Immediate-early gene induction and MAP kinase activation during recovery from metabolic inhibition in cultured cardiac myocytes

To investigate how cardiac myocytes recover from a brief period of ischemia, we used a metabolic inhibition (MI) model, one of the in vitro ischemic models, of chick embryo ventricular myocytes, and examined the induction of immediate-early (IE) genes mRNAs and the activity of mitogen-activated protein (MAP) kinase. We performed Northern blot analysis to study the expression of c-jun, c-fos, and c-myc mRNAs during MI using 1 mM NaCN and 20 mM 2-deoxy-d-glucose, and also during the recovery from MI of 30 min. The c-fos mRNA was induced transiently at 30 and 60 min during the recovery. The expression of c-jun mRNA was significantly augmented at 30, 60, 90, and 120 min during the recovery (3.0-, 4.7-, 2.4-, and 1.9-fold induction, respectively) and so did the expression of c-myc mRNA (1.4-, 1.7-, 1.8-, and 2.0-fold induction, respectively). In contrast, the levels of these mRNAs remained unchanged during MI. The electrophoretic mobility shift assay revealed that AP-1 DNA binding activity markedly increased at 120 min during the recovery. When the cells were pretreated with protein kinase C (PKC) inhibitors, 100 microM H-7 or 1 microM staurosporine, the induction of c-jun mRNA at 60 min during the recovery was markedly suppressed (95 or 82% reduction, respectively). The c-jun induction was partially inhibited when the cells were treated with 2 mM EGTA during MI and the recovery (42% reduction). MAP kinase activity quantified with in-gel kinase assay was unchanged during MI, but significantly increased at 5, 10, and 15 min during the recovery (3.0-, 4.1-, and 3.4-fold increase, respectively). S6 kinase activity was also augmented significantly at 15 min during the recovery. Thus, these data suggest that IE genes as well as MAP kinase may play roles in the recovery process of cardiac myocytes from MI, and that the augmentation of c-jun expression needs the activation of PKC and to some extent, [Ca2+]i.

Pimobendan directly sensitizes reconstituted thin filament to slide on cardiac myosin

To elucidate the mechanism of the Ca(2+)-sensitizing action of pimobendan, cardiac thin filaments were reconstituted from actin and tropomyosin-troponin complex and made to slide on a myosin layer. Although filaments showed Brownian movement with a low Ca2+ concentration, they slid at a constant velocity above a certain level of Ca2+ concentration, showing that the sliding was regulated by Ca2+ within a narrow pCa range. Acidosis, addition of inorganic phosphate, and phosphorylation of troponin I increased the threshold Ca2+ concentration. Addition of pimobendan reversed these desensitization effects. These results clearly demonstrated that pimobendan directly increases the Ca2+ sensitivity of thin filament.

MCI-154 increases Ca2+ sensitivity of reconstituted thin filament. A study using a novel in vitro motility assay technique

MCI-154 (6-[4-(4'-pyridylamino)phenyl]-4,5-dihydro-3(2H)pyridazinone hydrochloride trihydrate) is a potent novel cardiotonic agent whose positive inotropism is shown to be mainly based on an increase in Ca2+ sensitivity of the contractile apparatus. To elucidate the exact mechanism through which this drug acts, we investigated the movement of the reconstituted thin filament on a myosin layer in vitro. Cardiac thin filaments were reconstituted from actin and tropomyosin-troponin complex purified from rat cardiac acetone powder separately. Double staining of the filament showed that tropomyosin-troponin complex was integrated along actin filament homogeneously. Thin filaments thus prepared were fluorescently labeled and made to slide on rat cardiac myosin fixed on a glass coverslip while varying the [Ca2+] of the medium (control, pH 7.2 at 25 degrees C). When [Ca2+] was low, the filaments showed only brownian motion. However, above a certain level of [Ca2+] (the threshold [Ca2+]), the filaments started to slide, and the velocity increased, reaching the maximum velocity within a very narrow range of [Ca2+]. The regulation was completely abolished by using simple actin filaments without tropomyosin-troponin complex, demonstrating that the regulatory proteins are responsible for this Ca2+ regulation of the movement of the reconstituted thin filament. Under the control condition, addition of MCI-154 shifted the threshold [Ca2+] to a lower level (sensitization) in a concentration-related manner. And 10(-4) mol/L of MCI-154 reversed the desensitization effect induced by either acidosis (pH 6.8), low temperature (15 degrees C), or the addition of inorganic phosphate (10 mmol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

