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Biomedical subjects

K S Roth

Publications and source records attributed to K S Roth.

At least 19 recordsLinked to original sources
PubMed2001

Renal tubular acidosis: a new look at an old problem.

Although the definition of renal tubular acidosis (RTA) is simple, understanding the physiologic basis underlying the various types of this clinical entity is much more difficult. The pathophysiology of this disorder is reviewed using the normal acid-base functions of the involved segments of the nephron as a guide to understanding. Clinical and laboratory features of the subtypes of RTA are addressed, and diagnosis and treatment discussed. New developments in the knowledge and understanding of the associated growth disturbances, mineral metabolism, and molecular biology of RTA are also reviewed to provide the most current view of this relatively common pediatric entity.

Acidosis, Renal Tubular↗
PubMed2001

Pediatric hematuria and thin basement membrane nephropathy: what is it and what does it mean?

Hematuria is seen frequently in the pediatric population and may signal either benign or serious renal patholosis. A significant proportion of children with asymptomatic hematuria will have thin basement membrane nephropathy (TBMN), a benign disorder, yet there is little information about this entity outside the nephrology literature. This article is designed to provide an information base for pediatric practitioners to assist them in making appropriate decisions regarding diagnosis and care. A review of experience over a decade with 9 children with biopsy-proven TBMN, including follow-up to the present; is presented. In addition, review of literature regarding TBMN, Alport's and Berger's syndromes, which comprise the major clinical entities associated with asymptomatic pediatric hematuria, is presented. Each patient was evaluated for asymptomatic, documented and persistent hematuria. Renal biopsy was performed after clinical evaluation and follow-up. TBMN and Berger's disease (IgA nephropathy) are separable only by renal biopsy results; TBMN is benign and IgA nephropathy may be progressive, mandating referral to a nephrologist. The prognosis of TBMN is excellent.

Adolescent↗
PubMed2001

Obstructive nephropathy in children: long-term progression after relief of posterior urethral valve.

BACKGROUND: Approximately one third of children with end-stage renal disease have the illness because of urinary tract malformations, obstructive uropathy, and hypoplasia/dysplasia. The significant drop in infant mortality from obstructive uropathies in recent decades, attributable to prenatal diagnosis with renal ultrasonography and coordinated surgical and medical care, necessitated a reevaluation of the long-term outcome. METHODS: To that end, we examined the long-term progression of obstructive nephropathy after neonatal relief of posterior urethral valves in our center over a span of 21 years, with diagnosis and care being provided by the same pediatric and urology team. RESULTS: The 10 consecutive cases of posterior urethral valves represented 7% of all patients with congenital malformative uropathies seen over this period. The following procedures were performed: primary valve ablation (90%) and vesicostomy (40%). Seventy percent of patients progressed to end-stage renal disease over a (mean +/- standard error of the mean) follow-up of 11.3 +/- 2.1 years. The linear plot of the log of the inverse of serum creatinine versus time suggested unrelenting progression. The rate of progression was rapid after serum creatinine exceeded 5 mg/dL but the rate was slow and steady from serum creatinine of 1.5 to 5 mg/dL. CONCLUSIONS: To test the effect of a therapeutic intervention to ameliorate the rate of progression, this steady and prolonged progression of 0.5 mg/dL per year between serum creatinine concentration of 1.5 to 5 mg/dL would seem the optimal study.

Adolescent↗
PubMed1999

Jaclyn's story.

Explore the source record for details and available documents.

Adolescent↗
PubMed1996

Prediction of students' USMLE step 2 performances based on premedical credentials related to verbal skills.

PURPOSE: To examine the relationship between the objective premedical credentials and performances on Step 2 on the United States Medical Licensing Examination (USMLE) of 480 students in three classes at the Virginia Commonwealth University Medical College of Virginia School of Medicine. The purpose of the study was to seek those selection criteria that might best predict performance on an examination designed to assess problem-solving skills, the essence of clinical medicine. METHOD: Premedical data from two classes (1193, 1994) were analyzed, and a regression equation was used to calculate theoretical USMLE Step 2 scores for the students in the class of 1995, who had not yet taken this examination. The premedical variables were scores on the verbal and math section on the Scholastic Aptitude Test (SAT), scores on the six sections of the pre-1991 Medical College Admission Test (MCAT), grade-point average (GPA) in science courses required of premedical students, and undergraduate major. Once the class of 1995 had taken the USMLE Step 2, the equation was cross validated, and the theoretical and actual scores of the class of 1995 were correlated. RESULTS: The correlation between theoretical and actual scores was r = .443. In the analysis for the classes of 1993 and 1994, the single variables most highly predictive of USMLE Step 2 performance were scores on the verbal section of the SAT (r = .317) and the Skills Analysis: Reading section of the MCAT (r = .331). However, the MCAT scores were excluded from the final regression analysis because of the pre-1991 MCAT cannot be useful in predicting the performances of present medical school applicants. The resulting regression equation (using the SAT verbal section and premedical GPA) was able to account for 21.2% of the variance for the class of 1995. CONCLUSION: The use of the verbal section of the SAT as a predictive factor is unique. It is significant that this variable was strongly related to premedical GPA, suggesting that high verbal aptitude serves one well, even when coping with complex scientific concepts.

Aptitude↗
PubMed1994

On 'being led by the nose'. Rapid detection of inborn errors of metabolism.

We reviewed and emphasized the importance of olfaction for the diagnosis of inborn errors of metabolism. The "trained" nose has a remarkable sensitivity and specificity for discriminating odors that are associated with certain inborn errors of metabolism. These odors are often the first abnormality noticed on physical examination and should prompt the pediatrician to seek confirmatory laboratory studies.

