Reversion from erythromycin dependence in Escherichia coli: strains altered in ribosomal sub-unit association and ribosome assembly

A mutant of Escherichia coli dependent on erythromycin for growth spontaneously gives erythromycin-independent strains with altered or missing ribosomal proteins. strains with defects in ribosome assembly were sought and obtained from among these revertants. Two organisms in which ribosomal protein L19 is altered and absent respectively have 70S ribosomes whose dissociation into sub-units is particularly sensitive to pressures generated during centrifuging. The mutant that lacks protein L19 also accumulates ribosome precursor particles during exponential growth as do others including mutants that lack proteins S20 or L1. These strains also show unbalanced synthesis of RNA and so will be useful in investigating both the pathways and the regulation of ribosome assembly.     

Electron Microscopic Studies of Spruce Needles in Connection with the Occurrence of Novel Forest Decline

Needles of four spruce trees showing different degrees of novel kinds of forest decline were investigated by electron microscopy. Green needles appearing at least superficially still intact were selected for the present investigation. Most of the mesophyll appeared to be undamaged. However, groups of atypical mesophyll cells were found close to the endodermis or the hypodermis. The chloroplasts of the apparently damaged cells were particularly affected. Changes in the matrix of the chloroplasts, i.e,. increased affinity to osmium, occurrence of extensive nests of plastoglobuli, as well as damage to the membranes, i.e. lesions in the envelope and abnormal thylakoid membranes, were observed. Signs of decomposition of other cellular structures including mitochondria were also detectable. There appeared to be a close correlation between the degree of damage at the whole tree level and the degree of damage occurring at the cellular level. It is concluded that particularly the lipids and the proteinsof, the membranes are affected by anthropogenic air pollutants and natural stressors. The altered membrane structure may for instance cause abnormal osmotic conditions for the cellular compartments and may impair transport processes and thus lead to lossof function not only of the cells but also of the whole needle.     

Referral patterns to an ophthalmic outpatient clinic by general practitioners and ophthalmic opticians and the role of these professionals in screening for ocular disease.

Case notes of 1113 consecutive new patients referred to a consultant ophthalmologist at a district general hospital were reviewed to determine the source and efficacy of referrals and the current screening practices of general practitioners and ophthalmic opticians. General practitioners initiated referral in 546 cases (49%) and ophthalmic opticians referral in 439 (39%). Visual loss or visual disturbance was the most important single reason for referral (345 cases; 31%), followed by suspected glaucoma (145 cases; 13%), abnormalities of binocular vision (140; 12.5%), disorders of eyelids or ocular adnexa (127; 11%), and red eye (86; 8%). General practitioners referred many more patients with disorders of the eyelids and adnexa and ophthalmic opticians many more patients with suspected glaucoma. Ophthalmic opticians were far more likely than general practitioners to refer patients with suspected glaucoma correctly. A total of 180 patients (16%) were referred from ocular screening, in 149 cases by ophthalmic opticians and in 10 by general practitioners. Seventy patients had glaucoma or incomplete features of glaucoma, all of them referred by ophthalmic opticians. Of eight diabetic patients referred by ophthalmic opticians, three had asymptomatic disease and in two diabetes was diagnosed as a result of ocular screening. No patient was referred for asymptomatic diabetic retinopathy from screening by general practitioners. Ophthalmic opticians were more likely than general practitioners to diagnose retinopathy requiring photocoagulation. Use of a community based service to screen for glaucoma could save unnecessary consultant outpatient appointments. A similar service could facilitate detection of diabetic retinopathy at a stage when treatment is most effective.     

Lotus japonicus, an autogamous, diploid legume species for classical and molecular genetics

In the Leguminosae plant family, few of the individual plant species have been used for plant molecular biology research. Among the species investigated no obvious representative ‘model’ legume has emerged. Here a member of the tribe Loteae, Lotus japonicus (Regel) Larsen is proposed as a candidate. L. japonicus is a diploid, autogamous species, with a good seed set, and a generation time of approximately 3 months. The haploid genome consists of six chromosomes and the genome size was estimated to be relatively small (0.5 pg per haploid complement). L. japonicus is susceptible to Agrobacterium tumefaciens and transgenic plants can be regenerated after hygromycin or kanamycin selection. Tissue culture conditions and procedures for transformation and regeneration are described. Stable transformation is demonstrated by segregation of the hygromycin selectable marker after selfing of transgenic plants or test crosses. The possibility of mapping polymorphic DNA markers inbred lines of L. japonicus is also discussed.     

Resistance in the wild crop relatives Avena macrostachya and Hordeum bogdani to the aphid Rhopalosiphum padi

In previous screening tests the two wild crop relatives Avena macrostachya (Bal., ex Coss. et Dur.) and Hordeum bogdani (Wil.) demonstrated a high degree of resistance to the aphid Rhopalosiphum padi (L.). In a choice situation using wild and cultivated oats and barley, alate aphids settled in lower numbers on the wild species. The results were, however, variable in the Avena combination. Nymph production was significantly higher, development time shorter and adult weight higher on the cultivated varieties. From the third instar and onwards the excretion of honeydew was significantly lower on the resistant plants. In general the honeydew contained less than 1% free amino acids although excreta from H. vulgare contained 3.5%. The percentage of free amino acids found in the honeydew was similar for all plant species (5.2–7.6%) except for H. vulgare, on which the aphids excreted 22% of the amounts ingested. Amino acids excreted in high proportions on all plants included asparagine, -aminobutyric acid, glutamic acid, and glycine. Tissue sectioning did not reveal any obvious mechanical barriers to stylet penetration. The potential use of these wild species as sources for aphid resistance breeding in oats and barley is considered.