A new in vitro motility assay technique to evaluate calcium sensitivity of the cardiac contractile proteins

We attempted to introduce calcium regulation into in vitro motility assay. Cardiac thin filament was reconstituted from actin and tropomyosin-troponin complex purified from rat myocardium separately. Double staining of the filaments showed tropomyosin-troponin complex was integrated along actin filaments homogeneously. The reconstituted thin filaments were made to slide on cardiac myosin fixed on a glass coverslip in the presence of MgATP while varying free Ca2+ concentration of the medium ([Ca2+]). Filaments showed only Brownian motion when [Ca2+] was below 10(-6.4) M. However, filaments slid at a constant velocity when [Ca2+] exceeded 10(-6.4) M, showing that the sliding was regulated in an on-off manner. The threshold [Ca2+] increased to 10(-5.0) M under acidic conditions, indicating a decrease in Ca2+ sensitivity of the contractile proteins. Simple actin filaments slid at a constant velocity independently of [Ca2+], demonstrating that the regulatory proteins were responsible for this on-off manner regulation. This new assay technique may be a powerful tool to directly evaluate the Ca2+ sensitivity of the contractile apparatus and to investigate how cardiac contraction is regulated by Ca2+.

Effect of lateral forces on the movement of myosin-coated beads on actin cables studied using a centrifuge microscope

We developed an in vitro motility assay system, in which myosin-coated polystyrene beads were made to slide on actin filament arrays (actin cables) in giant algal cells and subjected to centrifugal forces, which were parallel to the direction of bead movement to serve as external loads on actin-myosin sliding (Oiwa et al. (1990) Proc Natl Acad Sci USA 87: 7893-7897), and succeeded in determining the steady-state force-velocity relation of ATP-dependent actin-myosin sliding. To give further information about the properties of actin-myosin sliding, we have applied centrifugal forces, in parallel with the plane of actin-myosin sliding but at right angles with the direction of bead movement, and have found that such "lateral" centrifugal forces reduced the velocity of bead movement. In addition, we have also found that the velocity of bead movement is reduced more markedly with lateral forces applied from the left side of the bead ("left" lateral forces) than those applied from the right side of the bead ("right" lateral forces). These results are discussed in connection with the direction of sliding force generated by the myosin heads on the bead which interact with the right-handed double helix of actin monomers constituting actin filaments.

ADP inhibits the sliding velocity of fluorescent actin filaments on cardiac and skeletal myosins

We studied the effect of MgADP on the mechanical interaction of actomyosin in cardiac and skeletal muscles using an in vitro motility assay. The sliding velocities of fluorescently labeled actin filaments on rat cardiac and skeletal myosins were measured at various MgATP and MgADP concentrations. The filament velocity depended on MgATP concentration according to classic Michaelis-Menten kinetics with apparent Michaelis constants (Km) of 43 and 137 mumol/L and maximum velocity of 5.6 and 8.6 microns/s for cardiac and skeletal myosins, respectively. The presence of 2 mmol/L MgADP decreased the filament velocity and shifted the substrate concentration dependence of the velocity toward higher MgATP concentrations, yielding the inhibition constants of 194 and 478 mumol/L for cardiac and skeletal myosins, respectively. The activation energies determined by the temperature dependence of the velocity were 61 and 83 kJ/mol for rat V1 and rabbit cardiac myosins, which were similar to those of the dissociation rate constant of actomyosin-ADP complex reported in a solution study. The inhibition of the velocity by MgADP can be explained by the crossbridge scheme in which MgADP competes with MgATP for the substrate site on myosin molecules. In cardiac myosin, addition of a concentration of MgADP as low as 25 mumol/L significantly inhibited the velocity in the presence of 2 mmol/L MgATP, suggesting that increased intracellular MgADP may reduce the rate of crossbridge detachment, resulting in a decreased ATP consumption and an increased economy of force production under ischemic conditions. The present results support the idea that MgADP may be a physiologically important modulator of contraction in cardiac muscle.

