Biomedical subjects

C M Brophy

Publications and source records attributed to C M Brophy.

At least 37 records · Page 2Linked to original sources

PubMed1997

Cyclic nucleotide-dependent vasorelaxation is associated with the phosphorylation of a small heat shock-related protein.

Activation of cyclic nucleotide-dependent signaling pathways leads to the relaxation of various smooth muscles. One of the major phosphorylation events associated with cyclic nucleotide-dependent vasorelaxation in bovine trachealis and carotid artery smooth muscle is the phosphorylation of two 20-kDa phosphoproteins with pI values of 5.7 and 5.9 (previously designated pp8 and pp3, respectively). The present studies sought to determine the identities of pp3 and pp8 in vascular smooth muscle. The phosphopeptide maps for the pp8 and pp3 proteins were similar. Preparative two-dimensional gel electrophoresis and amino acid sequencing of a peptide fragment of the pp3 protein revealed a sequence identical to a 20-kDa heat shock-related protein (HSP20) previously purified from skeletal muscle. Western blot and immunoprecipitation analysis with anti-HSP20 antibodies demonstrated that the pp3 and pp8 proteins are phosphorylated forms of HSP20. In addition, HSP20 could be phosphorylated in vitro by both cAMP-dependent protein kinase and cGMP-dependent protein kinase. These data suggest that the phosphorylation of the heat shock-related protein HSP20 is associated with cyclic nucleotide-dependent relaxation of vascular smooth muscle.

Animals↗

PubMed1997

Inadequate cerebral perfusion is an unlikely cause of perioperative stroke.

The purpose of this study was to determine the importance of hypoperfusion ischemia as a cause of stroke during carotid endarterectomy (CEA). A retrospective analysis of 128 consecutive CEA procedures were examined in patients at risk for hypoperfusion ischemia, namely, patients with occlusion of the contralateral carotid artery. All procedures were performed under general anesthesia without the use of a temporary indwelling shunt. Sixty-one percent of patients had cerebrovascular symptoms preoperatively and 39% were asymptomatic. The degree of stenosis of the carotid artery was 80%-99% in 67% (86/128) of patients, 60%-79% in 25% (32/128), 20%-59% in 7% (9/128), and 0-19% in 0.8% (1/128). The perioperative mortality was 0.8% (1/128), the incidence of permanent neurologic morbidity was 1.6% (2/128), and the incidence of transient neurologic morbidity was 3.9% (5/128). In conclusion, these data suggest that hypoperfusion ischemia is a rare cause of stroke during CEA even in patients with occlusion of the contralateral carotid artery and that CEA can be performed safely even in patients with contralateral occlusion without the use of a temporary indwelling shunt.

Aged↗

PubMed1997

Mitogen-activated protein kinase activation: an alternate signaling pathway for sustained vascular smooth muscle contraction.

PURPOSE: The vascular smooth muscle determines the dynamic caliber of the blood vessel and hence is the final effector cell in modulating vasomotor tone. Although considerable information is available regarding the physiologic agonists that induce contraction, less is known about the cellular signaling events that lead to long-lasting contractions or vasospasm. We examined the hypothesis that activation of mitogen-activated protein (MAP) kinase may be associated with sustained smooth muscle contractions. METHODS: Physiologic contractile responses were determined in intact bovine carotid artery smooth muscles in a muscle bath. Corresponding signaling events were determined with immunoblots using antiphosphotyrosine antibodies or immunoprecipitation of whole-cell phosphorylated strips of muscle. RESULTS: The tyrosine kinase inhibitor, genestein, significantly inhibited the magnitude of contractions induced by phorbol ester, endothelin, angiotensin, and serotonin. In addition, genestein inhibited the sustained phase of contractions induced by serotonin. Serotonin-induced vascular smooth muscle contractions were temporally associated with an increase in the phosphorylation of MAP kinase. CONCLUSIONS: These data suggest that the activation of MAP kinase is associated with sustained vascular smooth muscle contractions. Pharmacologic manipulation of MAP kinase activation may lead to new approaches to treat pathologic circumstances of increased vasomotor tone such as vasospasm.

Angiotensin II↗

PubMed1997

Cellular mechanisms of cyclic nucleotide-induced vasorelaxation.

