Analytical subcellular fractionation of needle-biopsy specimens from human liver.

1. Fragments (2-20 mg wet wt.) of closed needle-biopsy specimens from human liver were disrupted in iso-osmotic sucrose and subjected to low-speed centrifugation. The supernatant was layered on a linear sucrose-density gradient in the Beaufay small-volume automatic zonal rotor. The following organelles, with equilibrium densities (g/ml) and principal marker enzyme shown in parentheses, were resolved: plasma membrane (1.12-1.14; 5'-nucleotidase); lysosomes (1.15-1.20; N-acetyl-beta-glucosaminidase); mitochondria (1.20; malate dehydrogenase); endoplasmic reticulum (1.17-1.21; neutral alpha-glucosidase); peroxisomes (1.22-1.24; catalase). 2. The distribution of particulate alkaline phosphatase and, to a lesser degree, leucine 2-naphthylamidase followed that of 5'-nucleotidase. gamma-Glutamyltransferase was associated with membranes of significantly higher equilibrium density than was 5'-nucleotidase. 3. The distribution of 12 acid hydrolases was determined in the density-gradient fractions. beta-Glucosidase had a predominantly cytosolic localization, but the other enzymes showed a broad distribution of activity throughout the gradient. Evidence was presented for two populations of lysosomes with equilibrium densities of 1.15 and 1.20 g/ml, but containing differing amounts of each enzyme. Further evidence of lysosomal heterogeneity was demonstrated by studying the distribution of isoenzymes of hexosaminidase and of acid phosphatase. 4. The resolving power of the centrifugation procedure can be further enhanced with membrane perturbants. Digitonin (0.12 mM) selectively disrupted lysosomes, markedly increased the equilibrium density of plasma-membrane components and lowered the density of the endoplasmic reticulum, but did not affect the mitochondria or peroxisomes. Pyrophosphate (15 mM) selectively lowered the equilibrium density of the endoplasmic reticulum.     

Degradation of the radula in the snails Biomphalaria glabrata say and Limnaea stagnalis L. (Gastropoda,Pulmonata)

Summary The radula of snails is formed at the posterior end of the radular gland or pocket, and degraded at the same rate at its anterior end. Degradation is due to different secretory activities of the inferior epithelium of the radular gland. Its secretions seem to degrade enzymatically the matrix of the radular membrane and basal plates of teeth, leaving only chitin containing microfibres and degradation products. The sclerotized parts of the teeth remain unchanged, but as they are now only loosely connected with the radular membrane. they are torn off easily during feeding movements. The rest of the degraded and frayed radular membrane and the subradular membrane are also lost by abrasion during feeding. The cells of the inferior epithelium are connected with each other by septate desmosomes and an elaborate system of deep lateral interdigitation which may provide tensile strength. Extrusion of degraded cells of the inferior epithelium into the subradular membrane takes place, although the thick basal lamina forms a continuous sheath which is closely adjoined to the basal parts of the inferior epithelium. Nerve fibres containing vesicles with electron dense neurosecretory material (deduced from the diameter of 200–250 nm) are attached to this sheath or penetrate into it; they may be involved in the regulation of production and degradation processes during radula replacement. Problems of the forward transport of radula and inferior epithelium are discussed.     

Sub-antarctic House mice: colonization, survival and selection

House mice have colonized and survived successfully on a number of Sub-Antarctic islands, where the mean annual temperature is only about 5°C, but where there is little seasonal fluctuation in climate. Surprisingly this allows almost continuous breeding. On at least two islands (Macquarie and Marion), there are significant changes in gene frequency in electro-phoretically detected enzymes between young (less than three months of age) and old animals from the same population. This indicates natural selection acting in opposite directions at different stages of the life cycle. However the genetical compositions of the Macquarie and Marion populations are more distinct from each other than either is from most British samples. This means that detailed studies of the Sub-Antarctic mouse populations are likely to reveal much about local adaptation, while comparison between the responses of different populations may lead to important generalisations about the possible reaction to evolutionary challenges of a species living close to its physiological limit.     

