I-Ad antigen expression of pyran copolymer-induced peritoneal cells in tumor vaccine-primed mice and its association with the host antitumor response

Summary Mice inoculated IP with L1210 murine leukemia vaccine and subsequently with pyran copolymer-induced macrophages (pyran-M) lived for a prolonged time after live L1210 inoculation IP. Pyran-M as tentatively identified by anti-AcM.1 monoclonal antibody expressed I-A^d antigen in tumor vaccine-primed recipient mice and contributed to maintaining I-A^d antigen positive (I-A^d+) macrophages at high cell density in the peritoneal cavity of recipient mice. The relevance of these I-A^d+ cells to the host antitumor response was examined by experiments in which I-A^d+ cell density in the peritoneal cavity and host antitumor response behaved in a parallel fashion. Human interferon-A/D, an agent selectively inhibiting Ia antigen expression, and silica, a general antimacrophage agent, strongly suppressed I-A^d antigen expression of peritoneal mcrophages of tumor vaccine-primed and pyran-M-inoculated mice and, consistently with this, the antitumor response was nullified in these mice. Tumor vaccine-primed mice inoculated with sodium caseinate or thioglycollate-induced peritoneal cells did not survive L1210 inoculation and, in these mice, I-A^d+ peritoneal macrophages were suppressed in number as compared with those of tumor vaccine-primed and pyran-M-inoculated mice. These results warrant further study on the contribution of I-A^d+ macrophages to pyran copolymer-induced augmentation of the antitumor response in tumor vaccine-primed mice.     

Identification of Photosynthetic Mutants of Arabidopsis by Automatic Screening for Altered Effective Quantum Yield of Photosystem 2

Quantification of chlorophyll (Chl) fluorescence is a versatile tool for analysing the photosynthetic performance of plants in a non-intrusive manner. A pulse-amplitude modulated fluorometer was combined with a CNC router for the automated measurement of the effective quantum yield of photosystem 2 (₂) of Arabidopsis thaliana plants. About 90 000 individual plants representing 7 500 lines derived from En-transposon and T-DNA mutagenised Arabidopsis populations were screened for mutants with altered ₂. Forty-eight recessive ₂ mutations were identified of which most exhibit also altered pigmentation and increased photosensitivity. For three ₂ mutants the corresponding mutated genes were identified that code all for chloroplast-located proteins. Comparison of the ₂ mutant screen with other screening methods based on the measurement of Chl fluorescence shows that the ₂ mutants identified are different to mutants identified by high Chl fluorescence. Some ₂ mutants, on the contrary, are common to mutants identified by screens based on non-photochemical quenching.     

Factors Limiting Photosynthetic Recovery in Sweet Pepper Leaves After Short-Term Chilling Stress Under Low Irradiance

The effects of chilling treatment (4 °C) under low irradiance, LI (100 mol m^–2 s^–1) and in the dark on subsequent recovery of photosynthesis in chilling-sensitive sweet pepper leaves were investigated by comparing the ratio of quantum yields of photosystem (PS) 2 and CO₂ assimilation, _PS2/_CO2, measured in normal air (21 % O₂, NA) and low O₂-air (2% O₂, LOA), and by analyzing chlorophyll (Chl) a fluorescence parameters. Chilling treatment in the dark had little effect on F_v/F_m and _PS2/_CO2, but it caused the decrease of net photosynthetic rate (P _N) under saturating irradiance after 6-h chilling treatment, indicating that short-term chilling alone did not induce PS2 photoinhibition. Furthermore, photorespiration and Mehler reaction also did not obviously change during subsequent recovery after chilling stress in the dark. During chilling treatment under LI, there were obvious changes in F_v/F_m and _PS2/_CO2, determined in NA or LOA. F_v/F_m could recover fully in 4 h at 25 °C, and _PS2/_CO2 increased at the end of the treatment, as determined in both NA and LOA. During subsequent recovery, _PS2/_CO2 in LOA decreased faster than in NA. Thus the Mehler reaction might play an important role during chilling treatment under LI, and photorespiration was an important process during the subsequent recovery. The recovery of PN under saturating irradiance determined in NA and LOA took about 50 h, implying that there were some factors besides CO₂ assimilation limiting the recovery of photosynthesis. From the progress of reduced P700 and the increase of the Mehler reaction during chilling under LI we propose that active oxygen species were the factors inducing PS1 photoinhibition, which prevented the recovery of photosynthesis in optimal conditions because of the slow recovery of the oxidizable P700.     

