Hippocampal HDAC6 promotes POCD by regulating NLRP3-induced microglia pyroptosis via HSP90/HSP70 in aged mice

BACKGROUND

Postoperative Cognitive Dysfunction (POCD) has attracted increased attention, but its precise mechanism remains to be explored. This study aimed to figure out whether HDAC6 could regulate NLRP3-induced pyroptosis by modulating the functions of HSP70 and HSP90 in microglia to participate in postoperative cognitive dysfunction in aged mice.

METHODS

Animal models of postoperative cognitive dysfunction in aged mice were established by splenectomy under sevoflurane anesthesia. Morris water maze was used to examine the cognitive function and motor ability. Sixteen-months-old C57BL/6 male mice were randomly divided into six groups: control group (C group), sham surgery group (SA group), splenectomy group (S group), splenectomy + HDAC6 inhibitor ACY-1215 group (ACY group), splenectomy + HDAC6 inhibitor ACY-1215 + HSP70 inhibitor Apoptozole group (AP group), splenectomy + solvent control group (SC group). The serum and hippocampus of mice were taken after mice were executed. The protein levels of HDAC6, HSP90, HSP70, NLRP3, GSDMD-N, cleaved-Caspase-1 (P20), IL-1β were detected by western blotting. Serum IL-1β, IL-6 and S100β were measured using ELISA assay, and cell localization of HDAC6 was detected by immunofluorescence. In vitro experiments, BV2 cells were used to validate whether this mechanism worked in microglia. The protein levels of HDAC6, HSP90, HSP70, NLRP3, GSDMD-N, P20, IL-1β were detected by western blotting and the content of IL-1β in the supernatant was measured using ELISA assay. The degree of acetylation of HSP90, the interaction of HSP70, HSP90 and NLRP3 were analyzed by coimmunoprecipitation assay.

RESULTS

Splenectomy under sevoflurane anesthesia in aged mice could prolong the escape latency, reduce the number of crossing platforms, increase the expression of HDAC6 and activate the NLRP3 inflammasome to induce pyroptosis in hippocampus microglia. Using ACY-1215 could reduce the activation of NLRP3 inflammasome, the pyroptosis of microglia and the degree of spatial memory impairment. Apoptozole could inhibit the binding of HSP70 to NLRP3, reduce the degradation of NLRP3 and reverse the protective effect of HDAC6 inhibitors. The results acquired in vitro experiments closely resembled those in vivo, LPS stimulation led to the pyroptosis of BV2 microglia cells and the release of IL-1β due to the activation of the NLRP3 inflammasome, ACY-1215 showed the anti-inflammatory effect and Apoptozole exerted the opposite effect.

CONCLUSIONS

Our findings suggest that hippocampal HDAC6 promotes POCD by regulating NLRP3-induced microglia pyroptosis via HSP90/HSP70 in aged mice.

Transcription factor EBF1 mitigates neuropathic pain by rescuing Kv1.2 expression in primary sensory neurons

Nerve injury-induced alternations of gene expression in primary sensory neurons of the dorsal root ganglion (DRG) are molecular basis of neuropathic pain genesis. Transcription factors regulate gene expression. In this study, we examined whether early B cell factor 1 (EBF1), a transcription factor, in the DRG, participated in neuropathic pain caused by chronic constriction injury (CCI) of the sciatic nerve. EBF1 was distributed exclusively in the neuronal nucleus and coexpressed with cytoplasmic/membrane Kv1.2 in individual DRG neurons. The expression of Ebf1 mRNA and protein was time-dependently downregulated in the ipsilateral lumbar (L) 3/4 DRGs after unilateral CCI. Rescuing this downregulation through microinjection of the adeno-associated virus 5 expressing full-length Ebf1 mRNA into the ipsilateral L3/4 DRGs reversed the CCI-induced decrease of DRG Kv1.2 expression and alleviated the development and maintenance of mechanical, heat and cold hypersensitivities. Conversely, mimicking the downregulation of DRG EBF1 through microinjection of AAV5-expressing Ebf1 shRNA into unilateral L3/4 DRGs produced a reduction of Kv1.2 expression in the ipsilateral L3/4 DRGs, spontaneous pain, and the enhanced responses to mechanical, heat and cold stimuli in naive mice. Mechanistically, EBF1 not only bound to the Kcna2 gene (encoding Kv1.2) promoter but also directly activated its activity. CCI decreased the EBF1 binding to the Kcna2 promoter in the ipsilateral L3/4 DRGs. Our findings suggest that DRG EBF1 downregulation contributes to neuropathic pain likely by losing its binding to Kcna2 promoter and subsequently silencing Kv1.2 expression in primary sensory neurons. Exogenous EBF1 administration may mitigate neuropathic pain by rescuing DRG Kv1.2 expression.

