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Biomedical subjects

D M Shah

Publications and source records attributed to D M Shah.

At least 91 records · Page 5Linked to original sources
PubMed1994

Retroperitoneal approach for bilateral renal and visceral artery revascularization.

Revascularization for renal and visceral arterial occlusive disease has traditionally been performed via a transperitoneal approach. Exposing these arteries transperitoneally is often difficult, however, and may require extensive medial visceral rotation. An alternative is a left retroperitoneal approach for renal and visceral arterial revascularization, including procedures involving the right renal artery. Over the past 7 years, a total of 186 such procedures have been performed using this approach. Of 30 that involved primarily the celiac and mesenteric arteries, 20 were completed with a bypass graft and 10 with transaortic endarterectomy. Of 156 procedures performed for renal arterial occlusive disease or aneurysmal disease extending above the renal arteries, 32 were treated with transluminal endarterectomy, 21 were treated with bilateral bypasses, and 72 were treated with unilateral bypass. Concomitant aortic endarterectomy or graft replacement was performed in 110 of this group. Operative mortality was 3.3%. Reconstructions were followed-up (for 1 to 76 months) with serial duplex and renal flow ultrasonography scans. One thrombosis developed in a renal artery bypass. We conclude that the left retroperitoneal approach may conveniently be used to reconstruct the celiac artery, superior mesenteric artery, and both renal arteries. These reconstructions may be performed with either an endarterectomy or bypass technique. In particular, the need to revascularize the right renal artery should not be regarded as a contraindication to using a left retroperitoneal approach.

Adolescent↗
PubMed1994

Increased limb salvage by the use of unconventional foot amputations.

PURPOSE: Limb salvage in the presence of ischemic foot necrosis requires revascularization followed by debridement or partial foot amputation. Necrosis extending beyond the toes and metatarsal heads may require the use of unconventional types of amputations. METHODS: Over a 15-year period 2105 ischemic limbs were treated with infrainguinal revascularization. In 98 cases, extensive foot necrosis was than managed with amputations, including 59 modified Chopart, 14 Lisfranc, 17 Pirogoff and 8 Syme amputations. Patients were not allowed to bear weight for several days to weeks. RESULTS: Skin flap necrosis in 14 cases was managed successfully by debridement and skin grafting. Ambulation required the use of a "clamshell" prosthesis and foot spacer. The overall limb salvage rate in this group was 84% (82 of 98). In general, the modified Chopart amputation most frequently produced ambulatory limb salvage and is technically easier to perform than a Syme amputation. Patient satisfaction and long-term ambulatory function was highest with the modified Chopart. CONCLUSION: Ischemic foot necrosis extending beyond the limits of conventional transmetatarsal amputation need not be treated with major amputation. This requires the surgeon to be well versed in the use of less common types of partial foot amputations. Acceptable limb salvage and good functional results may be attained by the motivated patient and surgeon with the use of these procedures in the revascularized limb.

Activities of Daily Living↗
PubMed1994

Carotid endarterectomy in awake patients: its safety, acceptability, and outcome.

PURPOSE: The purpose of this study was to determine the safety and efficacy of performing carotid endarterectomy procedures with the patient receiving cervical block anesthetic. METHODS: Over the last 14 years, 654 carotid endarterectomy procedures were performed with patients receiving regional anesthetic. Intraluminal shunts were placed on demand, if neurologic changes with clamping of the carotid artery developed in the patient. During the same period, 419 cases were done with the patients receiving general anesthetic. Choice of anesthetic was based on surgeon and patient preference. RESULTS: In the regional anesthetic group the indications for operation included transient ischemic attack (311), asymptomatic hemodynamically significant stenosis (146), amaurosis fugax (106), stroke (86), restenosis (3), and aneurysm (2). Shunts were used in 46 of 654 cases (7%). Conversion from regional to general anesthetic was required in seven patients (1.1%). The operative mortality rate was 0.76% (5 of 654). Permanent nonfatal neurologic deficits occurred in 0.76% (5 of 654), and temporary neurologic deficits occurred in 1.07% (7 of 654). CONCLUSIONS: On the basis of these results, we believe regional cervical block anesthetic is an acceptable option to the routine use of shunts performed with the patient receiving general anesthetic during carotid endarterectomy. In addition, the ability to continuously assess the awake patient receiving cervical block may contribute to a decrease in perioperative stroke and mortality rates while simplifying functional cerebral monitoring during carotid endarterectomy.

