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Biomedical subjects

D M Mock

Publications and source records attributed to D M Mock.

87 records · Page 5Linked to original sources
PubMed1985

Vitamin E deficiency associated with vision loss and bulbar weakness.

We describe a 14-year-old boy who was severely debilitated by the neurological syndrome associated with vitamin E deficiency secondary to chronic cholestatic liver disease. In addition to the usual neurological deficits described with this deficiency, the patient had severe bulbar weakness and vision loss which we attribute to the degree and duration of his vitamin E deficiency. Vitamin A deficiency may have contributed to his visual disturbance. Early recognition of vitamin E deficiency is important, as the neurological and visual disorders which result are treatable.

Adolescent↗
PubMed1985

Biotin deficiency complicating parenteral alimentation: diagnosis, metabolic repercussions, and treatment.

Biotin deficiency associated with total parenteral nutrition is an emerging clinical problem; criteria for diagnosis and dosage for treatment are unclear. We have diagnosed and successfully treated biotin deficiency in three patients. Each patient had alopecia totalis, hypotonia, and developmental delay. Two developed the characteristic scaly periorificial dermatitis; one had only an intermittent scaly rash on the cheeks and occipital scalp. Zinc and essential fatty acid supplements were adequate; serum zinc levels and triene/tetraene ratios confirmed sufficiency of these nutrients. None of the patients received biotin prior to diagnosis, and each had decreased excretion of urinary biotin and increased urinary excretion of organic acids diagnostic of deficiency of two biotin-dependent enzymes (methylcrotonyl-coenzyme A carboxylase and priopionyl-coenzyme A carboxylase). Only one patient had a plasma biotin concentration below the normal range (Ochromonicas danica assay). The rash, alopecia, and neurologic findings responded dramatically to biotin therapy (100 micrograms/day in all patients; an initial larger dose of 1 mg/day for 1 week plus 10 mg/day for 7 weeks in one patient), and did not recur. However, abnormal organic acid excretion persisted in one patient who did not receive the larger dose. We conclude that plasma biotin concentration does not reflect biotin status in all cases and speculate that the biotin supplement currently recommended for pediatric patients (20 micrograms/day) may not be adequate therapy for biotin deficiency and might not even be adequate to maintain normal biotin status during TPN.

Alopecia↗
PubMed1983

Chronic fructose intoxication after infancy in children with hereditary fructose intolerance. A cause of growth retardation.

In two unrelated boys, 5.3 and 3.8 years of age with hereditary fructose intolerance, apparently isolated growth retardation (-2.71 S.D. and -2.40 S.D.) occurred after infancy, even though acute symptomatic fructose intoxication was prevented by restriction of dietary fructose. When more stringent restriction of dietary fructose was instituted (approximately 40 mg per kilogram of body weight per day), growth velocity increased from the 25th to the 97th percentile in one child and from well below the 3d to above the 75th percentile in the other. When restriction of dietary fructose was experimentally relaxed (from 10 to 250 mg per kilogram per day), neither boy had symptoms, hypoglycemia, or evidence of hepatic or renal dysfunction, but both had sustained hyperuricemia and hyperuricosuria and increases in the plasma concentration and urinary excretion of magnesium. We conclude that in patients with hereditary fructose intolerance, clinically important chronic fructose intoxication can occur after infancy without causing symptoms of acute fructose intoxication and can be expressed as an apparently isolated, reversible retardation of somatic growth with a continuing disorder of adenine nucleotide metabolism, characterized in part by recurrently increased rates of degradation of adenine nucleotides.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1983

The proportion of mitochondrial isoenzyme of aspartate aminotransferase is not elevated in Reye's syndrome.

We reexamined a previously reported, highly specific increase in the relative proportion of the mitochondrial isoenzyme of aspartate aminotransferase (AST) in the serum of patients with Reye's Syndrome. Using ion exchange chromatography, we measured mitochondrial, cytosolic, and total AST in serum samples from (1) 10 patients early in the course of Reye's Syndrome; (2) nine controls with normal serum AST; and (3) seven controls with other diseases causing an increase in serum AST. The mitochondrial percentage (2.8 +/- 2.0%) in Reye's Syndrome was significantly lower (P less than 0.05) than that of both the normal control group (6.1 +/- 7.1%) and the group with increased AST (5.6 +/- 4.0%). We thus failed to confirm the previous report of a specific increase in the % of mitochondrial isoenzyme in Reye's Syndrome, and conclude that the % of mitochondrial isoenzyme is not likely to be a useful marker of (or predictor for progression to) Reye's Syndrome.

Adolescent↗
PubMed1979

Cytochrome P-450cam and putidaredoxin interaction during electron transfer.

Cytochrome P-450cam, the bacterial hemeprotein which catalyzes the 5-exo-hydroxylation of d-camphor, requires two electrons to activate molecular oxygen for this monooxygenase reaction. These two electrons are transferred to cytochrome P-450cam in two one-electron steps by the physiological reductant, putidaredoxin. The present study of the kinetics of reduction of cytochrome P-450cam by reduced putidaredoxin has shown that the reaction obeys first order kinetics with a rate constant of 33 s-1 at 25 degrees C with respect to: 1) the appearance of the carbon monoxide complex of Fe(II) cytochrome P-450cam; 2) the disappearance of the 645 nm absorbance band of high-spin Fe(III) cytochrome P-450cam; and 3) the disappearance of the g = 1.94 EPR signal of reduced putidaredoxin. This data was interpreted as indicative of the rapid formation of a bimolecular complex between reduced putidaredoxin Fe(III) cytochrome P-450cam. The existence of the complex was first shown indirectly by kinetic analysis and secondly directly by electron paramagnetic resonance spectroscopic analysis of samples which were freeze-quenched approximately 16 ms after mixing. The direct evidence for complex formation was the loss of the EPR signal of Fe(III) cytochrome P-450cam upon formation of the complex while the EPR signal of reduced putidaredoxin decays with the same kinetics as the appearance of Fe(II) cytochrome P-450. The mechanism of the loss of the EPR signal of cytochrome P-450 upon formation of the complex is not apparent at this time but may involve a conformational change of cytochrome P-450cam following complex formation.

Anaerobiosis↗