Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.1 (aspartate aminotransferase)
 21,665 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Methylation of guanine in the O6 position by N-nitrosodimethylamine is higher in liver DNA of mice fed a diet restricted in essential amino acids than in controls. A diminished content of the repair enzyme O6-methylguanine-DNA methyltransferase (AAT) may be responsible for the elevated level of O6-methylguanine observed after amino acid deficiency. A delayed repair of O6-methylguanine can be ascribed to diminished AAT activity in amino-acid-restricted mice. In adults, but not in subadults, the diminished AAT activity in liver correlated well with a 40% decrease in overall protein synthesis.
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PMID:Diet- and age-dependent modulation of O6-methylguanine-DNA methyltransferase levels in mouse tissues. 367 99

In this work we intended: a) to confirm the correlation between the increase of serum levels of alpha 1-antitrypsin (ATT) and neoplastic disease; b) to verify in what tumoural diseases the increase of ATT has a specific significance. Therefore we have examined 164 patients: 60 represented the control group and 104 were suffering from neoplastic diseases. We have subdivided the nest group according to histological type and tumour location. The result of this work has demonstrated that the increase of ATT is really determined by the existence of neoplastic disease, more than histological type or location of cancer. The AAT represents a diagnostic index of neoplastic diseases, highly sensitive but little specific.
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PMID:[Alpha 1-antitrypsin as a tumor marker]. 387 14

The tightness of DNA-protein binding in the nuclei of mouse spleen T- and B-lymphocytes was assessed, using nucleoprotein celite chromatography, and changes in the number of T- and B-suppressors in the course of o-AAT-induced chemical hepatocarcinogenesis were studied. Attenuation of DNA-protein bonds in T-lymphocytes at the early stages (up to 3 months) was observed, and by the time of hepatoma formation (8 months) about 50% of T-lymphocyte DNA was loosely bound to proteins, which is a typical feature of quiescent cells. In B-lymphocytes attenuation of DNA-protein interaction was only observed by the 8th month of carcinogenesis. By the time of hepatoma formation the number of T-suppressors in mouse spleen increased 2.8-fold, while the number of B-suppressors in lymph nodes remained unchanged.
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PMID:[Change in the strength of DNA-protein binding in T- and B-lymphocytes of the spleen of C3HA mice during chemical hepatocarcinogenesis]. 387 31

Highly efficient promoters of coliphage T5 were identified by selecting for functional properties. Eleven such promoters belonging to all three expression classes of the phage were analyzed. Their average AT content was 75% and reached 83% in subregions of the sequences. Besides the well-known conserved sequences around -10 and -33, they exhibited homologies outside the region commonly considered to be essential for promoter function. Interestingly, the consensus hexamers around -10 (TAT AAT) and -35 (TTG ACA) were never found simultaneously within the sequence of highly efficient promoters. Several of these promoters compete extremely well for Escherichia coli RNA polymerase and can be used for the efficient in vitro synthesis of defined RNA species. In addition, some of these promoters accept 7-mGpppA as the starting dinucleotide, thus producing capped mRNA in vitro which can be utilized in various eucaryotic translation systems.
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PMID:Promoters recognized by Escherichia coli RNA polymerase selected by function: highly efficient promoters from bacteriophage T5. 390 50

Two new methods are developed for synthesis of conjugated antigens of o-aminoazotoluene-bovine serum albumin (o-AAT--BSA): (1) from the microsomal fraction of the guinea pig liver which contains the cytochrome-P-450-dependent monooxygenase enzymic system and (2) from the m-chloroperbenzoic acid. A possible mechanism of the covalent binding of o-AAT with albumin under the effect of monooxigenases and of their chemical model is considered. Differences of antigenic determinants in conjugated antigens of o-AAT--BSA synthetized by the chemical and enzymic methods are detected.
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PMID:[Antibody formation to o-aminoazotoluene via the administration of conjugated antigens synthesized by enzymatic and chemical methods]. 391 Apr 3

