The stochastic properties of spontaneous quantal release of transmitter at the frog neuromuscular junction

1. Earlier results showed that it is unlikely that spontaneous quantal release of transmitter at the frog neuromuscular junction is produced by a Poisson process.2. Data sets were tested, by using the u statistic, to see whether if they are assumed to be generated by a Poisson process, the mean interval is changing monotonically with time. By this critieria, some of the data sets are stationary, others are not.3. A variety of mathematical transforms are employed on empirical data sets to characterize the properties of the spontaneous quantal release.(a) The intensity function, which calculates the frequency distribution of all possible combinations of intervals, shows an excess of short intervals, without any sign of periodicity.(b) The variance-time curve, which estimates the accumulated variance of the series as a function of time into the series, lies significantly above the Poisson prediction.(c) The power spectrum, whether calculated on the intervals or on the number of intervals in time bins, deviates significantly from the Poisson prediction at the low frequencies.(d) The ln-survivor curve has two phases: a concave section for the short intervals, and a roughly linear section for the intervals of greater length.These transforms indicate that the min.e.p.p.s are clustered.4. A series of models for spontaneous quantal release were considered.(a) A Poisson model. Rejected because of consistent failure to fit the data.(b) A periodic model. Rejected because the intervals should be ordered rather than clustered.(c) A time-dependent model, in which quantal release is governed by a Poisson process with a mean interval that is oscillating in time. This model will generate clustering; by the transforms the model can be shown to closely fit the data. However, an autocorrelation of min.e.p.p. amplitudes shows that there is a relationship between the amplitudes and their position in the series. This is not predicted by the time-dependent oscillating model.(d) A branching Poisson model, in which a primary release, generated by a Poisson process, is likely to be followed by one or more subsidiary releases from the same site. The parameters of the branching model can be determined from ln-survivor curves. Theoretical curves, created with these parameters, give power spectra, variance-time curves, and ln-survivor curves that strongly resemble those calculated from the data. The model also predicts a significant autocorrelation of amplitudes.5. Min.e.p.p.s recorded with an extracellular electrode also fit well to a branching Poisson model.6. The effects of raised [Ca(2+)](o) on the intervals between min.e.p.p.s were studied. In our experiments the change in extracellular solution did not produce any notable change in release statistics.7. The effects of elevated [K(+)](o) on the intervals between spontaneous releases were studied. Depolarization of the nerve terminal increases the frequency of primary releases and decreases the chance of having subsidiary releases.8. Possible physical mechanisms by which quantal release of transmitter from a nerve terminal would fit a branching Poisson model are described.

Stochastic properties of spontaneous transmitter release at the crayfish neuromuscular junction

1. Miniature excitatory junctional potentials (min.e.j.p.s) were recorded with an intracellular electrode from the adductor muscle of the dactyl of the first or second walking leg of the crayfish, Orconectes virilis.2. The intervals between the min.e.j.p.s were compared to the exponential prediction by five goodness of fit tests. The results indicate that the intervals are not exponentially distributed.3. The autocorrelogram of intervals shows that the intervals are unlikely to be independent.4. A stochastic analysis that includes the power spectrum of intervals, the variance-time curve, and the ln-survivor curve suggest that there is a clustering of min.e.j.p.s. The results are similar to those on the frog neuromuscular junction.5. An autocorrelogram of the min.e.j.p. amplitudes suggests that sizes are not independently distributed.6. These results, which are similar to those previously reported from the frog neuromuscular junction, support the use of the branching Poisson process as a theoretical model for the stochastic properties of spontaneous quantal release of transmitter.

Effects of IL-1 molecules on growth patterns of 3-MCA-induced cell lines: an interplay between immunogenicity and invasive potential