Surgeon Perspectives on Daily Presentation of Ethical Dilemmas: A Qualitative Study

BACKGROUND

Surgeons encounter and navigate a unique set of ethical dilemmas. The American College of Surgeons (ACS) previously identified 6 core ethical issues central to the practice of surgery, but there have been no reports of the true range and complexity of ethical dilemmas encountered by surgeons in their daily practice. Qualitative research is well positioned to address this question.

STUDY DESIGN

We conducted in-depth interviews with attending surgeons across multiple surgical subspecialties at a large, urban, academic medical center asking them to describe the most common ethical dilemmas they encounter in day-to-day practice. Interviews were recorded, transcribed, and coded according to a grounded theory, inductive approach.

RESULTS

Thirty attending surgeons were interviewed, representing twelve different general surgery subspecialties. The majority of dilemmas identified pertained to 4 of the 6 ACS identified core ethical issues: professional obligations, competition of interests, truth telling, and end-of-life care. No participants described dilemmas relating to the themes of confidentiality or surrogate decision-making. Approximately one-third of participants identified ethical issues not well characterized by the ACS core principles, most often relating to the pressure to provide care that is not medically indicated. There was strong support for a formalized surgical ethics curriculum.

CONCLUSIONS

Although the ACS-defined core ethical issues in surgery appropriately captured many ethical dilemmas identified by participants, surgeons described several scenarios not well characterized by these themes. A dedicated surgical ethics curriculum may help to better equip surgeons to navigate the ethical dilemmas they are likely to face in practice.

Society for Cardiovascular Angiography and Interventions Shock Classification to Stratify Outcomes of Extracorporeal Membrane Oxygenation

We applied the Society for Cardiovascular Angiography and Interventions (SCAI) schema to cardiogenic shock (CS) patients treated with venoarterial extracorporeal membrane oxygenation (VA-ECMO) to assess performance in this high acuity group of patients. Records of adult patients receiving VA-ECMO for CS at our institution from 01/2015 to 12/2019 were reviewed. Post-cardiotomy and noncardiogenic shock patients were excluded. A total of 245 patients were included, with a median age of 59 years [IQR: 48-67]; 159 (65%) were male. There were 34 (14%) patients in Stage C, 82 (33%) in D, and 129 (53%) in E. Of E patients, 88 (68%) were undergoing cardiopulmonary resuscitation. Median ECMO duration decreased with stage (C:7, D:6, E:4 days, P < 0.001). In-hospital mortality increased (C:35%, D:56%, E:71%, P < 0.001) and myocardial recovery decreased with stage (C:65%, D:35%, E:30%, P < 0.001). Acute kidney injury (C:35%, D:45%, E:54%, P = 0.045), acute liver failure (C:32%, D:66%, E:76%, P < 0.001), and infection (C:35%, D:28%, E:16%, P = 0.004) varied among groups. Multivariable analysis revealed age (HR=1.02), male sex (HR=0.62), and E classification (HR=2.69) as independently associated with 1-year mortality. Competing-risks regression identified D (SHR=0.53) and E classification (SHR=0.45) as inversely associated with myocardial recovery. In patients treated with VA-ECMO for CS, the SCAI classification provided robust risk stratification.

Clinical efficacy of direct or indirect left ventricular unloading during venoarterial extracorporeal membrane oxygenation for primary cardiogenic shock

OBJECTIVE

Left ventricular (LV) distention is a feared complication in patients receiving venoarterial (VA) extracorporeal membrane oxygenation (ECMO). LV unloading can be achieved indirectly with intra-aortic balloon pump (IABP) or directly with an Impella device (Abiomed, Danvers, Mass). We sought to assess the clinical and hemodynamic effects of IABP and Impella devices on patients supported with VA ECMO.

METHODS

We conducted a retrospective review of VA ECMO patients at our institution from January 2015 to June 2020. Patients were categorized as either ECMO alone or ECMO with LV unloading. LV unloading was characterized as either ECMO with IABP or ECMO with Impella. We recorded baseline characteristics, survival, complications, and hemodynamic changes associated with device initiation.

