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Biomedical subjects

R M Murphy

Publications and source records attributed to R M Murphy.

48 records · Page 3Linked to original sources
PubMed1990

Selective serotonin1A/1B agonists differentially affect spinal nociceptive reflexes.

The purpose of the present experiments was to determine whether serotonin-1A (5-HT1A) and serotonin-1B (5-HT1B) binding sites, recently characterized in the spinal cord of the rat, mediate differential effects of 5-HT on spinal nociceptive processing. Several days after spinal transection at T10, rats were injected intraperitoneally at 20 min intervals, with increasing doses (0, 0.1, 0.4, 2.0, 9.0 mg/kg) of either a 5-HT1A selective agonist (8-OH-DPAT, buspirone) or a 5-HT1B agonist (mCPP, TFMPP). Nociceptive sensitivity was determined by quantifying, in cm2, changes from baseline in the receptive field areas of three spinal nociceptive withdrawal reflexes after noxious (greater than 400 mmHg) levels of mechanical stimulation. The 5-HT1A agonist 8-OH-DPAT and buspirone, significantly increased in a dose-dependent manner the receptive field areas of the three reflexes, with the following log ED50 values (nmol/kg): ventroflexion reflex--buspirone (2.75), 8-OH-DPAT (2.70); dorsiflexion reflex--buspirone (2.91), 8-OH-DPAT (2.67); lateral flexion reflex--buspirone (3.51), 8-OH-DPAT (2.77). The hypersensitivity of the reflexes after pretreatment with buspirone was effectively blocked by the 5-HT1A selective antagonist spiperone, at all doses (0.001, 0.01, 0.1 and 1.0 mg/kg) tested. The 5-HT1B selective agonists mCPP and TFMPP significantly decreased the receptive field are of the ventroflexion reflex (log ED50 values: mCPP, 3.79 nmol/kg; TFMPP, 3.61 nmol/kg) with no significant effect on the dorsiflexion or lateral flexion reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Staphylococcal protein A adsorption in neoplastic disease: analysis of physicochemical aspects.

Staphylococcus aureus organisms and immobilized Staphylococcal protein A have been used as extracorporeal immunoadsorbents for the treatment of neoplastic disease. In a significant number of cases, a biologic response has been documented. This review analyzes the experimental results to date, correlates experimental design parameters with response to treatment, and discusses possible mechanisms of action. The evidence implicates protein A as the tumoricidal agent, although bacterial or complement components may act independently or synergistically. A more quantitative and fundamental approach is needed to exploit the potential for protein A immunoadsorption in treating neoplastic disease.

Adsorption↗
PubMed1988

Selective 5-HT1B agonists identify the 5-HT autoreceptor in lumbar spinal cord of rat.

The purpose of the present study was to characterize the 5-HT autoreceptor in the lumbar spinal cord of the rat. The effect of selective 5-HT1A and 5-HT1B agonists on K+-evoked release of [3H]5-HT and the binding of [3H]5-HT were examined. The 5-HT1B compounds, mCPP and quipazine were more potent than exogenous 5-HT at decreasing K+-evoked release of [3H]5-HT in slices of spinal cord. The pEC40 values of 5-HT agonists tested, determined from release assays, significantly correlated with the relative affinities (pKD's) of these compounds for the binding of [3H]5-HT to the 5-HT1B receptor subtype in the presence of 2 microM 8-OHDPAT, as determined from radioligand binding studies (r = 0.98, P = 0.003). Conversely, the potencies of the 5-HT1A agonists 5-MeODMT and 8-OHDPAT, at the 5-HT autoreceptor, were negatively correlated (r = -0.77, P less than 0.10) with their potencies at displacing [3H]5-HT from the 5-HT1A subsite (binding of [3H]5-HT in the presence of 1 microM mCPP). Thus, the 5-HT autoreceptor in spinal cord appears to bear a significant pharmacological similarity to the 5-HT1B binding site. Further testing of the present results requires the development of new 5-HT1 agonists which are selective (1000-fold difference) for the 5-HT1A and 5-HT1B subsites.

