Abstract: 7589 Background: There has been some question regarding the predictive value of 111 In scans in FL. We report imaging results with fusion PET-CT scans and 111 In scans in a single-institution, non-randomized, phase II trial in patients with FL treated with CHOP-R followed by 90 Y ibritumomab tiuxetan (Zevalin (Z)) and R. Methods: Eligible patients have CD20 positive FL, Grade 1–3 or transformed, Stage II-IV, no prior treatment with monoclonal antibody or chemotherapy, and symptomatic disease (if grade 1–2). CHOP-R is given every 21 days for 3 cycles. Four weeks after the last dose of CHOP-R, patients receive the Zevalin regimen, which includes 111 In imaging and 90 Y therapy. One week after Z, patients receive R 375 mg/m 2 IV weekly for 4 doses. Bone marrow examination and fusion PET-CT scans are performed at baseline, after CHOP-R, and 12 weeks after Z. The primary endpoint is CR, and responses are reported using the International Working Group (IWG) criteria with the additional requirement of a negative PET scan for CR/CRu. Results: Thirty-six FL patients have been accrued, and 16 patients have completed therapy and follow-up studies. One patient did not have a positive PET scan at baseline. Following therapy, the proportion with a negative PET scan improved from 8 of 15 (53.3%) after CHOP-R to 15 of 15 (100%) after Z. Using IWG criteria in combination with PET scan results, the CR rate increased from 4 of 15 (26.7%) after CHOP-R to 12 of 15 (80%) after Z. Five of 6 patients (83%) with tumor uptake by 111 In scan and 7 of 9 (78%) with a 111 In scan negative for tumor achieved a CR. Conclusions: There was no significant difference in CR between those patients with 111 In tumor uptake versus patients with a negative 111 In scan. Functional imaging with PET-CT may be a more sensitive method than CT alone in determining residual disease in FL. This trial continues to accrue patients, and more time is needed to determine the duration of response and time to next therapy. No significant financial relationships to disclose.

Abstract: 8005 Background: Therapy with CHOP-R and radioimmunotherapy (RIT) is a promising treatment for untreated FL. Press reports complete responses (CR) of 69% in FL patients (pts.) with 6 cycles of CHOP followed by I-131 tositumomab. We report efficacy and safety using 3 cycles of CHOP-R followed by IT and extended R. Methods: Eligibility criteria include symptomatic or grade 3 untreated FL. 60 pts. have been accrued and 47 evaluated. The treatment consists of two phases: CHOP-R for 3 cycles followed by IT. One week after IT, pts receive R weekly × 4. Bone marrow (BM) biopsies and fusion PET-CT scans are obtained at baseline, after CHOP-R, and 12 weeks post RIT. The primary endpoint is CR rate. CR requires a neg. PET scan and conventional Working Group criteria. Results: Toxicity data are available for 47 pts of median age 56 (range, 39–78), 44 of whom completed both phases of therapy and are evaluated for response. Characteristics and CR rates after IT are shown: 3 pts. did not receive RIT (1 second malignancy, 1 non-compliance, 1 septic death). Of the 44, CR after CHOP-R is 41%. After IT, CR improved to 89%. Of the 5 pts who did not achieve CR, 3 had neg. PET scans (2 with PR, 1 with SD by CT), and 2 had residual disease by PET with PR by CT. At a mean follow-up of 16 months (range, 6–33 months), there are 4 relapses: 3 who achieved CR by PET-CT, 1 with PR by PET-CT. Toxicity was predominantly myelosuppression. There was 1 episode of febrile neutropenia after RIT. Conclusions: 3 cycles of CHOP-R followed by IT and R achieve a high CR in previously-untreated pts. with FL. Addition of RIT increased CR from 41% to 89%. Data will be presented on the affect of bulky disease, positive BM, grade 2 or 3 histology, and high FLIPI score on CR. Further follow-up is necessary to evaluate response duration and determine whether there is a correlation with early or late CR. [Table: see text] [Table: see text]

Abstract: The pathogenicity of a Streptococcus ictaluri isolate in channel catfish Ictalurus punctatus at the fry (0.5 g), fingerling (15 g), and juvenile (55 g) stages was determined by experimental bath immersion and injection experiments. Channel catfish were exposed in 1‐L immersion baths containing 10 8 , 10 9 , 10 10 , 10 11 , or 10 12 colony‐forming units (cfu) of S. ictaluri . Fish were also injected intraperitoneally with 0.1 mL of bacterial solution for final doses of 10 4 , 10 5 , 10 6 , 10 7 , or 10 8 cfu of S. ictaluri per fish. Streptococcus ictaluri caused mortality in fry, fingerling, and juvenile channel catfish within 21 d postinfection. When mortalities were calculated based on size and challenge route, the cumulative percent mortalities were 11% for fry and 0% for fingerlings by the bath immersion route and 14% for fingerlings and 6% for juveniles by the injection route. Isolation of S. ictaluri from moribund and dead catfish was confirmed by the newly established BIOLOG profile (MicroLog3 system). The results indicate that channel catfish were only susceptible to high concentrations of S. ictaluri and that juvenile channel catfish were less susceptible, possibly explaining why little mortality has been attributed to S. ictaluri infection in catfish aquaculture.

