Antimicrobial defense mechanisms in the horseshoe crab, Limulus polyphemus: preliminary observations with heat-derived extracts of Limulus amoebocyte lysate.

Heat-derived (60°C) extracts of Limulus amoebocyte lysate (LAL) were found to contain potent “broad-spectrum” antimicrobial activity. Additional heating of the LAL extracts to 100°C for 30 min completely inactivated the antimicrobial activity and served as a control. Antimicrobial activity was observed over a temperature range of 0° to 37°C (higher temperatures not tested) with greatest activity at 37°C. Antimicrobial activity of LAL extracts was variable when tested against Gram-negative bacteria of the family Enterobacteriaceae. A twofold concentration of the extracts resulted in a significant decrease in antimicrobial effectiveness. Dialysis of single- and double-strength LAL extracts against deionized water produced a marked and significant enhancement of antimicrobial activity against both resistant and sensitive species, confirming the presence of a dialyzable inhibitor(s). Dialyzed LAL extracts were active against 13 of 14 species of Enterobacteriaceae tested. Two strains of Pseudomonas aeruginosa were susceptible as were two of three Gram-positive cocci tested. Highly sensitive bacterial species were rapidly killed with a greater than 90% reduction in viable counts occurring within the first 30 min of reaction time. Dialyzed LAL extracts also possessed considerable antifungal activity. The role of the Limulus polyphemus amoebocyte in defense against microbial invasion and dissemination is discussed.     

Pyrroline-5-carboxylate reductase in soybean nodules: isolation/partial primary structure/evidence for isozymes

Electrophoretic evidence was obtained for two forms of pyrroline-5-carboxylate reductase (P5CR) in soybean nodules. One form was purified over 2300-fold. The apparent sizes of the polypeptides comprising the pyrroline-5-carboxylate reductases from soybean cytosol (29,700) and Escherichia coli (28,000) were consistent with those predicted from the sequences of the genes encoding them (Deutch et al., 1982 Nucleic Acid Res. 10, 7701-7714; Delauney and Verma, 1990 Mol. Gen. Genet. 221, 299-305). Primary structural analysis of the intact soybean P5CR subunit indicated that the amino-terminal residue is blocked. Analyses of a 12-mer and a 21-mer isolated from a cyanogen bromide digest were consistent with the proposition that the soybean P5CR isolated in these studies is very similar, although perhaps not identical, to the polypeptide predicted for the recently cloned soybean reductase (Delauney and Verma, 1990 Mol. Gen. Genet. 221, 299-305).     

Lamellar/inverted cubic (L alpha/QII) phase transition in N-methylated dioleoylphosphatidylethanolamine

Inverted cubic (QII) phases form in hydrated N-methylated dioleoylphosphatidylethanolamine (DOPE-Me). Previous work indicated that QII phases in this and other systems might be metastable structures. Whether or not QII phases are stable has important implications for models of the factors determining the relative stability of bilayer and nonbilayer phases and of the mechanisms of transitions between those phases. Here, using X-ray diffraction and very slow scan rate differential scanning calorimetry (DSC), we show that thermodynamically stable QII phases form slowly during incubation of multilamellar samples of DOPE-Me at constant temperature. The equilibrium L alpha/QII phase transition temperature is 62.2 +/- 1 degree C. The transition enthalpy is 174 +/- 34 cal/mol, about two-thirds of the L alpha/HII transition enthalpy observed at faster scan rates. This implies that the curvature free energy of lipids in QII phases is substantially lower than in L alpha phases and that this reduction is substantial compared to the reduction achieved in the HII phase. The L alpha/QII transition is slow and is not reliably detected with DSC until the temperature scan rate is reduced to ca. 1 degrees C/h. At faster scan rates, the HII phase forms at a reproducible temperature of 66 degrees C. This HII phase is metastable until ca. 72-79 degrees C, where the equilibrium QII/HII transition seems to occur. These results, as well as the induction of QII phases in similar systems by temperature cycling (observed by others), are consistent with a theory of L alpha/QII/HII transition mechanisms proposed earlier (Siegel, 1986c).     

Non-covalent interactions result in aggregation of surface antigens of the parasitic nematode Trichinella spiralis.

Surface antigens of three stages of the nematode worm Trichinella spiralis has been labelled with iodine and examined by sodium dodecyl sulphate (SDS)/polyacrylamide-gel electrophoresis under reducing and non-reducing conditions. A variety of interactions were defined: the infective larva surface antigens formed a spectrum of aggregates from 50kDa to greater than 1000kDa from subunits of 47kDa and 90kDa; in the adult worms of 60kDa complex arose fron interaction between two dissimilar molecules of 40kDa and 20kDa; the new-born larvae components formed homologous dimers from a 58kDa molecule. Aggregating molecules were adherent to lentil lectin-Sepharose and are therefore glycoproteins. The interactions observed were completely abolished by boiling in SDS/mercaptoethanol, but only partially destroyed by boiling in SDS/iodoacetamide. Based upon this, the associations can be characterized as non-covalent, but disulphide-bond-dependent. It is suggested, but not proved, that the aggregates arise from strong non-covalent hydrophobic interaction sites which are stabilized by intrachain disulphide bonds in the molecules concerned.     