RESULTS

During the study, 143 patients received ECMO alone whereas 140 received ECMO with LV unloading (68 ECMO with IABP, 72 ECMO with Impella). ECMO with Impella patients had a higher incidence of bleeding events compared with ECMO alone or ECMO with IABP (52.8% vs 37.1% vs 17.7%; P < .0001). Compared with ECMO alone, ECMO with IABP patients had better survival at 180 days (log rank P = .005) whereas survival in ECMO with Impella patients was not different (log rank P = .66). In a multivariable Cox hazard analysis, age (hazard ratio [HR], 1.02; 95% confidence interval [CI], 1.00-1.03; P = .015), male sex (HR, 0.54; 95% CI, 0.38-0.80; P = .002), baseline lactate (HR, 1.06; 95% CI, 1.02-1.11; P = .004), baseline creatinine (HR, 1.06; 95% CI, 1.00-1.11; P = .032), need for extracorporeal membrane oxygenation-cardiopulmonary resuscitation (HR, 2.09; 95% CI, 1.40-3.39; P = .001), and presence of pre-ECMO IABP (HR, 0.45; 95% CI, 0.25-0.83; P = .010) were associated with reduced mortality. There was no significant difference in hemodynamic changes in the ECMO with IABP versus ECMO with Impella cohorts.

CONCLUSIONS

Concomitant support with IABP might help reduce morbidity and improve 180-day survival in patients receiving VA ECMO for cardiogenic shock.

Implantable Peripheral Nerve Stimulation for Peripheral Neuropathic Pain: A Systematic Review of Prospective Studies

Peripheral nerve stimulation (PNS) has been utilized for over 50 years with accumulating evidence of efficacy in a variety of chronic pain conditions. The level and strength of evidence supporting the use of PNS for peripheral neuropathic pain remains unclear. The purpose of this review is to synthesize data from prospective studies on the efficacy of PNS for neuropathic pain as it pertains to pain intensity, neurological deficits/neuropathy (e.g., weakness, sensory deficits, gait/balance), and other secondary outcomes (quality of life, satisfaction, emotional functioning, and adverse events). In compliance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, this review identified articles from MEDLINE(R), EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus. Overall, per the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria, pooled results demonstrate very low quality or low quality of evidence supporting modest to substantial improvement in pain and neurological function after PNS implantation for treatment of peripheral neuropathic pain. PNS for phantom limb pain was the only indication that had moderate level evidence. Future prospective and well-powered studies are warranted to assess the efficacy of PNS for peripheral neuropathic pain.

Perioperative Management of Calciphylaxis: Literature Review and Treatment Recommendations

Calciphylaxis is a serious and rare medical condition that leads to substantial clinical manifestations including pain, creating perioperative and treatment challenges. No standard treatment protocol exists nor are comprehensive guidelines available for perioperative management of patients with calciphylaxis. In this review, we evaluate existing literature (January 2000 to May 2021) with the aim to offer guidance for treating patients with this challenging disease through the perioperative period. Although no therapies are currently considered standard for treating calciphylaxis, multiple interventions are available for improving symptoms. Preoperative and intraoperative management involves monitoring and optimizing patient comorbid conditions and any possible electrolyte imbalances. Postoperative management can be challenging when potential calciphylaxis triggers are indicated, such as warfarin and corticosteroids. In addition, poor wound healing and difficult pain control are common. Therefore, a multifactorial approach to controlling postoperative pain is recommended that includes the use of nerve blocks, renal-sparing opioids, benzodiazepines, and/or ketamine. We present preoperative, intraoperative, and postoperative recommendations for treating calciphylaxis with levels of evidence when appropriate.

Anesthetic Management of a Patient With an Implantable Hypoglossal Nerve Stimulator: A Case Report

Obstructive sleep apnea (OSA) is a common condition, particularly in obese men and in those with an increased neck circumference. Management with a continuous positive airway pressure (CPAP) machine has been the mainstay of treatment over many years; although, it is not acceptable to all. Recently, innovative medical devices, such as hypoglossal nerve stimulators, have emerged and are now being increasingly utilized. We present a case report of a patient undergoing rotator cuff repair on the same side as the implanted device and our recommendations on the anesthetic management.

452. Correlation of Charleston Comorbidity Index Score as the COVID-19 Pandemic Surged Throughout HCA Healthcare Facilities and Patient Outcomes

Background

As the COVID-19 pandemic raged throughout the United States, the healthcare system was strained due to a sudden increase in demand. Testing was initially limited, and the perception was that patients with high comorbidity burden were at higher risk for poor outcomes. The Charleston Comorbidity Index (CCI) is widely used as a predictor of prognosis and one-year mortality for a wide range of pathologies. This study aims to assess whether a correlation exists between CCI score, COVID-19 incidence throughout the pandemic and patient outcomes.

