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D M Shah

Publications and source records attributed to D M Shah.

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

Characterization of acquired resistance in lesion-mimic transgenic potato expressing bacterio-opsin.

The lesion-mimic mutants of certain plants display necrotic lesions resembling those of the hypersensitive response and activate local and systemic defense responses in the absence of pathogens. We have engineered a lesion-mimic phenotype in transgenic Russet Burbank potato plants through constitutive expression of a bacterio-opsin (bO) proton pump derived from Halobacterium halobium. Transgenic potato plants exhibiting a lesion-mimic phenotype had increased levels of salicylic acid and overexpressed several pathogenesis-related messenger RNAs, all hallmarks of systemic acquired resistance (SAR). The lesion-mimic plants also displayed enhanced resistance to the US1 isolate (A1 mating type) of a fungal pathogen, Phytophthora infestans, a causal agent of late blight disease. In contrast, little resistance was observed against the US8 isolate (A2 mating type) of this pathogen. Furthermore, a majority of the transgenic plants displaying the lesion-mimic phenotype had increased susceptibility to potato virus X. The tubers of these plants were not resistant to the bacterial pathogen Erwinia carotovora. These results indicate that expression of bO can result in the activation of defense responses in transgenic potato plants and show for the first time that bO expression can confer resistance to a pathogenic fungus. However, our results also demonstrate that like SAR, this "engineered" resistance is likely to be limited to certain pathogens and particular cultivars.

Bacteriorhodopsins↗
PubMed1997

Choice of peroneal or dorsalis pedis artery bypass for limb salvage.

BACKGROUND: Arterial reconstructions performed for limb salvage have increasingly used peroneal and dorsalis pedis arteries as outflow vessels. However, there have been few published reports comparing the patency and limb salvage of these alternative outflow tracts. In this report, we have examined our experience with the peroneal and dorsalis pedis artery bypasses for limb salvage. METHODS AND MATERIALS: During a 19-year period, more than 3,500 infrageniculate reconstructions were performed for limb salvage at our institution. Eight hundred and eighty were performed to the peroneal artery and 291 were performed to the dorsalis pedis. Patients' demographics were similar in both groups. Sixty-three percent of patients were male and 52% were diabetic. All surgeries were performed for patients with critical ischemia. In situ technique was used in 68% of peroneal reconstructions and 66% of dorsalis pedis bypasses, respectively. Translocated veins were used in 28% of bypasses and spliced veins were used in 32%. RESULTS: Secondary patency rates to the peroneal reconstructions were 89% and 76% at 1 and 5 years, and 88% and 68% for the dorsalis pedis bypasses, respectively. No statistical difference was found. Sixteen (1.8%) of peroneal artery reconstructions were hemodynamic failures and four (1.4%) were hemodynamic failures in the dorsalis pedis group. Wound complications were observed in 19 (2.2%) of the peroneal group and 7 (2.4%) of the dorsalis pedis group. Limb salvage rates for the peroneal artery are 96% and 93% at 1 and 5 years, respectively, and 95% and 87% for the dorsalis pedis reconstructions, respectively. CONCLUSION: This experience indicates that both peroneal and dorsalis pedis artery reconstructions have acceptable patency and limb salvage rates. Selection of one of these two outflow tracts, when a choice exists, may depend on the conduit limitation and the adjacent tissue infection. However, both outflow tracts are durable and hemodynamically effective for limb salvage.

Arteries↗
PubMed1996

Isolation and characterization of a 30 kDa protein with antifungal activity from leaves of Engelmannia pinnatifida.

During the course of screening plants for novel antifungal activity, we found that a high-molecular-mass fraction of an extract from leaves of Engelmannia pinnatifida exhibited potent and broad-spectrum antifungal activity. In this study a 30 kDa protein from E. pinnatifida leaves was purified to homogeneity by ammonium sulphate precipitation, gel filtration, Mono-Q and C18 reverse-phase column chromatographies. The purified protein showed potent antifungal activity against various plant pathogens with as little as 50 ng. The N-terminal amino acid sequence of the purified protein was determined as XXTKFDFFTLALQXPAXF, where X indicates an unidentified residue. This sequence showed 35-50% sequence identity with purified style glycoproteins associated with self-incompatibility from wild tomato, tobacco and petunia, a phosphate-starvation-induced ribonuclease from cultured tomato cells and the SIR 63.4 kDa protein from yeast.

Amino Acid Sequence↗
PubMed1996

ATP-MgCL2 reduces intestinal permeability during mesenteric ischemia.

