To examine the role of the accessory gene regulator (agr) in staphylococcal osteomyelitis, we compared a Staphylococcus aureus osteomyelitis isolate (UAMS-1) with a derivative of the same strain (UAMS-4) carrying an inactivated agr locus. Virulence was assessed with a rabbit model of acute, exogenous osteomyelitis. Bacteria were delivered by microinjection into the midradial region of the forelimb. After 4 weeks, UAMS-1 was identified in the bone of 12 of 13 rabbits infected with >2 ؋ 10 6 CFU and 5 of 6 infected with <2 ؋ 10 5 CFU. In contrast, UAMS-4 was found in 6 of 13 infected with the higher dose and 1 of 6 infected with the lower dose. Additionally, on the basis of a five-point scale assessing radiographic evidence of disease, rabbits infected with UAMS-1 had average scores of 2.64 ؎ 0.30 (high dose) and 1.43 ؎ 0.39 (low dose) while rabbits infected with UAMS-4 had average scores of 0.95 ؎ 0.23 (high dose) and 0.63 ؎ 0.20 (low dose). Uninfected controls had an average score of 0.53 ؎ 0.08. The results obtained with UAMS-1 were significantly different from those obtained with UAMS-4 at both doses (P < 0.047). The results obtained with UAMS-4 were not significantly different from those obtained with the controls at either dose of UAMS-4 (P > 0.150). On the basis of a similar five-point scale assessing histopathological evidence of disease, rabbits infected with UAMS-1 had average scores of 2.31 ؎ 0.22 (high dose) and 1.96 ؎ 0.36 (low dose) while rabbits infected with UAMS-4 had average scores of 1.58 ؎ 0.29 (high dose) and 0.83 ؎ 0.32 (low dose). Controls had an average score of 0.33 ؎ 0.05. The results obtained with UAMS-1 were significantly different from those obtained with UAMS-4 at both doses (P < 0.040). However, the results obtained with UAMS-4 were significantly different from the controls only at the high dose of UAMS-4 (P ‫؍‬ 0.025). We conclude that mutation of agr reduces the incidence and severity of disease but does not eliminate the ability to colonize bone and cause histopathological evidence of osteomyelitis.

We previously described a rabbit osteomyelitis model that involved the direct introduction of Staphylococcus aureus into devascularized bone. To further evaluate the model, we performed experiments aimed at correlating the microbiological, radiographic, and histologic parameters involved in the development of experimental osteomyelitis. Using the strain UAMS-1, we achieved an infection rate of 75% with an inoculum as small as 2 x 10(3) colony-forming units. However, development of significant radiographic and histologic signs of disease required an inoculum of at least 2 x 10(4) colony-forming units. Radiographic signs were minimal 1 week after infection and progressed steadily to a maximum 3 weeks after infection. In contrast, histologic signs of disease were observed within 1 week and remained essentially unchanged throughout the 4-week evaluation period. Unlike the results obtained with UAMS-1, rabbits infected with the heavily encapsulated Staphylococcus aureus strain Smith diffuse exhibited little evidence of disease even when infected with 2 x 10(6) colony-forming units. The reduced virulence of strain Smith diffuse was surprising given its greatly enhanced virulence (relative to UAMS-1) in a murine peritonitis model of staphylococcal disease. These results suggest that UAMS-1 expresses virulence factors that are important in the pathogenesis of osteomyelitis and that some or all of these virulence factors are either absent or are not expressed in strain Smith diffuse. Most importantly, the results suggest that our model may be appropriate for the identification and characterization of these virulence factors.

Leaf reflectance in the 0.40‐ to 0.75‐μm wavelength interval is influenced primarily by the pigments chlorophyll and carotenoid. However, the literature contains very few references to the relation between reflectance from leaves and their carotenoid content. Our objectives in this study were to determine which of three wavelengths in the visible spectral region best related leaf reflectance to total chlorophyll and carotenoid concentrations, and the relative effect of these pigments on reflectance. Hemispherical reflectances of single leaves at each of the 0.45‐, 0.55‐, and 0.67‐μm wavelengths for cantaloupe (Cucumis melo L. cv. reticulatus Naud.), corn (Zea mays L.), cotton (Gossypium hirsutum L.), cucumber (Cucumis sativus L.), head lettuce (Lactuca sativa L. cv. capitata L.), grain sorghum (Sorghum bicolor (L.) Moench), spinach (Spinacia oleracea L.), and tobacco (Nicotiana tabacum L.) were regressed on each crop's leaf total chlorophyll and carotenoid concentrations. The crops were grown in sand culture, and their leaf pigment concentrations were varied by supplying N at rates of 14, 28, 84, 140, and 196 ppm to a basic nutrient solution. Hemispherical reflectance of leaves was inversely related to each crop's leaf chlorophyll and carotenoid concentrations. However, of the three wavelengths tested, the 0.55‐μm wavelength seemed superior for individually relating the two pigments to leaf reflectance. The independent effects of carotenoid on hemispherical reflectance were small and generally not statistically significant, whereas the independent effects of chlorophyll while small were generally significant. The combined effects of these variables were highly significant and accounted for 39 to 95% of the reflectance variability. This study indicated that even though including carotenoid with total chlorophyll measurements improved the correlation of reflectance with pigment concentration, satisfactory results would be obtained by chlorophyll analysis alone.

