PubMed Health⌕ Search

Biomedical subjects

R F Sheldrake

Publications and source records attributed to R F Sheldrake.

At least 37 records · Page 2Linked to original sources
PubMed1985

Specific antibody-containing cells in the mammary gland of non-lactating sheep after intraperitoneal and intramammary immunisation.

Ewes were immunised intraperitoneally with ovalbumin and Brucella abortus in Freund's complete adjuvant, followed seven days later by intramammary immunisation in which ovalbumin was presented to one mammary gland and Brucella abortus to the other. Mammary tissue taken after a further seven days contained more antigen-specific plasma cells than ewes given intraperitoneal or intramammary immunisation alone. These cells were found predominantly in the specifically immunised gland and only a few were found in the contralateral gland. Most of these cells were of the IgG1 isotype. There was also an increase in the total number of IgG1- and IgG2-containing cells in mammary gland tissues of these ewes, indicating a non-specific response to immunisation. Following either intraperitoneal or intramammary immunisation there was also a significant increase in the number of antigen-specific IgA cells in the lamina propria of the jejunum. The gut response following intramammary immunisation alone was abrogated by chronic drainage of intestinal lymph but not mammary lymph. This suggests that antigen may relocate from the mammary gland to the intestine where an IgA response is generated from gut associated lymphoid tissue. These data provide evidence for interaction between the gut and mammary gland of sheep in response to antigen.

Animals↗
PubMed1985

The effect of lactation on the transport of serum-derived IgA into bile of sheep.

The effect of lactation on the selective transport of IgA from serum into bile and the relationship between volume of milk production and IgA recovery in bile was examined in sheep following intravenous injection of radiolabelled dimeric IgA. Bile: plasma radioactivity ratios for lactating and non-lactating sheep were 6.20 +/- 1.50 and 1.97 +/- 0.35, respectively, and in lactating sheep the milk : plasma ratio was 8.20 +/- 0.81. When biliary flow rates and milk yield were taken into account, 7.3% and 42.0% of the radiolabelled IgA present in plasma at 1 min after injection was recovered in bile and milk, respectively, of low milk yielding ewes, whereas in high milk yielding ewes, recoveries were 4.0% and 66.0%, respectively. The data suggest that during lactation there is an overall increase in transport of IgA into bile, possibly due to the effect of lactogenic hormones on secretory epithelia, but that there may be competition between hepatocytes and mammary epithelial cells for available serum-derived IgA, depending on the secretory activity of the gland.

Animals↗
PubMed1985

Intestinal uptake of intact maternal lymphocytes by neonatal rats and lambs.

Two experiments were conducted using neonatal rats and lambs. The intestinal lumen of neonatal rats was infused with radiolabelled syngeneic lymphocytes, whereas the intestine of lambs was infused with radiolabelled allogeneic maternal lymphocytes. The results of both experiments indicated that radiolabelled cells were absorbed by the intestine as judged by autoradiographic studies of intestinal tissue. Furthermore, in lambs it was possible to show that these cells were transported via the lacteal lymph ducts to the mesenteric lymph nodes. These findings suggest another mechanism by which the lactating ewe may confer immunity to its suckled young.

Animals↗
PubMed1985

The effect of intraperitoneal and intramammary immunization of sheep on the numbers of antibody-containing cells in the mammary gland, and antibody titres in blood serum and mammary secretions.

The contribution of gut-associated lymphoid tissue (GALT) to the local response in the mammary gland is well documented in laboratory animals and has been evaluated in this study in ruminants. Ewes were immunized intraperitoneally (IP) with antigen in Freund's complete adjuvant (FCA), a procedure which stimulates the production of antibodies of the IgA class in the intestine, and challenged intramammarily (IMam) either during colostrum formation or mammary gland involution. Despite a substantial IgA antibody-containing cell (ACC) response in the intestine in IP immunized sheep, there was no evidence to suggest a relocation of IgA-specific ACC to the mammary gland. There was, however, an IgA antibody response in mammary secretion of IP immunized animals, regardless of whether the mammary gland was locally immunized, but the origin of this antibody is unclear. IP/IMam immunized sheep did have an enhanced antigen-specific ACC response of the IgG1 isotype in locally immunized glands, but whether these cells were of GALT or systemic origin is also unclear.

