ALBERT

Notes: Aluminum is a phytotoxic element in many soils and occurs in a variety of chemical species. In order to determine whether AlSO+4 is toxic, seedlings of wheat (Triticum aestivum L. cv. Tyler) and red clover (Trifolium pratense L. cv. Kenland) were transferred to solutions containing controlled activities of Al3+, AlSO+4, Na+ and Ca2+. Root elongation was inhibited by Al3+ (or mononuclear hydroxy-Al species that are in equilibrium with Al3+), but not by AlSO+4. We assumed a formation constant (KAlSO+4= {AlSO+4}/[{Al3+} {SO2-4}]; braces indicate activities} of 103.2 for AlSO+4 in the computation of ionic activities, but use of KAlSO+4 values ranging from 102.8 to 103.6 had very little effect on the computed toxicities of Al3+ and AlSO+4. Sulfate did not promote the formation of polynuclear Al complexes in our experiments. A practice in studies of Al phytotoxicity has been to attribute toxicity to mononuclear Al, but now it would seem advisable to exclude AlSO+4. That AlSO+4 is non-toxic, or is at least 10-fold less toxic than Al3+, has implications for the physiology of Al toxicity and for the use of sulfate salts in experimental work and in agriculture.

Notes: . The life cycle and morphology of a previously undescribed species of Cryptosporidium isolated from commercial broiler chickens is described. The prepatent period for Cryptosporidium baileyi n. sp. was three days post oral inoculation (PI) of oocysts, and the patent period was days 4–24 PI for chickens inoculated at two days of age and days 4–14 for chickens inoculated at one and six months of age. During the first three days PI, most developmental stages of C. baileyi were found in the microvillous region of enterocytes of the ileum and large intestine. By day 4 PI, most parasites occurred in enterocytes of the cloaca and bursa of Fabricius (BF). Mature Type I meronts with eight merozoites first appeared 12 h PI and measured 5.0 × 4.9 μm. Mature Type II meronts with four merozoites and a large granular residuum first appeared 48 h PI and measured 5.1 × 5.1 μm. Type I meronts with eight short merozoites and a large homogeneous residuum first appeared 72 h PI and measured 5.2 × 5.1 μm. Microgamonts (4.0 × 4.0 μm) produced 16 micro-gametes that penetrated into macrogametes (4.7 × 4.7 μm). Macrogametes gave rise to two types of oocysts that sporulated within the host cells. Most were thick-walled oocysts (6.3 × 5.2 μm), the resistant forms that passed unaltered in the feces. Some were thin-walled oocysts whose wall (membrane) readily ruptured upon release from the host cell. Sporozoites from thin-walled oocysts were observed penetrating enterocytes in mucosal smears. The presence of thin-walled, autoinfective oocysts and the recycling of Type I meronts may explain why chickens develop heavy intestinal infections lasting up to 21 days. Oocysts of C. baileyi were inoculated orally into several animals to determine its host specificity. Cryptosporidium baileyi did not produce infections in suckling mice and goats or in two-dayold or two-week-old quail. One of six 10-day-old turkeys had small numbers of asexual stages only in the BF. Four of six one-day-old turkeys developed mild infections only in the BF, and sexual stages of the parasite were observed in only one of the four. All seven one-day-old ducks and seven two-day-old geese developed heavy infections only in the BF with all known developmental stages present.

Notes: Abstract Two monoclonal antibodies (AFRC MAC 184 and 185) have been raised in rats against a synthetic octadecapeptide corresponding to the N-terminus of Avena phytochrome. The peptide was conjugated to tuberculin purified protein derivative (PPD) for immunization and the cell lines screened by ELISA using the free peptide. Both antibodies bind to intact 124-kDa phytochrome on Western blots and in a double antibody sandwich ELISA. In the ELISA, they have an approximately four-fold higher affinity for Pr than Pfr. Conformational changes during photoconversion, therefore, involve the extreme N-terminus of the phytochrome molecule.

Notes: Investigations of Al phytotoxicity, including the identification of the Al species responsible for toxicity, require a rapid assay procedure employing very low concentrations of Al and a chemically simple rooting medium. Root elongation in newly germinated red clover (Trifolium pratense L. cv. Kenland) was inhibited by submicromolar concentrations of Al. Ca2+ at concentrations of at least 0.2 mM was essential for optimal elongation in control seedlings. Ca2+ also relieved Al toxicity with the net effect that maximum reduction of elongation by 1 μM Al was achieved at 0.2 mM Ca2+. Elongation in control seedlings was at least 90% of maximum from pH 4.5 to 5.7. Increases in pH relieved Al toxicity so that maximum sensitivity to 1 μM Al occurred at pH 4.7. As a consequence of these experiments and other considerations we chose for our basic assay a medium composed of 0.2 mM CaSO4 adjusted to pH 4.5 with H2SO4, variously supplemented with Al2(SO4)3.Day-old seedlings were incubated in this aerated medium in the dark at 23°C for one day. No additions of other solutes increased the sensitivity of the assay, but amelioration of Al toxicity was effected by Mg2+, F-, phosphate and citrate. Increases in ionic strength per se had comparatively little effect on the toxic effects of Al. Two barley cultivars (Hordeum vulgare L. cv. Dayton and Kearney) and two wheat cultivars (Triticum aestivum L. cv. Hart and Thorne) known to differ in sensitivity to Al were reliably separated at submicromolar Al concentrations by the assay procedure, which was slightly modified. Suggestions for the improvement of the assay and for applications to future research are offered.

Notes: Incubation of oat (Avena sativa L. cv. Victory) coleoptile segments in 4 mM L-cysteine reduced the tissue ATP level to 42 nmol (g fresh weight)−1 (35% of normal) over a 2 h period. Emissions of H2S accompanied this depletion in ATP suggesting an H2S production by desulfhydration of cysteine similar to that reported in other plants. Additions of exogenous H2S to the sections also caused ATP depletion. Aminooxyacetate, an inhibitor of cysteine desulfhydrase (EC 4.4.1.1), eliminated the cysteine-induced H2S emission and the ATP depletion. Prolonged exposure to cysteine depressed the electrical polarity of the cell membrane from – 116 mV to –85 mV. That and other electrical responses appear to reflect a reduced capacity for ATP-dependent H+ extrusion. These effects should be taken into account whenever cysteine is used in physiological experiments.