bluuebunny/crossref_metadata_2025 huggingface dataset:
Survival ofEnterococcus faecalisin infected dentinal tubules after root canal filling with different root canal sealersin vitro
Authors: Saleh I. M. , Ruyter I. E. , Haapasalo M. , Ørstavik D.
Published: March 2004

Aim To investigate the ability of different endodontic sealers and calcium hydroxide to kill bacteria in experimentally infected dentinal tubules.

Methodology Fifty‐six human root segments were enlarged to size 2 (ISO size 090) Largo®Peeso Reamer. After treatment with 17% EDTA and 5% NaOCl for 4 min each, the specimens were infected withEnterococcus faecalisfor 3 weeks. The roots were divided into eight groups and filled with gutta‐percha and AH Plus (AH); Grossman's sealer (GS); Ketac‐Endo (KE); Apexit (AP); RoekoSeal Automix (RSA); or RoekoSeal Automix with an experimental primer (RP), or calcium hydroxide (CH) only. One group of specimens was left unfilled for control (CT). Following storage in humid conditions at 37 °C for 7 days, the root canals were re‐established with new sterile Largo®size 2. Dentine samples from each canal were then collected using a sterile size 5 (ISO size 150) Largo®Peeso Reamer. The number of colony‐forming units (CFU) was determined for each sample.

Results The mean log10CFU in all test groups was significantly lower (P < 0.05) than that in the CT group. Root filling with AH and GS killed bacteria (mean CFU = 0) in the dentinal tubules. The mean log10CFU for the CH group (0.53) was lower than that of RSA, AP, RP and KE (1.36, 1.40, 1.46 and 1.94, respectively), but only the difference between the CH and the KE groups was statistically significant (P < 0.05).

Conclusion Root fillingsin vitrowith gutta‐percha and AH or GS were effective in killingE. faecalisin dentinal tubules. Other endodontic sealers, as well as CH, were less effective.
The poplar K+ channel KPT1 is associated with K+ uptake during stomatal opening and bud development
Authors: Langer Katharina , Levchenko Victor , Fromm Jörg , Geiger Dietmar , Steinmeyer Ralf , Lautner Silke , Ache Peter , Hedrich Rainer
Published: March 2004

To gain insights into the performance of poplar guard cells, we have measured stomatal conductance and aperture, guard cell K+ content and K+‐channel activity of the guard cell plasma membrane in intact poplar leaves. In contrast to Arabidopsis, broad bean and tobacco grown under same conditions, poplar stomata operated just in the dynamic range – any change in conductance altered the rate of photosynthesis. In response to light, CO2 and abscisic acid (ABA), the stomatal opening velocity was two to five times faster than that measured for Arabidopsis thaliana, Nicotiana tabacum and Vicia faba. When stomata opened, the K+ content of guard cells increased almost twofold, indicating that the very fast stomatal opening in this species is mediated via potassium uptake. Following impalement of single guard cells embedded in their natural environment of intact leaves with triple‐barrelled microelectrodes, time‐dependent inward and outward‐rectifying K+‐channel‐mediated currents of large amplitude were recorded. To analyse the molecular nature of genes encoding guard cell K+‐uptake channels, we cloned K+‐transporter Populustremula (KPT)1 and functionally expressed this potassium channel in a K+‐uptake‐deficient Escherichia coli mutant. In addition to guard cells, this K+‐transporter gene was expressed in buds, where the KPT1 gene activity strongly correlated with bud break. Thus, KPT1 represents one of only few poplar genes associated with bud flush.
Special education services and school performance in a regional cohort of low‐birthweight infants at age nine
Authors: Pinto‐Martin Jennifer , Whitaker Agnes , Feldman Judith , Cnaan Avital , Zhao Huaqing , Rosen‐Bloch Joan , McCulloch Dawn , Paneth Nigel
Published: March 2004

Previous research has shown that low birthweight is a predictor of several adverse educational outcomes, including special educational placement, by middle school age. Most low‐birthweight follow‐up studies that have extended to school age have focused on very small infants – < 1500 or < 1000 g; less is known of the school age outcomes for infants with only moderately low birthweight (1500–2000 g).

This study examines the prevalence of special educational placement and the relationship of such placement to grade retention, verbal and performance scores on tests of general intelligence, reading and maths achievement scores and classroom hyperactivity among low‐birthweight children. In a regional birth cohort of 1105 infants born between 1984 and 1987 and weighing 500–2000 g, 868 children were available for follow‐up at age nine. Information on special education placement as well as grade retention, intelligence, academic achievement and classroom behaviour was available on 645 (74% completion rate).

Nearly a third of the cohort was classified as needing special education. Special education placement followed a birthweight gradient, occurring among 29.3% of children with birthweights 1500–2000 g, among 32.5% in children 1000–1500 g and 49.4% in children < 1000 g. Among children in special education, a similar birthweight gradient was found for maths achievement and hyperactivity, but not for reading achievement or IQ scores. Among children not in special education, only maths achievement showed such a decline with birthweight.

