Biomedical subjects

M L Chen

Publications and source records attributed to M L Chen.

At least 109 records · Page 6Linked to original sources

PubMed1996

Mean difference vs. variability reduction: tradeoffs in aggregate measures for individual bioequivalence. FDA Individual Bioequivalence Working Group.

Aggregate criteria for individual bioequivalence allow a tradeoff between difference in average bioavailability and reduction in within-subject variability. That is, a large difference in the average bioavailability between a test and a reference formulation can be offset by a sufficient reduction in variability of the test formulation. This offset could allow the test formulation to pass many individual bioequivalence criteria. We have identified 4 possible approaches for dealing with this tradeoff issue: say "No problem," since a reduction in variability is desirable; use disaggregate criteria; use general weighted forms of the individual bioequivalence criteria that weight the variance terms; and change the acceptable upper limits to reduce the impact of scaling to the reference formulation's within-subject variability. A dataset with a 14% increase in average bioavailability and a 48% reduction in within-subject standard deviation is used as an example of these issues.

Biological Availability↗

PubMed1996

Clinical uses for calciotropic hormones 1,25-dihydroxyvitamin D3 and parathyroid hormone-related peptide in dermatology: a new perspective.

The skin is not only the organ for the photosynthesis of vitamin D3, but also a target tissue for its activated form 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Vitamin D3 is absolutely essential for the development and maintenance of a healthy skeleton. Without an adequate source of vitamin D, children develop rickets and the elderly develop osteomalacia and exacerbation of osteoporosis. 1,25(OH)2D3 is a potent inhibitor of proliferation of epidermal cells and, with its analogs, it has been developed for the successful treatment of psoriasis. Not all psoriasis patients, however, respond to 1,25(OH)2D3 and its analogs. Evidence suggests that there may be a defect in the regulation of levels of mRNA for the vitamin D receptor in patients who have partial or no response to 1,25(OH)2D3 therapy. The degree of responsiveness to 1,25(OH)2D3 therapy may also be related to the allelic variations in the vitamin D receptor gene. Parathyroid hormone-related peptide is synthesized by the epidermis and is an endogenous antiproliferative factor. Parathyroid hormone-related peptide agonists and 1,25(OH)2D3 inhibit in vitro and in vivo epidermal proliferation, whereas parathyroid hormone-related peptide antagonists stimulate both epidermal proliferation and hair growth in vivo. Therefore, the calciotropic hormones 1,25(OH)2D3 and parathyroid hormone-related peptide have wide-ranging clinical applications in dermatology.

Calcitriol↗

PubMed1995

Structure-activity studies of RFamide analogues on central neurones of Helix aspersa.

The effects of FMRFamide were compared with those of FMRFamide analogues, FLRFamide, LFRFamide, FFRFamide, LLRFamide, D-FMRFamide, F-D-MRFamide and FM-D-RFamide, and the fragments, MRFamide and LRFamide, on identified central neurones, F1, F2, F5 and E16, of the snail Helix aspersa, using intracellular recording and two electrode voltage clamp techniques. All FMRFamide analogues showed an inhibitory effect on F1 neurones with an order of potency: FLRFamide > FMRFamide > FFRFamide > LFRFamide >> LLRFamide. FMRFamide and FLRFamide exhibited a biphasic response on F2 neurones. At lower concentrations (< 10 microM), both peptides usually only excited while at higher concentrations (> 30 microM), exhibited an excitation followed by an inhibition. FFRFamide only excited F2 while LFRFamide and LLRFamide only inhibited F2. LRFamide and MRFamide (100 microM) were inactive on both F1 and F2. FLRFamide, LFRFamide, LLRFamide, FFRFamide and D-FMRFamide showed cross-interaction on the outward current induced by FMRFamide in F5. All peptides induced an outward current and also reduced the FMRFamide-induced current reversibly. In contrast, MRFamide, LRFamide and F-D-MRFamide failed to have direct effects on these neurones nor interact with the FMRFamide-induced current. We conclude that on F2 neurones Phe is essential for the activation of the RFamide receptor mediating the excitation and Met or Leu are important to activate the RFamide receptors mediating the inhibition. Removal of the N-terminal Phe, to give LRFamide and MRFamide render the peptides inactive. Therefore a tetrapeptide sequence is essential for the biological activity of FMRFamide analogues on these Helix neurones. FLRFamide, LFRFamide, LLRFamide, FFRFamide and D-FMRFamide exhibit a cross-interaction with FMRFamide. It is possible that these peptides also act on the same class of RFamide receptors as agonists to cause cross desensitization.

