Effects of seed-irradiation on meiosis in M1 plants of Lactuca and related plants

Meiosis was studied in control and seed-irradiated materials of Lactuca sativa, cultivars Tom, Cos and Webbs, L. serriola from the wild, and Cichorium intybus. In meiosis of the M₁ plants from irradiated seed, observations of univalent and multivalent formation, bridge formation at Anaphase I and II, micronucleus formation and persistence, and pollen fertility, were carried out, and compared with controls. Quantitative estimations of bridge formation were made in L. sativa Tom and Cos and in L. serriola, at anaphase I only. It was found that the frequency of anaphase I bridges and reduction of pollen fertility in the M₁ and also M₂ generation, were different for each variety or species; these could be sequenced radiation-resistant to sensitive in the order Tom, Cos and L. serriola.     

Low degree of ubiquitination of histone 2A in the dipteran Chironomus tentans

A polyclonal antibody to ubiquitin has been prepared and shown to react with both ubiquitin and ubiquitinated histone 2A (uH2A). Applying this antibody in Western blotting experiments, we have observed that the salivary glands of Chironomus tentans contain an unusually low amount of uH2A (1% of histone 2A), while the amount of free ubiquitin is as abundant as in other animal cells, e.g. HeLa cells. The same low content of uH2A was also found in diploid epidermal cells of Chironomus origin suggesting that the low amount is not a characteristic of the polytene state of chromatin in salivary gland cells but rather a property of C. tentans as a species. The significance of the low degree of ubiquitination is discussed in relation to the information available on the organization of Chironomus chromatin into unusually large chromomeric entities.     

Intramuscular loading dose of quinine for falciparum malaria: pharmacokinetics and toxicity.

In a study of intramuscular injection of quinine eight adults with moderately severe falciparum malaria resistant to chloroquine were treated with quinine dihydrochloride, being given a loading dose of 20 mg salt (16.7 mg base)/kg followed by three or four eight hourly maintenance doses of 10 mg salt (8.3 mg base)/kg injected into the anterior thigh. All patients responded to treatment. Fever and parasite clearance times (mean (SD) 60 (23) h and 53 (22) h respectively) were comparable with those obtained with intravenous quinine. The mean peak plasma quinine concentration of 11.0 mg/l (34.4 mu mol/l) [corrected] was reached a median of five hours after administration of the loading dose. In all patients plasma quinine concentrations exceeded the high minimum inhibitory concentration for Plasmodium falciparum malaria prevalent in Thailand within four hours of the start of treatment but did not cause toxicity other than mild cinchonism. When intravenous infusion is not possible an intramuscular quinine loading dose is an effective means of starting treatment in patients with moderately severe falciparum malaria who cannot swallow tablets.     

Changes in fiber composition of soleus muscle during rat hindlimb suspension

Chronic reduction of gravitational load in the rear limbs of rats to simulate the influence of near-zero gravity in skeletal muscles has been shown previously to elicit atrophy in the soleus muscle. Use of this model by the present investigation indicates that soleus atrophy was characterized by a decline in the number of fibers in groups that contained the slow isoenzyme of myosin and which were classified as type I from intensity of staining to myofibrillar actomyosin adenosinetriphosphatase (ATPase) and to NADH tetrazolium reductase. Furthermore total fiber number was not changed, whereas fibers containing the intermediate isoenzyme and those classified as type IIa increased. There results could be explained by either a change in the composition within existing fibers or a simultaneous loss of slow fibers and de novo synthesis of intermediate and fast fibers. Evidence for transformation included an absence of embryonic or neonatal myosin in muscles from suspended rats and the constant fiber number that was unchanged by 4 wk of suspension. Furthermore although fiber areas of both groups of type I and IIa fibers declined during suspension, variability of the fiber areas within each group did not increase.     

Expression of ultraviolet-induced restriction alleviation in Escherichia coli K-12. Detection of a lambda phage fraction with a retarded mode of DNA injection

Ultraviolet-induced restriction alleviation is an SOS function which partially relieves the K-12-specific DNA restriction in Escherichia coli. Restriction alleviation is determined by observing elevated survival of unmodified phage lambda in cells irradiated with ultraviolet prior to infection. We demonstrate that restriction of lambda is also relieved when log-phase cells are irradiated as late as 50 min after adsorption of lambda. At this time more than 60% of the lambda DNA is already released as acid-soluble material from the cells. Experiments involving reextraction of lambda DNA from infected cells and a mild detergent treatment removing absorbed phages from the cellular surface showed that only a small specific fraction of all lambda infections is destined to escape restriction due to restriction alleviation. This fraction (10-20%) has a retarded mode of DNA injection (60 min or longer) after adsorption which allows the expression of the restriction alleviation function before the phage DNA is exposed to restriction endonucleases. This behaviour of a fraction of lambda phages explains why the SOS function restriction alleviation could initially be discovered. We show that the retarded mode of DNA injection is not required for another SOS function acting on lambda DNA, the increased repair of ultraviolet-irradiated DNA (Weigle reactivation).     