Adult↗
PubMed1994

Characterization and expression of an antifungal zeamatin-like protein (Zlp) gene from Zea mays.

A cDNA clone encoding a basic thaumatin-like protein of Zea mays was recovered from a mid-development seed cDNA library. The gene, Zlp, encoded a protein that was nearly identical with maize zeamatin and alpha-amylase/trypsin inhibitor. Expression of Zlp mRNA was highest in the endosperm tissue of seed 4 weeks after pollination. Expression of zeamatin-like (ZLP) protein correlated with mRNA; also, a low basal level of ZLP expression in leaf was not appreciably induced by abiotic stresses. ZLP was expressed with its own signal peptide in insect cells and in transgenic Arabidopsis and tomato plants. ZLP was secreted in all three systems, with correct processing of the signal peptide. ZLP expressed in transgenic tomato was found to be partially subjected to a proteolytic cleavage after residue 180, by an unknown mechanism, to give a "nicked" isoform of ZLP. Purified ZLP from all three sources, as well as purified "nicked" ZLP from tomato, demonstrated fungal inhibition against Candida albicans and Trichoderma reesei, with marginal inhibition observed against Alternaria solani and Neurospora crassa.

Amino Acid Sequence↗
PubMed1993

Structure and expression of a barley acidic beta-glucanase gene.

A barley acidic beta-1,3-glucanase gene was recovered from a barley genomic library by homology with a partial cDNA of barley basic beta-1,3-glucanase isoenzyme GII. The gene, Abg2, is homologous to the PR2 family of pathogenesis-related beta-1,3-glucanase genes. The ABG2 protein has 81% amino acid similarity to barley basic beta-1,3-glucanase GII. The ABG2 protein is encoded as a preprotein of 336 amino acids including a 28 amino acid signal peptide. A 299 bp intron occurs within codon 25. The mature ABG2 protein has a predicted mass of 32,642 Da and a calculated isoelectric point of 4.9. The second exon of the Abg2 gene shows a strong preference for G + C in the third position of degenerate codons. The Abg2 gene was functionally expressed in Escherichia coli. Abg2 mRNA is constitutively expressed in barley root; leaf expression of Abg2 mRNA is induced by mercuric chloride and infection by Erysiphe graminis f. sp. hordei. Southern blot analysis indicates that Abg2 is a member of a small gene family.

Acids↗
PubMed1993

Aortic replacement for abdominal aortic aneurysm in elderly patients.

Improvements in the operative mortality and morbidity rates in elective aortic replacement, which are largely a result of refinements in surgical technique and perioperative management, have allowed a more aggressive approach in the treatment of abdominal aortic aneurysm (AAA) in elderly patients. To evaluate this approach, we reviewed the records of 116 patients 80 years of age and older (range: 80 to 93 years) who consecutively underwent aortic replacement for AAA. Seventy-seven patients underwent elective aortic replacement with 8 complications and a 3% operative mortality rate (2 of 77). Emergent aortic replacement was performed in 39 patients (14 with symptomatic nonruptured AAA and 25 with ruptured AAA) with 12 complications. In this nonselective subset, there were eight deaths, for an operative mortality rate of 20% (symptomatic 14%, ruptured 24%). In comparison, 780 patients less than 80 years of age underwent aortic replacement during the same time period. Within this group, 622 patients who were treated on an elective basis had a similar operative mortality (2%) as did patients 80 years of age and older. On the basis of these results, we believe that elective aortic replacement in elderly patients is justified and can be achieved with low operative mortality and morbidity rates. We suggest that the chronologic age of the patient should not deter aortic replacement.

Aged↗
PubMed1993

Is the iliac artery a suitable inflow conduit for iliofemoral occlusive disease: an analysis of 514 aortoiliac reconstructions.

