Search

The thigh-cuff release (TCR) maneuver is a physiological challenge that is widely used to assess dynamic cerebral autoregulation (dCA). It is often applied in conjunction with Transcranial Doppler ultrasound (TCD), which provides temporal information of the global flow response in the brain. This established method can only yield very limited insights into the regional variability of dCA, whereas functional MRI (fMRI) has the ability to reveal the spatial distribution of flow responses in the brain with high spatial resolution. The aim of this study was to use whole-brain blood-oxygenation-level-dependent (BOLD) fMRI to characterize the spatiotemporal dynamics of the flow response to the TCR challenge, and thus pave the way toward mapping dCA in the brain. We used a data driven approach to derive a novel basis set that was then used to provide a voxel-wise estimate of the TCR associated haemodynamic response function (HRFTCR). We found that the HRFTCR evolves with a specific spatiotemporal pattern, with gray and white matter showing an asynchronous response, which likely reflects the anatomical structure of cerebral blood supply. Thus, we propose that TCR challenge fMRI is a promising method for mapping spatial variability in dCA, which will likely prove to be clinically advantageous.

Traditional models of academic leadership are based largely on managerial and transactional approaches. Such efforts frequently support status quo individual success rather than values-based leadership based on collective institutional or sustainability-centered pursuits. Evolved reward systems and leaderships modes that support collective and institution-level effort and innovations prioritizing community and sustainability require new leadership models. Innovative leadership models that transcend traditional gatekeeping are needed and four leadership modes to support innovation and collective efforts are discussed, including shared leadership that draws on distributed contributions of multiple individuals; creative or innovative leadership that requires risk-taking, experimentation, and experiential learning; qualitative leadership that is data-driven and includes evidence-based innovation; and, dynamic leadership based on demonstrated agility and ability to traverse different spaces using diverse modes of doing and thinking. Progressive leaders can move in and out of these modes in response to ecosystem needs, demands, and changes through the use of design thinking and initiatives to support innovation and sustainability in higher education. Success in evolved leadership approaches, including centering sustainability goals that impact institutions themselves and communities in which they exist, require aligning reformed leadership goals and practices with funding models and reward systems, as well as policies and institutional change strategies.

Introduction: Alcohol dependence is one of the most common substance use disorders, and novel treatment options are urgently needed. Neurofeedback training (NFT) based on real-time functional magnetic resonance imaging (rtf­MRI) has emerged as an attractive candidate for add-on treatments in psychiatry, but its use in alcohol dependence has not been formally investigated in a clinical trial. We investigated the use of rtfMRI-based NFT to prevent relapse in alcohol dependence. Methods: Fifty-two alcohol-dependent patients from the UK who had completed a detoxification program were randomly assigned to a treatment group (receiving rtfMRI NFT in addition to standard care) or the control group (receiving standard care only). At baseline, alcohol consumption was assessed as the primary outcome measure and a variety of psychological, behavioral, and neural parameters as secondary outcome measures to determine feasibility and secondary training effects. Participants in the treatment group underwent 6 NFT sessions over 4 months and were trained to downregulate their brain activation in the salience network in the presence of alcohol stimuli and to upregulate frontal activation in response to pictures related to positive goals. Four, 8, and 12 months after baseline assessment, both groups were followed up with a battery of clinical and psychometric tests. Results: Primary outcome measures showed very low relapse rates for both groups. Analysis of neural secondary outcome measures indicated that the majority of patients modulated the salience system in the desired directions, by decreasing activity in response to alcohol stimuli and increasing activation in response to positive goals. The intervention had a good safety and acceptability profile. Conclusion: We demonstrated that rtfMRI-neurofeedback targeting hyperactivity of the salience network in response to alcohol cues is feasible in currently abstinent patients with alcohol dependence.

