Experience with SGLT2 Inhibitors in Patients with Single Ventricle Congenital Heart Disease and Fontan Circulatory Failure

Heart failure is the leading cause of morbidity and mortality in patients with Fontan circulation. Sodium-glucose-cotransporter 2 inhibitors (SGLT2i) have become a mainstay of heart failure therapy in adult patients, however, there remains a paucity of literature to describe its use in pediatric heart failure patients, especially those with single ventricle physiology. We describe our early experience using SGLT2i in patients with single ventricle congenital heart disease surgically palliated to the Fontan circulation. We conducted a single-center retrospective chart review of all patients with Fontan circulation who were initiated on an SGLT2i from January 1, 2022 to March 1, 2023. Patient demographics, diagnoses, clinical status, and other therapies were collected from the electronic medical record. During the study period, 14 patients (median age 14.5 years, range 2.0-26.4 years) with Fontan circulation were started on a SGLT2i. Mean weight was 54 kg (range 11.6-80.4 kg). Median follow-up since SGLT2i initiation was 4.1 months (range 13 days-7.7 months). Four patients had a systemic left ventricle and 10 had a systemic right ventricle. Half the patients had Fontan Circulatory Failure with reduced Ejection Fraction (FCFrEF) of the systemic ventricle and the other half had Fontan Circulatory Failure with preserved Ejection Fraction (FCFpEF) of the systemic ventricle. In addition, 3 patients experienced Protein Losing Enteropathy (PLE) and 2 patients had plastic bronchitis, one of whom also was diagnosed with chylothorax. There were no genitourinary infections, hypoglycemia, ketoacidosis, hypotension or other significant adverse effects noted in our patient population. One patient experienced significant diuresis and transient acute kidney injury. Patients with FCFrEF showed a decrease in natriuretic peptide levels. Given the lack of proven therapies, demonstrated benefits of SGLT2i in other populations, and some suggestion of efficacy in Fontan circulation, further study of SGTLT2i in patients with Fontan circulation is warranted.

Paediatric cardiology training: burnout, fulfilment, and fears

BACKGROUND

Burnout is well characterised in physicians and residents but not in paediatric cardiology fellows, and few studies follow burnout longitudinally. Training-specific fears have been described in paediatric cardiology fellows but also have not been studied at multiple time points. This study aimed to measure burnout, training-specific fears, and professional fulfilment in paediatric cardiology fellows with the attention to time of year and year-of-training.

METHODS

This survey-based study included the Professional Fulfillment Index and the Impact of Events Scale as well as an investigator-designed Fellow Fears Questionnaire. Surveys were distributed at three-time points during the academic year to paediatric cardiology fellows at a large Midwestern training programme. Fellow self-reported gender and year-of-training were collected. Descriptive analyses were performed.

RESULTS

10/17 (59%) of fellows completed all surveys; 60% were female, 40% in the first-year class, 40% in the second-year class, and 20% in the third-year class. At least half of the fellows reported burnout at each survey time point, with lower mean professional fulfilment scores. The second-year class, who rotate primarily in the cardiac ICU, had higher proportions of burnout than the other two classes. At least half of fellows reported that they "often" or "always" worried about not having enough clinical knowledge or skills and about work-life balance.

CONCLUSIONS

Paediatric cardiology fellows exhibit high proportions of burnout and training-specific fears. Interventions to mitigate burnout should be targeted specifically to training needs, including during high-acuity rotations.

Pediatric Heart Transplant Rejection After COVID-19 Infection

BACKGROUND

Infections have been associated with rejection episodes in solid organ transplant recipients. We report an association between COVID-19 infection and heart transplant (HT) rejection.

CASE DESCRIPTION

The patient was 14 years old and 6.5 years post-HT. He developed symptoms of rejection within 2 weeks of COVID exposure and presumed infection.

CONCLUSIONS

In this case, COVID-19 infection closely preceded significant rejection and graft dysfunction. Further study is needed to establish a correlation between COVID-19 infection and rejection in HT patients.

Medical and End-of-Life Decision-Making Preferences in Adolescents and Young Adults with Advanced Heart Disease and Their Parents

Importance

Despite high disease morbidity and mortality and complex treatment decisions, little is known about the medical and end-of-life decision-making preferences of adolescents and young adults (AYA) with advanced heart disease. AYA decision-making involvement is associated with important outcomes in other chronic illness groups.

Objective

To characterize decision-making preferences of AYAs with advanced heart disease and their parents and determine factors associated with these preferences.

