On the shoulders of giants: the discovery of atrial natriuretic factor

Investigations culminating at the beginning of this century clearly established that the cardiac muscle cell (cardiocytes) is differentiated for excitation, conduction, and contraction. All of the physiology and pathophysiology of the heart was developed subsequently based on this concept. However, morphological investigations in the mid 1950s suggested a secretory function for mammalian atrial cardiocytes. These cells contain storage granules, the specific atrial granules, which resemble granules found in polypeptide hormone-producing cells. The development of techniques for the study of these granules using a combined biochemical-morphological approach during the 1970s defined their general chemical nature and their behaviour under different experimental conditions. Because the number of atrial granules change dramatically following upsets of water and electrolyte balance, atrial muscle extracts were tested for effects on kidney function. In 1981, it was reported that atrial extracts contain a natriuretic factor (ANF) capable of inducing massive diuresis, increases in hematocrit, and lowering of blood pressure. It was demonstrated soon thereafter that ANF is stored within specific atrial granules. More recent work has defined ANF as a polypeptide hormone that appears to modulate or antagonize the renin-angiotensin-aldosterone system. Current work attempts to define the physiological and pathophysiological role for ANF as well as possible therapeutic uses.     

Synthesis of 5'-O-beta-D-glucopyranosyl and 5'-O-beta-D-galactopyranosyl derivatives of ribavirin

The synthesis of 5'-O-beta-D-glucopyranosyl and 5'-O-beta-D-galactopyranosyl derivatives (13 and 15, respectively) of the antiviral agent ribavirin are described. Direct glycosylation of 2',3'-O-isopropylideneribavirin with either tetra-O-acetyl-alpha-D-glucopyranosyl bromide (4) or tetra-O-acetyl-alpha-D-galactopyranosyl bromide (8) under Koenigs-Knorr conditions (i.e., silver carbonate, silver perchlorate, and Drierite in dichloromethane) followed by O-deacetylation of the reaction product gave the corresponding ortho esters. However, treatment of 2',3'-di-O-acetyl-5'-O-tritylribavirin (11) with 4 under the Bredereck modification of the Koenigs-Knorr reaction (i.e., silver perchlorate and Drierite in nitromethane) and subsequent deacetylation furnished the desired 1-(5-O-beta-D-glucopyranosyl-beta-D-ribofuranosyl)-1,2,4-triazole-3-carb oxamide (13). Similarly, reaction of 11 with 8 in the presence of AgClO4, and deprotection of the condensation product, gave 5'-O-beta-D-galactopyranosylribavirin (15). The beta-anomeric configuration of the D-glucosyl and D-galactosyl groups of 13 and 15 was assigned by 1H-n.m.r. studies.     

Labeling of phosphatidylcholines of retina subcellular fractions by [1-14C]eicosatetraenoate (20:4(n-6)), docosapentaenoate (22:5(n-3)) and docosahexaenoate (22:6(n-3))

The labeling of molecular species of phosphatidylcholine (PC) has been studied in bovine retinas incubated for 2 h with (1-14C)-labeled (n-6) eicosatetraenoate (n-3) docosapentaenoate and (n-3) docosahexaenoate (20:4, 22:5 and 22:6, respectively) and in four subcellular fractions isolated after such incubations. Of the total radioactivity incorporated in PC, the following percentages of the above fatty acids, respectively, are found in its dipolyunsaturated species: 58, 56 and 53% in rod outer segments; 29, 41 and 49% in mitochondria; 24, 28 and 39% in microsomes; 12, 14 and 16% in postmicrosomal supernatants; 28, 36 and 58% in entire retinas. The remainder percentages are in tetra-, penta- and hexaenoic species of PC, respectively. The levels of pentaenoic species in the PCs of all fractions are similar, while tetraenes are lowest and hexaenes highest in photoreceptor membranes. Dipolyunsaturated species are highly concentrated in photoreceptor membranes, but are minor components of mitochondrial, microsomal and cytosolic PC. The specific radioactivities of tetraenoic, pentaenoic and hexaenoic PCs are decreasingly lower in the following order: postmicrosomal supernatants, microsomes, mitochondria, photoreceptor membranes. In contrast, the specific radioactivities of dipolyunsaturated PCs are higher in mitochondria and microsomes than in the other fractions, especially with 22:5 and 22:6. It is suggested that mitochondria as well as the endoplasmic reticulum could play a role in the synthesis and further modifications of dipolyunsaturated PCs before being supplied to photoreceptor membranes.     

