3D Bioprinting of Food Grade Hydrogel Infused with Living Pleurotus ostreatus Mycelium in Non-sterile Conditions

Mycelium is the root-like network of fungi. Mycelium biocomposites prepared by template replication (molding) can function as environmentally friendly alternatives to conventional polystyrene foams, which are energy- and carbon-intensive to manufacture. Recently, several studies have shown that 3D bioprinting technologies can be used to produce high value functional mycelium products with intricate geometries that are otherwise difficult or impossible to achieve via template replication. A diverse range of nutrients, thickeners, and gelling agents can be combined to produce hydrogels suitable for 3D bioprinting. 3D bioprinting with hydrogel formulations infused with living fungi produces engineered living materials that continue to grow after bioprinting is complete. However, a hydrogel formulation optimized for intricate 3D bioprinting of Pleurotus ostreatus mycelium, which is among the strains most commonly used in mycelium biocomposite fabrication, has yet to be described. Here, we design and evaluate a versatile hydrogel formulation consisting of malt extract (nutrient), carboxymethylcellulose and cornstarch (thickeners), and agar (gelling agent), all of which are easily sourced food grade reagents. We also outline a reproducible workflow to infuse this hydrogel with P. ostreatus liquid culture for 3D bioprinting of intricate structures comprised of living P. ostreatus mycelium and characterize the changes in height and mass as well as hardness of the prints during mycelium growth. Finally, we demonstrate that the workflow does not require a sterile bioprinting environment to achieve successful prints and that the same mycelium-infused hydrogel can be supplemented with additives such as sawdust to produce mycelium biocomposite objects. These findings demonstrate that 3D bioprinting using mycelium-based feedstocks could be a promising biofabrication technique to produce engineered living materials for applications such as mushroom cultivation, food preparation, or construction of the built environment.

Cytonuclear disequilibrium in a hybrid zone involving deep-sea hydrothermal vent mussels of the genus Bathymodiolus

A hybrid zone involving the deep-sea mussels, Bathymodiolus azoricus and B. puteoserpentis, was recently discovered at Broken Spur hydrothermal vent field (29 degrees 10' N, 43 degrees 10' W) along an intermediate segment of the Mid-Atlantic Ridge axis. Examination of nuclear (allozymes) and cytoplasmic (mitochondrial DNA) gene markers in a new sample from Broken Spur revealed significant cytonuclear disequilibrium caused by an excess of the parental types (coupling phase) and a deficiency of recombinants (repulsion phase). An assignment test of individual multilocus genotypes also revealed an excess of parental genotypes in the admixed population. These results support the hypothesis that the Broken Spur mussel population comprises a nonequilibrium mixture of parental immigrants and hybrid individuals.

Constitutive expression of cellular retinoic acid binding protein II and lack of correlation with sensitivity to all-trans retinoic acid in acute promyelocytic leukemia cells

The up-regulation of cellular retinoic acid binding protein-II (CRABP-II) has been invoked as an important mechanism of clinically acquired resistance to all-trans retinoic acid (RA) therapy in acute promyelocytic leukemia (APL). To test this hypothesis, we used quantitative reverse transcription-PCR and fast performance liquid chromatography procedures to examine the levels of CRABP-II mRNA and RA binding activity in APL patient samples. We found that CRABP-II mRNA in APL cells from pretreatment patients (n = 36) was constitutively expressed at relatively high levels (median, 0.92; range, 0.16-4.13) relative to the level in CRABP-H protein-expressing NB4 cells (arbitrarily set at 1.0 unit). Consistent with this finding, the RA binding activity of CRABP in APL cells from three pretreatment cases (range, 27.2-53.2 fmol/mg protein) was similar to that of NB4 cells (22.6 +/- 5.4 fmol/mg protein). Furthermore, in the pretreatment samples, there was no association between CRABP-H mRNA expression level and APL cellular sensitivity to RA-induced differentiation in vitro. After 45 days of remission induction therapy on Eastern Cooperative Oncology Group protocol E2491, CRABP-II mRNA was modestly increased from day 0 values in patients treated with either RA (median increase, 0.41) or chemotherapy (median increase, 0.56), and there was no significant difference between the two treatment groups (P = 0.91). In patients studied after relapse from RA therapy (n = 7), there was a significant decline in APL cell sensitivity to RA-induced differentiation in vitro compared with patients after relapse from chemotherapy (n = 5; P = 0.015-0.055 at three RA concentrations tested), but in the RA relapse cases, there was no change from pretreatment levels of CRABP-II mRNA (median, 0.98) or, in three relapse cases studied, of RA protein binding activity (range, 22.1-70.7 fmol/mg protein). Taken together, our data strongly imply that variations in CRABP-II expression and RA binding activity are not causally related to the development of clinically acquired APL cellular RA resistance, but rather, they suggest that constitutive expression of CRABP-II could have a facilitative role in the response of APL cells to RA.

lin-14 regulates the timing of synaptic remodelling in Caenorhabditis elegans

In the nematode Caenorhabditis elegans six GABAergic motor neurons, known as DDs, remodel their patterns of synaptic connectivity during larval development. DD remodelling involves a complete reversal of the direction of information flow within nerve processes without marked changes in process morphology. We used a marker localized in vivo to DD presynaptic zones to analyse how the timing of DD remodelling is controlled. In wild-type animals, DDs remodel their synaptic outputs within a 3-5-hour period at the end of the first larval stage. We show that the heterochronic gene lin-14, which controls the timing of stage-specific cell lineages, regulates the timing of DD synaptic output remodelling. In lin-14 loss-of-function mutants, DDs remodel precociously. The degree of precocious remodelling is correlated with the level of lin-14 activity. Expression of lin-14(+) in the DDs of lin-14-null mutants rescues the precocious remodelling, indicating that lin-14 can act cell-autonomously. Consistent with this hypothesis, LIN-14 protein levels decrease in the DDs before remodelling. Our observations reveal a role of heterochronic genes in non-dividing cells, and provide an example of cell-autonomous respecification of neuronal connectivity.

Effect of retinoic acid and interferon alpha on granulocyte-macrophage colony forming cells in chronic myeloid leukemia: increased inhibition by all-trans- and 13-cis-retinoic acids in advanced stage disease

Granulocyte-macrophage colony forming units (CFU-GM) from patients with advanced stage chronic myelogenous leukemia (CML), i.e. in blastic crisis (BC) or accelerated phase (AP), were inhibited by all-trans-retinoic acid (tRA) approximately 1000-fold more potently than those from chronic phase (CP) CML patients (median IC50 = 10(-9) M tRA for six CML-AP/BC cases vs > 10(-6) M tRA for seven CML-CP cases). A similar activity pattern was observed for the stereoisomer 13-cis-RA (cRA). There was no apparent correlation of CFU-GM retinoid sensitivity with cloning efficiency or other colony characteristics. Interferon alpha-2a (INF alpha) alone strongly inhibited CFU-GM growth in all four CML-AP/BC cases (IC50 < or = 250 IU/ml) and three out of seven CML-CP cases (IC50 < or = 500 IU/ml), but there was little or no interactive effect between various concentrations of tRA and INF alpha (50 IU/ml) on CFU-GM from either CML-AP/BC or CML-CP cases. These results suggest that CML-AP/BC CFU-GM have some intrinsic molecular alteration(s) which markedly enhances their responsiveness to tRA and cRA, which may be clinically exploitable.