PURPOSE: The aorta is the conventional inflow source for reconstructions in patients with aortoiliofemoral occlusive disease. In patients with unilateral iliac or femoral disease, femoral-to-femoral bypasses have been used but with less favorable patency rates. The purpose of this study is to evaluate the performance of the unobstructed iliac artery as an inflow source for ipsilateral, contralateral, or bilateral reconstructions in iliofemoral occlusive disease. METHODS: Over the past 6 years 322 reconstructions have been performed with the iliac artery as the donor vessel. Patients were evaluated for proximal hemodynamically significant lesions by augmented pullout pressures during aortography. Patients who had balloon angioplasty were excluded. RESULTS: Results were compared with 192 patients who underwent conventional aortodistal bypass operation for occlusive disease during the same period. Both groups were similar in risk factors, age, sex, and indications for operation. For the iliac group the operative mortality rate was 1.6%, and the 30-day patency rate was 97%, similar to those in the aortic group (3.6% and 95%, respectively). Cumulative patency rates at 5 years by life-table analysis were 82% for iliac artery inflow and 77% for aortic inflow reconstructions. CONCLUSIONS: Our experience suggests that an unobstructed iliac artery is a reasonable inflow source for reconstructions in iliofemoral occlusive disease. The long-term patency rate is comparable to aortodistal bypasses and superior to other extraanatomic bypasses.

Aorta, Abdominal↗
PubMed1993

Transvascular albumin flux in rabbit hindlimb after tourniquet ischemia.

Transvascular clearance of labeled rabbit albumin was measured in gastrocnemius muscle and heel skin from anesthetized rabbits after 1 or 2 h of tourniquet ischemia. Albumin clearance, calculated as a 1-h extravascular uptake, was 4.7 +/- 0.4 and 29 +/- 1 microliter.h-1 x g dry wt-1 for control gastrocnemius muscle and heel skin, respectively. During the first hour of reperfusion, the clearance was 101 +/- 23 and 56 +/- 6 microliters.h-1 x g dry wt-1 in the muscle and skin, respectively. The clearance in skin during the second and third hour of reperfusion was not different from control. The increased clearance in muscle persisted during 2 h of reperfusion but returned to control levels during the third hour of reperfusion. The solvent drag reflection coefficient was measured by increasing venous pressure during reperfusion in one leg after bilateral ischemia. In skin, the reflection coefficient, calculated as 1 minus the change in clearance divided by the change in water weight, was 0.94 +/- 0.05 and did not change with tourniquet ischemia. The reflection coefficient in muscle was 0.98 +/- 0.01 for control animals and decreased to 0.66 +/- 0.11 during the first hour of reperfusion. The reflection coefficient was not different from control during the third hour of reperfusion. The transitory increase in microvascular permeability to albumin in skeletal muscle is more indicative of an acute inflammatory response than of endothelial injury.

Animals↗
PubMed1993

Outcome following blunt vascular trauma of the upper extremity.

Blunt trauma to the upper extremity may cause extensive vascular damage in addition to severe musculoskeletal injury. Over a 5.5-year period, 17 patients with a total of 23 arterial injuries were treated. Diagnosis was made in 16 patients before surgery by physical and Doppler ultrasonographic examination. Angiography performed in ten patients assessed the extent of injury. Associated orthopedic injuries were present in 11 patients and neurologic injury in 16. At surgery, 21 of 23 arterial repairs required autologous vein. The initial limb salvage rate was 76%. Four patients underwent above-elbow amputation because of progressive sepsis and myonecrosis. A fifth underwent delayed amputation at 7 months due to loss of limb function. Neurologic impairment was the major long-term morbidity. The data show that outcome following blunt vascular trauma of the upper extremity is governed by the associated injuries.

Adolescent↗
PubMed1993

Alternative conduits for coronary revascularization: a novel approach for harvest of the lesser saphenous vein.

Previous use of the greater saphenous vein limits the subsequent availability of conduit for coronary artery bypass grafting (CABG). One readily available alternative conduit is the lesser saphenous vein (LSV). During a 4-year period, 34 LSVs were explored in 23 patients using a novel surgical approach. The incision used for LSV harvest was carried through and deep into the muscular fascia, posterior to the tibia, along the length of the leg, developing a fascial-cutaneous flap. The LSV in all patients was imaged before operation by venous duplex scanning. Important anatomic details were mapped on the patient's leg before surgery using indelible ink. Findings at operation correlated well with the duplex imaging results. Of the 34 LSVs explored 31 were judged usable by the operating surgeon. In eight patients bilateral LSVs were used and in two this vein was the only conduit available. Among patients undergoing LSV harvest there was no operative mortality and minimal operative morbidity related to harvesting. Only one wound infection developed at the incision site. There were no documented cases of deep vein thrombosis. A case-control study was performed in which a control group of 25 patients undergoing CABG without use of the LSV were compared with the 23 who had LSVs harvested; patients in both groups underwent preoperative venous duplex studies. There were no significant differences in operative mortality or morbidity rate between groups (statistical power > 0.8 for these negative observations), suggesting that harvest of the LSV is usually successful when used in conjunction with preoperative venous duplex scanning.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Ultrasonic characterization of the saphenous vein.

