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Biomedical subjects

A Wong

Publications and source records attributed to A Wong.

At least 217 records · Page 12Linked to original sources

Gamma-actin: unusual mRNA 3'-untranslated sequence conservation and amino acid substitutions that may be cancer related.

beta-Actin mutations in chemically transformed human cell lines have been associated with tumorigenicity, an association consistent with other evidence suggesting that altered cytoskeletal proteins may have an important role in cancer initiation or progression. From a human promyelocytic leukemia cell line, we have isolated a gamma-actin cDNA clone with amino acid substitutions in a region highly conserved in the many actins analyzed. To our knowledge, this is the first example of a variant gamma-actin in a human neoplasm. A separate finding from the analysis of this clone is that the gamma-actin 3'-untranslated region is among the most highly conserved of all 3'-untranslated sequences so far reported, but is entirely different from the beta-actin 3'-untranslated region. The high degree of evolutionary conservation suggests that the 3'-untranslated regions of these two mRNAs have important and distinct functional roles that were already fully differentiated more than 100 million years ago. Mutations affecting four major cytoskeletal components have now been identified in human neoplastic cells. These findings suggest that mutated cytoskeletal genes may be members of a class of oncogenes, fundamentally different from both the nuclear-acting (e.g., myc and simian virus 40 large tumor antigen) and growth factor/receptor/protein kinase-related (e.g., sis, erbB, and ras) types of oncogenes.

Actins↗

Arginine deiminase system and bacterial adaptation to acid environments.

The arginine deiminase system in a variety of streptococci and in Pseudomonas aeruginosa was found to be unusually acid tolerant in that arginolysis occurred at pH values well below the minima for growth and glycolysis. The acid tolerance of the system allowed bacteria to survive potentially lethal acidification through production of ammonia to raise the environmental pH value.

Adaptation, Physiological↗

Secondary palate development in the domestic duck (Khaki Campbell). An electron microscopic, histochemical, autoradiographic and biochemical study.

Prenatal development of the secondary palate in duck was studied using light and electron microscopic, histochemical, autoradiographic and biochemical techniques. The secondary palate of duck develops between Days 7-12 of incubation (HH 25-37). During this period the palatal shelves grow horizontally toward one another but, unlike those in mammals and the alligator, they never fuse, and a physiological cleft persists between them. In contrast to both chick, where the MEE differentiates to orthokeratinisation, and quail, where the MEE becomes parakeratinised, the MEE of duck differentiates to a non-keratinised stratified type. A continuation of DNA synthesis in the MEE, unchanged levels of cyclic AMP in the palatal tissues and an absence of programmed cell death in the MEE during duck palatogenesis distinguish it from the mammalian palate morphogenesis. Also, although the morphogenesis of palate in duck, chick and quail is similar, the cytodifferentiation of their MEE is different.

Animals↗

Structure-activity relationships of beta-adrenergic receptor-coupled adenylate cyclase: implications of a redox mechanism for the action of agonists at beta-adrenergic receptors.

The present studies have tested the hypothesis that agonists at beta-adrenergic receptors activate the beta-receptors by reducing them. This was examined by analyzing the interactions of 41 beta-agonists and antagonists with the receptors. The structural features which determined binding affinity (KD) were shown to be distinct from those which determined intrinsic, activity (IA). The IA was shown to be related to the oxidation-reduction properties which were determined primarily by the nature of the substituents on the phenyl ring. Thus, the parent compound phenylethanolamine, having no phenolic substituent, acted as an antagonist (IA = 0) and was also redox inactive. All of the antagonists tested (19) exhibited EP (peak potential for the first oxidative wave) values greater than 0.75 V, suggesting that they were difficult to oxidize. Agonists, however, exhibited a wide range of EP (0.25-0.7 V) with values lower than those of the antagonists. The agonists tested include catecholamines, catecholamine analogs bearing meta-substituted amino functionalities (such as amino, methylamino, formanilide, sulfonamide, urea, and carbamate), resorcinol, and hydroxymethyl congeners. It is proposed that the oxidizing tendency of the substituent on the phenyl ring is one of the factors that influences IA. To test the hypothesis further, we electrolytically oxidized isoproterenol to adrenochrome or to the o-quinone intermediate and tested for activity. The 4e-, 4H+-oxidation product adrenochrome did not bind to or stimulate adenylate cyclase, suggesting that the reducing ability to isoproterenol is important for its agonistic activity. A cyclic redox mechanism for the action of agonists at beta-adrenergic receptors is presented. We propose that agonist are electron donors. Their interactions with receptors result in reduction leading to activation of the receptors.

