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Biomedical subjects

S A Martin

Publications and source records attributed to S A Martin.

At least 19 recordsLinked to original sources
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↗
PubMed1991

The gingival immune response to Actinobacillus actinomycetemcomitans in juvenile periodontitis.

The established and advanced lesions of juvenile periodontitis-localized form (JP) are predominated by B-lymphocytes and plasma cells. Local immune processes may participate in protective or immunopathologic roles in the pathogenesis of this disease. Actinobacillus actinomycetemcomitans (A.a.) is implicated as a primary etiologic agent in JP. An in vitro gingival explant culture system was utilized to study the specificity of immunoglobulins produced by diseased JP tissues. A dot-immunobinding assay demonstrated that 46% of the supernatant fluids (SF) from explant cultures of diseased tissues (n = 39) were positive for the presence of antibody to A.a. Y4, while 61% of autologous JP sera (n = 39) tested positive. For rapidly progressive (RP) and adult periodontitis (AP) SF, 50% and 40% were positive for A.a. Y4, respectively. Seventeen percent of SF from healthy tissue were positive for A.a. Y4. There was no significant difference between JP SF reactivities to A.a. Y4 when compared to reactivities of SF from AP and RP patients. Only 10% of JP SF were positive for Porphyromonas asaccharolytica, a non-oral control microorganism. The de novo biosynthesis of antibody in JP tissue, reactive with A.a. Y4, was demonstrated with Staph Protein A isolated 14C-labeled IgG (SPAG) and the use of a dot-immunobinding assay and autoradiography. The in vitro gingival tissue explant culture system described provides a useful model for the study of the synthesis and specificity of localized immunoglobulins produced by diseased tissues of JP patients.

Adolescent↗
PubMed1991

Effect of a Saccharomyces cerevisiae culture on lactate utilization by the ruminal bacterium Selenomonas ruminantium.

The objective of this study was to examine the effects of a Saccharomyces cerevisiae culture (YEA-SACC) on lactate utilization by the predominant ruminal bacterium Selenomonas ruminantium. Lactate uptake was stimulated by YEA-SACC concentrations between 2.5 and 10 g/liter, and the 5-g/liter level increased uptake 3.8-fold. When YEA-SACC concentrations were increased above the 5-g/liter level lactate uptake was decreased, but 10 g/liter still stimulated uptake more than threefold. A filter-sterilized YEA-SACC filtrate also increased lactate uptake more than fourfold at all concentrations tested (10 to 100 microliters/ml), and the 25-microliters/ml level increased uptake ninefold. Growth of S. ruminantium in medium that contained 2 g/liter of DL-lactate was stimulated more than twofold by either 2 or 5% (vol/vol) YEA-SACC filtrate after 24 h. The YEA-SACC filtrate also increased the production of acetate, propionate, total VFA, and YLACTATE (grams of cells/mole of lactate) from lactate-grown cells. Because the increase in propionate production was greater relative to acetate, a decrease in the acetate:propionate ratio was observed. Growth on lactate and uptake of radiolabeled lactate by S. ruminantium was stimulated by a filter-sterilized YEA-SACC filtrate. The concentration of L-malic acid in the YEA-SACC filtrate was 4.9 mM, and it seemed that L-malic acid played a role in the stimulation of growth on lactate as well as lactate uptake by S. ruminantium treated with YEA-SACC.

Animals↗
PubMed1991

Effect of growth conditions on the Streptococcus bovis phosphoenolpyruvate glucose phosphotransferase system.

Four strains of the ruminal bacterium Streptococcus bovis were surveyed for phosphoenolpyruvate (PEP) and ATP-dependent phosphorylation of glucose and the nonmetabolizable glucose analog 2-deoxyglucose. All four strains had high rates of glucose phosphorylation with either phosphoryl donor, but 2-deoxyglucose activity was much higher in the presence of PEP. These results provide evidence for a PEP-dependent glucose phosphotransferase system in these bacteria. Mannose and 2-deoxyglucose inhibited PEP-dependent phosphorylation of glucose by S. bovis JB1 by 50 and 38%, respectively, whereas alpha-methylglucoside had little effect. Mannose was a competitive inhibitor of PEP-dependent phosphorylation of glucose with an inhibition constant of 2.8 mM, and PEP-dependent activity in cells grown in batch culture was optimal at pH 7.2. When S. bovis JB1 was grown in continuous culture, PEP-dependent phosphorylation of glucose and 2-deoxyglucose was highest in cells grown at a dilution rate of .10/h and at low glucose concentrations. Phosphoenolpyruvate-dependent activity was optimum at a growth pH of 5.0 for cells grown in medium that contained less than 6.0 g/liter of glucose. These data indicate that PEP-dependent glucose phosphotransferase system activity can be influenced depending on the growth conditions used to culture S. bovis. Furthermore, these results suggest that environmental conditions within the rumen will affect how glucose is transported by S. bovis.

