Fiber-optic measurement of intracellular pH in intact rat liver using pH-sensitive dyes

The pH-sensitive fluorescent dye 1,3-dihydroxy-pyrene-6,8-disulfonic acid (DHPDS) was used to measure intracellular pH (pHi) from the surface fluorescence of the isolated perfused rat liver. Monochromatic light from a fluorometer was focused on the liver with a fiber optic, emitted light was collected with a second fiber bundle and returned to the spectrometer. To correct for changes in intracellular dye concentration, the excitation wavelength was changed between the pH-sensitive excitation peak wavelength and the isosbestic wavelength, then a ratio was computed between fluorescence intensities at these two wavelengths. Intracellular calibration of the dye was performed by clamping the intracellular to the extracellular pH with H+/K(+)-ionophore Nigericin. This method was used to monitor transient changes in intracellular pH caused either by addition and removal of NH4Cl or by changing perfusate CO2 and HCO3- concentrations while keeping their ratio constant. The effects of these maneuvers on bileflow were studied, too. Data obtained in the perfused liver were in good agreement with those obtained in isolated liver cells except that the steady-state pHi (7.46 +/- 0.02) was slightly higher than reported values. Measurements in livers of mutant TR- rats that are defective of dye secretion revealed similar pHi values, indicating that secretion of the dye into bile canaliculi did not affect measurements. The technique appears adequate to measure pHi in the liver and will allow to study pH regulatory mechanisms in the intact organ.

Cl(-)-HCO3- exchanger in isolated rat hepatocytes: role in regulation of intracellular pH

In rat hepatocytes, basolateral Na(+)-H+ exchange and Na(+)-HCO3- cotransport function as acid extruders. To assess mechanisms of acid loading, intracellular pH (pHi) recovery from an alkaline load was analyzed in short-term cultured rat hepatocyte monolayers using the pH-sensitive dye BCECF. Electrophysiological techniques were also used to assess the role of the membrane potential (Vm). Cells were alkaline loaded by suddenly reducing external CO2 and HCO3- (from 10% and 50 mM, respectively, to 5% and 25 mM) at constant pHo. After this maneuver, pHi rapidly rose by 0.13 +/- 0.03 pH units (pHu) and recovered to baseline at an initial rate of 0.026 +/- 0.009 pHu/min. Intracellular buffering power was estimated from the dependence of pHi on [NH4+]o and varied between 70 and 10.5 mM/pHu in a pHi range of 6.5-7.6. Initial pHi recovery corresponded to a rate of OH- efflux (JOH) of 1.76 +/- 0.71 mM/min and was blocked by 0.5 mM DIDS (0.003 +/- 0.002; JOH = 0.18 +/- 0.06) or by 1 mM H2DIDS (0.001 +/- 0.002; JOH = 0.26 +/- 0.08) and by removal of [Cl-]o (0.003 +/- 0.007; JOH = 0.28 +/- 0.07). The dependence of JOH on [Cl-]o exhibited saturation kinetics with an apparent Km for [Cl-]o of 5.1 mM. pHi recovery was Na+ independent and was not inhibited by substitution of Na+ with NMDG (0.045 +/- 0.09; JOH = 2.94 +/- 0.59). During an alkaline load, cell Vm hyperpolarized from -33.4 +/- 1.8 to -43.4 +/- 2.8 mV, mainly due to an increase in K+ conductance by a factor of 2.8 +/- 0.3.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of chloride ions in liver cell volume regulation

Hypotonic swelling of liver cells is followed by regulatory volume decrease (RVD), which has been shown to involve facilitated release of K+. In this study, the role of C1- in RVD was examined by videoplanimetric analysis of cell volume and measurement of membrane potential (Vm) and resistance (Rm) in single isolated rat hepatocytes, and by measurement of 36Cl efflux in the isolated perfused liver preloaded with the isotope. Liver cells subjected to hypotonic stress by removal of 50 mM external NaCl (70% of control osmolality) swelled from an initial volume of 6.68 +/- 0.77 to 8.27 +/- 0.88 pl (24.3 +/- 3.4% increase) within 1 min and exhibited RVD at an initial rate of 0.26 +/- 0.01 pl/min. A step decrease in external Cl- accelerated the initial rate of RVD to 0.53 +/- 0.08 pl/min. RVD was abolished in cells that had been depleted of Cl-. Vm and Rm displayed biphasic responses to hypotonic stress. An initial (less than 15 s) hyperpolarization of Vm from -35.4 +/- 2.2 to -38.8 +/- 2.6 mV was followed by a gradual depolarization reaching -30.2 +/- 2.0 mV by 1 min. In parallel, Rm initially (less than 15 s) increased from 101 +/- 13 to 121 +/- 17 M omega (19 +/- 3% increase) and then declined to 55 +/- 4 M omega (59 +/- 4% of initial Rm) within 1 min. These changes were reversible upon return to isotonicity.(ABSTRACT TRUNCATED AT 250 WORDS)

[Rare occurrence of villonodular synovitis of both shoulder joints]

Presentation of the radiological, histological, and clinical findings in one patient with bilateral villonodular synovitis of the shoulder is made. This synovitis is a nonmalignant disease entity of controversial origin and nature.

