228Th retention and dosimetry in beagles

Total-body and skeletal retention of 228Th were determined in a group of 104 young adult male and female beagles for about the first 7 years after the injection of 0.00159 to 2.76 muCi/kg. Ratios of 224Ra / 228Th , 212Pb / 228Th , and 212Bi / 228Th in the skeleton and in soft tissues of 20 beagles were measured as a function of time after injection. A humerus, femur, and ulna from 20 dogs dying 7 to 554 days after injection were sectioned, and the 228Th concentration was obtained for each piece. Percentage biological retention in the skeleton of 228Th at t days after injection could be described as 68.1 e-0. 000180t . Ratios of daughter-to-parent activity in soft tissue showed no definite trend with dose level or time and averaged Ra/Th = 0.56, Pb/Th = 0.83, and Bi/Th = 0.91, whereas the ratios for the skeleton varied with both dose level and time. Ratios of activity in the skeleton from lowest to highest dose level after 2 years following injection ranged between Ra/Th = 0.88 to 0.95, Pb/Th = 0.78 to 0.92, and Bi/Th = 0.77 to 0.90. Retained 228Th was deposited most heavily in parts of the skeleton with much trabecular bone, much bone surface area, and high bone remodeling rates. No changes in this deposition pattern could be discerned during the 554 days over which the measurements of sectioned long bones were made.     

Logical elements in living cells

Recognition processes with enhanced accuracy (as performed by structures like enzymes or ribosomes) are investigated using elementary ideas of statistical mechanics and related concepts of thermodynamics. The analysis starts from a formal definition of recognition and provides a correspondence with appropriate physical properties of the macromolecular logical elements. Transitions of the recognizing system between different modifications are a necessary feature of a more exacting recognition process. Rearrangement steps provide the process with higher accuracy by performing two physical operations: (1) rearranging the phase space of the system so that the "correct" states be better separated from the "wrong" states and the probability of occupation of the "correct" states be enhanced, (2) directing the process toward the more favourable modifications thus formed. Both operations are related to changes in the physical properties of the recognizing system. These changes can be expressed as differences of macromolecular Gibbs energy levels; if ligand binding or release participate in a step, directivity of the step depends also on the actual chemical potentials of the ligands in solution. The two operations just mentioned resemble two basic operations known to be necessary in electronic digital networks: directivity of control and signal standardization. An analysis of the entire reaction catalysed by a macromolecular logical element takes into account the requirements imposed by the logical functions as well as the need that the chemical potential of the product be not restricted to very low values. To satisfy these conditions, the reaction must be supported by a so-called non-specific reaction, usually implemented by the cleavage reaction of a nucleoside triphosphate.     

Specific parameters for the calculation of dose after aerosol inhalation of transuranium elements

A review on specific parameter measurements to calculate doses per unit of incorporation according to recommendations of the International Commission of Radiological Protection has been performed for inhaled actinide oxides. Alpha activity distribution of the particles can be obtained by autoradiography analysis using aerosol sampling filters at the work places. This allows us to characterize granulometric parameters of "pure" actinide oxides, but complementary analysis by scanning electron microscopy is needed for complex aerosols. Dissolution parameters with their standard deviation are obtained after rat inhalation exposure, taking into account both mechanical lung clearance and actinide transfer to the blood estimated from bone retention. In vitro experiments suggest that the slow dissolution rate might decrease as a function of time following exposure. Dose calculation software packages have been developed to take into account granulometry and dissolution parameters as well as specific physiological parameters of exposed individuals. In the case of poorly soluble actinide oxides, granulometry and physiology appear as the main parameters controlling dose value, whereas dissolution only alters dose distribution. Validation of these software packages are in progress.     

Familial hyperlipoproteinemia in beagles

Canine serum lipoproteins (Lp) were studied by electrophoretic and immunologic techniques. Two of five normal beagles on a regular diet were spontaneously “hyperlipidemic”.Using the double-layer separating gel, polyacrylamide gel (PAG) block electrophoresis method, α₁-, α₂-, and β-Lps were consistently detected. While α₁-Lp was the major serum Lp in normolipidemic dogs, α₂- and β-Lps were elevated in the “hyperlipidemic” animals. The α₁-Lp and α₂-Lp exhibited A₁ and A₂ antigenic components and β-Lp had B and C components. We propose that in all probability α₁- and α₂-Lp have similar A₁, A₂ components, but that β-Lp contains both B and C components. This suggests that α₁- and α₂-Lps, particularly in beagles with familial hyperlipoproteinemia are distinct Lp entities with similar lipid composition and with two common major antigenic components. The albumin fraction of PAG block electrophoretograms contained lipid materials other than free fatty acids. This albumin-lipid complex may be similar to that observed in guinea pig serum. On the basis of this study, the α₂-Lp of dogs is a distinct and important Lp moiety which is elevated in the early stages of both familial and experimental canine hyperlipoproteinemia.     

