A mutation in integrase can compensate for mutations in the simian immunodeficiency virus att site

Sequences at the left terminus of U3 in the left long terminal repeat (LTR) and at the right terminus of U5 in the right LTR are important for integration of retroviral DNA. In the infectious pathogenic molecular clone of simian immunodeficiency virus strain mac239 (SIVmac239), 10 of the 12 terminal base pairs form an imperfect inverted repeat structure (5' TGGAAGGGATTT 3' [nucleotides 1 to 12] and 3' ACGATCCCTAAA 5' [nucleotides 10279 to 10268]). Nineteen different mutant forms of SIVmac239 proviral DNA with changes at one or more of the positions in each of the 12-terminal-base-pair regions were constructed. Viral replication was severely or completely compromised with nine of these mutants. Revertants appeared 40 to 50 days after transfection in two independent experiments with mutant 7, which contained changes of AGG to TAC at positions 5 to 7 in U3 and TCC to GAA at positions 10275 to 10273 in U5. Virus produced at these times from mutant 7 transfection replicated upon reinfection with only a slight delay when compared to the wild type. Sequence analysis of the LTR and integrase regions from infected cultures revealed two predominant changes: G to A at position 10275 in U5 and Glu to Lys at position 136 in integrase. Derivatives of clone 7 in which these changes were introduced individually and together were constructed by site-specific mutagenesis. Each change individually restored replication capacity only partially. However, the combination of both mutations restored replicative capacity to that of the original revertants. These results indicate that changes in integrase can compensate for mutations in the terminal nucleotides of the SIV LTR. The results further indicate that resistance to integrase inhibitors may include both integrase and LTR mutations.

[Sequence of HLA-DQA1 promoter region in the Han people]

Polymorphism of HLA-DQA1 promoter region (QAP) in the Han people has been identified. The results revealed a number of differences, some of which are in the critical class II boxes, and generally conserved in HLA-DQA1 promoter region. The major differences occurred in the X box, Y box and S box. Within the X box, the Hans carry a A at position -111, instead of a G, and a G or a A can be present at position -98. Within the S box, the Hans carry a G at position -131. Within the Y box, position -71 is a A rather than a G. Some single base substitutions have been detected from IDDM patients at the 5'-flanking region of the S box and between X box and Y box. Particularly, the insertion of CCA bases has been identified at the position between -157 and -158 in a IDDM patient. These data suggest that the polymorphism of HLA-DQA1 promoter region may play a role in susceptibility to IDDM.

Effect of recombinant human IL-4 on tryptase, chymase, and Fc epsilon receptor type I expression in recombinant human stem cell factor-dependent fetal liver-derived human mast cells

The effect of recombinant human IL-4 (rhIL-4) on the development of recombinant human stem cell factor-dependent fetal liver-derived mast cells was examined. RhIL-4 attenuates the number of mast cells that develop, preferentially affecting the MC(T) type of mast cell. Cellular levels of tryptase and chymase mRNA normalized to that of glyceraldehyde-3-phosphate dehydrogenase were not appreciably affected. Tryptase mRNA levels peaked at least 2 wk before tryptase protein and before chymase mRNA and protein, indicating that tryptase mRNA expression is an early marker of commitment to a mast cell lineage. In contrast, alpha-tryptase and beta-tryptase mRNA levels increased and decreased in parallel. The most dramatic effect of rhIL-4 was to induce expression of functional surface Fc epsilonRI. Expression was maximal by 21 days with 20 ng/ml of rhIL-4 and reached a plateau by 2 ng/ml of rhIL-4 at 4 wk. Fc epsilonRI+ cells increased modestly when myeloma IgE was added to the developing mast cells, but increased synergistically when both myeloma IgE and rhIL-4 were present together. Delayed addition of rhIL-4 progressively diminished Fc epsilonRI expression, as did withdrawal of rhIL-4 during the first 2 wk of culture. RhIL-4 selectively increased Fc epsilonRI alpha mRNA levels at least 10-fold. Mast cells developed in the presence of rhIL-4 released tryptase when exposed to anti-Fc epsilonRI alpha. In conclusion, induction of functional Fc epislonRI on recombinant human stem cell factor-dependent human fetal liver-derived mast cells by rhIL-4 harmonizes with the well-accepted ability of this cytokine to enhance IgE production by B cells.