Abstract: A series of experiments were conducted to determine the toxicity, behavior, blood glucose stress response, and disease susceptibility in Nile tilapia Oreochromis niloticus following un‐ionized ammonia (UIA) exposure. The acute toxicity of un‐ionized ammonia to Nile tilapia was measured in a 96‐h static test. The median lethal concentration (LC50) was 1.46 mg/L UIA at 24 and 48 h postexposure, 1.33 mg/L at 72 h postexposure, and 0.98 mg/L at 96 h postexposure. No mortalities were noted in unexposed (0 mg/L) control fish or fish exposed to 0.5 mg/L UIA. However, 93–100% mortalities were observed within 24 h among fish exposed to 2.0, 3.0, or 4.0 mg/L UIA. In additional UIA exposure experiments, Nile tilapia were exposed to sublethal concentrations (0.32–0.37 mg/L UIA) for 24 h and then administered an intraperitoneal injection with 750 colony‐forming units (CFU) of Streptococcus agalactiae per fish. Mortalities of UIA‐exposed and control fish were not significantly different 21 d postchallenge. Blood glucose levels were not significantly different between exposed and control fish 24 h after the beginning of UIA exposure or between preexposure fish and 24‐h postexposure fish. Glucose levels in both groups increased significantly after UIA exposure and subsequent bacterial challenge, suggesting that Nile tilapia experienced handling or infection stress and not necessarily UIA exposure stress alone. During a time course study with 24‐h UIA exposure, sequential blood glucose samples indicated acute stress responses 1–4 h postexposure that decreased by 24 h postexposure. The results of this study indicate that exposure to increased UIA concentrations alone had acute, transient effects on stress responses in Nile tilapia and that 24‐h exposure to sublethal UIA concentrations up to 0.37 mg/L did not increase susceptibility to S. agalactiae .

Abstract: Cholesterol, fatty acids, fat-soluble vitamins, and other lipids present in our diets are not only nutritionally important but serve as precursors for ligands that bind to receptors in the nucleus. To become biologically active, these lipids must first be absorbed by the intestine and transformed by metabolic enzymes before they are delivered to their sites of action in the body. Ultimately, the lipids must be eliminated to maintain a normal physiological state. The need to coordinate this entire lipid-based metabolic signaling cascade raises important questions regarding the mechanisms that govern these pathways. Specifically, what is the nature of communication between these bioactive lipids and their receptors, binding proteins, transporters, and metabolizing enzymes that links them physiologically and speaks to a higher level of metabolic control? Some general principles that govern the actions of this class of bioactive lipids and their nuclear receptors are considered here, and the scheme that emerges reveals a complex molecular script at work. Nuclear receptors function as ligand-activated transcription factors that regulate the expression of target genes to affect processes as diverse as reproduction, development, and general metabolism. These proteins were first recognized as the mediators of steroid hormone signaling and provided an important link between transcriptional regulation and physiology. In the mid-1980s, the steroid receptors were cloned and found to exhibit extensive sequence similarity. The subsequent cloning of other receptor genes led to the unexpected discovery that there were many more nuclear receptor–like genes than previously suspected. Today, the human genome is reported to contain 48 members of this transcription factor family (1). This superfamily includes not only the classic endocrine receptors that mediate the actions of steroid hormones, thyroid hormones, and the fat-soluble vitamins A and D (2), but a large number of so-called orphan nuclear receptors, whose ligands, target genes, and physiological functions were initially unknown (3). Exciting progress has been made over the last several years to elucidate the role of these orphan receptors in animal biology. Here we review recent discoveries that suggest that unlike the classic endocrine nuclear hormone receptors, many of the orphan receptors function as lipid sensors that respond to cellular lipid levels and elicit gene expression changes to ultimately protect cells from lipid overload. The structural organization of nuclear receptors is similar despite wide variation in ligand sensitivity ( Fig. 1 ). With few exceptions, these proteins contain an NH 2 -terminal region that harbors a ligand-independent transcriptional activation function (AF-1); a core DNA-binding domain, containing two highly conserved zinc finger motifs that target the receptor to specific DNA sequences