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Clinical improvement of DM1 patients reflected by reversal of disease-induced gene expression in blood. BMC Med 2022; 20:395. [PMID: 36352383 PMCID: PMC9646470 DOI: 10.1186/s12916-022-02591-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 09/30/2022] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Myotonic dystrophy type 1 (DM1) is an incurable multisystem disease caused by a CTG-repeat expansion in the DM1 protein kinase (DMPK) gene. The OPTIMISTIC clinical trial demonstrated positive and heterogenous effects of cognitive behavioral therapy (CBT) on the capacity for activity and social participations in DM1 patients. Through a process of reverse engineering, this study aims to identify druggable molecular biomarkers associated with the clinical improvement in the OPTIMISTIC cohort. METHODS Based on full blood samples collected during OPTIMISTIC, we performed paired mRNA sequencing for 27 patients before and after the CBT intervention. Linear mixed effect models were used to identify biomarkers associated with the disease-causing CTG expansion and the mean clinical improvement across all clinical outcome measures. RESULTS We identified 608 genes for which their expression was significantly associated with the CTG-repeat expansion, as well as 1176 genes significantly associated with the average clinical response towards the intervention. Remarkably, all 97 genes associated with both returned to more normal levels in patients who benefited the most from CBT. This main finding has been replicated based on an external dataset of mRNA data of DM1 patients and controls, singling these genes out as candidate biomarkers for therapy response. Among these candidate genes were DNAJB12, HDAC5, and TRIM8, each belonging to a protein family that is being studied in the context of neurological disorders or muscular dystrophies. Across the different gene sets, gene pathway enrichment analysis revealed disease-relevant impaired signaling in, among others, insulin-, metabolism-, and immune-related pathways. Furthermore, evidence for shared dysregulations with another neuromuscular disease, Duchenne muscular dystrophy, was found, suggesting a partial overlap in blood-based gene dysregulation. CONCLUSIONS DM1-relevant disease signatures can be identified on a molecular level in peripheral blood, opening new avenues for drug discovery and therapy efficacy assessments.
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MYOTONIC DYSTROPHY. Neuromuscul Disord 2021. [DOI: 10.1016/j.nmd.2021.07.262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Palliative care research promotion in policy and practice: a knowledge exchange process. BMJ Support Palliat Care 2021; 12:bmjspcare-2021-003096. [PMID: 34400402 PMCID: PMC9380483 DOI: 10.1136/bmjspcare-2021-003096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 07/24/2021] [Indexed: 11/04/2022]
Abstract
In palliative care, as in many areas of medicine, there is a considerable amount of research conducted that makes sound recommendations but does not result consistently in improved care. For instance, though palliative care has been shown to benefit all people with a life-threatening illness, its main reach continues to be for those with cancer. Drawing on relational models of research use, we set out to engage policy-makers, educators, clinicians, commissioners and service providers in a knowledge exchange process to identify implications of research for Scottish palliative care priorities. First, we mapped the existing palliative care research evidence in Scotland. We then organised evidence review meetings and a wider stakeholder event where research producers and users came together to coproduce implications of the evidence for policy, education and practice. We used questionnaires and key stakeholder feedback meetings to explore impacts of this process on research uptake and use immediately after the events and over time. In this paper, we reflect on this knowledge exchange process and the broader context in which it was set. We found that participation fostered relationships and led to a rich and enthusiastic exploration of research evidence from multiple perspectives. Potential impacts relating to earlier identification for palliative care, education and need-based commissioning ensued. We make suggestions to guide replication.
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Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study. Br J Surg 2020; 107:1023-1032. [PMID: 32026470 DOI: 10.1002/bjs.11453] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 09/21/2019] [Accepted: 11/08/2019] [Indexed: 01/14/2023]
Abstract
BACKGROUND This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. METHODS This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery. RESULTS A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498). CONCLUSION There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.
