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P Christensen

Publications and source records attributed to P Christensen.

At least 73 records · Page 4Linked to original sources
PubMed1994

Active lithium transport by rat renal proximal tubule: a micropuncture study.

We tested the hypothesis that proximal tubular Li+ reabsorption is due to passive transport. Clearances of [14C]inulin (CIn) and Li+ (CLi), proximal transepithelial electrical potential difference (PD), and tubular fluid-to-plasma Li+ concentration ratios [(TF/P)Li] were measured in anesthetized rats before and after induction of osmotic mannitol diuresis. Late proximal (TF/P)Li was measured after acute intravenous LiCl administration and after addition of LiCl to the diet for 2 days. Glomerular filtration rate (CIn) decreased, whereas CNa and CLi increased during osmotic diuresis. Control early proximal PD was -0.6 mV (lumen negative); late proximal PD (PDLP) was 1.1 mV (lumen positive). PDLP decreased by 1.5 mV to -0.4 mV (lumen negative) after mannitol infusion. Late proximal (TF/P)Li was 1.01 after oral Li+, 1.16 after intravenous Li+ (P < 0.01), and 1.00 during osmotic diuresis. It is concluded that proximal Li+ transfer is distinct from that of Na+, closely parallels proximal water transfer, and involves an active transport mechanism independent of the PD. The data suggest that acute elevation of plasma Li+ concentration may activate a delayed Li+ transport pathway in the proximal convoluted tubule.

Anesthesia↗
PubMed1994

Improved analysis of picomole quantities of lithium, sodium, and potassium in biological fluids.

The analysis of picomolar lithium, sodium, and potassium by electrothermal atomic absorption spectrophotometry was studied using a Perkin-Elmer Zeeman 3030 spectrophotometer. With ordinary pyrolytically coated graphite tubes, a number of interference effects associated with the sample matrix were observed. In particular, the lithium and potassium absorbance signal was depressed by chloride, an effect shown to be dependent on the preatomization heating. When an in situ tantalum-coated atomization surface was used, matrix interferences observed in lithium and potassium analyses were abolished, and the linear range for the potassium assay was extended. Technical difficulties encountered during sodium analysis at the primary wavelength were effectively circumvented by analysis at a less-sensitive wavelength (303.3 nm), at which tantalum coating also prevented significant chloride interference. The improved microanalyses were employed to reevaluate the handling of lithium, sodium, and potassium along the proximal convoluted tubule (PCT) of the anesthetized rat. The average tubular fluid-to-plasma concentration ratios for lithium [(TF/P)Li] and sodium [(TF/P)Na] were 1.13 +/- 0.08, n = 26, and 0.99 +/- 0.07 (n = 26), respectively. The tubular fluid-to-plasma ultrafiltrate concentration ratio for potassium [(TF/UF)K] was 1.09 +/- 0.05 (n = 13). Ratios did not change significantly with puncture site along the PCT for any of the ions. (TF/P)Li and (TF/UF)K were significantly greater than (TF/P)Na, indicating that lithium and potassium reabsorption do not directly parallel sodium reabsorption in the PCT.

Animals↗
PubMed1994

A modified photo- and magnetoacoustic multigas analyzer applied in gas exchange measurements.

The feasibility of replacing a conventional mass spectrometer (MS) with a specially modified multicomponent (O2, CO2, Freon 22, and SF6) acoustic infrared and paramagnetic (IR/PM) gas analyzer in inert gas-rebreathing and metabolic gas exchange measurements has been investigated. Rebreathing variables were determined simultaneously with the MS and IR/PM analyzers in duplicate measurements at rest and during submaximal exercise in 10 subjects. The differences (means +/- SD, IR/PM - MS) were 0.028 +/- 0.048 liters [functional residual capacity (FRC)], 0.18 +/- 0.38 l/min [cardiac output (Qc)], -0.006 +/- 0.030 l/min [O2 consumption (VO2)], and -33 +/- 108 ml [combined lung tissue and capillary blood volume (Vti,c)]. The coefficients of variation on repeated estimates were 5.8% (FRC), 5.4% (Qc), 6.2% (VO2), and 17% (Vti,c) with the IR/PM analyzer and 5.9% (FRC), 4.2% (Qc), 5.0% (VO2), and 9.8% (Vti,c) with the MS. The differences (IR/PM - MS) obtained in mixed-expirate measurements were -0.006 +/- 0.020 l/min (VO2) and 0.020 +/- 0.021 l/min (CO2 production). Breath-by-breath estimates of VO2 and CO2 production with the IR/PM analyzer were, on average, 2.4 and 4.4% higher than the MS estimates, respectively. Our results demonstrate that the IR/PM gas analyzer, when appropriately modified, can substitute for a complex MS in a variety of noninvasive pulmonary gas exchange measurements.

