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.     

Molecular Characterization of the D Surface Protein Gene Subfamily in Paramecium tetraurelia

ABSTRACT. When Paramecium tetraurelia expresses the D serotype, detectable by serum tests, high molecular mRNA could be isolated, which corresponds to the molecular mass of the D surface protein. Using this D specific mRNA as a probe for screenings in different genomic libraries a subfamily of five very similar genes was found, named α-51D, _γ1-51D, _γ2-51D, δ-51D and ε-51D. Each of them is about 8-kb long, they show regions of identity to each other, and there is no evidence that any are defective genes or pseudogenes. Up to now serotype D is the only known serotype showing this phenomenon. Another novel feature is that two of the D isogenes are closely linked. The sequence for the entire coding region of the α-51D gene has been determined, as well as the upstream and downstream noncoding regions. Its deduced amino acid sequence shows the same characteristic cysteine periodicity displayed by all other immobilization antigen (i-ag) genes from Paramecium. However, in contrast to most other such genes, tandem repeats are missing from the 7599-bp long coding region of the α-51D gene. When the sequences of the type 51D genes are compared to each other, the similarity is very high and extends to coding as well as to noncoding regions. Similarity within noncoding regions is usually only observed for allelic i-ag genes. We conclude that the type D genes constitute a family of isogenes that are nonallelic. They contain slightly different consensus sequences with possible functions as regulatory regions.     

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.