NSAID and other analgesic use by endurance runners during training, competition and recovery

Background. An increasing popularity of ultra-endurance events coupled with excessive or inappropriate non-steroidal anti-inflammatory drug (NSAID) use during such events could pose considerable potential risks to runners’ health.Objective. To evaluate the incidence of NSAID and other analgesic use in distance runners during training, competition and recovery.Methods. We performed an observational cross-sectional study at the Desert Race Across the Sand race (Colorado to Utah, USA) in June 2011 and the Empire State Marathon half-marathon, and relay races in Syracuse, NY, October 2011. A total of 27 ultramarathon runners and 46 marathon, half-marathon and marathon relay runners participated in the study. Surveys were distributed to runners during race registration. Self-reported use of common analgesic medications during training, racing and recovery was assessed.Results. Among all runners at all stages, NSAIDs were the most commonly used analgesic medication. NSAID use by ultramarathon runners compared with all other runners was similar during training (59% and 63%, respectively; χ2=0.008; p=0.93) and recovery (59% and 61%, respectively; χ2=0.007; p=0.93). However, ultramarathon runners were more likely than all other runners to use NSAIDs during the race (70% and 26%, respectively; χ2=11.76; p=0.0006).Conclusion. Despite undesirable side-effects associated with the use of NSAIDs, there was a high prevalence of use in all runners, particularly during training and recovery. NSAID use during the race was significantly greater in ultramarathon runners. Medical staff at endurance events need to be aware of, and prepared for potential complications related to the high use of NSAIDs in runners. Future efforts should focus on teaching runners about the undesirable effects of medication and emphasising alternatives to pain medication.

NSAID and other analgesic use by endurance runners during training, competition and recovery

Background. An increasing popularity of ultra-endurance events coupled with excessive or inappropriate non-steroidal anti-inflammatory drug (NSAID) use during such events could pose considerable potential risks to runners’ health.Objective. To evaluate the incidence of NSAID and other analgesic use in distance runners during training, competition and recovery.Methods. We performed an observational cross-sectional study at the Desert Race Across the Sand race (Colorado to Utah, USA) in June 2011 and the Empire State Marathon half-marathon, and relay races in Syracuse, NY, October 2011. A total of 27 ultramarathon runners and 46 marathon, half-marathon and marathon relay runners participated in the study. Surveys were distributed to runners during race registration. Self-reported use of common analgesic medications during training, racing and recovery was assessed.Results. Among all runners at all stages, NSAIDs were the most commonly used analgesic medication. NSAID use by ultramarathon runners compared with all other runners was similar during training (59% and 63%, respectively; χ2=0.008; p=0.93) and recovery (59% and 61%, respectively; χ2=0.007; p=0.93). However, ultramarathon runners were more likely than all other runners to use NSAIDs during the race (70% and 26%, respectively; χ2=11.76; p=0.0006).Conclusion. Despite undesirable side-effects associated with the use of NSAIDs, there was a high prevalence of use in all runners, particularly during training and recovery. NSAID use during the race was significantly greater in ultramarathon runners. Medical staff at endurance events need to be aware of, and prepared for potential complications related to the high use of NSAIDs in runners. Future efforts should focus on teaching runners about the undesirable effects of medication and emphasising alternatives to pain medication.

Multisite randomised controlled trial to evaluate polypropylene clips applied to the breech of lambs as an alternative to mulesing. I: effects on body weight, breech bare area measurements and scores, wrinkle scores and faecal and urine staining

OBJECTIVE

 To assess the effects of application of occlusive polypropylene clips to lambs on body weight, breech bare area measurements and scores, wrinkle scores, and faecal and urine stain scores.

PROCEDURES

 A randomised controlled trial using 32,028 lambs was conducted on 208 properties across Australia. Polypropylene clips were applied at lamb marking. At each site, 160 lambs were weighed, measured for breech bare area and scored for bare area, wrinkle, dag and urine staining, and skin type and thickness. Lambs were allocated to a control (no clips) or treatment (breech and tail clips) group. Lambs were assessed on days 14 (range 10-19) and 55 (range 34-129) after clip application for body weight, breech bare area measurements and scores. On day 55 the operators also scored wrinkling and urine staining.

RESULTS

 At an average of 55 days after treatment, treated ewe and wether lambs had 16% and 21% greater horizontal bare area measurements, and 31.7% and 32.7% higher bare area scores than control lambs, respectively. The ewes and wether lambs also had lower wrinkle (6.8% and 5.8%, respectively) and dag scores (12% and 12.3%, respectively) than controls. Treated ewes had lower urine stain scores (18.8%) than controls. However, body weight was slightly lower in clip-treated lambs compared with controls by 0.320 kg (1.2%) and 0.430 kg (1.6%) for ewes and wethers, respectively.

CONCLUSION

 Polypropylene clips applied to the breech and tail of lambs increased breech bare area and reduced dag, urine and wrinkle scores. Improvements in these measures of factors that predispose to blowfly strike suggest that the application of clips may reduce the risk of breech flystrike.

Effect on the breech and tail characteristics of Merino lambs of varying the duration of application of occlusive plastic clips as an alternative to mulesing

OBJECTIVE

The objective of the study was to determine the minimum duration of clip application required to increase the size of the perineal and tail bare areas and reduce breech wrinkle, dag or urine stain scores of Merino lambs.

