The T cell receptor V alpha 3 gene segment is associated with reactivity to p-azobenzenearsonate

The murine T cell receptor V alpha 3 gene segment is associated with reactivity to p-azobenzenearsonate, as indicated by several independent lines of evidence. First, three out of four arsonate-reactive T cell clones tested (two I-Ad-and one I-Ak-restricted) utilized V alpha 3. Second, bulk splenic cultures enriched for arsonate/H-2d and arsonate/H-2k responsive T cells showed increased expression of V alpha 3 mRNA. Third, a V alpha 3-containing alpha chain (Ar-5: arsonate/I-Ad) transferred arsonate responsiveness to an appropriate recipient T cell (O3: ovalbumin/I-Ad). Fourth, an independently derived V alpha 3-expressing T cell clone (2C: alloreactive to Ld) showed a response to arsonate/Ld. Thus, a V alpha 3 gene segment, in conjunction with at least two different J alpha segments (J alpha 20'(Ar-5) and J alpha pHDS58(2C)) and at least three different beta chains (V beta 2(Ar-5), V beta 6(O3), and V beta 8(2C], confers reactivity to arsonate in association with at least three different MHC proteins (I-Ad, I-Ak, and Ld). We suggest that V alpha 3 encodes a protein sequence with a binding site for the arsonate hapten.     

Hepatocellular Carcinoma in Hepatitis B Surface Antigen Carriers in Eight Institutions

We reviewed records of all persons dying between 1979 and 1986 in eight California institutions for the mentally retarded. Autopsies had been done in 71% of the 1,181 deaths. Nine deaths were due to hepatocellular carcinoma, which invariably developed in carriers of hepatitis B surface antigen (HBsAg) and was fatal within four months of diagnosis. The mean age at death was 32.7 years. The incidence of hepatocellular carcinoma in HBsAg carriers was 140 times greater than in the US population. Persistent hepatitis B infection was probably etiologically related to hepatocellular carcinoma in this population, which is relatively free of exposure to other hepatocarcinogens.     

Selective solubilization of xylan in pulp using a purified xylanase fromTrichoderma harzianum

Summary The specificity of action of a cellulase-free xylanase preparation on pulp fibers was revealed by the composition of the solubilized products after enzyme treatment. The neutral carbohydrates released by the treatment of two hardwood kraft pulps were composed exclusively of xylooligomers. A similar treatment of Solka Floc showed no detrimental effect on the degree of polymerization of the cellulose fibers, as determined by size exclusion chromatographic analysis.     

Metal Ion Interactions with Phosphoenolpyruvate Carboxylase from Crassula argentea and Zea mays

Metal ion interactions with phosphoenolpyruvate carboxylase from the CAM plant Crassula argentea and the C₄ plant Zea mays were kinetically analyzed. Fe²⁺ and Cd²⁺ were found to be active metal cofactors along with the previously known active metals Mg²⁺, Mn²⁺, and Co²⁺. In studies with the Crassula enzyme, Mg²⁺ yielded the highest V_max value but also generated the highest values of K_m(metal) and K_m(pep). For these five active metals lower K_m(metal) values tended to be associated with lower K_m(pep) values. PEP saturation curves showed more kinetic cooperativity than the corresponding metal saturation curves. The activating metal ions all have ionic radii in the range of 0.86 to 1.09 Å. Ca²⁺, Sr²⁺, Ba²⁺, and Ni²⁺ inhibited competitively with respect to Mg²⁺, whereas Be²⁺, Cu²⁺, Zn²⁺, and Pd²⁺ showed mixed-type inhibition. V_max trends with the five active metals were similar for the C. argentea and Z. mays enzymes except that Cd²⁺ was less effective with the maize enzyme. K_m(metal) values were 10- to 60-fold higher in the enzyme from Z. mays.     

