The Yersinia enterocolitica pYV virulence plasmid contains multiple intrinsic DNA bends which melt at 37 degrees C

Temperature has a pleiotropic effect on Yersinia enterocolitica gene expression. Temperature-dependent phenotypes include the switching between two type III protein secretion systems, flagellum biosynthesis (</=30 degrees C) and virulence plasmid-encoded Yop secretion (37 degrees C). The mechanism by which temperature exerts this change in genetic programming is unclear; however, altered gene expression by temperature-dependent changes in DNA topology has been implicated. Here, we present evidence that the Y. enterocolitica virulence plasmid, pYV, undergoes a conformational transition between 30 and 37 degrees C. Using a simplified two-dimensional, single-gel assay, we show that pYV contains multiple regions of intrinsic curvature, including virF, the positive activator of virulence genes. These bends are detectable at 30 degrees C but melt at 37 degrees C, the temperature at which the cells undergo phenotypic switching. We also show that pACYC184, a plasmid used as a reporter of temperature-induced changes in DNA supercoiling, has a single region of intrinsic bending detected by our assay. Topoisomers of pACYC184, with and without this bend, isolated from Y. enterocolitica were resolved by using chloroquine gels. The single bend has a dramatic influence on temperature-dependent DNA supercoiling. These data suggest that the Y. enterocolitica pYV plasmid may undergo a conformational change at the host temperature due to melting of DNA bends followed by compensatory adjustments in superhelical density. Hence, changes in DNA topology may be the temperature-sensing mechanism for virulence gene expression in Y. enterocolitica and other enteric pathogens.

Identification of a cell surface protein from Crandell feline kidney cells that specifically binds Aleutian mink disease parvovirus

Aleutian mink disease parvovirus (ADV) is the etiological agent of Aleutian disease of mink. The acute disease caused by ADV consists of permissive infection of alveolar type II cells that results in interstitial pneumonitis. The permissive infection is experimentally modeled in vitro by infecting Crandell feline kidney (CrFK) cells with a tissue culture-adapted isolate of ADV, ADV-G. ADV-G VP2 empty virions expressed in a recombinant baculovirus system were analyzed for the ability to bind to the surface of CrFK cells. Radiolabeled VP2 virions bound CrFK cells specifically, while they did not bind either Mus dunni or Spodoptera frugiperda cells, cells which are resistant to ADV infection. The binding to CrFK cells was competitively inhibited by VP2 virions but not by virions of cowpea chlorotic mottle virus (CCMV), another unenveloped virus similar in size to ADV. Furthermore, preincubation of CrFK cells with the VP2 virions blocked infection by ADV-G. The VP2 virions were used in a virus overlay protein binding assay to identify a single protein of approximately 67 kDa, named ABP (for ADV binding protein), that demonstrates specific binding of VP2 virions. Exogenously added VP2 virions were able to competitively inhibit the binding of labeled VP2 virions to ABP, while CCMV virions had no effect. Polyclonal antibodies raised against ABP reacted with ABP on the outer surface of CrFK cells and blocked infection of CrFK cells by ADV-G. In addition, VP2 virion attachment to CrFK cells was blocked when the VP2 virions were preincubated with partially purified ABP. Taken together, these results indicate that ABP is a cellular receptor for ADV.

Construction of pathogenic molecular clones of Aleutian mink disease parvovirus that replicate both in vivo and in vitro

The ADV-G isolate of Aleutian mink disease parvovirus (ADV) replicates permissively in Crandell feline kidney (CRFK) cells but is nonpathogenic for mink, whereas the highly pathogenic ADV-Utah isolate is nonviable in CRFK cells. To assign control of host range in CRFK cells and pathogenicity to specific regions of the ADV genome, we constructed a full-length molecular clone chimeric between ADV-G and ADV-Utah. If either the map unit (MU) 54-65 (clone G/U-5) or MU 65-88 (clone G/U-7) sections were ADV-Utah, viability in CRFK cells was abolished, thus indicating that in vitro host range was controlled by two independent determinants: A in the MU 54-65 segment and B in the MU 65-88 segment. Determinant B could be divided into two subregions, B1 (MU 65-69) and B2 (MU 73-88), neither of which alone could inhibit replication in CRFK cells, an observation suggesting that expression of the B determinant required interaction between noncontiguous sequences. Adult mink of Aleutian genotype inoculated with G/U-8 or G/U-10 developed viremia, antiviral antibody, and histopathological changes characteristic of progressive Aleutian disease. The capsid sequences of G/U-8 and G/U-10 differed from ADV-G at five and four amino acid residues, respectively. Our results suggested that the host range and pathogenicity of ADV are regulated by sequences in the capsid protein gene.

