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Results for “Assay development”

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At least 19 recordsLinked to original sources

PubMed1976

Enzymic methods for estimation of the somatic cell count in bovine milk. 1. Development of assay techniques and a study of their usefulness in evaluating the somatic cell content of milk.

Assay procedures were developed for a number of enzymes in milk which apparently originate from leucocytes. The enzymes studied were acid phosphatase, N-acetyl-beta-D-glucosaminidase, beta-glucuronidase, arylsulphatase, alpha-mannosidase, and catalase. Quarter-milk samples were analysed for enzyme activity and results compared with the electronic cell count and the Wisconsin Mastitis Test. All enzymes measured except acid phosphatase and alpha-mannosidase showed good correlation with the electronic cell count. Of the other 4 enzymes tested, beta-glucuronidase and arylsulphatase were unsuitable as diagnostic aids owing to the lengthy incubation periods required in their assay procedures. The assay of catalase, which involved the measurement of the initial rate of release of O2 using an O2 analyser apparatus, was rapid, sensitive and reasonably reliable, if fresh milk samples were used. The assay procedure for N-acetyl-beta-D-glucosaminidase was considered to be the most reliable, simple and rapid enzymic method for estimating the number of somatic cells in milk.

Acetylglucosaminidase↗

PubMed2026

Identification of lineage-associated polymorphisms in the ROP18 3' flanking region and development of molecular assays for differentiation of Toxoplasma gondii lineages.

BACKGROUND: Toxoplasma gondii (T. gondii) exhibits substantial genetic diversity, and different parasite lineages are associated with distinct epidemiological distributions and biological characteristics. Accurate molecular characterization of T. gondii strains is important for understanding parasite population structure and transmission patterns. However, existing genotyping approaches often require multiple loci, extensive experimental procedures, or complex data analysis. Therefore, simplified and reliable molecular markers for rapid lineage differentiation are still needed. METHODS: In this study, comparative genomic analysis was performed using representative T. gondii strains with well-defined genetic backgrounds and virulence phenotypes. The ROP18 genomic region, including partial genomic sequences, 5' flanking regions, coding sequence (CDS), and 3' flanking regions, was analyzed to identify informative polymorphic signatures. A short conserved sequence region containing lineage-associated polymorphic sites was identified within the ROP18 3' flanking region. Based on these sequence signatures, HRM-PCR and TaqMan MGB probe-based real-time PCR assays were developed and evaluated using plasmid standards and representative T. gondii genomic DNA samples. RESULTS: Phylogenetic analyses based on different ROP18 genomic regions demonstrated distinct clustering patterns among analyzed strains. Although the ROP18 3' flanking region was highly conserved, a short conserved sequence region containing informative polymorphic sites was identified, and the combination of these sites generated three distinct lineage-associated ROP18 patterns. Analysis of publicly available genomic datasets further demonstrated that individual strains contained one of these defined patterns rather than multiple patterns simultaneously. The developed HRM-PCR assay successfully discriminated the three ROP18-associated patterns based on distinct melting profiles with good reproducibility. Furthermore, the TaqMan MGB probe-based assay enabled specific identification of different ROP18-associated patterns through defined probe-recognition combinations and showed good analytical performance. CONCLUSION: This study identifies novel lineage-associated molecular signatures within the ROP18 3' flanking region and establishes complementary HRM-PCR and TaqMan MGB probe-based approaches for rapid molecular differentiation of T. gondii strains. These findings highlight the potential of conserved non-coding regions adjacent to functionally important genes as informative targets for parasite genotyping and provide a practical complementary tool for epidemiological surveillance and strain characterization.

HRM-PCR↗

PubMed1978

Improved assay procedures for thyroid peroxidase; application to normal and adenomatous human thyroid tissue.

We have developed assays for thyroid peroxidase in crude thyroid tissue preparations, in which a linear relationship between activity and amount of tissue could be demonstrated. Linear assays were developed based on the following peroxidase catalyzed reactions in the presence of H2O2:(1) oxidation of I- to I(-3), (2) oxidation of guaiacol, and (3) iodination of human goiter thyroglobulin. To attain satisfactory linearity we found it necessary to solubilize the enzyme beforehand. This was accomplished by a brief treatment of the particulate fraction with trypsin and deoxycholate, followed by centrifugation at 40 000 X g and dialysis. Not only did this treatment facilitate the development of linear assays, but it also resulted in a substantial increase in enzyme activity compared with that in the untreated particulate fraction. The use of a Polytron homogenizer for the initial disruption of the tissue also proved helpful in developing these assay procedures. The three different assays were used to measure peroxidase activities in human thyroid adenomas and in normal tissue derived from adenomatous glands. T he adenomas generally displayed a higher level of peroxidase activity than normal tissue. The greatest difference was observed with the iodination assay and the smallest difference with the guaiacol assay.

