Caesarean section and childhood obesity at age 3 years derived from the Japan Environment and Children's Study

Caesarean section (CS) birth is widely reported to be a risk factor for childhood obesity. Although susceptibility to childhood obesity is influenced by race and ethnicity, it is unclear whether this risk of childhood obesity with CS birth also applies in the Japanese population. We investigated the impact of CS birth on obesity at 3 years of age in Japanese children. We obtained data from 60,769 mother-toddler pairs in the Japan Environment and Children's Study, a large-scale birth cohort study. Obesity was determined by body mass index measured at 3 years of age. Analysis revealed that 11,241 toddlers (18.5%) had a CS birth and that 4912 toddlers (8.1%) were obese. The adjusted risk ratio for obesity at 3 years of age when born by CS compared with vaginal delivery, estimated using inverse probability of treatment weighting, was 1.16 (95% confidence interval 1.08-1.25). These results suggest that CS birth modestly increases the risk of obesity at 3 years of age in Japanese children.

Glucokinase maturity-onset diabetes of the young as a mimicker of stress hyperglycemia: a case report

Febrile seizures are frequently accompanied by stress-induced hyperglycemia. Herein, we report the case of a 1.5-yr-old girl with hyperglycemia during febrile seizures who was subsequently diagnosed with glucokinase (GCK) maturity-onset diabetes of the young (MODY), considering its distinction from stress hyperglycemia. Following the development of febrile seizures owing to adenovirus infection, the patient presented a casual blood glucose level was 185 mg/dL. She had a multigenerational family history of diabetes and a hemoglobin A1c (HbA1c) level of 6.4%. Owing to the persistent glucose intolerance until the age of 5 years, genetic testing was performed, which revealed a heterozygous mutation in GCK, and the patient was diagnosed with GCK-MODY. Precise diagnosis of GCK-MODY individuals is important to avoid administering unnecessary antidiabetic medications. Even during hyperglycemia under stress, multigenerational diabetes and mildly elevated HbA1c levels can suggest GCK-MODY.

SUN-064 Diversity of Endocrine Function in Patients with CHARGE Association

Context: CHARGE association consists of congenital malformation of Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, Ear anomalies and/or deafness. It is often caused by CHD7 gene mutation, which also one of the causative gene for Kallmann syndrome. The endocrine dysfunction in CHARGE association has been reported but not fully understood. Objective: To clarify the mode of growth and frequency of endocrine dysfunction in CHARGE association. Subjective: We investigated the characteristics of growth and puberty, and endocrine function in 23 children (15 males and 8 females, 0~20 years old) with CHARGE association. Results: The birthweight was from -2.74 to +1.14 SDS and the birth length was from -2.86 to +1.10 SDS. 5 children were born small for gestational age. The height below -2SDS in 18 children. GH secretion was evaluated in 11 children with short stature (-9 to -2.3SD) except for one with normal height (-0.3 SD in 6 years old girl); 5 children including one with normal stature were revealed to have GH deficiency. One short girl with GH deficiency previously showed normal GH response to provocation test at 1 year old but has developed to be GH deficient at 7 years old. Gonadotropin-releasing hormone loading tests were performed in 7 males and 3 females. Nine out of 10 children showed hypogonadotropic hypogonadism; one girl showed hypergonadotropic hypogonadism, whose ovaries were undetectable on ultrasound. Human chorionic gonadotrophin (HCG) tests were performed in 6 males with micropenis and/or cryptorchidism. Peak testosterone levels after HCG stimulation were from 0 to 6.99 ng/ml. 4 patients showed peak testosterone levels less than 1 ng/ml. Four boys showed combined gonadotropin deficiency and primary hypogonadism. Conclusions: Our data showed the diversity of endocrine function in children with CHARGE association. GH deficiency can be developed over time. Hypogonadotropic hypogonadism is common, while isolated/combined primary hypogonadism should be taken into consideration in children with CHARGE association.