Charleston Comorbidity Index Score

Scoring system for Charleston Comorbidity Index (CCI). Plus 1 point for every decade age 50 years and over, maximum 4 points. Higher scores indicate a more severe condition and consequently, a worse prognosis.

Methods

Multicenter, retrospective review of patients diagnosed with COVID-19 from January 2020 to September 2020 throughout the HCA Healthcare system. The percent of total encounters that were COVID-19 positive by state was calculated along with the average CCI score for COVID-19 patients in 2-month increments. Patient outcomes were obtained across the entire population.

Results

A clear surge of infected patients was seen in almost all states in the dataset from May 2020 onward except in Colorado and Louisiana where the percentage of COVID-19 positive encounters decreased until July 2020. As summer 2020 progressed, the highest percentage of COVID-19 positive encounters among HCA Healthcare facilities was in Florida and Texas. However, despite the fact that more patients were COVID-19 positive in these states, the CCI score was the lowest (Figure 1). The highest average CCI throughout the 9-month period was 7.66 in Colorado. In the first two months of the pandemic, patients who tested positive for COVID-19 had higher CCI scores on average than those who became COVID-19 positive later in the pandemic. Missouri had the lowest CCI average but the highest ICU admissions and in-hospital mortality. Indiana had the lowest average CCI score, and lowest admission rate (Figure 2).

COVID-19 Encounters and Average CCI score by State from January 2020 to September 2020

Graph 1: Percentage of COVID-19 Encounters in 9 Months at an HCA Healthcare Facility by State: Graph presents data obtained for the total of 92,800 patient encounters from January to September 2020 and recorded in 2-month increments. The rate of positive encounters throughout 18 states increased on average from May to September. From January to March 2020, the facilities with the highest rate of COVID-19 encounters were in Colorado, Louisiana and Texas. The states with the highest increment increase of COVID-19 positive patients were Texas, Florida and South Carolina and were trending up as the pandemic wore on through the summer of 2020. Graph 2: Average Charleston Comorbidity Index of COVID-19 Patient Seen at an HCA Healthcare Facility by State in 9 Months: In winter 2020 (January to March 2020) the average CCI score for patients seen with COVDI-19 was higher than in the Spring and Summer 2020 in all states except in Montana and Kentucky. Summer 2020 (May to July 2020) demonstrated some of the lowest average CCI scores for COVID-19 positive patients seen at an HCA Healthcare Facility.

Rate of Positive COVID-19, Patient Outcomes and Average Charleston Comorbidity Index Score by State

Graph 3: Outcomes of COVID-19 Positive Patients Seen at an HCA Healthcare Facility: Mortality and ICU admission was the highest in Missouri, however, the state had the least COVID-19 patients admitted. The rate of positive test per encounter was the highest in Florida and Texas. Texas had a higher mortality among admitted COVID-19 patients than Florida, however, Florida had a higher percentage of COVID-19 patients admitted. Graph 4: Average Charleston Comorbidity Index Score of COVID-19 Positive Patients Seen at an HCA Healthcare Facility: Average CCI was the lowest in Missouri. The states with the highest CCI score were Indiana, California, New Hampshire and Nevada.

Conclusion

We observed an inverse correlation between CCI score and COVID-19 incidence while seeing that, on average, COVID-19 positive patients had higher CCI score in the first few months of the pandemic when incidence rate was lower. CCI score did not correlate to ICU admission, but a higher CCI score correlated to higher admission rate.

Disclosures

All Authors: No reported disclosures

28. Utilizing the Charleston Comorbidity Index as an Independent Predictor for Outcomes in SARS-Cov-2 Positive Patients

Background

Since COVID-19 was declared a pandemic, it has seemed that the virus is nondiscriminatory causing 3.73 million deaths worldwide. The Charleston Comorbidity Index (CCI) is a scoring system predicting the one-year mortality for patients with a range of comorbid conditions and is widely used as a predictor of prognosis and survival for a range of pathologies. This study aims to assess if there is an impact of comorbidity burden on COVID-19 patients by utilizing their CCI score.

Charleston Comorbidity Index Score

Scoring system for Charleston Comorbidity Index (CCI). Plus 1 point for every decade age 50 years and over, maximum 4 points. Higher scores indicate a more severe condition and consequently, a worse prognosis.