No abstract

No abstract

Calcium sulfate was used as a biodegradable delivery system for the administration of antibiotics in musculoskeletal infection. New Zealand white rabbits were infected with Staplylococcus aureus, debrided, and randomized to one of four treatment groups: calcium sulfate pellets with 10% tobramycin sulfate, placebo calcium sulfate pellets and IM tobramycin, placebo calcium sulfate pellets, or debridement. Serum and wound exudate tobramycin concentrations and serum calcium levels were measured. Radiographs, cultures, and histology were analyzed for efficacy and treatment. Rabbits treated with 10% tobramycin sulfate pellets showed a significantly higher eradication of infection (11/13) than rabbits treated with debridement only (5/12), placebo pellets and IM tobramycin (5/14). or placebo pellets (3/13). In the group receiving 10% tobramycin sulfate pellets, serum tobramycin concentrations peaked 3 h post-operatively at 5.87 microg/ml and were non-detectable after day 1. In the group receiving placebo pellets and IM tobramycin, serum concentrations peaked at 7.82 microg/ml 1 h post-operatively, fell to 6.12 microg/ml on day 2, and averaged 4.18 microg/ ml for the remainder of the treatment period. The wound exudate tobramycin concentrations in the animals treated with tobramycin sulfate pellets peaked at 11.9 mg/ml on day 1 and dropped to 2.5 microg/ml on day 7. There was no significant difference in the serum calcium levels in any of the treatment groups. Calcium sulfate containing tobramycin sulfate has potential utility as a biodegradable local antibiotic delivery system in the treatment of musculoskeletal infections.

A study was conducted to determine the feasibility of using spectrophotometrically measured diffuse light reflectance from top (adaxial) leaf surfaces of sweet pepper (Capsicum annum, L. var. ‘Yolo Wonder’) leaves to quickly estimate their N status. Reflectance was found to be inversely correlated (p = 0.01) with the leaf N content. Regression equations expressing reflectance as a function of leaf N content of greenhouse‐grown sweet peppers were used to estimate the N content of fieldgrown sweet peppers. The difference between Kjeldahldetermined and reflectance‐estimated N contents was less than 0.7%. The regression equation at the 550‐nm wavelength suggests that near the 4% N level a 1% change in reflectance would change the predicted N content by 0.2%. Results show that leaf reflectance can be used to quickly estimate the N status of sweet peppers.

In non-neoplastic tissues, the expression of protein gene product 9.5 (PGP 9.5), a member of the ubiquitin hydrolase family of proteins, is confined to neural and neuroendocrine cells. Although it has been claimed that PGP 9.5 is a specific marker of neural and/or nerve sheath differentiation in human tumors, careful review of the literature suggests that relatively few nonneural or nerve sheath tumors have been studied. Prompted by our recent observation of a PGP 9.5-positive malignant fibrous histiocytoma, we undertook a study of PGP 9.5 expression in a large group of well-characterized mesenchymal neoplasms. Sections from 95 mesenchymal tumors were retrieved from our archives and immunostained for PGP 9.5 using standard avidin-biotin complex technique and heat-induced epitope retrieval. Scoring was as follows: negative, 1+ (<10-25% of cells), 2+ (25-50% of cells), and 3+ (>50% of cells). Normal nerves and fibrous tissue were internal positive and negative controls, respectively. Positive immunostaining was seen in 80/95 (84%) of cases. Positive results by tumor subtype were as follows: (1) nerve sheath tumors: malignant peripheral nerve sheath tumor (7/10), neurofibromas (10/10), and perineuriomas (3/3); (2) (Myo) fibroblastic tumors: malignant fibrous histiocytoma (18/20), low-grade fibromyxoid sarcomas (8/9), fibromatoses (7/7), and desmoplastic fibroblastomas (2/2); (3) vascular tumors: angiosarcomas (4/4), hemangioendotheliomas (3/5), and hemangiomas (3/4); and (4) other non-nerve sheath tumors: pleomorphic liposarcoma (4/4), dermatofibrosarcoma protuberans (2/5), rhabdomyosarcomas (2/2), synovial sarcomas (8/8), melanomas (1/2). All positive cases were 2-3+ except 6 malignant peripheral nerve sheath tumor, 1 neurofibroma, 3 malignant fibrous histiocytoma, 2 low-grade fibromyxoid sarcoma, and 1 dermatofibrosarcoma protuberans. Positive staining was seen in normal smooth muscle and germinal centers in addition to nerves. We conclude that in this, the largest study to date of PGP 9.5 expression in mesenchymal neoplasms, we have found strong (2-3+) expression in the vast majority of nonneural or nerve sheath neoplasms studied. Although PGP 9.5 is a sensitive neural/nerve sheath marker, it is essentially totally nonspecific for diagnostic purposes. It is possible that our findings reflect cross-reactivity of the 13C4 clone with epitopes present on other ubiquitin hydrolases. Alternatively, PGP 9.5 expression may be aberrantly up-regulated in a variety of mesenchymal neoplasms.