A safety assessment of fixed combinations of acetaminophen and acetylsalicylic acid, coformulated with caffeine

Overuse and abuse of phenacetin-containing mixed analgesics has contributed to end-stage renal disease. Combination analgesics, especially those coformulated with caffeine, have been implicated as imparting a greater risk of analgesic-associated nephropathy (AAN) than single or coformulated analgesics without caffeine. This has led to a recommendation that the sale of "two plus caffeine" analgesic mixtures be reclassified from over-the-counter to prescription only availability. There is a rational basis for coformulating acetylsalicylic acid (ASA) and acetaminophen (paracetamol) as this reduces the dose of each, without altering efficacy. The coformulation of caffeine with these analgesics has a significant adjuvant effect and increases analgesic efficacy 1.4-1.6-fold. Currently available animal and human data do not support the notion that the nephrotoxic risk from coformulated ASA and acetaminophen is higher than the risk from either ASA or acetaminophen alone, in equivalent analgesic doses. There are no epidemiological data that implicate caffeine in AAN, and only limited evidence that links excessive acetaminophen usage to renal disease. There is no evidence that caffeine increases analgesics papillotoxicity directly. The presence of caffeine in mixtures of analgesics are no more addictive than other sources of caffeine. There is no evidence to suggest that adding caffeine to analgesic mixtures enhances the potential for promoting analgesic misuse in the general population. Thus distinct therapeutic benefits of ASA, acetaminophen and caffeine appear to outweigh any known risk. It is doubtful if preventing the availability of these products will significantly affect the role of analgesic abuse/overuse in end-stage renal disease. Better risk management would come from a focused educational program, developed in a close collaboration between industry, healthcare professionals and consumer organizations, such a program must warn against the potential dangers of analgesic and non-steroidal anti-inflammatory drug misuse.

Randomized trial of daily versus three-times-weekly prophylactic ganciclovir after lung and heart-lung transplantation

BACKGROUND

Cytomegalovirus is an important cause of morbidity and mortality risk after lung transplantation. Ganciclovir, when given for a period of up to 3 months after lung transplantation, has been shown to reduce the incidence and severity of cytomegalovirus. However, daily prophylaxis is associated with considerable expense, inconvenience, and morbidity risk. The goal of this study was to determine whether 3-times-weekly dosage is as effective as daily prophylaxis with ganciclovir in preventing cytomegalovirus disease.

METHODS

Seventy-two consecutive subjects who had either donor or recipient cytomegalovirus seropositivity were randomized to the daily group (n = 35) or the 3-times-weekly group (n = 37). All subjects received twice-daily ganciclovir treatment for 2 weeks. Thereafter, subjects received either daily or 3-times-weekly ganciclovir dosing until 90 days after transplantation. Subjects were then monitored for 28 +/- 13 months to identify outcomes and complications.

RESULTS

There were no significant differences between the daily and 3-times-weekly groups with respect to survival free from cytomegalovirus infection or survival free from cytomegalovirus disease. In both groups, cytomegalovirus infection and disease frequently emerged after the termination of prophylaxis. However, in most cases the cytomegalovirus syndromes observed were mild and in many cases could be treated on an outpatient basis. There was no significant difference between the groups in the incidence of obliterative bronchiolitis or time to onset of grade 2 bronchiolitis obliterans syndrome. Overall patient survival was better in the daily group, but the survival advantage did not appear to be related to a reduction in cytomegalovirus-related disease. Complications of ganciclovir prophylaxis included leukopenia in 2 subjects in the 3-times-weekly group and catheter-related sepsis in 6 subjects from each group.

CONCLUSIONS

We conclude that intravenous ganciclovir given 3 times weekly for 3 months after transplantation is as effective as daily ganciclovir given for a similar time period. The 3-times-weekly dosing regimen did not result in increased infection, disease, or sequelae of cytomegalovirus infection when compared with the daily regimen.

