AHA Life's Essential 8 and new-onset CKD: a prospective cohort study from the UK Biobank

BACKGROUND

The AHA has recently introduced a novel metric, Life's Essential 8, to assess cardiovascular health (CVH). Nevertheless, the association between varying levels of LE8 and the propensity for CKD is still unclear from a large prospective cohort. Our objective is to meticulously examine the relationship between LE8 and its associated susceptibilities to CKD.

METHODS

A total of 251,825 participants free of CKD from the UK Biobank were included. Cardiovascular health was scored using LE8 and categorized as low, moderate, and high. Cox proportional hazard models were employed to evaluate the associations of LE8 scores with new-onset CKD. The genetic risk score for CKD was calculated by a weighted method.

RESULTS

Over a median follow-up of 12.8 years, we meticulously documented 10,124 incident cases of CKD. Remarkably, an increased LE8 score correlated with a significant reduction of risk in new-onset CKD (high LE8 score vs. low LE8 score: HR = 0.300, 95% CI 0.270-0.330, p < 0.001; median LE8 score vs. low LE8 score: HR = 0.531, 95% CI 0.487-0.580, p < 0.001). This strong LE8-CKD association remained robust in extensive subgroup assessments and sensitivity analysis. Additionally, these noteworthy associations between LE8 scores and CKD remained unaffected by genetic predispositions to CKD.

CONCLUSIONS

An elevated degree of CVH, as delineated by the discerning metric LE8, exhibited a pronounced and statistically significant correlation with a marked reduction in the likelihood of CKD occurrence.

Cardiovascular health metrics defined by Life's Essential 8 scores and subsequent macrovascular and microvascular complications in individuals with type 2 diabetes: A prospective cohort study

AIM

To investigate the association between cardiovascular health metrics defined by Life's Essential 8 (LE8) scores and vascular complications among individuals with type 2 diabetes (T2D).

MATERIALS AND METHODS

This prospective study included 11 033 participants with T2D, all devoid of macrovascular diseases (including cardiovascular and peripheral artery disease) and microvascular complications (e.g. diabetic retinopathy, neuropathy and nephropathy) at baseline from the UK Biobank. The LE8 score comprised eight metrics: smoking, body mass index, physical activity, non-high-density lipoprotein cholesterol, blood pressure, glycated haemoglobin, diet and sleep duration. Cox proportional hazards models were established to assess the associations of LE8 scores with incident macrovascular and microvascular complications.

RESULTS

During a median follow-up of 12.1 years, we identified 1975 cases of incident macrovascular diseases and 1797 cases of incident microvascular complications. After adjusting for potential confounders, each 10-point increase in the LE8 score was associated with an 18% lower risk of macrovascular diseases and a 15% lower risk of microvascular complications. Comparing individuals in the highest and lowest quartiles of LE8 scores revealed hazard ratios of 0.55 (95% confidence interval 0.47-0.62) for incident macrovascular diseases, and 0.61 (95% confidence interval 0.53-0.70) for incident microvascular complications. This association remained robust across a series of sensitivity analyses and nearly all subgroups.

CONCLUSION

Higher LE8 scores were associated with a lower risk of incident macrovascular and microvascular complications among individuals with T2D. These findings underscore the significance of adopting fundamental strategies to maintain optimal cardiovascular health and curtail the risk of developing diabetic vascular complications.

The association between tinnitus and risk of cardiovascular events and all-cause mortality: insight from the UK Biobank

BACKGROUND

The potential influence of tinnitus on cardiovascular disease (CVD) and all-cause mortality has yet to be explored. We aim to examine the correlations between tinnitus and the risk of cardiovascular events and all-cause mortality.

METHODS

We conducted a prospective cohort study utilising data from the UK Biobank. The presence of tinnitus was evaluated through a questionnaire. The primary outcome was defined as a composition of cardiovascular events, including myocardial infarction (MI), stroke, and mortality from CVD, as well as all-cause mortality. Cox proportional hazard models were employed to examine the associations between tinnitus and both the primary outcome and its individual components. Sensitivity analyses were conducted to evaluate the robustness of the primary analysis.