Synchronous and anti-synchronous activity between neural elements at rest reflects the physiological processes underlying complex cognitive ability. Regional and pairwise-connectivity investigations suggest perturbations in these activity patterns may relate to widespread cognitive impairments seen in bipolar disorder (BD). Here we take a network-based perspective to more meaningfully capture interactions among distributed brain regions compared to focal measurements and examine network-cognition relationships across a range of commonly affected cognitive domains in BD in relation to healthy controls. Resting-state networks were constructed as matrices of correlation coefficients between regionally averaged resting-state time series from 86 cortical/subcortical brain regions (FreeSurferv5.3.0). Cognitive performance measured using Weschler Adult Intelligence Scale, Cambridge Automated Neuropsychological Test Battery (CANTAB) and Reading the Mind in the Eyes tests was examined in relation to whole-brain connectivity measures and patterns of connectivity using a permutation-based statistical approach. Faster response times in controls (n=49) related to synchronous activity between frontal, parietal, cingulate, temporal and occipital regions while similar response times in BD (n=35) related to anti-synchronous activity between regions of this subnetwork. Across all subjects, anti-synchronous activity between frontal, parietal, temporal, occipital, cingulate, insula and amygdala regions related to improved memory performance. No resting-state subnetworks related to intelligence, executive function, short-term memory or social cognition performance in the overall sample or in a manner that would explain deficits in these facets in BD. Our results demonstrate alterations in the intrinsic connectivity patterns underlying response timing in BD that are not specific to performance or errors on the same tasks. Across all individuals, no strong effects of resting-state global topology on cognition are found, while distinct functional networks supporting episodic and spatial memory highlight intrinsic inhibitory influences present in the resting-state that facilitate memory processing.

BACKGROUND: Functional abnormalities, mostly involving functionally specialized subsystems, have been associated with disorders of emotion regulation such as bipolar disorder (BD). Understanding how independent functional subsystems integrate globally and how they relate with anatomical cortical and subcortical networks is key to understanding how the human brain's architecture constrains functional interactions and underpins abnormalities of mood and emotion, particularly in BD.METHODS: Resting-state functional magnetic resonance time series were averaged to obtain individual functional connectivity matrices (using AFNI software); individual structural connectivity matrices were derived using deterministic non-tensor-based tractography (using ExploreDTI, version 4.8.6), weighted by streamline count and fractional anisotropy. Structural and functional nodes were defined using a subject-specific cortico-subcortical mapping (using Desikan-Killiany Atlas, FreeSurfer, version 5.3). Whole-brain connectivity alongside a permutation-based statistical approach and structure-function coupling were employed to investigate topological variance in individuals with predominantly euthymic BD relative to psychiatrically healthy control subjects.RESULTS: Patients with BD (n = 41) exhibited decreased (synchronous) connectivity in a subnetwork encompassing frontolimbic and posterior-occipital functional connections (T > 3, p = .048), alongside increased (antisynchronous) connectivity within a frontotemporal subnetwork (T > 3, p = .014); all relative to control subjects (n = 56). Preserved whole-brain functional connectivity and comparable structure-function coupling among whole-brain and edge-class connections were observed in patients with BD relative to control subjects.CONCLUSIONS: This study presents a functional map of BD dysconnectivity that differentially involves communication within nodes belonging to functionally specialized subsystems-default mode, frontoparietal, and frontolimbic systems; these changes do not extend to be detected globally and may be necessary to maintain a remitted clinical state of BD. Preserved structure-function coupling in BD despite evidence of regional anatomical and functional deficits suggests a dynamic interplay between structural and functional subnetworks. This research is supported by the Irish Research Council (IRC) Postgraduate Scholarship, Ireland awarded to Dr Leila Nabulsi, PhD and by the Health Research Board (HRA-POR324) awarded to Dr Dara M. Cannon, PhD. We gratefully acknowledge the participants and the support of the Wellcome-Trust HRB Clinical Research Facility and the Centre for Advanced Medical Imaging, St. James Hospital, Dublin, Ireland. peer-reviewed 2020-11-11

Resting-state functional magnetic resonance imaging (rs-fMRI) is a widely used technique for mapping the brain’s functional architecture, so delineating the main sources of variance comprising the signal is crucial. Low frequency oscillations (LFO) that are not of neural origin, but which are driven by mechanisms related to cerebral autoregulation (CA), are present in the blood-oxygenation-level-dependent (BOLD) signal within the rs-fMRI frequency band. In this study we use a MR compatible device (Caretaker, Biopac) to obtain a non-invasive estimate of beat-to-beat mean arterial pressure (MAP) fluctuations concurrently with rs-fMRI at 3T. Healthy adult subjects (n=9; 5 male) completed two 20-minute rs-fMRI scans. MAP fluctuations were decomposed into different frequency scales using a discrete wavelet transform, and oscillations at approximately 0.1Hz show a high degree of spatially structured correlations with matched frequency fMRI fluctuations. On average across subjects, MAP fluctuations at this scale of the wavelet decomposition explain ~ 2.2% of matched frequency fMRI signal variance. Additionally, a simultaneous multi-slice multi-echo acquisition was used to collect 10-minute rs-fMRI at three echo times at 7T in a separate group of healthy adults (n=5; 5 male). Multiple echo times were used to estimate the R2* decay at every time point, and MAP was shown to strongly correlate with this signal, which suggests a purely BOLD (i.e. blood flow related) origin. This study demonstrates that there is a significant component of the BOLD signal that has a systemic physiological origin, and highlights the fact that not all localized BOLD signal changes necessarily reflect blood flow supporting local neural activity. Instead, these data show that a proportion of BOLD signal fluctuations in rs-fMRI are due to localized control of blood flow that is independent of local neural activity, most likely reflecting more general systemic autoregulatory processes. Thus, fMRI is a promising tool for studying flow changes associated with cerebral autoregulation with high spatial resolution.

