Recommend with caution: A meta-analysis investigating papillary thyroid carcinoma tumor progression under active surveillance

BACKGROUND

Papillary thyroid carcinoma (PTC) is an indolent disease with favorable outcomes. The non-surgical treatment approach known as active surveillance (AS) has been introduced as an alternative treatment instead of the traditional thyroidectomy. However, 10-15 % of PTC tend to progress. We sought to determine factors predicting the progression of PTC under AS.

METHODS

A systematic search was performed in January 2022 using PubMed, Embase, Google Scholar, Web of Science, and ScienceDirect. PRISMA guidelines were used by multiple reviewers to extract study characteristics (author name, publication date, journal name, country, institution, and study design), as well as main outcomes and measures. A combination of utilization of thyroid replacement therapy, baseline tumor size and volume, follow-up tumor size and volume, and the presence of lymph node metastasis and its distribution, as well as surveillance duration, were the main measures of this study.

RESULTS

Nine studies with 4166 patients were included, of which 354 showed tumor progression during AS (15 %; 95%CI = 7 % - 23 %). The average follow-up period was 41.58 months. The mean tumor maximum diameter was 8.54 mm (95%CI = 7.04-10.03). Tumor progression was most commonly secondary to an increase in volume by ≥50 % (75 %; 95%CI = 68 % - 80 %), then increase in diameter by ≥3 mm (41 %; 95%CI = 13 % - 76 %), and finally the development of lymph node metastasis (13 %; 95%CI = 9 % - 19 %). Approximately only 2 % of all patients thus developed new lymph node metastasis. Patient age, sex, and tumor size were not associated with higher risks of tumor progression. 12 % of AS patients eventually underwent surgery, though only 40 % (95%CI = 27 % - 53 %) of these patients displayed tumor progression.

CONCLUSIONS

Our meta-analysis determined a tumor progression rate of 15 % in patients who underwent AS management, 13 % of which (2 % of all patients) developed lymph node metastasis. We found no protective or risk factors for tumor progression, and that almost half of all patients who underwent delayed surgery did so for reasons other than tumor progression. While not biopsying small (<1 cm) or very low suspicious nodules is already recommended, AS may be an appropriate treatment option in patients appropriately counseled, considering the low risk of advanced tumor progression but also the considerable patient population who fail to adhere to treatment. Alternatively, in aim of preventing overtreatment in patients who would rather take proactive measures against their low-risk carcinoma, minimally-invasive ablation techniques may be an attractive option.

A combination of computed tomography scan and ultrasound provides optimal detection of cervical lymph node metastasis in papillary thyroid carcinomas: A systematic review and meta-analysis

BACKGROUND

Lymph node metastasis (LNM) in patients with papillary thyroid carcinoma (PTC) is common. This meta-analysis assesses the diagnostic accuracy of computed tomography (CT), ultrasound (US), and CT + US in detecting central and lateral LNM.

METHODS

A systematic review and meta-analysis was performed by searching PubMed, Embase, and Cochrane for studies published up to April 2022. The pooled sensitivity, specificity, and diagnostic odds ratio (DOR) were calculated. The area under the curve (AUC) for summary receiver operating curves (sROC) were compared.

RESULTS

The study population included 7902 patients with a total of 15 014 lymph nodes. Twenty-four studies analyzed the sensitivity of the overall neck region in which dual CT + US imaging (55.9%) had greater sensitivities (p < 0.001) than either US (48.4%) or CT (50.4%) alone. The specificity of US alone (89.0%) was greater (p < 0.001) than CT alone (88.5%) or dual imaging (86.8%). The DOR for dual CT + US imaging was greatest (p < 0.001) at 11.134, while the AUCs of the three imaging modalities were similar (p > 0.05). Twenty-one studies analyzed the sensitivity of the central neck region in which both CT (45.8%) and CT + US imaging (43.4%) had greater sensitivities (p < 0.001) than US alone (35.3%). The specificity of all three modalities was higher than 85%. The DOR for CT (7.985) was greater than US alone (4.723, p < 0.001) or dual CT + US imaging (4.907, p = 0.015). The AUC of both CT + US (0.785) and CT alone (0.785) were significantly greater (p < 0.001) than US alone (0.685). Of the 19 studies that reported lateral LNM, CT + US imaging sensitivity (84.5%) was higher than CT alone (69.2%, p < 0.001) and US alone (79.7%, p = 0.038). The specificity of all imaging techniques was all greater than 80.0%. CT + US imaging DOR (35.573) was greater than CT (20.959, p = 0.024) and US (15.181, p < 0.001) individually. The AUC of independent imaging was high (CT: 0.863, US: 0.858) and improved significantly when combined (CT + US: 0.919, p = 0.024 and p < 0.001, respectively).

CONCLUSIONS

We report an up-to-date analysis elucidating the diagnostic accuracy of LNM detection by either CT, US, or in combination. Our work suggests dual CT + US to be the best for overall detection of LNM and CT to be preferable in detecting central LNM. The use of either CT or US alone may detect lateral LNM with acceptable accuracy, yet dual imaging (CT + US) significantly improved detection rates.

Hashimoto's Thyroiditis: A Protective Factor against Recurrence in BRAF-Wild Type Differentiated Thyroid Carcinoma

A recent work analyzing the concomitant factors BRAF mutation (risk factor) and Hashimoto's thyroiditis (HT) (protective factor) found that the presence of HT reduced lymph node metastasis in BRAF-mutated papillary thyroid carcinoma. Whether this notion is upheld with respect to disease recurrence and differentiated thyroid carcinoma (DTC), however, is unknown. We aimed to investigate the effect of underlying HT in DTC patients and its influence on recurrence with a specific emphasis in BRAF-mutated tumors. A total of 469 patients were included. Patients were stratified according to BRAF and HT status. Multivariate regression analysis was conducted to determine protective and risk factors of disease recurrence in patients with DTC. HT was associated with less-aggressive carcinomas including more frequent microcarcinomas (HT: 45.0% vs. no-HT: 34.0%, p = 0.02), less lymph node involvement (HT: 16.4% vs. no-HT: 26.1%, p = 0.02), and less disease recurrence (HT: 2.9% vs. no-HT: 11.9%, p = 0.002). BRAF mutation was also significantly associated with higher rates of lymph node involvement (BRAF-mutant: 41.9% vs. BRAF-wild type: 14.6%, p < 0.001) and almost two times the rate of recurrence (BRAF-mutant: 14.9% vs. BRAF-wild type: 6.5%, p = 0.004). Underlying HT was the only protective factor determined, reducing the odds of developing recurrence by 70% (HR: 0.30, 95%CI: 0.11-0.88). In the BRAF-wild type cohort, regression analysis continued to determine HT as a protective factor (p = 0.03). However, in the BRAF-mutant cohort, HT was no longer an independent protective factor (p = 0.20) against recurrence. Sub-group regression analysis, including PTC patients, similarly found HT as a protective factor only in BRAF-wild type patients (p = 0.039) and not BRAF-mutant (p = 0.627). The presence of underlying HT is associated with less aggressive tumors and is an independent protective factor against DTC recurrence, reducing the risk by 70%. HT remains a protective factor in BRAF-wild type carcinoma, but not in patients with BRAF-mutant carcinoma. HT may potentially be considered as a parameter which enhances American Thyroid Association patient risk stratification.

