Assigning forensic body fluids to donors in mixed body fluids by targeted RNA/DNA deep sequencing of coding region SNPs.

Biological traces found at crime scenes are analysed not only to genetically identify the donor(s) but also to determine the composition of the stain. For some cases, it is essential to associate a body fluid with a donor. Especially in mixed body fluid stains, but also in body fluid stains that appear to be single-source, this may be of importance. Linking a DNA profile (sub-source level) with evidence from a presumptive test or mRNA analysis (source level) is not straightforward. Our results support that associating donors and body fluids by means of comparing mixture ratios in RNA and DNA is not recommended. We introduce a set of 35 coding region SNPs (cSNPs) in body fluid-specific mRNA transcripts that represent a direct link between the body fluids and their donors. The discrimination power of the cSNPs was estimated based on allele frequencies calculated from a population sample (n = 188), and we investigated the practical application of the cSNPs in different scenarios. The results demonstrate that more cSNPs are needed to improve the discrimination power. However, the findings are promising as we were able to associate donors with body fluids in mixtures of different body fluids as well as in stains where both donors have contributed the same body fluid, e.g. a blood-blood mixture. In addition, the cSNP assay can be used for body fluid identification. The results of this proof-of-concept study support the use of cSNPs to assign body fluids to the respective donors.

Lessons learned from a pilot randomized clinical trial of home-based exercise prescription before allogeneic hematopoietic cell transplantation.

Allogeneic hematopoietic cell transplantation (alloHCT) is a life-saving technology that can cure otherwise incurable diseases, but imposes significant physiologic stress upon recipients. This stress leads to short-term toxicity and mid- to long-term physical function impairment in some recipients. Exercise interventions have demonstrated preliminary efficacy in preserving physical function in HCT recipients, but the role of these interventions prior to HCT (prehabilitative) is less known. We tested a 5- to 12-week, prehabilitative higher intensity home-based aerobic exercise intervention in a randomized study of alloHCT candidates. Of 113 patients screened, 34 were randomized to control or intervention groups, 16 underwent pre- and post-intervention peak oxygen consumption (VO2peak) testing, and 12 underwent pre- and post-intervention 6-min walk distance (6MWD) testing. No significant differences in VO2peak or 6MWD were seen pre- to post-intervention between intervention and control groups, but final numbers of evaluable participants in each group were too small to draw inferences regarding the efficacy of the intervention. We conclude that the design of our prehabilitative intervention was not feasible in this pilot randomized study, and make recommendations regarding the design of future exercise intervention studies in alloHCT.

Altered stress hormone response following acute exercise during prostate cancer treatment.

Exercise training reduces the side effects of cancer treatments; however, the stress hormone response to acute exercise during prostate cancer (PCa) treatment is unclear. The study purpose was to examine the effects of acute exercise on circulating cortisol, epinephrine (Epi), and norepinephrine (NE) concentrations during PCa treatment with and without androgen deprivation therapy (ADT). Men with PCa (n = 11), with PCa on ADT (n = 11), and with non-cancer controls (n = 8) had blood samples for stress hormones collected before and immediately (0 hour), 2 hours, and 24 hours after 45 minutes of intermittent cycling at 60% of peak wattage. NE increased by 385% (P < .001) at 0 hour and remained elevated at 2 hours (P < .05) with no group differences. Overall, cortisol significantly increased at 0 hour (36%, P < .012) and then significantly decreased below baseline at 2 hours (-24%, P < .001) before returning to resting levels at 24 hours. Cortisol levels during ADT were 32% lower than PCa (P = .006) with no differences vs controls. Epi increased immediately after exercise more in controls (817%, P < .001) than with ADT (700%) and PCa (333%) patients, and both cancer groups' absolute levels were attenuated relative to controls (ADT: -54%, PCa: -52%, P = .004). Compared with age-matched controls, PCa and ADT patients exhibited similar stress hormone responses with acute exercise for NE and cortisol but an attenuated EPI response that suggests altered adrenal function. Future studies should examine the physical stress of multiple exercise bouts to verify these findings and to explore the functional hormonal effects, such as immune and metabolic responses, during cancer treatment.

Prospective first-trimester screening for trisomies by cell-free DNA testing of maternal blood in twin pregnancy.

