Ontogeny of lymphatic structures in the pig omentum

Summary The development of lymphoid populations in the omentum majus during the prenatal and postnatal life of the pig was studied. T lymphocytes, monocytes and mast cells were first found on the 40th day of gestation. B lymphocytes appeared on the 72nd day of gestation when the first macrophage aggregates were formed. Macrophages appeared to be the prerequisite for the formation of dense lymphatic areas (DLA's). At later stages T cells were observed only in the omentum of germfree pigs. DLA's of conventional pig omentum are filled exclusively with B cells.     

Succession,diversité et amplitude de niche dans les påturages du centre de la péninsule ibérique

Some diversity and niche amplitude parameters were applied to rangeland pastures of the Central Iberian Peninsula and to their succession stages after the periodical ploughing typical of the traditional management of these areas. Four different slopes within a large area of undulating terrain were selected for the monitoring of succession as they contained the characteristical geomorphological pattern of the area (denudation, transport and accumulation sectors).If we consider the total entropy theorem, H (E.P.)=H(E)+H(P/E), the total entropy of the slope H(E.P) and the entropy of species H(E) increase as succession progresses. As the value of the entropy of the sampling plots conditioned by the species H(P/E) is affected by the number of plots utilized, we employed the expression A=H(P/E)/log₂ number of plots, similar to Pielou's index for niche amplitude, W=H(P/E)/H(P).This values decreases with succession, indicating that plant species tend to occupy more definite sectors along the slope. The number of low entropy species H(P/E) _i or specialist species, confined to narrow sectors also increases. When computed separately within the different sectors niche amplitude results in small values for the low slope regions (accumulation sector). This effect becomes more pronounced when succession advances.

Nous remercions le Conseil d'Administration de La Paranza, propriétaire du Castillo de Vañuelas, et particulièrement Mrs. C. Hernandez-Ros et J. A. Léon-Vrquijò, pour les faeilités qu'ils ont données à cette équipe durant la réalisation de ce travail.     

Genetic Evaluation and Utilization (GEU) program

Summary The Genetic Evaluation and Utilization (GEU) program of the International Rice Research Institute (IRRI) is an interdisciplinary program for the improvement of rice crops. Scientists trained in diverse disciplines such as plant breeding, plant pathology, entomology, agronomy, cereal chemistry, plant physiology, and soil chemistry work together and contribute their specialized skills to this joint endeavor. The program has five interrelated components: (1) germ plasm collection and conservation, (2) research in disciplinary areas, (3) development of improved germ plasm, (4) distribution, evaluation and exchange of germ plasm internationally, (5) training of young scientists.Over forty thousand rice varieties from different countries are being maintained in the IRRI germ plasm bank. These varieties have been screened for grain quality, resistance to various diseases and insects, and tolerance to various environmental stresses such as drought, high and low temperatures and problem soils. Donor parents for resistances to each of the problem areas have been identified. These parents were utilized for developing improved germ plasm. Varieties with resistance to as many as five diseases and five insect species have been developed. These multiple resistant varieties are grown on millions of hectares of rice land. Seeds of improved breeding materials are exchanged internationally and 194 scientists from different countries have been trained in rice improvement work.     

Molecular mechanisms of the origin of chromosome aberrations and the structural organisation of eukaryotic DNA

Summary A new hypothesis on the appearance of exchange chromosomal aberrations has been suggested. According to this hypothesis, temporal duplex polynucleotide structure should arise during G₁ and G₂ phases during the correction of DNA. The size of the duplex, as a rule, should be restricted to the size of complementary nucleotide sequences in the regions of repetitions. Any polynucleotide break in a duplex zone would result in chromosome breakage and if complementary broken ends interact with each other, then exchange chromosome aberrations may be formed. This hypothesis would explain such previously obscure phenomena as extremely high frequencies of exchanges after mutagen treatment, the nature of mitotic crossing-over, negative interference, change of aberration types before replication, the low frequency of damaged structural genes during aberration formation, etc.     

The relative importance of prenatal and postnatal maternal influences on growth in mice

Summary The cross-nursing technique was used to assess the relative importance of prenatal and postnatal maternal influences on growth in mice from an unselected population originated from a cross of four highly inbred strains. Body weights were studied at birth, 7-, 14-, 21- and 42-days, in addition to the weight gains between these ages and tail length at 21 and 42 days of age. At littering, each dam in each nursing set retained two of her own offspring and two were transfereed to each of the other dams in the set, so that each nursed litter contained six young representing three mothers. Prenatal influences accounted for 37, 15, 10, 11 and 13 % of the total variation in the respective body weights, while postnatal influences accounted for 0, 64, 65, 49 and 14% at the respective ages. In the case of weight gains, prenatal influences were responsible for 16, 4, 6 and 30%, while postnatal influences were responsible for 66, 66, 31 and 7% of the total variation in gain during the respective four periods examined. Apparently the individual weight gain from 7 to 14 days was a better measure of the lactational performance of the dam than individual 14-day weight. For tail length, prenatal influences accounted for 6 % and 4 % of the total variation in tail length at 21 and 42 days, respectively, while postnatal influences accounted for 60 % and 24 % at the respective ages. Generally, there was no indication of an important interaction between the nurse and the nursed young at any stage studied.     