Adenoma↗

PubMed1977

Mutagenic studies of folic acid antagonists.

Compounds that compete with folic acid (folic acid antagonists [FAAs]) become limited in their usefulness in the treatment of leukemia, malaria, and bacterial infections by the rapid development of resistance. Assays of the plasma levels of certain of these FAAs led to the observation, in about 25% of the determinations, that a higher density of growth of Streptococcus faecium var. durans (ATCC 8043) was obtained at an FAA concentration just below the completely inhibitory level than at one-half this concentration. This and other considerations suggested that FAAs may act not only as selective agents for resistant organisms but also as mutagens. Seven FAAs including amethopterin, pyrimethamine, trimethoprim, chlorguanide triazine, an experimental quinazoline, WR-158,122, and two experimental triazines, WR-99,210 and WR-38,839, were tested for mutagenicity in the Salmonella reversion assay developed by Ames et al. (1975). All were found to be negative for strains TA1535, TA1537, TA1538, TA98, and TA100, both with and without microsomal activation. These compounds were then tested as mutagens for three traits in the folic acid-requiring S. faecium. FAAs were shown to cause mutations to folic acid independence, rifampin resistance, and FAA resistance. It is postulated that the FAAs induce mutations by causing thymine deprivation in the folic acid-requiring host.

Culture Media↗

PubMed2026

Disruption of Polycystin Ciliary Localization and Channel Function by Autosomal Dominant Polycystic Kidney Disease-Causing Polycystin-1 Variants.

KEY POINTS: We developed assays to measure genetic variant effects on polycystin-1, the protein mutated in most autosomal dominant polycystic kidney disease. All tested pathogenic variants disrupted either polycystin-1 ciliary trafficking or channel function. Trafficking and channel function of some pathogenic variants was restored by low temperature culture to promote polycystin folding. BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the leading monogenic cause of kidney failure and affects millions of people worldwide. Despite the prevalence of ADPKD, limited mechanistic understanding has hindered therapeutic development. Most ADPKD is caused by loss-of-function variants in polycystin-1 (PC1). METHODS: We developed assays that quantify the effect of nontruncating variants on PC1 ciliary localization, membrane trafficking, and polycystin channel function. RESULTS: We evaluated 29 nontruncating variants in PC1 and found that pathogenic variants disrupt two molecular phenotypes: ( 1 ) localization of PC1 at the primary cilium or ( 2 ) polycystin ion channel activity. Ciliary localization of a subset of polycystin variants was restored when cells were cultured at low temperature. A subset of variants with localization restored by low temperature formed functional channels. CONCLUSIONS: This study demonstrated that disruptions in polycystin ciliary trafficking and channel function are common causes of ADPKD. Defects in ciliary trafficking and channel function can be rescued for a subset of pathogenic variants, establishing a foundation for polycystin-targeted therapies in ADPKD.

Polycystic Kidney, Autosomal Dominant↗

PubMed2026

Development and epidemiological investigation of a TaqMan-based multiplex real-time quantitative PCR assay for simultaneous detection of five bovine viruses (BVDV, AKAV, BNoV, BEV, and BCoV).

INRODUCTION: Infectious diseases caused by bovine viral diarrhea virus (BVDV), Akabane virus (AKAV), bovine norovirus (BNoV), bovine enterovirus (BEV), and bovine coronavirus (BCoV) significantly threaten the cattle industry, resulting in substantial economic losses. These pathogens often present similar clinical signs, such as diarrhea, vomiting, and reproductive disorders in pregnant cattle, and frequent covert or mixed infections further complicate accurate diagnosis. Therefore, rapid, sensitive, and field‑deployable diagnostic methods are essential for effective disease surveillance and control in the cattle industry. METHODS: In this study, we report for the first time the establishment of a TaqMan‑based real‑time quantitative PCR (qPCR) assay that enables simultaneous detection of these five bovine viruses. Multiple sequence alignment of conserved genomic regions was performed, and virus‑specific primers and probes were designed and optimized using Beacon Designer 7 software. Subsequently, a TaqMan‑based multiplex real‑time qPCR assay was established for simultaneous detection of BVDV, AKAV, BNoV, BEV, and BCoV. The established detection method was applied to 200 clinical samples collected from 10 farms in multiple regions of Jilin Province. RESULTS: The results showed that the detection rates for BVDV, AKAV, BNoV, BEV, and BCoV were 33.50%, 0.50%, 4.50%, 7.50%, and 12.00%, respectively. Mixed infections were detected in 9 samples co‑infected with two of the five pathogens, with an overall mixed infection rate of 4.50%. Compared with conventional PCR, coincidence rates were 100% for BVDV, AKAV, BNoV, BEV, and BCoV. DISCUSSION: These findings indicate that the TaqMan multiplex real‑time qPCR assay developed here demonstrates favorable specificity, sensitivity, and reproducibility. This assay enables efficient detection and surveillance of bovine viruses, offering a reliable technical tool for the diagnosis and control of corresponding viral diseases in cattle.

