Intracellular free calcium accumulation in ferret vascular smooth muscle during crystalloid and blood cardioplegic infusions

OBJECTIVE

The effects of magnesium- and potassium-based crystalloid and blood-containing cardioplegic solutions on coronary smooth muscle intracellular free calcium ([Ca2+]i) accumulation and microvascular contractile function were examined.

METHODS

Isolated ferret hearts were subjected to hyperkalemic (25 mmol/L K+) blood cardioplegic infusion, hypermagnesemic (25 mmol/L Mg2+, K+-free) crystalloid cardioplegic infusion, or hyperkalemic crystalloid cardioplegic infusion for 1 hour. Coronary arterioles were isolated, cannulated, and loaded with fura 2. Reactivity and [Ca2+]i were assessed with videomicroscopy. [Ca2+]i was measured at baseline and after application of 50 mmol/L KCl. In addition, [Ca2+]i and vascular contraction were measured during exposure to Mg2+ and K+ cardioplegic solution at both 4 degrees C and 37 degrees C.

RESULTS

From a baseline [Ca2+]i of 177 +/- 52 nmol/L, K+ cardioplegic infusion (302 +/- 80 nmol/L potassium) markedly increased [Ca2+]i, whereas blood cardioplegic infusion (214 +/- 53 nmol/L) and Mg2+ cardioplegic infusion (180 +/- 42 nmol/L) did not alter [Ca2+]i. Although a difference between groups in percentage contraction after application of 50 mmol/L KCl was not observed, [Ca2+]i increased significantly more in vessels in the control group (764 +/- 327 nmol/L) and the K+ crystalloid cardioplegic infusion group (698 +/- 215 nmol/L) than in vessels in the blood cardioplegic infusion group (402 +/- 45 nmol/L) and the Mg2+ cardioplegic infusion group (389 +/- 80 nmol/L). Mg2+ cardioplegic solution induced no microvascular contraction at either 4 degrees C or 37 degrees C, nor was an increase in [Ca2+]i observed. K+ cardioplegic solution induced microvascular contraction at 37 degrees C but not at 4 degrees C; it increased [Ca2+]i at both 4 degrees C and 37 degrees C.

CONCLUSION

An Mg2+-based cardioplegic solution, or appropriate Mg2+ or blood supplementation of a K+ crystalloid cardioplegic solution, may decrease the accumulation of [Ca2+]i in the vascular smooth muscle during ischemic arrest.

Clinical characteristics of amiodarone-induced thyrotoxicosis and hypothyroidism in Japan

Since amiodarone was introduced in Japan in 1992, the incidence of the drug-induced thyroid dysfunction has been increasing. We studied the thyroid function of 13 patients with amiodarone-induced thyrotoxicosis (AIT) and 11 patients with amiodarone-associated hypothyroidism (AAH) who had been referred to our Institute in the last 6 years. AIT and AAH developed after 39+/-21 and 20+/-16 months of amiodarone treatment, respectively. One patient developed AAH followed by AIT. The AIT ranged from subclinical to overt thyrotoxicosis. Four patients with moderate to marked AIT were treated with methimazole. Their thyrotoxicosis persisted for 3 to 9 months, despite administration of antithyroid agents. One patient with mild thyrotoxicosis was treated with prednisolone, resulting in a euthyroid state in a few months. Eight patients with asymptomatic to moderate thyrotoxicosis resolved spontaneously without any treatment. In four asymptomatic patients with AIT, serum levels of T3 and T4 were in the upper normal range or slightly high (< 12 microg/dl), accompanied by suppressed TSH (<0.1 microU/ml) and high thyroglobulin levels, suggesting destruction-induced thyrotoxicosis. Such a subclinical thyrotoxicosis developed repeatedly in one patient. Ultrasonographic studies revealed no nodular lesion in the thyroid, and color flow Doppler sonography demonstrated no hypervascularity in the thyroid gland in any AIT patient. Although it is postulated in Europe that there are two types of AIT, namely type I, which develops in patients with latent Graves' disease or toxic multinodular goiter, and type II, which develops in an apparently normal thyroid as destructive thyroiditis, all AIT patients we have seen so far had developed destructive type AIT. Sufficient intake of iodide and a very low incidence of toxic multinodular goiter may account for the rare incidence of type I AIT in our country. Mild to moderate AIT resolved spontaneously without discontinuing amiodarone, but it was discontinued in two of 13 AIT patients because of extrathyroidal adverse reactions.