Nuclear retention elements of U3 small nucleolar RNA

The processing and methylation of precursor rRNA is mediated by the box C/D small nucleolar RNAs (snoRNAs). These snoRNAs differ from most cellular RNAs in that they are not exported to the cytoplasm. Instead, these RNAs are actively retained in the nucleus where they assemble with proteins into mature small nucleolar ribonucleoprotein particles and are targeted to their intranuclear site of action, the nucleolus. In this study, we have identified the cis-acting sequences responsible for the nuclear retention of U3 box C/D snoRNA by analyzing the nucleocytoplasmic distributions of an extensive panel of U3 RNA variants after injection of the RNAs into Xenopus oocyte nuclei. Our data indicate the importance of two conserved sequence motifs in retaining U3 RNA in the nucleus. The first motif is comprised of the conserved box C' and box D sequences that characterize the box C/D family. The second motif contains conserved box sequences B and C. Either motif is sufficient for nuclear retention, but disruption of both motifs leads to mislocalization of the RNAs to the cytoplasm. Variant RNAs that are not retained also lack 5' cap hypermethylation and fail to associate with fibrillarin. Furthermore, our results indicate that nuclear retention of U3 RNA does not simply reflect its nucleolar localization. A fragment of U3 containing the box B/C motif is not localized to nucleoli but retained in coiled bodies. Thus, nuclear retention and nucleolar localization are distinct processes with differing sequence requirements.     

Distribution of elements in rabbit liver lobule

The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P, S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam application to biological materials were also discussed.     

Nonteratogenicity of captan in beagles.

Thirty and 60 mg/kg captan, administered in the diet during the entire gestation period or during gestation and an 8-week lactation period, caused no adverse effects in either mothers or progeny, and captan is thus judged to be nonteratogenic in beagles.     

Cytochrome P450 in living donor liver transplantation

Cytochrome P450 metabolizes many drugs in the liver. Three genotypes of CYP2C19 with extensive, intermediate, and poor metabolizing activity, respectively, have been identified in peripheral blood of transplant recipients and new liver grafts in living donor liver transplantation (LDLT). The expression of the final genotype in liver graft biopsies depends on the donor, whereas the expression in peripheral blood mononuclear cells depends on the recipient. The metabolizing isoenzyme of the major anti-rejection agents passes through CYP3A4, CYP3A5 and MDR1, which have also been identified to have similar biological characteristics as genotype of CYP2C19 in liver tissue. Recently, pyrosequencing has been used to investigate the expressions of different genotypes in liver grafts in LDLT. This review focuses on recent findings regarding the biological expressions of the CYP2C19, CYP3A4, CYP3A5 and MRD1 genotypes in liver grafts before and after LDLT. The application of pyrosequencing may be beneficial in further research on liver transplantation. Laser capture microdissection of hepatocytes in liver grafts may be a direction for future research.     

Analysis of histone deposition on specific DNA elements in living mammalian cells

DNA replication and repair involve the deposition of newly synthesized histones. After their deposition on a specific locus, histones are extensively modified on their protruding N-terminal tails to restore the histone code corresponding to this locus. These processes require a complex machinery of histone chaperones and histone-modifying enzymes. The precise kinetics of these events and the identity of the factors involved are still not clear. Here we present a technique based on transient expression of tagged histones followed by chromatin immunoprecipitation that allows the detection of newly synthesized histone deposition on specific DNA elements in mammalian cells at high resolution. This strategy could have important applications in chromatin dynamic studies.     

Spontaneous cor pulmonale in laboratory beagles

Right heart failure associated with postmortem evidence of pulmonary hypertension (cor pulmonale) was observed in nearly 1% of the young beagles of a large research colony. During the past 18 years, 176 dogs with cor pulmonale were observed. Most cases occurred between September and April of each year. Nearly equal numbers of males and females were involved, and some siblings were affected. Ninety-six percent of known affected dogs died, and 85% of the deaths occurred by 5 weeks of age. Clinically, most dogs were stunted and exhibited ascites, subcutaneous edema, hypothermia, dyspnea, cyanosis, and systolic murmur. Radiography revealed cardiomegaly, and electrocardiography revealed right axis deviation and an enlarged right atrium. Postmortem evidence of cor pulmonale included subcutaneous edema, ascites, hydrothorax, mediastinal and mesenteric edema, splenomegaly, centrolobular hepatic congestion and necrosis, right ventricular hypertrophy, interstitial pneumonia, and medial hypertrophy of pulmonary arteries and arterioles. The specific cause of the disease was not determined.