Ground substance mucopolysaccharides and plasma proteins: their role in capillary water balance

Hypovolemia with peripheral edema: What is wrong?

Fluid normally exchanges freely between the plasma and interstitial space and is returned primarily via the lymphatic system. This balance can be disturbed by diseases and medications. In inflammatory disease states, such as sepsis, the return flow of fluid from the interstitial space to the plasma seems to be very slow, which promotes the well-known triad of hypovolemia, hypoalbuminemia, and peripheral edema. Similarly, general anesthesia, for example, even without mechanical ventilation, increases accumulation of infused crystalloid fluid in a slowly equilibrating fraction of the extravascular compartment. Herein, we have combined data from fluid kinetic trials with previously unconnected mechanisms of inflammation, interstitial fluid physiology and lymphatic pathology to synthesize a novel explanation for common and clinically relevant examples of circulatory dysregulation. Experimental studies suggest that two key mechanisms contribute to the combination of hypovolemia, hypoalbuminemia and edema; (1) acute lowering of the interstitial pressure by inflammatory mediators such as TNFα, IL-1β, and IL-6 and, (2) nitric oxide-induced inhibition of intrinsic lymphatic pumping.

Pulmonary vascular heterogeneity and the Starling hypothesis

It has generally been assumed that movement of fluid between the pulmonary microvasculature and surrounding tissues is governed by a "Starling" balance of hydrostatic and protein osmotic forces similar to that which prevails in the extremities. However, both recent and older observations suggest that the lungs are more resistant to edema formation than most other organs. Several structural aspects of the lung may account for protection of the airspaces from edema formation. The pulmonary microvasculature, which comprises >70% of the pulmonary circulatory bed, appears to be less permeable to fluid and electrolytes than the endothelium of the pulmonary arteries and veins and other microvascular exchange areas. This arrangement may help explain why early edema is confined to the perivascular and peribronchial regions and why lymphatics do not reach the alveoli. Unlike the peripheral vasculature, which is compressed by edema formation, the extra-alveolar vessels remain tethered open by airway distention, even when interstitial pressures rise above those in the vessels. This may also facilitate return of proteins to the circulation. Ultrafiltration of plasma may lower local protein concentrations in the interstitium, thereby slowing further edema formation. Transendothelial reabsorption of fluid may also be altered by vesicular transport.

Water content, body weight and acid mucopolysaccharides, hyaluronidase and beta-glucuronidase in response to aestivation in Australian desert frogs

This study investigates the effects of aestivation on body water content, body mass, acid mucopolysaccharide (AMPS) and some of its degrading enzymes in different tissues for some Australian desert frogs. The AMPS component of the liver, kidney, skin and cocoon alter during aestivation to help retain water, which is unchanged in most tissues of all frog species, and to protect the frogs from desiccation during extended periods of aestivation. Hepatic AMPS was unaltered in Cyclorana maini, C. platycephala and Neobatrachus sutor but increased significantly after 2 months of aestivation in C. australis. The level of AMPS in the kidney was elevated in all four frog species after 5 months of aestivation. Skin AMPS content in the skin of awake frogs decreases with aestivation period and increases in the cocoon. AMPS in the cocoon probably works as a cement between the cocoons' layers and its physical presence presumably contributes to preventing water flux. Changes in AMPS content in different tissues were accompanied by significant changes in both hyaluronidase and beta-glucuronidase activities, which play an important role in AMPS metabolism. Alcian blue staining of control and digested skin of C. australis and C. platycephala with testicular hyaluronidase indicated the presence of AMPS, concentrated in a thin layer (called ground substance, GS) located between stratum compactum and stratum spongiosum, and acid mucin concentrated in the mucous glands and in a 'tubular' structure which could be observed in the epidermal layer. Hyaluronidase digestion of the cocoon slightly changed the Alcian Blue colour, suggesting the presence of a large amount of acid mucin similar to that found in the skin mucous gland. The results of this study present data for the redistribution of AMPS, which may help in reducing water loss across the cocoon and reabsorption of water in the kidney during aestivation.

