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Biomedical subjects

A A Fokin

Publications and source records attributed to A A Fokin.

At least 19 recordsLinked to original sources
PubMed2006

Acquired deformities of the anterior chest wall.

BACKGROUND: Acquired chest wall deformities are difficult to describe and to classify. We propose the following classification and treatment options. METHODS: We observed 11 patients with acquired deformities (AD) that required surgical correction. RESULTS: AD of the chest can be classified into 4 groups: (1) AD resulting from a pathological process within the thorax (heart enlargement, mediastinal tumors), (2) AD resulting from chest wall disease (rib osteomyelitis or tumors), (3) iatrogenic deformities (following rib graft harvesting, acquired Jeune's syndrome), and (4) post-traumatic deformities. Group 1 requires treatment of the pathological process. Group 2 is guided by oncological or infectious disease principles. Groups 3 and 4 require chest wall reconstruction. Iatrogenic AD usually occur after pectus excavatum repair with rib cartilage extirpation in young patients, which results in a reduced, restricted thorax. Post-traumatic AD often have pathological chest wall mobility owing to pseudo-articulation of injured ribs. CONCLUSIONS: To prevent AD formation and to protect thoracic growth and mobility, costosternal and costochondral junctions should be preserved during cartilage resection. Substernal suturing of the perichondrium should be avoided.

Cartilage↗
PubMed2006

[Surgical management of stenosing lesions of carotid arteries based on comparative results of an ultrasonographic and angiographic study].

Surgical treatment of stenosing lesions of carotid arteries has proved to be a reliable method of prevention and management of chronic cerebrovascular insufficiency. The purpose of this study was to assess the diagnostic possibilities of duplex scanning from the position of an isolated diagnostic method for safe and efficient reconstruction of carotid arteries. The study comprised 177 patients presenting with occlusive-and-stenotic lesions of carotid arteries, who underwent a total of 204 reconstructive operations. We believe that duplex scanning alone may safely be considered sufficient to make a definite diagnosis of carotid arteries stenosis in the overwhelming majority of the patients involved. The indications for reconstructive operations on carotid arteries are largely predetermined by the degree of stenosis, structure of the plaque, and the condition of its surface, as well as by the presence or absence of the < > of the plaque. The outcomes of reconstructive operations carried out on carotid arteries based on the findings of duplex scanning do not significantly differ from the outcomes of the operations performed on the basis of angiographic data.

Angiography↗
PubMed2004

Changes in sternal blood flow after different methods of internal thoracic artery harvesting.

OBJECTIVE: The study was designed to assess the early changes in sternal perfusion after midline sternotomy and different (skeletonized versus semiskeletonized) techniques of internal thoracic artery (ITA) harvesting. METHODS: The experiments were performed in the swine model. After midline sternotomy, ITA harvesting (skeletonized technique) was performed unilaterally in Group I (6 animals). The ITA and the internal thoracic vein (ITV) were harvested (semiskeletonized technique) in Group II (5 animals). The contralateral sternal half served as a control. Using a thermographic camera with a 0.06 degrees C sensitivity, sternal perfusion was assessed 2 and 5 hours after surgery. RESULTS: Midline sternotomy alone did not affect sternal blood flow. A statistically significant ( p < 0.05) reduction in perfusion of the involved sternal half in comparison to the control side was detected at 2 and 5 hours after surgery. The degree of perfusion deficit was not related to the harvesting technique. CONCLUSIONS: Skeletonized and semiskeletonized ITA harvesting techniques caused a similar acute reduction in sternal perfusion during the early postoperative period and this effect lasted for at least 5 hours.

Animals↗
PubMed2004

Multiyear experience in endoscopic thoracic sympathectomy.

The results of endoscopic thoracic sympathectomy performed for 787 patients during a 30-year period are presented. Six hundred seventy three patients were operated on for upper limb arterial occlusion of distal and diffuse type, Raynaud's disease or syndrome, 7 patients - for causalgic pain in upper limbs and Sudeck's syndrome, 85 - for hyperhidrosis. Twelve patients underwent lower thoracic sympathectomy for painful chronic pancreatitis, 4 - total destruction of thoracic sympathetic trunk due to pernicious hypertension of unknown origin, and 6 - endoscopic thoracic sympathectomy for acute thrombosis of upper limb arteries with distal circulation impairment. Immediate positive effect of interventions was detected in all cases except for acute arterial thrombosis. One patient died postoperatively due to arrhythmia-related cardiac arrest. Postoperative complications - lung border damage and intercostal vascular hemorrhage - were detected in 0.2% of cases. Increased air effusion from pleural cavity and intercostal neuralgia were observed postoperatively in some cases but did not require any special management. Long-term outcomes were followed up for period of 5-10 years, 72.7% of monitored patients had stable positive outcomes. Our experience has demonstrated that endoscopic thoracic sympathectomy is a safe, minimally invasive and effective intervention for upper limb chronic arterial insufficiency of distal and diffuse type or for hyperhidrosis.

