Evaluation of antibiotic effects on phosphorus digestibility and utilization by growing-finishing pigs fed a phosphorus-deficient, corn-soybean meal diet

Evaluations of the nutritional impact of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. Recent research has demonstrated that virginiamycin increases P digestibility. Because of the importance of P in diet cost and in waste management plans, the present study evaluated the potential impact of 2 additional antibiotics, bacitracin methylene disalicylate (bacitracin) and tylosin, on P digestibility in swine. A total of 48 barrows (mean initial BW, 63.0 to 82.9 kg) were used in 2 nutrient balance experiments. A basal corn-soybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 33.1 mg of bacitracin/kg of diet. In Exp. 2, two diets were also tested: basal vs. basal plus 44.1 mg of tylosin/kg of diet. In both experiments, the pigs were fed their diets for a minimum of 12 d before fecal and urine collection, and pigs were fed the diet at 2.7% of BW during the adaptation and collection period. In Exp. 1, the apparent DM, Ca, and P digestibility values for the basal and bacitracin diets were 91.69, 65.96, and 43.03 vs. 91.47, 65.46, and 41.79%, respectively, and did not differ by diet. In Exp. 2, the DM, Ca, and P digestibility values for the basal and tylosin diets were 91.03, 62.17, and 38.80 vs. 91.11, 63.20, and 40.10%, respectively, and did not differ by diet. The effect of the antibiotics on gut microflora was also appraised but the evaluations failed to demonstrate an effect on the microflora measured, with the exception that tylosin decreased the number of phytate-utilizing bacteria (P = 0.05). Therefore, because these 2 antibiotics did not demonstrate an improvement in P digestibility, improvements in P digestibility seem to be an antibiotic-specific response rather than a generalized antibiotic response.

Virginiamycin improves phosphorus digestibility and utilization by growing-finishing pigs fed a phosphorus-deficient, corn-soybean meal diet1,2

Evaluations of the nutritional effect of antibiotics have largely centered on effects related to the digestibility and utilization of protein and energy. The current study evaluated the potential effect of virginiamycin (VIR) on P digestibility in swine. A total of 70 barrows (mean initial BW = 51 to 64 kg) were used in 4 nutrient-balance experiments. A basal, corn-soybean meal diet that was not supplemented with any inorganic source of P was used in each experiment. In Exp. 1, two diets were tested: basal vs. basal plus 11 mg/kg of VIR. In Exp. 2, four diets were used with a 2 x 2 factorial arrangement of 0 and 11 mg/kg of VIR and 0 and 750 phytase (PHY) units/kg of diet (PU/kg). Experiments 3 and 4 were the same as Exp. 2, except PHY was reduced to 300 PU/kg. For all experiments, VIR improved P digestibility (32.71 to 37.72%, P < 0.001) and Ca digestibility (54.99 to 58.30%, P = 0.002). The addition of PHY improved both P and Ca digestibility (P < 0.001); 750 PU/kg increased P digestibility 27.3% (from 34.6 to 61.9%, P < 0.001), whereas 300 PU increased it 13.8% (from 33.4 to 47.2%, P < 0.001). In an experiment conducted to evaluate the long-term effects of VIR on gut microbial profile, pigs (24 gilts and 8 barrows; mean BW = 29.1 +/- 0.50 kg) were fed a simple corn-soybean meal diet for 16 wk with a 2 x 2 factorial arrangement of VIR (0 and 11 mg/kg) addition and 0.15% dicalcium phosphate deletion. The long-term feeding of VIR in both the control diet and the diet with a marginally reduced P level resulted in a change in ileal microbial profile. A positive numerical increment in the number of phytate-utilizing bacteria was observed in both the normal and P-deleted diets (log unit increments of 12.4 and 17.2% over the respective controls, P = 0.13) when VIR was added. The addition of VIR also tended to affect lactobacilli populations (main effect, P = 0.11; interaction, P = 0.02); VIR decreased lactobacilli in the normal-P diet but did not affect this bacterial population in the P-deleted diet. In conclusion, the antibiotic VIR improves both Ca and P digestibility in pigs. The increase in digestibility is not as great as that provided by PHY, but because the potential mechanism of action (altered microbial populations) differs from that of PHY (direct addition of an enzyme), there can be a degree of additivity in P digestibility improvement when both products are used.

Immune parameters of dry cows fed mannan oligosaccharide and subsequent transfer of immunity to calves

The objective of this study was to evaluate the benefits of supplementation of mannan oligosaccharide (MOS) to cows during the last 3 wk of the dry period on immune function of the cows and subsequent transfer of passive immunity to their calves. Indicators of nonspecific and specific immunity were evaluated. Cows were vaccinated against rotavirus at 4 and 2 wk before expected parturition. Blood samples were obtained from cows before vaccination and at weekly intervals until calving and from calves at birth and 24 h for analysis of serum protein concentrations, packed cell volume, white blood cell counts, white blood cell differentials, and serum rotavirus neutralization titers. Colostrum quantity and quality were measured at calving, and immunoglobulin isotype concentrations in colostrum were determined. Specific immunity was enhanced by MOS supplementation as evidenced by greater serum rotavirus neutralization titers at calving in cows supplemented with MOS compared with control cows. Colostral rotavirus neutralization titers were not affected by treatment. Although numerical differences appeared large, there was a high degree of variability in the colostral rotavirus neutralization titers. Calves from cows fed MOS tended to have greater serum rotavirus neutralization titers compared with calves from cows fed the control diet. There was a tendency for greater increases in serum protein concentrations from birth to 24 h in calves from cows fed MOS compared with calves from cows fed the control diet. Results indicate that supplementation of MOS to cows during the dry period enhanced their immune response to rotavirus and tended to enhance the subsequent transfer of rotavirus antibodies to calves.

