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Biomedical subjects

M D Clark

Publications and source records attributed to M D Clark.

At least 19 recordsLinked to original sources
PubMed1998

AmphiBMP2/4, an amphioxus bone morphogenetic protein closely related to Drosophila decapentaplegic and vertebrate BMP2 and BMP4: insights into evolution of dorsoventral axis specification.

Amphioxus AmphiBMP2/4 appears to be a single gene closely related to vertebrate BMP2 and BMP4. In amphioxus embryos, the expression patterns of AmphiBMP2/4 suggest patterning roles in the ectodermal dorsoventral axis (comparable to dorsoventral axis establishment in the ectoderm by Drosophila decapentaplegic and vertebrate BMP4). In addition AmphiBMP2/4 may be involved in somite evagination, tail bud growth, pharyngeal differentiation (resulting in club-shaped gland morphogenesis), hindgut regionalization, differentiation of olfactory epithelium, patterning of the anterior central nervous system, and establishment of the heart primordium. One difference between the developmental role of amphioxus AmphiBMP2/4 and vertebrate BMP4 is that the former does not appear to be involved in the initial establishment of the dorsoventral polarity of the mesoderm.

Amino Acid Sequence↗
PubMed1998

Diagnosis of aortocaval fistula by computed tomography.

A case of an aortocaval fistula documented by contrast-enhancement computed tomography is reported. In the presence of a large abdominal aortic aneurysm, the computed tomography (CT) triad findings of: (1) vena caval effacement, (2) loss of the fat plane between the aorta and vena cava, and (3) rapid flow of contrast from the aorta into a dilated inferior vena cava is characteristic of an aortocaval fistula.

Aged↗
PubMed1998

The valvular apparatus in venous insufficiency: a problem of quantity?

Abnormal venous valvular function may produce venous reflux and venous insufficiency. While valvular agenesis is a known, but rare cause of venous insufficiency. While valvular agenesis is a known, but rare cause of venous insufficiency, little work has been done on the relative number of greater saphenous vein (GSV) valves in patients with venous insufficiency. This study investigates whether the GSV in patients with symptomatic venous insufficiency has fewer valves than the GSV of patients without venous insufficiency. The number of GSV valves in patients (n = 51) with symptomatic venous insufficiency undergoing saphenectomy (VI) were compared with the number of GSV valves in patients (n = 26) without venous insufficiency undergoing in situ GSV bypass under angioscopic surveillance who served as a control group. The two groups differed, as expected, in age and sex distribution. The VI group had a mean of 25.7 +/- 11.0 centimeters of GSV between valves, while the control group had 19.0 +/- 9.7 centimeters of GSV between valves (F = 6.99; p = 0.01). The mean number of valves in the saphenous veins of the two groups also differed significantly: VI = 2.3 +/- 0.83 versus control (CTRL) = 4.8 +/- 2.01 (F = 61.86; p < 0.0001). That properly functioning valve leaflets help maintain physiologic antegrade venous flow is indisputable. This study, however, suggests that the relative lack of valves may be related to the development of venous insufficiency. This report documents that patients with symptomatic reflux in the GSV have significantly fewer valves than patients with apparently normal functioning saphenous veins.

Adult↗
PubMed1998

Iliofemoral venous thrombosis caused by compression of an internal iliac artery aneurysm: a minimally invasive treatment.

PURPOSE: To report the success of a minimally invasive treatment for phlegmasia cerulea dolens without gangrene caused by compression from an internal iliac artery aneurysm. METHODS AND RESULTS: An 81-year-old male with a 1-month history of paralysis owing to a hemorrhagic stroke presented with massive edema and skin mottling of the right lower extremity. Imaging confirmed right iliofemoral deep vein thrombosis caused by compression from a 4-cm internal iliac artery aneurysm. With thrombolysis ruled out, a minimally invasive treatment plan was undertaken, featuring percutaneous coil embolization of the aneurysm and surgical venous thrombectomy with proximal arteriovenous fistula creation and iliac vein stent placement. Failure of the coils to embolize the iliac aneurysm prompted the use of an endovascular graft to exclude the aneurysm. The patient's symptoms subsided, and he has a patent right iliofemoral venous system and internal iliac artery at his latest (16-month) follow-up. CONCLUSIONS: This case demonstrates that minimally invasive endovascular and open techniques can be combined to achieve an optimum outcome in patients at high risk for standard surgical approaches.

Aged↗
PubMed1998

Popliteal artery aneurysm treated with a minimally invasive endovascular approach: an initial report.