Dynamic interaction between cardiac myosin isoforms modifies velocity of actomyosin sliding in vitro

To study the functional significance of cardiac isomyosin heterogeneity, active sliding of actin-myosin was studied using two different types of in vitro motility assay systems: (1) a sliding actin filament assay, in which fluorescently labeled actin filaments were made to slide on a myosin layer attached to a glass coverslip, and (2) a myosin-coated bead assay, in which myosin-coated latex beads were made to slide on actin cables of an alga. Two different isomyosins were obtained from 3-week-old (V1) and hypothyroid (V3) rat hearts and were mixed to form solutions with various mixing ratios [V1/(V1 + V3)]. For these myosin mixtures, both ATPase activity and sliding velocity of actin-myosin were determined. As the relative content of V1 increased, both ATPase activity and velocity increased. However, in contrast to the linear relation between the mixing ratio and ATPase activity, the relation between the mixing ratio and sliding velocity was sigmoid, suggesting the existence of mechanical interaction between different isomyosins. To clarify the nature of this interaction, sliding velocity was measured for mixtures of V1 and p-N,N'-phenylene-dimaleimide-treated V1 myosin (pPDM-M). A convex relation was observed between the relative content of pPDM-M and velocity. Because pPDM-M is known to form a noncycling and weakly bound crossbridge with actin, it is expected to exert a constant internal load on V1, in contrast to the actively cycling V3. In conclusion, in actomyosin sliding, different isomyosins mechanically interact when they coexist. The interaction may be a dynamic one that cannot be explained by a simple load effect.

Thermodynamic and kinetic analyses of DNA triplex formation: application of filter-binding assay

We have developed a simple and efficient method for studying equilibrium thermodynamics and kinetics of DNA triplex formation, which utilizes a filter-binding procedure. The application of this method to the triplex formation between a double-stranded homopurine-homopyrimidine and a single-stranded homopyrimidine oligonucleotides has demonstrated its ability in the quantitative estimation of equilibrium binding constants and rate constants under various conditions. Thus, this simple method can serve as a powerful tool for the systematic analysis of sequence and environmental effects on the equilibrium and kinetic quantities in the triplex formation.

A pseudo-symmetric DNA binding motif of purified Rep dimer of plasmid pSC101

The Rep protein, a replication initiator of plasmid pSC101, also functions as an autorepressor for its own structure gene, rep, through binding to the operator which consists of imperfectly dyad-symmetric (pseudo-symmetric) sequences, IR-1 and IR-2. In order to define the DNA binding motif of Rep, we have analyzed its binding affinity for each half repeat of the IR sequences and found that the right half of IR-2 was the preferred sequence for Rep, although its affinity was much lower than those of the IR sequences. Next, dimeric sequences of each half repeat with different configurations, head to head (the same configuration as natural IRs), head to tail, and tail to tail, were constructed and their affinities for Rep were examined. Almost all of sequences with the head-to-head configuration had binding affinity for Rep but these, including even the symmetric sequence of the right half of IR-2, exhibited lower Rep-binding abilities than natural IR sequences. We presume a pseudo-symmetric sequence, 5'GGNNTAGNNATTNNNATNN(N)CTAGNCC3', to be the Rep-binding motif from a sequence comparison. Some single-base substitution experiments confirmed the motif and suggested that each subunit of the Rep dimer recognizes each half repeat of IR asymmetrically.