Comparison of the native CCMV virion with in vitro assembled CCMV virions by cryoelectron microscopy and image reconstruction

Cryoelectron microscopy and three-dimensional image reconstruction analysis has been used to determine the structure of native and in vitro assembled cowpea chlorotic mottle virus (CCMV) virions and capsids to 25-A resolution. Purified CCMV coat protein was used in conjunction with in vitro transcribed viral RNAs to assemble RNA 1 only, RNA 2 only, RNA 3/4 only, and empty (RNA lacking) virions. The image reconstructions demonstrate that the in vitro assembled CCMV virions are morphologically indistinguishable from native virions purified from infected plants. The viral RNA (vRNA) is packaged similarly within the different types of virions. The centers of all assembled particles are generally devoid of density and the vRNA packs against the interior surface of the virion shell. The vRNA appears to adopt an ordered conformation at each of the quasi-threefold axes.

Virion swelling is not required for cotranslational disassembly of cowpea chlorotic mottle virus in vitro

The mechanism by which virions of cowpea chlorotic mottle virus (CCMV) disassemble and allow for translation of the virion RNA is not well understood. Previous models have suggested that virion swelling is required to expose the virion RNA for translation in a process referred to as cotranslational disassembly (M. Brisco, R. Hull, and T. M. A. Wilson, Virology 148:210-217, 1986; J. W. Roenhorst, J. W. M. van Lent, and B. J. M. Verduin, Virology 164:91-98, 1988; J. W. Roenhorst, J. M. Verduin, and R. W. Goldbach, Virology 168:138-146, 1989). Previous work in our laboratory has identified point mutations in the CCMV coat protein which result in virions with altered swelling characteristics (J. Fox, F. G. Albert, J. Speir, and M. J. Young, Virology 227:229-233, 1997; J. M. Fox, X. Zhao, J. A. Speir, and M. J. Young, Virology 222:115-122, 1996). The wild-type and mutant CCMV virions were used to correlate virion swelling with the ability of virion RNA to be translated in a cell-free wheat germ extract. Mutant virions unable to swell (cpK42R) are as infectious as wild-type virions in vivo, and the levels of translated encapsidated virion RNA are similar to those of wild-type virions in vitro. Mutant virions capable of swelling but not of disassembling in vitro (cpR26C) are noninfectious and have severely reduced levels of translation of the encapsidated virion RNA in vitro. These studies suggest that virion swelling is not required for the cotranslational disassembly of CCMV. Additionally, the results indicate that there is a pH-dependent structural transition in the virion, other than swelling, that results in the RNA's being exposed for translation in vitro. An alternative model suggesting that cotranslational disassembly of CCMV involves presentation of the virion RNA through the virion fivefold axis is proposed.

Characterization of a disassembly deficient mutant of cowpea chlorotic mottle virus

An understanding of virus disassembly requires a detailed understanding of the protein-protein and protein-nucleic acid interactions which stabilize the virion. We have characterized a mutant of cowpea chlorotic mottle virus [cpR26C (coat protein R26C)] that displays increased virion stability and is abnormal in virion disassembly when purified under nonreducing conditions. Reduced virions are infectious, whereas nonreduced virions are noninfectious. The cpR26C mutant virions purified under nonreducing conditions resist disassembly in 0.5 M CaCl2, pH 7.5. The nonreduced cpR26C mutant virions swell in neutral pH conditions (pH 7.5) but do not disassociate when the ionic strength is increased. In contrast, wild-type virions or cpR26C mutant virions isolated under reducing conditions completely disassociate into the RNA and capsid protein components at pH 7.5 and high ionic strength (i > 1.0). Sequence analysis of the cpR26C mutant identified a single C to U nucleotide change at position 1435 of RNA 3 (position 86 of RNA 4), which results in a arginine to cysteine change at position 26 of the coat protein. The cpR26C mutant provides an ideal chemical switch for examining virion assembly and disassembly.

