The staircase phenomenon at the corrugator supercilii muscle in comparison with the hand muscles.

BACKGROUND: Phonomyography (PMG) is a novel method to monitor neuromuscular block. It is non-invasive and can be applied to any muscle. It can be used interchangeably with mechanomyography (MMG). The staircase phenomenon has not been investigated for this method or at the corrugator supercilii muscle. The purpose of this work was to determine the staircase effect at three different muscles using two different methods. METHODS: In 10 patients undergoing general anaesthesia with sevoflurane, using a laryngeal mask airway without the aid of neuromuscular block, one piezo-electric microphone each was applied to the corrugator supercilii muscle and the first dorsal interosseus muscle. In addition, a force transducer was attached to the tip of the thumb to determine the force of the adductor pollicis muscle. Supramaximal stimulation at 1 Hz was used at the ulnar and the facial nerve. All signals were simultaneously recorded for 30 min. Data are presented as means (SD). RESULTS: The staircase effect was significantly positive for the first dorsal interosseus muscle and the adductor pollicis muscle. The signal potentiation was not significantly different between the first dorsal interosseus muscle with a maximum increase at 148 (19)% using PMG, and the adductor pollicis muscle at 154 (22)% using MMG. The evoked signals reached a plateau after 15-18 min at both muscles. There was only a small initial increase in signal height at the corrugator supercilii to a maximum of 117 (20)% at 7 min, after which the signals decreased to reach a plateau at 25 min. In comparison with the signal height of 105 (25)% at 30 min, there was no significant difference of signal heights throughout the observation period. CONCLUSIONS: A positive staircase phenomenon is found equally at the first dorsal interosseus muscle and the adductor pollicis muscle. There is no significant staircase effect at the corrugator supercilii muscle.

Flow Velocity Induces a Switch From Active to Passive Suspension Feeding in the Porcelain Crab Petrolisthes leptocheles (Heller).

A flow-induced switch in suspension-feeding behavior of the porcelain crab Petrolisthes leptocheles was investigated in a laboratory flow tank. Crabs were exposed to two types of experimental water flow to stimulate them to switch from active to passive suspension feeding. In the first experiment, feeding crabs were exposed to a unidirectional accelerating water current, and they switched from active to passive suspension feeding at a mean water velocity of 3.49 cm s-1. In the second experiment, crabs were exposed to flow that was fixed at a constant velocity for at least 10 min, and their feeding behavior in this steady flow was observed. This procedure was repeated, using a range of constant-velocity flows that were successively adjusted to increased velocity levels. Crabs exposed to these different constant-velocity flows fed exclusively actively at flows below 1.5 cm s-1 and exclusively passively at those above 4.5 cm s-1. Switches from active to passive feeding occurred throughout the range of constant-velocity flows from 1.5 to 4.5 cm s-1. Changes in feeding activity rate induced by an increase in water velocity were measured. The mean activity rate of active feeding (1.05 Hz) was 3.4 times higher than that of passive feeding (0.31 Hz). The porcelain crab's ability to switch feeding modes in response to increased water velocity probably enhances energetic feeding efficiency in two ways. First, the passive feeding activity rate is lower than the active one and should reduce energetic expenditure. Additionally, the flux of suspended food increases with water flow velocity, so passive feeders are likely to catch more food per unit time than active feeders do. The ability to switch feeding modes is quite similar to that already described for balanomorph barnacles and appears to represent convergent evolution of flexible feeding behavior in response to variable water flow environment.

Grazing in a turbulent environment: behavioral response of a calanoid copepod, Centropages hamatus.

Models of marine ecosystem productivity rely on estimates of small-scale interactions, particularly those between copepods and their algal food sources. Rothschild and Osborn [Rothschild, B. J. & Osborn, T. R. (1988) J. Plankton Res. 10, 465-474], hypothesized that small-scale turbulence in aquatic systems increases the perceived abundance of prey to predators. We tested this hypothesis by exposing the planktonic copepod Centropages hamatus to turbulent and nonturbulent environments at different prey concentrations. Our results fell into two main categories. First, the response to turbulence was characterized by an initial period having a high number of escape reactions. This period was followed by one of increased foraging. C. hamatus responded to the higher encounter rates due to turbulence as if it were experiencing altered prey concentrations. Second, the termination of turbulence resulted in an increased foraging response, which was not directly related to the encounter rate. Functional response curves do not adequately explain this foraging response because the time course of the foraging response depends on prior encounter experience and foraging motivation.

All-terrain vehicle accidents: the experience of one hospital located near a major recreational area.

In two separate studies, charts of 169 all-terrain vehicle (ATV) accident victims admitted to the emergency department of Desert Hospital in Palm Springs, California, were reviewed. Twenty-four percent of the cases were women, 30% were hospitalized, and 1% (two patients) died. The youngest patient was 3 and the oldest was 76. About 31% had been drinking, and the major type of bony injury (16%) was to the clavicle, ribs, or sternum. The accident rate was calculated as ten accidents per 1,000 ATV rider days, which is comparable to the ski accident rate of six per 1,000 skier days. The three-wheeled variety of ATV is responsible for nearly all the accidents.

