Photocontrol of the germination of onoclea spores: v. Analysis of germination processes by means of temperature

The physiological nature of photoinduced germination of Onoclea sensibilis L. spores was investigated by temporarily applying a range of temperatures, particularly 40 C, before and after short light treatment. Controls were germinated at 25 C.     

LONGITUDINAL MICROFIBRILLAR ALIGNMENT IN THE WALL OF CYLINDRICAL NITELLA RHIZOIDAL CELLS: OBSERVATION UNDER POLARIZING AND INTERFERENCE MICROSCOPES

Polarizing and interference microscopes were employed to measure overall orientation of microfibrils and dry matter (expressed in optical thickness) in the cell wall of Nitella rhizoids. The microfibrils are aligned predominantly parallel to the cell's long axis (positively birefrengent), except in the apical dome where the arrangement appears to be random. The optical thickness, however, is greater at the very tip and the base region. The wall contains about 50-60% of acid extractable amorphous, noncrystalline substance. This extraction does not make a significant change in the alignment, but the remaining dry matter becomes less at the tip and increases slightly toward the base. The alignment parallel to the direction of cell growth in the rhizoidal cell is different from that of the elongating Nitella internodal cell where the alignment is transverse.     

Perturbance analysis of nuclear determination in Tetrahymena I: background, rationale, and illustrative example, employing temperature responses

A model based on comparative considerations, is presented for the nuclear determination of mating type in Tetrahymena thermophila. The model proposes a system of three binary control elements, each capable of stable persistence in one of two states. A general method is proposed for evaluating the model and for assigning particular mating types to particular compound states. Preliminary assignments of mating types are made from the responses of nuclei to temperature differentials.     

Hyphal anastomosis inPyricularia oryzae cav.

Summary Hyphal anastomosis inPyricularia oryzae occurs naturally in the lower epidermal cells and in the vascular bundles of young lesions on rice. In those cells the invading blast fungus are active. Two hyphal cells lying side by side start an anastomosis by forming two, one from each, very short penetration pegs which are opposite to each other. The cell wall of the pegs and the wall in the vicinity of them are then gradually eliminated and thus form a fusion aperture of 0.2–0.6 m in diameter that is big enough for the migration or exchange of nucleus and cytoplasm between two hyphal cells. The explanation of genetical variation inP. oryzae may be sought on the basis of the ultrastructural evidence of hyphal anastomoses presented in this paper.     

Recombinant human acid alpha-glucosidase generated in bacteria: antigenic, but enzymatically inactive.

Genetic deficiency of acid alpha-glucosidase (GAA) results in glycogen storage disease type II. To investigate whether we could generate a functional recombinant human GAA protein for future enzyme replacement therapy, we subcloned the GAA cDNA into the bacterial expression plasmid pMaI and analyzed the recombinant protein produced. This nonglycosylated recombinant human GAA was found to be antigenic by reacting with polyclonal rabbit antibody to human placental GAA using ELISA and Western techniques. However, the protein was not enzymatically active, suggesting that glycosylation may play a role in enzymatic function.     

与胎儿珠蛋白基因持续表达有关的(A_γδβ)°—地贫纯合子及杂合子的分子鉴别

我们分子鉴别了一个缺失型中国(A_γδβ)°-地贫家系。先证者为这一缺失的纯合子,具有中度贫血症状。家系的另五个成员均为这一缺失的杂合子,其胎儿血红蛋白(HbF)为16—21％,接近或达到HPFH杂合子的HbF水平,并且几乎不表现贫血症状。限制性内切酶图谱分析证明了β-珠蛋白基因簇内的DNA顺序缺失,缺失的5′端点位于Aγ基因IVSⅡ内,3′端点在β-珠蛋白基因下游区远端,距HPFH-2的3′缺失端点上游区约11kb。缺失的总长度约为80kb。本文讨论了这一缺失导致胎儿血红蛋白在成人中持续活跃表达的可能机制。     

Delayed removal of 125I-labeled very low density lipoprotein from plasma of rats with insulin-deficient diabetes mellitus.

The present studies demonstrate that the removal rate of exogenously labelled 125I-VLDL-protein is prolonged when total serum from insulin-deficient rats combined with isolated 125I-VLDL is injected into normal recipient rats (6.8 +/- 0.7 vs 4.2 +/- 0.4 min; p < 0.01), but not when 125I-VLDL-protein is isolated and injected alone (4.2 +/- 0.8 vs 4.3 +/- 0.8 min). Furthermore, the present studies demonstrate that when isolated 125I-VLDL-protein is recombined with either VLDL-free (d > 1.006 g/ml), or lipoprotein-free serum (d > 1.215 g/ml) from insulin-deficient rats, the defect in removal rate of VLDL-protein observed in total serum is reestablished (125I-VLDL + VLDL-free serum from insulin-deficient rat vs that from normal rat: 7.6 +/- 1.2 vs 4.6 +/- 0.7 min, p < 0.05; and 125I-VLDL + lipoprotein-free serum from insulin-deficient rat vs that from normal rat: 6.4 +/- 0.7 vs 4.1 +/- 0.4 min, p < 0.01). These data suggest that a factor or factors exist in lipoprotein-free serum of insulin-deficient rats which interfere with the normal removal of 125I-VLDL. Since we have previously demonstrated a prolongation in the removal rate of endogenously labeled VLDL-3H-TG, the defect in removal of VLDL from the plasma of insulin-deficient rats appears to include both the lipid and protein moieties of the VLDL particles.     

