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The molecular mechanisms underlying SARS-CoV-2 host cell invasion and life cycle have been studied extensively in recent years, with a primary focus on viral entry and internalization with the aim of identifying antiviral therapies. By contrast, our understanding of the molecular mechanisms involved in the later steps of the coronavirus life cycle is relatively limited. In this review, we describe what is known about the host factors and viral proteins involved in the replication, assembly, and egress phases of SARS-CoV-2, which induce significant host membrane rearrangements. We also discuss the limits of the current approaches and the knowledge gaps still to be addressed., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The skeletal dysplasia spondyloepiphyseal dysplasia tarda (SEDT) is caused by mutations in the TRAPPC2 gene, which encodes Sedlin, a component of the trafficking protein particle (TRAPP) complex that we have shown previously to be required for the export of type II collagen (Col2) from the endoplasmic reticulum. No vertebrate model for SEDT has been generated thus far. To address this gap, we generated a Sedlin knockout animal by mutating the orthologous TRAPPC2 gene (olSedl) of Oryzias latipes (medaka) fish. OlSedl deficiency leads to embryonic defects, short size, diminished skeletal ossification and altered Col2 production and secretion, resembling human defects observed in SEDT patients. Moreover, SEDT knock-out animals display photoreceptor degeneration and gut morphogenesis defects, suggesting a key role for Sedlin in the development of these organs. Thus, by studying Sedlin function in vivo, we provide evidence for a mechanistic link between TRAPPC2-mediated membrane trafficking, Col2 export, and developmental disorders., (© 2023 The Authors. Traffic published by John Wiley & Sons Ltd.)

SARS-CoV-2, like other coronaviruses, builds a membrane-bound replication organelle to enable RNA replication 1 . The SARS-CoV-2 replication organelle is composed of double-membrane vesicles (DMVs) that are tethered to the endoplasmic reticulum (ER) by thin membrane connectors 2 , but the viral proteins and the host factors involved remain unknown. Here we identify the viral non-structural proteins (NSPs) that generate the SARS-CoV-2 replication organelle. NSP3 and NSP4 generate the DMVs, whereas NSP6, through oligomerization and an amphipathic helix, zippers ER membranes and establishes the connectors. The NSP6(ΔSGF) mutant, which arose independently in the Alpha, Beta, Gamma, Eta, Iota and Lambda variants of SARS-CoV-2, behaves as a gain-of-function mutant with a higher ER-zippering activity. We identified three main roles for NSP6: first, to act as a filter in communication between the replication organelle and the ER, by allowing lipid flow but restricting the access of ER luminal proteins to the DMVs; second, to position and organize DMV clusters; and third, to mediate contact with lipid droplets (LDs) through the LD-tethering complex DFCP1-RAB18. NSP6 thus acts as an organizer of DMV clusters and can provide a selective means of refurbishing them with LD-derived lipids. Notably, both properly formed NSP6 connectors and LDs are required for the replication of SARS-CoV-2. Our findings provide insight into the biological activity of NSP6 of SARS-CoV-2 and of other coronaviruses, and have the potential to fuel the search for broad antiviral agents., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Endogenous reactive oxygen species (ROS) are by-products of the aerobic metabolism of cells and have an important signalling role as secondary messengers in various physiological processes, including cell growth and development. However, the excessive production of ROS, as well as the exposure to exogenous ROS, can cause protein oxidation, lipid peroxidation and DNA damages leading to cell injuries. ROS accumulation has been associated to the development of health disorders such as neurodegenerative and cardiovascular diseases, inflammatory bowel disease and cancer. We report that spores of strain SF185, a human isolate of Bacillus megaterium, have antioxidant activity on Caco-2 cells exposed to hydrogen peroxide and on a murine model of dextran sodium sulfate-induced oxidative stress. In both model systems spores exert a protective state due to their scavenging action: on cells, spores reduce the amount of intracellular ROS, while in vivo the pre-treatment with spores protects mice from the chemically-induced damages. Overall, our results suggest that treatment with SF185 spores prevents or reduces the damages caused by oxidative stress. The human origin of SF185, its strong antioxidant activity, and its protective effects led to propose the spore of this strain as a new probiotic for gut health.