Interactive effect of chondroitin sulphate C and hyaluronan on fluid movement across rabbit synovium

The polysaccharide hyaluronan (HA) conserves synovial fluid by keeping outflow low and almost constant over a wide pressure range ('buffering'), but only at concentrations associated with polymer domain overlap. We therefore tested whether polymer interactions can cause buffering, using HA-chondroitin sulphate C (CSC) mixtures. Also, since it has been found that capillary filtration is insensitive to the Starling force interstitial osmotic pressure in frog mesenteries, this was assessed in synovium. Hyaluronan at non-buffering concentrations (0.50-0.75 mg ml(-1)) and/or 25 mg ml(-1) CSC (osmotic pressure 68 cmH(2)O) was infused into knees of anaesthetised rabbits in vivo. Viscometry and chromatography confirmed that HA interacts with CSC. Pressure (P(j)) versus trans-synovial flow (;Q(s)) relations were measured.;Q(s) was outwards for HA alone (1.2 +/- 0.9 microl min(-1) at 3 cmH(2)O, mean +/- S.E.M.; n = 6). CSC diffused into synovium and changed;Q(s) to filtration at low P(j) (-4.1 microl min(-1), 3 cmH(2)O, n = 5, P < 0.02, t test). Filtration ceased upon circulatory arrest (n = 3). At higher P(j), 0.75 mg ml(-1) HA plus CSC buffered;Q(s) to approximately 3 microl min(-1) over a wide range of P(j), with an outflow increase of only 0.04 +/- 0.02 microl min(-1) cmH(2)O(-1) (n = 4). With HA or CSC alone, buffering was absent (slopes 0.57 +/- 0.04 microl min(-1) cmH(2)O(-1) (n = 4) and 0.86 +/- 0.05 microl min(-1) cmH(2)O(-1) (n = 5), respectively). Therefore, polymer interactions can cause outflow buffering in joints. Also, interstitial osmotic pressure promoted filtration in fenestrated synovial capillaries, so the results for frog mesentery capillaries cannot be generalised. The difference is attributed to differences in pore ultrastructure.

Lung water and proton magnetic resonance relaxation in preterm and term rabbit pups: their relation to tissue hyaluronan

The present study was performed to investigate simultaneously total lung water, T(1) and T(2) relaxation times, and hyaluronan (HA) in preterm and term rabbits. Attempts were also made to establish the relationship of HA to total lung water and to T(2)-derived motionally distinct water fractions. Experiments were performed in fetal Pannon white rabbit pups at gestational ages of 25, 27, 29, and 31 d and at a postnatal age of 4 d. Lung tissue water content (desiccation method), T(1) and T(2) relaxation times (H(1)-NMR method), and HA concentration (radioassay) were measured, and free and bound water fractions were calculated by using multicomponent fits of the T(2) relaxation curves. Lung water content and T(1) and T(2) relaxation times were highest at a gestational age of 27 d and then declined steadily during the whole study period. Similar trends and time courses were seen for the fast and slow components of the T(2) relaxation curve. The T(2)-derived free water fraction remained unchanged at a gestational age of 25-29 d ( approximately 67%), but increased progressively to a value of 78.5 +/- 7.9% at 31 d (p < 0. 001) and to 83.4 +/- 9.4% at the postnatal age of 4 d (p < 0.01). Opposite changes occurred in the bound water fraction. Lung HA concentration decreased with advancing gestation from 870.8 +/- 205.2 microg/g dry weight at 25 d to 162.6 +/- 32.4 microg/g dry weight at 31 d (p < 0.001), but it was increased 2-fold postnatally. HA correlated positively with total lung water (r = 0.39; p < 0.001) but not with the bound water fraction. It is suggested that the physiologic lung dehydration is associated with macromolecule-related reorganization of lung water and that the role of HA in this process needs to be further investigated.