Minimal essential origin of plasmid pSC101 replication: requirement of a region downstream of iterons

The minimal replication origin (ori) of the plasmid pSC101 was defined as an about 220-bp region under the condition that the Rep (or RepA) protein, a plasmid-encoded initiator protein, was supplied in trans. The DnaA box is located at one end of ori, as in other plasmids, like mini-F and P1. The other border is a strong binding site (IR-1) of Rep which is palindromic sequence and lies in an about 50-bp region beyond the repeated sequences (iterons) in ori. This IR-1 is located just upstream of another strong Rep binding site (IR-2), the operator site of the structure gene of Rep (rep), but its function has not been determined. The present study shows that the IR-1 sequence capable of binding to Rep is essential for plasmid replication with a nearly normal copy number. Furthermore, a region between the third iteron and IR-1 is also required in a sequence-specific fashion, since some one-base substitution in this region inactivate the origin function. It is likely that the region also is a recognition site of an unknown protein. Three copy number mutations of rep can suppress any one-base substitution mutation. On the other hand, the sequence of a spacer region between the second and the third iterons, which is similar to that of the downstream region of the third iteron, can be changed without loss of the origin function. The requirement of the region downstream of iterons in pSC101 seems to be unique among iteron-driven plasmid replicons.

Analysis of cardiac assistance by latissimus dorsi cardiomyoplasty with a time varying elastance model

OBJECTIVE

The clinical use of skeletal muscle cardiomyoplasty is limited because of its inadequate haemodynamic benefits. To facilitate experimental and clinical efforts to improve the efficacy of this technique, a mathematical model was proposed and its validity was tested in acute experiments.

METHODS

The model was based on the assumption that the skeletal muscle wrapped around the heart behaves as a time varying elastance that is connected in series with another time varying elastance representing the native heart. From this model two predictions were made: (1) Skeletal muscle augments the contractility of the heart by increasing the slope (Ees) of the end systolic pressure-volume relation; (2) time varying elastance of the skeletal muscle chamber (Es(t)) can be estimated from that of the assisted heart. These predictions were examined in experiments. In nine anaesthetised, open chest dogs, preconditioned latissimus dorsi muscle was transposed to wrap the heart. Left ventricular pressure (catheter tipped micromanometer), and volume (conductance catheter) were measured while reducing the preload by vena caval occlusion to evaluate Ees with 1:2 (stimulation:heart beat ratio) stimulation of the skeletal muscle.

RESULTS

With the stimulation of latissimus muscle, the end systolic pressure-volume relation was linear and Ees increased from 8.6(SEM 2.4) to 11.9(SEM 3.4) mm Hg.ml-1. Estimated Es(t) reflected the stimulation pattern and could account for the mechanism of the cardiac assistance.

CONCLUSIONS

Skeletal muscle cardiomyoplasty improved the haemodynamic variable (Ees) as predicted by a mathematical model.

Characterization of a temperature-sensitive influenza B virus mutant defective in neuraminidase

ts5, a temperature-sensitive mutant of influenza B virus, belongs to one of seven recombination groups. When the mutant 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 and enzymatic activities were undetectable. However, viral protein synthesis and transport of hemagglutinin (HA) and neuraminidase (NA) to the cell surface were not affected. The NA was found as a monomer within cells even at 32 degrees C, in contrast to wild-type virus NA, existing mostly as an oligomer, but the mutant had oligomeric NA, like the wild-type virus. Its enzymatic activity was more thermolabile than that of wild-type virus. Despite the low yield, large aggregates of progeny virus particles were found to accumulate on the cell surface at the nonpermissive temperature, and these aggregates were broken by treatment with bacterial neuraminidase, with the concomitant appearance of hemagglutinating activity, suggesting that NA prevents the aggregation of progeny virus by removal of neuraminic acid from HA and cell receptor, allowing its release from the cells. Further treatment with trypsin resulted in the recovery of infectivity. When bacterial NA was added to the culture early in infection, many hemagglutinable infectious virus was produced. We also suggest that the removal of neuraminic acid from HA by NA is essential for the subsequent cleavage of HA by cellular protease. Nucleotide sequence analysis of RNA segment 6 revealed that ts5 encoded five amino acid changes in the NA molecule but not in NB.

