The effect of 2 M hydrochloric acid on silicone rubber central venous catheters.

BACKGROUND: It has been suggested that the instillation of 2 M hydrochloric acid (HCl) can clear bacterial and fungal colonization in central venous catheters (CVCs). The aim of the study was to determine the physical effect of HCl on the inner surface of silicone rubber Hickman CVCs. METHODS: Five CVCs had 2 M HCl installed and 5 CVCs had saline installed for 30 minutes once a week for 12 weeks. Before instillation and after infusion, a section of each CVC was removed and examined by scanning electron microscopy. The examination was blinded. RESULT: Over 12 weeks no damage was detected in the CVCs. There was no difference between the CVCs flushed with saline compared with those flushed with HCl. CONCLUSIONS: Repetitive instillation of 2 M HCL in CVCs did not cause electron microscopically detectable damage of the silicone rubber CVCs.

Stereological estimation of total cell numbers in the young human utricular macula.

UNLABELLED: Abstract Conclusion: There is no change in the total cell population and hair cell:supporting cell ratio in the human utricular macula from gestational week 16 and onwards, whereas the lower hair cell:supporting cell ratio and lower total number of cells in the youngest specimens indicate that the utricle is still differentiating and adding new cells at the 10th to 12th gestational week. OBJECTIVES: Archival temporal bones were investigated to quantify cell numbers in the utricular macula in fetuses and children. METHODS: The age of the subjects ranged from gestational week 10 to 15 years. The optical fractionator was used to estimate the total number of cells in the utricular macula. RESULTS: The total cell number was found to be 143 000 in subjects older than gestational week 16. The number of hair cells and supporting cells did not change between the 16th gestational week and 15 years and was 36 000 and 107 000, respectively. In the youngest specimen (10th and 12th gestational week) there was a statistically significant lower total number of cells (62 000) and a lower hair cell:supporting cell ratio, resulting in a mean number of 13 000 hair cells and 49 000 supporting cells.

Type I hair cell degeneration in the utricular macula of the waltzing guinea pig.

Waltzing guinea pigs are an inbred guinea pig strain with a congenital and progressive balance and hearing disorder. A unique rod-shaped structure is found in the type I vestibular hair cells, that traverses the cell in an axial direction, extending towards the basement membrane. The present study estimates the total number of utricular hair cells and supporting cells in waltzing guinea pigs and age-matched control animals using the optical fractionator method. Animals were divided into four age groups (1, 7, 49 and 343 day-old). The number of type I hair cells decreased by 20% in the 343 day-old waltzing guinea pigs compared to age-matched controls and younger animals. Two-photon confocal laser scanning microscopy using antibodies against fimbrin and betaIII-tubulin showed that the rods were exclusive to type I hair cells. There was no significant change in the length of the filament rods with age. Taken together, our data show that despite rod formation in the type I hair cells and deformation of hair bundles being present at birth, the type I hair cell population is not affected quantitatively until a year after birth.

2,3-Dihydroxybenzoic acid attenuates kanamycin-induced volume reduction in mouse utricular type I hair cells.

The aminoglycoside kanamycin is a commonly used antibiotic, but unfortunately it is oto- and nephrotoxic in large doses. The negative effects are thought to be due to the formation of free radicals which is why strong antioxidants and iron chelators like 2,3-dihydroxybenzoic acid (DHB) are of great interest. This study estimates cellular quantitative changes in the utricular macula of mice following systemic treatment with kanamycin alone or in combination with DHB. The animals were injected with either saline, kanamycin or kanamycin + DHB for 15 days and perfusion fixed three weeks after last injection. Total volume of the utricle, as well as total number of hair and supporting cells, were estimated on light microscopic sections. Total volume and mean volume of hair cell types I and II and supporting cells were estimated on digital transmission electron micrographs. Total volume of the utricular macula, hair cell type I and supporting cells decreased significantly in animals injected with kanamycin but not in animals co-treated with DHB. Hair and supporting cell numbers remained unchanged in all three groups. In conclusion, the kanamycin-induced volume reduction of type I hair cells was attenuated by DHB.

Structure and growth of the utricular macula in the inner ear of the slider turtle Trachemys scripta.

In general, postembryonic production of inner ear vestibular hair cells (HCs) is believed to occur in all nonmammalian vertebrates. However, no study on this topic has been published on reptiles and, consequently, it is not known whether this also applies to these vertebrates. Therefore, the present study applied stereological methods in order to estimate the total number of HCs in turtles of varying sizes. The findings are that in prehatchlings the utricular macula (UM) contains approximately 4000 HCs as compared to approximately 5000 in juveniles, approximately 8000 in medium-sized turtles, and approximately 12,000 in large, sexually mature turtles. Scanning electron microscopy (SEM) reveals that presumably newly generated HCs with small surface areas and thin stereovilli are found in all regions of the UM. Furthermore, it reveals that utricular HCs can be classified as belonging to a specific region from the morphology of their apical structure. Striolar HCs have a large free oval-to-ovoid surface, a hair bundle with numerous stereovilli, and a short kinocilium. Rampary and cotillary HCs have smaller and slimmer free surfaces, comparatively fewer stereovilli, but much longer kinocilia. In conclusion, the current study demonstrates that postembryonic production of HCs does occur in reptiles and thereby supports the general view that this is a common trait in all nonmammalian vertebrates.