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At least 1,099 records · Page 61Linked to original sources
PubMed1996

Characterization of the interstitial cells associated with the submuscular plexus of the guinea-pig colon.

Interstitial cells associated with the submuscular plexus of the guinea pig colon were studied by electron microscopy and by light microscopic wholemount stretch preparations. Their cytoplasmic features are similar to those of fibroblasts and they contain a well-developed Golgi apparatus, granular endoplasmic reticulum and many mitochondria. Intermediate filaments are abundantly distributed throughout the perinuclear region and processes. Numerous caveolae, a basal lamina and subsurface cisterns are observed on the cell membrane as in smooth muscle cells. The most characteristic feature of this cell type is the existence of many large gap junctions that interconnect these cells to each other and with the smooth muscle cells. Nerve varicosities containing synaptic vesicles are observed in close apposition with cells of this type. Whole-mount preparations stained by the zinc iodide-osmic acid method and by vimentin immunohistochemistry clearly demonstrated the stellate form of these gap junction-rich cells and suggested that they correspond to the interstitial cells of Cajal.

Animals↗
PubMed1995

Regressors of whole-carcass zinc phosphide/phosphine residues in voles: indirect evidence of low hazards to predators/scavengers.

Whole-carcass residues of the rodenticide zinc phosphide (Zn3P2) and hydrolyzed phosphine (PH3) were determined for voles (Microtus spp.) that died following ingestion of a 2% Zn3P2 steam rolled oat (SRO) groats bait. Procedures involved: a three-day acceptance test to assess vole consumption (n = 27) of control SRO groats and several one-day Zn3P2- (n = 13) or control-bait (n = 4) tests to characterize onset of pharmacotoxic signs and to obtain fatally-dosed carcasses for residue analyses. Carcasses were stored in liquid nitrogen (LN2) to maximize retention of Zn3P2/PH3 residues prior to chemical determinations. Linear regressions were computed between pairs of consumption and residue variables. Main results were the following: (1) mean (+/- SD) consumption of control bait was 2.5 (+/- 0.9), 3.0 (+/- 0.9), and 2.8 (+/- 0.8) g on days 1, 2, and 3, respectively (> or = 10.6 +/- 4.6% of body weight); (2) all test-bait voles (n = 13) died approximately 4-12 h after bait presentation, with lethargy and respiratory distress key signs of toxicosis; (3) whole-carcass Zn3P2 residues averaged 1.73 mg (min-max: 0.31-4.95), and PH3 residues averaged 10.6 micrograms (min-max: 0.5-21.0); and (4) significant linear regressions were found between bait consumption/Zn3P2 intake and body weight (r2 = 0.64, p < or = 0.001), carcass Zn3P2 and bait consumption/Zn3P2 intake (r2 = 0.32, p < or = 0.043), and carcass Zn3P2 and body weight (r2 = 0.60, p < or = 0.002). Certain analytical and hazards issues are discussed.

Animals↗
PubMed1984

Localization of zinc in the thymic reticulum of mice by electron-probe microanalysis.

Thymulin, a thymic hormone, is a nonapeptide requiring zinc for biological activity. It has been shown that epithelial cells, forming part of the thymic reticulum, secrete this hormone and/or store it within cytoplasmic vacuoles. X-ray electron-probe microanalysis (EPMA) has been used to detect zinc in the thymus. Low concentrations of zinc have been demonstrated in the dense granules contained in clear vacuoles of some epithelial cells in normal and ZnCl2-injected mouse thymuses, thus suggesting that the metal may be coupled to the peptide before the secretion of the hormone from the cells.

Animals↗
PubMed1986

Ultracytochemical evidence for the presence of GERL in pinealocytes of the Mongolian gerbil (Meriones unguiculatus).

Ultracytochemical reactions for the demonstration of acid phosphatase, glucose-6-phosphatase and thiamine pyrophosphatase, as well as zinc iodide-osmium tetroxide impregnation, revealed the existence of GERL (Golgi apparatus-Endoplasmic Reticulum-Lysosomes) in pinealocytes of the Mongolian gerbil (Meriones unguiculatus). The spatial arrangement of this structure was studied on thick sections using a goniometric stage. Although it was not possible to determine whether GERL in pinealocytes belongs to the Golgi apparatus or to endoplasmic reticulum, it can be concluded that its presence in studied cells signifies that they are considerably more active synthetically than has been believed to date.

