Autogenetic inhibition of γ-motoneurons in the spinal cat uncovered by Dopa injection

Summary The response of identified gastrocnemius -efferents to stretch of the triceps surae muscle was recorded in the acute spinal cat before and after the injection of Dopa. A strong tonic inhibition during static muscle extension was detectable only in those -efferents which had no resting and reflex activity in the spinal cat, but which responded to Dopa injection with an initially high discharge rate. In contrast -motoneurons with background and reflex activity before Dopa, and some previously quiescent units acquiring a low discharge rate after Dopa did not exhibit any signs of a stretch-dependent inhibition. It is concluded that the observed autogenetic inhibition is limited to the static -motoneurons. The responsiveness to stretch-evoked inhibition was found to be correlated with that to antidromic inhibition induced by repetitive stimulation of the ventral root. This could imply that the activation of -motoneurons by muscle stretch leads to a Renshaw inhibition of the -motoneurons. However, this pathway may be only partly responsible for the autogenetic inhibition of -motoneurons in the spinal cat after Dopa, since the inhibitory effects of muscle stretch were more pronounced than those obtained by antidromic activation of motor axons in the ventral root.     

Short latency cutaneous reflex responses of γ-efferents in the decerebrate cat

Summary The effect of single shock stimulation, up to 20 × threshold (T), of the sural nerve on the discharges of triceps surae -efferents was investigated in decerebrate cats. Units were classified as static (12) or dynamic (7) on the basis of their resting discharge rates (Murphy et al. 1984). All neurones were excited at short latency by sural nerve stimulation and response size was graded with stimulus intensity. Short latency mixed or inhibitory responses were not evident. Although reflex effects first occurred at low stimulus strengths (<-1.5T) in both types of efferent, most responses appeared at higher intensities (> 1.5T). The estimated central delays of the responses of static (3.0 ±1.1 ms, mean± SD) and dynamic (3.4 ± 1.0 ms) -motoneurones were not significantly different and are consistent with spinal oligosynaptic pathways. The present results differ from those of the only previous study (Johansson and Sojka 1985) of the short latency responses of triceps surae static and dynamic -motoneurones to sural nerve stimulation, in which mixed and inhibitory effects were common in anaesthetised cats. Although differences in recording techniques and sampling may account for the apparent disparity between these studies, it is also feasible that a difference in the setting of interneuronal pathways in the two types of preparation is responsible. The results are discussed in relation to the control of -motoneurones with particular reference to the final common input hypothesis (Johansson 1981; Appelberg et al. 1983).     

Operant conditioning of primate triceps surae H-reflex produces reflex asymmetry

Summary Monkeys are able to increase or decrease triceps surae H-reflex when reward depends on reflex amplitude. Operantly conditioned change occurs over weeks and produces persistent alterations in the lumbosacral spinal cord which should be technically accessible substrates of primate memory. Previous work monitored and conditioned triceps surae H-reflex in one leg. To determine whether H-reflex conditioning in one leg affects the control leg, the present study monitored H-reflexes in both legs while the reflex in one leg underwent HR or HR conditioning. Under the HR mode, H-reflex increase was much greater in the HR leg than in the control leg. Under the HR mode, H-reflex decrease was confined to the HR leg. By showing that conditioning of one leg's H-reflex produces H-reflex asymmetry, the data further define the phenomenon and indicate that the other leg can serve as an internal control for physiologic and anatomic studies exploring the sites and mechanisms of the spinal cord memory substrates.     

Identification of time-varying dynamics of the human triceps surae stretch reflex

We examined the time-varying dynamics of the human triceps surae stretch reflex before, during, and after a large stretch was imposed upon the ankle joint, during a constant voluntary contraction of 15% of maximum voluntary contraction. Stretch reflex dynamics were estimated by superimposing a small stochastic displacement on many such stretches and using an ensemble-based time-varying identification procedure to compute impulse response functions relating the perturbation to the evoked electromyogram (EMG) at each point throughout the task. We found that stretch reflex magnitude (relating joint velocity to EMG) varied directly with baseline EMG activity during steady-state conditions before and after the large imposed stretch. Following the large stretch and the reflex activity it evoked, both background EMG and stretch reflex magnitude declined for up to 100 ms; changes in the stretch reflex were substantially greater in magnitude and followed a different time course from the corresponding changes in background EMG, however, indicating that stretch reflex properties were modulated independently of motoneuron pool activation level. Based on timing and the invariance of stretch reflex dynamics across time, it is argued that this behavior is largely mediated via peripheral neural mechanisms. This peripheral modulation of the stretch reflex presumably supplements various descending influences to adjust reflex properties.     

