Liver disease and compensatory growth: unexpected lessons from genetically altered mice

Over the last decade, several animal models have been established that permit exploration of liver biology and disease. Although these models have been developed using diverse strategies, including transgene targeting, homozygous gene disruption and administration of hepatotoxic chemicals, each approach creates an animal with hepatocyte damage, resulting in an hepatic microenvironment that supports proliferation of healthy hepatocytes. These models have been used to demonstrate: (1) the remarkable ability of adult hepatocytes to clonally proliferate in response to liver growth signals, (2) the effectiveness of transplanted donor hepatocytes in repopulating damaged liver parenchyma, and (3) the feasibility of reconstituting liver with xenogeneic hepatocytes. This paper reviews the development and use of these models, and outlines their potential future application to the study of hepatic stem cells, therapy of liver disease and hepatic toxicology.     

Detection of lead in environmental objects and biologic materials during monitoring]

The authors specified methods to detect lead in biologic materials. The quality control covered use of Russian and foreign standard samples, the results proved to agree. Lead was detected by AAS technique (direct and flow-type variants with preliminary concentration of lead) and ELRA method. The authors determined measurement limits sufficient for analysis of complex biologic materials. The measurement range for lead varied from 0.002 mg/kg (plants) to 3,000 mg/kg (soil); the range of serum lead levels was < 0.5-39 mg/dl.     

Hypermutability of mouse chromosome 2 during the development of x-ray-induced murine myeloid leukemia

In an effort to identify the precise role of a deletion at regions D-E of mouse chromosome 2 [del2(D-E)] during the development of radiation-induced myeloid leukemia, we conducted a serial sacrifice study in which metaphase chromosomes were examined by the G-banding technique. Such metaphase cells were collected from x-irradiated mice during the period of transformation of some of the normal hematopoietic cells to the fully developed leukemic phenotype. A group of 250 CBA/Ca male mice (10-12 weeks old) were exposed to a single dose of 2 Gy of 250-kilovolt-peak x-rays; 42 age-matched male mice served as controls. Groups of randomly selected mice were sacrificed at 20 hr, 1 week, and then at intervals of 3 months up to 24 months after x-irradiation. Slides for cytogenetic, hematological, and histological examination were prepared for each animal at each sacrifice time. An expansion of cells with lesions on one copy of chromosome 2 was evident in 20-25% of treated mice at each sacrifice time. The majority of such lesions were translocations at 2F or 2H, strongly suggesting hypermutability of these sites on mouse chromosome 2. No lesions were found in control mice. The finding leads to the possibility that genomic lesions close to 2D and 2E are aberrants associated with radiation leukemogenesis, whereas a single clone of cells with a del2(D-E) may lead directly to overt leukemia. The data also indicate that leukemic transformation arises from the cumulative effects of multiple genetic events on chromosome 2, reinforcing the thesis that multiple steps of mutation occur in the pathogenesis of cancer.     

Design and synthesis of a series of potent and orally bioavailable noncovalent thrombin inhibitors that utilize nonbasic groups in the P1 position

As part of an ongoing effort to prepare therapeutically useful orally active thrombin inhibitors, we have synthesized a series of compounds that utilize nonbasic groups in the P1 position. The work is based on our previously reported lead structure, compound 1, which was discovered via a resin-based approach to varying P1. By minimizing the size and lipophilicity of the P3 group and by incorporating hydrogen-bonding groups on the N-terminus or on the 2-position of the P1 aromatic ring, we have prepared a number of derivatives in this series that exhibit subnanomolar enzyme potency combined with good in vivo antithrombotic and bioavailability profiles. The oxyacetic amide compound 14b exhibited the best overall profile of in vitro and in vivo activity, and crystallographic studies indicate a unique mode of binding in the thrombin active site.     

Direction determination in the minus-end-directed kinesin motor ncd

Motor proteins of the kinesin superfamily transport intracellular cargo along microtubules. Although different kinesin proteins share 30-50% amino-acid identity in their motor catalytic cores, some move to the plus end of microtubules whereas others travel in the opposite direction. Crystal structures of the catalytic cores of conventional kinesin (a plus-end-directed motor involved in organelle transport) and ncd (a minus-end-directed motor involved in chromosome segregation) are nearly identical; therefore, the structural basis for their opposite directions of movement is unknown. Here we show that the ncd 'neck' made up of 13 class-specific residues next to the superfamily-conserved catalytic core, is essential for minus-end-directed motility, as mutagenesis of these neck residues reverses the direction of ncd motion. By solving the 2.5 A structure of a functional ncd dimer, we show that the ncd neck (a coiled-coil) differs from the corresponding region in the kinesin neck (an interrupted beta-strand), although both necks interact with similar elements in the catalytic cores. The distinct neck architectures also confer different symmetries to the ncd and kinesin dimers and position these motors with appropriate directional bias on the microtubule.     

