Determinación de la composición corporal en varones jovenes mediante el análisis de Impedancia Biolectrica y la antropometría

La trancisión demográfica determina la aparición de un nuevo perfil epidemiológico en lo referente a patología nutricional en la población. El disponer de métodos válidos y confiables para determinar la composición corporal de las personas tiene implicaciones importantes en la salud individual y colectiva, no sólo en los ambitos: preventivo y recuperativo, sino también en el ámbito deportivo ya que el establecimiento del somatotipo orienta y racionaliza la práctica deportiva. El presente estudio se realizó en 50 varones jóvenes que realizan el servicio militar obligatorio (S.M.O.), en consecuencia tienen semejanzas en cuanto a edad, sexo, estilo de vida y actividad física. Se usaron dos métodos para la determinación de la composición corporal: a) Antropométrico, mediante la medición de pliegues cutáneos y b) Análisis de impedancia Bioeléctrica (BIA). Con ambas métodos se determinaron los elementos: masa grasa y masa magra. Los sujetos de estudio fueron sometidos ambos métodos en condiciones semejantes en cuanto a hora, lugar o ambiente, condiciones de ingesta de alimento y líquidos y eliminación de orina. Parala medición de pliegues cutáneos se usó un calibrador de pliegues cutáneos Slinguide (Creative Health Product, Plyouth, MICH) y para el análisis de la impedancia bioeléctrica el bioanalizador Biodynamics modelo-310 (Biodynamics Co.,USA). Los resultados obtenidos son los siguientes: a) Antropometría; masa grasa6,79 Kg (ñ 2,2 Kg), masa magra 51,8 Kg(ñ4,99 Kg) y porcentaje de grasa corporal 11,27 por ciento (ñ1,89 por ciento) y b) Análisis de impedancia bioeléctrica; masa grasa 9,41 Kg (ñ4,02 Kg), masa magra 49,03 Kg (ñ5,8 Kg) y porcentaje de grasa corporal 15,82 por ciento (ñ5,31 Kg). los valores determinados por ambos métodos mostraron diferencia estadística significativa (p<0.05), tanto en los valores de masa grasa como de masa magra. El nivel de correlación entre ambos métodos fue bueno para los valores de masa magra (r=0,857,p<0.05), bajo para los valores de masa grasa (r=0,412,p<0.05) y también un nivel de correlación bajo para los valores del porcentaje de grasa (r=0.342,p<0.05).

Voltage dependence of beta-adrenergic modulation of conduction in the canine Purkinje fiber.

Although recent voltage-clamp and microelectrode studies have demonstrated beta-adrenergic modulation of Na+ current (INa) the modulation of conduction by catecholamines and the voltage dependence of that process have not been elucidated. To determine whether voltage-dependent modulation of conduction occurs in the presence of a beta-adrenergic agonist, the effect of 1 mumol/L isoproterenol on impulse propagation in canine Purkinje fibers was examined by using a dual-microelectrode technique. At physiological membrane potentials ([K+]o 5.4 mmol/L), isoproterenol increased squared conduction velocity [theta 2, 0.39 +/- 0.25 (m/s)2 (mean +/- SD)] from 3.46 +/- 0.86 to 3.85 +/- 0.98 (m/s)2 (P < .011), an 11% change, without altering the maximum first derivative of the upslope of phase 0 of the action potential (Vmax, 641 +/- 50 versus 657 +/- 47 V/s, P = NS). At transmembrane potential of -65 mV, produced by 12 mmol/L [K+]o titration, theta 2 declined 79% to 0.73 +/- 0.44 (m/s)2 as Vmax decreased 85% to 95 +/- 43 V/s (P < .02). The addition of isoproterenol further decreased theta 2 to 0.49 +/- 0.33 (m/s)2 (P = .02) in parallel with a further decline in Vmax to 51 +/- 25 V/s (P < .05). Isoproterenol produced a 3-mV hyperpolarizing shift of apparent Na+ channel availability curves generated from both theta 2 and Vmax, used as indexes of the fast inward INa, without changing the slopes of the relation. The relation between normalized theta 2 and Vmax over a range of depolarized potentials was linear and was not appreciably altered by isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of single cardiac and skeletal ryanodine receptor channels by flash photolysis of caged Ca2+.