Comparison of parameters of 123I-MIBG scintigraphy for predicting prognosis in patients with dilated cardiomyopathy

123I-metaiodobenzylguanidine (MIBG) scintigraphy has been used to predict prognosis of patients with dilated cardiomyopathy (DCM), although it is unknown which parameter of MIBG is the most useful clinically. We studied MIBG in 59 patients with DCM, and followed them up to evaluate the prognosis of DCM. Single photon emission tomography (SPET) and planar imaging were performed, both early (e) and 4 h (delayed, d) post-injection. 201Tl (TL) SPET and radionuclide-ventriculography were also investigated. The total defect score of early and delayed MIBG and 201 Tl (MIBGeDS, MIBGdDS, TLDS) was analysed visually for each SPET image. The heart to mediastinum ratio (H/M) for both the early and delayed MIBG planar images and myocardial washout rate at 4 h were analysed quantitatively. Sixteen patients died during follow-up. Cox Hazards univariate analysis selected washout rate (P < 0.0001), H/Me (P = 0.0012), H/Md (P = 0.0001) and left ventricular ejection fraction (P = 0.0004) as indices for the prediction of cardiac death. Multivariate analysis selected washout rate as the most powerful independent predictor of prognosis (P < 0.0001). Survival curves with a threshold value of 52% for washout rate were able to differentiate a negative outcome from survival (P < 0.0001). TLDS, MIBGeDS and MIBGdDS were not useful in the prediction of prognosis. The washout rate of MIBG is the most potent predictor of cardiac death and is considered clinically useful.

Synthesis of 6- and 7-hydroxyestradiol 17-sulfates: the potential metabolites of estradiol 17-sulfate by female rat liver microsomes

The potential ring-B hydroxylated metabolites of estradiol 17-sulfate (1) by female rat liver microsomes were chemically prepared as authentic compounds. They are 6alpha- and 6beta-hydroxyestradiol 17-sulfates (7 and 9), and 7alpha- and 7beta-hydroxyestradiol 17-sulfates (12 and 16), whose synthetic procedures are described.

Molecular cloning and sequencing of the cDNA for vacuolar H+-pyrophosphatase from Chara corallina1

We have cloned a cDNA for vacuolar proton-translocating pyrophosphatase of Chara corallina that is one of the closest green algae to the land plants. The deduced protein consists of 793 amino acid residues. Its sequence is 71% identical to the H+-pyrophosphatases of land plants, and is less than 46% identical to those of marine alga and phototrophic bacterium.

Coronary microvascular protection with mg2+: effects on intracellular calcium regulation and vascular function

The use of Mg2+-supplemented hyperkalemic cardioplegia preserves microvascular function. However, the mechanism of this beneficial action remains to be elucidated. We investigated the effects of Mg2+ supplementation on the regulation of intracellular calcium concentration ([Ca2+]i) and vascular function using an in vitro microvascular model. Ferret coronary arterioles (80-150 micrometer in diameter) were studied in a pressurized (40 mmHg) no-flow, normothermic (37 degrees C) state. Simultaneous monitoring of internal luminal diameter and [Ca2+]i using fura 2 were made with microscopic image analysis. The microvessels (n = 6 each group) were divided into four groups according to the content of MgCl2 (nominally 0, 1.2, 5.0, and 25.0 mM) in a hyperkalemic cardioplegic solution ([K+] 25.0 mM). After baseline measurements, vessels were subjected to 60 min of hypoxia with hyperkalemic cardioplegia (equilibrated with 95% N2-5% CO2) containing each concentration of Mg2+ ([Mg2+]) and were then reoxygenated. During hyperkalemic cardioplegia, [Ca2+]i increased in a time-dependent manner in all groups. In the lower [Mg2+] cardioplegia groups, [Ca2+]i was significantly increased at the end of the 60-min cardioplegic period (247 +/- 44 nM and 236 +/- 49 nM in [Mg2+] 0 and 1.2 mM groups, respectively; both P < 0.05 vs. baseline) with 19.6-17.2% vascular contraction. Conversely, there was no significant [Ca2+]i increase in the higher [Mg2+] cardioplegia groups and less vascular contraction (5.4-4.1%, both P < 0.05 vs. [Mg2+] 1.2 mM group). After reperfusion, agonist (U-46619, thromboxane A2 analog)-induced vascular contraction was significantly enhanced in the lower [Mg2+] cardioplegia groups (both P < 0.05 vs. control) but was normalized in the higher [Mg2+] cardioplegia groups. Intrinsic myogenic contraction was significantly decreased in the lower [Mg2+] cardioplegia groups (both P < 0.05 vs. control) but was preserved in the higher [Mg2+] cardioplegia groups. These results suggest that supplementation of the solution with >5.0 mM [Mg2+] may prevent hyperkalemic cardioplegia-related intracellular Ca2+ overloading and preserve vascular contractile function in coronary microvessels.

