Local activation of CA1 pyramidal cells induces theta-phase precession.

Hippocampal theta-phase precession is involved in spatiotemporal coding and in generating multineural spike sequences, but how precession originates remains unresolved. To determine whether precession can be generated directly in hippocampal area CA1 and disambiguate multiple competing mechanisms, we used closed-loop optogenetics to impose artificial place fields in pyramidal cells of mice running on a linear track. More than one-third of the CA1 artificial fields exhibited synthetic precession that persisted for a full theta cycle. By contrast, artificial fields in the parietal cortex did not exhibit synthetic precession. These findings are incompatible with precession models based on inheritance, dual-input, spreading activation, inhibition-excitation summation, or somato-dendritic competition. Thus, a precession generator resides locally within CA1.

Short-term auditory priming in freely-moving mice.

Priming, a change in the mental processing of a stimulus as a result of prior encounter with a related stimulus, has been observed repeatedly and studied extensively in humans. Yet currently, there is no behavioral model of short-term priming in lab animals, precluding research on the neurobiological basis of priming. Here, we describe an auditory discrimination paradigm for studying response priming in freely moving mice. We find a priming effect in success rate in all mice tested on the task. In contrast, we do not find a priming effect in response times. Compared to non-primed discrimination trials, the addition of incongruent prime stimuli reduces success rate more than congruent prime stimuli, suggesting a cognitive mechanism based on differential interference. The results establish the short-term priming phenomenon in rodents, and the paradigm opens the door to studying the cellular-network basis of priming.

Positive and biphasic extracellular waveforms correspond to return currents and axonal spikes.

Multiple biophysical mechanisms may generate non-negative extracellular waveforms during action potentials, but the origin and prevalence of positive spikes and biphasic spikes in the intact brain are unknown. Using extracellular recordings from densely-connected cortical networks in freely-moving mice, we find that a tenth of the waveforms are non-negative. Positive phases of non-negative spikes occur in synchrony or just before wider same-unit negative spikes. Narrow positive spikes occur in isolation in the white matter. Isolated biphasic spikes are narrower than negative spikes, occurring right after spikes of verified inhibitory units. In CA1, units with dominant non-negative spikes exhibit place fields, phase precession, and phase-locking to ripples. Thus, near-somatic narrow positive extracellular potentials correspond to return currents, and isolated non-negative spikes correspond to axonal potentials. Identifying non-negative extracellular waveforms that correspond to non-somatic compartments during spikes can enhance the understanding of physiological and pathological neural mechanisms in intact animals.

Error correction and improved precision of spike timing in converging cortical networks.

The brain propagates neuronal signals accurately and rapidly. Nevertheless, whether and how a pool of cortical neurons transmits an undistorted message to a target remains unclear. We apply optogenetic white noise signals to small assemblies of cortical pyramidal cells (PYRs) in freely moving mice. The directly activated PYRs exhibit a spike timing precision of several milliseconds. Instead of losing precision, interneurons driven via synaptic activation exhibit higher precision with respect to the white noise signal. Compared with directly activated PYRs, postsynaptic interneuron spike trains allow better signal reconstruction, demonstrating error correction. Data-driven modeling shows that nonlinear amplification of coincident spikes can generate error correction and improved precision. Over multiple applications of the same signal, postsynaptic interneuron spiking is most reliable at timescales ten times shorter than those of the presynaptic PYR, exhibiting temporal coding. Similar results are observed in hippocampal region CA1. Coincidence detection of convergent inputs enables messages to be precisely propagated between cortical PYRs and interneurons.

Hybrid Offspring of C57BL/6J Mice Exhibit Improved Properties for Neurobehavioral Research.

C57BL/6 is the most commonly used mouse strain in neurobehavioral research, serving as a background for multiple transgenic lines. However, C57BL/6 exhibit behavioral and sensorimotor disadvantages that worsen with age. We bred FVB/NJ females and C57BL/6J males to generate first-generation hybrid offspring (FVB/NJ x C57BL/6J)F1. The hybrid mice exhibit reduced anxiety-like behavior, improved learning, and enhanced long-term spatial memory. In contrast to both progenitors, hybrids maintain sensorimotor performance upon aging and exhibit improved long-term memory. The hybrids are larger than C57BL/6J, exhibiting enhanced running behavior on a linear track during freely-moving electrophysiological recordings. Hybrids exhibit typical rate and phase coding of space by CA1 pyramidal cells. Hybrids generated by crossing FVB/NJ females with transgenic males of a C57BL/6 background support optogenetic neuronal control in neocortex and hippocampus. The hybrid mice provide an improved model for neurobehavioral studies combining complex behavior, electrophysiology, and genetic tools readily available in C57BL/6 mice.