A substantial proportion of low‐birthweight children, including those of moderate low birthweight, receive special education services, although the need is greatest among those with the lowest birthweights. Maths achievement declined with birthweight regardless of educational placement. The medical and social risk factors that accompany low birthweight and may account for these findings, require further study.
Auxin activates KAT1 and KAT2, two K+‐channel genes expressed in seedlings of Arabidopsis thaliana
Authors: Philippar Katrin , Ivashikina Natalya , Ache Peter , Christian May , Lüthen Hartwig , Palme Klaus , Hedrich Rainer
Published: March 2004

The transcript abundance of the K+‐channel gene ZMK1 (Zea mays K+ channel 1) in maize coleoptiles is controlled by the phytohormone auxin. Thus, ZMK1 is thought to function in auxin‐regulated coleoptile elongation, as well as during gravitropism and phototropism. To investigate related growth phenomena in the dicotyledonous plant Arabidopsis thaliana, we screened etiolated seedlings for auxin‐induced K+‐channel genes. Among the members of the Shaker‐like K+ channels, we thereby identified transcripts of the inward rectifiers, KAT1 (K+ transporter of Arabidopsis thaliana) and KAT2, to be upregulated by auxin. The phloem‐associated KAT2 was localised in cotyledons and the apical part of etiolated seedlings. In contrast, the K+‐channel gene KAT1 was expressed in the cortex and epidermis of etiolated hypocotyls, as well as in flower stalks. Furthermore, KAT1 was induced by active auxins in auxin‐sensitive tissues characterised by rapid cell elongation. Applying the patch‐clamp technique to protoplasts of etiolated hypocotyls, we correlated the electrical properties of K+ currents with the expression profile of K+‐channel genes. In KAT1‐knockout mutants, K+ currents after auxin stimulation were characterised by reduced amplitudes. Thus, this change in the electrical properties of the K+‐uptake channel in hypocotyl protoplasts resulted from an auxin‐induced increase of active KAT1 proteins. The loss of KAT1‐channel subunits, however, did not affect the auxin‐induced growth rate of hypocotyls, pointing to compensation by residual, constitutive K+ transporters. From gene expression and electrophysiological data, we suggest that auxin regulation of KAT1 is involved in elongation growth of Arabidopsis. Furthermore, a role for KAT2 in the auxin‐controlled vascular patterning of leaves is discussed.
Arabidopsis pdr2 reveals a phosphate‐sensitive checkpoint in root development
Authors: Ticconi Carla A. , Delatorre Carla A. , Lahner Brett , Salt David E. , Abel Steffen
Published: March 2004

Plants have evolved complex strategies to maintain phosphate (Pi) homeostasis and to maximize Pi acquisition when the macronutrient is limiting. Adjustment of root system architecture via changes in meristem initiation and activity is integral to the acclimation process. However, the mechanisms that monitor external Pi status and interpret the nutritional signal remain to be elucidated. Here, we present evidence that the Pi deficiency response, pdr2, mutation disrupts local Pi sensing. The sensitivity and amplitude of metabolic Pi‐starvation responses, such as Pi‐responsive gene expression or accumulation of anthocyanins and starch, are enhanced in pdr2 seedlings. However, the most conspicuous alteration of pdr2 is a conditional short‐root phenotype that is specific for Pi deficiency and caused by selective inhibition of root cell division followed by cell death below a threshold concentration of about 0.1 mm external Pi. Measurements of general Pi uptake and of total phosphorus (P) in root tips exclude a defect in high‐affinity Pi acquisition. Rescue of root meristem activity in Pi‐starved pdr2 by phosphite (Phi), a non‐metabolizable Pi analog, and divided‐root experiments suggest that pdr2 disrupts sensing of low external Pi availability. Thus, PDR2 is proposed to function at a Pi‐sensitive checkpoint in root development, which monitors environmental Pi status, maintains and fine‐tunes meristematic activity, and finally adjusts root system architecture to maximize Pi acquisition.
A novel approach to plastid transformation utilizes the phiC31 phage integrase
Authors: Lutz Kerry A. , Corneille Sylvie , Azhagiri Arun K. , Svab Zora , Maliga Pal
Published: March 2004

Thus far plastid transformation in higher plants has been based on incorporation of foreign DNA in the plastid genome by the plastid's homologous recombination machinery. We report here an alternative approach that relies on integration of foreign DNA by the phiC31 phage site‐specific integrase (INT) mediating recombination between bacterial and phage attachment sites (attB and attP, respectively). Plastid transformation by the new approach depends on the availability of a recipient line in which an attB site has been incorporated in the plastid genome by homologous recombination. Plastid transformation involves insertion of an attP vector into the attB site by INT and selection of transplastomic clones by selection for antibiotic resistance carried in the attP plastid vector. INT function was provided by either expression from a nuclear gene, which encoded a plastid‐targeted INT, or expressing INT transiently from a non‐integrating plasmid in plastids. Transformation was successful with both approaches using attP vectors with kanamycin resistance or spectinomycin resistance as the selective marker. Transformation efficiency in some of the stable nuclear INT lines was as high as 17 independently transformed lines per bombarded sample. As this system does not rely on the plastid's homologous recombination machinery, we expect that INT‐based vectors will make plastid transformation a routine in species in which homologous recombination rarely yields transplastomic clones.
Investigation of the ways in which patients’ reports of their satisfaction with healthcare are constructed
Authors: Edwards Carol , Staniszewska Sophie , Crichton Nicola
Published: March 2004

