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Biomedical subjects

J Christoffersen

Publications and source records attributed to J Christoffersen.

At least 37 records · Page 2Linked to original sources
PubMed1986

Detrusor instability in children with recurrent urinary tract infection and/or enuresis. I. Clinical conditions and symptomatology.

Forty-one children, aged 5-15 years, were referred because of recurrent urinary infections and/or enuresis. They were examined prospectively by means of cystometry. CO2 cystometry revealed detrusor instability in 18 children (44%), but if complete reproducibility were to be requested in repeated tests, only 7 children (17%) would have presented instability. Detrusor instability was not significantly related to definite pathological changes in the urinary tract or to irritative bladder symptoms.

Adolescent↗
PubMed1986

Detrusor instability in children with recurrent urinary tract infection and/or enuresis. II. Treatment.

Of 41 children, aged 5-15 years, referred consecutively because of recurrent urinary tract infections (UTIs) and/or enuresis, 18 (44%) showed detrusor instability (DI) in at least 2 of 6 CO2 cystometries. One child was excluded from the study because of lack of follow-up. Four children with less pronounced DI (instability during less than or equal to 50% of the cystometries performed) and frequent UTIs were given antibiotics prophylactically for 3 months. In the remaining 13 children, DI was found during more than half the cystometries performed, and 11 of these children, who also had urge incontinence, were treated with emepronium bromide, 400-600 mg daily (10-12 mg/kg) for 3 months. In 7 of the patients this treatment was supplemented by antibiotics prophylactically because of frequent UTIs. Two children with special problems received other types of treatment. All children were free from symptoms at a clinical check-up 6 months later, 95% confidence limits 0-20%.

Adolescent↗
PubMed1986

The nature of early caries lesions in enamel.

Since 1935, various mechanisms have been suggested for the formation of subsurface lesions and, in particular, the surface layer covering enamel lesions. The relatively intact mineral-rich and porous surface layer is most likely caused by kinetic events. The suggested mineral-rich outer layer in sound enamel, the organic matrix, the pellicle, or a non-uniform ion distribution have all been shown to be non-essential for surface layer formation; they may, however, influence the rate of surface layer formation. Models based on outer surface protection by adsorbed agents, the dissolution-precipitation mechanism, and combinations of these two models, as well as models based on porosity or solubility gradients, are discussed in this paper together with their advantages and disadvantages. Most models have not explained some important recent experimental observations on initial in vivo caries lesion formation: e.g., initial enamel lesions formed in vivo do not have a surface layer initially but develop this mineral-rich layer later on; and the fact that the F- level in the solid sound enamel is not determining the subsurface lesion formation. Furthermore, the observations that in vitro fluoride ions in the liquid at very low levels (approximately equal to 0.02 ppm) determine surface layer formation are difficult to explain. A new kinetic model for subsurface lesion formation is described, in which inhibitors such as F- or proteins play an important role. The model predicts that if lesions depth and demineralization period are denoted by df and t, lesion progress can be described by: dfp = alpha t + c, where alpha and c are constants with 1 less than or equal to p less than or equal to 3, depending on the lesion formation conditions. If lesion progress is entirely diffusion-controlled, p = 3, corresponding to low inhibitor concentrations; if the inhibitor content is so high that the progress is controlled by processes at the crystallite surface, p = 1. A kinetic mechanism for surface layer formation in vivo is proposed, based on the assumption that F- is a main inhibitor in the plaque-covered acidic in vivo situation. The inhibiting fluoride, adsorbed onto the crystallite surfaces at OH- vacancies, originates from the so-called fluoride in the liquid phase (FL) between the enamel crystallites. Under acidic conditions (plaque), we have, due to an influx of fluoride from the saliva or plaque as FL, an aqueous phase in the enamel supersaturated with respect to the mineral for a small distance (x*) only.(ABSTRACT TRUNCATED AT 400 WORDS)

Absorption↗
PubMed1985

The effect of aluminum on the rate of dissolution of calcium hydroxyapatite--a contribution to the understanding of aluminum-induced bone diseases.

