Multigenerational impacts of EE2 on reproductive fitness and immune competence of marine medaka

Estrogenic endocrine disrupting chemicals (EEDC) have been suspected to impact offspring in a transgenerational manner via modifications of the germline epigenome in the directly exposed generations. A holistic assessment of the concentration/ exposure duration-response, threshold level, and critical exposure windows (parental gametogenesis and embryogenesis) for the transgenerational evaluation of reproduction and immune compromise concomitantly will inform the overall EEDC exposure risk. We conducted a multigenerational study using the environmental estrogen, 17α-ethinylestradiol (EE2), and the marine laboratory model fish Oryzias melastigma (adult, F0) and their offspring (F1-F4) to identify transgenerationally altered offspring generations and phenotype persistence. Three exposure scenarios were used: short parental exposure, long parental exposure, and a combined parental and embryonic exposure using two concentrations of EE2 (33ng/L, 113ng/L). The reproductive fitness of fish was evaluated by assessing fecundity, fertilization rate, hatching success, and sex ratio. Immune competence was assessed in adults via a host-resistance assay. EE2 exposure during both parental gametogenesis and embryogenesis was found to induce concentration/ exposure duration-dependent transgenerational reproductive effects in the unexposed F4 offspring. Furthermore, embryonic exposure to 113 ng/L EE2 induced feminization of the directly exposed F1 generation, followed by subsequent masculinization of the F2 and F3 generations. A sex difference was found in the transgenerationally impaired reproductive output with F4 females being sensitive to the lowest concentration of EE2 (33 ng/L) upon long-term ancestral parent exposure (21 days). Conversely, F4 males were affected by ancestral embryonic EE2 exposure. No definitive transgenerational impacts on immune competence were identified in male or female offspring. In combination, these results indicate that EEDCs can be transgenerational toxicants that may negatively impact the reproductive success and population sustainability of fish populations.

Paternal morphine exposure enhances morphine self-administration and induces region-specific neural adaptations in reward-related brain regions of male offspring

Background

A growing body of preclinical studies report that preconceptional experiences can have a profound and long-lasting impact on adult offspring behavior and physiology. However, less is known about paternal drug exposure and its effects on reward sensitivity in the next generation.

Methods

Adult male rats self-administered morphine for 65 days; controls received saline. Sires were bred to drug-naïve dams to produce first-generation (F1) offspring. Morphine, cocaine, and nicotine self-administration were measured in adult F1 progeny. Molecular correlates of addiction-like behaviors were measured in reward-related brain regions of drug naïve F1 offspring.

Results

Male, but not female offspring produced by morphine-exposed sires exhibited dose-dependent increased morphine self-administration and increased motivation to earn morphine infusions under a progressive ratio schedule of reinforcement. This phenotype was drug-specific as self-administration of cocaine, nicotine, and sucrose were not altered by paternal morphine history. The male offspring of morphine-exposed sires also had increased expression of mu-opioid receptors in the ventral tegmental area but not in the nucleus accumbens.

Conclusions

Paternal morphine exposure increased morphine addiction-like behavioral vulnerability in male but not female progeny. This phenotype is likely driven by long-lasting neural adaptations within the reward neural brain pathways.

Transcriptomics in the nucleus accumbens shell reveal sex- and reinforcer-specific signatures associated with morphine and sucrose craving

Incubation of craving is a well-documented phenomenon referring to the intensification of drug craving over extended abstinence. The neural adaptations that occur during forced abstinence following chronic drug taking have been a topic of intense study. However, little is known about the transcriptomic changes occurring throughout this window of time. To define gene expression changes associated with morphine consumption and extended abstinence, male and female rats underwent 10 days of morphine self-administration. Separate drug-naive rats self-administered sucrose in order to compare opioid-induced changes from those associated with natural, non-drug rewards. After one or 30 days of forced abstinence, rats were tested for craving, or nucleus accumbens shell tissue was dissected for RNA sequencing. Morphine consumption was predictive of drug seeking after extended (30 days) but not brief (1 day) abstinence in both sexes. Extended abstinence was also associated with robust sex- and reinforcer-specific changes in gene expression, suggesting sex differences underlying incubation of morphine and sucrose seeking respectively. Importantly, these changes in gene expression occurred without re-exposure to drug-paired cues, indicating that chronic morphine causes long-lasting changes in gene expression that prime the system for increased craving. These findings lay the groundwork for identifying specific therapeutic targets for curbing opioid craving without impacting the natural reward system in males and females.

Sex-specific immunomodulatory action of the environmentalestrogen 17α-ethynylestradiol alongside with reproductive impairment in fish

Estrogenic endocrine disrupting chemicals (EEDCs) are present ubiquitously in sediments and aquatic ecosystems worldwide. The detrimental impact of EEDCs on the reproduction of wildlife is widely recognized. Increasing evidence shows the immunosuppressive effects of EEDCs in vertebrates. Yet, no studies have considered concomitantly EEDC-induced impacts on reproductive impairment and immune suppression in vivo, which are deemed essential for risk assessment and environmental monitoring. In this study, EE2 was used as a representative EEDC, for parallel evaluation of EEDC-induced immune suppression (immune marker gene expression, leukocyte numbers, host resistance assay, and immune competence index) and reproductive impairment (estrogen responsive gene expression, fecundity, fertilization success, hatching success, and reproductive competence index) in an established fish model (marine medaka Oryzias melastigma), considering sex-specific induction and adaptation and recovery responses under different EE2 exposure scenarios. The findings in marine medaka reveal distinct sex differences in the EE2-mediated biological responses. For female fish, low concentration of exogenous EE2 (33 ng/L) could induce hormesis (immune enhancement), enable adaptation (restored reproduction) and even boost fish resistance to bacterial challenge after abatement of EE2. However, a prolonged exposure to high levels of EE2 (113 ng/L) not only impaired F0 immune function, but also perturbed females recovering from reproductive impairment, resulting in a persistent impact on the F1 generation output. Thus, for female fish, the exposure concentration of EE2 is more critical than the dose of EE2 in determining the impacts of EE2 on immune function and reproduction. Conversely, male fish are far more sensitive than females to the presence of low levels of exogenous EE2 in water and the EE2-mediated biological impacts are clearly dose-dependent. It is also evident in male fish that direct contact of EE2 is essential to sustain impairments of immune competence and reproductive output as well as deregulation of immune function genes in vivo. The immunomodulatory pathways altered by EE2 were deciphered for male and female fish, separately. Downregulation of hepatic tlr3 and c3 (in female) and tlr3, tlr5 and c3 (in male) may be indicative of impaired fish immune competence. Taken together, impaired immune competence in the EE2-exposed fish poses an immediate thread on the survival of F0 population. Impaired reproduction in the EE2-exposed fish can directly affect F1 output. Parallel evaluation of immune competence and reproduction are important considerations when assessing the risk of sublethal levels of EE2/EEDCs in aquatic environments.

