Indole-3-acetic acid content and glutamine synthetase activity in the pericarp, and peroxidase activity and isoenzymes in the meso- and exocarp of growing peach fruits

The indole-3-acetic acid (IAA) content in peach pericarp (Prunus persica L. Batsch cv. Merry) was highest at early stage I of development (200 ng/g fresh wt), decreased to the lowest level during stage II, and rose again at stage III to 60–70 ng/g fresh wt. High activity of glutamine synthetase was found in the pericarp during stage I. The soluble peroxidase activity was highest in the meso- and exocarp at stage II, and isoenzymatic changes in this fraction corresponded to the transition from cationic isoenzymes, predominant at stage I, to anionic isoenzymes at stage III. The ionically bound peroxidase activity in these tissues was highest at stage I. The three developmental stages showed marked differences in auxin content and enzyme activities; for peroxidases these changes reflect a developmental expression pattern for the isoenzymes.     

Altered levels of tissue and urinary prostacyclin in rats subjected to pancreas transplantation

Significant increases of TXB2 and PGE2 are reported to occur in pancreas transplantation. These increases are prevented with scavengers of oxygen-free radicals. In this communication, we report on changes of prostacyclin metabolites such as tissue 6-keto prostaglandin F1 alpha and urinary 2,3-dinor 6-keto prostaglandin F1 alpha in rats subjected to pancreas transplantation after different periods of organ cold preservation ischemia as well as the effect of superoxide dismutase (SOD) on these changes. For this purpose, male Lewis rats were classified as follows: Group I, Control; Group II, syngenic pancreas transplantation after 15 min of organ preservation in Collins solution at 4 degrees C; Group III, same as II but with 12 hours of organ preservation; Group IV, same as III, but with SOD pretreatment. Results have shown significant posttransplantation increases of both tissue 6-keto PGF1 alpha and urinary 2, 3 dinor 6-keto PGF1 alpha, the latter being a useful marker to evaluate systemic prostacyclin (PGI2) production by rat pancreas. This effect was prevented when the organ had been exposed to SOD during the period of cold preservation ischemia. These results confirm the implication of oxygen-free radicals (OFR) in the ischemia-reperfusion process associated to rat pancreas transplantation leading to enhanced arachidonic acid metabolism.     

Temporal Profiles of Proteins Responsive to Transient Ischemia

The responses of long and short half-lived proteins to ischemia were measured in rat brain during 6 days of recovery from 30 min of transient forebrain ischemia produced by four-vessel occlusion. At the end of the ischemic interval, the neocortical activities of four vulnerable enzymes [ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylases, and RNA polymerases I and II] were unchanged, but within 30 min of reperfusion, their activities dropped by 25-50%. The loss of substance P in the striatum and substantia nigra was slower, reaching about 50% by 12 h. On the other hand, the activities of 5 long half-lived enzymes did not change in the neocortex at 5 and 15 h of reperfusion and regional protein concentrations were essentially unaffected over 6 days survival. The rate and extent of normalization of the amounts or activities of the vulnerable proteins varied. RNA polymerase II and ODC activities were restored within 4 h, and ODC showed a biphasic increase in activity, with peaks at 10 h and 2-3 days. RNA polymerase I and SAMDC activities were restored by 18 h and 5 days, respectively, whereas substance P concentrations did not completely recover, even at 6-15 days. The greater the regional reduction of blood flow during ischemia, the larger the net change (gain or loss) of SAMDC or ODC activity and the longer the time required to normalize the activities of these enzymes. The average rate of proteolysis, assessed by measuring the rate of clearance of 14C from protein prelabeled with [14C]bicarbonate, was abnormal during the first 2 days of reperfusion. Postischemic changes in both protein synthesis and degradation could affect the amounts of some of the proteins responsive to transient ischemia.     

Modulation of endogenous prostaglandins by thymosin-α1 in lymphocytes

The effects of thymosin-α₁ on the stimulation of specific release of prostaglandin E₂ (PGE₂) from splenic lymphocytes and thymocytes were studied. Experiments were also performed to study in parallel the absolute levels of thymosin-α₁ in the blood and the induction of serum FTS activity and of azathioprine sensitivity of spleen cells from adult thymectomized (ATx) mice. A significant difference in the release of PGE₂ between normal splenocytes and splenocytes from ATx mice was observed. Thymosin-α₁ at certain concentrations was able to stimulate PGE₂ release from lymphocytes of ATx mice while inhibiting release in lymphocytes of normal mice. Also, thymocytes were stimulated to release PGE₂ after incubation with α₁ in a manner similar to that seen in spleen cells of ATx mice. Approximately the same concentration of α₁ was found to also correct the low azathioprine sensitivity of splenocytes from ATx mice. Determinations of FTS-like activity in the blood and the pharmacokinetics of α₁ after administration of this synthetic molecule show a clear dissociation. A maximum peak of α₁ activity was obtained after 1 hr, while maximal FTS-like activity was observed after 24 hr. The inhibition of the induction by α₁ of FTS-like activity and of Thy 1.2 antigen by indomethacin suggests that the action of α₁ requires prostaglandin biosynthesis.     

Physiology of a choline-requiring strain of Torulopsis pintolopesii

Summary A choline-requiring strain of Torulopsis pintolopesii when growing on choline-methyl-¹⁴C or choline-methyl-³H excretes the radioactivity incorporated in the first 24–48 h of incubation up to ca. 85–95% of the radioactivity added at the beginning of the incubation. The addition of non-radioactive methionine did not interfere with the uptake and excretion of radioactivity from choline-Me-¹⁴C. Radioactive methyl group of methionine previously incorporated by growing cells of T. pintolopesii on varying concentrations of choline was not excreted in appreciable amounts. No evidence was obtained for the oxidation of choline to betaine, degradation to trimethylamine, or net incorporation of labelled choline into lecithin. The occurrence of a new pathway for the utilization of choline in yeasts is suggested. The requirement of choline by T. pintolopesii is explained tentatively by the formation and excretion of a compound containing the carbon and hydrogen atoms from the methyl groups of choline and whose chemical structure still under study, may comprise a heteroside containing mannitol as the polyhydroxylated moiety.     

Mouse blastocyst immunosurgery with commercial antiserum to mouse erythrocytes

Summary Immunosurgery is a useful technique for the isolation of inner cell masses from murine blastocysts. Conventionally, rabbit antisera made ad hoc against murine splenic or fetal cells or fibroblasts have been used as antibody sources. We investigated the feasibility of using commercially available rabbit antiserum to murine erythrocytes (anti-RBC) and compared it with rabbit antiserum generated ad hoc to murine L-cells (anti-L-cell). Our results indicate that anti-RBC is at least as effective as anti-L-cell serum for the immunosurgical isolation of inner cell masses, which became either miniblastocysts (later forming outgrowths) or embryoid bodies (undergoing ectoderm-endodermlike differentiation within 48 h). Because anti-RBC is commercially available, the technical modification described herein increases the accessibility of the immunosurgical protocol for the isolation of murine inner cell masses.