Genomic breeding value prediction for simple maize hybrid yield using total effects of associated markers, under different imbalance levels and environments.

The main objective of a maize breeding program is to generate hybrid combinations that are more productive than those pre-existing in the market. However, the number of parents, and consequently the number of crosses, increases so rapidly that the phenotypic evaluation of all the possible combinations becomes economically and technically infeasible. In this context, predicting the performance of the most promising genotypes may increase the genetic gains with increased selection intensity and reduced breeding cycles. Thus, the present study aimed to use the total effects of associated markers method to predict genomic breeding values (GBVs) via cross-validation and by using different imbalance levels (10, 30, 50, and 70%). A set of 51 genotyped strains was used with 79 microsatellite markers and 273 hybrids that were generated by a partial diallel. A total of 186 and 272 hybrids were analyzed in the experiments within the southern and central regions of Brazil, respectively. The GBVs were, thus, predicted for each location in both the regions, and for training in one region and validation in another region. The correlation between the predicted and observed GBVs ranged from 0.48 to 0.91, depending on the imbalance level and the region analyzed. Overall, the results obtained in the present study were promising, particularly considering that a small number of markers were used and that the training and predictions occurred in the very distinct regions of southern and central Brazil.

Atrial myxoma with remote metastasis: case report and review of the literature.

The occurrence of a metastatic atrial myxoma after complete resection of the intracardiac lesion is rare. We treated a 66-year-old man who 13 years earlier had undergone resection of a left atrial myxoma, which had been diagnosed during a work-up of symptomatic cerebellar infarcts. He initially had a painless nonpulsatile mass near the radial artery. Surgery was performed to confirm the presumptive diagnosis of calcified ganglion, and subsequently he was found to have a pseudoaneurysm. The pathologic examination identified the tissue as myxoma. The results of echocardiography and cardiac magnetic resonance imaging failed to reveal any residual or new intracardiac tumor. The patient subsequently experienced swelling of the right leg and was found to have a 6 x 10 cm mass in the medial portion of his proximal thigh. At exploration this mass was found to extend from the profunda femoris artery, and it also compressed the femoral vein. Pathologic evaluation based on histologic and electron microscopic features of this lesion confirmed this lesion to be myxoma. Review of the literature reveals that metastatic atrial myxoma is a rare lesion, and such a delayed occurrence after resection of the cardiac lesion has been infrequently reported. This suggests that patients with atrial myxoma may be at risk for the appearance of intravascular metastatic tumor long after resection of their original intracardiac tumor.

Retroperitoneal inflow procedures for iliac occlusive vascular disease.

We reviewed our experience over the past six years with retroperitoneal inflow procedures (aortofemoral and iliofemoral bypass grafts) in high-risk patients with aortoiliac occlusive disease. There were 57 limbs in 40 patients. Twenty percent of the patients were diabetic, 80% were smokers, 40% had heart disease, 54% had hypertension, and 25% had symptomatic chronic obstructive pulmonary disease. The average patient age was 64 years. There was no operative mortality and cumulative patency rate by life-table analysis at four years was 84%. The site of the proximal anastomosis (aorta vs iliac) or the configuration of the graft (unifemoral vs bifemoral) did not influence the patency rate. Retroperitoneal inflow procedures are an excellent alternative in patients who present an unacceptably high risk for standard aortofemoral reconstruction.

A comprehensive approach to extremity vascular trauma.

A review of our experience with 368 patients with 382 extremity injuries has resulted in a treatment plan resulting in improved patient care and limb survival. A thorough examination of the injured extremity will help diagnose a significant vascular injury in the presence of certain clinical findings, eg, bruit or thrill (100%), signs of acute ischemia (100%), absent pulse (91%), shock (89%), neurologic deficit (78%), and hematoma (55%). Arteriography in proximity injuries has resulted in an abnormal finding in 16% of cases. A total of 165 vascular injuries, including 112 arterial and 53 venous injuries, were repaired using a variety of techniques. In 136 patients undergoing operative intervention, there was no operative mortality and a 1.5% amputation rate.

The use of arm veins for infrainguinal bypass in end-stage peripheral vascular disease.

Thirty-six infrainguinal bypass grafts were performed in 33 patients with the use of autologous arm vein. Indications for operation were ischemic rest pain or tissue loss in all patients. The average age of the patients was 70.0 years-27% were diabetic and 66% were smokers. Sixty-five percent of the grafts were performed as secondary reconstructions. Follow-up ranged from three weeks to six years, with a mean of 12.1 months. Life-table primary and secondary patencies for all grafts are 73% and 82% at one year, respectively. Simple (noncomposite) arm vein grafts had primary and secondary patencies of 75% and 85%, respectively. The limb salvage rate was 86%. No grafts required thrombectomy for early occlusion (less than 30 days), and no graft failures have occurred beyond nine months (n = 18). Arm vein bypass grafts demonstrate excellent patency rates and provide the preferred conduit in the absence of autologous saphenous vein.

