Search PubMed⌕ Search

Biomedical subjects

B Hess

Publications and source records attributed to B Hess.

At least 55 records · Page 3Linked to original sources
PubMed1998

Drug-induced urolithiasis.

Drugs can cause renal stone formation either by raising excretion rates of naturally occurring stone components or by directly precipitating within the urinary tract. In large series of analysed renal stones, the overall frequency of drug-induced urolithiasis is less than 0.5%. Five clinical presentations of drug-induced crystallization in the kidneys can be recognized: asymptomatic crystalluria, symptomatic crystalluria; stone passage; obstructive uropathy and tubulointerstitial nephritis. In the current literature review, the protease inhibitors used for treatment of patients infected with the human immunodeficiency virus stand out as a new class of drugs that frequently causes crystallization within the urinary tract. The most widely used compound, indinavir, may lead to crystalluria and renal stone formation in up to 50% of patients, and occasionally also causes acute renal failure caused by obstructive uropathy or tubulointerstitial nephritis. On the other hand, ritonavir appears more often to induce (reversible) acute renal failure than stone formation.

Journal Article↗
PubMed1997

[Nephrolithiasis--rational etiological assessment].

Although underlying metabolic abnormalities do not differ fundamentally in patients with either first or recurrent nephrolithiasis and 35% of patients with a first event may have to face a recurrence 5 years later, extended metabolic investigations in patients with a first renal calculus should be restricted to particular, exceptional cases. However, in patients with a first calculus basic investigations with respect to specific causes for a concrement such as primary hyperparathyroidism, incomplete renal-tubular acidosis, recurrent urinary tract infection and cystinuria are mandatory. This includes, in addition to a laboratory investigation of blood and urine after a 2-hour-fasting period, analysis of the stone and a urography. The extended metabolic investigation in patients with recurrences or a first occurrence in a patients with a risk constellation includes evaluation of the most important lithogenic (calcium, oxalate, phosphate, uric acid) and inhibiting components (citrate) in the 24-hour urine, in patients with cystine calculi quantitation of cystine. A metabolic investigation should never be undertaken in the hospital or under standardized diet, but always under accustomed, unrestricted nutrition. At least 2 urine samples should be investigated from each patient, preferably not prior to 3-4 months after the event when homeostasis of the patient is restored analogously to the onset of concrement development.

Acidosis, Renal Tubular↗
PubMed1997

Metabolic evaluation of patients with recurrent idiopathic calcium nephrolithiasis.

BACKGROUND: Metabolic evaluation in recurrent idiopathic calcium renal stone-formers (RCSF) was analysed with respect to the following questions: (1) do three 24-h urines provide more diagnostic accuracy in the metabolic evaluation of RCSF than 1 or 2 urines?; (2) does time after stone event influence the diagnostic yield?; (3) is urine composition at weekends different from that at mid-week?; (4) what are the prevalences of the most important risk factors (RF) of idiopathic calcium nephrolithiasis, i.e. low volume (LV), hypercalciuria (HC), hyperoxaluria (HO), hyperuricosuria (HU), hypocitraturia (Hypo-Cit), and hypomagnesiuria (Hypo-Mg)?; and (5) do male RCSF differ from females with respect to urinary RFs? METHODS: Seventy-five RCSF (59 men, 16 women) collected three 24-h urines (U1-3) while on free-choice diet. To account for possible variations in lifestyle and diet, U1 and U3 had to be collected midweek and U2 at a weekend. RESULTS: When considering all three urines together (U1 + U2 + U3), the number of RF abnormalities/patient was 2.8 +/- 0.1, higher than numbers of any combination of two urines or of any single urine (P = 0.0001 for all comparisons). The number of RF abnormalities also rose with time after stone event, from 0.8 +/- 0.1 (range 0-4) in U1 to 1.1 +/- 0.1 (range 0-4) in U3 (P = 0.011 vs U1). Whereas all other RF did not change between collections, urine volume was lower in U2 (1793 +/- 90 ml) than in U1 (2071 +/- 97 ml, P = 0.0001 vs U2) and U3 (1946 +/- 97 ml, P = 0.046 vs U2). At least 1 abnormality was found in 85.3% of all RCSF, and multiple abnormalities occurred in 47%. The most frequent RF was HC (39%), followed by HO and LV (32% each), Hypo-Cit (29%), HU (23%) and Hypo-Mg (19%). Males more often had Hypo-Cit (P < 0.001) and Hypo-Mg (P < 0.01) than females, whereas HO was more frequent in female RCSF (P < 0.025 vs males). CONCLUSIONS: Diagnostic accuracy of metabolic evaluation in RCSF increases both with the number of urines collected and the time passing after a stone event. Urines collected at weekends differ from those of the week only by their lower volumes. Abnormalities of RF for calcium nephrolithiasis can be detected in 85.3% of RCSF, and HC is the most common RF both in male and female RCSF.

