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Hospital-acquired respiratory infections develop in approximately 5% of patients admitted to a general hospital [1, 2]. In a previous study [3] we analyzed factors predisposing to hospitalacquired necrotizing pneumonia. That study was based on the work of Fraenkel [4], which indicated that Pseudomonas aeruginosa produces a specific necrotizing hemorrhagic pneumonia recognizable by histologic appearance. Subsequently, other investigators have confirmed that such lesions occur in patients dying with gram-negative bacillary pneumonia [5, 6]. However, other histologic descriptions have been reported in pneumonias caused by gram-negative bacilli [7-10], and necrotizing pneumonia has been reported with infection caused by other types of bacteria [11]. The present study was undertaken to define the microbiologic spectrum of necrotizing pneumonia and to determine whether histopathologic criteria are sufficient to make a diagnosis of gramnegative bacillary pneumonia.

Epstein-Barr Virus (EBV) infects B-lymphocytes circulating through the oral epithelium and establishes a lifelong latent infection in a subset of mature-memory B cells. In these latently infected B cells, EBV exhibits limited gene expression with the latent membrane protein 2A (LMP2A) being the most consistently detected transcript. This persistent expression, coupled with many studies ofthe function of LMP2A in vitro and invivo, indicates that LMP2A is functioning to control some aspect of viral latency. Establishment and maintenance of viral latency requires exquisite manipulation of normal B cell signaling and function. LMP2A is capable of blocking normal B cell signal transduction in vitro, suggesting that LMP2A may act to regulate lytic activation from latency in vivo. Furthermore, LMP2A is capable of providing B cells with survival signals in the absence of normal BCR signaling. These data show that LMP2A may help EBV-infected cells to persist in vivo. This review discusses the advances that have been made in our understanding of LMP2A and the effects it has on B cell development, activation, and viral latency.

The activation of helper T lymphocytes has been proposed to result from the sum of low-affinity interactions between the specific immune receptor, as well as nonpolymorphic receptors such as L3T4 on the T cell surface, and nominal antigen and Ia displayed in a multivalent array on the antigen-presenting cell surface. The present work takes advantage of a T cell hybridoma specific for pigeon cytochrome c in the context of I-Ek, which responds to tobacco hornworm moth cytochrome c at one hundredth the concentration of the homologous antigen, to determine if the T cell's requirement for L3T4 and Ia is directly related to its functional affinity for antigen. The results demonstrate that the T cell's activation by pigeon cytochrome c was blocked by antibodies directed to L3T4 and to I-Ek, even at antigen concentrations twofold to fourfold above those required for maximal responses. In contrast, the response to tobacco hornworm moth cytochrome c was not as affected by these antibodies under equivalent superoptimal conditions. The same phenomenon was observed for the T cell's activation by the carboxyl-terminal peptide fragments of the two cytochromes c, which do not require processing, indicating that the differences were not due to the relative efficiency of processing and/or presentation of the antigens. Although both I-Ek- and L3T4-specific antibodies blocked the T cell response to pigeon cytochrome, antibodies to I-Ak had no effect, even though I-Ak had been considered to be a ligand for L3T4. Thus, either Ia does not bind L3T4 or, if it does, I-Ek must be a sufficient ligand for L3T4 for T cells that recognize their antigen in the context of I-Ek. These studies provide more definitive evidence that the T cell's requirement for the functions of Ia and of L3T4 is dependent on the T cell's functional affinity for its antigenic determinant. This data is consistent with a model of T cell activation in which, given a high enough affinity of the T cell receptor for the processed antigen, the requirement for other components of a stimulatory complex, such as Ia and L3T4, may diminish to undetectable levels.

After aerosol deposition of Pseudomonas aeruginosa strains in mice and rats, completely different patterns of pulmonary bacterial clearance were observed in each animal species.

We report an photospheric limb-darkening measurements obtained at the McMath Solar Telescope in 1980 July, September, and October as part of a continuing program to study possible long-term variations in the photospheric emergent flux. A total of 243 usable full-diameter scans was recorded over 7 days in the clean continuum window at 4451.25 A. Individual scans were fitted to a fifth order polynomial in xi = ln..mu.., and a mean limb-darkening curve was derived for each day. The standard deviation of the daily mean of intensities ranged between 0.08% and 0.12% for all ..mu..>0.15. We note that the limb darkening decreased significantly between September 25 and 26. This change of the limb-darkening curve is not readily understandable in terms of variations in scattered light, seeing, or nonlinear photometric gain. We suggest that it is caused by a decrease of the temperature gradient in the upper photosphere, in the region above approximately tau/sub 5000/ = 0.5. The small increase in effective temperature that might accompany this limb-darkening variation is estimated using a standard radiative equilibrium photospheric model. We note that the increase of effective temperature corresponds in sign with an increase in the solar irradiance reported between September 25 and 26more » from both the Nimbus 7 ERB and the SMM ACRIM radiometers.« less

