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Mechanisms of zinc transport into pig small intestine brush-border membrane vesicles.

1. The purpose of the present work was to examine certain membrane transport mechanisms likely to carry zinc across the brush-border membrane of pig small intestine, isolated in a vesicular form. 2. In initial velocity conditions, saturation kinetics revealed a great effect of pH on zinc transport: optimal conditions were observed with an intravesicular pH of around 6.6 with or without a H+ gradient; however, this did not allow us to conclude the existence of a neutral exchange between Zn2+ and H+ ions. 3. By measuring 36Cl uptakes, the presence of the Cl(-)-HCO3- or Cl(-)-OH-antiporter with typical 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) sensitivity was detected in vesicles; zinc did not alter this anionic exchange activity. A 65Zn time course, performed in conditions identical with those for 36Cl uptake, was DIDS insensitive and was greatly inhibited by an outward OH- gradient. This could argue against a transport of zinc as a complex with Cl- and HCO3- through the anion antiporter. 4. When external Cl- and HCO3- were replaced by SCN-, able to form a Zn(SCN)4(2-) complex, we observed a stimulating effect of outward HCO3- gradients on 65Zn uptake but neither DIDS nor diphenylamine-2-carboxylate (DPC) inhibited the transport in these conditions. This suggested that the intestinal anion antiporter was not a major route for zinc reabsorption. 5. The tripeptide Gly-Gly-His at low concentrations stimulated 65Zn uptake, then inhibited it in a dose-dependent manner either in the presence of an inward H+ gradient or in the presence of a membrane potential 'negative inside' or in both situations. These conditions are necessary for the active transport of the peptide and this strongly suggests that zinc can be transported as a [Gly-Gly-His-Zn] complex, utilizing the peptide carrier system.

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

Efficacy and toxicity of zinc salts as candidate topical microbicides against vaginal herpes simplex virus type 2 infection.

Zinc salt solutions administered as topical microbicides provided significant protection against herpes simplex virus type 2 infection in a mouse vaginal challenge model. However, at the therapeutic concentration, the salt solutions caused sloughing of sheets of vaginal epithelial cells. These observations limit the utility of zinc salts as microbicides and suggest that the application of zinc solutions to mucosal surfaces has the potential to cause damage that might increase susceptibility to secondary infections at a later time.

Animals↗

Autoradiographic method to screen for soil microorganisms which accumulate zinc.

An autoradiographic method was developed to screen for and isolate soil microorganisms which accumulate zinc (Zn). Diluted soil samples (Rubicon fine sand, Entic Haplorthods [pH 5.9]) were plated on soil extract-glucose agar containing radioactive 65Zn. After 7 days of incubation, individual colonies which accumulated sufficient 65Zn could be detected by autoradiography. These colonies were isolated and confirmed as Zn accumulators in pure culture by using the autoradiographic plate technique. Most Zn accumulators were filamentous fungi, identified as Penicillium janthinellum, Aspergillus fumigatus, and Paecilomyces sp. Isolates of Penicillium janthinellum were the most common Zn accumulators. The most abundant Zn-accumulating bacteria were Bacillus spp. The validity of the autoradiographic plate technique to differentiate soil microbes which accumulate Zn was examined independently by energy dispersive X-ray analysis in a scanning electron microscope. This method confirmed that fungal isolates which gave positive autoradiographic responses in the plate assay bioaccumulated more Zn in their biomass than fungal isolates from the same soil sample which gave negative autoradiographic responses. Thus, this technique can be applied to specifically screen for and isolate microbes from the environment which bioaccumulate Zn.

Aspergillus fumigatus↗

Rhabdovirus-induced apoptosis in a fish cell line is inhibited by a human endogenous acid cysteine proteinase inhibitor.

