Opportunities for Cellular Rejuvenation in Alzheimer's Disease: How Epigenetic Reprogramming and Chaperone-Mediated Autophagy Are Enabling Next Generation Therapeutic Approaches.

Age remains the largest risk factor in the development of neurodegenerative diseases such as Alzheimer's disease (AD). Numerous cellular hallmarks of aging contribute to the advancement of the pathologies associated with neurodegenerative disease. Not all cellular hallmarks of aging are independent and several fall into the broader category of cellular rejuvenation, which captures returning cells to a more youthful, improved functional state. Cellular rejuvenation is quickly becoming a hot topic in the development of novel therapeutic modalities for a range of diseases. Therapeutic approaches utilizing cellular rejuvenation technologies are rapidly advancing and will represent the next phase of AD therapeutics. This review focuses on two important processes, epigenetic reprogramming, and chaperone-mediated autophagy (CMA) that play a critical role in aging and in neurodegenerative diseases and the potential therapeutic approaches (gene therapy, small molecule) towards targeting these mechanisms. In aging and in AD, epigenetic changes on DNA (e.g., hypermethylation on CpG islands) lead to alterations in gene expression. Partial epigenetic reprogramming utilizes transcription factors to remove the epigenetic marks and to rejuvenate cells to a more youthful state. During aging and in neurodegenerative disorders, CMA becomes impaired resulting in a buildup of proteins known to be associated with neurodegenerative pathologies. The protein buildups lead to aggregates that preclude proteostasis leading to cell toxicity. Small-molecule CMA activators restore proteostasis and limit toxicity enabling cellular rejuvenation.

Phase-retrieval method for measuring small contact angles of pentane on water.

Pentane drops on a water surface are predicted to have contact angles of the order of 1 degree or less in the phase of frustrated complete wetting. We have developed an optical method of measuring such small contact angles, applicable to cases where the refractive indices of the substrate and adsorbate are very similar and the fluid dynamics do not allow delay between image acquisitions, by using phase retrieval to map the surface profile of the drops. It is empirically shown that, with our method, a difference of nanometer order can be achieved for the phase-retrieved dimensions relative to their expected value. Results agree with numerical predictions by Weiss and Widom [Physica A292, 137 (2001)PHYADX0378-437110.1016/S0378-4371(00)00619-1].

Disparities in eating disorder diagnosis and treatment according to weight status, race/ethnicity, socioeconomic background, and sex among college students.

OBJECTIVE: Eating disorders (EDs) present a significant threat to the health of adolescents and young adults, yet remain under-diagnosed and under-treated at a population-level. EDs have historically been thought to afflict "skinny, white, affluent girls" (the SWAG stereotype). As such, higher-weight individuals, racial/ethnic minorities, those from socioeconomically disadvantaged backgrounds, and males may not recognize their need for treatment, may not be properly screened for EDs, and/or may not be referred to treatment. METHOD: Using large-scale survey data from the healthy bodies study, we examined variations in prevalence of perceived need for ED treatment, ED diagnosis, past-year ED treatment, and treatment barriers according to weight status, race, socioeconomic background, and sex among undergraduate and graduate students with symptoms of an ED (N = 1,747). RESULTS: Among students with symptoms of an ED, 30.7% perceived a need for treatment, 10.5% had received a diagnosis, and 13.6% had received treatment in the past year. Individual characteristics were highly associated with perceived need, diagnosis, and past-year treatment. Females were more likely than males to perceive a need for treatment (OR = 1.97), to be diagnosed (OR = 4.66), and to be treated (OR = 1.64) for their ED symptoms. Socioeconomic background was associated with perceived need for treatment and past-year treatment, with students from affluent backgrounds having higher odds of perceiving need (OR = 1.52) and of receiving treatment (OR = 1.89) compared with their non-affluent peers. DISCUSSION: At a population-level, the unmet need for ED treatment disproportionately affects certain groups. Stereotypes about who develops EDs could contribute to disparities in ED treatment and outcomes.

