Biomedical subjects
Publications and source records attributed to D L Nelson.
Four new N-alkyl-2-mercapto-1-octylamine hydrochlorides were synthesized via the reaction of 1,2-epithio-octane with corresponding amines following by conversion to the hydrochlorides. The disulfides were obtained by oxidation of the respective thiols. Upon biological assay of the products for activity against infection by Schistosoma mansoni, only 2,2'-dithiobis(N-isobutyl-1-octylamine) exhibited activity.
Alterations in Golgi tendon organs' (Ib afferent receptors) stretch sensitivity were assessed in fatigued gastrocnemius muscle of cats. Muscle fatigue to 60-50% peak tension was induced in 13 cats by electrical stimulation of L7 and S1 ventral roots. Forty-three group Ib afferent fibers were recorded in L7 or S1 dorsal root filaments before and during fatigue. Fiber activity was assessed by applying to the Achilles tendon a 5-mm ramp stretch at 5 or 25-30 mm X s-1. Group Ib afferent responses to both velocities of stretch were either completely abolished or depressed over several seconds compared to pre-fatigue firing frequencies. When responding, longer latencies (measured at 5 mm X s-1 only) to firing onset occurred during fatigue. Increasing the rate of stretch (250 mm X s-1) to produce a 5-mm stretch approximately equivalent to twitch tension time revealed a depression more selective to static stretch sensitivity. Post-excitation depression of the Ib receptor potential appears to be one possible mechanism. These acute adaptations in Ib afferent discharge to muscle stretch were opposite in direction to those recently reported in fatigued muscle for group Ia and group II muscle spindle afferents. Functional implications of these results are discussed.
Perfusion of the coronary artery distal to an occluding angioplasty balloon was performed in 34 patients undergoing coronary angioplasty (PTCA). A randomized crossover study was employed using two exogenous substances as perfusates: lactated Ringer's solution (LR) and a fluorocarbon emulsion (FL), Fluosol-DA 20%. Both substances are electrolyte solutions, but the FL will dissolve more oxygen than the LR. During two attempted coronary artery occlusions of 90 seconds each, we perfused through the central lumen (guidewire channel) of the PTCA catheter at 60 ml/min. With FL perfusion the mean time to onset of angina after occlusion was delayed (41 +/- 21 vs 33 +/- 16 seconds, mean +/- SD; p less than 0.05), the mean duration of angina was shortened (77 +/- 58 vs 92 +/- 70 seconds, p less than 0.05), and the rise in the ST segment of the ECG was reduced (0.15 +/- 0.24 vs 0.2 +/- 0.23 mV, p less than 0.001) when compared to LR perfusion. Balloon occlusion time was able to be extended with FL perfusion (71 +/- 22 vs 59 +/- 22 seconds p less than 0.001). These results indicate that perfusion of the distal coronary artery is possible during PTCA and can reduce ischemia during a prolonged balloon occlusion time.
Words having larger numbers of related associates are more difficult to recall under conditions of intentional learning. This finding indicates that memory performance is inversely related to natural category size. The purpose of the experiments presented in this article was to evaluate the potential influence of orienting task and attention shifts associated with delayed testing on the natural category size effect. The results of Experiments 1 and 2 indicate that it is obtained regardless of task orientation. However, the results of Experiments 2 and 3 indicate that the effect is easily disrupted. Even after only 5 min of solving multiplication problems, words having larger sets of associates are no more difficult to recall than those having smaller sets. These findings suggest that related associates are automatically activated and encoded whenever a familiar concept is experienced in the absence of specific semantic cues. However, words having larger sets will be more difficult to recall only when these related associates are in a state of current activation.