Animals↗

PubMed1995

Structure of the gene for the catalytic subunit of human DNA polymerase delta (POLD1).

We have isolated genomic DNA clones covering the gene for human DNA polymerase delta catalytic subunit (POLD1) and its 5' flanking sequence. This gene is divided into 27 exons and is distributed over at least 32 kb of DNA. The exons and most of the introns are relatively small. The sizes of the exons range from 55 to 201 bp. Seven introns are smaller than 100 bp. Intron 1 is the largest intron, with a size of greater than 10 kb. All of the intron-exon junctions match well with the reported consensus sequences. Multiple copies of the Alu repetitive sequence and the variable number of tandem repeats were found in several introns. Transcription of POLD1 appears to initiate at multiple sites. The major start site was 53 nucleotides upstream of the ATG start codon. The sequence of the promoter and upstream DNA is G+C rich and does not contain a TATA sequence. Several potential transcription factor-binding sites, including the AP2-, CTF-, Ets1-, GCF-, MBF-1-, NF-E1-, and Sp1-binding sites, were found in this region. A 1.8-kb pol delta promoter DNA directed the expression of a luciferase reporter gene when transfected into HeLa cells.

Base Sequence↗

PubMed1995

Characterization of 5'-upstream sequence of the latent membrane protein 1 (LMP-1) gene of an Epstein-Barr virus identified in nasopharyngeal carcinoma tissues.

Sequence variations of the 5'-upstream region of latent membrane protein 1 (LMP-1) in two Epstein-Barr virus (EBV) strains have been reported before (Chen et al., 1992). To investigate the effect of these variations on gene expression, we constructed a series of deletion plasmids encompassing positions -950 to +20 of the LMP-1 promoter region and tested for the ability to drive chloramphenicol acetyltransferase (CAT) gene expression in C33A cells. Results showed that the promoter activities of constructs from NPC strain were 3-fold lower than the corresponding constructs from the B95-8 strain. In addition, the region between -54 and +20 contained the basic, constitutive promoter activity for both strains. Sequence analysis of this region indicated that an activating transcription factor (ATF) binding site, TGACGTAG, which is present in B95-8 strain was changed to TCTCGTAG in NPC strain. A chimeric plasmid study suggested that these sequence variations in the ATF binding site may contribute to the 3-fold increase of CAT activity observed for B95-8 strain. Furthermore, the activity of the promoter constructs was not activated by EBV-encoded nuclear antigen 2 (EBNA-2) in C33A cells. However, the promoter activities were upregulated in B-lymphocyte cells such as CG3 and CA46 cells. The biological significance of this difference in promoter activity of LMP-1 gene between two strains and the involvement of the cellular factors were discussed.

Base Sequence↗

PubMed1995

Actions of a small cardioactive peptide from Mytilus, APNFLAYPRLamide, on central neurones of Helix aspersa.

1. Mytilus small cardioactive peptide (SCP) was originally isolated from the anterior byssus retractor muscle of Mytilus edulis, with a primary structure, APNFLAYPRLamide. The mechanisms of action of this peptide were examined on identified central neurones of the snail, Helix aspersa, using intracellular recordings and a two electrode voltage clamp. 2. 50 microM APNFLAYPRLamide could elicit a long term excitation on F2 neurones, in normal saline, Na(+)-free saline, Ca(2+)-free saline or in 10 mM Co2+ saline. This indicates that the excitatory effect of APNFLAYPRLamide involved an increase in membrane conductance to both Na+ and Ca2+. 3. 10 microM APNFLAYPRLamide potentiated the Ca2+ inward current of F2 neurones while reversibly reducing the ACh-induced membrane current of these neurones. Forskolin had identical effects to those of APNFLAYPRLamide. This indicates that the action of APNFLAYPRLamide may be through a second messenger. In contrast APNFLAYPRLamide potentiated a cholinergic EPSP evoked in F2 neurones. 4. YPRLamide was inactive even at higher concentrations, for example, 100 microM, while LAYPRLamide exhibited activity but with a lower potency. This indicates that LAYPRLamide is the minimum structure required for activating this class of SCP-like peptide receptor. However, the mode of action of APNFLAYPRLamide on the Na+ current of F2 neurones requires further investigation.

