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Biomedical subjects

A K Percy

Publications and source records attributed to A K Percy.

At least 91 records · Page 5Linked to original sources
PubMed1986

Acute management of seizures in children.

Seizures in children are not uncommon, and more than half of these seizures have no known cause. This discussion and review of seizures covers three types of presentations: the child who presents following an initial seizure; the child who presents with serial seizures or continuous seizures (status epilepticus); and the child who presents following a febrile seizure. The nurse practitioner can play a critical role in the assessment and management of children presenting with each of these three types of seizures. A review of drug management of childhood seizures and a comprehensive review of the critical areas to cover in counseling the child, family and community are included.

Anticonvulsants↗
PubMed1985

Reduction of biogenic amine levels in the Rett syndrome.

The Rett syndrome is a progressive disorder in female patients that is characterized by autistic behavior, dementia, ataxia, loss of purposeful use of the hands, and seizures. The results of laboratory investigations are usually normal, with the exception of electroencephalography. In an attempt to understand the pathogenesis of this syndrome, we assayed biogenic amine metabolites in the cerebrospinal fluid of six patients, 2 to 15 years of age. 3-Methoxy-4-hydroxyphenylethylene glycol (MHPG, a metabolite of norepinephrine), homovanillic acid (a metabolite of dopamine), and 5-hydroxyindoleacetic acid (5-HIAA, a metabolite of serotonin) were quantitated by a method involving gas chromatography and mass spectrometry. Levels of MHPG and homovanillic acid were significantly reduced in all the patients as compared with those in controls of similar age (P = 0.01 and 0.008, respectively). The reduction in the level of 5-HIAA was not significantly different from that in the controls (P = 0.15). These findings suggest an underlying disorder of biogenic amines in the Rett syndrome and may provide new insight into its pathogenesis.

Adolescent↗
PubMed1985

Rett syndrome: initial experience with an emerging clinical entity.

Five female patients have been presented with the typical clinical appearance of the Rett syndrome. A systematic evaluation of a variety of anatomic, physiologic and biochemical parameters has revealed two potential leads regarding the pathogenesis of this disorder. First, a reduction in the levels of neurotransmitter metabolites in cerebrospinal fluid was noted in each patient, a dopamine metabolite, homovanillic acid, being reduced to the greatest extent. Second, a sural nerve biopsy from one patient examined by electron microscopy revealed intact myelin with an axonopathy. Confirmation of these studies is necessary. This initial description of patients from the United States is quite consistent with previous reports by Professor Rett and Professor Hagberg and colleagues.

Adolescent↗
PubMed1984

Phosphoglyceride biosynthesis by brain microsomes: centrophenoxine, SaH-42-348, and DH-990 inhibit phospholipid N-methylation.

The effects of centrophenoxine, SaH-42-348, and DH-990 on several enzymes involved in aminophospholipid biosynthesis in brain have been examined in vitro. Relatively high concentrations of centrophenoxine were required to achieve 50% inhibition of the microsomal enzymes CDP-ethanolamine:1,2-diacylglycerol ethanolaminephosphotransferase (EPT), CDP-choline:1,2-diacylglycerol cholinephosphotransferase (CPT), phosphatidyl-N-methylethanolamine N-methyltransferase (PME-NMT), and phosphatidyl-N,N-dimethylethanolamine N-methyltransferase (PDE-NMT). Intermediate concentrations of SaH-42-348 inhibited CPT (IC50 = 2.0 mM), EPT (IC50 = 1.9 mM), PME-NMT (IC50 = 0.19 mM), and PDE-NMT (IC50 = 0.17 mM). Of the three drugs tested, DH-990 was the most potent inhibitor of the phospholipid-synthesizing enzymes. Phosphatidylserine decarboxylase, a mitochondrial inner-membrane enzyme [A. K. Percy, J. F. Moore, M. A. Carson, and C. J. Waechter (1983) Arch. Biochem. Biophys. 223, 484-494], was virtually unaffected by the three drugs added at millimolar concentrations. Kinetic analyses indicated that the inhibitory action of DH-990 on the brain enzymes was noncompetitive with respect to all substrates. The relatively high sensitivity of CPT (IC50 = 0.6 mM), EPT (IC50 = 2.2 mM), PME-NMT (IC50 = 2.5 microM), and PDE-NMT (IC50 = 2.5 microM) to inhibition by DH-990 in brain microsomes suggests that this compound may be useful for cellular studies on the possible relationships between phospholipid metabolism and neurobiological functions.

