Stuart Myers - Academia.edu (original) (raw)

Papers by Stuart Myers

Journal of Applied Physiology, 1997

Rothenbach, Patricia, Richard H. Turnage, Jose Iglesias, Angela Riva, Lori Bartula, and Stuart I.... more Rothenbach, Patricia, Richard H. Turnage, Jose Iglesias, Angela Riva, Lori Bartula, and Stuart I. Myers. Downstream effects of splanchnic ischemia-reperfusion injury on renal function and eicosanoid release. J. Appl. Physiol.82(2): 530–536, 1997.—This study examines the hypothesis that intestinal ischemia-reperfusion (I/R) injury contributes to renal dysfunction by altered renal eicosanoid release. Anesthetized Sprague-Dawley rats underwent 60 min of sham or superior mesenteric artery (SMA) occlusion with 60 min of reperfusion. The I/R groups received either allopurinol, pentoxifylline, 1-benzylimidazole, or carrier before SMA occlusion. In vivo renal artery blood flow was measured by Transonic flow probes, the kidneys were then perfused in vitro for 30 min, and the effluent was analyzed for eicosanoid release and renal function. Intestinal I/R caused a twofold increase in the ratio of renal release of thromboxane B2to prostaglandin E2and to 6-ketoprostaglandin F1αcompared with the ...

The Internet Journal of Surgery, 2004

Handgrip strength testing has long been used as a tool in the clinical assessment of hand and wri... more Handgrip strength testing has long been used as a tool in the clinical assessment of hand and wrist injury. Of particular interest have been attempts to utilise strength testing to detect sincerity of maximum voluntary effort. This has particular relevance to monetary payment in worker's compensation, motor vehicle accident and medical insurance claims. This paper recommends using the Jamar dynamometer as a measurement tool because it is the most widely researched and reported grip strength measurement device available. It also looks at the different tests developed to determine an individual's level of effort during grip strength testing. A protocol is suggested for a time and cost efficient grip strength assessment that should be used in conjunction with clinical acumen when assessing hand and wrist disability.

Gastroenterology, 1993

Bac&Yound: Acute cholecystitis increases gallbladder prostanoid synthesis. The percent study exam... more Bac&Yound: Acute cholecystitis increases gallbladder prostanoid synthesis. The percent study examined the hypothesis that increased endogenous gallbladder release of prostaglandin I, (PGI,) after bile duct ligation is caused by both increased ductal pressure and altered biliary lipids. Methods: Prostanoid release, biliary lipids, and in vitro fluid absorption of sham gallbladders were compared with those of gallbladders in which acute cholecystitis was induced after common bile duct ligation for 6, 24, and 72 hours. Results: Bile duct ligation for 6, 24, and 72 hours increased gallbladder PGI, release twofold and increased gallbladder bile levels of lysolecithin and taurine-conjugated bile acids fivefold compared with sham groups (P < 0.05). In vitro gallbladder fluid absorption was decreased by 50% or more in the 6-, 24-, and 72-hour bile duct-ligated groups (P < 0.05) but was reversed by indomethacin only in the 6-hour ligated group. Conclusions: Decreased gallbladder fluid absorption following bile duct ligation for 6 hours was caused by increased gallbladder release of PGI,. Decreased gallbladder fluid absorption following bile duct ligation for 24 and 72 hours was not a prostanoid-mediated process (not reversed by indomethacin) but was associated with increased bile levels of proinflammatory biliary lipids. Male New Zealand white rabbits (2-3 kg) were anesthetized with 0.4 mg/kg of an anesthetic cocktail made up of ketamine (75 mg/mL) and acepromazine (2.5 mg/mL) and maintained on halothane. The abdomen was shaved and washed with soap and then by alcohol and Betadine (General Medical Corp., Richmond, VA). A midline laparotomy was performed, and the common bile duct was ligated (before entry into the duodenum) with a 4-O silk suture and compared with that of sham-operated controls.'5J6 Avoidance of the gallbladder allowed subsequent rapid removal. Controls did not undergo anesthesia or surgery. All animals (100% survival) tolerated water and standard chow without discomfort. Guidelines for the ethical use of animals instituted by the University of Texas Southwestern Medical Center and the Dallas Veterans Administration Medical