Design, Setting, and Participants

Cross-sectional survey between July 2018 and April 2021 at a single-center heart failure/transplant service at a Midwestern US children's hospital. Participants were AYAs aged 12 to 24 years with heart failure, listed for heart transplantation, or posttransplant with life-limiting complications and a parent/caregiver. Data were analyzed from May 2021 to June 2022.

Main Outcomes and Measures

Single-item measure of medical decision-making preferences, MyCHATT, and Lyon Family-Centered Advance Care Planning Survey.

Results

Fifty-six of 63 eligible patients enrolled in the study (88.9%) with 53 AYA-parent dyads. Median (IQR) patient age was 17.8 (15.8-19.0) years; 34 (64.2%) patients were male, and 40 patients (75.5%) identified as White and 13 patients (24.5%) identified as members of a racial or ethnic minority group or multiracial. The greatest proportion of AYA participants (24 of 53 participants [45.3%]) indicated a preference for active, patient-led decision-making specific to heart disease management, while the greatest proportion of parents (18 of 51 participants [35.3%]) preferred they and physician(s) make shared medical decisions on behalf of their AYA, representing AYA-parent decision-making discordance (χ2 = 11.7; P = .01). Most AYA participants stated a preference to discuss adverse effects or risks of treatment (46 of 53 participants [86.8%]), procedural and/or surgical details (45 of 53 participants [84.9%]), impact of condition on daily activities (48 of 53 participants [90.6%]), and their prognosis (42 of 53 participants [79.2%]). More than half of AYAs preferred to be involved in end-of-life decisions if very ill (30 of 53 participants [56.6%]). Longer time since cardiac diagnosis (r = 0.32; P = .02) and worse functional status (mean [SD] 4.3 [1.4] in New York Heart Association class III or IV vs 2.8 [1.8] in New York Heart Association class I or II; t-value = 2.7; P = .01) were associated with a preference for more active, patient-led decision-making.

Conclusions and Relevance

In this survey study, most AYAs with advanced heart disease favored active roles in medical decision-making. Interventions and educational efforts targeting clinicians, AYAs with heart disease, and their caregivers are needed to ensure they are meeting the decision-making and communication preferences of this patient population with complex disease and treatment courses.

Data-driven computational models of ventricular-arterial hemodynamics in pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex disease involving increased resistance in the pulmonary arteries and subsequent right ventricular (RV) remodeling. Ventricular-arterial interactions are fundamental to PAH pathophysiology but are rarely captured in computational models. It is important to identify metrics that capture and quantify these interactions to inform our understanding of this disease as well as potentially facilitate patient stratification. Towards this end, we developed and calibrated two multi-scale high-resolution closed-loop computational models using open-source software: a high-resolution arterial model implemented using CRIMSON, and a high-resolution ventricular model implemented using FEniCS. Models were constructed with clinical data including non-invasive imaging and invasive hemodynamic measurements from a cohort of pediatric PAH patients. A contribution of this work is the discussion of inconsistencies in anatomical and hemodynamic data routinely acquired in PAH patients. We proposed and implemented strategies to mitigate these inconsistencies, and subsequently use this data to inform and calibrate computational models of the ventricles and large arteries. Computational models based on adjusted clinical data were calibrated until the simulated results for the high-resolution arterial models matched within 10% of adjusted data consisting of pressure and flow, whereas the high-resolution ventricular models were calibrated until simulation results matched adjusted data of volume and pressure waveforms within 10%. A statistical analysis was performed to correlate numerous data-derived and model-derived metrics with clinically assessed disease severity. Several model-derived metrics were strongly correlated with clinically assessed disease severity, suggesting that computational models may aid in assessing PAH severity.

Indole-3-carbinol inhibits the proliferation of colorectal carcinoma LoVo cells through activation of the apoptotic signaling pathway

Indole-3-carbinol (I3C) is a phytochemical that exhibits growth-inhibitory activity against various cancer cells. However, there are limited studies on the effects of I3C on colon cancer cells. In this study, the growth-inhibitory activity of I3C against the human colorectal carcinoma cell line (LoVo) was examined. The results of the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide, colony formation, and cell counting assays revealed that I3C suppressed the proliferation of LoVo cells. Microscopy and wound-healing analyses revealed that I3C affected the morphology and inhibited the migration of LoVo cells, respectively. I3C induced apoptosis and DNA fragmentation as evidenced by the results of fluorescein isothiocyanate-conjugated annexin V staining and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling assay, respectively. Additionally, I3C arrested the cell cycle at the G0/G1 phase and enhanced the reactive oxygen species levels. Western blotting analysis revealed that treatment with I3C resulted in the activation of apoptotic proteins, such as poly(ADP-ribose) polymerase, caspase-3, caspase-7, caspase-9, Bax, Bim, and p53 in LoVo cells. These results indicate that I3C induces apoptosis in LoVo cells by upregulating p53, leading to the activation of Bax and caspases. Taken together, I3C exerts cytotoxic effects on LoVo cells by activating apoptosis.