Background Alterations in functional connectivity between the nucleus accumbens (NAcc) and frontal cortices have been previously associated with the presence of psychiatric syndromes, including bipolar disorder (BD). Whether these alterations are a consequence or a risk factor for mental disorders remains unresolved. Methods This study included 35 patients with BD, 30 nonaffected siblings of patients with BD, and 23 healthy control subjects to probe functional connectivity at rest between NAcc and the rest of the brain in a cross-sectional design. Blood oxygen level–dependent time series at rest from NAcc were used as seed region in a voxelwise correlational analysis. The strength of the correlations found was compared across groups after Fisher’s Z transformation. Results We found increased functional connectivity between the NAcc and the ventromedial prefrontal cortex—comprising mainly the subgenual anterior cingulate—in patients compared with healthy control subjects. Participants at increased genetic risk but yet resilient—nonaffected siblings—showed functional connectivity values midway between the former two groups. Conclusions Our results are indicative of the potential for the connectivity between NAcc and the ventromedial prefrontal cortex to represent an endophenotype for BD.

There is increasing interest in exploring the use of functional MRI neurofeedback (fMRI-NF) as a therapeutic technique for a range of neurological conditions such as stroke and Parkinson's disease (PD). One main therapeutic potential of fMRI-NF is to enhance volitional control of damaged or dysfunctional neural nodes and networks via a closed-loop feedback model using mental imagery as the catalyst of self-regulation. The choice of target node/network and direction of regulation (increase or decrease activity) are central design considerations in fMRI-NF studies. Whilst it remains unclear whether the primary motor cortex (M1) can be activated during motor imagery, the supplementary motor area (SMA) has been robustly activated during motor imagery. Such differences in the regulation potential between primary and supplementary motor cortex are important because these areas can be differentially affected by a stroke or PD, and the choice of fMRI-NF target and grade of self-regulation of activity likely have substantial influence on the clinical effects and cost effectiveness of NF-based interventions. In this study we therefore investigated firstly whether healthy subjects would be able to achieve self-regulation of the hand-representation areas of M1 and the SMA using fMRI-NF training. There was a significant decrease in M1 neural activity during fMRI-NF, whereas SMA neural activity was increased, albeit not with the predicated graded effect. This study has important implications for fMRI-NF protocols that employ motor imagery to modulate activity in specific target regions of the brain and to determine how they may be tailored for neurorehabilitation., Highlights • Graded fMRI neurofeedback can separate self-regulation effects from general cognitive ones. • There is a significant negative BOLD response in M1 during kinaesthetic motor imagery. • SMA shows robust positive BOLD responses during kinaesthetic motor imagery. • Participants can target discrete levels of BOLD response in SMA using kinaesthetic motor imagery. • For our paradigm neurofeedback provides only minimal extra control of BOLD signals in SMA.

An urgent need to broaden diversity and support the preparation of students and faculty members along proactive pathways to research and success can be facilitated by targeted faculty development and formalization of policies built on institutional commitment, engagement, and accountability. Involvement of the faculty in building institutional diversity will recognize equity-building initiatives as valid forms of faculty scholarship and as one way to address the growing public problem of educational disparities in the STEM fields. We propose systemic, institutional transformation centered on a foundation of faculty engagement, empowerment, and reward that reflects intentionality and accountability for developing diverse institutional communities.