Multigenerational Disruption of the Thyroid Endocrine System in Marine Medaka after a Life-Cycle Exposure to Perfluorobutanesulfonate

Accumulation of perfluorobutanesulfonate (PFBS) is frequently detected in biota, raising concerns about its ecological safety. However, hazardous effects of PFBS remain largely unexplored, especially for endocrine disrupting potency. In the present study, the multigenerational endocrine disrupting potential of PFBS was investigated by exposing F0 marine medaka eggs to PFBS at different concentrations (0, 1.0, 2.9, and 9.5 μg/L) until sexual maturity. The F1 and F2 generations were reared without continued exposure. Thyroidal disturbances were examined in all three generations. PFBS exposure decreased the levels of 3,5,3'-triiodothyronine (T3) in F0 female blood; however, it increased T3 or thyroxine (T4) levels in F0 brains, in which hyperthyroidism suppressed the local transcription of 5'-deiodinase 2 ( Dio2). Obviously decreased T3 was transferred to F1 eggs, although the parental influences were reversed in F1 larvae. Delayed hatching was coupled with elevated T3 levels in F1 larvae. F1 adults showed comparable symptoms of thyroidal disruption with F0 adults. A slight recovery was noted in the F2 generation, although F2 larvae still exhibited thyroid disruption and synthesized excessive T4. Our results suggested that the offspring suffered more severe dysfunction of the thyroidal axis albeit without direct exposure. This study provided the first molecular insight about PFBS toxicology on the thyroid, beneficial to both human and environmental risk assessment.

Immune competence assessment in marine medaka (Orzyias melastigma)-a holistic approach for immunotoxicology

Many anthropogenic pollutants in coastal marine environments can induce immune impairments in wild fish and reduce their survival fitness. There is a pressing need to establish sensitive and high throughput in vivo tools to systematically evaluate the immunosuppressive effects of contaminants in marine teleosts. This study reviewed a battery of in vivo immune function detection technologies established for different biological hierarchies at molecular (immune function pathways and genes by next generation sequencing (NGS)), cellular (leukocytes profiles by flow cytometry), tissues/organ system (whole adult histo-array), and organism (host resistance assays (HRAs)) levels, to assess the immune competence of marine medaka Oryzias melastigma. This approach enables a holistic assessment of fish immune competence under different chemical exposure or environmental scenarios. The data obtained will also be useful to unravel the underlying immunotoxic mechanisms. Intriguingly, NGS analysis of hepatic immune gene expression profiles (male > female) are in support of the bacterial HRA findings, in which infection-induced mortality was consistently higher in females than in males. As such, reproductive stages and gender-specific responses must be taken into consideration when assessing the risk of immunotoxicants in the aquatic environment. The distinct phenotypic sexual dimorphism and short generation time (3 months) of marine medaka offer additional advantages for sex-related immunotoxicological investigation.

Sex-dependent telomere shortening, telomerase activity and oxidative damage in marine medaka Oryzias melastigma during aging

Marine medaka Oryzias melastigma at 4months (young), 8months (middle-aged) and 12months old (senior) were employed to determine age-associated change of sex ratios, sex hormones, telomere length (TL), telomerase activity (TA), telomerase transcription (omTERT) and oxidative damage in the liver. Overall, O. melastigma exhibited gradual senescence, sex differences in longevity (F>M), TL (F>M) and oxidative damage (F<M) during aging. In females, the plasma E2 level was positively correlated with TL (TRF>5kb), TA and omTERT expression (p≤0.01), and negatively correlated with liver DNA oxidation (p≤0.05). The results suggest high levels of E2 in female O. melastigma may retard TL shortening by enhancing TA via TERT transcription and/or reducing oxidative DNA damage. The findings support TL shortening as a biomarker of aging and further development of accelerated TL shortening, abnormal suppression of TA and excessive oxidative DNA damage as early molecular endpoints, indicative of advanced/premature aging in marine medaka/fish.

Modification of the plasma complement protein profile by exogenous estrogens is indicative of a compromised immune competence in marine medaka (Oryzias melastigma)

Growing evidence suggests that the immune system of teleost is vulnerable to xenoestrogens, which are ubiquitous in the marine environment. This study detected and identified the major circulatory immune proteins deregulated by 17α-ethinylestradiol (EE2), which may be linked to fish susceptibility to pathogens in the marine medaka, Oryzias melastigma. Fish immune competence was determined using a host resistance assay to pathogenic bacteria Edwardsiella tarda. Females were consistently more susceptible to infection-induced mortality than males. Exposure to EE2 could narrow the sex gap of mortality by increasing infection-induced death in male fish. Proteomic analysis revealed that the major plasma immune proteins of adult fish were highly sexually dimorphic. EE2 induced pronounced sex-specific changes in the plasma proteome, with the male plasma composition clearly becoming "feminised". Male plasma was found to contain a higher level of fibrinogens, WAP63 and ependymin-2-like protein, which are involved in coagulation, inflammation and regeneration. For the first time, we demonstrated that expression of C1q subunit B (C1Q), an initiating factor of the classical complement pathway, was higher in males and was suppressed in both sexes in response to EE2 and bacterial challenge. Moreover, cleavage and post-translational modification of C3, the central component of the complement system, could be altered by EE2 treatment in males (C3dg down; C3g up). Multiple regression analysis indicated that C1Q is possibly an indicator of fish survival, which warrants further confirmation. The findings support the potential application of plasma immune proteins for prognosis/diagnosis of fish immune competence. Moreover, this study provides the first biochemical basis of the sex-differences in fish immunity and how these differences might be modified by xenoestrogens.

