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Biomedical subjects

A L Andreev

Publications and source records attributed to A L Andreev.

15 recordsLinked to original sources
PubMed2005

High frequency hysteresis-free switching in thin layers of smectic-C* ferroelectric liquid crystals.

The insulating layers used for the alignment of ferroelectric liquid crystals (FLC) in electro-optical cells usually have non-negligible thickness and their capacitance determines the type of the director switching caused by a triangular-form external voltage U(tr) . With decreasing frequency of U(tr) , the hysteresis in a switching direction changes from the normal to the abnormal one at a characteristic hysteresis inversion frequency f(i) . In the vicinity of f(i) , the electro-optical response is thresholdless and the optical transmission manifests the V -shape field dependence. The V -shape regime is very interesting for certain applications, in particular to microdisplays due to a possibility of the gray scale realization. However, f(i) has to be enhanced from the usually observed frequency of a few Hz up to the range of hundreds of Hz. To this effect, a special FLC material has been designed and its basic properties (tilt angle, spontaneous polarization, rotational viscosity, and electric conductivity) have been measured over the entire range of the smectic-C* phase. Upon variation of cell parameters (thickness of both the FLC and alignment layers), temperature, and external voltage, the frequency of the V -shape effect as high as 150-1000 Hz (in the temperature range 30-75 degrees C) has been found experimentally. The operating voltage remains lower than 8 V. A quantitative interpretation of these results has been done using the modeling procedure developed earlier [S.P. Palto, Cryst. Rep. 48, 124 (2003)]. The modeling has been performed with the experimental values of the FLC material and the cell parameters and has shown very good agreement with experiment. The key point of this approach is consideration of the internal voltage on the FLC layer, the sign, amplitude, and form of which differ from U(tr) . The results of the modeling allow further improvement of the performance of electro-optical FLC cells for high frequency V-shape effect.

Journal Article↗
PubMed2004

[Laparoscopic splenectomy through a lateral access].

The investigation included 35 patients with diseases of blood and spleen pathology (30) and wounds and traumas of the abdomen with injuries of that organ (5), treated by laparoscopic splenectomy through a lateral access. The technique and stages of the operation and advantages of the lateral access are described. The laparoscopic splenectomy was shown to be possible in 90% of cases if patients were selected with special reference to the main disease, size and degree of pathological alterations in the spleen. An adequate approach to selections of patients with injuries of the organ allowed to make operations in more than a third of the patients and casualties. When using the lateral access laparoscopic splenectomy is thought to be more convenient, gives better visualization of the anatomical structures and reduces risk of injury of adjacent organs, thus resulting in less frequency of complications and conversions.

Abdominal Injuries↗
PubMed2003

[Physical methods of dissection and coagulation in surgery].

The paper presents 20-year experience in using various devices for tissue dissection and coagulation of such as electrosurgical ones EN-57M, Efa-0201 (Russia), Karl Storz-endoscope (Germany), Force-300, Force-FX, LigaSure ("Valley-lab", USA), Erbotom ICC 350 ("Erbe"), Argo-3000 ("Soring", Germany), a Surgitrone radioknife ("Ellman", USA), ultrasonic Auto Sonix devices ("Auto Suture", USA), a harmonic Ultracision scalpel ("Ethicon Endo-Surgery", USA), laser Scalpel-1 and Romashka-1 devices (Russia), plasma Fakel-01 and Prometey devices (Russia). The results of 424 experimental studies and clinical application of different energies in 1683 patients are analyzed. The influence of different types of energy on tissue and reparative processes were revealed, morphological changes were studied. Advantages and shortcomings of each type of energy are demonstrated, recommendations for their optimum application are formulated.

Dissection↗
PubMed2001

[Diagnosis and surgical treatment of mediastinal neoplasms].

The authors share their experiences with examination and surgical treatment of 163 patients with various neoplasms of the mediastinum. The first place among the neoplasms is occupied by tumors of the lymphatic apparatus (33%), the second--by tumors of the thymus (21%). The video-thoracoscopic technique was used in 17 of 131 operations performed. Complications after the operations took place in 6 patients (4.5%), two patients died (1.5%). A conclusion is made that the patients of this category must be treated not only by thoracic surgeons but also by hematologists, neurologists, neurosurgeons and specialists in radiation therapy.