Isolation of a halobacterial phage with a fully cytosine-methylated genome

Summary A new bacteriophage from Halobacterium halobium has been isolated and partially characterized. It is not homologous to the phage H (Schnabel, et al. 1982) which infects the same bacterium, though it appeared spontaneously in a culture of H adapted to H. halobium NRL/JW. The size and morphology of N are comparable to that of other known halophages. The genome of N consists of linear double-stranded DNA, 56 kb in size, whose dCMP is totally replaced by 5-methyl-dCMP. This is the second case of a fully cytosine-methylated genome, the bacteriophage XP12 from Xanthomonas oryzae, being so far the only one reported. Like H, the N, genome seems to have terminal redundancy and circular permutation. N is the first halobacterial phage which survives prolonged exposure to low ionic strength environments. After 48 h incubation in distilled water a loss in infectivity of less than 50% is observed.     

Virulence as a consequence of genome instability of a novel temperate bacteriophage, ΦRsG1, of Rhodobacter sphaeroides Y

A novel temperate bacteriophage, designated RsG1, was isolated from Rhodobacter sphaeroides Y (previously designated Rhodopseudomonas sphaeroides) following exposure to mitomycin C. The phage morphology, as revealed from electron microscopy, showed a hexagonal head (90 by 46.5 nm) connected with a tail (116 by 9.4 nm), to which a collar was proximally attached. A morphologically similar phage was also produced by spontaneous lysis of the cells. While RsG1 did not grow on any other bacterial strain tested, spontaneously produced phage particles propagated (and formed plaques) on R. sphaeroides Y still carrying RsG1 in the prophage state. The genome of RsG1 consisted of double stranded linear DNA with cohesive ends and a GC-content of 71.8 mol%. The DNA molecules formed circles in vitro with a mean contour length of 17.18±0.4 m, which corresponds to a size of 49 kbase pairs (kb). On the other hand, DNA extracted from the virulent phage particles was heterogeneous and consisted of two DNA species of different size, occurring in a ratio of about 1:1. These molecules also circularized having contour lengths of 17.18±0.4 m and 14.02±0.41 m corresponding to 49 and 40 kb, respectively. Restriction digest analysis of the two DNA species and DNA from RsG1 indicated that they are similar, and allowed the indentification of an 11.5 kb EcoRI fragment that carries the cohesive ends. Because DNA from RsG1 and the 49 kb DNA of the virulent phage particles were indistinguishable with the criteria applied, it is suggested that phage particles containing the 40 kb DNA represent the virulent type of phage, termed RsG1.1.     

Is There a Field-Theoretic Explanation For Precursor Biopolymers?

A Hu-Barkana-Gruzinov cold dark matter scalarfield may enter a weak isospin invariant derivative interactionthat causes the flow of right-handed electrons to align parallelto (). Hence, in the outer regions of galaxies where () islarge, as in galactic halos, the derivative interaction mayinduce a chirality-imbued quantum chemistry. Such a chirality-imbued chemistry would in turn be conducive to the formation ofabundant precursor biopolymers on interstellar dust grains,comets and meteors in galactic halo regions, with subsequentdelivery to planets in the inner galactic regions where and() are concomitantly near zero and left-right symmetricterrestrial quantum chemistry prevails.     

Host factor requirements and some properties of ΦXtB

Summary Replication of XtB, a capsid mutant of bacteriophage X174, depends on the host functions directed by the E. coli genes dnaE, dnaF, dnaG, dnaZ, lig and rep. The cellular products of dnaA, dnaB, dnaC(D), dnaI, dnaP, polA, polB and xth genes are, however, dispensable for the viral growth. In these host factor requirements, XtB resembles phages K and St-1, rather than X174. Host ranges of XtB, St-1 and K overlap considerably, and growth temperature of the three phages is somewhat higher than that of X174. Furthermore, XtB is, like K, inactivated by antiserum against St-1. XtB may thus fill an evolutionary gap between the X174 group and the St-1 group.     

