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Biomedical subjects

J M Porter

Publications and source records attributed to J M Porter.

At least 235 records · Page 13Linked to original sources
PubMed1986

Non-invasive measurement of limb and digit blood flow.

There are many clinical applications for non-invasive measurements of limb and digit blood flow, but often plethysmographs are inconvenient to use. Most experimental work has been carried out on patients with vascular disease. The variation of blood flow with various environmental and physiological factors has been investigated. Little information is available on the effects of injury or surgical trauma on blood flow in limbs. Plethysmographic methods measure arterial flow or pulse volume by several techniques including volumetric displacement, electrical impedance, gravimetry and the mercury in rubber strain gauge. Calorimetric, Doppler and isotope clearance techniques have also been applied to the measurement of blood flow in digits. None of these methods fulfils all the criteria for the requirements of an ideal device and some are too complicated, uncomfortable or cumbersome for widespread use. The results from different techniques are compared and the reasons for variability are discussed. Possible mechanisms for the effects of trauma on limb blood flow are suggested. Experimental comparisons of different plethysmographs are described and the requirements for future development of these devices are defined.

Blood Flow Velocity↗
PubMed1986

Template requirements for in vivo replication of adenovirus DNA.

The adenovirus (Ad) DNA origin of replication was defined through an analysis of the DNA sequences necessary for the replication of plasmid DNAs with purified viral and cellular proteins. Results from several laboratories have shown that the origin consists of two functionally distinct domains: a 10-base-pair sequence present in the inverted terminal repetition (ITR) of all human serotypes and an adjacent sequence constituting the binding site for a cellular protein, nuclear factor I. To determine whether the same nucleotide sequences are necessary for origin function in vivo, we developed an assay for the replication of plasmid DNAs transfected into Ad5-infected cells. The assay is similar to that described by Hay et al. (J. Mol. Biol. 175:493-510, 1984). With this assay, plasmid DNA replication is dependent upon prior infection of cells with virus and only occurs with linear DNA molecules containing viral terminal sequences at each end. Replicated DNA is resistant to digestion with lambda-exonuclease, suggesting that a protein is covalently bound at both termini. A plasmid containing only the first 67 base pairs of the Ad2 ITR replicates as well as plasmids containing the entire ITR. Deletions or point mutations which reduce the binding of nuclear factor I to DNA in vitro reduce the efficiency of plasmid replication in vivo. A point mutation within the 10-base-pair conserved sequence has a similar effect upon replication. These results suggest that the two sequence domains of the Ad origin identified by in vitro studies are in fact important for viral DNA replication in infected cells. In addition, we found that two separate point mutations which lie outside these two sequence domains, and which have little or no effect upon DNA replication in vitro, also reduce the apparent efficiency of plasmid replication in vivo. Thus, there may be elements of the Ad DNA origin of replication which have not yet been identified by in vitro studies.

Adenoviruses, Human↗
PubMed1986

Long-term hemodynamic and clinical sequelae of lower extremity deep vein thrombosis.

Forty-seven patients with phlebographically confirmed lower extremity deep vein thrombosis (DVT) were reexamined 5 to 10 years (mean, 7 years) after the thrombotic event. Clinical symptoms were recorded and the following noninvasive venous vascular laboratory tests were performed: Doppler examination to determine venous valve competence and photoplethysmography to measure ambulatory venous pressure and venous recovery time. Twenty-eight control subjects underwent similar examination. Although only 10 of 47 patients (21%) were asymptomatic, venous ulceration had developed in only two patients. The symptomatic patients had varying degrees of edema, pigmentation, and varicosities. Eighty-three percent of DVT patients had abnormal vascular laboratory findings. Both the severity of clinical symptoms and the magnitude of the hemodynamic abnormalities generally correlated with the extent of the initial thrombus. However, only 47% of patients whose initial thrombus appeared limited to the calf were asymptomatic, and only 25% of this group had normal venous hemodynamic findings. This study indicates that 5 to 10 years after lower extremity DVT 80% of patients will have both symptoms and abnormal venous hemodynamics regardless of the initial site of the thrombosis.

Female↗
PubMed1986

Present status of reversed vein bypass for lower extremity revascularization.

During the past 4 years we have performed 239 reversed vein bypasses for leg ischemia in 196 patients including 45 to the above-knee popliteal artery, 118 to the below-knee popliteal artery, and 76 to infrapopliteal arteries. The cumulative primary patency results by the life-table method through 24 months are 97% at 6 months, 91% at 1 year, and 88% at 2 years. No difference was evident in patency rates with respect to site of distal anastomosis or reason for graft performance (i.e., for claudication [31%] or for limb salvage [69%]). Twenty-two percent of these patients did not have an intact ipsilateral greater saphenous vein. By a variety of techniques including the use of cephalic and lesser saphenous veins, vein splicing, and proximal superficial femoral endarterectomy, we have been able to perform autogenous vein bypass in 94% of all patients who require lower extremity revascularization. The patency of bypasses made from conduits other than greater saphenous vein does not differ from that of the entire series. Both the graft patency and vein utilization rates in the present report are equal to those of recently published series of in situ saphenous vein bypasses and are clearly better than the published results with reversed vein bypass a decade and more ago. We conclude that, although in situ saphenous vein bypass is a good procedure, it is not superior to reversed vein bypass performed in the same time period. This report again emphasizes the hazards of evaluating any new treatment by use of historic controls.