[Joint chondromatosis. Results in 40 surgically and conservatively treated patients]

The clinical findings seen in chondromatosis (Henderson-Jones syndrome) and the treatment of this rare disease are presented. The etiology is also discussed. The authors suggest a therapy, drawing on their own experience in 40 patients with an average follow-up of 12.6 years and on numerous articles from the literature. They recommend total synovectomy with removal of loose bodies at an early stage to prevent mechanical destruction of articular cartilage.

[Hyperphalangia in Pierre-Robin syndrome]

Pierre Robins syndrome associated with symmetric hyperphalangia of the index fingers is called Catel-Manzke syndrome. Connate radial deviation of the index fingers is caused by an odd bone. The deformity is demonstrated by two personal cases. The deviation is progressive and because of increasing functional limitation the operative correction of the index fingers at the age of 2-3 years is advised. Surgical technique and success of treatment are presented.

[Definition of patellar chondropathy and patellar chondromalacia]

In the course of a review of the literature the definition, etiology, diagnosis and treatment of the disease entities chondropathy and patellar chondromalacia are compared. Without exception, the descriptions found are inconsistent and inaccurate. A new classification--chondromalacia, patellar and peripatellar syndrome--is proposed. Possible causes of these diseases in the subchrondral vascular system are mentioned explicitly ("patellar migraine", "patellar claudication").

[Microcirculation of the Achilles tendon and significance of the paratenon. A study with the plastination method]

Rupture of a healthy Achilles tendon is disputed. A previous degenerative process with ischemia after recurrent microtraumas is usually held to be responsible. The vascular anatomy of eight human specimens was defined with a new method after perfusion through the femoral artery. This method allows exact analysis of the vessels even at a microscopic level. In contrast with the literature, the authors found a large number of anastomoses between the extra- and the intratendinous vessel system. The well-vascularized paratenon is therefore very important for the nutrition of the Achilles tendon. This fact must be taken into account during the surgical treatment of a rupture. The authors agree with the studies of the anatomist Lang who found a decrease of the intratendinous vascularization in an area 3 to 5 cm above the insertion in the os calcis. However a relationship between the frequency of rupture in this area and the vascular anatomy has not yet been shown.

[Long-term results following subcutaneous Achilles tendon rupture]

From 1972 to 1982, 132 ruptures of the achilles tendon were treated at the Orthopedics Division, University of Heidelberg. Surgical treatment was carried out in 125 cases, and seven patients were treated conservatively. The average age of the patients was 42 years. 84% of the achilles tendon ruptures occurred during sport. After an average investigation period of 6.5 years, 33 patients could be followed up. The rate of complications and the final functional results are communicated. The blood supply to the achilles tendon is described separately. Twelve cadaver achilles tendons were investigated by means of the plastination method. It could be demonstrated that a reduced blood supply to the Achilles tendon is present about 3-5 cm above the calcaneal tuber. This finding corresponds to the most frequent site of rupture. It is unclear to what extent there is a connection between the blood supply and the rupture site of typical locations.

Separation of hepatocytes of different acinar zones by flow cytometry

Hepatocytes in the proximal (zone 1) and distal (zone 3) regions of the liver acinus are selectively stained by perfusion of the isolated rat liver with 0.2-20 microM acridine orange (AO). After 10-60 min of anterograde perfusion, AO fluorescence is visible in zone 1 cells, whereas retrograde perfusion stains cells of zone 3. In this paper, we describe a technique to isolate a mixed population of fluorescent and nonfluorescent hepatocytes (cells from all acinar zones, which do not loose the zone specific AO labeling) and to separate these cells according to their zonal origin by fluorescence activated cell sorting. The zonal populations obtained were either fluorescent or nonfluorescent (purity greater than 95%). Separated cell fractions differed in their enzyme content (5' nucleotidase, succinate-dehydrogenase, beta-glucuronidase). An unidentified AO metabolite, which is not found in bile after retrograde perfusion (not formed in zone 3 cells), is also absent after retrograde perfusion in sorted fluorescent cells (zone 3 cells), indicating zonal purity of sorted cells.