Analysis of a salt stable mutant of cowpea chlorotic mottle virus

An understanding of virion assembly and disassembly requires a detailed understanding of the protein-protein and protein-nucleic acid interactions which stabilize the virion. We have characterized a mutant of cowpea chlorotic mottle virus (CCMV) that is altered in virion stability. The mutant virions resist disassembly in 1.0 M NaCl, pH 7.5, whereas the wild-type virions completely disassociate into RNA and capsid protein components. Sequence analysis of the mutant coat protein gene identified a single A to G nucleotide change at position 1484 of RNA 3 (position 134 of RNA 4), which results in a lysine to arginine change at position 42 of the coat protein. Introduction of the K42R mutation into wild-type CCMV coat protein results in a salt stable virion phenotype. Likewise, expression of the K42R mutant coat protein in Escherichia coli followed by in vitro assembly produces virions that exhibit the salt stable phenotype. Analysis of this mutation demonstrates how a single amino acid change in the primary structure of the coat protein leads to tertiary interactions which stabilize the virion.

Meniscal repair. Where do we go from here?

In summary, it has been the task of this article to try to forecast the future of meniscal surgery over the next decade. As we enter the twenty-first century, it becomes evident that a combination approach will be the most likely procedure. The code phrase will be, "Save as much meniscus as possible." The authors predict that accomplishing this objective will involve the use of adhesive materials, possibly autologous but more probably exogenous, supported by the insertion of a collagenous type material, which will serve as a scaffolding for the ingrowth of fibrocartilage, and the healing will be stimulated by hormonal methods. Whether this occurs through recombinant DNA techniques or better methods of precipitation remains an issue. Dose-specific mitogens and chemotactic agents will be placed in the area of injury to potentiate the vascular fibrous response of the host tissue. With earlier and more exuberant fibrous response and initial tissue adhesion from the fibrin adhesive, better stability will be established to allow for primary healing of meniscal tissues. This procedure will work well for longitudinal tears of the meniscus. A dilemma arises with more complex tears of the meniscus, however. Previously irreparable tears may be conducive to resection then replacement with cultured autologous fibrochondrocytes, either in a gel-type form or on scaffolds made of collagen or biodegradable materials. These scaffold/fibrochondrocyte replacements may be contoured to the defect present and bonded tightly with the fibrin adhesives previously discussed. Again, growth factors would be needed for ultimate success as the fibrochondrocytes mature into the appropriate morphologic subpopulations and begin to turn over their own extracellular matrix. The patient would have a neomeniscal autologous transplant with normal host cell turnover of matrix. A brave new era lies ahead for meniscal repair, and the journey promises to be a most exciting one.

Critical analysis of knee ligament rating systems

Sixty-five patients who consecutively underwent anterior cruciate ligament reconstruction were studied using four individual, categoric, knee score rating systems. Different results were noted at followup (mean, 35 months; range, 24 to 58) depending on the rating method used. Ali patients were graded using the Hospital for Special Surgery, Lysholm, Tegner activity, and Cincinnati Knee Ligament rating systems. The Cincinnati Knee Ligament rating individual scores were noted to be lower than the Hospital for Special Surgery and Lysholm scores for subjective and objective outcome assessment. The Hospital for Special Surgery and Lysholm scores did not correlate highly with the Cincinnati Knee Ligament rating final rating, but they did correlate with each other. The use of ligament rating scores tended to inflate results, particularly when raw scores were converted to overall categoric ratings (e.g., excellent, good). The Cincinnati Knee Ligament rating system correlates more highly with individual grading and most precisely defines outcome in athletically active patients. Sources of error may be introduced by a disproportionate combination of unrelated scores or by overrating low-activity-level individuals who avoid stressing their knees. Avoidance of data generalization remains the optimal method for studying anterior cruciate ligament surgery outcome.

Paramyxovirus infection in lung transplant recipients

BACKGROUND

Respiratory infections are common after lung transplantation. The significance of respiratory paramyxoviruses, respiratory syncytial virus, and parainfluenza virus in lung transplant recipients has not been determined.

METHODS

In a retrospective fashion, we examined the incidence and clinical characteristics of paramyxovirus infection in 84 consecutive lung transplant recipients at the University of Minnesota Hospital and Clinics from 1986 through 1993.