METHOD

The study was conducted on a single farm in western New South Wales using 491 unmulesed lambs of a plain body type (9-14 weeks of age; mean (±SD) bodyweight 26.9 ± 5.0 kg; 82% wrinkle score 1 or 2) randomly allocated into 10 groups. Groups 1-9 included 39-46 lambs treated with the clips, which were removed at 1-7, 10 or 14 days, respectively, after application. Group 10 comprised 53 lambs that were unclipped, unmulesed controls. Visual scores, bare area measurements and bodyweights were assessed before and at 28 and 60 days following clip application.

RESULTS

Clips increased the size of the perineal and tail bare areas if left on the lambs for a minimum of 4-6 days. The increases in the size of the perineal and tail bare areas were similar to the results of previous studies. This indicates that the clips performed as expected, despite the current study being conducted on lambs with a plain body type.

CONCLUSION

When used as an alternative to mulesing, clips should remain on lambs for a minimum of 4-6 days to effectively increase the size of the perineal and tail bare areas. Further research is required to determine the degree of protection against flystrike provided by the clip method.

Insights into mechanisms of intracellular protein turnover from studies on pinocytosis

Pinocytosis is a widespread phenomenon and involves the internalization of large amounts of plasma membrane. Much of this membrane is probably returned to the plasma membrane in vesicular form, and reasons are advanced why this recycling may occur chiefly before pinosome--lysosome fusion and may be related to vacuole fusion events. Some internalized membrane must nevertheless enter the lysosomal compartment and, in order to maintain a steady state, must be removed at the same rates as it enters. This constant lysosomal involution probably occurs by the budding of vesicles either inward (for digestion) or outward (for return to the plasma membrane). The former process allows for the transfer of cytosol components into the lysosome. Quantitative studies on pinocytosis have shown that selective substrate capture is commonly achieved by the adsorption of substances to the plasma membrane being internalized. In contrast the basal rate of uptake of liquid and membrane is not easily modified. If similar considerations apply to uptake by the quasi-pinocytic lysosomal involution, modification of proteins leading to adsorption to the cytoplasmic face of the lysosome could be the rate-determining step in the degradation of endogenous cytoplasmic proteins by lysosomes.

Recovery of Mycobacterium avium subsp. paratuberculosis from nematode larvae cultured from the faeces of sheep with Johne's disease

A study was conducted to determine whether trichostrongylid nematode larvae become contaminated with Mycobacterium avium subsp. paratuberculosis when they develop in the faeces of sheep with Johne's disease. Nematode larvae were hatched from ova in the faecal samples of affected sheep. Larval sheaths were removed and these as well as exsheathed larvae were subjected to radiometric culture for M. paratuberculosis. The organism was recovered from washing water used to prepare the larvae, third stage larvae and larval sheaths, but not from exsheathed larvae. The recovery of M. paratuberculosis from larvae was associated with the severity of the histological lesions in affected sheep and with the results of culture of the organism from intestinal tissues and faeces. Nematode parasites of sheep might be able to act as mechanical vectors for M. paratuberculosis as the organism associates with infective third stage larvae when these develop in the faeces of sheep with Johne's disease.

Presence of Mycobacterium avium subspecies paratuberculosis in suspensions of ovine trichostrongylid larvae produced in faecal cultures artificially contaminated with the bacterium

A reference strain of Mycobacterium avium subspecies paratuberculosis was added to faecal larval cultures of Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis. Samples of the larvae produced were cultured for the presence of the bacterium in modified BACTEC 12B medium, both before and after exposure to gamma irradiation. The water used to wash the larvae off the faecal cultures was also tested for the presence of the bacterium. Positive growth was confirmed as M. avium subspecies paratuberculosis by IS900 polymerase chain reaction and restriction endonuclease analysis of the product. M. avium subspecies paratuberculosis was detected in the unirradiated larval suspensions and wash waters of all three nematode species, and in the irradiated H. contortus larval suspension.

Evaluation of a laboratory test to detect resistance to closantel in Haemonchus contortus

OBJECTIVE

To evaluate a laboratory test for closantel resistance in Haemonchus contortus.

PROCEDURE

Field isolates of H contortus, known to be resistant to closantel, were tested in the assay. In addition, mixtures of closantel-susceptible and closantel-resistant laboratory reference strains were tested to develop a method of predicting the proportion of resistant worms in a sample from the field.

RESULTS

The assay correctly identified as resistant all of the closantel-resistant field isolates of H contortus. It also identified one isolate with an in vivo efficacy of 98% as having emerging resistance. Testing of the mixtures of laboratory reference strains revealed that an isolate would be classified as resistant when it consists of about 25% or more resistant worms. Test samples that are not fully susceptible yet contain less than 25% resistant worms may be classified as emerging resistance.

CONCLUSION

The in vitro migration assay is a sensitive method of detecting closantel resistance in H contortus.

In vivo T-cell subset depletion suggests that CD4+ T-cells and a humoral immune response are important for the elimination of orf virus from the skin of sheep

In vivo lymphocyte subset depletion offers a unique opportunity to study the roles of different cellular components of the immune system of sheep during infection with orf virus. Lambs were depleted of specific lymphocyte subsets by the intravenous administration of monoclonal antibodies against ovine lymphocyte surface markers and then challenged with orf virus. The skin lesions that developed were scored visually as to their severity. Blood samples were collected to monitor the lymphocyte depletions and to measure orf-virus-specific antibody levels. Skin biopsies were collected from the lesion site and studied to determine the course of the infection and the presence of various cell types and orf virus. All the sheep developed orf virus lesions after infection. All three of the CD4-depleted lambs were unable to clear virus from their skin and did not have an antibody response to the virus. Virus was also detected in the skin of one each of the three CD8-depleted, WC1-depleted and control sheep on the final day of the trial. CD8(+) lymphocytes did not appear to be essential for viral clearance later in the infection. Depletion of the majority of gammadelta(+) T-cells did not affect the outcome of orf virus infection. In sheep with high orf-virus-specific antibody titres at the time of infection, orf lesions healed faster than lesions in sheep with low antibody levels, and this occurred regardless of the lymphocyte depletion status of the animals. This study suggests that the presence of CD4(+) T-cells and orf-virus-specific antibodies are important for the control of viral replication in the skin of infected sheep.

