Kinetics of unfolding of proteins on hydrophobic surfaces in reversed-phase liquid chromatography

As a continuation of previous studies, we present in this paper measurements on the kinetics of denaturation of papain, soybean trypsin inhibitor and lysozyme on n-butyl-bonded silica gel surfaces used in reversed-phase liquid chromatography (RPLC). In all cases, native and denatured peaks widely separated from one another are observed. The rate constants for denaturation or unfolding are determined by the measurement of the peak area of the native protein as a function of the incubation time that the species spends on the bonded-phase surface. The results reveal that a slow denaturation step occurs with a half-life of ca. 15 min. In addition, studies of denaturation as a function of the amount of 1-propanol in the initial mobile phase suggest an additional unfolding step when the protein comes in contact with the bonded-phase surface. The extent of this latter step decreases as the concentration of 1-propanol increases, further suggesting that 1-propanol sorption on the bonded stationary phase may play a role in this behavior. Other studies are conducted with alpha-chymotrypsinogen, in which injection is made after the start of the gradient. The extent of denaturation is observed to be a function of the organic modifier employed. The results of this paper provide insight into the denaturation process in RPLC and suggest approaches to minimize this behavior.

Congenital blood cysts of the heart valves

Congenital blood cysts of the heart valves are found most commonly on the tricuspid and mitral valves of fetuses and infants. Hearts available following 38 random autopsies of fetuses and infants 2 years of age or younger were examined. Blood cysts were found in 18 cases (47 per cent) in which ages ranged from 26 weeks of gestation to 11 months. The cysts varied in diameter, from microscopic to 3 mm. Affected valves had from one to 20 cysts. Light microscopic examination of serially sectioned paraffin-embedded tissue and plastic-embedded tissue and scanning electron microscopic examination revealed connections between the cyst lumens and ventricles via small endothelium-lined channels. The cyst structure suggested formation from ventricular endothelial infoldings in the valve leaflet base, which bulged into the atrium because of the pressure gradient present during valve closure. Blood cysts are a common finding in neonates dying of various causes and probably have no clinical significance. There is no association with asphyxia as previously described. Blood cysts may persist and enlarge to form giant cysts of the heart valves.

Glomerular accumulation of monocytes and macrophages in experimental glomerulonephritis associated with Trypanosoma rhodesiense infection

Experimental infection in rabbits with a human isolate of Trypanosoma rhodesiense led to the formation of circulating immune complexes and glomerulonephritis. Granular deposits of C3 and lesser amounts of IgM and IgG were seen deposited in the glomeruli in a primarily mesangial pattern. The glomeruli became hypercellular beginning on day 7. This was associated with diffuse swelling and vacuolation of endothelial cells with focal loss of fenestrae, as well as vacuolation of mesangial cells processes protruding into the capillary lumina. The hypercellularity became maximal on day 21 and was accompanied by proteinuria and increased tubular hyaline droplets. The hypercellularity was in large part due to the accumulation of monocytes as demonstrated by nonspecific cytoplasmic esterase stains. Counts of the number of monocytic cellular profiles per glomerulus showed that maximal numbers were reached on the 21st day of the infection. Ultrastructural examination confirmed the presence of monocytes within capillary lumina and macrophages within mesangial regions. Electron-dense deposits were rarely seen by transmission electron microscopy, and the heavy granular deposits of IgM and C3 observed by immunofluorescence were attributed to ingested proteins within macrophages. This study implies an active role for monocytes and macrophages in immune complex-mediated glomerulonephritis.

The ultrastructure of the thin limbs of Henle in Kidneys of the desert heteromyid (Perognathus penicillatus)

The thin limbs of both long- and short-looped nephrons in Perognathus kidneys were studied with transmission and scanning electron microscopy. The superficial nephrons have a short thin limb located in the vascular bundles of the outer medulla and are characterized by a simple, low-lying epithelium (0.4 +/- 0.1 mu thickness). In contrast, the first descending part of the thin limb of the majority of midcortical and juxtamedullary nephrons has a relatively thick epithelium (1.7 +/- 0.6 mu in thickness) with marked lateral and basal interdigitation and a dense surface covering of microvilli. The remaining part of the long descending thin limb is relatively simple with a low-lying epithelium (0.6 +/- 0.1 mu in thickness), decorated on its surface by sparse microplicae. The bend of the loop and the ascending limb are covered by a very simple low-lying epithelium (0.6 +/- 0.2 mu in thickness) with relatively little surface modification. The extreme urine-concentrating ability of Perognathus does not appear to be due to the development of a unique thin loop epithelium but rather to the extensive length of the inner and outer medulla.

Pathology of experimental African trypanosomiasis in rabbits infected with Trypanosoma rhodesiense

The pathologic response of New Zealand White rabbits to experimental infection with Trypanosoma rhodesiense is described. Autopsies of 18 rabbits killed from 30-44 days after infection revealed focal perivascular inflammation of the ears, eyes and testes. Examination by electron microscopy revealed extravascular trypanosomes in the dermis of the ear and interstitium of testes. Deposits of IgG, IgM and C3 were in renal glomeruli associated with glomerular hypercellularity; proteinuria was present as evidenced by an increase in tubular hyaline droplets. There was marked hyperplasia of lymph nodes and spleen with generalized increase in the number of macrophage and plasma cells. In contrast there was thymic atrophy. The findings suggest an immunologic host response associated with severe localized vascular injury.

Values for tissue magnesium as a guide in detecting magnesium deficiency

A large-scale survey of the normal magnesium content of various human tissues was carried out to facilitate clinical detection of magnesium deficiency, especially occult deficiency.A review of the literature favours the magnesium content of skeletal muscle as the most reliable index of the body's store of magnesium. There is a significant difference (P < 0.001) in both the serum and erythrocyte magnesium levels between normal pregnant women in the third trimester and the average normal population. The reason for this difference is discussed.