Maria Schell

Antibody-Mediated Resolution of Light Chain-Associated Amyloid Deposits

Primary light-chain-associated (AL) amyloidosis is characterized by the deposition in tissue of monoclonal light chains as fibrils. With rare exception, this process is seemingly irreversible and results in progressive organ dysfunction and eventually death. To determine whether immune factors can effect amyloid removal, we developed an experimental model in which mice were injected with amyloid proteins extracted from the spleens or livers of patients with AL amyloidosis. Notably, the resultant amyloidomas were rapidly resolved, as compared to controls, when animals received injections of an anti-light-chain monoclonal antibody having specificity for an amyloid-related epitope. The reactivity of this monoclonal antibody was not dependent on the V(L) or C(L) isotype of the fibril, but rather seemed to be directed toward a beta-pleated sheet conformational epitope expressed by AL and other amyloid proteins. The amyloidolytic response was associated with a pronounced infiltration of the amyloidoma with neutrophils and putatively involved opsonization of fibrils by the antibody, leading to cellular activation and release of proteolytic factors. The demonstration that AL amyloid resolution can be induced by passive administration of an amyloid-reactive antibody has potential clinical benefit in the treatment of patients with primary amyloidosis and other acquired or inherited amyloid-associated disorders.

Regulation of nod gene expression in Bradyrhizobium japonicum

SummaryThe best inducers of nod:: lacZ translational fusions in Bradyrhizobium japonicum are isoflavones, primarily genistein and daidzein. Upstream of the nodABC genes in B. japonicum is a novel gene, nodY, which is coregulated with nodABC. Measurements of the activity of lacZ fusions to the nodD gene of B. japonicum show that this gene is inducible by soybean seed extract and selected flavonoid chemicals. The induction of the nodY ABC and nodD operons appears to require a functional nodD gene, indicating that the nodD gene product controls its own synthesis as well as other nod genes.

Quantitative high-resolution microradiographic imaging of amyloid deposits in a novel murine model of AA amyloidosis

The mouse model of experimentally induced systemic AA amyloidosis is long established, well validated, and closely analogous to the human form of this disease. However, the induction of amyloid by experimental inflammation is unpredictable, inconsistent, and difficult to modulate. We have previously shown that murine AA amyloid deposits can be imaged using iodine-123 labeled SAP scintigraphy and report here substantial refinements in both the imaging technology and the mouse model itself. In this regard, we have generated a novel prototype of AA amyloid in which mice expressing the human interleukin 6 gene, when given amyloid enhancing factor, develop extensive and progressive systemic AA deposition without an inflammatory stimulus, i.e., a transgenic rapidly inducible amyloid disease (TRIAD) mouse. Additionally, we have constructed high-resolution micro single photon emission computed tomography (SPECT)/computed tomography (CT) instrumentation that provides images revealing the precise anatomic location of amyloid deposits labeled by radioiodinated serum amyloid P component (SAP). Based on reconstructed microSPECT/CT images, as well as autoradiographic, isotope biodistribution, and quantitative histochemical analyses, the 125I-labeled SAP tracer bound specifically to hepatic and splenic amyloid in the TRIAD animals. The ability to discern radiographically the extent of amyloid burden in the TRIAD model provides a unique opportunity to evaluate the therapeutic efficacy of pharmacologic compounds designed to inhibit fibril formation or effect amyloid resolution.

High-resolution x-ray CT screening of mutant mouse models

A dedicated small animal x-ray computed tomography system has been developed to screen mutagenized mice for anatomical phenotypes. The key components of the data acquisition instrumentation are described along with the system performance parameters. Image reconstruction, visualization and segmentation software algorithms are described. Two contrast media regimens are described and representative studies of mice with adipose, soft and skeletal tissue abnormalities are presented.

