The fate of IgE bound to rat basophilic leukemia cells.

The present study investigates the fate of the cell-bound IgE by using a well-characterized rat basophilic leukemia cell line and a purifed IgE myeloma protein. Both histamine-releasing and nonreleasing cell lines were examined. In both cases, no evidence for cell-mediated IgE catabolism could be elicited. Both the dissociated IgE and the receptors remained intact for prolonged periods of time, as demonstrated by binding assays. Internalization and/or recycling of membrane-bound IgE could not be demonstrated by E. M. autoradiography. We found only limited time-dependent changes in accessibility to anti-IgE antibody, trypsin, or elution at low pH (2.9 to 3.1). A biphasic dissociation of cell-bound 125I-IgE during incubation in the presence of excess unlabeled IgE was reproducibly observed; the more slowly dissociated IgE was also less readily dissociated at pH 3.4. These studies lead us to conclude that, in vitro, IgE resides in a functional orientation on the surface of RBL-1 cells, for prolonged periods of time.     

Linear electric field effect in electron paramagnetic resonance for two bisimidazole--heme complexes, model compounds for B and H hemichromes of hemoglobin and for cytochrome b5.

Bisimidazole-ferric heme is considered to be the structure at the heme site of cytochrome b5 and two different low spin ferric hemochromes spontaneously formed from ferric hemoglobin. The addition of strong base to bisimidazole-ferric heme in organic solvents alters the optical and magnetic properties of this compound. With the use of the linear electric field effect in the electron paramagnetic resonance, we demonstrate that addition of base does not lead to the exchange of hydroxide anion for ligated imidazole and that the bisimidazole structure is retained. Analysis of optical titrations indicates that 2 equiv of base react reversibly with bisimidazole-ferric heme. It is suggested that the two hemichromes formed from hemoglobin differ in structure from one another by the state of protonation of N-1 in the bound imidazoles.     

Brucella abortus in coyotes. I. A serologic and bacteriologic survey in eastern Texas.

Prevalence of Brucella abortus serum antibodies in coyotes from east central Texas was determined by the buffered Brucella antigen (card test), rivanol, standard agglutination tube, and cold complement fixation tube tests. Eighteen percent (9 of 51) of the coyotes were positive serologically. B. abortus biotype 1 was isolated from various tissues from 7 of 43 coyotes by bacteriologic culture. Congenital transmission was found.     

Assignment of a ligand in stellacyanin by a pulsed electron paramagnetic resonance method.

The electron spin echo decay envelope for the blue copper protein, stellacyanin, and for a number of other Cu(II) complexes has been studied. Particular attention was given to the form of the "nuclear modulation" patterns, which show the effects of coupling between the electron spin and the neighboring nuclei. The envelopes for the hydrated cupric complex and for copper(II) glycylglycine were essentially the same and indicative of the coupling to protons. The peptide complex contains nitrogen nuclei coupled directly to Cu(II), but the coupling constant is so large for these nuclei that a modulation pattern ascribable to 14N is not seen. For copper(II) bovine serum albumin, on the other hand, a contribution due to the coupling of the remote nitrogen belonging to a histidyl imidazole ligand was observed. The modulation pattern for this complex and for stellacyanin closely resembled one another, strongly suggesting that an imidazole is ligated to the copper in this blue protein.     

Characteristics of sperm acrosin-like activity of paddlefish (Polyodon spathula Walbaum)

Spermatozoa of paddlefish and sturgeon fishes (Acipenseriformes), unlike teleost fish, have an acrosome. The objectives of this study were to characterize acrosin-like activity of cryopreserved sperm of paddlefish (Polyodon spathula) and to test and compare stability of paddlefish acrosin-like activity with that of lake sturgeon and bull spermatozoa. Mean acrosin-like activity of cryopreserved paddlefish sperm was 0.372 +/- 0.067 microU/10(6) spermatozoa. This activity was 79% higher in the whole semen than in spermatozoa. Highest activity was recorded at pH 8.0 and 8.5. Triton X-100, zinc ions and 4'-acetamidophenyl 4-guanidinobenzoate (AGB) inhibited the activity. Amidase activity was also inhibited by N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK). TLCK at concentrations of 0.1 and 1.0 mM gave a significant decrease in activity of 19 and 61%, respectively. However, TPCK significantly inhibited amidase activity (by 19%) only at concentration 1.0 mM. After acidification and 60 min incubation at 4 degrees C of sperm suspensions only 4% of the activity was retained. A similar phenomenon was observed in the case of lake sturgeon but not bull sperm. These results suggest that trypsin-like activity of Acipenserid fish resembles rather fish trypsin that mammalian one. In frozen-thawed paddlefish sperm a minute chymotrypsin-like activity was also indicated, when GPNA was used as substrate. This activity amounted to 0.0415 +/- 0.0138 microU/10(6) spermatozoa and was 18% of total amidase activity. This suggests that chymotrypsin-like activity may also be present in paddlefish spermatozoa.     

