Drought-Induced Root Pressure in Sorghum bicolor

Root pressure, also manifested as profusive sap flowing from cut stems, is a phenomenon in some species that has perplexed biologists for much of the last century. It is associated with increased crop production under drought, but its function and regulation remain largely unknown. In this study, we investigated the initiation, mechanisms, and possible adaptive function of root pressure in six genotypes of Sorghum bicolor during a drought experiment in the greenhouse. We observed that root pressure was induced in plants exposed to drought followed by re-watering but possibly inhibited by 100% re-watering in some genotypes. We found that root pressure in drought stressed and re-watered plants was associated with greater ratio of fine: coarse root length and shoot biomass production, indicating a possible role of root allocation in creating root pressure and adaptive benefit of root pressure for shoot biomass production. Using RNA-Seq, we identified gene transcripts that were up- and down-regulated in plants with root pressure expression, focusing on genes for aquaporins, membrane transporters, and ATPases that could regulate inter- and intra-cellular transport of water and ions to generate positive xylem pressure in root tissue.

Creatine Supplementation Does Not Prevent the Development of Alcoholic Steatosis

BACKGROUND

Alcohol-induced reduction in the hepatocellular S-adenosylmethionine (SAM):S-adenosylhomocysteine (SAH) ratio impairs the activities of many SAM-dependent methyltransferases. These impairments ultimately lead to the generation of several hallmark features of alcoholic liver injury including steatosis. Guanidinoacetate methyltransferase (GAMT) is an important enzyme that catalyzes the final reaction in the creatine biosynthetic process. The liver is a major site for creatine synthesis which places a substantial methylation burden on this organ as GAMT-mediated reactions consume as much as 40% of all the SAM-derived methyl groups. We hypothesized that dietary creatine supplementation could potentially spare SAM, preserve the hepatocellular SAM:SAH ratio, and thereby prevent the development of alcoholic steatosis and other consequences of impaired methylation reactions.

METHODS

For these studies, male Wistar rats were pair-fed the Lieber-DeCarli control or ethanol (EtOH) diet with or without 1% creatine supplementation. At the end of 4 to 5 weeks of feeding, relevant biochemical and histological analyses were performed.

RESULTS

We observed that creatine supplementation neither prevented alcoholic steatosis nor attenuated the alcohol-induced impairments in proteasome activity. The lower hepatocellular SAM:SAH ratio seen in the EtOH-fed rats was also not normalized or SAM levels spared when these rats were fed the creatine-supplemented EtOH diet. However, a >10-fold increased level of creatine was observed in the liver, serum, and hearts of rats fed the creatine-supplemented diets.

CONCLUSIONS

Overall, dietary creatine supplementation did not prevent alcoholic liver injury despite its known efficacy in preventing high-fat-diet-induced steatosis. Betaine, a promethylating agent that maintains the hepatocellular SAM:SAH, still remains our best option for treating alcoholic steatosis.

Disparate cleavage of poly-(ADP-ribose)-polymerase (PARP) and a synthetic tetrapeptide, DEVD, by apoptotic cells

In the present investigations, we have shown differential cleavage of cellular PARP and a caspase 3-selective synthetic tetrapeptide substrate, Z-DEVD-AFC or Ac-DEVD-AMC using a T lymphoblastoid cell line Jurkat, and its variant clone E6.1(J-E6). Anti-Fas antibody-mediated apoptosis resulted in DNA fragmentation and PARP cleavage in both Jurkat and J-E6 cells. However, unlike Jurkat, J-E6 cells did not cleave a synthetic tetrapeptide substrate efficiently. The failure to cleave the DEVD tetrapeptide by apoptotic J-E6 cells was not due to insufficient expression or processing of caspase 3 in J-E6 cells. Interestingly, when the J-E6 cells were transiently transfected with a cDNA encoding caspase 3, efficient cleavage of Z-DEVD-AFC was achieved. The observations that apoptotic J-E6 cells barely cleaved a synthetic DEVD tetrapeptide, but efficiently cleaved endogenous PARP, potentially at the most preferred DEVD site, suggest that active caspases may have disparate characteristics to recognize substrates presented in different context.

Novel NEMO/IkappaB kinase and NF-kappa B target genes at the pre-B to immature B cell transition

The IkappaB kinase (IKK) signaling complex is responsible for activating NF-kappaB-dependent gene expression programs. Even though NF-kappaB-responsive genes are known to orchestrate stress-like responses, critical gaps in our knowledge remain about the global effects of NF-kappaB activation on cellular physiology. DNA microarrays were used to compare gene expression programs in a model system of 70Z/3 murine pre-B cells versus their IKK signaling-defective 1.3E2 variant with lipopolysaccharide (LPS), interleukin-1 (IL-1), or a combination of LPS + phorbol 12-myristate 13-acetate under brief (2 h) or long term (12 h) stimulation. 70Z/3-1.3E2 cells lack expression of NEMO/IKKgamma/IKKAP-1/FIP-3, an essential positive effector of the IKK complex. Some stimulated hits were known NF-kappaB target genes, but remarkably, the vast majority of the up-modulated genes and an unexpected class of repressed genes were all novel targets of this signaling pathway, encoding transcription factors, receptors, extracellular ligands, and intracellular signaling factors. Thirteen stimulated (B-ATF, Pim-2, MyD118, Pea-15/MAT1, CD82, CD40L, Wnt10a, Notch 1, R-ras, Rgs-16, PAC-1, ISG15, and CD36) and five repressed (CCR2, VpreB, lambda5, SLPI, and CMAP/Cystatin7) genes, respectively, were bona fide NF-kappaB targets by virtue of their response to a transdominant IkappaBalphaSR (super repressor). MyD118 and ISG15, although directly induced by LPS stimulation, were unaffected by IL-1, revealing the existence of direct NF-kappaB target genes, which are not co-induced by the LPS and IL-1 Toll-like receptors.

