Calicotyle urolophi n. sp. (Monogenea: Monocotylidae) from stingarees,Urolophus spp. (Elasmobranchii: Urolophidae) taken in coastal waters of Southern Australia

Calicotyle urolophi n. sp. is proposed for calicotylines found in the cloaca of three stingaree species, Urolophus cruciatus, U. bucculentus and U. paucimaculatus, collected off the southeastern coast of Tasmania. Variations in the soft body parts were observed between specimens taken from U. cruciatus and U. bucculentus but were not considered sufficient for separation into two species. C. urolophi is differentiated from other Calicotyle spp. found in the South Pacific by the configuration of the tubular male copulatory organ, the structure of the intestinal caeca and the arrangement of the vaginae. Amended diagnoses for the subfamily Calicotylinae and the genus Calicotyle are provided.     

Regulation of ANP secretion in insulin-dependent diabetes mellitus and the influence of autonomic neuropathy.

In order to determine the effect of diabetic autonomic neuropathy (DAN) on the atrial natriuretic peptide (ANP) response to dynamic stimuli, we studied the ANP response to 60 degrees head-up and 60 degrees leg-up tilt in diabetic subjects with (DAN + ve, n = 8) and without (DAN - ve, n = 8) evidence of autonomic neuropathy and seven matched non-diabetic controls. Mean baseline plasma ANP concentrations were similar in all three groups. Head-up tilt was associated with a fall in plasma ANP in all seven healthy controls (21.8 (16.8-30.7) to 16.8 (7.1-29.1), P = 0.06, mean (range)), seven of the eight DAN - ve (16.9 (6.5-33.7) to 8.5 (3.0-21.1), P = 0.015) and all eight DAN + ve subjects (27.3 (8.5-101.5) to 15.4 (1.0-67.6), P = 0.044). Leg-up tilt caused a rise in plasma ANP in six of the seven healthy controls (17.6 (7.5-27.9) to 22.4 (15.2-48.1), P = 0.041), six of the eight DAN - ve (12.5 (7.8-27.8) to 15.5 (7.3-31.3), P = 0.054) and seven of the eight DAN + ve subjects (18.2 (2.8-55.1) to 25.1 (4.5-92.8), P = 0.013). There was no significant difference in the fall in plasma ANP during head-up tilt or in the rise in plasma ANP during leg-up tilt between the three groups. We conclude that the regulation of ANP secretion is normal in diabetes mellitus, and is unaffected by the presence of autonomic neuropathy.     

Identification of a minus end-specific microtubule-associated protein located at the mitotic poles in cultured mammalian cells.

A mitosis-specific centrosomal component was studied with a human autoantibody, SP-H, which immunostained mitotic poles and interphase nuclei, and a single polypeptide with an apparent molecular mass of 200 to 230 kDa in various lines of cultured cells. Early mitotic PtK1 cells treated with 10 micrograms/ml taxol contained short bundles of parallel microtubules around the nuclei and cell periphery. At the time of nuclear envelope breakdown, the nuclear staining by SP-H disappeared, and the antigen relocated at one end of the parallel microtubules. Determination of the microtubule polarity demonstrated that the peripheral bundles of microtubules were arranged with their minus ends directed to the cell periphery, and the SP-H antigen was specifically localized at this end. Parallel microtubules were further rearranged first into a fan-like shape, and then into completely radial structures as observed by De Brabander et al. (Int. Rev. Cytol. 101, 215-274 (1986)). The SP-H antigen was always detected at the minus end domain of such microtubule-containing structures during the transformation process. When microtubules were depolymerized by nocodazole treatment, the SP-H antigen appeared as discrete cytoplasmic foci, suggesting that the antigen may self-associate, forming multimeric structures. The antigen in mitotic HeLa cell extracts co-sedimented in vitro with exogenous brain microtubules. The microtubule-associated SP-H antigen was insensitive to ATP extraction, but was removed from microtubules by treatment with 0.5 M NaCl. Thus the 200 to 230 kDa centrosomal component could be a novel microtubule-associated protein with affinity for the minus end of microtubules, and it might play an essential role in the organization of spindle poles during mitosis.     

Molecular Genetic Characterization of a Locus That Contains Duplicate Adh Genes in DROSOPHILA MOJAVENSIS and Related Species

Drosophila mojavensis and other species of the mulleri subgroup contain a duplicate gene encoding the enzyme alcohol dehydrogenase (ADH). Studies on the genetic relationship of the two genes using electrophoretic variants show them to be closely linked. We have cloned a 13.5-kb fragment of D. mojavensis DNA into the lambda vector, Charon 30. This fragment contains both Adh genes separated by approximately 2 kb of DNA. The clone hybridized to a single position on chromosome 3 in D. mojavensis following in situ hybridization. It is likely that the genes are tandemly arranged in the genome. One of the two genes shows a complexity in its structure that suggests the close linkage of a pseudogene or part of a gene. The structure of the Adh locus in five species of the mulleri subgroup have been compared by constructing restriction maps of genomic DNA. Two of these species D. arizonensis and D. mojavensis express Adh-1 in the ovaries; the others do not. In comparing these species it is evident that there has been one or two insertions into the region between the Adh genes. It is possible that one of these structural changes is related to the change in Adh tissue-specific expression that has occurred during the evolution of these species.     

