Uropathogenicity in rats and mice of Providencia stuartii from long-term catheterized patients

Providencia stuartii, a frequent and persistent isolate from the urinary tract of chronically catheterized elderly patients, is multiply antibiotic resistant and may cause fatal bacteremia in those patients. We studied P. stuartii strains in rats and mice to determine differences in uropathogenicity. Strains studied varied in expression of factors which contribute to pathogenicity of other bacterial species. Urinary tract responses following challenge with P. stuartii strain HO (factors expressed) were similar to responses reported for uropathogenic E. coli strains both in bacterial persistence and histologic change. In animals similarly challenged with P. stuartii strain RO (factors not expressed), responses were similar to those reported for non-uropathogenic E. coli strains. Results indicate that: a) animal model studies may be useful in differentiating P. stuartii strains based on uropathogenicity, b) P. stuartii uropathogenicity may be related to identifiable factors associated with virulence in other species, and c) the CBA mouse model appears to be the most suitable for studies of P. stuartii uropathogenicity.     

The relationship between nasal airway cross-sectional area and nasal resistance

Mouth breathing in response to an impaired nasal airway is thought to have clinical consequences. Physiologically, mouth breathing occurs whenever the body senses that nasal resistance is inappropriately high. In physical terms mouth breathing is a response that enlarges the upper airway and, by doing so, reduces airway resistance. In the past measurements of nasal resistance have been used as an index of airway impairment. Recently, we introduced a technique that estimates cross-sectional size of the airway, a variable that directly determines the magnitude of airway resistance. The purpose of the present study was to determine the precise effects of nasal airway size on nasal airway resistance so that the relationship between the two could be described in mathematic terms. There were two phases to the study--one involving a model and simulated breathing, and the other involving 100 subjects demonstrating normal and impaired nasal airways. The pressure-flow technique for estimation of nasal airway size and nasal airway resistance was used. The following equation was generated from the data: Resistance = 1.9 + (Formula: see text). The relationship between the two variables is nonlinear--that is, size of the airway has its greatest effect on resistance when the airway is less than 0.4 cm2 and a much lesser effect at larger airway sizes. The study also showed that nasal airway resistance generally does not fall very much below 1.9 cm H2O/L/S during breathing even when the airway is very large. This probably relates to the need to maintain an adequate level of airway resistance for alveolar gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postoperative radiotherapy for locally advanced colon cancer

Background: The role of adjuvant postoperative radiotherapy for locally advanced colon cancer is not well documented. Methods: Seventy-eight patients who underwent a complete resection of B2-C colon cancer received postoperative radiotherapy. Twenty-eight patients received ⩽45 Gy; 50 patients received 50–55 Gy. Twenty-seven patients received adjuvant fluorouracil-based chemotherapy. All patients were followed for a minimum of 3 years; no patients were lost to follow-up. Results: The overall local control rate was 88%. The 5-year actuarial rate of local control was 96% after 50–55 Gy postoperative radiotherapy compared with 76% after <50 Gy (p=0.0095). Multivariate analysis of local control showed that only radiotherapy dose significantly influenced this end point. Cause-specific survival rates at 5 years were B2, 67%; B3, 90%; C1, 100%; C2, 61%; C3, 36%; and overall, 63%. Multivariate analysis of cause-specific survival showed that only stage significantly influenced this end point. Bowel obstruction caused by adhesions developed in three patients and required a laparotomy; radiation-induced sarcoma developed in one additional patient. Conclusions: Postoperative radiotherapy appears to reduce the risk of local recurrence in patients with locally advanced colon cancer. The optimal dose is probably 50–55 Gy at 1.8 Gy per fraction. Postoperative radiotherapy may improve cause-specific survival for patients with stages B3 and C2 cancers.     