RESULTS

A total of 140,146 participants were included in the study. The presence of tinnitus was found to be associated with a higher incident rate of the primary outcome (HR = 1.057, 95%CI: 1.017-1.099, p = 0.005), MI (HR = 1.139, 95%CI: 1.061-1.222, p < 0.001) and all-cause mortality (HR = 1.053, 95%CI: 1.003-1.105, p = 0.038) after adjusting for confounders. However, there was no significant association between tinnitus and stroke or mortality from CVD. Subgroup analysis revealed that the association between tinnitus and the primary outcome was significant in females, participants with abnormal BMI, and those without hearing difficulty, depression or anxiety. Sensitivity analyses yielded consistent results.

CONCLUSION

The findings from this study contribute to the existing body of evidence suggesting an association between tinnitus and an increased risk of cardiovascular events and all-cause mortality.

Association between daytime napping and incident arrhythmias: A prospective cohort study and mendelian randomization analysis

BACKGROUND

Emerging evidence has linked daytime napping with the risk of cardiovascular events. Cardiac arrhythmias are considered an early clinical stage for cardiovascular diseases. However, whether napping frequency is associated with incident arrhythmias remains unknown.

OBJECTIVE

This study aimed to prospectively investigate the association between napping frequency and cardiac arrhythmias.

METHODS

Daytime napping frequency was self-reported in response to touchscreen questionnaires. The primary outcomes were incident arrhythmias including atrial fibrillation/flutter (AF/Af), ventricular arrhythmia, and bradyarrhythmia. Cox regression analysis was conducted on the basis of 491,117 participants free of cardiac arrhythmias from the UK Biobank. The 2-sample mendelian randomization (MR) and 1-sample MR were used to ensure a causal effect of genetically predicted daytime napping on the risk of arrhythmias.

RESULTS

During a median follow-up of 11.91 years, 28,801 incident AF/Af cases, 4132 incident ventricular arrhythmias, and 11,616 incident bradyarrhythmias were documented. Compared with never/rarely napping, usually napping was significantly associated with higher risks of AF/Af (hazard ratio, 1.141; 95% CI, 1.083-1.203) and bradyarrhythmia (hazard ratio, 1.138; 95% CI, 1.049-1.235) but not ventricular arrhythmia after adjustment for various covariates. The 2-sample MR and 1-sample MR analysis showed that increased daytime napping frequency was likely to be a potential causal risk factor for AF/Af in FinnGen (odds ratio, 1.626; 95% CI, 1.061-2.943) and bradyarrhythmia in the UK Biobank (odds ratio, 1.005; 95% CI, 1.002-1.008).

CONCLUSION

The results of this study add to the burgeoning evidence of an association between daytime napping frequency and an increased risk of cardiac arrhythmias including AF/Af, ventricular arrhythmia, and bradyarrhythmia.

Remnant cholesterol and risk of incident hypertension: a population-based prospective cohort study

Remnant cholesterol (RC) has been associated with atherosclerotic cardiovascular disease, but its relationship with hypertension remains unclear. This prospective cohort study aimed to investigate the association between RC and subsequent hypertension risk. Data from the UK Biobank, comprising 295,062 participants initially free of hypertension, were analyzed. Cox proportional hazards regression assessed the association between RC quartiles and hypertension risk. Discordance analysis evaluated the risk of hypertension in discordant/concordant groups of RC and low-density lipoprotein cholesterol (LDL-C) using the difference in percentile units (>10 units). Restricted cubic spline curves were used to model the relationship between RC and hypertension risk. The mean ± SD age of participants was 55.1 ± 8.1 years, with 40.6% being men and 94.7% White. During a median follow-up of 12.8 years, 39,038 participants developed hypertension. Comparing extreme quartiles of RC, the hazard ratio (HR) for incident hypertension was 1.20 (95% CI: 1.17-1.24). After adjusting for traditional risk factors, each 1 mmol/L increase in RC levels was associated with a 27% higher risk of incident hypertension (HR: 1.27; 95% CI: 1.23-1.31). The discordant group with high RC/low LDL-C exhibited a higher risk of incident hypertension compared to the concordant group (HR: 1.06; 95% CI: 1.03-1.09). Spline curves further demonstrated a positive association between RC and the risk of incident hypertension. We concluded that elevated RC emerged as an independent risk factor of incident hypertension, extending beyond traditional risk factors. Monitoring RC levels and implementing interventions to lower RC may have potential benefits in preventing hypertension.