The balance between inflammation and immunity is cardinal for the outcome of the malignant process. Local attenuated inflammatory responses mediated by innate cells may provide accessory signals for the development of acquired immunity against malignant cells. In contrast, excessive inflammatory responses accompany tumorigenesis and tumor invasiveness, by the induction of immunosuppression. In the present study, we have assessed the role of tumor cell-derived IL-1 in determining the invasive versus immunostimulatory potential of tumor cells. For this purpose, we have used 3-MCA-induced fibrosarcoma cell lines from IL-1 knockout (KO) versus control mice. Cell lines with no IL-1 failed to establish tumors in intact mice, while lines obtained from control mice were invasive and induced a potent angiogenic response. In contrast, cell lines from IL-1KO mice were more immunogenic. SDF-1 and IL-6, each induced by IL-1, were the two major cytokines whose levels differed in cell lines with or without IL-1. We could not detect differences in cell surface markers related to immunogenicity, such as MHC Class I, co-stimulatory, or adhesion molecules between both types of cells. However, more T-cells were observed at the inoculation site of tumor cells devoid of IL-1 and more pronounced parameters related to anti-tumor immunity were observed in the spleen (IL-12 and IFNgamma) of these mice, compared to mice bearing tumors derived from control mice, where host-derived IL-1 is present. In addition, injection of tumor cells devoid of IL-1, which failed to grow in mice, induced an anti-tumor cell immune memory, while in mice injected with tumor cells from control mice; no immune memory could be detected. From the results, it seems that IL-1 is a crucial factor in determining the balance between immunity and inflammation in tumor-bearing mice. This suggests that manipulation of IL-1 could be useful in anti-tumor therapy, by reducing invasiveness and promoting immunity against the malignant cells.

IL-1-induced inflammation promotes development of leishmaniasis in susceptible BALB/c mice

The role of host-derived IL-1 on the course of Leishmania major infection in susceptible BALB/c mice was assessed. Manifestations of the disease were more severe in mice deficient in the physiological inhibitor of IL-1, the IL-1 receptor antagonist (IL-1Ra) in comparison with control mice. In mice lacking one of the IL-1 genes (IL-1alpha or IL-1beta), there was delayed development of the disease and more attenuated systemic inflammatory responses. IL-1alpha-deficient mice were slightly more resistant to L. major infection compared with IL-1beta-knockout mice. During disease progression in IL-1Ra KO and control mice, myeloid-derived suppressor cells invaded the spleen, concomitant to suppression of T cell-mediated immunity and expression of systemic high levels of pro-inflammatory cytokines. In IL-1-deficient mice, T(h)1 responses were still apparent, even at late stages of the disease. Thus, dose-dependent effects of IL-1 were shown to influence the pathogenesis of murine leishamaniasis in susceptible BALB/c mice. Physiological and supra-physiological levels of IL-1 in the microenvironment promoted an exacerbated form of disease, whereas sub-physiological doses of IL-1 induced a less progressive disease. Thus, manipulation of IL-1 levels in the host, using the IL-1Ra or specific antibodies, has the potential to alleviate symptoms of visceral manifestations of leishmaniasis.

Molecular analysis of the selective pro-apoptotic effect of BN107 on estrogen receptor negative breast cancer cells

Abstract #3128

While advances in early detection and adjuvant therapy for breast cancer have had a favorable impact on survival, patients who develop metastatic breast cancer generally succumb to death. Hormonal, targeted or chemotherapeutic strategies largely depend on the expression of their cognate receptors and are often accompanied by toxicities and intolerable side effects. Effective and less toxic therapies against the more aggressive and hormonal therapy-resistant estrogen receptor negative (ER-) breast cancer are urgently needed.
 Botanical medicine is one of the most popular complementary and alternative medical approaches, and Chinese herbal therapies are frequently sought and used by breast cancer patients. However, the molecular mechanisms through which certain herbal extracts exert anti-breast cancer activities remain largely unknown. Bionovo Inc. has a pipeline of anti-breast cancer products (BN#) based on herbal medicine in development. Here, we present preclinical data on the potential mechanisms of the pro-apoptotic effect of BN107 on breast cancer cells.
 A panel of breast cancer cell lines was examined and the most significant cytotoxic effect was observed in the less-differentiated, more aggressive, ER- breast cancer lines. Apoptosis appeared to be the major cellular pathway mediating the cytotoxicity of BN107 as evident from Annexin V binding, dissipation of mitochondrial potential, activation of caspases, and DNA fragmentation. Transcriptomic analysis comparing sensitive (ER+) versus resistant (ER-) cell lines revealed distinct patterns of gene expression in response to BN107. ER- breast cancer cells responded to BN107 by upregulating genes involved in apoptotic responses and cholesterol synthesis pathways; while ER+ breast cancer cells did so by regulating genes involved in cell growth and IGF-1 receptor signaling pathways. Further molecular analysis showed that BN107 induced death preferentially in ER- cells via rapid inactivation of AKT/ mTOR pathways. In addition, the sensitivity to BN107 was greatly reduced when ER expression was introduced in MDA-MB-231, an ER- cell line highly sensitive to BN107.
 BN107, an extract rich in triterpenoids, caused rapid alterations in cholesterol metabolism, presumably by interfering with cell membrane permeability/integrity. Co-administration of BN107 and cholesterol abolished the pro-apoptotic effect of BN107. We found that ER- breast cancer cells rich in caveolae/lipid rafts were highly sensitive to BN107. We showed that BN107 treatment in these cells resulted in subcellular redistribution of proteins that are associated with these specialized membrane/cellular structures.
 In conclusion, BN107 exerts pro-apoptotic activity preferentially on the more aggressive, ER- breast cancer cells. The cytotoxic activity of BN107 may be attributed to its ability to modify membrane permeability/integrity. Activity-guided isolation and further mechanistic studies are underway to identify potential chemical constituents responsible for the selective cytotoxic activities against ER- breast cancer cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3128.