Acid Phosphatase↗
PubMed1982

Differentiation of endoplasmic reticulum in the developing oocyte of the golden hamster (Mesocricetus auratus).

The differentiation of the endoplasmic reticulum (ER) in the developing oocyte of the golden hamster is accompanied by changes in susceptibility to impregnation with a zinc iodide-osmium tetroxide (ZnOs) mixture. The staining of two of the three categories of oocyte ER is first seen at or about the time when rapid oocyte growth is initiated. Staining reaches a peak before antrum formation, then declines. A third category of ER remains unstained at all stages. Aberrant reactivity to ZnOs is seen on oocytes which become atretic, and differs with the stage of oocyte development at which atresia occurs. Relationships between the three categories are described, and an attempt made to relate changes in form and distribution to developmental processes. The frequent contact/continuity between ER and mitochondria is discussed with regard to its possible role in lipid metabolism.

Age Factors↗
PubMed1991

Components of the dynamic response of mammalian muscle spindles that originate in the sensory terminals.

One component of the dynamic response of muscle spindles is characterized by a phase lead and frequency dependent sensitivity in response to sinusoidal stretches at frequencies around 1 Hz. Possible mechanisms producing this component, designated the "mid-frequency" dynamics, were investigated by testing the hypotheses that they arise from the mechanical behavior of the intrafusal muscle and alternatively from within the sensory terminals. Destruction of the myofibrillar structure of the intrafusal muscle fibers did not alter the mid-frequency dynamics, indicating that they do not arise from viscoelastic properties of the intrafusal muscle. An Arrhenius plot of the temperature dependence of the mid-frequency dynamics yielded an equivalent activation energy of 6.5 Kcal/M in the temperature range 23-42 degrees C and a 3-fold higher activation energy at lower temperatures. These observations are consistent with a dynamic process associated with a membrane-bound biochemical process. The addition of Ca++ and Ca(++)-activated-K+ (K(Ca] channel blockers (ZnCl2, Apamin and TEA) to the bathing solution altered the response dynamics by reducing the mid-frequency phase lead. The results suggest a negative feedback on the membrane potential generated by K+ efflux following a Ca++ influx that opens K(Ca) channels. A quantitative model fit to the experimental data yields a time constant of about 80 ms representing the limiting process associated with activation of the K(Ca) channels in this system. The results indicate that the mechanism underlying the mid-frequency dynamics includes at least two processes: one, not identified in this study, generates the phase lead and another, involving Ca++ and K(Ca) channels, provides a negative feedback that modifies the phase lead.

Animals↗
PubMed1992

Cl- channels in intact human T lymphocytes.

We recently described a large, multiple-conductance Cl- channel in excised patches from normal T lymphocytes. The properties of this channel in excised patches are similar to maxi-Cl- channels found in a number of cell types. The voltage dependence in excised patches permitted opening only at nonphysiological voltages, and channel activity was rarely seen in cell-attached patches. In the present study, we show that Cl- channels can be activated in intact cells at physiological temperatures and voltages and that channel properties change after patch excision. Maxi-Cl- channels were reversibly activated in 69% of cell-attached patches when the temperature was above 32 degrees C, whereas fewer than 2% of patches showed activity at room temperature. Upon excision, the same patches displayed large, multiple-conductance Cl- channels with characteristics like those we previously reported for excised patches. After patch excision, warm temperatures were not essential to allow channel activity; 37% (114/308) of inside-out patches had active channels at room temperature. The voltage dependence of the channels was markedly different in cell-attached recordings compared with excised patches. In cell-attached patches, Cl- channels could be open at cell resting potentials in the normal range. Channel activation was not related to changes in intracellular Ca2+ since neither ionomycin nor mitogens activated the channels in cell-attached patches, Ca2+ did not rise in response to warming and the Cl- channel was independent of Ca2+ in inside-out patches. Single-channel currents were blocked by internal or external Zn2+ (100-200 microM), 4-acetamido-4' isothiocyanostilbene-2,2'-disulfonate (SITS, 100-500 microM) and 4,4'-diisothiocyanostilbene 2,2'-disulfonate (DIDS, 100 microM). NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate) reversibly blocked the channels in inside-out patches.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1988

ARDS after accidental inhalation of zinc chloride smoke.