Burnout, professional fulfillment, and post-traumatic stress among pediatric solid organ transplant teams

BACKGROUND

Adverse effects of clinician burnout have been studied across multiple specialties; however, there have been no studies examining rates of burnout among pediatric solid organ transplant teams. This study aimed to measure burnout, work exhaustion, professional fulfillment, and post-traumatic stress symptoms among clinicians and administrators practicing in this high-stress field.

METHODS

This cross-sectional study utilized a 50 item web-based survey that included the Personal Fulfillment Index and the IES-R. This survey was distributed across four pediatric solid organ transplant centers in North America. Basic demographics, clinician characteristics, and information regarding wellness and self-care activities were collected. Descriptive and correlational analyses were performed.

RESULTS

One hundred and thirty five participants completed the survey, 76% were female and 78% were Caucasian. One-third (34%) of participants endorsed burnout, while 43% reported professional fulfillment. Approximately 15% of respondents endorsed clinically significant levels of post-traumatic stress symptoms related to patient deaths, with female clinicians more likely to endorse symptoms (p = .01). Nearly 80% of participants reported engaging in self-care activities outside of work and only 10% of participants reported participation in hospital-sponsored wellness programs.

CONCLUSIONS

Pediatric solid organ transplant team members exhibited moderate levels of burnout, professional fulfillment, and post-traumatic stress. Female clinicians were the most likely to experience both work exhaustion and post-traumatic stress symptoms. Transplant centers are encouraged to consider interventions and programming to improve clinician wellness.

Psychosocial outcomes in pediatric patients with ventricular assist devices and their families: A systematic review

Ventricular assist device (VAD) therapy has provided pediatric patients with severe heart failure new therapeutic options. However, pediatric patients and families receiving VAD therapy also experience psychosocial challenges. No synthesis of the literature on psychosocial outcomes within the pediatric VAD population has been conducted; thus, the current review sought to systematically investigate the impact of pediatric VAD on patient, parent, and family psychosocial outcomes and assess variables associated with poorer outcomes. Literature searches were conducted in PsycInfo, PubMed, and Cumulative Index to Nursing and Allied Health Literature databases and full texts were assessed according to pre-established inclusion criteria. Main findings and study quality were reviewed. Sixteen studies were included in the present review. Findings highlighted the likelihood for psychological sequelae among pediatric patients and families receiving VAD therapy, including decreased psychological and emotional well-being, elevated stress, and difficulty coping with changes to family dynamics and responsibilities. Health-related quality of life was reported comparable to that of healthy peers and children with other cardiac conditions. Patients and families on VAD therapy experience significant difficulties in psychological well-being and challenges related to adjustment. The current review underscores the importance of ongoing support for families and continued assessment of psychosocial functioning across VAD support. Three critical periods for increased distress were identified: 1) immediately following VAD implantation, 2) discharge home and the weeks following discharge, and 3) long-term VAD therapy.

The Korean version of the Carpal Tunnel Questionnaire. Cross cultural adaptation, reliability, validity and responsiveness

The purpose of this study was to translate and culturally adapt the Carpal Tunnel Questionnaire to produce an equivalent Korean version. A total of 53 patients completed the Korean version of the Carpal Tunnel Questionnaire pre-operatively and 3 months after open carpal tunnel release. All 53 also completed the Korean version of the Disabilities of Arm, Shoulder, and Hand questionnaire pre-operatively and 3 months post-operatively. Reliability was measured by determining the test-retest reliability and internal consistency. Test-retest reliability was assessed using intraclass correlation coefficients and paired t-tests, and internal consistency using Cronbach's alpha coefficients. Pearson correlation analysis was carried out on the Korean version of the Carpal Tunnel Questionnaire scores and the Korean version of the Disabilities of Arm, Shoulder, and Hand scores to assess construct validity. Responsiveness was evaluated using effect sizes and standardized response means. The reliability of the Korean version of the Carpal Tunnel Questionnaire was good. The scores in the Korean version of the Disabilities of Arm, Shoulder, and Hand strongly correlated with the scores in the Korean version of the Carpal Tunnel Questionnaire. Standardized response mean and effect size were both large for the Korean version of the Carpal Tunnel Questionnaire. The study shows that the Korean version of the Carpal Tunnel Questionnaire is a reliable, valid and responsive instrument for measuring outcomes in carpal tunnel syndrome.

