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Bromodeoxyuridine 5'-monophosphate incorporation into yeast nuclear and mitochondrial deoxyribonucleic acid.

Standard laboratory yeast strains can be enriched for thymidine 5'-monophosphate (TMP) uptake derivatives that generate only a low percentage of respiratory-deficient colonies (petites) under inhibition of TMP biosynthesis. Such mutants incorporated bromodeoxyuridine 5'-monophosphate (BrdUMP) into both nuclear and mitochondrial deoxyribonucleic acid (mtDNA); however, they showed a selectivity for TMP over BrdUMP incorporation. The preferential incorporation of [3H]TMP or BrdUMP into mtDNA was strain dependent. The density increments after growth in the presence of BrdUMP reached 50 mg/ml for nuclear DNA and 22 mg/ml for mtDNA in CsCl gradients. Density shifts corresponding to 4% bromouracil substitution were easily detected. Preliminary density transfer experiments confirm that mtDNA does not replicate in synchrony with nuclear DNA.

Bromodeoxyuridine↗

Trimethoprim-produced F-specific insertion mutations in Escherichia coli K-12.

Besides producing thymine-requiring mutants (thy), trimethoprim (TMP) cured the mini-ColE1 replicon pML21 at an appreciable frequency. The cured Escherichia coli K-12 cells behaved like polA mutants by failing to support the stable maintenance of the ColE1 plasmid. The mini-F replicon pSC138, which was lacking all three insertion sequences (IS3, gammadelta, and IS2) normally used for F-specific integration and excision, was not cured by TMP. Instead, it integrated into specific regions of the E. coli chromosome and thus caused auxotrophic mutations in operons which were always localized on either side of oriC (origin of chromosomal replication). The incompatibility and replication functions of the integrated plasmid in auxotrophs were retained, and the plasmid DNAs recovered from spontaneously occurring revertants did not show any alterations in their contour lengths as determined by electron microscopy. The F replicon (fragment 5) contained in plasmid pSC138 carried two origins of replication, the primary origin, oriV(1) at 42.6F and the secondary origin, oriV(2), at 44.1F. Another mini-F plasmid pMF21, deleted of the primary origin of replication (oriV(1)), was still capable of autonomous replication but failed to integrate onto the chromosome after TMP treatment. Furthermore, the composite plasmid pRS5, which normally uses only the replication origin and functions of the pSC101 component, was also insensitive to TMP. On the basis of these results, we propose a new scheme of F integration via the functional oriV(1) and suggest the involvement of a similar mechanism in the formation of Hfr strains by integrative suppression.

Amino Acids↗

Phenotypic and genotypic changes in Vibrio cholerae O139 Bengal.

To find reasons for the recent decline of Vibrio cholerae O139 Bengal cholera in Bangladesh, phenotypic and genotypic changes in O139 isolates obtained from patients with cholera from 1993 to 1996 were studied. The isolates were tested for the presence of ctx and tcpA genes, hemagglutinin/protease (HA/P), capsule, D-mannose-sensitive hemagglutinin (MSHA), L-fucose-sensitive hemagglutinin (FSHA), tube test (tube) and CAMP test (CAMP) hemolytic activities, resistance to 2,4-diamino-6,7-diisopropyl pteridine (O/129) and trimethoprim-sulfamethoxazole (TMP-SMX), and genotype by pulsed-field gel electrophoresis (PFGE). All isolates possessed ctx and tcpA genes, HA/P, and a capsule. Most isolates were negative for FSHA, but although the majority of the isolates were positive for MSHA, no discernible trend in the activity was found during the study period. All early isolates were CAMP hemolysin positive and resistant to the vibriostatic compound O/129 and TMP-SMX, the two properties that could be used for the presumptive diagnosis of O139 cholera. However, subsequently, isolates that were CAMP hemolysin negative and susceptible to TMP-SMX and O/129 were increasingly encountered, with all the 1996 isolates being so, which suggested that these properties can no longer be used for the presumptive diagnosis of O139 cholera. V. cholerae O139 isolates that were CAMP hemolysin positive and resistant to O/129 and TMP-SMX produced a disease of greater severity than that caused by the CAMP hemolysin-negative and susceptible isolates on the basis of the lengths of stay of the hospitalized patients. The study period witnessed the evolution of four different genotypes by PFGE. All of these data suggested that the V. cholerae O139 isolates have undergone changes in some properties. However, how these changes influenced their prevalence relative to that of V. cholerae O1 in human infection is not clear. Studies of the environmental factors will provide the key for an understanding of the relative abundance of these vibrios.