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Résumè Lors d'examens systématiques antérieurs, Avena macrostachya (Bal. ex Coss. & Dur.) et Hordeum bogdani (Wil.) ont présenté une résistance élevée au puceron Rhopalosiphum padi (L.). Lorsqu'ils avaient un choix comprenant de l'avoine et de l'orge cultivés, les pucerons ailés ont atterri en nombres moins importants sur les espèces sauvages. Les résultats étaient cependant variables dans le complexe avoine. La production de nymphes et le poids des adultes étaient plus élevés sur espèces cultivées, ainsi que la durée du développement était plus longue sur les espèces sauvages. A partir du troisième stade, l'excrétion de miellat a été significativement plus faible sur les espèces résistantes. En général, le miellat y contenait moins de 1% d'acides aminés bien que sur H. vulgare il en contînt 3,5%. Les pourcentages d'acides aminés libres du miellat étaient semblables sur toutes les plantes (5,2–7,6%), à l'exception de H. vulgare sur lequel les pucerons excrétaient 22% des taux ingérés. Les acides aminés excrétés en fortes quantités sur les différentes plantes, comprenaient l'asparagine, l'acide -aminobutyrique, l'acide glutamique et la glycine. Des coupes de tissus n'ont révélé aucun obstacle mécanique clair à la pénétration des stylets. Les possibilités d'utiliser ces espèces sauvages comme source de résistance aux pucerons dans la sélection de l'avoine et de l'orge ont été examinées.

     

Cowpea aphid performance and behaviour on two resistant cowpea lines

In a series of laboratory and climate chamber tests we compared the growth and behaviour of Aphis craccivora on one susceptible (ICV-1) and two aphid-resistant (ICV-11 and ICV-12) cowpea lines. The aphids' growth rates were much lower on the resistant cowpea lines than on the susceptible one, indicating strong antibiosis. In addition, the aphids invariably settled in higher numbers on the susceptible line than on either of the resistant. Compared to ICV-1, damaged leaves of the resistant line ICV-12 were settled upon to a higher degree than undamaged leaves, and leaf discs from the same line were even less resistant.On resistant lines individual aphids waited a significantly longer time before making their first test probe. Total probing time as well as the time preceding a decision to stay or leave was also longer.These results are discussed in relation to the possible mechanisms involved, and we also consider the effects of previous leaf feeding on the expression of resistance in the field.

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Résumé Au cours d'expériences au laboratoire et en chambres climatisées nous avons comparé la croissance et le comportement de A. craccivora sur une lignée sensible (ICV-1) et deux lignées résistantes (ICV-11 et ICV-12) de V. unguiculata. Les vitesses de croissance des pucerons ont été beaucoup plus lentes sur les lignées résistantes que sur la lignée sensible, ce qui révèle une forte antibiose. De plus, les pucerons atterrissent invariablement en plus grand nombre sur la variété sensible. Par comparaison avec ICV-1, les atterrissages sur lignée résistante ICV-12 étaient plus nombreux sur les feuilles endommagées que sur les feuilles intactes; les disques de feuilles de cette même lignée étaient encore moins résistants.Les pucerons ont séjourné individuellement un temps plus long sur les lignées résistantes avant de faire leur premier sondage. Le temps consacré aux sondages ainsi que le temps précédant de choix entre départ ou maintien sur la feuille étaient plus longs avec les lignées résistantes.Ces résultats ont été discutés en fonction des mécanismes impliqués. Nous avons aussi examiné les effets de la consommation antérieure sur les manifestations de la résistance dans la nature.

     

Ultrastructural alterations in mammalian parathyroid glands induced by fixation

The influence of fixation methods, buffers and ions on the ultrastructure of parathyroid cells was studied in dogs, cats, rats and mice. Parathyroids fixed by immersion showed 3 chief cell variants referred to as cells in active, intermediate and resting stages, multinucleated syncytial cells, atrophic cells and, only in 1 feline parathyroid, a few oxyphil cells. Parathyroid glands fixed by perfusion, however, consisted only of 1 cell type. Satisfactory preservation was achieved by perfusion with 2.5% glutaraldehyde in 0.1 M Na cacodylate containing 0.25 mM CaCl2 and 0.5 mM MgCl2, and postfixation with 1% OsO4 in 0.1 M s-collidine containing 0.5 mM CaCl2 and 1.0 mM MgCl2. Good preservation was also obtained using Na phosphate during prefixation and postfixation. Other combinations of buffers led to shrinkage, dilation of rough endoplasmic reticulum cisternae, disruption of membranes or loss of matrix and secretory granules. The results demonstrate that the variants of parathyroid chief cells, multinucleated syncytial cells and atrophic cells arise during fixation.     

A Bioluminescence Method for the Measurement of l-Glutamate: Applications to the Study of Changes in the Release of l-Glutamate from Lateral Geniculate Nucleus and Superior Colliculus After Visual Cortex Ablation in Rats

We have developed a rapid, simple, specific, and very sensitive bioluminescence method for the measurement of L-glutamate (L-Glu). Oxidation of L-Glu by glutamate dehydrogenase has been coupled with bacterial FMN reductase and luciferase. Light production (i.e., peak height or integral) was linear from less than 0.5 to 500 pmol of L-Glu. Potential interfering substances that may be encountered in brain tissue have been identified. The most potent inhibitors were ascorbate and the biogenic amines. Procedures that conferred long-term stability of the reagent mixture (greater than 8 h) were established. Bioluminescence analysis of L-Glu content in brain tissue extracts, fractions from release experiments, and human CSF corroborated respective results obtained by HPLC analysis. In this study, we have applied the method to monitor changes in the KCl-evoked release of endogenous L-Glu from milligram amounts of brain tissue, i.e., from lateral geniculate nucleus and superior colliculus after visual cortex ablation.