Single ryanodine-sensitive sarcoplasmic reticulum (SR) Ca2+ release channels isolated from rabbit skeletal and canine cardiac muscle were reconstituted in planar lipid bilayers. Single channel activity was measured in simple solutions (no ATP or Mg2+) with 250 mM symmetrical Cs+ as charge carrier. A laser flash was used to photolyze caged-Ca2+ (DM-nitrophen) in a small volume directly in front of the bilayer. The free [Ca2+] in this small volume and in the bulk solution was monitored with Ca2+ electrodes. This setup allowed fast, calibrated free [Ca2+] stimuli to be applied repetitively to single SR Ca2+ release channels. A standard photolytically induced free [Ca2+] step (pCa 7-->6) was applied to both the cardiac and skeletal release channels. The rate of channel activation was determined by fitting a single exponential to ensemble currents generated from at least 50 single channel sweeps. The time constants of activation were 1.43 +/- 0.65 ms (mean +/- SD; n = 5) and 1.28 +/- 0.61 ms (n = 5) for cardiac and skeletal channels, respectively. This study presents a method for defining the fast Ca2+ regulation kinetics of single SR Ca2+ release channels and shows that the activation rate of skeletal SR Ca2+ release channels is consistent with a role for CICR in skeletal muscle excitation-contraction coupling.

beta-Amyloid increases choline conductance of PC12 cells: possible mechanism of toxicity in Alzheimer's disease.

When beta-amyloid-(1-40) is added to PC12 cells, there is an increase in choline conductance that is proportional to the beta-amyloid concentration. If a similar effect occurs in cholinergic brain cells of Alzheimer's disease patients, the intracellular choline concentration would be reduced, leading to a decrease in the production of acetylcholine. This could explain the reduced level of acetylcholine that has been found in post-mortem brain tissue of Alzheimer's disease patients.

Development of a H(+)-selective conductance during granulocytic differentiation of HL-60 cells.

The NADPH oxidase is one of the main microbicidal systems of granulocytes. Stimulation of the oxidase during infection leads to a burst of metabolic acid generation. Potentially deleterious cytosolic acidification is prevented by the simultaneous activation of homeostatic H+ extrusion mechanisms, including a recently described H+ conductance. Studies in granulocytes from chronic granulomatous disease patients have suggested a relationship between the oxidase and the H+ conductive pathway. In this report we compared the expression of the H+ conductance and the NADPH oxidase during granulocytic differentiation of dimethyl sulfoxide-induced HL-60 cells. Patch-clamp determinations demonstrated that the H(+)-selective current detectable in differentiated HL-60 cells is virtually absent in uninduced cells. The H+ conductance was also estimated fluorimetrically, measuring changes in the cytosolic pH of suspended cells. Imposition of an inward protonmotive force failed to induce significant cytosolic acidification. In contrast, a sizable conductive H+ extrusion was detected in acid-loaded differentiated cells, consistent with the rectifying properties of the current measured electrophysiologically. By the spectroscopic method, the H+ conductance was not detectable in uninduced cells, developing gradually during granulocytic differentiation. Development of the conductive pathway was found to parallel the biochemical and functional appearance of the NADPH oxidase. These findings suggest that the H+ extrusion mechanisms required for the maintenance of the intracellular pH during granulocyte activation develop pari passu with the acid generating systems and suggest a functional and possibly structural association between the H+ conductance and the NADPH oxidase.

Overexpression of a potassium channel gene perturbs neural differentiation.

Functional regulation of potassium currents in developing neurons is pivotal for changes in excitability and action potential waveform. Here, we test whether an excess of potassium channel transcripts is sufficient to drive functional expression of potassium current and shortening of the duration of the action potential. Injection of Shaker-like potassium channel transcripts into two-cell stage embryos achieves increases in RNA levels. The elevated levels of potassium channel RNA produce larger delayed-rectifier currents. Action potential durations are briefer, indicating that larger potassium currents are not compensated by changes in inward currents. Strikingly, overexpression of potassium current RNA leads to a reduction in the number of morphologically differentiated neurons in culture. We suggest that, by prematurely reducing the duration of the impulse, early overexpression of potassium channel activity suppresses normal developmental cues.

The effect of pH on the block by L-cis-diltiazem and amiloride of the cyclic GMP-activated conductance of salamander rods.