Cardiovascular Health by Graves' Disease Management Modality - Surgery Versus Radioactive Iodine Versus Antithyroid Medications: A Network Meta-Analysis

INTRODUCTION

Graves' disease is an autoimmune disorder of the thyroid gland associated with the overproduction of thyroid hormones. Excess secretion of thyroid hormones leads to cardiovascular consequences. Treatment options include antithyroid medications (ATM), radioactive iodine (RAI) ablation, and total thyroidectomy. We examined the cardiovascular outcomes following Graves' disease management modality.

METHODS

A systematic search was performed up to September 22nd, 2021, using PubMed, EMBASE, and Web of Science databases. We conducted a network meta-analysis analyzing cardiovascular outcomes of interest, including congestive heart failure (CHF), arrhythmia, atrial fibrillation (AF), and hypertension.

RESULTS

Three studies were included in this analysis totaling 6700 patients with Graves' disease, of which 74% were female. The mean age was 44.34 y. When compared to pretreatment, management options lowered the risk of maintaining arrhythmia 81% with surgery (relative risk [RR] = 0.19; 95% confidence interval [CI] = 0.12 to 0.31), 67% with ATM (RR = 0.33; 95% CI = 0.23 to 0.49), and 50% with RAI (RR = 0.50; 95% CI = 0.13 to 1.95). Risk of maintaining CHF was reduced 80% with surgery (RR = 0.20; 95% CI = 0.08 to 0.49), 41% with ATM (RR = 0.59; 95%CI = 0.52 to 0.67), and only 7% with RAI (RR = 0.93; 95%CI = 0.68 to 1.26). Treatment-ranking analysis found all parameters, including CHF, arrhythmia, AF, and hypertension, to be in favor of surgical treatment over medical treatment and RAI ablation.

CONCLUSIONS

This is the first network meta-analysis analyzing the cardiovascular outcomes in Graves' disease patients by treatment option. Our study demonstrated that surgery is superior to RAI and medical treatment.

Hashimoto’s Thyroiditis Minimizes Lymph Node Metastasis in BRAF Mutant Papillary Thyroid Carcinomas

Hashimoto’s thyroiditis (HT) (autoimmune thyroiditis) is a clinicopathological entity associated with chronic lymphocytic infiltration resulting in hypothyroidism. HT is a double-edged sword that increases the risk of papillary thyroid cancer (PTC), yet it serves as a protective factor for PTC progression. BRAF mutation in PTCs is associated with rapid cell growth, aggressive tumor characteristics, and higher mortality rates. Here, we aimed to analyze the influence of HT in patients with PTCs and its effect on lymph node metastasis (LNM) in BRAF mutant tumors. Adults diagnosed with PTC between 2008 and January 2021 were retrospectively included. A total of 427 patients, 128 of whom had underlying HT, were included. The HT group had significantly higher rates of microcarcinoma (49.2% vs. 37.5%, p = 0.025) and less lateral LNM (8.6% vs. 17.1%, p = 0.024). Interestingly, BRAF-mutated PTCs were found to have significantly less overall LNM (20.9% vs. 51%, p = 0.001), central LNM (25.6% vs. 45.1%, p = 0.040) and lateral LNM (9.3% vs. 29.4%, p = 0.010) in patients with HT when compared to those without underlying HT. HT was found to be an independent protective predictor of overall and lateral LNM. Altogether, HT was able to neutralize the effect of BRAF mutation and was determined to be an independent protective factor against LNM. Specifically, our work may influence treatment-aggressiveness decision making for endocrinologists, oncologists and surgeons alike.

Excess of cesarean births in pregnant women with COVID-19: A meta-analysis

BACKGROUND

Studies have suggested that cesarean birth in pregnant women with COVID-19 may decrease maternal adverse events and perinatal transmission. This systematic review aimed to evaluate variations in clinical presentation, laboratory findings, and maternal/neonatal outcomes in COVID-19 patients who delivered vaginally versus via cesarean.

METHODS

A comprehensive search following PRISMA guidelines was performed for studies published up to May 23, 2020, using PubMed, Web of Science, Scopus, Embase, Cochrane, Science Direct, and clinicaltrials.gov. Original retrospective and prospective studies, case reports, or case series with sufficient data for estimating the association of COVID-19 with different pregnancy outcomes with no language restriction and published in peer-reviewed journals were included. Pooled mean and arcsine transformation proportions were applied. Next, a two-arm meta-analysis was performed comparing the perinatal outcomes between the study groups.

RESULTS

Forty-two studies with a total of 602 pregnant women with COVID-19 were included. The mean age was 31.8 years. Subgroup analysis showed that Americans had the lowest gestational age (mean = 32.7, 95%CI = 27.0-38.4, P < 0.001) and the highest incidence of maternal ICU admission (95%CI = 0.45%-2.20, P < 0.001) of all nationalities in the study. There was no significant difference in perinatal complications, premature rupture of membrane, placenta previa/accreta, or gestational hypertension/pre-eclampsia between women who delivered vaginally versus by cesarean. Importantly, there were also no significant differences in maternal or neonatal outcomes.

CONCLUSION

Vaginal delivery was not associated with worse maternal or neonatal outcomes when compared with cesarean. The decision to pursue a cesarean birth should be based on standard indications, not COVID-19 status.

The Effect of Patient Positioning on Intraoperative Neuromonitoring During Thyroid and Parathyroid Surgery

BACKGROUND

Intraoperative neuromonitoring (IONM) has been accepted as a routine adjunct among surgeons who perform thyroid and parathyroid surgeries. Thyroid and parathyroid surgeries use various patient positioning strategies that have poorly understood effects on IONM. The aim of this study was to compare IONM signals between the transaxillary and transcervical approaches.

METHODS

In this retrospective cohort study, we evaluated 463 adult patients who underwent a total of 502 procedures. The procedures performed included total thyroidectomy, right or left hemithyroidectomy, and parathyroidectomy. Vagus nerve and recurrent laryngeal nerve (RLN) latency and amplitude measurements were analyzed intra-operatively. The distances between the vagus nerve and the trachea were measured via ultrasound during transaxillary procedures.

RESULTS

Compared to the transcervical approach, the right vagus nerve latency was significantly decreased in the transaxillary approach. Transaxillary surgery was not associated with increased latency or decreased amplitude on IONM. The distance between the vagus nerve and trachea was significantly decreased post-positioning during transaxillary approaches.

DISCUSSION

Despite differences in patient positioning, a transaxillary approach was not associated with increased stress on the vagus nerve or RLN, according to IONM data. The decreased right vagus nerve latency associated with a transaxillary approach highlights the importance of considering patient positioning and laterality while interpreting IONM data.

Altered mental status is a predictor of poor outcomes in COVID-19 patients: A cohort study

Introduction

Several studies have described typical clinical manifestations, including fever, cough, diarrhea, and fatigue with COVID-19 infection. However, there are limited data on the association between the presence of neurological manifestations on hospital admission, disease severity, and outcomes. We sought to investigate this correlation to help understand the disease burden.

