Effect of simian virus 40 infection on albumin production by hepatocytes cultured in chemically defined medium and plated on collagen and non-collagen attachment surfaces

Simian virus 40 (SV40)-infected rat hepatocytes were tested for albumin production (a marker of differentiated hepatocyte function) by growth in serum-free medium for 30-40 days. We observed a biphasic peak of albumin production, with the first peak at 4-6 and the second at 10-20 days after plating. A 2- to 3-fold increase in the second peak was observed when albumin production by SV40-infected cultures was compared with that by uninfected cultures. No increase in cell number in SV40-infected cultures was observed during this 20-day period. By 25-35 days, albumin production by uninfected cultures ceased but was detected in 50-60% of SV40-infected cultures. SV40-induced stimulation and persistence occurred regardless of the attachment surface and did not require collagen. Transformation occurred regardless of whether stimulation or persistence of albumin production was seen; however, stimulation and persistence were necessary to yield transformed cultures that produced albumin.     

The many faces of Notch signaling in skin‐derived cells

Since the cloning of the Drosophila gene in the 1980s, decades of research have sought to dissect the intricacies of the mammalian Notch signaling cascade. The intrigue of this pathway undoubtedly lies in its ability to influence diverse cellular processes, including differentiation, cell fate, homeostasis, survival, proliferation and angiogenesis. Based on its evolutionary conservation and its fundamental role in development, it is not surprising that deregulation of the Notch signaling pathway can result in neoplastic growth. While originally of particular interest to immunologists based on its chief role in influencing T‐cell fate decisions and tumor oncogenesis in T‐cell acute lymphoblastic leukemia, pigment cell biologists have recently taken notice of the Notch cascade based on studies suggesting the importance of this pathway in regulating melanocyte stem cell survival and melanoma progression. We will review the Notch signaling literature as it relates to skin homeostasis, melanocytic stem cells and melanoma tumorigenesis.     

Signatures of host–pathogen evolutionary conflict reveal MISTR—A conserved MItochondrial STress Response network

Host–pathogen conflicts leave genetic signatures in genes that are critical for host defense functions. Using these “molecular scars” as a guide to discover gene functions, we discovered a vertebrate-specific MItochondrial STress Response (MISTR) circuit. MISTR proteins are associated with electron transport chain (ETC) factors and activated by stress signals such as interferon gamma (IFNγ) and hypoxia. Upon stress, ultraconserved microRNAs (miRNAs) down-regulate MISTR1(NDUFA4) followed by replacement with paralogs MItochondrial STress Response AntiViral (MISTRAV) and/or MItochondrial STress Response Hypoxia (MISTRH). While cells lacking MISTR1(NDUFA4) are more sensitive to chemical and viral apoptotic triggers, cells lacking MISTRAV or expressing the squirrelpox virus-encoded vMISTRAV exhibit resistance to the same insults. Rapid evolution signatures across primate genomes for MISTR1(NDUFA4) and MISTRAV indicate recent and ongoing conflicts with pathogens. MISTR homologs are also found in plants, yeasts, a fish virus, and an algal virus indicating ancient origins and suggesting diverse means of altering mitochondrial function under stress. The discovery of MISTR circuitry highlights the use of evolution-guided studies to reveal fundamental biological processes.

Host-pathogen conflicts leave genetic signatures in genes that are critical for host defense functions. This study uses these “molecular scars” as a guide to identify a vertebrate-specific mitochondrial stress response circuit that interacts with the electron transport chain and is activated by stress signals such as interferon-gamma and hypoxia.     

6-MBOA affects testis size, but not delayed-type hypersensitivity, in white-footed mice (Peromyscus leucopus).

