Enzymatic activity of albumin shown by coelenterazine chemiluminescence

Bioluminescence, the emission of light from live organisms, occurs in 18 phyla and is the major communication system in the deep sea. It has appeared independently many times during evolution but its origins remain unknown. Coelenterazine bioluminescence discovered in luminous jellyfish is the most common chemistry causing bioluminescence in the sea, occurring in seven phyla. Sequence similarities between coelenterazine luciferases and photoproteins from different phyla are poor (often < 5%). The aim of this study was to examine albumin that binds organic substances as a coelenterazine luciferase to test the hypothesis that the evolutionary origin of a bioluminescent protein was the result of the formation of a solvent cage containing just a few key amino acids. The results show for the first time that bovine and human albumin catalysed coelenterazine chemiluminescence consistent with a mono-oxygenase, whereas gelatin and haemoglobin, an oxygen carrier, had very weak activity. Insulin also catalysed coelenterazine chemiluminescence and was increased by Zn(2+). Albumin chemiluminescence was heat denaturable, exhibited saturable substrate characteristics and was inhibited by cations that bound these proteins and by drugs that bind to human albumin drug site I. Molecular modelling confirmed the coelenterazine binding site and identified four basic amino acids: lys195, arg222, his242 and arg257, potentially important in binding and catalysis similar to naturally occurring coelenterazine bioluminescent proteins. These results support the 'solvent cage' hypothesis for the evolutionary origin of enzymatic coelenterazine bioluminescent proteins. They also have important consequences in diseases such as diabetes, gut disorders and food intolerance where a mono-oxygenase could affect cell surface proteins.

Soluble corticotropin-releasing hormone receptor 2alpha splice variant is efficiently translated but not trafficked for secretion

CRH directs the physiological and behavioral responses to stress. Its activity is mediated by CRH receptors (CRH-R) 1 and 2 and modulated by the CRH-binding protein. Aberrant regulation of this system has been associated with anxiety disorders and major depression, demonstrating the importance of understanding the regulation of CRH activity. An mRNA splice variant of CRH-R2alpha (sCRH-R2alpha) was recently identified that encodes the receptor's ligand-binding extracellular domain but terminates before the transmembrane domains. It was therefore predicted to serve as a secreted decoy receptor, mimicking the ability of CRH-binding protein to sequester free CRH. Although the splice variant contains a premature termination codon, predicting its degradation by nonsense-mediated RNA decay, cycloheximide experiments and polysome profiles demonstrated that sCRH-R2alpha mRNA escaped this regulation and was efficiently translated. However, the resulting protein was unable to serve as a decoy receptor because it failed to traffic for secretion because of an ineffective signal peptide and was ultimately subjected to proteosomal degradation. Several other truncated splice variants of G protein-coupled transmembrane receptors regulate the amount of full-length receptor expression through dimerization and misrouting; however, receptor binding assays and immunofluorescence of cells cotransfected with sCRH-R2alpha and CRH-R2alpha or CRH-R1 indicated that sCRH-R2alpha protein does not alter trafficking or binding of full-length CRH-R. Although sCRH-R2alpha protein does not appear to function as an intracellular or extracellular decoy receptor, the regulated unproductive splicing of CRH-R2alpha pre-mRNA to sCRH-R2alpha may selectively alter the cellular levels of full-length CRH-R2alpha mRNA and hence functional CRH-R2alpha receptor levels.

Novel expression of type 1 corticotropin-releasing hormone receptor in multiple endocrine cell types in the murine anterior pituitary

The CRH family of ligands signals via two distinct receptors, CRH-R1 and CRH-R2. Previous studies localized CRH-R1 and CRH-R2 to a subset of anterior pituitary corticotropes and gonadotropes, respectively. However, numerous studies have indicated that stress and CRH activity can alter the secretion of multiple anterior pituitary hormones, suggesting a broader expression of the CRH receptors in pituitary. To examine this hypothesis, the in vivo expression of CRH-R1 and CRH-R2 mRNA was further characterized in adult mouse pituitary. Quantitative RT-PCR analysis demonstrated that CRH-R1 mRNA is greater than 100-fold more abundant than CRH-R2 mRNA in male and female mouse pituitaries. Dual in situ hybridization analysis identified cell-specific CRH-R1 expression in the anterior pituitary. At least half of the CRH-R1-positive cells expressed proopiomelanocortin-mRNA (50% in females; 70% in males). In females, a significant percentage of the cells expressing CRH-R1 also expressed transcript for prolactin (40%), LHbeta (10%), or TSH (3%), all novel sites of CRH-R1 expression. Similarly in males, a percentage of CRH-R1-positive cells expressed prolactin (12%), LHbeta (13%), and TSH (5%). RT-PCR studies with immortalized murine anterior pituitary cell lines showed CRH-R1 and/or CRH-R2 expression in corticotropes (AtT-20 cells), gonadotropes (alphaT3-1 and LbetaT2 cells), and thyrotropes (alphaTSH cells). Whereas CRH-R1 expression in corticotropes is well established, the presence of CRH-R1 mRNA in a subset of lactotropes, gonadotropes, and thyrotropes establishes these cell types as novel sites of murine CRH-R1 expression and highlights the pituitary as an important site of interaction between the hypothalamus-pituitary-adrenal and multiple endocrine axes.

Isolation of viruses from clinical outbreaks of inclusion body hepatitis

Sixteen outbreaks of inclusion body hepatitis (IBH) in fowls were investigated. Most cases occurred in broilers, and birds 4-9 weeks old were affected. Mortality occurred over a period of 3-5 days, and reached 5% in some cases. The main pathological finding was a diffuse and generalised hepatitis, with eosinophilic intranuclear inclusions in the hepatocytes. From these outbreaks 46 adenoviruses and 6 reoviruses were isolated. The adenoviruses were classified into 5 serological types. Two outbreaks of IBH in pigeons were also examined. Herpesviruses and adenoviruses were isolated from both cases. It was possible to assign one adenovirus isolate to a known fowl adenovirus serotype.

