Effect Of Sample Type Research Articles

Bacterial communities along parrot digestive and respiratory tracts: the effects of sample type, species and time

Digestive and respiratory tracts are inhabited by rich bacterial communities that can vary between their different segments. In comparison with other bird taxa with developed caeca, parrots that lack caeca have relatively lower variability in intestinal morphology. Here, based on 16S rRNA metabarcoding, we describe variation in microbiota across different parts of parrot digestive and respiratory tracts both at interspecies and intraspecies levels. In domesticated budgerigar (Melopsittacus undulatus), we describe the bacterial variation across eight selected sections of respiratory and digestive tracts, and three non-destructively collected sample types (faeces, and cloacal and oral swabs). Our results show important microbiota divergence between the upper and lower digestive tract, but similarities between respiratory tract and crop, and also between different intestinal segments. Faecal samples appear to provide a better proxy for intestinal microbiota composition than the cloacal swabs. Oral swabs had a similar bacterial composition as the crop and trachea. For a subset of tissues, we confirmed the same pattern also in six different parrot species. Finally, using the faeces and oral swabs in budgerigars, we revealed high oral, but low faecal microbiota stability during a 3-week period mimicking pre-experiment acclimation. Our findings provide a basis essential for microbiota-related experimental planning and result generalisation in non-poultry birds.

Effect of sample type and the use of high or low fishmeal diets on bacterial communities in the gastrointestinal tract of Penaeus monodon.

In shrimp aquaculture, manufactured diets that include various supplements and alternative fishmeal ingredients are increasingly being used and their effect on the gastrointestinal (GI) microbiota studied. However, dietary effects on different shrimp GI samples are not known. We investigated how a high (HFM) or low (LFM) fishmeal diet affects bacterial communities from different sample types collected from Penaeus monodon gastrointestinal tract. Bacterial communities of the stomach, intestine tissue and intestine digesta were assessed using 16s rRNA gene sequencing. The feed pellets were also assessed as a potential source of bacteria in the GI tract. Results showed substantial differences in bacterial communities between the two diets as well as between the different sample types. Within the shrimp GI samples, stomach and digesta communities were most impacted by diet, while the community observed in the intestine tissue was less affected. Proteobacteria, Firmicutes and Bacteroidetes were the main phyla observed in shrimp samples, with enrichment of Bacteroidetes and Firmicutes in the LFM fed shrimp. The feed pellets were dominated by Firmicutes and were largely dissimilar to the shrimp samples. Several key taxa were shared however between the feed pellets and shrimp GI samples, particularly in the LFM fed shrimp, indicating the pellets may be a significant source of bacteria observed in shrimp GI samples. In summary, both diet and sample type influenced the bacterial communities characterised from the shrimp GI tract. Thus, it is important to consider the sample type collected from the GI tract when investigating dietary impacts on gut bacterial communities in shrimp. KEY POINTS: • Shrimp gastrointestinal communities are influenced by diet and sample type. • The low fishmeal diet enriched bacteria that aid in polysaccharide metabolism. • Feed pellets can be a source of bacteria-detected gastrointestinal tract of shrimp.

Validation of a commercial magnetic bead-based multiplex assay for 5 novel biomarkers of acute kidney injury in canine serum.

Interest is growing in measurement of novel biomarkers for the diagnosis of acute kidney injury. Multiplex assays may provide a rapid and cost-effective way of measurement; however, sparse information is published regarding their use in dogs. We aimed to validate a commercial magnetic bead-based assay for 5 biomarkers: clusterin (Clus), cystatin C (CysC), kidney injury molecule 1 (KIM-1), monocyte chemoattractant protein 1 (MCP-1), and neutrophil gelatinase-associated lipocalin (NGAL). Intra- and inter-assay imprecision, linearity under dilution (LUD), spike recovery (S-R), and hemoglobin interference were evaluated using serum from healthy and diseased dogs. Additionally, the effect of sample type (serum vs. plasma) was investigated. All values for Clus and MCP-1 were outside the assay's measurable range. Intra- and inter-assay precision were acceptable for NGAL (CVs 8.8% and 13.2%, respectively). Regression analysis of LUD and S-R indicated good linearity for CysC and NGAL. Hemolysis did not affect measurement of any biomarker. Measured concentrations of CysC (p = 0.018) and NGAL (p = 0.015) were significantly lower in sodium citrate plasma compared to serum. We conclude that this magnetic bead-based assay is precise and accurate for NGAL measurement in canine serum. Inappropriate standards for MCP-1 and Clus, and poor accuracy for KIM-1 measurement, suggest that this assay cannot reliably quantify those biomarkers in canine blood. Measurements of CysC in canine blood using this assay must be interpreted with caution given inter-assay imprecision.

