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Biomedical subjects

R M Green

Publications and source records attributed to R M Green.

At least 73 records · Page 4Linked to original sources
PubMed1999

Femoral-infrapopliteal bypass with prosthetic grafts.

BACKGROUND: Patients who require prosthetic infrapopliteal of the lower extremity have historically had dismal long-term results. This study examined the outcome of patients undergoing femoral-distal arterial bypass with expanded polytetrafluoroethylene (ePTFE) grafts. METHODS: Femoral to infrapopliteal artery bypasses with ePTFE performed between 1990 and 1997 were reviewed. Graft patency, limb salvage, and survival rates were calculated by actuarial analysis. Different anastomotic adjuncts (direct end-to-side anastomosis, vein patch anastomosis, and arteriovenous fistula [AVF] anastomosis) were compared with the log-rank test. RESULTS: Seventy-four femoral-infrapopliteal bypasses with ePTFE were performed in 67 patients for limb salvage. At 24 months the primary patency, assisted primary patency, and secondary patency rates were 40% +/- 10% (SEMAI), 48% +/- 11%, and 52% +/- 11%, respectively. Limb salvage was successful in 62 % +/- 10% of the bypasses at 24 months. Forty-six percent of the bypasses were performed with an AVF; 35% were performed with direct end-to-side anastomosis, and 19% were performed with a vein patch anastomosis. Apparent trends in favor of the AVF group did not attain statistical significance with 24-month patency rates of 65% +/- 19%, 44% +/- 16%, and 35% +/- 20%, respectively, in the 3 subgroups. Limb salvage rates were similar (64% +/- 17%, 56% +/- 15%, and 76% +/- 22%, respectively) at 24 months. CONCLUSIONS: Patency and limb salvage rates are sufficient to justify the use of ePTFE grafts in infrapopliteal bypass when adequate autogenous material is unavailable.

Adult↗
PubMed1998

Protein kinase CK2 interacts with and phosphorylates the Arabidopsis circadian clock-associated 1 protein.

The circadian clock-associated 1 (CCA1) gene encodes a Myb-related transcription factor that has been shown to be involved in the phytochrome regulation of Lhcb1*3 gene expression and in the function of the circadian oscillator in Arabidopsis thaliana. By using a yeast interaction screen to identify proteins that interact with CCA1, we have isolated a cDNA clone encoding a regulatory (beta) subunit of the protein kinase CK2 and have designated it as CKB3. CKB3 is the only reported example of a third beta-subunit of CK2 found in any organism. CKB3 interacts specifically with CCA1 both in a yeast two-hybrid system and in an in vitro interaction assay. Other subunits of CK2 also show an interaction with CCA1 in vitro. CK2 beta-subunits stimulate binding of CCA1 to the CCA1 binding site on the Lhcb1*3 gene promoter, and recombinant CK2 is able to phosphorylate CCA1 in vitro. Furthermore, Arabidopsis plant extracts contain a CK2-like activity that affects the formation of a DNA-protein complex containing CCA1. These results suggest that CK2 can modulate CCA1 activity both by direct interaction and by phosphorylation of the CCA1 protein and that CK2 may play a role in the function of CCA1 in vivo.

Amino Acid Sequence↗
PubMed1998

Cellular and molecular mechanisms of radiation inhibition of restenosis. Part I: role of the macrophage and platelet-derived growth factor.