Inhibition of macrophage activation by isoquinolinesulfonamides, phenothiazines, and a napthalenesulfonamide

The influence of isoquinolinesulfonamides (H-7 and H-8), phenothiazines(trifluoperazine and fluphenazine), and a naphthalenesulfonamide (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) on stimulated superoxide anion production and phosphatidyl inositol (PI) cycle activity was investigated in the guinea pig alveolar macrophage. All five drugs were able to inhibit superoxide anion production stimulated by n-formyl-nel-leu-phe (FNLP), leukotriene B4 (LTB4), and phorbol-12,13-dibutyrate (PDB). The order of potency was trifluoperazine greater than or equal to fluphenazine greater than H-7 = W-7 greater than H-8. The dose response curves could be shifted to less efficacy by increasing extracellular calcium. By itself, W-7 markedly stimulated 45Ca+2 efflux, fluphenazine and trifluoperazine slightly stimulated 45Ca+2 efflux, while H-7 and H-8 had no effect on 45Ca+2 efflux from macrophages preloaded with 45Ca+2. Consistent with these results, W-7 markedly stimulated PI cycle activity, fluphenazine and trifluoperazine slightly stimulated PI cycle activity, while H-7 and H-8 had no significant effects on PI cycle activity. In addition, W-7 by itself was able to stimulate a weak and short-lived "burst" of superoxide anion production. In order to evaluate whether a site of action of the inhibitors was at protein kinase C and whether protein kinase C was involved in terminating the normally short-lived FNLP- and LTB4-stimulated macrophage activation, fluphenazine and H-7 were used to evaluate the duration of FNLP- and LTB4-stimulated PI cycle activity, at concentrations of the inhibitors that significantly blocked stimulated superoxide anion production. In all cases, FNLP and LTB4 still stimulated PI cycle activity, which still terminated even though protein kinase C was inhibited. These results suggest that all five drugs block protein kinase C, but H-7 was the most specific in its action at protein kinase C, while the phenothiazines and W-7 have multiple sites of action. In addition, these results suggest that protein kinase C may not function to cause the termination of FNLP- and LTB4-stimulated PI cycle activity and subsequent superoxide anion production.     

Evidence for neuropeptide Y mediation of eating produced by food deprivation and for a variant of the Y1 receptor mediating this peptide's effect.

Neuropeptide Y (NPY) elicits eating when injected directly into the paraventricular nucleus (PVN) or perifornical hypothalamus (PFH). To identify the essential regions of the NPY molecule and the relative contributions of Y1 and Y2 receptors, the eating stimulatory potency of NPY was compared to that of its fragments, analogues, and agonists when injected into the PVN or PFH of satiated rats. Additionally, antisera to NPY was injected into the cerebral ventricles (ICV) to determine whether passive immunization suppresses the eating produced by mild food deprivation. Tests with NPY fragments revealed that NPY(2-36) was surprisingly potent, nearly three times more so than intact NPY. In contrast, fragments with further N-terminal deletions were progressively less effective or ineffective, as was the free acid form of NPY. Collectively, this suggests that both N- and C-terminal regions of NPY participate in the stimulation of eating. Tests with agonists revealed that the putative Y1 agonist [Pro34]NPY elicited a strong dose-dependent feeding response, while the putative Y2 agonist, C2-NPY, had only a small effect at the highest doses. Although this suggests mediation by Y1 receptors, the uncharacteristically high potency of NPY(2-36) may additionally suggest that the receptor subtype underlying feeding is distinct from that mediating other responses. Additional results revealed that ICV injection of antisera to NPY, which should inactivate endogenous NPY, produced a concentration-dependent suppression of eating induced by mild food deprivation. This finding, along with published work demonstrating enhanced levels of hypothalamic NPY in food-deprived rats, suggests that endogenous NPY mediates the eating produced by deprivation.     

The modification of a radiation lesion in animals with an aqueous extract of Hypericum perforatum L. 2.]

