Incomplete rescue of cystic fibrosis transmembrane conductance regulator deficient mice by the human CFTR cDNA

We have used a mouse model to study the ability of human CFTR to correct the defect in mice deficient of the endogenous protein. In this model, expression of the endogenous Cftr gene was disrupted and replaced with a human CFTR cDNA by a gene targeted 'knock-in' event. Animals homozygous for the gene replacement failed to show neither improved intestinal pathology nor survival when compared to mice completely lacking CFTR. RNA analyses showed that the human CFTR sequence was transcribed from the targeted allele in the respiratory and intestinal epithelial cells. Furthermore, in vivo potential difference measurements showed that basal CFTR chloride channel activity was present in the apical membranes of both nasal and rectal epithelial cells in all homozygous knock-in animals examined. Ussing chamber studies showed, however, that the cAMP-mediated chloride channel function was impaired in the intestinal tract among the majority of homozygous knock-in animals. Hence, failure to correct the intestinal pathology associated with loss of endogenous CFTR was related to inefficient functional expression of the human protein in mice. These results emphasize the need to understand the tissue- specific expression and regulation of CFTR function when animal models are used in gene therapy studies.      

Capillarity, fibre types and fibre morphometry in different sampling sites across and along the tibialis anterior muscle of the rat

Capillarity, fibre types, fibre cross-sectional areas and perimeters were studied along and across the rat tibialis anterior muscle. The muscle was sectioned at three different levels (proximal, equatorial and distal) choosing five sampling fields for measurements at each level (from anterior to posterior and lateral to medial zones). Significant differences were found in the percentage of fibre types and capillarity between different fields of the same muscle section. Slow oxidative fibres were confined to the posterior muscle zone with a maximum of 3.7%. The posterior fields also had a greater percentage of fast oxidative glycolytic fibres at proximal (72.3%) and equatorial (61.3%) levels, but a lower value at the distal level (44.8%) and lower capillary density counts in total cross-section means (758 vs. 1,069 capillaries/mm(2) in equatorial and 1,035 capillaries/mm(2) at proximal levels). The uneven distribution of both fast fibre types and the different degrees of capillarisation along the muscle are statistically significant and may be due to different biomechanical performances along the rat tibialis anterior. Fibre size was significantly larger at the distal level, but no morphometric differences were found across the section of the same level. At the distal level, the mean total fibre area of fast glycolytic fibres (5,130 microm(2)) and fast oxidative glycolytic fibres (2,493 microm(2)) contrasted with values at the proximal (fast glycolytic: 4,070 microm(2), fast oxidative glycolytic: 1,970 microm(2)) and equatorial (fast glycolytic: 3,535 microm(2), fast oxidative glycolytic: 1,714 microm(2)) levels. The differences along and across the muscle show the need to design a standardised procedure for sample location when performing comparative studies of morphofunctional adaptive changes in skeletal muscle. A significant difference between individuals (animals) in all parameters was evident and should be taken into consideration when analysing the variability: the factor 'animal' should be considered in multiway ANOVAs, especially when low sample sizes are used.     

Hurthle cell adenoma of the mediastinum: intraoperative cytology and differential diagnosis with correlative gross, histology, and ancillary studies

A 66-year-old man was found to have a 7.5 cm mediastinal mass detected on routine chest X-rays as part of his preoperative work up for an inguinal hernia repair. An orthotopic (normally located) nongoitrous thyroid gland without evidence of connection to the mediastinal mass was also identified. The clinical differential diagnoses included lymphoma, thymoma, and germ cell tumor. Fine-needle aspiration (FNA) biopsy smears and touch imprints of the mediastinal mass showed a loosely cohesive, highly cellular population of relatively uniform cells with abundant granular cytoplasm, low nuclear to cytoplasmic (N/C) ratios, and prominent nucleoli consistent with a Hurthle cell (HC) neoplasm. Subsequently, the diagnosis of HC adenoma was confirmed on the surgically excised mediastinal mass. To the best of our knowledge, the surgical pathology and cytologic features of an HC adenoma of the mediastinum have not been reported in the literature. The gross, histologic, immunohistochemical, and electron microscopic (EM) findings, in addition to the cytologic features, are presented along with a differential diagnosis of this mediastinal neoplasm.     

Multiple cerebral metastases: detectability with Gd-DTPA-enhanced MR imaging

Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.     

Nonpuerperal breast infection

Objective: We undertook a microbiological study of purulent specimens from women with symptomatic breast abscesses.Methods: Fifty-one purulent samples were collected in 2 periods (December 1991-April 1992 and January 1994-June 1994) from nonpuerperal breast abscesses in 44 patients attending our hospital.Results: One of the most frequently isolated microorganisms was Proteus mirabilis (9 patients, 20.4%), present as a pure culture in all but 1 specimen (isolated together with Peptostreptococcus spp.). Staphylococcus aureus was isolated in 10 specimens, 6 of which were post-tumorectomy abscesses. Polymicrobial anaerobic flora were isolated in 11 specimens (21.5%); Staphylococcus epidermidis in 4 (8%); and Streptococcus milleri,Alcaligenes sp., and mixed aerobic-anaerobic flora in 1 specimen each. The 7 remaining samples (13.7%) were negative bacteriological cultures.Conclusions: We draw attention to the frequent isolation of P. mirabilis in recurrent and torpid breast abscesses in 4 women in whom surgery was necessary in addition to antibiotic treatment.