Decision support for ecological river rehabilitation using fish habitat database

After the recent success of several river rehabilitation projects including the Cheong-gye river case, a large number of local governments have been promoting their own projects in Korea. Most of the projects are aimed at securing the soundness of aquatic ecosystems according to the guidelines presented by the Korea Ministry of Environment. However, there is no clear guidance for the management goals of water quality and quantity. In this study, we have made an attempt to construct a habitat database (DB) for each domestic freshwater fish species. The fish population, and physical and physicochemical properties of the habitat of 70 domestic freshwater fish species were investigated using field monitoring data. After the statistical processing, the inhabitable range and optimal range of each species were suggested. Furthermore, based on the DB, a decision support system for ecological river restoration and rehabilitation has been developed, and applied for field tests. It became clear that the decision support procedure based on the fish habitat DB is useful in the planning stage of river rehabilitation projects to select the flagship fish, to decide the restoration goals considering their appropriate habitat and to suggest the optimum quantitative combination of each available water resource.

Quartiles of peak troponin are associated with long-term risk of death in type 1 and STEMI, but not in type 2 or NSTEMI patients

BACKGROUND

The prognostic value of peak cardiac troponin (cTn) in different types of acute myocardial infarction (AMI) under the universal clinical classification is unknown.

HYPOTHESIS

We tested the hypothesis that the prognostic value of cTn varies with its peak level and type of AMI.

METHODS

We studied 345 consecutive patients with AMI with mean follow-up of 30.6 months according to quartiles of peak cTn level (QPTL) and the type of AMI. The study outcomes were the major adverse cardiovascular events (MACE; composite of all causes of mortality and recurrent AMI) and the individual components of MACE.

RESULTS

The study included patients with AMI Type 1 (n = 276), type 2 (n = 54), ST-segment elevation myocardial infarction (STEMI; n = 159), and non-ST-segment elevation myocardial infarction (NSTEMI; n = 186). Overall, peak cTn level was an independent predictor of MACE (hazard ratio [HR]: 1.001, 95% confidence interval [CI]: 1.000-1.003, P = 0.01) and death (HR: 1.002, 95% CI: 1.001-1.004, P = 0.003), but not of recurrent AMI. The highest risk of MACE and death was in the highest QPTL (61.6%, P = .016 and 66.3%, P = 0.021, respectively) while the highest risk of recurrent AMI was in the lowest QPTL (83.7%, P = 0.04). Quartiles of peak cTn level were significantly associated with increased risk of MACE and death in patients with Type 1 (all P = 0.01) and STEMI (P = 0.01 and P = 0.02, respectively), but no association existed in type 2 or NSTEMI patients.

CONCLUSIONS

Overall, peak cTn predicts the risk of MACE and death but not the risk of AMI. While in Type 1 and STEMI patients, QPTL are associated with risk of MACE and death, no association exists in type 2 or NSTEMI patients.

A "master" in base unpairing during isomerization of a promoter upon RNA polymerase binding

Isomerization of a closed to open complex of a promoter upon RNA polymerase binding involves base unpairing at the -10 region. After potassium permanganate sensitivity of unpaired thymine residues, we studied base unpairing at the -10 region during isomerization upon RNA polymerase binding at the P1 and P3 promoters of the gal operon. Substitution of adenine by 2-amino purine (2-AP) at the invariable A small middle dotT base pair at the -11 position of P1 and P3 prevented unpairing not only at that position but also at the other downstream positions, suggesting a "master" role of the adenine base at -11 of the template strand in overall base unpairing. 2-AP at -11 did not inhibit the formation of RNA polymerase small middle dotpromoter complex and subsequent isomerization of the polymerase. Substitution of adenine by 2-AP at several other positions did not affect thymine unpairing. Changing the position of the amino group from C6 in adenine to C2 in 2-AP is mutational only at the master switch position, -11.