Quantifying Protein Folding Transition States with ΦT

A number of reaction coordinates have been proposed for reduced-dimensionalityrepresentations of a protein's folding free energy surface. We discuss in detail the entropic reaction coordinate _T = SS, recently introduced to quantify the conservation of mutations and the location of the folding transition state based on experimental temperature-tuning data. Numerical simulations illustrate the advantages as well as the limitations of _T. _T can be determined from experiment,computation, and analytical theory; _T can also be used to investigate structurally localized perturbations of the free energy surface. However, _T is only a relative reaction cordinate; furthermore, proteins undergo cold denaturation at sufficiently low temperatures, and care must be taken ininterpreting _T near the region where G/T = 0, particularly if the heat capacity change upon folding is small.     

An improved method,using saturating light pulses,for the determination of photosystem I quantum yield via P700+-absorbance changes at 830 nm

An improved method is introduced for the determination of the quantum yield of photosystem I. The new method employs saturating light pulses with steep rise characteristics to distinguish, in a given physiological state, centers with an open acceptor side from centers with a reduced acceptor side. The latter do not contribute to PSI quantum yield (_I). Oxidation of P700 is measured by a rapid modulation technique using the absorbance change around 830 nm. The quantum yield _I is calculated from the amplitude of the rapid phase of absorbance change (A; 830 nm) upon application of a saturation pulse in a given state, divided by the maximal A (830 nm) which is induced by a saturation pulse with far-red background illumination. Using this technique, _I can be determined even under conditions of acceptor-side limitation, as for example in the course of a dark-light induction period or after elimination of CO₂ from the gas stream. Thus determined _I values display a close-to-linear relationship with those for the quantum yield of PSII (_II) calculated from chlorophyll fluorescence parameters. It is concluded that the proposed method may provide new information on the activity of the PSI acceptor side and thus help to separate the effects of acceptorside limitation from those of cyclic PSI, whenever a non-linear relationship between _II and the P700-reduction level is observed.Abbreviations and Symbols A absorbance change - _I quantum yield of photosystem I - _II quantum yield of photosystem II - PAR photosynthetically active radiation This work was supported by the Deutsche Forschungsgemeinschaft (SFB 176 Molekulare Grundlagen der Signalübertragung und des Stofftransportes in Membranen and SFB 251 Ökologie, Physiologie und Biochemie pflanzlicher Leistung unter Streß).     

The relationship between Photosystem II intrinsic quantum yield and millisecond luminescence in thylakoids

The relationship between charge recombination at Photosystem II (PS II), as indicated by millisecond luminescence, and PS II quantum yield was studied in spinach thylakoids during electron flow to methylviologen. Under the low magnesium conditions used, a decrease in quantum yield was observed in the absence of non-photochemical excitation quenching, and therefore cannot be due to a restriction in excitation delivery to the reaction centre. It was found that the decrease of the parameter _p, which is a measure of the intrinsic quantum yield of open PS II centers, correlates with an increase in luminescence per open center. The relationship between these two parameters was the same whether _p was manipulated by dissipation of the transthylakoid pH gradient or of the electrical potential. This indicates that the mechanism by which _p decreases depends in the same way on the two components of the protonmotive force as does the charge recombination at PS II. Calculation of the yield of luminescence with respect to the back reaction will be necessary to determine whether the charge recombination occurs at a sufficiently high rate to be directly responsible for the _p decrease.     