Adult↗

Treatment of chancroid. A comparison of sulphamethoxazole and trimethoprim-sulphamethoxazole.

Since sulphonamides are no longer predictably effective in the treatment of chancroid the combination of trimethoprim-sulphamethoxazole (TMP-SMX) was evaluated to identify other effective regimens. One hundred and nine patients with genital ulcers (75 men and 34 women) seen at the Special Treatment Clinic in Nairobi, Kenya, were randomly assigned to treatment with a seven day course of either sulphamethoxazole 1000 mg twice daily or trimethoprim (160 mg)-sulphamethoxazole (800 mg) (TMP-SMX) twice daily. Haemophilus ducreyi was isolated from the ulcer in 57 patients (33 men and 24 women). 16 patients were subsequently diagnosed serologically as having syphilis. No aetiological diagnosis was made in 40 patients. Treatment with sulphamethoxazole failed in five of 21 (24%) culture positive patients who were available for evaluation after seven days, whereas all 19 of such patients who were treated with TMP-SMX responded to treatment. Of the 21 isolates available for susceptibility testing, all were susceptible to trimethoprim alone (MIC less than 0.5 mg/l) and three were resistant to sulphonamides, all three containing a 4.9 megadalton (Mdal) plasmid. Two of the three patients from whom these isolates had been obtained were treated with sulphamethoxazole and both were clinical and bacteriological failures. Five of six patients with sulphonamide-susceptible H ducreyi responded to treatment with sulphamethoxazole. Failure of sulphonamides to eradicate H ducreyi in some patients with chancroid is associated with the presence of a sulphonamide resistant plasmid. In regions where this plasmid is present in H ducreyi TMP-SMX is the preferred treatment for chancroid.

Adolescent↗

Treatment of acute gonococcal urethritis in men with simultaneous infection with Chlamydia trachomatis.

Each of 201 men with symptoms and signs of acute urethritis was randomly assigned to one of two treatment regimens: ampicillin (2g) plus probenecid (1g), or sulphamethoxazole-trimethoprim (SMX-TMP) (sulphamethoxazole 1600 mg plus trimethoprim 320 mg) four tablets twice daily for two days. Before treatment Neisseria gonorrhoeae was isolated from 162 patients, while coexistent Chlamydia trachomatis was recovered from 42 (26%) men. After treatment N gonorrhoeae persisted in 11 (14.3%) of the 77 patients treated with ampicillin and probenecid and in three (3.5%) of the 85 treated with SMX-TMP (p less than 0.05), while C trachomatis persisted in four (16%) of the 25 men treated with SMX-TMP and in all 17 patients treated with ampicillin and probenecid. SMX-TMP was thus more effective than ampicillin in treating acute gonorrhoea in men and in eradicating concurrent C trachomatis infection.

Acute Disease↗

Comparing cardiac action potentials recorded with metal and glass microelectrodes.

Machine-pulled high-impedance glass capillary microelectrode is standard for transmembrane potential (TMP) recordings. However, it is fragile and difficult to impale, especially in beating myocardial tissues. We hypothesize that a high-impedance pure iridium metal electrode can be used as an alternative to the glass microelectrode for TMP recording. The TMPs were simultaneously recorded from isolated perfused swine right ventricles with a metal microelectrode and a standard glass microelectrode during pacing and during ventricular fibrillation. The basic morphology of TMP recorded with these electrodes was comparable. The action potential duration (APD) at 90% repolarization was 241 +/- 29 ms for the metal microelectrode and 236 +/- 31 ms for the glass microelectrode with a good correlation (r = 0.99, P < 0.0001). The maximum slope value of the APD restitution curves during pacing was also significantly correlated. One metal microelectrode and >20 glass microelectrodes were needed per study. We conclude that, in isolated perfused swine right ventricles, the TMP recorded by the metal microelectrode is comparable with that recorded by the glass microelectrode. Because the metal microelectrode is more durable than the glass microelectrode, it can serve as an alternative for APD recording and for restitution analyses.