Effects of dimer interface mutations in Hin recombinase on DNA binding and recombination

Previous biochemical assays and a structural model of the protein have indicated that the dimer interface of the Hin recombinase is composed of two alpha-helices. To elucidate the structure and function of the helix, amino acids at the N-terminal end of the helix, where the two helices make their most extensive contact, were randomized, and inversion-incompetent mutants were selected. To investigate why the mutants lost their inversion activities, the DNA binding, hix pairing, invertasome formation, and DNA cleavage activities were assayed using in vivo and in vitro methodologies. The results indicated that the mutants could be divided into four classes based on their DNA binding activity. We propose that the alpha-helices might serve to place a DNA binding motif of Hin in the correct spatial relationship to the minor groove of the recombination site. All the mutants except those that failed to bind DNA were able to perform hix pairing and invertasome formation, suggesting that the dimer interface is not involved in either of these processes. The inversion-incompetent phenotype of the binders was caused by the inability of mutants to perform DNA cleavage. The mutants that showed less binding ability than the wild type nevertheless exhibited a wild-type level of hix pairing activity, because the hix pairing activity overcomes the defect in DNA binding. This phenotype of the mutants that are impaired in DNA binding suggests that the binding domains of Hin may mediate Hin-Hin interaction during hix pairing.

Kainate-induced neuronal injury leads to persistent phosphorylation of cAMP response element-binding protein in glial and endothelial cells in the hippocampus

Intracerebroventricular kainate treatment in rats induces neuronal cell death, followed by proliferation and hypertrophy of glial cells in the lesioned area. To further understand the activated signal transduction pathways and to get insights into potential target gene activation, the present study aims to elucidate long-term effects on the phosphorylation state of cAMP response element-binding protein (CREB) in the hippocampal formation. One to four weeks after kainate injection, we found high levels of phosphorylated and hence activated CREB (pCREB) in glial cells of the degenerating CA fields. As shown by electron microscopy, pCREB immunoreactivity was present in reactive astrocytes, oligodendrocyte precursor cells and endothelial cells of blood vessels. It is postulated that pCREB could drive the expression of downstream genes in these cells to promote cell proliferation and survival.

In vivo assay of protein-protein interactions in Hin-mediated DNA inversion

In order to form the catalytic nucleoprotein complex called the invertasome in the Hin-mediated DNA inversion reaction, interactions of the DNA-binding proteins Hin and Fis are required. Assays for these protein-protein interactions have been exploited with protein cross-linkers in vitro. In this study, an in vivo assay system that probes protein-protein interactions was developed. The formation of a DNA loop generated by protein interactions resulted in transcriptional repression of an artificially designed operon, which in turn increased the chance of survival of Escherichia coli host cells in a streptomycin-containing medium. Using this system, we were able to assay the Hin-Hin interaction that results in the pairing of the two recombination sites and protein interactions that result in the formation of the invertasome. This assay system also led us to find that an individual Hin dimer bound on a recombination site can form a stable complex with Fis bound on the recombinational enhancer; this finding has never been observed in in vitro studies. Possible pathways toward the formation of the invertasome are discussed based on the assay results for a previously reported Hin mutant.

The role of polarization of Xe by di- and monovalent cations in 129Xe NMR studies in zeolite A

We consider the role of polarization in the adsorption of Xe in zeolites of type A by direct comparative analysis of the adsorption isotherms, distributions of occupancies, and 129Xe NMR chemical shifts of Xe(n) in cages containing CaxNa12-2x ions per alpha cage (x = 0, 1, 2, 3, 5). We find that the qualitative trends in the adsorption isotherms, and in the progressions of Xe(n) chemical shifts (for n = 0-8 in cages with x = 0, 1 Ca2+ ions and for n = 0-5 in cages with x = 2, 3 Ca2+ ions) upon increasing the level of Ca2+ ion for Na+ ion substitution could only be accounted for by including polarization of the Xe atom by the zeolite framework and its ions. This system, which permits observation of individual Xe(n) peaks and of directly comparable adsorption isotherms in several cage types, provides a good model system for the interpretation of the more general case in which only the overall average 129Xe NMR chemical shift is observed in open network zeolites, arising from free exchange of Xe among cavities of variable occupancy and variable cation distribution.

Hin-mediated inversion on positively supercoiled DNA

Hin recombinase requires negatively supercoiled DNA for an efficient inversion. We have generated positively supercoiled plasmid DNA using reverse gyrase from Sulfolobus shibatae and subjected it to the Hin-mediated inversion reaction. Both Hin and Fis showed the same DNA binding activity regardless of the superhelical handedness of the substrate plasmid. However, inversion activity on positively supercoiled DNA was less than 1% of negatively supercoiled DNA. Assays designed to probe steps in inversion, showed that on positively supercoiled DNA, Hin was able to cleave the recombination sites with the same efficiency shown on negatively supercoiled DNA but was not able to exchange the cleaved DNA. Based on the theoretical differences between positive and negative supercoiling, our data may suggest that unwinding of the double helix at recombination sites is needed after DNA cleavage for strand exchange to occur.

