PubMed Health⌕ Search

Biomedical subjects

G Falk

Publications and source records attributed to G Falk.

At least 73 records · Page 4Linked to original sources
PubMed1976

Tumor eradication by radiofrequency therapy. Responses in 21 patients.

Tumor blood flow, measured by an isotope dilution technique, is only 2% to 15% of that of the surrounding tissue. This sluggish circulation differentiates cancer from normal tissue and forms the basis for a new therapy that entails the transfer of radiofrequency (RF) energy for heating tissues locally. The heated tissue is cooled by the circulation of blood, which carries away the heat. Impaired perfusion, as in cancers, impedes cooling. Heating by RF elevated the temperatures of animal and human cancers by 5 to 9.5 C above that of healthy tissue. The heat eradicated the animal cancers without destruction of normal tissue. Radiofrequency therapy produced tissue necrosis or substantial regression of cancer in 21 patients.

Animals↗
PubMed1976

Effects of prophylactic antibiotics on colonic healing.

The effect of antibiotic colon preparation on the tensile strength and morphologic appearance of colonic anastomoses has been investigated in dogs. Preparation with preoperative kanamycin did offer a slight benefit over mechanical bowel cleansing. The addition of erythromycin and kanamycin to the preoperative bowel preparation significantly (p less than 0.001) improved the mean tensile strengh of the healing colonic anastomosis. Continuation of erythromycin and kanamycin for one week postoperatively almost doubled the mean tensile strength of the healing anastomosis. Continuation of erythromycin without kanamycin in the postoperative period provided little protection over the preoperative administration of kanamycin and erythromycin. Histologic examination showed that erythromycin and kanamycin given during the pre- and postoperative period changed the mode of healing from that of secondary intention to healing by first intention. The findings support the concept that soilage of the peritoneal cavity at the time of elective colon surgery is not as important as leakage caused by poor anastomotic healing. Antibiotic bowel preparation with kanamycin and erythromycin improves the healing of colonic anastomoses.

Animals↗
PubMed1974

Peritoneo-venous shunting for ascites.

A new minor surgical procedure for ascites has been devised wherein a specially designated one way pressure activated valve is implanted to create a permanent peritoneo-venous shunt. The normally closed valves opens only when the peritoneal pressure rises 3-5 cm higher than the intrathoracic venous pressure thus preventing backflow of blood and closing the valve should the venous pressure rise from the over-infusion of ascitic fluid. The procedure has been performed on 45 patients but nine were terminal at the time of surgery. Prolonged relief of ascites occurred in 28 of 37 cases.

Animals↗
PubMed1973

An analysis of light-induced admittance changes in rod outer segments.

1. Measurements were made of the time course and amplitude of the change in real part of admittance, DeltaG, of a suspension of frog rod outer segments, following a flash of light bleaching about 1% of the rhodopsin content of the rods. The measurements, based on the use of a specially designed marginal oscillator, covered the frequency range between 500 Hz and 17 MHz.2. The components of response, previously described for rods prepared by a method involving exposure to strongly hypertonic sucrose solutions, are present in similar form when rods are isolated and maintained in isotonic solutions made up with equi-osmotic concentrations of NaCl and sucrose or with Na(2)SO(4).3. Component I, identified as a slowly developing positive DeltaG apparent at very low frequencies, is frequency-independent up to the characteristic frequency of admittance for the suspension, f(Y) (about 2 MHz for rods suspended in a solution having the conductivity of Ringer solution), but decreases at still higher frequencies.4. Component II, identified as a rapidly developing positive DeltaG which appears only above a critical frequency about 2.5 decades below f(Y), increases approximately logarithmically with frequency to reach a limiting amplitude in the region of f(Y).5. The amplitude of component II, DeltaG(II), measured in the region of f(Y), varies linearly with the conductivity of the suspending medium, G(o), under conditions in which the conductivity of the rod interior is also a linear function of the external conductivity. The relation for a flash bleaching 1% of the rhodopsin content of the dark-adapted rod is [Formula: see text]6. Measurements made on rods suspended in a low-conductivity solution, which has the effect of reducing the conductivity of the rod interior to about one ninth its value for rods suspended in Ringer solution, reveal a decline in component II for frequencies above 8 MHz.7. To explain the frequency dependence of component II and its dependence on conductivity, it is proposed that component II arises from a light-induced increase in conductance of the disk membranes which obstruct the longitudinal flow of current through the rod interior except at very high frequencies.8. The disk-membrane conductance increase for rods suspended in a solution having the conductivity of Ringer solution is calculated to be 4.3 x 10(-11) mho/rhodpsin molecule bleached, a value which is similar to what has been found for ionic channels operated by membrane potential change in the nerve membrane and by synaptic transmitter in the postjunctional membrane.9. No component of response has been observed which could be reliably attributed to a surface membrane conductance decrease of the type observed in receptor cells in the retina.

Animals↗
PubMed1973

Isolation of components of admittance change in rod outer segments.

1. Rods were separated by equilibration on a bovine serum albumin (BSA) density gradient into two major fractions, differing in their response to light.2. In one fraction the response, measured as a change in the real part of admittance DeltaG, appeared to consist exclusively of component I, while in the other, component II was prominent.3. Evidence is presented that component I arose in damaged rods. This follows from observations on rods which have been deliberately damaged by freezing followed by thawing, or by fragmentation.4. In such damaged rods, component II was absent while component I was increased in amplitude.5. The frequency dependence of component I in isolation was characterized as a positive DeltaG of constant amplitude from low frequencies up to the characteristic frequency f(Y) for the major dispersion of admittance. Above this frequency, it declined to a variable extent.6. The frequency dependence of component II observed in isolation was consistent with the previous analysis.7. A negative-going DeltaG is described which was linear with the amount of rhodopsin bleached and which was frequency independent up to the highest frequency of measurement (17 MHz).8. The origins of component I and the negative component are discussed.

Animals↗