Effect of recombinant human IL-4 on tryptase, chymase, and Fc epsilon receptor type I expression in recombinant human stem cell factor-dependent fetal liver-derived human mast cells

The effect of recombinant human IL-4 (rhIL-4) on the development of recombinant human stem cell factor-dependent fetal liver-derived mast cells was examined. RhIL-4 attenuates the number of mast cells that develop, preferentially affecting the MC(T) type of mast cell. Cellular levels of tryptase and chymase mRNA normalized to that of glyceraldehyde-3-phosphate dehydrogenase were not appreciably affected. Tryptase mRNA levels peaked at least 2 wk before tryptase protein and before chymase mRNA and protein, indicating that tryptase mRNA expression is an early marker of commitment to a mast cell lineage. In contrast, alpha-tryptase and beta-tryptase mRNA levels increased and decreased in parallel. The most dramatic effect of rhIL-4 was to induce expression of functional surface Fc epsilonRI. Expression was maximal by 21 days with 20 ng/ml of rhIL-4 and reached a plateau by 2 ng/ml of rhIL-4 at 4 wk. Fc epsilonRI+ cells increased modestly when myeloma IgE was added to the developing mast cells, but increased synergistically when both myeloma IgE and rhIL-4 were present together. Delayed addition of rhIL-4 progressively diminished Fc epsilonRI expression, as did withdrawal of rhIL-4 during the first 2 wk of culture. RhIL-4 selectively increased Fc epsilonRI alpha mRNA levels at least 10-fold. Mast cells developed in the presence of rhIL-4 released tryptase when exposed to anti-Fc epsilonRI alpha. In conclusion, induction of functional Fc epislonRI on recombinant human stem cell factor-dependent human fetal liver-derived mast cells by rhIL-4 harmonizes with the well-accepted ability of this cytokine to enhance IgE production by B cells.

[Studies on the spectral characteristics of argon in a novel microwave plasma enhanced glow discharge source]

This paper describes a investigation about the spectral characteristics of argon in a novel microwave plasma enhanced glow discharge source. In different discharge conditions, such as glow discharge, microwave plasma and microwave plasma enhanced glow discharge, there are different distributions of argon spectral lines.

A role for natural simian immunodeficiency virus and human immunodeficiency virus type 1 nef alleles in lymphocyte activation

A T-lymphoid cell line termed 221 was derived from a rhesus monkey infected with herpesvirus saimiri. Growth of 221 cells was dependent on the addition of interleukin-2 (IL-2) to the culture medium. In the absence of IL-2, 221 cells arrested in G0-G1 but did not die. Simian immunodeficiency virus (SIV) replicated efficiently in IL-2-stimulated 221 cells whether or not the nef gene was present. In the absence of IL-2, nef-containing SIV replicated 8 to 100 times more efficiently in 221 cells than did the same virus lacking nef. nef-containing virus preferentially stimulated the production of IL-2 from 221 cells. HIV-1 nef and v-ras genes, but not the c-ras gene, were shown to substitute functionally for SIV nef when tested as recombinant viruses in this assay system. These results demonstrate a role for natural nef in causing lymphoid cell activation, and they provide a system for delineating the biochemical mechanisms responsible for this activation.

Base-pairings within the RNA pseudoknot associated with the simian retrovirus-1 gag-pro frameshift site

Frameshift and readthrough sites within retroviral messenger RNAs are often followed by nucleotide sequences that have the potential to form pseudoknot structures. In the work presented here, NMR methods were used to characterize the base-pairings and structural features of the RNA pseudoknot downstream of the gag-pro frameshift site of simian retrovirus type-1 (SRV-1) and a functional mutant of the SRV-1 pseudoknot. Evidence is presented that these pseudoknots contain two A-form helical stems of six base-pairs each, connected by two loops, in a classic H-type pseudoknot topology. A particularly interesting feature is that the shorter of the two connecting loops, loop 1, consists of only a single adenosine nucleotide that spans the major groove of stem 2. In this respect, the frameshift-associated pseudoknots are structurally similar to the pseudoknot within the gene 32 mRNA of bacteriophage T2, previously characterized by NMR methods. Despite having similar nucleotide sequences, the solvent exchange rates of the imino protons at the junction of the helical stems in the wild-type and mutant frameshifting pseudoknots differ from each other and from the bacteriophage T2 pseudoknot. The implications of this finding are discussed.