[Analysis of the whole genome traceability and transmission path simulation experiment of the local cluster COVID-19 epidemic]

Objective: To trace and characterize the whole genome of SARS-CoV-2 of confirmed cases in the outbreak of COVID-19 on July 31, 2021 in Henan Province. Method: Genome-wide sequencing and comparative analysis were performed on positive nucleic acid samples of SARS-CoV-2 from 167 local cases related to the epidemic on July 31, 2021, to analyze the consistency and evolution of the whole genome sequence of virus. Results: Through high-throughput sequencing, a total of 106 cases of SARS-CoV-2 whole genome sequences were obtained. The results of genome analysis showed that the whole genome sequences of 106 cases belonged to the VOC/Delta variant strain (B.1.617.2 clade), and the whole genome sequences of 106 cases were shared with the genomes of 3 imported cases from Myanmar admitted to a hospital in Zhengzhou. On the basis of 45 nucleotide sites, 1-5 nucleotide variation sites were added, and the genome sequence was highly homologous. Conclusion: Combined with the comprehensive analysis of viral genomics, transmission path simulation experiments and epidemiology, it is determined that the local new epidemic in Henan Province is caused by imported cases in the nosocomial area, and the spillover has caused localized infection in the community. At the same time, it spills over to some provincial cities and results in localized clustered epidemics.

Glycolysis Inhibition Alleviates Cardiac Fibrosis After Myocardial Infarction by Suppressing Cardiac Fibroblast Activation

Objective: To explore the role of glycolysis in cardiac fibroblast (CF) activation and cardiac fibrosis after myocardial infarction (MI).

Method:In vivo: 2-Deoxy-D-glucose (2-DG), a glycolysis inhibitor, was injected into the abdominal cavity of the MI or sham mice every day. On the 28th day, cardiac function was measured by ultrasonic cardiography, and the hearts were harvested. Masson staining and immunofluorescence (IF) were used to evaluate the fibrosis area, and western blot was used to identify the glycolytic level. In vitro, we isolated the CF from the sham, MI and MI with 2-DG treatment mice, and we also activated normal CF with transforming growth factor-β1 (TGF-β1) and block glycolysis with 2-DG. We then detected the glycolytic proteins, fibrotic proteins, and the concentrations of lactate and glucose in the culture medium. At last, we further detected the fibrotic and glycolytic markers in human fibrotic and non-fibrotic heart tissues with masson staining, IF and western blot.

Result: More collagen and glycolytic protein expressions were observed in the MI mice hearts. The mortality increased when mice were treated with 2-DG (100 mg/kg/d) after the MI surgery (Log-rank test, P < 0.05). When the dosage of 2-DG declined to 50 mg/kg/d, and the treatment was started on the 4th day after MI, no statistical difference of mortality between the two groups was observed (Log-rank test, P = 0.98). The collagen volume fraction was smaller and the fluorescence signal of α-smooth muscle actin (α-SMA) was weaker in mice treated with 2-DG than PBS. In vitro, 2-DG could significantly inhibit the increased expression of both the glycolytic and fibrotic proteins in the activated CF.

Conclusion: Cardiac fibrosis is along with the enhancement of CF activation and glycolysis. Glycolysis inhibition can alleviate cardiac fibroblast activation and cardiac fibrosis after myocardial infarction.

Timing of continuous renal replacement therapy in severe acute kidney injury patients with fluid overload: A retrospective cohort study

PURPOSE

We aimed to evaluate the association of early versus late initiation of Continuous renal replacement therapy (CRRT) with mortality in patients with fluid overload.

METHODS

This was a retrospective cohort study of patients with fluid overload (FO) treated with CRRT due to severe acute kidney injury (AKI) between January 2015 and December 2017 in a mixed medical intensive care unit of a teaching hospital in Beijing, China. Patients were divided into early (≤15 h) and late (>15 h) groups based on the median time from ICU admission to CRRT initiation. The primary outcome was all-cause mortality at day 60. Multivariable Cox model analysis was used for analysis.

