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H Jacobs

Publications and source records attributed to H Jacobs.

At least 73 records · Page 4Linked to original sources
PubMed1996

Domains of the TCR beta-chain required for early thymocyte development.

The T cell receptor beta (TCR beta) chain controls the developmental transition from CD4-CD8- to CD4+8+thymocytes. We show that the extracellular constant region and the transmembrane region, but not the variable domain or cytoplasmic tail of the TCR beta chain are required for this differentiation step. TCR beta mutant chains lacking the cytoplasmic tail can be found at the cell surface both in functional TCR/CD3 complexes and in a GPI-anchored monomeric form indicating that the cytoplasmic tail of the TCR beta chain functions as an ER retention signal. The concordance between cell surface expression of the mutant chains as TCR/CD3 complexes and their capacity to mediate thymocyte differentiation supports the CD3 mediated feedback model in which preTCR/CD3 complexes control the developmental transition from CD4-CD8- to CD4+CD8+thymocytes.

Animals↗
PubMed1996

Effects of hormone replacement therapy on the circadian pattern of atherothrombotic risk factors.

Onset of acute atherothrombotic events (acute myocardial infarction, unstable angina, ischemic stroke) exhibit a circadian pattern that parallels the diurnal pattern of endogenous fibrinolytic activity. Hormone replacement therapy in postmenopausal women has been shown to enhance fibrinolytic capacity by lowering plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator inhibitor (tPA) antigen values. We evaluated the impact of 4 weeks of estrogen alone (Premarin 0.625 mg/day) and 2 weeks of estrogen plus progesterone (Provera 2.5 mg/day) on PAI-1 and tPA in 17 postmenopausal women at multiple time points to assess hormone impact on the diurnal pattern of fibrinolytic potential. At baseline, both PAI-1 and tPA exhibited circadian variability. Estrogen alone selectively lowered 8 A.M. PAI-1 (35.8 +/- 7.1 ng/ml at baseline, 19.8 +/- 3.7 ng/ml on estrogen; p = 0.0002 vs baseline). There was no significant change in the noon or 4 P.M. values, and the diurnal pattern was attenuated. The 8 A.M. PAI-1 remained low at 17.1 +/- 3.6 ng/ml (p = 0.0001 vs baseline) with total loss of the circadian rhythm. Estrogen supplementation reduced tPA antigen at all time points, and the diurnal pattern, although blunted, persisted. Addition of progesterone to estrogen did not reverse effects of the estrogen alone phase of either PAI-1 or tPA values. This hormone-associated reduction of PAI-1 was observed despite increased triglycerides, a known inducer of PAI-1 levels. These observations suggest that hormone replacement therapy may protect postmenopausal women from excess early morning acute ischemic events.

Circadian Rhythm↗
PubMed1996

Oncogenic potential of a pre-T cell receptor lacking the TCR beta variable domain.

In transgenic mice expressing a mutated T cell receptor (TCR) beta chain lacking the variable domain (DeltaV-TCRbeta) T cell differentiation is arrested at the CD4+ CD8+ thymocyte stage. Here, we report that these transgenic animals develop CD4+, CD8+, IL-2 receptor alpha-positive T cell lymphomas at a very high incidence. Introduction of a normal TCRbeta gene into the DeltaV-TCRbeta transgenic mice drastically reduces the tumor incidence, while crossing the DeltaV-TCRbeta transgene onto a recombinase-deficient RAG-1-/- background does not prevent tumor development. Therefore, the induction of T cell lymphomas is a property of the mutated TCRbeta chain. The DeltaV-TCRbeta chain appears at the cell surface as a disulfide-linked DeltaV-TCRbeta/pTalpha dimer in association with CD3gamma and -episilon, but not with CD3delta. This mutated preTCR/CD3 complex is shown to induce pre-T cell proliferation and differentiation, but does not permit formation of a normally sized CD4+8+ thymic compartment. DeltaV-TCRbeta transgenic mice frequently show an expansion of CD4+8+, IL-2 receptor alpha+ pre-T cells early in life. These cells likely represent the population that is subject to oncogenic transformation.

Amino Acid Sequence↗
PubMed1996

Composition and function of T-cell receptor and B-cell receptor complexes on precursor lymphocytes.

The precursor T-cell receptors (TCRs) and B-cell receptors (BCRs) direct lymphocyte development to the mature T-cell and B-cell stage, respectively. Recent genetic and biochemical experiments reveal the striking parallel in structure and function of these receptors. They consist of TCR beta and BCR mu chains paired with surrogate TCR alpha and BCR light chains. Both receptors employ a two-component signal transduction unit: CD3 gamma epsilon for the pre-TCR, and CD79ab for the pre-BCR. Plasma membrane levels of pre-TCR/BCR complexes are kept extremely low, most probably by a mechanism involving specific retention in the endoplasmic reticulum. This mechanism may control the signalling activity of pre-TCR/BCR and therewith the lymphocyte differentiation process.

