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Biomedical subjects

J Peters

Publications and source records attributed to J Peters.

At least 181 records · Page 10Linked to original sources
PubMed1999

Effect of lactacidosis on cell volume and intracellular pH of astrocytes.

Acute traumatic or ischemic cerebral lesions are associated with tissue acidosis leading to cytotoxic brain edema, predominantly affecting astrocytes. Glial swelling from acidosis is believed to be the attempt of cells to maintain a physiological intracellular pH (pHi). However, this concept, potentially important for the development of new treatment strategies for cytotoxic brain edema, has not been validated experimentally. In the present study, cell volume and pHi of astrocytes were measured simultaneously in vitro. Exposure of suspended astrocytes to levels of acidosis found in vivo during ischemia and trauma (pH 6.8-6.2) led to a maximal increase in cell volume of 121.2% after 60 min (n = 5, p < 0.05) and to immediate intracellular acidification close to extracellular levels (pH 6.2, n = 5, p < 0.05). Inhibition of membrane transporters responsible for pHi regulation (0.1 mM amiloride for the Na+/H+ antiporter or 1 mM SITS for HCO3- -dependent transporters) inhibited cell swelling from acidosis but did not affect the profound intracellular acidification. In addition, acidosis-induced cell swelling and intracellular acidification were partly prevented by the addition of ZnCl2 (0.1 mM), an inhibitor of selective proton channels not yet described in astrocytes (n = 5, p < 0.05). In conclusion, these data demonstrate that glial swelling from acidosis is not a cellular response to defend the normal pHi, as had been thought. If these results obtained in vitro are transferable to in vivo conditions, the development of blood-brain barrier-permeable agents for the inhibition of acidosis-induced cytotoxic edema might be therapeutically useful, since they do not enhance intracellular acidosis and thus cell damage.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1999

Effects of ambient air pollution and environmental tobacco smoke on respiratory health of non-smoking women in Hong Kong.

BACKGROUND: Two-thirds of complaints received by the Hong Kong Environmental Protection Department in 1988 were related to poor air quality. In July 1990 legislation was implemented to reduce fuel sulphur levels. The intervention led to a reduction in respiratory symptoms and bronchial hyperresponsiveness of primary school children. The objectives of this study were to investigate the differences in respiratory health between non-smoking women living in the more polluted district (Kwai Tsing) and those living in the less polluted district (Southern); to assess the impact of the government air quality intervention; and to study the effect of environmental tobacco smoke on respiratory health in non-smoking women in both districts. METHOD: A total of 3405 non-smoking women, aged 36.5 years (standard deviation = 3.0), from two districts with good and poor air quality respectively before the intervention were followed yearly from 1989 to 1991. Binary latent variable modelling was used to summarize the six respiratory symptoms and to estimate the effects of risk factors. RESULTS: In 1989, living in the polluted district was associated with poor respiratory health (odds ratio [OR] = 1.55, 95% confidence interval [CI]: 1.11-2.17, P < 0.01). After the intervention, in the polluted district only, sulphur dioxide levels fell by up to 80% and sulphate concentrations in respirable particulates by 38%. Between 1989 and 1990-1991, there was no significantly greater decline (P > 0.241) in the more polluted compared with the less polluted district for poor respiratory health. In 1989, the effects on poor respiratory health for exposure to two or more categories of smokers relative to none in the home (OR = 1.80, 95% CI: 1.15-2.83, P < 0.01) were higher but not significantly than those for living in polluted relative to less polluted district (95% CI of the two effects overlapping each other). CONCLUSIONS: Environmental tobacco smoke (ETS) and outdoor air pollution had independent adverse effects on respiratory health of non-smoking women and improvement in air quality had produced some but non-significant benefits.

Adolescent↗
PubMed1999

Combined antithrombin III and C1-esterase inhibitor treatment decreases intravascular fibrin deposition and attenuates cardiorespiratory impairment in rabbits exposed to Escherichia coli endotoxin.

