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Biomedical subjects

O Christensen

Publications and source records attributed to O Christensen.

At least 37 records · Page 2Linked to original sources
PubMed1993

[The circulating occupational medical record in the county of Roskilde].

The aim of the circulating occupational medical record (COMR) is to coordinate activities and documents concerning the patient who has an occupational disease. This new case record belongs to the patient, which solves the problems concerning the professional secrecy of the involved authorities. The general practitioner, the trade union and amongst others the safety organisation of the work place all have their own schematic pages in the record. The number and use of COMRs were studied. Postal questionnaires were sent to the primary users of the COMRs. Altogether 345 COMRs were started over the two year period 1989-1991. Two hundred and ninety-eight COMRs were evaluable. The page of the general practitioner was used in 90% of the records, versus 64% in the case of the unionpage and 21% in the case of the safety organisation. In 78% there were documents from medical specialists, psychologists or physiotherapists. The majority of the documents were from the department of occupational medicine. In half of the COMRs there were documents from more than four different sources. Only 76% of the patients were referred to the department of occupational medicine. It is recommended that the COMR should be extended to the whole country.

Denmark↗
PubMed1993

The influence of thoracic epidural analgesia alone and in combination with general anesthesia on cardiovascular function and myocardial metabolism in patients receiving beta-adrenergic blockers.

Thoracic epidural analgesia combined with chronic beta-adrenergic blocker medication may cause cardiac depression. We investigated the cardiovascular and myocardial metabolic effects of a T1-T12 epidural block in 18 patients (age < 65 yr, ejection fraction > 0.5), receiving chronic beta-adrenergic blocker medication and scheduled for aortocoronary bypass surgery. After randomization into a light or deeper general anesthetic group, the cardiovascular and myocardial metabolic effects of a subsequent general anesthesia induction were investigated. Thoracic epidural analgesia induced a moderate decrease in mean arterial pressure, coronary perfusion pressure, free fatty acids, and myocardial consumption of free fatty acids. General anesthesia with thiopental (2-4 mg/kg) and a low fentanyl dose (5 micrograms/kg) increased heart rate, coronary perfusion pressure, and coronary vascular resistance, whereas mean pulmonary arterial pressure and pulmonary capillary wedge pressure decreased. After thiopental (2-4 mg/kg) and a high fentanyl dose (30 micrograms/kg), mean arterial pressure and left ventricular stroke work index decreased. We conclude that a T1-T12 epidural block in well sedated, beta-adrenergic blocked patients does not induce clinically significant cardiovascular effects. Induction of general anesthesia was well tolerated, but the light general anesthetic could not prevent an increase in heart rate and coronary vascular resistance, whereas the deeper anesthetic induced slight myocardial depression. No effect on the atrioventricular conduction, as measured by the PQ-time, was noted.

Adrenergic beta-Antagonists↗
PubMed1992

Cell swelling activates K+ and Cl- channels as well as nonselective, stretch-activated cation channels in Ehrlich ascites tumor cells.

Cell-attached patch-clamp recordings from Ehrlich ascites tumor cells reveal nonselective cation channels which are activated by mechanical deformation of the membrane. These channels are seen when suction is applied to the patch pipette or after osmotic cell swelling. The channel activation does not occur instantaneously but within a time delay of 1/2 to 1 min. The channel is permeable to Ba2+ and hence presumably to Ca2+. It seems likely that the function of the nonselective, stretch-activated channels is correlated with their inferred Ca2+ permeability, as part of the volume-activated signal system. In isolated inside-out patches a Ca(2+)-dependent, inwardly rectifying K+ channel is demonstrated. The single-channel conductance recorded with symmetrical 150 mM K+ solutions is for inward current estimated at 40 pS and for outward current at 15 pS. Activation of the K+ channel takes place after an increase in Ca2+ from 10(-7) to 10(-6) M which is in the physiological range. Patch-clamp studies in cell-attached mode show K+ channels with spontaneous activity and with characteristics similar to those of the K+ channel seen in excised patches. The single-channel conductance for outward current at 5 mM external K+ is estimated at about 7 pS. A K+ channel with similar properties can be activated in the cell-attached mode by addition of Ca2+ plus ionophore A23187. The channel is also activated by cell swelling, within 1 min following hypotonic exposure. No evidence was found of channel activation by membrane stretch (suction). The time-averaged number of open K+ channels during regulatory volume decrease (RVD) can be estimated at 40 per cell. The number of open K+ channels following addition of Ca2+ plus ionophore A23187 was estimated at 250 per cell. Concurrent activation in cell-attached patches of stretch-activated, nonselective cation channels and K+ channels in the presence of 3 mM Ca2+ in the pipette suggests a close spatial relationship between the two channels. In excised inside-out patches (with NMDG chloride on both sides) a small 5-pS chloride channel with low spontaneous activity is observed. The channel activity was not dependent on Ca2+ and could not be activated by membrane stretch (suction). In cell-attached mode single-channel currents with characteristics similar to the channels seen in isolated patches are seen. In contrast to the channels seen in isolated patches, the channels in the cell-attached mode could be activated by addition of Ca2+ plus ionophore A23187.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Patency of the internal mammary artery used as sequential graft.