Water content and proton magnetic resonance relaxation times of the brain in newborn rabbits

The present study, using proton nuclear magnetic resonance relaxation (H1 NMR) measurements, was undertaken to quantitate water fractions with different mobility in the brain tissue obtained form New Zealand White rabbit pups. Serial studies were carried out at the postnatal age of 0-1, 24, 48, 72, and 96 h in pups nursed with their mothers and suckling ad libitum (group I) and in those pups separated from their mothers and completely withheld from suckling (group II). Tissue water content (desiccation method) and T1 and T2 relaxation times (H1 NMR method) were measured. Free, loosely bound, and tightly bound water fractions were calculated by applying multicomponent fits of the T2 relaxation curves. It was demonstrated that brain water content and T1 and T2 relaxation times did not change with age in the suckling pups. In pups withheld from suckling brain water decreased from 89.4 +/- 0.5% at birth to 87.7 +/- 0.1% at the age of 96 h (p < 0.05), T1 remained unchanged, and there was a significant fall in T2 by the age of 72 h (188 +/- 12 versus 178 +/- 4 ms, p < 0.05) and 96 h (171 +/- 6 ms, p < 0.01). Partition of brain water into bound and free fractions as derived from biexponential fits of T2 decay curve showed that the percent contribution of bound water fraction in pups of group I fell progressively from 61% at birth to 3% at the age of 72-96 h (p < 0.05). This fall was accelerated by the complete deprival of fluid intake, and the level of about 4% could be attained as early as the age of 24 h. Triexponential analysis of T2 relaxation curves revealed that the loosely bound fraction (middle component) predominated over the free (slow component) and the tightly bound (fast component) water fractions. In response to withholding fluid intake, the free water fraction increased 4-fold at the expense of tightly bound brain water. It is concluded that the majority of neonatal brain water is motion-constrained. The free, the loosely bound, and the tightly bound water fractions appear to be interrelated; from the brain water store water can be released to supply free water for volume regulation.

Estimating rat renal medullary interstitial oncotic pressures and the driving force for fluid uptake into ascending vasa recta

1. We have investigated the potential contribution of medullary interstitial oncotic pressure to the net balance of forces influencing fluid movement through the walls of the ascending vasa recta (AVR) in the exposed papillae of 2-week-old Sprague-Dawley rats. 2. Using a capillary zone electrophoresis (CZE) assay, hyaluronan (HA) concentrations were measured in fresh tissue slices from the renal papilla. HA content per wet weight of tissue decreased from tip to base of the papilla, but as a function of cell-free interstitial space (IS) HA concentration was relatively constant at 1.6 micrograms HA per mg IS up to 1600-1800 microns from the tip. Thereafter the concentration fell rapidly to near zero levels. 3. The volume of the IS was determined using a transmission electron micrographic study of the papilla in age-matched rats. Total interstitial volume (i.e. IS + IC, the interstitial cell volume), as a function of total tissue volume, decreased only slightly between 0 and 1800 microns (i.e. from about 40 to 35%). IS and IC were found to be reciprocally related with IS decreasing from 21.8 to 10.2%, while IC increased from 18.3 to 25.2% over the 1800 microns. 4. Total interstitial oncotic pressures were estimated as the sum of the oncotic pressure due to HA alone plus the oncotic pressure of albumin (A) in an HA matrix. Taking into account reflection coefficients to HA and A, there was an effective oncotic pressure (E pi) of between 3.46 and 6.0 cm H2O on the interstitial side of the AVR. Under free flow conditions an E pi in this range is sufficient to result in a net inward driving force of between 5.4 and 9.3 cm H2O, sufficient to account for current estimates of water reabsorption by the AVR. 5. HA concentrations in the papilla increased over the first 3 weeks of life from 0.313 +/- 0.09 microgram (mg wet weight of slice)-1 (mean +/- S.E.M.) at 1 week to 0.563 +/- 0.06 at 3 weeks of age (P > 0.01)1 in parallel with an age-dependent increase in mean urine osmolarity. It is suggested that the increasing interstitial concentrations of HA may contribute to the development of urinary concentrating ability, which occurs concurrently.

