Photosynthesis,water use and growth of a C4 grass stand at high CO2 concentration

Leaf photosynthesis rate of the C₄ species Paspalum plicatulum Michx was virtually CO₂-saturated at normal atmospheric CO₂ concentration but transpiration decreased as CO₂ was increased above normal concentrations thereby increasing transpiration efficiency. To test whether this leaf response led growth to be CO₂-sensitive when water supply was restricted, plants were grown in sealed pots of soil as miniature swards. Water was supplied either daily to maintain a constant water table, or at three growth restricting levels on a 5-day drying cycle. Plants were either in a cabinet with normal air (340 mol (CO₂) mol^-1 (air)) or with 250 mol mol^-1 enrichment. Harvesting was by several cycles of defoliation.With abundant water supply high CO₂ concentration did not cause increased growth, but it did not cause an increase in growth over a wide range of growth-limiting water supplies either. Only when water supply was less than 30–50% of the amount used by the stand with a water-table was there evidence that dry weight growth was enhanced by high CO₂. In addition, with successive regrowth, the enhancing effect under a regime of minimal water allocations, became attenuated. Examination of leaf gas exchange, growth and water use data showed that in the long term stomatal conductance responses were of little significance in matching plant water use to low water allocation; regulation of leaf area was the mechanism through which consumption matched supply. Since high CO₂ effects operate principally via stomatal conductance in C₄ species, we postulate that for this species higher CO₂ concentrations expected globally in future will not have much effect on long term growth.     

Radioimmunoassay for fibroblast growth factor (FGF): release by the bovine anterior pituitary in vitro

A radioimmunoassay (RIA) was developed to measure fibroblast growth factor (FGF) using antiserum generated against a synthetic replicate of [Tyr¹⁰]FGF(1–10). The antisera, previously shown to be capable of inhibiting the biological action of FGF on bovine aortic arch endothelial cells in vitro [1], are highly specific for the amino-terminus of FGF. In the RIA, the antisera recognize the decapeptide antigen [Tyr¹⁰]FGF(1–10) and the intact mitogen on an equimolar basis and show less than 0.01% cross-reactivity with N-acetyl-[Tyr¹⁰]FGF(1–10).

Bovine adenohypophysial cells maintained in primary monolayer culture release and ir-FGF which is indistinguishable from the intact mitogen in as much as it is retained on heparin-Sepharose affinity columns and shows a dose-dependent and parallel displacement in RIA. The release of ir-FGF by the bovine adenohypophysis can be increased with forskolin (10⁻⁵ M) or KCl (50 mM). Preincubation of pituitary cells with 17β-estradiol has no measurable effects on basal ir-FGF, but increases the release after KCl treatment 2–3-fold. These results show that ir-FGF can be released by the bovine adenohypophysis in vitro and lend credence to the hypothesis that FGF plays a physiological role in the homeostatic mechanisms regulating mesoderm-derived cell growth.     

Captan alters transcription in Escherichia coli permeabilized by toluene

RNA synthesis was measured in toluenized E. coli by the incorporation of radiolabeled precursor into either acid precipitable or phenol extracted RNA. Exposure to captan (100 microM) caused a 2.6 fold increase in the apparent rate of RNA synthesis. When captan was tested for its effect on the initiation of RNA synthesis, using either rifampicin-treated cells or by measuring the incorporation of gamma [32P]ATP or gamma [32P]GTP, no change was observed in the number of RNA chains being initiated. Thus, captan does not exert its influence at the level of initiation of nascent chains. However, captan did have an effect on chain growth. From calculations of the incorporation of precursors molecules, RNAs isolated from treated cells were measured to be an average of 2.7 times longer than those from untreated cells. RNA chain lengths were also analyzed by polyacrylamide gel electrophoresis. By this latter technique it was also shown that cells exposed to captan synthesized RNAs that were longer than those of untreated cells. Alterations in the degradation of RNA molecules do not account for the captan mediated response in RNA synthesis.     

The importance of bacterial utilization of released phytoplankton photosynthate in two humic forest lakes in southern Finland

Bacterial utilization of photosynthetically fixed dissolved organic carbon (PDOC) released from natural phytoplankton assemblages was studied in two small, extremely humic, forest lakes in southern Finland. Bacterial activity (measured as uptake of ¹⁴C-glucose) and phytoplankton photosynthesis (measured as light uptake of ¹⁴CO₂) could be most effectively separated using Nuclepore filters of pore size 1–2 μm. Released PDOC was 10–67% of total phytoplankton carbon fixation during in situ experiments, and represented about 0.1% of total DOC. Net uptake of PDOC by bacteria was found to be about 20% during 24 hour laboratory incubations, although about 40% of PDOC present at the start of an experiment could be utilized by bacteria during a 24 hour period. PDOC does not provide a quantitatively important substrate supply for bacterial respiration in humic forest lakes.     

