Search PubMed⌕ Search

Biomedical subjects

H Arita

Publications and source records attributed to H Arita.

At least 163 records · Page 9Linked to original sources
PubMed1987

Detection of enterotoxigenic Escherichia coli by colony hybridization with biotinylated enterotoxin probes.

By using biotinylated enterotoxin DNA probes, a method to detect enterotoxigenic Escherichia coli by colony hybridization was developed. The treatment of colonies on nitrocellulose membrane filters with proteinase K and Triton X-100 was essential for obtaining the specific hybridization. A total of 200 E. coli strains isolated from travelers with diarrhea were tested for colony hybridization by using a probe encoding heat-labile toxin (LT) type h. All strains (86 of 86) that produced LT, but none of the non-LT producers, hybridized with 32P-labeled and biotinylated LT type h probes. A total of 36 strains chosen randomly from the 200 isolates were tested for colony hybridization by using heat-stable enterotoxin (ST) probes. All but two strains that hybridized with the 32P-labeled ST type Ia probe also hybridized with the biotinylated ST type Ia probe. All strains that hybridized with the 32P-labeled ST type Ib probe also hybridized with the biotinylated ST type Ib probe. Thus, almost all E. coli strains tested were judged to be the same by colony hybridization with biotinylated or 32P-labeled enterotoxin probes. These results demonstrate that the biotinylated enterotoxin probes are useful in the diagnosis of enterotoxigenic E. coli strains by colony hybridization.

Bacterial Toxins↗
PubMed1987

Influence of beta-lactam antibiotics on platelets. II. In vitro effects of some beta-lactam antibiotics on the biochemical responses of rat platelets.

The inhibitory mechanism of beta-lactam antibiotics on rat platelet activation was studied using carbenicillin (CBPC) as a representative of the antibiotics. CBPC suppressed all thrombin-induced cellular responses, including shape change, secretion and aggregation; however, it only suppressed aggregation of adenosine diphosphate (ADP)-induced responses. This suggested that ADP-binding to its own receptor was not affected by CBPC while thrombin-binding was inhibited. Inhibition of thrombin binding was confirmed using [125I]thrombin. In the case of ADP-stimulated platelets, fibrinogen-binding, which has an essential role for ADP-induced primary aggregation, was significantly suppressed by CBPC. Increase in a net negative charge of the membrane surface was observed after treatment of platelets with antibiotics and a good correlation was obtained between suppression of the platelet responses and increase in net negative charge of the antibiotics. These findings strongly suggest that the inhibition of ligand binding to their own receptors was due to the increase in the negative charge of the platelet membrane, which was probably caused by the antibiotic bound to the platelet membrane.

Adenosine Diphosphate↗
PubMed1987

Seadragon VI: a 7-day saturation dive at 31 ATA. V. Cardiovascular responses to a 90 degree body tilt.

Cardiovascular deconditioning (CD) has been reported to occur in weightlessness, bed rest, and head-out water immersion. An expanded intrathoracic blood volume results, at least initially, in all these diverse conditions. Subjects in hyperbaric environments exhibit cephalad redistribution of blood volume, which also occurs in weightlessness, bed rest, and head-out water immersion. This physiologic similarity led us to suspect that CD may also occur as a consequence of hyperbaric exposure. We examined this possibility in 3 young male subjects during a 7-d dry saturation dive at 31 ATA. Changes in blood pressure, heart rate, and stroke volume were measured before and during 15 min of the 90 degree body tilt. These changes, expressed either singly or in combination, provided indications of CD during and immediately after hyperbaric exposure. One of the principal indicators of CD was the inability to exert adequate vasoconstriction. In addition, 1 subject fainted during hyperbaric exposure, whereas no such episode occurred before or after the exposure. These findings suggest that inappropriate orthostatic reflexes may be evoked by hyperbaria and reduced physical activity over the period of confinement. It should be noted, however, that CD was already evident within 24 h of hyperbaric exposure, suggesting that the initial phase of CD was unrelated to physical confinement. We postulate that CD occurs during hyperbaric exposure as an expression of cardiovascular and neurohumoral adaptation to an expanded central blood volume with a reduced total blood volume.

Adult↗
PubMed1986

Measurement of thromboxane A2-induced elevation of ionized calcium in collagen-stimulated platelets with the photoprotein, aequorin.

Using aequorin-loaded rat platelets stimulated with collagen, we found two phases of Ca2+ mobilization, one coinciding with a shape change and the other with aggregation, which have not yet been detected in quin2-loaded platelets. U46619, a stable analogue of prostaglandin H2, induced only a shape change and a concomitant rapid rise in the cytoplasmic ionized calcium concentration ([Cai2+]). However, upon addition of U46619 to platelets previously stimulated with collagen in the presence of indomethacin, a rapid increase in [Cai2+] and a shape change occurred, and, after about 1 min, second increase in [Cai2+] and aggregation occurred. The actions of U46619 were inhibited by an antagonist for the thromboxane A2 (TXA2) receptor. These results suggest that the collagen-induced shape change is initiated by TXA2-induced Ca2+ mobilization, and aggregation is induced by the secondary Ca2+ mobilization induced by TXA2 and the occupation of the receptor by collagen.

Aequorin↗
PubMed1986

Conjugal acquisition and stable maintenance of Ent plasmids in nontoxigenic wild-type strains of Escherichia coli.

