A Multi-Unit Sampling System and Its Use in the Characterization of Ultradian and Infradian Growth in Tetrahymena*

SYNOPSIS. A multi-unit automatic sampling device for investigation of microbial growth under a wide variety of conditions is described. The kinetics of asynchronous population growth for batch cultures of Tetrahymena pyriformis (W) at several temperatures show that there are 2 distinct growth phases: an exponential ultradian growth phase that is strongly temperature dependent and a non-stationary growth phase, the infradian phase, that shows little or no temperature dependence over the range from 15–27 C.     

Salt Stress Causes Acceleration of Purine Catabolism and Inhibition of Pyrimidine Salvage in Zea mays Root Tips

Nucleotide metabolism was studied in apical 5.0 mm root tipsof corn plants (Zea mays L., cv. Pioneer 3906) hydroponicallycultured for 7 d and then salinized for 19 d at a rate calculatedto reduce the osmotic potential (_o) of the solutions by O.1MPad^–1 to a final _o = -0.4 MPa. Saline treatments withtwo different molar ratios of Ca₂₊/Na⁺ were employed, viz.,0–03 (2.5 mol m^–3 CaCl₂ + 86.5 mol m^–3 NaCl)for the NaCl treatment and 0.73 (31.5 mol m^–3 CaCl₂ +43.1 mol m^–3 NaCl) for the NaCl + CaCl₂ treatment. Bothsalt treatments reduced root growth by more than 30%. The capacityof roots to provide purine nucleotides either by de novo synthesisor by re-utilization of existing bases, e.g. salvage of hypoxanthineto adenine nucleotides, was not affected by either salt treatment.However, catabolism of hypoxanthine was accelerated more than3.5-fold by both salt treatments, demonstrating an increasedcapacity for purine catabolism which would shift the normal1: 1 ratio of synthesis: degradation of purine nucleotides observedfor the roots of healthy control plants to less than 0.2 duringsalt stress. The ratio of pyrimidine nucleotide synthesis: degradationwas also reduced. In this case, the unfavourable shift towardnucleotide degradation resulted because both salt treatmentsreduced salvage capacity by more than 25%, but had no compensatingeffect on de novo synthesis or catabolism of pyrimidines. Key words: Salinity, osmotic potential, nucleotide metabolism     

Coccidia (Apicomplexa: Eimeriidae) from Sciurid Rodents (Eutamias,Sciurus, Tamiasciurus spp.) from the Western United States and Northern Mexico with Descriptions of Two New Species1

ABSTRACT. Since May 1979, 190 rodents in the family Sciuridae, representing three genera and nine species, have been collected in the western United States and northern Mexico and examined for coccidia; 71 (37%) had coccidian oocysts in their feces. These included 2 of 12 (17%) Eutamias canipes; 7 of 12 (58%) E. dorsalis; 18 of 50 (36%) E. merriami; 33 of 96 (34%) E. obscurus; 3 of 4 (75%) E. townsendii; 3 of 9 (33%) Sciurus aberti; 1 of 1 S. griseus; 1 of 1 Tamiasciurus hudsonicus mogollonensis; and 3 of 5 (60%) T. mearnsi. The following coccidians were identified from infected rodents: Eimeria cochisensis n. sp. and Eimeria dorsalis n. sp. from E. canipes; E. cochisensis, E. dorsalis, and E. tamiasciuri from E. dorsalis; E. dorsalis and E. tamiasciuri from E. merriami; E. cochisensis, E. dorsalis, E. tamiasciuri, and E. wisconsinensis from E. obscurus; E. cochisensis and E. dorsalis from E. townsendii; E. ontarioensis and E. tamiasciuri from S. aberti; E. tamiasciuri from S. griseus; E. tamiasciuri and E. toddi from T. h. mogollonensis; and E. tamiasciuri from T. mearnsi. Sporulated oocysts of Eimeria dorsalis n. sp. were ovoid, 21.9 × 16.8 (17–24 × 14–20) μm with sporocysts ovoid, 11.5 × 6.9 (10–14 × 6–8) μm. Sporulated oocysts of Eimeria cochisensis n. sp. were spheroid to subspheroid, 16.7 × 15.3 (15–18 × 14–17) μm, with sporocysts ovoid, 8.4 × 5.6 (6–11 × 4–7) μm. Fifty-five of 71 (77%) infected hosts had oocysts of only one eimerian species in their feces at the time they were examined. One eimerian, E. tamiasciuri, was found in seven of nine host species in three genera. A list is provided of all eimerians (22, including the species described here) that have been described in the literature from Eutamias, Sciurus, and Tamiasciurus spp.     