Deconvolution improves the detection and quantification of spike transmission gain from spike trains.

Accurate detection and quantification of spike transmission between neurons is essential for determining neural network mechanisms that govern cognitive functions. Using point process and conductance-based simulations, we found that existing methods for determining neuronal connectivity from spike times are highly affected by burst spiking activity, resulting in over- or underestimation of spike transmission. To improve performance, we developed a mathematical framework for decomposing the cross-correlation between two spike trains. We then devised a deconvolution-based algorithm for removing effects of second-order spike train statistics. Deconvolution removed the effect of burst spiking, improving the estimation of neuronal connectivity yielded by state-of-the-art methods. Application of deconvolution to neuronal data recorded from hippocampal region CA1 of freely-moving mice produced higher estimates of spike transmission, in particular when spike trains exhibited bursts. Deconvolution facilitates the precise construction of complex connectivity maps, opening the door to enhanced understanding of the neural mechanisms underlying brain function.

High Fidelity Theta Phase Rolling of CA1 Neurons.

Single hippocampal cells encode the spatial position of an animal by increasing their firing rates within "place fields," and by shifting the phase of their spikes to earlier phases of the ongoing theta oscillations (theta phase precession). Whether other forms of spatial phase changes exist in the hippocampus is unknown. Here, we used high-density electrophysiological recordings in mice of either sex running back and forth on a 150-cm linear track. We found that the instantaneous phase of spikes shifts to progressively later theta phases as the animal traverses the place field. We term this shift theta "phase rolling." Phase rolling is opposite in direction to precession, faster than precession, and occurs between distinct theta cycles. Place fields that exhibit phase rolling are larger than nonrolling fields, and in-field spikes occur in distinct theta phases in rolling compared with nonrolling fields. As a phase change associated with position, theta phase rolling may be used to encode space.SIGNIFICANCE STATEMENT Theta phase precession is a well-known coding scheme in which neurons represent the position of the animal by the timing of their spikes with respect to the phase of ongoing theta oscillations. Here, we show that hippocampal neurons also undergo "theta phase rolling," a phase change faster and opposite in direction to precession. As the animal advances in space, spikes occur at progressively later phases of consecutive theta cycles. Future studies may reveal whether phase rolling constitutes a novel coding mechanism of space.

Photoacoustic clinical imaging.

Photoacoustic is an emerging biomedical imaging modality, which allows imaging optical absorbers in the tissue by acoustic detectors (light in - sound out). Such a technique has an immense potential for clinical translation since it allows high resolution, sufficient imaging depth, with diverse endogenous and exogenous contrast, and is free from ionizing radiation. In recent years, tremendous developments in both the instrumentation and imaging agents have been achieved. These opened avenues for clinical imaging of various sites allowed applications such as brain functional imaging, breast cancer screening, diagnosis of psoriasis and skin lesions, biopsy and surgery guidance, the guidance of tumor therapies at the reproductive and urological systems, as well as imaging tumor metastases at the sentinel lymph nodes. Here we survey the various clinical and pre-clinical literature and discuss the potential applications and hurdles that still need to be overcome.

Interactions between the circadian clock and TGF-ß signaling pathway in zebrafish.

