Effects of Growth Regulators and Glutamine on In Vitro Development of Zygotic Embryos of Taro (Colocasia esculenta var. antiquorum)

Zygotic embryos of taro, Colocasia esculenta var. antiquorumcultured on Linsmaier-Skoog (LS) medium without the additionof hormones develop into mature plants only in the presenceof endosperm tissue. Growth is usually evident within the firstweek of culture when embryos swell and become green. Embryosexcised from endosperm and cultured on LS containing 0-01 mg1^–1 naphthaleneacetic acid (NAA), and 0–01 mg 1^–16-dimethylaminopurine (6-DMAP) grow at a rate comparable withcontrols for the first week of culture. During the second week,growth rates are higher than controls primarily because embryosform elongated hypocotyl regions which often produce swollentissues and/or callus. In the presence of 200 mg 1^–1 glutamineand a range of concentrations of 6-dimethylaminopurine, benzyladenine,or NAA, elongation of the hypocotyl axis is inhibited, and acompact callus may develop. Embryos grown on LS containing 200mg 1^–1 glutamine and 2.0 mg 1^–1 2, 4, 5-trichlorophenoxyaceticacid form friable callus which was used to generate short-livedsuspension cultures. Growth Regulators, Glutamine, tygotic embryos, Colocasia esculenta, endosperm     

Effects of Incubation Temperature on Crocodiles and the Evolution of Reptilian Oviparity

Crocodylus porosus is a mound-nesting crocodilian in which incubationtemperature influences the rate of embryonic development, theprobability that embryos will survive to hatching, post-hatchinggrowth rates and the probability of hatchlings surviving to2 yr of age. Similar responses have been described in Alligatormississippiensis (Joanen et al., 1987) and C. niloticus (Hutton,1987), and they reflect a suite of "non-sexual" effects of incubationtemperature. Temperature-dependent sex determination allocatessex on the basis of these "non-sexual" effects. In C. porosus,it results in maleness being assigned to embryos with high probabilitiesof surviving and good potential for post-hatching growth. Withinthe limits of survival, effects of the moisture environmenton embryological development rate and hatchling fitness seemminor relative to those of the temperature environment. Reptilian orders have either obligate oviparity (chelonians,crocodilians and rhynchocephalians) or facultative oviparity(squamates), depending on the extent of embryonic developmentwithin the oviducts. The distinction is equally one betweenembryos which are buffered from thermal effects within a female'sbody (facultative oviparity) and those that are not (obligateoviparity). Facultative oviparity and internal thermal bufferingmay be the primitive condition within the Class Reptilia, andthe "shell-less" eggs of extant squamates may reflect the originalamniote egg. Obligate oviparity, which also exists in birds,appears to have been a specialized development, and is a blindend in the evolution of viviparity among vertebrates. The significanceof thermal buffering being lost in obligate oviparous reptilesremains unclear.     

Scrape cytology in the diagnosis of Paget's disease of the breast

Eczema of the nipple is an important symptom presenting to the general surgeon in the out-patient department. the diagnosis of Paget's disease of the nipple has traditionally been made by incision biopsy necessitating at least a local anaesthetic. We present 14 patients with nipple skin change, in whom the technique of scrape cytology was used to identify patients with Paget's disease. In our series eight cases of Paget's disease were successfully identified by scrape cytology with no false negatives or positives. We suggest that this is a quick, easy, non-invasive method of screening eczema of the nipple in the out-patient clinic.     

The Incorporation of C14-labelled Substrates into the Amino-acids of Groundnut Plants (Arachis hypogaea)

The amino-acid metabolism of groundnut plants has been studiedwith special reference to -methyleneglutamic acid (-MGA) andy-methyleneglutamine (-MG), constituents not found in the greatmajority of plant species. The sequence in which C¹⁴ from radioactive C¹⁴-carbon dioxideenters the amino-acids of leaves was determined. The patternof labelling was very similar to that found for leaves of otherspecies. The metabolic relationships existing between photosynthesisand amino-acid synthesis therefore do not seem to be affectedby the large quantities of -MGA and -MG present in the leaves.-MGA and -MG only gained traces of radioactivity. Experiments designed to study the incorporation of C¹⁴ fromuniformly labelled C¹⁴-alanine into the amino-acids of roots,immature leaves and cotyledons of seedlings and young plantsindicated that the main site of synthesis of -MGA was the cotyledons. Various C^I4-labelled substrates were fed to germinating seedsand, after a period of growth, the specific activities of theamino-acids of seedlings receiving different treatments weredetermined. Comparison of the specific activities enabled certaindeductions to be made concerning the probable biosynthetic pathwaysleading to -MGA and -MG. The results were consistent with theintact incorporation of pyruvate molecules, or another related3-carbon-atom containing compound, into -MGA.     