Adolescent↗
PubMed2004

[Differential diagnosis of venous aneurysm of femoral hernia].

Eight hundred and twelve patients with varicose disease were examined, 18 (2.2%) of them had aneurysms in the region of sapheno-femoral anastomosis. Venous aneurysm was diagnosed before surgery in all 18 patients. All of them underwent surgery with positive result. Diagnosis of aneurysm of great saphena vein in inguinal region is not difficult in most cases. Difficulties usually occur in patients with overweight. In 5 patients with obesity aneurysm was initially diagnosed as femoral hernia. Duplex scanning is the best non-invasive method of diagnosis of venous aneurysm in obese patients.

Adult↗
PubMed2004

[The treatment of varicosity associated with persistent edema of the lower limbs].

From February 1998 to September 2002, 36 patients suffering from varicosity of the saphenous veins of the lower limbs associated with edema were operated on. All of them were provided different variants of intraoperative sclerotherapy (IOST). By the character of venous disorders the patients were divided into 2 groups. The first group (n=19) comprised patients with stages 2 and 3 varicosity according to the clinical classification of the CEAP. The maximal diameter of the varicose greater saphenous vein (GSV) in these patients did not exceed 1 cm, with no trophic disorders. The second group (n=17) included patients suffering from stages 2-4 varicosity according to the clinical classification of the CEAP. In these patients, the diameter of the varicose GSV on the thigh exceeded 1 cm and there were trophic disorders on the leg in the form of pigmentation and/or skin induration. The first group patients underwent crossectomy and IOST of the GSV over the whole length. The second group patients were provided combined intervention: crossectomy, GSV stripping on the thigh and IOST: of the GSV on the leg. To define the effectiveness of the surgical treatment using sclerotherapy, the reference group including 38 persons with varicosity also complicated by edema of the lower limbs was under our observation. This group underwent surgical intervention which consisted in radical venectomy according to Babcock and excision of the lateral venous branches according to Narat. Analysis of the immediate results has demonstrated that in the basic group, the complications occurred in 5.6% of patients versus 29% in the reference group; the postoperative bed day in the basic group was 1.8 times less. Evaluation of the edematous syndrome carried out in the long-term period (after 2 years) showed its complete absence in 96,4% of the basic group patients versus 72.4% of the reference group patients. So, the use of different variants of IOST in the treatment of patients suffering from varicosity complicated by edema evidences the advantages of the treatment tactics offered by us as compared to the routine surgical techniques.

Adult↗
PubMed2004

[Therapy of cancer patients with concurrent critical atherosclerosis of the aorta and peripheral arteries].

The results are presented of 5-year experience with therapy of concurrent neoplasia and atherosclerotic lesions of the aorta and peripheral arteries gained at the Center for Oncosurgery, Regional Oncological Dispensary, Chelyabinsk. The analysis was concerned with the treatment received by 118 patients, irrespective of tumor stage or localization: surgical correction of blood flow was carried out in 60. Clinically significant atherosclerotic lesions of the aorta and peripheral arteries in a cancer patient should not be regarded as absolute or relative contraindication for combined treatment. Atherosclerotic occlusion of the femoral or shin arteries was managed conservatively in most cases (p<0.05). In cases of similar lesions of the carotid arteries and aortal aneurysm, surgical correction of blood flow was mostly used.

Aged↗
PubMed2001

Selective radical reactions in multiphase systems: phase-transfer halogenations of alkanes.

The present paper shows that selective radical reactions can be initiated and carried out in multiphase systems. This concept is applied to the selective functionalization of unactivated aliphatic hydrocarbons, which may be linear, branched, and (poly)cyclic, strained as well as unstrained. The phase-transfer system avoids overfunctionalization of the products and simplifies the workup; the selectivities are excellent and the yields are good. This is the only method for direct preparative iodination of alkanes applicable to large scale as well. We demonstrate that the reaction systems are indeed phase-transfer catalyzed through a systematic study of variations of the reactants, solvents, catalysts, and by measuring as well as computing the H/D kinetic isotope effects for the rate-limiting C-H abstraction step by *CHal3 radicals which are held responsible for the observed radical reactions. In the case of *CBr3, this key intermediate could also be trapped under otherwise very similar reaction conditions. To stimulate further work, the tolerance of some functional groups was tested as well.