Abstract  A characteristic feature of patient satisfaction research is the consistently high level of satisfaction recorded. More reliable and relevant inquiry tools are constantly being developed, but underlying psychological and social pressures that could promote such a consistent and undiscriminating response have been little investigated. Williams et al. (1998) explored the phenomenon and concluded that, by considering issues of duty and culpability, patients could make allowances for poor care, and avoid evaluating it negatively. Their study was in community mental health. This study follows up their work within elective orthopaedic surgery, and investigates the pressures promoting such apparent transformation of opinion. Using a longitudinal design, and in‐depth qualitative interviews, the patient's process of reflection was explored. Three psycho‐social pressures were identified that appear to work together to make the transformation of opinion almost the default process. They are: the relative dependency of patients within the healthcare system; their need to maintain constructive working relationships with those providing their care; and their general preference for holding a positive outlook. It is suggested that, while it is the patient's prerogative to re‐interpret the quality of their care positively, it is not the prerogative of the inquirer to accept this re‐interpretation as representative of the patient's experience. Methods of inquiry are needed which access something of patients’ development of opinion, and thereby something of their initial, often more negative, untransformed responses to their healthcare experiences.
Moving forward? Complementary and alternative practitioners seeking self‐regulation
Authors: Welsh Sandy , Kelner Merrijoy , Wellman Beverly , Boon Heather
Published: March 2004

Abstract  Complementary and alternative medicine (CAM) occupations continue to struggle towards achieving professional status, especially in the form of statutory regulation. Many consider professional status a worthwhile goal for CAM occupations, yet it is a process fraught with tensions. In this paper we present in‐depth interview data from the leaders of three CAM groups (naturopaths, traditional Chinese medicine practitioners acupuncturists, and homeopaths) in Ontario, Canada that demonstrate four main strategies used by these groups to professionalize. The strategies discussed are related to how the knowledge base of each group is organised and transmitted. These strategies include: improving educational standards, improving practice standards, engaging in peer‐reviewed research and increasing group cohesion. At the core of these strategies is the demarcation of who is qualified to practice, and a signalling to ‘outsiders’, such as medicine and the government, that practitioners are qualified and legitimate. Across the three groups, the leaders referred to the inclusion of medical science as a basis for distinguishing between ‘science’ and ‘non‐science’ as well as who should practice and who should not. We highlight how internal battles over the infusion of medical science into the knowledge base are part of the process for establishing legitimacy for the three CAM groups in our study. We end with a brief discussion of the implications of these internal battles over medical science knowledge for the future of CAM groups.
General and Culturally Specific Factors Influencing Black and White Rape Survivors' Self-Esteem
Authors: Neville Helen A. , Oh Euna , Spanierman Lisa B. , Heppner Mary J. , Clark Mary
Published: March 2004

Grounded in a culturally inclusive ecological model of sexual assault recovery framework, the influence of personal (e.g., prior victimization), rape context (e.g., degree of injury during last assault), and postrape response factors (e.g., general and cultural attributions, rape related coping) on self-esteem of Black and White college women, who were survivors of attempted and completed rape, were examined. As predicted, Black and White women identified similar general variables (e.g., general attributions) as important in the recovery process. Black women, however, identified a cultural factor (i.e., cultural attributions) as more important in influencing their reactions to the last rape compared to their White counterparts. Using path analysis, findings from this cross-sectional study indicated that severity of the last assault and prior victimization were related to lower self-esteem indirectly through avoidance coping strategies, and victim blame attributions for the latter. Results also suggested that the link between cultural attributions and self-esteem was explained through victim blame attributions, primarily for Black participants. The model accounted for 26% of variance in self-esteem.
Cardioprotection by chronic estrogen or superoxide dismutase mimetic treatment in the aged female rat
Authors: Xu Yi , Armstrong Stephen J. , Arenas Ivan A. , Pehowich Daniel J. , Davidge Sandra T.
Published: March 2004

Aging and estrogen deficiency increase the risk for developing cardiovascular disease (CVD). Oxidative stress has also been implicated in the pathophysiology of CVD and in ischemia-reperfusion (I/R) injury. We tested the hypothesis that chronic in vivo estrogen treatment or superoxide inhibition with the SOD mimetic EUK-8 improves cardiac functional recovery after I/R in the aged female rat. Sprague-Dawley rats (12–14 mo) were used as follows: intact ( n = 6), ovariectomized + placebo (OVX, n = 6), OVX + EUK-8 (EUK-8, 3 mg/kg, n = 6), and OVX + estrogen (1.5 mg/pellet, 60 days release, n = 6). Perfused isolated hearts were subjected to global ischemia (25 min) followed by reperfusion (40 min). Functional recovery after I/R and myocardial protein expression of NADPH oxidase (p22, p67, and gp91 phox), inducible nitric oxide synthase (NOS), endothelial NOS, and SOD1, as well as nitrotyrosine levels (as a marker for peroxynitrite), were assessed. Compared with OVX, EUK-8 and estrogen markedly improved functional recovery after I/R, which was associated with a decrease in NADPH oxidase expression and nitrotyrosine staining. However, estrogen increased inducible NOS expression, whereas EUK-8 had little effect. There were no significant changes in endothelial NOS and SOD1 expression among the groups. These results indicate that EUK-8 and estrogen improved cardiac recovery after I/R. Given the controversy surrounding hormone replacement therapy, EUK-8 may be an alternative to estrogen in protecting those at risk for myocardial ischemia in the aging population.
Enhanced heart rate variability and baroreflex index after stress and cholinesterase inhibition in mice
Authors: Joaquim Luis F. , Farah Vera M. , Bernatova Iveta , Fazan Rubens , Grubbs Robert , Morris Mariana
Published: March 2004

