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Biomedical subjects

J Guo

Publications and source records attributed to J Guo.

At least 145 records · Page 8Linked to original sources

Cytokines, IgG subclasses and costimulation in a mouse model of thyroid autoimmunity induced by injection of fibroblasts co-expressing MHC class II and thyroid autoantigens.

AKR/N mice injected with fibroblasts expressing MHC class II (RT4.15HP cells) and the TSH receptor (TSHR) develop antibodies similar to those in Graves' disease. We were unable to analyse the subclass of these antibodies because of unexpectedly high non-specific binding by ELISA or flow cytometry. The non-specific binding reflected generalized immune activation which occurred even when the fibroblasts did not express the TSHR. However, the IgG subclasses were determined for thyroid peroxidase (TPO) antibodies induced using TPO-expressing RT4.14HP cells and found to be IgG2a > IgG1. This Thl pattern is consistent with spontaneous secretion of interferon-gamma (but not IL-4 or IL-10) by splenocytes from injected mice. The Th1 bias was related to fibroblast injection because conventional immunization of the same mouse strain with purified TPO and adjuvant induced a Th2 response (IgG1 >> IgG2a). Further, untransfected fibroblasts themselves induced powerful, non-specific proliferative responses when used as antigen-presenting cells (APC) in vitro. Flow cytometry revealed that the RT4.15HP fibroblasts (and TSHR- and TPO-transfected derivatives) expressed B7-1. Unexpected constitutive expression of this key molecule may bypass the requirement for up-regulation of other costimulatory molecules involved in T cell stimulation. Our data support the concept that RT4.15HP fibroblasts present the TSHR (or TPO), at least for initiating the immune response. However, the accompanying generalized immune stimulation creates difficulties for analysis of TSHR-specific T and B lymphocytes. On the other hand, extension of the model to TPO, an easier antigen to study, will facilitate analysis of murine T cell responses likely to resemble those in human thyroid autoimmunity.

Animals↗

Structure of the Sm binding site from human U4 snRNA derived from a 3 ns PME molecular dynamics simulation.

A molecular dynamics simulation of the Sm binding site from human U4 snRNA was undertaken to determine the conformational flexibility of this region and to identify RNA conformations that were important for binding of the Sm proteins. The RNA was fully-solvated (>9,000 water molecules) and charge neutralized by inclusion of potassium ions. A three nanosecond MD simulation was conducted using AMBER with long-range electrostatic forces considered using the particle mesh Ewald summation method. The initial model of the Sm binding site region had the central and 3' stem-loops that flanked the Sm site co-axial with one another, and with the single-stranded Sm binding site region ([I] conformation). During the course of the trajectory, the axes of the 3' stem-loop, and later the central stem-loop, became roughly orthogonal from their original anti-parallel orientation. As these conformational changes occurred, the snRNA adopted first an [L] conformation, and finally a [U] conformation. The [U] conformation was more stable than either the [I] or [L] conformations, and persisted for the final 1 ns of the trajectory. Analysis of the structure resulting from the MD simulations revealed the bulged nucleotide, U114, and the mismatched Ag91-G110 base pair provided distinctive structural features that may enhance Sm protein binding. Based on the results of the MD simulation and the available experimental data, we proposed a mechanism for the binding of the Sm protein sub-complexes to the snRNA. In this model, the D1/D2 and E/F/G Sm protein sub-complexes first bind the snRNA in the [U] conformation, followed by conformational re-arrangement to the [I] conformation and binding of the D3/B Sm protein sub-complex.

Base Sequence↗

A locus for brachydactyly type A-1 maps to chromosome 2q35-q36.

Brachydactyly type A-1 (BDA1) was, in 1903, the first recorded example of a human anomaly with Mendelian autosomal dominant inheritance. Two large families, the affected members of which were radiographed, were recruited in the study we describe here. Two-point linkage analysis for pedigree 1 (maximum LOD score [Zmax] 6.59 at recombination fraction [theta] 0.00) and for pedigree 2 (Zmax=5.53 at straight theta=0.00) mapped the locus for BDA1 in the two families to chromosome 2q. Haplotype analysis of pedigree 1 confined the locus for family 1 within an interval of <8.1 cM flanked by markers D2S2248 and D2S360, which was mapped to chromosome 2q35-q36 on the cytogenetic map. Haplotype analysis of pedigree 2 confined the locus for family 2 within an interval of <28. 8 cM flanked by markers GATA30E06 and D2S427, which was localized to chromosome 2q35-q37. The two families had no identical haplotype within the defined region, which suggests that the two families were not related.

