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Biomedical subjects

R M Green

Publications and source records attributed to R M Green.

At least 37 records · Page 2Linked to original sources
PubMed2001

Diagnosis and management of the "difficult" abdominal aortic aneurysm: pararenal aneurysms, inflammatory aneurysms, and horseshoe kidney.

All "difficult" abdominal aortic aneurysms-whether pararenal or inflammatory or associated with abnormal renal parenchymal anatomy-often best are approached with some combination of retroperitoneal exposure and supraceliac clamping. Preoperative recognition that an unusual case may exist, complete and appropriate imaging and formulation of a sensible plan before operation are absolutely critical to success. Following such a plan can convert a relatively complex situation into a relatively simple one.

Aortic Aneurysm, Abdominal↗
PubMed2001

Access to services at assisted reproductive technology clinics: a survey of policies and practices.

OBJECTIVE: Our goal was to investigate policy on patient access to services at assisted reproductive technology clinics in the United States. STUDY DESIGN: Surveys asked about a variety of ethically and socially challenging cases and were mailed to directors of all Society for Assisted Reproductive Technology-associated assisted reproductive technology clinics. RESULTS: Written policies on access to services are present at 40% of assisted reproductive technology clinics. Universal agreement was not found on any issue; 79% of clinics treat single women, 27% treat patients with a history of schizophrenia, 10% treat patients who use alcohol excessively, 7% treat human immunodeficiency virus-positive women, and 2% would treat patients previously convicted of child abuse. A breakdown of the responses indicated that some clinics are more permissive in terms of access to services than others, whereas some are more restrictive. CONCLUSIONS: The data demonstrate considerable variability in policy among clinics on most access-to-services questions. The results highlight the importance of ongoing discussion of the ethical and legal issues related to access and the need to develop consistent methods to deal with complex cases.

Alcoholism↗
PubMed2001

Results of an aortic endograft trial: impact of device failure beyond 12 months.

PURPOSE: Analysis endpoints of patient survival and aortic rupture at a reporting interval of 12 months are regularly used to compare endograft aortic aneurysm (EAG) repair to conventional open surgical (COS) repair. This study reports a multicenter EAG repair versus COS repair parallel cohort trial at 12 months and additional observations of specific device failure types and their impact on an aortic endograft design beyond that follow-up period. METHODS: From August 1997 to September 1998, 240 patients who were treated with bifurcation EAG repairs and 28 patients who were treated with straight EAG repairs were compared with 98 patients who were treated with COS repair for elective infrarenal aortic aneurysm repair. Allocation to treatment was based on aneurysm anatomy. All cohorts underwent infrarenal procedures. Data from concurrent, nonrandomized patient accrual from 17 United States institutions were prospectively gathered and independently adjudicated for safety and efficacy. An independent core laboratory evaluated all imaging data. RESULTS: There were 308 men and 58 women (mean age, 72 years; range, 42-94 years) treated for infrarenal aortic aneurysm (mean diameter, 55 mm; range, 40-115 mm). Mean preoperative aneurysm diameters were clinically similar (EAG repair, 54 mm vs COS repair, 57 mm). The two cohorts were not significantly different in terms of gender (P = .30) or age (P = .32). EAG repair technical success (aneurysm exclusion, graft patency, patient survival) at 30 days was 89.2%. Five patients required immediate conversion to COS repair, four caused by access complications and one caused by operator-induced EAG repair malposition. The 30-day mortality rate was 1.5% for EAG repair and 3.1% for COS repair (P = .59). The 12-month survival rate was 94.3% for EAG repair and 95.9% for COS repair. The intermediate-term cumulative survival rate at 24 months was 84.9% for EAG repair and 80.3% for COS repair (P = .48). EAG repair device failure occurred from fabric erosion in six patients, with two deaths from ruptured aneurysm at 18 and 28 months after endografting and four device failures resolved by secondary procedures. Five endograft limb dislocations were all resolved by secondary endovascular procedures. Major or minor endograft migration required secondary procedures in five patients, including conversion in two patients. CONCLUSION: The clinical outcome at 12 months demonstrated effective aneurysm treatment and comparable safety between EAG repair and COS repair by conventional endpoints. Ongoing follow-up beyond 12 months revealed device-related adverse events that required endograft design changes. Diligent surveillance of outcomes beyond 12 months is necessary to adequately evaluate EAG repair devices.

Adult↗
PubMed2001

Combined free tissue transfer and infrainguinal bypass graft: an alternative to major amputation in selected patients.

