Low colloid osmotic pressure in very low birthweight infants receiving assisted ventilation.

Plasma colloid osmotic pressure (COP) was measured in three groups of very low birthweight infants. Babies in Group 1 (n = 8) were breathing spontaneously and had no respiratory disease. Those in Group 2 (n = 9) received assisted ventilation for hyaline membrane disease (HMD), and those in Group 3 (n = 7) received assisted ventilation for other reasons (five apnoea, two pneumonia). Both assisted ventilation groups had lower mean COP values than spontaneously breathing infants. Mean values (s.e.m.) for Groups 1, 2 and 3, respectively, were: 15.3 (0.6), 11.3 (0.4) and 11.9 mmHg (0.5) (P less than 0.001) on Day 1; and 15.2 (0.4), 12.9 (0.4) and 12.8 mmHg (0.3) (P less than 0.001) on Day 2. The increase from Day 1 to Day 2 was significant for those with HMD (P less than 0.05). Colloid osmotic pressure correlated with mean blood pressure (r = 0.51; P less than 0.001) but not with birthweight, gestation, crystalloid fluid intake or pH. The role of low COP in the pathogenesis of acute respiratory failure in infants with uncomplicated HMD is unclear, but such low COP may contribute to development of pulmonary oedema as a complication, particularly if the ductus arteriosus is still patent and the infants are given high volume intravenous fluids.

A colloid osmotic model of macromolecular aggregation to explain tissue water loss in aging.

We have evolved from the sea, are composed mostly of water, the medium and solvent wherein most vital processes occur, and phylogenetically and ontogenetically lose water continually as we age. An embryo is about 90% water, a newborn child about 80% water, a mature adult about 70% water, an older adult about 60% water with recent work indicating that in senescence the percentage of body water is actually below 60%. The mechanisms of the water loss in aging have not been elucidated. From a theoretical point of view, there is good reason to believe that there may be profound changes in the chemical potential of intracellular and interstitial water with age due to increased macromolecular interaction or aggregation from cross linking, polymerization, insolubility, etc.; all of which are known to increase with aging. The resultant increased macromolecular solute-solute interaction would be accompanied by decreased macromolecular solute-solvent interaction, thereby causing a higher solvent (water) chemical potential. This would facilitate the loss of bound water, thereby explaining the observed losses in body water with age. The ocular lens is a microcosm of aging, in that from its nucleus to cortex, the oldest to youngest cells are concentrically arranged, as in a tree. We have developed a method to directly measure lens tissue oncotic pressure in an attempt to experimentally test the above cited hypothesis.

Failure of the colloid oncotic-pulmonary artery wedge pressure gradient to predict changes in extravascular lung water.

Colloid oncotic pressure (COP), pulmonary artery wedge pressure (WP), and the COP-WP gradient were measured in seven critically ill adult patients and compared with extravascular lung water determined using the thermal-dye double-indicator dilution technique and a bedside lung water computer. Correlation coefficients for changes in extravascular lung water vs. COP, WP, and COP-WP were not significant, and in this patient population the COP-WP gradient did not predict changes in extravascular lung water.

Mixed colloid cyst-xanthogranuloma of the third ventricle. A light and electron microscopic study.

A mixed colloid cyst-xanthogranuloma of the third ventricle is described. The xanthogranuloma associated with the cyst completely occupied the third ventricle. On light microscopy, a single epithelial layer with a basal lamina was seen lining the cyst wall. Electron microscopic study revealed three different kinds of cells in the epithelial layer: ciliated, nonciliated, and basal cells. Many lipid droplets were present in the superficial epithelial cells, macrophages, pericytes, and endothelia. The pathogeneses of the cyst and of the xanthogranuloma are discussed.

Colloid osmotic pressure at birth. Effect of sample site, type, and mode of delivery.