OBJECTIVE: To assess the effect of a combined antithrombin III and C1-esterase inhibitor treatment on intravascular organ fibrin deposition and cardiorespiratory changes following intravenous Escherichia coli endotoxin (lipopolysaccharide [LPS] 80 microg/kg i.v.) exposure. DESIGN: Prospective, randomized trial. SETTING: Research laboratory of a university medical center. SUBJECTS: Anesthetized, instrumented and mechanically ventilated rabbits ([Chbb:CH); n = 40). INTERVENTIONS: Endotoxin was given to 30 animals. Ten animals received no inhibitor (endotoxin control group). The other animals were either treated by high-dose (300 units/kg; n = 10) or low-dose (100 units/kg; n = 10) combined antithrombin III and C1-esterase inhibitor administration. Ten rabbits (time control group) were given placebo (sodium chloride 0.9%). Cardiorespiratory variables were assessed at baseline, 120 mins, and 240 mins after endotoxin or placebo administration. Four hours after endotoxin injection, liver, lung, and kidney tissue samples were examined for intravascular fibrin deposition by light microscopy. MEASUREMENTS AND MAIN RESULTS: Inhibitor treatment significantly decreased clot formation in lungs and livers without, however, demonstrating a clear dose-dependent effect. Combined antithrombin III/C1-esterase treatment attenuated the decrease of mean arterial pressure and cardiac output observed following endotoxin injection. Blood pressure improvement was significantly dependent on dosage administered. CONCLUSION: Combination of antithrombin III and C1-esterase inhibitor treatment during early endotoxin shock decreased organ fibrin deposition and improved cardiovascular stability.

Animals↗
PubMed1999

A randomized, prospective study to evaluate the efficacy and acceptance of three bowel preparations for colonoscopy in children.

OBJECTIVE: We performed a prospective, randomized, single-blind study in children undergoing colonoscopy to evaluate the acceptance and efficacy of three different bowel preparations. METHODS: Seventy patients (ages 3-20 yr, 38 males) were randomly assigned to one of the three study preparations: Magnesium citrate with X-prep and clear liquid diet for 2 days (group A); Dulcolax for 2 days and Fleet enema without dietary restriction (group B); and Golytely 20 ml/kg (up to 1 L) per hour for 4 h with clear liquid diet for 1 day (group C). Endoscopists blinded to bowel preparation graded the adequacy of colon cleansing. The preparations were rated by patients for tolerance, willingness to retake them, adverse effects, and compliance. RESULTS: Data analysis using Fisher exact test and trend test showed that colon cleansing in groups A and C was superior to that in group B (p < 0.0001) and better in group C than A (p < 0.075). Overall tolerance and compliance were significantly better for groups A and B than group C (p < 0.003), but not different between A and B. More of group B patients were willing to retake the preparation than in group C (p < 0.002) and group A (p < 0.05), but this was not different between groups A and C. Adverse effects were reported more frequently by patients in group C than in groups A and B (p < 0.01). CONCLUSIONS: Although the least well tolerated, Golytely provided the best cleansing. Dulcolax without dietary restriction provided unsatisfactory colon cleansing. Magnesium citrate with X-prep was acceptable and provided good cleansing.

Adolescent↗
PubMed1999

Effect of spirometer temperature on FEV1 in a longitudinal epidemiological study.

OBJECTIVES: To assess the magnitude of error in pulmonary function measurements introduced by variation in spirometer temperature under field conditions. In a large scale epidemiological study of school children, the influence was investigated of spirometer temperature on forced expiratory volume in 1 second (FEV1) measured with dry rolling seal volumetric spirometers and conventional body temperature, pressure, and saturation (BTPS) corrections. METHODS: Linear regression analyses were performed on data from 995 test-retest pairs on 851 different children, with 1-110 days between test and retest, and spirometer temperature differences between -13 degrees C and +9 degrees C. RESULTS: After adjusting for effects of growth (test-retest intervals) and circadian variation (changes in times of testing), differences in standard BTPS corrected FEV1 showed significant (p < 0.05) dependence on differences in spirometer temperature between tests (-0.24%/degree C). CONCLUSIONS: When spirometer temperatures vary widely, standard BTPS correction does not fully adjust for gas contraction. To improve accuracy of volume measurements in epidemiological studies, additional correction for variation in spirometer temperature should be considered.

Adolescent↗
PubMed1999

Local renin-angiotensin system is involved in K+-induced aldosterone secretion from human adrenocortical NCI-H295 cells.

