Necrotizing staphylococcal pneumonia in a neonate.

Hospitalized neonates are commonly colonized soon after birth with Staphylococcus aureus. The majority of neonates do not develop infectious sequelae; however, premature neonates appear to be more susceptible to serious infections, such as pneumonia. We report a case of an extremely low birth weight infant who developed necrotizing pneumonia due to methicillin-resistant Staphylococcal aureus (MRSA). The MRSA isolate from this neonate is identical to the strains that have been causing primarily community-associated skin and soft tissue infections. The severe course of this patient may be attributed to the presence of the Panton-Valentine leukocidin gene, a well-known virulence factor leading to soft tissue and pulmonary infections.     

Deltoid flap combined with fascia lata autograft for rotator cuff defects: a histologic study

The purpose of this study was to compare the histological characteristics of an autogenous fascia lata graft alone and a fascia lata graft combined with a deltoid flap in the reconstruction of rotator cuff tears. Ten New Zealand white rabbits were divided into two groups. Infraspinatus tendon defects (1 × 1 cm) were created in each animal. Reconstruction consisted of either a fascia lata graft alone or a fascia lata graft combined with a distally based deltoid flap. At 3 months, tissue harvest and histological analysis was performed. Compared to the fascia lata graft alone, there was significantly increased remodeling activity and neovascularization in the group that included a deltoid flap. Also, there was pronounced interdigitation at the graft/flap interface in the latter group. A mutually beneficial relationship may exist when an autogenous fascial graft is combined with a functional deltoid flap for reconstructing large rotator cuff defects.     

Gene conversion is a likely cause of mutation in PKD1

Approximately 70% of the gene responsible for the most common form of autosomal dominant polycystic kidney disease ( PKD1 ) is replicated in several highly homologous copies located more proximally on chromosome 16. We recently have described a novel technique for mutation detection in the duplicated region of PKD1 that circumvents the difficulties posed by these homologs. We have used this method to identify two patients with a nearly identical cluster of base pair substitutions in exon 23. Since pseudogenes are known to be reservoirs for mutation via gene conversion events for a number of other diseases, we decided to test whether these sequence differences in PKD1 could have arisen as a result of this mechanism. Using changes in restriction digest patterns, we were able to show that these sequence substitutions are also present in N23HA, a rodent-human somatic cell hybrid that contains only the PKD1 homologs. Moreover, these changes were also detected in total DNA from several affected and unaffected individuals that did not harbor this mutation in their PKD1 gene copy. This is the first example of gene conversion in PKD1 , and our findings highlight the importance of using gene-specific reagents in defining PKD1 mutations.      

Reye's syndrome simulacra in liver of mice after treatment with chemical agents and encephalomyocarditis virus

In children with Reye's syndrome, liver specimens exhibit the following characteristics: mitochondrial dysfiguration, fatty infiltration, decreased activity of carbamyl phosphate synthetase and of ornithine transcarbamylase, histochemically reduced activity of succinic dehydrogenase and cytochrome oxidase, and depletion of glycogen. We intended to create an animal model for Reye's syndrome by treating mice with encephalomyocarditis virus, and/or salicylate, fructose, Atlox, butylated hydroxytoluene, pentachlorophenol, and an equal mixture of butylated hydroxytoluene and monosodium stearate. Liver specimens were then examined for the listed characteristics as well as for the activity of argininosuccinic lyase, arginase, phosphorylase, and glucose-6-phosphatase. Results of interest in regard to the experimental intention were obtained in livers of mice treated with virus and Atlox (A) or virus and butylated hydroxytoluene (B). In these specimens, we found a significant reduction (p less than 0.05)--except for ornithine transcarbamylase (A)--to the following levels (in percentage of normal mean): carbamyl phosphate synthetase (A, 79 per cent; B, 57 per cent); ornithine transcarbamylase (A, 91 per cent; B, 75 per cent); glycogen (A, 26 per cent; B, 37 per cent). Simultaneous morphologic analysis of these liver specimens indicated mitochondrial dysfiguration, absence of dense granules, fatty infiltration, and normal activity of succinic dehydrogenase and cytochrome oxidase. The induction of Reye's syndrome-like features in mouse liver may be useful for the study of disease mechanisms and therapy.     

Dynamic and static phantoms for evaluation of digital subtraction angiographic systems

Two types of phantoms were developed with which to evaluate the overall performance of digital subtraction angiography (DSA) systems. A dynamic phantom, called a "fish bone" phantom, consists of polyethylene tubes that simulate blood vessels with various lesions, such as stenoses, ulcers, and aneurysms. With this phantom, washout curves were obtained representing the relationship between iodine content and time. It will be useful for qualitative assessment of DSA images, evaluation of different image-processing schemes, and studies of blood flow analysis. A static phantom, called a "C-D" phantom, can be used for measurement of quantitative contrast-detail (C-D) diagrams and for daily monitoring of DSA systems. This was constructed of tubes of seven different diameters (2.15-0.28 mm) and 14 different concentrations of contrast medium (100%-1.1% Renografin-76 [meglumine and sodium diatrizoate]). The C-D diagrams were determined from an observer performance study using C-D phantom images obtained at four different DSA settings.