Weak acid accumulation in the serosal extracellular compartment of the frog gastric mucosa.

The dimethyloxazolidine dione distribution in the extracellular compartments of the frog gastric mucosa was analyzed by washout kinetics. The volumes of the two extracellular compartments, serosal and mucosal, were estimated by inulin washout as 0.435 +/- 0.019 and 0.176 +/- 0.018 microliter/microliter tissue water, respectively. In the serosal extracellular space, significant dimethyloxazolidine dione accumulations of 2.63 +/- 0.25, 2.28 +/- 0.16, and 1.86 +/- 0.08 times that of the bathing media were found for bathing solutions with pH values of 6.9, 7.4, and 7.9 respectively. A high pH of the serosal extracellular fluid by itself could not account for the high values of dimethyloxazolidine dione accumulation. A difference in the total dimethyloxazolidine dione accumulation requires: (a) the existence of differences in the pH values and also the existence of a difference in the diffusion coefficient of the two forms of dimethyloxazolidine dione; or (b), a binding of one of the two forms, i.e., binding of dimethyloxazolidine dione form by fixed charges.     

The gastric mucosa of the human fetus. I. The surface epithelium

The ontogenesis of the surface epithelium in the gastric mucosa was studied by means of light and electron microscopy in 41 human foetuses ranging from 7th to 12th week of gestational age. The results obtained can be summarized as follows: 1) At the 7th week the gastric mucosa shows a simple pseudostratified epithelium; the epithelial cells are undifferentiated and filled, with glycogen clusters. 2) From the 8th week the epithelial surface shows small depressions that become deeper in the mesenchyme making the first bud of the gastric foveolae. 3) At the 9-10th week the gastric foveolae are more developed. The cells of the gastric epithelium can be therefore separated in two populations: a) the cells of the foveolae; b) the cell of the mucosal surfaces. 4) At the 12th week the cells of the mucosal surface become, on the basis of their histochemical and ultrastructural characteristics, surface mucous cells. The morphological differentiation is testified mainly by the transposition of the nuclei in the basal parts of the cells and by the gradual substitution of the cytoplasmic glycogen by mucous granules.     

Ultrastructural organization of the surface epithelium of gastric mucosa in vitamin A deficiency

Under conditions of experimental A-avitaminosis in cells of superficial epithelium of the chicken stomach mucous membrane certain ultrastructural changes of cytoplasmic membranes takes place. Amount of transport vesicles decreases, regeneration of membranes in the Golgi complex cisterns, secretory vesicles and apical part of the external cellular membrane with development of apical erosions is disturbed. The problem on influence of the changes mentioned to the process of mucus formation, in particular to protein glycosylation in the Golgi complex is discussed. Insufficient vitamin A amount, getting into the organism results in a decreased resistivity of the stomach mucous membrane as a consequence of disturbances in processes of mucus formation and in safety of the apical part of the external cellular membrane of the superficial epithelium.     

A helical,polymeric extracellular protein associated with the luminal surface of Haemonchus contortus intestinal cells

The structure of the intestinal cells of the parasitic nematode Haemonchus contortus is described. The cells have numerous microvilli about 0.09 μ in diameter; most being 5.5–7.5 μ in length. The microvillar (plasma) membrane is coated with a layer of amorphous material (glycocalyx) about 60 Å thick which is electron dense in sectioned preparations. Associated with the surface of this material, and filling the spaces between the microvilli, are filaments in the form of helices about 400 Å in diameter and of variable pitch. The helices appear to be flexible but they are aligned approximately with the long axes of the microvilli. There are up to ten helices per microvillus; they extend beyond the tips of the microvilli and are up to 10 μ long. The material has been obtained nearly pure in small amounts. It is primarily protein and it is proposed that it should be called contortin. The monomeric form (of molecular weight about 60,000) has been identified with a Y-shaped structure with arms about 45 Å long and 25 Å wide seen in negatively stained preparations. The helical filament appears to be formed by lateral polymerization of pairs of these units.     

Weak acid accumulation in the serosal extracellular compartment of the frog gastric mucosa

The dimethyloxazolidine dione distribution in the extracellular compartments of the frog gastric mucosa was analyzed by washout kinetics. The volumes of the two extracellular compartments, serosal and mucosal, were estimated by inulin washout as $\text{0.435 ± 0.019}$ and $\text{0.176 ± 0.018 μl/μl}$ tissue water, respectively. In the serosal extracellular space, significant dimethyloxazolidine dione accumulations of $\text{2.63 ± 0.25}$, $\text{2.28 ± 0.16}$, and $\text{1.86 ± 0.08}$ times that of the bathing media were found for bathing solutions with pH values of 6.9, 7.4, and 7.9 respectively. A high pH of the serosal extracellular fluid by itself could not account for the high values of dimethyloxazolidine dione accumulation. A difference in the total dimethyloxazolidine dione accumulation requires: (a) the existence of differences in the pH values and also the existence of a difference in the diffusion coefficient of the two forms of dimethyloxazolidine dione; or (b), a binding of one of the two forms, i.e., binding of dimethyloxazolidine dione form by fixed charges.     