Journal Article↗
PubMed2001

Molecule-induced alkane homolysis with dioxiranes.

The mechanisms of C-H and C-C bond activations with dimethyldioxirane (DMD) were studied experimentally and computationally at the B3LYP/6-311+G**//B3LYP/6-31G* density functional theory level for the propellanes 3,6-dehydrohomoadamantane (2) and 1,3-dehydroadamantane (3). The sigma(C-C) activation of 3 with DMD (Delta G(*) = 23.9 kcal mol(-1) and Delta G(r) = -5.4 kcal mol(-1)) is the first example of a molecule-induced homolytic C-C bond cleavage. The C-H bond hydroxylation observed for 2 is highly exergonic (Delta G(r) = -74.4 kcal mol(-1)) and follows a concerted pathway (Delta G(*) = 34.8 kcal mol(-1)), in contrast to its endergonic molecule-induced homolysis (Delta G(*) = 28.8 kcal mol(-1) and Delta G(r) = +9.2 kcal mol(-1)). The reactivities of 2 and 3 with CrO(2)Cl(2), which follow a molecule-induced homolytic activation mechanism, parallel the DMD results only for highly reactive 3, but differ considerably for more stable propellanes such as 4-phenyl-3,6-dehydrohomoadamantane (1) and 2.

Journal Article↗
PubMed2001

The rearrangement of the cubane radical cation in solution.

The rearrangement of the cubane radical cation (1*+) was examined both experimentally (anodic as well as (photo)chemical oxidation of cubane 1 in acetonitrile) and computationally at coupled cluster, DFT, and MP2 [BCCD(T)/cc-pVDZ//B3LYP/6-31G* ZPVE as well as BCCD(T)/cc-pVDZ//MP2/6-31G* + ZPVE] levels of theory. The interconversion of the twelve C2v degenerate structures of 1*+ is associated with a sizable activation energy of 1.6 kcalmol(-1). The barriers for the isomerization of 1*- to the cuneane radical cation (2*+) and for the C-C bond fragmentation to the secocubane-4,7-diyl radical cation (10*+) are virtually identical (deltaH0++ = 7.8 and 7.9 kcalmol(-1), respectively). The low-barrier rearrangement of 10*+ to the more stable syn-tricyclooctadiene radical cation 3*+ favors the fragmentation pathway that terminates with the cyclooctatetraene radical cation 6*+. Experimental single-electron transfer (SET) oxidation of cubane in acetonitrile with photoexcited 1,2,4,5-tetracyanobenzene, in combination with back electron transfer to the transient radical cation, also shows that 1*+ preferentially follows a multistep rearrangement to 6*+ through 10*+ and 3*+ rather than through 2*+. This was confirmed by the oxidation of syn-tricyclooctadiene (3), which, like 1, also forms 6 in the SET oxidation/rearrangement/electron-recapture process. In contrast, cuneane (2) is oxidized exclusively to semibullvalene (9) under analogous conditions. The rearrangement of 1*+ to 6*+ via 3*+, which was recently observed spectroscopically upon ionization in a hydrocarbon glass matrix, is also favored in solution.

Journal Article↗
PubMed2001

The protonation of gaseous cyclopropane.

The protonation of cyclopropane by gaseous Brønsted acids of varying strength in radiolytic experiments at atmospheric pressure leads to two distinct C3H7- isomers that have been sampled by their reaction with benzene. The neutral end products, nC3H7-C6H5 and iC3H7-C6H5, arise from the electrophilic aromatic substitution reaction with the cC3H7+ and iC3H7+ ions, respectively. Their relative abundance was studied as a function of pressure, temperature, and the presence of additives in the gaseous systems; the results indicate a large extent of isomerization to the thermodynamically favored iC3H7+ from the protonation by strong acids. The presence of a kinetic barrier prevents any thermal isomerization from taking place in the time frame of 10(-8) s. In the peculiar case in which protonated benzene is the Brønsted acid, C3H7+ ions are formed in the presence of neutral benzene within the same ion - molecule complex. The ensuing reaction shows that cC3H7+ ions are formed exclusively and react in the 10(-10) s(-1) estimated lifetime of the complex. Still, such cC3H7+ ions undergo complete randomization of their hydrogen atoms; this points to a low kinetic barrier for the process. Agreement is found between the reported experimental results and updated computations of the relevant species in the C3H7+ potential energy surface.

