Association of Viral Reverse Transcriptase with an Enzyme degrading the RNA Moiety of RNA-DNA Hybrids

DURING replication of RNA tumour viruses, the genetic information contained in the viral RNA seems to be transferred to DNA^1,2. Studies on the enzymatic activities present in the virus particles suggest that this transfer is mediated by an RNA dependent DNA polymerase^3,4. RNA-DNA hybrids have been demonstrated to occur as intermediates in this reaction⁵ and single stranded DNA is generated as an early reaction product⁶, which is then replicated to give a double stranded DNA product^6–8. The mechanism by which the single stranded DNA is displaced from the RNA template is, however, not known.     

Morphological profiling using machine learning reveals emergent subpopulations of interferon-γ–stimulated mesenchymal stromal cells that predict immunosuppression

Background

Although a preponderance of pre-clinical data demonstrates the immunosuppressive potential of mesenchymal stromal cells (MSCs), significant heterogeneity and lack of critical quality attributes (CQAs) based on immunosuppressive capacity likely have contributed to inconsistent clinical outcomes. This heterogeneity exists not only between MSC lots derived from different donors, tissues and manufacturing conditions, but also within a given MSC lot in the form of functional subpopulations. We therefore explored the potential of functionally relevant morphological profiling (FRMP) to identify morphological subpopulations predictive of the immunosuppressive capacity of MSCs derived from multiple donors, manufacturers and passages.

Asymmetric impacts of two herbivore ecotypes on similar host plants

1. Ecotypes may arise following allopatric separation from source populations. The simultaneous transfer of an exotic plant to a novel environment, along with its stenophagous herbivore, may complicate more traditional patterns of divergence from the plant and insect source populations. 2. The present study evaluated herbivory effects by two Cyrtobagous salviniae ecotypes on two species of Salvinia: the larger S. molesta and the smaller S. minima. Evaluations were based on relative growth rates, biomass production, coverage, and nutrient cycling in a series of complementary and comparative laboratory and outdoor tank experiments. 3. In general, the experiment results indicated that the smaller Florida ecotype of C. salviniae impacted both Salvinia species more than the larger Brazil ecotype. Herbivory, especially by the Florida ecotype, also improved water quality and accelerated nutrient cycling by increasing the rates of litterfall from the standing crops of salvinia. 4. The smaller size of the Florida ecotype may be adaptive by allowing maximal exploitation of host plants via internal larval feeding, which presumably reduces predation risk while increasing damage to the plant. These findings provide support for relying on the suppressive effects of the Florida ecotype in Florida, rather than introducing the Brazil ecotype to counter new infestations of S. molesta.     

Fine needle aspiration (FNA) cytology in the diagnosis of recurrent soft tissue sarcoma

trovik c. s., bauer h. c. f., brosjö o., skoog l. and söderlund v. (1998) Cytopathology 9, 320–328
Fine needle aspiration (FNA) cytology in the diagnosis of recurrent soft tissue sarcoma
We have used FNA cytology to diagnose suspected local recurrences of soft tissue sarcoma. Since 1991, a total of 95 FNA cytologies were performed on 86 patients. There were 47 local recurrences, of which 44 were diagnosed correctly by FNA cytology; one biopsy was inconclusive, and two lesions were incorrectly assessed as benign. Thirty-nine patients proved to have benign lesions in the scar area examined cytologically on 50 occasions. None of the specimens was regarded as malignant, but in four cases FNA cytology was inconclusive. Overall, there were 5% inconclusive cytological biopsies, 0% falsely malignant and 5% falsely benign. The inconclusive and false-negative cytological diagnoses had no important clinical consequences. FNA biopsy provides a simple means of diagnosing local recurrence of soft tissue sarcoma.     

Coat colour variation in the banded palm civet Hemigalus derbyanus and in Owston's civet Chrotogale owstoni

1. Coat colour variation was studied in two viverrid species belonging to the subfamily Hemigalinae, on the basis of museum specimens and observations of live animals. 2. In both species, polymorphism and ontogenetic colour change occur, and in the Owston's civet, sexual dimorphism in coat colour was identified.     

Responses of Cyprinodon maya and C. labiosus females to visual and olfactory cues of conspecific and heterospecific males

Premating isolating mechanisms, based on visual and olfactory cues, were studied in two members of a young species flock which is endemic to Lake Chichancanab in Mexico. The two species, Cyprinodon maya and C. labiosus, differ in morphological traits that may be associated with trophic differentiation, but show little genetic change. Female C. maya strongly preferred conspecific males over C. labiosus males, based on visual as well as olfactory cues. C. labiosus females discriminated between conspecific and heterospecific males based on olfactory cues but not visual ones. Asymmetries in the strength of female preferences for conspecific males in this species pair suggest that mate recognition systems based on visual and olfactory cues evolve at different rates and track the degree of genetic differentiation.