Methods

Multicenter, retrospective review of patients diagnosed with COVID-19 from January 2020 to September 2020 throughout the HCA Healthcare system. CCI scores for all COVID-19 positive patients were calculated and logistic regression analysis was performed to predict hospitalization and ICU admission by CCI controlling for age, sex and race. A multinomial regression model was also performed to predict discharge status by CCI controlling for age, sex and race. ROC curves to indicate the CCI cut-off point for each outcome (hospitalization, ICU admission and mortality) was performed, and Youden’s Index was used to identify the optimal point.

Results

In the study timeframe, 92,800 patients were diagnosed with COVID-19 and of those, 48,270 were hospitalized. A one-point increase in CCI was associated with higher odds of hospitalization [OR 1.718; 95% CI 1.696-1.74]. The threshold for significance to predict hospitalization was a CCI of 1.5 (AUC 0.804, Youden Index 0.48) with a specificity (73%) and sensitivity (75%). A one-point increase in CCI was associated with 1.444 higher odds of an ICU admission (95% CI 1.134-1.155). A one-point increase in CCI significantly increased the odds of discharge to hospice compared to any discharge other than hospice [OR 1.162; 95% CI 1.142-1.182]). A one-point increase in CCI score was associated with 1.188 higher odds of in-hospital mortality (95% CI, 1.173-1.203) with a CCI threshold of 3.5 having the highest specificity (50.9%) and sensitivity (79.9%) to predict mortality outcome (AUC 0.704, Youden Index 0.31).

Conclusion

In conclusion CCI score is an adequate predictor of hospitalization and in-hospital mortality but less so in predicting ICU admission in COVID-19 positive patients.

Disclosures

All Authors: No reported disclosures

Evaluation of distal radial artery cross-sectional internal diameter in neonates and infants by ultrasound and adequate selection of an intra-arterial catheter size

BACKGROUND

Radial artery catheterization in neonates, infants, and young children is a common and useful invasive procedure that brings technical placement challenges and potential complications due to the small diameter size of the radial artery in these patients. The aim of this study is to determine appropriate catheter sizes in infants up to 6 months of age.

MATERIALS AND METHODS

A total of fifty infants undergoing general anesthesia or hospitalized in the neonatal intensive care unit were included. Images of the radial artery diameter were obtained from the infant's wrist using Philips EPIQ Diagnostic Ultrasound System CVX Release 4.0. All images obtained were distal in the forearm, medial to the border of the styloid process of the radius, at the point of maximal impulse of the radial artery, and with the wrist at a 45-degree angle position. We recorded postmenstrual age, chronological age, gender, weight, location, comorbidities, medications, weight, and vital signs of each individual.

RESULTS

In this single cohort study of 50 children whose ages ranged from 0 to 6 months chronological age, their radial artery diameters were averaged proportionally to their weight and age. Use of a 22G catheter would result in 100% occlusion of the diameter of the artery in most study subjects. Use of a 24G catheter would result in a range of 75%-99% occlusion depending on weight, postmenstrual age, and chronological age of the infants.

CONCLUSIONS

In view of these findings, we recommend using US to measure the diameter of the radial artery and choose the most appropriate catheter size before proceeding with US-guidance for radial artery cannulation in infants. This will prevent inappropriate sizing of the catheter and the thrombotic complications this can incur.

Deviation from Clinical Routines Can Reveal Sources of Device Design Vulnerability

The ability to adequately ventilate a patient is critical and sometimes a challenge in the emergency, intensive care, and anesthesiology settings. Commonly, initial ventilation is achieved through the use of a face mask in conjunction with a bag that is manually squeezed by the clinician to generate positive pressure and flow of air or oxygen through the patient's airway. Large or small erroneous openings in the breathing circuit can lead to leaks that compromise ventilation ability. Standard procedure in anesthesiology is to check the circuit apparatus and oxygen delivery system prior to every case. Because the face mask itself is not a piece of equipment that is associated with a source of leak, some common anesthesia machine designs are constructed such that the circuit is tested without the mask component. We present an example of a leak that resulted from complete failure of the face mask due to a tiny tear in its cuff by the patient's sharp teeth edges. This subsequently prevented formation of a seal between the face mask and the patient's face and rendered the device incapable of generating the positive pressure it is designed to deliver. This instance depicts the broader lesson that deviation from clinical routines can reveal unappreciated sources of vulnerability in device design.

