Cytogenetic study of an interspecific cross of Nicotiana debneyi X N. umbratica

Summary Interspecific F₁ hybrids of Nicotiana debneyi Domin (2n=48) and N. umbratica Burbidge (2n=46), both belonging to the section Suaveolentes, showed a high degree of meiotic chromosome pairing. Two of the five F₂ plants obtained exhibited chromosome mosaicism. The first colchiploid generation (C₁) had the expected chromosome number of 2n=94 while C₂ showed 2n=88, a loss of three pairs of chromosomes. This same chromosome number continued in further colchiploid generations, followed up to C₅, except for a few plants in C₃ which showed chromosome mosaicism. The F₁ phenotype was stable through C₁ to C₅ and fertility was normal in colchiploids through all generations in spite of the loss of three pairs of chromosomes and chromosome mosaicism. This stability and fertility apparently reflect the tolerance of the genomes to the genetic adjustment of chromosome complements which is believed to be associated with the originally polyploid nature of the parental species and the chromosome doubling brought about in the amphidiploids.     

The electrolytic preparation of bioactive radioiodinated parathyroid hormone of high specific activity.

A technique for the preparation of microgram quantities of bovine parathyroid hormone (bPTH) labeled with carrier-free ¹²⁵I to a specific activity of 1300 Ci/mmol is described. A restructured and simplified apparatus was used for electrolytic iodination, making it feasible to use reaction volumes of 100 to 200 ml. The miniaturized setup requires only a small platinum crucible connected via an agar-KCl salt bridge to a saturated KCl solution, a battery to drive the reaction, and a voltmeter to monitor the potential difference between the reference-saturated KCl solution (via a calomel electrode) and the platinum crucible. The [¹²⁵I]-labeled bPTH elutes as a single species when chromatographed on a Biogel P-10 column equilibrated in 3 m guanidine HCl-2.3 m formic acid, and it retains full biologic activity when bioassayed in vivo. It is evident that bPTH labeled to a high specific activity with ¹²⁵I does not suffer in regard to its biological potency.     

Secondary structure of mouse and rabbit α- and β-globin mRNAs: Differential accessibility of α and β initiator AUG codons towards nucleases

The nucleotide sequence from the 5′ terminus inward of one third of mouse α- and β^maj-globin messenger RNAs has been established. In addition, using 5′ ³²P end-labeled mRNAs as substrates and S1 and T1 nucleases as probes for single-stranded regions, the secondary structures of mouse and rabbit α- and β-globin mRNAs have been analyzed. Our results indicate that the AUG initiator codon in both mouse and rabbit β-globin mRNA is quite susceptible to cleavage with S1 and T1 nucleases, suggesting that it resides in a single-stranded exposed region. In contrast, the initiator AUG in the α-globin mRNA of both species is inaccessible to cleavage, indicating that it is either buried by tertiary structure or is base-paired. Since the rate of initiation of protein synthesis with β-globin mRNA in rabbit reticulocyte is 30–40% faster than for α-globin mRNA, these results imply a possible correlation between the differential rates of initiation with these two mRNAs and the accessibility of the respective AUG initiator codons.     

Inhibitors of superoxide dismutases: A cautionary tale

An extensive search resulted in the identification of pamoic acid as an inhibitor of superoxide dismutases. Pamoic acid appeared to rapidly and reversibly inhibit all types of superoxide dismutases and did so in both the cytochrome c reduction and in the dianisidine photooxidation assays, used to measure this activity. It could nevertheless be shown that pamoic acid did not at all inhibit superoxide dismutase but rather diminished the sensitivity of the assays. The mechanism proposed to account for this effect involved oxidation of pamoate, by O₂^?, to yield a pamoate radical which can then reduce cytochrome c or oxidize pyrogallol. Pamoate thus competes with superoxide dismutase for the available O₂^?, without affecting the observable effects of that O₂^? upon cytochrome c or upon pyrogallol. It consequently makes these assays less responsive to superoxide dismutase, while appearing to be without effect in the absence of superoxide dismutase. Several of the predicted consequences of this proposal were affirmed. Other workers, interested in finding inhibitors for superoxide dismutases, are hereby forwarned of this subtle snare.     

Effects of morphine on visual evoked responses recorded in five brain sites.

The effects of morphine on averaged evoked responses to visual stimulation were examined in specific brain structures relevant to pain, analgesia, tolerance and motor disturbances. Permanent electrodes (60 μ in diameter) were implanted stereotaxically in the central gray, mesencephalic reticular formation, caudate nucleus, parafasicular-centromedian complex and the lateral geniculate body as a control site. Visual evoked responses were obtained in unanesthetized, unrestrained rats prior to and following the administration of morphine in successive doses of 1, 5, 10 and 30 mg/kg and 1 mg/kg of naloxone (a morphine antagonist). The parafasicular-centromedian complex and the reticular formation exibited a progressive increase in response amplitude to increased dose of morphine. These effects were reversed by naloxone. In this study the parafasicular-centromedian complex was found to be the most sensitive structure to morphine, displaying the largest changes in response amplitude as a result of morphine administration.     