A retrospective analysis of 50 patients who had been observed to aspirate gastric contents was performed to define better the course of patients with this syndrome. The patients invariably had a disturbance of consciousness, most commonly due to sedative drug overdose or general anesthesia. The onset of clinical signs occurred prompty after aspiration and tended to be similar in all patients, irrespective of their subsequent course or outcome. These findings usually included fever, tachypnea, diffuse rales, and serious hypoxemia. Cough, cyanosis, wheezing, and apnea were each seen in approximately one third of the cases. Apena, shock, and early severe hypoxemia were particularly ominous events. Initial roentgenograms revealed diffuse or localized alveolar infiltrates, which progressed during the next 24 to 36 hours. Subsequent clinical courses followed 3 patterns: 12 per cent of the patients died shortly after aspiration; 62 per cent had rapid clinical and radiologic improvement, with clearing, on average, within 4.5 days; 26 per cent demonstrated rapid improvement, but then had clinical and radiographic progression associated with recovery of bacterial pathogens from the sputum and a fatal outcome in more than 60 per cent. Treatment from the outset by adrenocortical steroids or antimicrobial agents had no demonstrable effect on the outcome. The clinical features of aspiration of gastric contents are characteristic and distinguish it from other forms of aspiration-related lung disease.

Excerpt Gram-negative bacilli are assuming an increasing role in nosocomial infections, having surpassed staphylococci in frequency of occurrence. In addition to the well-recognized syndromes of py...

The following article on nebulization equipment calls attention to the fact that there is no single simple method of humidification which does not carry at least some risk of contamination. A study is made of several mechanical devices that are in common use and well known by their trade names. It is shown that techniques for decontamination are not equally effective in all cases. Strongly implied is the conclusion that all such pieces of mechanical equipment should in their distribution be accompanied by carefully specified instructions for effective decontamination.—Ed.

Endotracheal tubes have been used with increasing frequency to avoid the use of tracheostomies in patients with respiratory depression. Use of the tubes seems justified in decreasing patient morbidity when an episode of respiratory depression is transient or when episodes of respiratory failure are unlikely to recur. The use of endotracheal tubes, however, may be associated with certain complications with which the attending physician should be familiar.1-5This communication describes one such complication, namely, the tendency of some types of endotracheal tubes to collapse and thus obliterate the lumen when the cuff is excessively inflated. Report of a Case A 42-year-old woman was admitted to a local hospital with a one-week history of increasing cough, yellow sputum, and dyspnea, all of which were unresponsive to antibiotics. She had had a long-standing cough and exertional dyspnea despite a lower lobectomy on the right side in 1960 for bronchiectasis. On examination

ONE OF the major hazards in radical pelvic surgery for malignant disease is injury to the ureters. The purpose of this report is to describe a method of repair of the ureter when the site of injury is in the lower segment, i. e., that portion lying within the parametria. If the transection is complete, a no. 7 or 8 (French) ureteral catheter is inserted upward in the upper segment and the lower end of the catheter is then placed into the lower segment and pushed into the bladder. The whole catheter is then threaded downward, coiling in the bladder until the upper tip is about 8 to 10 cm. above the site of injury. The transected ureter is repaired over the catheter, four or five interrupted 00000 surgical gut sutures with an atraumatic needle being used. The posterior-superior portion of the bladder is grasped with Allis clamps and pulled

Inhalation therapy equipment may potentially act as a vector of hospital-acquired pneumonia due to gram-negative bacilli. The major mechanism by which bacteria are disseminated is aerosolization of organisms in particle sizes that are sufficiently small to be deposited in terminal lung units. Ventilators and humidifiers are relatively innocuous in this regard, and small-volume Venturi nebulizers (medications nebulizers) are not frequently incriminated in nosocomial epidemics. Large-volume nebulizers of all designs (Venturi, spinning disk, or ultrasonic) are the primary source of aerosolized bacteria. The method of decontamination differs with nebulizer design, but any system of decontamination must be carried out at least once every 24 hours while the equipment is in use. No hospital can consider its procedure of decontamination satisfactory unless it has a continuing monitoring program to demonstrate that the degree of contamination does not exceed that of hospital air.