Cytidine 3',5'-monophosphate phosphodiesterase: decreased activity in the regenerating and developing liver

A decrease in the activity of the enzyme cytidine 3',5'-monophosphate (cyclic CMP) phosphodiesterase was noted in the regenerating liver of young rats as early as 8 hours after partial hepatectomy, with a maximum decrease occurring 12 hours after the surgery. In comparison, in old rats which showed a slower liver growth, the maximum decrease in the activity of cyclic CMP phosphodiesterase was smaller and occurred at a much later time (2 days after surgery). A similar decrease in the enzyme activity was observed in the fetal liver of guinea pigs. These findings suggest that regulation of tissue concentration of cyclic CMP may be crucial for the regeneration and development of the liver.

Cytidine 3':5'-monophosphate phosphodiesterase in mammalian tissues. Occurrence and biological involvement

A phosphodiesterase activity that preferentially hydrolyzed cytidine 3':5'-monophosphate was partially purified from rat liver extract. The enzyme was best activated by Fe2+ (5 to 10 mM). Mn2+ and Mg2+ were less effective, whereas Zn2+, Co2+, and Ca2+ were ineffective. It exhibited kinetics typical of a high Km phosphodiesterase, with a Km for cycli CMP of 2.4 mM. The enzyme, inhibited by theophylline and 1-methyl-3-isobutyl xanthine to much less extents than cyclic AMP and cyclic GMP phosphodiesterases, was found in all rat tissues examined, with highest levels seen in the liver, kidney, and intestine, and lowest levels found in the skeletal muscle, cerebellum, aorta, and blood cells. The enzyme levels in the regenerating liver were found to be about 40% lower than the control liver of rats; they were also 3 to 10 times lower in the fetal liver, lung, and heart than the corresponding adult tissues of guinea pigs. These findings suggest that depressed cyclic CMP phosphodiesterase may be in part related to cell proliferation, in line with reports that the regenerating liver has higher levels of cyclic CMP (Bloch, A. (1975) Adv. Cycli Nucleotide Res. 5, 331-338) and cytidylate cyclase (Cech, S. Y., and Ignarro, L.J. (1977) Science 198, 1063-1065).

Modified cyclic nucleotide systems in Morris hepatoma 3924A favoring expression of cyclic GMP effect

Modifications in the cyclic nucleotide systems favoring the expression of cyclic GMP effects were found to occur in the transplanted fast-growing Morris hepatoma 3924A. These included: (a) a decreased level of cyclic GMP phosphodiesterase and an increased level of cyclic AMP phosphodiesterase; (b) a disproportionately increased level of cylic GMP-dependent protein kinase relative to that of cyclic AMP-dependent protein kinase; (c) a disproportionately increased level of stimulatory modulator of cyclic AMP-dependent protein kinase relative to that of inhibitory modulator of cyclic AMP-dependent protein kinase; and (d) an increased level of phosphoprotein phosphatase.

Isolation and characterization of the glycoprotein (JBB5) in the urine of a patient with carcinoma of the colon

Patient J. B. with metastatic carcinoma of the colon excreted 0.5 to 1.0 g protein daily, about one-third of which was in Molecular Weight Class 30,000 to 60,000. The major component of this class was isolated by gel filtration and ion-exchange chromatography. The purified protein, labeled JBB5, contained about 11% sialic acid, 8% hexose, and 4% hexosamine. Its molecular weight was between 51,000 and 59,000. It did not react detectably with antisera to any of the recognized normal human plasma proteins. A specific antiserum to JBB5 was raised in the rabbit. Urine from 4% of subjects with nonneoplastic illnesses reacted in double immunodiffusion with anti-JBB5. Thirty-three % positive reactions were obtained with urines from patients with advanced neoplastic disease, the percentage varying from 64% in metastatic cancer of the pancreas to 15% in chronic lymphocytic leukemia.

Urinary excretion of the cancer-related glycoprotein EDCl: effect of chemotherapy

The effect of chemotherapy on the urinary excretion of a cancer-related glycoprotein labeled EDCl, recently isolated from the urine of a patient with acute myelocytic leukemia, has been studied by radioimmunoassay in eight cancer patients who were excreting 200 to 500 mg/day before treatment. In five patients, chemotherapy caused marked clinical improvement, and the glycoprotein disappeared from the urine within 10 days after chemotherapy began. In the two patients with solid tumor who responded to chemotherapy, disappearance of glycoprotein EDCl from the urine preceded clinical improvement by 1 to 2 months. Four of the five responsive patients relapsed within 6 months; in each instance, the glycoprotein reappeared in the urine (greater than 100 mg/day) 2 to 5 weeks before clinical relapse. Three patients were resistant to chemotherapy, and their urinary glycoprotein did not decline during chemotherapy. Measurement of urinary glycoprotein EDCl will be useful in rapidly ascertaining which drug will be effective in a cancer patient and in predicting relapse.