PURPOSE: To report a minimally invasive approach to popliteal artery aneurysm (PAA) treatment. METHODS AND RESULTS: A 48-year-old male with a 3-cm PAA was treated electively with an endovascular in situ saphenous vein bypass and transluminal antegrade coil embolization of the PAA prior to completion of the proximal anastomosis. Two short incisions at the anastomosis sites resulted in no wound complications, and the patient was discharged after 2 days. After 14 months of follow-up, the patient is asymptomatic with continued patency of the in situ bypass and occlusion of the PAA. CONCLUSIONS: This endovascular approach for minimally invasive femoropopliteal in situ saphenous vein bypass grafting appears feasible for treatment of PAAs. This method may reduce the rate of wound complications attending classic open in situ bypass grafts.

Anastomosis, Surgical↗
PubMed1997

Parenting classes as a part of a hospice bereavement program.

The impact of a loss is felt throughout the family system with the parent-child relationship being particularly vulnerable. The experience of The Mount Carmel Hospice Evergreen Center with a parenting program is presented. Responding to the expressed concerns of grieving parents, a time-limited parenting group was held. The quantitative and qualitative results of that experience are presented. In addition to normalizing the experience of parenting grieving children, the group provided the opportunity for parents to enhance skills and learn about the need to respect the individuality and uniqueness of the grief work of the child.

Adult↗
PubMed1997

Traumatic carotid artery dissection and pseudoaneurysm treated with endovascular coils and stent.

PURPOSE: To report a case of post-traumatic internal carotid artery dissection and pseudoaneurysm formation at the C-1 level successfully treated by a percutaneous endovascular technique. METHODS AND RESULTS: A 20-year-old female presented 72 hours after a motor vehicle accident with incomplete occulosympathetic paresis (Horner's syndrome), carotidynia, and leftsided 1.5-cm x 2.5-cm pseudoaneurysm at the C-1 level. Neuroradiologists embolized the pseudoaneurysm with Guglielmi detachable coils and controlled the dissection with placement of a Wallstent. CONCLUSIONS: This report illustrates successful percutaneous endovascular treatment of a carotid dissection and pseudoaneurysm near the base of the skull.

Accidents, Traffic↗
PubMed1996

Extraluminal endoscopic-assisted ligation of venous tributaries for infrainguinal in situ saphenous vein bypass: a preliminary report.

In an attempt to obviate the need for an incision the length of the leg during in situ saphenous vein bypass, a minimally invasive operation using 'laparoscopic techniques' was developed. At operation, standard incisions were made over the proximal femoral artery/vein and the saphenous vein at the distal popliteal artery level. An angioscopic valvulotome was used to perform valvulotomy under direct vision. After valvulotomy, a distention balloon system was used to form a 'pocket' into which a laparoscope was inserted. Trocars were then inserted under direct vision and the saphenous vein dissected and side branches individually clipped. After occlusion of the venous side branches, proximal and distal arterial anastomoses were performed in the standard fashion. This minimally invasive operation using laparoscopic techniques precludes the need for a long leg incision and saphenous vein dissection, except at the proximal and distal arterial anastomoses.

Aged↗
PubMed1995

Preoperative control of a ruptured anastomotic femoral "pseudoaneurysm" by balloon catheter: a combined radiologic and surgical approach.

Inflow control of a rapidly expanding or ruptured femoral anastomotic "pseudoaneurysm" can be fraught with hazard. Occlusion of an anastomotic femoral aneurysm with a balloon catheter offers the surgeon a simple method of gaining inflow control prior to surgery. After achieving inflow control with the balloon catheter, the surgeon can incise the anastomotic aneurysm without significant blood loss, control back bleeding with balloon occlusion catheters, and with relative ease and safety repair or replace the anastomotic aneurysm as indicated. An illustrative case is presented.

Anastomosis, Surgical↗
PubMed1994

Infrainguinal endovascular in situ saphenous vein bypass: ongoing results.