Adult↗
PubMed1996

Phenotype of arylsulfatase A-deficient mice: relationship to human metachromatic leukodystrophy.

Metachromatic leukodystrophy is a lysosomal sphingolipid storage disorder caused by the deficiency of arylsulfatase A. The disease is characterized by progressive demyelination, causing various neurologic symptoms. Since no naturally occurring animal model of the disease is available, we have generated arylsulfatase A-deficient mice. Deficient animals store the sphingolipid cerebroside-3-sulfate in various neuronal and nonneuronal tissues. The storage pattern is comparable to that of affected humans, but gross defects of white matter were not observed up to the age of 2 years. A reduction of axonal cross-sectional area and an astrogliosis were observed in 1-year-old mice; activation of microglia started at 1 year and was generalized at 2 years. Purkinje cell dendrites show an altered morphology. In the acoustic ganglion numbers of neurons and myelinated fibers are severely decreased, which is accompanied by a loss of brainstem auditory-evoked potentials. Neurologic examination reveals significant impairment of neuromotor coordination.

Animals↗
PubMed1996

Targeted disruption of the arylsulfatase B gene results in mice resembling the phenotype of mucopolysaccharidosis VI.

Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease with autosomal recessive inheritance caused by a deficiency of the enzyme arylsulfatase B (ASB), which is involved in degradation of dermatan sulfate and chondroitin 4-sulfate. A MPS VI mouse model was generated by targeted disruption of the ASB gene. Homozygous mutant animals exhibit ASB enzyme deficiency and elevated urinary secretion of dermatan sulfate. They develop progressive symptoms resembling those of MPS VI in humans. Around 4 weeks of age facial dysmorphia becomes overt, long bones are shortened, and pelvic and costal abnormalities are observed. Major alterations in bone formation with perturbed cartilaginous tissues in newborns and widened, perturbed, and persisting growth plates in adult animals are seen. All major parenchymal organs show storage of glycosaminoglycans preferentially in interstitial cells and macrophages. Affected mice are fertile and mortality is not elevated up to 15 months of age. This mouse model will be a valuable tool for studying pathogenesis of MPS VI and may help to evaluate therapeutical approaches for lysosomal storage diseases.

Animals↗
PubMed1996

[Episodic headache, diminished performance and depressive mood].

By the example of two case reports, typical signs of caffeine withdrawal like headache, increased irritability, decreased performance and disturbed concentration are described. These symptoms occurred two times within one week in two healthy nonsmoking individuals volunteering in a scientific study including periods of 24 hours with standardized caffeine-free-diet. The two volunteers were used to a regular coffee consumption of eight cups per day (about 600 mg/day). Since caffeine obviously represents the most common psycho-stimulant worldwide and since even moderate coffee consumption may lead to dependence, withdrawal symptoms induced by sudden reduction of consumption or withdrawal of caffeine may occur more often than usually assumed.

Adult↗
PubMed1996

Determination of the arotinoid mofarotene in human, rat and dog plasma by high-performance liquid chromatography with automated column switching and ultraviolet detection.