Deviation from Clinical Routines Can Reveal Sources of Device Design Vulnerability

The ability to adequately ventilate a patient is critical and sometimes a challenge in the emergency, intensive care, and anesthesiology settings. Commonly, initial ventilation is achieved through the use of a face mask in conjunction with a bag that is manually squeezed by the clinician to generate positive pressure and flow of air or oxygen through the patient's airway. Large or small erroneous openings in the breathing circuit can lead to leaks that compromise ventilation ability. Standard procedure in anesthesiology is to check the circuit apparatus and oxygen delivery system prior to every case. Because the face mask itself is not a piece of equipment that is associated with a source of leak, some common anesthesia machine designs are constructed such that the circuit is tested without the mask component. We present an example of a leak that resulted from complete failure of the face mask due to a tiny tear in its cuff by the patient's sharp teeth edges. This subsequently prevented formation of a seal between the face mask and the patient's face and rendered the device incapable of generating the positive pressure it is designed to deliver. This instance depicts the broader lesson that deviation from clinical routines can reveal unappreciated sources of vulnerability in device design.

Dorsal Root Ganglion Stimulation for Chronic Groin Pain: A Review

INTRODUCTION

Chronic neuropathic groin pain develops in a significant number of postsurgical patients; however, multiple etiologies have been identified, and this makes it a challenging condition to treat. While treatment often involves a multimodal approach, advancements in neuromodulation technology, particularly dorsal root ganglion (DRG) stimulation, have benefited patients plagued by chronic pain refractory to standard treatment modalities. Our goal was to provide a definitive source of information for interventional pain physicians regarding groin pain and the use of DRG stimulation for its treatment.

MATERIALS AND METHODS

In this narrative review, we provide an overview of groin pain and discuss potential pain generators. We also outline appropriate treatment options with particular interest on DRG stimulation. Lastly, we provide a narrative review of the published literature regarding DRG stimulation for chronic groin pain from a variety of etiologies.

CONCLUSION

DRG stimulation has emerged as an alternative neuromodulatory technique for patients with chronic groin pain. While previous studies suggest substantial sustained pain relief with DRG stimulation in this patient population, prospective randomized controlled studies are necessary before formal recommendations can be made.

Even the Simplest Devices May Malfunction: Split Septum Design Revisited

Split septum medical devices are used in tubing for intravenous (IV) fluid administration-an extremely common clinical task. These tubing caps contain a needleless, valveless system that allows fluid to flow directly through the lumen of the catheter but prevents backflow of fluid or blood when the tubing extension is not connected. We experienced complete failure of a needle-free connector extension set with a Luer-access split septum device in multiple patients due to the split septum remaining fused and essentially unsplit despite being connected on both ends. This led to an adverse event in a patient due to repeated unnecessary IV insertion attempts. This case shows how even the simplest of devices can malfunction and highlights the need for vigilance in clinical practice.

Even the Simplest Devices May Malfunction: Split Septum Design Revisited

Split septum medical devices are used in tubing for intravenous (IV) fluid administration-an extremely common clinical task. These tubing caps contain a needleless, valveless system that allows fluid to flow directly through the lumen of the catheter but prevents backflow of fluid or blood when the tubing extension is not connected. We experienced complete failure of a needle-free connector extension set with a Luer-access split septum device in multiple patients due to the split septum remaining fused and essentially unsplit despite being connected on both ends. This led to an adverse event in a patient due to repeated unnecessary IV insertion attempts. This case shows how even the simplest of devices can malfunction and highlights the need for vigilance in clinical practice.

Does CagA contribute to ulcer pathogenesis in a developing country, such as Sudan?

BACKGROUND AND OBJECTIVE

In Western populations, peptic ulcer disease is closely associated with Helicobacter pylori (H. pylori) strains expressing the CagA antigen. In Africa the prevalence of H. pylori infection and peptic ulcer disease is high, although information regarding potential virulence factors is lacking. This study examines the prevalence of antibodies to CagA both in African patients with dyspepsia who are undergoing gastroscopy, and in asymptomatic healthy African volunteers.

METHODS

Eighty two consecutive patients (median age 34 years, range 15-73 years), attending for gastroscopy were studied, of whom 78 (95.1%) were subsequently found to be Helicobacter positive. Three antral biopsies were obtained from each patient and 5 ml of blood was taken for determination of CagA seropositivity using western blot analysis. CagA seropositivity was also determined in 65 H. pylori positive healthy volunteers (median age 30 years, range 18-70 years), with no symptoms or previous history of gastroduodenal disease.

