Search PubMed⌕ Search

Biomedical subjects

D M Shah

Publications and source records attributed to D M Shah.

At least 19 recordsLinked to original sources
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↗
PubMed1992

Long-term follow-up of poor-risk patients undergoing small-diameter portacaval shunts.

The small-diameter portacaval H-graft has been shown to be a reliable method of controlling variceal hemorrhage. However, little has been written about the long-term follow-up of poor-risk patients treated by this method. Over the last 11 years, we have performed 38 portacaval H-grafts; 79% of the patients were Child's B or C, and 79% were alcoholic. The mean age was 52 years, and the mean period of follow-up was 44 months. Over 37% of the grafts were performed in patients who were bleeding at the time of operation. Our 30-day operative mortality was 13%. Postoperatively, the small-diameter H-graft was associated with mild to moderate encephalopathy in 33% of the patients and ascites in 42%. Both these conditions were easily controlled with diet and medication. Early recurrent variceal bleeding was seen in 13% of patients. However, on late follow-up, recurrent hemorrhage and encephalopathy have been seen in only 12% and 14% of patients, respectively. We conclude that the portacaval H-graft is a reliable and lasting method for controlling variceal bleeding with an acceptable postoperative morbidity and mortality.

Adolescent↗
PubMed1992

Liver and spleen phagocytic depression after peripheral ischemia and reperfusion.

Liver and spleen phagocytic clearance of blood-borne microparticulate tissue debris and products of intravascular coagulation after trauma and surgical injury is an important mechanism to limit the deposition of debris in the pulmonary vascular bed. Plasma fibronectin (pFn) modulates this clearance process. We evaluated the effect of a localized peripheral ischemia and reperfusion injury on liver and spleen phagocytic function. Male rats (250 to 350 g) underwent 4 hours of tourniquet-induced bilateral hindlimb ischemia, followed by 18 hours of reperfusion after release of the tourniquet. Rats subjected to ether anesthesia alone or anesthesia followed by groin incision without ischemia were the control and sham groups, respectively. Reticuloendothelial (RE) phagocytic function was assessed at 15 minutes and 18 hours after the start of reperfusion by the in vivo liver and spleen removal of blood-borne iodine 125 (125I)-test microparticles, which were coated with gelatin (denatured collagen) to enhance their interaction with pFn. Liver and spleen particle uptake in control and sham rats was similar. In contrast, after 4 hours of ischemic injury with 15 minutes of reperfusion, we observed a 30% to 40% decrease (p less than 0.05) in liver and spleen particle uptake as compared with sham controls with partial restoration of this removal mechanism by 18 hours. This depression in liver and spleen phagocytic function was associated with a significant (p less than 0.05) increase in the deposition of the 125I-test particles in the lung. RE depression was not due to a deficiency of pFn; indeed, a marked elevation (588 +/- 12 micrograms/mL versus 1,083 +/- 40 micrograms/mL) of pFn was observed by immunoassay over the 18-hour reperfusion interval. Comparative bioassay of humoral (opsonic) versus cellular (Kupffer's cell) activity revealed that Kupffer's cells in livers from controls or ischemia-reperfusion rats exhibited normal phagocytic function when incubated in plasma harvested from either control or 4-hour ischemic rats. The opsonic activity of plasma harvested after ischemia and reperfusion was also more than adequate, consistent with the immunoassay analysis. Thus, the impaired liver and spleen clearance mechanism after peripheral ischemia and reperfusion injury did not appear to be due to either a macrophage cellular deficit or a lack of pFn. This clearance depression may be mediated by splanchnic malperfusion, which is known to develop after peripheral ischemia and reperfusion and associated soft tissue injury.

Animals↗
PubMed1992

Adventitial cystic disease of the femoral vein: a case report and review of the literature.

Painless edema of the left leg developed in a 65-year-old man without a history of venous disease, and he was found to have a mass compressing the lumen of the left common femoral vein. The intramural cyst was drained through transvenous exposure and found to contain mucoid material. This is the seventh case of adventitial cystic disease of a vein in the world literature. Analogous to adventitial cystic disease of arteries, it is defined by venography, CT scanning, and duplex ultrasonography. Surgical drainage is the treatment of choice.

Aged↗
PubMed1992

The lesser saphenous vein: an underappreciated source of autogenous vein.