Methods

We delivered a multi-center retrospective study of positive laboratory-confirmed COVID-19 patients. Clinical presentation, laboratory values, complications, and outcomes data were reported. Our findings of interest were Intensive Care Unit (ICU) admission, intubation, mechanical ventilation, and in-hospital mortality.

Results

A total of 502 patients with a mean age of 60.83 ± 15.5 years, of them 71 patients (14.14%) presented with altered mental status, these patients showed higher odds of ICU admission (OR = 2.06, 95%CI = 1.18 to 3.59, p = 0.01), mechanical ventilation (OR = 3.28, 95%CI = 1.86 to 5.78, p < 0.001), prolonged (>4 days) mechanical ventilation (OR = 4.35, 95%CI = 1.89 to 10, p = 0.001), acute kidney injury (OR = 2.18, 95%CI = 1.28 to 3.74, p = 0.004), and mortality (HR = 2.82, 95%CI = 1.49 to 5.29, p = 0.01).

Conclusion

This cohort study found that neurological presentations are associated with higher odds of adverse events. When examining patients with neurological manifestations, clinicians should suspect COVID-19 to avoid delayed diagnosis or misdiagnosis and lose the chance to treat and prevent further transmission.

Medication-related harm and the newspapers - what has been communicated to the public in Ireland: A systematic content analysis

Introduction

Reducing the global prevalence of severe, avoidable medication-related harm (MRH) by 50% by the end of 2022 is the WHO’s third global patient safety challenge [1]. MRH is reported frequently in the academic literature, with increasing age being a key risk factor. The WHO have highlighted the need to improve public health literacy and knowledge about medications. Little is known about the frequency and nature of Irish newspaper reports about MRH. This study sought to address this gap and to examine reporting during the calendar years 2019 and 2009.

Methods

In this mixed-methods study, LexisNexis® [2], an online newspaper archive database, was searched for newspaper articles reporting on MRH, published in the Republic of Ireland during the calendar years 2019 and 2009. The search strategy focussed on “medication” AND “harm” AND “patient”. Quantitative data extraction aimed to describe the frequency (by count of articles) of reporting of MRH and the nature by describing the publishing newspaper titles and the reported details of: drug class(es), demographics (age or life stage, gender) of those experiencing harm and the severity of harm. Qualitatively, a systematic content analysis, using inductive coding is ongoing and will be reported separately. Research ethics committee approval for this study is not required because this is an analysis of material in the public domain.

Results

In total, 7098 newspaper articles were identified through database searching for 2019 (n=3217) and 2009 (n=3881). To date, 54% (3867: n=3217, 45% 2019, n=650, 9% 2009) of these were screened, of which 63 newspaper articles (n=44 2019, n=19 2009) were included and quantitative data were extracted. Within these 63 articles, 71 cases of individual people experiencing MRH were reported (52 in 2019 and 19 in 2009). The newspapers most commonly reporting MRH were Irish Daily Mail (31/63: 27 in 2019 and 4 in 2009) and Irish Times (17/63:9 in 2019 and 8 in 2009). Drug classes most frequently reported as causing MRH were central nervous system drugs (antiepileptics n=10, opioid analgesics n=5, antidepressants n=9, and anxiolytics n=1), cancer chemotherapy (23 cases) and non-steroidal anti-inflammatories (n=3). MRH was reported as being fatal (13 /71:8 in 2019 and 5 in 2009) and non-fatal (58/71), with seven cases (5 in 2019 and 2 in 2009) of permanent harm. Among the 71 individual cases of MRH, the majority were adults aged 18–64 years (n=36), children (n=7), older adults (n=8), foetus (n=3) and newborn (n=1), while the remainder did not report the person’s age.

Conclusion

MRH is frequently reported to the public through Irish newspapers. The study is limited by focus on newsprint media with the exclusion of other forms of digital or social media and restriction to two calendar years in a single country, which likely stifles the generalisability of findings to other contexts. Future work could explore this issue across a wider range of media platforms and examine changes in reporting over time. The study findings may support an agenda to improve the general public's exposure to information and knowledge of MRH and medication safety.

References

1. Donaldson, L.J., et al., Medication without harm: WHO's third global patient safety challenge. 2017. 389(10080): p. 1680–1681.

2. https://advance-lexis-com.elib.tcd.ie/firsttime?crid=d5f713e8-8107-4efd-91cc-1e99c82cdb58&pdmfid=1519360.

Robotic-assisted parathyroidectomy via transaxillary approach: feasibility and learning curves

Background

There have been few reports of robotic-assisted transaxillary parathyroidectomy in the literature. We aim to report our experience with robotic-assisted transaxillary parathyroidectomy for primary hyperparathyroidism (PHPT) in the Western population.

Methods

A retrospective study was performed from July 2010 through July 2019 at two institutions, one in the United States and one in France. Demographic characteristics and perioperative data were collected for all patients undergoing robotic-assisted transaxillary parathyroidectomy by a single surgeon at each institution. A linear regression model was developed to describe the learning curve for this procedure at each institution.

Results

One-hundred and two patients with PHPT were included with a median age of 55.6±12.4 years and median body mass index (BMI) of 25.5±6.1 kg/m². The majority of patients were female (80.4%). Median total operative time was 116±53 minutes. Minor complications were reported in 2 patients (1.96%), and one case was converted to a trans-cervical approach (TCA) for four-gland exploration. Median patient follow-up time was 6.5±12.2 months, and disease recurrence was reported in one patient. Calculated learning curves showed that one surgeon achieved proficiency by the eighth case, and the other achieved proficiency by the fourteenth case.

Conclusions

This is the largest reported experience of robotic-assisted transaxillary parathyroidectomy for PHPT in the Asian and Western population. Analysis of the procedural learning curve demonstrates that proficiency in this technique was achieved after performance of less than 15 surgeries. This procedure is safe and feasible in the hands of experienced surgeons for select patients with localized disease.

Gastroenterology manifestations and COVID-19 outcomes: A meta-analysis of 25,252 cohorts among the first and second waves

A meta-analysis was performed to identify patients with coronavirus disease 2019 (COVID-19) presenting with gastrointestinal (GI) symptoms during the first and second pandemic waves and investigate their association with the disease outcomes. A systematic search in PubMed, Scopus, Web of Science, ScienceDirect, and EMBASE was performed up to July 25, 2020. The pooled prevalence of the GI presentations was estimated using the random-effects model. Pairwise comparison for the outcomes was performed according to the GI manifestations' presentation and the pandemic wave of infection. Data were reported as relative risk (RR), or odds ratio and 95% confidence interval. Of 125 articles with 25,252 patients, 20.3% presented with GI manifestations. Anorexia (19.9%), dysgeusia/ageusia (15.4%), diarrhea (13.2%), nausea (10.3%), and hematemesis (9.1%) were the most common. About 26.7% had confirmed positive fecal RNA, with persistent viral shedding for an average time of 19.2 days before being negative. Patients presenting with GI symptoms on admission showed a higher risk of complications, including acute respiratory distress syndrome (RR = 8.16), acute cardiac injury (RR = 5.36), and acute kidney injury (RR = 5.52), intensive care unit (ICU) admission (RR = 2.56), and mortality (RR = 2.01). Although not reach significant levels, subgroup-analysis revealed that affected cohorts in the first wave had a higher risk of being hospitalized, ventilated, ICU admitted, and expired. This meta-analysis suggests an association between GI symptoms in COVID-19 patients and unfavorable outcomes. The analysis also showed improved overall outcomes for COVID-19 patients during the second wave compared to the first wave of the outbreak.