RESULTS

Of the 78 H. pylori positive patients, CagA seropositivity was present in all 22 patients with active peptic ulcer disease (100%), in eight of nine patients with duodenitis (89%), in 15 of 19 patients with macroscopic gastritis (78.9%), and in 24 of 28 patients with a normal endoscopy (85.7%). On histological assessment, 46 patients had chronic active gastritis, 29 patients had gastritis with atrophy and three patients had intestinal metaplasia. CagA seropositivity rates were 84.7%, 93% and 100%, respectively, for these groups. In the 89 healthy volunteers studied, 57 of the 65 H. pylori positive subjects (87.7%) were seropositive for the CagA protein.

CONCLUSIONS

As in Western countries, CagA seropositivity in this African population was closely related to endoscopic gastroduodenal disease, and to the presence of more advanced histological lesions in the antrum. However, there was also a high prevalence of CagA seropositivity in asymptomatic healthy individuals, suggesting that factors other than CagA predominate in ulcer pathogenesis in this population.

Codon usage in Cryptosporidium parvum differs from that in other Eimeriorina

Codon usage of Crytosporidium parvum was compared with those of other Eimeriorina Toxoplasma gondii and Eimeria tenella and revealed a biased use of synonymous codons with a preference for NNU (40.0%) and NNA (33.4%). There was no close resemblance of the codon usage of C. parvum to T. gondii (correlation coefficient, r = 0.14) or E. tenella (r = 0.14) but it was similar to Entamoeba histolytica (r = 0.75) and Plasmodium falciparum (r = 0.5). Analysis of the codon usage in homologous gene sequences (actin, beta-tubulin) also failed to reveal a close relationship between C. parvum and T. gondii or E. tenella. The low usage codons in C. parvum were most frequently used codons in T. gondii and E. tenella. These observations are consistent with 18S rRNA sequence analysis which shows no close relationship of Cryptosporidium with other Eimeriorina (Sarcocystis, Toxoplasma and Eimeria) and questions the validity of the current classification of C. parvum.

Impaired IgA response to Giardia heat shock antigen in children with persistent diarrhoea and giardiasis

The serum antibody response in Gambian children with persistent diarrhoea and giardiasis has been studied. Total serum IgG, IgA, and IgM concentrations were increased in these patients as compared with controls from the same area. Determination of the concentrations of Giardia specific antibodies by enzyme linked immuno adsorbent assay (ELISA), however, revealed that only IgM was raised while those of IgA and IgG were similar to the controls. Analysis of the antigenic determinants of the IgG and IgA responses by immunoblotting showed that patients with chronic infection unlike those who clear the infection have no IgA response to a 57 kDa Giardia heat shock antigen. The association of high concentrations of Giardia specific IgM, low concentrations of Giardia specific IgA and IgG and inability to clear the infection suggests that the switch from an IgM to an IgG or IgA response is inefficient.

Codon usage in Giardia lamblia

A codon usage table for the intestinal parasite Giardia lamblia was generated by analysis of the nucleotide sequences of eight genes comprising 3,135 codons. Codon usage revealed a biased use of synonymous codons with a preference for NNC codons (42.1%). The codon usage of G. lamblia more closely resembles that of the prokaryote Halobacterium halobium (correlation coefficient r = 0.73) rather than that of other eukaryotic protozoans, i.e. Trypanosoma brucei (r = 0.434) and Plasmodium falciparum (r = -0.31). These observations are consistent with the view that G. lamblia represents the first line of descent from the ancestral cells that first took on eukaryotic features.

Codon usage in Entamoeba histolytica

The codon usage of 10 E. histolytica genes comprising 4455 codons was analysed. The codon usage revealed an extremely biased use of synonymous codons with a preference for NNU (44%) and NNA (41.4%) codons. Codons CGG (arg), AGG (arg) and CCG (pro) were absent in the E. histolytica genes examined. The codon usage of E. histolytica resembled that of Plasmodium falciparum.

Serum antibody response in children with Giardia lamblia infection and identification of an immunodominant 57-kilodalton antigen

Giardia lamblia antigens which react with sera from children with G. lamblia infection were investigated by sodium-dodecyl polyacrylamide gel electrophoresis and immunoblotting. Serum IgG, IgM and IgA response to the antigens were immunochemically characterized. Serum antibodies from all giardiasis patients, but none of the controls, was found to react with a 57-kilodalton antigen. The 57 kDa antigen elicited IgG and IgA but not IgM antibodies. The protein nature of the 57 kDa antigen was demonstrated by loss of antibody recognition after trypsin treatment of G. lamblia trophozoites. Subcellular fractionation of G. lamblia trophozoites followed by SDS-PAGE and immunoblotting showed that the 57 kDa antigen was probably not a component of the cytoskeleton.

