Mechanisms involved in chronic neuropathic pain after avulsion injury

PhDMotor vehicle accidents are the most common cause of injuries involving avulsion of spinal roots from the brachial or lumbosacral plexuses. This results in chronic intractable pain that is refractory to pharmacotherapy. This is largely due to lack of information on underlying mechanisms, and lack of an established animal model to test drug treatments. This thesis has: 1) compared the neuroanatomical effects of dorsal root rhizotomy (DRR) and avulsion (DRA) in the spinal cord. DRR is commonly used to model avulsion injury but unlike avulsion it does not damage the spinal cord, as often happens clinically. 2) Developed a behavioural model of spinal root avulsion injury (SRA). 3) Evaluated the behavioural effects of drugs prescribed to treat neuropathic pain or those used clinically to treat other conditions like motoneuron disease or spinal cord injury. DRA produced a greater and prolonged glial, inflammatory, vascular response and cell loss than DRR. SRA produced thermal and mechanical hypersensitivity in the affected hind-paw. Neurodegenerative and neuroinflammatory responses were observed in both the avulsed and adjacent spinal segments, but produced no changes in the neuronal phenotype adjacent dorsal root ganglion neurons, suggesting that the evoked behaviour is mediated by central mechanisms. Administration of amitriptyline or carbamazepine reduced behavioural hypersensitivity in SRA, confirming their limited clinical efficacy in treatment of avulsion injury. Minocycline and riluzole produced therapeutic efficacy. Both compounds prevented the establishment of behavioural hypersensitivity, which correlated histologically with microglial inhibition, although riluzole was transiently effective. Additionally, minocycline reversed the hypersensitivity, an effect that persisted beyond drug washout, whereas riluzole had a limited effect that only lasted whilst the drug was administered. This thesis provides insight into the mechanisms of avulsion-induced neuropathic pain. The establishment of a behaviourally reproducible avulsion model provides a platform to test new pharmacological candidates for treatment, such as minocycline

Measuring plume-related exhumation of the British Isles in Early Cenozoic times

Mantle plumes have been proposed to exert a first-order control on the morphology of Earth's surface. However, there is little consensus on the lifespan of the convectively supported topography. Here, we focus on the Cenozoic uplift and exhumation history of the British Isles. While uplift in the absence of major regional tectonic activity has long been documented, the causative mechanism is highly controversial, and direct exhumation estimates are hindered by the near-complete absence of onshore post-Cretaceous sediments (outside Northern Ireland) and the truncated stratigraphic record of many offshore basins. Two main hypotheses have been developed by previous studies: epeirogenic exhumation driven by the proto-Iceland plume, or multiple phases of Cenozoic compression driven by far-field stresses. Here, we present a new thermochronological dataset comprising 43 apatite fission track (AFT) and 102 (U–Th–Sm)/He (AHe) dates from the onshore British Isles. Inverse modelling of vertical sample profiles allows us to define well-constrained regional cooling histories. Crucially, during the Paleocene, the thermal history models show that a rapid exhumation pulse (1–2.5 km) occurred, focused on the Irish Sea. Exhumation is greatest in the north of the Irish Sea region, and decreases in intensity to the south and west. The spatial pattern of Paleocene exhumation is in agreement with the extent of magmatic underplating inferred from geophysical studies, and the timing of uplift and exhumation is synchronous with emplacement of the plume-related British and Irish Paleogene Igneous Province (BIPIP). Prior to the Paleocene exhumation pulse, the Mesozoic onshore exhumation pulse is mainly linked to the uplift and erosion of the hinterland during the complex and long-lived rifting history of the neighbouring offshore basins. The extent of Neogene exhumation is difficult to constrain due to the poor sensitivity of the AHe and AFT systems at low temperatures. We conclude that the Cenozoic topographic evolution of the British Isles is the result of plume-driven uplift and exhumation, with inversion under compressive stress playing a secondary role

A Case Study in Physical-Layer Steganography Applied to Multicarrier Transmissions

Covert communications can be a force for good, such as providing a means of message authentication to prevent malicious actors from spoofing networks. This dissertation explores the design of a covert signal to be hidden inside the bandwidth of an Orthogonal Frequency Division Multiplexing (OFDM) signal. In order to make detection by unintended observers as difficult as possible, the covert signal operates as interference inside the OFDM signal and is set to a high Signal to Interference Ratio (SIR). Given the high SIR, the OFDM signal must be cancelled in order to recover the covert signal. The detectability of the covert signal is tested using multiple detectors with and without cancellation. Among the detectors used is a Convolutional Neural Network (CNN) designed for image classification that has been repurposed through transfer learning to detect signal activity in noise and interference. The CNN detector demonstrates resilience in the presence of narrowband interference. The cancellation algorithm is enhanced with an estimate of OFDM windowing as applied at the transmitter, which is an often-overlooked parameter in cancellation applications. The enhanced cancellation-algorithm improves the cancellation of OFDM signals by 5.3 dB in an over-the-air test. The enhanced cancellation-algorithm also improves the Packet Error Rate of OFDM signals and improves the recovery of the covert signal. The improved recovery has direct application to Power-Domain Non-orthogonal Multiple Access and Rate-Splitting Multiple Access, which both rely on successive interference cancellation. Lastly, to frustrate any efforts to analyze the covert waveform, the covert signal is augmented with an adversarial waveform designed to exploit weaknesses in CNNs used for modulation classification. The classification system suffers from uncertainty in the bandwidth estimate of the covert signal. The system will likely err on the side of making the bandwidth wider than necessary. It is demonstrated that a wider bandwidth makes the attack more successful, as opposed to other estimation errors which prior literature has shown to weaken the effectiveness of these attacks