Identification of Molecular Targets for 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in Teleosts: New Insight into Mechanism of Toxicity

Environmental pollutants are capable of concomitantly inducing diverse toxic effects. However, it is largely unknown which effects are directly induced and which effects are secondary, thus calling for definitive identification of the initiating molecular event for a pollutant to elucidate the mechanism of toxicity. In the present study, affinity pull-down assays were used to identify target proteins for 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), a costal pollutant of emerging concern, in various tissues (e.g., brain, liver, plasma, and gonad) from marine medaka (Oryzias melastigma) and zebrafish (Danio rerio). Pull-down results showed that, in male and female brains from medaka and zebrafish, DCOIT had a consistently high affinity for G protein alpha subunits (Gα), suggesting the targeted effects of DCOIT on signaling transduction from G protein-coupled receptors (GPCRs) and an extrapolatable mode of action in teleost brains. Validation using recombinant proteins and molecular docking analysis confirmed that binding of DCOIT to Gα protein competitively inhibited its activation by substrate. Considering the involvement of GPCRs in the regulation of myriad biological processes, including the hypothalamus-pituitary-gonadal-liver axis, binding of DCOIT to upstream Gα proteins in the brain may provide a plausible explanation for the diversity of toxic effects resulting from DCOIT challenge, especially abnormal hormonal production through the mitogen-activated protein kinase pathway. A new mechanism of action based on GPCR signaling is thus hypothesized for endocrine disrupting chemicals and warrants further research to clearly elucidate the link between GPCR signaling and endocrine disruption.

A Kinematic Approach to Understanding Performance in Upper-Extremity Function during a Goal-Directed Man-Machine Interface Task in a Submariner Environment

In December of 2014, the United States Congress funded a fundamental shift in the recruiting policy of the US Navy Submarine Force to include the integration of women. As a result, design modifications became necessary, especially those that facilitate integration without inflating costs. Current cost levels associated with new submarine design(s) are maintained through the use of legacy components and systems. Additionally, many of the systems aboard are computer controlled, necessitating man-machine interfaces. As common practice, military activities that involve man-machine interfaces have always focused on the dexterity of the hands, often neglecting the role of movement in the task; therefore, there is a need to understand upper-extremity kinematics issues associated with man-machine interfaces. Joint kinematics of the right upper extremity of 10 subjects was measured using an optoelectronic motion capture system. Center of gravity displacements were measured using a force plate during touchscreen movement tasks paced by six different movement frequencies from a metronome (0, 1.0, 1.3, 1.7, 2.0, and 2.7 Hz). Results showed no significant difference in touch accuracy, task completion time, shoulder and elbow angular displacements, and shoulder and elbow flexion/extension velocity; however, a significant difference (0.002; p ≤ 0.05) in shoulder adduction/abduction velocity was observed. In arranging systems and components in submarine and surface vessel environments, consideration in not only providing a means of adjustability (e.g., height, proximity, and orientation) but in the dimensions of the systems and components themselves must also be considered based on the required operation.

Insight into the transgenerational effect of benzo[a]pyrene on bone formation in a teleost fish (Oryzias latipes)

Recent cross-generational studies in teleost fish have raised the awareness that high levels of benzo[a]pyrene (BaP) could affect skeletal integrity in the directly exposed F0 and their F1-F2. However, no further details were provided about the causes for abnormalities on the molecular and cellular level and the persistence of such sub-organismal impairments at the transgenerational scale (beyond F2). Adult Oryzias latipes were exposed to 1μg/L BaP for 21days. The F1-F3 were examined for skeletal deformities, histopathological alterations of vertebral bodies and differential expression of key genes of bone metabolism. Significant increase of dorsal-ventral vertebral compression was evident in ancestrally exposed larvae. Histopathological analysis revealed abnormal loss of notochord sheath, a lack of notochord epithelial integrity, reduced bone tissue and decreased osteoblast abundance. A significant downregulation of ATF4 and/or osterix and a high biological variability of COL10, coupled with a significant deregulation of SOX9a/b in the F1-F3 suggest that ancestral BaP exposure most likely perturbed chordoblasts, chondroblast and osteoblast differentiation, resulting in defective notochord sheath repair and rendering the vertebral column more vulnerable to compression. The present findings provide novel molecular and cellular insights into BaP-induced transgenerational bone impairment in the unexposed F3. From the ecological risk assessment perspective, BaP needs to be regarded as a transgenerational skeletal toxicant, which exerts a far-reaching impact on fish survival and fitness. Given that basic mechanisms of cartilage/bone formation are conserved between medaka and mammals, the results may also shed light on the potential transgenerational effect of BaP on the genesis of skeletal diseases in humans.

Valproic acid adjunctive therapy for HIV-associated cognitive impairment: a first report

In vitro and animal model data demonstrate that valproic acid (VPA) can ameliorate HIV-associated neurotoxicity. The authors conducted a pilot 10-week placebo-controlled study of VPA 250 mg twice daily in 22 HIV-infected individuals with (n = 16) and without (n = 6) cognitive impairment. VPA was safe and well tolerated, with trends toward improved neuropsychological performance and brain metabolism in the impaired subjects.

Monitoring, modelling and environmental exposure assessment of industrial chemicals in the aquatic environment

Monitoring and laboratory data play integral roles alongside fate and exposure models in comprehensive risk assessments. The principle in the European Union Technical Guidance Documents for risk assessment is that measured data may take precedence over model results but only after they are judged to be of adequate reliability and to be representative of the particular environmental compartments to which they are applied. In practice, laboratory and field data are used to provide parameters for the models, while monitoring data are used to validate the models' predictions. Thus, comprehensive risk assessments require the integration of laboratory and monitoring data with the model predictions. However, this interplay is often overlooked. Discrepancies between the results of models and monitoring should be investigated in terms of the representativeness of both. Certainly, in the context of the EU risk assessment of existing chemicals, the specific requirements for monitoring data have not been adequately addressed. The resources required for environmental monitoring, both in terms of manpower and equipment, can be very significant. The design of monitoring programmes to optimise the use of resources and the use of models as a cost-effective alternative are increasing in importance. Generic considerations and criteria for the design of new monitoring programmes to generate representative quality data for the aquatic compartment are outlined and the criteria for the use of existing data are discussed. In particular, there is a need to improve the accessibility to data sets, to standardise the data sets, to promote communication and harmonisation of programmes and to incorporate the flexibility to change monitoring protocols to amend the chemicals under investigation in line with changing needs and priorities.

The ethics of research into schizophrenia prevention: a carer's perspective

OBJECTIVE

To outline from a carer's/family's perspective the ethical concerns raised by research into screening for factors in people at risk of schizophrenia.

