Two monoclonal antibodies against small-cell lung cancer show existence of synergism in binding

Summary Murine IgG1 monoclonal antibodies (mAbs), ITK-2 and ITK-3, were generated against a small-cell lung cancer (SCLC) cell line. Enzyme-linked immunosorbent assay using a variety of established cell lines as substrates, immunoperoxidase staining of freshly frozen tissue sections, and fluorescence-activated cell sorter analysis of peripheral blood leukocytes showed that these mAbs recognize a part of the SCLC-associated cluster 1 antigen. In immunoprecipitation studies, both ITK-2 and ITK-3 bound to a 145-kDa glycoprotein of SCLC cell membrane extracts, as did MOC-1 and NKH-1, which both recognize the cluster 1 antigen. However, because the binding of¹²⁵I-labeled ITK-2 to SCLC cells was not inhibited by MOC-1 or NKH-1, the binding site of ITK-2 on SCLC cells appeared to be different from that of either MOC-1 or NKH-1. Unexpectedly, binding of¹²⁵I-labeled ITK-2 to SCLC cells increased in the presence of ITK-3. This ITK-3-induced increase in ITK-2 binding was due partly to an increase in the number of binding sites for ITK-2 on SCLC cells. Addition of ITK-3 may, therefore, improve the effectiveness of ITK-2-based tumor detection or therapy.     

Incorporation of fatty acids by Streptococcus mutans

In a series of investigations into the cariogenicity of Streptococcus mutans, we studied the incorporation of exogenous fatty acids with reference to glucosyltransferase secretion and membrane fatty acid changes. When cells were grown with different fatty acids, both saturated and unsaturated fatty acids were readily incorporated into the membrane lipids and were biotransformed and elongated preferentially to the longer 16- and 18-carbon-chain fatty acids. This incorporation and chain-elongation led to significant changes in fatty acids composition. By adding fatty acids to the medium, it was possible to appropriately modify the degree of unsaturation and the relative ratio between specific fatty acids in the membrane lipids of S. mutans.     

Identification of two cell-cycle-controlling cdc2 gene homologs in Arabidopsis thaliana

The cdc2 gene product (p34cdc2) has been thought to play a central role in control of the mitotic cell cycle of yeasts and animals. To approach an understanding of the cell-cycle-control system in higher plants, we isolated, from an Arabidopsis thaliana cDNA library, two clones (CDC2a and CDC2b) similar to the Schizosaccharomyces pombe cdc2 gene. Genomic Southern-blot analysis with the CDC2a and CDC2b cDNA probes suggested that the A. thaliana genome contains several additional cdc2-like genes, which together with the CDC2a and CDC2b genes may constitute a CDC2 gene family. The CDC2a cDNA expressed in Sc. pombe corrected the elongated morphology, caused by the temperature-sensitive cdc2-33 mutation, to the normal shapes, indicating that the A. thaliana CDC2a gene product resembles Sc. pombe p34cdc2 functionally as well as structurally. These results support the view that the cell cycle of higher plants is controlled by an analogue of a p34cdc2-centered regulatory system like that of yeasts and animals.     

Cloning of a rabbit brain glucose transporter cDNA and alteration of glucose transporter mRNA during tissue development

A full-length cDNA clone that codes for glucose transporter protein was isolated from a rabbit brain cDNA library by using synthetic oligonucleotide probe derived from the sequence of human glucose transporter cDNA. The coding region shared 93.2% nucleotide and 97.0% amino-acid similarities with those of human glucose transporter and 89.4% nucleotide and 97.4% amino-acid similarities with those of rat transporter. Northern blot analysis revealed that glucose transporter mRNA is most abundant in the placenta and that it is also abundant in the brain. The fat tissue, heart, liver, and skeletal muscle of adult rats contained a very small amount of mRNA, while heart, liver, skeletal muscle and kidney of fetal rats contained a very high amount of glucose transporter mRNA. These results suggest that this type of glucose transporter might be closely related with cell proliferation and tissue development.     

A note on a theoretical study of erythrocyte sedimentation in inclined tubes

The expression for the sedimentation rate in inclined tubes given by Nakamura et al (Nakamura, H. and Kuroda, K. Keijo J. Med. 8, 256-296, 1937) is improved to be applicable to the problem that the falling velocity of a particle from the top wall of the tube v' differs from the one from the interface between the particle free layer and the suspended layer v. The effects of the shape at the bottom of the tube and the increase in height of the layer closely packed with particles are taken into account.     

Visual interneurons in the lobula complex of the fleshfly,Boettcherisca peregrina

Summary The physiology and morphology of visual interneurons in the lobula complex of the fleshfly,Boettcherisca peregrina, were studied using intracellular recordings and intracellular cobalt stainings, respectively. Using responses to movements of a spot of light and on-off stimuli at single positions, we classified the interneurons into five physiological groups ON, OFF, ON-OFF, nondirectional motion sensitive (NDM) and directional motion sensitive (DM) neurons. They could be further divided into four morphological types, depending on the location and extent of their dendrites and terminal branches.     

