Local production of fibronectin by ectopic human retinal cells

Summary The distribution of fibronectin mRNA and fibronectin in adult human retina and epiretinal membranes was investigated by in situ hybridisation and immunohistochemical techniques. The cells in normal adult retina contained little or no fibronectin mRNA and the retina only showed fibronectin immunoreactivity in retinal vessels. The cells in detached neuroretina did not contain fibronectin message but the vitreoretinal interface of the detached retina exhibited variable fibronectin immunoreactivity. Retinal glia, retinal pigment epithelium and fibroblast-like cells in membranes at the vitreoretinal juncture (epiretinal membranes) showed variable labelling with the fibronectin mRNA probe and all the membranes immunostained for fibronectin. No difference could be detected between membrane cell types in the intensity of labelling with the mRNA probe or for fibronectin immunoreactivity. The results indicate that cells in situ in attached and detached adult human retina do not produce fibronectin. Although fibronectin at the vitreoretinal juncture in retinal detachment is probably partly derived from plasma fibronectin resulting from breakdown of the blood-retinal barrier, ectopic retinal cells produce fibronectin and contribute to the glycoprotein in epiretinal membranes.     

Life history patterns of parental and hybrid Daphnia differ between lakes

1. We investigated whether Daphnia galeata × hyalina hybrids of Lake Constance and Lake Greifensee show the same pattern of life history parameters as previously reported for D. galeata × cucullata hybrids and whether such a pattern is consistent between Daphnia populations from those two lakes. 2. Hybrids in Lake Constance were intermediate in size compared with the parental species. Hybrids in Lake Greifensee were smaller than D. galeata. The intrinsic growth rate (r) of hybrids from Lake Constance was not significantly different from the faster growing parental taxon D. galeata. However, r of hybrids from Lake Greifensee was significantly lower than that of D. galeata. 3. The observed juvenile body length differences between the taxa varied with the clutch number. The first clutch juvenile lengths of the three taxa did not differ for Lake Constance. First clutch juveniles of Lake Greifensee D. galeata were smaller than hybrid first clutch juveniles. The third clutch juvenile length did not differ between taxa from Lake Greifensee, but D. galeata juveniles from Lake Constance were bigger than those of D. hyalina. 4. The life history pattern found in Lake Constance corresponds to previous findings from other studies. The hybrids in this lake combine the faster population growth of one parental species with a relatively small size. In the case of Lake Greifensee hybrids, the relatively large size of first clutch juveniles and the small size of the adults could be interpreted as dual adaptations to invertebrate and fish predation. We speculate that the lower population growth rate of the hybrids is a trade‐off for this twofold protection.     

A cDNA clone encoding Brassica calmodulin

A 834 bp cDNA encoding calmodulin (CaM) has been isolated from Brassica juncea. On Northern analysis this cDNA hybridises this cDNA to mRNAs of about 0.9 kb in leaf, silique and peduncle. Genomic Southern analysis indicates the presence of a CaM multigene family in Brassica juncea. Comparison of the predicted amino acid sequence of Brassica CaM with that of Arabidopsis CaM ACaM-2 and ACaM-3 showed 100% homology, which is not unusual, since both plants belong to the family Cruciferae. In situ hybridisation studies on Brassica seedlings using a digoxigenin-labelled RNA probe showed that high levels of CaM mRNA were detected in the leaf primordia and the shoot apical meristem, and to a lesser degree, in the zone of root elongation of the root tip. The occurrence of a higher rate of cell division and growth in these regions than its surrounding tissue may possibly be related to higher levels of CaM mRNA.     

The human genome contains multiple sequences of varying homology to mouse mammary tumour virus DNA

Sequences related to the mouse mammary tumour virus (MuMTV) DNA were isolated from a genomic library of human DNA by screening under conditions of relaxed stringency. It is estimated that there are in the order of 50 MuMTV-like sequences per haploid genome and that the homology between the different human sequences and MuMTV varies by 15%.     