Asthma and COVID-19; different entities, same outcome: a meta-analysis of 107,983 patients

OBJECTIVE

There are varying reports of the prevalence and effect of comorbid asthma in coronavirus disease-2019 (COVID-19) patients. We sought to conduct a meta-analysis comparing asthmatic and non-asthmatic patients to determine the clinical significance of preexisting asthma in COVID-19 patients.

DATA SOURCES

Online databases PubMed, ScienceDirect, Web of Science, and Scopus, were searched up to July 15, 2020, for papers comparing asthma versus non-asthma COVID-19 patients.

STUDY SELECTION

According to prespecified inclusion criteria, this analysis included eleven retrospective studies with 107,983 COVID-19 patients. Subgroup analysis was performed based on age groups.

RESULTS

The mean age of the patients was 59.9 years (95%CI = 51.9-67.9). Across studies, the prevalence of asthma was 11.2% (95%CI: 9.1%-13.3%) among COVID-19 patients who attended the hospitals. Asthma patients were more likely to be younger (SMD = -0.36, 95%CI = -0.61 to -0.10, p = 0.005), and obese (OR = 1.98, 95%CI = 1.54-2.55, p < 0.001), there was no differential risk of hospitalization rate, ICU admission, or development of acute respiratory distress syndrome (ARDS) between asthmatic and non-asthmatic cohorts. However, asthmatic patients had increased risk of endotracheal intubation (RR = 1.27, 95%CI = 1.02-1.58, p = 0.030) especially patients aged <50 years (RR = 6.68, 95%CI = 1.76-11.13, p = 0.009). Despite this result, asthmatic patients had better recovery with a higher liability of being discharged and were less likely to die (RR = 0.80, 95%CI = 0.65-0.97, p = 0.026).

CONCLUSION

To our knowledge, our meta-analysis is the largest to shed light on preexisting asthma as a predictor of intubation in COVID-19, especially in young and obese patients. Identifying high-risk groups is crucial for designing more effective intervention plans and optimization of efficient resource allocation.

Evaluation of YouTube videos as a patient education source for novel surgical techniques in thyroid surgery

Background

Patients and physicians are increasingly utilizing online video sharing sites such as YouTube for obtaining and disseminating health-related information in multimedia format; however, due to its free, open-access platform, YouTube videos fall short in providing validated, up-to-date medical information, and may even convey unintended messages to patients who are seeking additional information on surgeries. We evaluated the relevance, reliability, and quality of YouTube videos on novel surgical techniques in thyroid surgery.

Methods

The top 50 indexed YouTube videos for the queries, "robotic thyroid surgery" and "transoral thyroid surgery", were assessed by two independent reviewers for video quality and reliability for patient understanding. Videos were scored using Global Quality Score (GQS), a scale for video quality, and DISCERN Scoring, a questionnaire for reliability and quality measures of information presented.

Results

The mean ± standard deviation (SD) duration of the videos (n=50) was 8.1±3.7 minutes. Total views were 261,440 and the mean ± SD time since upload was 3.6±2.6 years. The median and interquartile range of video power index (VPI) was 1.9 (0.5-3.7), GQS was 3.0 (2.0-4.0), and DISCERN score was 2.8 (2.3-3.2). Most videos were uploaded by physicians (75.8%) and the highest number of videos (63.6%) uploaded were from the United States (US). Videos with higher quality and reliability scores were uploaded by academic professionals, and included videos of physicians who described procedural information, perioperative instructions, and possible postoperative complications (P<0.05). Adequate medical information on the procedure and discussion of complications in YouTube videos were independent predictors of advanced educational quality and reliability.

Conclusions

Clinical information on new surgical techniques such as transoral and robotic thyroid surgeries in YouTube videos scored low on quality and reliability as a source of patient education. Physicians should provide supplemental educational material online and offline to aid patient understanding of novel procedures.

Multisystem inflammatory syndrome in pediatric COVID-19 patients: a meta-analysis

BACKGROUND

We aimed to systematically review the clinical and laboratory features of patients with the multisystem inflammatory syndrome in pediatrics diagnosed during the COVID-19 pandemic.

DATA SOURCES

A literature search in Web of Science, PubMed, Scopus, and Science Direct was made up to June 29, 2020.

RESULTS

Analysis of 15 articles (318 COVID-19 patients) revealed that although many patients presented with the typical multisystem inflammatory syndrome in pediatrics, Kawasaki-like features as fever (82.4%), polymorphous maculopapular exanthema (63.7%), oral mucosal changes (58.1%), conjunctival injections (56.0%), edematous extremities (40.7%), and cervical lymphadenopathy (28.5%), atypical gastrointestinal (79.4%) and neurocognitive symptoms (31.8%) were also common. They had elevated serum lactic acid dehydrogenase, D-dimer, C-reactive protein, procalcitonin, interleukin-6, troponin I levels, and lymphopenia. Nearly 77.0% developed hypotension, and 68.1% went into shock, while 41.1% had acute kidney injury. Intensive care was needed in 73.7% of cases; 13.2% were intubated, and 37.9% required mechanical ventilation. Intravenous immunoglobulins and steroids were given in 87.7% and 56.9% of the patients, respectively, and anticoagulants were utilized in 67.0%. Pediatric patients were discharged after a hospital stay of 6.77 days on average (95% CI 4.93-8.6).

CONCLUSIONS

Recognizing the typical and atypical presentation of the multisystem inflammatory syndrome in pediatric COVID-19 patients has important implications in identifying children at risk. Monitoring cardiac and renal decompensation and early interventions in patients with multisystem inflammatory syndrome is critical to prevent further morbidity.

A Single Surgeon's 10-Year Experience in Remote-Access Thyroid and Parathyroid Surgery

BACKGROUND

Remote-access thyroid and parathyroid surgery has gained popularity recently due to its benefit of avoiding visible neck scars. Most of these techniques were described and performed in Asia, on patients with different body habitus compared to American patients. We aim to analyze the learning curve in performing these operations in North America. .

METHODS

This is a retrospective cohort study of a 10-year experience by a single surgeon at a North American institute. Patients who underwent thyroid or parathyroid procedures by a transaxillary, retroauricular, or transoral endoscopic thyroidectomy vestibular approach (TOETVA) were included. Cumulative sum (CUSUM) was used to analyze learning curves based on intraoperative blood loss and total operative times and learning phases were divided accordingly.

RESULTS

Three hundred seventy-two remote-access thyroid and parathyroid procedures were performed during the study period. Total operative time for transaxillary procedures was initially reduced after the 69th procedure and then again after the 134th case. For retroauricular procedures, marked reduction in the operative time was observed after 21 procedures. Most patients (57.02%) were discharged home on the same day during the mastering phase. In the transaxillary procedures, only 1 case of brachial plexus injury occurred prior to the routine use of somatosensory evoked potential (SSEP) monitoring.

DISCUSSION

Remote-access thyroid and parathyroid surgeries can be performed safely with minimal complications in a select group of patients. Analysis of the learning curve in performing these operations aids in structuring a safe and effective learning period for endocrine surgeons seeking to venture into this modality of treatment.