[Cardiac contractile proteins]

Structure and function of cardiac contractile proteins were summarized in connection with the pathophysiology of the heart muscle. Myosin is a large molecule consisting of two heavy chains and four light chains. Functional domains including ATP binding and actin binding sites reside in heavy chain. Heavy chain has two functionally distinct isoforms and their relative content changes in response to various pathological stimuli. The structure of myosin heavy chain also plays an important role in pathogenesis of familial hypertrophic cardiomyopathy. Another component of contractile machine is the F-actin, polymer of actin molecules. Actin is also a polymorphic protein and its expression changes under various conditions. However, the functional significance of actin polymorphism is yet to be determined.

Depressed sliding velocity of isolated cardiac myosin from cardiomyopathic hamsters: evidence for an alteration in mechanical interaction of actomyosin

We measured the relative sliding velocity of cardiomyopathic hamster cardiac myosin on actin cables by using an in vitro motility assay system. We also investigated the relationship between the velocity and both myosin isozyme content and ATPase activity. Cardiac myosin was obtained from cardiomyopathic hamsters (BIO 14.6; B) aged 3, 6, 9, and 18 months and age-matched controls (F1B; F). Long well-organized actin cables of an alga, Nitellopsis, were used for the motility assay. Small latex beads (2 microns in diameter) were coated with purified cardiac myosin. When myosin-coated beads were introduced into an algal cell in the presence of Mg-ATP, myosin interacted with actin and dragged the beads. Active movement of the beads along the actin cables was observed under a photomicroscope and the velocity was measured. The velocity was significantly lower in B than in F for each age group (0.47 vs. 0.71 microns/s at the age of 3 months, p < 0.05; 0.44 vs. 0.88 microns/s at 6 months, p < 0.01; 0.44 vs. 0.67 microns/s at 9 months, p < 0.01; 0.35 vs. 0.52 microns/s at 18 months, p < 0.05). Both Ca(2+)-activated ATPase activity and the percentage of alpha-myosin heavy chain were also lower in B than in F for each age group. When examined for individual specimens, there was a positive correlation between the velocity and both myosin Ca(2+)-activated ATPase activity (r = 0.84) and percentage of alpha-myosin heavy chain (r = 0.83). These data points of both control and cardiomyopathic hamsters were distributed near the regression line obtained from control and thyroxine-treated rabbits reported previously. The present results indicate that the difference in mechanical properties between control and cardiomyopathic cardiac myosin is attributed to isozyme redistribution and not to a qualitative change in each myosin molecule.

Dementia in cerebral amyloid angiopathy: a clinicopathological study

Dementia is in addition to cerebral haemorrhage major symptom of cerebral amyloid angiopathy (CAa). In order to explore the pathological basis for dementia in CAa-related conditions, we made a clinicopathological analysis of CAa, with special attention to dementia. Among 150 patients (mean age 78.6 years) with autopsy-proven intracranial haemorrhage in Tokyo Metropolitan Geriatric Medical Center, CAa with cerebral haemorrhage accounted for 8.0% (12 cases), associated with hypertension and metastatic brain tumour. Among 38 patients with lobar haemorrhage, CAa represented the second most common cause (21.1%) of intracranial haemorrhage after hypertension. A total of 20 patients with CAa (mean age 82.5 years) were studies clinically and pathologically. Hypertension was present in 50%. Thirteen had a history of stroke and others had either ill-defined or no strokes. The average number of strokes 2.9. Fifteen patients (75%) had dementia. Based on the clinicopathological grounds for dementia, CAa-related conditions could be divided into three subtypes: "haemorrhagic", "dementia-haemorrhagic" and "dementia" type. Haemorrhagic type (30%, 6 cases) showed multiple recurrent lobar haemorrhages caused by CAa. Hypertension was present in only 1 patient. The incidence of senile plaques and neurofibrillary tangles was generally correlated with age. Only 1 patient had dementia. The dementia-haemorrhagic type (40%, 8 patients) had recurrent strokes with cerebral haemorrhage after preceding dementia. There were two different neuropathological subsets: CAa with atypical senile dementia of Alzheimer type (SDAT) and CAa with diffuse leucoencephalopathy. Patients with CAa with atypical SDAT had multiple cerebral haemorrhages caused by CAa combined with atypical Alzheimer-type pathology. Patients with CAa with diffuse leucoencephalopathy had cerebral haemorrhages in combination with diffuse white matter damage like Binswanger's subcortical vascular encephalopathy (BSVE). The incidence of senile changes correlated with age. Patients with the dementia type (30%, 6 patients) showed progressive dementia with or without haemorrhage. All had hypertension. They had a combined condition of Alzheimer-type pathology with conspicuous CAa with BSVE. Dementia in CAa-related conditions may be responsible for multiple factors including not Alzheimer-type degeneration, but also diffuse leucoencephalopathy like Binswanger's disease. We also found an asymptomatic type, an ischaemic type, a vasculitis type and an hereditary type in this condition.