Effect of temperature on the velocity of erythrocyte aggregation

The velocity of the aggregation of human erythrocytes was examined in the range of 5-43 degrees C with a rheoscope combined with a video camera, an image analyzer and a computer. (1) With increasing temperature, the velocity of erythrocyte aggregation induced by fibrinogen, immunoglobulin G and artificial macromolecules (dextran of 70 kDa and poly(glutamic acid) of 50 kDa) increased. However, the relationship between the velocity of erythrocyte aggregation and the temperature was different among these macromolecules. (2) In 70% autologous plasma, the velocity of erythrocyte aggregation was minimum at 15-18 degrees C, and increased at both higher and lower temperatures. (3) The shape of erythrocyte aggregates in 12 mumol/l fibrinogen (containing 770 mumol/l albumin) and in 70% autologous plasma was dependent on temperature: three-dimensional below 15-18 degrees C and one-dimensional (mainly rouleaux) above 15-18 degrees C. However, the shape of aggregates in 27 mumol/l immunoglobulin G (containing 770 mumol/l albumin) was three-dimensional in all temperature ranges. (4) The temperature dependency of erythrocyte aggregation was discussed in terms of the changes of medium viscosity, of erythrocyte properties and of bridging macromolecules.     

Immunohistochemical localization of gamma-aminobutyric acid (GABA) in the rat pancreas

The localization of gamma-aminobutyric acid (GABA) in rat pancreas was investigated using antiserum raised against GABA conjugated to bovine serum albumin with glutaraldehyde. Immunoreactive cells were only found in the center of the pancreatic islets, and these cells were surrounded by nonimmunoreactive cells. When two serial sections of rat pancreas were consecutively stained with GABA antiserum and with antibodies against insulin, both antisera stained the same population of endocrine cells within the islets. In rats pretreated with streptozotocin, a B-cell toxin, we observed a marked decrease in the number of cells exhibiting GABA-like immunoreactivity. These observations indicate that GABA is present in the B cells of rat pancreatic islets.     

Silica and Ash in Native Plants of the Central and Southeastern Regions of the United States

Ash and silica contents and depositional patterns were determinedfor different tissues of 11 plants growing in the southeasternand central parts of the USA. Silica content was high in theleaves, sheaths and inflorescences of the grasses studied, especiallyso in the inflorescence of the C₃ grass, Stipa comata Trise.and Rupr. The ash content was especially high in leaves of Polymniauvedalia L., which are also high in calcium. Calcium depositionwas largely in trichomes and in veins of the leaf. Energy-dispersiveX-ray analysis showed that the distribution of the element siliconis closely related to certain epidermal structures such as ridges,cell walls, rows of irregularly-shaped structures lying lenghthwisealong the leaf, dumb-bell shaped structures and trichomes. Thesestructures also correspond to the phytoliths left behind afterdecay of the plant. The C₃ grasses differed from the C₄ in thatthey showed oval structures and produced correspondingly ovalphytoliths. Silicified trichomes (particularly in the C₃ grasses)and long, narrow, silica fibres were common in the inflorescencesof the grasses studied. These sharp particles could be irritatingto oesophageal and other tissues. Similar fibres in other grasseshave been implicated in certain cancers. High silicificationof the inflorescence structures might afford protection forthe seed, as reported for other grasses. C₃ and C₄ grasses, silica and ash content, scanning electron microscopy, energy-dispersive X-ray analysis, silicon distribution, spectra of elements in plants, trichomes, silica fibres, phytoliths     

Rescue of developmental lens abnormalities in chimaeras of noncataractous and congenital cataractous mice

In the study of the lens of a congenital cataractous mouse mutant (CAT), it has been shown that a loss of growth regulation at the cellular level causes gross lens abnormalities. The phenotypic characteristics of the cataractous mouse lens are similar to those seen in human congenital cataract and thus serves as a model system for medical research. In this present investigation, we have demonstrated that the abnormalities of the congenital cataractous lens can be rescued by forming chimaeras between DBA/2 (a noncataractous strain of mouse) and the CAT mutant. This report describes the histological, cellular and biochemical analysis of the resultant chimaeric eyes, and discusses possible mechanisms by which these results were achieved.     

Comparison of the catalytic and structural properties of Ca2+-ATPase in longitudinal tubules and terminal cisternae of the sarcoplasmic reticulum

The catalytic behavior and structural features of Ca2+-ATPase in the vesicles of longitudinal tubules and terminal cisternae of the sarcoplasmic reticulum isolated from rabbit skeletal muscles was analysed. pH measurements have shown under optimal conditions Ca2+-ATPase has similar catalytic behavior both in the fractions of longitudinal tubules and terminal cisternae. Under non-optimal conditions, the behavior similarity was not observed. The specific activity of the ATPase enzyme under optimal conditions was shown to be much higher in the fraction of longitudinal tubules than in the fraction of terminal cisternae. Caffeine added to both fractions had no effect on the catalytic behavior of Ca2+-ATPase. As judged from fluorescence analysis, the structure of Ca2+-ATPase of longitudinal tubules differs from that structure of terminal cisternae. In sarcoplasmic reticulum membrane, at least half of the tryptophan residues of Ca2+-ATPase was shown to be buried in the lipid bilayer. Our findings suggest that in terminal cisternae some of the Ca2+-ATPase molecules exist as an oligomeric protein and do not participate in ATP hydrolysis (named "silent" Ca2+-ATPase).