PURPOSE: With 70 cm "cutter" valvulotomes for valvulotomy and an electronically steerable nitinol catheter to occlude venous tributaries with platinum coils, endovascular in situ saphenous vein (EISV) bypass can be safely performed from within the saphenous vein. To determine whether EISV bypass could reduce hospital length of stay (LOS) and perioperative morbidity without compromising patency, another 53 EISV bypasses for limb salvage were performed. METHODS: Tributary occlusion was accomplished with only fluoroscopic surveillance with a new, smaller, and more steerable silicone-tipped nitinol catheter. RESULTS: Two (3.7%) wound complications occurred. The mean hospital LOS after operation was 4.2 days (range 2 to 29 days). All tributaries initially embolized remained occluded, and three "missed" arteriovenous fistulas were identified during follow-up extending to 15 month (mean 8.4 months). Eighty-eight percent (49 of 54) of phase II bypasses remained patent, whereas life-table analysis of all bypasses (phase I and II) was 77% (69/99) at 24 months follow-up (mean 13.6 months). By comparison, 41 infrainguinal saphenous vein in situ bypasses with "classic" open techniques were performed concurrently. The mean postoperative LOS was 11.6 days (range 4 to 42 days), wound complications occurred in 24% (10) of patients, and two "missed" arteriovenous fistulas were identified during follow-up. Eighty-three percent (34 of 41) of bypasses remain patent at 24 months follow-up (mean 16.2 months). CONCLUSIONS: If EISV bypass long-term patency rates remain similar to classic in situ bypass patency results, the additional benefits of decreased hospital LOS, reduced wound-related complications, shortened recuperation, and therefore increased health care savings gives this endovascular technique strong consideration as the possible future operation for infrainguinal saphenous veins in situ bypass.

Aged↗
PubMed1994

Use of the Greenfield filter in patients with major trauma.

Patients with major trauma often cannot be given the benefit of preventive measures such as pneumatic compression boots and low-dose heparin against pulmonary embolism. The Greenfield filter is accepted as a safe and effective method of prophylaxis of this complication. The aim of this study was to evaluate the efficacy of placement of the Greenfield filter in 161 patients with major trauma. Between January 1984 and July 1988, 94 patients with an injury severity score (ISS) of > 16 were treated. This score is predictive of a mortality rate of at least 10% and defines major trauma based on anatomic injury. Some 20% (19 of 94) of these patients developed deep vein thrombosis despite standard prophylactic measures and 8% (eight of 94) suffered pulmonary embolism, two of which were fatal. Pulmonary embolism occurred without antecedent evidence of deep vein thrombosis in another 15% of patients (14 of 94), three of which caused death. From August 1988 until July 1992, of 67 other patients with an ISS > 16, 13% (nine of 67) developed deep vein thrombosis and 1% (one of 67) had a pulmonary embolism; this was not statistically significant (P > 0.25). Of these 67 patients who were considered to be at high risk of pulmonary embolism, because of a contraindication to anticoagulation or physical impediment to sequential compression boots, 29 had prophylactic placement of a Greenfield filter. No pulmonary emboli occurred in these patients. During long-term follow-up (mean 32.8 (range 4-58) months), 84% of the surviving patients (21 of 25) underwent duplex ultrasonography of the inferior vena cava; patency of the vessel was confirmed in all patients.

Adolescent↗
PubMed1993

NMR measurements of Na+ and cellular energy in ischemic rat heart: role of Na(+)-H+ exchange.

Interleaved 23Na- and 31P-nuclear magnetic resonance (NMR) spectra were continuously collected on perfused rat hearts subjected to low-flow ischemia (30 min, 10% flow) or zero-flow ischemia (21 min) followed by reperfusion. During untreated low-flow and zero-flow ischemia, intracellular Na+ (Nai+) increased by 53 +/- 11 (+/- SE) and 78 +/- 8%, respectively, and remained elevated for zero-flow hearts. However, during both low- and zero-flow ischemia, Nai+ did not increase in hearts treated with the Na(+)-H+ exchange inhibitor, 5-(N-ethyl-N-isopropyl)amiloride (EIPA). The pH decreases during ischemia were unchanged. EIPA treatment reduced ATP depletion during ischemia. During reperfusion from zero-flow ischemia, EIPA-treated hearts displayed more rapid and extensive recoveries of phosphocreatine and ATP. Recovery of left ventricular developed pressure was improved for zero-flow hearts treated with EIPA during the ischemic period exclusively (104 +/- 13%) compared with untreated hearts (36 +/- 21%). These data indicate that Na(+)-H+ exchange is an important mechanism for Nai+ accumulation, but not for pH regulation, during myocardial ischemia. Additionally, Nai+ homeostasis plays an important role in the postischemic recovery of cellular energy and ventricular function.

Amiloride↗
PubMed1992

Amaurosis fugax: is it innocuous?