Adult↗
PubMed1993

Endocrine correlates of placental permeability during gestation in the pig.

1. Hormone and electrolyte concentrations were determined in amniotic and allantoic fluid collected from sows at 47-112 days of gestation and correlated with placental and fetal membrane electrolyte permeability. 2. Significant differences between the electrolyte and endocrine gestational profiles of amniotic and allantoic fluid were identified. 3. The principal endocrine correlate (r > 0.62; P < 0.01) of gestational changes in the sodium and chloride permeabilities of the porcine placenta and fetal membranes was found to be the concentration of oestrogen in the amniotic fluid.

Allantois↗
PubMed1993

Accuracy of a new bedside method for estimation of circulating blood volume.

OBJECTIVE: To evaluate the accuracy of a modification of the carbon monoxide method of estimating the circulating blood volume. DESIGN: Prospective, clinical study comparing two methods for estimating the circulating blood volume. Carbon monoxide kinetics were studied by computer simulation. SETTING: Intensive care unit in a university hospital. PATIENTS: Intensive care patients receiving intermittent positive-pressure ventilation and healthy volunteers. MEASUREMENTS AND MAIN RESULTS: The circulating blood volume was determined from measurements of the carbon monoxide saturation of hemoglobin before and after rebreathing a gas mixture containing 20 to 50 mL of carbon monoxide for a period of 10 to 15 mins. A specially designed Water's "to & fro" system was developed to avoid any leakage during intermittent positive-pressure ventilation. Blood samples were taken before, during, and immediately after rebreathing. The amount of carbon monoxide administrated during each rebreathing maneuver resulted in an average increase in the carbon monoxide saturation of hemoglobin of 3.6%. The washin of carbon monoxide was completed within the first 4 to 6 mins of the rebreathing period in nine healthy subjects and within 10 mins in 12 intensive care patients. The 95% limits of agreement between the carbon monoxide method and the radioactive isotope-labeling method was +/- 540 mL (+/- 2 SD). CONCLUSION: Determination of circulating blood volume can be performed with sufficient accuracy using an amount of carbon monoxide that gives rise to an unharmful increase in the carboxyhemoglobin concentration.

Adult↗
PubMed1993

Precision of a new bedside method for estimation of the circulating blood volume.

The present study is a theoretical and experimental evaluation of a modification of the carbon monoxide method for estimation of the circulating blood volume (CBV) with respect to the precision of the method. The CBV was determined from measurements of the CO-saturation of hemoglobin before and after ventilation with a gas mixture containing 20-50 ml of CO for a period of 10-15 min. A special Water's to and fro system was designed in order to avoid any leakage when measuring during intermittent positive pressure ventilation (IPPV). Blood samples were taken before and immediately after ventilation with the CO gas mixture. The amount of CO administered during each determination of CBV resulted in an increase in the CO saturation of hemoglobin of 2.1%-3.9%. A theoretical noise propagation analysis was performed by means of the Monte Carlo method. The analysis showed that a CO dose corresponding to an increase of less than 2% will result in an unacceptable coefficient of variation of repeated estimates. In the experimental study the coefficient of variation of repeated estimates of CBV was determined from duplicate measurements of CBV in nine healthy subjects and in nine intensive care patients. The coefficients of variation were 6.2% and 4.7% in healthy and diseased subjects, respectively. Furthermore, the day-to-day variation of the method with respect to the total amount of circulating hemoglobin (nHb) and CBV was determined from duplicate estimates separated by 24-48 h. In conclusion, determination of CBV can be performed with an amount of CO that gives rise to a harmless increase in the carboxyhemoglobin concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Circulation↗
PubMed1993

A comparison of spirapril and isradipine in patients with diabetic nephropathy and hypertension.

