Effect of sexed semen on different production and functional traits in German Holsteins.

The aim of this study was to analyze possible effects of semen type (conventional vs. female sexed) and calf sex on fertility and production traits. For this purpose, field data of German Holstein heifers in Lower Saxony were evaluated. Sexed semen was mainly used for first insemination. 87.0% female calves were born from sexed semen, while 52.7% female calves were born from conventional semen. Heifers inseminated with sexed semen were on average 43 to 48 days younger at their first calving than heifers inseminated with conventional semen. Calf sex had an influence on the average calving ease and the dystocia rates. Male calves showed higher calving ease scores and caused a higher risk for dystocia than female calves. The semen type had no influence on these characteristics. Within the same calf sex, sexed semen had only minor effects on most traits, except for stillbirth rates: the stillbirth rate for male calves from female sexed semen was 30.6%, which was 2.86 times the stillbirth rate of male calves from conventional semen, possibly due to trisomies. Sexed semen played only a minor role for production traits in first lactations. The extrapolated 305-day milk yield was 200 kg lower for first calf heifers, which were inseminated with sexed semen compared to heifers inseminated with conventional semen. Fat and protein yield were 6 kg to 8 kg lower after use of sexed semen. Animals with female offspring from sexed semen showed higher survival rates than the other groups.

A reaction norm sire model to study the effect of metabolic challenge in early lactation on the functional longevity of dairy cows.

Due to the discrepancy of the high energy demand for rapidly increasing milk production and limited feed intake in the transition period around parturition, dairy cows require considerable metabolic adaptations. We hypothesize that some cows are genetically less suited to cope with these metabolic needs than others, leading to adverse follow-up effects on longevity. To test this, we designed a reaction norm model in which functional lifetime was linked to the metabolic challenge in the beginning of the first lactation. As challenge variables, we used either the sum of milk yield or the accumulated fat-to-protein ratio of the first 3 test-days (<120 d in milk), pre-adjusted for herd-test-day variance. We defined a random regression sire model, in which a random slope was estimated for each sire to assess whether a bull had robust (neutral or positive slopes) or non-robust (negative slopes) daughters. We fitted the model to data of ∼580,000 daughters of ∼5,000 Brown Swiss bulls with suitable observations available (≥10 daughters per bull). To validate our proposed model and assess the reliability of the estimated (co)variance components, we conducted an extensive bootstrap approach. For both challenge variables, we found the sire variance for the slope of the random regression to be significantly different from zero, suggesting a genetic component for metabolic adaptability. The results of the study show that the ability to cope with metabolic stress in the transition period has a genetic component, which can be used to breed metabolically robust dairy cows.

Esophageal function tests are not helpful in symptoms suspicious of extraesophageal reflux - a prospective study in 74 patients.

BACKGROUND/AIMS: Symptoms suspicious of extraesophageal reflux (SSEER) include globus, chronic cough, mucous obstruction and hoarseness. Reports of conventional esophageal function tests and measurement of extraesophageal reflux (EER) in these patients are spare providing conflicting results. METHODS: In a prospective study we evaluated 60 patients with SSEER by esophageal function tests (esophageal manometry, combined 24 h pH - metry - impedance and oropharyngeal pH measurement, Dx - pH measurement) and esophagogastroduodenoscopy (EGD). The patients were stratified into 2 groups according to their accompanying reflux symptoms. Group 1, n = 23, comprised patients with SSEER solely and group 2, n = 37 patients with SSEER and reflux symptoms. The patients were compared to patients with reflux symptoms solely (group 3, n = 14). RESULTS: There were no significant differences between the groups according to age, sex and BMI. Patients with SSEER and reflux symptoms (group 2) showed significantly increased proportion of pathological acid reflux, de Meester Score, pH < 4 overall and in upright positon and hypotensive lower esophageal sphincter pressure compared to patients with SSEER solely (group 1) but no significant difference to patients with reflux symptoms solely (group 3). All the other parameters of esophageal testing including non-acid reflux and EER were not significantly different between the three groups. CONCLUSION: The results of the present study do not support a causal link between SSEER and esophageal motility disorders, acid or non-acid reflux and EER as measured by conventional esophageal function tests and oropharyngeal pH measurement.

Clinical impact of esophageal function tests and argon plasma coagulation in heterotopic gastric mucosa of the esophagus and extraesophageal reflux symptoms - a prospective study.

