Multiple resistance to aminoglycoside antibiotics in actinomycetes

Actinomycetes were characterized in terms of resistance to 11 different aminoglycoside antibiotics (AGs). Strains freshly isolated in AG containing media showed wide varieties of multiple AG resistance, while the majority of ISP (International Streptomyces Project) cultures and the actinomycete strains isolated in an AG free medium were susceptible to all or most of the AGs tested. Marked characteristics were noted in multiple AG resistance of gray and yellow colored actinomycetes and AG-producing strains. In gray colored isolates, multiple resistance to kanamycin A, dibekacin, ribostamycin, butirosin A, istamycin A and neamine was often observed. Yellow colored isolates having multiple AG resistance were mostly resistant to neamine, ribostamycin and streptomycin and, to a lesser extent, istamycin A, dibekacin and butirosin A. Most of the AG producers tested showed unique multiple AG resistance patterns.

[Effect of diltiazem on experimental cerebral vasospasm incomparison with effects of cinnarizine, verapamil and nifedipine]

The contractile activity of arterial muscle cells is controlled by the intercellular free Ca2+ concentration. The membrane systems of both the cell surface and internal organs, seem to be responsible for controlling the myoplasmic Ca2+ level. The mechanism of action of Ca2+ antagonists, typified by verapamil and nifedipine, has been postulated to be a blockade of transmembrane calcium influx. In this study, the vasodilating effect of diltiazem on experimental cerebral vasospasm in vivo was examined using dogs and was compared with those of cinnarizine, verapamil and nifedipine which have already been reported by us. Cerebral vasospasms were induced in adult dogs by injecting 5 ml of fresh arterial blood into the cisterna magna. 10(-6)M diltiazem was injected by one shot into the vertebral artery with cerebral vasospasm. Dilatation of the cerebral arteries were monitored by angiography after administration of diltiazem. Blood pressure, intracranial pressure and pulse rate were measured during intravenous application of the drug in normal animals. Administration of diltiazem released the vasospasm for 30 minutes comparable to the times of the other Ca2+ antagonists. Diltiazem had cerebral vasodilator actions similar to cinnarizine at doses that did not decrease systemic blood pressure, while the other drugs decreased intracranial pressure slightly and nifedipine decreased pulse rate slightly. Therefore, we consider diltiazem to be satisfactory for the treatment of experimental cerebral vasospasm.

Effect of geranylgeranylacetone on aspirin-induced changes in gastric glycoproteins

The effects of aspirin and treatment with geranylgeranylacetone (GGA), an antiulcer drug, on the content of gastric glycoproteins were investigated in pylorus-ligated rats. In normal rats, the amount of gastric glycoproteins in the mucous layer was about 1.5 times higher than that in the gastric mucosa, indicating that the glycoproteins were distributed in the mucous layer as a highly concentrated state. Aspirin (100 mg/kg, p.o.) decreased the content of gastric glycoproteins both in the mucous layer and in the gastric mucosa. The amount of the macromolecular fraction in the gastric juice, which corresponded to the gastric glycoproteins on the basis of molecular size, was not affected by aspirin. GGA (300 mg/kg, i.d.) could prevent the decreases of the total amount of gastric glycoproteins in the mucous layer plus gastric mucosa. These results indicated that the glycoproteins coating the surface of the gastric mucosa may play a role as a defensive mechanism and that GGA exerted an antiulcer effect on aspirin-induced mucosal damage through preventing the decreases in gastric glycoproteins.

The effect of changing free Ca2+ on light diffraction intensity and correlation with tension development in skinned fibers of frog skeletal muscle

The relationship between the diffraction intensity change of the first order line and tension development was examined in mechanically skinned single fibers from the dorsal head of the semitendinosus of frogs. Passive stretch of the fibers resulted in an increase in intensity over the range of sarcomere lengths from 2.5 to 3.6 microns, indicating that the intensity is a function of sarcomere length. Activation of skinned fibers caused a decrease in the intensity, at all sarcomere lengths, where the thick and thin filaments overlapped. The magnitude of the intensity decrease and that of the tension development depended on the Ca2+ concentration in the medium. The drop of intensity-pCa and the tension-pCa curves showed a similarly steep S-shape within a range of 0.5pCa unit, although the intensity-pCa curve shifted to the left; the pCa for 50% decrease in light signal was 6.48 and that for 50% tension development was 6.40. Caffeine (25 mM) added to the medium produced a decrease in the intensity of skinned fibers with the simultaneous development of tension, thereby indicating that caffeine induces a release of Ca2+ from the sarcoplasmic reticulum and disorder in the filaments ensues. Changes in diffraction intensity with electrical stimulation to the intact single fiber were similar, although a more striking summation was observed in the optical response, as compared to the tension development. These results suggest that tension development upon stimulation can be monitored by assessing the magnitude of diffraction intensity decrease in the first order line, except for some shift in the short fiber.