Electrolyte measurement in goats: Comparison of 2 blood gas analyzers and evaluation of the preanalytical blood sample preparation on measurement results.

1) To evaluate agreement for electrolyte measurements in goats between a handheld point-of-care analyzer (Abaxis VetScan i-STAT 1) (POC) and a benchtop blood gas analyzer (Opti CCA-TS2) (VBG) and 2) to evaluate effect of sample type on electrolytes values reported by both analyzers. In 21 hospitalized caprine patients and 9 healthy research goats, blood samples were collected into heparin-containing tubes (Sodium Heparin 33 IU/2 ml) (TUBE) and a heparinized syringe (Sodium Heparin 430 IU/ml) (SYRINGE). Samples were analyzed using a POC analyzer as well as VBG. Analyzer results were compared using Bland-Altman analysis and Pearson correlation. Comparison between samples was performed using repeated measures ANOVA. Between analyzers, TUBE yielded a bias (95 % limits of agreement) of 0.07 mmol/l (-4.37 to 4.52) for sodium, while SYRINGE yielded a bias of -6.13 mmol/l (-11.04 to -1.22). Comparison of potassium yielded a bias of 0.09 mmol/l (-0.5 to 0.67) and 0.08 mmol/l (-0.4 to 0.56) for TUBE and SYRINGE, respectively. Comparison of ionized calcium showed a bias of 0.05 mmol/l (0.01-0.1) and -0.02 mmol/l (-0.18 to 0.14) for TUBE and SYRINGE, respectively. Between sample types, the POC yielded a bias of 5.13 mmol/l (0.18-10.09) for sodium, 0.04 mmol/l (-0.12 to 0.2) for potassium, and 0.40 mmol/l (0.12-0.68) for ionized calcium. The POC exhibited clinically negligible bias for electrolyte analysis as compared to VBG. Ionized calcium concentrations were lower in self-prepared heparinized syringes than in heparin-containing tubes, suggesting an effect of heparin concentration on ionized calcium.

Precision and accuracy of a point-of-care glucometer in horses and the effects of sample type

Point-of-care glucometry is used commonly in clinical and research settings; however, accuracy and precision of this method are concerns. The objectives of this study were to determine the accuracy of glucometry in adult horses and the precision of duplicate measurements. Blood samples were collected from 62 horses into one plain syringe, one EDTA tube and three fluoride oxalate (FO) tubes. Immediately after collection, glucose concentrations in whole blood were determined, in duplicate, by glucometry from the syringe (plain whole blood [WB] group), EDTA tube (EDTA group) and one FO tube (FO group). One FO sample was used to measure plasma glucose concentration by a laboratory chemistry analyser (LAB group) ≤1 h after collection. The third FO tube was used to measure plasma glucose concentration by glucometry after 3 h storage (FO3hr group).Adequate precision was present for all groups (coefficient of variation: 0.7–3.5%) except WB (5.5–9.4%). Between groups, correlations were significant (P < 0.05; except for WB-EDTA), varied with group comparison, and tended to be lowest for comparisons involving WB. Mean bias was lowest for WB-LAB and greatest for FO-LAB and FO3hr-LAB; however, the limits of agreement were ≥4.65 mmol/L for WB-LAB and ≤2.75 mmol/L for most other comparisons. For the glucometer used, performance was influenced by sample type: WB was unsuitable, while FO or EDTA samples resulted in adequate precision and accuracy, provided under-estimation of glucose concentrations is accounted for by using method-specific reference ranges. Glucometer performance and optimal sample type(s) should be determined prior to use in horses.

