Estrogen modulates sexually dimorphic contextual fear conditioning and hippocampal long-term potentiation (LTP) in rats(1)

The present study examined the role of ovarian steroids in contextual fear conditioning and hippocampal synaptic plasticity in female rats. In experiment 1, adult female rats were ovariectomized and submitted to contextual fear conditioning, a procedure in which rats received unsignaled footshock in a novel observation chamber; freezing behavior served as the measure of conditional fear. Ovariectomized female rats froze at levels comparable to male rats, both of which froze significantly more than sham-operated female rats. In experiment 2, estrogen replacement in ovariectomized female rats reduced fear conditioning to a level comparable to that of sham-operated females in experiment 1. In experiment 3, the influence of estrogen on the induction of long-term potentiation (LTP) at perforant path-dentate granule cell synapses in ovariectomized female rats was examined. Estrogen decreased both population spike LTP and EPSP-spike potentiation at perforant path synapses. Taken together, these experiments indicate that ovarian steroids regulate both sexually dimorphic behavior and hippocampal plasticity in a fear-conditioning paradigm.     

Functional observational battery and motor activity in rats after single administration of two NHE 1 inhibitors

Two tests, a functional observational battery (FOB) and measurement of motor activity, have been used to screen the two NHE inhibitors EMD 96785 and EMD 125021 for neurobehavioral effects. These two NHE inhibitors, which exhibit a marked selectivity for the NHE 1 isoform, are under development in the research laboratories of Merck KGaA. NHE inhibitors are developed for the treatment of acute myocardial infarction and chronic heart failure. In prior studies with EMD 96785 and EMD 125021, clinical symptoms, such as uncoordinated movements and weakness of the hindlimbs, were detected in rats. The aim of this study was the evaluation of clinical findings in more detail using a FOB and measurement of motor activity in 96 female rats. The time course and reversibility of the adverse effects were investigated. The animals were treated with EMD 96785 or EMD 125021 by intravenous injection at a single dose of 100 mg/kg and four different time points (2 h, 1 day, 7 days and 21 days after treatment) were chosen for the clinical examination. This neurobehavioral test battery clearly detected neurological activity and defined time-course characteristics after treatment with EMD 96785 or EMD 125021. The various clinical parameters were grouped into functional-related domains and most alterations were seen in the domains of central nervous system and neuromuscular system. The most prominent clinical findings were seen with the pharmacologically more potent NHE inhibitor EMD 125021 when compared to EMD 96785. The clinical symptoms were proven to be reversible by 7 days after the single treatment for both compounds.     

Development and evaluation of an integrated musculoskeletal disease course for medical students

BACKGROUND: A recent survey of medical and surgical residents in the United States suggested that our current training of physicians may be inadequate to meet the increasing demand for diagnosis and treatment of musculoskeletal disorders. In response, we developed an integrated, multidisciplinary course to teach knowledge and skills related to musculoskeletal disease to second-year medical students. A three-year prospective outcomes study was conducted to evaluate the new course. METHODS: The primary outcomes that were studied during the first year of the new course were the gains in knowledge, changes in levels of confidence, and long-term retention of skills. Secondary outcomes consisted of student and faculty satisfaction. Ten-item pre-tests and post-tests covering core course concepts were administered to students. A matched-pairs t test was used to evaluate the difference between pre-test and post-test scores. Students were also asked to rate, on a 10-point scale, how much confidence they had in their ability to perform the musculoskeletal physical examination before and after the institution of the new curriculum. A general linear model analysis with post hoc pairwise comparisons (F test) was used to evaluate the changes in the confidence levels of the students. Also, a knee examination station was organized to compare students' scores before and after revision of the course. At the conclusion of the course, students rated each aspect of it on a scale of 1 to 5. Instructors were asked to rate the effectiveness of all elements of the course on the same scale. RESULTS: On the basis of student satisfaction and confidence and faculty satisfaction, the most effective changes in the curriculum were the introduction of a physical examination workshop and simulated clinical situations. Students' knowledge increased significantly (p < 0.001), and their level of confidence increased significantly in thirteen specifically targeted areas (p < 0.0001). On the end-of-the-year examination assessing retention of physical examination skills, the scores for the skills emphasized in the revised course increased significantly whereas the scores for a skill not emphasized in the course remained the same. Revisions made in the second and third years after implementation of the course expanded the more successful elements and further improved student ratings. CONCLUSIONS: Integration of the three clinical disciplines related to musculoskeletal disease--orthopaedics, rheumatology, and physical medicine and rehabilitation--resulted in a highly effective introductory course for second-year medical students. The heuristic strategy of introducing core content through lectures and workshops followed by small-group teaching sessions for practice with the new knowledge effectively increased students' knowledge, confidence, and satisfaction.     