Recombinant human granulocyte-macrophage colony-stimulating factor (CSF), but not recombinant human granulocyte CSF, down-regulates the recombinant human stem cell factor-dependent differentiation of human fetal liver-derived mast cells

The effects of recombinant human granulocyte CSF (rhG-CSF) and recombinant human granulocyte-macrophage CSF (rhGM-CSF) on the recombinant human stem cell factor (rhSCF)-dependent development of human mast cells from fetal liver progenitors were examined. Mast cells were identified by immunohistochemical staining for tryptase and by flow cytometric analysis of surface Kit expression. Only rhGM-CSF affected mast cell development. When rhGM-CSF (1, 10, or 100 ng/ml) and rhSCF (50 ng/ml) were added to cell cultures from day 0, both the percentage and absolute numbers of mast cells were diminished after 4 wk compared with cultures exposed to rhSCF alone. Half of the maximal response was achieved at a dose of rhGM-CSF between 0.1 and 1 ng/ml. The Kit+ cells developing in the presence of rhGM-CSF and rhSCF exhibited an intensity of surface Kit expression comparable to that of cells exposed to rhSCF alone. Also, if the initial exposure to rhGM-CSF was delayed for 1 to 3 wk, attenuation of mast cell development waned. These findings are consistent with uncommitted progenitor cells being diverted to nonmast cell lineages by rhGM-CSF, while cells committed to a mast cell lineage, albeit immature, appear to be resistant to the lineage directives of rhGM-CSF. Exposure of fetal liver cells to rhGM-CSF for 1 to 3 days before addition of rhSCF further diminishes the number of mast cells that develop compared with the simultaneous addition of these growth factors on day 0. Whether administration of rhGM-CSF to humans before or together with rhSCF diminishes the mast cell hyperplasia that occurs with rhSCF alone remains to be determined.

Recombinant human granulocyte-macrophage colony-stimulating factor (CSF), but not recombinant human granulocyte CSF, down-regulates the recombinant human stem cell factor-dependent differentiation of human fetal liver-derived mast cells

The effects of recombinant human granulocyte CSF (rhG-CSF) and recombinant human granulocyte-macrophage CSF (rhGM-CSF) on the recombinant human stem cell factor (rhSCF)-dependent development of human mast cells from fetal liver progenitors were examined. Mast cells were identified by immunohistochemical staining for tryptase and by flow cytometric analysis of surface Kit expression. Only rhGM-CSF affected mast cell development. When rhGM-CSF (1, 10, or 100 ng/ml) and rhSCF (50 ng/ml) were added to cell cultures from day 0, both the percentage and absolute numbers of mast cells were diminished after 4 wk compared with cultures exposed to rhSCF alone. Half of the maximal response was achieved at a dose of rhGM-CSF between 0.1 and 1 ng/ml. The Kit+ cells developing in the presence of rhGM-CSF and rhSCF exhibited an intensity of surface Kit expression comparable to that of cells exposed to rhSCF alone. Also, if the initial exposure to rhGM-CSF was delayed for 1 to 3 wk, attenuation of mast cell development waned. These findings are consistent with uncommitted progenitor cells being diverted to nonmast cell lineages by rhGM-CSF, while cells committed to a mast cell lineage, albeit immature, appear to be resistant to the lineage directives of rhGM-CSF. Exposure of fetal liver cells to rhGM-CSF for 1 to 3 days before addition of rhSCF further diminishes the number of mast cells that develop compared with the simultaneous addition of these growth factors on day 0. Whether administration of rhGM-CSF to humans before or together with rhSCF diminishes the mast cell hyperplasia that occurs with rhSCF alone remains to be determined.