Adolescent↗

Analysis of maxillopedia expression pattern and larval cuticular phenotype in wild-type and mutant tribolium.

The Tribolium castaneum homeotic gene maxillopedia (mxp) is the ortholog of Drosophila proboscipedia (pb). Here we describe and classify available mxp alleles. Larvae lacking all mxp function die soon after hatching, exhibiting strong transformations of maxillary and labial palps to legs. Hypomorphic mxp alleles produce less severe transformations to leg. RNA interference with maxillopedia double-stranded RNA results in phenocopies of mxp mutant phenotypes ranging from partial to complete transformations. A number of gain-of-function (GOF) mxp alleles have been isolated based on transformations of adult antennae and/or legs toward palps. Finally, we have characterized the mxp expression pattern in wild-type and mutant embryos. In normal embryos, mxp is expressed in the maxillary and labial segments, whereas ectopic expression is observed in some GOF variants. Although mxp and Pb display very similar expression patterns, pb null embryos develop normally. The mxp mutant larval phenotype in Tribolium is consistent with the hypothesis that an ancestral pb-like gene had an embryonic function that was lost in the lineage leading to Drosophila.

Alleles↗

Water relations and leaf expansion: importance of time scale.

The role of leaf water relations in controlling cell expansion in leaves of water-stressed maize and barley depends on time scale. Sudden changes in leaf water status, induced by sudden changes in humidity, light and soil salinity, greatly affect leaf elongation rate, but often only transiently. With sufficiently large changes in salinity, leaf elongation rates are persistently reduced. When plants are kept fully turgid throughout such sudden environmental changes, by placing their roots in a pressure chamber and raising the pressure so that the leaf xylem sap is maintained at atmospheric pressure, both the transient and persistent changes in leaf elongation rate disappear. All these responses show that water relations are responsible for the sudden changes in leaf elongation rate resulting from sudden changes in water stress and putative root signals play no part. However, at a time scale of days, pressurization fails to maintain high rates of leaf elongation of plants in either saline or drying soil, indicating that root signals are overriding water relations effects. In both saline and drying soil, pressurization does raise the growth rate during the light period, but a subsequent decrease during the dark results in no net effect on leaf growth over a 24 h period. When transpirational demand is very high, however, growth-promoting effects of pressurization during the light period outweigh any reductions in the dark, resulting in a net increase in growth of pressurized plants over 24 h. Thus leaf water status can limit leaf expansion rates during periods of high transpiration despite the control exercised by hormonal effects on a 24 h basis.

Cell Division↗

Characterization of human CYP2G genes: widespread loss-of-function mutations and genetic polymorphism.

CYP2G1 is an abundant, olfactory mucosa-specific cytochrome P450 enzyme active in the metabolism of sex steroids and xenobiotic substrates in mammalian animals. Two different human CYP2G genes, CYP2GP1 and CYP2GP2, were characterized in the present study. Polymorphisms in these genes were also studied. CYP2GP1 contained a single nucleotide deletion in exon 2 (deltaC) and a 2.4-kb deletion between exons 3 and 7 (deltaE4-6), whereas CYP2GP2 contained a nonsense mutation in exon 1 and another in exon 3. The coding region sequences in exons 1-3 and 7-9 of the two genes were 96.7% identical. Both genes were localized to human chromosome 19, and Southern blot analysis of human genomic DNA did not detect any additional copies of the CYP2G gene. The occurrence of these loss-of-function mutations was analysed by polymerase chain reaction-based genotyping in more than 200 individuals. The deltaE4-6 deletion in CYP2GP1 was detected in 94% of subjects (either homozygous or heterozygous), and an allele which does not contain this deletion was detected in 11.6% of individuals. The nonsense mutation in CYP2GP2 exon 3 was detected in 86% of individuals (either homozygous or heterozygous); however, a potentially functional CYP2GP2 allele based on the absence of the nonsense mutation in exon 3 was also detected in 31% of individuals. These results indicate that a functional CYP2G allele is rare in humans. Analysis of the allelic distribution in different ethnic groups suggested that a functional CYP2G allele, if present, is more likely to be found in Black and Hispanic subjects.

