Visualizing pneumococcal infections in the lungs of live mice using bioluminescent Streptococcus pneumoniae transformed with a novel gram-positive lux transposon

Animal studies with Streptococcus pneumoniae have provided valuable models for drug development. In order to monitor long-term pneumococcal infections noninvasively in living mice, a novel gram-positive lux transposon cassette, Tn4001 luxABCDE Km(r), that allows random integration of lux genes onto the bacterial chromosome was constructed. The cassette was designed so that the luxABCDE and kanamycin resistance genes were linked to form a single promoterless operon. Bioluminescence and kanamycin resistance only occur in a bacterial cell if this operon has transposed downstream of a promoter on the bacterium's chromosome. S. pneumoniae D39 was transformed with plasmid pAUL-A Tn4001 luxABCDE Km(r), and a number of highly bioluminescent colonies were recovered. Genomic DNA from the brightest D39 strain was used to transform a number of clinical S. pneumoniae isolates, and several of these strains were tested in animal models, including a pneumococcal lung infection model. Strong bioluminescent signals were seen in the lungs of the animals containing these pneumococci, allowing the course and antibiotic treatment of the infections to be readily monitored in real time in the living animals. Recovery of the bacteria from the animals showed that the bioluminescent signal corresponded to the number of CFU and that the lux construct was highly stable even after several days in vivo. We believe that this lux transposon will greatly expand the ability to evaluate drug efficacy against gram-positive bacteria in living animals using bioluminescence.     

4-Hydroxy-1-[2-(4-hydroxyphenoxy)ethyl]-4-(4-methylbenzyl)piperidine: a novel, potent, and selective NR1/2B NMDA receptor antagonist.

A structure-based search and screen of our compound library identified N-(2-phenoxyethyl)-4-benzylpiperidine (8) as a novel N-methyl-D-aspartate (NMDA) receptor antagonist that has high selectivity for the NR1/2B subunit combination (IC(50) = 0.63 microM). We report on the optimization of this lead compound in terms of potency, side effect liability, and in vivo activity. Potency was assayed by electrical recordings in Xenopus oocytes expressing cloned rat NMDA receptors. Side effect liability was assessed by measuring affinity for alpha(1)-adrenergic receptors and inhibition of neuronal K(+) channels. Central bioavailability was gauged indirectly by determining anticonvulsant activity in a mouse maximal electroshock (MES) assay. Making progressive modifications to 8, a hydroxyl substituent on the phenyl ring para to the oxyethyl tether (10a) resulted in a approximately 25-fold increase in NR1A/2B potency (IC(50) = 0.025 microM). p-Methyl substitution on the benzyl ring (10b) produced a approximately 3-fold increase in MES activity (ED(50) = 0.7 mg/kg iv). Introduction of a second hydroxyl group into the C-4 position on the piperidine ring (10e) resulted in a substantial decrease in affinity for alpha(1) receptors and reduction in inhibition of K(+) channels with only a modest decrease in NR1A/2B and MES potencies. Among the compounds described, 10e (4-hydroxy-N-[2-(4-hydroxyphenoxy)ethyl]-4-(4-methylbenzyl)piperid ine, Co 101244/PD 174494) had the optimum pharmacological profile and was selected for further biological evaluation.     

In Vitro and In Vivo Activity of 16,17-dehydro-epipregnanolones: 17,20-Bond Torsional Energy Analysis and D-ring Conformation

Purpose. Certain neuroactive pregnane steroids (also known as “epalons”) are allosteric modulators of the GABA_A receptor and have been shown to be potent anticonvulsants, anxiolytics, sedative/hypnotics, and anesthetic agents. The purpose of this study was to calculate the structural consequences of introduction of a double bond in the 16,17-position and to determine if this modification would selectively reduce sedative activity, but maintain the potent anticonvulsant activity of neuroactive steroids. Methods. We have studied the biochemical and behavioral effects of introducing a 16,17 double bond into the naturally occurring neuroactive steroids, 3α-hydroxy-5α-pregnan-20-one (3α,5α-P) and 3α-hydroxy-5β-pregnan-20-one (3α,5β-P) and three synthetic neuroactive steroid derivatives, 3α-hydroxy-3β-methyl-5α-pregnan-20-one (3α,3βMe,5α-P), 3α-hydroxy-5α-androstane (3α,5α-A), and alphaxalone (3α,5α-11-one-P). Results. The 16-ene analogs of most of these neuroactive steroids were found to be 7- and 16-fold less potent in inhibiting [³⁵S]TBPS binding to GABA_A receptors and in a similar fashion, had reduced anticonvulsant and sedative potency in proportional amounts. The exception was the androstane (3α,5α-A) without a 17-acetyl group, that had virtually identical IC₅₀ and ED₅₀ values for the saturated and unsaturated derivatives. Calculation of the torsional energy profile for each of the 17-acetyl side chain conformations showed that the conformational energy minima found in the α,β-unsaturated keto systems, produce an orientation of the 20-keto group that is rotated by 165 degrees when compared to the non-conjugated acetyl group (determined by X-ray crystallography and its minimum energy conformation). Conclusions. The modified orientation of the 20-keto group of neuroactive steroids containing a 16-ene, provides an explanation for their decreased biological activity overall, but did not lead to an enhanced protective index.     

