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Approximately 30% of people admitted to ICU in the UK have co-existing cardiovascular disease (CVD), and this may rise as life-expectancy increases. Patients with CVD have impaired compensatory mechanisms to enable maximum oxygen delivery to the tissues in the event of critical illness, which itself increases global oxygen demand, further stressing the heart. This is exacerbated by tachycardia and hypotension, which may relatively reduce blood flow to the coronary arteries, and catecholamines which increase myocardial oxygen demand. The myocardium extracts 75% of the oxygen supplied by the coronary arteries at rest, and atheroma-related flow limitation further compromises myocardial oxygen delivery. However, the diagnosis of acute coronary syndrome in critical illness is not straightforward, due to patient inability to communicate symptoms, non-specific ECG changes, and poorly understood cardiac biomarker troponin elevation. My overall hypothesis is that patients with CVD benefit from increased oxygen delivery to the myocardium during critical illness. A focus is the importance of anaemia. The aims of the studies presented in this thesis are (i) to systematically review the literature regarding blood transfusion thresholds specifically in patients with CVD; (ii) to explore the association between Troponin I (TnI) within 24 hours of ICU admission and hospital mortality (iii) to describe and quantify the dynamics of TnI in patients with CVD during the first ten days after ICU admission; and (iv) to define myocardial infarction in the context of critical illness. I have performed a systematic review and meta-analysis of randomised controlled trials comparing a restrictive with liberal transfusion threshold and that included patients with CVD. In total, 11 trials enrolling patients with CVD (n=3033) were included for meta-analysis (restrictive n=1514, liberal=1519). The pooled risk ratio for the association between a restrictive transfusion threshold and 30 day mortality was 1.15 (95% CI 0.88 to 1.50, p=0.50, I2=14%). The risk of acute coronary syndrome in patients managed with restrictive compared with liberal transfusion was increased (nine trials, risk ratio 1.78, 95% CI 1.18 to 2.70, p=0.0, I2=0%). In contrast to broader literature supporting restrictive thresholds, our systematic review shows that a restrictive transfusion threshold of less than 80g/l may not be safe in patients with co-existing CVD, and highlights the variability in diagnostic definitions of ACS and the potential for ascertainment bias in transfusion trials. I undertook a retrospective cohort study in two independently collected cohorts of general ICU patients who had TnI measured within 24 hours of ICU admission. Importantly, the majority of TnI samples were collected routinely rather than for clinical indications. We used the Abbott ARCHITECT Stat assay (limit of detection 0.01mcg/l. We performed multivariable regression, adjusting for components of the APACHE II model. We derived the risk prediction score from the multivariable model with TnI. TnI was associated with all cause hospital mortality (OR per doubling TnI 1.16, 95% CI 1.13 to 1.20, p < 0.001) which persisted after adjustment for APACHE II model components (OR TnI 1.05, 95% CI 1.01 to 1.09, p=0.003). TnI correlated highly with the Acute Physiological Score component of APACHE II (r=0.39), suggesting that TnI release may be largely explained by acute physiological stress. Addition of TnI to the APACHE II model did not improve the performance of the risk prediction model and we would not advocate the adoption of a routine single troponin sample at admission. I designed, set up, and recruited 279 patients to a prospective cohort study TROPonin I in Cardiovascular patients in CriticAL care (TROPICCAL, UKCRN 19253) in 11 UK centres. The aims were to (i) determine the incidence of Myocardial Injury and Infarction, defined by the Third Universal Definition of Myocardial Infarction; (ii) explore factors associated with Injury and Infarction from multivariable analyses; and (iii) explore the relationship between Injury/Infarction and outcome in unadjusted and adjusted analyses. We recorded baseline characteristics, and took daily hs-TnI for ten days after ICU admission, severity of illness measures and ECGs for 5 days. There was a wide range of peak TnI (med 114ng/l (min 3, Q1 27, Q3 412, max 58820ng/l)) and a high prevalence of myocardial injury on systematic screening: 71% of patients had peak TnI greater than the sex-specific diagnostic threshold ('Injury'), and 24% had peak TnI greater than the sex-specific diagnostic threshold