A clinical investigation of the efficacy of low level laser therapy in reducing orthodontic postadjustment pain

Low level laser therapy (LLLT) has been shown to produce analgesic effects in many clinical applications. The aim of this clinical study was to test the efficacy of LLLT in controlling orthodontic postadjustment pain. Thirty-nine volunteers were selected for this study that used a double-blind design with placebo control. Elastomeric separators were placed at the proximal contacts of one premolar in each quadrant of the dentition to induce orthodontic pain. The tip of a 30 mW gallium-arsenide-aluminium (830 nm) diode laser probe was then placed at the buccal gingiva and directed at the middle third of the root. Three different treatment durations of 15, 30, and 60 seconds and one placebo treatment of 30 seconds were tested within each subject. The study was conducted over 5 days, and the visual analogue scale (VAS) was used to quantify the pain experienced by the subjects before and after laser applications for each day. Analysis of the VAS median scores showed that teeth exposed to laser treatment had lower levels of pain as compared with those with the placebo treatment. However, nonparametric statistical analysis of the data showed that the differences between treatments and placebo within each subject were not statistically significant.

Analysis of subunit interaction by introducing disulfide bonds at the dimerization domain of Hin recombinase

The Hin recombinase exists as a homodimer in solution and binds to its recombination site (hix) as a dimer (Glasgow, A. C., Bruist, M. F., and Simon M. I. (1989) J. Biol. Chem. 264, 10072-10082). Previous mutational and structural studies of related proteins suggested the location of a putative dimerization domain. In order to probe the function of this region of the protein, cysteine residues were introduced at each of the seven positions comprising the domain. Proteins containing cysteine substitutions at positions 101 and 104 were able to form disulfide bonds spontaneously in crude extracts. M101C showed wild type inversion activity only if the cysteine residue was not engaged in a disulfide bond. This mutant, which is cross-linked by a disulfide bond at the dimeric interface, was found to be defective in the DNA cleavage step during inversion. H107C displayed the wild type DNA cleavage activity, even though its DNA binding activity was not detected by three different binding assays. This suggests that it maintains specificity for DNA binding but dissociates rapidly after binding. The remaining inversion-defective mutants fell into two groups. One group lost its capacity to specifically bind to DNA (G102C, F105C, and F106C), and the other group (R103C and F104C), while able to bind to DNA, was defective in subsequent steps of the inversion reaction. Characteristics of these mutants led me to postulate that movement of subunits at the dimerization interface is critical during DNA binding and during formation of the invertasome, which is the recombination structure. Furthermore, the relative position of subunits within the dimer may be important for maintaining stable DNA binding.

Molecular cloning and sequencing of sulfated glycoprotein-2 cDNA from testis of mouse: implications of two different mRNAs of SGP-2

We cloned a mouse homolog of sulfated glycoprotein-2 (SGP-2) cDNA by screening a mouse testicular cDNA library and its nucleotide sequence was determined. The predicted amino acid sequence of the cDNA shares 93% identity with that of rat SGP-2. The nucleotide sequences of both cDNAs show extensive homology throughout the open reading frames and 3' untranslated regions. The 5' untranslated regions, however, share homology only up to 28 bp upstream from the start codons; the rest of sequences are quite different. DNA sequence homology search to mouse SGP-2 cDNA through the EMBL/GenBank database and a recent study on the genomic organization of rat TRPM-2 gene suggest a possibility that there are at least two different SGP-2 mRNAs as a result of alternative splicing and/or different promoter usage in mouse.

The role of negative supercoiling in Hin-mediated site-specific recombination

A series of biochemical assays were developed and performed to monitor the molecular events that occur during the Hin-mediated DNA inversion reaction. These events can be divided into five different stages: 1) binding of proteins (Hin, Fis, and HU) to DNA; 2) pairing of Hin-binding sites; 3) invertasome formation; 4) DNA strand cleavage; 5) strand rotation and religation. A series of topoisomers of the wild type DNA substrate plasmid (ranging from fully relaxed molecules to those with more than the physiological superhelical density (the physiological superhelical density of pKH336 from Escherichia coli DH10B is -0.072 in this study)) was generated, and the role of negative supercoiling in each step of the inversion reaction was investigated. We found differences in the dependence of the formation of paired Hin-binding sites and of the invertasome formation on the superhelical density of the substrate plasmid. Pairing of Hin-binding sites occurs independently from invertasome formation, and a relatively low degree of negative supercoiling is enough to promote maximal pairing. However, efficient invertasome formation requires higher levels of negative supercoiling.