Adolescent↗
PubMed1999

[Laparoscopic surgery in colorectal tumors].

The authors describe their first experience with using less invasive laparoscopic methods in patients with tumors of the rectum and the colon. Twelve operative interventions were performed. The method and technique of endovideosurgical operations on the colon are described. The intraoperative and postoperative complications are analyzed. The authors not rich experience with performing laparoscopic interventions on the colon shows the necessity of stepwise and thorough mastering the method and of using strictly individual indications for such operations.

Colectomy↗
PubMed1997

[The combined endoscopic surgery of gallstones complicated by diseases of the terminal common bile duct].

The article deals with combined endoscopic treatment of cholelithiasis complicated by pathological changes of the terminal part of the common bile duct in 104 patients: in 81 of them there was choledocholithiasis (5 of them had the Mirizzi syndrome). 15 patients had choledocholithiasis and papillostenosis, 8 patients had papillostenosis. Papillosphincterotomy with laparoscopic cholecystectomy was performed in 50 patients, in 4 senile patients only papillosphincterotomy was performed. Laparoscopic cholecystectomy and interventions on the common bile duct were fulfilled in 46 patients; in 27 cases the duct was drained by the method of Holsted-Pikovskiĭ, in 13 cases--after Kehr, in 3--after Vishnevskiĭ. In 2 cases the concrements were removed through the cystic duct, the common bile duct was not drained. The supraduodenal choledochoduodenoanastomosis was made in one patient. The open operation was performed in 4 cases (3.9%). One patient died (1%). The experience shows that the modern endoscopic technique allows the whole program of intraoperative revision and sanitation of the hepaticocholedochus and its drainage to be realized. Advantages of the combined endoscopic treatment of the cholelithic disease complicated by a lesion of the terminal part of the common bile duct as compared with traditional surgery are evident. They are: decreased postoperative pain syndrome, less amount of complications, good cosmetic affect, shorter period of reconvalescence, high economic effect.

Adolescent↗
PubMed1992

[Endoscopic interventions in cicatricial strictures of esophageal anastomoses].

Endoscopic balloon hydrodilation was conducted in 39 patients with cicatricial stenoses of esophageal anastomoses, in 12 patients it was combined with electrodissection of the esophageal anastomosis, in 3 with bougienage, and in 10 with temporary endoprosthetics. The anastomosis was dilated adequately (to 2.0-2.5 cm) in 38 patients. In one case endoscopic treatment was ineffective; another surgical intervention was performed. In another case endoprosthetics was complicated by decubitus of the cervical esophagus (favorable outcome). In late-term period of 2 months to 4 years restenosis occurred in 6 of 38 patients; the course of dilation was repeated in 4 patients, 2 patients underwent a reconstructive operation. The authors believe that in development of cicatricial stenosis of the esophageal anastomosis modern methods of therapeutic endoscopy should be resorted to in the first place, and only if they prove ineffective should the question of repeated surgical intervention be discussed. Balloon hydrodilation is the principal method of operative endoscopy in cicatricial stenoses of esophageal anastomoses, which in some cases should be combined with other endoscopic interventions (electroincision and temporary endoprosthetics).

Adolescent↗
PubMed1990

[Endoscopic study using a superthin endoscope in benign esophageal strictures].

To increase the diagnostic possibilities, the authors suggested a method of endoscopic examination of patients with esophageal strictures by means of a superthin PF-28 fibroscope produced by the Olympus firm (Japan), which was introduced along a string-guide. The examination was successful in 24 of 26 patients. Clinical observations have shown that esophagogastroscopy with a superthin endoscope makes it possible to recognize the exact length of the stenosed segment, detect the second zone of stenosis, and determine the condition of the mucous membrane of the esophago-gastric junction and the proximal part of the stomach.

Adult↗
PubMed1990

[Current possibilities of diagnostic and surgical endoscopy in cicatricial esophageal stenosis].

Endoscopic methods of examination have been employed in 153 cases of burn and peptic strictures of the esophagus. The experience has shown that the use of small-diameter (including ultrathin) fiber endoscopes provides maximum information of the status of the esophagus along its whole length as well as of the stomach and duodenum, which is of importance in the choice of therapeutic tactics in this category of patients. Eighty one patients with cicatricial stenosis of the esophagus and esophageal anastomoses were subjected to various endoscopic interventions: balloon hydrodilation, bougienage, electrocision, and endoprosthesis . Balloon hydrodilatation was the major technique and in many cases was combined with other modes of therapeutic endoscopy. The authors' experience suggest that endoscopy adds to the available treatments for cicatricial strictures of the esophagus and esophageal anastomoses.

