Higher glucose and insulin responses to a mixed meal are associated with increased risk of diabetic retinopathy in Indigenous Americans.

PURPOSE: Prior research has focused on glucose/insulin responses to meal challenges to create personalized diets to improve health, though it is unclear if these responses predict chronic diseases. We aimed to identify glucose and insulin responses to a mixed meal tolerance test (MMTT) that predict the development of diabetic retinopathy (DR) and compare the predictive abilities with the oral glucose tolerance test (OGTT). METHODS: Indigenous American adults without diabetes (n = 168) underwent a 4-h MMTT, body composition assessment, and a 3-h OGTT at baseline. During follow-up (median 13.4 years), DR was diagnosed by direct ophthalmoscopy (n = 28) after onset of type 2 diabetes. Total and incremental area under the curve (AUC and iAUC) were calculated from glucose/insulin responses after the MMTT and OGTT. RESULTS: In separate Cox proportional hazards models adjusted for age, sex, and body fat (%), MMTT glucose AUCs (180-min and 240-min) and iAUC (180-min) predicted DR (HR 1.50, 95% CI 1.06, 2.12; HR 1.50, 95% CI 1.05, 2.14; HR 1.58, 95% CI 1.01, 2.46). The predictive abilities were better than the fasting OGTT glucose (p < 0.01) but similar to the 120-min OGTT glucose (p = 0.53). MMTT insulin AUCs (180-min and 240-min) and iAUC (180-min) also predicted DR (HR 1.65, 95% CI 1.09, 2.51; HR 1.58, 95% CI 1.00, 2.35; HR 1.53 95% CI 1.06, 2.22) while insulin AUC and iAUC from the OGTT did not (p > 0.05). CONCLUSIONS: Higher MMTT glucose and insulin responses predicted DR and were comparable to the OGTT, supporting the use of a meal challenge for precision nutrition. TRIAL REGISTRATIONS: Clinical Trial Registry: ClinicalTrials.gov identifier: NCT00340132, NCT00339482.

Barriers to Women Entering Surgical Careers: A Global Study into Medical Student Perceptions.

BACKGROUND: Barriers to female surgeons entering the field are well documented in Australia, the USA and the UK, but how generalizable these problems are to other regions remains unknown. METHODS: A cross-sectional survey was developed by the International Federation of Medical Students' Associations (IFMSA)'s Global Surgery Working Group assessing medical students' desire to pursue a surgical career at different stages of their medical degree. The questionnaire also included questions on students' perceptions of their education, resources and professional life. The survey was distributed via IFMSA mailing lists, conferences and social media. Univariate analysis was performed, and statistically significant exposures were added to a multivariate model. This model was then tested in male and female medical students, before a further subset analysis by country World Bank income strata. RESULTS: 639 medical students from 75 countries completed the survey. Mentorship [OR 3.42 (CI 2.29-5.12) p = 0.00], the acute element of the surgical specialties [OR 2.22 (CI 1.49-3.29) p = 0.00], academic competitiveness [OR 1.61 (CI 1.07-2.42) p = 0.02] and being from a high or upper-middle-income country (HIC and UMIC) [OR 1.56 (CI 1.021-2.369) p = 0.04] all increased likelihood to be considering a surgical career, whereas perceived access to postgraduate training [OR 0.63 (CI 0.417-0.943) p = 0.03], increased year of study [OR 0.68 (CI 0.57-0.81) p = 0.00] and perceived heavy workload [OR 0.47 (CI 0.31-0.73) p = 0.00] all decreased likelihood to consider a surgical career. Perceived quality of surgical teaching and quality of surgical services in country overall did not affect students' decision to pursue surgery. On subset analysis, perceived poor access to postgraduate training made women 60% less likely to consider a surgical career [OR 0.381 (CI 0.217-0.671) p = 0.00], whilst not showing an effect in the men [OR 1.13 (CI 0.61-2.12) p = 0.70. Concerns about high cost of training halve the likelihood of students from low and low-middle-income countries (LICs and LMICs) considering a surgical career [OR 0.45 (CI 0.25-0.82) p = 0.00] whilst not demonstrating a significant relationship in HIC or UMIC countries. Women from LICs and LMICs were 40% less likely to consider surgical careers than men, when controlling for other factors [OR 0.59 CI (0.342-1.01 p = 0.053]. CONCLUSION: Perceived poor access to postgraduate training and heavy workload dissuade students worldwide from considering surgical careers. Postgraduate training in particular appears to be most significant for women and cost of training an additional factor in both women and men from LMICs and LICs. Mentorship remains an important and modifiable factor in influencing student's decision to pursue surgery. Quality of surgical education showed no effect on student decision-making.

