Age- and strain-related differences in dehydrogenase activity and glycogen levels in CBA and C57 mouse cochleas

In the C57 mouse strain, loss of sensory hair cells (HCs) begins during early adulthood, starting in the base of the cochlea and progressing toward the apex as aging continues. In contrast, the CBA mouse strain exhibits no significant cochlear histopathology until relatively late in life. These strain and age differences may be related to differences in cochlear energy metabolism. To examine this possibility, we used dehydrogenase and glycogen histochemistry to evaluate the metabolic capacities of HCs and stria vascularis (SV) in cochleas of C57 and CBA mice. Reaction product density was quantified and compared as a function of strain (1.5-month-old C57 mice vs. CBA mice) and age (CBA mice, 1.5, 18 and 36 months). Young C57 mice had significantly less HC dehydrogenase activity than CBA mice of any age, lower HC glycogen levels than 18-month-old CBA mice and lower SV glycogen levels than 18- or 36-month-old CBA animals. Within the CBA strain, HC dehydrogenase activity decreased significantly between 1.5 and 18 months of age, while glycogen levels in both HCs and SV increased over the same time period. Between 18 and 36 months, HC dehydrogenase activity and SV glycogen levels remained stable. The results show that there are significant age-related changes in energy metabolism in the inner ear of CBA mice that are correlated with age-related hearing loss. Genetically determined deficits in cochlear metabolic capacity in C57 mice could be linked to the early onset of hearing loss in this strain.     

Preferential injury of oligodendroblasts by a short hypoxic-ischemic insult

One-week-old rat pups were subjected to an acute 10 min severe hypoxic-ischemic insult. Over the next 24 h, during the reperfusion period, O4 immunocytochemistry demonstrated that oligodendroblasts underwent degenerative changes that were coincident with induction of heme oxygenase. We suggest that the increased vulnerability of oligodendroblasts to oxidative stress following an hypoxic-ischemic insult may contribute to the pathogenesis of periventricular leukomalacia.     

Cost-effectiveness of case management: experiences of a university managed health care organization

Primary seborrhoea was diagnosed in 14 English springer spaniels over a 17-year period. Seven of the dogs developed clinical signs by two years of age. The dermatosis began as a generalised non-pruritic dry scaling which gradually worsened. Some dogs remained in this dry (seborrhoea sicca) stage, but in most cases the dermatosis became greasy and inflamed (seborrhoea oleosa and seborrhoeic dermatitis). Eight of the dogs suffered from recurrent episodes of superficial or deep bacterial pyoderma. Histological findings in skin biopsy specimens included marked orthokeratotic hyperkeratosis of surface and infundibular epithelium, papillomatosis, parakeratotic capping of the papillae, and superficial perivascular dermatitis in which lymphocytes and mast cells were prominent. The dogs with seborrhoea sicca responded more satisfactorily to therapy with topical emollient-humectant agents or oral omega-3/omega-6 fatty acid supplementation. Dogs with seborrhoea oleosa and seborrhoeic dermatitis did not respond satisfactorily to topical therapy. One dog, however, responded well to etretinate and omega-3/omega-6 fatty acid administration. No dog was cured.     

Transport properties are not altered across Caco-2 cells with heightened TEER despite underlying physiological and ultrastructural changes

Selected properties of Caco-2 cells were examined after disparate transepithelial electrical resistance (TEER) measurements were observed in two populations of Caco-2 cells. Comparisons were made between the early passages of Caco-2 cells (Caco-2E, passages 35-47) and the later passages of cells (Caco-2L, passages 87-112). Transmission electron microscopy revealed that regions of Caco-2L cells were composed of multiple cell layers rather than the monolayers observed in Caco-2E cells. Epithelial cell height (or barrier thickness) was not significantly different between the two cell populations. Intercellular and intracellular lumina were observed in the Caco-2L cells, but not in the Caco-2E cells. Results of [3H]thymidine incorporation assays showed significantly higher cell proliferation rates in Caco-2L cells relative to Caco-2E cells. Despite morphological and physiological changes, there were no significant differences in the apparent permeabilities for D-mannitol (paracellular diffusion marker), hydrocortisone (transcellular diffusion marker), or dipeptide, Gly-Sar (carrier-mediated transcellular transport marker) between the two populations of cells. The higher TEER values in Caco-2L cells may be the results of a slight perturbation of tight junctions associated with both the multiple cell layers and the presence of intercellular lumina.     