BACKGROUND: TGF-ß signaling is a cellular pathway that functions in most cells and has been shown to play a role in multiple processes, such as the immune response, cell differentiation and proliferation. Recent evidence suggests a possible interaction between TGF-ß signaling and the molecular circadian oscillator. The current study aims to characterize this interaction in the zebrafish at the molecular and behavioral levels, taking advantage of the early development of a functional circadian clock and the availability of light-entrainable clock-containing cell lines. RESULTS: Smad3a, a TGF-ß signaling-related gene, exhibited a circadian expression pattern throughout the brain of zebrafish larvae. Both pharmacological inhibition and indirect activation of TGF-ß signaling in zebrafish Pac-2 cells caused a concentration dependent disruption of rhythmic promoter activity of the core clock gene Per1b. Inhibition of TGF-ß signaling in intact zebrafish larvae caused a phase delay in the rhythmic expression of Per1b mRNA. TGF-ß inhibition also reversibly disrupted, phase delayed and increased the period of circadian rhythms of locomotor activity in zebrafish larvae. CONCLUSIONS: The current research provides evidence for an interaction between the TGF-ß signaling pathway and the circadian clock system at the molecular and behavioral levels, and points to the importance of TGF-ß signaling for normal circadian clock function. Future examination of this interaction should contribute to a better understanding of its underlying mechanisms and its influence on a variety of cellular processes including the cell cycle, with possible implications for cancer development and progression.

BioNSi: A Discrete Biological Network Simulator Tool.

Modeling and simulation of biological networks is an effective and widely used research methodology. The Biological Network Simulator (BioNSi) is a tool for modeling biological networks and simulating their discrete-time dynamics, implemented as a Cytoscape App. BioNSi includes a visual representation of the network that enables researchers to construct, set the parameters, and observe network behavior under various conditions. To construct a network instance in BioNSi, only partial, qualitative biological data suffices. The tool is aimed for use by experimental biologists and requires no prior computational or mathematical expertise. BioNSi is freely available at http://bionsi.wix.com/bionsi , where a complete user guide and a step-by-step manual can also be found.

Particulate organic matter as a food source for a coral reef sponge.

The ability of sponges to feed in diverse (including oligotrophic) ecosystems significantly contributes to their ubiquitous aquatic distribution. It was hypothesized that sponges that harbour small amounts of symbiotic bacteria in their mass feed mainly on particulate organic matter (POM). We examined the nearly symbiont-free (by microscopic observation) filter-feeding Red Sea sponge Negombata magnifica in order to: (a) study removal efficiency of naturally occurring organic particles, (b) measure the total amount of absorbed particulate organic carbon (POC) and nitrogen (PON), and (c) estimate organic carbon and nitrogen flux in this sponge. Total amount of organic carbon and nitrogen in the Gulf of Aqaba was found to be 48.46+/-5.69 microg l(-1) and 6.45+/-0.7 microg l(-1), respectively. While detritus contributed 54% of POC, most PON (84%) came from planktonic microorganisms, mainly prokaryotes. Particle removal efficiency ranged from 99% (the cyanobacterium Synechococcus sp.) to 37% (for eukaryotic cells >8 microm). On average, N. magnifica ingested 480 microg C day(-1) g(-1) (wet mass, WM) sponge and 76.6 microg N day(-1) g(-1) sponge. Ingested POC balanced 85% of the sponge's energetic demand but more is needed for biomass production because it cannot digest all of the carbon. 54.4+/-16.1 microg N day(-1) g(-1) (WM) nitrogen was excreted as total ammonia nitrogen (TAN); however, nitrogen allowance should be higher because more nitrogen is deposited for sponge biomass during growth. It is hypothesized that the discrepancy in the nutritional requirements should be covered by the sponge absorbing carbon and nitrogen from sources that are not dealt with in the present research, such as dissolved organic carbon and nitrogen. This study highlights the significance of detritus as a carbon source, and prokaryotes as a PON source in sponge feeding.

Simultaneous carcinoma of the endometrium and ovary vs endometrial carcinoma with ovarian metastases: a clinical and immunohistochemical determination.