Molecular analysis of the selective pro-apoptotic effect of the herbal extract BN108 on breast cancer cells

Abstract #3018

We present preclinical data on the potential mechanisms of the cytotoxic effect of the herbal extract BN108 towards cancer cells. Botanical medicine is one of the most popular complementary medical approaches, and herbal therapies are frequently sought and used by breast cancer patients. However, the molecular mechanisms through which certain herbal extracts exert growth inhibitory activity on breast cancer cells remain largely unknown.
 Treatment of a panel of breast cancer cell lines and normal mammary cells with BN108 induced cell death selectively in breast cancer lines. Normal mammary epithelial cells and fibroblasts were resistant to the cytotoxic effects of BN108. Breast cancer cells sensitive to BN108 underwent apoptotic death confirmed by Annexin V staining, caspase activation, cleavage of PARP and DNA fragmentation. In particular, caspases 4 and 9, whose activation is observed during apoptosis induced by endoplasmic reticulum stress, were proteolytically activated. Inhibition of caspase 4 partially protected breast cancer cells from cell death induced by BN108.
 Expression array analysis of cells treated with BN108 showed induction of expression of several known pro-apoptotic and anti-proliferative genes such as REDD1, p21CIP, cyclin G2, stratifin and more. BN108 induced rapid inactivation of AKT and mTOR kinases in breast cancer but not in non-transformed cells. Moreover, the well-defined targets of mTORC1, S6kinase and 4eBP1 were inactivated in BN108 treated cells.
 The expression array analysis also showed the induction by BN108 of numerous genes whose products code for enzymes within the cholesterol synthesis pathway. Interestingly, a transient increase in cholesterol synthesis was seen in breast cancer cells but not in normal cells following BN108 treatment. In general, cholesterol levels are higher in breast cancer cells compared to normal cells. Steroidal saponins are major components of BN108 extract, and they are known to deplete cell membrane cholesterol. Similar to BN108 extract, treatment with purified timosaponin AIII (a component of BN108 extract) also induced apoptosis and changes in cholesterol production in breast cancer cells but not in normal cells. It is possible that steroidal saponins induce a very transient depletion of cholesterol, followed by inactivation of AKT and mTOR, and negative feedback inhibition of the cholesterol synthesis pathway that is, in the end, is futile. None of these events are observed in normal cells.
 In conclusion, BN108 extract contains cytotoxic activity selective for transformed versus normal cells. These selective cytotoxic properties of BN108 could be related to its differential effects on cholesterol synthesis in breast cancer cells versus normal cells, as well as inhibition of major oncogenic pathways. Future studies will be aimed at understanding the molecular relationship between the BN1008 effect on cholesterol synthesis and induction of apoptosis, which may give rise to a unique pathway for targeting tumor cells.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3018.

[Epileptiform activities generated in vitro by human temporal lobe tissue]

Drug-resistant partial epilepsies, including temporal lobe epilepsies with hippocampal sclerosis and cortical dysplasias, offer the opportunity to study human epileptic activity in vitro since the preferred therapy often consists of the surgical removal of the epileptogenic zone. Slices of this tissue retain functional neuronal networks and may generate epileptic activity. The properties of cells in this tissue do not seem to be significantly changed, but excitatory synaptic characteristics are enhanced and GABAergic inhibition is preserved. Typically, epileptic activity is not generated spontaneously by the neocortex, whether dysplastic or not, but can be induced by convulsants. The initiation of ictal discharges in neocortex depends on both GABAergic signaling and increased extracellular potassium. In contrast, a spontaneous interictal-like activity is generated by tissues from patients with temporal lobe epilepsies associated with hippocampal sclerosis. This activity is initiated not in the hippocampus but in the subiculum, an output region that projects to the entorhinal cortex. Interictal events seem to be triggered by GABAergic cells, which paradoxically excite approximately 20% of subicular pyramidal cells, while simultaneously inhibiting the majority. Interictal discharges are therefore sustained by both GABAergic and glutamatergic signaling. The atypical depolarizing effects of GABA depend on a pathological elevation in the basal levels of chloride in some subicular cells, similar to those of developmentally immature cells. This defect is caused by the perturbation of the expression of the cotransporters regulating the intracellular chloride concentration, the importer NKCC1, and the extruder KCC2. Blockade of excessive NKCC1 by the diuretic bumetanide restores intracellular chloride and thus hyperpolarizing GABAergic actions, suppressing interictal activity.

