The presence of Nissl's bodies and neurofibrillae in the freshly fixed spinal nerve cell

Submitted in partial fulfillment of the requirements for the degree of master of arts in the graduate school of the University of MissouriIncludes a reprint of the complete revision of the thesis as published in the Journal of Comparative Neurology Vol 23, No 3, August, 1913TypescriptM.A. University of Missouri 1912Since the discovery of Nissl's bodies and neurofibrillae much work has been done on these structures. Nevertheless, some have even questioned their presence in the living nerve cell and have considered them as artifacts. Mollgaard, especially, in a recent article strongly doubts the existence of both in the "vitally-fixed" nerve cell. Thus it has seemed desirable to do some further work in this direction. This investigation was carried out in the Anatomic laboratory, University of Missouri, and under the supervision of Dr. C. M. Jackson

Computational models of cardiovascular response to orthostatic stress

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2004.Includes bibliographical references (p. 163-185).The cardiovascular response to changes in posture has been the focus of numerous investigations in the past. Yet despite considerable, targeted experimental effort, the mechanisms underlying orthostatic intolerance (OI) following spaceflight remain elusive. The number of hypotheses still under consideration and the lack of a single unifying theory of the pathophysiology of spaceflight-induced OI testify to the difficulty of the problem. In this investigation, we developed and validated a comprehensives lumped-parameter model of the cardiovascular system and its short-term homeostatic control mechanisms with the particular aim of simulating the short-term, transient hemodynamic response to gravitational stress. Our effort to combine model building with model analysis led us to conduct extensive sensitivity analyses and investigate inverse modeling methods to estimate physiological parameters from transient hemodynamic data. Based on current hypotheses, we simulated the system-level hemodynamic effects of changes in parameters that have been implicated in the orthostatic intolerance phenomenon. Our simulations indicate that changes in total blood volume have the biggest detrimental impact on blood pressure homeostasis in the head-up posture. If the baseline volume status is borderline hypovolemic, changes in other parameters can significantly impact the cardiovascular system's ability to maintain mean arterial pressure constant. In particular, any deleterious changes in the venous tone feedback impairs blood pressure homeostasis significantly. This result has important implications as it suggests that al-adrenergic agonists might help alleviate the orthostatic syndrome seen post-spaceflight.by Thomas Heldt.Ph.D

Computational Analysis of Cardiovascular Hemodynamics

The human body requires a complex circulatory system to supply nutrients to, and to remove metabolic waste products from, its tissues. Given this primary purpose, circulatory function is closely related to the hemodynamic characteristics of blood vessels. This includes not only macroscale fluid dynamics, but also mass transfer in the microvasculature. Many experimental and clinical studies have examined these characteristics of vascular function. Over the past 50 years, mathematical modeling has become a powerful adjunct to such studies, as modeling provides a rational framework within which to analyze the cardiovascular system

Biochar as Additive in Biogas-Production from Bio-Waste

Previous publications about biochar in anaerobic digestion show encouraging results with regard to increased biogas yields. This work investigates such effects in a solid-state fermentation of bio-waste. Unlike in previous trials, the influence of biochar is tested with a setup that simulates an industrial-scale biogas plant. Both the biogas and the methane yield increased around 5% with a biochar addition of 5%-based on organic dry matter biochar to bio-waste. An addition of 10% increased the yield by around 3%. While scaling effects prohibit a simple transfer of the results to industrial-scale plants, and although the certainty of the results is reduced by the heterogeneity of the bio-waste, further research in this direction seems promising

Model-Based Noninvasive Estimation of Intracranial Pressure from Cerebral Blood Flow Velocity and Arterial Pressure