Akabane virus (AKAV)↗

PubMed1976

Roles of individual mgl gene products in the beta-methylgalactoside transport system of Escherichia coli K12.

Previous findings showed that galactose-binding protein defective mutants (mgl B-,A+,C+) of Escherichia coli K12 are still capable of growth on methyl-beta-D-galactopyranoside, while mgl A- and mgl C- mutants are not. When assayed by previous methods, none of these mutants exhibited methylgalactoside transport system activity. In this study, we present a modified assay developed for measuring low levels of transport. Using this assay, we found that mgl B-,A+,C+ mutants defective in galactose-binding protein accumulate methyl-beta-D-galactopyranoside up to six times the concentration gradient while mgl A- and mgl C- mutants failed to accumulate this substrate. Similar results were obtained using D-glyceryl-beta-D-galactopyranoside, another substrate of the methylgalactoside transport system. In contrast, all sugars tested which are not substrates of this system were transported equally by all mgl- mutants. The kinetic parameters of transport in mgl B- mutants were compared to those of the isogenic mgl+ strain which accumulates methyl-beta-D-galactopyranoside against a 10,000-fold concentration gradient. The apparent Km of methyl-beta-D-galactopyranoside influx was 1,000 times greater in mgl B- than in mgl+ strains. In contrast, there was no significant difference between these strains in either the Vmax of substrate influx or the rate of substrate exit. D-Galactose competitively inhibited methyl-beta-D-galactopyranoside influx into both mgl B- and mgl+ strains; the Ki of inhibition in mgl B- cells was 2,000-fold greater than that in mgl+ cells.

Biological Transport, Active↗

PubMed2026

Development of a cell-based nanoluciferase reporter system for high-throughput screening of HBV cccDNA inhibitors.

Hepatitis B virus (HBV) persistence is sustained by the viral covalently closed circular DNA (cccDNA) minichromosome, which remains a major barrier to curative antiviral therapies. The lack of reliable quantitative cccDNA detection methods and surrogate markers has hindered efforts to target cccDNA in antiviral high-throughput screening (HTS). Here, we established a novel inducible cccDNA-dependent nanoluciferase (NLuc) reporter cell line, designated HepBLE12, by inserting an in-frame 11-amino acid split-NLuc HiBiT tag into the precore (pC) coding region of an HBV transgene. The resulting 1.3-kDa HiBiT tag on pC serves as the detection module of the split NLuc system, generating quantitative luminescence upon high-affinity complementation with the cognate 18-kDa LgBiT subunit in cell lysates. Notably, the HiBiT assay enables direct detection of intracellular HiBiT-pC protein rather than secreted HBeAg, providing a reporter signal more closely linked to cccDNA activity. HepBLE12 cells exhibited inducible and robust viral DNA replication, and the cccDNA-dependent HiBiT signal was validated under diverse experimental conditions that modulate cccDNA formation or transcription. We further miniaturized the assay to a 384-well format and optimized key parameters following standard HTS assay development practices. The assay was successfully automated and demonstrated excellent performance in a multi-day variability study and a pilot screen, with signal-to-background (S/B) ≈ 9, coefficient of variance (CV) < 10%, and average Z-factor value of 0.74, exceeding canonical HTS quality benchmarks. Together, the HepBLE12 cell-based HTS platform provides a robust and practical tool for identifying inhibitors targeting HBV cccDNA.

Hepatitis B virus↗

PubMed1978

Bone marrow acid phosphatase in staging of prostatic cancer: how reliable is it?

