Statistics of differential Lissajous EMG for normal occlusion and Class II malocclusion

Differential Lissajous electromyography (DL-EMG), a method of representing the simultaneous EMG values of two paired muscles as a single, continuous figure, was used in chewing tests with a sample of Japanese women having normal occlusion compared with a like group of Japanese female adolescents, having Class II, Division 1 malocclusion. For the normal sample, the DL-EMG figures described by the coordinated activity of the bilateral temporal and masseter muscles during chewing gum mastication typically appeared as repetitions of loops. Statistical data were gathered on the total EMG voltages, and on the location, rotational direction, and orientations of the DL-EMG loops when graphed onto Cartesian coordinates. These data were compared with those taken from the Class II sample. Significant differences were observed in the latter group for the EMG voltage levels of the balancing-side masseter muscles. The DL-EMG figures of the Class II group also showed irregularities in the shapes, locations, rotational directions, and orientations of the loops, indicative of irregular masticatory patterns. These data suggest that with sufficient control of factors such as age and sex, electromyography and especially DL-EMG techniques can be useful for characterizing masticatory differences between various occlusal groups.

Ability of hydroxyapatite-bone morphogenetic (corrected from morphologenetic) protein (BMP) complex to induce dentin formation in dogs

This histological investigation examined the formation and differentiation of pulp cells under the influence of HAP/BMP complex. HAP/BMP complex was implanted in exposed pulp of the mandibular premolars and alveolar bone defect in the dog. Sequential changes in these areas were examined mainly under a light microscope and partly under a scanning electron microscope. Two weeks after the operation, fibroblast-like cells proliferated right beneath the implanted complex, and after 3 weeks, dentin including dentin tubules grew in the pulp. After four weeks a dentin bridge composed of osteoid dentin was found, and after 8 weeks this dentin calcified and covered the defective surface of the root and adhered to new bone surrounding the HAP granules. The results indicated that the dentin induced by HAP/BMP complex may be of two types: tubular dentin and osteodentin. This complex exhibited outstanding ability to induce dentinogenesis and osteogenesis.

Detection of micrometastatic prostate cancer cells in lymph nodes by reverse transcriptase-polymerase chain reaction

We have developed a highly sensitive method for detecting prostate cancer cells using reverse transcriptase-polymerase chain reaction (RT-PCR) with primers specific for prostate-specific antigen gene. Forty-four lymph nodes obtained from 22 patients with prostate cancers were analyzed by RT-PCR to detect metastatic prostate cancer cells. RT-PCR could detect prostate-specific antigen mRNA in five lymph nodes with histologically and/or immunohistochemically identifiable metastases and in four lymph nodes with negative histological and immunohistochemical analyses for metastases. RT-PCR was a more sensitive method than histology and immunohistochemistry in detecting metastatic prostate cancer cells and could be applied for diagnosing micrometastases of prostate cancer to lymph nodes. This highly sensitive RT-PCR will be a relevant tool to allow a more accurate clinical assessment of lymph node metastases of prostate cancer and to understand lymphatic dissemination of prostate cancer biologically.

A case of xanthogranulomatous pyelonephritis in a child

We report an additional case of histopathologically confirmed xanthogranulomatous pyelonephritis in a 9-year-old boy. He was admitted to hospital with a two-day history of sustained fever. Physical examination revealed tenderness in the right upper quadrant of the abdomen. Results of a complete blood count and serum biochemical investigations showed slight anemia and positive C reactive protein. Culture of urine failed to grow any bacteria. Excretory urography revealed deformity of the right renal calyces. Computed tomography showed a focal area of low density in the right kidney. Nephrectomy was carried out as fever had been sustained despite intensive treatment with antibiotics. Sectioning revealed that the renal parenchyma had been replaced by a butter yellow nodule, which was histopathologically confirmed as xanthogranulomatous pyelonephritis. This is the nineteenth reported case in children in Japan to our knowledge.

Comparison of body height and mandibular length between Caucasian and Japanese children

This study compared pubertal growth of Japanese males and females with that of Caucasian children matched by age and gender. Total body height and mandibular length were compared between the two groups. Total body height showed that Caucasian males were taller than Japanese males from the ages of 10 to 15 years (p< 0.01-0.05). The annual maximum growth of Caucasian females peaked at the age of twelve, but Japanese females had a "spurtless" growth pattern, peaking one year earlier than Caucasian females. Total mandibular length, calculated at the age of 10, was about 3 mm greater in Japanese males and 5 mm greater in Japanese females than in Caucasians. At the age 15, the mandibles of Japanese males and females were about 7 mm and 9 mm longer than those of Caucasians, respectively. Adolescent mandibular growth spurt occurred, on the average, at the age of 13 in both Caucasian and Japanese males. Both female groups showed mandibular growth peaks at the age of 12.