RESULTS

We identified 19 cases of paramyxovirus infection in 18 patients (21% of all transplant recipients). All patients had symptoms with lower respiratory tract involvement, and nine (47%) had coexisting upper respiratory involvement. Symptom onset was 24 to 2056 days after transplantation (median = 260 days). Respiratory syncytial virus infection was seasonal (January through June), but parainfluenza virus infection occurred throughout the year. Six patients showed a decline in spirometry (26% +/- 2.8% decrease in forced expiratory volume in 1 second); four returned to baseline. Diagnosis was made by bronchoalveolar lavage in 15 cases, nasopharyngeal swab in three cases, and sputum in one case. Most patients (74%) were treated with ribavirin, and all but one treated patient recovered fully. In untreated patients, respiratory syncytial virus contributed to one death and one parainfluenza virus infection resulted in a persistent reduction in spirometry. Age was the strongest predictor of infection, with a higher incidence in patients under 18 years old (57%, p < 0.05). Preexisting obliterative bronchiolitis did not correlate with an increased incidence of paramyxovirus infection (20% with obliterative bronchiolitis, 22% without obliterative bronchiolitis; p > 0.05).

CONCLUSIONS

Lower respiratory tract infection with paramyxovirus is common in lung transplant recipients and capable of causing death or a permanent reduction in pulmonary function.

In vitro assembly of cowpea chlorotic mottle virus from coat protein expressed in Escherichia coli and in vitro-transcribed viral cDNA

The small spherical plant virus, cowpea chlorotic mottle virus (CCMV), provides an ideal system to examine spherical virus assembly. We have modified the CCMV in vitro assembly system to produce virions from coat protein expressed in Escherichia coli and viral RNA transcribed in vitro from full-length cDNAs. Examination of the in vitro-assembled particles with cryoelectron microscopy and image reconstruction techniques demonstrates that the particles are indistinguishable from plant purified particles at 2.5 nm resolution. Mutational analysis of the coat protein N- and C-terminal extensions demonstrate their respective roles in virus assembly. The N-terminus is required for assembly of RNA containing particles but not for the assembly of empty virions. The C-terminus is essential for coat protein dimer formation and particle assembly.

Malignant pleural effusion

Pleural effusion is a frequent complication of malignant disease. With a realization of pathophysiological mechanisms, symptomatology, and specific care needs of patients, the nurse can make appropriate assessments and provide thorough and essential care to improve patient outcome.

Thermoregulation in Yersinia enterocolitica is coincident with changes in DNA supercoiling

Yersinia enterocolitica is a facultative intracellular parasite, displaying the ability to grow saprophytically or invade and persist intracellularly in the mammalian reticuloendothelial system. The transition between such diverse environments requires the co-ordinated regulation of specific sets of genes on both the chromosome and virulence plasmid. Temperature has a profound pleiotropic effect on gene expression and phenotypically promotes alterations in cell morphology, outer-membrane protein synthesis, urease production, lipopolysaccharide synthesis, motility, and synthesis of genes involved in invasion of eukaryotic host cells. By examining thermoregulated flagella biosynthesis, we have determined that motility is repressed at 25 degrees C (permissive temperature) with subinhibitory concentrations of novobiocin. These conditions also induce virulence gene expression suggesting novobiocin addition simulates, at least partially, a high-temperature environment. Furthermore, temperature-shift experiments, using Y. enterocolitica containing pACYC184 as a reporter plasmid, indicate that thermo-induced alterations of DNA supercoiling coincide with temperature-induced phenotypic changes. A class of putative DNA gyrase mutant (novobiocin resistant) likewise demonstrates the 37 degrees C phenotype when cultured at 25 degrees C; it is non-motile, urease negative, calcium growth dependent, and positive for Yop expression. These results support a model implicating DNA topology as a contributing factor of Y. enterocolitica thermoregulation.

MR diagnosis of recurrent tears in the knee: value of intraarticular contrast material

OBJECTIVE

After surgical resection or repair of a torn meniscus, the healed area may have areas of abnormal signal intensity on MR images. Consequently, routine MR imaging is not reliable for detecting recurrent meniscal tears. As a result, we studied the efficacy of MR imaging with intraarticular contrast material (MR arthrography) for detecting recurrent tears of the meniscus.

SUBJECTS AND METHODS

Thirty-seven patients who previously had a meniscal tear treated by either meniscal resection or repair had conventional MR imaging and MR arthrography with 40-50 ml of a 1:100 solution of gadopentetate dimeglumine in saline. All patients had arthroscopy shortly after the MR studies. Follow-up arthroscopic surgery was performed within an average of 6.6 weeks after the MR arthrograms. The routine MR images and MR arthrograms were reviewed separately and randomly, and these results were compared with the arthroscopic findings. Meniscal morphology, signal intensity, and the presence of joint fluid tracking into recurrent tears were evaluated.

