Nitrogen fixation efficiency,natural15N abundance,and morphology of mesquite (Prosopis glandulosa) root nodules

Summary The relative nitrogen fixation efficiencies (RE 1-[H₂ evolved÷C₂H₂ reduced]·100) of four mesquite (Prosopis glandulosa var.torreyana) rhizobia (Strains WR 1001, WR 1002, L5, L9) and a cowpea rhizobia (Strain 176A32) on mesquite were evaluated in a glasshouse experiment. Plant yield, shoot N accumulation, and the natural¹⁵N abundance (¹⁵N) of nodule tissue were determined. Strain WR 1002 failed to nodulate mesquite and strain L5 produced ineffective nodules. Among the three effective strains (WR 1001, L9, 176A32) the cowpea strain (176A32) and strain L9 had significantly higher RE than strain WR 1001. Differences in RE, however, were not accompanied by significantly higher plant yield and shoot N accumulation. The difference in¹⁵N abundance between foliar tissue and nodules (nodules minus leaves) was 0.47 ¹⁵N for the ineffective L5 nodules, while for the effective WR 1001, L9, and 176A32 nodules, respectively, this difference was 8.35, 7.81, and 8.35 ¹⁵N. This indicates a similar relationship between N₂-fixing effectiveness and natural¹⁵N enrichment of nodules that was previously observed in soybeans (Glycine max, L. Merr.). Strains WR 1001 and L9 produced elongate, indeterminate nodules typical for mesquite. The ineffective L5 nodules had few infected cells and an abundance of cortical amyloplasts. Mesquite nodules produced by the cowpea strain were spherical and were somewhat more similar in internal morphology to determinate nodules typical of cowpea than indeterminate nodules normally associated with mesquite.     

Characterization of a New Type of Human Papillomavirus That Causes Skin Warts

A human papillomavirus (HPV) was isolated from the lesions of a patient (ML) bearing numerous hand common warts. This virus was compared with the well-characterized HPV found in typical plantar warts (plantar HPV). ML and plantar HPV DNAs have similar molecular weights (5.26 x 10(6) and 5.23 x 10(6), respectively) but were shown to be different by restriction enzyme analysis. When the cleavage products of both DNAs by endonuclease EcoRI, BamI, HpaI, or Hind were analyzed by electron microscopy, one, two, one, and four fragments were detected for ML HPV DNA instead of the two, one, two, and six fragments, respectively, detected for plantar HPV DNA. In contrast to plantar HPV DNA, a high proportion of ML HPV DNA molecules were resistant to these restriction enzymes. Most, if not all, of the molecules were either resistant to BamI and sensitive to EcoRI or sensitive to BamI and resistant to EcoRI. After denaturation and renaturation of the cleavage products of ML HPV DNA by a mixture of the two enzymes, the circular "heteroduplexes" formed showed one to three heterology loops corresponding to about 4 to 8% of the genome length. No sequence homology was detected between ML and plantar HPV DNAs by cRNA-DNA filter hybridization, by measuring the reassociation kinetics of an iodinated plantar HPV DNA in the presence of a 25-fold excess of ML HPV DNA, or by the heteroduplex technique. The two viruses had distinct electrophoretic polypeptide patterns and showed no antigenic cross-reaction by immunodiffusion or immunofluorescence techniques. Preliminary cRNA-DNA hybridization experiments, using viral DNAs from single or pooled plantar or hand warts, suggest that hand common warts are associated with viruses similar or related to ML HPV. The existence of at least two distinct types of HPVs that cause skin warts was demonstrated; they were provisionally called HPV type 1 and HPV type 2, with plantar HPV and ML HPV as prototypical viruses, respectively.     