A 10 year retrospective study of 103 patients with amaurosis fugax was done. Sixty-two patients with symptoms of amaurosis fugax underwent arteriography, which demonstrated ulcerated carotid plaque in 36 and hemodynamically significant stenoses (greater than 75% diameter reduction) in 26. These 62 patients underwent carotid endarterectomy. The other 41 patients who had proven ulcerated plaque (33 patients) or hemodynamic stenoses (eight patients) were not treated surgically and served as a control series. No strokes or deaths occurred in the immediate postoperative period. Follow-up of the 62 operated patients extending to 10 years (mean 4.2 years), revealed one (1.6%) patient with recurrent amaurosis fugax symptoms, two (3.2%) with transient ischemic attacks, and one (1.6%) with a stroke in the operated hemisphere. In the nonoperated group, despite aspirin or warfarin treatment, four (9.7%) patients had ongoing amaurosis fugax symptoms, and two (4.8%) developed transient ischemic attacks that led to carotid endarterectomy. One (2.4%) other patient developed sudden, permanent monocular blindness, and two (4.8%) suffered hemispheric strokes, one of which was fatal. The cumulative morbidity (ongoing ocular or transient ischemic attack symptoms, perioperative and late stroke) in the operated group was 6.4% (four patients), while the cumulative morbidity in the nonoperated group was significantly higher at 21.9% (nine patients) (p = 0.02). When patients present with symptoms of amaurosis fugax and have demonstrable carotid bifurcation disease, carotid endarterectomy is recommended. Amaurosis fugax should be regarded as a harbinger of monocular blindness and stroke.

Adult↗
PubMed1991

When the same is different. A comparison of the information processing strategies of deaf and hearing people.

In this study, the information processing strategies of Gallaudet University students who are profoundly and prelingually deaf were evaluated. The subjects demonstrated the highest levels of recognition to the left and right of the fixation point, often referred to as a reading strategy when found in hearing people. Additionally, they demonstrated higher levels of recognition at positions in the top right quadrant of the display, a pattern not found in hearing people. A main effect was found: subjects whose primary and secondary school backgrounds were oral and manual combined had significantly higher levels of recognition overall than did subjects from oral-only educational backgrounds. Differences in background did not interact with strategy use in this study. These findings lead to the conclusion that the information processing strategies of deaf people need to be evaluated closely before general conclusions can be made. Alternative means for evaluating these types of findings are suggested.

Adult↗
PubMed1990

Case report 589: Use of Ostamer in fusion of lumbar spine, postoperative appearance.

In the late 1950s and early 1960s there was intense orthopedic interest in a plastic polyurethane foam (Ostamer) that could be used in the fixation of fractures, performance of arthrodesis, and in spinal fusions. It saw limited success at that time but eventually fell from favor. A patient presenting with a draining sinus in the buttock, back pain, and a history of lumbar spinal fusion with Ostamer was recently scanned in our department. The CT appearance of Ostamer and a brief review of the literature are reported.

Bone Cements↗
PubMed1990

Carotid patch angioplasty: immediate and long-term results.

To determine the benefit of carotid patch angioplasty, a retrospective study of 1000 consecutive carotid endarterectomies was done. Based on the type of carotid endarterectomy closure, patients were divided into four groups: 250 had primary closure, 250 had expanded polytetrafluoroethylene patch, 250 had Dacron patch, and 250 had saphenous vein patch. On the basis of operative technique or type of carotid artery closure, no statistical difference was found in the incidence of postoperative stroke (p greater than 0.25): primary closure 1.6% (4), expanded polytetrafluoroethylene 2.0% (5), Dacron patch 1.6% (4), and saphenous vein patch (0). Postoperative carotid patency was determined by B-mode ultrasonography, and 717 patients were evaluated in follow-up extending to 6 years (mean 37.8 months). Based on the method of carotid endarterectomy closure, no significant difference (p greater than 0.25) was found in the incidence of significant restenosis (greater than 50% diameter reduction): primary closure 4.0% (7), expanded polytetrafluoroethylene 4.0% (6), Dacron 5.4% (9), and saphenous vein 1.0% (2). Significant restenosis was most frequent in habitual smokers (93%, 25/28) and females (78%, 22/28) despite the method of carotid endarterectomy closure. No statistical difference was found in the incidence of late ipsilateral stroke either (p greater than 0.25): primary closure 2.9% (5), expanded polytetrafluoroethylene 2% (3), Dacron 5% (3), and saphenous vein 0%. These results indicate that the incidence of postoperative stroke, regardless of method of arterial closure, was not statistically different. The method of carotid closure did not appear to affect the occurrence of late ipsilateral stroke or restenosis; however, patch angioplasty with saphenous vein appears appropriate in habitual smokers, and likely in patients with small internal carotid arteries.

Blood Vessel Prosthesis↗