Analytical and clinical assessment of a commercial kit for the simultaneous determination of free thyroxine and thyrotropin

The SimulTRAC FT4/TSH kit (Becton Dickinson), allowing a simultaneous determination of free thyroxine (FT4) and thyrotropin (TSH), was assessed in terms of analytical quality and clinical performance. The results of a multicenter trial were included in this study to obtain a more complete and reliable information. The current validation procedures (ie evaluation of analytical imprecision and sensitivity, between-kit comparison of estimates and--limited to TSH--check of response linearity on dilution) demonstrated quite acceptable analytical characteristics for both the FT4 and the TSH tests. The diagnostic sensitivity and predictive value were derived for separate and combined tests from a relatively large number of cases (ie 401 euthyroids, 127 overt and 48 subclinical hypothyroids, 205 overt and 80 compensated hyperthyroids). The TSH test proved more effective than FT4 in discriminating both overt and subclinical dysfunctions, and, in this respect, the test association was found to add a little advantage--if any. However, the extension of the concepts of diagnostic efficiency to any combination of test results--favoured by their production in a single assay--provides a basis to establish diagnostic protocols and to predict costs and benefits of medical actions.     

A new highly sensitive chemiluminescent assay of alkaline phosphatase using lucigenin and its application to enzyme immunoassay

The chemiluminescent reaction of lucigenin with various reducing sugars and reducing compounds has been studied. It was found that dihydroxyacetone gave the most intense chemiluminescence (CL). We have developed highly sensitive chemiluminescent methods for alkaline phosphatase (ALP) based on the production of dihydroxyacetone using NADP⁺ or glycerol-3-phosphate as substrate. The detection limits for ALP using each substrate were 1.25 × 10^?19 mol/assay and 2.5 × 10^?19 mol/assay, and the coefficient of variation (n = 7) was 2.8% and 3.7%, respectively. We have also applied the method using NADP⁺ as substrate in enzyme immunoassays (EIA) for cholecystokinin (CCK) and human chorionic gonadotropin (hCG). CCK-8 (octapeptide sulphated form of a carboxy terminal fragment of CCK) concentrations released from alimentary canal of rat were assayed using the chemiluminescent EIA (CLEIA) and a fluorimtric EIA (ALP label). The correlation between CCK-8 values obtained by these methods was y = 1.04x + 18.21, r = 0.946, n = 28. hCG values in serum and in urine were measured. The correlation between hCG values in serum samples obtained using the CLEIA and a time-resolved fluoroimmunoassay (TR-FIA), and in urine samples obtained using the CLEIA and the fluorimetric EIA using ALP were satisfactory. The correlations were y = 1.00x ? 0.04, r = 0.997 (n = 51) and y = 1.00x ? 0.03, r = 0.999 (n = 10), respectively.     

Chemiluminescent enzyme immunoassay for alpha-fetoprotein using β-D-galactosidase as label and 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside as substrate

We developed a sensitive chemiluminescent sandwich-type enzyme immunoassay (CLEIA) of alpha-fetoprotein (AFP) using b?-D -galactosidase (b?-gal) as a label and 5-bromo-4-chloro-3-indolyl-b?-D -galactopyranoside as a substrate. The CL-EIA for AFP was performed using two monoclonal antibodies, one antibody is labelled with b?-gal, the other is coated onto the inside surface of a polystyrene tube. The detection limit for AFP was 0.5 ng/mL, equivalent to 10 pg/assay tube. The coefficient of variation for within and between assay imprecision were 2.0%?4.9% (n = 10) and 4.4%?9.8% (n = 5), respectively. AFP values in serum determined by this method correlated well with those obtained by radioimmunoassay (n = 26, r = 0.99). This sensitive AFP assay can be performed within 4 h and can be used as a routine assay in clinical diagnosis.     