Calcium bioavailability and kinetics of calcium ascorbate and calcium acetate in rats

The objective was to investigate the bioavailability and mechanism of calcium absorption of calcium ascorbate (ASC) and calcium acetate (AC). A series of studies was performed in adult Sprague-Dawley male rats. In the first study, each group of rats (n = 10/group) was assigned to one of the five test meals labeled with (45)Ca: (i) 25 mg calcium as heated ASC or (ii) unheated ASC, (iii) 25 mg calcium as unheated AC, (iv) 3.6 mg Ca as unheated ASC, or (v) unheated AC. Femur uptake indicated better calcium bioavailability from ASC than AC at both calcium loads. A 5-min heat treatment partly reduced bioavailability of ASC. Kinetic studies were performed to further investigate the mechanism of superior calcium bioavailability from ASC. Two groups of rats (n = 10/group) received oral doses of 25 mg Ca as ASC or AC. Each dose contained 20 micro Ci (45)Ca. Two additional groups of rats (n = 10/group) received an intravenous injection (iv) of 10 micro Ci (45)Ca after receiving an unlabeled oral dose of 25 mg calcium as ASC or AC. Sequential blood samples were collected over 48 hrs. Urine and fecal samples were collected every 12 hrs for 48 hrs and were analyzed for total calcium and (45)Ca content. Total calcium and (45)Ca from serum, urine, and feces were fitted by a compartment kinetics model with saturable and nonsaturable absorption pathways by WinSAAM (Windows-based Simulation Analysis and Modeling). The difference in calcium bioavailability between the two salts was due to differences in saturable rather than passive intestinal absorption and not to endogenous secretion or calcium deposition rate. The higher bioavailability of calcium ascorbate was due to a longer transit time in the small intestine compared with ASC.     

Effect of Immune Reconstitution on the Incidence of HIV-Related Hodgkin Lymphoma

Background

The incidence of Hodgkin lymphoma (HL) has increased since introduction of combined antiretroviral therapy (cART). While HIV-related HL is highly associated with EBV, the causes underlying the rising incidence remain unclear. The aim of this study was to evaluate the effect of immune reconstitution on HL incidence among a cohort of HIV-infected male veterans ever receiving cART.

Methods

We performed a retrospective cohort study utilizing data from the Veterans Affairs HIV Clinical Case Registry from 1985-2010. HL cases were identified using ICD-9 codes (201.4-9). Poisson regression was conducted to evaluate relationships between cART-related immunologic measures (e.g., nadir CD4 before cART, time-updated CD4, % time undetectable HIV RNA) and HL incidence. Additionally, we examined CD4 change after cART initiation.

Results

31,056 cART users contributed 287,256 person-years and 196 HL cases (IR=6.8/10,000 person-years). Rate of CD4 increase after cART was worse among HL cases than non-cases (p<0.05). In multivariate regression, HL risk was elevated among veterans with recent CD4 200-350 cells/µL (IRR=1.67, 95%CI=1.16-2.40) and <200 cells/µL (IRR=1.61, 95%CI=1.09-2.39), compared to >350 cells/µL. HL risk was lower among veterans with >80% time undetectable HIV RNA (IRR=0.57, 95%CI=0.35-0.92) and 40-80% undetectable (IRR=0.68, 95%CI=0.47-0.99), compared to <40% undetectable. HL risk was higher in the first 12 months (IRR=2.02, 95%CI=1.32-3.10) and 12-24 months (IRR=1.75, 95%CI=1.16-2.64) after cART initiation, compared to >36 months.

Conclusion

These data highlight immunosuppression and poor viral control may increase HL risk, specifically during immune reconstitution in the interval post cART initiation. Findings suggest an immune reconstitution type mechanism in HIV-related HL development.