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  • Key words Phenylketonuria  (6)
  • Phosphate transport  (3)
  • SITS  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Coupling between proximal tubular transport processes (1977)
    Springer
    Pflügers Archiv 368 (1977), S. 245-252 
    Details
    ISSN: 1432-2013
    Keywords: Renal tubule ; H+ ion secretion ; Na+ coupled transport ; Ouabain ; SITS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The rate of active transport by the proximal renal tubule of amino acid (l-histidine), sugar (α-methyl-d-glycoside), H+ ions (glycodiazine), phosphate and para-aminohippurate was evaluated by measuring the zero net flux concentration difference (Δc) of these substances. In the case of calcium the electrochemical potential differenceΔc +zFci Δϕ/RT) was the criterion employed. The rate of isotonic Na+-absorption (JNa) was measured with the shrinking droplet method. The effect of ouabain on the transport of these substances was tested in the golden hamster and the effect of SITS (4-acetamido-4′isothiocyanatostilbene 2,2′-disulfonic acid) was observed in rats. Ouabain (1 mM) applied peritubularly incompletely inhibited JNa (80%), but in combination with acetazolamide (0.2 mM) the inhibition was almost complete (93%). In addition, ouabain inhibited the sodium coupled (secondary active) transport processes ofl-histidine, α-methyl-d-glycoside, calcium and phosphate by more than 75%. It did not affect H+ (glycodiazine) transport and PAH transport was only slightly affected. When SITS (1 mM) was applied from both sides of the cell it inhibited H+ (glycodiazine) transport by 72% and reduced JNa by 38% when given from only the peritubular cell side. SITS (1 mM), however, had no significant affect on H+ secretion and sodium reabsorption if it was applied from only the luminal side. Furthermore it had no affect on the other transport processes tested, regardless of the cell side to which it was applied. When the HCO 3 − buffer or physically related buffers were omitted from the perfusate the absorption of Na+ was reduced by 66%, phosphate by 44%, andl-histidine by 15%. All the other transport processes tested were not significantly affected. The data are consistent with the hypothesis that the active transport processes of histidine, α-methyl-d-glycoside and phosphate, which are located in the brush border, are driven by a sodium gradient which is abolished by ouabain. This may also apply to the Na+-Ca2+ countertransport located at the contraluminal cell side. The residual Na+ transport remaining in the presence of ouabain is likely to be passively driven by the continuing H+ transport which probably is driven directly by ATP. SITS seems to inhibit the exit step of HCO 3 − from the cell and secondary to that, the luminal H+-Na+ exchange and consequently the Na+ reabsorption. In the absence of HCO 3 − buffer in the perfusates the luminal H+-Na+ exchange seems to be affected and the pattern of inhibition of the other transport processes is almost the same as with SITS. The different effects onP i reabsorption observed under these conditions might be explained by possible variations in intracellular pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585203
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  • 2
    Electronic Resource
    Electronic Resource
    Bicarbonate reabsorption in the papillary collecting duct of rats (1981)
    Springer
    Pflügers Archiv 389 (1981), S. 271-275 
    Details
    ISSN: 1432-2013
    Keywords: Adaptation, HCO 3 − transport ; Glycodiazine transport ; Metabolic acidosis ; Metabolic alkalosis ; Acetazolamide ; SITS ; Potassium deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using the technique of capillary perfusion and simultaneous luminal stop flow microperfusion the reabsorption of bicarbonate and glycodiazine from the papillary collecting duct was evaluated. Starting with equal H14CO 3 − and3H-glycodiazine concentrations in the luminal and peritubular perfusates, the decrease in the luminal concentration at 10 and 45 s contact time was measured. In control rats with 25 mmol/l HCO 3 − in the perfusates the rate of HCO 3 − reabsorption calculated from the 10 s values was 0.34 nmol cm−2s−1. In acute metabolic acidosis, the rate of bicarbonate reabsorption was 2,3 times higher. In metabolic alkalosis, the rate of bicarbonate absorption dropped to 13% of the control values. Also the 45 s values of acidotic and alkalotic animals differed significantly from each other. With 25 mmol/l glycodiazine in both perfusates the rate of biffer reabsorption as calculated from the 10 s values was 0.76 nmol cm−2s−1 in control rats and did not deviate significantly from this value in acidotic and alkalotic animals. In control rats the bicarbonate reabsorption in % was the same, no matter whether both luminal and capillary perfusate contained 25 mmol/l bicarbonate or 10 mmol/l. In acidotic rats the rate of HCO 3 − reabsorption did not change significantly if all Na+ in the perfusates was replaced by choline (0.88 versus 0.79 nmol cm−2s−1 at 25 mmol/l HCO 3 − ). When in acidotic rats 0.1 mmol/l acetazolamide or 1 mmol/l SITS (4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid) was added to both perfusates the rate of HCO 3 − reabsorption dropped by 75 and 58%, respectively. A potassium deficient diet for one week and DOCA administration had no influence on the bicarbonate reabsorption of rats which were on standard diet. The data indicate that (1) the buffer reabsorption from the papillary collecting duct is rather due to H+ ion secretion than to buffer anion reabsorption. (2) The adaptation to metabolic acidosis and alkalosis is specific for bicarbonate and not seen with glycodiazine. (3) Within the concentration range tested the HCO 3 − reabsorption rises linearly with the HCO 3 t- concentration. (4) The HCO 3 − reabsorption in the papillary collecting duct is Na+-independent, it can be inhibited by acetazolamide and SITS, but is not influenced by K+-deficient diet plus DOCA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584789
