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R Boland

Publications and source records attributed to R Boland.

At least 55 records · Page 3Linked to original sources
PubMed1997

Influence of age on 1,25(OH)2-vitamin D3 activation of protein kinase C in rat duodenum.

We have studied age-related changes in the non-genomic regulation of protein kinase C (PKC) by 1,25-dihydroxy-vitamin D3 [1,25(OH)2D3] and their role in 1,25(OH)2D3-dependent calcium uptake in the rat duodenum. Treatment of duodenal mucosae from 3 month-old (young) rats with hormone physiological concentrations (0.1 nM) induced an acute and transient stimulation of total tissue PKC activity which was maximal at 1 min (+80%). The responses were evidenced up to 10 nM 1,25(OH)2D3. The duodenum from 22 to 24 month old (aged) rats exhibited higher basal PKC activity which was not significantly modified after addition of the hormone. In the young duodenum PKC activation by 1,25(OH)2D3 was dependent on extracellular Ca2+ influx as it could be abolished to a great extent by EGTA and the Ca2+ channel blocker verapamil. In addition, the Ca2+ ionophore A23187 elicited a marked stimulation of duodenal mucosae PKC in young rats but was without effects in aged animals. 1,25(OH)2D3 increased the influx of 45Ca2+ in duodenal mucosae of young rats in a dose-(0.1-1 nM) and time-(1-10 min) dependent fashion. This response to the hormone was impaired in aged animals. Similarly as 1,25(OH)2D3, the PKC activator dioctanoylglycerol (DOG) rapidly (1-5 min) increased [45Ca2+] influx in duodena from young rats whereas the response to DOG was blunted in senescent animals. Furthermore, PKC inhibitors (bisindolylmaleimide, staurosporine and compound H7) abolished 1,25(OH)2D3 stimulation of Ca2+ uptake in the young duodenum. These results suggest that 1,25(OH)2D3 regulates PKC activity in the mammalian duodenum by a non-genomic mechanism which involves the rapid influx of extracellular Ca2+, and that activation of PKC, in turn, mediates hormone stimulation of intestinal Ca2+ uptake. The data also indicates that 1,25(OH)2D3 regulation of Ca2+ transport through the PKC messenger system is impaired with aging.

Age Factors↗
PubMed1997

Recognition and treatment of depressive disorders by internal medicine attendings and housestaff.

Depression is underdiagnosed and undertreated by nonpsychiatric practitioners. Research suggests improvement is needed in the recognition and treatment of depressive disorders by primary care physicians. This study was undertaken to better understand internists' ability to recognize depressive disorders, choice of appropriate medications, dosage, and treatment patterns. Questionnaires were distributed to 45 internal medicine attendings, 45 internal medicine housestaff, and 32 adult psychiatry residents. Each questionnaire contained four vignettes: major depressive disorder (MDD), MDD with melancholic features, MDD with atypical features, and MDD with psychotic features. Eleven questions per case covered diagnoses, management, and treatment. Data analysis with intragroup comparisons on 20 internal medicine attendings, 33 internal medicine housestaff, and 32 psychiatry residents suggested that many internal medicine attendings and housestaff had difficulty in recognizing major depression and its subtypes. Although the findings indicated that internists would initiate pharmacological treatment, they frequently made incorrect or questionable pharmacological choices. Psychiatric referral or consultation was often endorsed. Our findings among internists are consistent with previous research examining other primary care physicians suggesting that depression is underdiagnosed and undertreated.

Adult↗
PubMed1997

Parathyroid hormone stimulates calcium influx and the cAMP messenger system in rat enterocytes.

Direct effects of parathyroid hormone (PTH) on calcium uptake by isolated rat duodenal cell preparations enriched in enterocytes were investigated. PTH significantly stimulated enterocyte 45Ca2+ influx in a time-dependent (1-10 min) manner and at all doses tested (2 x 10(-13) to 10(-7) M). The Ca2+ channel antagonists verapamil (10 microM) and nitrendipine (1 microM) completely blocked the stimulation of Ca2+ influx by the hormone (10(-8) M). PTH markedly increased cAMP levels in rat duodenal cells (88, 167, and 67%, after 1, 2, and 3 min, respectively). In agreement with these observations, forskolin (adenylate cyclase activator), dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), and Sp-cAMPS (cAMP analogs) mimicked, whereas Rp-cAMPS (cAMP antagonist) suppressed PTH and DBcAMP activation of enterocyte calcium uptake. Furthermore, the effects of DBcAMP were abolished by nitrendipine. These results show direct rapid effects of PTH on duodenal cells' Ca2+ influx, which involve the activation of a dihydropyridine-sensitive Ca2+ influx pathway and the cAMP second messenger system.