Healing of segmental bone defects in rats induced by a beta-TCP-MCPM cement combined with rhBMP-2

A beta-tricalcium phosphate-monocalcium phosphate monohydrate (beta-TCP-MCPM) cement was evaluated as an effective carrier of recombinant human bone morphogenetic protein-2 (rhBMP-2) in rat femoral critical-size defects. Hard cement cylinders (4 x 5 mm) impregnated with two different doses of rhBMP-2 (1.26 or 6.28 microg) were implanted into each defect, and the results were compared with those in rats that had implantations of cylinders only. Implantation of the 6.28 microg dose of rhBMP-2 caused a large bone shell to form around the defect, resulting in osseous union in all cases within 3 weeks. Except for beta-TCP granules, the cement was resorbed and replaced by bone tissue at 6 weeks. A torsion test at 9 weeks showed that the failure torque and bone stiffness had recovered 99% and 141%, respectively, compared with the intact contralateral femur. The defects that received 1.26 microg of rhBMP-2 resulted in 40% union and 41% of the failure torque at 9 weeks. However, no instances of union were observed in the defects implanted with cylinders only. In conclusion, the beta-TCP-MCPM cement was shown to be effective as a rhBMP-2 carrier. Combined with rhBMP-2, this cement was rapidly resorbed and completely healed the defects.

Role of epidermal growth factor and its receptor in mechanical stress-induced differentiation of human periodontal ligament cells in vitro

The periodontal ligament (PDL) contains precursor cells for osteoblasts and cementoblasts. It has been shown that epidermal growth factor (EGF) inhibits dexamethasone-induced differentiation and up-regulates EGF-receptor (EGF-R) expression, whereas EGF-R is down-regulated in the course of differentiation. Thus it was suggested that EGF and its receptors act as a negative regulator of osteoblastic differentiation in PDL cells. In order to investigate further this hypothesis, human PDL cells were now used to elucidate the role of EGF and EGF-R in their proliferation and differentiation under mechanical stress-loaded conditions in vitro, as the PDL regularly receives mechanical stress from occlusal forces. As a model of mechanical stress, a cyclic stretch of 9 or 18% elongation was applied to the cells with a Flexercell cell-strain unit system. Alkaline phosphatase activity and osteocalcin mRNA expression were significantly induced by loading cyclic stretch for more than 4 days, whereas stretch slightly inhibited cell proliferation. Visualization of the actin stress fibres of the cells by rhodamine phalloidin revealed that approx. 10% of the total number of cells had become aligned perpendicularly to the direction of the stretch. The effects of stretch on alkaline phosphatase activity and cell proliferation were totally abolished by the presence of 10 ng/ml EGF. Western blotting of EGF-R protein demonstrated that stretch-induced differentiation accompanied the decreased expression of EGF-R protein in the cells. However, the amount of tyrosine-phosphorylated EGF-R upon EGF stimulation was restored to the control level in stretched cells. These results suggest that the EGF/EGF-R system acts as a negative regulator of differentiation of PDL cells regardless of the type of differentiation stimuli. Also, interaction between mechanical stress and the EGF/EGF-R system may participate in the osteoblastic differentiation of PDL cells and thereby regulate the source of cementoblasts and osteoblasts.

