The early changes of parietal cell structure in the course of secretory activity in the rat

The fine structure of the rat parietal cell was studied, both at rest and after stimulation by refeeding or insulin administration. Experiments on fixation procedures showed that whenever the fixative contained sucrose at a concentration higher than 0.2 M, the system of cytoplasmic membranes was clearly tubular in arrangement, whereas the omission of sucrose in the fixative usually resulted in a vesicular structure. The study with the high-voltage electron microscope of thick sections prepared by conventional techniques or by impregnation with zinc iodide-osmium (ZIO) revealed that the tubules are grouped into fascicles, and that these form a feltwork that is especially thick toward the cell apex. The development of the secretory canaliculus after stimulation appears to take place by an in situ remodeling of the cytoplasmic domain occupied by the tubular system. Cells examined after short periods of stimulation (5-15 min) showed images of the tubular system and of the canalicular structure which differed both from the nonstimulated and from the fully active (30-45 min of stimulation) cell. These features include the formation of wide cisternae and of pericanalicular cytoplasmic trabeculae or laminae, whose fine structure bears close resemblance to that of the intracanalicular processes in the same cells. These images can be ordered into a hypothetical sequence which is proposed as a model to explain the transformation of the tubular system and intervening cytoplasmic matrix into secretory canaliculus.

[Subaortic stenosis in ankylosing spondylitis: a new hypothesis of cardiac involvement]

Ankylosing spondylitis is a chronic inflammatory rheumatism with associated heart involvement, fundamentally circumscribed to the aortic root area. Of these anomalies, the fibrous proliferation of the supra and sub-valvular tissue appears to be pathognomonic. We present two cases of ankylosing spondylitis studied by means of bidimensional echocardiography. The study showed a fixed sub-aortic stenosis, without alterations of the mitral or aortic valves. In our opinion, the aortic subvalvular membrane, could constitute the initial alteration of the valvular affection of ankylosing spondylitis.

Cloning of a DNA sequence that complements glutamine auxotrophy in Saccharomyces cerevisiae

Glutamine (gln) requiring mutants of Saccharomyces cerevisiae have been isolated. They synthesize small amounts of glutamine synthetase (GS), which is more thermolabile than the enzyme from the parental strain. The gln auxotrophy was complemented in transformation experiments using an S. cerevisiae gene library constructed in the plasmid vector YEp13. The transformants were mitotically unstable and synthesized almost tenfold higher amounts of GS than wild-type cells. This activity was as thermoresistant as that from the wild-type strain. A recombinant plasmid was isolated from one of the transformants and partially mapped. Upon reintroduction into the auxotrophic strain, the transformation frequency to gln prototrophy was the same as that for the marker LEU2 gene. The evidence presented suggests that we have cloned the structural gene for GS from S. cerevisiae.

Candida lignophila sp. nov., a new basidiomycetous yeast anamorph from rotting wood of Drimys winteri

Two strains of an undescribed Candida species were isolated from samples of a rotting trunk of Drimys winteri collected on the isle of Chiloé in South Chile. A description of the new species Candida lignophila is given and its relationship to other species is discussed with particular emphasis on its typical basidiomycetous properties as well as on its ecological habitat.

Effects of diterpene forskolin on the release reaction and protein phosphorylation of human platelets

The effects of diterpene forskolin on the human platelet release reaction and on platelet protein phosphorylation were studied. This drug is shown to have the same effects as other agents which increase cAMP levels, namely, it inhibits the secretory response to diverse agonists and causes changes in the phosphorylation of several specific proteins. An increase of the 32P content is seen in the MW 47 000, 24 000 and 21 000 polypeptides while a decrease is observed in the MW 41 000 and 27 000 and 20 000 species. Forskolin also inhibits the changes in protein phosphorylation pattern induced by the powerful platelet secretagogue, thrombin. Our results relate the effects of antagonists of platelet secretion such as prostaglandins more closely to changes in cAMP levels and in protein phosphorylation than to other possible effects of the receptor-ligand interaction, which is by-passed by the use of forskolin. Our results also provide additional evidence involving these changes in the mechanisms which regulate the secretory process in platelets.

[An experience of mental health promotion in an educational institution]

This article describes the work done by an interdisciplinary team belonging to a Mental Health Center in a secondary school situated within its area limits. The socio-political situation had developed opposition among the students towards the established school regulations provoking disturbances in communications and alliances between some of the different school groups. This situation created difficulties for the staff in connection with the specific management of the conflict. The written goals of the educational institution and those of the Mental Health Promotion team of this Mental Health Center were similar as follows: 1. Developing human being's potentialities; 2. Promoting more freedom and better communications. These facts, and the shared goals described above constituted the main reasons and explain why the Mental Health Promotion Team was able to work with the school groups in counseling during 3 1/2 years. It is important to emphasize that one of the main objectives achieved was that of transforming each staff member, such as professors and students into a mental health agent, that is to say someone who through his role is capable of influencing a significant number of people. Additional efforts were made towards turning intergroups communications more fluid breaking alliances and encouraging different groups to participate in school decisions.

Neurospora crassa mutant impaired in glutamine regulation

The final products of the catabolism of arginine that can be utilized as nitrogen sources by Neurospora crassa are ammonium, glutamic acid, and glutamine. Of these compounds, only glutamine represses arginase and glutamine synthetase. We report here the isolation and characterization of a mutant of N. crassa whose arginase, glutamine synthetase, and amino acid accumulations are resistant to glutamine repression (glnI). This mutant has a greater capacity than the wild type (glns) to accumulate most of the arginine and some of the glutamine in osmotically sensitive compartments while growing exponentially. Nonetheless, the major part of the glutamine remains soluble and metabolically available for repression. We propose that the lower repression of glutamine synthetase by glutamine in this mutant could be a necessary condition for sustaining the higher flow of nitrogen for the accumulation of amino acids observed in ammonium excess and that, if glutamine is the nitrogen signal that regulates the arginine accumulation of the vesicle, the glnr mutant has also escaped this control. Finally, in the glnr mutant, some glutamine resynthesis is necessary for arginine biosynthesis and accumulation.