Lysosome membrane permeability: implications for drug delivery

The membrane of the lysosome contains substrate-specific porters for a wide range of metabolites. Their physiological role is in promoting the efflux of the products of intralysosomal catabolism. With few exceptions, the specificity of these porters makes them unlikely candidates for the translocation of xenobiotics across the lysosome membrane. Where efflux from the lysosome is possible, it is likely to be accomplished by passive diffusion. Experimental studies on passive diffusion across the lysosome membrane have shown that its characteristics are similar to those of other biological membranes. Ease of permeation decreases with increasing hydrophilicity. Macromolecules and some highly hydrophilic molecules as small as sucrose are effectively non-permeant. The notional hydrogen-bonding capacity of molecules (an inverse correlate of oil:water partition coefficient) has been found a good predictor of permeance. Predictions of ease of permeation across lysosome membranes is of value when drug delivery strategies are contemplated that involve a drug-conjugate reaching the lysosome compartment and drug release there by the lysosomal enzymes. These strategies will be unsuccessful if the drug is unable to leave the lysosome and reach the cellular sites where its pharmacological action is required.

Radiolabeling, stability, and body distribution in rats, of low molecular weight polylactide homopolymer and polylactide-polyethyleneglycol copolymer

In order to study its fate in vivo, a low molecular-weight polylactide homopolymer was derivatized with a p-methoxyphenyl moiety, so as to make it susceptible to radiolabeling with 125I. A low molecular weight polylactide-polyethyleneglycol copolymer capped with ap-methoxyphenyl residue was also synthesized. The derivatized polymers were successfully [125I]iodinated in organic medium. The radiolabeled products were freed from [125I]iodide by dialysis and shown to be stable for 24 h on incubation at 37 degrees C in buffered saline or in blood. On longer incubation at 37 degrees C in buffered saline the radiolabeled polylactide released [125I]iodide and [125I]iodinated 3-(p-methoxyphenyl)propionic acid. The radiolabeled copolymer was more stable on incubation at 37 degrees C in buffered saline, but some [125I]iodide was released. The tissue distribution of radioactivity was determined 5 min, 1, 5 and 24 h after injecting male rats with 125I-labeled homopolymer or copolymer. Intravenous, intraperitoneal and subcutaneous injection routes were employed. Further rats were injected with [125I]iodide, to aid interpretation of the data. After administration of labeled homopolymer, a high concentration of radioactivity was found in the liver tissue. The levels slowly decreased over 24 h, and the polymer was successively found in the small and large intestine and the faeces. This is probably indicative of excretion via the bile. Concurrently radioactivity was excreted in the urine. After administration of labeled copolymer, a high concentration of radioactivity was found in the liver and the residual soft tissue, the latter fraction containing two-thirds of the radioactivity one hour after injection. The precise tissue location that this result indicates was not identified. After 1 h radioactivity was excreted in the faeces, again probably via the bile, and in the urine. Tissue distributions after intraperitoneal or subcutaneous injections were concordant with the above results and interpretations, with the additional factor of slow clearance from the injection site.

Effects of methionine supplement on methionine incorporation in rat embryos cultured in vitro

The effect of supplementary L-methionine (Met) on the incorporation of methionine was evaluated in 9.5-day rat conceptuses cultured in vitro. Parallel experiments with L-leucine (Leu) were performed for comparison. Conceptuses were cultured for 24 hr in the presence of 3H-labeled Met or Leu, and the incorporation of radiolabel into the embryo and visceral yolk sac was measured. Supplementary Met proportionately increased the incorporation of Met, but supplementary Leu did not have as great an effect on the incorporation of Leu. A hypothesis is presented to explain these findings. It is proposed that Met, but not Leu, is a rate-limiting nutrient for organogenesis-stage rat embryos cultured in rat serum. The results are also discussed with reference to the established efficacy of supplementary folic acid in decreasing the incidence of neural tube defects in human populations and to claims that Met reverses certain teratogenic phenomena, both in vitro and in vivo.

Cellular uptake and release of two contrasting iron chelators

Desferrioxamine and CP94 (1,2-diethyl-3-hydroxypyridin-4-one) are metal chelators used or proposed for use in the clinical treatment of iron overload. Recent data on their capacity to deplete intracellular iron led to the conjecture that the differences observed arose from the different membrane-penetration properties of the two compounds. The time-course of accumulation and subsequent release of [14C]CP94 by the rat visceral yolk sac in-vitro was compared with that of [14C]desferrioxamine and for 125I-labelled poly(vinylpyrrolidone), a marker for fluid-phase endocytosis. The results indicate that [14C]CP94 crosses the plasma and lysosome membranes rapidly whereas [14C]desferrioxamine and 125I-labelled poly(vinylpyrrolidone) are effectively incapable of crossing these membranes, entering cells only by endocytosis. It is concluded that although CP94 readily enters and leaves cells, desferrioxamine has the potential to accumulate to high concentration in the lysosomes and complex with intralysosomal iron. The results support and extend the proposed correlation between pharmacological activity and capacity for membrane penetration.