Experiments tested the effect of stress coupled with cholinesterase inhibition on blood pressure, heart rate, baroreflex index, and variability in time and frequency domain in conscious mice. The objective was to determine whether cholinergic systems interact with stress to alter cardiovascular responses. Male C57BL/6J mice with arterial catheters were exposed to 3-day treatments: 1) intermittent shaker stress, 2) pyridostigmine (10 mg·kg−1·day−1); or 3) combined pyridostigmine and stress. Pyridostigmine reduced blood cholinesterase (−33%) with no added effects of stress. Twenty-four-hour blood pressure recordings showed that there were no differences in blood pressure and heart rate with the treatments. Pulse interval standard deviation was greatly increased in the pyridostigmine/stress group compared with stress or pyridostigmine groups (11.0 ± 1.4, 5.0 ± 0.9, and 7.5 ± 0.9 ms, respectively). Spectral analysis showed two distinct components for pulse interval variability (low and high frequency). Variability in the low-frequency range was greatly enhanced in the pyridostigmine/stress group, seen as a doubling of the power (9.5 ± 1.7, 3.3 ± 0.9, and 5.0 ± 0.6 ms for pyridostigmine/stress, stress and pyridostigmine groups, respectively). Baroreflex sensitivity was also increased in the pyridostigmine/stress group (3.6 ± 0.5 compared with 1.8 ± 0.3 and 1.7 ± 0.5 ms/mmHg in the stress and pyridostigmine groups, respectively). There was no difference in blood pressure variability or its spectral components. Results demonstrate that there are potent interactions between a mild stressor and cholinesterase inhibition seen as an accentuation of low-frequency variability in pulse interval time series, probably associated with baroreflex input and autonomic drive.
Preoptic hypothalamic warming suppresses laryngeal dilator activity during sleep
Authors: McGinty Dennis , Metes Agnes , Alam Md. Noor , Megirian David , Stewart Darya , Szymusiak Ron
Published: March 2004

Upper airway dilator activity during sleep appears to be diminished under conditions of enhanced sleep propensity, such as after sleep deprivation, leading to worsening of obstructive sleep apnea (OSA). Non-rapid eye movement (NREM) sleep propensity originates in sleep-active neurons of the preoptic area (POA) of the hypothalamus and is facilitated by activation of POA warm-sensitive neurons (WSNs). We hypothesized that activation of WSNs by local POA warming would inhibit activity of the posterior cricoarytenoid (PCA) muscle, an airway dilator, during NREM sleep. In chronically prepared unrestrained cats, the PCA exhibited inspiratory bursts in approximate synchrony with inspiratory diaphragmatic activity during waking, NREM, and REM. Integrated inspiratory PCA activity (IA), peak activity (PA), and the lead time (LT) of the onset of inspiratory activity in PCA relative to diaphragm were significantly reduced in NREM sleep and further reduced during REM sleep compared with waking. Mild bilateral local POA warming (0.5–1.2°C) significantly reduced IA, PA, and LT during NREM sleep compared with a prewarming NREM baseline. In some animals, effects of POA warming on PCA activity were found during waking or REM. Because POA WSN activity is increased during spontaneous NREM sleep and regulates sleep propensity, we hypothesize that this activation contributes to reduction of airway dilator activity in patients with OSA.
Human ACE I/D polymorphism is associated with individual differences in exercise heat tolerance
Authors: Heled Yuval , Moran Daniel S. , Mendel Liran , Laor Arie , Pras Elon , Shapiro Yair
Published: March 2004

We hypothesized that there is an association between the angiotensin I-converting enzyme (ACE) insertion (I)/deletion (D) polymorphism with the variability in exercise heat tolerance in humans. Fifty-eight Caucasian men were exposed to a 2-h exercise heat-tolerance test. We analyzed the association between their heat-tolerance levels with the ACE DD ( n = 25) and I+ ( n = 33) genotypes and with various anthropometrical parameters and aerobic fitness. It was found that the relative changes in body core temperature, heat storage, and heart rate during the 120-min exposure to exercise heat stress was consistently lower in the I+ genotype group compared with the DD genotype group (0.8 ± 0.2 vs. 1 ± 0.1°C, P < 0.05; 17.7 ± 1.8 vs. 19.8 ± 1.3 W/M2, P < 0.05; and 33 ± 7 vs. 44 ± 5 beats/min, respectively, P = 0.06). No significant association was found between heat strain response and the anthropometrical measurements or aerobic fitness in the various genotype groups. We suggest that the ACE I+ polymorphism may be considered as a possible candidate marker for increased heat tolerance.
Mapping From Motor Cortex to Biceps and Triceps Altered By Elbow Angle
Authors: Graziano Michael S. A. , Patel Kaushal T. , Taylor Charlotte S. R.
Published: March 2004

This experiment used cortical microstimulation to probe the mapping from primary motor cortex to the biceps and triceps muscles of the arm in monkeys. The mapping appeared to change depending on the angle at which the elbow was fixed. For sites in the dorsal part of the arm and hand representation, the effects of stimulation were consistent with initiating a movement of the elbow to an extended angle. Stimulation evoked more triceps activity than biceps activity, and this difference was largest when the elbow was fixed in a flexed angle. For sites in the ventral part of the arm and hand representation, stimulation had the opposite effect, consistent with initiating a movement of the elbow to a flexed angle. For these sites, stimulation evoked more biceps activity than triceps activity, and the difference was largest when the elbow was fixed in an extended angle. For sites located in intermediate positions, stimulation evoked an intermediate effect consistent with initiating a movement of the elbow to a middle, partially flexed angle. For these sites, when the elbow was fixed at a flexed angle, the evoked activity was largest in the triceps, and when the elbow was fixed at an extended angle, the evoked activity was largest in the biceps. These effects were obtained with 400-ms-long trains of biphasic pulses presented at 200 Hz and 30 μA. They were also obtained by averaging the effects of individual, 30-μA pulses presented at 15 Hz. How this stimulation-evoked topography relates to the normal function of motor cortex is not yet clear. One hypothesis is that these results reflect a cortical map of desired joint angle.
In situ measurement of growth stress in alumina scale
Authors: Specht E. D. , Tortorelli P. F. , Zschack P.
Published: March 2004