Light dependence of quantum yields of Photosystem II and CO2 fixation in C3 and C4 plants

The light dependence of quantum yields of Photosystem II (_II) and of CO₂ fixation were determined in C₃ and C₄ plants under atmospheric conditions where photorespiration was minimal. Calculations were made of the apparent quantum yield for CO₂ fixation by dividing the measured rate of photosynthesis by the absorbed light [A/I=_CO2 and of the true quantum yield by dividing the estimated true rate of photosynthesis by absorbed light [(A+R_l)/I_a=_CO2·], where R_L is the rate of respiration in the light. The dependence of the _II/_CO2 and _II/_CO2 ^* ratios on light intensity was then evaluated. In both C₃ and C₄ plants there was little change in the ratio of _II/_CO2 at light intensities equivalent to 10–100% of full sunlight, whereas there was a dramatic increase in the ratio at lower light intensities. Changes in the ratio of _II/_CO2 can occur because respiratory losses are not accounted for, due to changes in the partitioning of energy between photosystems or changes in the relationship between PS II activity and CO₂ fixation. The apparent decrease in efficiency of utilization of energy derived from PS II for CO₂ fixation under low light intensity may be due to respiratory loss of CO₂. Using dark respiration as an estimate of R_L, the calculated _II/_CO2 ^* ratio was nearly constant from full sunlight down to approx 5% of full sunlight, which suggests a strong linkage between the true rate of CO₂ fixation and PS II activity under varying light intensity. Measurements of photosynthesis rates and _II were made by illuminating upper versus lower leaf surfaces of representative C₃ and C₄ monocots and dicots. With the monocots, the rate of photosynthesis and the ratio of _II/_CO2 exhibited a very similar patterns with leaves illuminated from the adaxial versus the abaxial surface, which may be due to uniformity in anatomy and lack of differences in light acclimation between the two surfaces. With dicots, the abaxial surface had both lower rates of photosynthesis and lower _II values than the adaxial surface which may be due to differences in anatomy (spongy versus palisade mesophyll cells) and/or light acclimation between the two surfaces. However, in each species the response of _II/_CO2 to varying light intensity was similar between the two surfaces, indicating a comparable linkage between PS II activity and CO₂ fixation.Abbreviations A measured rate of CO₂ assimilation - A+R_L true rate of CO₂ assimilation; e - CO₂ estimate of electrons transported through PSII per CO₂ fixed by RuBP carboxylase - f fraction of light absorbed by Photosystem II - F'_m yield of PSII chlorophyll fluorescence due to a saturating flash of white light under steady-state photosynthesis - F_s variable yield of fluorescence under steady-state photosynthesis; PPFD-photosynthetic photon flux density - I_a absorbed PPFD - PS II Photosystem II - R_d rate of respiration in the dark - R_I rate of respiration in the light estimated from measurement of R_d or from analysis of quantum yields - apparent quantum yield of CO₂ assimilation under a given condition (A/absorbed PPFD) - true quantum yield of CO₂ assimilation under a given condition [(A+R_L)/(absorbed PPFD)] - quantum yield for photosynthetic O₂ evolution - electrons transported via PS II per quantum absorbed by PS II Supported by USDA Competitive Grant 90-37280-5706.     

Leaf anthocyanin content changes in Zea mays L. grown at low temperature: Significance for the relationship between the quantum yield of PS II and the apparent quantum yield of CO2 assimilation

The quantum yield of non-cyclic electron transport from PS II (PS II) and the apparent quantum yield of CO2 fixation (CO2) were measured in the maize genotype, R-CH HOPI, which shows a high leaf anthocyanin content when grown at a temperature slightly below 20 °C. Thus, the leaf anthocyanin content was thirty-five times higher in plants grown at 18 °C when compared to plants grown at 23 °C. The relationship between PS II and CO2 obtained at different CO2 partial pressure was linear for plants with both high and low leaf anthocyanin content. The PS II/CO2 ratio was about 16 in plants with high leaf anthocyanin content and about 10 in plants with low leaf anthocyanin content. The leaf light absorptance in the 400–700 nm region was higher in plants with higher leaf anthocyanin content. Since leaf absorptance between 400 and 600 nm and leaf anthocyanin content also resulted in a strict linear relationship, an indirect estimation of the absorbed light by leaf anthocyanins and thus at chloroplasts was derived. Using the correct estimation of the absorbed light at chloroplasts, to obtain CO2, differences in PS II/CO2 ratios between plants with different leaf anthocyanin content were eliminated. The modulation of leaf anthocyanin content by growth temperature is regarded as an effective strategy to modulate the light available at the chloroplasts.     

