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Biomedical subjects

J Gordon

Publications and source records attributed to J Gordon.

At least 307 records · Page 17Linked to original sources
PubMed1987

Synergistic interaction between interleukin 4 and anti-Bp50 (CDw40) revealed in a novel B cell restimulation assay.

Highly purified resting B lymphocytes stimulated for 3 days to high-rate DNA synthesis by a synergistic combination of phorbol dibutyrate and ionomycin soon returned to quiescence once those signals had been removed. The maintenance of DNA synthesis in such cultures was found to provide a sensitive assay for revealing the factors that interact with cycling B cells. Whereas several activities-namely, interleukin 4, anti-Bp50 and a low molecular weight B cell growth factor-were, by themselves, capable of prolonging DNA synthesis over a further day or so, no single factor was capable of sustaining the replication cycle out to day 6 of culture. By contrast, certain combinations of activities displayed significant synergy in the restimulation assay. The most striking observed was that between interleukin 4 and anti-Bp50 where, by day 6, their combined effect on maintaining DNA synthesis in 3-day stimulated cells was the same as having kept phorbol dibutyrate and ionomycin in the culture system. The implications of these findings are discussed.

Antibodies, Monoclonal↗
PubMed1987

Recombinant human interleukin 5 is an eosinophil differentiation factor but has no activity in standard human B cell growth factor assays.

Following the observation that mouse interleukin 5 (IL5) is active as a B cell growth factor (BCGF) as well as an eosinophil differentiation factor, this work was carried out to test recombinant human IL5 for BCGF activity. A highly active, partially purified batch of recombinant human IL5 was prepared and tested for BCGF activity in four laboratories. This batch gave a 50% endpoint of 1:77,450 in the human eosinophil differentiation assay, 1:983 in the mouse eosinophil differentiation assay and 1:42 in the mouse BCL1 assay, thus demonstrating that, like mouse IL5, human IL5 has cross-species activity. By comparison with the assays in the mouse this batch would be expected to have 50% maximal human BCGF activity of about 1:4000. In each assay a known positive factor was used as a positive control, and there was no inhibitory activity in the preparation. However, despite the activity towards the mouse B cell lymphoma, the results showed no detectable activity in a panel of assays used to identify human BCGF and B cell differentiation factors. These assays included (a) proliferation assays with tonsillar or splenic B cells in the presence of the co-stimulators anti-mu or phorbol myristate acetate; (b) a restimulation assay in which tonsillar B cells are first activated with either Staphylococcus aureus Cowan 1 or a mixture of phorbol dibutyrate and ionomycin, or splenic B cells are first activated with anti-mu; (c) production of immunoglobulin by B cells in a restimulation assay with Staphylococcus aureus Cowan 1; (d) production of immunoglobulin by the Epstein-Barr virus-transformed B lymphoblastoid CESS cell line; (e) the ability to stimulate proliferation of chronic lymphocytic leukemia (B-CLL) cells freshly explanted from three different patients; (f) the ability to stimulate the B lymphoma (L4) cell line and the mature B cell (HBF1) line, and (g) the ability to replace T cells in specific antibody responses. It therefore seems unlikely that recombinant human IL5 is either a growth or a differentiation factor for human B cells, and raises the interesting question of the biological significance of the BCGF activity of this factor in the mouse.

B-Lymphocytes↗
PubMed1987

PHNO, a novel dopamine agonist, in animal models of parkinsonism.

PHNO, a naphthoxazine compound, was investigated in animal models of central dopaminergic activity. The drug in doses of 5-300 micrograms/kg when administered subcutaneously, or transdermally, induced stereotypic behavior in rats which was blocked by haloperidol but not by reserpine pretreatment. In rats with unilateral 6-hydroxydopamine lesions of the substantia nigra PHNO induced dose-dependent contralateral turnings. The drug caused emesis in dogs and hypothermia in mice. PHNO bound to D-2 dopamine receptors in the rat striatum. Chronic injection with PHNO did not induce behavioral supersensitivity or increase dopamine receptor density. These data indicate that PHNO is a direct acting dopamine agonist that is highly potent. PHNO differs from other dopaminergic drugs and may be useful in the treatment of Parkinson's disease.