Somatic hybridization of sexually incompatible petunias: Petunia parodii,Petunia parviflora

Summary Somatic hybrid plants were regenerated following the fusion of leaf mesophyll protoplasts of P. parodii with those isolated from a nuclear-albino mutant of P. parviflora. Attempts at sexual hybridization of these two species repeatedly failed thus confirming their previously established cross-incompatibility. Selection of somatic hybrid plants was possible since protoplasts of P. parodii would not develop beyond the cell colony stage, whilst those of the somatic hybrid and albino P. parviflora produced calluses. Green somatic hybrid calluses were visible against a background of albino cells/calluses, and upon transfer to regeneration media gave rise to shoots. Shoots and the resultant flowering plants were confirmed as somatic hybrids based on their growth habit, floral pigmentation and morphology, leaf hair structure, chromosome number and Fraction 1 protein profiles. The relevance of such hybrid material for the development of new, and extensively modified cultivars, is discussed.     

Comparison of the chromosomes of Triticum timopheevi with related wheats using the techniques of C-banding and in situ hybridization

Summary The chromosomes of the tetraploid wheats Triticum timopheevi (Genome AAGG) and T. araraticum (Genome AAGG) were C-banded at mitosis. The identity of the banded and unbanded chromosomes was then established by firstly making comparisons with the hexaploid species T. zhukovskyi which has the genome formula AAAAGG. Secondly, the meiotic pairing in F₁ hybrids between T. timopheevi and diploid wheats was examined by means of C-banding. The results showed that the banded chromosomes belonged to the G genome, while the unbanded chromosomes belonged to the A genome. Only one of the two pairs of satellited chromosomes had strong heterochromatic bands. The relationship between the genomes of T. timopheevi and T. dicoccum (Genome AABB) was then assessed at meiosis in hybrids between these species, using the techniques of C-banding and in situ hybridisation of a cloned ribosomal RNA gene probe. It was concluded that there were differences both in the amount and distribution of heterochromatin and also translocation differences between the species.     

Morphological and molecular evidence for interspecific hybridisation in the introduced African genus Crassocephalum (Asteraceae: Senecioneae) in Asia

Abstract

The genus Crassocephalum in Asia, introduced there from Africa, was examined by extensive field work, herbarium studies, analyses of pollen and seed fertility, chromosome counts and ITS and trnL‐F sequencing. We found that Crassocephalum in Asia comprises two species and their interspecific hybrid. The two species are C. crepidioides (Benth.) S. Moore and C. rubens (Juss. ex Jacq.) S. Moore, of which the latter is a new record for Asia (north Thailand). The hybrid between these two species in north Thailand originated from a cross between C. crepidioides (2n = 40) as female and C. rubens (2n = 40) as male parent.     

Mathematical modelling and computer simulation of Brownian motion and hybridisation of nanoparticle–bioprobe–polymer complexes in the low concentration limit

A wide variety of nano-biotechnological applications are being developed for nanoparticles based on in vitro diagnostic and imaging systems. Some of these systems allow highly sensitive detection of molecular biomarkers. Frequently, the very low concentration of the biomarkers makes very difficult the mathematical simulation of the motion of nanoparticles based on classical, partial differential equations. We address the issue of incubation times for low concentration systems using Monte Carlo simulations. We describe a mathematical model and computer simulation of Brownian motion of nanoparticle–bioprobe–polymer contrast agent complexes and their hybridisation to immobilised targets. We present results for the dependence of incubation times on the number of particles available for detection, and the geometric layout of the DNA-detection assay on the chip.     

PROCLAMATION

Natural hybridisation in Old World buzzards (Buteo) is an uncommon phenomenon with important ecological implications. This genus constitutes an intricate radiation of genetically poorly differentiated raptors whose taxonomic classification is a frequent subject of debate. We report the first case of successful hybridisation between the African subspecies of the Long-legged Buzzard Buteo rufinus cirtensis and Common Buzzard Buteo buteo buteo in a new contact zone in the Strait of Gibraltar (southern Spain). The hybrid offspring showed mixed characters from parental species indicating that, among others, hybridisation could explain the increasing presence of phenotypically odd reddish buzzards in southern Spain and northern Morocco. Given their close phylogenetic relation and their recently reduced allopatry, an increase in the hybridisation rate, fertile descendants and genetic introgression seem to be viable. We identify the potential contact zones where genetic monitoring is needed to gain insight on the real extent of this hybridisation and its possible effects on the current climate change scenario.