Action Potentials↗

In vitro investigation of the antimicrobial activities of novel tetramethylpiperidine-substituted phenazines against Mycobacterium tuberculosis.

The intra- and extracellular activities of 5 novel tetramethylpiperidine (TMP)-substituted phenazines against Mycobacterium tuberculosis H37Rv (ATCC 27294) were determined and compared with those of clofazimine and rifampicin. Two of these agents, together with clofazimine, were also tested for their activities against drug-resistant strains of M. tuberculosis. Three of the TMP-substituted phenazine compounds were significantly more active than clofazimine against M. tuberculosis, including multidrug-resistant clinical strains of this microbial pathogen, demonstrating a lack of cross-resistance between the riminophenazines and standard anti-tuberculous drugs. Using M. tuberculosis-infected monocyte-derived macrophages, all of the TMP-substituted phenazines were found to possess intracellular activity which was superior to that of both clofazimine and rifampicin. In this model of intracellular bioactivity, the experimental compounds inhibited bacterial growth at concentrations which were approximately 10-fold lower than the corresponding minimal inhibitory concentration values obtained using conventional in vitro sensitivity testing procedures. These results demonstrate that the novel TMP phenazines are active against multidrug-resistant M. tuberculosis strains, and particularly effective intracellularly.

Antibiotics, Antitubercular↗

Isoproterenol increases renal tubular reabsorption of phosphate in X-linked hypophosphatemic (Hyp) mice.

Hypophosphatemic (Hyp) mice have a reduced renal retention of phosphate. The beta-adrenergic agonist isoproterenol reverses phosphaturia induced by parathyroid hormone in the rat. This study determined whether isoproterenol could raise the renal tubular maximum transport of phosphate (TmP) in Hyp mice. Male 10- to 12-week-old normal and Hyp mice were infused with (3)H-inulin and isoproterenol (0.0, 0.25, 0.5 and 1.0 microg/kg/min) in 0.9% NaCl. Glomerular filtration rate, plasma phosphate, urinary phosphate excretion, TmP, urinary sodium excretion, and urinary cyclic adenosine monophosphate were measured. As expected, Hyp controls (0.0 dose) had a TmP which was significantly below that of normal controls: 1.15+/-(SEM) 0.6 (n = 9) versus 2.13+/-0.10 (n = 11) micromol P/ml glomerular filtrate (p<0.001). Isoproterenol at doses of 0.5 and 1.0 microg/kg/min elevated the TmP of Hyp mice to the level of normal controls: 1.94+/-0.19 (n = 7) and 1.98+/-0.10 (n = 9) micromol P/ml glomerular filtrate, respectively. These results indicate that the low tubular reabsorption of phosphate in Hyp mice is not due to a fixed low level of phosphate transport, but to decreased stimulation of phosphate transporters, since Hyp mouse kidneys increase phosphate reabsorption with suitable stimulus.

Adrenergic beta-Agonists↗

Effect of high hematocrit and high blood flow rates on transmembrane pressure and ultrafiltration rate in hemodialysis.

Removal of prescribed ultrafiltration volumes in hemodialysis requires knowledge of both the ultrafiltration coefficient of the dialyzer and the average transmembrane pressure (TMP) in the dialyzer. While it has been a fairly common practice to assume that the TMP is constant along the length of the dialyzer, it actually decreases linearly from a maximum value at the blood inlet to a minimum value at the blood outlet. In the past, ignoring the difference between arterial and venous TMPs when calculating the dialysate pressure setting did not result in significant errors in ultrafiltration volume. However, with the introduction of erythropoietin therapy and the trend toward high-efficiency dialysis, increases in hematocrit and blood flow rate have led to axial variations in TMP which, if ignored, can lead to inaccurate fluid removal. The goals of this paper are to provide an understanding of how high hematocrits and high blood flow rates affect TMP and ultrafiltration rate, and to provide simple guidelines for ensuring accurate fluid removal. Sample calculations are given on the last page for easy reference.

Blood Flow Velocity↗

Bacterial resistance to trimethoprim in geriatric medical wards.