Color stability of semitendinosus, semimembranosus, and biceps femoris steaks packaged in a high-oxygen modified atmosphere

The objectives of this study were to evaluate visual and chemical attributes of beefsteaks from various USDA quality grades and muscles packaged in high-oxygen (80% O2/20% CO2) modified-atmosphere packaging (MAP). A total of nine carcasses were selected to represent Select (n = 3), low Choice (n = 3), and high Choice (n = 3) USDA quality grades. The semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) muscles were removed from each carcass and allotted to two packaging types (MAP or polyvinyl chloride over-wrap) and were displayed for up to 10 d, with evaluation on d 1, 3, 5, 7, and 10. Fifty-four steaks were evaluated on each day by a five-member trained panel for visual color (lean color and discoloration) and were also analyzed with a Minolta Chroma Meter CR-310 for L* and a* values (lightness and redness, respectively). Chemical properties measured included percentage of metmyoglobin formation and fat content. Visual color scores did not differ (P > 0.05) at d 1 and 3 with respect to all quality grades, but decreased after d 3, with a greater reduction (P < 0.05) in high Choice steaks for both lean color and discoloration. The low Choice steaks packaged in MAP displayedhigher (P < 0.05) lean color scores and less (P < 0.05) discoloration at d 7 and 10 than did Select and high Choice steaks. Redness (a*) values also decreased (P < 0.05) after d 3, whereas (lightness) L* values declined (P < 0.05) from d 1 to 5. The high Choice steaks had higher (P < 0.05) metmyoglobin content than low Choice and Select steaks, but packaging had no effect (P > 0.05) on metmyoglobin content. Muscle type did affect metmyoglobin content; however, the metmyoglobin content of the SM was greatest (P < 0.05), followed by the BF, with the ST having the lowest (P < 0.05) metmyoglobin formation. Results indicate that low Choice steaks react the best in MAP, and the ST maintained greater storage characteristics regardless of quality grade or packaging.

Influence of postmenopausal hormone replacement therapy on an estrogen metabolite biomarker of risk for breast cancer

Whether postmenopausal hormone-replacement therapy (HRT) increases the risk of breast cancer remains controversial, despite numerous epidemiological studies. We approached the question from a biochemical rather than an epidemiological direction - we hypothesized that if estrogen administration increases the risk of breast cancer, it should also alter a known estrogen biomarker of risk towards what has been observed in patients who already have breast cancer. The specific biomarker we studied was the ratio of the urinary excretion of two principal estradiol metabolites, 2-hydroxyestrone and 16 alpha-hydroxyestrone, which is markedly decreased in women with breast cancer and women with familial risk for breast cancer. We studied 34 healthy postmenopausal women not on HRT and 19 women on HRT (Premarin 0.625 mg daily plus Provera, 2.5 mg daily, in women with a uterus and Premarin alone in women without a uterus); treatment duration ranged from 3 months to 15 years. We also studied four women with recently diagnosed, untreated breast cancer. The women with breast cancer showed a significantly lower 2-hydroxyestrone to 16 alpha-hydroxyestrone ratio than control women on HRT (1.35 +/- 0.13 vs. 2.71 +/- 0.84; p < 0.0001). There was no significant difference in the metabolite ratio between healthy women on HRT and women not on HRT (2.82 +/- 0.92 vs. 2.71 +/- 0.84). There was no significant difference between women receiving Premarin alone and women receiving Premarin plus Provera (2.46 +/- 0.84 vs. 3.13 +/- 0.90), and neither differed significantly from women not on HRT (2.71 +/- 0.84). The finding that the ratio of women on HRT was not decreased to or toward the ratio in women with breast cancer can be interpreted, we believe, as a suggestive item of biochemical evidence that HRT is not a risk for breast cancer.