A Distinct Gut Microbiota Exists Within Crohn's Disease–Related Perianal Fistulae

BackgroundGut bacteria are strongly suspected to play a key role in the pathogenesis of Crohn's disease (CD). Studies have demonstrated alterations in the gut microbiota in this patient population. The purpose of this study was to characterize the gut microbiota of fistulizing perianal CD. Materials and MethodsStool and fistula samples were obtained from patients undergoing surgery for CD-related anorectal fistulae. Microbial compositions of matched stool and fistula samples were characterized using 16S rRNA gene profiling. The effect of sample type, patient gender, disease classification (Montreal A/B), disease activity (Harvey Bradshaw Index), antibiotic use, and presence of active proctitis on microbial composition was assessed. ResultsSamples were obtained from 18 patients. Bacteroides was the most abundant genera across all samples collected, followed by Streptococcus and Bifidobacterium. Bifidobacterium was present at significantly higher levels in fecal samples than fistula samples, whereas Achromobacter and Corynebacterium were present at significantly higher levels in fistula samples. Antibiotic, but not thiopurine or antitumor necrosis factor medication, exposure affected the gut microbial composition. Patient gender, disease classification, disease activity, and presence of active proctitis did not alter stool or fistula microbiota. ConclusionsOur data show that the gut microbiota within CD-related anorectal fistulae is distinct from that in stool samples obtained from the same patients. We also observe a dysbiosis in patients treated with antibiotics compared with those not treated with antibiotics.

Effect of sample type on plasma concentrations of cell-free DNA and nucleosomes in dogs

Cell-free DNA (cfDNA) and nucleosomes are two biomarkers of cell death and neutrophil extracellular trap formation that are increased in dogs with sepsis, immune-mediated haemolytic anaemia, cancer and following trauma...

Proper zinc evaluation in clinical practice: Effect of sample type and it's stability

Zinc (Zn) is a ubiquitous element that plays a vital role in the growth and development of human body. Traditionally, Zn has been measured in plasma samples using “trace element” dedicated sampling tubes. However, the recent increase in its assessment leads to the need to use others than plasma samples and the use of sera could be a justified and valid alternative. We evaluated the differences between plasma and serum, for Zn quantification. 307 blood paired samples from patients enrolled for the treatment of obesity-related pathology at our out-patient department were assessed. The quantification of Zn was performed by Flame atomic absorption spectroscopy. Using 123 serum samples randomly selected from our own biobank and stored at −80 °C for 5 years, we further investigated the long-term stability of serum Zn. The mean result for Zn was 77.8 ± 13.2 μg·dL−1 and 77.4 ± 12.8 μg·dL−1, respectively for plasma and for serum, (p = 0.43). Bland-Altman analyses demonstrated excellent concordance of the assay in the two different blood matrices. The mean difference ± SD between serum and plasma matrices was 0.32 ± 3.40 μg·dL−1. The assessment of serum Zn long-term stability indicated a significant change after 5 years storage. The mean value was 74.2 ± 10.9 μg·dL−1 for fresh samples and 83.3 ± 10.9 μg·dL−1 after 5 years of storage at −80 °C, corresponding to a mean difference of +9.1 μg·dL−1(+10,9%, p < 0.05). The increase in Zn values described after long-term storage has to be considered though that should not have a significant clinical value. In conclusion, the routine measurement of Zn can be made in an accurate way using a serum sample, without the need for a specific tube for trace elements assessment.

