Cholestyramine loading test to assess hepatic reserve for bile acid synthesis in patients with chronic liver diseases

BACKGROUND & AIMS

Serum 7alpha-hydroxycholesterol level reflects hepatic bile acid synthesis in humans. The aim of this study was to examine the maximal bile acid synthesis in patients with chronic liver diseases.

METHODS

Cholestyramine (12 g/day) was administered for 3 days to patients with compensated liver cirrhosis (n = 7), patients with chronic hepatitis (n = 10), and control subjects (n = 9), and serum total 7alpha-hydroxycholesterol level was measured by gas-liquid chromatography-mass spectrometry.

RESULTS

A preliminary study showed that cholestyramine increased the serum value to the maximum by the third day. Before cholestyramine treatment, there were no significant differences in serum 7alpha-hydroxycholesterol levels among the groups. Three days of cholestyramine treatment increased the serum levels 5.71 +/- 2.90-fold in the controls, 3.25 +/- 0.85-fold in patients with chronic hepatitis, and 1.70 +/- 0.78-fold in cirrhotic patients. Cirrhotic patients had significantly lower serum 7alpha-hydroxycholesterol levels after the treatment compared with other groups. Serum 7alpha-hydroxycholesterol levels stimulated by cholestyramine significantly correlated with serum albumin levels and indocyanine green retention rate.

CONCLUSIONS

Three days of cholestyramine loading increased the bile acid synthesis to its maximal level. The cholestyramine test showed that patients with chronic hepatitis had enough hepatic reserve for bile acid synthesis; however, patients with compensated liver cirrhosis had significantly decreased capacity.

Differential expression of Rho family GTP-binding proteins and protein kinase C isozymes during C6 glial cell differentiation

The differential expression of Rho family of low molecular weight GTP-binding proteins and protein kinase C (PKC) isozymes were examined during differentiation of rat C6 glial cells to astrocytic phenotypes induced by dibutyryl cAMP (dbcAMP)/theophylline. The cells showed rapid and distinct morphological changes, resembling stellate astrocytes at 12 h after the treatment. The treated cells had a round cell body that extended several long processes each with a beaded appearance. In addition to morphological changes, Western blot analysis revealed that S-100 protein, known as a glial cell differentiation marker, increased and reached the maximal level (approximately 6-fold increase) at 24 h following the addition of dbcAMP. In the control experiments with cells cultured in the absence of serum but also without dbcAMP/theophylline, morphological changes were marginal and apparent increases of S-100 protein were not observed by Western blotting. In response to dbcAMP/theophylline treatment, RhoA showed increases in the mRNA level followed by the protein level, as inferred by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting, respectively. Rac1 and Cdc42 proteins were undetectable by Western blot analyses. In PKC isozymes, increases were observed in PKC beta 1, epsilon, and zeta by RT-PCR, and in beta 1 and epsilon by Western blotting. Among them, PKC epsilon showed the most distinct changes. Its mRNA level transiently increased from 3 to 6 h and then decreased even below the basal level at 18 h after the treatment. In contrast, Western blot analysis revealed that PKC epsilon gradually increased time-dependently to 24 h (approximately 6-fold increase), and remained elevated until 48 h. These results suggested that RhoA and PKC epsilon, and probably also PKC beta 1 and PKC zeta, were closely implicated in C6 cell differentiation.