Block by L-cis-diltiazem and amiloride of the cyclic GMP-activated conductance was studied in inside-out patches excised from the salamander rod outer segment. When cytoplasmic pH was varied, the steady-state level of block by L-cis-diltiazem changed in the way that would be predicted if it were the protonated ammonium group that is responsible for effecting block. This is in contrast to the recent results of Haynes (J. gen. Physiol. 100, 783 (1992)) in catfish cones, where no such change was seen. Amiloride was found to block the conductance with a similar voltage dependence to that of L-cis-diltiazem. The dependence of amiloride block on cytoplasmic pH was found to be shifted relative to that of L-cis-diltiazem, consistent with the 1 pH-unit higher pKa value of amiloride and the idea that it is only the charged form of amiloride which can effect block. This suggests that the results seen with L-cis-diltiazem were indeed due to changes in the proportion of blocker in the protonated form, and not to effects of protons on the channel.

Charge displacement induced by rapid stretch in the basolateral membrane of the guinea-pig outer hair cell.

The properties of the basolateral membrane of cochlear outer hair cells were studied under whole-cell patch clamp to measure currents and capacitance changes associated with mechanical deformation. Stretching the membrane of outer hair cells along the cell axis generated a transient inward current, and subsequent relaxation of the membrane produced a similar transient outward current. These mechanically activated currents were velocity dependent with a mean sensitivity of 29 pA s mm-1. Unlike ionic currents, these currents did not reverse, but reached a peak magnitude at -33 mV. Stretching the cell also resulted in a measurable capacitance decrease of 0.3-1.1 pF microns-1. These results suggest that membrane stretch can induce a rapid charge movement resulting from the reversal of the electromechanical transduction process in outer hair cells.

Adenosine decreases action potential duration by modulation of A-current in rat locus coeruleus neurons.

The possibility that adenosine modulates voltage-dependent conductances in locus coeruleus neurons was investigated in current-clamp and voltage-clamp experiments in a totally submerged rat brain slice preparation. Adenosine (100 microM) reduced the duration of control action potentials and action potentials prolonged by 1 mM barium. Adenosine (100 microM) also reduced the amplitude and slightly reduced the duration of TTX-resistant "calcium" action potentials. Action potential duration was also reduced by the adenosine receptor agonist 2-chloroadenosine in a concentration-dependent manner and the adenosine-induced reduction of action potential duration was blocked by the adenosine receptor antagonist 8-(p-sulfophenyl)theophylline, indicating that this action of adenosine is mediated by an adenosine receptor. The adenosine-induced reduction of action potential duration persisted in the presence of externally applied tetraethylammonium ion (6 mM) and cesium (3 mM). By contrast, adenosine did not reduce the duration of the action potential in the presence of 500 microM 4-aminopyridine (4-AP). Furthermore, 4-AP (30 microM) blocked the adenosine-induced reduction of action potential duration recorded in the presence of 1 mM barium. These data suggested that adenosine may be acting on the voltage-dependent, 4-AP-sensitive potassium current, IA. Single-electrode voltage clamp was used to study IA directly. IA was activated by depolarizing voltage pulses from a hyperpolarized holding potential and was blocked by 1 mM 4-AP. Adenosine (300 microM) enhanced IA by shifting the steady-state inactivation curve in the depolarizing direction.(ABSTRACT TRUNCATED AT 250 WORDS)

Nerve growth factor increases nicotinic ACh receptor gene expression and current density in wild-type and protein kinase A-deficient PC12 cells.

Although neuronal nicotinic ACh receptors (nAChR) play a key role in synaptic transmission and information transfer in the nervous system, little is known about the molecular mechanisms that govern the expression of the multiple subunits that form the receptors and determine their functional properties. Using electrophysiological and molecular biological approaches, we have investigated the NGF-mediated regulation of nAChR expression in rat pheochromocytoma (PC12) cells and protein kinase A (PKA)-deficient PC12 cells. We report that NGF treatment increases steady state levels of mRNA encoding the alpha 3, alpha 5, alpha 7, beta 2, and beta 4 subunits, increases the occurrence of ACh-induced single-channel activity in excised patches, and increases ACh-induced macroscopic current density, all by mechanisms independent of PKA activity.

Modulation of a voltage-activated potassium channel by peptide growth factor receptors.

