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Biomedical subjects

H E Amos

Publications and source records attributed to H E Amos.

At least 37 records · Page 2Linked to original sources
PubMed1990

Effects of zinc sulfate concentration and feeding frequency on ruminal protozoal numbers, fermentation patterns and amino acid passage in steers.

Effects of zinc sulfate (0 vs 1,142 ppm supplemental zinc from zinc sulfate) and feeding frequency (1 x vs 12x daily) on ruminal protozoa numbers, fermentation patterns and amino acid passage were investigated using four ruminally and abomasally cannulated mature Jersey steers in a 4 x 4 Latin square experiment. Steers (530 kg) were fed a 50:50 roughage:concentrate diet at 1.5 times their NEm requirement. Experimental periods were 14 d in duration; ruminal, abomasal and fecal samples were collected at 6-h intervals during the last 3 d of each period. Protozoa numbers tended to be lowest (1.82 x 10(6)/ml) in steers fed zinc 1 x and tended to be highest (3.83 x 10(6)/ml) in steers fed zinc 12 x daily (P less than .10). Frequent feeding decreased ruminal pH .24 units and increased total VFA 20.7%, ammonia 22.7% and ruminal digestion of dietary amino acids (AA) 61.6% (P less than .05). Zinc supplementation decreased ruminal digestion of dietary AA 35.8% (P less than .05) and the abomasal passage of bacterial OM and AA 21.2% (P less than .05) and increased ruminal output of amino acids as a percentage of intake 15.1% (P less than .05). Although it increased escape of dietary AA, zinc sulfate decreased postruminal passage of bacterial AA and resulted in a net negative effect on total postruminal AA passage as a percentage of intake. The effects of zinc on ruminal AA digestion may be more closely related to an interaction of zinc with dietary CP rather than to an effect of Zn on ruminal microbial populations.

Amino Acids↗
PubMed1989

The incidence of IgE and IgG antibodies to chlorhexidine.

IgE antibodies to the antiseptic agent chlorhexidine have recently been detected in the majority of sera from a small group of predominantly Japanese individuals showing anaphylactic-type adverse reactions towards chlorhexidine. In this study the prevalence of IgE and IgG antibodies with specificity for chlorhexidine was investigated in groups of Japanese and British individuals. The RAST data, using a better defined semi-chlorhexidine-HSA antigen than previously employed, revealed that chlorhexidine-specific IgE was only detected in Japanese individuals who had experienced anaphylactic-type reactions and was not detected in groups of Japanese nurses and patients, or in groups of British nurses and hospital staff, all in regular contact with chlorhexidine. A group of British blood donors was also negative. In contrast, IgG antibodies were detected not only in sera from chlorhexidine-sensitive Japanese patients, but also in several sera from Japanese nurses, non-sensitive Japanese patients and several British individuals. The possible reasons for these observations are discussed.

Adult↗
PubMed1989

Effects of a salivary stimulant, slaframine, on ruminal fermentation, bacterial protein synthesis and digestion in frequently fed steers.

Slaframine (SF), a parasympathomimetic salivary stimulant, was administered i.m. (10, 15 or 20 micrograms SF/kg BW) to ruminally and abomasally fistulated steers at 12-h intervals for 18-d periods in a latin square-designed experiment. Steers were fed semicontinuously (12 times daily) a 40:60 roughage:concentrate diet at twice their net energy requirement for maintenance. Ruminal digestion coefficients for DM, ADF and starch were 10 to 16% lower and linearly related in an inverse manner to the level of SF administered (P less than .05). Postruminal digestion of DM, ADF and starch increased as much as 46.7, 9.5 and 44.0%, respectively, in a fashion linearly related (P less than .05) to the level of SF administered. Total tract digestion of DM and ADF were not affected by SF; however, total tract starch digestion was increased as much as 5% and was related linearly (P less than .05) to SF treatment. With SF administration, as much as 13% more bacterial protein exited the rumen, resulting in a 16.5% linear improvement (P less than .1) in the efficiency of ruminal bacterial protein production per 100 g of OM fermented. Ruminal concentrations of VFA, ammonia and pH were not affected by SF. These results demonstrate a positive relationship between salivation and ruminal bacterial protein synthesis and suggest that feed utilization by ruminants may be improved by pharmacological stimulation of salivary secretions.