Journal Article↗
PubMed2001

A consecutive double-Criegee rearrangement using TFPAA: stepwise conversion of homoadamantane to oxahomoadamantanes.

Rearrangement of 4-methylhomoadamantan-4-ol (1) with trifluoroperacetic acid (TFPAA) in trifluoroacetic acid (TFAA) proceeds with the formation of 4-oxahomoadamantane 6 and its derivatives (4 and 5). 2-exo-Hydroxy-4-oxahomoadamantane (5) and 6 were identified as a result of consecutive O-insertion Criegee rearrangement processes. The absence of methyl trifluoroacetate and methyl trifluoroperacetate among the reaction products, as well as the presence of acetyltrifluoroacetyl peroxide, is consistent with a double rather that a triple oxygen insertion during the course of the Criegee reaction. A mechanism involving initial Criegee rearrangement followed by a Baeyer-Villiger reaction is also excluded by kinetic considerations. The parallel formation of 4-ethyl-3-oxahomoadamantan-2-one (4) was determined to be the result of 4-methylhomoadmantan-4-ol (3) dehydration, with subsequent epoxidation of 4-methylhomoadamant-4-ene (32) to 4,5-epoxy-4-methylhomoadamantane (33), acid-catalyzed isomerization of 33 to 3-methylhomoadamantan-2-one (34), and Baeyer-Villiger oxidation to 3-methyl-5-oxabishomoadamantan-6-one (35). This sequence of reactions was followed by the acid-catalyzed isomerization to the final product 4. The proposed mechanisms for these transformations are discussed on the basis of model experiments and supporting density functional theory (DFT) calculations.

Journal Article↗
PubMed2001

Halogenation of cubane under phase-transfer conditions: single and double C-H-bond substitution with conservation of the cage structure.

The first highly selective C-H chlorination, bromination, and iodination of cubane (1) utilizing polyhalomethanes as halogen sources under phase-transfer (PT) conditions is described. Isomeric dihalocubanes with all possible combinations of chlorine, bromine, and iodine in ortho, meta, and para positions were also prepared by this method; m-dihalo products form preferentially. Ab initio and density functional theory (DFT) computations were used to rationalize the pronounced differences in the reactions of 1 with halogen (Hal(*)) vs carbon-centered trihalomethyl (Hal(3)C(*)) radicals (Hal = Cl, Br). For Hal(3)C radicals the C-H abstraction pathway is less unfavorable (DeltaG(double dagger)(298) = 21.6 kcal/mol for Cl(3)C(*) and 19.4 kcal/mol for Br(3)C(*) at B3LYP/6-311+G//B3LYP/6-31G) than the fragmentation of the cubane skeleton via S(H)2-attack on one of the carbon atoms of 1 (DeltaG(double dagger)(298) = 33.8 and 35.1 kcal/mol, respectively). In stark contrast, the reaction of 1 with halogen atoms preferentially follows the fragmentation pathway (DeltaG(double dagger)(298) = 2.1 and 7.5 kcal/mol) and C-H abstraction is more unfavorable (DeltaG(double dagger)(298) = 4.6 and 12.0 kcal/mol). Our computational results nicely agree with the behavior of 1 under PT halogenation conditions (where Hal(3)C(*) is involved in the activation step) and under free-radical photohalogenation with Hal(2) (Della, E. W., et al. J. Am. Chem. Soc. 1992, 114, 10730). The incorporation of a second halogen atom preferentially in the meta position of halocubanes demonstrates the control of the regioselectivity by molecular orbital symmetry.

Journal Article↗
PubMed2000

Inhibition of needlestick-induced simulated viremia by local measures.

