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PubMed1985

Beyond lecture and laboratory in the physical therapy classroom.

The purpose of this paper is to describe how two teaching models, the Inquiry Training Model and the Simulation Model, have been adapted for use in the physical therapy classroom. To help students synthesize the various physical therapy skills they were learning, variations of the Inquiry Training Model and the Simulation Model were used in addition to standard lectures and laboratories to teach the Evaluation Unit to junior level physical therapy students. The feedback obtained at the end of each class from both students and faculty members indicated that the learning experiences were considered both helpful and fun. This article summarizes the important components of the Inquiry Training Model and the Simulation Model. I recommend learning experiences based on these models to augment lecture and laboratory classes.

Feedback↗

PubMed2003

Visual feedback induces opposite effects on elementary centre of gravity and centre of pressure minus centre of gravity motions in undisturbed upright stance.

OBJECTIVE: To evaluate the instantaneous effects of visual feedback on undisturbed stance control mechanisms. DESIGN: The controlling variable, the centre of pressure trajectories, recorded using a force platform, were decomposed into two elementary motions: (1) the horizontal displacements of the centre of gravity and (2) the vertical projection of the difference between centre of pressure and the centre of gravity. These motions were processed through frequential analysis and modelled as fractional Brownian motion. BACKGROUND: Even though visual feedback protocols are advantageously used for rehabilitation purposes, their immediate effects from biomechanical and motor control points of view need to be assessed. METHODS: Twelve healthy adult subjects were tested through eyes open and visual feedback conditions. RESULTS: A significant amplitude increase in the difference between the centre of pressure and the centre of gravity motions and a decrease in the centre of gravity motions are observed during visual feedback. The fractional Brownian motion modelling analysis reveals an enhanced control of these elementary motions. The point at which the corrective process is initiated is increased with visual feedback whereas the time delay remains the same. CONCLUSIONS: The decrease of the centre of pressure displacements classically observed through visual feedback protocol initially results in a reduction of the centre of gravity motions and an augmentation of the difference between centre of pressure and centre of gravity motions, hence suggesting increased muscular activity. RELEVANCE: Precise knowledge of the effects generated by such feedback protocol should allow to optimise it as a rehabilitation tool.

Adult↗

PubMed2001

Muting of androgen negative feedback unveils impoverished gonadotropin-releasing hormone/luteinizing hormone secretory reactivity in healthy older men.

Plasma bioavailable testosterone concentrations decline in healthy older men without a uniformly commensurate rise in serum LH concentrations, which disparity is consistent with a hypothesis of relative hypogonadotropism. Likewise, preserved gonadotrope responsiveness to exogenous GnRH stimulation, despite an attenuated amplitude of endogenous LH pulses, points to reduced hypothalamic GnRH feedforward signaling in aging males. To appraise GnRH/LH secretory reserve more directly in older men, we have compared daily LH secretion, driven by profound short-term blockade of androgen biosynthesis by oral ketoconazole administration, in nine young (ages, 18-32 yr) and seven older (ages, 60-73 yr) volunteers. The ability to unleash endogenous GnRH-driven LH secretion in response to acute testosterone withdrawal was quantitated by sampling blood every 10 min, for 24 h, followed by high-precision immunoradiometric assay. The resultant serum LH concentration profiles were analyzed by: 1) model-free discrete peak detection (Cluster) analysis; 2) the approximate entropy statistic to quantitate pattern regularity; and 3) 24-h rhythmic (cosinor) analysis. At baseline, mean and integrated (24-h) serum LH concentrations were similar in both age cohorts. However, Cluster analysis established an elevated LH peak frequency [18 +/- 0.86 (older) vs. 13 +/- 1.3 pulses/24 h (young), P = 0.0028] and a reduced incremental LH pulse area [37 +/- 6.9 (older) vs. 106 +/- 20 (young) IU/L x min, P = 0.016] in older men. Approximate entropy calculations also revealed more irregular LH release patterns in older men before intervention (P = 0.00089). Feedback stress, achieved by ketoconazole-induced androgen deprivation, unmasked further neuroregulatory defects in older volunteers, who failed to equivalently increase the: 1) mean (24-h) serum LH concentration [i.e. to 5.0 +/- 0.99 (older men) vs. 9.0 +/- 1.1 (young) IU/L, P = 0.000071]; 2) maximal LH peak height (to 6.1 +/- 1.1 vs. 10.4 +/- 1.2 IU/L, P = 0.00043); 3) incremental LH pulse area (to 41 +/- 8.8 vs. 87 +/- 20 IU/L x min, P = 0.016); 4) interpeak nadir serum LH concentration (to 4.0 +/- 0.77 vs. 7.9 +/- 1.0 IU/L, P < 10(-6)); 5) the quantitable irregularity of LH release (P = 0.00089); and 6) the mesor of 24-h rhythmic LH secretion (P = 0.000062). In summary, experimental imposition of a novel hypoandrogenemic open-loop feedback stressor, for 48 h, to heighten hypothalamic GnRH feedforward drive, unveils impoverished augmentation of LH pulse mass, impaired orderliness of LH release, and diminished 24-h rhythmic LH secretion in older men. The foregoing trilogy of neuroregulatory defects identifies unequivocally attenuated hypothalamo-pituitary reactivity to muting of androgen negative feedback in the aging male.

