[A device for rapid elevation of plasma methotrexate (MTX) concentration and its maintenance in high-dose MTX therapy]

For 5 osteosarcomas and one synovial sarcoma, 24 courses of high-dose methotrexate (MTX) therapy were performed. At MTX doses of 300 mg/kg with several infusion patterns, the plasma MTX concentrations were measured by fluorescence polarization immunoassay. In the various types of infusions, five hours oblique and five hours bolus infusions were well maintained at 1,000 micromol/l for several hours. In particular, five hours bolus infusion of MTX needed only 20 minutes to reach 822 micromol/l and maintained 1,000 micromol/l during almost the entire infusion period. Optimization of chemotherapy for sarcomas by MTX requires individual adaptation of the infusion pattern.

Differences in hemostasis among sclerosing agents in endoscopic injection sclerotherapy

Endoscopic injection sclerotherapy is useful in stopping bleeding from esophageal varices. We compared the in vivo effects of sclerosants on thrombogenesis, hemostasis, and endothelial injury. We injected aethoxysclerol (AS) of ethanolamine oleate (EO) into the small veins of the rat intestine. The maximum thrombogenic index with AS was 30.7 and with EO was 9.2. The venous flow stopped sooner with EO than with AS. The thrombi caused by EO were mixed with red blood cells. Heparin pretreatment decreased the thrombogenic index with AS by 96.7%, but not that with EO. The area of the fluorescein-albumin conjugate that permeated from veins with AS was larger than that with EO. The fluorescent intensity with AS was lower than that with EO. We thus conclude that: (1) the size of thrombi is not necessarily proportional to the hemostatic efficacy; (2) change in a patient's coagulation may affect the potential of sclerosants; (3) the excellent hemostatic efficacy of EO is based on localized injury to the endothelium and the involvement of red blood cells aggregation; and (4) in vivo microscopy is useful in determining the rational selection of sclerosants.

[So-called carcinosarcoma of the lung: A case report]

A 50-year-old male was admitted to our hospital because of an abnormal shadow in chest X-ray films. The diagnosis of adenocarcinoma was obtained by transbronchial brushing cytology. Right lower lobectomy with hilar and mediastinal lymph node dissection was performed. Histological examinations of the resected specimen showed that the tumor was composed predominantly of spindle-shaped cells containing scattered islands of moderately differentiated adenocarcinoma. Immunohistochemically, the spindle cells were positively stained by vimentin, keratin and epithelial membrane antigen, suggesting sarcomatous transformation of adenocarcinoma cells.

[Preliminary screening for antiviral AIDS drugs. VI. Report for fiscal year 1993]

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 138 samples tested, two were found to inhibit the growth of HIV in vitro. Neither of the positive samples has hopeful signs, as the ranges of effective doses of the samples are very narrow.

Comparison of effects of calcitriol and calcium carbonate on secretion of interleukin-1 beta and tumour necrosis factor-alpha by uraemic peripheral blood mononuclear cells

We studied 26 non-dialysed patients with chronic renal failure [creatinine clearance (CCr) 32.6 +/- 12.7 ml/min]. They were divided into three groups according to their CCr and serum intact parathyroid hormone (PTH) and were given 0.5 micrograms/day oral calcitriol (calcitriol group, n = 8), 3 g/day calcium carbonate (CaCO3 group, n = 10), or neither (control uraemic group, n = 8). Serum intact PTH decreased from 154 +/- 75 to 90 +/- 43 pg/ml in the calcitriol group (P < 0.01) and from 162 +/- 97 to 77 +/- 62 pg/ml in the CaCO3 group (P < 0.001). Calcium carbonate was also effective in suppressing serum tartrate-resistant acid phosphatase, alkaline phosphatase and intact osteocalcin levels, while calcitriol did not suppress serum osteocalcin. Secretion of interleukin-1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF-alpha) by phytohaemagglutinin A (PHA)-activated peripheral blood mononuclear cells (PBMC) was greater in uraemic patients than in age-matched healthy controls (n = 8). Calcitriol was effective in suppressing secretion of both cytokines, while calcium carbonate was capable of suppressing only TNF-alpha secretion. CCr decreased from 37.4 +/- 15.4 to 33.0 +/- 11.8 ml/min (P < 0.05) in the CaCO3 group, while it did not decrease in either the calcitriol group or the control uraemic group during a 6 month period. These results suggest that supplementation with calcitriol is necessary to maintain bone formation and normalize IL-1 beta and TNF-alpha secretion by activated PBMC in uraemic patients.

[Preliminary screening for antiviral AIDS drugs. VII. Report for fiscal year 1994]

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 246 samples of different origin tested, six were shown to inhibit the growth of HIV in vitro. Two of the positive samples have hopeful signs, as the ranges of effective doses are wider than those of most of positive samples which had been found by us.

[Changes in nurses' knowledge and attitudes regarding AIDS in Mie Prefecture, Japan]

In 1990, we conducted a questionnaire survey showing that many nurses had incorrect knowledge of AIDS resulting in inappropriate attitudes toward AIDS patients. Following the first survey conducted in 1990, nurses were given various forms of AIDS education. The effectiveness of the AIDS education requires assessment. Therefore a second questionnaire survey was performed in 1993 to assess changes in nurses' knowledge and attitudes regarding AIDS. The same questionnaire as used in the first survey was sent to a random sample of nurses working at general hospitals in Mie Prefecture, Japan. The questionnaire covered knowledge of AIDS, psychological responses, attitudes and conduct around infected persons and measures against AIDS. Results of both questionnaire surveys showed that the majority of nurses acquired their knowledge predominantly from the mass media, and a large number of nurses worried that AIDS would spread in Japan. Almost half of the nurses were worried that they might be infected with AIDS. The second survey showed that nurses who acquired knowledge of AIDS from printed material, pamphlets and other educational resources, including lectures had increased. In 1993, many more nurses had accurate knowledge compared to the number in the first survey. In 1993 the number of nurses who discriminated against AIDS patients and HIV-infected persons had decreased.