MON-269 Analysis of Clinical Features of Congenital Hypothyroidism with Eutopic Thyroid Gland

Background: Newborn screening test for congenital hypothyroidism (CH) may detect mild forms of CH, associated with eutopic thyroid gland, but there is no clear provision of the management. We analyzed the clinical features of CH with eutopic thyroid gland and necessity of continuation of treatment. Materials and methods: Retrospective, single center cohort study of children with CH treated between 2002 and 2018. CH patients initiating levothyoxin (LT4) within 2 months of age and reaching 3 years of age at the analysis were eligible. Aged >3 years CH patients with LT4 administration underwent re-evaluation test, which included thyroid function testing after LT4 therapy withdrawal, scan of thyroid using ultrasonography and computed tomography, and ¹²³I thyroid scintigraphy with potassium thiocyanate discharge test. The forms of CH were classified as thyroid dysgenesis or dyshormogensis, and the necessity of treatment were classified as permanent CH (PCH) or transient CH (TCH). PCH was defined when the subject was kept on administration of LT4 at the final observation. TCH was defined when a trial-off therapy was successful for at least 6 months. Developmental analysis and genetic analysis were performed in selected cases. Results: Of 209 CH patients, 103 cases were excluded from this study mainly because of age less than 3 years, incomplete medical records and lost to follow-up. 106 cases eligible for this study and 12 cases discontinued LT4 administration before 3 years of age without re-evaluation test. 94 cases underwent re-evaluation test, 69 cases had PCH and 25 cases had TCH. Median of final observation point for PCH was 12.0 years. In the PCH group, thyroid dysgenesis was the most prevalence form (31 had eutopic thyroid gland and 19 had ectopic thyroid gland or agenesis), 5 cases had dyshormogenesis and 14 cases were unclassifiable. All TCH patient had eutopic thyroid gland. PCH patients with eutopic thyroid gland had higher mean dose of LT4 at 3 years old than patients with TCH (2.27 µg/kg/day vs 1.39 µg/kg/day, p<0.01), but no other clinical features and developmental test results differed. LT4 dose at 3 years of age < 1.60 µg/kg/day was a predictive factor of TCH; sensitivity 78.2% and specificity 94.7%. Conclusion: PCH patients with eutopic thyroid gland presents a difference of LT4 dose at 3 years of age compared with TCH, and TCH is strongly suggested when the dose of LT4 is less than 1.60 µg/kg/day.

Longitudinal study on the effectiveness of vitamin D supplements in exclusively breast-fed infants

Vitamin D deficiency is a common health problem in infancy. Breast-fed infants are at a higher risk of rickets than formula-fed infants. We observed fluctuations in vitamin D levels in infancy (phase I, 2009–2010) and considered the benefits of vitamin D supplementation specifically in exclusively breast-fed infants in Japan (phase II, 2015). Infants born at our hospital were enrolled in this study. In phase I, we measured 25-hydroxyvitamin D [25(OH)D] levels at 1- to 6-mo intervals from birth. In phase II, we measured 25(OH)D levels before and after supplementation. Vitamin D deficiency was defined as 25(OH)D levels of < 20 ng/mL. All 38 infants in phase I were deficient at birth, and none of the exclusively breast-fed infants achieved 25(OH)D sufficiency by 5 mo of age. Formula-fed infants achieved 25(OH)D sufficiency earlier. The majority of the 71 infants in phase II were deficient at birth. We recommended an oral vitamin D supplement at a daily dose of 4.0 µg for the 15 exclusively breast-fed infants, starting at 1 mo of age; 14 (93.3%) of them achieved 25(OH)D sufficiency by 5 months of age. Exclusively breast-fed infants are at a high risk of vitamin D deficiency; adequate supplementation is an effective preventative strategy.

Identification and relative contributions of human cytochrome P450 isoforms involved in the metabolism of glibenclamide and lansoprazole: evaluation of an approach based on thein vitrosubstrate disappearance rate

1. The identification and relative contributions of human cytochrome P450 (CYP) enzymes involved in the metabolism of glibenclamide and lansoprazole in human liver microsomes were investigated using an approach based on the in vitro disappearance rate of unchanged drug. 2. Recombinant CYP2C19 and CYP3A4 catalysed a significant disappearance of both drugs. When the contribution of CYPs to the intrinsic clearance (CL(int)) of drugs in pooled human microsomes was estimated by relative activity factors, contributions of CYP2C19 and CYP3A4 were determined to be 4.6 and 96.4% for glibenclamide, and 75.1 and 35.6% for lansoprazole, respectively. 3. CL(int) of glibenclamide correlated very well with CYP3A4 marker activity, whereas the CL(int) of lansoprazole significantly correlated with CYP2C19 and CYP3A4 marker activities in human liver microsomes from 12 separate individuals. Effects of CYP-specific inhibitors and anti-CYP3A serum on the CL(int) of drugs in pooled human liver microsomes reflected the relative contributions of CYP2C19 and CYP3A4. 4. The results suggest that glibenclamide is mainly metabolized by CYP3A4, whereas lansoprazole is metabolized by both CYP2C19 and CYP3A4 in human liver microsomes. This approach, based on the in vitro drug disappearance rate, is useful for estimating CYP identification and their contribution to drug discovery.

