The clinical spectrum of Staphylococcus aureus pulmonary infection

Staphylococcus aureus causes serious pulmonary infections in adults. Prior descriptions of this entity have depended on diagnosis of expectorated sputum cultures that are often contaminated. To better characterize this infection, we retrospectively reviewed the medical records of 31 adults with S aureus pulmonary infection diagnosed by culture specimens uncontaminated by the upper respiratory flora. Our results support the concept that S aureus pulmonary infections usually occur in older adults (sixth decade or older) with concomitant illnesses that are typically nosocomial. However, in contrast to previous reports, the chest roentgenograms in these patients typically showed multilobar infiltrates (60 percent), predominantly in the lower lobes (64 percent), and often bilateral (48 percent). Pleural involvement (48 percent) was more common than previously reported, and abscess formation (16 percent) occurred infrequently. Sputum cultures were found to be sensitive but nonspecific diagnostic tools. Despite antibiotic therapy, reinfection occurred in 10 percent of patients and the mortality rate was 32 percent.

Effects of inhaled leukotriene D4 and platelet-activating factor on airway reactivity in normal subjects

Inflammatory mediators such as platelet-activating factor (PAF) and the sulfidopeptide leukotrienes (LT) may contribute to airway hyperreactivity and asthma. PAF has been reported to produce bronchoconstriction and a sustained increase in airway reactivity when inhaled by normal subjects. Leukotrienes produce bronchoconstriction in both normal and asthmatic subjects, but whether they increase airway reactivity is unclear. Before initiating studies to determine how these bioactive mediators influence airway function, we sought to confirm that PAF increases airway reactivity and identify whether one of the sulfidopeptide leukotrienes, LTD4, has a similar effect. Eight normal male subjects inhaled saline and increasing concentrations of either histamine (0.1 to 50 mg/ml), PAF (1 to 1,000 micrograms/ml), or LTD4 (1 to 500 micrograms/ml) on separate days, at least 1 wk apart, until specific airway conductance (SGaw) decreased 50% or the maximal concentration was reached. After inhaling the test substance, methacholine (MCh) challenges were performed at 6 h, at 1, 3, and 7 days, and weekly thereafter until airway reactivity (measured as the MCh concentration that decreased SGaw 35% [PC35SGaw]) normalized. The four postsaline MCh challenges (6 h to 7 days) were used to determine the 95% confidence interval for PC35SGaw (in each subject) and identify significant changes in airway reactivity after inhaling each test substance. Airway reactivity did not change after inhaling histamine. After inhaling PAF, six of eight subjects developed increased airway reactivity, which was maximal at 1 day and persisted for 14 days in three. After inhaling LTD4, six of eight subjects also developed increased airway reactivity, which was maximal at 7 days and persisted for 14 days in two.(ABSTRACT TRUNCATED AT 250 WORDS)

The permanence of the visual recovery that follows reverse occlusion of monocularly deprived kittens

While the behavioral and physiologic effects of an early period of monocular deprivation can be extremely severe, they are not necessarily irreversible. Considerable recovery can occur if visual input is restored to the deprived eye sufficiently early, particularly if the nondeprived eye is occluded at the same time (reverse occlusion). This study examines the permanence of the visual recovery promoted by a period of reverse occlusion in kittens that were monocularly deprived from near birth for periods ranging from 3 to 18 weeks. During the period of reverse occlusion, the vision of the initially deprived eye improved from apparent blindness to good levels of acuity. However, upon restoring visual input to the formerly nondeprived eye a surprisingly rapid and reciprocal change occurred in the visual acuity of both eyes. Much of the substantial gain in the vision of the initially deprived eye that occurred during reverse occlusion was lost within 3 weeks, while at the same time the vision of the initially nondeprived eye improved substantially. Nevertheless, in many animals the acuity of the initially nondeprived eye did not recover to levels it had reached prior to reverse occlusion. These results hold important implications for the nature of the mechanisms responsible for the dramatic physiologic effects of monocular occlusion and reverse occlusion on the visual cortex. The results also may help elucidate recent observations on patching therapy in human amblyopia.

Immediate and long-term effects on visual acuity of surgically induced strabismus in kittens

In order to isolate some of the factors responsible for strabismic amblyopia as well as to ascertain the time course of its development, frequent measurements were made of the visual acuity of the two eyes of kittens following imposition of surgically induced strabismus. Following behavioural training on a jumping stand, strabismus was induced in all but one animal by simple section of either the lateral (esotropia) or medial (exotropia) rectus muscle of one eye. The one exception was a kitten on which esotropia was induced by another common but more radical surgical procedure that involved removal of the body of both the lateral rectus and superior oblique muscles of one eye. There was a surprising difference between the immediate consequences for vision of section of the lateral and medial rectus muscles that were reflected by equally large differences in the magnitude of the amblyopia that developed eventually in the two situations. Following section of the lateral rectus muscle, there was an immediate reduction in the visual acuity of the operated eye of as much as 2 octaves after which vision returned to normal levels over 4 to 8 days. The acuity of the two eyes remained comparable for a few days after which the vision of the operated eye began to decline once more, signalling the onset of amblyopia some 10 to 12 days following imposition of strabismus. In contrast to the severity of these effects, the effects observed following section of the medial rectus were both mild and transitory. Furthermore, whereas all kittens that were rendered esotropic early developed amblyopia, none of the kittens that were made exotropic at the same age did so. Together, these results suggest that factors associated with the immediate consequences of the surgical procedure employed to produce a misalignment of the visual axes may contribute to the severity of the effects of surgically induced strabismus.

Labile nature of the visual recovery promoted by reverse occlusion in monocularly deprived kittens

Kittens were monocularly deprived by closing one eye at the time of natural eye opening for periods that ranged from 4 to 14 weeks. This eye was then opened, and the other eye was closed for an approximately equal period of time. During this period of reverse occlusion, the vision of the initially deprived eye improved from apparent blindness to a level of good visual acuity. Surprisingly, however, this recovery was largely eliminated in only 2 weeks once the initially nondeprived eye was opened to restore visual input to both eyes. This finding has important implications for the nature of the mechanism(s) responsible for the dramatic physiological effects of monocular occlusion on the visual cortex. It may also help to elucidate recent observations on patching therapy in human amblyopia.