PURPOSE: Endothelial-derived vasorelaxants such as prostacyclin and nitric oxide (NO) induce vascular smooth muscle relaxation through activation of cyclic nucleotide-dependent cellular signalling pathways. However, the specific events that lead to dissociation of actin and myosin and relaxation are not known. The purpose of this investigation was to determine the late phase signaling events that modulate vascular smooth muscle relaxation. METHODS: Fresh bovine carotid artery smooth muscle (BCASM) contractile responses were determined in a muscle bath under Ca(2+)-containing and Ca(2+)-free conditions. Physiologic responses were correlated with phosphorylation events using whole cell phosphorylation and two-dimensional gel electrophoresis. RESULTS: Cyclic nucleotide-dependent vasorelaxation can occur without detectable changes in intracellular Ca2+ concentrations. However, vascular smooth muscles that had been precontracted with the phosphatase inhibitor calyculin were refractory to relaxation. Vascular smooth muscle relaxation was associated with an increase in the phosphorylation of two 20 kDa proteins under Ca(2+)-containing and Ca(2+)-free conditions. CONCLUSIONS: These results suggest that Ca(2+)-independent mechanisms may also modulate vascular smooth muscle relaxation. Two possible late phase signaling mechanisms include phosphatase activation and an increase in the phosphorylation of two 20 kDa phosphoproteins.

Animals↗

PubMed1997

Small heat shock proteins and vasospasm in human umbilical artery smooth muscle.

Human umbilical artery smooth muscle is uniquely refractory to cyclic nucleotide-dependent vasorelaxation. Small heat shock proteins (HSPs) have been implicated as contractile regulatory proteins. Thus, we hypothesized that alterations in the phosphorylation of small HSPs may contribute to human umbilical artery smooth muscle vasospasm. Physiologic contractile responses were determined in a muscle bath and compared with phosphorylation events determined with whole-cell phosphorylation and 2-dimensional gel electrophoresis. Precontraction of bovine carotid artery smooth muscle with serotonin followed by relaxation with forskolin was associated with increases in the phosphorylation of HSP27 and HSP20. Precontraction of umbilical artery with serotonin followed by forskolin treatment led to increases in the phosphorylation of HSP27. However, the umbilical artery smooth muscle did not relax, nor was there an increase in the phosphorylation of HSP20 with forskolin treatment. These data suggest that impaired cyclic nucleotide-dependent relaxation of umbilical artery smooth muscle is associated with a lack of phosphorylation of HSP20.

Colforsin↗

PubMed1997

Activation of diacylglycerol in cultured endothelial cells exposed to cyclic strain.

Confluent bovine aortic endothelial cells (EC) were grown on flexible membranes and subjected to 10% average strain at 60 cycles/min for up to 500 s. A biphasic increase in diacylglycerol (DAG) occurred, with an initial transient peak at 10 s followed by sustained elevation to 500 s. The early peak corresponded to the transient formation of inositol 1,4,5-trisphosphate, demonstrating hydrolysis of L-alpha-phosphatidylinositol (PI) by PI-specific phospholipase C. To determine the origin of the sustained DAG phase, we incubated confluent bovine aortic EC with 1 microCi/ml [14C]myristate overnight and subjected them to cyclic strain. There was a decrease in phosphatidylcholine (PC) and a corresponding increase in DAG at 10 s and 250 s, suggesting PC hydrolysis with the generation of DAG at both an early (10 s) and a late (250 s) phase. [14C]phosphatidylethanol, a specific product of phospholipase D (PLD) in the presence of 1% ethanol, was measured in EC preincubated with [14C]myristate. Cyclic strain led to an immediate and sustained activation of PLD. Increased ethanol concentration led to a consistent decrease in DAG. Furthermore, when EC were pretreated with 1% ethanol, the strain-induced proliferative response was attenuated.

Animals↗

PubMed1996

Renal artery smooth muscle is refractory to contraction by angiotensin II.