Receptor-mediated gene delivery to human peripheral blood mononuclear cells using anti-CD3 antibody coupled to polyethylenimine

Gene transfer to primary cells, especially to lymphoid cells, using a nonviral delivery system has been very challenging. In the present studies, we have used a cationic polymer, polyethylenimine (PEI) coupled to an anti-CD3 antibody for achieving receptor-mediated gene delivery to human peripheral blood mononuclear cells (PBMC). Naive, unstimulated PBMC did not express transfected genes, whereas the transgenes were expressed efficiently in PHA activated PBMC. Transiently expressed gene products were detected maximally at 24 and 48 h following transfection. Gene expression was detected until 96 h with a gradual diminution in the signal after 48 h. Receptor-mediated gene delivery was successfully used for freshly isolated, as well as previously frozen lymphocyte samples. The transfections performed using ligands other than anti-CD3 were not as efficient as anti-CD3-PEI. These results suggest that in addition to receptor-mediated endocytosis, signaling subsequent to engagement of the CD3 receptor with anti-CD3-PEI appears to be important for the efficacy of anti-CD3-PEI mediated gene delivery.

Effect of deoxycoformycin and Val-boroPro on the associated catalytic activities of lymphocyte CD26 and ecto-adenosine deaminase

CD26 and ecto-adenosine deaminase (ADA) are found associated on the plasma membrane of T lymphocytes and each possess distinct catalytic activities. CD26 has a proteolytic activity identical to dipeptidylpeptidase IV (DPPIV; E.C. 3.4.14.5), and ecto-ADA (E.C. 3.5.4.4) degrades extracellular adenosine. The cell surface expression of CD26 and ecto-adenosine deaminase (ecto-ADA) is regulated on stimulated T lymphocytes, and ADA binding to CD26 produces a synergistic costimulatory response with T cell receptor activation. This study addresses the potential regulation by allosteric interactions of the catalytic activities of CD26 associated with ecto-ADA, which could define the mechanism of the synergism observed in T cell signaling. Cell lines genetically deficient in ADA, ligands for ADA such as adenosine, and a specific inhibitor of ADA, deoxycoformycin, were used to define the effect of ADA activity on CD26 DPPIV activity and affinity for dipeptide substrate. Conversely, a recombinant Chinese hamster ovary cell line expressing human CD26 with or without a mutation in the DPPIV catalytic domain, and the boronic acid inhibitor Val-boroPro, were used to determine the effect of DPPIV activity on ecto-ADA activity and association with CD26. These studies found no significant allosteric interaction between the catalytic activities of CD26 and ecto-ADA when associated. Therefore, signaling events in T cells involving costimulation with CD26 and ecto-ADA and the synergism observed upon ADA binding to CD26 occur independently of the catalytic activities of these cell surface molecules.

Structure-activity relationships of boronic acid inhibitors of dipeptidyl peptidase IV. 1. Variation of the P2 position of Xaa-boroPro dipeptides

A series of prolineboronic acid (boroPro) containing dipeptides were synthesized and assayed for their ability to inhibit the serine protease dipeptidyl peptidase IV (DPPIV). Inhibitory activity, which requires the (R)-stereoisomer of boroPro in the P1 position, appears to tolerate a variety of L-amino acids in the P2 position. Substitution at the P2 position which is not tolerated include the D-amino acids, alpha,alpha-disubstituted amino acids, and glycine. Specificity against DPPII and proline specific endopeptidase is reported. A correlation between the ability to inhibit DPPIV in cell culture and in the human mixed lymphocyte reaction is demonstrated. A synthesis of prolineboronic acid is reported as well as conditions for generating the fully unprotected boronic acid dipeptides in either their cyclic or acyclic forms.

Solution structures of active and inactive forms of the DP IV (CD26) inhibitor Pro-boroPro determined by NMR spectroscopy

Synthesis of the boronic acid analog of the dipeptide Pro-Pro yields a mixture of diastereomers Pro-L-boroPro and Pro-D-boroPro, one of which is a potent inhibitor [Ki = 16 pM; Gutheil, W. G., & Bachovchin, W. W. (1993) Biochemistry 32, 8723-8731] of dipeptidyl amino peptidase type IV (DP IV), also known as CD26. The structures of both diasteremers are determined here in aqueous solution by means of 1D and 2D NMR of 1H, 13C, and 11B, and force-field calculations, and the inhibitor is proven to have the L-L configuration. At low pH values (approximately 2), both diastereomers are trans with respect to the peptide bond. Populations of proline ring conformers are determined by pseudorotation analysis, using vicinal proton spin-coupling constants obtained by computer analysis of 1D1H NMR spectral fine structure. At neutral pH values, the Pro-boroPro inhibitor of DP IV undergoes slow, reversible inactivation (Gutheil & Bachovchin, 1993). By structural determination of the decomposition products of both diasteromers, the process is shown here to involve formation of a six-membered ring between the residues by means of trans-cis conversion and formation of a B-N bond, producing chiral nitrogen atoms in both cases having the S configuration. Analogy to cyclic dipeptides suggests the new compounds be named cyclo(Pro-L-boroPro) and cyclo(Pro-D-boroPro).