Postoperative evaluation of pylorus-preserving procedures compared with conventional distal gastrectomy for early gastric cancer

We evaluated postoperative function in 98 patients who underwent surgery for early gastric cancer between 1995 and 1998 to compare the results of pylorus-preserving procedures to those of conventional distal gastrectomy with Billroth I (B-I). The pylorus-preserving procedures included endoscopic mucosal resection (EMR), performed in 12 patients; local resection (Local), performed in 14 patients; segmental resection (Seg), performed in 8 patients; and pylorus-preserving gastrectomy (PPG), performed in 19 patients. B-I was performed in 45 patients. The nutritional status and serum albumin (Alb) levels after PPG, the hemoglobin (Hb) levels after EMR, Local, and PPG, and the present/preoperative body weight ratios after EMR, Local, Seg, and PPG were superior to those after B-I. The time before oral intake was recommenced after EMR and Local, the volume of oral intake tolerated after EMR, Local, Seg, and PPG, and the postoperative hospital stay after EMR were all superior to those after B-I. Moreover, significantly fewer patients suffered reflux symptoms after EMR, Local, and PPG, abdominal fullness after EMR, and early dumping syndrome after EMR, Local, and PPG than after B-I. There was also less evidence of gastritis after EMR, Local, and PPG, and of bile reflux after EMR, Local, and PPG, than after B-I. These findings indicate that pylorus-preserving procedures may result in a better postoperative quality of life for selected patients with early gastric cancer.

Prediction of human hepatic clearance from in vivo animal experiments and in vitro metabolic studies with liver microsomes from animals and humans

We investigated the quantitative prediction of human hepatic metabolic clearance from in vitro experiments focusing on cytochrome P450 metabolism with eight model compounds, FK1052, FK480, zolpidem, omeprazole, nicardipine, nilvadipine, diazepam, and diltiazem. For the compounds, in vivo human hepatic extraction ratios ranged widely from 0.03 to 0.87. In vitro and in vivo hepatic intrinsic clearance (CL(int)) values for each compound were measured and calculated in rats and/or dogs and humans. CL(int,in vitro) was determined from a substrate disappearance rate at 1 microM in hepatic microsomes, which was a useful method. CL(int,in vivo) was calculated from in vivo pharmacokinetic data using three frequent mathematical models (the well stirred, parallel-tube, and dispersion models). The human scaling factor values (CL(int,in vivo)/CL(int,in vitro)) showed marked difference among the model compounds (0.3-26.6-fold). On the other hand, most of the animal scaling factors were within 2-fold of the values in humans, suggesting that scaling factor values were similar in the different animal species. When human CL(int,in vitro) values were compared with the actual CL(int,in vivo), correlation was not necessarily good. By contrast, using human CL(int,in vitro) corrected with the rat and/or dog scaling factors yielded better predictions of CL(int,in vivo) that were mostly within 2-fold of the actual values. Furthermore, successful predictions of human CL(oral) and hepatic extraction ratio (E(H)) were obtained by use of the human CL(int,in vitro) corrected with animal scaling factors. The new variant method is a simple one, incorporating additional information from animal studies and providing a more reliable prediction of human hepatic clearance.

Molecular cloning and functional expression of a rabbit renal organic cation transporter

A cDNA encoding an organic cation transporter (rbOCT1) was isolated from rabbit kidney. The cDNA encodes a 554 amino acid protein that is highly homologous to other mammalian organic cation transporters. rbOCT1 mediated 3H-1-methyl-4-phenylpyridinium (3H-MPP+) transport in Xenopus laevis oocytes was saturable, sensitive to membrane potential, and inhibited by various organic cations. rbOCT1 mRNA transcripts are expressed in the kidney, liver, and intestine.