Regulation of the activity of a cloned component of a voltage-activated K+ channel, Kv1.5, was studied by expressing the K+ channel and receptors for platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF) simultaneously in Xenopus oocytes. Receptor activation mediated a decline in the Kv1.5 current amplitude, with a half-time of about 20 min. The reduction in K+ current amplitude occurred with little change in the kinetics or voltage sensitivity of activation. A similar phenomenon was found when the human thrombin or rat 5-HT1c receptors, two receptors that increase phospholipase C activity, were tested in coexpression experiments. A mutant FGF receptor, which does not activate phospholipase C-gamma 1 but retains several of its other functions, did not modulate the Kv1.5 current. Simultaneous injection of inositol trisphosphate and superfusion of phorbol 12-myristate 13-acetate reproduced the modulation of the Kv1.5 current. These results demonstrate that the PDGF and FGF receptors can modulate a voltage-activated K+ channel by increasing phospholipase C activity, and suggest that PDGF or FGF may be able to alter rapidly the electrical excitability of neurons.

Conductance catheter measurements of left ventricular volume in the intact dog: parallel conductance is independent of left ventricular size.

OBJECTIVE: It has recently been suggested that conductance catheter parallel conductance (alpha Vc) is a function of left ventricular volume. To confirm this, alpha Vc was measured in this study over a wide range of steady state volumes. In addition, conductance derived volumes were compared to those obtained by radionuclide angiography to determine if the conductance catheter can be used to measure absolute left ventricular volume accurately in the intact dog heart. METHODS: Seven dogs were anaesthetised and instrumented with left ventricular conductance and pressure tip catheters, a flow through rho cuvette to continually measure blood resistance, a thermodilution catheter, and a venous catheter for volume infusion/withdrawal. Conductance and angiographic data were acquired at 8(SD 1) variably loaded states. Parallel conductance was measured twice at each state using a saline dilution technique and a new non-linear algorithm that allows variability in the observations of both maximum and minimum conductance volumes. RESULTS: The mean value of alpha Vc was 89.1(18.0) ml (71.8 to 111.3 ml) with a mean within-animal coefficient of variation of 7.3(3.4)%. Multiple linear regression using dummy variables to account for the large interanimal variability did not reveal any relationship between alpha Vc and either maximum or minimum left ventricular volume. Furthermore, no difference was found when alpha Vc values measured at the lowest and highest loading levels in each dog were compared. Linear regression showed good agreement between conductance and radionuclide derived end diastolic volumes (slope = 0.94, R = 0.9, p < 0.001). CONCLUSIONS: While alpha Vc varies between animals, it remains constant within any given animal over a broad range of left ventricular volumes. Thus the conductance catheter can provide reliable absolute left ventricular volume measurements under steady state conditions.

Influence of membrane potential on conductance sublevels of chloride channels activated by GABA.

Single-channel chloride currents activated by 0.5 microM GABA were recorded in cell-attached and inside-out membrane patches from rat cultured hippocampal neurons. The currents displayed multiple conductance states and outward rectification. The number and amplitude of conductance levels were determined over a range of potentials by using digital signal-processing techniques. It was found that, except for a level close to zero, subconductance levels were regularly spaced. There were fewer sublevels at hyperpolarized than at depolarized potentials, and the spacing between levels varied linearly with potential giving an incremental conductance of 8-10 pS that was independent of membrane potential. Outward rectification is related to the change in the number of conductance levels with potential. One hypothesis that is consistent with these observations is that a channel is composed of a number of synchronized, non-rectifying, conducting pores, and that the number of pores activated changes with membrane potential.

Rheogenic Cl- conductance and Cl(-)-Cl(-)-exchange activities in guinea pig jejunal basolateral membrane vesicles.