Generation and characterization of an anti-idiotypic antibody specific for intercellular adhesion molecule-1

Intercellular adhesion molecule-1 (ICAM-1) is an inducible ligand for the LFA-1/MAC-1 family of leukocyte adhesion molecules. The results reported herein show that a mouse monoclonal anti-idiotypic antibody, CA3, specific for R6.5 anti-ICAM-1 mAb, shares conformational homology with the original epitope bound by R6.5. The CA3 bound specifically to R6.5 F(ab) fragments and blocked the binding of R6.5 to its ICAM-1 epitope; no CA3 binding was detected to a second anti-ICAM-1 mAb F(ab) fragment nor to control mouse IgG F(ab) fragments. Similarly, the interaction of CA3 with R6.5 was inhibited by sICAM-1. However, CA3 was ineffective in inhibiting CD18-dependent cell aggregation. A rabbit anti-CA3 response (Ab3) further indicated that CA3 is of the Ab2 beta type. Significant binding of anti-CA3 to sICAM-1 was demonstrated and anti-CA3 competed with R6.5 for binding to sICAM-1. Anti-CA3 bound to both soluble and cell-surface-associated ICAM-1. However, unlike R6.5, significant binding both to reduced sICAM-1 and to native sICAM-1 was exhibited by anti-CA3, whereas the binding of R6.5 to reduced sICAM-1 was undetectable.

Interactions of leukocyte integrins with intercellular adhesion molecule 1 in the production of inflammatory vascular injury in vivo. The Shwartzman reaction revisited

We have investigated the role of leukocyte-endothelial cell interactions in a rabbit model of hemorrhagic vasculitis. Microvascular injury was produced in the skin by intradermal injection of Salmonella typhosa endotoxin followed 20 h later by intravenous zymosan, which activates complement. Hemorrhagic necrosis develops in the "prepared" skin sites which is characterized by microthrombi, neutrophil aggregation, platelet and fibrin deposition, and massive extravasation of erythrocytes. Hemorrhage in these Shwartzman-like lesions was quantitated by 99mTc-labeled autologous erythrocytes. Inhibition of the hemorrhagic response was obtained with mAb reactive with ICAM-1 as well as mAb against the leukocyte CD18 when either was administered intravenously just before intravenous zymosan challenge. This observation suggests that an intravascular event occurring in response to complement activation is required for the development of hemorrhagic vasculitis. We hypothesize that agents which successfully prepare the skin for the Shwartzman response after their intradermal injection do so by promoting increased intercellular adhesion molecule 1 (ICAM-1) expression on the vascular endothelium. Activation of complement then induces CD11/CD18 expression on circulating leukocytes thus producing an intravascular CD11/CD18-ICAM-1 (leukocyte-endothelium) adhesion event. Inhibition of intravascular leukocyte-leukocyte aggregation with mAb against CD11b (Mac-1) showed partial inhibition of hemorrhage, while mAb against CD11a (LFA-1) showed no inhibitory activity. This type of cytokine-primed, neutrophil-dependent vascular damage may be a model of human vasculitic processes where microvascular damage is produced in the absence of immune-complex deposition.

The effects of an anti-CD18 antibody (R15.7) in antigen-induced airway hyperresponsiveness (AH) and cell influx in guinea pigs

Aerosol ovalbumin challenge (OA) of sensitized guinea pigs induced airway hyperreactivity (AH) to i.v. acetylcholine (Ach) and serotonin (5-HT) 24 hr post OA. Bronchoalveolar lavage fluid 24 hrs after OA showed increased leukocytes compared to unsensitized unchallenged animals. Treatment with monoclonal antibody R15.7 (3 mg/kg i.v.,) 1 hr prior and 4 hours after OA prevented the induction of AH to Ach but not to 5-HT and reduced influx of leukocytes. We conclude: 1) antigen inhalation induces an increase in AH with an increase in proinflammatory cell influx and 2) treatment with anti-CD18 antibody inhibits cell influx and airway hyperreactivity.

The Shwartzman response: a model of ICAM-1 dependent vasculitis

The local Shwartzman response was produced in rabbits by the intradermal injection of endotoxin, followed 24 h later by intravenous zymosan. Hemorrhagic lesions developed in the prepared skin sites. We quantitated the Shwartzman-induced hemorrhage with autologous 99mTc-erythrocytes. We show that the development of the Shwartzman response depends on both leukocyte membrane CD18 glycoprotein activity as well as the participation of intercellular adhesion molecule-1 (ICAM-1). We discuss the possibility that the common property shared by the agents capable of preparing the skin for the Shwartzman response is the ability to induce ICAM-1 expression.

Binding of the T cell activation monoclonal antibody Ta1 to dipeptidyl peptidase IV

The monoclonal antibodies, Ta1 and IOT15, define T cell activation cell surface markers and have been assigned to the CD26 leukocyte differentiation antigen cluster. Dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5) is an exoaminopeptidase that, among leukocytes, is expressed almost exclusively on activated T cells. Comparative binding studies showed that the Ta1 mAb binds to DPP IV purified from human placenta as well as in extracts of the human YT lymphoid cell line and of CD3 stimulated normal human peripheral blood mononuclear cells. The mAb IOT15 did not bind to DPP IV from any source even upon repeated incubations. Western blot analysis of YT cell extracts revealed that Ta1 and IOT15 bound to distinctly different molecular weight molecules. Immunofluorescent cell surface capping experiments showed that capping of the IOT15 did not alter the surface distribution of the Ta1 fluorescence. The capping results combined with the DPP IV binding results indicate that IOT15 and Ta1 mAb's bind to different, apparently unassociated, molecules on the surface of T cells and that only Ta1 binds the T cell surface enzyme DPP IV.