Acetylcholine↗

PubMed1995

The role of metabolites in bioequivalency assessment. II. Drugs with linear pharmacokinetics and first-pass effect.

Simulations were conducted to address the question of whether metabolite data are required for bioequivalence evaluation of immediate release formulations with drugs exhibiting linear pharmacokinetics and first-pass effect. Plasma level-time profiles were generated for parent drug and metabolite using relevant rate constants obtained from a bivariate normal distribution and designated random error. Simulation results showed that the need for metabolite data (Cmax) in the assessment of bioequivalence depends on the relative variability between the absorption process of the drug and first-pass route for metabolite(s). The importance of metabolite Cmax data in the evaluation of rate of availability is clearly demonstrated for drugs with a high degree of intra-subject variation in the first-pass metabolism compared to the absorption process of the drug. Under such conditions, a wider confidence interval was found for the metabolite rather than parent drug. Opposite results were obtained when the intra-subject variance was high for drug absorption relative to first-pass effect. Discrepancies were observed for the scenarios in which the elimination pathway of the metabolite is more variable than the absorption process of the drug. The simulation results were in agreement with real bioequivalence data. It is thus recommended that, in the absence of the information on the relative variability of absorption and first-pass process, both parent drug and metabolite data be included for documentation of bioequivalence, should the metabolite(s) play an important role in the determination of efficacy and safety of the drug.

Absorption↗

PubMed1995

Identification of an internal promoter of the latent membrane protein 1 gene of Epstein-Barr virus.

The latent membrane protein 1 (LMP 1) gene of an Epstein-Barr virus (EBV) variant derived from an nasopharyngeal carcinoma (NPC) biopsy in Taiwan was isolated and characterized (Chen et al., 1992). Transient expression of the genomic sequence containing this gene showed two proteins with molecular masses of 62 kD and 50 kD, respectively, recognized by LMP-specific antibody S12. To determine if these two proteins were derived from independent promoters, we generated a series of mutant plasmids from plasmid pT7(E) that contained the upstream and the coding regions of the LMP 1 gene. These mutants were introduced into a human epithelial cell line, C33A, and LMP 1 proteins were examined by Western blotting analysis with the S12 antibody. Data showed that plasmid with a fragment containing approximately 3 kb of upstream sequence of LMP 1 gene produced the 62-kD protein. Removal of 2.7 kb of the upstream sequence (plasmid delta 2710, deleted to nucleotide 169,571) resulted in the production of both 62-kD and 50-kD proteins. This suggested that the upstream sequence interfered with the production of the 50-kD protein. Plasmid DNA deleted to Acc I site (nucleotide 169,223) generated only the 50-kD protein, designated as tr-LMP. Further deletion to nucleotide 169,038 resulted in the expression of another smaller LMP1 (49 kD, named as str-LMP1). The region between nucleotides 168,789 and 169,038 was tested to see if it possessed a promoter activity by using the luciferase gene as a reporter. Data showed that this region contained promoter activity with a level compatible to the previously reported ED-L1A promoter.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

The antiproliferative and differentiative activities of 1,25-dihydroxyvitamin D3 are potentiated by epidermal growth factor and attenuated by insulin in cultured human keratinocytes.