Background: Alveolar clefts are traditionally treated with secondary bone grafting, but this is associated with morbidity and graft resorption. Although recombinant human bone morphogenetic protein-2 (rhBMP-2) is under investigation for alveolar cleft repair, safety concerns remain. Dipyridamole is an adenosine receptor indirect agonist with known osteogenic potential. This study compared dipyridamole to rhBMP-2 at alveolar cleft defects delivered using bioceramic scaffolds., Methods: Skeletally immature New Zealand White rabbits underwent unilateral, 3.5 × 3.5-mm alveolar resection adjacent to the growing suture. Five served as negative controls. The remaining defects were reconstructed with three-dimensionally printed bioceramic scaffolds coated with 1000 μm of dipyridamole (n = 6), 10,000 μm of dipyridamole (n = 7), or 0.2 mg/ml of rhBMP-2 (n = 5). At 8 weeks, new bone was quantified. Nondecalcified histologic evaluation was performed, and new bone was evaluated mechanically. Statistical analysis was performed using a generalized linear mixed model and the Wilcoxon rank sum test., Results: Negative controls did not heal, whereas new bone formation bridged all three-dimensionally printed bioceramic treatment groups. The 1000-μm dipyridamole scaffolds regenerated 28.03 ± 7.38 percent, 10,000-μm dipyridamole scaffolds regenerated 36.18 ± 6.83 percent (1000 μm versus 10,000 μm dipyridamole; p = 0.104), and rhBMP-2-coated scaffolds regenerated 37.17 ± 16.69 percent bone (p = 0.124 versus 1000 μm dipyridamole, and p = 0.938 versus 10,000 μm dipyridamole). On histology/electron microscopy, no changes in suture biology were evident for dipyridamole, whereas rhBMP-2 demonstrated early signs of suture fusion. Healing was highly cellular and vascularized across all groups. No statistical differences in mechanical properties were observed between either dipyridamole or rhBMP-2 compared with native bone., Conclusion: Dipyridamole generates new bone without osteolysis and early suture fusion associated with rhBMP-2 in skeletally immature bone defects.

The survival of cells exposed to adverse environmental conditions entails various alterations in cellular function including major changes in the transcriptome as well as a radical reprogramming of protein translation. While in mammals this process has been extensively studied, stress responses in non-mammalian vertebrates remain poorly understood. One of the key cellular responses to many different types of stressors is the transient generation of structures called stress granules (SGs). These represent cytoplasmic foci where untranslated mRNAs are sorted or processed for re-initiation, degradation, or packaging into mRNPs. Here, using the evolutionarily conserved Y-box binding protein 1 (YB-1) and G3BP1 as markers, we have studied the formation of stress granules in zebrafish (D. rerio) in response to different environmental stressors. We show that following heat shock, zebrafish cells, like mammalian cells, form stress granules which contain both YB-1 and G3BP1 proteins. Moreover, zfYB-1 knockdown compromises cell viability, as well as recruitment of G3BP1 into SGs, under heat shock conditions highlighting the essential role played by YB-1 in SG assembly and cell survival. However, zebrafish PAC2 cells do not assemble YB-1-positive stress granules upon oxidative stress induced by arsenite, copper or hydrogen peroxide treatment. This contrasts with the situation in human cells where SG formation is robustly induced by exposure to oxidative stressors. Thus, our findings point to fundamental differences in the mechanisms whereby mammalian and zebrafish cells respond to oxidative stress.

Up until the first half of the 20th century, silver found significant employment in medical applications, particularly in the healing of open wounds, thanks to its antibacterial and antifungal properties. Wound repair is a complex and dynamic biological process regulated by several pathways that cooperate to restore tissue integrity and homeostasis. To facilitate healing, injuries need to be promptly treated. Recently, the interest in alternatives to antibiotics has been raised given the widespread phenomenon of antibiotic resistance. Among these alternatives, the use of silver appears to be a valid option, so a resurgence in its use has been recently observed. In particular, in contrast to ionic silver, colloidal silver, a suspension of metallic silver particles, shows antibacterial activity displaying less or no toxicity. However, the human health risks associated with exposure to silver nanoparticles (NP) appear to be conflicted, and some studies have suggested that it could be toxic in different cellular contexts. These potentially harmful effects of silver NP depend on various parameters including NP size, which commonly range from 1 to 100 nm. In this study, we analyzed the effect of a colloidal silver preparation composed of very small and homogeneous nanoparticles of 0.62 nm size, smaller than those previously tested. We found no adverse effect on the cell proliferation of HaCaT cells, even at high NP concentration. Time-lapse microscopy and indirect immunofluorescence experiments demonstrated that this preparation of colloidal silver strongly increased cell migration, re-modeled the cytoskeleton, and caused recruitment of E-cadherin at cell-cell junctions of human cultured keratinocytes.

