Properties of neural crest-like cells differentiated from human embryonic stem cells.

Neural crest cells (NCCs) derive early in vertebrate ontogenesis from neural tube as a population of migratory cells with exquisite differentiation potential. Abnormalities in NCC behaviour are cause of debilitating diseases including cancers and a spectrum of neurocristopathies. Thanks to their multilineage differentiation capacity NCCs offer a cell source for regenerative medicine. Both these aspects make NCC biology an important issue to study, which can currently be addressed using methodologies based on pluripotent stem cells. Here we contributed to understanding the biology of human NCCs by refining the protocol for differentiation/propagation of NCClike cells from human embryonic stem cells and by characterizing the molecular and functional phenotype of such cells. Most importantly, we improved formulation of media for NCC culture, we found that poly-L-ornithine combined with fibronectin provide good support for NCC growth, we unravelled the tendency of cultured NCCs to maintain heterogeneity of CD271 expression, and we showed that NCCs derived here possess the capacity to react to BMP4 signals by dramatically up-regulating MSX1, which is linked to odontogenesis.

Rhesus monkeys with orbital prefrontal cortex lesions can learn to inhibit prepotent responses in the reversed reward contingency task.

Monkeys with lesions of the orbital prefrontal cortex (PFo) are impaired on behavioral tasks that require the ability to respond flexibly to changes in reward contingency (e.g., object reversal learning and extinction). These and related findings in rodents and humans have led to the suggestion that PFo is critical for the inhibitory control needed to overcome prepotent responses. To test this idea, we trained rhesus monkeys with PFo lesions and unoperated controls on acquisition of the reversed reward contingency task. In this task, selecting the smaller of 2 food quantities (1 half peanut [1P]) leads to receipt of the larger quantity (4 half peanuts [4P]) and vice versa. Choice of a larger quantity of food is a reliable prepotent response, and, accordingly, all monkeys initially selected 4P rather than one. With experience, however, all monkeys learned to select 1P in order to receive 4. Surprisingly, monkeys with PFo lesions learned as quickly as unoperated controls. Thus, PFo lesions do not yield a deficit in all tests that require the inhibition of a prepotent response.

What guides a search for food that has disappeared? Experiments on cotton-top tamarins (Saguinus oedipus).

When food is launched down a vertically positioned S-shaped opaque tube, cotton-top tamarins (Saguinus oedipus) search for the food in the position directly beneath the release point, even though over several trials it never appears in this position (B. M. Hood et al., 1999). Experiment 1 showed that when the trajectory of the food shifts from the vertical to the horizontal plane, tamarins no longer show systematic perseverative errors and, in general, perform better on this invisible displacement task. Experiment 2 showed that tamarins with experience on the horizontal task show less of a bias when tested on the vertical task but nonetheless fail overall to solve this invisible displacement problem; their performance is substantially worse than it was on the horizontal task. Experiment 3 revealed that when the vertically positioned tube is replaced by an occluded ramp, tamarins consistently search in the compartment below the release point, even though most of the tamarins had experience in Experiments 1 and 2. Overall, results indicate that tamarins have a significant gravity bias when searching for food that has disappeared along the vertical plane but also have more general problems finding food that has moved out of sight.

Techniques for long-term multisite neuronal ensemble recordings in behaving animals.

Advances in our understanding of neural systems will go hand in hand with improvements in the experimental techniques used to study these systems. This article describes a series of methodological developments aimed at enhancing the power of the methods needed to record simultaneously from populations of neurons over broad regions of the brain in awake, behaving animals. First, our laboratory has made many advances in electrode design, including movable bundle and array electrodes and smaller electrode assemblies. Second, to perform longer and more complex multielectrode implantation surgeries in primates, we have modified our surgical procedures by employing comprehensive physiological monitoring akin to human neuroanesthesia. We have also developed surgical implantation techniques aimed at minimizing brain tissue damage and facilitating penetration of the cortical surface. Third, we have integrated new technologies into our neural ensemble, stimulus and behavioral recording experiments to provide more detailed measurements of experimental variables. Finally, new data analytical techniques are being used in the laboratory to analyze increasingly large quantities of data.