Five soldiers were injured by inhalation of hexite smoke (ZnCl2) during military training. Two soldiers, not wearing gas masks breathed hexite for 1 or 2 min, they slowly developed severe adult respiratory distress syndrome (ARDS) over the ensuing 2 weeks. This slow, progressive clinical course has not been previously described. In both patients, an increased plasma zinc concentration was measured 3 weeks after the incident. Intravenous and nebulized acetylcysteine increased the urinary excretion of zinc, and briefly decreased the plasma levels. In an attempt to arrest collagen deposition in the lungs, L-3,4 dehydroproline was administered. Both patients died of severe respiratory failure (25 and 32 days after inhalation). At autopsy diffuse microvascular obliteration, widespread occlusion of the pulmonary arteries and extensive interstitial and intra-alveolar fibrosis was observed. Three soldiers wearing ill fitting gas masks, immediately developed severe coughing and dyspnea. They improved, and 12 months after exposure their lung function tests were nearly normal, but they still had slight dyspnea on exercise.

Acetylcysteine↗
PubMed1986

A comparative study of the acute inhalation toxicity of smoke from TiO2-hexachloroethane and Zn-hexachloroethane pyrotechnic mixtures.

Rats was exposed to white smoke generated from mixtures of titanium dioxide-hexachloroethane (TiO2-HC) and zinc-hexachloroethane (Zn-HC), respectively, in an inhalation chamber operated in the static mode. The dose was varied by varying the amount of smoke mixture and/or the exposure time. The acute inhalation toxicity of TiO2-HC smoke was much lower than the Zn-HC smoke. Thus, the animals survived exposure to TiO2-HC smoke, even at relatively high smoke concentrations. This smoke was irritating to the animals and minor, acute inflammatory changes were seen in lung tissue. In contrast, Zn-HC smoke was very toxic and caused lethal injuries to the experimental animals, even at relatively low concentrations. Pulmonary injuries were extensive and death was due to blood congestion with pulmonary oedema. Since the TiO2-HC and Zn-HC mixtures form TiCl4 and ZnCl2, respectively, a separate study was performed in which rats were exposed to TiCl4 gas or ZnCl2 aerosol. No animals died from exposure to TiCl4 at concentrations between 370 and 2900 mg/m3 for 10 min. The LC50 of ZnCl2 was found to be around 2000 mg/m3 during a 10-min exposure period. The difference between the two types of smoke is explained by the difference in toxicity between TiCl4 and ZnCl2.

Acute Disease↗
PubMed1983

Investigation of the mechanism of cadmium toxicity at cellular level. I. A light microscopical study.

Chromatin condensation occurs within 15 min to 1 h after the addition of CdCl2 in a concentration of 1 microgram/ml to a liver cell culture and seems to be the first event demonstrable by light microscopy. This chromatin condensation, which precedes membrane leakage, is irreversible and leads to cell death of almost all cells. It does not occur after the administration of equimolecular concentrations of some other bivalent metallic ions.

Animals↗
PubMed1984

Structure of amyloplasts and endoplasmic reticulum in the root caps of Lepidium sativum and Zea mays observed after selective membrane staining and by high-voltage electron microscopy.

The structure of plastids in the root cap of cress and maize was studied by low- and high-voltage electron microscopy after staining their membranes with a mixture of zinc iodide and osmium tetroxide. In plastids of both species electron-opaque membranes were found in the plastid interior while membranes of lesser electron-opacity comprised the outer envelope and vesicles and cisternae underlying it. Electron-opaque tubules, often in groups attached to the inner membrane of the amyloplast envelope, were found in cress but not in maize. The internal, less-opaque membranes were often found associated with the starch grains. No specific association could be seen between amyloplasts and endoplasmic reticulum (ER); their surfaces showed no regular contact or connexion, though the amyloplasts clearly indented the underlying ER. The ER in statocytes was predominantly tubular in cress but predominantly cisternal in maize.