Foraging strategies ofDrosophila melanogaster: A chromosomal analysis

Two larval foraging strategies inDrosophila melanogaster were identified, rover and sitter. Rovers traverse a large area while feeding whereas sitters cover a small area. The difference between rovers and sitters was analyzed genetically by chromosomal substitutions between isogenic stocks. Differences in larval locomotor behavior (crawling behavior) can be attributed to the second chromosome, the rover strategy being dominant over the sitter strategy. Differences in feeding rate (shoveling behavior) are affected additively by both the second and third chromosomes. Natural populations ofDrosophila larvae were sampled three times over a 2-month period; rovers and sitters were at constant frequencies in these populations. The two foraging strategies are discussed in the light of resource utilization in environments where food is distributed continuously or discontinuously.     

Release of leukotrines C (LTC) and D (LTD) from inflammatory macrophages during phagocytosis of zymosan and bacteria

Release of slow-reacting substance (SRS) was obtained from resident mouse peritoneal macrophages (R-M) upon stimulation with phagocytic stimuli (zymosan, bacteria). The release of SRS from thioglycollate elicite M was impaired, whereas that from BCG-elicited M was quantitatively unaffected. However, using a high pressure liquid chromatography separation procedure, quantitative variations between SRS released from R-M and BCG-M were observed. In both cases, LTC was the major component released from M, but greater amounts of LTD were released from BCG-M than from R-M. These data indicate that local environment alters leukotriene generation by M.     

The effects on primary and secondary spindle afferents of fusimotor reflex during ramp and sinusoidal muscle stretch

Summary Tetanic stimulation of ipsilateral Triceps surae afferents leads to a reflex increase in the initial burst from the primary spindle afferents during ramp stretch in both intercollicular decerebrate and spinal preparations. The dynamic index does not change significantly.Slow, low-amplitude sinusoidal muscle stretches (1.6 Hz, 0.55 mm peak-peak) disclose an increased dynamic sensitivity of primary afferents during reflex activation. The same activation in the statically adapted muscle results in a great many cases in little or no increase in spindle discharge rate.In the frequency-stretch relation, the discharge rates of primary afferents in the spinal cat and of secondaries in decerebrate animals are greatly increased by combined fusimotor activation and low-amplitude sinusoidal stretch.We conclude that both static and dynamic motoneurons are implied in this reflex.     

Oncogenic activity of the BK type of human papova virus in inbred rat strains

Summary The oncogenicity of the human polyomavirus BK (BKV) was tested in newborn inbred rats.It was found that the tumor rate was negatively correlated with the levels of T antibody 3 months after inoculation and the frequency of animals with detectable T antibodies 1.5 months after inoculation.By contrast, no influence of viral HI titers on the tumor rates was found. Thymectomy of animals resulted in most experiments in increased tumor rates. Inoculation with BKV of animals later than 24 hours after birth yielded a decrease of tumor rates.The results obtained suggest that T antibody titers present at a critical time after inoculation are associated with low oncogenicity of BKV.The oncogenicity of BKV was comparatively tested in rat strains possessing the allele l or the allele a, respectively. The oncogenicity was significantly higher in rats with the allele l than in rats with the allele a. Rats with the allele l showed lower T antibody response than rats with the allele a.These differences could be explained by the finding that cells of a origin showedin vitro a higher percentage of T antigen bearing cells than did cells of a strain possessing the allele l. In comparison to previous results obtained with BKV inoculated outbred WISTAR rats, the oncogenicity of comparable BKV doses in inbred rats was generally higher and the latency period of tumor manifestation shortened.     