Sinking properties of some phytoplankton shapes and the relation of form resistance to morphological diversity of plankton – an experimental study

Form resistance () is a dimensionless number expressing how much slower or faster a particle of any form sinks in a fluid medium than the sphere of equivalent volume. Form resistance factors of PVC models of phytoplankton sinking in glycerin were measured in a large aquarium (0.6 × 0.6 × 0.95 m). For cylindrical forms, a positive relationship was found between and length/width ratio. Coiling decreased in filamentous forms. Form resistance of Asterionella colonies increased from single cells up to 6-celled colonies than remained nearly constant. For Fragilaria crotonensis chains, no such upper limit to was observed in chains of up to 20 cells (longer ones were not measured). The effect of symmetry on was tested in 1–6-celled Asterionella colonies, having variable angles between the cells, and in Tetrastrum staurogeniaeforme coenobia, having different spine arrangements. In all cases, symmetric forms had considerably higher form resistance than asymmetric ones. However, for Pediastrum coenobia with symmetric/asymmetric fenestration, no difference was observed with respect to symmetry. Increasing number and length of spines on Tetrastrum coenobia substantially increased . For a series of Staurastrum forms, a significant positive correlation was found between arm-length/cell-width ratio and : protuberances increased form resistance. Flagellates (Rhodomonas, Gymnodinium) had a < 1: they sank faster than the spheres of equivalent volume. Ceratium ( = 1.61) proved an exception among flagellates: in most forms tested in this study (ellipsoid flagellates, Staurastrum forms with no or very short protuberances, and Cosmarium forms), > 1. The highest value ( = 8.1) was established for a 20-celled Fragilaria crotonensis chain. Possible origin of the so-called `vital component' (a factor that shows how much slower viable populations sink than morphologically similar senescent or dead ones) is discussed, as is the role of form resistance in evolution of high diversity of plankton morphologies.An erratum to this article can be found at     

Untersuchungen über die Inaktivierung und Radikalbildung an suspendiertem Trypsin nach UV-Bestrahlung

Zusammenfassung Es wird eine Methode zur UV-Bestrahlung von Enzymsuspensionen in Alkohol angegeben. Durch Eintauchen der UV-Lampe in die homogene Suspension läßt sich auf einfache Weise die vom Enzym absorbierte Energie bestimmen. Die Inaktivierung wird in Abhängigkeit von der Bestrahlungsdauer gemessen und mittels der ESR-Spektroskopie die Radikalbildung untersucht. Die ESR-Spektren zeigen, daß eine sauerstoff- und wasserfreie Äthanolsuspension vakuumähnliche Bestrahlungsbedingungen liefert. Man erhält ein Radikal am-Kohlenstoff und ein Schwefelradikal vom Typ RS ·. Es wurden die Quantenausbeuten für die Inaktivierung _i und für die Radikalbildung _r ermittelt. Für Trypsin finden wir nach Bestrahlung mit UV-Licht der Wellenlänge 254 nm _i=2,4·10_–2 und _r =1,7·10_–3. Daraus ergibt sich für die Anzahl der Radikale pro inaktiviertem Molekül ein Wert von 0,07, der nahelegt, daß zwischen der gemessenen Inaktivierung und den noch vorhandenen Radikalen kein direkter Zusammenhang besteht. Untersuchungen mit einem kontinuierlichen UV-Spektrum ergaben dieselbe Radikalzahl pro inaktiviertem Molekül, wobei jedoch die Schwefelradikalausbeute geringer ist als nach Bestrahlung mit der Linie 254 nm. Bestrahlung mit Wellenlängen > 300 nm bewirkte eine teilweise Löschung der durch die Linie 254 nm erzeugten Radikale.

