Evaluation of rumen-protected choline additive to diet on productive performance of male Zaraibi growing goats during hot summer season in Egypt.

Twenty Zaraibi goat bucks were used in this experiment which lasted 3 months during summer season of Egypt. The animals were divided randomly into two equal groups. The first group was kept without treatment as control while in the second group, rumen-protected choline (RPC) at the level of 20 g/buck/day was added to the concentrate feed mixture at the morning feeding. RPC additives to diet of Zaraibi goat bucks during the period of hot summer season increased (P < 0.01) total gain and average daily gain compared to the control group. RPC increased (P < 0.05) dry matter intake and feed conversion while water intake was not affected by RPC additives. RPC increased (P < 0.05) red and white blood cell (RBC × 106, WBC × 103) counts and hemoglobin concentration and hematocrit percentage. RPC increased total protein (P < 0.05), globulin, and γ-globulin (P < 0.01). On the other hand, total lipids, total cholesterol, and triglyceride concentrations decreased (P < 0.05 and P < 0.05) while phospholipids, glucose, and choline concentrations increased (P < 0.01) due to RPC supplementation. RPC increased (P < 0.01) thyroxin and triiodothyronine, increased (P < 0.05) testosterone levels, and decreased (P < 0.01) cortisol level compared with control bucks. It is concluded that dietary RPC at the rate of 20 g daily is required for growing male goats, especially, under heat stress conditions of summer season in Egypt and showed the best results concerning the growth, feed conversion, blood metabolites, and economic efficiency.

Changes in the integrity of large unilamellar vesicles due to their interaction with tobacco cell suspensions.

Negatively charged large unilamellar vesicles (LUV) were incubated with tobacco (Nicotiana tabacum var. xanthi) cell suspensions and with the cell-free medium of the cell suspensions. The extent of cell-LUV interaction was determined by the leakage of the LUV contents. Cells enhanced the leakage of LUV contents and this effect increased with cell age. Addition of polylysine to the reaction mixture increased even further the leakage of the LUV contents. The cell-free medium of the cell suspension also affected the integrity of the LUV. Cell-free medium, by itself, promoted leakage of LUV contents and caused a reduction in the leakage exerted by polylysine. Centrifugation (8000g) of the cell-free medium decreased its effect, heat treatment (122°C) did not alter its effect and sonication enhanced it. The effects of the cell-free medium are attributed to the presence of cell wall debris of disintegrated cells.

Liposome-mediated introduction of the chloramphenicol acetyl transferase (CAT) gene and its expression in tobacco protoplasts.

The expression plasmid vector pUC8CaMVCAT, containing the chloramphenicol acetyl transferase (CAT) gene, was encapsulated in large unilamellar vesicles (LUV) and introduced into tobacco protoplasts derived from either cell suspension culture or leaf mesophyll. Treatment with liposomes took place in a buffer containing either NaCl or CaCl2, but no polyethylene glycol. The presence of polylysine in the incubation buffer increased the adsorption of liposomes to protoplasts but decreased the efficiency of CAT gene expression.The expression of the introduced CAT gene could be monitored for at least seven days, following the treatment (about 25% acetylation at day 3 as well as at day 7). Plasmid DNA sequences could be detected, apparently unmodified, for at least nine days in the plant cells, though unintegrated in the host genome.

Promotion and inhibition of vesicle fusion by polylysine.

Polylysine induced rapid aggregation of large unilamellar vesicles composed of phosphatidylcholine-cardiolipin (1:1 molar ratio) but not their fusion. Application of the terbium-dipicolinic acid fusion assay showed that addition of polylysine at nanomolar concentrations enabled a significant lowering of the Ca2+ threshold concentration for vesicle fusion from 9 to 1 mM. Analysis of the kinetics of fusion with a mass-action kinetic model showed that polylysine enhanced significantly the rate of aggregation but affected only slightly the rate of fusion per se. Maximal enhancement of overall fusion rates occurred at a charge ratio (polylysine/cardiolipin) of about 0.5. At larger polylysine concentrations, e.g., at charge ratios greater than 3, polylysine inhibited vesicle fusion.

Cationic polypeptide-induced fusion of acidic liposomes.