A sensitive and specific high-performance liquid chromatographic method was developed and validated for the determination of the third-generation retinoid (arotinoid) mofarotene (Ro 40-8757) in human, rat and dog plasma, using direct injection of deproteinated plasma samples, automated column switching (on-line solid-phase extraction) and ultraviolet detection. Plasma (0.5 ml) was deproteinated by adding ethanol (1 ml) containing the internal standard Ro 42-8659 (200 ng/ml). After centrifugation, 0.9 ml of the supernatant were directly injected onto a precolumn packed with C18 Corasil 37-50 microns. Polar plasma components were washed out from the precolumn using 1% ammonium acetate-acetic acid-acetonitrile (900:9:100, v/v/v). After valve switching, the pre-concentrated compounds were transferred to the analytical column (C18) in the backflush mode, separated by gradient elution and detected at 300 nm. The retention times (total run times) were approximately 15 and 20 min for the internal standard and mofarotene, respectively. The method was linear in the range 10-1000 ng/ml with a limit of quantification of 10 ng/ml. The mean recoveries were 80.4%, 81.7% and 77.8% (range 10-1000 ng/ml) and the inter-assay precision was 2.7% (range 20-1000 ng/ml), 1.5% and 2.0% (both range 100-1000 ng/ml) for human, rat and dog plasma, respectively. Mofarotene was found to be stable in human, rat and dog plasma stored at -20 degrees C for 3 months and 22 degrees C for 24 h. The method was successfully applied to clinical, pharmacokinetic and toxicokinetic studies.

Animals↗
PubMed1996

[A 17-year-old female patient with recurring fever, chills, exanthema, myalgia and polyserositis].

The 17-year-old was admitted for investigation of a fever persisting for three weeks in spite of antibiotic treatment. Based on the clinical picture presenting with fugitive exanthema during febrile episodes, myalgia, polyserositis, leucocytosis with toxic granulations and-- after an antibiotic window--negative cultures of all investigated fluids (blood, pleural and peritoneal fluid), adult-type Still's disease was diagnosed. Treatment with steroids and indomethacine was only temporarily successful. Therapeutic stabilization first occurred under administration of phenylbutazone. The course was complicated by three surgical abdominal interventions because of an unclear acute abdomen, a strangulation ileus and a small-bowel perforation.

Adolescent↗
PubMed1996

Characterization of two arylsulfatase A missense mutations D335V and T274M causing late infantile metachromatic leukodystrophy.

Metachromatic leukodystrophy is a lysosomal storage disorder caused by the deficiency of arylsulfatase A. We describe a novel missense mutation in exon 6 causing the substitution of Asp335 by Val. In transient transfections no enzyme activity could be expressed from the arylsulfatase A cDNA carrying this mutation. Examination of the effects of the mutation in cells stably overexpressing the mutant enzyme revealed, that the mutant enzyme is catalytically inactive and degraded in an early biosynthetic compartment. We have also investigated the effects of a previously identified mutation (T274M). The specific catalytic activity of the Met274 substituted arylsulfatase is reduced to about 35% of the normal enzyme when measured with an artificial substrate. Most of this enzyme is also degraded in an early biosynthetic compartment.

Age of Onset↗
PubMed1996

Spectrally silent transitions in the bacteriorhodopsin photocycle.

The photocycle kinetics of bacteriorhodopsin were analyzed from 0 to 40 degrees C at 101 wavelengths (330-730 nm). The data can be satisfactorily approximated by eight exponents. The slowest component (half-time 20 ms at 20 degrees C) belongs to the 13-cis cycle. The residual seven exponentials that are sufficient to describe the all-trans photocycle indicate that at least seven intermediates of the all-trans cycle must exist, although only five spectrally distinct species (K, L, M, N, and O) have been identified. These seven exponentials and their spectra at different temperatures provide the basis for the discussion of various kinetic schemes of the relaxation. The simplest model of irreversible sequential transitions includes after the first K--> L step the quasiequilibria of L<-->M, M<-->N, and N<-->O intermediates. These quasiequilibria are controlled by rate-limiting dynamics of the protein and/or proton transfer steps outside the chromophore region. Thus there exists an apparent kinetic paradox (i.e., why is the number of exponents of relaxation (at least seven) higher than the number of distinct spectral intermediates (only five)), which can be explained by assuming that some of the transitions correspond to changes in the quasiequilibria between spectrally distinct intermediates (i.e., are spectrally silent).

Bacteriorhodopsins↗
PubMed1996

Low calcium diet in hypercalciuric calcium nephrolithiasis: first do no harm.

