No description available.

Only a small amount of the available literature is concerned with venous control in lower vertebrates, such as fish. It has even been suggested that veins in fish are not important factors in active regulation of venous return. Preliminary work carried out for this thesis strongly refuted this assumption, highlighting gaps in the existing literature. As a result of the lack of information pertaining to the physiology of the central venous compartment of the circulation, my objective has been to investigate various aspects of this in the hagfish Eptatretus cirrhatus. Hagfishes, with the lowest arterial blood pressures and highest blood volumes amongst the chordates, are the earliest surviving group to separate off from the chordate lineage. They provide a unique opportunity to investigate likely physiological mechanisms in ancestral chordates. The data presented in this thesis suggest thtat 1) E. cirhatus exhibit some cardiovascular compensation during volume manipulation, however this only occurs with volume loading and not during volume depletion, 2) Veins from E. cirrhatus can respond vasoactively to adrenergic stimulation in vitro and 3) Plasma catecholamines in E. cirrhatus also respond to volume manipulation and provide a potential in vivo mechanism for the control of changes in cardiovascular parameters that were observed during volume loading.

Die biochemische Diagnostik von Phäochromozytomen und Paragangliomen (PPGL) basiert auf einem gesteigerten Katecholaminmetabolismus in dessen Folge es zu erhöhten Plasmametanephrinkonzentrationen (Normetanephrin NMN und/oder Metanephrin MN) kommt. Die variable endokrine Aktivität der Tumoren sowie Hormonzentrationen im Nanomol-pro-Liter-Bereich stellen hohe Anforderungen an analytische Messmethoden. Nicht oder spät diagnostizierte PPGL können lebensbedrohliche katecholaminerge Krisen verursachen. Demzufolge sind präzise Nachweisverfahren und validierte Messmethoden für die biochemische Diagnostik unerlässlich. Inwiefern die Messverfahren enzymgekoppelter Immunoassay (EIA) und Flüssigkeitschromatographie mit Tandem-Massenspektrometrie (LC-MS/MS) zur Analyse von Plasmametanephrinen in gleichem Maße geeignet sind, ist aufgrund der kontroversen Studienlage unklar. Hierfür wurde eine Substudie im Rahmen der prospektiven monoaminproduzierenden Tumor (PMT)-Studie an fünf europäischen Zentren durchgeführt. Es wurden 341 Patienten (174 Männer, 167 Frauen), darunter 54 Patienten mit PPGL eingeschlossen. Die Blutproben wurden unter Standardbedingungen entnommen und mit beiden Messmethoden in spezialisierten Zentren analysiert. Für den EIA zeigte sich ein negativer Bias von 60% für NMN und 39% für MN. Dieser führte unter Verwendung oberer Grenzwerte nach Herstellerangaben zu einer Sensitivität von 74,1% und einer Spezifität von 98,9%. Für LC-MS/MS wurde eine signifikant höhere Sensitivität von 98,1% und eine Spezifität von 99,7% gezeigt. Die Berechnung der area under the curve (AUC) im Zuge der receiver-operating-characteristic (ROC)-Kurven-Analyse indizierte jedoch eine vergleichbar hohe diagnostische Testleistung für EIA (0,993) und LC-MS/MS (0,985). Durch eine Bias-korrigierte Grenzwertoptimierung stieg die Sensitivität des EIAs auf 96,2% bei einer Spezifität von 95,1% und führte dadurch zu einer vergleichbaren diagnostischen Testqualität wie LC-MS/MS. Fazit: Bei diesem kommerziell erhältlichen EIA resultiert die Verwendung oberer Grenzwerte nach Herstellerangaben in einer insuffizienten Sensitivität. Dies birgt das Risiko, Patienten mit PPGL nicht zu diagnostizieren. Eine Rekalibrierung des EIAs sowie eine Validierung der Referenzintervalle sind erforderlich. / Context: Reports conflict concerning measurements of plasma metanephrines for diagnosis of pheochromocytomas/paragangliomas (PPGL) by immunoassays compared to other methods. Objective: To compare the performance of a commercially available enzyme-linked immunoassay (EIA) with liquid chromatographic tandem mass spectrometric (LC-MS/MS) measurements of metanephrines to diagnose PPGLs. Design: Sub-study of a prospective, multicenter trial to study the biochemical profiles of monoamine-producing tumors Patients: Patients included 174 males and 167 females with suspected PPGL (median age 54 years), of whom 54 had confirmed PPGL. Interventions: Plasma metanephrines were measured by EIA and LC-MS/MS, each in a specialized laboratory. Results: Plasma normetanephrine and metanephrine were measured 60% and 39% lower by EIA than by LC-MS/MS. Using upper cut-offs stipulated for the EIA, diagnostic sensitivity was only 74.1% at a specificity of 99.3%. In contrast, use of similar cut-offs for metanephrine and overall lower age-adjusted cutoffs for normetanephrine measured by LC-MS/MS returned a diagnostic sensitivity and specificity of 98.1% and 99.7%. Areas under receiver-operating characteristic curves, nevertheless, indicated comparable diagnostic performance of the EIA (0.993) and LC-MS/MS (0.985). Diagnostic sensitivity for the EIA increased to 96.2% with minimal loss in specificity (95.1%) following use of cut-offs for the EIA adapted to correct for the negative bias. Conclusions: EIA underestimates plasma metanephrines and diagnostic sensitivity is poor using commonly stipulated cut-offs, resulting in high risk for missing patients with PPGLs. Correction of this shortcoming can be achieved by appropriately determined cut-offs resulting in comparable diagnostic performance of EIA and LC-MS/MS assays.