Effects of dairy cow diet forage proportion on duodenal nutrient supply and urinary purine derivative excretion

Four mature Holstein-Friesian dairy cows were used in a 4 x 4 Latin square change-over design experiment made up of four 4-wk periods to investigate the relationship between microbial protein flow to the duodenum and excretion of purine derivatives (PD) in the urine. Four dietary treatments based on ad libitum access to ryegrass silage were offered, with a standard dairy concentrate included at different forage:concentrate (F:C) ratios, calculated on a dry matter basis: 80:20, 65:35, 50:50, and 35:65. Feed intakes increased as the proportion of concentrate in the diet increased, despite a concurrent decrease in silage intake. Increased feed intake led to increased nutrient flow to the duodenum. Milk yields increased as the diet F:C ratio decreased, with cows offered the 35:65 diet yielding nearly 8 kg/d more milk than cows offered the 80:20 diet; the concentrations of milk fat decreased and milk protein increased with a decreasing F:C ratio. Purine derivative excretion in the urine increased with an increasing proportion of concentrate in the diet, and there was a strong linear relationship between total PD excretion (allantoin and uric acid) and microbial N flow to the duodenum: microbial N (g/d) = 19.9 + 0.689 x total PD (mmol/d); R = 0.887. This strengthens the case for using PD excretion as a noninvasive marker of microbial protein flow from the rumen in dairy cows.

Tannerella forsythia-induced alveolar bone loss in mice involves leucine-rich-repeat BspA protein

Tannerella forsythia (formerly Bacteroides forsythus) is one of the periodontal pathogens recently implicated in the development of periodontal disease. The cell-surface-associated, as well as the secreted, leucine-rich-repeat protein (BspA) of this bacterium have been suggested to play roles in bacterial adherence, and also in inflammation, by triggering release of pro-inflammatory cytokines from monocytes and chemokines from osteoblasts, leading to inflammation and bone resorption. In this study, we sought to determine the pathogenic potential of T. forsythia and the in vivo role of the BspA protein in pathogenesis in the mouse model of infection-induced alveolar bone loss. The results showed alveolar bone loss in mice infected with the T. forsythia wild-type strain, whereas the BspA mutant was impaired. In conclusion, evidence is presented in support of T. forsythia as an important organism involved in inducing alveolar bone loss, and the BspA protein is an important virulence factor of this bacterium.

Effects of diet and larval trematode parasitism on lutein and beta-carotene concentrations in planorbid snails as determined by quantitative high performance reversed phase thin layer chromatography

High performance thin layer chromatography (HPTLC) was used to quantify the concentrations of beta-carotene and lutein in Biomphalaria glabrata and Helisoma trivolvis (Colorado and Pennsylvania strains) snails under various conditions. These conditions were: snails fed a lettuce (L) vs. a yolk (Y) diet; B. glabrata infected with Echinostoma caproni vs. uninfected snails; and H. trivolvis (PA) infected with Echinostoma trivolvis vs. uninfected snails. The pigments were extracted from the snail whole bodies and digestive gland-gonad complexes, separated by reversed phase HPTLC, and quantified by densitometric scanning with standard calibration curves. Snails on the L-diet showed significant increases (Student's t-test, P<0.05) in the concentrations of beta-carotene and lutein compared to snails on the Y-diet. Snails infected with echinostomes showed no significant differences (Student's t-test, P>0.05) in the concentrations of lutein and beta-carotene compared to the uninfected cohorts. Our results were compared with previous studies that analyzed beta-carotene and lutein in snails infected with larval trematodes. Variations in the results of our study compared with others reflect intrinsic differences in the larval trematode-snail systems used.

Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function

Two experiments were conducted to investigate the basis for higher voluntary intakes and increased alpha-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of isobutyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of alpha-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of alpha-linolenic acid passing through the rumen. This explains the increased recovery of alpha-linolenic acid from feed into milk with diets based on red clover silage.

Effects of level of concentrate feeding during the second gestation of Holstein-Friesian dairy cows. 2. Nitrogen balance and plasma metabolites

We offered 43 Holstein-Freisian dairy heifers that calved for the first time at either 2 or 3 yr of age ad libitum access to ryegrass silage and a standard concentrate allowance of either 2 or 7 kg/d from the middle to the end of their first lactation. All animals were given the same relatively poor quality dry period diet of a mixture of ryegrass silage and barley straw (63:37 dry matter basis) from 6 wk before their predicted second-calving date. Following their second calving, all animals received access to the same ration of ad libitum grass silage and concentrates at a rate of 8 kg/d to 120 d of lactation and 5 kg/d thereafter until the end of the experimental recording at about 150 d of lactation. Nitrogen balance was significantly higher at the end of the first lactation for animals that were given the higher concentrate allowance and tended to be higher for older animals. There was no effect of age or residual effect of concentrate allowance on N balance during the dry period or during the second lactation. Labile body protein reserves, as estimated by the depth of the muscle Longissimus dorsi (which was significantly correlated with body condition score), were similar for all animals during the dry period, but younger animals previously offered the lower concentrate allowance did not lose L. dorsi depth early in the second lactation as did other animals. Arterial plasma concentrations of amino acids Phe, Trp, and Leu were significantly higher in younger animals at wk 8 of the second lactation, and Gly was significantly lower, although mammary blood flow, arteriovenous differences, and rates of uptake of the AA measured were unaffected by treatment. It is concluded that differences in second-lactation milk yield were not mediated through the availability of labile body protein or the supply of nutrients to the mammary gland.

Interlaboratory study into the proficiency of serum cholinesterase activity measurement

The measurement of cholinesterase activity is an important function of a clinical laboratory. Participation in appropriate quality assurance schemes is essential in ensuring a high analytical standard. Samples of human serum were distributed to thirty-five laboratories for the measurement of cholinesterase activity. Because of methodological differences between the participants, findings of each laboratory were compared either by the use of duplicate samples or by analysis of six mixtures of two samples, one having a high and one a low activity. Of 4,964 distributed samples 95% were analysed and findings reported in 596 reports. Thirty-four percent of all reports were considered very good (less than 5% within-run error) and 38% less than satisfactory (within-run error over 10%). Access to a proficiency programme such as this enables laboratories to evaluate the quality of their analytical service.

