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B A Walker

Publications and source records attributed to B A Walker.

At least 37 records · Page 2Linked to original sources
PubMed1991

Adenosine-5'-O-(3-thiotriphosphate) binding to human neutrophils. Evidence for a common nucleotide receptor.

Human polymorphonuclear neutrophils (PMN) respond to ATP with an elevation in intracellular calcium and a marked enhancement of O2-production in response to stimulation by the chemotactic peptide N'-formyl-Met-Leu-Phe (FMLP). These pertussis toxin-sensitive pathways appear to be mediated by a nucleotide receptor(s) on the surface of human PMN. In the current study, we have examined the binding to intact human PMN of the ATP analog, adenosine 5'-O-(3-thio[35S] triphosphate) [( 35S]ATP gamma S). On the basis of Scatchard analysis, the binding of [35S]ATP gamma S involves at least two sites, one of high and one of low affinity. In the presence of sodium thiophosphate, a compound which did not affect intracellular increases in calcium induced by ATP or N'-formyl-Met-Leu-Phe, a significant fraction of the [35S]ATP gamma S binding was eliminated. This reduction involved both high and low affinity binding of [35S]ATP gamma S and was related to a reduction in numbers of binding sites. The Kd values for the high affinity binding site were unaffected by the presence of sodium thiophosphate, although the low affinity Kd values were numerically increased by 2-fold. In the presence of thiophosphate, [35S]ATP gamma S binding was specific, saturable, and reversible, and was related to a single class of high affinity (Kd = 36 +/- 19 nM) binding sites (184 +/- 144 sites/cell), together with a second class of low affinity (Kd = 1110 +/- 503 nM) binding sites (13,562 +/- 6,851 sites/cells). Competitive binding experiments, based on the ability of nucleotides and ATP analogs to block [35S]ATP gamma S binding to PMN, revealed a rank order of ATP gamma S greater than ATP greater than 2-MeS-ATP = 8-Bromo ATP greater than ADP = ITP greater than AMP-PCP = GTP much greater than CTP. A comparison between the ability of nucleotides to compete with [35S]ATP gamma S binding and their ability to induce a biologic response (elevation of intracellular calcium) revealed a close correlation (r2 = 0.83). These findings support the possibility of a common nucleotide PMN receptor functionally linked to a cellular response which involves increases in intracellular calcium.

Adenosine Triphosphate↗
PubMed1991

Nucleotide responses of human neutrophils.

Since human polymorphonuclear neutrophils (PMN) exposed to ATP or its poorly hydrolyzable analogue, adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S), respond with increases in intracellular calcium and enhanced O2- responses to the chemotactic peptide N'-formyl-Met-Leu-Phe (fMLP), we systematically evaluated responses of PMN to various nucleotides. The P2X and P2Y receptor agonists, 2-methylthioadenosine triphosphate and beta, gamma-methyleneadenosine triphosphate, failed to induce increases in intracellular calcium and did not desensitize PMN to increases in intracellular calcium induced by ATP gamma S. Since it has been suggested that P2Z receptor occupancy with the ATP4- species caused nonselective increases in cell permeability, the ability of ATP to induce increases in intracellular calcium was evaluated in the presence and absence of extracellular Ca2+ and Mg2+. In the presence of these cations, 5-fold greater concentrations of ATP were required. The effects of ATP4- were not associated with changes in cell membrane permeability. This suggests that ATP4- is the active species but that its effect on PMN is not linked to a nonselective increase in permeability of the cell membrane. With respect to responses of PMN to purine and pyrimidine nucleotides as defined by increases in intracellular calcium, the rank order of potency for the nucleotides was ATP = UTP greater than ATP gamma S greater than or equal to ITP greater than GTP greater than or equal to CTP. These responses were blocked by pretreatment of PMN with pertussis toxin. Prior exposure of PMN to ATP gamma S blocked cellular responses (calcium increases) to these nucleotides but not to fMLP. Likewise, exposure of PMN to any nucleotides blocked subsequent cellular responses to ATP gamma S but not to fMLP. These data support the concept that nucleotide responses of PMN utilize either a common receptor or a common signal transduction pathway involving a guanine nucleotide binding protein in events leading to elevations in intracellular calcium. Nucleotide interaction with PMN does not follow the established pattern of responses associated with P2X or P2Y purinergic receptor occupancy.

