[Accurate localization and successful treatment of 23 cases of migrating pharynx and cervical esophageal foreign bodies]

Objective: To explore clinical features, diagnosis, localization, and therapeutic strategy of migratory pharyngeal and cervical esophageal foreign bodies. Methods: A total 23 cases of pharyngeal and cervical esophageal migratory foreign bodies were admitted between January 2015 and December 2021. There were 14 females and 9 males with the age ranged from 35 to 82 (55.0±12.7)years. In all the cases, esophageal CT was taken to confirm the esophageal foreign body. Multiplanar reconstruction (MPR) was performed to locate the foreign body from the horizontal, coronal and sagittal dimensions as well as the corrected reconstructed MPR. According to the location of the foreign body, appropriate surgical method was selected.The symptoms, complications, types of foreign body, positioning, surgical methods, and relevant information were recorded.Data were analyzed using the descriptive method and SPSS 25.0 software. Results: The clinical symptoms of 23 migrating esophageal foreign bodies included pharyngodynia (20/23), foreign body sensation (6/23), hoarsenss (1/23), difficulty in turning neck(1/23), difficulty in opening mouth (1/23), fever (7/23), poor appetite (1/23), and abdominal pain (1/23). The foreign bodies included 19 fish bones, 2 wires, 1 embroidery needle and 1 chicken bone. There were 9 cases (39.1%) of foreign bodies located in extraluminal cervical esophagus, 2 cases (8.7%) of foreign bodies located in the muscular layer of the cervical esophagus and 12 cases (52.2%) of foreign bodies located in pharynx. Twenty-one cases of foreign bodies were removed by cervical lateral incision, in which 11 were removed by cervical lateral incision directly, 10 by the second lateral cervical incision after the foreign bodies were accurately located by MPR and/or corrected MPR, 1 foreign body was removed by incision of the pharyngeal mucosa under suspension laryngoscope, 1 foreign body was removed by tracheoscopy. Compared with patients with intraluminal foreign bodies (n=308) treated in the same period, intake of fishbone [19 (19/23) vs. 133 (82.6% (43.2%, 133/308), OR=7.31] and first visit was more than 24 hours [20(87.0%, 20/23) vs. 77(25.0%, 77/308),OR=17.2] were the significant risk factors of migratory esophageal foreign bodies. Conclusions: MPR and the corrected MPR can accurately locate the migrating pharyngeal and cervical esophageal foreign bodies, by providing more intuitive imaging evidence for doctors, which provide imaging basis for formulation of surgical programs. Foreign bodies in pharyngeal and cervical esophagus need to be treated as soon as possible, otherwise they are easy to migrate, leading lead to serious complications.

Formation of bacterial microcolonies on feed particles in the rumen

Examination of particulate feed that had been digested in vivo in the rumen, and of the leaves of specific legumes that had been digested in vitro by a mixed population of rumen bacteria, showed that very extensive glycocalyx-enclosed bacterial microcolonies developed on many of the available surfaces. Some of these adherent bacteria colonized a surface almost exclusively and attracted another specific type of bacteria as the second members of a distinct morphological consortium. The true extent of the exopolysaccharide glycocalyces of these adherent rumen bacteria was seen in cases where the fibers were attached at multiple points, and their role in microcolony formation and adhesion could be unequivocally ascribed.

Cytochemical Localization of Urease in a Rumen Staphylococcus sp. by Electron Microscopy

We describe a technique whereby intracellular urease activity can be localized by transmission electron microscopy. The ammonia produced from the enzymatic hydrolysis of urea is first precipitated with sodium tetraphenylboron and then replaced with silver to produce electron-dense silver tetraphenylboron. This direct reaction product deposition procedure was used to demonstrate the presence of membrane-bound urease of Staphylococcus sp. H3-22, a gram-positive ruminal bacterium.

Reduction of Selenate and Selenite to Elemental Selenium by a Pseudomonas stutzeri Isolate

A Pseudomonas stutzeri isolate rapidly reduced both selenite and selenate ions to elemental selenium at initial concentrations of both anions of up to 48.1 mM. Optimal selenium reduction occurred under aerobic conditions between pH 7.0 and 9.0 and at temperatures of 25 to 35 degrees C. Reduction of both selenite and selenate was unaffected by a number of anions except for sulfite, chromate, and tungstate ions, which inhibited both growth and reduction.

An improved method to illuminate and record a phytase assay in SDS-PAGE zymogram gels

Experimentation at the Lethbridge Research Center in Alberta, Canada using cross-polarized transmitted light to photographically record a staining technique on zymograms has proved to be successful with both color and black and white films. It has been possible to obtain the desired visible contrast without compromising the intensity of the enzyme activity bands. Increasing numbers of such PAGE gels are being submitted for photographic recording when it is believed that the image will be used for records, publication, scientific posters or AV presentations.

Directed evolution to produce an alkalophilic variant from a Neocallimastix patriciarum xylanase

The catalytic domain of a xylanase from the anaerobic fungus Neocallimastix patriciarum was made more alkalophilic through directed evolution using error-prone PCR. Transformants expressing the alkalophilic variant xylanases produced larger clear zones when overlaid with high pH, xylan-containing agar. Eight amino acid substitutions were identified in six selected mutant xylanases. Whereas the wild-type xylanase exhibited no activity at pH 8.5, the relative and specific activities of the six mutants were higher at pH 8.5 than at pH 6.0. Seven of the eight amino acid substitutions were assembled in one enzyme (xyn-CDBFV) by site-directed mutagenesis. Some or all of the seven mutations exerted positive and possibly synergistic effects on the alkalophilicity of the enzyme. The resulting composite mutant xylanase retained a greater proportion of its activity than did the wild type at pH above 7.0, maintaining 25% of its activity at pH 9.0, and its retention of activity at acid pH was no lower than that of the wild type. The composite xylanase (xyn-CDBFV) had a relatively high specific activity of 10128 micromol glucose x min(-1) x (mg protein)(-1) at pH 6.0. It was more thermostable at 60 degrees C and alkaline tolerant at pH 10.0 than the wild-type xylanase. These properties suggest that the composite mutant xylanase is a promising and suitable candidate for paper pulp bio-bleaching.

3(2H)-Benzofuranones and chromanes from liquid cultures of the mycoparasitic fungus Coniothyrium minitans

Two 3(2H)-benzofuranones and three chromanes were isolated from the mycoparasitic fungus Coniothyrium minitans. Their structures and absolute stereochemistry were determined by spectroscopic methods.