Na+ and Ca2+ channel expression in cultured newt retinal pigment epithelial cells: comparison with neuronal types of ion channels

We cultured retinal pigment epithelial (RPE) cells dissociated from adult newt eye and analyzed their voltage-gated ion channels during culture using whole-cell patch-clamp techniques. The results were compared with those of retinal neurons under identical experimental conditions. After 6-9 days in culture (early stage), > 60% of RPE cells developed voltage-gated Na+ and Ca2+ channels that were not observed in freshly dissociated RPE cells. The number of cells expressing Na+ channels and Na+ current density were high after 12-15 days in culture (intermediate stage), while the number of Ca2+ channel-expressing cells and Ca2+ current density were high after 20-30 days in culture (late stage). The activation voltage of the Na+ current in the RPE cells was similar to that in neurons. The voltage dependence of Na+ current inactivation was somewhat different between two cell types. The steepness of the inactivation curve tended to be less in cultured RPE cells than in neurons, and the half-inactivation voltage was about-54 mV for the RPE cells and -45 mV for neurons. The Ca2+ current expressed in cultured RPE cells was too small to detect without replacement of external Ca2+ with Ba2+. The Ba2+ current, like Ca2+ current in neurons, was enhanced by Bay-K 8644 and blocked by nicardipine. These results suggest that the RPE cells, like neurons, expressed L-type Ca2+ channels in culture. The possibility that the development of both Na2+ and Ca2+ channels in cultured RPE cells is a manifestation of the transdifferentiation of RPE cells into neurons is discussed.

Inhibition of interleukin-2 receptor (CD25) expression induced on T cells from children with acute lymphoblastic leukemia

Peripheral blood lymphocytes obtained from children with acute lymphoblastic leukemia (ALL) at onset were studied for the expression of interleukin-2 (IL-2) receptor alpha-chain (CD25) by two-color flow-cytometric analysis. Stimulated with anti-CD3 monoclonal antibody (mAb) alone. CD25 expression was significantly suppressed in CD4+ T cells from 27 of 48 (56.3%) cases and in CD8+ T cells from 29 of 48 (60.4%) cases. When stimulated with anti-CD3 mAb plus phorbol 12-myristate 13-acetate (PMA), CD25 expression was clearly restored in certain cases of ALL. When PMA plus ionomycin were used for stimulation of T cells. CD25 was inducible in a majority of cases. Interestingly CD25 expression upon anti-CD3 mAb stimulation was recovered after complete remission had been achieved. These observations suggest the presence in ALL children at onset of an in vitro defect in the signal transduction pathway of the T-cell-receptor/CD3 complex, resulting in inefficient CD25 expression. However, immune-staining analysis indicated that protein kinase C was normally translocated from the cytosol fraction to the cell membrane fraction. The mobilization of cytoplasmic free calcium is also normal.

cAMP-mediated c-fos expression in pressure-overloaded acceleration of protein synthesis in adult rat heart

OBJECTIVES

The aim was to determine whether proto-oncogene c-fos expression and acceleration of protein synthesis by acute pressure overload to the heart were coupled with a cAMP- and protein-kinase-A-dependent system in adult rat heart.

METHODS

Isolated adult rat hearts were perfused as Langendorff preparations at a constant aortic pressure of 60 mmHg. In the pressure-overloaded group, aortic pressure was raised from 60 to 120 mmHg for the time indicated. Agents that increase cAMP were added to the perfusate at an aortic pressure of 60 mmHg. Furthermore, a selective protein kinase A inhibitor (H-89) or a selective protein kinase C inhibitor (calphostin C) was administered before the elevation of aortic pressure or the addition of the agents. cAMP content or rates of protein synthesis were measured by RIA or the incorporation of [14C]phenylalanine into total heart protein, respectively. c-fos mRNA expression was determined by Northern blot analysis.

RESULTS

Elevation of aortic pressure in beating hearts and arrested hearts increased cAMP content at 2 min of perfusion by 36 and 41%, induced c-fos mRNA expression at 30-60 min of perfusion by 4.8- and 2.0-fold, and accelerated rates of protein synthesis during the 2nd hour of perfusion by 39 and 41% over control levels, respectively. Glucagon, forskolin or IBMX mimicked increases in these parameters by elevated aortic pressure. H-89 prevented these changes by elevated pressure overload or exposure to forskolin or IBMX in arrested hearts. On the other hand, calphostin C prevented the pressure-induced increases in c-fos expression and protein synthesis rates in arrested hearts.