In 28 patients with the left internal mammary artery (IMA) used as a sequential coronary artery graft, clinical and angiographic evaluation was made 19-47 months postoperatively. Patency was 96% in the proximal anastomoses and 93% in all the anastomoses. Angiography, however, showed optimal function in only 75% of the distal graft ends. These observations indicate that routine use of left IMA as a sequential graft should be restricted to experienced surgeons. Clinical and angiographic findings did not always correlate, emphasizing that evaluation of IMA-graft patency should include angiography.

Adult↗
PubMed1991

Geographic stomatitis: report of 6 cases.

The macro- and microscopic appearance and results of microbiologic and immunohistochemical investigations in six patients with geographic stomatitis are described. On the background of similarities in both the clinical, histologic and immunohistochemical findings it is felt that psoriasis and stomatitis geographica are related lesions.

Adult↗
PubMed1989

Anion channels in a leaky epithelium. A patch-clamp study of choroid plexus.

We have used the patch-clamp technique to characterize three anion channels in the ventricular membrane of the choroid plexus epithelium from Necturus. The most frequently occurring channel had a nonlinear IV-curve. The conductance in excised patches with 112 mM chloride at both sides was 28 pS at 0 mV, increasing towards positive membrane potentials. The selectivity ratios were PNa:PCl less than or equal to 0.1 and PNO3:PCl:PHCO3 = 1.6:1:0.43. SITS and furosemide (1 mM) on the inside reduces chloride flux to 0.15 and 0.37 times the control value. In attached patches, the most commonly observed channel had a conductance of 7.5 pS. The single-channel current for this channel reversed direction at 15 mV hyperpolarization, indicating accumulation of chloride to a factor of 1.8 above equilibrium. External stimulation of the tissue by theophylline, IBMX and dbcAMP, or by hypotonic shock did not increase the activity of this channel. In very few excised patches, we have observed a chloride channel with a conductance of 7 pS with 112 mM chloride at both sides. The 7 pS channel appears to be identical to a 2 pS channel found in attached patches. The 2 pS channel was not normally active in attached patches but was activated in 28% of the patches by external stimulation. Finally, in few excised patches we have found a 375 pS channel which inactivates within seconds when membrane potential is stepped from 0 mV to a value that differs more than 10-20 mV from zero. The channel did not conduct gluconate but PNO3:PCl = 1.08 and PNa:PCl less than or equal to 0.1. Internal SITS and furosemide (1 mM) reduced chloride flux to 0.3 and 0.5 times the control value. The channel was never seen in attached patches. The current carried through these channels can not account for the transepithelial steady state Cl- -flux measured by microelectrodes. KCl exit from the cell is suggested to be carried by KCl-cotransport or by channels that are too small to be seen in patch-clamp experiments.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Fat consumption and schizophrenia.

This report describes the statistical association between the average ratings of course and outcome of schizophrenia in 8 national centres participating in the World Health Organization international 2-year follow-up study (1) and the amount of fat in the average national diets as published by the Food and Agriculture Organization of the United Nations (2). Highly significant correlations were found between favourable ratings of course and outcome of schizophrenia and a low percentage of total fat (r = 0.80-0.90; P less than 0.05) and of fat from land animals and birds (composed mainly of saturated fat) (r = 0.91-0.95; P less than 0.01). High percentage of fat from vegetables, fish and seafood (having a relatively high content of unsaturated fatty acids) tended to be associated with a favourable course and outcome (r = 0.23-0.50; P greater than 0.10). A multivariate analysis revealed that 97% (P = 0.0002) of the variation in the overall outcome of schizophrenia between the national centres could be explained by the combined variation in the percentages of fat from land animals and birds and from vegetables, fish and seafood, respectively, in the national diets. These results suggest that the course and outcome of schizophrenia may be influenced through diet. They should encourage investigators to perform controlled clinical trials of low-fat diets with a sufficient amount of essential fatty acids.

