Blocking effect of 1389-S on the sodium current in isolated guinea-pig ventricular myocytes

Under whole cell patch conditions, 1389-S blocked the INa in guinea-pig ventricular myocytes under steady state conditions (Kdrest = 30 microM, Kdi = 2.4 microM) with a shift of the inactivation curve to the hyperpolarizing direction. Both brief and long conditioning pulses could produce a use-dependent block of 1389-S. These results suggest that 1389-S had a higher affinity to the inactivated than to the rested state under steady state conditions and had a higher affinity to the activated state during train pulses as well as to the inactivated state, making channels unavailable for conduction upon activation.     

Distortion and movement of the expander during skin expansion.

Distortion and movement of tissue expanders can cause expansion of the wrong area, such as the naevus or the scar that is to be resected. In 71 rectangular expanders, we examined the incidence of distortion (over 15 degrees) and movement (over 3 cm). We divided the expanders into three anatomical site groups: scalp, body, and extremities, and compared the complication rate between two study groups (distortion or movement, or not). In total, the incidence of distortion was 15/71 (21%) and that of movement 5/71 (7%). Distortion occurred mainly in the extremities (11/33,33%). The implanted expanders tended to move more often in the body part (3/15, 20%). In the extremities, the bigger the angle between the axis of the implanted expander and that of the extremity, the bigger the angle of distortion. Although the incidence of complications between the two groups was not significant, except for alteration in design of the flap, we recommend that these points should be considered when preoperative plans are being made for appropriate patients.     

Acute effect of thyroid hormone on insulin secretion in rats

To elucidate the mechanism of thyroid hormone-induced hyperinsulinemia, the acute and direct effect of thyroid hormone administration on insulin secretion was investigated in rats in vivo and in vitro. In the perfused rat pancreas, the addition of thyroxine (10 micrograms/dL) or 3,5,3'-triiodothyronine (150 ng/dL) to the perfusing medium did not affect insulin secretion. The administration of thyroxine (40 micrograms/kg, s.c.) in vivo increased the plasma insulin level from 11 +/- 2 microUnits/mL (mean +/- SD) to 30 +/- 7 microUnits/mL, while blood glucose and plasma glucagon were unchanged. This phenomenon was inhibited completely by the preadministration of oxprenolol hydrochloride (2 mg/kg, s.c.), and inhibited partly by the preadministration of metoprolol tartrate (35 mg/kg, s.c.). These results suggest that thyroid hormone induces hyperinsulinemia via beta-adrenergic stimulation in the rat.     

Two cases of persistent hypouricemia associated with diabetes mellitus.

Two patients with diabetes mellitus had persistent hypouricemia due to increased urate clearance; the degree of the apparent renal hypouricemia with uricosuria was quite mild. At the onset of diabetes, their serum urate levels were normal. Even after good diabetes control in both cases, hypouricemia continued. Based on the pharmacological evaluation in both patients, pyrazinamide administration could partially decrease urate clearance, however, suppression by pyrazinamide was less than in normal subjects, and probenecid increased urate clearance. These results suggest that the present cases had a renal abnormality affecting tubular presecretory reabsorption of urate, which might be due to diabetes mellitus.     

Gadolinium-based balloon angioplasty for pulmonary artery stenosis in an infant with a right isomerism.

We report here the first described case of utilizing gadolinium-based contrast material as the contrast agent during a catheter intervention treatment for pulmonary artery stenosis. The patient, a male infant with complex heart disease associated with a right isomerism, had a history of severe allergic reaction to iodine-containing contrast agents. A combination of digital subtraction angiography and a gadolinium contrast agent, however, provided us with good-quality images both before and after balloon angioplasty without any associated complications. This method should therefore be considered as an alternative angiographic procedure in children with a high risk of iodine-related allergic complications.     

Safety evaluation of surgical materials by cytotoxicity testing

The cytotoxicity of three kinds of commercially available absorbable hemostats [oxidized cellulose (Surgicel, gauze and cotton types), microfibrillar collagen (Avitene), and cotton-type collagen (Integran)] and one adhesion barrier [sodium hyaluronate and carboxymethyl-cellulose membrane (Seprafilm)] were comparatively assessed by a colony assay using V79 cells and a minimum essential medium (MEM) elution assay in combination with a neutral red assay using L929 cells. Strong cytotoxicity was detected for Surgicel by both the MEM elution assay and the colony assay. For Avitene, both methods revealed weak cytotoxicity. For Seprafilm, no cytotoxicity was detected by the MEM elution assay, while a moderate degree of cytotoxicity was observed in the colony assay. For Integran cytotoxicity was not detected by either the MEM elution or the colony assay. The results of the different methods showed some inconsistency in terms of the degree of cytotoxicity of the materials. It is proposed that the combination of two or more sensitive cytotoxicity testing methods for the evaluation of biomaterials is necessary to avoid false-negative results for biomaterials at the preclinical stage. Furthermore, investigation of the correlation between the cytotoxicity and the extraction period of the surgical materials is helpful for predicting the effect of prolonged in vivo use of biomaterials on surrounding cells, tissues, and organs.     