CONCLUSIONS

These results suggest that c-fos expression induced by acute pressure overload may be coupled with increased cAMP content and protein kinase A activity in addition to increased protein kinase C activity in adult rat heart.

A novel acute lymphoid leukaemia type BCR/ABL transcript in chronic myelogenous leukaemia

Using a reverse transcription-polymerase chain reaction (RT-PCR), we identified a patient with typical clinical features of chronic myelogenous leukaemia (CML) in the chronic phase who showed no amplification of the CML-type BCR/ABL transcript. RT-PCR with primers detecting the acute lymphoid leukaemia (ALL)-type transcript disclosed a novel fragment co-amplified with an ALL-type fragment. Sequencing revealed the novel transcript to be a chimaeric mRNA produced by fusion of a segment of BCR exon 2 (e2) to ABL exon 2 (a2), with a 21 base-pair insertion of ABL intron 1b sequence between them. This transcript has not been reported previously.

Expression of thromboxane synthase in kidney tissues from patients with IgA nephropathy

Thromboxane A2 (TXA2) is a potent vasoconstrictor which is known to be involved in the pathogenesis of experimental glomerulonephritis, although its exact pathogenic significance is not clear in human glomerulonephritis. We have investigated the expression of thromboxane synthase (TXS) in kidney tissues from patients with IgA nephropathy (IgAN), using RT-PCR and immunohistochemical methods. Biopsied renal tissues from thirty-four patients with IgAN (24 whole tissues and 10 isolated glomeruli) and normal renal tissues from 11 nephrectomized kidneys (control, eight whole tissues and three isolated glomeruli) were included in this study. TXS mRNA expression was observed in 10 out of 24 (42%) whole tissue specimens from IgAN, but no such message was disclosed in the control tissue. There was no detectable TXS mRNA expression in the isolated glomeruli either from IgAN patients or controls, although constant mRNA expressions for GAPDH and VPF/VEGF were observed. IgAN patients with positive TXS mRNA had significantly reduced GFR with elevated serum creatinine and serum beta 2-microglobulin levels. Immunostaining, using a monoclonal anti-TXS antibody, identified the localization of the TXS protein in the interstitial areas where monocyte/macrophage infiltration was abundant, as well as in the arterioles of the kidney tissues with advanced tissue damage. It was concluded that TXA2 produced by the interstitial infiltrating cells during the inflammatory process might be involved in the progression of IgA nephropathy.

Identification of a second transcriptional start site for the insecticidal protein gene cryIVA of Bacillus thuringiensis subsp. israelensis

Expression of cryIVA, one of the insecticidal protein genes of B. thuringiensis subsp. israelensis, is regulated at the transcriptional level. The cryIVA gene is specifically transcribed during the stationary phase of this bacterium. As shown in our previous report [Yoshisue et al. (1993a)], the transcription from the -364 position of the cryIVA gene is conducted by the major promoter P1 that is functional during middle stages of the stationary phase of B. thuringiensis. In the present study, we have identified a second transcriptional start point P2 for the cryIVA gene in addition to P1, the major transcriptional start point. The transcription from P2 of the cryIVA gene occurred later than that from P1, during later stages of stationary phase of B. thuringiensis subsp. israelensis. The -10 and -35 nt sequences upstream from P2 of cryIVA are similar to those of the omega 28-specific promoters of B. thuringiensis genes and of the omega K-specific promoters of B. subtilis genes. It is most likely that the region upstream from P2 of cryIVA contains the nt sequences that determine the omega 28-specific promoter, the second one, for the cryIVA gene.

