Treatment of experimental chronic osteomyelitis due to Staphylococcus aureus with ampicillin/sulbactam

Ampicillin/sulbactam was used for the treatment of experimental osteomyelitis due to Staphylococcus aureus in rabbits. Treatment with 200 mg/kg (ampicillin) three times a day sterilized 40% of infected rabbit bones. The results of 4 weeks of treatment with ampicillin/sulbactam for chronic experimental staphylococcal osteomyelitis were comparable to those obtained previously with cephalothin and with oxacillin in previous studies and were not as good as those with clindamycin alone or combination therapy that included rifampin.     

Experimental osteomyelitis. V. Therapeutic trials with oxacillin and sisomicin alone and in combination

Oxacillin was used alone and in combination with sisomicin in the treatment of experimental osteomyelitis due to Staphylococcus aureus in rabbits. Within diseased bone, levels of oxacillin and sisomicin remained higher than the minimal inhibitory concentration for 2 and 6 hr, respectively, after injection of 50 mg of oxacillin/kg and 10 mg of sisomicin/kg. Treatment with 50 mg of oxacillin/kg four times daily or 50 mg/kg every 4 hr around the clock for 28 days sterilized 30% of the rabbit bones. Sisomicin (10 mg/kg) injected twice daily for 28 days sterilized only 5% of the rabbit bones. In contrast, treatment with the combination of oxacillin and sisomicin for either 14 or 28 days was significantly more effective, sterilizing 78% and 85%, respectively, of the bones of treated animals. S. Aureus isolated from bones of animals treated with sisomicin alone contained aminoglycoside-resistant microcolonies. Resistant microcolonies were not recovered from animals treated with oxacillin or with the combination of oxacillin plus sisomicin. In vitro studies of bacterial killing by each antibiotic alone and in combination showed more bacterial killing with the combination than with either agent alone; in vitro the combination prevented emergence of resistant microcolonies. Combination antibiotic therapy appears to be more effective in treatment of experimental osteomyelitis due to S. aureus than therapy with a single agent.     

Serologic responses of children with meningitis due to Haemophilus influenzae type b.

The immunologic responses of 100 children hospitalized with meningitis due to Haemophilus influenzae type b were measured by the bactericidal antibody assay (BAA) and radioimmunoassay (RIA) for detection of antibody. Short-term (14-17 days after onset of illness) responses were detected by RIA alone in 20 children, by BAA alone in six, and by both tests in 23. The more sensitive RIA detected 20 children who would have been labeled "immunologically unresponsive" had only BAA been used. The magnitude of the antibody response was clearly related to age. Of 26 children with no immediate antibody response, 11 still had no rise in titer of antibody when restudied two to 20 months later; the remaining 15 had subsequent increases in titer. Nine of 10 children who showed an immediate antibody response remained positive when additional blood smaples were taken two to 18 months later. Over half of the children initially unresponsive to H. influenzae type b meningitis subsequently developed specific antibodies. The remainder, who failed to acquire detectable antibodies at either the acute stage of illness or late in convalescence, deserve further investigation as to the nature of their immunologic hyporesponsiveness to H. influenzae type b meningitis.     

Amplification of genes encoding human myeloid membrane antigens after DNA-mediated gene transfer

Spontaneous amplification of genes encoding two different human myeloid surface antigens was observed after DNA-mediated gene transfer of cellular DNA from the human myeloid cell line HL-60 into NIH-3T3 mouse fibroblasts. Transformed recipient cells with highly amplified expression of either of two donor membrane polypeptides, gp150 or p67, were isolated with a fluorescence-activated cell sorter (FACS), using monoclonal antibodies specific for human myeloid cells. Immunoprecipitation of enzymatically radioiodinated polypeptides from the surface of transformed NIH-3T3 cells confirmed that expression of these proteins was amplified tenfold to 20-fold in comparison to their expression on human myeloid cell lines. The cellular DNA of cloned secondary and tertiary transformants expressing high levels of gp150 and p67 contained amplified sets of DNA restriction fragments that hybridized with human repetitive DNA sequences. Cytogenetic analysis of subclones overexpressing gp150 revealed extrachromosomal double minutes (DMs), whose presence correlated with the unstable expression of the membrane polypeptide. Human sequences in gp150-positive clones did not localize to chromosomes, consistent with their association with extrachromosomal DMs. By contrast, p67-positive subclones stably expressed the antigen, and in situ hybridization to metaphase spreads demonstrated that amplified human DNA sequences were integrated into a specific marker chromosome. Cytogenetic analysis of the parental NIH- 3T3 subclone used in these studies disclosed DMs in a low percentage of metaphases, suggesting that the recipient cells have a propensity for amplifying donor DNA.     