OBJECTIVES: First, to examine in twin pregnancies the performance of first-trimester screening for fetal trisomies 21, 18 and 13 by cell-free (cf) DNA testing of maternal blood and, second, to compare twin and singleton pregnancies regarding the distribution of fetal fraction of cfDNA and rate of failure to obtain a result. METHODS: This was a prospective study in 438 twin and 10 698 singleton pregnancies undergoing screening for fetal trisomies by cfDNA testing at 10 + 0 to 13 + 6 weeks' gestation. Chromosome-selective sequencing of cfDNA was used and, in twin pregnancies, an algorithm was applied that relies on the lower fetal fraction contributed by the two fetuses. Multivariate regression analysis was used to determine significant predictors of fetal fraction and a failed result. RESULTS: In twin pregnancies, the median fetal fraction was lower (8.0% (interquartile range (IQR), 6.0-10.4%) vs 11.0% (IQR, 8.3-14.4%); P < 0.0001) and failure rate after first sampling was higher (9.4% vs 2.9%; P < 0.0001) compared to in singletons. Multivariate logistic regression analysis demonstrated that the risk of test failure increased with increasing maternal age and body mass index and decreased with fetal crown-rump length. The risk was increased in women of South Asian racial origin and in pregnancies conceived by in-vitro fertilization (IVF). The main contributor to the higher rate of failure in twins was conception by IVF which was observed in 9.5% of singletons and 56.2% of twins. In the 417 twin pregnancies with a cfDNA result after first or second sampling, the detection rate was 100% (8/8) for trisomy 21 and 60% (3/5) for trisomies 18 or 13, at a false-positive rate (FPR) of 0.25% (1/404). In the 10 530 singleton pregnancies with a cfDNA result after first or second sampling, the detection rate was 98.7% (156/158) for trisomy 21 and 80.3% (49/61) for trisomies 18 or 13, at a FPR of 0.22% (23/10 311). CONCLUSIONS: In twin pregnancies undergoing first-trimester screening for trisomies by cfDNA testing, the fetal fraction is lower and failure rate higher compared to in singletons. The number of trisomic twin pregnancies examined was too small for an accurate assessment of performance of screening, but it may be similar to that in singleton pregnancies. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Quality of life in major depressive disorder before/after multiple steps of treatment and one-year follow-up.

OBJECTIVE: This study examines the impact of major depressive disorder (MDD) and its treatment on quality of life (QOL). METHOD: From the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) trial, we analyzed complete data of 2280 adult MDD out-patients at entry/exit of each level of antidepressant treatments and after 12 months of entry to follow-up. QOL was measured using the QOL Enjoyment and Satisfaction Questionnaire (Q-LES-Q). The proportions of patients scoring 'within-normal' QOL (within 10% of Q-LES-Q community norms) and those with 'severely impaired' QOL (>2 SD below Q-LES-Q community norms) were analyzed. RESULTS: Before treatment, no more than 3% of MDD patients experienced 'within-normal' QOL. Following treatment, statistically significant improvements were detected; however, the proportion of patients achieving 'within-normal' QOL did not exceed 30%, with >50% of patients experiencing 'severely impaired' QOL. Although remitted patients had greater improvements compared with non-remitters, 32-60% continued to experience reduced QOL. 12-month follow-up data revealed that the proportion of patients experiencing 'within-normal' QOL show a statistically significant decrease in non-remitters. CONCLUSION: Symptom-focused treatments of MDD may leave a misleading impression that patients have recovered when, in fact, they may be experiencing ongoing QOL deficits. These findings point to the need for investigating specific interventions to ameliorate QOL in MDD.

Genomic haplotype within the Peroxisome Proliferator-Activated Receptor Delta (PPARD) gene is associated with elite athletic status.

Peroxisome proliferator-activated receptor delta (PPARδ; encoded by the PPARD gene) plays a role in energy metabolism and mitochondrial function. We have investigated the distribution of PPARD rs2267668, rs2016520 and rs1053049 polymorphisms, individually and in haplotype, in a cohort of 660 elite athletes which was subdivided into four different groups based on the different metabolic demands of their respective sports and 704 healthy controls. PPARD rs2016529 and rs1053049 were individually associated with overall elite athletic performance (P = 0.00002; and P = 0.0002) and also with athletes grouped as strength endurance (P = 0.00008; and P = 0.0003). Furthermore, PPARD A/C/C haplotype (rs2267668/rs2016520/rs1053049) was significantly underrepresented in all athletes and each subgroup of athletes when compared with controls (P < 0.000001), suggesting that harboring this specific haplotype is unfavorable for becoming an elite athlete. These results help to identify which genetic profiles may contribute to elite athletic performance, specifically the role of variants within the PPARD gene, and may be useful in talent identification or optimizing the response to training.