Mapping and characterization of the interaction domains of human papillomavirus type 16 E1 and E2 proteins

The papillomavirus E1 and E2 proteins are both necessary and sufficient in vivo for efficient origin-dependent viral DNA replication. The ability of E1 and E2 to complex with each other appears to be essential for efficient viral DNA replication. In this study, we used the yeast two-hybrid system and in vitro binding assays to map the domains of the human papillomavirus type 16 (HPV16) E1 and E2 proteins required for complex formation. The amino-terminal 190-amino-acid domain of HPV16 E2 was both required and sufficient for E1 binding. The carboxyl-terminal 229 amino acids of E 1 were essential for binding E2, and the amino-terminal 143 amino acids of HPV16 E1 were dispensable. Although the ability of the E1 minimal domain (amino acids [aa] 421 to 649) to interact with E2 was strong at 4 degrees C, it was significantly reduced at temperatures above 25 degrees C. A larger domain of E1 from aa 144 to 649 bound E2 efficiently at any temperature, suggesting that aa 144 to 420 of E1 may play a role in the HPV16 E1-E2 interaction at physiological temperatures.

Interactive communication in high-technology home care: videophones for pediatric ventilatory care

OBJECTIVE

To develop and to assess the clinical impact of a near-television quality home digital videophone system (Integrated Services Digital Network [ISDN] 64, 320 x 200 resolutions, 10 to 12 frames per second), which would provide respiratory care specialists' resources to primary care physicians and their pediatric patients receiving home respiratory care.

METHOD

A prospective study comparing the preceding 6 months and following 6 months of implementation of a videophone system on seven pediatric home respiratory care patients (group I) and a prospective analytical study of three patients (group II) being introduced to home ventilatory care were carried out. Clinical effectiveness and time-saving benefits were studied.

RESULTS

There were large reductions in the number of house calls by the physicians (from 5 to 0), unscheduled hospital visits by patients (from 24 to 5), and hospital admission days (from 22 to 10), with a fivefold increase in phone calls (from 11 to 58) in group I. This reduced the net number of hours spent by both patients and physicians in unscheduled medical care by 95 hours for the patients and 51.2 hours for the physicians. A total of 45 videophone calls, of which 27 were related to mechanical concerns and 18 to medical concerns, were made in group II. There were 7 mechanical and 10 medical problems of clinical significance, but all were directly handled by physicians by videophone. The majority (35 of 45) of videophone calls were made in the first 3-month period, indicating a decrease in nonspecific concerns after this period. The specifications of the system we used were found acceptable by both patients and health care professionals. The system seemed to be useful in effectively using the time of specialists and in relieving the anxieties of families. No deleterious effects were noted. The current initial cost is substantial but rapidly falling. The running cost is similar to a regular telephone bill when one ISDN 64 line is used.

CONCLUSIONS

The videophone system using ISDN 64 can now be considered a practical and effective tool to recruit specialist resources into home care and to improve the quality of pediatric home ventilatory care. This study encourages the use of videophones to help establish designated home care support systems that may extend beyond national borders and time zones.

An abnormal sodium metabolism in Japanese patients with essential hypertension, judged by serum sodium distribution, renal function and the renin-aldosterone system

OBJECTIVE

The role of the renin-aldosterone system and the ability of renal sodium reabsorption to facilitate pressure natriuresis were analyzed by using a sufficient number of Japanese patients with essential hypertension.

METHODS

We studied 3222 normal Japanese subjects (610 in Kashiwa City Hospital and 2612 in Shinshu University Hospital), 741 Japanese patients with essential hypertension (256 in Kashiwa City Hospital and 485 in Shinshu University Hospital), 20 patients with aldosterone-producing adenomas and 11 patients with idiopathic hyperaldosteronism to determine the possible roles of sodium, renal function, and plasma aldosterone concentration (PAC) on blood pressure elevation. Inappropriate elevation of aldosterone levels [elevation of the aldosterone:plasma renin activity (PRA) ratio] was used to assess aldosterone action.