Effect of paracetamol on gastric mucosa.

The effect of paracetamol on the gastric mucosa was examined in seven healthy volunteers. The dose used (2 g instilled in 100 ml isotonic saline) was equivalent to about six tablets taken with water. Biopsy specimens were taken before and 10 and 60 minutes after instillation. The mean incidence of damaged surface cells in the control period was 1.7%. Ten minutes after instillation 3.5% of the surface cells were damaged. This increase was not significant. Light microscopy showed focal cell disruption and infiltration of red blood cells. Scanning electronmicroscopy showed minimal loss of normal cell apices. No erosions were seen on microscopy. Biopsy specimens taken 60 minutes after paracetamol showed similar changes. These findings differ appreciably from the extensive cell damage and microscopic erosions caused by therapeutic doses of 600 mg (two tablets) of aspirin. We conclude that large "analgesic" doses of paracetamol cause minimal ultrastructural changes in normal human gastric mucosa. The continued use of paracetamol in place of aspirin appears to be justified when there is a possibility of gastric mucosal injury.     

A neutral collagenase from human gastric mucosa.

Biopsy specimens of human gastric mucosa, maintained in culture for 7 days in the absence of serum, released a collagen-degrading enzyme into the medium. The yield of active enzyme reached a maximum after 2-3 days, and viable tissue, capable of protein synthesis, was essential for its production. 2. At 25 degrees C the enzyme attacked undenatured collagen in solution, resulting in a 55% loss of specific viscosity and producing the two products TCA and TCB characteristic of neutral-collagenase action. 3. Electron microscopy of segment-long-spacing crystallites of these reaction products showed the exact cleavage locus of the collagen molecules to be between bands 43 and 44 (I-43). The larger TCA and smaller TCB products were fragments representing 77 and 23% respectively of the length of the collagen molecule. 4. Optimal enzyme activity was observed over the pH range 7.5-8.5 and a mol.wt. of approx. 38000 was derived from gel-filtration studies. 5. The enzyme was shown to be inhibited by the human serum proteins alpha2-macroglobulin and a smaller component of mol.wt. approx. 40000; alpha1-anti-trypsin was not inhibitory. 6. EDTA, 1, 10-phenanthroline, cysteine and dithiothreitol all inhibited collagenase activity. 7. The gastric enzyme has properties similar to other well characterized collagenases, but differences exist with respect to its molecular size and the site of attack on the collagen molecule.     

Alkaline O leads to N-transacylation. A new method for the quantitative deacylation of phospholipids.

1. Quantitative O-deacylation of phospholipids has been achieved by incubation with a reagent containing monomethylamine, methanol and water. The reaction is primarily an O leads to N-transacylation with N-methyl fatty acid amides being formed. 2. The reagent can be removed easily by volatilization and under defined conditions no secondary decomposition of the phosphorus-containing deacylation products occurs. 3. The water-soluble phosphorus compounds derived by deacylation of mammalian tissue O-diacylated phospholipids have been completely separated by a single-dimensional paper ionophoresis with a volatile pH9 buffer. 4. The O-deacylated alkyl and alkenyl phospholipids have been examined by t.l.c. before and after catalytic hydrolysis with Hg2+. 5. A complete analysis of rat brain phospholipids by the above methods agrees closely with that obtained by other procedures.     

Homeostasis of the gastric mucosa and blood circulation. 2. Role of ischemia in disruption of the gastric mucosa

To date there is a lot of data of literature indicating that microcirculatory disorders play the main role in the development of gastric mucosal damages induced by stress, ethanol, nonsteroidal antiinflammatory drugs and tobacco smoke. Under stress gastric mucosal blood flow disorders may be caused by the actication of sympathetic nervous system. Ulcer healing is accompanied by the angiogenesis and by the increase of blood flow in the ulcer border and tissues surrounding the ulcer. Therefore now the main studies are concentrated on the search of defence-enhancing agent rather than drugs for antisecretory therapy. Therapeutic strategy suggests the use of some potential vasodilators such as NO donors, prostaglandin analogues, oxygen radical scavengers, endothelin, leukotrienes, platelet-activating factor antagonists and/or their synthesis inhibitors. At present, the therapeutic possibilities seem to be restricted and nothing indicates that stimulation of the defensive factor only, is more effective in the treatment of peptic ulcer than inhibition of aggressive factors. However we suggest that blood flow correction may be very important for the treatment of refractory ulcers or for prophylaxis of stress ulceration and peptic ulcer recurrence.     