This study examines the use of unmodified magnetite nanoparticles (Fe3O4 NPs) for selective extraction and enrichment of the catecholamines dopamine (DA), noradrenaline (NE), and adrenaline (E), prior to analysis using capillary electrophoresis with UV detection. Coordination between Fe3+ on-the-surface Fe3O4 NPs and the catechol moiety of catecholamines enables Fe3O4 NPs to capture catecholamines from an aqueous solution. We obtained maximum loading of catecholamines on the NP surface by adjusting the pH of the solution to 7.0. In addition, catecholamine loading on the Fe3O4 NPs increased in conjunction with NP concentrations. Ligand exchange found H3PO4 to be efficient in the removal of adsorbed catecholamines on the NP surface. Adding 1.2% poly(diallyldimethylammonium chloride) to the background electrolyte caused efficient separation of the liberated catecholamines with baseline resolution within 20 min. Under optimal extraction and separation conditions, the limit of detections at a signal-to-noise ratio of 3 for E, NE, and DA were 9 nM, 8 nM, and 10 nM, respectively. Significantly, we successfully used the combination of a phenylboronate-containing spin column and the proposed method to determine the concentrations of NE and DA in urine and the content of NE in Portulaca oleracea L. leaves.

Typescript (photocopy) / v, 243 leaves, [4] leaves of plates : ill. ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Physiology and Pharmacology, University of Adelaide, 1975

Only a small amount of the available literature is concerned with venous control in lower vertebrates, such as fish. It has even been suggested that veins in fish are not important factors in active regulation of venous return. Preliminary work carried out for this thesis strongly refuted this assumption, highlighting gaps in the existing literature. As a result of the lack of information pertaining to the physiology of the central venous compartment of the circulation, my objective has been to investigate various aspects of this in the hagfish Eptatretus cirrhatus. Hagfishes, with the lowest arterial blood pressures and highest blood volumes amongst the chordates, are the earliest surviving group to separate off from the chordate lineage. They provide a unique opportunity to investigate likely physiological mechanisms in ancestral chordates. The data presented in this thesis suggest thtat 1) E. cirhatus exhibit some cardiovascular compensation during volume manipulation, however this only occurs with volume loading and not during volume depletion, 2) Veins from E. cirrhatus can respond vasoactively to adrenergic stimulation in vitro and 3) Plasma catecholamines in E. cirrhatus also respond to volume manipulation and provide a potential in vivo mechanism for the control of changes in cardiovascular parameters that were observed during volume loading.

