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Biomedical subjects

S Christensen

Publications and source records attributed to S Christensen.

At least 127 records · Page 7Linked to original sources
PubMed1991

Suitability of tritiated inulin for determination of glomerular filtration rate.

Purity of different batches of [3H]inulin delivered from leading manufacturers was elevated with a chromatographic method (Sephadex G-25 column) that allowed simultaneous analysis of cold inulin, [3H]inulin, and [14C]inulin in the same run. Among four batches of [3H]inulin received within 5 mo, two were found relatively pure, whereas two were partly decomposed to lower-molecular-weight fragments. The chromatographic profile of pure isotopes was not significantly affected by redistribution and freeze drying, nor by subsequent storage in the freeze-dried state at -20 degrees C for up to 5 mo, nor by incubation in aqueous solution at 37 degrees C for 24 h. Three batches of [3H]inulin with different grades of decomposition (noninulin percentages 13%, 38%, and 61%, respectively) were selected for clearance experiments and infused simultaneously with cold and undecomposed [14C]inulin to conscious rats. [14C]inulin had a significantly higher clearance than cold inulin (+7.6 +/- 0.6%) and relatively pure [3H]inulin (+12.4 +/- 0.4%). Decomposed [3H]inulin isotopes progressively underestimated clearance of cold inulin to an extent related to the degree of decomposition. Thus at the end of the 5-h clearance experiment, ratios between clearance of tracer and of cold inulin were 0.92, 0.71, and 0.60 for the three 3H isotopes, respectively. This study indicates that [3H]inulin delivered from leading manufacturers may be decomposed to an extent that invalidates its use as a marker for glomerular filtration rate (GFR). It is thus necessary to check the purity routinely before use. Within the same rat, clearance of undecomposed [3H]inulin and [14C]inulin may differ by 12%, and for this reason they should not be used interchangeably as GFR markers.

Animals↗
PubMed1991

Comparative study of fluconazole and clotrimazole in the treatment of vulvovaginal candidiasis.

Fluconazole is a new oral triazole antifungal with good activity against Candida spp. In this study, we investigated the effectiveness and tolerability of a three-day course of treatment with fluconazole compared with clotrimazole vaginal tablets in nonpregnant women with acute Candida vaginitis. Of the 90 evaluable patients who received fluconazole, 76 (84 percent) were asymptomatic seven to ten days after treatment compared with 84 of 95 (88 percent) treated with clotrimazole. An additional ten patients in the fluconazole group (11 percent) and seven in the clotrimazole group (7 percent) had improvement in their signs and symptoms. Only four patients in each group (4 percent) were considered treatment failures. Mycological cures were obtained in 89 and 93 percent of patients treated with fluconazole and clotrimazole, respectively, seven to ten days posttreatment. Clinical cure rates remained high one month posttreatment: 79 percent in the fluconazole group and 83 percent in the clotrimazole group. Both therapies were well tolerated. One patient discontinued treatment after she developed diarrhea while receiving fluconazole. The most common adverse effects associated with fluconazole use were nausea (six percent) and diarrhea (three percent). No clinically significant laboratory abnormalities were observed. In this investigation, oral fluconazole therapy was found to be as safe and effective as clotrimazole vaginal tablets in women with acute vulvovaginal candidiasis.

Administration, Intravaginal↗
PubMed1990

Stereospecificity of the effects of ozolinone on renal hemodynamics and on segmental tubular sodium reabsorption in conscious rats.

The study was performed to elucidate the effects of the two stereoisomers of ozolinone (d,l) on renal hemodynamics and proximal tubular Na reabsorption. Clearance experiments were performed in conscious water-loaded female Wistar rats. The clearances of [3H]inulin, [14C]tetraethylammonium and lithium were used as estimates for glomerular filtration rate, renal plasma flow and delivery of fluid from the proximal tubules, respectively. When the baseline parameters had stabilized, d- or l-ozolinone was injected i.v. in doses of 4, 20 and 100 mg/kg. 1-Ozolinone caused a transient and dose-dependent diuretic-natriuretic response with no evidence of a ceiling. At peak natriuresis, 2.5-5 min after 100 mg/kg of 1-ozolinone, the fractional Na excretion was increased from 0.5 to 25%; this was associated with an increased fractional excretion of lithium from 27 to 60%, and small transient decreases of renal hemodynamic parameters. d-Ozolinone had no significant effects except for a small natriuresis after 100 mg/kg. It is concluded that in water-loaded conscious rats 1-ozolinone is a powerful diuretic which, in contrast to d-ozolinone, increases the delivery of fluid from the proximal tubule as judged from changes in lithium clearance.

Animals↗
PubMed1990

Effect of chronic oral furosemide administration on the 24-hour cycle of lithium clearance and electrolyte excretion in humans.

