Accumulation of a Polyhydroxyalkanoate Containing Primarily 3-Hydroxydecanoate from Simple Carbohydrate Substrates by Pseudomonas sp. Strain NCIMB 40135

A number of Pseudomonas species have been identified which accumulate a polyhydroxyalkanoate containing mainly 3-hydroxydecanoate monomers from sodium gluconate as the sole carbon source. One of these, Pseudomonas sp. strain NCIMB 40135, was further investigated and shown to accumulate such a polyhydroxyalkanoate from a wide range of carbon sources (C₂ to C₆); however, when supplied with octanoic acid it produced a polyhydroxyalkanoate containing mainly 3-hydroxyoctanoate monomers. Polymer synthesis occurred in batch culture after cessation of growth due to exhaustion of nitrogen. In continuous culture under nitrogen limitation up to 16.9% (wt/wt) polyhydroxyalkanoate was synthesized from glucose as the carbon source. The monomer units are mainly of the R-(−) configuration. Nuclear magnetic resonance studies confirmed the composition of the polymer. Differential scanning calorimetry suggested that the solvent-extracted polymer contained a significant proportion of crystalline material. The weight-average molecular weight of the polymer from glucose-grown cells was 143,000.     

Hereditary spherocytosis of man. Altered binding of cytoskeletal components to the erythrocyte membrane

The endogenous respiration of the rumen ciliate Dasytricha ruminantium maintained under an O2 tension of 2kPa (approximately 0.02 atm) was partially inhibited by KCN (40% inhibition) and NaN3 (58% inhibition). The organisms lack cytochromes, and sensitivity of respiration to KCN, NaN3, chloroquine and quercetin suggest that the operation of flavoprotein-iron-sulphur-mediated electron transport. As in Tritrichomonas foetus, hydrogenosomal respiration can be stimulated by the addition of CoA in the presence of 0.025% Triton X-100; stimulation by ADP was not detected. Stimulation of pyruvate-supported O2 uptake by Pi suggests that acetate is produced via acetyl phosphate.     

Early electrochemical events in lectin-lymphocyte interaction

Concanavalin A, at extremely low concentrations, will produce significant increases in the electrophoretic mobility of murine splenic T lymphocytes. It has been established that the alteration in cellular surface charge is mediated by a factor produced by those lymphocytes that have reacted directly with con A. We originally conjectured that the mobility change might be the consequence of an alteration in the distribution of the charged moieties of membrane glycoproteins. The results of experiments conducted at low temperature raise some questions about this mechanism. Further experiments have been performed to establish the nature of the physicochemical alterations in the peripheral zone of the factor-stimulated lymphocytes that are manifest as changes in cellular surface charge. The results of these studies indicate that, subsequent to the interaction of T lymphocytes with con A, there is a reduction in the number of positively charged amino groups effective at the electrophoretic surface of the cells.     

Complete amino acid sequence of a variant surface glycoprotein (VSG 117) from Trypanosoma brucei

The amino acid sequence of a variant surface glycoprotein (VSG 117) of Trypanosoma brucei has been determined by manual sequencing of tryptic. staphylococcal protease and cyanogen bromide peptides and fragments derived from these peptides. Some overlaps needed for completion of the sequence were deduced from the nucleotide sequence of complementary DNA derived from messenger RNA coding for VSG 117. The glycoprotein consists of 470 amino acid residues with two carbohydrate chains attached at Asn420 and Asp470. No pronounced hydrophobic regions, which are characteristic of many membrane proteins, are present in the isolated glycoprotein, and the carboxy-terminal region, which is close to the membrane, is remarkably hydrophilic. These observations indicate that the molecule probably does not penetrate the lipid bilayer of the plasma membrane. The high proportion of charged residues in the carboxyterminal region is more consistent with electrostatic interaction with the polar head groups of the phospholipids.     

Thyrotrophin-Releasing Hormone Analogues Increase Dopamine Release from Slices of Rat Brain

Abstract: Rat brain slices were incubated with a high concentration of K⁺, thyrotrophin-releasing hormone (TRH), or one of two biologically stable TRH analogues (CG 3509 or RX 77368). Basal release of endogenous dopamine, measured by electrochemical detection, was increased by K⁺ (30 m M ) from slices of hypothalamus, septum, nucleus accumbens, and striatum. CG 3509 (10⁵–10⁻³ M ) increased the release of dopamine from slices of nucleus accumbens, septum, and hypothalamus in a dose-dependent fashion, whereas RX 77368 (10⁻⁴ M ) increased the release of dopamine from the septum only. Neither analogue increased the release of striatal dopamine. The results provide further evidence for specific regional interactions between TRH and dopamine in rat brain.     

