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Biomedical subjects

R K Reed

Publications and source records attributed to R K Reed.

At least 127 records · Page 7Linked to original sources
PubMed1986

Measurement of interstitial fluid pressure: comparison of methods.

Interstitial fluid pressure (IFP), i.e., the pressure in a saline-filled tube brought into contact with the interstitium, has been measured in cats with two "acute" [micropipettes and wick-in-needle (WIN)] and two chronic (perforated and porous capsules) methods. In a control situation, similar pressures of -1.5 and -1.6 mm Hg were recorded in skin with micropipettes and both types of capsules, respectively, while WIN pressure in subcutis was -1.2 mm Hg. IFP in skeletal muscle was -0.5, -0.5, and -1.1 mm Hg as recorded with micropipettes, WIN, and porous capsules, respectively. During infusion of Ringer's solution, pressures in both types of capsules rose by 4 to 6 mm Hg, while pressure recorded with the acute methods increased by 1 to 1.5 mm Hg only. Two hours after infusion all techniques gave similar pressures. Peritoneal dialysis for 2 hours reduced micropipette and WIN pressures by 3 to 4 mm Hg. Pressure in perforated capsules fell by 10 mm Hg during dialysis and remained low for an additional 2 hours, while porous capsule pressure fell by 7 mm Hg during dialysis but thereafter increased and reached the pressure recorded with micropipettes and WIN 2 hours after ended dialysis. In both overhydration and dehydration, capsules probably react to changes in interstitial fluid colloid osmotic pressure; in overhydration the capsules react also to changes in capillary pressure, resulting in the discrepancy between chronic and acute methods during non-steady-state conditions. In conclusion, acute and chronic methods record similar pressures during steady-state conditions, but the chronic methods are sensitive to changes in vascular pressure and interstitial fluid colloid osmotic pressure and are therefore not suitable for measuring the changes that occur in IFP within a few hours.

Animals↗
PubMed1986

Interstitial compliance and transcapillary fluid balance in renal hypertensive rats.

Local interstitial fluid volume (IFV) and pressure (IFP) were used to estimate interstitial compliance (= delta IFV/delta IFP) in skin and skeletal muscle of normotensive (NT) and renal hypertensive rats (HT). The IFV was measured as the extravascular 51Cr-EDTA space, and IFP with micropipettes (tip diameter 2-4 microns) connected to a servocontrolled counter-pressure system. After control measurements, overhydration was induced by infusion of saline, 10% of body weight i.v. with or without venous stasis. Alternatively, dehydration was induced by peritoneal dialysis with 20% glucose or by furosemide infusion with or without 24 h fluid deprivation. Control ECV averaged 24.94 and 24.73 ml per 100 g in NT and HT, respectively (P greater than 0.05). Control PV averaged 2.81 and 3.28 ml per 100 g in NT and HT, respectively (P = 0.061), and control IFP was more positive in HT than in NT: 0.4 mmHg in skin (P less than 0.05) and 0.2 mmHg in skeletal muscle (P greater than 0.05). Dehydration changed PV significantly more in HT than in NT (P less than 0.05). The interstitial volume-pressure curve was linear in dehydration and the initial part of overhydration but gradually levelled off, and the maximal rise in IFP was 1-1.5 mmHg in skin and muscle. Interstitial compliance was calculated from the dehydration part of the volume-pressure curve and was in NT 14% per mmHg both in skin and skeletal muscle. In HT, compliance during dehydration was 10.2 and 20.7% reduction in IFV per mmHg fall in IFP in skin and muscle, respectively, not significantly different from corresponding values in NT (P greater than 0.05). We conclude that HT had unaltered ECV and a tendency to higher PV, and that interstitial compliance was not significantly different in normotensive and hypertensive rats.

Animals↗
PubMed1986

Acute hemodynamic effects of thermal skin injury in the rat.