Purification and characterization of an extracellular beta-1,4-mannanase from a marine bacterium, Vibrio sp. strain MA-138

A beta-mannanase (EC 3.2.1.78) from Vibrio sp. strain MA-138 was purified by ammonium sulfate precipitation and several chromatographic procedures including gel filtration, adsorption, and ion-exchange chromatographies. The final ion-exchange chromatography Mono Q yielded one major active fraction and three minor active fractions. The major active fraction was purified to homogeneity on the basis of native polyacrylamide gel electrophoresis (PAGE). This purified enzyme was identified as a glycoprotein by periodic acid-Schiff staining and a monomeric protein with a molecular mass of 49 kDa by sodium dodecyl sulfate-PAGE. The pI of the enzyme was 3.8. The purified enzyme exhibited maximal activity at pH 6.5 and 40 degrees C and hydrolyzed at random the internal beta-1,4-mannosidic linkages in beta-mannan to give various sizes of oligosaccharides. The first 20 N-terminal amino acid sequence of the purified enzyme showed high homology with the N-terminal region of beta-mannanase from Streptomyces lividans 66.

Molecular biological and quantitative abnormalities of ADP/ATP carrier protein in cardiomyopathic hamsters

The adenine nucleotide translocator or ADP/ATP carrier protein (AAC) is an integral protein present in the inner mitochondrial membrane, which performs the exchange of cytoplasmic and intramitochondrial ADP and ATP. The myocardial AAC content was studied in J-2-N cardiomyopathic hamsters. The AAC content was found to be significantly decreased in J-2-N hamsters. For molecular biological analysis, hamster AAC (T1 isoenzyme) cDNA was cloned by the plaque hybridization method. This AAC cDNA hybridized specifically with AAC mRNA, so RNA dot-blot hybridization was performed. The highest AAC mRNA level was observed in control hamsters followed by J-2-N hamsters with mild myocardial damage, J-2-N hamsters with severe myocardial damage and Bio 14-6 cardiomyopathic hamsters. These results suggest that a decreased AAC content may contribute to the pathogenesis of cardiomyopathy and that a decrease of AAC mRNA levels may explain the abnormalities of AAC in J-2-N cardiomyopathic hamsters.

Requirement of Saccharomyces cerevisiae Ras for completion of mitosis

In the yeast Saccharomyces cerevisiae, Ras regulates adenylate cyclase, which is essential for progression through the G1 phase of the cell cycle. However, even when the adenosine 3',5'-monophosphate (cAMP) pathway was bypassed, the double disruption of RAS1 and RAS2 resulted in defects in growth at both low and high temperatures. Furthermore, the simultaneous disruption of RAS1, RAS2, and the RAS-related gene RSR1 was lethal at any temperature. The triple-disrupted cells were arrested late in the mitotic (M) phase, which was accompanied by an accumulation of cells with divided chromosomes and sustained histone H1 kinase activity. The lethality of the triple disruption was suppressed by the multicopies of CDC5, CDC15, DBF2, SPO12, and TEM1, all of which function in the completion of the M phase. Mammalian ras also suppressed the lethality, which suggests that a similar signaling pathway exists in higher eukaryotes. These results demonstrate that S. cerevisiae Ras functions in the completion of the M phase in a manner independent of the Ras-cAMP pathway.

[Usefulness of 123I-MIBG myocardial SPECT in patients with hematologic malignancies with chemotherapeutic agent-induced cardiomyopathy]

In 59 patients with hematologic malignancy undergoing chemotherapy regimens including adriamycin (ADR), myocardial imaging was performed by SPECT with 123I-metaiodobenzylguanidine (MIBG) to detect cardiac sympathetic nerve abnormalities. SPECT imaging was performed 20 min and 4 hr after intravenous injection of 123I-MIBG, and the washout rate (WR) for the entire left ventricle was calculated. Then the relationship of the WR to the total dose of ADR, the left ventricular ejection fraction, and the frequency of arrhythmias was evaluated. It was found that the WR was related to the total dose of ADR, suggesting that it is a useful parameter for cardiac sympathetic nerve damage. As the WR increased, the frequency of ventricular arrhythmias also increased. The WR was usually normalized 3-6 months after the discontinuation of ADR. In patients with a WR > or = 50%, however, prolonged follow-up was required. In conclusion, the WR on 123I-MIBG myocardial SPECT scans may be useful as a parameter for predicting cardiac toxicity requiring the discontinuation of ADR or dose reduction.

Anti-inflammatory effect of flurbiprofen tape applied percutaneously to rats with adjuvant-induced arthritis

The anti-inflammatory effect of flurbiprofen tape (FP-T) by topical application was investigated, and the findings were compared with the results of oral administration of flurbiprofen to adjuvant arthritic rats. The topical application of FP-T significantly suppressed both applied and non-applied hind paw edema, with a potency similar to that seen with the oral administration of flurbiprofen. Body weight also increased with these treatments. Plasma levels of flurbiprofen differed little between topical application of FP-T and oral administration of flurbiprofen. Gastric damage induced by topical application of FP-T was significantly less than that seen in case of oral administration of flurbiprofen. These results suggest that the anti-inflammatory effects of FP-T cannot be entirely explained by flurbiprofen permeating inflamed tissue below the application site; rather, flurbiprofen penetrating into the systemic circulation may explain these actions.

[Significance of cancer cell purification determining chemosensitivities for gastric cancer cells]

To evaluate the difference of anticancer drug sensitivities of cancer cells among altered cancer cell-populations in the MTT assay, we compared the results of MTT assay of cancer cells obtained by the conventional technique and of the cancer cell rich fraction from centrifugal elutriation (CE) system in 17 tumors and 3 peritoneal and pleural aspirates from 20 gastric cancer patients. CE raised the population of the cancer cells from 36.1% to 75.4% in tumors and from 37.6% to 94.9% in aspirates respectively. And the rate of yield of cancer cells after CE was 51.9% in tumors and 61.9% in aspirates. In 10 cases, anticancer drug sensitivities of cancer cell rich fraction were different from those of cancer cell obtained by the conventional technique, and mostly in these cases the population of the cancer cells before purification by CE was less than 30%. Pathologically, mostly in undifferentiated type, severe infiltrated type, and scirrhous type carcinoma the population of the cancer cells before purification was less than 30%. Therefore, in these cases, cancer cell rich samples should be used in determining the correct chemosensitivity of cancer cells.