Abomasum↗
PubMed1989

Long-term feeding of high zinc sulfate diets to lactating and gestating dairy cows.

Thirty dairy cows, fed a control diet consisting of silage and concentrates, were given either 0, 1000, or 2000 ppm of supplemental Zn (DM basis), from zinc sulfate monohydrate (ZnSO4.H2O) for most of a lactation. Feeding 2000 ppm Zn decreased milk yield and feed intake after several weeks. Some cows were affected more severely than others. Generally, primiparous animals were more tolerant of the high Zn diet than multiparous cows. Milk Zn was materially higher for cows fed 1000 ppm added Zn than controls. With 2000 ppm Zn, milk Zn was elevated further but returned to control values when the high Zn diet was discontinued. Plasma Zn was higher in cows fed supplemental Zn with the increase from 1000 to 2000 greater than that for the first addition. Plasma Cu was lower in cows feed 2000 ppm Zn but milk Cu was not reduced. Milk fat content was not affected, but protein and SNF were reduced by the 12th wk with the 2000 ppm Zn diet. There was no apparent effect on long-term health or performance after the cows were removed from the 2000 ppm Zn diet. Except for lower calf weights with 2000 ppm Zn, reproductive performance was not measurably affected by the dietary treatments. The 1000 ppm added Zn diet had no adverse effect on the cows in any parameter measured.

Animal Feed↗
PubMed1988

Effect of dietary energy source and level on serum growth hormone, insulin-like growth factor 1, growth and body composition in beef heifers.

Effects of fiber vs starch energy supplements on endogenous growth hormone (GH), insulin-like growth factor (IGF-1) and animal performance from weaning to breeding age were evaluated in 18, 9-mo-old beef heifers. Heifers had ad libitum access to wheat silage plus an average daily supplement intake of 1) 4.08 kg corn-soybean meal (SBM) (high energy-starch, HS), 2) 4.54 kg soyhulls (SH)-SBM (high energy-fiber, HF) or 3) 1.36 kg SH-SBM (low energy-fiber, LE). Serum samples were collected via jugular puncture every 10 d and were analyzed for IGF-1 by RIA. On d 45 and d 176, four heifers per treatment were fasted 18 h and serial blood samples collected via jugular cannulas every 15 min for 6.5 h. Arginine (.5 g/kg BW) was administered intravenously (ARG) to induce release of GH, and four additional samples of blood were collected. Samples were analyzed by RIA for GH. Mean fasted GH (6.4 +/- .4, 8.3 +/- .4 and 13.8 +/- .4 ng/ml for HS, HF and LE, respectively) varied with energy source and level (P less than .01). Mean GH following ARG was higher (P less than .01) in heifers receiving LE (46.2 +/- 4.7) than in those receiving HS and HF (23.5 +/- 4.4 and 24.1 +/- 4.6 ng/ml). Basal GH concentration and peak amplitude were higher (P less than .05) in LE than in HS and HF treatments. Diet did not influence number or frequency of GH peaks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Practolol inhibits human skin fibroblast cell mat hydroxyproline accumulation.

Despite being poorly absorbed practolol (N-4-2-hydroxy-3-(1-methyl-ethyl)-amino propoxy phenyl acetamine) inhibited the accumulation of cell mat hydroxyproline, a measure of collagen synthesis, by human skin fibroblasts (DT2PH) in vitro, (ID50 0.8 X 10(-3) M). The degree of inhibition was dependent on the concentration of practolol used and the incubation time. Neither preinitiation of collagen synthesis nor omitting ascorbic acid from the incubation medium modified this inhibitory action. In contrast, in vitro generated metabolites of practol, using normal and aroclor induced hamster liver preparation, and structural analogues of practolol had no effect on cell mat hydroxyproline levels. Related compounds, propranolol, (1-(isopropylamino)-3(1-naphthyl-oxy)2-propranolol), and paracetamol, (N-(4-hydroxyphenyl)acetamide), both inhibited hydroxyproline levels. Fibroblasts derived from uninvolved skin of a psoriasis patient (PS1) were several fold more sensitive to practolol and propranolol than cells derived from normal skin but showed little change in sensitivity towards paracetamol.

Cells, Cultured↗
PubMed1987

Factors influencing the immunogenicity of the haptenic drug chlorhexidine in mice--Part I. Molecular requirements for the induction of IgE and IgG anti-hapten antibodies.