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is a potent inhibitor of keratinocyte proliferation, as well as a stimulator of epidermal terminal differentiation. In the present studies, we investigated the influence of epidermal growth factor (EGF) and insulin on the antiproliferative and differentiation activities of 1,25(OH)2D3. Our results indicate the following: (1) EGF caused a dramatic potentiation of the 1,25(OH)2 D3-induced inhibition of 3H-thymidine incorporation into keratinocytes in a dose-dependent manner; (2) insulin acted antagonistically on the EGF-dependent potentiation of the 1,25(OH)2D3-induced antiproliferative activity; (3) transforming growth factor-alpha potentiated 1,25(OH)2D3-induced antiproliferative activity similar to EGF; (4) the EGF effect was not dependent upon 1,25(OH)2D3 receptor mRNA up-regulation; and (5) removal of insulin from medium supplemented with growth factors significantly potentiated the 1,25(OH)2D3-induced inhibition on the number of basal cells and the 1,25(OH)2D3-dependent cornified envelope formation. In conclusion, the antiproliferative activity of 1,25(OH)2D3 in cultured normal human keratinocytes is greatly enhanced by EGF or transforming growth factor-alpha and reduced by insulin. Insulin also inhibits 1,25(OH)2D3-induced terminal differentiation of cultured normal human keratinocytes.

Calcitriol↗

PubMed1995

The human immunodeficiency virus type 1 vpr gene arrests infected T cells in the G2 + M phase of the cell cycle.

Human immunodeficiency virus type 1 (HIV-1) infection causes profound immunological defects in afflicted patients. Various mechanisms have been proposed to account for the immune dysfunction in AIDS ultimately leading to loss of CD4+ T cells, including HIV-1 envelope-mediated syncytium formation, apoptosis, and cytokine modulation. Here we present results which suggest a novel hypothesis for T-cell dysfunction. We show, using HIV-1 bearing a novel cell surface reporter gene, that infected cells are unable to progress normally through the cell cycle and became arrested in the G2 + M phase. Furthermore, we identify the HIV-1 vpr gene product as being both necessary and sufficient for eliciting this cell cycle arrest. Cell cycle arrest induced by Vpr correlates with an increase in the hyperphosphorylated (inactive) form of the cyclin-dependent serine/threonine kinase CDC2, consistent with an arrest of cells at the boundary of G2 and M.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Ethanol and acetaldehyde metabolism in chinese with different aldehyde dehydrogenase-2 genotypes.

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the major enzymes responsible for ethanol metabolism in humans. Both enzymes exhibit genetic polymorphisms among racial populations. About half of the Chinese population lack mitochondrial ALDH2 activity and such a deficiency has been believed to be a negative risk factor for the development of alcoholism. To assess ethanol and acetaldehyde metabolism in Chinese with different ALDH2 genotypes, we genotyped 273 male adults at the ADH2, ADH3, and ALDH2 loci by using polymerase chain reaction-directed mutagenesis and restriction fragment length polymorphisms. Of the 143 individuals homozygous for both the ADH2*2 and the ADH3*1 alleles, 80, 55, and 8 were identified as ALDH2*1/*1, ALDH2*1/*2, and ALDH2*/*2, respectively. Five each from the above three ALDH2 genotypic subjects underwent alcohol elimination testing. Blood ethanol and acetaldehyde levels were determined at various times up to 130 min after intaking a low dose of ethanol (0.2 g/kg body weight) by using head-space gas chromatography and high-performance liquid chromatography with fluorescence detection, respectively. The mutant homozygotes of ALDH2*2/*2 and the heterozygotes exhibited significantly higher peak acetaldehyde concentrations and also greater areas under the blood concentrations-time curve (AUC) than did the normal homozygotes of ALDH2*1/*1, with the mutant homozygotes both being the largest. The mutant homozygotes displayed significantly higher peak ethanol levels and AUC compared to the normal homozygotes. Of the 17 subjective feeling items tested, palpitation, facial warming, effects of alcohol, and dizziness were found to be most pronounced among the mutant homozygotes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗

PubMed1995

Co-assembly of potassium channel subunits in Drosophila: the combinatorial hypothesis revisited.

A diversity of voltage-gated K+ channels has been identified which participates in the regulation of membrane excitability and neural plasticity. After decades of intensive molecular, genetic, pharmacological and electrophysiological studies, the structure and function of K+ channels have been elucidated in great detail. In particular, impressive progress has been made in recent years from studies in Drosophila and the Xenopus oocyte expression system. This review will focus on the variety and physiological functions of K+ channels found in Drosophila. Also discussed is the possible role of coassembly of different combinations of channel subunits in the generation of K+ channel diversity. Various lines of evidence from in situ experiments in Drosophila and heterologous channel expression in Xenopus oocytes will be reviewed.

