Additional freeze hardiness in wheat acquired by exposure to -3 {degrees}C is associated with extensive physiological, morphological, and molecular changes

Vol. 57, No. 14, 2006,     

A synergistic effect of albumin and fibrinogen on immunoglobulin-induced red blood cell aggregation

Therapeutic administration of immunoglobulins (Ig) has the potential to precipitate thrombotic events. This phenomenon may be explained by red blood cell (RBC) aggregation, which can be potentiated by Ig. The contribution of plasma albumin and fibrinogen to Ig-induced RBC aggregation is unclear. We examined RBC aggregation in three settings: 1) patients receiving therapeutic infusions of Ig; 2) patients receiving plasma supplemented in vitro with Ig; and 3) patients receiving RBC suspensions in standard buffer with varying concentrations of albumin, Ig, and fibrinogen. Ig infusion augmented aggregation of RBCs from patients with normal or high plasma levels of albumin but decreased aggregation in those with lower plasma albumin concentrations. In vitro, RBC aggregation was significantly increased only when all three components, fibrinogen, albumin, and Ig, were present at or above normal concentrations in the suspension but was unaffected when any one of the components was absent from the suspension. Our results suggest a three-way interaction among fibrinogen, Ig, and albumin that synergistically induces RBC aggregation in plasma. Understanding these interactions may help predict clinically important phenomena related to RBC aggregation, such as thrombotic complications of Ig infusion.     

Monozoic cysts of Hepatozoon canis

Small monozoic cysts found in the spleen of dogs infected with Hepatozoon canis are described from naturally and experimentally infected dogs. These forms of H. canis resemble cysts formed by other Hepatozoon species that infect frogs, lizards, and grey squirrels as intermediate hosts. The H. canis cyst stage differs in size and morphology from the large cysts of H. americanum, the second Hepatozoon species known to infect dogs.     

Pleiotropy and heterogeneity in the expression of atherogenic lipoproteins: the IRAS Family Study

OBJECTIVE: Dyslipidemia is an important determinant of coronary disease. Phenotypic correlations between atherogenic lipids are well established, but the contribution of common genetic influences is less clear. METHODS: This study investigates the pair-wise genetic (rhog) and environmental (rhoe) correlations between apoB, LDL-C, HDL-C, and triglyceride (Tg) from Hispanic and African American families of the IRAS Family Study. RESULTS: Heritability estimates (?2) indicate significant genetic effects on apoB (?2=0.46+/-0.05), LDL-C (?2=0.40+/-0.05), HDL-C (?2=0.47+/-0.05), and Tg (?2=0.35+/-0.05) (all p<0.001). Genetic and environmental correlations were strong for apoB-LDL-C (rhog=0.87, rhoe=0.84), apoB-Tg (rhog=0.38, rhoe=0.65), and HDL-C-Tg (rhog=-0.42, rhoe=-0.46). Environmental correlations were strong for apoB-HDL-C (rhoe=-0.40), LDL-C-HDL-C (rhoe=-0.24), and Tg-LDL-C (rhoe=0.33) with weak genetic correlations for these pairs (rhog=-0.09, 0.10, 0.09 respectively). CONCLUSIONS: These results suggest multiple pathways leading to atherogenic dyslipidemia. There are common genetic and environmental influences contributing to variations in apoB and LDL-C as well as apoB and Tg. In addition, the inverse relation between Tg and HDL-C appears to have both genetic and environmental basis. Identifying genes involved in atherogenic dyslipidemia will require careful dissection of the genetic architecture of these pathways.     

Voltage-Dependent Anion Channel Proteins in Synaptosomes of the Torpedo Electric Organ: Immunolocalization, Purification, and Characterization

In this study, we purified and characterized the voltage-dependent anion channel (VDAC) from the Torpedo electric organ. Using immunogold labeling, VDAC was colocalized with the voltage-gated Ca²⁺ channel in the synaptic plasma membrane. By immunoblot analysis, five protein bands in synaptosomes isolated from the Torpedo electric organ cross reacted with two monoclonal anti-VDAC antibody. No more than about 7 to 10% mitochondrial contains could be detected in any synaptosomal membrane preparation tested. This was estimated by comparing the specific activity in mitochondria and synaptosomes of succinate–cytochrome-c oxidoreductase and antimycin-insensitive NADH–cytochrome-c oxidoreductase activities; mitochondrial inner and outer membrane marker enzymes, respectively. [¹⁴C]DCCD (dicyclohexylcarbodiimide), which specifically label mitochondrial VDAC, labeled four 30–35 kDa protein bands that were found to interact with the anti-VDAC antibody. The distribution of the Torpedo VDAC protein bands was different among membranes isolated from various tissues. VDAC was purified from synaptosomes and a separation between two of the proteins was obtained. The two purified proteins were characterized by their single channel activity and partial amino acid sequences. Upon reconstitution into a planar lipid bilayer, the purified VDACs showed voltage-dependent channel activity with properties similar to those of purified mitochondrial VDAC. Amino acid sequence of four peptides, derived from VDAC band II, exhibited high homology to sequences present in human VDAC1 (98%), VDAC2 (91.8%), and VDAC3 (90%), while another peptide, derived from VDAC band III, showed lower homology to either VDAC1 (88.4%) or VDAC2 (79%). Two more peptides show high homology to the sequence present in mouse brain VDAC3 (100 and 78%). In addition, we demonstrate the translocation of ATP into synaptosomes, which is inhibited by DCCD and by the anion transport inhibitor DIDS. The possible function of VDAC in the synaptic plasma membrane is discussed.     

