Postburn dermal scars can be aesthetically disfiguring and severely disabling. Existing medical and surgical strategies to prevent or to treat scars are all too often disappointing. More effective strategies are needed. It has been postulated that cell membrane calcium channel blockers could potentially trigger extracellular matrix degradation in dermal scars, resulting in scar volume reduction. To test this hypothesis, we studied the effects of intralesional verapamil hydrochloride therapy, 0.1 to 0.5 mmol/L, on scar volume and color in patients with burns. Our study chronicles five reports on arbitrarily selected clinical cases of hypertrophic burn scarring and the effect of therapy with intralesional verapamil. The cellular functions and processes explaining this effect are discussed. There were no significant side effects or complications from the verapamil therapy. It is now clear that regulation of fibroblast calcium metabolism is a safe and often effective strategy to treat hypertrophic scars. To our knowledge, this is the first clinical report of control of burn scar with calcium channel blockers.

Adolescent↗

PubMed1994

Altered ion channel conductance and ionic selectivity induced by large imposed membrane potential pulse.

The effects of large magnitude transmembrane potential pulses on voltage-gated Na and K channel behavior in frog skeletal muscle membrane were studied using a modified double vaseline-gap voltage clamp. The effects of electroconformational damage to ionic channels were separated from damage to lipid bilayer (electroporation). A 4 ms transmembrane potential pulse of -600 mV resulted in a reduction of both Na and K channel conductivities. The supraphysiologic pulses also reduced ionic selectivity of the K channels against Na+ ions, resulting in a depolarization of the membrane resting potential. However, TTX and TEA binding effects were unaltered. The kinetics of spontaneous reversal of the electroconformational damage of channel proteins was found to be dependent on the magnitude of imposed membrane potential pulse. These results suggest that muscle and nerve dysfunction after electrical shock may be in part caused by electroconformational damage to voltage-gated ion channels.

Animals↗

PubMed1994

An improved double vaseline gap voltage clamp to study electroporated skeletal muscle fibers.

An improved voltage clamp with a double vaseline gap chamber was designed to study electroporated skeletal muscle fibers. The new clamp eliminated spike overshock of membrane potential when applying step stimulation occurring in the traditional configuration. It allowed greater consistency in membrane potential distribution. After the intracellular resistances of the fiber segment at the vaseline gap area were compensated, it was possible to change membrane potential more quickly. Using this technique, strong electrical pulses used to mimic the situation of electrical shock can be delivered to the cell membrane by voltage clamp. Transmembrane currents of skeletal muscle cell were simultaneously measured during a high pulsed shock and resolved into different components. Distinct transient changes of the transmembrane current, involving the time courses of the formation of electroporation and their recovery time constants, can be recorded. Because of more even membrane potential distribution and faster response to pulsed membrane potential change, this technique is also suitable for membrane study under physiological conditions.

Animals↗

PubMed1994

Intralesional verapamil injection for the treatment of Peyronie's disease.

Peyronie's disease remains a therapeutic dilemma for the practicing urologist. Multiple nonoperative therapies have been offered with variable suboptimal response rates. Calcium channel blockers have been shown to alter the metabolism of fibroblasts, resulting in decreased extracellular matrix secretion of collagen as well as increased collagenase activity. In this nonrandomized dose-escalating format study 14 men received biweekly injections of verapamil into the Peyronie's plaques for 6 months. Subjectively, there was significant improvement in plaque-associated penile narrowing (100%) and curvature (42%). Objectively, a decreased plaque volume of greater than 50% was noted in 30% of the subjects. Plaque softening was noted in all patients, while 83% noticed that plaque-related changes in erectile function had arrested or improved. There was no toxicity nor did symptoms recur when improvement was noted. This preliminary study suggests that intralesional calcium antagonist (verapamil) therapy offers an economical and sensible nonoperative approach to the treatment of Peyronie's disease.

Adult↗

PubMed1994

Induced redistribution of cell surface receptors by alternating current electric fields.

The molecular mechanisms that underlie the biological effects of low frequency sinusoidal electric fields may involve induced changes in the physical state of charged cell surface receptors. We have used intensified fluorescence video microscopy to study the redistribution of cell surface receptors, including transferrin receptors (TFR) and low density lipoprotein receptors (LDL-R), in response to externally applied alternating current electric fields in the 3 to 23 V/cm range (peak to peak). Redistribution of both TFR and LDL-R was prominent at frequencies of 1 and 10 Hz but negligible at frequencies of 60 and 120 Hz. Application of a 1 Hz, 23 V/cm field for 15 min caused a twofold change in local TFR surface density, whereas application of a 60 Hz, 23 V/cm field resulted in no significant TFR redistribution. The extent of TFR redistribution induced by a 1 Hz field changed by only 20% over the field strength range from 3.5 to 23 V/cm. AC field-induced cell surface receptor migration did not consistently follow electric field lines, suggesting that mechanisms more complex than classical electrophoresis and electroosmosis mediate receptor redistribution. Joule heating and plasma membrane calcium channel activation were shown not to be involved in the mechanism of receptor redistribution. Applied external electric fields may reorganize cytoskeletal and plasma membrane structures, providing pathways for cell surface receptors to migrate anharmonically.