Adenylyl Cyclases↗
PubMed1997

HIV and depression.

Explore the source record for details and available documents.

Depressive Disorder↗
PubMed1997

[Changes in bone mass and in glucose homeostasis in subjects with high spontaneous fluoride intake].

This paper reports metabolic data of 24 women and two men, 44-66 years old, ex-residents in an area of endemic fluorosis close to Bahía Blanca city. Fasting fluoremias of these subjects (0.5 to 9.2 microM) and daily urinary fluoride excretion (> 60 mumoles/day) are characteristics of zones with endemic fluorosis. Bone mineral density (BMD) at the lumbar spine (L2-4 1330 +/- 41 mg/cm2) and femoral neck (1045 +/- 10 mg/cm2) were significantly above average of normal subjects of the same age and sex. A significant correlation was observed between the daily excretion of fluoride and BMD L2-4 (r = 0.43, P < 0.05). The Area Under the Curve of insulin during a standard glucose tolerance test showed an inverse relationship with fluoremia. This observation coincides with experiments published elsewhere indicating that fluoride intake at concentrations 5 microM or greater, inhibits the secretion of insulin.

Adult↗
PubMed1996

1,25(OH)2-vitamin D3 stimulation of phospholipases C and D in muscle cells involves extracellular calcium and a pertussis-sensitive G protein.

The steroid hormone 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] activates in chick myoblasts the breakdown of phosphoinositides by phospholipase C and the hydrolysis of phosphatidylcholine by phospholipase D. Extracellular Ca2+ requirement and GTP-binding protein mediation of 1,25(OH)2D3-dependent activation of phospholipases C and D were investigated in cells prelabelled with [3H]glycerol or [3H]arachidonic acid. Generation of diacylglycerol by phospholipase C and phosphatidylethanol by phospholipase D were shown to be dependent on extracellular calcium, since both responses were suppressed by EGTA and the Ca(2+)-channel blockers nifedipine and verapamil, and were mimicked by the calcium ionophore A23187. The G-protein activators guanosine 5'-O-(3-thiotriphosphate) and AlF4- strongly enhanced diacylglycerol and phosphatidylethanol release in myoblasts while guanosine 5'-O-(2-thiodiphosphate), which inhibits G-protein-mediated signals, abolished 1,25(OH)2D3-dependent diacylglycerol and phosphatidylethanol release. Bordetella pertussis toxin pretreatment suppressed the hormone action. These results suggest that 1,25(OH)2D3-stimulation of phosphoinositide-specific phospholipase C and phospholipase D in chick myoblasts is mediated by a pertussis-sensitive GTP-binding protein(s) and the influx of extracellular calcium.

Aluminum Compounds↗
PubMed1996

Acute stimulation of intestinal cell calcium influx induced by 17 beta-estradiol via the cAMP messenger system.