Vitamin D insufficiency as a potential culprit in critical COVID-19 patients

BACKGROUND

As an immune modulator, vitamin D has been implicated in the coronavirus disease-2019 (COVID-19) outcome. We aim to systematically explore the association of vitamin D serum levels with COVID-19 severity and prognosis.

METHODS

The standardized mean difference (SMD) or odds ratio and 95% confidence interval (CI) were applied to estimate pooled results from six studies. The prognostic performance of vitamin D serum levels for predicting adverse outcomes with detection of the best cutoff threshold was determined by receiver operating characteristic curve analysis. Decision tree analysis by combining vitamin D levels and clinical features was applied to predict severity in COVID-19 patients.

RESULTS

Mean vitamin D serum level of 376 patients, was 21.9 nmol/L (95% CI = 15.36-28.45). Significant heterogeneity was found (I²  = 99.1%, p < .001). Patients with poor prognosis (N = 150) had significantly lower serum levels of vitamin D compared with those with good prognosis (N = 161), representing an adjusted standardized mean difference of -0.58 (95% Cl = -0.83 to -0.34, p < .001).

CONCLUSION

Serum vitamin D levels could be implicated in the COVID-19 prognosis. Diagnosis of vitamin D deficiency could be a helpful adjunct in assessing patients' potential of developing severe COVID-19. Appropriate preventative and/or therapeutic intervention may improve COVID-19 outcomes.

Impact of surgery versus medical management on cardiovascular manifestations in Graves disease

BACKGROUND

Graves disease is well known to have multiple adverse effects on the cardiovascular system. We compared the cardiovascular outcomes after surgical intervention versus medical treatment in patients with Graves disease.

METHODS

We performed a retrospective study of all Graves disease patients with a cardiovascular comorbidity who underwent either surgical or medical management (N = 151). Perioperative biochemical and cardiovascular outcomes from the surgical versus the medical groups were analyzed.

RESULTS

Of 151 patients, 69 (45.6%) patients underwent total thyroidectomy and 82 (54.3%) patients received medical treatment. Hypertension resolved in 44.7% of the patients from the surgical group vs 18% in the medical group (P = .03). Tachyarrhythmias, including atrial fibrillation and tachycardia, improved in 85.9% of patients in the surgical group vs 66% in the medical group (P = .01). All cardiovascular manifestations examined, hypertension, tachyarrhythmias, and heart failure, improved in 69% of patients in the surgical group and 42.6% of patients in the medical group during the follow-up period (P < .01).

CONCLUSION

Surgical treatment offers a significant and rapid clinical improvement of cardiovascular manifestations in Graves disease patients, such as hypertension, tachyarrhythmias, and heart failure. Surgery should be considered and recommended in Graves disease patients with known cardiovascular manifestations.

Identification of a role for actin in translational fidelity in yeast

Numerous studies have suggested a role for actin in translation, but the molecular details of this role are unknown. To elucidate the function(s) of actin in translation, we have studied 25 isogenic, conditional yeast actin mutants. Strikingly, analysis of these mutants indicates that none of those tested have conditional growth defects caused by reduced rates of protein synthesis; and analysis of latrunculin A-treated wild-type cells indicates that even complete disruption of the actin cytoskeleton has no significant effect on the rate of translation. However, analysis of the effect of the 25 actin mutations on fidelity and sensitivity to translation inhibitors identified two mutations ( act1-2 and act1-122) that cause a significant reduction in the fidelity of translation, as assayed by nonsense suppression, and several mutants that are sensitive to paromomycin, which affects translational fidelity. Translation elongation factor 1A (eEF1A) also has a role in fidelity, and in the presence of excess eEF1A four of the mutants ( act1-2, act1-20, act1-120, and act1-125) are even more sensitive to paromomycin, while one mutant ( act1-122) becomes less sensitive. Together, these findings suggest that actin may not be important for the rate of translation, but may have a critical role in ensuring translational fidelity.

Characterization of a general stabilizer element that blocks deadenylation-dependent mRNA decay

mRNA degradation is a regulated process that can play an important role in determining the level of expression of specific genes. The rate at which a specific mRNA is degraded depends largely on specific cis-acting sequences located throughout the transcript. cis-Acting destabilizer sequences that promote increased rates of decay have been identified in several short-lived mRNAs. However, little is known about elements that promote stability, known as stabilizer elements (STEs), and how they function. The work presented here describes the characterization of a STE in the PGK1 transcript. The PGK1 stabilizer element (P-STE) has been delineated to a 64-nucleotide sequence from the coding region that can stabilize a chimeric transcript containing the instability elements from the 3'-untranslated region of the MFA2 transcript. The P-STE is located within the PGK1 coding region and functions when located in the translated portion of the transcript and at a minimum distance from the 3'-untranslated region. These results further support the link between translation and mRNA degradation. A conserved sequence in the TEF1/2 transcript has been identified that also functions as a STE, suggesting that this sequence element maybe a general stability determinant found in other yeast mRNAs.

Overexpression of translation elongation factor 1A affects the organization and function of the actin cytoskeleton in yeast

The translation elongation factor 1 complex (eEF1) plays a central role in protein synthesis, delivering aminoacyl-tRNAs to the elongating ribosome. The eEF1A subunit, a classic G-protein, also performs roles aside from protein synthesis. The overexpression of either eEF1A or eEF1B alpha, the catalytic subunit of the guanine nucleotide exchange factor, in Saccharomyces cerevisiae results in effects on cell growth. Here we demonstrate that overexpression of either factor does not affect the levels of the other subunit or the rate or accuracy of protein synthesis. Instead, the major effects in vivo appear to be at the level of cell morphology and budding. eEF1A overexpression results in dosage-dependent reduced budding and altered actin distribution and cellular morphology. In addition, the effects of excess eEF1A in actin mutant strains show synthetic growth defects, establishing a genetic connection between the two proteins. As the ability of eEF1A to bind and bundle actin is conserved in yeast, these results link the established ability of eEF1A to bind and bundle actin in vitro with nontranslational roles for the protein in vivo.

Replication of nuclei from cycling and quiescent mammalian cells in 6-DMAP-treated Xenopus egg extract

Nuclear membrane permeabilization is required for replication of quiescent (G0) cell nuclei in Xenopus egg extract. We now demonstrate that establishment of replication competence in G0 nuclei is dependent upon a positive activity present in the soluble egg extract. Our hypothesis is that G0 nuclei lose the license to replicate following growth arrest and that this positive activity is required for relicensing DNA for replication. To determine if G0 nuclei contain licensed DNA, we used the protein kinase inhibitor, 6-dimethylaminopurine (6-DMAP), to prepare egg extracts that are devoid of licensing activity. Intact nuclei, isolated from mammalian cells synchronized in G1-phase (licensed), G2-phase (unlicensed), and G0 were permeabilized and assayed for replication in 6-DMAP-treated and untreated extracts supplemented with [alpha-32P]dATP or biotinylated-dUTP. Very little radioactivity was incorporated into nascent DNA in each nuclear population; however, nearly all nuclei in each population incorporated biotin in 6-DMAP extract. The pattern of biotin incorporation within these nuclei was strikingly similar to the punctate pattern observed within nuclei incubated in aphidicolin-treated extract, suggesting that initiation events occur within most replication factories in 6-DMAP extract. However, density substitution and alkaline gel analyses indicate that the incorporated biotin within these nuclei arises from a small number of active origins which escape 6-DMAP inhibition. We conclude that 6-DMAP-treated egg extract cannot differentiate licensed from unlicensed mammalian somatic cell nuclei and, therefore, cannot be used to determine the "licensed state" of G0 nuclei using the assays described here.