and dynamic changes on ECG consistent with ischaemia ('Infarction'). TnI consistently showed a rise-and-fall pattern consistent with an acute myocardial 'hit' rather than persisting injury, which peaked early during ICU stay. Importantly, only 12 (4.4%) patients were diagnosed with MI by the clinicians looking after the patients. Independent predictors of peak TnI in the preceding 24 hours were SOFA score, dynamic ECG ischaemia, lactate, haemoglobin, and age. The lack of association with CRP (representing systemic inflammation), with stronger association with lactate (representing inadequate perfusion/oxygen supply), Hb and ECG ischaemia support the conjecture that injury results in part from an acute ischaemic hit in this population. Patients with Infarction had similar baseline demographics to patients with Injury, but had higher peak TnI concentrations, and higher hospital and six month mortality (Figure 2). This supports the importance of including systematic assessment of dynamic ECG changes in the myocardial injury 'construct' in ICU. My work has shown an increased risk of ACS in patients with CVD randomised to restrictive transfusion thresholds. TnI elevation is prevalent in general ICU patients, and is independently associated with hospital mortality. A systematic approach to the detection of myocardial injury in critically ill patients with co-existing CVD who are unable to communicate symptoms, can identify a high risk population who have poorer survival than patients with no injury. Markers of ischaemia are more associated with TnI rise than markers of inflammation, supporting the hypothesis that myocardial injury in this population is at least in part due to oxygen supply-demand imbalance 'myocardial infarction'. From this work, I would recommend (i) a more liberal transfusion threshold of at least 80g/l in patients with coexisting CVD; (ii) systematic use of sequential ECGs in ICU to screen for myocardial injury in 'at risk' patients; and (iii) manipulation of physiological parameters such as anaemia, hypotension and tachycardia should be considered for patients with dynamic ECG changes plus troponin increase consistent with Infarction. Future research should include 'precision medicine' trials in the substantial cohort of ICU patients with co-existing CVD to explore whether interventions that increase myocardial oxygen supply and/or treat infarction alter outcomes.

At Kungsberget ski-resort in Gävleborg county all wastewater produced at the facility is treated on-site. The treatment takes place at their own wastewater treatment plant in a so-called Sequence Batch Reactor (SBR), which has been in operation for about a year before this study. Kungsberget AB is currently in charge of the facility but their goal is to hand responsibility over to Sandviken Energy AB. In order for this handover to occur Kungsberget has to produce three approved treatment results. This means that the concentrations of BOD7 needs to lie under 0.3 mg/l and total phosphorous under 10 mg/l in the effluent water for three consecutive samples. The results show momentaneous values. These limits are stated in the permit Kungsberget received from the Environmental Protection Division. Kungsberget has had problems with high and fluctuating phosphorous concentrations and therefore the transfer has not yet taken place. In this project several parameters have been analysed in order to obtain an overview of prevailing influent and effluent concentrations. Some of the parameters that have been analysed are; phosphorous, nitrogen, BOD7, suspended solids and pH. A lot of time and effort has been put into elucidating operational routines at the wastewater treatment plant (WWTP) and gaining knowledge from available literature regarding different parameters’ effect on treatment results.   Kungsberget has had problems adapting operating routines and reaching stable treatment results as the load is highly effected of seasonal fluctuation. This has not been taken into account earlier and the WWTP has been operated in the same manner all year around. Suggestions to how operating routines can be modified in to better meeting the needs have been produced and alternative treatment methods have been presented in the report. Two of the suggestions include biological phosphorous removal and adding carrier media to increase bacteria growth. An aerobic solids retention time has been calculated in order to evaluate whether nitrifying bacteria have enough time for grow and maintain a stable population. The calculation was carried out by measuring suspended solids and aeration time and the result was a solids retention time of approximately 6 days.