To evaluate the reliability of bone marrow acid phosphatase in the staging of prostatic carcinoma we analyzed 50 bone marrow samples collected at random from the hematology service at this hospital. The samples were assayed for acid phosphatase content by a colorimetric method using sodium thymolphthalein monophosphate as a substrate and by 2 immunochemical assays developed at our laboratory (counter immunoelectrophoresis and radioimmunoassay). We found a high percentage (61 per cent) of falsely positive results in patients with various hematological diseases without evidence of prostatic carcinoma by the colorimetric evaluation. All of these patients except 1 had negative immunochemical assay. Until a specific assay for prostatic acid phosphatase is developed for clinical use we caution the use of a single elevation of bone marrow acid phosphatase as a parameter of metastatic disease.

Acid Phosphatase↗

PubMed2026

Comparative prevalence of the mercury resistance gene merA in human feces, food, and environmental water from Japan, Vietnam, and Ghana.

In this study, we investigated the prevalence and abundance of the mercury resistance gene merA in human feces, retail chicken meat, and environmental water samples collected from Japan, Vietnam, and Ghana. A real-time PCR assay developed in this study demonstrated high specificity toward merA sequences from more than 12 bacterial species. Using this assay, merA was detected in 6.8% of human fecal samples in Japan (n = 29), in contrast to significantly higher rates observed in Vietnam (70.2%, n = 47) and Ghana (97.4%, n = 39). Similar geographic trends were evident in the chicken meat samples: 18.5% in Japan (n = 27), 66% in Vietnam (n = 91), and 90% in Ghana (n = 10). Environmental water samples showed a consistently high merA detection rate across all countries (75-100%, n = 21), with substantially higher gene copy numbers in Vietnam and Ghana than in Japan. merA was detected in some water samples, even when total mercury concentrations were below the detection limit, indicating that molecular detection may offer greater sensitivity than traditional physicochemical methods. Mercury-resistant bacteria were successfully isolated and cultured, and Citrobacter freundii was identified as the representative strain. Genomic analysis revealed that merA was located on an IncFIB plasmid, flanked by insertion sequences, suggesting its potential for horizontal gene transfer. These findings highlight merA as a promising biomarker for environmental mercury exposure and support the utility of fecal merA analysis as a proxy for assessing mercury-related public health risks.

Humans↗

PubMed1977

Evaluation of estrogen receptor assays in human breast cancer tissue.

Standard dextran-coated charcoal (DCC) and sucrose gradient centrifugation assays for estrogen receptor were compared in a series of human breast cancer tissues. From a quantitative standpoint the results were remarkably similar. A simplified version of the DCC assay compared to the sucrose gradient assay yielded acceptable results. We conclude that, in spite of the lack of specificity controls inherent in the sophisticated standard assays, the simplified DCC assay might be useful if the biopsy specimen is too small to provide the number of aliquots for a standard DCC assay or sufficient protein for a sucrose gradient analysis. It also might be useful in research laboratories attempting to develop assays for multiple receptors or other constituents in a single tumor biopsy specimen.

Breast Neoplasms↗

PubMed1975

[Radioimmunoassay of synthetic steroids].

The sensitivity of a radioimmunoassay depends on the intrinsic association constant of the interaction between ligand and antibody. Its specificity depends on the position of the chain which forms the link with the antigen. Thus, an antibody specific of estradiol has been obtained by coupling estradiol to albumin via a chain at position 7. For synthetic steroids the structure of which is sufficiency different from that of natural hormones, the requirements for a sensitive assay method not involving chromatography are simply maximum affinity and positioning of the couple at a site which does not undergo metabolic attack. These criteria were used to develop assays for R 2858 and R 2453 which obviate the need to administer radioactive product in clinical pharmacology. Cross-reaction with structural analogs may be used to assay competitors. Thus, R 2323 antibody, highly specific for endogenous steroids, may be used to assay other trienes such as R 1697 (trenbolone) and R 2010 (norgestrienone).

Antibody Specificity↗

PubMed2025

Biochemical assays for AID/APOBECs and the identification of AID/APOBEC inhibitors.