To determine the mechanisms of cell death in rhabdovirus-infected cells, we studied the infection of the epithelial papilloma of carp cell line with spring viremia of carp virus. Studies using electron microscopy, confocal microscopy, and agarose gel electrophoresis revealed changes in cell morphology and DNA fragmentation indicative of apoptosis. The virus-induced apoptosis was inhibited in cells treated with a human endogenous acid cysteine proteinase inhibitor.

Animals↗

Role of olfaction in starch and oil preference.

Two different techniques were used to assess the role of olfaction in the preference rats show for dilute nutrient suspensions and solutions. Removal of the olfactory bulbs reduced but did not abolish preference for 1% starch and oil emulsions. Removal of the olfactory bulbs also reduced preference for sucrose, Polycose, and saccharin. In another experiment, rats were rendered anosmic with intranasal zinc sulfate. The degree of anosmia was evaluated by measuring preference for an aqueous solution of citral and vanillin. Rats whose avoidance of citral plus vanillin had been abolished by zinc sulfate continued to prefer a 1% starch suspension over vehicle, although starch preference was significantly reduced. It is concluded that starch and oil preference is mediated by both olfactory and nonolfactory cues.

Animals↗

Compartmental analysis of zinc kinetics in mature male rats.

A compartmental model of zinc kinetics in mature male rats was developed. The model was based on zinc and radioisotopic zinc measured in samples of plasma, skeletal muscle, kidneys, testes, spleen, bone, and intestinal segments collected at various times for up to 4 days after 65Zn was injected intravenously. Zinc intake, excretion of zinc and 65Zn in urine and feces, and the whole body retention of 65Zn were also determined. Other data used to develop the model included published information on zinc concentration and zinc kinetics in tissues that were not sampled. In the model, the intestinal tract was represented by five compartments. Plasma, spleen, kidneys, and testes were each represented by an individual compartment. In contrast, two compartments each were used to represent exchangeable zinc in liver, bone, skeletal muscle, skin, and red blood cells. The present model extends earlier models of zinc kinetics, describes the distribution of zinc in the whole body, and may provide a means to evaluate the influence of either pathophysiological conditions or dietary extremes on the metabolism of zinc.

Animals↗

Magnetic properties of doped II-VI semiconductor nanocrystals.

We investigate the magnetic properties of two typical II-VI semiconducting nanocrystals, namely, ZnS and ZnO, doped with various concentrations of a transition metal ion, Mn. A wide range of dopant concentrations was explored without changing the size of the nanocrystal, thereby allowing us to study the concentration dependence of various properties independent of any size variation of the host. However, only small doping concentrations could be realized in each case. All the studies were thus carried out with ZnS and ZnO nanocrystals with their respective average sizes fixed at about 1.6 and 4.7 nm. We show that the magnetic properties of such doped systems, remaining paramagnetic down to the lowest temperature (<3 K), can provide important and accurate information concerning the dopant level in such samples.

Crystallization↗

Preparation of high purity ZnO nanobelts by thermal evaporation of ZnS.

High purity one-dimensional ZnO nanobelts were synthesized by thermally evaporating commercial ZnS powders in a hydrogen-oxygen mixture gas at 1050 degrees C. It was found that these ZnO nanobelts had a single crystal hexagonal wurtzite structure growing along the [0001] direction. They had a rectangle-shaped cross-section with typical widths of 20 to 100 nanometers and lengths of up to hundreds of micrometers with lattice constants of a = 0.325 nm and c = 0.520 nm. The self-catalytic hydrogen-oxygen assisted growth of ZnO nanobelt is discussed. The photoluminescence (PL) characterization of the ZnO nanobelts shows strong near-band UV emission (about 383 nm) and one broad peak at 501 nm, which indicates that the ZnO nanobelts have good potential application in optoelectronic devices.

Crystallization↗

The histopathology of rat lung following exposure to zinc oxide/hexachloroethane smoke or installation with zinc chloride followed by treatment with 70% oxygen.