Whole-brain dynamic CT angiography and perfusion imaging.

The availability of whole brain computed tomography (CT) perfusion has expanded the opportunities for analysing the haemodynamic parameters associated with varied neurological conditions. Examples demonstrating the clinical utility of whole-brain CT perfusion imaging in selected acute and chronic ischaemic arterial neurovascular conditions are presented. Whole-brain CT perfusion enables the detection and focused haemodynamic analyses of acute and chronic arterial conditions in the central nervous system without the limitation of partial anatomical coverage of the brain.

ACTN3 genotype does not influence muscle power.

The R577X polymorphism within the ACTN3 gene has been associated with elite athletic performance, strength, power, fat free mass, and adaptations to strength training, though inconsistencies exist in the literature. The specific muscle power phenotypes most influenced by the polymorphism are uncertain. The purpose of this study was to examine the association between ACTN3 R577X genotype and muscle power phenotypes. Recreationally active young men and women (N=57) were selected to complete 2 muscle performance assessments, an isokinetic fatigue protocol at testing speeds of 180° s (-1) and 250° s (-1) and a 30 s Wingate test. Isokinetic torque and Wingate power significantly decreased over the duration of each test, but no differences in the rate of decline were observed among ACTN3 genotype groups. Similarly, no significant genotype differences were observed for isokinetic peak torque, Wingate absolute or relative peak power, or fatigue index. These results indicate that in recreationally active individuals the ACTN3 R577X polymorphism is not associated with muscle performance phenotypes, supporting recent findings that R577X may only be important for predicting performance in elite athletes. Our data also indicate that using this polymorphism for genetic screening in the lay population is scientifically questionable.

Body fluid identification and assignment to donors using a targeted mRNA massively parallel sequencing approach - results of a second EUROFORGEN / EDNAP collaborative exercise.

In a previous EUROFORGEN/EDNAP collaborative exercise, we tested two assays for targeted mRNA massively parallel sequencing for the identification of body fluids/tissues, optimized for the Illumina MiSeq/FGx and the Ion Torrent PGM/S5 platforms, respectively. The task of the second EUROFORGEN/EDNAP collaborative exercise was to analyze dried body fluid stains with two different multiplexes, the former Illumina 33plex mRNA panel for body fluid/tissue identification and a 35plex cSNP panel for assignment of body fluids/tissues to donors that was introduced in a proof-of-concept study recently. The coding region SNPs (cSNPs) are located within the body fluid specific mRNA transcripts and represent a direct link between the body fluid and the donor. We predicted the origin of the stains using a partial least squares discriminant analysis (PLS-DA) model, where most of the single source samples were correctly predicted. The mixed body fluid stains showed poorer results, however, at least one component was predicted correctly in most stains. The cSNP data demonstrated that coding region SNPs can give valuable information on linking body fluids/tissues with donors in mixed body fluid stains. However, due to the unfavorable performance of some cSNPs, the interpretation remains challenging. As a consequence, additional markers are needed to increase the discrimination power in each body fluid/tissue category.

Neuroprotective effects of cannabidiol in endotoxin-induced uveitis: critical role of p38 MAPK activation.

PURPOSE: Degenerative retinal diseases are characterized by inflammation and microglial activation. The nonpsychoactive cannabinoid, cannabidiol (CBD), is an anti-inflammatory in models of diabetes and glaucoma. However, the cellular and molecular mechanisms are largely unknown. We tested the hypothesis that retinal inflammation and microglia activation are initiated and sustained by oxidative stress and p38 mitogen-activated protein kinase (MAPK) activation, and that CBD reduces inflammation by blocking these processes. METHODS: Microglial cells were isolated from retinas of newborn rats. Tumor necrosis factor (TNF)-alpha levels were estimated with ELISA. Nitric oxide (NO) was determined with a NO analyzer. Superoxide anion levels were determined by the chemiluminescence of luminol derivative. Reactive oxygen species (ROS) was estimated by measuring the cellular oxidation products of 2', 7'-dichlorofluorescin diacetate. RESULTS: In retinal microglial cells, treatment with lipopolysaccharide (LPS) induced immediate NADPH oxidase-generated ROS. This was followed by p38 MAPK activation and resulted in a time-dependent increase in TNF-alpha production. At a later phase, LPS induced NO, ROS, and p38 MAPK activation that peaked at 2-6 h and was accompanied by morphological change of microglia. Treatment with 1 microM CBD inhibited ROS formation and p38 MAPK activation, NO and TNF-alpha formation, and maintained cell morphology. In addition, LPS-treated rat retinas showed an accumulation of macrophages and activated microglia, significant levels of ROS and nitrotyrosine, activation of p38 MAPK, and neuronal apoptosis. These effects were blocked by treatment with 5 mg/kg CBD. CONCLUSIONS: Retinal inflammation and degeneration in uveitis are caused by oxidative stress. CBD exerts anti-inflammatory and neuroprotective effects by a mechanism that involves blocking oxidative stress and activation of p38 MAPK and microglia.