Heart rate (HR), mean arterial pressure (MAP), central venous pressure (CVP), and cardiac index (CI) were measured in anesthetized rats subjected to thermal injury covering 10 and 40% of the body surface area (BSA). These were compared to corresponding sham controls. No fluid substitution was provided. MAP decreased rapidly from 110 mm Hg preburn and leveled off at 75-80 mm Hg after 60 min postburn in the 40% burn group and at 80-95 mm Hg in the 10% burn group. CVP was not influenced by thermal injury. CI fell from about 270 to 208 and to 173 ml X min-1 X kg-1 during the first 15 min after injury in the 10 and 40% burn groups, respectively. Thereafter, CI continued to fall more slowly in both groups, being lower in the 40% than the 10% burn group for the whole postburn course (P less than .001). HR fell slightly in both burn groups (P greater than .05). Stroke volume index followed the same pattern as CI indicating that the fall in CI was caused by reduction in stroke volume. Total peripheral resistance increased slightly after injury. Previous measurement of hematocrit in thermal injury of the same type and extent suggests a 35% increase in viscosity. Consequently, vascular hindrance was unchanged. Compensatory tachycardia or vasoconstriction could not be demonstrated.

Animals↗
PubMed1986

Microvascular fluid exchange following thermal skin injury in the rat: changes in extravascular colloid osmotic pressure, albumin mass, and water content.

Microvascular fluid exchange was studied in rats subjected to 0, 10, and 40% body surface area (BSA) full-thickness cutaneous burns without providing fluid substitution. The total amounts of water and of albumin entering the entire burned skin area following 10% BSA burns were similar to that in 40% BSA burns. Colloid osmotic pressure in interstitial fluid (COPi) was around 10 mmHg and did not change in the control group or in burned skin from the 40% BSA burn group. COPi after 10% burns increased to 15 mmHg in injured skin, while plasma COP fell from 16 to 12.5 mmHg. Preburn, the interstitial albumin mass (Qalb) was 14.9 mg/g dry tissue weight (DW) and increased to 42 and 20 mg/g DW in injured skin after 10 and 40% burns, respectively. Extravasation of radiolabeled albumin (Ealb) estimated as plasma equivalents per 30 min increased from 6.0 to 321 microliters/g DW at 30-60 min postburn (PB) in injured skin following 10% BSA burns. At 90-120 and 150-180 min PB Ealb in this group was reduced to approximately 120 microliters/g DW. These levels of Ealb were roughly 6 times higher than those after 40% BSA burns. Total tissue water (TTW) was 1.78 ml/g DW preburn and increased to 3.0 and 2.0 ml X g-1 DW PB in the 10 and 40% burn groups, respectively. TTW and Qalb did not change beyond 60 min PB.

Albumins↗
PubMed1985

Osmotic properties of the chromogranins and relation to osmotic pressure in catecholamine storage granules.

The soluble proteins (chromogranins) of bovine chromaffin granules have been studied by micro-osmometry with semi-permeable membranes (UM2, PM10 and PM30 with cut-offs greater than 1, greater than 10 and greater than 30 kD, respectively) at 1 = 0.15 and pH 5-8 for protein concentrations up to 20 mg X ml-1. After lysis of chromaffin granules in phosphate buffer pH 6, the released chromogranins behaved as aggregating solutes, consistent with an inconspicuous osmotic pressure contribution from the chromogranins at the protein concentration of the intact granules. Thus, in the presence of phosphate about 90% of the molecules behaved as colloids with Mr = 30,300 at c = o. After lysis in phosphate-free buffers the chromogranins behaved as highly non-ideal solutes in a manner which was incompatible with isotonicity at the protein concentration of the intact granules. About two-thirds of the molecules in the lysates in Na-succinate pH 5-6 and K-acetate pH 6 exhibited Mr = 66,000 and 79,000, respectively. In dilute solutions (less than 12 mg protein X ml-1) and ATP/protein ratios corresponding to those in the intact granules, the UM2 pressures were markedly increased, indicating release of polypeptides with Mr 2000-3000 from aggregates. CaCl2 was without specific effect on the colloid osmotic pressures but reduced the ATP-dependent increase in pressure, suggesting release of molecules twice the size of those released by ATP alone. A model is presented for the contribution of the chromogranins to osmotic pressure regulation in the bovine adrenomedullary catecholamine-storing granules.

