Search PubMed⌕ Search

Biomedical subjects

I Fleming

Publications and source records attributed to I Fleming.

At least 73 records · Page 4Linked to original sources
PubMed1995

Control and consequences of endothelial nitric oxide formation.

The intention of this chapter is to give a brief overview of the continuously expanding field of endothelium-derived NO. Over the past few years it has become apparent that the mechanisms controlling the activation of NOS are more complex than was previously thought, with factors such as pHi, [Ca2+]i, shear stress, and gender all contributing to the control of "basal" NO production as well as the regulation of NOS levels in endothelial cells. The list of the functional consequences of endothelial NO formation has also grown, with antiproliferative, antihypertensive, and antiatherogenic effects all being described. Recent advances at the molecular biology level have facilitated the pioneering of a whole new field of research, and a number of groups have shown that NO can modulate the expression of several genes, such as that encoding MCP-1, an effect that is probably due to an interaction between NO and transcription factors. Further elucidation of the signals that influence the production and actions of NO will, without doubt, further the understanding of numerous physiological and pathophysiological processes.

Animals↗
PubMed1995

Calcium signaling in endothelial cells involves activation of tyrosine kinases and leads to activation of mitogen-activated protein kinases.

The activation of endothelial cells following exposure to a variety of receptor-dependent and -independent stimuli is associated with the release of Ca2+ from intracellular stores as well as the influx of Ca2+ from the extracellular space. In the present study, we investigated the interaction between Ca2+ signaling in cultured human umbilical vein endothelial cells and tyrosine phosphorylation. Stimulation of endothelial cells with either bradykinin (100 nmol/L), histamine (1 mumol/L), or the Ca(2+)-ATPase inhibitor thapsigargin (30 nmol/L) resulted in a slightly delayed but prolonged tyrosine phosphorylation of two low molecular weight proteins (approximately 42 and approximately 44 kD). These proteins were identified by immunoprecipitation as the 42- and 44-kD isoforms of mitogen-activated protein kinase (MAP kinase). The agonist-induced tyrosine phosphorylation of the 42-/44-kD doublet was sensitive to the tyrosine kinase inhibitors genistein (100 mumol/L) and piceatannol (10 mumol/L) and was inhibited by the removal of Ca2+ from the extracellular medium. In fura 2-loaded endothelial cells, inhibition of tyrosine kinases attenuated Ca2+ signaling after stimulation with either bradykinin (30 nmol/L) or thapsigargin (30 nmol/L). Since inhibition of tyrosine kinases specifically attenuates the plateau phase of the Ca2+ response after stimulation, the effect of tyrosine kinase inhibition appeared to be mostly associated with the influx of Ca2+ from the extracellular space.(ABSTRACT TRUNCATED AT 250 WORDS)

Bradykinin↗
PubMed1995

Regulation and functional consequences of endothelial nitric oxide formation.

Since its discovery, endothelium-derived nitric oxide (NO) has become one of the most intensely investigated molecules in the field of cardiovascular physiology. Although initial investigations centred on the role of NO in mediating vasodilation and inhibition of platelet activation it has since become clear that this small, atypical signal molecule is also involved in regulating cell growth and proliferation as well as affecting the transcription of certain genes, the products of which have been implicated in the pathogenesis of such states as atherosclerosis and hypertension. Our understanding of the intracellular regulation of the NO synthases has also progressed and the constitutive endothelial enzyme is now known to be controlled by both intracellular Ca2+ and pH. In addition it would appear that this enzyme can also be upregulated in response to stimuli such as fluid shear stress and oestrogen. This review is intended to give the reader a glimpse of the multifaceted actions of endothelium-derived NO.

Chemokine CCL2↗
PubMed1994

Risk of genital human papillomavirus infection in women with human immunodeficiency virus-induced immunosuppression.