BACKGROUND: The possibility of confinement of simulated retrovirus to the inoculation site after needlestick injuries to enhance chances of local intervention and function of lymphaticovenous communications was investigated. METHODS: Using the canine model, technetium-99 m sulfur colloid particles were injected subcutaneously and into the vein and lymphatics. Blood and lymph were collected at a higher level from the femoral vein and the major lymphatic. Flow rates, particle arrival times, concentrations, and other variables were evaluated for 45 minutes by gamma counting. A tourniquet was used to slow dissemination after subcutaneous injection. RESULTS: After subcutaneous inoculation, particles arrived in the blood at 2.81 +/- 0.54 minutes and in the lymph at 6.0 +/- 1.47 minutes. Application of a tourniquet delayed appearance in the blood to 7.11 +/- 1.5 minutes and in the lymph to 40.0 +/- 5.1 minutes. Concentration of particles in lymph was 1,000 times higher than in the blood. Flux values were comparable in both pathways, but accumulation patterns were different. After intravenous injection, particles arrived in lymph at 25.4 +/- 6.44 minutes. After intralymphatic injection particles arrived in the blood within 4 seconds. CONCLUSIONS: There are functional lymphaticovenous communications at the peripheral level. The period between virus inoculation and blood and lymph invasion may be extended by application of a tourniquet; therefore, time could be gained for local intervention.

Animals↗
PubMed2000

Accidental injuries by HIV-contaminated instruments in health provider or research environments: can seroconversion be prevented?

The rate of seroconversion from percutaneous needlestick exposure to HIV infection is approximately 0.3 per cent. To investigate the possibility of local confinement of HIV, 100 to 200 nm Tc-99m sulfur colloid particles were injected in the canine model subcutaneously at the knee level and collected proximally at the groin from the cannulated femoral vein and lymphatic channel. Tourniquet compression (250 mm Hg) was used as an intervention to possibly restrict particle spread. It was found that particles arrived in the blood at 2.81 +/- 0.54 minutes, with later arrival in the lymph at 6.0 +/- 1.47 minutes. Tourniquet application delayed the appearance of the particulate matter in the blood up to 7.11 +/- 1.5 minutes and in lymph up to 40.0 +/- 5.10 minutes. The concentration of radioactivity in the lymph was higher than in the venous blood. The distribution of the particles reflected by flux was comparable in both pathways. The accumulation curves did not reach plateaus during 45 minutes in lymph and 15 minutes in blood. Radioactive scanning revealed that about 90 per cent of the injected particles remained locally with gradual release for at least 45 minutes. Our results suggest that HIV, introduced by needlestick injury, can be contained for possible viricidal treatment if the response includes rapid immobilization and tourniquet of the area.

Analysis of Variance↗
PubMed2000

Cleft sternum and sternal foramen.

Cleft sternum is a rare congenital defect of the anterior chest wall and is the result of a failed midline fusion of the sternum. Depending on the degree of separation, there are complete and incomplete forms. Its clinical significance is that it leaves the heart and great vessels unprotected. Association with craniofacial hemangiomas and omphalocele is common. Prenatal diagnosis by ultrasonography is possible. Surgical correction should be performed during the neonatal period when the direct suturing of the sternal halves is possible and the thorax can accommodate the thoracic viscera. At an older age, surgical repair is feasible, but it may require additional measures, such as sliding chondrotomies of the adjacent costal cartilages and notching of the sternal bars, to facilitate the approximation. Lung herniation at the base of the neck should be corrected by uniting the cervical muscles. The first postoperative day is the most critical because of acute reduction of the mediastinal space. Long-term results are satisfactory. Sternal foramen is a congenital oval defect at the lower third of the sternum that is asymptomatic and could be detected by CT scanning. The awareness of the anomaly is important in acupuncture practice because of the danger of heart damage.

Abnormalities, Multiple↗
PubMed2000

Pouter pigeon breast.

Pouter pigeon breast is a rare congenital deformity of the chest characterized by a protrusion of the manubriosternal junction and premature sternal ossification. The adjacent costal cartilages, usually from the second to fifth, also protrude. One third of the patients with pouter pigeon breast presented with concomitant depression of the lower third of the sternum. Several cardiovascular abnormalities have been associated with premature sternal ossification, with ventricular septal defect being the most common. All patients with pouter pigeon breast should undergo echocardiography in search of occult cardiac lesions. The measurement of the angle of Louis on lateral chest radiograms allows the objective assessment of the deformity and appreciation of the sternal fusion. Surgical correction includes the wide wedge transverse sternotomy at the angle of Louis and subperichondrial resection of the adjacent costal cartilages. When the deformity is part of a syndrome or in cases of severe depression of the lower sternum, we recommend the technique using Marlex mesh support as described by Robicsek. Preferable age for repair is 5 to 7 years old. Long-term outcomes are encouraging.

Humans↗