Animals↗
PubMed1987

Trajectory control in targeted force impulses. I. Role of opposing muscles.

The functional role of opposing muscles in the production of isometric force trajectories was studied in six adult subjects producing impulses and steps of elbow flexor force, with different rise times and amplitudes. Rapidly rising forces were invariably associated with an alternating pattern of EMG activity in agonist and antagonist muscles: an agonist burst (AG1) initiated the development of force in the desired direction while a reciprocal burst in the antagonist (ANT-R) led to the deceleration of the force trajectory prior to the peak force. The temporal pattern of agonist and antagonist activation was dependent on force rise time. Force trajectories with long rise times (greater than 200 ms) were entirely controlled by the agonist, and EMG activity closely followed the contours of the rising force trajectory. For rise times of about 120 to 200 ms, agonist activation formed a discrete EMG burst, and force continued to rise during the subsequent silent period. For brief force rise times (less than 120 ms), reciprocal activation of the antagonist muscle occurred at about the time of the peak dF/dt. The integrated magnitude of AG1 was dependent on peak force but was independent of force rise time. AG1 duration varied directly with both peak force and force rise time. The integrated value of ANT-R varied as an inverse function of force rise time and was minimally influenced by peak force. ANT-R was present with the same magnitude and timing in both force impulses and steps when rise times were equal; therefore it did not serve to return force to baseline. Rather it served to truncate the rising force when very brief rise times were required, thus compensating for the low-pass filter properties of the agonist muscle. Subjects were able to voluntarily suppress ANT-R in rapidly accelerated force trajectories, indicating that the linkage between the commands controlling agonist and antagonist is not obligatory; however AG1 was then prolonged. Our findings emphasize that neuronal commands to opposing muscles acting at a joint must be adapted to constraints imposed by the properties of the neuromuscular plant.

Adult↗
PubMed1987

Trajectory control in targeted force impulses. II. Pulse height control.

The present report examines the control strategy adopted by subjects to modulate the amplitude of transient force responses aimed to a target. Previous studies (Freund and Budingen 1978; Ghez and Vicario 1978) suggest that subjects modulate the rate of rise of force while maintaining force rise time at a near-constant value, independent of peak force. Such studies, however, have examined only the most rapid responses where force rise time could have been at a physiological limit. We now examine whether this control policy is dependent on an instruction to produce the fastest possible trajectories, or whether it is freely selected by subjects to maximize accuracy when rise time is unconstrained. We compared responses made by six subjects, under two task conditions: 1. Fast, "make the force impulse as brief as possible"; and 2. Accurate, "be as accurate as possible without regard to rise time". Subjects were trained to produce monotonic flexion force impulses at the elbow to match the amplitudes of visually presented target shifts. Targets of three different were presented in randomized order. Responses made under the Accurate condition were less variable at each target amplitude than those under the Fast condition. Under both conditions, the initial peaks of the first and second time derivatives of force, early measures of trajectory dynamics, were strongly predictive of the peak force achieved and were correlated with the required force (target amplitude). Therefore, response trajectories must have been largely preprogrammed, and, further, the degree to which the initial peak d2F/dt2 predicts the peak force achieved represents a measure of the contribution of a preplanned motor program to trajectory formation. Subjects showed two systematic differences in trajectories between conditions. First, in all subjects force rise time was greater in the Accurate condition than in the Fast condition. Second, while in the Fast condition there was a modest dependence of force rise time on peak force, in the Accurate condition this dependence disappeared. Thus, when subjects were attempting to be as accurate as possible, they more consistently regulated force rise time around a constant value. This pulse height control policy allows responses of different amplitudes to be produced by proportional scaling of a stereotyped waveform. We conclude that a pulse height control policy with regulation of force rise time is a strategy adopted by subjects to simplify accurate control of response amplitude.

Adult↗
PubMed1987

Trajectory control in targeted force impulses. III. Compensatory adjustments for initial errors.