Hepatobiliary transport of the anionic organomercury compound (mersalyl) is carrier mediated

The hepatobiliary excretion of the anionic organic mercury compound (mersalyl) was studied in the isolated perfused rat liver and in isolated rat liver plasma membrane vesicles. In the isolated perfused liver, mersalyl is immediately taken up from the perfusion medium and concentratively excreted into bile. Uptake is characterized by saturation kinetics (S)0.5 = 20 microM, Vmax = 117 nmoles/min/g liver, cooperatively of mersalyl binding sites, stimulation by extracellular sodium and temperature dependence. Uptake of mersalyl into basolateral membrane vesicles also exhibits characteristics of a carrier mediated transport: saturation kinetics (S)0.5 = 28 microM, Vmax = 1.6 nmoles/min/mg protein, dependence on extravesicular sodium, cooperativity of mersalyl binding sites, temperature dependence and transstimulation by intravesicular non-radioactive mersalyl. Uptake was inhibited by alpha-naphthylacetic acid and mercapto group reagents, indicating involvement of mercapto groups on the carrier and a binding site for carboxylic anions. Data from the isolated perfused liver and from isolated basolateral vesicles indicate that mersalyl uptake into the liver is carrier mediated. Uptake mechanism and driving forces appear analogous to those for the uptake of chemically related compounds such as taurocholic acid. Therefore it is speculated that mersalyl may be transported by carrier molecules which apparently accept numerous chemically unrelated compounds.

Volume-regulatory K+ fluxes in the isolated perfused rat liver: characterization by ion transport inhibitors

Net hepatic release and uptake of K+ were examined in isolated perfused rat livers subjected to a 10-min period of hypotonic stress. Effluent Na+, K+, and Ca2+ activities were monitored throughout. Initiation and termination of hypotonic stress triggered sharp transient (less than 1 min) changes in effluent ion activities that indicated net water movement into and out of the liver, respectively. In addition, hypotonic stress caused a large transient net release of hepatic K+, whereas return to isotonicity triggered a transient net hepatic K+ uptake. The hypotonically induced K+ release was inhibited by 2 mM barium (95%) and by 1 mM quinine (60%). Net K+ influx, on the other hand, was inhibited by 1 mM ouabain (100%) and by 1 mM amiloride (50%). Osmotically induced K+ fluxes were not significantly affected by bicarbonate removal and were only partially inhibited by 0.1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) or bumetanide. The results suggest that K+ conductance increases during hypotonic stress, whereas return to isotonicity induces a ouabain-sensitive K+ uptake partly because of increased Na+-H+ exchange. These mechanisms probably participate in regulatory volume decrease and regulatory volume increase, respectively.

Identification of a second active site in laminin for promotion of cell adhesion and migration and inhibition of in vivo melanoma lung colonization

Previously we reported that a pentapeptide (Tyr-Ile-Gly-Ser-Arg or YIGSR) from domain III of the B1 chain of laminin is a cell attachment site with the ability to stimulate cell adhesion and migration and to block experimental metastases. Here we report studies on the activities of synthetic peptides that cover domain III and report a second biologically active peptide PDSGR from this domain with activities similar to YIGSR. We also show that cyclic YIGSR is more potent in these assays than the linear peptide as expected since this sequence on laminin is bracketed by cysteines. Due to their proximity and similar spectrum of activities, it is possible that these sequences act in concert in the native laminin molecule.

Interaction of different strains of Entamoeba histolytica with target cells: characterization of electrophysiological and morphological features

Two strains of Entamoeba histolytica with pathogenic zymodemes (SFL3, HK9), one strain with non-pathogenic zymodeme ("Bru") and one non-pathogenic Entamoeba sp. strain ("cold strain"), were investigated with respect to their interaction with target cells. Three test systems were used: 1) direct microscopical observation and qualitative as well as quantitative evaluation of contact and binding events with MDCK cells as targets, 2) kinetics of cytotoxic activity as measured by means of chromium release from 51Cr-labelled K562 cells, and 3) electrophysiological observations with freshly prepared mouse liver cells. We observed that the non-pathogenic cold strain interacted only shortly with target cells (statistical events, interaction type "I"), but did not induce morphological changes, chromium release or depolarization of targets. Non-pathogenic and avirulent strain "Bru" showed, apart from type "I"-binding, the ability to establish tight (type "II") and long-lasting contact (type "III") with targets, but again without cytotoxic effects. The pathogenic but avirulent strain HK9 tightly interacted (type "II") and sometimes long-lasting with target cells, but morphological changes and chromium release were of a moderate degree during the first 20 min, and depolarization was only a rare event. In contrast, strain SFL3 produced tight and long-lasting contacts (type "III" binding), leading to cell death in 83% (type "IV" interaction) within 20 min, substantial chromium release within 10 min and rapid depolarization ("electric collapse") of target cells.