Ionic mechanisms involved in the strontium-induced spike and plateau in the smooth muscle of rat portal vein

The action of Sr on the smooth muscle of rat portal vein was studied electrophysiologically using micro-electrodes. By replacing Ca with Sr (2.5 mM), the spontaneous membrane activity was altered and spikes were followed by a long lasting plateau potential. The mechanisms which generated the spike and the plateau in the Sr-induced activity were elucidated. As the concentration of Sr was increased, the peak potential and the maximum rates of rise and fall of the initial spike in each discharge increased. The peak potential varied by 15.2 mV with a 10-fold change in [Sr]o. As there was a decrease in the membrane resistance during the plateau, an increase in the permeability of the membrane for Sr, Cl or Na could be responsible for generation of the plateau. The amplitude of the plateau decreased with increase in the concentration of Sr, remained unchanged in a low-Cl solution, but was diminished in a low-Na solution. Mn (1-2 mM) inhibited not only the spike but also the plateau. TEA (20 mM) shifted the plateau potential in a positive direction and the plateau became permanent. When inward currents were applied in the presence of TEA, spikes with large overshoots and small rates of fall were induced. These results indicate that Sr and K conductances of the membrane generate the spike and that slow-inactivating voltage-dependent Na conductance produces the plateau.

Relationship between light diffraction intensity and tension development in frog skeletal muscle

Laser diffraction intensity decrease in active muscles precedes tension development at sarcomere lengths below 2.76 microns, but not at greater lengths. This suggests that the time lag is caused by random sarcomere shortenings inside each myofibril.

Membrane potential of rat urinary bladder epithelial cells

Rat urinary bladder epithelial cells exhibited a membrane potential of about -22 (apical) and -24 (basal) mV in normal Krebs solution. Blockade of Na+ entry through the apical membrane by Na+ depletion of administration of amiloride, or inactivation of the Na pump in the basal membrane by ouabain resulted in marked hyperpolarization of the epithelial cells. N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN), a specific carcinogen, and saccharin, a potent enhancer of carcinogenesis, inhibited development of the Na+ channel and/or Na pump on the bladder epithelium. This physiology may contribute to the abnormal intracellular environment leading to bladder carcinoma.

Mechanical, electrical, and morphological characteristics of skeletal muscle fibers from Xenopus and other species of frogs

Mechanical, electrical, and morphological properties of iliofibularis or semitendinosus of Xenopus laevis, Rana catesbeiana, and Rana nigromaculata were investigated in an attempt to find out the differences between them which will give the basic knowledge for the study of excitation-contraction coupling. With application of electrical stimulation, a single muscle fiber from Xenopus contracted at a faster rate of rise than did the other muscles tested. The maximum rate of rise (Tmax) of tension was in the order of Xenopus, R. catesbeiana, and R. nigromaculata. Ca2+ sensitivity and Tmax of mechanically skinned fibers of Xenopus resembled those of R. catesbeiana. Xenopus muscle had a small cross-sectional area of T-tubule compared with that in other species and the action potential exhibited a small positive-going hump. The volume density of the terminal cisternae of sarcoplasmic reticulum (SR) to the myofibril was the largest in the Xenopus muscle, with a statistically significant difference. Therefore, the Xenopus muscle appears to be good material for investigation of mechanisms related to Ca2+ release from SR, as elicited by the excitation of T-tubules.

The site of sulfated glycoprotein biosynthesis in rat gastric mucosa

The site of the synthesis of the sulfated glycoproteins in rat gastric mucosa using organ culture system has been studied. About 98% of the 35S radioactivity associated with the glycoproteins was found in corpus region. The sulfated glycoproteins were synthesized mainly in corpus, poorly in antrum and none in forestomach. The synthesized sulfated glycoproteins were heterogeneous by equilibrium centrifugation in CsCl density gradients. The 35S-labeled oligosaccharides released from the glycoproteins under alkaline condition were composed of 4-8 sugar residues.