Molecular heterogeneity in acute leukemia lineage switch

Six cases of acute leukemia that underwent lineage switch from acute lymphocytic leukemia to acute myelogenous leukemia are reported. The mean age of the patients was 24 years, time to conversion was 36 months, and survival after conversion was only 3 months. Of the three cases which showed abnormal metaphases at both diagnosis and conversion, two (cases 2, 5) showed related cytogenetic abnormalities, and the third showed (case 3) independent chromosomal changes. Molecular analysis for immunoglobulin heavy chain and T-cell receptor beta chain genes showed that five of the six cases had rearrangement of at least one of these lymphoid associated genes at conversion to acute myelogenous leukemia. The single case (case 3) in which there were no lymphoid gene rearrangements at conversion was also the only case in which independent karyotypic abnormalities at diagnosis and conversion were demonstrated. Our findings suggest that lineage switch can represent either relapse of the original clone with heterogeneity at the molecular level or the emergence of a second new leukemic clone without molecular heterogeneity.     

Biological evaluation of intervertebral disc cells in different formulations of gellan gum‐based hydrogels

Gellan gum (GG)‐based hydrogels are advantageous in tissue engineering not only due to their ability to retain large quantities of water and provide a similar environment to that of natural extracellular matrix (ECM), but also because they can gelify in situ in seconds. Their mechanical properties can be fine‐tuned to mimic natural tissues such as the nucleus pulposus (NP). This study produced different formulations of GG hydrogels by mixing varying amounts of methacrylated (GG‐MA) and high‐acyl gellan gums (HA‐GG) for applications as acellular and cellular NP substitutes. The hydrogels were physicochemically characterized by dynamic mechanical analysis. Degradation and swelling abilities were assessed by soaking in a phosphate buffered saline solution for up to 170 h. Results showed that as HA‐GG content increased, the modulus of the hydrogels decreased. Moreover, increases in HA‐GG content induced greater weight loss in the GG‐MA/HA‐GG formulation compared to GG‐MA hydrogel. Potential cytotoxicity of the hydrogel was assessed by culturing rabbit NP cells up to 7 days. An MTS assay was performed by seeding rabbit NP cells onto the surface of 3D hydrogel disc formulations. Viability of rabbit NP cells encapsulated within the different hydrogel formulations was also evaluated by Calcein‐AM and ATP assays. Results showed that tunable GG‐MA/HA‐GG hydrogels were non‐cytotoxic and supported viability of rabbit NP cells. Copyright © 2012 John Wiley & Sons, Ltd.     

Use of intrinsic modes in biology: Examples of indicial response of pulmonary blood pressure to ± step hypoxia

Recently, a new method to analyze biological nonstationary stochastic variables has been presented. The method is especially suitable to analyze the variation of one biological variable with respect to changes of another variable. Here, it is illustrated by the change of the pulmonary blood pressure in response to a step change of oxygen concentration in the gas that an animal breathes. The pressure signal is resolved into the sum of a set of oscillatory intrinsic mode functions, which have zero “local mean,” and a final nonoscillatory mode. With this device, we obtain a set of “mean trends,” each of which represents a “mean” in a definitive sense, and together they represent the mean trend systematically with different degrees of oscillatory content. Correspondingly, the oscillatory content of the signal about any mean trend can be represented by a set of partial sums of intrinsic mode functions. When the concept of “indicial response function” is used to describe the change of one variable in response to a step change of another variable, we now have a set of indicial response functions of the mean trends and another set of indicial response functions to describe the energy or intensity of oscillations about each mean trend. Each of these can be represented by an analytic function whose coefficients can be determined by a least-squares curve-fitting procedure. In this way, experimental results are stated sharply by analytic functions.