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Biomedical subjects

R Ferrer

Publications and source records attributed to R Ferrer.

34 records · Page 2Linked to original sources
PubMed1986

Hexose transport by chicken cecum during development.

Hexose accumulation during development has been studied in tissue slices from chicken cecum. The age of birds ranged from 0 to 7 weeks after hatch. Ceca were divided into six portions according to their situation either proximal (PC), medial (MC) or distal (DC) to the ileocecal junction. In 0-day-old chicks all segments can accumulate 3-O-methyl-D-glucose (0.5 mmol/l) against a concentration gradient through a phloridzin-sensitive mechanism. Cumulative capacity is lower in DC than in PC and declines with development. Distal segments lose sugar transport ability 1-2 days after hatch whereas the medial region retains some concentrative ability in older birds. In 7-week chickens, PC slices have a similar cumulative ability to that of jejunum (yolk sac region). Kinetic studies showed that in PC the apparent Km for phloridzin-sensitive transport was half that in 1-day- than in 7-week-old birds; apparent Vm increased by 50% in this time range. The ability to transport sugars by the cecum was further confirmed in isolated enterocytes from 5- to 7-week-old chickens using alpha-methyl-D-glucoside (0.1 mmol/l) as substrate. Cell sugar concentration was greater in PC than in jejunal cells and jejunal greater than MC enterocytes. Sugar present in cells from DC was the same as in phloridzin-treated cells. It is concluded that cecal epithelium may play a significant role in the absorption of sugars during development.

3-O-Methylglucose↗
PubMed1986

Characteristics of the chicken proximal cecum hexose transport system.

The properties of the sugar transport system present in chicken proximal cecum have been studied and compared to the jejunal transport system. Experiments were carried out in isolated enterocytes from 5- to 7-weak-old birds. Results show that: (1) Cecal cells are capable of high sugar transport rates by a phloridzin-sensitive mechanism. After 60 min incubation, the accumulation ratio (control/phloridzin-incubated cells) for 0.1 mmol/l alpha-methyl-D-glucoside (alpha-MG) was 43 and that of 3-oxy-methyl-D-glucose (3-OMG) was 25. In jejunal cells, ratios were 37 for alpha-MG and 13 for 3-OMG. The differences found in cumulative capacity of 3-OMG between cecal and jejunal cells suggest that the sodium-independent pathway offers a very small contribution to sugar efflux in the steady-state in the former cells. (2) Lowering external Na+ concentration reduces the steady-state alpha-MG accumulation in cecal cells (as in jejunal cells), indicating that the transport system is Na+-dependent. (3) The process depends on the electrochemical Na+ gradient across the cell membrane since both 2,4-dinitrophenol (0.2 mmol/l) and ouabain (0.25 mmol/l) abolish sugar accumulation. (4) Addition of 10 mmol/l) 3-OMG to the incubation medium markedly reduces the uptake of alpha-MG (concentration: 0.1 mmol/l), indicating that the cecal transport system can be inhibited by analogues of the transported substrate. (5) The specific sugar transport process is a saturable function of alpha-MG concentration, the apparent Km being 1.02 mmol/l and Vm 10.7 mmol/mg cell protein X min.(ABSTRACT TRUNCATED AT 250 WORDS)

3-O-Methylglucose↗
PubMed1986

Preparation and properties of isolated epithelial intestinal cells from chicken cecum and jejunum.

The isolating agents, one enzymatic (hyaluronidase) and two chemical (sodium citrate and EDTA) have been used to search for the best technique to prepare suspensions of viable cells from chicken cecum and jejunum. Viability of enterocytes was assessed in terms of cell membrane integrity (trypan blue exclusion test), metabolic activity (oxygen uptake, lactate production and ATP content) and monosaccharide cumulative capacity. Results show that: In both cecum and jejunum, membrane integrity is better in cells harvested with citrate than those isolated with hyaluronidase or EDTA; The best metabolic status was found in cecal cells isolated with citrate and in jejunal cells obtained with hyaluronidase; The capacity to support alpha-methyl-D-glucoside gradients is highest in the cells harvested with citrate. The citrate-containing isolation medium is thus considered to yield epithelial cell suspensions with the best functional conditions.

Adenosine Triphosphate↗
PubMed1986

Morphological study of chicken cecal and jejunal mucosa during epithelial cell isolation.