Simple preoperative risk scale accurately predicts perioperative mortality following esophagectomy for malignancy.

Surgery remains one of the major treatment options available to patients with esophageal cancer, with high mortality in certain cohorts. The aim of this study was to develop a simple preoperative risk scale based on patient factors, hospital factors, and tumor pathology to predict the risk of perioperative mortality following esophagectomy for malignancy. The Nationwide Inpatient Sample database was used to create the risk scale. Patients who underwent open or laparoscopic transhiatal and transthoracic esophageal resection were identified using International Classification of Diseases, 9th edition codes. Patients <18 years and those with peritoneal disease were excluded. Multivariate logistic regressions were used to define a predictive model of perioperative mortality and to create a simple risk scale. From 1998 to 2011, a total of 23 751 patients underwent esophagectomy. The observed overall perioperative mortality rate for this cohort was 7.7%. Minimally invasive techniques, and operations performed in higher volume centers were protective, whereas increasing age, comorbidities and diagnosis of squamous cell carcinoma were independent predictors of mortality. Based on this population, a risk scale from 0-16 was created. The calibration revealed a good agreement between the observed and risk scale-predicted probabilities. A set of sensitivity/specificity analyses was then performed to define normal (score 0-7) and high risk (score 8-16) patients for clinical practice. Mortality in patients with a score of 0-7 ranged from 1.3-7.6%, compared with 10.5-34.5% in patients with a score of 8-16. This simple preoperative risk scale may accurately predict the risk of perioperative mortality following esophagectomy for malignancy and can be used as a clinical tool for preoperative counseling.

Reduced perioperative death following laparoscopic colorectal resection: results of an international observational study.

BACKGROUND: Laparoscopic approaches to colorectal surgery are known to accelerate recovery but the effect on postoperative mortality is uncertain. The purpose of this study was to determine whether differences exist in postoperative mortality between patients undergoing laparoscopic and open colorectal surgery in a group of international healthcare institutions. METHODS: Administrative data from 30 worldwide institutions were searched for patients who underwent elective colorectal surgical resection between January 2007 and December 2011. The primary outcome measure was 30-day-in-hospital mortality rate. Secondary outcome measures were 30-day readmission rate, length of stay, and 30-day reoperation rate. RESULTS: There were 30,369 (20,641 colonic and 9728 rectal) resections recorded over the 5 years. Eight thousand eighty-six were laparoscopic (26.6%) and 22,283 (73.4%) were open. Following propensity-score matching of the laparoscopic and open cohorts, mortality was 0.5% following laparoscopic colectomy and 1.2% after conventional surgery (P < 0.001). After adjusting for differences in preoperative risk factors including gender, age, comorbidity, type of surgery and diagnosis, by matching on propensity score, laparoscopic surgery was a strong determinant of reduced 30-day mortality (odds ratio 0.44; 95% confidence interval 0.31-0.62; P < 0.001), reduced hospital stay (odds ratio 0.42, 95% confidence interval 0.39-0.45; P < 0.001), reduced readmission (odds ratio 0.78, 95% confidence interval 0.71-0.86; P < 0.001) and reduced re-operation (odds ratio 0.75, 95% confidence interval 0.65-0.76; P < 0.001). CONCLUSIONS: Minimally invasive colorectal surgery is associated with reduced in-hospital mortality when compared with conventional techniques. This finding is consistent across international healthcare institutions and supports efforts to disseminate laparoscopic skills.

Validating the Injury Severity Score (ISS) in different populations: ISS predicts mortality better among Hispanics and females.