Adenosine Triphosphate↗
PubMed1990

Sequence analysis of homogeneous peptides of shark immunoglobulin light chains by tandem mass spectrometry: correlation with gene sequence and homologies among variable and constant region peptides of sharks and mammals.

Morphologically, sharks are living fossils that are remarkably similar to their Devonian ancestors of ca. 400 million years ago. If a parallel conservation in biochemical properties characterizes shark evolution, knowledge of the properties of shark immunoglobulins should provide information on the structure of primordial immunoglobulins and their genes. The problem of polyclonality of shark immunoglobulins has precluded detailed analysis of shark immunoglobulin light polypeptide chains. Here, we approach the problem of obtaining direct sequence information on polyclonal light chains of shark immunoglobulins by isolating homogeneous peptides from tryptic digests of shark light chains and sequencing these by tandem mass spectrometry. To confirm the location of the peptides, we isolated a complementary DNA (cDNA) clone from a sandbar shark cDNA library in the expression vector lambda gt11, identifying the clone by its ability to produce a peptide serologically detectable using rabbit antibody to purified shark light chain. The correspondence between peptide sequence and that derived from gene sequence provided direct proof that the gene studied was that of a major expressed serum light chain. Using this combined approach, we isolated homogeneous peptides from both constant and variable regions. The variable region peptides showed homology to corresponding sequences of mammalian V lambda and V kappa sequences. The constant region gene sequence we obtained was homologous to mammalian C lambda sequence. The four constant region tryptic peptides we sequenced corresponded exactly to stretches of the C lambda sequence derived from the DNA sequence. The combined approach described here shows that shark light chains exhibit heterogeneity at both the protein and gene level, but that the constant regions of these chains can be identified as homologs of mammalian lambda chains and that evolutionary conservation has occurred in V region sequences ranging from elasmobranchs to man.

Amino Acid Sequence↗
PubMed1990

Xylose uptake by the ruminal bacterium Selenomonas ruminantium.

Selenomonas ruminantium HD4 does not use the phosphoenolpyruvate phosphotransferase system to transport xylose (S. A. Martin and J. B. Russell, J. Gen. Microbiol. 134:819-827, 1988). Xylose uptake by whole cells of S. ruminantium HD4 was inducible. Uptake was unaffected by monensin or lasalocid, while oxygen, o-phenanthroline, and HgCl2 were potent inhibitors. Menadione, antimycin A, and KCN had little effect on uptake, and acriflavine inhibited uptake by 23%. Sodium fluoride decreased xylose uptake by 10%, while N,N'-dicyclohexylcarbodiimide decreased uptake by 31%. Sodium arsenate was a strong inhibitor (83%), and these results suggest the involvement of a high-energy phosphate compound and possibly a binding protein in xylose uptake. The protonophores carbonyl cyanide m-chlorophenylhydrazone, 2,4-dinitrophenol, and SF6847 inhibited xylose uptake by 88, 82, and 43%, respectively. The cations Na+ and K+ did not stimulate xylose uptake. The kinetics of xylose uptake were nonlinear, and it appeared that more than one uptake mechanism may be involved or that two proteins (i.e., a binding protein and permease protein) with different affinities for xylose were present. Excess (10 mM) glucose, sucrose, or maltose decreased xylose uptake less than 40%. Uptake was unaffected at extracellular pH values between 6.0 and 8.0, while pH values of 5.0 and 4.0 decreased uptake 28 and 24%, respectively. The phenolic monomers p-coumaric acid and vanillin inhibited growth on xylose and xylose uptake more than ferulic acid did. The predominant end products resulting from the fermentation of xylose were lactate (7.5 mM), acetate (4.4 mM), and propionate (5.1 nM), and the Yxylose was 24.1 g/mol.

Animals↗
PubMed1990

Information-processing differences and laterality of students from different colleges and disciplines.