Interaction between antagonist muscles of the human trunk in resting conditions and during postural activity

Summary Under the equitonometric conditions of rest, man is found to have a predominance of the muscular tone of the trunk flexors, which is manifested by the anterior bending of the trunk (bending posture of rest). This predominance is connected in the main with the resilient traction of the iliac-lumbar muscles. The length of rest for the iliac-lumbar muscles is attained at a coaxial angle of about 120° It is presumed that in postural activity the system of reflex to extension of the spine extensors is activated through the receptors of the extended iliac-lumbar muscles. This activating influence is ended upon attainment of the length of rest for the iliac-lumbar muscles, i. e, at a coaxial angle of about 120°. This mechanism is used for explaining the electrical silence in the spine extensors occurring in the standing and sitting posture at a coaxial angle of about 120°. A special case is the flexor relaxation of the spine muscles described by Floyd and Silver.(Presented by Active Member of the Academy of Medical Sciences of the USSR A. V. Lebedinskii). Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 62, No. 10, pp. 7–11, October, 1966.     

Secretion of proinflammatory cytokines by villous chorion tissue in spontaneous abortion

Secretion of proinflammatory cytokines IL-1, TNF-, IL-6, IFN-, and IFN- by the chorion tissue (8-12 weeks) was studied in normal gestation and spontaneous abortion. The production of IL-1, TNF-, and IFN- virtually did not change in spontaneous abortion, while IFN- was not secreted in all experimental groups. The production of IL-6 increased more than 2-fold in patients with spontaneous abortion during the first trimester. These data confirm the involvement of this cytokine in the reproductive processes and in the pathogenesis of miscarriage.     

The glycoprotein nature of murine gamma interferon

Summary Synthesis of murine gamma interferon (MuIFN) by phytohemagglutinin (PHA)-stimulated spleen cells was inhibited in a dose-dependent manner by graded concentrations of tunicamycin or 2-deoxy-glucose, both of which inhibit glycosylation. The homologous (murine) and heterologous (rat) antiviral activities of the MuIFN preparations secreted in the presence of the various concentrations of either glycosylation inhibitor were reduced to similar degrees. MuIFN synthesized in the presence of tunicamycin (tunicamycin-MuIFN) exhibited a lower molecular weight (MW), a lack of binding to immobilized Concanavalin-A (Con A), and different charge properties when compared to MuIFN produced in absence of inhibitor (control-MuIFN). Potent rabbit and rat neutralizing antibodies raised against a control-MuIFN subcomponent, isolated by its specific binding to a Con A affinity column, neutralized the antiviral activity of tunicamycin-MuIFN to the same degree as the immunogen.With 4 Figures     

Sprouting of fusimotor neurones after partial denervation of the cat soleus muscle

Summary Normally, motoneurones innervate only the intrafusal fibres of muscle spindles. This is a report of sprouting of motoneurones to innervate extrafusal muscle fibres following partial denervation of the soleus muscle of kittens. In eight newborn animals, the L7 ventral root was cut on one side under anaesthesia and the animals were then allowed to recover. At approximately 100 days of age animals were reanaesthetised and a study made of mechanical properties of motor units whose axons ran in the S1 ventral root and supplied the partially denervated soleus muscle. Evidence was obtained for sprouting of all surviving motoneurones. In addition, in four experiments axons conducting within the range, on stimulation, produced measurable tension. In one experiment, stimulation of one such axon also produced specific fusimotor effects on four afferents identified as coming from primary endings of muscle spindles. The axon was therefore a fusimotor axon. The effect observed on stimulation of the axon suggested a largely dynamic action. Other examples of axons were encountered that on stimulation produced tension, but which could not be specifically associated with spindles. In addition, a number of axons that did not develop tension were shown, on stimulation, to have fusimotor effects that were static in action. It is concluded that in extensively denervated muscles motoneurones may sometimes sprout to innervate extrafusal fibres. The mechanical properties of the extrafusal fibres innervated by such axons were similar to those of ordinary motor units.     

