The effect of osmotic `shock'' on the swelling pattern and respiratory control of rat-liver mitochondria

1. Rat-liver mitochondria suspended in 0.25m-sucrose were exposed for a few seconds to strongly hypo-osmotic conditions, and then the osmolarity of the medium was raised again to 0.25 with the aid of tris chloride (osmotic ;shock'). 2. Mitochondria after hypo-osmotic pretreatment lost their capacity for slow energy-dependent swelling in iso-osmotic tris buffer and showed no respiratory control. 3. Swelling could be induced in the ;shocked' mitochondria by ATP but not by addition of respiratory substrates. 4. It was shown that cytochrome c is lost from ;shocked' mitochondria when they come into contact with the tris buffer present in the assay medium, and that the changes observed in the pattern of swelling, as well as in respiratory control, are directly connected with this loss of cytochrome c. 5. The results of the investigation are discussed with regard to the role of cytochrome c in swelling and respiratory control.     

Differential Effect of Polyamines on T4 Morphogenesis

The 5-fluorouracil (5 FU) technique for the phenotypic reversion of amber mutants was used to demonstrate that under certain circumstances, in the presence of putrescine or spermidine, early mutants have an enhanced response to 5 FU, whereas late mutants have a delayed response. Bacteria infected by T4D wild-type bacteriophage did not produce phage in the presence of high putrescine concentrations. Pulse treatments with putrescine showed that the production of lysozyme depends on a putrescine-sensitive process that begins immediately after infection at 26 C and ends at 36 min or even later. The addition of putrescine at any time during the critical period between 0 and 36 min led to a corresponding delay in lysozyme synthesis after the inhibitor was removed. Intracellular phage maturation was delayed by the addition of 100 mumoles of putrescine per ml. Early enzymes were not affected by the diamine, but the level of phage deoxyribonucleic acid was considerably decreased by the inhibitor. The putrescine-sensitive process that affects the timing of maturation is suggested to be the natural process controlling the T4 "clock."     

Phytochrome-mediated effects on extracellular peroxidase activity, lignin content and bending resistance in etiolated Vicia faba epicotyls

Etiolated Vicia faba seedlings were exposed to continuous red light to investigate whether changes in extracellular peroxidase activity were correlated in time and localization with changes in extension growth and/or lignin content in the subapical region of the epicotyl. Continuous red light: (a) increased extracellular peroxidase activity after a lag of ca 0.5 h, followed by a maximum peak after 2.5 h due to slightly acidic isoforms (pI = 6–6.5, according to isoelectrofocusing gels), a minimum after 4 h and a second maximum after 8 h due to acidic isoforms (pI=4–5), (b) increased lignin content and epicotyl resistance to bending after a lag of ca 4 h, i.e. simultaneously with changes in acidic extracellular peroxidase activity, and (c) reduced extension growth to a stable rate after a lag of ca 1 h, not coinciding with the kinetics of any of the extracellular peroxidase isoforms. These effects of continuous red light were at least partially mediated by phytochrome. Tissue printing and anatomical studies revealed red light effects on extracellular peroxidase activity and lignin content mainly in the outer cortical parenchyma. The results are consistent with the involvement of phyto-chrome-mediated effects on extracellular peroxidases (acidic isoforms) in the transduction chain leading to lignin responses to red light.     

Modulation by glycine on vascular effects of NMDA:in vivo experimental research

Summary The present study has been carried out to determine if glycine, an allosteric modulator of NMDA receptor, is involved in the vascular effect induced by the activation of the CNS NMDA receptors.Icv NMDA (from 0.01 to 1µg/rat in the 3rd ventricle) caused a significant increase in arterial blood pressure in conscious freely moving rats. Moreover, the hypertension was associated with behavioural modifications (jumping, rearing, teething and running). Glycine pretreatment (1 and 10µg/raticv), significantly increased the NMDA hypertension. Glycine alone did not cause any arterial blood pressure modification while it induced a slight sedation. HA-966 (an antagonist of the glycine site on NMDA receptor) administration (1–10µg/raticv 5 min before glycine) significantly antagonized the glycine effects on NMDA hypertension.Alone HA-966 neither modified arterial blood pressure nor antagonized NMDA hypertension. In conclusion, our investigations confirm NMDA receptor involvement in cardiovascular function and they demonstrate thatin vivo glycine positively modulates NMDA receptors.