Assessment of rumen processes by selected-ion-flow-tube mass spectrometric analysis of rumen gases

This work investigated the potential to use measurement of the concentration of certain gases in the rumen headspace to gain information about rumen processes and as a potential diagnostic tool. We used new equipment (selected-ion-flow-tube mass spectrometer) that allows rapid and precise analysis of many of the gases present in a sample. Samples of rumen headspace gas and corresponding samples of rumen liquor were taken from three lactating cows, prepared with rumen fistulae, at intervals after receiving their morning feed allocation (grass silage and concentrates). Hydrogen sulfide, methyl sulfide, and dimethyl sulfide, were the predominant gases that were measured in the rumen headspace by this technique. The concentrations of these sulfur compounds declined over the interval after feeding, mirroring ammonia concentrations measured in rumen liquor, reflecting their common dependence on the fermentation of sulfur amino acids. Ammonia concentrations in rumen headspace gas varied in the opposite direction to the concentration of ammonia in rumen liquor and likely depend more on the pH of rumen liquor. Consideration of the pKa of ammonia suggests that ammonia concentrations in rumen gas will be very low below pH 6, representing a useful diagnostic for subacute ruminal acidosis. Low concentrations of volatile fatty acids were detected in rumen gas. The molar proportions of volatile fatty acids were similar in gas and liquor samples, with rumen gas containing slightly less acetic acid and disproportionately more valeric and caproic acids.

Oral immunization with recombinant Streptococcus gordonii expressing porphyromonas gingivalis FimA domains

Porphyromonas gingivalis, a gram-negative anaerobe, is implicated in the etiology of adult periodontitis. P. gingivalis fimbriae are one of several critical surface virulence factors involved in both bacterial adherence and inflammation. P. gingivalis fimbrillin (FimA), the major subunit protein of fimbriae, is considered an important antigen for vaccine development against P. gingivalis-associated periodontitis. We have previously shown that biologically active domains of P. gingivalis fimbrillin can be expressed on the surface of the human commensal bacterium Streptococcus gordonii. In this study, we examined the effects of oral coimmunization of germfree rats with two S. gordonii recombinants expressing N (residues 55 to 145)- and C (residues 226 to 337)-terminal epitopes of P. gingivalis FimA to elicit FimA-specific immune responses. The effectiveness of immunization in protecting against alveolar bone loss following P. gingivalis infection was also evaluated. The results of this study show that the oral delivery of P. gingivalis FimA epitopes via S. gordonii vectors resulted in the induction of FimA-specific serum (immunoglobulin G [IgG] and IgA) and salivary (IgA) antibody responses and that the immune responses were protective against subsequent P. gingivalis-induced alveolar bone loss. These results support the potential usefulness of the S. gordonii vectors expressing P. gingivalis fimbrillin as a mucosal vaccine against adult periodontitis.

Effects of altering energy and protein supply to dairy cows during the dry period. 1. Intake, body condition, and milk production

We used 48 Holstein-Friesian cows to investigate the effects of altering energy and protein supply to dry cows. Cows were fed one of three diets for 6 wk prior to parturition: (a) a 60:40 (DM basis) mixture of grass silage with barley straw ad libitum; (b) grass silage ad libitum; or (c) 0.5 kg/d of prairie meal with grass silage ad libitum. The standard lactation diet was a flat-rate allocation of concentrates and grass silage ad libitum. We evaluated dry-period diets using four dry fistulated cows; rumen pH remained high (mean = 6.6) and ammonia concentrations followed N intake. The inclusion of straw reduced apparent ruminal digestion of OM, N, and NDF as well as microbial protein yield, though microbial yield per unit of OM apparently digested in the rumen remained unchanged. Voluntary intake of forage was reduced by the inclusion of straw, while the inclusion of prairie meal had little effect. The decline in intake as calving approached was lower with the silage and straw mix diet. There were large differences in the BW change over the final 5 wk of the dry period, although the opposite effect was seen in early lactation, and differences in BW and body condition score were small by lactation wk 22. Despite the substantial differences in nutrient supply and effects on body reserves, there was little effect of dry-period diet on subsequent performance. Lower forage intakes and yields of protein and lactose were confined to the first month of lactation for cows previously offered straw.

Heterogeneity of Porphyromonas gingivalis strains in the induction of alveolar bone loss in mice

These experiments examine alveolar bone loss in a model in which specific pathogen-free mice are exposed orally with Porphyromonas gingivalis. Alveolar bone loss was induced as a result of a specific infection with P. gingivalis, rather than other environmental antigens. Infection with live P. gingivalis was required, as significant bone loss did not follow gavage with formalin-killed P. gingivalis. The virulence of different strains of P. gingivalis was compared. Two laboratory strains of the bacteria (ATCC 53977 and W50) and a mutant strain lacking the 43-kDa fimbrillin (strain DPG3) induced bone loss. P. gingivalis 381, however, did not induce bone loss. There was a strong immunoglobulin G (IgG) antibody response to infection with each strain but a significant serum IgA response only to strain 381. These studies show that in mice with a background oral microflora bone loss is induced by a specific infection with P. gingivalis and that bacterial strain variation is important in determining whether alveolar bone loss will ensue.

Lesions in cattle exposed to Mycobacterium bovis-inoculated calves

Nine calves were housed for periods ranging from 24 to 117 days in close contact with cattle inoculated intranasally with Mycobacterium bovis. These "in-contact" calves were examined immunologically and bacteriologically during the period of exposure, and pathologically and immunocytochemically post mortem. Three became infected by day 14, as indicated by the detection of M. bovis in nasal mucus. In-vitro interferon-gamma production and lymphocyte proliferation were detected after stimulation of peripheral blood with M. bovis antigens in the majority of in-contact animals by day 28; this provided support for the role of immunological mechanisms in pathogenesis. Tuberculous lesions were found in the submandibular and bronchomediastinal lymph nodes and in the lungs of the in-contact calves; in distribution and appearance the lesions resembled those observed in naturally occurring disease. The distribution of M. bovis antigen and the numbers of mycobacteria within pulmonary lesions are reported. 1999 Harcourt Publishers Ltd.