Design and development of virtual reality based perceptual-motor rehabilitation scenarios

Virtual reality technology may provide new options for conducting perceptual-motor assessment within simulated 3D environments for persons with a wide range of disabilities. This paper outlines our work developing a series of game-like VR scenarios to assess and rehabilitate eye-hand coordination, range of motion and other relevant perceptual-motor activities. Our efforts have focused on building engaging game-based stereoscopic graphic scenarios that allow clients to participate in perceptual-motor rehabilitation by interacting with 3D stimuli within a full 360-degree space using a head mounted display or by way of a "face-forward" format using 3D projection displays. Exploratory work using multiple video sensors to detect and track 3D body motion, identify body postures and quantify motor performance is also described.

Aromatase inhibitors reverse tamoxifen induced endometrial ultrasonographic changes in postmenopausal breast cancer patients

OBJECTIVE

Aromatase inhibitors may decrease endometrial thickness in breast cancer patients previously having short-term tamoxifen treatment. There is a necessity to find out if aromatase inhibitors can also decrease endometrial thickness in patients previously treated with long-term tamoxifen treatment.

METHODS

Prospective comparison of the last ultrasonographic endometrial thickness measurement taken before discontinuation of long-term tamoxifen treatment in 36 postmenopausal breast cancer patients, with further measurements, performed following aromatase inhibitors administration.

RESULTS

There was a significant decrement of endometrial thickness, following 36.2 +/- 16.8 months of tamoxifen treatment, from a mean value of 9.1 +/- 5.8 mm, measured at the last ultrasonographic measurement performed before discontinuation of tamoxifen treatment, down to a mean value of 6.0 +/- 5.0 mm, measured following 5.8 +/- 5.8 months of aromatase inhibitors therapy (P = 0.001). A second ultrasonographic measurement performed in 8 patients following of additional 7.5 +/- 4.0 months of aromatase inhibitors treatment revealed further decrement of mean endometrial thickness to 4.8 +/- 2.1 mm (P = 0.002 compared to baseline). In 28 patients (77.8%), endometrial thickness was reduced following the administration of aromatase inhibitors, in four patients (11.1%) there was no change in endometrial thickness and four (11.1%) patients demonstrated an increase of endometrial thickness.

CONCLUSIONS

Aromatase inhibitors may reverse endometrial thickening induced by long-term tamoxifen treatment in postmenopausal breast cancer patients.

A conserved mechanism controls translation of Rubisco large subunit in different photosynthetic organisms

We previously proposed a mechanism for control of Rubisco expression and assembly during oxidative stress in Chlamydomonas reinhardtii. The N terminus of the large subunit (LSU) comprises an RNA recognition motif (RRM) that is normally buried in the protein, but becomes exposed under oxidizing conditions when the glutathione pool shifts toward its oxidized form. Thus, de novo translation and assembly of Rubisco LSU stop with similar kinetics and the unpaired small subunit (SSU) is rapidly degraded. Here we show that the structure of the N-terminal domain is highly conserved throughout evolution, despite its relatively low sequence similarity. Furthermore, Rubisco from a broad evolutionary range of photosynthetic organisms binds RNA under oxidizing conditions, with dissociation constant values in the nanomolar range. In line with these observations, oxidative stress indeed causes a translational arrest in land plants as well as in Rhodospirillum rubrum, a purple bacterium that lacks the SSU. We highlight an evolutionary conserved element located within alpha-helix B, which is located in the center of the RRM and is also involved in the intramolecular interactions between two LSU chains. Thus, assembly masks the N terminus of the LSU hiding the RRM. When assembly is interrupted due to structural changes that occur under oxidizing conditions or in the absence of a dedicated chaperone, the N-terminal domain can become exposed, leading to the translational arrest of Rubisco LSU. Taken together, these results support a model by which LSU translation is governed by its dimerization. In the case that regulation of type I and type II Rubisco is conserved, the SSU does not appear to be directly involved in LSU translation.