The immunogenicity of a novel hapten, the anti-microbial agent, chlorhexidine (1,1'-hexamethylene bis [5-(p-chlorophenyl)biguanide]) was assessed in mice, using alum as adjuvant. The i.p. injection of electrostatically-linked chlorhexidine + keyhole limpet haemocyanin (KLH) mixtures induced low level primary IgG anti-chlorhexidine antibody synthesis. In contrast, covalently-linked chlorhexidine-KLH complexes induced both IgE and IgG anti-chlorhexidine antibody synthesis. Covalent binding was facilitated by the N-chlorination of secondary amide groups on the biguanide moeities of the chlorhexidine molecule. The immunogenicity of such complexes was related to the degree of conjugation of chlorhexidine to KLH; which, in turn, was related to the molarity of chlorine used to effect N-chlorination. Immune responses to covalently-linked complexes could be enhanced by carrier priming. The induction of low levels of IgG anti-hapten antibodies by electrostatically-linked complexes may reflect T cell-independent specific B cell activation, either by chlorhexidine itself or by a "pseudo-plurivalent" chlorhexidine + KLH antigen.

Animals↗
PubMed1987

The specificity of murine polyclonal and monoclonal antibodies to the haptenic drug chlorhexidine induced by chlorine-generated chlorhexidine-protein conjugates.

Polyclonal and monoclonal antibodies to the antibacterial agent chlorhexidine (1,1'-hexamethylene bis [5-(p-chlorophenyl)]biguanide, mol. wt = 505) were raised using a chlorine-generated N-chloro chlorhexidine-keyhole limpet haemocyanin (NCC-KLH) conjugate as the immunogen. Antibodies were detected by ELISA, using a semi-chlorhexidine derivative conjugated to human serum albumin (SC-HSA) as the antigen. Free chlorhexidine could completely inhibit both polyclonal and monoclonal antibody binding to SC-HSA. Direct binding and inhibition ELISA studies revealed that the N-chlorination of chlorhexidine does not significantly alter its specificity as an immunogen or antigen and that chlorhexidine has two identical epitopes. Each epitope consists of the p-chlorophenyl biguanide structure of which the terminal p-chlorophenyl group appears to be immunodominant. Chlorhexidine is, therefore, a symmetrical divalent hapten and this implies that it may be capable of eliciting immediate hypersensitivity reactions by divalent interaction with antibodies induced by chlorine-generated N-chloro-chlorhexidine-protein immunogens. The clinical significance of these findings is discussed.

Animals↗
PubMed1986

Influence of dietary protein degradability and energy concentration on growth of heifers and steers and intraruminal protein metabolism.

Two studies with 4-mo old Holstein steers and heifers and one abomasal digesta collection study were used to determine the influence of altering the dietary energy content and crude protein escape on growth, intraruminal protein metabolism, and site of digestion of dry matter, starch, cellulose, hemicellulose, and protein. Dietary energy concentration was increased by tallow, and rumen protein escape was increased by dehydrated alfalfa and distillers dried grains with solubles substituted for soybean meal. Tallow appeared to depress intake and gain, but gain was increased by protein escape from the rumen. Total and particulate digesta crude protein reaching the abomasum was increased by protein escape; however, percentage crude protein digested was decreased in these treatments due to increased acid detergent insoluble nitrogen. Decreasing crude protein solubility decreased ruminoreticular digestion of dry matter, cellulose, hemicellulose, and starch; however, lower intestinal starch digestion compensated for decreased ruminoreticular digestion. In a third study, with growing steers and heifers, corn gluten meal provided the escape protein and soybean meal the degradable protein. Total and average daily gain were greater for the corn gluten meal diet, but intake was not influenced by energy concentration or protein escape.

Abomasum↗
PubMed1986

Factors influencing the immunogenicity of the haptenic drug chlorhexidine in mice. II. The role of the carrier and adjuvants in the induction of IgE and IgG anti-hapten responses.