How the environment shapes the function and evolution of DNA repair systems is poorly understood. In a comparative study using zebrafish and the Somalian blind cavefish, Phreatichthys andruzzii, we reveal that during evolution for millions of years in continuous darkness, photoreactivation DNA repair function has been lost in P. andruzzii. We demonstrate that this loss results in part from loss-of-function mutations in pivotal DNA-repair genes. Specifically, C-terminal truncations in P. andruzzii DASH and 6-4 photolyase render these proteins predominantly cytoplasmic, with consequent loss in their functionality. In addition, we reveal a general absence of light-, UV-, and ROS-induced expression of P. andruzzii DNA-repair genes. This results from a loss of function of the D-box enhancer element, which coordinates and enhances DNA repair in response to sunlight. Our results point to P. andruzzii being the only species described, apart from placental mammals, that lacks the highly evolutionary conserved photoreactivation function. We predict that in the DNA repair systems of P. andruzzii, we may be witnessing the first stages in a process that previously occurred in the ancestors of placental mammals during the Mesozoic era., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The prototype cold-shock Y-box binding protein 1 (YB-1) is a multifunctional protein that regulates a variety of fundamental biological processes including cell proliferation and migration, DNA damage, matrix protein synthesis and chemotaxis. The plethora of functions assigned to YB-1 is strictly dependent on its subcellular localization. In resting cells, YB-1 localizes to cytoplasm where it is a component of messenger ribonucleoprotein particles. Under stress conditions, YB-1 contributes to the formation of stress granules (SGs), cytoplasmic foci where untranslated messenger RNAs (mRNAs) are sorted or processed for reinitiation, degradation, or packaging into ribonucleoprotein particles (mRNPs). Following DNA damage, YB-1 translocates to the nucleus and participates in DNA repair thereby enhancing cell survival. Recent data show that YB-1 can also be secreted and YB-1-derived polypeptides are found in plasma of patients with sepsis and malignancies. Here we show that in response to oxidative insults, YB-1 assembly in SGs is associated with an enhancement of YB-1 protein secretion. An enriched fraction of extracellular YB-1 (exYB-1) significantly inhibited proliferation of receiving cells and such inhibition was associated to a G2/M cell cycle arrest, induction of p21WAF and reduction of Np63 protein level. All together, these data show that acute oxidative stress causes sustained release of YB-1 as a paracrine/autocrine signal that stimulate cell cycle arrest., Competing Interests: The authors declare no conflicts of interest.