Bisphenols that stimulate cells to release alkali metal cations: a structure-activity study

The laxative action of phenolphthalein (5) is believed to result from induction of potassium and water efflux from the colon epithelium. In cultured cells, K+ efflux is promoted by 5 and by a contaminant (1) present in commercial phenol red. Six compounds with chemical structures related to those of 5 and 1 were tested for ability to induce the release of 86Rb from COS-7 cells preloaded with this isotope: 4,4'-(9-fluorenylidene)diphenol (2), 4, 4'-(9-fluorenylidene)dianiline, 4, 4'-(9-fluorenylidene)bisphenoxyethanol, 1,1'-bi-2-naphthol, 4, 4'-biphenol, and bis(4-hydroxyphenyl)methane. With one exception these compounds were all inactive at a concentration of 10 microM. However, 2 caused profound 86Rb efflux at concentrations as low as 100 nM. Concentrations of 5 1-2 orders of magnitude higher were needed to achieve similar levels of activity. The three compounds known to be active in this experimental system share a common feature that is absent in all the inactive compounds: a five-membered ring structure, one of whose carbon atoms is disubstituted with p-hydroxyphenyl residues. Because 2 and 5 are readily available, comparative studies on the mechanism of action of these biphenols at the cellular level can now be undertaken.

Lysosome membrane permeability to anions

The permeability of rat liver lysosomes to some inorganic and aliphatic organic anions was investigated, using an osmotic-protection methodology. Lysosomes were incubated at 25 degreesC in 250 mOsm solutions of potassium salts of the anions, in the presence of valinomycin, and the latency of lysosomal hexosaminidase measured at intervals. Lysosomes suspended in 250 mM sucrose at 25 degreesC were stable for up to 4 h. When suspended in 250 mOsm solutions of potassium salts of inorganic acids, latency was lost at rates indicating anion permeance decreasing in the order thiocyanate, nitrate and iodide>bromide>chloride>sulfate. This rank order does not correspond with the anion selectivity of any known anion transporter, and is closer to that of the lyotropic series. Results with the potassium salts of aliphatic organic acids indicate little correlation between permeation and hydrocarbon chain length, although formate was more rapidly permeant than acetate and its higher homologs. By contrast, oxalate was less permeable than other dicarboxylic acids. The presence of one or more hydroxy groups decreased permeance. A correlation between permeance and the acid's lowest pKa suggested that penetration was due principally to the entry of the undissociated acid, but there is evidence that the (much more abundant) singly charged anionic form is also significantly permeant.

Effects of polyethyleneimine on endocytosis and lysosome stability

Polyethyleneimine (PEI) is shown to destabilize isolated rat liver lysosomes, as indicated by a decrease in the latency of their acid N-acetyl-beta-glucosaminidase. PEI also inhibited the generation of radiolabeled digestion products from 125I-labeled bovine serum albumin endocytosed by rat visceral yolk sac in vitro. However, PEI did not greatly inhibit the endocytic uptake of a nondigestible fluid-phase substrate, fluorescein isothiocyanate (FITC)-dextran. It is hypothesized that PEI inhibits the adsorptive endocytosis of 125I-labeled bovine serum albumin, and thus its subsequent intralysosomal digestion, by competing with and displacing the labeled protein from its binding sites on the visceral yolk sac cell surface. This hypothesis suggests a plausible explanation for the ability of PEI to act as an efficient vector for gene and oligonucleotide transfer into mammalian cells. PEI present in the culture medium is carried into cells by adsorptive endocytosis. Concentrated thus on the endosome membrane, it permeabilizes this membrane and so affords DNA conjugated to the PEI an otherwise unavailable mode of access into the cytoplasm.

Intestinal permeability to polyethyleneglycol and sugars: a re-evaluation

1. Previous studies have indicated that the permeability of polyethyleneglycol across the human intestine is anomalously high in comparison with the permeability of sugars with similar molecular mass. In consequence it has been proposed that two or more distinct mechanisms must exist for the translocation of these classes of molecule or, alternatively, that the molecular parameter determining rate of penetration is each molecule's minimum molecular dimension. 2. The notional hydrogen-bonding capacity of a molecule correlates well with oil-water partition coefficient and also, in a variety of experimental systems, with rate of passive diffusion across biological membranes. A molecule's hydrogen-bonding capacity is calculated by inspecting the structural formula and summing the individual theory-derived hydrogen-bonding capacities of the molecule's functional groups. 3. A classic set of intestinal permeability data that includes several ethyleneglycol oligomers and several sugars is re-analysed. A good correlation between permeability and hydrogen-bonding capacity is demonstrated. Specifically, there is no discontinuity between the polyethyleneglycols and the sugars. The data are compatible with a simple model in which all the molecules studied cross the intestine by passive diffusion across cellular membranes.

Lysosome membrane permeability to amines

The permeability of rat liver lysosomes to xenobiotic organic compounds possessing nitrogen functions was investigated, using an osmotic-protection methodology. It was first shown that rat liver lysosomes are stable for at least one hour when incubated in 250 mM sucrose within the pH range 5 to 9. Primary and tertiary amines with pKa values within this pH range, and with differing numbers of aliphatic hydroxy or ether groups, were chosen for study and their permeability investigated at a range of pH values. The results indicate that uncharged amines can cross the lysosome membrane, and that the permeability of such molecules can be predicted from their total hydrogen-bonding capacity. The notional hydrogen-bonding capacity of an uncharged tri-substituted nitrogen with no attached hydrogen atom, as in pyridine or in a tertiary aliphatic amine, is deduced to be approximately 1, and that of an uncharged primary amine approximately 2. A hydrogen-bonding capacity of at least 11 is deduced for cationic nitrogen, implying that most if not all molecules containing a charged nitrogen atom cannot cross the lysosome membrane by passive diffusion. The implications for lysosome physiology and pharmacology are discussed.