Spatial heterogeneity of mucosal blood flow during ischemia-reperfusion injury of rat stomach investigated by laser Doppler perfusion imaging

Spatial alterations in blood flow during the development of mucosal injury induced by ischemia-reperfusion in rats were determined with a two-dimensional laser Doppler tissue perfusion imager. The rats were anesthetized with pentobarbital, and the stomach was exteriorized on a stage; the mucosa was then sequentially scanned. The mucosa was constantly superfused with 0.1 N HCl in physiological saline. Systemic arterial pressure was continuously monitored and blood was stepwisely withdrawn from the femoral artery by 20-mmHg stage and then maintained at 20 mmHg for 20 min. The shed blood was reinfused and the stomach was removed 30 min later. Under control conditions, the average perfusion of the forestomach was usually greater than that in the glandular stomach. When systemic blood pressure was stepwisely decreased, the extent of decrease in the mucosal blood perfusion unit was always greater than that in systemic blood pressure, but mucosal perfusion appeared to be uniformly decreased throughout the stomach. Ten min after reperfusion, a hypoperfused area began to appear in the corpus near the greater curvature, and this area subsequently increased. The area of ulcer formation corresponded with the hypoperfused area in the gastric mucosa 30 min after reperfusion. Pretreatment with CV-6209, a platelet-activating factor antagonist, significantly attenuated the hypoperfusion induced by reperfusion and also prevented gastric mucosal damage. Our results suggest that hypoperfusion in the mucosal microcirculation is indeed an important factor contributing to the localized occurrence of gastric mucosal lesions and that the laser Doppler perfusion imager is useful for the detection of local hypoperfused areas in the gastric mucosa.

Effect of administering calcium carbonate to treat secondary hyperparathyroidism in nondialyzed patients with chronic renal failure

We administered calcium carbonate orally to determine its safety and efficacy in treating nondialyzed patients with mild to moderate renal failure and secondary hyperparathyroidism. Twenty patients with chronic renal failure (creatinine clearance levels ranging from 7.9 to 42.7 mL/min) participated in this study. After a 6-month control period, 3 g calcium carbonate was administered daily for 6 months. We studied the effect for another 6 months after discontinuation of the regimen. We found that serum-intact parathyroid hormone was suppressed from 183 +/- 149 pg/mL to 85 +/- 61 pg/mL (P < 0.05) by treatment. This suppression was achieved with no increase in serum concentrations of 1,25(OH)2D3. Serum phosphorus levels decreased from 3.4 +/- 0.7 to 3.0 +/- 0.7 mg/dL (P < 0.01) and Ca2+ concentration increased significantly from 2.40 +/- 0.12 mEq/L to 2.57 +/- 0.08 mEq/L (P < 0.001) at 6 months. These changes were reversed after the 6-month period of withdrawal from calcium carbonate. Deterioration of renal function was not exacerbated by the therapy. Calcium carbonate administration also suppressed the serum concentrations of alkaline phosphatase and osteocalcin, indicating that improvement of hyperparathyroid bone disease is possible without a vitamin D3 supplement at an earlier stage of renal failure. Thus, administration of 3 g oral calcium carbonate daily was highly effective in treating secondary hyperparathyroidism in patients with mild to moderate renal failure.

Efficacy of slow-releasing anticancer drug delivery systems on transplantable osteosarcomas in rats

New drug delivery systems for cis-diamminedichloroplatinum (CDDP) incorporated into vehicles, such as polymethylmethacrylate (PMMA), fibrin glue (F.G.), alpha-tricalciumphosphate (TCP) and ethylenevinyleacetate copolymer (Polymer) were examined using a rat osteosarcoma model. The materials containing CDDP were directly implanted into the tumors or subcutaneous tissue of rats, and the inhibitory effects on tumor growth and lung metastasis were evaluated. Data on in vitro kinetics of CDDP release revealed good results for both TCP and F.G., and the release pattern from TCP to be most appropriate for a slow-releasing drug delivery system. This was supported by the results of the implantation experiments, whereby the direct implantation of TCP containing CDDP (CDDP-TCP) into tumors, gave significantly better inhibitions of tumor growth and metastasis than either non-treatment (P < 0.01) or subcutaneous implantation (P < 0.05). In a second experiment, using different administration procedures, different inhibitory effects on tumor growth and lung metastatic potency were observed with intra-arterial and intravenous CDDP administration, as well as with CDDP-TCP implanted subcutaneously. Suppression effects of CDDP (10 mg/kg)-TCP directly implanted into tumors were equal to those of intra-arterial (2.5 mg/kg) and intravenous (5.0 mg/kg) administrations. The present results suggest CDDP-TCP implantation to be effective as a slow-release drug delivery system for inhibiting tumor growth and metastasis, and that it should be a useful adjuvant to conventional i.v. or i.a. chemotherapy.

Efficacy of the angiogenesis inhibitor O-(chloroacetyl-carbamoyl)fumagillol (AGM-1470) on osteosarcoma growth and lung metastasis in rats

The efficacy of the anti-angiogenic agent, O-(chloroacetyl-carbamoyl)fumagillol (AGM-1470), against primary tumor growth and spontaneous lung metastasis was evaluated experimentally using a transplantable osteosarcoma line in rats previously established in our laboratory. Male Fischer 344 rats bearing the tumor with a high potential for metastasis received intermittent or continuous subcutaneous administrations of AGM-1470. Both treatment regimens resulted in significant inhibitions of spontaneous lung metastasis and primary tumor growth in a dose-dependent manner, with continuous administration of AGM-1470 exerting the most pronounced inhibitory effects on both parameters.

Ultrastructural cytochemical demonstration of proteoglycans and calcium in the extracellular matrix of chondroblastomas

To clarify the characteristics of the extracellular matrix of chondroblastomas, six cases were studied under the electron microscope, with special reference to proteoglycans and calcium in the cellular areas. In ruthenium hexammine trichloride (RHT)-stained sections the matrix was observed to be composed of rounded or polygonal fine granules and unbanded thin filaments that appeared to link neighboring granules together. Treatment with potassium-pyroantimonate showed intracellular accumulation of precipitates, mainly localized within the cisternae of the rough endoplasmic reticulum as well as in the extracellular matrix. The presence of calcium in the precipitates was confirmed using x-ray energy dispersive analysis. These findings, similar to characteristic features observed in calcifying systems, support the theory that chondroblastomas are of chondrogenic origin.