Cytological effects of urecholine stimulation on the rat pancreas

Summary Stimulation of the exocrine pancreas by the secretagogue urecholine causes degranulation of the acinar cells. Under in vivo conditions, this degranulation is not uniform throughout the tissue. Indeed some of the acini are almost completely depleted of their granules while others display the appearance of resting acini. A noticeable feature is that all the cells of the same acinus display a comparable degree of degranulation. Moreover, groups of neighbouring acini seem to respond simultaneously suggesting that the secretory stimulus is propagated from one acinus to the other. In vitro stimulation of dispersed acini also showed that some of the acini are more responsive than others indicating that this phenomenon can not be attributed to accessibility of the secretagogue to its receptor. These observations lead us to the concept that the response of the pancreatic acinar cell is controlled at the level of the acinus.     

Earthworm coelomocytes in vitro

Summary Contamination and low viability of earthworm coelomocytes in tissue culture have delayed in vitro studies. Using penicillin, streptomycin, tetracycline and Amphotericin B,Lumbricus terrestis coelomocytes were maintained viable and uncontaminated for 10 days at 15°C in medium L-15 supplemented with 5 to 10% fetal bovine serum. The coelomocytes survived for at least 10 days with 85% viability as assessed by trypan blue exclusion assays and phagocytosis of heat-killed yeast. Studies on the thymidine uptake, however, were negative. With the involvement of coelomocytes in tissue graft rejection, in vitro techniques can now be applied to study their capacity in the immune response. Supported in part by USPHS Research Grant 1 RO 1 HD09333-01 to E. L. Cooper.     

Establishment of bovine mammary epithelial cells (MAC-T): An in vitro model for bovine lactation

The hallmark of differentiated mammary epithelial cells is a copious secretion of milk-specific components regulated by lactogenic hormones. We describe an established clonal cell line produced from primary bovine mammary alveolar cells (MAC-T) by stable transfection with SV-40 large T-antigen. MAC-T cells show a population doubling time of approximately 17 h and have been cultured more than 350 passages without showing any sign of senescence. They show the characteristic “cobblestone” morphology of epithelial cells when grown on plastic substratum. Differentiation was induced by augmenting cell-cell interaction on a floating collagen gel in the presence of prolactin. The differentiated phenotype was characterized to include (1) increased abundance in β-casein mRNA, (2) increased number and size of indirect immunofluorescent casein secretory vesicles in each cell and (3) α_s- and β-casein protein secretion. The clonal nature of the cells, their immortality, and their ability to uniformly differentiate and secrete casein proteins make this cell line unique.     

Measurement and simulation of the morphological development of filamentous microorganisms

Growth of Streptomyces tendae was investigated in submerged culture. Images of several mycelia were analyzed by means of an image-processing system. The studies revealed that tip growth angles and branching outgrowth angles could be regarded as normally distributed. Based on these results, a random model for directional growth of hyphal tips as well as directional growth of branches is proposed. This model shows curved elongation of hyphal tips, so that the morphological development of a mycelium up to the formation of a pellet is predicted, similar to that observed in nature.     

Localization of a novel integrin of the beta 1 subfamily in human tissues.

We have previously described a novel integrin composed of a beta 1-chain non-covalently linked to an alpha-chain which is biochemically different from those known so far (i.e., alpha 1-alpha 7 and alpha v). This molecule has been identified with a monoclonal antibody (MAb) termed 10.1.2 raised against long-term cultured human thymic epithelial cells (TEC). In this study we analyzed the immunohistochemical distribution of this new integrin in a variety of human tissues. MAb 10.1.2 stains several types of endothelial and epithelial cells. Among the endothelia, a strong reaction was detected in the HEV of lymphoid organs including thymus, lymph node, tonsil, and mucosa-associated lymphoid tissue. Epithelial localizations of note were those in the basal layer of the epidermis and of other stratified squamous epithelia, where the lateral and apical but not the deep surfaces of most cells were stained. A variety of water-electrolyte transporting cells in sweat glands, salivary glands, and kidney were also stained at their deep surface. The latter findings suggest that this molecule may subserve other functions in addition to those related to cell adhesion.