Biomedical subjects

J H Burton

Publications and source records attributed to J H Burton.

At least 19 recordsLinked to original sources

PubMed1995

Evidence that the death of macrophage foam cells contributes to the lipid core of atheroma.

Sections of human atherosclerotic lesions of different stages show that, in early lesions, the acellular lipid core is usually immediately adjacent to the deepest edge of a collection of macrophage foam cells. Advanced lesions with a large lipid core have variable numbers of macrophage foam cells, close to the lateral edges, or shoulders, of the core. In both early and advanced lesions, some of the macrophages nearest the core appear to be dying. Lipid cores contain two materials which in earlier lesions are found only in macrophages, namely ceroid and CD68 antigen, but do not contain recognisable smooth muscle cell actin. It is concluded that death of macrophage foam cells contributes to the origin and slow enlargement of the lipid core. The cause of macrophage death is not yet certain, but is under investigation.

Adult↗

PubMed1995

Nonlinearity in the relationship between bone Sr/Ca and diet: paleodietary implications.

Strontium in archaeological human bones is widely, almost paradigmatically, used as a measure of the relative dietary abundances of plants and meat. Quantitative modeling reveals, however, that there is not a simple proportional relationship between bone strontium and the dietary plant/meat ratio. While knowledge of specific foods and their compositions may permit accurate calculation of average bone strontium levels, knowledge of bone strontium does not inversely allow accurate calculation of specific foods. Although bone strontium quantitatively reflects the average dietary Sr/Ca ratio, it is disproportionately sensitive to high-calcium foods and can be easily affected by minor dietary constituents and culinary practices. Bone strontium, and by analogy, barium, should be seen as a reflection of the high-mineral dietary components rather than a quantitative index of trophic position.

Animals↗

PubMed1995

Etomidate.

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Adrenal Glands↗

PubMed1994

Somatotropin and insulin-like growth factor-I concentrations in plasma and milk after daily or sustained-release exogenous somatotropin administrations.

Effects of daily injectable or sustained-release bovine somatotropin (bST) administrations on plasma and milk bST and insulin-like growth factor-I (IGF-I) concentrations were monitored in 74 lactating cows through early, mid- and late lactation. Treatments beginning at wk 4 of lactation were excipient (CO, 24 cows) at 2 wk intervals, daily injections of 10.3 mg bST (DI, 25 cows) and 350 mg sustained-release bST at 2 wk intervals (SR, 25 cows). The duration of treatments was 40 wk. Data were first analyzed for the overall mean concentrations covering the 40 wk treatment period. Overall mean plasma bST, milk bST and plasma IGF-I concentrations were significantly increased by both bST treatments (p < 0.05). On the other hand, milk IGF-I concentrations were significantly increased (p < 0.05) only in the DI group. Next, data were analyzed according to stage of lactation. The bST treatments resulted in significant increases (p < 0.05) in plasma and milk bST concentrations for all early, mid- and late lactation periods. Even though plasma IGF-I concentrations were higher (p < 0.05) in all lactation periods for bST treatment groups, higher milk IGF-I concentrations (p < 0.05) occurred only in mid- and late lactation periods for the DI group. The patterns of bST and IGF-I concentrations in milk follows those of the plasma after bST treatments.

Animals↗

PubMed1993

Effects of insulin-like growth factor-I and its analogues on bovine hydrogen peroxide release by neutrophils and blastogenesis by mononuclear cells.