Correlation of symptoms with occurrence of paroxysmal supraventricular tachycardia or atrial fibrillation: a transtelephonic monitoring study. The Flecainide Supraventricular Tachycardia Study Group.

The purpose of this study was to determine whether symptoms recorded at the time of transtelephonic ECG monitoring (TTEM) correlate with attacks of paroxysmal supraventricular tachycardia (PSVT) or paroxysmal atrial fibrillation (PAF). We studied 113 patients with these arrhythmias who made a total of 3319 TTEM calls during their participation in double-blind, placebo-controlled, crossover, multicenter trials of flecainide therapy. Among 49 patients with PSVT, 62.7% of symptomatic calls were associated with ECG-documented PSVT as compared with 6.8% of asymptomatic calls (p less than 0.001). Similarly, among 69 patients with PAF, 69% of symptomatic calls were associated with ECG-documented PAF compared with 10.6% of asymptomatic calls (p less than 0.001). Both in patients with PSVT and PAF, an attack of PSVT or PAF could be documented by ECG in more than 70% of the calls when patients complained of tachycardia, increased sweating, or dyspnea. The sensitivity of a symptomatic call was 91% for PSVT and 89% for PAF, and it was not influenced by flecainide therapy. However, flecainide therapy was associated with a decrease in the positive predictive value of symptomatic TTEM calls and an increase in false positive TTEM transmissions. We conclude that in patients with symptomatic PSVT or PAF, there is a temporal relationship between symptoms and the occurrence of ECG-documented attacks of PSVT or PAF. However, sole reliance should not be placed on the presence or absence of symptoms as a measure of drug failure or efficacy, and it is important to document the cardiac rhythm by TTEM at the time symptoms are recorded.     

Flecainide acetate prevents recurrence of symptomatic paroxysmal supraventricular tachycardia. The Flecainide Supraventricular Tachycardia Study Group

Oral flecainide acetate was administered to 34 patients with documented symptomatic paroxysmal supraventricular tachycardia (PSVT) with a double-blind, placebo-controlled, 8-week crossover trial design. PSVT was defined as a regular tachycardia of at least 120 beats/min without evidence of atrioventricular dissociation. The study required considerable patient cooperation. Patients first entered a 4-week qualifying phase followed by a 3-week, open label, flecainide dose-ranging phase. They were then randomized in a blind fashion to receive either placebo or tolerated flecainide dose for an 8-week treatment period and then crossed over after four symptomatic documented episodes of PSVT or at the end of the treatment period. By all efficacy parameters analyzed, flecainide was superior to placebo. Flecainide was associated with an actuarial 79% freedom from symptomatic PSVT events compared with only 15% on placebo at 60 days (p less than 0.001). Of the 34 patients, 29 had recurrence of symptomatic PSVT at least once during the placebo phase; only eight patients had a recurrence during the flecainide phase (p less than 0.001). The median time to the first symptomatic PSVT event was 11 days in the placebo group and greater than 55 days in the flecainide group (p less than 0.001). Likewise, the interval between attacks was a median of 12 days on placebo compared with more than 55 days on flecainide (p less than 0.001). Finally, the flecainide slowed symptomatic PSVT heart rates to 143 +/- 12 beats/min from 178 +/- 12 on placebo (p less than 0.02) in the seven patients who had events in the placebo and flecainide treatment phases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ethylene oxide dispersion from gas sterilizers

Ethylene oxide (EtO) is widely used by the health industry for sterilizing heat-sensitive devices. About 100 000 workers are regularly exposed to this chemical, used in an estimated 10 000 sterilizing units in U.S. health care facilities. Based on recent findings. NIOSh has recommended that EtO be regarded as a potential carcinogen and has urged OSHA to reexamine its present standard of 50 ppm. The ACGIH Notice of Intended Changes for 1982 has proposed reducing the recommended limit from 10 ppm TWA to 1 ppm and considers EtO a suspect carcinogen for man. Because of this increasing concern for its toxicity, it is imperative that the exposures to EtO be assessed, and that all reasonable steps to reduce these exposures be taken. This study demonstrates the effects of local exhaust ventilation, sterilizer chamber temperature, and sterilizer relative humidity in relation to their influence on EtO plume directionality, concentration and duration. Using two Foxboro/Wilks Miran 1A General Purpose Gas Analyzers, EtO concentrations were simultaneously monitored both immediately above and below the sterilizer door during various process runs, at three different types of sterilizers. Sterilizer operating conditions were representative of temperatures (38-54 degrees C (100-130 degrees F)), and relative humidities (30-50%) commonly employed in the sterilization process. The effects of varying local exhaust parameters were observed. Results clearly demonstrated that EtO tends to flow upward when the sterilizer door is opened. In all cases, the highest concentrations were observed at the upper location. Local exhaust ventilation significantly reduced the concentration of EtO observed and lessened the duration for which these levels persisted. Changes in temperature and relative humidity, within the range cited, have not shown any significant differences in EtO evolution patterns, concentrations or duration.