A modified technique for tail cuff pressure measurement in unrestrained conscious rats

In physiological experiments, it is essential to measure arterial pressure (AP) and heart rate (HR) in animals. Tail cuff pressure (TCP) measurement using photoelectric volume oscillometry has been commonly used. We designed a new technique for continuous measurement of AP and HR in conscious, unrestrained rats. This is based on the observation that fixation of the rat's tail with tape keeps the animal in position without struggling. The animal is free to move its body. To test the accuracy of this new technique, Sprague-Dawley rats underwent four AP and HR measurement techniques. These included a new unrestrained method (UR), which was compared to the following three methods: traditional restrained TCP method with restrainer, direct monitoring of AP and HR with femoral artery catheterization and a combination of photoelectric volume oscillometry (with body heating to 37 degrees C) and femoral arterial recording. The results show that the modified UR measurement provides accurate data on AP and HR. This method obtains a lower value of HR and similar mean AP when compared to direct monitoring from femoral arterial catheterization. Accordingly, the modified unrestrained TCP measurement can be used in conscious rats as a noninvasive method.     

A technique for the long term measurement of intra-compartmental pressure in the lower leg

The early diagnosis of an acute compartmental pressure syndrome is often difficult, but can be facilitated by long term, up to several days, measurement of intra-compartmental pressures. A measuring system has been developed, together with its associated surgical and operational procedures, which may be applied in a variety of situations, including an immobile patient or a patient mobilized following surgery. If the technique is adopted as soon as the patient enters hospital, or immediately postoperatively, an acute compartmental syndrome may be recognized early and measures taken to alleviate its consequences.     

New technique for measurement of left ventricular pressure in conscious mice

Concern about the effects of anesthesia on physiological measurements led us to develop methodology to assess left ventricular (LV) pressure in conscious mice. Polyethylene-50 tubing filled with heparinized saline was implanted in the LV cavity through its apex via an abdominal approach and exteriorized to the back of the animal. This surgery was done under anesthesia with either an intraperitoneal injection of ketamine (80 mg/kg) and xylazine (5 mg/kg) (K+X) in 11 mice or isoflurane (ISF; 1.5 vol%) by inhalation in 14 mice. Postoperatively, mice were trained daily to lie quietly head first in a plastic cone. LV pressure, the first derivative of LV pressure (dP/dt), and heart rate (HR) in the conscious state were compared between the two groups at 3 days and 1 wk after recovery from surgery using a 1.4-Fr Millar catheter inserted into the LV through the tubing, with the mice lying quietly in the plastic cone. Acutely during anesthesia, K+X decreased HR (from 698 to 298 beats/min), LV systolic pressure (from 107 to 65 mmHg), and maximal dP/dt (dP/dt(max)) (from 15,724 to 4,445 mmHg/s), all P < 0.01. Similar but less marked negative chronotropic and inotropic effects were seen with ISF. HR and dP/dt(max) were decreased significantly in K+X mice 3 days after surgery compared with those anesthetized with ISF (655 vs. 711 beats/min, P < 0.05; 14,448 vs. 18,048 mmHg/s, P < 0.001) but increased to the same level as in ISF mice 1 wk after surgery. In ISF mice, recovery of function occurred rapidly and there were no differences in LV variables between 3 days and 1 wk. LV pressure and dP/dt can be measured in conscious mice with a micromanometer catheter inserted through tubing implanted permanently in the LV apex. Anesthesia with either K+X or, to a lesser extent, ISF, depressed LV function acutely. This depression of function persisted for 3 days after surgery with K+X (but not ISF) and did not recover completely until 1 wk postanesthesia.     

Development of a noninvasive technique for the measurement of intracranial pressure.

Intracranial pressure (ICP) dynamics are important for understanding adjustments to altered gravity. Previous flight observations document significant facial edema during exposure to microgravity, which suggests that ICP is elevated during microgravity. However, there are no experimental results obtained during space flight, primarily due to the invasiveness of currently available techniques. We have developed and refined a noninvasive technique to measure intracranial pressure noninvasively. The technique is based upon detecting skull movements of a few micrometers in association with altered intracranial pressure. We reported that the PPLL technique has enough sensitivity to detect changes in cranial distance associated with the pulsation of ICP in cadavera. In normal operations, however, we place a transducer on the scalp. Thus, we cannot rule out the possibility that the PPLL technique picks up cutaneous pulsation. The purpose of the present study was therefore to show that the PPLL technique has enough sensitivity to detect changes in cranial distance associated with cardiac cycles in vivo.     

A novel right-heart catheterization technique for in vivo measurement of vascular responses in lungs of intact mice

The present study employed a new right-heart catheterization technique to measure pulmonary arterial pressure, pulmonary arterial wedge pressure, and pulmonary vascular resistance in anesthetized intact-chest, spontaneously breathing mice. Under fluoroscopic guidance, a specially designed catheter was inserted via the right jugular vein and advanced to the main pulmonary artery. Cardiac output was determined by the thermodilution technique, and measured parameters were stable for periods of 相似文献   

A technique for normalizing centre of pressure paths

Centre of pressure paths may be expected to provide useful information in the analysis of gait. In this paper, a technique for normalizing and averaging centre of pressure paths is presented. It utilizes force data obtained from force platform measurements together with information about the placement of the foot on the force platform. This placement is described by specifying the location of the 'centre' and 'midline' of the foot which are defined for a footprint. The coordinate system associated with a footprint is defined and centre of pressure locations are determined in relation to this system. A comparison of the centre of pressure paths obtained using this method and the method proposed by Cavanagh [J. Biomechanics 11, 487-491 (1978)] shows significant differences. It is concluded that the selection of an appropriate technique to obtain centre of pressure paths is important.     