[Postoperative therapy using human atrial natriuretic peptide in cases of valve replacement]

The effect of hANP (atrial natriuretic peptide) was investigated clinically in 40 patients who underwent isolated valve replacement. Patients were divided into four groups: aortic regurgitation (AR), aortic stenosis (AS), mitral regurgitation (MR) and mitral stenosis (MS). Each group was divided into two subgroups: one was administered hANP after the operation until leaving ICU, and the other was not administered hANP. We measured the levels of hANP and c-GMP and blood pressure, pulmonary artery pressure, central venous pressure and levels of Na, K of urine and blood prcoperatively, immediately postoperatively and 1, 2, 4, 6 hours after operation. First, to examine the relationship between preoperative level of hANP and cardiac function, the relationship between preoperative level of hANP and history of cardiac failure and pulmonary artery wedge pressure (PAWP) were evaluated. Also, we evaluated the relationship between preoperative level of hANP and each dimension on echocardiography. There was a weak statistical relationship between hANP and PAWP (row = 0.39 (p = 0.04) Pearson correlation method) and there was no statistical relationship between hANP and duration of cardiac failure (row = 0.00445 (p = 0.98) Pearson correlation method). Preoperatively Left atrial diameter (LAD) showed a statistical relationship with level of hANP in every group using Spearman correlation method. Other dimensions such as left ventricular diastolic diameter (LVDd) and left ventricular systolic diameter (LVDs) and also fractional shortening (FS) did not show a strong correlation with preoperative level of hANP. Especially, in AS group there was a strong relationship between every dimension and preoperative level of hANP. Only in MS group LAD and the level of hANP were negatively related. This finding suggests that atrial dilatation results in reduction of secretion of hANP in cases of MS on long term follow up. Finally, hNAP therapy was shown to have a continuous diuretic effect, with stable hemodynamics.

Influence of calcium on proliferation and phenotype alteration of cardiomyocyte in vitro

An accelerated weight gain is noted in the heart of Ca-deficient, hypertensive chick embryos maintained in a shell-less culture in vitro. We previously observed that the Ca handling property of cardiomyocytes isolated from the shell-less embryo is altered, i.e., faster Ca uptake, suggesting a requirement for adequate Ca supply and/or proper Ca handling in embryonic cardiac development. In this study, we have examined the function of Ca on cardiomyocytes by analyzing the effects of 1) various Ca concentration in the culture medium (NCa, 1.8 mmol/ L; HCa, 2.8 mmol/L; LCa, 0.9 mmol/L), and 2) various modulators of Ca handling on cell proliferation and phenotype regulation in chick embryonic cardiomyocytes. The analytical parameters included cell number, DNA content, expression of cell cycle-specific and cardiomyocyte-specific proteins, and creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) enzyme activities. Cell number and total DNA were significantly larger (P < 0.01) in LCa cultures compared with those in NCa. The level of LDH was elevated (P < 0.01), but that of CPK was lowered in LCa. Expression of the G1-S-specific protein PCNA was raised, but that of the contractile proteins myosin and tropomyosin was substantially suppressed in LCa; in HCa, the cells did not proliferate as well, whereas the level of contractile proteins was higher. Thapsigargin, a sarcoplasmic reticulum (SR)-specific, Ca-ATPase inhibitor, simulated the effects of LCa by enhancing cell proliferation and lowering the expression of tropomyosin. These results suggest that culturing in low Ca concentration and inhibition of SR Ca pumping enhance myocardial cell proliferation and suppress sarcomeric protein expression, perhaps by inducing cellular de-differentiation. The in vitro effects of medium Ca concentration and Ca handling modulators on cardiomyocytes also suggest that the in vivo cardiomegaly of the SL embryos is a direct result of Ca-deficiency, and that Ca is important in the phenotype regulation of cardiomyocytes.

[Computer-assisted education of laboratory medicine based on common disease database and electric RCPC system using Internet technology]

We are developing computer-assisted instruction systems (CAI) for efficient education of laboratory medicine. To practice evidence-based laboratory medicine and put the education along the way, we gathered a large number of clinical records and constructed a database of clinical symptoms and signs of major diseases. We also constructed a web-based RCPC system featuring interactive multimedia materials and Q/A sessions to guide the students along important points in laboratory interpretations. We have been using these systems for 5th grade medical students and evaluated the effectiveness of them for the students to obtain knowledge regarding laboratory diagnosis. Although we still have a lot of aspects to improve, students showed interests in them and used them willingly. We believe that these CAI systems contribute to raise students' ability of problem solving in laboratory medicine.