INTRODUCTION: The Injury Severity Score (ISS) is the most commonly used measure of injury severity. The score has been shown to have excellent predictive capability for trauma mortality and has been validated in multiple data sets. However, the score has never been tested to see if its discriminatory ability is affected by differences in race and gender. OBJECTIVE: This study is aimed at validating the ISS in men and women and in three different race/ethnic groups using a nationwide database. METHODS: Retrospective analysis of patients age 18-64 y in the National Trauma Data Bank 7.0 with blunt trauma was performed. ISS was categorized as mild (<9,) moderate (9-15), severe (16-25), and profound (>25). Logistic regression was done to measure the relative odds of mortality associated with a change in ISS categories. The discriminatory ability was compared using the receiver operating characteristics curves (ROC). A P value testing the equality of the ROC curves was calculated. Age stratified analyses were also conducted. RESULTS: A total of 872,102 patients had complete data for the analysis on ethnicity, while 763,549 patients were included in the gender analysis. The overall mortality rate was 3.7%. ROC in Whites was 0.8617, in Blacks 0.8586, and in Hispanics 0.8869. Hispanics have a statistically significant higher ROC (P value < 0.001). Similar results were observed within each age category. ROC curves were also significantly higher in females than in males. CONCLUSION: The ISS possesses excellent discriminatory ability in all populations as indicated by the high ROCs.

Hyperbaric oxygen ameliorates delayed neuropsychiatric syndrome of carbon monoxide poisoning.

OBJECTIVES: Delayed neuropsychiatric syndrome (DNS) is characterized by mental impairment, motor dysfunction, dementia, or psychosis that develops between a few days and weeks after acute carbon monoxide (CO) poisoning. One possible mechanism responsible for CO-mediated encephalopathy involves oxidative stress, such as lipid peroxidation, caused by the cellular uptake of CO and which leads to an inflammatory cascade. There is no current effective treatment for DNS. We applied 8-40 sessions of hyperbaric oxygen therapy (HBO2) to patients with DNS and evaluated its effectiveness. METHODS: After admission, all patients were administered piracetam or bromocriptine, or both, and received HBO2. Neuropsychiatric tests included EEG, mini-mental status examination (MMSE), brain MRI, event-related potential (ERP), and brain perfusion scan (brain SPECT). Results of these tests were compared before and after HBO2, and the clinical features were monitored during this period. RESULTS: The symptoms of DNS for all patients improved significantly after HBOT. Although white matter changes remained evident in the brain MRI scans, other examinations such as EEG, MMSE, ERP, and 99mTc-ECD brain SPECT were nearly normal after HBOT. CONCLUSION: Our results suggest that HBO2 decreases the severity of impairment in patients with DNS. Although a large randomized trial is required to address the efficacy of this therapy, therapeutic application of HBO2 may be recommended in patients with DNS after CO poisoning.

A localized elevation of cytosolic free calcium is associated with cytokinesis in the zebrafish embryo.

Cytokinesis, a key step in cell division, is known to be precisely regulated both in its timing and location. At present, the regulatory mechanism of cytokinesis is not well understood, although it has been suggested that calcium signaling may play an important role in this process. To test this notion, we introduced a sensitive fluorescent Ca2+ indicator into the zebrafish embryo and used confocal microscopy to measure the spatiotemporal variation of intracellular free Ca2+ concentration ([Ca2+]i) during cell cleavage. It was evident that a localized elevation of [Ca2+]i is closely associated with cytokinesis. First, we found that during cytokinesis, the level of free Ca2+ was elevated locally precisely at the cleavage site. Second, the rise of free Ca2+ was very rapid and occurred just preceding the initiation of furrow contraction. These observations strongly suggest that cytokinesis may be triggered by a calcium signal. In addition, we found that this cytokinesis-associated calcium signal arose mainly from internal stores of Ca2+ rather than from external free Ca2+; it could be blocked by the antagonist of inositol trisphosphate (InsP3) receptors. These findings suggest that the localized elevation of [Ca2+]i is caused by the release of free Ca2+ from the endoplasmic reticulum through the InsP3-regulated calcium channels.

Pseudo-outbreak of Mycobacterium abscessus Infection Caused by laboratory contamination .