Epithelial cells from jejunum and proximal cecum of the chicken were isolated by using a sodium citrate containing medium. Cell dissociation during the isolation process was studied by scanning electron microscopy. Results after 5, 15 and 30 min incubation show a sequential cell detachment from the tip to the lower regions of the villi. Inspection of the cell suspension by scanning and transmission electron microscopy reveals that most cells are enterocytes that retain their characteristic cylindrical shape. The brush border of isolated cells maintains its architecture, while organelles remain intact.

Animals↗
PubMed1984

Electrophysiological evidence for the inhibition of potassium permeability in pancreatic beta-cells by glibenclamide.

The effects of glibenclamide on the electrical activity of the beta-cells of the islets of Langerhans of normal mice have been investigated in the absence and presence of glucose (11.1 mM). Glibenclamide depolarized the cell membrane and this has been interpreted in terms of an increase in the ratio of the Na+ and K+ permeabilities, PNa/PK. This ratio increased from 0.05 to 0.24 in the presence of 4 microM glibenclamide and zero glucose. The input resistance of the beta-cells also increased. These observations indicate a decrease in K+ permeability. The effect is only slowly reversed after removal of glibenclamide. Uncouplers of oxidative phosphorylation do not reverse the depolarization induced by glibenclamide. It is suggested that glibenclamide is acting directly to inhibit the [Ca2+]i-gated K+ permeability in the beta-cell membrane.

Animals↗
PubMed1984

Effects of Zn2+ on glucose-induced electrical activity and insulin release from mouse pancreatic islets.

The effects of Zn2+ and CO2+ on glucose-induced beta-cell electrical activity and on insulin release from microdissected mouse pancreatic islets were studied. In 11 mM glucose the electrical activity is characterized by a burst pattern with a bimodal distribution of spike amplitudes along the plateau phase. Zn2+ at 0.05 mM induced a reduction in the number of spikes during the bursts and preferentially blocked the large action potentials. Zn2+ at 0.1 mM and CO2+ at 1.0 mM completely inhibited the electrical activity in response to glucose. Zn2+ inhibition of electrical activity was poorly reversible, whereas CO2+ inhibition was rapidly and completely reversible. Zn2+ and CO2+ inhibited the glucose-stimulated insulin release from microdissected perifused islets. Half-maximal inhibition occurred at about 0.3 mM for both metals. Zn2+ also inhibited K+-induced insulin release in the absence of glucose, indicating that Zn2+ inhibition does not involve glucose metabolism. It is proposed that Zn2+ blocks the voltage-gated Ca2+ channels in pancreatic beta-cells.

Action Potentials↗
PubMed1983

Effects of adrenaline and noradrenaline on glucose-induced electrical activity of mouse pancreatic beta cell.

The effects of adrenaline and noradrenaline on membrane potential and glucose-induced electrical activity were studied in micro-dissected mouse Islets of Langerhans. Both catecholamines induced hyperpolarization and blocked electrical activity in the presence of 11.1 mM glucose. Phentolamine, but not propranalol, blocked these effects, indicating predominantly alpha receptor action. Quinine, but not tetraethylammonium ions, antagonized the inhibitory effects of the catecholamines. The data are consistent with the hypothesis that alpha receptor activation induces a transient increase in intracellular Ca2+ concentration which in turn leads to an increase in K+ permeability.

Drug Antagonism↗
PubMedDate not supplied

Cytology of fine needle aspiration biopsy of primary breast rhabdomyosarcoma in an adolescent girl.

A bilateral breast tumor in an 11-year-old girl was diagnosed as a malignant mesenchymal neoplasm by fine needle aspiration biopsy, and its muscular origin was suggested. An immunoperoxidase stain for the demonstration of intracellular myoglobin in destained cytologic aspirates exhibited a positive reaction of variable intensity in some of the undifferentiated round cells and in the more mature bipolar sarcomatous elements. These findings were confirmed in the histologic sections of the excised tissue. Needle aspiration is helpful in these rare cases of primary breast rhabdomyosarcoma, which often present with a solid, undifferentiated histologic pattern in this age group. In addition to the cytologic characteristics, the possibility of detecting muscle antigens as markers for these embryonal small cells, even in previously stained slides, provides a successful method for defining the specific type of sarcoma.

Biopsy, Needle↗