The most frequently used conduit for infrainguinal or coronary artery bypass is the saphenous vein, and this report describes the ultrasonic evaluation of anatomic variations in over 1400 limbs. The thigh portion of the greater saphenous vein consisted of a single venous conduit in 67% of the limbs, a complete double system in 8%, a branching double system in 18% and a closed loop double system in 7%. In 92% of the cases, the vein was in medial position, with the remaining 8% positioned laterally. In the calf, a single vein was observed in 65% of the limbs with the remainder demonstrating a double venous system. The vein was positioned anteriorly in 85% of the limbs. The remaining 15% were positioned posteriorly, with 7% of these being a single dominant vein. Proper knowledge of saphenous vein anatomy is vital to the surgeon preparing to use this vein as a bypass conduit and can aid in its preoperative assessment.

Arteriosclerosis↗
PubMed1993

Treatment of the diabetic foot from a vascular surgeon's viewpoint.

Diabetic foot lesions are caused by neurologic, orthopaedic, immunologic, and vascular derangements. Whereas some lesions may be initially caused by trauma and others directly caused by vascular disease, improvement of arterial perfusion often plays an important role in the successful salvage of these limbs. Fortunately, in the last several years, there has been a major improvement in the identification and treatment of those patients in whom correction of arterial occlusive disease is necessary for healing.

Angiography↗
PubMed1993

Optimal outcome after tibial arterial bypass.

To evaluate factors for the optimal outcome after tibial arterial bypass for lower extremity ischemia, we analyzed our experience with 1,359 such bypasses during the last ten years. There were 869 males and 490 females, of whom 739 patients (54 percent) had diabetes. The average age was 68 years. One thousand and twenty-four bypasses were performed using the atraumatic valve incision in situ technique, 281 bypasses using free vein grafts and 54 bypasses with synthetic materials. These bypasses were taken to the anterior tibial (312 patients), posterior tibial (341 patients), peroneal (520 patients) and dorsalis pedis arteries (125 patients). Inflow arteries included external iliac (two patients), common (435 patients), superficial (472 patients) and profunda femoris arteries (259 patients). In certain instances, popliteal and tibial arteries were used for inflow (short bypasses). Limb salvage was the significant indication (95 percent). The overall cumulative primary patency rate at five years was 68 percent and secondary patency was 76 percent. In situ bypasses had the best secondary patency rate of 80 percent at five years followed by free vein grafts of 70 percent and synthetic bypasses of 33 percent. The choice of inflow or outflow arteries did not influence the patency rate in any category. The overall limb salvage rate was 94 percent at five years. Short bypasses using free vein grafts had a similar patency to long free vein graft but lower patency than long in situ bypasses. These data demonstrate that bypasses to tibial arteries, using autogenous vein for ischemia of the lower extremity and limb salvage, have long term durability. In situ bypass with a complete saphenous vein is the best conduit for such reconstructions. We suggest that tibial arterial bypass should be strongly considered in all instances for limb salvage when autogenous vein is available before resorting to primary amputation.

Aged↗
PubMed1992

Antifungal proteins from plants. Purification, molecular cloning, and antifungal properties of chitinases from maize seed.

We have purified two 28-kDa chitinases, designated Chitinase A (Chit A) and Chitinase B (Chit B), from maize seeds to homogeneity and isolated cDNA clones encoding these two enzymes using an oligonucleotide probe based on an amino acid sequence of a peptide derived from Chit A. Although these two enzymes share 87% homology in their amino acid sequences, which were deduced from the nucleotide sequences of the isolated cDNA clones, they are significantly different in their biochemical and in vitro antifungal activities. When tested in vitro for antifungal activity against the growth of Trichoderma reesei, Alternaria solani, and Fusarium oxysporum, Chit A showed greater antifungal activity than Chit B. The specific activity of Chit A was determined to be 3-fold higher than that of Chit B. Chit A also had a 10-fold lower binding constant (Kd) against the substrate analogue N,N',N'',N'''-tetraacetyl chitotetrose than Chit B, indicating that the two enzyme may differ in their affinities for binding to the substrate chitin. Comparison of the amino acid sequences of maize seed chitinases with those of previously published chitinases from monocot and dicot plants indicates that maize seed chitinases have diverged significantly from other chitinases.

Alternaria↗