This study examined the risk factors for genital human papillomavirus (HPV) infection, including HIV-related immunosuppression as well as demographic and behavioral factors. Subjects were 207 women with known HIV serologic status, the majority of whom were intravenous drug users recruited from a methadone treatment program in the Bronx, New York. A structured questionnaire interview, cervico-vaginal lavage, and CD4 cell measurements were obtained. HPV genomes in the cervico-vaginal cells were detected by Southern-blot hybridization. HPV prevalence was 23% among HIV seronegatives, 45% among HIV seropositives with CD4 percent > 20 and 61% among HIV seropositives with CD4 percent < or = 20. Multivariate analysis identified the following independent risk factors that were significantly associated with HPV positivity: HIV-related immunosuppression, < 35 years of age, and never used oral contraceptive pills. HIV-related immunosuppression was also associated with a stronger Southern-blot signal strength. HIV infection, however, did not increase the susceptibility to HPV infection with the oncogenic types (16, 18, 31, 33 and 35). Women with HIV infection or immunosuppression had a higher prevalence of HPV infection with the oncogenic types, but they also had an increased prevalence of infection with other HPV types as compared to the HIV-seronegative women. The results suggest that HIV-related immunosuppression increases the risk of genital HPV infection and has an effect on HPV replication.

Adult↗
PubMed1994

Risk factors for squamous intraepithelial lesions on Pap smear in women at risk for human immunodeficiency virus infection.

To determine risk factors for squamous intraepithelial lesions (SIL) on Pap smear, 253 women at risk for human immunodeficiency virus (HIV) infection had Pap smear, HIV antibody testing, CD4+ cell measurements, and human papillomavirus (HPV) genome detection by Southern blot hybridization. Associated with SIL (P < .05) on univariate analysis were genital HPV (SIL prevalence in HPV-positive subjects, 36.3%; odds ratio [OR], 9.3; 95% confidence interval [CI], 4.2-20.3) and HIV infection (SIL prevalence in seropositive subjects, 21.9%; OR, 2.5; 95% CI, 1.2-5.1). No demographic or behavioral variables were associated with risk for SIL. Multivariate analyses identified genital HPV infection (OR, 6.78; 95% CI, 2.9-15.7), detection of known high-risk HPV types (OR, 11.8; 95% CI, 4.1-34.1), strong HPV Southern blot signal strength (OR, 10.8; 95% CI, 3.5-33.7), and severe HIV-related immunosuppression (OR, 3.1; 95% CI, 1.04-9.5) as independent risk factors associated with SIL. Thus, severe immunosuppression due to HIV infection increases the risk for SIL mediated by HPV infection.

Adult↗
PubMed1994

Intracellular alkalinization induced by bradykinin sustains activation of the constitutive nitric oxide synthase in endothelial cells.

The transient increase in [Ca2+]i in endothelial cells after stimulation with bradykinin can account for the initiation but not the sustained production of nitric oxide (NO). Therefore, we investigated whether this sustained activation of the constitutive NO synthase (cNOS) could be mediated by an increase in pHi, which is induced by an activation of the Na(+)-H+ exchanger rather than an increase in [Ca2+]i. Cultured human endothelial cells grown on coverslips were loaded with either C.SNAFL-2 or fura 2-AM for fluorometric analysis of either pHi or [Ca2+]i. NO release was assayed by the ability of effluent from endothelial cells to stimulate purified soluble guanylyl cyclase. The pH dependence of a microsomal cNOS preparation was determined by assay of L-[3H]citrulline formation from L-[3H]arginine. Bradykinin (10 nmol/L) induced a biphasic change in endothelial pHi consisting of an initial acidification followed by a prolonged alkalinization above resting values. Inhibition of the Na(+)-H+ exchanger using HOE 694 (10 mumol/L) prevented this increase in pHi. The L-citrulline assay revealed a twofold increase in cNOS activity on increasing pH from 6.7 to 7.4, an optimum at pH 7.5, and a complete abolition of activity at pH 8.6. Endothelial production of NO 15 minutes after starting the infusion of bradykinin was maintained at significantly higher levels in control cells compared with cells pretreated with HOE 694. The latter effect cannot be accounted for by an increase in intracellular Ca2+, since [Ca2+]i levels were not significantly different between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1994

Control of nitric oxide and prostacyclin synthesis in endothelial cells.