METHOD

The need for families and carers of people with schizophrenia to seek a voice in the ethics of research into schizophrenia prevention is described. The possibility that societal myths, literature and language have created sustained ignorance about psychotic illnesses, resulting in fear and/or prejudice, is considered. The impact of these factors greatly exacerbating the burden of schizophrenia for sufferers and their families is discussed.

RESULTS

There is evidence that people with schizophrenia share the disadvantages of other disempowered minorities. It is necessary for ethical constraints to be cognisant of this; research should include critically exploring reasons for attempting to eliminate the condition.

CONCLUSIONS

Development of an ethical framework for prevention research into schizophrenia should include carer/family input. From a carer/family perspective, research into schizophrenia should be directed at ameliorating the effects of the illness by advancing methods of early diagnosis and by finding suitable treatments that do not carry punitive side-effects, thus allowing people with the illness to reach their potential in all aspects of their lives. Therapeutic relief combined with the elimination of social ostracism would greatly benefit people with schizophrenia and their families.

A risk assessment of selected phthalate esters in North American and Western European surface waters

Potential risks to aquatic organisms by four commercial phthalate esters, dimethyl (DMP), diethyl (DEP), di-n-butyl (DBP), and butylbenzyl (BBP), were assessed using measured and calculated concentrations in North American and Western European surface waters. Predicted no effect concentrations (PNECs) were calculated using statistical extrapolation procedures and the large aquatic toxicity database. Surface water concentrations of DMP, DEP, DBP, and BBP were calculated using reported emissions to US surface waters from the toxics release inventory (TRI). Monitoring data obtained from the US EPA STORET database and literature surveys from North America and Western Europe show that DMP, DEP, DBP, and BBP are infrequently detected in surface water. Calculated and measured concentrations of DMP, DEP, DBP, and BBP are typically several orders of magnitude below their respective PNECs, indicating that these phthalate esters do not pose a ubiquitous threat to aquatic organisms in North American and Western European surface waters.

An 'inherent' biodegradability test for oil products: description and results of an international ring test. CONCAWE Biodegradation Task Force

Current test guidelines for assessing 'inherent' (potential) biodegradability were designed for water-soluble, organic compounds of low volatility and are unsuitable for most oil products. It was against this background, that CONCAWE (the oil companies' European organisation for environment, health and safety) formed a task force to develop a standard test protocol for assessing the 'inherent' biodegradability of oil products.

Isolation of rat fibrillin-1 cDNA and its relevance in metanephric development

The role of fibrillin-1 in metanephrogenesis was investigated. Fibrillin-1 cDNA was isolated from the rat kidney cDNA library and sequenced, and its spatiotemporal expression was studied. It had approximately 88% homology with human fibrillin-1 and had Ca2+ binding epidermal growth factor-like domains, transforming growth factor-beta binding protein motifs, and an RGD binding site. Northern blot analysis revealed an approximately 10-kb transcript, and fibrillin-1 expression was developmentally regulated. In situ hybridization and immunofluorescence studies indicated that at day 15 of gestation, fibrillin-1 is expressed in the metanephric mesenchyme. At day 18, its expression was confined to nascent blood vessels and glomeruli, and it increased in the newborn and neonatal kidneys. Immunoprecipitation revealed an approximately 300-kDa band by SDS-PAGE. Treatment with fibrillin-1 antisense oligodeoxynucleotide induced marked dysmorphogenesis of the embryonic metanephroi. Concomitantly, the fibrillin-1 mRNA, antibody reactivity in the metanephroi, and fibrillin-1-specific radioincorporation were reduced. These data indicate that, like alphavbeta3 integrin, a known morphogen and a putative receptor of fibrillin-1, the fibrillin-1 modulates events related to early organogenesis and possibly also the vascularization of the rat kidney.

Relevance of extracellular matrix, its receptors, and cell adhesion molecules in mammalian nephrogenesis

Mammalian nephrogenesis begins by the reciprocal interaction of the ureteric bud with the undifferentiated mesenchyme. The mesenchyme differentiates into an epithelial phenotype with the development of the glomerulus and proximal and distal tubules. At the same time, the mesenchyme stimulates the branching morphogenesis of the ureteric bud that differentiates into the collecting ducts. These inductive interactions and differentiation events are modulated by a number of macromolecules, including the extracellular matrix (ECM), integrin receptors, and cell adhesion molecules. Many of these macromolecules exhibit spatiotemporal developmental regulation in the metanephros. Some are expressed in the mesenchyme, whereas others appear in the ureteric bud epithelia. The molecules expressed in the mesenchyme or at the epithelial:mesenchymal interface may serve as ligands while those in the epithelia serve as the receptors. In such a scenario the ligand and the receptor would be ideally suited for epithelial:mesenchymal paracrine/juxtacrine interactions that are also influenced by RGD sequences and Ca2+ binding domains of the ECM proteins and their receptors. This review addresses the role of such interactions in metanephric development.

Glutamine transport by the blood-brain barrier: a possible mechanism for nitrogen removal

Glutamine and glutamate transport activities were measured in isolated luminal and abluminal plasma membrane vesicles derived from bovine brain endothelial cells. Facilitative systems for glutamine and glutamate were almost exclusively located in luminal-enriched membranes. The facilitative glutamine carrier was neither sensitive to 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid inhibition nor did it participate in accelerated amino acid exchange; it therefore appeared to be distinct from the neutral amino acid transport system L1. Two Na-dependent glutamine transporters were found in abluminal-enriched membranes: systems A and N. System N accounted for approximately 80% of Na-dependent glutamine transport at 100 microM. Abluminal-enriched membranes showed Na-dependent glutamate transport activity. The presence of 1) Na-dependent carriers capable of pumping glutamine and glutamate from brain into endothelial cells, 2) glutaminase within endothelial cells to hydrolyze glutamine to glutamate and ammonia, and 3) facilitative carriers for glutamine and glutamate at the luminal membrane may provide a mechanism for removing nitrogen and nitrogen-rich amino acids from brain.