The effects of inhaled zinc oxide/hexachloroethane smoke (11,580 mg x min/m3) and intratracheally instilled zinc chloride (2.5 mg/kg body weight) have been studied in rat lung. The effects of subsequent treatment with 70% oxygen have been studied after both procedures. Both the inhalation of the smoke and instillation of zinc chloride produced similar effects that included pulmonary edema, alveolitis and, at a later stage, some fibrosis. After zinc chloride instillation, the pathological changes largely spared the periphery of the lung, while following smoke inhalation they were more diffuse. Subsequent oxygen administration had little effect on the development or progression of the pathological changes.

Administration, Inhalation↗

Effect of different zinc sources and levels on inhibition of the apoptosis induced by glucocorticoid of thymocytes in vitro.

This experiment was conducted to investigate the effects of zinc sulfate and zinc methionine (Zn-Met) and their levels on apoptosis induced by glucocorticoid of thymocytes and the possible mechanism. Dexamethasone was used to make the apoptosis model of thymocytes; zinc sulfate and zinc methionine were supplemented to the medium at levels of 0, 50, 100, 500, and 1000 microM. The activity of cells, Cu,Zn superoxide dismutase (Cu,Zn-SOD), DNA ladder pattern, intracellular calcium concentration, and the percentage of apoptosis nuclei were determined. Both ZnSO4 and Zn-Met could modulate apoptosis; they inhibited apoptosis and decreased DNA fragmentation. The regulation was concentration dependent. At levels of 50 and 100 microM, the effect of Zn-Met on inhibiting apoptosis was less efficient than that of ZnSO4 (p<0.05), but the activity of the cells cultured with Zn-Met was higher than those cultured with ZnSO4; they showed no difference in modulating apoptosis when added at levels of 500 and 1000 microM to the medium (p>0.05). Intracellular calcium concentrations of cells cultured with Zn-Met were higher than those cultured with ZnSO4 at the same levels. Zinc supplementation decreased the concentration of intracellular calcium significantly (p<0.05) and increased the activity of Cu,Zn-SOD in the extract of the cells (p<0.05). Both zinc sulfate and Zn-Met could modulate apoptosis of thymocytes induced by glucocorticoid; the mechanism might involve the exchange of intracellular calcium, the redox of cells, and the two forms of zinc might go different ways in the regulations.

Animals↗

Effect of zinc supplementation from different sources on growth, nutrient digestibility, blood metabolic profile, and immune response of male Guinea pigs.

Forty weaned male guinea pigs of 208.20 +/- 6.62 g mean body weight were divided into 4 groups of 10 animals in a randomized block design. All of the guinea pigs were fed a basal diet [25% ground maize hay, 30% ground maize grain, 22% ground chickpea (Cicer arietinum L.), 9.5% deoiled rice bran, 6% soybean meal, 6% fish meal, 1.45% mineral supplement (without Zn) and 0.05% ascorbic acid] and available green fodder. Group I served as the control (no Zn supplementation), whereas 20 ppm Zn was added in the diet in groups II, III, and IV either as zinc sulfate (ZnSO(4)), zinc amino acid complex (ZAAC), and ZnSO4 + ZAAC in equal parts, respectively. Experimental feeding lasted for 70 d, including a 3-d digestibility trial. Blood was collected through cardiac puncture from four animals in each group at d 0 and subsequently at the end of experimental feeding. After 40 d of experimental feeding, four animals from each group were injected with 0.4 mL of Brucella abortus cotton strain-19 vaccine to assess the humoral immune response of the animals. After 10 wk of study, four animals from each group were sacrificed to study the concentration of Zn, Cu, Co, Fe, and Mn in the liver, pancreas and spleen. Results revealed no significant difference in the feed intake, body weight gain, and digestibility of the nutrients, except for crude protein (CP) digestibility, which was significantly (p < 0.05) lower in group IV. Although concentrations of serum glucose, Ca, and P and the albumin:globulin (A:G) ratio were similar in the different groups, the total protein, albumin, and serum alkaline phosphatase activity were higher in all of the Zn-supplemented groups on d 70. The serum Zn levels at the end of experimental feeding were significantly higher in groups II and III, whereas serum Mn levels were found to be significantly (p < 0.05) higher in groups III and IV. The organ weights (as percentage of body weights) did not show any differences among the treatment groups. Although the Mn concentration was significantly (p < 0.05) higher in the pancreas, the Cu concentration was significantly (p < 0.05) reduced in the spleen in all of the Zn-supplemented groups. The humoral immune response (antibody titer values) on d 14 of vaccination was significantly (p < 0.05) higher in all of the Zn-supplemented groups. It was concluded that the 20-ppm level of Zn in the diet might be adequate for growth and nutrient utilization in guinea pigs, but supplementation of 20-ppm zinc significantly improved the immune response and impact was more prominent with the ZAAC (organic source) compared to ZnSO(4) (inorganic source).

