The Saccharomyces cerevisiae weak-acid-inducible ABC transporter Pdr12 transports fluorescein and preservative anions from the cytosol by an energy-dependent mechanism.

Growth of Saccharomyces cerevisiae in the presence of the weak-acid preservative sorbic acid results in the induction of the ATP-binding cassette (ABC) transporter Pdr12 in the plasma membrane (P. Piper, Y. Mahe, S. Thompson, R. Pandjaitan, C. Holyoak, R. Egner, M. Muhlbauer, P. Coote, and K. Kuchler, EMBO J. 17:4257-4265, 1998). Pdr12 appears to mediate resistance to water-soluble, monocarboxylic acids with chain lengths of from C(1) to C(7). Exposure to acids with aliphatic chain lengths greater than C(7) resulted in no observable sensitivity of Deltapdr12 mutant cells compared to the parent. Parent and Deltapdr12 mutant cells were grown in the presence of sorbic acid and subsequently loaded with fluorescein. Upon addition of an energy source in the form of glucose, parent cells immediately effluxed fluorescein from the cytosol into the surrounding medium. In contrast, under the same conditions, cells of the Deltapdr12 mutant were unable to efflux any of the dye. When both parent and Deltapdr12 mutant cells were grown without sorbic acid and subsequently loaded with fluorescein, upon the addition of glucose no efflux of fluorescein was detected from either strain. Thus, we have shown that Pdr12 catalyzes the energy-dependent extrusion of fluorescein from the cytosol. Lineweaver-Burk analysis revealed that sorbic and benzoic acids competitively inhibited ATP-dependent fluorescein efflux. Thus, these data provide strong evidence that sorbate and benzoate anions compete with fluorescein for a putative monocarboxylate binding site on the Pdr12 transporter.

Chlorhexidine and chondrolysis in the knee.

We have summarised the clinical and pathological changes in the knees of three patients in whom aqueous chlorhexidine 0.02% had been used as the irrigation solution during arthroscopically-assisted reconstruction of the anterior cruciate ligament. Even very dilute solutions of chlorhexidine can cause marked chondrolysis of articular cartilage leading to severe permanent damage to the knee. Irrigation solutions should be checked carefully to ensure that their composition is appropriate to the procedure being carried out. Exposure of articular cartilage to chlorhexidine should be avoided.

Inhibitory action of a truncated derivative of the amphibian skin peptide dermaseptin s3 on Saccharomyces cerevisiae.

The inhibitory activity of a truncated derivative of the natural amphibian skin peptide dermaseptin s3-(1-16)-NH2 [DS s3 (1-16)] against Saccharomyces cerevisiae was studied. Significant growth inhibition was observed after exposure to 3.45 microgram of the peptide per ml at pH 6.0 and 7.0, with complete growth inhibition occurring at 8.63 microgram of peptide per ml for all pH values tested. Using confocal scanning laser microscopy, we have shown that DS s3 (1-16) disrupted the yeast cell membrane resulting in the gross permeabilization of the cell to the nuclear stain ethidium bromide. However, the principal inhibitory action of the peptide was not due to disruption of intracellular pH homeostasis. Instead, growth inhibition by the peptide correlated with the efflux of important cellular constituents such as ADP, ATP, RNA, and DNA into the surrounding medium. The combination of DS s3 (1-16) with mild heating temperatures as low as 35 degreesC significantly enhanced the inhibitory effect of the peptide (8.63 microgram/ml), and at 45 degreesC greater than 99% of the population was killed in 10 min. In summary, a derivative of a natural antimicrobial peptide has potential, either alone or in combination with mild heating, to prevent the growth of or kill spoilage yeast.

Comparison of the inhibitory effect of sorbic acid and amphotericin B on Saccharomyces cerevisiae: is growth inhibition dependent on reduced intracellular pH?