Noninvasive detection of carotid stenosis following endarterectomy.

Noninvasive diagnostic studies (oculoplethysmography, pulsed Doppler arteriography, and phonoangiography) were used to follow the postoperative courses of 172 patients who had 199 carotid endarterectomies. There were 24 restenotic arteries in 21 patients who underwent 29 operations. Fifteen restenotic lesions in 14 patients were detected solely by noninvasive testing. These patients are being observed closely and remain asymptomatic. One has been operated on for progression of disease. Either transient or permanent neurologic deficits developed in nine as the initial indication of recurrent stenosis or occlusion; three of these subsequently have undergone reoperation. Patients with bilateral disease are at increased risk of restenosis. Routine testing of all patients undergoing carotid endarterectomy is recommended 1, 3, and 12 months postoperatively to detect and observe stenosis on both the side operated on and the contralateral side before clinical symptoms develop.

Successful vein bypass in patients with an ischemic limb and a palpable popliteal pulse.

Patients presenting with an ischemic foot who have a palpable popliteal pulse have not always been considered to be suitable candidates for arterial reconstruction. Since 1976, 32 distal bypasses were performed in 30 such patients, 77% of whom were diabetic. Proximal anastomoses were from the distal superficial femoral or popliteal artery. Autologous vein was used in all cases. There were six graft failures, all of which occurred within eight months. Three failures, which all occurred within the first month, required below-the-knee amputation. Using life-table analysis, the one- and three-year patency rates were both 79%. One- and three-year limb-salvage rates were 89% and 82%, respectively. We conclude that the results of distal vein graft reconstruction originating from the superficial femoral or popliteal artery are comparable with those of any group of patients with arterial occlusive disease of a lower extremity.

Evaluation and management of vascular injuries of the extremities.

We reviewed our experience with 315 extremity injuries in 306 patients for the possibility of accurately evaluating the presence of a potential vascular injury. Indications for surgical exploration based on the clinical finding of a bruit and/or thrill, ischemia, absent, pulse, shock, hemorrhage, neurologic deficit, hematoma, and proximity resulted in a rate of positive surgical exploration results of between 20% and 100%. Angiography was performed in 65 patients; 24 angiograms showed vascular injury and 41 did not. Angiography for proximity alone revealed 12% abnormal finding. Operative morbidity in the surgically explored group was 2%. We developed an algorithm for the treatment of these patients.

Collateral flow changes through the anterior communicating artery during carotid endarterectomy.

To evaluate early changes in collateral flow through the anterior communicating artery, 11 patients undergoing carotid endarterectomy were monitored. All had angiographically demonstrated collateral flow towards the hemisphere on the side of surgery. The middle cerebral artery ipsilateral to the operated side and the contralateral anterior cerebral artery were simultaneously insonated with a transcranial Doppler instrument equipped with dual transducers, and flow velocity values were obtained at specific surgical stages. Mean flow velocity in the contralateral anterior cerebral artery's A1 segment increased at clamp placement (p = 0.036), did not change during clamping, and decreased at clamp release (p = 0.004). The rise in velocity occurred within seconds of clamp placement in all patients with an increase, reaching the 10 cm/s threshold within 1 min. No consistent increase was detected after 5 min. A decrease in pulsatility index, indicating a drop in resistance, was detected at clamp placement in the middle cerebral artery on the side of surgery (p = 0.012). The index did not change during clamping, but increased at clamp release (p = 0.002). Our findings indicate that significant changes in anterior communicating artery collateral flow occur during carotid endarterectomy, starting within seconds of carotid artery clamping. These changes are associated with arterial resistance alterations in the territory of the middle cerebral artery on the endarterectomy side. Our observations should be useful to assess intracranial early collateral flow changes in surgical and non-surgical settings.

Cerebral microembolism during carotid endarterectomy.