Uptake of microparticles by rat visceral yolk sac

The visceral yolk sac (VYS) is responsible for a major part of the amino acid nutrition of the early post-implantation rat embryo and possibly also at the fetal stage of gestation. The mechanism involves endocytic uptake of proteins by the tissue's epithelial cells followed by intralysosomal digestion to amino acids. The amino acid so generated are used for protein synthesis in both the embryo and the VYS. Previous reports had indicated that the endocytic capacity of the VYS might be limited to exclude larger macromolecules. This study demonstrates that Percoll, which comprises 30-nm silica particles coated with polyvinylpyrrolidone (PVP), is as effectively captured by the 17.5-day rat VYS cultured in vitro as PVP itself. Uptake of 125I-labelled Percoll was progressive with time over 5 h and was inhibited by a low incubation temperature, 2,4-dinitrophenol (50 micrograms/ml), EGTA (5 mM), colchicine (10 micrograms/ml) or cytochalasin B (10 micrograms/ml). After uptake of 125I-labelled Percoll, VYSs released only 20 per cent of their radioactivity when re-incubated in fresh medium for 3 h. These data, and electron micrographs showing Percoll in intracellular vacuoles, are all consistent with uptake by endocytosis. Percoll's rate of uptake by the VYS indicates that, like 125I-labelled PVP, it enters the cell chiefly by fluid-phase pinocytosis. It is concluded that endocytosis by the VYS will efficiently capture even the largest globular proteins, and that previous indications of a relatively low size exclusion reflected the loosely coiled configuration of the synthetic polymers used in the earlier studies.

Uptake and processing of 59Fe-labelled and 125I-labelled rat transferrin by early organogenesis rat conceptuses in vitro

The delivery of iron to the early organogenesis rat embryo has been studied, using 59Fe- and 125I-labelled rat transferrin. Rat conceptuses at 9.5 days postconception were cultured for 27 or 51 h in whole rat serum. Rat transferrin labelled with 59Fe was added for the final 0.1, 0.5, 6, 24 or 48 h of culture. Radioactivity accumulated progressively in both the embryo and the visceral yolk sac. Similar results were obtained when unconjugated 59Fe3+ was added to the rat serum used as culture medium. Both acid-soluble and acid-insoluble 59Fe were substantially present in the embryo and yolk sac after all exposure periods. When conceptuses were cultured in the presence of 125I-labelled rat transferrin, acid-soluble radioactivity was progressively released into the culture medium, but accumulation into the embryo and visceral yolk sac was slight and did not change with duration of exposure to the labelled protein. Similar findings were obtained using 125I-labelled bovine serum albumin. In these experiments, there was a close correspondence between the amount of iron accumulated by the embryo and visceral yolk sac in the final 24 h of a 51-h culture and the amount of transferrin converted into acid-soluble products in the same period. Visceral yolk sacs from 17.5-day pregnant rats were explanted and cultured in the presence of 59Fe-labelled rat transferrin, 125I-labelled rat transferrin or 125I-labelled bovine serum albumin, for periods up to 3 h. Again uptake of 59Fe increased with time of incubation, and the 125I-labelled proteins were digested to acid-soluble products which were released into the culture medium. The results indicate that transferrin delivers iron for incorporation into both the embryo and the visceral yolk sac, and are consistent with a mechanism involving receptor-mediated endocytosis of iron-laden transferrin by the cells of the visceral yolk sac. The transferrin itself appears to be quantitatively degraded, following delivery of iron to the yolk sac cells, a result that differs from findings in other cell types, in which the protein is not degraded but returns to the plasma membrane to participate in further cycles of iron acquisition and delivery.

Investigations into mechanisms of amino acid supply to the rat embryo using whole-embryo culture

The technique pioneered by D.A.T. New for the in vitro culture of early post-implantation rat embryos has been used to study nutritional mechanisms during early organogenesis. The results indicate that the principal route for amino acid supply to the 8.5- to 11.5-day embryo involves the endocytosis of proteins into cells of the visceral yolk sac endoderm, their digestion in lysosomes, and transmission of the amino acids to the growing embryo. Free amino acids constitute a comparatively unimportant source. Inhibition of either endocytosis or intralysosomal proteolysis diminishes amino acid supply to the embryo, and this can result in embryonic death or maldevelopment during organogenesis.

Leucine sources for the rat fetus

Fetal and maternal plasma were assayed for the concentration of free leucine, acid-insoluble radioactivity and acid-soluble radioactivity at intervals after an intravenous bolus injection of [3H]leucine into anaesthetized pregnant rats at 17.5 days post-conception. The concentrations of total free leucine and of free [3H]leucine in maternal and fetal plasma were effectively unchanged from 5 to 180 min post-injection. Plasma free leucine concentrations in the fetus were five times those in the mother. The concentration of free [3H]leucine in fetal plasma was similar to that in maternal plasma. Thus the specific radioactivity of free leucine in fetal plasma is substantially lower than that in maternal plasma, indicating that a significant portion of the free leucine in plasma of the 17.5-day rat fetus comes from a source other than the free leucine in the maternal plasma. The data are consistent with a major contribution of amino acids coming from the degradation of extraembryonic protein in the yolk sac. Other possible sources of unlabelled leucine are discussed.