Evaluation and routine application of the novel restricted-access precolumn packing material Alkyl-Diol Silica: coupled-column high-performance liquid chromatographic analysis of the photoreactive drug 8-methoxypsoralen in plasma

A fully automated coupled-column HPLC method for on-line sample processing and determination of the photoreactive drug 8-methoxypsoralen (8-MOP) in plasma has been developed. The method is based on the novel internal-surface reversed-phase precolumn packing materials Alkyl-Diol Silica (ADS). This new family of restricted-access materials has a hydrophilic, electroneutral outer particle surface and a hydrophobic internal pore surface. The supports tolerate the direct and repetitive injection of proteinaceous fluids such as plasma and allow a classical C₁₈-, C₈- or C₄-reversed-phase partitioning at the internal (pore) surface. The total protein load, i.e. the lifetime of the precolumn used in this study (C₈-Alkyl-Diol Silica, 25 μm, 25 × 4 mm I.D.), exceeds more than 100 ml of plasma. 8-MOP was detected by its native fluorescence (excitation 312 nm, emission 540 nm). Validation of the method revealed a quantitative and matrix-independent recovery (99.5–101.3% measured at five concentrations between 21.3 and 625.2 ng of 8-MOP per milliliter of plasma), linearity over a wide range of 8-MOP concentrations (1.2–3070 ng of 8-MOP/ml, r = 0.999), low limits of detection (0.39 ng of 8-MOP/ml) and quantitation (0.79 ng of 8-MOP/ml) and a high between-run (C.V. 1.47%, n = 10) and within-run (C.V. 1.33%, n = 10) reproductivity. This paper introduces coupled-column HPLC as a suitable method for on-site analysis of drug plasma profiles (bedside-monitoring).     

Automated determination of 5-fluorouracil and its metabolite in urine by high-performance liquid chromatography with column switching

We report a quantitative assay of 5-fluorouracil (FU) and its metabolite, 5-fluorodihydrouracil (FDHU) in human urine by used a column-switching high-performance liquid chromatographic method. The analyses were carried out using a molecular exclusion column for sample purification, and a cation-exchange column for separation. Each sample required only 40 min to analyze, and required no preparation other than filtration. Linearity was verified up to 1000 nmol/ml (r>0.993). The recovery of FU was 96–101%; recovery of FDHU was 96–105%. The imprecision (RSD) for FU (10–100 nmol/ml) was <1.5%, same-day (n=5), and <1.8%, day-to-day (n=5). The imprecision (RSD) for FDHU (10–100 nmol/ml) was <3.2%, same-day (n=5), and <4.0%, day-to-day (n=5). The detection limits were, respectively, 0.1 nmol/ml. We measured FU and FDHU in urine of seven cancer patients after oral administration of FU. The cumulative quantity ratio of the FDHU and FU (FDHU/FU) excreted in their urine within 120 min after FU administration was a constant value in all seven patients. Based on these results, we believe that our method provides a useful tool for evaluating FU metabolism.     

Super-sensitive Enzyme Immunoassay for Thyroid Stimulating Hormone Using a New Synergistic Enhanced Chemiluminescent Endpoint

The enhancers 1,1′-biphenyl-4-yl boronic acid and 4-iodophenol act synergistically in the horseradish peroxidase-catalysed oxidation of luminol. This concentration-dependent effect reduces background, increases signal and hence improves signal/background for detection of peroxidase. The same type of synergistic effect was found when 1,1′-biphenyl-4-yl boronic acid was added to a commercial enhanced chemiluminescence signal reagent (Amerlite Signal Reagent). This synergistic enhanced chemiluminescent endpoint (Amerlite Signal Reagent containing 1,1′-biphenyl-4-yl boronic acid) for a horseradish peroxidase label has been tested in the Amerlite TSH and the Amerlite TSH-30 Ultrasensitive assays. The detection limit (mean of 20 replicates of the zero standard + 2SD) in the Amerlite TSH assay was 0.0029 mIU/L, and in the Amerlite TSH-30 Ultrasensitive assay the detection limit was 0.0005 mIU/L using the synergistic enhanced endpoint. Reassessment of the detection limit using a 1 : 40 dilution of the first standard (0.119 mIU/L) as the lowest assay standard gave a value of 0.0015 mIU/L for the Amerlite TSH-30 Ultrasensitive assay with the synergistic endpoint. A limited (n = 29) method comparison using samples from euthyroid, hyperthyroid and hypothyroid patients revealed excellent correlation between the conventional and synergistic TSH immunoassays.     