Intracranial pressure (ICP) is affected in many neurological conditions. Clinical measurement of pressure on the brain currently requires placing a probe in the cerebrospinal fluid compartment, the brain tissue, or other intracranial space. This invasiveness limits the measurement to critically ill patients. Because ICP is also clinically important in conditions ranging from brain tumors and hydrocephalus to concussions, noninvasive determination of ICP would be desirable. Our model-based approach to continuous estimation and tracking of ICP uses routinely obtainable time-synchronized, noninvasive (or minimally invasive) measurements of peripheral arterial blood pressure and blood flow velocity in the middle cerebral artery (MCA), both at intra-heartbeat resolution. A physiological model of cerebrovascular dynamics provides mathematical constraints that relate the measured waveforms to ICP. Our algorithm produces patient-specific ICP estimates with no calibration or training. Using 35 hours of data from 37 patients with traumatic brain injury, we generated ICP estimates on 2665 nonoverlapping 60-beat data windows. Referenced against concurrently recorded invasive parenchymal ICP that varied over 100 millimeters of mercury (mmHg) across all records, our estimates achieved a mean error (bias) of 1.6 mmHg and SD of error (SDE) of 7.6 mmHg. For the 1673 data windows over 22 hours in which blood flow velocity recordings were available from both the left and the right MCA, averaging the resulting bilateral ICP estimates reduced the bias to 1.5 mmHg and SDE to 5.9 mmHg. This accuracy is already comparable to that of some invasive ICP measurement methods in current clinical use.National Institutes of Health (U.S.) (R01 EB001659)CIMIT: Center for Integration of Medicine and Innovative Technolog

A Multidimensional Approach to Pain Assessment in Critically Ill Infants During a Painful Procedure

Objectives: Inferring the pain level of a critically ill infant is complex. The ability to accurately extract the appropriate pain cues from observations is often jeopardized when heavy sedation and muscular blocking agents are administered. Near-infrared spectroscopy is a noninvasive method that may provide the bridge between behavioral observational indicators and cortical pain processing. We aimed to describe regional cerebral and systemic hemodynamic changes, as well as behavioral reactions in critically ill infants with congenital heart defects during chest-drain removal after cardiac surgery. Methods: Our sample included 20 critically ill infants with congenital heart defects, less than 12 months of age, admitted to the cardiac intensive care unit after surgery. Results: Cerebral deoxygenated hemoglobin concentrations significantly differed across the epochs (ie, baseline, tactile stimulus, noxious stimulus) (P=0.01). Physiological systemic responses and Face Leg Activity Cry Consolability (FLACC) pain scores differed significantly across the events (P<0.01). The 3 outcome measures were not found to be associated with each other. Mean FLACC pain scores during the painful procedure was 7/10 despite administration of morphine. Midazolam administration accounted for 36% of the variance in pain scores. Discussion: We demonstrated with a multidimensional pain assessment approach that significant cerebral, physiological, and behavioral activity was present in response to a noxious procedure in critically ill infants despite the administration of analgesic treatment. Considering that the sedating agent significantly dampened pain behaviors, assessment of cerebral hemodynamic in the context of pain seems to be an important addition.National Institutes of Health (U.S.) (Grant R01EB001659)National Institutes of Health (U.S.) (Grant K24NS057568)National Institutes of Health (U.S.) (Grant R21HD056009)National Institute for Biomedical Imaging and Bioengineering (U.S.)National Institute of Neurological Disorders and Stroke (U.S.)Eunice Kennedy Shriver National Institute of Child Health and Human Development (U.S.

Continuous quantitative monitoring of cerebral oxygen metabolism in neonates by ventilator-gated analysis of NIRS recordings

Oxidative stress during fetal development, delivery, or early postnatal life is a major cause of neuropathology, as both hypoxic and hyperoxic insults can significantly damage the developing brain. Despite the obvious need for reliable cerebral oxygenation monitoring, no technology currently exists to monitor cerebral oxygen metabolism continuously and noninvasively in infants at high risk for developing brain injury. Consequently, a rational approach to titrating oxygen supply to cerebral oxygen demand – and thus avoiding hyperoxic or hypoxic insults – is currently lacking. We present a promising method to close this crucial technology gap in the important case of neonates on conventional ventilators. By using cerebral near-infrared spectroscopy and signals from conventional ventilators, along with arterial oxygen saturation, we derive continuous (breath-by-breath) estimates of cerebral venous oxygen saturation, cerebral oxygen extraction fraction, cerebral blood flow, and cerebral metabolic rate of oxygen. The resultant estimates compare very favorably to previously reported data obtained by non-continuous and invasive means from preterm infants in neonatal critical care.National Institutes of Health (U.S.) (Grant R01EB001659)National Institutes of Health (U.S.) (Grant K24NS057568)National Institutes of Health (U.S.) (Grant R21HD056009