Calcium Channels↗

PubMed1994

Intestinal schistosomiasis japonica: CT-pathologic correlation.

PURPOSE: To study the pathologic basis of intestinal wall calcification caused by Schistosoma japonicum visualized with computed tomography (CT). MATERIALS AND METHODS: Twelve patients underwent CT of the abdomen to detect what pathologic examination proved to be schistosomiasis japonica. Eight intestinal specimens from five of the patients were subjected to radiography, and the pathologic and radiographic findings were correlated. RESULTS: CT demonstrated curvilinear or nodular calcification in the colon in 11 patients, in the appendix in two, and in the distal ileum in one. In five patients, calcifications resembling tram tracks were found in the sigmoid colon. Pathologic examination of the specimens showed calcified eggs of S japonicum deposited more extensively in the submucosa and subserosa than in the muscularis propria, which led to the tram-track appearance. CONCLUSION: The extensive curvilinear or tram-track calcification found in the colon in patients with schistosomiasis japonica is calcification of deposited eggs.

Aged↗

PubMed1993

The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14.

lin-4 is essential for the normal temporal control of diverse postembryonic developmental events in C. elegans. lin-4 acts by negatively regulating the level of LIN-14 protein, creating a temporal decrease in LIN-14 protein starting in the first larval stage (L1). We have cloned the C. elegans lin-4 locus by chromosomal walking and transformation rescue. We used the C. elegans clone to isolate the gene from three other Caenorhabditis species; all four Caenorhabditis clones functionally rescue the lin-4 null allele of C. elegans. Comparison of the lin-4 genomic sequence from these four species and site-directed mutagenesis of potential open reading frames indicated that lin-4 does not encode a protein. Two small lin-4 transcripts of approximately 22 and 61 nt were identified in C. elegans and found to contain sequences complementary to a repeated sequence element in the 3' untranslated region (UTR) of lin-14 mRNA, suggesting that lin-4 regulates lin-14 translation via an antisense RNA-RNA interaction.

Animals↗

PubMed1993

Cell shape-dependent rectification of surface receptor transport in a sinusoidal electric field.

In the presence of an extracellular electric field, transport dynamics of cell surface receptors represent a balance between electromigration and mutual diffusion. Because mutual diffusion is highly dependent on surface geometry, certain asymmetrical cell shapes effectively create an anisotropic resistance to receptor electromigration. If the resistance to receptor transport along a single axis is anisotropic, then an applied sinusoidal electric field will drive a net time-average receptor displacement, effectively rectifying receptor transport. To quantify the importance of this effect, a finite difference mathematical model was formulated and used to describe charged receptor transport in the plane of a plasma membrane. Representative values for receptor electromigration mobility and diffusivity were used. Model responses were examined for low frequency (10(-4)-10 Hz) 10-V/cm fields and compared with experimental measurements of receptor back-diffusion in human fibroblasts. It was found that receptor transport rectification behaved as a low-pass filter; at the tapered ends of cells, sinusoidal electric fields in the 10(-3) Hz frequency range caused a time-averaged accumulation of receptors as great as 2.5 times the initial uniform concentration. The extent of effective rectification of receptor transport was dependent on the rate of geometrical taper. Model studies also demonstrated that receptor crowding could alter transmembrane potential by an order of magnitude more than the transmembrane potential directly induced by the field. These studies suggest that cell shape is important in governing interactions between alternating current (ac) electric fields and cell surface receptors.

Biological Transport, Active↗

PubMed1992

Surfactant-induced sealing of electropermeabilized skeletal muscle membranes in vivo.

Victims of major electrical trauma frequently suffer extensive skeletal muscle and nerve damage, which is postulated to be principally mediated by electroporation and/or thermally driven cell membrane permeabilization. We have investigated the efficacy of two blood-compatible chemical surfactants for sealing electroporated muscle membranes. In studies using cultured skeletal muscle cells, poloxamer 188 (P188; an 8.4-kDa nonionic surfactant) blocks, and neutral dextran (10.1 kDa) substantially retards, carboxyfluorescein release from electropermeabilized cell membranes. To test whether P188 administered intravenously could have the same therapeutic effect in vivo, the rat biceps femoris muscle flap attached by its arteriovenous pedicle was electropermeabilized until its electrical resistivity dropped to 50% of the initial value. P188 (460 mg/kg) administered intravenously 20 min postshock restored the resistivity to 77% of the initial value. When P188 was administered intravenously 5 min before shock, a dose-dependent impedance recovery rate was observed. Neither neutral dextran (460 mg/kg) nor sterile saline was effective. Histopathologic studies indicated that postshock poloxamer administration reduced tissue inflammation and damage in comparison with dextran-treated or control tissues. Electrophysiologic evidence of membrane damage was not observed in flaps of animals pretreated with poloxamer. These results suggest that it may be possible to seal in vivo tissue membranes injured by electrical, thermal, or other membrane-damaging forces.