High-performance liquid chromatographic determination of a new oral thrombin inhibitor in the blood of rats and dogs

A reliable reversed-phase high-performance liquid chromatographic method has been developed for the determination of a new oral thrombin inhibitor (compound I) in the blood of rats and dogs. The analyte was deproteinized with a 1.5 volume of methanol and a 0.5 volume of 10% zinc sulfate, and the supernatant was injected into a 5-μm Capcell Pak C₁₈ column (150×4.6 mm I.D.). The mobile phase was a mixture of acetonitrile and 0.2% triethylamine of pH 2.3 (31:69, v/v) with a flow-rate of 1.0 ml/min at UV 231 nm. The retention time of compound I was approximately 9.3 min. The calibration curve was linear over the concentration range of 0.05–100 mg/l for rat blood (r²>0.9995, n=6) and dog blood (r²>0.9993, n=6). The limit of quantitation was 0.05 mg/l for both bloods using a 100-μl sample. For the 5 concentrations (0.05, 0.1, 1, 10, and 100 mg/l), the within-day recovery (n=4) and precision (n=4) were 98.1–104.1% and 1.5–6.8% for rat blood and 95.4–105.7% and 1.4–5.3% for dog blood, respectively. The between-day recovery (n=6) and precision (n=6) were 99.8–105.3% and 3.7–12.6% for rat blood and 87.5–107.1% and 2.9–15.3% for dog blood, respectively. The absolute recoveries were 82.4–93.3%. No interferences from endogenous substances were observed. In conclusion, the presented simple, sensitive, and reproducible HPLC method proved and was used successfully for the determination of compound I in the preclinical pharmacokinetics.     

Serum selenium versus lymphocyte subsets and markers of disease progression and inflammatory response in human immunodeficiency virus-1 infection

Serum selenium levels were determined cross-sectionally in 57 HIV-infected patients who were classified according to the Centers for Disease Control (CDC) 1993 classification system. Mean serum selenium levels were lower in CDC stage II (58.7±12.2 μg/L;p<0.01;n=18) and stage III (47.6±11.3 μg/L;p<0.01;n=19) HIV-infected patients, than in healthy subjects (80.6±9.6 μg/L;n=48) and stage I patients (73.6±16.5 μg/L;n=20). Serum selenium levels were positively correlated with CD4 count, CD4/8 ratio, hematocrit, and serum albumin (r=0.42;r=0.39;r=0.48; andr=0.45;p<0.01, respectively) and inversely with serum levels of thymidine kinase (r=−0.49;p<0.01;n=49) and β2-microglobulin (r=−0.46;p<0.001;n=49). In addition, serum selenium levels in 20 randomly selected AIDS-free individuals (CDC I:n=10; CDC II:n=10) were inversely correlated with serum concentrations of interleukin-8 (IL-8) and soluble tumor necrosis factor receptors (sTNFR) types I and II. There was no correlation with serum immuneglobulin A and total serum protein levels. The results show that the progressive deprivation of serum selenium in HIV-infection is associated with loss of CD4⁺-cells and with increased levels of markers of disease progression and inflammatory response.     

Thyroidal responses to human chorionic gonadotropin in the chick and rat

The thyrotropic activity of human chorionic gonadotropin (hCG) has been examined in the chick and the rat. Uptake of 32PO4 by chick thyroid increased significantly with injection of bovine thyrotropin (bTSH) with a maximum response at 2.4 mU per chick. On the other hand, no significant stimulation of 32PO4 uptake was detected with injection of graded doses of highly purified hCG up to 0.25 mg per chick. 1 mg of partially purified hCG, equivalent in biological potency to the maximum dose of highly purified hCG used in the chick, did induce a significant increase in 32PO4 uptake. In rats, highly purified hCG stimulated a very significant release (p less than 0.001) of 125I from the thyroid and partially purified hCG had a thyrotropic activity equivalent to 0.42 microU bTSH/U hCG, identical to the value we reported in mice, 0.42 microU bTSH/U hCG. The duration of hCG action on thyroidal release of 125I in the rat was longer than that for bTSH, as it is in the mouse. hCG also induced a significant rise in the serum level of triiodothyronine in rats. We conclude that pure hCG is a weak thyrotropic substance in the rat but not in the chick. These results and other evidence suggest an inhibitory role for the densely glycosylated 30 amino acid residue C-terminal extension on the beta-subunit of hCG which limits, by steric hindrance, the interaction of the TSH-like hCG 'core' with thyrotropin receptors.     

Serum thyrotropin response to thyrotropin-releasing hormone and free thyroid hormone indices in patients with familial thyroxine-binding globulin deficiency.