5-HT1C receptor-mediated phosphoinositide hydrolysis in the rat choroid plexus after chronic treatment with clozapine

Chronic treatment with clozapine (14 days; 10 and 25 mg/kg/day) decreases 5-HT1C receptor density but not affinity in rat choroid plexus measured with [3H]mesulergine. We now report the effects of the same clozapine treatment regimens on the function of 5-HT1C receptors (measured by maximal stimulation of 5-HT1C receptor-mediated phosphoinositide hydrolysis) in relation to receptor changes in rat choroid plexus. Quantitative 5-HT1C receptor autoradiography indicated that chronic clozapine treatment decreased, in a dose-related manner, 5-HT1C receptor binding sites labeled by antagonist ([3H]mesulergine) and agonist ([125I](+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, [125I]DOI) radioligands. However, only the higher dose of clozapine decreased statistically significantly the maximal 5-HT1C receptor-mediated phosphoinositide hydrolysis response. Chronic administration of haloperidol (0.5 mg/kg/day) did not change any of the 5-HT1C receptor parameters. In conclusion, chronic clozapine treatment is able to modulate the function of 5-HT1C receptors. This further strengthens the possibility that 5-HT1C receptors may contribute to some of the atypical effects of clozapine.     

Molecular characterisation of a distinct South African cassava infecting geminivirus

African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV) are whitefly-transmitted geminiviruses (WTGs) which are widespread in cassava in Africa and cause serious yield losses. Recently, a new geminivirus affecting cassava in South Africa (SACMV) has been reported. In this work SACMV was found to have DNA-A and DNA-B components. Comparisons of amino acid sequences of the putative coat protein, and nucleotide sequences of the common region and a 687-bp DNA B fragment of SACMV with other WTGs, showed that SACMV clustered with the Old World subgroup of the Begomovirus genus of geminiviruses. Despite its bipartite nature, SACMV was most closely related to monopartite TYLCVs, but was sufficiently different to justify designating it as a distinct virus. In serological studies, SACMV grouped biologically with EACMV isolates.     

Effect of protein content on low temperature inactivation of the extracellular proteinase from Pseudomonas fluorescens 22F

The formation of cholic acid and chenodeoxycholic acid through cleavage of the side chains of CoA esters of 3alpha,7alpha,12alpha-trihydroxy-5beta-choles tan-26-oic acid and 3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid is believed to occur in peroxisomes. Recently, we found a new peroxisomal enzyme, D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein, and suggested that this bifunctional protein is responsible for the conversion of 3alpha,7alpha,12alpha-trihydroxy-5beta-cholest-2 4-en-26-oyl-CoA and 3alpha,7alpha-dihydroxy-5beta-cholest-24-en-26-oyl-CoA to their 24-oxo-forms. In the present study, the products of this bifunctional protein reaction were analyzed by gas chromatography-mass spectrometry, and the formation of 24-oxo-27-nor-cholestanes was confirmed. Previously, we found a new thiolase in Caenorhabditis elegans, P-44, and suggested that P-44 and sterol carrier protein x, a peroxisomal protein, constitute a second group of 3-oxoacyl-CoA thiolases. The production of cholic acid and chenodeoxycholic acid from the precursors on incubation with the bifunctional protein and sterol carrier protein x or P-44 was confirmed by gas chromatography.     

Right-sided sciatalgia complicating Crohn's disease

Neurological complications of Crohn's disease due to involvement of the extradural space are extremely rare. A 40-yr-old woman with Crohn's disease affecting the terminal ileum presented with a right-sided sciatalgia. The patient did not complain of diarrhea or constipation. The serum fibrinogen and the C-reactive protein were elevated. Magnetic resonance imaging and computed tomography scan of the abdomen and pelvis demonstrated a mass in front of the sacrum up to but not including the first sacral vertebra. Surgical intervention, with resection of 15 cm of terminal ileum, led to the complete resolution of symptoms. In this case, the underlying cause of the neurological symptoms was most likely an infiltration of the right lumbosacral nerve caused by edema and inflammation of the terminal ileum in the vicinity of the presacral space. Unexplained lumbosacral neurological symptoms in a patient with Crohn's disease necessitate a magnetic resonance imaging or computed tomography scan to detect potential neurological compression.