Use of the ipsilateral greater saphenous vein for arterial bypass procedures is frequently limited by previous stripping, bypass operations, or anatomic unsuitability. In such cases the contralateral greater saphenous vein or arm veins are often used. However, over the past 5 years we have used the lesser saphenous vein as a preferred alternative autogenous vein. Duplex scanning has been used in 311 cases for preoperative mapping and assessment with excellent correlation with actual anatomy found at operation. Harvest of the lesser saphenous vein has been facilitated by the use of a medial subfascial approach not requiring special positioning of the leg. A total of 91 lesser saphenous veins have been used for arterial bypass procedures; 66 of these were repeat cases. Vein use was 90.2%. In 40 of these cases the lesser saphenous vein was used as the entire conduit, including 10 in situ, 20 reversed vein (including 18 for coronary artery bypass), and 10 orthograde vein bypasses. In the remaining 33 cases the lesser saphenous vein was spliced to another vein to complete a bypass procedure. In the entire group, patency was 77% at 2 years. These data suggest that the lesser saphenous vein should be a principal alternative to ipsilateral greater saphenous vein for arterial bypass because of its ready availability, high use rate, ease of harvesting and preparation, and ideal handling characteristics.

Adult↗
PubMed1992

Rebound elevation of fibronectin after tissue injury and ischemia: role of fibronectin synthesis.

Plasma fibronectin (pFn) stimulates macrophage phagocytosis of tissue debris; pFn deposition in tissues may influence vascular integrity. Although the acute depletion of pFn after surgery and/or injury has been described, less attention has been given to the rebound hyperfibronectinemia presumably "triggered" by the early pFn depletion. Using a model that compartmentalized the site of tissue injury and thus attenuated the initial pFn depletion, we studied this rebound elevation of pFn in anesthetized rats (250-350 g) after the surgical trauma of groin dissection alone (sham group) or surgery coupled with 4 h of hindlimb ischemia (experimental group). Nonoperated control rats were also anesthetized. Shams had baseline (preoperative) 6-, 8-, and 22-h postoperative pFn levels of 573 +/- 61, 598 +/- 62, 695 +/- 57, and 929 +/- 87 micrograms/ml, respectively. In the surgery-ischemia group, pFn also elevated to 1,117 +/- 40 micrograms/ml at 22 h postsurgery. Nonoperated control rats (only anesthetized) had no elevation of pFn. Intravenous infusion of gelatin-coated lipid particles (50 mg/100 g) depleted pFn by 89.3% but was unable to prevent the rebound elevation of pFn. The blood clearance of 125I-labeled pFn was very similar in control, sham, and experimental rats. In contrast, pFn synthesis over the 22-h period was dramatically altered and equal to 2.12 +/- 0.16, 3.40 +/- 0.56, and 4.49 +/- 0.17 mg pFn synthesized/100 g body wt, in control, sham, and experimental rats respectively. Thus a rapid increase in pFn synthesis contributes to the rebound hyperfibronectinemia after sublethal surgical injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Fick-derived hemodynamics. Oxygen consumption measured directly vs oxygen consumption calculated from CO2 production under steady state and dynamic conditions.

Indirect calorimetry is being used increasingly as a tool for hemodynamic monitoring via the Fick equation. This investigation was undertaken to examine the use of carbon dioxide elimination (VCO2A) and related respiratory quotient (RQA) to calculate oxygen uptake (VO2A) and estimate oxygen consumption (VO2) during steady-state and dynamic hemodynamic conditions. Nine patients undergoing abdominal aortic surgery were studied intraoperatively and Fick-derived hemodynamic measurements were made using a monitoring system employing indirect calorimetry, pulse oximetry, and pulmonary artery oximetry. Comparisons were made between measured VO2A and calculated VO2A derived from the VCO2A and the initial RQA (RQi), which is assumed not to change. Prior to aortic crossclamping (steady state), there were no significant differences between the measured and calculated methods with respect to oxygen consumption (184 +/- 24 ml/min vs 185 +/- 17 ml/min), oxygen delivery (753 +/- 141 ml/min vs 769 +/- 178 ml/min), and cardiac output (4.7 +/- 0.6 L/min vs 4.7 +/- 0.7 L/min). However, immediately following aortic unclamping (dynamic state), the RQA changed precipitously from the baseline RQi. Consequently, significant differences between the measured and calculated methods were noted in oxygen uptake (213 +/- 41 ml/min vs 193 +/- 25 ml/min, p < 0.001), oxygen delivery (780 +/- 297 ml/min vs 716 +/- 296 ml/min, p < 0.001), and cardiac output (5.8 +/- 2.2 L/min vs 5.3 +/- 1.8 L/min, p < 0.001). Additionally, following unclamping, the peak VO2A was 242 +/- 49 compared with a cVO2A of only 198 +/- 22 (p < 0.01). We conclude that the use of VCO2A to calculate VO2A may lead to erroneous measurements under dynamic conditions, such as unclamping of the abdominal aorta.