BACKGROUND/AIMS: Globus, chronic cough, mucous obstruction and hoarseness are frequently interpreted and classified as manifestation of extraesophageal reflux (EER) or laryngopharyngeal reflux (LPR). Recent studies have indicated that ablation of heterotopic gastric mucosa of the proximal esophagus (HGMPE) by argon plasma coagulation (APC) significantly reduces EER/LPR symptoms. METHODS: In a prospective study we evaluated 14 patients with HGMPE and EER/LPR symptoms by esophageal function testing (esophageal manometry, combined 24 h-pH-metry-impedance - oropharyngeal-pH measurement), standardized symptom questionnaire (visual analogue scales), and esophagealgastroduodenoscopy (EGD). The patients were stratified into 3 groups: GERD (n = 5), functional heartburn (n = 5) and non-GERD-non-functional heartburn (n = 4). Patients (n = 12) received endoscopic ablation of HGMPE by APC. RESULTS: 73 % of the patients responded to APC with a reduction of frequency and intensity of their EER/LPR symptoms. The response to APC varied between the quality of symptoms and was most frequently seen in globus, swallowing difficulty and mucous obstruction. The magnitude of symptom reduction was highest in heartburn, sore throat, and globus. The response to APC was comparable between the three groups of patients irrespective of GERD and the presence or absence of reflux symptoms. Although 50 % of the patients showed an increased Ryan Score as measured by acid reflux in the posterior oropharynx, comparison between responders and non-responders to APC showed no significant differences with regard to symptom quality, acid and non-acid reflux, LES resting pressure, esophageal motility and Ryan Score. CONCLUSION: The study indicates that a large proportion of patients with HGMPE and EER/LPR symptoms responded to APC. However, we could not demonstrate a clinical or functional parameter that differentiated between responders and non-responders to APC or could predict the response to APC.

Prospective and randomized study to evaluate the clinical impact of cap assisted colonoscopy (CAC).

BACKGROUND: Although colonoscopy is the standard procedure in the diagnosis of colorectal neoplasia, a significant number of clinical relevant lesions may be missed even by experienced endoscopists using current technology. A transparent cap mounted at the tip of a colonoscope may be an easy way to extend the visual field during colonoscopy and may improve the detection rate of mucosal lesions. MATERIAL AND METHODS: The significance of cap assisted (CAC) vs. conventional colonoscopy (CC) on polyp detection rate was evaluated in a prospective randomized controlled trial in 504 patients. RESULTS: CC and CAC detected polyps in 39.3 % and 31.8, not significantly different. There was also no significant difference between CAC and CC according to age, sex, indication for colonoscopy, diverticulosis, sedation, bowel cleansing, withdrawal time, time/number of attempts to intubate the cecal walve, number, localization, size or histology of polyps,. However, the time to reach the cecal floor and the overall time of colonoscopy were significantly lower for CAC (1 minute). CONCLUSION: CAC was without clinical impact on polyp detection rate or performance of colonoscopy.

Sedation-associated complications in endoscopy--prospective multicentre survey of 191142 patients.

BACKGROUND/AIMS: Propofol sedation is applied as moderate sedation for almost all diagnostic and interventional endoscopies. Propofol sedation bears the risk of complications such as respiratory as well as cardiopulmonary insufficiency including sedation-induced death. According to recent guidelines, non-anesthesiologist-administered propofol (NAAP) should be performed by an additional person who has NAAP as their sole task. METHODS: In a prospective multicentre survey involving 191,142 patients, clinically relevant endoscopy-associated complications were registered from 02/2010 to 01/2012. RESULTS: The majority of propofol sedations were applied without additional persons for NAAP. Overall endoscopy-related complication rate was 0.0022 % (n = 424) and sedation-related complications 0.00 042 % (n = 82). Variability over time and between the clinics was low and not influenced by the number of endoscopies performed during the investigation period. Sedation-related death occurred in 6 patients (0.00 003 %), 50 % during emergency endoscopies. In all sedation-associated deaths the patients had ASA class 3 before endoscopy. All fatal complications occurred in the presence of an additional trained person for NAAP. CONCLUSION: This large prospective survey shows that propofol sedation in gastrointestinal endoscopy is a safe procedure with a low potential of risk in daily routine. However, high risk patients (ASA ≥ 3) should be identified, especially before emergency endoscopies and managed by additional persons for NAAP and under intensive care surveillance.

Raising awareness about chronic intestinal pseudo-obstruction (CIPO): a case report showing CIPO as initial manifestation of atypical seronegative systemic sclerosis.