Utilization of Ammonium as a Nitrogen Source : Effects of Ambient Acidity on Growth and Nitrogen Accumulation by Soybean

Dry matter accumulation of plants utilizing NH₄⁺ as the sole nitrogen source generally is less than that of plants receiving NO₃⁻ unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH₄⁺ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH₄⁺ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 ± 0.1 by automatic additions of 0.01 n H₂SO₄ or Ca(OH)₂. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH₄⁺ uptake per gram root dry weight were calculated from these data. Net CO₂ exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO₂ exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH₄⁺ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO₂ exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH₄⁺, which were initially about 50% lower at pH 4.1 than at 6.1, continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.     

Correlation of Rates of Calcium Entry and Release of Endogenous Norepinephrine in Rat Brain Region Synaptosomes

Voltage-dependent 45Ca2+ uptake and endogenous norepinephrine (NE) release were measured simultaneously in synaptosomes isolated from rat hypothalamus, brainstem, and cerebellum at 1, 3, 5, 15, and 30 s. In synaptosomes depolarized by 125 mM KCl, 45Ca2+ uptake and NE release exhibited fast and slow components. Rates of NE release and 45Ca2+ uptake were fastest from 0 to 1 s. NE release and 45Ca2+ uptake rates from 1 to 5 s were less than 15% of 0-1 s rates. Both resting (5 mM KCl) and depolarization-induced (125 mM KCl) NE release paralleled 45Ca2+ uptake from 1 to 30 s. Voltage-dependent NE release was approximately 1% and 2% of total synaptosomal NE content at 1- and 30-s measurement intervals, respectively, and did not differ between the three brain regions studied. Calcium and potassium dependence studies showed that NE release was stimulated by increased potassium and that depolarization-induced NE release was dependent on the presence of external calcium. These results show that calcium-dependent NE release from synaptosomes is correlated with calcium entry. Both processes exhibit fast and slow temporal components.     

Permeability of the squid giant axon to organic cations and small nonelectrolytes

Summary The permeability of the Na channel of squid giant axon to organic cations and small nonelectrolytes was studied. The compounds tested were guanidinium, formamidinium, and¹⁴C-labeled urea, formamide, thiourea, and acetone. Permeability was calculated from measurements of reversal potential and influx on internally perfused, voltage clamped squid axons. The project had two objectives: (1) to determine whether different methods of measuring the permeability of organic cations yield similar values and (2) to see whether neutral analogs of the organic cations can permeate the Na channel. Our results show that the permeability ratio of sodium to a test ion depends upon the ionic composition of the solution used. This finding is consistent with the view put forward previously that the Na channel can contain more than one ion at a time. In addition, we found that the uncharged analogs of permeant cations are not measurably permeant through the Na channel, but instead probably pass through the lipid bilayer.     

Recessive Mutations from Natural Populations of NEUROSPORA CRASSA That Are Expressed in the Sexual Diplophase

Wild-collected isolates of Neurospora crassa Shear and Dodge were systematically examined for recessive mutations affecting the sexual phase of the life cycle, which is essentially diploid. Seventy-four of 99 wild-collected isolates from 26 populations in the United States, India and Pakistan carried one or more recessive mutations that reduced fertility significantly when homozygous; mutations affecting spore morphology were also detected. Limited complementation tests indicate that most of the 106 recovered mutations are unique.--The recessive diplophase (= sexual phase) mutations were uncovered by crossing each wild-collected isolate to a marked two-chromosome double-reciprocal translocation strain as "balancer." Surviving progeny receive approximately 60% of their genome from the wild parent, but receive the mating-type allele from the "balancer" parent. These progeny were backcrossed to the wild parent and were also crossed with a standard laboratory strain (fl). Reduced fertility in the backcross vs. normal fertility in the cross with the laboratory standard signals the presence of a recessive mutation in the wild-collected isolate.--Most of the mutants (95 of 106) fall into two major classes: those producing barren perithecia with no or few viable ascospores (51) and those with spore maturation defects (44). Most of the recessive barrens result either from an early block in meiosis of ascus development (25) or from a late disturbance in postmeiotic ascus behavior (18).--These recessive mutations are formally equivalent to recessive lethals in higher eukaryotes and may be important in determining the breeding structure of natural Neurospora populations.     

Modulation of [3H]Diazepam Binding in Rat Cortical Membranes by GABAA Agonists

GABAA receptor agonists modulate [3H]diazepam binding in rat cortical membranes with different efficacies. At 23 degrees C, the relative potencies for enhancement of [3H]diazepam binding by agonists parallel their potencies in inhibiting [3H]gamma-aminobutyric acid [( 3H]GABA) binding. The agonist concentrations needed for enhancement of [3H]diazepam binding are up to 35 times higher than for [3H]GABA binding and correspond closely to the concentrations required for displacement of [3H]bicuculline methochloride (BMC) binding. The maximum enhancement of [3H]diazepam varied among agonists: muscimol = GABA greater than isoguvacine greater than 3-aminopropane sulphonic acid (3APS) = imidazoleacetic acid (IAA) greater than 4,5,6,7-tetrahydroisoxazolo (4,5,6)-pyridin-3-ol (THIP) = taurine greater than piperidine 4-sulphonic acid (P4S). At 37 degrees C, the potencies of agonists remained unchanged, but isoguvacine, 3 APS, and THIP acquired efficacies similar to GABA, whereas IAA, taurine, and P4S maintained their partial agonist profiles. At both temperatures the agonist-induced enhancement of [3H]diazepam binding was reversible by bicuculline methobromide and by the steroid GABA antagonist RU 5135. These results stress the importance of studying receptor-receptor interaction under near-physiological conditions and offer an in vitro assay that may predict the agonist status of putative GABA receptor ligands.