ATP-MgCl2 has been demonstrated to have beneficial attributes in numerous models of organ ischemia. In this study we examined whether ATP-MgCl2 could decrease permeability in ischemic segments of rat ileum. Ileal segments (nonischemic and ischemic) from the same rat were cannulated and perfused, and the plasma to lumen clearance of 51Cr-EDTA was measured. Ischemia increased permeability from a baseline value of 0.59 +/- 0.14 (mean +/- SEM in ml/min/g dry wt of intestine) to 1.10 +/- 0.14 at 90 min (n = 12), significantly higher than that of the nonischemic segments (0.55 +/- 0.07) at 90 min (P < 0.05). This was associated with a significant reduction in blood flow from 0.84 +/- 0.08 (n = 4) (mean +/- SEM ml/min/g wet wt of intestine) to 0.16 +/- 0.06 (n = 4) (P < 0.05) as measured by labeled microspheres. Rats receiving ATP-MgCl2 (100 micromol) (n = 8) pretreatment showed no increase in clearance over 90 min (baseline 0.69 +/- 0.07; 90 min 0.70 +/- 0.07) and no significant difference in blood flow from untreated ischemic segments (0.21 +/- 0.9) (n = 4). Tissue ATP levels determined enzymatically were significantly reduced by 5 min postischemia to 4.19 +/- 0.35 (n = 7) (P < 0.05) from a control value of 6.77 +/- 0.77 micromol/g dry wt (n = 14). ATP levels remained depressed at 30 min (3.45 +/- 0.35) and 90 min (3.38 +/- 0.26). ATP-MgCl2 treatment did not significantly alter these tissue ATP levels. These data indicate that ATP-MgCl2 prevents the increase of 51Cr-EDTA permeability during ischemia without alterations in tissue ATP levels or increases in intestinal blood flow.

Adenosine Triphosphate↗
PubMed1996

Beneficial effects of hypertonic mannitol in acute ischemia--reperfusion injuries in humans.

Acute ischemia-reperfusion of extremities is characterized by edema, compartment syndrome and neuromuscular dysfunction. Intravenous hypertonic mannitol has been shown to be of benefit in several experimental models. The authors' 5-year experience with the use of hypertonic mannitol and the treatment of acute ischemia reperfusion injuries in humans has been reviewed. Some of 186 patients with acute arterial occlusion following thromboembolism (149) and trauma (37) were treated. Hypertonic mannitol (25 g intravenous bolus followed by 5-10 g intravenous/h) was given perioperatively. Length of preoperative ischemia varied from 1 to 24h. Some of 57.5% of patients had preoperative neuromuscular dysfunction. Following revascularization, limb salvage was obtained in 97.7% of surviving patients and neuromuscular dysfunction improved in 89%. Overall, 15% required fasciotomy. The mortality rate was 3.2%. These data suggest that hypertonic mannitol may have some protective effect in acute ischemia-reperfusion injuries of human extremities. It may decrease the need for fasciotomy and minimize neuromuscular dysfunction.

Adolescent↗
PubMed1996

Carotid artery bypass in acute postendarterectomy thrombosis.

BACKGROUND: Carotid endarterectomy has demonstrated excellent results over the past 2 decades with combined stroke mortality of < 4% in most active centers. However, the optimal technique for surgical reconstruction for patients with acute postoperative deficits is more controversial. PATIENTS AND METHODS: In the last 10 years (1985 to 1995), we performed 1,267 carotid endarterectomies, with 17 strokes (1.3%) and 16 deaths (1.2%). Twenty-four patients developed acute (within 72 hours) postoperative neurologic deficits. In 10 patients, the carotid artery was confirmed patent by duplex scan or angiography, and the neurologic deficit resolved without further therapy. Early reexploration was performed in 14 cases for suspected thrombosis associated with a new neurologic deficit. In each case, resection of the endarterectomy site and an interposition bypass was performed with greater saphenous vein (11), jugular vein (2), or polytetrafluoroethylene (2) grafts. (One patient required a new bypass for acute occlusion of the initial vein bypass.) Postoperatively, 8 patients had complete resolution of their deficit, 3 had minimal residual deficits, and 3 suffered permanent stroke. However, 2 of these patients died. RESULTS: Carotid artery bypass with exclusion of the endarterectomy site resulted in improvement in symptoms in 79% (11 of 14) of the patients and complete resolution in 57% (8 of 14). In long-term follow up (1 to 41 months), there have been no occlusions and one restenosis requiring revision at 11 months. CONCLUSIONS: Carotid artery bypass can be performed safely with acceptable results. The use of autogenous venous conduits allows reconstruction with an endothelial lined conduit that may improve results in patients with acute postoperative neurologic deficit secondary to thrombosis of the endarterectomized carotid artery.

