Ischaemic preconditioning is related to decreasing levels of extracellular adenosine that may be metabolically useful in the at-risk myocardium: an experimental study in the pig.

AIM: 'Pre-treatment' with short repetitive periods of ischaemia (ischaemic preconditioning) has proved to be a powerful mechanism for modification of the extent of myocardial damage following acute coronary artery occlusion. The exact mechanism of protection induced by ischaemic preconditioning is not known. We herewith put forward a contributing component for protection with preconditioning involving a shift in the adenylate kinase (AK) equilibrium reaction in favour of adenosine triphosphate (ATP) formation. METHODS: A coronary artery was occluded in anaesthetized thoracotomized pigs to induce ischaemic preconditioning as well as a longer period of ischaemia. Microdialysis probes were inserted in ischaemic and control myocardium and were infused with (14)C- adenosine with two different specific activities. (14)C-lactate was identified and measured in the effluent. RESULTS: (14)C-adenosine was taken up by non-preconditioned and preconditioned myocardium during ischaemia. Significantly increased levels of (14)C-lactate were recovered in preconditioned myocardium. (14)C-adenosine with high specific activity resulted in a specific activity of lactate that was 2.7 times higher than that of lactate after administration of (14)C-adenosine with low specific activity. Mass spectrography verified the identity of (14)C-lactate. CONCLUSIONS: Preconditioning up-regulates a new metabolic pathway (starting with 5'-nucleotidase and ending up with lactate) resulting in ATP formation in the micromolar range on top of another effect terminating in a useful shift in the AK equilibrium reaction in favour of ATP generation in the millimolar range. Although the up-regulation of the purine nucleoside phosphorylase pathway is clearly demonstrated, its biological relevance remains to be proved.

Metabolic responses in ischemic myocardium after inhalation of carbon monoxide.

BACKGROUND: To clarify the mechanisms of carbon monoxide (CO) tissue-protective effects, we studied energy metabolism in an animal model of acute coronary occlusion and pre-treatment with CO. METHODS: In anesthetized pigs, a coronary snare and microdialysis probes were placed. CO (carboxyhemoglobin 5%) was inhaled for 200 min in test animals, followed by 40 min of coronary occlusion. Microdialysate was analyzed for lactate and glucose, and myocardial tissue samples were analyzed for adenosine tri-phosphate, adenosine di-phosphate, and adenosine mono-phosphate. RESULTS: Lactate during coronary occlusion was approximately half as high in CO pre-treated animals and glucose levels decreased to a much lesser degree during ischemia. Energy charge was no different between groups. CONCLUSIONS: CO in the low-doses tested in this model results in a more favorable energy metabolic condition in that glycolysis is decreased in spite of maintained energy charge. Further work is warranted to clarify the possible mechanistic role of energy metabolism for CO protection.

Point-of-care testing of group A streptococcal antigen: performance evaluated by external quality assessment.

The purpose of this study was to evaluate the overall performance of rapid antigen detection (RAD) in group A streptococcus (GAS) in Finland by using the results of external quality assurance (EQA) samples. We also compared the performance of laboratory professionals to that of nursing professionals. Around 22,800 EQA results among a total of 383 laboratories and physician's offices were analysed. Vocational data on the personnel who carried out the tests were available for 10,088 EQA samples, 7,428 of which were tested by laboratory technicians and 2,531 by nursing staff. The best overall performance was found with GAS-negative samples: 99% of the reports were correct. In contrast, the overall performance was only 76% when the samples were weakly positive for GAS antigen. The laboratory technicians performed statistically significantly better than the nursing staff, with both strongly positive (correct results 98.9% vs. 95.1%, respectively; p<0.001) and weakly positive (79.3% vs. 65.3%, respectively; p<0.001) samples. With negative samples, no difference in performance between the laboratory and nursing staff was found (99.5% vs. 99.0%, respectively). The professional skills of the person performing the RAD test for GAS have a major impact on the sensitivity of the test. Based on the results of this study, we suggest that EQA-like artificial specimens could be used as a tool to improve and validate the quality of RAD testing in individual testing sites.

Molecular cloning and tissue expression of the murine analog to human stratum corneum chymotryptic enzyme.