RESULTS

The study patients were male predominant (84/150) with a mean age of 64.8 ± 16.7 years. The median FO value before CRRT initiation was 10.1% [6.2-16.1%]. The 60-day mortality rates in the early vs the late CRRT groups were 53.9% and 73%, respectively. On multivariable Cox modelling, the late initiation of CRRT was independently associated with an increased risk of death at 60 days (HR 1.75, 95% CI 1.11-2.74, p = 0.015).

CONCLUSIONS

Early initiation of CRRT was independently associated with survival benefits in severe AKI patients with fluid overload.

[Analysis on the epidemiology and etiology characteristics of first imported Chikungunya fever case in Henan Province in 2017]

To study the epidemiology and etiology characteristics of first imported Chikungunya fever case in Henan province, China, 2017. The patient was confirmed by Chikungunya virus (CHIKV) infected as CHIKV ribonucleotide was continuously detected in his serum specimens. BHK-21 cell line was used for virus isolation, the strain was named CHIKV/Henan001/2017. CHIKV/Henan001/2017 belonged to genotype ECSA. The highest ribonucleotide homology sequence of highly conserved region E1 with CHIKV/Henan001/2017 was hk02 strain (99.8%), who was an imported strain to Hong Kong, China, 2016. Epidemiological information and laboratory testing confirmed it was an imported Chikungunya fever case in Henan province, 2017. No secondary case has been reported.

Pathogenic FBN1 variants in familial thoracic aortic aneurysms and dissections

Marfan syndrome (MFS) due to mutations in FBN1 is a known cause of thoracic aortic aneurysms and acute aortic dissections (TAAD) associated with pleiotropic manifestations. Genetic predisposition to TAAD can also be inherited in families in the absence of syndromic features, termed familial TAAD (FTAAD), and several causative genes have been identified to date. FBN1 mutations can also be identified in FTAAD families, but the frequency of these mutations has not been established. We performed exome sequencing of 183 FTAAD families and identified pathogenic FBN1 variants in five (2.7%) of these families. We also identified eight additional FBN1 rare variants that could not be unequivocally classified as disease-causing in six families. FBN1 sequencing should be considered in individuals with FTAAD even without significant systemic features of MFS.

Lys63-linked ubiquitin chain adopts multiple conformational states for specific target recognition

A polyubiquitin comprises multiple covalently linked ubiquitins and recognizes myriad targets. Free or bound to ligands, polyubiquitins are found in different arrangements of ubiquitin subunits. To understand the structural basis for polyubiquitin quaternary plasticity and to explore the target recognition mechanism, we characterize the conformational space of Lys63-linked diubiquitin (K63-Ub2). Refining against inter-subunit paramagnetic NMR data, we show that free K63-Ub2 exists as a dynamic ensemble comprising multiple closed and open quaternary states. The quaternary dynamics enables K63-Ub2 to be specifically recognized in a variety of signaling pathways. When binding to a target protein, one of the preexisting quaternary states is selected and stabilized. A point mutation that shifts the equilibrium between the different states modulates the binding affinities towards K63-Ub2 ligands. This conformational selection mechanism at the quaternary level may be used by polyubiquitins of different lengths and linkages for target recognition.

Effects of γ-ray irradiation on optical absorption and laser damage performance of KDP crystals containing arsenic impurities

The effects of γ-irradiation on potassium dihydrogen phosphate crystals containing arsenic impurities are investigated with different optical diagnostics, including UV-VIS absorption spectroscopy, photo-thermal common-path interferometer and photoluminescence spectroscopy. The optical absorption spectra indicate that a new broad absorption band near 260 nm appears after γ-irradiation. It is found that the intensity of absorption band increases with the increasing irradiation dose and arsenic impurity concentration. The simulation of radiation defects show that this absorption is assigned to the formation of AsO₄⁴⁻ centers due to arsenic ions substituting for phosphorus ions. Laser-induced damage threshold test is conducted by using 355 nm nanosecond laser pulses. The correlations between arsenic impurity concentration and laser induced damage threshold are presented. The results indicate that the damage performance of the material decreases with the increasing arsenic impurity concentration. Possible mechanisms of the irradiation-induced defects formation under γ-irradiation of KDP crystals are discussed.