Membrane potentials of urinary bladder epithelium in F344 rats treated with N-butyl-N-(4-hydroxybutyl)nitrosamine or sodium saccharin

Membrane potentials of the urinary bladder epithelium in F344 male rats treated with N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) or sodium saccharin were measured. In experiment 1, membrane potentials were measured sequentially in the early stage of their change on treatment with 0.05% BBN in the drinking water or with basal diet containing 5% sodium saccharin. Membrane potentials were measured with microelectrodes in weeks 1, 2, 4 and 8 of the experiment. The potential of the group treated with BBN was significantly higher than that of the controls from as early as week 1 until the end of the experiment. In experiment 2, the dose-dependence of the effects of BBN and sodium saccharin on the membrane potential was examined. F344 male rats were treated with 0.05, 0.01, 0.005 or 0.001% BBN in the drinking water, or 5, 1, 0.2 or 0.04% sodium saccharin in basal diet. Clear dose-dependence was observed in the effect of BBN on the potential, but of the doses of sodium saccharin used, only 5% saccharin caused a significantly higher potential than in the control group. These findings suggested that in the early stage of urinary bladder carcinogenesis induced by BBN, the Na+ channel located in the apical membrane may be inactivated.

Ca2+ release from sarcoplasmic reticulum vesicles derived from longitudinal reticulum and terminal cisternae of frog skeletal muscle

Fragmented sarcoplasmic reticulum (FSR) of bullfrog skeletal muscle was fractionated into light and heavy sarcoplasmic reticulum (LSR and HSR) by sucrose density gradient centrifugation. Morphological and biochemical studies revealed that large parts of LSR and HSR were derived from longitudinal reticulum and terminal cisternae of SR, respectively. The Ca2+ uptake ability and ATPase activity of LSR were higher than those of HSR. Ca2+ release from Ca2+ preloaded SR vesicles by changing the medium from K-gluconate to KCl was suppressed by addition of 0.3 M sucrose or glucose; there was no correlation between Ca2+ release and membrane potential change either in LSR or HSR vesicles. Dantrolene sodium (DAN, 20 microM) had no effect on Ca2+ release. It is concluded that ion-induced Ca2+ release from SR (both HSR and LSR) in the isolated system is due to an osmotic effect.

Mechanism of resistance to aminoglycoside antibiotics in nebramycin-producing Streptomyces tenebrarius

Streptomyces tenebrarius ISP 5477, which produces nebramycins, was highly resistant to the following aminoglycoside antibiotics: neamine, ribostamycin, butirosin A, neomycin B, paromomycin, kanamycin A, dibekacin, gentamicin C complex, lividomycin A, istamycin B and streptomycin. Polyphenylalanine synthesis on the ribosomes of this strain was highly resistant to neamine, ribostamycin, butirosin A, kanamycins A, B and C, dibekacin, gentamicin C complex and istamycin B, moderately resistant to lividomycin A and streptomycin, but sensitive to neomycin B and paromomycin. Moreover, cell free extract of the strain contained phosphotransferase and N-acetyltransferase. The former enzyme was confirmed to be an aminoglycoside 6-phosphotransferase which inactivated streptomycin; the latter inactivated kanamycins B and C, dibekacin, neamine, neomycin B, paromomycin, lividomycin A, butirosin A and ribostamycin, but did not inactivate kanamycin A, gentamicin C complex and sagamicin, suggesting an aminoglycoside 2'-acetyltransferase. These results indicated that the high resistance of S. tenebrarius ISP 5477 to a wide range of aminoglycoside antibiotics is due to ribosomal resistance and to the inactivating enzymes, aminoglycoside N-acetyltransferase(s) and aminoglycoside 6-phosphotransferase.

Human gastric glycoproteins corresponding to paradoxical concanavalin A staining

Glycoproteins were isolated from human gastric mucosa, and their reactivities with concanavalin A, periodate oxidation and subsequent reduction, are described. Gastric glycoproteins corresponding to the paradoxical concanavalin A staining-class II and III mucins were proved biochemically. The analytical results suggest that N-acetylglucosamine residues in the glycoproteins mediate the interaction with concanavalin A.