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Studies on inactivation and radical formation after UV-irradiation of trypsin in suspension

Summary A method for UV irradiation of suspensions of enzymes in alcohol has been described. The UV lamp was dipped into the suspension which was stirred during irradiation in order to provide a homogeneous exposure of the enzymes and to facilitate the determination of the energy absorbed in the enzymes. The inactivation has been studied as a function of exposure time, radical formations being analysed by way of EPR-spectroscopy. The EPR spectra indicated that oxygen- and waterfree suspensions in ethanol provide vacuumlike conditions for UV irradiation. A radical at the C position and a sulfur radical of the RS · type were observed. Quantum yields for the inactivation ( _i) and for radical formation ( _r) were obtained. UV irradiation of trypsin at 254 nm yielded _i=2,4·10^–2 and _r=1,7·10^–3. As a result the value of 0.07 free radicals per inactivated molecule leads to the suggestion that there is no direct relation between the inactivation and the observed radical formation. The same number of free radicals per inactivated molecule was obtained after irradiation with a continuous UV spectrum, the yield of sulfur radicals however was lower than in the 254 nm investigation. Irradiation with > 300 nm partially quenches the radicals produced at 254 nm.

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Abschließend möchte ich des im Februar 1969 verstorbenen Prof. Dr. Kurt Sommermeyer gedenken, dem ich für die Anregung zu diesem Thema und für wertvolle Diskussionen zu danken habe. Dem Deutschen Akademischen Austauschdienst danke ich für das Stipendium, das mir die Durchführung der Arbeit im Radiologischen Institut ermöglicht hat.     

Physiological relationship between the temperate phages lambda and phi80

Summary This work deals with the ability of phage 80 to provide defective mutants of with their missing functions. Functions Involved in Recombination. As shown by others, the Int mechanism of 80 cannot excise prophage . However, 80 efficiently excises recombinants from tandem dilysogens, using its Ter mechanism. Likewise, the nonspecific mechanism Red is interchangeable between 80 and . Maturation of DNA by 80. The Ter recombinants excised by 80 from tandem dilysogens are packaged into a 80 protein coat. This contrasts with the fact, already mentionned by Dove, that 80 is extremely inefficient for packaging phage superinfecting a -lysogen. The latter result is also found when the helper phage is a hybrid with the left arm of (80hy4 or 80hy41 — see Fig. 1). However, the maturation of the superinfecting is much more efficient if the 80hy used as a helper has the att-N region of (like 80hy1). Conversely a with the att-N region of 80 (hy6 — see Fig. 1) is packaged more efficiently by 80 or 80hy4 than by 80hy1. It is suggested that the maturation of chromosome superinfecting an immune cell requires a recombination with the helper phage. Vegetative Functions. Among the replicative functoons O and P, the latter only can be supplied by 80. That N mutants are efficiently helped by 80 does not tell that 80 provides the defective with an active N product; the chromosomes are simply packaged into a 80 coat. This shows that 80 is unable to switch on the late genes of . That neither 80 nor any of the 80hy tested can provide an active N product is shown in a more direct way by their complete failure to help N ^-r₁₄; this phage carries a polar mutation which makes the expression of genes O and P entirely N-dependant. The maturation of a N ^- by 80 contrasts with the fact that mutants affected in late genes (A, F or H) are not efficiently helped by 80. This suggests that the products coded by these genes are not interchangeable between 80 and , and that packaging of DNA into 80 coats is possible but inhibited when late proteins are present in the cell. Activation of the Late Genes. Among the im ₈₀ h ⁺ hybrids tested, only 80hy41 is able to switch on the late genes of a N defective mutant. This hybrid differs from the other hybrids studied here, by the fact that it has the Q-S-R region of (see Fig. 1). The results are consistant with the view that the product of Q gene is sufficient for activating the late genes of a DNA. N would thus control the expression of late genes only indirectly by controlling the expression of gene Q (Couturier & Dambly have independantly reached the same conclusion, 1970). Furthermore the failure of 80 and of the 80hy1 and 80hy4 to activate the late genes of would imply that these phages are unable to provide an Q product active on the chromosome Reciprocally, switches on the late genes of prophage 80hy41, but not of prophages 80hy1 and 80hy4. This suggests that the initiation of late genes expression takes place at a main specific site located in the Q-S-R region of the chromosome. The expression of the late genes would thus be sequential, and proceed through the left arm only when steaky ends cohere. Similar conclusions were reached independantly by Toussaint (1969) and by Herskowitz and Signer (1970).