Uncaria tomentosa (Willd.) DC. (Rubiacee), also known as uña de gato, is a plant that grows wild in the upper Amazon region of Peru and has been widely used in folk medicine to treat several health conditions including cancer. We have produced an aqueous extract from Uncaria tomentosa (UT-ex) and analyzed its effects on squamous carcinoma cells and immortalized HaCaT keratinocytes. Squamous cell carcinoma (SCC) is an uncontrolled growth of abnormal cells arising in the skin's squamous layer of epidermis. When detected at an early stage, SCCs are almost curable, however, if left untreated, they can penetrate the underlying tissue and become disfiguring. We have evaluated cell proliferation, apoptosis and the level of reactive oxygen species following UT-ex treatment. UT-ex affected cell cycle progression and reduced cell viability in a dose and time-dependent manner. From a mechanistic point of view, this delay in cell growth coincided with the increase of reactive oxygen species (ROS). Furthermore, PARP1 cleavage was associated to the reduction of Y-box binding protein 1 (YB-1) 36kDa, a nuclear prosurvival factor involved in DNA damage repair. These data indicate that UT-ex-induced cell death can be ascribed, at least in part, to its ability both to induce oxidative DNA damage and antagonize the mechanism of DNA repair relying upon YB-1 activity. They also show that non metastatic SCCs are more susceptible to UT-ex treatment than untransformed keratinocytes supporting the use of UT-ex for the treatment of precancerous and early forms of squamous cell carcinomas. Preliminary chemical investigation of UT-ex revealed the presence of hydrophilic low-medium molecular weight metabolites with anticancer potential towards squamous carcinoma cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The Wound Healing (WH) assay is widely used to investigate cell migration in vitro, in order to reach a better understanding of many physiological and pathological phenomena. Several experimental factors, such as uneven cell density among different samples, can affect the reproducibility and reliability of this assay, leading to a discrepancy in the wound closure kinetics among data sets corresponding to the same cell sample. We observed a linear relationship between the wound closure velocity and cell density, and suggested a novel methodological approach, based on transport phenomena concepts, to overcome this source of error on the analysis of the Wound Healing assay. In particular, we propose a simple scaling of the experimental data, based on the interpretation of the wound closure as a diffusion-reaction process. We applied our methodology to the MDA-MB-231 breast cancer cells, whose motility was perturbed by silencing or over-expressing genes involved in the control of cell migration. Our methodological approach leads to a significant improvement in the reproducibility and reliability in the in vitro WH assay., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Y-box binding protein 1 (YBX-1 or YB-1) is an oncoprotein that promotes replicative immortality, tumor cell invasion and metastasis. The increase in the abundance of YB-1 in the cell or YB-1 translocation from the cytoplasm to the nucleus is characteristic of malignant cell growth. We have previously reported that ΔNp63α, a transcription factor that is known to play a pivotal role in keratinocyte proliferation and differentiation, promotes YB-1 nuclear accumulation. Here, we show that YB-1 is highly expressed in proliferating keratinocytes and is down-regulated during keratinocyte differentiation. ΔNp63α reduces YB-1 protein turnover and leads to accumulation of ubiquitin-conjugated YB-1 into the nucleus. Reduction of YB-1 protein level, following treatment with a DNA-damaging agent, is inhibited by ΔNp63α suggesting that YB-1 and ΔNp63α interplay can support keratinocyte proliferation and protect cells from apoptosis under genotoxic stress., (© 2016 Molecular Biology Society of Japan and John Wiley & Sons Australia, Ltd.)

The advantage of focusing on biliary excretion of drugs and other xenobiotics is emphasized in this discussion of the regulatory and scientific roles for biodistribution studies in aquatic species. The role of the hepatobiliary system in the overall disposition of absorbed chemicals is briefly reviewed. The present survey includes 18 drugs, 6 petroleum hydrocarbons, and 16 different fish species. The fact that aquatic species concentrate most xenobiotics and their metabolites into bile to as much as several orders of magnitude underscores the advantage of using bile rather than tissue to determine whether aquatic species are being exposed to given chemicals. Until these advantages are recognized, analysis of edible muscle tissue remains the method of choice for assessment of human exposure to chemicals.

The absorption into the systemic circulation of compounds administered intraperitoneally in large volumes was investigated in the rat. The influence on absorption of molecular weight, lipid-water partition coefficient (K), and dissociation constant (pKa) was studied. Nine neutral compounds ranging in molecular weight from 18 to 2 million demonstrated absorptions that decreased with increasing molecular weight. Five compounds were tested with variable lipid partition (K) values (0.001--3.3) and the absorptions increased from 57 to 96% as the K values increased. A series of nine acids and bases covering a wide range of pKa values )0.9--9.9) were investigated. For the acids, absorption increased with increasing pKa value, while for the bases absorption decreased with increasing pKa. For both groups of compounds absorption was directly related to the extent of ionization at physiologic pH. As has been documented for other biological membranes, the peritoneal membrane in the rat was found to behave in a lipoid manner. Unionized or lipid-soluble compounds are absorbed to a greater extent than ionized or lipid-insoluble compounds, and neutral compounds are absorbed in relation to their molecular weights.