The effects of sequential inoculation of mixed rumen protozoa on the degradation of orchard grass cell walls by anaerobic fungus Anaeromyces mucronatus 543

The effects of protozoa on the degradation of plant cell walls (CW) during different growth stages of the fungus Anaeromyces mucronatus have been investigated. Since fungi show a marked lag in their in vitro cultures and many protozoa rapidly die during a prolonged incubation time, the effects of protozoa may vary according to the growth phase of the fungi. Therefore, the approach adopted was (i) to inoculate CW with fungus monoculture, (ii) to inoculate CW with fungus-protozoa coculture, or (iii) to sequentially inoculate fungal cultures that had been grown in CW for 24 (initial stage of growth), 48, and 72 h (late stage of growth) with mixed protozoa. When a fungus was associated with protozoa, a growth phase dependent effect was observed. Ruminal protozoa adversely affected the growth and activity when introduced in the initial growth stage of A. mucronatus, but a synergetic interaction was detected when added to late growth stage cultures. Although there is no immediate explanation for these results, the data suggested that protozoa can engulf the fungal zoospores, which are in ruminal fluids and (or) attached to small feed particles, but cannot engulf the fungal thallus that is tightly attached to feed particles by a rhizoidal system. Our data indicated that the protozoa did not influence cellulolysis by the fungi in exponential and (or) stationary phase, but they had a marked inhibitory effect on fungi that were in lag phase. Inhibition during lag phase could result from the protozoal predation of fungal zoospores that had failed to attach to substrates.

The impact of a clinic-based literacy intervention on language development in inner-city preschool children

OBJECTIVE

To determine the effect of a clinic-based literacy intervention on the language development of preschool children.

METHODS

A convenience sample of families presenting to 2 urban pediatric clinics for well-child care met the following criteria: the family was Latino or black and English- or Spanish-speaking; the child was 2 to 5.9 years old, with no neurodevelopmental disability, at a gestational age of 34 weeks or more, and not attending kindergarten. Participants at the first clinic (intervention group) were exposed to a literacy support program, based on Reach Out and Read (ROR), during the previous 3 years. At the second clinic (comparison group), a similar program started 3 months before the study. Parent-child reading activities were measured using the READ Subscale of the StimQ. Language development was measured using the One-Word Expressive and Receptive Picture Vocabulary Tests, and was performed in the child's primary language.

RESULTS

A total of 122 study participants (49 interventions and 73 comparisons) met inclusion criteria and completed all measures. Intervention and comparison families were similar for most sociodemographic variables. Intervention families reported reading together with their children approximately 1 more day per week. Intensity of exposure to ROR (measured by total number of contacts with the program) was associated with increased parent-child reading activities, as measured by the StimQ-Read Subscale (r = 0.20). Intervention children had higher receptive language (mean: 94.5 vs 84.8) and expressive language (mean: 84.3 vs 81.6). After adjusting for potential confounders in a multiple regression analysis, intervention status was associated with an 8.6-point increase (95% confidence interval [CI]: 3.3, 14.0) in receptive language (semipartial correlation [SR]coefficient = 0.27), and a 4.3-point increase (95% CI: 0.04, 8.6) in expressive language (SR = 0.17). In a similar multiple regression, each contact with ROR was associated with an adjusted mean 0.4-point increase (95% CI: 0.1, 0.6) in receptive score, and an adjusted mean 0.21-point increase (95% CI: 0. 02, 0.4) in expressive score.

CONCLUSIONS

ROR is an important intervention, promoting parental literacy support and enhancing language development in impoverished preschool children. Integration of literacy promoting interventions such as these into routine pediatric health care for underserved populations can be recommended.

Purification and characterization of a cellulase from the ruminal fungus Orpinomyces joyonii cloned in Escherichia coli

A cellulase from the ruminal fungus Orpinomyces joyonii cloned in Escherichia coli was purified 88-fold by chromatography on High Q and hydroxyapatite. N-terminal amino acid sequence analyses confirmed that the cellulase represented the product of the cellulase gene Cel B2. The purified enzyme possessed high activity toward barley beta-glucan, lichenan, carboxymethyl cellulose (CMC), xylan, but not toward laminarin and pachyman. In addition, the cloned enzyme was able to hydrolyze p-nitrophenyl (PNP)-cellobioside, PNP-cellotrioside, PNP-cellotetraoside, PNP-cellopentaoside, but not PNP-glucopyranoside. The specific activity of the cloned enzyme on barley beta-glucan was 297 units/mg protein. The purified enzyme appeared as a single band in SDS-polyacrylamide gel electrophoresis and the molecular mass of this enzyme (58000) was consistent with the value (56463) calculated from the DNA sequence. The optimal pH of the enzyme was 5.5, and the enzyme was stable between pH 5.0 and pH 7.5. The enzyme had a temperature optimum at 40 degrees C. The K(m) values estimated for barley beta-glucan and CMC were 0.32 and 0.50 mg/ml, respectively.

Localization of phytase in Selenomonas ruminantium and Mitsuokella multiacidus by transmission electron microscopy

The localization of phytase (myo-inositol-hexaphosphate phosphohydrolase) in the ruminal bacteria, Selenomonas ruminantium JY35 and Mitsuokella multiacidus 46/5(2), was determined with transmission electron microscopy. Phosphate produced from the enzymatic dephosphorylation of the calcium salt of phytic acid is precipitated as calcium phosphate. The calcium is then replaced with lead to produce electron-dense lead phosphate. This deposition of lead phosphate localized phytase in S. ruminantium JY35 and M. multiacidus 46/5(2) to the outer membrane, and confirmed intracellular expression of the enzyme in Escherichia coli pSrP.2, the recombinant clone which possesses the gene (phyA) encoding phytase (phyA) in S. ruminantium.

Effects of Tween 60 and Tween 80 on protease activity, thiol group reactivity, protein adsorption, and cellulose degradation by rumen microbial enzymes

Microbial enzymes extracted from mixed ruminal microorganisms were incubated for 2 h with casein and Tween 60 or Tween 80 at 10 concentrations ranging from 0 to 2.0% (vol/vol) to determine the effects of these nonionic surfactants on protease activation and thiol reactivity (unmasking of thiol groups). Rate and extent of protein adsorption to cellulosic substrate (barley straw) was measured in the presence of 0, 0.05, 0.10, 0.25, and 0.50% (vol/vol) Tween 80. Degradation of cellulose by a rumen bacterial fraction was measured over 48 h of incubation with and without Tween 60 or Tween 80 at 0.25% (vol/vol). Maximum accelerations of protease activity achievable with Tween 60 and Tween 80 (calculated from a Michaelis-Menten kinetics model) were 99.2 and 166.8%, respectively. Concentrations of Tween 60 and Tween 80 at which half the maximal velocities were attained were 0.28 and 0.20% (vol/vol), respectively. Tween 80 increased (P < 0.05) the rate and extent of adsorption of microbial protein to barley straw, and the effect was related to concentration of Tween 80 up to 0.10% (vol/vol). Initial rates of cellulose degradation with no surfactant, 0.25% Tween 60, or 0.25% Tween 80 were 0.60, 0.87, and 1.04 micrograms/ml per h, respectively. These nonionic surfactants were effective for enhancing rumen microbial protease and cellulase activities. Thus, further study is warranted to determine their potential for improving ruminant feeding.

