Non-Mendelian transmission in dentatorubral-pallidoluysian atrophy and Machado-Joseph disease: the mutant allele is preferentially transmitted in male meiosis

Autosomal dominant dentatorubral-pallidoluysian atrophy (DRPLA) and Machado-Joseph disease (MJD) are neurodegenerative disorders caused by CAG trinucleotide repeat expansions. An inverse correlation of age at onset with the length of the expanded CAG trinucleotide repeats has been demonstrated, and the intergenerational instability of the length of the CAG trinucleotide repeats, which is more prominent in paternal than in maternal transmissions, has been shown to underlie the basic mechanisms of anticipation in DRPLA and MJD. Our previous observations on DRPLA and MJD pedigrees, as well as a review of the literature, have suggested that the numbers of affected offspring exceed those of unaffected offspring, which is difficult to explain by the Mendelian principle of random segregation of alleles. In the present study, we analyzed the segregation patterns in 211 transmissions in 24 DRPLA pedigrees and 80 transmissions in 7 MJD pedigrees, with the diagnoses confirmed by molecular testing. Significant distortions in favor of transmission of the mutant alleles were found in male meiosis, where the mutant alleles were transmitted to 62% of all offspring in DRPLA (chi2 = 7.69; P<.01) and 73% in MJD (chi2 = 6.82; P<.01). The results were consistent with meiotic drive in DRPLA and MJD. Since more prominent meiotic instability of the length of the CAG trinucleotide repeats is observed in male meiosis than in female meiosis and meiotic drive is observed only in male meiosis, these results raise the possibility that a common molecular mechanism underlies the meiotic drive and the meiotic instability in male meiosis.

[Intraocular lens power calculation for short eye]

The accuracy of intraocular lens power calculation formulas for short eyes was examined. We examined 217 eyes with an axial length of shorter than 22.5 mm, with postoperative visual acuity of 0. 5 or more, and postoperative astigmatism of less than +/- 2D. Five formulas were tested for accuracy in prediction for postoperative refraction, the S-SRK, the SRK, the SRK II, the SRK/T, and the Binkhorst formulas. The best results were produced by the S-SRK formula which predicted 74% of the cases within +/- 1D error, if the axial length was shorter than 22 mm. The A-constant was also examined to study the effect of postoperative refraction. The A-constant takes into consideration the depth of the anterior chamber lens, so that the differences in depth would be influenced for short eyes rather than regular eyes in prediction. However, there was no significant difference among the different A-constant groups.

[A study of the intraorbital blood flow using ultrasound color Doppler mapping images in optic canal fracture cases]

Ultrasound color Doppler flow mapping image (CFMI) equipment, SSA-270A (Toshiba Co) was used to measure the blood flow velocity of the ophthalmic artery (OA) and the central retinal artery (CA) in eyes with optic canal fracture. The maximal blood flow velocity (V max), the minimal blood flow velocity (V min), the mean blood flow velocity (V mean), and the resistance index (RI) before and after transethmoidal decompression of the optic nerve were compared. The examination was conducted on 13 patients. There was no difference in blood flow velocity in the CA after the operation. Pre-operative V max and RI of the OA in the damaged eyes were lower than in normal eyes, but they increased the day after the operation. We measured the intraorbital blood flow velocity by CFMI because ultrasound does not penetrate bone. Since the peripheral artery from the optic foramen did not change after the operation, we concluded that the peripheral blood flow of OA had been quantitatively improved by the trans-ethmoidal decompression of the optic nerve.

[Central ocular hypotensive effect of noradrenaline]

We investigated the effects of topical and central administration of noradrenaline (NA) on the intraocular pressure (IOP) in pigmented rabbits. Unilateral instillation of NA (200 micrograms) produced no significant change in IOP. On the other hand, intracerebroventricular (ICV) administration of NA (0.01-1 micrograms) decreased IOP in both eyes in a dose-related fashion. The ocular hypotensive effect of NA was diminished by sympathectomy of the superior cervical sympathetic nerve or by ICV pretreatment with yohimbine hydrochloride 1-10 micrograms). These results suggest that the hypotensive effects of contrally administered NA might be mediated by alpha 2-adrenoceptor stimulation in the central nervous system.