Biochemical Journal, 1992

Ligation of the common bile duct (BDL) in the male rabbit resulted in increased gall-bladder micr... more Ligation of the common bile duct (BDL) in the male rabbit resulted in increased gall-bladder microsomal total cyclo-oxygenase activity with prostaglandin E2 (PGE2) and 6-oxoprostaglandin F1 alpha [6-oxo-PGF1 alpha, stable metabolite of prostaglandin I2 (PGI2; prostacyclin)] as the major prostanoids synthesized after 24 and 72 h. Kinetic analysis of gallbladder microsomal membrane fractions incubated with increasing levels of [14C]arachidonic acid indicated that BDL for 24 and 72 h did not change substrate affinity (apparent Km) but markedly increased the rate of conversion (apparent Vmax.) suggesting the presence of more total enzyme responsible for synthesis of 6-oxo-PGF1 alpha and PGE2. BDL for 24 and 72 h significantly increased gall-bladder tissue slice basal release of 6-oxo-PGF1 alpha, but not PGE2, when compared with the controls. Gall-bladder slice release of PGE2 was 3-fold less than 6-oxo-PGF1 alpha in the control gall-bladder slices. Immunoblot analysis of 72 h BDL gall-b...

Biochemical Journal, 1981

The ipsilateral kidney was removed from a rabbit 48h after unilateral partial renal-vein-constric... more The ipsilateral kidney was removed from a rabbit 48h after unilateral partial renal-vein-constriction and was perfused with Krebs–Henseleit media at 37°C. Hourly administration of a fixed dose of bradykinin to the renal-vein-constricted kidney demonstrated a marked time-dependent increase in the release of bioassayable prostaglandin E2 and thromboxane A2 into the venous effluent as compared with the response of the contralateral control kidney. The renal-vein-constricted kidney produced up to 60 times more prostaglandin E2 in response to bradykinin after 6h of perfusion as compared with the contralateral kidney; thromboxane A2 was not demonstratable in the contralateral kidney. Inhibition of protein synthesis de novo in the perfused renal-vein-constricted kidney with cycloheximide lessened the hormone-stimulated increase in prostaglandin E2 by 94% and in thromboxane A2 by 90% at 6h of perfusion. Covalent acetylation of the renal cyclo-oxygenase by prior oral administration of aspiri...

Annals of Vascular Surgery, 2008

The current study was designed to investigate our hypotheses that balloon-expandable covered sten... more The current study was designed to investigate our hypotheses that balloon-expandable covered stents display acceptable function over longitudinal follow-up in patients with complex vascular pathology and provide a suitable alternative for the treatment of recurrent in-stent restenosis. All stents were Atrium iCast, which is a balloon-mounted, polytetrafluoroethylene-covered stent with a 6F/7F delivery system. A retrospective review was performed of 49 patients with 66 stented lesions. Data were analyzed with life tables and t-tests. The most commonly treated vessels were the iliac (61%) and renal (24%) arteries. Indications for covered stent placement were unstable atheromatous lesions (50%), recurrent in-stent restenosis (24%), aneurysm (8%), aortic bifurcation reconstruction (7.5%), dissection (4.5%), endovascular aneurysm repair-related (4.5%), and stent fracture (1.5%). Patency was assessed by angiogram or duplex ultrasonography. The primary end point was patency and secondary end points were technical success and access-site complications. Mean follow-up was 13 months (range 1.5-25). The technical success rate was 97%. Unsuccessful outcomes were due to deployment error (n ¼ 1) and stent malpositioning (n ¼ 1). The cohort (n ¼ 64) 6-and 12-month primary patency rates were 96% and 84%, respectively. Twelve-month assisted primary patency was 98%. Iliac artery stents (n ¼ 38) had a primary patency of 97% at 6 months and 84% at 12 months with an assisted primary patency of 100% at 12 months. Renal artery stents (n ¼ 16) had a primary patency of 92% at 6 months and 72% at 12 months with an assisted primary patency of 92% at 6 and 12 months. Stents placed for recurrent in-stent restenosis (n ¼ 16) had a primary patency of 85%, assisted primary patency of 93%, and a 15% restenosis rate at 12 months. Specifically, stents placed for renal artery recurrent in-stent restenosis (n ¼ 10) had a primary patency of 73%, assisted primary patency of 82%, and a restenosis rate of 27%. The restenosis rate included two renal artery occlusions in patients noncompliant with clopidogrel use and resulted in ipsilateral kidney loss in both patients. In-stent peak systolic velocities decreased significantly (p < 0.05) from preoperation to 12 months in iliac stents and to 18 months in renal stents. Ankle-brachial index increased significantly in iliac stents from preoperation (0.62 ± 0.18) to 18 months (0.86 ± 0.16). Successful exclusion of atheromatous lesions and aneurysm/dissection/endoleak was 100%. Access-site complications occurred in 6%: pseudoaneurysm (n ¼ 2), dissection (n ¼ 1), and bleeding (n ¼ 1). Balloon-expandable covered stents have an acceptable primary patency with an excellent assisted patency after salvage angioplasty. The clinical utility of this technology is broad for the treatment of aneurysms, extravasation, unstable atheromatous lesions, and recurrent in-stent restenosis.