Comparison of long-chain alcohols and other volatile compounds emitted from food-borne and related Gram positive and Gram negative bacteria

Numerous reports have been published on the antimicrobial activity of synthetic volatile long chain alcohols, such as 1-decanol and 1-dodecanol, against bacteria and fungi. The objective of the present study was to survey microorganisms for emission patterns of naturally occurring long chain alcohols and other volatile components to determine if these compounds are associated with certain groups of bacteria. Cultures were grown in trypticase soy broth overnight and volatile compounds were trapped on a porous polymer and identified by mass spectrometry. Subsequently, volatile compounds were collected from 26 strains of food associated bacteria using solid-phase microextraction and analyzed by gas chromatography. Alcohols comprising 1-octanol, 1-decanol, and 1-dodecanol occurred as products from enteric Gram negative bacteria, which included Citrobacter, Enterobacter, Klebsiella, Salmonella, and Shigella. However, the long chain alcohols were not detected as products from the nonenteric Gram negative species studied which included Acinetobacter, Pseudomonas, and Shewanella. Among Gram positive bacteria, including Bacillus, Enterococcus, Lactococcus, Leuconostoc, Listeria, Staphylococcus, and Streptococcus, the only long chain alcohol detected was 1-decanol and, if present, it occurred in relatively small amounts. Other classes of compounds emitted by bacteria included methylketones and sulfides. The methylketones were found as products from Gram positive and Gram negative bacteria, whereas the sulfides were closely associated with Gram positive bacteria. In summary, the emission patterns of volatile compounds from bacteria showed many trends including the association of long chain alcohols with enteric Gram negative bacteria. The results provide a basis for future in vivo studies to determine if volatile compounds such as natural long chain alcohols function in the ecology of food-borne Gram negative bacterial pathogens.

Brewers dried yeast as a source of mannan oligosaccharides for weanling pigs

Brewers dried yeast, a source of mannan oligosaccharides (MOS), was assessed as an alternative to an antimicrobial agent (carbadox) for young pigs in two experiments. The yeast contained 5.2% MOS. Agglutination tests confirmed adsorption of several serovars of E. coli and Salmonella spp. onto the yeast product. In Exp. 1, seven replicates (five pigs per pen) of 22-d-old pigs were fed a nonmedicated basal diet or the basal diet with carbadox (55 mg/kg), yeast (3%), or a combination of 3% yeast and 2% citric acid for 28 d. Carbadox did not improve growth performance. Growth rate and feed intake were depressed (P < 0.05) in pigs fed yeast alone or in combination with acid. Log counts of total coliforms, Escherichia coli, and Clostridium perfringens in feces were not affected by diet, but Bifidobacteria spp. counts were lower (P < 0.05) in pigs fed the yeast + acid diet and lactobacilli counts were higher (P < 0.05) in pigs fed yeast. Fecal pH and VFA concentrations and intestinal morphological traits were not consistently affected by diet. Serum IgG levels were elevated in the yeast + acid (P < 0.01) group. In Exp. 2, the effects of yeast and carbadox additions to the diet on enteric microbial populations in young pigs housed in isolation units were evaluated. Pigs (n = 24) were weaned at 11 d of age (4.1 kg BW) and placed in isolation chambers (two pigs per chamber) equipped with individual air filtering systems and excrement containers. Treatments were a nonmedicated basal diet and the basal diet with 55 mg/kg of carbadox or with 3% yeast. Diets were fed for 29 d, then each pig was orally dosed with approximately 9.5 x 10(8) CFU of E. coli K88. Daily fecal E. coli K88 counts were not different (P > 0.05) among treatments, but fecal shedding of carbadox-resistant coliforms was higher (P < 0.01) during the 9-d period in pigs fed carbadox. Total fecal coliforms were consistently lower throughout the postinoculation period in pigs fed yeast (P < 0.05). Yeast reduced colonization oftotal coliforms in the duodenum,jejunum, cecum, and colon, but it did not have a consistent effect on colonization of E. coli K88. Pigs fed yeast tended (P < 0.10) to have higher serum IgG levels than controls. In these experiments, brewers dried yeast and carbadox had minimal effects on growth, microbial populations, and intestinal health traits of early-weaned pigs, but certain serum immunological traits were enhanced by feeding yeast.

Survival of Escherichia coli O157:H7 on strawberry fruit and reduction of the pathogen population by chemical agents

Survival of Escherichia coli O157:H7 was studied on strawberry, a fruit that is not usually washed during production, harvest, or postharvest handling. Two strains of the bacteria were tested separately on the fruit surface or injected into the fruit. Both strains of E. coli O157:H7 survived externally and internally at 23 degrees C for 24 h and at 10, 5, and -20 degrees C for 3 days. The largest reduction in bacterial population occurred at -20 degrees C and on the fruit surface during refrigeration. In all experiments, the bacteria inside the fruit either survived as well as or better than bacteria on the surface, and ATCC 43895 frequently exhibited greater survival than did ATCC 35150. Two strains of E. coli also survived at 23 degrees C on the surface and particularly inside strawberry fruit. Chemical agents in aqueous solution comprising NaOCl (100 and 200 ppm), Tween 80 (100 and 200 ppm), acetic acid (2 and 5%), Na3PO4 (2 and 5%), and H2O2 (1 and 3%) were studied for their effects on reduction of surface-inoculated (10(8) CFU/ml) E. coli O157:H7 populations on strawberry fruit. Dipping the inoculated fruit in water alone reduced the pathogen population about 0.8 log unit. None of the compounds with the exception of H2O2 exhibited more than a 2-log CFU/g reduction of the bacteria on the fruit surface. Three percent H202, the most effective chemical treatment, reduced the bacterial population on strawberries by about 2.2 log CFU/g.

