Tolerance induced by grafting semi-allogeneic adult skin to larval Xenopus laevis: Possible involvement of specific suppressor cell activity

Major histocompatibility complex (MHC)-homozygous Xenopus laevis were rendered tolerant to semi-allogeneic antigens by grafting skins of adult frogs during larval stages (larvally induced tolerance), and this tolerant state was compared with the tolerance induced in early thymectomized frogs by the grafting of semi-allogeneic nonlymphoid thymuses (thymus-reconstituted tolerance). In contrast to a total inability of thymus-reconstituted frogs both to reject skins and to exhibit a mixed leukocyte reaction (MLR) against the semi-allogeneic donor, larvally induced tolerant frogs showed a strong MLR against leukocytes of the tolerizing skin donor (split tolerance). Breakdown of the tolerant state in thymus-reconstituted frogs were easily accomplished by inoculation with syngeneic splenocytes, but this breakdown was extremely difficult to achieve in frogs with larvally induced tolerance. The injection of splenocytes from larvally induced tolerant frogs into normal frogs significantly suppressed semi-allogeneic graft rejection in the latter group; no suppression was obtained when splenocytes from thymus-reconstituted frogs were used. In addition, in the thymectomized frogs, recovery of allograft rejection capacity against the pertinent semi-allogeneic antigens were suppressed by the injection of splenocytes from larvally induced tolerant frogs, with the degree of suppression depending on the splenocyte dose. These results indicate that the larvally induced tolerant state is maintained by specifically induced suppressor cells affecting the in vivo allograft response but not the MLR.     

Carboxyl-terminal deletion analysis of the Streptococcus mutans glucosyltransferase-I enzyme

Sequential deletion of the carboxyl-terminal amino acids (including the six direct repeating units) of the glucosyltransferase-I (GTF-I) enzyme of Streptococcus mutans revealed differential effects on sucrase and GTF activities. Removal of all but one repeating unit resulted in a truncated enzyme with significant sucrase activity but no detectable GTF activity. These results are compatible with the presence of two functional domains in the enzyme.     

High pressure conditions stimulate expression of chloramphenicol acetyltransferase regulated by the lac promoter in Escherichia coli

Abstract Recombinant plasmids with the chloramphenicol acetyltransferase (CAT) structural gene behind several kinds of promoters were tested for expression in Escherichia coli during growth at atmospheric pressure (0.1 MPa) and at high pressure (30 MPa). Expression of the CAT gene from the lac promoter was remarkably activated (approx. 78-fold) by high pressure in the absence of the inducer isopropyl-β-d-thiogalactopyranoside (IPTG). The stimulation of the CAT activity by the lac promoter at high pressure did not simply result from an increased plasmid copy number, because the CAT activities from the other promoters and β-lactamase activities were unaffected at high pressure.     

Remodeling of Human Sperm Chromatin Mediated by Nucleoplasmin from Amphibian Eggs

The molecular events associated with decondensation of human sperm nuclei were analyzed by incubating sperm with egg extracts from an amphibian, Bufo japonicus . Acid-urea-Triton polyacrylamide gel electrophoresis (AUT-PAGE) showed that the nuclear basic proteins of human sperm consist mainly of protamines (HPI, HPII) with minor amounts of nucleosomal histones. On incubation of lysolecithin (LC)- and dithiothreitol (DTT)-treated human sperm with the egg extract, the nuclei lost HPI and HPII within 15 min in association with extensive nuclear decondensation, and the acquirement of a whole set of nucleosomal histones. Incubation of LC-DTT-sperm with nucleoplasmin purified from Bufo eggs also induced nuclear decondensation and loss of protamines within 30 min. Native-PAGE and Western blot analyses of incubation medium indicated tight association of the released protamines to nucleoplasmin, strongly suggesting that protamines are removed from sperm nuclei not enzymatically but by their specific binding to nucleoplasmin. On incubation of LC-DTT-sperm with nucleoplasmin and exogenous nucleosomal core histones, micrococcal nuclease-protected DNA fragments were released, although their unit repeat length was slightly less than that of somatic nucleosomes. Thus remodeling of human sperm during fertilization can be mimicked under defined conditions with nucleoplasmin and exogenous histones.     

Characterizations and constructions of reverberating networks

Consider the family $\text{G}$_n of all n neuron networks whose dynamical behaviors are described by Caianiello's neuronic equations, and also its subfamily $\text{R}$_n of all reverberating networks each of whose neuronic equations have only periodic solution (states), i.e., without having any transient states. This paper is specifically concerned with characterizations of the subfamily $\text{R}$_n. First, we show that $\text{R}$_n is contained in a subfamily $\text{S}$_n of $\text{G}$_n consisting of all self-dual networks. We introduce Chow's matrix corresponding to each network of $\text{S}$_n, using Chow parameters and some algebraic operations {$\text{2}$_α} applied to the coefficient matrix of the network in $\text{S}$_n, such as interchanges of coefficients between two neurons or changes of their signs. Then we give some necessary conditions on Chow's matrix under which any network in $\text{S}$_n belong to $\text{R}$_n, and a necessary and sufficient condition on the coefficient matrix. We also discuss relations between Chow's matrix and the maximum period of reverberations. In particular, it is shown that Chow's matrix of a network in $\text{R}$_n is symmetric if and only if the maximum period of reverberations is less than three. By virtue of these results, we propose two methods of construction of networks in $\text{R}$_n. The first method is an inductive construction. The second is based on the algebraic operations.     

Distribution of gangliosides in parenchymal and non-parenchymal cells of rat liver

Parenchymal and non-parenchymal cells were isolated from rat liver with purities of more than 90%. Total and ganglioside sialic acid contents were higher in non-parenchymal cells than in parenchymal cells. Thin-layer chromatography of gangliosides showed that the main component in rat liver was ganglioside GM3 and that this was abundant in non-parenchymal cells. Parenchymal cells had ganglioside GD1b as the main component and less GM3 than non-parenchymal cells. These results suggested that the main ganglioside of rat liver, GM3, arises mainly from non-parenchymal cells.     

Changes in intracellular location of DNA polymerase-α during oocyte maturation of the toad,bufo bufo japonicus

Intracellular location of DNA polymerase-α during oocyte maturation of the toad was studied. Quantitative and qualitative changes in the activity of DNA polymerase-α were not observed during the maturational process. Nearly all activity was found in isolated germinal vesicles from full grown oocytes and in enucleated mature oocytes. The cytoplasmic DNA polymerase-α of mature oocytes was recovered at buoyant densities equivalent to microsome by isopycnic centrifugation. These findings indicate that DNA polymerase-α in the germinal vesicle is released into the cytoplasm and binds to the endoplasmic reticulum when the germinal vesicle breaks down.