Purification of Photosystem II particles from Phormidium laminosum using the detergent dodecyl-β-d-maltoside. Properties of the purified complex

The purification and properties of a new oxygen-evolving Photosystem (PS) II particle from the thermophilic blue-green alga Phormidium laminosum are described. The activity of the lauryldimethylamine N-oxide PS II-enriched supernatant described previously (Stewart, A.C. and Bendall, D.S. (1979) FEBS Lett. 107, 308–312) was found to be stabilized for several days at 4°;C by the addition of a second detergent, dodecyl-β-d-maltoside (lauryl maltoside). The lauryl maltoside/lauryldimethylamine N-oxide extract could be fractionated by sucrose density gradient centrifugation. Very high rates of oxygen evolution, typically 1900–2400 μmol O₂/mg chlorophyll a per h at pH 7 with dimethylbenzoquinone and ferricyanide as acceptors, were observed for the lowest green band from the gradient. This fraction contained cytochromes b-559 (high-potential) and c-549, but was completely devoid of P-700 and cytochromes b-563 and f. The purified oxygen-evolving particles comprised seven major polypeptides (M_r 58 900, 52 400, 43 200, 33 900, 30 000, 16 000 and 15 000) and approximately five minor polypeptides. The particles contained 3–4 Mn atoms per reaction centre and had a chlorophyll antenna of approx. 50 chlorophyll a. The fast phase of fluorescence induction curves in the presence of hydroxylamine and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) could be described by an exponential, suggesting that no energy transfer was occurring between the PS II units responsible for this phase. Comparison of the area above the fluorescence induction curves in the absence and presence of DCMU suggested an acceptor pool size of 2–3 equivalents per centre.     

Degradation of the heparin matrix of mast cell granules by cultured fibroblasts

The ability of cultured rat fibroblasts to phagocytose rat peritoneal mast cell granules has been previously demonstrated by light and electron microscopy. To determine if the heparin matrix of ingested granules could be degraded by fibroblasts after phagocytosis, the heparin within peritoneal mast cells was labeled with [35S]sulfate in vivo. The 35S-labeled rat peritoneal mast cells were purified and their granules were isolated and shown to contain [35S]heparin proteoglycan. Incubation of [35S]heparin proteoglycan-containing granules with cultured rat fibroblasts revealed internalization of radioactivity by the fibroblasts over the first 24 hr consistent with phagocytosis of the granules by these fibroblasts. The [35S]heparin proteoglycan internalized by the fibroblasts was shown to decrease in size over 72 hr indicating that the fibroblasts were capable of degrading the heparin within the ingested granules. Degradation of [35S]heparin proteoglycan within the fibroblast was accompanied by the appearance of free [35S]sulfate in the extracellular compartment. Similar findings were obtained using cultured human fibroblasts. These data demonstrate for the first time that both rat and human fibroblasts are not only capable of ingesting mast cell granules but also of degrading mast cell granule heparin proteoglycan. This ingestion and degradation of mast cell granules by fibroblasts may represent an important mechanism in the regulation of the biologic expression of heparin and other granule-associated mediators in immediate hypersensitivity reactions.     

Production and HPLC analysis of black tea theaflavins and thearubigins during in vitro oxidation

A model fermentation system has been designed which utilizes pure catechins and partially purified polyphenol oxidase (EC 1.14.18.1 from green tea shoots. HPLC analysis of the products formed during in vitro oxidation has demonstrated a close similarity between this system and in vivo oxidation occurring during factory fermentation. Furthermore, changes in theaflavin and thearubigin levels, revealed by time courses of fermentation, show in vitro and in vivo systems to be qualitatively similar, although the former system produces considerably higher levels of both components. The model fermentation system, therefore, appears to be a suitable experimental system for studying the formation of theaflavin and thearubigin pigments under strictly controlled conditions. In preliminary experiments the theaflavins have been identified on HPLC profiles by enzymic oxidation of the relevant catechin pairs. Similarly, major coloured components other than theaflavins, which are considered to be thearubigins, have been shown to be formed by the oxidation and reaction of two gallocatechins (epigallocatechin and epigallocatechin gallate). The model fermentation system, in conjunction with HPLC as described in this paper, provides a means whereby precise data on theaflavin and thearubigin formation can be obtained and, in the case of the thearubigins, one which could yield additional structural information.     

An automatic system to study the responses of respiration and photosynthesis by submerged macrophytes to environmental variables

An apparatus to measure the rates of respiration and photosynthesis of aquatic plants in water at velocities of up to 200 mm s^–1 in a closed water-flow system with partial recirculation, is described. The temperature, the light regime and the concentration of dissolved oxygen are controlled automatically. Typical results are given for Ranunculus penicillatus var. calcareus which were repeatable between the same season in different years and compared with published data.     