OBJECTIVE: To investigate the cause(s) of an increased incidence of clinical cultures growing Mycobacterium abscessus at a hospital in Florida. DESIGN: Outbreak investigation. SETTING: University-affiliated, tertiary-care hospital. METHODS: A site visit was done during the first week of September 2006. We reviewed the medical records of patients from whom M. abscessus was recovered during the period from January 1, 2003, through June 30, 2006. We collected environmental samples from various sites and evaluated specimen processing procedures in the microbiology laboratory. Isolates of M. abscessus recovered from the environment and from 12 randomly selected patients who sought medical care in 2006 were compared by pulsed-field gel electrophoresis (PFGE). Follow-up case surveillance was continued through March 31, 2007. RESULTS: Specimens from 143 patients obtained from various anatomical sites grew M. abscessus on culture in 2005-2006, compared with specimens from 21 patients in 2003-2004. The 12 isolates from patients that were selected for molecular typing had indistinguishable PFGE patterns. Observations revealed no major breaches in the processing of mycobacterial specimens in the laboratory. Isolates grew only after prolonged incubation (mean +/- SD, 45 +/- 15 days) in test tubes containing diagonally oriented Middlebrook and Cohn 7H10 agar or Lowenstein-Jensen medium. Environmental samples obtained from the inside of the specimen incubator grew M. abscessus on culture. A test tube containing diagonally oriented, uninoculated Middlebrook and Cohn 7H10 agar that was incubated in the same incubator as clinical specimens grew M. abscessus with a PFGE pattern that matched the pattern of the patient isolates. Cases of M. abscessus infection decreased to baseline after the hospital changed suppliers of mycobacterial media and cleaned the incubator. CONCLUSIONS: Although the source was never confirmed, our investigation suggests that this was a pseudo-outbreak of M. abscessus infection that resulted from contamination of mycobacterial cultures during incubation. Our findings emphasize the need for guidance on the disinfection of specimen incubators.

A high throughput drug screen based on fluorescence resonance energy transfer (FRET) for anticancer activity of compounds from herbal medicine.

BACKGROUND AND PURPOSE: We report the development of a very efficient cell-based high throughput screening (HTS) method, which utilizes a novel bio-sensor that selectively detects apoptosis based on the fluorescence resonance energy transfer (FRET) technique. EXPERIMENTAL APPROACH: We generated a stable HeLa cell line expressing a FRET-based bio-sensor protein. When cells undergo apoptosis, they activate a protease called 'caspase-3'. Activation of this enzyme will cleave our sensor protein and cause its fluorescence emission to shift from a wavelength of 535 nm (green) to 486 nm (blue). A decrease in the green/blue emission ratio thus gives a direct indication of apoptosis. The sensor cells are grown in 96-well plates. After addition of different chemical compounds to each well, a fluorescence profile can be measured at various time-points using a fluorescent plate reader. Compounds that can trigger apoptosis are potential candidates as anti-cancer drugs. KEY RESULTS: This novel cell-based HTS method is highly effective in identifying anti-cancer compounds. It was very sensitive in detecting apoptosis induced by various known anti-cancer drugs. Further, this system detects apoptosis, but not necrosis, and is thus more useful than the conventional cell viability assays, such as those using MTT. Finally, we used this system to screen compounds, isolated from two plants used in Chinese medicine, and identified several effective compounds for inducing apoptosis. CONCLUSIONS AND IMPLICATIONS: This FRET-based HTS method is a powerful tool for identifying anti-cancer compounds and can serve as a highly efficient platform for drug discovery.

Gastroschisis in the United States 1988-2003: analysis and risk categorization of 4344 patients.

OBJECTIVE: Gastroschisis is a rare congenital abdominal wall defect through which intraabdominal organs herniate and it requires surgical management soon after birth. The objectives of this study were to profile patient characteristics of this anomaly utilizing data from two large national databases and to validate previous risk stratification categories of infants born with this condition. METHODS: An analysis was performed using 13 years of the National Inpatient Sample database (1988-1996, 1998, 1999, 2001, 2002) and 3 years of the Kids' Inpatient Database (1997, 2000, 2003). These combined databases contain information from nearly 93 million discharges in the United States. Infants with gastroschisis were identified by International Classification of Disease-9 procedure code 54.71 (repair of gastroschisis) and an age at admission of <8 days. Variables of gender, race, geographic region, co-existing diagnoses, length of stay, hospital charges adjusted to 2005 dollars, complications and inpatient mortality were collected from the databases. Infants were divided into simple and complex categories based on the absence or presence of intestinal atresia, stenosis, perforation, necrosis or volvulus. Comparisons between groups were performed using Pearson's chi (2) for categorical outcomes and the Kruskal-Wallis test for non-normally distributed continuous variables. RESULTS: A total of 4344 infants with gastroschisis were identified. These were comprised of 44.0% female infants (n=1910), 46.4% male infants (n=2017) whereas 9.6% were not reported (n=415). Racial analysis showed the largest subset being white in 40.9% of infants (n=1775) with Hispanic infants being the next highest group reported at 17.2% (n=745). Co-existing intestinal anomalies were the most common, affecting 9.9% (n=429) infants, whereas certain cardiac (6.8%, n=294) and pulmonary (1.7%, n=72) conditions were also identified. Simple gastroschisis represented 89.1% (n=3870) of the group whereas 10.9% (n=474) were complex in nature. Simple and complex patients differed in median length of stay (28 vs 67 days, P<0.01), inpatient mortality (2.9 vs 8.7%, P<0.01) and median inflation-adjusted hospital charges (90,788 dollars vs 197,871 dollars, P<0.01). CONCLUSIONS: These data represent a national analysis of the largest group of infants with gastroschisis to date which further aids the characterization and understanding of this serious congenital condition.

