The clinically and biochemically heterogeneous group of diseases characterized by Idiopathic Lactic Acidosis are a major therapeutic and diagnostic challenge in the pediatric patient. They often present in infancy leading to major morbidity and death. Patients are frequently severely neurologically damaged as a consequence of both the ongoing metabolic defect and episodic deterioration. These diseases are very probably genetically determined, but in most cases the biochemical nature of the defect remains unknown and adequate treatment is not available. The usual approach to the investigation of these patients involves fasting and dietary challenges along with the assay in blood or fibroblasts of a few of the enzymes concerned with pyruvate metabolism. Occasionally other specific enzyme assays are carried out on a """"""""hit and miss"""""""" basis. Over 80% of these patients remain undiagnosed. Citric acid cycle or cytochrome chain defects are the likely errors in many of these children. The propsed studies will provide an overview of these areas of metabolism indicating sites of specific metabolic defect. Location of the exact defect provides the best chance of designing effective therapy for the patient.
The specific aims of this proposal are the development and application of three different techniques for studying the citric acid cycle and oxidative phosphorylation in tissue samples and cultured cell lines. Control samples will be used to establish normal patterns and cells and muscle tissue from patients with lactic acidosis will be studied. These techniques are: 1) High pressure liquid chromatography (HPLC) assay of citric acid cycle intermediates in fibroblasts and muscle tissue. The extracts will also be analyzed for nucleotides, ketones, and pyruvic and lactic acid. 2) Mitochondria isolated from fibroblass wil be polarographically assayed utilizing a microchamber developed by this investigator. These mitochondria will also undergo HPLC analysis. 3) Fibroblast mitochondria will be used to measure the protonmotive force and proton conductance across the inner mitochondrial membrane. This assay provides information on the integrity of the inner mitochondrial membrane and along with the polarographic assay provides an excellent overview of oxidative phosphorylation and the cytochrome chain. The HPLC techniques will be used to investigate the metabolic effects of thiamine deficiency in the rat pyrithiamine treated/thiamine deficient model of lactic acidosis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08NS001024-03
Application #
3083682
Study Section
Neurological Disorders Program Project Review B Committee (NSPB)
Project Start
1985-08-01
Project End
1990-07-31
Budget Start
1987-08-01
Budget End
1988-07-31
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of California San Diego
Department
Type
Schools of Medicine
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Haas, R H; Light, M; Rice, M et al. (1995) Oxidative metabolism in Rett syndrome: 1. Clinical studies. Neuropediatrics 26:90-4
Haas, R H; Nasirian, F; Hua, X et al. (1995) Oxidative metabolism in Rett syndrome: 2. Biochemical and molecular studies. Neuropediatrics 26:95-9
Murakami, J W; Courchesne, E; Haas, R H et al. (1992) Cerebellar and cerebral abnormalities in Rett syndrome: a quantitative MR analysis. AJR Am J Roentgenol 159:177-83