Monte Carlo methods for localization of cones given multielectrode retinal ganglion cell recordings.

It has recently become possible to identify cone photoreceptors in primate retina from multi-electrode recordings of ganglion cell spiking driven by visual stimuli of sufficiently high spatial resolution. In this paper we present a statistical approach to the problem of identifying the number, locations, and color types of the cones observed in this type of experiment. We develop an adaptive Markov Chain Monte Carlo (MCMC) method that explores the space of cone configurations, using a Linear-Nonlinear-Poisson (LNP) encoding model of ganglion cell spiking output, while analytically integrating out the functional weights between cones and ganglion cells. This method provides information about our posterior certainty about the inferred cone properties, and additionally leads to improvements in both the speed and quality of the inferred cone maps, compared to earlier "greedy" computational approaches.

High-flow priapism leading to the diagnosis of lung cancer.

We report on a patient with spontaneous high-flow priapism. Magnetic resonance imaging showed a sacral tumor. Prior to tumor surgery, signs of lung cancer were found on chest X-ray. The diagnosis was confirmed by bronchoscopy. Priapism in this case can be explained either as a paraneoplastic symptom or as an isolated manifestation of cauda compression. Both are very uncommon reasons for priapism.

New methods of searching for medical literature: comparison of two systems, implementation and user reactions in a urologic department.

Knowledge Finder is the first Medline retrieval system based on CD-ROM technology that allows natural-language queries and accounts for deviations in spelling and terminology. Retrieved citations are ranked in accordance with their possible relevance (fuzzy logic algorithms), thus resulting in speedy orientation on a topic of interest. EasyOrder is an additional software module that enables the user to place an automatic electronic order at the library of choice, via modem, to receive a copy of a full-text article by mail or facsimile. We performed a study comparing search results and times when using a Boolean versus a fuzzy system. This article describes the underlying new concepts, implementation in a urologic department and user reactions to the new possibilities.

[Electronic expert system in medicine. For example ILIAD]. / Elektronische Expertensysteme in der Medizin, Am Beispiel von ILIAD.

Expert systems are knowledge data bases founded on patient data, literature searches and opinions of experts. With these systems it is for instance possible to test or to take clinical decisions. ILIAD, USA version 4.2, an adaptable software using probabilistic strategies, was investigated. This system is, among other uses, employed for quality assurance and documentation, as a teaching instrument as well as a knowledge base. It comprises the ICD-9 index of diagnoses and a selected and commented up-to-date review of the literature from 'Mosby's Year Book of Medicine'. The features of ILIAD are presented, and the possibilities and limitations of its use as well as that of expert systems in general are discussed.

In vivo development of cholinesterase at a neuromuscular junction in the absence of motor activity in Xenopus laevis.

Embryos of Xenopus laevis were selected prior to the onset of innervation and were raised for 2 days in the anaesthetic tricaine methanesulphonate (200 micrograms/ml). The gross development of these tricaine-reared animals appeared normal despite the absence of spontaneous motor activity and the lack of motor responses to prodding with a pin. Motor activity quickly appeared when the anaesthetic was withdrawn. Intracellular recording from the myotomes of intact, tricaine-maintained animals failed to reveal any spontaneous muscle action potentials. Synaptic potentials increased in frequency and amplitude upon withdrawing tricaine, but resting potentials remained unchanged. Cholinesterase activity, detected histochemically, was observed at the ends of the myotomes, the main site of innervation. The intensity of the histochemical reaction product at these sites appeared to be about as great in the myotomes of tricaine-reared animals as in control myotomes. Miniature end-plate currents (m.e.p.c.s), examined by focal external recording, declined with a time constant of 2.9 +/- 0.2 ms (mean +/- S.E. of mean) in the myotomes of tricaine-reared animals (stages 40-41). The time constants in the myotomes of control animals were 1.8 +/- 0.1 ms at stages 40-41 and 8.7 +/- 0.7 ms at stages 24-26 (shortly after the onset of innervation). The anticholinesterase neostigmine doubled m.e.p.c. time constants in the myotomes of tricaine-reared animals as well as in control myotomes at stages 40-41. It is concluded that motor activity is not required for the in vivo development of physiological levels of synaptic cholinesterase in Xenopus myotomal muscle.