Animals↗

PubMed1995

Idiotype specific peptides bind to the surface immunoglobulins of two murine B-cell lymphoma lines, inducing signal transduction.

Using a random combinatorial synthetic peptide library method based on a one-bead one-peptide concept for ligand identification (Lam et. al, Nature 1991, 354, 82-84.), idiotype specific peptides were retrieved and optimized for interaction with the cell surface immunoglobulins [IgM(kappa)] of two murine B lymphoma cell lines. Several of the identified peptides were characterized with respect to cell binding and signal transduction. These peptides were able to bind specifically to the surface immunoglobulins of these lymphoma cells. In addition to binding, when synthesized in tetrameric or multimeric forms, the peptides were able to trigger signal transduction resulting in an increase in protein tyrosine phosphorylation. Since D-amino acid peptide libraries were used in some of our efforts to identify binding ligands, several of the idiotype-specific peptides are composed of all D-amino acids (e.g. wGeyvmvnG). These findings may have important therapeutic implications for targeted-therapy of B-cell lymphoma as these D-amino acid ligands are more resistant to proteolysis resulting in a prolonged pharmacokinetic disposition in vivo.

Amino Acid Sequence↗

PubMed1995

[Secular trends in the etiology of nosocomial infection at a teaching hospital in Taiwan, 1981-1994].

Surveillance system of nosocomial infection was established in 1980 at the National Taiwan University Hospital (NTUH). To identify pathogens and the secular trends in the etiology of nosocomial infection from 1981 to 1994, the prospective, hospital-wide nosocomial surveillance data were analysed. During this period, 22,146 pathogens causing nosocomial infections were isolated. Gram-negative aerobic bacteria remained the major pathogens, but gram-positive cocci and fungi increased rapidly in the past 14 years. When the overall pathogen distribution is examined, Pseudomonas areuginosa was the most frequently isolated pathogen, but Candida albicans and other yeasts have taken the leading position since 1993. Staphylococcus aureus and coagulase-negative staphylococci also increase significantly in recent years. When the pathogens causing infection at the 4 major sites were examined. P. aeruginosa was the pathogen most often associated with respiratory tract and surgical wound infections. In blood stream and urinary tract infections, we observed Escherichia coli was replaced by C. albicans and other yeasts as a most common isolate in these years. In addition, C. albicans and other yeasts and methicillin-resistant S. aureus (MRSA) are emerging as major nosocomial pathogens at NTUH. C. albicans and other yeast increased from 1.8% in 1981 to 14.9% in 1994 in the overall nosocomial infection. The increase was found in the blood stream (2.1% to 16.2%) and urinary tract infections (5.4% to 24.7%). Of 1,742 nosocomial S. aureus isolates, the percentage of MRSA rose from 12.5% in 1981 to 55.2% in 1994. The high percentage of MRSA was observed at 4 major anatomic sites of infection. In summary, significant shifts in the pathogens of nosocomial infection have occurred in the past 14 years at NTUH, and the distribution of nosocomial pathogens was similar to those reported in the United States in recent years.

Bacteremia↗

PubMed1994

Actions of Fusinus FMRFamide-related peptides on the identified central neurones of the snail, Helix aspersa.

The actions of Fusinus FMRFamide-related peptides, that is FMRFamide, FLRFamide, GSLFRFamide, SSLFRFamide, the analogue, GSFFRFamide, and the fragments, LFRFamide and RFamide, were examined on the F1, F2 and F5 neurones of Helix aspersa. All Fusinus peptides exhibit an inhibitory effect on F1 and F5 neurone. On F2 neurone, FMRFamide and FLRFamide exhibit an excitatory effect but GSLFRFamide and SSLFRFamide exhibit an inhibition. The fragment, LFRFamide, is 10-times less potent than GSLFRFamide. GSFFRFamide and RFamide are inactive on F1, F2 and F5 neurone. This evidence indicates that the fragment, LFRFamide, is crucial for the biological activity of Fusinus hexapeptides. The inhibition induced by Fusinus hexapeptides had a reversal potential around -75/-80 mV. It was potentiated in K(+)-free saline, partially abolished either in 10 mM TEA or in 10 mM Co2+ saline and completely abolished in 500 microM 4-AP saline. This evidence indicates that there are multiple K+ channels which are activated by Fusinus hexapeptides and that the IA is more susceptible than IK and IKCa to these peptides.