Animals↗
PubMed1988

Quasi-elastic light scattering of antigen-antibody complexes.

Many biological properties of immune complexes (IC) depend upon their size. Quasi-elastic light scattering (QLS) was used to measure a mean equivalent hydrodynamic radius (Rh) and variance of the distribution of model IC composed of bovine serum albumin (BSA) as antigen (Ag) and combinations of two or three well-characterized monoclonal antibodies (MAb) which bound noncompetitively to unique epitopes on BSA. With the molar ratio (X) of each MAb to Ag fixed, Rh increased with concn. Rh was maximal at equivalence (X = 0.5) with two MAb and at slight MAb excess (X = 0.67) with three MAb. The largest Rh with two MAb was about 200 A, and Rh was uniformly different amongst the three combinations of two MAb IC. The largest hydrodynamic radius of individual complexes which formed with two MAb was estimated to be about 400 A; even larger individual complexes were formed with three MAb. Size changes following alteration of solution concns were also followed with QLS. Kinetics of two MAb IC association were too fast to observe; dissociation following large dilution (40-fold) required 5-10 min to attain a new steady state, much less at small dilution. With three MAb, Rh dropped sharply in 5 min and became steady after 1-2 hr. These results suggest that conventional chromatographic and ultracentrifugation techniques for studying IC size, involving large dilution and long measurement time, provide misleading results. Association of three MAb produced a rapid initial increase of Rh in several min, followed by diverse behavior which depended upon concn. From high to low concn, these included (1) exponential growth of Rh with time and appearance of visible macroscopic particles; (2) metastable states for several hr followed by slow growth to large size over several days, leading to formation of particles; and (3) rapid growth to steady state conditions with no visible particles. This heretofore unobserved equilibrium and kinetic behavior of model IC in solution may be reflected in the behavior of more complex, naturally occurring IC.

Animals↗
PubMed1988

Size and structure of antigen-antibody complexes. Electron microscopy and light scattering studies.

Size parameters of model antigen-antibody (Ag-Ab) complexes formed by the interaction of bovine serum albumin (BSA) and pairs of monoclonal anti-BSA antibodies (mAb) were evaluated by quasielastic light scattering, classical light scattering, and electron microscopy (EM). Mean values for the hydrodynamic radius, radius of gyration, and molecular weight were determined by light scattering. Detailed information regarding the molecular weight distribution and the presence of cycles or open chains was obtained with EM. Average molecular weights were calculated from the EM data, and the Porod-Kratky wormlike chain theory was used to model the conformational behavior of the Ag-mAb complexes. Ag-mAb complexes prepared from three different mAb pairs displayed significantly different properties as assessed by each of the techniques employed. Observations and size parameter calculations from EM photomicrographs were consistent with the results from light scattering. The differences observed between the mab pairs would not have been predicted by idealized thermodynamic models. These results suggest that the geometric constraints imposed by the individual epitope environment and/or the relative epitope location are important in determining the average size of complexes and the ratio of linear to cyclic complexes.

Antibodies, Monoclonal↗
PubMed1987

Differential effects of substance P on serotonin-modulated spinal nociceptive reflexes.