The effects of spirapril and isradipine on blood pressure, urinary albumin excretion and sodium-volume homeostasis in hypertensive insulin-dependent diabetic patients with nephropathy were assessed. Fifteen Type 1 diabetic patients aged 28-53 years with a diabetes duration of 19-37 years were studied. All had hypertension and diabetic nephropathy with a urinary albumin excretion of more than 300 mg/24 h. After a single blind placebo treatment period of 4 weeks the patients were randomly assigned to treatment with the calcium antagonist isradipine SRO 5 mg once daily or the ACE inhibitor spirapril 6 mg once daily for 6 months in a double-blind design. Isradipine lowered ambulatory systolic blood pressure from 152 +/- 12 to 141 +/- 11 mmHg (p < 0.05) and ambulatory diastolic pressure from 91 +/- 9 to 86 +/- 8 mmHg (p < 0.05). The blood pressure lowering effect of spirapril was similar: 156 +/- 13 vs 143 +/- 11 mmHg (p < 0.01) and 90 +/- 4 vs 84 +/- 4 mmHg (p < 0.05). The fractional albumin clearance was unchanged on isradipine but decreased after 6 months treatment with spirapril with on average 20% (p < 0.05). Total body exchangeable sodium decreased on spirapril treatment: 2994 +/- 296 vs 2636 +/- 194 meq/1.73 m2 (p < 0.05) and extracellular volume tended to do so (p = 0.12). On isradipine treatment these parameters remained unchanged. In conclusion both isradipine and spirapril lowered blood pressure in patients with diabetic nephropathy. Only the ACE inhibitor had demonstrable beneficial effects on urinary albumin excretion rate and the sodium-volume expansion seen in these patients.

Adult↗
PubMed1992

Prevention of excess neonatal morbidity associated with group B streptococci by vaginal chlorhexidine disinfection during labour. The Swedish Chlorhexidine Study Group.

Streptococcus agalactiae transmitted to infants from the vagina during birth is an important cause of invasive neonatal infection. We have done a prospective, randomised, double-blind, placebo-controlled, multi-centre study of chlorhexidine prophylaxis to prevent neonatal disease due to vaginal transmission of S agalactiae. On arrival in the delivery room, swabs were taken for culture from the vaginas of 4483 women who were expecting a full-term single birth. Vaginal flushing was then done with either 60 ml chlorhexidine diacetate (2 g/l) (2238 women) or saline placebo (2245) and this procedure was repeated every 6 h until delivery. The rate of admission of babies to special-care neonatal units within 48 h of delivery was the primary end point. For babies born to placebo-treated women, maternal carriage of S agalactiae was associated with a significant increase in the rate of admission compared with non-colonised mothers (5.4 vs 2.4%; RR 2.31, 95% CI 1.39-3.86; p = 0.002). Chlorhexidine reduced the admission rate for infants born of carrier mothers to 2.8% (RR 1.95, 95% CI 0.94-4.03), and for infants born to all mothers to 2.0% (RR 1.48, 95% CI 1.01-2.16; p = 0.04). Maternal S agalactiae colonisation is associated with excess early neonatal morbidity, apparently related to aspiration of the organism, that can be reduced with chlorhexidine disinfection of the vagina during labour.

Administration, Intravaginal↗
PubMed1992

Benzodiazepine-induced sedation and cortisol suppression. A placebo-controlled comparison of oxazepam and nitrazepam in healthy male volunteers.

The sedative and cortisol suppressing properties of oxazepam (45 and 60 mg) and nitrazepam (10 and 15 mg) were examined in eight healthy male subjects. The most clear differences between oxazepam and nitrazepam were those seen with respect to the time course and until maximal effect (Tmax) of the different measurements. Nitrazepam showed maximal sedation after 1 h, maximal benzodiazepine level (RRA), and reaction time prolongation after 2 h, and maximal cortisol suppression after 3 h. Oxazepam showed maximal sedation after 2 h, maximal benzodiazepine levels, reaction time prolongation and cortisol suppression after 3 h. After administration of oxazepam (both doses) a transient return to baseline levels of cortisol was demonstrated. Whereas the degree of sedation correlated significantly within drug groups with the concurrent benzodiazepine levels, the Tmax of sedation was recorded 1 h earlier than the peak blood concentration (RRA) for both nitrazepam and oxazepam. The time course for cortisol suppression for the two compounds differed clearly from the other measurements and was not related to the peak blood concentration.

Affect↗
PubMed1992

A factor secreted by a human pulmonary alveolar epithelial-like cell line blocks T-cell proliferation between G1 and S phase.