Nodulation of Soybean: Bradyrhizobium Japonicum Physiology and Genetics

The establishment of a successful symbiotic association between rhizobia and legumes is a complex process requiring functions of both symbiont and host. The symbiotic relationship resulting from rhizobia-plant interactions is an intimate one requiring close coordination. In addition, rhizobia-host combinations exhibit specificity; particular rhizobia species-host species combinations are favored, others are excluded. The intimacy and specificity of rhizobia-plant interaction suggest the necessity for the exchange of regulatory signal molecules between host and symbiont.

Fibrillogenesis and therapy of amyloidosis: an equilibrium approach

Amyloid diseases are characterized by the deposition of normally soluble proteins as insoluble fibrillar aggregates. In most cases amyloidogenesis is an insidious disease often proceeding undetected for many years. Diagnosis is generally made when the amyloid burden (or precursor protein) reaches a concentration at which it disrupts normal physiological functions. The occurrence of amyloid deposits, their organ distribution and extent is dependent upon numerous physiological factors including: the site and rate of synthesis of the amyloidprecursor protein1–5; posttranslational modification of the precursor6; selective proteolysis7; tissuespecific ‘receptors’ 8,9; the introduction of amyloid-enhancing amino acid mutations10,11, and the inherent stability of the protein’s three-dimensional structure 12–18. At present more than 21 proteins have been identified as clinical constituents of amyloid fibrils19.

Genetics of Host Specific Nodulation by Bradyrhizobium Japonicum

Rapid progress has been made in identifying and characterizing nodulation genes in Bradyrhizobium japonicum. The results of this research indicate that many similarities exist between Bradyrhizobium and the taxonomically distinct Rhizobium spp. However, clear differences are also emerging. Unique nod genes have recently been identified in B. japonicum and further DNA sequence data suggest that this list will grow. Further examination of Bradyrhizobium genetics focusing on these differences will greatly add to and broaden our understanding of the molecular mechanism of (Brady)Rhizobium-plant interaction.

Determinants of Host Specificity in the Bradyrhizobium Japonicum-Soybean Symbiosis

One of the most fascinating, and still largely unexplained, aspects of Rhizobium/Bradyrhizobium- legume interaction is the host specificity exhibited. Investigations of Rhizobium meliloti and R. leguminosarum bv. viciae and trifolii have shown that host specificity is determined by the respective nodD gene as well as unique host specificity genes (reviewed in Long 1989). Against this background of work with various Rhizobium species, comparatively little is known about the determinants of host specificity in Bradyrhizobium species. Clearly, the specificity of the nodD gene product for specific isoflavone inducers from the plant plays an important role in legume infection by Bradyrhizobium (Kosslak et a1 1988; Banfalvi et al 1988). In addition, a few loci have been identified by mutagenesis in Bradyrhizobium that appear to affect nodulation on only particular host species (Bender et al 1987; Nieuwkoop et al 1987; Hahn and Hennecke 1988).

Molecular Genetics of Nodulation of Soybean by Bradyrhizobium Japonicum

The Gram-negative, aerobic, soil bacteria of the root nodule group comprise two taxonomically distinct genera; the fast-growing Rhizobium species and the slow-growing Bradyrhizobium species (1). All species of rhizobia have the ability to infect leguminous plants and establish a nitrogen fixing symbiosis. The genetics of this process has been intensely studied in several fast-growing Rhizobium. The initial interactions of plant and symbiont that lead to establishment of the symbiosis requires at least two sets of genes. One set (nodABCDIJ), the so-called “common” nodulation genes due to their sequence homology between species, encodes functions necessary for the early events of nodulation (2, 3, 4). A second set of genes, nodEFGH, imposes on the plant-symbiont interaction a degree of specificity; these genes determine the host range of the particular rhizobia (5, 6). Induction of the above nodulation genes takes place in response to the presence of the plant. Induction appears to be due to the Rhizobium sensing plant produced flavones (7, 8). Induction also requires that a functional nodD gene be present (7). In addition, Rostas et al. (9) have identified a 47 bp sequence upstream of all the known nodulation genes of R. meliloti that is essential for nod gene induction. This sequence has been termed the Nod Box.