Messenger RNA biomarker signatures for forensic body fluid identification revealed by targeted RNA sequencing.

The recovery of a DNA profile from the perpetrator or victim in criminal investigations can provide valuable 'source level' information for investigators. However, a DNA profile does not reveal the circumstances by which biological material was transferred. Some contextual information can be obtained by a determination of the tissue or fluid source of origin of the biological material as it is potentially indicative of some behavioral activity on behalf of the individual that resulted in its transfer from the body. Here, we sought to improve upon established RNA based methods for body fluid identification by developing a targeted multiplexed next generation mRNA sequencing assay comprising a panel of approximately equal sized gene amplicons. The multiplexed biomarker panel includes several highly specific gene targets with the necessary specificity to definitively identify most forensically relevant biological fluids and tissues (blood, semen, saliva, vaginal secretions, menstrual blood and skin). In developing the biomarker panel we evaluated 66 gene targets, with a progressive iteration of testing target combinations that exhibited optimal sensitivity and specificity using a training set of forensically relevant body fluid samples. The current assay comprises 33 targets: 6 blood, 6 semen, 6 saliva, 4 vaginal secretions, 5 menstrual blood and 6 skin markers. We demonstrate the sensitivity and specificity of the assay and the ability to identify body fluids in single source and admixed stains. A 16 sample blind test was carried out by one lab with samples provided by the other participating lab. The blinded lab correctly identified the body fluids present in 15 of the samples with the major component identified in the 16th. Various classification methods are being investigated to permit inference of the body fluid/tissue in dried physiological stains. These include the percentage of reads in a sample that are due to each of the 6 tissues/body fluids tested and inter-sample differential gene expression revealed by agglomerative hierarchical clustering.

Body fluid identification using a targeted mRNA massively parallel sequencing approach - results of a EUROFORGEN/EDNAP collaborative exercise.

In a previous study we presented an assay for targeted mRNA sequencing for the identification of human body fluids, optimised for the Illumina MiSeq/FGx MPS platform. This assay, together with an additional in-house designed assay for the Ion Torrent PGM/S5 platform, was the basis for a collaborative exercise within 17 EUROFORGEN and EDNAP laboratories, in order to test the efficacy of targeted mRNA sequencing to identify body fluids. The task was to analyse the supplied dried body fluid stains and, optionally, participants' own bona fide or mock casework samples of human origin, according to specified protocols. The provided primer pools for the Illumina MiSeq/FGx and the Ion Torrent PGM/S5 platforms included 33 and 29 body fluid specific targets, respectively, to identify blood, saliva, semen, vaginal secretion, menstrual blood and skin. The results demonstrated moderate to high count values in the body fluid or tissue of interest with little to no counts in non-target body fluids. There was some inter-laboratory variability in read counts, but overall the results of the laboratories were comparable in that highly expressed markers showed high read counts and less expressed markers showed lower counts. We performed a partial least squares (PLS) analysis on the data, where blood, menstrual blood, saliva and semen markers and samples clustered well. The results of this collaborative mRNA massively parallel sequencing (MPS) exercise support targeted mRNA sequencing as a reliable body fluid identification method that could be added to the repertoire of forensic MPS panels.

Neurogenic coronary vasoconstrictor effects of digitalis during acute global ischemia in dogs.