NMR model of PrgI-SipD interaction and its implications in the needle-tip assembly of the Salmonella type III secretion system

Salmonella and other pathogenic bacteria use the type III secretion system (T3SS) to inject virulence proteins into human cells to initiate infections. The structural component of the T3SS contains a needle and a needle tip. The needle is assembled from PrgI needle protomers and the needle tip is capped with several copies of the SipD tip protein. How a tip protein docks on the needle is unclear. A crystal structure of a PrgI-SipD fusion protein docked on the PrgI needle results in steric clash of SipD at the needle tip when modeled on the recent atomic structure of the needle. Thus, there is currently no good model of how SipD is docked on the PrgI needle tip. Previously, we showed by NMR paramagnetic relaxation enhancement (PRE) methods that a specific region in the SipD coiled coil is the binding site for PrgI. Others have hypothesized that a domain of the tip protein-the N-terminal α-helical hairpin-has to swing away during the assembly of the needle apparatus. Here, we show by PRE methods that a truncated form of SipD lacking the α-helical hairpin domain binds more tightly to PrgI. Further, PRE-based structure calculations revealed multiple PrgI binding sites on the SipD coiled coil. Our PRE results together with the recent NMR-derived atomic structure of the Salmonella needle suggest a possible model of how SipD might dock at the PrgI needle tip. SipD and PrgI are conserved in other bacterial T3SSs; thus, our results have wider implication in understanding other needle-tip complexes.

A decadentate Gd(III)-coordinating paramagnetic cosolvent for protein relaxation enhancement measurement

Solvent paramagnetic relaxation enhancement (sPRE) arises from random collisions between paramagnetic cosolvent and protein of interest. The sPRE can be readily measured, affording protein structure information. However, lack of an inert cosolvent probe may yield sPRE values that are not consistent with protein structure. Here we synthesized a new sPRE probe, triethylenetetraamine hexaacetate trimethylamide gadolinium, or Gd(III)-TTHA-TMA. With a total of 10 coordination sites, this paramagnetic cosovlent eliminates an inner-sphere water molecule that can otherwise transfer relaxation to protein through exchange. With the metal ion centered, the new probe is largely spherical with a radius of 4.0 Å, permitting accurate back calculation of sPRE. The effectiveness Gd(III)-TTHA-TMA as a sPRE probe was demonstrated on three well-studied protein systems.

Subtle dynamics of holo glutamine binding protein revealed with a rigid paramagnetic probe

Bacterial periplasmic binding proteins (PBPs) are involved in the translocation of small molecules in the periplasm. To unload, the two domains of a PBP open up, allowing the ligand to exit. However, it is not clear whether there are dynamics near the binding site which can facilitate the rapid dissociation of a ligand. To visualize such dynamics, we utilized paramagnetic relaxation enhancement (PRE) NMR and introduced a rigid paramagnetic probe to a PBP, glutamine-binding protein (QBP) with its cognate ligand bound. A paramagnetic Cu(II) ion is sandwiched between an engineered di-histidine motif at a helix and an NTA capping molecule. The afforded paramagnetic probe is so rigid that PRE values calculated from a single structure of holo QBP largely agree with the observed values. The remaining PRE discrepancies, however, manifest dynamics of a loop in the opposite domain from the paramagnetic probe. This loop packs against the glutamine ligand in the holo QBP and undergoes fluctuations upon ligand dissociation, as assessed by steered molecular dynamics simulations. As such, the loop dynamics, occurring for a small population in nanosecond to microsecond time scale, may be related to the ligand dissociation process. The rigid paramagnetic probe described herein can be grafted to other protein systems for structure and dynamics studies.

