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Biomedical subjects

S A Martin

Publications and source records attributed to S A Martin.

At least 91 records · Page 5Linked to original sources
PubMed1995

Effect of malate on in vitro mixed ruminal microorganism fermentation.

The objective of this study was to evaluate the effects of different concentrations of DL-malate (disodium salt) on the in vitro mixed ruminal microorganism fermentation of soluble starch or cracked corn. Ruminal fluid was collected from a steer fed 6.8 kg of forage and 2.3 kg of concentrate supplement once daily, and mixed ruminal microorganisms were incubated in anaerobic media (40 mL) that contained 20% (vol/vol) ruminal fluid in batch culture for 24 h at 39 degrees C. Malate was added to the incubation bottles (n = 4) to achieve final concentrations of 0, 4, 8, and 12 mM. When mixed ruminal microorganisms were incubated with only DL-malate as the substrate, final pH numerically increased, propionate and total VFA concentrations increased (P < .05), and the acetate:propionate ratio decreased (P < .05) as the concentration of DL-malate increased from 0 to 12 mM. Fermentation of cracked corn in the presence of 8 or 12 mM DL-malate resulted in an increase (P < .05) in final pH and propionate concentration. Total VFA tended to increase (P < .21), whereas final concentrations of L-lactate numerically decreased. In the case of soluble starch, 8 and 12 mM DL-malate caused a decrease (P < .05) in methane concentration. When only ruminal fluid (no added anaerobic medium) was used as the inoculum rather than 20% ruminal fluid medium, similar results for final pH, propionate, L-lactate, and total VFA were observed for soluble starch and corn incubations treated with DL-malate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The effect of unilateral injury to the vas deferens on the contralateral testis in immature and adult rats.

The relationship between alterations in testicular histology and antisperm antibodies in immature and mature Lewis rats subjected to unilateral vasectomy was studied. Forty percent of immature rats and 90% of mature rats (p < 0.01) demonstrated significant alterations in both the obstructed (vasectomy) testis and the contralateral testis. There were significant changes in antisperm antibodies (ELISA) in the animals which demonstrated histologic changes.

Age Factors↗
PubMed1994

The gingival immune response to periodontal pathogens in juvenile periodontitis.

A gingival explant culture system was utilized to evaluate the reactivity of local immunoglobulins produced by juvenile periodontitis tissue. Gingival explant culture supernatant fluids were screened, via a standardized dot-immunobinding assay, for antibodies reactive to: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Campylobacter rectus, Eikenella corrodens, Peptostreptococcus micros, Peptostreptococcus anaerobius, Capnocytophaga ochracea, Eubacterium nodatum and Fusobacterium nucleatum and one nonoral microorganism, Porphyromonas asaccharolytica. Of the 75 juvenile periodontitis supernatant fluids tested, the organisms that reacted with the highest numbers of supernatant fluids were E. nodatum (72%) and A. actinomycetemcomitans (49%). More juvenile periodontitis than healthy tissue samples showed supernatant fluid reactivity to P. intermedia, C. ochracea, E. nodatum and P. micros. No significant difference was observed between the juvenile periodontitis group supernatant fluids reactivity and the supernatant fluids of the other periodontal disease groups tested. Cluster analysis revealed the association, as determined by supernatant fluid reactivity, of P. micros and C. ochracea in the juvenile periodontitis group. The data from this investigation are consistent with a hypothesis of multiple possible etiologies of periodontal destruction in juvenile periodontitis and other forms of periodontal diseases.

Adolescent↗
PubMed1994

Nutrient transport by ruminal bacteria: a review.

Fermentation pathways have been elucidated for predominant ruminal bacteria, but information is limited concerning the specific transport mechanisms used by these microorganisms for C, energy, and N sources. In addition, it is possible that changes in ruminal environmental conditions could affect transport activity. Five carrier-mediated soluble nutrient transport mechanisms have been identified in bacteria: 1) facilitated diffusion, 2) shock sensitive systems, 3) proton symport, 4) Na+ symport, and the 5) phosphoenolpyruvate phosphotransferase system (PEP-PTS). Several regulatory mechanisms are also involved at the cell membrane to coordinate utilization of different sugars. Recent research has shown that predominant ruminal bacteria are capable of transporting soluble nutrients by several of the mechanisms outlined above. Megasphaera elsdenii, Selenomonas ruminantium, and Streptococcus bovis transport glucose by the PEP-PTS, and S. ruminantium and S. bovis also possess PEP-PTS activity for disaccharides. Glucose PTS activity in S. bovis was highest at a growth pH of 5.0, low glucose concentrations, and a dilution rate of .10 h-1. The cellulolytic ruminal bacterium Fibrobacter succinogenes uses a Na+ symport mechanism for glucose transport that is sensitive to low extracellular pH and ionophores. Sodium also stimulated cellobiose transport by F. succinogenes, and there is evidence for a proton symport in the transport of both arabinose and xylose by S. ruminantium. A chemical gradient of Na+ seems to play an important role in AA transport in several ruminal bacteria. Studying nutrient transport mechanisms in ruminal bacteria will lead to a better understanding of the ruminal fermentation.