Cloning and functional expression of a human liver organic cation transporter

Polyspecific organic cation transporters in the liver mediate the elimination of a wide array of endogenous amines and xenobiotics. In contrast to our understanding of the mechanisms of organic cation transport in rat liver, little is known about the mechanisms of organic cation transport in the human liver. We report the cloning, sequencing, and functional characterization of the first human polyspecific organic cation transporter from liver (hOCT1). hOCT1 (554 amino acids) is 78% identical to the previously cloned organic cation transporter from rat, rOCT1 [Nature (Lond.) 372:549-552 (1994)]. In Xenopus laevis oocytes injected with the cRNA of hOCT1, the specific uptake of the organic cation 3H-1-methyl-4-phenylpyridinium (3H-MPP+) was significantly enhanced (8-fold) over that in water-injected oocytes. Uptake of 3H-MPP+ was saturable (K(m) = 14.6 +/- 4.39 microM) and sensitive to membrane potential. Both small monovalent organic cations such as tetraethylammonium and N1-methylnicotinamide and bulkier organic cations (e.g., vecuronium and decynium-22) inhibited the uptake of 3H-MPP+. In addition, the bile acid taurocholate inhibited the uptake of 3H-MPP+ in oocytes expressing hOCT1. Northern analysis demonstrated that the mRNA transcript of hOCT1 is expressed primarily in the human liver, whereas the mRNA transcript of rOCT1 is found in rat kidney, liver, intestine, and colon [Nature (Lond.) 372:549-552 (1994)]. In comparison to rOCT1, hOCT1 exhibits notable differences in its kinetic characteristics and tissue distribution. The functional expression of hOCT1 will provide a powerful tool for elucidation of the mechanisms of organic cation transport in the human liver and understanding of the mechanisms involved in the disposition and hepatotoxicity of drugs.

A species comparison of 14C-labeled 7-ethoxycoumarin metabolism in precision-cut liver slices from guinea pig and dog using a phosphor imaging system

The metabolism of 14C-labeled 7-ethoxycoumarin (7EC) has been investigated in precision-cut liver slices from guinea pigs and dogs. 7EC was incubated with slices in 12-well plates (4 slices/well; n = 3) for up to 8 hr. In addition, a new simple method was established for analyzing 7EC and its metabolites simultaneously by using thin-layer chromatography-radioluminography (TLC-RLG). In both species, 7EC was taken up rapidly into the slices and metabolized extensively under the conditions used (no serum fraction supplemented), showing both phase I and phase II metabolism. In guinea pig medium samples, 4-ethoxy-2-hydroxyphenylacetic acid (EHPA) and 7-hydroxycoumarin (7HC) glucuronide were major metabolites. In dogs, conjugated 7HCs (with D-glucuronic acid and sulfate) were major products but EHPA was formed only to a small extent. These results suggest that deethylation in dogs occurs to a much greater extent than in guinea pigs. These results demonstrate the advantages of precision-cut liver slices as a powerful tool to investigate the species specific metabolism of xenobiotics, since the conditions employed enabled both phase I and phase II reactions in vitro.

Sex-dependent and independent renal excretion of nilvadipine metabolites in rat: evidence for a sex-dependent active secretion in kidney

1. To clarify the mechanism of sex-dependent and independent kidney secretion of major nilvadipine metabolites (3, 7) in rat, renal clearance corrected for protein binding and glomerular filtration rate (GFR) was measured in both sexes. The effect of probenecid, an inhibitor of organic anion transport, on these measurements was also investigated. 2. Clear sex-dependent active secretion was observed in the renal excretion of 3 (3-carboxylic acid pyridine derivative). In the female rat, 3, clearance was approximately 32-fold greater than GFR and was markedly decreased by probenecid. Conversely, in the male rat, renal clearance of 3 was only a fraction of GFR and was unaffected by probenecid. 3. Sex-independent active secretion was observed in the renal excretion of 7 (5-carboxylic acid pyridine derivative). In both sexes of rat 7 clearance was about 22-fold greater than GFR and was markedly reduced by probenecid. 4. A clear presence of sex-dependent and independent active secretion mechanisms in the kidney has been demonstrated in rat. The female rat is able to eliminate 3 and 7 in urine by an active secretion mechanism that is inhibited by probenecid. In the male rat, a transport mechanism for 7 is present, but either lacks or is apparently inactive for 3.