Adolescent↗

PubMed1973

The cyanide gasp and spontaneous deep breaths.

Stimulation of the carotid body chemoreceptors with cyanide in anaesthetized rabbits usually causes a deep breath or gasp, but only if the vagus nerves are intact. This gasp has several similarities with spontaneous deep breaths in eupnoea. In paralysed rabbits, artificially ventilated, chemoreceptor stimulation induces an augmented discharge in the phrenic nerve equivalent to a gasp. In spontaneously breathing rabbits spontaneous deep breaths are more frequent with hypoxia than with normoxia. The results are interpreted in relation to (i) positive feedback from the lungs and (ii) summation of chemoreceptor and tonic vagal drive causing augmented deep breaths.

Anesthesia↗

PubMed1998

Regulation of interleukin-6 and interleukin-6R alpha (gp80) expression by murine immunoglobulin-secreting B-cell hybridomas.

We have examined the contribution of endogenous interleukin-6 (IL-6) to the differentiation of murine B-cell hybridomas. AT73 was established by somatic hybridization between BALB/c mice B cells and 2.52M, a hypoxanthine-aminopterine-thymidine (HAT) medium-sensitive B-cell line mutant. It spontaneously secreted IgM, and addition of exogenous IL-6 augmented IgM secretion. Triggering of CD40 led to an augmentation of IL-6 expression and IgM secretion. Blocking the binding of IL-6 to its cellular receptor through the use of inhibitory monoclonal antibodies inhibited CD40-induced IgM secretion, suggesting a possible autocrine role of IL-6 for the differentiation of a CD40-activated B-cell hybridoma. Co-triggering with CD40 and B-cell receptor or activation through CD40 and IL-4 led to a synergistic augmentation of IL-6 expression as well as additive IgM secretion; this was followed by a marked decrease in the expression of B-cell surface markers on the cell membrane. Furthermore, under conditions where IL-6 expression was augmented, gp80 expression was down-regulated, suggesting a negative feedback mechanism in this B-cell hybridoma. These findings provide a role by which T-cell-dependent activation through CD40 regulates an IL-6 autocrine loop, controlling B-cell differentiation.

Animals↗

PubMed2002

Small area analysis on a large scale--the California experience in mapping teenage birth "hot spots" for resource allocation.

Small-area analysis has become an important tool in the effective targeting of limited public health resources. In California, new funding for teenage pregnancy prevention programs required more and better information to justify the allocation of these funds to areas with the greatest need. Consequently, these funds were allocated using maps with census tract analyses of teenage birth rates and an overlay of geographic frequencies. State and local agencies' programs have responded with positive feedback to the maps, and public health management subsequently has augmented funding for mapping equipment and training. The lessons learned and future directions are discussed.