Intraruminal supplementation with increasing levels of exogenous polysaccharide-degrading enzymes: effects on nutrient digestion in cattle fed a barley grain diet

The effects of supplying increasing ruminal doses of exogenous polysaccharide-degrading enzymes (EPDE) on rumen fermentation and nutrient digestion were studied using eight ruminally cannulated heifers, four of which were also duodenally cannulated, in a replicated Latin square. The heifers were fed a diet of 85.5% rolled barley grain and 14% barley silage (DM basis), and once daily they were given intraruminal doses of 0 (Control), 100, 200, or 400 g of a preparation containing polysaccharide-degrading enzymes. Enzyme treatment decreased ruminal pH (linear, P<.001) and increased ammonia N (quadratic, P<.001) concentration. The ruminally soluble fraction and effective degradability of feed DM in situ were increased (quadratic response, P<.001) by enzyme treatment. Ruminal administration of EPDE increased ruminal fluid carboxymethylcellulase and xylanase activities linearly (P<.001) and beta-glucanase activity quadratically (P<.01), decreased (quadratic response, P<.05) ruminal fluid viscosity, and did not affect (P>.05) ruminal fluid amylase activity. Elevated levels of fibrolytic activities in the rumen resulted in increased (quadratic, P<.001) carboxymethylcellulase, xylanase, and beta-glucanase (P<.01) activities in duodenal digesta. Duodenal amylase activity and reducing sugar concentration were also increased (quadratic responses, P<.001 and P<.05, respectively) by EPDE. Xylanase activity of fecal DM was increased linearly (P<.05) with increasing ruminal EPDE levels. Apparent digestibilities of DM, crude protein, and NDF were not affected by EPDE supplementation. Enzyme treatment did not affect (P>.05) urinary excretion of allantoin and uric acid, or concentrations of glucose and urea in blood.

A novel staining method for detecting phytase activity

Differential agar media for the detection of microbial phytase activity use the disappearance of precipitated calcium or sodium phytate as an indication of enzyme activity. When this technique was applied to the study of ruminal bacteria, it became apparent that the method was unable to differentiate between phytase activity and acid production. Strong positive reactions (zones of clearing around microbial colonies) observed for acid producing, anaerobic bacteria, such as Streptococcus bovis, were not corroborated by subsequent quantitative assays. Experimentation revealed that acidic solutions generated false positive results on the selected differential medium. Empirical studies undertaken to find a solution to this limitation determined the false positive results could be eliminated through a two step counterstaining treatment (cobalt chloride and ammonium molybdate/ammonium vanadate) which reprecipitates acid solubilized phytate. This report discusses the application of the developed two step counterstaining treatment for the screening of phytase producing ruminal bacteria as well as its use in phytase zymogram assays.

Characterization of a Neocallimastix patriciarum xylanase gene and its product

A xylanase gene (xynC) isolated from the anaerobic ruminal fungus Neocallimastix patriciarum was characterized. The gene consists of an N-terminal catalytic domain that exhibited homology to family 11 of glycosyl hydrolases, a C-terminal cellulose binding domain (CBD) and a putative dockerin domain in between. Each domain was linked by a short linker domain rich in proline and alanine. Deletion analysis demonstrated that the CBD was essential for optimal xylanase activity of the enzyme, while the putative dockerin domain may not be required for enzyme function.

Pneumonia in HIV-infected patients: a case-control survey of factors involved in risk and prevention

OBJECTIVE

To assess the factors that increase or decrease the risk of pneumonia with particular attention to immunization with pneumococcal and influenza vaccines in a group of HIV-infected persons.

DESIGN

A retrospective, case-control study based on information entered into a standard database and the medical record.

SETTING

Patients attending a referral clinic specializing in AIDS/HIV care at a public hospital.

PATIENTS

Among over 2000 subjects entered into a database in 8 years, 127 incidents of pneumonia were identified from the record. These cases were matched with 127 CD4 cell count matched, concurrent controls.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

The principal hypothesis was that chart review would find a decreased frequency of pneumococcal immunization in the pneumonia cases compared with matched controls.

RESULTS

Pneumococcal immunization was associated with a reduction of the risk of pneumonia by nearly 70%. The effect was seen even when immunization was given with a CD4 cell count of less than 100/mm3. Injection drug users and African-Americans had a twofold increased risk of pneumonia.

CONCLUSION

The study provides data to support the current recommendation for pneumococcal immunization of all HIV-infected persons. Although this conclusion could lead to renewed enthusiasm for increasing pneumococcal immunization rates in HIV-infected persons, it must be recognized that the study is observational and ascertainment bias cannot be excluded.

Isolation and characterization of angiogenin-1 and a novel protein designated lactogenin from bovine milk

This paper reports the isolation and characterization from bovine milk of two proteins: angiogenin-1, a recently discovered angiogenin, and lactogenin, a novel protein. Both proteins were adsorbed on and eluted closely from CM-Sepharose and Mono S. Lactogenin possessed a molecular weight (17 kDa) slightly higher than that of angiogenin-1 (15 kDa). Lactogenin had a higher ribonucleolytic (RNase) activity than angiogenin-1 towards yeast transfer RNA (tRNA). The Km values estimated for the RNase activities of angiogenin-1 and lactogenin were 51 microM and 40 microM respectively. Both were specific for poly C. The optimal pH for the RNase activities of angiogenin-1 and lactogenin was 7.75 and 7.5 respectively. Comparison of the amino acid sequences of cyanogen bromide fragments and the pyroglutaminase-treated N-terminal fragment of lactogenin with the sequence of bovine liver RNase (RNase BL4) revealed identity in residues 3-22, 24, 26-27, 37, 41-44, 46-50, 54, 56, 63, 72-80, and 83. Considerable similarity to the N-terminal sequence of angiogenin-2 was also noted. Both lactogenin and angiogenin-1 inhibited cell-free translation in a rabbit reticulocyte lysate system with an IC(50) below 100 nM.

Effect of Yucca schidigera on ruminal fermentation and nutrient digestion in heifers

In a replicated 3 x 3 Latin square experiment, six heifers (443 +/- 6.1 kg) fed a 61% barley grain:39% alfalfa silage diet (DM basis) were given intraruminal doses of powdered Yucca schidigera (YS). Doses of 0 (control), 20, or 60 g/d were given at 0800 daily. Ruminal content was sampled 0, 2, 4, and 6 h after dosing. Acidity, concentrations of reducing sugars, free amino acids, and peptides in the rumen were not affected (P > .05) by YS. Relative to control, ruminal ammonia concentration was reduced (P < .05) 2 h after YS dosing. Ruminal propionate concentration was increased (P < .05) by YS. Protozoal numbers in the rumen were lower (P < .05) with YS than without. Yucca did not affect (P > .05) rate or extent of in situ DM degradability. Fibrolytic, amylolytic, and proteolytic activities in ruminal contents were similar among treatments (P > .05). Dry matter intake, apparent digestibilities of DM, NDF, and CP, nitrogen balance, and microbial protein synthesis in the rumen were not affected (P > .05) by treatment. The effect of YS on ruminal ammonia concentration likely resulted from a decreased concentration of protozoa and, presumably, from ammonia binding by YS. The effect on ruminal propionate was probably a result of a selective inhibitory effect of YS on rumen microbial species.