Endothelial cells produce a variety of factors involved in the control of vascular tone, platelet activation and cell growth, the most important being nitric oxide (NO) and prostacyclin (PGI2). Although continuously produced in small amounts, synthesis and release of these autacoids are enhanced by mechanical (e.g. fluid shear stress) and humoral stimuli (e.g. acetylcholine, bradykinin, histamine). By counteracting neuro- and myogenic vasoconstriction, the continuous release of NO and PGI2 from the vascular endothelium represents a sensitive and highly effective local system for the maintenance of an adequate blood flow to the organs. This overview resumes current knowledge concerning the intracellular pathways which link endothelial cell activation by receptor-dependent and -independent stimuli to the formation of NO and PGI2.

Animals↗
PubMed1993

Implications of psychological research on stress and technological accidents.

Psychological research on stress, disasters, and human-made technological accidents have important implications for policy, planning, and legal resolution of situations caused by environmental hazards. The incidence of technological accidents and catastrophes seems to have increased, and the biobehavioral sequelae of such accidents among victims have implications for mental and physical health as well as for intervention and prevention. In this article, research on the long-term effects of human-made disasters is discussed in the context of contributions that psychological research and theory can make in decisions regarding where potential hazards are located, how they are managed, and how accidents are handled. Unique psychophysiological processes associated with toxic accidents make these stressors more potent and likely to cause long-term uncertainty and chronic stress.

Accidents↗
PubMed1993

Influence of endothelium on induction of the L-arginine-nitric oxide pathway in rat aortas.

The role of the endothelium in the onset and persistence of vascular hyporeactivity induced by bacterial lipopolysaccharide (LPS) and the implication of the L-arginine-nitric oxide (NO) pathway in this phenomenon were investigated in rat aortic rings exposed to LPS for different times. LPS (100 ng/ml) induced a decrease in the contractile response obtained by norepinephrine (NE) in rings without endothelium after a delay of 6 h. This delay was reduced to 4 h in the presence of the endothelium and corresponded temporally with the development of relaxation after addition of L-arginine (1 mM). This effect of L-arginine along with hyporeactivity to NE was reversed by both NG-nitro-L-arginine methyl ester (300 microM) and methylene blue (3 microM). The effects of LPS on reactivity, L-arginine-dependent relaxation, and tissue guanosine 3',5'-cyclic monophosphate content were prevented by cycloheximide (100 micrograms/ml) whether present throughout the experiment or added 6 h after LPS. Increasing the concentration of LPS to 1 mg/ml reduced the delay between addition of LPS and response to L-arginine in endothelium-denuded rings to 4 h but was without effect on the delay observed in rings with endothelium. These results demonstrate that the time course of development of hyporeactivity to NE corresponds to that of activation of the L-arginine-NO pathway after LPS challenge as assessed by development of sensitivity to L-arginine. The induction process was accelerated by the presence of the endothelium, which also increased the sensitivity of the preparation to LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Endothelium-derived bradykinin: implications for angiotensin-converting enzyme-inhibitor therapy.