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Optimising Radium 223 Therapy for Metastatic Castration-Resistant Prostate Cancer -5-year Real-World Outcome: Focusing on Treatment Sequence and Quality of Life. Clin Oncol (R Coll Radiol) 2020; 32:e177-e187. [PMID: 32448724 DOI: 10.1016/j.clon.2020.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 04/15/2020] [Accepted: 04/22/2020] [Indexed: 01/04/2023]
Abstract
AIMS Real-world evidence of radium 223 (Ra-223) for the treatment of men with metastatic castration-resistant prostate cancer is emerging. In this prospective single-centre service evaluation, we report for the first time in the UK, real-world quality of life (QoL) and survival outcomes, including the sequencing impact, in 228 treated patients. We aim to share our 5-year experience on how to optimise Ra-223 treatment. MATERIALS AND METHODS Patients who received Ra-223 therapy between 2014 and 2018 at the Northern Centre for Cancer Care, Newcastle upon Tyne, UK were included in this evaluation. Demographics, clinical characteristics, blood parameters, treatment sequencing and QoL data using abbreviated Functional Assessment of Cancer Therapy-Prostate questionnaires were prospectively collected and analysed. RESULTS In total, 228 patients were included; median age 72 years (51-87). The medium overall survival was 11.1 months. Overall survival in post-chemotherapy and chemotherapy-naïve patients was 8.1 and 12.3 months, respectively (P = 0.02, hazard ratio 1.52, 95% confidence interval 1.06-2.17); in pre-enzalutamide and post-enzalutamide patients was 11.3 and 10.4 months, respectively (P = 0.65, hazard ratio 0.92, 95% confidence interval 0.63-1.33); in pre-abiraterone and prednisolone and post-abiraterone and prednisolone patients was 11.8 and 10.5 months, respectively (P = 0.08, hazard ratio 0.74, 95% confidence interval 0.51-1.06); in this latter group, the fracture rate was 24% (15/63). QoL post Ra-223 (n = 101 evaluated) showed that pain scores improved in 54%, there was no change in 17% and pain scores worsened in 30% of treated patients. Overall QoL scores showed a similar trend. QoL was not significantly associated with overall survival. CONCLUSIONS Ra-223 palliates pain and improves disease-related QoL in most patients in the real-world setting. Our survival outcome is comparable with other real-world studies. Chemotherapy-naïve patients seemed to have better survival than those who received prior chemotherapy. No significant survival differences were observed between pre- and post-abiraterone and prednisolone or enzalutamide patients. The fracture rate in the post-abiraterone and prednisolone group seemed to be high. Bone health evaluation and protection should be incorporated as standard of care.
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Abstract
Reducing injuries to youth players is of primary importance to academies, as injuries can result in a significant loss in both training and match time, as well as, negatively affecting player development. In total, 76 talented young football players were analysed over two full competitive seasons. The injury incidence and burden for all non-contact and overuse injuries were recorded. Exposure was calculated as the total number of competitive matches hours played. Somatic maturation was estimated by expressing the current height of each player as a percentage of their predicted adult height [Roche, A. F., Tyleshevski, F., & Rogers, E. (1983). Non-invasive measurements of physical maturity in children. Research Quarterly for Exercise and Sport, 54(4), 364-371.]. The period of circa-peak height velocity (PHV) (24.5 injuries per 1000 h) was associated with a significantly higher injury incidence rate and burden compared to pre-PHV (11.5 injuries per 1000 h; RR:2.15, 95%CI:1.37-3.38, P < .001). No significant differences in injury risk between maturity timing groups were observed. The interaction effect between maturity status and maturity timing confirmed there is a risk period circa-PHV, but this was not dependent on maturity timing. The main practical application of this study is that football academies should regularly assess the maturity status of young footballers to identify those players with increased susceptibility to injury. Moreover, academies should individualise training and injury prevention strategies based on maturation.