RESULTS

The peak of the serum sodium distribution curve was approximately 2 mmol/l higher in the patients with essential hypertension than it was in controls. The prevalence of higher serum sodium concentrations (> or = 147 mmol/l) also was increased significantly hypertensive patients. Age-related deterioration of renal function did not explain the hypertension and abnormal sodium metabolism in the hypertensive patients. In stepwise regression analysis, the serum sodium concentration was related inversely to the PRA and positively to the PAC:PRA ratio. Although there was an inverse relationship between urinary sodium excretion (representing sodium intake) and the PRA, urinary sodium excretion proved not to be significant as a source of variation in the PAC or in the PAC:PRA ratio in the hypertensive patients. Although the PAC was within the normal range in patients with serum sodium concentrations of 147 mmol/l or more and an elevated PAC:PRA ratio, it was inappropriately high for the stimulus applied, as indicated by the PRA; this is similar to the situation with aldosterone-producing adenomas or idiopathic hyperaldosteronism.

CONCLUSION

Serum sodium distribution patterns differed between normal subjects and patients with essential hypertension in this Japanese population. The deterioration of renal function and increased sodium intake did not explain this abnormal sodium metabolism. A higher serum sodium concentration is related to an elevated blood pressure, and, in some patients, an inappropriate elevation of plasma aldosterone levels. Of the Japanese hypertensive patients, 10-14% exhibited serum sodium concentrations of 147 mmol/l or more and inappropriate elevations of aldosterone level (suppressed PRA and normal aldosterone level). The defect in these patients presumably lies in the inappropriately high secretion of aldosterone.

Construction of artificial methemoglobin reduction systems in Hb vesicles

The hemoglobin vesicle (HbV) is a red cell substitute encapsulating purified concentrated Hb in a phospholipid vesicle. In order to suppress metHb formation for the long term maintenance of oxygen transporting capability in vivo, thiols (cysteine, Cys; homocysteine, Hcy) were studied as reductants of metHb. Hcy showed a suppressive effect on metHb formation, while Cys adversely accelerates metHb formation at the rate of twice the Hb solution without any reductants. The suppression of Cys-induced metHb formation by the addition of superoxide dismutase (SOD) and catalase indicated that Cys was easily oxidized by oxygen and simultaneously generated a large amount of active oxygens. The rate of metHb formation was influenced by PO2 and pH. Furthermore, the reducing systems (methylene blue (MB), NADH or ascorbic acid) were added to the outer aqueous phase of HbV, and the artificial reduction systems constructed through the bilayer membrane were evaluated.

Messenger RNA fingerprinting analysis using arbitrarily primed PCR (RAP) of genes expressed during rat C6 glioma cell differentiation

To identify differentially expressed genes involved in rat C6 glioma cell differentiation induced by cyclic AMP, we adopted mRNA fingerprinting using arbitrarily primed polymerase chain reaction (PCR) (RAP). Four complementary DNA (cDNA) fragments differentially expressed during differentiation were isolated, and they appeared to contain coding regions of corresponding mRNAs. RAP can be used to efficiently identify cDNA fragments by comparing nucleotide and deduced amino acid sequences with those in databases, and is thus a useful method to search for and identify important genes involved in complex cellular processes such as glioma cell differentiation.

Standardization of low attenuation area versus total lung area in chest X-ray CT as an indicator of chronic pulmonary emphysema

We examined the methods for measuring the LAA% (100 x low attenuation area/total lung area) on thoracic X-ray CT scans in order to develop a useful indicator of chronic pulmonary emphysema (CPE). First, we modified the method for calculating the LAA% to be applicable by the programming tool installed in a commercially available CT machine in order to minimize manual procedures. This new method proved to be applicable in all CT machines produced after 1987. Second, we examined the difference in the Hounsfield Unit (HU) between different CT machines using two kinds of phantoms. One phantom was composed of Styrofoam, which has a density similar to the low attenuation areas. The other phantom was composed of Styrofoam and water, which has a density similar to the lung. We proved that the difference of LAA% with the correct value was 5% at maximum among four different CT machines. Thus, the phantom developed in the present study may play an important role in the standardization of HU. Finally, the possibility of decreasing the X-ray levels was examined. Twenty-five percent of the standard electrical current provided the same LAA% in cases where the subject was an established CPE patient, whereas the LAA% was overestimated in subjects with a normal LAA% value. However, a correction using a linear regression equation may be possible in the latter cases. It may be concluded that LAA% analysis can easily be performed in many city hospital, without much investment of manual procedures or any corrections to the HU levels between different CT machines. This method may be useful as a routine follow up for CPE patients because of the smaller irradiated dose given when using a CT machine.