Effect of mercury and Gpi-2 genotype on standard metabolic rate of eastern mosquitofish (Gambusia holbrooki)

Previous studies demonstrated differential mortality among mosquitofish of different Gpi-2 genotypes during acute mercury and arsenate exposures. Mercury-exposed mosquitofish also had Gpi-2 genotype-specific differences in glycolytic and Krebs cycle metabolite pools. The mortality and metabolite data suggested that mosquitofish bearing specific Gpi-2 genotypes might differ in metabolic efficiency, with less efficient Gpi-2 genotypes having higher standard metabolic rates (SMRs) and shorter times to death during acute mercury exposure. Effect of Gpi-2 genotype on SMR was assessed with a factorial arrangement of six Gpi-2 genotypes and two exposure sequences (Control - Control; Control - 100 microg/L Hg). The SMRs were estimated by measuring oxygen consumption using an indirect, closed-circuit, computer-controlled respirometer. A 48-h exposure to 100 microg/L of mercury resulted in a 16.7% elevation of SMR above control levels (p = 0.001). The Gpi-2 genotype and the number of heterozygous loci per individual had no significant effect on SMR in mercury-exposed mosquitofish. The experimental results do not support the hypothesis that Gpi-2 genotype-specific differences in glycolytic and Krebs cycle metabolite pools and mortality in mosquitofish exposed to mercury are associated with differences in SMR.

The practice of structure activity relationships (SAR) in toxicology

Both qualitative and quantitative modeling methods relating chemical structure to biological activity, called structure-activity relationship analyses or SAR, are applied to the prediction and characterization of chemical toxicity. This minireview will discuss some generic issues and modeling approaches that are tailored to problems in toxicology. Different approaches to, and some facets and limitations of the practice and science of, SAR as they pertain to current toxicology analyses, and the basic elements of SAR and SAR-model development and prediction systems are discussed. Other topics include application of 3-D SAR to understanding of the propensity of chemicals to cause endocrine disruption, and the use of models to analyze biological activity of metal ions in toxicology. An example of integration of knowledge pertaining to mechanisms into an expert system for prediction of skin sensitization to chemicals is also discussed. This minireview will consider the utility of modeling approaches as one component for better integration of physicochemical and biological properties into risk assessment, and also consider the potential for both environmental and human health effects of chemicals and their interactions.

Early detection of probable idiopathic Parkinson's disease: I. Development of a diagnostic test battery

We developed a test battery as an inexpensive and objective aid for the early diagnosis of idiopathic Parkinson's disease (iPD) and its differential diagnoses. The test battery incorporates tests of motor function, olfaction, and mood. In the motor task, a wrist flexion-and-extension task to different targets, movement velocities were recorded. Olfaction was tested with the University of Pennsylvania Smell Identification Test. Mood was assessed with the Beck Depression Inventory. An initial regression model was developed from the results of 19 normal control subjects and 18 patients with early, mild, probable iPD. Prospective application to an independent validation set of 122 normal control subjects and 103 patients resulted in an 88% specificity rate and 69% sensitivity rate, with an area under the Receiver Operator Characteristic curve of 0.87.

Pharmacokinetics of intravascularly administered (65)Zinc in channel catfish (Ictalurus punctatus)

Comparison was made of the pharmacokinetics of the radioisotope (65)Zinc ((65)Zn) in blood, plasma, and whole body of adult channel catfish (Ictalurus punctatus) following intravascular (iv) administration. A two-compartment model described the pharmacokinetics of (65)Zn in plasma and blood during the first 40 days following iv administration, but was unable to describe the long-term disposition of (65)Zn. Whole-body counting revealed that approximately half of the (65)Zn dose was sequestered in a slowly exchangeable pool with a half-life of 1.5 years. Greater than 99% of the circulating (65)Zn was bound to plasma proteins, whereas there was less than 1% binding to red blood cells. Synthesis of the results for channel catfish and existing data in other species indicates three phases in the pharmacokinetics of zinc. The first phase consists of initial distribution outside the vascular system to kidney, liver, and other organs (alpha phase in blood and plasma; t(1/2) of 4 to 5 h). The second phase involves distribution from organs to a slowly exchangeable zinc pool, likely consisting of bone (beta phase in blood and plasma; alpha phase in whole body; t(1/2) of 4 to 20 days). The third phase appears to involve a slow turnover of sequestered zinc (t(1/2) greater than 1 year). Blood sampling or short-term whole-body measurements will underestimate the persistence of zinc in fish, thus prolonged sampling and measurement of whole-body concentrations are necessary to characterize the pharmacokinetics of zinc.

