Salus Platform: A Digital Health Solution Tool for Managing Syphilis Cases in Brazil-A Comparative Analysis

(1) Introduction: Syphilis is a sexually transmitted infection (STI) that constitutes a serious public health problem in Brazil and worldwide; (2) Methods: This was a descriptive and exploratory study that sought to analyze and compare the characteristics of Brazilian health systems with a new platform (Salus) developed by the Laboratory of Technological Innovation in Health in the scope of notification and management of disease data, including syphilis. In addition, this analysis aimed to assess whether Salus fully meets the necessary data management fields and can be indicated as a tool to improve health management in the context of syphilis in Brazil. (3) Results: In this study, the Salus functionalities were demonstrated and compared with the current Brazilian systems by discovering the existing gaps in the evaluated systems. The gaps found may explain the delay in meeting demands, the difficulty of making routine therapeutic follow-ups, in addition to interference with the vital purpose of follow-up in the epidemiological surveillance of diseases. As a result, Salus demonstrates functionalities that surpass all others and meet case management demands in a superior way to the systems currently used in the country. (4) Conclusions: The Brazilian health information systems related to the response to syphilis do not fulfill the purpose for which they were developed. Instead, they contribute to the fragmentation of health data and information, delays in diagnosis, incomplete case management, and loss of data due to inconsistencies and inadequate reporting. In addition, they are systems without interconnection, which do not articulate epidemiological surveillance actions with primary health care. All these factors may be obscuring accurate data on syphilis in Brazil, resulting in high and unnecessary public spending and late care for users of the Unified Health System (SUS).

Histology-verified myocardial fibrosis and quantification in severe AS patients: correlation with non-invasive LV myocardial tissue assessment

Background

Myocardial fibrosis (MF) is a common finding and a potential adverse prognostic marker in several cardiac diseases, including in severe aortic stenosis (AS). While histological analysis obtained through endomyocardial biopsy remains the gold-standard for MF assessment, non-invasive cardiac imaging may offer surrogate biomarkers for fibrosis. We tried to assess the correlation between MF quantification at histopathology and cardiac magnetic resonance (CMR)-derived tissue characterization data in patients with severe AS.

Methodology

Single-center prospective cohort enrolling 71 patients with severe symptomatic high-gradient AS undergoing surgical aortic valve replacement (SAVR) (mean age 71±9 years; 49% male, mean valvular transaortic gradient 60±20 mmHg; mean left ventricle [LV] ejection fraction 58±9%). Those with past history of myocardial infarction or cardiomyopathy were excluded. All patients underwent pre-operative CMR study with LV tissue characterization and quantification. Normal T1 mapping value was defined as >1021ms as per center protocol. Myocardial tissue was obtained during SAVR either through myocardial biopsy at basal LV septum or harvested from surgical myectomy specimens. Masson's trichrome stain was used for collagen/fibrosis assessment. Automatic quantification was obtained at QuPathTM digital pathology software after applying a dedicated artificial intelligence algorithm on ultra-high-resolution digital slide scanning images.

Results

Histology-confirmed MF was observed in all patients (median percentage of fibrotic myocardial tissue 15% [IQR 9–22%]). Median global T1 mapping and extracellular volume (ECV) percentage was 1048ms (IQR 1027–1078) and 24% (IQR 20–30%), respectively. Late gadolinium enhancement (LGE) with a non-ischemic pattern was present in 42 patients (59%) with a median LGE mass of 5.8g [IQR 1.0–10.2]; median percentage of 3.7% [IQR 0.6–10.4]. While neither T1 mapping (global or basal LV septum), ECV nor LGE had any significant correlation with histology-confirmed MF (Figure 1) the vast majority had significantly elevated global and basal LV septum T1 mapping – 81% and 92%, respectively.

Conclusion

In this single-center prospective study, microscopic MF was present in all patients with severe symptomatic high-gradient AS, was accompanied by elevated T1 mapping values but no correlation was found between myocardial fibrosis at histopathology analysis and CMR-derived LV tissue characterization parameters. This may not only stem from sampling (single point biopsy vs. whole myocardial tissue assessment) but also from distinct evaluation of different types of fibrosis by different methods.