OBJECTIVES: The purpose of this study was to document outcome and adverse prognostic factors in patients requiring combined free tissue transfer and distal bypass grafting for otherwise nonreconstructible infrainguinal arterial occlusive disease and advanced tissue necrosis. METHODS: Between July 1990 and November 1999, 65 patients, all of whom would have required at least below-knee amputation, underwent free tissue transfer in conjunction with infrainguinal bypass grafting at the University of Rochester. Preoperative variables were assessed for their influence on outcome with chi(2) and outcome with life-table analysis with Cox proportionate hazard testing. RESULTS: Free tissue transfer was performed synchronously with arterial reconstruction with autologous vein in 49 patients and after a previous functioning venous bypass graft in 16 patients. The 30-day mortality rate was 5%, and major complications occurred in another 16% of patients. Flap location, weight-bearing status, preexisting osteomyelitis, and the timing of bypass grafting relative to flap construction had no effect on outcome. All five free flap failures occurred within the first 30 days. All other flaps subsequently survived, even in seven patients whose bypass grafts thrombosed. Five-year limb salvage and patient survival rates were 57% and 60%, respectively, and 65% of patients regained meaningful ambulation. The combination of diabetes and dialysis-dependent renal failure was the strongest predictor of overall limb loss (P <.005; relative risk = 4.0), and diabetes alone was the strongest predictor of death (P <.02; relative risk = 5.2). CONCLUSION: Free tissue transfer combined with infrainguinal bypass grafting in selected patients is safe and effective. The combination of diabetes and chronic renal insufficiency, particularly the need for dialysis, is a powerful predictor of failure and should be considered a strong contraindication for this procedure.

Amputation, Surgical↗
PubMed2001

Safety and efficacy of limited-dose tissue plasminogen activator in acute vascular occlusion.

OBJECTIVE: The purposes of this study were to evaluate the safety and efficacy of limited-dose tissue plasminogen activator (t-PA) in patients with acute vascular occlusion and to compare these results with those obtained in equivalent patients receiving urokinase. METHODS: We compared the results of 60 patients receiving catheter-directed urokinase from November 1997 to November 1998 (240,000 units/h x 4 h, 120,000 units/h thereafter for a maximum of 48 h) with those of 45 patients receiving catheter-directed t-PA from November 1998 to August 2000 (2 mg/h, total dose < or =100 mg) for acute arterial occlusion (AAO) and acute venous occlusion (AVO). Interventional approaches such as cross-catheter and coaxial techniques were used to reduce the dose of lytic agent needed to achieve pre-lysis-treatment goals (eg, complete lysis of all thrombus/unmasking graft stenosis or establishing outflow target). Statistical analysis was performed using Student t test and Fisher exact test. RESULTS: The urokinase and t-PA groups were comparable with regard to age, comorbidities (coronary artery disease, hypertension, diabetes, renal insufficiency, smoking), duration of ischemic or occlusive symptoms, location of occlusive process, pretreatment with warfarin, and thrombotic versus embolic and native versus graft occlusion in patients with AAO. In patients with AAO and in those with AVO, t-PA was equivalent to or better than urokinase with regard to percent of clot lysis, incidence of major bleeding complications, limb salvage, and mortality. Achievement of pretreatment goals (arterial patients only) was 50% for urokinase patients and 76% for t-PA patients (P =.02). Analysis of success in individual pretreatment-goal achievement showed urokinase and t-PA to be equivalent in unmasking stenoses (85% and 84%, respectively; P = NS), whereas t-PA was superior to urokinase in the more critical task of establishing run-off (39% versus 81% for urokinase and t-PA, respectively; P =.001). Additional interventions, either endovascular or surgical, were required in 60% and 51% (P = NS) of patients receiving urokinase and t-PA, respectively, for AAO, and in 54% and 62% (P = NS) of patients receiving urokinase and t-PA, respectively, for AVO. CONCLUSIONS: Limited-dose t-PA is a safe and effective therapy for AAO and AVO when administered by experienced teams using innovative but well-established interventional techniques.

Acute Disease↗
PubMed2001

shygrl1 is a mutant affected in multiple aspects of photomorphogenesis.

We have used a counter-selection strategy based on aberrant phytochrome regulation of an Lhcb gene to isolate an Arabidopsis mutant designated shygrl1 (shg1). shg1 seedlings have reduced phytochrome-mediated induction of the Lhcb gene family, but normal phytochrome-mediated induction of several other genes, including the rbcS1a gene. Additional phenotypes observed in shg1 plants include reduced chlorophyll in leaves and additional photomorphogenic abnormalities when the seedlings are grown on medium containing sucrose. Mutations in the TATA-proximal region of the Lhcb1*3 promoter that are known to be important for phytochrome regulation affected reporter gene expression in a manner similar to the shg1 mutation. Our results are consistent with the possibility that the mutation either leads to defective chloroplast development or to aberrant phytochrome regulation. They also add to the evidence of complex interactions between light- and sucrose-regulated pathways.