Volatile compounds from Escherichia coli O157:H7 and their absorption by strawberry fruit

Volatile compounds emitted by cultures of two strains of the pathogenic bacterium Escherichia coliO157:H7 and a nonpathogenic strain of E. coli were trapped on Super-Q porous polymer and identified by GC-MS. The predominant compound produced by all three strains was indole with lesser amounts of other components including methyl ketones, 2-heptanone, 2-nonanone, 2-undecanone, and 2-tridecanone. The vapor-phase profiles of these strains were similar for most chemicals identified but differed with regard to ketones. Strawberry fruit was shown to be a suitable host for E. coli O157:H7 with the population of the bacterium either increasing or remaining stable after 3 days depending on inoculation level. Headspace analysis of the volatile compounds from inoculated fruit yielded no detectable quantity of indole. Strawberry fruit readily absorbed indole and other volatile compounds produced by the bacteria and in some cases metabolized the compounds to new volatile products. Thus, headspace "marker" compounds indicating possible bacterial contamination of fruit were largely removed from the vapor phase by the strawberries.

137Cs elimination by chronically-contaminated largemouth bass (Micropterus salmoides)

The temperature-dependent 137Cs biological half-times (Tb) of lifetime-exposed largemouth bass (Micropterus salmoides) from a nuclear cooling reservoir at the U.S. Department of Energy's Savannah River Site were calculated from whole-body measurements of live fish and compared with literature records for acutely and chronically-contaminated fish. The Tb's of the bass averaged 322 d (95% CI: 311-333 d), 225 d (95% CI: 220 to 230 d), and 140 d (95% CI: 137 to 143 d) at 15, 20, and 26 degrees C, respectively. These mean Tb's were 1.7 to 2.5 times longer than would be expected for acutely contaminated fish, and 1.2 to 1.8 times longer than those predicted for fish at steady-state with their environment according to recent models. This slower elimination did not appear to result from slower elimination from skeletal muscle compared with other soft tissues, in that the muscle to whole-body 137Cs concentration ratios after the elimination period were similar to those of freshly-caught bass. Our results suggested that elimination rates estimated from the terminal elimination components of acutely-dosed fish may not reflect the elimination rates of fish exposed to contaminants throughout their lifetime, even when care is taken to allow sufficient time for absorption of the dose.

Using metal-ligand binding characteristics to predict metal toxicity: quantitative ion character-activity relationships (QICARs)

Ecological risk assessment can be enhanced with predictive models for metal toxicity. Modelings of published data were done under the simplifying assumption that intermetal trends in toxicity reflect relative metal-ligand complex stabilities. This idea has been invoked successfully since 1904 but has yet to be applied widely in quantitative ecotoxicology. Intermetal trends in toxicity were successfully modeled with ion characteristics reflecting metal binding to ligands for a wide range of effects. Most models were useful for predictive purposes based on an F-ratio criterion and cross-validation, but anomalous predictions did occur if speciation was ignored. In general, models for metals with the same valence (i.e., divalent metals) were better than those combining mono-, di-, and trivalent metals. The softness parameter (sigma p) and the absolute value of the log of the first hydrolysis constant ([symbol: see text] log KOH [symbol: see text]) were especially useful in model construction. Also, delta E0 contributed substantially to several of the two-variable models. In contrast, quantitative attempts to predict metal interactions in binary mixtures based on metal-ligand complex stabilities were not successful.

A 3 year retrospective review of intrauterine insemination, using cryopreserved donor spermatozoa and cycle monitoring by urinary or serum luteinizing hormone measurements

Insemination with donor spermatozoa is an integral part of infertility treatment. For the last 3 years in our unit, intrauterine insemination with donor spermatozoa (IUID) has been used in preference to vaginal insemination. In this retrospective study, patients were offered an initial course of five single intrauterine inseminations with cryopreserved donor spermatozoa and treatment was then reviewed. A total of 389 patients received 1465 inseminations. In all, 1119 cycles were monitored using luteinizing hormone serum analyses and 346 cycles using the urine home test kits. The clinical pregnancy rate per insemination for the cycles monitored by the serum assay was 18.0% (202/1119) compared with the urine cycles (13.7%, 46/346) (P <05). The pregnancy loss rate was not significantly different (14.4%, 29/202 and 21.7%, 10/46) (serum and urine cycles respectively). The viable clinical pregnancy rate was significantly higher (P <03) for the serum cycles than for the cycles using the urinary monitoring (15.5%, 173/1119 and 10.4%, 36/346 respectively). The cycles monitored by serum assay had a significantly higher cumulative viable clinical pregnancy rate (P <0001) of 70.2% after nine inseminations compared with the urine monitored cycles of 54.8%. The majority of patients opted for the serum cycles, with a minority self-selecting the urine cycles mainly for travelling convenience. The explanation for the significant differences between the viable clinical pregnancy rates per insemination and the cumulative viable clinical pregnancy rates may be due to the sensitivity of the urine home test kit or the patients' interpretation of the result.