The toxicity, absorption, distribution, metabolism, and effects on reproduction of DDT was studied using the killifish (Fundulus heteroclitus), a species of economic importance because of its widespread abundance and its presence toward the lower end of the food chain. 14C-DDT was administered by exposure from the ambient water. There was a rapid removal of the radioactive pesticide from the water accompanied by uptake of radioactivity primarily by carcass (primarily muscle tissue) and eggs of the fish. Most (greater than 92%) of the radioactivity in the carcass was shown by TLC methods to be the parent pesticide. One day after a single 24-hr exposure to 14C-DDT, approximately 70% of the administered radioactivity was found in the carcass and the levels of the tissue decayed with a t 1/2 of three days. One day after a single 24-hr exposure to 0.1 ppm of 14C-DDT, the organs that contained the highest concentration of the pesticide (ca. 5 ppm) were intestine and liver. When the pesticide was administered by two 24-hr exposures from water, the intestine, liver and ovaries contained the major concentration of radioactivity (7 to 14 ppm). Untreated Fundulus contained less than 0.2 ppm of total DDT-like compounds. A variety of doses and schedules were tested in an effort to maximize the absorption of DDT, while minimizing the mortality to the fish. An intermittent schedule of 24 hr in 0.1 ppm DDT followed by 24 hr in DDT-free sea water, repeated two times, was found to be optimal. At the levels examined, DDT delayed the rate of normal development of fertilized eggs from Fundulus, but did not appear to cause any observable alterations in the hatched fry. Fertilization of Fundulus eggs was significantly diminished when insemination was carried out in DDT-containing sea water.

The currently accepted therapies for ovarian cancer have produced only limited numbers of extended complete remissions in advanced-stage disease. Studies of high-volume intraperitoneal chemotherapy have been initiated to define the toxicology, pharmacokinetics, and the therapeutic effectiveness of this treatment modality. This technique has been virtually ignored until recently, because little success has been achieved with it except in one study (Rutledge, 1966), in which large intraperitoneal fluid volumes were used. The general lack of success probably reflects inadequate attention to physiologic and pharmacologic principles of drug distribution and absorption in a space as large as the peritoneal cavity. Biomedical engineers, pharmacologists, and clinicians at the NCI have cooperated in the development of a rational chemotherapy for ovarian cancer. Following mathematical pharmacokinetic modeling and toxicologic studies in rat, a Phase I clinical trial of intraperitoneal methotrexate administered in large volumes of dialysis fluid was initiated. Results in three patients confirm the practicality of this approach, and further investigation is warranted.

Previous retrospective analyses have suggested a very positive correlation in toxic doses of antineoplastic agents between mice and humans. Additional toxicological information has now been accumulated and reveals a noticeable variability in the existing data base. Nevertheless, it is likely that mouse toxicological studies will become a principal determinant for estimating initial doses to be used in humans. Recognition of the factors responsible for differences in determinations of toxic dose levels in mice will enhance the proper utilization of this approach.

1. The biliary and urinary excretion of phenol red and its glucuronide was measured in dogfish sharks, Squalus acanthias, in both intact animals and animals with biliary fistula. 2. Phenol red is extensively metabolized to its glucuronide by the dogfish shark and both forms of the compound are actively transported into bile and urine. 3. Both compounds are transferred from plasma to urine and bile against a large concentration gradient; the transfer process is saturable most easily in the renal compartment but also in the hepatic compartment; and both excretion routes for the free drug and the glucuronide are inhibited by probenecid. 4. There were no significant differences in the 48 h biliary excretion of total (free + glucuronide) phenol red, but the urine or intact fish contained two-fold more total drug than did animals with fistulae.

The rate of disappearance of fluorouracil from peritoneal fluid has been experimentally measured and mathematically modeled. The experimental data were obtained following the instillation of 50 ml of dialysis fluid which contained an initial fluorouracil concentration ranging from 24 microM to 12 mM. The rate of disappearance was strongly dependent upon concentration. A distributed model has been formulated which incorporates concepts of diffusion with saturable metabolism and nonsaturable capillary uptake in the tissue surrounding the peritoneal fluid. This model successfully describes the experimental observations and also suggests that the effective penetration depth into tissue is highly dependent upon concentration.