Background: Real-time functional magnetic resonance imaging (rtfMRI) is used for neurofeedback training (NFT). Preliminary results suggest that it can help patients to control their symptoms. This study uses rtfMRI NFT for relapse prevention in alcohol dependence.Methods/design: Participants are alcohol-dependent patients who have completed a detoxification programme within the past 6 months and have remained abstinent. Potential participants are screened for eligibility, and those who are eligible are randomly assigned to the treatment group (receiving rtfMRI NFT in addition to treatment as usual) or the control group (receiving only treatment as usual). Participants in both groups are administered baseline assessments to measure their alcohol consumption and severity of dependence and a variety of psychological and behavioural characteristics that are hypothesised to predict success with rtfMRI NFT. During the following 4 months, experimental participants are given six NFT sessions, and before and after each session various alcohol-related measures are taken. Participants in the control group are given the same measures to coincide with their timing in the experimental group. Eight and 12 months after the baseline assessment, both groups are followed up with a battery of measures. The primary research questions are whether NFT can be used to teach participants to down-regulate their brain activation in the presence of alcohol stimuli or to up-regulate their brain activation in response to pictures related to healthy goal pursuits, and, if so, whether this translates into reductions in alcohol consumption. The primary outcome measures will be those derived from the functional brain imaging data. We are interested in improvements (i.e., reductions) in participants’ alcohol consumption from pretreatment levels, as indicated by three continuous variables, not simply whether or not the person has remained abstinent. The indices of interest are percentage of days abstinent, drinks per drinking day, and percentage of days of heavy drinking. General linear models will be used to compare the NFT group and the control group on these measures.Discussion: Relapse in alcohol dependence is a recurring problem, and the present evaluation of the role of rtfMRI in its treatment holds promise for identifying a way to prevent relapse.Trial registration: ClinicalTrials.gov Identifier: NCT02486900, registered on 26 June 2015.

Melatonin and its autonomic regulation serve important physiological functions. We recently demonstrated that stimulation of beta-adrenergic receptors only increases nighttime arylalkylamine N-acetyltransferase (Aa-Nat, the rate-limiting enzyme in melatonin synthesis) mRNA levels in mouse pineal gland in vitro, which suggests that pineal clocks may gate Aa-Nat gene expression. In the present study, our data reveal that cAMP analog increased Aa-Nat at any time of day but only in the presence of ionomycin. Using Fura-2AM in ratiometric calcium measurements, we show that isoproterenol stimulation increased intracellular free calcium levels at night, contrary to previous reports. Further, intra- or extracellular calcium depletion suppressed the isoproterenol-induced calcium responses as well as Aa-Nat gene expression. These results suggest calcium may be a critical factor in isoproterenol-induced Aa-Nat gene expression, which may be limited in the daytime. We also found that basal intracellular calcium levels were lower during the night and responses to isoproterenol and KCl depolarization were more robust. In addition, pineals of Cryptochrome mutant mice exhibited no significant difference between day and nighttime basal calcium or isoproterenol response. Together, these results suggest that basal calcium levels in the pineal may be controlled by the endogenous pineal clock, which may influence calcium dynamics, cellular homeostasis and sensitivity to external stimulation. Although the mechanism underlying Aa-Nat gene expression has been well studied, the role of calcium as a link between the pineal clock and Aa-Nat gene expression has been underestimated in rodent pineals.

We captured, marked, and recaptured southern short-tailed shrews (Blarina carolinensis) during a 30-month livetrapping study in a woodlot in Jackson County, Illinois, to compare aspects of their life history with those of the northern short-tailed shrew (B. brevicauda). A total of 106,496 trap checks (15,782 trap nights) resulted in 3,430 captures of 313 B. carolinensis from February 1996 through August 1998. Trapping mortality was only 18 individuals. Sex ratio did not differ from 1:1. Estimated population density peaked at 57 individuals/ha in late summer and autumn then declined during winter. Recruitment, including birth and immigration, peaked in spring and late summer each year. Individuals entering the population in the spring and early summer had higher survival rates than those entering in the autumn. A weak correlation was found between recruitment and precipitation, and between population density and humidity. Shrew activity (timing of captures) showed significant relationships with light condition and season. During summer, shrews were caught more frequently at night. In the winter, they were captured more frequently during the day. Capture rate was negatively related to precipitation and positively related to humidity. Population dynamics and activity patterns were similar to those of B. brevicauda.