Mechanism of Anti-rotavirus Synergistic Activity by Epigallocatechin Gallate and a Proanthocyanidin-Containing Nutraceutical.

Epigallocatechin gallate (EGCG) of green tea and the nutraceutical CystiCran®-40 (containing 40% proanthocyanidins) of the cranberry plant have been associated with antiviral activity. The purpose of this work was to determine the mechanism of antiviral synergy between each compound. Coliphage T4II (phage T4) and the rotavirus strain SA-11(RTV) were used as model virus systems. Individual and combined flavonoids structural and molecular weight analyses were performed by NMR and HPCL/MS, respectively. A suboptimal concentration of EGCG or C-40 alone or in combination reduced phage infectivity by ≤10%. Similarly, EGCG (30 µg/ml) and C-40 (25 µg/ml), respectively, reduced RTV titers by 3 and 13%. However, RTV titers were reduced by 32% (p < .05) with both flavonoids used in combination. RTV was not recognized in host cells by electron microscopy 24-h post-inoculation. NMR and HPLC/MS findings revealed significant structural and potential changes in molecular weight of the flavonoids in complex.

Evaluation of a dietary screener: the Mediterranean Eating Pattern for Americans tool.

BACKGROUND: Evidence exists for an association between accordance with a Mediterranean diet pattern and slower rates of cognitive decline. However, an 'Americanised' version of the Mediterranean diet screener is needed to assess accordance in the USA. Thus, the Mediterranean Eating Pattern for Americans (MEPA) tool was developed to assess accordance with a Mediterranean-like food pattern when time is limited. The present study aimed to determine whether the MEPA screener captured the key elements of the Mediterranean diet compared to the more comprehensive food frequency questionnaire (FFQ). METHODS: The study comprised a cross-sectional study in which 70 women completed both the VioScreen™ FFQ (Viocare, Princeton, NJ, USA) electronically and the 16-item MEPA screener, either electronically or by telephone, aiming to evaluate the inter-method reliability of the proposed screener. The convenience sample included patients (n = 49) and healthcare providers (n = 21) recruited from a tertiary care medical centre. RESULTS: The overall score from the MEPA screener correlated with corresponding overall MEPA FFQ score (ρ = 0.365, P = 0.002). Agreement between screener items and FFQ items was moderate-to-good for berries (κ = 0.47, P < 0.001), nuts (κ = 0.42, P < 0.001), fish (κ = 0.62, P < 0.001) and alcohol (κ = 0.64, P < 0.001), whereas those for olive oil (κ = 0.33, P = 0.001) and green leafy vegetables (κ = 0.36, P = 0.0021) were fair. Usual intakes of potassium, magnesium, vitamin C, saturated fat, selected carotenoids, folate and fibre derived from the FFQ varied with MEPA screener scores in the anticipated directions. CONCLUSIONS: The MEPA screener captures several components of the Mediterranean style pattern, although further testing of the MEPA screener is indicated.

Eating disorder symptoms among undergraduate and graduate students at 12 U.S. colleges and universities.

OBJECTIVES: We sought to estimate the prevalence of eating disorder symptoms in a large sample of U.S. college students and variations therein across student characteristics. METHODS: Participants were 9713 students from 12 colleges and universities participating in the Healthy Bodies Study. We used gender-stratified logistic regression to estimate bivariate correlates of elevated eating disorder symptoms, past-month objective binge eating, and past-month compensatory behaviors across student characteristics including age, degree-level, sexual orientation, race/ethnicity, first-generation status, citizenship, academic and extracurricular characteristics, and weight status. Eating disorder outcomes were based on the Eating Disorder Examination Questionnaire. RESULTS: We observed higher prevalence of objective binge eating among females relative to males (49% versus 30%, p<0.001), but similar prevalence of compensatory behaviors (31% versus 29%). Weight status was the most consistent predictor of eating disorder risk with significantly more symptoms seen among individuals with overweight and obesity. When compared to individuals with a healthy weight, those with overweight had greater eating disorder risk (males OR=3.5; females OR=2.0), binge eating (males OR=2.1; females OR=1.9), and use of compensatory behaviors (males OR=1.5; females OR=1.3). CONCLUSIONS: This study suggests smaller gender difference in prevalence of eating disorder symptoms than previously reported and identifies students with overweight/obesity as salient targets for campus-based eating disorder screening and early intervention efforts.