Sources of amino acids for protein synthesis during early organogenesis in the rat. 3. Methionine incorporation

Rat conceptuses at 9.5 days post-conception were cultured for 27 h in whole rat serum. [3H]Methionine, or rat serum proteins containing [3H]methionine, was introduced at 24 or 6 h before the termination of the culture. The total clearance of radioactivity into the embryo and the visceral yolk sac from the two sources was measured; also the extent to which the accumulated radioactivity was acid-insoluble. Similar experiments, but using [3H]leucine, were performed for comparison. The results indicate that free amino acid and protein can both serve as sources of amino acids for incorporation into the embryo and yolk sac, and it is estimated that in vivo over 95 per cent of the methionine (and the leucine) incorporated into these tissues arises from protein captured and digested by the yolk sac. Almost all the leucine accumulated into the conceptus is present as protein, but a larger fraction of the methionine accumulated is found in acid-soluble form. When the amino acids were delivered in the form of plasma proteins, the incorporation of methionine was two to three times more efficient than that of leucine, an observation most readily explained by leucine being provided in excess of requirements. In the light of reports that an adequate concentration of free methionine is important for the normal development of rat embryos in vitro, it is concluded that, although most of the amino acid required by the embryo is supplied as protein, the small fraction supplied as free amino acid may be critical for methionine but probably not for leucine.

Sources of amino acids for protein synthesis during early organogenesis in the rat. 4. Mechanisms before envelopment of the embryo by the yolk sac

It was previously shown that uptake and digestion of protein by the visceral yolk sac supplies almost all of the amino acid needed by the 9.5-11.5-day rat conceptus cultured in vitro. Our aim was to test the hypothesis that protein uptake and digestion may not be as important as an amino acid source in the 8.5-9.5-day period, a stage of development before the yolk sac placenta envelops the embryo and before the vitelline circulation is established. Eight and a half-day rat conceptuses were cultured in serum supplemented with trace amounts of free [3H]leucine, [3H]leucine-containing serum proteins, free [3H]methionine or [3H]methionine-containing serum proteins. The incorporation of radiolabelled amino acid into acid-soluble and acid-insoluble fractions of the conceptus was determined. Leucine from either source was incorporated principally into proteins of the conceptus, but a greater proportion of the methionine incorporated was found in the low molecular weight fraction. It is estimated that 88 per cent of the leucine and 96 per cent of the methionine used by the conceptus was derived from protein in the culture serum; free amino acid comprised a minor supply source. We conclude that, despite the different anatomic relationships, the majority of amino acid incorporated into newly synthesized proteins of the conceptus very early in organogenesis is supplied by the digestion of protein in extraembryonic tissue, most likely the visceral yolk sac.

In vivo depletion of T-cells and cytokines during primary exposure of sheep to parasites

This study examined the role of CD8+ and WC1+ T-cells and of interferon (IFN)-gamma in the development of protective immunity against infection with the enteric nematode parasite Trichostrongylus colubriformis in sheep. Monoclonal antibodies (mAb) were administered during induction of the immune response to deplete or neutralise these components. Protection against the primary and challenge infections was assessed by faecal egg count and total worm count. Prolonged administration of mAb recognising IFN-gamma and CD8 resulted in significantly increased protection during the 6 week primary infection and following challenge. CD8+ cells were depleted from blood but not from intestinal mucosa. After injection of mAb (CC15) recognising the surface antigen WC1, WC1+ and Tcr gamma delta + cells were depleted from blood but not markedly from enteric mucosa, and protection against challenge, although variable, was increased by up to 88%. It appears that CD8+ and WC1+/gamma delta+ cells and IFN-gamma all retard the potential development of naturally acquired immunity against the parasite.

Depletion of IFN-gamma, CD8+ or Tcr gamma delta+ cells in vivo during primary infection with an enteric parasite (Trichostrongylus colubriformis) enhances protective immunity

In order to examine the role of CD8+ and WCI+ T cells and of IFN-gamma in the development of protective immunity against infection with the enteric nematode parasite Trichostrongylus colubriformis in sheep, mAb were administered during induction of the immune response to deplete or neutralize these components. Protection against the primary and challenge infections were assessed by faecal egg count and total worm count. Prolonged administration of mAb recognizing IFN-gamma and CD8+ resulted in significantly increased protection during the 6-week primary infection. CD8+ cells were depleted from blood but not intestinal mucosa. After injection of mAb (CC15) recognizing the surface antigen WCI, WCI+ and T cell receptor (Tcr) gamma delta+ cells were depleted from blood but not from enteric mucosa, and protection against challenge, although variable, was increased by up to 88%. It appears that CD8+ and WCI+/gamma delta+ cells and IFN-gamma all retard the potential development of naturally-acquired immunity against the parasite.

Glycogen metabolism in the rat visceral yolk sac. 2. Activity of glycogen-degrading enzymes

In an attempt to explain the previous observation of the rise and subsequent fall in glycogen content of the rat visceral yolk sac during the latter half of gestation, the activities of glycogen phosphorylase, glucose-6-phosphatase and lysosomal alpha-glucosidase were measured. Glycogen phosphorylase was found to be present in the yolk sac and, as in adult rat liver, was predominantly in the 'a' (active) form. The specific activity of the enzyme was lower than in adult rat liver, when expressed per mg tissue protein or per mg tissue wet weight, but similar when expressed per mg tissue glycogen. Phosphorylase activity in yolk sac was similar at 16.5 and 18.5 days of gestation. Glucose-6-phosphatase activity was not detectable in the yolk sac at either 15.5 or 18.5 days of gestation. Two lysosomal enzymes, acid alpha-glucosidase and N-acetyl-beta-hexosaminidase, were shown to be present in the yolk sac at higher specific activity than in adult liver. Alpha-Glucosidase activity in yolk sac was similar at 15.5 and 18.5 days of gestation. It is concluded that the net degradation of yolk sac glycogen initiated around 18.5 days of gestation does not serve to provide glucose for the fetus, and may indicate an increased demand for metabolic energy within the yolk sac itself.

