Molecular mechanism of troponin-C function

Conclusions There is now a large body of evidence in support of the view that Ca²⁺ binding to the low affinity sites of TnC induces a movement of helices B and C away from helices A and D, thus opening a hydrophobic cavity, the site of interaction with TnI. Another site of similar structure is formed by the helical segments in the C-terminal domain. Both sites appear to interact with the inhibitory segment of TnI. Whereas the interactions at both sites are necessary for the full regulatory activity of TnC, the interaction at the C-terminal domain stabilizes the complex and that involving the N-terminal domain is directly linked to the release of inhibition. In the absence of Ca²⁺ the inhibitory region of TnI would preferentially bind to actin and on Ca²⁺ binding to sites I and II it would switch to the site in the N-terminal domain of TnC. Detachment of TnI from actin gives rise to further events in thin filament regulation.     

Vancomycin-induced thrombocytopenia

Vancomycin-induced thrombocytopenia has only been reported once previously in the medical literature. We describe a patient in whom sudden severe reversible thrombocytopenia developed on two separate occasions after exposure to vancomycin hydrochloride. A 54-year-old man was admitted to the hospital for bilateral swelling and erythema of his extremities. At the time of admission he received 2 days of vancomycin therapy without incident. On day 14 he was reexposed to vancomycin and thrombocytopenia developed, with a nadir value of 17 x 10(9)/L. On day 30, a single dose of vancomycin was administered, and thrombocytopenia once again developed, with a nadir value of 11 x 10(9)/L. Hematologic cytopenias are infrequent adverse effects of vancomycin therapy. It is postulated that these effects may be due to an immunologically mediated mechanism. With the increasing use of vancomycin due to the emergence of methicillin-resistant Staphylococcus aureus, this case should alert clinicians to this rare but potentially lethal manifestation of vancomycin.     

Usefulness of carotid artery compression test in the diagnosis of cerebral circulation disorders in patients with cerebral aneurysm. Evaluation by the rheoencephalographic method

Rheoencephalographic investigations (REG) was carried out in patients with intracranial aneurysms and in healthy subjects. The purpose of the study was to obtain approximate data on the efficiency of collateral circulation of the brain before ligation of the internal carotid artery. For this purpose REG was associated with common artery compression test. It was found that this combined examination gives good prediction of the efficiency of collateral circulation after ligation of one carotid artery. This method is more sensitive than the Matas test combined with EEG used previously.     

Ischemic optic neuropathy. Pathogenesis, clinical features, diagnostics and treatment

Ischemic optic neuropathy is a common cause of visual loss in the older population. This disease is classified into anterior and posterior type according to the location the lesions. The anterior type is due to transient nonperfusion or hypoperfusion of the ciliary circulation in the optic nerve head. The etiology of this disease is multifactorial. The most important risk factors for developing anterior ischemic optic neuropathy (AION) include hypertension, nocturnal hypotension, diabetes mellitus, atherosclerosis and small cup in the optic disc. AION presents with sudden painless loss of vision, pale edema of the optic disc, afferent papillary defect and visual field defects, typically in lower quadrants. Posterior ischemic optic neuropathy (PION) is a rare condition and diagnosis of it usually is made only after other causes of a retrobulbar optic neuropathy have been excluded. There are three distinct subtype of PION: perioperative, arteritic and nonarteritic. They are characterized by acute visual loss, variable visual field defects, relative afferent pupillary defect and normal optic disc.     

Application of Color Doppler ultrasonography in the evaluation of the blood flow in the ocular vessels in patients with anterior ischemic optic neuropathy--the preliminary report

PURPOSE: Anterior ischemic optic neuropathy (AION) is one of the most common causes of acute loss vision in the middle-aged and elderly persons. It occurs due to hypoperfusion in the short posterior ciliary arteries supplying the optic nerve head. The aim of our study was evaluation of the usefulness of colour Doppler ultrasonography in diagnostics of AION. MATERIAL AND METHODS: Color Doppler imaging of the ophthalmic artery, central retinal artery and posterior ciliary arteries were performed in 10 patients with clinically evident AION. The peak-systolic velocity (PSV), end-systolic velocity (EDV) and resistance index (RI) were measured. RESULTS: No significant differences in the mean values of PSV, EDV and RI of ophthalmic arteries and posterior ciliary arteries between the affected and non-affected eyes were found. Reduction of mean flow velocities as well as significantly increased resistance index were observed in the central retinal artery in eyes with AION. CONCLUSIONS: The Color Doppler findings in the ciliary arteries do not reflect the ischemic changes in patients with AION. It is probably due to anatomical limitation of this method in evaluation of the blood flow in posterior ciliary arteries supplying the optic nerve head. Abnormal blood flow parameters in the central retinal artery are secondary changes due to optic disc oedema.     

Choroidal detachment--pathogenesis, etiology and clinical features

Serous choroidal detachment is characterized by exudative detachment of the retina and choroid following leakage of fluid from the choriocapillaris into suprachoroidal space. This accumulation of fluid has been known to be a complication of various intraocular surgeries (cataract, glaucoma and retinal detachment surgery), where hypotony is combined with postoperative inflammation. Among other non surgical conditions associated with uveal effusion are idiopathic (uveal effusion syndrome, microphthalmia) and inflammatory diseases (scleritis, sympathic ophthalmia, pars planitis, Harada's disease). Idiopathic serous detachment of choroids is caused by scleral abnormalities associated with hypoplasia or partial absence of the vortex venous system. The most cases of postoperative choroidal detachment resolve spontaneously. Resolution is usually associated with rapid normalization of the intraocular pressure and reduction of intraocular inflammation. The natural course of idiopathic condition is variable but tends to be prolonged with remissions and exacerbations. Surgical management involving vortex vein decompression and/or sclerotomy is the most effective treatment in this patients.     

Rare localization of extrarenal nephroblastoma in 1-month-old female infant

Extrarenal occurrence of Wilms' tumor is exceptional and the diagnosis is almost always made after surgery. The exact mechanism whereby a Wilms' tumor occurs in extrarenal tissue is unknown. The tumor is most commonly located in the retroperitoneum or inguinal region. Localization in subcutaneous tissue is extremely rare. In this paper, the case of a 1-month-old female infant with an extrarenal Wilms' tumor located in the lumbosacral region is presented. Surgical excision is the treatment of choice, and the same general therapeutic rules should be followed as when the kidney is affected.     

Detection of Helicobacter pylori: A faster urease test can save resources

AIM: To investigate whether differences in the rapidity of a positive result for Helicobacter pylori can save res ources, by comparing two commercially available urease kits. METHODS: One hundred and eighty-five adults (130 outpatients, 55 inpatients) undergoing gastroscopy were entered prospectively. Patients were divided into two groups: Group 1 (if they were not on PPIs, antibiotics, H2A, bismuth or sucralfate for up to 14 d prior to the endoscopy) and Group 2 (if they were on, or had been on, any of the...