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Biomedical subjects

J L Ambrus

Publications and source records attributed to J L Ambrus.

At least 19 recordsLinked to original sources
PubMed1995

Hemorrheologic effects of metabolites of pentoxifylline (Trental).

Pentoxifylline (Trental) is metabolized by red blood cells and the liver into seven metabolites. Metabolites I and V have significant hemorrheologic effects. They are both similar to pentoxifylline in their activity on red blood cell membrane fluidity. Metabolite I is more active than pentoxifylline in inhibiting ADP-induced platelet aggregation. Metabolite V is more active than pentoxifylline in inhibiting epinephrine-induced platelet aggregation.

Adenosine Diphosphate↗
PubMed1995

Calcitriol analogs cause differentiation of neoplastic cells in culture.

Several investigators are developing calcitriol (DHCC, Compound A) derivatives which have less effect on mineral metabolism and are effective in causing differentiation of neoplastic cells. In the present study we investigated three new DHCC derivatives (Compounds B, C, D) for differentiation inducing effect in human neoplastic cell lines HL-60 and U-937.

Calcitriol↗
PubMed1994

Influence of cold storage altered red cell surface on the function of platelets.

In previous studies, we have shown that in the hemoocclusive crisis of sickle cell disease, red blood cells (RBC) develop reversible membrane changes which may represent a thrombogenic surface for platelets. As a result there is platelet activation and platelet derived procoagulant activity. Platelet activation is also enhanced when platelets come into contact with stored RBC in comparison with freshly obtained red blood cells from normal individuals. Pentoxifylline (P, Trental), a trisubstituted xanthine derivative, acts on the red cell membrane and decreases its effect on platelet activation. In addition, it may have direct platelet aggregation inhibitory effects. By decreasing red cell "stiffness", it may also increase the circulating life span of stored red blood cells. It is suggested that pentoxifylline may be explored as an additive in the preservation of RBC.

Blood Coagulation↗
PubMed1994

Study of the mechanisms of action of sodium meclofenamic acid (Meclomen) a "double inhibitor" of the arachidonic acid cascade.

Meclofenamic acid sodium (Meclomen) was found to inhibit both the cyclooxygenase and the lipoxygenase pathways of arachidonic acid metabolism. It inhibited both 5-lipoxygenase and 15-lipoxygenase activities. Meclomen was also shown to interfere with leukotriene receptors or possibly post-receptor mechanisms. In isolated lung parenchyma strip preparations Meclomen inhibited leukotriene C4 and D4 induced contractions, but had no effect on histamine induced contractions. Ibuprofen, naproxen and indomethacin had no effect on lipoxygenases or on leukotriene receptors but were powerful inhibitors of cyclooxygenases.

Animals↗
PubMed1992

Effect of red blood cells from patients with sickle cell disease on platelet factor 3 release.

Red cells from two SS genotype and two SA genotype patients were sampled. When the samples were deoxygenated and mixed with platelet-rich plasma, they caused the release of platelet factor 3 as recorded in a coagulometer. This phenomenon was not present in control blood samples from normal individuals. Membrane changes in abnormal red cells during hypoxia may be responsible in part for platelet activation and its role in vasoocclusive crisis. Vasoocclusive crisis could be prevented by increasing the red cell membrane fluidity and inhibiting the platelet aggregation with pentoxifylline.

Adult↗
PubMed1992

Studies on tumor induced angiogenesis.

Methods were developed to test angiogenic response to human tumor implants and various biologic agents in the cornea of rabbits and non-human primates (Macaca arctoides). Crude PDGF preparations were found to have significant angiogenic effect. Purified, recombinant PDGF preparations were also effective inhibitors (e.g. pentoxifylline (Px) (which also were found to release PgI2 and t-PA) inhibited human tumor implant induced angiogenesis and reduced spontaneous metastases in 3 transplantable murine tumors (Furth-Columbia Wilms' tumor in Furth-Wistar rats, C-1300 neuroblastoma in A/J mice and HM-Kim mammary carcinoma in Wistar rats) but not in the NIH adenocarcinoma in Balb/c mice. Sodium diethyldithiocarbamate (DDTC), a metal complexing agent with special affinity to copper and anti-thyroid as well as, immune stimulating activity was shown to be anti-angiogenic and to potentiate the effect of Px. The anti-fibrinolytic agents epsilon amino caproic acid (EACA) and tranaxamic acid (t-AMCHA) were anti-angiogenic. DDTC and Px were synergistic from this point of view.

Adenocarcinoma↗
PubMed1992

Prevention and treatment of osteoporosis. One of the most frequent disorders in American women: a review.