The effects of angiotensin-converting enzyme (ACE) inhibitors on endothelial autacoid formation were determined in human cultured endothelial cells and in endothelium-intact bovine coronary arteries under resting conditions and after stimulation with bradykinin. Incubation of cultured human endothelial cells with moexiprilat or ramiprilat (0.3 microM) caused a maintained increase in resting intracellular calcium [Ca2+]i, which was prevented by the selective B2-receptor antagonist Hoe 140 (0.1 microM). Both ACE inhibitors also significantly enhanced the increase in [Ca2+]i elicited by bradykinin (3 nM). In parallel with their effect on resting [Ca2+]i, moexiprilat and ramiprilat both induced an increase in intracellular cyclic GMP (cGMP). This increase was prevented by Hoe 140 (0.1 microM) and was abolished by NG-nitro-L-arginine (30 microM), indicating a kinin-induced nitric oxide (NO) formation in this response. The elevation in [Ca2+]i also led to an enhanced production of prostacyclin (PGI2), as indicated by an increase in the concentration of 6-keto prostaglandin F1 alpha (PGF1 alpha) in the cell supernatant. Similar effects of the ACE inhibitors on endothelial autacoid production were observed in endothelium-intact bovine coronary arteries. Like bradykinin (30 nM), moexiprilat (0.3 microM) elicited a nearly twofold increase in the cGMP content of these arteries, which was abolished by both NG-nitro-L-arginine and removal of the endothelium. The functional consequences of this ACE inhibitor-induced increase in vascular cGMP were reflected by a distinct relaxation of arteries preconstricted with PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1993

Effect of dexamethasone on the onset and persistence of vascular hyporeactivity induced by E. coli lipopolysaccharide in rats.

The effects of dexamethasone (DEX) were studied on early and delayed hyporesponsiveness to noradrenaline (NA) induced by Escherichia coli lipopolysaccharide (LPS) in pentobarbitone-anesthetized rats, and in aortic rings, which were either removed from LPS-treated rats or exposed to LPS in vitro. In all three preparations, the LPS-impaired responses to NA were restored by N omega-nitro-L-arginine methyl ester. In addition, delayed depression of NA-induced aortic contractions was enhanced by L-arginine (1 mM). In control conditions, DEX had no effect on responses to NA. When administered before LPS, or before hyporeactivity was fully developed, DEX (5-10 mg/kg or 10 microM) entirely prevented both the early decline in responses to NA or its progression, and the delayed impaired aortic contraction induced by LPS. However, DEX did not prevent the transient drop in mean arterial blood pressure (which was maximal at 20 min after the onset of LPS infusion) observed before the full development of impaired reactivity to NA (reached after 55 min). Neither did DEX modify the responses to NA, in vivo or in vitro, once LPS-induced hyporesponsiveness was fully established. These results indicate that DEX inhibits both the onset of impaired responsiveness to NA, which probably involves the early stimulation of the constitutive nitric oxide (NO) synthase, and persistent vascular hyporeactivity resulting from the delayed induction of NO-synthase by LPS. In addition, they show that DEX has no effect on hyporeactivity to NA once fully established.

Amino Acid Oxidoreductases↗
PubMed1993

Signal transduction in endothelium-dependent vasodilatation.

Modulation of vascular tone is one important function of the endothelium. This can occur via two principal mechanisms: by modulating the local concentration of circulating vasoactive substances (e.g. adenine nucleotides, angiotensin II, biogenic amines, bradykinin), and by synthesizing and releasing vasoactive autacoids. The most important endothelium-derived vasodilator autacoids are nitric oxide (NO) and prostacyclin (PGI2). By counteracting neuro- and myogenic vasoconstriction, the continuous release of these autacoids from the vascular endothelium represents a sensitive and highly effective local system for maintaining an adequate blood flow to the organs. Impaired production of NO (and PGI2), either as a result of endothelial injury or dysfunction, has been implicated in the pathology of a variety of cardiovascular diseases, such as hypertension, hypercholesterolaemia, atherosclerosis and diabetes. Therefore, the prevention and/or reversal of the functional and morphological changes of the endothelium associated with these diseases is an important therapeutic goal. This brief overview covers current knowledge concerning the intracellular pathways that link endothelial activation by receptor-dependent and -independent stimuli to the formation of NO and PGI2.

Animals↗
PubMed1993

Women with human immunodeficiency virus infection and abnormal Papanicolaou smears: a prospective study of colposcopy and clinical outcome.