A choroid papilloma in the choroid plexus of the ala of the fourth ventricle in a mature male elasmobranch, Squalus acanthias, was described. This is apparently the first report of a neoplasm of the central nervous system in a member of the class Chondrichthyes.

The large body of literature and techniques generated by mammalian toxicity studies provides a conceptual and technical framework within which the absorption, fate, and disposition of xenobiotics in aquatic organisms can be studied. This review emphasizes the similarities and differences between mammalian and aquatic systems, e.g., lung vs. gill as site of absorption and toxicity. These must be taken into consideration when designing aquatic toxicity studies. Studies of phenol red in dogfish shark as an example show physiologic-based pharmacokinetic modeling to be a useful tool for investigating and eventually predicting species differences in xenobiotic disposition and drug differences within the same species. This discussion demonstrates that both laboratory and modeling procedures are now available to carry out sophisticated studies of xenobiotic fate and disposition in fish. Such studies are needed to pinpoint sites and mechanisms of pollutant toxicity in aquatic organisms.

cis-Diamminedichloroplatinum(II) is an antineoplastic drug that is undergoing a renewed clinical interest as a drug for use in combination regimens. In order to increase the understanding of the pharmacokinetics of this drug, the plasma clearance and organ distribution of platinum were followed in female beagle dogs treated with a single i.v. dose of cis-diamminedichloroplatinum(II). Plasma levels of platinum were determined by flameless atomic absorption spectrometry and showed a distinctly biphasic clearance pattern with a rapid-phase half-time of considerably less than 1 hr and a slow-phase half-time of nearly 5 days. During the first 4 hr after treatment, plasma levels fell by 90% while 60 to 70% of the applied dose was recovered in the urine. Sixteen tissues plus plasma, bile, and urine were routinely analyzed for platinum content. An easily measurable plasma concentration of platinum was still detectable 12 days after treatment, with no significant change in plasma concentration between Days 4 and 12. Initial concentrations of platinum were highest in organs of excretion, gonads, spleen, and adrenals but remained significantly elevated only in kidney, liver, ovary, and uterus, where a tissue: plasma ratio of 3 to 4 was maintained for as long as 6 days posttreatment. The apparent in vitro binding of platinum to dog plasma and to bovine serum albumin was studied by ultrafiltration and increased progressively during 48 hr of incubation at 37 degrees.

The model system developed in the dogfish shark was reviewed to determine the kinds of studies that can be done on in vivo metabolism and disposition of drugs. Biliary and urinary sampling provided a compilation on the distribution and pharmacokinetics of 16 drugs and model compounds. The major transport and excretory and metabolic parameters in this fish were similar to those found in mammals. The use of such studies for scientific and regulatory purposes is considered.

After iv administration of cis-dichlorodiammineplatinum(II) (cis-platinum) to animals, plasma levels of platinum decline in a biphasic manner, with a distribution phase (alpha) half-life of minutes and an elimination phase (beta) half-life of days. Urinary excretion of platinum is extensive on the first day after drug administration with a final urinary recovery of 70%--90% of the administered dose. Platinum is initially distributed to nearly all tissues with the highest levels appearing in kidney, liver, ovary, uterus, skin, and bone. There is no preferential uptake of platinum into tumor, although the presence of a tumor may alter the rate of platinum excretion and the extent of whole-body retention. No effect is seen on hepatic microsomal drug metabolism after ip administration of cis-platinum to rats. Platinum is excreted more rapidly from hydrated animals than from controls although total urinary recovery of platinum is nearly equal in both groups. Most analogs of cis-platinum appear to follow the same elimination and distribution patterns as cis-platinum itself.

The renal handling of 2,2-bis(p-chlorophenyl) acetic acid (DDA) was examined in the isolated tubules of the winter flounder (Pseudopleuronectes americanus) in vitro in conjunction with clearance studies in the flounder and in the aglomerular goosefish (Lophius americanus). In vitro, both uptake studies and autoradiography showed extensive energy-dependent accumulation within the cytoplasm of tubular cells and the tubular lumen. The uptake was strongly inhibited by p-aminohippurate and chlorophenol red. A second component of uptake was insensitive to metabolic inhibitors or organic acids and represented tissue binding. In vivo, both species showed net secretion which was inhibited by probenecid. Comparison of DDT and DDA distribution and excretion emphasized the importance of the greater water solubility of DDA and of its secretory transport, since DDA was excreted at over 200 times the rate of DDT. Liver, kidney, and bile also showed elevated DDA tissue-to-plasma ratios. Thus, the organic acid system mediates the accumulation and excretion of DDA in these fish.