Amino Acids↗
PubMed1994

Factors affecting L-lactate utilization by Selenomonas ruminantium.

Studies were conducted to evaluate factors that affect L-lactate utilization by the ruminal bacterium Selenomonas ruminantium HD4. L-Lactate uptake decreased over time both in the presence and absence of 10 mM L-malate. Compared with uptake in the absence of malate, 10 mM L-malate increased L-lactate uptake at 30 s and 45 min. Because L-malate had little effect on L-lactate uptake for cells grown on soluble carbohydrates compared to lactate-grown cells, it seems that the stimulation due to L-malate is inducible. Sodium concentrations between 25 and 100 mM stimulated long-term (45 min) L-lactate uptake in the presence of 10 mM L-malate, whereas uptake in the absence of L-malate was low regardless of the Na+ concentration. Monensin inhibited L-lactate uptake by 42%, and this is consistent with the involvement of Na+ in L-lactate utilization. Initial uptake (30 s) of L-lactate was not dependent on Na+. L-Lactate uptake was stimulated by 10 mM L-malate at extracellular pH values between 4.0 and 8.0. No inhibition of L-lactate uptake was observed in the presence of 10 mM glucose, maltose, sucrose, xylose, or D-lactate. The metabolic inhibitors carbonyl cyanide m-chlorophenyl-hydrazone, 2,4-dinitrophenol, and NaF inhibited L-lactate uptake (> 79%), suggesting that protons may be involved in L-lactate uptake by this bacterium. Collectively, these experiments show that L-lactate uptake by S. ruminantium HD4 is stimulated in the presence of 10 mM L-malate at pH values and Na+ concentrations commonly found in the rumen.

Animals↗
PubMed1994

Wet brewers grains for lactating dairy cows during hot, humid weather.

Twenty lactating Jersey cows were offered diets containing 0, 15, or 30% wet brewers grains or 30% wet brewers grains plus liquid brewers' yeast during hot, humid weather. The DMI was not different, even though diets with 30% wet brewers grains contained only 35.5% DM and approximately 50 versus 36.8% NDF for the control diet. Yields of milk and FCM did not differ for cows offered the control diet versus wet brewers grains or diets with 15 versus 30% wet brewers grains, but milk yield for diets with 30% wet brewers grains was greater with added liquid brewers' yeast than without it. Milk fat percentage was not different, but milk protein percentage was lower, for diets with wet brewers grains than for controls and for 30% wet brewers grains than for 15% wet brewers grains. Serum urea N was lower for control cows than for cows receiving the diets with wet brewers grains. Feed cost per cow was lower for wet brewers grains versus the control diet, and income over feed cost was greater for diets with 30 versus 15% wet brewers grains. Large quantities of wet brewers grains can be added to the diet during hot weather without depressing DMI.

Animal Feed↗
PubMed1994

Current controversies in pediatric transplantation.

Transplantation in children has become a therapeutic option for several end stage organ diseases. The kidney, liver, and heart are the most common organs' transplanted; however, an increasing number of children are undergoing successful intestine, lung, and multiple organ transplant combinations. Through case study reports, emerging transplant options for the child experiencing end stage liver, intestine, heart, and lung failure are described. Critical care nurses play a crucial role in the postoperative recovery of these patients. An understanding of the transplant process and consequences of immunosuppression will help the critical care nurse identify signs of rejection, infection, and posttransplant lymphoproliferative disease.

Child, Preschool↗
PubMed1994

Stage specific differences in steady state levels of mRNA encoding the major surface glycoprotein of Brugia pahangi.

The glycoprotein, gp30, is the major soluble cuticular antigen of the adult lymphatic fiarial worm Brugia pahangi (Maizels et al., 1983, Devaney, 1988). Cookson et al., 1992 suggested that gp30 may function as an antioxidant enzyme protecting B. pahangi from the vertebrate host defence mechanism. In this communication we report that the gp30 transcript is present in each of the life cycle stages, including mosquito derived L3's, and that there is a 50 fold increase in the transcription of gp30 in young adults (28 days post infection) compared to mature adults. These findings suggest that gp30 performs a general function relevant throughout the B. pahangi life cycle and in particular to young adults.

Animals↗
PubMed1993

Identification of the facile gas-phase cleavage of the Asp-Pro and Asp-Xxx peptide bonds in matrix-assisted laser desorption time-of-flight mass spectrometry.