Animals↗
PubMed1996

Intermittent pneumatic compression in chronic venous insufficiency favorably affects fibrinolytic potential and platelet activation.

Nineteen patients with symptoms of chronic venous insufficiency (CVI) were treated with 13-week cycles of intermittent pneumatic compression (IPC) during 2 h sessions twice weekly, with most treatments at home. At study completion, quantitative subjective scores for total symptomatology were improved in 16/19 patients (84%). Enhancement of fibrinolytic potential in vivo was detected in 86% of observations on specimens from CVI patients over 2 h of IPC, with accelerated euglobulin clot lysis times (ELT) noted within 15 min of initiating compression. The enhanced fibrinolytic potential was attributed to increased urokinase plasminogen activator (u-PA), probably released from perturbed endothelial cells by IPC. Significant decreases in total t-PA antigen (mass concentration) but not t-PA activity, were produced by IPC in CVI patients only (P = 0.0001), with greater effects noted in the non-anticoagulated versus the anticoagulated cohort. Plasminogen activator inhibitor type 1 (PAI-1) levels rose rapidly after IPC only in the controls and non-anticoagulated CVI patients. PAI-1 decreased in those receiving anticoagulation. No platelet perturbation was detected during IPC by measuring levels of beta-thromboglobulin or the thromboxane A2 metabolite, 11-dehydrothromboxane B2; however, significant (P < 0.003) decreases in plasma prostacyclin (PGI2) levels (measured as the stable 6-ketoprostaglandin F-1-alpha-metabolite) were observed after 15 min of IPC in non-anticoagulated CVI patients only. There was no evidence of increased thrombin generation by IPC, determined by urinary excretion of fibrinopeptide A and prothrombin fragment 1. Concurrent anticoagulation appears to mediate more favorable biochemical alterations in CVI, although subjective improvement did not correlate with anticoagulation. The mechanism(s) by which these physiologic changes compliment the mechanical effects of IPC remain to be elucidated and will require adequately controlled and powered studies.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Design of nonthrombogenic polymer surfaces for blood-contacting medical devices.

Although significant progress has been made in the design of blood-compatible polymers in the past decades, there is no ideal polymer surface which is comparable with a natural endothelial surface in preventing surface-induced thrombosis and maintaining hemostasis. This is due to the complex pattern of protein and cellular interactions with foreign surfaces, which still demands defining a proven hypothesis to develop non-thrombogenic surfaces. Synthesis of new polymers with optimal mechanical properties and the in vitro and in vivo characterization of these surfaces will require many more years of work. In this article, the surface modification of existing medical polymers for the improvement of blood compatibility is introduced. Surface immobilizing of heparin onto polyurethane, coatings of a polyurethane-poly(ethylene oxide)-heparin graft copolymer, and a coating of thermosensitive polymers on polyurethane will be discussed. All modified surfaces demonstrated superior blood compatibility both in vitro and in vivo. The biological response of these designed systems in vitro, ex vivo and in vivo should provide state-of-the-art materials for the specific application of controlling thrombosis and solving biocompatibility problems.

Anticoagulants↗
PubMed1995

Exit from mitosis is regulated by Drosophila fizzy and the sequential destruction of cyclins A, B and B3.

While entry into mitosis is triggered by activation of cdc2 kinase, exit from mitosis requires inactivation of this kinase. Inactivation results from proteolytic degradation of the regulatory cyclin subunits during mitosis. At least three different cyclin types, cyclins A, B and B3, associate with cdc2 kinase in higher eukaryotes and are sequentially degraded in mitosis. We show here that mutations in the Drosophila gene fizzy (fzy) block the mitotic degradation of these cyclins. Moreover, expression of mutant cyclins (delta cyclins) lacking the destruction box motif required for mitotic degradation affects mitotic progression at distinct stages. Deltacyclin A results in a delay in metaphase, deltacyclin B in an early anaphase arrest and deltacyclin B3 in a late anaphase arrest, suggesting that mitotic progression beyond metaphase is ordered by the sequential degradation of these different cyclins. Coexpression of deltacyclins A, B and B3 allows a delayed separation of sister chromosomes, but interferes wit chromosome segregation to the poles. Mutations in fzy block both sister chromosome separation and segregation, indicating that fzy plays a crucial role in the metaphase/anaphase transition.

Anaphase↗
PubMed1995

Heparin release from thermosensitive polymer coatings: in vivo studies.