OBJECTIVE: To determine the effect of human immunodeficiency virus (HIV) infection on colposcopic and histologic findings and clinical outcome in women who have abnormal Papanicolaou smears. METHODS: We conducted a prospective study of women with abnormal Papanicolaou smears from among those participating in a longitudinal study of HIV infection, human papillomavirus infection, and genital neoplasia. Women with squamous intraepithelial lesions (SIL) on blindly interpreted Papanicolaou smears were referred for colposcopy and standard gynecologic care. Colposcopic and histologic findings were correlated with cytology, and differences between HIV seropositives and seronegatives were analyzed. RESULTS: Thirty-eight of 48 women referred underwent colposcopy, of whom 36 (94.7%) had colposcopic or histologic findings no more severe than those suggested by Papanicolaou smear. Seventeen of 25 HIV seropositives (68%) had cervical or vaginal condyloma or neoplasia, compared with three of 13 seronegatives (23%) (odds ratio [OR] 7.1, 95% confidence interval [CI] 1.5-33.0). Among seropositives, seven (28%) had cervical intraepithelial neoplasia (CIN) grade II or III; ten (40%) had cervical or vaginal condyloma, CIN I, or both; and eight (32%) had no vaginal or cervical SIL. There was no case of invasive carcinoma. Seven seropositives (28%) had or developed multicentric disease, compared with no seronegatives (P = .07). Follow-up ranged at 3-37 months and showed that all three treated seronegative women and five of ten treated seropositive women had normal examinations. Three seropositive patients had persistent disease without progression, and two had progression of condyloma. No CIN II, CIN III, or invasive carcinoma was seen during follow-up. CONCLUSIONS: Among women seropositive for HIV who had SIL on a Papanicolaou smear, colposcopic and histologic findings were predicted reliably by the cytologic smear. Rapid progression of CIN after standard gynecologic care for early genital lesions was not seen.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Effect of endotoxin on circulating cyclic GMP in the rat.

The aim of this study was to investigate the possible use of plasmatic cyclic GMP as an index of L-arginine/nitric oxide (L-Arg/NO) pathway activation by E. coli endotoxin in vivo. Endotoxin (20 mg kg-1 i.p.) caused a time-dependent increase in plasmatic cyclic GMP in anaesthetised rats which corresponded with the time course of L-Arg/NO pathway activation in aortas from the same rats, but was not prevented by a specific inhibitor of this pathway, NG-nitro-L-arginine methyl ester (1 mg kg-1 or 20 mg kg-1 h-1 i.v.). Elevated plasmatic cyclic GMP was however also associated with an increased plasma concentration of atrial natriuretic peptide (ANP) in endotoxin-treated rats. We conclude that plasma cyclic GMP cannot be used as a direct marker of L-Arg/NO pathway activation by endotoxin but may instead be a reflection of an endotoxin-induced increase in plasma ANP activity.

Animals↗
PubMed1992

Sarcomas of the flexor fossae in children: is amputation necessary?

Successful management of sarcomas of the extremities in children implies not only achievement of local control but also satisfactory function and maintenance of the growth potential. The popliteal and antecubital fossae, because of their complex neurovascular anatomy, all of which is essential, make resection with satisfactory margins difficult. We reviewed our experience with 14 patients (3 to 20 years old; median, 13 years) with soft tissue sarcomas arising in the popliteal (11 patients) or antecubital (3 patients) fossae. There were four rhabdomyosarcomas (3 alveolar, 1 embryonal) and 10 other sarcomas, the most frequent being synovial sarcoma (5 patients). Chemotherapy was given to all patients with rhabdomyosarcomas. The one patient presenting with metastatic disease was treated, after biopsy of the primary, by chemotherapy and radiation and survived 21 months. In three patients, the primary management was an above-the-knee amputation and two of three survived (3 and 43 months). In 10 patients a wide local excision of the primary tumor was performed. Radiation therapy was administered to five, either as external beam (3 patients) or as brachytherapy (2 patients). In this group, there were no local recurrences. Four patients remain free of disease (4 months to 18 years) and one developed pulmonary metastasis. Among the five non-irradiated patients, three developed local recurrences, requiring above-the-knee amputation for disease. The fourth patient relapsed in the lung and only one of the five is free of disease at 36 months. Of the 8 patients not treated with amputation, one acquired a leg length discrepancy, which required correction, and one has a minimal extension deficit of the knee.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Endothelium-derived kinins account for the immediate response of endothelial cells to bacterial lipopolysaccharide.