Brassicaceae↗
PubMed1984

Primary Sjögren's syndrome treated with Efamol/Efavit. A double-blind cross-over investigation.

Thirty-six patients with primary Sjögren's syndrome participated in a randomised double-blind, cross-over, 3-week, study to compare the effect of Efamol (1500 mg X 2) with that of placebo. Efamol contains 9% of the prostaglandin-E1 precursor gamma-linolenic acid, which is presumed to occur in reduced levels in Sjögren's syndrome. Efamol treatment improved the Schirmer-I-test (P less than 0.03) while values of break-up time,-van Bijsterveld score, corneasensitivity, tear-lysozyme and nuclear chromatin in conjunctival epithelial cells did not reach the statistical 0.05 level.

Adult↗
PubMed1996

Mengo virus 3C proteinase: recombinant expression, intergenus substrate cleavage and localization in vivo.

Mengo virus 3C proteinase was cloned and expressed to high levels in a bacterial vector system. The protein was solubilized from inclusion bodies then purified to homogeneity (> 95%) by ion exchange chromatography. The recombinant enzyme was proteolytically active in cell-free processing assays with a Mengo capsid precursor substrate, L-P1-2A, correctly and proficiently cleaving it into L, 1AB, 1C, 1D and 2A protein products. Further analyses with synthetic peptide substrates encompassing the Mengo or rhinovirus-14 2C/3A cleavage sequences, showed the Mengo 3C could recognize and process specific glutamine-glycine sites within these peptides. The reactivity with the rhinovirus peptide was unexpected, because cross-reactivity between a picornavirus 3C enzyme and a protein substrate from different genus of this family has otherwise never been observed. In reciprocal reactions, a rhinovirus-14 3C preparation was unable to cleave the Mengo-derived synthetic peptide substrate. The recombinant Mengo 3C reactions were also characterized with regard to substrate Km, optimum pH and temperature. The protein was additionally used to raise monoclonal antibodies (mAbs) in mice, which in turn localized natural 3C, 3ABC, 3CD and P3 in immunoblots, immunoprecipitations and indirect immunofluorescence assays of Mengo-infected HeLa cells. The monoclonals showed cross-reactivity with 3C and 3C-containing precursors from encephalomyocarditis virus (EMCV), but did not react with 3C proteins from rhinovirus-14 or poliovirus-1M.

3C Viral Proteases↗
PubMed1979

Study of erythrocyte delta-aminolevulinic acid dehydratase activity in porphyria cutanea tarda.

The erythrocyte delta-aminolevulinic acid dehydratase activity was studied in porphyria cutanea tarda patients, compared to healthy controls, in an attempt to resolve the contradictions in the relevant literature data. In an in vitro experimental system, a study was also made of how the erythrocyte delta-aminolevulinic acid dehydratase activity varies on the action of the activators -SH and Zn2+. It was found that, compared to the healthy controls, the erythrocyte delta-aminolevulinic acid dehydratase activity of porphyria cutanea tarda patients is significantly decreased, but it is restored to the original activity level on the addition of -SH and Zn2+. Since there is a general -SH requirement of delta-aminolevulinic acid dehydratase, the most obvious explanation for the decrease of the activity in the case of the patients is the shift of the natural redox systems of the erythrocytes, and the decrease of the reduced glutathione/oxidized glutathione ratio.

Adult↗
PubMed1995

Modulated red blood cell survival by membrane protein clustering.

Human and murine blood cells treated with ZnCl2 and bis(sulfosuccinimidyl)suberate (BS3) (a cross linking agent) undergo band 3 clustering and binding of hemoglobin to red blood cell membrane proteins. These clusters induce autologous IgG binding and complement fixation, thus favouring the phagocytosis of ZnCl2/BS3 treated cells by macrophages. The extension of red blood cell opsonization can be easily modulated by changing the ZnCl2 concentration in the 0.1-1.0 mM range thus providing an effective way to affect blood cell recognition by macrophages. In fact, murine erythrocytes treated with increasing ZnCl2 concentrations have proportionally reduced survivals when reinjected into the animal. Furthermore, the organ sequestration of ZnCl2/BS3 treated cells strongly resembles the typical distribution of the senescent cells. Since the ZnCl2/BS3 treatment can also be performed on red blood cells loaded with drugs or other substances, this procedure is an effective drug-targeting system to be used for the delivery of molecules to peritoneal, liver and spleen macrophages.