Preanalytical study of fetuin-A: effect of sample type, processing speed and freeze–thaw cycles

It has been suggested that fetuin-A may be a potential biomarker of cardiometabolic disease. However, few studies have investigated preanalytical factors that might impact the measurement of fetuin-A in the circulation. This pilot study aimed to investigate the preanalytical variables of sample type, timing of sample centrifugation and the impact of freeze-thaw cycles on the concentration of fetuin-A in serum or EDTA-plasma. Blood samples were taken from 19 male or female healthy volunteers, aged 18-70 years, and left at ambient room temperature for 2 h or 48 h. The tubes were then centrifuged, serum and EDTA-plasma separated, and fetuin-A concentrations measured using a commercially available enzyme-linked immunosorbent assay (ELISA). There was no significant difference between the concentrations of fetuin-A in EDTA-plasma and serum following separation from whole blood at 2 h postcollection (P=0.78). The median (interquartile range) concentrations of fetuin-A in EDTA-plasma separated at 2 h and 48 h postcollection were 589 µg/mL (484-703 µg/mL) and 767 µg/mL (687-942 µg/mL), respectively (P<0.0005). For serum, equivalent concentrations were 606 µg/mL (501-669 µg/mL) at 2 h and 607 µg/mL (564-757 µg/mL) at 48 h postcollection (P=0.06). Fetuin-A concentrations measured in EDTA-plasma and serum showed no significant change following three freeze-thaw cycles in samples separated at 2 h postcollection (EDTA-plasma P=0.16; serum P=0.89). This small pilot study has shown that serum is preferable to EDTA-plasma for the measurement of fetuin-A. It has also shown that fetuin-A appears to be as stable after three freeze-thaw cycles as it is after one.

EGG and Acoustic Analyses of Different Voice Samples: Comparison between Perceptual Evaluation and Voice Activity and Participation Profile

Objective: This study investigated whether different electroglottographic (EGG) parameters may be used to estimate voice quality and loading related to it, and whether voice quality is related to self-estimation of voice problems and laryngeal status. The effect of sample type was also considered. Methods: EGG and acoustic signals of a sustained vowel [a:] (90 dB_{6 cm}) and text reading during noise exposure were recorded from 93 female kindergarten teachers. Analyses were made from the sustained vowel and vowel [a:] from a stressed word. Contact quotient (CQ) was calculated. Maximum velocity of increase in contact area inferred from derivative (MDEGG) was examined. Fundamental frequency was calculated from the EGG signal. From the acoustic signal sound pressure level (SPL) was computed and pressedness in voice quality was evaluated perceptually. Self-evaluation was made with Voice Activity and Participation Profile (VAPP). Indirect laryngoscopy was also performed. Results: Pressedness in voice correlated with EGG results only for the sustained vowel, and better with MDEGG than CQ values. VAPP and laryngeal evaluation did not correlate with the acoustic or EGG parameters or with perception. Conclusions: MDEGG is worth testing as an indicator of impact stress. Sustained vowel at a controlled SPL is more suitable for voice quality evaluation than a long stressed vowel from connected speech.

Meta-analysis and systematic review of factors biasing the observed prevalence of congenitally missing teeth in permanent dentition excluding third molars.

No meta-analyses or systematic reviews have been conducted to evaluate numerous potential biasing factors contributing to the controversial results on congenitally missing teeth (CMT). We aimed to perform a rather comprehensive meta-analysis and systematic review on this subject. A thorough search was performed during September 2012 until April 2013 to find the available literature regarding CMT prevalence. Besides qualitatively discussing the literature, the meta-sample homogeneity, publication bias, and the effects of sample type, sample size, minimum and maximum ages of included subjects, gender imbalances, and scientific credit of the publishing journals on the reported CMT prevalence were statistically analyzed using Q-test, Egger regression, Spearman coefficient, Kruskal-Wallis, Welch t test (alpha = 0.05), and Mann-Whitney U test (α = 0.016, α = 0.007). A total of 111 reports were collected. Metadata were heterogeneous (P = 0.000). There was not a significant publication bias (Egger Regression P = 0.073). Prevalence rates differed in different types of populations (Kruskal-Wallis P = 0.001). Studies on orthodontic patients might report slightly (about 1%) higher prevalence (P = 0.009, corrected α = 0.016). Non-orthodontic dental patients showed a significant 2% decline [P = 0.007 (Mann-Whitney U)]. Enrolling more males in researches might significantly reduce the observed prevalence (Spearman ρ = -0.407, P = 0.001). Studies with higher minimums of subjects' age showed always slightly less CMT prevalence. This reached about -1.6% around the ages 10 to 13 and was significant for ages 10 to 12 (Welch t test P < 0.05). There seems to be no limit over the maximum age (Welch t test P > 0.2). Studies' sample sizes were correlated negatively with CMT prevalence (ρ = -0.250, P = 0.009). It was not verified whether higher CMT rates have better chances of being published (ρ = 0.132, P = 0.177). CMT definition should be unified. Samples should be sex-balanced. Enrolling both orthodontic and dental patients in similar proportions might be preferable over sampling from each of those groups. Sampling from children over 12 years seems advantageous. Two or more observers should examine larger samples to reduce the false negative error tied with such samples.