Utility of electronystagmography in the prediction of post-operative outcome following cochlear implantation.

OBJECTIVE: To examine the relationship between pre-operative electronystagmography and videonystagmography test results and post-operative outcomes in dizziness, auditory sensitivity and speech recognition. METHODS: A retrospective chart review was performed. Auditory sensitivity and speech perception ability were tested pre- and post-operatively in 37 adult cochlear implant recipients. Auditory sensitivity was evaluated using either pure tones (for testing with earphones) or frequency-modulated warble tones (for sound-field testing). Speech perception ability was evaluated using Northwestern University Auditory Test Number 6. RESULTS: No correlation was found between pre-operative electronystagmography test results and post-operative subjective dizziness. However, pre-operative electronystagmography testing and post-operative hearing sensitivity as measured by warble tone average (dB HL) correlated significantly at six months or later after cochlear implant activation (r  ≥  -0.34, n = 34, p < 0.05). CONCLUSION: This study, which has a level of evidence 4, demonstrates that pre-operative electronystagmography testing has a potential use in predicting post-operative outcomes in hearing sensitivity following cochlear implantation. However, larger studies are needed to confirm this novel finding.

Negative allosteric modulation of metabotropic glutamate receptor 5 results in broad spectrum activity relevant to treatment resistant depression.

Evidence suggests that 30-50% of patients suffering from major depressive disorder (MDD) are classified as suffering from treatment resistant depression (TRD) as they have an inadequate response to standard antidepressants. A key feature of this patient population is the increased incidence of co-morbid symptoms like anxiety and pain. Recognizing that current standards of care are largely focused on monoaminergic mechanisms of action (MOAs), innovative approaches to drug discovery for TRD are targeting glutamate hyperfunction. Here we describe the in vitro and in vivo profile of GRN-529, a novel negative allosteric modulator (NAM) of metabotropic glutamate receptor 5 (mGluR5). In cell based pharmacology assays, GRN-529 is a high affinity (Ki 5.4 nM), potent (IC50 3.1 nM) and selective (>1000-fold selective vs mGluR1) mGluR5 NAM. Acute administration of GRN-529 (0.1-30 mg/kg p.o.) had dose-dependent efficacy across a therapeutically relevant battery of animal models, comprising depression (decreased immobility time in tail suspension and forced swim tests) and 2 of the co-morbid symptoms overrepresented in TRD, namely anxiety (attenuation of stress-induced hyperthermia, and increased punished crossings in the four plate test) and pain (reversal of hyperalgesia due to sciatic nerve ligation or inflammation). The potential side effect liability of GRN-529 was also assessed using preclinical models: GRN-529 had no effect on rat sexual behavior or motor co-ordination (rotarod), however it impaired cognition in mice (social odor recognition). Efficacy and side effects of GRN-529 were compared to standard of care agents (antidepressant, anxiolytic or analgesics) and the tool mGluR5 NAM, MTEP. To assess the relationship between target occupancy and efficacy, ex vivo receptor occupancy was measured in parallel with efficacy testing. This revealed a strong correlation between target engagement, exposure and efficacy across behavioral endpoints, which supports the potential translational value of PET imaging to dose selection in patients. Collectively this broad spectrum profile of efficacy of GRN-529 supports our hypothesis that negative allosteric modulation of mGluR5 could represent an innovative therapeutic approach to the treatment of TRD. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.

A factor analysis approach to examining relationships among ovarian steroid concentrations, gonadotrophin concentrations and menstrual cycle length characteristics in healthy, cycling women.