The biological potencies of recombinant human insulin-like growth factor-I (IGF-I) and two of its analogues were examined for hydrogen peroxide release by neutrophils and blastogenesis by mononuclear cells. The binding affinities of these peptides for bovine serum IGF-binding proteins (IGFBPs) and IGF-I receptors on bovine neutrophils and mononuclear cells were also investigated. Relative to control treatment containing no IGF-I, preincubation of neutrophils with 12.5 micrograms/l of IGF-I, des(1-3)IGF-I (an analogue of human IGF-I lacking the N-terminal tripeptide Gly-Pro-Glu) and long R3 IGF-I (an analogue of human IGF-I with arginine replacing glutamate at position 3 of human IGF-I and the N-terminal extension Met-Phe-Pro-Ala-Met-Pro-Leu-Ser-Ser-Leu-Phe-Val-Asn) increased the release of H2O2 by 65%, 64% and 32% respectively. However, the difference in stimulating the release of H2O2 between long R3 IGF-I and other two (IGF-I and des(1-3)IGF-I) was reduced at a dosage of 100 micrograms/l. In the absence or presence of 2.5% fetal calf serum (FCS), 100 micrograms/l of IGF-I, des(1-3)IGF-I but not long R3 IGF-I significantly stimulated thymidine incorporation into mononuclear cells. In addition, des(1-3)IGF-I was more potent than IGF-I in stimulating thymidine incorporation into mononuclear cells in the presence of 2.5% FCS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Function of bovine mammary macrophages as antigen-presenting cells.

The ability of mammary macrophages treated with Staphylococcus aureus to induce antigen-specific T-cell proliferation was compared to that of the autologous blood monocytes. Induction of T-cell proliferation has been correlated with changes in major histocompatibility complex (MHC) class II antigen expression and interleukin 1 (IL-1) production by mammary macrophages and blood monocytes. The present study showed that both monocytes and mammary macrophages treated with S. aureus induced T-cell proliferation. However, there was a 3-fold decrease (P less than 0.05) in T-cell proliferation in macrophage cultures compared to those of blood monocytes, when these cells were treated with S. aureus. Mammary macrophages, the cells less effective in stimulating T-cell proliferation, expressed lower levels (2-fold) of MHC class II molecules and produced less IL-1 (3-fold) than blood monocytes. These data suggest that S. aureus may affect macrophage-T cell interaction by modulating the expression of MHC class II molecules and the synthesis of IL-1 by macrophages.

Animals↗

PubMed1992

Receptor binding and growth-promoting activity of insulin-like growth factor-I in a bovine mammary epithelial cell line (MAC-T3).

Insulin-like growth factor-I (IGF-I) has been known to be mitogenic to a variety of cell types, although a growth-regulatory role for IGF-I on bovine mammary epithelial cells has not been fully investigated. In the present study, we examined the receptor binding of IGF-I and its effect on growth in a bovine mammary epithelial cell line (MAC-T3). Specific receptors for IGF-I were detected on cultured bovine mammary epithelial cells. Competitive binding revealed that half-maximal inhibition of 125I-labelled IGF-I binding by IGF-I was approximately 3 micrograms/l. Dissociation rate constant of the IGF-I receptor was 3.10 +/- 0.06 nmol/l (S.E.M.) with a receptor site concentration of 366 +/- 8 fmol/mg protein for the average of three experiments. IGF-I exerted a positive mitogenic effect on MAC-T3 cells according to both direct DNA assay and thymidine incorporation assay. Moreover, the mitogenic effect of IGF-I on MAC-T3 cells was enhanced by the addition of fetal calf serum in the culture media. The present results suggest that the bovine mammary epithelial cell line (MAC-T3) provides a useful model system with which to study the biological actions of insulin-like growth factors on the bovine mammary secretory tissue in vitro.

Animals↗

PubMed1992

Hematological profiles in dairy cows treated with recombinant bovine somatotropin.