Adenylyl Cyclases↗

2',5'-Phosphodiesterase activity depends upon the presence of a 3'-hydroxyl moiety in the penultimate position of the oligonucleotide substrate.

3'-Deoxyadenosine (3'dA, cordycepin)-substituted analogs of 2-5A core 5'-monophosphate (p5'A2'p5'A2'p5'A) were examined for their sensitivity toward degradation by the 2'-phosphodiesterase activity in cytoplasmic extracts of mouse L cells. The analogs, p5'(3'dA)-2'p5'A2'p5'A, p5'(3'dA)2'p5'A2'p5'(3'dA) and p5'A2'p5'A2'p5'(3'dA) were degraded at a rate comparable to p5'A2'p5'A2'p5'A itself. On the other hand, under the assay conditions examined p5'A2'p5'(3'dA)2'p5'A, like p5'(3'dA)2'p5'(3'dA)2'p5'(3'dA), was completely resistant to degradation. The data imply that sensitivity to the 2',5'-phosphodiesterase activity of mouse L cells requires the presence of 3'-hydroxyl moiety in the penultimate nucleotide.

Adenine Nucleotides↗

Formation of the thiol adducts of 4'-(9-acridinylamino)methanesulfon-m-anisidide and their binding to deoxyribonucleic acid.

We investigated the interactions of 4'-(9-acridinylamino)methanesulfon-m-anisidide (mAMSA) with thiol-containing compounds and the potential binding of the thiolytic adducts to DNA. All thiols tested (glutathione, cysteine, coenzyme A, 2-mercaptoethanol and lactate dehydrogenase) formed adducts with mAMSA as evidenced by changes in the absorption spectrum of mAMSA and induction of fluorescence. Spectral changes induced by the thiols were different, suggesting that each thiol induced specific changes in the electronic structure of the acridine nucleus. Treatment of glutathione with p-chloromercuribenzoate eliminated the absorption spectral changes and induction of fluorescence, indicating that the reduced-thiol group is involved. In high ionic strength buffer, addition of calf thymus DNA induced fluorescence-quenching of both the mAMSA-glutathione and mAMSA-cysteine adducts without spectral shift. Viscometric studies showed that mAMSA and mAMSA-glutathione intercalated into DNA and produced similar increases in the length of linear DNA.

Aminoacridines↗

Identification of the active species in deoxyribonucleic acid breakage induced by 4'-(9-acridinylamino)methanesulfon-m-anisidide and copper.

Cyclic voltammetry and UV/VIS spectrometry studies show that 4'-(9-acridinylamino)methanesulfon-m-anisidide (mAMSA) can be oxidized electrochemically to N1-methylsulfonyl-N4-(9-acridinyl)-3-methoxy-2,5-cyclohexadiene-1,4-d iimine (mAQDI) in Tris buffer, pH 7.5. The formal potential of this 2-electron process, as determined by spectroelectrochemical techniques, was 0.141 V versus saturated calomel electrode. Voltammetric data also indicate that an electron transfer reaction between mAMSA and Cu(II) was thermodynamically favored. Two lines of evidence suggest that mAQDI and Cu(I) are the active species in DNA breakage: (1) mAQDI, in the presence of Cu(I), induced both single- and double-strand DNA breakage of the superhelical pDPT275 form I DNA. mAQDI or Cu(I), when used alone, was less effective. (2) The DNA-breaking activity of an mAMSA-Cu(II) mixture was kinetically correlated with the production of both Cu(I) and mAQDI. Thin-layer chromatographic studies showed that mAMSA was oxidized to mAQDI which, in turn, was hydrolyzed. The end product was identified as 9-aminoacridine. When DNA breakage activity was measured as a function of reaction time, a biphasic response was observed. Maximal DNA-breaking activity was obtained upon mixing mAMSA and Cu(II) for 2-4 hr, depending on the concentrations of mAMSA and Cu(II), and was followed by a subsequent decrease in breakage. The decrease appears to be due to the decrease in Cu(I) production and the hydrolysis of mAQDI. These results substantiate the proposed mechanism that DNA breakage induced by mAMSA-Cu(II) involves a rate-limiting electron transfer step to form mAQDI and Cu(I), which are the active species for DNA breakages.