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EP-1584 Radium-223 treatment in Metastatic Prostate Cancer: Prognostic Factors: Real-world Outcome. Radiother Oncol 2019. [DOI: 10.1016/s0167-8140(19)32004-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study. Br J Anaesth 2019; 122:42-50. [PMID: 30579405 DOI: 10.1016/j.bja.2018.07.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 07/19/2018] [Accepted: 07/23/2018] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery. METHODS This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy. RESULTS Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI. CONCLUSIONS After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.
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Excessive daytime sleepiness, executive dysfunction and structural brain changes in myotonic dystrophy type 1: an update on the DM1-Neuro Study. Neuromuscul Disord 2017. [DOI: 10.1016/s0960-8966(17)30254-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Australian diagnostic radiographers' attitudes and perceptions of imaging obese patients: A study of self, peers and students. Radiography (Lond) 2016. [DOI: 10.1016/j.radi.2016.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Associations between breakfast frequency and adiposity indicators in children from 12 countries. INTERNATIONAL JOURNAL OF OBESITY SUPPLEMENTS 2015; 5:S80-8. [PMID: 27152190 DOI: 10.1038/ijosup.2015.24] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Reports of inverse associations between breakfast frequency and indices of obesity are predominantly based on samples of children from high-income countries with limited socioeconomic diversity. Using data from the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE), the present study examined associations between breakfast frequency and adiposity in a sample of 9-11-year-old children from 12 countries representing a wide range of geographic and socio-cultural variability. METHODS Multilevel statistical models were used to examine associations between breakfast frequency (independent variable) and adiposity indicators (dependent variables: body mass index (BMI) z-score and body fat percentage (BF%)), adjusting for age, sex, and parental education in 6941 children from 12 ISCOLE study sites. Associations were also adjusted for moderate-to-vigorous physical activity, healthy and unhealthy dietary patterns and sleep time in a sub-sample (n=5710). Where interactions with site were significant, results were stratified by site. RESULTS Adjusted mean BMI z-score and BF% for frequent breakfast consumers were 0.45 and 20.5%, respectively. Frequent breakfast consumption was associated with lower BMI z-scores compared with occasional (P<0.0001, 95% confidence intervals (CI): 0.10-0.29) and rare (P<0.0001, 95% CI: 0.18-0.46) consumption, as well as lower BF% compared with occasional (P<0.0001, 95% CI: 0.86-1.99) and rare (P<0.0001, 95% CI: 1.07-2.76). Associations with BMI z-score varied by site (breakfast by site interaction; P=0.033): associations were non-significant in three sites (Australia, Finland and Kenya), and occasional (not rare) consumption was associated with higher BMI z-scores compared with frequent consumption in three sites (Canada, Portugal and South Africa). Sub-sample analyses adjusting for additional covariates showed similar associations between breakfast and adiposity indicators, but lacked site interactions. CONCLUSIONS In a multinational sample of children, more frequent breakfast consumption was associated with lower BMI z-scores and BF% compared with occasional and rare consumption. Associations were not consistent across all 12 countries. Further research is required to understand global differences in the observed associations.
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Starting treatment according to guidelines evaluation: a multicentre audit of HIV patients in the UK. Int J STD AIDS 2014; 24:243-4. [PMID: 24400349 DOI: 10.1177/09564624124728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The aim of this audit was to assess whether HIV patients are being started on antiretroviral therapy (ART) according to British and European guidelines. Data were collected from the Survey of Prevalent HIV Infections Diagnosed (SOPHID) return for 2010 at five major HIV management centres in the UK. Data from this 3873 patient cohort revealed 52 patients who should have been receiving ART according to the guidelines but were not. Of these, 23 patients elected not to start ART despite clinical advice to the contrary. Information required to assist in the decision for earlier ART initiation (CD4 count 350–500 cells/mL) was missing for some patients. Clinicians must pay attention to the regular assessment of patients with a CD4 count of 351–500 cells/mL so that all those who may benefit from earlier treatment are identified. Future research should investigate patient barriers to initiating therapy following recommendation by a clinician.