The effect of chronic furosemide treatment on the circadian cycle of lithium clearance (CLLi) and electrolyte excretion has been examined in 8 young, male volunteers, by performing two 24 h clearance experiments, before and after one week of treatment with furosemide 80 mg once daily. After 8 days on furosemide there was a significant decrease in creatinine clearance (-21%), plasma Na (-8.4 mM) and plasma K (-0.58 mM). At that time, however, there were no changes in 24 h-values of CLLi or Na excretion, although the magnitude of the circadian variation in CLLi and other renal parameters was increased. Both CLLi and CLNa were increased in the first 3 h following furosemide administration and thereafter they fell below the control level in the remaining hours of the experiment. From the absolute and fractional changes in CLLi it is suggested that compensatory Na conservation in response to chronic furosemide treatment occurs between doses, and that it involves decreased output from the proximal tubules combined with increased fractional Na reabsorption in the distal nephron.

Adult↗
PubMed1990

Ultrastructural quantitation of atubular and hypertrophic glomeruli in rats with lithium-induced chronic nephropathy.

The very heterogeneous population of glomeruli in rats with lithium-induced chronic nephropathy which includes small glomeruli without connection to a proximal tubule (atubular glomeruli) and large hypertropic glomeruli with connection to a normal proximal tubule, was studied at the ultrastructural level, using stereological methods. After 8 weeks of lithium treatment followed by 8 weeks without lithium the hypertrophic glomeruli showed no changes in their relative ultrastructural composition, including normal mesangium, basement membrane-like material and peripheral basement membrane. The absolute quantities of each component were, however, increased due to the increased volume of the glomeruli. The atubular glomeruli had increased volume fractions of mesangium, peripheral basement membrane, basement membrane-like material and epithelium, whereas the absolute quantities were decreased due to the decreased volume. The thickness of the basement membrane was within normal limits in the group of hypertrophic glomeruli but increased by 31% above controls in the group of atubular glomeruli. Both groups of glomeruli in lithium-treated animals showed normal mean foot process width, but with a slightly abnormal distribution. The atubular glomeruli showed a disproportionate large decrease in peripheral filtration surface and capillary length, compared with the reduction in glomerular volume, whereas the hypertrophic glomeruli showed changes in proportion with the increased volume.

Animals↗
PubMed1990

Unusual radiographic presentation of IgA nephropathy.

An adolescent male presented with hematuria and flank pain. Transient focal renal parenchymal defects were demonstrated by ultrasonography, radionuclide scintigraphy and computed tomography. Renal biopsy revealed IgA nephropathy with acute tubular necrosis. This peculiar radiographic pattern has not, to our knowledge, been previously described in IgA nephropathy and may relate to tubule cell damage by red blood cell casts or patchy renal ischemia.

Adolescent↗
PubMed1990

Distal lithium reabsorption in the sodium-restricted rat is not dependent on the urinary sodium to lithium concentration ratio.

1. High fractional reabsorption of lithium occurs when rats and dogs are given a low sodium diet. This has been suggested to be due to the low tubular fluid sodium to lithium concentration ratio which arises during sodium restriction allowing transport mechanisms along the distal nephron segment to accept significant quantities of lithium instead of sodium by simple competition. 2. Clearance experiments in conscious water-loaded Wistar rats maintained on either a low sodium (6 mmol/kg) or a normal sodium (120 mmol/kg) diet were performed. The rats were infused with a solution of 120 mmol/l glucose and 10 mmol/l NaCl at a rate of 6 ml/h. 3. The median fractional excretion of lithium was 19.4% in the group with a normal sodium intake, and 2.5% in the group given a low sodium diet. The urine to plasma concentration ratio of lithium was 2.5 in the normal sodium group and 0.4 in the sodium-restricted group. The urinary sodium to lithium concentration ratio was 13 in the control group and 63 in the sodium-restricted group. 4. It is concluded that the increased fractional reabsorption of lithium initiated by a low sodium intake is not likely to be due to simple competition at distal tubular nephron sites between lithium and sodium.

Absorption↗
PubMed1990

Effects of ranitidine and metoclopramide on gastric fluid pH and volume in children.

To determine the effects of ranitidine and metoclopramide on gastric fluid in children, 40 healthy children (aged 2-8 yr) were allocated randomly to groups of 10 to receive one of four oral premedications 4 h before surgery: no premedication, metoclopramide 0.1 mg kg-1, ranitidine 2 mg kg-1 and metoclopramide 0.1 mg kg-1 with ranitidine 2 mg kg-1. After tracheal intubation, gastric fluid was aspirated and analysed for pH and total fluid volume. Ranitidine, with or without metoclopramide, increased gastric fluid pH significantly compared with control (P less than 0.05). Gastric fluid volume did not change significantly.

Child↗
PubMed1990

Effects of duration of fasting on gastric fluid pH and volume in healthy children.