Acute Disease↗
PubMed1996

Eversion endarterectomy of the internal carotid artery: technique and results in 449 procedures.

BACKGROUND: Preservation of neurological function with a low incidence of restenosis is a measure of the long-term durability of carotid endarterectomy. Routine and selective patch angioplasty of the internal carotid artery have both been used to reduce the incidence of restenosis. The European literature has had many reports of lower restenosis rates in patients undergoing eversion carotid endarterectomy. We evaluated our experience with the eversion carotid endarterectomy procedure over a 2-year period to identify any advantage of this technique. METHODS: Between August 1993 and August 1995, 376 patients underwent 449 carotid endarterectomies (CEAs) using the eversion technique (described below). During the same period, 307 patients underwent 353 CEAs by standard endarterectomy. Demographics were similar in both groups. Fifty-two patients in the eversion group underwent combined open cardiac procedures and carotid endarterectomy. There were 47 such patients in the standard group. Duplex examination was performed after surgery at regular intervals to identify any recurrent stenosis. RESULTS: Operative mortality was 4 of 376 (1.1%) and 6 of 307 (2%) in the eversion and standard groups, respectively. Shunts were used in 15 of 449 patients in the eversion group and 24 of 353 patients in the standard group. Cervical block anesthesia was used in 669 of 687 (97%) of patients undergoing CEA without coronary artery bypass grafting (CABG). There were four permanent neurologic deficits in the eversion group and seven in the standard group, for respective stroke rates of 0.9% and 2%, and there were three transient neurologic deficits in the eversion group and nine in the standard group. There was one (0.2%) restenosis in the eversion group; there were four (1.1%) in the standard group by follow-up duplex scan. CONCLUSIONS: These data demonstrate that eversion carotid endarterectomy can be performed with low stroke and mortality rates in the treatment of extracranial carotid occlusive disease. The incidence of restenosis was lower and approached significance in eversion endarterectomy when compared to standard carotid endarterectomy in the short-term follow-up in this series.

Aged↗
PubMed1996

Fate of the excluded abdominal aortic aneurysm sac: long-term follow-up of 831 patients.

PURPOSE: Nonresective treatment of the infrarenal abdominal aortic aneurysm by proximal and distal ligation of the aneurysm sac (exclusion) combined with aortic bypass has been previously reported. A 10-year experience with 831 patients undergoing this procedure was reviewed. METHODS: From 1984 to 1994, 831 (761 elective, 70 urgent) of 1103 patients being treated for abdominal aortic aneurysm underwent repair with the retroperitoneal exclusion technique. Perioperative morbidity and mortality, estimated blood loss, transfusion requirements, natural history of the excluded aneurysm sac, and long-term survival were all assessed. RESULTS: The operative mortality rate for patients undergoing exclusion and bypass was 3.4%. The incidence of nonfatal perioperative complications was 5.2%. Colon ischemia requiring resection occurred in 2 (0.2%) of the 831 patients. Estimated blood loss was 638 +/- 557 cc (50 to 330 cc). On follow-up 17 (2%) patients were found to have patent aneurysm sacs as detected by duplex examination. Fourteen patients required surgical intervention. No cases of graft infection or aortoenteric fistula have been noted. CONCLUSION: Retroperitoneal exclusion and bypass is a viable alternative to traditional open endoaneurysmorraphy in surgery for abdominal aortic aneurysm. Most excluded aneurysm sacs have thrombosis without any long- or short-term complications; however, in a small number of patients delayed rupture of patent aneurysm occurs, thus emphasizing the need for diligent follow-up and appropriate intervention.

Adult↗
PubMed1996

Results of 1000 consecutive elective abdominal aortic aneurysm repairs.

In order to identify major risks for death and complications from elective repair of abdominal aortic aneurysm, the authors analyzed their experience with the last 1000 such repairs over a 15-year period. Of the patients, 772 were men and 228 were women; average age was 70 (range 37-92) years. Some 20% of the patients had severe chronic obstructive pulmonary disease and 33% had baseline creatinine level > 115 mumol/l. Fifteen patients were dialysis-dependent and 24% (242/1000) had significant cardiac disease. Operation used a retroperitoneal approach in 834 patients and a transperitoneal approach in 166. The perioperative mortality rate was 2.4%, but this did not change either chronologically or with technique: some 50% of the deaths were due to cardiac causes. Renal and pulmonary impairment did not affect mortality or complication; 64% of non-fatal complications were distributed in the renal (17%), pulmonary (19%) and cardiac groups (28%). The authors' experience showed that patients with cardiac disease remain at significant risk for post-abdominal aortic aneurysm repair complications in spite of selective preoperative cardiac evaluation. Renal and pulmonary risk factors did not cause additional mortality or morbidity. They suggest that elective abdominal aortic aneurysm repair can be performed with low mortality and morbidity, even in increasing numbers of high-risk patients.