Animals↗

Insulin-releasing pituitary cells as a model for somatic cell gene therapy in diabetes mellitus.

Insulin delivery by somatic cell gene therapy was evaluated using murine pituitary AtT20MtIns-1.4 cells. These cells have been stably transfected to release human insulin by the introduction of a recombinant plasmid bearing a human preproinsulin cDNA under the control of a zinc-sensitive metallothionein promoter. 6 x 10(7) AtT20MtIns-1.4 cells were implanted subcutaneously into streptozotocin-diabetic mice immunosuppressed with cyclosporin A. Release of human insulin was assessed using a specific plasma human C-peptide assay. On days 1 and 2 after implantation human C-peptide concentrations were about 0.02 pmol/ml. Consumption of zinc sulphate solution (500 mg/l) as drinking fluid for days 3-5 increased plasma human C-peptide concentrations to 0.11 +/- 0.01 pmol/ml (mean +/- S.E.M.), n = 11, P < 0.01, and concentrations declined when zinc was discontinued. The extent of hyperglycaemia was slightly lower (P < 0.05) than in a group implanted with non-transfected AtT20 cells. The study was terminated after 9 days, and tumour-like aggregations of implanted cells were identified at autopsy. These comprised a large necrotic core with insulin-containing cells at the periphery. The study provides support for the view that somatic cell gene therapy offers a potential approach to insulin delivery in diabetes mellitus.

Animals↗

Effectiveness of adjunctive irrigation in early periodontitis: multi-center evaluation.

The purpose of this study was to determine the effect of daily water irrigation versus regular oral hygiene alone on gingival and periodontal health in periodontitis patients receiving supportive periodontal treatment. The study also sought to determine if there are enhanced benefits from using an antiplaque zinc sulfate rinse as an irrigant. One hundred fifty-five patients who have had periodontitis and had been treated either surgically or non-surgically completed the 6-month multi-center multi-national study. Patients with at least two 5 mm sites demonstrating bleeding on probing were assigned to 3 equal groups by balanced randomization. In all centers Group A (n = 57) performed regular oral hygiene only, and Group B (n = 58) irrigated with 500 ml water once daily after regular oral hygiene. Group C (n = 40) patients irrigated with a total of 500 ml once daily; following irrigation with 300 ml water, the patients then irrigated with an additional 200 ml with a zinc sulfate solution. The irrigants were diluted to provide the manufacturer's recommended daily dosage. The supragingival irrigation was performed with a commercially available oral irrigator. Bacterial measurements at baseline, 3 months, and 6 months were taken to determine the effect of irrigation on the target organisms and will be reported elsewhere. Gingival index: irrigation with water (Group B) was significantly better than normal oral hygiene (Group A) and irrigation with zinc sulfate (Group C) (P < 0.05) in reducing gingival inflammation. Bleeding on probing: significant reductions in bleeding on probing occurred for water (Group B) compared to normal oral hygiene (Group A) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