Nucleolar localization of an isoform of the IGF-I precursor

BACKGROUND: Alternative exons encode different isoforms of the human insulin-like growth factor-I (IGF-I) precursor without altering mature IGF-I. We hypothesized that the various IGF-I precursors may traffic IGF-I differently. Chimeric IGF-I precursors were made with green fluorescent protein (GFP) cloned between the signal and mature IGF-I domains. RESULTS: Chimeras containing exons 1 or 2 were located in the cytoplasm, consistent with a secretory pathway, and suggesting that both exons encoded functional signal peptides. Exon 5-containing chimeras localized to the nucleus and strongly to the nucleolus, while chimeras containing exon 6 or the upstream portion of exon 5 did not. Nuclear and nucleolar localization also occurred when the mature IGF-I domain was deleted from the chimeras, or when signal peptides were deleted. CONCLUSIONS: We have identified a nucleolar localization for an isoform of the human IGF-I precursor. The findings are consistent with the presence of a nuclear and nucleolar localization signal situated in the C-terminal part of the exon 5-encoded domain with similarities to signals in several other growth factors

Who gave you the right?: Exploring power and politics in journalism and academic work chronicling Hurricane Maria

Hurricane Maria impacted Puerto Rico on September 20, 2017 and caused severe damage to the island. During the year after Hurricane Maria, government agencies and news organizations struggled to arrive at a consensus regarding the hurricane's death toll. The early death estimates that were severe- ly underreported affected the amount of relief that Puerto Rico received from government institutions, as well as from private groups. As a result, it is im- perative to understand how these consequential numbers were constructed following Hurricane Maria. We interviewed journalists and academic researchers who produced and disseminated information following Hurricane Maria and considered the role that these individuals played in communicating the number of deaths caused by the hurricane, how their methods differed, and how these factors contribute to the production of death toll numbers and narratives. We discuss our results in the context of validation and the consequences of colonization on information production and dissemination

Adaptations to iron deficiency: cardiac functional responsiveness to norepinephrine, arterial remodeling, and the effect of beta-blockade on cardiac hypertrophy.

BackgroundIron deficiency (ID) results in ventricular hypertrophy, believed to involve sympathetic stimulation. We hypothesized that with ID 1) intravenous norepinephrine would alter heart rate (HR) and contractility, 2) abdominal aorta would be larger and more distensible, and 3) the beta-blocker propanolol would reduce hypertrophy.Methods1) 30 CD rats were fed an ID or replete diet for 1 week or 1 month. Norepinephrine was infused via jugular vein; pressure was monitored at carotid artery. Saline infusions were used as a control. The pressure trace was analyzed for HR, contractility, systolic and diastolic pressures. 2) Abdominal aorta catheters inflated the aorta, while digital microscopic images were recorded at stepwise pressures to measure arterial diameter and distensibility. 3) An additional 10 rats (5 ID, 5 control) were given a daily injection of propanolol or saline. After 1 month, the hearts were excised and weighed.ResultsEnhanced contractility, but not HR, was associated with ID hypertrophic hearts. Systolic and diastolic blood pressures were consistent with an increase in arterial diameter associated with ID. Aortic diameter at 100 mmHg and distensibility were increased with ID. Propanolol was associated with an increase in heart to body mass ratio.ConclusionsID cardiac hypertrophy results in an increased inotropic, but not chronotropic response to the sympathetic neurotransmitter, norepinephrine. Increased aortic diameter is consistent with a flow-dependent vascular remodeling; increased distensibility may reflect decreased vascular collagen content. The failure of propanolol to prevent hypertrophy suggests that ID hypertrophy is not mediated via beta-adrenergic neurotransmission

Practical remediation of 3-nitro-1,2,4-triazol-5-one wastewater

Limiting environmental impact is a top priority for the chemical industry, and manufacturing practices need to be well controlled to avoid any potential contamination. In order to reduce waste streams during the processing of 3-nitro-1,2,4-triazol-5-one (NTO), potentially evironmental hazardous at concentrations of 1 g/l, we investigated the potential remediation and recycling of water using a wide range of commercial sorption media. We studied the effect of experimental conditions, including flow rate, initial contaminant concentration and temperature. This led to the selection of Amberlyst A26 OH in a batch process and Activated Carbon in continuous flow, as the most effective sorption methods. Using high performance liquid chromatography photodiode array detection (HPLC-PDA), NTO was quantified from solutions, before and after remediation, showing a complete removal from a 10 g/l NTO solution. Our purification method therefore appears to be suitable for the remediation of NTO-contaminated wastewater