Glucose transport by isolated plasma membranes of the bovine blood-brain barrier

Luminal and abluminal endothelial plasma membrane vesicles were isolated from bovine cerebral microvessels, the site of the blood-brain barrier. Glucose transport across each membrane was measured using a rapid-filtration technique. Glucose transport into luminal vesicles occurred by a stereospecific energy-independent transporter [Michaelis-Menten constant (K(m)) = 10.3 +/- 2.8 (SE) mM and maximal velocity (Vmax) = 8.6 +/- 2.0 nmol.mg protein(-1).min-1]. Kinetic analysis of abluminal vesicles also showed a transport system with characteristics similar to the luminal transporter (K(m) = 12.5 +/- 2.3 mM and Vmax = 10.0 +/- 1.0 nmol.mg protein-1.min-1). These functional, facilitative glucose transporters were symmetrically distributed between the luminal and abluminal membrane domains, providing a mechanism for glucose movement between blood and brain. The studies also revealed a Na-dependent transporter on the abluminal membrane with a higher affinity and lower capacity than the facilitative transporters (K(m) = 130 +/- 20 microM and Vmax = 1.59 +/- 0.44 nmol.mg protein-1.min-1. The abluminal Na-dependent glucose transporter is in a position to transport glucose from the brain extracellular fluid into the endothelial cells of the blood-brain barrier. The functional significance of its presence there remains to be determined.

Role of oxoproline in the regulation of neutral amino acid transport across the blood-brain barrier

Regulation of neutral amino acid transport was studied using isolated plasma membrane vesicles derived from the bovine blood-brain barrier. Neutral amino acids cross the blood-brain barrier by facilitative transport system L1, which may allow both desirable and undesirable amino acids to enter the brain. The sodium-dependent amino acid systems A and Bo,+ are located exclusively on abluminal membranes, in a position to pump unwanted amino acids out. gamma-Glutamyl transpeptidase, the first enzyme of the gamma-glutamyl cycle, is an integral protein of the luminal membrane of the blood-brain barrier. We demonstrate that oxoproline, an intracellular product of the gamma-glutamyl cycle, stimulates the sodium-dependent systems A and Bo,+ by 70 and 20%, respectively. Study of system A showed that 2 mM oxoproline increased the affinity for its specific substrate N-methylaminoisobutyrate by 50%. This relationship between the activity of the gamma-glutamyl cycle and system A transport may provide a short term regulatory mechanism by which the entry of potentially deleterious amino acids (i.e. neurotransmitters or their precursors) may be retarded and their removal from brain accelerated.

Gentamicin inhibits carrier-mediated dipeptide transport in kidney

The effect of gentamicin on transport of pyroglutamylhistidine (pGlu-His) was examined in rabbit renal brush-border membrane vesicles (BBMV). Gentamicin, an aminoglycoside antibiotic, is limited in its usage because of nephrotoxicity characterized in part by transport defects in the proximal tubule. Since there is no information regarding the effects of gentamicin on renal peptide carriers, uptake of [3H]pGlu-His was measured in BBMV following either in vivo or in vitro exposure to the antibiotic. One hour after in vivo administration, the maximal rate (Vmax) for pGlu-His transport was significantly reduced in isolated membrane vesicles washed free of the drug, but the apparent Michaelis constant (Km) was unaltered. Coincubation of membranes with gentamicin during measurements of pGlu-His uptake had a similar effect, causing a significant decrease in the Vmax but not the Km of transport. The addition of 5 mM magnesium to the uptake medium prevented the in vitro but not the in vivo effect. The data indicate that high doses of gentamicin inhibit the capacity but not the affinity of dipeptide transport in the kidney, prior to morphological changes which typify acute tubular necrosis. The in vitro effect is rapid and involves a direct action of gentamicin on the brush-border membrane. The in vivo experiments show that toxicity may be prolonged and remains following removal of the drug from the renal brush border.

The reflective educator

Since the Boulder conference on training in clinical psychology in 1949, at least 13 national conferences have been convened to examine issues in training for practice in psychology, all based on the assumption that extensive training is required to develop professional skills in psychotherapy, psychodiagnosis, and related professional functions. This assumption is challenged by a large body of research that fails to show any relationship between training and efficacy in common forms of practice. Educators of professional psychologists are urged to heed the challenge closely and examine its implications critically. At the same time, educators of researchers in psychology are encouraged to examine common assumptions about the nature of practice in psychology and to consider conceptions of professional work that emphasize reflection in action and disciplined inquiry, rather than psychotherapy and psychodiagnosis, as defining features. Education for practice is neither science nor art, but a profession in itself. When the educational process is approached from this vantage point, novel opportunities for systematic investigation emerge. Decisive studies of the appropriate kind have yet to be done.

Neutral amino acid transport characterization of isolated luminal and abluminal membranes of the blood-brain barrier

The neutral amino acid carrier composition of luminal and abluminal membranes of the blood-brain barrier has been studied using isolated membrane vesicles. Phenylalanine was carried almost exclusively by a high affinity (Km = 10 +/- 2 microM), Na(+)-independent amino acid transport system, presumably L1 system, that was found to be symmetrically distributed between luminal and abluminal membranes. Inhibition of phenylalanine uptake was used to determine the affinities (Ki values) toward leucine (17 +/- 3 microM), tryptophan (8 +/- 1), 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BCH) (11 +/- 2), alanine (628 +/- 117), and glutamine (228 +/- 51). Alanine was found to be transported by two Na(+)-dependent transport systems that were located exclusively on the abluminal membrane. Kinetic and inhibition experiments indicated that one of these activities was due to system A, which is probably the main route for Na(+)-dependent alanine transport (Km = 0.6 +/- 0.2 mM) under physiological conditions. The other Na(+)-dependent activity was attributed to a B(o,+)-like system based on its sensitivity toward BCH. This latter system showed greater affinity for large neutral amino acids. The affinities of these two transport systems for several other amino acids were also studied.

Biochemical discrimination between luminal and abluminal enzyme and transport activities of the blood-brain barrier

Luminal and abluminal membrane vesicles derived from bovine brain endothelial cells, the site of the blood-brain barrier, were fractionated in a discontinuous Ficoll gradient. A mathematical analysis was developed to determine the membrane distribution of membrane marker enzyme activities as well as the ratio of luminal to abluminal membrane in each fraction of the gradient. The results of this analysis indicate that gamma-glutamyl transpeptidase and amino acid transport system A are located on the luminal and abluminal membranes, respectively. Conversely, 5'-nucleotidase and alkaline phosphatase activities are evenly distributed between both membranes. Although Na+/K(+)-ATPase activity is primarily located on the abluminal membrane, approximately 25% of the activity is of luminal origin. Na+/K(+)-ATPase activities associated with each membrane showed different ouabain sensitivities, suggesting that different isoenzymes are located in luminal and abluminal membranes. The analytical procedure used in this study provides a quantitative means to determine the distribution of marker enzymes and transport proteins in partially purified membrane vesicle populations.