Sliding velocity of isolated rabbit cardiac myosin correlates with isozyme distribution

To investigate the relationship between the mechanical and biochemical properties of cardiac myosin, the sliding velocity of isolated cardiac myosin obtained from both euthyroid and hyperthyroid rabbits on actin cables was measured with an in vitro motility assay system. Ten rabbits (T) were treated with L-thyroxine to induce hyperthyroidism, and eight nontreated animals (N) were used as controls. Myosin was purified from the left ventricles of anesthetized animals. Myosin isozyme content was analyzed by the pyrophosphate gel electrophoresis method, and myosin adenosinetriphosphatase (ATPase) activity was determined on the same sample. Long well-organized actin cables of green algae, Nitellopsis, were used in the in vitro motility assay. Small latex beads were coated with purified cardiac myosin and introduced onto the Nitellopsis actin cables. Active unidirectional movement of the beads on the actin cables was observed under a photomicroscope, and the velocity was measured. The velocity was dependent on ATP concentrations, and the optimal pH for bead movement was approximately 7.0-7.5. The mean velocity was higher in T than in N (0.66 +/- 0.12 vs. 0.32 +/- 0.09 micron/s, P less than 0.01). Both Ca(2+)-activated ATPase activity and the percentage of alpha-myosin heavy chain were also higher in T than in N (0.691 +/- 0.072 vs. 0.335 +/- 0.072 microM Pi.mg-1.min-1, P less than 0.01, and 79 +/- 12 vs. 26 +/- 7%, P less than 0.01, respectively). The velocity of myosin closely correlated with both Ca(+2)-activated myosin ATPase activity (r = 0.87, P less than 0.01) and the percentage of alpha-myosin heavy chain (r = 0.87, P less than 0.01).

Cardiac adaptation and its limitation in an experimental model of congestive heart failure

To elucidate mechanisms of adaptation and maladaptation in heart failure, abnormalities of left ventricular function and their relationships to myocardial contractile protein were studied in the Syrian hamster Bio 14.6. Left ventricular and heart weights were both increased in 20-week-old cardiomyopathic hamsters, indicating cardiac hypertrophy as a compensatory mechanism to the disease process of cardiomyopathy. However further increase in the left ventricular weight was not observed in older (40-week-old) cardiomyopathic hamsters. On the other hand left ventricular volume and volume/mass ratio were increased progressively. Correspondingly, V3 type myosin was increased and myosin sliding velocity was decreased. Left ventricular function of cardiomyopathic hamsters evaluated using an isovolumically beating perfused heart preparation was depressed, and this functional impairment was also progressive. Chronic administration of metoprolol, a beta-blocking agent, induced further increase in left ventricular volume and mass without changing left ventricular function and myosin isozyme pattern. Thus in cardiomyopathic hamsters, left ventricular function progressively deteriorates in spite of a variety of adaptive mechanisms, and remodeling occurs.

Active movement of cardiac myosin on Characeae actin cables

The active sliding of cardiac myosin on actin cables was studied using an in vitro movement assay. Cardiac myosin prepared from either adult rabbit or rat hearts was mixed with small latex beads to coat them. Actin cables were obtained from the internodal cells of green algae, Characeae. When the myosin-coated beads suspended in physiological buffer were introduced into the internodal cells, the myosin started to interact with the actin causing the beads to move. The sliding movement of the beads was observed under microscopy and the sliding velocity measured. The observed movement was smooth and the velocity was constant over a long distance. The movement was physiological in nature: a) it was ATP-dependent, but above a certain level of ATP, the velocity was constant; b) the velocity was maximum at pH 7.0, and decreased in both acidic and alkaline conditions. The average sliding velocity of cardiac myosin obtained from rabbit ventricles (0.31 +/- 0.11 micron/s) was slower than that from rat ventricles (1.04 +/- 0.26 micron/s) reflecting the lower ATPase activity of rabbit cardiac myosin. This assay system is considered to be a useful tool linking biochemistry and physiology at the molecular level.

