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Biomedical subjects

J Hemming

Publications and source records attributed to J Hemming.

13 recordsLinked to original sources
PubMed2005

Evolutionary implications of permanent odd polyploidy in the stable sexual, pentaploid of Rosa canina L.

In Rosa canina (2n = 5x = 35), the pollen and ovular parents contribute, respectively, seven and 28 chromosomes to the zygote. At meiosis I, 14 chromosomes form seven bivalents and 21 chromosomes remain as univalents. Fluorescent in situ hybridization to mitotic and pollen mother cells (PMC) of R. canina showed that 10 chromosomes (two per genome) carry ribosomal DNA (rDNA) loci. Five chromosomes carry terminal 18S-5.8S-26S rDNA loci; three of these also carry paracentric 5S rDNA loci and were designated as marker chromosomes 1. Five chromosomes carry only 5S rDNA loci and three of these were designated as marker chromosomes 2. The remaining four of the 10 chromosomes with rDNA loci were individually identifiable by the type and relative sizes of their rDNA loci and were numbered separately. At PMC meiosis, two marker chromosomes 1 and two marker chromosomes 2 formed bivalents, whereas the others were unpaired. In a gynogenetic haploid of R. canina (n = 4x = 28), obtained after pollination with gamma-irradiated pollen, chromosomes at meiosis I in PMC remained predominantly unpaired. The data indicate only one pair of truly homologous genomes in R. canina. The 21 unpaired chromosomes probably remain as univalents through multiple generations and do not recombine. The long-term evolutionary consequence for the univalents is likely to be genetic degradation through accumulated mutational change as in the mammalian Y chromosome and chromosomes of asexual species. But there is no indication that univalents carry degenerate 5S rDNA families. This may point to a recent evolution of the R. canina meiotic system.

Chromosome Banding↗
PubMed2001

Effects of wood-related sterols on the offspring of the viviparous blenny, Zoarces viviparus L.

The parent generation of the viviparous blenny, Zoarces viviparus L., were exposed to phytosterols (a) from oogenesis to parturition and (b) from breeding to parturition. The experiments were performed under laboratory conditions in a test unit supplied with continuous renewal of brackish water. After parturition the offspring were further reared either in clean or in phytosterol-contaminated brackish water. The objective was to study the significance of preexposure of the parent on the effects of phytosterols on the offspring in comparison with effects occurring directly on previously unexposed offspring. The phytosterol concentrations used were (a) 0, 10, 20, and 30 microg/L and (b) 0, 10, and 20 microg/L. Offspring exposed in (a) was further reared in clean water and in (b) offspring from parents exposed to 10 microg/L was either exposed further in the same concentration or left in clean water. Offspring from parents exposed to 20 microg/L was further exposed in the same concentration. Finally one group from unexposed parents was exposed to 10 microg/L after birth. The offspring was studied for 6 months after birth. The results showed that blenny offspring are affected by phytosterols at exposure through the parental generation. The results imply that phyto- sterols affect embryological development of the larvae before hatching as well as the levels of circulating hormones of the parent fish. The larvae contained higher levels of phytosterols as did controls and the bile of exposed female fish contained lower levels of phytosterols implying a link between the higher levels in larvae and lower excretion of the females. The growth of the larvae at 10 microg/L was stimulated regardless of whether the larvae were further exposed, indicating that newborn larvae carried within the female are sensitive to exposure to phytosterols.

Abnormalities, Drug-Induced↗
PubMed1999

Effects of wood-related sterols on the reproduction, egg survival, and offspring of brown trout (Salmo trutta lacustris L.).

Maturing lake trout (Salmo trutta lacustris) of both sexes were exposed to 10 and 20 microg/liter phytosterols, mainly ss-sitosterol, for 4.5 months prior to spawning. Eggs from preexposed females were artificially fertilized with milt from preexposed males in clean water, whereupon the eggs were incubated in clean water until hatching. Yolk sac fry were followed until swim-up, and mortality as well as deformities was recorded. The physiological status of the parent fish was documented, as was the occurrence of phytosterols in bile liquid and gonads. In addition, eggs from preexposed females were fertilized with milt from unexposed males to evaluate the existence of possible sex-linked differences. The results indicate a markedly increased dose-dependent egg mortality, smaller egg size, and lower mean weight of the the yolk sac stage larvae. There was a higher prevalence of deformed or otherwise diseased larvae, especially at the higher dose, but also in the groups where unexposed males were used for fertilization, indicating a female-linked effect mechanism. A causal link between effects on eggs and brood was obtained through a dose-dependent increase in phytosterols in the roe. Several physiological parameters (higher plasma estradiol, higher 7-ethoxyresorufin O-deethylase activity) implied slower maturation of the exposed female fish, whereas indications of accelerated maturation were obtained for the male fish from the same groups. The results indicate that naturally occurring wood-derived compounds in pulp mill effluents may be responsible for reproductive impacts previously observed in fish both in the laboratory and in the receiving waters of pulp mill effluents. The results also suggest that more attention should be paid to process streams emanating from the unbleached part of the mill.

Animals↗
PubMed1998

Experimental field exposure of brown trout to river water receiving effluent from an integrated newsprint mill.

Effects of effluents from mechanical pulp production on brown trout were studied for 8 weeks at environmentally relevant concentrations. The exposure took place in laboratory-based pools upstream and downstream of the effluent discharge point of an integrated newsprint mill using ground wood/thermomechanical pulp. The mill had no secondary treatment of the wastewater. The pools were supplied with water pumped directly from the river. To determine the relevance of this approach, wild fish were also caught at the respective sites upstream and downstream from the mill. Sublethal effects were assessed using physiological and biochemical parameters including liver histology, hematology, serum biochemistry, and hepatic enzyme assays. Exposure was verified by analyzing water samples, fish bile, and tissues for resin acid concentrations. The downstream experimental fish and captured feral fish displayed responses and changes in physiological parameters similar to those previously observed in laboratory experiments with untreated effluents. The most obvious effects were liver damage and growth inhibition.

Animals↗