Funding Acknowledgement

Type of funding sources: None.

Late gadolinium enhancement patterns in severe symptomatic high-gradient aortic stenosis

Background

Left ventricular (LV) remodeling in patients with severe aortic valve stenosis (AS) is a complex process that goes beyond hypertrophic response and may involve reparative/replacement fibrosis. Currently, cardiac magnetic resonance (CMR) is the gold-standard imaging technique for detecting focal myocardial fibrosis through late gadolinium enhancement (LGE). However, myocardial fibrosis prevalence and distribution is quite variable among series. Our goal was to assess LGE prevalence and distribution pattern in severe symptomatic high-gradient AS.

Methodology

Single-center prospective cohort of 132 patients with severe symptomatic high-gradient AS (mean age 73±11 years; 48% male, mean valvular transaortic gradient 60±20 mmHg; mean aortic valve area 0.7±0.2 cm2/m2; mean LV ejection fraction by 2D echocardiogram 58±9%), all with normal flow (except one) undergoing surgical aortic valve replacement. Those with previous history of acute myocardial infarction, ischemic cardiomyopathy or other cardiomyopathy were excluded. All patients performed 1.5T CMR assessment with LV myocardium tissue characterization prior to surgery. Segmental LGE presence was assessed by two independent operators and classified according to the AHA 16 segment model, using 5-standard deviations from remote myocardium as the signal intensity cut-off for LGE identification and quantification.

Results

Overall, 96 patients (74%) had non-ischemic LGE (median LGE mass 3.2 g [IQR 0.2–8.3] g; median percentage of LGE myocardial mass 2.5% [IQR 0.1–6.1]%); 22 patients [17%] with exclusively junctional LGE); in one patient an incidental ischemic scar (subendocardial distribution) was identified. No cases of subepicardial distribution were found. Intramyocardial LGE was most frequently observed in basal and mid-anterior and inferior interventricular septum – see Figure 1. In these segments, LGE was most often junctional at right-ventricular insertion points (54%), followed by mid-wall LGE (32%) or both sites involvement (14%).

Conclusion

LGE is frequent in symptomatic high-gradient AS patients with preserved left ventricular ejection fraction, most often presenting as junctional enhancement in basal/mid-anterior and inferior interventricular septum. Future studies may address whether distinct LGE patterns may impact patient prognosis.

Funding Acknowledgement

Type of funding sources: None.

Left ventricular myocardial work in patients with high gradient severe symptomatic aortic stenosis

Background

Left ventricular myocardial work (LVMW) is a novel method to evaluated left ventricular (LV) function using pressure-strain loops. It might correct global longitudinal strain (GLS) for afterload, being eventually useful to assess whether GLS reduction is due to reduced contractility (reflected as reduced myocardial work) or increased afterload (reflected as increased myocardial work).

Aim

To describe indices of LVMW in a group of patients with severe symptomatic aortic stenosis (AS).

Methods

We prospectively studied 104 consecutive patients (age: 71 years [IQR 66.5–75.5] years, 51% men) with severe symptomatic high gradient AS: mean transaortic pressure gradient: 56.5mmHg [IQR 46.8–67.8]; aortic valve area: 0.73cm2 [IQR 0.61–0.88]; indexed stroke volume: 47.7±1.3 mL/m2 (11 patients with low-flow AS), preserved LV ejection fraction (EV) (LVEF: 56.0% [51.0–61.3]; GLS: −14.5% [IQR −16.1 to −10.6]), with no previous coronary artery disease and no history of cardiomyopathy. Beyond complete transthoracic echocardiography, all patients underwent cardiac magnetic resonance for LV myocardium tissue characterization. As proposed for AS, LV systolic pressure was corrected adding the mean transaortic pressure gradient to non-invasive systolic blood pressure cuff measurement in the echocardiographic algorithm. Four LVMW indices were collected in 83 patients (patients excluded for atrial fibrillation, left bundle branch block or absence of non-invasive blood pressure registration) and correlated to LV function indexes, LV hypertrophy and remodeling, myocardial tissue characterization, BNP and troponin levels (Pearson or Spearman correlation). These same indexes were compared in patients with LV ejection fraction (EF) below and above 50%, normal and reduced flow and presence of replacement fibrosis.