Annales de Chirurgie Vasculaire, 2008

Surgery, 1998

THE PULMONARY MICROVASCULATURE is an important target for the systemic inflammatory response asso... more THE PULMONARY MICROVASCULATURE is an important target for the systemic inflammatory response associated with intestinal ischemia-reperfusion injury (IR). Previous studies in our laboratory 1 and that of other investigators 2,3 have suggested that nitric oxide (NO) release may be an important protective mechanism by which the lung responds to remote organ injury. This conclusion is based principally on the observation that interventions that increase NO availability attenuate the leakage of plasma proteins into the pulmonary parenchyma, whereas inhibition of NO synthesis appears to exacerbate this injury. 1-3 Others have suggested that NO may play a direct pathogenic role in the development of acute lung injury. 4 These disparate findings are likely related to differences in experimental models and the varying specificity of commonly used nitric oxide synthase (NOS) inhibitors. 5 The latter factor is likely to be particularly important, because the most commonly used agents, substituted L-arginine analogues such as N G-nitro-L-arginine methylester, inhibit principally the constitutive isoforms of NOS with much less activity for the inducible isoform. 5-7 This is likely to be of significance because the constitutive release of picomolar quantities of NO by endothelial cells is an important determinant of normal microvascular tone, permeability, and cellular adhesion. 8-10 In contrast, the inducible

Science, 2004

Female gender affords relative protection from cardiovascular disease until the menopause. We rep... more Female gender affords relative protection from cardiovascular disease until the menopause. We report that estrogen acts on estrogen receptor subtype alpha to up-regulate the production of atheroprotective prostacyclin, PGI 2 , by activation of cyclooxygenase 2 (COX-2). This mechanism restrained both oxidant stress and platelet activation that contribute to atherogenesis in female mice. Deletion of the PGI 2 receptor removed the atheroprotective effect of estrogen in ovariectomized female mice. This suggests that chronic treatment of patients with selective inhibitors of COX-2 could undermine protection from cardiovascular disease in premenopausal females.

Journal of Vascular Surgery, 2008

A 65-year-old female presented with upper gastrointestinal hemorrhage thirty years following an a... more A 65-year-old female presented with upper gastrointestinal hemorrhage thirty years following an aorta-to-right renal artery bypass constructed with saphenous vein. Upper endoscopy demonstrated a duodenal ulcer, and a CAT scan demonstrated aneurysmal degeneration of her renal artery bypass with duodenal impingement. Laparotomy demonstrated erosion of the aneurysm through the posterior wall of the duodenum; extra-anatomic renovascular reconstruction and primary duodenal repair was performed. Although aneurysmal degeneration of intraabdominal saphenous vein grafts is well described and rupture likewise reported, this report represents the first description of an intraabdominal autogenous vein graft aneurysm presenting with gastrointestinal erosion and fistula.

Journal of Vascular Surgery, 2009

With respect to outcome evaluation bias, Drs Brar and Gray mention the disparity in neurological ... more With respect to outcome evaluation bias, Drs Brar and Gray mention the disparity in neurological or National Institute of Health (NIH) Stroke Scale evaluations, which is standard of care in CAS but not CEA resulting in under-reporting. The authors concede that lack of neurological evaluations in standard of care practices for CEA is a limitation of this real-world registry. However, it is also unreasonable to impose neurological evaluation in this patient population due to cost and lack of reimbursement for such neurological evaluation regarding the vast majority of patient who are asymptomatic after CAS and CEA. The authors would like to reiterate what it was concluded at the end of the manuscript that "The debate about the interpretation of the results of this study as well as results of other CAS studies will continue until randomized trials such as International Carotid Stenting Study (ICSS) in Europe and Carotid Revascularization Endarterectomy vs. Stenting Trial (CREST) in North America are reported." 1

