A COMPARISON OF FOUR EAST AFRICAN CROCODILE (CROCODYLUS NILOTZCUS LAURENTI) POPULATIONS

Four crocodile populations have been examined by aerial photography with a view to assessing their length frequency distributions. The assumptions, and the limitations attached to such assumptions, necessary to convert length frequency information into information on the age structure, and hence the status, of the population are considered. Environmental conditions of value in understanding the status of the populations are listed. The Victoria Nile population is considered to show adequate recruitment, but dispersal of young crocodiles tends to give the converse impression. The population is probably stable and has not been heavily exploited in the past. The Grumeti River population may represent a local aggregation mostly of large males from Lake Victoria, probably retreating from human induced pressures. There is little recruitment through breeding, and the largest crocodile encountered in this study are members of this population. The Lake Rudolf population is a typical healthy population with high recruitment and high juvenile mortality. The population is probably stable, but may be expected to decline as fishing interests on the west shore expand. Growth is retarded in the Rudolf population. The Lorian swamp population is expanding rapidly probably after a period of heavy mortality wrought by hunters shooting for skins. The present conflicts with human/livestock interests is expected to increase, resulting in stabilization and decline of crocodile in the swamp. Some comments are made on the possible influence of various environmental parameters on present status and trends of the populations.     

Use of fragment–sharing estimates from DNA fingerprinting to determine relatedness in a tropical wren

We assessed the usefulness of DNA fragment–sharing scores from DNA fingerprints for assigning relatedness to unknown pairs of individuals in a population of stripe–backed wrens (Campylorhynchus nuchalis). Preliminary investigation of scoring biases revealed consistency both within and between scorers in relative band–sharing scores, but a tendency for scores to be inflated and for inter–scorer agreement to decline as distance between lanes on an autoradiograph increased. Distributions of band–sharing values matched expected distributions well, which suggests that variability in scores is mostly inherent and not a result of errors in scoring. Confidence intervals based on band–sharing scores or means of scores across enzymes, probes and scorers revealed that unrelated (r= 0) and first–order dyads (r=Vi) could be distinguished on the basis of single band–sharing scores from the best combination of enzyme and probe (HaeIII/33.15) and that first– and second–order dyads could be distinguished when confidence intervals were based on means of band–sharing scores across two enzymes, two probes and two scorers.     

Protein Body Inclusions in Developing Wheat Endosperm

Endosperm tissue of two wheat cultivars, Maris Freeman and Mardlerwas examined by light and electron microscopy from early stagesof development until maturity. Spherical electron-dense inclusionswere first seen embedded in the periphery of endosperm proteinbodies of both cultivars 11 days after anthesis. The inclusions,which gave a positive histochemical reaction for both proteinand lipid, persisted throughout endosperm development and werepresent in the protein matrix of mature grain. Two types ofmembranous inclusions were found. In Maris Freeman and Mardler,vesicles and myelin whorls were associated with the surfaceof the protein mass during development and maturation. In MarisFreeman, membrane lattices of branched tubules with a basiccubic repeat unit of 44.8 nm were found in close contact withthe protein mass, but these were not present in mature grain. Triticum aestivum L., wheat, endosperm, protein body inclusions, ultrastructure     

Regulators of Cell Division in Plant Tissues XIV. The Cytokinin Activities and Metabolism of 6-Acylaminopurines

Certain 6-acylaminopurines have been shown to exhibit activity in several cytokinin bioassays. The active compunds included 6-N,2′-O-dibutyryladenosine 3’:5′-cyclic monophosphate, but adenosine 3′:5′-cyclic monophosphate was inactive. The metabolites formed from [2,8-³H] 6-benzoylaminopurine by radish seedlings and excised radish cotyledons were investigated. When compared with zeatin, this amide showed considerable stability in vivo. Conversion to 6-benzylaminopurine and its riboside was not detected but slight degradation to adenine was indicated. The principal metabolite was an unidentified compund.     

Assessing the phytotoxicity of mononuclear hydroxy-aluminum

Abstract Al³⁺ is an important rhizotoxic ion in acid soils around the world. Al³⁺ is in equilibrium with mononuclear hydroxy-Al species, such as AlOH²⁺ and AL(OH)₂⁺, but the toxicity of these species has not been determined. Polynuclear Al may also coexist with Al³⁺, and one of these species, AlO₄Al₁₂(OH)₂₄(H₂O)₁₂⁷⁴, is very toxic. In order to determine the toxicity of mononuclear hydroxy-Al we have reanalysed the results of previously published, solution-culture experiments and have performed new experiments. Several problems are inherent in these studies. At pH values less than 5.0, the activities of the mononuclear hydroxy-Al species are low relative to Al³⁺, but attempts to change the ratio by raising the pH generally initiate the formation of polynuclear Al. (We discovered that mononuclear solutions are stable for many days when {Al³⁺}/{H⁺}³≤ 10^8.8, where braces denote activities.) We avoided, or accounted for, polynuclear Al in our studies. In addition, we used up-to-date equilibrium constants to compute Al species, very simple culture media (generally containing CaCl₂, AlCl₃ and HCl as the only inputs), short-term (2d) growth, and an Al-sensitive wheat variety (Triticum aestivum L. cv. Tyler) that permitted low Al levels and, consequently, higher pH values without Al polymerization. Experiments were designed in which the solutions were constant in {Al³⁺} and variable in mononuclear hydroxy-Al or were orthonal (factorial) in {Al³⁺} and {AlOH²⁺}. Linear and nonlinear, simple and multiple, regression analyses of these and previous experiments failed to reveal any toxicity for mononuclear hydroxy-Al to Tyler wheat.     

Non-glaucousness, a probable aphid-resistance character of wheat

Cuticular waxes from wheat cultivars that have a bluish-green waxy bloom under field conditions were compared with those of non-glaucous (NG) variants that appeared dark green and glossy in the field. Cuticular wax from NG variants was deficient in diketones and hydroxydiketones, and did not form the micro-spicules of epicuticular wax which were characteristic of the normal bloom. Typically, NG wheats were resistant to Sitobion avenae in the field, but in environments where wax secretion was diminished, resistance was reduced or absent. Possible causes of this resistance, which appears likely to be easy to exploit, are discussed.     

TWO CONCEPTS OF EMPIRICAL ETHICS

The turn to empirical ethics answers two calls. The first is for a richer account of morality than that afforded by bioethical principlism, which is cast as excessively abstract and thin on the facts. The second is for the facts in question to be those of human experience and not some other, unworldly realm. Empirical ethics therefore promises a richer naturalistic ethics, but in fulfilling the second call it often fails to heed the metaethical requirements related to the first. Empirical ethics risks losing the normative edge which necessarily characterizes the ethical, by failing to account for the nature and the logic of moral norms. I sketch a naturalistic theory, teleological expressivism (TE), which negotiates the naturalistic fallacy by providing a more satisfactory means of taking into account facts and research data with ethical implications. The examples of informed consent and the euthanasia debate are used to illustrate the superiority of this approach, and the problems consequent on including the facts in the wrong kind of way.