Surface modification of hemoglobin vesicles with poly(ethylene glycol) and effects on aggregation, viscosity, and blood flow during 90% exchange transfusion in anesthetized rats

Poly(ethylene glycol) (PEG5000)-conjugated phosphatidylethanolamine was introduced onto the surface of hemoglobin vesicles (HbV); phospholipid vesicles encapsulating concentrated Hb (d = 0.257 +/- 0.087 micron; P50 = 32 Torr). The obtained PEG-modified HbV (HbV-PEG) was studied for use as a red cell substitute from the viewpoint of rheology, surface properties, and hemodynamics. The viscosity of the unmodified HbV suspended in saline ([Hb] = 10 g/dL) was 2.6 cP (shear rate = 358 s-1, 37 degrees C), less than that of human blood (4 cP). However, when suspended in a 5 g/dL albumin solution (HbV/ albumin), it increased to 8 cP due to the molecular interaction between albumin and vesicles, and the viscosity increased with decreasing shear rate, e.g., 37 cP at 0.58 s-1. As for the HbV-PEG/albumin, on the other hand, the viscosity was 3.5 cP at 358 s-1 and was comparable with that of human blood. Optical microscopy showed formless flocculated aggregates of the unmodified HbV, while no aggregates were confirmed for the HbV-PEG. The steric hindrance of PEG chains seemed to be effective in preventing intervesicular access and the resulting aggregation. To estimate the flow profiles in the capillaries, the suspensions were allowed to penetrate through isopore membrane filters (pore size = 0.4-8 microns, cf. capillary diameter = 4-10 microns). The penetration rate of the HbV-PEG/albumin was higher than that of the unmodified HbV/albumin due to the suppression of aggregation, whereas both of them were significantly higher than that of human blood due to the smaller size of vesicles than RBC. Ninety percent exchange transfusion was performed with the HbV-PEG/albumin or HbV/albumin in anesthetized Wistar rats (n = 6). The blood flow in the abdominal aorta increased 1.5 times, and the total peripheral resistance decreased in the HbV-PEG/albumin-administered group in comparison with the HbV/albumin group. As for the blood gas parameters, the base excess and pH remained at higher levels in the HbV-PEG/albumin group, and the O2 tension in mixed venous blood for the HbV-PEG/albumin group tended to be maintained at a higher level than that for the HbV/albumin group. Thus, the PEG modification of HbV reduced the viscosity by the suppression of aggregation and resulted in prompt blood circulation in vivo.

Pure silicate fragment in a recurrent stone former of calcium oxalate

Long-time oral intake of magnesium-silicate-containing drugs is thought to be a causative factor inducing silicate urolithiasis. Besides, magnesium seems to play an anti-urolithogenic part in the formation of calcium oxalate stones. We report a recurrent calcium oxalate former who had been treated with magnesium aluminometasilicate antacid for gastric ulcer for approximately 17 years. One of the fragments found during extracorporeal shock wave lithotripsy was identified as 100% silicate. Deposition of silica was also found on other fragments. A large dose of magnesium (given in a part of the drug) might have little influence on the formation of calcium oxalate.