Analysis of apolipoproteins in high density lipoproteins by high performance liquid chromatography

A simple and rapid method for the analysis of apolipoproteins in high density lipoprotein (HDL) by high performance liquid chromatography (HPLC) has been developed (Kinoshita et al. (1983) J. Biochem. 94, 615-617). With this method, using a sodium phosphate buffer containing 0.1% sodium dodecyl sulfate (SDS) as an eluent, apolipoproteins can be analyzed from a very small amount of HDL fraction without delipidation using organic solvents. Separation profiles of apolipoproteins by this method were examined using several techniques. The elution pattern monitored by A280 can give precise quantitative as well as qualitative information about size-distribution of apolipoproteins, except for the apo C group. Moreover, separation of apo E from apo A-I was found to be improved by column elongation.     

The Lyt phenotype of the T cells responsible for in vivo tumor rejection in syngeneic mice

Summary Spleen cells of BALB/c mice hyperimmunized with a transplantable methylcholanthrene-induced sarcoma Meth A (Meth A-Im-SPL) inhibited the growth of Meth A tumor in vivo in a tumor neutralizing test. Meth A-Im-SPL did not neutralize another antienically distinct sarcoma, Meth 1, indicating that the antitumor activity is tumor specific. Lyt-1⁺2^– cells of Meth A-Im-SPL (Im-Lyt-1⁺2^–) were the effectors since in vitro treatment of Meth A-Im-SPL with anti-Thy 1.2 or anti-Lyt 1.2 antibody plus complement completely abrogated their neutralizing activity, whereas treatment with anti-Lyt 2.2 plus complement did not. To further confirm the effector activity of Im-Lyt-1⁺2^– cells, T cell subpopulations were separated from Meth A-Im-SPL by the panning method. The purified Im-Lyt-1⁺2^–, but not Im-Lyt-1⁺2⁺ cells neutralized the tumor in athymic nu/nu mice as efficiently as in +/+ mice, suggesting that the donor Im-Lyt-1⁺2^– cells but not recipient T cells were primarily responsible for neutralizing the tumor. The present study, however, did not exclude the possible contribution of recipient T cells to the tumor neutralization and this is open to further investigation.Abbreviations Meth A-Im-SPL Meth A-immune mouse spleen cells - Meth 1-Im-SPL Meth 1-immune mouse spleen cells - sIg⁺ cells surface immunoglobulin positive cells - moAb monoclonal antibody     

Intracistronic mapping of the defective site and the biochemical properties of beta subunit mutants of Escherichia coli H+-ATPase: correlation of structural domains with functions of the beta subunit

Sixteen mutants of Escherichia coli defective in H+-ATPase (proton-translocating ATPase) were tested for their ability to recombine with hybrid plasmids carrying various portions of the beta subunit cistron. Twelve mutations were mapped within the carboxyl half of the cistron corresponding to amino acid residues 279 to 459 (domain II), while four mutations were mapped within residues 17 to 278 (domain I). The biochemical properties of these mutants were analyzed in terms of the proton permeability of their membranes and the assembly properties of their F1F0 complex. The mutants were classified according to the properties into three types, I, II, and III. In 12 mutants of type I, proton conduction in membrane vesicles was blocked and little F1 was released from the membranes under conditions in which F1 could be released from wild-type membranes, suggesting that assembly of the F1F0 complex is structurally and functionally defective. F1 was partially purified with very low recovery from one of the type I mutants, KF16. ATPase activity was reconstituted from this F1 with the beta subunit of the wild type, confirming the genetic results. Only one mutant, KF38, was classified as type II. Its membranes were partially leaky to protons and its F1 was releasable, suggesting that the interaction of its F1 and F0 was unstable. Type III mutants, KF11 and KF43, had an F1F0 complex with very low activity, in which the structure of F1 was relatively similar to that of the wild type. F1 was purified as a single complex from KF43 in this study and from KF11 previously (H. Kanazawa, Y. Horiuchi, M. Takagi, Y. Ishino, and M. Futai (1980) J. Biochem. 88, 695-703). Reconstitution experiments in vitro showed that the F1's of both mutants were defective in the beta subunit. The properties of the altered F1 of KF43 differed from those of F1 of KF11, suggesting that the mutation sites of KF43 and KF11 were different. From the results of mapping mutation sites and the biochemical properties of the mutants, the correlation of structural domains with function of the beta subunit is discussed. Most type I and type II mutations except that of KF39 were mapped in domain II, while the type III mutations were mapped in domain I, suggesting that domain II is more important than domain I for the function of the beta subunit, especially in terms of proper assembly of the F1F0 complex.     

Possible physiological role of epidermal growth factor in the development of the mouse mammary gland during pregnancy

Epidermal growth factor stimulated cell proliferation in a primary mammary epithelial cell culture derived from mice at different stages of pregnancy. Moreover, the peptide hormone inhibited casein production induced by the synergistic actions of insulin, cortisol and prolactin. The inhibitory effect of epidermal growth factor was influenced by the gestational stages of the mammary gland. These effects of epidermal growth factor were exerted at physiological concentrations. The dual actions of epidermal growth factor on mammary cells implicate its participation in regulation of the growth and differentiation of the mammary gland during pregnancy.