Results

Global constructive work (GCW) (2658.6±76.4mmHg%), global myocardial work (GMW) (2218.7±74.9mmHg%) and global wasted work (GWE) (262.0mmHg% [198.8–339.5]) were high above normal with concomitant lower work efficiency (WE) (88.0% [83.2–91.8]. Weak correlations were found between LVMW indexes and parameters describing aortic valve severity, flow and LV function (table). Except for significant differences of LVMI in patients with reduced LV ejection fraction (GCW 2770.3±687.4 vs 2056.0±380.7mmHg%, p=0,014 and GMW 2362.5±657.9 vs 1621.3±319.9, p=0,021 in patients with LV EF>50% vs. LV EF<50%, respectively) work indexes were neither significantly different in low-flow patients nor in those with myocardial late gadolinium enhancement.

Conclusions

Global constructive and myocardial work are increased in these patients with severe aortic stenosis. This might reflect an increased afterload predominance rather than a LV functional impairment, particularly relevant in this group of patients with exclusive high gradient disease and preserved LVEF.

Funding Acknowledgement

Type of funding sources: None. Correlations between LVMI – LV function

P–016 Using artificial intelligence to predict semen upgrading after microsurgical varicocele repair

Study question

Can we use artificial intelligence models to predict semen upgrading after microsurgical varicocele repair?

Summary answer

A machine learning model performed well in predicting clinically meaningful post-varicocelectomy semen upgrade using pre-operative hormonal, clinical, and semen analysis data.

What is known already

Varicocele repair is recommended in the presence of a clinical varicocele together with at least one abnormal semen parameter, and male infertility. Unfortunately, up to 50% of men who meet criteria for repair will not see meaningful benefit in outcomes despite successful surgery. Nomograms exist to help predict success, but these are based out of single-center databases, do not incorporate hormonal data, and are rarely designed to predict pre-defined, clinically meaningful improvements in semen parameters.

Study design, size, duration

Data were collected from an international, multi-center retrospective cohort. A total of 240 men were identified. Data from 160 men from Miami, USA and 80 men from Toronto, Canada were included. Data was collected from 2006 to 2020.

Participants/materials, setting, methods

We collected pre and postoperative clinical data following varicocele surgery. Clinical upgrading was defined as an increase in sperm concentration that would allow a couple to access new reproductive technologies/techniques. The tiers used for upgrading were 0–1million/cc (Intracytoplasmic Sperm Injection), 1–5 million (In Vitro Fertilization), 5–15 million (Intrauterine Insemination), and >15 million (Natural conception). Artificial intelligence models were trained and tested using R to predict which patients upgraded after surgery.

Main results and the role of chance

51% of men underwent bilateral varicocele repair. The majority of men had grade 2 varicocele on the left, and (when present) a grade 1 varicocele on the right. Overall, 47% of men experienced an upgrade following varicocele surgery, 47% did not change, and 6% downgraded. The data from Miami were used to create a random forest model for predicting clinically significant upgrade in sperm concentration. The most informative model parameters were preoperative FSH, sperm concentration, and surgical laterality. The model identified three clinical categories: men with unfavorable, intermediate, and favorable features to predict varicocele upgrade. On external validation using data from Toronto, the model accurately predicted upgrade in 87% of men with favorable features, and in 49% and 36% of men with intermediate and unfavorable features, respectively. Overall, the model performed well on external validation with an AUC of 0.72 and good calibration.

Calibration plots, using cross-validation, define how well the predicted probabilities match the actual probability of sperm concentration upgrade. The random forest model was run twelve times. All model characteristics are the mean of ten model runs with the highest and lowest performing runs removed.

The model was translated to an online calculator that can be used by clinicians.