Induction of erythropoietin responsiveness in murine hematopoietic cells by the gag-myb-ets-containing ME26 virus.

ME26 virus, which was generated by inserting the coding region of the acute avian leukemia-inducing virus E26 into a murine retrovirus vector, encodes a 135-kDa gag-myb-ets fusion protein. Amphotropic murine leukemia virus pseudotypes of ME26 virus induce a high incidence of erythroleukemia 2 to 4 months after injection into newborn NFS/N mice. Spleen cells from the majority of these mice proliferate to high levels in the presence of the erythroid hormone erythropoietin (Epo) and can easily be established as permanent Epo-dependent cell lines. The cell lines contain multiple copies of ME26 viral DNA and express viral message and protein. An Epo receptor mRNA of normal size can be detected in these cells, and binding studies reveal a single class of lower-affinity Epo receptor with an affinity for Epo that is in the range of that previously reported for erythroid cells. The ME26 virus-induced Epo-dependent cell lines, however, appear more immature than previously described erythroid cell lines and more closely resemble early hematopoietic precursor cells, suggesting that the virus may be activating the Epo receptor in hematopoietic cells that do not normally express it. Consistent with this idea, we are able to infect an interleukin-3-dependent myeloid cell line, FDC-P2, with ME26 virus and convert it to Epo dependence. The ME26 virus-infected FDC-P2 cells, even before growth on Epo, showed a large increase in the amount of Epo receptor mRNA. However, no ME26 viral integrations can be detected adjacent to the Epo receptor gene, indicating that the virus is not activating the Epo receptor gene by promoter/enhancer insertion. Our results are more consistent with the hypothesis that the gag-myb-ets-encoded viral fusion protein, which is known to bind DNA, is directly or indirectly activating the expression of the Epo receptor gene in these cells.     

A molecular thermodynamic approach to predict the secondary structure of homopolypeptides in aqueous systems.

Under physiological conditions, many polypeptide chains spontaneously fold into discrete and tightly packed three-dimensional structures. The folded polypeptide chain conformation is believed to represent a minimum Gibbs energy of the system, governed by the weak interactions that operate between the amino acid residues and between the residues and the solvent. A semiempirical molecular thermodynamic model is proposed to represent the Gibbs energy of folding of aqueous homopolypeptide systems. The model takes into consideration both the entropy contribution and the enthalpy contribution of folding homopolypeptide chains in aqueous solutions. The entropy contribution is derived from the Flory-Huggins expression for the entropy of mixing. It accounts for the entropy loss in folding a random-coiled polypeptide chain into a specific polypeptide conformation. The enthalpy contribution is derived from a molecular segment-based Non-Random Two Liquid (NRTL) local composition model [H. Renon and J. M. Prausnitz (1968) AIChE J., Vol. 14, pp. 135-142; C.-C. Chen and L. B. Evans (1986) AIChE J., Vol. 32, pp. 444-454], which takes into consideration of the residue-residue, residue-solvent, and solvent-solvent binary physical interactions along with the local compositions of amino acid residues in aqueous homopolypeptides. The UNIFAC group contribution method [A. Fredenslund, R. L. Jones, and J. M. Prausnitz (1975) AIChE J., 21, 1086-1099; A. Fredenslund, J. Gmehling, and P. Rasmussen (1977) Vapor-Liquid Equilibrium Using UNIFAC, Elsevier Scientific Publishing Company, Amsterdam], developed originally to estimate the excess Gibbs energy of solutions of small molecules, was used to estimate the NRTL binary interaction parameters. The model yields a hydrophobicity scale for the 20 amino acid side chains, which compares favorably with established scales [Y. Nozaki and C. Tanford (1971) Journal of Biological Chemistry, Vol. 46, pp. 2211-2217; E. B. Leodidis and T. A. Hatton (1990) Journal of Physical Chemistry, Vol. 94, pp. 6411-6420]. In addition, the model generates qualitatively correct thermodynamic constants and it accurately predicts thermodynamically favorable folding of a number of aqueous homopolypeptides from random-coiled states into alpha-helices. The model further facilitates estimation of the Zimm-Bragg helix growth parameter s and the nucleation parameter sigma for amino acid residues [B. H. Zimm and J. K. Bragg (1959) Journal of Chemical Physics, Vol. 31, pp. 526-535]. The calculated values of the two parameters fall into the ranges suggested by Zimm and Bragg.