Selective mediation of ℵ-opioid central cardiovascular effects by ascending noradrenergic pathways

Summary The role of ascending noradrenergic pathways in the mediation of central opiate-induced cardiovascular effects has been investigated. The effects of selective - and -opiate agonists microinjected into the nucleus tractus solitarius (NTS) of urethane anaesthetized rats were compared following 6-hydroxydopamine lesions of either the dorsal (DNAB) or ventral (VNAB) noradrenergic bundles. In sham lesioned animals both opiates elicited a significant pressor effect and a variable but consistent bradycardia. The -agonist responses were not modified in lesioned rats. In marked contrast the pressor effect of the -agonist was abolished in both DNAB and VNAB lesioned rats. The bradycardic response was not significantly modified. These findings are consistent with previous observations that the cardiovascular effects of - and -opiates in the NTS are mediated via different mechanisms, and provide evidence for selective functional actions of endogenous opioids within brain nuclei.     

Differential expression of β1, β3 and β4 integrins in sarcomas of the small,round, blue cell category

Integrins are a large and complex family of membrane spanning heterodimeric cell surface glycoproteins mediating cell/cell and cell/matrix interactions. Small, round, blue cell sarcomas (SRBCS) are a group of poorly differentiated tumours of various and in part uncertain histogenesis displaying similar cytomorphology. Among them are rhabdomyosarcomas (RMS), ganglioneuroblastomas [(G)NB], primitive peripheral neuroectodermal tumours (pPNET) and Ewing's sarcomas (ES). Thirty-two SRBCS were studied immunohistochemically for the distribution of 1, 3 and 4 integrins in situ. We found complex and to some extent differential patterns of 1, 3 and 4 integrin subunit expression in different types of SRBCS: all of the sarcomas studied were consistently 1⁺, 4^–, 2^–. Four of nine RMS were completely negative for all other integrin subunits studied while one RMS was 5⁺ throughout and three RMS were focally 5⁺. Three RMS expressed the 6 and v chains. In contrast to RMS, pPNET and ES, all of which were 1^–, 3^–, (G)NB were 3⁺ and frequently co-expressed 1. The eight pPNET and seven ES studied showed a similarily restricted integrin profile that was limited to the expression of 1 and 5 in nearly all cases. In summary, RMS were 1⁺, 1^–, 3^– and heterogeneously expressed 5 and 6. (G)NB were generally 1⁺, 1⁺, 3⁺, 5^–, 6^–. pPNET and ES were 1⁺, 1^–, 3^–, 5⁺, 6^–. The data illustrate a complex expression pattern of various integrins in SRBCS, a differential expression pattern of some of the integrin subunits among different types of SRBCS and almost identical integrin profiles in pPNET and ES.This paper is dedicated to Prof. Dr. Dres. h.c. Wilhelm Doerr on the occasion of his 80^th birthday     

Anti-5-hydroxytryptamine antibodies: studies on their cross-reactivity in vitro and their immunohistochemical specificity

Summary Antibodies to 5-hydroxytryptamine (5-HT) were obtained from 4 rabbits after injections of 5-HT coupled to bovine serum albumin by means of paraformaldehyde (PF). Two methods were used to monitor the developement of antibodies (AB): the one based on the in vitro competitive binding properties of the antibodies with³(H)5-HT, the other, on their in situ binding properties to endogenous 5-HT, using the peroxidase-anti-peroxidase immunohistochemical technique, applied to paraffin embedded sections of cat brainstem. No pharmacological processing, detergents or proteolytic enzymes were used. The specificity of the antiserum was tested by competitive procedures with 20 analogs using the in vitro and in situ techniques. In vitro studies were performed with 5-HT free analogs and with analogs previously coupled with PF to lysine. Radioimmunological tests showed that the antibodies recognize mainly the ethylamine (CH₂-CH₂-NH₂)-cham of the free analogs and that the best specificity was obtained with the 5-HT conjugate (5-HT-lysine-PF). The results suggest that the hapten is coupled through the phenolic positions C4 or C5. The in situ immunohistochemical extinction assays also revealed a distinct specificity for 5-HT. Possible optical and ultrastructural applications are illustrated in the raphé nuclei of the cat. These results confirm the reliability of radioimmunological tests for studying the specificity of AB directed against haptens, provided that haptens and analogs tested were first chemically transformed to resemble the immunogen (herewith lysine-PF coupling) with regard to its antigenic structure.     

