Sequence and embryonic expression of the murine Hox-3.5 gene.

The murine Hox-3.5 gene has been mapped and linked genomically to a position 18 kb 3' of its most 5' locus neighbour, Hox-3.4, on chromosome 15. The sequence of the Hox-3.5 cDNA, together with the position of the gene within the locus, show it to be a paralogue of Hox-2.6, Hox-1.4 and Hox-4.2. The patterns of embryonic expression for the Hox-3.5 gene are examined in terms of three rules, proposed to relate a Hox gene's expression pattern to its position within the locus. The anterior boundaries of Hox-3.5 expression in the hindbrain and prevertebral column lie anterior to those of Hox-3.4 and all other, more 5'-located Hox-3 genes. Within the hindbrain, the Hox-3.5 boundary is seen to lie posterior to that of its paralogue, Hox-2.6, by a distance equal to about the length of one rhombomere. Patterns of Hox-3.5 expression within the oesophagus and spinal cord, but not the testis, are similar to those of other Hox-3 genes, Hox-3.3 and Hox-3.4.     

Molecular variation and phylogeny of members of the Minimus Group of Anopheles subgenus Cellia (Diptera: Culicidae)

Intra‐ and interspecific molecular variation were investigated in four members of the Minimus Group of Anopheles subgenus Cellia: An. aconitus, An. varuna, An. minimus A and An. minimus C. DNA sequence divergence between these species at a mitochondrial locus (cytochrome oxidase II) and at three nuclear loci (ITS2 and D3 regions of rDNA and guanylate cyclase) is reported. The data confirm the presence of two cryptic species, A and C, within An. minimus and provide evidence for the existence of a third species. Anopheles minimus A and C are estimated to have diverged 0.57–1.5 million years ago. The discrepancy observed using the guanylate cyclase intron, which is the fastest evolving region known in the Gambiae Complex but is relatively slowly evolving in the Minimus Group, is discussed. The long‐term effective population sizes of An. minimus A and C are estimated to be in their millions, with that of species A being approximately twice the size of species C. This implies that An. minimus C has a much wider distribution than currently recognized, with possible widespread implications for vector control. No evidence was found for population structuring in either species A or C: there was greater variation of mitochondrial haplotypes within than among localities. The phylogenetic relationships of Oriental members of the Myzomyia Series are reconstructed.     

Automated food microbiology: potential for the hydrophobic grid-membrane filter.

Bacterial counts obtained on hydrophobic grid-membrane filters were comparable to conventional plate counts for Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus in homogenates from a range of foods. The wide numerical operating range of the hydrophobic grid-membrane filters allowed sequential diluting to be reduced or even eliminated, making them attractive as components in automated systems of analysis. Food debris could be rinsed completely from the unincubated hydrophobic grid-membrane filter surface without affecting the subsequent count, thus eliminating the possibility of counting food particles, a common source of error in electronic counting systems.     

Auxin-independent growth of maize tissue culture cells

Wall-regenerating protoplasts and suspension culture cells of Zea mays L. ‘Black Mexican Sweet’ were co-cultivated] with Ti plasmid-containing Agrobacterium tumefaciens strain ACH5. After elimination of the bacteria, putative transformants were selected for their ability to grow in the absence of added auxin. Althoug some of the treated cells grew, untreated controls and cells treated with the Ti plsmidless strain ACH5C3 also proliferated. The frequency of auxin-independent growth was similar in all treatments. Because none of 75 candidate transforms contained detectable T-DNA, the hormone-independent phenotype appears to be a consequence of habituation. Although some of the habituated colonies grew as undifferentiated callus, others produced rootlike structures. Miaze cells subcultured in liquid media containing progressively reduced concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) also became habituated.     

LEAF GROWTH AND PHENOLOGY OF THE DIMORPHIC HERBACEOUS LAYER FERN DANAEA WENDLANDII (MARATTIACEAE) IN A COSTA RICAN RAIN FOREST

Leaf growth and spore release in Danaea wendlandii were monitored under temperate greenhouse conditions and in a rain forest at the La Selva Biological Station in Costa Rica. Sterile leaf (trophophyll) growth occurs in four phases, and fertile leaf (sporophyll) growth occurs in five phases. Trophophylls show an initial rapid increase in length for a 4-week period, attain full maturity at 8 weeks, and remain on the plant for about 3 years. There appears to be a seasonal pattern of trophophyll growth, with crozier emergence rates in May and June three times higher than the mean annual rate. Sporophyll growth shows a double sigmoid pattern. For about 3 weeks after crozier emergence, there is a rapid increase in length. This phase is followed by a 10-week period with no appreciable change in length. Rapid elongation over a 2-week period precedes spore release; this is followed within 2 weeks by disappearance of the sporophyll. Sporophylls in the rain forest are subject to 14% mortality prior to maturation, with most mortality occurring in later stages of growth. A projected phenology based on the sporophyll growth curve shows peaks in spore release late in the wet season with a concomitant peak in sporophyll emergence early in the wet season during the 15-month period from June 1986 through September 1987.     

CORNEAL SURFACE PROPERTIES OF TWO MARINE MAMMAL SPECIES1

Compared to the anterior surface of the normal human cornea, all Tursiops showed pronounced random, local curvature changes typical of old keratitis and scarring. Comparable but less severe findings apply to Zalophus. These irregularities were superimposed on the mild regular astigmatism of the spoon-shaped Tursiops cornea (mean central power is 26.8 D, SD = 3.8, N = 82). All Zalophus corneas showed no reliable regular astigmatism (overall mean power is 21.7 D, SD = 4.4, N = 53) but exhibited a flat, circular region about 6.5 mm in diameter along the nasal aspect of the horizontal meridian. Refraction through this cornea1 region showed aerial emmetropia, which accounts for equivalent marine and aerial visual resolution in this species.