An NMR and mutational study of the pseudoknot within the gene 32 mRNA of bacteriophage T2: insights into a family of structurally related RNA pseudoknots

NMR methods were used to investigate a series of mutants of the pseudoknot within the gene 32 messenger RNA of bacteriophage T2, for the purpose of investigating the range of sequences, stem and loop lengths that can form a similar pseudoknot structure. This information is of particular relevance since the T2 pseudoknot has been considered a representative of a large family of RNA pseudoknots related by a common structural motif, previously referred to as 'common pseudoknot motif 1' or CPK1. In the work presented here, a mutated sequence with the potential to form a pseudoknot with a 6 bp stem2 was shown to adopt a pseudoknot structure similar to that of the wild-type sequence. This result is significant in that it demonstrates that pseudoknots with 6 bp in stem2 and a single nucleotide in loop1 are indeed feasible. Mutated sequences with the potential to form pseudoknots with either 5 or 8 bp in stem2 yielded NMR spectra that could not confirm the formation of a pseudoknot structure. Replacing the adenosine nucleotide in loop1 of the wild-type pseudoknot with any one of G, C or U did not significantly alter the pseudoknot structure. Taken together, the results of this study provide support for the existence of a family of similarly structured pseudoknots with two coaxially stacked stems, either 6 or 7 bp in stem2, and a single nucleotide in loop1. This family includes many of the pseudoknots predicted to occur downstream of the frameshift or readthrough sites in a significant number of viral RNAs.

Changes of plasma tPA and PAI activities in patients with diabetic retinopathy

PURPOSE

To investigate the relationship between the diabetic retinopathy (DR) and the activity of plasma tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI).

METHODS

tPA and PAI activities were measured by chromatogenous substrate assay in plasma samples obtained from patients with and without diabetic retinopathy (n = 42). Retinopathy was determined by stereoscopic color fundus photographs graded according to a modification of Chinese National Fundus Disease Academic Meeting. And 21 sex-age matched normal people were as controls. This study was in a masked fashion.

RESULTS

1. tPA activity was lower and PAI activity was higher in all of diabetic patients than those in controls (P < 0.001); 2. tPA activity was lower and PAI activity was higher in proliferative DR (PDR) subgroup than those in non-DR (NDR) and background-DR (BDR) subgroups (P < 0.01, respectively); 3. there was no significant difference between BDR and NDR subgroups (P > 0.05); and 4. the results also suggested that the severity of DR and duration of diabetes were correlated negatively with the activity of tPA but positively with that of PAI (r = -0.564, -0.416, 0.671, 0.442; P < 0.01, respectively).

CONCLUSIONS

Reduced plasma tPA activity and enhanced PAI activity in diabetic patients, probably is one of the causes for thromboembolic diseases and are related to the severity of DR and duration of diabetes. Therefore, the change and imbalance between activities of plasma tPA and PAI might play a role in developing and progression of DR.

[Expression of FGF-b and C-myc in rats lung tissue affected by hypoxia]

OBJECTIVE

To study FGF's roles in the reconstruction of vascular walls owing to chronic hypoxia.

METHOD

40 SD rats [corrected] were divided into different hypoxia groups and proceeded with various hypoxic intervals. Expression of FGF-b and transcription of c-myc mRNA of the rats [corrected] lung tissues were detected by immunohistochemical method and in situ hybridization.

RESULTS

FGF-b increased obviously in the smooth muscle and advential tissue of pulmonary arteries after 14 days of hypoxia, whereas C-myc mRNA showed overexpression in rats [corrected] lung tissue from 7th to 21st day of hypoxia.

CONCLUSION

(1) Hypoxia may lead to activation of C-myc oncogene and increase of FGF-b expression in lung tissue. (2) FGF-b and C-myc oncogene takes part in reconstruction of pulmonary arterial wall affected by chronic hypoxia.

In vivo phosphorylation of phosphoenolpyruvate carboxylase in guard cells of Vicia faba L. is enhanced by fusicoccin and suppressed by abscisic acid

Plants regulate water loss and CO2 gain by modulating the aperture sizes of stomata that penetrate the epidermis. Aperture size itself is increased by osmolyte accumulation and consequent turgor increase in the pair of guard cells that flank each stoma. Guard cell phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31), which catalyzes the regulated step leading to malate synthesis, is crucial for charge and pH maintenance during osmolyte accumulation. Regulation of this cytosolic enzyme by effectors is well documented, but additional regulation by posttranslational modification is predicted by the alteration of PEPC kinetics during stomatal opening (FEBS Lett. 352, 45-48). In this study, we have investigated whether this alteration is associated with the phosphorylation status of this enzyme. Using sonicated epidermal peels ("isolated" guard cells) preloaded with 32PO4, we induced stomatal opening and guard cell malate accumulation by incubation with 5 microM fusicoccin (FC). In corroboratory experiments, guard cells were incubated with the FC antagonist, 10 microM abscisic acid (ABA). The phosphorylation status of PEPC was assessed by immunoprecipitation, electrophoresis, immunoblotting, and autoradiography. PEPC was phosphorylated when stomata were stimulated to open, and phosphorylation was lessened by incubation with ABA. Thus, we conclude that regulation of guard cell PEPC in vivo is multifaceted; the effects of regulatory metabolites and the activation status of the enzyme are integrated to control malate synthesis. These results, together with the coincident alteration in the kinetics of the enzyme (FEBS Lett. 352, 45-48), constitute the first unequivocal demonstration of regulatory posttranslational modification of a guard cell protein that is specifically implicated in stomatal movements.