Transport Exchange of Carbon,Nitrogen and Water in the Context of Whole Plant Growth and Functioning — Case History of a Nodulated Annual Legume

The economy of carbon, nitrogen and water during growth of nodulated, nitrogen-fixing plants of white lupin (Lupinus albus L.) was studied by measuring C, N and H₂O content of plant parts, concentrations of C and N in bleeding sap of xylem and phloem, transpirational losses of whole shoots and shoot parts, and daily exchanges of CO₂ between shoot and root parts and the surrounding atmosphere. Relationships were studied between water use and dry matter accumulation of shoot and fruits, and between net photosynthesis rate and leaf area, transpiration rate and nitrogen fixation. Conversion efficiencies were computed for utilization of net photosynthate for nitrogen fixation and for production of dry matter and protein in seeds. Partitioning of the plant's intake of C, N and H₂O was described in terms of growth, transpiration, and respiration of plant parts. An empirically-based model was developed to describe transport exchanges in xylem and phloem for a 10-day interval of growth. The model depicted quantitatively the mixtures of xylem and phloem streams which matched precisely the recorded amounts of C, N and H₂O assimilated, absorbed or consumed by the various parts of the plant. The model provided information on phloem translocation of carbon and nitrogen to roots from shoots, the cycling of carbon and nitrogen through leaves, the relationship between transpiration and nitrogen partitioning to shoot organs through the xylem, the relative amount of the plant's water budget committed to phloem translocation, and the significance of xylem to phloem transfer of nitrogen in stems as a means of supplying nitrogen to apical regions of the shoot.     

Nitrogen Nutrition and Xylem Transport of Nitrogen in Ureide-producing Grain Legumes

Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO₃ and in eight other ureide-forming legumes utilizing NO₃ or N₂ as sole source of nitrogen. A ¹⁵N dilution technique determined the proportions of plant nitrogen derived from N₂ in the nodulated cowpeas fed NO₃. Xylem sap composition of NO₃-fed, nodulated cowpea varied predictably with the relative extents to which N₂ and NO₃ were being utilized. The ratios of asparagine to glutamine (N/N) and of NO₃ to ureide (N/N) in xylem sap increased with increasing dependence on NO₃ whereas per cent of xylem nitrogen as ureide and the ratio of ureide plus glutamine to asparagine plus NO₃ (N/N) in xylem sap increased with increasing dependence on N₂ fixation. The amounts of NO₃ and ureides stored in leaflets, stems plus petioles, and roots of cowpea varied in a complex manner with level of NO₃ and the presence or absence of N₂ fixation. All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N₂ than when utilizing NO₃. In nodulated (minus nitrate) cowpea and mung bean (Vigna radiata [L.] Wilczek) the percentage of xylem nitrogen as ureide remained constant during growth but the ratio of asparagine to glutamine varied considerably. The biochemical significance of the above differences in xylem sap composition was discussed.     

Biosynthesis of Ureides from Purines in a Cell-free System from Nodule Extracts of Cowpea [Vigna unguiculata (L) Walp.

The synthesis of ¹⁴C-labeled xanthine/hypoxanthine, uric acid, allantoin, allantoic acid, and urea from [8-¹⁴C]guanine or [8-¹⁴C]hypoxanthine, but not from [8-¹⁴C]adenine, was demonstrated in a cell-free extract from N₂-fixing nodules of cowpea (Walp.). The ¹⁴C recovered in the acid/neutral fraction was present predominantly in uric acid and allantoin (88-97%), with less than 10% of the ¹⁴C in allantoic acid and urea. Time courses of labeling in the cell-free system suggested the sequence of synthesis from guanine to be uric acid, allantoin, and allantoic acid. Ureide synthesis was confined to soluble extracts from the bacteroid-containing tissue, was stimulated by pyridine nucleotides and intermediates of the pathways of aerobic oxidation of ureides, but was completely inhibited by allopurinol, a potent inhibitor of xanthine dehydrogenase (EC 1.2.1.37). The data indicated a purine-based pathway for ureide synthesis by cowpea nodules, and this suggestion is discussed.     

Optimizing development time in a seasonal environment: The ‘ups and downs’ of clinal variation

Summary This paper explores the problem of adapting development time to changes in the length of time conditions are favourable for growth and reproduction (season length). It is shown that systematic changes in season length along some gradient such as latitude can generate either simple clines in development time or saw-tooth clines. The relationship between development time and body size gives rise to a corresponding variation in body size. The generation of a saw-tooth cline does not require sharp environmental changes. Both types of clinal variation are observed in insects.