BACKGROUND: This study was designed to assess the intraoperative risk of cerebral microembolism, as detected by transcranial Doppler ultrasonography, during carotid endarterectomy. PATIENTS AND METHODS: Thirty-six patients (37 procedures) with symptomatic (n = 35) or asymptomatic (n = 2) internal carotid artery origin stenosis(> 50%) were monitored continuously during carotid endarterectomy. Special instrumentation was used to detect high-intensity transient signals (HITS) in the middle cerebral artery on the carotid endarterectomy side. All HITS satisfied a priori established criteria. RESULTS: The incidence of carotid endarterectomies with formed-element HITS increased at clamp release (23/37, P < 0.001) and shunt opening (7/11, P = 0.014), and during wound closure (13/22, P< 0.005) and shunting (5/11, P = 0.046). HITS with air microbubble characteristics were detected at clamp release (22/37, P < 0.001) and shunt opening (5/11, P = 0.025). CONCLUSIONS: HITS do not occur randomly during carotid endarterectomy. Shunting, unclamping, and wound closure are high-risk periods.

Effect of inflow and outflow sites on the results of tibioperoneal vein grafts.

We have reviewed our experience with the tibial vessel bypass operation and have found the overall patency and limb salvage rates to be acceptable. Patients were divided into two groups based on the site of the proximal anastomosis. In Group I, the proximal anastomosis was at the common femoral artery and in Group II, the proximal anastomosis was at the distal superficial femoral artery or the popliteal artery. The patients in the two groups were similar with regard to indications for operation, age, and sex. However, in Group I, 35 percent of the patients were diabetic and in Group II, 74 percent of the patients were diabetic. In the Group I patients, the 72 month graft patency rate was 65 percent with a limb salvage rate of 75 percent. In the Group II patients, the 72 month patency rate was 81 percent with a limb salvage rate of 89 percent. Some possible explanations for this slightly better result in Group II patients are discussed. All tibial bypasses were divided into three groups based on the recipient tibial artery. Analysis revealed that the 72 month patency rates were as follows: the anterior tibial artery 63 percent, the posterior tibial artery 81 percent, and the peroneal artery 80 percent. These differences were not significant but indicate, as others have recently pointed out, that the peroneal artery is indeed an acceptable recipient artery for tibial bypass surgery.

Therapeutic and clinical course of deep vein thrombosis.

We have reviewed our experience with the treatment of 250 patients with deep vein thrombosis diagnosed by contrast venography. The level of thrombosis was recorded according to the anatomic level to which it extended. A third of the patients had cancer, and the most common clinical findings were swelling and pain. The risk of the development of pulmonary embolism, based on the anatomic level of initial deep vein thrombosis, revealed the following: 12 of 115 patients (10 percent) with level I (calf) deep vein thrombosis developed pulmonary embolism, as did 2 of 27 patients (7 percent) with level II (popliteal) disease, 5 of 60 (8 percent) with level III (thigh) disease, 1 of 19 patients (5 percent) with level IV (groin) disease, and 2 of 26 patients (8 percent) with level V (iliac) disease. Based on our favorable experience with heparin we believe that heparin is the treatment of choice for deep vein thrombosis regardless of the anatomic level. The incidence of pulmonary embolism does not appear to be influenced significantly by the level of the deep vein thrombosis.

The preoperative angiogram as a predictor of peripheral vascular runoff.

The preoperative angiogram is widely used as a means of assessing peripheral vascular runoff before bypass grafting, but the correlation between preoperative angiographic findings and actual measurements of peripheral vascular resistance has not been adequately examined. To test this correlation, we first devised a simple technique for measuring peripheral resistance and validated it in five dogs. Increases in peripheral resistance were artificially produced by temporarily occluding either the deep or superficial femoral artery or by intravenous administration of phenylephrine hydrochloride, a vasoconstrictor. In each instance, significant increases in resistance could be measured. We then used a similar technique to measure resistance in 23 patients undergoing peripheral bypass surgery. In addition, preoperative angiograms for these 23 patients were independently scored by four readers as 0, 1, 2, or 3 based on the number of patent vessels seen below the knee. Variations in scoring from reader to reader suggested that the present criteria for grading angiograms on this basis are unclear. Moreover, the correlation between angiographic score and measured resistance was poor for three of the four scorers (-0.21 to -0.29, p greater than 0.05). The angiographic scores of one reader, however, correlated reasonably well with the peripheral resistance measured at surgery (-0.59, p = 0.01). These findings demonstrate that current criteria for grading the preoperative angiogram are not sufficiently standardized to reliably predict runoff from a preoperative angiogram. However, these findings also suggest that it may be possible to identify angiographic findings that correlate well with changes in measured resistance.

Combined transluminal angioplasty and infrainguinal reconstruction in multilevel atherosclerotic disease.