Urinary tract infections (UTI) caused by organisms resistant to trimethoprim (TMP), as well as their faecal carriage were studied in two geriatric wards. TMP-resistant UTI was common (26 and 50% of admission and ward-acquired infections, respectively) and was associated with male sex, recurrent and transferred admissions and length of stay. There was a strong relationship between faecal carriage and isolation of TMP-resistant organisms from urine. Antimicrobial exposure was the major determinant of TMP-resistant faecal carriage.

Aged↗

Bladder instillations with trimethoprim-sulfamethoxazole in the treatment of urinary infection.

205 paraplegic inpatients with urinary infections were treated with trimethoprim-sulfamethoxazole (TMP-SMZ) bladder instillations (160 mg TMP 800 mg SMZ daily for 2 consecutive weeks). 89.3% out of 84 patients with recent vertebral trauma and no history of previous urinary infection (group A), and 68.6% out of 121 patients with paraplegia since more than 2 years, severe chronic infection and various pathological conditions of the urinary tract (group B) were found to be sterile at the end of the trial. The intravesical concentrations of 3.2 mg/ml TMP and 16 mg/ml SMZ which are reached immediately after instillation are 50--100 times superior to the minimal growth-inhibitory concentrations for most sensitive germs as determined with agar dilution tests. Several strains of Klebsiella and Proteus which had previously proved resistant to oral treatment were eliminated with intravesical TMP-SMZ. The incidence of reinfection, evaluated 1 month after interruption of treatment, was particularly high (62.7%) in patients with known involvement of the upper tract of intravesical obstruction with postmicturition residuals above 75 ml. On the other hand, 28% only among the patients with recent spinal injury and integrity of the upper urinary tract became reinfected after the same interval. The absence of local intolerance could be confirmed in all 21 cystoscopically examined patients between the 6th and 11th day of treatment. Hematuria was never encountered. Systemic side effects were noted in 7.8% Serum concentrations of both drug components are being investigated; results will be published elsewhere.

Adolescent↗

Difference in trimethoprim pharmacokinetics between children and adults.

We used a new micromethod, an application of a previously published high-performance liquid chromatography assay, to investigate trimethoprim (TMP) pharmacokinetics in children. The subjects were 5 girls who were treated for urinary tract infection with a TMP suspension, 6 mg/kg/day, twice daily for 10 days. Elimination studies were done after the last dose. The girls were 1.08-9.71 years old. 3 healthy adult males, aged 26.35-37.31 served as controls. The half-life (t 1/2) of TMP in the children was 3.0-5.5 versus 9.3-13.6 h in the adults. The volume of distribution (Vd) was 0.7-1.1 1/kg in the children and 0.5-0.9 1/kg in the adults. Plasma clearance (Clp) was 2.1-2.8 ml/min/kg for the children. The adults had a smaller Clp of 0.4-1.2 ml/min/kg. From this and previous studies we conclude that the t 1/2 of TMP is much shorter in children than in adults.

Adult↗

Pharmacokinetics of co-trimazine (sulphadiazine plus trimethoprim) in geriatric patients.

The study was aimed at analyzing the pharmacokinetics of sulphadiazine (SDZ) and trimethoprim (TMP) in geriatric patients and was carried out in two stages. The first stage compared 11 geriatric patients (68-89 years old) and 9 healthy volunteers (21-34 years old). Serum concentration and urine elimination were determined on day 4 after 12-hourly administration of 1 tablet of co-trimazine containing 410 mg sulphadiazine (SDZ) plus 90 mg trimethoprim (TMP). The mean serum concentrations of SDZ were significantly higher in the older subjects than in the volunteers after 1, 8 and 12 h (p less than 0.05, 0.01, 0.01), but were not differentiable after 2 or 4 h. For TMP, the serum levels were higher (p less than 0.05) in the patients only after 8 h. The amounts collected in urine were higher in the normal volunteers for SDZ during the intervals 0-2 h (p less than 0.05), 2-4 h (p less than 0.01), and 4-8 h (p less than 0.01), but not for 8-12 h. The 12-hour recovery was 69% SDZ + acetyl-SDZ recovered in the patients compared to 66.0% in the volunteers. Indistinguishable amounts of TMP were recovered during each interval in the two groups of subjects, 59.2% in the patients compared to 70.0% in the volunteers. The second stage of the study comprised 9 geriatric patients of mean age 83.6 years and creatinine clearance 59.2 ml/min who were followed for 11 days. A steady increase in serum levels was observed. The mean peak serum concentration for SDZ was 16.7 +/- 4.2 mg/l after the first dose and 44.7 +/- 11.3 mg/l on day 10. For acetyl-SDZ, the respective concentrations were 2.1 +/- 0.9 and 7.1 +/- 3.1 mg/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

