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Biomedical subjects

T Iijima

Publications and source records attributed to T Iijima.

At least 397 records · Page 22Linked to original sources
PubMed1982

Modification of the baroreceptor reflex by superfusion of the canine posterior hypothalamus with tetrodotoxin.

The role of the posterior hypothalamus in the baroreceptor reflex was investigated in dogs. The posterior hypothalamus was superfused bilaterally through push-pull cannulae with artificial cerebrospinal fluid. After bilateral superfusion with tetrodotoxin (10(-5) M) for 120 min, the increases in mean arterial pressure and heart rate induced by the electrical stimulation of the posterior hypothalamus were almost abolished, and the resting mean arterial pressure was significantly decreased. Under these circumstances the increases in mean arterial pressure and heart rate in response to bilateral carotid occlusion were significantly reduced. The decrease in mean arterial pressure induced by intravenous injection of sodium nitroprusside (5 micrograms/kg) was significantly augmented while the associated increase in heart rate was suppressed. These results suggest that the posterior hypothalamus plays an important role in maintaining the resting arterial pressure and in the baroreceptor reflex to increase the arterial pressure and heart rate.

Animals↗
PubMed1982

Inhibition by theophylline of the early component of canine ventricular contraction.

Changes in mechanical characteristics of the isolated canine ventricular muscle were investigated during interaction of isoproterenol with theophylline or caffeine. An early and a late component with time to peak tension of 80 and 150 ms, respectively, were differentiated in a single contraction of the muscle stimulated at 0.5 Hz at 37 degrees C during the interaction of isoproterenol and theophylline, or isoproterenol and caffeine. Isoproterenol increased preferentially the early component and affected only slightly the late one. Theophylline or caffeine elevated the early component less than the late one. In the presence of theophylline + isoproterenol or caffeine + isoproterenol the peak tension was achieved by a late component, whereas the increase in the early one induced by isoproterenol in 3 X 10(-7) M and higher was depressed significantly. During the interaction the rate of twitch relaxation was accelerated further rather than depressed. Changes in action potential indicate that the calcium influx via the myocardial cell membrane during depolarization was increased: the peak plateau potential was significantly elevated by theophylline alone and further by theophylline + isoproterenol. These results indicate that theophylline and caffeine (2 mM) may act intracellularly to inhibit the isoproterenol-induced promotion of the early component without impairing the isoproterenol-induced acceleration of relaxation in the canine ventricular muscle.

Animals↗
PubMed1982

Depression by carbachol of calcium-dependent action potentials in the canine ventricular muscle depolarized by potassium.

Effects of carbachol on the Ca2+-dependent action potentials were investigated in the canine ventricular muscle which was depolarized and made inexcitable by elevation of the extracellular concentration of K+ ([K+]0) to 30 mM. Regenerative action potentials ("the slow response") were induced by electrical stimulation at low frequency with high intensity (0.1 Hz, 5 msec duration and 5 mA). The amplitude of the slow response varied 31 mV for a tenfold change in [Ca2+]0. The amplitude and duration of the slow response were increased by isoproterenol (10(-7) M) and were decreased by carbachol (3 X 10(-6) M). The actions of carbachol on the slow response were antagonized by atropine (10(-6) M). Propranolol (3 X 10(-7) M) decreased the amplitude and duration of the slow response. In the presence of propranolol, carbachol (3 X 10(-6) M) produced a further decrease in the amplitude and duration of the slow response. These results suggest that electrical stimulation induces the slow response which is augmented by catecholamines released from the adrenergic nerve endings in response to the stimulation and/or K+-depolarization. Carbachol depresses the slow response by its muscarinic action which may involve both "indirect" and "direct" effects, the former being the effect caused by counteracting the catecholamine-induced augmentation of the slow response and the latter, the effect irrespective of catecholamines.

Action Potentials↗
PubMed1981

Biochemical and genetic characterization of an auxotroph of Bacillus subtilis altered in the Acyl-CoA:acyl-carrier-protein transacylase.

