Biomedical subjects

F J Alonso

Publications and source records attributed to F J Alonso.

24 records · Page 2Linked to original sources

PubMed1996

The G-cells in the dog: a light and electron microscope immunocytochemical study.

An immunohistochemical study has been performed to analyse the distribution of gastrin cells in the gastrointestinal tract of the dog. This study revealed that G-cells immunoreactive for gastrin were almost exclusively present in the pyloric antral mucosa, mainly in the middle third of the pyloric mucosa. The calculated number of G-cells per surface unit area was 8.5 x 10(3)-1.2 x 10(4) cells cm-2. Some gastrin-immunopositive cells were found in the first 10 mm of the proximal duodenum, mainly in the villous region. The fundic area of the dog stomach, the oesophagus, small intestine, caecum, colon, rectum, salivary glands, liver and pancreas were all immunonegative for gastrin. At the ultrastructural level, three different types of granules (150-400 nm) were evident in G-cells: electron-dense, electron-lucent and intermediate forms. Most of them were located in the subnuclear region of the cell. The effect of fixation of the antral mucosa at different pH levels was studied. In samples fixed with acid solutions, most of the G-cell granules were of the electron-dense type and were strongly immunopositive for gastrin. Fixation of samples at a basic pH resulted in most of the gastrin granules losing their contents into the cytoplasm, and the positive reaction to gastrin was then located in the cytoplasm and at the periphery of the electron-lucent granules.

Animals↗

PubMed1996

Bovine Reissner's fiber (RF) and the central canal of the spinal cord: an immunocytochemical study using a set of monoclonal antibodies against the RF-glycoproteins.

The subcommissural organ secretes N-linked complex-type glycoproteins into the cerebrospinal fluid. These glycoproteins condense to form Reissner's fiber (RF), which extends along the fourth ventricle and central canal of the spinal cord. A set of three monoclonal antibodies (Mabs 3E6, 3B1, and 2A5) has been obtained using these glycoproteins as immunogens. Competitive and sandwich enzyme-linked immunoassay methods have demonstrated that the three monoclonal antibodies are directed against different epitopes, and that there is no competition among them for their binding to glycoproteins of RF. Mab 3E6 displays immunoblotting properties that are similar to those of a polyclonal antibody against the pool of glycoproteins from RF, but that are different from those of Mabs 3B1 and 2A5. All three antibodies immunostain the bovine subcommissural organ and RF. A population of ependymal cells is stained by the polyclonal antibody, and Mabs 2A5 and 3E6, but not by Mab 3B1. The material present in a population of ependymal cells of the central canal, and the glycoproteins secreted by the subcommissural organ thus probably have partial chemical identity. Some evidence suggests that the immunoreactive ependymal cells are secretory cells. The luminal surface of the central canal is coated by a thin layer of material with immunocytochemical characteristics different from those of the ependymal cells; such a coat may correspond to material released from RF.

Animals↗

PubMed1994

Phosphate-activated glutaminase expression during tumor development.

Changes in phosphate-activated glutaminase activities determined in intact cells and isolated mitochondria have been followed during mouse Ehrlich ascites carcinoma development. Glutaminase activities parallel the levels of poly(A)+ RNAs encoding for the mitochondrial phosphate activated glutaminase. During the exponential growth phase, maximum activity was observed and the relative abundance of glutaminase mRNA significantly increased with regard to the stationary growth phase. The presented results show that tumor phosphate-activated glutaminase is subject to long-term regulation by differential gene expression.

Animals↗

PubMed1994

Mouse placental cells secrete immunoreactive growth hormone-releasing factor.

The initial objective of this study was to establish a placental cell culture system in which the secretion of mouse growth hormone-releasing factor (mGHRF) could be examined during a several-day period. To determine when during pregnancy placental cells begin to express mGHRF, Northern blot analysis was carried out on total RNA from placentas collected on Days 6, 9, 11, 13, 15, 17, and 18 of pregnancy. Mouse GHRF mRNA could be detected as early as Day 11 of pregnancy. Its steady-state levels increased to maximum values on Days 15-17 and then declined slightly on Day 18. Placentas from Day 12 of pregnancy were selected for cell culture. The basal zone and labyrinth were dispersed in collagenase, and the cells were fractionated on a Percoll gradient. Two bands of cells were selected for further study. Both released significant amounts of immunoreactive mGHRF during a 5-day culture period. Effects of prolonged exposure of the cells to 8-bromo-cAMP and to agents that elevate intracellular cAMP concentration were then examined. Treatment of the cells with 0.5 mM 8-bromo-cAMP resulted in a significant decrease in the mGHRF concentration of the medium by the second day of culture. Mouse GHRF secretion was also inhibited by treatment of the cells with 100 ng/ml cholera toxin or 0.1 mM forskolin. The effect of 8-bromo-cAMP was concentration-dependent, with 0.1 mM being the lowest concentration that was active. 8-Bromo-cAMP treatment also reduced the steady-state level of mGHRF mRNA in the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1989

Glycolysis and glutaminolysis in perifused Ehrlich ascites tumour cells.

A perifusion system was designed in order to study glucose and glutamine metabolism by freshly harvested Ehrlich ascites tumour cells in steady state conditions. Cells were perifused in the presence of 5 mM glucose, 0.5 mM glutamine or 5 mM glucose and 0.5 mM glutamine. The results in steady state reveal that both substrates glucose and glutamine are continuously wasted by tumour cells, excreting two moles of lactate per mol of glucose and one mol of glutamate and ammonia per mol of glutamine consumed into the medium. Glutamine consumption in the presence of glucose was higher than with glutamine alone.

Ammonia↗

PubMedDate not supplied

Effect of dehydrodidemnin B on human colon carcinoma cell lines.

Didemnins are cytotoxic agents belonging to a depsipeptide family isolated from marine tunicates. In the present study, a new member, dehydrodidemnin B (DDB), isolated from the mediterranean tunicate Aplidium albicans, was used. The effect of the drug on human colon cultured cell lines was tested using multiple approaches: proliferation studies, long term survival after three hours of exposure to DDB by means of a clonogenic assay and the decrease of the protooncogen, ornithine decarboxylase, activity. A dehydrodidemnin B concentration of 10(-8) M completely inhibited cell growth. The IC50 obtained using the MTT proliferation test, indicated that the most proliferative cell line (CT-2) was the most sensitive to the drug. Using a clonogenic assay a clear dose-response was obtained for the three cell lines used; HT-29 cell line showed the minimum survival after 3 hours of dehydrodidemnin B treatment. A dose-dependent decrease in ornithine decarboxylase activity was also observed in three cell lines assayed. The data presented indicate that the dehydrodidemnin B is a potent cytotoxic agent on rapidly dividing human colon cancer cells.

Antineoplastic Agents↗