Murine splenocytes immune to influenza virus-activated human T-cells were fused with SP2/0 cells, selected in chemically defined HAT media, and subcloned to yield a monoclonal antibody (MAb) termed 7G7/B6. 7G7/B6 binds to lectin- and antigen-activated T-cells, but not resting T-cells or B-lymphoblastoid lines from the same donor. 7G7/B6 immunoprecipitates a 50-55 kD band from cell surface iodinated PHA-activated T-cells or the T-cell leukemia line HUT 102B2, as shown on SDS-PAGE. Cross-clearing studies demonstrate that 7G7/B6 binds the same cell surface molecule(s) as anti-Tac, a MAb which has been shown previously to recognize the human receptor for IL-2. 35S-methionine pulse chase experiments in HUT 102B2 cells reveal that 7G7/B6 binds to an early (less than 30 min) 35-37 kD and late (greater than 4 h) 50 kD protein. Sequential immunoprecipitations demonstrate that these are identical to the molecules identified by anti-Tac under similar conditions. However, only anti-Tac coprecipitates a higher molecular band at 110 kD. 7G7/B6 and anti-Tac do not competitively inhibit the binding of each other to PHA-activated T-cells. Functional studies reveal that in contrast to anti-Tac, 7G7/B6 has almost no inhibitory effect in vitro on IL-2-driven proliferation of IL-2-dependent T-cell lines, or alloimmune cytotoxic T-cell generation (however, once generated, these cytotoxic T-cells were both 7G7/B6 and anti-Tac positive). Finally, IL-2 does not inhibit the binding of 7G7/B6 to activated T-cells under conditions which result in up to 75% inhibition of anti-Tac binding. Therefore, 7G7/B6 is another MAb recognizing the human IL-2 receptor, but binding to an epitope distinct from that recognized by either IL-2 or anti-Tac.
This single-subject experimental design examined the immediate effects of four neurodevelopmental treatment (NDT) activities on two dependent variables: dorsiflexor muscle activity during an equilibrium response and frequency of heel contact during movement to a standing position. The subject was a 2.5-year-old boy with spastic quadriplegia. During the seven days of Baseline 1 Phase, the nine days of Treatment Phase, and the seven days of Baseline 2 Phase, dorsiflexor muscle activity was examined using an EMG instrument with surface electrodes. Frequency of heel contact was recorded as the number of times in seven trials that the child came to a standing position with his heel contacting the floor. Conditions were identical across all three phases except that four NDT activities were introduced during the Treatment Phase and were withdrawn during the Baseline 2 Phase. The results demonstrated that these NDT activities increased dorsiflexor muscle activity during a posterior equilibrium reaction and increased the frequency of heel contact when the child came to a standing position. This study contributes to the growing body of literature in NDT.
Right to Education legislation has brought physical therapists and adapted physical educators together in the public school setting to serve the child with special needs. Investigation of the role responsibilities of these professionals would facilitate not only communication between the groups, but also understanding of their functions by other school personnel and administrators. We analyzed questionnaires returned by 79 physical therapists and 30 adapted physical educators to determine areas of uniqueness or similarity in 18 identified role responsibilities performed by these two groups. Each subject rated the appropriateness of each role to physical therapists and to adapted physical educators. On 10 of the 18 items, a statistically significant interaction indicated disagreement with regard to the relative contributions of the two professions. On the other 8 items, the two groups agreed that the role responsibility tends to belong to one profession or agreed that either profession could assume the responsibility. These data should provide information to help further delineate the role definitions for each of these professionals. In addition, the most efficient use of available resources may be used to meet the educational needs of these children.
The purpose of this study was to investigate the effects of selected assistive devices on normal standards of gait. The gait characteristics of stride length, step length, step width, and foot angle were analyzed for 24 right-dominant, healthy men under four conditions: right ankle-foot orthosis (AFO), right hemiplegic arm sling (HAS), both devices (AFO+HAS), and no devices. The dependent variables were measured by a standard method from ink traces left by subjects walking on newsprint. Order of conditions was controlled, and cadence remained consistent across all four conditions for each subject. The AFO and AFO+HAS conditions produced statistically significant changes from normal gait characteristics. The HAS alone did not produce significant changes. Data from the study may be used as a basis for goal setting and as a guideline for the optimal level of function possible for a person wearing these devices. The extent of the patient's orthopedic and neurologic involvement should of course be considered.
This article describes a method for generating gray scale analog hard copy images on ordinary paper using a laser printer system. Operation of the computer-controlled laser printer is described. The cost of the laser printer/paper technology is estimated and compared with the cost of multiformat camera/conventional film systems. Results of an initial clinical evaluation of laser printed paper images are presented.