Biomer/poly(N-isopropylacrylamide)/[poly(NiPAAm)] thermosensitive polymer blends were prepared and their application as heparin-releasing polymer coatings for the prevention of surface-induced thrombosis was examined. The advantage of using poly (NiPAAm)-based coatings as heparin-releasing polymers is based on the unique temperature-dependent swelling of these materials. At room temperature, i.e., below the lower critical solution temperature (LCST) of poly (NiPAAm), the Biomer/(poly(NiPAAm) coatings are highly swollen. The high swelling enables fast loading of hydrophilic macromolecules (e.g., heparin) into the coating by a solution sorption technique. At a body temperature, i.e., above the LCST of poly (NiPAAm) the coatings are in a deswollen state and the absorbed macromolecules may be slowly released from a dense coating via a diffusion controlled mechanism. Biomer/poly(NiPAAm) coatings were obtained by blending and coprecipitation of the two linear polymers, Biomer and (poly(NiPAAm). The structure and water-swelling properties of the coatings were examined. Significant differences in water swelling at room temperature (RT) and 37 degrees C were observed as a result of the thermosensitivity of poly (NiPAAm). The surface structure of the coatings in dry and swollen states at RT and 37 degrees C was examined by scanning electron microscopy. Heparin was loaded into the coatings via a solution sorption at room temperature. Kinetic studies of heparin loading demonstrated that maximum loading was obtained within 1 h. The in vitro (37 degrees C) release profiles were characterized by a rapid initial release due to the squeezing effect of the collapsing polymer network, followed by a slower release phase controlled by heparin diffusion through the dense coating. The short-term antithrombogenicity of intravenous polyurethane catheters coated with heparin-releasing Biomer/poly(NiPAAm) thermosensitive coating was evaluated in a canine animal model. The results show that the heparin release from Biomer/poly(NiPAAm)-coated surfaces resulted in a significant reduction of thrombus formation on test surfaces in contact with venous blood as compared to control surfaces.

Acrylic Resins↗
PubMed1995

Effect of continuous arteriovenous hemofiltration combined with systemic vasopressor therapy on depressed left ventricular contractility and tissue oxygen delivery in canine Escherichia coli sepsis.

BACKGROUND: In a previous study, we showed that continuous arteriovenous hemofiltration (CAVH) reversed the depression in left ventricular (LV) contractility in canine Escherichia coli sepsis by the removal of a circulating substance the molecular weight of which is less than 30,000. Despite the normalization of LV contractility, however, we were unable to demonstrate an improvement in systemic arterial blood pressure (BP), presumably because the mechanisms underlying the depression in LV contractility and the decrease in BP are different in sepsis. In the current study, we examined the effect of combined treatment with CAVH and the alpha-adrenergic agonist phenylephrine on LV mechanics and tissue oxygen delivery in our canine E. coli model. METHODS: Measurements were obtained at baseline (condition B), after 4 h of sepsis (condition S), and after 2 h of CAVH and phenylephrine (condition P) (total of 6 h of sepsis). During P, phenylephrine was infused to restore BP to that found at baseline. The slope of the end-systolic pressure-dimension relation was used as the index of LV contractility; LV anterior-posterior dimensions were measured by sonomicrometry. RESULTS: During combined CAVH and phenylephrine treatment, the decrease in the slope of the end-systolic pressure-dimension relation otherwise observed at S was reversed. The slope (mean +/- SD) was 57.5 +/- 32 mmHg/mm at B versus 22.2 +/- 8 mmHg/mm at S (P < 0.05, B vs. S) versus 62 +/- 37 mmHg at P (P < 0.05 S vs. P) (analysis of variance). Mean BP was restored to that found at B (123 +/- 19 mmHg versus 82 +/- 14 mmHg (P < 0.05 B vs. S) versus 116 +/- 27 mmHg (P < 0.05 S vs. P). Combination treatment with CAVH and phenylephrine also improved stroke volume (39.3 +/- 13.5 versus 32 +/- 8 versus 44 +/- 12 ml) and tissue oxygen delivery during P compared with results obtained when phenylephrine was given alone. CONCLUSIONS: Our study offers a rationale for the combined use of phenylephrine and CAVH in the reversal of cardiac depression and hypotension in sepsis.

Animals↗
PubMed1994

CD3 components at the surface of pro-T cells can mediate pre-T cell development in vivo.