Animals↗
PubMed1995

Phospholipase C-mediated release of neuraminidase from Tritrichomonas foetus cell surface.

The release of the Tritrichomonas foetus plasma-membrane ectoenzyme neuraminidase by exogenous specific phospholipase C (PI-PLC) was investigated. Neuraminidase activity was determined using both the peanut agglutinin (PNA) hemagglutination test and the specific substrate N-acetylneuramin-lactose in a colorimetric assay. The release of the neuraminidase by PI-PLC was dependent on the reaction time and the concentration of PI-PLC. Neuraminidase activity was also detected in supernatant of untreated T. foetus. Spontaneous or PI-PLC-induced release of neuraminidase from protozoan cells was markedly decreased by 10 mM ZnCl2, suggesting the occurrence of an endogenous PI-PLC in the parasite. After T. foetus lysis at 37 degrees C with a solution of Triton X-114, neuraminidase activity was preferentially found in the aqueous phase rather than in the detergent phase, again suggesting that the parasite contains an endogenous PI-PLC that converts the hydrophobic form of neuraminidase anchored to the T. foetus cell membrane into a hydrophilic form. These results show that neuraminidase is linked to the T. foetus plasma membrane via a glycosylphosphatidylinositol anchor.

Animals↗
PubMed1989

Interaction of lead and zinc in cultured astroglia.

Astroglia take up lead (Pb) in vivo and in vitro. In view of the fact that zinc affects both tissue deposition of Pb and clinical signs of Pb intoxication, the present study was carried out to test the effects of various Zn levels on lead toxicity in astroglia. Primary cultures of astroglia from 1- to 3-day-old neonatal rats were divided into three groups and cultured in Waymouth's 752/l medium with 0, 1, or 2 microM ZnCl2. Each group was further divided into two subgroups which were treated with either 0, 29.9, or 32.5 mumol of Pb acetate. Cultures were assayed for viability and metal content after 1 and 3 days of continuous exposure to Pb (designated days 1 and 3) as well as 10, 17, and 24 days after the initiation of a 3-day exposure to Pb. The Trypan blue dye exclusion viability assay showed no significant differences between controls and Pb-treated groups except on day 3, at which time the 0 and 2 microM Zn groups treated with Pb had reduced viability. 3H-Leucine incorporation into acid-precipitable proteins (cpm/micrograms protein) was unaffected by Pb or Zn except on days 1 and 17, when cultures given 2 microM Zn and no Pb showed increased incorporation. Pb-treated cultures showed a reduction in cell number which was partially offset in a dose-dependent manner by the presence of Zn in the medium but not enough to mask completely the reduction caused by Pb. Pb produced the following effects on intracellular trace metal concentrations: (1) increased intracellular [Pb]. (2) increased intracellular [Fe], (3) increased intracellular [Cu], and increased intracellular [Zn]. By day 24, intracellular Cu concentrations were normal, but intracellular [Zn] and [Pb] remained elevated in all Pb-treated subgroups. Furthermore, intracellular Fe levels remained increased in the Pb-treated subgroup cultured with 0 microM Zn. Zinc showed a protective effect by (1) reducing intracellular Pb levels and (2) delaying or preventing the Pb-induced increase in intracellular [Fe] and [Zn] but not the increase in intracellular [Cu]. These effects became more pronounced with increasing extracellular Zn concentrations, although intracellular Zn levels did not increase in response to extracellular levels. Increased dietary zinc in rats is known to reduce Pb accumulation in organs. Our results extend this observation to cells in culture and, furthermore, suggest that the Pb-Zn interaction is complex and not simply a substitution of Pb by Zn at the point of absorption through the plasma membrane.

Animals↗