Thirty robotic adrenalectomies: a single institution's experience.

BACKGROUND: Robotic adrenalectomy is a minimally invasive alternative to traditional laparoscopic adrenalectomy. To date, only case reports and small series of robotic adrenalectomies have been reported. This study presents a single institution's series of 30 robotic adrenalectomies, and evaluates the procedure's safety, efficacy, and cost. METHODS: Thirty patients underwent robotic adrenalectomy at the Johns Hopkins Hospital between April 2001 and January 2004. Patient morbidity, hospital length of stay, operative time, and conversion rate to traditional laparoscopic or open surgery are presented. Improvement in operative time with surgeon experience is evaluated. Hospital charges are compared to charges for traditional laparoscopic and open adrenalectomies performed during the same time period. RESULTS: Median operative time was 185 min. Patient morbidity was 7%. There were no conversions to traditional laparoscopic or open surgery. The median hospital stay was 2 days. Operative time improved significantly by 3 min with each operation. Hospital charges for robotic adrenalectomy (12,977 dollars) were not significantly different than charges for traditional laparoscopic (11,599 dollars) or open adrenalectomy (14,600 dollars). CONCLUSIONS: Robotic adrenalectomy is a safe and effective alternative to traditional laparoscopic adrenalectomy.

Distinction of normal, preneoplastic, and neoplastic mouse mammary primary cell cultures by water nuclear magnetic resonance relaxation times.

Normal, preneoplastic, and neoplastic primary cultures of mouse mammary epithelial cells were distinguishable on the basis of water proton nuclear magnetic resonance (NMR) relaxation times--i.e., spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). T1 values were 916 +/- 24 msec for normal cells, 1,029 +/- 24 msec for preneoplastic cells, and 1,155 +/- 42 msec for neoplastic cells. This method of distinction between normal and neoplastic cells (P less than 0.001) and normal and preneoplastic cells (P less than 0.005) supported previous findings in whole tissues. NMR relaxation times resulted in better distinction between these cell populations than any other technique except direct histology. The T1 and T2 values of water protons in cells grown in primary culture were higher than those of established mouse mammary cancer cell lines. The differences in T1 and T2 did not correlate with cellular hydration. The data suggested a basic difference in water-macromolecular surface interactions among normal, preneoplastic, and neoplastic cells.

Systemic effect of benign and malignant mammary tumors on the spin-lattice relaxation time of water protons in mouse serum.

The spin-lattice relaxation time (T1) for water protons in sera was significantly (P less than 0.001) elevated above that for normal sera in mice bearing benign ductal papilloma and malignant mammary carcinoma. Serum T1 values did not differ significantly in mice with ductal hyperplasia or preneoplastic alveolar nodules. Elevated serum T1's could not be explained on the basis of serum iron levels or serum protein concentrations. This was the first report of a "systemic effect" of serum T1 elevation by a benign tumor.

Nuclear magnetic resonance studies on human breast dysplasias and neoplasms.

The ability of nuclear magnetic resonance (NMR) spectroscopy to distinguish normal, diseased non-neoplastic, and neoplastic human breast tissues was investigated with T1 and T2 relaxation times used. The results indicated that NMR relaxation times could distinguish between the mean values of breast neoplasms and other diseased or normal tissues, with P values less than 0.001. Given a single sample, the probability of classifying it nonneoplastic or carcinoma could be accomplished with 85% confidence. For human breast tissues, the relaxation time T2 may be more discriminating that T1. These results support the view that the use of NMR spectroscopy in cancer detection may be of significant value and warrants considerable more interest and effort to determine the beneficial applications and limits of this technology.