We have analyzed a mutation of Bacillus subtilis (bfmB) that results in an acyl-CoA:acyl-carrier-protein transacylase with low affinity for branched acyl-CoA substrates; it maps in the acf-hisH region of the chromosome. The aceA mutation, present in the parent of the bfmB mutant, causes a deficiency in pyruvate dehydrogenase and maps in the pycA-pyrA region. Strains carrying the bfmB mutation synthesize branched-chain fatty acids at a rate sufficient for normal growth only if branched acyl-CoA precursors are present in the medium. They grow well if the medium is supplemented with 0.1 mM 2-methylbutyrate, isobutyrate or isovalerate, or with 1.0 mM isoleucine or valine; leucine does not support growth. Growth supported by valine and isoleucine is inhibited by butyrate and other straight short-chain fatty acids at concentrations (0.1 mM) which do not inhibit growth of the standard strain; the inhibition is prevented by short branched fatty acids which are converted to long-chain fatty acids appearing as activity of B. subtilis is controlled by separate enzymatic sites for the acyl-CoA precursors of branched and straight-chain fatty acids. Whether these sites are contained in one or two enzymes is not known.

Acetyl Coenzyme A↗
PubMed1981

Urinary excretion of cyclic nucleotides and principal electrolytes in healthy humans of different ages.

Urinary excretion of cyclic AMP, cyclic GMP, inorganic phosphorus, calcium, sodium, potassium and creatinine was measured in 138 healthy male and 104 healthy female humans from 2 to 68 years old. The range of cyclic nucleotide excretion was as follows: cyclic AMP (mumol/day), 1.01-10.89; cyclic GMP (mumol/day), 0.13-2.00; cyclic AMP (mumol/g creatinine), 1.52-8.93; cyclic GMP (mumol/g creatinine), 0.11-1.87. The 242 volunteers were grouped into seven classes according to age: A, 2-9 years old; B, 10-19; C, 20-29; D, 30-39; E, 40-49; F, 50-59 and G, 60-68. Average excretion (mumol/day) of cyclic AMP in class A (2.62 +/- 0.29 for males and 2.30 +/- 0.18 for females) was significantly smaller than that in other classes (4.59 +/- 0.12 for males and 3.90 +/- 0.13 for females) (p less than 0.01). Such a significant difference was not observed in cyclic GMP excretion. In terms of mumol/g creatinine, however, average excretion of both cyclic AMP and cyclic GMP in class A was greater than that in other classes. The amounts of urinary cyclic AMP and cyclic GMP (mumol/day) were correlated with age in the subjects from 2 to 16 years. A reverse correlation between the amounts of both nucleotides (mumol/g creatinine) and age was found in the young subjects. No correlation between the excretion of either urinary cyclic nucleotide and age was found in adults. A significantly positive correlation between cyclic AMP (mumol/day) and inorganic phosphorus (g/day) was found (r = 0.50 for males and 0.56 for females) (p less than 0.01). This correlation suggests that urinary cyclic AMP might reflect the activity of parathyroid hormone in normal humans. There was no significant correlation between cyclic GMP and electrolytes tested. The above results are considered to provide basic data for clinical evaluation of relevant disorders.

Adolescent↗
PubMed1981

Occurrence of uranaffin-positive synaptic vesicles in both adrenergic and non-adrenergic nerves of the rat anococcygeus muscle.

The uranaffin reaction in rat anococcygeus muscle, which receives a dual innervation of both adrenergic and non-cholinergic, non-adrenergic nerves was examined. Dense reaction product was observed in the vesicular membranes and/or the cores of some synaptic vesicles in the adrenergic nerve terminals. Occasional vesicles were filled up with dense reaction product. In the prominent population of small clear vesicles, however, no dense reaction product was observed. The number of small granular vesicles in the adrenergic nerve terminals was markedly increased after the administration of 5-hydroxydopamine (5-OHDA). These granular vesicles were moderately stained with uranaffin deposit on the cores but their limiting membranes possessed no uranaffin deposit at all. In the non-adrenergic nerve terminals, on the other hand, uranaffin deposit of variable density was observed on the cores of large granular vesicles but never on their limiting membranes or on the small clear vesicles. There was no change in the axon profiles after the administration of 5-OHDA. The possible occurrence of purines in the cores of large granular vesicles in the non-adrenergic nerves is discussed.