Adenosine Triphosphate↗
PubMed1985

Turnover rate of interstitial albumin in rat skin and skeletal muscle. Effects of limb movements and motor activity.

Fractional removal rate (FRR) of radioactive-labelled human serum albumin (I-HSA) injected subcutaneously or intramuscularly was determined by external gamma-detecting equipment. Radioactivity over the injection site fell monoexponentially during registration periods up to 6 h. The FRR was calculated as the turnover rate constant of the radioactivity removal. The FRR fell into one of two ranges: in anaesthetized rats FRR was 0.02-0.03 h-1, and in awake and freely moving rats FRR was 0.08-0.11 h-1. In awake rats, FRR was similar during day and night (spontaneous motor activity is four times higher during the night). Passive limb movements at 1 Hz in anaesthesia increased FRR in skin to that in awake rats, while FRR in skeletal muscle was unchanged. Immobilization resulted in FRR similar to that in anaesthesia. Interstitial albumin mass did not change during 6 h of anaesthesia. It is concluded that the observed FRR reflects steady state changes in albumin turnover. In the awake and freely moving rats at least 3/4 of the removal of albumin is by the lymphatics. Calculated lymph flow was 10 microliters g-1 h-1 and 40 microliters g-1 h-1 in skeletal muscle and skin respectively with corresponding figures during anaesthesia of 3 microliters g-1 h-1 and 10 microliters g-1 h-1 respectively.

Animals↗
PubMed1985

Transcapillary extravasation rate of albumin in rat skeletal muscle. Effect of motor activity.

Transcapillary extravasation of albumin in hindlimb and neck skeletal muscle of rats was determined as extravascular plasma equivalent volumes (I-HSAev), 1-168 h after a single intravenous injection of radiolabelled human serum albumin (I-HSA). One experimental group was immobilized in pentobarbital anaesthesia for the first 8 h after injection of I-HSA. With longer extravasation periods, the rats then woke up and moved freely. In the other experimental group, injections were made in ether anaesthesia allowing the rats to move freely within 10 min after injection. One hour after injection, I-HSAev in the immobilized group averaged 1.5 10(-3) ml g-1 in neck and hindlimb muscle. In the mobile group, I-HSAev was two to three times higher than in the immobilized rats up to 12 h in both muscle groups (P less than 0.05). At 24 h and later I-HSAev was similar in mobile and immobile rats (P greater than 0.05). The I-HSAev increased up to 48 h, levelling off at about 0.06 and 0.08 ml g-1 in hindlimb and neck skeletal muscle, respectively. Corresponding interstitial albumin concentration, calculated from steady-state I-HSAev and interstitial fluid volume (51Cr-EDTA space), averaged 48% and 34% of plasma albumin concentration, respectively.

Animals↗
PubMed1985

Interstitial compliance and transcapillary Starling pressures in cat skin and skeletal muscle.