Effects of tea infusions of various varieties or different manufacturing types on inhibition of mouse mast cell activation

We investigated effects of various tea infusions on mast cell activation using mouse mast cells. Among various tea extracts, infusions from cultivar 'Benihomare' and Taiwan lineage strongly inhibited histamine release after Fc epsilon RI cross-linking. Among three types of tea (from cultivar 'Benihomare'), extract from oolong tea or black tea inhibited histamine release more strongly than green tea extract. Furthermore, 'Benihomare' oolong tea extract suppressed tyrosine phosphorylation of cellular proteins after Fc epsilon RI cross-linking, but polyvinyl polypyrrolidone treatment of the extract to remove phenolic compounds, weakened the suppressive effect.

[Multivariate analysis of the associations between laboratory data and clinical features among patients with infectious mononucleosis syndrome]

Infectious mononucleosis (IM) syndrome is typically caused by EBV, but also by drugs and other organisms such as CMV and HBV. It demonstrates a wide range of clinical and laboratory characteristics, presumably depending on the age of onset. However, associations of laboratory abnormalities with the clinical features have not been well documented. We evaluated here, the associations among patients with IM syndrome using of multiple regression (MR) and multiple logistic regression (MLR) analyses. We examined 90 (40 males, 50 females) patients, who were admitted to our hospital with IM syndrome. The diagnostic criteria were fever and presence of atypical lymphocytes (> 5% of the WBC or the count including monocytes > 5000/microliter), and at least 3 of 7 clinical features: tonsillitis, lymphadenopathy, skin rash, hepato-, spleno-megaly, hepatic dysfunction. The diagnosis of EBV was serologically confirmed in 41 cases. MR revealed that the higher age group tended to have lower platelet counts, and that lower platelet counts were associated with higher ALT levels. In addition, MLR revealed that patients with skin rash tended not to have splenomegaly. The frequency of splenomegaly was not related to age, contrary to the findings of previous reports. These findings are useful to differentiate IM syndrome based on laboratory data.

[Consultation service for efficacious usage of laboratory tests based on logical reasoning and evidence]

To effectively respond to the desire for consultation in clinical practice, we must prepare logical reasoning and evidence which rationally supports laboratory test selection, the interpretation of test results and recommendation of certain tests to physicians. Standard of medical decision making can be used for logic issues such as posttest probability, test characteristics and receiver operating characteristics (ROC) curves and establishing appropriate cut-off points. Although we usually obtain evidence by consulting authorities or the literature, good evidence can also be obtained from meta-analysis. In addition, we can demonstrate the relationship of laboratory tests among several frequently occurring diseases and epidemiological tendencies such as frequency of causative organisms at several infection sites and bacterial sensitivities to antimicrobial agents, because we have access to a large-scale laboratory database. To construct a well-organized knowledge base with explicit evidence, cooperation among many facilities is necessary to develop system, which allows the free exchange of data.

Inter-laboratory difference among eleven clinical laboratories in the Okayama City area

The aim of the present study was to find the cause of inter-laboratory differences in laboratory test data and to examine whether control assessment helps to reduce inter-laboratory differences. Blood and serum samples of one healthy subject and one subject with liver cirrhosis were analyzed by 11 laboratories in the Okayama City area. No differences were found in the assay units of 26 tests surveyed. However, considerable differences were observed in test data, reference interval, and clinical level (CL), though most laboratories pointed out that the test data for the normal subject was within the reference intervals and those for the patient with liver cirrhosis showed abnormalities in tests for liver function. The difference in reference intervals was serious in the tests of direct bilirubin (D-Bil), thymol turbidity test (TTT), alkaline phosphatase (ALP), gamma-glutamyltranspeptidase (GGTP) and choline sterase. Marked differences in CLs were found in the tests of D-Bil, TTT, ALP, GGTP, creatine phosphokinase, amylase, heavy density lipoprotein cholesterol and white blood cell count. However, three hepatologists independently suggested that such inter-laboratory differences would not seriously affect a clinical decision on the disease status of the cirrhotic patient. Most tests that showed a trend error in a recent quality control survey appeared to have the same trend in the present study. These results indicate that inter-laboratory differences occur at various levels and control assessment are helpful in establishing, and therefore reducing, the level of inter-laboratory differences.