Aorta, Abdominal↗
PubMed1992

Extracorporeal circulation as an alternative to open-chest cardiac compression for cardiac resuscitation.

Open-chest direct cardiac compression represents a more potent but highly invasive option for cardiac resuscitation when conventional techniques of closed-chest cardiac resuscitation fail after prolonged cardiac arrest. We postulated that venoarterial extracorporeal circulation might be a more effective intervention with less trauma. In the setting of human cardiac resuscitation, however, controlled studies would be limited by strategic constraints. Accordingly, the effectiveness of open-chest cardiac compression was compared with that of extracorporeal circulation after a 15-min interval of untreated ventricular fibrillation in a porcine model of cardiac arrest. Sixteen domestic pigs were randomized to resuscitation by either peripheral venoarterial extracorporeal circulation or open-chest direct cardiac compression. During resuscitation, epinephrine was continuously infused into the right atrium, and defibrillation was attempted by transthoracic countershock at 2-min intervals. Systemic blood flows averaged 198 ml.kg-1.min-1 with extracorporeal circulation. This contrasted with direct cardiac compression, in which flows averaged only 40 ml.kg-1.min-1. Coronary perfusion pressure, the major determinant of resuscitability on the basis of earlier studies, was correspondingly lower (94 vs 29 mm Hg). Extracorporeal circulation, in conjunction with transthoracic DC countershock and epinephrine, successfully reestablished spontaneous circulation in each of eight animals after 15 min of untreated ventricular fibrillation. This contrasted with the outcome after open-chest cardiac compression, in which spontaneous circulation was reestablished in only four of eight animals (p = .038). We conclude that extracorporeal circulation is a more effective alternative to direct cardiac compression for cardiac resuscitation after protracted cardiac arrest.

Acidosis↗
PubMed1992

Retroperitoneal in-line aortic bypass for treatment of infected infrarenal aortic grafts.

Since 1970, we have treated 43 patients with infected aortic grafts. Early in the series, four patients were treated with resection of the fistula or erosion and systemic and topical antibiotics without removal of the graft. All four patients died. Thirty-two patients were treated by conventional therapy; there were 13 deaths (40 percent). More recently, seven patients were managed by the left retroperitoneal placement of a new in-line polytetrafluoroethylene (PTFE) aortic graft through clean tissue planes, followed by the immediate transperitoneal removal of the infected graft without cross-contamination. Patients were maintained postoperatively on antibiotics for a minimum of two weeks. All seven patients survived without septic complications, with a mean follow-up time of 36 months (six months to four years). The surgical technique consists of initial suprarenal control of the aorta, followed by infrarenal division and oversewing of the distal aorta. A PTFE bifurcation graft is placed connecting the proximal aorta and the appropriate femoral vessels, the right limb tunneled through the space of Retzius. After closure of the incisions, through the space of Retzius. After closure of the incisions, the patient is placed in the supine position and the infected graft is removed transperitoneally. We believe that retroperitoneal in-line aortic bypass for treatment of an infected aortic graft offers a favorable alternative to conventional therapy by avoiding the use of an extra-anatomic bypass and associated risk of stump blowout.

Anti-Bacterial Agents↗
PubMed1992

Human cerebrovascular response to oxygen and carbon dioxide as determined by internal carotid artery duplex scanning.

Alterations in arterial oxygen and carbon dioxide influence cerebrovascular resistance and therefore cerebral blood flow (CBF), but the magnitude of these CBF responses have not been well defined in normal humans. Duplex scanning (B-mode imaging and pulsed Doppler shift analysis) was used to measure internal carotid blood flow (ICBF) as an indicator of CBF in 20 normal subjects during alterations of arterial O2 and CO2. End-tidal PCO2 (PETCO2) was measured by mass spectrometry, arterial oxygen saturation by pulse oximetry, and unilateral (right) ICBF by duplex scanning. A variety of gas mixtures were administered to achieve hypoxemia (FIO2 = 0.075-0.10) and hypercapnia (FICO2 = 0.05) or the subject was asked to hyperventilate to PETCO2 = 16-24 mm Hg. The ICBF was determined five times in each of six conditions: (1) normoxia/normocapnia; (2) normoxia/hypercapnia; (3) normoxia/hypocapnia; (4) hypoxia/normocapnia; (5) hypoxia/hypercapnia; and (6) hypoxia/hypocapnia. During normoxia and normocapnia, the mean ICBF was 330 +/- 19 (SEM) mL/min. Specific CO2 reactivity was 7.4 +/- 0.7 mL/min/mmHg, which is equivalent to 2.3% +/- 0.1% of normocapnic blood flow per mm Hg change in CO2. During normocapnia, ICBF increased by 2.9 +/- 0.9 mL/min for each percentage decrease in oxygen saturation. Using an ANOVA with repeated measures to fit the responses, the following statistically significant relationship was found: ICBF (mL/min) = 333 + 6.3.(PETCO2 - 40) + 2.7 DSO2 +/- 81 where DSO2 is arterial desaturation (100 - arterial saturation). An additional "between subject" variation had a mean of 0 and a standard deviation of 82 mL/min. There was no statistically significant evidence of an interaction between O2 and CO2 response. Our data suggest that hypoxia and carbon dioxide changes will alter CBF simultaneously and additively. Duplex scanning of the internal carotid artery, which can be performed at the bedside, is sufficiently sensitive to detect changes in ICBF and internal carotid artery oxygen delivery.