Postnatal changes in water content and proton magnetic resonance relaxation times in newborn rabbit tissues

In the present study, using proton nuclear magnetic resonance relaxation (H1 NMR) measurements, an attempt was made to quantitate water fractions with different mobility in the skin, skeletal muscle, and liver tissues obtained from New Zealand white rabbit pups. Serial studies were carried out at the postnatal age of 0-1, 24, 48, and 72 h in pups nursed with their mothers and suckling ad libitum (group I) and in those pups separated from their mothers and completely withheld from suckling (group II). Tissue water content (desiccation method) and T1 and T2 relaxation times (H1 NMR method) were measured. Free, loosely bound, and tightly bound water fractions were calculated by applying multicomponent fits of the T2 relaxation curves. It was demonstrated that skin water content and T1 and T2 relaxation times decreased with age (p < 0.01), the decrease in T2 proved to be more pronounced in group II than in group I (p < 0.05). Muscle and liver water, and T1 and T2 relaxation times did not change with age in the suckling pups. In response to with-holding fluid intake muscle water remained constant, liver water increased paradoxically (p < 0.05). T1 relaxation time showed no consistent change in either tissues, whereas T2 relaxation time decreased significantly (muscle, p < 0.01) or tended to decrease (liver, p < 0.06). Using biexponential analysis fast and slow components of T2 relaxation curve could be distinguished that corresponded to the bound and free water fractions. Bound water accounted for 42-47%, 50-57%, and 34-40% of total tissue water in the skin, skeletal muscle, and liver, respectively, regardless of age and fluid intake. Triexponential fits of the T2 relaxation curve made possible the further partition of tissue water into tightly bound (fast component), loosely bound (middle component), and free (slow component) water fractions. In all tissues studied, loosely bound fraction predominated (skin, 48-64%; muscle, 54-65%; liver, 45-63%), followed by the free (skin, 26-45%; muscle, 23-32%; liver, 20-25%) and the tightly bound water fraction (skin, 6-14%; muscle, 10-16%; liver, 14-33%). Postnatal age and fluid intake had no apparent influence on this pattern of distribution. It is concluded that the majority of neonatal tissue water is motion-constrained. The free, the loosely bound, and the tightly bound water fractions appear to be interrelated and dependent on age, fluid intake, the tissues studied, and their hydration.

High osmotic stress behavior of hyaluronate and heparin

Using polyethylene glycol and dextran as osmotic stressing agents, the concentrations of hyaluronate and heparin were measured as a function of osmotic pressure II over the range of 0.03 to nearly 50 atmospheres. The experimental results were analyzed in terms of the Donnan osmotic pressure, the virial expansion, and Flory's first neighbor interaction parameter. In addition, II was looked at as a function of the reciprocal cube root of the concentration, which represents an average intermonomer spacing at high concentrations. The decay lengths in the so-called hydration region were found to be around 2.6 A and negligibly salt dependent. In the electrostatically dominated region the decay lengths were found to be dependent on the ionic strength, but not simply so. The osmotic compressibilities were also calculated, and were compared to compressibility data of corneal stroma and articular cartilage. These latter compressibilities were close to those for the pure hyaluronate and heparin, strengthening the evidence that glycosaminoglycans (GAGs) are largely responsible for connective tissue compressibility. Higher compressibilities for previously reported GAG data is thought to be related to the protein content of those samples.

A theoretical view of interstitial fluid pressure--volume measurements

A theoretical description of the mechanics of the interstitium is used to derive a relation for interstitial fluid pressure. The nature of this relation is examined and the dependence of fluid pressure on imbibed fluid, free fluid, and osmotic balances is defined. When the theory is applied to an idealized osmometer configuration, the predicted pressure-volume curve is analogous to the experimental observations of A. C. Guyton (1965, Circ. Res., 16, 452-460). Further, it is suggested that the similarity between the present theory and the experimental data of Guyton supports the hypothesis that a negative interstitial pressure and a dearth of free fluid is an expected and perhaps dominant state of normal tissue.

Measurement of colloid osmotic pressure in body fluids: errors caused by preheparinized glass capillaries and by CO2 loss