In the preceding study (Gordon and Ghez 1987), we showed that accurately targeted isometric force impulses produced by human subjects are governed by a pulse height control policy. Different peak forces were achieved by modulating the rate of rise of force while force rise time was maintained close to a constant value and independent of peak force. An early measure of the rate of rise of force, peak d2F/dt2, was scaled to the required force (target amplitude) and highly predictive of the peak force achieved. In six subjects examined, peak d2F/dt2 accounted for between 70% and 96% of the total variance in peak force. In the present study, we further examined these targeted responses to determine whether the residual variability not predicted by peak d2F/dt2 could be accounted for by adjustments to the force trajectories which compensated for initial errors in the scaling of the d2F/dt2. A statistical model of the determinants of peak force was tested. This model included two paths by which the target amplitude could independently influence the peak force achieved. The first path was preprogrammed pulse height control. In this path, target amplitude determined the initial rate of rise of force (peak d2F/dt2) which in turn determined the final peak force achieved. The second path was an independent influence of errors in the initial scaling of peak d2F/dt2 on peak force. Multiple regression analysis was performed on trajectory variables within the sets of responses by each subject in each condition to determine whether the second path contributed significantly to explaining the variance in peak force. In each subject and condition, there was a significant independent influence of error in d2F/dt2 on peak force, and the direction of this effect was to decrease the magnitudes of peak force errors. These compensatory adjustments accounted for between 1% and 14% of the total variance in peak force. Further multiple regression analyses revealed that inappropriate scaling of the initial phase of the trajectories was compensated for by shortening or prolonging the force rise time. These trajectory adjustments were in turn implemented by modulation of the timing and magnitude of the contractions in the agonist and antagonist muscles that produced the force trajectories. Because these compensatory adjustments were evident in the EMG pattern at latencies too short to be accounted for by peripheral feedback, we assume that they depend on internal monitoring of the unfolding neural commands. These internal feedback processes act in parallel with the programmed commands, both determining the force trajectory.

Adaptation, Physiological↗
PubMed1987

Quinpirole hydrochloride, a potential anti-parkinsonism drug.

Quinpirole hydrochloride, a putative dopamine agonist, was investigated in animal models of central dopaminergic activity, to evaluate its possible role in the treatment of Parkinson's disease. The drug induced stereotyped sniffing in rats but, unlike apomorphine, did not produce a maximal behavioural response (stereotyped gnawing). Pretreatment with neuroleptics blocked the stereotypy induced by quinpirole. Quinpirole reversed the effects of reserpine and alpha-methyl-paratyrosine, caused dose-dependent contralateral rotations in rats with unilateral lesions of the substantia nigra induced by 6-hydroxydopamine and induced vomiting in dogs. Small doses of quinpirole decreased locomotor activity, an effect presumably mediated by pre-synaptic autoreceptors. Quinpirole bound to D2 dopamine receptors in the striatum of the rat. The chronic injection of both subthreshold and suprathreshold doses, failed to induce behavioral supersensitivity. These data indicate that quinpirole can stimulate central dopaminergic receptors, and that it is a partial agonist with direct-acting properties. Quinpirole differs from other dopaminergic drugs and may be useful for the therapy of Parkinson's disease.

Animals↗
PubMed1987

Coordinated action of IgE and a B-cell-stimulatory factor on the CD23 receptor molecule up-regulates B-lymphocyte growth.