Only few case studies address pseudo-obstruction, a disorder - which often frustrates clinicians and patients due to an unclear diagnosis and limited therapeutic options. Thus, the aim of this paper is to investigate a relevant case concerning a patient presenting with symptoms of acquired chronic intestinal pseudo-obstruction (CIPO). After one year of extensive diagnostic tests and unsuccessful treatment with prokinetics, the patient underwent a subtotal ileocolectomy. The histology of the intestinal specimen revealed continuous atrophy and fibrosis mainly within the circular, inner muscle layer of muscularis propria of the ileum and colon. Even though serum markers were lacking, a subsequent skin biopsy showed signs of scleroderma supporting an initial diagnosis of intestinal involvement in systemic sclerosis. Despite treatment with steroids and methotrexate, the increasingly emaciated patient died. In conclusion, there is a bias against the publishing of pseudo-obstruction studies, in particular, due to the obscure underlying causes. To raise awareness of this problem, we call for clinicians to systematically generate comprehensive data about patients presenting these symptoms.

Cap-assisted colonoscopy (CAC) significantly extends visualization in the right colon.

BACKGROUND: Although colonoscopy is the standard procedure in the diagnosis of colorectal neoplasia, a significant number of clinically relevant lesions may be missed even by experienced endoscopists using current technology. Particular problems may occur with blind spots behind the semilunar folds and within the right colon. A transparent cap mounted at the tip of a colonoscope may be an easy way to extend the visual field during colonoscopy and may improve the detection rate of mucosal lesions. However, data in the literature are controversial and the quantity of the potential extension of visualization by a transparent cap has not been reported yet. MATERIAL AND METHODS: The significance of cap-assisted colonoscopy (CAC) to increase visualization within different colonic segments (rectum, sigmoid colon, descending colon, transverse colon, ascending colon, cecum) was quantitatively analyzed by randomized back-to-back colonoscopies with and without cap. The investigations were performed in a colonic training model by 5 investigators. The inner colonic surface was stained by a raster of dots and the number of dots counted during colonoscopy served as a measure for the visible surface area of each segment. RESULTS: The time to advance the colonoscope to the respective colonic segments and the overall time to reach the cecum were not significantly different between conventional and CAC. In contrast, overall withdrawal time and withdrawal times for the cecum, ascending colon, descending colon and rectum were significantly longer for CAC, but not for the transverse and sigmoid colon. Visualization of the colonic surface was significantly increased during CAC. Overall, 59.76 ± 2.70 % of the maximal countable dots were visualized without cap and 85.36 ± 9.62 % with cap. The improvement of visualization was only significant for the right colon, but not for the rectum, sigmoid or descending colon. CONCLUSION: The finding of the present study suggests that the extension of visualization by CAC may be of particular value for the right colon.

Fructose malabsorption: how much fructose can a healthy subject tolerate?

BACKGROUND/AIMS: In a prospective study, we evaluated fructose absorption capacity in 17 healthy female volunteers aged 16-27 years. METHODS: All volunteers underwent analysis of their daily food intake diary and standardized breath tests. The volunteers were challenged consecutively with oral intake of 50, 25 and 15 g of fructose. RESULTS: The average daily ingestion of fructose (19.54 ± 14.95 g) was not different between volunteers with positive and negative breath tests. On day 1, 53% of subjects exhibited a significant (≥20 ppm) increase in breath hydrogen and gastrointestinal symptoms upon challenge with 50 g of fructose. Moreover, 37.5% of the volunteers with a negative breath test became positive upon a second challenge with 50 g of fructose but remained asymptomatic. On day 2, 1 of the 9 volunteers (12.5%) with a positive breath test on day 1 exhibited an asymptomatic positive breath test upon exposure to 25 and 15 g of fructose on day 3. The 8 volunteers with a negative test (25 g of fructose) remained negative after a second exposure to 25 g of fructose. CONCLUSION: The results of this study indicate that hydrogen breath tests with fructose challenge of 50 g of fructose are inappropriate to characterize clinically significant fructose malabsorption.

Krefeld CONTRA study: conventional peroral Esophago-Gastro-Duodenoscopy (EGD) vs. transnasal EGD--a prospective and randomised study with independent evaluation of conscious sedation, endoscope diameter, and access path.

