Integumental lesions caused by ectoparasites in a wild population of the side-blotched lizard (Uta stansburiana)

Histopathological effects of ectoparasites on integument were examined for a wild population of the side-blotched lizard Uta stansburiana. These included the trombiculid Neotrombicula californica, the pterygosomatid mite Geckobiella texana; the macronyssid mite Ophionyssus natricis (Macronyssidae) and the ixodid tick Ixodes pacificus. A diffuse inflammatory response occurred at the site of chigger and tick attachment which consisted of histiocyte, heterophil, fibroblast and lymphocyte infiltration that often extended into the dermis. Granuloma formation also was noted. The most prevalent parasite was N. californica which frequently occurred in large aggregations above the eyelids. Ectoparasites were most abundant from February through April.     

Thermodynamics of the disproportionation of adenosine 5'-diphosphate to adenosine 5'-triphosphate and adenosine 5'-monophosphate. I. Equilibrium model

The thermodynamic treatment of the disproportionation reaction of adenosine 5′-diphosphate to adenosine 5′-triphosphate and adenosine 5′-monophosphate is discussed in terms of an equilibrium model which includes the effects of the multiplicity of ionic and metal bound species and the presence of long range electrostatic and short range repulsive interactions. Calculated quantities include equilibrium constants, enthalpies, heat capacities, entropies, and the stoichiometry of the overall reaction. The matter of how these calculations can be made self-consistent with respect to both calculated values of the ionic strength and the molality of the free magnesium ion is discussed. The thermodynamic data involving proton and magnesium-ion binding data for the nucleotides involved in this reaction have been evaluated.     

Co-distribution of annexin VI and actin in secretory ameloblasts and odontoblasts of rat incisor

Summary Annexin VI and actin were detected by immunoblot analysis in the enamel- and dentin-related portions of dental tissues. Annexin VI was found mainly in the particulate fraction whereas actin was detected in both the soluble and particulate fractions. By immunoelectron microscopy, annexin VI antibodies conjugated with colloidal gold were seen to label the mitochondria, the cytosol and the nucleus of secretory ameloblasts and odontoblasts of rat incisor. In the processes of these cell, the plasmalemmal undercoat was labeled. Antiactin antibodies labeled the desmosome-like junctions, the cytosol, and the mitochondria of the cell bodies. Extensive labeling was seen at the periphery of the Tomes' processes and odontoblast processes. These results suggest that annexin VI may play a role in Ca²⁺-regulation in the cell bodies, especially as a calcium receptor protein in the mitochondria. Moreover, annexin VI and actin seem to be co-distributed in secretory processes. Thus, these proteins might be both involved in exocytotic and endocytotic events.     

A high melting structure in DNA distinguishes phases of the cell cycle

Differential scanning microcalorimetry of the nuclei of dividing CHO cells revealed DNA structures that showed structural transitions at 60, 76, 88, and 105 degrees C (transitions I to IV, respectively). In cultures synchronized by isoleucine deprivation the enthalpies of transitions I and II were rather constant throughout the cell cycle. While the sum of the enthalpies of III and IV was nearly constant, the ratio of IV to III varied substantially from one phase of the cycle to another. A high IV:III ratio of 6 characterized G1 while S phase gave a IV:III ratio of about 2. Cells containing metaphase chromosomes also showed a IV:III ratio near 2. The IV:III ratio for CHO cells showed a progressive decrease as the cells were maintained in isoleucine-free medium from 0 to 6 days.     

