Dynamic changes in spatial representation within the posterior parietal cortex in response to visuomotor adaptation

Recent studies used functional magnetic resonance imaging (fMRI) population receptive field (pRF) mapping to demonstrate that retinotopic organization extends from the primary visual cortex to ventral and dorsal visual pathways, by quantifying visual field maps, receptive field size, and laterality throughout multiple areas. Visuospatial representation in the posterior parietal cortex (PPC) is modulated by attentional deployment, raising the question of whether spatial representation in the PPC is dynamic and flexible, and whether this flexibility contributes to visuospatial learning. To answer this question, changes in spatial representation within the PPC and early visual cortex were recorded with pRF mapping before and after prism adaptation (PA)-a well-established visuomotor technique that modulates visuospatial attention according to the direction of the visual displacement. As predicted, results showed that adaptation to left-shifting prisms increases pRF size in left PPC, while leaving space representation in the early visual cortex unchanged. This is the first evidence that PA drives a dynamic reorganization of response profiles in the PPC. These findings show that spatial representations in the PPC not only reflect changes driven by attentional deployment but dynamically change in response to modulation of external factors such as manipulation of the visuospatial input during visuomotor adaptation.

Molecular characterisation of isogenic taxane resistant cell lines identify novel drivers of drug resistance

Background

Taxanes such as paclitaxel and docetaxel are used successfully to treat breast cancer, usually in combination with other agents. They interfere with microtubules causing cell cycle arrest; however, the mechanisms underlying the clinical effects of taxanes are yet to be fully elucidated.

Methods

Isogenic paclitaxel resistant (PACR) MDA‒MB‒231, paclitaxel resistant ZR75‒1 and docetaxel resistant (DOCR) ZR75‒1 cell lines were generated by incrementally increasing taxane dose in native cell lines in vitro. We used aCGH analysis to identify mechanisms driving taxane resistance.

Results

Taxane resistant cell lines exhibited an 18-170 fold increased resistance to taxanes, with the ZR75-1 resistant cell lines also demonstrating cross resistance to anthracyclines. Paclitaxel treatment of native cells resulted in a G2/M block and a decrease in the G1 phase of the cell cycle. However, in the resistant cell lines, minimal changes were present. Functional network analysis revealed that the mitotic prometaphase was lost in the resistant cell lines.

Conclusion

This study established a model system for examining taxane resistance and demonstrated that both MDR and mitosis represent common mechanism of taxane resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-762) contains supplementary material, which is available to authorized users.

Proximity ligation assays for isoform-specific Akt activation in breast cancer identify activated Akt1 as a driver of progression

The PI3K/Akt signal transduction pathway plays an important role in cancer progression and cell survival. Akt activation is associated with poor outcome in endocrine-treated breast cancer, whereas high levels of cytoplasmic Akt2 are associated with an improved overall survival. Proximity ligation assays (PLAs) were used to determine quantitative expression levels of isoform-specific activation (phosphorylation) of Akt1 and Akt2 in formalin-fixed, paraffin-embedded cell lines and breast cancer tumour tissues in situ. PLAs demonstrated a range of expression in breast cancer samples for total pAkt1 and pAkt2. High levels of pAkt1 were associated with reduced DRFS (HR: 1.45, 95% CI 1.14-1.83, p = 0.002) and OS (HR: 1.42, 95% CI 1.10-1.83, p = 0.007). When PLA results were combined, patients that had high levels of pAkt1 only had a significantly decreased DRFS (HR: 1.92, 95% CI 1.34-2.76, p = 0.005) and OS (HR: 1.94, 95% CI 1.32-2.86, p = 0.008) compared to other patients. Using PLAs to discriminate activation of Akt1 versus Akt2 suggests that Akt1 drives progression in early breast cancers. In cases where both Akt1/Akt2 are activated, Akt2 may act to reverse this effect. Using PLAs, we have measured activation of Akt1 and Akt2 proteins separately in situ in FFPE breast cancer samples.

Double-blind study of pulsing magnetic field effects on multiple sclerosis

We performed a double-blind study to measure the clinical and subclinical effects of an alternative medicine magnetic device on disease activity in multiple sclerosis (MS). The MS patients were exposed to a magnetic pulsing device (Enermed) where the frequency of the magnetic pulse was in the 4-13 Hz range (50-100 milliGauss). A total of 30 MS patients wore the device on preselected sites between 10 and 24 hours a day for 2 months. Half of the patients (15) randomly received an Enermed device that was magnetically inactive and the other half received an active device. Each MS patient received a set of tests to evaluate MS disease status before and after wearing the Enermed device. The tests included (1) a clinical rating (Kurtzke, EDSS), (2) patient-reported performance scales, and (3) quantitative electroencephalography (QEEG) during a language task. Although there was no significant change between pretreatment and posttreatment in the EDSS scale, there was a significant improvement in the performance scale (PS) combined rating for bladder control, cognitive function, fatigue level, mobility, spasticity, and vision (active group -3.83 +/- 1.08, p < 0.005; placebo group -0.17 +/- 1.07, change in PS scale). There was also a significant change between pretreatment and posttreatment in alpha EEG magnitude during the language task recorded at various electrode sites on the left side. In this double-blind, placebo-controlled study, we have demonstrated a statistically significant effect of the Enermed magnetic pulsing device on patient performance scales and on alpha EEG magnitude during a language task.

