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This retrospective study investigated the stability of the small AO external fixator in a radioradial configuration used in the treatment of 42 mostly unstable distal radius fractures (types A-3.2, C-1.2 and C-2.1 according to the AO classification). No bone grafting was performed. All cases were documented with antero-posterior and lateral X-rays preoperatively, 0, 2 and 6 weeks postoperatively and after consolidation. Early functional aftertreatment was started one week after surgery. Thirty-six fractures showed a dorsal comminution, combined with osteopenia in 18 cases. The mean preoperative radial angle of 17 degrees was normalized to 25 degrees postoperatively. The mean preoperative volar angle of minus 30 degrees was reduced to 12 degrees postoperatively. None of these mean angles changed until consolidation. The external fixator was removed on average after 7 weeks (range 6-10 weeks) depending on the radiological fracture healing. The small AO external fixator in a radioradial configuration proved to be stable enough for early functional aftertreatment of the wrist. Its stability is related to a proper operative technique and correct indication (unstable Colles type with one or two distal fragments). Bone grafting is unnecessary if the external fixator is left in situ until bony consolidation.

Pteridines were originally described as pigments of insects and lower vertebrates. The electron-donating function of tetrahydrobiopterin for aromatic amino acid hydroxylation and thus, for neurotransmitter biosynthesis adduced the participation of unconjugated pterins in cellular metabolism. There has been increasing evidence moreover that they are signal molecules for intercellular recognition in primitive eucaryotes, as well as modifiers of signal polypeptides in higher vertebrates.

1. A chlorophyll-less Pisum sativum mutant showed - in contrast to the normal form - no increase in the activity of the NADP(+)-dependent glycerinaldehyde-3-phosphate-dehydrogenase following illumination. 2. In both forms of Pisum the amount of the enzyme present in the dark was about equal. 3. DCMU, an inhibitor of the noncyclic electron flow in photosynthesis reduces the light-induced synthesis of the enzyme to about half in a concentration of 10(-6) m and inhibits it totally at higher concentrations. The dark values of enzyme activity were not influenced by the presence of the inhibitor. 4. Salicylaldoxime also blocks the enzyme synthesis in the light; this effect increases with increasing concentration of the inhibitor. The inhibition is complete at a concentration of 5 · 10(-4) m. 5. Sodium azide in a concentration of 10(-3) m inhibits the photosynthesis and the light-induced GPD-synthesis almost completely; respiration is diminished by more than 50% whereas the dark value of the GPD-activity remains unchanged. 6. 2,4-Dinitrophenol in a low concentration (10(-6) m) increased the oxygen consumption in the dark considerably, but the photosynthesis only slightly. The light synthesis of the enzyme was not affected, nor was the dark value influenced. At a concentration of 10(-5) m there was a slight decrease in respiration and a greater decrease in the photosynthesis. The dark value of the GPD was not different from that of the controls whereas the synthesis in the light was markedly diminished. A concentration of 10(-4) m completely blocks the respiration, the photosynthesis, and the light-induced GPD-synthesis; the dark value is decreased to about 50%. 7. It is concluded that the reversible synthesis of the NADP(+)-dependent GPD in light is dependent on chlorophyll and on an intact photosynthesis; the decisive reaction in this connection is the photoreaction II, the noncyclic electron flow.

