Trypanosoma cervi from Alaskan Reindeer,Rangifer tarandus1

Twenty-nine (64.4%) of 45 reindeer, Rangifer tarandus, examined over a two-year period were infected with trypanosomes. Trypomastigotes and dividing epimastigotes were found in the blood of fawns, cows, and bulls. Morphometric analysis of bloodstream trypomastigotes from reindeer and comparison of these parasites with similar stages of trypanosomes from elk, mule deer, and white-tailed deer from the contiguous United States proved them conspecific; the trypanosomes from these members of the Cervidae are identified as Trypanosoma cervi Kingston & Morton, 1975. This is the first report of trypanosomes from reindeer. No pathogenic effects are known to be caused by these parasites.     

DNA fingerprints of dogs and cats

Human minisatellite probes consisting of tandem repeats of the 'core' sequence, a putative recombination signal in human DNA, cross-hybridize to multiple polymorphic fragments in dog and cat DNA to produce individual-specific DNA 'fingerprints'. Pedigree analysis shows that most of the DNA fragments detected in an individual are heterozygous, and that these fragments are derived from multiple dispersed autosomal loci. DNA fingerprints of cats and dogs should prove suitable for individual identification and for establishing family relationships. They are also suitable for rapid marker generation in large pedigrees and could be applied to linkage analysis in these animals.     

EVIDENCE FOR CHEMICAL BORING IN PETRICOLA LAPICIDA (GMELIN, 1791) (BIVALVIA: PETRICOLIDAE)

Specimens of the dead coral-boring bivalve Petri-cola lapicidahave been obtained from Thailand and Jamaica. Although formerlyconcluded to be a mechanical borer, examination of the burrowand the shell strongly suggests chemical boring. Two glandslocated in the inner mantle folds around the antero-ventr'alpedal gape are thought to be involved in this, although onemay secrete the calcareous material cemented to the posteriorshell margin Less specialised petricolids are mechanical borers of stiffmuds, shales and calcareous rocks. A few are nestlers, e.g.,Claudiconcha. As has been recently suggested for other familiesof borers, the Petricolidae constitute another example of theevolution of a specialised chemical borer from a less specialisedmechanically-boring ancestor (Received 20 July 1987;     

Penultimate Aspartyl unnecessary for Stimulation of Acid Secretion by Gastrin-related Peptide

THE carboxy-terminal tetrapeptide of gastrin, Trp-Met-Asp-Phe-NH₂, has the same biological activity as the parent hormone¹. Morley^2,3 showed that certain substitutions in the Trp, Met and Phe positions gave active analogues and concluded that these positions are concerned only with binding at the site of action. In contrast, the only substitution in aspartic acid that gave activity was tetrazolyl for the β-carboxyl, thereby maintaining a proton donor of similar size at this position. Morley concluded that the aspartyl residue has a functional rather than a binding role and presumably is indispensable. The carboxy-terminal octapeptide of cholecystokinin (OP-CCK) contains the carboxy-terminal tetrapeptide of gastrin and has gastrin-like activity⁴. We report here that the synthetic analogue of OP-CCK, in which alanyl is substituted for aspartyl at the position in question illustration, stimulates gastric acid secretion. In conscious cats with gastric fistulas⁵, dose-response curves were established for gastric acid response to OP-CCK, 7-Ala OP-CCK and pentagastrin⁶. The peptides were given by continuous intravenous infusion and response is taken as peak 10 min output during a 30 min infusion at each dose level (Fig. 1). Assigning a potency of 1 to OP-CCK the relative molar potency of 7-Ala OP-CCK is about 1/110 and of pentagastrin is about 1/4. We also tested the analogue of gastrin tetrapeptide in which alanyl is substituted for aspartyl illustration and found no detectable stimulation of acid secretion at doses as high as 15 mg/kg h, confirming similar negative findings by Morley² in rat. This suggests that the weak action of alanyl substituted analogues cannot readily be detected without the enhancement of potency conferred by the sulphated tyrosyl of OP-CCK⁷. Ondetti et al.⁷ showed that 7-Ala OP-CCK contracts guinea-pig gallbladder with a potency about 1/150th that of OP-CCK, comparable with that reported here for acid secretion. This suggests that the same part or parts of the molecule are required for cholecystokinetic action and for gastric secretory action; the aspartyl residue in the penultimate position is dispensable for both of these actions. On the assumption that gastrin and CCK act at the same site⁸, we propose that the corresponding aspartyl residue of gastrin is similarly dispensable. For a direct test of this hypothesis, studies are needed of the synthetic analogue in which alanyl is substituted for the penultimate aspartyl in gastrin hepta-decapeptide, perferably gastrin II with sulphated tyrosyl because it is more potent than gastrin I in certain species⁹.

Open image in new window

Open image in new window

     

Variation in the glucosinolate content of oilseed rape (Brassica napus L.) leaves

The glucosinolate content of oilseed rape {Brassica napus) leaves was monitored over the growth period 30–70 days after planting, and a comparison made between a single-low cultivar (low in erucic acid), Bienvenu, and a double-low cultivar (low in erucic acid and glucosinolate), Cobra. In older, fully-expanded leaves the glucosinolate concentration was very low (< 0.3 μmol/ml tissue water) and did not alter during the course of the experiment. In developing sixth leaves glucosinolate content increased rapidly and reached a maximum concentration (4–5 μmol/ml tissue water) 40 days after planting (6 days after leaf emergence). The concentration then declined, to about 1 μmol/ml after 60 days although the total glucosinolate content in leaves continued to increase until 50 days; much of the reduction in concentration was simply a result of leaf expansion. No major differences were seen between the two varieties in total glucosinolate content or in the individual compounds present. Cv. Cobra developed more quickly than cv. Bienvenu so direct comparison between leaves of the two cultivars was complex. When comparing the glucosinolate content of oilseed rape leaves, between cultivars or between treatments, it is vital to ensure that carefully matched leaves of comparable developmental age are selected.