Clinical efficacy of moxalactam with emphasis on infections due to multidrug-resistant organisms in patients with renal insufficiency.

The efficacy of moxalactam, a new beta-lactam antibiotic with an expanded spectrum of in vitro activity, was evaluated in 22 patients with 27 sites of infection. The pathogens included six strains of multidrug-resistant Serratia marcescens and one of Pseudomonas aeruginosa. The minimal inhibitory concentration of moxalactam for the study isolates ranged from less thant 0.12 to 32 microgram/ml. Peak serum levels exceeded the minimal inhibitory concentration of the pathogen in every instance with mean peak serum levels of 43.0, 65.0 and 123 microgram/ml for doses of 0.5, 1.0 and 2.0 g, respectively. Pharmacokinetic data was obtained in patients with normal and abnormal renal function and during hemodialysis. Moxalactam was found to have excellent penetration into synovial, peritoneal, pleural and cerebrospinal fluids. 23 of the 27 infections were cured, There were six episodes of recurrent infections at the 4-week follow-up among the 12 patients treated for urinary tract infections. Drug toxicity was not a major problem. There were nine instances of superinfection noted (three each due to Candida spp., enterococci and P. aeruginosa), only of which was clinically significant.

In vitro comparison of three new cephalosporins: LY-127935, cefotaxime and cefoperazone.

The comparative in vitro activity of three new cephalosporin antibiotics Ly-127935 (LY), cefotaxime (CTX) and cefoperazone (CFP) was examined. LY, CTX and CFP had similar activity against Staphylococcus aureus, Escherichia coli and Proteus mirabilis while CFP was less inhibitory than LY or CTX against Klebsiella spp.; indole + Proteus and gentamicin (GM)-susceptible Serratia. LY and CTX were effective while CFP was inactive against Enterobacter spp. and GM-resistant Serratia. CFP was more active than LY or CTX against GM-susceptible Pseudomonas aeruginosa but was the least active agent against GM-resistant isolates. Bacteroides fragilis were more susceptible to LY than CTX or CFP. Combination studies against P. aeruginosa with cephalosporin-GM pairs demonstrated synergy.

Klebsiella species: antimicrobial susceptibilities, bactericidal kinetics, and in vitro inactivation of beta-lactam agents.

In vitro properties of 19 antimicrobial agents were tested with 56 isolates of Klebsiella spp. The aminoglycosides and the new beta-lactam compounds cefotaxime and moxalactam were the most inhibitory drugs tested. Chloramphenicol, tetracycline, trimethoprim, and trimethoprim-sulfamethoxazole were moderately active, whereas piperacillin, mezlocillin, and furazlocillin were ineffective against 25% of the isolates. Gentamicin was the only agent tested that was uniformly bactericidal in time-kill experiments with drug concentrations of four times the minimal inhibitory concentration. In combination studies with gentamicin, moxalactam and furazlocillin each increased the rate of bacterial killing for three of five isolates as compared with gentamicin alone, whereas chloramphenicol significantly retarded the rate of bacterial killing for the same number of strains. Furazlocillin was completely inactivated after 24 h of incubation with each of five selected strains. The inactivation of moxalactam, cefoxitin, and cephalothin was 36, 56, and 72%, respectively. In all instances in which these four agents were inactivated to levels below the minimal bactericidal concentration, there was accelerated growth after initial inhibition. However, regrowth also occurred in three instances in which drug levels were higher than the minimal bactericidal concentration. Retesting after drug exposure revealed a 4- to 32-fold rise in the minimal inhibitory concentration and minimal bactericidal concentration in two of these isolates.

Recovery from Bacillus cereus sepsis.

A patient with acute leukemia developed two separate episodes of Bacillus cereus septicemia during one hospitalization. Leukopenia as a consequence of cytotoxic chemotherapy preceded both illnesses. The course of the infections was favorably influenced by the return of adequate numbers of circulating granulocytes and aminoglycoside therapy. Only one other compromised host is known to have recovered from this otherwise fatal disease.

LY-127935: a novel beta-lactam antibiotic with unusual antibacterial activity.

The in vitro activity of LY-127935, a new beta-lactam antibiotic, was examined by using 370 clinical bacterial strains. In comparison with several other beta-lactam agents, LY-127935 was the most inhibitory against the Enterobacteriaceae. It was remarkably active against multi-drug-resistant strains of Enterobacter spp., Serratia spp., and Pseudomonas aeruginosa. LY-127935 had four- to eightfold greater activity than did cefoxitin against Bacteroides fragilis. Production of beta-lactamase by Enterobacteriaceae did not influence the minimal inhibitory concentration of LY-127935. However, the beta-lactamase-producing strains of B. fragilis and Haemophilus influenzae had generally higher minimal inhibitory concentrations. LY-127935 was the least active agent tested against gram-positive aerobic cocci. Variations in pH, salt content, protein content, or inocula size had little influence on susceptibility to LY-127935. Although combination studies with LY-127935 and gentamicin demonstrated synergy for P. aeruginosa, the rates of killing for the combination and for gentamicin alone were similar.