Adolescent↗

PubMed2003

Nonlinear dynamics of a semiconductor laser with filtered optical feedback and the influence of noise.

We investigate the influence of quantum noise on the highly complex nonlinear dynamics that arise in a single-mode semiconductor laser subject to filtered optical feedback. Our numerical study, which utilizes rate equations that are augmented by Langevin noise terms to account for the spontaneous-recombination noise, shows that for relatively broad filters the noise may lead to qualitatively different dynamics than predicted by a deterministic analysis. In particular, we find that certain attractors that are predicted in the absence of noise may no longer be available when the effects of noise are correctly incorporated. For narrow bandwidth filters we demonstrate optical-injection-like behavior and identify locking of the semiconductor laser to the relaxation oscillation side peaks. In general, the results indicate that shot noise in the laser can influence the dynamics quite substantially.

Journal Article↗

PubMed2004

Interactions among human immunodeficiency virus (HIV)-1, interferon-gamma and receptor of activated NF-kappa B ligand (RANKL): implications for HIV pathogenesis.

We reported recently that exposure of human T cells to soluble HIV-1 envelope glycoprotein gp120 induced biologically active tumour necrosis factor (TNF)-alpha-related cytokine receptor of activated NF-kappaB ligand (RANKL), the primary drive to osteoclast differentiation and bone resorption. Furthermore, certain anti-HIV protease inhibitors linked clinically to accelerated bone loss in HIV disease blocked the physiological control of RANKL activity by interferon (IFN)-gamma through inhibition of degradation of the RANKL nuclear adapter signalling protein, TNF receptor associated protein 6 (TRAF6). We now report a series of reciprocal interactions among HIV-1, RANKL and IFN-gamma. RANKL augmented HIV replication in acutely and chronically infected cells of T lymphocyte and monocyte lineage, effects which occurred at a transcriptional level in conjunction with activation of NF-kappaB. TNF-alpha and RANKL were markedly synergistic in induction of HIV. Low pharmacological levels of IFN-gamma (0.75-3 ng/ml) suppressed RANKL-driven enhancement of HIV replication, as did L-T6DP-1, a cell-permeable peptide inhibitor of TRAF6. In contrast, HIV replication induced by TNF-alpha and phorbol ester were not inhibited, and in some cases augmented, by IFN-gamma. We conclude that a positive feedback loop exists between RANKL production and HIV replication, which may be relevant to both the pathophysiology of HIV-linked osteopenia and control of HIV growth. This pathway appears distinct from those of other cytokine activators of HIV, with respect to its utilization of TRAF6 and its suppression by IFN-gamma. These data raise the possibility that TRAF-specific inhibitory peptides, alone or in conjunction with IFN-gamma, could be used to regulate HIV activation in vivo.

Bone Diseases, Metabolic↗

PubMed1974

Studies on the mechanism of endogenous pyrogen production. II. Role of cell products in the regulation of pyrogen release from blood leukocytes.

Some characteristics of the process by which endogenous pyrogen (EP), the mediator of fever, is released from cells were examined by using human blood leukocytes incubated in vitro. Studies were designed to examine a possible role for leukocyte products, including EP, in the induction, augmentation, or suppression of pyrogen release by blood leukocytes. Products of stimulated leukocytes, including a partially purified preparation of EP, did not induce significant activation of nonstimulated cells. Also, no evidence was obtained that stimulated cell products either augment or inhibit pyrogen production by other stimulated cells. A feedback control of EP production was thus not observed. A crude preparation of EP, containing other products of activated cells, maintained its pyrogenicity when incubated at pH 7.4 but not at pH 5.0. These studies thus provide no support for hypothesized control mechanisms regulating production of EP by blood leukocytes. By contrast, local inactivation of EP at inflammatory sites may modify the amount of EP entering the blood, and hence fever.