Impact of oxidative stress on human cytomegalovirus replication and on cytokine-mediated stimulation of endothelial cells

Transplantation-related pathogenic factors such as ischemia or allograft-directed inflammation are associated with oxidative changes that might lead to cellular oxidative stress. The aim of this study was to investigate the impact of oxidative stress on: (1) CMV replication in cultured human endothelial cells and (2) the stimulation of endothelial cells by proinfiammatory cytokines. Both pathomechanisms are known to contribute to graft rejection crises in vivo. Oxidative stress was induced in endothelial cell cultures with 10-200 microM buthionine sulfoximine. Western blotting showed a significant increase in the production of CMV-specific immediate early and late proteins in buthionine sulfoximine-treated cultures. Immunocytochemical staining suggested that this effect was caused by increased numbers of CMV antigen expressing cells (66% immediate early; 78%, late). Quantitative polymerase chain reaction for CMV-specific DNA and virus titration revealed that enhanced viral replication levels correlated with increased virion production. As a measure for the endothelial cell activation status, the surface expression of HLA-ABC and HLA-DR and adhesion molecules (ICAM-1, ELAM-1, VCAM-1) was quantified by fluorometric methods. Whereas oxidative stress alone did not modulate any surface molecule expression, the IFN-gamma-mediated expression of HLA-ABC and HLA-DR and the IL-1-mediated expression of ICAM-1, but not of ELAM-1 and VCAM-1 (IL-1 + TNF-alpha), was amplified. Interestingly, the amplification of HLA molecule expression was even higher in CMV-infected endothelial cells. This study provides evidence that oxidative stress contributes to the regulation of CMV replication, virus shedding, and the activation of endothelial cells by proinflammatory cytokines as it is observed in transplant recipients.     

Occult lumbar lateral spinal stenosis in neural foramina subjected to physiologic loading

PURPOSE: To measure the effect of extension, flexion, lateral bending, and axial rotation loads applied to the spine on the anatomic relationship of the spinal nerves in the neural foramen to the ligamentum flavum and the intervertebral disk, anc to determine the effect of disk degeneration on the response to loading. METHODS: Cadaveric lumbar motion segments were examined with CT and MR imaging, loaded with pure moment forces, frozen in situ, reexamined with CT, and sectioned with a cryomicrotome. The morphology of the intervertebral disks was classified on the basis of the appearance of the cryomicrotome sections. The neural foramina were classified as having no evident stenosis, as being stenotic, as having occult stenosis, or as showing resolved stenosis on the basis of the images and sections before and after loading. The stenotic and nonstenotic foramina were stratified by disk level, intervertebral disk classification, and type of loading applied. The effect of spinal level, disk type, and load type on the prevalence of stenosis was studied. RESULTS: On average, extension, flexion, lateral bending, and axial rotation resulted in the ligamentum flavum or intervertebral disk contacting or compressing the spinal nerve in 18% of the neural foramina. Extension loading produced the most cases of nerve root contact, and lateral bending produced the fewest cases. Each of the loading types resulted also in diminished contact between the spinal nerve and the intervertebral disk or ligamentum flavum in some cases. Disk degeneration significantly increased the prevalence of spinal stenosis. All foramina associated with advanced disk degeneration and half of the foramina associated with disks having radial tears of the annulus fibrosus either developed occult stenosis or were stenotic before loading. CONCLUSIONS: The study supports the concept of dynamic spinal stenosis; that is, intermittent stenosis of the neural foramina. Flexion, extension, lateral bending, and axial rotation significantly changed the anatomic relationships of the ligamentum flavum and intervertebral disk to the spinal nerve roots.     

Didactic value of the clinical evaluation exercise. Missed opportunities

BACKGROUND: Primary cholesteatoma of the temporal bone is a very rare disease. Initially, the tympanic membrane is intact, and often facial palsy may be the presenting symptom. The authors present a case of primary cholesteatoma which was surgically treated using a transmastoid-translabyrinthine approach. Other surgical approaches to the petrous apex are discussed.     

Sequence limitations of triple helix formation by alternate-strand recognition

Until recently, oligonucleotide-directed triplex formation has been limited to oligopurine tracts of target DNA. Triplex formation by alternate-strand recognition relaxes this limitation by allowing triplexes to form at 5'-(Pu)m(Py)n-3' and 5'-(Py)m(Pu)n-3' sequences, with the third strand pairing first with purines on one strand and then switching to pair with purines on the other strand. In this study, the interaction of several oligonucleotides with the potential to form triplexes by alternate-strand recognition at the sequence 5'-A8C8A8-3' was studied by chemical probing and affinity cleaving. The results show that triplex formation can be readily accomplished at the 5'-A8C8-3' part of the sequence; however, base triplet formation is disrupted on either side of the strand switch and the Watson-Crick helix is distorted in such a way as to expose the N7 positions of purines adjoining the strand switch. Triplex formation is weak or nonexistent at the 3'-most A8 block, despite the opportunity for recruiting a spacer sequence for the second (C8-A8) strand switch by "slippage". This finding indicates that the C8-A8 strand switch is energetically unfavorable, although pairing at other 5'-(Py)n(Pu)n-3' sequences has been observed, with or without a spacer [Beal, P. A., & Dervan, P. B. (1992) J. Am. Chem. Soc. 114, 1470-1478; Jayasena, S. D., & Johnston, B. H. (1992) Nucleic Acids Res. 20, 5279-5288]. Thus, alternate-strand recognition may not be feasible for certain sequences of 5'-(Py)m(Pu)n-3', at least under the conditions examined.