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  • 3
    Electronic Resource
    Electronic Resource
    Phosphate transport in the proximal convolution of the rat kidney (1978)
    Springer
    Pflügers Archiv 377 (1978), S. 33-42 
    Details
    ISSN: 1432-2013
    Keywords: Renal tubule ; Phosphate transport ; Extracellular pH ; Intracellular pH ; Acetazolamide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Inorganic phosphate (Pi) transport was evaluated using the standing droplet method with simultaneous microperfusion of the peritubular capillaries. To evaluate rather small differences in Pi transport and to eliminate the influence of tubular heterogeneity, the technique of crossed paired samples was applied. 1. In chronic PTX rat changing the luminal or both luminal and peritubular pH by varying the HCO 3 − -concentration between 4 and 50 mmol/l at constant 5% CO2 had no influence on Pi transport. 2. If, however, bicarbonate was omitted from the perfusate and 2 mmol/l phosphate (pH 7.4) was the only buffer, Pi transport was decreased from the control. It was, however, further reduced when the perfusates were gased with 5% CO2 i. e. the starting pH was 5.6. 3. When the solutions contained HEPES buffer (25 mmol/l), Pi transport at pH 8 was much larger than at pH 6.0. 4. Raising the CO2 pressure from 35 to 70 mm Hg did not change the Pi transport when both perfusates had a HCO 3 − -concentration of 25 mmol/l. It reduced, however, the Pi transport, when the luminal perfusate had only 4 mmol/l bicarbonate. 5. Lowering the CO2 pressure from 38 to 7.6 mm Hg did hardly change the Pi transport when the luminal perfusate contained 4 mmol/l bicarbonate. It lowered, however, the Pi transport significantly when the luminal perfusate had 25 mmol/l bicarbonate. 6. Acetazolamide, 10−4 M, lowered the Pi transport when the luminal perfusate contained 4 or 25 mmol/l bicarbonate. At 4 mmol/l luminal HCO 3 − , raising thepCO2 to 228 mmol/l depressed Pi transport even more. At 25 mmol/l luminal bicarbonate, raising thepCO2 from 38 to 114 mm Hg reversed the acetazolamide inhibition of the Pi transport almost completely. The data indicate that luminal acidosis and intracellular alkalosis inhibits the transtubular Pi transport. A shift of the intracellular pH to a more alkaline value seems to be responsible for the inhibition of Pi transport by acetazolamide, while omission of buffer from the perfusate inhibits Pi transport by effecting an acidic luminal pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584371
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  • 4
    Electronic Resource
    Electronic Resource
    Reabsorption of monocarboxylic acids in the proximal tubule of the rat kidney (1982)
    Springer
    Pflügers Archiv 395 (1982), S. 212-219 
    Details
    ISSN: 1432-2013
    Keywords: SITS ; Probenecid ; Phloretin ; Acetazolamide ; Lactate ; Renal tubule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The transport ofd-lactate across the epithelium of the late proximal convolution was investigated by two methods: 1. by measuring the zero net flux transtubular concentration difference (Δc tt,45s) and the permeability (P) ofd-lactate and calculating from both the transtubular active transport rate (J lac act ). 2. By measuring the 3.5 s efflux ofd-lactate from the tubular lumen, while blood was flowing through the capillaries. The 3.5 s efflux comprises two components, one going through the brush border (J lac bb ) and one going the paracellular pathway (J lac paracell =P lac·c lac lumen). Both,J lac act andJ lac bb ofd-lactate gave the sameK m 1.9 and 1.7 mmol/l and the same maximal transport rate 3.2 and 2.9 pmol cm−1 s−1. TheK i ofl-lactate tested againstJ lac act andJ lac bb ofd-lactate was also the same: 1.1 and 1.0 mmol/l. These data indicate that under our experimental conditions only the flux through the brush border seems to be rate limiting and thatd-lactate uses the same transport system asl-lactate. When Na+ was omitted from the perfusatesJ lac act disappeared completely, whileJ lac bb was reduced by 64%. These data reflect the Na+ dependence of thed-lactate transport through the brush border. Variation of intra-and extracellular pH by raisingpCO2, omitting HCO 3 − from the perfusates or adding acetazolamide had no effect on the transport ofd-lactate when α-ketoglutarate was used as fuel. However, when acetate was used as fuel, intracellular acidosis brought the reducedJ lac act back to the values obtained with α-ketoglutarate as fuel. It is suggested that this is an effect on a contraluminal transport step. Probenecid (5 mmol/l) and phloretin (0.25 mmol/l) inhibitedJ lac act significantly.J lac bb , however, was only inhibited by probenecid when acetate was used as fuel. These data indicate that both compounds act on thed-lactate exit at the contraluminal cell side, but that probenecid acts in addition at the luminal cell side. SITS (1 mmol/l) augmentedJ lac bb when acetate was used as fuel and is similar to the effect of lowering intracellular pH as described above. The SH reagents mersalyl (1.0 mmol/l) and maleolylglycine (1 mmol/l) did not influenceJ lac bb .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584812
