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Biomedical subjects

D Kovachev

Publications and source records attributed to D Kovachev.

At least 19 recordsLinked to original sources
PubMed1999

Inductively coupled wideband transceiver for bioimpedance spectroscopy (IBIS).

Most measurement devices for bioimpedance spectroscopy are coupled to the measured object (tissue) via electrodes. At frequencies > 500 kHz, they suffer from artifacts due to stray capacitances between electrode leads as well as between the ground and object. The noninvasive measurement of the brain conductivity is hardly possible with surface electrodes. These disadvantages can be obviated by inductive coupling. The aim of this work was the development of a wideband transceiver for inductive impedance spectroscopy. In order to define its specifications, a feasibility study has been carried out with a simulation model for three different coil systems above a homogeneous conducting plate. According to simulation results, all systems render it possible to resolve conductivity changes down to 10(-3) (omega m)-1 at frequencies > 50 kHz. The transceiver electronics must then provide a resolution of > or = 1 microV and an excitation current of up to 1 A. The realized receiver matches these specifications with an S/N ratio of 22 dB at 1 microV in the frequency range of 50 kHz to 5 MHz.

Brain Chemistry↗
PubMed1987

[Determination of the effectiveness of plasma exchange in kidney diseases by a biological test].

Plasma toxicity and plasma exchange efficacy were studied in two groups of patients: I gr.--8 patients with various degree of disturbed renal function who did not need hemodialysis treatment; II gr.--9 patients treated by periodic hemodialysis. A biologic toxicity test was used together with the clinical, immunologic and biochemical indices as a criterion for plasma exchange efficacy. The test gives direct information for the total plasma toxicity which is of great advantage and helps in the decision for another plasma exchange.

Animals↗
PubMed1986

Abdominal wall reconstruction.

Patients with abdominal wall reconstruction present a difficult management problem to the oncological surgeon. There were 36 patients treated for abdominal wall primary and secondary tumors between the years 1973 and 1982 at the Memorial Hospital. There were 25 abdominal wall sarcomas, 6 recurrent colon cancers, 2 recurrent bladder cancers, 1 cervical cancer, 1 recurrent endometrial cancer and 3 complications of radiotherapy treated by excision and reconstruction of the defect. The desmoid tumors were closed primarily. The recurrent sarcomas after radical excision, were reconstructed with Marlex mesh and local mobilization of skin and subcutaneous tissue. The recurrent colon bladder and endometrial cancers had been treated with over 5,000 cGy each. Three patients had significant full thickness skin loss secondary to radiotherapy. These patients comprised the group that required a myocutaneous flap to provide full thickness skin and fascia. The tensor fascia lata flap was used in eight patients. This group of patients did extremely well in contrast to the group of radiated patients with Marlex mesh reconstruction. There were less complications in the TFL group. We recommended the TFL flap for a large abdominal wall defect and for a previously radiated abdominal wall.

Abdominal Muscles↗
PubMed1980

Neurovascular flap repair of the foot for sarcoma.

Wide excision of soft tissues of the foot for sarcoma invariably creates a large defect requiring closure in a way that will withstand the trauma of bearing weight. Neurovascular flap reconstruction provides a thick, well-vascularized cover with good sensation, functional durability, and brief immobilization.

Adolescent↗
PubMed1980

[Stimulation of mitotic activity and blast transformation of lymphocytes in vitro caused by phaseolosaxin and its fractions].

Mitogenic and blast-transforming properties of phytohemagglutinin Phaseolosaxin of the Bulgarian production, and of its three fractions have been studied in vitro. The greatest part of the biological activity is due to fraction 1, which represents, in fact, a highly purified phytohemagglutinin. These results may be useful in regard to the large scale of application of Phaseolosaxin.

Humans↗
PubMed1977

[Electrophoretic study of different types of phytohemagglutinins].

The author compared the number and the percentage distribution of the preparations faseolaxin (FHA-F), produced in this country by the method of Coneva and phytohemaglutinines from the firms "Difko" VASTO-M and VASTO-P, by means of disc electrophoresis and acrylamide gel. He found similarity in the fractions of FHA-F and VASTO-P. The difference was in the quickly mobile components, which were respectively 6,5% and 14,5% of the total amount. The examination of the initial extract for obtaining FHF-F showed that the method of Coneva had advantages in respect of the purity of the preparation.

Electrophoresis↗
PubMed1975

Silicone elastomer sheeting in the development of pedicle flaps.

A "delay" of a pedicle flap stimulates improvement in the flap circulation, probably through partial ischemia. The degree of stimulation prsent at any given time is inversely proportional to the length of time that has passed after the delay because progressive revascularization across the delay lines reduces the ischemis stimulus. This revascularization can ve prevented by placing silicone elastomers (Silastic) sheeting between the flap and its bed.

Animals↗