The rapid i.v. administration of digitalis has recently been shown to cause a substantial increase in coronary vascular resistance in the normal heart. This neurogenically mediated decrease in coronary blood flow would be potentially detrimental if it occurred during ischemia. The present study evaluates the effects of i.v. acetylstrophanthidin and digoxin on coronary vascular resistance during acute global ischemia in 29 dogs anesthetized with chloralose and urethane. Under these conditions, 0.5 mg of i.v. acetylstrophanthidin in 15 dogs resulted in erratic increases in coronary vascular resistance. The peak rise was 12+/-5% above control (P less than 0.01). In 7 of the 15 dogs, the initial erratic rise in coronary vascular resistance culminated in a steep rise associated with acute elevation in left ventricular end-diastolic pressure, which in four dogs terminated in ventricular fibrillation. During the nonischemic control periods, the peak rise in coronary vascular resistance with acetylstrophanthidin was 16+/-1% above control (P less than 0.01). In five dogs, prior alpha adrenergic receptor blockade with phenoxybenzamine prevented the rise in coronary vascular resistance with acetylstrophanthidin during ischemia. Similar erratic increases in coronary vascular resistance were observed with i.v. digoxin (1 mg) during ischemia in three dogs. In two of these dogs, there was a progressive rise in coronary vascular resistance associated with elevation of left ventricular end-diastolic pressure and ventricular fibrillation. The increase in coronary vascular resistance with digoxin during ischemia was abolished with phenoxybenzamine in two additional dogs. Thus, i.v. digitalis in the ischemic heart results in potentially detrimental increases in coronary vascular resistance mediated through alpha adrenergic receptor stimulation.

Sequence-independent assembly of spermatid mRNAs into messenger ribonucleoprotein particles.

During mammalian spermatogenesis, meiosis is followed by a brief period of high transcriptional activity. At this time a large amount of mRNA is stored as messenger ribonucleoprotein (mRNP) particles. All subsequent processes of sperm maturation occur in the complete absence of transcription, primarily using proteins which are newly synthesized from these stored mRNAs. By expressing transgene mRNAs in the early haploid spermatids of mice, we have investigated the sequence requirements for determining whether specific mRNAs in these cells will be stored as mRNP particles or be assembled into polysomes. The results suggest that mRNAs which are transcribed in spermatids are assembled into mRNP particles by a mechanism that acts independently of mRNA sequence. Our findings reveal a fundamental similarity between the mechanisms of translational control used in spermatogenesis and oogenesis.

The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients.

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

Heterotypic adherence between murine leukemia/lymphoma cells and marrow stromal cells involves a recognition mechanism with galactosyl and mannosyl specificities.

We have previously shown that leukemia/lymphoma (LL) cells adhere to marrow stromal cells (MSC), and MSC induce clonal growth of LL cells. Even though CD11a/18 and CD54 are important in leukocyte and endothelial cell interaction, the literature suggested that these adhesion proteins are not involved in adhesion of hematopoietic stem cells to MSC. We therefore utilized a unique ICAM-1- murine MSC line (MLT) to evaluate the mechanisms of adherence of LL cells (L5178Y and L1210) to MLT. Adherence of LL cells to extracellular matrix (ECM) proteins was also examined. L1210 cells attached to collagen types III and IV, laminin, and fibronectin, but not to collagen type I. L5178Y cells did not attach to any of the ECM proteins tested. The adherence of both L1210 and L5178Y to MSC was unaffected by rat monoclonal antibodies to murine CD11a, CD11b, and CD18. Neoglycoprotein probes, mannosyl-bovine serum albumin (BSA) and galactosyl-BSA, inhibited the adherence of L5178Y and L1210 cells to MSC by 34%-63% of controls at concentrations of 10(-3) and 5 x 10(-3) M. In contrast, fucosyl-BSA had no inhibitory effect on LL cell adherence of MLT. These data suggest that 1) LL cells may adhere to MSC by a lectin mechanism with mannosyl and galactosyl specificities; and 2) other mechanisms of adherence, not yet defined, are also important in this system.

RNA/DNA co-analysis from human skin and contact traces--results of a sixth collaborative EDNAP exercise.