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  • 5
    Electronic Resource
    Electronic Resource
    Neurotransmitter positron emission tomographic-studies in adults with phenylketonuria, a pilot study (1996)
    Springer
    European journal of pediatrics 155 (1996), S. S78 
    Details
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; Positron emission tomography ; Dopamine D2-receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Patients with phenylketonuria (PKU) may suffer from cognitive and neurological deficits which are related to reduced intracerebral concentrations of catecholamines. The function of phenylalanine (Phe) as an inhibitor of the uptake of the precursor amino acid tyrosine (Tyr) through the blood-brain barrier as well as an inhibitor of the expression of dopamine receptors in the brain is under investigation. Positron emission tomography (PET) is a method for quantitatively determining biochemical and physiological processes in vivo. In the current pilot study, l-[1-11C]-Tyr and 18F-fluoro-ethyl-spiperone (FESP) have been used. The metabolic pathway of carboxylic labelled Tyr is mainly incorporation into protein. From the measured tissue and plasma activity as a function of time in combination with a compartimental model the Protein Synthesis Rate (PSR) for Tyr can be calculated. FESP is a ligand which binds irreversibly to the dopamine D2-receptor and has also a low non specific binding, although affinity to the serotonin receptor has been described. The ratio of FESP concentration in striatum and in cerebellum is a measure of the receptor status in vivo. In patients with plasma Phe levels above the maximum therapeutic concentration (〉 700 μmol/l) the PSR for Tyr was decreased as compared to controls and patients with plasma Phe concentrations within the therapeutic range, indicating a decreased availability of Tyr for neurotransmitter synthesis, and hence explaining the reduced cerebral concentration of catecholamines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00014257
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  • 6
    Electronic Resource
    Electronic Resource
    German Maternal Phenylketonuria Study (1996)
    Springer
    European journal of pediatrics 155 (1996), S. S173 
    Details
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; Maternal phenylketonuria ; Phenylalanine ; Pregnancy outcome ; Phenylalanine restricted diet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The German maternal phenylketonuria (MPKU) Study began in 1989 and since 1992 works together with the American-Canadian MPKU Study. Main goals of the study are: (1) to find women with phenylketonuria (PKU) and mild untreated hyperphenylalaninaemia (HPA); (2) to inform them about the risks of an untreated pregnancy with PKU and HPA; (3) to evaluate the efficacy of the phenylalanine (Phe) restricted dietary treatment prior to and during pregnancy by following the physical and cognitive development of offspring from treated pregnancies. An interim report of the study is presented. Until now, 43 pregnancies have been followed. They resulted in 34 live births, 24 from women with PKU and 10 from women with HPA. There are significant negative correlations between the gestational age in which the dietary control (blood Phe level 〈 360 μmol/l) was reached and pregnancy outcome as measured by growth parameters and early cognitive and motor developmental quotients at the age of 2 years. For minimizing risks of MPKU, preconceptional dietary control is strongly recommended. Tracking and timely information of young women about risks of MPKU is of outmost importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00014241
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  • 7
    Electronic Resource
    Electronic Resource
    Untreated non-Phenyketonuric-hyperphenylalaninaemia: intellectual and neurological outcome (1996)
    Springer
    European journal of pediatrics 155 (1996), S. S26 
    Details
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; Non-PKU HPA ; intellectual and neurological outcome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The intellectual, neurological, and neuropsychological outcome of patients with non-phenylketonuric-hyperphenylalaninaemia (PKU-HPA) (serum phenylalanine levels under free diet 〈 600 μmol/l) has not been systematically studied so far. We therefore tested 28 patients (mean age = 21.8, SD = 4.2 years) for IQ (WAIS-R/WISC-R), school performance, job career, clinical neurological examination, fine motor performance (motor performance task), and selective and sustained attention (stroop task, Dot Pattern Exercise from the Sonneville visual attention task). In addition, cranial MRI (1.5 T unit) was obtained in 10 of these patients. Clinical-neurological examination revealed no significant abnormalities in the non-PKU-HPA patients. They also had a normal IQ (mean = 101.9, SD = 13.6). Compared to their healthy siblings, they attended a normal school and had a normal job career. The motor performance task revealed no deficits in fine motor abilities. The patients performed normally in the stroop task and the dot pattern exercise. Their MRIs were normal. Our results indicate that patients with non-PKU-HPA are not at risk for developing intellectual, neurological, and neuropsychological impairment, as described for patients with treated mild or classical phenylketonuria. From this point of view a dietary treatment is not necessary in patients with hyperphenylalaninaemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00014244