Animals↗
PubMed1984

Induction and delivery of mucosal immune responses.

The oral cavity is relatively deficient in lymphoid tissue capable of directing the inductive and effector events required for effective mucosal IgA responses to local antigen. Recent evidence regarding a common mucosal immune system has raised new possibilities in immunization of mucosal surfaces. This review describes the role of the intestine in contributing to responses at distant mucosal sites and in particular emphasizes the immune potential of the intestine in determining the success of immunization strategies to control dental caries.

Antigens, Bacterial↗
PubMed1984

Selective transport of serum-derived IgA into mucosal secretions.

The relative contribution of serum-derived and locally produced IgA has been estimated in sheep mammary secretion at various stages of lactation by comparing the transport of radiolabeled IgA and IgG2 from serum to secretions. During early and mid-lactation, but not during involution, serum IgA was selectively transported to mammary secretion on a large scale; in comparison, there was no transport of serum IgA into intestinal secretion. Estimates of local production indicated that the bulk of the IgA in mammary involution secretion and intestinal secretion was locally produced, whereas there was no evidence for local production of IgA in early or mid-lactation secretion. Our studies reveal an inverse relationship between the extent of local production of IgA by plasma cells underlying secretory epithelia and the selective transport of IgA from serum. This finding suggests that selective transport of serum IgA occurs at a number of mucosal sites, but is dependent on secretory component availability, because where local production is predominant, there are fewer secretory component molecules available for serum IgA transport. For this reason, bile transport of IgA does not represent a unique mechanism for the removal of IgA from serum.

Animals↗
PubMed1983

Lactation stage, parity, and infection affecting somatic cells, electrical conductivity, and serum albumin in milk.

Effects of stage of lactation and parity on cell concentration, electrical conductivity, and serum albumin concentration of milk from quarters of known infection status were examined. For quarters free from infection, somatic cell concentration rose from 80 to 160 x 10(3) cells/ml between 35 and infected with Staphylococcus aureus the increase was from 250 to about 1000 x 10(3) cells/ml. As lactation number advanced, there was little change in cell concentration for quarters free from infection, whereas for quarters infected with Staphylococcus aureus, cell concentration rose from approximately 450 x 10(3) cells/ml for first lactation to about 1500 x 10(3) cells/ml for cows in their sixth or more lactations. Trends in electrical conductivity were similar to those for cell concentration, with the main influence on electrical conductivity being Staphylococcus aureus infection. For serum albumin concentration only the effect os stage of lactation was significant. Concentration of serum albumin rose from 150 mg/liter at the beginning of lactation to 280 mg/liter at 215 days postpartum. Effects of stage and number of lactation were minor compared with effects of infection by Staphylococcus aureus.

Animals↗
PubMed1983

Somatic cell count, electrical conductivity, and serum albumin concentration for detecting bovine mastitis.

Cell concentration, electrical conductivity, and serum albumin concentration of milk were evaluated for predicting infection status of quarters in three herds. Probability of misclassifying quarters was lowest for cell concentration. For discriminating quarters infected with Staphylococcus aureus from quarters free from infection, probability of misclassification for cell concentration ranged from 8 to 20% among herds. For electrical conductivity probability of misclassification ranged between 22 and 32%, whereas for serum albumin the range among herds was from 15 to 48%. Among herds there was also considerable variation of the trait, which minimized the probability of misclassification. Cell concentrations for the three herds were 158, 200, and 251 x 10(3) cells/ml whereas for electrical conductivity counts were 4.6, 5.8, and 6.5 mS/cm. For electrical conductivity and serum albumin comparisons within cow by differences and ratios from different quarters yielded little advantage over absolute estimations. For a single sampling, cell concentration provided the most accurate prediction of quarter infection status. We suggest that 200 x 10(3) cells/ml should be the threshold above which quarters are considered likely to be infected with a major pathogen.

Animals↗
PubMed1982

Investigations into falsely elevated somatic cell counts of bulked herd milk.