PURPOSE: The major radiobiological issue in determining the rationale for the use of radiation to inhibit vascular restenosis is the identification of the target cell(s) and/or cytokine(s) responsible for neointimal hyperplasia and vascular remodeling. The central hypothesis of this report is that the macrophage/monocyte and PDGF are key elements in the process of neointimal hyperplasia seen following angioplasty, similar to their role in lesion formation and progression found in atherosclerotic thickening. Specific immunohistochemical and cytochemical stains were applied to a rat carotid model in a temporal series after balloon angioplasty to determine macrophage activity vs. smooth muscle cell proliferation, the latter being classically thought to be the cell responsible for restenosis. METHODS AND MATERIALS: Neointimal hyperplasia was created in an established rat carotid artery model by a balloon catheter technique. Immediately following injury, treatment groups received irradiation via high dose rate (HDR) brachytherapy, the 192Ir source being placed externally to the vessel. Radiation was delivered to a length of 2 cm of the injured vessel at doses of 5, 10, and 15 Gy, and the animals were sacrificed at various time points following treatment (24 h to 6 months). Serial sections of tissue were stained immunohistochemically with the primary antibodies CD11b, mac-1, anti-PDGF, and alpha-smooth muscle actin. RESULTS: Immediately (24 h) postinjury, there is an apparent migration of macrophages seen in the adventitia; after 1 week, proliferation and migration of macrophages could be seen clearly within all the vessel layers, especially in the intima; by 3 weeks, when there was evidence of neointimal hyperplasia, macrophages could still be seen, mainly in the intima scattered among the smooth muscle cells and myofibroblasts, and to a lesser degree at 6 months. There was corresponding expression of PDGF, whenever and wherever there were zones of activation/neointimal hyperplasia. Alpha-smooth muscle actin staining identified the smooth muscle cells distinct from the macrophages, and these SMCs exhibited activation in the neointimal hyperplasia zones at all later time points. Furthermore, we showed that radiation significantly reduced the macrophage population, while the onset of neointimal hyperplasia was accompanied by a return of the macrophage population. CONCLUSION: Our results suggest that the activated adventitial macrophage/monocyte are the key cells responsible for initiating the arterial neointimal hyperplasia and vascular remodeling developing postangioplasty as they are in the initiation and perpetuation of atheromatous thickening. Irradiation delivered immediately postinjury is, therefore, highly effective, because the macrophage population is exquisitely radiosensitive.

Animals↗
PubMed1998

Genetic, common environment, and individual specific components of variance for bone mineral density in 10- to 26-year-old females: a twin study.

Lean mass and areal bone mineral density at the lumbar spine, femoral neck, and total forearm were measured in 215 volunteer female twin pairs (122 monozygotic, 93 dizygotic), aged 10-26 years, using dual energy X-ray absorptiometry. The study was conducted in Melbourne from 1990 to 1994. Under the classic twin model, there was evidence for a genetic component of variation in bone mineral density, adjusted for age or for age and lean mass, at all sites. Adjusting for lean mass almost halved the genetic variances in the adolescent years of peak growth, during which genetic variances peaked. Genetic variances were reduced in the late teenage years and increased in early adulthood. The latter may reflect gene-environment interactions or covariation. Importantly, there was evidence for environmental effects shared by twins on lumbar spine and femoral neck bone mineral density, even when adjusted for lean mass as well as age. These were greatest during the late teenage years, abated over the years when pairs started to live apart, and appear to be independent of lean mass during adolescence but not in early adulthood. In summary, the genetic and environmental etiology of bone mineral density is more complex than previously thought.

Absorptiometry, Photon↗
PubMed1998

A 12-month prospective study of the relationship between stress fractures and bone turnover in athletes.

Bone remodeling may be involved in the pathogenesis of stress fractures in athletes. We conducted a 12-month prospective study to evaluate bone turnover in 46 female and 49 male track and field athletes aged 17-26 years (mean age 20.3; SD 2.0) 20 of whom developed a stress fracture. Baseline levels of bone turnover were evaluated in all athletes and monthly bone turnover levels were evaluated in a subset consisting of the 20 athletes who sustained a stress fracture and a matched comparison group who did not sustain a stress fracture. Bone formation was assessed using serum osteocalcin (OC) measured by human immunoradiometric assay and bone resorption by urinary excretion of pyridinium cross-links (Pyr and D-Pyr); high performance liquid chromatography and N-telopeptides of type 1 collagen (NTx) using ELISA assay. Athletes who developed stress fractures had similar baseline levels of bone turnover compared with their nonstress fracture counterparts (P > 0.10). Results of serial measurements showed no differences in average levels of Pyr, D-Pyr, or OC in those who developed stress fractures (P = 0.10) compared with the control group. In the athletes with stress fractures, there was also no difference in bone turnover levels prior to or following the onset of bony pain. Our results show that single and multiple measurements of bone turnover are not clinically useful in predicting the likelihood of stress fractures in athletes. Furthermore, there were no consistent temporal changes in bone turnover associated with stress fracture development. However, our results do not negate the possible pathogenetic role of local changes in bone remodeling at stress fracture sites, given the high biological variability of bone turnover markers and the fact that levels of bone turnover reflect the integration of all bone remodeling throughout the skeleton.