BACKGROUND: The guidelines of the German Gastroenterology Society (Deutsche Gesellschaft für Verdauungs- und Stoffwechselkrankheiten, DGVS) demand the presence of an additional qualified person solely responsible for patient monitoring during sedated endoscopy. Transnasal esophagogastroduodenoscopy (EGD) allows easy access to the upper gastrointestinal tract and may avoid the complications induced by conscious sedation and reduce medical costs. PATIENT AND METHOD: 120 patients referred to diagnostic EGD were assigned to six groups: group 1, unsedated peroral EGD with normal-caliber endoscope; group 2, unsedated peroral EGD with small-caliber endoscope; group 3, sedated peroral EGD with normal-caliber endoscope; group 4, sedated peroral EGD with small-caliber endoscope; group 5, unsedated transnasal EGD with small-caliber endoscope; group 6, sedated transnasal EGD with small-caliber endoscope. Outcome parameters included objective (duration, oxygen saturation) and subjective measures (standardised visual analogue scales) of the endoscopy staff (handling, insertion, retroflexion, tolerability, overall assessment) and patients (pain, unpleasantness, sore throat, choking, gagging, meteorism, anxiety, acceptability). RESULTS: The patients were comparable according to age, sex, anxiety, and respiratory function before EGD. Sedoanalgesia was without effect on EGD handling and duration, patient tolerability and overall assessment by endoscopists and assistants. Negative effects of sedoanalgesia (decreased oxygen saturation, patient acceptability) were much lower and without significance for transnasal compared to peroral EGD. Patient tolerability and acceptability of the endoscopic staff (handling, insertion, retroflexion) were significantly better for the small-caliber endoscope. Duration of unsedated transnasal EGD was slightly but significantly longer, pain, unpleasantness, and anxiety slightly but significantly higher compared to sedated peroral EGD. However, these differences could no loner be detected seven days after endoscopy. Cost analysis revealed major advantage for transnasal EGD. CONCLUSION: Unsedated transnasal EGD may replace diagnostic peroral EGD, reduces costs with acceptable patient discomfort and has advantagous acceptability of the endoscopic staff.

Prospective comparison between double-balloon enteroscopy and spiral enteroscopy.

BACKGROUND AND STUDY AIMS: Push enteroscopy, balloon-guided, and single- and double-balloon enteroscopy (DBE) are now well established techniques in gastrointestinal endoscopy for small-bowel imaging and therapy. There are no published prospective studies comparing DBE with spiral enteroscopy and so the aim of the current study was to compare the performance of the two techniques in patients undergoing diagnostic enteroscopy. PATIENTS AND METHODS: Between January and December 2009, 35 patients referred for diagnostic enteroscopy were prospectively assigned to either spiral enteroscopy (n=18) or DBE (n=17). The performance of the two techniques was compared. RESULTS: The patients were comparable with regard to age, sex, and indication for enteroscopy. Investigation performance, as assessed by time of insertion into the pylorus, the depth of insertion, the duration of the enteroscopy, and the amount of sedoanalgesia required were not significantly different between spiral enteroscopy and DBE. In 40% of the investigations, enteroscopy could detect abnormalities in the intestinal mucosa, in particular inflammatory changes and ulcers and, to a lesser extent, angiodysplasia. No significant difference in pathological findings could be detected between the two groups; however, clinically, diagnostic yield appeared to be higher for DBE (47.1% vs. 33.4%; n.s.). CONCLUSION: Although this small study appears to show that DBE has a clinically higher diagnostic yield than spiral enteroscopy, larger studies are needed to confirm this preliminary finding.

Multiple colon ulcerations, perforation and death during treatment of malignant melanoma with sorafenib.

BACKGROUND: Sorafenib (Nexavar) is an oral multi-kinase inhibitor with anti-angiogenic and antiproliferative effects. It has shown in-vitro and clinical activity against several kinds of tumors, such as malignant melanoma. HISTORY, DIAGNOSIS, TREATMENT AND COURSE: A 66-year-old man with malignant melanoma was treated with sorafenib, 2 yen 400 mg per day. Because of severe diarrhea and abdominal pain, sorafenib was eventually discontinued and the patient was hospitalized for further treatment. Diagnostic work-up by upper gastrointestinal endoscopy and colonoscopy revealed multiple deep ulcerations within the whole colon. One week after admission the patient developed symptoms of acute abdomen with signs of bowel perforation requiring an emergency operation. Colectomy of the right colon with ileostomy revealed multiple (20-30) acute and subacute colonic perforations. Despite intensive care treatment the patient died of septic complications 13 days after surgery. CONCLUSION: Treatment with anti-angiogenic multi-kinase inhibitors may be associated with gastrointestinal perforations. This has been reported for sorafenib in up to 2.3 % of cases.