The effects of sorbic acid and amphotericin B on the growth and intracellular pH (pHi) of Saccharomyces cerevisiae were studied and compared. Past evidence has suggested that the inhibitory action of sorbic acid on yeast is due to reduction of pHi per se. However, using a novel method to measure pHi in growing cells, little correlation was found between reduced growth rate on exposure to sorbic acid and reduction of pHi. In fact, growth inhibition correlated with an increase in the intracellular ADP/ATP ratio due to increased ATP consumption by the cells. This was partly attributed to the activation of protective mechanisms, such as increased proton pumping by the membrane H(+)-ATPase, which ensured that pHi did not decline when cells were exposed to sorbic acid. Therefore, the available evidence suggested that the inhibitory action of sorbic acid was due to the induction of an energetically expensive protective mechanism that compensated for any disruption of pHi homeostasis but resulted in less available energy for normal growth. In contrast to sorbic acid, with amphotericin B there was a direct correlation between growth inhibition and reduction of pHi due to the uncoupling effect of this compound on the plasma membrane. The inhibitory effect of amphotericin B was consistent with membrane disruption, or 'proton-uncoupling' leading to growth inhibition due to proton influx, decline in pHi and partial dissipation of the proton gradient.

Cardiac arrest following the use of hydrogen peroxide during arthroplasty.

A case is reported in which cardiac arrest immediately followed the use of hydrogen peroxide during preparation of the femoral canal during hip arthroplasty. The most likely cause of the arrest was thought to be oxygen embolism. The authors suggest that the use of peroxide in an unvented femoral canal may be hazardous, as it has been shown to be in other closed cavities in the body.

The acutely locked knee--is a manipulation worth while?

Over a 10-year period, 85 consecutive patients presented to the Accident and Emergency Department with an acutely locked knee and were all treated by manipulation under anaesthesia. Out of 69 patients who could be adequately followed up, 46 (67 per cent) subsequently required arthrotomy for an internal derangement. In 41 of these patients there was a bucket-handle tear of a meniscus. Twenty-three patients (33 per cent) made a full recovery from manipulation alone. In view of the high incidence of correctable lesions, immediate arthroscopy and, if necessary, definitive operation would be a better treatment for the acutely locked knee.

A prospective controlled trial of valgus osteotomy in the fixation of unstable pertrochanteric fractures of the femur.

A total of 62 patients with unstable pertrochanteric fractures of the neck of the femur was subjected to either nail plating with 130 degrees neck-shaft angle or valgus osteotomy using a neck-shaft angle of at least 140 degrees. The patients were assessed in terms of ability to walk and stability of fracture fixation. A clear superiority of valgus osteotomy over the controls was demonstrated in terms of fracture fixation, but the difference in terms of ability to walk was less remarkable.

Habitual extensor tendon dislocation.

Dislocated tendons are frequently seen in the rheumatoid hand. Habitual dislocation is rare. Five patients, all sero-negative with this problem, are described. The causation of the deformity and its treatment is discussed in relation to other cases reported in the literature. An extensor loop operation is recommended.

A comparison of internal fixation and prosthetic replacement in the treatment of displaced subcapital fractures.

This paper presents a retrospective review of 348 operations performed for subcapital fractures of the neck of the femur. A similar proportion of satisfactory results was obtained with internal fixation and prosthetic replacement. The mortality was higher in those treated by prosthetic replacement and careful selection of patients for this treatment is required.

The middle care round.

As an experiment in postgraduate education a 25-week course in weekly ward rounds for general practitioners and local authority nurses was established at a district general hospital of 340 beds. A total of 73 rounds were held, divided into 12-, 4-, and 9-week courses, from January to December 1969. Ninety-nine general practitioners and district nurses (including health visitors) attended one or more of these rounds. Seventeen consultants participated and there were 273 doctor attendances and 190 nurse attendances. The average attendance per round was four doctors and two nurses. The number of rounds conducted by each of the consultants throughout the course varied from two to six. This paper presents an evaluation of the course.