Membrane properties of an unusual intrinsically oscillating, wide-field teleost retinal amacrine cell

In the retina, amacrine cells modulate the transfer of information from bipolar to ganglion cells. The nature of the modulation depends on the synaptic input and the membrane properties of the cells. In the retina of white bass, we identified a class of bistratified, wide-field amacrine cell characterized by immunopositive labelling for GABA and calmodulin. In isolation, the cells presented resting membrane potentials averaging -69 mV although some cells settled at more depolarized values (-30 mV). Injection of depolarizing current pulses induced oscillatory membrane responses. When elicited from depolarized cells, the oscillations were short-lived (< 40 ms). For the most part, the oscillatory potentials of hyperpolarized cells remained unattenuated throughout the depolarizing pulse. The frequency of the oscillations increased logarithmically with mean membrane potential, ranging from 74 to 140 Hz. Cells exhibiting depolarized membrane potentials oscillated at twice that rate. When the membrane potential of these cells was hyperpolarized to -70 mV, the oscillations became unattenuated and slowed. We found the cells expressed voltage-gated sodium, potassium and calcium currents and calcium-dependent potassium currents. We demonstrate that the oscillatory potentials arose as a result of the interplay between calcium and potassium currents. The cells responded to local application of GABA and glycine, both of which modulate the oscillatory potentials. Glutamate and its analogues depolarized the cell and induced oscillatory potentials. Our results indicate that oscillatory responses of a type of wide-field amacrine cell are an intrinsic feature of the cell and not due to circuit properties.     

Application of radiosurgery principles to a target in the breast: a dosimetric study

PURPOSE: To investigate the technical and physical feasibility of using a radiosurgery-like technique to irradiate a small target within the breast with a single fraction. MATERIAL AND METHODS: During diagnostic biopsy, a tantalum surgical clip is placed in the lesion identified at mammography. Transverse CT scans over the entire breast are obtained, as the patient lies prone on a special table that allows the breast to hang down. The clip is used as a reference point to define the isocenter of the radiation treatment. RESULTS: The clip is visible on port films taken with a 4 MV beam, allowing the isocenter to be set to its planned location. No movement of the hanging breast is visually detected. The possible beam directions are enclosed by a 220 degrees horizontal x 180 degrees vertical angular interval. Dosimetry of two "radiosurgical" examples, (A) seven fixed horizontal beams and (B) six 45 degrees arcs and a 90 degrees sagittal arc using a 4 MV x-ray beam with a 32 mm diameter collimator, are discussed. Both field arrangements produce adequate tumor coverage: the minimum target dose is 83% of the dose maximum in the fixed beam arrangement and 86% in the multiarc setup. In arrangement A the lung and other tissues external to the breast receive dose only from scattered radiation. In arrangement B the maximum lung dose is less than 5% of the dose to isocenter. CONCLUSION: From a dosimetric point of view both described techniques are feasible, and the radiosurgery-like treatment is executable.     

Immunocytochemical localization of corticotropin-releasing factor (CRF) in the rat brain

The immunocytochemical localization of neurons containing the 41 amino acid peptide corticotropin-releasing factor (CRF) in the rat brain is described. The detection of CRF-like immunoreactivity in neurons was facilitated by colchicine pretreatment of the rats and by silver intensification of the diaminobenzidine end-product. The presence of immunoreactive CRF in perikarya, neuronal processes, and terminals in all major subdivisions of the rat brain is demonstrated. Aggregates of CRF-immunoreactive perikarya are found in the paraventricular, supraoptic, medial and periventricular preoptic, and premammillary nuclei of the hypothalamus, the bed nuclei of the stria terminalis and of the anterior commissure, the medial septal nucleus, the nucleus accumbens, the central amygdaloid nucleus, the olfactory bulb, the locus ceruleus, the parabrachial nucleus, the superior and inferior colliculus, and the medial vestibular nucleus. A few scattered perikarya with CRF-like immunoreactivity are present along the paraventriculo-infundibular pathway, in the anterior hypothalamus, the cerebral cortex, the hippocampus, and the periaqueductal gray of the mesencephalon and pons. Processes with CRF-like immunoreactivity are present in all of the above areas as well as in the cerebellum. The densest accumulation of CRF-immunoreactive terminals is seen in the external zone of the median eminence, with some immunoreactive CRF also present in the internal zone. The widespread but selective distribution of neurons containing CRF-like immunoreactivity supports the neuroendocrine role of this peptide and suggests that CRF, similarly to other neuropeptides, may also function as a neuromodulator throughout the brain.     