The effect of anti-intercellular adhesion molecule-1 on phorbol-ester-induced rabbit lung inflammation

The role of the CD18 complex of leukocyte glycoproteins in adhesion-dependent functions of human leukocytes in vitro has been well documented. A ligand, intercellular adhesion molecule-1 (ICAM-1), for at least one member of the CD18 complex has been identified. This molecule is inducible on many cell types including vascular endothelium and keratinocytes by inflammatory mediators such as IL-1, TNF, and IFN-gamma. ICAM-1 has been shown to mediate, in part, the in vitro adhesion of lymphocytes and neutrophils to endothelial cells expressing ICAM-1. In the present study we have shown that mAb's to the human CD18 complex and to human ICAM-1 cross react with rabbit cells and that both anti-CD18 and anti-CD11b but neither anti-CD11a nor anti-ICAM-1 mAb's inhibit neutrophil migration, an adhesion-dependent function, in vitro. Pretreatment of rabbits with anti-CD18 and anti-ICAM-1 but not anti-CD11a mAb inhibited by greater than 60% neutrophil migration into PMA-induced inflamed rabbit lungs. This effect of anti-ICAM-1 mAb on pulmonary neutrophil influx after PMA injection has important implications. Specifically, that ICAM-1 can function as a ligand for CD18 and can mediate, at least in part, the migration of neutrophils to inflammatory sites.

The effect of anti-intercellular adhesion molecule-1 on phorbol-ester-induced rabbit lung inflammation

The role of the CD18 complex of leukocyte glycoproteins in adhesion-dependent functions of human leukocytes in vitro has been well documented. A ligand, intercellular adhesion molecule-1 (ICAM-1), for at least one member of the CD18 complex has been identified. This molecule is inducible on many cell types including vascular endothelium and keratinocytes by inflammatory mediators such as IL-1, TNF, and IFN-gamma. ICAM-1 has been shown to mediate, in part, the in vitro adhesion of lymphocytes and neutrophils to endothelial cells expressing ICAM-1. In the present study we have shown that mAb's to the human CD18 complex and to human ICAM-1 cross react with rabbit cells and that both anti-CD18 and anti-CD11b but neither anti-CD11a nor anti-ICAM-1 mAb's inhibit neutrophil migration, an adhesion-dependent function, in vitro. Pretreatment of rabbits with anti-CD18 and anti-ICAM-1 but not anti-CD11a mAb inhibited by greater than 60% neutrophil migration into PMA-induced inflamed rabbit lungs. This effect of anti-ICAM-1 mAb on pulmonary neutrophil influx after PMA injection has important implications. Specifically, that ICAM-1 can function as a ligand for CD18 and can mediate, at least in part, the migration of neutrophils to inflammatory sites.

A human urine-derived interleukin 1 inhibitor. Homology with deoxyribonuclease I

We have previously reported that the urine of febrile humans contained large quantities of an inhibitor of IL-1-induced murine thymocyte proliferation that was a glycoprotein between 30 and 40 kD in size. In the present study this factor has been purified to homogeneity using a sequence of eight purification steps (ammonium sulfate precipitation, ion exchange chromatography, molecular sieve chromatography, hydrophobic affinity chromatography, hydroxylapatite chromatography, fast protein liquid chromatography, and two HPLC steps). SDS-PAGE analysis indicates that the purified material is a 38-kD molecule. Evidence based on a partial amino acid sequence analysis as well as enzyme studies indicates that this inhibitor is a type of human DNase I.

A model of pulmonary granulomata induced by beryllium sulfate in the rat

In humans beryllium is known to cause pulmonary granulomata which are histologically indistinguishable from sarcoidosis. There is some evidence in man that beryllium-induced pulmonary granulomata are immunologically mediated. We set out to develop an animal model to study the immunopathogenesis of beryllium-induced granulomatous lung disease. Beryllium sulfate (BeSO4) was injected intratracheally (i.t.) into F344 rats previously immunized to BeSO4. This results in well-formed, sarcoid-like lung granulomata at 6 weeks post BeSO4. There was a conspicuous presence at 4 weeks post BeSO4 of numerous, perivascularly located Langhans' giant cells which preceded the development of well-formed granulomas at 6 weeks. Rats were sacrificed at 4, 6, 8 and 12 weeks after i.t. BeSO4. At the time of sacrifice bronchoalveolar lavage (BAL) was performed; B and T (W3/25+ helper 0X8+ suppressor/cytotoxic) lymphocyte populations were quantitated and compared to lymphocyte populations obtained from lung tissue. Both B and T cells were significantly elevated in lung tissue post BeSO4. At 4 weeks when granulomata were just developing, a W3/25+ to 0X8+ ratio of 20:1 in lavage and 2:1 in lung tissue was seen. At 6 weeks when granulomata were well-formed there was a predominance of W3/25+ cells in lavage but not in lung tissue. At 8 and 12 weeks, when the granulomata were regressing, lavage fluid still contained a W3/25+ predominance in contrast to lung tissue which contained a predominance of 0X8+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

A rat model of purine nucleoside phosphorylase deficiency

Purine nucleoside phosphorylase (NP; EC 2.4.2.1) deficiency is associated with selective T-cell dysfunction and normal B-cell immunity. In order to create an in vivo model of this immune deficiency, we administered 8-aminoguanosine to rats. This water-soluble nucleoside was rapidly converted by NP to the more potent inhibitor 8-aminoguanine, which has a Ki of 0.19 microM. The accumulation of inosine in plasma showed that administration of 8-aminoguanosine was effectively inhibiting NP activity. The administration of 8-aminoguanosine with deoxyguanosine produced increased levels of dGTP only in thymus cells, and increased levels of GTP in cells from thymus, spleen and lymph node and in red cells. This correlated with assays of deoxyguanosine kinase, which showed significantly higher activity in thymus cells than in cells from spleen and lymph node. The intraperitoneal injection of 8-aminoguanosine alone or with deoxyguanosine for 8 consecutive days caused significant decreases in the number of thymus cells (P less than 0.001) and in lymph node and spleen lymphocytes (P less than 0.01). These data showed that the administration of 8-aminoguanosine to rats provided an animal model of NP deficiency that will allow studies of the specific regulation of T-cell function.

