Basic neuroscience

Poster Session 1

Basic neuroscience     

Biophysical, histopathological and pharmacological characterization of crotamine isoforms F22 and F32.

Two major crotamine isoforms (F22 and F32) were obtained after three chromatographic steps and were assayed in mouse phrenic nerve-diaphragm preparations. F32 and F22 (0.5 microg/ml, n=4) produced a facilitatory effect, which increased isometric twitch-tension by 300 and 230%, respectively, after a 120 min incubation. At a concentration of 0.1 microg/ml, both isoforms increased the twitch-tension by about 160%. However, when the isoforms were co-incubated (final concentration, 0.5 microg/ml) for 30 min prior to testing, they did not cause the facilitation seen with > or =0.1 microg/ml of each isoform alone. Histologically, F32 and F22 at 0.5 and 1 microg/ml were quantitatively alike in inducing tissue myonecrosis. However, a mixture of the two isoforms (final concentration, 0.5 microg/ml) significantly attenuated the damage seen with either toxin alone. Mass spectrometry analysis showed that the isoforms had the same molecular mass (4.8 kDa) and that they existed as monomers with a highly stable structure. These results indicate that F22 and F32 acted on muscle cells of the mouse phrenic-nerve diaphragm preparation through similar mechanisms. Since the isoforms did not produce the expected summation in the increase in muscle twitch-tension, it is possible that they may have different affinities for the sodium channel subunits.     

Health status and quality of life in patients with early-stage Hodgkin's disease treated on Southwest Oncology Group Study 9133.

PURPOSE: We describe the short and intermediate-term quality-of-life (QOL) outcomes in patients treated on a randomized clinical trial in early-stage Hodgkin's disease (Southwest Oncology Group [SWOG] 9133) comparing subtotal lymphoid irradiation (STLI) with combined-modality treatment (CMT). PATIENTS AND METHODS: Two hundred forty-seven patients participated in the QOL study (SWOG 9208), completing several standardized instruments (Symptom Distress Scale; Cancer Rehabilitation Evaluation System - Short Form; Medical Outcomes Study 36-Item Short-Form Health Survey Vitality Scale; and a health perception item), as well as questions about work, marital status, and concerns about having children. This article reports on results from baseline before random assignment, at 6 months, and at 1 and 2 years after random assignment. RESULTS: Patients receiving CMT experienced significantly greater symptom distress (P <.0001), fatigue (P =.001), and poorer QOL (P =.015) at 6 months than the STLI patients, reflecting a shorter time since completion of therapy in the CMT arm. Importantly, patients in the two groups did not differ on any outcomes at the 1-and 2-year assessments. Both patient groups reported significantly more fatigue before treatment than healthy reference populations, and fatigue did not improve in either group after treatment. CONCLUSION: This study demonstrated that patients with early-stage Hodgkin's disease experience a short-term decrease in QOL and an increase in symptoms and fatigue with treatment, which is more severe with CMT; by 1 year, however, CMT and STLI patients report similar outcomes. Fatigue scores for both arms were lower at baseline than scores for the general population and did not return to normal levels 2 years after random assignment. The mechanisms responsible for this lingering problem warrant further investigation.     

The relationship between dietary fat intake and risk of colorectal cancer: evidence from the combined analysis of 13 case-control studies

The objective of this study was to examine the effects of the intakeof dietary fat upon colorectal cancer risk in a combined analysis of datafrom 13 case-control studies previously conducted in populations withdiffering colorectal cancer rates and dietary practices. Original datarecords for 5,287 cases of colorectal cancer and 10,470 controls werecombined. Logistic regression analysis was used to estimate odds ratios (OR)for intakes of total energy, total fat and its components, and cholesterol.Positive associations with energy intake were observed for 11 of the 13studies. However, there was little, if any, evidence of anyenergy-independent effect of either total fat with ORs of 1.00, 0.95, 1.01,1.02, and 0.92 for quintiles of residuals of total fat intake (P trend =0.67) or for saturated fat with ORs of 1.00, 1.08, 1.06, 1.21, and 1.06 (Ptrend = 0.39). The analysis suggests that, among these case-control studies,there is no energy-independent association between dietary fat intake andrisk of colorectal cancer. It also suggests that simple substitution of fatby other sources of calories is unlikely to reduce meaningfully the risk ofcolorectal cancer.     