Mineral-binding proteoglycans of fetal porcine calvarial bone

To provide a more definitive characterization of the hydroxylapatite-associated proteoglycans (HAPG) of bone, proteins were extracted from the mineralized matrix of fetal porcine calvaria with 0.5 M EDTA in the absence of guanidine HCl. The small proteoglycans obtained in the extract were fractionated by gel filtration on Sepharose CL-6B, purified by ion-exchange chromatography on Polyanion matrix (fast protein liquid chromatography), and then separated into three major populations of chondroitin sulfate proteoglycans by chromatography on hydroxylapatite, all in the presence of 7 M urea. Based on immunological and chemical properties, two classes of bone proteoglycan were resolved. In one class (HAPG1), the proteoglycan and specific CNBr-derived peptides cross-reacted with three monoclonal antibodies that recognize different epitopes of the protein core of bovine skin proteodermatan sulfate. The other class of proteoglycan included two species (HAPG2, HAPG3) which were not recognized by these antibodies. In addition, these proteoglycans did not stain with Coomassie Blue R-250 nor with silver stain nor did they bind to nitrocellulose membranes used in Western blots. However, the cationic dye Stains-all stained both HAPG2 and HAPG3; the protein cores of these proteoglycans were stained a characteristic turquoise blue, whereas the protein core of HAPG1 was stained pink. The average Mr values of the bone proteoglycans, from gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis were: HAPG1, 120,000, with a protein core (chondroitinase AC-digested) of 45,000; HAPG2 and HAPG3, 110,000, with protein cores of 37,000-38,000. On 15% polyacrylamide gel electrophoresis, the protein cores of HAPG2 and HAPG3 migrated with an Mr 30,000, while HAPG1 protein core was unchanged (Mr 45,000). Based on amino acid analysis, the protein chains of HAPG2 and HAPG3 appear to be identical, although minor differences in the relative amount of glucosamine were evident. In contrast, the composition of HAPG1 was quite different, with higher relative amounts of hydrophobic and aromatic residues and lower amounts of Asx and Glx. The presence of 360 residues/1,000 of Asx and Glx in HAPG2 and HAPG3 may in part explain the characteristic staining and immunotransfer properties of these proteoglycans. The unique amino-terminal sequence of HAPG2 (Asn-Pro-Val-Ala-Arg-Tyr-Gln), together with the immunological and chemical properties, would indicate that HAPG2 and HAPG3 are novel proteoglycans and, unlike HAPG1, could be unique to mineralized tissues.     

Kinetics of appearance of an early immunoreactive species during the refolding of acid-denatured Escherichia coli tryptophan synthase beta 2 subunit

A reversible acid-denaturation process of the beta 2 subunit of Escherichia coli tryptophan synthase has been set up. The acid-denatured state has been physically characterized: though not in a random-coiled conformation, it is extensively denatured. The renaturation of this denatured state of beta 2 has been observed in a stopped-flow system, in the presence of a monoclonal antibody directed against native beta 2. It is shown that the association occurs very early in the folding of beta 2. The association rate constants of the antibody with the immunoreactive folding intermediate and with native beta 2 are the same (3 X 10(5) M-1.s-1). But at high antibody concentrations the formation of the antigen/antibody complex is rate limited by a rapid (5.4 X 10(-2) s-1) isomerization of refolding beta chains. This isomerization appears to reflect the formation of at least part of the epitope recognized by the antibody during the folding of beta 2. Further conformational adjustments occurring later in the folding pathway would then allow the ultimate structuring of the epitope.     

Evidence for heterogeneity of low-density lipoprotein metabolism in the cynomolgus monkey

Preliminary studies were performed to establish whether there was kinetic heterogeneity in the metabolism of subclasses of low-density lipoproteins (LDL) in the cynomolgus monkey. Previous studies of the effects of inhibition of hepatic triglyceride lipase in this species had shown an increase in the mass of lighter LDL (Sf greater than 9) and a decrease in the mass of denser LDL. LDL (1.019 less than d less than 1.063) were subdivided into two subfractions LDL1 (1.019 less than d less than 1.035) and LDL2 (1.035 less than d less than 1.063) by ultracentrifugation. The lipoproteins in these two fractions could be shown to have different flotation by analytic and isopycnic ultracentrifugation. When tracer amounts of homologous 125I-labeled very-low-density lipoproteins (VLDL) were injected into chow-fed cynomolgus monkeys, apoB radioactivity appeared in LDL1 prior to its appearance in LDL2. [125I]LDL1 injected into the monkey was removed from the LDL1 density subclass with a half-life of 5.5-10.3 h. Much of the radioactivity injected as LDL1 was converted to denser LDL (LDL2). Labeled LDL2 injected into the monkey was not converted to LDL1. Thus, at least two kinetically distinct subpopulations of LDL circulate in the plasma of this species. The lighter LDL is to a large extent a metabolic precursor of the more dense LDL (LDL2).     