Recent immunohistochemical studies indicate the presence of a bulbospinal substance P (SP) system, as well as a bulbospinal serotonin (5-HT) system, involved in spinal pain transmission. Although electrophysiological studies indicate that SP may modulate the effects of 5-HT on postsynaptic spinal nociceptive neurons, the functional relationship between SP and 5-HT on "pain behavior" remains obscure. To bridge this gap between mechanism and behavior, the purpose of the present study was to determine specific postsynaptic behavioral effects of SP and 5-HT on local spinal nociceptive reflexes in spinally transected animals. Administration of the 5-HT agonists 5-methoxydimethyltryptamine (5-MeODMT) (0, 0.5, 1.5, 2.0 mg/kg) and quipazine (0, 5, 10, 20 mg/kg) 2 days after transection significantly expanded the receptive field (RF) areas of three spinal reflexes, as previously reported. Intrathecal administration of SP alone (0, 0.25, 2.5, 7.5 ng) also resulted in hyperalgesia, indicated by a significant expansion of the RF areas of all three nociceptive reflexes. However, administration of SP, in animals pretreated with 5-HT agonists, decreased the 5-HT-induced expansion of RF size. Therefore, SP had opposite effects on spinal nociceptive reflexes depending on whether or not the animal was pretreated with 5-HT agonists, i.e., hyperalgesia in the absence of 5-HT agonists, and analgesia in the presence of 5-HT agonists. The two effects of SP on local spinal reflexes may be related to the anatomical organization of the two spinal SP systems: 1) SP released from primary afferents facilitates nociceptive reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Functional change in the 5-HT presynaptic receptor in spinal cord of aged rats.

The present study assessed the functional integrity of the serotonin (5-HT) presynaptic receptor in the spinal cord of aged (18-20 months) rats. Previous research determined that exogenous 5-HT and 5-HT1B agonists, in adult (3 months) rats, activated the 5-HT presynaptic receptor resulting in a dose-dependent decrease in 3H-5-HT release from spinal cord slices. Contrastively, exogenous 5-HT and the selective 5-HT1B agonist 1-(m-chlorophenyl) piperazine HCl (mCPP) produced a dose-dependent increase in depolarization-evoked 3H-5-HT release from spinal cord of aged rats. The selective 5-HT1A agonist 8-hydroxy-2(di-n-propylamino) tetralin (8-OHDPAT) increased 3H-5-HT release from aged rat spinal cord slices similar to results previously obtained from adult rat spinal cord slices. The inability of 5-HT and mCPP to inhibit 3H-5-HT release from spinal cord of aged rats indicates a functional change in the 5-HT presynaptic receptor in these animals. Possible mechanisms mediating this functional change are discussed.

Aging↗
PubMedDate not supplied

Synthesis and characterization of membrane-active GALA-OKT9 conjugates.

Cellular processing of immunotoxins is inefficient, limiting the overall effectiveness of current immunotoxin therapies. Specifically, translocation of ribosome-inactivating toxins across intracellular membranes is agonizingly slow. In one strategy to improve immunotoxin efficacy, membrane-active peptides are attached to immunotoxins to facilitate transfer of the toxic moiety across a cellular membrane to the cytosol. pH-sensitive peptides are of particular interest, as the membrane activity can be localized to the endosomal/lysosomal pathway, reducing nonspecific interactions at the cell surface. In this study, GALA, a pH-sensitive peptide that forms multimeric pores in membranes, was chemically attached to OKT9, an anti-transferrin receptor mAb. Conjugates were tested by measuring release of encapsulated dyes from liposomes to determine the extent to which the membrane-lytic properties of GALA were retained. The most significant feature affecting the lytic properties of GALA-OKT9 conjugates was the number of attached GALA per OKT9. Conjugates with a single GALA per OKT9 caused almost no leakage while conjugates with two or three GALA per OKT9 caused significant leakage in a concentration-dependent manner. Invariably, GALA-OKT9 conjugates were significantly less active than unconjugated GALA, attributable to a decrease both in partitioning and in surface aggregation. No improvement in membrane-lytic activity was achieved by using a longer, more flexible poly(ethylene glycol) cross-linker. Attachment of GALA via C- versus N-terminal linkage had no effect on membrane-lytic properties. Size-selective release of high molecular weight dextrans was almost identical for conjugated and unconjugated GALA, suggesting that GALA forms the same pore structure regardless of conjugation state.

Animals↗
PubMedDate not supplied

Creatively teaching the interrelationships of a nursing model.

Nursing students find that the abstract description of nursing models is difficult to understand and apply. On the other hand, strategies that operationalize these concepts through concrete applications within everyday experiences help to promote the students' understanding. The author describes an exercise for teaching nursing students the central concepts of a nursing model.

Curriculum↗