The response in serum thyrotropin (TSH) to synthetic thyrotropin-releasing hormone (TRH) as well as serum free thyroxine index (FT4I) and free triiodothyronine index (FT3I) was investigated in six patients with familial thyroxine-binding-globulin (TBG) deficiency. The total serum thyroxine (T4) and triiodothyronine (T3) concentrations were significantly decreased, compared with those of normal subjects (3.4 +/- 0.9 microgram/dl, mean +/- SD. vs. 9.0 +/- 1.5 microgram/dl, p less than 0.01 and 87 +/- 27 ng/dl vs. 153 +/- 37 ng/dl, p less than 0.01, respectively). FT4I was lower than the normal range in all but one (5.3 +/- 1.5 vs. 8.9 +/- 1.6, p less than 0.01), whereas FT3I was all in the normal range and of no significant difference from the normal control (132 +/- 22 vs. 148 +/- 25). Serum TSH concentrations in TBG deficiency were all in the normal range (1.0-4.2 muU/ml) and the maximum TSH increments following TRH 500 microgram iv were 8.9 +/- 2.0 muU/ml and of no significant difference from the normal control (10.2 +/- 4.5 muU/ml). These results indicate that the euthyroid state in familial TBG deficiency is more clearly defined by TRH-test and the normal response to TRH in familial TBG deficiency is presumably under the control of the serum free T3 level rather than the serum free T4 level.     

Thyroid dysfunction in adult long-term survivors after hemapoeitic stem-cell transplantation (HSCT).

Thyroid function was evaluated in 72 adult survivors (41 females and 31 males) at 16 to 56 years of age, 1.5 years mean time (range 0.2 - 9.8) after hemapoeitic stem cell transplantation (HSCT) with no known prior history of thyroid dysfunction. Thyroid stimulating hormone (TSH) and free thyroxin levels (FT4) were determined before and after stimulation with thyrotropin releasing hormone (TRH). Conditioning regimens for HSCT did not include TBI. Overt hypothyroidism (basal TSH > 8 microIU/ml, FT4 < 0.8 ng/dl) was observed in 6% of male patients and 5% of female patients; subclinical hypothyroidism (basal TSH 4 - 8 microIU/ml, low normal FT4 0.8 - 1.9 ng/dl) was observed in 13% of males and 5% of females. A significant number of euthyroid patients (40% males and 54% females) with normal basal TSH and FT4 levels overresponded to TRH stimulation; the finding being statistically significant (p < 0.005). A heavy TSH response after TRH stimulation indicates compensated subclinical dysfunction of the thyroid gland. Chemotherapy-only conditioning regimens may have an adverse effect on thyroid gland function not always detected by determination of basal TSH and FT4 levels. This finding warrants long-term evaluation of thyroid function in HSCT patients.     

Thermodynamics of oligo (A) N -2poly(U) from the dependence of the temperature of the helix-coil transition on oligomer concentration

On the basis of elementary two-state, ideal solution thermocynamics, a modified expression for the melting of oligo. polynucleotide helices is derived which is applicable to variations in T_m^N and/or oligomer concentration, C_m with oligomer length, N: ((I)) ΔH_r is the enthalpy per helix residue, i.e., per base-pair or base-triplet, V_r^f is the thermodynamic “available” or “reaction” volume, in liters/mole of helical residues; and n is the number of polynucleotide strands, e.g., n = 2 for oligo (A)_N·2 poly(U)∞. Some earlier treatments have engendered confusion in the interpretation of the “reaction volume,” but with the derivation herein, the entropic origin and physical significance of V_r^f is unequivocal. The following approximation was arrived at for the reduction expected in the configurational entropy, ΔS_r^{conf, ∞}, for (A)∞·2(U)∞, when the poly(A), strand is substituted for by an equivalent strand of contiguous oligo(A)_N,′s: ((II)) This adjustment of ΔS_r^{conf, ∞} represents the source of the coefficient to 1/T_m^∞ in expression (I). The expectation that ΔS_r^{conf, N} < ΔS_r^{conf, ∞} is due to the effect of releasing normal internucleotide configurational restrictions every Nth residue in one-third of the strands of the (A)_N·2(U)∞ helix. Although the reduction in ΔS_r^{conf, ∞} (II) may seem small (i.e., only 5.5% for the tetramer), its effect on the magnitude of V_r^f in expression (I) is exponential. Thus, without these considerations the quantitative applicability of earlier expressions is questionable. By examining the variation in T_m^N with c_m for a single N, all assumptions, required for evaluating V_r^f or the entropic effects of discontinuities in the (A)_N strand are avoided in the determination of a reliable enthalpy. We have therefore examined the system ((III)) and obtained a ΔH_r = 12.58 ± 0.08 kcal per mole (A)·2(U) base-triplets between 5 and 2.5°C. That this value for ΔH_r is in such excellent agreement with all calorimetric values reported for (A)∞·2(U)∞ suggests that the enthalpy for reaction(III) is not significantly affected by disconnections in the backbone of (A)₄·2(U)∞. From (I), V_r^f = 6.0 × 10^?4 1/mole or 1 Å ³per helical residue. ΔH_r°, corrected for residual single-strand stacking in (A)₄, is in excellent agreement with that found earlier for (A)₁·2(U)∞. A residual heat capacity of 90 kcal(±20) per mole (A)·2(U) base-triplets per °C is deduced from the decrease of ΔH_r° with temperature.     