Activation-induced cytidine deaminase (AID) and apolipoprotein B-mRNA editing catalytic polypeptide 3 (APOBEC3 or A3) proteins belong to the AID/APOBEC family of cytidine deaminases. While AID mediates somatic hypermutation and class-switch recombination in adaptive immunity, A3s restrict viruses and retroelements by hypermutation. Mis-regulated expression and off-target activity of AID/A3 can cause genome-wide mutations promoting oncogenesis, immune evasion, and therapeutic resistance due to tumor and viral evolution. In these contexts, inhibition of AID/A3 represents a promising therapeutic approach. Competitive inhibition could be achieved with different strategies: one class would be small molecules that bind in the catalytic pocket (active site) and block access for the substrate cytidine. Another type of larger molecule inhibitor would bind the enzymes' surface more broadly and compete with the binding of the polynucleotide substrates prior to deamination catalysis. Several biochemical assays developed to assess AID/A3 activity can be employed to screen for potential inhibitors. These include in cellulo and in vitro activity-based as well as binding-based assays. In this chapter, we discuss the key considerations for designing robust enzyme assays and provide an overview of assays that we and others have established or modified for specific applications in AID/A3 enzymology, including measurement of inhibition. We provide detailed protocols for the two most widely used in vitro enzyme assays that directly measure the activities of purified AID/A3s on DNA and/or RNA substrates, namely, the gel-based alkaline cleavage assay and multiple variations of PCR/sequencing-based assays.

Cytidine Deaminase↗

PubMed1977

Some immunological effects of penicillamine.

Immunological effects of D- and D,L-penicillamine (PA) were studied in efforts to develop assays for synthetic D or D,L analogs and to contribute to the understanding of the mechanism(s) of action of D-PA in rheumatoid arthritis. At the highest doses tolerated by mice, D,L-PA did not significantly inhibit the development of haemagglutinating antibodies in vivo. In studies in vitro with T lymphocytes, D-PA at 1 mM concentration inhibited both concanavalin A- and phytohaemagglutinin-induced transformation as assayed by [3H]thymidine incorporation, but D-PA concentrations of 5 mM were required to inhibit concanavalin A-induced amino acid uptake. No effect of D-PA was observed either on the induction of cytotoxic T cells or on the attack of specifically sensitized T cells on target cells. It is of interest that D-PA at 1 mM concentration did inhibit lipopolysaccharide-induced transformation, which predominately stimulates B lymphocytes. The effects of PA on the induced transformation of T and B cells deserve further attention for studies with analogs of PA.

Animals↗

PubMed2026

Artificial intelligence in molecular diagnostics for pandemic preparedness.

INTRODUCTION: Molecular diagnostics focusing on the detection and analysis of nucleic acids are indispensable tools for early pathogen identification, transmission monitoring, and genomic surveillance during pandemics. Recent technological advances have broadened the diagnostic landscape, incorporating PCR-based methods, isothermal amplification, high-CRISPR-based amplification detection, and sequencing. Despite their diagnostic potential, widespread implementation remains limited by high validation costs, time and logistical constraints, the need for specialized professional knowledge, and a lack of adaptability in resource-limited settings. Artificial intelligence (AI) is increasingly recognized as a promising but challenging approach, offering tools that streamline assay development, automate data interpretation, and optimize real-time diagnostic performance. AREAS COVERED: This review introduces recently published AI tools with potential to enhance the in-silico design validation process of oligonucleotides for molecular assays. These cover tools for initial assay design and optimization to validation and continuous assay updates. The limitations, including concerns regarding data accuracy, the lack of transparency in data processing ('black box' models), and unresolved licensing and regulatory issues, are highlighted for each tool and as expert opinion. EXPERT OPINION: Collectively, these challenges currently confine most AI-based approaches to research settings and prevent their routine implementation in clinical molecular diagnostics. Their widespread adoption depends on addressing remaining technical, regulatory, and practical challenges.

Humans↗

PubMed2026

A transcriptome-wide approach for rapid pathotype discrimination of Puccinia striiformis f. sp. tritici in north-western India.