Arabidopsis↗
PubMed2001

What does it mean to use someone as "a means only": rereading Kant.

Debates about commodification in bioethics frequently appeal to Kant's famous second formulation of the categorical imperative, the formula requiring us to treat the rational (human) being as "an end in itself" and "never as a means only." In the course of her own treatment of commodification, Margaret Jane Radin observes that Kant's application of this formula "does not generate noncontroversial particular consequences." This is so, I argue, because Kant offers three different--and largely incompatible--interpretations of the formula. One focuses on the obligation to preserve rational willing; the second stresses respect for human (physical) dignity and integrity; the third views respect for others as "ends in themselves" as primarily involving a willingness to govern one's conduct by a procedure of impartial co-legislation. Only the third of these interpretations, I conclude, offers a reasonable and coherent approach to moral judgment about the limits of commodification.

Bioethics↗
PubMed2001

Drug resistance trends in M. tuberculosis: Blackburn 1990-1999.

SETTING: Blackburn, United Kingdom. OBJECTIVE: To describe the drug resistance data for Mycobacterium tuberculosis in white and Indian Subcontinent (ISC) ethnic patients in a high prevalence district in the United Kingdom (UK) over a 10-year period. DESIGN: Data from a detailed prospective clinical and epidemiological database of all notified patients were examined for the years 1990-1999 inclusive. RESULTS: Primary isoniazid resistance was found in 17/229 (7.4%) of ISC and 3/67 (4.5%) of white isolates. There was no statistical difference in the rates of drug resistance in those of ISC ethnic origin, whether they were ISC or UK born and whether or not they had made return visits to the ISC. CONCLUSION: The rate of primary isoniazid resistance remains between 5-10% in ISC patients in Blackburn, showing no fall from previous surveys. The rate of drug resistance was not lower in those born in the UK, irrespective of whether return visits had been made to the ISC. These data will need to be further monitored.

Antitubercular Agents↗
PubMed2000

Molecular cloning and characterization of the murine bile salt export pump.

Hepatic bile salt secretion and bile formation are essential functions of the mammalian liver, and the rate-limiting step of hepatocellular secretion of bile salts is canalicular secretion. Recently, the rat sister-of-p-glycoprotein/bile salt export pump (spgp/BSEP) was demonstrated to encode for the rat ATP-dependent canalicular bile salt export protein, and mutations of human BSEP were identified as the cause of PFIC 2. Since mouse models are vital for studies in hepatocellular transport and metabolism, cloning and characterization of the murine gene are essential. In this study, we have cloned a full-length, functional cDNA for the mBsep. The deduced amino acid sequence encodes for a 1321-amino-acid protein and is 94% similar to rat and 89% similar to human bsep. Western immunoblotting using an antibody directed against a carboxy-terminal peptide of mbsep protein reveals a 160kDa protein, which is highly enriched in mouse canalicular membranes. Transfection of mBSEP into Sf-9 insect cells or mammalian Balb-3T3 cells confers functional transport of the bile salt taurocholate. The mBsep mRNA is expressed in murine liver, but not in other tissues. Hepatic mBsep levels appear highly regulated, being markedly diminished in both LPS and estrogen models of cholestasis. These data are important for further murine studies of hepatocellular transport physiology and metabolism.

3T3 Cells↗
PubMed2000

Direct graft puncture with use of a crossed catheter technique for thrombolysis of peripheral bypass grafts.

PURPOSE: To determine the efficacy and safety of direct graft puncture of peripheral arterial bypass grafts with placement of retrograde and antegrade catheters within the graft for thrombolytic therapy. This study also evaluated potential clinical benefit to patients. MATERIALS AND METHODS: A retrospective study was performed on 19 patients with 24 peripheral bypass grafts and lower extremity ischemia of less than 1 month duration. Thrombolysis was performed with a continuous high-dose infusion of urokinase. Successful lysis was defined as greater than 95% clot dissolution with antegrade flow within the graft. RESULTS: Technical success was achieved in 17 of 19 patients (89%). The complexity of operative intervention was diminished in 12 of 19 patients (63%). The major complication rate (16%) was significantly higher and, therefore, this technique has a role for patients in whom traditional access is not optimal, such as in those in whom access cannot be achieved or in those with long bypass grafts. CONCLUSION: Direct graft puncture with placement of catheters across the proximal and distal anastomoses of bypass grafts is a safe method of access, with a major complication rate similar to conventional access techniques. This mode of graft access demonstrates efficacious thrombolysis and acts as a conduit for ancillary procedures.

Aged↗
PubMed2000

Irradiation for intimal hyperplasia: implications for peripheral arterial bypass.

