An In Vitro Model for Studying Neuromuscular Transmission in the Mouse Pharynx

The muscles of the pharynx are controlled by networks of neurons under the control of specific regions in the brain stem, which have been fairly well studied. However, the transmission between these neurons and the pharyngeal muscles, at the motor end plates, is less well understood. Therefore, an in vitro model for the study of neuromuscular transmission in the pharyngeal muscle of the mouse was developed. Ring preparations from the inferior constrictor and the cricopharyngeus muscles were isolated and mounted for isometric force recording at physiologic temperature. Preparations from the diaphragm and the soleus muscles were examined in parallel. The muscles were stimulated at supramaximal voltage with short tetani at 100 Hz. Following direct stimulation of the muscle fibers, using a longer pulse duration, the rate of force development of the pharyngeal muscles was similar to that of the diaphragm and faster than that of the soleus muscle. By varying the duration of the stimulation pulses, conditions where the nerve-mediated activation contributed to a major extent of the contractile responses were identified. Gallamine completely inhibited the nerve-mediated responses. In separate experiments the dose dependence of gallamine inhibition was examined, showing similar sensitivity in the inferior pharyngeal constrictor compared to the diaphragm and soleus muscles. We conclude that reproducible contractile responses with an identifiable nerve-induced component can be obtained from the mouse inferior pharyngeal constrictor. The pharyngeal muscles have contractile characteristics similar to those of the faster diaphragm. The sensitivity to the neuromuscular blocking agent gallamine of the inferior pharyngeal constrictor was in the same concentration range as that of the diaphragm and soleus muscles.

One-Hour Plasma Glucose Identifies Insulin Resistance and ��-Cell Dysfunction in Individuals With Normal Glucose Tolerance: Cross-sectional data from the Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study

OBJECTIVE

Some individuals with normal glucose tolerance (NGT) exhibit a 1-h excursion of plasma glucose during oral glucose tolerance testing as high as that of individuals with impaired glucose tolerance (IGT). The aim of this study was to characterize their metabolic phenotype.

RESEARCH DESIGN AND METHODS

A total of 1,205 healthy volunteers (aged 29–61 years) underwent assessment of 1) oral glucose tolerance and 2) insulin sensitivity (standardized euglycemic-hyperinsulinemic clamp), as part of the Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study.

RESULTS

One-hour plasma glucose correlated better than 2-h plasma glucose with total insulin secretion (r = 0.43), β-cell glucose sensitivity (r = −0.46), and β-cell rate sensitivity (r = −0.18). Receiver operating characteristic analysis identified 8.95 mmol/l as the best cutoff value for prediction of IGT from 1-h plasma glucose (sensitivity 77% and specificity 80%). Participants with NGT with 1-h plasma glucose >8.95 mmol/l had larger waist circumference, higher BMI, lower insulin sensitivity, higher fasting glucose, and higher insulin secretion than their counterparts with 1-h plasma glucose ≤8.95 mmol/l (P < 0.001 for all comparisons). Moreover, they exhibited lower β-cell glucose sensitivity (P < 0.001), β-cell rate sensitivity (P < 0.001), and potentiation factor (P = 0.026). When compared with conventionally defined IGT, they were not different in waist circumference and BMI, hepatic insulin extraction, β-cell glucose sensitivity, β-cell rate sensitivity, and potentiation factor but did have greater insulin sensitivity along with reduced basal (P = 0.001) and total insulin secretion (P = 0.002).

CONCLUSIONS

Higher values of 1-h plasma glucose may identify an intermediate condition between NGT and IGT characterized by greater insulin resistance, reduced β-cell glucose sensitivity, and reduced β-cell rate sensitivity.Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are states of carbohydrate metabolism intermediate between normal glucose tolerance (NGT) and type 2 diabetes, which represent two partially overlapping conditions with distinct metabolic characteristics (1,2). In IFG, there is marked hepatic insulin resistance with near-normal muscle insulin sensitivity, whereas this pattern is reversed in IGT (2). Although both conditions are characterized by reduced early-phase insulin secretion, there is an additional impairment of late-phase insulin secretion in IGT. Accordingly, individuals with IGT have a rapid early (30 min) rise in plasma glucose during an oral glucose tolerance test (OGTT) which continues to rise until 60 min (1-h plasma glucose) and thereafter remains ≥7.8 mmol/l (140 mg/dl) at 120 min (2-h plasma glucose).As longitudinal studies have demonstrated that 40% of patients who develop type 2 diabetes after 10 years have NGT at baseline (1), there may be additional information beyond conventional IFG/IGT categories that may better discriminate future progression to type 2 diabetes (3). We have noted a subset of individuals with NGT who have early glucose excursions during an OGTT as high as those observed in individuals with IGT. However, because plasma glucose concentrations decline adequately by 2 h, due to preservation of late-phase insulin secretion, these individuals do not have, by current definitions, any form of disordered carbohydrate metabolism (4). Data from the San Antonio Study have shown that β-cell glucose sensitivity and insulin sensitivity contribute to values of 2-h plasma glucose independently of each other (5); thus, we hypothesized that individuals with NGT with 1-h plasma glucose levels as high as in those with IGT might represent an intermediate phenotype of abnormal carbohydrate metabolism with either impaired insulin sensitivity or β-cell glucose sensitivity, who are potentially at increased risk of progression to type 2 diabetes.To investigate this hypothesis we analyzed cross-sectional data from the European Relationship between Insulin Sensitivity and Cardiovascular Risk (RISC) study (6), examining the metabolic phenotype of individuals with NGT who had high 1-h plasma glucose excursions. We aimed to identify a new glucose tolerance subgroup who might benefit from targeted lifestyle advice and/or pharmacological intervention.     