Toward development of imaging modalities for islets after transplantation: insights from the National Institutes of Health Workshop on Beta Cell Imaging

BACKGROUND: Pancreatic islet transplantation can provide insulin independence and near normal glucose control in selected patients with type 1 diabetes mellitus. However, in most cases, achieving insulin independence necessitates the use of at least two donor pancreases per recipient and the rate of insulin independence may decline after transplantation. To better understand the fate of transplanted islets and the relationship between transplanted islet mass, graft function, and overall glucose homeostasis, an accurate and reproducible method of imaging islets in vivo is needed. METHODS: Recent advances in noninvasive imaging techniques such as magnetic resonance imaging, positron emission tomography, and other imaging modalities show great promise as potential tools to monitor islet number, mass, and function in the clinical setting. A recent international workshop, "Imaging the Pancreatic Beta Cell," sponsored by the National Institute of Biomedical Imaging and Bioengineering, the National Institute of Diabetes and Digestive and Kidney Diseases, and the Juvenile Diabetes Research Foundation International focused on these emerging efforts to develop novel ways of imaging pancreatic beta cells in vivo. RESULTS: Potential clinically applicable techniques include the use of directed magnetic resonance contrast agents such as lanthanides (Ln(3+)) and manganese (Mn(2+)) or magnetic resonance imaging probes such as superparamagnetic iron oxide nanoparticles. Potential techniques for positron emission tomography imaging include the use of beta cell-specific antibodies, or pharmacologic agents such as glyburide analogs, or d-mannoheptulose. Optical imaging techniques are also being used to evaluate various aspects of beta cell metabolism including intracellular Ca(2+) flux, glucokinase activity, and insulin granular exocytosis. CONCLUSIONS: The consensus among investigators at the imaging workshop was that an accurate and reproducible in vivo measure of functional islet mass is critically needed to further the strides that have been made in both islet transplantation and diabetes research as a whole. Such measures would potentially allow the assessment of islet engraftment and the early recognition of graft loss, leading to greater improvements in islet graft survival and function.     

Significant differences in the effects of magnetic field exposure on 7,12-dimethylbenz(a)anthracene-induced mammary carcinogenesis in two substrains of Sprague-Dawley rats

We have shown previously (S. Thun-Battersby et al., Cancer Res., 59: 3627-3633, 1999) that power-line frequency (50-Hz) magnetic fields (MFs) at micro T-flux densities enhance mammary gland tumor development and growth in the 7,12-dimethylbenz(a)anthracene (DMBA) model of breast cancer in female Sprague-Dawley (SD) rats. We also demonstrated that MF exposure results in an enhanced proliferative activity of the mammary epithelium of SD rats (M. Fedrowitz et al., Cancer Res., 62: 1356-1363, 2002), which is a likely explanation for the cocarcinogenic or tumor-promoting effects of MF exposure in the DMBA model. However, in contrast with our data, in a similar study conducted by Battelle in the United States, no evidence for a cocarcinogenic or tumor-promoting effect of MF exposure was found in the DMBA model in SD rats (L. E. Anderson et al., Carcinogenesis, 20: 1615-1620, 1999). Probably the most important difference between our and the Battelle studies was the use of different substrains of SD rats; the United States rats were much more susceptible to DMBA than the rats used in our studies. This prompted us to compare different substrains of SD outbred rats in our laboratory in respect to MF effects on cell proliferation in the mammary gland, susceptibility to DMBA-induced mammary cancer, and MF effects on mammary tumor development and growth in the DMBA model. The SD substrain (termed "SD1") used in all of our previous studies was considered MF-sensitive and used for comparison with another substrain ("SD2") obtained from the same breeder. In contrast with SD1 rats, no enhanced cell proliferation was determined after MF exposure in SD2 rats. MF exposure significantly increased mammary tumor development and growth in SD1 but not SD2 rats. These data indicate that the genetic background plays a pivotal role in effects of MF exposure. Different strains or substrains of rats may serve to evaluate the genetic factors underlying sensitivity to cocarcinogenic or tumor-promoting effects of MF exposure.     

Graded reoxygenation with chemical inhibition of oxidative phosphorylation improves posthypoxic recovery in murine hippocampal slices

Rapid and complete tissue reoxygenation is a prime goal of present stroke therapy. However, reoxygenation may trigger detrimental cascades that partially antagonize beneficial effects. It was our goal to investigate selective grading of reoxygenation with targeting of single mitochondrial complexes in murine hippocampal slices. Population spike amplitude (PSAP) and NADH were measured during hypoxic hypoxia (15 min) and recovery (45 min). With onset of reoxygenation, slices were treated for different times with amobarbital (1 mM), malonate (2 mM), or cyanide (1 mM), inhibitors of mitochondrial complex I, II, or IV, respectively. Other slices were treated with nicotinamide (1 mM). Posthypoxic recovery of PSAP increased from 32% +/- 43% of onset in control slices to 52% +/- 59% (P <.05) upon treatment with amobarbital for 1 min and to 62% +/- 37% (P <.05) upon treatment with malonate. With nicotinamide, posthypoxic recovery improved to 73% +/- 25% (P <.05). Oxidation of NADH was prolonged upon treatment with amobarbital, whereas no change in NADH oxidation was observed with malonate and nicotinamide. Thus, grading of reoxygenation with selective targeting of mitochondrial complex I or II but not of complex IV improves outcome upon reoxygenation in murine hippocampal slices.     

Microstructural white matter changes in carriers of the DYT1 gene mutation

We tested the hypothesis that the DYT1 genotype is associated with a disorder of anatomical connectivity involving primarily the sensorimotor cortex. We used diffusion tensor magnetic resonance imaging (DTI) to assess the microstructure of white matter pathways in mutation carriers and control subjects. Fractional anisotropy (FA), a measure of axonal integrity and coherence, was reduced (p < 0.005) in the subgyral white matter of the sensorimotor cortex of DYT1 carriers. Abnormal anatomical connectivity of the supplementary motor area may contribute to the susceptibility of DYT1 carriers to develop clinical manifestations of dystonia.