Stress in the early stages of growth has been measured in α-Al2O3 (alumina) scales formed on FeCrAl- and NiAl-based alloys during heating in air at 1000 °C to 1200 °C. Scale thickness ranges from 0.5 to 5 μm, times from 5 to 720 min. Stress was measured using the multiple-tilt method. In order to measure the thinnest scales at the earliest times, focused, monochromatic synchrotron radiation was used for high intensity, and a fixed, small angle of incidence was used along with an appropriate wavelength to maximize scattering from the film relative to the background from the substrate. Depending on the composition, transient tensile stresses of up to 1.2 GPa were observed, with maximum stress at times ranging from >10 h at 1000 °C to <10 min at 1200 °C. Thermal stresses induced by an abrupt temperature change were found to relax much more quickly, suggesting that the kinetics observed during isothermal growth reflect a dynamic competition between stress generation and stress relaxation. These results challenge commonly accepted models of growth stress in scales that predict that a compressive stress will be generated as the metal converts to a larger-volume oxide in a constrained location such as an interface. The observed tensile stress may be due to another mechanism altogether (e.g., grain coalescence), or to the conversion of a transitional Al2O3 to the equilibrium α-Al2O3 phase. For one composition, transitional Al2O3 is observed during the period of tensile stress
X-ray microdiffraction study of the half-V-shaped switching liquid crystal
Authors: Takada Kazuhiro , Noma Takashi , Togano Takeshi , Mukaide Taihei , Iida Atsuo
Published: March 2004

Local layer structures and their formation process in a half-V-shaped switching ferroelectric liquid crystal (HV-FLC) were investigated by means of synchrotron X-ray microdiffraction. The HV-FLC is a FLC that has a cholesteric–chiral smectic C (Ch–SmC*) phase transition sequences. X-ray microdiffraction measurements revealed that the SmC* phase in the HV-FLC was composed of asymmetric chevron and inclined-bookshelf structures. In addition, temperature-controlled X-ray diffraction measurements showed that the transient layer structures appeared during the Ch to SmC* phase transition.
Fos modulates myeloid cell survival and differentiation and partially abrogates the c-Myc block in terminal myeloid differentiation
Authors: Shafarenko Marianna , Amanullah Arshad , Gregory Bernard , Liebermann Dan A. , Hoffman Barbara
Published: March 2004

Previously, we have shown that Fos/Jun transcription factor complexes function as positive modulators of myeloid differentiation. Fos, which is stably induced during normal myeloid differentiation, is not induced upon differentiation of M1 myeloblastic leukemia cells. Establishing M1 cells that express a β-estradiol-conditional FosER chimera, we show that in the absence of the differentiation inducer interleukin-6 (IL-6), Fos expression in M1 myeloblasts promoted apoptotic cell death, entailing cytochrome c release and caspase-9 activation. In contrast, in the presence of IL-6, Fos-mediated apoptosis was abrogated, and Fos promoted terminal differentiation, increasing the sensitivity of M1 cells to be induced for differentiation by IL-6. Fos-mediated apoptosis was accelerated by deregulated c-Myc. Furthermore, restoring Fos expression in M1 partially abrogated the block imparted by deregulated c-Myc on the myeloid differentiation program, increased the sensitivity of the cells to be induced for differentiation, and curtailed their leukemic phenotype. These data provide evidence that Fos/Jun transcription factor complexes play a role in modulating both myeloid cell survival and differentiation and suggest that genetic lesions that alter Fos expression may cooperate with deregulated c-Myc in leukemogenesis. (Blood. 2004;103:4259-4267)
Gene silencing by lentivirus-mediated delivery of siRNA in human CD34+ cells
Authors: Schomber Tibor , Kalberer Christian P. , Wodnar-Filipowicz Aleksandra , Skoda Radek C.
Published: March 2004

To derive an efficient system for gene silencing in human hematopoietic stem cells (HSCs) we modified a lentiviral vector for small interfering RNA (siRNA) delivery. For this purpose, an H1 promoter-driven siRNA expression cassette was introduced into a lentiviral vector, and the p53 mRNA was chosen as a target for siRNA-mediated gene silencing. Using the recombinant lentivirus we infected human cord blood-derived CD34+ cells and obtained a transfection efficiency of up to 50%, as determined by expression of enhanced green fluorescent protein (EGFP). In EGFP-positive long-term culture-initiating cell (LTC-IC)- and colony-forming unit cell (CFU-C)-derived cells, we observed a reduction of p53 mRNA of up to 95%. Importantly, this reduction remained stable during several weeks of cell culture. Furthermore, p53 gene silencing resulted in decreased p21 mRNA levels and reduced the sensitivity of CD34+ cells toward the cytotoxic drug etoposide. Thus, lentiviral delivery of siRNA can allow for efficient and stable gene silencing in human HSCs and will be very valuable for further gene function studies. (Blood. 2004;103:4511-4513)
Somatic inactivation of Nf1 in hematopoietic cells results in a progressive myeloproliferative disorder
Authors: Le Doan T. , Kong Namie , Zhu Yuan , Lauchle Jennifer O. , Aiyigari Abigail , Braun Benjamin S. , Wang Endi , Kogan Scott C. , Le Beau Michelle M. , Parada Luis , Shannon Kevin M.
Published: March 2004