Recent studies have provided evidence for nuclear estrogen receptor-mediated calcium transport in intestinal mucosal cells. The possibility that, in addition, estrogens directly stimulate intestinal Ca2+ fluxes through second-messenger pathways was investigated. Exposure of enterocytes isolated from female rat duodenum to low physiological levels of 17 beta-estradiol (10(-11), 10(-10) and 10(-8) M) rapidly (1-10 min) increased (50-170%) cell 45Ca2+ influx. 17 alpha-Estradiol, dihydrotestosterone and progesterone were devoid of activity, suggesting specificity of the estrogen effect. Maximum responses induced by 17 beta-estradiol (5 min at 10(-10) M) could be abolished to a great extent (84%) by pretreating the cells with verapamil (10 microM) and nitrendipine (1 microM), involving the activation of voltage-dependent Ca2+ channels in the fast increase of rat duodenal calcium uptake by the hormone. Evidence was obtained indicating that the acute estrogen stimulation of enterocyte Ca2+ influx is mediated by the cyclic AMP/PKA pathway. 17 beta-Estradiol rapidly increased cAMP content of rat duodenal cells in parallel to the changes in Ca2+ uptake. In addition, forskolin, dibutyryl cAMP and Sp-cAMPS mimicked and Rp-cAMPS suppressed the prompt 17 beta-estradiol-induced stimulation of Ca2+ influx. These results are consistent with a direct action of estrogens in the enterocyte, presumably a non-genomic one, initiated on the cell surface and resulting in rapid activation of the cAMP pathway and Ca2+ channels, which may be relevant for regulation of intestinal calcium transport.

Adenylyl Cyclases↗
PubMed1995

Modulation by 1,25(OH)2-vitamin D3 of the adenylyl cyclase/cyclic AMP pathway in rat and chick myoblasts.

We have previously reported that the calciotropic hormone 1,25(OH)2-vitamin D3 stimulates influx of Ca2+ into cultured rat and embryonic chick myoblasts via voltage sensitive Ca(2+)-channels. In the present study, we show that this effect of 1,25(OH)2D3 requires the mediation of the adenylylcyclase signalling system since the hormone-dependent Ca2+ influx is abolished by specific inhibitors of adenylylcyclase and protein kinase A and mimicked by forskolin and dibutyryl cAMP. 1,25(OH)2D3-stimulated elevations in cellular cAMP paralleled increases in Ca2+ uptake, further suggesting a coupling of adenylylcyclase activation and calcium influx. Fluoride and GTP gamma S mimicked 1,25(OH)2D3-stimulation of calcium influx while GDP beta S suppressed the effect of the hormone. Cholera toxin and Bordetella pertussis toxin both increased 45Ca2+ uptake in rat and chick myoblasts. The hormone further increased cholera toxin actions, but was unable to modify pertussis toxin-induced 45Ca2+ uptake, suggesting a similar target of action for pertussis toxin and 1,25(OH)2D3. Incubation of microsomal membranes with the sterol (10 nM, 2 min) markedly displaces (-32%) [35S]GTP gamma S binding to the membranes. ADP-ribosylation of the pertussis toxin-sensitive 41 kDa substrate was significantly increased (+40%) in 1,25(OH)2D3-pretreated cells. These results suggest that 1,25(OH)2D3-stimulated influx of Ca2+ into rat and embryonic chick cultured myoblasts sequentially requires inhibition of a pertussis toxin-sensitive G protein, accumulation of cAMP and activation of dihydropyridine-sensitive Ca(2+)-channels through PKA-mediated phosphorylation events.

Adenylyl Cyclases↗
PubMed1995

1,25(OH)2-vitamin D-3 stimulates phospholipase A2 activity via a guanine nucleotide-binding protein in chick myoblasts.

The steroid hormone 1,25(OH)2-vitamin D-3 [1,25(OH)2D3] stimulated phospholipase A2 (PLA2) activity in embryonic chick myoblasts releasing [3H]arachidonic acid from the sn-2 position of phospholipids. GTP-binding protein mediation of 1,25(OH)2D3-dependent PLA2 activity was investigated in cells prelabeled with [3H]arachidonic acid. AIF4-, a G-protein activator, mimicked 1,25(OH)2D3-stimulated arachidonic acid release from myoblasts in a dose-dependent manner. Consistent with the involvement of a G-protein in the activation of PLA2 by the hormone, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S), a stable GTP analogue which activates G-protein mediated signals, strongly enhanced arachidonic acid release in myoblasts. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), which competitively inhibits G-protein activation by GTP and its analogues, abolished 1,25(OH)2D3-dependent arachidonic acid release. Bordetella pertussis toxin pretreatment significantly suppressed the hormone action whereas cholera toxin had minor effects on 1,25(OH)2D3 action. Hormone-induced activation of PLA2 was mimicked by the Ca2+ ionophore A23187 and blocked by nifedipine, but was unaffected by neomycin, a phospholipase C inhibitor, ruling out the contribution of phosphoinositide metabolism to arachidonic acid release. These results suggest that 1,25(OH)2D3-stimulation of PLA2 activity in embryonic chick myoblasts is mediated by a pertussis toxin-sensitive GTP-binding protein coupled to influx of extracellular calcium.