Diagnosis, Differential↗
PubMed1994

Rapid and accurate random urinary porphyrin quantitation.

Urinary metabolite profiling, using randomly voided samples, has become accepted practice for such compounds as organic acids. To date, however, published methods for examining urinary porphyrin excretion have been based upon examination of 24-h urine collections. The inherent difficulties of obtaining an accurate collection, coupled with the intrinsic liabilities of porphyrins suggest that a method based upon random void analysis would be of great use. Thus, we have examined the porphyrin pattern of randomly excreted urine samples from normal adults of both genders, comparing our results with those obtained from analysis of 24-h collections. We have also evaluated the use of different alkalinizing agents. Finally, we have investigated the possibility that an underlying diurnal pattern of porphyrin excretion might influence the results obtained from random urine voids. The results indicate that NaOH retards spontaneous conversion of porphyrins within the first 24 h, thus optimizing recovery of uroporphyrin. Data from random voids mirror those obtained from 24-h collections and diurnal variations were not found to influence these results. Normal values are provided for random samples obtained from males and females. Thus, we conclude that random urine profiling is a rapid and accurate means of initial evaluation.

Adult↗
PubMed1993

Tissue distribution of succinylacetone in the rat in vivo: a possible basis for neurotoxicity in hereditary infantile tyrosinemia.

Neurologic dysfunction is a significant component of hereditary infantile tyrosinemia, an autosomal recessive disorder of man. The specific enzyme defect leads to endogenous production of the biochemical marker compound, succinylacetone (SA). Earlier study of the role which SA plays in generation of the renal Fanconi syndrome, also associated with this disorder, led to speculation that SA might also have neurotoxic effects. Thus, we have studied the distribution and impact on heme metabolism of SA in brain, liver and kidney from rats treated in vivo. Our results show far greater retention of SA in brain and kidney than in liver, by a ratio of approx. 3:1. Delta-aminolevulinate dehydratase (ALAD) was reduced to less than 10% of control activity in all three tissues after three daily injections; after a 7-day recovery, activity was regained at different rates in the three tissues. Total heme content of each tissue showed a steady decline beyond the treatment period, the most marked reduction being found in kidney. Porphyrin intermediates, heme oxygenase activity and cytochrome P-450 content evidenced varying responses to SA exposure which differed from tissue to tissue. Our results show that brain tissue sequesters SA and that heme biosynthesis in brain, as distinct from liver and kidney, is adversely affected. Such effects could result in impaired oxidative metabolism in brain, producing the CNS manifestations of tyrosinemia.

Animals↗
PubMed1993

Hyperammonemia: the silent killer.

Nitrogen, derived from breakdown of dietary amino acids as ammonia, is normally converted to urea and excreted. Impairment in the conversion process (called the urea cycle) can occur, either as a consequence of primary genetic defects or through secondary suppression of enzyme activity. Either process results in hyperammonemia, producing a clinical picture virtually indistinguishable from many other diseases of infancy. Moreover, there is no way to detect hyperammonemia except to measure the blood ammonia level. Thus, the capability to do so is a minimum standard of care in any hospital setting. Use of commonly obtained laboratory studies is discussed in the context of rapid, presumptive diagnosis of the causes of hyperammonemia.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

delta-Aminolevulinic acid dehydratase: effects of succinylacetone in rat liver and kidney in an in vivo model of the renal Fanconi syndrome.

Succinylacetone (SA) is a known inhibitor of the heme biosynthetic pathway in liver. We have demonstrated previously the SA enhancement of delta-aminolevulinic acid dehydratase (ALAD) in renal tubules, while this enzyme is known to be impaired by SA in the liver. The present studies, based on in vivo treatment of animals with SA, show equivalent degree of inhibition of specific ALAD activity in liver and kidney. Both tissues evidenced an ability to restore enzyme activity with time, the recovery occurring much more slowly in kidney than in liver. The discrepant in vitro and in vivo effect of SA on renal ALAD may be due to differences between a direct inhibitor-enzyme interaction and inhibitor actions in the living cell, respectively. Persistent tissue levels of SA, consistent with demonstrated SA in plasma and urine, might account for continuing inhibition, with the greatest tissue accumulation in kidney where the substance must be cleared for excretion.

Animals↗
PubMed1992

Physiological basis for an animal model of the renal Fanconi syndrome: use of succinylacetone in the rat.

1. The biochemical basis for the human renal Fanconi syndrome, including glucosuria, phosphaturia and aminoaciduria, remains enigmatic. This is due, in part, to the lack of an appropriate animal model. Since there is an association between the human genetic disease hereditary tyrosinaemia, for which urinary excretion of the compound succinylacetone constitutes a biochemical marker, and a renal Fanconi syndrome, we have examined the relationship between succinylacetone and renal tubular function in the rat. 2. Intraperitoneal injection of succinylacetone for 3 consecutive days into adult male Sprague-Dawley rats resulted in succinylacetone plasma concentration of 3 mmol/l. This concentration was associated with glucosuria, aminoaciduria, polyuria, reduced renal phosphate reabsorption and normal creatinine clearance. In addition, urinary porphobilinogen and total porphyrin excretions were markedly reduced. In animals permitted to recover for 7 days after succinylacetone administration, these renal functional changes remitted partially or completely. Ultrastructural examination of the kidneys after the 3 days of treatment showed no fine structural changes. 3. We conclude that the physiological alterations produced in normal rat renal tubules by succinylacetone provide the basis for the study of the biochemical changes underlying the human renal Fanconi syndrome.

Amino Acids↗