Tübingen, Univ., Diss., 2008.

No description available.

The ability of the adult heart to generate new myocytes after injury is not established. Our purpose was to determine if the adult heart has the capacity to generate new myocytes after injury, and to gain insight into their source. Cardiac injury was induced in the adult feline heart by infusing Isoproterenol (ISO) for 10 days with minipumps and then animals were allowed to recover for 7 or 28 days. Cardiac function was measured with echocardiography and proliferative cells were identified by nuclear incorporation of 5-bromodeoxyuridine (BrdU; 7 day minipump infusion). BrdU was infused for 7 days before euthanasia at Day 10 (injury), Day 17 (early recovery), and Day 38 (late recovery) and, with a separate group of animals, was infused during injury and removed at Day 10, with animals euthanized at Day 38 for a pulse-chase experiment. Isoproterenol caused a reduction in cardiac function with evidence of myocyte loss from necrosis. During the injury phase there was a significant increase in the number of proliferative cells in the atria and ventricle, including an increase in cKit+/BrdU+ proliferative cardiac precursor cells, but there was no increase in the number of BrdU+ new myocytes (Day 10). During the first seven days of recovery (Day 17) there was a significant reduction in cellular proliferation (total BrdU+ nuclei, including cKit+/BrdU+ proliferative cardiac precursor cells) but a significant increase in BrdU+ myocytes. There was modest improvement in cardiac structure and function during recovery. At Day 38 (late recovery), overall cell proliferation (BrdU+ cells) was not different than control (BrdU infused from Days 31-38); however, increased numbers of ("bright") BrdU+ myocytes were found at Day 38 in the pulse-chase experiment, when BrdU was infused during injury (and removed at Day 10). Some of the newly formed myocytes (from the pulse-chase group; Day 38), derived from BrdU+ cardiac precursors appear to be transiently proliferative (between Days 10-38) producing a population of "dimly" BrdU+ myocytes in our pulse-chase protocol (BrdU infused during injury, Days 3-10, and removed at Day 10, with heart explant at Day 38). No significant numbers of "dimly" BrdU+ nuclei were found in any of the hearts in which BrdU was infused for 7 days prior to the animal being euthanized (Control, Day 10, Day 17, Day 38). These observations are most consistent with the conclusions stated. Our results also suggest that myocyte regeneration, as defined by BrdU+ myocytes, was more robust in the atria than the ventricle. The reasons for these differences are not clear and deserve additional study. If true, our findings suggest that cardiac precursors isolated and expanded from atrial tissue might be a better source of cells for autologous cardiac cell therapy. In summary, our data shows that the adult heart has the ability to generate new myocytes after injury, suggests that ISO injury activates cardiac precursor cells that can differentiate into new myocytes during cardiac repair, but that the environment of the ISO injured heart blunts the differentiation of cardiac precursors into functional new myocytes. The contribution of new myocytes to improved function of the ventricle would appear to be small, unless we have underestimated the number of these cells. This is quite possible, and further study is warranted to incorporate the number of "dimly" BrdU+ myocytes that may have undergone a proliferative phase as a progenitor cell and/or as an immature cardiac myocyte. Further understanding the factors that limit endogenous new myocyte formation could significantly contribute to new therapeutic applications and improve the quality of life, and potentially the lifespan, of patients in heart failure. / Physiology