Ca2+ channel subtypes expressed by dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) were studied using whole cell patch-clamp recordings and blockers selective for different channel types (L, N, and P/Q). Nimodipine (Nim, 2 μM), ω-conotoxin GVIA (Ctx, 1 μM), or ω-agatoxin IVA (Atx, 50 nM) blocked 27, 36, and 37% of peak whole cell Ca2+ channel current, respectively, indicating the presence of L-, N-, and P-type channels. Nim blocked approximately twice as much Ca2+ channel current near activation threshold compared with Ctx or Atx, suggesting that small depolarizations preferentially opened L-type versus N- or P-type Ca2+ channels. N- and L-channels in DA neurons opened over a significantly more negative voltage range than those in rat dorsal root ganglion cells, recorded from using identical conditions. These data provide an explanation as to why Ca2+-dependent spontaneous oscillatory potentials and rhythmic firing in DA neurons are blocked by L-channel but not N-channel antagonists and suggest that pharmacologically similar Ca2+ channels may exhibit different thresholds for activation in different types of neurons.

Human African trypanosomiasis (HAT, sleeping sickness) is a devastating disease caused by infection with Trypanosoma brucei ssp. These hemoflagellates invade the central nervous system (CNS) and induce meningo-encephalitis, neuronal demyelination, blood-brain-barrier (BBB) dysfunction, peri-vascular infiltration, astrocytosis and apoptosis. The molecular basis of these manifestations is unclear. We previously reported T. brucei-induced apoptosis in cerebella and brain-stem nuclei in mice at peak parasitemia. Here, we identify and characterize a trypanosome apoptotic factor (TAF) expressed by T. brucei that mediates apoptosis in mouse-brain and human-brain vascular endothelial cells (HBVEC). Molecular, biochemical and apoptotic assays, coupled with surface enhanced laser desorption ionization (SELDI), and protein database analyses were utilized to show that TAF is a soluble, non-serum, parasite-derived, heat-labile protein that causes DNA laddering and apoptosis in HBVEC. Protein-chip assay analysis of the SELDI spectrum of infected mouse serum and procyclic culture supernatants revealed a single major peak at 8652.7 Da. Further database analysis indicated that the TAF may be a procyclin or procyclin derivative. A synthetic 27 mer peptide (ProEP2-1), corresponding to a region common to EP procyclins (EP2-1), induced apoptosis in HBVEC and in cerebella of mice similar to that induced in T. brucei-infected mice. Western blot analysis utilizing an anti-procyclin monoclonal antibody (mAb) revealed that TAF is present in infected but not uninfected brain tissue lysates. Furthermore, this mAb blocked T. brucei- and ProEP2-1-induced apoptosis in HBVEC in vitro. We conclude that T. brucei TAF or its derivative(s) play a major role in the apoptosis associated with HAT pathology.

We have demonstrated that continuous administration of a gonadotropin-releasing hormone agonist (GnRH-Ag) in vivo suppressed progesterone production and induced apoptosis in the corpus luteum (CL) of the pregnant rat. To investigate the mechanism(s) by which progesterone secretion is suppressed and apoptosis is induced in the luteal cells, we studied nitric oxide (NO) as a messenger molecule for GnRH action. Rats were treated individually on Day 8 of pregnancy with 5mg/day of GnRHAg for 4, 8, and 24 h. GnRH-Ag decreased the production of progesterone and pregnenolone 8 and 24 h after the administration. Corresponding with the reduction in these steroid hormones, luteal NO concentrations decreased at 8 and 24 h. Western blotting and immunohistochemical studies of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and neuronal nitric oxide synthase (nNOS) in the CL demonstrated that administration of GnRH-Ag was associated with a marked decrease in eNOS and iNOS compared with sham controls at 4 and 8 h, but nNOS did not change throughout the experimental period. We demonstrated, for the first time, the presence of nNOS protein in the CL of the pregnant rat. To determine if this suppressive action of GnRH-Ag is directly on the CL, luteal cells were treated with GnRH-Ag for 4, 8, 12, and 24 h in vitro. Progesterone and NO concentrations in the media decreased at 8 and 12 h after the treatment and recovered at 24 h. Western blots revealed that eNOS and iNOS decreased in luteal cells treated with GnRH-Ag compared with controls at 4 and 8 h. These results demonstrate that suppression of luteal NO synthesis by GnRH-Ag is direct and leads to a decrease in the luteal production and release of progesterone and pregnenolone and thus suggest that GnRH could induce luteolysis in pregnant rats via NO.