Epidermal growth factor inhibits cytoskeleton-related changes in the surface of parietal cells

The effect of epidermal growth factor (EGF) on gastric acid secretion was correlated with the morphological changes of the apical pole of rat parietal cells studied by transmission electron microscopy. Gastric acid secretion was stimulated by histamine, carbachol, pentagastrin, and insulin-induced hypoglycemia, and estimated by continuous recording of pH variations of gastric luminal perfusate. EGF inhibits acid secretion in these conditions. The action of the hormone also results in the arrest or reversal of the changes in shape undergone by parietal cells as they go into secretion. In view of the evidence involving cytoskeletal elements in the generation of these structural alterations, our observations suggest that the action of EGF on gastric acid secretion may be a consequence of a general effect of this hormone on cytoskeletal function.

Massive pulmonary embolism associated with a right ventricular myxoma

A 12 year old boy had a massive pulmonary embolism associated with a right ventricular myxoma. This caused complete occlusion of the main trunk of the left pulmonary artery and of a branch of the right pulmonary artery supplying the basal area of the lower lobe of the right lung. The patient died despite two surgical attempts to remove the tumor clots. To our knowledge this constitutes the first report of a massive pulmonary artery embolism associated with a right ventricular myxoma.

Intercalative binding to DNA of antitumour drugs derived from 3-nitro-1,8-naphthalic acid

Two new antitumour drugs, imide derivatives of 3-nitro-1,8-naphthalic acid having different basic side chains linked to the imide nitrogen, have been shown to bind to double-helical DNA by intercalation. At ionic strength 0.01 mol/litre, pH 7, their intrinsic association constants are about 1.45 x 10(5) M-1 and each bound ligand molecule occludes about 3.4 nucleotides of the DNA lattice. They remove and reverse the supercoiling of closed circular duplex PM2 DNA with apparent unwinding angles of 11-12 degrees per bound drug molecule, referred to an assumed unwinding angle of 26 degrees for ethidium. They increase the viscosity of sonicated rod-like DNA fragments, each bound drug molecule producing a calculated increment in length of 2.2 - 2.5 A. No important differences between the DNA-binding characteristics of the two drugs were detected, though one appears marginally more active than the other in certain biological tests.

Inhibition of translation in bacterial and eukaryotic systems by the antibiotic anthelmycin (hikizimycin)

Anthelmycin inhibits protein synthesis on both pro- and eukaryotic ribosomes by preventing the peptide bond-forming reaction. The drug is structurally similar to certain other 4-aminohexosyl cytosine antibiotics including blasticidin S, gougerotin, amicetin and bamicetin although unlike these compounds anthelmycin lacks an aminoacyl moiety. It is proposed that anthelmycin inhibits the ribosomal peptidyl transferase centre by associating with a site that overlaps the (related) ribosomal receptor site(s) for the other four inhibitors.

Studies on the mode of action of hygromycin B, an inhibitor of translocation in eukaryotes

Hygromycin B is an unusual aminoglycoside antibiotic active against both prokaryotic and eukaryotic cells. Hygromycin B at 0.38 mM concentration completely halts yeast cell growth in rich media, presumably by preventing protein synthesis by cytoplasmic ribosomes. Polypeptide synthesis in cell-free extracts from rabbit reticulocytes, wheat germ and yeast is strongly blocked by low concentrations of hygromycin B. The antibiotic inhibits peptide chain elongation by yeast polysomes by preventing elongation factor EF-2-dependent translocation, although it does not affect either the formation of the EF-2-GTP-ribosome complex or the EF-2- and ribosome-dependent GTP hydrolysis which takes place uncoupled from translocation. The inhibition of translocation by hygromycin B might result from the stabilization of peptidyl-tRNA bound to the ribosomal acceptor site, since the stability of [3H]Phe-tRNA-EF-1-poly(U)-ribosome and [3H]Phe-tRNA-poly(U)-ribosome complexes is increased in the presence of hygromycin B. The inhibition of polyphenylalanine synthesis by reticulocyte ribosomes and enzymic translocation of peptidyl-tRNA by yeast polysomes can be reversed by increasing concentrations of EF-2 suggesting a relationship between the binding sites of EF-2 and hygromycin B on the ribosome. Neither non-enzymic translocation, that takes place in the presence of high potassium concentrations, nor the peptide bondforming step are affected by hygromycin B.

[Cimetidine in the treatment of the active duodenal ulcer]

Thirty six patients with active duodenal ulcers were studied in this double blind work. 19 received placebo and 17 Cimetidine: 1 gr./day. The endoscopic control after 21 days, showed healing in 81,2% of the cases treated with Cimetidine and in 22,2% of those with placebo. After 42 days of continous treatment with Cimetidine the healing of duodenal ulcers was 82,3% against 50% with placebo; the difference being highly statestically significant; p less than 0.01. The symptoms improved with Cimetidine revealing less diurnal and nocturnal pain complete disappearance of nausea and vomit and a significant decreased ingestion of alkali tablets.

Common carotid artery stenosis due to subintimal hematoma following blunt trauma to the neck. Report of a case

A case of cerebral ischemia secondary to carotid artery stenosis produced by a subintimal hematoma following blunt trauma to the neck is presented. A carotid endarterectomy with removal of the thrombus and intima was performed with satisfactory recovery of the patient. The various mechanisms involved in producing such stenoses and occlusions are reviewed.