Postoperative prophylactic administration of beta-adrenergic blockers in patients at risk for myocardial ischemia

Perioperative myocardial ischemia (MI) is associated with postoperative cardiac morbidity. Postoperative sympatholysis may reduce the incidence of MI. This study evaluated such a reduction postoperatively with the administration of prophylactic beta-blockers in patients undergoing elective total knee arthroplasty with epidural anesthesia and postoperative epidural analgesia. One hundred seven patients were preoperatively randomized into two groups, control and beta-blockers, who received postoperative esmolol infusions on the day of surgery and metoprolol for the next 48 h to maintain a heart rate less than 80 bpm. Patients were followed for ST segment depression by using a Holter monitor and adverse cardiac outcomes. Postoperative electrocardiographic ischemia was significantly more prevalent in the control group compared with the beta-blocker group during esmolol blockade (0 of 52 vs 4 of 55; P = 0.04) and tended to be more common in the control group the next two days (8 of 55 vs 3 of 52; P = 0.135). In addition, the number of ischemic events (control, 50; beta-blockers, 16) and total ischemic time (control, 709 min; beta-blocker, 236 min) were also significantly different from the control group. Myocardial infarctions and cardiac events were more common in the control group, but these differences were not significant. Our results suggest that the use of prophylactic beta-blocker therapy may reduce the incidence of postoperative MI. Implications: Prophylactic beta adrenergic blockade administered after elective total knee arthroplasty was associated with a reduced prevalence and duration of postoperative myocardial ischemia detected with Holter monitoring.     

Characterization of Healthcare-Associated and Community-Associated Clostridioides difficile Infections among Adults,Canada, 2015–2019

We investigated epidemiologic and molecular characteristics of healthcare-associated (HA) and community-associated (CA) Clostridioides difficile infection (CDI) among adult patients in Canadian Nosocomial Infection Surveillance Program hospitals during 2015–2019. The study encompassed 18,455 CDI cases, 13,735 (74.4%) HA and 4,720 (25.6%) CA. During 2015–2019, HA CDI rates decreased by 23.8%, whereas CA decreased by 18.8%. HA CDI was significantly associated with increased 30-day all-cause mortality as compared with CA CDI (p<0.01). Of 2,506 isolates analyzed, the most common ribotypes (RTs) were RT027, RT106, RT014, and RT020. RT027 was more often associated with CDI-attributable death than was non-RT027, regardless of acquisition type. Overall resistance C. difficile rates were similar for all drugs tested except moxifloxacin. Adult HA and CA CDI rates have declined, coinciding with changes in prevalence of RT027 and RT106. Infection prevention and control and continued national surveillance are integral to clarifying CDI epidemiology, investigation, and control.     

Indexing of Fatty Acids in Poultry Meat for Its Characterization in Healthy Human Nutrition: A Comprehensive Application of the Scientific Literature and New Proposals

Chicken meat is becoming the most consumed in the world for both economic and nutritional reasons; regarding the latter, the lipid profile may play positive or negative roles in the prevention and treatment of diseases. In this study, we define the state of the art of lipid-based nutritional indexes and used the lipid content and fatty acid profile (both qualitative and quantitative) of breast meat of two poultry genotypes with different growth rates and meat traits. Further, we summarize and review the definitions, implications, and applications of nutritional indexes used in recent years and others of our own design to provide a useful tool to researchers working in the field of meat quality (not only in poultry) to select the most appropriate index for their own scientific purposes. All indexes show advantages and disadvantages; hence, a rational choice should be applied to consider the nutritional effect of meat on human health and for a possible assessment of the most suitable rearing systems (genotype, feeding, farming system or postmortem handling).     

Vitamin D and Diseases of Mineral Homeostasis: A Cyp24a1 R396W Humanized Preclinical Model of Infantile Hypercalcemia Type 1

Infantile hypercalcemia type 1 (HCINF1), previously known as idiopathic infantile hypercalcemia, is caused by mutations in the 25-hydroxyvitamin D 24-hydroxylase gene, CYP24A1. The R396W loss-of-function mutation in CYP24A1 is the second most frequent mutated allele observed in affected HCINF1 patients. We have introduced the site-specific R396W mutation within the murine Cyp24a1 gene in knock-in mice to generate a humanized model of HCINF1. On the C57Bl6 inbred background, homozygous mutant mice exhibited high perinatal lethality with 17% survival past weaning. This was corrected by crossbreeding to the CD1 outbred background. Mutant animals had hypercalcemia in the first week of life, developed nephrolithiasis, and had a very high 25(OH)D₃ to 24,25(OH)₂D₃ ratio which is a diagnostic hallmark of the HCINF1 condition. Expression of the mutant Cyp24a1 allele was highly elevated while Cyp27b1 expression was abrogated. Impaired bone fracture healing was detected in CD1-R396^w/w mutant animals. The augmented lethality of the C57Bl6-R396W strain suggests an influence of distinct genetic backgrounds. Our data point to the utility of unique knock-in mice to probe the physiological ramifications of CYP24A1 variants in isolation from other biological and environmental factors.