STUDY QUESTION: How are ovarian steroid concentrations, gonadotrophins and menstrual cycle characteristics inter-related within normal menstrual cycles? SUMMARY ANSWER: Within cycles, measures of estradiol production are highly related to one another, as are measures of progesterone production; however, the two hormones also show some independence from one another, and measures of cycle length and gonadotrophin concentrations show even greater independence, indicating minimal integration within cycles. WHAT IS KNOWN ALREADY: The menstrual cycle is typically conceptualized as a cohesive unit, with hormone levels, follicular development and ovulation all closely inter-related within a single cycle. Empirical support for this idea is limited, however, and to our knowledge, no analysis has examined the relationships among all of these components simultaneously. STUDY DESIGN, SIZE, DURATION: A total of 206 healthy, cycling Norwegian women participated in a prospective cohort study (EBBA-I) over the duration of a single menstrual cycle. Of these, 192 contributed hormonal and cycle data to the current analysis. PARTICIPANTS/MATERIALS, SETTING, METHODS: Subjects provided daily saliva samples throughout the menstrual cycle from which estradiol and progesterone concentrations were measured. FSH and LH concentrations were measured in serum samples from three points in the same menstrual cycle and cycle length characteristics were calculated based on hormonal data and menstrual records. A factor analysis was conducted to examine the underlying relationships among 22 variables derived from the hormonal data and menstrual cycle characteristics. MAIN RESULTS AND THE ROLE OF CHANCE: Six rotated factors emerged, explaining 80% of the variance in the data. Of these, factors representing estradiol and progesterone concentrations accounted for 37 and 13% of the variance, respectively. There was some association between measures of estradiol and progesterone production within cycles; however, cycle length characteristics and gonadotrophin concentrations showed little association with any measure of ovarian hormone concentrations. LIMITATIONS, REASONS FOR CAUTION: Our summary measures of ovarian hormones may be imprecise in women with extremely long or short cycles, which could affect the patterns emerging in the factor analysis. Given that we only had data from one cycle on each woman, we cannot address how cycle characteristics may covary within individual women across multiple cycles. WIDER IMPLICATIONS OF THE FINDINGS: Our findings are generalizable to other healthy populations with typical cycles, however, may not be applicable to cycles that are anovulatory, extreme in length or otherwise atypical. The results support previous findings that measures of estradiol production are highly correlated across the cycle, as are measures of progesterone production. Estradiol and progesterone concentrations are associated with one another, furthermore. However factor analysis also revealed more complex underlying patterns in the menstrual cycle, highlighting the fact that gonadotrophin concentrations and cycle length characteristics are virtually independent of ovarian hormones. These results suggest that despite integration of follicular and luteal ovarian steroid production across the cycle, cycle quality is a multi-faceted construct, rather than a single dimension. STUDY FUNDING/COMPETING INTEREST(S): The EBBA-I study was supported by a grant from the Norwegian Cancer Society (49 258, 05087); Foundation for the Norwegian Health and Rehabilitation Organizations (59010-2000/2001/2002); Aakre Foundation (5695-2000, 5754-2002) and Health Region East. The current analyses were completed under funding from the National Institutes of Health (K12 ES019852). No competing interests declared.

Evidence for sustained elevation of IL-6 in the CNS as a key contributor of depressive-like phenotypes.

There is compelling clinical literature implicating a role for cytokines in the pathophysiology of major depressive disorder (MDD). Interleukin-6 (IL-6) and interleukin-1ß (IL-1ß) are pleiotropic inflammatory cytokines that have been reported to be elevated in patients with MDD. The present studies were undertaken to investigate the relationship between IL-6 and IL-1ß in animal models of depressive-like behavior. Analysis of brain tissue homogenates in the cortex of rats subjected to chronic stress paradigms revealed elevated levels of IL-6 protein in the absence of elevations in IL-1ß. Central administration of recombinant mouse IL-6 produced depressive-like phenotypes in mice, which were not accompanied by IL-1ß-induced increases in the brain tissue or IL-1ß-related sickness behavior typical of a general central nervous system inflammatory response. Systemic administration of fluoxetine in the presence of centrally administered IL-6 failed to produce the expected antidepressant-like response in mice relative to sham-infused controls. Further, administration of fluoxetine to mice with endogenous overexpression of brain IL-6 (MRL/MpJ-Fas(LPR/LPR) (LPR mice)) failed to produce the expected antidepressant-like effect relative to fluoxetine-treated control mice (MRL/MpJ(+/+)). Interestingly, blockade of IL-6 trans-signaling by coadministration of a gp130/Fc monomer or an anti-mouse IL-6 antibody with IL-6 prevented the IL-6-induced increases in immobility time as well as attenuated IL-6-induced increases of protein in the cortex. Taken together, these data indicate that elevations in IL-6 may have a pathophysiological role underlying depression and more specifically resistance to current classes of antidepressant medications and suggest that modulation of the IL-6 signaling pathway may have therapeutic potential for treatment-resistant depression.