The roles of carrier and adjuvant in the induction of primary antibody responses to the haptenic drug chlorhexidine (which interacts only electrostatically with proteins) and its N-chlorinated derivative (which binds covalently to proteins) were investigated. N-chloro chlorhexidine, covalently linked to either ovalbumin, KLH, thaumatin, LPS-associated protein or human serum protein, but not autologous mouse serum protein or LPS itself, induced both IgE and IgG anti-chlorhexidine antibody synthesis when injected, with alum adjuvant, into BALB/c mice. Bordetella pertussis (BP) could function as both carrier and adjuvant, but no response was obtained by injection of N-chloro chlorhexidine alone or with alum adjuvant. The immunogenicity of N-chlorinated chlorhexidine was directly related to the degree of its substitution onto the carrier which, in turn, was proportional to the level of chlorine (mM) employed. Chlorine also affected the immunogenicity of the various carriers. In the absence of chlorine, chlorhexidine induced only low level IgG antibody synthesis, but only if presented in a 'pseudoplurivalent' form, as a chlorhexidine-mediated protein precipitate (with alum) or electrostatically bound to a particulate carrier such as BP.

Adjuvants, Immunologic↗
PubMed1985

Influence of milking frequency on productive and reproductive efficiencies of dairy cows.

Thirty-four mature Holstein cows were blocked into two groups on their 305-day, twice daily milked, mature equivalent milk production of the previous lactation; groups were assigned at random to a twice or thrice daily milking frequency. In addition, six pairs of paternal half-sisters and one pair of nonsibling heifers also were assigned to twice daily or thrice daily milking frequency. Half-sisters were assigned to milking frequency on alternate calvings, and the nonsibling pair was assigned at random. Milk production peaked at 6 wk lactation in mature cows in both treatments, at 7 wk for cows in first lactation milked twice daily, and at 9 wk for cows in first lactation milked thrice daily. Cows milked thrice daily reached higher peak milk production and were more persistent in milk production. Multiparous and first-lactation cows milked thrice daily produced 18.5 and 25.2% more milk than their counterparts milked twice daily, and after 15 wk heifers milked thrice daily were producing more milk per day than mature cows milked twice daily. The combined increased average production for cows and heifers milked thrice daily, 1299 kg, required only 92 kg more dry matter intake and resulted in an apparent preferential utilization of feed nutrients for milk production or higher rate of tissue catabolism in cows milked thrice daily. Milk composition was not influenced by milking frequency; total milk fat was 36 kg more for cows milked thrice daily. Reproductive performance measured as days to first estrus, days open, or services per conception also was not influenced by milking frequency.

Animals↗
PubMed1980

Immunologically mediated toxicity.

A major consideration which precedes the release of a new chemical into the environment of human beings is the possibility of its producing an undesirable or toxic effect. Toxicity is the clinical end-point of a mechanism which results in tissue damage. One such mechanism is mediated via the immunological system. The effect of some chemicals on immunologically competent cells has been to induce perturbations of immunological competence. This is currently under debate as a toxic hazard, and the concept is explored here, particularly in relation to the action of alkyl tins. Hypersensitivity, which is tissue damage resulting directly from an allergic reaction, depends on a substance acting as an antigen. Since many compounds of toxicological interest have a molecular weight less than 5000, the ability to induce an allergic state is governed in part by factors that influence antigen formation, covalent interactions with macromolecules and metabolism. These factors, together with an analysis of 'immunological specificity', are illustrated by experimental work on practolol, which demonstrates that an antibody present in human sera reacts with a product of first-phase metabolism.

Animals↗
PubMed1980

Nitrogen balance, abomasal crude protein and amino acids in wethers fed formaldehyde-treated coastal bermudagrass and infused with methionine, glucose or monensin.