The effect of storage on immunophenotyping of sheep peripheral blood lymphocytes by flow cytometry

We have shown that when a whole blood method of cell staining is used for flow cytometric analysis of sheep lymphocytes (i.e. red cell lysis after addition of antibody), staining may be delayed for up to 48 h after blood collection without significant effect on expression of CD4, CD5, CD8 or B cell markers. If cells were stained immediately after blood collection, using the same whole blood method, and then fixed with paraformaldehyde, cell samples could be stored for 24 h without change in marker expression. However, by 7 days there was a significant decrease in the percentage of cells expressing CD8, T19 and B cell markers. Cryopreservation prior to staining was found to markedly affect the expression of all cell surface markers investigated. These results indicate that storage of sheep blood prior to flow cytometric analysis is feasible but may affect the results obtained. Thus is it important to standardise the handling of samples, especially when comparative studies are being undertaken.

Mechanism of lysosome rupture by dipeptides

Low concentrations of some neutral dipeptides, such as L-Ala-L-Ala, rapidly disrupt rat liver lysosomes. The phenomenon has been attributed to an osmotic imbalance generated by the production of amino acids in the lysosome by lysosomal dipeptidase activity. This hypothesis is challenged by testing several pairs of dipeptides available in both D- and L-forms and a range of dipeptides whose susceptibility to lysosomal dipeptidase activity is known. A good correlation was found between the lytic ability of dipeptides and their capacity to cross the lysosome membrane and be hydrolysed by lysosomal dipeptidase. The osmotic-imbalance hypothesis is critically evaluated in the light of the results and of recent information concerning the carrier-mediated transport of amino acids and dipeptides across the lysosome membrane. It is concluded that intralysosomal generation of amino acids remains the most plausible explanation of the lytic activity of dipeptides, and that the dipeptide porter(s) in the lysosome membrane must have higher Km than the amino acid porters.

Amino acid requirements in the early post-implantation rat conceptus

Amino acid analysis has been performed on hydrolysates of embryos/fetuses, visceral yolk sacs and ectoplacental cones/placentae from early post-implantation rat conceptuses. The increments in each amino acid between 10.5 and 11.5 days, between 11.5 and 12.5 days, and between 12.5 and 13.5 days, are expressed as percentages of the total amino acid increment. These three profiles are very similar to each other and also strongly resemble the amino acid composition of hydrolysates of rat serum. The results are discussed in the context of the hypothesis that a transudate of plasma is responsible for the amino acid nutrition of the embryo at this stage of gestation, and that inhibition of this pathway can lead to the induction of congenital defects. The results suggest that an inhibition of pinocytosis or lysosomal proteolysis would affect the supply of all protein-derived amino acids to approximately the same extent: there is no indication that the supply of any particular amino acid would be particularly vulnerable.

Pinocytosis in the rat visceral yolk sac: potential role in amino acid nutrition during the fetal period

At 9.5 to 10.5 days post-conception (p.c.) the rat embryo receives amino acids primarily by pinocytosis of maternal proteins by the visceral yolk sac (VYS) endodermal cells and their subsequent digestion in lysosomes. As this mechanism may also contribute to the nutritional support of the rapidly growing fetus later in gestation, this study determines the potential of the VYS to contribute to the amino acid needs of the rat fetus on 13.5, 15.5 and 17.5 days p.c. Wistar rats were killed on 11.5, 13.5, 15.5, 17.5 and 19.5 days p.c. and the protein content of fetuses, VYSs and serum was determined. Additional VYSs were isolated on the same days p.c. and the uptake of [14C]sucrose, a measure of fluid-phase pinocytosis, was determined. The rate of protein accretion by the fetus and the capacity of the VYS to pinocytose and digest proteins were calculated on 13.5, 15.5 and 17.5 days p.c. There was a decrease in pinocytic capacity, per mg protein, over the period of development studied but, owing to the growth of the tissue, the total capacity of the yolk sac to pinocytose and digest proteins increased from 13.5 to 17.5 days p.c. Comparison of the VYSs capacity to pinocytose and digest proteins and the rate of protein accretion by the fetus suggests that the VYS could support a significant proportion of the increase in protein content of the growing fetus. This conclusion is reinforced by the limited capacity of the maternal plasma to supply free amino acids to the fetus.(ABSTRACT TRUNCATED AT 250 WORDS)

Small unilamellar liposomes from mixed natural and polymeric phospholipids: stability and susceptibility to phospholipase A2

The concept of the uncorkable liposome composed of phase-separated mixtures of a polymerized phospholipid and an enzymically digestible phospholipid has been investigated, using small unilamellar vesicles composed of mixtures of (polymerized) dienoylphosphatidylcholine (DENPC) and dimyristoylphosphatidylcholine (DMPC). Mixed liposomes, even those containing only 10% DENPC, were much more stable than DMPC liposomes, as indicated by the release of entrapped [3H]inulin or [14C]glucose. DMPC liposomes released entrapped solute on exposure to phospholipase A2, whereas mixed vesicles were resistant. The results are compared with those of an earlier study on monolayers of similar compositions. It is concluded that the liposomes, like the monolayers, are phase-mixed, and that uncorkable liposomes cannot be constructed from the phospholipid mixture employed. It is proposed that, until further experimental evidence is produced, the enzymatically uncorkable liposome must be regarded as a theoretical construct.