Pattern of dry-matter accumulation,and nitrogen concentration and uptake as influenced by levels and methods of nitrogen application in rainfed-upland rice

Summary Dry-matter accumulation, and concentration and uptake of nitrogen increased with increasing level of nitrogen at all the stages of crop growth. The differences in nitrogen concentration due to nitrogen levels were greatest at panicle initiation stage and started becoming narrower with the advancement in crop age. Split application of nitrogen with its heavier fractions at tillering and panicle initiation stages either through soil alone or soil+foliage (1/3+1/3+1/3) resulted in higher dry-matter accumulation, and higher nitrogen concentration and uptake than other methods. The crop, on an average, removed 61 kg N/ha. Plants accumulated nearly 15% of the total absorbed nitrogen, up to tillering, 50% up to panicle initiation and 85–90% up to heading. Proportionately lesser nitrogen uptake and dry-matter accumulation at post-heading stage is an indicative of a major constraint for production efficiency of rainfed-upland rice culture.     

Effects of inorganic amendments (N,P and K) to soil on the rhizosphere microflora of antirrhinum plants infected withVerticillium dahliae Kleb

Summary A study of the inorganic amendments (N, P and K) to soil, and their effect on the rhizosphere microflora, as well as their relation to the control of wilt of antirrhinum plants caused byVerticillium dahliae Kleb. was done. Ammonium sulphate was the only chemical found to be significantly inhibitory toV. dahliae in vitro. Soil amendments (NPK) affected the rhizosphere microorganisms of the antirrhinum plants. Higher concentration of the chemicals were phytotoxic. It was further observed that ammonium sulphate, and the combined chemicals (NPK 25%) in soil delayed the senescence in healthy plants, suggests that chemical fertilisers affected the host plants directly. Addition of ammonium sulphate (0.25%), calcium nitrate (0.25%, 0.5%) combined NPK (0.25%) to soil caused considerable reduction in disease severity. It is assumed that this reduction may be caused by the (1) fungitoxic nature of the chemicali.e. ammonium sulphate, (2) antagonistic environment for the pathogen in the rhizosphere was boostedi.e. where calcium nitrate was added as soil amendments and (3) reduction in disease severity in soil-amended with combined NPK, may be due to the fact that antagonistic actinomycete population was boosted in the rhizosphere.     

Effects of N-serve (2-chloro-6-(trichloromethyl)pyridine) formulations on nitrification and on loss of nitrate in sand culture experiments

Summary N-serve (2-chloro-6-(trichloromethyl)pyridine) was tested as an inhibitor of nitrification of ammonium or urea in sand cultures. Nitrification was reduced but not prevented by N-Serve present at between 5 and 20 ppm in solution or by weight of sand. In the presence of root debris and acetone, used in some experiments at 2–4 ml/l of nutrient to convey N-Serve, denitrification was stimulated under the same conditions and resulted in loss of a large proportion of nitrate, probably mainly as gaseous products and some nitrite. These losses were greater when N-serve was also present. There was also conversion of nitrate to an insoluble form in the sand. A smaller proportional loss of nitrate occurred in other treatments in the presence of root debris when N-Serve was added without acetone, either as the commercial formulation 24E or as a solid. Thus, using N-Serve to inhibit nitrification may encourage denitrifying organisms especially in the presence of carbon sources including root debris or acetone. Large decreases of nitrate reductase activity in plants produced by using N-Serve in the presence of ammonium or urea were caused as much by losses of nitrate in the presence of acetone as by prevention of nitrate formation. Other N-Serve treatments (solid or 24E) decreased enzyme induction by between 50 and 90 per cent as a result mainly of reduced nitrification.     

Nodulation ofTrifolium subterraneum byRhizobium leguminosarum

Summary Four cultivars ofTrifolium subterraneum were nodulated by five strains ofRhizobium leguminosarum; all combinations except one gave 100% nodulation. Rates of nodule formation and total nodule numbers were similar to those with an effectiveR. trifolii strain. The nodules were more commonly associated with lateral roots and were ineffective in nitrogen fixation.     

Systematics of the Monodelphic Species of Trichodoridae (Nematoda: Diphtherophorina) With Descriptions of a New Genus and Four New Species

To show the relationship of the monodelphic species of Trichodoridae with the nominal taxa, the genus Monotrichodorus is redefined, with the addition of one new species. The new genus Allotrichodorus is proposed on the basis of new species found in Brazil; and one new species is described in the genus Paratrichodorus.