A 5 X 5 Latin square design was used to study the effects on nitrogen balance, wool growth and plasma amino acids of infusing methionine and (or) glucose into the abomasum of growing wethers fed formaldehyde-treated Coastal bermudagrass (F-CBG) or untreated Coastal bermudagrass hay. Daily treatments were: (1) CBG; (2) F-CBG + 3 g methionine (met); (4) F-CBG + 96 g glucose and (5) F-CBG + 3 met + 96 g glucose. Glucose infusion decreased (P < .005) moles/100 g of total essential amino acids in plasma; moles/100 g of lysine, valine, leucine and isoleucine were also reduced (P < .005). Moles/100 g of methionine in plasma were increased significantly by methionine infusion, but nitrogen retention was not affected (P > .10). The grams digestible protein to megacalorie digestible energy (DE) ratio was 36.6, 35.9 and 32.4 for CBG, F-CBG and F-CBG + glucose, respectively. The decrease (36.6 to 32.4) resulted in increased nitrogen retained (P < .05), increased percentage nitrogen intake retained (P < .05) and increased percentage digested nitrogen retained (P < .01). Urinary nitrogen excretion was lower (P < .01) in wethers receiving the F-CBG + glucose treatment than in those receiving the F-CBG treatment (3.60 vs 5.09 g/day). Effects of formaldehyde treatment of CBG and rumen infusion of monensin on quantities of various crude protein (CP) components reaching the abomasum were also determined in a 4 X 4 Latin square design experiment. Total CP reaching the abomasum increased (P < .01) with formaldehyde treatment and resulted in increased quantities of amino acids reaching the abomasum (P < .05). Monensin had no effect on these two parameters, and no interaction between monensin and formaldehyde was observed. Dietary CP reaching the abomasum increased with formaldehyde treatment (P < .005) and with infusion of monensin (P < .025). Total microbial protein (MP) and MP reaching the abomasum per 100 g dry matter digested were not influenced by either formaldehyde or monensin.

Abomasum↗
PubMed1980

Nitrogen metabolism of growing lambs fed coastal bermudagrass as influenced by formaldehyde treatment and glucose.

Six abomasally-cannulated wethers (average initial weight 18 kg) were used in a split 3 X 3 Latin square design experiment with a crossover to determine effects of glucose (G) administered orally (O) or infused (I) into the abomasum on nitrogen metabolism and forage fiber digestion. Basal diets were Coastal bermudagrass (CBG) or CBG treated with 1% formaldehyde (F-CBG). Individual treatments were: (1) CBG, (3) CBG + G(O), (3) CBG + G(I), (4) F-CBG, (5) F-CBG + G(O) and (6) F-CBG + G(I). Nitrogen balance was 3.67, 4.86, 4.80, 5.04, 5.73 and 6.04 g/day and urinary N was 6.50, 4.10, 4.42, 5.25, 3.26 and 3.00 g/day for treatments 1,2,3,4,5 and 6, respectively. Nitrogen balance was increased and urinary nitrogen decreased (P < .005) by formaldehyde treatment and addition of G. Crude protein digested was decreased (P < .005) by G but was unaffected by formaldehyde (P > .05). Concentration of essential amino acids in plasma was decreased by addition of G (P < .005). Digestion of cellulose and hemicellulose was decreased by G (P < .005) administered orally but was unaffected by G infusion or formaldehyde treatment. Addition of G thus increased the overall efficiency of nitrogen and energy utilization.

Animals↗
PubMed1979

Immunological aspects of practolol toxicity.

It is unfortunate that there is conflicting immunological data relating to the practolol syndrome. It has not been established if "practolol patients" have some altered T cell function. The work of Behan et al. (1976) strongly supports this interpretation but other groups have not come to the same conclusion. The role of the antibody specific for a practolol metabolite needs to be determined. In practice this is going to be very difficult to do; the drug is no longer used and patients, for obvious reaons, are unwilling to take part in clinical experiments. It is likely that the nature of the metabolite will eventiually be defined and it would be a significant step forward if it could be shown that the antigenic determinant was not formed by other structurally related beta-blocking drugs. Meanwhile the stimulus to further research must be to produce an animal model system, but, for various political and economic reasons, support for such a research effort is difficult to justify.

Animals↗
PubMed1979

Mode of attack on orchardgrass leaf blades by rumen protozoa.

Leaf blade sections of orchardgrass were incubated with rumen fluid and examined by scanning and transmission electron microscopy for the mode of attack on tissues by rumen protozoa. Rumen protozoa resembling Epidinium ecaudatum from caudatum degraded forage tissue in diluted, whole rumen fluid suspensions of microbes containing 1.6 mg of streptomycin per ml, which inhibited bacterial fiber-digesting activity. Cell walls of mesophyll, parenchyma bundle sheath, and epidermis became swollen and frayed to reveal a microfibrillar network and loss of electron density, indicating partial degradation. Then the protozoa ingested whole cells and fragments of cell walls with the aid of their cilia. Plant cells with partially degraded walls as well as chloroplasts without walls were present within the protozoa. These entodiniomorphs digested orchardgrass leaves by partially degrading the plant cell walls apparently by extracellular enzymes and then ingestion of the plant cells and cell wall fragments.

Journal Article↗