Edward J. Mitzen

Olivopontocerebellar atrophy: Immunocytochemical and Golgi observations

Brain tissue was obtained promptly after death from a patient with autosomal dominant olivoponto-cerebellar atrophy and studied by immunocytochemistry and a Golgi technique. Antiglutamic acid decarboxylase showed severe loss of Purkinje cells and their terminals in the dentate nucleus. Stains for neuron-specific enolase (NSE) and microtubule-associated proteins (MAP) confirmed the integrity of the dentate nucleus. Basket and stellate cells revealed secondary changes, but Golgi neurons were intact. Methods for NSE and MAP disclosed dendritic alterations and loss of neurons in the basis pontis and inferior olivary nuclei. Golgi impregnation of Purkinje cells showed loss of major dendrites, paucity of spiny branchlets, and axonal expansions.

METABOLISM OF MALONIC ACID IN RAT BRAIN AFTER INTRACEREBRAL INJECTION

Labeled malonic acid ([1‐14C] and [2‐14C]) was injected into the left cerebral hemisphere of anesthetized adult rats in order to determine the metabolic fate of this dicarboxylic acid in central nervous tissue. The animals were allowed to survive for 2, 5, 10. 15 or 30min. Blood was sampled from the torcular during the experimental period and labeled metabolites were extracted from the brain after intracardiac perfusion.

Developmental changes in malonate-related enzymes of rat brain

Abstract Mitochondria and high-speed supernatant were prepared from rat brain homogenates at 0–50 days of age. The development of malonyl-CoA synthetase, malonyl-CoA decarboxylase, coenzyme A-transferases and acetyl-CoA hydrolase was examined and compared to de novo fatty acid biosynthesis. The specific activity of malonyl-CoA synthetase rose steeply between 6 and 10 days, and this sudden increase coincided with peak specific activity of fatty acid synthetase. Similarly, malonate activation by coenzyme A-transfer from succinyl-CoA increased rapidly at the same time. Transfer of the coenzyme A moiety from acetoacetyl-CoA was only minimal during this period. Brain mitochondria had active malonyl-CoA decarboxylase which showed an almost linear increase of specific activity between 0 and 50 days. Acetyl-CoA resulting from malonyl-CoA decarboxylation underwent enzymatic hydrolysis to acetate and free coenzyme A. Only traces of acetoacetate were recovered. In mitochondria, acetyl-CoA hydrolase increased progressively whereas the cytosolic enzyme had high specific activity at birth which declined slowly during maturation.

Phospholipids, fatty acids and fatty aldehydes in rat brain subcellular fractions

Summary Subcellular fractions of rat brain were prepared by differential and sucrose density gradient centrifugation and examined for their lipid composition. Two fractions, retained by 0.9 and 1.0 M sucrose, respectively, had the morphological characteristics of synaptic membranes. The former was characterized by a high concentration of serine phosphoglyceride. The lipids (sphingomyelin excepted) of both synaptic membrane fractions differed from the lipids of myelin and mitochondria in that fatty acids had shorter chain lengths and lesser degrees of unsaturation. Charged phospholipids may play a role in attracting soluble enzymes to membrane fractions. An example is the high relative specific activity of carboxylic ester hydrolases and acetylcholinesterase in synaptic membranes. The data suggest that the short chain length of fatty acids in synaptic membranes militates against strong London-van der Waals forces, while the high concentration of serine phosphoglyceride in membranes retained by 0.9 M sucrose promotes ionic interaction and formation of phospholipid-enzyme complexes.

Lipid Labeling After Intracerebral Injection of Radioactive Malonic Acid

Growing albino rats between the ages of birth and 50 days received single intracranial injections of either [2‐14C]malonate or [1‐14C]malonate. After 1 h, 90% of the nonmalonate radioactivity was recovered in the free amino acids. Fatty acids and sterols accounted for the remainder. Most of the fatty acid radioactivity resided in palmitate and stearate. The label of the polar lipid fraction was concentrated in choline phosphoglyceride (CPG) (65%).Over half of the CPG‐fatty acid radioactivity was present in the 2‐acyl group. Fatty acid biosynthesis occurred predominantly by a de novo mechanism although some elongation was also present. The incorporation of the precursor into amino acids increased rapidly after birth and reached stable levels at 14 days. Fatty acid labeling also increased with brain growth but the fatty acid‐amino acid ratio declined steadily from birth to 50 days. Synthesis of malonyl‐CoA is the rate‐limiting step in the biosynthesis of amino acids, fatty acids, and sterols from free malonic acid.

FATTY ACID BIOSYNTHESIS IN RAT SCIATIC NERVE UNDERGOING WALLERIAN DEGENERATION

ABSTRACT Fatty acid biosynthesis was determined in fragments of normal rat sciatic nerve and in nerve undergoing Wallerian degeneration. Fatty acids were biosynthesized from malonyl-coenzyme A and acetyl-coenzyme A in the presence of reduced nicotinamide adenine dinucleotide phosphate. The predominant mechanism was de-novo biosynthesis rather than elongation, and free palmitic acid was the reaction product. During Wallerian degeneration, the biosynthesis of fatty acids increased rapidly in the distal segment of the sectioned nerve when compared to the contralateral unoperated nerve. The enhancement reached a level of 350 percent at 25 days survival (contralateral nerve = 100 percent). Activity then declined and fell to control values after 50 days.