Inward-rectifying potassium channels in rat hepatocytes

The patch-clamp technique has been used to investigate single-channel and whole cell conductances in freshly isolated rat hepatocytes. Whole cell experiments, with high (144 mM) intracellular and extracellular potassium as the principal conductive species, show some variation between cells in the current-voltage relationship (mean whole-cell conductance at physiological potentials being 2.7 nS). This may suggest functional heterogeneity of cells. The most common finding is that the current-voltage relationship shows inward rectification. This is reflected in cell-attached single-channel recordings in which channels displaying strong inward rectification and K+ selectivity are seen. The channels show a mean inward conductance (with 144 mM potassium in the pipette) of 44 pS and an outward conductance of 23 pS. The open probability is not voltage dependent, and the channels do not exhibit calcium dependence. The channels are quite different from others described in hepatocytes, but they show marked similarities to channels recently described in renal epithelial cells. Current-voltage relationships in the whole cell mode exhibit an increase in slope conductance at large hyperpolarizing and depolarizing potentials.

Voltage-driven, taurocholate-dependent secretion in isolated hepatocyte couplets

Bile formation by the liver is largely dependent on the transport of bile acids by hepatocytes. This process is thought to result from Na-coupled uptake of bile acids into the cell and voltage-dependent, carrier-mediated transport from cell to canaliculus. However, the dependence of bile secretion on membrane potential has not yet been observed. In this study, the effect of changes in membrane potential differences on bile secretion was tested by impaling rat hepatocyte couplets with microelectrodes, changing membrane potential by intracellular current injection, and measuring fluid secretion by optically determining canalicular size. In the presence of 50 microM taurocholate, membrane potential was -33.3 +/- 5.8 mV and canalicular area increased by 6 +/- 6%/min, corresponding to a fluid secretion rate of 2-4 fl/min. In contrast, when intracellular voltage was suddenly changed to -109.9 +/- 15.0 mV, the canalicular area increased by 20 +/- 4%/min, corresponding to a secretion rate of 19 fl/min. When these experiments were repeated in the absence of taurocholate, the negative clamp had no effect on canalicular size. Taurocholate itself did not alter membrane potential. These findings support the hypothesis that canalicular bile secretion depends on a process equivalent to electrodiffusion. We therefore conclude that membrane voltage is a driving force for taurocholate-dependent fluid secretion by the liver.

Membrane potential measurements in isolated rat liver plasma membrane vesicles: effect of transmembrane ion concentration gradients

In isolated basolateral and canalicular rat liver plasma membrane vesicles the membrane potential (measured with DiS-C2 (5] varied with transmembrane concentration gradients of Na+, K+ and Cl- revealing the following ion permeabilities: basolateral vesicles: PNa/PK: 0.76, PCl/PK: 0.45 and canalicular vesicles: PNa/PK: 0.69, PCl/PK: 0.56. The data indicate a permselectivity of PK greater than PNa greater than PCl for both membranes.

Effect of hypertonic stress on liver cell volume, bile flow, and volume-regulatory K+ fluxes

Net hepatic uptake and release of K+ were studied in the isolated-perfused rat liver subjected to a 10-min period of hyperosmotic stress by addition of 80 mM mannitol or sucrose to the perfusing solution. Bile flow and effluent Na+, K+, and Ca2+ activities were monitored throughout. Upon initiation of hypertonic stress, a sharp transient dilution of effluent ion activities indicated hepatic water losses that were larger and occurred more rapidly with sucrose than with mannitol. During continuous hyperosmotic perfusion, portocaval differences in K+ uncovered a steady net influx of the ion into the liver that reached a higher maximum and led to a greater accumulation in experiments with sucrose compared with mannitol. This hepatic K+ uptake was completely blocked by 1 mM ouabain. Upon return to isotonic conditions, a sharp transient concentration of effluent ion activities suggested hepatic water uptake that was again more rapid and pronounced in sucrose- than mannitol-treated livers. This was followed by a transient phase of net hepatic K+ release whose magnitude and duration were proportional to the water movements induced by the removal of each carbohydrate. Administration of 2 mM Ba2+ abolished this K+ efflux. These results indicate that mannitol equilibrates between extra- and intracellular compartments, whereas sucrose apparently does not. The data also suggest that net movements of K+ may be involved in the regulatory volume responses induced by hyperosmotic stress and return to normal tonicity, respectively.