[An intraocular lens power calculation for high myopia]

The accuracy of intraocular lens power calculation formulas for the axial high myopia were examined, especially regarding the point of the predictive refraction. We examined 170 eyes with axial lengths of 27 mm or longer, with postoperative visual acuity of 0.5 or more, and postoperative astigmatism of less than +/- 2D. Five formulas were tested for accuracy in predicting postoperative refraction. They were the L-SRK, SRK, SRK II, SRK/T, and Binkhorst formulas. The SRK formula tended to predict less myopia than the actual postoperative refraction. The SRK II and Binkhorst formulas predicted more myopia than the actual postoperative refraction. The best results were produced by the L-SRK and SRK/T formulas. The accuracy of the L-SRK formula predictions were measured for each of the four myopic levels. The same was done for the SRK/T formula. For both formulas, there was no statistically significant difference in accuracy of prediction for the four myopic categories. The two formulas are considered to be useful for high myopic cases.

Dentatorubral-pallidoluysian atrophy: clinical features are closely related to unstable expansions of trinucleotide (CAG) repeat

Dentatorubral-pallidoluysian atrophy is an autosomal dominant neurodegenerative disease characterized by various combinations of ataxia, choreoathetosis, myoclonus, epilepsy, and dementia as well as a wide range of ages at onset. A specific unstable trinucleotide repeat expansion in a gene on the short arm of chromosome 12 was recently identified as the pathogenic mutation for this disease. We investigated how the degree of expansion of the CAG repeat effects the clinical manifestations of dentatorubral-pallidoluysian atrophy. The size of the expanded alleles was well correlated with the age at onset (r = -0.696, p < 0.001). Patients with the progressive myoclonus epilepsy phenotype had larger expansions (62-79 repeats) and an earlier age at onset (onset before age 21). Furthermore, most of the patients with the progressive myoclonus epilepsy phenotype inherited their expanded alleles from their affected fathers. On the other hand, patients with the non-progressive myoclonus epilepsy phenotype showed smaller expansions (54-67 repeats) and a later age at onset (onset at or after age 21). Detailed analyses of clinical features demonstrated that ataxia, involuntary movement of either myoclonus or choreoathetosis, and intellectual decline are cardinal features of dentatorubral-pallidoluysian atrophy, with myoclonus and epilepsy being observed more frequently in patients with an earlier age at onset. Thus the wide variation in clinical manifestations of dentatorubral-pallidoluysian atrophy can now be clearly explained based on the degree of CAG repeat expansion, which strongly indicates that the expanded alleles are intimately involved in the neuronal degeneration in dentatofugal and pallidofugal systems.

[Distribution of free amino acids and related compounds in ocular fluids of rat--I. Aging and inherited cataracts]

The distribution of free amino acids and their related compounds has been determined in the aqueous humors of Wistar strain and Ihara cataract f-strain (ICR) aging rats. Taurine was the most abundant amino acid in aqueous humors except in ICR rats of 16 and 70 weeks. It was supposed that the increase of serine and glutamine, and the decrease of aspartate, proline and glycine in aqueous humors were related to aging. There were interesting changes in amino acids related to opacity of lens, concentration of taurine was lower than that of Wistar rats in ICR rats of 4, 16, and 70 weeks, alanine and citrulline increased in Wistar rats and decreased in ICR rats, and histidine increased in ICR rats with aging. The changes in free amino acids in aqueous humors were the greatest in ICR rats, and these data will provide useful clues for the formation of cataract and the transportation of amino acids.

[Application of microdialysis for pharmacokinetic study in rabbit anterior chamber]

We evaluated a microdialysis technique for analyzing the pharmacokinetics of instilled or orally administered ofloxacin in the anterior chamber of pigmented rabbits. A microdialysis probe was inserted into the anterior chamber and was perfused (2 microliters/min) with Ringer solution using a microinjection pump. Two hours later, 20 microliters of 0.15 and 0.3% ofloxacin was instilled into an eye, or 20 mg/kg of the drug was administered into the stomach through an intubated catheter. Dialysate was then collected every 15 or 20 min for 6 (instillation) or 8 (oral administration) hours. Ofloxacin concentration in dialysates was determined with a HPLC-spectrofluorometry system. Ofloxacin levels in dialysates increased after the instillation in a dose-related manner, reached a maximum at 30 and 45 min, and then decreased gradually with t1/2 of 136 and 114 min after the 0.15% and 0.3% instillation, respectively. After oral administration, ofloxacin levels in dialysates reached a maximum at 120 min and decreased with t1/2 of 175 min. These data suggest the usefulness of microdialysis for pharmacokinetic studies in the anterior chamber, since continuous and stable data can be obtained from each animal.