Nephrotic syndrome and acute renal failure associated with hepatitis A virus infection

Acute renal failure has been documented in association with hepatitis A virus (HAV) infection. This report describes a temporal relationship between HAV infection and immune complex mesangial proliferative glomerulonephritis associated with nephrotic syndrome. Animal experimental data have already shown that this is indeed a histological lesion associated with HAV infection. This case report is the first English documentation associating HAV infection with immune complex mesangial proliferative glomerulonephritis.

Parameter sensitivity of a model of viral epidemics simulated with Monte Carlo techniques. IV. Parametric ranges and optimization

A model is presented of the spread of influenza into and within a nursing home. To use this model for studies involving surveillance and vaccine efficacy, it is necessary to estimate optimal ranges of a group of parameters. Attempts to do so by manual methods proved unsatisfactory. Initial use of the methods presented in the previous three papers of this series led to points that were also unsatisfactory. However, by noting which parameters were placed at the outer surface of the chosen hypervolume, it was possible to choose new ranges and to select an optimal point in hyperspace that satisfied the epidemiologically preselected characteristics.

Neutral amino acid transport by the blood-brain barrier. Membrane vesicle studies

Endothelial cell membranes, the site of the blood-brain barrier, were obtained from the capillaries of cow brain. The luminal and abluminal membranes were separated by centrifugation on a discontinuous Ficoll gradient. Electron microscopy revealed that the membrane preparations consisted almost entirely of sealed vesicles. The release of latent enzyme activity showed that both membrane preparations were primarily right side out. Radiolabeled L-phenylalanine uptake by luminal vesicles was proportional to membrane protein concentration, with less than 10% binding. Transport was by a high affinity carrier (Km 11.8 +/- 0.1 microM, asymptotic standard error) that showed little or no stereospecificity, and was independent of Na+ or H+ gradients. Transport was inhibited by L-tryptophan, L-leucine, 2-aminobicyclo[2,2,1]heptane-2-carboxylate and D-phenylalanine, but not by N-(methylamino)-isobutyrate. Abluminal membranes showed an additional component in which a Na+ gradient accelerated the transport of both phenylalanine and N-(methylamino)-isobutyrate. These studies demonstrate the utility of membrane vesicles as a model to characterize the transport properties of the distinct membranes of the polar endothelial cells that form the blood-brain barrier.

Sudden infant death syndrome and maternal smoking

Data from Missouri for the period 1980 to 1985 suggest a dose-response relationship between smoking during pregnancy and the incidence of sudden infant death syndrome (SIDS). However, data from the National Institute of Child Health and Human Development SIDS Cooperative Epidemiological Study did not support a dose-response relationship. Neither the Missouri data nor the Cooperative Study data support a relationship between the age of occurrence of SIDS and smoking during pregnancy.

Activation of proximal tubular Na(+)-H+ exchange by angiotensin II

Stimulation of Na(+)-H+ exchange by angiotensin II (ANG II) was characterized in renal proximal tubular cells. Rabbit proximal nephron segments were incubated in the presence or absence of ANG II (5 x 10(-10) M), after which brush-border membrane vesicles (BBMV) were isolated and assayed for Na(+)-H+ antiporter activity using the acridine orange technique. Both the affinity (for sodium) and capacity of the carrier were elevated significantly (P less than 0.05) within 15 min of incubation with ANG II. To determine whether the stimulation of transport capacity involved a change in Na(+)-H+ antiporter density in the luminal membrane, binding of tritiated 5-(N-methyl-N-isobutyl)amiloride ([3H]MIA) was measured in BBMV derived from control and ANG II-treated nephron segments, following maximal stimulation. This demonstrated a significant (P less than 0.05) increase in the maximal specific binding (Bmax) of [3H]MIA binding in the ANG II-treated group compared with control, of a magnitude sufficient to account for the observed change in maximal velocity (Vmax). The data indicate that the Vmax effect is caused by an apparent increase in the number (density) of active Na(+)-H+ carriers present in the luminal membrane. Finally, to test the possibility that the observed kinetic change involves an exocytic mechanism, the effect of colchicine on ANG II-stimulated antiporter activity was examined. The increase in Vmax due to ANG II was blocked by the addition of 0.5 mM colchicine to the incubation medium, whereas colchicine alone had no significant effect on the Vmax of Na(+)-H+ kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple carriers for dipeptide transport: carrier-mediated transport of glycyl-L-proline in renal BBMV

To determine whether multiple carriers are responsible for luminal uptake of glycyl-L-proline (Gly-Pro) in the renal proximal tubule, transport of Gly-[3H]Pro was measured in brush-border membrane vesicles (BBMV). A Line-weaver-Burk analysis of Michaelis-Menten kinetics revealed the presence of two carriers: a lower affinity, higher capacity carrier (Km = 1.3 x 10(-2) M; Vmax = 4.6 x 10(-8) mol.mg-1.min-1) and a higher affinity, lower capacity carrier (Km = 2.7 x 10(-7) M; Vmax = 7.8 x 10(-13) mol.mg-1.min-1). The dipeptides Gly-Sar, beta Ala-His, and pyroGlu-His competitively inhibited the low-affinity carrier. No effect on the Km or Vmax of Gly-Pro transport in this range was seen in the presence of the dipeptides Gly-Gly or cycloHis-Pro. The high-affinity carrier exhibited a different inhibition spectrum. Competitive inhibition of Gly-Pro transport was demonstrated for the dipeptides Gly-Gly and Gly-Sar. However, none of the other peptides tested above altered Gly-Pro transport in the high-affinity range, including pyroGlu-His, which is transported by a high-affinity carrier. At both low (4 x 10(-8) M) and high (4 x 10(-3) M) concentrations, uptake of Gly-Pro was stimulated in the presence of an inwardly directed H+ gradient but was unaffected by the presence of an inward Na+ gradient. In addition, measurements in the presence of valinomycin and an outwardly directed K+ gradient strongly suggest that H(+)-stimulated uptake at both concentrations is electrogenic.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term neurologic outcome in psychogenic water drinkers with severe symptomatic hyponatremia: the effect of rapid correction

PURPOSE

The purpose of our study was to ascertain the safety of rapidly correcting acute symptomatic hyponatremia in psychogenic water drinkers, particularly in regard to any delayed adverse neurologic sequelae.