A novel technique for viable cell determinations

We have developed a simple method to determine cell viability using two fluorescent dyes, Hoechst 33258 and acridine orange. When these dyes are used in combination, dead cells fluoresce brilliant blue and live cells fluoresce green. This method works over a range of dye concentrations (Hoechst 33258, 0.25-2 micrograms/ml; acridine orange, 1-5.0 micrograms/ml) and the fluorescence spectra of the two dyes are such that only one set of filters is required to visualize the effects of both dyes simultaneously. It is insensitive to a wide range of exogenous serum concentrations and is read with greater uniformity by different observers.     

A radiometric technique for the measurement of adenylosuccinate lyase

When radioactive adenylsuccinic acid (AMP-S) is metabolized to AMP and fumaric acid by the enzyme adenylsuccinate lyase (EC 4.3.2.2), a proton is released to the solvent as ³H₂O. This removal is believed to be stereospecifically identical to that catalyzed by the enzyme, l-aspartase [1–5], and therefore entails the loss of a proton from C-3 of the dicarboxylic acid moiety of the nucleotide. Advantage has been taken of this fact in the design of a facile assay for this enzyme. Adenylosuccinic acid, tritiated on C-2 and C-3 of the l-aspartase moiety, is prepared by chemical synthesis. This product is purified, lyophilized to dryness and reconstituted in a solution of unlabelled AMP-S, bringing the final concentration to 5·10^?3 M, and the final specific activity to 8.0 μCi/mol. 5-μl aliquots of this substrate are then incubated at 37°C with 5-μl aliquots of tissue extract; after an appropriate period, any tritium released to the solvent water is distilled at room temperature overnight into a 5 μl droplet of saturated aqueous KOH adherent to the lid of the sealed reaction vessel. The lid is removed and tritium thereon is measured by scintillation spectrometry. The assay, performed as prescribed, is facile, in that it permits the simultaneous estimation of the lyase activity in a large battery of samples, is not interfered with by opalescent or proteinaceous suspensions, is accurate and outstandingly sensitive.     

A novel method for measurement of submembrane ATP concentration

There has been considerable debate as to whether adenosine triphosphate (ATP) is compartmentalized within cells and, in particular, whether the ATP concentration directly beneath the plasma membrane, experienced by membrane proteins, is the same as that of the bulk cytoplasm. This issue has been difficult to address because there is no indicator of cytosolic ATP, such as those available for Ca(2+), capable of resolving the submembrane ATP concentration ([ATP](sm)) in real time within a single cell. We show here that mutant ATP-sensitive K(+) channels can be used to measure [ATP](sm) by comparing the increase in current amplitude on patch excision with the ATP dose-response curve. In Xenopus oocytes, [ATP](sm) was 4.6 +/- 0.3 mm (n = 29) under resting conditions, slightly higher than that measured for the bulk cytoplasm (2.3 mm). In mammalian (COSm6) cells, [ATP](sm) was slightly lower and averaged 1.4 +/- 0.1 mm (n = 66). Metabolic poisoning (10 min of 3 mm azide) produced a significant fall in [ATP](sm) in both types of cells: to 1.2 +/- 0.1 mm (n = 24) in oocytes and 0.8 +/- 0.11 mm for COSm6 cells. We conclude that [ATP](sm) lies in the low millimolar range and that there is no gradient between bulk cytosolic and submembrane [ATP].     

A novel technique for efficient multiple sample dialysis

Conventional methods for dialyzing numerous samples are either expensive or tedious and inefficient. These disadvantages were overcome through the construction and use of a Plexiglas dialysis sample holder (DSH). Large numbers of dialysis samples having 0.5 to 2.0-ml volumes may be attached to numbered positions on the DSH. Sample identification is greatly simplified and considerable savings in time and material are achieved. Furthermore, the risk of sample spill or mixing during filling or emptying of dialysis sacks, and the risk of leaks in dialysis tubing, are minimized.     

A technique for the measurement of cadence using walkway vibrations

A new method has been developed to measure cadence while walking. The method uses instrumentation to detect the vibrations transmitted in the walkway surface. These vibrations are produced when a subject's foot makes initial contact with the walking surface. The method was tested against heel switches and was found to measure stride duration with RMS errors of around 1%. The vibration method requires no instrumentation to be attached to the subject, can be used with bare feet or any other footwear, is simple to use and is very robust and reliable.     

A device for the routine measurement of plasma oncotic pressure

Plasma colloid oncotic pressure(COP) is an important determinant of interstitial oedema and relates to mortality in critically ill patients. A simple device for the routine measurement of COP has been developed which gives stable readings in less than three minutes ∼0.2 ml. of plasma. It is easy to calibrate, simple to use and has a short equilibration time.