Developmentally arrested pro-T cells (CD4-8-, IL-2R+, HSA++) of RAG-1-deficient mice appear to express low levels of CD3 molecules in the absence of T cell receptor (TcR) chains at their surface, while developmentally arrested pre-T cells of TcR alpha-deficient mice express low levels of a disulfide-linked TcR beta chain in association with CD3 molecules. Cross-linking of the CD3 modules on pro-T cells of RAG-1-/- mice in vivo, with either of two different CD3 epsilon-specific monoclonal antibodies, induces differentiation of these pro-T cells into pre-T cells (CD4+8+, IL-2R-, HSA+), concomitant with a rapid expansion of the thymic T cell compartment, up to 175-fold within 12 days. The same effects can be produced by introduction of a mutant TcR beta transgene lacking most of the variable domain (delta V-TcR beta) into the RAG-1-/- background. These experiments suggest that cross-linking of the CD3 modules on pro-T cells mimics the signaling function expected of the pre-TcR complex, which is found at the surface of pre-T cells prior to functional TcR alpha gene rearrangement. The variable domain of the TcR beta chain is apparently not essential for inducing these aspects of T cell development.

Animals↗
PubMed1993

Subcutaneous sumatriptan in the treatment of acute episodes of posttraumatic headache.

Seven patients with posttraumatic headaches refractory to other medical treatment were treated with sumatriptan, 6 mg subcutaneously, at the peak of a headache. In all, the throbbing temporal part of the headache disappeared leaving a persistent occipital pain. It is postulated that involvement of the trigeminovascular system is involved in part of the pain of posttraumatic headache, making it amenable to treatment with sumatriptan.

Adult↗
PubMed1993

Effects of E. coli sepsis and myocardial depressant factor on interval-force relations in dog ventricle.

We examined whether depressed left ventricular (LV) contractility during Escherichia coli sepsis in dogs was due to a decrease in the fractional release of calcium from the sarcoplasmic reticulum (SR) or a reduction in calcium content in this organelle. To indirectly assess SR calcium availability in a right ventricular (RV) trabecular muscle preparation, we utilized functional indexes of cellular myocardial calcium metabolism, which included rapid-cooling contracture (RCC), an indicator of SR calcium content, and postrest contraction (PRC), an index of calcium availability from the release compartment of the SR. Measurements were made during steady-state stimulation at 0.5 and 1.5 Hz, during which time rest intervals of 30-240 s were periodically imposed. SR calcium availability was measured in RV trabeculae of dogs subjected to 4 h of E. coli sepsis and was compared with calcium availability measured in nonseptic dogs. We further characterized a filterable cardiodepressant substance (FCS), which has been previously shown to be associated with LV depression in this model, to determine whether it produced changes in calcium metabolism similar to those found in sepsis. The results showed that calcium availability from the SR of septic dogs was not impaired. Furthermore, FCS was found in the 10,000- to 30,000-mol wt fraction of plasma and produced changes in PRC in canine trabeculae that were similar to those produced during sepsis. We conclude that, as assessed by PRC and RCC, SR calcium content and release are not impaired in sepsis.

Animals↗
PubMed1993

Single-dose pharmacokinetics and pharmacodynamics of recombinant human follicle-stimulating hormone (Org 32489*) in gonadotropin-deficient volunteers.

OBJECTIVE: To assess safety, pharmacokinetic, and pharmacodynamic properties of recombinant human follicle-stimulating hormone (FSH; Org 32489, Organon International, Oss, The Netherlands) after a single intramuscular injection in the buttock. DESIGN: In a prospective study, safety variables, serum FSH, luteinizing hormone, inhibin, estradiol (females only), and testosterone (males only) were evaluated up to a maximum of 11 days after injection of 300 IU recombinant FSH. SETTING: Four specialist Reproductive Endocrinology and Infertility units. VOLUNTEERS: Fifteen men and women exhibiting all pituitary gonadotropin deficiency. RESULTS: A single bolus of 300 IU recombinant FSH was well tolerated, and no drug-related adverse effects were noted. Comparison of before and after treatment safety variables, including serum antirecombinant FSH antibodies, showed no changes of clinical relevance. Analysis of serum FSH levels revealed comparable elimination half-lives of 44 +/- 14 (mean +/- SD) and 32 +/- 12 hours in women and men volunteers, respectively. In contrast, peak FSH concentrations were significantly lower in women than in men volunteers (4.3 +/- 1.7 versus 7.4 +/- 2.8 IU/L), and the time required to reach peak levels of FSH was significantly longer in women than in men (27 +/- 5 versus 14 +/- 8 hours). The area under the serum level versus time curve tended to be smaller in women than in men volunteers (339 +/- 105 versus 452 +/- 183 IU/L x hours), but the difference did not reach statistical significance. Together these data suggest that recombinant FSH is absorbed from its intramuscular depot to a lower rate and extent in women than in men. In both sexes a relationship between serum FSH levels and body weight was apparent. During the experimental period, other hormones remained low at baseline levels or were only slightly increased. CONCLUSION: Our findings indicate that recombinant FSH is well tolerated and that it is absorbed from its intramuscular depot to a higher rate and extent in men than in women. After intramuscular administration, its half-life is in good agreement with that previously reported for natural FSH.

Adult↗