Outcome of neonates with electrographically identified seizures, or at risk of seizures

A prospective study was conducted to investigate survival at 1 month and survival and developmental outcome at 1 year in a cohort of 53 neonates either suspected of or at risk of having seizures. For all patients, presence of seizures, diagnoses, and structural abnormalities were identified. If seizures were present, seizure variables were quantified. Correlations between neonatal parameters and subsequent outcome were investigated. Forty-three patients survived the first month of life. Background EEG was the only significant predictor of survival at 1 month. Three patients died after 1 month, and 2 of the three had extremely depressed interictal EEGs. Development outcome at 1 year was determined for all available surviving patients. Abnormal findings from brain imaging studies and number of independent electrographic seizure foci were correlated with some aspects of outcome at 1 year. No other correlations were identified between neonatal parameters and outcome.

Pulmonary rehabilitation with respiratory complications of postpolio syndrome

Pulmonary rehabilitation strives to relieve symptoms, improve functional status, and enhance quality of life for patients with pulmonary disease. This article describes the condition called postpolio syndrome and its associated pulmonary complications. Forty-two percent of the respondents to a national survey on the late effects of polio were experiencing new problems related to breathing. Pulmonary rehabilitation, originally developed to address functional impairment and disability related to chronic obstructive pulmonary disease, can benefit patients with postpolio syndrome. A case study is presented.

Naloxone does not improve hemodynamics following graded hemorrhage in a canine model

Two recent studies have demonstrated no improvement in hemodynamic parameters or survival following naloxone administration in hemorrhagic shock. This finding is in contrast to those of earlier studies, which consistently demonstrated a beneficial effect. The current study evaluated naloxone's ability to improve hemodynamics when administered following a fixed-volume hemorrhage, during a period of partial hemodynamic compensation. Thirteen conditioned beagles were anesthetized with pentobarbital (25 mg/kg intravenously), endotracheally intubated, and instrumented with a femoral arterial line and a pulmonary artery thermodilution catheter. Animals were then subjected to an estimated 50% graded hemorrhage (45 ml/kg) over one hour. Following hemorrhage, animals were observed for 90 minutes, then reinfused with shed blood over 30 minutes, and finally observed for an additional 60 minutes. Six animals received naloxone (2 mg/kg intravenously) 30 minutes after completion of hemorrhage and then 2 mg/kg/hr for the duration of the study. Seven control animals received an equivalent volume of saline. Heart rate, mean arterial pressure, central venous pressure, cardiac output, arterial and mixed venous blood gases, and serum lactate level were measured at regular intervals throughout the study. Cardiac index and systemic vascular resistance index were calculated at the same intervals. Overall, there were no statistically significant differences in the mean data values for mean arterial pressure, cardiac index, systemic vascular resistance index, or lactate, although lactate values were consistently higher in the naloxone group (two-tailed independent Student's t test). We conclude that naloxone does not significantly improve hemodynamics when administered after a fixed-volume hemorrhage.

The effects of chronic hypoxemia on central auditory processing in patients with chronic obstructive pulmonary disease

This study was designed to discover if chronic hypoxemia produced measurable deficits in subjects' ability to process complex auditory stimuli. In Part I, a group of normal middle-aged subjects and a group of middle-aged subjects with hypoxemia secondary to chronic obstructive pulmonary disease (COPD) were compared with respect to their performance on a central auditory test battery. (The test battery included the Staggered Spondaic Word, Synthetic Sentence Identification with Ipsilateral Competing Message, Synthetic Sentence Identification with Contralateral Competing Message, Memory for Unrelated Words, Memory for Sentences, and a Competing Sentence-Binaural Separation Test). The COPD group's scores were significantly poorer than the normal group's on two of the six tests. The pattern of test scores suggested that chronic hypoxemia produced its principle deficiency at the brain stem level. Part II of this study examined the specific relationships between pulmonary function, arterial blood gas levels, and central auditory performance in this same group of COPD subjects. Statistical analyses revealed that subjects with better pulmonary function and higher arterial blood oxygen levels had better performance on tests of central auditory function.