Relief of reflux symptoms after endoscopic gastroplication may be associated with reduced esophageal Acid sensitivity: a pilot study.

BACKGROUND AND STUDY AIMS: Although the new endoscopic techniques for the treatment of gastroesophageal reflux disease (GERD) lead to marked clinical benefit, the underlying mechanism of this is unknown. MATERIALS AND METHODS: In this prospective study, the effect of endoscopic gastroplication was investigated in six patients with GERD, who were assessed before and 4 weeks after treatment. The effect on reflux symptoms, quality of life, proton pump inhibitor (PPI) consumption, reflux esophagitis, acid exposure, esophageal motility, lower esophageal sphincter pressure (LESP), and gastric emptying was measured. Esophageal acid sensitivity before and after treatment was investigated using a standardized acid provocation test, and compared with that of six age- and sex-matched healthy controls. RESULTS: Significant clinical benefit and discontinuation of PPI consumption after gastroplication was seen. Among the objectively measured parameters, only acid exposure was significantly reduced and gastric emptying significantly delayed. However, acid exposure remained pathologically high. Esophageal acid sensitivity was significantly reduced. The induction of heartburn and/or pain was abolished in four patients after gastroplication. In two patients the intensity of heartburn/pain was significantly reduced by 40 % or 60 %, and the time to provoke heartburn/pain significantly prolonged by 40% or 100%. CONCLUSION: These preliminary data suggest that the decrease of esophageal sensitivity to acid after endoscopic gastroplication is part of the mechanism responsible for the reduction of reflux symptoms.

[Adenocarcinoma of the esophagogastric junction: prognostic factors and results of primary surgery]. / Ergebnisse der primär chirurgischen Therapie beim Adenokarzinom des ösophagogastralen Ubergangs.

INTRODUCTION: The incidence of adenocarcinoma of the esophagogastric junction (AEG) is increasing worldwide, and classification systems and resection procedures are being controversially discussed. METHODS AND PATIENTS: We report on 225 AEG patients undergoing primary resection in our unit (1986-2000) with a special focus on perioperative morbidity, mortality, and long-term prognosis under consideration of the AEG type (Siewert classification) and operative procedure performed (subtotal esophagectomy with proximal gastric resection in AEG I, total gastrectomy with distal esophageal resection in AEG II and AEG III). RESULTS: Types I, II, and III carcinomas were found in 32%, 42%, and 26% of the patients, respectively, with R(0) resections in 65%, 69%, and 51% ( P=0.039). The overall 5-year survival rates were 29%, 31%, and 14% ( P=0.068), respectively; in R(0)-resected patients, they were 40%, 41%, and 27% ( P=0.771). In univariate analysis, the TNM classification ( P<0.001), R classification ( P<0.001), and tumor stage ( P<0.001) were relevant prognostic factors. In multivariate analysis, only the R classification ( P=0.003), LN ratio ( P=0.012), and N stage ( P=0.027) were independent prognostic factors. In 35 of 177 patients resected with curative intent, R(0) resections could not be achieved, mainly because of residual tumor in the circumferential plane (22/35=63%). Only in 37% of cases (13/35) was the R(1) situation due to exclusive positive oral or aboral resection margins. Therefore, in only 7% of all patients resected with curative intent (13/177) did the question arise of whether the R(1) resection could have been avoided by a different surgical approach. Surgical, pulmonary, and cardiac complications were found in 33%, 26%, and 10%, respectively. The mortality within 30 days was 4%. CONCLUSIONS: Failure of R(0) resection in patients treated with curative intent is mostly caused by residual tumor in the circumferential plane. Therefore, different surgical approaches with varying oral and aboral resection margins are of minor importance for reducing the frequency of R(1) resections. Downstaging of tumors by neoadjuvant treatment may increase the R(0) resection rate.

Expense and benefit of neoadjuvant treatment in squamous cell carcinoma of the esophagus.

