The exchange of phosphatidyicholine was investigated between two separate monolayers and between monolayer and liposomes. The phosphatidylcholine exchange protein from beef liver acted in those systems as a carrier of phosphatidyicholine.
Haematology. Edited by William S. Beck. (Harvard Pathophysiology Series, Vol. 1.) Pp. xii + 366. (MIT: Cambridge, Massachusetts and London, May 1973.) $14.95.
LIFE in the cell is a function of its membranes. Much current research effort is directed toward the plasma membrane because of its profound importance in transport, cell recognition and many other communication processes.
DNA base sequence complexity is commonly calculated from k′2, the observed second order rate constant of renaturation corrected to constant molecular weight and defined renaturation conditions1–4. Several investigators have cautioned that k′2 is influenced by base pair mismatching in the reacting DNA sequences5–7, but no other serious difficulties have been noticed in using k′2 values to measure base sequence complexity except for the case of mouse satellite DNA. Waring et al.3 and Flamm et al.8 calculated a repeat length of 350 nucleotides from k′2 measurements, but Southern9 found a repeating unit of approximately twelve nucleotides by analysis of pyrimidine tracts. Hutton and Wetmur10 have recently shown that the kinetic complexity of mouse satellite DNA defies conventional analysis: the apparent repeat size calculated from k′2 depends upon the DNA fragment size. I shall show that for a particular kind of DNA structure, of which mouse satellite DNA is an example, the usual method of calculating base sequence complexity from k′2 cannot be used. The difficulty stems from an altered molecular weight dependence of k2 for DNA repeated sequences which are shorter than the length of the reacting DNA strands.
ACCORDING to the Lyon principle of X chromosome inactivation, somatic cells of mammalian females form random mosaic populations resulting from irreversible and heritable differentiation of the two X chromosomes at an early stage of development. One X chromosome remains capable of gene transcription, the other becomes unresponsive to inducers and remains genetically inert1. Consequently, any one cell only expresses genes that are located on either the maternal or paternal X chromosome. Data in support of this principle have come from in vivo studies of X-linked murine coat colour genes2 and in vitro studies of X-linked human genes that are expressed in cultured cells3. Furthermore, two non-allelic X-linked loci tested in the same population of cloned cells are expressed in the cis position as would be expected from a single parental contribution8.
ADENO-ASSOCIATED satellite viruses (ASV)1,2, like other members of the parvovirus group, contain single-stranded DNA3. However, satellite viruses are unique in that each capsid contains either a plus or a minus strand of nucleic acid4,5. Although adeno-associated satellite viruses are extreme in their defectiveness and they do not appear to replicate unless viable adenoviruses6,7 or herpes viruses8–10 are present in the system, they do apparently code for their own protein coats which are antigenically distinct from those of the helper adenoviruses11,12. Adeno satellite viruses interfere with the growth of helper adenoviruses13 and also with each other14.
Precursors to the bacteriophage T4 tRNAs consist of polynucleotide chains containing two tRNA species
AFTER addition of various mitogens such as phytohaemagglutinin (PHA) in vitro lymphocytes shift from a “resting” state to one of rapid enlargement, culminating in DNA synthesis and mitosis. The mechanism initiating transformation and proliferation is not yet fully understood. Some observations, however, suggest that alterations of cellular membranes might be involved in these processes. In their cytochemical studies, Allison and Mallucci1 observed increased permeability of lysosomes in normal human peripheral blood lymphocytes after exposure to PHA for 5 h. Hirschhorn et al.2 demonstrated that during the early phase of stimulation 30–120 min after addition of PHA in normal human blood lymphocytes a redistribution of lysosomal acid hydrolases from a sedimentable into a non-sedimentable form as well as an increased release by agents which disrupt membranes, such as streptolysin S and filipin, of lysosomal enzymes from a subcellular fraction rich in lysosomes are taking place. It has been suggested that these alterations, both reflecting enhanced fragility of lysosomal membranes, might be due to increased endocytosis induced by the mitogen and the hypothesis was raised that lysosomal hydrolases might be involved in intracellular processes leading to lymphocyte activation2. We have therefore studied the fragility of lysosomes in unstimulated and PHA-treated lymphocytes from patients with chronic lymphocytic leukaemia (CLL), because lymphocytes in most patients with this disease show a diminished and/or delayed or even no response to PHA3 and other mitogens4,5.