The subject matter of this Bachelor´s thesis is the Eastern Baltic Sea cod. A literature review has been done regarding how environmental factors such as salinity, oxygen supply and temperature but also the size of the cod populations affects the migration patterns and the habitat choice of the cod. The result of the review shows that, when the eastern Baltic cod population is small, its area of distribution is restricted to the southern parts of the Baltic Sea. Moreover, high salinity leads to a larger area of distribution, while low oxygen content in the Deep Basins leads to vertical migrations, as well as further migrations south and north, to areas with better hydrological conditions. Finally the the cod tend to prefer habitats with warmer water, if the oxygen and salinity conditions are suitable, at least during the spawning period. This thesis also include estimation on how well the annual scientific trawl surveys performed by coastal Baltic countries, reflects the actual cod population size. This estimation is partly based on a critical review of available information about the trawl survey design in relation to cod migration patterns, distribution and habitat choice. Furthermore, a test has been done of how well the annual stock size estimates for the latest year, presented in the International Council for the Exploration of the Sea (ICES) Annual Reports of the Baltic Fisheries Assessment Working Group (WGBFAS), between the years 1996-2009 reflected the best available stock size estimates from 2010. The results indicate that the scientific trawl surveys might not work satisfactory. This indicates that further research must be done in the field, therefore possible alternatives such as comparisons of positioning data of commercial and scientific trawls and interviews with fishermen are suggested. / Denna uppsats handlar om torsken i det östra Östersjöbeståndet. En litteratursammanfattning har gjorts gällande hur miljömässiga faktorer såsom salthalt, syretillgång, temperatur samt storleken på bestånden påverkar migrationsmönster och habitatval hos torsken. Resultaten visar bland annat att när torskbestånden är små blir torskens utbredningsområden begränsade till de södra delarna av Östersjön. Höga salthalter leder till större utbredningsområden medan låga syrehalter i djupbassängerna leder till vertikala migrationer såväl som längre migrationer söder och norr om bassängerna, till områden med bättre syretillgång. Torsken verkar dessutom föredra habitat med varmare vatten om syre- och salthaltsförhållandena är gynnsamma, åtminstone under lekperioden. Vidare inkluderar denna uppsats en bedömning av hur väl de årliga vetenskapliga trålningsundersökningarna som utförs av länder med kust mot Östersjön, återspeglar den faktiska storleken på torskbestånden. Denna bedömning baseras på en kritisk granskning av den information som finns tillgänglig gällande de vetenskapliga trålningsundersökningarna, i förhållande till torskens migrationsmönster, distribution och habitatval. Dessutom har ett test gjorts av hur väl de årliga beståndsuppskattningarna för 1996-2009 presenterade i International Council for the Exploration of the Sea (ICES) Annual Report of the Baltic Sea Fisheries Assessment Working Group (WGBFAS), reflekterar de bästa tillgängliga beståndsuppskattningarna från 2010. Resultaten indikerar att de vetenskapliga provtrålningsundersökningarna inte fungerar tillfredsställande, vilket visar på att vidare studier måste göras inom området. Möjliga alternativ, såsom jämförelser av positioneringsdata för kommersiell- samt vetenskaplig trålning, samt intervjuer med yrkesfiskare presenteras.

Purpose: To review the roles of the different vascular beds nourishing the inner retina [retinal ganglion cells (RGCs)] during normal development of the human eye, using our own tissue specimens to support our conclusions. Methods: An extensive search of the appropriate literature included PubMed, Google scholar, and numerous available textbooks. In addition, choroidal and retinal NADPH-diaphorase stained whole mount preparations were investigated. Results: The first critical interaction between vascular bed and RGC formation occurs in the sixth to eighth month of gestation leading to a massive reduction of RGCs mainly in the peripheral retina. The first 3 years of age are characterized by an intense growth of the eyeball to near adult size. In the adult eye, the influence of the choroid on inner retinal nutrition was determined by examining the peripheral retinal watershed zones in more detail. Conclusion: This delicately balanced situation of RGC nutrition is described in the different regions of the eye, and a new graphic presentation is introduced to combine morphological measurements and clinical visual field data.

