The modulating effect of isoproterenol on DNA replication and protein synthesis

The effect of ageing on parenchymal cell populations in adult female mouse submandibular gland

The submandibular gland shows an array of responses that accompany ageing, which are usually modest. However, the submandibular acinar-cell mucin shows a substantial decline in total amount per gland. In the submandibular gland, there is also a loss of secretory parenchyma. A number of factors that could influence either parenchymal loss or a change in its cellular composition were examined in three ages of adult female mice. The goal was to see if there are ageing-related cellular changes that might have an effect on mucin production or secretion. The factors examined included DNA, protein, rates of cell division and apoptosis, cell volume and cellular composition of the parenchymal population. The parenchymal cell composition showed significant differences during ageing, with a substantial decrease in the percentage of acinar cells and increases in the percentage of both types of ductal cell components. This decline in the proportion of acinar cells in the parenchyma also reflected an overall reduction in the total number of acinar cells in the gland. Thus, the change in proportions of cells may potentially be a direct cause of the ageing-related decline in the submandibular acinar-cell mucin. The alteration in cellular composition was not attributable to changes in the cell-division indices; however, there was an increased rate of apoptosis for acinar cells that was significantly different between 3 and 28 months. The apoptotic rate doubled for acinar cells but showed no significant change in ductal cells. This selective change in the rate of apoptosis with ageing suggests that it is one of the main reasons for the decline in the proportion of acinar cells in the submandibular gland.

HMG-like chromosomal proteins in Trypanosoma cruzi

HMG-like chromosomal proteins from Trypanosoma cruzi were studied. Four HMG-like proteins, designated HMG A, HMG-B, HMG-C, and HMG-E, were isolated and found to have molecular weights of 35.5 kd, 27.5 kd, 21.8 kd and 10.4 kd, respectively. Immunological relatedness was demonstrated between the mammalian HMG 1,2 and the HMG-A and HMG-B from T. cruzi. The relative amounts of HMG-C and HMG-E proteins vary in T. cruzi depending to the proliferative stage of the cells. HMG-E protein is increased in proliferating cells when compared to its level in non-proliferating cells. HMG-C is increased in the non-proliferating cells. Probably, the shifts observed in the relative amounts of HMG-like proteins are related to the proliferating cells of this flagellate. The results are consistent with those described for other lower eukaryotes where the HMG-like proteins isolated are similar but not identical to HMG proteins from vertebrates.

Retinoic acid induction of stress proteins in fetal mouse limb buds

Retinoic acid (RA) is teratogenic in rodent embryos. Several teratogens have been shown to induce the synthesis of a subset of heat shock proteins (stress proteins) in Drosophila. To determine if RA induces the synthesis of these proteins in rodent embryos, pregnant ICR mice were dosed with 100 mg/kg RA on Day 11 of gestation. Forelimb buds were removed from embryos 2.5 hr post-RA-treatment and nuclei were isolated, stained, and sorted from stages of the cell cycle. Nuclear proteins were extracted and analyzed by two-dimensional polyacrylamide gel electrophoresis. Nuclear proteins with molecular weights of approximately 84 and 25 kDa were synthesized in embryos in the G0 + G1 phase after pregnant dams were treated with RA. Isoelectric points, molecular weights, immunochemical blotting, and polypeptide mapping demonstrated that these proteins are indistinguishable from stress proteins isolated under a variety of conditions from rat submaxillary glands and mouse lymphoma cells. These results suggest that treatment with RA induces the synthesis of a subset of stress proteins; the role of these proteins in the teratogenic effects of RA is not known.

High mobility group (HMG) proteins in the tammar wallaby Macropus eugenii: quantitative variations between tissues and testis-specific co-extracted proteins

1. Tammar wallaby (Macropus eugenii, Marsupialia) proteins with similar electrophoretic mobilities to calf non-histone chromosomal proteins HMG 1, 2, 14 and 17 are perchloric acid extracted from whole tissues (liver, kidney, spleen, brain and testis) and purified liver nuclei (using PCA or 0.35 M NaCl). 2. Tammar and calf HMG 1 have similar amino acid compositions. 3. Two testis-specific basic proteins co-extracting with HMG-like proteins from both tammar and red kangaroo (Megaleia rufa) are found in whole testis, purified testis nuclei, but not epididymis. 4. Tammar HMG 2 separates into two components on both acid urea and SDS gels. The larger, more basic protein, HMG 2b, is relatively abundant in proliferating tissues (testis, spleen).

The effect of isoproterenol and hydroxyurea on the presence of ubiquitin and protein A24 in the rat salivary gland

The in vivo administration of hydroxyurea for 12 h counteracts DNA synthesis and cell cycling stimulated by 72 h of isoproterenol treatment in rat salivary gland, as determined by fluorescence-activated flow cytometry. Hydroxyurea has little effect on [3H]leucine incorporation (protein synthesis) of the nuclear proteins soluble in 0.35 M NaCl, when examined by polyacrylamide gel chromatography and autoradiography from electrostatically sorted nuclei of (G0 + G1) and (G2 + M) phases of the in vivo cell cycle. Differential incorporation of [3H]leucine into nuclear proteins was observed during various phases of the cell cycle. Proteins 'X' and 'Z', observed in stained gel chromatographs of the 0.35 M NaCl-soluble nuclear proteins, were identified by biochemical analyses as ubiquitin and protein A24, respectively. Ubiquitin appeared transiently while A24 increased in gel chromatograms concomitant with progressive quiescence of the salivary gland induced by hydroxyurea.

A microsample collection device for electrostatically sorted cells or particles and its preparative use for biochemical analysis

Biochemical analysis of proteins extracted from mammalian cell nuclei which were sorted according to DNA content was greatly simplified using a special collection device to recover sorted nuclei. The device was developed for use with a sorting flow cytometer to provide sufficient numbers of particles to achieve adequate sensitivity and resolution while minimizing sample degradation and loss. The design, evaluation and application of the collection device were described with emphasis on sample preparation. Nuclear populations G0 + G1, S, and G2 + M, were sorted form regenerating rat liver tissue preparations and collected separately in the special chambers. Nuclear proteins were extracted and analyzed by polyacrylamide gel isoelectric focusing or capillary isotachophoresis.