Catálogo de publicaciones - libros

It is proposed that the redox state of mitochondrial NADH1 will complement blood gas analysis for measuring the health and welfare of human tissues. Use of arterial oxygen saturation levels (SaO), especially as assayed by the Nellcor instrument, has spread almost everywhere in medicine despite the fact that hypoxia of internal organs, liver, kidney, brain, pancreas, etc. is not well indicated by peripheral digital oxygenation. Indeed, there is an implied liability in the failure to infer central oxygenation from peripheral values. Near infrared (NIR) sensing of deep tissue saturation of hemoglobin (StO) requires multi-wavelength, multi-site measurement of both absorption and scattering properties by time or frequency domain NIR methods. Corrections for underlying water and lipid absorptions can be made so that the correct value for, and saturation oh hemoglobin are obtained.

Nevertheless, the significance of blood oxygen saturation, even localized to particular organs, can be questioned from the standpoint of what is the critical value of the desaturation from which the tissue can recover2; for example, in the case of cortical neurons where stroke, compression ischemia, etc. cause O lack, this value becomes of significant clinical importance in both the brain and the spinal chord. These approaches are actively pursued and the possibility of subsurface redox state measurement in human tissues may eventually emerge as the quantitative metric of tissue metabolic state and of hypoxic stress.

The great flexibility and versatility of the fast, economical and “tetherless” nature of opto-electronic technology is appropriate to the manifold challenges of neuronal function as currently measured by intrinsic signals and soon to be studiable by extrinsic signals of metabolism and electrophysiological functions.

Protein C (PC) is the pivotal anticoagulant and antithrombotic in the human coagulation cascade. PC deficiency can disturb the blood hemostasis and cause thrombosis, inhibiting oxygen transport to tissue, and resulting in major medical problems such as deep vein thrombosis (DVT). The current treatment can cause bleeding and other major medical problems. PC circulates in the blood as a zymogen and is only activated when and where it is needed. PC is a safe anticoagulant without harmful side effects.

A combination of ion-exchange chromatography and IMAC IDA-Cu was studied for the relatively large scaled PC separation from Cohn fraction IV-1. Almost half of the active PC was recovered by using this process. In future work, we will verify the linearity of the IMAC column scale-up. This process can be used to produce PC from Cohn fraction IV-1 at large quantities and low cost to treat PC-deficient patients.

Hyaluronan (HA), a large negatively-charged polysaccharide, is a major component of vessel basal membrane. HA is expressed by a variety of cells, including tumor and endothelial cells. We hypothesized that HA could be up-regulated by hypoxia to enhance vessel formation. To determine the effect of hypoxia on the production of HA, tumor cells were treated with either media alone (control) or a hypoxia inducer (CoCl or NaN) for 24 h. The level of HA in the media was then measured by ELISA. The results showed that both CoCl and NaN induced the production of HA. Since the low molecular weight form of HA (SMW) possesses pro-angiogenic properties, we investigated whether hypoxia-induced HA can be processed into SMW. Under hypoxic conditions, the activity of hyaluronidase, the enzyme responsible for degrading HA, was measured by an ELISA-like assay. The activity of hyaluronidase was shown to be up-regulated by hypoxia and, further, could carry out the function of processing HA into SMW. In addition, the hypoxic areas of tumor tissues were stained strongly with biotinylated HA-binding proteins, indicating that the level of HA was high compared to the oxic areas. This study demonstrates that hypoxia can stimulate the production of HA and the activity of hyaluronidase, which may promote angiogenesis as a compensation mechanism for hypoxia.

When flow to a region is arrested, the amount of oxygen contained within the stationary blood decreases at a rate dependent on the oxygen utilization of the surrounding tissue. We used phosphorescence quenching microscopy to measure arteriolar PO in the mesentery of male Sprague-Dawley rats. Flow was quickly stopped (< 1 s) by occluding the microvessels using an inflatable Saran bag attached to the microscope objective. The rate of decline in PO following occlusion yielded a calculated initial flux of oxygen out of the vessel lumen of 8.0 × 10 ml O cm sec. An upper limit on the oxygen consumption of the arteriolar wall was calculated by assuming that all of the oxygen in the lumen was consumed by the wall at the initial rate. This value was 2.5 × 10 ml O cm sec and is an overestimate since the oxygen consumption of the nearby parenchymal cells was neglected. The calculated maximum oxygen consumption of the wall is more than an order of magnitude smaller than that reported previously for arterioles in the rat mesentery (6.5 × 10 ml O cm sec). We conclude that oxygen consumption of the arteriolar wall is similar to previous values for other vascular tissues.