Dentatorubral-pallidoluysian atrophy (DRPLA): close correlation of CAG repeat expansions with the wide spectrum of clinical presentations and prominent anticipation

Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare autosomal dominant neurodegenerative disease characterized by various combinations of ataxia, choreoathetosis, myoclonus, epilepsy and dementia as well as various ages of onset. We have identified a specific unstable trinucleotide repeat expansion in a gene on the short arm of chromosome 12 as the pathogenic mutation for DRPLA. We investigated how the degree of the expansion of the CAG repeat affects the clinical manifestations of DRPLA. The sizes of the expanded alleles were well correlated with the ages of onset (r = -0.6955, P < 0.001). Patients with progressive myoclonus epilepsy (PME) phenotype had larger expansions (62-79 repeats) and earlier ages of onset (onset before age 20). Furthermore, most of the patients with PME phenotype inherited their expanded alleles from their affected fathers. On the other hand, patients with non-PME phenotype showed later ages of onset (onset after age 20) and smaller expansions (54-67 repeats). When ages of onset of each clinical symptoms are compared with sizes of the CAG repeat, there is again a remarkably high correlation of the sizes of CAG repeat with each of the clinical symptoms. Thus the wide variation in clinical manifestations of DRPLA can now be clearly explained based on the degree of CAG repeat expansion, which strongly indicates that the expanded alleles are intimately involved in the neuronal degeneration in dentatofugal and pallidofugal systems.

[A sporadic dentatorubral-pallidoluysian atrophy (DRPLA) diagnosed by gene analysis]

We report a 48-year-old woman with dentatorubral-pallidoluysian atrophy (DRPLA). She is the only patient in her 15 family members in two generations. She developed cerebellar ataxia and epilepsy at age 43. On admission at 48, she showed mild dementia and choreic movement in her face and extremities as well as truncal and limb ataxia. Routine laboratory examinations were normal. The point mutations in the tRNALys gene of mitochondrial DNA specific for MERRF were not found. A cranial CT scan and MRI showed mild atrophy of the cerebellum and prominent atrophy in the pons, especially in the tegmentum. Although she was thought to have DRPLA from the clinical point of view, absence of family history made the diagnosis difficult. Her parents were healthy until their 80's and died of cerebrovascular diseases and her 5 siblings had no symptoms. Hereditary DRPLA is known as an autosomal dominant disorder, with a high rate of penetrance and low rate of new mutation. According to our recent findings of a CAG repeat expansion in the DRPLA gene, this patient was diagnosed as a sporadic DRPLA. Considering the wide varieties of clinical manifestations, it is essential to examine this gene abnormality for diagnosing sporadic DRPLA.

Unstable expansion of CAG repeat in hereditary dentatorubral-pallidoluysian atrophy (DRPLA)

Hereditary dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurologic disorder characterized by variable combinations of myoclonus, epilepsy, cerebellar ataxia, choreoathetosis and dementia. By specifically searching published brain cDNA sequences for the presence of CAG repeats we identified unstable expansion of a CAG in a gene on chromosome 12 in all the 22 DRPLA patients examined. A good correlation between the size of the CAG repeat expansion and the ages of disease onset is found in this group. Patients with earlier onset tended to have a phenotype of progressive myoclonus epilepsy and larger expansions. We propose that the wide variety of clinical manifestations of DRPLA can now be explained by the variable unstable expansion of the CAG repeat.

[A case of juvenile onset ataxia with dystonia, myoclonus, sensorineural hearing loss and mental retardation]

A 35-year-old female was reported who presented early onset and slowly progressive ataxia and retrocollis which appeared at the age of nine. On admission, neurological examination revealed cerebellar ataxia, dystonia of the neck and the right arm, myoclonus of the neck and the shoulder, slight mental retardation, supranuclear upper gaze palsy, and sensorineural hearing loss. Laboratory examination showed high serum CK activity. Electromyography and muscle biopsy findings suggested slight muscular involvement. CSF level of HVA and 5-HIAA were reduced. MRI demonstrated marked cerebellar atrophy and slight atrophy of the brain stem. To our knowledge, the characteristic combination of the neurological sign in this case has not been reported. This case was compared with EOCA (early onset cerebellar ataxia with retained tendon reflexes) and other juvenile onset cerebellar ataxia and dystonia.