Limitations, reasons for caution

One limitation to our study is that we were not able to predict total motile sperm count (TMSC), which has been shown to perform slightly better than concentration at predicting assisted reproduction outcomes. By focusing on clinically significant upgrading, this difference should be minimized.

Wider implications of the findings: Predicting the chances of clinically significant semen upgrading after varicocele repair is essential for patients and clinicians to understand. Several men undergo surgery with no subsequent benefit, which may lead to a delay in definitive treatment with IVF/IUI. Understanding their chances will help couples make better informed decisions moving forward.

Trial registration number

Not applicable

P–070 Evaluation of SARS-CoV–2 in human semen and effect on total sperm number: A prospective observational study

Study question

Is the SARS-CoV–2 virus present in human semen and what is the impact on semen parameters following an infection?

Summary answer

SARS-CoV–2 infection, though not detected in semen of recovered men, can affect TSN in ejaculate in the acute setting.

What is known already

Early epidemiological data has suggested that the primary mode of transmission is through respiratory droplets, but the presence of SARS-CoV–2 has been identified in other bodily fluids such as feces, urine, and semen.

Study design, size, duration

We prospectively recruited thirty men diagnosed with acute SARS-CoV–2 infection using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) of pharyngeal swab specimens. Thirty semen samples from recovered men were obtained 11–64 days after testing positive for SAR-CoV–2 infection. The median duration between positive SAR-CoV–2 test and semen collection was 37 days (IQR=23).

Participants/materials, setting, methods

Semen samples were collected from each individual using mailed kits. Follow-up semen samples were done with mailed kits or in-person in office setting. Semen analysis and PCR was performed after samples were received.

Main results and the role of chance

The median total sperm number (TSN) in ejaculate was 12.5 million (IQR=53.1). When compared with age-matched SARS-CoV–2(-) men, TSN was lower among SARS-CoV–2(+) men (p = 0.0024). Five men completed a follow-up sperm analysis (median 3 months) and had a median TSN of 18 million (IQR=21.6). No RNA was detected by means of RT-PCR in the semen in 16 samples tested.

Limitations, reasons for caution

First, most of the semen samples came from non-severe men of whom were in the recovery stage and lacked symptoms. Additionally, our sample size was relatively small and overnight mail-in semen analysis kits were used during the acute phase of infection to minimize contact with positive subjects.

Wider implications of the findings: Our findings suggest extremely low risk of viral transmission during sexual contact and assisted reproductive techniques, although further data need to be obtained. The impact on TSC in recovered men from SARS-CoV–2 infection is concerning, nevertheless long-term follow-up of these men is critical to determine the nadir of TSC.

Trial registration number

20200401

National registry for amyotrophic lateral sclerosis: a systematic review for structuring population registries of motor neuron diseases

BACKGROUND

This article comprises a systematic review of the literature that aims at researching and analyzing the frequently applied guidelines for structuring national databases of epidemiological surveillance for motor neuron diseases, especially Amyotrophic Lateral Sclerosis (ALS).

METHODS

We searched for articles published from January 2015 to September 2019 on online databases as PubMed - U.S. National Institutes of Health's National Library of Medicine, Scopus, Science Direct, and Springer. Subsequently, we analyzed studies that considered risk factors, demographic data, and other strategic data for directing techno-scientific research, calibrating public health policies, and supporting decision-making by managers through a systemic panorama of ALS.

RESULTS

2850 studies were identified. 2400 were discarded for not satisfying the inclusion criteria, and 435 being duplicated or published in books or conferences. Hence, 15 articles were elected. By applying quality criteria, we then selected six studies to compose this review. Such researches featured registries from the American (3), European (2), and Oceania (1) continent. All the studies specified the methods for data capture and the patients' recruitment process for the registers.

DISCUSSIONS

From the analysis of the selected papers and reported models, it is noticeable that most studies focused on the prospect of obtaining data to characterize research on epidemiological studies. Demographic data (ID01) are present in all the registries, representing the main collected data category. Furthermore, the general health history (ID02) is present in 50% of the registries analyzed. Characteristics such as access control, confidentiality and data curation. We observed that 50% of the registries comprise a patient-focused web-based self-report system.