RESULTS

The overall accuracy in diagnosing recurrent meniscal tears in the post-operative meniscus was 66% when conventional MR imaging was used and 88% when MR arthrography was used. In patients who had only minimal meniscal resection, both methods had an accuracy of 89%. In patients who had more extensive meniscal resection, accuracy was 65% with conventional MR imaging and 87% with MR arthrography. In four patients who had only a small meniscal remnant, the accuracy was 50% with routine MR imaging and 100% with MR arthrography. On conventional MR images, the presence of an effusion tracking into a meniscal tear had a sensitivity and positive predictive value of 90% for detection of recurrent meniscal tears; however, the sensitivity was only 41%.

CONCLUSION

Our results show that the sensitivity of MR imaging in detecting meniscal tears after surgery varies with the extent of the resection. Sensitivity was considerably improved when intraarticular contrast material was used. MR arthrography should be considered as an alternative to arthroscopy in patients who have had resection or repair of the meniscus.

Trephination of incomplete meniscal tears

The meniscus performs several roles that are important to the function of the knee joint. In an effort to preserve these functions of the meniscus, methods to promote the healing of meniscal lesions have been investigated. One such method involves trephination or the creation of vascular access channels by removal of a core of tissue from the periphery of the meniscus to the tear, thus connecting a lesion in the avascular portion of the meniscus to the peripheral blood supply. The purpose of this study is to describe our experience with arthroscopic trephination of symptomatic incomplete meniscal tears in humans. This is a simple technique that avoids the risk associated with suture repair of the meniscal tissue, yet preserves the meniscus. Overall results were good or excellent in 90% of the cases. In conclusion, symptomatic incomplete meniscal tears can be treated by stimulation of vascular channels without the risk associated with suturing of this tissue, while preserving the important functions of the meniscus.

Overuse injuries of the knee in basketball

Overuse injuries of the knee are abundant in basketball players. This article discusses the pathophysiology of overuse and the principles of treatment. The diagnosis and clinical management of jumper's knee, patellofemoral pain, and stress fractures are outlined with specific attention to rehabilitation techniques and training.

Arthroscopically assisted anterior cruciate ligament reconstruction with the pes anserine tendons. Comparison of results in acute and chronic ligament deficiency

Fifty anterior cruciate ligament-deficient knees treated consecutively with arthroscopically assisted reconstruction using a pes anserine tendon autograft were retrospectively studied. The mean followup was 36.7 months (range, 26 to 58). All patients had reconstruction with a double-stranded graft. The mean injury to surgery interval was 9.6 days in 22 patients (acute group) and 22.5 months in 28 patients (chronic group). Objective outcome, which was noted to be more optimal in the acute group, was better than subjective outcome in either group. Examination revealed 95% of patients treated acutely and 82% of those treated later to have 1+ or less Lachman test result (P < 0.036) and 96% of the acute group and 82% of the chronic group to have an absent pivot shift (P < 0.036). Eighty-eight percent of acutely treated patients had a KT-1000 result of < or = 3 mm, as compared to 61% of chronically treated patients (P < 0.001). Loss of range of motion was significantly greater in the acute group (P < 0.018). Using a strict overall rating system, patients reconstructed earlier were noted to have a better outcome compared to those after delayed reconstruction (P < 0.021). Cumulative meniscal injury appears to be the most significant contributing factor.

Obliterative bronchiolitis after lung transplantation: a fibroproliferative disorder associated with platelet-derived growth factor

Fibroproliferative disorders are characterized by accumulations of mesenchymal cells and connective tissue in critical locations, leading to organ dysfunction. We examined the role of platelet-derived growth factor (PDGF) in the pathogenesis of obliterative bronchiolitis, a fibroproliferative process that occurs after lung transplantation and results in small airway occlusion. Bronchoalveolar lavage fluid from obliterative bronchiolitis patients significantly stimulated fibroblast migration, whereas fluid from patient controls did not. Quantitation by radioligand binding assay demonstrated increased concentrations of PDGF in lavage fluid from obliterative bronchiolitis patients (patients, 104 +/- 26.9 pM; controls, 8.4 +/- 6.9 pM; P < 0.01). Heparin affinity, gel filtration, and Western blot analysis confirmed the presence of PDGF in lavage fluid. Immunohistochemical and in situ hybridization studies of histologic sections and bronchoalveolar lavage cells suggest that alveolar macrophages are one cellular source. Prospective evaluation of sequential bronchoalveolar lavage samples from a patient who developed obliterative bronchiolitis demonstrated markedly increased PDGF concentrations before the onset of irreversible airflow obstruction. These findings are consistent with a role for PDGF in the fibroproliferative changes observed in obliterative bronchiolitis.