[Stability of jingu tongxial pills]

The stability of Jingu Tongxiao Pills was studied on the basis of accelerated destruction and sample-reserving observation at room temperature. According to the changes of tanshinone IIA in the sample, the time of efficacy determined by the two methods is 1.89 and 2.30 years respectively. Based on the analysis of other indices, the effective period is tentatively determined as two years.

Copper metabolism of holstein and jersey cows and heifers fed diets high in cupric sulfate or copper proteinate

Eight Holstein and 8 Jersey primiparous cows (3 d postcalving) and 8 Holstein and 8 Jersey growing heifers were randomly assigned to 1 of 8 treatments in a 2 x 2 x 2 factorial arrangement to compare Cu metabolism between Holsteins and Jerseys and the bioavailabilities of Cu in Cu proteinate and CuSO4. The variables were Holstein or Jersey, Cu supplementation at 5 or 80 mg/kg of DM, and supplements of CuSO4 or Cu proteinate. Jerseys had higher hepatic Cu concentrations than did Holsteins on d 60 (346 vs. 303 micrograms/g of DM). At the high Cu supplementation, hepatic Cu increased more rapidly, and content was higher in Jerseys than in Holsteins by d 60 (520 vs. 439 micrograms/g of DM). On d 0, plasma Cu concentrations were 0.99 and 0.80 microgram/ml, and, on d 60, concentrations were 0.96 and 0.88 microgram/ml for Jerseys and Holsteins, respectively. Overall, serum ceruloplasmin oxidase activity was greater for Jerseys than for Holsteins. Jersey cows and heifers also had greater hepatic Fe (208 vs. 173 micrograms/g of DM) and lower hepatic Zn (82 vs. 91 micrograms/g of DM) than did Holstein cows and heifers at d 60. The bioavailability of Cu in Cu proteinate and CuSO4 was the same. Plasma Cu concentration and ceruloplasmin have limited value as indicators of Cu status and availability to dairy cows and heifers.

A hammerhead ribozyme that cleaves perforin and fas-ligand RNAs in vitro

Polyfunctional ribozymes targeting more than one RNA might be ideal for treatment of diseases caused by the expression of more than one mRNA. This is the case of Graft versus Host Disease, which in the mouse model is due to the action of two proteins responsible for different lytic pathways: perforin and fasligand. We have created a bifunctional ribozyme fusing two antiperforin and antifas-ligand hammerhead ribozymes with a stretch of CA dinucleotides. This bifunctional ribozyme is able to recognize and cleave in vitro perforin and fas-ligand mRNA in a specific and selective fashion, with a catalytic efficiency similar to that of its individual components.

Utilization of copper in copper proteinate, copper lysine, and cupric sulfate using the rat as an experimental model

One hundred twenty male Sprague-Dawley rats, averaging 108.6 g initial body weight, were used in two feeding experiments to evaluate the utilization of Cu in Cu proteinate, Cu lysine, and cupric sulfate. In Exp. 1, 60 rats were randomly assigned to 12 treatments in a 2 x 2 x 3 factorial arrangement of treatments, with Zn supplementation at 0 or 1000 mg/kg diet, Cu supplementation at 5 or 15 mg/kg diet, and Cu form of CuSO4.5H2O, Cu proteinate, or Cu lysine. The purified basal diet contained .81 mg Cu, 20 mg Zn, and 60 mg Fe/kg diet. Experiment 2 was similar to Exp. 1 except Zn was replaced by Fe. In Exp. 1, feed intake of Cu proteinate (15.74 g/d) and Cu lysine (15.74 g/d) treatments was higher (P < .05) than that of CuSO4 (15.33 g/d). Body weight gain and feed intake were increased by high dietary Cu at either requirement or high levels of dietary Zn (P < .05). There were no differences in feed intake or body weight gain among the treatment groups in Exp. 2 (P > .05). The Cu utilization of Cu proteinate and Cu lysine were higher (P < .05) based on the liver Cu content. The rats fed Cu complexes had a higher liver Fe or Zn content (P < .05) than the rats fed CuSO4, suggesting that Cu complexes are absorbed via another mechanism that differs from that of inorganic Cu and does not interfere with Zn and Fe. Spleen Cu content may be a sensitive indicator of Cu status. High dietary Zn decreased Cu utilization, but this effect was overcome by high dietary Cu.