We have recently shown that cultured endothelial cells produce kinins that can stimulate endothelial nitric oxide (NO) production in an autocrine manner. Because both the kallikrein-kinin system and the L-arginine/NO pathway have been implicated in the pathogenesis of septic shock, we investigated the possible involvement of endothelium-derived kinins in the response of cultured endothelial cells to bacterial lipopolysaccharide (LPS). In primary cultures of human umbilical vein and porcine aortic endothelial cells, LPS (0.3 to 3 micrograms/ml) induced significant concentration-dependent increases in cyclic GMP and 6-keto-PGF1 alpha, both of which were abolished in the presence of the selective bradykinin B2-receptor antagonist HOE 140 (0.1 microM). These LPS-induced increases in cyclic GMP and 6-keto-PGF1 alpha were short lived, being maximal after 5 min but were not apparent after 60 min. In parallel with these effects, LPS (30 micrograms/ml) induced a distinct, HOE 140-sensitive increase in the intracellular calcium concentration of human endothelial cells loaded with indo-1. In summary, these data suggest that the release of endothelium-derived kinin and subsequent stimulation of endothelial cells, followed by the enhanced production of NO and prostacyclin (PGI2), are implicated in the immediate hypotension induced by LPS in vivo.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Evidence that an L-arginine/nitric oxide dependent elevation of tissue cyclic GMP content is involved in depression of vascular reactivity by endotoxin.

1. The aim of this investigation was to study the relationship between contractile responsiveness, activation of the L-arginine pathway and tissue levels of guanosine 3':5'cyclic monophosphate (cylic GMP) in aortic rings removed from rats 4 h after intraperitoneal administration of bacterial endotoxin (E. coli. lipopolysaccharide, LPS, 20 mg kg-1). 2. LPS-treatment resulted in a reduction of the sensitivity and maximal contractile response to noradrenaline (NA). 3. Depression of the maximal contractile response was restored to control by 6-anilo-5,8-quinolinedione (LY 83583, 10 microM), which prevents activation of soluble guanylate cyclase. 4. Cyclic GMP levels in tissue from LPS-treated rats were 2 fold greater than cyclic GMP levels detected in tissue from control (saline-treated) rats. The LPS-induced increase in cyclic GMP content was observed both in the presence and absence of functional endothelium. 5. Addition of L-arginine 1 mM) to maximally contracted aortic rings produced significantly relaxation of rings from LPS-treated rats but not rings from control animals. In the LPS-treated group, addition of L-arginine was also associated with a significant increase in cyclic GMP content. L-Arginine had no effect on the cyclic GMP content of control rings. D-Arginine (1 mM) was without effect. 6. In rings from LPS-treated rats, NG-nitro-L-arginine methyl ester (L-NAME, 300 microM), an inhibitor of nitric oxide (NO) production, increased the contractile response to NA and prevented the LPS-induced increase in cyclic GMP content. In control rings, L-NAME increased the NA sensitivity only when the endothelium remained intact and reduced the cyclic GMP content of these rings to that of control endothelium-denuded rings. 7. These results demonstrate that LPS-induced hyporeactivity to NA occurs secondarily to activation of the L-arginine pathway and subsequent activation of soluble guanylate cyclase in vascular tissue. In addition they suggest that LPS induces the production of an NO-like relaxing factor in non-endothelial cells.

Aminoquinolines↗