[A case of TSS complicated with SSSS in an adult with liver cirrhosis]

This paper reports a case of TSS complicated with SSSS in an adult with liver cirrhosis. A 52-year-old male, heavy drinker, was referred to our clinic complaining lumbago and painful swelling of the right arm. The patient had peeling of the skin over the hips, knees and elbows with positive Nikolsky's sign. The patient was in a state of shock on admission. Pyrexia persisted for 4 days and finally the body temperature rose up to 39 degrees C. The laboratory studies revealed hypoxia, DIC and multiple organ failure, and these became progressively worse. He died 4 days after admission. According to the criteria, he was diagnosed as TSS, and TSST-1 was detected from his serum. Staphylococcus aureus, coagulase type V was cultured both from the blood and from the wound of his right middle finger. This isolated strain did not produce TSST-1. The skin specimen at autopsy showed that the cleavage plane lied at the subcorneal region and close to the granular layer, with specific changes caused by exfoliative toxin. It was compatible to the exfoliation which was caused by exfoliative toxin produced from the S. aureus coagulase type V. The autopsy also revealed alcohol liver injury, liver cirrhosis and multiple organ failure due to shock state. SSSS is rare in adults, to our knowledge this is the first reported case of TTS complicated with SSSS.

A novel mammalian Ras GTPase-activating protein which has phospholipid-binding and Btk homology regions

We have previously purified a novel GTPase-activating protein (GAP) for Ras which is immunologically distinct from the known Ras GAPs, p120GAP and neurofibromin (M. Maekawa, S. Nakamura, and S. Hattori, J. Biol. Chem. 268:22948-22952, 1993). On the basis of the partial amino acid sequence, we have obtained a cDNA which encodes the novel Ras GAP. The predicted protein consists of 847 amino acids whose calculated molecular mass, 96,369 Da, is close to the apparent molecular mass of the novel Ras GAP, 100 kDa. The amino acid sequence shows a high degree of similarity to the entire sequence of the Drosophila melanogaster Gap1 gene. When the catalytic domain of the novel GAP was compared with that of Drosophila Gap1, p120GAP, and neurofibromin, the highest degree of similarity was again observed with Gap1. Thus, we designated this gene Gap1m, a mammalian counterpart of the Drosophila Gap1 gene. Expression of Gap1m was relatively high in brain, placenta, and kidney tissues, and it was expressed at low levels in other tissues. A recombinant protein consisting of glutathione-S-transferase and the GAP-related domain of Gap1m stimulated GTPase of normal Ras but not that of Ras having valine at the 12th residue. Expression of the same region in Saccharomyces cerevisiae suppressed the ira2- phenotype. In addition to the GAP catalytic domain, Gap1m has two domains with sequence closely related to those of the phospholipid-binding domain of synaptotagmin and a region with similarity to the unique domain of Btk tyrosine kinase. These results clearly show that Gap1m is a novel Ras GAP molecule of mammalian cells.

[Clinical usefulness of 123I-MIBG myocardial SPECT in patients with adriamycin-induced cardiomyopathy]

In 29 patients who had been administrated adriamycin (ADR) for the treatment of hematopoietic malignancies, myocardial SPECT was performed 20 minutes and 4 hours after an intravenous dose of 123I-metaiodobenzylguanidine (MIBG). Findings of the myocardial SPECT were compared with the total dose of ADR, ejection fraction (EF) and left ventricular wall motion, as assessed by ultrasound echocardiography. The mean total dose of ADR was 329.3 mg/m2 (range, 150-550 mg/m2). 1) Although the cardiac function was normal, the washout rate (WR) of MIBG was high in 75% of the patients whose MIBG myocardial SPECT showed abnormality on ADR, suggesting the presence of adrenergic nerve disorder. 2) The total dose of ADR was significantly correlated with WR of MIBG (p < 0.001). Consequently, WR of MIBG may be an index which reflects adrenergic nerve disorder in the myocardium earlier than EF. 3) It was suggested that adrenergic nerve disorder was involved in pathogenesis of myocardial complications associated with ADR administration. In summary, MIBG myocardial SPECT could be a useful test for determining a dosage regimen of ADR therapy of individual patients.

Hepatitis A, B and C seroprevalence in Pakistan

A cross sectional study was conducted to determine the seroprevalence of Hepatitis A, B, and C virus in healthy Pakistani children. HAV IgG antibody was assayed in 258 subjects and it was found that 94% children by 5 years of age had HAV IgG-antibody. The overall seroprevalence of HAV IgG antibody was 55.8% and IgM 5.3%. HBVsAb levels assayed in 236 healthy children showed a seroprevalence of 2.97%. Similarly, HCV antibody seroprevalence was found to be a low 0.44% in healthy children. HAV is a major cause of Hepatitis, as compared to HBV and HCV which are of low endemicity.

Evaluation of a monoclonal antibody-based colony blot test for rapid identification of virulent Rhodococcus equi

We recently generated a monoclonal antibody immunoglobulin G1 (MAb 10G5), which can recognize 15- to 17-kDa antigens, virulence-associated antigens of Rhodococcus equi, and developed a colony blot enzyme-linked immunosorbent assay with MAb 10G5 for the rapid identification of virulent R. equi. In this epidemiologic study, we evaluated the results of the colony blot test in the identification of virulent isolates of R. equi from feces of horses and soil and compared them with those from a conventional procedure (plasmid profiles of isolates by agarose gel electrophoresis). Environmental isolates (778 isolates from feces of foals, 170 isolates from feces of dams, and 1,267 isolates from soil on horse-breeding farms in Hokkaido) were tested by the colony immunoblot test, and 238 of the 778 isolates, 6 of the 170 isolates, and 85 of the 1,267 isolates showed positive signals. Positive isolates were then analyzed for the presence of virulence plasmid DNA, and 235 (98.7%) of the 238 isolates from foals, 6 (100%) of the 6 isolates from dams, and 75 (88.2%) of the 85 isolates from soil showed the presence of virulence plasmids. On the other hand, 50 isolates from each source, which were randomly selected from the isolates that showed negative signals by colony immunoblot, did not contain virulence plasmids. These results demonstrated that the colony blot test that uses a monoclonal antibody specific for virulence-associated antigens is a rapid and reliable test for the identification of virulent R. equi.