The NF1 tumor suppressor gene encodes a guanosine triphosphotase (GTPase)-activating protein that negatively regulates Ras signaling and is inactivated in a subset of juvenile myelomonocytic leukemias (JMMLs). Adoptive transfer of fetal liver cells from Nf1 mutant mice models JMML; however, this system has important limitations as a platform for performing biologic and preclinical studies. We have exploited the interferon-inducible Mx1-Cre transgene to ablate a conditional mutant Nf1 allele in hematopoietic cells. Somatic inactivation of Nf1 induces a myeloproliferative disorder with 100% penetrance that is associated with a sub-acute clinical course, tissue infiltration by myeloid cells, hypersensitivity to granulocyte-macrophage colony stimulating factor, hyperproliferation, and resistance to apoptosis. These Mx1-Cre, Nf1flox/flox mice establish a tractable experimental model for testing therapeutics and for identifying mutations that cooperate with hyperactive Ras in myeloid leukemogenesis. (Blood. 2004;103:4243-4250)
Management of depression in later life
Authors: Baldwin Robert , Wild Rebecca
Published: March 2004

Both antidepressants and psychological treatments are effective in the management of late-life depression. Nevertheless, there remains a considerable challenge to improve the prognosis for depression in older people. Endlessly increasing the range of antidepressants does not seem to be the answer, so attention is turning to new combinations of treatments and new ways of delivering care and improving treatment uptake. Collaboration between specialist and primary care, case management and multifaceted interventions are currently the most exciting prospects. There is good evidence for the role of both medication and psychological treatment in keeping the patient well after recovery.
Conditional Regulation of Neurosteroid Sensitivity of GABAA Receptors
Authors: BRUSSAARD ARJEN B. , KOKSMA JAN‐JURJEN
Published: March 2004

Abstract: Nongenomic gonadal steroid feedback to oxytocin containing neurons in the supraoptic nucleus of the hypothalamus is mediated via the neurosteroid allopregnanolone (3α‐OH‐DHP) that acts as an allosteric modulator of the postsynaptic GABAA receptors. We found evidence to support the idea that neurosteroids not only potentiate GABAA receptor function but also prevent its suppression by PKC. In addition, we found that neurosteroid sensitivity of GABAA receptor itself is dependent on the balance between endogenous phosphatase and PKC activity and not, as previously suggested, on subunit composition changes of the GABAA receptor. These data imply that native GABAA receptors are only sensitive to 3α‐OH‐DHP if there is endogenous phosphatase activity. In contrast, when, due to endogenous release of oxytocin in the hypothalamus, the intracellular balance is shifted from high phosphatase activity toward a higher level of PKC‐dependent phosphorylation, this leads to 3α‐OH‐DHP‐insensitivity of the GABAA receptors. How the regulatory mechanisms of the GABAA receptor physiology for the hypothalamus may also account for alterations in GABA transmission observed in other brain areas is discussed.
Neurosteroid Biosynthesis in the Human Brain and Its Clinical Implications
Authors: STOFFEL‐WAGNER BIRGIT
Published: March 2004

Abstract: This paper summarizes the current knowledge concerning the biosynthesis of neurosteroids in the human brain, the enzymes mediating these reactions, their localization, and the putative effects of neurosteroids. The presence of the steroidogenic enzymes cytochrome P450SCC, aromatase, 5α‐reductase, 3α‐hydroxysteroid dehydrogenase, and 17β‐hydroxysteroid dehydrogenase in the human brain has now been firmly established by molecular biological and biochemical studies. Their presence in the cerebral cortex and in the subcortical white matter indicates that various cell types, either neurons or glial cells, are involved in the biosynthesis of neuroactive steroids in the brain. The following functions are attributed to specific neurosteroids: modulation of GABAA, N‐methyl‐d‐aspartate (NMDA), nicotinic, muscarinic, serotonin (5‐HT3), kainate, glycine and sigma receptors, neuroprotection and induction of neurite outgrowth, dendritic spines, and synaptogenesis. We still do not know whether and how the steroidogenic enzymes are involved in the pathophysiology of the nervous system. The first clinical investigations in humans produced evidence for an involvement of neuroactive steroids in conditions such as fatigue during pregnancy, premenstrual syndrome, postpartum depression, catamenial epilepsy, and depressive disorders. Further and improved knowledge of the biochemical pathways of neurosteroidogenesis and their actions on the brain may enable new perspectives in the understanding of the physiology of the human brain as well as in the pharmacological treatment of its disturbances.
Neuroprotection by Estrogen in Animal Models of Global and Focal Ischemia
Authors: MERCHENTHALER ISTVAN , DELLOVADE TAMMY L. , SHUGHRUE PAUL J.
Published: March 2004

