Guanine nucleotide regulatory protein alterations in young Milan hypertensive strain rats

Vascular smooth muscle cell membranes from prehypertensive rats of the Milan hypertensive strain (MHS) were used to examine adenylyl cyclase activity and its regulation by guanine nucleotide regulatory proteins (G-proteins). Basal adenylyl cyclase activity was similar in MHS and Milan normontensive strain (MNS) membranes. Forsokolin (10^?4 M) produced a significantly greater stimulatory response in MHS membranes, but this was not observed with NaF (10^?2 M). Isoporterenol (10^?4 M) caused a significantly decreased stimulation of adenylyl cyclase activity in MHS membranes, while prostaglandin E₁ (10^?5 M) produced similar responses in the two strains. G_i function and GTP responses, as observed by biphasic effects of GTP on isoproterenol-stimulated membranes, were similar in both strains. The levels of G_i2α and G_qα/G₁₁α were similar in the two strains, while the levels of G_sα (44 and 42 kDa forms) and the β-subunit were significantly reduced by ～20% in MHS membranes. The α-subunit of G_i3 was dramatically reduced by ～80% in MHS membranes. The affinities of β-adrenergic receptors for the antagonist, cyanophindolol, were similar in the two strains; however, the number of β-adrenoceptors was substantially reduced in MHS membranes. These findings may be of relevance to altered vascular reactivity and transmembrane ion distribution observed in the MHS.     

Utilization of cofactors expands metabolism in a new RNA world

RNA has been hypothesized to have preceded proteins as the major catalysts of the biosphere, yet there are only a very limited number of chemical reactions that are known to be catalyzed by modern RNA. Cofactors are used by the majority of protein enzymes to supply additional functional groups to the active site. RNA should also be able to utilize some of these same cofactors to extend its own catalytic potential. We describe here how it could be possible to use selection — amplification from a population of random RNA to obtain a coenzyme A mediated RNA transacylase. Exploitation of some of the sulphur chemistry mediated by coenzyme A could have significantly expanded a prebiotic RNA directed metabolism.     

The post-copulation withdrawal response in female baboons: A functional analysis

Rapid withdrawal of females from males at the end of the copulatory sequence (prior to male dismounting) characterizes several primate species. The purpose of this paper is to make a preliminary investigation into possible functional aspects of these “copulatory darts.” Two hypotheses are proposed; (1) females use darts to aid competing males to locate the source of copulation calls; and (2) females dart in order to promote re-mating with the same male. Both hypotheses postulate that darts may thus enhance male-male competition, although acquisition of other benefits may be the primary drive to darting according to the re-mating hypothesis. Using data from 157 copulations collected from six females spread across four groups in a wild population of chacma baboonsPapio cynocephalus ursinus, darting behaviour is described. Within females, darting distance is highly variable. Darting distance is greatest at the time of ovulation (and maximal sexual swelling), and there is some evidence that darting may also be more frequent, and cover greater distances, when the mating male is adult rather than juvenile. While darting behaviour appears unrelated to the presence or absence of ejaculation, it tends to correlate positively with the duration of the female copulation call. These preliminary results are consistent with a mediating role in male-male competition and therefore provide support for both hypotheses.     

Allotype suppression in rabbits: the requirement for CH3 domain of anti-allotype antibody.

Facb fragments of rabbit anti-allotype antibody were prepared by plasmin digestion and isolated by gel chromatography. The antibody preparation was used in an attempt to induce allotype suppression in newborn rabbits. The Facb fragments were found to be ineffective in inducing the allotype suppression. Administration of Facb fragments caused a "burst" of immunoglobulin synthesis almost immediately after the administration of the antibody. It was concluded that the CH3 domain, which is responsible for the cytophilic activity of the antibody, is essential in induction of allotype suppression.     

The evolutionary ecology of corals

Corals display a wide range of complex life histories. The evolutionary consequences of factors such as clonality, indeterminate growth, asexual reproduction coupled with various (sexual) breeding systems, different levels of gene flow, and strongly overlapping generations have only just begun to be explored. We identify a series of problems and areas for new research that may be resolved b y the application of novel theoretical approaches (including nonequilibrium population genetic models and demographic models incorporating modular processes such as colony fission and polyp mortality), greater in situ experimentation, long-term monitoring of population dynamics and the use of new genetic techniques.     

Altered G-protein expression and adenylate cyclase activity in platelets of non-insulin-dependent diabetic (NIDDM) male subjects

Adenylate cyclase activity and levels of guanine nucleotide regulatory proteins (G-proteins) were compared in platelets from normal and non-insulin-dependent diabetic (NIDDM) male subjects. Whilst no differences were noted in basal and NaF-stimulated adenylate cyclase activities the degree of stimulation achieved by both forskolin and prostaglandin, E1 was lower by some 34 and 52% respectively, in platelet membranes from diabetic subjects compared with those from normal control subjects. Altered alpha 1-adrenoceptor-mediated inhibition of prostaglandin E1-stimulated adenylate cyclase activity was evident; it being some 34% lower in platelet membranes from diabetic subjects compared to controls. Analysis of G-protein alpha-subunits, using specific anti-peptide antisera, showed that platelets from all subjects exhibited the Gi-2 and Gi-3, but not the Gi-1 forms of the inhibitory G-protein 'Gi' and all expressed the 42 kDa species of alpha-subunit of the stimulatory G-protein Gs. Whilst platelets of diabetic subjects had levels of Gs which were comparable to those found in control subjects their levels of Gi-2 and Gi-3 were some 49 and 75%, respectively, of those found in platelets from control subjects. It is suggested that changes in adenylate cyclase functioning and G-protein expression may contribute to altered platelet functioning in non-insulin-dependent diabetic subjects.     

Immunization of sheep with larval antigens of Lucilia cuprina

Sheep were immunized with antigens extracted from third-instar larvae of L. cuprina. This procedure produced substantial titres of circulating antibody as measured by solid-phase radioimmunoassay or immunodiffusion or by both techniques. However, immunization did not confer protection against subsequent implant challenge with first-instar larvae. In vitro studies indicated that pooled sera from immunized sheep (mean immunodiffusion titre = 3) significantly reduced larval survival. Antigen specificity and the modulating effects of concomitant humoral responses to larval challenge are discussed in relation to the findings.     

Fb''2, a new peptic fragment of human immunoglobulin G.

The digestion of a human IgG1 K myeloma protein with pepsin in the presence of 8M-urea was observed to produce a fragment, designated Fb'2, which differed from the products of aqueous peptic digestion and from other characteristic immunoglobulin digestion products. 2. Fragment Fb's was also found when two other IgG1/K proteins were treated similarly. 3. Sedimentation-equilibrium studies showed the mol.wt. of fragment Fb'2 to be 56800. 4. On reduction, two equivalents of each of three peptides were released from fragment Fb's; these were characterized by N- and C-terminal determinations and by amino acid sequencing. 5. Fragment Fb'2 was shown to consist of the constant regions of both light chains, from residue Ile-117 to the C-terminus, and the CH1 domains and hinge region of the heavy chains, from residue Val-113 to residue Met-252, with a gap of five residues within the intrachain disulphide loop, between residues Leu-174 and Tyr-180.