known as hormone response elements; a hinge region that permits protein flexibility to allow for simultaneous receptor dimerization and DNA binding; and a large COOH-terminal region that encompasses the ligand-binding domain, dimerization interface, and a ligand-dependent activation function (AF-2). Upon ligand binding, nuclear receptors undergo a conformational change that coordinately dissociates corepressors and facilitates recruitment of coactivator proteins to enable transcriptional activation (4). The importance of nuclear receptors in maintaining the normal physiological state is illustrated by the enormous pharmacopoeia that has been developed to combat disorders that have inappropriate nuclear receptor signaling as a key pathological determinant. These disorders affect every field of medicine, including reproductive biology, inflammation, cancer, diabetes, cardiovascular disease, and obesity. Therefore, to maintain a normal physiological state, the spatial and temporal activity of nuclear receptors must be tightly controlled by tissue-specific expression of the receptors, as well as ligand availability. Interestingly, an evaluation of the pathways involved in ligand availability reveals the existence of two distinctly different nuclear receptor paradigms. The first paradigm is represented by the classic nuclear steroid hormone receptors ( Fig. 1 ). Members of this group include the glucocorticoid (GR), mineralocorticoid (MR), estrogen (ER), androgen (AR), and progesterone (PR) receptors. Steroid receptors bind to DNA as homodimers, and their ligands are synthesized exclusively from endogenous endocrine sources that are regulated by negative-feedback control of the hypothalamic-pituitary axis (5). After synthesis, steroid hormones are circulated in the body to their target tissues where they bind to their receptors with high affinity (dissociation constant K d = 0.01 to 10 nM). In vertebrates, the steroid receptor system evolved to regulate a variety of crucial metabolic and developmental events, including sexual differentiation, reproduction, carbohydrate metabolism, and electrolyte balance. The endocrine steroid receptors, their ligands, and the pathways they regulate have been the subject of decades of research, and their mechanism of action is well documented (5). The second nuclear receptor paradigm is represented by the adopted orphan nuclear receptors that function as heterodimers with the retinoid X receptor (RXR) ( Fig. 1 ). Orphan receptors become adopted when they are shown to bind a physiological ligand. In contrast to the endocrine steroid receptors, the adopted orphan receptors respond to dietary lipids and, therefore, their concentrations cannot be limited by simple negative-feedback control ( Fig. 2 ). Members of this group include receptors for fatty acids (PPARs), oxysterols (LXRs), bile acids (FXR), and xenobiotics [steroid xenobiotic receptor/pregnane X receptor (SXR/PXR) and constitutive androstane receptor (CAR)]. Furthermore, the receptors in this group bind their lipid ligands with lower affinities comparable to physiological concentrations that can be affected by dietary intake ( 〉 1 to 10 μM). An emerging theme regarding these receptors is that they function as lipid sensors. In keeping with this notion, ligand binding to each of these receptors activates a feedforward, metabolic cascade that maintains nutrient lipid homeostasis by governing the transcription of a common family of genes involved in lipid metabolism, storage, transport, and elimination. In addition to the adopted orphan receptors, there are four other RXR heterodimer receptors that do not fit precisely into either the feedforward or feedback paradigms mentioned. These include the thyroid hormone (TR), retinoic acid (RAR), vitamin D (VDR), and ecdysone (EcR) receptors (6–9). The ligands for these four receptors and the pathways they regulate employ elements of both the endocrine and lipid-sensing receptor pathways. For example, like other RXR heterodimer ligands, both retinoic acid and ecdysone are derived from essential dietary lipids (vitamin A and cholesterol, respectively), yet they are not calorigenic and the transcriptional pathways that these ligands regulate (i.e., morphogenesis and development) more closely resemble those of the endocrine receptors. Likewise, vitamin D and thyroid hormone require exogenous elements for their synthesis (sunshine for vitamin D, iodine for thyroid hormone), yet the ultimate synthesis of these hormones and the pathways they regulate are under strict endocrine control. Thus, it is possible that these four receptors provide an evolutionary segue, spanning the gap between the endocrine receptors and the adopted orphan receptors that have recently been shown to be lipid sensors.