Aminoacridines↗

Home support of patients with end-stage malignant bowel obstruction using hydration and venting gastrostomy.

Palliative terminal care of patients with malignant bowel obstruction is a major clinical and ethical challenge. These patients are often mentally alert and ambulatory, but are kept in the hospital for hydration, nasogastric suction, and pain control. Parenteral nutrition requires frequent metabolic monitoring, is expensive, and is ethically questionable. We have used an alternative method of home management for 27 patients who met the following criteria: inoperable bowel obstruction due to untreatable cancer, an estimated life expectancy of between 2 weeks and 3 months, and understanding of the goals and limits of therapy. Hydration was provided by 10 percent dextrose and electrolyte solutions administered as overnight infusions through long-term central venous catheters. Thirteen patients with complete bowel obstruction required a venting gastrostomy which, when connected to passive drainage, relieved nausea and vomiting. The mean duration of survival was 64 days (range 9 to 223 days). Acceptance by patients and families was excellent, although most acknowledged increased costs due to limited insurance coverage for outpatient care. Seven patients returned to the hospital for terminal care (average stay 3.2 days), and 20 chose to die at home. The mean daily expense for fluids and supplies was +73.50, with an overall cost decrease of $900,000 compared with inpatient care. Home support with fluids and gastric venting is a humane, cost-effective alternative to in-hospital care for selected patients.

Abdominal Neoplasms↗

Interaction of DNA polymerase III gamma and beta subunits in vivo in Salmonella typhimurium.

We show that temperature-sensitive mutations in dnaZ, the gene for the gamma subunit of DNA polymerase III holoenzyme, can be suppressed by mutations in the dnaN gene, which encodes the beta subunit. These results support a direct physical interaction of these two subunits during polymerase assembly or function. The suppressor phenotype is also sensitive to modulation by the dnaA genotype. Since dnaA is organized in an operon with dnaN, and dnaA is a regulatory gene of this operon, we propose that the dnaA effect on suppression can best be explained by modulation of suppressor dnaN levels.

Cloning, Molecular↗

Structure and expression of ferritin genes in a human promyelocytic cell line that differentiates in vitro.

HL-60 is a human promyelocytic cell line with the capability of differentiating in vitro to give neutrophils, macrophages, or eosinophils. We screened libraries of HL-60 cDNA clones representing different time points during these differentiation processes to isolate clones corresponding to mRNAs whose expression is regulated during terminal differentiation. Upon sequencing this group of regulated clones, one clone encoding the heavy subunit and two clones encoding the light subunit of human ferritin were identified by reference to published amino acid sequences. Southern blot analyses showed that these clones are encoded by distinct multigene families. These clones identify two mRNAs whose ratios vary in a complex manner during both neutrophil and macrophage differentiation.

Amino Acid Sequence↗

Aspergillus deflectus infection in four dogs.

Four cases of disseminated aspergillosis caused by Aspergillus deflectus in German Shepherds are presented. Three of the cases, which involved multiple organs, terminated in euthanasia. One case, with bony involvement of the limbs and skull, lived. The unique morphological characteristic of the conidial head resembling a briar pipe led to the identification of A. deflectus. To the authors' knowledge these are the first reported cases of infections caused by A. deflectus in man or animal.