EFFECTS OF HUMAN LEUKOCYTE CONDITIONED MEDIUM ON MOUSE HAEMOPOIETIC PROGENITOR CELLS

Medium conditioned by human peripheral blood leukocytes (HLCM) was studied for its in vitro effects on haemopoietic progenitor cells (CFU-s and CFU-c) present in mouse bone marrow. HLCM has poor colony stimulating activity in semi-solid cultures of mouse bone marrow cells. but invariably increases the number of colonies obtained in the presence of plateau levels of semi-purified colony stimulating factor (CSF). In liquid cultures, HLCM appears to contain a potent initiator of DNA synthesis in CFU-s. an activity which coincides with an increased CFU-s maintenance and causes a three- to four-fold increase in CFU-c number. It is apparent from this study that HLCM, in addition to stimulating colony formation in cultures of human bone marrow cells, has a profound in vitro effect on primitive haemopoietic progenitor cells of the mouse, which cannot be attributed to CSF.     

Comparative electron microscope study of pellicular structures in coccidia (Sarcocystis, besnoitia and Eimeria)

D'Haese J., Mehlhorn H. and Peters W. 1977. Comparative electron microscope study of pellicular structures in coccidia (Sarcocystis, Besnoitia and Eimeria). International Journal for Parasitology7: 505–518. Negatively stained zoites of Sarcocystis ovifelis (= S. tenella pro parte) and Besnoitia jellisoni and sporozoites of Eimeria falciformis were studied by means of electron microscopy and compared with results obtained by other techniques. A new concept for the pellicle of motile coccidia was achieved, which throws some light on the mechanism of motility of these parasites,     

Effect of glutaraldehyde treatment on enzyme-loaded erythrocytes.

In principle, enzyme-loaded erythrocytes can be used as a vehicle for enzyme replacement therapy in lysosomal storage diseases. Glutaraldehyde treatment renders these erythrocytes more resistant to lysis without inactivating the enzymes that have been entrapped inside them. Glutaraldehyde treatment does not prevent ingestion of enzyme-loaded erythrocytes by macrophages in vitro so that these cells can be used to deliver enzymes to lysosomes. In vivo, the glutaraldehyde-treated cells are quickly removed from the circulation by the spleen or liver. The degree of glutaraldehyde treatment allows the erythrocytes to be targeted either to the spleen (low glutaraldehyde concentrations) or to the liver (higher glutaraldehyde concentrations).     

The effects of serotonergic and adrenergic receptor antagonist on prolactin release in the monkey.

The influence of serotonergic and adrenergic antagonists on serum prolactin levels was studied in ketamine anesthetized monkeys. Methysergide, a serotonergic receptor blocker, at 0.035, 0.1 and 1 mg/kg body weight induced a rapid and transient increase in serum prolactin. Cyproheptadine, another serotonergic receptor blocker, at 0.05, 0.5 and 1 mg/kg induced a rapid and sustained increase in serum prolactin. SQ 10631, a third serotonergic receptor blocker, had a minimal effect on increasing basal prolactin levels even at doses as high as 10 mg/kg. Propranolol, a β adrenergic blocker, at a dose of 5 mg/kg induced a small sustained increase in serum prolactin, while a lower dose (1 mg/kg) had a slight but significant effect. Phentolamine, an α adrenergic receptor blocker, at a dose of 5 mg/kg induced a rapid and transient increase in plasma prolactin while a lower dose (1 mg/kg) had no effect. Phenoxybenzamine, a potent α adrenergic receptor blocker, had only a minimal effect on prolactin release even at doses of 3 and 5 mg/kg. It appears that the time course and extent of prolactin release differs among neural antagonists even within the same biogenic amine system.     

Triple-spot proteins in two-dimensional gel electrophoresis.

A triple-spot pattern of polypeptides occurring in two-dimensional gel electrophoresis of proteins is described. The presence of a mutant protein, Pc 1 Duarte, which results in a splitting of all three polypeptides, is evidence that they are produced by the same gene. This pattern is seen in about 1% of the proteins from a variety of sources. Typically, about 50% of the protein occurs as a single major spot, the remainder occurring as two polypeptides with an additional negative charge and slightly different molecular weight. The reproducibility of this pattern implies a functional significance which is presently unknown. The implication of this configuration for patterns seen by one-dimensional gel electrophoresis is discussed.