Rearing stable fly larvae (Diptera: Muscidae) on an egg yolk medium

The growth and survival of Stomoxys calcitrans (L.) larvae on egg yolk medium inoculated with bacteria isolated from a colony of stable flies was evaluated. Five species of bacteria--Acinetobacter sp., Aeromonas sp., Empedobacter breve (Holmes & Owen), Flavobacterium odoratum Stutzer, and Serratia marcescens Bizio--were identified according to fatty acid profiles using a microbial identification system. Larvae failed to develop on uninoculated plates, confirming that bacteria are required to complete development. Larvae also failed to complete development on plates inoculated with Aeromonas sp. and S. marcescens, and died during the 1st instar. Larvae completed development on the remaining 3 bacterial species as well as on Escherichia coli (Migula). Survival was generally higher when larvae were reared on Acinetobacter sp. and F. odoratum compared with E. coli and E. breve. Egg density did not influence larval survival, although the variability in survival was lowest using 20 and 40 eggs per plate. Larval survival in mixed cultures of Acinetobacter and Flavobacterium averaged 22.7% lower than survival in the pure cultures, and averaged 21.6% higher in mixed cultures of Empedobacter and Flavobacterium compared with pure cultures. Larval survival in mixed cultures did not differ significantly from mean survival in pure cultures for combinations of Acinetobacter and E. coli, Acinetobacter and Empedobacter, E. coli and Empedobacter, and E. coli and Flavobacterium. Larval developmental time was faster on all mixed bacterial cultures compared with developmental time on pure bacterial cultures. Optimal sample sizes and egg numbers are presented for detecting specified differences in larval survival. This rearing procedure will be useful for studying insect-microbe interactions and evaluating mortality using bacterial agents.

Effect of micronizing full fat canola seed on amino acid disappearance in the gastrointestinal tract of dairy cows

Ruminal and total tract digestion of the amino acids (AA) in full fat canola seed was studied in two in situ experiments with three nonlactating, ruminally and duodenally fistulated dairy cows. Whole, full fat canola seed was hand-cracked or micronized (an infrared heat treatment) for 90 s and then studied in that form or after grinding to pass a 1.25-mm sieve. In the first experiment, the four sample types were ruminally incubated in nylon bags for up to 96 h. In the second experiment, they were sealed in mobile nylon bags, incubated ruminally for 16 h, placed in acidified pepsin for 1 h, and then inserted into duodenal cannulas for passage through the intestine. Amino acids in the canola seed and in the residues from in situ incubations were analyzed by HPLC. Micronization reduced ruminal disappearance of total AA and essential AA from full fat canola seed. Degradation kinetics from Experiment 1 indicated reduced soluble fraction and increased slowly degradable fraction of both total AA and essential AA following micronization. Micronization reduced disappearances of total AA and essential AA from whole canola seed in the total digestive tract but did not affect total tract digestion of total AA or essential AA in ground seed. Intestinal disappearance of total AA and essential AA from both whole and ground full fat canola seed were increased by micronization. Micronizing canola seed may be of value in improving AA utilization in ruminants.

Effect of dietary or abomasal supplementation of exogenous polysaccharide-degrading enzymes on rumen fermentation and nutrient digestibility

The effect of site of supplementation of a mixture of two crude preparations (Enzyme C and Enzyme X) of exogenous polysaccharide-degrading enzymes (EPDE) was studied in vivo using four ruminally and duodenally cannulated heifers (Exp. 1). The treatments were as follows: control (no EPDE), EPDE supplied through the diet (EF, 47.0 g/d), and EPDE infused continuously into the abomasum (EA, 41.6 g/d). Enzyme treatment increased the concentration of soluble reducing sugars (P < .05) and decreased NDF content (P < .05) in the treated feed, but this did not increase the rate or extent of in sacco disappearance of DM from the feed. Compared with control, ruminal fermentation was not affected by EF, but abomasal infusion increased (P < .05) rumen ammonia levels and shifted ruminal VFA patterns. Ruminal carboxymethylcellulase (CMCase) and xylanase activities were not affected by treatment. Abomasal infusion increased (P < .05) duodenal xylanase activity as compared with control and EF, but apparent digestion of DM, NDF, and CP were not affected by treatment. Negligible levels of CMCase and amylase reached the duodenum. During an in vitro experiment (Exp. 2), abomasal stability of the two EPDE was studied over a range of pH from 3.39 to .85, with or without pepsin. Carboxymethylcellulase activity (in Enzymes C and X) and beta-glucanase activity (in Enzyme C) were largely unstable against pepsin proteolysis (P < .001) and low pH (P < .001). Xylanase and amylase activities were resistant to pepsin but irreversibly inactivated at low pH. These two experiments showed that abomasal supplementation of EPDE did not successfully supply cellulases and amylases to the intestine, due partially to their limited resistance to low pH and pepsin proteolysis. Although EPDE significantly increased the level of xylanase activity at the duodenum, this did not significantly improve total tract digestion.

Effect of melengestrol acetate on development of 3-methylindole-induced pulmonary edema and emphysema in sheep

The involvement of melengestrol acetate (MGA) in susceptibility to developing pulmonary edema and emphysema following oral administration of 3-methylindole (3MI) was investigated using 10 Suffolk ewes receiving 0 or 0.15 mg of MGA daily (n = 5). Blood, urine and ruminal fluid were collected immediately prior to 3MI dosing (0.2 g/kg BW) and 1, 2, 3, 4, 5, 6, 12 and 24 h (blood); 3, 6, 9, 12 and 15 h (urine) and 1, 2, 3 and 12 h (ruminal fluid) afterward. Ewes receiving MGA experienced earlier (P < 0.05) onset of respiratory distress than the control ewes (2.5 vs 4 h), and upon euthanasia at 96 h, their lung weight relative to body weight tended (P < 0.10) to be lower. Ruminal 3MI concentrations did not differ between treatments (P > 0.05). Ewes receiving MGA had higher (P < 0.05) concentrations of 3MI metabolites in plasma prior to dosing than did control ewes, and these values tended to remain higher throughout the sampling period. Immunoreactivity assays indicated more pneumotoxin present in the lungs of MGA-treated ewes than controls. Lung damage was apparently more acute and accelerated in the MGA-treated ewes than in the controls. Urinary 3MI mercapturate concentrations differed (control > MGA-treated, P < 0.05) at 9, 12, and 15 h, but this difference was not apparent when urinary production (as estimated by creatinine concentration) was considered. The implications of these findings for MGA-treated feedlot heifers are currently under investigation.