The European DNA profiling group (EDNAP) organized a sixth collaborative exercise on RNA/DNA co-analysis for body fluid/tissue identification and STR profiling. The task was to identify skin samples/contact traces using specific RNA biomarkers and test three housekeeping genes for their suitability as reference genes. Eight stains, a skin RNA dilution series and, optionally, bona fide or mock casework samples of human or non-human origin were analyzed by 22 participating laboratories using RNA extraction or RNA/DNA co-extraction methods. Two sets of previously described skin-specific markers were used: skin1 pentaplex (LCE1C, LCE1D, LCE2D, IL1F7 and CCL27) and skin2 triplex (LOR, KRT9 and CDSN) in conjunction with a housekeeping gene, HKG, triplex (B2M, UBC and UCE). The laboratories used different chemistries and instrumentation. All laboratories were able to successfully isolate and detect mRNA in contact traces (e.g., human skin, palm-, hand- and fingerprints, clothing, car interiors, computer accessories and electronic devices). The simultaneous extraction of RNA and DNA provides an opportunity for positive identification of the tissue source of origin by mRNA profiling as well as a simultaneous identification of the body fluid donor by STR profiling. The skin markers LCE1C and LOR and the housekeeping gene marker B2M were detected in the majority of contact traces. Detection of the other markers was inconsistent, possibly due to the low amounts and/or poor quality of the genetic material present in shed skin cells. The results of this and the previous collaborative RNA exercises support RNA profiling as a reliable body fluid/tissue identification method that can easily be combined with current STR typing technology.

Elevated corticosterone is not required for the rapid induction of neuropeptide Y gene expression by an overnight fast.

Fasting stimulates corticosterone (B) secretion and the expression and secretion of hypothalamic neuropeptide Y in rats. These studies tested the hypothesis that the rapid and marked fasting-induced increases in plasma B are responsible for stimulation of neuropeptide Y (NPY) gene expression. Plasma leptin and insulin were measured because they are also signals known to affect NPY messenger RNA (mRNA). Intact or adrenalectomized rats given a low fixed level of corticosterone (B replaced) were fasted for 48 h. NPY mRNA in the mediobasal hypothalamus, measured by nuclease protection assay, was elevated similarly above ad lib-fed controls in both intact and B replaced groups at 15 and 48 h after the onset of fasting. NPY immunoreactivity in the mediobasal hypothalamus increased between 3 and 48 h after onset of the fast in intact but not in B replaced groups. The fasting-induced decreases in leptin observed in intact rats at 48 h did not occur in B replaced rats. Fasting-induced decreases in insulin occurred in B replaced rats but not in intact rats. We conclude that: 1) elevated B is not required for fasting-induced increases in hypothalamic NPY gene expression; and 2) decreases in neither leptin nor insulin alone signal the changes that occur in NPY mRNA in fasted rats.

Hypothyroidism and abnormalities in the kinetics of thyroid hormone metabolism in rats treated chronically with polychlorinated biphenyl and polybrominated biphenyl.

Studies were directed at the question of whether polychlorinated biphenyl (PCB; Aroclor 1254) and polybrominated biphenyl (PBB; Fire Master BP-6), when administered in the diets of female Sprague-Dawley rats over long periods of time (5-7 months) and at low dosages (0, 1, 5, 10, and 50 ppm), would depress the thyroid. By examining serum T3 and T4, kinetics of T4 metabolism, and in vivo thyroid response to exogenous TSH injections, an estimate of the degree of hypothyroidism was made, and abnormalities in T4 disappearance from serum were encountered. Serum T3 and T4 levels were greatly suppressed in a dose-related manner by PCB or PBB treatment. There was a diminished response of serum T3 and T4 to TSH injection in rats pretreated with PCB or PBB (5 and 10 ppm), the exception being T3 in the 5 ppm PCB treatment group. Had the PCB and PBB treatment-induced suppression of T4 and T3 been on the hypothalamo-pituitary axis, the response of the treated rats to exogenous TSH might have exceeded that of controls; however, the opposite occurred. Disappearance of injected doses of L-[125I]T4 diminished as treatment concentrations of PCB or PBB increased. Disappearance slopes (r = 0.98) and fractional turnover rate constants (k) were decreased (t1/2 was lengthened) at each treatment level compared to the control values. The T4 distribution space (per 100 g BW) was expanded with increasing dosage by as much as 8-fold in the 50 pmm PCB treatment group. T4 MCRs were not increased by PCB or PBB treatment; thus, decreases in serum T3 and T4 were not caused by increased catabolism. T4 production rates were decreased at all treatment levels, but maximally 6-fold by 50 ppm PCB treatment. Together these data indicate that PCB-PBB-induced decreases in serum T3 and T4 result primarily from direct damage to the thyroid rather than any enhanced hepatic or other peripheral catabolism per se. Expanded T4 distribution space demonstrated that nonthyroid damage was also an important factor in reducing serum T4. Cell membrane damage associated with PCB-PBB intoxication may have expanded pools for T4 dilution. The findings are consistent with reported histological and ultrastructural damage caused by PCB and PBB. It also appears that TSH plays little role in PCB-PBB-induced hypothyroidism.