Effect of the new calcium antagonist (+/-)-(R*)-3-[(R*)-1-benzyl-3- piperidyl] methyl 1,4-dihydro-2,6-dimethyl-4-(m-nitrophenyl)-3,5- pyridinedicarboxylate hydrochloride (KW-3049) on cardiac hypertrophy in spontaneously hypertensive rats

Using spontaneously hypertensive rats (SHR), we studied the effects of a new calcium antagonist, (+/-)-(R*)-3-[(R*)-1-benzyl-3-piperidyl] methyl 1,4-dihydro-2,6-dimethyl-4-(m-nitrophenyl)-3,5-pyridinedicarboxylate hydrochloride (KW-3049) on the development of hypertension and cardiac hypertrophy. When KW-3049 was administered orally to 5-week-old SHR, a stage before the onset of hypertension, for 12 consecutive weeks, it showed a dose-dependent and marked antihypertensive action. Administration of 3 mg/kg of KW-3049, once a day, significantly suppressed the rise in blood pressure to a similar extent to 15 mg/kg of nicardipine, twice a day. After 12 weeks of administration, the heart weight was decreased or tended to be decreased. Co-administration with propranolol markedly decreased the heart rate, but little affected the heart weight, suggesting changes in the heart rate during the long-term administration of KW-3049 did not largely affect cardiac hypertrophy. KW-3049 did not increase plasma renin activity (PRA) or plasma aldosterone concentration (PAC). There was no significant change in the myocardial DNA and RNA contents. These results suggest the clinical usefulness of KW-3049 as an antihypertensive drug.

An improved method for genotyping of N-acetyltransferase polymorphism by polymerase chain reaction

Polymorphic N-acetyltransferase in human liver catalyzes N-acetylation of various arylamine-containing drugs and environmental chemicals. To accelerate the pharmacogenetic and ecogenetic studies of N-acetyltransferase polymorphism, we have developed a rapid and simple method for genotyping using a polymerase chain reaction based restriction fragment length polymorphism. This method distinguishes four kinds of allele of the N-acetyltransferase gene using a single polymerase chain reaction starting with a set of primers, followed by successive Asp718, BamHI and TaqI digestions, and then running the samples on a single electrophoresis lane. This method allows us to determine ten different genotypes easily and reliably.

[Renin-secreting renal tumor. A case report]

We reported a case of juxtaglomerular cell tumor, which excessively produced renin, resulting in secondary hypertension. A 25-year-old woman complained of headache and nausea. Hypertension and elevation of plasma renin activity were found by physical and laboratory examination. US and CT showed a space occupying lesion at upper pole of the right kidney. Angiography showed a hypovascular area at the corresponding area of the right kidney. Renin-secreting renal tumor of the right kidney was diagnosed and right nephrectomy was performed. Postoperatively, blood pressure and plasma renin activity became normalized and symptoms ameliorated. The juxtaglomerular cell tumor was pathologically confirmed and localization renin in the tumor cells was shown by immunohistochemical study. Forty one cases of juxtaglomerular cell tumor have been reported, since Robertson reported the first case. We discussed the clinical and pathological characteristics of the disease in this report.

Multiple mRNA species of choline acetyltransferase from rat spinal cord

A cDNA library directed by a specific primer was constructed from the rat spinal cord and screened with 32P-labeled rat choline acetyltransferase cDNA which was recently isolated in this laboratory. Sequence analysis of 29 clones indicated that there are four types of cDNA (R1-, R2-, N1- and M-types). The nucleotide sequences in these cDNAs were identical in the coding region and the first 38 bp of the 5'-noncoding region, but differed in the 5'-noncoding region upstream of -38 bp. The R1-type was identical to the cDNA previously cloned from the rat spinal cord. The M and N1-type cDNAs both had sequences homologous to that of the cDNA previously obtained from the mouse spinal cord. Polymerase chain reaction analysis confirmed the presence of these 4 types of mRNA and found another type (N2-type) of transcript. The numbers of cDNA clones isolated and the relative amounts of polymerase chain reaction products for each type of mRNA suggested that the most abundant transcript was M-type. Sequencing of the genomic clone containing the 5'-region of choline acetyltransferase mRNA revealed that these five types of mRNA species were transcribed from three different promoter regions and produced by differential splicing of the 5'-noncoding exons.