Recombinant bovine somatotropin (bST) was administered at 0, 10.3, or 20.6 mg per cow per day to 32 Holsteins for 38 wk. Fifteen currently treated cows had been treated in the previous lactation. Eighteen hematological variables and blood concentration of insulin-like growth factor I (IGF-I) were measured at five sample periods. The objectives of the study were to test the effects of bST treatments on hematological profiles and to relate blood IGF-I concentration to these variables. Results indicated little influence (P greater than .10) of previous bST treatments on hematological profiles measured in the current lactation. Current bST treatments, however, altered hematocrits (P = .10), mean corpuscular volume (P = .03), mean corpuscular hemoglobin (P = .009), and fraction of blood lymphocytes (P = .09). A week x bST treatment interaction also contributed to variation in hematocrit (P = .09), mean corpuscular hemoglobin (P = .05), fraction of neutrophils (P = .02), and fraction of lymphocytes (P = .04). Blood IGF-I concentration influenced fractions and counts of neutrophils (P = .06, .09), lymphocytes (P = .04, .02), and monocytes (P = .08, .05). Further in vivo and in vitro studies are warranted because this preliminary evidence suggests that bST and(or) IGF-I contribute to regulation of hematopoiesis in mature dairy cows.

Analysis of Variance↗

PubMed1992

Specific insulin-like growth factor-I receptors on circulating bovine mononuclear cells.

We have examined the presence and properties of specific receptors for IGF-I on bovine mononuclear cells. Competitive binding studies showed that binding of [125I]IGF-I to mononuclear cells was inhibited by unlabelled peptides with the rank of IGF-I greater than IGF-II greater than insulin. The binding of [125I]IGF-I was a function of the cell concentration. Equilibrium dissociation constant and receptor concentration values for the average of 9 adult cows were 1.13 +/- 0.11 nM and 108.9 +/- 24.1 fMol/10(7) cells, respectively. Moreover, IGF-I stimulated thymidine incorporation into bovine mononuclear cells in the absence of serum and phytohemagglutinin (PHA). The existence of specific and functional IGF-I receptors on circulating bovine mononuclear cells would provide an easily accessible source for studying IGF-I receptor changes in the bovine, both in physiologic and pathologic states.

Animals↗

PubMed1992

Contact sensitivity and systemic antibody responses in dairy cows treated with recombinant bovine somatotropin.

Effects of exogenous bST on humoral and cell-mediated immune responses in lactating dairy cows were determined. The systemic antibody response to human erythrocytes and the cutaneous sensitivity response induced by dinitrochlorobenzene were the immune responses investigated. Cows were treated with either 0, 10.3, or 20.6 mg of bST/d for 266 d starting between wk 4 and 5 of lactation. Systemic immunizations and contact sensitivity were initiated during midlactation, 22 wk after bST treatments began. Hemagglutinating antibody titers and areas under the response profiles were not statistically different for bST-treated versus control cows. The cutaneous sensitivity response was similarly not affected by bST administration. Present antibody titer results agreed with our previous observations that bST did not affect serum IgM concentrations, but the cutaneous sensitivity results were in contrast with our finding of augmented proliferative responsiveness of mitogen-stimulated peripheral blood lymphocytes in bST-treated versus control cows. It is possible that exogenous bST affects some immune processes and lymphocyte subsets and not others. Further research is required to determine the practical significance of the variable immunomodulation elicited by exogenous bST.

Analysis of Variance↗

PubMed1992

Effect on production traits of bovine somatotropin for up to three consecutive lactations.

Thirteen (control) cows were injected daily with saline and 22 with bST (12 at 10.3 mg/d and 10 at 20.6 mg/d) through wk 5 to 42 of lactation. Nine of the treated cows had received bST in the previous lactation, and 7 cows received bST in the previous two lactations. All control cows and 6 treated cows had not previously received bST. Treatment with bST caused substantial increases in milk production, feed intake, and efficiency of feed conversion in the current lactation, which is consistent with previous trials. Increases in feed intake were established fully within 9 wk of starting bST administration, somewhat earlier than usually reported. Treatment with bST in one or two previous lactations caused a statistically significant 14% reduction in production and 8% reduction in efficiency of feed conversion during the first 9 wk of bST treatment in the current lactation; reductions observed later in lactation were not statistically significant. Differences for other traits were not statistically significant. In combination with earlier trials, these results suggest that, although bST has beneficial effects on production and efficiency traits, these benefits may be considerably lower in the second and subsequent lactations of bST use. However, carry-over effects on cows not receiving bST in the current lactation were not explored in this trial.