Both cytosolic (c-AAT) and mitochondrial (m-AAT) isozymes of aspartate aminotransferase (EC 2.6.1.1) appear in serum in some diseases including hepatobiliary dysfunction. The present study aimed at elucidation of the mechanism by which AAT isozymes are cleared from blood. Intravenous injection into rats of m-AAT and c-AAT purified from rat liver exhibited a biphasic clearance curve with an overall half-life of 42 min and 4.7 hr, respectively. The tissue distribution of the radioactivity following intravenous administration of 125I-labeled isozymes revealed that the liver is a major organ involved in plasma clearance of these isozymes. This conclusion was also supported by the significant retardation in plasma clearance of m-AAT in hepatectomized as well as CCl4-intoxicated rats. Furthermore, clearance rate of each AAT isozyme in an isolated perfused liver exhibited a single exponential process with the uptake rate for m-AAT being much faster than that for c-AAT. Separation of hepatocytes and sinusoidal liver cells from the rat intravenously injected with 125I-labeled AAT isozymes revealed that sinusoidal cells were responsible for the plasma clearances. In vitro uptake study showed that both isozymes were exclusively taken up by sinusoidal liver cells. The uptake rate for m-AAT was considerably greater than that for c-AAT. Endocytotic index for uptake by sinusoidal cells was 16 times with c-AAT and 34 times with m-AAT as compared with that for inulin or dextran which are taken up by fluid-phase endocytosis, suggesting involvement of adsorptive endocytosis in the uptake of the isozymes.
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PMID:Plasma clearance of intravenously injected aspartate aminotransferase isozymes: evidence for preferential uptake by sinusoidal liver cells. 399 68

No correlation was found between the frequency of spontaneous and o-aminoazotoluene (o-AAT)-induced hepatic tumours in mice. High susceptibility to tumour induction with o-AAT in mice both genetically susceptible (strains CBA and A/He) and resistant (strains DBA/2J and DD) to spontaneous hepatocarcinogenesis was detected. The CC57BR mice predisposed to spontaneous hepatomas were insensitive to their induction with o-AAT. The model described may be helpful in studies of the nature of the initiation and promotion stages of hepatocarcinogenesis.
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PMID:[Ratio of spontaneous and o-aminoazotoluene-induced hepatocarcinogenesis in mice]. 408 94

In 500 consecutive autopsies there were 27 cases in which the livers contained PAS-positive, diastase-resistant globules within hepatocytes. On the basis of morphologic findings and immunoperoxidase staining the inclusions were separable into two groups. There were 14 (2.8%) cases in which the globules were periportal in location and stained positively with the specific AAT immunoperoxidase method (Type 1 globules). In 13 (2.6%) cases, the globules were located in the centrilobular region of the liver or at the edge of the central ischemic zone. These globules did not stain with the specific immunoperoxidase technic (Type 2 globules). Cirrhosis was found in 10 (71%) of the 14 livers containing Type 1 globules. Dysplastic liver cells were present in four cases. No liver cell cancer was present in any of the cases. No fibrosis or cirrhosis was found in any of the 13 livers containing Type 2 globules. They were always present in the centrilobular areas and most likely were the result of sinusoidal congestion and anoxia. The immunocytochemical method is useful in separating the two types of PAS-positive, diastase-resistant globules. Type 1 inclusions are associated with alpha 1 antitrypsin deficiency.
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PMID:Alpha 1 antitrypsin liver disease differential diagnosis of PAS-positive, diastase-resistant globules in liver cells. 618 89

A patient who had an atrial demand pacemaker (AAI) presented with irregular pacing at a routine examination 5 months after implantation. When a magnet was applied over the pulse generator regular fixed rate pacing was obtained, thus proving oversensing in the system. Reprogramming the input sensitivity level to 2.5 and 5.0 mV did not solve the problem. Programming the pulse generator to the triggered mode (AAT) showed acceleration of the stimulation rate but also inhibition of the system. An S-S interval of 1260 ms was measured at a programmed interval of 857 ms (70 bpm). The pulse generator was disconnected and the intra-atrial electrogram was recorded. This showed different spurious signals varying in morphology and amplitude. Fortunately we were able to remove the lead (Medtronic 6991-U) from the atrial appendage. Subsequently a Helifix 12 mm AT lead was successfully implanted in the right atrial appendage and the same pulse generator was connected to the newly implanted lead. When the removed lead was examined by the manufacturer, a small tear in the insulation of the wire was detected. The dimensions of the tear were 0.1 X 0.7 mm. The tear was caused by stress corrosion cracking in the polyurethane tubing of the lead.
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PMID:False inhibition of an atrial demand pacemaker caused by an insulation defect in a polyurethane lead. 619 1

Two methods are developed for synthesis of conjugated antigens to o-aminoazotoluene (o-AAT)-albumin: the enzymatic method--using horseradish peroxidase (HP) and the chemical one--diazomethod. A possible mechanism is suggested for the covalent binding of o-AAT to albumin which is catalyzed by HP. Antibodies to o-AAT are obtained by immunization of animals. An essential difference is established for antigenic o-AAT determinants in conjugates synthesized by the enzymatic and chemical methods.
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PMID:[Preparation of antibodies against o-aminoazotoluene using chemically and enzymatically synthesized conjugated antigens]. 620 89


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