Bulk milk cell counts obtained by a Coulter Milk Cell Counter were shown to be falsely elevated because of the formation of non-cellular particles (NCP). The NCP, which were detected by the use of a particle size analyser, were removed if the milk samples were heated to 55 degrees C for 15 min before the addition of formalin. A survey of bulk milk supplies in New South Wales showed that NCP occurred in milk from 2% of farms, the counts being falsely elevated by about 200 000 cells/ml. Surveys of milking equipment of farms where the bulk milk had shown this phenomenon demonstrated a relationship between the use of centrifugal milk pumps and the presence of NCP with a much lower prevalence in herds where spit chamber releasers were used. These particles were not air bubbles since air was removed from the milk by heating to 60 degrees C for 15 min, vacuum at 65 mmHg for 15 min or 0.5% v/v octan-2-ol; only the heat treatment removed the NCP.

Animals↗
PubMed1981

Effect of teat skin disinfection on the rate of infection and interval to infection in cows exposed to high levels of Staphylococcus aureus.

All teats of a herd of lactating cows were contaminated after each milking with Staphylococcus aureus. Two teats of each cow were subsequently dipped in an iodine solution, while the remaining 2 teats were not dipped. For cows with a single infection the interval to infection in dipped and undipped quarters was 64 and 60 d respectively, while for the first infected quarter of cows with multiple infections the interval to infection in dipped and undipped quarters was 50 and 39 d respectively. For the second quarter infected in cows with multiple infections, the period between the first and second infection was 21 and 12 d for dipped and undipped quarters respectively. It is suggested that while teat skin disinfection was effective in reducing the rate of new infection, it had little effect on the process of infection in those quarters becoming infected. The occurrence of an infection in one quarter doubled the rate of infection in the other quarters.

Animals↗
PubMed1981

Relationship of somatic cell count and cell volume analysis of goat's milk to intramammary infection with coagulase-negative staphylococci.

The prevalence of intramammary infection in 4 commercial goat herds was studied in conjunction with electronic somatic cell count and volume analysis determined using a Coutler Counter and volume analyser. Neither streptococci nor mycoplasma were isolated from any half and the prevalence of intramammary infection with Staphylococcus aureus ranged from 0 to 3% between herds. For coagulase-negative staphylococci the range from infected halves was 36-71%. There was no significant difference between the mean total microscopic somatic cell count for halves infected with coagulase-negative staphylococci and those free from infection. A similar trend was observed for electronic somatic cell counts although the mean electronic cell count was greater than the mean total microscopic count on the 2 occasions that they were compared. The correlation coefficients between the 2 cell counting methods were 0.86 and 0.94. Between herds there were significant differences in mean electronic somatic cell count, with herd means ranging from 438 x 103 to 1684 x 103 cells/ml. In 2 of the 4 herds studied, milk samples from halves infected with coagulase-negative staphylococci had a significantly higher prevalence of cell volume distributions with a modal cell volume between 65 mu 3 and 100 mu 3. This was attributed to a higher proportion of polymorphonuclear neutrophils. Use of electronic somatic cell count and cell volume analysis were considered of little value in predicting infection caused by coagulase-negative staphylococci as there was a high proportion of false negative and false positive predictions.

Animals↗
PubMed1981

The detection of mastitis in individual quarters using electrical conductivity or somatic cell concentration.

In this investigation electrical conductivity (EC) and somatic cell concentration (SCC) were compared in 3 herds for their ability to correctly identify the infection status of quarters. For EC, thresholds of 6.0 and 6.8 mS/cm were used and comparisons were made between quarters within each cow. The method of comparison between quarters was the same as that described by the manufacturers of the AHI Mastitis Detector. For SCC a threshold of 500 x 10(3) cells/ml was used. For both EC and SCC considerable variation was found between herds for sensitivity (the proportion of quarters infected with a major pathogen and detected as abnormal), and specificity (the proportion of quarters free from infection and detected as normal). The mean sensitivity and specificity of EC for the three herds was 49% and 79% respectively, whereas for SCC the means were 71% and 81% respectively. The variation in sensitivity and specificity of EC between herds was attributed to differences in the distribution of EC for quarters of similar infection status. It was concluded that these differences in herd EC precluded the use of pre-determined EC thresholds which were applicable for detecting mastitis in all herds.