Local reproductive tract immunity to sperm-specific lactate dehydrogenase-C4

Immunity to sperm-specific lactate dehydrogenase C4 (LDH-C4) results in reduction of fertility in females. Stimulation of a local mucosal immune response to LDH-C4 in the reproductive tract would guarantee the presence of antibodies at the site of fertilization, which should enhance suppression of fertility. After intrauterine immunization with LDH-C4, SJL/J female mice secrete immunoglobulin (Ig)A antibodies specific for LDH-C4 into their uterine fluids. Furthermore, these animals demonstrate a lower pregnancy rate than controls receiving an intrauterine immunization without LDH-C4. Thus, induction of a local immune response is an effective alternative to systemic immunization for administering a contraceptive vaccine.     

Activating and 'anxiogenic' effects of corticotropin releasing factor are not inhibited by blockade of the pituitary-adrenal system with dexamethasone

Central administration of corticotropin releasing factor (CRF) in rats produces pituitary-adrenal activation and a variety of "anxiogenic-like" effects. The present study was designed to explore the contribution of the peripheral pituitary-adrenocortical axis in mediating these CRF responses. Intraventricularly administered CRF produced suppression of responding in the conflict test and a marked locomotor activation. Neither behavioral effect was altered by the prior administration of dexamethasone in a dose that blocked pituitary-adrenal activation to CRF. These results support the hypothesis that behavioral effects of CRF are mediated by its action at central sites and not via an action on the pituitary-adrenocortical system.     

Light-induced increases in cGMP metabolic flux correspond with electrical responses of photoreceptors

The metabolism of photoreceptor cGMP and the relationship of its light-sensitive regulation to rhodopsin photoisomerization and to the photoreceptor electrical response was examined in isolated, intact rabbit retinas. The dynamics of cGMP metabolism were assessed by measuring the rate of 18O incorporation from 18O-water into the alpha-phosphoryls of the guanine nucleotides. The photoreceptor electrical response was determined by measuring the aspartate-isolated mass receptor potential. Basal cGMP flux in dark-adapted retinas was 33 pmol cGMP X mg protein-1 X s-1 which translates into a metabolic rate in the rod outer segment (ROS) of 1.7 mM/min in ATP equivalents. Photic stimulation increased this flux as much as 4.5-fold. With continuous illumination, increasing intensity caused increments in cGMP metabolic flux to a maximum of 4.5-fold, with corresponding increases in the electrical response over the same 3-log unit intensity range. Tight coupling between activation of guanylate cyclase and phosphodiesterase was indicated by either no changes in cGMP steady state concentrations or relatively small fluctuations represented by increases of 50% at lower light intensities and a 12% decrease at one of the highest intensities. A stoichiometry of about 10,000 molecules of cGMP generated and hydrolyzed per photon absorbed was calculated for the lowest light intensity when the increment in cGMP metabolic flux per photon was maximal. Flashing light caused an increase in flux in proportion to frequency up to 1 Hz and a nearly proportional increase in the voltage time integral of the electrical response up to 0.5 Hz. This indicates that the temporal resolution, or "on"/"off" rate, of the cGMP metabolic response was as fast or faster than the temporal resolution of the electrical response. The concentration of cGMP remained relatively stable in spite of the marked acceleration of cGMP flux that occurred over the 32-fold range of frequencies tested. Taken together these results show that the light-accelerated rate of cGMP synthesis tightly coupled to hydrolysis becomes a primary energy-utilizing system in the photoreceptor and represents a response that fulfills certain of the fundamental criteria required of a metabolic event playing an essential role in phototransduction.