A study on impact and tensile strength of acrylic resin filled with short ultra-high molecular weight polyethylene fibers

In dentistry, acrylates have been used for preparing denture bases for 50 years. Although polymethylmethacrylates (PMMA) are known to be an ideal base material, they possess some undesirable mechanical properties, especially their impact strength and tensile strength, which appear to be unsatisfactory for some applications. Additives and fibers have therefore been used to enhance and improve these properties over the last two decades. The present article describes the mechanical properties, impact and tensile strength of PMMA reinforced with chopped ultra-high molecular weight polyethylene fiber (6 mm long). It was found that, although the processing involved for high loading of fibers into the PMMA was difficult, the resulting improvement of impact strength was substantial.     

Hyperacute spinal subdural haematoma as a complication of lumbar spinal anaesthesia: MRI

We report two cases of hyperacute spinal subdural haematoma secondary to lumbar spinal anaesthesia, identified with MRI. Prompt diagnosis of this infrequent, potentially serious complication of spinal anaesthesia is essential, as early surgical evacuation may be needed. Suggestive MRI findings in this early phase include diffuse occupation filling of the spinal canal with poor delineation of the spinal cord on T1-weighted images, and a poorly-defined high-signal lesion with a low-signal rim on T2-weighted images. Received: 10 November 1998 Accepted: 6 April 1999     

Reversal of Cerebral Vasospasm by the Nitric Oxide Donor SNAP in an Experimental Model of Subarachnoid Haemorrhage

The constant release of nitric oxide (NO) is essential to maintain basal cerebrovascular tone. Oxyhaemoglobin, liberated by lysis of red blood cells after subarachnoid haemorrhage binds NO and prevents its entry into vascular smooth muscle cells. While endothelium-dependent vasoconstriction is preserved, decreased levels of NO inhibit endothelium-dependent relaxation and may cause vasospasm. S-nitrosothiols are potent vasodilators and precursors of NO. The authors' aim was to determine whether S-nitroso-N-acetylpenicillamine (SNAP), a stable S-nitrosothiol compound, could reverse vasospasm in an experimental vasospasm model in rabbit. Experimental subarachnoid haemorrhage (SAH) was induced in 37 New Zealand white rabbits. The animals were divided into four groups. Control (no SAH), SAH only, SAH plus saline and SAH plus SNAP. SNAP (15 micrograms/kg/min) or 0.09% saline (equal volume) was infused 46 hours after induction of SAH. All animals were killed by perfusion fixation 48 hours after SAH occurred. Basilar arteries were removed, sectioned and their cross sectional areas were evaluated in a blind manner, by light microscopy and by using computer assisted morphometry. Experimental SAH elicited vasospasm in all animals of SAH only and SAH plus saline group. In animals treated with SNAP, arterial narrowing was markedly attenuated without producing systemic hypotension. This widening achieved statistical significance when compared to the arteries of the SAH only and SAH plus saline group (p < 0.01). This study indicates that the NO donor SNAP is a potentially useful drug to reverse cerebral vasospasm due to SAH.     

Biliary–enteric fistulas: report of five cases and review of the literature

Internal biliary fistulas (IBF) are seen rarely. Because the symptoms and signs of IBF are not specific and the diagnosis is not suspected, these patients are commonly investigated with plain abdominal films (PAF), ultrasonography (US), upper gastrointestinal series (UGIS), barium enema (BE), and computed tomography (CT), but not always with endoscopic retrograde cholangiopancreatography (ERCP). The purposes of this article are (a) to attract attention of radiologists to presumptive findings of IBF, so as not to misdiagnose this unsuspected and rare disease, and (b) review of the literature while presenting radiologic features of our cases. Five cases of IBFs in which extrahepatic biliary tree communicating with duodenum (four cases) and colon (one case) are reported. Diagnostic work-up of cases were done by PAF, US, UGIS, BE, and CT. Aerobilia, which cannot be explained using other means, ectopic gallstone and small bowel dilatation, nonvisualization of the gallbladder despite no history of cholecystectomy, and thick-walled shrunken gallbladder adherent to neighboring organs were suggestive findings of IBF in our study. Knowledge of imaging findings suggestive of IBF and a high index of suspicion increase the diagnostic rate of IBFs. Received: 4 June 1998; Revision received: 28 July 1998; Accepted: 14 October 1998     

Vaginal atresia and Bardet-Biedl syndrome association: a component or a distinct entity?

Bardet-Biedl syndrome is an autosomal recessive disorder. It is characterized by cardinal anomalies including retinal dystrophy, digital malformations, mental retardation, obesity, and hypogonadism. Recently, renal anomalies also are mentioned among the cardinal signs. Although association of genital anomalies among affected boys are well known, the association of vaginal atresia and other structural genital anomalies are not mentioned among the less-common manifestations of Bardet-Biedl syndrome in girls. Two girls with Bardet-Biedl syndrome presented with hematometrocolpos in the preadolescent period and vaginal atresia was diagnosed. After surgical treatment and extended hospitalization, uncontrolled sepsis resulted in progressive renal failure and death of both patients. Vaginal atresia is often delayed or missed in the early childhood period. In girls with Bardet-Biedl syndrome, vaginal atresia or other structural genital anomalies should be evaluated more systematically during the initial diagnosis of the syndrome. In infancy, the evaluation of a child with vaginal atresia also should include the differential diagnosis of Bardet-Biedl syndrome. Vaginal atresia may either form a component of the syndrome, or girls who present with vaginal atresia in addition to other components of Bardet-Biedl syndrome might form a distinct entity.