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Biomedical subjects

C Stock

Publications and source records attributed to C Stock.

At least 37 records · Page 2Linked to original sources
PubMed1991

Analysis of unstable RNA transcripts of insecticidal crystal protein genes of Bacillus thuringiensis in transgenic plants and electroporated protoplasts.

We have examined expression of several insecticidal crystal protein (ICP) genes of Bacillus thuringiensis in transgenic tobacco plants and electroporated carrot protoplasts. We determined that low levels of lepidopteran toxin cryIA(b) ICP gene expression in plants and electroporated carrot cells is due to RNA instability. We used a series of 3' deleted by cryIA(b) constructs directed by the cauliflower mosaic virus 35S promoter to demonstrate that this instability is minimally contained in the first 579 bases of the gene in both systems. This instability may result from 5'----3' as well as 3'----5' RNA metabolism. The coleopteran toxic cryIIIA gene was also examined in electroporated carrot cells, and found to be poorly expressed. A model for improvement of ICP RNA stability in plants is presented.

Bacillus thuringiensis↗
PubMed1991

Nasal resonometer: an instrument for the assessment and treatment of hypernasality.

We describe an instrument which enables the measurement of the ratio of nasal to oral sound pressures to be made during normal speech. The technique incorporates a novel phase locking technique which effectively discriminates the spectral characteristic of resonant peaks occurring during nasalized speech from other nasal emissions. The results enable an assessment of the degree of resonance in real time, the trend of diagnostic measurements within a treatment session and the success achieved in reaching targets set during treatment.

Adolescent↗
PubMed1990

Immune response in patients with amoebiasis: evaluation of IgG-subclasses.

In order to evaluate the immune response with respect to IgG-subclasses (IgG1-IgG4) in patients with extraintestinal amoebiasis, an ELISA technique was established. It was the aim of this pilot study to quantify the IgG subclass response and to compare the resulting pattern with other systemic protozoal infections. Our results give evidence that IgG4 contributes to more than one third of the total immune response, followed by IgG2, IgG3 and IgG1. Regarding the IgG4 response in patients with Plasmodium falciparum malaria or Chagas disease, IgG4 plays only a minor role in these systemic protozoal infections. The interpretation of a prognostic value of the high IgG4 titres in our patients is not possible at present. However, in patients with a prolonged clinical course of extraintestinal amoebiasis, extremely high IgG4 titres were observed.

Amebiasis↗
PubMed1982

Copper accumulation in primary biliary cirrhosis. An electron and X-ray microanalytical study.

Ultrastructural and X-Ray microanalytical aspects of primary biliary cirrhosis were analysed and compared to those of normal liver. Electron microscopic studies showed a significant increase of dense lipofuscin-like granules in PBC compared to the hepatocytes of normal liver (665%). These granules (0.3-2.7 micrometers in diameter) were formed by the association of primary lysosomes and lipid droplets. X-Ray microanalysis of these structures showed the presence of Calcium, Phosphorus, Potassium, Chlorine, Sulphur, Aluminium and Copper. The coexistence of Sulphur with other mineral elements suggests the occurrence of metalloproteins binding these elements. These findings provide evidence that intralysosomal sequestration of mineral elements, especially copper protects the hepatocytes from cytotoxic effects.

Copper↗
PubMed1982

Effect of small bowel bypass on the rat exocrine pancreas.

Biochemical, structural, and functional studies of the exocrine pancreas were performed in adult male Wistar rats over a 3-month period following a 90 per cent jejunoileal bypass or sham operation. The wet weight of the gland, its content in total protein and DNA, as well as its structural organization were similar in both groups. The enzyme content was globally reduced after bypass surgery. However, amylase was much more and earlier affected than lipase and chymotrypsinogen. In addition, zymogen granules diminished in size while lipid droplets deposited in acinar cells. Enzyme secretion stimulated or not by increasing concentrations of caerulein in vitro was generally reduced after intestinal bypass and approximately parallel to the depressed amount of enzymes in the pancreas. These findings suggest that jejunoileal bypass does not modify the size of the rat pancreas despite protein deficiency, but its enzymatic composition and secretory function is altered.

Amylases↗
PubMed1981

BSP clearance as the most reliable criterion of hepatic dysfunction after jejunoileal bypass in the rat: arguments in favor of the existence of a pathogenetic mechanism involving a transient malnutrition state.

In rats subjected to 90% jejunoileal by-pass or in sham-operated controls, liver function was compared to plasma nutritional state and adaptation of the intestine in continuity over a period of 3 months. While the plasma levels of GOT, GPT, and esterases A and C as cholinesterase C did not differ in either group, the percentage of retention of BSP increased until 8 weeks, then returned progressively to control values 12 weeks after small-bowel bypass. In contrast, plasma nonesterified fatty acid levels decreased significantly until 6 weeks, then recovered control values over the following periods. Plasma total protein and albumin levels also diminished after jejunoileal bypass, the most marked decrease being at the 4th postoperative week. The increase in villus size following the intestinal bypass was considered pronounced for the ileum between the 8th and the 12th week. These results suggest that BSP clearance is the most reliable criterion for hepatic dysfunction in the rat subjected to a jejunoileal bypass. In addition, the parallelism between the variations of BSP clearance, intestinal adaptation, and plasma nutritional state argue for the "nutritional" theory as the most probable explanation for the formation of hepatic lesions.

Animals↗
PubMed1981

Ultrastructural changes in the rat exocrine pancreas after jejunoileal bypass.