Adult↗
PubMed1996

Bilateral carotid endarterectomy during the same hospital admission.

The efficacy of carotid endarterectomy for the prevention of strokes has been well demonstrated in recent multicenter randomized trials. However, patients presenting with bilateral significant disease pose a difficult problem to the vascular surgeon. Currently, bilateral carotid endarterectomies are staged at varying intervals between operations, with surgeon and patient weighing the risks of waiting for surgery versus the risks of having both procedures done within a shortened interval. There are few data and no consensus on the optimal time interval between these operations. In order to evaluate the timing of carotid endarterectomies in patients with severe bilateral disease, the authors reviewed their experience with patients who had bilateral procedures performed during one hospitalization. Over the past 5 years, they have performed 204 such carotid endarterectomies in 102 patients. Cervical block anesthesia was used in 99% (201/204) of these procedures. All patients either had symptomatic disease, > 60% stenosis or severe ulcerative plaque as defined by duplex scan and/or preoperative angiography. Symptomatic stenoses were the operative indications in 39% (80/204) of the patients; the remaining 61% (124/204) were symptom-free. The majority of patients (80%; 164/204) had their second procedure performed within 2 days of their first operation. There was no operative mortality and only one permanent neurologic defect in this group for a combined stroke mortality rate of 1%. Three patients (1.5%) had transient neurologic deficits postoperatively which completely resolved by discharge. These data show that bilateral carotid endarterectomies can be performed safely and effectively during one hospital admission with a short interprocedural interval and without an increase in mortality or morbidity.

Aged↗
PubMed1996

Access to the right renal artery from the left retroperitoneal approach.

One of the perceived limitations of the left retroperitoneal approach to the aorta is inadequate access to the right renal artery. Many consider the need for a concomitant right renal artery revascularization a contraindication to performing an aortic reconstruction through the left retroperitoneum. Exposure of the right renal artery can be difficult due to the posterior course of the artery behind the vena cava. However, when the aorta is transected, the right renal artery can be easily approached with anterior and cephalad displacement of the aortic root. Over the past 3 years, 52 patients have had right or bilateral renal artery revascularization via the left retroperitoneal approach; of these procedures, 37 were performed with concomitant aortic procedures. In total, 34 patients had bilateral and 18 had unilateral revascularizations. Five patients had a transaortic endarterectomy performed, and 36 were bypassed with 6-mm expanded polytetrafluoroethylene side limbs from the aortic graft. Indications for revascularization were: 39 for suprarenal aortic bypass, seven for renal salvage and six for primary renovascular hypertension. All reconstructions have remained patent and all have been followed by serial duplex and renal flow scans (follow-up for 1-42 months). The operative mortality rate was 5.8% (3/52). There were no major cardiorespiratory complications in this group. Adequate exposure to the proximal right renal artery can be obtained through the left retroperitoneal approach to the aorta, and successful revascularization of one of both renal arteries can be technically performed with acceptable mortality and morbidity.

Adolescent↗
PubMed1996

Advances in the surgical repair of ruptured abdominal aortic aneurysms.

Over the past two decades, the mortality rate for elective repair of infrarenal abdominal aortic aneurysms has improved to an acceptable level (< 5%). However, surgical results of ruptured abdominal aortic aneurysms have remained fairly constant with about 50% in hospital mortality rates. Growing experience with the use of the left retroperitoneal exposure for elective aortic surgery allowed the authors to extend the use of this technique to the repair of ruptured abdominal aortic aneurysm. The extended left retroperitoneal approach using a posterolateral exposure through the 10th intercostal space allowed the surgeon expeditiously and reliably to obtain supraceliac aortic control by dividing the left crus of the diaphragm in all patients. In total, 104 aortic replacements were performed for ruptured abdominal aortic aneurysm during the past 7 years. Of these patients, 87 were men and 17 women; mean(range) age was 72(52-95) years. Hemodynamic instability (as defined by a systolic blood pressure of < 90 mmHg) was present before surgery in 41% (43/104) of patients. The operative mortality rate was 27.9% (29/104). Preoperative hemodynamic instability, time of operative delay and aortic cross-clamp time did not correlate with operative mortality. The median duration of intensive care unit stay was 4 (range 1-60) days and hospital stay 11 (range 6-175) days. The results of this series identified that a change in the operative technique for the repair of ruptured abdominal aortic aneurysm beneficially affected patient survival. The authors suggest that expeditious supraceliac control without thoracotomy is an excellent alternative and offers an advantage in the surgical management of ruptured abdominal aortic aneurysm.