[A case of pulmonary thromboembolism with pulmonary hypertension with marked improvement by oral PGI2 analogue]

The patient was a 71-year-old man with dyspnea and bilateral leg edema. He was admitted to our hospital with worsening of dyspnea and had received therapy for chronic heart failure in another hospital. On admission, chest X-ray film revealed dilatation of the cardiac silhouette (CTR: 58%). Electrocardiogram showed atrial fibrillation and negative T wave in II, III, and aVF. Cardiac arteriogram showed no organic lesions, but pulmonary hypertension, pulmonary artery pressure of 60/21/34 mmHg, right ventricular pressure of 40/9/20 mmHg were recognized in pulmonary hemodynamics. The diagnosis of chronic pulmonary thromboembolism was made on the basis of pulmonary arteriogram findings and multiple defects of lung perfusion scintigram. After administration of oral PGI2 analogue for one month, lung perfusion scintigram and right cardiac pressure were markedly improved.

In vivo visualization of lymphatic microvessels and lymphocyte migration through rat Peyer's patches

BACKGROUND/AIMS

In the small intestine, lymphocytes migrate through Peyer's patches. The distribution of lymphatic microvessels in rat Peyer's patches and lymphocyte traffic through them were studied.

METHODS

Vital dyes were injected via a micropipette into the Peyer's patches tissue to fill lymphatic microvessels and to stain lymphocytes in lymphatic microvessels.

RESULTS

Direct microscopic observation revealed a dense plexus of lymphatic microvessels in the perifollicular and interfollicular areas. Injection of the dyes into the germinal center failed to delineate lymphatic microvessels. The lymphatic microvessels in the perifollicular area were filled with lymphocytes. Most lymphocytes in the perifollicular lymphatics stayed in the lymphatic microvessels. Some lymphocytes became detached and drained into lymphatic microvessels in the interfollicular areas. Lymphocytes then moved toward the submucosal lymphatics beneath the villi around the Peyer's patches. The interfollicular lymphatics did not display contractile activity but had valves. Opening and closing of valves was synchronized with the respiration and the back and forth flow of lymphocytes.

CONCLUSIONS

There are numerous lymphocytes in a dense lymphatic network in the perifollicular and interfollicular areas of Peyer's patches. This well-developed lymphatic network has the potential capacity for storage of lymphocytes and modulation of lymphocyte migration.

C3G, a guanine nucleotide-releasing protein expressed ubiquitously, binds to the Src homology 3 domains of CRK and GRB2/ASH proteins

CRK protein, together with GRB2/ASH and Nck proteins, belongs to the adaptor-type Src homology (SH)2-containing molecules, which transduce signals from tyrosine kinases. Here another guanine nucleotide-releasing protein (GNRP), C3G, has been identified as a CRK SH3-binding protein. The nucleotide sequence of a 4.1-kb C3G cDNA contains a 3.2-kb open reading frame encoding a 121-kDa protein, and antibodies against C3G have been shown to detect a protein of 130-140 kDa. The carboxyl terminus of C3G has a peptide sequence homologous to GNRPs for Ras, and the expression of this carboxyl terminus region suppresses the loss of CDC25 function in the yeast Saccharomyces cerevisiae. The C3G protein expressed in Escherichia coli binds to CRK and GRB2/ASH proteins. Mutational analysis of C3G assigns the SH3 binding region to a 50-amino acid region containing a proline-rich sequence. The mRNAs of both the C3G and CRK proteins are expressed ubiquitously in human adult and fetal tissues. The results of these studies suggest that the complex of CRK and C3G, or GRB2/ASH and C3G, may transduce the signals from tyrosine kinases to Ras in a number of different tissues.

Evaluation of the efficacy of nicorandil in patients with ischemic heart disease by exercise Tl-201 myocardial SPECT

The effect of nicorandil on myocardial perfusion in ischemic heart disease was studied using exercise-load Tl-201 myocardial SPECT (Ex-SPECT). ExSPECT was carried out in 12 patients with previous myocardial infarction (OMI) and 9 with angina pectoris (AP) before and after administration of nicorandil 15 mg/day, for three or more weeks; %Tl uptake and the washout rate in infarcted or ischemic areas were calculated from short axial images using the Bull's eye method. In the OMI group, %Tl uptake and washout rates in the infarction areas improved significantly from 52.4% and 0.25 before nicorandil to 60.4% and 0.38 after nicorandil. In the AP group, too, %Tl uptake and washout rates showed a significant improvement from 56.9% and 0.10 before to 69.1% and 0.33 after administration of nicorandil. Six subjects who had not received the drug, and who showed negative washout rates, had high improvement rates when nicorandil was administered, suggesting that the drug could increase myocardial perfusion during exercise loading as well as suppressing coronary spasm. Ex-SPECT was carried out in 4 subjects before and after the administration of nicarandil and after subsequent surgical treatment (PTCA or CABG) and the effects of the two therapies were compared. The washout rate was improved from 0.01 to 0.34 by the administration of nicorandil, and a notable increase in coronary artery blood flow was achieved compared to the level after surgical treatment, i.e. 0.50. It is concluded that normal dosages of nicorandil have a powerful direct effect of dilating the coronary arteries without any influence on preload or afterload.

[Clinical meaning of 123I-MIBG myocardial SPeCT in patients with dilated cardiomyopathy]

MIBG-myocardial SPECT was performed on patients with dilated cardiomyopathy (DCM) undergoing treatment with beta blocker (Nipradilol). The findings of MIBG-myocardial SPECT were compared with the changes in cardiac function obtained by echocardiograms. The patients enrolled in the study were seven males who has been diagnosed as definitely suffering from DCM according to diagnostic guidelines provided by the Ministry of Health and Welfare. The patients were aged 57.5 +/- 10.2 years. Following intravenous administration of 111 MBq (3 mCi) of MIBG, myocardial SPECT was taken 20 minutes, and 4 hours later. The washout rate of the left ventricular wall was higher in the unchanged group (40.7 +/- 1.2%) than in the improved group (30.3 +/- 6.1%). Both the early and delayed images showed higher extent and severity scores for the unchanged group than for the improved group. A correlation of LVEF with the washout rates was demonstrated (r = -0.819, p < 0.05). A correlation was also observed between the variations in LVEF before and after beta blocker therapy with the washout rates (r = -0.969, p < 0.01), MIBG-myocardial SPECT suggested possibility of the evaluation of severity and prognosis in the patients with DCM.

Alternative splicing of bovine terminal deoxynucleotidyl transferase cDNA

Two cDNA fragments of terminal deoxynucleotidyl transferase, which contained new insertion sequences, were found from bovine thymus cDNA. One of the clones encoded 18 new amino acids and the other encoded 9 new amino acids. In the results of genomic structure analysis around the new insertion sequences, alternative splicing of the bovine terminal deoxynucleotidyl transferase gene was suggested.