1023 college students were assessed for hemispheric brain dominance using the paper-and-pencil test, the Human Information Processing Survey. Analysis of scores of students majoring in Advertising, Interior Design, Music, Journalism, Art, Oral Communication, and Architecture suggested a preference for right-brain hemispheric processing, while scores of students majoring in Accounting, Management, Finance, Computer Science, Mathematics, Nursing, Funeral Service, Criminal Justice, and Elementary Education suggested a preference for left-hemispheric strategies for processing information. The differential effects of hemispheric processing in an educational system emphasizing the left-hemispheric activities of structured logic and sequential processing suggests repression of the intellectual development of those students who may be genetically favorable to right-hemispheric processing.

Adolescent↗
PubMed1990

Effects of Aspergillus oryzae fermentation extract on fermentation of amino acids, bermudagrass and starch by mixed ruminal microorganisms in vitro.

The objective of this study was to examine the effects of Aspergillus oryzae fermentation extract (Amaferm) on the in vitro ruminal fermentation of coastal bermudagrass, soluble starch and amino acids. Mixed ruminal microorganisms were incubated in anaerobic media for either 24 h (Amaferm alone, soluble starch, amino acids) or 48 h (bermudagrass). Amaferm was added to the incubation bottles (n = 4) at concentrations of 0, .4 or 1.0 g/liter. When mixed ruminal microorganisms were incubated with only Amaferm, the 1.0 g/liter concentration increased the production of hydrogen (H2; P less than .001), methane (CH4; P less than .01), acetate (P less than .05), butyrate (P less than .01), total VFA (P less than .05) and NH3 (P less than .05). Addition of both levels of Amaferm to soluble-starch fermentations tended to enhance the production of H2 (P less than .11), CH4 (P less than .15), acetate (P less than .29) and total VFA (P less than .19); propionate production was increased (P less than .10) by 1.0 g/liter Amaferm, resulting in a decrease (P less than .05) in the acetate:propionate ratio. Fermentation of amino acids plus 1.0 g/liter Amaferm enhanced the production of acetate (P less than .05), propionate (P less than .05), valerate (P less than .01) and total VFA (P less than .10) and decreased the acetate:propionate ratio (P less than .05). In addition, NH3 production tended (P less than .19) to increase with both levels of Amaferm. When bermudagrass was the substrate, few changes in fermentation products were observed with Amaferm treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Strategies of nutrient transport by ruminal bacteria.

The survival of bacteria in natural environments like the rumen depends on the ability of the bacteria to scavenge nutrients. It is now evident that ruminal bacteria use a variety of transport mechanisms. Hydrophobic substances, such as ammonia and acetate, are permeable to the lipid bilayers of cell membranes and can be taken up by passive diffusion. Hydrophilic compounds (e.g., sugars, amino acids, peptides) do not easily pass through lipid bilayers and must be transported across cell membranes on carrier proteins. Facilitated diffusion can display saturable kinetics but does not result in accumulation of solute. Active transport can establish extremely high concentration gradients, and this work may be driven by the hydrolysis of chemical bonds (e.g., ATP) or ion gradients, which are coupled to solute symport. Many solute symports involve protons, but sodium systems also are common in ruminal bacteria. The phosphotransferase system chemically modifies sugars as they pass across the cell membrane, and several ruminal bacteria have this method of group translocation. Many feed additives have either a direct or indirect effect on rumen bacterial transport. For instance, ionophores can inhibit transport by destroying (sometimes even reversing) ion gradients, lowering intracellular pH, or causing excessive ATP hydrolysis.

Animal Feed↗
PubMed1989

Guidelines for practical utilization of intraoperative frozen sections.

We reviewed 4057 intraoperative frozen sections from 1980 through 1984 to assess the accuracy, strengths, and weaknesses of this technique. Breast, lymph node, and skin comprised half of the sites evaluated. Frozen-section and final diagnoses agreed in 91.5% and disagreed in 6.8% of the cases; 1.7% of the cases were deferred. False-negative frozen-section diagnoses were due to pathologist sampling or judgment errors and surgeon sampling errors. There were eight (0.15%) false-positive diagnoses, none of which altered patient treatment. We recommend that lymph nodes for lymphoproliferative disorders and breast tissue for which a malignant diagnosis will not result in an immediate mastectomy not be submitted for frozen-section diagnosis. Appropriate studies of these tissues can be carried out without an intraoperative diagnosis; such a policy will increase the cost-effectiveness of frozen sections without compromising patient care.

False Negative Reactions↗
PubMed1989

Characterization of a plasmid from the ruminal bacterium Selenomonas ruminantium.