Das Vorkommen von über den Umgebungsdruck erhöhten Sauerstoffpartialdrucken in Geweben ist im Tierreich nur von der Schwimmblase und dem Auge von Knochenfischen bekannt. Die physiologischen Mechanismen dieser Sauerstoffkonzentrierung wurden an der Schwimmblase insbesondere des Aals intensiv untersucht, entsprechende Untersuchungen zu den Vorgängen im Auge der Knochenfische fehlen jedoch. In dieser Arbeit wurde daher eine Methode etabliert, mit der die Sauerstoffkonzentrierung im Auge der Knochenfische an isolierten Augen untersucht werden kann. 1. Das Gefäßsystem der Regenbogenforelle (Oncorhynchus mykiss, Walbaum 1792) wurde durch Gefäßausgüsse dargestellt. Das im Auge gelegene choroidale Rete mirabile wird über die Arteria ophthalmica, die gleichzeitig die efferente Pseudobranchienarterie darstellt, versorgt. Die Pseudobranchie selber empfängt das Blut aus der efferenten Arterie des ersten Kiemenbogens. Diese Gefäßtopologie, Versorgung der Pseudobranchie mit bereits im ersten Kiemenbogen oxygeniertem Blut und auschließliche Versorgung des choroidalen Rete mirabile mit Blut aus der Pseudobranchie, weist auf die Bedeutung der Pseudobranchie für die Prozesse im Auge hin. 2. Die Retina der Regenbogenforelle wurde mikroskopisch untersucht. Die einzelnen Schichten der Retina entsprechen denen anderer Wirbeltiere. Die Forellenretina ist mit 407 µm aber wesentlich dicker als z.B. die Retina von Mammaliern. Zusätzlich fehlt der Retina der Forelle die bei vielen Mammaliern vorhandene retinale Blutgefäßversorgung. Mit den der Retina am nächsten gelegenen Gefäßen in der Choroidea bestehen bei der Forelle wesentlich größere Diffusionsstrecken von den Blutgefäßen zum Ort des Sauerstoffverbrauchs in den Zellen der Retina als bei anderen Wirbeltieren. Dies wir durch den erhöhten Sauerstoffpartialdruck in den Choriokapillaren kompensiert. 3. Für die Messung des intraretinalen Sauerstoffpartialdrucks wurden im Rahmen dieser Arbeit Sauerstoffmikroelektroden inklusive der zur Betreibung der Elektroden notwendigen Elektronik entwickelt. Die Elektroden waren vom Recess-Typ: die reaktive Oberfläche schloss nicht mit dem Ende der Glaskapillare ab, sondern war unter Belassung eines Hohlraumes in der Elektrodenspitze (Recess) in das innere der Glaskapillare verlagert. Dadurch waren die Elektroden unempfindlich gegenüber Rühreffekten. Die Mikroelektroden hatten eine Spitzendurchmesser von < 10 µm und eine mittlere Empfindlichkeit von 172 fA Torr-1 O2. Die Linearität der Elektroden über eine Partialdruckbereich von 0 bis 760 Torr O2 war besser als r = 0,9998. 4. Zur Überprüfung des normale Sauerstoffpartialdrucks in der Retina wurden Regenbogenforellen betäubt und künstlich ventiliert. Die systemischen Parameter wie arterieller PO2-Wert, Blutdruck und Herzschlag entsprachen dabei im Mittel mit 99 Torr (arterieller PO2), 28 Torr (Blutdruck) und 1,23 Hz (Herzschlag) den Werten unbetäubter, freischwimmender Forellen. Lediglich der arterielle pH-Wert war mit 8,02 während der künstlichen Ventilation durch eine ungenügende Kompensation einer respiratorischen Alkalose leicht gegenüber dem normalen Wert von 7,9 erhöht. 5. Die Auswirkungen der Präparation des Auges zur Messung des intraretinalen Sauerstoffpartialdrucks auf den Augeninnendruck wurde überprüft. Der Augeninnendruck betrug 4,9 Torr. Die Einbringung der Sauerstoffmikroelektrode hatte keine Auswirkung auf den Augeninnendruck. Erst das Entfernen der Elektrode nach der Messung führte zu einer deutlichen Verringerung des Augeninnendrucks. 6. Zum ersten Mal wurde in der vorliegenden Arbeit die Durchblutungsrate des Auges eines Knochenfisches bestimmt. Aus präparatorischen Gründen wurde die Messung an der afferenten Pseudobranchienarterie durchgeführt. Der mittlere Blutfluss in dem Gefäß betrug 745 µl min-1 kg-1. Durch Verschluss des kontralateralen Gefäßes stieg der Fluss auf 135% des ursprünglichen Wertes, da jetzt durch das ipsilaterale Gefäß und über die zwischen den beiden Gefäßen bestehende Anastomose beide Augen durch das ipsilaterale Gefäß mit Blut versorgt wurden. 