Studies on the efficacy of intranasal vaccination for the prevention of experimentally induced parainfluenza type 3 virus pneumonia in calves

The efficacy of intranasal vaccination in preventing or limiting disease of the lower respiratory tract induced by parainfluenza 3 (PI3) virus was evaluated under experimental conditions, using a commercially available live vaccine containing a temperature-sensitive strain of PI3 virus. In a preliminary study four colostrum-deprived calves were vaccinated intranasally at one week and again at two months of age, and two similar calves were given an intranasal placebo. After the second vaccination serum antibodies to PI3 virus were detected in all four vaccinated calves, but not in the control animals. Seventeen days after the second vaccination all six calves were challenged with virulent PI3 virus, and they were killed six days later. The clinical scores and the extent of pulmonary consolidation were reduced in the vaccinated animals; PI3 virus was detected in the upper and lower respiratory tract of the control calves but in none of the vaccinated calves. In a larger scale study with 14 colostrum-fed calves, seven were vaccinated at one week and again at five weeks of age, and seven were given an intranasal placebo. Two weeks after the second vaccination all 14 calves were challenged with virulent PI3 virus. The clinical scores and lung consolidation were significantly reduced in the vaccinated calves in comparison with the controls. Six days after infection, 10 of the 14 calves were killed; PI3 virus was detectable in the nasal secretions of all seven control calves but in only one of the vaccinated animals, and PI3 viral antigen was detected in the lungs of the control calves but not in those of the vaccinated animals. One of the vaccinated calves had developed a severe clinical response after the challenge, but it had only minor lung consolidation when killed.

Serum antibody response to oral infection precedes but does not prevent Porphyromonas gingivalis-induced alveolar bone loss in mice

The purpose of this study was to determine whether humoral immunity prevents bacterially induced alveolar bone loss. BALB/cByJ mice were orally infected with the human periodontopathic bacterium Porphyromonas gingivalis, and were compared with sham-infected mice. Specific serum antibody titers to P. gingivalis were measured by enzyme-linked immunosorbent assay. Alveolar bone levels were measured as the distance from the cementoenamel junction to the alveolar bone crest and bone loss was defined as a change in bone levels over time or between infected and sham-infected animals. The specific humoral response was predominantly of the IgG isotype, although low levels of specific serum IgA were also present. Antibody titers in the infected animals were significantly different from those in the sham-infected animals by 18 days and remained at maximal levels at 47 days. Bone loss became significant by 26 days and continued to progress at 47 days. Thus the serum antibody response to oral infection with P. gingivalis preceded detectable bone loss and remained elevated while bone loss increased. The presence of specific antibody did not prevent the onset or progression of bone loss.

CD4(+) T cells and the proinflammatory cytokines gamma interferon and interleukin-6 contribute to alveolar bone loss in mice

In this study, we used a mouse model to examine the role of the adaptive immune response in alveolar bone loss induced by oral infection with the human gram-negative anaerobic bacterium Porphyromonas gingivalis. Severe combined immunodeficient mice, which lack B and T lymphocytes, exhibited considerably less bone loss than did immunocompetent mice after oral infection, suggesting that lymphocytes contribute to this process. Bone loss after oral infection was decreased in mice deficient in major histocompatibility complex (MHC) class II-responsive CD4(+) T cells, but no change in bone loss was observed in mice deficient in MHC class I-responsive CD8(+) T cells or NK1(+) T cells. Mice lacking the cytokine gamma interferon or interleukin-6 also demonstrated decreased bone loss. These results suggest that the adaptive immune response, and in particular CD4(+) T cells and the proinflammatory cytokines that they secrete, are important effectors of bone loss consequent to P. gingivalis oral infection. The studies also reinforce the utility of the mouse oral infection model in dissecting the pathobiology of periodontal disease.

An explanation for the different inhibitory characteristics of human serum butyrylcholinesterase phenotypes deriving from inhibition of atypical heterozygotes

The time course of inhibition of butyrylcholinesterase (EC 3.1.1.8) by the dimethylcarbamate Ro 02-0683 in sera taken from patients heterozygous for the usual (U), atypical (A), K or J variants was followed using propionylthiocholine as substrate. Data obtained were used to determine rate constants of inhibition together with the contribution made by each variant to total enzyme activity. The findings substantiate earlier reports that J and K mutations lead to quantitative changes in the concentration of usual enzyme in contrast to the qualitative changes of the atypical variant. The contribution of the atypical enzyme to the total activity in serum from UA, AK and AJ heterozygotes was respectively 17-20, 24-31 and 34-53%. The altered ratios of atypical to usual, K or J enzyme in UA, AK and AJ together with the constants on the usual enzyme alone, explain the differences in observed inhibitor numbers which enable these heterozygotes to be identified.

Catalytic parameters for the hydrolysis of butyrylthiocholine by human serum butyrylcholinesterase variants

Catalysed hydrolysis of butyrylthiocholine (BTCh) by the usual (UU), fluoride-resistant (FS), AK, AJ and atypical (AA) human serum butyrylcholinesterase (EC 3.1.1.8) variants was measured in phosphate buffer pH 7.4 at 25 degrees C. pS-curves for all phenotypes were S-shaped; the activities rose to a plateau with increasing substrate concentration except at 100 mM where there was a small decrease. To obtain the catalytic constants, three equations were applied: Michaelis-Menten equation (Eq. 1), Hill equation (Eq. 2) and an equation which assumes simultaneous binding of the substrate to the catalytic site and to a peripheral site on the enzyme (Eq. 3). Over a range from 0.01 to 50 mM BTCh, the activity versus substrate concentration relationship deviated from Michaelis-Menten kinetics (Eq. 1) while data fitted well with Eqs. 2 and 3. The Michaelis-Menten equation was applied separately to two BTCh concentration ranges: the corresponding Km constants for the UU, FS, AK, AJ and AA phenotypes ranged from 0.1 to 0.2 mM (at 0.01-1.0 mM BTCh) and from 0.3 to 2.0 mM (at 1.0-50 mM BTCh). Hill coefficients (nH) calculated from Eq. 2 were similar for all phenotypes (nH approximately 0.5). The dissociation constants K1 and K2 calculated from Eq. 3 for two sites on the enzyme fell between 0.02 and 0.12 mM (K1) and 0.89 and 4.9 mM (K2) for the five phenotypes. Experimental data support the assumption that the phenotypes studied have two substrate binding sites.