In spite of the ability of the genetic determinants for enterotoxin production to be conjugally transferred, mobilized or transposed, enterotoxigenic Escherichia coli (ETEC) isolated from diarrheal patients is restricted to certain serotypes. Four conjugative enterotoxigenic plasmids (Ent plasmids) encoding either a heat-labile enterotoxin or a heat-stable enterotoxin or both and belonging to one of three incompatibility groups IncFI, IncHl, or IncX, were examined for their transferability to and stability in 157 nonenterotoxigenic Escherichia coli strains belonging to various serotypes and 89 clinical isolates nonenterotoxigenic but belonging to those serotypes in which ETEC from diarrheal patients are usually found. The serotypes of the strains to which Ent plasmids were efficiently transferred and in which they were maintained stably were not always the serotypes in which ETEC had usually been found and vice versa. The frequencies of transfer of four Ent and two R plasmids to each of the 157 recipients were correlated with each other, indicating that the frequency of transfer of the plasmid is not determined by a resident plasmid, if there is one, but by a recipient factor which commonly affects transferability to all donors. These results have led to the conclusion that the reason why only certain serotypes are found among ETEC isolated from diarrheal patients is not the ability of these strains specifically and preferentially to acquire and maintain the Ent plasmids.

Conjugation, Genetic↗
PubMed1986

Influence of beta-lactam antibiotics on platelets. I. In vivo effects of latamoxef and related beta-lactam antibiotics on membrane proteins and glycoproteins of rat platelets.

The effects of latamoxef (moxalactam) and the other beta-lactam antibiotics on platelet membrane were studied by intravenous administration of these drugs to rats for 8 d. Blood was taken from the abdominal aorta and washed platelets were prepared by centrifugation. Platelet membrane proteins labeled with 125I and the glycoproteins with 3H were used and analyzed by electrophoresis. Differences of membrane proteins and glycoproteins, compared with the control, were not observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two dimensional electrophoresis.

Animals↗
PubMed1983

Responses of cat's internal intercostal motor units to hypercapnia and lung inflation.

Single motor unit potentials from the eighth internal intercostal (IIC) muscle were recorded along with tracheal pressure and end-tidal CO2 (PETCO2) in spontaneously breathing, Dial-urethane anesthetized cats during hypercapnia (3, 5, or 7% CO2) and during lung inflation (LI, 100 ml above functional residual capacity) before and after vagotomy. Hypercapnia depressed IIC activity in 5 of 7 cats; the higher the PETCO2, the lower was the firing rate and the fewer the number of spikes per breath. LI evoked an initial silent phase (ISP) in 6 of 10 cats followed by a prolonged IIC burst. Hypercapnia combined with LI abolished or diminished the ISP and shortened the prolonged burst with an increase in firing rate and a recruitment of new units. Vagotomy silenced IIC activity in 7 of 10 cats, but LI after vagotomy activated IIC activity in 10 of 10 cats, though neither an ISP nor prolonged activity occurred. Our data suggest that major factors in controlling IIC activity are reciprocal inhibition from bulbospinal inspiratory neurons, excitatory and inhibitory inputs mediated by vagal afferents, and a modulation of IIC activity via gamma-loop. Hypercapnia affects the former two factors.

Action Potentials↗
PubMed1983

Firing profile of diaphragm single motor unit during hypercapnia and airway occlusion.

To define interaction between chemical and vagal-volume feedback we recorded diaphragm single motor unit (SMU) potentials, tracheal pressure, and end-tidal CO2 in spontaneously breathing, anesthetized cats during hypercapnia and during airway occlusion at functional residual capacity (FRC) or end-inspiratory level (EIL) before and after vagotomy. Hypercapnia increased onset, mean, and peak firing frequencies of early-onset SMUs, caused no change in number of spikes per breath (NSPB), and decreased inspiratory burst duration (Tdi). Airway occlusion increased both NSPB and Tdi without changing onset or mean frequencies. NSPB and Tdi increased more during FRC occlusion than during EIL occlusion. Vagotomy caused effects similar to airway occlusion, except that onset frequency decreased. Increases in NSPB or Tdi following vagotomy were greater than those during FRC occlusion. After vagotomy, airway occlusion no longer altered SMU activity, but hypercapnia still increased onset, mean, and peak frequencies, caused no change in NSPB, and decreased Tdi. New findings in this study are 1) the constancy in NSPB of diaphragm SMUs in response to hypercapnia and 2) the decrease in the onset frequency after vagotomy.

Airway Obstruction↗
PubMed1983

Multiplicity of functional behavior of human intercostal muscles.

Single motor unit activity from the 6th intercostal space in five healthy adults was analyzed during rebreathing, voluntary deep inspiration, Valsalve maneuver and phonation. Action potentials and pneumotach flow were stored on tape and fed to the computer for subsequent analysis. Spike-by-spike analyses revealed three functional types of intercostal motor units. One unit fired almost exclusively during inspiration and its firing was augmented by rebreathing and voluntary deep inspiration (phasic I unit). The second type fired continuously throughout the respiratory cycle with an increase in firing during expiration (tonic E unit); its activity was disrupted during phonation but not during rebreathing, suggesting a postural rather than respiratory function. The third type, silent during quiet breathing, was recruited during rebreathing, voluntary deep inspiration or Valsalve maneuver; its firing started in late inspiration and ceased in early expiration (phase-spanning I-E unit). The relationships between tidal volume and inspiratory time during rebreathing showed that the third type was recruited when tidal volume reached a critical 'volume threshold', suggesting that vagal volume feedback is essential for its activation.

Adult↗