The CD23 (BLAST-2) antigen, recently identified as the low-affinity IgE receptor of B lymphocytes, has also been implicated as the focus for growth-promoting signals delivered to activated B cells by a low molecular weight B-cell growth factor (BCGF). Here we show that IgE and BCGF can coordinate B-lymphocyte growth through their opposing effects on the CD23 molecule. While the activation of purified quiescent B cells with phorbol 12-myristate 13-acetate led to the induction of 45-kDa CD23 at the surface membrane, the inclusion of IgE increased CD23 expression by a factor of approximately equal to 5. The addition of BCGF resulted in the rapid release of a 35-kDa form of CD23 from the cell surface. This shed molecule is associated with autocrine growth factor activity. Substantially more of this material was generated by BCGF acting on cells that had been stimulated in the presence of IgE. The combined effects of IgE and BCGF on DNA synthesis in activated B cells were more than additive. IgE similarly augmented the stimulatory capacity of a CD23 antibody that mimics the biological actions of BCGF. Binding of the anti-receptor antibody to its 45-kDa target at the B-cell surface also prompted the release of the 35-kDa soluble species. These results demonstrate a pleiotropy in the CD23 molecule with regard to both ligand binding and the subsequent behavior of the receptor. The ability of this single receptor to orchestrate a B-lymphocyte response through a variety of ligands and its role in normal and transformed autocrine growth are discussed.

Antibodies↗
PubMed1987

Induction of B-cell differentiation antigens in interferon- or phorbol ester-treated Daudi cells is impaired by inhibitors of ADP-ribosyltransferase.

Treatment of the Daudi Burkitt lymphoma-derived cell line with human interferon alpha, which inhibits cell proliferation in this system, induces differentiation of these B-lymphoid cells into cells with a plasmacytoid phenotype. This differentiation, quantified by the appearance of surface antigens characteristic of mature plasma cells, is impaired by addition to the culture medium of the ADP-ribosyltransferase (ADPRT; EC 2.4.2.30) inhibitors 3-methoxybenzamide or 3-aminobenzamide. These agents also protect the cells against the inhibition of proliferation induced by low doses of interferon alpha. In contrast, the large inhibition of thymidine incorporation into DNA caused by interferon treatment is not affected by the ADPRT inhibitors. The phorbol ester phorbol 12-tetradecanoate 13-acetate induces the same plasma cell surface antigens that are induced by interferon treatment, and this effect is also impaired by the ADPRT inhibitors. These results suggest that interferons and phorbol esters share a mechanism of action that requires ADPRT activity. Protection of the cells against the antiproliferative effect of interferons by the ADPRT inhibitors suggests that growth inhibition may be a consequence of cell differentiation. In contrast, the inhibition of thymidine incorporation alone is not sufficient for the cessation of cell proliferation and is not a true reflection of the rate of DNA synthesis.

Antigens, Surface↗
PubMed1987

Triggering of B lymphocytes through CD23: epitope mapping and studies using antibody derivatives indicate an allosteric mechanism of signalling.

By using five monoclonal antibodies in reciprocal cross-locking studies, a minimum of three epitope clusters have been defined for the B-cell restricted, activation-associated CD23 antigen. Two of the five antibodies were capable of replacing low molecular weight B-cell growth factor (BCGF) in B-cell co-stimulation assays. These two antibodies belonged to the same epitope group, while non-stimulatory antibodies fell outside this cluster. By prior coating of activated B lymphocytes at 4 degrees, all five CD23 antibodies interfered with the subsequent uptake of BCGF activity onto the cells. However, only the two stimulatory antibodies were capable of inhibiting the absorption of BCGF completely. From one of these antibodies, F(ab')2 and Fab fragments were generated and both were found to be equivalent to whole antibody in their ability to mimic BCGF. Immobilized antibody, however, failed to stimulate over a wide range of concentrations. These findings demonstrate that the ability of certain CD23 antibodies to deliver a growth-promoting signal to activated B cells is independent not only of the Fc portion of the molecule but also of receptor cross-linking. The latter observation is indicative of an allosteric mechanism of triggering, a notion supported by the epitope specificity of activation through CD23. The findings are discussed in relation to the putative natural ligands for CD23 and the way they may influence B-cell function through this receptor.

Antibodies, Monoclonal↗
PubMed1986

Redistribution of protein kinase C during mitogenesis of human B lymphocytes.