Free-living turtles are a reservoir for Salmonella but not for Campylobacter.

Different studies have reported the prevalence of Salmonella in turtles and its role in reptile-associated salmonellosis in humans, but there is a lack of scientific literature related with the epidemiology of Campylobacter in turtles. The aim of this study was to evaluate the prevalence of Campylobacter and Salmonella in free-living native (Emys orbicularis, n=83) and exotic ( Trachemys scripta elegans, n=117) turtles from 11 natural ponds in Eastern Spain. In addition, different types of samples (cloacal swabs, intestinal content and water from Turtle containers) were compared. Regardless of the turtle species, natural ponds where individuals were captured and the type of sample taken, Campylobacter was not detected. Salmonella was isolated in similar proportions in native (8.0±3.1%) and exotic (15.0±3.3%) turtles (p=0.189). The prevalence of Salmonella positive turtles was associated with the natural ponds where animals were captured. Captured turtles from 8 of the 11 natural ponds were positive, ranged between 3.0±3.1% and 60.0±11.0%. Serotyping revealed 8 different serovars among four Salmonella enterica subspecies: S. enterica subsp. enterica (n = 21), S. enterica subsp. salamae (n = 2), S. enterica subsp. diarizonae (n = 3), and S. enterica subsp. houtenae (n = 1). Two serovars were predominant: S. Thompson (n=16) and S . typhimurium (n=3). In addition, there was an effect of sample type on Salmonella detection. The highest isolation of Salmonella was obtained from intestinal content samples (12.0±3.0%), while lower percentages were found for water from the containers and cloacal swabs (8.0±2.5% and 3.0±1.5%, respectively). Our results imply that free-living turtles are a risk factor for Salmonella transmission, but do not seem to be a reservoir for Campylobacter . We therefore rule out turtles as a risk factor for human campylobacteriosis. Nevertheless, further studies should be undertaken in other countries to confirm these results.

Comparison of Escherichia coli Recovery and Antimicrobial Resistance in Cecal, Colon, and Fecal Samples Collected from Wild House Mice (Mus musculus)

Escherichia coli isolated from colon, cecal, and fecal samples are commonly used as indicator organisms to monitor antimicrobial resistance (AMR) in wild animals. The effect of sample type on E. coli recovery and AMR detection is unknown. We compared the prevalence of E. coli, the frequency of AMR, and the level of agreement between cecal, colon, and fecal samples collected from individual wild house mice (Mus musculus). Samples were collected from 49 mice trapped at swine farms, May-October 2008. We found no difference in the proportion of E. coli-positive samples (82%) among sample types and the agreement among sample types for E. coli recovery ranged from moderate to almost perfect. The percentage of E. coli positive samples resistant to one or more antimicrobial varied from 53% for colon samples to 71% for cecum samples; however, there was no significant difference in the proportion of resistant samples among sample types. The agreement among sample types for resistance to one or more antimicrobial ranged from fair to substantial. These findings indicate that there is no definitive sample type for studies of AMR in house mice. However, we suggest that fecal samples, which have direct contact with the environment, are likely the best sample to use in studies assessing the potential impact of AMR in wildlife on environmental and public health.