Adenosine Triphosphate↗
PubMed1990

Superoxide responses of immune complex-stimulated rat alveolar macrophages. Intracellular calcium and priming.

ATP is known to induce calcium transients in rat and human neutrophils and to "prime" these cells for enhanced oxygen radical responses after stimulation with chemotactic peptide, FMLP, or immune complexes. Calcium ionophores are also well known for their ability to prime phagocytic cells. In the current studies, nonelicited rat alveolar macrophages were analyzed for the ability of ATP as well as FMLP, C5a, platelet-activating factor and calcium ionophore (A23187) to modify levels of intracellular calcium and to enhance superoxide anion (O2-) production in response to immune complexes. Although none of these agents induced a O2- response under the conditions employed, all, except FMLP and C5a (human, recombinant) increased intracellular calcium, although the temporal features of the increases varied with the agent. In contrast to the inability of FMLP and C5a to cause intracellular calcium increases in macrophages, these same peptides caused dose-dependent intracellular calcium increases in rat neutrophils, whether the cells were derived from the blood or from the peritoneal cavity. On the basis of the effects of EGTA, the calcium increases in alveolar macrophages were caused by intracellular release of calcium in addition to some influx of extracellular calcium. Although ATP caused a dose-related increase in the level of intracellular calcium in alveolar macrophages, the cells were not "primed" for enhanced O2- responses to immune complexes. In contrast, platelet-activating factor and A23187, each of which induced increased intracellular levels of calcium, were able to prime macrophages for enhanced O2- responses. C5a and FMLP neither increased intracellular calcium levels nor primed macrophages for enhanced O2- responses to immune complexes. It is not clear if the inability of ATP to prime alveolar macrophages is caused entirely by insufficient increases in intracellular calcium or if ATP is unable to bring about additional changes that are relevant to the priming phenomenon.

Adenosine Triphosphate↗
PubMed1990

Effects of adenosine on inositol 1,4,5-trisphosphate formation and intracellular calcium changes in formyl-Met-Leu-Phe-stimulated human neutrophils.

In the presence of adenosine, formyl-Met-Leu-Phe-stimulated human neutrophils show a greatly diminished production of superoxide anion. Analysis of changes in levels of intracellular calcium revealed that the immediate increase (occurring within seconds) in intracellular calcium following addition of formyl-Met-Leu-Phe is not affected by the presence of adenosine, although there are significantly lower intracellular calcium levels during the late phase (occurring 1-4 min after addition of formyl-Met-Leu-Phe). Consistent with these findings is the fact that adenosine does not affect the production of inositol 1,4,5-triphosphate in formyl-Met-Leu-Phe-stimulated neutrophils. These data suggest that the profound inhibitory effects of adenosine on superoxide responses in formyl-Met-Leu-Phe-stimulated neutrophils may be related to an action of adenosine occurring late in the sequence of events of signal transduction.

Adenosine↗
PubMed1990

Thyrotoxicosis in a patient with Addison's disease.

We report the case of a patient who suffered recurrent episodes of hypoadrenal crisis, despite conventional replacement therapy for Addison's disease. She was found to have hyperthyroidism and after this was treated, she had no further relapse. Thyrotoxicosis should be considered when patients taking replacement therapy for Addison's disease present in hypoadrenal crisis.

Addison Disease↗
PubMed1989

Study of airway epithelial permeability with dextran.

We studied the penetration of fluorescein isothiocyanate (FITC) T-40 dextran into the paracellular spaces in the tracheal mucosa and its appearance in the blood plasma of guinea pigs exposed to cigarette smoke or (controls) breathing room air. Under general anesthesia, the dextran solution was instilled onto the tracheal surface via a tracheotomy tube, arterial blood was sampled serially for 40 min, and then the trachea was fixed by perfusion or immersion. Examination of the tracheal mucosa with light microscopy, with and without epifluorescence, and transmission electron microscopy, revealed dextran in the paracellular spaces in mucosa from experimental animals but not controls. In all control animals, the levels of the dextran in plasma was below the sensitivity of the assay. By contrast, dextran levels in the plasma from the experimental animals fell within the sensitivity range of the assay and increased in blood at a rate of 0.00125 +/- 0.00023 (SE) expressed as a percentage of the instilled dose/min. We conclude that FITC T-40 dextran provides a reliable, fairly simple, fast method for assessing major, but not subtle, changes in paracellular permeability of the tracheal mucosa.