Enhancement of in vitro mineralization in human osteoblasts by a novel prostaglandin A1 derivative TEI-3313

Human osteoblasts derived from long bone periosteum were induced to mineralize in culture in the presence of 2 mM alpha-glycerophosphate, with typical characteristics of mineralization, namely, accumulation of hydroxyapatite and increases in alkaline phosphatase activity and in osteocalcin production. Mineralization was also enhanced by 10(-8) M 1 alpha, 25-dihydroxyvitamin D3. In this system, a prostaglandin A1 derivative, TEI-3313, with the chemical structure 5-[(Z,2E)-4,7-dihydroxy-2-heptenyridene]-4-hydroxy-2-methylthio-4- (4- phenoxybutyl)-2-cyclopentenone, was found to enhance mineralization as effectively as 1 alpha, 25-dihydroxyvitamin D3, although its potency was 10 times lower than that of the vitamin D3 metabolite. Osteocalcin, a bone-specific noncollagenous matrix protein, accumulated onto the cell layers by treatment with TEI-3313 to a much greater extent than those released into the culture medium. TEI-3313 also enhanced collagen synthesis. Based on the finding that TEI-3313 enhanced the synthesis of both collagen and noncollagenous protein, it is speculated that TEI-3313 enhanced the mineralization by stimulating the expression of various genes in osteoblasts.

Effect of a bradycardic agent on the isolated blood-perfused canine heart

Bradycardic agents could limit the consequences of myocardial ischemia via two mechanisms: by decreasing myocardial oxygen demand (MVO2) and by increasing diastolic coronary blood flow (CBF). We investigated whether the benzazepinone UL-FS 49 affects only sinus node cells or also smooth muscle and/or myocardial cells. To avoid confounding interactions with the periphery, we performed experiments on 11 isolated, blood-perfused canine hearts. Injection of UL-FS 49 (1 mg/kg i.c.) significantly reduced heart rate (HR) from 104 +/- 7 to 93 +/- 7 min-1 (mean +/- SEM) and increased stroke volume (n = 6: 9.8 +/- 1.1 vs. 13.2 +/- 1.6 ml), so that cardiac output remained unchanged (n = 6: 1.1 +/- 0.1 vs. 1.2 +/- 0.1 l/min). The contractile state, assessed by isovolumic peak systolic pressure, was unaltered by UL-FS 49 (n = 5: 72 +/- 6 vs. 72 +/- 6 mmHg). At a constant coronary arterial pressure (CAP) of 80 mmHg, mean CBF was slightly decreased (102 +/- 11 vs. 97 +/- 10 ml/[min.100 g]) by UL-FS 49, such that mean coronary resistance remained unchanged (0.9 +/- 0.1 vs 1.0 +/- 0.1 mmHg.min.100 g/ml). The slight decreases in arteriovenous oxygen content difference (n = 6: 6.6 +/- 0.7 vs. 6.5 +/- 0.7 ml/100 ml) and in CBF lead to a calculated, significant decrease in MVO2 (n = 6: 6.9 +/- 0.5 vs. 6.0 +/- 0.4 ml.100 g/min). In conclusion, UL-FS 49 at the dose used decreases MVO2 by reducing HR in isolated canine hearts. In the absence of negative inotropic and vasodilating effects, cardiac output is maintained via increased stroke volume, and CAP will likely be preserved in situ. Thus, this specific bradycardic agent could be useful in treating ischemic myocardial disease.