[14C] Methyl mercury was administered by three different routes: intravascular (iv) injection, ingestion, and absorption from the ambient water. After iv administration (0.1 mg/kg) [14C] methyl mercury was rapidly removed from the plasma, followed by slow loss from the hepatopancreas and a strikingly persistent increase in the amount of radioactivity in the tail muscle. Most (80-90%) of the radioactivity in the hepatopancreas was shown by TLC methods to be the parent compound, and approximately 10% of this persisted for 6 days after injection. The half-life in this organ was found to be 21 days. One month after iv treatment with methyl mercury, the only organs that contained more than 0.1 ppm of this xenobiotic were egg masses, male gonads, heart, brain, intestine, and tail muscle. The half-lives for disappearance from sexual organs were greater than 1 month. After ingestion of [14C] methyl mercury (0.1 mg/kg) in food the hepatopancreas contained most of the administered dose at 6 days (68%), while the stomach (10%), tail muscle (8%), and carcass (15%) contained less. A unique distribution pattern emerged 6 days after exposure to [14C] methyl mercury-containing ambient water (0.1 ppm). The tail muscle contained most (50%) of the absorbed dose, whereas the hepatopancreas and carcass contained only 23 and 10%, respectively. In view of the small molecular size and high lipid solubility of methyl mercury and the lipophilic properties of the chitin-protein exoskeleton of the lobster, it is likely that significant uptake directly from the water as well as storage of absorbed methyl mercury occurred in the tail region. Residue analysis on untreated lobsters indicated that the egg masses contained the largest amount of methyl mercury (0.1 ppm). The hepatopancreas and carcass (muscle) levels were less than 0.05 ppm.

Adriamycin (ADR) is rapidly cleared from plasma and enters tissues, while it is extensively eliminated in bile and moderately in urine following i.v. injection of 20 mg/kg to anesthetized rats. In bile duct- and bladder-cannulated rats with physiologic bile and urine production, 26.6% of the injected ADR is excreted in bile as total ADR equivalents during a 3 hr period and 4.4% in urine. When the elimination of the drug in urine is prevented by ligation of the kidneys, no significant differences are observed in the disposition of the total drug equivalents. Conversely, when bile flow is inhibited by the administration of sodium taurolithocholate, the biliary excretion of the total ADR equivalents declines significantly and in a fashion related to the degree of bile flow reduction. In parallel with the diminished biliary elimination, the urinary excretion increases significantly and is responsible for most of the drug eliminated when severe cholestasis is produced. However, despite the increased urinary excretion, the overall elimination of the total ADR equivalents in cholestatic rats is significantly reduced and both plasma and tissue levels of the total drug equivalents rise significantly and in a fashion closely related to the degree of the induced cholestasis.

1. The urinary and biliary excretion, tissue distribution and metabolism of 14C-labelled 2,4-dichloro- or 2,4,5-trichloro-phenoxyacetic acids (2,4-D or 2,4,5-T) were measured in dogfish sharks, Squalus acanthias. 2. Both herbicides are extensively metabolized (greater than 90%) to the corresponding taurine conjugates, and are excreted predominantly via the urine, where ca. 70% of the administered dose appears within 4-6 days after treatment. 3. The highest tissue levels of 2,4-D or 2,4,5-T were found in liver and kidney. Penetration of both herbicides into the CNS was restricted. 4. Plasma elimination was rapid and the 0.5 for either phenoxyacetic acid was less than 45 min. Similarly, rapid clearance as seen from renal tissue. Final t0.5 values for muscle were about 2-3 days while the major organ showing 2,4-D or 2,4,5-T retention was the liver, where t0.5 values were about 5 days for both the herbicides. 5. The overall pharmacokinetics in the dogfish shark for these herbicides resembled those seen in some mammals.