Aluminum ions, Al3+, as these ions exist in aqueous solutions at pH approximately equal to 7, adsorb onto calcium hydroxyapatite (HAP) crystals and severely inhibit the dissolution process of these crystals at 0.1 microM concentrations of aluminum. Human bone crystals have also been shown to adsorb these ions or molecules. A mechanism explaining why aluminum, in connection with bone resorption, causes less demineralization in the osteoid/calcified bone region than deeper in the calcified bone, is suggested.

Adsorption↗
PubMed1984

The effect of bendroflumethiazide and hydrochlorothiazide on the rate of dissolution of calcium hydroxyapatite.

Inhibition of dissolution of calcium hydroxyapatite in the presence of bendroflumethiazide, Centyl, and of hydrochlorothiazide has been investigated. The former compound has a pronounced larger inhibitory effect than the latter. The trifluormethyl group in bendroflumethiazide has been shown to hydrolyze, with the release of fluoride and hydrogen ions, presumably forming a carboxylic acid. The inhibitory effect of hydrolyzed bendroflumethiazide is found to be similar to the effect of a potassium fluoride solution with the same fluoride ion concentration, as measured by a fluoride selective ion electrode.

Bendroflumethiazide↗
PubMed1984

Transabdominal dynamic ultrasonography in detection of bladder tumors.

The accuracy of dynamic transabdominal ultrasonography in the detection of bladder tumors is examined. Of 49 bladder tumors 34 between 2 mm. and several centimeters in size could be demonstrated ultrasonographically. Ultrasound failed to visualize tumors less than 5 mm. in size in 14 patients. Dynamic transabdominal ultrasonography cannot replace cystoscopy in the diagnosis or followup of patients with bladder tumors but it may be used instead of cystoscopy in some selected cases.

Adult↗
PubMed1983

Effects of urine pretreatment on calcium oxalate crystallization inhibition potentials.

Activated carbon and calcium oxalate solids have been used as adsorbents to remove crystallization inhibiting species from centrifuged and dialyzed normal urines. The urine supernatants, following adsorption treatments, have been examined for their calcium oxalate monohydrate crystallization inhibitory potentials by means of a constant composition potentiostatic seeded growth method. The supersaturation of the reactant solution was maintained constant during the crystallization process by the potentiometrically monitored addition of solutions containing crystal lattice ions controlled by a specific calcium ion selective electrode. The experimental results indicate that normal urine contains a number of inhibiting species of variable molecular weight and adsorbability. In addition, preliminary results indicate that substances present in normal urine interfere substantially with the adsorption of crystallization inhibiting species by calcium oxalate monohydrate crystal surfaces. Both charcoal and CaOx adsorbents have been successfully used to completely remove a synthetic, model urinary crystallization inhibitor, ethylene-diamine-tetramethylene-phosphonic acid, ENTMP, from relatively concentrated solutions in 0.15 M NaCl.

Adsorption↗
PubMed1982

Assessment of renal function from plasma urea and plasma creatinine in children.

The diagnostic value of plasma urea and plasma creatinine, used separately and in combination, for assessment of renal function in children was determined from simultaneously measured values of plasma urea, plasma creatinine and glomerular filtration rate (GFR) in 357 children with different nephro-urological disorders. GFR was determined from the total [51Cr]EDTA plasma clearance measured by a reliable single injection method. Four levels of renal function (with the limits expressed as % of the age-dependent normal mean standard GFR) were defined: normal (greater than 75%); moderately decreased (75-52%); considerably decreased (51-28%); and severely decreased (less than 28%). Plasma concentrations of urea (mmol/l) and creatinine (expressed as a percentage of age-dependent normal mean value) were graded into low and high normal, moderately increased, considerably increased and severely increased values. Only by using plasma urea and plasma creatinine in combination all four levels of renal function could be predicted in the individual child with a high degree of certainty (probability 0.94-1.00). The results of the study indicate that the plasma concentration of urea and creatinine should be measured simultaneously, the results being used in combination with due consideration to the variability of plasma creatinine with age. By this procedure the majority of children, i.e. approximately 80%, with nephro-urological disorders who are referred to a paediatric clinic can have their level of renal function predicted with a high degree of certainty. Using plasma urea and plasma creatinine separately the corresponding figure is 50 and 60%, respectively.

Adolescent↗