Animals↗

PubMed2004

The potential of robotic technology applied to meet requirements for tools to support microsurgery and cellular surgery.

Microsurgery and processes involving cell manipulation or cell surgery are clinical practices where the operator works at or beyond the threshold of human dexterity. Current tools available are conventional in their design, and this limits consistency and the level of reliability and achievement. Surgical robotic devices have been explored to improve precision in minimal access surgical procedures to augment control of tool points in tissues, and have enabled feedback of sensory data from which the operator is able to deduce information on the tool at the working site. In this paper, relevant technologies are described that can be harnessed to improve perception of tool point interaction with tissues at the working site and to improve tool control at the small scale required in clinical practice for microsurgery and for cell surgery.

Humans↗

PubMed2004

Robotic technology applied to meet the requirements of tools to support microsurgery and cellular surgery.

Humans↗

PubMed1994

Vagal input enhances responsiveness of respiratory discharge to central changes in pH/CO2 in bullfrogs.

This study investigated the interaction between vagal afferent input and central chemosensitivity in modulating the respiratory motor output of in vitro brain stem-spinal cord preparations from adult bullfrogs. With this preparation, the spatiotemporal distribution of respiratory-related motor output emulated that of intact bullfrogs; that is, the fictive breathing pattern was mostly episodic. Recordings from cranial motor nerves (V and X) showed that, without peripheral feedback, increasing the PCO2 of the mock cerebrospinal fluid (thereby reducing pH from 8.3 to 7.7) caused a modest increase in respiration-related burst frequency. When the pulmonary branch of a vagus nerve was stimulated phasically (2 V, 20 Hz, 0.2 ms) during each fictive breath to simulate afferent pulmonary stretch receptor feedback 1) the responsiveness of the preparation to the same changes in pH was augmented nearly threefold and 2) the breathing pattern remained episodic. It appears, therefore, that episodic breathing is an intrinsic property of the central nervous system in bullfrogs. It is concluded that there is a strong interaction between vagal feedback and central chemodetection in controlling the temporal relationships that characterize this episodic breathing pattern.

Animals↗

PubMed1999

Systems conceptualization and treatment of anger.

Clinicians, researchers, and patients tend to view anger as attributable to immediate circumstances and current thoughts. In contrast, systems-oriented thinking approaches anger as a contextual and dynamic phenomenon. Personal dispositional systems of anger (cognitive, physiological, and behavioral) are embedded in an interdependent network of interpersonal and environmental systems. Anger coevolves with and is in equilibrium with these systems. The more adaptive and embedded it is within a system, the greater will be its inertia or resistance to change. The automaticity of anger further challenges its regulation, as does its transfer across domains. Other troublesome systems phenomena associated with anger and aggression are escalation and threshold effects. Anger arousal, as a deviation from homeostasis, is inhibited and counteracted by various negative feedback loops that are properties of internal, interpersonal, and environmental systems. Treatment augments anger-regulatory mechanisms. Interventions aimed at anger reduction should consider the systems in which anger is embedded and the adaptive functions anger serves within those systems. These and other systems concepts are explicated and are illustrated with material from two clinical cases.

Adaptation, Psychological↗

PubMed1996

Interferon-gamma plays a key role in the human mixed lymphocyte culture.

Measurement of cytokines in the mixed lymphocyte culture (MLC) is thought to be a new and relevant parameter for bone marrow transplantation (BMT). Our experiments showed that IFN-gamma plays a central role in the cytokine network following alloantigenic recognition. IFN-gamma itself is induced by IL-2 since anti-IL-2 strongly reduced the secretion of IFN-gamma. As anti-IFN-gamma also diminished the response of IL-2 and sIL-2R, a feedback mechanism between these two cytokines is assumed. Addition of rIFN-gamma to the MLC augmented the release of sCD8 molecules, whereas sCD4 molecules were reduced, indicating that IFN-gamma led to T cell differentiation instead of IL-2 dependent proliferation. In the MLC, a feedback mechanism between TNF-alpha and IFN-gamma exists, since anti-TNF-gamma reduced the secretion of IFN-gamma and anti-IFN-gamma inhibited the release of TNF-alpha. Therefore, IFN-gamma plays a critical role in monocyte activation, T cell differentiation, and IL-2-induced cell growth. We conclude that measurement of IFN-gamma might be a new and more sensitive parameter for BMT than the established proliferation assay, since IFN-gamma directly quantifies T cell activation.