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  • 8
    Electronic Resource
    Electronic Resource
    Psychosocial aspects in phenylketonuria (1996)
    Springer
    European journal of pediatrics 155 (1996), S. S101 
    Details
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; Psychological characteristics ; Social ; findings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Psychosocial aspects in phenylketonuric (PKU) patients are reported. In two separate studies patients with PKU differing in age (children versus adolescents), were assessed. The main message of the first prospective study on 58 10-year-old patients is that normally intelligent PKU patients who were treated early and strictly did not show a higher risk for severe emotional and behavioural maladjustment compared with healthy controls at the age of 10 years. The data were obtained in the course of the German PKU Collaborative Study by the “Personality Questionnaire for Children (PFK 9–14)”. All patients received nutritional, medical, and psychological counselling every 6 months. In the second retrospective study, 34 early treated, normally intelligent adolescents with PKU (age: mean = 14.6, SD = 2.0, range = 11–18 years) and their mothers were assessed with several psychometric personality inventories and self-developed questionnaires concerning their psychosocial situation and their disease- and diet-specific knowledge. Using the Mannheimer Biographic Inventory (MBI), the Personality Questionnaire for Children (PFK 9–14), and the Freiburger Personality Inventory (FPI) the adolescent patients described their social life and their emotional development as being distinctly restricted. Their knowledge concerning disease and diet was alarmingly poor and the majority had great difficulties in satisfactory dietetic management without parental help. In addition to the burdensome diet, developmental crises like puberty may cause more frequently emotional and behavioural problems in PKU patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00014225
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  • 9
    Electronic Resource
    Electronic Resource
    Rationale for the German recommendations for phenylalanine level control in phenylketonuria 1997 (1999)
    Springer
    European journal of pediatrics 158 (1999), S. 46-54 
    Details
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; Hyperphenylalaninaemia ; Phenylalanine levels ; Treatment recommendations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Treatment of hyperphenylalaninaemias due to phenylalanine hydroxylase deficiency with a low phenylalanine (Phe) diet is highly successful in preventing neurological impairment and mental retardation. There is consensus that, for an optimal outcome, treatment should start as early as possible, and that strict blood Phe level control is of primary importance during the first years of life, but for adolescent and adult patients international treatment recommendations show a great variability. A working party of the German Working Group for Metabolic Diseases has evaluated research results on IQ data, speech development, behavioural problems, educational progress, neuropsychological results, electroencephalography, magnetic resonance imaging, and clinical neurology. Based on the actual knowledge, recommendations were formulated with regard to indication of treatment, differential diagnosis, and Phe level control during different age periods. The development of the early-and-strictly-treated patient in middle and late adulthood still remains to be investigated. Therefore, the recommendations should be regarded as provisional and subject to future research. Efficient treatment of phenylketonuria has to go beyond recommendations for blood Phe level control and must include adequate dietary training, medical as well as psychological counselling of the patient and his family, and a protocol for monitoring outcome. Conclusions Early-and-strictly-treated patients with phenylketonuria show an almost normal development. During the first 10 years treatment should aim at blood Phenyl-alanine levels between 40 and 240 μmol/L. After the age of 10, blood phenylalanine level control can be gradually relaxed. For reasons of possible unknown late sequelae, all patients should be followed up life-long.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004310051008
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of l-dopa on visual evoked potentials and neuropsychological tests in adult phenylketonuria patients (1996)
    Springer
    European journal of pediatrics 155 (1996), S. S74 
    Details
    ISSN: 1432-1076
    Keywords: Key words Phenylketonuria ; l-dopa therapy ; Neuropsychological tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eight adult, untreated patients with classical phenylketonuria received L-dopa and a decarboxylase inhibitor for 2 weeks. No effect of l-dopa therapy on choice reaction time tasks, sustained attention, frontal lobal function as well as latencies of visual evoked potentials was found. The results raise the question if adult patients with phenylketonuria really suffer from functional dopamine deficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00014256
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