Journal of Vascular Surgery, 2005

A 58-year-old man with hypertension, severe abdominal pain, and pulseless extremities was diagnos... more A 58-year-old man with hypertension, severe abdominal pain, and pulseless extremities was diagnosed with an isolated abdominal intramural hematoma (IMH). The IMH extended from the distal descending thoracic aorta to just proximal to the renal arteries. ␤-Blockade treatment resolved the abdominal pain but induced progressive oliguria; decreasing ␤-blockade treatment increased urine output but caused return of abdominal pain. An axillobifemoral bypass allowed distal perfusion and retrograde visceral artery perfusion while maintaining normal blood pressure. The abdominal pain resolved, urine output increased, and the patient was discharged on day 7. Six months later the patient required an emergent thrombectomy of the axillobifemoral graft and normal antegrade aortic flow was found. A computed tomography scan showed resolution of the IMH.

Journal of Vascular Surgery, 1993

Journal of Vascular Surgery, 1995

The purpose of this study was to determine the effect of desmopressin acetate (DDAVP) on blood lo... more The purpose of this study was to determine the effect of desmopressin acetate (DDAVP) on blood loss, transfusion requirements, and thromboembolic complications in patients undergoing elective aortic operations. Methods: A randomized, double-blind trial was carried out during a 3-year period with patients receiving 20 wg DDAVP or identical-appearing placebo at the time of aortic cross-clamp placement. In addition to major bleeding and thromboembolic end points, bleeding times and platelet counts were monitored serially. Results: Forty-three patients were randomized to receive DDAVP, and 48 were assigned to a placebo. An equivalent proportion of patients with aneurysm and patients with occlusive disease was in each group. In spite of mild prolongation in the postoperative bleeding times and moderate thrombocytopenia, DDAVP had no beneficial effect on blood loss or transfusion requirements. Total blood transfusion amotmt (mean-+ standard deviation) for patients receiving DDAVP was 3.1 + 3.0 U compared with 2.7 +-3.0 U for those receiving placebo. For all patients the period associated with the greatest blood loss was the time between heparin administration with cross-clamp application and reversal of heparin with protamine sulfate. The incidence of major thromboembolic complications was similar in both groups. Conclusion: Thrombocytopenia and mild platelet dysfunction are common after aortic operation, but DDAVP does not improve hemostasis or lessen transfusion requirements. This study does not rule out a beneficial effect of DDAVP in patients who are undergoing more complex aortic operations or who have major hemostatic aberrations. (J VAse SuRa 1995;22:223-30.) Desmopressin acetate, 1-deamino-8-D-arginine vasopressin (DDAVP), is a synthetic vasopressin analog that lacks vasoconstrictor activity and acutely increases levels of Factor VIII and von Willebrand factor (vWF) when administered intravenously. 1 It has been used to improve hemostasis in patients with mild hemophilia and von Willebrand's disease; it shortens the bleeding time in these patients apparently by inducing endothelial release of large multi-From the

Circulation Research, 1980

Isolated perfused kidneys removed from a rabbit 24-48 hours after renal vein constriction exhibit... more Isolated perfused kidneys removed from a rabbit 24-48 hours after renal vein constriction exhibited a markedly enhanced release of renal prostaglandins (PG's) induced by vasoactive peptides. Stimulation of the perfused renal vein-constricted kidney with 300 ng of bradykinin (BK) caused the release of 5980 ± 1409 ng of PGE 2 compared to a release of 290 ± 45 ng from the contralateral control kidney. Infusion of indomethacin abolished the PGE 2 formation (confirmed by radiochromatography) in both the renal vein-constricted and contralateral kidneys. Bradykinin and angiotensin II stimulation of the renal vein-constricted kidney (but not the contralateral kidney) also revealed the presence in the renal venous effluent of a rabbit aorta-contracting substance (RCS). Identification of the RCS as thromboxane A 2 (TxA 2) was confirmed by determining the biological half life (38 ± 6 sec) in comparison with standard TxA 2 (30 ± 3 sec) and PG endoperoxide (135 ± 13 sec). Incubation with [ l4 C]arachidonate of the renal vein-constricted cortical or medullary microsomes resulted in the formation of [ 14 C]thromboxane B 2. The renal thromboxane synthetase was inhibited by preincubation with imidazole. This study demonstrates exaggerated prostaglandin and thromboxane production by the kidney with renal vein constriction. These in vitro experiments suggest that relative changes in cortical synthesis of vasodilating PGE 2 and vasoconstricting TxA 2 may function to modulate renal vascular resistance in states of increased renal venous pressure.

