Enzymic Differentiation in Mammalian Liver

Greengard, Olga

doi:10.1126/science.163.3870.891

Cited by 255 publications

(112 citation statements)

References 21 publications

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“…This view has been supported by the absence of some of the pathways essential for amino acid homeostasis and for glucose syn¬ thesis (Greengard, 1971) and the low activity of the pathway for fatty acid oxidation (Warshaw, 1972) in some of the tissues of the fetal rat and rabbit. The metabolic autonomy of the fetus and its ability to compensate for alterations in nutrient supply have been considered therefore to be small.…”

Section: Fetal Metabolismmentioning

confidence: 72%

“…The role of amino acids in providing precursors for glucose synthesis, respiration or the produc¬ tion of other compounds such as lipids has been considered small because of the low transaminase activity and urea production in fetal rate and rabbit liver (Greengard, 1971;Raiha & Schwartz, 1973). However, substantial transaminase activity has been observed in the liver of the fetal guineapig (Test- fig.…”

Section: Fetal Metabolismmentioning

confidence: 99%

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Fetal metabolism and fetal growth

Jones¹

1976

Reproduction

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Section: Fetal Metabolismmentioning

confidence: 72%

Section: Fetal Metabolismmentioning

confidence: 99%

Fetal metabolism and fetal growth

Jones¹

1976

Reproduction

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“…As previously ponents into fully differentiated membranes reported (1)(2)(3)(4), during the time immediately remains an unsolved problem in cell biology . A surrounding birth these cells undergo striking particularly favorable system for studying this morphological and enzymatic changes .…”

Section: Introductionmentioning

confidence: 98%

Differentiation of Endoplasmic Reticulum in Hepatocytes

Leskes

Siekevitz

Palade

1971

The Journal of Cell Biology

284

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The distribution of glucose-6-phosphatase activity in rat hepatocytes during a period of rapid endoplasmic reticulum differentiation (4 days before birth-1 day after birth) was studied by electron microscope cytochemistry . Techniques were devised to insure adequate morphological preservation, retain glucose-6-phosphatase activity, and control some other possible artifacts . At all stages examined the lead phosphate deposited by the cytochemical reaction is localized to the endoplasmic reticulum and the nuclear envelope . At 4 days before birth, when the enzyme specific activity is only a few per cent of the adult level, the lead deposit is present in only a few hepatocytes . In these cells a light deposit is seen throughout the entire rough-surfaced endoplasmic reticulum . At birth, when the specific activity of glucose-6-phosphatase is approximately equal to that of the adult, nearly all cells show a positive reaction for the enzyme and, again, the deposit is evenly distributed throughout the entire endoplasmic reticulum. By 24 hr postparturition all of the rough endoplasmic reticulum, and in addition the newly formed smooth endoplasmic reticulum, contains heavy lead deposits ; enzyme activity at this stage is 250% of the adult level. These findings indicate that glucose-6-phosphatase develops simultaneously within all of the rough endoplasmic reticulum membranes of a given cell, although asynchronously in the hepatocyte population as a whole . In addition, the enzyme appears throughout the entire smooth endoplasmic reticulum as the membranes form during the first 24 hr after birth . The results suggest a lack of differentiation within the endoplasmic reticulum with respect to the distribution of glucose-6-phosphatase at the present level of resolution .

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“…Recently, hormones have been identified decade about enzymic differentiation in mam-which promote the developmental formation of malian liver during late gestation and early post-distinct groups of enzymes in fetal and neonatal rat liver (1,2) . The cytology of the liver is a much older subject but the microscopic descriptions are largely qualitative in nature, whereas the biochemical information is quantitative .…”

Section: Introductionmentioning

confidence: 99%

Cytomorphometry of Developing Rat Liver and Its Application to Enzymic Differentiation

Greengard

Federman

Knox

1972

The Journal of Cell Biology

Self Cite

315

109

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Quantitative stereological methods have been adapted for the measurement of the volume of liver attributable to parenchymal, hematopoietic, and Kupffer cells and for the measurement of the relative and absolute number (per unit volume) of these cell types and the mean volume of the parenchymal cell . These morphological parameters are the main ones for interpreting the biochemical differentiation of liver . Quantitative changes in these parameters, in rat liver between the 15th day of gestation and adult life, are presented . Despite the large number of hematopoietic cells, the parenchymal cells fill more than half of the liver volume between the 15th and 18th days of gestation and 0 .85 of the liver volume at term . The fraction of liver volume occupied by Kupffer cells is never more than 0 .02 ; the number of Kupffer cells per cubic centimeter increases less than twofold between fetal and adult life . The mean volume of individual parenchymal cells undergoes a threefold rise during late fetal life, declines in the neonatal period, and doubles between the 12th and 28th postnatal days . With the morphometric data obtained, it is impossible to convert enzyme concentrations (units per gram, determined in homogenates of whole liver) to enzyme amounts per unit volume of parenchymal or hematopoietic tissue or per individual cell of either type . In late fetal liver, only rises in enzyme concentration less than twofold may be attributed to the enrichment of parenchymal tissue at the expense of hematopoietic elements . The sudden upsurge, by more than twofold, of hepatic enzymes of the late fetal cluster (and also of the neonatal and late suckling cluster) reflects rises per parenchymal mass and per parenchymal cell . Thyroxine and glucagon, the administration of which to fetal rats promotes enzyme differentiation in liver, are without appreciable effect on the cytological parameters studied . Hydrocortisone accelerates the involution of hematopoietic tissue in fetal liver . Enzymes that are diminished by prenatal injection of hydrocortisone may be concentrated in hematopoietic cells .

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Enzymic Differentiation in Mammalian Liver

Cited by 255 publications

References 21 publications

Fetal metabolism and fetal growth

Fetal metabolism and fetal growth

Differentiation of Endoplasmic Reticulum in Hepatocytes

Cytomorphometry of Developing Rat Liver and Its Application to Enzymic Differentiation

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