Dynamic properties of left ventricular response to changes in coronary perfusion

To determine the dynamic property of cardiac function response to alterations in coronary perfusion, we varied coronary arterial pressure (CAP) sinusoidally around one of four mean CAP levels with a constant amplitude at several frequencies in isolated, isovolumically contracting canine heart preparations. From the frequency spectrum of the peak left ventricular pressure (PLVP) response, we arrived at a phenomenological model with two components coupled in parallel and estimated the parameter values. One component is a first-order delay system having a short time constant (approximately 1 s) and a small gain (range 0.08-0.16); it probably represents a hydraulic effect of coronary perfusion. The other component is a second-order delay system with longer time constants (approximately 15 and 6 s) and a larger gain (range 0.14-0.69); this probably represents a metabolic effect. The gain value of the slow component varied inversely with the mean CAP level, and studies with adenosine suggested that this dependence was due to the coronary autoregulation. The model prediction of the transient responses of PLVP to step changes in CAP agreed reasonably well with those experimental data of transient responses obtained in the identical hearts but not used to determine the model parameter values.

[Individual differences in image and pulse-wave responses elicited by listening to music]

This study was undertaken to clarify individual differences in psycho-physiological responses observed in subjects listening to music. Forty-five healthy females listened to the third movement of Mozart's "Eine Kleine Nachtmusik" via a biaural headphone at 69.4 dB(A) in Leq and 83.6 dB(A) in Lmax. This was undertaken twice with an interval of six days between sessions. Pulse-waves were recorded continuously before, during, and after listening by using a photoelectric plethysmograph. The psychological image each listener had of the music was measured immediately after listening by the SD method composed of fifteen scales with five rating points. The following results were obtained: 1) The pulse-wave height initially became low right after the onset of listening, though the degree of the decrement weakened in the second trial. Spectral analysis of pulse-waves revealed that the power percentage in the low frequency-bands below 0.3912 Hz grew markedly and that in the frequency-bands above 0.4238 Hz it dwindled during and after listening at the first trial. However, these changes of power percentage weakened in the second trial. 2) The image of the music being listened to changed significantly in 11 scales from the first trial to the second trial. 3) Subjects having a previous experience of listening to the music showed smaller image changes and responses in pulse-waves in the second trial than subjects having no such experience. 4) Previous experience of learning any music and the amount of contact with any music were not related to the image changes and pulse-wave responses in the second trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Preservation of ventricular function by treatment of ventricular fibrillation with phenylephrine

Epinephrine promotes resuscitation from ventricular fibrillation because of its peripheral vasoconstrictive effects. However, the beta-adrenergic effects of epinephrine may be detrimental because of the stimulation of myocardial oxygen demand. To test whether functional recovery from fibrillation in hearts treated with a selective alpha-adrenergic agent is greater than in hearts treated with epinephrine, ventricular fibrillation was induced in eight isolated dog hearts while coronary perfusion pressure was maintained at 30 mm Hg. In random order, epinephrine (5 micrograms/min), phenylephrine (50 micrograms/min) or no drug was infused for 5 min. The heart was then defibrillated, the drug infusion stopped and coronary perfusion pressure increased to 100 mm Hg. Coronary blood flow (ml/min per 100 g), arteriovenous oxygen difference (ml O2/dl) and myocardial oxygen consumption (ml O2/min per 100 g) measured after 4 min of ventricular fibrillation were greater with epinephrine (mean +/- SD 30.9 +/- 11.7, 17.5 +/- 1.6 and 5.4 +/- 1.9, respectively) than with phenylephrine (24.4 +/- 6.0, 15.7 +/- 2.6 and 3.8 +/- 1.1, respectively) or no drug (19.8 +/- 5.2, 12.8 +/- 1.8 and 2.6 +/- 0.7, respectively) (p less than 0.05, p less than 0.05 and p less than 0.05, respectively). The slope of the end-systolic pressure-volume relation 10 min after defibrillation and restoration of normal coronary perfusion pressure was depressed (percent of prefibrillation value) most by epinephrine infusion (72 +/- 17%, n = 6), less by no drug infusion (82 +/- 12%, n = 4) and was increased after phenylephrine infusion (143 +/- 17%, n = 6) (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)