Aged↗
PubMed1996

Expeditious management of ischemic invasive foot infections.

Management of infected ischemic diabetic limbs requires antibiotic therapy, abscess drainage, and revascularization. However, revascularization is often delayed for several days or weeks as the infection is controlled. In an effort to decrease hospital stay and costs and to increase limb salvage, a series of 974 extremities with distal occlusive disease were managed with autogenous distal bypass. Some 136 of these limbs (125 diabetic) had severe invasive infections. These patients received intravenous antibiotics in all cases and abscess drainage if necessary. Vascular reconstruction was carried out as soon as possible, within 48 h of admission. An in situ bypass was used preferentially (107 cases). Patients were maintained on intravenous antibiotics in the perioperative period. Partial foot amputations, when necessary, were performed in 111 cases, usually 3-5 days after vascular reconstruction. There were no graft infections or major wound infections. There were two cases of skin edge necrosis requiring reoperation due to flap mobilization and consequent ischemia. Urgent revascularization with an autogenous conduit may be carried out in patients with invasive foot infections expeditiously, with high rates of limb salvage. Graft and wound infections are not common in this setting. Costly prolonged pre-bypass hospitalization in these cases is unnecessary.

Amputation, Surgical↗
PubMed1996

Current status of the use of retroperitoneal approach for reconstructions of the aorta and its branches.

OBJECTIVE: The objective of this article is to determine whether retroperitoneal approach for aortic surgery has certain physiologic, technical advantages. SUMMARY BACKGROUND DATA: The retroperitoneal approach for abdominal aortic reconstruction classically had been reserved for select patients with either high-risk comorbid disease or specific anatomic problems that preclude the transabdominal approach. With increasing appreciation of the physiologic, anatomic, and technical advantages of the extended posterolateral retroperitoneal approach, the authors have expanded its use for repair of all types of aortic visceral and renal artery disease as well as ruptured abdominal aortic aneurysm and infected aortic grafts. METHODS: From January 1981 to September 1995, 2340 retroperitoneal aortoiliac reconstructions were performed in 2243 patients. Aortic reconstructions accounted for 1756 cases: 1109 for elective abdominal aortic aneurysms, 210 for ruptured and symptomatic aortic aneurysms, 399 for occlusive disease, 18 for infected aortic grafts, and 20 for other indications. Iliofemoral disease was the indication for 584 procedures. As experience was gained, this approach also was used for 417 renal and 50 celiac and superior mesenteric artery reconstructions. RESULTS: The mean age was 67 years with 1590 men and 653 women. Overall mortality was 5.2% for all aortic cases: 2.4% for elective, 12.6% for symptomatic, and 29.0% for ruptured aortic aneurysms. Major complications occurred in 12.5% of the elective procedures and in 38.3% of emergency procedures. Over the past 5 years, the average length of hospital for uncomplicated elective abdominal aortic aneurysms was 6.1 days, intensive care unit stay was 0.7 day, and diet was resumed by postoperative day 1. Five-year graft patency was 99% for aneurysms and 95% for occlusive disease. CONCLUSIONS: The retroperitoneal approach offers certain physiologic advantages associated with minimal disturbance of gastrointestinal and respiratory function, thereby reducing the length of intensive care unit and hospital stay. In addition, its technical advantages and flexibility facilitates visceral and juxtarenal aortic reconstructions without the need for thoracotomy.

Aged↗
PubMed1996

In situ prosthetic graft replacement for mycotic thoracoabdominal aneurysms.

Infected aortic aneurysms remain a difficult surgical problem associated with high morbidity and mortality. We report three cases of mycotic thoracoabdominal aneurysms treated by debridement of infected aortic tissue, in situ prosthetic graft replacement, and intensive antibiotic therapy. One early death occurred in a patient with systemic sepsis related to Salmonella enteritidis infection of the thoracic aorta secondary to a colovesical fistula. The two other patients remain alive at 2 years without further complications of the surgery. Bacteriology is as follows: Staphylococcus aureus, Streptococcus pneumoniae, and Salmonella enteritidis. In all patients the operation was performed immediately after the diagnosis was confirmed. Antibiotic therapy was begun intraoperatively and was continued for at least 6 months. Two patients were followed regularly, and there have been no septic recurrences in our 2-year follow-up period. In situ prosthetic graft replacement in conjunction with intensive antibiotic therapy is a viable option in the treatment of mycotic thoracoabdominal aortic aneurysms.

Aged↗