Heart rate variability (HRV) has been used to evaluate cardiac autonomic function by measuring variations in electrocardiographic R-R intervals between cardiac cycles. HRV was first used to associate decreases in autonomic nervous system (ANS) control with an increased risk of mortality in coronary heart disease and in the diagnosis of diabetes (1). Current clinical research interest has extended to investigate uses of HRV to evaluate changes in the cardiovascular system due to disease, aging, physical activity, and cardiac rehabilitation treatment (2, 5). HRV scores are derivatives of R-R intervals and these may be represented as a function of either time or frequency domain parameters. Time domain analysis is the simplest and includes: the standard deviation of R-R intervals and the number of adjacent RR intervals that differ by >50ms (dRR50). Frequency domain measures involve more elaborate calculation and have been applied in studies to evaluate sympathetic and parasympathetic autonomic balance. The latter include: Low Frequency Power (LF), High Frequency Power (HF), and LF/HF ratio. HRV has been measured in a variety of ways, the most common being a continuous 24-hour collection of R-R data. In recent years, several investigators have sought to assess HRV by utilizing brief collection periods. Controversy exists about the potential of these short-term sampling intervals to yield reproducible and meaningful measurements of HRV. Many confounders such as respiration, stress, and body positioning can influence HRV, which is why a longer collection period has been accepted as the standard for providing a stable index of ANS function. However, short sampling periods would be useful to evaluate HRV when faced with time constraints. The purpose of the current study was to evaluate the reproducibility of HRV using 8-hour daytime measures with the Polar R-R RecorderTM (Polar Electro Oy, Kempele, Finland) and with short sampling duration of 512 cardiac cycles, using the Schiller AT-10TM device (Schiller AG, Baar, Switzerland). Methods: 10 apparently healthy adult volunteers participated in the study, which was conducted at the Sleep Disorders Clinic in Christiansburg, VA. Each subject performed two HRV trials with the Cardiovit AT-10TM device using recordings of 512 cardiac cycles. Within one or two days following the Schiller, the same subjects wore a Polar R-R RecorderTM device to obtain an 8-hour recording of HRV during waking hours; 24-hour urine samples were collected on the same day. Urine was analyzed for catecholamine levels, including norepinephrine and epinephrine in order to evaluate sympathetic nervous system globally. Each subject recorded their personal impressions of unavoidable physical activity and daytime stress demands on the day of the 8-hour recording and urine collection. This entire protocol was repeated one week later. On one of the days of the short sampling recording, VO2pk also was evaluated for each subject using a ramp protocol on the cycle ergometer and a metabolic cart. Results: The correlation analysis for the HRV response variables using the Schiller method indicated a high-to-very high correlation between trials within a day for the time domain measures (r = 0.75-0.99). The frequency domain measures, however, were low-to-moderately correlated (r = 0.24-0.66) between trials within a day for the Schiller method. Correlations between days for HRV response variables using the Schiller method were similarly low for both time (r < 0.5) and (r < 0.4) frequency domain measures. Correlation coefficients between days for the HRV response variables using the Polar method were moderate (r = 0.59-0.67) for the time domain and only low-moderate for the frequency domain measures (r = 0.37-0.69). However, an important finding was that Polar R-R data for two of the subjects contained excessive signal artifact, which affected the fidelity of the HRV scores. When these two cases were excluded from the group analyses, the resulting correlations were high-very high for all time and frequency domain measures (r = 0.70-0.93). The means for each response HRV time and frequency domain variable between the Polar method and Schiller method were significantly different (P < 0.05). Additional correlational analyses did not reveal any systematic associations between HRV measures and simple markers of sympathetic activity (urinary NE or E) and aerobic fitness (VO2pk) in this small sample of subjects. Conclusions: Due to this important change in reproducibility with the Polar method, the consequence of artifact-free recordings is unmistakable. Within the limitations of this small study sample it is concluded that, while HRV in apparently healthy adults may not be measured reliably with brief data collection periods, longer daytime sampling periods of 8 hours (e.g. Polar device) yields acceptable reliability for both time and frequency domain parameters of HRV. / Master of Science