Interstitial compliance, defined as change in local interstitial fluid volume (delta IFV) divided by the corresponding change in local interstitial fluid pressure (delta IFP), has been measured in skin and muscle of pentobarbital-anesthetized cats. IFP was measured with micropipettes and IFV as the difference between 51Cr-ethylenediaminetetraacetic acid space and 125I-human serum albumin space. IFV was altered by overhydration (saline infusion, 10% of body wt, or by femoral vein ligation plus saline infusion, 20% of body wt) or by dehydration (peritoneal dialysis with 20% glucose). Control IFV in skin and muscle averaged 1.45 (SD 0.44, n = 22) and 0.37 (SD 0.04, n = 22) ml/g dry wt, respectively, with corresponding IFP of -1.9 (SD 0.4, n = 22) and -0.8 (SD 0.6, n = 22) mmHg. During dehydration, IFV fell by 5.5 and 10.4% per mmHg fall in IFP in skin and muscle, respectively. The maximal rise in IFP during overhydration was about 2 mmHg in both tissues. Analysis of covariance showed that compliance was lower in cats than in rats during dehydration (P less than 0.05). At subnormal IFV, IFP will therefore be more powerful in opposing capillary absorption of interstitial fluid in cats than in rats. IFP is, however, of similar importance in edema prevention in the two species.

Animals↗
PubMed1985

Dextran 70 versus donor plasma as colloid in open-heart surgery under extreme haemodilution.

Dextran 70 and donor plasma were compared as colloid in the priming solution during heart-lung perfusion in open-heart surgery. The patients underwent surgery for coronary artery or aortic valve disease. One group of nine patients had plasma in the priming solution, while ten patients received dextran 70. Prior to perfusion the patients in the dextran group received monovalent hapten to prevent anaphylactic reactions towards dextran. During the perfusion the same level of haemodilution was established in both groups; the haematocrit values fell from about 39 vol. per cent before perfusion to about 19 vol. per cent after 45 min of perfusion. Eighteen hours postoperatively, the haematocrit had increased to about 35 vol. per cent. The mean concentrations of total serum protein in preoperative samples from the plasma and dextran group were 66.0 g/l and 66.3 g/l, respectively, and fell to 42.6 g/l and 28.3 g/l in samples taken after 45 min of perfusion. The serum-protein concentration in the dextran group remained significantly lower than that of the plasma group throughout the postoperative period. A similar pattern was seen for the albumin concentration. Preoperatively the mean values of the colloid osmotic pressure of plasma were 24.2 mmHg and 25.5 mmHg in the plasma and dextran group, respectively. Corresponding figures 45 min after start of perfusion were 13.9 mmHg and 16.9 mmHg, respectively, significantly higher in the dextran group than in the plasma group. The colloid osmotic pressure exerted by dextran was about 9 mmHg during heart-lung perfusion and about 4 mmHg 18 h later.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve Insufficiency↗
PubMed1984

Membrane dopamine beta-hydroxylase: a precursor for the soluble enzyme in the bovine adrenal medulla.

Searching for endogenous proteolytic activities converting the membrane form of dopamine beta-hydroxylase (dopamine beta-monooxygenase, DBH) into the soluble and releasable form, DBH was monitored enzymatically and immunologically in aqueous and detergent-solubilized extracts of the adrenomedullary fractions. Degradation of the soluble DBH and acidic chromogranins by activation of endogenous proteases occurred during lysis in H2O. Shifts in the hydrophobicity of the membrane DBH were also apparent. Loss in enzyme protein or activity was, on the other hand, not observed for buffer-dialysed CG (pH 5-6). Limited proteolysis within the membrane phase was, however, indicated by the shift towards dominance of the intermediate hydrophobic DBH in the buffer-dialysed CG. By two-dimensional, crossed immunoelectrophoresis with cationic detergent the microsomal DBH was immunologically identical to the granule-bound enzyme but differed from the latter in molecular heterogeneity and in susceptibility to proteolytic solubilization by endogenous protease activities. DBH in the membranes of the chromaffin granules was proteolytically solubilized at pH 6-8 and the soluble DBH further degraded at pH 5. The results indicate that a post-translational conversion of the amphiphilic DBH into the soluble form, initiated at the level of the microsomes, may continue within the light and the heavy granule fractions which contain several DBH-converting and degrading proteolytic activities with acid optima.

Adrenal Medulla↗
PubMed1984

Compliance of the interstitial space in rats. III. Contribution of skin and skeletal muscle interstitial fluid volume to changes in total extracellular fluid volume.