Animals↗
PubMed1995

Using science to influence the Supreme Court on the right to refuse treatment: amicus curiae briefs in Washington v. Harper.

The Supreme Court's use of empirical behavioral science data has grown dramatically in the 40 years since Brown v. Board of Education. Most of these data are submitted in amicus curiae (friend of the court) briefs submitted by parties with an interest in the outcome of the significant mental health law cases coming before the court. The increasing use of such briefs raises important questions. Is there evidence that the court is actually influenced by such briefs? Can scientific/professional organizations present scientific data objectively in a clearly adversarial document? A review of the nine amicus briefs filed in Washington v. Harper, a right to refuse treatment case, and a comparison of the Court's opinion with that of the dissent demonstrate that both the majority and the dissent refer to arguments contained in the briefs, incorporate elements of these arguments, and occasionally paraphrase references cited in the briefs. It remains unclear whether the Court uses such arguments to formulate opinions or to justify them. A comparison of the briefs presented by the American Psychological Association and the American Psychiatric Association highlights the challenge to scientific objectivity inherent in participation in the amicus process.

Antipsychotic Agents↗
PubMed1994

1,25(OH)2-vitamin D3 signal transduction in chick myoblasts involves phosphatidylcholine hydrolysis.

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) rapidly stimulates the biphasic formation of diacylglycerol (DAG) in chick myoblasts. Neomycin (0.5 mM), an inhibitor of phosphoinositide hydrolysis, abolished the first phase (1 min) but had no effect on the second 1,25(OH)2D3-induced DAG peak (5 min). In myoblasts prelabeled with [3H]choline, 1,25(OH)2D3 increased the release of [3H]choline (maximally at 5 min), with a concomitant decrease in phosphatidylcholine and the absence of significant changes in phosphocholine. 1,25(OH)2D3 caused a significant increase in phosphatidylethanol (PEt) formation in myoblasts in the presence of 1.5% ethanol. The effects of 1,25(OH)2D3 were time- and dose-dependent (10(-11) to 10(-8) M) and specific as 25OHD3 and 24,25(OH)2D3 failed to accumulate PEt. 12-O-Tetradecanoylphorbol-13-acetate failed to accumulate PEt. 12-O-Tetradecanoylphorbol-13-acetate also stimulated PEt formation. The combination of 1,25(OH)2D3 and 12-O-tetradecanoylphorbol-13- acetate was more effective than either compound alone. Neither the PKC inhibitor H7 nor PKC down-regulation blocked the hormone-induced increase in PEt. The effects of 1,25(OH)2D3 were, however, inhibited in the absence of extracellular Ca2+ (+EGTA) and by nifedipine and verapamil, whereas the Ca2+ ionophore A23187 also increased PEt generation. The data support the notion that 1,25(OH)2D3 triggers the hydrolysis of phosphatidylcholine in myoblasts through a Ca(2+)-dependent, PKC-independent, phospholipase D-catalyzed mechanism.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Modulation of calcium uptake in cultured cardiac muscle cells by 1,25-dihydroxyvitamin D3.

Recent studies have provided evidence indicating that 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] rapidly stimulates calcium influx through Ca2+ channels in isolated chick heart tissue and cells. Studies were performed both to evaluate the characteristics of the hormone action in cultured myocytes and to obtain information on the metabolic pathway which mediates its effects. Treatment of 70-80% confluent chick embryo myocyte monolayers with 1,25(OH)2D3 induced a fast (within 3-5 min) stimulation of 45Ca uptake which was dose-dependent, maximum responses (130% above controls) being elicited at a concentration of 10(-10) M. Physiological levels of 25(OH)D3 and 24,25(OH)2D3, and the synthetic analog 1 alpha (OH)D3, had lower activity. Coincident with the rapid changes in Ca uptake, 1,25(OH)2D3 significantly increased cAMP levels. The hormone-induced increase in cAMP was not blocked by nifedipine. Compound SQ 22536, a specific inhibitor of adenylate cyclase, completely suppressed the effects of the sterol on cAMP and Ca uptake. Furthermore, GDP-beta-S inhibited the increase in Ca uptake by 1,25(OH)2D3. These results involve the adenylate cyclase pathway and the participation of G proteins in 1,25(OH)2D3 stimulation of Ca influx in chick heart cells.