Induction of lymphocyte proliferation and severe gastrointestinal disease in macaques by a nef gene variant SIVmac239

The molecularly cloned virus known as SIVmac239/YEnef causes extensive lymphocyte activation in unstimulated peripheral mononuclear cell cultures and induces an acute disease syndrome in macaque monkeys. Here we describe the histopathological and immunophenotypic changes and viral localization in peripheral lymph nodes, spleen, and gastrointestinal tract (including the gut-associated lymphoid tissue (GALT) in rhesus monkeys inoculated with SIVmac239/YEnet beginning at day 3 postinoculation (pi). The findings are compared with those of rhesus monkeys inoculated with the same dose of parental SIVmac239. Histopathological examination of peripheral lymphoid tissue and GALT demonstrated marked hyperplasia of T-cell-dependent regions and involution of germinal centers as early as day 7 pi. The most striking lesions were multifocal areas of lymphohistiocytic gastroenteritis and colitis. Cellular infiltrates peaked between day 7 and 14 pi and were composed primarily of CD3+ T lymphocytes and HAM-56+ monocyte/macrophages. Many of these inflammatory cells were also strongly immunoreactive for teh nuclear proliferation antigen Ki-67. Despite the presence of severe gastrointestinal pathology by day 7 pi, no significant difference in the numbers of virus-positive cells in the gastrointestinal tract was observed between these animals and SIVmac239-infected animals examined at the same time point. However, the distribution of virus in the gastrointestinal tract was markedly different, with virus localized to lymphoid nodules of GALT in SIVmac239-infected animals and restricted to areas of lymphohistiocytic gastroenteritis and colitis in animals infected with SIVmac239/YEnef. Our data indicate that the acute disease syndrome induced by SIVmac239/YEnef is not simply related to increased viral replication in the gastrointestinal tract but is likely due to inappropriate virus-induced T lymphocyte activation and proliferation in GALT and subsequent mucosal destruction.

Requirements for lymphocyte activation by unusual strains of simian immunodeficiency virus

When residues 17 and 18 in nef of simian immunodeficiency virus strain SIVmac239 were changed from RQ to YE, the resultant virus was able to replicate in peripheral blood mononuclear cell cultures without prior lymphocyte activation and without the addition of exogenous interleukin-2, caused extensive lymphocyte activation in these cultures, and produced an acute disease in rhesus and pigtail macaques (Z. Du, S. M. Lang, V. G. Sasseville, A. A. Lackner, P. 0. Ilyinskii, M. D. Daniel, J. U. Jung, and R. C. Desrosiers, Cell 82:665-674, 1995). These properties are similar to those of the acutely lethal pathogen SIVpbj14 but dissimilar to those of the parental SIVmac239. We show here that the single change of R to Y at position 17 in nef of SIVmac239 is sufficient to confer the full, unusual phenotype. Conversely, the lymphocyte-activating properties of SIVpbj14 were lost by the single change of Y to R at position 17 of nef. The change of R17F or Q18E in SIVmac239 nef did not confer the unusual in vitro properties. Since SIVpbj14 has a duplication of the NF-kappaB binding sequence in the transcriptional control region, we also constructed and tested strains of SIVmac239/Rl7Y with zero, one, and two NF-kappaB binding elements. We found no difference in the properties of SIVmac239/R17Y, either in cell culture or in vivo, whether zero, one, or two NF-kappaB binding sites were present. Thus, tyrosine at position 17 of nef is absolutely necessary for the unusual phenotype of SIVpbj14 and is sufficient to convert SIVmac239 to a virus with a phenotype like that of SIVpbjl4. Multiple NF-kappaB binding sites are not required for the in vitro properties or for acute disease.