Animals↗
PubMed1984

Control of phosphatidylethanolamine metabolism in yeast: diacylglycerol ethanolaminephosphotransferase and diacylglycerol cholinephosphotransferase are separate enzymes.

Membrane preparations from Saccharomyces cerevisiae catalyze the transfer of phosphoethanolamine and phosphocholine from the cytidine dinucleotide derivatives to endogenous and exogenous 1,2-diacylglycerols. Utilizing CDP-[14C]ethanolamine and CDP-[14C]choline as isotopic substrates, diacylglycerol ethanolaminephosphotransferase (EPT) and diacylglycerol cholinephosphotransferase (CPT) have been characterized in vitro. Both enzymes (i) require Mn2+; (ii) are stimulated by exogenous 1,2-diacylglycerols; and (iii) are inhibited by p-hydroxymercuribenzoate and CMP. Yeast EPT and CPT can be clearly distinguished on the basis of their different (i) pH optima; (ii) thermal sensitivities at 50 degrees C; (iii) concentration-dependent inhibition by CMP; and (iv) sensitivities to the hypolipidemic drug, DH-990. Reversibility experiments demonstrate that CDP-ethanolamine can be resynthesized by enzymatic reactions involving CMP and phosphatidylethanolamine (PE) formed from the cytidine dinucleotide derivative or by the decarboxylation of phosphatidylserine (PS). Similarly, CDP-choline can be reformed by the reaction of CMP with PC synthesized from CDP-choline or by the sequential N-methylation of PE. A double-isotope experiment provides evidence that PE molecules synthesized via CDP-ethanolamine or by the decarboxylation of PS are converted to phosphatidylcholine (PC) by the methylation pathway at similar, if not identical, rates. The N-methylation of the metabolically specific pool of PE, synthesized from CDP-ethanolamine, is drastically reduced in membranes prepared from choline-grown cells. Neither EPT nor CPT appear to be induced by the addition of ethanolamine or choline, respectively, to the growth medium. However, the addition of 10 mM choline to the growth medium results in a 46% reduction in EPT activity. This change in EPT activity may be a regulatory response to lower rates of PE N-methylation in choline-grown cells.

Catalysis↗
PubMed1984

Necrotizing fasciitis of the parapharyngeal space with carotid artery occlusion and acute hemiplegia.

Necrotizing fasciitis is characterized by necrosis with extension over fascial planes and mixed aerobic-anaerobic etiologies. Necrotizing fasciitis is uncommon in children and seldom involves the head and neck area. An infant who developed necrotizing fasciitis involving the parapharyngeal space is described. Chronic dental pathology was probably the initial focus of infection. The patient had a left hemiparesis due to a right middle cerebral artery infarct. Carotid angiography demonstrated complete occlusion of the right internal carotid artery, probably secondary to inflammatory arteritis or direct compression along its course through the parapharyngeal space. Mixed aerobic-anaerobic etiologies predominate in infections of the potential spaces of the head and neck as was demonstrated in this patient. The patient recovered, but had neurologic sequelae. Prompt and aggressive therapy is necessary in patients with necrotizing fasciitis syndromes in order to avoid such severe complications.

Acute Disease↗
PubMed1983

Characterization of brain phosphatidylserine decarboxylase: localization in the mitochondrial inner membrane.