PATIENTS AND METHODS

We reviewed the medical records of all known psychogenic water drinkers (34) in our hospital from 1977 to 1989. Using seizure as a marker of severity, we identified 13 patients having a total of 27 episodes associated with severe hyponatremia. We evaluated the charts of those patients in detail to assess the mode of treatment, rate of correction, and long-term neurologic outcome. None of the patients experienced respiratory arrest before treatment, which was initiated within 2 hours of seizure.

RESULTS

For all 27 episodes, the initial serum sodium level (mean +/- SE) was 110.9 +/- 1.2 mmol/L, and the rate of correction (mean +/- SE) was 1.65 +/- 0.2 mmol/L/hour. All but one episode were corrected "rapidly" (initial correction rate of 0.7 or more mmol/L/hour) to 120 to 130 mmol/L within 12 hours. The absolute change in the serum sodium level was 15.1 +/- 1.2 mmol/L in 12 hours, 21.6 +/- 1.4 mmol/L in 24 hours, and 25.9 +/- 1.4 mmol/L in 48 hours. In no instance did therapy induce hypernatremia. All patients recovered immediately after treatment. There was no clinical or radiologic evidence of adverse neurologic sequelae immediately after treatment or after 6 years of follow-up.

CONCLUSION

In this series of male psychogenic water drinkers, early "rapid" correction of acute symptomatic hyponatremia by raising the serum sodium level 15 mmol/L in 12 hours while maintaining an absolute change in the serum sodium level of 26 mmol/L within 48 hours produced no long-term neurologic sequelae.

Low-affinity transport of pyroglutamyl-histidine in renal brush-border membrane vesicles

These studies were performed to determine if a low-affinity carrier is present in the luminal membrane of proximal tubular cells for the transport of the dipeptide, pyroglutamyl-histidine (pGlu-His). We have previously described the existence of a specific, high-affinity, low-capacity [transport constant (Kt) = 9.3 X 10(-8) M, Vmax = 6.1 X 10(-12) mol.mg-1.min-1] carrier for pGlu-His in renal brush-border membrane vesicles. In the present study, we sought to demonstrate that multiple carriers exist for the transport of a single dipeptide by determining whether a low-affinity carrier also exists for the uptake of pGlu-His. Transport of pGlu-His into brush-border membrane vesicles was saturable over the concentration range of 10(-5)-10(-3) M, yielding a Kt of 6.3 X 10(-5) M and a Vmax of 2.2 X 10(-10) mol.mg-1.min-1. Uptake was inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and carnosine but not by the tripeptide pyroglutamyl-histidyl-prolinamide. We conclude that 1) pGlu-His is transported across the luminal membrane of the proximal tubule by multiple carriers and 2) the lower affinity carrier, unlike the higher affinity carrier, is nonspecific with respect to other dipeptides.

Effects of charge on membrane processing in the proximal nephron

To examine the effects of molecular charge on membrane processing in renal tubular cells, the distribution of cationic and anionic ferritin was characterized in microperfused proximal nephron segments. During the first 7 min of proximal tubule perfusion, cationic ferritin was observed 1) bound to the brush-border membrane, 2) in apically positioned vesicles and vacuoles, 3) in lysosomes, 4) in vesicles adjacent to the basolateral plasmalemma, and 5) bound to the basolateral plasmalemma. Compared with anionic ferritin, the distribution of cationic ferritin was characterized by 1) a smaller relative grain density for lysosomes, 2) an accumulation of granules in an enlarged pool of apical cytoplasmic vesicles and vacuoles, and 3) a greater number of granules reaching the basolateral plasmalemma. During incubation directly in the presence of isolated renal cortical microvilli, binding of cationic ferritin increased significantly as pH was lowered from 8.0 to 4.5 and was greater than that of anionic ferritin, which varied little with pH. The data indicate that the molecular charge of endocytosed substances affects routing and membrane processing in proximal tubular cells, suggesting that their membrane-binding characteristics may influence transport patterns.

Carrier-mediated transport of pyroglutamyl-histidine in renal brush border membrane vesicles

These studies were performed to determine if a transmembrane carrier for pyroglutamyl-histidine (pGlu-His) is present in the luminal membrane of renal proximal tubular cells. Previous studies have suggested the intact transepithelial transport of pGlu-His, a dipeptide formed by the hydrolysis of luteinizing hormone-releasing hormone by enzymes associated with the brush border in the proximal nephron. With the use of a renal brush border membrane vesicle preparation, pGlu-His showed H+-stimulated, Na-independent, saturable transport into an osmotically active space. High-pressure liquid chromatographic analysis of both the intravesicular and extravesicular fluids indicated intact uptake of the dipeptide. The transport constant (Kt) and Vmax for pGlu-His transport were 9.3 X 10(-8) M and 6.1 X 10(-12) mol.mg-1.min-1, respectively. Transport of pGlu-His was not inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and N-beta-alanyl-L-histidine, which have been previously shown to be transported into renal brush border vesicles via a single, low-affinity, high-capacity, Na-independent, and H+-stimulated peptide carrier. In addition, the gamma-glutamyl-containing peptides gamma-glutamyl-histidine and N(N-L-gamma-glutamyl-L-cysteinyl)glycine and the tripeptide pyroglutamyl-histidyl-prolinamide were without an inhibitory effect. In contrast, transport of pGlu-His was inhibited by the dipeptide pyroglutamyl-alanine. This study demonstrates the existence of a high-affinity, low-capacity H+ cotransport system for pGlu-His in the proximal tubular luminal plasmalemma, which appears to be specific for pyroglutamyl-containing dipeptides. The data indicate that multiple dipeptide carriers are present in the proximal nephron.

Outcomes of pregnancy with an IUD in situ--a population based case-control study

Use of IUDs was examined among 962 women whose pregnancy was terminated at the University Hospital of Trondheim, Norway during 1983. Ectopic pregnancy was significantly more often diagnosed among women with an IUD in place at conception compared to non-users (7.8% vs 1.3%, p less than 0.01). Despite removal of the IUD during the first trimester, women who became pregnant with an IUD in situ had spontaneous abortion more often than non-users (15.6% vs 7.0%, p less than 0.05). The causal significance of these findings will require further investigation. The small number of ectopic pregnancies subsequent to an IUD contraceptive failure in relation to the number of all pregnancies within the same time frame may explain the lack of a demonstrable link between increasing IUD use and increasing rates of ectopic pregnancy.