The effects of an induced adenosine deaminase deficiency on T-cell differentiation in the rat

Inherited deficiency of the enzyme adenosine deaminase (ADA) has been found in a significant proportion of patients with severe combined immunodeficiency disease and inherited defect generally characterized by a deficiency of both B and T cells. Two questions are central to understanding the pathophysiology of this disease: (1) at what stage or stages in lymphocyte development are the effects of the enzyme deficiency manifested; (2) what are the biochemical mechanisms responsible for the selective pathogenicity of the lymphoid system. We have examined the stage or stages of rat T-cell development in vivo which are affected by an induced adenosine deaminase deficiency using the ADA inhibitors, erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) and 2'-deoxycoformycin (DCF). In normal rats given daily administration of an ADA inhibitor, cortical thymocytes were markedly depleted; peripheral lymphocytes and pluripotent hemopoietic stem cells (CFU-S) all were relatively unaffected. Since a deficiency of ADA affects lymphocyte development, the regeneration of cortical and medullary thymocytes and their precursors after sublethal irradiation was used as a model of lymphoid development. By Day 5 after irradiation the thymus was reduced to 0.10-0.5% of its normal size; whereas at Days 9 and 14 the thymus was 20-40% and 60-80% regenerated, respectively. When irradiated rats were given daily parenteral injections of the ADA inhibitor plus adenosine or deoxyadenosine, thymus regeneration at Days 9 and 14 was markedly inhibited, whereas the regeneration of thymocyte precursors was essentially unaffected. Thymus regeneration was at least 40-fold lower than in rats given adenosine or deoxyadenosine alone. Virtually identical results were obtained with both ADA inhibitors, EHNA and DCF. The majority of thymocytes present at Day 9 and at Day 14 in inhibitor-treated rats had the characteristics of subcapsular cortical thymocytes which are probably the most ancestral of the thymocytes. Thus, an induced ADA deficiency blocked the proliferation and differentiation of subcapsular cortical thymocytes which are the precursors of cortical and medullary thymocytes.

Phenotypic heterogeneity of Gross virus-induced thymic lymphomas in the rat: cellular origins and migratory properties

Neoplastic thymocytes from rat thymic lymphoma-leukemias induced by the rat-adapted Gross leukemia virus (RAGV) were analyzed for a variety of differentiation markers. The neoplasms from individual rats all expressed the antigenic phenotype MP+, W3/13+, Thy-1+, RT-1+, RT-7+, W3/25-. However, approximately two-thirds of the neoplasms were positive for the OX 8 antigen, and one-third were negative. The OX 8- neoplasms only involved the thymus, whereas approximately 40% of the OX 8+ neoplasms involved the spleen as well as the thymus. Virtually all OX 8+ and OX 8- neoplastic cells contained terminal deoxynucleotidyl transferase (TdT), and both OX 8+ and OX 8- lymphomas expressed the lactate dehydrogenase (LDH)-5' isozyme and the primary, but not the secondary, ADA isozyme. This enzymatic phenotype is characteristic of thymocyte precursors, but not thymocytes. Our results therefore indicate that RAGV-induced lymphomas arise from transformed prethymic TdT+ cells which contain the LDH-5' and the primary ADA isozymes. These preleukemic cells presumably migrate to the thymus where they express the RT-7 pan-T-cell antigen and, in some instances, the OX 8 antigen during the development of overt leukemia. The OX 8+ neoplasms, being more differentiated than their OX 8- counterparts, then migrate to peripheral lymphoid tissues.

Somatostatin has an antiproliferative effect on concanavalin A-activated rat thymocytes

Somatostatin, a cyclic tetradecapeptide which is widely distributed in different tissues of the body, exerts an inhibitory effect on numerous cellular processes. It has been observed recently that somatostatin and its analogs were antimitogenic in several established cultured cell lines and in rat tumors. To determine whether this ubiquitous peptide had an antiproliferative effect on a primary culture of rat thymocytes, we observed its effect on the separation of the centrosome (a cell maker of the G1 to S traverse) and DNA synthesis of rat thymocytes activated by concanavalin A. Somatostatin inhibited both indices of proliferation in rat thymocytes at a concentration of 10(-8)M. This observation suggests that somatostatin, which has been localized in the thymus, may play a regulatory role in the growth and development of the cells found in the thymus gland, and may affect thymocyte function in disease states characterized by elevated circulating concentrations of somatostatin.