The effects of symmetrical recombination site hixC on Hin recombinase function

An artificial recombination site hixC composed of two identical half-sites that bind the Hin recombinase served as a better operator in vivo than the wild type site hixL (Hughes, K. T., Youderian, P., and Simon, M. I (1988) Genes & Dev. 2, 937-948). In vitro binding assays such as gel retardation assay and methylation protection assay demonstrated that Hin binds to hixC as tightly as it binds to hixL, even when the sites are located in negatively supercoiled plasmids. However, hixC served as a poor recombination site when it was subjected to the standard inversion assay in vitro. hixC showed a 16-fold slower inversion rate than the wild type. A series of biochemical assays designed to probe different stages of the Hin-mediated inversion reaction, demonstrated that Hin dimers bound to hixC have difficulty in forming paired hix site intermediates. KMnO4 and S1 nuclease assays detected an anomalous structure of the center of hixC only when the site was in negatively supercoiled plasmids. Mutational analysis in the central region of hixC and assays of paired hix site formation with topoisomers of the hixC substrate plasmid suggested that Hin is not able to pair hixC sites because of the presence of the anomalous structure in the center of the site. The structure does not behave like a DNA "cruciform" since Hin dimers still bind efficiently to the site. It is thought to consist of a short denatured "bubble" encompassing 2 base pairs. During the study of mutations in the center of hixC, it was found that Hin is not able to cleave DNA if a guanine residue is one of the two central nucleotides close to the cleavage site. Furthermore, Hin acts in a concerted fashion and cannot cleave any DNA strand if one of the four strands in the inversion intermediate is not cleavable.

Site-directed mutagenesis of dicarboxylic acids near the active site of Bacillus cereus 5/B/6 beta-lactamase II

An amino acid residue functioning as a general base has been proposed to assist in the hydrolysis of beta-lactam antibiotics by the zinc-containing Bacillus cereus beta-lactamase II [Bicknell & Waley (1985) Biochemistry 24, 6876-6887]. Oligonucleotide-directed mutagenesis of cloned Bacillus cereus 5/B/6 beta-lactamase II was used in an 'in vivo' study to investigate the role of carboxy-group-containing amino acids near the active site of the enzyme. Substitution of asparagine for the wild-type aspartic acid residue at position 81 resulted in fully functional enzyme. An aspartic acid residue at position 90 is essential for beta-lactamase II to confer any detectable ampicillin and cephalosporin C resistance to Escherichia coli. Conversion of Asp90 into Asn90 or Glu90 lead to the synthesis of inactive enzyme, suggesting that the spatial position of the beta-carboxy group of Asp90 is critical for enzyme function.

Some factors that influence the plasma lipoprotein 1H NMR spectra of normal and cancer patients: an oncolipid test?

Selected factors have been evaluated in order to determine their influences on the plasma lipoprotein proton NMR spectra of normal and cancer patients. The variables were donor's diet (fasting/non-fasting), temperature and time of sample storage, processing procedure, centrifugation speed, and water pre-saturation time. Plasma samples from fasting individuals that were placed immediately on ice, spun at 1,000 and 3,000 g for 15 minutes, and the proton NMR spectrum acquired with the Carr-Purcell Meiboom-Gill (CPMG) pulse sequence, using a two-second water pre-saturation time, consistently gave reproducible results. Resonances attributed to lactate were minimized under these processing conditions. Centrifugation speed and pre-saturation time did not affect the average line width; however, donor fasting state, processing temperature, and storage time did alter the line width. Most important, blood chemistry analysis revealed an inverse correlation between triglyceride levels and average methyl and methylene line widths. Thus, these factors alone caution against the indiscriminate use of proton NMR spectra to differentiate plasma from normal and cancer patients.