Characterization of the Raptor/4E-BP1 interaction by chemical cross-linking coupled with mass spectrometry analysis

mTORC1 plays critical roles in the regulation of protein synthesis, growth, and proliferation in response to nutrients, growth factors, and energy conditions. One of the substrates of mTORC1 is 4E-BP1, whose phosphorylation by mTORC1 reverses its inhibitory action on eIF4E, resulting in the promotion of protein synthesis. Raptor in mTOR complex 1 is believed to recruit 4E-BP1, facilitating phosphorylation of 4E-BP1 by the kinase mTOR. We applied chemical cross-linking coupled with mass spectrometry analysis to gain insight into interactions between mTORC1 and 4E-BP1. Using the cross-linking reagent bis[sulfosuccinimidyl] suberate, we showed that Raptor can be cross-linked with 4E-BP1. Mass spectrometric analysis of cross-linked Raptor-4E-BP1 led to the identification of several cross-linked peptide pairs. Compilation of these peptides revealed that the most N-terminal Raptor N-terminal conserved domain (in particular residues from 89 to 180) of Raptor is the major site of interaction with 4E-BP1. On 4E-BP1, we found that cross-links with Raptor were clustered in the central region (amino acid residues 56-72) we call RCR (Raptor cross-linking region). Intramolecular cross-links of Raptor suggest the presence of two structured regions of Raptor: one in the N-terminal region and the other in the C-terminal region. In support of the idea that the Raptor N-terminal conserved domain and the 4E-BP1 central region are closely located, we found that peptides that encompass the RCR of 4E-BP1 inhibit cross-linking and interaction of 4E-BP1 with Raptor. Furthermore, mutations of residues in the RCR decrease the ability of 4E-BP1 to serve as a substrate for mTORC1 in vitro and in vivo.

Purification and Characterization of an Extracellular Acid Proteinase from the Ectomycorrhizal Fungus Hebeloma crustuliniforme

Hebeloma crustuliniforme produced an extracellular acid proteinase in a liquid medium containing bovine serum albumin as the sole nitrogen source. The proteinase was purified 26-fold with 20% activity recovery and was shown to have a molecular weight of 37,800 (as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and an isoelectric point of 4.8 +/- 0.2. The enzyme was most active at 50 degrees C and pH 2.5 against bovine serum albumin and was stable in the absence of substrates at temperatures up to 45 degrees C and pHs between 2.0 and 5.0. Pepstatin A, diazoacetyl-dl-norleucine methylester, metallic ions Fe and Fe, and phenolic acids severely inhibited the enzyme activity, while antipain, leupeptin, N-alpha-p-tosyl-l-lysine chloromethyl ketone, and trypsin inhibitor inhibited the activity moderately. The proteinase hydrolyzed bovine serum albumin and cytochrome c rapidly compared with casein and azocasein but failed to hydrolyze any of the low-molecular-weight peptide derivatives tested.

Detection and identification of avian, duck, and goose reoviruses by RT-PCR: goose and duck reoviruses are part of the same genogroup in the genus Orthoreovirus

A reverse transcription-polymerase chain reaction (RT-PCR) procedure for the detection of avian, duck, and goose reovirus (ARV, DRV, and GRV) RNA from cell culture supernatant and clinical samples was established. Based on multiple sequence alignment, a pair of degenerate primers was selected and synthesized. The amplified, cloned, and sequenced 598-base-pair products from the sigmaA-encoding gene fragment from 16 isolates (ranging over 30 years) indicated that the primer regions were well conserved. The sensitivity of this method was determined to be 10(-2) PFU. The specificity of the RT-PCR method was determined by testing specimens containing avian influenza A viruses, Newcastle disease virus, and infectious bronchitis virus, all of which yielded negative results with no discernible background. The efficiency of the system for detection of ARV, DRV, and GRV directly in 71/83 clinical samples was confirmed. The nucleotide sequence analysis indicated that DRV and GRV isolated from China in different locales and years were closely related, showing 97.4-100% homology to each other, but with only 86.7-88.5% identity to DRV 89026. The nucleotide and amino acid sequence identities in the amplified sigmaA-encoding gene were 74.2-78.4% and 86.9-92.0%, respectively, between duck/goose and chicken species. Phylogenetic analysis indicated that GRV and DRV aggregated into the same specified genogroup within subgroup II of the genus Orthoreovirus and are more closely related to ARV than to Nelson Bay virus. Overall, this study developed a sensitive and specific technique for the identification ARV, DRV, and GRV, and sequencing analysis has enhanced our understanding of the evolutionary relationship between ARV, DRV, and GRV.