Muscle-associated triglyceride measured by computed tomography and magnetic resonance spectroscopy

Objective: Muscle triglyceride can be assessed in vivo using computed tomography (CT) and ¹H magnetic resonance spectroscopy (MRS), two techniques that are based on entirely different biophysical principles. Little is known, however, about the cross‐correlation between these techniques and their test—retest reliability. Research Methods and Procedures: We compared mean muscle attenuation (MA) in soleus and tibialis anterior (TA) muscles measured by CT with intra‐ and extramyocellular lipids (IMCL and EMCL, respectively) measured by MRS in 51 volunteers (26 to 72 years of age, BMI = 25.5 to 39.3 kg/m²). MA of midthighs was also measured in a subset (n = 19). Test—retest measurements were performed by CT (n = 6) and MRS (n = 10) in separate sets of volunteers. Results: MA of soleus was significantly associated with IMCL (r = ?0.64) and EMCL, which by multiple regression analysis was explained mostly by IMCL (p < 0.001) rather than EMCL (β = ?0.010, p = 0.94). Muscle triglyc‐eride was lower in TA than in soleus, and MA of TA was significantly correlated with EMCL (r = ?0.40) but not IMCL (r = ?0.16). By CT, MA of midthighs was correlated with MA in soleus (r = 0.40, p = 0.07) and whole calf (r = 0.62, p < 0.05). Finally, both MA and IMCL were highly reliable in soleus (coefficient of variation = <2% and 6.7%, respectively) and less reliable in TA (4% and 10%, respectively). Discussion: These results support the use of both CT and MRS as reliable methods for assessing skeletal muscle lipid.     

Bioremediation of Soil Contaminated with Diesel Using Inorganic Nitrogen Sources: Incorporating nth-Order Algorithm in the Evaluation of Process Kinetics

In the present study, we investigated the effects of inorganic nitrogen sources—(NPK fertilizer, 15:15:15), (urea fertilizer, 46:0:0), (NH₄)₂SO₄ as well as monitored natural attenuation on the bioremediation of diesel-polluted soil. At the end of the 6-week study, the highest degradation was recorded in soil amended with NPK fertilizer (95 ± 2.77%) while the least total petroleum hydrocarbon removal was observed in monitored natural attenuation (89 ± 2.91%). Nth-order kinetics effectively described three of the treatments out of the four treatment plans. These include urea amendment (r² = 0.9925, average relative error (ARE) = 1.45%, root mean square error (RMSE) = 0.038, k_n = (3.57 ± 0.61) × 10^?2, n = 1.33), NPK fertilizer amendment (r² = 0.9751, ARE = 3.241%, RMSE = 0.086, k_n = (8.04 ± 0.23) × 10^?1, n = 0.74), and monitored natural attenuation (r² = 0.9697, ARE = 2.77%, RMSE = 0.073, k_n = (1.57 ± 0.50) × 10^?2, n = 1.16). The values of n from the nth-order kinetics parameter estimation indicated that all the treatments resulted in diesel degradation that followed a first-order kinetics path. Thus, the outcome of kinetic modeling showed that nth-order can be used as validating tool when many kinetic orders are under consideration. The phytotoxicity assay with Zea mays showed that the treatments plans resulted in germination indices of 17–55%.     