Mutations affecting the catalytic activity of Bacillus cereus 5/B/6 beta-lactamase II

Random in vitro mutagenesis of a cloned Bacillus cereus 5/B/6 beta-lactamase II gene was used to select defective genes unable to confer ampicillin or cephalosporin C resistance to Escherichia coli. DNA sequencing of mutant genes identified histidine at position 28 as important to beta-lactamase II function. In addition, the isolation of six identical frameshift mutants established that the carboxyl-terminal end of beta-lactamase II is critical for enzyme function. Random mutagenesis also revealed that His88 (implicated previously as one of 4 residues acting as a zinc ligand) is crucial to enzymatic activity and that a glycine to glutamic acid substitution at position 148 produced a defective beta-lactamase. Oligonucleotide mutagenesis directed at Glu37 and Glu212 suggests that these residues are inconsequential to enzyme function but that histidine at position 28 may be involved in substrate binding or recognition.

Lichen planus: a study of 72 cases in Singapore

Seventy-two patients attending this hospital with a diagnosis of lichen planus were examined. There was a striking predominance of Indians (69%) and a surprisingly low incidence of Chinese (24%) and Malays (4%) in the study population, compared to the racial composition of the general clinic population. The age distribution curve of the study population was bimodal with peaks at age groups 21-30 (22%) and 41-60 (33%) years. The most common morphologic variant was lichen planus vulgaris (common type) which we observed in 46 (64%) patients, followed by lichen planus hypertrophicus in 8 (11%) and lichen planus atrophicus in 2 (3%). Lichen planus confined to the skin was observed in 49 (68%) patients. Mucous membrane involvement was seen in 21 (29%)-17 (24%) had oral mucosa membrane involvement and 4 (6%) genital mucous membrane involvement. In 16 (22%) cases, mucous membranes were exclusively involved--12 (17%) had oral mucous membrane involvement and 4 (6%) genital mucous membrane involvement. Nail changes were only observed in 2 (3%) patients. Eight (11%) patients had associated diabetes mellitus. Overall, lichen planus appeared to pursue a protracted course with only 4 (6%) patients clearing completely after a disease duration of 5-12 months.

Chicken riboflavin-binding protein. cDNA sequence and homology with milk folate-binding protein

The Rd gene is expressed in the livers and oviducts of laying hens and codes for the riboflavin-binding protein (RfBP) of egg yolk and egg white. A lambda gt11 cDNA library derived from chicken oviduct poly(A)+ RNA was screened with polyclonal rabbit antiserum to chicken RfBP. Positive clones were isolated and rescreened with a mixed oligonucleotide probe corresponding to residues 20-25 of the mature protein. The largest cDNA clone (969 base pairs) was subcloned into plasmid pIBI21, and the nucleotide sequence was determined by the dideoxynucleotide method. This clone contained the entire coding region for RfBP. The published amino acid sequence of the mature protein was confirmed. In addition, the following 17-residue signal peptide was deduced: Met-Leu-Arg-Phe-Ala-Ile-Thr-Leu-Phe-Ala-Val-Ile-Thr-Ser-Ser-Thr-Cys. Unexpectedly, the nucleotide sequence codes for 2 adjacent arginine residues at the carboxyl terminus that are not observed in the mature protein. The amino acid sequence of RfBP is homologous with bovine milk folate-binding protein. Eight of the nine pairs of cysteines involved in disulfide bonds in RfBP are conserved in folate-binding protein, as are all of the tryptophan residues. Sequence identity between homologous regions of these two vitamin-binding proteins is more than 30%.

Cloning, nucleotide sequence, and expression of the Bacillus cereus 5/B/6 beta-lactamase II structural gene

Two forms of heat-stable, zinc-containing beta-lactamase II have been described for strains of Bacillus cereus and have been shown to differ in substrate specificity (R. B. Davies, E. P. Abraham, J. Fleming, and M. R. Pollock, Biochem. J. 145: 409-411, 1975). We report here the nucleotide sequence, inferred amino acid sequence, and expression of beta-lactamase II from B. cereus 5/B/6 and compare our results with those for its homolog characterized in B. cereus 569/H (M. Hussain, C. Anthony, M. J. Madonna, and J. O. Lampen, J. Bacteriol. 164: 223-229, 1985) to document amino acid differences contributing to the specific properties of these enzymes.

Optimal conditions for supercoil DNA sequencing with the Escherichia coli DNA polymerase I large fragment

Sequencing ladders produced from supercoiled DNA templates with the Escherichia coli DNA polymerase Klenow fragment are often unreadable because of a high background and misincorporated nucleotides. This study showed that contaminating RNA molecules can interfere with template:primer hybridization. Procedures are provided for the purification of template DNA and stringent conditions for primer-template hybridization that overcome these problems.