Porphyromonas gingivalis lipopolysaccharide modulates the responsiveness of human periodontal ligament fibroblasts to platelet-derived growth factor

Lipopolysaccharides (LPS) prepared from periodontopathic bacteria have been known to induce various biological responses which may lead to periodontal tissue breakdown. The purpose of this study was to determine if Porphyromonas gingivalis LPS could affect cellular functions of human periodontal ligament fibroblasts (HPLF). We showed here the responsiveness of cultured HPLF to platelet-derived growth factor (PDGF)-BB, a growth factor for mesenchymal cells, in the presence of P. gingivalis LPS. DNA synthesis of HPLF was enhanced in a dose-dependent manner when LPS were co-incubated for 48 h; thereafter, it decreased to the baseline level within 24 h incubation. The stimulating effect of PDGF-BB was further enhanced by the pretreatment of HPLF with LPS (10 micrograms/ml) for 48 h. The binding assay of [125I]PDGF-BB and the flow cytometric assay using rabbit antiserum to human PDGF receptor (PDGF-R) beta-type indicated that this enhancement was due to the increase of the number of PDGF-R beta-type on HPLF. Immunoprecipitation using antiserum to human PDGF-R beta-type also showed that the synthesis of PDGF-R beta-type was augmented in the LPS-treated HPLF. These results indicate that P. gingivalis LPS stimulate cellular proliferation and responsiveness to PDGF-BB of cultured HPLF. These cellular reactions may be mediated by PDGF-BB binding, followed by increased synthesis of the receptor protein.

Proliferation and differentiation of human osteoblastic cells associated with differential activation of MAP kinases in response to epidermal growth factor, hypoxia, and mechanical stress in vitro

In an attempt to elucidate the specificity of pathways from environmental stress to cellular outcome via mitogen activated protein kinases (MAPKs) activation, we examined the responsiveness of cultured human osteoblastic periodontal ligament (PDL) cells to epidermal growth factor (EGF), hypoxia, and mechanical stress, in terms of cell proliferation, differentiation, and associated activation of three different types of MAPK. Cell proliferation was promoted in the presence of 10ng/ml of EGF or in hypoxic conditions (5% O2), whereas it was inhibited by cyclic stretch (9% strain, 6 cycles/min), which was used as a model of mechanical stress. Conversely, the alkaline phosphatase activity, a marker for osteoblastic differentiation of the cells, was increased by cyclic stretch but decreased by EGF and hypoxia. The mitogenic response of PDL cells to EGF or hypoxia was associated with the selective phosphorylation and activation of extracellular-related kinase (ERK) 1/2, while phosphorylation and activation of c-Jun N-terminal kinase (JNK) was observed in mechanical stretch loaded cells. No such changes were seen in p38 protein. These findings suggested that stress-responsive changes in proliferation and osteoblastic differentiation of PDL cells are selectively mediated by ERK 1/2 and by JNK, respectively, and that a balance between these two pathways determines the cell fate.

[Clinical study on chlormadinone acetate alone followed by combination with LH-RH analogue for prostatic cancer: effects on lipid metabolism]

Twenty-four previously untreated patients with a diagnosis of prostatic cancer were treated with chlormadinone acetate (CMA) alone (100 mg/day) for 4 weeks, and luteinizing hormone-releasing hormone analogue (LH-RHa) was added for the next 24 weeks. Marked decreases in blood LH, testosterone (T), prostate specific antigen (PSA), gamma-seminoprotein (gamma-Sm), and prostatic acid phosphatase (PAP) were observed after a single dose of CMA. T levels were significantly increased 3 days after the initial dose of LH-RHa, and did not return to the pretreatment level. There were no significant increases in any of the markers, nor were there any flare-up cases. Triglyceride levels, which were slightly elevated before the start of treatment, were significantly decreased 24 weeks after the completion of combined therapy. PSA was evaluated as partial response (PR) or better in 86.7% of the patients. Overall evaluation showed PR or better in 75.0% of the patients. These findings suggest that prior administration of CMA followed by combined administration with LH-RHa is useful in the treatment of prostatic cancer. No negative effects on lipid metabolism were observed at any time during the treatment period.