Real-time prediction of hand trajectory by ensembles of cortical neurons in primates.

Signals derived from the rat motor cortex can be used for controlling one-dimensional movements of a robot arm. It remains unknown, however, whether real-time processing of cortical signals can be employed to reproduce, in a robotic device, the kind of complex arm movements used by primates to reach objects in space. Here we recorded the simultaneous activity of large populations of neurons, distributed in the premotor, primary motor and posterior parietal cortical areas, as non-human primates performed two distinct motor tasks. Accurate real-time predictions of one- and three-dimensional arm movement trajectories were obtained by applying both linear and nonlinear algorithms to cortical neuronal ensemble activity recorded from each animal. In addition, cortically derived signals were successfully used for real-time control of robotic devices, both locally and through the Internet. These results suggest that long-term control of complex prosthetic robot arm movements can be achieved by simple real-time transformations of neuronal population signals derived from multiple cortical areas in primates.

Problem solving and functional design features: experiments on cotton-top tamarins, Saguinus oedipus oedipus.

In any problem-solving situation, there are features associated with the problem that are relevant from a functional perspective and other features that are irrelevant. To determine whether animals are sensitive to the distinction between functionally relevant and irrelvant features of a problem, we conducted two main experiments with a New World monkey, the cotton-top tamarin. In the first condition of both experiments, subjects were required to pull a piece of cloth to gain access to a piece of food. The first experiment involved choosing between food that was on the cloth and food that was off the cloth. The second experiment involved choosing between food that was on a connected piece of cloth and food that was on two pieces of cloth separated by a horizontal gap. Having learned to solve either of these two problems, we conducted a series of probe conditions to determine whether the tamarins would generalize to changes in the shape, size, colour, and texture of the cloth and food, the position of the food relative to the cloth, and the type of connection between two pieces of cloth. For most of the probe conditions, the tamarins readily generalized, showing no decrement in performance, even on the first trial. For other conditions, involving apparently more subtle discrimination (e.g. a narrow vertical gap between the two pieces of cloth), explicit training was required. These results indicate that tamarins solve means-end relationships, and that their ability depends on a discrimination between properties that are functionally relevant as opposed to irrelevant. Copyright 1999 The Association for the Study of Animal Behaviour.

[The role of the portosystemic shunt in modern treatment of portal hypertension]. / Místo portosystémové spojky v dnesní lécbe portální hypertenze.

The authors discuss the importance of portosystemic anastomoses in contemporary treatment of portal hypertension, in particular in relation to TIPS. As a basis they use their own experience with 28 portosystemic anastomoses during the last five years and conclude that a correctly indicated anastomosis has certain advantages over TIPS. The basic requirements for indication of surgical peripheral portosystemic anastomoses are: 1. stage Child A (or onset of B), 2. posthaemorrhagic conditions, 3. satisfactory general condition, 4. stabilized liver disease and planned surgery.

Life beyond the mirror: a reply to Anderson & Gallup

No abstractCopyright 1997 The Association for the Study of Animal BehaviourCopyright 1997The Association for the Study of Animal Behaviour.

[Monitoring of selected biochemical markers of tissue ischemia, particularly of the digestive tract, in experiments and clinical practice]. / Monitorování vytypovaných biochemických markeru tkánové ischémie, zejména trávicího ústrojí v experimentu a klinice.

The increase of organ transposition ill tile reconstruction of digestive tract, particularly transposition of the stomach and colon, is essential ill gullet surgery. The transposition is always accompanied by certain bigger or less degree of ischemia. In this study the authors followed the biochemical markers of tissue ischaemia, capable to lay down both pre- and postoperative vitality of the tucked organ an the anastomosis. Disclosing of the initial and later stadium of intestine ischemia is tile aim. Monitoring of the lactate in the serum is very useful. Its using was proved in the rich experimental group and it was certified in clinical practice.