A membranous fraction from calf brain, sedimenting at 10,000g, catalyzes the decarboxylation of exogenous phosphatidyl[14C]serine presented in an aqueous dispersion in detergent. The product formed by the enzymatic decarboxylation reaction is chemically and chromatographically identical to phosphatidyl[14C]ethanolamine. The calf brain decarboxylase activity: (1) did not require divalent cations; (2) was optimally active at neutral pH; (3) exhibited maximal activity in the presence of 0.1% Cutscum or sodium taurocholate; (4) was inhibited by hydroxylamine or p-hydroxymercuribenzoate; and (5) has an apparent Km = 2.4 mM for the phospholipid substrate. When this fraction was further separated by metrizamide density centrifugation, 90% of the phosphatidylserine decarboxylase activity was associated with the mitochondria. Resolution of the inner and outer membranes of the mitochondria revealed that greater than 99% of the decarboxylase activity was bound to the inner membrane. In contrast to this result, diacylglycerol ethanolaminephosphotransferase, another enzyme responsible for phosphatidylethanolamine biosynthesis in brain, was greatly enriched in the microsomal fraction. The highest level of phospholipid N-methyltransferase activity was also localized in the microsomal fraction. Thus, phosphatidylethanolamine formation via cytidine diphosphate ethanolamine in brain occurs at a membrane site where it should be available for the biosynthesis of phosphatidylcholine by stepwise methylation. In order for phosphatidylethanolamine formed by the decarboxylation reaction to be available for N-methylation, translocation from mitochondria to the microsomal site would be required.

Animals↗
PubMed1982

Properties of particulate and detergent-solubilized phospholipid N-methyltransferase activity from calf brain.

Calf brain membranes catalyze the enzymatic transfer of [CH3-3H]methyl groups from S-adenosyl-L-[CH3-3H]methionine into endogenous phosphatidyl-N-methylethanolamine (PME), phosphatidyl-N,N-dimethylethanolamine (PDE), and phosphatidylcholine (PC). Phospholipid N-methylation can be stimulated by the addition of exogenous PME or PDE, added in aqueous dispersions with sodium taurocholate. When membranes are incubated in the presence of exogenous PME, [CH3-3H]PDE represents 86% of the labeled phospholipid products. When exogenous PME is replaced by PDE, 91% of the label is incorporated into PC. Thus, under these in vitro conditions it is possible to assay PME- and PDE-N-methyltransferase activity separately. The calf brain phospholipid N-methyltransferase activity has also been solubilized by treating the membranes ultrasonically in the presence of Triton X-100 and 10 mM monothioglycerol. When the detergent extracts are incubated in the presence of exogenous PME, [CH3-3H]PDE represents 86% of the enzymatically labeled products. In the presence of exogenous PDE, more than 97% of the label is incorporated into PC. Optimal conditions for the membrane-bound and detergent-solubilized PME- and PDE-N-methyltransferase activity have been established. These conditions have been used as a basis for testing the hypothesis that the conversion of PME to PC is catalyzed by a single enzyme in calf brain. In these studies, PME- and PDE-N-methyltransferase activities have been found to be similar, if not identical, with respect to: (1) extractability with Triton X-100; (2) pH optimum; (3) response to divalent cations; (4) apparent Km for S-adenosyl-L-methionine and K1 for S-adenosyl-L-homocysteine, (5) sensitivity to N-ethylmaleimide; and (6) thermal inactivation at 55 degrees. Overall, these results are consistent with the conclusion that in calf brain, PME and PDE are methylated by the same enzyme or by two phospholipid N-methyltransferases having very similar properties.

Animals↗
PubMed1982

The computed tomographic appearance of cerebral cysticercosis in adults and children.

The computed tomographic (CT) scans of 45 patients (30 adults, 15 children) with cerebral cysticercosis were reviewed. These patients had undergone complete diagnostic evaluations including skin tests, laboratory tests, plain skull radiography, radionuclide brain scanning, CT, and cerebral angiography. All of these tests were unrewarding except CT and the indirect hemagglutination test on the serum. A classification of cerebral cysticercosis based on the location of the lesions in the brain and the CT appearance was developed. Cerebral cysticercosis can be diagnosed by CT findings when there is also a history of seizures and of the patient having lived in an area where the disease is endemic.

Adolescent↗
PubMed1981

The parenchymal form of cerebral cysticercosis.