Adrenergic Fibers↗
PubMed1981

Chromosomal loci of genes controlling site-specific restriction endonucleases of Bacillus subtilis.

We constructed transformation of B. subtilis 168 which acquired genes for site-specific restriction endonucleases. These endonucleases originated from various strains of B. subtilis and were classified into five groups based on the specificity of the sequences recognized by the enzymes. We examined the loci of genes for site-specific restriction endonucleases belonging to different groups: hsrE determined Endo. R. Bsu1231 (I), hsrB Endo.R.Bsu1247(I), hsrR Endo.R.BsuR and hsrC Endo.R.Bsu-1247(II). One gene, hsrE, was located between sacA and purA by transduction crosses with phage PBS1, and another gene, hsrB, between hsrE and purA. Genes hsrR and hsrC had been suggested to be allelic or closely linked by previous studies with transformation. We located hsrR and hsrC between purB and tre. Our previous observation and this study show that B. subtilis 168 has at least three independent loci on the chromosome for four genes for site-specific restriction endonucleases in addition to the locus for the original restriction activity (Bsu168-specific restriction) of strain 168.

Bacillus subtilis↗
PubMed1981

Dependence on ionic strength of charge-induced coil-helix transition of sodium poly(L-glutamate) in aqueous solution.

Helix contents of sodium poly(L-glutamate) in aqueous NaCl solutions were estimated as functions of the degree of ionizalion, alpha. and the salt concentration by CD measurement. The helix content increases with increasing salt concentration but this helix stabilization decreases with decreasing alpha and at alpha<0.25 the helix conformation is destabilized by salt addition. The alpha dependence of the helix stabilization was qualitatively interpreted by Manning's theory in which electrostatic interactions between charges on alternatively arrayed coil and helix segments in a simplified polymer model were incorporated.

Journal Article↗
PubMed1981

Twitch potentiation by rest in canine ventricular muscle: effects of theophylline.

Short rest of the regular stimulation of the isolated canine right ventricular muscle induced a large transient increase of subsequent twitch tension (rest-twitch potentiation, RTP). This RTP attained the maximum level when the rest period was 120 s and decayed progressively at longer rest periods. The rate of regular stimulation prior to rest affected the degree of RTP but not the time course of RTP. The action potential duration was prolonged progressively after rest until 120 s and maintained this level at longer rest periods. Under the same experimental condition, RTP was not induced in the rabbit papillary muscle. Theophylline, caffeine, and epinephrine increased the strength of steady-state contraction, whereas RTP was inhibited by theophylline and caffeine and unaffected by epinephrine. Manganese and D 600 significantly reduced the strength of steady-state contraction but did not affect the degree of RTP. These results indicate that RTP is induced via a mechanism different from that regulating the steady-state contraction.

Action Potentials↗
PubMed1981

The fine structure of the merozoites and gametocytes of Leucocytozoon caulleryi.

The fine structure of the merozoites and gametocytes of Leucocytozoon caulleryi from the peripheral blood of chickens was studied by means of electron microscopy. Merozoites are oval to elongate and are surrounded by a pellicle. They possess a large nucleus, numerous ribosomes, microtubules, a mitochondrion with tubular cristae, a cytostome, an apical complex consisting of three polar rings, electron-dense paired rhoptries, and micronemes. Mature gametocytes are irregular in shape and are surrounded by a three layered pellicle, and contain a large nucleus, mitochondria with tubular cristae, endoplasmic reticulum, numerous ribosomes, food vacuoles, cytostomes, and lipid inclusions. Macrogametocytes are easily distinguished from the microgametocytes by more ribosome concentration and the presence of well developed endoplasmatic reticulum.

Animals↗