NCI-H295, a human adrenocarcinoma cell line, has been proposed as a model system to define the role of the renin-angiotensin system in the regulation of aldosterone production in humans. Because the precise cellular localization of the components of the renin-angiotensin system in human adrenal cortical cells remains unclear, we investigated their localization in this defined cell system. NCI-H295 cells expressed both angiotensinogen and renin as shown by reverse transcriptase polymerase chain reaction and immunohistochemistry. Human angiotensin-converting enzyme (ACE) was not detectable by immunocytochemistry, ACE binding, or reverse transcriptase polymerase chain reaction. However, 3.5 mmol/L K+ stimulated the formation of both angiotensin I and angiotensin II 1. 9- and 2.5-fold, respectively, and increased aldosterone release 3. 0-fold. The K+-induced stimulation of aldosterone release was decreased by captopril and enalaprilat (24% and 26%, respectively) and by the angiotensin type 1 (AT1)-receptor antagonist losartan (28%). Angiotensin II-induced stimulation of aldosterone release was abolished by losartan treatment. Specific [125I]Sar1-angiotensin II binding was detected by receptor autoradiography. The binding of [125I]Sar1-angiotensin II was completely displaced by the AT1 antagonist losartan but not by the AT2 receptor ligand PD 123319, confirming the expression of angiotensin II AT1 receptors in NCI-H295 cells. Our results demonstrate that NCI-H295 cells express most of the components of the renin-angiotensin system. Our failure to detect ACE, however, suggests that the production of angiotensin II in NCI-H295 cells may be ACE independent. NCI-H295 cells are able to produce angiotensin II, and K+ increases aldosterone secretion in part through an angiotensin-mediated pathway. The production of angiotensin II in NCI-H295 cells demonstrates that this human cell line can be useful to characterize the role of locally produced angiotensin II in the regulation of aldosterone release.

Adrenal Cortex↗
PubMed1999

Both intravenous and inhaled lidocaine attenuate reflex bronchoconstriction but at different plasma concentrations.

Intravenous lidocaine can attenuate bronchial hyperreactivity. However, lidocaine inhalation might yield the same or better results at higher airway and lower lidocaine plasma concentrations. Therefore, we tested in awake volunteers with bronchial hyperreactivity the effect of lidocaine on histamine-induced bronchoconstriction administered either intravenously or as an aerosol. After approval of the local ethics committee, 15 volunteers were enrolled in this placebo-controlled, double-blinded, randomized study. Volunteers were selected by showing a decrease in FEV1 greater than 20% of baseline (PC20) in response to histamine inhalation. On three different days the challenge was repeated after pretreatment with either intravenous lidocaine, inhaled lidocaine, or placebo. Blood samples for determination of lidocaine plasma concentration were drawn. Comparisons were made using the Friedman and Wilcoxon signed-rank tests. Baseline PC20 was 6.4 +/- 1.1 mg. ml-1. Both inhalation of lidocaine and intravenous administration significantly increased PC20 to 14.8 +/- 3.5 mg. ml-1 and 14.2 +/- 2. 5 mg. ml-1, respectively (p = 0.0007). Peak plasma lidocaine concentrations at the end of challenges were 0.7 +/- 0.1 microg. ml-1 (inhaled) and 2.2 +/- 0.1 microg. ml-1 (i.v.). However, 7 of 15 subjects showed an initial decrease of FEV1 greater than 5% following lidocaine inhalation. While both intravenous as well as inhaled lidocaine attenuate reflex bronchoconstriction significantly, lidocaine plasma concentrations are significantly lower after inhalation. However, the high incidence of initial bronchoconstriction to lidocaine inhalation may limit its use in patients with asthma and thus offers therapeutic advantages for intravenous lidocaine.

Administration, Inhalation↗
PubMed1999

Losartan and angiotensin II inhibit aldosterone production in anephric rats via different actions on the intraadrenal renin-angiotensin system.