Adolescent↗
PubMed1998

A model for merging vascular surgery and interventional radiology: clinical and economical implications.

BACKGROUND: The traditional separation of vascular surgery and interventional radiology into distinct units is associated with inefficiencies in patient care, practice management, and training. Traditional departmental politics, discrepant clinical backgrounds and philosophies, fear of decreasing remuneration, and basic differences in education, training, and practice have all rendered mergers difficult. METHODS: We have implemented a model that incorporates all the clinical, fiscal, and educational activities of the 2 former entities into a single unit. A 5-physician vascular surgery group, its noninvasive laboratory, and a 3-physician interventional radiology group were unified. The revenue was deposited into a single account from which all the expenses were paid. The net income of the joint unit was apportioned on a predetermined pro rata basis, with scaled percentages for each practitioner. In an effort to separate clinical decision making from economic pressures, the individual physician remuneration was not on the basis of productivity. Clinical volume, gross revenue, and remuneration were compared with the 12-month period that immediately preceded the merger and contrasted to the previous 3-year historical trend (HT). RESULTS: The number of vascular surgical procedures fell after the merger (-9.3%; HT, +4.7%). By contrast, the number of interventional radiology procedures rose (+56.1%; HT, +15.2%), as did the number of noninvasive testing (+9.2%; HT, +3.5%). In concordance with the number of procedures, the gross revenue of vascular surgery fell (-23.7%; HT, +1.1%) and that of interventional radiology rose (+53.5%; HT, +46.0%). The increased efficiencies allowed the total expenses of the 2 units to fall (-13.2%; HT, +7. 5%), and, despite the reduced revenue, the vascular surgeon remuneration was preserved (+0.7%; HT, -3.9%) and the radiology remuneration rose (+22.3%; HT, +8.3%). The merger allowed the vascular surgery fellows to actively participate in 26 interventional cases per month and the interventional radiology fellows to actively participate in 8 open surgical cases per month. CONCLUSION: The merger of vascular surgery and interventional radiology resulted in a decrease in the surgical procedures and revenue, with a corresponding increase in the interventional radiology procedures and revenue. Despite these effects, the physician remuneration increased as a result of the improved efficiencies in practice management and the reduction in expenses. The merger of the 2 units excludes the economic pressures from clinical decision making and appears to be warranted on the basis of the fiscal and educational benefits that are achieved.

Hospital Departments↗
PubMed1998

Fetal internal iliac artery: case report and embryologic review.

A 25-year-old woman with anomalous circulation to the right leg was seen with a symptomatic aneurysm of the abnormal vessel. The artery, which did share some features of the classic persistent sciatic artery, also had important differences that were not previously described in the literature. The patient manifested several associated vascular and nonvascular congenital anomalies. She underwent resection of the aneurysm and primary operative repair of the artery without difficulty. An embryologic interpretation is offered, and the clinical implications and management strategy are discussed.

Adult↗
PubMed1998

Ruptured popliteal artery aneurysm.

Popliteal artery aneurysms rarely rupture. We treated a 91-year-old man who presented with a deep venous thrombosis and anemia; rupture of a popliteal artery aneurysm was suspected only after compartment syndrome isolated to the thigh developed as the result of bleeding. Although fasciotomy was required on the basis of the clinical examination alone, the cause of the problem, operative strategy, and definitive treatment (i.e., resection and bypass) were clarified by the preoperative computed tomography scan. Ruptured popliteal aneurysm can manifest as a massively swollen leg with anemia and should be suspected if no other cause is evident.

Aged↗
PubMed1998

Value of preoperative EEG for carotid endarterectomy.