7. Die Funktion der Retina während der intraretinalen Sauerstoffmessung wurde durch Ableitung des Elektroretinogramms kontrolliert. Trotz der während der Versuche fortbestehenden Betäubung mit dem Betäubungsmittel MS222, welches sich negativ auf das Elektroretinogramm auswirken soll, konnten normale Elektroretinogramme aufgezeichnet werde. Die invasive Messung des intraretinalen PO2 wirkte sich nicht negativ auf die Funktionalität der Retina aus. 8. Der intraretinale Sauerstoffpartialdruck wurde an betäubten, künstlich ventilierten Forellen überprüft. Der mittlere maximale PO2 im Bereich der Bruch´schen Membran betrug 382 Torr. An der Innenseite der Retina wurde ein PO2 von 10 Torr gemessen. Der Bereich des O2-Partialdruckgradienten in der Retina, gemessen über den Vorschub der Sauerstoffmikroelektrode vom niedrigsten bis zum höchsten PO2, betrug 433 µm, ein Wert der gut mit der mikroskopisch bestimmten Dicke der Retina (407 µm) übereinstimmt. 9. Zur Untersuchung der Einflüsse von Blutparametern auf die Sauerstoffkonzentrierung im Auge der Forelle wurden isolierte Augen künstlich mit verschiedenen Erythrozytensuspensionen perfundiert. Dazu wurde zum einen eine Suspension von Forellenerythrozyten eingesetzt, bei der erst der Root-Effekt in Abhängigkeit vom pH-Wert der Suspension bestimmt wurde. Bei basischem pH-Werten war das Hämoglobin der Erythrozyten vollständig gesättigt. Bei einem pH-Wert von 7,68 war noch eine Sättigung von 90% vorhanden, die bis zu einem pH-Wert von 7,31 auf 50% abnahm. 10% Sättigung wurden bei einem pH-Wert von 6,94 erreicht. Für die Perfusion wurde die Suspension der Forellenerythrozyten mit einem pH-Wert von 7,48 eingesetzt. Bei diesem pH-Wert liegt die Sättigung bei ca. 82% und eine Änderung des pH hat in diesem Bereich eine deutliche Änderung der Sättigung zur Folge, was die Freisetzung von O2 von Hämoglobin erleichtert. Als alternative Perfusionslösung wurde eine Suspension von Humanerythrozyten eingesetzt. Humanhämoglobin weist keinen Root-Effekt auf, es kann also durch die im Auge der Knochenfische vorhandenen Mechanismen kein Sauerstoff freigesetzt werden. 10. Der mittlere intraretinale Sauerstoffpartialdruck isolierter Augen betrug bei Perfusion mit der Suspension von Forellenerythrozyten 99 Torr. Nach dem Wechsel auf die Suspension mit Humanerythrozyten fiel der intraretinale Sauerstoffpartialdruck sofort auf 30 Torr ab. Der Perfusionsdruck änderte sich bei dieser Umstellung nicht. Bei Perfusion mit Ringerlösung fiel der intraretinale PO2 auf 20 Torr, gleichzeitig fiel jetzt auch der Perfusionsdruck ab. 11. Eine Konzentrierung des Sauerstoffs konnte bei der künstlichen Perfusion isolierter Augen nicht nachgewiesen werden. Die Notwendigkeit des Root-Effekts für einen hohen Sauerstoffpartialdruck im Auge wird trotzdem deutlich, da bei Perfusion mit einer Suspension von Humanerythrozyten, die einen höheren Sauerstoffgehalt aufwies als die Suspension der Forellenerythrozyten, der intraretinale Sauerstoffpartialdruck deutlich geringer war. 12. Das Modell des isoliert perfundierten Auges ist zur physiologischen Untersuchung des choroidalen Rete mirabile und Sauerstoffkonzentrierung besser geeignet als in vivo - Experimente, da systemische Einflüsse vermieden und die Auswirkungen der Pseudobranchie auf die Blutchemie ausgeschaltet werden können. / Oxygen partial pressures (Po2) above ambient levels are found only in the swimbladder and the eye of teleost fish species. The mechanisms related to the involved oxygen concentration processes have been investigated to some detail in eel swimbladder, but little attention has been paid to analogous mechanisms of the teleost eye. This thesis has accordingly concentrated on developing a method promoting investigation of oxygen concentrating mechanisms in teleost eyes by application of an isolated perfused eye preparation. 