Phytase activity of anaerobic ruminal bacteria

Phytase catalyses the release of phosphate from phytate (myo-inositol hexakisphosphate), the predominant form of phosphorus in cereal grains, oilseeds and legumes. The presence of phytase activity was investigated in 334 strains of 22 species of obligately anaerobic ruminal bacteria. Measurable activities were demonstrated in strains of Selenomonas ruminantium, Megasphaera elsdenii, Prevotella ruminicola, Mitsuokella multiacidus and Treponema spp. Strains isolated from fermentations with cereal grains proved to have high activity, and activity was particularly prevalent in S. ruminantium, with over 96% of the tested strains being positive. The measured phytase activity was found exclusively associated with the bacterial cells and was produced in the presence of approximately 14 mM phosphate. The most highly active strains were all S. ruminantium, with the exception of the one Mitsuokella multiacidus strain examined. Phytase activity varied greatly among positive strains but activities as high as 703 nmol phosphate released (ml culture)-1 were measured for a S. ruminantium strain and 387 nmol phosphate released (ml culture)-1 for the Mitsuokella multiacidus strain.

A method for the selective enumeration and isolation of ruminal Lactobacillus and Streptococcus

Ruminal lactic acid-producing bacteria were selectively isolated and enumerated using a one hour aerobic exposure prior to incubation on a semi-selective Lactobacillus medium, MRS, under anaerobic conditions. The technique allowed growth of pure cultures of ruminal Lactobacillus spp. and Streptococcus bovis without supporting the growth of pure cultures of any of the prominent ruminal bacterial species. In mixed cultures, the one hour aerobic pre-incubation inhibited the growth of the obligate anaerobic ruminal bacteria which can otherwise grow on the MRS medium, and the subsequent anaerobic incubation permitted maximal recovery of the weakly aerotolerant ruminal lactic acid-producing Lactobacillus spp. and Streptococcus spp. The efficacy of this technique in selecting exclusively for the lactic acid-producing bacteria was also demonstrated from populations of rumen bacteria from mixed culture end-point in vitro fermentation, continuous in vitro culture and isolations from fresh ruminal samples.

A review of bloat in feedlot cattle

Improvements in feedlot management practices and the use of various feed additives have reduced, but not eliminated, the occurrence of bloat in feedlot cattle. Feedlot bloat reduces the profitability of production by compromising animal performance and more directly by causing fatalities. In feedlots, bloat is associated with the ingestion of large amounts of rapidly fermented cereal grain and destabilization of the microbial populations of the rumen. An abundance of rapidly fermented carbohydrate allows acid-tolerant bacteria (e.g., Streptococcus bovis and Lactobacillus spp.) to proliferate and produce excessive quantities of fermentation acids. As a result, ruminal pH becomes exceedingly low, and this impairs rumen motility. Further, the excessive production of mucopolysaccharide or "slime" increases the viscosity of ruminal fluid and stabilizes the foam implicated in frothy feedlot bloat. Although protocols have been developed to treat feedlot bloat, the most profitable approach is to use management strategies to reduce its likelihood. Amount of roughage, grain processing techniques, selection of cereal grain (e.g., corn, barley, and wheat), dietary adaptation periods, and various additives (e.g., ionophores) can influence the occurrence of bloat in feedlot cattle. Successful management of these factors depends on a thorough understanding of the behavioral, dietary, and microbial events that precipitate bloat in feedlot cattle.

An endoglucanase from the anaerobic fungus Orpinomyces joyonii: characterization of the gene and its product

An endoglucanase gene (celA) was isolated from a genomic library of the ruminal fungus Orpinomyces joyonii. DNA sequence analysis of celA revealed an intronless gene encoding a typical signal sequence, an N-terminal catalytic domain, two repeated regions linked by a short Ser/Thr-rich linker and a domain of unknown function. The deduced amino acid sequence of the catalytic domain showed homology with the family 5 cellulases. While the catalytic domain of CelA was not homologous to the catalytic domain of the endoglucanase gene (EG3) from the ruminal bacterium Fibrobacter succinogenes, the repeated regions of CelA were very similar to the noncatalytic domain of EG3. This suggests that evolutionary shuffling of endoglucanase domains might occur among bacteria and fungi within the anaerobic ecosystem of the rumen. The celA gene was expressed in Escherichia coli, and the periplasmic endoglucanase was used for the characterization studies of the enzyme. CelA exhibited both endoglucanase and xylanase activities. Its pH optimum was 4 and the temperature optimum was 40 degrees C. Deletion analysis showed that the repeated sequences and C-terminal domain of CelA were not required for enzyme activity.

Efficacy of fenbendazole for treatment of giardiasis in calves

OBJECTIVE

To determine efficacy of fenbendazole for treatment of giardiasis in calves.

ANIMALS

Twenty male and 15 female Holstein calves (100 to 180 kg), naturally infected with Giardia sp.

PROCEDURE

In vitro fenbendazole susceptibility and resistance development was determined for a ruminant Giardia isolate by use of an adherence assay. Calves were treated as follows: group 1, a single administration of 5 mg of fenbendazole/kg of body weight; group 2, a single administration of 10 mg of fenbendazole/kg; group 3, 5 mg of fenbendazole/kg, every 24 hours for 3 days; group 4, 10 mg of fenbendazole/kg, every 24 hours for 3 days; group 5, 20 mg of fenbendazole/kg, every 24 hours for 3 days; group 6, 0.833 mg of fenbendazole/kg, every 24 hours for 6 days; and group 7, saline solution. Fecal Giardia cysts were counted on days -3 through -1 and 1 through 7, 9, 11, 13, 21, and 28 by use of sucrose gradient concentration and staining with a fluorescent monoclonal antibody.

RESULTS

The 50% adherence inhibition concentration was 0.024 +/- 0.002 microgram/ml, and resistance could not be detected after 5 weeks of continuous culture at sublethal concentration of fenbendazole (0.01 microgram/kg). Fenbendazole was 100% effective in eliminating cysts from the feces within 6 days for calves in treatment groups 2-6. Reinfection was observed in some calves within the 28-day study period.

CONCLUSIONS

Fenbendazole is effective in the elimination of Giardia infections in calves, but repeat treatments may be required in reinfected animals.

CLINICAL RELEVANCE

Fenbendazole is an effective and economical treatment for Giardia-associated diarrhea and growth rate reduction in calves.