Transcriptional regulation of choline acetyltransferase gene by cyclic AMP

The effect of cyclic AMP on the gene expression of choline acetyltransferase (ChAT) was studied in NG108-15, mouse neuroblastoma and rat glioma hybrid cell lines. Addition of dibutyryl cyclic AMP to the culture medium increased both the ChAT mRNA level and ChAT activity twofold. Polymerase chain reaction analysis of the ChAT mRNA indicated that, among the multiple mRNA species, M-type mRNA was transcribed most efficiently, with or without the addition of dibutyryl cyclic AMP. The 5' region of the mouse ChAT gene was ligated to the bacterial chloramphenicol acetyltransferase gene, and the expression of chloramphenicol acetyltransferase activity was determined by transfection analysis. Cyclic AMP derivatives enhanced the reporter gene expression in both transiently and stably transfected cells. DNA deletion analysis indicated that the intron region downstream of the M-type exon is necessary for the cyclic AMP responsiveness, and that cyclic AMP derivatives increase ChAT gene transcription mainly from M-type promoter. These results suggest that a cis-acting DNA element that confers the cyclic AMP responsiveness of the ChAT gene is present in the intron downstream of the M-type exon.

The structure and characteristics of a fourth allele of polymorphic N-acetyltransferase gene found in the Japanese population

Polymorphic N-acetyltransferase (NAT2), which exists in the human liver and metabolizes a wide spectrum of arylamine, is encoded by one gene (NAT2). We have identified the mutations of a fourth NAT2 allele (allele 4) which we previously found in the Japanese population. Compared with allele 1, which expresses a high enzyme activity, allele 4 has 3 nucleotide differences. 2 are missense mutations at nucleotide position (nt) 341 and 803. The other is a silent mutation at the KpnI site. From the result of expression studies of chimeric gene constructs between allele 1 and allele 4 in Chinese hamster ovary cells, nt 341 missense mutation of the allele 4 which causes the Ile-114 to Thr change is responsible for the low enzyme activity of NAT2 protein.

A histological study of the exfoliation of human deciduous teeth

For clarification of the histological details of the shedding of human deciduous teeth, exfoliated and extracted deciduous teeth were examined by light and electron microscopy. After the roots were completely resorbed, the dentogingival junction migrated along the inner resorbing surface and finally reached the pulpal surface of the crown. At the same time, the gingival epithelium also proliferated and migrated under the crown of the deciduous tooth in such a way that part of it lined the residue of the pulp and another part lined the surface overlying the erupting successional tooth. This phenomenon took place from various sides of the tooth surface. Therefore, just before exfoliation, the migrated gingival epithelium formed narrow necks of tissue, and the crown was only superficially attached to the gingiva by them. The final shedding of the tooth appeared to occur by a tearing of these narrow tissue regions. The results of the present study suggest that the dento-gingival junction as well as gingival epithelium play important roles in the process of exfoliation of human deciduous teeth.

[A study of methicillin-resistant Staphylococcus aureus (MRSA) infection in urological field]

Out of 110 strains of Staphylococcus aureus isolated from 1985 to 1990, isolation rate of methicillin-resistant S. aureus (MRSA) was investigated. Nineteen strains of 59 S. aureus from outpatients and 20 strains of 51 S. aureus from inpatients were determined as MRSA. Isolation frequency of MRSA from inpatients was increasing in the recent two years. Coagulase type, enterotoxin type and production of toxic shock syndrome toxin-1 (TSST-1) were examined in 22 strains of MRSA. Coagulase type II (86%), enterotoxin type C (68%) and TSST-1 positive strain was most dominant. Susceptibility of MRSA to 4 antimicrobial agents were measured, MRSA were sensitive to vancomycin (VCM), arbekacin (ABK) and minocycline, but resistant to flomoxef. Thirty-four patients from whom MRSA was isolated including 20 patients from urine, 13 from pus and 1 from blood, were analyzed clinically. Pyuria was not recognized in some cases in whom MRSA was isolated from their urine. Concomitant polymicrobial infection was frequently noted in those patients with MRSA in their urinary tract. These facts show that the pathogenic role of MRSA in the urinary tract infection was not significant. On the other hand, when MRSA was isolated from pus or blood, serious infections could be caused by MRSA, especially in compromised host. Regarding the treatment in these cases, administration of VCM or ABK was though to be necessary.