Sequence changes in both flanking sequences of a pre-tRNA influence the cleavage specificity of RNase P

The cleavage specificities of the RNase P holoenzymes from Escherichia coli and the yeast Schizosaccharomyces pombe and of the catalytic M1 RNA from E. coli were analyzed in 5'-processing experiments using a yeast serine pre-tRNA with mutations in both flanking sequences. The template DNAs were obtained by enzymatic reactions in vitro and transcribed with phage SP6 or T7 RNA polymerase. The various mutations did not alter the cleavage specificity of the yeast RNase P holoenzyme; cleavage always occurred predominantly at position G + 1, generating the typical seven base-pair acceptor stem. In contrast, the specificity of the prokaryotic RNase P activities, i.e. the catalytic M1 RNA and the RNase P holoenzyme from E. coli, was influenced by some of the mutated pre-tRNA substrates, which resulted in an unusual cleavage pattern, generating extended acceptor stems. The bases G - 1 and C + 73, forming the eighth base pair in these extended acceptor stems, were an important motif in promoting the unusual cleavage pattern. It was found only in some natural pre-tRNAs, including tRNA(SeCys) from E. coli, and tRNAs(His) from bacteria and chloroplasts. Also, the corresponding mature tRNAs in vivo contain an eight base pair acceptor stem. The presence of the CCA sequence at the 3' end of the tRNA moiety is known to enhance the cleavage efficiency with the catalytic M1 RNA. Surprisingly, the presence or absence of this sequence in two of our substrate mutants drastically altered the cleavage specificity of M1 RNA and of the E. coli holoenzyme, respectively. Possible reasons for the different cleavage specificities of the enzymes, the influence of sequence alterations and the importance of stacking forces in the acceptor stems are discussed.

The methylation of one specific guanosine in a pre-tRNA prevents cleavage by RNase P and by the catalytic M1 RNA

Several modified nucleosides were introduced during in vitro RNA synthesis into a pre-tRNA(Ser). The pre-tRNAs were used as substrates for RNase P enzymes. No effects were observed with biotin-8-ATP or [alpha-S]-GPT, whereas with m7GTP, the cleavage reaction was completely inhibited. Analysis of pre-tRNAs which contained m7G at various positions has revealed a single base at the 5'-end of the acceptor stem where this modification absolutely prevents cleavage by catalytic M1 RNA, eukaryotic and prokaryotic RNase P holoenzymes. These results suggest that a critical contact must be made between pre-tRNA substrate and enzyme/ribozyme or that the approach of the potential cleaving agent (a positive magnesium ion) is made impossible by the positive charge at N-7 of the guanosine. In addition, we have shown that a pre-tRNA containing only m7G's can still form a complex with M1 RNA in a gel retardation assay.

The RNA components of Schizosaccharomyces pombe RNase P are essential for cell viability

The fission yeast Schizosaccharomyces pombe contains in the haploid genome one copy of the gene (designated rrkl) for the RNA components of RNase P. Gene disruption in diploid cells of one copy of rrkl resulted in a moderate reduction of the level of cellular RNase P activity. Haploidization by meiosis demonstrated that rrkl is required for cell growth. Thus, the RNA components of S. pombe RNase P are essential in vivo. This is similar to the situation in Escherichia coli.

Arginyl-tRNA synthetase from Mycobacterium smegmatis SN2: purification and kinetic mechanism

Arginyl-tRNA synthetase [L-Arg: tRNAArg ligase (AMP forming) EC 6.1.1.19] has been purified to homogeneity from Mycobacterium smegmatis SN2. The enzyme is a monomer of molecular weight 56,000. The kinetic patterns obtained by initial velocity and product inhibition studies are consistent with a rapid equilibrium random ter ter mechanism. Polyamines stimulated the formation of arginyl-tRNA, the stimulation being more significant at sub-optimal Mg2+ concentrations. Initial velocity studies performed in the presence of sub-optimal Mg2+ and spermine also indicated that the kinetic mechanism remained sequential random. Various attempts to reveal the formation of enzyme-bound arginyl-adenylate provided no evidence for its existence. The reverse reaction, i.e., the deacylation of arginyl-tRNA, required both AMP and PPi. This observation is consistent with the mechanism proposed.