimulated enzymes were at pH 4.9, 6.2 and 6.7, respectively, for duodenum, liver and metanephros. The enzymes responsible for the low level of soluble activity without added Zn2+ or with added Mg2+ showed maximal activity at pH 5.4–5.8 in all three tissues. 3. 3.|The soluble Zn2+-stimulated p-nitrophenyl phosphatase enzymes of liver and duodenum were similar in most other properties examined. With preparations from both tissues, a marked (10- to 20-fold) stimulation of p-nitrophenyl phosphatase activity was elicited only by Zn2+, but Mg2+, Mn2+ and Co2+ caused some stimulation. The optimal concentration of Zn2+ varied over the range 3–10 mM, depending on pH and type of buffer used. A marked and specific stimulatory effect of Zn2+ was seen only for hydrolysis of p-nitrophenyl phosphate, of the many phosphate compounds tested. Hydrolysis of ATP by these preparations was moderately stimulated by both Mg2+ and Zn2+. Indirect evidence suggests that the Zn2+-stimulated hydrolysis of p-nitrophenyl phosphate was not due to the inorganic pyrophosphatase (pyrophosphate phosphohydrolase, EC 3.6.1.1), fructose-1,6-diphosphatase (fructose-1,6-diphosphate 1-phosphohydrolase, EC 3.1.3.11), or ATPase (ATP phosphohydrolase, EC 3.6.1.3) present in these preparations.

Phosphatase activities of chicken liver and duodenum: Characteristics, levels during development, and hydrocortisone-induced changes

Abstract 1. 1.|Changes in specific activity levels of phosphatases were studied in homogenates and cell fractions of liver and duodenum from chick embryos and chicks at various stages of development. The phosphatases studied included the activities with glucose-6-phosphate, fructose-1,6-diphosphate, inorganic pyrophosphate, or ATP as substrate, all at pH 6.5 in the presence of 5 mM Mg2+, and activity with p-nitrophenyl phosphate as substrate at pH 5.0, 6.5, and 9.5 in the presence of 5 mM Mg2+ or 5 mM Zn2+ or without added metal. In liver, there were increases about the time of hatching in the largely particulate phosphatase activities with ATP and with p-nitrophenyl phosphate in the presence of Mg2+, but decreases in the primarily soluble activity with p-nitrophenyl phosphate at pH 6.5 in the presence of Zn2+ and in the activities with Glc-6-P or Fru-1,6-P2 as substrate. In duodenum there was a marked and persistent increase about the time of hatching in activity with Glc-6-P, in addition to a dramatic increase of phosphatase activity with p-nitrophenyl phosphate or β-glycerophosphate at pH 9.5 which began shortly before hatching and reached a transient peak shortly after hatching. The duodenum also showed moderate increases in activities with Fru-1,6-P2, PPi and ATP, in the largely particulate activity with p-nitrophenyl phosphate at pH 5 or 6.5 in the presence of Mg2+, and in a largely soluble activity with p-nitrophenyl phosphate at pH 5 in the presence of Zn2+. No marked changes in intracellular distribution of activities between particulate and soluble state were observed during the developmental period studied. 2. 2.|The phosphatase activities of the chick tissues showed varied patterns of stimulation by or requirement for Mg2+, usually similar to the patterns known for analogous mammalian enzymes, and activities with several substrates were substantially inhibited by 5 mM Zn2+. 3. 3.|Administration of hydrocortisone to developing 13-day embryos gave rise in 18-day embryo duodenum to marked increases above normal 18-day levels of phosphatase activity with p-nitrophenyl phosphate and β-glycerophosphate at pH 9.5 and with Glc-6-P at pH 6.5, and to modest increases of the other activities studied. The changes are consistent with a general acceleration of normal duodenal development by hydrocortisone. In the liver, hydrocortisone administration led to substantial decreases in activity with Glc-6-P, Fru-1,6-P2 and p-nitrophenyl phosphate, but no appreciable changes in the other activities studied.

The phenylalanine-hydroxylating system of avian liver. Pattern of appearance during embryonic development and limiting component.

Summary The phenylalanine-hydroxylating system of chick liver was found to resemble the mammalian liver system in characteristics and components, with apparent involvement of a phenylalanine hydroxylase, a pteridine cofactor and a cofactor reductase. Studies on the pattern of appearance of the avian liver system during embryonic and post-hatching development of the chick showed that the activity rises from a low level in early embryo to a peak shortly before hatching, in apparent contrast to the developmental pattern reported for the mammalian system. Also in apparent contrast to recent studies on the mammalian system, the limiting factor primarily responsible for the pattern of development in avian liver appeared to be a relative lack of active phenylalanine hydroxylase component in the early chick embryo. The authors wish to acknowledge the technical assistance of Mr. Ernest Jones and Mr. Walter Wiley.

Specific Effects of a Hepatoma on Metabolic Capabilities of the Liver in Tumor-Bearing Rats

Summary The presence of a transplantable hepatoma led to changes in host liver metabolic capabilities during the early stages of tumor growth. The changes included increases of liver wet weight and cathepsin activity and decreases of fructose-1,6-diphosphatase activity, microsomal drug-metabolizing activities, cytochrome P-450 and NADPH-cytochrome c reductase activity. The nature and early appearance of these changes and the failure of liver implants to produce similar changes suggest that there may be specific directive effects of the tumor on host tissues. The low respiratory control ratio seen with hepatoma mitochondria preparations did not reflect an increased rate of deterioration with storage.