Stripe rust of wheat caused by Puccinia striiformis f. sp. tritici (Pst) remains a major constraint to wheat production in India due to the rapid evolution and frequent emergence of virulent pathotypes. Rapid and reliable discrimination of Pst pathotypes is essential for effective resistance deployment and surveillance. In the present study, transcriptome-wide simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs) were exploited to develop and validate molecular markers for pathotype-specific detection of Pst pathotypes prevalent in North India (110S119, 238S119, 46S119, 110S84 and 78S84). Microsatellite mining from 6103 core orthologous clusters comprising 51,127 transcripts mined 14,634 SSR loci, from which 93 primer pairs were synthesized. However, only three SSR markers exhibited polymorphism indicating limited discrimination potential of expressed sequence-derived (EST) SSRs for pathotype differentiation. In contrast, SNP discovery through stringent variant calling and filtration yielded 186 pathotype-specific homokaryotic SNPs, of which 56 high-confidence loci were selected for Kompetitive Allele-Specific PCR (KASP) assay development. A total of 48 KASP markers were synthesized and 14 demonstrated clear pathotype- or cluster-specific polymorphism representing substantially higher resolution than SSR markers. The high SNP-to-KASP conversion efficiency (~ 95%) and reproducible fluorescence-based clustering emphasize the robustness of KASP assay. Comparative evaluation revealed that SNP-based KASP markers provide superior discriminatory capacity for closely related Pst pathotypes and represent a promising complementary molecular approach for rapid identification of predominant Indian Pst pathotypes. The validated marker panel developed in this study can complement conventional virulence phenotyping and field pathogenomics approaches for surveillance of currently known pathotypes, while continued refinement may accommodate future changes in pathogen populations.

India↗

PubMed1977

Characterization of rat lung epoxide (styrene oxide) hydrase with a modified radioactive assay of improved sensitivity.

The epoxide hydrase assay developed by Oesch et al. (Biochim. Biophys. Acta, 227: 685-691, 1971) using [3H]styrene oxide as substrate was modified in three ways for use with rat lung microsomes: the substrate was purified before use, the volume of the incubation mixture was scaled down 4-fold, and the incubation time was extended to 45 min (activity was found to be linear for at least 60 min). These modifications increased the sensitivity of the assay procedure 75- to 150-fold. The procedure was found to be linear with lung microsomal protein up to at least 1.8 mg protein per incubation mixture. This modified assay for epoxide hydrase was used to characterize the enzyme in rat lung. Its apparent vmax is 0.5 nmole of styrene glycol formed per min per mg microsomal protein, and its apparent Km was 0.11 to 0.25 mM. The pH optimum is around 9.7. Upon subcellular fractionation of lung tissue, expoxide hydrase distributes in the same manner as a marker for the endoplasmic reticulum (reduced nicotinamide adenine dinucleotide phosphate-cytochrome c reductase) and in a different way from markers for the nuclei, mitochondria, concentric lamellar organelles, lysosomes, Golgi membranes, plasma membrane and soluble cytoplasm. The specific activity of epoxide hydrase in rough and smooth lung microsomes is aobut the same. Treatment i.p. of rats with methylcholanthrene (3 injections of 20 mg/kg), phenobarbital (5 daily injections of 80 mg/kg) or styrene oxide (5 daily injections of 40 mg/kg), did not induce lung microsomal epoxide hydrase activity. 1,1,1-Trichloropropene 2,3-oxide was shown to be an uncompetitive inhibitor, and cyclohexene oxide was a noncompetitive inhibitor of this enzyme. Ethanol and butanol activate the epoxide hydrase of lung microsomes at low concentrations and inhibit it at higher concentrations.

Alcohols↗

PubMed1978

Assay of vitamins D2 and D3, and 25-hydroxyvitamins D2 and D3 in human plasma by high-performance liquid chromatography.

I describe a new assay that is capable of measuring vitamin D2, vitamin D3, 25-hydroxyvitamin D2, and 25-hydroxyvitamin D3 in 2 ml of plasma or serum. Plasma is extracted by the Bligh and Dyer technique [Can. J. Biochem. Physiol. 37, 911 (1959)], the lipid component is fractionated by two high-performance liquid-chromatographic systems based upon adsorption and reversed-phase chromatography, and each of the four vitamin D metabolites is measured by its absorbance at 254 nm. The method has a sensitivity limit of 0.5 mug/liter of plasma. The identity of metabolite peaks was confirmed by mass spectrometry, ultraviolet absorption spectrophotometry, and rechromatography, and there was good correlation (r=0.84) between plasma 25-hydroxyvitamin D as measured by the present method and by a protein binding assay developed in our laboratory. Mean concentrations of vitamin D and 25-hydroxyvitamin D in normal adults (n=25) in December were 2.2 +/- 1.1 (SD) and 16 +/- 3.9 (SD) mug/liter, respectively. 25-Hyroxyvitamin D2 made up 31% of the total 25-hydroxyvitamin D. Patients receiving pharmacological doses of vitamin D had values for vitamin D and 25-hydroxyvitamin D that were 10- to 100-fold normal. This method provides a rapid, reliable physico-chemical assay that appears to have advantages over existing protein binding assays and can be used to measure circulating vitamin D.

Adult↗