Higher luteal progesterone is associated with low levels of premenstrual aggressive behavior and fatigue.

Contradictory findings show both positive and negative effect of progesterone on the premenstrual mood changes in women. Here we present the study investigating this relationship on the large sample of premenstrual women. 122 healthy, reproductive age women collected daily morning saliva samples and recorded intensity scores for the mood symptoms: irritability, anger, sadness, tearfulness, insomnia, and fatigue. Saliva samples were assayed for progesterone concentrations and mood intensity scores were used to calculate behavioral indices. Women with low Aggression/Irritability and Fatigue had consistently higher progesterone levels during the luteal phase than women with high Aggression/Irritability and Fatigue. Additionally, Aggression/Irritability and Fatigue correlated negatively with maximal progesterone value during the luteal phase. Our results demonstrated a negative effect of low progesterone level on the premenstrual mood symptoms such as aggressive behavior and fatigue in healthy reproductive age women. This supports a previously proposed model of biphasic action of progesterone metabolites on mood.

Ovarian hormones and reproductive risk factors for breast cancer in premenopausal women: the Norwegian EBBA-I study.

BACKGROUND: Ovarian hormones, parity and length of 'menarche-to-first birth' time interval are known risk factors for breast cancer, yet the associations between 17ß-estradiol, progesterone and these reproductive factors remain unclear. METHODS: A total of 204 women (25-35 years) who participated in the Norwegian EBBA-I study collected daily saliva samples for one complete menstrual cycle, and filled in a reproductive history questionnaire. Anthropometry was measured and saliva samples were analyzed for ovarian hormones. Associations between parity, the interval and ovarian hormones, and effects of hormone-related lifestyle factors were studied in linear regression models. RESULTS: Mean age was 30.7 years, and age of menarche 13.1 years. Parous women had on average 1.9 births, and age at first birth was 24.5 years. No association was observed between parity and ovarian steroids. In nulliparous women, higher waist circumference (≥ 77.75 cm) and longer oral contraceptive (OC) use (≥ 3 years) were associated with higher levels of 17ß-estradiol. Short (<10 years) versus long (>13.5 years) 'menarche-to-first birth' interval was associated with higher overall mean (P(trend) = 0.029), 47% higher maximum peak and 30% higher mid-cycle levels of 17ß-estradiol. We observed a 2.6% decrease in overall mean salivary 17ß-estradiol with each 1-year increase in the interval. CONCLUSIONS: Nulliparous women may be more susceptible to lifestyle factors, abdominal overweight and past OC use, influencing metabolic and hormonal profiles and thus breast cancer risk. Short time between 'menarche-to-first birth' is linked to higher ovarian hormone levels among regularly cycling women, suggesting that timing of first birth is related to fecundity.

Preclinical characterization of WAY-211612: a dual 5-HT uptake inhibitor and 5-HT (1A) receptor antagonist and potential novel antidepressant.