Binding of human lymphocyte-specific monoclonal antibodies to common marmoset lymphoid cells

Commercially available monoclonal antibodies which bind to human lymphocyte subsets were screened for their ability to bind to lymphoid cells from the common marmoset Callithrix jacchus. Anti-Leu-5 and T11 were the only pan T-cell antibodies which reacted strongly. None of the antibodies which bind human lymphocytes of the helper/inducer subpopulation reacted with C. jacchus cells and only one antibody, T8, specific for the cytotoxic/suppressor subset, bound to the marmoset cells. The two antibodies tested which bind human B cells, B1 and anti-HLA-DR, were also reactive with marmoset cells. The cellular specificity of the T11, T8, and B1 antibodies was determined by dual binding studies on the fluorescence-activated cell sorter. The B1 antibody bound only Ig+ cells and all Ig+ cells were B1+. The T11 and T8 antibodies bound only to Ig- marmoset lymphoid cells and, as in the human, all T8+ marmoset cells were also T11+. Thus, using these monoclonal antibodies in the common marmoset one can identify three populations of lymphoid cells: (1) T11+, T8+ cells; (2) T11+, T8- cells; (3) B1+ cells.

A comparison of lymphocyte populations in lung tissue and in bronchoalveolar lavage fluid of rats at various times during the development of bleomycin-induced pulmonary fibrosis

The purpose of this study was to compare lymphocyte populations in lung lavage fluid and in lung tissue during the development of bleomycin-induced pulmonary fibrosis. At various times after bleomycin treatment, animals were killed and lavaged, and lung tissue cells were extracted. Lymphocyte populations were identified by immunofluorescent techniques, using monoclonal antibodies, and quantitated on the fluorescence-activated cell sorter. Normal control rat lung tissue was comprised of 91% T-cells (helper-to-suppressor cell ratio of approximately 1:1) and 9% B-cells. After bleomycin administration, a significant increase in the percentage of B-cells in lung tissue was observed within 3 days, with peak levels (approximately 28%) occurring at 7 days. Changes in the T-cell subset populations were also observed in lung tissue; at 14 days after the administration of bleomycin, the helper-to-suppressor T-cell ratio was 2:1, at 30 and at 120 days, the ratio was reversed to 1:2. These represent significant changes from the 1:1 ratio found in control animals. No lymphocytes were observed in the lavage fluid of control animals or in animals at 30 and 120 days after bleomycin treatment. Significant populations of lymphocytes were found in the lavage fluid at 3, 7, and 14 days after bleomycin treatment. These lymphocytes consisted of approximately 90% T-cells (helper-to-suppressor cell ratio of 1:1) and 10% B-cells. There were no significant changes in the lymphocyte populations found in the lavage fluid after the administration of bleomycin. The results demonstrate that specific lymphocyte populations are changing in lung tissue during the development of the fibrotic process, whereas this shift in populations does not occur in the lymphocyte populations found in lavage fluid.

Anti-idiotypic immunity and autoimmunity. II. Idiotypic determinants of autoantibodies and lymphocytes in spontaneous and experimentally induced autoimmune thyroiditis

In a previous report, it was demonstrated that heterologous anti-idiotypic antibodies to autoantibodies against rat thyroglobulin (ART) were capable of inhibiting the in vitro binding between ART and rat thyroglobulin. It has also been shown that repeated injections of anti-idiotypic antibodies into Buffalo (BUF) rats with spontaneous autoimmune thyroiditis were followed by a significant decrease in the levels of circulating ART. In this report, cross-reacting idiotypic determinants, detectable by rabbit anti-idiotypic antibodies to ART, are shown to also be present on ART from rats with experimentally induced autoimmune thyroiditis. In addition, antibodies to rat thyroglobulin from animals of various strains and species are shown to also express idiotypes cross-reacting with those of spontaneous ART of BUF rats. Finally, it is reported that idiotypic determinants similar to those of circulating ART are present on spleen lymphocytes from rats with autoimmune thyroiditis.

Identification of thymocyte progenitors in hemopoietic tissues of the rat. II. Enrichment of functional prothymocytes on the fluorescence-activated cell sorter

A quantitative thymocyte regeneration assay was used to monitor the isolation of functional prothymocytes from rat bone marrow on the FACS. Two prothymocyte subpopulations were tentatively identified on the basis of their relative resistance to dexamethasone. Both populations were comprised of undifferentiated, medium-size cells that displayed large amounts of Thy-1 antigen. Simultaneous sorting of bone marrow cells according to relative low angle light scatter (size) and relative fluorescence intensity for Thy-1 resulted in enrichments of 112-fold and 260-fold, respectively, in prothymocyte activity in untreated and dexamethasone-treated bone marrow. These prothymocyte-enriched cell fractions contained or approximately 75% of total functional prothymocyte activity in bone marrow, and represented 1.1 and 0.35% of total untreated and dexamethasone-treated bone marrow cells. Using these enriched cell fractions, significant thymocyte regeneration is possible with as few as 2 X 10(4) and 1 X 10(4) bone marrow cells, respectively. The possible relationship of these functional prothymocyte subpopulations with CFU-S and with TdT-positive cells is discussed.

Differential cellular analysis of bronchoalveolar lavage fluid obtained at various stages during the development of bleomycin-induced pulmonary fibrosis in the rat

The purpose of this study was to analyze the cellular components of bronchoalveolar lavage fluid throughout the development of bleomycin-induced pulmonary fibrosis in the rat. Animals were killed and lavaged at various times after the administration of a single intratracheal injection of bleomycin. The results demonstrate that a significant influx of inflammatory cells appear in the lavage fluid as early as Day 1 after bleomycin treatment. Polymorphonuclear leukocytes are the first cells to appear and significant concentrations persist for as long as 1 month after bleomycin treatment. There is a very transient yet significant influx of eosinophils on Day 7 after bleomycin treatment. Lymphocytes are present from 3 to 14 days after bleomycin treatment; greater than 97% are T-cells and less than 3% are B-cells. There is a 1:1 ratio of W3/25+ cells (helper cell activity) to OX8+ cells (suppressor cell activity) comprising the lymphocyte population. The blood and lymphoid tissue of these animals contain a normal 2:1 ratio of these subsets. The data demonstrate that specific T-cell populations are present in the air spaces of the lung in response to bleomycin-induced pulmonary fibrosis in this model.