Regulation of intracellular calcium concentrations by calcium and magnesium in cardioplegic solutions protects rat neonatal myocytes from simulated ischemia

The effects of calcium and magnesium ions in cardioplegic solutions on cardioprotection and intracellular calcium ion handling during ischemia and reoxygenation were investigated in cultured neonatal rat myocardial cells. Myocytes were subjected to simulated ischemia for 60 min at 37 degrees C in hyperkalemic cardioplegic solutions containing various concentrations of calcium and magnesium ions, followed by 30 min of reoxygenation. For each Ca2+ concentration (0.1, 0.6, 1.2, or 2.4 mM), the Mg2+ concentration was either 0, 1.2, 8, or 16 mM. The increase in intracellular Ca2+ concentration during ischemia and reoxygenation was suppressed by the addition of magnesium ion, independent of cardioplegic Ca2+ concentration. The recovery of spontaneous contraction rate and enzyme leakage (creatine phosphokinase and lactate dehydrogenase) during both ischemia and reoxygenation correlated with the degree of inhibition of intracellular Ca2+ accumulation. However, in the 0.1 mM Ca2+ groups in which the Mg2+ concentration was greater than 8 mM, the intracellular Ca2+ concentration increased during reoxygenation in a dose-dependent fashion of Mg2+, and was associated with increased enzyme leakage. The findings suggest that in immature cardiac myocytes, the concentrations of Ca2+ and Mg2+ present in cardioplegic solutions control the intracellular Ca2+ concentration during ischemia and reoxygenation, which, in turn, influences the cardioprotective effect of the cardioplegic solution.

RMA1, an Arabidopsis thaliana gene whose cDNA suppresses the yeast sec15 mutation, encodes a novel protein with a RING finger motif and a membrane anchor

To identify molecules that function in the plant secretory pathway, we screened for Arabidopsis thaliana cDNA clones that complement the temperature-sensitive (ts), secretion-deficient sec15 mutation of yeast Saccharomyces cerevisiae. RMA1, one of the genes obtained in this screening, suppressed not only the ts growth of sec15 but also its secretory defect. RMA1 is not a structural homologue of SEC15 but encodes a novel 28 kDa protein with a RING finger motif and a C-terminal membrane-anchoring domain. Mutational analysis indicates that the RING finger motif of RMA1 is important for its suppression activity. In Arabidopsis plant, RMA1 is ubiquitously expressed. A search for homologous proteins in the database revealed that Arabidopsis, nematode, mouse and human possess close homologues of RMA1.

Perioperative changes in plasma brain natriuretic peptide concentrations in patients undergoing cardiac surgery

The plasma concentrations of brain natriuretic peptide (BNP), a cardiac hormone, were measured in 30 consecutive adult patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) during the perioperative period. BNP concentrations remained unchanged until 6 h after the cessation of bypass, and were elevated 12, 24, and 48 h post-bypass (P < 0.0001 versus baseline). They had returned to the baseline values when measured 3 weeks postoperatively. The preoperative plasma BNP concentration correlated significantly with the left ventricular ejection fraction (r = -0.895). The peak plasma BNP concentration 24 h after bypass correlated with the cardiac index (r = -0.64), stroke volume index (r = -0.62), injection rate of dopamine hydrochloride (r = 0.65), and aortic crossclamp time (r = 0.57). There was also a significant correlation between the preoperative BNP concentration and the plasma BNP concentration 24 h post-CPB. These findings led us to conclude that the plasma concentrations of BNP become markedly and acutely elevated after cardiac surgery with CPB, and reflect the state of left ventricular function. Moreover, the severity of acute heart failure after cardiac surgery can be predicted by the preoperative plasma BNP concentration.

Experience of patients with end-stage heart failure who underwent heart transplant at UCLA

From 1993 to 1997, nine Japanese heart transplant candidates were accepted by the University of California at Los Angeles (UCLA) Medical Center, because no donor heart was available in Japan from a brain-dead patient. In all nine heart transplant patients described in this investigation, the preoperative diagnosis was dilated cardiomyopathy. One patient underwent implantation with a Novacor left ventricular assist device (Baxter Japan, Tokyo, Japan) as a bridge to heart transplant. All patients survived surgery and for a long-term period. The actuarial 1-year and 3-year survival curves of these patients were both 100%. The postoperative functional status was New York Heart Association Class 1 in all patients (100%). Immunosuppressive triple drug therapy (azathioprine, steroids, and cyclosporine) was given in seven patients; in two patients, cyclosporine was withdrawn and replaced by FK506 due to refractory rejection. The incidence of acute rejection per patient of more than grade 3 according to the International Society for Heart and Lung Transplantation was 6% within 3 months and 4.5% in 3-6 months; there was no rejection episode more than 6 months after transplantation. Post-transplant coronary artery disease was seen in two patients. However, no disease progression was seen after diltiazem therapy. These results may encourage heart transplantation in Japan.