Abstract: Estrogen has been demonstrated to protect against brain injury, neurodegeneration, and cognitive decline. Furthermore, estrogen seems to specifically protect cortical and hippocampal neurons from ischemic injury. Here our data evaluating the neuroprotective effects of estrogens, the selective estrogen receptor modulators (SERMs), and estrogen receptor α‐ and β‐selective ligands in animal models of ischemic injury are discussed. In rats and mice, the middle cerebral artery occlusion (MCAO) model was used as models representing cerebrovascular stroke, while in gerbils the two‐vessel occlusion model, resenting acute heart attack, was used. Using focal ischemia in ovariectomized ERαKO, ERβKO, and wild‐type mice, we clearly established that the ERα subtype is the critical ER‐mediating neuroprotection in mouse focal ischemia. Because of the characteristic blood supply of the gerbil, the gerbil global ischemia model was used to evaluate the neuroprotective effects of estrogen, SERMs, and ERα‐ and ERβ‐selective compounds in the hippocampus. Analysis of neurogranin mRNA, a marker of viability of hippocampal neurons, with in situ hybridization, revealed that estrogen treatment resulted in a complete protection in the CA1 regions not only when administered before, but also when given 1 hour after occlusion. Our in vivo binding studies with 125I‐estrogen in gerbils revealed the presence of nuclear estrogen binding sites primarily in CA1 neurons, but not in the CA3 region, as we saw in rats and mice. Together, these observations demonstrate that estrogen protects from ischemic injury in both the focal and global ischemia models by acting primarily via classical nuclear receptors.
An ICI 182,780‐Sensitive, Membrane‐Related Estrogen Receptor Contributes to Estrogenic Neuroprotective Actions against Amyloid‐Beta Toxicity
Authors: MARTIN R , GUERRA B , MORALES A , DÍAZ M , ALONSO R
Published: March 2004

Abstract: Although estrogen (E2)‐related neuroprotection has been repeatedly demonstrated in different models, the involvement of non‐classical estrogen receptors (ERs) in this activity remains unclear. Using SN56 murine cholinergic cell line from the basal forebrain, we present evidence indicating that an ER associated with the plasma membrane participates in estrogen‐dependent reduction of neuronal death induced by amyloid‐β peptide (Aβ) toxicity. Exposure to either E2 or estradiol‐horseradish peroxidase (E‐HRP) for 15 min significantly reduced Aβ‐induced cell death. This effect was decreased by the ER antagonist ICI 182,780 as well as by MC‐20 antibody directed to a region neighboring the ligand‐binding domain of ERa. Using MC‐20 antibody in unpermeabilized SN56 cells, we detected a protein at the plasma membrane region. The binding of impermeant forms of E2, E‐HRP, and E‐BSA‐FITC to specific sites of SN56 plasma membrane was blocked by pre‐incubation with E2, ICI 182,780, and MC‐20 antibody in a concentration‐dependent manner. Thus, a membrane‐related ER that shares some structural homologies with ERα may participate in estrogen‐mediated neuroprotection.
Neurosteroids in the Retina
Authors: GUARNERI P , CASCIO C , RUSSO D , D'AGOSTINO S , DRAGO G , GALIZZI G , DE LEO G , PICCOLI F , GUARNERI M , GUARNERI R
Published: March 2004

Abstract: Steroids may have a powerful role in neuronal degeneration. Recent research has revealed that steroids may influence the onset and progression of some retinal disorders as well as neurodegenerative diseases and, as in brain, they accumulate in the retina via a local synthesis (neurosteroids) and metabolism of blood‐circulating steroid hormones. Their crucial role as neurodegenerative and neuroprotective agents has been also upheld in a retinal excitotoxic paradigm. These findings are reviewed especially from the emerging perspective that after an insult local changes in steroidogenic responses and consequent neurosteroid availability might turn out to be offensive or defensive cellular adaptations for the potentiation or prevention of neuronal death.
Ovarian Steroid and Growth Factor Regulation of Female Reproductive Function Involves Modification of Hypothalamic α1‐Adrenoceptor Signaling
Authors: ETGEN ANNE M.
Published: March 2004

Abstract: The ovarian steroids estradiol (E2) and progesterone (P) act on target neurons in the hypothalamus and preoptic area to coordinate the expression of female reproductive behaviors with the timing of the preovulatory luteinizing hormone (LH) surge. This chapter will summarize evidence that E2 and P facilitation of the receptive component of female reproductive behavior, lordosis, involves changes in both the expression of and intracellular signal transduction pathways engaged by α1‐adrenergic receptors in the hypothalamus and preoptic area. The α1‐adrenoceptors are thought to mediate the facilitatory effects of the catecholamine neurotransmitter norepinephrine on both lordosis behavior and LH release. E2 first induces the expression of the α1B‐adrenergic receptor subtype in the hypothalamus and preoptic area. P then acts in an E2‐dependent manner to promote linkage of hypothalamic α1‐adrenoceptors to an intracellular signaling pathway involving nitric oxide and cyclic GMP. This chapter will also describe recent findings that implicate brain insulin‐like growth factor‐I (IGF‐I) receptors as obligatory co‐mediators of hormonal regulation of hypothalamic α1‐adrenoceptors and female neuroendocrine function. Additional studies suggest that E2 and IGF‐I facilitate lordosis behavior by activating kinases traditionally associated with growth factor signal transduction (mitogen‐activated protein kinases and phosphatidlyinositol‐3‐kinases). These molecular events are proposed to help coordinate the timing of ovulation with the expression of sexual receptivity, thereby maximizing reproductive success.
Steroid Hormones and Growth Factors Act in an Integrated Manner at the Levels of Hypothalamic Astrocytes
Authors: GALBIATI MARIARITA , SAREDI SIMONA , MELCANGI ROBERTO C.
Published: March 2004