Interaction of renal excretion between nilvadipine metabolites, M3 and M7 in rats: characterization of sex-dependent and sex-independent active secretion in the kidney

The interaction of renal clearance between nilvadipine metabolites, M3 and M7, in male and female rats including protein binding and renal excretion was investigated to clarify the mechanisms involved. In male rats, active renal secretion of M7 (the 5-carboxylic acid pyridine derivative) was reduced in inverse proportion to the molar ratio of the plasma concentration M3/M7 after an i.v. dose of M3 (the 3-carboxylic acid pyridine derivative), and the dosed M3 was excreted only by glomerular filtration. In female rats, the active renal secretion of M7 was unaffected after an i.v. dose of M3, and the dosed M3 was excreted by active secretion. These results indicate an interference of the active secretion of M7 in male rats by M3 on competitive interaction at the renal tubular secretion, even though M3 was excreted only via a filtration process. Female rats may have two distinct and separate active renal secretion mechanisms for M7 and M3, even though these carboxylic acid compounds were eliminated by active transport in the kidney.

Clinical evaluation of chemotherapy under angiotensin II-induced hypertension in patients with advanced cancer

The clinical efficacy and indications for Angiotensin II (AT II)-induced hypertension chemotherapy were evaluated as a drug delivery system in 101 patients with advanced carcinoma. The sites of primary tumor studied included stomach (44), pancreas (18), colon (16), esophagus (6), bile duct (4), liver (3), breast (7) and 3 other single organs. Seventy four cases had distant metastases (lymph node (25), liver (29), peritoneum (16), and lung (4)). Additionally, the protocol was used 12 cases as postoperative adjuvant chemotherapy and 15 cases following exploratory laparotomy. The blood pressure was elevated to a level 1.5 times base-line. The regimens used consisted of MMC + ADR (55), FAM (38) and CDDP (8). The dosages administered were MMC 7 mg/m2, ADR 14 mg/m2 and 5-FU 350 mg/m2. The cancer chemotherapy protocol with AT II was repeated for an average of 2.6 cycles with a 2-3 week interval. The drug concentration in tumor tissues was increased 1.7 fold by AT II treatment. The response rate was 15.8% (CR 7 and PR 9), and in those patients with lymph node, liver and peritoneal metastases was 48.0, 6.9 and 6.3%, respectively. The serum levels of tumor markers decreased in 9 patients. Subjective symptoms, such as hoarseness, edema and pain, were improved. The mean survival in patients with distant metastasis who responded was 343 days, and in nonresponders was only 168 days (p less than 0.05). The side effects of this therapy were slight, typically being grade 1 and 2. Thus, the chemotherapeutic agents studied in conjunction with AT II were effective in patients with lymph node metastasis. Additionally, this regimen could be performed safely with minimal side effects.

Sex differences in the metabolism and excretion of nilvadipine, a new dihydropyridine calcium antagonist, in rats

1. The metabolic profiles of nilvadipine in the urine and bile of male and female rats were studied after i.v. dosing with 1 mg/kg of the 14C-labelled compound. 2. Excretion rates of the dosed radioactivity in male and female rats, respectively, in the first 48 h were 84.1% and 59.1% in bile, 12.0% and 36.9% in urine, and 2.5% and 3.6% in faeces. 3. Comparison of biliary and urinary excretion for each radioactive metabolite after dosing with 14C-nilvadipine, showed marked sex-related differences in the excretion routes of several metabolites. In male rats, metabolite M3, having a free 3-carboxyl group on the pyridine ring, was not excreted in urine, but in female rats urinary excretion of M3 accounted for 4.7% of the dose. One reason for the lower urinary excretion of radioactivity by males than by females was that the main metabolite, M3, was not excreted in the urine of the male rats. 4. To clarify the sex difference in the route of excretion of M3, this metabolite (M3) was given i.v. to rats. No excretion of the metabolite was observed in urine of male rats within 24 h but, in marked contrast, 41.5% of the dose was excreted in urine of females in the same period.