In vitro susceptibility of Salmonella to ciprofloxacin and pefloxacin compared with three other antibiotics.

The in vitro susceptibilities of 703 clinical isolates of Salmonella to ciprofloxacin (CIP) and pefloxacin (PEF) were compared with those to trimethoprim-sulfamethoxazole (TMP-SMZ), chloramphenicol (CO) and ampicillin (AP). All isolates were susceptible to CIP, while PEF inhibited 90.7% of the strains. In contrast, resistance rates of 40, 29.2 and 27% were detected for AP, TMP-SMZ and CO, respectively. PEF resistance was detected in S. panama (1), S. typhi (3) and S. typhimurium (17), the latter representing the most frequently serovar isolated in our country. None of the S. typhi isolates was resistant to CO. Combined resistance was most frequently found among S. typhimurium isolates, with the patterns PEF-TMP-SMZ-AP (10) and PEF-TMP-SMZ-CO-AP (5) predominating.

Ampicillin↗

Influence of brodimoprim on polymorphonuclear leukocyte phagocytosis and oxidant radical production.

Antibiotics not only reach the site of infection, but also penetrate cyclically, during a treatment, into polymorphonuclear leukocytes (PMNs) and may influence their functions positively or negatively. With reference to these aspects, the influence of brodimoprim (BMP), a dimethoxybenzylpyrimidine recently entered into clinical use, on human PMN phagocytosis and oxidant radical production (chemiluminescence) was investigated. PMNs from healthy adult donors were incubated for 50 min in medium alone or in medium containing increasing concentrations (3.7, 7.5, 15, and 30 micrograms/ml) of BMP and trimethoprim (TMP). In unwashed PMNs, phagocytosis was not modified by BMP, but was significantly reduced by 30 micrograms/ml TMP; chemiluminescence was significantly reduced by 15 and 30 micrograms/ml BMP and by all concentrations of TMP. When PMNs were washed after incubation, phagocytosis was unaffected and chemiluminescence was significantly restored. BMP at therapeutic concentrations did not influence PMNs and was less toxic than TMP.

Anti-Bacterial Agents↗

Trimethoprim-induced elevation of dihydrofolate reductase activity in human leukocytes.

The administration of trimethoprim (TMP)--a diamino benzylpyrimidine compound which binds very tightly the bacterial dihydrofolate reductase--was accompanied by the appearance of measurable levels of dihydrofolate reductase in peripheral leukocytes from patients with nonhematological diseases. In all instances, enzyme activity rose rapidly between the fourth and eighth day after TMP. The time course of the rise and fall of dihydrofolate activity approaches cellular life span and is similar to that obtained after methotrexate or triamterene administration. Dihydrofolate reductases, partially purified from leukocytes of patients treated with TMP, bone marrow and leukemic leukocytes, had simila molecular weights, pH optima, Ki of inhibitor (methotrexate); they were stimulated to the same degree by KCl and urea. Electrophoresis of the enzyme on cellulose acetate strip resulted in the separation of two enzymatically active protein components. No differences in the electrophoretic behavior of the three blood cell enzymes were noted. The findings noted above are consistent with the suggestion that the observed rise in dihydrofolate reductase activity is a quantitative one. Moreover, the effect of TMP in vivo is discussed in comparison with the currently held hypothesis for methotrexate action (stabilization by the drug of a previously synthetized enzyme).

Electrophoresis, Cellulose Acetate↗

Transmembrane potential properties at the core of functional reentrant wave fronts in isolated canine right atria.