Inactivation of FBXW7/hCDC4-β expression by promoter hypermethylation is associated with favorable prognosis in primary breast cancer

Introduction  

Mutational inactivation of the FBXW7/hCDC4 tumor suppressor gene (TSG) is common in many cancer types, but infrequent in breast cancers. This study investigates the presence and impact of FBXW7/hCDC4 promoter methylation in breast cancer.     

Disappearance of myocardial perfusion defects on prone SPECT imaging: Comparison with cardiac magnetic resonance imaging in patients without established coronary artery disease

Background  

It is of great clinical importance to exclude myocardial infarction in patients with suspected coronary artery disease who do not have stress-induced ischemia. The diagnostic use of myocardial perfusion single-photon emission computed tomography (SPECT) in this situation is sometimes complicated by attenuation artifacts that mimic myocardial infarction. Imaging in the prone position has been suggested as a method to overcome this problem.     

Assessment of competence and progressive independence in postgraduate clinical training

Context At present, competency‐based, outcome‐focused training is gradually replacing more traditional master–apprentice teaching in postgraduate training. This change requires a different approach to the assessment of clinical competence, especially given the decisions that must be made about the level of independence allowed to trainees. Methods This study was set within postgraduate obstetrics and gynaecology training in the Netherlands. We carried out seven focus group discussions, four with postgraduate trainees from four training programmes and three with supervisors from three training programmes. During these discussions, we explored current opinions of supervisors and trainees about how to determine when a trainee is competent to perform a clinical procedure and the role of formal assessment in this process. Results When the focus group recordings were transcribed, coded and discussed, two higher‐order themes emerged: factors that determine the level of competence of a trainee in a clinical procedure, and factors that determine the level of independence granted to a trainee or acceptable to a trainee. Conclusions From our study, it is evident that both determining the level of competence of a trainee for a certain professional activity and making decisions about the degree of independence entrusted to a trainee are complex, multi‐factorial processes, which are not always transparent. Furthermore, competence achieved in a certain clinical procedure does not automatically translate into more independent practice. We discuss the implications of our findings for the assessment of clinical competence and provide suggestions for a transparent assessment structure with explicit attention to progressive independence.     

A stiff and straight back preoperatively is associated with a good outcome 2 years after lumbar disc surgery: A prospective study of 80 patients

Background and purpose The degree of lumbar lordosis and reduced lumbar mobility are regarded as important clinical features in patients with low back pain, and in lumbar disc herniation A more stiff back preoperatively in a proportion of patients has been shown to be associated with sequestered disc herniation. The main aim of this study was to investigate whether there was any correlation between lumbar lordosis and flexion on the one hand in patients with lumbar disc herniation who were scheduled for surgery, and postoperative pain and disability on the other. Our second aim was to determine the patterns of postoperative improvement in pain, perceived disability, and flexion/lordosis for 2 years after surgery.Methods Pain (VAS), disability (DRI), lumbar flexion and lordosis (Debrunner''s kyfometer) were measured pre- and postoperatively in 80 patients who underwent microscopic lumbar disc surgery.Results Patients with preoperative hyperlordosis had more severe pain and more disability postoperatively than patients with hypolordosis. The level of pain did not change much from 2–6 weeks postoperatively until 2 years, while the perceived disability did not reach a steady state until 6 months after surgery.Interpretation Patients with a stiff and flat back have a good prognosis after lumbar disc surgery, and in most cases the pain will reach the 2-year level during the first 2–6 weeks, while the physical restoration measured by the lumbar flexion and lordosis, and the perceived disability, will continue to improve over the first 6 months after surgery.     

Functional in vitro model to examine cancer therapy cytotoxicity in maturing rat testis

Childhood cancer treatment can lead to infertility. Organ culture of early postnatal testicular tissue might provide a valuable approach to the study of acute testicular toxicity. The aim of the present study was to develop a functional in vitro organ culture method, in order to identify sensitive target cells to doxorubicin-induced cytotoxicity in immature rat testis during germ cell migration prior initiation of the first wave of spermatogenesis. Testicular tissue fragments from 5-day-old Sprague–Dawley rats were cultured in the absence or presence of doxorubicin (40 and 100 ng/ml) and morphology, apoptosis, proliferation and testosterone secretion was analyzed. Postnatal testicular development proceeded normally in control samples for 48 h in vitro. In these untreated culture conditions germ and Sertoli cell numbers and germ cell migration were comparable to in vivo. Germ cells were the primary, most sensitive targets for in vitro-induced doxorubicin (100 ng/ml) toxicity and their death was not associated with any morphological defects in the Sertoli cells. Organ culture which reduces the need of animal experimentation can be used to study the cytotoxic effects of doxorubicin on the immature testis.