Canadian Journal of Anesthesia/Journal canadien d'anesthésie, 2007

Anales de Cirugía Vascular, 2008

Annals of Surgery, 1990

The effect of reperfusion following hemorrhagic shock on splanchnic prostanoid release was studie... more The effect of reperfusion following hemorrhagic shock on splanchnic prostanoid release was studied. Anesthetized male rats were bled to a mean arterial blood pressure of 30 mmHg for 30 minutes and either killed or treated with shed blood for 60 minutes and then killed. The superior mesenteric arterial bed was cannulated and perfused in vitro with oxygenated Krebs. Collected venous effluent (up to 180 minutes) was analyzed for 6-keto-PGF1 alpha (PGI2 metabolite), PGE2, PGF2 alpha, and thromboxane B2 by radioimmunoassay in shock, shock plus reperfusion, and sham groups. The major prostanoid released was 6-keto-PGF1 alpha and was three times higher in the shock group compared to the sham group (p less than 0.05). Reperfusion of shed blood abolished the increase in 6-keto-PGF1 alpha found in the shock group (p less than 0.05). These data show that the attempt of the rat splanchnic bed to compensate for hemorrhagic shock by increasing release of PGI2 (potent vasodilator) was abolished during reperfusion of blood.

Circulation Research, 1989

Lower torso ischemia and reperfusion lead to respiratory dysfunction characterized by pulmonary h... more Lower torso ischemia and reperfusion lead to respiratory dysfunction characterized by pulmonary hypertension and increased lung microvascular permeability. This is associated with lung leukosequestration and thromboxane (TX) generation. This study tests the role of elevated TX levels following muscle ischemia in mediating remote lung injury. Anesthetized sheep prepared with chronic lung lymph fistulae underwent 2 hours of bilateral hind limb tourniquet ischemia. In untreated controls (n = 7), 1 minute after reperfusion there was a transient increase in plasma immunoreactive (i)-TXB2 levels from 211 to 735 pg/ml (p less than 0.05), and at 30 minutes, lung lymph i-TXB2 levels rose from 400 to 1,005 pg/ml (p less than 0.05). At 1 minute, the mean pulmonary arterial pressure (MPAP) increased from 13 to 38 mm Hg (p less than 0.05) and pulmonary microvascular pressure (Pmv) from 7 to 18 mm Hg (p less than 0.05). Lung lymph flow (QL) rose from 4.3 to 8.3 ml/30 min (p less than 0.05), the l...

The American Journal of Surgery, 1986

The external carotid artery is a major collateral pathway for retinal and cerebral blood flow in ... more The external carotid artery is a major collateral pathway for retinal and cerebral blood flow in the presence of chronic internal carotid artery occlusion. Naturally occurring anastomotic channels between external carotid branches and the intracranial cerebral circulation have been well demonstrated in several studies [I-4]. Paradoxically, these channels may also provide access to the brain and eye for events leading to recurrent neurologic symptoms in patients with occlusion of the internal carotid artery. Transient ocular and cerebral ischemic episodes have been attributed to microemboli emanating from the internal carotid stump [5] or to decreased flow through an external carotid stenosis ]61. External carotid revascularization has been advocated to correct stenoses and to obliterate sources of microemboli. This procedure has gained in popularity after reports of patients who obtained relief of symptoms [5,7-g]. However, the durability of the operation has not been clearly demonstrated. Moreover, the safety of the procedure in a patient population at increased risk for stroke has not been proved. This retrospective study was conducted to determine the safety and durability of applying this operation to a select group of patients with diffuse cerebral atherosclerosis. Patlents and Methods During a 31 month period, 14 external carotid revascularizations were performed at the Dallas Veterans Administration Hospital in 13 patients with ipsilateral internal carotid artery occlusion. Preoperative symptoms included amaurosis fugax in six patients, hemispheric transient ischemic attacks in five patients, and ipsilateral stroke in