Effect of salinomycin on giardiasis and coccidiosis in growing lambs

An experiment was undertaken to determine the effect of salinomycin on Giardia in vitro and on Giardia and coccidia in growing lambs. Concentrations of salinomycin above (3.9 micrograms/mL) reduced the adherence (index of viability) of Giardia S2 trophozoites by more than 50%. This strain did not develop resistance after repeated exposure to sublethal concentrations of salinomycin. Five of 40 lambs escaped natural infection by Giardia, and these were inoculated with > or = 500,000 cysts. Giardiasis (presence of cysts in feces) was confirmed in all lambs before commencement of the experiment. Coccidiosis (presence of oocysts) developed by natural exposure. Lambs were assigned randomly to diets containing 0, 4, 10, or 16 ppm of salinomycin. Giardia cyst and coccidia oocyst excretions were determined on 6 d during the first week and weekly thereafter. Giardia cysts were detected at each sampling date in all treatments (highest release, 2.3 x 10(6) cysts/g feces). The number of Giardia cysts shed in feces was not affected (P > .05) by salinomycin but did decline (P < .05) with time. Average infection rates remained above 50% until d 41 of the experiment and declined linearly (P < .05) with salinomycin concentration and time. The number of coccidia oocysts in feces was low (highest release, 6.8 x 10(4) oocysts/g feces), but shedding occurred in 38 of the 40 lambs. Treatment with salinomycin had a cubic effect (P < .05) on coccidia oocyst excretion, and no oocysts were detected beyond d 28. Treatment effect on average daily gain (P < .002), dry matter intake (P < .02), and final live weight (P < .07) was cubic, whereas carcass weight (P < .003) and dressing percentage (P < .08) were linearly affected by salinomycin concentration. Although a beneficial effect of 10 ppm salinomycin on lamb performance was apparent, the development of natural resistance makes it difficult to attribute this response to the control of coccidiosis or giardiasis.

The Rumen: A Unique Source of Enzymes for Enhancing Livestock Production

Increasing competition in the livestock industry has forced producers to cut costs by adopting new technologies aimed at increasing production efficiency. One particularly promising technology is feeding enzymes as supplements for animal diets. Supplementation of diets for non-ruminants (e.g., swine and poultry) with fibrolytic enzymes, such as cellulases, xylanases and beta-glucanases, increases the feed conversion efficiency and growth rate of the animals. Enzymatic hydrolysis of plant cell wall polymers (e.g., cellulose, xylan, beta-glucans) releases glucose and xylose and eliminates the antinutritional effects of beta-glucans and arabinoxylans. Enzyme supplementation of diets for ruminants has also been shown to improve growth performance, even though the rumen itself represents the most potent fibrolytic fermentation system known. Implementation of this technology in the livestock industry has been limited largely because of the cost of development and production of enzymes. Over the last decade, however, developments in recombinant DNA technology have increased the efficiency of existing microbial production systems and facilitated exploitation of alternative sources of industrial enzymes. The ruminal ecosystem is among the novel enzyme sources currently being explored. Understanding the role of enzymes in feed digestion through characterization of the enzymology and genetics involved in digestion of feedstuffs by ruminants will provide insight required to improve the products currently available to producers. Characterization of genes encoding a variety of hydrolytic enzymes, such as cellulases, xylanases, beta-glucanases, amylases, pectinases, proteases, phytases and tannases, will foster the development of more efficacious enzyme supplements and enzyme expression systems for enhancing nutrient utilization by domestic animals. Characteristics of the original source organism need no longer restrict the production of a useful enzyme. Recent reports of transgenic plants expressing fibrolytic or phytase activity and of transgenic mice able to produce endoglucanase in the pancreas speak to the feasibility of improving feed digestion through genetic modification of the feedstuffs and the animals.

Retrieval of clinical science information using an interactive activation and competition network

A method for storing and retrieving tabulated clinical science information is described. This method uses the interactive activation and competition network and belongs to the realm of parallel distributed processing. The advantages of this method are that information is readily retrievable by name and by any content, and that the best matched information is automatically returned when partially incorrect cues are given. Furthermore, it allows a variable degree of association among different units of information. The basic principles of this method are illustrated through a simple example from clinical bacteriology. In addition an application of this method to the retrieval of information in cardiology is presented.

Effects of giardiasis on production in a domestic ruminant (lamb) model

OBJECTIVE

To examine the effects of giardiasis on production and carcass quality, using growing lambs as a domestic ruminant model.

DESIGN

Randomized block.

ANIMALS

Giardia-free lambs: 23 in infected group, 24 in control group.

PROCEDURE

Six-week-old, specific-pathogen-free lambs were infected with Giardia trophozoites; control lambs received saline solution. Clinical signs of infection, body weight, and feed intake were determined for 10 weeks. Carcass weight and quality were determined at slaughter weight of 45 kg.

RESULTS

Giardia infection persisted from weeks 7 to 16. For 5 weeks after challenge exposure, abnormal feces were more frequently observed in infected lambs. Giardia infection was associated with a decrease in rate of weight gain and impairment in feed efficiency. Time to reach slaughter weight was extended in infected lambs, and the carcass weight of Giardia-infected lambs was lower than that of control lambs.

CONCLUSION

Giardiasis has a negative effect on domestic ruminant production.

CLINICAL RELEVANCE

Giardiasis in domestic ruminants is an economically important disease, thus necessitating control or elimination of the infection.

Emerging patterns of HIV transmission: the value of alternative surveillance methods

OBJECTIVE

To assess the current patterns of HIV transmission in Los Angeles County and determine if AIDS surveillance data accurately reflect these patterns.

DESIGN

Records-based cohort study.

METHODS

The demographic and HIV risk characteristics of persons considered to be recently infected with HIV (CD4+ count > 700 x 10(6)/l) were determined and compared with the characteristics of persons meeting the Centers for Disease Control and Prevention (CDC) 1993 AIDS case definition. Data were obtained for patients with HIV infection enrolled from four HIV outpatient clinics and analyzed between August 1991 and July 1993.

RESULTS

The patient cohort included 1857 persons with HIV infection; 1096 (59.1%) met the CDC 1993 AIDS case definition and 134 (7.2%) had a CD4+ lymphocyte count > 700 x 10(6)/l. The median CD4+ count for the group presumed to be recently infected was 809 x 10(6)/l. Persons considered recently infected with HIV were more likely than those meeting the AIDS case definition to be female (26.1 and 14.5%, respectively; P < 0.001), black (28.4 and 18.2%, respectively; P = 0.001), or male homosexual injecting drug users (IDU; 6.7 and 3.4%, respectively; P = 0.05). After controlling for confounding variables by logistic regression, persons recently infected were more likely to be female [adjusted odds ratio (OR), 3.4; 95% confidence interval (CI), 1.8-6.5; P < 0.001], black (adjusted OR, 1.6; 95% CI, 1.1-2.5; P = 0.02) or male homosexual IDU (adjusted OR, 2.4; 95% CI, 1.1-5.2; P = 0.02) than persons with AIDS.