Adolescent↗
PubMed1990

[Use of electron video-endoscopic system in the diagnostic and therapeutic endoscopy].

Welch Allyn videoendoscopic system (USA) was used in 739 diagnostic and therapeutic investigations of 573 patients with various diseases of the gastrointestinal tract. Clinical experience has demonstrated the advantages of videoendoscope over common fibroscopes: it permits monitoring of the investigation by several specialists simultaneously, improves the training of specialists in endoscopy, permits recording and storage of endoscopic information, etc. At the same time videoendoscopes of this system are not devoid of shortcomings, i.e. the working part is too flexible, the image is frequently misrepresented during operation, this necessitating additional designing. On the whole videoendoscopic systems hold good promise in gastrointestinal endoscopy.

Adolescent↗
PubMed1989

Endoscopic balloon hydrodilatation and endoprosthetic treatment of esophageal and esophageal anastomotic strictures.

In 37 patients with benign stenosis of the esophagus and esophageal anastomoses, the method of dilatation using special balloon catheters under endoscopic control was employed, and adequate dilatation of the stenotic region accomplished. In comparison with balloon dilators, bougies exert forces along the radial axis, and no tension is applied to the esophagus along the longitudinal axis. To obtain prolonged remission and decrease the number of "supporting" dilatations of esophageal benign stenosis and esophageal anastomoses, temporary intubation of the esophagus with a silicone prosthesis was performed in 7 patients. Further clinical application, and a study of the long-term results of endoscopic balloon hydro-dilatation and endoprosthesis for treating esophageal and anastomotic esophageal strictures, will help to elaborate more precise indications for the combined use of these methods.

Adolescent↗
PubMed1989

[Endoscopic balloon hydro-dilatation of cicatricial strictures of the esophagus and esophageal anastomoses].

Endoscopic balloon hydro-dilatation produced good results in 36 patients with cicatricial strictures of the esophagus and esophageal anastomoses and in 6 patients with 3rd-4th stage of cardiospasm. The authors claim that an endoscopic intervention may be used as an effective method of nonoperative treatment of cicatricial strictures of the esophagus and esophageal anastomoses which causes little injury as well as a method of preoperative restoration of normal oral feeding for rapid preparation of patients for surgical operations.

Adolescent↗
PubMedDate not supplied

[Biofilm formation by different strains of Salmonella typhimurium in artificial systems].

The ability of 14 different strains of Salmonella typhimurium to biofilm formation depending on genotype and culture conditions was investigated in artificial systems: in 96-well plastic microtitre plates, plastic and glass tubes, plastic Petri dishes and on microscope glasses. Quantitative biofilm growth was monitored by using an assay based on crystal violet staining, while planctonic growth in the same cultures was monitored by absorbance in iEMS Reader MF, and qualitatively--by digital photo and visually. Optimal rate between growth and biofilm indications for all strains was determined at initial cell concentration 10(6-7) KOE/ml and culture incubation at t degrees 28 degrees C. The nutrient content of the medium significantly influenced the quantity of produced biofilm. The nutrient broth LB without NaCl was more effective in promoting biofilm formation, than LB itself. The least quantity of biofilm was formed in water. The genotype of the strains also critically influenced the quantity of produced biofilm. Nonmotile mutants cells had reduced ability to form biofilm. RpoS mutant cells produced significantly less biofilm as compared with cells of isogenic parent strains. The chemical content of plastic and glass also influenced biofilm formation.

Bacterial Proteins↗
PubMedDate not supplied

[Formation of biofilms as an example of the social behavior of bacteria].

This paper is a brief review of data on bacterial biofilms that occur inside and outside of host organisms. Such biofilms are of great ecological and clinical importance. The role of interspecies communications in the development of bacterial biofilms and infectious diseases is particularly emphasized. Considerable attention is given to the electron microscopic study of biofilms formed by Salmonella typhimurium cells incubated as a broth culture in microtubes without aeration. Bacterial samples taken from the biofilm and planktonic culture grown in the same microtube were comparatively investigated by transmission electron microscopy.

Bacteria↗