Alleles↗

Identification of G protein-coupled receptor kinase 2 phosphorylation sites responsible for agonist-stimulated delta-opioid receptor phosphorylation.

Agonist-induced receptor phosphorylation is an initial step in opioid receptor desensitization, a molecular mechanism of opioid tolerance and dependence. Our previous research suggested that agonist-induced delta-opioid receptor (DOR) phosphorylation occurs at the receptor carboxyl terminal domain. The current study was carried out to identify the site of DOR phosphorylation during agonist stimulation and the kinases catalyzing this reaction. Truncation (Delta15) or substitutions (T358A, T361A, and S363G single or triple mutants) at the DOR cytoplasmic tail caused 80 to 100% loss of opioid-stimulated receptor phosphorylation, indicating that T358, T361, and S363 all contribute and are cooperatively involved in agonist-stimulated DOR phosphorylation. Coexpression of GRK2 strongly enhanced agonist-stimulated phosphorylation of the wild-type DOR (WT), but Delta15 or mutant DOR (T358A/T361A/S363G) failed to show any detectable phosphorylation under these conditions. These results demonstrate that T358, T361, and S363 are required for agonist-induced and GRK-mediated receptor phosphorylation. Agonist-induced receptor phosphorylation was severely impaired by substitution of either T358 or S363 with aspartic acid residue, but phosphorylation of the T361D mutant was comparable with that of WT. In the presence of exogenously expressed GRK2, phosphorylation levels of T358D and S363D mutants were approximately half of that of WT, whereas significant phosphorylation of the T358/S363 double-point mutant was not detected. These results indicate that both T358 and S363 residues at the DOR carboxyl terminus are capable of serving cooperatively as phosphate acceptor sites of GRK2 in vivo. Taken together, we have demonstrated that agonist-induced opioid receptor phosphorylation occurs exclusively at two phosphate acceptor sites (T358 and S363) of GRK2 at the DOR carboxyl terminus. These results represent the identification of the GRK phosphorylation site on an opioid receptor for the first time and demonstrate that GRK is the prominent kinase responsible for agonist-induced opioid receptor phosphorylation in vivo.

Amino Acid Sequence↗

Zinc finger structures in the human immunodeficiency virus type 1 nucleocapsid protein facilitate efficient minus- and plus-strand transfer.

The nucleocapsid protein (NC) of human immunodeficiency virus type 1 (HIV-1) has two zinc fingers, each containing the invariant metal ion binding residues CCHC. Recent reports indicate that mutations in the CCHC motifs are deleterious for reverse transcription in vivo. To identify reverse transcriptase (RT) reactions affected by such changes, we have probed zinc finger functions in NC-dependent RT-catalyzed HIV-1 minus- and plus-strand transfer model systems. Our approach was to examine the activities of wild-type NC and a mutant in which all six cysteine residues were replaced by serine (SSHS NC); this mutation severely disrupts zinc coordination. We find that the zinc fingers contribute to the role of NC in complete tRNA primer removal from minus-strand DNA during plus-strand transfer. Annealing of the primer binding site sequences in plus-strand strong-stop DNA [(+) SSDNA] to its complement in minus-strand acceptor DNA is not dependent on NC zinc fingers. In contrast, the rate of annealing of the complementary R regions in (-) SSDNA and 3' viral RNA during minus-strand transfer is approximately eightfold lower when SSHS NC is used in place of wild-type NC. Moreover, unlike wild-type NC, SSHS NC has only a small stimulatory effect on minus-strand transfer and is essentially unable to block TAR-induced self-priming from (-) SSDNA. Our results strongly suggest that NC zinc finger structures are needed to unfold highly structured RNA and DNA strand transfer intermediates. Thus, it appears that in these cases, zinc finger interactions are important components of NC nucleic acid chaperone activity.

Genome, Viral↗

Characterization of the interaction between the interferon-induced protein P56 and the Int6 protein encoded by a locus of insertion of the mouse mammary tumor virus.