Animals↗

PubMed1992

The effects of genetic and phenotypic production potential on response to recombinant bovine somatotropin.

Evidence was sought for an interaction between both phenotypic and genetic production potential and response of milk production to administration of bST in three trials of 38, 43, and 35 cows. In each trial, bST was administered in doses of 0, 10.3, 20.6, and, in trial 1 only, 41.2 mg/d for 38 wk from wk 4 of lactation. Data were analyzed for each experiment separately and combined across experiments. Analyses included separate regressions for treated and untreated animals for milk production during the production period on pretreatment production and estimated breeding value for milk production. Breeding value was estimated as the sire's estimated transmitting ability plus one-half of the maternal grandsire's estimated transmitting ability. With the exception of regression on estimated breeding value in trial 1 and in combined data, differences between treated and untreated animals in the regression of milk production on pretreatment milk production or on estimates of breeding value were not statistically significant. However, regressions on pretreatment production were substantially lower for treated than for untreated animals in each of the three trials. Regressions on breeding value estimated from sire and maternal grandsire estimated transmitting abilities were substantially, but not significantly, lower for untreated than for treated animals in all three trials. The results suggest that cows with high production potential for nongenetic reasons may show diminished response to bST, whereas cows with genetically high production potential show enhanced response. However, borderline statistical significance argues for considerable further examination before drawing firm conclusions.

Animals↗

PubMed1992

Lactation, health, and reproduction of dairy cows receiving daily injectable or sustained-release somatotropin.

Seventy-four Holstein cows (26 primiparous) were utilized to compare the efficacy and safety of sustained-release versus daily injectable formulations of recombinant bST. Twenty-four control cows were injected biweekly with oil microsphere; 25 cows were injected biweekly with 350 mg of bST microsphere; and 25 cows were injected daily with 10.3 mg of bST. Injections were initiated between wk 4 and 5 of lactation and continued for 280 d. Administration of bST caused a moderate increase in milk and FCM production and improved the efficiency of feed and energy conversions. Most health-related and reproduction-related variables did not differ among treatment groups. However, incidence of teat and udder disorders and feet and leg problems tended to be higher during the 40-wk injection period for the bST-treated cows than for the control cows. Incidence of GnRH therapy and number of days to first service were higher for daily bST-treated cows than for controls. No differences existed between sustained-release and daily bST-treated cows for any parameters monitored.

Animals↗

PubMed1991

Influence of exogenous bovine somatotropin on the responsiveness of peripheral blood lymphocytes to mitogen.

Our objectives were to determine the effects of exogenous bovine somatotropin on peripheral blood lymphocyte responsiveness to mitogen and on concentrations of serum insulin-like growth factor-I and to determine whether a statistical relationship exists between these two variables. The cows on trial were treated with 0, 10.3, or 20.6 mg/d somatotropin, starting between wk 4 and 5 of lactation and continuing for 266 consecutive d. Lymphocyte proliferation (counts per minute) and concentration of insulin-like growth factor-I (nanograms per milliliter) were recorded from blood sampled at wk 3, 10, 26, 35, and 46 of lactation. The results showed that lymphocytes from the blood of treated cows responded to mitogen with higher proliferative responsiveness than cells from control cows, but that this effect required long-term treatment and adequate mitogen concentrations to be detected. The blood of treated cows also had elevated concentrations of insulin-like growth factor-I relative to that of control cows, but these were not statistically associated with the proliferative responsiveness of the peripheral blood lymphocytes to mitogen. Our results suggest that somatotropin has a role in the immune system of cows, but its mode of action and target tissues must be determined. Bovine somatotropin, injected at doses that increase milk yield, can augment cow immunity as judged by the proliferative responsiveness of peripheral blood lymphocytes in culture.

Analysis of Variance↗

PubMed1991

Serum immunoglobulin profiles of dairy cows chronically treated with recombinant bovine somatotropin.