Root-surface caries in rats and humans: inhibition by a non-antimicrobial property of tetracyclines

The incidence of root caries has been found to increase as the population ages and as edentulism becomes less prevalent due to improved dental awareness and care, and as exposure of roots due to gingival recession has also increased in the elderly. The mechanism of root caries is thought to be mediated by both bacterial and mammalian proteases produced by plaque and the periodontal tissues, respectively. In the current study, a rat model of periodontal disease was used in which gnotobiotic rats were infected intra-orally with a periodontal pathogen (P. gingivalis). Infecting the rats with P. gingivalis increased the collagenase activity in the gingival tissue in association with severe alveolar bone loss. Treating P. gingivalis-infected rats with doxycycline or CMT-1 prevented the destruction of the periodontium by MMPs, thus preventing exposure of roots to subgingival bacterial plaque and host tissue collagenases and the subsequent development of root caries. In addition, a low-dose doxycycline (LDD, 20 mg bid, non-antimicrobial dose) for 3 months was used in humans predisposed to increased root caries as the result of heavy use of smokeless (chewing) tobacco, causing gingival recession, subgingival plaque accumulation with Gram-negative bacteria, increased gingival crevicular fluid flow (GCF), and elevated GCF collagenase. Daily administration of LDD in smokeless tobacco patients reduced the GCF collagenase and prevented the further development of root caries.

Early lesion formation in cattle experimentally infected with Mycobacterium bovis

Early lesion formation was examined in 13 calves inoculated intranasally with 2 x 10(7) colony-forming units of Mycobacterium bovis and killed either singly or in pairs at intervals of < or = 7 days from post-inoculation day (pid) 3 to pid 42. Immunological examinations were carried out before and after infection, and sequential necropsies were performed. M. bovis was recovered as early as pid 3, from the upper respiratory tract mucosae, retropharyngeal lymph nodes and caudal lung lobe. Gross tuberculous lesions were detected in both the upper respiratory tract mucosae and in the lungs of the calves killed from pid 14 onwards. Lesions were also present in the lymph nodes draining these areas. On histological examination, neutrophils appeared to play a key role in the earliest stages of lesion formation, and lesion mineralization was observed for the first time at pid 35. The contemporaneous development of lesions and cellular immunity, as demonstrated by in-vitro lymphocyte proliferation and interferon-gamma assay responses, provided further evidence of the role of immunopathogenic mechanisms in the development of bovine tuberculosis.

Immunostimulatory activity of LT-IIa, a type II heat-labile enterotoxin of Escherichia coli

Certain bacterial molecules potentiate immune responses to parenterally administered antigens. One such molecule that has been intensely investigated is cholera toxin, a type I heat-labile enterotoxin produced by the Gram-negative bacterium Vibrio cholerae. Immunization with a mixture of a foreign antigen and cholera toxin enhances the immune response to the antigen. Similar adjuvant activity is associated with LT-I, a closely related type I heat-labile enterotoxin produced by Escherichia coli. The adjuvant activities of LT-IIa, a member of the type II heat-labile enterotoxins produced by E. coli, have not been described. LT-IIa and CT differ significantly in amino acid sequence of the B polypeptides and in receptor binding affinity. In this study, rats were subcutaneously immunized with fimbrillin, a protein isolated from the bacterium Porphyromonas gingivalis, and with fimbrillin in combination with LT-IIa, the prototypical type II enterotoxin. Previous studies documented that fimbrillin administered alone is a poor immunogen. Animals immunized with the mixture of fimbrillin and LT-IIa produced high titers of specific IgG antibody directed against fimbrillin. Anti-fimbrillin antibody titers in sera from animals receiving the combination of LT-IIa + fimbrillin were comparable to those obtained from sera of animals immunized with cholera toxin + fimbrillin. The results of these experiments demonstrate that LT-IIa exhibits an adjuvant activity that is equal to that of cholera toxin. Recombinant methods have been established for producing large amounts of LT-IIa, an advantage that will likely provide an economic impetus to consider incorporating the enterotoxin as an immunostimulatory agent in future vaccines.

Serum CRP and IL-6 levels after trauma. Not predictive of septic complications in 31 patients

We studied 31 blunt trauma victims, Injury Severity Score (ISS) mean 14 (9-57), for the pattern of release of C-reactive protein (CRP) and cytokine interleukin-6 (IL-6). Blood samples were taken on admission (within 6 hours of injury), as well as at 24 hours, and 3, 5 and 7 days. Serum CRP and IL-6 were measured by ELISA. Subsequent surgical events and sepsis were noted. Serum IL-6 levels on admission were considerably higher (median 135 pg mL-1) than our laboratory reference range (< 5 pg mL-1), slowly returning towards reference values during the study. Serum CRP levels were similar to laboratory normal values on admission (median 8.5 mg L-1 vs 7.5 mg L-1), reaching peak values (median 110 mg L-1) after 3 days. There was a correlation between IL-6 release and ISS but not between CRP and ISS. Patients undergoing surgery showed further increases in IL-6 and CRP levels postoperatively. Of 24 surgical patients, 9 developed postoperative sepsis. In blunt trauma patients, early assessment of the markers CRP or IL-6 were not useful for the diagnosis of sepsis. Levels of CRP following accidental or surgical trauma should be assessed with caution.

Oral infection with Porphyromonas gingivalis and induced alveolar bone loss in immunocompetent and severe combined immunodeficient mice

The suitability of a mouse model for host response in the induction of alveolar bone loss by Porphyromonas gingivalis was explored. The mouths of immunocompetent and severe combined immunodeficient (SCID) mice were infected with P. gingivalis ATCC 53977. P. gingivalis was not isolated from the mouths of these mice before infection, but was present at least 42 days after infection. P. gingivalis-specific IgG was present in sera from the infected, immunocompetent mice at the end of these experiments (42 days). Specific IgG was not present in sham-infected or uninfected immunocompetent mice, nor in any immunodeficient mice. Specific IgM was not present in any sera at 42 days. Infected, immunocompetent mice of two strains showed significant bone loss in comparison to sham-infected or uninfected immunocompetent mice (p < 0.05). Infected SCID mice, which are genetically lacking both B and T lymphocytes, also showed significant bone loss compared with sham-infected or uninfected SCID mice (p < 0.05). However, the degree of bone loss was greater in immunocompetent than immunodeficient mice: the relative amount of bone in infected mice was 77% of that in sham-infected immunocompetent mice, and 86% of sham values in SCID mice (p = 0.025). Thus oral infection of mice is a feasible model for studying the effects of host response on P. gingivalis-induced alveolar bone loss. Because bone loss was induced both in immunocompetent and SCID mice but was greater in immunocompetent mice, it appears that neither B nor T cells are absolutely necessary for bone resorption in response to P. gingivalis infection but they may significantly modulate the degree of resorption.