Isolation and detailed characterization of human cell lines resistant to -threo-chloramphenicol

The isolation and characterization of chloramphenicol resistant derivatives of the human cell line HeLa B is described. Growth of resistant lines was unaffected in the presence of 100 μg/ml -threo-chloramphenicol, whereas growth of the parental cells was inhibited at 12.5 μg/ml. The incorporation of [³⁵S]methionine into mitochondrial protein of intact resistant cells continued normally in the presence of 100 μg/ml chloramphenicol (cytoplasmic protein synthesis was blocked by addition of 50 μg/ml emetine). Under these conditions the electrophoretic profile of labelled, presumptive mitochondrially-made proteins was similar to that of the parental cell line labelled in the absence of chloramphenicol. The cell lines selected in the presence of chloramphenicol also showed increased resistance to some other inhibitors of mitochondrial protein synthesis, e.g. carbomycin and mikamycin. [¹⁴C]Chloramphenicol was found to have normal access to the interior of resistant cells and it is therefore unlikely that resistance results from altered cell permeability. No modification of the drug by acetylation or glucuronide conjugation mechanisms was observed. The possibilities remain that resistance is mediated by altered permeability of the mitochondrial membrane, or from modification to a component of the mitochondrial protein synthetic system.     

Non-coding RNAs and ferroptosis: potential implications for cancer therapy

Ferroptosis is a recently defined form of regulated cell death, which is biochemically and morphologically distinct from traditional forms of programmed cell death such as apoptosis or necrosis. It is driven by iron, reactive oxygen species, and phospholipids that are oxidatively damaged, ultimately resulting in mitochondrial damage and breakdown of membrane integrity. Numerous cellular signaling pathways and molecules are involved in the regulation of ferroptosis, including enzymes that control the cellular redox status. Alterations in the ferroptosis-regulating network can contribute to the development of various diseases, including cancer. Evidence suggests that ferroptosis is commonly suppressed in cancer cells, allowing them to survive and progress. However, cancer cells which are resistant to common chemotherapeutic drugs seem to be highly susceptible to ferroptosis inducers, highlighting the great potential of pharmacologic modulation of ferroptosis for cancer treatment. Non-coding RNAs (ncRNAs) are considered master regulators of various cellular processes, particularly in cancer where they have been implicated in all hallmarks of cancer. Recent work also demonstrated their involvement in the molecular control of ferroptosis. Hence, ncRNA-based therapeutics represent an exciting alternative to modulate ferroptosis for cancer therapy. This review summarizes the ncRNAs implicated in the regulation of ferroptosis in cancer and highlights their underlying molecular mechanisms in the light of potential therapeutic applications.Subject terms: Tumour biomarkers, Oncogenes     

Demographic responses to climate‐driven variation in habitat quality across the annual cycle of a migratory bird species

The demography and dynamics of migratory bird populations depend on patterns of movement and habitat quality across the annual cycle. We leveraged archival GPS‐tagging data, climate data, remote‐sensed vegetation data, and bird‐banding data to better understand the dynamics of black‐headed grosbeak (Pheucticus melanocephalus) populations in two breeding regions, the coast and Central Valley of California (Coastal California) and the Sierra Nevada mountain range (Sierra Nevada), over 28 years (1992–2019). Drought conditions across the annual cycle and rainfall timing on the molting grounds influenced seasonal habitat characteristics, including vegetation greenness and phenology (maturity dates). We developed a novel integrated population model with population state informed by adult capture data, recruitment rates informed by age‐specific capture data and climate covariates, and survival rates informed by adult capture–mark–recapture data and climate covariates. Population size was relatively variable among years for Coastal California, where numbers of recruits and survivors were positively correlated, and years of population increase were largely driven by recruitment. In the Sierra Nevada, population size was more consistent and showed stronger evidence of population regulation (numbers of recruits and survivors negatively correlated). Neither region showed evidence of long‐term population trend. We found only weak support for most climate–demographic rate relationships. However, recruitment rates for the Coastal California region were higher when rainfall was relatively early on the molting grounds and when wintering grounds were relatively cool and wet. We suggest that our approach of integrating movement, climate, and demographic data within a novel modeling framework can provide a useful method for better understanding the dynamics of broadly distributed migratory species.