Antigens, CD↗

PubMed2004

Chronic treatment with the monoamine oxidase inhibitor phenelzine increases hypothalamic-pituitary-adrenocortical activity in male C57BL/6 mice: relevance to atypical depression.

Atypical depression has been linked to low hypothalamic-pituitary-adrenocortical axis activity and exhibits physical and affective symptoms resembling those of glucocorticoid deficiency. Because atypical depression has also been defined by preferential responsiveness to monoamine oxidase inhibitors (MAO-I), we hypothesized that MAO-I reverse these abnormalities by interfering with glucocorticoid feedback and increasing hypothalamic-pituitary-adrenocortical activity. To test this hypothesis, we measured plasma hormones and ACTH secretagogue gene expression in male C57BL/6 mice treated chronically with saline vehicle or phenelzine, a representative MAO-I. Changes in glucocorticoid feedback were evaluated using adrenalectomized (ADX) mice with and without corticosterone replacement. Antidepressant efficacy was confirmed by decreased immobility during forced swim testing. Phenelzine significantly increased circadian nadir and postrestraint plasma corticosterone levels in sham-operated mice, an effect that correlated with increased adrenocortical sensitivity to ACTH. Phenelzine increased circadian nadir, but not poststress ACTH in ADX mice, suggesting that phenelzine augmented corticosterone secretion in sham-operated mice by increasing stimulation and decreasing feedback inhibition of hypothalamic-pituitary activity. Consistent with the latter possibility, phenelzine significantly increased plasma ACTH and paraventricular hypothalamus CRH mRNA in ADX, corticosterone-replaced mice. Phenelzine did not increase paraventricular hypothalamus CRH or vasopressin mRNA in ADX mice lacking corticosterone replacement. We conclude that chronic phenelzine treatment induces sustained increases in glucocorticoids by impairing glucocorticoid feedback, increasing adrenocortical responsiveness to ACTH, and increasing glucocorticoid-independent stimulation of hypothalamic-pituitary activity. The resulting drive for adrenocortical activity could account for the ability of MAO-I to reverse endocrine and psychiatric symptoms of glucocorticoid deficiency in atypical depression.

Adrenal Cortex↗

PubMed1975

Effects of gonadal steroids on the basal and LRF-induced gonadotropin secretion by cultures of rat pituitary.

The effects of 17beta-estradiol (E2), progesterone (P4), 20alpha-hydroxypregn-4-en-3-one (20alpha-OHP4), and testosterone (T) on the basal and LRF-induced secretion of LH and FSH were studies in monolayer cultures prepared from the pituitaries of adult female rats. Day 4 cultures were used and all steroids were tested at 10-8M concentration for 4 hr. E2 (2.72 ng/ml) alone caused a nonsignificant increase in basal secretion of both LH and FSH; however, the same dose of E2 significantly (p less than 0.001) inhibited the LRF-induced secretion of LH but not of FSH (74% and 88% of 10-8M LRF-treated level, respectively), Testosterone (2.88 ng/ml) alone significantly increased the basal secretion of LH (136% of control level, p less than 0.05) and augmented the effect of LRF on FSH secretion to 130% of the LRF-treated level (p less than 0.05). Contrary to its negative feedback action on the basal secretion of FSH (46% of control level, P less than 0.05), 20ALPHA-OPH4 (3.15 ng/ml) augmented the effect of LRF on LH secretion (130% of LRF-treated level, P less than 0.05). On the other hand, P4 (3.14 ng/ml) did not cause any significant inhibition in the basal and LRF-induced secretion of either LH or FSH. These data indicate that both of the LH- and FSH-LRF; however, their secretory activities are modulated differently by various steroids.