Comparison of the Petrifilm dry rehydratable film and conventional culture methods for enumeration of yeasts and molds in foods: collaborative study

A collaborative study was performed involving 18 laboratories and 6 food types to compare 3M Petrifilm yeast and mold count plates with the method described in the U.S. Food and Drug Administration's Bacteriological Analytical Manual. Four species of mold and 2 species of yeast were used to inoculate the following foods: hot dogs, corn meal, ketchup, orange juice, yogurt, and cake mix. Each collaborator received 15 samples of each food type: 5 low-level inoculations, 5 high-level inoculations, and 5 uninoculated samples. There was no significant difference between the means of the 2 methods for any product or inoculation level. The Petrifilm yeast and mold count plate method for enumeration of yeasts and molds in foods has been adopted first action by AOAC INTERNATIONAL.

A prospective evaluation of cryopreservation strategies in a two-embryo transfer programme

A total of 364 consecutive patients requesting in-vitro fertilization (IVF) treatment were divided randomly into two groups. In the first group, two embryos in the original IVF cycle were allowed to divide prior to transfer, with any remaining embryos being cryopreserved at the pronucleate (PN) stage. In the second group, all the embryos were allowed to divide to the early cleavage (EC) stage, and the best two replaced; any suitable remaining embryos were frozen at the 2- to 4-cell stage. A total of 134 cycles (36.8%) fulfilled the study criteria for a fresh embryo replacement and supernumerary embryos cryopreserved. In the PN group, 72 out of 182 (39.6%) patients had a fresh embryo replacement accompanied by embryo cryopreservation, which was not significantly different from the EC group (62/182; 34.1%). The livebirth rate per fresh embryo transfer in the EC group (17/62; 27.4%) was significantly higher than that for the PN group (8/72; 11.1%; P < 0.05). Embryo survival following thawing was similar for the PN (96/129; 74.4%) and EC (79/102; 77.4%) stages. Although not significant, the livebirth rate following the transfer of thawed embryos was higher in the PN group (11/44; 25.0%) than in the EC group (4/38; 10.5%). Following one fresh and two freeze-thaw embryo replacements, the observed cumulative viable pregnancy rates were comparable for patients in both the PN (40.2%) and EC (41.1%) groups.

TECRA Listeria Visual Immunoassay (TLVIA) for detection of Listeria in foods: collaborative study

A collaborative study involving 26 laboratories and 5 food types was performed to compare the TECRA Listeria Visual Immunoassay (TLVIA) with standard culture methods. Three foods (lettuce, ice cream, and fish fillets), under the jurisdiction of the U.S. Food and Drug Administration, and 2 foods (cooked chicken and cooked ground turkey), under the jurisdiction of the U.S. Department of Agriculture, were used to determine the effectiveness of the TLVIA. Of the 900 samples tested, 300 were inoculated with low levels (1-5 cells/25 g) of Listeria spp. and 300 were inoculated with high levels of Listeria spp. (10-50 cells/25 g). Method agreement between the conventional culture methods and TLVIA (visual) was 94.7%. Method agreement between the conventional culture methods and TLVIA (reader) was 93.6%. The colorimetric polyclonal enzyme immunoassay (TLVIA) for detection of Listeria in foods has been adopted first action by AOAC INTERNATIONAL.

Toxicokinetics and disposition of inorganic mercury and cadmium in channel catfish after intravascular administration

To better understand the distribution and elimination of inorganic mercury (Hg) and cadmium (Cd) in fishes, channel catfish (Ictalurus punctatus) were administered either 6.4 micrograms/kg 203Hg as HgCl2 or 4.0 micrograms/kg 109Cd as CdCl2 via a dorsal aortic cannula. Blood, plasma, and red blood cells (RBCs) were serially sampled up to 156 (Hg) or 335 (Cd) days. The fraction of the injected dose remaining in the animal (Xf) was also determined at selected times by whole animal counting. The blood concentration and Xf-time profiles were simultaneously fitted to a three-compartment toxicokinetic model. The plasma concentration-time profile was also separately fitted to the same three-compartment model for comparison of parameter estimates. Toxicokinetic analysis of the blood concentration and Xf-time profile provided the following values: steady-state volume of distribution = 13.8 +/- 2.8 ml/g (Hg), 41.4 +/- 0.3 ml/g (Cd); total body clearance = 0.021 +/- 0.0006 ml/day/g (Hg), 0.0031 +/- 0.0008 ml/day/g (Cd); biological half-life (t1/2, beta) = 722 +/- 309 days (Hg), 9627 +/- 2206 days (Cd). Estimates of the t1/2 beta were up to 94 times longer if determined by simultaneous fitting of the blood concentration and Xf-time profiles. A time-dependent accumulation of Hg and Cd by RBCs was observed with maximum RBC concentrations of Hg and Cd occurring at 7 and 12 days after injection. After injection, the tissues with the highest accumulation of Hg were the liver, trunk and head kidney, muscle, and skin, but the amount of Hg in the liver gradually increased over 156 days. Most of the Cd was accumulated by the liver and trunk kidney within 24 hr, with little change occurring after 335 days. This study demonstrates the usefulness of intravascular injection and simultaneous analysis of blood and whole body amount data in determining the elimination of metals from fishes.