The aim of this study was to perform a clinical and immunohistochemical comparison between simultaneous independent tumors involving endometrium and ovary and metastatic endometrial tumors, and to try to find clinical and /or immunohistochemical parameters differentiating between these two entities. Sixteen cases of simultaneous independent primaries of endometrium and ovary, presenting the same histologic type, were compared with 12 cases of primary endometrial cancer, demonstrating ovarian metastases. The comparison related to patients' characteristics and immunohistochemical expression of estrogen and progesterone receptors (ER,PR), bcl-2, HER-2 /neu, p53, and cell proliferation marker Ki-67 in endometrial and ovarian tumors. The only clinical parameter differentiating significantly between the groups was the prevalence of familial cancer, being more frequent in the group of metastatic tumors (P = 0.03). Immunohistochemical analysis demonstrated the same immunostaining in endometrium and ovary for all immunohistochemical parameters in cases of metastatic endometrial cancer. Conversely, 62.5% of cases with simultaneous tumors of endometrium and ovary could be differentiated from metastatic tumors by distinct immunohistochemical expression of ER and PR in endometrial and ovarian tumors (P = 0.0006), and 31.3% of cases could be differentiated by distinct immunostaining for bcl-2 (P = 0.03). Immunohistochemical parameters HER-2 /neu, p53 and Ki-67 were not appropriate for the distinction between the two study groups. We conclude that the application of immunohistochemical analysis may play an important role in the differentiation between cases of simultaneous independent carcinomas of endometrium and ovary vs. cases of endometrial carcinoma with ovarian metastases.

Uterine papillary serous carcinoma (pure and mixed type) compared with moderately and poorly differentiated endometrioid carcinoma. A clinicopathologic study.

OBJECTIVE: The aim of this study was to investigate the clinicopathologic features and the outcome in patients with pure and mixed type uterine papillary serous carcinoma (UPSC), and to compare these parameters with those observed in patients with moderately and poorly differentiated endometrioid endometrial carcinoma (MPD-EEC). METHODS: The charts of 34 patients with UPSC and 30 patients with MPD-EEC, operated on between January 1995 and December 2000, were retrospectively reviewed. The UPSC group included ten cases of pure and 24 cases of mixed type UPSC (admixed with endometrioid component). All patients had undergone full surgical staging. Clinical features, surgicopathological findings, recurrence rate and recurrence-free interval were compared between the study groups. RESULTS: Significantly more patients with MPD-EEC than with UPSC were operated on in FIGO stage I and II (p = 0.001). MPD-EEC patients were significantly older and more obese (p = 0.03 and p = 0.01, respectively) as compared with the UPSC patients. Significantly more patients with MPD-EEC presented with postmenopausal bleeding (p = 0.02), had a second primary cancer in the past (p = 0.03) and had a first degree relative with history of malignant disease (p = 0.0001). Conversely, the rates of positive abdominal cytology and cervical involvement were significantly higher in the group of UPSC (p = 0.02 and p = 0.02, respectively). Significantly more patients with UPSC were treated with adjuvant therapy (p = 0.01). No significant difference between the two study groups was observed comparing the recurrence rate, the recurrence free interval and the 3-year survival. There was also no significant difference between the pure and the mixed type UPSC, considering the clinical features and the follow-up data. CONCLUSION: The current study presented no significant difference in the outcome of MPD-EEC as compared with the pure and the mixed type UPSC, yet prospective studies are needed to evaluate the role of adjuvant therapy in each study group.

Primary peritoneal serous papillary carcinoma: a new epidemiologic trend? A matched-case comparison with ovarian serous papillary cancer.

The aim of the study was to examine the prevalence of primary peritoneal serous papillary carcinoma (PPSPC) as compared with ovarian serous papillary cancer (OSPC), and to study the clinicopathologic features and the frequency of germline BRCA1 and BRCA2 mutations in patients with PPSPC compared with those with OSPC. The study group included 28 cases of PPSPC. The comparison group included 35 female patients with OSPC, matched for stage, grade, and histologic subtype. All tumors were staged as either IIIB, IIIC or IV according to FIGO criteria. The patient characteristics, family and personal history of malignancies, the prevalence of germline BRCA mutations, clinicopathologic findings, presenting symptoms, pre- and intraoperative findings, and survival were compared in a matched-case retrospective study comparing patients with PPSPC vs. those with OSPC. Statistical analysis was made using Student's t-test, Chi-square, Wilcoxon, Kaplan-Meier and log-rank methods. Women with PPSPC had a significantly earlier menarche (P = 0.037) and a higher number or births (P = 0.03) than women with OSPC. No difference was found with regard to the prevalence of germline BRCA mutations in women with PPSPC compared with women with OSPC (7.1% vs. 25.7%). There was a significant increase (P = 0.02) in the incidence of abdominal distension as reported by PPSPC (64%) vs. OSPC patients (26%). Significantly more women with PPSPC than with OSPC presented with clinical ascites (P = 0.0001) and without palpable pelvic mass (P = 0.000001). On exploratory laparotomy, significantly more women with PPSPC than with OSPC had a minimal disease in the pelvis (P = 0.0087). Three-year survival analysis demonstrated a significantly worse survival rate for the PPSPC group than for the OSPC group (P = 0.017). A significant increase in the prevalence of PPSPC compared with OSPC was observed during the study years (P = 0.00001). We concluded that PPSPC and OSPC might be two distinct cancers, presenting a new epidemiologic trend regarding the increased incidence of PPSPC.