Identification of mouse chromosomes required for murine leukemia virus replication.

The replication patterns of five ecotropic and two amphotropic strains of murine leukemia virus (MuLV) were studied by infecting 41 Chinese hamster x mounse hybrid primary clones segregating mouse (Mus musculus) chromosomes. Ecotropic and amphotropic strains replicated in mouse and some hybrid cells, but not in hamster cells, indicating that replication of exogenous virus requires dominantly expressed mouse cellular genes. The patterns of replication of the five ecotropic strains in hybrid clones were similar; the patterns of replication of the two amphotropic strains were also similar. When compared to each other, however, the replication patterns of ecotropic and amphotropic viruses were dissimilar, indicating that these two classes of MuLV require different mouse chromosomes for replication. Chromosome and isozyme analyses assigned a gene, Rec-1 (replication of ecotropic virus), to mouse chromosome 5 that is necessary and may be sufficient for ecotropic virus replication. Because of preferential retention of mouse chromosomes 15 and 17 in the hybrid clones, however, the possibility that these chromosomes carry genes that are necessary but not sufficient for ecotropic virus replication cannot be excluded. Similarly, the data indicate that mouse chromosome 8 (or possibly 19) carried a gene we have designated Ram-1 (replication of amphotropic virus) which is necessary and may be sufficient for amphotropic virus replication. Because chromosomes 8 and 19 tended to segregate together and two of the three clones excluding 19 have chromosome reaggrangements, we cannot exclude 19 as being independent of amphotropic virus replication. In addition, because of preferential retention, chromosomes 7, 12, 15, 16 and 17 cannot be excluded as being necessary but not sufficient. Hybrid cell genetic studies confirm the assignment of the Fv-1 locus to chromosome 4 previously made by sexual genetics. In addition, our results demonstrate that hybrid cells which have segregated mouse chromosome 4 but have retained 5 become permissive for replication of both N and B tropic strains of MuLV.     

Transfer of purified herpes virus thymidine kinase gene to cultured mouse cells.

Treatment of Ltk^?, mouse L cells deficient in thymidine kinase (tk), with Bam I restriction endonuclease cleaved DNA from herpes simplex virus-1 (HSV-1) produced tk⁺ clones with a frequency of 10^?6/2 μg of HSV-1 DNA. Untreated cells or cells treated with Eco RI restriction endonuclease fragments produced no tk+ clones under the same conditions. The thymidine kinase activities of four independently derived clones were characterized by biochemical and serological techniques. By these criteria, the tk activities were found to be identical to HSV-1 tk and different from host wildtype tk. The tk⁺ phenotype was stable over several hundred cell generations, although the rate of reversion to the tk^? phenotype, as judged by cloning efficiency in the presence of bromodeoxyuridine, was high (1–5 × 10^?3). HSV-1 DNA Bam restriction fragments were separated by gel electrophoresis, and virtually all activity, as assayed by transfection, was found to reside in a 3.4 kb fragment. Transformation efficiency with the isolated fragment is 20 fold higher per gene equivalent than with the unfractionated total Bam digest. These results prove the usefulness of transfection assays as a means for the bioassay and isolation of restriction fragments carrying specific genetic information. Cells expressing HSV-1 tk may also provide a useful model system for the detailed analysis of eucaryotic and viral gene regulation.     

Further studies on the subcellular localization of lipid-degrading enzymes

Further work on the subcellular localization of two lipid-degrading enzymes, lipolytic acyl hydrolase (LAH) and lipoxygenase (LOX) has been carried out on brassica florets, potato shoots and pea roots. In all cases, the LAH profile on sucrose and Ficoll density gradients was coincident with ‘lysosomal’ acid phosphatase activity. However, the localization of LOX activity was different for each tissue. In pea roots the activity of LOX was localized in the ‘lysosomal’ fraction, whereas with brassica florets (cauliflower and calabrese) it was present in a heavy body with a similar density to plastids and in potato shoots LOX gave only low particulate recoveries.     

Hexane soluble non-volatiles in flowering to fruiting stages of Fatsia japonica

The n-hexane soluble non-volatile fraction of the acetone extracts from the flower buds, the flowers and the immature and the mature fruits of Fatsia japonica were all found to contain fatty acids, fatty acid methyl esters, squalene, β-amyrin and sterols. At all the stages between budding to the mature fruit, the major fatty acids were palmitic and linoleic acids and the major phytosterol was stigmasterol. In addition steryl and β-amyrenyl esters were found in the flowers and the immature and the mature fruits, but these esters were not present in the flower buds. Sitosteryl ester was the major constituent of the steryl ester fraction in the fruiting stages. Phytol was found in only the flowering stage and triglycerides in only the mature fruits. The variations in the lipid constituents is discussed in relation to the stages from budding to the mature fruit.