Changing Enzyme Patterns in Chick Organs
during Development

Greengard, Olga; Thorndike, Janet

doi:10.1159/000459345

Cited by 17 publications

(7 citation statements)

References 52 publications

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“…The time schedule of enzymic differentiation, like so many life processes, rctlccts an apparent purposefulness: as noted for rat and chick tissues (21 ), the sequential emergence of cnzymcs "makes sense" in terms of the changing functional requirements of the developing organism. A subtle aspect of this teleonomy can be seen in the hierarchy of hepatic functions that become operative at birth only.…”

Section: Piiysiologic Corollari Es and Und E Rlying 1\ieciianisi\ismentioning

confidence: 99%

Enzymic Differentiation of Human Liver: Comparison with the Rat Model

Greengard

1977

Pediatr Res

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125

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The cluantitative pattern of enzymes in the seconcl trimester h u~n a n fetal liver is sigllificantly different fro111 that of aclult liver.For some 20 enzymes, the activity quotient (AQ, i.e., activity of i n~n~a t u r e liver divicled by that in atlult liver) is appreciably different front 1.0. RIost of the enzynles increase their concentrations with age but, as one would expect, sollie contribute to differentiation by tlin~inishing in amount.In cleveloping hurnan liver the concentrations of the various enzynles tend to change in the sanle clirection as they d o in rat liver. 'I'hose that incriase in rat liver have been classifietl into three tnain cIu~ters, accortling to whether their rise begins o n about the 17th day of gestation (B), the first neonatal day (C), or just before weaning (D), respectively. The distribution of these enzynles anlong these three clusters correlates with their AQ's in the hutnan fetal liver. 111 general, enzyrnes with A Q around 0.5 belong to cluster (B) in rat liver whereas those with 0-0.16 belong to cluster C or D.Gross n~alforn~ations resulting fro111 the teratogenic action of drugs, hormones, or vitaniins on the early enlbryo attract n~ucll attention. The harn~ful in~pacts of such agents at late stages of gestation are less spectacular. 'They rnay be more frequent, however, ant1 inanifest then~selvcs in perlnanent inatlecluacies in n~etabolisn~ or growth with a tendency to succun~b to minor childhood cliseases. The underlying causes nlay not be n~irrored in the cytocolnposition or even the subcellular nlorphology -of autopsy specimens. Only deviations from the organ characteristic quantitative pattern of gene products woulcl provide sensitive enough inclictors of the metabolic lesions and of the aberrant aspects of differentiatiol~ that were responsible for them. In both the presence ancl absence of detectable ~norphologic abnornlalities, the stutly of enzymes, this rnost varied and largest class of specific chen~ical constituents, would greatly extend the resolving power of the usual diagnostic procedures postmortem. SpeculationThe sequence in which clifferent enzymes approach their adult concentration in human liver closely resembles that in rat liver.'I'his s~~g g e s t s that the n~echanislns responsible for the scheclule of gene expression rnust also be analogous: the synthesis of specific groups of enzynles at each correspondir~g critical period is regulated by the sarne horniones in both species. Hence, the "cnzyn~e pathology" of infant livers not only specifies basic n~etabolic lesions: aidecl by observations on the rat ~noclel, it coultl also identify the age of onset and the kind of aberrations in the fetal environment which initiated the lesions.

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Section: Piiysiologic Corollari Es and Und E Rlying 1\ieciianisi\ismentioning

confidence: 99%

Enzymic Differentiation of Human Liver: Comparison with the Rat Model

Greengard

1977

Pediatr Res

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125

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“…■a o that the food intake enhances but does not initiate the expression of the genes (14). It is established that the changes in activity are due more to new protein synthesis than to activa tion of preexisting inactive enzymes (27).…”

Section: )mentioning

confidence: 99%

Development of Hepatic Acetyl Coenzyme A Carboxylase in Hormone-Treated Chicks

Ryder¹,

Campos²

1977

Enzyme

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It has been suggested that the carbohydrate-rich diet of chicks after hatching is responsible for the emergence of hepatic enzymes involved in lipogenesis; the injection of glucose to newly hatched chicks gives rise to an appreciable elevation on the activities of acetyl coenzyme A carboxylase and fatty acid synthetase. The present study shows that during the first hours after hatching, there is a natural elevation of glycemia which parallels the increase in acetyl coenzyme A carboxylase activity. However, the administration of hormones which alter the blood glucose levels considerably (insulin, tolbutamide, glucagon and hydrocortisone) did not influence the enzyme activity. The administration of thyroxine, estradiol and cyclic AMP, was also without effect. These results do not support the theory that the increased amount of blood glucose is the natural effector of the induction of acetyl coenzyme A carboxylase. They also show that different lipogenic enzymes are not regulated via the same ‘operon’ since thyroxine or glucagon which alter the level of some enzymes on this pathway did not modify that of the acetyl coenzyme A carboxylase.

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“…The fact that both activities rise at the same developmental stage in retina and other tissues is not convincing evidence for their molecular identity. The well-known 'clustering' of increases in unrelated enzyme activities in different tissues at specific times during development in chick and rat (3,4) clearly argues against identifying GS and GT on the ground of their simultaneous increases in activities. The induction of GT in chick retina in vivo and in vitro (1, 11 -15, 17-19, 22) has been proposed as a model system for the evocation of functional differentiation.…”

Section: Discussionmentioning

confidence: 99%

Glutamine Synthetase and Glutamyltransferase in Developing Chick and Rat Tissues

Herzfeld¹,

Raper²

1975

Neonatology

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Concomitant determination of γ-glutamine-hydroxylamine-glutamyltrans-ferase (GT) and γ-glutamyl hydroxamate synthetase (GS) activities in chick retina, brain and liver between the 13th day of incubation and a day after hatching showed that while both activities increased late in incubation, in neural tissues their rises were not simultaneous throughout development; in liver both activities were already high on the 14th day of incubation and changed in parallel thereafter. GS and GT activities could be evoked prematurely in all three tissues by cortisol, but GT activity showed higher responses to the hormone. GT and GS were separable by differential solubilization in chick liver but not in retina of chick or rat. The wide spread of the ratios of GT:GS activities in homogenates of a number of chick and rat tissues (1:1 to 73:1) indicates that the GS reaction is not catalyzed by the same protein that catalyzes the GT reactions. Relative amounts of GT(T) (free of GS activity) and of variants of GS (with different competences to catalyze the GT reaction) may govern the changes between the two activities during development and their distribution among different adult tissues in chick and rat.

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Changing Enzyme Patterns in Chick Organs during Development

Cited by 17 publications

References 52 publications

Enzymic Differentiation of Human Liver: Comparison with the Rat Model

Enzymic Differentiation of Human Liver: Comparison with the Rat Model

Development of Hepatic Acetyl Coenzyme A Carboxylase in Hormone-Treated Chicks

Glutamine Synthetase and Glutamyltransferase in Developing Chick and Rat Tissues

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