CONCLUSION

The development of robust, interoperable, and secure electronic registries that generate value for research and patients presents itself as a solution and a challenge. This systematic review demonstrated the success of a population register requires actions with well-defined development methods, as well as the involvement of various actors of civil society.

Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) Oviposition Behavior in Previous Oviposition Situation

Blowflies use their sense of smell to locate oviposition substrates and their vision to direct and assist in landing decision. Blowflies' ovipositions are usually aggregated. Chrysomya megacephala (Fabricius) females, for example, prefer to lay eggs on substrates containing fresh eggs of the same species. However, it is possible that females would be capable of evaluating the substrate, reducing the size of egg cluster in sites with a high amount of eggs or larvae, or finding another site for laying their eggs, preventing the progeny from facing high competition for space and food. The present study aimed to investigate whether females of C. megacephala could distinguish and preferentially select previously infested substrates and whether females would lay their eggs attached or separate from eggs previously laid on the substrate. Behavioral measures were conducted inside cages under laboratory conditions in free-choice tests. Data analysis confirmed that C. megacephala females are able to distinguish the presence of cospecific eggs in the substrate and preferentially select previously infested substrates for egg laying, depositing their eggs separate from pre-existing large egg masses.

Osler-Weber-Rendu syndrome during pregnancy

Osler-Weber-Rendu syndrome is a very rare systemic fibrovascular dysplasia. Rupture of angiomas can cause haemorrhages, which sometimes can be severe with difficult bleeding control. The main manifestation is recurrent epistaxis. Treatment of this disorder is symptomatic. During pregnancy, there may be an increased risk of complications. We describe a case of a pregnant woman with Osler-Weber-Rendu syndrome. Besides frequent epistaxis and microcytic hypochromic anaemia that resolved with oral iron treatment, she had a normal pregnancy, vaginal delivery and puerperium without complications.

Valsalva manoeuvre effect on distribution of lung damage in heroin inhalation

This article reports the case of a patient demonstrating acute bilateral pneumonitis almost completely confined to the upper lobes as a result of inhaling heroin. We attribute this distribution to the patient performing the Valsalva manoeuvre immediately after inhaling heroin. This pattern has not been reported before and we believe it may be seen more frequently owing to a switch amongst drug users from intravenous to inhaled heroin.

Self-sampling for human papillomavirus (HPV) testing as cervical cancer screening option. Experience from the LAMS study

PURPOSE

To compare Hybrid Capture II (HC2) in detecting high-risk (HR) HPV in patient-collected vaginal samples with those obtained using gynaecologist collected samples.

METHODS

Patients were submitted to Pap smears, visual inspection with acetic acid (VIA) and HC2 for hr-HPV.

RESULTS

A total of 1,081 HC2 tests for HR-HPV were performed: 770 (71.2%) samples were collected by a physician and 311 (28.8%) were self-collected by the patients. In detecting any cervical lesion, the sensitivity of HC2 collected by a physician was higher (92.86%) than that (37.5%) in the self-sampling group. Negative predictive value (NPV) was high for both, 99.69% and 93.75%, respectively. Using the CIN2 cutoff, performance of HC2 was significantly improved: 92.9% and 62.5%, respectively. HC2 specificity for any cervical lesion and for CIN2 or higher were close to 90% in both groups.

CONCLUSIONS

Self-sampled HPV testing is a powerful option to increase the detection of cervical lesions in women segregated from prevention programs.