Histone H1 modulates DNA replication through multiple pathways in Xenopus egg extract

We investigated the effects of histone H1s on DNA replication using Xenopus egg extract. Mouse variants H1c and H10 were assembled onto Xenopus sperm chromatin by the extract during the remodeling that accompanies nuclear decondensation. The association of H1 with chromatin was rapid and concentration dependent. H1-associated chromatin displayed a typical nucleosomal repeat pattern indicating that linker histones are properly positioned along the DNA. The presence of H1 on sperm chromatin reduced both the rate and extent of DNA replication in egg extract. This reduction in rate is due, in part, to a delay in initiation of replication within individual nuclei. Initiation in extract is dependent upon nuclear assembly. Analysis of the assembly process revealed that H1 does not inhibit nuclear membrane formation or the import of nuclear protein, however, it does slow the rate of nuclear lamina formation. This H1-induced delay in lamina assembly is responsible for the delay in initiation as pre-assembled H1-containing nuclei initiate replication at the same time as control nuclei. However, H1 inhibits replication even when lamina assembly is complete suggesting that H1 also affects replication directly. These data indicate that H1 modulates DNA replication through multiple pathways in egg extract.

Reactivation of DNA replication in nuclei from terminally differentiated cells: nuclear membrane permeabilization is required for initiation in Xenopus egg extract

We have used Xenopus egg extract to investigate the requirements for reactivation of DNA replication in nuclei isolated from terminally differentiated chicken erythrocytes. Previous work has shown that reactivation of erythrocyte nuclei in egg extract is accompanied by chromatin decondensation, nuclear envelope reformation, and the accumulation of egg lamin, LIII. However, in those studies, erythrocyte nuclei were prepared by methods that were not designed to maintain the selective permeability of the nuclear membrane, and as such, it is not clear if loss of nuclear membrane integrity played a role in the reactivation process. Therefore, the purpose of this study was to determine if changes in nuclear membrane permeability are required for reactivation of erythrocyte nuclei in egg extract. Nuclei with intact nuclear membranes were prepared from erythrocytes with streptolysin O and permeable nuclei by treatment of intact nuclei with the detergent Nonidet-P40. Like permeable nuclei, most intact nuclei decondensed, imported nuclear protein, and accumulated lamin LIII from the extract. However, unlike permeable nuclei, which replicated extensively in the extract, few intact nuclei initiated replication under the same conditions. These data demonstrate that permeabilization of the nuclear membrane is required for reactivation of DNA replication in terminally differentiated erythrocyte nuclei by egg extract and suggest that loss of nuclear membrane integrity may be a general requirement for replication of quiescent cell nuclei by this system.

Initiation of DNA replication in nuclei from quiescent cells requires permeabilization of the nuclear membrane

We have investigated the replication capacity of intact nuclei from quiescent cells using Xenopus egg extract. Nuclei, with intact nuclear membranes, were isolated from both exponentially growing and contact-inhibited BALB/c 3T3 fibroblasts by treatment of the cells with streptolysin-O. Flow cytometry showed that > 90% of all contact-inhibited cells and approximately 50% of the exponential cells were in G0/G1-phase at the time of nuclear isolation. Intact nuclei were assayed for replication in the extract by incorporation of [alpha-32P]dATP or biotin-dUTP into nascent DNA. Most nuclei from exponential cells replicated in the egg extract, consistent with previous results showing that intact G1 nuclei from HeLa cells replicate in this system. In contrast, few nuclei from quiescent cells replicated in parallel incubations. However, when the nuclear membranes of these intact quiescent nuclei were permeabilized with lysophosphatidylcholine prior to addition to the extract, nearly all the nuclei replicated under complete cell cycle control in a subsequent incubation. The ability of LPC-treated quiescent nuclei to undergo DNA replication was reversed by resealing permeable nuclear membranes with Xenopus egg membranes prior to extract incubation demonstrating that the effect of LPC treatment is at the level of the nuclear membrane. These results indicate that nuclei from G1-phase cells lose their capacity to initiate DNA replication following density-dependent growth arrest and suggest that changes in nuclear membrane permeability may be required for the initiation of replication upon re-entry of the quiescent cell into the cell cycle.

P2U-purinergic receptors on C6-2B rat glioma cells: modulation of cytosolic Ca2+ and cAMP levels by protein kinase C

The activation of P2-purinergic receptors on C6-2B rat glioma cells caused a transient increase in cytosolic-free Ca2+ concentration ([Ca2+]i) as detected by Fura 2 fluorescence ratio imaging of single cells. These purinergic receptors are of the P2U subtype because UTP and ATP were equipotent and substantially more potent than the P2X- and P2Y-selective agonists alpha,beta-methylene ATP and 2-methylthio ATP, respectively. There was homologous desensitization of the Ca2+ responses between UTP and ATP but no heterologous desensitization between these nucleotides and another Ca(2+)-mobilizing receptor agonist, alpha-thrombin. The UTP-induced peak [Ca2+]i rise was insensitive to chelation of extracellular Ca2+ with EGTA. However, the response was abolished after either depletion of intracellular Ca2+ stores with the microsomal Ca(2+)-ATPase inhibitor thapsigargin or blockade of Ca2+ release from intracellular stores with the muscle relaxant dantrolene. The activation of P2U-purinergic receptors and thrombin receptors increased the formation of total inositol phosphates (IPs) and inhibited cAMP accumulation elicited with either the beta-adrenergic receptor agonist (-)-isoproterenol, or forskolin, a direct activator of adenylyl cyclase. UTP- and alpha-thrombin-induced changes in the levels of IPs, cytosolic Ca2+, and agonist-elicited cAMP accumulation were dramatically inhibited (> 80%) by acute treatment of the cells with the protein kinase C activator 4 beta-phorbol 12-myristate 13-acetate but not with the inactive ester 4 alpha-phorbol 12,13-didecanoate. We conclude that in C6-2B cells, the increase in [Ca2+]i after activation of P2U-purinergic receptors is primarily a result of IPs-mediated release of Ca2+ from intracellular stores with secondary influx of Ca2+ by capacitative mechanisms. Also, the inhibition by UTP and alpha-thrombin of agonist-elicited cAMP accumulation is mediated through an increase in [Ca2+]i.