CONCLUSIONS

Our results suggest that the HIV epidemic in Los Angeles County is currently advancing into different subpopulations and indicate that the current patterns of HIV transmission in the County are not fully reflected in standard AIDS surveillance activities. However, our data must be interpreted cautiously because of potential selection and misclassification biases. These findings illustrate the benefits of alternative surveillance mechanisms in detecting important changes in HIV transmission and defining groups at risk, especially in jurisdictions without HIV reporting.

A conjugative transfer system for the rumen bacterium, Butyrivibrio fibrisolvens, based on Tn916-mediated transfer of the Staphylococcus aureus plasmid pUB110

A limitation of genetic studies of the rumen bacterium, Butyrivibrio fibrisolvens, has been the availability of suitable vectors and transfer systems. Using the conjugative tetracycline resistant transposon, Tn916, the Staphylococcus aureus plasmid, pUB110, and the pUB110-based shuttle vector, pUBLRS, a conjugative transfer system was developed for B. fibrisolvens. B fibrisolvens donor strains H17c2 and H17c12, containing Tn916 and pUB110 or pUBLRS, respectively, were used in mating experiments with selected B. fibrisolvens strains. Kanamycin resistant transconjugants, containing pUB110, of strains 193, 194, and 195 were detected at a combined average frequency of 7.78 x 10(-7) per donor and 1.11 x 10(-5) per recipient. Transconjugants of strains 193 and 194, containing pUBLRS, were detected at an average frequency of 1.22 x 10(-6) per donor and 4.70 x 10(-8) per recipient. Southern hybridization analysis confirmed the presence of pUB110 and pUBLRS in transconjugants. Results indicated that Tn916 was necessary for mobilization of pUB110 as transconjugants were not detected when the transposon was absent from the donor strains. The ability to mobilize pUB110 and pUBLRS between B. fibrisolvens strains provides a conjugative transfer system that circumvents problems encountered with electroporation.

Microbial attachment and feed digestion in the rumen

Direct microscopic examination of the rumen and its contents shows microbial populations largely attached to feed particles in the digesta. Most feeds contain a surface layer that is resistant to attachment and therefore to digestion. Infiltration of these recalcitrant epidermal layers through damage sites or through focused enzymatic attack is essential for initiation of the digestive process. Proliferation of primary colonizing cells produces glycocalyx-enclosed microcolonies. Secondary colonizers from the ruminal fluid associate with microcolonies, resulting in the formation of multispecies microbial biofilms. These metabolically related organisms associate with their preferred substrates and produce the myriad of enzymes necessary for the digestion of chemically and structurally complex plant tissues. Upon accessing the internal, enzyme-susceptible tissues, microbial "digestive consortia" attach to a variety of nutrients, including protein, cellulose, and starch and digest insoluble feed materials from the inside out. Substances that prevent microbial attachment or promote detachment (e.g., condensed tannins, methylcellulose) can completely inhibit cellulose digestion. As the microbial consortium matures and adapts to a particular type of feed, it becomes inherently stable and its participant microorganisms are notoriously difficult to manipulate due to the impenetrable nature of biofilms. Properties of feed that place constraints on microbial attachment and biofilm formation can have a profound effect on both the rate and extent of feed digestion in the rumen. Developments in feed processing (i.e., chemical and physical), plant breeding, and genetic engineering (both of ruminal microorganisms and plants) that overcome these constraints through the promotion of microbial attachment and biofilm formation could substantially benefit ruminant production.

Production of 2-aminobutyrate by Megasphaera elsdenii

Production of the amino acid 2-aminobutyrate was studied in four strains of Megasphaera elsdenii grown on a lactate-based growth medium containing Bacto-casamino acids and yeast extract. Supplementation with threonine increased the production of 2-aminobutyrate in three of the four strains, but no substantial increase in production was noted with serine, methionine, or aspartate, all of which are potential sources for the precursor of 2-aminobutyrate, 2-oxobutyrate. L-Cycloserine, an inhibitor of alanine transaminases, decreased both alanine and 2-aminobutyrate production, suggesting that 2-aminobutyrate synthesis may share the same metabolic pathway as alanine synthesis or that 2-oxobutyrate can act as a substrate for alanine transaminases. Decreases in the production of 2-aminobutyrate were associated with a reduction in the catabolism of branched-chain amino acids in two of the four strains.

Effect of condensed tannins from birdsfoot trefoil on endoglucanase activity and the digestion of cellulose filter paper by ruminal fungi

The ruminal fungi Neocallimastix frontalis RE1, Neocallimastix patriciarum 27, Piromyces communis 22, and Orpinomyces joyonii 19-2 were examined for their ability to digest filter paper in the presence of condensed tannins from birdsfoot trefoil (Lotus corniculatus L.). For all four fungi, inhibition of endoglucanases was evident at 100 micrograms condensed tannins.mL-1 with nearly complete inhibition at 300 micrograms condensed tannins.mL-1. At 100 and 200 micrograms condensed tannins.mL-1, the endoglucanase activity of N. frontalis RE1 was greater (P < 0.01) than that of the other three fungal species. Exposure to 100 micrograms condensed tannins.mL-1 did not affect the ability of N. frontalis RE1 or N. patriciarum 27 to digest filter paper, and although digestion was reduced, N. frontalis RE1 and P. communis 22 solubilized more than 20% of the filter paper at 500 micrograms condensed tannins.mL-1. In contrast, O. joyonii 19-2 was virtually unable to digest filter paper at 300 micrograms condensed tannins.L-1. Mycelia of fungi grown with condensed tannins were covered by filamentous material, which may have arisen from the formation of condensed tannin-protein complexes. Less than 86% of the condensed tannins (as measured by the H2SO4 method) were recovered after 120 h of incubation with N. frontalis RE1, P. communis 22, and N. patriciarum 27. The need for detailed studies to examine the ability of ruminal fungi to metabolize condensed tannins is evident.

Effects of Sainfoin ( Onobrychis viciifolia Scop.) Condensed Tannins on Growth and Proteolysis by Four Strains of Ruminal Bacteria

Sainfoin leaf condensed tannins inhibited growth and protease activity in Butyrivibrio fibrisolvens A38 and Streptococcus bovis 45S1 but had little effect on Prevotella ruminicola B 1 4 or Ruminobacter amylophilus WP225. Tannins bound to cell coat polymers in all strains. Morphological changes in B. fibrisolvens and S. bovis implicated the cell wall as a target of tannin toxicity.