Time-to-event analyses of ecotoxicity data

: Intensity and duration of exposure dictate the effect of a toxicant. Consequently, any assessment of ecological risk that does not include a sound understanding of both concentration and duration effects is compromised. This being the case, it is surprising that the predominant approach in ecotoxicology (concentration-effect modeling) inefficiently includes exposure duration. Ecological risk assessment can be enhanced with time-to-event models that can easily include concentration, exposure duration, and other important covariates. Time-to-event methods are described and linkage made to relevant ecological techniques, i.e. life table analyses and genetic selection models.

The emotional impact of mistakes on family physicians

OBJECTIVE

To explore the emotional impact of the most memorable mistake on family physicians, the support they needed and received, and their response to a hypothetical scenario in which a colleague's decision was associated with a fatal outcome.

SETTING AND PARTICIPANTS

Randomly selected members of a county chapter of a midwestern state academy of family physicians.

DESIGN

Qualitative cross-sectional survey using in-depth interviews subject to content analysis.

METHODS

I audiotaped interviews with each of the physicians in their offices. Two medical sociologists and I first independently, and then consensually, categorized the data based on the frequency with which a word or idea appeared in the text.

RESULTS

Thirty (75 %) of the 40 physicians originally contacted participated in the study. Twenty-three (77%) of the 30 physicians admitted to making a mistake. The physicians experienced emotional adversity. Of 27 physicians, 17 (63%) needed someone to talk to, 13 (48 %) needed to review their case management, 16 (59%) needed professional reaffirmation, and eight (30%) needed personal reassurance. Having someone to talk to was the support that 12 (44%) of the 27 physicians valued most. Eighteen (67%) of 27 received this support from someone other than their peers. Although all subjects recognized their colleague's pain and need for support in the hypothetical scenario, only nine (32%) of 28 physicians would have unconditionally offered support.

CONCLUSION

Making mistakes unfavorably affects family physicians and creates a strong need for support. Family physicians may benefit from sharing experiences that diminish perfectionism and recognize mistakes as a natural part of practicing medicine. Further research needs to address how physicians can be encouraged toward therapeutic self-disclosure and peer support.

Cognitive screening of nursing home residents: factor structures of the Mini-Mental State Examination

OBJECTIVE

To examine factor structures of the Mini-Mental State Examination, attempting first to replicate any of previously proposed 2-factor solutions; and to explore, secondly, the presence of clinically more differentiated and statistically stable factor structures representing common neurocognitive dimensions.

DESIGN

Factor analytic investigation of descriptive dataset collected on nursing home residents. Two factor analyses were performed, one in which the number of factors was fixed at 2 in an effort to replicate previous studies, and one in which the number of factors to retain was determined by the scree test. Both factor analyses used established methods for judging the adequacy of the correlation matrix and the significance of factor loadings, and both applied principal components analysis for initial factor extraction and the equamax criterion for orthogonal rotation.

SETTING

Seven nursing homes with a total of 894 beds.

PARTICIPANTS

922 assessments on nursing home residents were performed, of which 892 were complete and entered into the factor analyses. The observation-to-variable ratio exceeded 81:1, assuring the statistical stability of factor solutions derived.

MEASUREMENT

The Mini-Mental State Examination, with standardization of words to be recalled and the inverted spelling of "world" as the mental reversal task.

MAIN RESULTS

Two factor structures were derived. A 2-factor solution, explaining 36.5% of the variance and statistically and conceptually different from those obtained in previous studies, distinguished between Perceptual-Organizational and Psychomotor skills. A 4-factor solution, which explained 56.1% of the variance, included a factor named Executing Psychomotor Commands, while also further differentiating the perceptual-organizational processes into the factors of Memory, Concentration, and Language.

CONCLUSION

The 2-factor solution shows that, notwithstanding previous claims to the contrary, the MMSE can make stable and independent distinctions between psychomotor and perceptual-organizational processes. However, this solution is statistically and conceptually limited and, therefore, of limited clinical and scientific relevance. The 4-factor solution of the MMSE maps well onto commonly recognized dimensions of neurocognitive ability. It offers a stable, intuitively sound, and statistically supported framework for clinical differentiation of cognitive screening data into independent clinical dimensions of neurocognitive functioning. Thus, it offers clinicians and researchers a 4-dimensional framework for interpreting data obtained by means of the MMSE. Studies with other populations of cognitively impaired and intact elderly are recommended to validate and extend the present findings.

Measurement of human chorionic gonadotropin during early pregnancy: a comparison of two immunoradiometric assays

Evidence of implantation following either in vitro fertilization and embryo transfer (IVF-ET) or gamete intrafallopian transfer (GIFT) was obtained by collecting blood on days 10, 12, 14, 16, and 18 after oocyte recovery (day 0), and retrospectively measuring human chorionic gonadotropin (hCG). This was done using immunoradiometric assays for hCG, manufactured either by Serono Diagnostics Ltd. (MAIAclone) or Diagnostics Products Corporation (IRMA-count). The analysis of 63 serum samples by both kits showed a good correlation (r = 0.99) but the Serono (y) method gave values which were consistently greater (y = 1.58x + 4.89) than those of the DPC (x) method. A comparison of the hCG profile of singleton pregnancies measured with either the Serono (n = 33) or DPC (n = 22) kits gave a similar relationship. These results suggest that great care must be taken when comparing results from different laboratories using different kits. Also, consideration must be given to the possible loss of a continuous database should a laboratory change kit.