Predominant expression of type-VI adenylate cyclase in C6-2B rat glioma cells may account for inhibition of cyclic AMP accumulation by calcium

In C6-2B cells, agonist-stimulated cyclic AMP accumulation is inhibited when the cytosolic Ca2+ concentration is increased. We now demonstrate that in C6-2B cells: (i) the early kinetics of the cyclic AMP inhibition by substance K (t1/2 = 35 s) and thapsigargin (t1/2 = 1.6 min) closely mimic the kinetics of the cytosolic Ca2+ increase evoked by either agent (t1/2 = 25 s and 1.5 min respectively); (ii) the Ca2+ rise and cyclic AMP inhibition by substance K or thapsigargin are similarly affected in EGTA-containing medium; (iii) PCR detects type-III and type-VI adenylate cyclase cDNAs, and RNAase protection assays show that the mRNA for type-VI adenylate cyclase, an isoform inhibitable by submicromolar Ca2+ concentrations, is the predominant species, strongly suggesting that type-VI adenylate cyclase is probably the target molecule for Ca(2+)-mediated inhibition of cyclic AMP accumulation.

Ca2+ inhibition of beta-adrenergic receptor- and forskolin-stimulated cAMP accumulation in C6-2B rat glioma cells is independent of protein kinase C

In C6-2B rat glioma cells, agonist-stimulated cAMP accumulation is potently inhibited after the stimulation of endogenous bradykinin receptors or stably transfected substance K receptors, coupled to phosphatidylinositol hydrolysis. In the present report, pharmacological tools were used to selectively stimulate either protein kinase C or Ca2+, the two final effectors activated upon phosphatidylinositol hydrolysis, and their role in the inhibition of the C6-2B cell cAMP signaling pathway was investigated. Activation of protein kinase C by an acute treatment with phorbol 12-myristate 13-acetate or L-alpha-1-oleoyl-2-acetyl-sn-3-glycerol did not reduce, but rather enhanced, the cAMP accumulation elicited by forskolin, a direct activator of adenylyl cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]. This effect was antagonized by the protein kinase inhibitor H-7 and mimicked by the protein phosphatase inhibitor okadaic acid. Thapsigargin, a selective microsomal Ca(2+)-ATPase inhibitor, evoked a sustained increase in the intracellular free Ca2+ concentration, with an EC50 of 24.8 +/- 4.3 nM, and inhibited the cAMP accumulation induced by the beta-adrenergic receptor agonist isoproterenol with comparable potency (IC50 = 19.3 +/- 0.2 nM), strongly suggesting a causal relationship between the two phenomena. The inhibition by thapsigargin of isoproterenol- or forskolin-stimulated cAMP accumulation was not affected by pertussis toxin or down-regulation or inhibition of protein kinase C. Dantrolene, a blocker of Ca2+ release from intracellular stores, antagonized 1) the Ca2+ transient in response to thapsigargin and substance K and 2) the inhibitory effect of these compounds on isoproterenol- or forskolin-induced cAMP accumulation. Moreover, sequestration of intracellular Ca2+ with the cell-permeable Ca2+ chelator ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid acetoxymethyl ester abolished the cAMP inhibition mediated by thapsigargin. Finally, isoproterenol- or forskolin-stimulated adenylyl cyclase activity in digitonin-permeabilized cells was not affected by either thapsigargin or substance K. These data provide compelling evidence that increases in intracellular free Ca2+ concentration without activation of protein kinase C suffice and are responsible for the inhibition of cAMP accumulation in C6-2B cells.

Indirect effect of guanine nucleotides on antagonist binding to A1 adenosine receptors: occupation of cryptic binding sites by endogenous vesicular adenosine

Guanine nucleotides such as guanosine 5'-(3-O-thio)triphosphate (GTP gamma S) have been found to increase the binding of antagonists to adenosine A1 receptors. This response can be attributed either to a direct effect of GTP on receptors to increase antagonist affinity or to an indirect effect to decrease the affinity of receptors for a pool of endogenous adenosine that cannot be readily removed from membranes. In this study, adenosine content was measured in preparations of membranes and 3-[(3-cholamidopropyl)dimethylamino]-1-propanesulfonate (CHAPS)-solubilized receptors by a sensitive radioimmunoassay. In both preparations, pools of adenosine (2.5-10 pmol/mg of protein) were detected that were resistant to deamination by added adenosine deaminase (0.5-3 units/ml) unless membrane lipids were first dissolved in acetone. Electron microscopic examination of crude CHAPS-solubilized receptors revealed the existence of small vesicles (< 1 microns in diameter). Furthermore, most "solubilized" receptors were retained by a 0.1-microns filter. The effects of GTP gamma S were evaluated on the binding of an antagonist, 3-(4-amino-3-125I-phenethyl)-1-propyl-8-cyclopentylxanthine (125I-BW-A844U), to A1 receptors of bovine brain membranes, receptors solubilized in CHAPS (crude solubilized), or receptors partially co-purified with G proteins by agonist affinity chromatography (partially purified). GTP gamma S (10 microM) increased antagonist binding to membranes (20-50%) and crude CHAPS-solubilized receptors (> 200%) but increased binding to partially purified receptors by only 10-15%. GTP gamma S decreased agonist (125I-N6-aminobenzyladenosine) binding and increased antagonist Bmax, but did not significantly decrease (5%) the dissociation rate of the antagonist. Omission of Mg2+ mimicked the effects of GTP gamma S on agonist and antagonist binding and increased both the association and dissociation rates of 125I-BW-A844U. These data suggest that a Mg(2+)-dependent GTP gamma S-induced increase in antagonist binding to membranes and solubilized receptors is primarily due to unmasking of cryptic binding sites occupied by contaminating vesicular adenosine. These findings are consistent with the observation that adenosine receptor antagonists have been found to have little or no inverse agonist physiological effects in well oxygenated tissues.

A1 adenosine receptors of bovine brain couple to guanine nucleotide-binding proteins Gi1, Gi2, and Go

A1 adenosine receptors and associated guanine nucleotide-binding proteins (G proteins) were purified from bovine cerebral cortex by affinity chromatography (Munshi, R., and Linden, J. (1989) J. Biol. Chem. 264, 14853-14859). In this study we have identified the pertussis toxin-sensitive G protein subunits that co-purify with A1 adenosine receptors by immunoblotting with specific antipeptide antisera. Gi alpha 1, Gi alpha 2, Go alpha, G beta 35, and G beta 36 were detected. Of the total [35S]guanosine 5'-O-(3-thio)triphosphate [( 35S]GTP gamma S) binding sites, Gi alpha 1 and Go alpha each accounted for greater than 37% whereas Gi alpha 2 comprised less than 13%. G beta 35 was found in excess over G beta 36. Low molecular mass (21-25 kDa) GTP-binding proteins were not detected. We also examined the characteristics of purified receptors and various purified bovine brain G proteins reconstituted into phospholipid vesicles. All three alpha-subunits restored GTP gamma S-sensitive high affinity binding of the agonist 125I-aminobenzyladenosine to a fraction (25%) of reconstituted receptors with a selectivity order of Gi2 greater than Go greater than or equal to Gi1 (ED50 values of G proteins measured as fold excess over the receptor concentration were 4.7 +/- 1.2, 24 +/- 5, and 34 +/- 7, respectively). Furthermore, receptors occupied with the agonist R-phenylisopropyladenosine catalytically increased the rate of binding of [35S]GTP gamma S to reconstituted G proteins by 6.5-8.5-fold. These results suggest that A1 adenosine receptors couple indiscriminately to pertussis toxin-sensitive G proteins.

