Respiratory disease and wasting in athymic mice infected with pneumonia virus of mice

Although pneumonia virus of mice (PVM) is ubiquitous among rodent colonies in the United States, it has not been reported to cause clinically apparent disease in euthymic mice. However, PVM has been reported to cause respiratory disease and death in experimentally infected euthymic and athymic mice. A group of nu/nu mice, housed in quarantine in a Trexler-type isolator, had weight loss and dyspnea. Gross necropsy findings included cachexia and diffuse pulmonary edema or lobar consolidation. Histologically there was diffuse interstitial pneumonia. Electron microscopy revealed filamentous virions budding from plasma membranes, and immunohistochemical staining of lung tissue was positive for PVM antigen. PVM was isolated from affected lung tissue in BHK 21 cells and mouse antibody production tests resulted in seroconversion to PVM. Experimental inoculation of athymic mice with lung homogenate from spontaneously infected mice resulted in clinically apparent respiratory disease and histologic lung changes similar to those in naturally infected mice. Inoculation of athymic mice with infected BHK 21 cell culture fluid resulted in pneumonia which was qualitatively similar to, but less severe than, that observed in mice with spontaneous disease. These findings indicate that naturally occurring PVM infection in athymic mice may cause respiratory disease and wasting.     

Allometric scaling of isokinetic peak torque: the Nebraska Wrestling Study

Allometric scaling has been used increasingly in the exercise sciences to control statistically for body size differences in physical performance variables. The purpose of this study was to use multivariate allometric scaling to examine the influence of fat-free mass (FFM) on age-related differences in strength in young club (8-13 years) and high-school (14-18 years) wrestlers. The dependent variables were log-transformed values of isokinetic peak torque for leg extension and flexion at 0.52, 3.14, and 5.24 rad x s(-1)(30, 180, and 300 x s(-1)). The independent variables used in the multiple regression analyses were log-transformed values for FFM, age, and the FFM versus age interaction. The resulting regression equations were of the form: log Y = log a + b1 log X1 + b2 log X2 + bn log Xn. The initial multiple regression analyses showed significant interaction effects (P < 0.05) for all dependent variables, therefore separate regression analyses were performed for the younger and older groups of wrestlers. The results indicate that for the younger wrestlers there were increases in isokinetic peak torque at all velocities across age after controlling for FFM. The FFM scaling exponents ranged from 0.94 to 1.31. All exponents included 1.0 in the 95% confidence interval, except for extension at 3.14 rad x s(-1). For the high-school wrestlers, both FFM and age were significant for the extension data, but only FFM was significant for the flexion data. All FFM exponents included 1.0 in the 95% confidence interval. These results indicate that the relationship between FFM and peak torque differed across age. In addition, with the exception of the flexion data for the high-school wrestlers, within each group increases in isokinetic peak torque occurred across age, independent of increases in FFM. The causes of the age effect for strength are speculative, but it may be due to developmental changes in neuromuscular function, alterations in the distribution of muscle mass as a percentage of FFM and/or the distribution of FFM across body segments.     

Characteristics of insulin and glucagon release from the perfused pancreas, intact isolated islets, and dispersed islet cells

There are a variety of different tissue preparations which have been used to study secretion from the endocrine pancreas and there are considerable differences in the results obtained from these. The purpose of this study was to compare several preparations in one laboratory using the same rats, buffers, and radioimmunoassays. The preparations included the isolated perfused rat pancreas, fresh isolated intact islets and dispersed cells, and cultured islets and cells. Insulin release from the perfused rat pancreas at 2.8 mM glucose was so low that it could not be measured, such that over a 90-min time period the amount of insulin released was less than 0.004% of pancreatic insulin content. In contrast, islets in static incubation appear to release 2.0% of their stored content and dispersed cells appear to release 2.6% of their content. Samples were taken at early time points during incubations of fresh islets and dispersed cells, and it was found that almost all of the insulin found at the end of a 90-min incubation period was present during the first 5 min. It is therefore suspected that the true secretory rate of insulin at a low glucose concentration is far lower than had been generally appreciated. Glucagon release patterns showed similarities in that with isolated islets and dispersed cells a disproportionate amount of glucagon release was found during a 0- to 30-min incubation period when compared with the 30- to 90-min period. In summary, artifacts have been identified in some of the in vitro systems used for the study of endocrine pancreatic secretion and these deserve greater recognition.     

Characterization of Escherichia coli strains isolated from urine of secretors and non-secretors

Strains of Escherichia coli isolated from urine of secretors (242) and non-secretors (121) were compared for their serotype and their ability to express mannose-sensitive (MS) haemagglutinins and mannose-resistant (MR) haemagglutinins and to produce haemolysin. The results of the survey refuted our hypothesis that strains with characteristics associated with virulence, those with MR haemagglutinins and/or haemolysins, would be isolated more frequently from non-secretors. MR haemagglutinins were detected among 36.4% of isolates from secretors and 27.3% of isolates from non-secretors. Haemolysin production was detected among 19.8% of isolates from secretors and 12.5% of isolates from non-secretors. Both MR haemagglutinins and haemolysin were detected only on 12.4% of strains from secretors and 6.7% of strains from non-secretors.     

The effect of Mycoplasma arthritidis infection on the phagocytic activity of macrophages in rats and mice

The phagocytic activity of mononuclear phagocytes of A/J mice and Wistar rats was estimated by the carbon clearance test following injection of Mycoplasma arthritidis. In mice, the overall phagocytic activity was significantly increased at the end of the first week (P less than 0.0001), but the increase was marginal by the third and fourth weeks after injection. A significant increase in the relative weight of liver and spleen was observed even when phagocytic activity had returned to levels similar to those of controls (P less than 0.001). In rats, the overall phagocytic activity was significantly increased until the fourth week (P less than 0.00001). There was not, however, an increase in the relative weight of liver and spleen as observed for the mice. The results are discussed in the context of factors contributing to the pathogenic mechanisms responsible for differences in the patterns of arthritis due to mycoplasma observed in mice and rats.     

A comparison of tests for independence in the FBI RFLP data bases

Several tests of independence of alletic frequencies within and between loci have been compared, and it has been found that Fisher's exact test is the best test to use. When this test is applied to RFLP databases established by the FBI, paying no attention to the single-band problem, there is generally evidence for independence at one locus but not at two loci. When the test is restricted to double-banded entries in the databases; there is overall evidence for independence.