Front Cover: Photoacoustic imaging of the human placental vasculature (J. Biophotonics 4/2020)

Successful therapy of twin‐to‐twin transfusion syndrome requires accurate imaging to guide laser photocoagulation of the anastomosing placental vessels. Photoacoustic (PA) imaging is an alternative imaging method that provides contrast for hemoglobin, and in this study, it was used to visualize chorionic superficial and subsurface vasculature in human placentas. The strong potential of PA imaging to guide minimally invasive fetal therapies was demonstrated. Further details can be found in the article by Efthymios Maneas, Rosalind Aughwane, Nam Huynh, et al. ( e201900167 ).

     

Partial purification and characterisation of an inhibitor of hepatocyte proliferation derived from nonparenchymal cells after partial hepatectomy.

We have investigated the influences that nonparenchymal cells from regenerating rat liver exert on hepatocyte proliferation. When primary adult rat hepatocytes isolated from resting liver were co-cultured with nonparenchymal cells (NPCs) from resting liver of a different syngeneic animal, the proliferative response of hepatocytes to epidermal growth factor (EGF) was unaffected by the presence of NPCs. In the presence of NPCs taken from livers that had undergone partial hepatectomy 24 hours before (regen-NPCs), the response of hepatocytes from resting liver to EGF, TGF-alpha, and hepatocyte growth factor (HGF) was markedly inhibited. Inhibitory activity was not dependent on cell-to-cell contact, and conditioned-medium from regen-NPCs, but not normal NPCs, inhibited EGF-induced hepatocyte DNA synthesis by approximately 50%. After concentration by gel chromatography and lyophilisation, inhibition was 98%. The inhibitory activity migrated on SDS-PAGE gel electrophoresis with an apparent molecular weight of 14 to 17 kDa and was trypsin-sensitive but relatively heat-stable. The effects of blocking antibodies established that it was not TGF-beta 1, IL1-beta, or IL6. Investigations of regen-NPCs taken at different time points demonstrated that inhibitory activity was released into conditioned medium of cells harvested at 24 and 48 hours after partial hepatectomy, but not 10 or 72 hours. This powerful inhibitor of hepatocyte response to proliferogens is released by cultures of NPCs with a time course suggesting that it may be involved in terminating the surge of hepatocyte replication induced by partial hepatectomy.     

Fusion between vesicles from the pathway of receptor-mediated endocytosis in a cell-free system

Fusion between endocytic vesicles containing 125I-transferrin and ones containing anti-transferrin antibody was monitored by the formation of an immune complex. Fusion required ATP and only occurred between specific populations of vesicles. Cytosol was also required. Trypsinisation of the preparations or pre-treatment with N-ethylmaleimide abolished the fusion reaction.     

Strategies for targeted transposon tagging of ABA biosynthetic mutants in tomato

The ABA biosynthetic pathway has been studied in detail and the steps impaired in some ABA-deficient mutants are known. However, little is known of the molecular control mechanisms regulating ABA production in planta. A direct route for improving our understanding of these mechanisms is to transposon tag and clone the wild-type counterparts of the ABA mutant alleles. On the basis of the observation that maize transposons move preferentially to linked sites in both homologous and heterologous systems and in doing so disrupt gene function, a targeted transposon mutagenesis strategy is being developed towards cloning ABA biosynthetic genes from tomato. The possibility of using marker genes to identify T-DNA insertion sites in selected parts of the genome has been examined and compared with an inverse PCR/RFLP approach to mapping T-DNAs.     

The nutrition of vegetables in sand

The yield data available from the author's series of investigations on vegetable nutrition in sand have been plotted against the concentrations of the elements concerned (nitrogen, phosphorus, and potassium), and the curves so obtained have been discussed. Within the ranges of concentrations employed, it is observed that too much available nitrogen or, especially, available phosphorus, causes depressions in yields with the tops and/or roots of certain vegetables, turnip roots being particularly susceptible to too much available phosphorus; no case of over-employment of available potassium, however, is noted. The turnip is recommended as a type plant for indicating the state of soil fertility as regards available (nitric) nitrogen.