[Measurement of serum PA values by a newly developed enzyme immunoassay]

Serum prostate-specific antigen (PA) values detected by a newly developed enzyme immunoassay (EIA, MARKIT-M PA) as a successor of MARKIT-F PA, which has been a leading kit in Japan, were evaluated for its role in the diagnosis of cancer of the prostate and follow-up of the patients afflicted with the disease. The system is one-step sandwich type EIA using horseradish peroxidase as a tracer and has 0.50-100 ng/ml of detectable range with small amount of sample volume (25 microliters) and reliable quality control data. Furthermore, serum PA values detected by the assay were almost equivocal to those detected by MARKIT-F PA. Serum PA values in prostate cancer patients (n = 122) were statistically higher than those in normal males (n = 90), urological malignancies other than prostate cancer (n = 48) or benign prostatic hypertrophy (BPH, n = 73). Even in the patients with stage A and B prostate cancer, serum PA values were observed to be statistically higher than those in BPH cases. If 3.6 ng/ml was used, which is normal value in MARKIT-F PA, as a cut-off value and BPH cases as a control, the sensitivity, specificity and efficacy for diagnosis of prostate cancer were 77.9, 91.8 and 83.1%, respectively, which showed the best results during the range examined. Serially determined serum PA values in following up the patients with prostate cancer were confirmed to be highly effective to evaluate treatment responses. These results suggest that MARKIT-M PA is thought to be one of the best tool for determination of serum PA values.

Cementum-like tissue deposition on the resorbed pulp chamber wall of human deciduous teeth prior to shedding

In the later stage of exfoliation in human deciduous teeth, odontoclastic resorption takes place at the pulpal surface of the coronal dentin. However, this resorption does not continue until the teeth are shed, and the resorbed pulp chamber wall is usually repaired by cementum-like tissue deposition. In this study, we examined the formation and characteristics of the cementum-like hard tissue on the resorbed dentin surface in the pulp chamber of deciduous teeth prior to shedding. The site and degree of deposition of newly formed cementum-like tissue on the resorbed pulp chamber wall varied from tooth to tooth. Furthermore, they also showed compositional and structural variations. Generally, however, the matrix of the cementum-like tissue was composed of intrinsic collagen fibers, acellular or cellular. There was a tendency for acellular cementum-like tissue to be deposited on small and shallow resorption bays, whereas the cellular type was found on larger and deeper ones. In both cases, the surface of the deposited cementum-like tissue on the resorbed dentin surface usually became flat. However, unlike the cementum repair of resorbed areas on the root surface, no acellular extrinsic fiber cementum-like tissue was found on the resorption pulp chamber wall. Although the role of the repair of the resorbed pulp chamber wall with cementum-like tissue deposition just before shedding is unknown, it might play some role in the retention of deciduous teeth until shedding.

Enhanced acetylcholine secretion in neuroblastoma x glioma hybrid NG108-15 cells transfected with rat choline acetyltransferase cDNA

Neuroblastoma x glioma hybrid NG108-15 cells and mouse neuroblastoma N18TG-2 and N1E-115 cells were transiently transfected with the sense cDNA coding for rat choline acetyltransferase (ChAT). All transfected cell lines showed a high level of ChAT activity. ACh secretion was monitored by recording miniature end-plate potentials (MEPPs) in striated muscle cells that had been co-cultured with transfected cells. The number of muscle cells with synaptic responses and the MEPP frequency were higher in co-culture with transfected NG108-15 cells than with control or mock cells. No synaptic response was detected in muscle cells co-cultured with transfected N18TG-2 or N1E-115 cells. The results show that ACh secretion into the synaptic cleft was enhanced due to ChAT overexpression in NG108-15 hybrid cells but not in neuroblastoma cells.

[Study on chemosensitivity test of urogenital tumors by ATP assay]

In order to improve the efficacy of chemotherapy against urogenital cancers, we developed a chemosensitivity test by measuring intracellular ATP in cancer cells. In the fundamental experiments using HeLa cells, a significant correlation was observed between intracellular ATP levels and numbers of viable cells. We employed 8 drugs, ADM, VCR, VLB, MTX, 5-FU, PEP, MMC, and CDDP for the assay Thirty-four renal tumors, 68 urothelial tumors and 19 testicular tumors were tested, and evaluable results were obtained in 25 specimens of renal tumors (76%) 55 specimens of urothelial tumors (80%) and 17 specimens of testicular tumors (98%). According to the ATP assay, renal tumors were sensitive to ADM and MMC, urothelial tumors to ADM, MMC and CDDP and testicular tumors to ADM and MMC. The ATP assay to determine the chemosensitivity to clinical specimens was sensitive and efficient. Thus the ATP assay could be applied for selection of anticancer drugs in the chemotherapy of urogenital cancers.