Joint angle variability in 3D bimanual pointing: uncontrolled manifold analysis

The structure of joint angle variability and its changes with practice were investigated using the uncontrolled manifold (UCM) computational approach. Subjects performed fast and accurate bimanual pointing movements in 3D space, trying to match the tip of a pointer, held in the right hand, with the tip of one of three different targets, held in the left hand during a pre-test, several practice sessions and a post-test. The prediction of the UCM approach about the structuring of joint angle variance for selective stabilization of important task variables was tested with respect to selective stabilization of time series of the vectorial distance between the pointer and aimed target tips (bimanual control hypothesis) and with respect to selective stabilization of the endpoint trajectory of each arm (unimanual control hypothesis). The components of the total joint angle variance not affecting (V_COMP) and affecting (V_UN) the value of a selected task variable were computed for each 10% of the normalized movement time. The ratio of these two components R_V=V_COMP/V_UN served as a quantitative index of selective stabilization. Both the bimanual and unimanual control hypotheses were supported, however the R_V values for the bimanual hypothesis were significantly higher than those for the unimanual hypothesis applied to the left and right arm both prior to and after practice. This suggests that the CNS stabilizes the relative trajectory of one endpoint with respect to the other more than it stabilizes the trajectories of each of the endpoints in the external space. Practice-associated improvement in both movement speed and accuracy was accompanied by counter-intuitive lack of changes in R_V. Both V_COMP and V_UN variance components decreased such that their ratio remained constant prior to and after practice. We conclude that the UCM approach offers a unique and under-explored opportunity to track changes in the organization of multi-effector systems with practice and allows quantitative assessment of the degree of stabilization of selected performance variables.     

12-Lipoxygenases and 12(S)-HETE: role in cancer metastasis

Arachidonic acid metabolites have been implicated in multiple steps of carcinogenesis. Their role in tumor cell metastasis, the ultimate challenge for the treatment of cancer patients, are however not well-documented. Arachidonic acid is primarily metabolized through three pathways, i.e., cyclooxygenase, lipoxygenase, and P450-dependent monooxygenase. In this review we focus our attention on one specific lipoxygenase, i.e., 12-lipoxygenase, and its potential role in modulating the metastatic process. In mammalian cells there exist three types of 12-lipoxygenases which differ in tissue distribution, preferential substrates, and profile of their metabolites. Most of these 12-lipoxygenases have been cloned and sequenced, and the molecular and biochemical determinants responsible for catalysis of specific substrates characterized. Solid tumor cells express 12-lipoxygenase mRNA, possess 12-lipoxygenase protein, and biosynthesize 12(S)-HETE [12(S)-hydroxyeicosatetraenoic acid], as revealed by numerous experimental approaches. The ability of tumor cells to generate 12(S)-HETE is positively correlated to their metastatic potential. A large collection of experimental data suggest that 12(S)-HETE is a crucial intracellular signaling molecule that activates protein kinase C and mediates the biological functions of many growth factors and cytokines such as bFGF, PDGF, EGF, and AMF. 12(S)-HETE plays a pivotal role in multiple steps of the metastatic cascade encompassing tumor cell-vasculature interactions, tumor cell motility, proteolysis, invasion, and angiogenesis. The fact that 12-lipoxygenase is expressed in a wide diversity of tumor cell lines and 12(S)-HETE is a key modulatory molecule in metastasis provides the rationale for targeting these molecules in anti-cancer and anti-metastasis therapeutic protocols.     

Why laparoscopic cholecystectomy today?

Traditional open cholecystectomy became the gold standard of surgical treatment for symptomatic gallstone disease during the last century. In spite of its good results, clinicians have been trying to establish effective nonsurgical methods of eliminating gallstones. Although oral, percutaneous, or retrograde litholysis can be used effectively for cholesterol stones, these represent only 10% of all gallstones. Moreover, intracorporeal lithotripsy is an invasive method, and while extracorporeal shock wave lithotripsy is a promising procedure, even after careful selection, only 70%–80% of the patients become stone-free within 1 year. In fact, none of the methods which leave the gallbladder intact are free of complications, and they are followed by 50% stone recurrence within 5 years. Since 1987, laparoscopic cholecystectomy has become the procedure of choice as it is safe and only minimally invasive. We believe that the laparoscopic technique is a promising way to the surgery of the future.     