For determining cellular functions of the interferon-inducible human cytoplasmic protein P56, we undertook a Saccharomyces cerevisiae two-hybrid screen that identified Int6 as a P56-interacting protein. That the interaction also occurs in human cells was confirmed by coimmunoprecipitation and the observed cytoplasmic displacement of nuclear Int6 upon coexpression of P56. Because Int6 has been claimed to be both a cytoplasmic and a nuclear protein, we investigated the structural basis of this discrepancy. By mutational analyses, we showed that the Int6 protein contains a bipartite nuclear localization signal and a nuclear export signal at the far end of the amino terminus. The 20 amino-terminal residues of Int6, when they were attached to a different nuclear protein, were sufficient to translocate that protein to the cytoplasm. Within this region, replacement of any of the three leucine residues with alanine destroyed the function of the export signal. The specific domain of P56 that is required for its interaction with Int6 was mapped using the yeast two-hybrid assay and a mammalian coimmunoprecipitation assay. Both assays demonstrated that the C-terminal region of P56 containing three specific tetratricopeptide motifs is required for this interaction. In contrast, removal of an internal domain of P56 enhanced the interaction, as quantified by the two-hybrid assay.

Adaptor Proteins, Signal Transducing↗

Domains in the SPT5 protein that modulate its transcriptional regulatory properties.

SPT5 and its binding partner SPT4 regulate transcriptional elongation by RNA polymerase II. SPT4 and SPT5 are involved in both 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB)-mediated transcriptional inhibition and the activation of transcriptional elongation by the human immunodeficiency virus type 1 (HIV-1) Tat protein. Recent data suggest that P-TEFb, which is composed of CDK9 and cyclin T1, is also critical in regulating transcriptional elongation by SPT4 and SPT5. In this study, we analyze the domains of SPT5 that regulate transcriptional elongation in the presence of either DRB or the HIV-1 Tat protein. We demonstrate that SPT5 domains that bind SPT4 and RNA polymerase II, in addition to a region in the C terminus of SPT5 that contains multiple heptad repeats and is designated CTR1, are critical for in vitro transcriptional repression by DRB and activation by the Tat protein. Furthermore, the SPT5 CTR1 domain is a substrate for P-TEFb phosphorylation. These results suggest that C-terminal repeats in SPT5, like those in the RNA polymerase II C-terminal domain, are sites for P-TEFb phosphorylation and function in modulating its transcriptional elongation properties.

Amino Acid Sequence↗

Effect of hydrogen peroxide on the membrane currents of sinoatrial node cells from rabbit heart.

The effects of H(2)O(2) on pacemaker activity and underlying membrane currents were studied in isolated rabbit sinoatrial (SA) node cells using perforated patch current- and voltage-clamp methods. Short-term exposure (<10 min) of the nodal cells to H(2)O(2) (200 microM) resulted in an initial shortening of spontaneous action potential cycle length (from 445 +/- 60 to 398 +/- 56 ms; P < 0.05) and a prolongation of action potential duration. H(2)O(2) (100 microM) significantly increased peak L-type Ca(2+) current (I(Ca,L)) from -384 +/- 77 to -439 +/- 84 pA (116 +/- 2%, n = 6). Additionally, the persistent or non-inactivating component of I(Ca,L) was increased from -52 +/- 3 to -88 +/- 14 pA (174 +/- 19%, n = 6). The hyperpolarization-activated current (I(f)) was decreased from -228 +/- 62 to -161 +/- 72 pA after exposure to H(2)O(2) (n = 7). There were no changes in the delayed rectifier K(+) current (I(K)) (n = 7). H(2)O(2)-induced Ca(2+) currents were blocked by 2 microM nicardipine (n = 6), 2 mM Ni(2+) (n = 2), and the protein kinase C (PKC) inhibitor bisindolylmaleimide (10(-7) M; n = 4) but not by 20 microM tetrodotoxin. These results suggest that H(2)O(2) can increase the spontaneous pacing rate in rabbit SA node cells by enhancing I(Ca,L) and that this effect is mediated by a PKC-dependent pathway.

Action Potentials↗

Therapy with antisense TGF-beta1 oligodeoxynucleotides reduces kidney weight and matrix mRNAs in diabetic mice.