Differential regulation of growth and invasiveness of MCF-7 breast cancer cells by antiestrogens

Estrogen increases the ability of the estrogen-dependent MCF-7 human breast cancer cell line to both proliferate and invade through an artificial basement membrane. In studying the response of MCF-7 cells to various antiestrogens, we found that 4-hydroxytamoxifen and tamoxifen inhibited cell proliferation but increased their invasiveness. In contrast, the structurally unrelated benzothiophene antiestrogens, LY117018 and LY156758, were potent antiproliferative agents which did not stimulate invasiveness. The differential effects of these antiestrogenic agents on invasion correlated with changes in production of collagenase IV, while no significant change was seen in the chemotactic activity of the cells. Invasiveness was increased by 17 beta-estradiol or 4-hydroxytamoxifen after a few hours of treatment and was rapidly lost when 17 beta-estradiol was withdrawn. Stimulation of invasiveness with 17 beta-estradiol was blocked by the antiestrogen, LY117018. Cells from the MDA-MB-231 line which lacks estrogen receptors were not affected by estrogen or antiestrogen in terms of proliferation or invasion. These studies indicate that the invasiveness of MCF-7 cells is regulated by antiestrogens through the estrogen receptor and may be mediated by collagenase IV activity. Antiestrogens which reduce both the proliferation and invasiveness of these cells may be interesting new candidates for clinical application.

Mechanisms of bile secretion: insights from the isolated rat hepatocyte couplet

This article reviews recent studies that have characterized the isolated rat hepatocyte couplet as a primary unit of canalicular bile formation. This cell culture system is proving to be particularly useful for identifying primary canalicular choleretics and for elucidating mechanisms of canalicular bile formation by electrophysiologic, fluorescent, and quantitative microscopic techniques.

[The femoro-patellar joint and cartilage damage of the knee joint]

This article surveys the update knowledge of diagnosis and treatment of damage to the cartilage with particular reference to the femoropatellar joint. Complementary to this the biomechanical fundamentals and special anatomic features are explained, the knowledge of which is imperative for an understanding of the complex linkups and interconnections.

Cell volume regulation in liver

The maintenance of liver cell volume in isotonic extracellular fluid requires the continuous supply of energy: sodium is extruded in exchange for potassium by the sodium/potassium ATPase, conductive potassium efflux creates a cell-negative membrane potential, which expelles chloride through conductive pathways. Thus, the various organic substances accumulated within the cell are osmotically counterbalanced in large part by the large difference of chloride concentration across the cell membrane. Impairment of energy supply leads to dissipation of ion gradients, depolarization and cell swelling. However, even in the presence of ouabain the liver cell can extrude ions by furosemide-sensitive transport in intracellular vesicles and subsequent exocytosis. In isotonic extracellular fluid cell swelling may follow an increase in extracellular potassium concentration, which impairs potassium efflux and depolarizes the cell membrane leading to chloride accumulation. Replacement of extracellular chloride with impermeable anions leads to cell shrinkage. During excessive sodium-coupled entry of amino acids and subsequent stimulation of sodium/potassium-ATPase by increase in intracellular sodium activity, an increase in cell volume is blunted by activation of potassium channels, which maintain cell membrane potential and allow for loss of cellular potassium. Cell swelling induced by exposure of liver cells to hypotonic extracellular fluid is followed by regulatory volume decrease (RVD), cell shrinkage induced by reexposure to isotonic perfusate is followed by regulatory volume increase (RVI). Available evidence suggests that RVD is accomplished by activation of potassium channels, hyperpolarization and subsequent extrusion of chloride along with potassium, and that RVI depends on the activation of sodium hydrogen ion exchange with subsequent activation of sodium/potassium-ATPase leading to the respective accumulation of potassium and bicarbonate. In addition, exposure of liver to anisotonic perfusates alters glycogen degradation, glycolysis and probably urea formation, which are enhanced by exposure to hypertonic perfusates and depressed by hypotonic perfusates.

Synthetic pentapeptide from the B1 chain of laminin promotes B16F10 melanoma cell migration

Laminin is a basement membrane-specific glycoprotein that promotes cell adhesion, proliferation, differentiation, and tumor cell migration. Synthetic peptides from the amino acid sequence deduced from a cDNA clone of the B1 chain of laminin were tested for their ability to promote the migration of B16F10 melanoma cells. A peptide, CDPGYIGSR, that is able to mediate epithelial cell attachment to laminin was found to promote migration, and the constituent pentapeptide YIGSR was also active but to a lesser degree. This nine-amino acid peptide blocked migration of melanoma cells to laminin but had no effect on migration to fibronectin. These data suggest that the cell-binding site and migration site on laminin share a common sequence that is unique to laminin.