Animals↗

PubMed1992

Thermal injury kinetics in electrical trauma.

The distribution of electrical current and the resultant Joule heating in tissues of the human upper extremity for a worst-case hand-to-hand high-voltage electrical shock was modelled by solving the Bioheat equation using the finite element method. The model of the upper extremity included skin, fat, skeletal muscle, and bone. The parameter sets for these tissues included specific thermal and electrical properties and their respective tissue blood flow rates. The extent of heat mediated cellular injury was estimated by using a damage rate equation based on a single energy barrier chemical reaction model. No cellular injury was assumed to occur for temperatures less than 42 degrees C. This model was solved for the duration of Joule heating required to produce membrane damage in cells, termed the lethal time (of contact) for injury. LT's were determined for contact voltages ranging from 5 to 20 kV. For a 10,000 volt electrical shock LT's for skeletal muscle are predicted to be: 0.5 second in the distal forearm, 1.1 second in the mid-forearm, 1.2 second in the proximal elbow, and 2.0 seconds in the mid-arm. This analysis of the electrical shock provides useful insight into the mechanisms of resultant tissue damage and provides important performance guidelines for the development of safety devices.

Arm Injuries↗

PubMed1991

Current approaches to shortage area designation.

This paper reviews the various indicators and criteria that are in use to identify rural and urban areas with shortages of primary care physicians, dentists, psychiatrists, or nurses; areas with medically underserved populations; high migrant impact areas; and areas of greatest need/shortage, leading to lists of designated shortage or underserved areas eligible for various federal and state programs; and to lists of areas with priority for resource placement. Presenting these shortage and underservice criteria at a workshop dealing with adequacy was not meant to suggest an equivalency between the concepts of "shortage," "underservice," and "adequacy," but the shortage and underservice criteria can be thought of as a floor on the definition of adequacy, and may contain elements of that definition. Refinements or revisions to the various criteria could probably better identify the needs in rural areas, or the kind of staffing mix needed in various types of areas, or improve priority setting among designated areas; but the existing criteria remain a good first screen to identify those areas with health services-related needs that require further attention.

Catchment Area, Health↗

PubMed1990

Calcium antagonists retard extracellular matrix production in connective tissue equivalent.

Hypertrophic and keloid scars are characterized by the overproduction of extracellular matrix collagen and proteoglycans. Because cellular secretion of macromolecules is known to be a calcium-dependent process, we have examined the effect of calcium antagonists on the rate of incorporation of [3H]proline into protein and Na235SO4 into sulfated glycosaminoglycans. Experiments were carried out in vitro using uniaxially oriented mammalian fibroblast-populated collagen matrices which exhibit many histoarchitectural features of scar matrix. We observed that nifedipine and verapamil in sufficient concentrations inhibited the incorporation of proline into extracellular matrix protein. The concentration range studied was 1 to 100 microM. Cobalt chloride (200 microM) had a similar effect on proline incorporation, but enhanced the incorporation of sulfate into extracellular matrix glycosaminoglycans. We conclude that cellular calcium metabolism appears to regulate extracellular matrix production and that hypertrophic disorders of wound healing may respond to therapy with calcium antagonist drugs.

Animals↗

PubMed1990

Rhabdomyolysis due to pulsed electric fields.

High-voltage electrical trauma frequently results in extensive and scattered destruction of skeletal muscle along the current path. The damage is commonly believed to be mediated by heating. Recent experimental and theoretical evidence suggests, however, that the rhabdomyolysis and secondary myoglobin release that occur also can result from electroporation, a purely nonthermal mechanism. Based on the results of a computer simulation of a typical high-voltage electric shock, we have postulated that electroporation contributes substantially to skeletal muscle damage and could be the primary mechanism of damage in some cases of electrical injury. In this study, we determined the threshold field strength and exposure duration required to produce rhabdomyolysis by the electroporation mechanism. The change in the electrical impedance of intact skeletal muscle tissue following the application of short-duration, high-intensity electric field pulses is used as an indicator of membrane damage. Our experiments show that a decrease in impedance magnitude occurs following electric field pulses that exceed threshold values of 60 V/cm magnitude and 1-ms duration. The field strength, pulse duration, and number of pulses are factors that determine the extent of damage. The effect does not depend on excitation-contraction coupling. Electron micrographs confirm structural defects created in the membranes by the applied electric field pulses, and these represent the first clear demonstration of rhabdomyolysis in intact muscle due to electroporation. These results provide compelling evidence in support of our postulate.

Animals↗