Construction and characterization of a recombinant adenovirus vector carrying the human preproinsulin gene under the control of the metallothionein gene promoter

A new adenovirus vector carrying human-preproinsulin (h-PPI) genomic DNA, which was placed under the control of the mouse metallothionein gene promoter, was constructed. In the recombinant virus-infected cells, h-PPI gene expression increased as a function of ZnSO4 concentration. Reversed-phase high-performance liquid chromatography analysis revealed that the recombinant adenovirus-infected cells secreted immature insulin containing proinsulin and incorrectly processed insulin. Tyrosyl phosphorylation of human insulin receptor substrate 1 occurred when HepG2 cells were treated with the cultured medium, indicating that the h-PPI gene product was functionally active in vitro. We also examined the biological activity of the product using diabetic severe combined immunodeficient mice and confirmed that the h-PPI gene product reduced the blood glucose concentration in vivo. This study suggests that the adenovirus vector can be used to express a foreign gene under the control of an external promoter in various human cells.

Inhibitory effect of thromboxane A2 synthetase inhibitor, DP-1904, on antigen-induced contraction of human lung parenchyma

BACKGROUND

Several mediators are released from mast cells during allergic reactions. These substances cause contraction of airway smooth muscles, increase the permeability of blood vessels, and enhance mucous secretion. Among these mediators, thromboxane A2 (TXA2) has a particularly strong bronchoconstrictive effect.

OBJECTIVES

We examined antigen-induced contraction of excised human lungs and the suppressive effects of TXA2 synthetase inhibitor on TXA2 release.

METHODS

Human lung parenchymal strips were subjected to passive sensitization with sera of 5+ RAST titer to the mite. They were suspended in magnus baths, to which buffer and 10(-4) to 10(-8) M of DP-1904, an inhibitor of TXA2 synthetase, were added. Following the measurement of TXB2 and leukotriene (LT) concentrations in each bath, parenchymal contraction was induced by the addition of a mite antigen. The concentration of TXB2 and LT was measured after contraction.

RESULTS

Antigen-induced release of TXB2 was significantly suppressed by DP-1904 in a concentration-dependent manner. DP-1904 did not inhibit parenchymal contraction and the release of LT.

CONCLUSIONS

Antigen-induced parenchymal contraction was not suppressed by inhibition of TXA2 release, suggesting that DP-1904 may not be effective in asthma.

A cyclic GMP-dependent housekeeping Cl- channel in rabbit gastric parietal cells activated by a vasodilator ecabapide

1. The membrane potential of rabbit gastric parietal cells is dominated by a Cl- channel with a subpicosiemens single channel conductance in the basolateral membrane. The effects of 3-[[[2-(3,4-dimethoxyphenyl)ethyl]carbamoyl]amino-N-methylbenzamide++ + (DQ-2511: ecabapide), a vasodilator, on the opening of this Cl-1 channel, the cyclic GMP content and the intracellular free Ca2+ concentration ([Ca2+]i) of parietal cells were investigated by whole-cell patch-clamp technique, enzyme immunoassay and Fura 2-fluorescence measurement. 2. Ecabapide stimulated the opening of the Cl-1 channel as determined by the reversal potential. This stimulation was concentration-dependent, and its EC50 value was 0.2 microM. Both the basal and ecabapide-induced openings of the channel were inhibited by 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB, 500 microM), a Cl- channel blocker. Another Cl- channel blocker, niflumic acid (500 microM) was much less effective. 3. The power spectra of the currents before and after the addition of ecabapide (10 microM) were analysed. Both spectra contained only one Lorentzian (1/f2) component. 4. 6-Anilino-5,8-quinolinedione (LY83583; 5 microM) which prevents activation of soluble guanylate cyclase, significantly inhibited both the basal and ecabapide (10 microM)-induced openings of the Cl- channel. 5. Ecabapide (0.01-100 microM) concentration-dependently elevated the cyclic GMP content in the parietal cell-rich suspension. The EC50 value was 0.2 microM. 6. In single Fura 2-loaded parietal cells, ecabapide (10-100 microM) did not increase [Ca2+]i. 7. These results indicate that ecabapide stimulates an intracellular production of cyclic GMP in the parietal cell without increasing [Ca2+]i, and leads to an activation of the housekeeping Cl- channel.