1. Preceding experiments had shown that irradiance of intact leaves or of isolated chloroplasts causes a reversible increase in the activity of NADP-GPD (Ziegler and Ziegler, 1965) as well as of ribulose-5-phosphate kinase (Latzko and Gibbs, 1969). Examination of several species which carry out the Calvin type of photosynthetic CO2 fixation (Vicia faba, Spinacia oleracea, Nicotiana tabacum, Avena sativa) now revealed that the dark level of NADP-GPD activity ranges between 300-400 μmol NADPH/mg chlorophyll·h; irradiance causes an activation to an turnover rate of 900-1600 μmol NADPH/mg chlorophyll·h. 2. The dark-level of ribulose-5-phosphate kinase in these Calvin type plants corresponds to about 400 \gmmol PO4---/mg chlorophyll\sdh. It rises to 900\2-1300 \gmmol PO4---/mg chlorophyll\sdh after irradiance. 3. In all species examined which carry out the C4-dicarboxylic acid type of CO2 fixation (Zea mays, Cyperus rotundus, Portulacca oleracea, Saccharum officinarum) the dark-level of NADP-GPD as well as of ribulose-5-phosphate kinase is already as high as the light-level of Calvin type plants. In these species irradiance either activates both enzymes only to a small extent (Saccharum officinarum, Portulacea oleracea) or it activates only one of the two enzymes to an exceptional high activity (NADP-GPD in Zea mays, ribulose-5-phosphate kinase in Cyperus rotundus), while the activity of the other one remains nearly constant. 4. The dark-level of NADP-GPD in young Zea mays (2 leaves expanded) is as high as in adult plants; moreover its further activation by light corresponds to that in adult plants. In contrast, the dark-activity of ribulose-5-phosphate kinase in young Zea mays corresponds to the lower level found in Calvin type plants and is activated by irradiance in the same manner as it is in the latter plants. 5. The activity of ribose-5-phosphate isomerase is not influenced by light.

1. NADP(+)-dependent GPD was clearly active in 8 out of 13 Rhodophyta and in 5 out of 8 Phaeophyta tested. 2. NAD(+)-specific GPD was detectable in all of the 6 red algae analysed and in the 3 brown algae tested. 3. Aldolase-activity was found unequivocally in 8 out of 10 red algae and in 7 out of 8 brown algae. 4. It is concluded that the absence of these enzymes is not a characteristic for these groups of algae. 5. Light increases the activity of the NADP(+)-dependent GPD in species of Chlorophyta and Rhodophyta, and probably also in species of Phaeophyta.

1. Tetrasporophytes as well as male and female gemetophytes of Ceramium rubrum show differences in the protein and pigment content, in the activity of the aldolase, and in the light-induced increase in the activity of the NADP(+)-dependent glyceraldehyde-3-phosphate-dehydrogenase (GPD). 2. A very high light intensity is necessary to diminish the increase of the GPD-activity; our Ceramium-material (from shallow water) thus behaves like a strong-light plant. 3. The activity of aldolase in the extract is not influenced by the preceding illumination of the algae. 4. The increase in activity of the NADP(+)-dependent GPD depends on the light quality in a similar way as the intensity of photosynthesis; the phycobilins are also effective as light acceptors in this case. 5. Certain wave-lengths were removed with "minus-filters" from a continuous spectrum (white light). Absence of red-light (663, 714 nm) had no influence on the activation of the enzyme, absence of green light (543, 492) diminished the activating effect, and absence of blue light (463 nm) increased it in comparison to the control (white light).

1. The photoreduction of K3[Fe(CN)6] by isolated and sonicated spinach chloroplasts is increased by SO 3 (--) (concentrations tested: 0.25-5 mM). This stimulation increases with SO 3 (--) concentrations from 0.25-3 mM. The ferricyanide-reduction with SO 3 (--) is inhibited by DCMU (10(-6)M) to about 90%. Inhibition of the photoreduction by pretreatment of the chloroplasts with Tris-buffer is compensated by increasing concentrations of SO 3 (--) (tested up to 3 mM). 2. The photoreduction of NADP in isolated chloroplasts is also enhanced by SO 3 (--) (concentrations tested: 0.25-3.0 mM). It is completely inhibited by DCMU (10(-6)M). In contrast to the results with ferricyanide as electron acceptor, SO 3 (--) does not overcome the inhibition of NADP reduction caused by pretreatment of the chloroplasts with Tris-buffer. 3. In illuminated isolated chloroplasts SO 3 (--) concentrations <1 mM do not alter the ATP-concentration, concentrations>1 mM decrease it. 4. The photosynthetic fixation of (14)CO2 by isolated chloroplasts is increased by SO 3 (--) concentrations <1 mM, but decreased by concentrations>1 mM. In total (14)CO2 fixed, at stimulating concentrations (0.25 and 0.5 mM SO 3 (--) ), the relative amount of sugar-monophosphates is increased, whereas that of sugardiphosphates and of PGA is decreased. 5. It is proposed that these specific effects on photosynthetic processes help to explain the well known fact that photosynthetic gas exchange and the yield of plants are stimulated by low doses of SO2.