Abundant ions corresponding to the gas-phase cleavage of the Asp-Pro and Asp-Xxx bonds of peptides in the process of matrix-assisted laser desorption were observed using a time-of-flight mass spectrometer equipped with both linear and reflector mass analyzers. Peptides containing the N-terminal sequence, Asp-Pro ... from an endoproteinase Asp-N digest yielded one peak in the molecular ion region in the linear mode and two equally abundant peaks in the reflector mode TOF mass spectra. The lower molecular masses in the reflector mode mass spectra could be eliminated by removing the Asp residue or derivatizing its side-chain carboxyl group. The observed mass differences did not correspond to any amino acid; however, by lowering the potential of the reflector to correct for the energy loss the mass difference was determined to be 115 Da, i.e., Asp. The extent and rate of this decomposition was compared with that obtained using a four-sector tandem mass spectrometer in the MS/MS mode of operation without and with a collision gas at collision cell potentials of 3.0 and 9.86 kV. These data suggest the Asp-Pro peptide bond is more labile than other peptide bonds in the gas phase. Abundant metastable decomposition of internal Asp-Pro bonds was also observed in larger peptides and proteins. Based on these latter data, a mechanism for this gas-phase cleavage is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Site-specific carbohydrate identification in recombinant proteins using MALD-TOF MS.

The utility of matrix-assisted laser desorption time-of-flight (MALD-TOF) mass spectrometry for the analysis of recombinant glycopeptides is discussed and compared to information which may be obtained by fast atom bombardment mass spectrometry (FABMS) and tandem mass spectrometry (MS/MS). MALD-TOF appears to be 10-100 times more sensitive than FAB MS for the analysis of underivatized glycopeptides, providing qualitative site-specific information regarding the carbohydrate microheterogeneity without the extensive isolation and derivatization procedures required to obtain similar information by FAB MS. Analysis of a digest mixture in the positive and negative ion mode of MALD-TOF indicated that, in mixtures, sialylated glycopeptides are preferentially detected in the negative ion mode. The determination of the molecular masses of a glycopeptide with MALD-TOF prior to and after treatment with a variety of specific glycosidases, often without removal of the buffers, coupled to a comparison of molecular mass information available from a carbohydrate database facilitates the assignment of a carbohydrate composition. The vast majority of the molecular ion signal observed in the linear mode for sialylated glycopeptides are metastable ions. Reflector mass spectra reveal a shift to lower mass consistent with the loss of most of the neuraminic acid residues. The loss of Hex and HexNAc residues is also observed. Sequential lowering of the reflector potential reveals structurally significant fragment ions representing the carbohydrate and peptide portions of the molecule.

Amino Acid Sequence↗
PubMed1993

Microbial delignification with white rot fungi improves forage digestibility.

Three wild-type white rot fungi and two cellulase-less mutants developed from Phanerochaete chrysosporium K-3 (formerly Sporotrichum pulverulentum) were tested for their ability to delignify grass cell walls and improve biodegradation by rumen microorganisms. Fungal-treated and control stems of Bermuda grass were analyzed for their content of ester- and ether-linked aromatics by using alkali extraction and gas chromatography, for in vitro dry weight digestion and production of volatile fatty acids in in vitro fermentations with mixed ruminal microorganisms, for loss of lignin and other aromatics from specific cell wall types by using microspectrophotometry, and for structural changes before and after in vitro degradation by rumen microorganisms by using transmission electron microscopy. P. chrysosporium K-3 and Ceriporiopsis subvermispora FP 90031-sp produced the greatest losses in lignin and improved the biodegradation of Bermuda grass over that of untreated control substrate. However, C. subvermispora removed the most lignin and significantly improved biodegradation over all other treatments. Phellinus pini RAB-83-19 and cellulase-less mutants 3113 and 85118 developed from P. chrysosporium K-3 did not improve the biodegradation of Bermuda grass lignocellulose. Results indicated that C. subvermispora extensively removed ester-linked p-coumaric and ferulic acids and also removed the greatest amount of non-ester-linked aromatics from plant cell walls. Microscopic observations further indicated that C. subvermispora removed esters from parenchyma cell walls as well as esters and lignin from the more recalcitrant cell walls (i.e., sclerenchyma and vascular tissues). C. subvermispora improved in vitro digestion and volatile fatty acid production by ruminal microorganisms by about 80%, while dry matter loss due to fungi was about 20% greater than loss in untreated control stems. The chemical and structural studies used identified sites of specific fungal attack and suggested mechanisms whereby improvement occurred.

Journal Article↗
PubMed1993

Effects of an Aspergillus oryzae fermentation extract and other factors on lactate utilization by the ruminal bacterium Megasphaera elsdenii.