The preparation Hypericum perforatum L. has been shown to decrease the intensity level of enzymatic and non-enzymatic processes of lipid peroxidation of rat liver microsomes in vitro and in vivo. In the mucus of the this intestine in vivo the increase of the number of non-enzymatic SH-groups is observed. Possible mechanisms of radioprotective action of the preparation is under discussion.     

Reversible inhibition of osteoclastic activity by bone-bound gallium (III).

Gallium(III) is a new therapeutic agent for hypercalcemia. Ga3+ reduces osteoclast action, but how it inhibits the cell's physiology is unknown. In vivo, 7-12 microM Ga(III) reduces calcium release from bone, but surprisingly, 10-100 microM Ga3+ added to isolated avian osteoclasts did not reduce their degradation of L-(5-3H)-proline bone. 3H-proline labels bone collagen specifically, and collagenolysis is an excellent indicator of bone dissolution because collagen is the least soluble component of bone. Ga(III) greater than 100 microM inhibited osteoclasts in vitro, but also killed the cells. To resolve this apparent conflict, we measured 67Ga distribution between bone, cells, and media. Gallium binds avidly but slowly to bone fragments. One hundred micrograms of bone clears 60% of 1 microM gallium from 500 microliters of tissue culture medium, with steady state at greater than 24 h. Osteoclasts on bone inhibited gallium binding capacity approximately 40%, indicating a difference in available binding area and suggesting that osteoclasts protect their substrate from Ga binding. Less gallium binds to bone in serum-containing medium than in phosphate-buffered saline; 30% reduction of the affinity constant suggests that the serum containing medium competes with bone binding. Consequently, the effect of [Ga] on bone degradation was studied using accurately controlled amounts of Ga(III) pre-bound to the bone. Under these conditions, gallium sensitivity of osteoclasts is striking. At 2 days, 100 micrograms of bone pre-incubated with 1 ml of 1 microM Ga3+, with 10 pmoles Ga3+/micrograms bone, was degraded at 50% the rate of control bone; over 50 pM Ga3+/micrograms bone, resorption was essentially zero. In contrast, pre-treatment of bone with [Ga3+] as high as 15 microM had no significant effect on bone resorption rate beyond 3 days, indicating that gallium below approximately 150 pg/micrograms bone acts for a limited time and does not permanently damage the cells. We conclude that bone-bound Ga(III) from medium concentrations less than 15 microM inhibits osteoclasts reversibly, while irreversible toxicity occurs at solution [Ga3+] greater than 50 microM.     

An immunofluorescence study of the effects of ultraviolet radiation on the organization of microfilaments, keratin intermediate filaments, and microtubules in human keratinocytes.

Indirect immunofluorescence microscopy has been used to investigate the ultraviolet (UV) radiation induced disruption of the organization of microfilaments, keratin intermediate filaments, and microtubules in cultured human epidermal keratinocytes. Following irradiation, concurrent changes in the organization of the three major cytoskeletal components were observed in cells incubated under low Ca2+ (0.15 mM) conditions. UV irradiation induced a dose-dependent condensation of keratin filaments into the perinuclear region. This collapse of the keratin network was accompanied by the reorganization of microfilaments into rings and a restricted distribution of microtubules, responses normally elicited by exposure to high Ca2+ (1.05 mM) medium. The UV induced alteration of the keratin network appears to disrupt the interactions between keratin and actin, permitting the reorganization of actin filaments in the absence of Ca2+ stimulation. In addition to the perinuclear condensation of keratin filaments, UV irradiation inhibits the Ca2+ induced formation of keratin alignments at the membrane of apposed cells if UV treatment precedes exposure to high Ca2+ medium. Incubation of keratinocytes in high Ca2+ medium for 24 hours prior to irradiation results in the stabilization of membrane associated keratin alignments and a reduced susceptibility of cytoplasmic keratin filaments to UV induced disruption. Unlike results from investigations with isogenic skin fibroblasts, no UV induced disassembly of microtubules was discernible in irradiated human keratinocytes.