Animals↗
PubMed1989

Regulation of superoxide responses of human neutrophils by adenine compounds. Independence of requirement for cytoplasmic granules.

Recent evidence suggests that the adenine compounds ATP, adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S), and adenosine have important regulatory effects on O2- responses of human neutrophils stimulated with the chemotactic peptide N-formyl-Met-Leu-Phe (fMLP). Because of evidence that receptors on neutrophils may be modified by granule fusion events, we assessed the extent to which these adenine compounds affect fMLP and CR3 (C3bi) receptors on neutrophils and whether cytoplasmic granules are required for the ability of the adenine compounds to modify O2- responses in neutrophils stimulated with fMLP. Incubation of neutrophils with ATP gamma S or adenosine led to a decrease in numbers of fMLP receptors (17 and 9.2%, respectively) but no change in receptor affinity (Kd). Paradoxically, ATP gamma S caused an increase in CR3 receptors (Mo1, CD-11b antigen), suggesting that fMLP and CR3 receptors may be under separate control. The ability of the adenine compounds to modify O2- responses in fMLP-stimulated cells was equivalent in both neutrophils and cytoplasts, suggesting that the regulatory effect of ATP, ATP gamma S, and adenosine do not require the presence of cytoplasmic granules. ATP gamma S caused enhancement of O2- responses of neutrophils to phorbol 12-myristate 13-acetate, raising the possibility that ATP gamma S may be affecting late events in the signal transduction pathway.

Adenosine↗
PubMed1988

Differing calcium requirements for regulatory effects of ATP, ATP gamma S and adenosine on O2.- responses of human neutrophils.

In formyl peptide stimulated human neutrophils the enhancement of O2.- responses by ATP and ATP S requires extracellular calcium. In contrast, the inhibitory effects of adenosine are independent of a calcium requirement. Rates of O2.- generation are not affected by these adenine compounds. Rather, ATP and ATP S cause a sustained period of generation whereas adenosine causes an abrupt early termination of the O2- response. The differing calcium requirements for regulatory effects of adenine compounds on O2.- responses of stimulated neutrophils suggests that ATP (or ATP gamma S) and adenosine may exert their effects at different points in the pathway of signal transduction events.

Adenosine↗
PubMed1986

Mutagenicity of benzylic acetates, sulfates and bromides of polycyclic aromatic hydrocarbons.

Studies were performed to determine the direct mutagenicity of the acetates and some bromides and sulfates of hydroxymethyl polycyclic aromatic hydrocarbons in S. typhimurium strains TA98 and TA100. Benzylic acetates, bromides and sulfates were synthesized and characterized. The compounds tested were benzyl alcohol, 5-hydroxymethylchrysene, 1-hydroxymethylpyrene, 6-hydroxymethylbenzo[a]pyrene, 6-(2-hydroxyethyl)benzo[a]pyrene, 6-hydroxymethylanthanthrene, 9-hydroxymethylanthracene, 9-hydroxymethyl-10-methylanthracene, 7-hydroxymethylbenz[a]anthracene, 7-(2-hydroxyethyl)benz[a]anthracene, 12-hydroxymethylbenz[a]anthracene, 7-hydroxymethyl-12-methylbenz[a]anthracene, 12-hydroxymethyl-7-methylbenz[a]anthracene, 1-hydroxy-3-methylcholanthrene, 2-hydroxy-3-methylcholanthrene, 3-hydroxy-3, 4-dihydrocyclopental[cd]pyrene and 4-hydroxy-3, 4-dihydrocyclopental[cd]pyrene. The benzylic sulfate esters of 6-hydroxymethylbenzo[a]pyrene and 7-hydroxymethylbenz[a]anthracene were the most mutagenic compounds, whereas the aliphatic sulfate ester of 7-hydroxyethylbenz[a]anthracene did not cause an increase in mutations above background. All meso-anthracenic benzylic acetate esters were mutagenic in both strains with various degrees of activity, whereas the corresponding non-benzylic esters were inactive, as expected. Of the non-meso-benzylic acetate esters, only the 3-acetoxy-3, 4-dihydrocyclopenta[cd]pyrene was mutagenic. In the benzylic bromide series, only the eight mesoanthracenic were mutagenic, whereas benzyl bromide and 5-bromomethylchrysene were inactive. The aliphatic bromides, 6-(2-bromoethyl)benzo[a]pyrene and 7-(2-bromoethyl)benz[a]anthracene did not display significant activity. The potencies of the acetate esters more accurately reflect the mutagenicity because the rate of solvolysis did not compete with the reactivity of the esters with bacterial DNA. In the case of benzylic sulfates and bromides, the rate of solvolysis was very rapid and could have diminished the level of mutagenicity, depending on the assay conditions. These results demonstrate that meso-anthracenic benzylic acetates, sulfates and bromides are mutagenic, whereas benzylic acetate esters attached to other carbon atoms are inactive.

