Self-Reported Long COVID and Its Association with the Presence of SARS-CoV-2 Antibodies in a Danish Cohort up to 12 Months after Infection.

The majority of long coronavirus disease (COVID) symptoms are not specific to COVID-19 and could be explained by other conditions. The present study aimed to explore whether Danish individuals with a perception that they suffer from long COVID have antibodies against the nucleocapsid antigen, as a proxy for detecting previous infection. The study was conducted in February and March 2021, right after the second surge of the COVID-19 pandemic in Denmark. All members of the social media group on Facebook "Covidramte med senfølger" ("long COVID sufferers'') above the age of 17 years and living in Denmark were invited to participate in a short electronic questionnaire about long COVID risk factors and symptoms. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein was detected in blood samples as a proxy for natural SARS-CoV-2 infection. The final study population comprised 341 participants (90.6% females) who completed blood sampling and answered the questionnaire. A total of 232 (68%) were seropositive (median age, 49.5 years; interquartile range [IQR], 41 to 55 years; 90.1% females). There was no significant difference between sexes and serostatus. Seronegative and seropositive individuals had a similar burden of symptoms that could be attributed to long COVID. Time since perceived COVID-19 was significantly longer in the group of seronegative individuals than the seropositive ones (P < 0.001). This study suggests that long-COVID sufferers are mostly women and showed that a third of the participants did not have detectable anti-N-protein antibodies. It emphasizes the importance of early confirmation of COVID-19, as this study indicates an overlap between long-COVID symptoms and symptoms that are possibly of another origin. IMPORTANCE This cohort study included questionnaire data as well as anti-nucleocapsid antibody analysis, allowing us to determine whether participants were seropositive due to vaccination or natural infection. The study emphasizes the importance of early confirmation of COVID-19, as antibodies recede with time, and it indicates an overlap between long COVID symptoms and symptoms possibly of another origin.

Quantification of biotin in plasma samples by column switching liquid chromatography - tandem mass spectrometry.

Biotin (or Vitamin B7) is a vitamin where deficiency can be caused by inadequate intake. Biotin deficiency is rare, as most people get enough biotin from diet, since many foods contain biotin. In addition to biotin from food, intestinal bacteria can synthesize biotin, which can then be absorbed by the body. Supplementation with biotin has been advocated, mainly due to proposed beneficial effects on skin, nail and hair growth. There is no evidence that high biotin intakes are toxic, but a high intake may interfere with diagnostic assays that use biotin-streptavidin technology. These tests are commonly used to measure plasma concentrations of a wide range of hormones. Erroneous results may lead to misdiagnosis of various endocrine disorders. Supplementation with high-dose biotin has been used experimental for the treatment of diseases (e.g. multiple sclerosis) and high doses are used to obtain effect on nail and hair growth. On this background a demand for tests to determine if there is a risk of obtaining false test results when using biotin-streptavidin based tests have appeared. In this paper we present a method based on column switching liquid chromatography tandem mass spectrometry for the quantification of biotin in plasma and serum and explore the effects of biotin on an immunoassay based on biotin strept(avidin) chemistry.

True Chromogranin A concentrations in plasma from patients with small intestinal neuroendocrine tumours.

Objective: The incidence of enteropancreatic neuroendocrine tumours (NET) is increasing. Chromogranin A (CgA) in plasma is a marker in patients suspected of NET tumours. CgA, however, is a precursor protein subjected to cellular processing that challenges quantitation and hence the use of CgA in diagnostics.Materials and methods: CgA concentrations in plasma sampled from 130 well-characterized patients with small intestinal NETs and from 30 healthy subjects were measured with eight commercial CgA kits, an in-house radioimmunoassay (RIA) and a processing-independent assay (PIA). For the evaluation of diagnostic accuracy, we performed regression analyses and plotted receiver-operating characteristic curves (ROC). The specificity was further assessed by size chromatography.Results: Five commercial assays (Thermo-Fisher, DRG Diagnostics, Eurodiagnostica (RIA and ELISA), and Phoenix), displayed a diagnostic accuracy with area under the curve (AUC) values >0.90, whereas three immunoassays (Yanaihara, CisBio RIA, and CisBio ELISA) discriminated poorly between disease stages (AUC: 0.60-0.78). Compared with the in-house assays, however, even the most accurate commercial immunoassay still missed patients with metastatic disease. Chromatography showed non-uniform patterns of large and small CgA fragments in plasma.Conclusion: Available commercial immunoassays measure CgA in plasma with gross variability. Three commercial CgA immunoassays discriminate so poorly between health and disease that they should not be used. The highest diagnostic accuracy was obtained with processing-independent measurement of total CgA concentrations in plasma.