G0 human tonsillar B-lymphocytes were stimulated to divide by the polyclonal mitogen Staphylococcus Aureus Cowan strain 1 (SAC) and by the combined use of 12-O-tetradecanoyl phorbol-13-acetate (TPA) and the calcium ionophore ionomycin. The activities of protein kinase C, which requires Ca++ and phospholipid as co-factors, and a proteolytically cleaved form of this enzyme (protein kinase M), which is independent of calcium and phospholipid control, were determined in soluble and particulate fractions obtained from activated B cells. Treatment of G0 B cells with SAC or TPA together with ionomycin caused redistribution of protein kinase C from the soluble to the particulate fraction where the 80,000-Dalton protein kinase C was cleaved to give rise to a 50,000-Dalton form of the kinase which was also found in the cytoplasm. These data suggest that redistribution and proteolytic cleavage of protein kinase C are key signal transduction events in B cell mitogenesis.

B-Lymphocytes↗
PubMed1986

Identification of antigenic determinants by polyclonal and hybridoma antibodies induced during the course of infection by vaccinia virus.

In order to extend the understanding of determinants involved in the humoral response in the infected host, mice were subjected to an immunization regimen using both active and uv-killed vaccinia virus. The spectrum of antibody specificity in hyperimmune sera was followed by Western blotting. Comparable studies involving Western blotting and immunofluorescence were conducted with a panel of monoclonal antibodies derived from hybridomas selected from similarly immunized animals. Hyperimmune sera contained circulating antibodies primarily against three polypeptides of 28K, 35K, and 62K. These antigens were shown to be located both at the surface and within the virion. The repertoire of monoclonal antibodies included some that reacted with the 28K and 35K antigens and others that recognized a 32K core complex component or a nonvirion cell surface component, corresponding to the viral hemagglutinin. Within the panel of monoclonal antibodies was a large group which reacted with a 32K antigen found in the IHD-J virion but absent from the IHD-W strain. This finding correlates with the absence of a 32K polypeptide from the IHD-W particle. Overall, the current findings reveal the absence of any particular correlation between the incidence of polyclonal antibodies in the circulation of the immune host and the frequency of selected hybridomas against vaccinia antigens. Application of this type of immunological analysis should provide useful data concerning the detection and mapping of the antigens and their epitopes which are significant for humoral immunity.

Animals↗
PubMed1986

An inherited deficiency of the third component of complement, C3, in guinea pigs.

Hereditary deficiency of the third component of complement, C3, is found very seldom in the human. C3 deficiency is associated with severe bacterial infections revealing the central role of C3 in complement activation via the classical or alternative pathway. We describe a new hereditary C3 deficiency in strain 2 guinea pigs. Serum from these animals had a markedly reduced lytic activity in a standard assay for complement-dependent, antibody-mediated cytotoxicity. In functional assays of individual components, the hemolytic activity of the components C4, C2, C5 and of factors B, D and H was in the normal range. The functional C3 titer, and similarly C3 antigenic activity in the serum of these C3-deficient animals (C3D) was on average only 5.7% of normal activity. Typing the animals with alloantisera or monoclonal antibodies to guinea pig Ia-antigens revealed that the C3D animals had the major histocompatibility complex-haplotype of inbred strain 2 guinea pigs (B.1, Ia.2,4). The C3 defect is not linked to the major histocompatibility complex and, in addition, is not linked to a C3a receptor deficiency. Macrophages and hepatocytes of the C3D animals have an unimpaired capacity for synthesis and secretion of C3 as measured by enzyme-linked immunosorbent assay. There was no indication for hypercatabolism of normal C3 by the animals as shown by plasma clearance of 125I-radiolabeled C3. Thrombocytes of the C3D animals responded normally to stimulation with purified C3a in an ATP-release assay without an indication for a desensitization in vivo. Possibly the fault resides in an enhanced susceptibility of their own C3 to proteolysis. However, C3 partially purified from the plasma of the C3D animals or secreted by hepatocytes exhibited no obvious structural differences to purified normal C3 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis or in immunoblotting. The C3D serum had a reduced bactericidal activity compared to normal or to C4-deficient serum. Nevertheless, the animals are apparently healthy without an indication for increased frequency of bacterial infections. These guinea pigs provide an unique model for analysis of the biological functions of C3 in vivo and in vitro without the need for artificial C3-depletion procedures with all their known and unknown side-effects.