Human stratum corneum chymotryptic enzyme (SCCE) may play a central part in epidermal homeostasis. Its proposed function is to catalyze the degradation of intercellular structures, including desmosomes, in the stratum corneum as part of the desquamation process. In order to facilitate physiologic and pathophysiologic studies on SCCE we have looked for the corresponding murine enzyme. A cDNA obtained by reverse transcription-polymerase chain reaction with total RNA prepared from mouse tails as starting material was cloned, and the expression of the corresponding mRNA studied. The murine cDNA showed 77% homology to human SCCE cDNA. It had an open-reading frame encoding a protein comprising 249 amino acids with 82% amino acid sequence homology to human SCCE including the conserved sequences of the catalytic traid of mammalian serine proteases. The murine protein was deduced to have a 21 amino acid signal peptide and a four amino acid propeptide ending with a tryptic cleavage site, followed by a sequence motif identical to the N-terminal amino acid sequence of native active human SCCE. As in human SCCE the P2 position of the propeptide was occupied by an acidic amino acid residue, and the position corresponding to the suggested bottom of the primary substrate specificity pouch occupied by an asparagine residue. Analyses of mouse tissues by reverse transcriptase-polymerase chain reaction showed high expression in the skin, low expression in lung, kidney, brain, heart, and spleen, and no expression in liver or skeletal muscle. In situ hybridization of mouse skin showed expression in high suprabasal keratinocytes and in the luminal parts of hair follicles. Our results strongly suggest that we have cloned the murine analog of human SCCE cDNA.

Expression of stratum corneum chymotryptic enzyme in human sebaceous follicles.

Stratum corneum chymotryptic enzyme (SCCE) may be involved in desquamation, a process necessary for maintaining a normal anatomy at all sites where there is continuous turnover of cornified epithelia. Using immunohistochemistry and in situ hybridization, we have, in this work, analysed SCCE expression in the sebaceous follicle. We found expression of SCCE in luminal parts of the pilary canal, common sebaceous ducts and proximal sebaceous ducts. In addition, SCCE was seen in cells apparently situated within the distal parts of the glandular lobules. Co-expression of SCCE and keratin 10 was seen only in the pilary canal and the common sebaceous ducts. The results give further support for SCCE being involved in desquamation-like processes. The association with cornification seems to be more general for SCCE than for keratin 10. The possible role of SCCE in diseases involving disturbances in the turnover of cornified cells in the sebaceous follicle, such as acne vulgaris, is a question for future studies.

Bacterial flora of the cervix in women using an intrauterine device.

The cervical bacterial flora of 18 healthy, parous, sexually active women was analysed before, and 3-5 months after insertion of a copper-releasing intrauterine device (IUD) and after long-term use of an IUD for 3-5.5 years in another nine women. No significant differences were found in the number of aerobic bacteria isolated before or after IUD insertion or after long-term use of an IUD. In contrast to aerobic bacteria, significantly more anaerobes were isolated in the cervix of women having used an IUD for several years when compared to those using barrier contraception with a condom. None of the women had clinical signs of pelvic infection and a cervical bacterial flora rich in anaerobes can be regarded as a normal finding in healthy sexually active women using an IUD for contraception.

Bacterial flora of the cervix in women using different methods of contraception.

Bacteriologic culture samples were taken from the cervix in three groups of 10 healthy, sexually active women using barrier contraception, oral contraceptives, or a levonorgestrel-releasing intrauterine contraceptive device. Culture samples for Candida albicans and Trichomonas vaginalis were taken, a cytologic vaginal smear was obtained, and an amine sniff test was performed; these were in addition to a routine gynecologic examination. Multiple bacteria were isolated from the cervix in women using oral contraceptives or an intrauterine contraceptive device, whereas lactobacilli alone dominated the flora of women using barrier contraception. Significantly more anaerobic bacteria were isolated from the cervix in oral contraceptive and intrauterine contraceptive device users when compared with the barrier method users. Symptoms and findings evident of anaerobic vaginosis were associated with the occurrence of anaerobic bacteria in the cervix of three patients using the intrauterine contraceptive device. The results showed that the cervical bacterial flora in sexually active healthy women is rich in anaerobes that can be regarded as a normal finding in women using oral contraceptives or intrauterine contraceptive devices. Barrier contraception with a condom prevents this anaerobic shift and maintains a lactobacilli-dominated flora in the cervix.