Animals↗
PubMed1980

Post-milking iodine teat skin disinfectants. I. Bactericidal efficacy.

An iodine teat skin disinfectant tested in lactating cows over a range of concentrations, 100 to 10 000 mg available iodine/l(mgavI/l) was found bactericidally effective against Staphylococcus aureus when containing 1000 mg avI/l or greater. Against Streptococcus dysgalactiae 5000 mg avI/l or greater was bactericidally effective. The addition of glycerine to a disinfectant containing 5000 or 1000 mg avI/l at levels of 225 ml/l and 105 ml/l, respectively, resulted in a reduction in bactericidal efficacy of the disinfectant. Emulsified paraffin added at concentrations of between 50 and 500 ml/l had no effect on the efficacy of the 5000 mg avI/l disinfectant, but the addition of 200 ml/l emulsified paraffin to a 1000 mg avI/l disinfectant significantly reduced its efficiency. Iodine disinfectants containing emulsified paraffin phase separated rapidly during storage, and the bactericidal efficacy of the phases differed significantly and diminished with time.

Animals↗
PubMed1980

Post-milking iodine teat skin disinfectants. 2. New intramammary infection rates.

Use of an iodine teat dip containing 5000 mg available iodine/l (mg avI/l) resulted in a significant reduction in the number of new Staphylococcus aureus infections in a lactating herd, while no significant reduction was found with a disinfectant containing only 1000 mg avI/l. When Streptococcus dysgalactiae was used as the challenge organism, the rate of new infection was extremely low, and no reduction in levels of new infection were found with either disinfectant. The pathogenicity of the Str. dysgalactiae strain was high, as 60% of the quarters becoming infected produced clinical symptoms.

Animals↗
PubMed1980

Post-milking iodine teat skin disinfectants. 3. Residues.

Teat dipping of lactating cows with either 1000 or 5000 mg available iodine/; (mg avI/;) solution and thoroughly washing and drying of the teats before sampling resulted in levels of 70 and 99 micrograms avI per quarter per milking respectively. Without any pre-milking udder preparation prior to sampling the levels of iodine recorded were 143 and 291 micrograms avI per quarter per milking respectively. Some systemic transfer of iodine from the teat skin to the milk was observed, but the bulk of iodine residue in milk was of direct teat skin origin.

Animals↗
PubMed1980

Analysis of somatic cell volume distribution as an aid to the diagnosis mastitis.

Electronic somatic cell counts (ESCC) and relative cell volume distributions (RCVD) in milk samples were obtained simultaneously on a Coulter Counter Model TA and their potential assessed, either singly or in combination, for identifying mastitic quarters and cows in 2 herds. Using log (ESCC) alone the probability P m of misclassifying quarters infected with major pathogens was 6.7% for herd 1 and 18.1% for herd 2. The inclusion of RCVD variables with log (ESCC) did not substantially improve the chance of detecting quarters infected with major pathogens. However, the RCVD variables did improve the chance of identifying quarters infected by major and minor pathogens compared to the use of log (ESCC) alone, the P m figures being reduced by about one third. When testing composite quarter samples, where milk from infected quarters was diluted with that from uninfected quarters, the inclusion of RCVD variables decreased the P m compared to the use of log (ESCC) alone. In hered 1 the improvement was from 26.1 to 3.0%, while in herd 2 the effect was less marked, the P m being reduced from 28.6 to 21.6%. However, as the RCVD assessment is provided simultaneously with ESCC, the additional information is obtained at minimal cost.

Animals↗
PubMed1980

Effect of a disinfectant udder wash and a post-milking teat dip on the bacterial population of the teat end and on the rate of new intramammary infection.

A pre-milking wash disinfectant procedure employing a 2% (w/v) chlorhexidine solution in a detergent basic did not reduce the rate of new intramammary infection in a lactating herd challenged with Staphylococcus aureus. Teat-end swabs showed no significant difference in the number of Staph. aureus isolated from the teat-ends pre-washed with either water, or water and chlorhexidine. In contrast, disinfecting teats after milking with a solution containing 5000 mg available iodine/l significantly reduced the staphylococcal population of the teat-ends and the rate of new intramammary infection, compared with teats not disinfected.

Animals↗