Many rodents use day length to time reproduction to occur when resources are abundant, but some species also use supplementary environmental cues. One supplementary cue is the plant-derived compound, 6-methoxy-2-benzoxazolinone (6-MBOA). Most rodents grow their gonads in response to 6-MBOA in their diets, but it is presently unknown whether they also use 6-MBOA to adjust other aspects of physiology, specifically their immune systems. 6-MBOA is structurally similar to melatonin, and seasonal changes in rodent immune activities are often mediated by melatonin. We therefore predicted that white-footed mice (Peromyscus leucopus), which breed seasonally and are reproductively sensitive to melatonin, would adjust their immune systems when fed 6-MBOA. 6-MBOA treated mice in long day lengths regressed their testes to a greater extent than mice fed a standard diet, or mice kept in short day lengths and fed 6-MBOA or a standard diet. One type of immune activity (delayed-type hypersensitivity) was not affected by 6-MBOA, however, although responses were greater in short versus long day mice. In sum, P. leucopus responded reproductively to 6-MBOA, although differently than other species; immune activity was unaffected. Other aspects of the immune system, especially in herbivorous rodents, may be affected by 6-MBOA and thus warrant further study.     

Extraction,Recovery, and Biostability of EDTA for Remediation of Heavy Metal-Contaminated Soil

Chelation removal of heavy metals from contaminated soil is seen as a viable remediation technique. A useful chelating agent should be strong, reusable, and biostable during metal extraction and recovery operations. This work tested the extraction, recovery, and biostability of EDTA as a potential remediating agent. Parameters, including EDTA concentration, soil type, soil content, washing cycle, precipitant concentration and type, and pH, were varied and tested during metal extraction and recovery operations. Factors, including EDTA concentration, aqueous and 5% soil slurry, presence of Pb, acclimated and unacclimated activated sludges, along with abiotic control, were varied and studied in the biodegradation of EDTA. The results showed that EDTA was able to extract lead completely from the tested soils, amenable to recovery by addition of cationic and anionic precipitants in the alkaline pH range, relatively biostable even under conditions very favorable toward biodegradation. Thus, EDTA is a strong, recoverable, and relatively biostable chelating agent that has potential for soil remediation application.     

Activation of Protein Kinase C by Trimethyltin: Relevance to Neurotoxicity

Abstract: The differentiated PC12 cell neuronal model was used to determine the effect of trimethyltin (TMT) on protein kinase C (PKC). Cells treated with 5–20 µ M TMT showed a partial and sustained PKC translocation within 30 min and persisted over a 24-h period. TMT treatment was accompanied by a low level of PKC down-regulation over 24 h, which was small compared with that produced by phorbol esters. Confocal imaging of differentiated PC12 cells showed that PKC translocates to the plasma membrane and the translocation is blocked by the PKC inhibitor chelerythrine (1 µ M ). Phorbol myristate-induced PKC down-regulation or inhibition with chelerythrine provided protection against TMT-induced cytotoxicity. It was concluded that TMT-induced PKC translocation and activation contribute to the cytotoxicity of TMT in differentiated PC12 cells.     

Fluid‐preserved fishes are one solution for assessing historical change in fish trophic level

1. There are few resources available for assessing historical change in fish trophic dynamics, but specimens held in natural history collections could serve as this resource. In contemporary trophic ecology studies, trophic and source information can be obtained from compound‐specific stable isotope analysis of amino acids of nitrogen (CSIA‐AA‐N).
2. We subjected whole Sebastes ruberrimus and Clupea pallasii to formalin fixation and 70% ethanol preservation. We extracted tissue samples from each fish pre‐fixation, after each chemical change, and then in doubling time for 32–64 days once placed in the final preservative. All samples were subjected to CSIA‐AA‐N, and their glutamic acid and phenylalanine profiles and associated trophic position were examined for differences over time by species.
3. Glutamic acid and phenylalanine values were inconsistent in direction and magnitude, particularly during formalin fixation, but stabilized similarly (in 70% ethanol) among conspecifics. In some cases, the amino acid values of our final samples were significantly different than our initial pre‐preservation samples. Nonetheless, significant differences in glutamic acid, phenylalanine, and estimated trophic position were not detected among samples that were in 70% ethanol for >24 hr.
4. Our results suggest that the relative trophic position of fluid‐preserved specimens can be estimated using CSIA‐AA‐N, and CSIA‐AA‐N estimates for fluid‐preserved specimens should only be reported as relative differences. Timelines of trophic position change can be developed by comparing specimens collected at different points in time, revealing trophic information of the past and cryptic ecosystem responses.

     

Mitochondrial metabolism is a key regulator of the fibro-inflammatory and adipogenic stromal subpopulations in white adipose tissue

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