Role of basement membranes in cell differentiation

Extracellular matrices have diverse biological effects, including promoting the growth and differentiation of various cells of epithelial origin. The components of one of these matrices, the basement membrane, are discussed, as well as studies using these components alone or in combination with cells in culture. The particular response observed varies with the cell type examined and appears to be dependent on multiple interactions with components of the matrix. Potential uses for a basement membrane-derived matrix in vitro and in vivo are being developed.

YIGSR, a synthetic laminin pentapeptide, inhibits experimental metastasis formation

The invasion of tumor cells through basement membranes is a critical step in the formation of metastases. The binding of the malignant cells to laminin in the basement membranes allows their attachment and activates their invasiveness. Recently a synthetic nonapeptide from the B1 chain sequence of laminin was identified as a major site for cell binding. A pentapeptide within the nonapeptide sequence was found to reduce the formation of lung colonies in mice injected with melanoma cells and also to inhibit the invasiveness of the cells in vitro.

A pentapeptide from the laminin B1 chain mediates cell adhesion and binds the 67,000 laminin receptor

Laminin promotes epithelial cell adhesion in part through a site of nine amino acids CDPGYIGSR on the B1 chain. Using smaller synthetic peptides from this sequence as well as various peptides with amino acid substitutions, we find that the minimum sequence necessary for efficient cell adhesion as well as receptor binding is YIGSR. The deletion of tyrosine or the substitution of arginine in the peptides resulted in a significant loss of activity. The presence of an amide group on the terminal arginine of either peptide increases activity significantly. YIGSR is active in promoting the adhesion of a variety of epithelial cells; however, it is inactive with chondrocytes, fibroblasts, and osteoblasts.

Cell membrane and transepithelial voltages and resistances in isolated rat hepatocyte couplets

The basic electrical properties of an isolated rat hepatocyte couplet (IRHC) system have been analyzed using classical techniques of epithelial electrophysiology, including measurement of electric potentials, resistances and intracellular ion activities. Applications of these techniques are discussed with respect to their limitations in small isolated cells. Mean intracellular and intracanalicular membrane potentials ranged from -23.7 to -46.7 and -4.3 to -5.9 mV, respectively. Membrane resistances were determined using an equivalent circuit analysis modified according to the geometry of the IRHC system. Resistances of the sinusoidal (basolateral) and canalicular (luminal) cell membranes and tight junctions averaged 0.15 and 0.78 G omega and 25 m omega, respectively. The cells are electrically coupled via low resistance intercellular communications (approximately 58 M omega). Intracellular ion activities for Na+, K+ and Cl- averaged 12.2, 88.1 and 17.7 mmol/liter, respectively. The basolateral membrane potential reveals a permeability sequence of PK greater than PCl greater than PNa. The luminal potential showed minimal dependence on changes in transjunctional ion gradients, indicating a poor ion selectivity of the paracellular pathway. The electrogenic (Na+-K+)-ATPase contributes little to the luminal and cellular negative electric potential. Therefore, the luminal potential probably results from the secretion of impermeant ions and a Donnan distribution of permeant ions, a mechanism which provides the osmotic driving force for bile formation. By providing the unique opportunity to measure luminal potentials, this isolated hepatocyte system permits study of secretory mechanisms for the first time in a mammalian gland using electrophysiologic techniques.

Identification of an amino acid sequence in laminin mediating cell attachment, chemotaxis, and receptor binding

We have probed for active sites in the B1 chain of laminin using synthetic peptides comprising certain regions of its amino acid sequence as deduced from cDNA clones. An antibody to a 19-mer from domain III inhibited attachment of HT-1080 and CHO cells to laminin, while the peptide itself was inactive. A nearby peptide (CDPGYIGSR) from domain III with homology to epidermal growth factor was synthesized and found to be one of the principle sites in laminin mediating cell attachment, migration, and receptor binding.