[A study on HTP organic signs]

A special version of the House-Tree-Person (H-T-P) technique was developed to differentiate organic psychosis from other disorders. H-T-P data of 126 psychiatric inpatients, including 16 patients with organic psychoses, 50 schizophrenics, 50 borderlines and 10 patients with other psychoses, were evaluated for the presence or absence of 29 possible features of houses, trees and persons. These features included those common to all three objects, as well as those specific to each object. Results for patients with organic psychoses were compared with those of patients with other disorders. The comparison disclosed that seven of the original 29 H-T-P features had diagnostical discrimination among treatment groups, giving higher H-T-P organic scores.

[The role of sympathetic cervical ganglion in the effect of clonidine for lowering intraocular pressure]

The contribution of sympathetic cervical ganglion to the mechanism of action of clonidine for lowering intraocular pressure (IOP) was investigated. Pigmented rabbits were used. The animals were divided into 3 groups: normal control group (group 1), animals in which the bilateral cervical sympathetic trunks had been amputated presynaptically (group 2), animals in which the superior cervical ganglion (SCG) had been bilaterally dissected (group 3). Changes in IOP were measured after topical application of clonidine unilaterally. In group 1, IOP was significantly decreased in eye treated by clonidine and contralateral eyes compared to pretreatment values. Decrease of IOP in the contralateral eye was greater than that in the treated eye. In group 2, IOP was decreased in the contralateral eye but increased in the eye treated by clonidine. Pretreatment of yohimbine administered orally antagonized the ocular hypotensive effect of clonidine in a dose-related manner. In group 3, where SCGs were dissected, no changes in IOP were observed in both eyes by unilateral administration of clonidine. These results suggested that the bilateral ocular hypotensive effect of clonidine administered unilaterally is in part due to direct action on the SCG and that the alpha 2 receptor in the SCG plays some role in the regulation of IOP.

[Ocular hypotensive effect of alpha-adrenoceptor agonist and antagonist in the conscious pigmented rabbit]

It has been reported that some of the topically-used antiglaucomatics have a central ocular hypotensive effect. In this study, the influence of topical and intracerebroventricular (i.c.v.) administration of phenylephrine, clonidine, guanfacine, prazosin, yohimbine on the intraocular pressure (IOP) was investigated in the rabbit. Male pigmented rabbits were used throughout the experiments. For measurement of IOP, an applanation pneumatonograph was used. By unilateral topical administration of phenylephrine, an increase in IOP in the eye in which instillation was performed was observed. On the other hand, a slight decrease in IOP was observed by similar treatment of prazosin and yohimbine. No significant change of IOP in the contralateral eye was observed with these drugs. On the contrary, unilateral topical administration of clonidine or guanfacine decreased the IOP of both eyes. Furthermore, the decrease of IOP was more remarkable in the contralateral eye compared to the eye which received instillation. The IOP of both eyes was decreased in a dose-related fashion by i.c.v. administration of clonidine or guanfacine. The ocular hypotensive effects of clonidine were diminished by the pretreatment by i.c.v. administration with yohimbine. These results suggest that the ocular hypotensive effect of clonidine and guanfacine is due to their alpha 2-adrenoceptor stimulation in the central nervous system.

[Estimating the quality of life in childhood cancer survivors from parent questionnaires]