Animals↗

Studies on the fluorescence labeling of human red blood cell membrane ghosts with 4'-(9-acridinylamino)methanesulfon-m-anisidide.

4'-(9-Acridinylamino)methanesulfon-m-anisidide (mAMSA) interacts with red cell membranes, resulting in the formation of fluorescent protein adducts. The mAMSA-membrane protein adducts exhibited an emission fluorescence maximum at 445 nm, with two shoulders at approximately 425 and 470 nm. The major labeled proteins were identified as spectrins 1 and 2 and bands 3, 4.1, 4.2 and 5. The fluorescence intensity increased with increasing mAMSA concentrations (0.03 to 1.5 mM), time (15-120 min), and temperature of the reaction. Results from sodium dodecyl sulfate gel electrophoresis show that mAMSA caused no detectable change in the molecular weight of membrane proteins. This indicates that mAMSA is a monofunctional, noncrosslinking agent. Other acridine analogs, 9-aminoacridine and acridine, did not fluorescently label membrane proteins, suggesting that the presence of the acridine nucleus is not sufficient for labeling. Addition of 2-mercaptoethanol to the mAMSA-membrane reaction mixtures reversed the fluorescence labeling. Furthermore, pretreatment of membrane proteins with N-ethylmaleimide or iodoacetamide prevented the formation of fluorescent mAMSA-membrane protein adducts. These data suggest that mAMSA interacts with sulfhydryl groups of the membrane proteins. When the membrane sulfhydryl groups were assayed by labeling with N-[ethyl-2-3H]ethylmaleimide, it was shown that the accessible membrane sulfhydryl groups were reduced after the mAMSA treatment. The above results suggest that mAMSA covalently binds to the sulfhydryl groups in the red cell membrane, with the production of fluorescent mAMSA-protein adducts.

Aminoacridines↗

Irreversible inhibition by acetaldehyde of cholecystokinin-induced amylase secretion from isolated rat pancreatic acini.

Acetaldehyde inhibited both amylase secretion induced by maximal concentrations (300 pM) of cholecystokinin octapeptide and the binding of radioiodinated cholecystokinin to receptors on isolated rat pancreatic acini. This inhibition was concentration dependent (10 mM to 1 M for amylase secretion and 100 mM to 1 M for binding). However, a correlation between the two inhibitory effects could not be obtained. Furthermore, the inhibitory effects were not reversible. Acetaldehyde did not alter the basal amylase secretion between 6 and 45 mM concentrations. However, 60, 100 and 300 mM acetaldehyde significantly decreased basal amylase secretion; no significant change in amylase secretion was observed at 600 mM and 1 M. Higher concentrations of acetaldehyde produced a 2- to 10-fold increase in basal amylase secretion. 51Cr release from prelabeled acini revealed no significant cell membrane damage between 10 and 600 mM acetaldehyde. These data suggest that acetaldehyde inhibition of cholecystokinin-induced amylase secretion is intracellularly mediated.

Acetaldehyde↗

Reversible acetaldehyde inhibition of A23187-stimulated amylase secretion from isolated rat pancreatic acini.

The Ca2+ ionophore, A23187, stimulated amylase secretion from isolated rat pancreatic acini in a dose-dependent manner with a maximal effect at 6 microM. Acetaldehyde, a metabolite of ethanol, caused a reduction in the magnitude of ionophore-stimulated secretion with no evidence of competitive inhibition. Furthermore, 6 microM ionophore-stimulated amylase secretion was dose-dependently inhibited by acetaldehyde. This inhibitory effect of acetaldehyde, however, was reversible on washing and reincubating acetaldehyde-treated acini. These results suggest that acetaldehyde reversibly inhibits intracellular components mediating stimulated secretion and this inhibition requires a continuous chemical interaction between acetaldehyde and intracellular component(s) regulating stimulated enzyme secretion.

Acetaldehyde↗