1. The vascular supply of eye and pseudobranch in rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) was depicted by corrosion casts of the vascular system. The choroid rete mirabile is supplied with blood by the ophthalmic artery as the efferent blood vessel of the pseudobranch, with a small anastomosis to the contralateral vessel. The pseudobranch in turn is fed by the efferent artery of the first gill arch. This pattern of serial vascular connection suggests a role for the pseudobranch in the process of providing high oxygen tensions required for the high metabolic demand of the visual perception in the retina. 2. Eyes of various fish species were sectioned after paraffin embedding and examined microscopically. The organisation of teleost fish retinae is characterised by the same features and organisation well known from other vertebrates. However, the total thickness of 407 µm found for the retina of the rainbow is much larger than that observed in other animals such as mammals. The conditions of diffusive oxygen supply of retinal nerve cells is further hampered by the complete lack of intraretinal blood vessels commonly found in mammals. In trout, blood is supplied to only the choroid layer, leaving large diffusion distances to the retinal nerve cells to be spanned by oxygen partial pressures, elevated as compared to the bulk arterial system in the choroid capillaries. 3. Intraretinal oxygen partial pressure was determined in long-term anaesthetised specimens of Oncorhynchus mykiss, using specially developed oxygen microelectrodes and required electronic circuitry. Characteristic features of the electrodes include insensitivity of the signal to stirring, achieved by a recess of the reactive metal surface in a glass capillary, an average tip diameter of less than 10 µm and a characteristic sensitivity to oxygen of 172 fA Torr-1. The response of the electrodes to oxygen was linear over a range of partial pressures from 0 to 760 Torr O2 (r= 0,9998). 4. Normal oxygen partial pressures in trout retina were measured in long-term anaesthetised and artificially ventilated specimens of Oncorhynchus mykiss. In order to conduct the experiments under conditions as close as possible to normal homoiostasis, several systemic valuables were monitored continuously. During experimentation arterial Po2 averaged 99 Torr, mean blood pressure was 28 Torr and heart frequency was on the average 74 bpm, respectively, data in the range of values determined in unanesthetized, freely swimming trout. As the one exception, arterial pH (8,02) was slightly elevated during artificial ventilation as compared to control values (7,89), a shift induced by an inadequately high rate of artificial ventilation. 5. The impact of insertion of electrodes required for intraretinal Po2 measurement into the eye was found to have little effect. The intraocular pressure remained unaffected by opening the eye by puncture with leading cannula and inserted micro-Po2-electrode. The intraocular pressure fell only after removing the electrode after completion of the experiment. 6. Normal function of the retina during experimentation in vivo was checked by repeatedly measuring electroretinograms provoked by light flashes under dark ambient conditions. Although extended anaesthesia with MS222 is expected to affect the electroretinogram in fish, there was no indication of abnormal or reduced electroretinograms during experimentation. Also puncture of the eye with insertion of electrodes did not affect the electroretinogram. 7. Intraretinal Po2 was measured in anaesthetised and artificially ventilated trout. Oxygen profiles were recorded during advancement of the electrode tip though the retina, from the lowest Po2 at the inner surface with about 10 Torr to the highest Po2 in the region of Bruch´s membrane with about 382 Torr, travelling a total distance of 433 µm. This distance closely corresponds to the thickness of the retina measured by microscopic sectioning. 