Distribution of mucosal macromolecular glycoproteins in rat stomach

1. The mucosal macromolecular glycoproteins were extracted from forestomach, corpus and antrum region of rat whose weight ratio was 2:5:1, respectively. 2. The glycoproteins were fractionated on Bio-Gel A-1.5 m. 96% of the glycoproteins was localized in glandular stomach. 3. The carbohydrate of the glycoproteins composed of N-acetylgalactosamine, N-acetylglucosamine, galactose, fucose and sialic acid in the proportions 1.0:2.7:3.2:1.0:0.14 for corpus, while 1.0:1.4:1.5:0.7:0.04 for antrum.

Resistance mechanisms of kanamycin-, neomycin-, and streptomycin-producing streptomycetes to aminoglycoside antibiotics

Streptomyces kanamyceticus ISP5500, S. fradiae ISP5063 and S. griseus ISP5236, which produce kanamycin, neomycin or streptomycin respectively, were highly resistant to the antibiotics they produced. Polyphenylalanine synthesis in cell free systems was also resistant to the action of the antibiotics. Reciprocal exchange between ribosomes and S150 fractions from the three strains revealed that the S150 fraction of each strain had an enzyme activity that inactivated the appropriate antibiotic whereas the ribosomes were susceptible to the antibiotics. It was concluded that the resistance of the in vitro polyphenylalanine synthesizing systems of these antibiotics was due to the presence of inactivating enzymes. Furthermore, S. fradiae and S. kanamyceticus were highly resistant to aminocyclitol-containing aminoglycoside antibiotics other than those produced by the two strains. In these cases, the inactivating enzymes were found to have a major role in the resistance mechanism. However, the resistance of S. kanamyceticus ISP5500 to streptomycin seems to be due to resistance at the ribosomal level.

Age-related changes of cardiac control function in man. With special reference to heart rate control at rest and during exercise

Heart rate control function at rest and during exercise in regard to age were studied in 39 healthy male volunteers (age 15 to 75). The heart rate control function during exercise was evaluated by using system analysis of heart rate response to two-step exercises (66 and 84 steps/min). No age-related changes were found in the resting heart rate at supine position or in oxygen consumption at upright rest and during the exercises. However, the mean value and the magnitude of variation of the heart rate at upright rest and the difference of heart rate at upright and supine rest showed significant negative correlations with age. As age advanced, the transfer function of the system during exercise exhibited characteristic changes depending on the frequency ranges. These findings suggest that activity of both sympathetic and parasympathetic nervous systems were depressed at rest, and that contributions of sympathetic and vagal nervous systems during exercise are more enhanced and more depressed, respectively, in older subjects than in younger subjects.

Efficacy of anti-ulcer drugs on the recovery of gastric mucosal glycoproteins with aspirin-induced gastric damage in rat

The efficacy of two anti-ulcer drugs, Cimetidine and Cetraxate, on the mucus glycoproteins of gastric mucosa in the aspirin-induced gastric damage was studied in rats. Simultaneous or previous oral administration of Cimetidine or Cetraxate with aspirin reduced the diminution of the mucus glycoproteins which was occurred by aspirin administration. The recovery of the content of mucus glycoprotein in drug dosed rats occurred within 3 h after aspirin dosing and was nearly 90% of control at 5 h in all cases. Single administration of Cetraxate or Cimetidine produced an increase in the mucus glycoprotein content greater than that of the untreated control. Although a macroscopical method for the measurement of gastric damage was applied to this work, neither erosions nor linear ulcers were observed in all cases except the single administration of aspirin. The biochemical method used should be able to assess the efficacy of drugs on the mucosal lesion which cannot be expressed as the ulcer index.

Self-resistance of a Streptomyces which produces istamycins

Streptomyces tenjimariensis SS-939, a producer of istamycins, is highly resistant to its own antibiotics and grows in Tryptic Soy Broth containing istamycin A or B at 3,000 microgram/ml. No istamycin-inactivating enzyme was detected in extracts of strain SS-939. Polyphenylalanine synthesis in an in vitro system, consisting of the S-150 fraction and ribosomes prepared from strain SS-939, was not inhibited by 200 microgram/ml of istamycins. Using reciprocally reconstituted systems consisting of S-150 fractions and ribosomes from strain SS-939 and those from Streptomyces griseus ISP5236 (istamycin-sensitive strain), ribosomes of strain SS-939 were found to be resistant to istamycins. Thus, ribosomes have the main role in the self-resistance mechanism of S. tenjimariensis SS-939.