Greater understanding of the rate of oxygen delivery and uptake in sick preterm and term infants undergoing intensive care is an important aim of brain-orientated neonatal medicine. Near infrared spectroscopy (NIRS) is a continuous, non-invasive and portable technique which can be used to measure cerebral blood flow (CBF) in infants. It is also possible to use spatially resolved spectroscopy to measure absolute mean cerebral oxygen saturation (SmcO). The aim of this study was to investigate the derivation of cerebral metabolic rate for oxygen (CMRO) from these two measurements. Nine preterm infants were studied, of median (range) gestational age 25 (23–37) weeks. A NIRO300 was used to measure CBF and SmcO simultaneously over the right and left hemisphere. Median (range) left and right cerebral hemisphere values for CMRO were 0.95 (0.79–1.53) ml 100g.min and 0.88 (0.69–1.46) ml 100g.min, respectively. No significant difference was seen between the left- and right-sided values. These values are similar to median (range) values previously reported in infants using positron emission tomography or more invasive NIRS methods. Further work is necessary to define limits on the use of this technique, particularly in the assumption of the venous:arterial compartment volume ratio across different infants.

Flow-metabolism coupling in brain is different from flow-metabolism coupling in other vascular beds. In the classic description of Krogh1, the capillary bed is a system of parallel tubes serving cylinders of tissue known as Krogh’s cylinders. This simple arrangement yielded a quantitative expression of oxygen delivery to the tissue. However, in brain tissue, the arrangement is so disorderly that no prediction of oxygen tensions in the tissue is possible2.

Only two claims of the capillary bed in the brain appear to be indisputable, i.e., the capillaries have a common arterial source and a common venous terminus, and their density is proportional to the average regional rates of metabolism at steady-state. The following revision of the mechanism of flow-metabolism coupling in brain arose from the simple assumption, first introduced by Erwin R. Weibel in ,3 that every segment of the capillary bed “feeds” the same amount of brain tissue, i.e., that every fraction of the tissue is served by commensurate fractions of capillary density and oxygen diffusibility and accounts for the same fraction of the total oxygen consumption.

It has been well-known for many years that cerebral oxygen consumption remains constant during moderate changes of blood flow, as measured during hypo- or hypercapnia or indomethacin administration. Current models of flow-metabolism coupling link blood-brain transfer of oxygen to oxygen metabolism in mitochondria.2–6 The resulting quantitative relations between flow and metabolism reveal that a close link between diffusion and metabolism prevents the enzyme from maintaining a constant oxygen consumption when blood flow changes, unless the enzyme’s affinity towards oxygen is adjusted commensurately.

Hypoxia is a physiological abnormality that has been detected in all solid tumours analysed to date. Studies using polarographic needle electrodes have shown an unequivocal link between the extent of tumour hypoxia and poor treatment outcome. The practical limitations of polarographic needle electrodes have warranted investigation into alternative strategies enabling routine assessment of tumour hypoxia in the clinical setting. This review focuses on the clinical evaluation of exogenous and endogenous markers of tumour hypoxia that may fulfil this role.

There has been rapid development of effective new tools that provide information on oxygenation and an increased recognition of how valuable such information can be. Consequently, there also has been considerable interest in comparing and evaluating the accuracy and usefulness of the different types of measurements.

The various types of measurements usually do not measure the same thing. They may measure pO or [O] or something less directly related, such as hemoglobin saturation. They may make measurements in different compartments (e.g. intracellular, extracellular, vascular) in the volume that they sample, the time span over which they average, the local perturbation that they may cause, etc. They also differ in their sensitivity, accuracy, ability to measure repetitively.

However, these potentially confounding and confusing differences can be made into an outstanding virtue, if their nature is considered carefully. Then a proper model can relate them to each other. The ability to relate the various measurements to each other can be a powerful tool to test the validity of models that attempt to explain fully the distribution of oxygen in real systems and the factors that affect this. We then could have a major advancement in our understanding of oxygen transport in tissues, with an ability to determine accurately the effects of physiological and pathophysiological perturbations on oxygenation at all levels of cells and tissues .

Protein C (PC), protein S (PS), antithrombin III, and plasminogen are four important anticoagulants in blood plasma. Deficiency of any of these biomolecules may lead to thrombo-embolic complications including lung embolism, heart attack, and stroke. A multi-factor sensing system is beneficial for identifying the cause of abnormal blood clotting more effectively, rapidly, and cost-effectively. As an initial effort toward simultaneous multi-anticoagulant detection, a PC and PS dual-sensing system has been under development in our research group.

A fiberoptic PC biosensor utilizing fluorophore-mediated sandwich immunoassay was already developed for rapid (∼5 minutes) PC deficiency diagnosis. After a single PS sensor was developed for the PS deficiency diagnosis, the two sensors were connected in series to form a dual-sensing system. The cross-reactivity between the analytes and the sensors was found to be minimal. For easier sensing operation, a mixture of fluorophore-linked anti-PC and anti-PS was applied. The results showed that the mixture can be used with a slight signal reduction. When PC and PS was mixed in a sample, the signal intensity was decreased by approximately 5% for both sensors. A study is currently being performed to overcome the signal reduction by increasing the flow velocity and incubation time.