Inhibition of gene expression by antisense oligodeoxynucleotides (ODNs) relies on their ability to bind complementary mRNA sequences and prevent translation. The proximal tubule is a suitable target for ODN therapy in vivo because circulating ODNs accumulate in the proximal tubule in high concentrations. Because increased proximal tubular transforming growth factor- beta1 (TGF-beta1) expression may mediate diabetic renal hypertrophy, we investigated the effects of antisense TGF-beta1 ODN on the high-glucose-induced proximal tubular epithelial cell hypertrophy in tissue culture and on diabetic renal hypertrophy in vivo. Mouse proximal tubular cells grown in 25 mM D-glucose and exposed to sense ODN as control (1 microM) exhibited increased (3)[H]leucine incorporation by 120% and total TGF-beta1 protein by 50% vs. culture in 5.5 mM D-glucose. Antisense ODN significantly decreased the high-glucose-stimulated TGF-beta1 secretion and leucine incorporation. Continuous infusion for 10 days of ODN (100 microg/day) was achieved via osmotic minipumps in diabetic and nondiabetic mice. Sense ODN-treated streptozotocin-diabetic mice had 15.3% increase in kidney weight, 70% increase in alpha1(IV) collagen and 46% increase in fibronectin mRNA levels compared with nondiabetic mice. Treatment of diabetic mice with antisense ODN partially but significantly decreased kidney TGF-beta1 protein levels and attenuated the increase in kidney weight and the alpha1(IV) collagen and fibronectin mRNAs. In conclusion, therapy with antisense TGF-beta1 ODN decreases TGF-beta1 production and attenuates high-glucose-induced proximal tubular cell hypertrophy in vitro and partially prevents the increase in kidney weight and extracellular matrix expression in diabetic mice.

Animals↗

Ocular nonnephropathic cystinosis: clinical, biochemical, and molecular correlations.

Ocular nonnephropathic cystinosis, a variant of the classic nephropathic type of cystinosis, is an autosomal recessive lysosomal storage disorder characterized by photophobia due to corneal cystine crystals but absence of renal disease. We determined the molecular basis for ocular cystinosis in four individuals. All had mutations in the cystinosis gene CTNS, indicating that ocular cystinosis is allelic with classic nephropathic cystinosis. The ocular cystinosis patients each had one severe mutation and one mild mutation, the latter consisting of either a 928 G-->A (G197R) mutation or an IVS10-3 C-->G splicing mutation resulting in the insertion of 182 bp of IVS10 into the CTNS mRNA. The mild mutations appear to allow for residual CTNS mRNA production, significant amounts of lysosomal cystine transport, and lower levels of cellular cystine compared with those in nephropathic cystinosis. The lack of kidney involvement in ocular cystinosis may be explained by two different mechanisms. On the one hand (e.g. the G197R mutation), significant residual cystinosin activity may be present in every tissue. On the other hand (e.g. the IVS 10-3 C-->G mutation), substantial cystinosin activity may exist in the kidney because of that tissue's specific expression of factors that promote splicing of a normal CTNS transcript. Each of these mechanisms could result in minimally reduced lysosomal cystine transport in the kidneys.

Amino Acid Transport Systems, Neutral↗

Developmental pathways to alcohol abuse and dependence in young adulthood.

OBJECTIVE: To determine if people who were diagnosed with alcohol abuse or dependence (AAD) at age 21 had different developmental patterns of alcohol use in adolescence than non-AAD individuals. METHOD: An ethnically diverse urban sample of 808 children was surveyed at age 10 in 1985 and followed prospectively to age 21 in 1996. AAD at age 21 was assessed following DSM-IV criteria. Latent Transition Analysis (LTA) was used to identify four statuses of alcohol use (nonuse, initiation only, current use only, heavy episodic drinking), as well as transition probabilities between these four statuses from elementary school to middle school and from middle school to high school among the AAD and non-AAD group. RESULTS: The prevalence of alcohol use statuses during elementary school was similar in the two groups. Differences in alcohol use emerged in middle school and became more pronounced in high school. In middle school, AAD individuals were more likely to have initiated or been current drinkers than non-AAD individuals. However, the two groups did not differ in the prevalence of heavy episodic drinking in middle school. In high school, most AAD individuals were in the heavy episodic drinking status (54%), while most non-AAD individuals were in the initiation only (33%) or current use only (34%) statuses. CONCLUSIONS: These findings suggest preventive intervention targets for different developmental periods. Alcohol abuse and dependence at age 21 may be prevented by delaying alcohol initiation, by reducing current use in middle school and by reducing heavy episodic drinking in high school.