Patients with multilevel atherosclerotic disease represent a difficult surgical challenge. This report is a retrospective review of 46 patients who were treated using a combination of iliac transluminal angioplasty and infrainguinal reconstruction. There were 42 male and 4 female patients with an average age of 62 years (range: 40 to 74 years). Follow-up ranged from 1 month to 10 years (mean: 27.3 months). These patients had multiple health problems typical of patients with peripheral vascular disease, including coronary artery disease (67%), hypertension (61%), and diabetes mellitus (42%); 80% of the patients were smokers. Forty-one patients were treated for rest pain and/or tissue loss, while five were treated for incapacitating claudication. Forty-three patients had a combination of angioplasty and distal bypass, while 3 patients had a form of femoral endarterectomy. Iliac artery pressure gradients were reduced from 35.4 +/- 4 mm Hg preangioplasty to 0.6 +/- 0.3 mm Hg postangioplasty. The procedures were well tolerated with no mortality and four serious complications. Vascular laboratory studies showed an improvement in the mean ankle-brachial index from 0.35 +/- 0.03 preoperatively to 0.71 +/- 0.04 postoperatively (p less than 0.05). Life-table analysis revealed a 72% 5-year primary patency rate, with a 93% 5-year limb salvage. Eight patients required a secondary procedure to maintain limb salvage. Five patients underwent amputation, three due to early graft thrombosis and two due to late graft failure. We conclude that combined iliac angioplasty and infrainguinal reconstruction is a safe and effective method for managing the patient with severe multilevel atherosclerotic disease.

Interactive videodisc as an instructional tool in medical education.

At a time when medical educators are actively revising the undergraduate medical school curriculum to make it more responsive to exigencies of the 21st century, the use of interactive videodisc technology may well prove to be a significant addition. Using interactive videodisc technology may be instrumental in reducing the amount of a large lecture didactic learning and improving small group problem-solving sessions that better synthesize factual knowledge. It also provides important and valuable exposure to varieties of computer technology that play an increasingly important role in training and medical practice.

Quantitative analysis of anastomotic intimal hyperplasia in paired Dacron and PTFE grafts.

The purpose of this investigation was to compare and contrast the occurrence and progression of anastomotic intimal hyperplasia in two commonly used prosthetic arterial grafts. Twenty paired carotid artery interposition grafts of Dacron and PTFE (polytetrafluoroethylene) were implanted in a canine model. The grafts were electively removed at intervals from one week to seven months or at the time of thrombosis. Areas of hyperplastic growth were determined at each anastomosis using a quantitative histologic technique. The number of grafts quantitatively evaluated was 16 Dacron and 12 PTFE, excluding all thrombosed grafts. In both materials, hyperplasia occurred to a significantly greater degree at the distal or downstream anastomosis as compared with the proximal or upstream anastomosis (Dacron P less than 0.001, PTFE P less than 0.05). Quantitative and qualitative evaluation of these two commonly used but different arterial grafts did not demonstrate a significant difference in the occurrence of anastomotic hyperplasia.

Traumatic popliteal artery pseudoaneurysms: case report and review of the literature.

Traumatic pseudoaneurysms of the popliteal artery are an uncommon late complication of arterial injury. Although reviewed extensively in wartime, they occur less frequently in civilian trauma and have accordingly been less frequently studied. A case report of a traumatic popliteal artery pseudoaneurysm and review of the literature are presented.

Management of the contused arterial segment.

When a contused arterial segment is found at surgical exploration and interposition graft is required, we propose a method of repair in which the posterior wall is not completely divided. This prevents retraction of the arterial ends and eliminates tension on the anastomosis.

Complications of caval interruption by Greenfield filter in quadriplegics.

Patients with acutely injured spinal cords are thought to be at increased risk for thromboembolic disease and often have contraindications to anticoagulation therapy. From 1981 to 1986, 13 patients with quadriplegia at the New England Regional Model Spinal Cord Injury Center had caval interruption with a Greenfield filter. Twelve patients had deep venous thrombosis documented by venogram results and one had pulmonary embolism documented by arteriogram results. "Quad cough" chest physical therapy was required for mobilization of pulmonary secretions in nine patients. Follow-up abdominal x-ray results revealed significant abnormalities referrable to the filter in five patients having undergone "quad cough" therapy. Four patients had distal migration of the filter; three of the four had deformation of the filter. Laparotomy for bowel perforation was required in two of these patients. Quadriplegia requiring vigorous chest physical therapy ("quad cough") for pulmonary toilet may be a contraindication to caval interruption by Greenfield filter. Alternative techniques in the management of patients with quadriplegia and pulmonary compromise must be considered.