Genetic linkage and cell distribution analysis of T cell alloantigens in the rat

The T cell alloantigens A.R.T.-1, A.R.T.-2, Pta, Ag-F and RT-Ly-2 were examined for linkage to albinism and the haemoglobin variant Hbb, and for cell expression similarities in the rat. The A.R.T.-1 alloantigen was not linked to either A.R.T.-2, albinism or Hbb. The A.R.T.-2 alloantigen was demonstrated to be closely associated to albinism and Hbb with a recombination frequency of approximately 3% with albinism and 1% with Hbb. The four recombinants (out of 104 animals examined) were subsequently analysed with alloantisera to Ag-F, Pta and RT-Ly-2. These alloantisera detected an antigenic system(s) which appeared to co-segregate with A.R.T.-2 in the recombinants studied Characterization of the specific T cell populations expressing each alloantigen demonstrated that removal of the cells bearing any one of the alloantigens removed all the cells expressing any of the other alloantigens. These results demonstrate that the four alloantigenic systems A.R.T.-2, Pta, Ag-F and RT-Ly-2 are located in the same genetic region of linkage group I, and appear to be expressed on the same peripheral T cell subpopulation(s) in the rat.

Evidence for the cellular origin of Gross virus-induced leukemia in the rat: description of a unique LDH isozyme sub-band in leukemic lymphoid cells and lymphohemopoietic precursor cells

Neoplastic thymocytes from rat thymic lymphoma-leukemias induced by the rat-adapted Gross-leukemia virus (RAGV) were analyzed for a variety of differentiation markers to define their differentiation state and possible cellular origin. A majority of thymocytes from leukemic rats had the phenotypic characteristics of subcapsular cortical thymocytes that are the most ancestral of the thymocytes. These cells exhibited readily detectable levels of Thy-1 and histocompatibility antigens on their surfaces, they contained terminal deoxynucleotidyl transferase (TdT) and they contained low adenosine deaminase (ADA) and high purine nucleoside phosphorylase (PNP) specific activity. The leukemic thymocytes also contained a sub-band of the LDH-5 isozyme (LDH-5') that was not detected in normal thymocytes but that was present in lymphocyte-rich fractions of postnatal bone marrow, fetal and prepubertal spleen, and fetal and neonatal liver. The tissue distribution and ontogeny of LDH-5'-containing cells is similar to prethymic TdT+ cells in the rat and both TdT and LDH-5' are enriched in a subset of bone marrow "null" cells. These results suggest that TdT+ thymocyte progenitors or their precursors are the targets of leukemic transformation of RAGV.

Evidence for the cellular origin of Gross virus-induced leukemia in the rat: description of a unique LDH isozyme sub-band in leukemic lymphoid cells and lymphohemopoietic precursor cells

Neoplastic thymocytes from rat thymic lymphoma-leukemias induced by the rat-adapted Gross-leukemia virus (RAGV) were analyzed for a variety of differentiation markers to define their differentiation state and possible cellular origin. A majority of thymocytes from leukemic rats had the phenotypic characteristics of subcapsular cortical thymocytes that are the most ancestral of the thymocytes. These cells exhibited readily detectable levels of Thy-1 and histocompatibility antigens on their surfaces, they contained terminal deoxynucleotidyl transferase (TdT) and they contained low adenosine deaminase (ADA) and high purine nucleoside phosphorylase (PNP) specific activity. The leukemic thymocytes also contained a sub-band of the LDH-5 isozyme (LDH-5') that was not detected in normal thymocytes but that was present in lymphocyte-rich fractions of postnatal bone marrow, fetal and prepubertal spleen, and fetal and neonatal liver. The tissue distribution and ontogeny of LDH-5'-containing cells is similar to prethymic TdT+ cells in the rat and both TdT and LDH-5' are enriched in a subset of bone marrow "null" cells. These results suggest that TdT+ thymocyte progenitors or their precursors are the targets of leukemic transformation of RAGV.

Nucleotide-metabolizing enzymes and lymphocyte differentiation

Inherited deficiencies of adenosine deaminase and purine nucleoside phosphorylase have been found to be associated with certain immunodeficiency syndromes which are characterized by deficiencies of mature peripheral lymphocytes. The immunodeficiency states associated with these enzyme deficiencies are thought to arise from blocks in lymphocyte differentiation. Deficiencies of these enzymes have profound and apparently selective effects on lymphocyte differentiation. Their discovery has focused attention on previously unknown relationships between purine nucleotide metabolism and lymphocyte development and function. In this article three aspects of nucleotide-metabolizing enzymes and lymphocyte differentiation will be discussed: 1) the distribution of the enzymes among lymphocyte populations at differing stages of differentiation; 2) the possible biochemical mechanisms which give rise to the immunodeficiencies; 3) the stages of lymphocyte differentiation which are affected by the enzyme deficiencies.

