Yoshiko Nakagomi

Disulfide bridges in extracellular domains of angiotensin II receptor type IA

Angiotensin II receptor type IA (AT1A) has a cysteine (Cys) residue in each of four extracellular domains, and these Cys residues are believed to form two disulfide bridges. However, the question as to which pairs of Cys residues form disulfide bridges have not been experimentally determined. We constructed four mutants of rat AT1A, in which extracellular Cys residues were individually replaced by glycine (mutant C-1, C-2, C-3 and C-4). Further, we constructed two double mutants, in which two extracellular Cys residues were simultaneously substituted for by glycine. The binding affinity for angiotensin II in a double mutant C-1 + 4 (Cys18,274Gly) was similar to that in individually substituted mutants (C-1, C-2, C-3 and C-4) whereas the ligand binding of a double mutant C-2 + 4 (Cys101,274Gly) was completely abolished. The bindings of the non-peptide AT1A antagonist [125I]EXP-985 to mutants C-1, C-4 and C-1 + 4 were only slightly reduced whereas in mutant C-2, C-3 and C-2 + 4 the specific binding for [125I]EXP-985 was completely abolished. These results suggest that disulfide bridges in AT1A are formed between Cys18 and Cys274, and between Cys101 and Cys180, and the latter disulfide bond is essential for the binding of the non-peptidic antagonists [125I]EXP-985 or losartan.

A Case of Benign Infantile Epilepsy with Complex Partial Seizures: Ictal EEG and Postictal Single‐Photon Emission‐Computed Tomography Study.

Autism is strongly associated with epilepsy with peak periods of seizure onset in childhood and puberty. There is a high incidence of EEG paroxysmal abnormalities in autism, but little is known about the nature of the paroxysm. We examined the paroxysmal abnormality in EEGs of autistic subjects to investigate brain dysfunction associated with autism. The subjects were 158 (1 19 male, 39 female) autistic patients whose EEGs had been regularly obtained up to at least age 15. The initial EEG was obtained at a mean age was I 1 years and the most recent EEG at 18 years. For comparison, we selected 75 nonautistic mentally retarded individuals (41 men, 34 women) whose EEGs had been recorded for 2 15 years. The initial EEG was obtained in these patients at a mean age was 15 years and the most recent EEG at age 19 years. Of the 158 subjects, 96 (60.8%) showed paroxysmal EEG abnormalities at least once during followup. Of the 75 mentally retarded controls, 37 (49.3%) showed paroxysmal abnormalities. To assess the change with age, all EEGs (693 of autistic subjects, 333 of mentally retarded controls) were divided into three age categories (age <9 years, 10-14 years, and > I 5 years). The paroxysms were divided into five groups according to the dominant area (F group: Fp1,2, F3,4, Fz, and Cz; CP group:,C3,4, and P3,4; 0 group: 01,2; T group: F7,8 and T3,4,5,6; and D group: diffuse). In the mentally retarded control group, there were no significant differences among the five groups divided according to dominant area, and no significant changes were detected during follow-up. On the other hand, in the autistic subjects, the number of paroxysms in the F group increased with subject age. We named these paroxysms in the F group of the auti-stic subjects “paroxysm at F.” In 62 of 158 autistic subjects, epilepsy developed. In 40 cases, epilepsy onset was at age 210 years. In these cases, the time of epilepsy onset was concordant with the time of emergence of paroxysm at F. However, there were subjects without epilepsy who showed paroxysm at F . Paroxysm at F was a common abnormality in autism regardless of intellectual level, sex, whether the subject had a history of setback phenomenon, or had been diagnosed as having another disease or syndrome (such as West syndrome, neurofibromatosis, fragile X syndrome, or progressive muscular dystrophy). Paroxysm at F might be a neurophysiologic finding characteristic of autism. Paroxysm at F has not been detected in infants and generally emerges before or during puberty. In contrast, symptoms of autism emerge in infancy, and brain dysfunction generally does exist before the appearance of paroxysm at F. Because the pathology of autism is strongly related to brain maturation, paroxysm at F is speculated to emerge before or during puberty.

Plasma Active and Inactive Renin Concentrations in Children

Plasma active and inactive renin concentrations (PARC and PIRC) were measured by immunoradiometric assay. Age-related changes in PARC, PIRC and the ratio of PARC/PIRC were studied in 78 normal children, age 1 month to 15 years. The effects of upright position for 15 min were also investigated in 7 postmenarcheal girls. PARC and PIRC in infants were significantly higher than in older children and their ratio of PARC/PIRC was significantly lower than in prepubertal children. During puberty, PARC, PIRC and their ratio were higher in premenarcheal girls than in postmenarcheal girls. In the upright position, PARC, PIRC and the ratio were increased significantly. These finding suggest that: (1) the production of inactive renin is increased but the activation of renin may be lowered in infants; (2) the activation of renin is affected by the menstrual cycle, and (3) the production and activation of renin are increased during short term standing.

Effect of Cyproterone Acetate on Active and Inactive Renin Secretion in Patients with Precocious Puberty and Genetic Short Stature

To evaluate the effect of cyproterone acetate (CA) on the renin-angiotensin-aldosterone axis, we measured the plasma active, inactive and total renin concentrations (PARC, PIRC and PTRC) during and after CA treatment in patients with precocious puberty and genetic short stature. CA was administered at a daily dose of 150-170 mg/m2 in all subjects. PARC and PTRC were measured by immunoradiometric assays. During CA treatment, PARC, PIRC, PTRC and the PARC/PTRC ratio were significantly decreased. The plasma renin activity, measured by enzymatic assay, and the plasma aldosterone concentration were also decreased. After CA discontinuation, all of these were increased immediately along normal ranges. PARC closely correlated with plasma renin activity. These results suggest that CA produces mineralocorticoid action and suppresses the production and activation of renin.