The effect of supplementary protein on in vivo metabolism of the mammary gland in lactating dairy cows

Four lactating cows equipped with rumen and duodenal cannulas were fed a diet of grass silage and concentrates containing either 12.4 or 17.2% CP (DM basis) in a change-over design. Additional protein was supplied as white fish meal. Fish meal did not affect molar proportions of VFA in the rumen, but duodenal NAN supply was increased .69 g/g of N in supplementary feed. In Experiment 2, three lactating dairy cows that had been prepared with catheters across the mammary gland were fed the same diets using a switchback design. Blood samples were taken to determine changes in metabolite flux to the mammary gland. In both experiments, milk production and protein yield were nonsignificantly increased by addition of fish meal. Milk urea output was increased from 3.18 to 4.74 g/d by fish meal supplementation, reflecting increased arterial concentrations of urea. Concentrations of glucose, VFA, and BHBA in blood showed no substantial changes because of dietary supplementation of fish meal. Supply of essential AA increased 26% with fish meal supplementation, mammary uptake increased 34%, but milk protein output only increased 5%. The low efficiency of conversion of supplementary protein to milk protein appears to be related to the inability of the gland to utilize the additional AA.

Tetracyclines inhibit Porphyromonas gingivalis-induced alveolar bone loss in rats by a non-antimicrobial mechanism

Tetracyclines have been widely used as adjuncts in periodontal therapy due to the antimicrobial efficacy of these drugs. Recently, their ability to inhibit host-derived matrix metalloproteinases (collagenase and gelatinase) and bone resorption in organ culture has also been invoked as a therapeutic rationale. The current study was undertaken to determine whether tetracyclines can inhibit alveolar bone loss in vivo due to a non-antimicrobial action of these drugs. Experimental periodontitis was induced by inoculating adult, male Sprague-Dawley rats with P. gingivalis (strain 381) following kanamycin/ampicillin pretreatment. Doxycycline, non-antimicrobial chemically-modified tetracycline (CMT-1) and vehicle alone were administered daily to 3 infected groups of rats (n = 6 rats per group; each group housed in a sterilized inflatable isolator) beginning 10 days after P. gingivalis inoculation. The control group (n = 6; non-infected rats) received only vehicle. After 5 weeks of daily drug administration by gastric intubation, the experiment was terminated and blood samples were taken from each animal to determine antibody levels against P. gingivalis. Plaque samples were collected from each group of animals before and after P. gingivalis inoculation and at the end of the experiment for microbiological examination. The jaws were removed from each rat, defleshed and then analyzed morphometrically and radiographically to assess bone loss. Serum antibody levels against P. gingivalis were significantly elevated in the 3 infected groups compared to the non-infected controls. This, together with the microbiologic findings, indicated that these groups of rats were infected with P. gingivalis.(ABSTRACT TRUNCATED AT 250 WORDS)

Inactivation of the Porphyromonas gingivalis fimA gene blocks periodontal damage in gnotobiotic rats

Fimbrial production by Porphyromonas gingivalis was inactivated by insertion-duplication mutagenesis, using the cloned gene for the P. gingivalis major fimbrial subunit protein, fimA. by several criteria, this insertion mutation rendered P. gingivalis unable to produce fimbrilin or an intact fimbrial structure. A nonfimbriated mutant, DPG3, hemagglutinated sheep erythrocytes normally and was unimpaired in the ability to coaggregate with Streptococcus gordonii G9B. The cell surface hydrophobicity of DPG3 was also unaffected by the loss of fimbriae. However, DPG3 was significantly less able to bind to saliva-coated hydroxyapatite than wild-type P. gingivalis 381. This suggested that P. gingivalis fimbriae are important for adherence of the organism to saliva-coated oral surfaces. Further, DPG3 was significantly less able to cause periodontal bone loss in a gnotobiotic rat model of periodontal disease. These observations are consistent with other data suggesting that P. gingivalis fimbriae play an important role in the pathogenesis of human periodontal disease.

Periodontopathic potential of two strains of Porphyromonas gingivalis in gnotobiotic rats

Germ-free rats were monoinfected with Porphyromonas gingivalis strains 381 or A7A1-28 for 42 or 84 days. Both strains induced substantial destruction of alveolar bone and soft tissue when compared to non-infected controls, but the patterns were different. Strain A7A1-28 was associated with increased activity of host collagenase and gelatinase at 42 days, whereas the activity was elevated to a lesser extent at 84 days. Strain 381 showed a moderate increase in host proteinase activity at 42 days, and this remained unchanged until day 84. Strain A7A1-28 was associated with more bone loss than strain 381 by a morphometric analysis that detects horizontal bone loss in the maxilla. Strain 381 was associated with more bone loss than strain A7A1-28 by a radiographic method that detects vertical intrabony defects in the mandible. Infection with one strain gave rise to serum and salivary antibodies strongly reactive to the infecting strain and moderately reactive to antigens from the other strain. This indicates that some antigenic similarity exists between the strains and that there are also strain or perhaps serotype differences in antibody responses induced by infection. Thus two strains of P. gingivalis differing in antigenicity and pathogenicity in the mouse model of the subcutaneous abscess cause substantial periodontal destruction in the germ-free rat. The disease pattern is, however, different, with strain A7A1-28 inducing mostly horizontal bone loss and strain 381 mostly vertical.