The effect on colloid osmotic pressure (COP) of heparinizing body fluids was estimated with a low compliant osmometer, using Diaflo PM-30 or PM-10 membranes (Amicon, Lexington, Mass., USA). It was found that collecting and storing samples in preheparinized glass capillaries may increase COP by up to 4.0 mmHg. Measurements on heparin and protein solutions, separately and mixed, show that these macromolecules have a mutually potentiating effect on COP, probably by excluding part of the water as distribution space for the other molecular species. While this 'heparin error' varies among various types and batches of capillaries (Vitrex, Modulohm I/S), the content of heparin in some batches appears to be two to three times greater than the declared minimum. Alternatively, the excess COP may result from addition of other water-soluble macromolecules in the heparinization process. Even if some batches do not give appreciable error, we recommend to avoid preheparinized capillaries for measurement of COP. Both defibrination, and the amount of heparin needed to anticoagulate macro blood samples, have insignificant effect on COP. Loss of CO2 by diffusion from separated plasma may increase pH towards 9.5. Concomitantly, COP increased by 2.1 mmHg per pH-unit. If plasma or serum samples are capped within some minutes after separation, they may be stored for weeks at 4 degrees C in polyethylene tubes without appreciable change of COP.

The effects of hyaluronidase on interstitial hydration, plasma protein exclusion, and microvascular permeability in the isolated perfused rat heart

Hyaluronic acid, a principal glycosaminoglycan of the cardiac interstitium, may have a role in interstitial hydration, interstitial plasma protein exclusion and microvascular transport process (Wiederhielm, 1976b). We have investigated whether hyaluronidase reduces myocardial hyaluronate concentrations and thereby alters these several physical aspects in the isolated rat heart. Studies were conducted in ischemic, as well as aerobic hearts because of the reported therapeutic efficacy of the enzyme in myocardial ischemia. Two hours of perfusion with hyaluronidase significantly reduced myocardial hyaluronate content. Additionally, hyaluronidase decreased interstitial volume of both aerobic and otherwise edematous ischemic hearts, and prevented ischemic induced increased coronary vascular resistance in ischemic hearts. However, hyaluronidase did not effect the albumin interstitial exclusion volume or microvascular albumin and sorbitol exchange in aerobic hearts. In ischemic hearts, the enzyme did not prevent nor enhance the increase in microvascular permeability which occurred. We conclude that hyaluronate is neither a determinant of interstitial protein exclusion nor microvascular permeability, but plays an important role in interstitial hydration.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 1

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.

Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 2

In the past, renal papillary necrosis (RPN) has been commonly associated with long-term abusive analgesic intake, but over recent years a wide variety of industrially and therapeutically used chemicals have been shown to induce this lesion experimentally or in man. Destruction of the renal papilla may result in: (1) secondary degenerative cortical changes which precede chronic renal failure or (2) a rapidly metastasizing upper urothelial carcinoma, which has a very poor prognosis. This article will briefly review the published data on the morphology, function, and biochemistry of the normal renal medulla and the pathology associated with RPN, together with the secondary changes which give rise to cortical degeneration or epithelial carcinoma. It will then examine in detail those chemicals which have been reported to cause RPN in an attempt to delineate structure-activity relationships. Finally, the many different theories that have been proposed to explain the pathophysiology of RPN will be examined and an hypothesis will be put forward to explain the primary pathogenesis of the lesion and its secondary consequences.

Macromolecular basis of globular protein exclusion and of swelling pressure in loose connective tissue (umbilical cord)

The macromolecular basis of tissue swelling pressure and of the ability of tissue to exclude globular proteins, according to size, have been investigated using human umbilical cord. Exclusion data of tissue, and tissue from which the polysaccharides had been removed by hyaluronidase were compared. Exclusion of globular proteins by the polysaccharides, obtained by difference from the two sets of data, was similar to that reported for isolated polysaccharides in solution. It can be described by a sphere/cylinder geometric exclusion model. The exclusion behavior of the polysaccharide-free tissue was accounted for in terms of the component collagen fibrils, glycoprotein microfibrils and cells. Average pore diameters of 18 and 110 nm, respectively, for the intact tissue and for the polysaccharide-free tissue were estimated. Swelling pressure measurements were performed on intact, on hyaluronidase-treated and on hyaluronidase and then Pronase-treated tissues to obtain the contributions of the polysaccharides, of collagen and of microfibrils. Close to the in vivo volume of tissue, the swelling pressure is given almost entirely by the polysaccharides and is consistent with the osmotic pressure expected from the relative amounts of hyaluronic acid and proteoglycan present and their distribution in the extrafibrillar, extracellular space. Upon swelling or deswelling a small net contribution of the fibrillar system to the swelling pressure is evident.