The contribution to the extracellular fluid volume (ECV) from plasma volume (PV) and the total interstitial volumes contained in skin ( IFVS ) and skeletal muscle ( IFVM ) has been studied in rats over a wide range of overhydration and dehydration. ECV was measured as the two-hour distribution space for 51Cr-EDTA after nephrectomy while PV was measured with radiolabelled albumin or erythrocytes. Total interstitial volumes in skin and skeletal muscle were calculated from measurement of local interstitial volumes and the amount of skin and skeletal muscle in the rat. In control conditions ECV was on average 24.12 ml/100 g body weight. PV was 11.0% of ECV in control while IFVS and IFVM was 28.1% and 19.0% respectively. In dehydration the change in PV was 13.3% of the change in ECV, while the change in IFVS and IFVM was 30.0% and 21.0% of the change in ECV respectively. In overhydration (ECV on average 33.76 ml/100 g rat) the changes in PV, IFVS and IFVM were 7.5%, 22.1% and 17.2% of the change in ECV respectively. The regression coefficients describing the change between ECV and IFVS and IFVM were not significantly different in overhydration and dehydration while the regression coefficient between ECV and PV in overhydration was significantly less than the regression coefficient in dehydration. Thus, the fraction of ECV contained in skin and skeletal muscle is similar over the range of hydration studied. The fraction of ECV located in plasma is similar in control and dehydration, while in overhydration less of ECV is localized in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

A telemetric technique for studies of venous pressure in the human leg during different positions and activities.

The pressure in the saphenous vein of the lower leg was monitored by ordinary ECG telemetry equipment supplied with a pressure transducer, a chopper and an extra filter. In eight healthy volunteers venous pressure averaged 80 +/- 5 (SD) mmHg in the standing position and 21 +/- 10 (SD) mmHg during slow walking. When the subjects were occupied with laboratory work in upright position the mean venous pressure was 40-50 mmHg, similar to that obtained sitting at a desk: 48 +/- 5 (SD) mmHg.

Adult↗
PubMed1983

Rat brain interstitial fluid pressure measured with micropipettes.

Interstitial fluid pressure (IFP) in the rat brain has been measured with micropipettes, 2-4 microns in diameter, after trepanation and incision of dura. IFP was compared with cerebrospinal fluid pressure (CSFP) measured by a 0.3-mm (OD) cannula in the lateral ventricle. Control IFP averaged 3.43 +/- 0.65 (SD) mmHg (n = 83) with a corresponding CSFP of 3.53 +/- 0.71 (n = 83). Pretreatment with indomethacin to reduce inflammation during preparation did not affect IFP and CSFP. Infusion of a 20% mannitol solution amounting to 5% of body weight resulted in an average IFP of -5.66 mmHg and CSFP of -4.56 mmHg 20 min after start of the infusion, after which a gradual rise in both pressures was observed. Similar results were obtained after infusion of hypertonic urea. Inflation of a cuff around the rat neck resulted in an immediate and similar rise in IFP and CSFP. Increasing the arterial CO2 partial pressure to 80 mmHg increased IFP to 12-14 mmHg and pial venular pressure to 13-15 mmHg, while CSFP rose to about 10 mmHg. The micropuncture technique for measurement of brain IFP is rapid and practically atraumatic and may be used in a variety of animals.

Animals↗
PubMed1983

Interstitial albumin mass and transcapillary extravasation rate of albumin in DMBA-induced rat mammary tumours.