Animals↗
PubMed1994

Involvement of protein kinase C in 1,25(OH)2-vitamin D3 regulation of calcium uptake by cultured myocytes.

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] produces an acute stimulation of calcium influx in cultured chick embryo myocytes through activation of voltage-gated Ca2+ channels and involvement of cyclic AMP-dependent protein kinase A (PKA). To investigate the participation of protein kinase C (PKC) in this hormone-induced response, calcium uptake was measured in myocytes treated with PKC activators 12-O-tetradecanoyl phorbol 13-acetate (TPA, 50 nM) or 1,2-dioctanoyl-rac-glycerol (DOG, 50 microM). TPA and DOG decreased 45Ca2+ uptake 37% below control cultures. Contrarily, the PKC inhibitors H7 and staurosporine increase myocyte Ca2+ uptake 51% and 54%, respectively. In addition, PKC activity was augmented in cytosol (39%) and membranes (31%) of myocytes after 5 min of treatment with 0.1 nM 1,25(OH)2D3. Likewise, the hormone induced a fast biphasic formation of diacylglycerol, the natural PKC activator, peaking at 30 s (26%) and 3 min (39%). On the other hand, the stimulation of Ca2+ uptake induced by compound H7 as well as 1,25(OH)2D3 was completely abolished with a specific PKA inhibitor. H7 also produced an increase in cAMP levels (172%) and PKA activity (204%). These results suggest the participation of PKC in 1,25(OH)2D3 regulated calcium influx in heart cells and the operation of a cross-talk mechanism between the PKC and PKA pathways.

Animals↗
PubMed1994

Rapid 1,25(OH)2-vitamin D3 stimulation of calcium uptake by rat intestinal cells involves a dihydropyridine-sensitive cAMP-dependent pathway.

The acute effects of 1,25-dihydroxy-vitamin D3 (1,25(OH)2D3) on Ca2+ influx in isolated rat enterocytes were studied. The hormone significantly increased 45Ca2+ uptake by the cells within 1-10 min in a specific dose-dependent manner (10(-11)-10(-9) M) since 25(OH)D3 and 24,25(OH)2D3 were devoid of activity. The effects of 1,25(OH)2D3 were mimicked by the Ca2+ channel agonist BAY K8644 and completely abolished by nifedipine (1 microM) and verapamil (10 microM). Incubation of duodenal cells with 1,25(OH)2D3 rapidly (1-5 min) increased cAMP levels. Forskolin caused a rapid increase in Ca2+ uptake by enterocytes which was similar to the action of the hormone. Moreover, pretreatment of cells with the specific cAMP inhibitor Rp-cAMPS suppressed the changes in 45Ca influx induced by 1,25(OH)2D3. These results provide the first evidence involving Ca2+ channel activation through the cAMP pathway by 1,25(OH)2D3 in mammalian intestinal cells.

Animals↗
PubMed1993

Involvement of the 3',5'-cyclic AMP pathway in the induction of calmodulin synthesis in myoblasts by 1,25(OH)2-vitamin D3.

The participation of second messenger pathways in 1,25(OH)2D3-induced stimulation of protein synthesis in chick embryo myoblasts undergoing proliferation was studied. Double-labelling experiments with 14C- and 3H-leucine showed the induction by the hormone of proteins with apparent molecular masses (treatment interval) of 60 kDa (1 to 2 h). 70 kDa (2 to 4 h), 80 kDa (4 h) and a 19 kDa protein (6 to 12 h) previously identified as calmodulin. The PKC activator TPA and the Ca2+ ionophore X-537 A did not mimic the effects of the sterol on protein synthesis whereas similar double-labelling patterns were obtained with forskolin, an adenylate cyclase activator. Dot-blot and Northern hybridization analysis revealed increased calmodulin mRNA levels in response to both the hormone and forskolin. These results involve the cAMP messenger system in 1,25(OH)2D3 stimulation of calmodulin synthesis and may be relevant to understand hormone regulation of muscle cell proliferation.