Multidisciplinary clinical research on childhood cancer has achieved a marked improvement in survival rate during the last two decades. Due to the increase of long-term survivors, the survey of quality of life (QOL) of cured children is essential. But methods to estimate QOL of children have not been established. We attempted to estimate the QOL of surviving patients from the responses to a questionnaire filled out by their parents. The total number of patients treated at the National Children's Hospital from 1965-1987 was 937, of which 296 patients are still surviving. Among these survivors 108 patients were selected to be surveyed because they were being followed up by our attending physicians. The originally elaborated questionnaire was sent to parents in June 1989. Seventy-eight parents responded. The questionnaire consisted of four major questions. The first was how the QOL of the child compared to that of an ordinary child. The parents circled the appropriate level of QOL determined by our scale (1 lower, 4 the same as ordinary child, 7 excellent). The average score was 5.61 showing that parents felt their child's QOL is superior to an ordinary child. The second question concerned how the present status of the child was influenced by the experience of cancer. Answers were divided into five categories as follows: 1) Good or positive (10%); 2) nothing in particular (49%); minimum (29%); negative (9%); and other (7%). The third question concerned any anxieties. Most parents had numerous anxieties about the relapse, late effects, education, job prospects, marriage and offspring and getting the latest information. The fourth question dealt with what to tell the child as to their true diagnosis. Answers were divided as follows: absolutely no (56%); yes, but in the future (23%); yes, already done (10%); and yes, through our physician; (13%). After studying the questionnaires we interviewed the parents. We noticed that the parent/child relationship was very close. A meeting was conducted with parents and all the staff (doctors, psychologists and nurses). In conclusion, the QOL in surviving childhood cancer patients is considered to be better than that of ordinary children by their parents. This result is likely due to the excellent parent/child relationship.

Improvement in the treatment of childhood cancer: analysis of survival data from the National Children's Hospital (1965-1987)

Developments in the treatment of childhood cancer have been evaluated in patients who had been treated in the National Children's Hospital from 1965 to 1987. The total number of patients was 867, of which leukemia accounted for 376, malignant lymphoma 61, neuroblastoma 174, Wilms' tumor 55, yolk sac tumor 29, rhabdomyosarcoma 36 and hepatoblastoma 30. Patients were divided into three time intervals: the 1960s, 1970s and 1980s. A marked improvement in five-year survival was recognized in Wilms' tumor and yolk sac tumor, amounting to 80%, followed by rhabdomyosarcoma, acute lymphoblastic leukemia and malignant lymphoma. There was no improvement in patients with acute non-lymphoblastic leukemia, neuroblastoma and hepatoblastoma. Prognostic factors for neuroblastoma were further analyzed, and the age of onset and stage of disease were found to have remained constant for 23 years. Factors relating to the improvement of survival were discussed.

[Bone metastasis of malignant solid tumors in childhood]

A total of 452 cases of childhood malignant solid tumors were treated over the last twenty years at the National Children's Hospital. These included 175 cases of neuroblastoma, 64 cases of Wilms' tumor, 65 cases of malignant lymphoma, 45 cases of soft tissue sarcoma, 31 cases of hepatoma, 20 cases of malignant teratoma, 17 cases of testicular tumor, 7 cases of ovarian tumor and 28 cases of other forms of malignant solid tumor. Bone metastasis was observed in 62 of 175 cases of neuroblastoma, 3 of 64 cases of Wilms' tumor, one of 65 cases of malignant lymphoma, 4 of 45 cases of soft tissue sarcoma, one case of pulmonary blastoma and one case of osteogenic sarcoma, giving a total occurrence of bone metastasis in 72 of the 452 cases. The main sites of bone metastasis in neuroblastoma were the skull (61.4%), femur (56.8%), orbit (27.3%) and spine (22.7%). The average values of serum calcium and alkaline phosphatase activity showed no significant difference. The patients with bone metastasis were treated with a combination of radiation therapy and intensive chemotherapy, resulting in temporary improvement. The survival of patients with stage IV neuroblastoma with bone metastasis was worse than that of similar patients without bone metastasis.

Serial determination of serum neuron-specific enolase in patients with neuroblastoma and other pediatric tumors

The importance of determination of serum neuron-specific enolase (NSE) in patients with neuroblastoma has been emphasized by several authors. However, the specificity and sensitivity of NSE have not yet been well studied in tumors of infancy and childhood, nor is the role of serial determination of NSE in monitoring these patients fully understood. Concentrations of serum NSE were determined by a newly developed radioimmunoassay technique in 241 samples from 111 patients. NSE was also assayed in sera of nude mice bearing human pediatric tumors (16 samples), as well as in 30 tumor specimens. Eighty-two serum samples from 19 patients with neuroblastoma all showed NSE values (mean 120.2 ng/mL, range 16.2 to 722.0 ng/mL) elevated beyond the upper border of the normal range (14.6 ng/mL), even though four of the 19 patients had normal urinary excretion of 3-methoxy-4-hydroxymandelic acid (VMA) and 3-methoxy-4-hydroxy-phenylacetic acid (HVA). Twelve of these patients were monitored with serial NSE determinations, and their serum NSE were found to correlate well with the tumor burden, but were transiently modified by chemotherapeutically induced cell death. All 68 samples from nine patients, free of neuroblastoma at assessment, showed NSE values within the normal range. Thirteen of 25 patients with tumors other than neuroblastoma, however, showed serum NSE values mildly elevated beyond the upper border of the normal range (mean of the 25 patients 36.7 ng/mL, range 5.0 to 234.0 ng/mL). Results from our nude mouse study and from NSE analysis of the tumor extracts paralleled the clinical results.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinicopathological study of histiocytosis X