Use of isoenzyme and protein phenotypes to discriminate between six Pratylenchus species from Great Britain

Six species of Pratylenchus indigenous to Great Britain, P. crenatus, P. fallax, P. neglectus, P. penetrans, P. pinguicaudatus and P. thornei were analysed by slab gel electrophoresis to compare protein patterns and isoenzyme phenotypes of esterase, glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase, phosphoglucose isomerase and phosphoglucomutase. Multiple electromorphs were obtained from all enzymes examined. The results demonstrated that isoenzyme phenotypes are useful to supplement the morphological characterisation of these nematode species. Pair-wise comparisons of the six species were performed giving coefficients of similarity in the range 11–41%. A dendrogram of the six species, generated from the five enzyme banding patterns, gave two groups: group 1 contained P. pinguicaudatus, P. fallax and P. thornei and group 2 contained P. penetrans, P. neglectus and P. crenatus.     

Natal dispersal and genetic structure in a population of the European wild rabbit (Oryctolagus cuniculus)

A combination of behavioural observation, DNA fingerprinting, and allozyme analysis were used to examine natal dispersal in a wild rabbit population. Rabbits lived in territorial, warren based social groups. Over a 6-year period, significantly more male than female rabbits moved to a new social group before the start of their first breeding season. This pattern of female philopatry and male dispersal was reflected in the genetic structure of the population. DNA fingerprint band-sharing coefficients were significantly higher for females within the same group than for females between groups, while this was not the case for males. Wrighfs inbreeding coefficients were calculated from fingerprint band-sharing values and compared to those obtained from allozyme data. There was little correlation between the relative magnitudes of the F-statistics calculated using the two techniques for comparisons between different social groups. In contrast, two alternative methods for calculating F_ST from DNA fingerprints gave reasonably concordant values although those based on band-sharing were consistently lower than those calculated by an ‘allele’ frequency approach. A negative F_IS value was obtained from allozyme data. Such excess heterozygosity within social groups is expected even under random mating given the social structure and sex-biased dispersal but it is argued that the possibility of behavioural avoidance of inbreeding should not be discounted in this species. Estimates of genetic differentiation obtained from allozyme and DNA fingerprint data agreed closely with reported estimates for the yellow-bellied marmot, a species with a very similar social structure to the European rabbit.     

A structural comparison of New Zealand and south-east Australian rain forests and their tropical affinities

An ecological comparison, with special reference to tropical affinities, is made between the rain forests of New Zealand and south-east Australia, based on the distribution of seventy physiognomic-structural attributes in mature forests at selected sites (ten in New Zealand, twenty in Australia, and four in New Guinea to represent authentic humid tropical lowland rain forest). The structural data were recorded in a standard pro forma and subjected to classification, ordination and two-parameter analysis. In the classification, the Australian and New Zealand sites, with two exceptions, separated at the four-group level. The more complex (cool subtropical) Australian types were the least related to the New Zealand forests, which are closest to Australian simple (submontane) types. There was a similar distinction in the ordination, in which the trend along the first two vectors was latitudinal, correlated with extremes of temperature and with moisture availability. The relative contributions of the structural attributes to the various site groupings in the classification and ordination are enumerated, and provide an objective scale of comparison of the forests. Structural attributes designated by analysis as exclusively or preferentially tropical by reference to the New Guinea sites are then used to assess degree of tropical affinity. The simplified cool temperate (montane) forests dominated by one species of Notho-fagus in New Zealand and Australia are closely related. The Australian forests of the sub-montane zone (mean annual temperature 12–15° C) which are typically dominated by Ceratopetalum apetalum, Nothofagus moorei or Doryphora sassafras, are similar to the podocarp-broadleaf forests, with or without kauri, of New Zealand. The Australian forests of the cool subtropical zone (mean annual temperature 15–17°C) which have mixed dominants, have some affinities with the kauri-podocarp-broadleaf forests of North Auckland. In New Zealand, a broadleaf type in which kauri is absent or rare on basalt in North Auckland (lat. 35° S) was the most complex forest sampled and is marginally subtropical.     

The Recent Terebratulina Community in the rocky subtidal zone of the Bay of Fundy, Canada

A distinctive rocky subtidal benthic community (the Terebratulina Community) is described from the Bay of Fundy, Canada. It is shown to consist of three closely intcrspersed sub-communities: a cavity sub-community, characterised by chitons, coelenterates, brachiopods, bryozoans, chordates and annelids; a rock-face subcommunity, similar in composition but enriched in brachiopods and sponges; and an upper-surface subcommunity, dominated by algae, chitons, bivalves and echinoids.
Comparison with recently described Jurassic, Cretaceous and Recent (Mediterranean) hard-ground communities suggests a relative constancy in composition, in terms of higher taxa, since the Mesozoic. Development of these (sub-)communities occurs wherever crevice or cavity systems on hard substrates lead to microenvironments differentiated mainly on the basis of water energy and light.
The composition and trophic structure of the community and the life habits of Terebratulina septentrionalis (Couthouy) are related to aspects of the environment. Marked differences in composition between the living cavity sub-community and the death assemblage in the sediments are shown to be due to differential preservation, fragmentation, population dynamics and limited local transportation.