Effect of isothermal radiofrequency radiation on cytolytic T lymphocytes

Previous in vitro studies provide evidence that RF electromagnetic radiation modulates proliferation of human glioma, lymphocytes, and other cell types. The mechanism of RF radiation cell proliferation modulation, as well as mechanisms for effects on other cell physiologic endpoints, are not well understood. To obtain insight regarding interaction mechanisms, we investigated effects of RF radiation exposure on interleukin 2 (IL-2) -dependent proliferation of cytolytic T lymphocytes (CTLL-2). After exposure to RF radiation in the presence or absence of IL-2 cells were cultured at various physiological concentrations of IL-2. Treatment effects on CTLL-2 proliferation were determined by tritiated thymidine incorporation immediately or 24 h after exposure. Exposure to 2450 MHz RIF radiation at specific absorption rates (SARs) of greater than 25 W/kg (induced E-field strength 98.4 V/m) induced a consistent, statistically significant reduction in CTLL-2 proliferation, especially at low IL-2 concentrations. At lower SARs, 2450 MHz exposure increased CTLL-2 proliferation immediately after exposure but reduced 24 h postexposure proliferation. RF radiation effects depended on the mitotic state of the cells at the time of exposure. Comparison of the effects of temperature elevation and RF radiation indicated significant qualitative and quantitative differences.

FTIR studies of recombinant human granulocyte-macrophage colony-stimulating factor in aqueous solutions: secondary structure, disulfide reduction and thermal behavior

Fourier transform infrared spectroscopy (FTIR) has been used to investigate the secondary structure, disulfide reduction and thermal behavior of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) in aqueous solutions. The contributions of amino-acid side-chain groups to the amide I bands of rhGM-CSF in H2O and in D2O solutions were carefully scrutinized, as 40% of the total 127 amino-acid residues of rhGM-CSF is side-chain absorptive (asparagine, glutamine, etc.). The FTIR results indicated that rhGM-CSF is composed of 46% alpha-helix, 7% beta-sheet, 23% turn and 24% loop/irregular structures which are in good agreement with the X-ray diffractional data. Reduction of rhGM-CSF with dithiothreitol caused apparent unfolding of the native conformation followed by the time-dependent increase of beta-aggregation bands which arose at 1622 and 1693 cm(-1) in H2O, 1613 and 1684 cm(-1) in D2O solutions. The result also showed that tertiary structure can change independently of the secondary structure. Thermal denaturation of rhGM-CSF took place at 55 to 70 degrees C and the denatured protein adopted an irregular structure as revealed by the FTIR spectra. The thermal denaturation did not show the formation of intermolecular beta-aggregates which is typical of most thermal denatured proteins. Moreover, it is partly reversible, indicating a special thermal stability of rhGM-CSF.

Internalization of Kit together with stem cell factor on human fetal liver-derived mast cells: new protein and RNA synthesis are required for reappearance of Kit

Kit, the receptor for stem cell factor (SCF) and the product of the c-kit proto-oncogene, is expressed on fetal liver-derived mast cell progenitors when cultured with SCF. Decreased levels of Kit on the surface of human fetal liver-derived mast cells after exposure to recombinant human SCF were demonstrated by flow cytometry using the YB5.B8 mAb against Kit. Internalization of Kit along with SCF appears to be the principal means by which Kit is lost from the mast cell surface. Neither the beta 3-integrin CD51/CD61 (alpha v beta 3), nor the beta 1-integrins CD49d,e/CD29 (VLA-4 and -5) appeared to be internalized along with Kit-SCF complexes. Reappearance of Kit on day 28 fetal liver-derived mast cells is complete 3 days after exposure of the cells to SCF and is detectable by 2 days. Recovery requires new protein and new RNA synthesis, because Kit did not reappear if cycloheximide or actinomycin D was added to the cells. No substantial change in total Kit mRNA was detected during the resynthesis period, suggesting that post-transcriptional regulation of Kit production is involved. Internalization of Kit in mast cells exposed to soluble SCF may represent a negative regulatory mechanism for this receptor-ligand interaction and down-regulate mast cell properties such as degranulation to SCF.

