Transformation ofBacillus spp.: An examination of the transformation ofBacillus protoplasts by plasmids pUB110 and pHV33

The protoplasting and transformation techniques described by Chang and Cohen [5] have been modified by the inclusion of mutanolysin and these techniques have been used to prepare protoplasts of a number ofBacillus spp. Cells of some, however, remained resistant to cell wall hydrolysis by both mutanolysin and lysozyme. Protoplasts were prepared from sixBacillus species, including a strain ofB. subtilis, and transformed with the plasmid pUB110. Transformation with the shuttle vector pHV33 was, however, less successful and antibiotic-resistant protoplasts, although detected, either failed to regenerate their osmotic stability or rapidly lost their antibiotic resistance.     

Host plant resistance for insect control in some important crop plants

Insect pests of cereal crop plants are among the most destructive and devastating factors limiting world food production. Insects often inflict losses of 15 to 50% of the yield of some crops in various parts of the world. Insects also provide infection courts for various pathogens that inflict even greater damage. The nature of these losses is especially tragic for poor farmers in the tropics since the insects consume dry matter already produced using limited resources. Reduction of these losses would enhance the world food supply available to man, even if actual production remains the same, by allotting to man and animals that proportion of production now consumed by insects. Control of insect‐inflicted damage on a world‐wide basis is a very difficult task. Chemical control is effective and readily available in some, but not all, countries. However, chemical control is often unavailable, ineffective, too expensive, and likely to create environmental and safety hazards that make it unsuitable for many parts of the world. Several excellent examples of biological control of insects also attest to the potential usefulness of this method of reducing insect‐inflicted losses, but this method also has been ineffective for certain major insect pests due to lack of effective identification, distribution, and maintenance of biological control agents. On the whole, host plant resistance (HPR) to insects has been the most successful and widely used method of control. HPR has been used successfully in a number of major crop species to help control damage inflicted by major insect pests. However, problems with identifying sources of resistance and transferring it to usable varieties have often been difficult to overcome. Also, once resistance is deployed, changes in insect populations which allow them to overcome the resistance sometimes eliminate the potential advantages of resistant varieties. However, methods to quantify host‐insect interactions have improved significantly over the past few years, and the prospects for developing and maintaining usable levels of resistance to several major insect pests of most major crops are good. Studies of the biochemical and biophysical mechanisms of insect resistance have added a new dimension to HPR work. Knowledge of specific factors that contribute to insect resistance can be extremely useful to plant breeders and entomologists. The ability to identify and select for one specific plant component or group of components can speed the development of resistant varieties. Studies of the effect of such resistance components on insect development and behavior can help determine the likelihood of insects being able to overcome the resistance factors. Studies of the effect of the resistance factors on host plant yield, performance, or quality may help plant breeders overcome the problems often associated with the development of high yielding and high quality resistant varieties. Identification of several different mechanisms of resistance could provide breeders the opportunity to adjust levels of several resistance components in order to arrive at a proper blend of resistance, quality, and yield. Furthermore, development of varieties with multiple mechanisms of resistance should slow the development of new biotypes of insects that could overcome the HPR since the insects would have to simultaneously or sequentially develop the ability to overcome several resistance factors. Therefore, knowledge of mechanisms of insect resistance could facilitate the development of more stable and long‐lasting types of resistance.     

Structure and function in the excretory systems of some terrestrial prosobranch snails (Cyclophoridae)

The excretory systems of terrestrial prosobranch snails of the family Cyclophoridae, collected in Jamaica, Costa Rica and South Africa, have been examined physiologically and as regards their gross and fine structure. The process of urine formation commences in the heart, where fluid is filtered across the wall of the ventricle. Filtration through the auricular wall is believed to be negligible. The kidney, which contains three types of cell, modifies the composition of the filtrate. One type of resorptive cell, characterized by basal infoldings associated with mitochondria, takes up salts. Another type, with basal subcellular spaces, may be responsible for taking up water. The third type of cell is secretory, producing concretions of uric acid and phospholipid which are liberated into the kidney lumen when the cell degenerates.
The rate and mechanism of urine production have been investigated using injections of inulin. The filtration rate at 25°C is 0.5 μl/g/min, and in 100% R.H. the average rate of urine production is 0–39 μl/g/min.
An accessory excretory organ has been developed from the hypobranchial gland of aquatic forms. It is composed of groups of subepithelial tubular glands opening into the mantle cavity by one or a series of pores, and secreting purines, phospholipids and mucus. There is evidence that this organ becomes progressively more complex in forms occupying drier habitats.
The systems of excretion and osmoregulation in the Cyclophoridae are considered to be very similar to those in their aquatic relatives, the Viviparidae and Ampullariidae. Certainly the cyclophorids are not as well adapted to a terrestrial life as are the Pulmonata, and in many respects they may be considered "aquatic" snails living on land.     