The vasomotor responses of vascular smooth muscle from different vascular smooth muscle beds have not been well characterized. The purpose of this study was to compare the contractile responses of vascular smooth muscle from two vascular beds, the peripheral vascular bed (carotid artery) and the visceral vascular bed (renal artery) to vasoactive agonists. Fresh bovine carotid and renal artery smooth muscle contractile responses to serotonin, endothelin, angiotensin, and dopamine were determined in a muscle bath. Serotonin and dopamine cause rapidly developing sustained contractions in carotid and renal artery smooth muscle. The magnitude of the contractile response to serotonin is significantly greater in carotid artery and the magnitude of the response to dopamine is similar between carotid and renal artery. Endothelin induces a slowly developing sustained contraction of greater magnitude in renal artery. Angiotensin II causes transient contractile responses in carotid artery but renal artery smooth muscle is uniquely refractory to angiotensin stimulation. This lack of response to angiotensin II may be protective in the role of the kidney in regulating blood pressure through the renin-angiotensin system. Differences in receptor expression or affinity or in postreceptor cellular signaling events may account for these differential responses to endogenous vasoactive agonists.

Angiotensin II↗

PubMed1996

Nitric oxide is an autocrine feedback inhibitor of vascular smooth muscle contraction.

BACKGROUND: Substances that increase intracellular calcium ([Ca2+]i), such as potassium chloride and serotonin, are known to induce vascular smooth muscle (VSM) contraction. One form of nitric oxide synthase, which converts L-arginine to nitric oxide, exists as a Ca(2+)-calmodulin dependent enzyme. The objective of this study was to determine whether agonists that induce VSM contraction by increasing [Ca2+]i might also activate Ca(2+)-calmodulin dependent nitric oxide synthase in VSM. METHODS: Strips of bovine carotid arterial smooth muscle denuded of endothelium were equilibrated in a physiologic muscle bath. A maximal contractile response to high extracellular potassium chloride and serotonin was established. The strips were then preincubated with NG-monomethyl-L-arginine (L-NMMA), a structural analog of L-arginine and specific inhibitor of nitric oxide synthase, and again treated with either KCl or 5-hydroxytryptamine. RESULTS: The contractile responses of muscle strips to KCl or 5-hydroxytryptamine were significantly greater in muscle strips pretreated with L-NMMA than responses in the absence of L-NMMA (p < 0.02, Student's t test). To determine whether this response was Ca2+ dependent, phorbolester-induced contractions in Ca(2+)-free conditions were examined. No difference was noted in the magnitude of Ca(2+)-free, phorbol ester-induced contractions in the presence and absence of L-NMMA. CONCLUSIONS: These data thus suggest that Ca(2+)-calmodulin dependent nitric oxide synthase is functionally present in VSM and may function as an autocrine regulatory mechanism of VSM contraction.

Animals↗

PubMed1995

Impaired cyclic nucleotide-dependent vasorelaxation in human umbilical artery smooth muscle.

Activation of either the adenylate cyclase pathway with forskolin or the guanylate cyclase pathway with sodium nitroprusside fails to induce active relaxation of serotonin-precontracted human umbilical artery smooth muscle (HUASM) but causes active relaxation of serotonin-precontracted bovine carotid artery smooth muscle (BCASM). This difference in response appears to be unique to HUASM in that all other vascular muscles exhibit relaxation in response to these substances. Forskolin and sodium nitroprusside stimulation leads to respective increases in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) concentrations in HUASM and BCASM. cAMP- and cGMP-dependent protein kinases are both present in HUASM and can be activated in homogenates of HUASM by the addition of exogenous cAMP and cGMP, respectively. When either forskolin or nitroprusside acts in BCASM, two low-molecular-weight proteins display an increase in the extent of phosphorylation. Neither protein shows such an increase when HUASM is treated with either agent. Thus the inability of HUASM to display active relaxation appears to be secondary to impaired activation of cyclic nucleotide-dependent protein kinases. The refractoriness to active relaxation may contribute to the vasospasm that occurs in the umbilical vasculature with parturition.

1-Methyl-3-isobutylxanthine↗

PubMed1993

Phospholipase C: a putative mechanotransducer for endothelial cell response to acute hemodynamic changes.