PURPOSE: This study was designed to determine whether the preoperative, baseline electroencephalogram (EEG) can be used for intraoperative decision making during carotid endarterectomy, and to identify circumstances where the EEG can be eliminated. METHODS: The charts of all patients undergoing carotid endartectomy at the authors' institution from June 1991 to May 1995 were reviewed to identify those patients that had adequate pre- and intraoperative EEG monitoring. EEGs during 331 carotid endartectomies in 303 patients were coded without knowledge of outcome; primary and secondary endpoints were EEG changes with clamping and clinical outcome, respectively. RESULTS: The incidence of mortality and major neurological morbidity was 1.8%. Baseline-EEGs were abnormal in 105 patients (32%). Whereas baseline-EEG changes were highly predictive of EEG changes after anesthetic induction (P < .0001), they were not predictive of EEG changes with clamping or of clinical outcome. Prior stroke (CVA) predicted abnormal baseline-EEGs (P < .0001) and abnormal post-anesthetic EEGs (P < .0001) but did not predict changes with clamping or perioperative CVA. EEG changes with clamping occurred during 18% of operations; such changes were predicted only by contralateral occlusion (P < .0016) and EEG changes during a prior contralateral carotid endartectomy (P < .0001). The only variable that predicted an adverse neurological outcome was the presence of contralateral occlusion, which increased the likelihood of a perioperative neurological event seven-fold (P = .0038). Clinical outcomes in the 57 of 105 patients with abnormal baseline-EEGs and the 49 of 83 with prior CVA who were shunted were not different from those who were not. CONCLUSIONS: baseline-EEG is not of value for the prediction of adverse events during carotid endartectomy and can be eliminated. Because contralateral occlusion is highly predictive of changes with clamping, and patients undergoing a second carotid endartectomy will usually manifest EEG changes identical to those at the first, operative EEG monitoring can also be eliminated from both these circumstances. Finally, prior stroke does not lead to a higher incidence of clamp-induced EEG changes, and thus is not an indication for shunting in and of itself.

Brain Ischemia↗
PubMed1998

A case of systemic pseudo-pseudoxanthoma elasticum with diverse symptomatology caused by long-term penicillamine use.

A 47 year old man presented with a two year history of increasing cervical dysphagia, dyspnoea, and cutaneous signs. He had been diagnosed 27 years previously with Wilson's disease and was treated with penicillamine (1.5 g daily). Systemic abnormality of elastic fibres was confirmed by light and electron microscopy following biopsy of skin, lung, oesophageal muscle, gum, pharyngeal tissue, and cervical connective tissue. Dysphagia was relieved by cricopharyngeal myotomy. Substitution of trientene dihydrochloride for penicillamine relieved cutaneous and systemic manifestations. This is possibly the first case demonstrating an association between prolonged penicillamine use and biopsy proved systemic pseudo-pseudoxanthoma elasticum. The presenting symptoms may have resulted from the abnormal numbers and properties of elastic fibres, and the changes were caused by penicillamine use, rather than by idiopathic, inherited pseudoxanthoma elasticum.

Chelating Agents↗
PubMed1998

Distribution, aerodynamic characteristics, and removal of the major cat allergen Fel d 1 in British homes.