Animals↗
PubMed1993

Evidence for the participation of protein kinase C and 3',5'-cyclic AMP-dependent protein kinase in the stimulation of muscle cell proliferation by 1,25-dihydroxy-vitamin D3.

Treatment with 1,25-dihydroxy-vitamin D3 (1,25(OH)2D3) (1-12 h, 10(-10) M) stimulates DNA synthesis in proliferating myoblasts, with an early response at 2-4 h of treatment followed by a maximal effect at 10 h. To investigate the mechanism involved in the mitogenic action of the hormone we studied the possible activation of intracellular messengers by 1,25(OH)2D3. The initial phase of stimulation of [3H]thymidine incorporation into DNA by the sterol was mimicked by the protein kinase C activator tetradecanoylphorbol acetate (TPA) in a manner which was dose dependent and specific as the inactive analog 4 alpha-phorbol was without effect. Maximal responses to TPA (100 nM) were obtained at 4 h. Staurosporine, a protein kinase C inhibitor, blocked the effect of 1,25(OH)2D3 on myoblast proliferation at 4 h. In addition, a fast (1-5 min) elevation of diacylglycerol levels and membrane-associated protein kinase C activity was observed in response to 1,25(OH)2D3. The adenylate cyclase activator forskolin (20 microM) and dibutyryl-cAMP (50 microM) increased DNA synthesis reproducing the second 1,25(OH)2D3-dependent stimulatory phase at 10 h. Inhibitors of protein kinase A blocked the increase in muscle cell DNA synthesis induced by 1,25(OH)2D3 at 10 h. Significant increases in cyclic AMP levels were detected in myoblasts treated with the sterol for 1-10 h. The calcium channel antagonist nifedipine (5-10 microM) abolished both the effects of 4-h treatment with 1,25(OH)2D3 or TPA and 10-h treatment with 1,25(OH)2D3 or dibutyryl-cAMP. Similar to the calcium channel agonist Bay K8644, 1,25(OH)2D3 stimulated myoblast 45Ca uptake and its effects were blocked by nifedipine.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Regulation of Ca2+ uptake in skeletal muscle by 1,25-dihydroxyvitamin D3: role of phosphorylation and calmodulin.

Experiments were carried out to obtain information about the mechanism underlying the fast action of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in skeletal muscle. N-2'-o-dibutyryladenosine-3',5'-cyclic monophosphate (dbcAMP), similarly as 1,25(OH)2D3 (5 x 10(-10) M), rapidly increased 45Ca uptake by soleus muscle from vitamin D-deficient chicks (+25% and +98% at 3 min and 10 min, respectively) in a dose-dependent manner. The effects of the cAMP analog (10 microM) and 1,25(OH)2D3 could be abolished by the Ca(2+)-channel blocker nifedipine and the calmodulin antagonist flufenazine. Calmodulin binding by two muscle microsomal proteins of 28 kDa and 30 kDa was stimulated within 1 min of exposure of the tissue to 1,25(OH)2D3. Direct effects of the sterol on membrane calmodulin binding were shown with isolated microsomes. The 1,25(OH)2D3-mediated rise of [125I]calmodulin binding to microsomal membranes was dependent on the presence of medium ATP. Forskolin (10 microM) and cAMP (10 microM) also increased [125I]calmodulin binding (+75% and +64%, respectively, with respect to controls). Pretreatment of microsomal membranes with cAMP-dependent protein kinase inhibitor (1 microgram/ml) or addition of alkaline phosphates (1 U/ml) after hormonal treatment caused complete inhibition of 1,25(OH)2D3-induced [125I]calmodulin binding to microsomal membrane proteins. These results imply modifications of membrane protein phosphorylation through the cAMP signal pathway and in turn of calmodulin binding in the mechanism by which 1,25(OH)2D3 rapidly stimulates skeletal muscle Ca2+ uptake.

Adenosine Triphosphate↗