Experimental acute hematogenous osteomyelitis in mice. I. Histopathological and immunological findings.

This study investigated immunological responses to Staphylococcus aureus bone infection. Because considerable immunological information is available on the mouse, a murine model of acute hematogenous osteomyelitis was established. Osteomyelitis was created in the proximal tibia of C3H/HeJ mice by a tibial epiphyseal fracture followed by intravenous bacterial inoculation with Staphylococcus aureus (strain LS-1). Swelling and warmth of the limb was found, and following limb exposure, abscess formation was evident in the proximal tibia. Histological examination revealed distortion primarily at the hypertrophic zone of the physis and polymorphonuclear leukocyte infiltration throughout the damaged area of the proximal tibia. Local infection was demonstrated at the fracture site, evidenced by the recovery of Staphylococcus aureus following microbiological analysis of tissue specimens. Polymerase chain reaction was utilized to detect 16S ribosomal prokaryotic nucleic acid to demonstrate that the diagnosis of osteomyelitis could be established in the absence of conventional microbiological techniques. The infected mice had an increase of circulating large leukocytes (granulocytes) and an elevation of total serum immunoglobulin. Flow cytometry revealed significant increases in splenic B lymphocytes and in lymph-node CD4+ T lymphocytes. These results indicate that an experimental model of acute hematogenous osteomyelitis that closely resembles the pathology of the disease in humans may be consistently induced in mice. Furthermore, marked immunological changes may be observed in response to the Staphylococcus aureus bone infection.

Molecular factors influencing drug transfer across the blood-brain barrier.

A recently reported approach to the prediction of blood-brain drug distribution uses the general linear free energy equation to correlate equilibrium blood-brain solute distributions (logBB) with five solute descriptors: R2 an excess molar refraction term; pi2H, solute dipolarity or polarizability; alpha2H and beta2H, the hydrogen bond acidity or basicity, and Vx, the solute McGowan volume. In this study we examine whether the model can be used to analyse kinetic transfer rates across the blood-brain barrier in the rat. The permeability (logPS) of the blood-brain barrier to a chemically diverse series of compounds was measured using a short duration vascular perfusion method. LogPS data were correlated with calculated solute descriptors, and octanol-water partition coefficients (logP(oct)) for comparison. It is shown that a general linear free energy equation can be constructed to predict and interpret logPS values. The utility of this model over other physicochemical descriptors for interpreting logPS and logBB values is discussed.

Hydrogen-bonding. Part 36. Determination of blood brain distribution using octanol-water partition coefficients.

It is shown that the octanol-water partition coefficient (Poct) cannot be used to predict blood brain distribution (BB) rectilinearly, but can be combined with Abraham solute descriptors to yield a predictive regression equation, eq (15), in which the solute descriptors sigma alpha H2 and sigma beta H2 are the overall summation hydrogen-bond acidity and basicity respectively. It is also demonstrated that of the various predictive models now available, that of Abraham, Chadha and Mitchell, eq (14), still yields the best results on a new test set of drug molecules; where the other solute descriptors are: R2, an excess molar refraction; pi H2, the dipolarity/polarisability; and Vx the characteristic volume of McGowan. Thus, solute dipolarity/polarizability, hydrogen-bond acidity and hydrogen-bond basicity favour blood, and solute size favours brain. logBB = +0.055 + 0.203logPoct - 0.507 sigma alpha H2 - 0.500 sigma beta H2 n = 49 rho = 0.9491 sd = 0.201 F = 136.1 (15) logBB = -0.038 + 0.198R2 - 0.607 pi H2 - 0.715 alpha H2 - 0.698 beta H2 + 0.995Vx n = 57 rho = 0.9522 sd = 0.197 F = 99.2 (14)

Cellular proliferation and cytokine responses to polymethylmethacrylate particles in patients with a cemented total joint arthroplasty.

The in vitro response of peripheral blood mononuclear cells (MNC) from patients with cemented total hip or knee arthroplasties, and control individuals, to polymethylmethacrylate (PMMA) was assessed by cell proliferation, cytokine production, and molecular techniques. After seven days in culture, a dose-dependent proliferative response to PMMA stimulation was observed in MNC from fifteen normal individuals. A concomitant dose-dependent production of both IL-1 beta and IL-2 in response to PMMA stimulation was detected. Reverse transcription-polymerase chain reactions (RT-PCR) indicated that both IL-1 beta and IL-2 mRNA was present after 48 hours in culture with PMMA. Cellular proliferation and cytokine production (both IL-1 beta and IL-2) in 10 patients with stable, painless, well-functioning, cemented arthroplasties was significantly lower (p < 0.025) than normal controls and patients with aseptically loosened, painful, arthroplasties. The findings suggest that patients with stable cemented total joint arthroplasties are either inherently or adaptively less responsive to PMMA at a cellular level.

Hydrogen bonding. 33. Factors that influence the distribution of solutes between blood and brain.

It is shown that neither the set of directly determined blood-brain concentration ratios (BB) of Young and Mitchell nor the set of indirectly obtained values of Abraham and Weathersby are suitable for the construction of a general equation for the interpretation and prediction of log BB values. However, combination of both sets leads to the general equation log BB = -0.038 + 0.198R2 - 0.687 pi H2 - 0.715 alpha H2 - 0.698 beta H2 + 0.995Vx (n = 57, rho = 0.9522, sd = 0.197, F = 99.2), where the solute descriptors are R2, an excess molar refraction; pi H2, the dipolarity/polarizability, alpha H2 and beta H2, the effective or summation hydrogen-bond acidity and basicity; and Vx, the characteristic volume of McGowan. Thus solute dipolarity/polarizability, hydrogen-bond acidity, and hydrogen-bond basicity favor blood, and solute size, as Vx, favors brain. Methods are given for the estimation of solute descriptors through fragment schemes, so that log BB values themselves may be obtained simply from knowledge of solute molecular structure.

Hydrogen bonding. 32. An analysis of water-octanol and water-alkane partitioning and the delta log P parameter of seiler.

A general linear solvation energy equation has been used to analyze published partition coefficients in the systems water-octanol (613 solutes), water-hexadecane (370 solutes), water-alkane (200 solutes), and water-cyclohexane (170 solutes). The descriptors used in the equation are R2, an excess molar refraction; phi H2, the solute dipolarity/polarizability; sigma alpha H2 and sigma beta H2, the effective solute hydrogen-bond acidity and basicity; and Vx, the characteristic volume of McGowan. It is shown that the water-octanol partition coefficient is dominated by solute hydrogen-bond basicity, which favors water, and by solute size, which favors octanol, but solute excess molar refraction and dipolarity/polarizability are also significant. For the water-alkane partition coefficients, the same factors are at work, together with solute hydrogen-bond acidity as a major influence that favors water. An analysis of 288 delta log P values shows that solute hydrogen-bond acidity is the major factor but that solute hydrogen-bond basicity and, to a lesser extent, solute dipolarity/polarizability and size are also significant factors that influence the delta log P parameter.