Dietary Fats↗
PubMed1988

Transcapillary fluid balance in subcutaneous tissue of patients undergoing aortocoronary bypass with extracorporeal circulation.

Colloid osmotic pressure in plasma (COPpl) from a cubital vein and in interstitial fluid (COPif) in the subcutaneous tissue at heart level, and interstitial fluid pressure (Pif) at the same level, were measured in 18 healthy subjects and in 28 patients requiring aortocoronary bypass. Interstitial fluid was collected via subcutaneously implanted double nylon wicks and Pif was measured with the 'wick-in-needle' technique. Measurements were made preoperatively and 1 1/2 to 8 hours (mean 4 hours) after termination of extracorporeal circulation. Pif rose to 2.3 mmHg above the pre-bypass level. COPpl concomitantly fell from 22.2 to 14.4 and COPif from 12.4 to 10.1 mmHg. These changes were statistically significant. Although the relatively large COPpl drop resulted in a net rise of 3.2 mmHg in filtration pressure, the incidence of pulmonary complications was low and no subcutaneous edema was discernible. The fall in COPif and rise in Pif may be regarded as important edema-preventing mechanisms.

Adult↗
PubMed1987

Maxi K+ channels in leaky epithelia are regulated by intracellular Ca2+, pH and membrane potential.

We have studied a Ca2+-activated K+ channel in the ventricular membrane of the epithelium of choroid plexus by means of the patch-clamp technique, using excised inside-out patches. The channel was highly K+ selective. It had a conductance of approximately 200 pS with 112 mM KCl on both sides of the membrane. The probability for the channel being open increased with intracellular Ca2+, pH and with membrane potential. The channel shows two gating modes. The primary gating mode has open and closed times which depend strongly on membrane potential, intracellular Ca2+ and pH. It accounts for the variation of the channel open probability. Lowering intracellular pH from 7.4 to 6.4 reduced the channel open probability mainly by increasing the channel closed time. It appears, that H+ can compete with Ca2+ in binding to the same site, thereby preventing channel opening. A second gating mode consisted of short-lived closures, or flickers. The open and closed time for this process were largely independent of membrane potential, intracellular Ca2+ and pH. The channel density was approximately 0.4 micron-2 corresponding to a K+-permeability of 2.2 10(-5) cm s-1 if the channels were fully open. In cell-attached patches we measured the open probability of the channel in the intact cell membrane. The channel is almost totally closed under normal cellular conditions. This type of channel is therefore not the membrane component that forms the electrodiffusive pathway for K+-ions.

Animals↗
PubMed1987

The mechanism of electrodiffusive K+ transport in leaky epithelia and some of its consequences for anion transport.

The ventricular membrane of the epithelium from the choroid plexus of Necturus maculosus was probed with double-barrelled ion-selective microelectrodes while the ventricular bathing solution was changed abruptly. The transient states induced by increasing the external concentration of K+ or by the application of ouabain showed that the passive movements of K+ across the ventricular membrane were electro-diffusive and could be described by the Goldmann equation and one constant permeability (PK) of 24 X 10(-6) cm s-1. The passive efflux was balanced by a ouabain-sensitive influx. PK was different in different steady states; when the cell was acidified by half a pH unit by increasing CO2 in the bathing solutions from 1 to 5%, then PK decreased to 13 X 10(-6) cm s-1. Removal of Cl- from the bathing solution increased PK by 50% and reduction of Cl- transport by furosemide did not alter PK, consequently major movements of K+ were independent of Cl- movements. Depolarizations of the cell caused an increase in the cellular HCO-3 concentration due to an electrodiffusive permeability (PHCO3), the value of which was estimated to 17 X 10(-6) cm s-1.

Animals↗
PubMed1987

Electrodiffusion of Cl- and K+ in epithelial membranes reconstituted into planar lipid bilayers.