Animals↗
PubMed1986

Ligation of the CD23,p45 (BLAST-2,EBVCS) antigen triggers the cell-cycle progression of activated B lymphocytes.

CD23,p45 (BLAST-2,EBVCS) is a 45-kDa lineage-restricted antigen which appears on the surface of human B cells shortly after activation. A monoclonal antibody (MHM6) to CD23,p45, as well as a polyclonal rabbit antibody raised against the purified antigen were found to promote DNA synthesis in purified tonsillar B cells which had been activated with phorbol ester. Interleukin 1, which was not, by itself, stimulatory for either resting or activated B cells, significantly augmented the growth-promoting properties of MHM6. Kinetic studies indicated that while MHM6 exerted its influence in early G1, interleukin 1 acted later in the cycle just prior to the entry of cells into S phase. The findings demonstrate a role for CD23,p45 in triggering the progression of activated B lymphocytes through the G1 phase of the cell cycle. The possibility that this antigen serves as a receptor for a B cell stimulatory factor is discussed.

Animals↗
PubMed1986

Evidence for an association between CD23 and the receptor for a low molecular weight B cell growth factor.

Low molecular weight B cell growth factor (BCGF) and a monoclonal antibody (MHM6) to the 45-kDa, B lineage-restricted, CD23 activation antigen (BLAST-2; EBVCS) were found to be indistinguishable in their biological effects. Individually, both augmented DNA synthesis in activated, but not resting, B lymphocytes while no additional enhancement resulted from using the two agonists in combination. Furthermore, by increasing the expression of Tac, both MHM6 and BCGF promoted activated B cells to respond more vigorously to the late addition of recombinant interleukin 2. The presence of BCGF during B cell activations was found to down-regulate the expression of the CD23 antigen while the coating of activated cells with MHM6 antibody diminished their capacity to absorb BCGF activity. The findings demonstrate that CD23 and a low molecular weight BCGF deliver a comparable growth-promoting signal to activated B cells. A possible relationship between CD23 and the receptor for the low molecular weight BCGF is discussed.

Antibodies, Monoclonal↗
PubMed1986

Regulation of inositol phosphate levels by prostaglandins in cultured endometrial cells.

Stimulation of cultured rabbit endometrial cells by one of the rabbit endometrial cell culture proliferation factors, prostaglandin F2 alpha (PGF2 alpha), resulted in a very rapid increase in the intracellular levels of [3H]-inositol triphosphate (IP3), [3H]-inositol biphosphate (IP2), and [3H]-inositol monophosphate (IP1) in cells prelabeled with [3H]-inositol. These increases in inositol phosphate levels were detected in periods of stimulation as short as 30 seconds, reached a maximum by 1 1/2-2 min and declined to control levels by 6-10 min. The stimulation was dose-dependent with maximal increases observed near 10(-6) M PGF2 alpha. The cholinergic agent, carbachol, also led to time and dose-independent increases in IP3. Lithium, cadmium, silver, copper, and zinc ions had no effect either on the breakdown of IP3 or on the accumulation of IP1. In contrast, vanadate at 10(-6) or 10(-5) M did lead to a decrease in the breakdown of IP1 and a concomitant increase in IP1, IP2, and IP3. PGF2 alpha was found previously to induce an increase in rabbit endometrial cell DNA synthesis which was inhibited by concomitant or prior addition of prostaglandin E1 (PGE1). PGE1, in a dose-dependent manner, was found to inhibit the observed IP3 increase by PGF2 alpha at 1 1/2 min of stimulation. PGF2 alpha treated and control cultures did not differ in cAMP or cGMP levels, cellular 45Ca uptake, nor cellular 22Na uptake. We propose that IP3 may be one of the intracellular messenger(s) synthesized following the treatment of rabbit endometrial cell cultures with the proliferation agent PGF2 alpha and that it may play a crucial role with cAMP in growth regulation.

Animals↗