Angiotensin II (ANG II) is a major stimulator of aldosterone biosynthesis. When investigating the relative contribution of circulating and locally produced ANG II, we were therefore surprised to find that ANG II, given chronically s.c. (200 ng/kg x min), markedly inhibits a nephrectomy (NX)-induced rise of aldosterone concentrations (from 10 +/- 2 to 465 +/- 90 ng/100 ml in vehicle infused, and from 9 +/- 2 to 177 +/- 35 in ANG II infused rats 55 h after NX and hemodialysis). We further observed, by in situ hybridization, that bilateral NX increases the number of adrenocortical cells expressing renin and that this rise was prevented by ANG II. Moreover, the rise of aldosterone levels was also inhibited by the AT1-receptor antagonist, losartan (10 microg/kg x min, chronically i.p. from 8 +/- 2 to 199 +/- 26 ng/100 ml), despite the absence of circulating renin and a reduction of ANG I to less than 10%. These data demonstrate that aldosterone production, after NX, is regulated by an intraadrenal renin-angiotensin system and that this system is physiologically suppressed by circulating angiotensin. Because the effects of losartan or ANG II on aldosterone production involved a latency period of at least 30 h after NX and were associated with a modulation or recruitment of renin-producing cells, we suggest that the intraadrenal renin-angiotensin system operates via regulation of cell differentiation on a long-term scale, rather than or additionally to its short-term effects on aldosterone synthase activity.

Adrenal Glands↗
PubMed1999

A theoretical basis for investigating ambient air pollution and children's respiratory health.

Acute respiratory health effects in children from exposure at current ambient levels of ozone are well documented; however, evidence for acute effects from other criteria pollutants such as nitrogen dioxide and respirable particles is inconsistent. Whether chronic effects result from long-term exposure to any of these pollutants during childhood is an important unresolved question. Establishing whether acute or chronic effects result from childhood exposure and identifying sensitive subgroups may require integration of biologic mechanisms of lung defenses, injury, and response into the study design and statistical models used in analyses. This review explores the theoretical basis for explaining such adverse effects in light of our contemporary understanding of mechanisms of lung injury and response at the cellular and molecular levels. The rapidly evolving understanding of the effects of air pollution on cellular and molecular levels presents an opportunity to develop and refine innovative biologically based hypotheses about the effects of childhood exposure. We hypothesize that children with low fruit and vegetable intake, low antioxidant levels, high polyunsaturated fat intake, or who have inherited certain alleles for genes involved in lung defenses and immune response regulation may be at increased risk for adverse effects. Because responses to air pollutants of interest are complex and involve a number of pathophysiologic processes, the magnitude of main effects of dietary factors, genes, and gene-environment interactions may be modest for individuals; however, each may make an important contribution to the population burden of preventable respiratory diseases.

Air Pollution↗
PubMed1999

The Janus face of the archaeal Cdc48/p97 homologue VAT: protein folding versus unfolding.

Members of the AAA family of ATPases have been implicated in chaperone-like activities. We used the archaeal Cdc48/p97 homologue VAT as a model system to investigate the effect of an AAA protein on the folding and unfolding of two well-studied, heterologous substrates, cyclophilin and penicillinase. We found that, depending on the Mg2+ concentration, VAT assumes two states with maximum rates of ATP hydrolysis that differ by an order of magnitude. In the low-activity state, VAT accelerated the refolding of penicillinase, whereas in the high-activity state, it accelerated its unfolding. Both reactions were ATP-dependent. In its interaction with cyclophilin, VAT was ATP-independent and only promoted refolding. The N-terminal domain of VAT, which lacks ATPase activity, also accelerated the refolding of cyclophilin but showed no effect on penicillinase. VAT appears to be structurally equivalent over its entire length to Sec18/NSF, suggesting that these results apply more broadly to group II AAA proteins.

Adenosine Triphosphatases↗
PubMed1999

Microbiological efficacy of superheated steam. I. Communication: results with spores of Bacillus subtilis and Bacillus stearothermophilus and with spore earth.

For the spores of Bacillus subtilis and Bacillus stearothermophilus as well as for spore earth (acc. DIN 58,946 Part 4 of August 1982), the dependence of resistance on the superheating of the steam used to kill germs was determined. A material (glass fibre fleece) was used as the germ carrier which does not superheat on contact with steam. The temperature of the saturated steam was 100 degrees C (B. subtilis) and 120 degrees C (B. stearothermophilus and spore earth). The yardstick for the resistance of the spores or bioindicators was the exposure period of the saturated or superheated steam at which 50% of the treated test objects no longer showed any viable test germs. The spores of Bacillus subtilis were far more sensitive to superheating of steam and reacted far more than the spores of Bacillus stearothermophilus and the germs in the spore earth. When superheating by 4 Kelvin the spores of Bacillus subtilis were approximately 2.5 times more resistant than they were to saturated steam. The resistance of Bacillus stearothermophilus and spore earth was only slightly higher up to superheating by 10 Kelvin. The spores of Bacillus subtilis had the highest resistance during superheating by 29 Kelvin; they were 119 times more resistant than they were to saturated steam. The resistance maximum of the spores of Bacillus stearothermophilus was at an superheating by around 22 Kelvin. However, the spores were only 4.1 times more resistant than they were to saturated steam. When using steam to kill germs, we must expect superheated steam. This raises the question whether the spores of Bacillus stearothermophilus, with their weaker reaction to the superheating of steam, are suitable as test germs for sterilisation with steam in all cases.