Mapping parathyroid hormone, β-globin,insulin, and LDH-A genes within the human chromosome 11 short arm by spot blotting sorted chromosomes

Summary Rearranged human chromosomes carrying segments of chromosome 11 were separated from the normal chromosome 11 by high-resolution chromosome sorting. Sorted chromosomes were tested with parathyroid hormone, -globin, insulin, and LDH-A gene-specific probes to determine the genes carried by each chromosome segment. Based on the gene content and karyotypes of these abnormal chromosomes, the parathyroid hormone, -globin, insulin, and LDH-A genes and the unique restriction fragment ADJ-762 are all located on the terminal band of the short arm of human chromosome 11 (band 11p15), with LDH-A proximal to the other loci.     

Migration of peripheral T and B cells into the thymus of aging (NZB × SJL)F1 female mice

Aging NZB × SJL (NS) female mice provide a unique model of thymopathology characterized by the intrathymic accumulation of large numbers of mature T and B cells. The purpose of the present work was to examine the possibility that this phenomenon results from the invasion of the thymus by cells from the periphery. Lymphoid cells labeled with chromium-51 or indium-111 were injected into syngeneic recipients to study their patterns of in vivo migration. Lymph node (LN) or spleen cells were found to localize significantly (1–2% of injected radioactivity) into the thymus of 12-month-old NS females but not into that of young recipients or of old NS males. However, intrathymic localization of injected LN cells was observed in castrated NS males which exhibit the same thymopathology as NS females. Both radiolabeled T and B cells were found to enter the thymus of aged NS females but the latter cells about three times less efficiently than the former. Moreover, while thymocytes from young NS females were unable to recirculate to LN, those of old NS females showed increased LN-seeking capacity and part (1%) of them did migrate back into the thymus of old but not young NS females. In additional cell transfer experiments, the intrathymic migration of B cells into old NS females was further documented by using the antibody response to sheep erythrocytes as a tracer. Taken together, these observations indicate that the thymus of aging NS female mice is permeable to recirculating lymphocytes, suggesting that at least part of the mature T and B cells detected in this thymus, are migrants from the periphery.     

Expression in Bacillus subtilis of the gene for human urogastrone using synthetic ribosome binding sites

Summary A chemically synthesised gene coding for human urogastrone which was earlier cloned in E. coli (Smith et al. 1982) has now been cloned into expression vectors for Bacillus subtilis Two types of constructs have been made, one giving production of methionylurogastrone and the other giving rise to a methionyl-urogastrone- galactosidase fusion polypeptide facilitating quantification of expression levels.The ribosome binding sites used in the expression plasmids are synthetically made oligonucleotides residing on short restriction fragments to allow easy replacement by other ribosome binding sites.Using shuttle vectors and constitutive promoters from Bacillus phages 105 and SPP1, we were able to detect levels of expression amounting to a few thousand molecules per cell during logarithmic growth in both E. coli and B. subtilis.     

Identification of the dye gene product, mutational loss of which alters envelope protein composition and also affects sex factor F expression in Escherichia coli K-12

Summary The product of the dye gene of Escherichia coli, mapping at 99–100 min, is required for expression of the sex factor F, and also appears to be involved in the regulation of envelope proteins. Mutation of dye thus results in loss of expression of the F-factor (Fex^–, i.e. male sterility, and dye sensitivity (Dye^s). We have isolated a plasmid, pRB38, in which a 6 kb SalI fragment carrying the dye ⁺ gene was cloned into the plasmid pACYC184. This 6 kb SalI fragment also carries two nearby markers, chlG, involved in the synthesis of the molybdenum cofactor, and phoM, required for constitutive expression of alkaline phosphatase.Some of the polypeptides synthesised by pRB38 were identified using the maxi-cell procedure. The product of the dye gene was found to be a polypeptide of M_r=29,000. Thus derivatives of pRB38 in which the transposon was inserted into dye, resulting in a Dye^S Fex^– phenotype when these plasmids were in a dye strain, failed to produce this polypeptide and in some cases produced a truncated product. Such insertions also resulted in a Chl^r and Pho^– phenotype when the plasmid was in a (dye-chlG-phoM) phoR strain, although complementation tests suggested that the phoM ⁺ and chlG ⁺ genes were still intact. Insertions of into the promoter distal end of dye did not result in a Dye^S Fex^– phenotype, although a truncated Dye protein was synthesised, and a Chl^r Pho^– phenotype was produced.It has been suggested (Gaffney et al. 1983) that the dye (=sfrA) gene product is necessary for F-factor expression because it is required for translocation of the F-factor TraJ protein to the outer membrane. Our results suggest that the Dye protein is also required for expression of the molybdenum cofactor and of alkaline phosphatase, and could perhaps be involved in the translocation of these proteins to the membrane.     

An interpretation of Fujita's frequency diagrams in phyllotaxis

Fujita's diagrams in phyllotaxis, showing the frequencies of divergence angles as a function of these angles for low phyllotactic patterns such as (2, 1) and (3, 2), which are approximately normal curves centered at the limitdivergence angle of 137.51°, are shown to be puzzling when compared to results and observations in the field. An analysis of these diagrams is proposed, in the context of Fujita's methodology, of data from other sources, of a mathematical theorem on lattices, and of the contact pressure theory of phyllotaxis.