Elevation of the phospholipase A2 activity in peritoneal fluid cells from women with endometriosis

OBJECTIVE

To assess the prostaglandin (PG) production on peritoneal fluid (PF) cells, phospholipase A2 (PLA2) activity of those cells in women with endometriosis was measured and compared with that of women without endometriosis.

DESIGN

Prospective clinical controlled study.

PATIENTS

Women who underwent laparoscopy and were found either to have endometriosis (n = 15) or not (n = 9) were included in this study. Mononuclear cells obtained from the patients at laparoscopy were immediately separated by a Ficoll-Paque technique, lysed by nitrogen cavitation, and stored at -80 degrees C.

INTERVENTIONS

Phospholipase A2 activity was measured by Dole assay using 1-palmitoyl-2-[1-14C] palmitoyl phosphatidyl choline and assessed on a protein basis and a cell number basis.

RESULTS

There were at least four measurable kinds of PLA2 activity detected in the cells: two calcium-dependent pH optima 7.0 and 9.0 activities and two calcium-independent pH optima 7.5 and 8.5 activities. A calcium-dependent and pH optima 9.0 activity was the highest, and it was significantly higher in women with endometriosis when compared with those who did not have endometriosis.

CONCLUSION

These results indicate that the increase in the PGs in PF with endometriosis may be produced by PF cells in which PLA2 activity is elevated.

[Viral etiology in travellers' diarrhea]

Virological examinations were performed on stools obtained from 1,264 overseas travellers with diarrhea at Nagoya International Airport between 1986 and 1991. Group A rotavirus was detected in 11 samples (0.87%) by latex agglutination method, but other viral agents such as atypical rotaviruses and small round structured viruses were not observed by electron microscopic analysis. Rotaviruses were detected in various age groups, but the positive rate of rotavirus in females (6/398) was higher than that in males (5/866). Seasonal variation in the detection of rotavirus was observed. Entero 71 was isolated from one of 11 rotavirus-positive cases, but the other 10 cases were not associated with enteroviruses. All rotavirus-positive cases were negative for isolation of enteropathogenic bacteria.

Role of neuraminidase in the morphogenesis of influenza B virus

When ts7, a temperature-sensitive (ts) mutant of influenza B/Kanagawa/73 virus, infected MDCK cells at the nonpermissive temperature (37.5 degrees C), infectious virus was produced at very low levels compared with the yield at the permissive temperature (32 degrees C) and hemagglutinating activity and enzymatic activity of neuraminidase (NA) were negligible. However, viral protein synthesis and transport of hemadsorption-active hemagglutinin to the cell surface were not affected. When the cell lysate was treated with bacterial NA, hemagglutinating activity was recovered but infectivity was not, even after further treatment with trypsin. It was found that ts7 was defective in transport of NA to the cell surface and formation of virus particles. Analysis of the genomes of non-ts recombinants obtained by crossing ts7 and UV-inactivated B/Lee showed that ts7 had the ts mutation only in RNA segment 6 coding for NA and the glycoprotein NB. Nucleotide sequence analysis of the RNA segment revealed that ts7 had four amino acid changes in the NA molecule but not in NB. We suggest that assembly or budding of influenza B virus requires the presence of NA at the plasma membrane, unlike influenza A virus.

Attenuating effect of antithrombin III on the fibrinolytic activation and microvascular derangement in rat gastric mucosa

The roles for the fibrinolytic activation and disorder of coagulation in formation of gastric ulcer induced by microvascular derangement were investigated. The rat stomach was exposed and repeated electrical stimuli (RES) were applied on the small arterial wall close to the lesser curvature to induce mucosal microcirculatory disturbances. The level of tissue-type plasminogen activator (t-PA), a key enzyme for fibrinolytic activity, in the regional blood of the stomach was significantly elevated immediately after RES. At 5 min after RES, the leakage of FITC-labeled albumin and thrombus formation in the mucosal microvasculature were visually demonstrated by using an intravital microscopic system. At 30 min, hemorrhagic erosions and linear ulcers were observed in the gastric mucosa. Pretreatment with human antithrombin-III (AT-III) in the range of 0.1-10 U/kg dose-dependently attenuated both the fibrinolytic activation and microvascular alteration promoted by RES. Human AT-III also prevented RES-induced gastric mucosal injury. Thrombin inhibitory activity in the gastric vein decreased (69.0 +/- 2.1%) just after RES, and further reduced at 30 min (47.7 +/- 5.3%). The present study suggests a hypothesis that human AT-III has a preventive effect on the gastric mucosal hemorrhagic changes via attenuating the fibrinolytic activation and subsequent microcirculatory disturbances.

Electron microscopic evidence of a viral nature for osteoclast inclusions in Paget's disease of bone

Circumstantial evidence from electron microscopic and immunological studies support the view that Paget's disease of bone represents a slow virus infection. However, there is only limited information available regarding its electron microscopic, enzyme and immunocytochemical characteristics. Two cases were studied using electron microscopy with particular emphasis on the inclusions in osteoclasts. Detailed ultrastructural and cytochemical studies including immuno-electron microscopy were performed. Some osteoclasts demonstrated specific virus-like structures composed of aggregations of microtubules in the nucleus and cytoplasm. The structures were easily digested by trypsin or protease, and were sensitive to RNase, which provided substantial evidence of a proteinaceous nature and inclusion of ribonucleic acid. Immunocytochemical examination identified binding of anti-respiratory syncytial virus and anti-measles virus antibodies in the tissue obtained from one of the two cases examined. The presence of viral antigens in structures in the cytoplasm of Pagetic osteoclasts supports the theory of paramyxovirus involvement in this disease.

[Application of PCR for isolation of Chlamydia pneumoniae]

Chlamydia pneumoniae was isolated from the throat swab of a 5-year-old girl with acute bronchitis. The titers of IgM and IgG antibodies to C. pneumoniae in the serum were 1:20 and 1:2560, respectively. C. pneumoniae genome was detected by polymerase chain reaction in the throat swab and the infected cells after three passages, while C. pneumoniae was isolated from the throat swab after five passages by cell culture. PCR is considered to be a helpful method to isolate C. pneumoniae efficiently in routine cell-cultures.