The asymmetric war of attrition

The paper, which has an informal discussion at the end, provides a game theoretical analysis of the asymmetric “war of attrition” with incomplete information. This is a contest where animals adopt different roles like “owner” and “intruder” in a territorial conflict, and where the winner is the individual prepared to persist longer. The term incomplete information refers to mistakes in the identification of roles. The idea by Parker & Rubenstein (1981) is mathematically worked out and confirmed that there exists only a single evolutionarily stable strategy (ESS) for the model with a continuum of possible levels of persistence and no discontinuities in the increase of cost during attrition. The ESS prescribes to settle the conflict according to “who has more to gain or less to pay for persistence”. The only evolutionarily stable convention is thus to give the player access to the resource who has the role which is favoured with respect to payoffs. By contrast, it was shown earlier (Hammerstein, 1981) for various asymmetric versions of the “Hawks-Doves” model that an ESS can exist which appears paradoxical with respect to payoffs. The nature of this contrast is further analyzed by introducing elements of discreteness in the asymmetric war of attrition. It turns out that some conditions must be satisfied in order to have the possibility of an alternative ESS which is not of the above simple commonsense type. First, a decision to persist (or escalate) further in a contest must typically commit a contestant to go on fighting for a full “round”, before he can give up without danger. Second, such a “discontinuity” must occur at a level of persistence where the contest is still cheap, and, finally, errors in the identification of roles must be rare.     

Tracheal slowly adapting stretch receptors: Theoretical models

Explanations and conditions given for the occurrence of diffusive structure in two-species ecosystem models do not generalize to systems with three or more species.     

3S,24S,25-Trihydroxytirucall-7-ene from Ailanthus excelsa

A new triterpene has been isolated from the root bark of Ailanthus excelsa (Simaroubaceae) and identified as 3S,24S,25-trihydroxytirucall-7-ene.     

The predatory behaviour of Caranx melampygus (Pisces) in the channel environment of Aldabra Atoll (Indian Ocean)

Aspects of the predatory behaviour of free ranging Curanx melampygus have been examined in the shallow channel environment of Aldabra Atoll, Indian Ocean. Differences in the frequency of occurrence and number of fish hunting at two adjacent observation areas are described. The numbers of Caranx moving through the area appears to be influenced by tidal factors and possibly the abundance of prey and other environmental factors. The percentage offish hunting increases progressively throughout the day and is most commonly performed by solitary fish or small groups. While approximately equal numbers of Caranx move up or down stream significantly more fish engage in hunting activity when moving down stream which suggests the mechanical advantage of moving with the flow of water has advantages to the hunting fish. Several types of interspecific feeding association are described in which the Caranx is able to scavenge from others or to exploit the hunting methods of other species. More small Caranx form associations than do large Caranx . There is a relationship between the length of a hunting Caranx and the size and/or type of prey that makes an avoidance reaction to it. This relationship between different group sizes and the prey avoidance response is less clearly defined and it is suggested that whether hunting in groups or singly the final interaction is between a single predator and single prey. Ways by which group advantages may occur on grouped prey are described and are considered the result of independent individual action rather than group co-operation. Coastal observations indicate that Caranx use topographic features to shield their approach to areas of high prey density.     

A comparison of the inhibitory effects of melatonin and indomethacin on platelet aggregation and thromboxane release

Collagen-induced platelet aggregation and thromboxane release is inhibited, in a concentration response relationship, by preincubation of gel-filtered platelets with melatonin in the concentration range 430 nM – 4.3 mM. Inhibition of platelet aggregation and thromboxane release also occurs in the presence of indomethacin (4.3 nM – 4.3 mM), a known potent inhibitor of prostaglandin synthesis. Arachidonic acid-induced platelet aggregation and thromboxane release was inhibited in the presence of 4.0 mM melatonin. We therefore propose that inhibition of prostaglandin synthesis maybe the mechanism by which melatonin expresses its activity. Its antigonadotropic activity may result from inhibition of PGE₂ synthesis in the hypothalamus and median eminence.