A statistical method for correlating tRNA sequence with amino acid specificity.

A statistical method for finding the nucleotide positions in tRNA sequences that correlate with amino acid specificity has been developed. The procedure involves finding the subset of nucleotide positions and groups of positions where the marginal density of one amino acid tRNA class does not overlap that of any other amino acid class. The procedure is an application of a statistical method known as the Expectation Maximization algorithm.     

Internode length in Pisum. I. The effect of the Le/le gene difference on endogenous gibberellin-like substances

The allelopathic potential of the dry fruits of Washingtonia filifera (L. Linden) H. Wendl. was investigated. Leachates from fruits inhibited the germination of lettuce, wheat, red cabbage and cucumber seeds. The inhibitory effect was partly neutralized by kinetin (20 mg 1⁻¹) and gibberellic acid (50 mg 1⁻¹). The effect of kinetin was more pronounced at 25°C than at 20°C. Substances inhibiting germination were localized in the pericarp of the fruit and were resistant to high temperature.     

Activated macrophages and antibodies against the plant lectin, GSI-B4, recognize the same tumor-associated structure (TAS)

Activated macrophages that were stabilized with either formalin or glutaraldehyde absorbed two polypeptides (Mr 100,000 and 60,000) from detergent extracts of all of the tumor cell lines tested, but not from detergent extracts of normal human peripheral blood lymphocytes. A major polypeptide (Mr 95,000) was retained from spent culture media of tumor cell lines. Polypeptides with molecular sizes of 100,000 and 60,000 daltons were also adsorbed by activated macrophages from detergent extracts of chicken embryo cell membranes, suggesting an oncofetal nature for these proteins. The 100,000 dalton polypeptide, but not the 60,000 dalton component, was found to be available to lactoperoxidase-catalyzed cell surface iodination. Polypeptides with identical molecular sizes could be adsorbed to immobilized galactopyranoside, indicating that they are vertebrate lectins. Activated macrophages and affinity adsorbents prepared by the covalent coupling of galactopyranoside to agarose also bind the plant lectin isolectin B4 prepared from the seeds of Griffonia simplicifolia. On the basis of these findings, we put forth the hypothesis that macromolecules of the same specificity, that is affinity to galactopyranosyl residues, must show homologies in their binding sites. We have predicted therefore that antisera prepared against this plant lectin should cross-react with galactopyranosyl-binding vertebrate lectins present on the surface of tumor cells. In this communication, we also report the generation of hybridomas that produce antibodies reactive with both the plant and vertebrate lectins. Inhibition experiments that make use of various mono- and disaccharides suggest that the specificities of these antibodies are for determinants intimately associated with the galactosyl binding site on the lectin molecule. Two of the antibodies were found to have moderate selectivity for tumor cells when tested in an immunohistochemical procedure that made use of fresh-frozen or paraffin-embedded sections of human biopsy material. These two antibodies on immunoblots of tumor cell membrane extracts reacted with a polypeptide with an apparent molecular size of 100,000 daltons.     

The stoichiometry of the Ca2+ pump in human erythrocyte vesicles: modulation by Ca2+, Mg2+ and calmodulin

Active Ca2+ uptake and the associated (Ca2+ + Mg2+)-ATPase activity were studied under the same conditions in an inside-out vesicle preparation of human red blood cells made essentially by the procedure of Quist and Roufogalis (Journal of Supramolecular Structure 6, 375-381, 1977). Some preparations were treated with 1 mM EDTA at 30 degrees to further deplete them of endogenous levels of calmodulin. As the Ca2+ taken up by the EDTA-treated inside-out vesicles, as well as the non-EDTA treated vesicles, was maintained after addition of 4.1 mM EGTA, the vesicles were shown to be impermeable to the passive leak of Ca2+ over the time course of the experiments. In the absence of added calmodulin, both active Ca2+ uptake and (Ca2+ + Mg2+)-ATPase were sensitive to free Ca2+ over a four log unit concentration range (0.7 microM to 300 microM Ca2+) at 6.4 mM MgCl2. Below 24 microM Ca2+ the stoichiometry of calcium transported per phosphate liberated was close to 2:1, both in EDTA and non-EDTA treated vesicles. Above 50 microM Ca2+ the stoichiometry approached 1:1. When MgCl2 was reduced from 6.4 mM to 1.0 mM, the stoichiometry remained close to 2:1 over the whole range of Ca2+ concentrations examined. In contrast to the results at 6.4 mM MgCl2, the Ca2+ pump was maximally activated at about 2 microM free Ca2+ and significantly inhibited above this concentration at 1 mM MgCl2. Calmodulin (0.5-2.0 microgram/ml) had little effect on the stoichiometry in any of the conditions examined. The possible significance of a variable stoichiometry of the Ca2+ pump in the red blood cell is discussed.