Actuarial Analysis↗
PubMed1986

Intermittent subclavian venous obstruction: utility of venous pressure gradients.

A 22-year-old-man with intermittent obstruction of the subclavian vein at the thoracic outlet was evaluated by a pullback venous pressure gradient measurement and phlebography. The use of venous pressure gradient measurement allowed precise definition of the site of venous obstruction in the thoracic outlet and guided appropriate surgical therapy. The gradient information is of potential importance as many normal individuals have positional phlebographic venous compression at the thoracic outlet. Early identification of subclavian compression syndromes may avoid venous thrombosis with its attendant morbidity.

Adult↗
PubMed1986

Composition and metabolism of symptomatic distal aortic plaque.

This study examines the composition of advanced human atherosclerotic lesions removed by endarterectomy and compares the collagen synthesis in the lesion with that of the intima-media layer of uninvolved vessel wall. The most striking feature of the lesions is an enormous accumulation of calcium that was raised more than tenfold, from a level of about 3% of dry tissue weight in the normal tissue to values approaching 50% in the pathologic specimens. The composition of the organic matrix was also altered. Elastin and glycosaminoglycan content decreased, whereas collagen content more than doubled, thus becoming the major component of the organic matrix. The cholesterol content increased severalfold above normal but even then accounted for less than 10% of the organic matrix. The lesion specimens synthesized collagen in vitro at a greater rate than normal tissue. The endarterectomy specimens with the highest calcium content exhibited the highest rate of collagen synthesis.

Adult↗
PubMed1985

Angiographic findings in mixed connective tissue disease. Correlation with fingernail capillary photomicroscopy and digital photoplethysmography findings.

Thirteen patients with mixed connective tissue disease underwent hand angiography to assess the degree of vascular abnormalities and their correlation to nailfold capillary microscopy and digital photoplethysmography findings. Organic obstruction was found in 60% of ulnar arteries, 87% of superficial arches, 13% of deep arches, and 65% of digital arteries. Fingernail capillary abnormalities were seen in 90% of patients. Normal photoplethysmography results had a predictive value of 91% for identifying digits without bilateral occlusions. These findings indicate a hitherto unrecognized propensity for disease of both small and medium-sized vessels in patients with mixed connective tissue disease.

Adult↗
PubMed1985

Lumbar sympathectomy for lower extremity vasospasm.

Ten patients, 8 female and 2 male, with refractory episodic lower extremity vasospasm were encountered during a 15 year period in which over 600 patients with upper extremity vasospasm were studied. Seven patients had associated upper extremity vasospasm. No patient had evidence of autoimmune disease. Lower extremity reserpine Bier block produced symptomatic relief for 1 to 3 days in all patients in whom it was used. Oral medications were ineffectual. A diagnostic toe photoplethysmographic pattern was noted in these patients, consisting of a normally pulsatile tracing after warming and a flat, nonpulsatile or minimally pulsatile tracing after cooling. Each patient underwent lumbar sympathectomy. During follow-up, which averaged 4 years, each patient remained free of episodic vasospasm on the side of surgery. We conclude that lumbar sympathectomy is an effective and durable treatment for lower extremity vasospasm.

Female↗
PubMed1985

Thrombolytic therapy followed by first rib resection for spontaneous ("effort") subclavian vein thrombosis.

Spontaneous (effort) subclavian vein thrombosis in young persons has historically produced long-term disability from arm swelling and exercise limitation because of failure of the occluded vein to recanalize. Several investigators have speculated that the use of thrombolytic therapy to produce clot dissolution followed by resection of the first rib to prevent recurrence might be ideal management of this condition. Our recent experience with treatment of two such patients formed the basis for this report. Two young men were seen within 24 hours of onset of acute arm swelling, found by venography to be caused by acute thrombosis of the subclavian vein at the level of the first rib. They were treated with systemic thrombolytic therapy with intravenous streptokinase. Both had prompt resolution of all signs and symptoms, confirmed by repeat venography to be accompanied by recanalization of the occluded veins. Both were then anticoagulated with heparin followed by warfarin and underwent elective first rib resection, after which anticoagulation was discontinued. Both patients have remained asymptomatic. Persistent venous patency has been confirmed by repeat venography. Thrombolytic therapy to recanalized spontaneous (effort) subclavian vein thrombosis followed by first rib resection appears to be an advance in the treatment of this condition and may avoid the long-term disability with which it has historically been associated.

Adolescent↗
PubMed1985

Current status of thrombolytic therapy.

The optimal role of thrombolytic therapy in clinical practice has not been defined precisely. A review of available information indicates that such therapy may be useful in a small number of carefully selected patients with deep vein thrombosis and/or pulmonary emboli. The superiority of thrombolytic therapy over conventional surgery for arterial thrombi has not been convincingly demonstrated. Available evidence suggests such therapy should be reserved for those conditions in which surgery may be expected to have a poor outcome or be associated with a high incidence of complications. Preliminary information suggests thrombolytic therapy may be of benefit in selected patients with acute myocardial infarction.