Transcapillary extravasation rate for radio-iodinated human serum albumin (I-HSA) from plasma to interstitial fluid, interstitial albumin mass and interstitial albumin concentration have been determined in dimethyl-benz-alpha-anthracene (DMBA)-induced mammary tumours in rats. The plasma radioactivity of tracer was kept constant in awake, freely moving rats by a continuous infusion of I-HSA from 1 to 72 h after an initial priming dose. Capillary leakiness for I-HSA was calculated as the plasma equivalent volume of I-HSA located extravascularly after 1 h infusion divided by the blood volume in the tissue, i.e. as the fractional extravasation rate (FER). The experiments showed that FER was highest in tumours while intestine and skin had FER of about 70% and 25% that of tumour respectively. Heart and skeletal muscle had similar FER about 1/8 that of tumour. Interstitial albumin concentration in tumour averaged 42% of plasma albumin concentration in tumour. Intestine, heart and skeletal muscle had interstitial albumin concentrations between 34 and 37% of plasma albumin concentration while skin had an albumin concentration averaging 20% that of plasma. Lymph flow was calculated as the product of the fractional turnover rate constant for interstitial albumin and interstitial volume (extravascular 51Cr-EDTA volume) and averaged 36.7 X 10(-3) mg/g X h in tumour while intestine and heart had lymph flows of 19.1 X 10(-3) and 14.1 X 10(-3) ml/g X h respectively. In muscle and skin lymph flow was 2.4 X 10(-3) and 18.3 X 10(-3) ml/g X h respectively. It is suggested that the high interstitial fluid pressure previously observed in these tumours will contribute in maintaining interstitial volume in a steady state by opposing fluid filtration into the interstitium and maintaining a lymph flow high enough to remove excess fluid and protein from the interstitium.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1982

Interstitial fluid pressure in DMBA-induced rat mammary tumours.

Interstitial fluid pressure (IFP) in DMBA-induced rat mammary tumours was measured by micropuncture with sharpened glass capillaries (diameter 1-3 micron) and by the 'wick-in-needle' technique (WIN). IFP in the superficial layers of the tumours (depth less than 800 micron) was measured with micropuncture, while WIN was used for measurements in deeper areas. IFP in the superficial layers of the tumours was 2.4 mmHg (SD 2.4, n=19), while IFP in deeper layers increased with increasing tumour weight. Thus central IFP in tumours weighing more than 5.5 g was 16.0 mmHg (SD 4.8, n=10), with a maximum value of 23.3 mmHg. When related to tumour histopathology a significant correlation was found between high cellular differentiation (i.e. low degree of malignancy) and high interstitial fluid pressure only. The high IFP may be secondary to a high capillary protein premeability and/or a relatively insufficient lymphatic drainage. A further rise in IFP might result from ischaemic cell swelling and/or a continuous cell proliferation within a tissue of rather low compliance. Together or alone one or more of these factors could facilitate the development of a compartment syndrome with concomitant cell death and tissue necrosis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Albumin concentration and colloid osmotic pressure of interstitial fluid collected by wick technique from rat skeletal muscle. Evaluation of the method.

Interstitial fluid from rat skeletal muscle has been collected by multifilamentous nylon wicks. The wicks consisted of 5-600 single filaments and had an overall diameter of 1-2 mm. The wicks were implanted in the muscle by means of a mending needle. The wicks were removed at various times after implantation, and colloid osmotic pressure (COP) or albumin concentration in wick fluid was measured. The fluid contained in the wick had a COP of 8-10 mmHg and an albumin concentration about 1/3 that of plasma. COP in wicks preloaded with serum of serum/saline dilution was higher after 1/2 and 1 h of implantation, but was nearly identical to that of saline soaked wicks after 2 h implantation. Intravenous injection of labelled albumin showed that wick implantation caused a marked leakage of proteins from plasma to the wick. However, 1/2 to 1 h after implantation the leakage was markedly reduced. The initial leakage of albumin could be diminished with protease inhibitor (aprotinin), but not with prostaglandin-, serotonin-, or histamine antagonists. The experiments show that wick fluid colloid osmotic pressure reflects interstitial fluid colloid osmotic pressure, while the protein composition of wick fluid may not be identical to that of undisturbed interstitial fluid.

Albumins↗