Hyperosmolar D-mannitol reverses the increased membrane excitability and the nodal swelling caused by Caribbean ciguatoxin-1 in single frog myelinated axons

The effects of hyperosmolar D-mannitol were studied on single frog myelinated nerve fibres previously poisoned with Caribbean ciguatoxin-1 (C-CTX-1), a new toxin isolated from the pelagic fish Caranx latus inhabiting the Caribbean region. In current-clamped myelinated axons, C-CTX-1 (50-120 nM) caused spontaneous and repetitive action potential discharges after a short delay. In addition, the toxin produced a marked swelling of nodes of Ranvier of myelinated axons that reached a steady state within about 90 min, as revealed by using confocal laser scanning microscopy. The increased excitability and the nodal swelling caused by C-CTX-1 were prevented or reversed by an external hyperosmotic solution containing 100 mM D-mannitol. Moreover, the C-CTX-1-induced nodal swelling was completely prevented by the blockade of voltage-sensitive sodium channels by tetrodotoxin (TTX). It is suggested that C-CTX-1, by increasing nerve membrane excitability, enhances Na(+) entry into nodes of Ranvier through TTX-sensitive sodium channels, which directly or indirectly disturb the osmotic equilibrium between intra- and extra-axonal media resulting in an influx of water that was responsible for the long-lasting nodal swelling. The fact, that hyperosmolar D-mannitol either reversed or prevented the neurocellular actions of C-CTX-1, is of particular interest since it provides the rational basis for its use to treat the neurological symptoms of ciguatera fish poisoning in the Caribbean area.     

Sex hormones and gender-related differences: their influence on chronic renal allograft rejection

BACKGROUND: Renal hemodynamics and immune responses differ between males and females. Thus, sex hormones and genetically determined gender differences may determine the process of chronic rejection to some extent. METHODS: Female (F) or male (M) F344 kidneys were orthotopically transplanted into ovariectomized female Lewis recipients and were treated for 16 weeks with either estradiol, testosterone, or vehicle. RESULTS: Testosterone treatment resulted in increased urinary protein excretion independently of the donor gender, as well as extended glomerular sclerosis, interstitial fibrosis, and severe vascular lesions. Additionally, mononuclear cell infiltration was most pronounced in these animals, in parallel to an increased expression of intercellular adhesion molecule-1 (ICAM-1), fibronectin, laminin, and transforming growth factor-beta (TGF-beta) in the grafts. Estradiol treatment resulted in an improved graft function, reduced glomerular sclerosis, and a diminished cellular infiltration, in parallel to a reduced ICAM-1, fibronectin, laminin, and TGF-beta expression. In animals treated with vehicle, the gender of the donor influenced the outcome. Grafts of male origin had good graft function and histology, whereas grafts from female donors developed severe proteinuria and glomerular, interstitial, and vascular damage. CONCLUSIONS: These results suggest that a protective effect of estradiol on the progression of chronic rejection exists that is independent of donor gender. Additionally, a male kidney may benefit from the absence of testosterone, whereas the function of a female kidney deteriorates in the absence of estradiol.     

Hyponatremia in the postoperative period after a neurosurgical tumor condition

A four-year-old girl suffered difficult-to-diagnose hyponatremia resistant to treatment following surgery for a suprasellar tumor. The final diagnosis was diabetes insipidus evolving in three stages. Hyponatremia is a common problem following surgery to remove brain tumors. Early diagnosis and treatment of this electrolytic imbalance are essential for preventing serious neurological symptoms or death. The conditions most closely related to hyponatremia are inappropriate antidiuretic hormone secretion syndrome (IADHSS) and cerebral salt wasting syndrome (CSWS). The latter has become more common in recent years among patients undergoing brain surgery. Whereas IADHSS is treated by restricting fluids, CSWS requires administration of salt and volume fluid volume. We believe that for differential diagnosis of postoperative hyponatremia, a fluid restriction test takes priority over of fluid loading following neurosurgery. The course of hyponatremia must be carefully monitored and a complete endocrinological workup must be performed to detect the possible presence of hypophyseal deficiencies, particularly hypothyroidism and suprarenal insufficiency.     