BACKGROUND: The characteristics of transmembrane potential (TMP) at the core of functional reentry in the atrium are not well understood. METHODS AND RESULTS: In protocol 1 (11 dogs), isolated perfused canine right atria were mapped from the endocardial surface while simultaneous TMPs were recorded from the epicardial surface. Episodes of reentry (n=64) were induced in the presence of 1 to 5 micromol/L acetylcholine. Successful simultaneous TMP recordings and activation maps were made in 8 episodes. The TMP was "near the core" if it was within 3.2 mm of the core; otherwise, it was considered to be "in the periphery." The mean cycle length of reentry was 110+/-35 ms. The TMP amplitude, duration (90% repolarization), and (dV/dt)max near the core (n=106) were 58+/-22 mV, 46+/-14 ms, and 33+/-20 V/s, respectively, significantly less than those in the periphery (n=241): 70+/-8 mV, 94+/-32 ms, and 55+/-10 V/s (P<0.001 for all). In 2 episodes of reentry, the cell at the core remained unexcited at its resting membrane potential. In protocol 2 (2 dogs), we performed simultaneous high-density mapping in 4 episodes of reentry and showed synchronous activation patterns on both surfaces with similar locations of the core. CONCLUSIONS: During meandering functional reentry in isolated canine right atria, (1) TMPs of cells near the core have a reduced amplitude, duration, and (dV/dt)max, and (2) cells at the core may remain unexcited at their resting membrane potential. These findings are compatible with the spiral wave concept of functional reentry in the atrium.

Acetylcholine↗

Middle cerebral artery function after stroke: the threshold duration of reperfusion for myogenic activity.

BACKGROUND AND PURPOSE: Myogenic activity of the cerebral arteries is an important contributor to autoregulation of cerebral blood flow. Previous studies have demonstrated that increasing periods of ischemia diminished the amount of myogenic tone in cerebral arteries. In the present study, we investigated the effect of different periods of postischemic reperfusion on the myogenic behavior of middle cerebral arteries (MCAs). We measured both the amount of spontaneous myogenic tone that developed at 75 mm Hg and the contractile response to increased transmural pressure (TMP), ie, myogenic reactivity. METHODS: The MCA occlusion model was used in male Wistar rats (n=45) to induce 30 minutes of temporary ischemia, followed by different periods of reperfusion (0 or sham; 30 minutes; and 6, 12, 18, 20, and 22 hours), confirmed by laser Doppler flowmetry. MCAs were studied in vitro using an arteriograph system that allowed control of TMP and measurement of lumen diameter. After equilibration for 1 hour at 75 mm Hg, TMP was increased stepwise in 25-mm Hg increments to 125 mm Hg and lumen diameter measured at each pressure. The amount of spontaneous myogenic tone was determined in both ischemic and contralateral arteries for each reperfusion period and compared with the right and left MCAs in the sham group. Arteries were then fixed with 10% formalin pressurized in the arteriograph bath and stained for filamentous (F)-actin with fluorescently labeled phalloidin, a specific probe for F-actin. The amount of F-actin was quantified using confocal microscopy. RESULTS: MCAs from the sham-operated control group possessed considerable myogenic tone (35%). However, the amount of tone in ischemic MCAs progressively diminished as the reperfusion duration increased. In addition, sham-operated control arteries responded myogenically to increases in TMP, decreasing diameter as pressure increased. There was a similar response in arteries exposed to 30 minutes and 6 hours of reperfusion, all producing a negative slope on the pressure-diameter curve; however, myogenic reactivity was diminished at the longer periods of reperfusion, producing a positive slope of the graph. The slopes of the pressure-diameter curves were as follows: -0.10+/--0.06 (sham), -0.07+/--0.12 (30 minutes), -0.08+/--0.11 (6 hours), +0.09+/-0.09 (12 hours), +0.25+/-0.16 (18 hours), +0.38+/-0.09 (20 hours), and +0.57+/-0.09 (22 hours). F-actin content was significantly less only in ischemic MCAs at 6 and 12 hours of reperfusion. CONCLUSIONS: These results demonstrate that longer periods of reperfusion significantly diminish myogenic activity of MCAs. Understanding how different periods of ischemia and reperfusion affect the function of the cerebral circulation may promote more effective treatment of ischemic stroke.

Actins↗