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Ce travail a été réalisé dans le cadre du contrat d'association Euratom-U. L. B. 007-61-10 ABIB et avec l'aide du Fonds de la Recherche Fondamentale Collective.     

Unigenic and multigenicI region control of the immune responses of mice to the GAT10 and GLΦ-GLT terpolymers

Recombinant strains of mice with known alleles in theI region of theH-2 complex were used to map theH-2 linked immune response genes controlling responsiveness to random terpolymers GAT¹⁰ and GL. TheIr-GAT gene was mapped to either theIA orIB subregions. In contrast, data obtained in the GL-GLT system indicated multigenic control. The responsiveness of the B10.A(3R), B10.A(5R), and B10.S(9R) recombinants indicated that one immune response gene,IrGL-GLT _A, mapped to the right ofIB, i.e., in theIC subregion. The nonresponsiveness of the B10.A(1R), B10.A(2R), B10.M(17R), and AQR mice having responderIC ^d alleles butIA ^k-IB ^k nonresponder alleles and the positive response of a (C57BL/6 × A/J)F₁ hybrid derived from two nonresponder parental strains indicated the presence of a second gene inIA-IB subregions,Ir-GL-GLT _B. The interaction between these two genes, each present in a differentI subregion, controls the immune response.     

Different Relationship Between Electron Transport and CO2 Assimilation in two Zea mays Cultivars as Influenced by Increasing Irradiance

Gas exchange and fluorescence parameters were measured simultaneously in two Zea mays L. cultivars (Liri and 121C D8) to assess the relationship between the quantum yield of electron transport (_PS2) and the quantum yield of CO₂ assimilation (_CO2) in response to photosynthetic photon flux density (PPFD). The cv. Liri was grown under controlled environmental conditions in a climate chamber (CC) while cv. 121C D8 was grown in CC as well as outdoors (OT). By exposing the two maize cultivars grown in CC to an increasing PPFD, higher photosynthetic and photochemical rates were evidenced in cv. Liri than in cv. 121C D8. In Liri plants the _PS2/_CO2 ratio increased progressively up to 27 with increasing PPFD. This suggests that the reductive power was more utilised in non-assimilatory processes than in CO₂ assimilation at high PPFD. On the contrary, by exposing 121C D8 plants to increasing PPFD, _PS2/_CO2 was fairly constant (around 11–13), indicating that the electron transport rate was tightly down regulated by CO₂ assimilation. Although no significant differences were found between _PS2/_CO2 of the 121C D8 maize grown under CC and OT by exposing them to high PPFD, the photosynthetic rate and photochemical rates were higher in OT maize plants.     

Involvement of growth differentiation factor-15/macrophage inhibitory cytokine-1 (GDF-15/MIC-1) in oxLDL-induced apoptosis of human macrophages in vitro and in arteriosclerotic lesions

Growth differentiation factor-15/macrophage inhibitory cytokine-1 (GDF-15/MIC-1) is a new member of the transforming growth factor beta (TGF-) superfamily, which has most recently been found in activated macrophages (M). We have now investigated GDF-15/MIC-1 in human M after exposure to oxidized low-density lipoproteins (oxLDL) related mediators in vitro and in arteriosclerotic carotid arteries. Using RT-PCR and Western blotting a pronounced induction of GDF-15/MIC-1 expression by oxLDL, C₆-ceramide, tumor necrosis factor (TNF) and hydrogen peroxide (H₂O₂) was found in cultured human M. In 11 human arteriosclerotic carotid arteries, immunohistochemical analyses supported by computer-assisted morphometry and regression analyses demonstrated a significant colocalization of GDF-15/MIC-1 immunoreactivity (IR) with oxLDL IR and manganese superoxide dismutase (MnSOD) IR in CD68 immunoreactive (ir) M, which were also expressing AIF-IR (apoptosis-inducing factor), caspase-3-IR (CPP32), PARP-IR, c-Jun/AP-1-IR and p53-IR. Our data suggest that GDF-15/MIC-1 is inducible in human M by oxLDL and its mediators in vitro and is supposed to contribute to oxidative stress dependent consequences in arteriosclerotic plaques, e.g. modulating apoptosis and inflammatory processes in activated M.The last two authors are senior authors.