BACKGROUND AND PURPOSE: As a combination of 5-HT selective reuptake inhibitor (SSRI) with 5-HT(1A) receptor antagonism may yield a rapidly acting antidepressant, WAY-211612, a compound with both SSRI and 5-HT(1A) receptor antagonist activities, was evaluated in preclinical models. EXPERIMENTAL APPROACH: Occupancy studies confirmed the mechanism of action of WAY-211612, while its in vivo profile was characterized in microdialysis and behavioural models. KEY RESULTS: WAY-211612 inhibited 5-HT reuptake (K(i) = 1.5 nmol.L(-1); K(B) = 17.7 nmol.L(-1)) and exhibited full 5-HT(1A) receptor antagonist activity (K(i) = 1.2 nmol.L(-1); K(B) = 6.3 nmol.L(-1); I(max) 100% in adenyl cyclase assays; K(B) = 19.8 nmol.L(-1); I(max) 100% in GTPgammaS). WAY-211612 (3 and 30 mg.kg(-1), po) occupied 5-HT reuptake sites in rat prefrontal cortex (56.6% and 73.6% respectively) and hippocampus (52.2% and 78.5%), and 5-HT(1A) receptors in the prefrontal cortex (6.7% and 44.7%), hippocampus (8.3% and 48.6%) and dorsal raphe (15% and 83%). Acute or chronic treatment with WAY-211612 (3-30 mg.kg(-1), po) raised levels of cortical 5-HT approximately twofold, as also observed with a combination of an SSRI (fluoxetine; 30 mg.kg(-1), s.c.) and a 5-HT(1A) antagonist (WAY-100635; 0.3 mg.kg(-1), s.c). WAY-211612 (3.3-30 mg.kg(-1), s.c.) decreased aggressive behaviour in the resident-intruder model, while increasing the number of punished crossings (3-30 mg.kg(-1), i.p. and 10-56 mg.kg(-1), po) in the mouse four-plate model and decreased adjunctive drinking behaviour (56 mg.kg(-1), i.p.) in the rat scheduled-induced polydipsia model. CONCLUSIONS AND IMPLICATIONS: These findings suggest that WAY-211612 may represent a novel antidepressant.

High-resolution surface-plasmon resonance real-time imaging.

We use surface-plasmon resonance in a silver film to obtain high-resolution real-time images of a transparent dielectric sample in contact with it. A new aspect of the work was the use of radially polarized illumination from a LED at 530 nm to obtain speckle-free images with high spatial resolution along all orientations. The sensitivity to refractive index changes in the sample is estimated to be better than 10(-3), and the modulation transfer function out to spatial frequency 1 microm(-1) was measured.

Body fat, energy balance and estradiol levels: a study based on hormonal profiles from complete menstrual cycles.

BACKGROUND: Female fecundity is regulated by nutritional status. Although widely cited, this hypothesis is not strongly supported by empirical data from non-obese, healthy women of reproductive age. METHODS: Healthy, reproductive aged women (n = 141) from Southern Poland collected daily morning saliva samples for one complete menstrual cycle. Levels of 17-beta-estradiol were analyzed by radioimmunoassay. Anthropometric measurements, including body fat percentage, were taken randomly with respect to phase of the menstrual cycle. Energy balance was specified based on changes in body fat percentage from the beginning to the end of the observation period. RESULTS: Women with very low and high body fat had significantly lower levels of E2 compared with women with low and average body fat. In women of very low to average body fat, a 10% increase in body fat was associated with a 5-7 pmol/l increase in estradiol levels. The association between fat percentage and E2 was even stronger in women with positive energy balance, who also showed significant differences between body fat groups in estradiol profiles across whole the menstrual cycle. No such relationship was found in women with negative energy balance. CONCLUSIONS: In healthy women, we found a non-linear association between body fat and estradiol levels. Both very low and high body fat was associated with decreased estradiol levels. The relationship between estradiol and body fat was strongly influenced by women's energy balance.

Formation and stability of band patterns in a rotating suspension-filled cylinder.