Because the pulmonary alveolar space is both the site of gas exchange for respiration and a portal of entry for foreign antigen, immunologic interactions within that space must be meticulously controlled. Alveolar epithelial cells are ideally situated to play a role in immune regulation within the alveolar space. We have used A549 cells, a cell line that is derived from a human alveolar cell carcinoma and that has been used as a model for alveolar type II epithelial cells, to examine the potential role of alveolar epithelial cells in local pulmonary immune regulation. Medium conditioned by confluent monolayers of A549 cells suppressed proliferation by human peripheral blood mononuclear cells (PBMC) stimulated with lectin, anti-CD3 antibodies, calcium ionophore and phorbol ester, or in a mixed leukocyte reaction. PBMC that had been incubated in and then removed from A549-conditioned medium went on to proliferate normally. Because the suppressive effect was abrogated by heating or acidification and was not blocked by neutralizing antibody to transforming growth factor-beta 1, this effect could not be attributed to transforming growth factor-beta. The factor mediating this effect has an approximate molecular weight of 70,000 D by gel filtration chromatography. Nonalveolar, pulmonary carcinoma cell lines did not exert this immunosuppressive influence nor did the alveolar epithelial cells inhibit proliferation by the transformed, Jurkat, T-cell line. Cell cycle analysis demonstrated that PBMC exposed to A549 cell-conditioned medium failed to enter S phase after mitogen stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Factors↗
PubMed1992

Occurrence of antibodies to pneumococcal protein antigens in experimental acute otitis media.

To study serological antibody response to pneumococcal protein antigens, experimental pneumococcal (type 3) acute otitis media (AOM) was induced in 6 rats, sera being analysed with the Western blot technique at different intervals after bacterial challenge. The most striking finding was a distinct antibody response to a protein of about 35 kDa visible in 5 of the rat sera within 14 days, and persisting throughout the remainder of the study (i.e., 56 days in all). Moreover, appear to be a phenomenon restricted to type 3 pneumococci. Both the pathogenetic importance of this protein and the immunological response it evokes are still unclear. However, as antibodies to protein antigens may contribute to inflammatory reactions in the middle ear (e.g., otitis media with effusion), this 35-kDa protein might be important for the development of sequelae to AOM.

Acute Disease↗
PubMed1992

[Pachymeningeosis(-itis) haemorrhagica chronica interna].

A case of chronic internal haemorrhagic pachymeningeosis, a rare disease with uncharacteristic clinical appearance is presented. Derived from pathomorphological and histological findings, the typical CT appearance is described and main differential diagnoses are marked off by their characteristic criteria.

Dura Mater↗
PubMed1991

Western blot analysis of immunoglobulin G antibodies to pneumococcal protein antigens in healthy adults.

Using the Western Blot technique, sera from apparently healthy individuals were shown to contain antibodies against pneumococcal protein antigens of different molecular weights. A remarkable correlation was found to exist between the number of protein bands stained and the level of antibodies to type-specific carbohydrate antigens and C-polysaccharide. The findings suggest that the presence of antibodies against protein antigens reflects past infection with pneumococci.

Adult↗
PubMed1991

Dietary supplementation with omega-3-polyunsaturated fatty acids decreases mononuclear cell proliferation and interleukin-1 beta content but not monokine secretion in healthy and insulin-dependent diabetic individuals.

The effects of dietary supplementation with omega-3-polyunsaturated fatty acids (omega-3-PUFA) on the proliferative response of PBMC and on the secretion of monokines and arachidonic acid metabolites from PBMC and monocytes (Mo) from healthy subjects and patients with recent-onset insulin-dependent diabetes mellitus (IDDM) were examined. Three groups of eight to nine healthy individuals were randomized to either 2.0 g/day or 4.0 g/day of omega-3-PUFA devoid of vitamins A and D, or an isocaloric amount of placebo. Furthermore, eight patients with recent-onset IDDM received 4.0 g/day of omega-3-PUFA. IL-1 beta production and TNF-alpha secretion was determined before and after 7 weeks of treatment, and 10 weeks after withdrawal of treatment. Significant increases in platelet and PBMC membrane eicosapentaenoic acid was found in omega-3-PUFA-treated individuals. omega-3-PUFA treatment significantly reduced the content of IL-1 beta in lysates of PBMC, but did not affect PBMC or Mo secretion of IL-1 beta, TNF-alpha or prostaglandin E2 (PGE2) or PBMC leukotriene B4 (LTB4) secretion in healthy subjects or in IDDM patients. A significant inhibition of the PHA-stimulated, but not the spontaneous or PPD-stimulated, proliferative response of PBMC was observed in healthy and diabetic subjects treated with omega-3-PUFA. No correlation was found between PHA-stimulated PBMC proliferation and PBMC secretion of TNF-alpha and IL-1 beta. There were no significant differences in the spontaneous or the PPD- or PHA-stimulated proliferative responses of PBMC between diabetic and healthy individuals at entry. We conclude that although dietary supplementation with 4.0 g/day of omega-3-PUFA inhibits the proliferation of PBMC and reduces IL-1 beta immunoreactivity in PBMC and Mo, it does not alter monokine, PGE2 or LTB4, secretion in healthy or IDDM subjects.