Neural responses to visual texture patterns in middle temporal area of the macaque monkey

1. We studied how neurons in the middle temporal visual area (MT) of anesthetized macaque monkeys responded to textured and nontextured visual stimuli. Stimuli contained a central rectangular "figure" that was either uniform in luminance or consisted of an array of oriented line segments. The figure moved at constant velocity in one of four orthogonal directions. The region surrounding the figure was either uniform in luminance or contained a texture array (whose elements were identical or orthogonal in orientation to those of the figure), and it either was stationary or moved along with the figure. 2. A textured figure moving across a stationary textured background ("texture bar" stimulus) often elicited vigorous neural responses, but, on average, the responses to texture bars were significantly smaller than to solid (uniform luminance) bars. 3. Many cells showed direction selectivity that was similar for both texture bars and solid bars. However, on average, the direction selectivity measured when texture bars were used was significantly smaller than that for solid bars, and many cells lost significant direction selectivity altogether. The reduction in direction selectivity for texture bars generally reflected a combination of decreased responsiveness in the preferred direction and increased responsiveness in the null (opposite to preferred) direction. 4. Responses to a texture bar in the absence of a texture background ("texture bar alone") were very similar to the responses to solid bars both in the magnitude of response and in the degree of direction selectivity. Conversely, adding a static texture surround to a moving solid bar reduced direction selectivity on average without a reduction in response magnitude. These results indicate that the static surround is largely responsible for the differences in direction selectivity for texture bars versus solid bars. 5. In the majority of MT cells studied, responses to a moving texture bar were largely independent of whether the elements in the bar were of the same orientation as the background elements or of the orthogonal orientation. Thus, for the class of stimuli we used, orientation contrast does not markedly affect the responses of MT neurons to moving texture patterns. 6. The optimum figure length and the shapes of the length tuning curves determined with the use of solid bars and texture bars differed significantly in most of the cells examined. Thus neurons in MT are not simply selective for a particular figure shape independent of whatever cues are used to delineate the figure.

Single lung transplantation for severe emphysema

Lung transplantation is effective therapy for patients with severe obstructive lung disease. We reviewed seven patients with severe emphysema (age, 48 +/- 5 years; forced expiratory volume in 1 second [FEV1] 0.76 +/- 0.26 liters) who received single-lung transplants (SLT) at our institution between August 1989 and September 1990. Studies to assess the adequacy of cardiac function before transplantation showed moderately reduced right ventricular function (by multiple gated acquisition, 34 +/- 6%), moderately elevated pulmonary artery pressure (25 +/- 3 mm Hg), and normal left ventricular function (by multiple gated acquisition 65% +/- 12%) and coronary arteriograms. Time on the waiting list before transplantation was reduced compared with heart-lung transplant (HLT) recipients (waiting time, 2.9 +/- 1.5 months for SLT, 9.6 +/- 10.2 months for HLT). Six of the SLT recipients are currently alive (after transplantation interval, 17 +/- 5 months); the remaining recipient died of pulmonary embolism 21 days after SLT. Number of ventilator days, intensive care unit days, and days to hospital discharge after transplantation did not differ significantly from HLT recipients. Cardiopulmonary bypass was necessary in four SLT recipients. Pulmonary function was markedly improved after SLT (FEV1, 1.78 +/- 0.73 L/min after SLT versus 0.75 +/- 0.3 L/min before SLT; p less than 0.01), and functional status is correspondingly improved.

CONCLUSIONS

SLT constitutes effective therapy for patients with severe emphysema, including those with moderate reduction of right ventricular function; and SLT offers distinct advantages over HLT, including decreased waiting time before transplantation, improved donor organ utilization, and less frequent need for cardiopulmonary bypass.