BACKGROUND: Sensitisation to cat allergen (Fel d 1) is an important risk factor for asthma in the UK. A study was undertaken to investigate the distribution of cat allergen in British homes, the aerodynamic characteristics and particle size distribution of airborne Fel d 1, and the method of removing it. METHODS: Dust was collected from 50 homes with a cat and from 50 homes without a cat, and airborne levels of Fel d 1 were measured in 50 homes with a cat and 75 homes without a cat. Particle size distribution was determined using an Andersen sampler (8 hours/day) in 10 homes with cats. This was repeated on five separate days in a house with four cats, and then one, two, four, seven, and 14 days after the cats were removed from the living room area. The effect of high efficiency particulate air (HEPA) cleaner on airborne levels of Fel d 1 was investigated in seven homes with cats. Samples were collected on two separate days from two rooms of each house concurrently, one of which contained the cat, one day with the HEPA cleaner on and the other day as a control. Three one hourly samples were collected over a nine hour period (baseline, 4-5 hours, 8-9 hours) using a high volume dust sampler (air flow rate 60 l/min) and the air sample was collected onto a microglass fibre filter (pore size 0.3 micron). RESULTS: Fel d 1 concentrations were much lower in houses without a cat than in those with a cat (260-fold difference (95% CI 167 to 590) in living room carpets: geometric mean (GM) 0.9 microgram/g (range 0.06-33.93) versus 237 micrograms/g (range 2.8-3000); 314-fold difference (95% CI 167 to 590) in upholstered furniture: 1.21 micrograms/g (range 0.06-61.9) versus 380 micrograms/g (range 7.1-6000); 228-fold difference (95% CI 109 to 478) in bedroom carpets: 0.24 microgram/g (range 0.06-2.24) versus 55 micrograms/g (range 0.06-2304); and 215-fold difference (95% CI 101 to 456) in mattresses: 0.2 microgram/g (range 0.06-2.3) versus 55 micrograms/g (range 0.06-3400). Airborne levels of Fel d 1 were detected in all houses with cats, and the levels varied greatly between the homes (range 0.7-38 ng/m3). Low concentrations of airborne Fel d 1 (range 0.24-1.78 ng/m3) were found in 22 of 75 homes without a cat. Although airborne Fel d 1 was mostly associated with large particles (> 9 microns, approximately 49% of the allergen recovered), small particles (< 4.7 microns) comprised approximately 23% of the total airborne allergen. Total airborne Fel d 1 was reduced by 61.7% two days after removal of the cat but this was due predominantly to the decrease in larger particles (> 4.8 microns) which fell to 13% of their baseline level. Fel d 1 levels associated with small particles (< 4.8 microns) remained largely unchanged on days 1, 2 and 4 and then slowly decreased to 33% of the baseline levels at day 14. With HEPA cleaner a significant reduction in airborne Fel d 1 was observed compared with the control sampling (GM 5.04-0.88 ng/m3 versus 3.79-1.56 ng/m3 at baseline and 8 hours, active versus control group; p = 0.008). CONCLUSIONS: Airborne Fel d 1 was detectable in undisturbed conditions in all homes with cats and in almost a third of homes without cats. In houses with cats a significant proportion (23%) of airborne Fel d 1 was associated with small particles (< 4.7 microns diameter). Removal of the cat from the living room and bedroom areas of the home and the use of HEPA air cleaner reduced airborne levels of cat allergen in homes with cats, but the reduction following cat removal was not evenly spread across the particle size range.

Air Pollution, Indoor↗
PubMed1998

Hepatocellular expression of glucose-6-phosphatase is unaltered during hepatic regeneration.

Gluconeogenesis and glycogenolysis are essential hepatic functions required for glucose homeostasis. During the initial phase of hepatic regeneration, the immediate-early genes (IEG) are rapidly expressed, and the IEG RL-1 encodes for glucose-6-phosphatase (G-6-Pase). G-6-Pase is a microsomal enzyme essential for gluconeogenesis and glycogenolysis. This study employs a partial-hepatectomy model to examine the expression and activity of G-6-Pase. After partial hepatectomy, rat hepatic G-6-Pase gene expression is transcriptionally regulated, and mRNA levels are increased approximately 30-fold. However, in contrast to this rapid gene induction, microsomal enzyme activity is unchanged after partial hepatectomy. Western blotting demonstrates that microsomal G-6-Pase protein expression is also unchanged after partial hepatectomy, and similar results are also noted in whole liver homogenate. Thus, despite marked induction in gene expression of the IEG G-6-Pase after partial hepatectomy, protein expression and enzyme activity remain unchanged. These data indicate that, although this hepatocyte IEG is transcriptionally regulated, the physiologically important level of regulation is posttranscriptional. This highlights the importance of correlating gene expression of IEG with protein expression and physiological function.

Animals↗
PubMed1998

Vascular manifestations of the thoracic outlet syndrome.

The thoracic outlet syndrome describes a variety of conditions caused by compression of one or a combination of neurovascular structures traversing the thoracic outlet. Although some believe that the neurological syndrome is overdiagnosed, the vascular syndromes each have characteristic symptoms, physical findings, definitive diagnostic tests, and a low incidence.

Angiography↗