Many studies indicate that up-regulated production of 1,25(OH)2-vitamin D3 (calcitriol) with increased intestinal absorption of calcium is the primary event causing idiopathic hypercalciuria. Thus, a low calcium diet appears to be a straightforward strategy in calcium stone formers with hypercalciuria (HCSF). However, the efficacy of such a regimen has never been established, and lowering calcium intake from 1000 to 400 mg/day further enhances calcitriol production. On a diet chronically restricted in calcium, many stone formers increase their intake of animal flesh protein. The latter is known to increase renal mass, and calcitriol levels indeed are positively correlated with renal mass in animals as well as in HCSF. Thus, low calcium and high animal flesh protein consumption are independent stimuli for further up-regulation of calcitriol production. The rise in calcitriol suppresses parathyroid hormone synthesis thereby diminishing renal tubular calcium reabsorption, and increasing urinary calcium losses. Since calcitriol up-regulation also increases bone resorption, the combination of low calcium and high protein intake is particularly likely to induce negative calcium balance and thus osteopenia. Finally, low calcium intake carries the risk of insufficient intestinal binding of oxalate with subsequent increases in intestinal absorption and urinary excretion of oxalate. Indeed, most recent studies suggest that high amounts of calcium, when ingested simultaneously with oxalate-containing meals, are able to prevent hyperoxaluria during severe oral oxalate loading.

Calcitriol↗
PubMed1995

[Diagnostic markers in calcium nephrolithiasis--current and traditional ideas with a new look].

About 80% of all renal stones contain calcium oxalate and/or calcium phosphate as their main crystalline components. The most important risk factors for increases in calcium oxalate crystallization are low urine volume, hyperoxaluria and hypocitraturia. Hypercalciuria, however, is of secondary importance as a cause of increased crystallization: whereas calcium and oxalate crystallize in a 1:1 ratio, the molar concentration ratio in urine amounts to about 10:1 in favor of calcium. Therefore, increases in urinary calcium will not be followed by a rise in crystallization as long as oxalate remains constant, whereas even the slightest increases in urinary oxalate immediately cause more crystals to precipitate. Thus, low calcium diet is not only unnecessary but is contraindicated since it may cause secondary hyperoxaluria (increased intestinal oxalate absorption) and osteopenia (negative calcium balance). On the other hand, overconsumption of animal protein (meat, poultry, fish) induces more pronounced hyperoxaluria and hypocitraturia and contributes to an overall negative calcium balance. It is, however, only by the interplay of "bad" dietary habits with underlying abnormalities such as up-regulation of calcitriol production, incomplete renal tubular acidosis or defective macromolecular crystallization inhibitors, that people become recurrent calcium renal stone formers.

Adult↗
PubMed1995

[Prevalence of medullary sponge kidney in patients with and without nephrolithiasis].

Reports on the prevalence of medullary sponge kidneys have given conflicting results. The present work is aimed at defining the prevalence of this abnormality in renal stone formers compared with a non-stone-forming control population by strict radiological criteria. Three separate studies have been carried out: the retrospective analysis of 191 intravenous urographies, which had been performed in 1988; the respective prospective analysis of 104 consecutive intravenous urographies and of 149 consecutive urographies, which had been performed at the end of intravenous digitalized subtraction renal angiographies. The 444 patients were classified according to presence or absence of nephrolithiasis. After exclusion of 70 patients (16%) of which the X-ray didn't fulfill the quality criteria, urographies were classified as 'medullary sponge kidneys', 'papillary blush' or 'negative' according to the radiological aspect of the papillae. Diagnosis of medullary sponge kidneys was based on presence of at least three linear or round papillary opacities seen in at least on papilla even of one kidney on late films (at least ten minutes after injection of contrast medium), taken without ureteral obstruction or abdominal compression. Overall results reveal that prevalence of a medullary sponge kidney in renal stone formers (8.5%) is significantly (p < 0.01) higher than in the control population (1.5%) and higher than what has been generally reported. Results of the retrospective and of both prospective analysis did not significantly differ. The best diagnostic tool to unmask medullary sponge kidneys remains urography.

Angiography, Digital Subtraction↗