Periodontal bone loss in Porphyromonas gingivalis-infected specific pathogen-free rats after preinoculation with endogenous Streptococcus sanguis

Anaerobic Gram-negative bacteria dominate in periodontitis locations, while Gram-positive bacteria characterize healthy sites. A well-established Gram-positive flora might therefore inhibit the colonization of Gram-negative pathogens. The purpose of the present investigation was to examine whether endogenous S. sanguis could prevent, or reduce, periodontal bone loss in rats infected with a virulent P. gingivalis strain. Sixty specific pathogen-free Wistar rats were divided into 6 groups. Doxycycline was administered in the drinking water for 2 weeks to the groups A, B, C, and D to suppress the preexisting microflora in the mouth. Rats in groups A and C were subsequently inoculated with an S. sanguis strain, isolated from one of the rats, once a day for 5 d. Infection with P. gingivalis 381 was then carried out for 5 d in groups A, B, and E. Group F was not treated with doxycycline nor infected with bacteria and served as untreated control. Six weeks after the P. gingivalis inoculation, the rats were killed. Periodontal bone levels were assessed radiographically and morphometrically, and serum antibody against P. gingivalis 381 was determined by a fluorescence immunoassay. Periodontal bone support, determined radiographically, was reduced in group B (doxycycline-treated, P. gingivalis-inoculated) compared with the other groups. In contrast, the morphometric determination showed no differences between the groups. In group B antibody levels against two different P. gingivalis 381 cell surface antigens were significantly elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunization with Porphyromonas (Bacteroides) gingivalis fimbriae protects against periodontal destruction

Adhesive fimbriae from Porphyromonas gingivalis are cell surface structures which may be important in the virulence of this oral pathogen and thus may serve as a critical or target antigen. Immunization with highly purified 43-kDa fimbrial protein protected against periodontal tissue destruction when tested in the P. gingivalis-infected gnotobiotic rat model. A similarly highly purified 75-kDa cell surface component did not provide protection. Heat-killed whole-cell and sonicated cell surface extracts which contain the 43-kDa protein as well as the 75-kDa component were protective also. This study indicates that the fimbrial protein may serve as a model for the development of effective vaccines against periodontitis, a major human oral disease.

Immunization with Fimbrial Protein and Peptide Protects against Porphyromonas Gingivalis-Induced Periodontal Tissue Destruction

In these studies we have attempted to show that cell surface structures are critical antigens for protection against P. gingivalis-induced periodontal destruction. Fimbrillin, and in particular a synthetic 20-amino-acid fimbrillin peptide, exerts a protective effect in gnotobiotic rats, thus identifying them as potentially useful in the development of a vaccine.

Periodontal bone level and gingival proteinase activity in gnotobiotic rats immunized with Bacteroides gingivalis

Bacteroides gingivalis is associated with various forms of periodontal disease. To assess the role of the immune response in modulating B. gingivalis-associated periodontal disease, the effect of immunization of B. gingivalis-induced periodontal bone loss was evaluated in gnotobiotic rats. Male Sprague-Dawley rats immunized with various doses of whole cells or sham-immunized with incomplete Freund's adjuvant were monoinfected with B. gingivalis in carboxymethylcellulose by gavage. Two additional groups served as either sham-immunized or untreated germ-free controls. Forty-two days after infection, all rats were killed, periodontal bone level was assessed morphometrically and radiographically, and gingival proteinase (mammalian collagenase and acid cathepsin) activity was assessed biochemically. B. gingivalis was present in oral samples from all monoinfected rats, and no contaminating bacteria were detected in any oral or fecal sample. Animals immunized with B. gingivalis cells had elevated serum and saliva antibodies to whole cells and partially purified fimbriae from B. gingivalis. Infected sham-immunized rats had significantly more periodontal bone loss than noninfected controls, whereas the periodontal bone level in infected rats immunized with 10(10) B. gingivalis cells was similar to that of the noninfected controls. The activities of gingival collagenase and cathepsin B and L were high in sham-immunized infected rats and low in all other animal groups. In conclusion, it is possible to reduce B. gingivalis-induced periodontal tissue loss in gnotobiotic rats by immunization.

Asymmetry in periodontal bone loss of gnotobiotic Sprague-Dawley rats

In five consecutive experiments involving 78 gnotobiotic rats, significant bone loss was seen in the maxillae of those mono-infected with strains of Porphyromonas gingivalis. No significant bone loss was seen in the mandibles, and when data from both jaws were combined, the significant loss in the maxillae was occasionally concealed. It is recommended, therefore, that the levels of maxillary and mandibular bone in rats be analysed separately. A possible lateral bias of periodontal bone level was investigated in the same rats. In a highly significant number of cases the right-hand side was more severely affected than the left. This asymmetry was found in both germ-free and infected rats, and consequently could not be ascribed to P. gingivalis infection. Asymmetry of bone loss may contribute to the total random variation in bone level in rats and should be accounted for in future studies of experimental periodontitis in this model.

A 2-year quantitative assessment of Chlamydia trachomatis in a sexually transmitted diseases clinic population by the MicroTrak direct smear immunofluorescence test

The MicroTrak direct smear immunofluorescence test was used to determine the prevalence of Chlamydia trachomatis elementary bodies (EBs) in groups of patients in various clinical categories, most of whom were seen in a clinic for sexually transmitted diseases (STD). Overall, 8138 adequate specimens were tested, of which 14.3% were found to contain chlamydial EBs. Of the samples from patients seen in the STD clinic, over 70% were from women and 14.9% of these were positive, as were 15.7% of those from men. EBs were detected in 27% of samples from infants and in 7.0% of those from adults with conjunctivitis. EBs were detected most often in men with nongonococcal urethritis (40.2%), infants with conjunctivitis (30%) and contacts of chlamydiae-positive patients (24.5%) and least often in 'prostatitis' (2.9%) and patients tested to determine the success of treatment (2.7%). Over 40% of samples from both the male urethra and the cervix contained 10 or fewer EBs, highlighting the importance of recognizing small numbers and the sensitivity required of other detection procedures.

Albumin-adjusted calcium concentration in serum increases during normal pregnancy

Concentrations of total calcium and albumin were measured in serum specimens from 41 women at intervals before, during, and after 42 pregnancies. The albumin concentration decreased but the calcium decreased more slowly, so that the albumin-adjusted calcium concentration increased from conception to term. These findings, taken in conjunction with published observations of hypercalciuria, increased concentrations of 1,25-dihydroxycholecalciferol and calcitonin in serum, and decreased concentrations of intact parathyrin in serum, strongly suggest that maternal ionized calcium increases throughout normal pregnancy.

Albumin-adjusted calcium concentration in serum increases during normal pregnancy

Concentrations of total calcium and albumin were measured in serum specimens from 41 women at intervals before, during, and after 42 pregnancies. The albumin concentration decreased but the calcium decreased more slowly, so that the albumin-adjusted calcium concentration increased from conception to term. These findings, taken in conjunction with published observations of hypercalciuria, increased concentrations of 1,25-dihydroxycholecalciferol and calcitonin in serum, and decreased concentrations of intact parathyrin in serum, strongly suggest that maternal ionized calcium increases throughout normal pregnancy.