22 cases of the parenchymal form of cerebral cysticercosis are discussed. The parenchymal form presents a variance of appearance on computer tomography (CT). The five most common CT findings are described. They are classified as (1) completely calcified lesions, (2) cystic lesions with ring enhancement (with or without calcification), (3) nonenhancing cystic lesions; (4) homogeneously enhancing lesions, and (5) mixed parenchymal lesions.

Adolescent↗
PubMed1980

Acute isoniazid poisoning in childhood.

Acute isoniazid poisoning is uncommon in children. Only 27 cases, to our knowledge, have been reported in the literature. Often, the first observation is of uncontrollable convulsions. The metabolic alterations are often striking and the treatment has mainly been supportive, with the judicious use of pyridoxine hydrochloride in those cases in which a history of ingestion of isoniazid is obtained. The response to the administration of pyridoxine has been difficult to evaluate.

Adolescent↗
PubMed1980

Studies on choline ad ethanolamine phosphoglyceride biosynthesis in developing rabbit brain.

Activities of cholinephosphotransferase (EC 2.7.8.2) and ethanolaminephosphotransferase (EC 2.7.8.1) were evaluated in microsomal preparations derived from rabbit cerebrum. Animals ranged in age from nineteen days' gestation through two months of postnatal development. Under optimal conditions the properties of these transferases in rabbit brain were remarkably similar relative to pH, divalent cation requirements, and apparent-Km values for the CDP-intermediates and the lipid acceptor, respectively. Cholinephosphotransferase-specific activity exhibited a dramatic rise during the last 15%-20% of fetal life and a second rise to a maximum near the 15th postnatal day. Ethanolaminephosphotransferase-specific activity exhibited a similar, but less striking age-related increase during the same period. Growth of rabbit cerebrum as determined by weight, increased 30-fold during this same period (24 days gestation to the 19th postnatal day). Specific activities of these transferase were similar in brain preparations from mid-fetal and early adult rabbits. The maximum specific activity of cholinephosphotransferase exceeded that of ethanolaminephosphotransferase by 3-4-fold. Age-related changes in the specific activities of these transferases appear to correlate with the developmental pattern of morphological and compositional events occurring in rabbit cerebrum during the last third of gestation and the first three weeks of postnatal life.

Age Factors↗
PubMed1980

Cerebral cysticercosis.

In this country, cerebral cysticercosis is not commonly implicated as the etiology of an otherwise uncomplicated seizure disorder occurring during childhood. Nine children with neurologic symptomatology and radiographic (computed tomography) evidence consistent with cerebral cysticercosis have been evaluated. Each patient was born and resided for some period (1 1/2 to 10 years) in an endemic area. Principal symptomatology consisted of a generalized seizure disorder. EEGs were normal in five patients and nonspecific in two. Serologic studies on serum and CSF were negative in 8/9 patients including the single patient requiring surgical intervention for excision of a cysticercal cyst. Cerebral nuclide scanning was not helpful and skull radiography was used to diagnose intracerebral calcifications in six patients. Computed tomography revealed multiple calcifications in six patients and a solitary lesion in one. Five patients had enhancing cystic lesions including three of those with diffuse calcifications. Since the natural history of cerebral cysticercosis presenting in this fashion is benign, symptomatic treatment is often sufficient. Anticonvulsants generally provide adequate seizure control. In one patient, cyst removal was necessary to achieve seizure control. On the basis of this experience, conclusions are (1) that the incidence of cerebral cysticercosis in exposed children is higher than commonly appreciated, and (2) that computed tomography may assist in the establishment of the diagnosis.

Adolescent↗
PubMed1977

Metachromatic leukodystrophy: comparison of early-and late-onset forms.

Comparative study of peripheral nerve biopsies and cultured skin fibroblasts from patients with late infantile and early adult-onset forms of metachromatic leukodystrophy revealed similar pathologic changes in the early stages of nerve degeneration. However, the peripheral nerves in the adult-onset cases eventually reached a more chronically demyelinated fibrotic state than did nerves in the infantile cases. Cultured skin fibroblasts from the adult-onset patients, although clearly abnormal, were able to catabolize sulfatide significantly more effectively than the cultured skin fibroblasts from late infantile patients.

Adolescent↗