Abstract: Several growth factors (e.g., transforming growth factors beta and alpha, basic fibroblast growth factor), produced by hypothalamic astrocytes, participate in the control of hypothalamic gonadotrophin‐releasing hormone (GnRH) neurons. On this basis, we have hypothesized that steroid hormones, like estrogens and progestagens, influence the GnRH neurons by modulating in glial cells the synthesis and the release of these growth factors. Data reported here indicate that the expression of transforming growth factor beta 1 is modulated in hypothalamic astrocytes by a progesterone derivative (i.e., dihydroprogesterone), while estrogens modulate that of basic fibroblast growth factor. Moreover, it is interesting to highlight that the effect of estrogens on basic fibroblast growth factor is mediated by another growth factor (i.e., transforming growth factor alpha). Altogether, the present findings support the concept that steroid hormones and growth factors act in an integrated manner at the level of hypothalamic astrocytes, thus adding a further piece of knowledge in the understanding of the mechanisms controlling GnRH neurons.
The MPN mag
Authors: SWANN JENNIFER M. , WANG JING , GOVEK ELIZABETH K.
Published: March 2004

Abstract:Mating behavior in male hamsters is regulated by a chemosensory pathway that converges on the bed nucleus of the stria terminalis (BST) and the medial nucleus of the amygdala (Me). Both the BST and the Me project to the lateral part of the medial preoptic area. Lesion studies have identified a small group of large cells referred to as the magnocellular medial preoptic nucleus (MPN mag) whose integrity is required for normal mating behavior. Our data, summarized within, indicate that the MPN mag is a sexually differentiated nucleus in a large steroid‐responsive network that relays pheromonal signals from the sensory systems to the motor areas to affect behavior.
The Aromatase Knockout (ArKO) Mouse Provides New Evidence That Estrogens Are Required for the Development of the Female Brain
Authors: BAKKER J , HONDA S , HARADA N , BALTHAZART J
Published: March 2004

Abstract: The classic view of sexual differentiation is that the male brain develops under the influence of testicular secretions, whereas the female brain develops in the absence of any hormonal stimulation. However, several studies have suggested a possible role of estradiol in female neural development, although they did not provide unequivocal evidence that estradiol is indispensable for the development of the female brain and behavior. As a result, the hypothesis subsequently languished because of the lack of a suitable animal model to test estrogen's possible contribution to female differentiation. The recent introduction of the aromatase knockout (ArKO) mouse, which is deficient in aromatase activity because of a targeted mutation in the CYP19 gene and therefore cannot aromatize androgen to estrogen, has provided a new opportunity to reopen the debate of whether estradiol contributes to the development of the female brain. Female ArKO mice showed reduced levels of lordosis behavior after adult treatment with estradiol and progesterone, suggesting that estradiol is required for the development of the neural mechanisms controlling this behavior in female mice. The neural systems affected may include the olfactory systems in that ArKO females also showed impairments in olfactory investigation of odors from conspecifics. Thus, the classic view of sexual differentiation, that is, the female brain develops in the absence of any hormonal secretion, needs to be re‐examined.
Sex Steroids and Human Behavior: Prenatal Androgen Exposure and Sex‐Typical Play Behavior in Children
Authors: HINES MELISSA
Published: March 2004

Abstract: Gonadal hormones, particularly androgens, direct certain aspects of brain development and exert permanent influences on sex‐typical behavior in nonhuman mammals. Androgens also influence human behavioral development, with the most convincing evidence coming from studies of sex‐typical play. Girls exposed to unusually high levels of androgens prenatally, because they have the genetic disorder, congenital adrenal hyperplasia (CAH), show increased preferences for toys and activities usually preferred by boys, and for male playmates, and decreased preferences for toys and activities usually preferred by girls. Normal variability in androgen prenatally also has been related to subsequent sex‐typed play behavior in girls, and nonhuman primates have been observed to show sex‐typed preferences for human toys. These findings suggest that androgen during early development influences childhood play behavior in humans at least in part by altering brain development.
Neurotrophic Factors and Estradiol Interact To Control Axogenic Growth in Hypothalamic Neurons
Authors: CARRER H F. , CAMBIASSO M J. , BRITO V , GOROSITO S
Published: March 2004

Abstract: Previous work from our laboratory has shown that in cultures of hypothalamic neurons obtained from male fetuses at embryonic day 16, the axogenic response to estrogen (E2) is contingent on coculture with target glia or target glia‐conditioned media (CM). Neither the estrogen receptor blockers tamoxifen nor ICI 182,780 prevented the axogenic effects of the hormone. Estradiol made membrane‐impermeable by conjugation to a protein of high molecular weight (E2‐BSA) preserved its axogenic capacity, suggesting the possibility of a membrane effect responsible for the action of E2. Western blot analysis of extracts from homogenates of cultured neurons grown with E2 and CM from target glia had more TrkB than cultures with CM alone or E2 alone. To further investigate the interaction between E2 and the neurotrophin receptors, we used a specific antisense oligonucleotide (AS) to prevent the estradiol‐induced increase of TrkB. The effect of E2 was suppressed in cultures in which TrkB was down‐regulated by the AS, showing decreased axonal elongation when compared with neurons treated with E2 without AS or with sense TrkB. In cultures grown with AS, the axonal length of E2‐treated cultures was not different from cultures without E2. Evidence suggesting cross‐talk between E2 and neurotrophic factor(s) prompted investigation of signaling along the MAPK cascade. Immuno blotting of E2‐treated cultures showed increased levels of phosphorylated ERK1 and ERK2. UO126 but not LY294002 blocked E2‐induced axonal elongation, suggesting that the MAPKs are involved in this response.