BACKGROUND: The effectiveness of neoadjuvant treatment (NT) prior to resection of squamous cell carcinoma of the esophagus (SCCE) in terms of prolonged survival has not been proven by randomized trials. Facing considerable financial expenses and with concerns regarding the consumption of the patient's remaining survival time, this study aims to provide rationales for pretreating resection candidates. METHODS: From March 1986 to March 1999, patients undergoing resection for SCCE were documented prospectively. Since 1989, NT was offered to patients with mainly upper and middle third T3 or T4 tumors or T2 N1 stage who were fit for esophagectomy. Until 1993, NT consisted of chemotherapy. Since that time chemoradiation has also been applied. The parameters for expense and benefit of NT are costs, pretreatment time required, postoperative morbidity and mortality, clinical and histopathological response, and actuarial survival. RESULTS: Two hundred and three patients were treated, 170 by surgery alone and 33 by NT + surgery. Postoperative morbidity and mortality were 52% to 30% and 12% to 6%, respectively (p = n.s.). The response to NT was detected in 23 patients (70%). In 11 instances (33%), the primary tumor lesion was histopathologically eradicated. Survival following NT + surgery was significantly prolonged in node-positive patients with a median survival of 12 months to 19 months (p = 0.0193). The average pretreatment time was 113 +/- 43 days, and reimbursement for NT to the hospital amounted to Euro 9.834. CONCLUSIONS: NT did not increase morbidity and mortality. Expenses for pretreatment, particularly time and costs, are considerable. However, taking into account that the results are derived from a non-randomized study, patients with regionally advanced tumor stages seem to benefit, as seen by their prolonged survival.

Long-term results following different extent of resection in chronic pancreatitis.

BACKGROUND/AIMS: To evaluate, whether the indication related varying extent of resection in chronic pancreatitis has a predictable impact on long-term outcome. METHODOLOGY: One hundred and twenty-six patients consecutively underwent surgery for chronic pancreatitis from March 1987 to September 1997. Three treatment categories were defined: Pancreatoduodenectomy, duodenum-preserving resection and drainage procedures, and left-sided pancreatectomy. Main outcome measures were late mortality, pain scores preoperatively and at follow-up, body-weight change, percentage of insulin dependent diabetes, patient's and physician's satisfaction with surgery. RESULTS: Forty-one patients underwent pancreatoduodenectomy, 59 drainage procedures, and 26 left-sided pancreatectomy, respectively. Hospital mortality was 1 (2.4%), 4 (6.8%), and 1 (3.8%) (P = NS), totaling 4.8%. After an average follow-up of 5.2 years, late mortality was 10 (24.4%), 9 (15.3%), and 4 (15.4%) (P = NS) for a total of 23 (18.3%). Two patients (1.6%) died of unsuspected pancreatic cancer. Three patients (2.4%) had to be reoperated upon for pain relapse. The mean pain score was 8.8 preoperatively and 2.1 at late follow-up and not different among groups. Body-weight gain averaged 3.0, 4.0, and 3.4 kg, with no significant differences. Percentage of insulin dependency in all patients rose from 14% prior to surgery to 30% at reevaluation, and was very similar in all treatment categories. CONCLUSIONS: The different kind and level of invasiveness of the surgical procedures did not significantly influence the late outcome. High rates of late mortality and deterioration of endocrine function are to a greater extent sequelae of comorbidity and the progression of the underlying pancreatic disease.

Discovery of a transient absorption edge in the X-ray spectrum of GRB 990705.

We report the discovery of a transient equivalent hydrogen column density with an absorption edge at approximately 3.8 kiloelectron volts in the spectrum of the prompt x-ray emission of gamma-ray burst (GRB) 990705. This feature can be satisfactorily modeled with a photoelectric absorption by a medium located at a redshift of approximately 0.86 and with an iron abundance of approximately 75 times the solar one. The transient behavior is attributed to the strong ionization produced in the circumburst medium by the GRB photons. The high iron abundance points to the existence of a burst environment enriched by a supernova along the line of sight. The supernova explosion is estimated to have occurred about 10 years before the burst. Our results agree with models in which GRBs originate from the collapse of very massive stars and are preceded by a supernova event.

Observation of X-ray lines from a gamma-ray burst (GRB991216): evidence of moving ejecta from the progenitor.

We report on the discovery of two emission features observed in the x-ray spectrum of the afterglow of the gamma-ray burst (GRB) of 16 December 1999 by the Chandra X-ray Observatory. These features are identified with the Ly(alpha) line and the narrow recombination continuum by hydrogenic ions of iron at a redshift z = 1.00 +/- 0.02, providing an unambiguous measurement of the distance of a GRB. Line width and intensity imply that the progenitor of the GRB was a massive star system that ejected, before the GRB event, a quantity of iron approximately 0.01 of the mass of the sun at a velocity approximately 0.1 of the speed of light, probably by a supernova explosion.