Electro-optic modulation in an anisotropic artificial Kerr medium.

We describe the performance of intensity and phase modulators that use an aqueous suspension of polytetrafluoroethylene (PTFE) microparticles. In this medium, the electro-optic effect is caused by the reorientation of anisotropic microparticles in an applied electric field. The intensity modulator was constructed in the Kerr geometry by the use of a sample path length of 20 µm. The response time of the modulator is less than 25 ms, and the depth of modulation was measured to be 28 dB for a switching voltage of 134 V(rms). The switching voltage necessary to achieve a π-phase shift with the phase modulator is less than 30 (Vrms).

Self-recognition in primates: phylogeny and the salience of species-typical features.

Self-recognition has been explored in nonlinguistic organisms by recording whether individuals touch a dye-marked area on visually inaccessible parts of their face while looking in a mirror or inspect parts of their body while using the mirror's reflection. Only chimpanzees, gorillas, orangutans, and humans over the age of approximately 2 years consistently evidence self-directed mirror-guided behavior without experimenter training. To evaluate the inferred phylogenetic gap between hominoids and other animals, a modified dye-mark test was conducted with cotton-top tamarins (Saguinus oedipus), a New World monkey species. The white hair on the tamarins' head was color-dyed, thereby significantly altering a visually distinctive species-typical feature. Only individuals with dyed hair and prior mirror exposure touched their head while looking in the mirror. They looked longer in the mirror than controls, and some individuals used the mirror to observe visually inaccessible body parts. Prior failures to pass the mirror test may have been due to methodological problems, rather than to phylogenetic differences in the capacity for self-recognition. Specifically, an individual's sensitivity to experimentally modified parts of its body may depend crucially on the relative saliency of the modified part (e.g., face versus hair). Moreover, and in contrast to previous claims, we suggest that the mirror test may not be sufficient for assessing the concept of self or mental state attribution in nonlinguistic organisms.

[Solitary liver metastasis of malignant schwannoma of the stomach treated with hemihepatectomy]. / Solitární jaterní metastáza maligního schwannomu zaludku, lécená hemihepatektomií.

The cause of large solitary hepatic metastasis is mostly the colorectal cancer, rarely also the cancer of breast, kidney, gynecologic organs, the melanoblastoma and the nonepithelial tumors of the stomach. These metastases, when they are proved as solitary, especially with long interval after removing the primary tumor, are well indicated for liver resection till hemihepatectomy. The authors treated successfully a large metastasis of malignant schwannoma, eight years after resection of the stomach with the primary tumor. Morphologic characteristics and biologic activity of primary tumors of this kind are discussed.

[An instrument for hepatic artery compression in palliative treatment of liver metastases using repeated ischemia. A model and experimental study]. / Kompresní zarízení na jaterní tepnu pro paliativní lécbu jaterních metastáz prerusovanou ischemizací. Modelová a experimentální studie.

Method of interrupted ischaemization of the liver afflicted with metastases from colorectal cancer is not definitively evaluated yet. Using the literary reports the authors proposed (in cooperation with MEDIN) a instrument for compression of the liver artery, economically easy available. The reability of this instrument was tested in model conditions and his safety to the tested artery was proved on the experimental animal.

[Esophagectomy without thoracotomy in advanced esophageal achalasia]. / Ezofagektomie bez torakotomie pro pokrocilou achalázii jícnu.

Patients with advanced achalasia, accompanied by severe complications can be seen only rarely today. In these patients, resection of the esophagus has to be considered. The modern technique of extirpation of the whole thoracic esophagus without thoracotomy is a sparing intervention capable to solve the problem of dysphagia as well as the complications of advanced achalasia. The authors describe their favourable experience with this technique in three patients. The evidence for such radical treatment appears from the clinical picture and the microscopical findings in the resected specimens.