The objective of this study was to determine the effects of exogenous somatotropin on blood profiles of the major bovine Ig isotypes. Holsteins were treated with either 0, 10.3, or 20.6 mg recombinant bST/d. Subcutaneous injections were started between wk 4 and 5 of lactation and continued for 266 d. Blood samples were collected by coccygeal venipuncture throughout lactation for serum IgG, G1, G2, A, and M concentration determination. Cows treated with 10.3 mg of bST/d exhibited modest increases in mean blood concentrations of IgG (12.4%) and IgG2 (18.4%) relative to the other groups of cows. In addition, treated cows had 10.1% higher average concentration of IgA than controls. Somatotropin did not influence average lactational concentrations of IgG1 or IgM, although the group receiving 10.3 mg/d had higher late lactation concentrations of IgG1 than did the other two groups. However, treatment mean isotype concentrations were always within normal ranges, except for IgG2 from the 10.3 mg/d group, which were higher. The practical significance of elevated serum Ig concentrations observed in the present study is not known. However, the present data do show that bST administered at doses that increased milk yield had no apparent detrimental effect on humoral immunity as measured by blood concentrations of Ig.

Analysis of Variance↗

PubMed1991

Effect of bovine skim milk and whey on monocyte function.

Previous studies have documented the ability of bovine milk to inhibit lymphocyte proliferation in response to mitogens. It is not known whether inhibition of lymphocyte proliferation is mediated through the action of monocytes. To address this question, we examined the ability of bovine skim milk and whey to affect monocyte function with emphasis on expression of major histocompatibility class II antigens and production of interleukin-1 by monocytes. Data showed that expression of major histocompatibility complex class II molecules and production of interleukin-1 by monocytes were not altered when monocytes were cultured in the presence of bovine skim milk or whey. Thus, it is unlikely that the suppressive effect of milk on lymphocyte proliferation could be mediated through alterations in the expression of major histocompatibility class II molecules or in production of interleukin-1 by monocytes. The role of other monocyte antigens or secretory products, however, should also be evaluated.

Animals↗

PubMed1991

Examination of chemotactic properties of bovine mammary macrophages.

An in vitro model system in which polymorphonuclear leukocytes (PMN) migration under agarose was employed to examine the ability of mammary macrophages to release chemoattractants for PMN. Mammary macrophages were incubated in Hanks' balanced salt solution for up to 12 h in the presence of Staphylococcus aureus. The possibility that the chemotactic activity is mediated through release of interleukin 1 (IL-1) and prostaglandins (PGs) by mammary macrophages was investigated. The data showed that release of chemotactic activity peaked 6 h following addition of S. aureus in the culture medium of mammary macrophages. Very low levels of IL-1 were detected in the same culture medium. Addition of indomethacin, a PGs synthesis inhibitor, was ineffective in altering the chemotactic activity detected in the culture medium of macrophages. These data suggest that it is highly unlikely that the chemotactic activity is mediated through the production of IL-1 and PGs by the mammary macrophages.

Animals↗

PubMed1991

Secretion of interleukin-1 by bovine milk macrophages.

The relative sensitivity of bovine blood monocytes and macrophages isolated from milk to lipopolysaccharide, with respect to interleukin 1 (IL-1) production, was evaluated. Addition of lipopolysaccharide (0 to 30 microgram/ml) to the culture medium resulted in increases in secreted and intracellular IL-1 activity for monocytes and milk macrophages, with maximal stimulation achieved at 30 micrograms of lipopolysaccharide/ml of medium. At this concentration of lipopolysaccharide, monocytes released 76% of the total IL-1, whereas milk macrophages released only 26% of the total IL-1 produced within the cell. Secretion of a small quantity of IL-1 was a common property of macrophages isolated from healthy and mastitic quarters. We concluded that limited secretion of IL-1 may render the milk macrophages less efficient in promoting lymphocyte activation.

Animals↗