Multiple antigens in the rat visceral yolk sac induce teratogenic antisera

Preparative isoelectric focusing was used to fractionate the supernatant from a homogenate of day 19 rat visceral yolk sac. Three fractions, of pI ranges 3.5-5.0, 5.0-7.0, and 7.0-9.0, were isolated and used to immunize rabbits, by four or six weekly injections, each containing 5 mg protein. The resulting antisera were all teratogenic when injected into rats on day 9 of gestation, but widely differing potencies were observed. The most potent antiserum was that against yolk sac components focusing in the pI 7.0-9.0 range: An optimum teratogenic dose of 50 mg protein per kg body weight was observed, and a dose of 100 mg/kg was shown to cause 100% embryonic resorption. Antiserum against the fraction focusing in the pI 3.5-5.0 range was the least teratogenic: A significant incidence of embryonic malformation and death was seen only at doses of 600 mg/kg and above. The two fractions that yielded the more teratogenic antisera were refocused over narrower pH ranges, yielding four subfractions in the pI 5.0-7.0 range and eight subfractions in the pI 7.0-9.0 range. Antisera against each of these 12 fractions were raised in rabbits; most of these antisera were shown to be teratogenic, although of differing potencies. It is concluded that the yolk sac contains many antigens that can elicit antibodies with teratogenic and yolk sac-localizing properties.

Evidence that desferrioxamine cannot enter cells by passive diffusion

Accumulation of [14C]desferrioxamine by rat visceral yolk sac in vitro has been compared with that of [14C]sucrose, a probe for fluid-phase pinocytosis. Kinetic parameters for both substrates are closely similar, as are the effects of inhibitors. It is concluded from these data, and from theoretical considerations, that desferrioxamine cannot enter cells other than by pinocytosis and that, once internalized, it will remain in the lysosomes. The results indicate the need for a re-evaluation of the pharmacokinetic mechanisms traditionally accepted for the drug's ability to deplete iron from cells and tissues.

Sources of amino acids for protein synthesis during early organogenesis in the rat. 2. Exchange with amino acid and protein pools in embryo and yolk sac

Tenth-day rat conceptuses were cultured in whole rat serum containing [3H]leucine and harvested after 24 or 48 h. Hydrolysates of the acid-precipitable fraction of embryo or yolk-sac homogenates were prepared and subjected to paper chromatography. Liquid scintillation counting of the separated amino acids showed that leucine was the only amino acid with above-background radioactivity. This established that radiolabel was not transferred from leucine to other amino acids in the cultured rat conceptus. Tenth-day rat conceptuses were cultured in whole rat serum containing [3H]leucine, as above. After 19 h, some conceptuses were harvested; other conceptuses were rinsed, transferred to culture medium without [3H]leucine, and after a further 24 h of culture the embryos and yolk sacs were harvested. A comparison of the protein-associated radioactivity of embryo and yolk sac before and after culturing for the further 24-h period showed that these structures quantitatively conserve radiolabelled leucine incorporated into their proteins. Further experiments involved culturing the rat conceptus for 24 h as above but in the presence of either [3H]leucine or [3H]leucine-labelled serum proteins. After harvesting the conceptuses, the specific radioactivity of [3H]leucine was determined in the acid-soluble and acid-precipitable fractions prepared from embryo and yolk-sac homogenates. The specific radioactivity of [3H]leucine in the acid-soluble fraction of embryos or yolk sacs from conceptuses grown in the presence of radiolabelled protein was about 120 per cent of that in the culture medium, while that in the acid-precipitable fractions was about 70 per cent of that in the culture medium. By comparison, the specific radioactivity of [3H]leucine in the acid-soluble fraction of embryos and yolk sacs from conceptuses grown in the presence of free [3H]leucine was only 3-4 per cent of that in the culture medium, while that in the acid-precipitable fraction was about 1 per cent of that in the culture medium. If our data on the fate of leucine incorporated into newly synthesized proteins of the early post-implantation rat embryo can be extrapolated to the other amino acids, they suggest that once amino acids have been incorporated into newly synthesized protein in embryo or yolk sac, they are not exchanged to any detectable extent with amino acid pools outside the conceptus. The results also provide independent confirmation of our earlier conclusion that the only significant source of amino acids utilized by the 10th-day embryo is protein taken up by the yolk sac and digested intracellularly.(ABSTRACT TRUNCATED AT 400 WORDS)

Quantitation of pinocytosis in human monocytes during in vitro maturation into macrophages

Methods are reported for the quantitative measurement of pinocytosis in human monocytes isolated from peripheral blood. The cells, in adherent culture in plastic wells, were exposed for periods of up to 48 h to culture medium containing 125I-labelled polyvinylpyrrolidone (50 micrograms/ml) and the pinocytosis enhancer suramin (500 micrograms/ml). Uptake of radiolabel was linear with time and was inhibited by colchicine (100 micrograms/ml), results that are consistent with uptake of radiolabelled substrate by pinocytosis but not with superficial adsorption of radiolabel. Similar results were obtained using a 125I-labelled vinylamine-vinyl-pyrrolidone copolymer as radiolabelled substrate. The rates of pinocytotic uptake of 125I-labelled polyvinylpyrrolidone (in the presence of suramin) and of 125I-labelled copolymer were measured at various stages of in vitro monocyte-to-macrophage maturation. In contrast to an earlier report, we found no consistent differences in pinocytotic activity between cells at different stages of differentiation.