Acetates↗
PubMed1986

An intrasellar pituitary tumour producing metastases in liver, bone and lymph glands and demonstration of ACTH in the metastatic deposits.

We report the history, laboratory and histological findings in a man who presented with Cushing's disease. Despite removal of the primary pituitary tumour, his disease progressed and after bilateral adrenalectomy, he became pigmented and plasma ACTH levels remained elevated. He had further pituitary surgery and radiotherapy, to relieve compression of the optic chiasma. Plasma ACTH levels remained elevated. He developed liver, bone and lymph gland metastases and after an acute paraparesis due to spinal metastases he died. Immunoperoxidase staining techniques demonstrated ACTH in the pituitary recurrence and metastases. The combination of bone, liver and lymph node metastases has not previously been reported, nor has ACTH been reported before in metastases from a primary intrasellar tumour.

Adrenocorticotropic Hormone↗
PubMed1984

Bladder freeze ulceration and sodium saccharin feeding in the rat: examination for urinary nitrosamines, mutagens and bacteria, and effects on hepatic microsomal enzymes.

We previously demonstrated that long-term feeding of sodium saccharin, a non-mutagen, induced bladder carcinomas when administered to F344 male rats with regenerative hyperplasia of the urothelium induced by the freeze-ulceration technique, even without prior chemical initiation (Cohen et al. Cancer Res. 1982, 42, 65). In the present study, we examined the urine of rats subjected to freeze ulceration of the bladder and then fed sodium saccharin at 5% in the diet to evaluate the possibility of a mutagen being generated as a result of ulceration and/or saccharin feeding. Urine was collected into a syringe by aspiration from the urinary bladder after ligating the urethra for 2 hr at intervals from day 0 to day 14 after ulceration. After ulceration and/or sodium saccharin feeding, the urine showed no bacterial contamination, no mutagenic activity in the standard Ames assay, no production of nitrosamines, and no nitrosating environment. In addition, no significant changes in activities of liver microsomal enzymes (i.e. cytochrome P-450, NADPH-cytochrome c reductase, aniline hydroxylase, or ethylmorphine N-demethylase) were observed in rats fed sodium saccharin for 1, 5 or 14 days. Thus, freeze ulceration, and the consequent regenerative hyperplasia of the epithelium, compared with sodium saccharin feeding do not involve the administration of an exogenous mutagenic substance or the generation of a detectable mutagen in the urine.

Administration, Oral↗
PubMed1983

Adolescent suicide--a family crisis: a model for effective intervention by family therapists.

Statistics attest to the increasing severity and tragic escalation of adolescent suicidal behavior. The consequences of such self-destructive acts are far-reaching and encompass the adolescent's entire family. By providing guidance, support and counseling throughout this crisis, a family therapist may convert a potentially fatal act into a constructive and viable growth experience for the adolescent and all family members. This paper presents a model of crisis intervention counseling which emphasizes and delineates a professionally appropriate and realistic structure for effectively treating adolescent suicidal patients and their families.

Adolescent↗
PubMed1982

Microbial mutagenicity of selected hydrazines.

Selected hydrazines and related compounds were examined for their mutagenic activity in S. typhimurium strains TA1535 and TA1537. These in vitro assays were conducted with and without metabolic activation by Aroclor-induced rat-liver enzymes. Relatively high levels of mutagenicity were observed with phenylhydrazine X HCl, methylhydrazine, N'-acetyl-4-(hydroxymethyl)phenylhydrazine, and 4-(hydroxymethyl)benzenediazonium tetrafluoroborate, the stabilized salt of a carcinogenic metabolite of agaritine; only low levels of mutagenicity were observed with other compounds, although most are strong carcinogens. Several of the compounds were highly toxic to the bacteria, and detection of mutagenicity was enhanced by calculating the increase in mutagenic activity on the basis of the surviving fractions of bacteria.

Animals↗