Bacillus subtilis↗
PubMed1999

Resistance of enterococci to heat and chemical agents.

Within the framework of the standardisation efforts on disinfectant testing on the European level the test germ Enterococcus hirae ATCC 10541 has been included for some time in the test requirements whereas the test strain Enterococcus faecium, which has frequently been used up to now, has been largely ignored. We compared the thermal and the chemical resistance of both test germ species. In the quantitative suspension test with active ingredients from the group of aldehydes, phenols, quaternaries and oxidizing agents with the exception of peracetic acid, no significant differences were determined between the two strains. In the case of the studies on thermal resistance at 65 degrees C and 68 degrees C, Enterococcus faecium ATCC 6057, by contrast, proved to be far more resistant than Enterococcus hirae ATCC 10541. According to these results, priority should be given to Enterococcus faecium over Enterococcus hirae as the test germ for chemical and also chemothermal disinfection.

Benzalkonium Compounds↗
PubMed1999

[History of surgical instruments. 9. Surgical instruments and development of surgical technique of lithotomy incision].

Lithotomy, i.e. the surgical method of cutting for stone in the bladder, belongs to the oldest and, due to the high risk, most notorious operating techniques. Records of stone-cuttings date as far back as Ancient Greece. The first detailed description of the procedure and instrumentation of lithotomy is to be found by Celsus (1. century AD). The patient in the lithotomy position, the neck of the bladder is approached by a median incision of the perineum. Celsus is also the first to mention special stone-hooking instruments ("uncus") to aid in extracting the bladder-stones. Medico-historical development lead to constant changes in the technique as well as in the instrumentation, since the lack of analgesia and anaesthesia necessitated quick operations of only a few minutes. A key step in the progress of operation was the introduction of so-called path-finders and directing probes in the 16th century. The opening of the bladder from the perineal incision was now accompanied by the simultaneous admission of a metal catheter into the bladder via urethra, thus providing the "Lithotomist", through manual control of the catheter, with an enhanced orientation towards the position of urethra and bladder. At that time, the dissection was conducted bluntly and without direct view of the situation, i.e. without an exact representation of the structures to be separated. Thanks to the improved instrumentation, the instruments could now be guided along a probe directly into the bladder, thus alleviating the tedious search for the opening after changing instruments, all the while with an agitated, pressing patient. Famous names in the development of the lithotomy with an perineal incision are the medical doctor Mariano Santo (around 1488-1564), the barber-surgeon Frère Jacques de Beaulieu (1651-1719) and later Johann Jakob Rau M.D. (1668-1719). Only later, to avoid injury to the perineum, the suprasymphyseal approach ("Sectio alta") was adopted (primarily by Pierre Franco 1556). Due to the construction of arrow-like probe by the barber-surgeon Frère Come (Jean Baseilhac [1703-1781]), which was pushed through the urethra into the bladder and up and above the symphysis, the danger of damaging or penetrating the peritoneum was greatly reduced. In the 19th century the upper lithotomy prevailed as the standard operating method over the perineal approach, known even by the ancient Greeks, but marked by its high complication rate. Since the end of the 19th century, however, the upper lithotomy in ist turn, has been nearly completely replaced by the cystoscopic transurethral lithotripsy.

Cystostomy↗
PubMed1999

Combining nursing roles in dermatology.

There is an increasing demand for dermatology expertise among patients and community nurses. Combining the role of dermatology nurse practitioner with that of community dermatology liaison nurse allowed dermatology expertise to be provided in both hospital and the community. The aim was to reduce waiting times, provide a nursing alternative to dermatologists and open access for community nurses to specialist expertise.

Community Health Nursing↗