We describe a method for the simultaneous purification of apical (brush-border membrane) and basolateral membrane (BLM) vesicles from the same sample of guinea pig jejunum. We applied functional tests to demonstrate the absence of reciprocal cross contamination between the two vesicle preparations. By using the BLM vesicles and a rapid filtration technique, we quantified 36Cl uptake under conditions of equilibrated pH (pHout = pHin = 7.5). The presence of 200 mM cis of either Na+ or K+, or an equimolar mixture of both, significantly increased the initial Cl- entry rate. In the presence of K+, valinomycin further increased Cl- uptake, but no Cl- uphill transport was ever observed under any of the conditions. All the increases were abolished by voltage clamping, indicating that the alkali-metal ions act by creating an inside-positive membrane potential capable of stimulating a Cl(-)-conductance pathway. In the absence of K+, BLM vesicle preloading to obtain a [Cl-]out/[Cl-]in = 16/200 mM gradient (delta Cl-) resulted in a 500% increase in the initial 36Cl- entry rate, accompanied by a transient Cl- accumulation, with an overshoot at approximately 5 min. In the presence of both a positive-inside electrical gradient (delta psi) and a delta Cl-, the initial Cl- uptake rate was increased by 800%, indicating that the effects of delta psi and of delta Cl- are additive. The delta Cl- effect was blocked, but only partially, by short-circuiting the membrane potential with equilibrated K+ and valinomycin, thus indicating that it has both rheogenic and electroneutral components. We conclude that Cl- influx across the guinea pig intestinal BLM involves a Cl(-)-conductance pathway plus a distinct Cl(-)-Cl(-)-exchange system, exhibiting both electroneutral and rheogenic components. Alternatively, the possibility can also be entertained that the conductance and the exchange pathways share a common molecular basis, e.g., a nonobligatory Cl(-)-Cl- exchanger or rheogenic uniport.

Electrical impedance compared with other non-invasive bioengineering techniques and visual scoring for detection of irritation in human skin.

A new, non-invasive device, which enables local measurements of electrical impedance to a controlled depth, has been used to evaluate the degree of irritation in human skin. The results have been compared with those obtained using other non-invasive techniques, i.e. with transepidermal water loss (TEWL), electrical capacitance moist measurement (ECM), laser-Doppler flowmetry (LDF), and visual scoring. Sodium lauryl sulphate solutions (0.1-5.0%), and a blank, were applied in Finn Chambers for 24 h on the volar forearm of 10 healthy volunteers. Values were recorded before application of the test chambers, and at 1 h, 24 h, 1 week and 2 weeks after removal. Thus, both the degree of initial damage and the healing process were monitored. There was close agreement among values obtained using electrical impedance, TEWL and visual readings. Results obtained using ECM and LDF were not consistent with the other three methods. In evaluating irritation of the skin, the practical situation may influence the choice of bioengineering tools. In most circumstances, a combination of methods would be preferable.

The anion transport inhibitor DIDS increases rat hepatocyte K+ conductance via uptake through the bilirubin pathway.

1. In confluent primary cultures of rat hepatocytes, membrane effects of the anion transport inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) were recorded with conventional microelectrodes. In addition, cell pH and cell Ca2+ were monitored by use of the fluorescent dyes BCECF and fluo-3, respectively. Uptake of DIDS was determined by measuring intracellular DIDS fluorescence between 470 and 520 nm (excitation wavelength 390 nm). 2. In the presence of 0.2 mM DIDS, membrane voltages hyperpolarized from -44.0 +/- 1.8 to -73.1 +/- 1.9 mV (n = 16). This change was monophasic and occurred with a time constant of 170 +/- 25 s. The effect was only partly reversible. 3. Cable analysis revealed a concomitant decrease in the specific cell membrane resistance from 3.2 to 1.5 k omega cm2. 4. In ion substitution experiments, a 10-fold elevation of external K+ (from 2.5 to 25 mM) depolarized cell membranes by 6.2 +/- 1.5 mV (n = 5). In the presence of 0.2 mM DIDS, this membrane response was increased 5-fold to 32.2 +/- 4.1 mV. 5. Replacement of Cl- by 99% with gluconate depolarized the cells by 9.3 +/- 1.9 mV. In contrast, with 0.2 mM DIDS present, Cl- removal led to a membrane hyperpolarization of 5.9 +/- 0.9 mV (n = 4). 6. DIDS had no effect on cytosolic pH or Ca2+. 7. To determine the sidedness of the DIDS effect, i.e. to analyse if the increase in K+ conductance is mediated by uptake of the compound, DIDS was added in the presence of different substrates of hepatocellular anion transport. Taurocholate (50 microM) and frusemide (0.5 mM), which are both taken up via the sinusoidal multi-specific bile acid transporter, did not change DIDS-induced membrane hyperpolarization. 8. In contrast, 0.5 mM bromosulphthalein (BSP), a substrate of the bilirubin transporter, competitively inhibited the membrane hyperpolarization elicited by various concentrations of DIDS (0.1-1.0 mM). 9. Hepatocellular uptake of BSP is known to be, in part, Cl- dependent and to be competitively inhibited by Indocyanine Green. When 0.2 mM DIDS was added to a superfusate, in which 99% of Cl- had been exchanged by gluconate, the velocity of membrane hyperpolarization was decreased by 45%. In the presence of Indocyanine Green (0.1 mM) DIDS-induced membrane hyperpolarization was reduced to approximately 20%. 10. Addition of 0.2 mM DIDS to hepatocyte monolayers led to a time-dependent increase in cell fluorescence which was absent at 4 degrees C and which was completely blocked by 0.5 mM BSP.(ABSTRACT TRUNCATED AT 400 WORDS)