Fate of corticotrophins in an isolated adrenal-cell bioassay and decrease of peptide breakdown by cell purification

1. The fate of corticotrophins in a trypsin-dispersed rat adrenal-cell assay system was investigated with a view to establishing whether differences in the rate of inactivation might contribute to potency differences observed between analogues. 2. Corticotrophin-(1-24)-tetracosapeptide and to a lesser extent synthetic 1-39 corticotrophins were found to be inactivated during incubation with cell suspension. 3. Peptide fragments were isolated by using [[(3)H(2)]Tyr(23)]corticotrophin-(1-24)- tetracosapeptide as a marker. The fragments indicate a peptidase with a predominantly tryptic specificity. 4. The peptidase is present in the extracellular fluid and is released from cells when they are damaged. 5. Cells were fractionated on an albumin gradient. Cells from the zona fasciculata and the zona intermedia or reticularis were present in fractions which produced fluorogenic steroids in response to corticotrophin. 6. Purification of the cells by centrifugation through albumin decreased degradation by peptidases, so that if the assay is carried out with a dilute suspension of purified cells peptide breakdown should not affect the observed potencies of adrenocorticotrophin analogues. 7. No binding of [[(3)H(2)]Tyr(23)]corticotrophin-(1-24)- tetracosapeptide to cells could be detected at low concentrations of the peptide. This indicated that less than 120 receptors/cell are occupied during stimulation by a dose that would elicit approx. 80% of the maximal response.     

Isolation and structure of nocobactin NA, a lipid-soluble iron-binding compound from Nocardia asteroides

Nocobactin NA, a lipid-soluble iron-chelating product with an unusual and characteristic u.v.-absorption spectrum, was isolated from Nocardia asteroides grown under conditions of iron deficiency. Its structure was determined by physical methods and by synthesis of one of its degradation products. Nocobactin NA was obtained as a homologous mixture of compounds with side chains of differing length, and resembles mycobactin M in structure except that it has an oxazole ring in place of an oxazoline ring, and the side chains in the cobactin fragment are considerably shorter.     

Branched-chain glycosyl α-amino acids : Part II. Synthesis of 2-D- and 2-L-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)glycine. Analogs of the sugar moiety of the polyoxins

Stereospecific hydroxylation of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-trans-and 3-C-cis-(methoxycarbonylmethylene)-α-D-ribo-hexofuranose (2 and 3, respectively), with potassium permanganate in pyridine afforded 3-C-[S- and R-hydroxy-(methoxycarbonyl)methyl]-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose, (6 and 7, respectively), in a combined yield, after chromatography, of 43%. Selective formation of monomethanesulfonates (9a and 10a) and p-toluenesulfonates (9b and 10b), followed by treatment with sodium azide and reduction of the azide, afforded the methyl 2-D-(and 2-L-)(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)-glycinates (12a and 13a, respectively). Basic hydrolysis of the latter compounds yielded 2-D- and 2-L-(3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-yl)glycine (12b and 13b, respectively). The structures of the glycosyl amino acids were correlated with that of L-alanine by circular dichroism.     

Investigation of Reported Aflatoxin Production by Fungi Outside the Aspergillus flavus Group

A screening study of 121 fungus isolates, representing 29 species, for aflatoxin synthesis demonstrated this property only in Aspergillus flavus and A. parasiticus. Eight of the organisms found negative were isolates reported by other investigators to produce aflatoxin. Since similar negative reports have come from several other workers, it is concluded that only the A. flavus group of Aspergillus can presently be certified as sources of these toxins. Reasons for possible false-positive findings are discussed along with precautionary measures and differential analytical procedures useful in aflatoxin screening studies.     

Protein carboxyl methyltransferase activity specific for age-modified aspartyl residues in mouse testes and ovaries: Evidence for translation during spermiogenesis

An antiserum prepared against the purified protein carboxyl methltransferase (PCMT) from bovine brain has been used to compare testicular and ovarian levels of the enzyme and to study the regulation of PCMT concentrations during spermatogenesis. The PCMT, which specifically modifies age-damaged aspartyl residues, is present at a significantly higher concentration in mature mouse testis than in ovary. However, the PCMT is present at nearly equal concentrations in extracts of germ cell-deficient ovaries and testes obtained from mutant atrichosislatrichosis mice. In normal testis, the concentration of the PCMT increases severalfold during the first 4–5 weeks after birth, paralleling the appearance and maturation of testicular germ cells. Both immunochemical and enzymatic measurements of PCMT specific activities in purified spermatogenic cell preparations indicate that PCMT levels are twofold and 3.5-fold higher in round spermatids and residual bodies, respectively, than in pachytene spermatocytes. The results are consistent with the enhanced synthesis and/or stability of the PCMT in spermatogenic cells and with the continued translation of the PCMT during the haploid portion of spermatogenesis. The relatively high levels of PCMT in spermatogenic cells may be important for the extensive metabolism of proteins accompanying spermatid condensation or for the repair of damaged proteins in translationally inactive spermatozoa.     

Measurement by HPLC of Desferrioxamine-Available Iron in Rabbit Kidneys to Assess the Effect of Ischaemia on the Distribution of Iron Within the Total Pool

A method for the determination of desferrioxamine-available iron in tissue fractions is described which involves incubation with desferrioxamine, extraction of desferrioxamine and its iron-bound form, ferrioxamine, and quantitation of these two forms of the drug by reversed-phase hplc analysis. Chelatable iron levels in the 1-10µMolar region could be accurately and reproducibly measured using this technique.

The desferrioxamine-available iron levels in both the cortex and medulla of rabbit kidneys were significantly elevated (up to 2-fold) after the organs had been subjected to 2 hours warm ischaemia or 24 hours cold storage at 0°C In hypertonic citrate solution. There was no change in the total iron content of the tissues under these circumstances and thus a redistribution of intracellular iron to more available pools had presumably taken place as a result of ischaemia. This redistribution of iron may be an important factor in the initiation of peroxidative damage to cell membranes upon reperfusion of the organ with oxygen.