Alveolar wall relations

We have presented a highly dynamic view of the alveolar septum and its main enclosed structure, the dense capillary network. The septal or perimicrovascular interstitium is the space between alveolar epithelial sheets after exclusion of the capillary network. It contains cells, fibers, and a viscous matrix. Capillaries form a very complex network, which closely follows the geometry of the terminal airways and participates in functional adaptations of the wall, particularly septal pleating. The level of filling and configuration of different capillaries ranging from collapse to full distension are variable, depending on factors such as transmural balance of forces but also on tissular configuration. Alveolar flooding of any cause will produce an immediate change of capillary configuration and volume.

Interstitial fluid volume, colloid osmotic and hydrostatic pressures in rat skeletal muscle. Effect of venous stasis and muscle activity

The effect of 24 h caval/iliac venous obstruction on interstitial fluid volume (IFV), hydrostatic (Pi) and colloid osmotic (COPi) pressure in hindlimb skeletal muscle was studied in three groups of rats: Group I (G I), Intact innervation, unrestricted motor activity. Group II (G II), Sympathectomized, unrestricted. Group III (G III), Motoric and sympathetic denervation + immobilization of the hindlimbs. Subcutaneous edema was present in all groups at femoral venous pressure (Pv) exceeding 13 mmHg. Skeletal muscle edema was seen in G III at Pv above 12 mmHg, in two rats in G II at Pv of 18 and 23 mmHg, but in no rats in GI. Without venous obstruction, control COPi was 8-10 mmHg in all groups. With increasing Pv, COP fell moderately in G I and G II: delta COPi/delta Pv = 0.22. In G III, COPi fell from a control of 8.2 to 3.5 mmHg at a Pv of 12 mmHg (delta COPi/delta Pv = 0.52), but remained constant with further rise in Pv. Pi was about 0 mmHg in controls and 1-2 mmHg in rats with muscle edema. IFV rose by 6% per mmHg increase in Pv in G III, and 2% in G I and G II. This expansion of IFV may explain about 70% of the fall in COPi, the remaining being due to lymphatic washout of interstitial proteins. It is concluded that normal muscle activity together with dilution and washout of interstitial proteins constitute the main edema preventing mechanisms in skeletal muscle.

The effects of severe thermal injury on the glycosaminoglycans of guinea pig skin

The central purpose of the present investigation was the qualitatively and quantitatively analyze the glycosaminoglycans of guinea pig skin at 2 hr after a third-degree burn injury. The data obtained from uronic acid determinations, fractionation by column chromatography and cellulose acetate electrophoresis indicate no significant alterations in the glycosaminoglycans at 2 hr postburn. The data presented in this study support the concept that the glycosaminoglycans are not immediately damaged by the heat of the burn.

Variations in the numbers and dimensions of tissue channels after injury

The dimensions and numbers of tissue channels were estimated, using transmission electron microscopy after filling them with ferri-ferrocyanide precipitate, in the subcutaneous tissue of mice. They were studied in the normal condition, and at varying times after a simple incised wound. After this injury they increased very greatly indeed in numbers and dimensions, being maximal at 1 week. Six months elapsed before they returned to normal. The hydraulic conductivity was calculated. It increased by 10(5) times at the maximum, when clinical oedema was present.

Histochemistry and ultrastructure of the interstitium of the renal papilla in rats with hereditary diabetes insipidus (Brattleboro strain)

The Brattleboro strain of Long-Evans hooded rats has hereditary hypothalamic diabetes insipidus due to the inability to produce antidiuretic hormone. Animals homozygous for this autosomal recessive trait have extreme polyuria and polydipsia, whereas heterozygotes are less severely affected. Light and electron microscopy were used to study the interstitial tissue of the renal papilla of Brattleboro rats and normal Long-Evans rats. Staining with alcian blue or colloidal iron revealed that homozygous Brattleboro rats (DI) have greatly reduced quantities of glycosaminoglycans in the papillary interstitium. Heterozygotes showed staining similar but not identical to that of normal rats. The papillary interstitial cells of DI rats lacked the cytoplasmic processes seen in normal rats, and the normal relationship of these cells to the tubular elements of the papilla was absent. Electron microscopy revealed that the papillary interstitial cells of DI rats appeared less active than those of heterozygous or normal rats. In DI rats these cells displayed reduced numbers of lipid droplets and mitochondria, and the Golgi apparatus and rough endoplasmic reticulum were poorly developed. The altered ultrastructure of the papillary interstitial cells may be responsible for the reduction of interstitial glycosaminoglycans in DI rats. Glycosaminoglycans possess properties which may contribute to urinary concentration, It is suggested that the interstitial tissue of the renal papilla is influenced by antidiuretic hormone.