Hypoxia-induced vagal withdrawal is independent of the hypoxic ventilatory response in men.

Hypoxia increases heart rate (HR) in humans by sympathetic activation and vagal withdrawal. However, in anaesthetized dogs hypoxia increases vagal activity and reduces HR if pulmonary ventilation does not increase and we evaluated whether that observation applies to awake humans. Ten healthy males were exposed to 15 min of normoxia and hypoxia (10.5% O2), while respiratory rate and tidal volume were volitionally controlled at values identified during spontaneous breathing in hypoxia. End-tidal CO2 tension was clamped at 40 mmHg by CO2 supplementation. ß-Adrenergic blockade by intravenous propranolol isolated vagal regulation of HR. During spontaneous breathing, hypoxia increased ventilation by 3.2 ± 2.1 l/min ( P = 0.0033) and HR by 8.9 ± 5.5 beats/min ( P < 0.001). During controlled breathing, respiratory rate (16.3 ± 3.2 vs. 16.4 ± 3.3 breaths/min) and tidal volume (1.05 ± 0.27 vs. 1.06 ± 0.24 l) were similar for normoxia and hypoxia, whereas the HR increase in hypoxia persisted without (8.6 ± 10.2 beats/min) and with (6.6 ± 5.6 beats/min) propranolol. Neither controlled breathing ( P = 0.80), propranolol ( P = 0.64), nor their combination ( P = 0.89) affected the HR increase in hypoxia. Arterial pressure was unaffected ( P = 0.48) by hypoxia across conditions. The hypoxia-induced increase in HR during controlled breathing and ß-adrenergic blockade indicates that hypoxia reduces vagal activity in humans even when ventilation does not increase. Vagal withdrawal in hypoxia seems to be governed by the arterial chemoreflex rather than a pulmonary inflation reflex in humans. NEW & NOTEWORTHY Hypoxia accelerates the heart rate of humans by increasing sympathetic activity and reducing vagal activity. Animal studies have indicated that hypoxia-induced vagal withdrawal is governed by a pulmonary inflation reflex that is activated by the increased pulmonary ventilation in hypoxia. The present findings, however, indicate that humans experience vagal withdrawal in hypoxia even if ventilation does not increase, indicating that vagal withdrawal is governed by the arterial chemoreflex rather than a pulmonary inflation reflex.

Plasma chromogranin A is a marker of death in elderly patients presenting with symptoms of heart failure.

Cardiovascular risk assessment remains difficult in elderly patients. We examined whether chromogranin A (CgA) measurement in plasma may be valuable in assessing risk of death in elderly patients with symptoms of heart failure in a primary care setting. A total of 470 patients (mean age 73 years) were followed for 10 years. For CgA plasma measurement, we used a two-step method including a screening test and a confirmative test with plasma pre-treatment with trypsin. Cox multivariable proportional regression and receiver-operating curve (ROC) analyses were used to assess mortality risk. Assessment of cardiovascular mortality during the first 3 years of observation showed that CgA measurement contained useful information with a hazard ratio (HR) of 5.4 (95% CI 1.7-16.4) (CgA confirm). In a multivariate setting, the corresponding HR was 5.9 (95% CI 1.8-19.1). WHEN ADDING N-TERMINAL PROBNP (NT-PROBNP) TO THE MODEL, CGA CONFIRM STILL POSSESSED PROGNOSTIC INFORMATION (HR: 6.1; 95% CI 1.8-20.7). The result for predicting all-cause mortality displayed the same pattern. ROC analyses in comparison to NT-proBNP to identify patients on top of clinical variables at risk of cardiovascular death within 5 years of follow-up showed significant additive value of CgA confirm measurements compared with NT-proBNP and clinical variables. CgA measurement in the plasma of elderly patients with symptoms of heart failure can identify those at increased risk of short- and long-term mortality.