Les AA. analysent la frequence avec laquelle les differents groupes de mammiferes (taxa) apparaissent sur les etiquettes de bouteilles de biere ou de cidre a travers le monde, afin de determiner les tendances des taxa representes. L'analyse montre que les frequences constatees pour les ordres et familles de mammiferes ne correspondent pas aux proportions des especes qu'ils contiennent ou de leur distribution geographique, mais a la perception des differents types de mammiferes par le public. Les images de mammiferes qui projettent les attributs de la force, du pouvoir, ou de la tenacite sont preferees comme symboles de commercialisation. Selon les AA., cette preference pour les attributs generalement associes avec la megafaune charismatique reflete la perception generale de la faune mammifere. Les rongeurs et les chauves souris, malgre leur distribution mondiale et le fait qu'ils soient facilement reconnaissables, sont souvent connotes negativement. De la meme maniere, les especes disparues vehiculent en general une image negative. La perception culturelle et l'empathie publique associee envers la megafaune mammifere se retrouvent clairement dans la publicite et les strategies marketing des brasseries.

This study was designed to determine the cellular distribution and pattern of expression for the mitochondria-associated protein, prohibitin, during the transitional stages of follicular differentiation within the rat ovary. Immunohistochemical staining techniques were used on frozen sections to examine the localization of prohibitin to preantral, antral, preovulatory, and atretic follicles. Prohibitin localization was also determined in corpus luteum from adult rats, in addition to those from infant and juvenile ovaries, before and after gonadotropin stimulation. Western and Northern blotting techniques were used for qualitative and quantitative assessment of prohibitin expression levels within the ovary. Prohibitin was localized within granulosa cells of infant and juvenile ovaries in a relatively heterogeneous staining pattern. The oocyte also exhibited robust prohibitin expression at all stages of follicular development. In addition, strong prohibitin expression was evident in the corpus luteum as well as in follicles undergoing atresia. Additional data derived from studies involving a GnRH-agonist indicate that increases in prohibitin protein expression correlate with the initial events of apoptosis. Collectively, these results support a growth regulatory role for prohibitin within the rat ovary. Therefore, we propose that prohibitin may serve as an important regulator of granulosa cell fate during follicular development. Anat Rec 256:40–48, 1999. © 1999 Wiley-Liss, Inc.

The need to increase the number of college graduates in Science, Technology, Engineering, and Mathematics (STEM) disciplines is a national issue. As the demographics of the United States’ population grow increasingly more diverse, the recognition that students of color are disproportionately under-represented among those individuals successful at completing STEM degrees requires exigent and sustained intervention. Although a range of efforts and funding have been committed to increasing the success of under-represented minority (URM) students at primarily white, or majority, institutions, widespread progress has been slow. Simultaneously, Historically Black Colleges and Universities and Minority Serving Institutions have demonstrated disproportionate successes in graduating URM students with STEM degrees and those that proceed to completing graduate-level degrees in the sciences. The differential successes of particular institutions with promoting the achievement of diverse individuals in obtaining academic STEM degrees suggest that with committed and strategic leadership, advancements in creating academic communities that promote the success of a diverse range of students in STEM can be achieved in part through assessing and mitigating environmental barriers that impede success at majority institutions. In this paper, we address issues related to the engagement of URM students in majority settings and describe some efforts that have shown success for promoting diversity in STEM and highlight continuing issues and factors associated with cultivating diversity in academic STEM disciplines at majority institutions. Recommended efforts include addressing academic assistance, professional and cultural socialization issues and institutional environmental factors that are associated with success or lack thereof for URMs in STEM.

The mechanism of L-leucine regulation of ilvGMEDA is thought to be by ribosome-mediated attenuation that is dependent upon the concentration of Leu-tRNA(Leu) which results from leucyl-tRNA synthetase (LeuRS) activity. The requirement for LeuRS activity in attenuation control was tested in an Escherichia coli K-12 strain containing a temperature-sensitive LeuRS and the ilvGMEDA operon with an active ilvGM. Growth of this strain at 30 degrees C followed by a shift to 37 degrees C to inactivate the LeuRS revealed that ilvGM expression decreased at the restrictive temperature whereas the downstream gene expression was slightly elevated. We suggest that ilvGM does not respond to a deattenuation signal, and that, possibly, a secondary repression/derepression mechanism exists.