Metabolism of nilvadipine, a new dihydropyridine calcium antagonist, in rats and dogs

1. The metabolic profiles of nilvadipine in the excreta of male rats and dogs were studied after i.v. and oral dosing. Six types of metabolites were isolated and identified from the urine of male rats and dogs or bile of rats. 2. Several metabolites were detected in the urine (12) and bile (17) of rats by two-dimensional t.l.c., after dosing with 14C-nilvadipine. The metabolic profiles in the excreta of rats and dogs were qualitatively similar but quantitative differences were observed. 3. The main metabolites were products of (i) oxidation of the 1,4-dihydropyridine ring to the corresponding pyridine, (ii) hydrolysis of the 5-isopropyl ester or 3-methyl ester group to carboxylic acid, and/or (iii) hydroxylation of the 6-methyl group or methyl group of the isopropyl ester chain. 4. Minor metabolites were products of hydrolysis from the 5-isopropyl ester to the carboxylic acid having a dihydropyridine ring, or reduction of the 3-nitro group of the phenyl moiety having a pyridine ring.

Reaction mechanism of 21S dynein ATPase from sea urchin sperm. II. Formation of reaction intermediates

The amounts of ATP and ADP bound to 21S dynein during the ATPase reaction were measured in the presence of 2.83 mg/ml 21S dynein, 2 mM PEP, 4 mg/ml PK, 0.1 M KCl, 5 mM MgCl2, 1 mM DTT, 0.1 mM PMSF, 50% [2-3H]glycerol, and 20 mM imidazole at pH 7.0 and 0 degrees C. The maximum amounts of ATP and ADP bound to 21S dynein were 0.29 and 0.55 mol/(10(6) g protein), respectively. The dissociation constants of ATP for the ATP and ADP binding (4 microM) were almost equal to the Km value (3.7 microM) of dynein-ATPase in the steady state. The amount of bound ADP during the initial phase showed an overshoot, which reached 0.6-0.8 mol/10(6) g protein at 5 s, then decreased to the steady state level within 20 s. Furthermore, the rate of TCA-Pi liberation during the initial 5 s was 6 times the steady-state rate. The apparent Pi-burst size, estimated by extrapolating the steady-state Pi liberation to zero time, was 1.33 mol/(10(6) g protein). The true Pi-burst size was calculated to be 1.56 mol/(10(6) g protein) by correcting for the effect of Pi liberation at steady state. All these findings could be explained quantitatively by the following reaction scheme for 21S dynein ATPase in the presence of glycerol: (formula; see text) where K1 = 25.5 microM, and k2, k3, and k4 were 0.39, 0.21, and 0.11 s-1, respectively.

Reaction mechanism of 21S dynein ATPase from sea urchin sperm. I. Kinetic properties in the steady state

21S Dynein ATPase [EC 3.6.1.3] from axonemes of a Japanese sea urchin, Pseudocentrotus depressus, and its subunit fractions were studied to determine their kinetic properties in the steady state, using [gamma-32P]ATP at various concentrations, 5 mM divalent cations, and 20 mM imidazole at pH 7.0 and 0 degrees C. The following results were obtained. 1. 21S Dynein had a latent ATPase activity of about 0.63 mumol Pi/(mg . min) in 1 mM ATP, 100 mM KCl, 4 mM MgSO4, 0.5 mM EDTA, and 30 mM Tris-HCl at pH 8.0 and 25 degrees C. Its exposure to 0.1% Triton X-100 for 5 min at 25 degrees C induced an increase in the ATPase activity to about 3.75 mumol Pi/(mg . min) and treatment at 40 degrees C for 5 min also induced a similar activation. 2. The double-reciprocal plot for the ATPase activity of dynein activated by the treatment at 40 degrees C consisted of two straight lines, while that of nonactivated 21S dynein fitted a single straight line. 3. In low ionic strength solution, the Mg- and Mn-ATPase of 21S dynein showed substrate inhibition at ATP concentrations above 0.1 mM; the inhibition decreased with increasing ionic strength. Ca- and Sr-ATPase showed no substrate inhibition. 4. Both the Vmax and Km values of dynein ATPase decreased reversibly upon addition of about 40% (v/v) glycerol. In the presence of glycerol, the dynein ATPase showed an initial burst of Pi liberation. The apparent Pi-burst size was 1.0 mol/(10(6) g protein) and the true size was calculated to be 1.6 mol/1,250 K after correcting for the effect of Pi liberation in the steady state and the purity of our preparation. 5. One of the subunit fractions of 21S dynein which was obtained by the method of Tang et al. showed substrate inhibition and an initial burst of Pi liberation of 1.4 mol/(10(6) g protein) in the presence of 54% (v/v) glycerol.