Synthesis and structural characterization of a novel covalently-bound corrole dimer.

The (triphenylphosphine)cobalt(III) complex (2) of 5,10,15-tris(pentafluorophenyl)corrole (1) is shown to be an valuable precursor to complexes that have not been fully characterized previously. In contrast to other cobalt corroles, aromatic amines can be substituted for the triphenylphosphine in 2 to form six-coordinate bis(amine)cobalt(III) complexes. This is demonstrated by spectroscopic methods and by X-ray crystallography of the bis-pyridine complex 4, the first of its kind. While 2 and 4 and even their one-electron oxidized complexes are stable, a spontaneous dimerization of the corrole takes place in the absence of strongly bound ligands. The bis-cobalt complex of the novel corrole dimer 6 was fully characterized by spectroscopic methods and X-ray crystallography.

Renal function and plasma levels of arginine vasotocin during free flight in pigeons.

We examined urinary water loss and plasma levels of arginine vasotocin (AVT) in free-flying, tippler pigeons trained to fly continuously for up to 5 h. First, we used [3H]polyethyleneglycol ([3H]PEG) as a glomerular filtration marker by implanting an osmotic minipump into each bird. In two flights (10 birds in winter at an ambient temperature of 13-15 degrees C and seven in summer at 23 degrees C), we measured pre-flight (hydrated, resting control birds) and post-flight [3H]PEG activity and osmolality in blood and ureteral urine. For comparison, we measured these variables in 10 birds in winter before and after controlled dehydration (24 h at 25 or 30 degrees C). Second, we measured plasma levels of AVT in 6-8 birds before and immediately after each of three different summer flights. Urine osmolality increased significantly by up to three times the control level in both post-flight and dehydrated pigeons; urine:plasma osmolality ratios did not exceed 2. Compared with controls, glomerular filtration rate (GFR) was significantly lower after flight in summer, but did not change in either post-flight or dehydrated winter pigeons. In winter, mean post-flight urine flow rate (UFR) decreased significantly to less than half the control level, while in summer, post-flight UFR did not differ from control levels. In general, mean filtered water reabsorption (FrH2O) increased from 95 % in controls to 98 % in post-flight and dehydrated birds. Plasma levels of AVT increased after flight to between three and eight times the preflight levels. The data from this first study of kidney function during flight are consistent with previous studies of dehydration in birds and exercise in mammals in which both increased FrH2O and decreased GFR contribute to renal conservation of water.

Role of Ethylene in Abscisic Acid-induced Callus Formation in Citrus Bud Cultures.

The induction of callus formation in cultured buds of Shamouti orange (Citrus sinensis [L.] Osbeck) by abscisic acid (ABA) is a multiphasic process. (Altman, and Goren 1974 Physiol Plant 32: 55.) A study of the mediation by ethylene on this effect of ABA was undertaken. It was found that: (a) ethylene and (2-chloroethyl) phosphonic acid, as well as ABA, induced callus formation; (b) callus induction is best attained when explants are exposed to ethylene during the 1st day after excision; and (c) ABA-induced callus formation is inhibited by rhizobitoxine analog, an inhibitor of ethylene biosynthesis. It is concluded that the effect of ABA on callus formation is mediated via ethylene.

Differential effects of sucrose, abscisic Acid, and benzyladenine on shoot growth and callus formation in the abscission zone of excised citrus buds.

The omission of sucrose from the basal medium stimulated callus formation in bud explants of Citrus sinensis (L.) Osbeck. Moreover, it increased the abscisic acid-induced callus proliferation reported earlier in the presence of 5% sucrose (Altman and Goren, Physiol. Plant. 32: 55, 1974). The inhibition of callus formation by the addition of sucrose was not due to the high osmotic potential of the medium. Benzyladenine induced callus formation slightly, in all sucrose concentrations up to 5%. The high level of sucrose was required, however, for the growth of shoots from buds cultured on both basal and benzyladenine-containing media.The uptake of (14)C-sucrose by bud explants was linear for at least 98 hr, and was enhanced significantly by both abscisic acid and benzyladenine during the initial 24-hour period. Abscisic acid enhanced the absorption of (14)C-sucrose and the accumulation of sugars in buds cultured at high levels of sucrose. More than 50% of the total label accumulated in the callus of abscisic acid-treated explants whereas only 16 and 23% were observed in the growing shoots of control and cytokinin-treated explants, respectively.Results suggested that while sucrose "starvation" induced initial callus formation, high levels retarded further proliferation of the callus.