To determine the effects of duration of fasting before elective surgery on gastric fluid pH and volume in children, a prospective, randomized, blinded study of 100 unpremedicated children, aged 1-14 yr, was undertaken. Each child was given 2 mL/kg of water orally and then fasted 2, 4, or 6 h preoperatively. After induction of anesthesia and tracheal intubation, gastric fluid was aspirated through a large-bore, multiorifice orogastric tube. Gastric fluid pH was measured using a calibrated PHM62 radiometer. Gastric fluid volume was the total volume of fluid aspirated from the stomach. The duration of fasting was between 2.0 and 8.5 h. We found that neither gastric fluid pH nor gastric fluid volume correlated with the duration of fasting. The mean (+/- SD) gastric fluid pH was 1.80 +/- 0.79 and the mean (+/- SD) gastric fluid volume was 0.56 +/- 0.39 mL/kg. Gastric fluid pH was less than 2.5 and volume greater than 0.4 mL/kg in 53% of children. We conclude that healthy children may receive 2 mL/kg of water up to 2 h before elective surgery without decreasing gastric fluid pH or increasing gastric fluid volume beyond values obtained after fasting for 6 h.

Adolescent↗
PubMed1989

Incidence of emesis and postanesthetic recovery after strabismus surgery in children: a comparison of droperidol and lidocaine.

The authors sought to compare the antiemetic and sedative postanesthetic effects of droperidol versus lidocaine given intravenously. One hundred and fifty children, ASA physical status I or II, ages 2-15 yr, were studied. Each child was randomly assigned to receive either droperidol, 0.075 mg/kg; lidocaine, 1.5 mg/kg; or a combination of lidocaine, 1.5 mg/kg, and a reduced dose of droperidol, 0.025 mg/kg, immediately after induction of anesthesia, which was with thiopental, atropine, and succinylcholine. Anesthesia was maintained with halothane and nitrous oxide. The incidence of postanesthetic vomiting was 22% in the droperidol-alone group, which was significantly less than the lidocaine-alone group (50%). The incidence of vomiting in the combination group (30%) was not significantly different from either the droperidol- or lidocaine-alone groups. The time in the recovery room was significantly shorter for patients given lidocaine alone than those given droperidol alone or the combination. However, the mean time intervals from completion of surgery to recovery of full alertness and to discharge from the hospital did not differ significantly among the three groups. In summary, the authors found that intravenous droperidol is significantly more effective than lidocaine in reducing the incidence of vomiting in unpremedicated children after strabismus surgery. Furthermore, droperidol did not delay either the time to recovery of full alertness or the time to discharge from hospital compared to lidocaine.

Adolescent↗
PubMed1989

Effects of intravenous bumetanide administration on renal haemodynamics and proximal and distal tubular sodium reabsorption in conscious rats.

The renal effects of 0.02-62.5 mg/kg bumetanide given as intravenous bolus injections were studied in water diuretic conscious rats. Clearances of 14C-tetraethylammonium, 3H-inulin and lithium were used as markers for renal plasma flow (RPF), glomerular filtion rate (GFR) and proximal tubular output, respectively. Bumetanide caused biphasic, transient and dose-independent changes in the renal haemodynamics without significant alterations of the filtration fraction. At dose-levels above 0.02 mg/kg bumetanide increased urine flow, absolute and fractional Na excretion as well as the indices for fractional output of Na from the proximal tubules (CLi/CIn) and the distal nephron segments (CNa/CLi). The changes in CLi/CIn became maximal at doses above 0.5 mg/kg, whereas CNa/CLi was increased with the dose up to 12.5 mg/kg. Paradoxically, doses above 12.5 mg/kg were less natriuretic due to a decrease of CNa/CLi. It is concluded that in rats bumetanide is an effective although short-acting diuretic when administered intravenously. When comparing peak responses bumetanide is equipotent to furosemide but has a lower maximal efficacy. Judged from the changes in fractional lithium excretion, the natriuretic effect of bumetanide is effected by inhibition of Na reabsorption in the proximal tubule in addition to the well-known effect on the distal nephron segment.

Animals↗
PubMed1989

Dose dependency of furosemide-induced sodium excretion.

Intravenous furosemide doses ranging from 5 to 120 mg were given to healthy young volunteers with and without individualized active rehydration with a sodium chloride solution. Sodium excretion rates and fractional sodium excretions (FENa) percentages were correlated significantly with dose and with urinary excretion rates of furosemide. The ED50 was below 5 mg and no additional natriuretic effect was seen above 40 mg. The efficiency (FENa percentage per microgram of furosemide excreted per minute during a certain clearance period) was dependent on hydration and on time. For the period 15 to 30 min a significant linear relationship between furosemide dose and the reciprocal of the efficiency indicated a higher efficiency for lower doses and a theoretical maximal value of FENa of 0.4% per micrograms of furosemide excreted per minute. A relative value for a dose-dependent efficiency reduction was calculated for each dose. The ED50 for dose-dependent efficiency reduction was about 12 mg i.v. Simultaneous measurements of lithium clearance indicated a proximal site of action for furosemide which was saturated at furosemide excretion rates above 50 micrograms/minute. For the major, distal, site of action no maximal value was demonstrated. It is concluded that a wanted balance between a strong natriuretic effect and weak sodium retaining mechanism not necessarily is achieved by a high dose and that information concerning that problem must be obtained from studies in relevant patient groups.

Adult↗