1. In the green alga Acetabularia mediterranea illumination increases the activity of the NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenase compared with the dark value just as it does in the leaves of higher plants. 2. One day after enucleation of the Acetabularia-cell (by removal of the rhizoids) no enzyme activity is detectable either in dark or in light. Five days after the treatment the dark value of the enzyme activity reaches approximately the level of the intact plants, and illumination again increases the activity. It is concluded that the effect is independent of the presence of the nucleus.

1. A method for determination of the initial rate in enzymic non-linear progress reactions is described. 2. The relation between the increase in the activity of the NADP(+)-dependent glyceraldehyde-3-phosphate-dehydrogenase (GPD) and the different light intensities shows that Lemna gibba is adapted to high light intensities. 3. The time-curves for the increase in the activity of the enzyme in dependence on the different light intensities are similar to the corresponding curves for the intensity of photosynthesis. 4. The activity of the NAD(+)-dependent GPD in the extract decreases after preceding illumination of the plants; this activity is thus inverse to that of the NADP(+)-specific enzyme. There are indications (also in the literature) that the two enzymes are interconvertible.

1. The increase in the activity of the NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenase by irradiance and its reversal by darkness were measured. A T-values (activity after irradiance: activity in the dark after complete loss of activation) were plotted against increasing time of irradiation as well as against increasing time of darkening. 2. The A T-values for irradiance as well as for darkening yield sigmoidal types of curves, and are similar to those corresponding to the integral of a curve of the type y=e (-x) (2)(Gauss-curve). The (theoretical) sigmoidal curve was transformed (by double variable transformation) to optimally cover the experimental data. By differentiation Gauss-curves are obtained which express the change of enzyme activity per unit of time. The maximal points of these curves correspond to the half maximum of activation (not activity!) and to the highest change of activity per unit of time. 3. Figs. 3, 4 and 5 show that the increase in activity after onset of irradiation starts earlier than does the decrease after onset of darkening. Conditions which may cause the preservation of the activated enzyme during about 100 sec after darkening are discussed. However, the decrease is much more rapid later on than is the increase in the light; the change in activity (change of A T) per unit of time is smaller in the activation process than it is in the inactivation process. Thus the Gauss-curve becomes much sharper in the latter case. 4. Constant irradiance (irradiation with constant E eduring a given time period) at different points of dark-inactivation causes an activation velocity which increases with the time of the preceding dark period (Fig. 6). Therefore the Gauss-curve becomes sharper with increasing time of the preceding dark period (Fig. 7). 5. Increasing irradiance (irradiation with constant E eduring an increasing time period) at 3 different points of inactivation by variation of the time of predarkening also results in an increase in activation velocity with increase of time of predarkening (Figs. 8 and 9). 6. The model which best fits earlier experimental results as well as the kinetic studies is one in which activation is accomplished by association of four subunits of the enzyme (E o) to the activated tetrameric form (E akt). NADPH, created during the non-cyclic electron flow, could be the allosteric effector. Thus the activation velocity (change in activity per unit of time) is dependent on the concentration of E o. Both increase with increasing time of darkness. In contrast the time period of activation at constant irradiation is independent of the concentration of E o and is only dependent on the amount of the effector (NADPH), which increases with increasing time (increasing irradiance).