Internalization of Kit together with stem cell factor on human fetal liver-derived mast cells: new protein and RNA synthesis are required for reappearance of Kit

Kit, the receptor for stem cell factor (SCF) and the product of the c-kit proto-oncogene, is expressed on fetal liver-derived mast cell progenitors when cultured with SCF. Decreased levels of Kit on the surface of human fetal liver-derived mast cells after exposure to recombinant human SCF were demonstrated by flow cytometry using the YB5.B8 mAb against Kit. Internalization of Kit along with SCF appears to be the principal means by which Kit is lost from the mast cell surface. Neither the beta 3-integrin CD51/CD61 (alpha v beta 3), nor the beta 1-integrins CD49d,e/CD29 (VLA-4 and -5) appeared to be internalized along with Kit-SCF complexes. Reappearance of Kit on day 28 fetal liver-derived mast cells is complete 3 days after exposure of the cells to SCF and is detectable by 2 days. Recovery requires new protein and new RNA synthesis, because Kit did not reappear if cycloheximide or actinomycin D was added to the cells. No substantial change in total Kit mRNA was detected during the resynthesis period, suggesting that post-transcriptional regulation of Kit production is involved. Internalization of Kit in mast cells exposed to soluble SCF may represent a negative regulatory mechanism for this receptor-ligand interaction and down-regulate mast cell properties such as degranulation to SCF.

Thermodynamics of folding of the RNA pseudoknot of the T4 gene 32 autoregulatory messenger RNA

Nucleotides U(-67) to C(-40) at the extreme 5' end of the gene 32 mRNA in bacteriophage T4 have been shown to fold into an RNA pseudoknot proposed to be important for translational autoregulation. The thermal denaturation of three in vitro transcribed RNAs corresponding to the pseudoknot region has been investigated as a function of Mg2+ concentration to begin to elucidate the determinants of the structure and stability of this conformation. T4-35 is a 35-nucleotide RNA containing a 5' G followed by the natural T4 sequence starting with the mature 5' end of the mRNA, nucleotides A(-71) to C(-38). A 32-nucleotide RNA, termed T4-32, contains the native sequence form U(-67) to C(40) with 5'GC and 5'CA single-stranded regions appended to the 5' and 3' ends of the core sequence, respectively. T4-28 contains only the 28 core nucleotides, and the predicted closing U(-67)-A(-52) base pair in stem 1 has been replaced with a phylogenetically allowed G(-67)-C(-52) base pair. Ribonuclease mapping of T4-32 and imino proton NMR experiments of T4-35 show that both sequences adopt a pseudoknotted conformation. At pH 6.9 and 50 mM NaCl, T4-35 and T4-32 RNAs are characterized by a single major melting transition over a wide range of [Mg2+] (0-6 mM). The delta H degree of unfolding for T4-35 and T4-32 shows a large dependence on Mg2+ concentration; the maximum delta H degree occurs at about 2.0 mM Mg2+ with further addition of Mg2+ simply increasing the tm. Investigation of the [Mg2+] dependence of the tm suggests that a net of one Mg2+ ion is released upon denaturation of T4-35 and T4-32 RNAs. Over the entire [Mg2+] range, the delta G degree (37 degrees C) for the folding of T4-35 is consistently 1-1.5 kcal mol(-1) more negative than T4-32 due to a higher stabilization enthalpy for the natural sequence molecule. In contrast to this behavior, T4-28 gives consistently higher tm's but less negative enthalpies and is destabilized (at 37 degrees C) by about 0.5-1.5 kcal mol(-1) relative to T4-32 and by about 2-3 kcal mol(-1) relative to T4-35, depending upon cation concentration. (1)H NMR experiments suggest that, even in the presence of 4.0 mM Mg2+, T4-28 RNA does not adopt a stable pseudoknotted conformation. These data show that the stability of the pseudoknot in the gene 32 mRNA encoded by the 28-nucleotide core sequence is significantly influenced by the number and nature of the immediately adjacent "single-stranded" 5' and/or 3' nucleotides appended to the core structure. These findings are discussed within the context of the structural model for the evolutionarily related phage T2 and T6 gene 32 mRNA pseudoknots presented in the following paper [Du, Z., Giedroc, D. P., & Hoffman, D. W. (1996) Biochemistry 35, 4187-4198].