Printable microscale interfaces for long-term peripheral nerve mapping and precision control

The nascent field of bioelectronic medicine seeks to decode and modulate peripheral nervous system signals to obtain therapeutic control of targeted end organs and effectors. Current approaches rely heavily on electrode-based devices, but size scalability, material and microfabrication challenges, limited surgical accessibility, and the biomechanically dynamic implantation environment are significant impediments to developing and deploying advanced peripheral interfacing technologies. Here, we present a microscale implantable device – the nanoclip – for chronic interfacing with fine peripheral nerves in small animal models that begins to meet these constraints. We demonstrate the capability to make stable, high-resolution recordings of behaviorally-linked nerve activity over multi-week timescales. In addition, we show that multi-channel, current-steering-based stimulation can achieve a high degree of functionally-relevant modulatory specificity within the small scale of the device. These results highlight the potential of new microscale design and fabrication techniques for the realization of viable implantable devices for long-term peripheral interfacing.https://www.biorxiv.org/node/801468.fullFirst author draf

Effects of solvent used for fabrication on drug loading and release kinetics of electrosprayed temozolomide-loaded PLGA microparticles for the treatment of glioblastoma

Glioblastoma multiforme (GBM) is the most common and invasive form of malignant brain tumors and despite advances in surgery, radiotherapy, and chemotherapy, the survival of patients with GBM still remains poor. Temozolomide (TMZ) is the chemotherapy drug that is most commonly given orally after surgical resection of these tumors. In this study, the effects of solvents (i.e., dichloromethane and acetonitrile) used for the fabrication of electrosprayed TMZ-loaded poly(lactic-co-glycolic acid) (PLGA) on drug loading, loading efficiency, drug release kinetics, surface morphology, and particle size were investigated. The results from this study demonstrated that by using a larger volume of a solvent with higher polarity (i.e., acetonitrile) which allows for a higher amount of hydrophilic TMZ to dissolve into the polymer solution, higher drug loading could be achieved. However, the particles fabricated with high amount of acetonitrile, which has a lower vapor pressure, had large pores and a smaller diameter which led to an initial burst release and high cumulative release at the end of the study. An optimal combination of the two solvents is needed to result in particles with a good amount of loading and minimal initial burst release. The electrosprayed microparticles were able to illicit a cytotoxic response in U-87 MG glioblastoma cells at a lower concentration of drug compared to the free drug. This work indicated that electrospraying is a promising method for the fabrication of TMZ-loaded PLGA microparticles for the treatment of GBM and solvent composition can be altered to control drug loading and release kinetics

Fed, but not Fasted, Adrenalectomized Rats Survive the Stress of Hemorrhage and Hypovolemia

We have recently shown that conscious adrenalectomized rats exhibit nearly normal recovery of arterial blood pressure during the 5 h after hemorrhage. In those experiments, it appeared that a previous reduction in food intake might have compromised the recovery of blood pressure and increased mortality. These experiments were designed to test in conscious sham-adrenalectomized (control) and adrenalectomized rats prepared with indwelling arterial and venous cannulae: 1. The effects of a 20- to 24-h fast (compared to rats fed ab libitum) on the mobilization of plasma substrates and recovery of arterial blood pressure after a 15 ml/kg - 5 min hemorrhage, and 2. Vascular responsivity to pressor agents in fed or fasted groups before or 2 h after hemorrhage. In all rats hemorrhage resulted in decreased arterial pressure and heart rate. Arterial pressure recovered to near normal in both fed and fasted control groups and in the led adrenalectomized rats, and all of these rats survived for 24 h after stress. By contrast, in the fasted adrenalectomized rats, arterial pressure recovered only during the first 1.5 - 2 h and then failed, resulting in 100% mortality by 3-5 h. Compared to the other three groups, in which substrate levels either increased or remained fairly stable, plasma glucose and beta-hydoxybutyrate concentrations fell steadily, from 1.5-2 h after hemorrhage until death occurred in the fasted adrenalectomized rats. Basal ACTH concentrations were elevated cormpared to control values in both adrenalectomized groups (fed and fasted). Hemorrhage caused increases in plasma ACTH in all groups; the magnitude of the responses did not differ among the groups. The dilution of Evans' blue dve after hemorrhage (used as an index of fluid movement into the vascular space) was not different in contol and adrenalectomized rats (either fed or fasted). There were no differences in pressor responses to phenylephrine, vasopressin, or angiotensin-II between the fed and fasted condition in the control rats either before or after hemorrhage. There was a fasting-associated decrease in vascular responsivity, to vasopressin, but normal responsivity to phenylephrine and angiotensin-II, in the adrenal-ectomized rats both before and after hemorrhage. We conclude that: (1) since fed adrenalectomized rats all survived the stress, adrenal hormones are not required for survival unless fasting is a prior condition; (2) vascular responsiveness to phenylephrine and angiotensin-II is not altered by fasting and is, therefore, probably not the proximate cause of cardiovascular svstem failure; and (3) from these data we cannot distinguish between a failure in substrate supply and a failure in some component of the cardiovascular svstem, other than vascular responsivity, that results in death after hemorrhage in fasted adrenalectomized rats