Effect of sample type, centrifugation and storage conditions on vitamin D concentration

Introduction:Studies about vitamin D [25(OH)D] stability in plasma are limited and preanalytical variables such as tube type may affect results. We aimed to evaluate effect of storage conditions, sample type and some preanalytical variables on vitamin D concentration.Materials and methods:Blood samples from 15 healthy subjects were centrifuged at different temperatures and stored under different conditions. Serum and plasma 25(OH)D difference, effect of centrifugation temperature and common storage conditions were investigated.Results:There was no difference between serum and plasma vitamin D concentration. Centrifugation temperature had no impact on vitamin D concentration. 25(OH)D is stable under common storage conditions: 4 hours at room temperature, 24 hours at 2–8 °C, 7 days at −20 °C, 3 months at −80 °C.Conclusion:Vitamin D does not require any special storage conditions and refrigeration. Both serum and plasma can be used for measurement.

The effect of sample type, temperature and RNA later™ on the stability of avian influenza virus RNA

As a result of continuing worldwide outbreaks of highly pathogenic avian influenza (HPAI) caused by the Asian lineage of H5N1, surveillance of targeted avian species in selected regions has been implemented. In these wild bird surveys, the use of real-time reverse transcription (rRT)-PCR has proved to be an invaluable tool as a frontline screening assay for the detection of avian influenza virus (AIV) RNA. However, verification of HPAI diagnosis, particularly in a primary outbreak situation, requires confirmation by a national, community or world reference laboratory. This may necessitate freezing and thawing of samples, sub-sampling and transportation to the reference laboratory. The deleterious effects of such handling on the infectivity of virus and the yield of viral RNA have been observed. The objective of this study was to investigate the effects of freezing and thawing, time, sample type and transportation on the yield of AIV RNA. Additionally, the effect of the RNA stabilisation agent, RNA later™ was investigated. It was demonstrated that the quality of AIV RNA in faecal homogenate was markedly reduced by freezing and thawing, but that treatment with RNA later™ protected the viral RNA from deterioration. When using RNA later™ even low titre AIV samples were protected from the detrimental effects of time and transportation conditions.

Effects of Storage and Sample Type on Ionized Calcium, Sodium and Potassium Levels in Captive Tortoises, Testudo spp.

ABSTRACT Blood samples were obtained from Hermann's tortoises, Testudo hermanni, spur-thighed tortoises, Testudo graeca, and Horsfield tortoises, Testudo horsfieldi, by jugular venipuncture and were collected into heparin. Ionized calcium, sodium and potassium analyses were performed using the ion selective electrode principle. The effect of sample type (heparinized whole blood vs. heparinized plasma) and storage were evaluated. No statistically significant differences were found between ionized calcium levels determined from heparinized plasma samples stored for 48 hr at 5°C (23°F) and fresh heparinized whole blood. Mean ionized calcium levels determined from the heparinized plasma were: males 3.72 mEq/L (1.86 mmol/L), females 3.86 mEq/L (1.93 mmol/L) and 3.80 mEq/L (1.90 mmol/L) for the combined data. Sodium and potassium levels were also determined and there were statistically significantly lower sodium levels and higher potassium levels in the stored heparinized whole blood compared to the fresh hepar...

The Sample Type used Affects the Levels of Gelatinases (MMP-2 and -9) and their Inhibitors (TIMP-1 and -2) in Circulating Blood of Healthy Controls and Breast Cancer Patients

New potential tumor markers such as matrix metalloproteinases and their inhibitors have been extensively studied during the last decades. The aim is to find prognostic markers that are measurable in easily available samples, such as serum or plasma. The proper sample type to use when measuring the levels of gelatinases and their inhibitors from blood samples is currently under critical evaluation. In this study, the effect of sample type is studied in 26 healthy controls, and the result is confirmed in a series of 80 breast carcinoma patients. Sample type had the most evident effect on the levels of TIMP-1 and MMP-9. Serum samples gave about two-fold levels of TIMP-1 compared to plasma samples (p &lt; 0.001), with a strong linear correlation between these two (r = 0.79). Pro-MMP-9 levels were significantly affected by the presence of a blood coagulation activator in the serum sample, or a different anticoagulant in the plasma sample. The serum and plasma values had only a weak correlation (r = 0.37). In conclusion, sample type should be carefully considered, especially when measuring proMMP-9, and plasma should be preferred for this measurement. For TIMP-1 the correlation of serum and plasma values is good; the use of serum samples can therefore be justified as long as the generally higher levels in the serum are acknowledged.