Contraluminal uptake of serine in the proximal nephron

Rabbit proximal nephron segments were microperfused in vitro to determine whether active contraluminal uptake of serine occurs in the renal proximal tubule during bath-to-lumen transport (influx) of the L- and D-isomers in the convoluted (pars convoluta) and straight (pars recta) segments. It is known that several amino acids are actively reabsorbed in the proximal nephron by a mechanism involving co-transport with sodium at the luminal membrane. There is some evidence that certain amino acids may also be accumulated across the contraluminal membrane by an energy-dependent mechanism, indicating that net reabsorption is the result of two oppositely directed active transport processes. During in vitro microperfusion of rabbit proximal nephron segments in this study, inward movement of L- and D-serine occurred in a bath-to-cell direction against a concentration gradient in the range 305-2735:1, indicating active uptake at the contraluminal membrane. The concentration gradients were maintained during influx of both isomers of serine in the proximal tubule. L-Serine accumulation by tubular cells was similar in the pars convoluta and recta, and significantly greater than that of D-serine, which was the same in both regions of the proximal tubule. The data support the conclusion that renal handling of serine involves active contraluminal uptake of the L- and D-isomers in both regions of the proximal tubule, and suggest that contraluminal events play an important role in renal handling of amino acids.

Diphtheria-tetanus-pertussis immunization and sudden infant death: results of the National Institute of Child Health and Human Development Cooperative Epidemiological Study of Sudden Infant Death Syndrome risk factors

The possible association between diphtheria-pertussis-tetanus (DTP) immunization and the subsequent occurrence of sudden infant death has been examined using data from the National Institute of Child Health and Human Development (NICHD) Sudden Infant Death Syndrome (SIDS) Cooperative Epidemiological Study, a large multicenter, population-based, case-control study. In a preliminary report based on the first 400 eligible singleton SIDS victims and 800 matched living control infants, no temporal association between SIDS and DTP immunization was found. From the final sample of 800 eligible singleton SIDS victims, 95% (n = 757) were defined as definitely or probably having died of SIDS on the basis of pathology data. Data from these 757 case infants and their corresponding control infants (n = 1,514) are presented in this report. Two control infants, both living, were randomly selected for each case infant: an age-matched control A and an age-, race-, and low birth weight-matched control B. Overall, case infants were less likely to have received any DTP immunization. Only 39.8% of case infants had received at least one DTP immunization compared to 55.0% of control A infants and 53.2% of control B infants. Based on maternal interviews and postnatal medical records, 1.8% of case infants (five infants) immunized with DTP died within the first 24 hours following immunization. Similarly, 5.0% of control A infants (n = 21) and 2.2% of control B infants (n = 9) had been immunized within 24 hours of the maternal interview, which represents the comparable time frame for the age-matched control infants. These results confirm the earlier preliminary findings from the NICHD SIDS Cooperative Epidemiological Study and suggest that DTP immunization is not a significant factor in the occurrence of SIDS.

Effects of D-amino acid substituents on degradation of LHRH analogues by proximal tubule

Less than Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, the luteinizing hormone-releasing hormone, LHRH, is degraded in renal proximal tubules (PT) in vivo (rat) and in vitro (rabbit) to less than Glu-His (2), less than Glu-His-Trp (3), and less than Glu-His-Trp-Ser (4). LHRH may be cleaved by endopeptidases simultaneously at multiple bonds, or initially at Ser4-Tyr5 followed by carboxypeptidase hydrolysis of 4 to 3 and then 2. To distinguish between these mechanisms, [3H]LHRH analogues were incubated with rabbit renal brush-border membranes (BBM), microinfused into PT in vivo or in vitro, and products were analyzed by HPLC. [D-Ser4]LHRH was not cleaved at D Ser4-Tyr5 but yielded less than Glu-His-Trp-D-Ser-Tyr-Gly as the major metabolite plus 2 and 3. [D-Trp6]LHRH was cleaved by BBM and PT to 2 and 3, but not to 4. [D-Ser4, D-Trp6]LHRH was not cleaved by BBM, but was degraded to 2 by PT in vivo. Thus, D-amino acid substituents altered the expected cleavage pattern of these analogues. [3H]LHRH was cleaved by BBM or by endopeptidase-24.11 from porcine PT to metabolites 2, 4, small amounts of 3, and less than Glu-His-Trp-Ser-Tyr-Gly, but cleavage was strongly inhibited by the specific inhibitor phosphoramidon. Thus, normally LHRH may be cleaved in PT by endopeptidase-24.11 to 2 and 4, and by angiotensin I-converting enzyme to 3, its known cleavage site.

Electrochemical determination of hemoglobin, hematocrit, and hemolysis

Novel electrochemical methods have been developed for determination of total hemoglobin, hematocrit, and detection of hemolysis in whole blood. Hemoglobin is measured through its peroxidase activity, a fluoride ion-selective electrode being used to monitor the rate of fluoride ion production from the oxidation of an organofluorine compound. Results agree well with those obtained with the cyanmethemoglobin method (r = 0.970). Hematocrit is determined from the ratio of the sodium ion concentrations measured with an ion-selective electrode before and after lysis of the erythrocytes. Results by this and the microhematocrit method correlated well (r = 0.987). Hemolysis in a whole-blood sample is detected by using an oxygen electrode to measure the oxygen released when hemoglobin in plasma is oxidized.

Electrochemical determination of hemoglobin, hematocrit, and hemolysis

Novel electrochemical methods have been developed for determination of total hemoglobin, hematocrit, and detection of hemolysis in whole blood. Hemoglobin is measured through its peroxidase activity, a fluoride ion-selective electrode being used to monitor the rate of fluoride ion production from the oxidation of an organofluorine compound. Results agree well with those obtained with the cyanmethemoglobin method (r = 0.970). Hematocrit is determined from the ratio of the sodium ion concentrations measured with an ion-selective electrode before and after lysis of the erythrocytes. Results by this and the microhematocrit method correlated well (r = 0.987). Hemolysis in a whole-blood sample is detected by using an oxygen electrode to measure the oxygen released when hemoglobin in plasma is oxidized.