[Diagnosis of gonococcal urethritis and chlamydial urethritis by polymerase chain reaction]

A polymerase chain reaction (PCR) method was compared to standard methods (cultures for Neisseria gonorrhoeae and Chlamydia trachomatis and an enzyme-immunoassay for C. trachomatis) in diagnosis of gonococcal and chlamydial urethritis in 40 male patients with urethritis. Gonococcal urethritis was diagnosed by detection of a 206 bp DNA fragment amplified by PCR with N. gonorrhoeae-specific primers. Chlamydial urethritis was diagnosed by detection of a 242 bp DNA fragment amplified by PCR with C. trachomatis-specific primers. Gonococcal and chlamydial urethritis, gonococcal and non-chlamydial urethritis, non-gonococcal and chlamydial urethritis, and non-gonococcal and non-chlamydial urethritis were diagnosed in 8, 10, 14 and 8 patients, respectively, by the PCR method. In 9 patients with gonococcal and chlamydial urethritis, 10 with gonococcal and non-chlamydial urethritis, 12 with non-gonococcal and chlamydial urethritis, and 9 with non-gonococcal and non-chlamydial urethritis, diagnosed by the standard methods, the coincidence rates of the PCR to the standard methods were 78% (7/9), 90% (9/10), 100% (12/12), and 89% (8/9), respectively. The overall coincidence rate between the PCR and the standard methods in diagnosis of urethritis were high (90%). In addition, N.gonorrhoeae and C.trachomatis could be simultaneously detected from one urethral sample in approximately 6 hours by means of the PCR. Thus, the PCR method could clinically be applied and would offer several advantages to diagnosis of urethritis, compared to the standard methods.

[Detection of Ureaplasma urealyticum by polymerase chain reaction]

A polymerase chain reaction (PCR) procedure for detection of Ureaplasma urealyticum was developed. A set of oligonucreotides based on sequences within the 16S ribosomal RNA gene from U. urealyticum were used as extension primers for the PCR. A DNA fragment of 397 bp was amplified by the PCR, when U. urealyticum DNA was template for the PCR. No amplified product was detected from other bacterial DNA including those of Mycoplasma genus. The amplified DNA fragment of 397 bp was detected on agarose gel electrophoresis, when DNA of > or = 10(2) cells of U. urealyticum per PCR was used as template for the PCR. Thus, the PCR procedure was shown to be a simple, rapid and specific method for detection of U. urealyticum and could be applied to detection of U. urealyticum from clinical specimens.

Pulpal and radicular changes following maxillary subapical corticotomy

Pulpal and radicular changes after subapical corticotomy in combination with posterior transfer of the maxilla were studied histopathologically using monkey jaws. When the surgical procedures were successful, the pulp tissues were kept alive, even though some slight atrophy and degeneration appeared. In some cases, however, severe reticular atrophy occurred which might be due to anaemia during operations.

A complementary DNA for human choline acetyltransferase induces two forms of enzyme with different molecular weights in cultured cells

Complementary DNA (cDNA) clones containing the entire coding region of human choline acetyltransferase (ChAT) were isolated from cDNA libraries prepared from the autopsied spinal cord. In the human cDNA, the ATG codon assigned to the putative initiation codon for pig, rat and mouse ChAT cDNAs was replaced by ACG. The human cDNA contained an in-frame ATG codon 324 nucleotides upstream of the ACG codon. Therefore, human ChAT cDNA should code for a 748 amino acid polypeptide of 82.6 kDa. This deduced molecular weight was larger than that of ChAT protein purified from the human brain and placenta (64-70 kDa). The human ChAT cDNA containing the entire coding region was ligated to an expression vector and introduced into African green monkey kidney (COS) cells and Chinese hamster ovary (CHO) cells. The cells expressed high ChAT activity and produced two protein bands immunostained with an antibody to monkey ChAT. The molecular weight of the proteins was estimated to be approximately 70 and 80 kDa by polyacrylamide-SDS gel electrophoresis. When partial cDNAs that lacked the first ATG but contained the replaced ACG codon were introduced into COS cells, the cells expressed moderate ChAT activity and an immunoreactive protein band of 70 kDa. These results indicate that translation of human ChAT mRNA starts at two sites and produces two enzyme proteins with different molecular weights. It might be that the larger form of ChAT molecule is an enzyme precursor for processing or that the N-terminal extrapeptide is needed for subcellular localization of the enzyme.