Increased expression of nucleoside diphosphate kinase/nm23 and c-Ha-ras mRNA is associated with spontaneous lung metastasis in rat-transplantable osteosarcomas

The relationship between expression of nucleoside diphosphate kinase (NDP kinase)/nm23, c-Ha-ras, and c-myc genes and metastatic potential was assessed in rat-transplantable osteosarcoma lines, derived from spontaneous and chemical carcinogen (4-hydroxyamino quinoline 1-oxide)-induced osteosarcomas in Fischer 344/NS1c rats. These osteosarcomas possess metastatic potential and highly metastatic lines spontaneous osteosarcoma-selected lung metastatic lesions and 4-hydroxyamino-quinoline 1-oxide-induced osteosarcoma-selected lung metastatic lesions were respectively established by selectively transplanting lung metastatic lesions. Northern blot analysis revealed that the levels of NDP kinase/nm23 and c-Ha-ras gene expression were increased in line with metastatic ability; thus transcript levels were remarkably greater in both spontaneous osteosarcoma-selected lung metastatic lesions and 4-hydroxyamino-quinoline 1-oxide-induced osteosarcoma-selected lung metastatic lesions highly metastatic lines than in their respective low metastatic spontaneous and chemical carcinogen (4-hydroxyamino quinoline 1-oxide)-induced osteosarcoma counterparts. c-myc mRNA expression was observed in all tumor lines, without any correlation with metastatic ability. Southern blot analysis did not show evidence of gross rearrangement or amplification of NDP kinase/nm23, c-Ha-ras, or c-myc genes suggesting regulation of their gene expression at the transcriptional and/or posttranscriptional level. These results indicate that NDP kinase/nm23 and c-Ha-ras might be cooperatively involved in a positive manner in signal transduction processes, especially involving G-protein reactions, responsible for metastasis of rat-transplantable osteosarcomas.

Monoclonal antibody specific to virulence-associated 15- to 17-kilodalton antigens of Rhodococcus equi

Virulent Rhodococcus equi produces 15- to 17-kDa surface protein antigens. These antigens are used as markers to identify virulent R. equi isolates from foals and their environment by Western blot (immunoblot) analysis with naturally infected foal serum. In the present study, a monoclonal antibody (MAb; 10G5) was generated against the 15- to 17-kDa antigens excised from sodium dodecyl sulfate-polyacrylamide gels to develop sensitive and specific immunoblot assays for the identification of virulent R. equi. MAb 10G5 strongly reacted with R. equi ATCC 33701 and L1, which expressed 15- to 17-kDa antigens by Western blot, colony blot, and dot immunobinding assays, but it did not react with strains ATCC 33701P- and L1P-, which lacked the antigens. For identification of virulent R. equi, clinical and environmental isolates were tested by these assays with the MAb, and all virulent strains were successfully identified; these strains possessed virulence plasmids. These results suggest that the MAb is a useful reagent for the identification of virulent R. equi.

Improvement in blastocyst hatching of mouse embryos cocultured with human placental cells

PURPOSE

Although the hatching of embryos is an important phenomenon, the mechanism of hatching remains controversial. Therefore, we attempted to develop a new coculture system with human placental cells to investigate the hatching of mouse embryos.

RESULTS

In our new system there was no difference in development from the two-cell stage to blastocysts between embryos cultured with a T6 medium and embryos cocultured with human placental cells at 1 x 10(5), 5 x 10(5), and 1 x 10(6) cells/ml. However, the hatching-rate cell number increased significantly in embryos cocultured with placental cells compared to embryos cultured without placental cells. [3H]Thymidine uptake did not show any significant difference from the beginning of in vitro culture to the hatching stage between the coculture group and the control group. Nevertheless, the [3H]uridine uptake was significantly different in the two groups, measuring 2167 +/- 532 cpm/10 embryos in the coculture group and 804 +/- 86 cpm/10 embryos in the control group at 114 hr after human chorionic gonadotropin injection (P < 0.01).

CONCLUSION

These results therefore seem to indicate that the hatching of blastocysts depends on the protein synthesis of the embryos and not on DNA duplications.

Host-specific hemagglutination of influenza A (H1N1) virus

H1N1 strains of influenza A virus isolated during the influenza season of 1991-92 were divided into two groups according to the property of host-specific hemagglutination. Group 1 viruses agglutinated human and chicken red blood cells. Group 2 viruses agglutinated human but not chicken red blood cells. The viruses of both groups, however, showed the same antigenic structure determined with ferret antisera. The virus clones which were plaque-purified twice from a group 2 virus retained the characteristic of host-specific hemagglutination after five successive passages in MDCK cells, indicating that this phenomenon is genetically determined. However, the amino acid sequences of the hemagglutinin (HA) polypeptides deduced from the nucleotide sequences of the HA gene of the two groups did not show any differences between them. This suggests a difference in amino acids in some other polypeptide(s), which affects the host-specific hemagglutination.

Fatty liver hemorrhagic syndrome in hens overfed a purified diet. Selected enzyme activities and liver histology in relation to liver hemorrhage and reproductive performance

A nutritionally adequate, purified diet was developed and used in studies to characterize selected aspects of laying hens in which fatty liver hemorrhagic syndrome (FLHS) was induced by overfeeding. Hens consuming the diet ad libitum or intubated with the diet in quantities equivalent to usual daily energy intake maintained normal rates of lay, did not become obese, and did not develop liver hemorrhage. Overfed hens had a 33% incidence of FLHS, as indicated by the presence of severe liver hemorrhage score, and displayed the full range of symptoms associated with spontaneous outbreaks of FLHS, including definitive lesions of hepatic reticulin. Among four groups of hens clinically classified according to rates of liver hemorrhage and egg production, there were no differences noted in total liver fat, liver fat concentration, or final body weight. Liver hemorrhage was associated with the degree of induction of liver lipogenic accessory enzymes. Serum enzyme activities indicate that overfed hens, unlike the overfed goose, retain hepatocellular membrane integrity. Overfeeding caused altered reproductive performance in 72% of hens. Alterations included erratic laying, increased incidence of double ovulations, shell defects, follicular collapse, and oviduct involution. Pattern of lay preceding necropsy seemed to influence follicle weight at necropsy. The data presented re-emphasize the interdependence among liver, ovary, and oviduct function in the etiology of FLHS.