Adult↗
PubMed1992

Is long vein bypass from groin to ankle a durable procedure? An analysis of a ten-year experience.

Long vein bypass from the femoral artery to the level of the ankle may be performed with good initial success despite extreme bypass length and limited outflow tracts. However, the long-term performance of these bypasses remains to be defined. During the last 10 years we have performed single greater saphenous vein in situ bypass to the ankle level in 270 patients. There were 187 male and 83 female patients, and 61% of the patients were diabetic. The operative mortality rate was 3.7%. Cumulative bypass patency was 79% at 3 years and 73% at 5 years. In a similar manner, limb salvage was 93% at 3 years and 89% at 5 years. The patency rate was similar for various inflow arteries (common femoral, 88 cases; proximal superficial femoral, 135 cases; and deep femoral, 41 cases) and outflow tracts (dorsal pedal, 72 cases; anterior tibial, 59 cases; posterior tibial, 72 cases, and peroneal, 67 cases). Short bypasses, composite bypasses, free-vein grafts, and bypasses proximal to 10 cm above the ankle were excluded from this analysis. These data show that a long bypass to the ankle level for limb salvage is a durable procedure. The basic concept of bypassing all occlusive disease to the distal open artery in patients undergoing limb salvage should be an acceptable dictum. Excellent long-term patency and limb salvage rates are achievable by following this principle.

Adult↗
PubMed1991

Site-directed mutagenesis of a conserved region of the 5-enolpyruvylshikimate-3-phosphate synthase active site.

The active site of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) has been probed using site-directed mutagenesis and inhibitor binding techniques. Replacement of a specific glycyl with an alanyl or a prolyl with a seryl residue in a highly conserved region confers glyphosate tolerance to several bacterial and plant EPSPS enzymes, suggesting a high degree of structural conservation between these enzymes. The glycine to alanine substitution corresponding to Escherichia coli EPSPS G96A increases the Ki(app) (glyphosate) of petunia EPSPS 5000-fold while increasing the Km(app)(phosphoenolpyruvate) about 40-fold. Substitution of this glycine with serine, however, abolishes EPSPS activity but results in the elicitation of a novel EPSP hydrolase activity whereby EPSP is converted to shikimate 3-phosphate and pyruvate. This highly conserved region is critical for the interaction of the phosphate moiety of phosphoenolpyruvate with EPSPS.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1991

Local anesthesia for surgery on the foot: efficacy in the ischemic or diabetic extremity.

The efficacy, risks, and benefits of the use of local anesthesia for surgery on the foot were assessed in 75 patients who underwent 127 procedures with lower calf, ankle, metatarsal-ray, and digital blocks. There were 23 procedures on digits alone, 97 forefoot operations (transmetatarsal amputations, wound debridements, closures, osteotomies, joint resections), six ankle or hind-foot amputations, and one open ankle disarticulation. There were no complications directly related to the use of local anesthesia; specifically, no extension of preexisting infection or ischemia due to injection in the foot. There were three deaths (30-day mortality 4%). The procedures were uniformly well tolerated, even in patients with ongoing myocardial ischemia or severe metabolic disorders. Local anesthesia is a safe and effective method to perform local debridement or amputation of the foot in an ischemic or diabetic extremity.

Aged↗
PubMed1991

Acute arterial insufficiency of the male genitalia.