This review summarizes basic pathophysiology, epidemiology, classification and theories on the etiology of osteoporoses. Diagnostic, preventative and therapeutic aspects are discussed including the use of hormones and hormone analogues (estrogen, progestins, calcitonins, anabolic steroids), calcium, fluoride, bisphosphonates, vitamins D and their metabolites and the recently proposed "coherence therapy". Reference is made to new compounds under study including imidazoquinazolinones, methylxanthines and benzothiophenes.

Calcitonin↗
PubMed1992

Increased prostaglandin E2 and cAMP phosphodiesterase levels in Kaposi's sarcoma--a virus against host defense mechanism.

In Kaposi's sarcoma tissue, prostaglandin E2 (PgE2) levels and cAMP phosphodiesterase levels were found to be higher than in surrounding normal tissue. We have shown earlier that PgE2 suppresses interferon (IFN) alpha production. High levels of cAMP phosphodiesterases result in low cAMP levels. Thus, this phenomenon may be involved in altered immunologic resistance, growth and differentiation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1991

Complement subcomponent C1q stimulates Ig production by human B lymphocytes.

The regulation of Ig production by human B lymphocytes is a complex process involving interactions among B cells, APC, T lymphocytes and soluble factors including activation, growth, and differentiation factors. Components of the complement system, including C3a, C3b, C3d, and C5a, have been shown to influence various stages in this process. In this study, we demonstrate that the C1q subcomponent of complement binds to both small resting and large activated B cells and stimulates immunoglobulin production by Staphylococcus aureus Cowan-activated tonsillar B lymphocytes. This effect is present whether C1q is added to the B cells either at the beginning or near the end of a 7-day culture period and is not associated with enhancement of proliferation. The C1q stimulation of Ig production is, however, associated with increased steady state levels of mRNA for the mu Ig H chain. Furthermore, C1q stimulated IgM production by the human B cell line SKW 6.4, which is capable of secreting IgM in response to B cell differentiation factors (BCDF). SLE is a disorder frequently associated with polyclonal activation of B lymphocytes. We studied the effect of C1q on B cells from two patients with this disorder and one with an SLE-like illness, all selected for the predominance of either IgM or IgG in serum. Spontaneous or BCDF-stimulated Ig secretion was of the isotype predominant in vivo, whereas C1q selectively stimulated B cells to produce the other isotype (IgG vs IgM). Thus, C1q interacts with B lymphocytes in a manner distinct from that of BCDF found in mixed lymphocyte supernatants. C1q may be an important factor influencing the production of Ig by B lymphocytes in normal individuals and in patients with abnormalities of B cell activity.

B-Lymphocytes↗
PubMed1991

Interferon inhibitors.

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Granulomatosis with Polyangiitis↗
PubMed1991

Intracellular signaling events associated with the induction of proliferation of normal human B lymphocytes by two different antigenically related human B cell growth factors (high molecular weight B cell growth factor (HMW-BCGF) and the complement factor Bb).

High molecular weight B cell growth factor (HMW-BCGF) and the complement component, Factor B, are antigenically related. HMW-BCGF and the physiologic Factor B activation fragment Bb, are both mitogenic for B lymphocytes and compete for binding to the B cell plasma membrane (Peters, M., Ambrus, J. L., Jr., Fauci, A., and Brown, E. (1988) J. Exp. Med. 168, 1225-1235). To understand which second messengers that occur after ligand-receptor interaction are associated with mitogenesis, we have examined the early signaling events after stimulation of activated B cells with these related growth factors. HMW-BCGF but not Bb increased [cAMP]i with a maximum between 45 and 60 min after stimulation. The increase in [cAMP]i was inhibited by indomethacin, suggesting that prostaglandin synthesis is involved in this response. Increase in [cAMP]i induced by HMW-BCGF, cholera toxin, or dibutyryl cAMP was associated with increased expression of the HMW-BCGF receptor, but there was no increase in proliferation of activated B cells when they were stimulated with cAMP agonists other than HMW-BCGF. These data suggest that cAMP is associated with regulation of receptor expression but is neither necessary nor sufficient for induction of proliferation. Both HMW-BCGF and Bb increased cellular levels of diacylglycerol and a water-soluble molecule which could be labeled with both [3H]myoinositol and [14C] glucosamine. However, only HMW-BCGF induced increases in intracellular calcium. Thus, two antigenically related B cell growth factors, HMW-BCGF and Bb, produce overlapping but distinct sets of second messengers after incubation with Sac-activated B cells. Since both induced increases in diacylglycerol and water-soluble inositol, one or both of these molecules may be involved in the proliferative signal generated by the related growth factors. In contrast, the increase in [cAMP]i caused by HMW-BCGF but not Bb is involved in the signal to increase HMW-BCGF receptor expression, but is unrelated to proliferation.