Adult↗
PubMed1985

Critical hand ischemia caused by forearm fibromuscular dysplasia.

This article describes our experience with the management of a 79-year-old woman who had abrupt onset of unilateral critical hand ischemia associated with advanced localized fibromuscular dysplasia of the forearm arteries and thrombotic occlusion of the palmar arch. The patient was successfully managed with local infusion of streptokinase, which was followed by excision and grafting of the radial and ulnar arteries. To our knowledge this represents the first case of hand ischemia associated with forearm fibromuscular dysplasia.

Aged↗
PubMed1985

A multiclinic, placebo-controlled, double-blind study of prostaglandin E1 in Raynaud's syndrome.

Prostaglandin E1 (alprostadil, Prostin VR Sterile Solution, PGE1) was evaluated in patients with Raynaud's syndrome in a multiclinic, placebo-controlled, double-blind study. A total of 55 patients with either primary Raynaud's disease or Raynaud's disease secondary to systemic sclerosis were randomly assigned to receive either PGE1 administered intravenously at 10 ng/kg/min for 72 hours or placebo administered in the same manner. The frequency and severity of Raynaud's attacks were then monitored for up to four weeks by use of in-clinic questionnaires and patients' daily diaries. Haemodynamic assessments included measurements of skin temperature and the finger systolic pressure response to localised digital cooling. Immediately after the infusion the overall symptoms in both the PGE1 and the placebo group showed marked improvement; by four weeks after infusion, in some cases, values had not returned to pretreatment levels. There was, however, no marked benefit of PGE1 treatment over that of placebo. Although PGE1 significantly increased skin temperature during and immediately after infusion, the effect did not persist at two- and four-week follow-up evaluations. The finger systolic pressure response to localised digital cooling (15 degrees C) increased more in the PGE1-treated group than in the placebo-treated group, but the difference was not statistically significant. There was no difference in ulcer healing between the two treatment groups. These results failed to substantiate earlier open-label reports that a 72-hour intravenous infusion of PGE1 in patients with Raynaud's syndrome produced significant clinical benefit.

Adult↗
PubMed1985

Measurement of limb blood flow by electrical impedance plethysmography.

Limb blood flow has been measured in 72 individuals by the noninvasive technique of electrical impedance plethysmography. Venous occlusion was not used. Blood flow was measured in 230 limbs in which 195 limbs were either in normal individuals or the clinically normal limbs of patients (normal limbs). Thirty-five limbs were clinically abnormal. Measurements on limbs with clinical abnormalities showed that blood flow values often fell within the limits of the normal range. However 3 cases of known vascular injury and 2 cases studied after hand surgery under tourniquet showed lowered blood flow values by comparison with the unaffected limb. A simultaneously recorded range of cardiac output and stroke volume measurements gave similar results to those obtained in a previous, unconnected study.

Adolescent↗
PubMed1984

Intraarterial streptokinase infusion for acute popliteal and tibial artery occlusion.

Eight consecutive patients with acute thrombotic or embolic occlusion of the popliteal or tibial artery were treated with low-dose intraarterial streptokinase followed by arterial reconstructive surgery where appropriate. Three patients had acute thrombosis of a popliteal aneurysm with limb-threatening ischemia. All three were relieved of their acute ischemia by streptokinase infusion accompanied by lysis of clots in the popliteal artery outflow tract. Each patient then underwent elective popliteal aneurysm bypass. Four patients had acute embolic popliteal or tibial artery occlusion. Each was relieved of ischemic symptoms. One required surgery to remove residual clot. One patient with thrombosis of the tibioperoneal trunk did not have a decrease in symptoms with streptokinase infusion, but did experience sufficient outflow tract thrombolysis to permit construction of a tibial bypass with resultant restoration of normal circulation. Low-dose intraarterial streptokinase may be the treatment of choice for selected patients who present with thrombosis of a popliteal aneurysm with tibial vessel involvement or with embolic popliteal or tibial artery occlusion.

Acute Disease↗
PubMed1984

Treatment of chronic visceral ischemia.

Herein, we have described the surgical management of 23 patients with chronic intestinal ischemia. The patients presented most commonly with postprandial pain and weight loss. Diagnosis was confirmed by angiography, including lateral aortography. Surgery included bypass with Dacron being the most common graft material. As many vessels as possible were revascularized using an infrarenal graft origin. Two patients died postoperatively from acute myocardial infarction. There were two graft failures in this group. At the present time, 19 of the 21 surviving patients are asymptomatic or greatly improved.

Adult↗
PubMed1984

The surgical management of intractable venous ulceration in the lower limbs: excision, decompression of the limb and split-skin grafting.

Fourteen patients with severe chronic venous ulceration and constricted lower limbs underwent an operation to release the constriction and to ligate the perforating veins in the calf. At 4-year follow-up 6 patients remained healed. Two further patients were healed when last seen 3 years and 19 months after surgery. The operation is suggested as a salvage procedure for selected patients, when all other methods of treatment have failed.

Aged↗