Autotomy and the sciatic functional index

The rat sciatic nerve serves as a good model of nerve regeneration and, as such, is often used in investigations of nerve repair. After transection of the sciatic nerve, rodents frequently scratch and bite their anesthetic foot, resulting in amputation of one or more toes. This is termed autotomy or autophagy. When these rats are part of a study using the sciatic functional index (SFI), autotomy results in unusable data, since necessary foot landmarks have been removed. It would be helpful, therefore, to be familiar with the phenomenon of autotomy and to know which rats are least likely to mutilate themselves. In our experiment involving 64 rats in which the sciatic nerve was transected and repaired, we found that female Sprague-Dawley rats were significantly less likely to perform autotomy than males (33% vs. 65%, P =.04). In addition, we noted that two-thirds of the autotomies that occurred did so by postoperative week 4 and that tabasco sauce did not decrease this activity. We present our experience and a survey of the literature on autotomy and the SFI. © 1993 Wiley-Liss Inc.     

Assessment of feature size abnormalities using receiver operating characteristic analysis

The ability of an observer to detect variations in size of a geometrical image feature have been investigated using receiver operating characteristic (ROC) analysis. Three types of image were constructed using computer graphics: disc-shaped targets of variable radius, model chest radiographs showing a variable heart diameter and model arterial angiograms with variable vessel width. Five factors were investigated: observer experience, variation of detectability with theoretical signal-to-noise ratio, the prior probability of the presence of an abnormality, viewing distance, and uncertainty in the location of an abnormality. In all but one experiment, excellent agreement was found between measured detectabilities and the predictions of signal detection theory, providing an initial practice session was included for each observer. No significant variation in detectability was found using six different prior probabilities and two different viewing distances, and the reduction in detectability for a four-alternative location task was in good agreement with theoretical predictions. The high statistical efficiencies found for the detection of geometrical signals suggest that the levels of observer "internal" noise arising from decision-making processes during an ROC experiment are very low.     

"Empty wall" and "vertical strut" signs of ACL insufficiency

We report our observation on the "empty wall" and "vertical strut" signs of anterior cruciate ligament (ACL) insufficiency. ACL tears most commonly occur in the midsubstance; arthroscopic evaluation of patients with these tears often reveals minimal evidence of previous ACL tissue along the intercondylar wall, thus giving the appearance of an "empty wall." In proximal ACL tears, the long remnant of ACL tissue may adhere to adjacent PCL tissue. Arthroscopically, one may see this vertically oriented strut of tissue, which to the casual arthroscopist may mimic a normal-appearing ACL except for orientation and tension. In addition, the "empty wall" sign will be noted because the lateral intercondylar wall becomes easily visible following ACL injury. In two separate prospective studies of 84 such patients, the combined incidence of the empty wall sign was 82%, and the incidence of the vertical strut sign was 50%. These findings should be sought for meticulously at the time of arthroscopic evaluation. The vertical strut should not be misinterpreted as an aberrantly oriented ACL or partial ACL tear.     

Determination of pipothiazine in human plasma by reversed-phase high-performance liquid chromatography

A method is described for the determination of pipothiazine in human plasma, based on reversed-phase HPLC. The method has been applied in a pharmacokinetic study of pipothiazine in six psychiatric patients receiving repeated depot intramuscular injections for six months. A number of compounds likely to be taken concurrently by patients were tested for potential to interfere with the assay. There was no evidence of "dose-dumping" in the period following injection. Comparison of the pharmacokinetic profiles after the first and sixth injections showed no evidence of drug accumulation.     

Demystified. Human endogenous retroviruses.

Human endogenous retroviruses (HERVs) are a family of viruses within our genome with similarities to present day exogenous retroviruses. HERVs have been inherited by successive generations and it is possible that some have conferred biological benefits. However, several HERVs have been implicated in certain cancers and autoimmune diseases. This article demystifies these retroviruses by providing an insight into HERVs, their means of classification, and a synopsis of HERVs implicated in cancer and autoimmunity. Furthermore, the biological roles of HERVs are explored.