B-Lymphocytes↗
PubMed1991

The interferon system in carcinoma of the cervix. Effect of radiation and chemotherapy.

Thirteen patients with advanced carcinoma of the cervix were studied for parameters of the interferon system compared with 40 age-matched and sex-matched controls. All patients had measurable serum interferon levels; controls did not. All patients had non-antibody-type interferon-inhibitory activity, and controls had none. Interferon-synthesizing potential was higher in controls than in patients. After successful radiation and chemotherapy, these parameters normalized in the patients. No change was seen in one patient who did not respond to therapy.

Adenocarcinoma↗
PubMed1991

Induction of proliferation by high molecular weight B cell growth factor or low molecular weight B cell growth factor is associated with increases in intracellular calcium in different subpopulations of human B lymphocytes.

The activation of resting B cells with anti-surface Ig is associated with transient increases in intracellular calcium. In the present study, we demonstrate that stimulation of B cells which have already been activated by Staphylococcus aureus Cowan I (Sac), with high molecular weight B cell growth factor (HMW-BCGF) or low molecular weight B cell growth factor (LMW-BCGF), but not IL-2, IL-4, or interferon-gamma, is associated with an increase in intracellular calcium, which is modest compared to that seen with anti-Ig (approximately 100 nM vs approximately 400 nM). The increases in intracellular calcium induced by HMW-BCGF or LMW-BCGF occur in distinct but overlapping subpopulations of B cells. Thus, increases in intracellular calcium in human B cells occur not only upon activation but also upon the induction of proliferation by certain (but not all) B cell growth factors. Presumably, the effect of increasing intracellular calcium during the induction of proliferation is to modify a different group of intracellular molecules than those induced during activation.

B-Lymphocyte Subsets↗
PubMed1991

Improved in vitro antigen-specific antibody synthesis in two patients with common variable immunodeficiency taking an oral cyclooxygenase and lipoxygenase inhibitor (ketoprofen).

In the process of performing a previously published study examining B cell function in 16 patients with common variable immunodeficiency (CVI)(J Allergy Clin Immunol 1991; 87:1138-49), we noted improved in vitro antibody (Ab) synthesis in a patient, H. B., while he was taking a cyclooxygenase and lipoxygenase inhibitor, ketoprofen. Addition of ketoprofen in vitro to B cells from patients with CVI resulted in improved proliferation and differentiation in four of five additional patients with CVI studied. One patient, besides H. B., M. K. B., whose B cells secreted increased amounts of antigen (Ag)-specific Ab in response to in vitro ketoprofen, underwent a trial of oral ketoprofen M. K. B., like H. B., demonstrated improved in vitro Ag-specific Ab production while she was taking oral ketoprofen. No increase in serum Ab levels was noted in either patient taking ketoprofen, but both patients remained infection free during the time of their ketoprofen trials (H. B., 9 months, and M. K. B., 36 months). No improvement in in vitro Ag-specific Ab synthesis was noted when H. B. and M. K. B. took oral cyclooxygenase inhibitors (naproxen or ibuprofen). Thus, additional study is warranted to examine the role of lipoxygenase products of arachidonic acid in the B cell dysfunction of CVI.

Administration, Oral↗
PubMed1991

Abnormal response to a human B cell growth factor in patients with common variable immunodeficiency (CVI).

Patients with common variable immunodeficiency (CVI) generally fail to produce antigen-specific IgG. We have identified a lymphokine called high molecular weight B cell growth factor (HMW BCGF) that expands an IgG-producing subpopulation of B cells. The B cells from 15 of 16 patients with CVI evaluated in this study failed to proliferate to HMW BCGF, although they proliferated normally to another BCGF, low molecular weight BCGF (LMW BCGF). Nevertheless, 11 patients had more than normal numbers of B cells expressing HMW BCGF receptors. The HMW BCGF receptors on the B cells of three patients with CVI studied were the same molecular weight as the normal HMW BCGF receptor. Examination of B cells from four patients with CVI for intracellular signals produced in normal B cells after stimulation with HMW BCGF revealed that B cells from patients with CVI failed to developed significant increases in cyclic adenosine monophosphate or phosphoinositides after HMW BCGF stimulation. However, cytoplasmic phosphoinositides in the B cells from all four patients with CVI were already increased above what is observed in normal B cells before stimulation with HMW BCGF (either freshly isolated or Staphylococcus aureus Cowan I-activated B cell). Thus, the failure of B cells from patients with CVI to respond to HMW BCGF may be related to their abnormal activation in vivo. Since HMW BCGF expands a subpopulation of memory B cells, the inability of CVI B cells to respond to HMW BCGF may contribute to their abnormal secondary responses to antigens.

Adolescent↗