Ontogeny of terminal deoxynucleotidyl transferase-positive cells in lymphohemopoietic tissues of rat and mouse

The ontogeny of hemopoietic cells which contain the enzyme terminal deoxynucleotidyl transferase (TdT) was studied in rats and mice. During fetal life, TdT-positive cells were first detected in the thymus, where they appeared on or about day 17 of gestation. TdT-positive cells were not found in fetal liver, spleen, or bone marrow, but appeared in bone marrow and spleen on the day after birth. In the rat, peak levels of TdT-positive cells were attained at 3 to 4 weeks of age in thymus, bone marrow, and spleen, accounting for 67, 3.9, and 2.3% of nucleated cells, respectively. The percentages of TdT-positive cells in thymus and bone marrow decreased gradually thereafter, whereas, TdT-positive cells in spleen were no longer detectable by 7 weeks of age. Normal percentages of TdT-positive cells were found in bone marrow and spleen from neonatally thymectomized rats and congenitally athymic (nu/nu) mice. Dexamethasone treatment resulted in a marked decrease in TdT-positive cells. The results are discussed with respect to the putative role of TdT-positive hemopoietic cells as thymocyte progenitors.

5'-Nucleotidase activity in subpopulations of rat lymphocytes

Rat lymphocyte populations were assessed for 5'-nucleotidase activity by both biochemical and histochemical methods. Enzyme-specific activity was enriched in lymphocyte plasma membrane fractions and was higher in lymph node and spleen lymphocytes than in thymocytes. Histochemical reactions on sections of spleen and lymph node revealed strong activity in the thymus-dependent regions, periarteriolar lymphoid sheath in spleen, and paracortex in lymph node; whereas the thymus-independent regions, follicles, and germinal centers were negative. In cellular depletion experiments, with three different methods to detect 5'-nucleotidase, it was observed that the depletion of T cells, but not B cells, was accompanied by a loss of enzyme activity and a decrease in the percentage of nucleotidase-positive cells. The results suggest that, among members of the lymphocyte series, high 5'-nucleotidase activity is selectively associated with the plasma membranes of peripheral T cells in the rat.

Intracellular distribution of terminal deoxynucleotidyl transferase in rat bone marrow and thymus

A subset of bone marrow cells that contains terminal deoxynucleotidyl transferase (DNA nucleotidylexotransferase; nucleosidetriphosphate:DNA deoxynucleotidylexotransferase, EC 2.7.7.31) can be identified in adult rats by immunofluorescence using affinity-column-purified antibody to homogeneous calf transferase. The transferase-positive cells comprise approximately 1.8% of bone marrow cells. Correcting the specific activity of terminal transferase in total bone marrow cells (0.21 units per 10(8) cells) for the percentage of transferase-positive bone marrow cells (1.8%) gives 11.7 units per 10(8) cells, a value approximately half that found for transferase-positive thymocytes. Fluorescence appears to be restricted to the nucleus of transferase-positive bone marrow cells, in contrast to the predominantly cytoplasmic fluorescence of small thymocytes from adult rats. Some large thymocytes contain intranuclear transferase fluorescence patterns similar to those seen in bone marrow. These thymocytes are especially numerous in neonatal rat thymus, where they are localized in the subcapsular region of the cortex. Thymocytes with combined patterns of nuclear and cytoplasmic transferase are also present. In addition, Thy-1.1 antigen, which is present on thymic and prethymic cells but not on the majority of post-thymic cells in the rat, is also present on transferase-positive bone marrow cells. The results suggest that the transferase-positive subset of bone marrow cells may contain the immediate progenitors of cortical thymocytes in the rat. The nuclear location of fluorescence may indicate the site of physiological activity of terminal transferase in thymocytes and their precursors.

Demonstration of terminal deoxynucleotidyl transferase in thymocytes by immunofluorescence

The cellular and subcellular distribution of terminal deoxynucleotidyl transferase (DNA nucleotidylexotransferase; nucleosidetriphosphate:DNA deoxynucleotidylexotransferase, EC 2.7.7.31) in thymocytes and peripheral lymphocytes from rat, mouse, and calf was studied by immunofluorescence using rabbit antiserum to homogeneous transferase from calf. Terminal transferase was readily detected in approximately 75% of cortical thymocytes, but not in medullary thymocytes or lymph node lymphocytes. The enzyme appeared to be present predominantly in the cytoplasm of positive thymocytes in ethanol-fixed cell smears and frozen sections. The reactivity of anti-terminal-transferase for thymocytes could be neutralized with purified calf enzyme. Results of experiments in which thymocytes were separated on 7-step discontinuous Ficoll density gradients suggested that cortical thymocytes are heterogeneous with respect to terminal deoxynucleotidyl transferase content.

Low molecular weight DNA polymerase: decreased activity in spleens of old Balb/c mice

The DNA polymerase activities in the spleens of young adult (3-8 months) and senescent (24-30 months) female BALB/c mice have been examined. Comparisons were made by direct assay of activated DNA-dependent and (rA)n-(dT)n-dependent activities in extracts from cytoplasmic and neclear fractions and also by sucrose gradient sedimentation analysis of the two major forms of DNA polymerase activity was equivalent in the spleens of young and old BALB/c mice. The low molecular weight DNA polymerase activity was decreased in the spleens of old BALB/c mice. This decreased activity was reflected most markedly in the nuclear fraction of the spleens. Mixing experiments did not indicate the presence of inhibitors in the nuclear extract from the old mouse spleens. Stepwise extractions of isolated nuclei with increasing NaCl concentrations showed consistent results without revealing any difference in extractability of the low molecular weight DNA polymerase from the old mouse chromatin. Isolated low molecular weight DNA polymerase preparations from the young and old BALB/c mouse spleens are similar in chromatographic migration, sucrose gradient sedimentation, heat lability in vitro and Km of substrates. The low molecular weight DNA polymerase activity was not found to decline in livers and kidneys of 24 to 30-month-old BALB/c mice, nor in spleens of 30 to 34-month-old BC3F1 mice.