Endothelial cells (EC) in vivo are exposed to a multitude of physical forces with each pulse of the cardiac cycle. Ongoing studies support the concept that EC respond to these forces through specific signal transduction pathways. Previous investigations in our laboratory have shown that EC respond to the initiation of cyclic strain or to an acute increase in cyclic strain frequency with the production of inositol 1,4,5-trisphosphate (IP3). This study demonstrates that EC also respond to an acute decrease in cyclic stretch frequency with a transient increase in IP3 production. Thus, EC detect both increases and decreases in cyclic stretch frequency with phospholipase C (PLC) activation leading to IP3 generation.

Animals↗

PubMed1993

Defecation syncope secondary to functional inferior vena caval obstruction during a Valsalva maneuver.

This report describes a case of defecation syncope secondary to functional inferior vena cava (IVC) obstruction. Preoperative hemodynamic assessment revealed a marked decrease in blood pressure and IVC obstruction when the patient performed a Valsalva maneuver. The intraoperative approach included continuous hemodynamic monitoring as well as transesophageal ultrasonography to assess IVC patency during surgical mobilization of the IVC. Functional obstruction of the IVC at the diaphragmatic hiatus was identified, and this obstruction was relieved with extensive mobilization of the IVC and right crural myotomy. This report describes an effective surgical approach to a rare functional disorder involving the IVC.

Adult↗

PubMed1993

Gastrointestinal vascular and ischemic syndromes.

Among the vascular disorders of the small intestine, two major categories are mesenteric ischemia and occult gastrointestinal bleeding secondary to a mucosal or muscular lesion. Mesenteric ischemia remains a clinical entity with a high mortality. Recent advances in the understanding of the pathogenesis of mesenteric ischemia have focused on the role of the neutrophil in modulating reperfusion injury. The advent of duplex scanning has provided a noninvasive method to detect hemodynamically significant stenoses in the mesenteric vessels. Effective small bowel endoscopy remains a critical requirement for endoluminal intestinal enteroscopy, and its application has proved of increasing advantage in the localization of small intestinal lesions that may be the source of occult gastrointestinal bleeding.

Gastrointestinal Hemorrhage↗

PubMed1993

Expression and sequence of the gene for tissue inhibitor of metalloproteinases in patients with abdominal aortic aneurysms.

PURPOSE: The tissue inhibitors of metalloproteinases (TIMPs) are major inhibitors of several enzymes that are destructive to connective tissue, and TIMP-1 has been reported to be deficient in the wall of abdominal aortic aneurysms. This deficiency could represent failure of expression resulting from either local tissue conditions or mutation in the primary structure of the gene (or one of its regulatory elements). METHODS: Southern blotting techniques were used to examine the possibility of global deletions or inserts in the gene (14 patients); Northern blot techniques were performed to examine the expression of the mRNAs in cultured fibroblasts under basal conditions (six patients); and sequence analysis of the cDNA derived from fibroblast mRNAs was done after amplification by polymerase chain reaction (six patients). RESULTS: The Southern blots revealed a normal distribution of the known alleles of the gene without unique restriction-length polymorphisms. Fibroblast expression of TIMP mRNA was normal under basal conditions. Sequence analysis of the cDNAs revealed an identical-point polymorphism in two of the six patients (a single base pair substitution of C-->T at the third position in codon 101), but the amino acid was conserved. CONCLUSION: The studies reported here do not support the hypothesis that deficiency of TIMP-1 in specimens of aorta of patients with abdominal aortic aneurysms results from a primary genetic defect.

Aortic Aneurysm, Abdominal↗

PubMed1992

Characterization of an elastase from aneurysmal aorta which degrades intact aortic elastin.

Accumulating evidence suggests that abdominal aortic aneurysms (AAA) are due to a pathologic process which results in the destruction of aortic elastin and other matrix components. In this study, protein extractions were performed on both aneurysmal and normal aorta. Extracts were applied to frozen section of normal aorta either alone or in combination with 10 mM ethylenediaminetetraacetic acid, recombinant tissue inhibitor of metalloproteases, 10 mM zinc, and 5 mM phenylmethylsulfonyl fluoride, under conditions where calcium was removed from the buffer. After incubation, the sections were stained for elastin and evaluated by computerized morphometry. Aneurysm extracts, only in the presence of calcium, showed significant elastolytic activity characterized by destruction of intact elastic lamellae that was inhibited by ethylenediaminetetraacetic acid, the recombinant metalloprotease inhibitor, and zinc. Phenylmethylsulfonyl fluoride showed no inhibitory activity. Healthy aortic extract showed no elastolytic activity. This inhibitory profile is consistent with a metalloenzyme. We conclude that aneurysmal aorta contains elastolytic activity that is secondary to a metalloenzyme which is not present in normal aorta. This activity may play a role in the destruction of the elastin matrix that is seen in AAA's.