Three patients developed severe ischemia of the penis or scrotum from acute arterial occlusion. In one case, nonhealing ulceration of the glans developed after atheroembolism to the dorsal penile artery. One patient had penile ischemia after ligation of pelvic and femoral collateral circulation during repair of an aorto-bilateral-iliac artery aneurysm. A third patient had ischemia of the penis and scrotum from thromboembolism to the iliac arteries during repair of an aortoenteric fistula. Only seven patients have been described with acute arterial occlusion and severe ischemia of the male genitalia. A rare phenomenon because of rich collateral circulation, acute ischemia of the genitalia nevertheless must be recognized as a sign of severe vascular disease and a consequence of major arterial ligation or occlusion in the pelvis and groins.

Acute Disease↗
PubMed1991

Effect of progesterone on renin secretion in endometrial stromal, chorionic trophoblast, and mesenchymal monolayer cultures.

Renin messenger ribonucleic acid expression has been shown in decidual tissue and endometrium, but weakly in chorion laeve, suggesting decidua as a primary source of uteroplacental renin. We proposed to confirm active renin secretion by endometrial stromal cells and examined the effect of progesterone-induced decidualization on secretion. Separate monolayer cultures of endometrial stroma, trophoblast, and mesenchymal cells were established and maintained for 10 to 15 days. Active renin concentration was measured with radioimmunoassay for angiotensin I generation and expressed as picograms per milliliter of angiotensin I generation per 10(5) cells. Active renin concentration was high in control secretory endometrial stromal cells (513 pg/ml) compared with trophoblast (none) and mesenchymal cell cultures (74 pg/ml). Marked decrease in active renin secretion occurred in control endometrial stromal cells (days 13 to 15, 86 pg/ml), whereas progesterone-induced decidualization sustained and increased secretion (days 13 to 15, 1017 pg/ml). This renin activity was quantitatively inhibited in culture fluid assays by specific human renal renin antibody in serial dilutions. Renin activity measurements before and after trypsin activation showed the majority of renin (91.15%) in the inactive form and a smaller fraction (8.85%) in the active form. Immunohistochemistry with the use of specific human renal renin antibody confirmed the presence of renin and its stimulation by progesterone in endometrial stromal cells. Progesterone had minimal effect on mesenchymal cells. These data confirmed endometrial stromal cells as a significant source of active renin and showed that progesterone induced a marked increase in this production.

Chorion↗
PubMed1991

Duplex Doppler sonography of the umbilical arteries: predictive value in IUGR and correlation with birth weight.

Forty-three women with either clinically high-risk singleton pregnancies or a predicted fetal weight less than the 10th percentile were studied in their third trimester by duplex Doppler sonography of the free umbilical artery to assess the associations between umbilical arterial flow resistance and intrauterine growth retardation (IUGR) and birth weight. Test criteria included: the greatest (GRI), mean (MRI), and least (LRI) resistive index. The criterion with the strongest association with IUGR (p = 0.001) was the parameter of the LRI predicting IUGR). Linear regression analysis showed a nonsignificant correlation between RI and percentile birth weight, with r2 = 0.05 and p = 0.131. While significant associations can be shown between RI and IUGR, the clinical use of the results of this test should reflect the imprecise nature of these correlations.

Birth Weight↗
PubMed1991

Treatment of abdominal aortic aneurysm by exclusion and bypass: an analysis of outcome.

Abdominal aortic aneurysm is conventionally treated by aneurysmorrhaphy with inlying graft. Alternatively, division of the aorta, with suture closure of the distal aorta and outflow vessels (exclusion of the aneurysm), and end-to-end proximal to distal bypass may be performed. However, the long-term fate of this operation has not been determined. Specifically, concern exists that the excluded blood filled aneurysm may not thrombose or may be the source of late sepsis. During an 8-year period we have treated 280 abdominal aortic aneurysms (urgent and elective) by exclusion of the abdominal aortic aneurysm sac and bypass via the posterolateral retroperitoneal approach. Mean age was 70 years (range, 44 to 88), with 217 men and 63 women. Preoperative CT scanning and aortography were performed to assess arterial anatomy. Seventy tube grafts and 260 bifurcation grafts were used. Thirty-day mortality rate was 4%. Estimated blood loss was 731 +/- 52 ml; mean transfusion requirements were 456 +/- 82 ml. The minor complication rate was 6%, and it is of great interest that there were no cases of ischemic colitis requiring colectomy. Aneurysm sacs thrombosed except in two anticoagulated patients who required further treatment. No late infections occurred. Five-year bypass patency rate was 98%. These data demonstrate that this method of treatment effectively minimized operative dissection and blood loss and therefore is a viable alternative for the management of abdominal aortic aneurysms.

Aged↗