Associations of serum 25-hydroxyvitamin D and components of the metabolic syndrome in obese adolescent females

Vitamin D deficiency may increase the risk for metabolic syndrome. We determined the relationship of serum 25‐hydroxyvitamin D (25(OH)D) with metabolic syndrome components in obese adolescent females and assessed whether vitamin D treatment corrects metabolic disturbances. Eighty postmenarchal adolescents (53 African American (AA) and 27 Caucasian American (CA)) were evaluated with blood pressures and fasting measurements of serum 25(OH)D, lipid profile, C‐reactive protein, alanine transaminases (ALTs) and aspartate transaminases followed by an oral glucose tolerance test. A subgroup (n = 14) of vitamin D deficient subjects were re‐evaluated following vitamin D treatment. Among all subjects, 25(OH)D was inversely associated with fasting glucose (r = ?0.28, P = 0.02) and positively associated with low‐density lipoprotein (LDL) cholesterol (r = 0.31, P = 0.008), independent of race and BMI. In analyses by race, adjusted for BMI, 25(OH)D was inversely associated with fasting insulin in CA (r = ?0.42, P = 0.03) but not AA (r = 0.11, P = 0.43) whereas 25(OH)D was positively associated with ALT in AA, but not CA (r = 0.29, P = 0.04 vs. r = ?0.21, P = 0.32). Fasting glucose improved in vitamin D treated subgroup (from 89.07 ± 8.3 mg/dl to 84.34 ± 8.4 mg/dl, P = 0.05). A trend toward improvement in fasting glucose remained after exclusion of four subjects whose serum 25(OH)D₂ did not improve following treatment (P = 0.12). In conclusion, serum 25(OH)D was inversely associated with fasting glucose, and vitamin D treatment had beneficial effects on fasting glucose. Relationships of 25(OH)D with fasting insulin and ALT were ethnic specific. The positive relationship with LDL and ALT were suggestive of possible adverse influences of vitamin D.     

Evaluation of Iron in Serum and Urine and their Relation with Thyroid Function in Female Goitrous Patients

In many developing countries, women are at high risk of goiter and iron deficiency anemia (IDA). Iron deficiency adversely affects thyroid metabolism and may decrease the efficiency of thyroid hormones in areas of endemic goiter. The aim of the present study was to compare the level of iron (Fe) in biological samples (serum and urine) and serum thyroid hormones, thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxin (FT4) of goitrous female patients (GFPs; n = 69) with those of nongoitrous women as control subjects (n = 117), age range 21–45 years. The biological samples were analyzed for Fe concentration using flame atomic absorption spectrophotometer, prior to microwave-assisted wet acid digestion. The validity and accuracy of the method was checked by the certified sample and with those obtained by conventional wet acid digestion method on the same CRM and real samples. The overall recoveries of Fe in serum and urine were found in the range of 97.2–98.6% of certified values. The results of this study showed that the mean values of Fe in serum and urine samples of GFPs were significantly reduced as compared to control subjects (p = 0.002 and p = 0.015, respectively). The mean values of FT3 and FT4 were found to be lower in GFPs than in the age-matched healthy control women; in contrast, high mean values of TSH were detected in GFPs (p = 0.003). There was a positive correlation between serum Fe concentration and TSH (r = 0.85, p = 0.01), FT3 (r = 0.95, p = 0.003), and FT4 levels (r = 0.98, p = 0.007) in GFPs. It was observed that iron deficiency is prevalent in GFPs, so the need of Fe supplementation will be required to improve the efficacy of thyroid metabolism in goitrous women.     

Delayed treatment with GnRH agonist, hCG and progesterone and reduced embryonic mortality in buffaloes

The present study examined the effect of delayed treatment with tropic hormones and progesterone (P₄) on embryonic mortality in buffaloes. Buffaloes with a conceptus on Day 25 after AI were assigned to the following treatments: Control (n = 41), i.m. physiological saline; GnRH agonist (n = 36), i.m. 12 μg buserelin acetate; hCG (n = 33), i.m. 1500 IU hCG; P₄ (n = 38), i.m. 341 mg P₄ every 4 days on three occasions. Control buffaloes had an embryonic mortality of 41.4% (17/41) between Days 25 and 45, and this was reduced (P < 0.01) by treatment with GnRH agonist (11.1%, 4/36), hCG (9.0%, 3/33) and P₄ (13.1%, 5/38). On Day 45, buffaloes treated with hCG and which ovulated had greater (P < 0.05) concentrations of P₄ in whey (453 ± 41 pg/ml) than buffaloes in the same treatment that did not ovulate (297 ± 32 pg/ml). A similar but non-significant trend was observed for buffaloes treated with GnRH agonist. It was concluded from the findings that the treatment of buffaloes on Day 25 after AI with tropic hormones or P₄ is beneficial to processes associated with embryonic implantation.     