Animals↗

PubMed1978

Effects of adenosine triphosphate and prostaglandins on vascular adrenergic transmission.

The effects of prostaglandins (PGs) on the adrenergic neuroeffector transmission and their relationship to the action of ATP were investigated. This was in view of the putative negative feedback mediated by ATP or a related purine compound, and the reported stimulation of PG synthesis by adenine nucleotides. The central ear artery and saphenous vein of the rabbit were isolated and their contractile responses to adrenergic nerve stimulation monitored. These responses were markedly reduced by PGE1 and PGE2 and significantly augmented by indomethacin and aspirin, suggesting the occurrence of the PGE-mediated negative feedback. PGF2a facilitated the response of the vein but was without affect on the artery, while arachidonic acid was facilitatory on the former and inhibitory on the latter. Possibly a PGF2a-like substance is formed in the presence of arachidonic acid and, in the vein, masks the effect of any PGE. ATP depressed the arterial and venous contractile response to adrenergic nerve stimulation. This inhibition was not significantly affected by indomethacin or aspirin. It was enhanced in the artery and diminished in the vein by arachidonic acid, but only to the extent of algebraic sum of the effects of ATP and the acid. It seems possible that the purine- and PGE-mediated feedback mechanisms are independent and parallel pathways.

Adenosine Triphosphate↗

PubMed1999

The role of polycyclic aromatic hydrocarbon metabolism in dimethylbenz[a]anthracene-induced pre-B lymphocyte apoptosis.

Previous studies indicated that two prototypic PAH, benzo[a]pyrene (B[a]P) and 7,12-dimethylbenz[a]anthracene (DMBA), suppress the developing immune system by inducing apoptosis in bone marrow pre-B lymphocytes. In bone marrow cultures consisting of pre-B cells growing on bone marrow stromal cell monolayers, pre-B cell apoptosis was shown to be dependent on the aryl hydrocarbon receptor/transcription factor (AhR) expressed in stromal cells. However, it was not determined if AhR activation alone is sufficient or if DMBA metabolism is required for induction of a stromal cell-derived apoptosis signal. To address these issues we assessed: 1) the ability of poorly metabolized AhR ligands to induce pre-B cell apoptosis and 2) the capacity for and the mechanism through which an early DMBA metabolite induces pre-B cell apoptosis. Three poorly metabolized AhR ligands, 2,3,7,8-tetrachlorodibenzo-p-dioxin, 3,3',4,4',5-pentachlorobiphenyl, and 3,3',4,4'-tetrachlorobiphenyl failed to induce pre-B cell apoptosis in bone marrow cultures, indicating that AhR activation alone is not sufficient to induce apoptosis and suggesting a role for PAH metabolism in induction of an apoptosis signal. Consistent with this hypothesis, DMBA-3, 4-dihydrodiol, an early DMBA metabolite, induced significant pre-B cell apoptosis. The ability of DMBA-3,4-dihydrodiol to activate the AhR, inhibition of DMBA-3,4-dihydrodiol-induced apoptosis by alpha-naphthoflavone, and the significantly lower levels of DMBA-3, 4-dihydrodiol-induced apoposis in pre-B cell populations maintained on AhR(-) stromal cells strongly support a role for the AhR in DMBA-3,4-dihydrodiol-induced apoptosis. Of two DMBA-metabolizing enzymes evaluated, CYP1A1 and CYP1B1, the latter appeared to be the more likely to play a role in DMBA-induced apoptosis. These data confirm a role for the AhR in PAH-induced pre-B cell apoptosis, indicate a role for DMBA metabolism, and suggest a feedback loop in which at least one product of DMBA metabolism augments AhR signaling, leading to induction of an apoptosis stimulus.

9,10-Dimethyl-1,2-benzanthracene↗