Na-H exchange regulates intracellular pH in isolated rat hepatocyte couplets

Intracellular pH (pHi) was measured directly in isolated rat hepatocyte couplets using pH sensitive microelectrodes. The hepatocytes were maintained in a minimal salt buffer without added hormones or serum. Values of pHi (6.99 +/- 0.12, mean +/- SE) were close to their Nernst equilibria. After intracellular acidification with ammonium chloride, pH regulation was inhibited with 1 mM amiloride or by omission of external sodium, consistent with a Na-H exchange mechanism. Mean intracellular buffering power, in the nominal absence of carbon dioxide, was 34.1 +/- 11.4 mM. In the presence of external bicarbonate, amiloride or omission of sodium slowed, but did not completely inhibit recovery from acidification, indicating that additional pHi regulation mechanisms may operate in this preparation. These studies provide a direct measurement of pHi in hepatocyte couplets and indicate that Na-H exchange, together with a bicarbonate dependent system are important mechanisms for pHi regulation in this preparation.

17 beta-estradiol regulates and v-Ha-ras transfection constitutively enhances MCF7 breast cancer cell interactions with basement membrane

The interaction of a line of human breast carcinoma cells (MCF7) with basement membrane components, particularly laminin, was altered by exposure of the cells to estrogen as well as by transfection of the cells with the v-Ha-ras oncogene. In both cases, the cells show a greater ability to attach to a laminin substrate, to migrate to laminin, to grow in the presence of a basement membrane matrix, and to cross barriers of reconstituted basement membrane. These responses were associated with an increase in the expression of laminin receptors. It is postulated that the increase in the invasive behavior of the cells treated with estrogen or transfected with v-Ha-ras is related to the increased number of laminin receptors and their interaction with laminin. Estrogen had no discernible effect on the v-Ha-ras transfected cells. It appears that in the MCF7 cells, the malignant phenotype is under hormonal control and that this control is bypassed after v-Ha-ras transfection.

Electrical and molecular coupling between sodium and proton fluxes in basolateral membrane vesicles of rat liver

Mechanisms of Na+-H+ exchange in the hepatocyte were studied utilizing isolated basolateral membrane vesicles prepared by two different methods: Evidence was obtained for the existence of molecular coupling of Na+ and H+ fluxes (Na+/H+-antiport) which exhibits saturation kinetics (Km 7 mmol/l Na+) and is inhibited by amiloride (1.0 mmol/l). Although the two membrane preparations showed differences with respect to ionic permeabilities, our data suggest that a relatively high H+ conductance exists in the basolateral plasma membrane. Hence, electrical coupling of conductive H+ and Na+ fluxes in the opposite direction could contribute to net Na+-H+ exchange across the basolateral hepatocyte plasma membrane.

Effects of 1 alpha,25-dihydroxycholecalciferol on sodium-ion translocation across chick intestinal brush-border membrane

By utilizing isolated brush-border vesicles, Na+ transport across the luminal membrane of chick small intestine was found to be a composite of (i) a saturable (Km 10mM-Na+) amiloride-sensitive Na+/H+ antiport and (ii) a potential-sensitive conductive pathway. No evidence was obtained for the existence of a Na+/Cl- symport system. With the exception of the duodenum, luminal Na+ transfer in the entire small intestine was subject to regulation by vitamin D. Repletion of vitamin D-deficient chicks with 1 alpha,25-dihydroxycholecalciferol [1 alpha,25(OH)2D3] significantly decreased net Na+ uptake by isolated membrane vesicles (by approximately 30%). The sterol suppresses the conductive pathway (25-45% inhibition) as well as the Na+/H+ antiport system. Kinetic analysis of the latter revealed that 1 alpha,25(OH)2D3 altered Vmax (from 12.9 to 4.8 nmol of Na+/20s per mg of protein), but did not change Km. Diminution of Na+ transfer, entailing an increase in the electrochemical transmembrane Na+ gradient, provides an explanation of the simultaneously observed stimulatory action of 1 alpha,25(OH)2D3 on Na+-gradient-driven solute transport in chick small intestine. Indirect evidence was obtained that the luminal plasma membrane of chick small intestine displays a definite H+ permeability that is positively affected by 1 alpha,25(OH)2D3.

[The rare radial flexor muscle of the wrist with a special presentation]

The m. flexor carpi radialis brevis is a very rarely observed muscle with various origins and insertions. Our investigation showed a muscle with its insertion into the base of the second and third metacarpal bone. The important role of this muscle in operations on the wrist-joint is discussed.