Microtubule complexes correlated with growth rate and water proton relaxation times in human breast cancer cells.

Ten established human breast cancer cell lines display patterns of microtubule organization which are characterized by growth rate of the cell populations and the freedom of mobility of cellular water molecules measured by nuclear magnetic resonance spectroscopy. Cell lines with population-doubling times of 1 to 2 days demonstrate rapid mobility of water molecules by proton spin-lattice and spin-spin relaxation times (T1 greater than 750 msec, T2 greater than 120 msec) and have diffuse patterns of tubulin immunofluorescent antibody staining. Moderately fast dividing cells (population-doubling times of 3 to 7 days) have T1 values of 600 to 750 msec and show approximately 50% organized complexes of polymerized microtubules in the cytoplasm. Slow-growing cell lines demonstrate more restricted mobility of water molecules (T1 values of 500 to 600 msec) and contain abundant networks of polymerized microtubules. The three-way correlation of the physical parameter of water proton relaxation times, the structural parameter of microtubule organization, and the physiological parameter of growth suggest a close interaction of water molecules with the cytoplasmic macromolecular network in the performance of physiological function.

High-efficiency gene transfection by in situ electroporation of cultured cells.

It is demonstrated in this study that high-efficiency gene transfection can be obtained by directly electroporating cultured mammalian cells in their attached state using a pulsed radio-frequency (RF) electric field. A plasmid DNA containing the reporter gene beta-gal was introduced into COS-M6 cells and CV-1 cells using this in situ electroporation method. At the optimal electric field strength (1.2 kV/cm), we found that over 80% of the M6 cells took up and expressed the beta-gal gene with a cell survival rate of about 50%. In contrast, the transfection efficiency was less than 20% when the M6 cells were electroporated in suspension. It was shown that CV-1 cells could also be electroporated highly efficiently using the in situ method. Furthermore, we have measured the time required to express the beta-gal gene after the plasmid DNA was introduced. We found that the percentage of cells expressing beta-gal reached a peak value about 10 h after electroporation. This time-course was the same for both attached and suspended cells, suggesting that the observed difference in transfection efficiency was mainly the result of effects of the detachment treatment on the electroporation process rather than on the gene expression.

Nuclear magnetic resonance study of squid giant axon.

Using a spin-echo technique, the spin-lattice and spin-spin relaxation times (T1 and T2) of water protons in a single nerve fiber (giant axon of squid) were determined. Similar measurements were also carried out on axoplasm extruded from these nerve fibers. It was found that the relaxation times of water protons of both the intact fiber and the extruded axoplasm are approximately equal (and much less than those of a free solution), suggesting that the relaxation times of cellular water are shortened mainly by water-protein interactions rather than by water-membrane interactions.

High efficiency gene transfection by electroporation using a radio-frequency electric field.

In order to develop a safe and effective way to introduce exogenous genes into cells, we have experimented with a new method of electroporation which uses a radio-frequency (RF) electric field to permeabilize the cell membrane. This RF method has several advantages over the conventional electroporation method which uses a direct current (DC) field. We have shown that the RF electroporation method can be used to introduce marker genes into a wide variety of cell lines, including COS-M6, CV-1, CHO, 3T3 and hepatocytes, and is able to increase substantially the efficiency of gene transfection. (For example, the amount of DNA required for transfecting two million COS-M6 cells can be as low as 0.1 microgram). The transfection efficiency is shown to be affected by a number of factors, including cell type, field strength, pulse protocol and medium buffer. Because of its wide range of applications, high transfection efficiency and lack of harmful side-effect, the RF electroporation method would be particularly useful for introducing genes into human cells for gene therapy.

The spin-lattice relaxation times of water associated with early post mortem changes in skeletal muscle.

We studied the spin-echo signal of muscle water in a large time domain and found that the motion of the nuclear magnetic moment of tissue water cannot be characterized by a single spin-lattice relaxation time (T1). The relaxation time T1B, which is the T1 characterized by those protons with a slower relaxation rate, is influenced by the early post mortem changes in skeletal muscle. T1B increased with time after the tissue was taken from the animal and reached a maximum at 3 h. However, the weighted average of T1 of all water protons (T1A) did not change throughout the time course of the experiments.