The importance of multiple endocrine neoplasia syndromes in differential diagnosis.

In the differential diagnosis of endocrine symptoms, the autosomal dominant multiple endocrine neoplasia (MEN) syndromes are rare but important. We found seven index cases of MEN-I in 176 patients with adenomas of the anterior pituitary and 26 patients with primary hyperparathyroidism. Of 23 cases of medullary thyroid carcinoma and eight cases of pheochromocytoma, 14 patients are classified as MEN-IIa and one as MEN-IIb. Family screening identified six MEN-I and seven MEN-II cases among 32 individuals examined. Because of autosomal dominant inheritance and sometimes-delayed manifestation of the complete syndrome, screening of healthy and affected family members should be repeated at least every other year.

Population coding of motion patterns in the early visual system.

Using extracellular recordings and computational modeling, we study the responses of a population of turtle (Pseudemys scripta elegans) retinal ganglion cells to different motion patterns. The onset of motion of a bright bar is signaled by a rise of the population activity that occurs within less than 100 ms. Correspondingly, more complex stimulus movement patterns are reflected by rapid variations of the firing rate of the retinal ganglion cell population. This behavior is reproduced by a computational model that generates ganglion cell activity from the spatio-temporal stimulus pattern using a Wiener model complemented by a non-linear contrast gain control feedback loop responsible for the sharp transients in response to motion onset. This study demonstrates that contrast gain control strongly influences the temporal course of retinal population activity, and thereby plays a major role in the formation of a population code for stimulus movement patterns.

Retroperitoneal laparoscopic nephrectomy and other procedures in the upper retroperitoneum using a balloon dissection technique.

This article describes a hydraulic balloon dissection technique. The retroperitoneum is developed via a small lumbodorsal incision between the edges of the musculus latissimus dorsi and musculus obliquus externus and then after visualization of its correct position the balloon catheter is filled with 500-1,200 ml of warm normal saline (according to patient size). The device consists of the finger of a surgeon's glove ligated around the end of a rigid bladder catheter. The balloon insufflation is maintained for 5 min to guarantee adequate hemostasis. Recently, we have replaced the balloon catheter by a balloon trocar sheath allowing direct endoscopic control of the hydraulic dissection. After retrieval of the balloon the CO2 insufflator is connected to the first trocar. All secondary trocars are placed under endoscopic control. The hydraulic dissection techniques also enable optimal creation of an effective pneumoperitoneum in children. Until now, we have used this technique for twelve procedures in the upper retroperitoneum including five nephrectomies, two nephroureterectomies, one tumor nephrectomy, one nephropexy, one renal cyst marsupialization and two renal biopsies. Up to now we have encountered no major complications. Three of the nephrectomized patients had undergone multiple previous abdominal surgical interventions. The retroperitoneal approach allows the surgeon to apply similar dissecting techniques as used in respective open procedures. It has become the routine approach for laparoscopic procedures in benign renal disease. This procedure can be performed even in cases with previous abdominal surgery.

Thyrotoxic crisis in Graves' disease: indication for immediate surgery.

Thyrotoxic crisis (thyroid storm) is a rare complication of hyperthyroidism. It can be observed not only in thyroid autonomy with latent hyperfunction after exposure to iodine, but also in Graves' disease with overt hyperfunction. Adequate management of thyrotoxic crisis is still controversial. We report about four patients (four women, mean age 75 years) with Graves' disease who developed thyrotoxic crisis during therapy with antithyroid drugs so that surgical intervention became necessary. The patients had been admitted to the hospital for nonspecific symptoms such as headache, cachexy, and psychosis. Thyroid hormone levels had reached twice the normal range prior to surgery. All patients showed severe neurological deficits leading to coma. In three cases euthyroidism was achieved within two days after surgery. The neurological symptoms disappeared after an average of four days. The postoperative course did not show severe complications and all patients recovered completely. Especially in the elderly a monosymptomatic or nonspecific course of thyroid storm with neurological symptoms may represent a severe and life-threatening situation. In these cases surgery can become necessary even if euthyroidism has not been achieved preoperatively.