Enzyme Glycogen Phosphorylase Research Articles

Spiradenoma. Histochemical and electron microscopic study

In two cases of spiradenoma, studies of enzymatic reactions showed complete absence of glycogen phosphorylase and acid phosphatase enzymes. Irregular foci of succinic dehydrogenase, as well as nicotinamide adenine dinucleotide, reduced (NADH), were observed. The small tumoral nodules were surrounded by nerve fibers, which can be readily demonstrated by techniques using cholinesterase. Study of the ultrastructure of the tumor revealed that it was composed of two main types of cells, but neither secretory granules nor glandular structures could be observed. The results of our study of the spiradenoma, its basic similarity to other tumors of the basaloid type, and its chemical and ultrastructural features suggest that it is a tumor of basal cell differentiation.

Spiradenoma

In two cases of spiradenoma, studies of enzymatic reactions showed complete absence of glycogen phosphorylase and acid phosphatase enzymes. Irregular foci of succinic dehydrogenase, as well as nicotinamide adenine dinucleotide, reduced (NADH), were observed. The small tumoral nodules were surrounded by nerve fibers, which can be readily demonstrated by techniques using cholinesterase. Study of the ultrastructure of the tumor revealed that it was composed of two main types of cells, but neither secretory granules nor glandular structures could be observed. The results of our study of the spiradenoma, its basic similarity to other tumors of the basaloid type, and its chemical and ultrastructural features suggest that it is a tumor of basal cell differentiation.

Human chorionic gonadotropin-mediated glycogenolysis in human placental villi: A role of prostaglandins

The acute “ in vitro” effects of human chorionic gonadotropin (HCG) and protaglandin E2 on human placental glycogen metabolism have been studied in immature placental villi in short-term culture. HCG elicited within 15 min of culture, an acute glycogenolytic response in placental tissue which included a decrease in placental glycogen, an activation of the glycogen phosphorylase enzyme system and a pronounced elevation in the cyclic AMP concentration of the placenta. The presence of prostaglandin E 2 in the culture medium evoked a similar glycogenolytic effect in immature human placental villi including the increase in tissue cyclic AMP levels. These findings suggest a second messenger role of the prostaglandins in HCG action and results are discussed in light of the mechanism of action of HCG on the human placenta.

Histamine effects on cardiac contractility, phosphorylase and adenyl cyclase

Histamine was found to produce a positive inotropic effect and to activate the enzyme glycogen phosphorylase in isolated, perfused guinea pig hearts. Both effects were greatly enhanced by theophylline and proved resistant to blockade by tripelennamine. Histamine stimulated cardiac adenyl cyclase and this stimulation also proved resistant to blockade by antihistamines whereas stimulation of the enzyme by epinephrine was blocked by propranolol. Betazole and a triazole derivative, both analogs of histamine, also increased adenyl cyclase activity but were less effective than histamine and more effective than epinephrine. The combined effects of maximum doses of betazole or the triazole derivative and epinephrine were greater than that obtained with either drug alone. Betazole decreased the histamine stimulation of adenyl cyclase. The data suggest that there are separate receptors for histamine and epinephrine on cardiac adenyl cyclase and that stimulation of adenyl cyclase could account for the cardiac actions of histamine. The data also confirm reports that the cardiac histamine receptor differs from other histamine receptors.

The effect of hypoxia and 2,4 dinitrophenol on human placental glycogen metabolism.

SummaryThe effects of 2,4 dinitrophenol and severe hypoxia (1% oxygen) on human placental glycogen metabolism were studied in immature and term human placental villi isolated in an organ culture system.It was observed that both treatments evoked similar changes in human placental glycogen turnover in terms of an acute dependent to independent form synthetase enzyme shift, an activation of the glycogen phosphorylase enzyme system, and a rapid breakdown in placental glycogen.These enzyme changes are consistent with an alteration in intracellular ATP, a known effect of these treatments, and suggest that human placental glycogen may be important to the metabolic energy balance of placental tissue during the course of gestation.

Thyroxine-induced supersensitivity to histamine and norepinephrine activation of cardiac phosphorylase a