Repair of cartilage defects. Technical aspects

Efficacious treatment of chondral and osteochondral defects of the weight bearing surfaces represents a real challenge for the orthopaedic surgeon. Treatment options for full thickness cartilage defects are discussed in this paper. Poor biomechanical characteristics of the reparative fibrocartilage promoted by "traditional resurfacing techniques" provide only moderate clinical outcome in the treatment of such lesions. During the last decade several new efforts have been expressed to provide a hyaline or hyaline-like gliding surface for a full thickness defected area on the weight bearing surface. Among several surgical procedures, autologous osteochondral transplantation methods, including osteochondral mosaicplasty, chondrocyte transplantation, periosteal and perichondrial resurfacement and allograft transplantation are the favoured "new methods". Experimental background, operative techniques and clinical results of these new procedures are detailed in this overview. According to the early and medium term experiences of these methods it seems that a hyaline or hyaline-like resurfacement of the defected area can provide a more durable gliding surface and a better clinical outcome than the so called "traditional resurfacing techniques". Autologous osteochondral mosaicplasty--as an easy, one-step procedure, providing a relatively quick rehabilitation--can be an alternative in the treatment of small and medium sized lesions. Excellent clinical outcome, low costs of the treatment and short rehabilitation time represent the main advantages of this method. Autologous chondrocyte transplantation seems to be a promising option in the treatment of larger full thickness defects but requires relatively expensive two-step procedure and longer rehabilitation period. Both of the above mentioned techniques have femoral, tibial, patellofemoral and talar applications as well. According to the present recommendations transplantation of osteochondral allografts can be indicated at massive osteochondral lesions. There are less experiences with the clinical use of periosteal and perichondrial resurfacing techniques and biomaterials. Beside the promising early and medium term results of these methods the authors express that a successful treatment of the full-thickness cartilage damages of the weight bearing surfaces depends not only the way of the cartilage repair but on the treatment of the underlying cause as well. According to this statement for an effective treatment of full thickness defects on the weight bearing surfaces requires careful patient selection, complex operative plan and well organized treatment course.     

Surgical aspects of gastro-esophageal reflux disease--indication for surgery. An update

Gastro-esophageal reflux disease is regarded as the single most common foregut disorder mainly in Western countries. The pathophysiological background of the disease is multifactorial. The primary aim of the management of gastro-esophageal reflux disease is relieving heartburn and healing esophagitis. The therapeutic objectives are alleviating symptoms, preventing complications and avoiding recurrence. Besides the effective medical treatment nowadays we possess the minimal invasive anti-reflux surgery which gives comparable, even better results than medical therapy does, in cases of patients who are suitable for anti-reflux surgery. The key question is the appropriate patient selection. In order to achieve the most adequate patient selection, diagnostic tools like endoscopy, radiotherapy, esophageal body and sphincter manometry, 24-hour esophageal pH monitoring and occasionally 24-hour bile exposure monitoring and gastric emptying studies are mandatory to carry out preoperatively. On the basis of the results of these tests the tailored concept of anti-reflux surgery can be applied. The importance of experienced surgeon should be pointed out, too.     

Laparoscopic wedge resection of the gastric wall for gastric benign tumour. The collaboration of the laparoscopic surgeon and the endoscopist

INTRODUCTION: By the introduction of the laparoscopy for the management of gastric pathology many techniques are applied by now. In these techniques the collaboration of the endoscopist and the laparoscopic surgeon is mandatory. AIMS OF THE STUDY: To emphasise the necessity of the collaboration of the endoscopist and the laparoscopic surgeon for the management of the gastric pathology using the double lifting and wedge resection technique. METHOD: A case of a female with 2 x 2.5 cm submucosal tumour is presented. The tumour was located in the antrum. After the onset of the general anaesthesia the gastroscope was introduced to locate the position of the tumour, the free edges of the tumour were elevated by a double lifting method and the tumour was resected by a laparoscopic linear stapler. The process of the proper resection was all through observed and directed by the view of the gastroscope. CONCLUSION: Correct wedge resection of the gastric wall can be safely performed, if the correct gastroscopic control is present. The collaboration of the endoscopist and the laparoscopic surgeon seems to be mandatory, thus avoiding the hazards arising from the use of tattooing.