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Effects of strength and aerobic-based training on functional fitness, mood and the relationship between fatness and mood in older adults. J Sports Med Phys Fitness 2011; 51:489-496. [PMID: 21904289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
AIM Physical independence and positive mood states contribute to successful aging. The aim of this study was to analyze the effects of aerobic and strength-based training programs on functional fitness and mood in older adults, and to assess the relationship between adiposity and mood states. METHODS Seventy eight participants (age 65 to 95 year old) were randomly assigned to a control group, aerobic training (AT), or strength training group (ST). Functional fitness was assessed using dimensions of the Senior Fitness Test battery relating to lower and upper body strength and flexibility, velocity, agility and dynamic balance, and aerobic endurance. Mood states (depression, tension, fatigue, vigour, anger, and confusion) were determined using the POMS-SF questionnaire. Participants were evaluated at the baseline and at the end of a 16-week exercise programme. RESULTS Both the ST and AT groups improved their functional fitness following the 16 week training. Body Mass Index (BMI) was positively associated with tension (r=0.30; P<0.01), fatigue (r=0.31; P<0.01) and confusion (r=0.24; P<0.05). At 16-week evaluation, control group reported increased levels of confusion, and the ST group reported increases in vigour (P<0.05). CONCLUSION Results support the idea that strength-based training can be as effective as aerobic-based training in improving physical skills that contribute to functional mobility in later years. Positive associations between increased BMI and mood disturbance were also found. Physical training also contributed to some improvements in mood.
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POSTMENOPAUSAL EVALUATION AND RISK-REDUCTION WITH LASOFOXIFENE (THE PEARL TRIAL): GYNAECOLOGICAL OUTCOMES AT FIVE-YEARS. Maturitas 2009. [DOI: 10.1016/s0378-5122(09)70156-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Computerized analysis of mammographic parenchymal patterns for breast cancer risk assessment: feature selection. Med Phys 2000; 27:4-12. [PMID: 10659732 DOI: 10.1118/1.598851] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Our purpose in this study was to identify computer-extracted, mammographic parenchymal patterns that are associated with breast cancer risk. We extracted 14 features from the central breast region on digitized mammograms to characterize the mammographic parenchymal patterns of women at different risk levels. Two different approaches were employed to relate these mammographic features to breast cancer risk. In one approach, the features were used to distinguish mammographic patterns seen in low-risk women from those who inherited a mutated form of the BRCA1/BRCA2 gene, which confers a very high risk of developing breast cancer. In another approach, the features were related to risk as determined from existing clinical models (Gail and Claus models), which use well-known epidemiological factors such as a woman's age, her family history of breast cancer, reproductive history, etc. Stepwise linear discriminant analysis was employed to identify features that were useful in differentiating between "low-risk" women and BRCA1/BRCA2-mutation carriers. Stepwise linear regression analysis was employed to identify useful features in predicting the risk, as estimated from the Gail and Claus models. Similar computer-extracted mammographic features were identified in the two approaches. Results show that women at high risk tend to have dense breasts and their mammographic patterns tend to be coarse and low in contrast.
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Abstract
Seventeen obsessive-compulsive disorder patients treated with psychosurgery were administered a comprehensive neuropsychological test battery. Their performance on neuropsychological testing was compared with that of an age and severity matched sample of 17 OCD sufferers who had not received psychosurgery. The psychosurgery and control groups did not differ in intellectual or memory functioning, consistent with earlier findings that psychosurgery does not reduce global ability estimates. The psychosurgery group performed more poorly than the control group on an adaptation of the Wisconsin Card Sorting Test, demonstrating the possible impact of frontal lobe lesions on the abilities underpinning the formation and shifting of response sets.