Dynamic and static stretch responses in muscle spindles were investigated in fatigued muscle to determine if acute adaptations do occur in receptor discharge as has been shown after contractions of short duration. Fatigue to 60-50% maximum tetanic tension was induced in the isolated gastrocnemius muscle in 16 cats by sustained, 7 X threshold electrical stimulation (100 Hz) of the cut L7 ventral root and S1 ventral root. Group Ia and II afferent fiber responses to slow ramp stretches (5 mm X s-1) and vibration (100 Hz) applied to the Achilles tendon were monitored before and immediately after muscle tetany to fatigue. Changes in firing characteristics were similar when results from faster (25-30 mm X s-1) ramp stretches were contrasted. During muscle fatigue, decreases in response latency to displacement and increases in resting discharge, mean frequency during stretch, and frequency of firing to vibration were predominant in both afferent fiber types. Static responses were generally lower, indicating a decrease in position sensitivity. Resting muscle force and passive peak muscle stiffness were consistently higher following contraction. The sum effects of these proprioceptive afferent and mechanical muscle responses would be to increase muscle stiffness and thus resist yield in muscle length to perturbations at lower muscle forces. The magnitude of these adaptations in proprioceptive discharge appears dependent on intrafusal muscle fiber activation.
The unique sources of stress for professional women are discrimination, stereotyping, the marriage/work interface, and social isolation. The behavioral, physiological, and psychological consequences of mismanaged stress are examined and four preventive stress management moderators specifically for professional women suggested. These moderators that influence the stress-strain relationships are a mentor, locus of control, self-confidence, and self-awareness. Finally, a three-point research agenda is outlined for extending understanding of stress among professional women.
Injections of cyclic AMP (cAMP) and 8-Br-cAMP into Paramecium and external application of isobutylmethylxanthine (IBMX), an inhibitor of cAMP breakdown, to these cells increased the frequency of ciliary beating and hyperpolarized the membrane potential. When the membrane potential was held equal to the resting potential under voltage clamp, the same experimental conditions which serve to increase intracellular cAMP did not raise the ciliary frequency. We conclude that cAMP is presumably not the direct mediator of the hyperpolarization-induced ciliary activation, although it may be associated with this motor response.
The function and immunoregulation of human IgA memory B cells producing anti-influenza virus antibody was analyzed in vitro in antigen-stimulated cultures. Peripheral blood mononuclear cells (PBMC) from seven of eight normal adult volunteers naturally immunized to influenza virus produced IgA anti-influenza virus antibody when stimulated in vitro with inactivated A/Aichi/68 [H3N2] influenza virus. This IgA antibody response was approximately one-eighth the IgG antibody response. PBMC from each of five patients with selective IgA deficiency failed to produce any measurable IgA antibody. When tonsillar mononuclear cells (TMC) were studied in a similar manner, a relatively higher IgA antibody response was obtained (one-third the IgG antibody) than with PBMC. Additional studies were undertaken to investigate the immunoregulation of this IgA antibody production and the relatively lower amount produced by PBMC than by TMC. Co-cultures of peripheral blood B cells with irradiated peripheral blood T cells (to possibly inactivate a radiosensitive IgA suppressor cell) did not result in a relative increase in IgA antibody production. Also, co-cultures of B cells with increasing numbers of T cells produced parallel increases of IgG and IgA antibody when plotted on a log scale with slopes of approximately 1, suggesting that a single helper T cell was limiting for both isotypes. Finally, pokeweed mitogen-stimulated co-cultures of peripheral blood and tonsillar B and T cells revealed that the B cell population, but not the T cell population, determined the amount of IgA anti-influenza virus antibody produced. Precursor frequency analyses of tonsillar and peripheral blood B cells in antigen-stimulated cultures confirmed that tonsils contained a higher precursor frequency of B cells for IgA anti-influenza virus antibody production (3.95/10(6) B cells) than did peripheral blood B cells (0.65/10(6) B cells). Thus, IgA memory cells are preferentially found in tonsillar tissue as compared with the peripheral blood, consistent with the role of the tonsils as a mucosal immune organ.