Gene expression of mouse choline acetyltransferase. Alternative splicing and identification of a highly active promoter region

Seven types of mRNA for choline acetyltransferase that differ in the 5'-noncoding region were identified in the mouse spinal cord by cDNA cloning and polymerase chain reaction. Among these transcripts, the M-type mRNA corresponding to the previously cloned mouse cDNA was most abundant in the spinal cord of mouse. A mouse genomic DNA clone containing the 5'-region of choline acetyltransferase mRNA was isolated and sequenced. Comparison of the sequences between the cDNAs and the genomic DNA revealed that the different mRNA species were transcribed from different promoter regions and produced by differential splicing. Two murine cholinergic cell lines, NS20Y and NG108-15, were shown to express the M-type mRNA almost exclusively, and were therefore used to study transcription of M-type mRNA. Fragments of the 5'-region of choline acetyltransferase gene were ligated with chloramphenicol acetyltransferase reporter gene and introduced into cultured cells. The fragment from -2752 to +46, which contained the M-type exon, a TATA-box like element upstream of the M-type exon, and the downstream intron, induced a significant expression of CAT activity in neuronal but not in non-neuronal cell lines. This result indicates that this region of choline acetyltransferase gene contains elements that regulate neuron-specific expression of choline acetyltransferase activity. However, there was no parallel correlation between reporter gene expression in the transfected cells and intrinsic choline acetyltransferase activity in these neuronal cell lines. Possible mechanisms that would explain this observation are discussed.

[Comparison of polymerase chain reaction and IDEIA Chlamydia in detection of Chlamydia trachomatis from first-voided urine of male urethritis patients]

We have reported a method for detection of Chlamydia trachomatis by polymerase chain reaction (PCR) with two oligonucleotides based on sequences within the major outer membrane protein gene from C. trachomatis serovar L2. In the previous report, in addition to treatment of the mixture of first-voided urine (FVU) sediment and 1 ml of urine with proteinase K. DNA purification by phenol extraction was necessary for preparation of template DNA for PCR. In this study, FVU sediment was suspended in 1 ml of Chlamydiazyme dilution buffer and a part of the suspension was treated with proteinase K for DNA extraction. The DNA extraction solution could be used as template for PCR without purification of DNA by phenol extraction. One hundred FVU specimens obtained from male urethritis patients were examined with the two methods (PCR and IDEIA) for detection of C. trachomatis. In 33 of 100 specimens, the DNA fragments of C. trachomatis was amplified by the PCR and in 32 of 100, the chlamydial antigen was detected by IDEIA. The positive and negative coincidence rate of the PCR to IDEIA were 93.8% (30.32) and 95.6% (65/68) respectively, resulting in a high overall coincidence rate at 95%. Thus, the improved method with PCR using FVU as a specimen is proved to be a useful, non-invasive diagnostic tool for diagnosis of chlamydial urethritis.

Sequences and expression of alleles of polymorphic arylamine N-acetyltransferase of human liver

Fifty human livers obtained at autopsy were analyzed for N-acetyltransferase and classified into six genotypes. Determination of N-acetyltransferase activity and proteins from supernatants of liver homogenates indicate that genotype I corresponds to rapid acetylator, genotypes II and III to intermediate acetylator, and genotypes IV, V, and VI to slow acetylator phenotypes. Northern blot analysis shows that levels of mRNA for N-acetyltransferase in the livers do not markedly differ among the six genotypes. Three alleles of the N-acetyltransferase gene were cloned and sequenced. mRNA is coded in two exons. Comparison of alleles 2 and 3, which correspond to low N-acetyltransferase activity, with allele 1, which corresponds to high N-acetyltransferase activity, revealed several polymorphisms. Two gene sequence differences occur in the coding exons of alleles 2 and 3, one of which would produce different amino acids in the proteins. Those sequence differences that lead to amino acid substitutions result in a loss of BamHI and TaqI sites for alleles 2 and 3, respectively. Expression studies of the alleles in Chinese hamster ovary cells show that allele 1 expresses high levels of N-acetyltransferase activity and enzyme protein, while alleles 2 and 3 express low levels of both protein and activity.