Acetylcholine↗

PubMed1994

Bioequivalence: performance of several measures of extent of absorption.

The determination of the area under the concentration-time curve (AUC) is the method most commonly used by regulatory agencies to assess extent of drug absorption after single-dose administration of oral products. Using simulations, several approaches toward measuring the actual area, in whole or part, were tested. In addition, the performance of the peak concentration (Cmax), usually taken as a measure of the rate of absorption was assessed evaluating extent. Model scenarios for drugs with typical mean characteristics and statistical distributions were investigated. Using different kinetic models of disposition, the time course of the drug concentration in plasma was simulated. Intraindividual and interindividual variability and assay error were modeled using Monte Carlo techniques. The accuracy, precision, and ease of use of the various measures of extent were evaluated, and statistical power analyses were performed. Among the measures tested, the most reliable were the AUC computed up to the time of the last quantifiable concentration, without extrapolation, and Cmax. However, being also sensitive to rate, Cmax as a measure of extent is of limited potential.

Absorption↗

PubMed1994

Bioequivalence: performance of several measures of rate of absorption.

The highest point of the plasma concentration-time profile, Cmax, is currently used by regulatory agencies to assess the rate of drug absorption after single dose administration of oral products. It is, however, quite insensitive, and a number of new measures of rate have been proposed. Using simulations, several approaches toward measuring rate were tested. A set of model scenarios for drugs with typical mean characteristics and statistical distributions was investigated. Using different kinetic models of disposition, the time course of the concentration in plasma was simulated. Intraindividual and interindividual variability and assay error were modeled using Monte Carlo techniques. The accuracy, precision, and ease of use of the various measures of rate were evaluated by simulating crossover design clinical trials and then determining the probability of declaring bioequivalence as a function of differences in rates of absorption between test and reference formulations. All of the rate measures tested showed a degree of insensitivity to changes in rate and no universally superior measure was found. Indeed, the main conclusion is that the choice of a measure should be based on simulations of the particular situation in a bioequivalence trials.

Computer Simulation↗

PubMed1994

Expression of 25-hydroxyvitamin D3-24-hydroxylase mRNA in cultured human keratinocytes.

It is well documented that 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25[OH]2D3), the most active vitamin D metabolite, inhibits epidermal keratinocyte proliferation and promotes differentiation. 1 alpha,25(OH)2D3 can be produced in keratinocytes from 25-hydroxyvitamin D3 by the enzyme 25-hydroxyvitamin D3-1 alpha-hydroxylase (1-OHase). Hydroxylation of 1 alpha,25(OH)2D3 by 25-hydroxyvitamin D3-24-hydroxylase (24-OHase), the first step in the catabolic pathway of 1 alpha,25(OH)2D3 could significantly reduce the intracellular concentration of 1 alpha,25(OH)2D3. Therefore, the expression of 24-OHase could have a critical regulatory role in 1 alpha,25(OH)2D3-dependent gene expression. As a first step to examine this possibility, the steady state level of 24-OHase mRNA in cultured human keratinocytes (CHK) was investigated. 24-OHase mRNA was not detected in control CHK. 1 alpha,25(OH)2D3 caused a dose- and time-dependent increase in 24-OHase mRNA level. The highest accumulation of 24-OHase mRNA was observed in CHK treated with 0.1-1 microM 1 alpha,25(OH)2D3. The level of 24-OHase mRNA reached a plateau 12-24 hr after 1 alpha,25(OH)2D3 treatment. 1 beta,25-dihydroxyvitamin D3, the stereoisomer of 1 alpha,25(OH)2D3, failed to induce 24-OHase mRNA expression significantly. In addition to 24-OHase mRNA, a 1.0-kb mRNA hybridized strongly with both rat and human 24-OHase cDNA probes. The origin of this 1.0-kb message is unknown at present, however, it was regulated by 1 alpha,25(OH)2D3. These results demonstrate that 1 alpha,25(OH)2D3 up-regulates the expression of 24-OHase mRNA, and this may be an important first step in the initiation of catabolism of 1 alpha,25(OH)2D3 in human keratinocytes.

Calcitriol↗