Human papillomavirus testing as an optional screening tool in low-resource settings of Latin America: experience from the Latin American Screening study

Hybrid capture II (HC II) test for oncogenic human papillomaviruses (HPV) was carried out in a cohort of 4284 women at their first clinical visit. Overall prevalence of HPV was 17.1%, decreasing with age from 33.9% among women below 20 years to only 11.0% among those older than 41 years. HPV prevalence was significantly higher among current smokers (odds ratio [OR] = 1.31; 95% CI 1.1-1.6), in women with two or more lifetime sexual partners (OR = 1.9; 95% CI 1.6-2.4), and those women with two or more sexual partners during the past 12 months prior to examination (OR = 1.6; 95% CI 1.2-2.2). HPV detection increased in parallel with increasing cytologic abnormality, being highest in women with high-grade squamous intraepithelial lesion (P= 0.001). Specificity of the HPV test in detecting histologically confirmed cervical disease was 85% (95% CI 83.9-86.1). Sensitivity of the HPV test in detecting histologic abnormalities increased in parallel with disease severity, ranging from 51.5% for cervical intraepithelial neoplasia (CIN) 1 to 96.5% for CIN 3 and 100.0% for cancer, with respective decline of positive predictive value. These data suggest that HPV testing with HC II assay might be a viable screening tool among this population with relatively high prevalence of cervical disease.

Human papillomavirus testing as an optional screening tool in low-resource settings of Latin America: experience from the Latin American Screening study

Hybrid capture II (HC II) test for oncogenic human papillomaviruses (HPV) was carried out in a cohort of 4284 women at their first clinical visit. Overall prevalence of HPV was 17.1%, decreasing with age from 33.9% among women below 20 years to only 11.0% among those older than 41 years. HPV prevalence was significantly higher among current smokers (odds ratio [OR] = 1.31; 95% CI 1.1–1.6), in women with two or more lifetime sexual partners (OR = 1.9; 95% CI 1.6–2.4), and those women with two or more sexual partners during the past 12 months prior to examination (OR = 1.6; 95% CI 1.2–2.2). HPV detection increased in parallel with increasing cytologic abnormality, being highest in women with high-grade squamous intraepithelial lesion (P = 0.001). Specificity of the HPV test in detecting histologically confirmed cervical disease was 85% (95% CI 83.9–86.1). Sensitivity of the HPV test in detecting histologic abnormalities increased in parallel with disease severity, ranging from 51.5% for cervical intraepithelial neoplasia (CIN) 1 to 96.5% for CIN 3 and 100.0% for cancer, with respective decline of positive predictive value. These data suggest that HPV testing with HC II assay might be a viable screening tool among this population with relatively high prevalence of cervical disease.

[Primary hyperaldosteronism. Update on a topic of physiopathology and clinical features]

The authors examine the various forms of primary hyperaldosteronism, outlining the most recent acquisitions in terms of etiopathogenesis and physiopathology. While Conn's original description of primary hyperaldosteronism is a syndrome based on corticoadrenal aldosteronesecreting adenoma, it was later seen that this condition could recognise other anatomic substrates, such as carcinoma and in particular bilateral corticoadrenal hyperplasia. A peculiar form of the latter can be suppressed with glucocorticoids sustained by an anomalous recombination of aldosterone-synthase and 11-beta-hydroxylase. The main focus in this paper is on clinical management, in particular the current diagnostic criteria which show that primary hyperaldosteronism affects a higher percentage of the hypertense population that was estimated in the past. Above all, the significance of the aldosterone/PRA (ARR) ratio in screening for this condition is discussed, above all in normokalemic forms, together with the role of molecular biology in identifying glucocorticoid-suppressible forms. Lastly, the principles of medical and surgical management are outlined, emphasising the role of laparoscopic surgery.

Evidence for an interaction between alpha-MSH and opioids in the regulation of gonadotropin secretion in man