Interaction of purified bovine brain A1-adenosine receptors with guanine nucleotide-binding proteins of human platelet membranes following reconstitution

A1-adenosine receptors and associated guanine nucleotide-binding proteins (G proteins) have been co-purified from bovine cerebral cortex by agonist affinity chromatography [J. Biol. Chem. 264:14853-14859 (1989)]. In this study we have reconstituted purified bovine brain A1 receptors into human platelet membranes that contain A2- but no detectable A1-adenosine receptors. The recovery of reconstituted receptors was assessed from the binding of the antagonist radioligand [125I]3-(4-amino-3-iodo)phenethyl-1-propyl-8-cyclopentyl-xanthine and ranged from 32 to 84%. Coupling of reconstituted A1 receptors to platelet G proteins was evaluated by measurement of the high affinity binding of an agonist radioligand, 125I-aminobenzyladenosine, to receptor-G protein complexes and by stereospecific photoaffinity labeling of a 35,000-Da receptor polypeptide with the agonist photoaffinity label 125I-azidobenzyladenosine. Fifty percent of receptors reconstituted into platelet membranes bound agonists with high affinity, indicative of coupling to platelet G proteins. Reconstituted A1 receptors bound various ligands with affinities characteristic of A1 receptors of bovine brain. Although platelets contain both pertussis toxin-sensitive and -insensitive G proteins, reconstituted high affinity agonist binding was almost completely abolished by treatment of platelet membranes with guanosine 5'-3-O-(thio)triphosphate, pertussis toxin, N-ethylmaleimide, or heparin. Following reconstitution, A1 receptors could be resolubilized in complexes with platelet G proteins. The data suggest that marked species differences in the binding affinity of ligands to adenosine receptors result from differences in the receptors rather than membrane structure or G proteins and, further, that A1 receptors couple selectively and tightly to pertussis toxin-sensitive G proteins.

Co-purification of A1 adenosine receptors and guanine nucleotide-binding proteins from bovine brain

A1 adenosine receptors and guanine nucleotide-binding proteins (G proteins) solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate have been co-purified from bovine cerebral cortex. A portion of solubilized receptors which displays high affinity GTP-sensitive agonist binding (40-50%) adheres tightly to agonist affinity columns composed of N6-aminobenzyladenosine-agarose. A1 adenosine receptors and G proteins are rapidly and selectively coeluted from agonist columns by the addition of 8-p-sulfophenyltheophylline, but only in combination with Mg2+-GTP or N-ethylmaleimide, agents which lower the affinity of receptors for agonists. Purified receptors and G protein alpha-subunits can be detected with the potent A1-selective antagonist radioligand, [125I]3-(4-amino-3-iodo)phenethyl-1-propyl-8-cyclopentylxanthine (125I-BW-A844U) and [35S]guanosine 5'-3-O-(thio)triphosphate [( 35S]GTP gamma S), respectively. Pretreatment of solubilized receptors with 0.1 mM N-ethylmaleimide or 0.1 mM R-phenylisopropyladenosine abolishes adsorption of receptors and G proteins to affinity columns. Following removal of 8-p-sulfophenyltheophylline and GTP, purified receptors bind agonists (2 sites) and antagonists (1 site) with affinities similar to crude soluble receptors and typical of A1 receptors. Some receptors may be denatured as a result of purification since only 23% of the radioligand binding sites which adhere to the affinity column can be detected in the eluate. The Bmax of purified receptors, 820 +/- 100 pmol/mg protein (n = 3) is 1800-fold higher than crude soluble receptors. The specific activity of [35S]GTP gamma S binding sites in affinity column eluates is 4640 pmol/mg protein. Assuming a 1:1 stoichiometry, this specific activity indicates that receptor-G protein complexes are greater than 50% pure following affinity chromatography. The photoaffinity labeled purified receptor was identified by polyacrylamide gel electrophoresis as a single band with a molecular mass of 35 kDa which when deglycosylated undergoes a characteristic shift in molecular mass to a sharp band at 32 kDa. In addition to the receptor, silver staining revealed polypeptides with molecular masses of 39 and 41 kDa, which are ADP-ribosylated by pertussis toxin, and 36 kDa corresponding to G protein beta-subunits.

5'-Deoxy-5'-methylthioadenosine: a nucleoside which differentiates between adenosine receptor types

The activities of an endogenous nucleoside, 5'-deoxy-5'-methylthioadenosine (MTA), on adenosine sensitive sites such as adenosine A1 and A2 receptors and the P-site, as well as on purine nucleoside transport, have been studied. This nucleoside competitively antagonized the A2 receptor-mediated stimulation of neuroblastoma adenylate cyclase, produced a GTP-dependent and 8-p-sulfophenyltheophylline-sensitive inhibition of adenylate cyclase activity in rat cerebellar membranes, and decreased the spontaneous contractile activity of isolated segments of rabbit jejunum. MTA was neither active at the P-site nor did it diminish the binding of [3H]nitrobenzylthioinosine, a nucleoside transport inhibitor. We conclude that (a) MTA is an agonist at the adenosine A1 receptor but an antagonist at the A2 receptor, and (b) the adenosine receptor which causes relaxation of rabbit jejunum is not a neuroblastoma-type A2 receptor which activates adenylate cyclase.

Characterization of forskolin binding sites in rat brain membranes using [14,15-3H]14,15-dihydroforskolin as a ligand

[14,15-3H]14,15-Dihydroforskolin [( 3H]DHF) has been used as a radioactive ligand to identify forskolin binding sites in rat brain membranes. The binding was saturable and reversible. The binding sites showed positive cooperative properties as evident from an upward convex Scatchard plot and a Hill coefficient of 1.6. The equilibrium dissociation constants (KD) were in the range between 10 microM and 10 nM as estimated from the limiting slopes of the curved Scatchard plot. Half-maximal saturation of the binding sites was observed at a ligand concentration of 225 nM. The binding kinetics were very rapid: Binding equilibrium was reached in less than 2 min and a large excess of cold forskolin displaced 80% of the radioligand within 2 min. The dissociation reaction was not first order, characterized by a decreasing dissociation rate constant. Bound [3H]DHF could be displaced with forskolin (IC50 0.3 microM), 14,15-dihydroforskolin (IC50 0.8 microM) and 7-desacetylforskolin (IC50 3 microM). However, nucleotides (ATP, GTP) and other receptor ligands (adenosine, isoproterenol) had no effect on the binding. Although the density of the forskolin binding sites (3.2 pmole/mg protein) is similar to those of other adenylate cyclase linked receptors, discrepancies between the KD and the ED50 obtained in adenylate cyclase studies and the finding that activation of the enzyme by forskolin is negative cooperative makes it difficult to clearly relate the binding sites to adenylate cyclase.

Radioiodination of p-hydroxyphenylisopropyladenosine: development of a new ligand for adenosine receptors

dl-p-Hydroxyphenylisopropyladenosine has been iodinated with 125I and tested as a ligand of adenosine receptors in membranes from rat brain using a filtration assay. Binding studies using l-[3H]phenylisopropyladenosine as a ligand were carried out in parallel, and the binding of both ligands could be displaced by dl-p-hydroxyphenylisopropyladenosine and l-phenylisopropyladenosine in a similar fashion. These data establish the feasibility of using radioiodinated derivatives of adenosine as ligands of suitable types of adenosine receptors.