Regional differences in microvascular response in rat intestine during acute elevation of portal pressure

The effect of acute elevation of portal pressure on the blood flow of rat intestinal microvessels was studied using a laser Doppler velocimeter and in vivo microscopy. The total intestinal blood flow decreased when portal pressure increased more than +15 cmH2O above the basal value. Blood flow in villus capillaries did not change at portal pressures of +5 to +15 cmH2O, but did decrease at +20 cmH2O. Blood flow in muscle capillaries decreased at all steps of portal hypertension. Red blood cell velocity was decreased by portal hypertension in large venules, but not in small venules of the submucosa. Large venules, but not small venules, dilated in acute portal hypertension. Large arterioles in the submucosa constricted, while small arterioles dilated at portal pressures of +10 to +15 cmH2O. In conclusion, the intestinal microvascular flow response differs according to the degree of portal hypertension and the location on the microvascular tree. Blood flow in villus capillaries and in small submucosal venules is maintained at a small degree of portal hypertension.

Fluorographic study on the oxidative stress in the process of gastric mucosal injury: attenuating effect of vitamin E

In vivo oxidative change was visualized in the gastric mucosa of rats and the alteration was analysed by using a fluorescence microscope equipped with a digital imaging processor during the development of mucosal damage. Dichlorofluorescein (DCF)-associated fluorescence increased after the repeated electrical stimulation on the gastric artery (irritation), suggesting the occurrence of lipid peroxidation. The increase was enhanced in the mid-zone of two adjacent collecting venules. Allopurinol attenuated the oxidative stress in mucosa, showing the involvement of xanthine oxidase. Luminol-dependent chemiluminescence value in the blood taken from gastric vein was elevated by the irritation, suggesting that leucocyte-generated oxygen radicals also participate in this oxidative process. alpha-Tocopherol attenuated both the DCF activation and the increase in chemiluminescence value and prevented gastric mucosal injury. The present results suggest that alpha-tocopherol may be useful for the prevention of oxidative alteration in gastric mucosa.

Changes in phospholipase A2 activity of the rabbit ampullary epithelium by ovarian steroids

Phospholipase A2 (EC 3.1.1.4) activity of the ampullary epithelium from rabbit oviducts was compared in the presence of various ovarian steroids to assess how they could modulate prostaglandins (PG) biosynthesis in the oviduct. The phospholipase A2 (PLA2) activity of the cells from ovariectomized rabbits (control) was 190.8 +/- 9.8 pmol/min/mg. The PLA2 activity of the cells from progesterone-treated rabbits was 156.0 +/- 41.8 pmol/min/mg and was not significantly different from the control activity. However, the PLA2 activity of the cells from the estrogen-treated rabbits was 233.5 +/- 29.0 pmol/min/mg, which was significantly higher than the control activity (p < 0.05). On the other hand, the PLA2 activity of the cells from progesterone-treated rabbits after being primed with estrogen was 116.3 +/- 25.9 pmol/min/mg, which was significantly lower than the control activity (p < 0.01). These results suggest that the effects on PLA2 activity of ovarian steroids could regulate the local production of PG which plays a role in both smooth muscle contractility and ciliary activity.

[AIDS-related knowledge among nurses in Mie Prefecture, Japan]

Levels of understanding and knowledge regarding AIDS were investigated for medical personnel working at general hospitals with more than 100 beds in Mie Prefecture by means of a questionnaire during May to June, 1990. The questionnaire covered general knowledge of AIDS, psychological response, attitudes and actions taken toward infected persons, and societal countermeasures against AIDS. Responses from 1,516 nurses and assistant nurses were statistically investigated among medicare persons. Mass media was the major source of knowledge on AIDS for the nurses and assistant nurses. Level of understanding on AIDS, however, appeared to be rather low, which may be due to difficulty in obtaining accurate information on AIDS and also due to lack of motivation to study. The responses of nurses were more positive than for assistant nurses for action taken in hypothetical cases of infection to themselves, spouses or familiar persons. Similar differences were also shown in responses regarding societal countermeasures against the disease.

Characterization of the cyr1-2 UGA mutation in Saccharomyces cerevisiae

cyr1-2 is a temperature-sensitive mutation of the yeast adenylate cyclase structural gene, CYR1. The cyr1-2 mutation has been suggested to be a UGA mutation since a UGA suppressor SUP201 has been isolated as a suppressor of the cyr1-2 mutation. Construction of chimeric genes restricted the region containing the cyr1-2 mutation, and the cyr1-2 UGA mutation was identified at codon 1282, which lies upstream of the region coding for the catalytic domain of adenylate cyclase. Alterations in the region upstream of the cyr1-2 mutation site result in null mutations. The complete open reading frame of the cyr1-2 gene expressed under the control of the GAL1 promoter complemented cyr1-d1 in a galactose-dependent manner. These results suggest that at the permissive temperature weak readthrough occurs at the cyr1-2 mutation site to produce low levels of active adenylate cyclase. An endogenous suppressor in yeast cells is assumed to be responsible for this readthrough.

Study of the efficacy of nicorandil in patients with ischaemic heart disease using Exercise-T1-201 myocardial tomography

The effect of nicorandil on myocardial perfusion in ischaemic heart disease has been studied using exercise-load T1-201 myocardial SPECT (Ex-SPECT). Ex-SPECT was carried out in 12 patients with previous myocardial infarction (OMI) and 9 with angina pectoris (AP) before and after administration of nicorandil 15 mg/day, for three or more weeks; % T1 uptake and the washout rate in infarcted or ischaemic areas were calculated from short axial images using the Bull's eye method. In the OMI group, % T1 uptake and washout rates in the infarction areas improved significantly from 52.4% and 0.25 before nicorandil to 60.4% and 0.38 after it. In the AP group, too, % T1 uptake and washout rates showed a significant improvement from 56.9% and 0.10 before to 69.1% and 0.33 after administration. Six subjects who had not received the drug, and who showed negative washout rates, had high improvement rates when nicorandil was administered, suggesting that the drug could increase myocardial perfusion during exercise loading as well as suppressing coronary spasm. Ex-SPECT was done in 4 subjects before and after nicorandil and after subsequent surgical treatment (PTCA or CABG) and the effects of the two therapies were compared. The washout rate was improved from 0.01 to 0.34 by administration of nicorandil, and a notable increase in coronary artery blood flow was achieved compared to the level after surgical treatment, i.e. 0.50. It was concluded that, normal dosages of nicorandil have a powerful direct effect of dilating the coronary arteries without any influence on preload or afterload.