The influence of a 90% jejunoileal bypass on the rat exocrine pancreas was studied by morphometrical procedures. In sham-operated animals exocrine acinar cells accounted for 80.3% of the pancreas volume. These cells are composed of 9.9% nuclei, 8.4% mitochondria, 12.2% zymogen granules, 0.3% lipid droplets and 69.2% of a compartment ("ERGLS") composed of endoplasmic reticulum, ribosomes, Golgi areas, lysosomes and the cytoplasmic ground substance. Intestinal bypass did not change the volume density of exocrine cells nor that of nuclei in the cells during the three postoperative months. The means nuclear diameter was approximately the same in both groups. However, the volume density of secretory granules diminished by 50%. This was accompanied by a decrease in mean granular diameter, but not in their numerical density. The volume density of lipid droplets increased 10 fold, that of mitochondria increased slightly from the 15th postoperative day but significantly from the 45th day. The remaining cellular compartment composed of "ERGLS" was not modified by intestinal bypass. These findings suggest that a 90% jejunoileal bypass induces major changes in the composition of pancreatic acinar cells but not in their size.

Animals↗
PubMed1981

Hyperplasia of the exocrine pancreas after small bowel resection in the rat.

The effect of a 90% small bowel resection on the exocrine pancreas was investigated over a three month period in adult Wistar rats. Control animals underwent a sham-resection consisting of a transection and reanastomosis of the small intestine. After jejunoileal resection, the wet weight of a gland increased significantly (52%) from the 15th day. The parallel increase in total protein, DNA and RNA content without any modification in the ratios of pancreatic weight, protein, and RNA to DNA suggests that there is cellular hyperplasia but not hypertrophy. Small intestinal resection decreased significantly the amount of amylase when expressed per unit pancreatic weight; it reduced slightly but not significantly that of chymotrypsin, while it did not modify the amount of lipase. However, the total amount of these enzymes in the pancreas remained unaltered when compared with controls. It is concluded that a massive resection of the small bowel induces cellular hyperplasia in the rat exocrine pancreas; this could compensate that reduced level of enzymes in acinar cells.

Adaptation, Physiological↗
PubMed1981

Imbalance in brush border enzyme activities as a possible cause of hepatic dysfunction after jejunoileal bypass in the rat.

Previous work in our laboratory and in others suggest that protein malnutrition plays an important role in the pathogenesis of hepatic dysfunction after jejunoileal bypass for morbid obesity. This experimental study was undertaken to attempt to correlate hepatic dysfunction (the criterion used was the bromsulphalein clearance) to morphological and enzymatic adaptation of the functioning intestine in the rat. It was observed that the period of impaired bromsulphalein clearance is concomitant with a slight ileal morphological adaptation and especially with a period of selective adaptation of maltase and sucrase activities, whereas there is no increase in aminopeptidase activity. These data support the hypothesis that after jejunoileal bypass a preferential absorption of carbohydrates along with a protein deficiency state could occur and as in kwashiorkor it results in an impaired nutritional status, a major contributing factor to bypass-induced liver injury.

Aminopeptidases↗
PubMed1980

Glucagon- and glicentin-immunoreactive cells in the human digestive tract.

The distribution and cellular location of substances reacting with anti-glucagon or anti-glicentin sera, i.e., glucagon-like and glicentin-like immunoreactivities, were studied in the human digestive tract using the immunofluorescence and immunoperoxidase methods. Both types of immunoreactivity were (1) absent in the antrum, (2) abundant in cells located at the periphery of pancreatic islets, (3) unevenly present in cells scattered in the epithelium of the small intestinal mucosa, the glicentin-immunoreactive cells being particularly abundant in the ileum. In the pancreas, and, when simultaneously present, in the intestine, both glucagon and glicentin immunoreactivities were located in the same cells. The precise ultrastructural location of each immunoreactivity was readily made using colloidal gold and ferritin tracers on ultrathin sections of glutaraldehyde-osmium fixed and epoxy resin-embedded tissues. In the pancreas, both glucagon and glicentin immunoreactivities were found in the granules of the A-type cells; the glucagon immunoreactivity was only present in the core of the granule, whereas the glicentin immunoreactivity was found either in the peripheral halo only, or throughout the entire granule. In the small intestine, both immunoreactivities were located inside the granules of the L-type cells. Quantitative specificity tests suggested that the glucagon- and the glicentin-like substances of the pancreas differ from those found in the intestine.

Cytoplasmic Granules↗
PubMed1978

Pancreatic acinar cell changes induced by caerulein, vinblastine, deuterium oxide, and cytochalasin B in vitro.

The effects of caerulein, vinblastine (VB), deuterium oxide (D2O), and cytochalasin B upon both the structure and the function of the pancreatic acinar cell were studied in vitro using rat pancreatic fragments. Caerulein (10 ng. per ml.) stimulates the release of enzymes and induces the appearance of numerous exocytotic images at the apical part of the acinar cell. Whereas VB (5.10(-5) M) and D2O (55 per cent) inhibit the secretory response to caerulein, they do not affect the general ultrastructure of the acinar cell. Prolonged incubation in the presence of VB provoked the disappearance of microtubles and the massive precipiation of microcrystalline material in all parts of the cytoplasmic space. Numerous microtubules were found in the acinar cell after exposure to D2O. Although VB and D2O do not alter the microfilamentous network localized at the apical part of the cell, cytochalasin B (2.10(-5) M) disrupts it. This drug decreases the number of microvilli projecting into the enlarged acinar lumen. Whether cytochalasin B is used alone or in association with VB or D2O, it inhibits the secretory response to caerulein and prevents the process of exocytosis. Thus, it is suggested that microfilaments act on a later step of the secretory cycle, i.e., exocytosis, than microtubules. The probable site of action of these latter organelles in the migration of zymogen granules toward the acinar lumen is discussed.

Animals↗