Clinical and molecular comparison between borderline serous ovarian tumors and advanced serous papillary ovarian carcinomas.

The aim of this study was to characterize the clinical and molecular markers of borderline serous ovarian tumors (BSOT), and to study their expression in the progression from benign lesions to advanced serous papillary ovarian carcinomas (SPOC). The clinical records of 20 patients with BSOT and 22 patients with SPOC were reviewed. Specimens from all these cases and from six benign ovarian serous cystadenomas were evaluated for expression of estrogen receptors (ER), progesterone receptors (PR), p53. HER-2/neu and Ki-67 by immunohistochemical techniques. The mean patient age and the age at menarche differed significantly between the compared groups of BSOT and SPOC (p=0.0006 and p=0.0014, respectively). No difference was observed comparing the other clinical parameters. The immunohistochemical analysis demonstrated a significant increase in the expression of ER (100% vs 72.7%), and a significant decrease in the immunoreactivity for p53 (0% vs 45.4%) and Ki-67 (2% vs 26.8%) in cases of BSOT compared with those of SPOC (p=0.007, p=0.0003 and p=0.012, respectively). No significant difference was demonstrated comparing the expression of PR and HER-2/neu. The immunostaining of benign ovarian serous cystadenoma specimens did not differ significantly from immunoreactivity observed in cases of BSOT. According to immunohistochemical analysis, BSOT had much more in common with benign serous tumors than with SPOC. The main difference between BSOT and SPOC was regarding the overexpression of p53 and Ki-67.

Immunohistochemical comparison of primary peritoneal and primary ovarian serous papillary carcinoma.

Twenty-six patients, meeting strict criteria for primary peritoneal serous papillary carcinoma (PPSPC), were matched to 22 patients with ovarian serous papillary cancer (OSPC) for age and stage. Immunohistochemistry was used to determine the status of estrogen receptors (ER), progesterone receptors (PR), the expression of cell proliferation marker Ki-67, and the overexpression of HER-2/neu and p53 protein. Of the PPSPCs, 53.8% were poorly differentiated, as were 18.2% of the OSPCs (p = 0.012). Positive immunostaining for ER and PR was less in PPSPCs (30.8% and 46.2%, respectively) than OSPCs (72.7% and 90.9%; p = 0.003 and p = 0.001, respectively). Conversely, a significant increase in the expression of Ki-67 was found in PPSPCs (37.7%) versus OSPCs (26.8%) (p = 0.039). The same trend was found for HER-2/neu, being overexpressed in 38.5% of the PPSPC versus 9.1% of the OSPCs (p = 0.019). Overexpression of p53 was found in 30.8% of the PPSPCs and 45.4% of the OSPCs (not significant). There was a significantly worse survival rate for PPSPCs than for OSPCs (p = 0.017), yet none of the studied parameters were significantly correlated with survival within the PPSPC and OSPC groups. The significantly different immunohistochemical expression of ER, PR, Ki-67, and HER-2 in PPSPCs compared with OSPCs suggests that different molecular events may lead to tumorigenesis in these two cancers.

Comparative immunohistochemical study of endometrioid and serous papillary carcinoma of endometrium.