Adult↗
PubMed1991

Measurement of transcutaneous PO2, PCO2 and skin blood flow at different probe temperatures using mass spectrometry.

Transcutaneously measured partial pressures of oxygen and carbon dioxide (PtcO2, PtcCO2) approximate the corresponding arterial values at a probe temperature of 44 degrees C. The temperature-dependent increase of PtcO2 and PtcCO2 is caused by an increased skin perfusion, a decrease in the mean diffusion path, a change of skin metabolism, a decrease of tissue solubility of oxygen and carbon dioxide and a right shift of the oxygen and carbon dioxide binding curves of blood. Seven healthy volunteer test subjects participated in the study. A transcutaneous probe connected to a mass spectrometer was placed on the earlobe of the test subject. Four measurements of the transcutaneous PO2, PCO2 and skin blood flow (from the washout kinetics of argon) were determined on each test subject. The first measurement was made with a transcutaneous probe temperature of 37 degrees C. The probe temperature was then increased to 44 degrees C before the next determination. Finally, two determinations were made at 37 degrees C, separated by a time interval of 1 h. The PtcO2 and skin blood flow increased when the probe temperature increased from 37 degrees C to 44 degrees C. However, when the probe temperature was decreased again from 44 degrees C to 37 degrees C, the estimated skin blood flow returned to the initial value while the PtcO2 remained unchanged. It required a further 1 h before the PtcO2 returned to the initial value at 37 degrees C. The most likely explanation of the experimental results is that heating of the skin to 44 degrees C causes a reversible decrease in the skin metabolism.

Adult↗
PubMed1991

Computer localization of some Gm markers on the surface of the Fc region of human immunoglobulin G.

The surface localization of some Gm markers on the Fc fragment of IgG has been identified from previously published amino acid sequences associated with known Gm markers using the atomic coordinates described by Deisenhofer, INSIGHT software and a Digital VAX 11/785 computer, which together permit a study of the three-dimensional structure of the Fc fragment. The G1m(x)-associated amino acid residue 431, the G3m(s)- and G3m(u)-associated residue 435 and the nG4m (a)- and (b)-associated residue 309 are all localized in the interface between the CH2 and CH3 domains. Furthermore, it is postulated that the G1m(a)-associated residue 356 (Asp, Glu) influences the interface formation through an ion pair interaction to Lys 439. Finally, G3m(b) and G3m(g) are associated with the interface via residues 435 and 436. The data explain why sera from patients with rheumatoid arthritis are useful tools for the detection of some Gm markers and support the view that rheumatoid factors from these patients are internal images of microbial Fc-binding proteins.

Computer Simulation↗
PubMed1991

Erythromycin and phenoxymethylpenicillin (penicillin V) in the treatment of respiratory tract infections as related to microbiological findings and serum C-reactive protein.

Respiratory tract pathogens (beta-haemolytic streptococci groups A, C and G, Haemophilus influenzae, Branhamella catarrhalis or pneumococci), were isolated from nasopharyngeal and/or throat swabs in 73/138 (53%) patients greater than 10 years of age with a clinical diagnosis of acute sinusitis, acute tonsillitis, purulent nasopharyngitis or acute bronchitis. Serological evidence of a viral infection (influenza A and B, parainfluenza 1, 2 and 3, respiratory syncytial virus, adenovirus) or Mycoplasma pneumoniae infection was found in 10% of the patients. The serum content of C-reactive protein (S-CRP) was increased (greater than 12 mg/l) in 26/33 (79%) patients with streptococci and in 22/59 (37%) patients without respiratory tract bacteria. In patients with a serological evidence of a virus tonsillitis, the S-CRP was also high (32-64 mg/l). At follow-up 10-12 days after the first visit, the clinical effect of erythromycin and penicillin V was judged to be similar (90% clinical effect). Relapse or re-infection with group A streptococci were seen in 7 patients (4 on erythromycin, 3 on penicillin). In another 6 patients (3 on erythromycin, 3 on penicillin), antibiotic treatment was switched owing to persisting symptoms, probably due to H. Influenzae infection in 3 cases. The patients' own estimates of their symptoms suggested treatment with erythromycin to have a more rapid effect than treatment with penicillin.

Acute Disease↗