Gonadotropin secretion is inhibited by the endogenous opioids and stimulated by their antagonist naloxone. LH secretion is stimulated by alpha-MSH, a tridecapeptide derived from the post-translational processing of POMC. The possibility that alpha-MSH interacts with the opioids, as suggested by the experimental evidence, was investigated in 7 normal males aged 24-29 through the performance of seven tests: naloxone (0.8 mg i.v. bolus, followed by infusion of 1.6 mg/h for 120'); alpha-MSH (2.5 mg i.v. bolus); naloxone + alpha-MSH (2.5 mg i.v. 15' after commencement of the naloxone infusion); naloxone + GnRH (100 micrograms i.v. 15' after commencement of the naloxone infusion); alpha-MSH + GnRH (respectively 2.5 mg and 100 micrograms at time 0), GnRH alone (100 micrograms at time 0), placebo (150 nmol/l NaCl solution). The LH AUCs during both naloxone (30.3 +/- 2.7 mIU/ml.min-1) and alpha-MSH test (32.9 +/- 4.6 mIU/ml.min-1) were significantly greater (p < 0.005) than that observed during placebo (16.9 +/- 3.6 mIU/ml.min-1). The LH AUC during alpha-MSH + naloxone (37.6 +/- 2.6 mIU/ml.min-1) was not significantly different from that recorded during their separate administration. GnRH injected alone, during the naloxone infusion and with alpha-MSH produced similar increases in LH, that were significantly higher than that observed during the other tests (AUCs: GnRH 89.4 +/- 10.6, GnRH + naloxone 100.5 +/- 9.1, GnRH + alpha-MSH 94.6 +/- 7.9 mIU/ml.min-1, p < 0.001). Significant increase in FSH (p < 0.001) was only observed during GnRH, GnRH + naloxone and GnRH + aMSH tests (AUCs: placebo 13.3 +/- 1.7; naloxone 14.7 +/- 2.5; alpha-MSH 15.5 +/- 2.3; alpha-MSH + naloxone 16.9 +/- 1.9; GnRH 19.1 +/- 1.1; GnRH + alpha-MSH 20.7 +/- 1.3; GnRH + naloxone 21.2 +/- 1.8 mIU/ml.min-1). These results are in line with the possibility of an interaction between alpha-MSH and the opioids in the regulation of gonadotropin secretion, perhaps with opposing effects on a final common pathway.

Multicopy single-stranded DNA of Escherichia coli enhances mutation and recombination frequencies by titrating MutS protein

Multicopy single-stranded DNA (msDNA) molecules consist of single-stranded DNA covalently linked to RNA. In Escherichia coli, such molecules are encoded by genetic elements called retrons. The DNA moieties of msDNAs have characteristic stem-loop structures, and most of these structures contain mismatched base pairs. Previously, we showed that retrons encoding msDNAs with mismatched base pairs are mutagenic when present in multicopy plasmids. In this study we show that such msDNAs, in a similar manner to genetic defects in mismatch repair, increase the frequency of interspecies recombination in matings between Salmonella typhimurium and E. coli. To demonstrate interference with mismatch repair by msDNA, we show that the addition of a plasmid containing the gene for MutS protein suppresses the mutagenic and recombinogenic effects of msDNAs. We also show that in mutS mutants, msDNA does not increase the frequency of either mutations or interspecies recombination. We conclude from these findings that the mutagenic and recombinogenic effects of msDNAs are due to titrating out MutS protein.

Multicopy single-stranded DNAs with mismatched base pairs are mutagenic in Escherichia coli

Retrons are genetic elements that encode multicopy single-stranded DNAs called msDNAs. They are clonally distributed in Escherichia coli and retrons in different clones produce DNAs with different nucleotide sequences. msDNAs consist of an RNA molecule covalently linked to a single-stranded DNA molecule. The latter contains an inverted repeat, resulting in a stem-loop structure. In two retrons, Ec83 and Ec78, the DNA is cleaved off from the RNA. All known retrons except Ec78, have one or more mismatched base pairs in the stem-loop structure. We found that two retrons, Ec86 and Ec83, when present in high copy numbers are mutagenic. The ratios of mutation frequencies observed in Lac- indicator strains were similar to the ratios observed for a mutant defective in mismatch repair. It is known that some proteins required for mismatch repair bind to mismatched base pairs prior to carrying out repair. The similarity in the mutation frequency ratios suggested that the mutagenesis caused by msDNAs of retrons Ec86 and Ec83 might be due to sequestration of a mismatch repair protein by msDNA. Strong support for this interpretation was obtained from the finding that the msDNA produced by retron Ec78 is not mutagenic.