Thirty-five cases of histiocytosis X in the National Children's Hospital were clinicopathologically studied. Fourteen cases were categorized in diffuse histiocytosis X, Letterer-Siwe type (DHX), 19 cases in multifocal eosinophilic granuloma (MEG) and 2 cases in unifocal eosinophilic granuloma (UEG). Nine of 14 DHX died, of which 6 died of opportunistic infection due to hypoproteinemia and pancytopenia, and 3 died of pulmonary fibrosis probably due to histiocytic infiltration and resultant lymphedema. Infiltration of histiocytes in the bone marrow, thymus and lungs, in addition to the lymphoreticular organs, was conspicuous in autopsy cases of DHX. Skin biopsy was valuable for diagnosis and the immunostaining with anti-S100 antibody was a good marker to characterize infiltrating histiocytes. Prognostic factors and effects of treatments were also evaluated. Only one of 19 MEG died of opportunistic viral infection, but a longer duration for treatment was usually necessary compared to that for DHX. Pathogenesis of histiocytosis X was discussed in relation to T-zone histiocytes.

Mass screening for neuroblastoma in infants in Japan. Interim report of a mass screening study group

A mass screening system for the early detection by means of a vanillylmandelic acid test of neuroblastoma in 6-month-old infants in Japan has been developed in eight districts. 16 of the 281 939 infants screened by this test had neuroblastoma, equivalent to a very high incidence of 1 in 17 621. 15 of the 16 children with neuroblastoma are alive; the other child died 1 month after surgery. This mass screening system for neuroblastoma used in infancy can help to improve prognosis in infants with this malignant disorder.

Acute myeloid leukemia with preceding systemic lupus erythematosus and autoimmune hemolytic anemia

A 10-year-old girl with systemic lupus erythematosus (SLE) and autoimmune hemolytic anemia developed acute leukemia 10 months after the diagnosis of SLE. Leukemic cells had both the myeloid character, as shown by peroxidase activity, and T-cell surface antigen. The SLE-like syndrome as a paraneoplastic syndrome is discussed.

Familial leukemia. HLA system and leukemia predisposition in a family

Four cases of acute lymphocytic leukemia occurred in a family comprising 30 members. Genetic and cytogenetic studies showed a possible linkage between an HLA haplotype and the leukemia predisposition that was suggested by site-directed chromosome rearrangements in cultured skin fibroblasts. The possession of genetic markers, other than HLA types, could not be linked to the occurrence of leukemia in the family. These findings suggest that the major histocompatibility complex or gene(s) linked to it may have played a part in the pathogenesis of the leukemic process in this family.

Studies on human placental monoamine oxidase using mixed substrates

The activity of mitochondrial monoamine oxidase (MAO) from human placenta was measured with mixtures of labelled and unlabelled tyramine, serotonin (5-HT), benzylamine and beta-phenylethylamine (PEA). Tyramine deamination was inhibited by benzylamine and PEA but not by 5-HT, while benzylamine deamination was inhibited by tyramine and PEA, but not by 5-HT, 5-HT deamination was inhibited by tyramine, benzylamine and PEA and PEA deamination was inhibited by tyramine, benzylamine and 5-HT. These results suggest that MAO in human placenta has multiple catalytic sites or consists of different enzymes. Probably, tyramine, benzylamine and PEA are deaminated oxidatively at a common catalytic site while 5-HT is deaminated at another catalytic site. Benzylamine deamination was inhibited in a mixed noncompetitive fashion by tyramine and PEA in air, but benzylamine deamination was competitively inhibited by PEA at higher concentrations of oxygen. The deaminations of other substrates were inhibited competitively by other substrates, in air. Reciprocal plots of PEA deamination with benzylamine, 5-HT and tyramine gave hyperbolic curves.