Isolated rat hepatocyte couplets: a primary secretory unit for electrophysiologic studies of bile secretory function

Hepatocyte couplets were isolated by collagenase perfusion from rat liver. Between adjacent cells, the bile canaliculus forms a closed space into which secretion occurs. As in intact liver, Mg2+-ATPase is localized at the canalicular lumen, the organic anion fluorescein is excreted, and secretion is modified by osmotic gradients. By passing a microelectrode through one cell into the canalicular vacuole, a transepithelial potential profile was obtained. In 27 cell couplets the steady-state intracellular (-26.3 +/- 5.3 mV) and intracanalicular (-5.9 +/- 3.3 mV) potentials were recorded at 37 degrees C with reference to the external medium. Input resistances were determined within the cell (86 +/- 23 M omega) and in the bile canalicular lumen (32 +/- 17 M omega) by passing current pulses through the microelectrode. These data define electrical driving forces for ion transport across the sinusoidal, canalicular, and paracellular barriers and indicate ion permeation across a leaky paracellular junctional pathway. These findings indicate that the isolated hepatocyte couplet is an effective model for electrophysiologic studies of bile secretory function.

[Muscular changes caused by suction drainage. Scanning electron microscopy, transmission electron microscopy, light microscopy and morphometric studies of dorsal muscles of the rat (Rattus rattus) using drainage]

Changes in the dorsal muscles of 22 rats (Wistar), resulting from surgical drain, have been studied under different morphological aspects. The lumen of drains were obstructed after a short time. In the drains without using low pressure, erythrocytes and fibrin network were seen by scanning microscopical investigation. Patent muscle fibres could be analyzed in the lumen of drain using negative pressure. They prevent the functional drain system. By the effect of surgical drains the fibres of dorsal muscles had become swollen. This fact could be analyzed by morphometrical technique. Some changes in fibres have been demonstrated by histological methods.

Canalicular bile salt-independent bile formation: concepts and clues from electrolyte transport in rat liver

Studies on canalicular electrolyte transport are reviewed with reference to the concept that hepatocellular inorganic ion secretion may provide an osmotic drive for canalicular water flow. Cellular transport of electrolytes and of some nonelectrolytes appears directly or indirectly (cotransport or potential-sensitive transport) related to the activity of Na+-K+-ATPase of the sinusoidal cell membrane, but the role of the enzyme in regulating bile flow remains undetermined. Bile secretion of the isolated rat liver continues in the absence of either Na+, K+, Cl-, or HCO-3 when these ions are replaced in the perfusion medium by other permanent ions. Transepithelial salt concentration gradients, established experimentally, cause transient changes of bile flow and dissipate very quickly. Isotopic ion equilibration between sinusoids and bile proceeds faster than between sinusoids and liver cells. Both observations indicate extensive electrolyte diffusion through a paracellular shunt pathway. This pathway appears preferentially permeable to cations, and it restricts permeation of molecules of the size of sucrose (no apparent diffusion or effects of solvent drag) or bile acids (no backleak). In promoting canalicular osmotic water flow, transepithelial concentration gradients of NaCl are less effective than those of sucrose, revealing a reflection coefficient of NaCl of 0.3. By perfusion with hypertonic medium containing sucrose, bile flow is reduced. Bile production against this opposing osmotic gradient is accomplished by an increase in biliary organic anion concentration. Inorganic ion concentrations essentially conform to a Gibbs-Donnan distribution across the canalicular epithelium, established by the presence of impermeant anions in bile. Hence, the luminal electrical potential is expected to be negative with respect to the sinusoids. It is concluded that biliary secretion of endogenous organic anions is the major osmotic driving force for canalicular bile salt-independent bile flow and that transport of inorganic ions into bile results mainly from diffusion and solvent drag.

Ionic currents across pancreatic acinar cell membranes and their role in fluid secretion

Fluid and enzyme secretion from a number of mammalian exocrine glands is controlled by the action of neurotransmitters and hormones on acinar cell membranes. Sustained stimulation evoking sustained fluid and enzyme secretion also evokes sustained membrane depolarization and increase in conductance. Mouse and rat pancreatic fluid and enzyme secretion, as well as membrane depolarization and conductance increase evoked by sustained stimulation with acetylcholine or cholecystokinin-gastrin peptides, are acutely dependent on extracellular calcium. However, the initial stimulant-evoked conductance increase and secretion appear to be triggered by calcium released from inside the cells. Direct measurement of membrane current during sustained stimulation in voltage-clamp experiments with resolution of the total current into its Na, Cl and K components has allowed calculations of stimulant-evoked Na and Cl uptake into the acinar cells. The NaCl uptake is quantitatively sufficient to account for the stimulant-evoked fluid secretion. The role of the stimulant-evoked transmembrane ionic current appears to be the supply of salt for the fluid secretion. Calcium derived from intracellular sources in the initial phase of secretion, and from the extracellular fluid in the sustained phase, couples fluid and enzyme secretion to hormone-receptor interaction.