Use of buserelin in an IVF programme for pituitary-ovarian suppression prior to ovarian stimulation with exogenous gonadotrophins

Daily s.c. injections of buserelin were commenced in the mid-luteal phase of the preceding cycle in 118 women undergoing in-vitro fertilization (IVF) and embryo transfer. Ovarian and pituitary suppression was said to have been adequately achieved when serum oestradiol was less than 50 pg/ml, serum LH less than 2.0 IU/l, no ovarian cysts greater than or equal to 10 mm diameter were present and menstruation had occurred. Nine groups of women were retrospectively identified after the administration of buserelin for 12 days according to whether pituitary and ovarian suppression had been achieved or not, and the reason for extended buserelin treatment prior to ovarian stimulation. Upon adequate suppression, patients were grouped in terms of the duration of exposure to buserelin, and ovarian stimulation was then started by daily injections of human menopausal gonadotrophin. There appeared to be no differences in the ovarian response for women down-regulated by day 12, 19 or greater than or equal to 26 days; those women requiring extended buserelin treatment did equally well compared to those women down-regulating quickly, in terms of number of oocytes recovered and fertilization rate. Clinical pregnancy rates per embryo transfer were 27/68(40%), 8/33(26%) and 4/17(24%) for those women down-regulated by days 12, 19 or greater than or equal to 26 respectively, and were not significantly different.

Quality control in an in-vitro fertilization laboratory: use of human sperm survival studies

A bioassay procedure is described for quality control testing of various disposable items used in routine IVF procedures. This bioassay is performed over 4 days and uses the survival of human sperm in vitro at room temperature to assess which products are suitable for use. New products were tested for cytotoxicity using a general screening method and subsequent batches of every suitable item tested to detect interbatch variation. Products were considered suitable or unsuitable for use depending upon a calculated sperm survival index. Two main types of product were found to be cytotoxic, namely certain brands of syringe and surgical gloves, the common feature of both being the presence of rubber components. The bioassay was also used to investigate further the cytotoxic effect of the powdered and starch-free surgical gloves. The cytotoxic substances from both types of surgical glove were readily transferred to an embryo replacement catheter by touch, and washing of the gloves reduced this effect only moderately. The bioassay has proved inexpensive and convenient but more importantly it has been invaluable for detecting potential sources of cytotoxicity before they are introduced into a standard IVF protocol.

Appropriateness of Aufwuchs as a monitor of bioaccumulation

Aufwuchs, procedurally defined as material accumulating on submerged surfaces, is being used increasingly to monitor trace element bioaccumulation in aquatic biota. Procedurally-defined aufwuchs is a complex mixture of biotic and abiotic components. Both biotic and abiotic components can be avid concentrators of trace elements. Consequently, bioaccumulation data generated from poorly-characterized, procedurally-defined aufwuchs may not accurately reflect accumulation by biota. Further, total concentrations of trace elements in procedurally-defined aufwuchs may not be indicative fo the amount of contaminant available for trophic transfer. Methods of minimizing abiotic component contribution to trace element accumulation and means of assessing the bioavailability of associated trace elements are discussed in this review.

Reduced sex hormone binding globulin and derived free testosterone levels in women with severe acne

Reduced circulating sex hormone binding globulin (SHBG) levels were found in 54% of a group of women with moderate to severe acne and in 60% of another group of twenty-three women who had acne complicated by hirsutism and/or irregular menstrual cycles. The concentrations of SHBG for the women with acne alone (mean 48 +/- 24 nmol/l) and for those with acne and hirsutes (mean 39 +/- 18 nmol/l) were compared with the SHBG concentrations of fifteen unaffected women with normal menstrual cycles (mean 70 +/- 19 nmol/l). The differences in mean SHBG values for both groups of women with acne were significant (P less than 0.001) on comparison with the mean for the unaffected women. Twenty-nine per cent of the women with acne had elevated testosterone values (mean testosterone concentration for the group 1.5 +/- 0.3 nmol/l) and 41% had elevated 'derived' free testosterone levels (mean 21 +/- 6 pmol/l). Of the women with acne and hirsutes 65% had elevated plasma testosterone levels (mean 2.1 +/- 0.6 nmol/l) and 89% had elevated free testosterone concentrations (mean 31 +/- 10 pmol/l). The mean values for testosterone and free testosterone in the plasma of unaffected women (mean testosterone concentration 1.1 +/- 0.3 nmol/l and free testosterone 13 +/- 4 pmol/l) were significantly lower than in women with acne alone (P less than 0.01 and P less than 0.001) and in women with acne and hirsutism (P less than 0.001). This study indicates that a deficiency in SHBG and an elevation in 'derived' free testosterone is a frequent finding in women with severe acne and may be a significant factor in the aetiology and/or perpetuation of this condition.