Emergence of Distinct Genotypes of Cryptosporidium parvum in Structured Host Populations

Cryptosporidium parvum is an apicomplexan parasite that infects humans and ruminants. C. parvum isolated from cattle in northeastern Turkey and in Israel was genotyped using multiple polymorphic genetic markers, and the two populations were compared to assess the effect of cattle husbandry on the parasite's population structure. Dairy herds in Israel are permanently confined with essentially no opportunity for direct herd-to-herd transmission, whereas in Turkey there are more opportunities for transmission as animals range over wider areas and are frequently traded. A total of 76 C. parvum isolates from 16 locations in Israel and seven farms in the Kars region in northeastern Turkey were genotyped using 16 mini- and microsatellite markers. Significantly, in both countries distinct multilocus genotypes confined to individual farms were detected. The number of genotypes per farm was higher and mixed isolates were more frequent in Turkey than in Israel. As expected from the presence of distinct multilocus genotypes in individual herds, linkage disequilibrium among loci was detected in Israel. Together, these observations show that genetically distinct populations of C. parvum can emerge within a group of hosts in a relatively short time. This may explain the frequent detection of host-specific genotypes with unknown taxonomic status in surface water and the existence of geographically restricted C. hominis genotypes in humans.     

Neurochemical Evidence for Agmatine Modulation of 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP) Neurotoxicity

Agmatine treatment is known to exert neuroprotective effects in several models of neurotoxic and ischemic brain and spinal cord injuries. Here we sought to find out whether agmatine treatment would also prove to be neuroprotective in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson’s disease. Concomitant daily treatment (intraperitoneal injections) with agmatine (100 mg/kg for 5 days) and MPTP (40 mg/kg for 2 days) exacerbated MPTP-related toxicity as evidenced by a larger reduction in dopamine uptake into striatal synaptosomes (42.4% as compared to 58.3% of control, respectively). In contrast, agmatine treatment commencing after MPTP, produced partial protection (31%) against MPTP dopaminergic toxicity. The findings implicate agmatine in mechanisms regulating MPTP neurotoxicity, but underscore the characteristic neuroprotective efficacy of agmatine when applied after the insult.     

Effect of T-R conformational change on sickle-cell hemoglobin interactions and aggregation

We compare the role of a conformational switch and that of a point mutation in the thermodynamic stability of a protein solution and in the consequent propensity toward aggregation. We study sickle-cell hemoglobin (HbS), the beta6 Glu-Val point mutant of adult human hemoglobin (HbA), in its R (CO-liganded) conformation, and compare its aggregation properties to those of both HbS and HbA in their T (unliganded) conformation. Static and dynamic light scattering measurements performed for various hemoglobin concentrations showed critical divergences with mean field exponents as temperature was increased. This allowed determining spinodal data points T(S)(c) by extrapolation. These points were fitted to theoretical expressions of the T(S)(c) spinodal line, which delimits the region where the homogeneous solution becomes thermodynamically unstable against demixing in two sets of denser and dilute mesoscopic domains, while remaining still liquid. Fitting provided model-free numerical values of enthalpy and entropy parameters measuring the stability of solutions against demixing, namely, 93.2 kJ/mol and 314 J/ degrees K-mol, respectively. Aggregation was observed also for R-HbS, but in amorphous form and above physiological temperatures close to the spinodal, consistent with the role played in nucleation by anomalous fluctuations governed by the parameter epsilon = (T - T(S))/T(S). Fourier transform infrared (FTIR) and optical spectroscopy showed that aggregation is neither preceded nor followed by denaturation. Transient multiple interprotein contacts occur in the denser liquid domains for R-HbS, T-HbS, and T-HbA. The distinct effects of their specific nature and configurations, and those of desolvation on the demixing and aggregation thermodynamics, and on the aggregate structure are highlighted.     

Identification of a gene in the process of being lost from the genus Agrostis

Lineage-specific gene loss is considered one of the processes contributing to speciation and genome diversity. Such gene loss has been inferred from interspecies comparisons of orthologous DNA segments. Examples of intraspecific gene loss are rare. Here we report identification of a gene, designated Crs-1 (creeping specific-1), that appears to be in the process of being lost from heterozygous populations of the species creeping bentgrass (Agrostis stolonifera). The Crs-1 gene encodes a protein with an N-terminal dirigent protein domain and a C-terminal lectin domain and is similar to the maize (Zea mays) beta-glucosidase aggregating factor. Most individual creeping bentgrass plants examined are lacking Crs-1. Some individuals are hemizygous for the Crs-1 locus, indicating major haplotype noncolinearity at that locus. Crs-1 was not detected in several other Agrostis species, indicating it is being lost from the genus. The Crs-1 locus in creeping bentgrass provides a rare example of the evolutionary process of gene loss occurring within a plant species.