An electrodiffusive permeability for Cl-, its activation by low extracellular Cl--concentrations and the interaction between electrodiffusive fluxes of Cl- and K+ are demonstrated in the ventricular membranes from the epithelium of the bovine choroid plexus. Membranes were fused into artificial lipid bilayers formed at the tip of micropipettes. What is thought to be the cytoplasmic side of the membrane (the trans-side or the inside of pipette) was clamped at negative potentials (0 to -90 mV). Under these conditions the current was discrete, fluctuating less than 2 pA. With Cl- as the only conducting ion on the two sides we observed a small electrodiffusive permeability which was reduced by bumetanide or furosemide by 62%. When the outside solution was rendered Cl--free then the permeability to Cl- increased by a factor of 2-5; this activation was reduced by bumetanide or furosemide by about 80%. We observed an interaction between inwards movements of K+ and outwards movements of Cl- via the activated permeability: The total current was smaller than the sum of the expected inward K+-current and the expected outward activated Cl--current. Bumetanide or furosemide increased the total current; apparently the loss of current carried by Cl- was smaller than the gain in current carried by K+. The presence of K+ on both sides of the membrane was a condition for this interaction.

Animals↗
PubMed1987

Surgical treatment of aneurysms of the descending thoracic aorta.

Six patients were operated on for aneurysm of the descending thoracic aorta in 1983-1985 by use of simple cross-clamping and interposition of a Dacron tube graft without extracorporeal circulation. The aneurysm had ruptured in three cases. The patients' mean age was 69 years. Anesthesia and muscle relaxation were obtained by drugs with only minor myocardial depressant action. There was no postoperative mortality or morbidity. Five of the patients have been followed up for at least a year. Careful pharmacologic control of the blood pressure is essential during such surgery. Despite the smallness of the series, it indicates that simple cross-clamping and Dacron graft interposition can be used for treatment of aneurysm of the descending thoracic aorta.

Adult↗
PubMed1986

Early complications with a new bovine arterial graft (Solcograft-P).

In three separate centers of vascular surgery in Norway, a total of 26 patients underwent implantation of a new bovine arterial graft (Solcograft-P) for femoropopliteal or femorotibial bypass or arterial patch-plasty. Serious complications--graft deterioration and formation of aneurysm or pseudoaneurysm--arose in eight patients, all within 4 months after the implantation. In central Europe only four anastomotic pseudoaneurysms have been reported after about 700 Solcograft implantations, even with longer observation time. Possible causes of the difference in complication rates are discussed.

Aged↗
PubMed1984

Estimates of Michaelis-Menten constants for the two membranes of the brain endothelium.

Tracer studies on facilitated diffusion across the blood-brain barrier lead to the calculation of Michaelis-Menten constants that describe the rate of transport. However, the barrier consists of two endothelial cell membranes, and the relevance of single Michaelis-Menten constants in relation to the two cell membranes is unknown. We have formulated a model of two endothelial cell membranes and show that the measured Michaelis-Menten constants are simple functions of the properties of the individual membranes when transport across the endothelium is rapid (P1 greater than 10(-6) cm s-1). We also show that the Michaelis-Menten constants determined in tracer experiments describe facilitated diffusion in the steady state only if the two membranes have similar transport properties. As an application of this observation, we have examined three experimental studies that measure glucose transport in the steady state and show that the Michaelis-Menten constants for glucose transport calculated from the tracer experiments are equal to the constants calculated from the steady-state experiments. We conclude that the luminal and abluminal membranes of brain capillary endothelial cells have equal glucose transport properties.

Biological Transport, Active↗
PubMed1984

Pivmecillinam, co-trimoxazole and oral mecillinam in gastroenteritis due to Vibrio spp.

The comparative efficacy of antibacterial therapy with pivmecillinam or cotrimoxazole and general supportive care only was studied in patients with severe bacterial gastroenteritis. Overall, treatment with antibiotics proved significantly superior to rehydration alone in 42 children. Active therapy also had a statistically beneficial effect in children infected with Vibrio cholerae and V. parahaemolyticus. Pivmecillinam and co-trimoxazole were equally effective. Pivmecillinam and oral mecillinam appeared to be of equal value in a further 22 adults infected by Vibrio spp. No side-effects were recorded in any of the subjects treated. Further investigations with pivmecillinam and oral mecillinam are advocated.

Adult↗