The ability of lymphocytes from 11 patients with ataxia-telangiectasia to produce specific antiinfluenza virus antibody in vitro was evaluated. Lymphocytes from these patients produced markedly less antibody than lymphocytes from normal controls when stimulated with type A influenza viruses. Additional studies were undertaken to evaluate the function of the B cells, T cells, and adherent cells of these patients in specific antibody production. B cells from the AT patients produced one-third to one-half as much antiinfluenza virus antibody as did B cells from normals when stimulated with the polyclonal activator Epstein-Barr virus or, in the two cases studied, when stimulated with influenza virus in the presence of normal HLA-identical T-cells, suggesting that a partial B-cell defect contributed to the deficient antibody response in these patients. Helper T-cell function of T-cells from two patients was evaluated in coculture with their HLA-identical sibling's B cells; these studies revealed that the patients' T-cells could provide less help than normals' T-cells but that this help was not entirely deficient. Furthermore, T-cells from AT patients could provide allostimulated helper T-cell function in coculture with allogeneic normal B cells. Taken together, these results suggest that partial defects of B- and T-cell function both contribute to the decreased antiinfluenza virus antibody production by patients with AT.
With the use of an enzyme-linked immunoabsorbent assay to measure soluble human interleukin 2 receptors (IL 2R), certain human T cell leukemia virus I (HTLV I)-positive T cell lines were found to spontaneously release large quantities of IL 2R into culture supernatants. This was not found with HTLV I-negative and IL 2 independent T cell lines, and only one of seven B cell-derived lines examined produced small amounts of IL 2R. In addition to this constitutive production of soluble IL 2R by certain cell lines, normal human peripheral blood mononuclear cells (PBMC) could be induced to release soluble IL 2R by plant lectins, the murine monoclonal antibody OKT3, tetanus toxoid, and allogeneic cells. Such activated cells also expressed cellular IL 2R measurable in detergent solubilized cell extracts. The generation of cellular and supernatant IL 2R was: dependent on cellular activation, rapid, radioresistant (3000 rad), and inhibited by cycloheximide treatment. NaDodSO4-polyacrylamide gel electrophoresis analysis of soluble IL 2R released from either the HTLV I-positive T cell line HUT 102B2 or normal phytohemagglutinin-activated PBMC demonstrated molecules of apparent Mr = 35,000 to 40,000, and 45,000 to 50,000, respectively, somewhat smaller than the mature surface receptor on these cells. The release of soluble IL 2R appears to be a characteristic marker of T lymphocyte activation and might serve an immunoregulatory function during both normal and abnormal cell growth and differentiation.
The purpose of this series of experiments was to determine if and when word recognition would depend on the number of related concepts represented in permanent memory. Words defining either large or small rhyme or meaning categories were studied and tested under various conditions. The results indicated that rhyme category size influenced recognition whenever rhyme was emphasized during both study and testing phases. Words belonging to larger rhyme sets were not recognized as well as those belonging to smaller rhyme sets. In contrast, meaning-related set size had no effect on recognition. These and other findings indicate that the breadth of prior knowledge can influence recognition but only under limited conditions that reactivate this knowledge at test.
Previous work indicates that our ability to recall a recently experienced word is reduced by the number of related concepts that it activates in permanent memory. The purpose of this research was to evaluate the possibility that dominance of primary associates, and not category size, is responsible for this observation. The results of three experiments involving manipulations of target and cue set size, as well as meaning and rhyme, indicate that category size effects are independent of dominance. In fact, the advantage of smaller categories and fewer activated items is substantially reduced for words having very dominant primary associates. The findings are discussed in relation to the Sensory-Semantic model.
The effect of all-trans retinoic acid (RA) on cell proliferation and protein synthesis was examined using neonatal human dermal fibroblasts in culture. Incorporation of [3H]-methylthymidine showed that cell proliferation decreased in response to increasing concentrations of RA. Analysis of proteins secreted into culture medium showed a decrease in the synthesis of both collagen and non-collagenous proteins, paralleling the effect on cell proliferation. Secreted proteins showed increased enzymatic processing of type I procollagen. The enhanced appearance of pc collagens, intermediates in the enzymatic conversion of procollagen to collagen, indicated that retinoic acid increased the activity of procollagen aminoterminal protease. Electrophoretic mobility and mannosylation of fibronectin was unchanged at RA concentrations tested. Cell morphology was unchanged at all concentrations of retinoic acid. The inhibitory effect of RA on cell proliferation is consistent with previous observations. The enhanced activity of procollagen aminoterminal protease may be important in the overall influence of RA on the elaboration of connective tissue.