Effect of sample type, and timing of assay, on feline blood potassium concentration

Blood samples were collected from 41 cats presented for pre-anaesthetic assessments, routine geriatric screening, or re-assessment of ongoing chronic medical disorders. Samples were either left to clot or anticoagulated with lithium heparin, then assessed for their potassium concentration within 1h of collection, and again after remaining in contact with their cell pellet for 48 h. There was a significantly higher potassium concentration in the serum samples compared to the plasma samples, both in the basal and 48-h samples (although this difference was most marked in the basal samples). Ageing of both serum and plasma samples also resulted in an increase in the potassium concentration when compared with the basal values for each sample type. The mean difference (basal serum minus basal plasma) in potassium concentration was 0.47 mmol/l. While it is probable that the potassium came from either leukocytes and/or thrombocytes the mean total leukocyte count and the mean thrombocyte count were below the upper limit of the reference intervals for our laboratory and the rise in the potassium level did not appear to be directly related to either of these values.

Effect of storage conditions on cortisol, total thyroxine, and free thyroxine concentrations in serum and plasma of dogs

Objective To determine for dogs stability of cortisol, thyroxine (T4). and free thyroxine (fT4) in plasma and serum stored in glass or plastic tubes at −20, 4, 25, and 37 C. Design Prospective study. Animals Phase I, 7 Greyhounds; Phase II, 6 mixed breed dogs. Procedure Phase I: blood was obtained after administration of thyroid-stimulating hormone and adrenocorticotropin. Serum and plasma samples from each dog were divided into 8 aliquots, 4 in glass and 4 in plastic tubes. A pair of aliquots, 1 in plastic and 1 in glass, were stored at −20, 4, 25, or 37 C for 5 days and then assayed for hormones. Phase II: blood was obtained without prior stimulation. For fT4 determination, serum from each dog was placed in plastic or glass tubes, assayed immediately, stored at −20 C for 5 days, and reassayed. Aliquots from each dog were also stored for 1 day at 4 or 25 C and then assayed. Samples for cortisol determination were handled as in phase I. Results Phase I: there was no effect of tube type (glass vs plastic) on cortisol. Cortisol concentrations decreased after storage in serum at 4, 25, and 37 C, and in plasma at 37 C, compared with storage at −20 C. There was no effect of sample type (serum or plasma) on T4. Thyroxine concentrations increased after storage at 37 C in glass, compared with storage at −20 C. The fT4 concentrations were lower in serum than plasma after storage at −20 C. Concentrations of fT4 increased after storage at 37 C in glass, compared with storage at −20 C. Phase II: the fT4 concentrations did not change after storage in any condition. There was no effect of tube type on cortisol concentrations. Serum cortisol concentrations decreased after storage at 37 C, compared with storage at −20 C. Clinical Implications For cortisol, cooling of plasma is not necessary, but serum should be shipped cold. For T4 and fT4, serum is sufficient; contained within plastic tubes, samples can be shipped without cooling if assayed within 5 days. (J Am Vet Med Assoc 1998;212:1564–1568)

Normal-phase high-performance liquid chromatography with highly purified porous silica microspheres

Column reproducibility and peak shapes are improved for polar and basic solutes in normal-phase chromatography using new highly purified, low-acidity unmodified porous silica microspheres. The chromatographic characteristics of this new type B silica are compared with a conventional type A silica to determine the type and level of mobile phase modifiers needed for good results. The effect of sample type and sample loading on retention, column efficiency and peak shape also was measured. Critical normal-phase tests compared this new silica with several commercial silicas. The new silica shows special promise for developing rugged separation methods to analyze polar and basic compounds that traditionally are handled by reversed-phase chromatography. Normal-phase chromatography is well-suited for highly organic-soluble compounds and certain structures such as positional isomers.