Temperature dependence of embryonic cardiac gap junction conductance and channel kinetics.

We have investigated the effects of temperature on the conductance and voltage-dependent kinetics of cardiac gap junction channels between pairs of seven-day embryonic chick ventricle myocytes over the range of 14-26 degrees C. Records of junctional conductance (Gj) and steady-state unit junctional channel activity were made using the whole-cell double patch-clamp technique while the bath temperature was steadily changed at a rate of about 4 degrees C/min. The decrease in Gj upon cooling was biphasic with a distinct break at 21 degrees C. In 12 cell pairs, Q10 was 2.2 from 26 to 21 degrees C, while between 21 and 14 degrees C it was 6.5. The mean Gj at 22 degrees C (Gj22) was 3.0 +/- 2.1 nS, ranging in different preparations from 0.24 to 6.4 nS. At room temperature, embryonic cardiac gap junctions contain channels with conductance states near 240, 200, 160, 120, 80 and 40 pS. In the present study, we demonstrate that cooling decreases the frequency of channel openings at all conductance levels, and at temperatures below 20 degrees C shifts the prevalence of openings from higher to lower conductance states: all 240 pS openings disappear below 20 degrees C; 200 pS openings are suppressed at 17 degrees C; below 16 degrees C 160 and 120 pS events disappear and only 80 and 40 pS states are seen. Temperature also affected the voltage-dependent kinetics of the channels. Application of a 6 sec, 80 mV voltage step across the junction (Vj80) caused a biexponential decay in junctional conductance. Decay was faster at lower temperatures, whereas the rate of recovery of Gj after returning to Vj0 was slowed. Cooling reduced the fast decay time constant, increased both recovery time constants, and decreased the magnitude of Gj decay, thus leaving a 10-16% larger residual conductance (Gss/Ginit, +/- 80 mV Vj) at 18 than at 22 degrees C. From these results we propose that embryonic chick cardiac gap junctions contain at least two classes of channels with different conductances and temperature sensitivities.

Effects of epidermal growth factor versus phorbol ester on kidney epithelial (LLC-PK1) tight junction permeability and cell division.

In polarized epithelia, the tight junctions (TJs) constitute a barrier that controls the paracellular flux of solutes and water. In the renal LLC-PK1 cells, the TJ permeability can be correlated directly with the unidirectional transepithelial flux of solutes, such as D-mannitol, which have negligible affinity for cell membrane transport systems, and inversely to the transepithelial electrical resistance (TER). This study investigates TJ permeability and cell proliferation in LLC-PK1 cells treated with the phorbol ester, tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA) or with epidermal growth factor (EGF), a mitogen without secondary carcinogenic effects. Both TPA and EGF induced mitogenesis in LLC-PK1 cells. The TJs in TPA-treated cells were leaky, as indicated by decreased TER, increased D-mannitol flux, and TJ penetration by ruthenium red. In contrast, EGF treatment did not result in a decrease in TER, only slightly increased the D-mannitol flux, and did not result in ruthenium red penetration of the TJs. This inability of ruthenium red to penetrate TJs between EGF-treated epithelial cells was true even for cells in mitosis. The data therefore indicate that mitogenesis per se does not increase TJ permeability, suggesting that the TJ leakiness observed during tumor promotion with phorbol esters does not arise from cell proliferation and is perhaps associated distinctly with or causal to the transformation of those cells.