Effects of mastication on digestion of whole cereal grains by cattle

A study was conducted to evaluate the effects of mastication on the physical breakdown and ruminal digestion of whole cereal grains by cattle. Three Hereford cows (initial BW 557 kg; SD, 17) surgically fitted with ruminal and esophageal fistulas were fed 5.5 kg/d (as-fed basis) of whole barley, corn, or wheat in an experiment designed as a 3 x 3 Latin square. Eating time and chews per kilogram of DM were greater (P < .10) for corn than for barley or wheat. Whole corn was substantially damaged after ingestive mastication, and the majority of kernels were broken into small pieces. Many barley and wheat kernels showed signs of dentition, but most kernels remained intact. Less saliva (P < .10) was added to whole wheat than to barley or corn during ingestive mastication. Cattle fed whole barley spent twice (P < .10) as long ruminating per kilogram of DM as those fed corn, with intermediate times for wheat. Less than 30% of the DM disappeared from unmasticated whole grains during 96 h of ruminal incubation. Ingestive mastication increased DM digestion to 53, 69, and 66% for barley, corn, and wheat, respectively. Mastication alters the kinetics of ruminal digestion of unprocessed cereal grains. Combined with the inherent protein and starch digestibilities of the grain, mastication affects the type and extent of processing required to optimize the utilization of cereal grains by cattle. Unlike barley and wheat, corn kernels are extensively damaged during ingestive mastication, reducing the need for physical processing.

Comparison of amylolytic and proteolytic activities of ruminal fungi grown on cereal grains

Strains of the ruminal fungi Neocallimastix patriciarum, Orpinomyces joyonii, and Piromyces communis were grown on cellobiose and on cereal grains and then examined for proteolytic and amylolytic activities. On cellobiose all three fungi displayed similar activities, with the exception of little amylolytic activity in the cell-associated fraction of N. patriciarum. Growth on the cereal grains barley, corn, and wheat showed differences in proteolytic and amylolytic activities amongst the ruminal fungi and between the cereal grains. The data suggest that while these fungi are capable of fermenting the cereal grains the mode of enzymatic attack varies both with the particular fungus and the type of cereal grain.

Effects of Condensed Tannins on Endoglucanase Activity and Filter Paper Digestion by Fibrobacter succinogenes S85

The effect of condensed tannins from birdsfoot trefoil ( Lotus corniculatus L.) on the cellulolytic rumen bacterium Fibrobacter succinogenes S85 was examined. Condensed tannins inhibited endoglucanase activity in the extracellular culture fluid, at concentrations as low as 25 μg ml -1 . In contrast, cell-associated endoglucanase activity increased in concentrations of condensed tannins between 100 and 300 μg ml -1 . Inhibition of endoglucanase activity in both the extracellular and the cell-associated fractions was virtually complete at 400 μg of condensed tannins ml -1 . Despite the sharp decline in extracellular endoglucanase activity with increasing concentrations of condensed tannins, filter paper digestion declined only moderately between 0 and 200 μg of condensed tannins ml -1 . However, at 300 μg ml -1 , filter paper digestion was dramatically reduced and at 400 μg ml -1 , almost no filter paper was digested. F. succinogenes S85 was seen to form digestive grooves on the surface of cellulose, and at 200 μg ml -1 , digestive pits were formed which penetrated into the interior of cellulose fibers. Cells grown with condensed tannins (100 to 300 μg ml -1 ) possessed large amounts of surface material, and although this material may have been capsular carbohydrate, its osmiophilic nature suggested that it had arisen from the formation of tannin-protein complexes on the cell surface. The presence of electron-dense extracellular material suggested that similar complexes were formed with extracellular protein.

Cereal grain digestion by selected strains of ruminal fungi

The ruminal fungi Orpinomyces joyonii strain 19-2, Neocallimastix patriciarum strain 27, and Piromyces communis strain 22 were examined for their ability to digest cereal starch. All strains digested corn starch more readily than barley or wheat starch. Orpinomyces joyonii 19-2 exhibited the greatest propensity to digest starch in wheat and barley, whereas the digestion of these starches by N. patriciarum 27 and P. communis 22 was limited. Media ammonia concentrations were lower when fungal growth was evident, suggesting that all strains assimilate ammonia. Fungi formed extensive rhizoidal systems on the endosperm of corn, but O. joyonii 19-2 was the only strain to form such systems on the endosperm of wheat and barley. All strains penetrated the protein matrix of corn but did not penetrate starch granules. Starch granules from all three cereals were pitted, evidence of extensive digestion by extracellular amylases produced by O. joyonii 19-2. Similar pitting was observed on the surface of corn starch granules digested by N. patriciarum 27 and P. communis 22, but not on wheat and barley starch granules. The ability of ruminal fungi to digest cereal grains depends on both the strain of fungus and the type of grain. The extent to which fungi digest cereal grain in the rumen remains to be determined.

Cloning of a xylanase gene from the ruminal fungus Neocallimastix patriciarum 27 and its expression in Escherichia coli

An endo-beta-1,4-xylanase gene was cloned from Neocallimastix patriciarum 27 in the bacteriophage vector lambda gtWES lambda B and was subcloned into the plasmid vectors pUC18 and pUC19 in which xylanase activity was expressed in both orientations. The xylanase was located in the periplasmic space of the host, Escherichia coli HB101. The pH and temperature optima for periplasmic xylanase activity were 6.2 and 40 degrees C, respectively, and the Km for oat spelt xylan hydrolysis was 0.89 mg.mL-1. It also exhibited hydrolytic activity on carboxymethyl cellulose that was equivalent to 28% of the activity exhibited by the enzyme on xylan. It bound to crystalline cellulose, but lacked hydrolytic activity on amorphous cellulose. SDS-PAGE followed by zymogram analysis showed active bands of 68, 58, and 51 kDa. Isoelectric focusing in gels combined with zymogram analysis showed one band of xylanase activity with a pI of 3.6.

Seasonal changes in the adherent microflora of the rumen in high-arctic Svalbard reindeer

Seasonal changes in bacterial colonization of the epithelial tissue were examined in the rumen of high-arctic Svalbard reindeer. Samples of tissue were collected from eight sites in the rumen of reindeer during summer and winter and bacterial colonization was examined using scanning and transmission electron microscopy. At two of these sites, colonization by adherent bacteria was estimated to cover approximately 30% of the ruminal epithelium in specimens collected from reindeer during summer. Bacteria at these sites resembled Ruminococcus sp. and were surrounded by large amounts of glycocalyx. In winter specimens, less than 10% of the epithelial surface was covered by adherent bacteria. Those bacteria that did colonize the epithelial surface were smaller and had virtually no glycocalyx on their surface. Bacteria attached to plant cell wall material in summer samples of reindeer ingesta contained large intracellular glycogen deposits, whereas feed particle-associated bacteria in ingesta collected in winter contained no intracellular glycogen. These data demonstrate that the ruminal bacterial population responds to seasonal changes in feed intake and quality. It is yet to be determined if these bacterial changes enhance the ability of Svalbard reindeer to survive in the hostile environment of the high Arctic.