Preparation and some properties of type I collagen from fish scales

Soluble collagen from fish (sardine) scales was yielded at about 5% with 0.5 M acetic acid after demineralization with EDTA, while a great portion of the collagen remained insoluble. The solubility of this insoluble collagen was about 20% at 45 degrees C (denaturation temperature of soluble collagen) for 24 h. The remaining 80% of the insoluble collagen was denatured in the form of insoluble gelatin, and that may be an interesting food material.

Membrane currents of murine osteoclasts generated from bone marrow/stromal cell co-culture

Whole cell clamp recordings were conducted to examine the general behavior of ion channels in osteoclasts which were generated from bone marrow/stromal cell co-culture. In the resting state, inwardly and outwardly rectifying (IR and OR) currents were observed in the osteoclasts cultured for 5-18 days and the whole cell currents were classified into three types according to the conductance ratio between the OR and IR currents, such as, the IR type (OR/IR conductance < or = 0.2), the IR-OR type (0.2 < OR/IR < or = 5), and the OR type (OR/IR > 5). The IR type was found in 73% of cells (n = 78), the IR-OR type in 26% and the OR type in 1%. No relation was found between the current types and the number of nuclei or cultured days. The conductances varied among cells, but the IR conductance was larger than the OR conductance. The IR current was characterized by voltage-dependent kinetics, a negative conductance region and Ba(2+)-sensitivity. The reversal potential depended on the extracellular K+ concentration, indicating that K+ mediates the IR current. On the other hand, the OR current was reversibly reduced by decreasing extracellular Cl- concentration but not affected by K+, suggesting that the OR current depends on Cl-. High intracellular Ca2+ (1-10 microM) transiently activated a different class of outward current. These electrophysiological features resemble those in freshly isolated osteoclasts. We suggest that the ion channels involved in osteoclastic functions are expressed in the in vitro-generated osteoclasts and that the channels develop early in differentiation and are maintained for at least up to 18 days. Thus the co-culture system provide a useful model to examine roles of ion channels in osteoclastic functions.

Mitosis-specific phosphorylation of smooth muscle regulatory light chain of myosin II at Ser-1 and/or -2 and Thr-9 in sea urchin egg extract

We analyzed the kinase activities capable of phosphorylating the regulatory light chain of myosin-II (MRLC) from chicken gizzard in unfertilized and fertilized sea urchin egg extracts. Total kinase activity phosphorylating MRLC in vitro did not fluctuate throughout the first cell cycle. Phosphopeptide mapping analysis showed that MRLC was phosphorylated at two different sites corresponding to myosin light chain purified from chicken gizzard (MLCK) and protein kinase C (PKC) phosphorylation sites, namely MLCK and PKC sites, respectively. The activity of the kinase(s) responsible for phosphorylation of MRLC at PKC sites showed a significant increase at metaphase. Phosphoamino acid analysis revealed that this increase in MRLC phosphorylation was due to phosphorylation at serine residue (Ser-1 and/or Ser-2) and a threonine residue (Thr-9). This increase in phosphorylation at PKC sites is occurred concomitantly with an increase in histone H1 kinase activity. In contrast, MRLC phosphorylation at MLCK sites showed no significant changes during the first cell cycle. Butyrolactone I, a selective inhibitor of p34cdc2 kinase, inhibited the activity of the kinase(s) responsible for phosphorylation of MRLC at PKC sites at metaphase. These results suggest that the increase in MRLC phosphorylation at PKC sites (Ser-1 and/or -2, and Thr-9) at metaphase may be induced by p34cdc2 kinase. Thus, p34cdc2 kinase may be involved in the regulation of MRLC phosphorylation during cell division.