A novel mutation in human PAX9 causes molar oligodontia

Experimental and animal studies, as well as genetic mutations in man, have indicated that the development of dentition is under the control of several genes. So far, mutations in MSX1 and PAX9 have been associated with dominantly inherited forms of human tooth agenesis that mainly involve posterior teeth. We identified a large kindred with several individuals affected with molar oligodontia that was transmitted as an isolated autosomal-dominant trait. Two-point linkage analysis using DNA from the family and polymorphic marker D14S288 in chromosome 14q12 produced a maximum lod score of 2.29 at theta = 0.1. Direct sequencing of exons 2 to 4 of PAX9 revealed a cytosine insertion mutation at nucleotide 793, leading to a premature termination of translation at aa 315. Our results support the conclusion that molar oligodontia is due to allelic heterogeneity in PAX9, and these data further corroborate the role of PAX9 as an important regulator of molar development.

Isolation and characterization of a gonadotropin-releasing hormone binding protein in goldfish serum

A binding protein (BP) specific for gonadotropin-releasing hormone (GnRH) was previously demonstrated in goldfish serum. In the present study the binding protein was isolated and further characterized. The GnRH-BP, partially purified from goldfish serum using polyacrylamide gel electrophoresis (PAGE) under nondenaturing conditions, was concentrated in a single band, separate from all major components of serum proteins. The binding ability of the partially purified GnRH-BP was conserved; the isolated GnRH-BP specifically bound salmon GnRH and chicken GnRH-II, the native forms of GnRH present in goldfish, but not other forms of GnRH. The relative binding affinity of the partially purified GnRH-BP was [D-Arg6,Pro9-NEt]-salmon GnRH greater than chicken GnRH-II greater than or equal to salmon GnRH. The GnRH-BP, in raw serum or partially purified by PAGE, was specifically covalently labeled using 125I-[D-Lys6,Pro9-NEt]-salmon GnRH and the bifunctional cross-linking reagent, disuccinimidyl suberate, and then subjected to sodium dodecyl sulfate-PAGE under reducing conditions. The location of the radiolabeled GnRH-BP on PAGE gels was determined by cutting gels into sections and counting the radioactivity, or by autoradiography; the molecular weight of the GnRH-BP was estimated to be 40 KD. The covalently labeled GnRH-BP extracted from SDS-PAGE was subjected to high pressure liquid chromatography, and it coeluted with a single protein peak of the GnRH-BP partially purified by PAGE under nonreducing conditions. These studies demonstrate that the GnRH-BP is a minor component of serum proteins in goldfish; it is a single nonglycoprotein of about 40 kDa.

Effects of ion-pairing reagents on the prediction of peptide retention in reversed-phase high-performance liquid chromatography

We have examined the resolution, on reversed-phase columns, of a series of model synthetic peptides and commercially available synthetic peptide standards under gradient elution conditions, using a water-acetonitrile mobile phase containing hydrophilic (phosphoric acid) or hydrophobic (trifluoroacetic acid, heptafluorobutyric acid) ion-pairing reagents. Increasing hydrophobicity or concentration of the ion-pairing reagents increased peptide retention times. It was clearly shown that these reagents effected changes in peptide retention time solely through interaction with the basic residues in the peptide. In general, each positive charge, whether originating from a lysine, arginine or histidine side-chain, or from an N-terminal alpha-amino group, exerts an equal effect on peptide retention. Different counterions have different effects on the change in peptide retention time per positively charged residue due to their differences in hydrophobicity. However, increasing concentrations of a specific counterion have an essentially equal effect per positively charged residue. These effects are also column dependent (n-alkyl chain length and ligand density). These results, demonstrating a simple relationship between peptide retention in different ion-pairing systems, enabled the determination of rules for prediction of peptide retention times in one ion-pairing system from observed or predicted retention times in another system. The small average deviation of predicted and observed retention times for a series of basic peptides was good evidence for the value of this predictive method. This study provides a clear understanding of the effect of changing counterion hydrophobicity or concentration on peptide retention, and thus can be extremely beneficial in the purification of peptides and for providing proof of peptide homogeneity.