The interaction between thyroid hormone and the adrenergic amines on the activation of the cardiac enzyme glycogen phosphorylase has been well documented ( Frazer et al. 1969;, Hess and Shanfeld 1965;, Hornbrook and Brody 1963; Hornbrook et al. 1965;, McNeill 1969, McNeill and Brody 1968). The mechanism of the enhancement is not understood but it does not involve blockade of catecholamine uptake ( McNeill and Brody 1968), cyclic AMP formation ( Frazer et al. 1969; McNeill and Brody 1968), adenyl cyclase stimulation or sensitization ( McNeill et al. 1969), or phosphodiesterase inhibition ( Levey and Epstein 1968;,McNeill et al. 1971). An increase in the activity of phosphorylase b kinase may, however, be a factor in the enhancement of adrenergic amine-induced activation of phosphorylase by thyroid hormone Frazer et al. 1969;. It is also not known whether the enhancement of drug-induced enzyme activation by thyroid hormone is specific for the adrenergic amines. This is probably due to the lack of non-adrenergic agonists capable of stimulating the enzyme. It has been demonstrated that histamine will increase the activity of cardiac phosphorylase (McNeill and Schulze, in press; Muschek and McNeill 1971 a and b; Poch and Kukovetz 1967). Therefore the present study was undertaken to investigate the interaction between thyroid hormone and histamine on guinea pig cardiac phosphorylase a. The results indicate that thyroid hormone can enhance both histamine and norepinephrine-induced activation of cardiac phosphorylase a. Possible mechanisms of this interaction are discussed.

On the fate of glycogen phosphorylase in the ischemic and infarcting myocardium

It is believed that glycogen phosphorylase and other enzymes of the glycogen cycle exist in the cell in a macromolecular complex with glycogen. When the glycogen stores become depleted, this complex is disrupted and conditions are created that facilitate the destruction and loss of phosphorylase. Experiments are reviewed which provide evidence that during incubation of 10 μm sections of ischemic, glycogen-depleted heart muscle the phosphorylase easily diffuses out into the medium. This is apparently the reason why histochemists have been led to believe that phosphorylase disappears within a few minutes in ischemic myocardium, although the loss of the enzyme from intact, i.e. not sectioned, ischemic and infarcting heart muscle can be demonstrated by quantitative biochemical analyses to be a slow process that goes on for many hours. Phosphorylase has been found, along with other enzymes, to appear or rise in the blood serum of animals following temporary ligation of a limb. The enzyme is also released from the isolated perfused heart following a temporary interruption of perfusion. If a method for determining phosphorylase can be developed that is sufficiently sensitive to permit the detection and measurement of the enzyme in the serum of patients, the existence of a heart-specific isoenzyme of phosphorylase could be made use of in the differential diagnosis of myocardial infarction.

Glycogen-bound enzymes: A new method of isolation

The plant protein concanavalin A is utilized as a tool in the isolation of glycogen-bound enzymes from an 8000 g supernatant fraction of mouse-liver homogenate. The protein binds to glycogen to form a complex that can be separated by a short centrifugation at low speed. The precipitate can then be used without further treatment and is shown to contain glycogen synthetase, phosphorylase, and branching enzyme activities. A 25-fold increase in the yield of glycogen synthetase is obtained by using this method, as compared to isolation of the particulate glycogen-bound enzyme by highspeed centrifugation. The fact that enzyme activity can be assayed only 30 min after extraction of tissue represents an additional advantage of this new method. It is likely that the method can be used with other tissues and other branched polysaccharide-bound enzymes.

Ultraviolet Light and Glycogen Formation in the Human Epidermis

Histochemically demonstrable glycogen may be found in the human epidermis when the level of glycogen is above 400 to 500 mμg/mg of fresh tissue, and it may be found normally in the malpighian cells of the epidermis. Seven to 12 hours after ultraviolet light irradiation glycogen accumulates in the malpighian cells, reaches a peak at 24 hours, and may persist for at least 18 days. Increases in malpighian cell glycogen may also be found in nonexposed areas after ultraviolet irradiation. Basal cell glycogen is not found in normal epidermis nor does it appear in nonexposed areas after ultraviolet irradiation. In exposed areas it appears 4½ hours after irradiation, reaches a peak at 7½ to 12 hours, and disappears by 24 to 44 hours. Changes in the activities of the enzymes glycogen synthetase and phosphorylase do not correlate with the changes in epidermal glycogen content.

Ultraviolet light and glycogen formation in the human epidermis

Histochemically demonstrable glycogen may be found in the human epidermis when the level of glycogen is above 400 to 500 mμg/mg of fresh tissue, and it may be found normally in the malpighian cells of the epidermis. Seven to 12 hours after ultraviolet light irradiation glycogen accumulates in the malpighian cells, reaches a peak at 24 hours, and may persist for at least 18 days. Increases in malpighian cell glycogen may also be found in nonexposed areas after ultraviolet irradiation. Basal cell glycogen is not found in normal epidermis nor does it appear in nonexposed areas after ultraviolet irradiation. In exposed areas it appears 4½ hours after irradiation, reaches a peak at 7½ to 12 hours, and disappears by 24 to 44 hours. Changes in the activities of the enzymes glycogen synthetase and phosphorylase do not correlate with the changes in epidermal glycogen content.