OBJECTIVE: The aim of this study was to determine whether immunohistochemical analysis of molecular parameters can provide an alternative method for classification of endometrial cancer cases according to their aggressiveness. METHODS: Sixty-four cases of endometrial carcinoma were assigned to three groups: group I--28 cases of endometrioid well and moderately differentiated (G1-G2) carcinoma; group II--14 cases of endometrioid poorly differentiated (G3) carcinoma; group III--22 cases of serous papillary endometrial cancer. Immunohistochemistry was used to determine the existence of estrogen receptors (ER), progesterone receptors (PR), and the expression of bcl-2, p53, HER-2/neu and Ki-67. RESULTS: There was a significant difference in the immunohistochemical profile of the studied molecular parameters comparing the three study groups. The endometrioid G1-G2 cases (group I) were characterized by increased immunoreactivity for ER and PR (85.7% and 78.6%, respectively), increased immunoreactivity for bcl-2 (42.8%) and low expression of p53 (14.3%) and HER-2/neu (14.3%). In contrast to group I cases, the serous papillary endometrial cancer cases (group III) were characterized by immunonegativity for ER, PR and bcl-2 and high immunoreactivity for p53 (81.8%) and HER-2/neu (45.4%). The endometrioid G3 cases (group II) demonstrated an intermediate immunoprofile, characterized by immunonegativity for ER, PR and HER-2/neu, low immunoreactivity for bcl-2 (7.1%) and high expression of p53 (57.1%). The expression of Ki-67 did not differ significantly comparing the different cases of endometrial cancer. CONCLUSION: This study provides evidence that the immunohistochemical analysis of endometrial carcinoma differentiates between different grades and histological types, thus being useful in the distinction of high risk cases.

Immunisation of lambs with drug-abbreviated Haemonchus contortus infections: protection against homologous and heterologous challenge.

Haemonchus contortus is known as a prolific parasite, producing high numbers of eggs. It could therefore be used as a cheap source of larvae for immunisation of lambs. The value of immunisation would be improved if the immunity produced gave protection against not only homologous but also heterologous infections. Because antibody cross-reactivity between Haemonchus and Ostertagia has been well established, we wanted to know whether drug-abbreviated infections of H. contortus would stimulate production of antibodies that would cross-react with Trichostrongylus colubriformis. The results obtained from these trials indicated that H. contortus drug-abbreviated infections produced significant immunity against not only Haemonchus but also O. circumcincta. Immunisation increased the level of immunoglobulin E (IgE) and IgE-specific antibodies against T. colubriformis, but the differences between experimental and control animals were not statistically significant. Significantly higher levels of IgG-specific antibodies against T. colubriformis were observed.

Immunomodulation of lambs following treatment with a proteasome preparation from infective larvae of Trichostrongylus colubriformis.

Proteinases are known to be capable of prolonging the survival of endoparasites in a host. We were therefore interested in knowing whether immunization of lambs against a proteasome (multisubunit proteinases) preparation obtained from Trichostrongylus colubriformis infective third-stage larvae (L3) would have any effect on the immune response to a single challenge infection with the same organism. A total of 21 penned lambs aged 8 months were divided into 3 equal groups. Group 1 was immunized on three occasions with increasing amounts of a proteasome-enriched fraction obtained from infective L3. Group 2 was given a similar amount of protein from the initial supernatant of homogenized larvae. Group 3 (controls) received adjuvant plus saline solution only. All groups were challenged with 60,000 infective T. colubriformis larvae at 28 days after the last immunization. Significant protection was obtained only when the initial supernatant extract was used to immunize lambs. The proteasome preparation seemed to have immunosuppressive effects through the stimulation of nonspecific IgE production. Significantly lower levels of specific IgE were observed in lambs immunized with the proteasome-enriched fraction, and levels of specific IgG antibodies were increased. We suggest that proteasome fractions of T. colubriformis may serve as useful preparations for the study of mechanisms of IgE production in parasitized sheep.

Placental levels of human decidua- associated protein 200 in normal pregnancy and missed abortion.

Levels of human decidua-associated protein (hDP)200 were measured in homogenized placental tissue samples obtained from 26 induced and 24 missed abortions at 8-23 weeks of pregnancy. No significant difference in the level of placental hDP200 was observed comparing normal pregnancies and missed abortions. Moreover, no significant change in the level of placental hDP200 was demonstrated throughout normal pregnancies and those ending with missed abortions. Our results show that the level of hDP200 in placental tissue, measured by double-site ELISA, is probably incompatible with the normal continuation of pregnancy.