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Abstract
We report a longitudinal study of 26 patients with medically intractable obsessive-compulsive disorder (OCD) who were treated with psychosurgery and had a comprehensive follow-up for a mean 10 years. Seventeen patients had combined orbitomedial and cingulate lesions, 6 cingulate lesions only and 3 orbitomedial lesions only. Eighteen patients were interviewed personally and lesions verified on magnetic resonance imaging scans in fourteen. On a 6-point global rating scale, 10 (38%) patients had obvious improvement, another 6 (23%) showed mild improvement of doubtful clinical value, and the remaining 10 showed either no change (n = 6; 23%) or were judged to be worse (n = 4; 15%). Both obsessive and compulsive symptoms improved, and this change was independent of the changes in anxiety and depression scores. No significant predictors of improvement were identified. Patients with cingulate lesions only fared worse. Eight patients who had a second operation did not show much improvement. A comparison of a subgroup of patients with 10 matched nonsurgical OCD controls supported the contention that the improvement in OCD was attributable to the psychosurgery. Important adverse effects in the stereotactic surgery group (n = 20) were epilepsy (1 patient) and personality change (2 patients). The psychosurgery group performed relatively poorly on the Wisconsin Card Sort Test but did not show any deterioration in Wechsler Intelligence and Memory scores.
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Abstract
A series of synthetic peptides corresponding to segments of HIV encoded proteins were selected using criteria described by Welling et al. [(1985) FEBS Lett. 188, 215]. Synthetic peptide analogs to gp120 (2-13), (55-65), gp41 (582-596) (659-670) and tatIII (71-83) were recognized by 41-67% of sera or plasma from individuals known to be infected with HIV on the basis of virus isolation or Western blot screening. The peptide which reacted with most sera or plasma was gp41 (582-596), a conserved region in the transmembrane glycoprotein. An extended peptide analog, gp41 (579-599), tested against the same samples showed almost 100% reactivity, confirming independent studies identifying a highly immunodominant region of gp41. There was an unexpected high prevalence of antibodies (25%) to the tatIII peptide.
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Gonadotropin-releasing hormone (GnRH) receptor dynamics and gonadotrope responsiveness during and after continuous GnRH stimulation. Biol Reprod 1986; 35:881-9. [PMID: 3028518 DOI: 10.1095/biolreprod35.4.881] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Gonadotrope responsiveness, serum and tissue levels of luteinizing hormone (LH), and tissue concentration of gonadotropin-releasing hormone (GnRH) receptors in ovariectomized rats were determined during and after continuous GnRH stimulation. Intraperitoneal placement of GnRH-containing osmotic minipumps for 96 h established a rate of GnRH delivery (1 microgram/h) that resulted in stable serum levels of GnRH (500-700 pg/ml). Secretion of LH increased 8-fold within 6 h; however, serum LH returned to pretreatment levels by 24 h, even with continued GnRH stimulation. Tissue concentration of LH was depressed within 48 h of initiation of treatment but levels were restored by 96 h. Tissue levels of GnRH receptor remained elevated during the first 6 h of treatment but were reduced by 60% within 24 h and remained depressed for the duration of treatment. Gonadotrope responsiveness 48 h and 96 h after initiation of treatment was reduced by 50% and 90%, respectively. Removal of the GnRH delivery vehicle resulted in rapid disappearance of GnRH from serum. Dramatic reduction (75%) in circulating levels of LH, and a 2-fold increase in tissue levels of LH and in GnRH receptor concentration were noted within 6 h of minipump removal. Although tissue concentration of GnRH receptor returned to pretreatment levels within 48 h of minipump removal, both basal LH secretion and gonadotrope responsiveness remained depressed even 96 h after cessation of continuous GnRH stimulation. These data indicate that GnRH can "down regulate" its receptor, gonadotrope responsiveness is not obligatorily linked to receptor concentration, and desensitization that follows hyperstimulation represents effects directed at post-receptor loci.
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