The decrease of hyaluronate synthesis by anti-inflammatory steroids in vitro

The effect of anti-inflammatory steroids (prednisolone and derivatives of hydrocortisone, dexamethasone and betamethasone) on the synthesis of hyaluronic acid and sulphated glycosaminoglycans in human skin fibroblast culture was studied. The concentrations of steroids varied between 1 x 10(-10)M and 1 x 10(-6)M. All tested steroids decreased the synthesis of hyaluronic acid to the same final level which was about 40--50% of the controls, but the concentrations required varied between different steroids. The relative inhibitory potencies of the steroids were calculated based on concentrations needed to decrease the synthesis of hyaluronate. When the inhibitory potency of hydrocortisone was calculated as one, the values of the other steroids were: prednisolone 5, hydrocortisone 17- butyrate 20, betamethasone alcohol 30, dexamethasone alcohol 38, betamethasone 17-valerate 350--400, dexamethasone monosodium phosphate and betamethasone disodium phosphate over 400. Hydrocortisone sodium succinate was as potent an inhibitor of hyaluronate synthesis as hydrocortisone alcohol. None of the tested steroids affected the synthesis of sulphated glycosaminoglycans at these concentrations. The changes ovbserved in glycosaminoglycans in the medium were in accordance with the changes in the cell layer. The possible significance of hyaluronate synthesis inhibition by anti-inflammatory steroids is discussed.

Plasma proteins in human peripheral nerve

Using the immunofluorescent technique, the distribution of nine plasma proteins, differing in molecular weight, was studied in sural nerve biopsies from 25 neurological patients. The results of this study show that endoneurial vessels are normally permeable to all plasma proteins, though not to an equal degree. Permeability of the nerve blood vessels may be increased in pathological conditions. Proteins of molecular weight equal to or greater than 340,000 tend to accumulate at the site of the perineurium, indicating a slow removal from this structure. A marked accumulation of plasma proteins at the site of the perineurium was observed in hypertrophic neuropathy.

Calcium diffusion in transient and steady states in muscle

Rates of diffusion through the extracellular space of thin sheets of myocardium from the right ventricular outflow tract of kittens were estimated at 23 degrees C for 45Ca2+ and an inert reference tracer, [14C]sucrose. The myocardial sheets were mounted in an Ussing chamber and equilibrated with Tyrode solution with varied calcium concentrations, Cao. The tracers were added to one side and their concentrations on the other side measured at 5-15-min intervals for 6 h. The apparent tracer diffusion coefficient for sucrose was 1.11 +/- 0.06 X 10(-6) cm2s-1 (mean +/- SEM, n = 74), 22% of the free diffusion coefficient; the lag time before reaching a steady state provided estimates of the intratissue volume of distribution or diffusion space of 0.41 +/- 0.15 ml/ml tissue (n = 74), a value compatible with expectations for extracellular fluid space. Over the range of Cao from 0.02 to 9.0 mM, the intratissue apparent diffusion coefficient for Ca, DCa, averaged 1.65 +/- 0.10 X 10(-6) cm2s-1, n = 74, which is 21% of the free DoCa, and was not influenced by Cao. Because transsarcolemmal Ca permeation is slow, DCa is the diffusion coefficient in the extracellular region. The paired ratios DCa/Ds averaged 1.32 +/- 0.05 (n = 67) for all levels of Cao but at physiologic or higher Cao averaged 1.45 +/- 0.07 (n = 39), close to the ratio of free diffusion coefficients, 1.53. Equations distinguishing transient from steady state diffusion were fitted to the data, showing that the apparent distribution volume of "binding sites" external to the diffusion pathway diminished at higher Cao in a fashion suggesting that a least two different Ca2+ binding sites were present.