Guanosine cyclic monophosphate-dependent protein kinase from foetal calf heart. Purification, general properties and catalytic subunit

Cyclic GMP-dependent protein kinase was purified from foetal calf hearts, and its general properties and subunit structure were studied. The enzyme was purified over 900-fold from the heart extract by pH 5.3-isoelectric precipitation, DEAE-cellulose chromatography, Sephadex G-200 filtration and hydroxyapatite treatment. The purified myocardial enzyme, free from cyclic AMP-dependent protein kinase contamination, exhibited an absolute requirement of stimulatory modulator (or crude modulator containing the stimulatory modulator component) for its cyclic GMP-stimulated activity. Inhibitory modulator (protein inhibitor) of cyclic AMP-dependent protein kinase could not stimulate nor inhibit the cyclic GMP target enzyme. The enzyme had Ka values of 0.013, 0.033 and 3.0 micronM for 8-bromo cyclic GMP, cyclic GMP and cyclic AMP respectively. The cyclic GMP-dependent enzyme required Mg2+ and Co2+ for its activity, with optimal concentrations of about 30 and 0.5 mM respectively. The pH optimum for the enzyme activity ranged from 6 to 9. Histones were generally effective substrate proteins. The enzyme exhibited a greater affinity for histones than did the cyclic AMP-dependent class of protein kinase. The holoenzyme (apparent mol.wt. 150 000) of the myocardial cyclic GMP-dependent protein kinase was dissociated into a cyclic GMP-independent catalytic subunit (apparent mol.wt. 60 000) by cyclic GMP and histone. The catalytic subunit required the stimulatory modulator for its activity, as in the case of the holoenzyme in the presence of cyclic GMP.

Stimulatory modulator of guanosine 3':5'-monophosphate-dependent protein kinase from mammalian tissues

The crude protein kinase modulator preparations obtained from several rat tissues (aorta, brain heart, liver, lung, skeletal muscle, small intestine and testis) were separated into their stimulatory and inhibitory modulator components by Sephadex G-100 gel filtration. The isolated stimulatory modulator augmented the activity of guanosine 3':5'-monophosphate-dependent protein kinase. The isolated inhibitory modulator, on the other hand, depressed the activity of cyclic AMP-dependent protein kinase; it was without effect on the activity of cyclic GMP-dependent protein kinease. The present findings indicate that in the mammal, apparently in contrast to the arthropoda, separate proteins are responsibile for the stimulatory and the inhibitory activities of protein kinase modulator and that the two classes of cyclic nucleotide-dependent protein kinase are regulated in an opposing manner by these two types of modulators.

Purification and general properties of guanosine 3':5'-monophosphate-dependent protein kinase from guinea pig fetal lung

Guanosine 3':5'-monophosphate (cyclic GMP)-dependent protein kinase was purified from the guinea pig fetal lung, a tissue shown to be the richest in this enzyme in all mammalian sources examined, and its general properties studied. The enzyme was purified 150-fold from crude extract by steps of pH 5.4 isoelectric precipitation, Sephadex G-200 filtration, hydroxylapatite treatment and DEAE-cellulose chromatography. The purified enzyme, free from contamination with adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase, had a specific activity at least equivalent to 600-fold purification of the enzyme from the adult lung. The pulmonary enzyme exhibited an absolute requirement of protein kinase modulator (prepared from various mammalian tissues with an exception of skeletal muscle) for its activity. Inhibitor protein of cyclic AMP-dependent protein kinase purified from rabbit skeletal muscle could not stimulate nor inhibit the cyclic GMP target enzyme, indicating the factors from mammalian sources regulating the two classes of protein kinases may not be the same. The enzyme had Ka values of 1.3 times 10(-8) and 3.3 times 10(-8) M for 8-bromo cyclic GMP and cyclic GMP, respectively, compared to 3.0 times 10(-6) M for cyclic AMP. Cyclic GMP lowered the Km of the enzyme for ATP from 6.3 times 10(-5) M in its absence to 2.1 times 10(-5) M in its presence, accompanied by an approximate doubling of the Vmax. The molecular weight of the enzyme (assayed by its catalytic and cyclic GMP-binding abilities) was estimated to be 123,000, corresponding to a sedimendation coefficient of 7.06 S, by means of sucrose density gradient ultracentrifugation. The cyclic GMP-dependent enzyme required Mg2+ and Co2+ for its activity with optimal concentrations of about 30 and 0.7 mM, respectively. The maximal activity seen in the presence of Mg2+, however, was nearly twice as high as that seen in the presence of Co2+. Histones were generally effective substrates for the enzyme, whereas protamine, casein, phosvitin, phosphorylase kinase, and activator protein of phosphodiesterase were not. The cyclic GMP-dependent enzyme exhibited a greater affinity for histones than did the cyclic AMP-dependent enzyme in the presence of Mg2+.

Diffuse type of senile plaques in the brains of Alzheimer-type dementia

We studied the nature of diffuse type of senile plaques (SP) in the brains of six autopsied subjects with Alzheimer-type dementia (ATD). The densities of SP in the entorhinal cortex were evaluated using serial sections stained by four different methods. Compared with beta protein immunostaining (100% as a reference), the modified Bielschowsky stain (103%) and the periodic acid-methenamine silver (PAM) stain (109%) labeled similar numbers of SP, whereas the Bodian stain labeled only a minor proportion (42%) of these. The vast majority of Bodian-negative plaques were diffuse plaques, which were seen as ill-defined areas of fine fibrillar material after beta protein immunostain with formic acid pretreatment, modified Bielschowsky stain, and PAM stain. They were not stained by Congo red or periodic acid-Schiff stains. Double staining using Bodian and beta protein methods demonstrated that diffuse plaques were free of swollen neurites. Argyrophilia of the diffuse plaques shown by the modified Bielschowsky and PAM stains, became undetectable when sections were pretreated with formic acid. Such treatment made the diffuse plaques immunoreactive to beta protein antiserum, suggesting that diffuse plaques consisted mainly of amyloid, but not neuritic components. The diffuse plaques were distributed in various cortical areas and in the amygdala, and comprised a considerable population of the SP in the ATD brains.