Studies of the effect of recombinant human-alpha 1 interferon on experimental parainfluenza type 3 virus infections of the respiratory tract of calves

The effect of the administration of recombinant human interferon on the severity of clinical disease and the extent of pneumonic lesions in calves infected experimentally with bovine parainfluenza 3 (PI3) virus was studied in two experiments. In the first, three pairs of calves aged seven to 10 days were used; one of each pair was injected intramuscularly with 10(6) units of interferon/kg bodyweight for three consecutive days, and the other was left untreated. On the day after the first injection of interferon all the calves were challenged with PI3 virus, a different dose being administered to each pair. There was no evidence of any protective effect from the treatment with interferon. The second experiment used eight, six-week-old calves; four were inoculated in the same way with interferon and all the calves were challenged with the same dose of PI3. Again, there was no evidence of a reduction either in the severity of clinical disease or in the extent of lung consolidation in the calves treated with interferon.

Two complementary methods of assessing periodontal bone level in rats

Several methods have been applied to measure periodontal disease in rats. The purpose of the present study was to test the reproducibility of a morphometric and a radiographic method and to describe the correlation between the two methods. Periodontal bone loss on 25 defleshed rat heads was assessed under microscopic by measuring the distances from the cementoenamel junction to the alveolar bone crest at 36 buccal sites in each animal. On magnified radiographs from 25 rat mandibles periodontal bone support was expressed by the ratio apex-deepest bony defect: apex-cusp tip distally on first molars. All measurements were performed blind and in duplicate on two separate occasions. The bilateral 95% confidence limits for the error of method of measurement were estimated from the t-distribution. In a second experiment 50 rat heads were assessed by both methods, and the correlation between the recordings was estimated by the Spearman rank correlation analysis. Compared to the considerable total variation in the material, the variations due to error of methods of measurement were small, i.e. the reproducibility of both methods was satisfactory. A significant correlation was found between the methods. Since the morphometric method mainly measures horizontal bone loss, whereas the radiographic method detects intrabony interproximal defects, it is concluded that future studies would benefit from applying both methods to assess alveolar bone loss in rats.

Blood alcohol levels in acute elderly admissions to hospital

Blood alcohol levels were estimated in 141 patients admitted acutely over a one month period to a geriatric unit. Only four (2.8%) had alcohol detectable in their blood. The levels were low, suggesting that alcohol intoxication is not a major factor in the admission of the elderly to hospital.

A longitudinal study of cholinesterase changes in pregnancy

Serum cholinesterase activity was measured at intervals before, during, and after 44 pregnancies in 43 women. Three patterns of change were seen: (a) A decline in activity after conception, with no return towards pre-conception values before delivery (20 pregnancies). (b) A decline in activity accompanied by a partial or complete return to pre-conception values before delivery (19 pregnancies). (c) Either no discernible decline or increased activity during gestation (five pregnancies). We saw no association between these patterns and either the sex of the child, parity, smoking history, or alcohol intake. However, the continuous decrease in cholinesterase activity occurred in the youngest group of women, a decrease followed by an increase in the intermediate age group, and no decrease at all in the oldest group. Although not all the age-related differences quite reached statistical significance, these findings suggest that the patterns of change may be determined by some aspect of maternal physical maturity.

A longitudinal study of cholinesterase changes in pregnancy

Serum cholinesterase activity was measured at intervals before, during, and after 44 pregnancies in 43 women. Three patterns of change were seen: (a) A decline in activity after conception, with no return towards pre-conception values before delivery (20 pregnancies). (b) A decline in activity accompanied by a partial or complete return to pre-conception values before delivery (19 pregnancies). (c) Either no discernible decline or increased activity during gestation (five pregnancies). We saw no association between these patterns and either the sex of the child, parity, smoking history, or alcohol intake. However, the continuous decrease in cholinesterase activity occurred in the youngest group of women, a decrease followed by an increase in the intermediate age group, and no decrease at all in the oldest group. Although not all the age-related differences quite reached statistical significance, these findings suggest that the patterns of change may be determined by some aspect of maternal physical maturity.

The digestion of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) by grazing cattle

1. Pure swards of perennial ryegrass (Lolium perenne cv. Melle) as a primary growth (May), trimmed primary growth (early June) and regrowth (late June), and white clover (Trifolium repens cv. Blanca) as a mature primary growth (July) and vegetative regrowth (August), were grazed by twelve Friesian steers (mean body-weights throughout experiment 152-231 kg) at daily allocation rates of forage which provided dry matter (DM) intakes ranging from 28 to 36 g/kg body-weight). 2. Total nitrogen contents of the three ryegrasses declined with season (37-20 g/kg DM), but in vitro organic matter (OM) digestibilities were relatively constant (0.76-0.79). The clovers had higher N (average 36.6 g/kg DM) and lower fibre and water-soluble carbohydrate contents than the grasses, and in vitro OM digestibilities of 0.70 and 0.76 respectively. 3. Duodenal digesta samples were obtained, using a portable sampling apparatus from the animals grazing the pasture, and estimates of the flow of nutrients into the small intestine were derived using two indigestible markers which were continuously infused into the rumen using a portable infusion apparatus. Forage intakes were calculated from estimates of faecal output of indigestible OM and the predicted in vivo OM digestibilities of the forages consumed. Coefficients of variation for OM flow to the small intestine and OM intake were 11.8 and 10.9% respectively. 4. The apparent digestion of OM in the rumen ranged from 722 to 741 g/kg digestible OM intake and from 681 to 711 g/kg digestible OM intake for the grass and clover diets respectively. Substantial losses of ingested N before the small intestine were measured on all diets except the regrowth ryegrass. Losses were 0.30 and 0.40 g/g N intake on the primary growth ryegrass and the regrowth clover respectively; N contents were 37 and 39 g/kg DM respectively. 5. Comparison of the values obtained at pasture with that obtained when similar diets were offered to housed cattle (Beever et al. 1985) indicated that combined relations relating duodenal OM and non-ammonia-N (NAN) flows to OM and N intakes respectively could be established for each diet. For two diets (primary-growth grass and regrowth clover) the relations were curvilinear; for the remaining diets, the derived relations were linear.(ABSTRACT TRUNCATED AT 400 WORDS)