A 4.8-kilobase-pair plasmid was isolated from the ruminal bacterium selenomonas ruminantium HD4 by using a sodium carbonate-EDTA washing buffer to improve cell lysis (R.G. Dean, S.A. Martin, and C. Carver, Lett. Appl. Microbiol. 8:45-48, 1989). This plasmid, designated pSR1, appears to be quite stable. No evidence of plasmid DNA was detected in S. ruminantium D or GA192. All three strains were tested for antibiotic resistance, and all were kanamycin resistant (MIC, 25 to 50 micrograms/ml). Only strain D was tetracycline resistant (MIC, 25 micrograms/ml), and all strains were sensitive to ampicillin (MIC, 1 microgram/ml). pSR1 was cloned into pBR322, and a map of pSR1 was constructed by using HindIII, ClAI, BamHI, and PvuII. Although ClaI, BamHI, ScaI, and EcoRV digested recombined plasmid isolated from Escherichia coli, these restriction endonucleases were not effective in digesting plasmid isolated directly from S. ruminantium HD4.

Ampicillin↗
PubMed1989

Somnogenic activity of O-acetylated and dimeric muramyl peptides.

Slow-wave sleep-promoting factors in brain and urine were identified as muramyl peptides (MPs), the building blocks of bacterial cell wall peptidoglycan. In this study, structural variations of MPs that occur naturally in bacterial peptidoglycan were investigated for somnogenic activity. Monomeric and dimeric MPs were isolated and purified from Neisseria gonorrhoeae and Actinomadura sp. strain R39. The structures of these MPs were verified by fast atom bombardment mass spectroscopy and tandem mass spectroscopy. After intracerebroventricular administration of MPs, electroencephalograms and brain temperatures of rabbits were recorded for 6 h and were analyzed to determine durations of slow-wave sleep, rapid-eye-movement sleep, and wakefulness. The 6-O acetylation of muramic acid enhanced the somnogenic effects of certain monomeric MPs relative to their non-O-acetylated (but otherwise identical) counterparts. Two monomeric MPs containing an unsubstituted amide (i.e., Iso-Gln) were inactive, thus confirming previous results showing that amidation of a variety of MPs can block somnogenic activity. Two peptide-cross-linked MP dimers tested had no effect on slow-wave sleep, although a third peptide-cross-linked MP containing a 1,6-anhydro muramyl end on one of its monomeric subunits, a structure that enhances somnogenic potency of un-cross-linked monomers, was somnogenic. Two dimers connected by glycosidic bonds and containing an Iso-Gln moiety were inactive. Two other glycosidically linked dimers that also contained an Iso-Gln moiety, but were of lower molecular weight, were somnogenic. In summary, 6-O acetylation of muramic acid in somnogenic MPs enhances activity, and as a class, peptide-linked dimeric MPs tend to be less active than their constituent monomers.

Acetylation↗
PubMed1989

A scanning electron microscopic study of in vitro toxicity of ethylene-oxide-sterilized bone repair materials.

Polylactic acid (PLA) and polyglycolic acid (PGA) have been under investigation for use in the management of hard- and soft-tissue wounds. Current research has included the incorporation of osteo-inductive substances into a PLA-PGA copolymer alloplastic implant material for enhancement of the healing of osseous defects. Conventional methods of sterilization--such as dry heat, steam heat, or 60Co--tend either to destroy or attenuate osteo-inductive activity and alter polymer biodegradation. Ethylene oxide (EO) gas sterilization is currently being tested as an alternate method. This study examined the relationship of EO-induced cytotoxicity to the length of time of polymer aeration following EO sterilization. Three groups of copolymer implant discs were studied: (1) 50:50 PLA-PGA copolymer, (2) PLA-PGA polymer with hydroxyapatite (HA), and (3) PLA-PGA with autolyzed, antigen-extracted (AA) bone particles. Polymer discs, as well as particulate HA and AA bone controls, were sterilized with EO for 12 hours. Following periods of two weeks, one week, one day, or no subsequent vacuum aeration, samples were placed into 24-well culture plates. A suspension of human fibroblasts was added to each well. Cell growth and attachment were permitted for 24 hours. Medium was then removed, and solutions for cell fixation, buffer washing, and dehydration were added to each well. SEM examination revealed changes in cell growth with increasing periods of aeration suggestive of increasing cell vitality. Cells growing on discs having no aeration were small, round, and lobulated, whereas those of seven to 14 days' aeration were more numerous, and flattened with many microvilli, pseudopodia, and dendritic processes, features consistent with normal cell morphology. These results suggest that EO-sterilized polymer implants should be aerated for least seven to 14 days prior to surgical use.

Bone and Bones↗