Aorta, Abdominal↗

PubMed1992

Disruption of proximal axillobifemoral bypass graft anastomosis.

Anastomotic disruption of axillobifemoral bypass grafts is a rare but serious complication. Previously described causes of anastomotic disruption include the following: infection, technical errors, and severe mechanical stress. In this report we describe a proximal anastomotic disruption of an axillobifemoral bypass graft in which the suture line remained intact on the axillary artery and tore through the polytetrafluoroethylene graft. This suggests a possible role of material failure contributing to axillobifemoral anastomotic disruption.

Aged↗

PubMed1992

Peripheral vascular bypass in juvenile-onset diabetes mellitus: are aggressive revascularization attempts justified?

This study was performed to evaluate the results of peripheral vascular reconstruction for arterial occlusive disease in patients with juvenile-onset diabetes mellitus. The results of 67 bypass procedures performed on 60 patients with juvenile-onset diabetes mellitus between Jan. 1, 1984 and Dec. 31, 1989, were reviewed. These patients had a mean age of 44.4 years (range, 29 to 59 years), with an average age of onset of diabetes mellitus of 9.8 years (range, 1 to 19 years). These procedures comprised 5.5% (67 to 1214) of the bypasses performed on diabetic patients during the same time period at a single institution. Fifty-four of 67 (91%) procedures were performed for limb salvage. Fifty-four (81%) procedures were primary infrainguinal bypasses with saphenous vein (femoropopliteal 19, femorodistal or popliteal-distal 35). Six procedures (9%) were revision procedures, four (6%) were in-flow procedures, and three (4%) were infrainguinal procedures with polytetrafluoroethylene. Thirty-day morbidity and mortality rates were 31% and 0%, respectively. Actuarial patency and limb salvage rates of the primary vein graft group were 66.0% (+/- 10.7) and 83.4% (+/- 8.0%), respectively, at 24 months. Cumulative survival of the entire group at 2 years was 84.1%. Although follow-up in this study is relatively short (24 months), the results suggest that the outcome of vascular reconstruction in patients with juvenile-onset diabetes mellitus is acceptable when compared with procedures performed in adult-onset diabetic and nondiabetic populations. The presence of juvenile-onset diabetes mellitus should not diminish the vascular surgeon's expectations of a successful outcome when considering lower extremity revascularization in these patients.

Actuarial Analysis↗

PubMed1991

Spiral laminar flow in arteries?

Spiral blood-flow patterns in infrainguinal blood-vessels were observed at angioscopy in 54 patients who underwent peripheral vascular reconstruction; the endoluminal surface had spiral folds in 51 of 75 arteries examined. Spiral flow patterns, congruous with inherent endoluminal anatomical features, might more accurately represent blood-flow in infrainguinal arteries than current models of laminar flow.

Arteries↗

PubMed1991

A new canine model for evaluating blood prosthetic arterial graft interactions.

Various models have been proposed to examine blood-prosthetic materials interactions in terms of the effect of the prosthetic material on platelet structure and function, blood coagulation and fibrinolysis, and tissue infiltrates (cellular or acellular). In addition, these models have been used to examine the change in the graft surface over time. Particular difficulties in examining graft-materials interactions include species differences, short residence time for blood-materials interactions with commonly employed short grafts, and length of study limitations with ex vivo shunts. In this paper we report a canine, carotid-aorta subcutaneous prosthetic graft model. The specific advantages of this model are the length of the graft, which allows prolonged contact of blood with the prosthetic surface; the subcutaneous location of the graft, which allows repeated sampling of blood along the graft; and the healing characteristics of canine grafts. We selected the canine model because the healing characteristics are morphologically similar to those in humans in that endothelialization of the prosthetic surface is limited. Other models, such as the pig, are favored for use when examining blood coagulation, platelet, or fibrinolytic studies; however, these models can fully endothelialize prosthetic surfaces.

Animals↗