Stimulatory effect of endogenous orexin A on gastric emptying and acid secretion independent of gastrin.

Orexin A (OXA) increases food intake and inhibits fasting small bowel motility in rats. The aim of this study was to examine the effect of exogenous OXA and endogenous OXA on gastric emptying, acid secretion, glucose metabolism and distribution of orexin immunoreactivity in the stomach. Rats equipped with a gastric fistula were subjected to intravenous (IV) infusion of OXA or the selective orexin-1 receptor (OX1R) antagonist SB-334867-A during saline or pentagastrin infusion. Gastric emptying was studied with a liquid non-nutrient or nutrient, using 51Cr as radioactive marker. Gastric retention was measured after a 20-min infusion of OXA or SB-334867-A. Plasma concentrations of OXA, insulin, glucagon, glucose and gastrin were studied. Immunohistochemistry against OXA, OX1R and gastrin in gastric tissue was performed. OXA alone had no effect on either acid secretion or gastric emptying. SB-334867-A inhibited both basal and pentagastrin-induced gastric acid secretion and increased gastric retention of the liquid nutrient, but not PEG 4000. Plasma gastrin levels were unchanged by IV OXA or SB-334867-A. Plasma OXA levels decreased after intake of the nutrient meal and infusion of the OX1R antagonist. Only weak effects were seen on plasma glucose and insulin by OXA. Immunoreactivity to OXA and OX1R were found in the mucosa, myenteric cells bodies and varicose nerve fibers in ganglia and circular muscle of the stomach. In conclusion, endogenous OXA influences gastric emptying of a nutrient liquid and gastric acid secretion independent of gastrin. This indicates a role for endogenous OXA, not only in metabolic homeostasis, but also in the pre-absorptive processing of nutrients in the gut.

Effect of peripherally administered ghrelin on gastric emptying and acid secretion in the rat.

Ghrelin is a gut peptide that is secreted from the stomach and stimulates food intake. There are ghrelin receptors throughout the gut and intracerebroventricular ghrelin has been shown to increase gastric acid secretion. The aim of the present study was to examine the effects of peripherally administered ghrelin on gastric emptying of a non-nutrient and nutrient liquid, as well as, basal and pentagastrin-stimulated gastric acid secretion in awake rats. In addition, gastric contractility was studied in vitro. Rats equipped with a gastric fistula were subjected to an intravenous infusion of ghrelin (10-500 pmol kg(-1) min(-1)) during saline or pentagastrin (90 pmol kg(-1) min(-1)) infusion. After administration of polyethylene glycol (PEG) 4000 with 51Cr as radioactive marker, or a liquid nutrient with (51)Cr, gastric retention was measured after a 20-min infusion of ghrelin (500 pmol kg(-1) min(-1)). In vitro isometric contractions of segments of rat gastric fundus were studied (10(-9) to 10(-6) M). Ghrelin had no effect on basal acid secretion, but at 500 pmol kg(-1) min(-1) ghrelin significantly decreased pentagastrin-stimulated acid secretion. Ghrelin had no effect on gastric emptying of the nutrient liquid, but significantly increased gastric emptying of the non-nutrient liquid. Ghrelin contracted fundus muscle strips dose-dependently (pD2 of 6.93+/-0.7). Ghrelin IV decreased plasma orexin A concentrations and increased plasma somatostatin concentrations. Plasma gastrin concentrations were unchanged during ghrelin infusion. Thus, ghrelin seems to not only effect food intake but also gastric motor and secretory function indicating a multifunctional role for ghrelin in energy homeostasis.