THE agglutination of erythrocytes by phytohaemagglutinin (PHA) from seeds of Phaseolus was first reported by Land-steiner and Raubitschek in 19081. Since then much work has been published on their effects on mammalian cells but little is known of their role in the plants from which they are derived. Saint-Paul2 suggested that PHA might be plant antibodies produced in response to antigenic stimulation by Rhizobium species, but his studies proved inconclusive. We have explored the possibility that the symbiotic relationship between Rhizobium phaseoli and beans (Phaseolus vulgaris L.) is influenced by PHA. Our hypothesis is that PHA may bind the bacteria to the roots.
To celebrate the year of centennial of X-ray discovery, we have to consider future development of radiology in 21st century. Since WC Röntgen discovered X-ray in 1895, the radiological science have been continuously expanded. Even reviewing the history of radiology in Japan, there have been several epoch-making masterpieces. We Japanese radiologists should be more proud of Japanese radiology. It is evident that radiology of the 21st century will develop more and more on the basis of computer technology. In clinical radiology, every procedure will become more rapid and non invasive, and imaging diagnoses cover not only morphology but also function of tissue and/or cell components. To foresee the future, it is essential to understand radiology in the past and the present. In this lecture, I have reviewed a history of radiology in Japan, clarified the problems at the present and emphasized the importance of computer skill. I would like to ask all of Japanese radiologists to march forward in the midstream of medical science in cooperation of Japanese society of Radiological Technology and Industries.
The DNA promoter sites for rRNA transcription undergo a cooperative transition between two conformational states. These states determine the rate of rRNA synthesis in vitro.
THE sex pheromone of the oriental fruit moth, Grapholitha molesta (Busck), which is emitted by the female to lure the male for mating, was reported by Roelofs et al. to be (Z)-8-dodecen-1-ol acetate1 (formerly referred to as cis-8-dodecen-1-ol acetate). The attraction of this lure is enhanced by the addition of a ten-fold quantity of synergist, dodecyl alcohol2.
THE aim of this report is to show that B lymphocytes can be active against tumour cells in vitro. Lymphocytes from Balb/c mice in which primary Moloney sarcoma virus (MSV) tumours have regressed are active in vitro against target cells bearing the Moloney leukaemia virus (MLV) determined cell surface antigen but not against control cells which are MLV antigen negative1,2. Fractionation of the lymphocytes in this system has shown the active effector cells to be both thymus processed lymphocytes (T cells)3 and non-T cells3,4. Both subpopulations are active before peak tumour size and soon after regression3. The T cell activity rapidly fades following regression3, whereas the non T-cell activity persists in regressors and by 30 d after virus infection the non-T cell activity is high and the T cell activity is low or undetectable3,4.
ONE of the basic problems of immunology is the distinction between self and non-self1. The mechanism of self non-reactivity (self tolerance) is not yet known in detail, but since unimpaired self reactive B cells have been detected in several circumstances it now seems that self tolerance is essentially a property of T cells2–4. An understanding of the mechanism by which virgin T cells discriminate between immunity (to non-self) and tolerance (to self) is thus the key to understanding self tolerance.
INJECTION of 6-hydroxydopamine (6-OHDA) in the cell bodies of the substantia nigra of the rat has been found to produce a selective degeneration of the nigro-striatal dopaminergic pathway1. Electron microscopic2 and biochemical3 investigations have determined the specificity and extent of the nigral 6-OHDA induced damage. This model has been used in the present work to study the metabolism of dopamine (DA) in striatal nerve terminals of still undamaged neurones after different partial destructions of the nigro-striatal dopaminergic system.
IN the past few years, several laboratories have used the principle of single step mutation in attempts to probe the visual processes of Drosophila melanogaster1–4 and have found several loci, mutations of which result in impaired vision and either complete absence of, or alteration of, the shape of the electroretinogram (ERG).