8. Blood flow to the eye as an important parameter for the establishment of an isolated eye preparation was measured in the afferent artery of the pseudobranch. Due to the anatomical situation this represents the closest possible approximation to measurement of flow in the ophthalmic artery. The blood flow was estimated by ultrasonic Doppler techniques with in situ calibration to be 216 µl min-1. Occlusion of the contralateral vessel resulted in an increase of the blood flow in the ipsilateral vessel to 135% of the original as a result of flow through the small anastomosis between the two ophthalmic arteries. This estimate is the first performed for blood flow to the eye of a fish. 9. An isolated eye preparation was used to investigate the influence of specific blood parameters on oxygen concentrating processes in the eye of Oncorhynchus mykiss. Eyes were perfused with suspensions of trout erythrocytes, human erythrocytes and Ringer´s solution. The Root Effect of trout haemoglobin was confirmed in suspension of erythrocytes. The haemoglobin was fully saturated at pH 8.45, still 90% saturated at 7.68, 50% at 7.31 and 10% at pH 6.94. In order to provide optimal starting conditions for the release of oxygen by relatively small changes in pH, pH 7.48 (resulting in 82 % saturation) was chosen for the perfusion of isolated eyes. As a control perfusion, suspensions of human erythrocytes provided a perfusate lacking any Root effect, thus not supporting the oxygen concentrating processes in fish eyes. 10. Perfusion of isolated trout eyes with pH 7.48 trout erythrocyte suspension resulted in an average intraretinal Po2 of 99 Torr, whereas perfusion with human erythrocytes resulted in an immediate decrease of Po2 to (of) 30 Torr, with a further drop to 20 Torr during perfusion with Ringer´s solution. Changes in perfusion between erythrocyte suspensions were performed without any changes in perfusion pressure, but the switch to control perfusion with Ringer´s solution exhibited a drop in perfusion pressure due to the reduced viscosity of the medium. 11. Although perfusion of isolated eyes did not exhibit Po2 above ambient values, the effect of oxygen concentrating processes were clearly indicated by comparison with Root effect-lacking human erythrocyte perfusate (Po2´s of 99 vs. 30 Torr, respectively). 12. It is concluded that studies of oxygen concentrating mechanisms are to be performed preferably on isolated eye preparations. For closer analysis of the involved mechanisms this preparation allows for isolated control of individual parameter of the perfusate. In particular, uncontrolled effects of the pseudobranch on the perfusate can be eliminated.

Purpose: To review the roles of the different vascular beds nourishing the inner retina [retinal ganglion cells (RGCs)] during normal development of the human eye, using our own tissue specimens to support our conclusions. Methods: An extensive search of the appropriate literature included PubMed, Google scholar, and numerous available textbooks. In addition, choroidal and retinal NADPH-diaphorase stained whole mount preparations were investigated. Results: The first critical interaction between vascular bed and RGC formation occurs in the sixth to eighth month of gestation leading to a massive reduction of RGCs mainly in the peripheral retina. The first 3 years of age are characterized by an intense growth of the eyeball to near adult size. In the adult eye, the influence of the choroid on inner retinal nutrition was determined by examining the peripheral retinal watershed zones in more detail. Conclusion: This delicately balanced situation of RGC nutrition is described in the different regions of the eye, and a new graphic presentation is introduced to combine morphological measurements and clinical visual field data.