Colloid osmotic pressure was measured at birth in 102 newborns. Umbilical vein plasma colloid osmotic pressure correlated with total serum protein, birth weight, and gestational age. Mean colloid osmotic pressure of 11 infants who were small for gestational age was less than, and that of seven infants who were large for gestational age was more than, that of average-sized infants of similar gestation. For infants weighing 1,501 to 3,000 g, mean (+/- SD) colloid osmotic pressure following cesarean section (15.1 +/- 1.6 mm Hg) was lower than that following vaginal delivery (18.4 +/- 2.2 mm Hg). This may reflect the fact that use of maternal fluid therapy preceding cesarean section was greater than before vaginal delivery. The definition of normative values for neonatal plasma colloid osmotic pressure makes it possible to investigate changes in relation to disease, therapy, and subsequent outcome in sick neonates.

Colloid cyst of the third ventricle. A scanning and transmission electron microscopic study.

Three colloid cysts of the third ventricle were examined by both transmission (TEM) and scanning electron microscopy (SEM). There was morphological diversity of the cyst surface on SEM, with ciliated and non-ciliated cells present. In some areas, the non-ciliated cells were more numerous and extended above the surface. Individual non-ciliated cells show a wrinkled cell surface and bleb-like structures. The TEM findings correlated well with SEM, revealing two cell types. The non-ciliated cells appeared to have both exocrine and apocrine activity. In ciliated cells, abnormal cilia were related to abnormal centrioles; also present were highly abnormal microvilli. The appearance of the surface was similar to a normal ventricular surface. By allowing a greater assessment of cell types and their distribution, SEM has added one additional dimension in the evaluation of colloid cysts and their possible derivation.

Intraventricular noncolloid neuroepithelial cysts.

Symptomatic intraventricular developmental cysts of neuroepithelial origin occurring in the lateral and fourth ventricles are extremely rare. We report the clinical, radiologic, and computed tomographic (CT) findings in three such cases, two occurring in the lateral ventricles and one in the fourth ventricle. Within lateral ventricles, these cysts are distinguished from colloid cysts by their large size, more posterior locations, and CSF-equivalent CT attenuation of their contents. Lack of contrast enhancement on CT and angiographic avascularity are also features. Fenestration in two cases and partial cyst excision in the third case relieved the predominant symptoms. The symptomatology and theories of histogenesis are reviewed and the differential diagnosis discussed.

Dynamics of glomerular ultrafiltration in Amphiuma means.

To study renal function in Amphiuma means, the hydrostatic pressures in vascular and tubular structures and the glomerular filtration rate were determined at different arterial blood pressures. In the arterial blood pressure range studied no evidence of autoregulation of the glomerular capillary pressure of the hydrostatic pressure gradient over the capillary membrane was found. The glomerular filtration ceases at an arterial blood pressure below 12 cm H2O. No significant difference between tubular free flow pressure and peritubular capillary pressure was noted. Furthermore, it was found that the glomerular capillary pressure could be estimated by measuring the intratubular stop-flow pressure and arterial colloid osmotic pressure at an arterial pressure above 15 cm H2O. It was also found possible to measure the glomerular capillary pressure at the very end of the afferent arteriole. The protein concentrations in afferent and efferent arteriolar blood were determined and the colloid osmotic pressures were calculated according to a new formula derived for Amphiuma plasma. The dynamics of glomerular ultrafiltration was evaluated. A filtration equilibrium across the glomerular membrane was reached, since the efferent colloid osmotic pressure was not significantly different from the hydrostatic pressure gradient across the glomerular capillary membrane.

Functional characteristics of the renal interstitium.

The renal interstitial space analyzed as "inulin space" comprises about 13% in the rat. The Starling forces of this compartment are governed by the balance between tubular and capillary fluid transport and also by the leakage of plasma proteins from the blood side. Protein transport will occur in a large-pore system in the peritubular capillary membrane. During control antidiuresis, the interstitial hydrostatic pressure is 2-4 mmHg. The colloid osmotic pressure shows a larger variability but is generally about 5 mmHg. During conditions of depressed capillary reabsorption but unchanged tubular reabsorption, as in saline expansion, the interstitial hydrostatic pressure rises 3-4 times, whereas the colloid osmotic pressure will show a steep fall resulting from the increased fluid entry and unchanged protein transport. The interstitial volume increases only slightly, since it is compressed by the expanding tubules. The influence of interstitial physical forces on tubular transport remains unclear, mainly due to the inaccessibility of the lateral interspaces to direct measurement of relevant parameters.