Redescription of Eimeria angusta Allen, 1934 and E. bonasae Allen, 1934 (Protozoa: Eimeriidae) from the Ruffed Grouse Bonasa umbellus1

SYNOPSIS Eimeria angusta Allen, 1934 and E. bonasae Allen, 1934 are redescribed from a ruffed grouse Bonasa umbellus. Oocysts of E. angusta were ellipsoidal to elongate ovoid, had micropyles and were 28-37 by 15-19 μ (mean 32.5 by 17.1 μ), with a length-width ratio of 1.67-2.19 (mean 1.91). Eimeria bonasae oocysts were spherical to subspherical and 18-25 by 18-23 μ (mean 21.6 by 20.6), with a length-width ratio of 1.00-1.16 (mean 1.05).     

Spinal Mechanisms in the Control of Lamprey Swimming

SYNOPSIS. The lamprey, an anguilliform fish, swims using lateralundulatory movement; a transverse wave passes backward, fromhead to tail, the amplitude of the wave increasing as it movestailward. The wave of muscle activity producing this movementtravels down the body faster than the mechanical wave. The wayin which certain features of anguilliform movement contributeto its efficiency have been described. The neural activity underlyingswimming is characterized by: 1) rhythmical alternation betweenthe two sides of a single segment; 2) a burst duration thatremains a constant proportion of the cycle time and is independentof the cycle frequency; 3) rostrocaudal phase lag that is constantand also independent of the cycle frequency. Local circuitsin the lamprey spinal cord can generate this locomotory patternin the absence of sensory feedback following activation of excitatoryamino acid receptors; the pattern is centrally generated. Ithas been hypothesized that the spinal central pattern generatorfor locomotion consists of a series of segmental burst generatorscoupled together by an intersegmental coordinating system. Theintersegmental coordinating system functions to keep the frequenciesof the oscillators along the cord constant and to provide theappropriate rostrocaudal phase lag. Mechanosensitive units withinthe spinal cord are sensitive to movement of the spinal cord\notochordand movement of the spinal cord/notochord can entrain the burstpattern. Entrainment occurs through movement-related feedbackonto neurons at the local level. The possible roles this movement-relatedfeedback plays during locomotion are discussed.     

A Nucleoside Diphosphate Kinase from Paramecium tetraurelia with Protein Kinase Activity

Nucleoside diphosphate kinase (NDP kinase) from Paramecium was purified to homogeneity. The native enzyme was 80 kDa (by gel filtration), with subunits of 18 and 20 kDa. Near the amino terminus, 15 of 20 residues were identical with those in human NDP kinase, and 17 of 20 with the awd gene product from Drosophila. NDP kinase bound α-labeled ATP and GTP, and a photoreactive GTP analog labeled both subunits. Purified NDP kinase underwent autophosphorylation on a histidine and a serine residue using either ATP or GTP as a substrate. The enzyme also catalyzed acid-stable phosphorylation of casein and phosvitin. This protein kinase activity is distinct from the histidine phosphorylation that is part of the NDP kinase catalytic cycle. Antiserum against the purified protein from Paramecium cross-reacted with 16- to 20-kDa proteins in most species tested, and with a larger protein (44 kDa) in Paramecium, Xenopus, and two human lines. The multiple forms (20 and 44 kDa) of the NDP kinase in Paramecium and its protein kinase activity, suggest that the protein is more than a housekeeping enzyme; it may have regulatory roles such as those of the NDP kinase-like awd protein of Drosophila and Nm23 protein of humans.