Search

SummaryMouse brains were extracted with a variety of solutions composed of inorganic salts, organic solvents, or mixtures of each. During these experiments, it was noted that a differential effect of certain salts and solvents on isozyme patterns could be demonstrated. These effects of isozyme systems [lactic dehydrogenase (LDH) and nonspecific esterase] could best be explained on the basis of lipid-enzyme complexes. Circumstantial evidence is provided for viewing LDH as a lipoprotein catalyst.

SummaryThe amount of cholesterol in brain tissue of male mice (5–10 weeks old) can be lowered by intraperitoneal injection of small amounts of Ritalin. Maximum effect occurs twenty-four hours after the initial dosage. Adjustment to normal levels occurs in the ensuing 48 and 72 hour periods. It is hypothesized that the stimulating effect of analeptics is related to brain sterol metabolism.

Twenty-four-hour urine was collected from normal and dystrophic mice and hamsters for catecholamine determinations. A new method of analysis was used whereby 3,4-dihydroxyphenylalanine (DOPA), dopamine (DA), norepinephrine (NE), and epinephrine (E) were measured simultaneously. The procedure is based on a combination of liquid-solid extraction, cation exchange chromatography, and controlled potential electrochemistry. The results of these experiments indicated that while DA levels were similar in both normal and pathological animal urine, DOPA levels decreased slightly in the dystrophic mouse but not the hamster, and NE and E levels in dystrophic groups were two and four times greater than normal in both species. The data supports the concept of biochemical alterations in tissue other than muscle. While not necessarily supportive to catecholamine abnormality as the primary cause of muscular dystrophy, the present data cast doubt that this disease is a primary muscle disease.

SummaryThe effect of a single injection of methylphenidate (Ritalin, 4 mg/kg) on precursor ([2-3H]acetate and [U-14C]glucose) incorporation into brain cholesterol was studied. The drug caused a steady decrease in the concentration of brain cholesterol during the 24-hr period examined. Incorporation studies during this time with [U-14C]glucose indicated higher than normal incorporation for all time periods studied. The most significant incorporation increases took place 2 and 4 hr after drug injection. Experiments using [2-3H]acetate as the sterol precursor gave incorporation values which tended (not significantly) to be lower than control values at 2 and 4 h. The values after 12 hr were less than normal, while the 24-hr group indicated an increase to or slightly higher than normal values.These data suggest that the pharmacological effect of methylphenidate may be due to lowering of brain cholesterol levels directly or on some more basic metabolic process leading to a decreased level of membrane sterols.

SummaryThree genetic groups of mice (DyDy, Dydy, and dydy) were studied at intervals of 6–14 wk. TCA intermediates were extracted, separated, and measured. Data indicate that mice with genetically induced muscular dystrophy (Strain 129) show alteration in several body tissues as well as in muscle itself. Of particular interest were changes measured in the brain of dystrophic mice. Support, but not proof, is given to the neurogenic concept of mouse muscular dystrophy.

The low molecular weight components of Elapidae venoms were investigated. The first separations of snake venom toxins by thin-layer chromatography (TLC) on silica gel were achieved. Sixteen Elapidae venoms were compared by starch gel electrophoresis and TLC. Almost three-quarters of the venom was dialyzable. The adsorption of toxins onto the larger protein molecules in snake venoms was demonstrated by measuring dialysis rates as well as showing that homogeneous electrophoretic bands yielded multiple spots by TLC. The feasibility of separating the low particle weight toxins of Elapidae venoms by silicic acid TLC and column chromatography was demonstrated. A low molecular weight toxic principle of Naja naja was isolated, partially characterized, and shown to be one of the most lethal materials isolated from biological sources (ld50 = 0·03 mg per kg).

Glucose-1 and glucose-6 labeled with tritium or carbon-14 were incorporated in vivo into brain and liver sterol. Differential incorporations of glucose labeled in both positions were compared. A higher than expected incorporation of C-1 from glucose was noted.

Clofibrate can both inhibit and stimulate the oxidation of succinate by mouse liver mitochondria, depending on whether the salt or the esterified form of the drug is used. Sodium clofibrate is a strong inhibitor whereas clofibrate ethyl ester is an active stimulator of succinate oxidation by mouse liver mitochondria.

The appearance of methyl esters of fatty acids in lipid extracts was studied. Experimental evidence indicates that these esters are both natural components of tissues as well as products of technical manipulation. Effect of temperature on the latter process was studied. The results of these experiments show that the post-mortem increase of fatty acid methyl esters could best be explained by postulating an enzymatic rather than a chemical process.

During the past decade, our laboratory has been involved in studying the biosynthesis of brain cholesterol under various conditions. As a result of these studies, we feel that the hypothesis of metabolic stability of cholesterol in adult life is untenable. Our data suggest that there are several compartments of sterol metabolism ranging from extremely fast to metabolically very slow. It is our hypothesis that (a) brain function is more nearly associated with fast turnover compartments than with metabolically slow ones; (b) these compartments can be altered by a variety of stress conditions.