This study was designed to determine the cellular and ultrastructural distribution of the gonadotropin-releasing hormone (GnRH) and the relative expression of its mRNA in the oviduct of rats during different time points (days 7, 9, 16, and 20) of pregnancy. Immunofluorescent localization and confocal microscopic techniques were used to determine the cellular distribution of GnRH in the oviduct. Immunogold electron microscopy indicated its localization at the ultrastructural level, and real-time PCR was used to study the expression pattern of GnRH mRNA in the oviduct during pregnancy. In general, GnRH was localized within the epithelial cells lining the oviductal lumen at each selected time point. A strong correlation between the fluorescence intensity of GnRH-immunoreactive cells and the relative expression of GnRH mRNA was noted on days 7 and 16, followed by a plateau by day 20. At the ultrastructural level, uniform labeling of colloidal gold particles was observed in secretory vesicles and lamella of the luminal epithelium as well as the lumen of the oviduct. Collectively, these results demonstrate for the first time that the oviductal epithelium synthesizes and secretes the decapeptide GnRH during pregnancy in rats, which may have a possible role in postimplantation embryonic development and the maintenance of pregnancy.

We document the first known occurrences of the cotton mouse (Peromyscus gossypinus) in Illinois since 1909. Mean hind foot length and body mass of cotton mice from study areas in two counties were significantly greater than sympatric white-footed mice (P. leucopus). The cotton mice occurred in forested bottomland habitat.

We have demonstrated that continuous administration of a gonadotropin-releasing hormone agonist (GnRH-Ag) in vivo suppressed progesterone production and induced apoptosis in the corpus luteum (CL) of the pregnant rat. To investigate the mechanism(s) by which progesterone secretion is suppressed and apoptosis is induced in the luteal cells, we studied nitric oxide (NO) as a messenger molecule for GnRH action. Rats were treated individually on Day 8 of pregnancy with 5 microg/day of GnRH-Ag for 4, 8, and 24 h. GnRH-Ag decreased the production of progesterone and pregnenolone 8 and 24 h after the administration. Corresponding with the reduction in these steroid hormones, luteal NO concentrations decreased at 8 and 24 h. Western blotting and immunohistochemical studies of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and neuronal nitric oxide synthase (nNOS) in the CL demonstrated that administration of GnRH-Ag was associated with a marked decrease in eNOS and iNOS compared with sham controls at 4 and 8 h, but nNOS did not change throughout the experimental period. We demonstrated, for the first time, the presence of nNOS protein in the CL of the pregnant rat. To determine if this suppressive action of GnRH-Ag is directly on the CL, luteal cells were treated with GnRH-Ag for 4, 8, 12, and 24 h in vitro. Progesterone and NO concentrations in the media decreased at 8 and 12 h after the treatment and recovered at 24 h. Western blots revealed that eNOS and iNOS decreased in luteal cells treated with GnRH-Ag compared with controls at 4 and 8 h. These results demonstrate that suppression of luteal NO synthesis by GnRH-Ag is direct and leads to a decrease in the luteal production and release of progesterone and pregnenolone and thus suggest that GnRH could induce luteolysis in pregnant rats via NO.

Prohibitin is an evolutionary conserved protein that is associated with cellular differentiation, atresia, and luteolysis in the rat ovary. However, the specific cellular location and function of prohibitin in ovarian cells has not been clearly elucidated. To characterize the expression of prohibitin during cell proliferation, differentiation, and cell death, we have successfully established a temperature-sensitive granulosa cell line, designated RGA-1. At a permissive temperature of 33 C, RGA-1 cells proliferate, but revert to a differentiated phenotype at a nonpermissive temperature of 39 C. Significant inductions of prohibitin mRNA and protein expression were observed in the differentiated phenotype when compared with proliferating cells. Differentiated RGA-1 cells were found to express inhibin alpha- and beta-transcripts, as well as steroidogenic acute regulatory protein and peripheral-type benzodiazepine receptor proteins in a manner reminiscent of steroidogenic functional responses observed in primary differentiated granulosa cells. Prohibitin expression correlated well with the expression of these steroidogenic proteins. At 39 C, RGA-1 cells also displayed increases in p53 protein levels, indicative of growth arrest in the nonproliferating cells. Confocal and electron microscopic examinations revealed increased prohibitin localization to the mitochondria at 39 C, along with changes in mitochondrial size and shape. These changes were accompanied by marked reductions in cytochrome c oxidase subunit II levels and in unit mitochondrial transmembrane potential. In addition, cell fractionation studies demonstrated that the prohibitin protein was mainly localized to the mitochondrial membrane. Collectively, these findings suggest a role for prohibitin in mitochondrial structure and function during growth and differentiation in ovarian granulosa cells. Prohibitin expression may also be indicative of mitochondrial destabilization during apoptosis-related events.