Localization of phospholipid-rich zones in rat gastric mucosa: possible origin of a protective hydrophobic luminal lining

Mammalian gastric mucosa is unusually hydrophobic or nonwettable, which may be an essential biophysical characteristic of the gastric mucosal barrier. Since this property may be attributable to an adsorbed layer of surface-active phospholipids (SAPL), we investigated the distribution of SAPL in rat oxyntic mucosa. Ferric hematoxylin (FH) and iodoplatinate (IP), selective histochemical stains for phospholipids (as confirmed by spot tests), were used to detect SAPL in frozen sections and aldehyde-fixed tissue, respectively. Using FH staining in conjunction with extraction procedures that either solvate or preserve SAPL, we determined that positive reactivity was the greatest in the apical third of the oxyntic mucosa between the glandular neck region and the surface. IP reactivity appeared to parallel the FH staining pattern. Mucous cells, especially the surface epithelial cells, were heavily stained. Electron microscopic examination revealed that these cells contain inclusion bodies associated with various subcellular organelles, e.g., nuclear envelope, endoplasmic reticulum, Golgi apparatus and its vesicles, and mucous secretory granules. Vesicles and myelin figures, which resembled those found in lung surfactant, were observed extracellularly in close association with the surface mucous cells. Our findings suggest that mucous cells are actively involved in synthesis and storage of SAPL, which may be an essential component of the stomach's protective hydrophobic lining.     

A simple method to preserve oceanic phytoplankton for flow cytometric analyses

A simple method was developed to preserve marine phytoplankton populations so that delayed flow cytometric analyses could be performed. The method consisted of immediate fixation with 1% glutaraldehyde (final concentration) followed by storage in liquid nitrogen. The method was tested on individual algal species and on natural samples from both coastal and pelagic waters. In most cases, it caused little cell loss and preserved well both forward angle light scatter and chlorophyll fluorescence, but phycoerythrin fluorescence sometimes was significantly increased. The technique performed best for the small-sized picoplankton (below 2 microns) such as Synechococcus cyanobacteria or the newly discovered oceanic prochlorophytes. For larger-sized cells it had to be applied on a case by case basis as some fragile species, particularly dinoflagellates and cryptophytes, were poorly preserved.     

Epithelial response of the rat gastric mucosa to chronic superficial injury.

Chronic injury to the healthy gastric mucosa with noxious agents such as aspirin or alcohol induces a progressive strengthening of the stomach wall against these insults. The present study examined the histologic response of the rat gastric mucosa to chronic destruction of the superficial mucosa for one month with hypertonic saline. The number, position and morphology of proliferating, parietal, G and D cells were followed during mucosal injury and one month of recovery. The results showed that chronic injury reduced parietal cell numbers by about 30 percent, particularly in the middle of the mucosal thickness where a clear zone was formed by hypertrophy of mucous neck-like cells. G cells were also reduced by about 50 percent, but there were no changes in D cells. Chronic injury induced a marked increase in the number of antral (+112 percent) and fundic (+250 percent) proliferating cells. CONCLUSION: The rat gastric mucosa responds to chronic superficial injury by down-regulation of acid secretory cells and gastrin secreting cells and an up-regulation of proliferating cells. The appearance of a prominent layer of mucous neck-like cells may indicate a new secretory function for these cells.     

Growth of neonatal rat uterine luminal epithelium on extracellular matrix

Summary We have developed a tissue culture system using an extract of basement membrane (extracellular matrix) which promotes the in vitro growth and development of uterine luminal epithelium from the 5-day-old rat. Uterine luminal epithelium, free of stroma, was obtained as short tubes by trypsinization of uterine segments followed by mechanical separation. Epithelial segments were grown in a serum-free medium on culture dishes coated with an extracellular matrix. After 2 days, rapid cell growth resulted in monolayer cultures, which subsequently formed organoid structures similar to differentiated uterine glands present in uterine tissue taken from older rats. Electron microscopy of cultures revealed columnar cells with basally located nuclei, apical microvilli, lateral membranes with interdigitations, desmosomes, and secretory Golgi complexes, all features found in functioning uterine epithelium in vivo. This model will allow the in vitro investigation of the development of uterine epithelium-specific functions free of the influence of stromal cell factors.