Adolescent↗

The dynamics of alcohol and marijuana initiation: patterns and predictors of first use in adolescence.

OBJECTIVES: This study, guided by the social development model, examined the dynamic patterns and predictors of alcohol and marijuana use onset. METHODS: Survival analysis and complementary log-log regression were used to model hazard rates and etiology of initiation with time-varying covariates. The sample was derived from a longitudinal study of 808 youth interviewed annually from 10 to 16 years of age and at 18 years of age. RESULTS: Alcohol initiation rose steeply up to the age of 13 years and then increased more gradually; most participants had initiated by 13 years of age. Marijuana initiation showed a different pattern, with more participants initiating after the age of 13 years. CONCLUSIONS: This study showed that: (1) the risk of initiation spans the entire course of adolescent development; (2) young people exposed to others who use substances are at higher risk for early initiation; (3) proactive parents can help delay initiation; and (4) clear family standards and proactive family management are important in delaying alcohol and marijuana use, regardless of how closely bonded a child is to his or her mother.

Adolescent↗

[Chinese Han population data obtained from fluorescently detected STR loci-vWA31A, TH01, F13A01, FES, TPOX and CSF1PO].

OBJECTIVE: This paper was designed to evaluate 6 short tandem repeats(STR) loci for their use in forensic personal identification. METHODS: The allele frequencies and genotype frequencies at 6 tetranucleotide STR loci were determined in a sample of 132 unrelated individuals from a Chinese population of Han nationality in Guangzhou. The PCR products were analysed on 4% denaturing PAGE and detected using fluorescently labeled primers in an automated 377 sequencer(PE). The resultant allele frequencies were compared with other population or race databases. RESULTS: All the 6 loci (vWA31A, TH01, F13A01,FES, TPOX, CSF1PO) met Hardy-Weinberg equilibrium. No random association of alleles among the 6 loci was noted. Except locus vWA31A, the observed heterozygosities at other 5 loci were significantly lower than those reported in Caucasian and Black population studies. The calculated DP=0.99999,PE=0.9708,pM=1.059 times 10(-5). CONCLUSION: The data obtained can be used in human identity and paternity testing, and in other genetic researches and population investigation.

Alleles↗

[The common C677T polymorphism in the methylenetetrahydrofolate reductase gene is associated with neural tube defects and preeclampsia].

OBJECTIVE: To assess whether methylenetetrahydrofolate reductase(MTHFR) gene C677T polymorphism is associated with neural tube defects and preeclampsia. METHODS: Twenty- four mothers who had given birth to normal children, 27 mothers who had given birth to NTDs children, 120 normal women, and 57 women who had suffered from preeclampsia were genotyped for C677T polymorphism by using PCR/RFLP method. RESULTS: (1) VV genotype frequency in the normal mothers group it was 0.13, while in the NTDs mothers group it was 0.33; mothers with VV genotype were at 3 times increased risk to have a NTDs child, compared with the normal mothers. (2) In the normal women group VV genotype frequency was 0.15, while in the preeclampsia women group it was 0.31; women with VV genotype were at 2.5 times increased risk to have preeclampsia, compared with the normal women. CONCLUSION: The authors believe that MTHFR VV genotype is associated with the development of NTDs and preeclampsia.

Female↗

Flow cytometric DNA analyses of epithelial dysplasia of the esophagus.

OBJECTIVE: To investigate, with flow cytometry, DNA aneuploidy as a marker of early carcinogenesis in dysplastic esophageal lesions. STUDY DESIGN: DNA content of exfoliated cells from 789 cases of esophageal dysplasia (including mild dysplasia, 195 cases; moderate dysplasia, 383 cases; and severe dysplasia, 211 cases) was determined with a FACS 420 flow cytometer. RESULTS: Cellular DNA content was closely related to the severity of dysplasia. The carcinogenesis rate in patients with dysplasia showed that DNA aneuploidy was significantly higher than in patients showing DNA diploidy. CONCLUSION: DNA aneuploidy in dysplastic lesions is a very important early signal of carcinogenesis. Patients with dysplastic lesions showing DNA aneuploidy should be treated and closely followed.

Aneuploidy↗