The missense mutation causing G71R is the first reported polymorphism for UGT1A1, and the mutation is a risk factor for nonphysiologic neonatal hyperbilirubinemia. The high incidence of hyperbilirubinemia in the Japanese may be attributable to the high frequency of this missense mutation.
In our mutation analyses of bilirubin UDP glycosyltransferase (UGT1A1) gene, we encountered six patients with Crigler-Najjar syndrome type II who were double homozygotes for G71R and Y486D, a patient with Gilbert's syndrome who was a single homozygote for G71R and six patients with Gilbert's syndrome who were single heterozygote for G71R. To clarify the role of each mutation in the occurrence of the two syndromes, we made four mutant expression models. Relative UGT1A1 activity of a single homozygous model of G71R was 32.2+/-1.6% of normal, that of a single homozygous model of Y486D was 7.6+/-0.5%, that of a double homozygous model of G71R and Y486D was 6.2+/-1.6% and that of a heterozygous model of G71R was 60.2+/-3.5%. The decreased activities of the single homozygous model of G71R and the double homozygous model were at an appropriate level to be diagnosed as Gilbert's syndrome and CN-II, respectively. The activity of a single heterozygous model of G71R was somewhat high to develop to the phenotype of Gilbert's syndrome, suggesting the presence of additional factors for the etiology of Gilbert's syndrome.
Distantly related varieties of cultivated rice (Oryza sativa L.) often show partial sterility in their F1 hybrids.The senior writer formerly demonstrated that this sterility could be accounted for by gametic-development genes, i.e., duplicate genes whose double recessive combinations interrupt the development of gametes carrying them (Oka 1953(Oka , 1957b. This hypothesis could plausibly explain segregation in certain ratios of fertile and partially sterile plants in experimental crosses, modification of F2 ratios for various characters and other phenomena characteristic of the hybrid sterility in cultivated rice.However, on its basis, sterility should occur only in heterozygotes for the gametic development genes. Thus, a fertile plant should produce only fertile plants in the progeny, while a semi-sterile plants should produce fertile plants and semi-sterile ones whose fertility is not lower than that of the parent, and a true-breeding semisterile line could not be established.Actually, partially sterile plants have often been found in the F2 and later generations derived from a highly fertile F1 hybrid, and lines true-breeding for sterility appeared in the progeny of such partially sterile plants.The present study showed that besides the gametic-development genes, there is another genic system responsible for the sterility in hybrid derivatives. Materials and MethodsAs mentioned in a previous paper of this series (Oka 1954), many rice strains from various Asian countries were crossed with a certain set of test-strains in order to survey the pattern of hybrid sterility relationships.Using a part of those crosses, fertility variations in F2 and later generations were observed. The parental strains, which were established after repeated self-pollination from a single plant, could be regarded as virtually pure, and were completely self-fertile. The partially sterile lines used for the present work were obtained from the above-mentioned crosses. Detailed accounts for particular strains and methods of analysis of the data will be given together with the results.
Oscillation and activated hyperpolarizing responses induced by electrical stimuli (H.A. responses) were studied in large nondividing L ceils (giant L cells) under a variety of ionic conditions. When C1-in the bathing fluid was partially replaced with SO 2-at fixed external Na + and K + concentrations, the membrane potential depolarized transiently, but recovered to the original potential level after about 10 rain. Under such a steady state in a low-C1-medium, the amplitudes of oscillations and H.A. responses remained almost identical with those in the control medium. On exposure to a low-Na + medium, both membrane potentials in the resting and hyperpolarized states were slightly hyperpolarized, but the pattern and the amplitude of oscillations and H.A. responses remained much the same. Changes in external K + concentrations remarkably affected the amplitudes of oscillations and H.A. responses: the amplitudes decreased with increases in external K + concentration. Calculation of the changes in K +, Na + and C1conductances during oscillations and H.A. responses under these various ionic conditions showed that the change in K + conductance is the only factor responsible for the oscillation and the H.A. response. The reversal potential for the potential oscillation is about -94mV under normal conditions, this value being quite close to that of the equilibrium potential of K +. The reversal potentials in various external K + concentrations satisfied the Nernst equation for a K + electrode. Valinomycin induced remarkable hyperpolarization of the resting potential, resulting in an inhibition of oscillations. The level of valinomycin-induced hyperpolarization of the resting potential required to inhibit H.A. responses was the same as that of the peak potentials of the oscillation and H.A. response. In the light of these observations, it is concluded that the spontaneous potential oscillation and the H.A. response are caused solely by increase in the K + conductance of the cell membrane.Nelson, Peacock and Minna (1972) found that L cells responded to an electrical, mechanical or chemical stimulus by producing a hyper-* Present Address: D6partment de physique, Universit6 de Montr6al,
Dielectric dispersion measurements over a frequency range 0.01-100 MHz were made with the suspensions of a cultured cell line, mouse lymphoma L5178Y, and an attempt to explain the observed dielectric behavior by taking explicitly into consideration the possible involvement of cell nucleus has been presented. The use of a conventional "single-shell" model in which the cell is represented by a homogeneous sphere coated with a thin limiting shell phase did not duplicate the observed dispersion curves, whereas a "double-shell" model in which one additional concentric shell is incorporated into the "single-shell" model gave a much better fit between the observed and the predicted dispersion curves. Based on the latter model, we analyzed the raw data of dielectric measurements to yield a set of plausible electrical parameters for the lymphoma cell: CM approximately or equal to 1.0 muF/cm2, CN approximately or equal to 0.4 muF/cm2, epsilonk approximately or equal to 300, kc/ka approximately to or equal to 0.9, and kk/kc approximately or equal to 0.7. Here, CM and CN are the specific capacities of plasma and nuclear membranes; epsilon and k are the dielectric constant and conductivity with subscript a, c and k referring respectively to the extracellular, the cytoplasmic and the karyoplasmic phases.
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