Infertility, ovulation induction treatments and the incidence of breast cancer--a historical prospective cohort of Israeli women

CONTEXT

Ovulation induction drugs may be associated with increased breast cancer risk. Results so far have been inconclusive.

OBJECTIVE

To evaluate the association between infertility, exposure to ovulation induction drugs and the incidence of breast cancer.

DESIGN

Historical prospective cohort and nested case-control study.

SETTING

Institutional practice

PATIENTS

About 5,788 women attending five infertility centers in Israel between 1964 and 1984.

INTENTION

Abstracting of medical records and telephone interviews.

MAIN OUTCOME MEASURE

Breast cancer incidence was determined through linkage with the National Cancer Registry database. Standardized incidence ratios (SIRs) and 95% confidence intervals were computed by comparing the observed to the expected cancer rates in the general population. In addition, a nested case-control study within the cohort was performed with interviews of breast cancer cases and two matched controls.

RESULTS

The study cohort included 120,895 women years of follow-up. Compared to 115.2 expected breast cancer cases, 131 cases were observed (SIR = 1.1; 95% CI 0.9-1.4). Risk for breast cancer was significantly higher for women treated with clomiphene citrate (SIR = 1.4; 95% CI 1.0-1.8). Similar results were noted when comparisons were carried out between treated and untreated women, and when multivariate models were applied. In the nested case-control study, higher cycle index (OR = 2.2; 95% CI 1.0-4.8) and treatment with clomiphene citrate (OR=2.7; 95% CI 1.3-5.7) were associated with higher risk for breast cancer.

CONCLUSION

Infertility and usage of infertility drugs in general are not associated with increased risk for breast cancer. However, for infertile women treated with clomiphene citrate, breast cancer risk is elevated.

Alkaline stress-induced apoptosis in human pulmonary artery endothelial cells

The effect of alkaline stress, or an increase in extracellular pH (pHext), on cell viability is poorly defined. Human pulmonary artery endothelial cells (HPAEC) were subjected to alkaline stress using different methods of increasing pHext. Viability and mode of cell death following alkaline stress were determined by assessing nuclear morphology, ultrastructural features, and caspase-3 activity. Incubation of monolayers in media set to different pHext values (7.4-8.4) for 24-h induced morphological changes suggesting apoptosis (35-45% apoptotic cells) following severe alkaline stress. The magnitude of apoptosis was related to the severity of alkaline stress. These findings were confirmed with an assessment of ultrastructural changes and caspase-3 activation. While there was no difference in the intracellular calcium level ([Ca(2+)](i)) in monolayers set to pHext 7.4 versus 8.4 following the first hour of alkaline stress, blockade of calcium uptake with the chelator, EGTA, potentiated the magnitude of apoptosis under these conditions. Potentiation of apoptosis was reduced by calcium supplementation of the media. Finally, alkaline stress was associated with an increase in intracellular pH. This is the first report of apoptosis following alkaline stress in endothelial cells in the absence of other cell death stimuli.

A proposed mechanism for the inhibitory effects of oxidative stress on Rubisco assembly and its subunit expression

In Chlamydomonas reinhardtii, a light-induced oxidative stress shifts the glutathione pool toward its oxidized form, resulting in a translational arrest of the large subunit (LSU) of Rubisco. We show here that the translational arrest of LSU is tightly coordinated with cessation of Rubisco assembly, and both processes take place after a threshold level of reactive oxygen species is reached. As a result, the small subunit is also eliminated by rapid degradation. We previously showed that the amino terminus of the LSU could bind RNA in a sequence-independent manner, as it shares a structural similarity with the RNA recognition motif. This domain becomes exposed only under oxidizing conditions, thus restricting the RNA-binding activity. Here we show that in vitro, thiol groups of both subunits become oxidized in the presence of oxidized glutathione. The structural changes are mediated by oxidized glutathione, whereas only very high concentrations of H2O2 confer similar results in vitro. Changes in the redox state of the LSU thiol groups are also observed in vivo, in response to a physiological light shock caused by transfer of cells from low light to high light. We propose that during a photooxidative stress, oxidation of thiol groups occurs already in nascent LSU chains, perhaps hindering their association with chaperones. As a result, their RNA recognition motif domain becomes exposed and will bind any RNA in its vicinity, including its own transcript. Due to this binding the ribosome stalls, preventing the assembly of additional ribosomes on the transcript. Polysome analysis using Suc gradients indeed shows that the rbcL RNA is associated with the polysomal fraction at all times but shifts toward fractions that contain smaller polysomes and monosomes during oxidative stress. Thus, translational arrest of the LSU most likely occurs at a postinitiation stage.