Peroxyoxalate chemiluminescent assay for oxidase activities based on detecting enzymatically formed hydrogen peroxide

A sensitive peroxyoxalate chemiluminescent (PO-CL) assay for activities of oxidases (uricase, choline oxidase, cholesterol oxidase and xanthine oxidase) which catalyse a formation of hydrogen peroxide was developed using 4,4′-oxalyl-bis[(trifluoromethylsulphonyl)imino]trimethylene-bis(4-methylmorpholinium)trifluoromethanesulphonate as a chemiluminogenic reagent and 2,4,6,8-tetramorpholinopyrimido[5,4-d]pyrimidine as a fluorophore. The standard curve for hydrogen peroxide was linear over the range 1 × 10^?7-1 × 10^?4 mol/L. Relative standard deviations for oxidase assays were 5.1–12.7% (n = 10). Detection limits were 1 × 10^?3 U/mL for uricase, 5 × 10^?4 U/mL for choline oxidase, 5 × 10^?3 U/mL for cholesterol oxidase and 5 × 10^?4 U/mL xanthine oxidase (sample to blank ratio, 3).     

Identification and antimicrobial susceptibility testing of clinical isolates of nonfermenting gram-negative bacteria by the Phoenix Automated Microbiology System

The Phoenix Automated Microbiology System (Becton Dickinson, Sparks, MD) was evaluated for its ability to identify nonfermenting gram-negative pathogens and measure their drug susceptibility. Isolates producing rare extended-spectrum beta-lactamases (PER-1, IMP-2, VIM-1, and VIM-2) were included in the study. Species identification was compared to that given by the ATB System (bio-Mérieux, Marcy l'Etoile, France), whereas susceptibility results were compared to those produced by a reference broth microdilution test (panels manufactured by Pasco Laboratories, Becton Dickinson). The Phoenix system consistently identified all isolates of Pseudomonas aeruginosa (n = 55) and Stenotrophomonas maltophilia (n = 28), while in other cases species agreement was obtained for 47/53 isolates (Acinetobacter baumannii, 29/31; Pseudomonas putida, 10/11; Burkholderia cepacia, 6/7; and Pseudomonas fluorescens, 2/4). Overall, the Phoenix and ATB systems gave equal results in 130/136 cases (95.6%). For two isolates, consistent identification was obtained at the genus level, thus bringing the cumulative agreement to 97.1%. MIC values (interpreted according to NCCLS guidelines) gave essential and categorical agreement in 94.2% and 93.1% of cases, respectively. Minor and major errors were 5.1% and 5.2%, respectively. No very major errors were produced. The mean time to results (TTR) for the Phoenix system was 14.8 +/- 1.6 h (mean +/- SD), with the shortest TTR being observedfor A. baumannii (13.0 +/- 1.8 h) and the longest one for P. aeruginosa (15.6 +/- 1.2 h). In conclusion, the Phoenix system performed rapidly and correctly in the identification of clinical isolates of important opportunistic pathogens and in measuring their susceptibility to antipseudomonal drugs.     

Polynucleotides. XI. Thermodynamics of (A) N -2(U) infinity from the dependence of T m N on oligomer length

The variation in the helix-coil transition temperature, T_m^N, with oligomer length, N, for the system ((I)) has been examined. The results for N = 4-13, measured in 0.2M Na+, have been analyzed in terms of the expression of Blake (1972): ((II)) where c_m is the free oligomer concentration at T_m^N, and V_r^f is the thermodynamic free volume available to a helical base-triplet residue. The correlation coefficient for the fit to expression (II) of data obtained over a 50° temperature range is 0.997 when ΔH_r = ?12.6 kcal/mole of base-triplets (independent of oligomer length (N ? 4) or temperature), the value previously obtained from both calorimetry of (A)_∞·2(U)_∞ and (A)₄ concentration dependence of T_m. It is found that V_r^f = 8.0 × 10^?4 1/mole (± 30%) or 1.33 ų per helical base-triplet, and is constant with temperature. A maximum value for V_r^f of 21.0 × 10^?4 1/M (± 1.3%), equivalent to 3.54 ų per helical basetriplet is obtained by the same treatment of the helix-coil transition data for the three-stranded helix formed by adenosine (N = 1) and 2(U)_∞ obtained by Davies and Davidson (1971).