Postischemic spontaneous hyperthermia and its effects in middle cerebral artery occlusion in the rat

This study examined the time course and effects of postischemic spontaneous hyperthermia after transient and permanent focal ischemia. Rats underwent a 90-min, 120-min, or permanent middle cerebral artery occlusion (MCAO). Body temperatures started rising 15-20 min after MCAO and reached 39-40.5 degrees C during the first hour. Sustained hyperthermia was observed during the rest of the first 24 h. In another experiment, rats were subjected to the same interventions, but a normothermic body temperature was maintained. Spontaneous hyperthermia significantly increased the infarct volumes measured 48 h after MCAO in all groups. Reperfusion 2 h after the onset of ischemia was not beneficial in the hyperthermic animals in contrast to the normothermic group. We also examined the effect of spontaneous hyperthermia on the temporal progression of infarcted and penumbral areas 4, 12, or 48 h after MCAO. During spontaneous hyperthermia, penumbral areas became infarcted areas more rapidly, which was most expressed at 4 h. These findings demonstrate that severe spontaneous hyperthermia can occur in rats after MCAO and that it not only increases the infarct volumes in both transient and permanent ischemia, but also accelerates the incorporation of penumbral areas into necrotic areas, which significantly decreases the window of opportunity for therapeutic interventions.     

Inhibitory effect of antagonists of bombesin and growth hormone-releasing hormone on orthotopic and intraosseous growth and invasiveness of PC-3 human prostate cancer in nude mice.

PURPOSE: To determine whether antagonists of growth hormone-releasing hormone (GHRH) and bombesin/gastrin-releasing peptide (BN/GRP) can inhibit the orthotopic and metastatic growth of PC-3 human androgen-independent prostate cancers. EXPERIMENTAL DESIGN: The effects of administration of GHRH antagonist MZ-J-7-118, BN/GRP antagonist RC-3940-II, and their combination on the growth and metastatic spread of PC-3 tumors implanted orthotopically into nude mice were evaluated. The efficacy of this treatment on PC-3 tumors implanted intratibially and s.c. was also determined. RESULTS: Treatment with MZ-J-7-118, RC-3940-II, or their combination significantly inhibited the growth of PC-3 tumors implanted orthotopically, intraosseously, and s.c. The combination of the two antagonists had the greatest effect, inhibiting orthotopic tumor growth by 77%, intratibially implanted tumors by 86%, and s.c. tumors by 86%. The therapy with BN/GRP and GHRH antagonists, especially in combination, also reduced the local tumor spread and distant metastases in animals bearing orthotopic tumors. Combination therapy was likewise the most effective in reducing the incidence and severity of tibial osteolytic lesions and pathologic fractures in intraosseously implanted tumors. High-affinity binding sites for BN/GRP and GHRH were found in s.c. and orthotopic PC-3 tumor samples. MZ-J-7-118, RC-3940-II, and the combination of both compounds inhibited in vitro growth of PC-3 cells. CONCLUSIONS: Our findings show the efficacy of BN/GRP antagonists and GHRH antagonists for the treatment of advanced prostate cancer in preclinical metastatic models. As BN/GRP antagonists are already in clinical trials and GHRH antagonists are effective in androgen-independent prostate cancer models, these analogues could be considered for the management of advanced prostate carcinoma.     

Intestinal Intramural Vascular Anastomoses

Introduction: Present surgical techniques are rarely relying on intestinal intramural vascular anastomoses; however, this could open new limits in reconstructive surgery. Our aim was to study the efficacy of the antimesenteric and the longitudinal intramural vascular anastomoses in a porcine model. Material and Methods: Five minipigs were used. Antimesenteric anastomoses: jejunal loops were detubularized by cutting along the antimesenteric line (Control), in the middle between the mesenteric and antimesenteric border (Group 1) and close to the mesenteric line (Group 2). Mucosal microcirculation (red blood cell velocity, perfusion rate) was recorded with orthogonal polarization spectral imaging (Cytoscan A/R) at the long edge of the detubularized bowel. Longitudinal anastomoses: records were made on a continuous jejunal loop following antimesenteric incision, detubularization, and subsequent ligation of 2, 4, and 6 neighboring vasa recta in the middle of the loop. The same study was repeated on the free end of completely divided jejunal segments with ligation of 2, 4, or 6 vasa recta. Results: Antimesenteric anastomoses: There was no statistically significant difference in red blood cell velocity and perfusion rate between Control and Groups 1 and 2. Longitudinal anastomoses: The red blood cell velocity dropped significantly, while the perfusion rate did not change significantly after ligation of 4 vasa recta in the continuous loop. In the loop with a free end, however, both parameters decreased significantly after ligation of four vessels. Conclusion: It is safe to rely on antimesenteric intramural anastomoses but strong limitation of longitudinal intramural vascular anastomoses should be considered in intestinal reconstructions.