SUMMARY This study was designed to determine the pattern of expression and cellular distribution of the steroidogenic acute regulatory protein (StAR) during the transitional stages of follicular differentiation in rat ovary. Using specific antisera against the StAR, immunohistochemistry, Western blotting, and immunoprecipitation analyses provide evidence confirming the localization and expression of StAR in granulosa cells (GCs) of juvenile rat ovaries before and after PMSG treatment. The results also show that StAR expression occurs in theca intersitial cells surrounding preantral, antral, and larger antral follicles in adult diestrous ovaries. Furthermore, we have demonstrated heterogenous StAR immunoreactivity in the granulosa cell layers and cells of the corpora lutea. A novel finding presented here is that, during ongoing growth and differentiation of the follicle, the immunoreactivity of StAR tends to shift from the GC of early antral follicles to the theca cell layers in the adult. The spatiotemporal changes or shifts in StAR expression and cellular localization also coincide with the appearance of more acidic isoforms of the 30-kD protein, as determined by two-dimensional gel electrophoresis. Although the functional implications of these observations remain unclear, the acute temporal changes in StAR expression and localization may not only reflect the dynamic steroidogenic capacity of follicular cells but may also support a possible role for FSH in the induction of follicular maturation. (J Histochem Cytochem 47:769‐776, 1999)

The role of isoleucyl-, valyl-, and leucyl-tRNA synthetases in attenuation of the ilvEDA operon was examined. The results indicate that the activities of isoleucyl- and valyl-tRNA synthetases are necessary to maintain attenuation of the ilvEDA operon. Leucyl-tRNA synthetase activity is nonessential for attenuation. These studies imply that uncharged tRNAIle and tRNAVal each may cause deattenuation.

Spontaneous mutants (146) of Escherichia coli K-12 were selected that were resistant to inhibition of growth by 1.2 mM L-valine (Valr). The Valr isolates, containing acetohydroxy acid synthase resistant to feedback inhibition by L-valine (AHASr), were classed according to cotransduction of the mutation with leu. Several mutations resulting in an AHASr phenotype were found to be cotransducible with glyA. However, no mutations causing a Valr phenotype were linked to ilv. AHAS activity was more closely examined in representatives of three classes of mutants with Valr linked to leu, labeled ilv-660, ilv-661, and ilv-662. The ilvE503 allele in E. coli K-12, known to cause a two- to three-fold derepression of AHAS, was found to affect regulation of synthesis of both valine-sensitive AHAS (AHASs) and AHASr in the mutants containing ilv-660 and ilv-661, whereas it affected repression of AHASs, only, in the mutant containing ilv-662. Further, both AHASs and AHASr in the ilv-661 mutant were repressed by valine, whereas valine did not repress AHASr synthesis in the strain carrying ilv-660 and only partially repressed AHASr in the strain carrying ilv-662. Unexpectedly, AHASr synthesis in strains carrying ilv-660 or ilv-662 was repressible by leucine. The ilv-660 locus appears to be similar in position to ilvH and encodes a product that confers valine-sensitivity upon AHAS activity in the wild-type E. coli K-12. The ilv-660 and ilv-662 loci may normally encode products that influence both the feedback sensitivity of AHAS and control of AHAS biosynthesis.

The assay for transaminase B (EC 2.6.1.6) activity, developed by D. E. Duggan and J. A. Wechsler (1973, Anal. Biochem. 51 , 67–79) has been modified to allow for the measurement of activity in Escherichia coli cells made permeable by cetyltrimethylammonium bromide (CETAB). A concentration of 10 mg% CETAB was found to be most effective in treating the cells without having a significant effect on transaminase B activity. Extraction of the dinitrophenylhydrazone of 2-oxoisovalerate by toluene was not affected by the CETAB treatment. We further report that the Na 2 CO 3 extraction step is not required to measure color formed by the dinitrophenylhydrazone of 2-oxoisovalerate. This CETAB-treated cell assay is accurate to study transaminase B activity through most of the logarithmic phase of growth of Escherichia coli .