We explore the phenomenon of segregation and pattern formation in the complex system of a rotating horizontal cylinder completely filled with a dilute suspension of non-Brownian particles. A general dimensionless analysis is presented, which reveals the importance of the different dimensionless parameters involved. A detailed account of the mechanism of segregation and formation of axial bands for the case of low viscosity fluids is given. According to the analysis the axial pressure gradient associated with an inertial-mode excitation within the bounded fluid is responsible for the formation of bands in interleaving nodal planes of the excitation. The question of stability of the band patterns is addressed and a phase diagram in the appropriate dimensionless space is presented.

Space-based intensity interferometer.

The intensity interferometer utilizes the correlations between intensity fluctuations to measure the coherence between light waves. Correlating the intensities of the waves and not their amplitudes can overcome the main disadvantage of the Michelson stellar interferometer in a space environment. It is shown that intensity interferometry should be applicable to stellar sources as weak as 8th magnitude, using techniques that are theoretically feasible today. Two approaches are proposed for a global sky observation campaign while minimizing spacecraft fuel consumption. In the second approach the computational interferometry observation method is introduced, which enables an observation of the full sky from a single orbit. Moreover, control laws were designed to relocate a spacecraft into the required baseline and to maintain it.

Simple beam combination for stellar interferometry.

In stellar interferometry, image quality improves significantly with the inclusion of more telescopes and the use of phase closure. We demonstrate, using first coherent and then partially coherent white light, a compact and efficient pairwise combination of 12 or more beams. The input beams are lined up and spread through a cylindrical lens into a comb of parallel ellipses, which interferes with a perpendicular copy of itself to form a matrix of interferograms between all pairs. The diagonal elements show interference of each beam with itself, for intensity calibration. The measured white-light visibilities were high and stable.

The relative kinetics of clotting and lysis provide a biochemical rationale for the correlation between elevated fibrinogen and cardiovascular disease.

BACKGROUND: Elevated plasma fibrinogen is a well known risk factor for cardiovascular disease. The mechanistic rationale for this is not known. OBJECTIVES: These studies were carried out to determine the fibrinogen concentration dependencies of clotting and lysis times and thereby determine whether these times rationalize the correlation between an increased risk of cardiovascular disease and elevated plasma fibrinogen. METHODS: The time courses of clot formation and lysis were measured by turbidity in systems comprising a) fibrinogen, thrombin and plasmin, or b) fibrinogen, thrombin, plasminogen and t-PA, or c) plasma, thrombin and t-PA. From the lysis times, k(cat) and K(m) values for plasmin action on fibrin were determined. RESULTS: The time to clot increased linearly from 2.9 to 5.6 minutes as the fibrinogen concentration increased from 1 to 9 microM and did not increase further as the fibrinogen concentration was raised to 20 microM. In contrast, the clot lysis time increased linearly over the input fibrinogen concentration range of 2 to 20 microM. A similar linear trend was found in the two systems with t-PA and plasminogen. Apparent K(m) and k(cat) values for plasmin were 1.1 +/- 0.6 microM and 28 +/- 2 min(-1), respectively. K(m) values for plasmin in experiments initiated with t-PA and plasminogen were 1.6 +/- 0.2 microM in the purified system and 2.1 +/- 0.9 microM in plasma. CONCLUSION: As the concentration of fibrinogen increases, especially above physiologic level, the balance between fibrinolysis and clotting shifts toward the latter, providing a rationale for the increased risk of cardiovascular disease associated with elevated fibrinogen.

Measurement of the spatial response of a detector pixel.

In order to measure the internal spatial response of a pixel in a detector, it is scanned by a beam smaller than its size. This becomes difficult as the wave length grows and becomes comparable to the pixel size, such as in the infra red. To overcome this difficulty, a special phase mask which makes the beam narrower was designed, constructed, and tested successfully. The mask was made from five alternating transparent rings, where the rings had half a wave phase difference between them. The beam was scanned with and without the mask in two dimensions in fine steps by a much smaller detector and its response was taken. The spot width dropped by 19% at half its height and by 42% at tenth its height, a significant narrowing. The scan was repeated with the full detector pixel. That beam scan served as a deconvolution kernel and allowed us to find the pixel point spread function (spatial response), the pixel modulation transfer function and the optical cross talk between the pixels.