The objective of this study was to determine the effects of an Aspergillus oryzae fermentation extract (Amaferm) as well as other factors on lactate utilization by the ruminal bacterium Megasphaera elsdenii B159. Addition of Amaferm or a filter-sterilized Amaferm filtrate stimulated L-lactate uptake by both M. elsdenii and the ruminal selenomonad strain H18. Growth of M. elsdenii in medium that contained DL-lactate (2 g/L), Trypticase, and yeast extract was only slightly stimulated by the addition of 5% (vol/vol) Amaferm filtrate after 24 h. However, growth of M. elsdenii in a similar medium lacking Trypticase and yeast extract was increased over twofold by the addition of either 2 or 5% (vol/vol) Amaferm filtrate. These results suggest that Amaferm provides growth factors (i.e., amino acids, B vitamins) to support growth of M. elsdenii on lactate. There was no inhibition of L-lactate uptake when lactate-grown cells of M. elsdenii were incubated with excess (10 mM) glucose, sucrose, or maltose. In addition, when cells were grown on glucose, sucrose, or maltose rather than lactate there was little difference in L-lactate uptake, suggesting that L-lactate transport in M. elsdenii is not subject to catabolite repression by these soluble sugars. Both K+ and Na+ had little effect on L-lactate uptake. Uptake was unaffected at extracellular pH values between 6.0 and 8.0, whereas pH values of 5.0 and 4.0 increased uptake. In addition, L-lactate uptake was inhibited between 34 and 61% by protonophores. These results suggest that protons may be involved in the uptake of L-lactate by M. elsdenii B159.

Animal Feed↗
PubMed1993

Effects of Aspergillus oryzae fermentation extract on in vitro equine cecal fermentation.

The objective of this study was to examine the effects of Aspergillus oryzae fermentation extract on the in vitro equine cecal fermentation of soluble starch, amino acids/peptides, coastal bermudagrass hay, and alfalfa hay. Cecal contents were obtained from a cecally fistulated Quarter Horse gelding fed coastal bermudagrass and grain (70:30) either unadapted or adapted to dietary A. oryzae supplementation (2 g/d). Mixed cecal microorganisms were incubated in anaerobic media for either 24 h (soluble starch, amino acids) or 48 h (bermudagrass hay, alfalfa hay). A. oryzae was added to the incubation bottles (n = 4) at concentrations of 0, .07, or .7 g/L. Fermentation of soluble starch in the presence of .7 g/L of A. oryzae resulted in increased concentrations of acetate, propionate, NH3, and L-lactate and decreased final pH. Addition of .7 g/L of A. oryzae to amino acid/peptide fermentations decreased final pH and increased concentrations of H2, acetate, propionate, butyrate, and total VFA. When alfalfa hay or bermudagrass hay was fermented with .7 g/L of A. oryzae, CH4, IVDMD, and digestion of NDF and ADF decreased. When adapted mixed cecal microorganisms were used, .7 g/L of A. oryzae did not inhibit methanogenesis or fiber digestion and L-lactate concentrations were not increased with soluble starch as the substrate. These results suggest that cecal microorganisms exposed to A. oryzae via the diet may adapt to the product. Incorporation of A. oryzae into in vitro incubations at concentrations similar to current recommended usage levels resulted in little change in final pH and fermentation products.

Animal Feed↗
PubMed1992

Effect of direct-fed microbials on rumen microbial fermentation.

Nonbacterial, direct-fed microbials added to ruminant diets generally consist of Aspergillus oryzae fermentation extract, or Saccharomyces cerevisiae cultures, or both. Results from in vivo research have been variable regarding effects of direct-fed microbials on ruminant feedstuff utilization and performance. Some research has shown increased weight gains, milk production, and total tract digestibility of feed components, but others have shown little influence of direct-fed microbials on these parameters. In vitro research with mixed ruminal microorganisms likewise has been inconsistent regarding the effects of direct-fed microbials. Several researchers observed that direct-fed microbials increased cellulolytic bacterial numbers in the rumen and stimulated the production of some fermentation end products. This suggests that direct-fed microbials may be providing growth factors for the ruminal microbes. However, other researchers have reported no effect of direct-fed microbials on in vitro fiber digestion. Recent research demonstrated that growth of the predominant ruminal bacterium Selenomonas ruminantium in lactate medium as well as lactate uptake by whole cells of Sel. ruminantium were markedly increased by an A. oryzae fermentation extract and an S. cerevisiae culture. In addition, both products increased the production of acetate, propionate, succinate, total VFA, and cell yield (grams of cells per mole of lactate). Therefore, it appears that these direct-fed microbials provide soluble factors that stimulate lactate utilization by Sel. ruminantium. Evidence is presented indicating that the malate content of the A. oryzae fermentation extract and S. cerevisiae culture may be involved in this stimulation.

Animals↗