Irradiation has been shown to inhibit postangioplasty intimal hyperplasia ("restenosis") in unbranched tubes. It seems likely that irradiation will similarly be able to inhibit intimal hyperplasia after a surgical anastomosis at a biochemical and cellular level, but whether it will produce a clinically relevant or even clinically detectable difference is unproved. One possibility is that no clinical effect may occur; the search for a "cure" for intimal hyperplasia has been long and, as yet, unsuccessful. On the other hand, if a strong effect without insurmountable logistical problems could be produced, one major cause of bypass graft failure would be preventable. Not only would the incidence of late graft occlusion, need for reoperation, and limb loss be reduced, but, if patency of prosthetics could be sufficiently improved, the initial operation could be made much easier, faster, and perhaps safer.

Angioplasty, Balloon↗
PubMed2000

All in good time: the Arabidopsis circadian clock.

Biological time-keeping mechanisms have fascinated researchers since the movement of leaves with a daily rhythm was first described >270 years ago. The circadian clock confers a approximately 24-hour rhythm on a range of processes including leaf movements and the expression of some genes. Molecular mechanisms and components underlying clock function have been described in recent years for several animal and prokaryotic organisms, and those of plants are beginning to be characterized. The emerging model of the Arabidopsis clock has mechanistic parallels with the clocks of other model organisms, which consist of positive and negative feedback loops, but the molecular components appear to be unique to plants.

Animals↗
PubMed2000

Seasonal synchrony: the key to tick-borne encephalitis foci identified by satellite data.

A previous analysis of tick infestation patterns on rodents in Slovakia suggested that the key to the focal distribution of western-type tick-borne encephalitis virus (TBEv) in Europe is the geographically variable degree of synchrony in the seasonal activity of larval and nymphal Ixodes ricinus ticks. This prediction is here tested by examining records, from 7 different countries, of the seasonal variation in the abundance of larvae and nymphs feeding on rodents or questing on the vegetation. Larvae consistently started feeding and questing earlier in the year at sites within TBEv foci than elsewhere, so that they appeared in the spring as soon as nymphs were active. Such larval nymphal synchrony is associated with a rapid fall in ground-level temperatures from August to October as revealed by the satellite-derived index of Land Surface Temperature (LST). Likewise, of 1992 pixels sampled on a grid across Europe, the 418 that fell within TBEv foci were characterized by a higher than average rate of autumnal cooling relative to the peak midsummer LST. It is proposed that such a seasonal temperature profile may cause unfed larvae to pass the winter in quiescence, from which they emerge synchronously with nymphs in the spring.

Animals↗
PubMed2000

The anatomy of deep venous thrombosis of the lower extremity.

BACKGROUND: The diagnosis, treatment, and long-term sequelae of lower extremity deep venous thrombosis (DVT) depend on the anatomic location and extent of the process, yet a lack of such fundamental knowledge has limited the development of effective protocols for managing patients with DVT. METHODS: Venograms with evidence of acute DVT were evaluated, and the extent of the thrombotic process was recorded and correlated with the clinical presentation. Thrombi were classified according to the venous segments involved and to the thrombus' isolation to one segment or multiple segments. The left-to-right ratio of the DVT was assessed for various etiologic subgroups. RESULTS: Among 2762 venograms performed in 2541 patients over a 10-year period, there were 885 cases (34.8%) of DVT documented. Of these cases, 344 cases (39%) were idiopathic, 307 cases (35%) were postoperative, 84 cases (10%) occurred in the setting of malignancy, and 70 cases (8%) occurred as the result of trauma. Distal thrombi were more common than proximal thrombi, with calf involvement in 734 patients (83%), femoropopliteal involvement in 470 patients (53%), and iliac involvement in 75 patients (9%). The most common site of thrombus was the peroneal vein, which was involved in 595 patients (67%). The ratio of left-to-right-sided DVT was 1.32:1 overall but was greater for proximal thrombi, with a ratio of 2.4:1 for iliac DVT versus 1.3:1 for infrainguinal DVT. The preponderance of left-sided DVT appeared to be related to the high-frequency, left common iliac vein involvement; the left-to-right ratio was much closer to equality (1.09:1) for isolated infrainguinal DVT. The anatomic configuration of the DVT was correlated with the etiologic subgroup; postoperative DVTs were more often distal, whereas DVT developing in the setting of malignancy was more frequently proximal and often right sided. Proximal, left-sided DVTs were common in the idiopathic subgroup, presumably as a result of undiagnosed left iliac vein webs. CONCLUSIONS: The frequency of distal vein involvement greatly exceeds that of proximal involvement in patients with DVTs. Proximal DVTs are more frequently left sided, whereas distal DVTs occur with a more equal left-to-right distribution. The anatomic extent of DVTs appears to depend on the etiology of the process. These observations may shed light on the pathophysiology of venous thrombosis. The findings are of value in planning therapeutic interventions directed at venous recanalization.

Female↗