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F A Raymond

Publications and source records attributed to F A Raymond.

9 recordsLinked to original sources
PubMed1979

Catechol-O-methyltransferase: thermolabile enzyme in erythrocytes of subjects homozygous for allele for low activity.

Low catechol-O-methyltransferase (COMT) activity (less than 8 units per milliliter) in the human erythrocyte is inherited as an autosomal recessive trait (COMTL). The average half-life of COMT in erythrocyte lysates incubated at 48 degrees C was significantly shorter in lysates from three subjects with low enzyme activity than in lysates from three subjects with high enzyme activity (12.5 +/- 0.9 minutes compared with 21.2 +/- 1.4 minutes, P less than .01). When the ratios of COMT activities in lysates heated at 48 degrees C for 15 minutes to enzyme activities in unheated samples were used as a measure of enzyme thermostability in blood samples from 316 randomly selected subjects, the ratios were significantly less for subjects with low enzyme activity than for subjects with higher enzyme activity. The presense of thermolabile COMT in blood of individuals homozygous for COMTL raises the possibility that the locus COMT may represent the structural gene for the human enzyme.

Catechol O-Methyltransferase↗
PubMed1978

Human erythrocyte thiopurine methyltransferase: radiochemical microassay and biochemical properties.

A radiochemical micromethod for the determination of thiopurine methyltransferase (TPMT) activity in human red blood cells (RBC) is described. Both 6-mercaptopurine and 6-thioguanine were substrates for the TPMT activity in the human RBC. Apparent Michaelis-Menten (KM) values for 6-mercaptopurine and 6-thioguanine were 3.2 X 10(-4) M and 2.0 X 10(-4) M, respectively. The apparent KM value for S-adenosyl-L-methionine, a co-substrate for the reaction, was 1.7 X 10(-6) M. The pH optimum for the reaction was approximately 7.5. Blood samples from 73 randomly selected adult subjects had a mean activity of 10.2 +/- 2.4 (mean +/- S.D.) units/ml packed red blood cells. The range of activities was from 4.6 to 14.2 units/ml. The results of experiments in which partially purified human kidney TPMT was added to RBC lysates and of experiments in which "low" and "high" activity lysates were mixed gave no indication that individual variations in RBC TPMT activity were due to endogenous inhibitors or activators of the enzyme.

Erythrocytes↗
PubMed1977

Inheritance of low erythrocyte catechol-o-methyltransferase activity in man.

Catechol-O-methyltransferase activity was measured in blood obtained from 373 randomly selected subjects aged 16-18, 262 consecutive adult blood donors, and 201 first-degree relatives of subjects with RBC COMT activity of less than 8 U. The distribution of RBC COMT activity in a randoly selected populations was apparently bimodal with a nadir at approximately 8 U. Of a randomly selected population, 23% had low RBC COMT activity (less than 8 U), Because of previous reports of a significant sibling-sibling correlation of RBC COMT activity and because of the presence of a subgroup of subjects with low enzyme activity, RBC COMT activity was measured in blood from first-degree relatives of probands with low erythrocyte enzyme activity in 48 families. The results of segregation analyses of the data were compatible with autosomal recessive inheritence of an allele for low RBC COMT activity. RBC COMT in blood samples from siblings of probands inthese families also showed an apparent biomodal distribution.

Adolescent↗
PubMed1975

Microassay of human erythrocyte catechol-O-methyltransferase: removal of inhibitory calcium ion with chelating resin.

A radiochemical micromethod for the determination of catechol-O-methyltransferase (COMT) activity in human red blood cells (RBC) is described. The method avoids artifacts that occur with other assay procedures. Erythrocyte lysates are exposed to a particulate chelating agent (Chelex-100) to remove endogenous divalent cations that inhibit COMT. 3,4-Dihydroxybenzoic acid rather than norepinephrine is used as a substrate to increase both the sensitivity and the reproducibility of the procedure. An internal standard of purified rat liver COMT is added to lysates to detect possible variations in endogenous activators or inhibitors of the enzyme. Blood samples from 373 unselected subjects age 16-18 were assayed for RBC COMT activity with this assay procedure. The COMT activity in these blood samples ranged from 3-25 units with a mean activity of 11.3 plus or minus 4.2 (mean plus or minus S.D.).

Adolescent↗
PubMed1975

Inheritance of very low serum dopamine-beta-hydroxylase activity.

Serum dopamine-beta-hydroxylas (DBH) activity was measured in blood samples obtained from 841 children ages 6-12, 277 adults subjects, and 114 relatives of children with serum DBH activity of less than 50 units. Approximately 4% of the children and 3% of the adult subjects tested had very low sweum DBH activity (50 units or less). Because these subjects appeared to make up a separate subgroup within the population and because of a striking familial aggregation of subjects with very low enzyme activity, serum DBH activity was measured in blood obtained from members of 22 families of probands with very low serum enzyme activity. The results of sibship and pedigree analyses of the data were compatible with autosomal recessive inheritance of very low serum DBH activity. Unaffected parents of probands had serum DBH activity intermediate between that found in affected individuals and in control population. No significant correlation of serum DBH activity with either systolic or diastolic blood pressure was found in this randomly selected population of children.

Adult↗
PubMed1973

Serum dopamine-beta-hydroxylase activity: sibling-sibling correlation.

Dopamine-beta-hydroxylase activity is released into the blood with catecholamines from the adrenal medulla and sympathetic nerves. This enzyme activity has been measured in the blood of 317 normal children and 227 normal adults. A significant sibling-sibling correlation of serum dopamine-beta-hydroxylase values was found in the 94 sibling pairs tested. Frequency distributions of serum enzyme values in both children and adults suggest the existence of two populations with regard to serum activity of this enzyme.

Adult↗