[Experimental verification of the hepatic perfusion index for monitoring direct liver perfusion by portal blood]. / Experimentální overení hepatoperfúzního indexu (HPI) pro sledování prímé perfúze jater portální krví.

The reliability of HPI measurement was studied in animal experiment. The portal vein of experimental dogs was narrowed by application of a metallic coil. The induced portal hypertension with important hepatofugal collaterals appeared to be a suitable model for the study of changes in HPI. A decrease in the index was statistically significant and corresponded to the hemodynamical efficiency of collateral circulation. The original experiment verified the reliability of HPI for an assessment of direct perfusion of the liver by portal blood.

[A pancreatic pseudocyst in the liver]. / Pankreatická pseudocysta v játrech.

A large cystic formation in the liver of 43-years old woman was identified as pancreatic pseudocyst, using histologic examination during laparotomy. The pancreas was found quite normal without any relation to the pseudocyst. Therefore it seems to be acceptable such a pathogenetic reflection, that the pseudocyst developed as a result of pathologic changes in heterotopic pancreatic tissue (embryonic malformation). The pseudocyst was partly resected and the large cavity in the liver was drained into the small intestine using Roux loop. After 8 months uncomplicated follow-up of the patient, the CT picture of her liver was nearly normal.

Oesophagus carcinoma amino acids control.

Serum amino acids level examination of the oesophagus carcinoma patients admitted to I Surgical Clinic of Teaching Hospital in Olomouc from 1/1/1990 to 31/7/1991 were carried out by the authors. The standard values were found with the group of patients with resectionable tumor or with a tumor in non-advanced stage on the one hand and on the other hand there were some lower values with the patients with a tumor in an advanced stage. In this way two groups of the sick were examined--the first one with benign oesophagus stenosis accompanied by nutritional disorder, the second with resectionable lung carcinoma without nutritional disorder. Serum amino acids level examination is therefore considered to be rather an indicator of the important factor of a possible surgical treatment of a tumor.

Function anatomy of vascular stem of the transposed stomach.

In morphological study on the dead bodies the authors have followed with coloured injections of stomach arteries of pyloroanthral region under "physiological" pressure the vascular supply of mobilized stomach applied for the substitution of chest gullet. They found that the right gastroepiploic artery is much more important compared with right gastric artery, and further, that the gastric tube formed from the great curvature is much better supplied than the whole stomach. These conclusions correspond with clinical experiences with esophagogastroplastics.

[Retrosternal esophagocoloplasty as current means of surgery for esophageal carcinoma]. / Stellenwert der retrosternalen Osophagokoloplastik beim heutigen stand der Chirurgie des Osophaguskarzinoma.

The authors present an account of their experience with retrosternal oesophagocoloplasty as a palliative by pas in inoperable carcinoma of the oesophagus. They differentiate secondary and primary indications. So far they used this operation in 27 patients. The total lethality is 33%, the mean survival period is 8 months. Some patients with the unilateral paresis of the left recurrent nerve have laryngoesophageal dysfunction with the danger of aspiration during swallowing. The shape, position and function of the paretic vocal cord can be favourable influenced by the administration of hydrophile gel into the vocal cord by the endoscopic route.

Some reflections about portosystemic shunt in portal hypertension.

The authors report on the group of 85 patients with portal hypertension in whom a portosystemic shunt was established for uncontrolled bleeding from varices--in the period from 1968 to 1993. A total lethality was 9.4%, in planned operations 5.9%, in acute interventions 22%. Some aspects of shunt-operation are discussed (prehepatic portal hypertension, acute shunt, shunt preceding liver transplantation). It is concluded that the portosystemic shunt still plays a role in the therapy of complicated portal hypertension, although only as a selective intervention.