Effects of multipurpose solutions (MPS) for hydrogel contact lenses on gap-junctional intercellular communication (GJIC) in rabbit corneal keratocytes

To ensure the effects of multipurpose solutions (MPS) for hydrogel contact lenses on the cornea, the inhibitory activity of three types of MPS on corneal cells has been evaluated with the use of scrape loading and dye transfer assay (SLDT assay) and Western blotting on rabbit corneal keratocytes (RC4). In SLDT assay, MPS-A and poloxamine showed dose-dependent inhibitory activity, suggesting the inhibitory action of MPS-A and poloxamine to gap junctional intercellular communication (GJIC) in the tested cells. Moreover, after treatment with MPS-A, the GJIC was initially inhibited within 4 h, and thereafter gradually turned to an approximately 60% level of the initial value. When MPS-A was removed from the incubation media after exposure of the cells, the recovery of GJIC was time dependent and returned to approximately initial levels at 8 h. Complete recovery was established after approximately 24 h. These findings suggested that the inhibitory action of MPS-A on corneal keratocytes was reversible. This inhibition was accompanied by a decrease in the quantity of connexin-43, which is a major protein constituting the gap junctional channel of these cells, and its change in the phosphorylation state. Taken together, it was suggested that MPS-A interacts with connexin-43, inducing an inhibitory action on GJIC.     

Increase in gap junctional intercellular communication by high molecular weight hyaluronic acid associated with fibroblast growth factor 2 and keratinocyte growth factor production in normal human dermal fibroblasts

The effects of different molecular weights of hyaluronic acid (HA), a major component of extracellular matrix, on gap junctional intercellular communication (GJIC) in normal human dermal fibroblasts (NHDF cells) were investigated. NHDF cells were cultured for 4 days with different molecular weights of HA and then the extent of GJIC was assessed by the scrape-loading dye transfer method, using Lucifer yellow. The area of dye transfer was greater in the dishes coated with HA than in those to which HA was added. Thus, NHDF cells cultured on surfaces coated with high molecular weight (HMW) HA (MW, 800 kDa) showed greatly enhanced GJIC. Furthermore, another aim of this study was to evaluate the effects of different molecular weights of HA on the production of FGF-2 and KGF, because both are important cytokines produced by NHDF cells. When FGF-2 and KGF cultured levels of cell extracts and media were determined by ELISA, both levels were significantly enhanced when cells were grown on plates coated with HMW HA. This finding indicated that the function of gap junction channels in NHDF cells grown on plates coated with HMW HA may promote the biosynthesis of growth factors such as FGF-2 and KGF.     

Novel mechanism of tumorigenesis: increased transforming growth factor-beta 1 suppresses the expression of connexin 43 in BALB/cJ mice after implantation of poly-L-lactic acid

Poly-L-lactic acid (PLLA) is a widely used promising material for surgical implants such as tissue-engineered scaffolds. In this study, we aimed to determine the in vivo effect of PLLA plates on the cellular function of subcutaneous tissue in the two mouse strains, BALB/cJ and SJL/J, higher and lower tumorigenic strains, respectively. Gap-junctional intercellular communication (GJIC) and the expression of connexin 43 (Cx43) protein were significantly suppressed, whereas the secretion of transforming growth factor-beta 1 (TGF-beta 1) level was significantly increased in PLLA-implanted BALB/cJ mice compared with BALB/cJ controls. However, no significant difference in TGF-beta 1 secretion was observed between the SJL/J-implanted and SJL/J control mice. We found for the first time that a significant difference was observed between the two strains; thus, the PLLA increased the secretion of TGF-beta 1 and suppressed the mRNA expression of Cx43 at the earlier stage after implantation into the higher-tumorigenic strain, BALB/cJ mice. This novel mechanism might have a vital role in the inhibition of GJIC and promote the tumorigenesis in BALB/cJ mice.     

The response of normal human osteoblasts to anionic polysaccharide polyelectrolyte complexes

Polyelectrolyte complexes (PEC) were prepared from chitosan as the polycation and several synthesized functional anion polysaccharides, and their effects on cell attachment, morphology, proliferation and differentiation were estimated using normal human osteoblasts (NHOst). After a 1-week incubation, PEC made from polysaccharides having carboxyl groups as polyanions showed low viability of NHOst on it although the NHOst on it showed an enhancement in their differentiation level. On the other hand, NHOst on PEC made from sulfated or phosphated polysaccharides showed similar attachment and morphology to those on the collagen-coated dish. When the number of NHOst was estimated after 1 week, the number on the PEC was ranged from 70% to 130% of those on the collagen-coated dish, indicating few effects of these PEC on cell proliferation. In addition, NHOst on PEC films made from sulfated polysaccharides differentiated to a level very similar to that observed on the collagen-coated dish, indicating that these PEC films maintain the normal potential of NHOst to both proliferate and differentiate. Measurement of gap junctional intercellular communication of NHOst on PEC revealed that PEC did not inhibit communication, suggesting that PEC films have few effects on cell homeostasis. Thus, PEC made from the sulfated polysaccharide may be a useful material as a new scaffold for bone regeneration.