Mammalian kinetochore/centromere composition: a 50 kDa antigen is present in the mammalian kinetochore/centromere

The composition of the mammalian kinetochore/centromere was studied by indirect immunofluorescence and immunoblotting protocols using serum from a patient with the CREST variant of scleroderma. The results of these studies suggest that a protein with a molecular weight of 50 kDa is localized at the surface of the primary constrictions (the kinetochore region) of both human and Indian muntjac chromosomes. In addition, we were able to verify the presence of a 19.5 kDa antigen (CENP-A), previously detected in human centromeres, within the kinetochore region of the Indian muntjac. These data suggest that the composition of the kinetochore region of the primary constriction is complex and that there is conservation in composition within the mammals. These features may reflect the important role of this unique chromosomal domain in the maintenance of ploidy.     

The structure of a mesokaryote chromosome

Condensed and dispersed forms of the chromosomes of the dinoflagellate, Prorocentrum micans, deposited on grids by the microcentrifugation technique were studied by electron microscopy. In the normally condensed form, the chromosomes appear as banded rods surrounded by a peripheral cloud of partially dispersed fibers. Single fibers in these and in extensively dispersed preparations appear as smooth threads of uniform diameter (55–65 Å). The chromosome fibers are contrasted by positive-group-specific stains, indicating the presence of cationic moieties associated with the DNA. Occasionally Y-shaped chromosomes are seen; these may be replicating structures. These observations are in general agreement with studies of dinoflagellate chromosomes by other techniques, and provide support for the suggestion that these organisms possess a genome organization whose structure is typical of neither prokaryotes nor eukaryotes, and hence may be intermediate forms.     

Centriole behavior in early mitosis of rat kangaroo cells (PTK2)

Behavior of the centriolar duplexes during early mitosis was investigated. In general, both duplexes are capable of migrating about the cell as a unit with little change in their center to center spacing prior to separation to form the spindle poles. This duplex separation may occur at any point within the mid-prophase-prometaphase period. If it is delayed to prometaphase, transitory monopolar spindles were observed.     

The action of calcium on the step of collagen metabolism, catalyzed by procollagen-proline hydroxylase]

Calcium effects on procollagen-proline-hydroxylase activity of chick embryo tibias was studied. Serial preincubation of the natural substrate, the enzymatic preparation or the mixture of both with and without calcium showed that calcium decreased procollagen-prolin-hydroxylase affinity for procollagen, decreased the maximum velocity of the reaction by binding to the substrate and by increasing the thermosensitivity of the enzyme -- substrate complex. Calcium could also increase the maximum velocity by dissociation of an enzyme -- inhibitor ligand complex. The resulting decrease of the overall reaction rate has been discussed in the context of the relationship between collagen metabolism and calcium fixation during calcification.     

Enolase is present at the centrosome of HeLa cells.

Antibodies raised against the C-terminus and N-terminus region of gamma gamma enolase, as well as a polyclonal antibody raised against bovine brain gamma gamma enolase, were used to study the distribution of this glycolytic enzyme during the cell cycle in HeLa cells. Enolase was found to be present throughout the cytoplasm of both interphase and dividing cells. In addition, a portion of cellular enolase was detected at the centrosome throughout the cell cycle. The capacity of glycolytic enzymes to play a structural as well as a glycolytic role suggests that the presence of enolase at the centrosome may be correlated with the organization of both the interphase cytoskeleton and the mitotic spindle.     

Plasma gonadotrophins, prolactin and corticosterone concentrations in male mice exposed to high altitude

Groups of sexually-naive male NFR/N mice were maintained at sea level or exposed to simulated altitudes of 18 000 ft (5486 m) or 22 000 ft (6705 m) for 1, 3, 7, 14 or 28 days. Plasma LH concentrations were slightly but not significantly depressed after 1 day of hypoxia. Plasma FSH values were reduced (P < 0.05) after 1, 7, 14 and 28 days of exposure to 22 000 ft when compared to the values in the other groups. Prolactin concentrations fluctuated considerably, but were not uniformly affected by high altitude exposure. Exposure to 18 000 ft resulted in an elevation of plasma corticosterone concentration (P < 0.05) for 3 days, which was followed by a decline to control group values, whereas at 22 000 ft corticosterone levels remained elevated. These findings indicate that plasma LH values are transiently reduced during the initial 24 h of exposure to high altitude and that plasma FSH concentrations are depressed in a sustained manner during severe hypoxia.