Fusion of acidic liposomes was induced by Mg2+, Ca2+, polylysine and polymyxin B. The extent of fusion and the concomitant change in liposome permeability induced by divalent cations depended on the concentration of liposomes in the suspension as well as on the cation concentration. In contradistinction, the extent of fusion and the change in permeability induced by the polypeptides depended only on the polycation concentration. The difference in the pattern of interaction, between the liposomes and the various cations, is a result of different binding affinities. The binding of the polypeptides to the liposomes, in contrast to divalent cations, is practically irreversible. The potential of polylysine to induce fusion of acidic phosphatidyl-ethanolamine-devoid liposomes was used to demonstrate that in order to obtain fusion, both membranes involved must be susceptible, at least to a certain degree, to fusion by the proper inducer. When lysophosphatidylcholine substituted for phosphatidylcholine in phosphatidylethanolamine-rich acidic liposomes, extensive polylysine-induced fusion was obtained without concomitant spillage of the liposome contents.

Interaction of acidic liposomes with red blood cells. Induction of endocytosis and shedding of particles.

Calcium ions induced tight binding of massive amounts of liposomes containing cardiolipin, phosphatidyl-ethanolamine and phosphatidylcholine to erythrocytes. Initially, liposome-liposome fusion occurred and only subsequently the resulting large structures adhered to cells. Large clumps composed of liposomes and cells were formed. Upon prolonged incubation, the clumps were dissipated spontaneously and excess liposomes were released. A constant amount of phospholipid (15-25 nmol/10(8) cells) were incorporated into the cell membranes. Upon disaggregation, the cells shed erythrocyte particles. The latter were isolated and shown to contain lipids from both cellular and liposomal origin. The particles lacked spectrins and contained variable amounts of band 3 content. Liposomes induced endocytosis in reticulocytes but not in mature erythrocytes. In most cases, the liposomes themselves were not engulfed by the cells and remained attached to their surface. The relevance of this phenomenon to delivery to liposome contents into cells is discussed.

Polycation-induced fusion of negatively-charged vesicles.

Sonicated vesicles of 20-50 nm in diameter consisting of neutral phospholipids and a variety of acidic phospholipids were interacted with polylysine, cytochrome c, Ca2+ and Mg2+. The addition of polycations caused massive aggregation accompanied by an increase of membrane permeability as determined by leakage of fluorescent dye. Aggregation was followed by fusion of the vesicles into structures that in some cases exceeded 1 micron in diameter. Polylysine induced aggregation and appreciable fusion at charge ratios (polylysine/phospholipid) of 0.5-2, while divalent cations did so only at charge ratios (cation/phospholipid) greater than 10. Aggregation and fusion induced by polylysine were dependent also on the size of the polycation, i.e., the longer the molecule the less needed to induce similar aggregation. It appears that, due to the concentration of charges on a single molecule, polylysine is at least an order of magnitude more effective than divalent cations at inducing fusion of membranes. Cytochrome c induced fusion of similar vesicles at moderately acidic pH (pH 4.2).

Calcium-induced fusion of proteoliposomes and protein-free liposomes. Effect of their phosphatidylethanolamine content on the structure of fused vesicles.

The acidic phospholipid cardiolipin was shown to be very efficient in promoting calcium-induced fusion of proteoliposomes. The degree of fusion was dependent on the phosphatidylethanolamine content of the vesicles. Addition of CaCl2 to proteoliposomes containing phosphatidylcholine and cardiolipin but without phosphatidylethanolamine did not induce fusion. Fusion of cytochrome oxidase vesicles, containing less than 50 mol% phosphatidylethanolamine resulted in monolamellar vesicles with a diameter of about 200 nm. The vesicles could be induced to fuse further by establishing an osmotic pressure across their membranes. When proteoliposomes containing more than 50 mol% phosphatidylethanolamine were fused, large vesicles with a diameter exceeding 1 micrometer were formed. They appeared in the electron microscope as a mixture of multilamellar and monolamellar vesicles. Fusion of corresponding liposomes resulted in formation of even larger structures appearing as dense multilamellar bodies and paracrystalline honeycomb-like lattices.