Length-dependent effects of osmotic compression on skinned rabbit psoas muscle fibers

The goal of this study was to characterize the interrelationship between sarcomere length and interfilament spacing in the control of Ca²⁺ sensitivity in skinned rabbit psoas muscle fibers. Measurements were made at sarcomere lengths 2.0, 2.7 and 3.4 m. At 2.7 m the fiber width was reduced by 17% relative to that at 2.0 m and the pCa₅₀ for force development was increased by 0.3 pCa units. In the presence of 5% Dextran T-500 the fiber width at sarcomere length 2.0 m was also decreased by 17% and the Ca²⁺ sensitivity was increased to the same value as at 2.7 m. In contrast, at sarcomere length 2.7 m the addition of as much as 10% Dextran T-500 had no effect on Ca²⁺ sensitivity. At sarcomere length 3.4 m there was an additional 7% compression and the Ca²⁺ sensitivity was increased slightly (0.1 pCa units) relative to that at 2.7 m. However at 3.4 m the addition of 5% Dextran T-500 caused the Ca²⁺ sensitivity to decrease to the level seen at 2.0 m. Given that the skinning process causes a swelling of the filament lattice it is evident that the relationship between sarcomere length and Ca²⁺ sensitivity observed in skinned fibers may not always be applicable to intact fibers. These data are consistent with measurements of Ca²⁺ in intact fibers which indicate that there might be a decline in Ca²⁺ sensitivity at long sarcomere lengths.     

An improved method for the quantitation of cellular migration: Role of αvβ3 integrin in endothelial and smooth muscle cell migration

The present study was undertaken to develop a simple and improvedmethod for the accurate quantitation of cellular migration and to examinethe role of v3 integrins in different cellular migration. Usingour newly developed micro-volume chemotaxis assay, we developed an improvedquantitative method to measure in vitro chemotaxis of smooth muscle orendothelial cells toward different extracellular matrix proteins. Theconvenience in setup and counting of migrated cells using this methodallows for large capacity screening and for various research applicationswith other cells as well. The signal. to noise ratios were in the range of10/1, along with about 10–20% intra- or inter-assayvariabilities. Using this method, we have determined that eithervitronectin at 0.4 µg/well or osteopontin at 0.4 µg/well areselective v3 chemoattractants for endothelial or smooth musclecells (0.5 × 105 cells/well). Additionally, a selective v3small molecule peptiddomimetic, monoclonal antibody LM609, or an anti-3 (v3/II3) anti-body, c7E3 demonstratedmaximal inhibition of cellular migration toward vitronectin or osteopontin.These data suggest the potential utility of this method in assessing therole of various mechanisms in cellular migration and also suggests the potential implication of an v3 antagonist in blocking pathologicalprocesses involving endothelial or smooth muscle cell adhesion/migration.     

Differential expression of SM22 isoforms in myofibroblasts and smooth muscle cells from rabbit bladder

The E-11 and 1-B8 monoclonal antibodies raised to the smooth muscle (SM)-specific SM22 protein from pig stomach were used to study the in vivo and in vitro phenotypic characteristics of myofibroblasts (MF) and SM cells (SMC) from the bladder detrusor muscle and serosal thickening of male rabbit. The 22-kDa SM22 band found in the SM extract appeared to be composed of distinct isoforms when examined in non-equilibrium two-dimensional gel electrophoresis (2D-EF): (the most basic), , , and (the most acidic) in the ratio of 34():23():36():8(). Western blots of 2D-electrophoresed bladder extracts treated with E-11 and 1-B8 showed that , , and , but not isoforms were labeled with E-11, whereas , , and isoforms were stained with 1-B8. This differential immunoreactivity was not influenced by phosphorylation. The tissue distribution of SM22 immunostaining was heterogeneous in the bladder SM and serosal thickening developed as a consequence of partial outflow obstruction of the urinary bladder. At the cellular level, the 1-B8 and E-11 antibodies stained the SMC in a diffuse (the whole cytoplasm) and honeycomb (the peripheral cytoplasm) manner, whereas MF immunostaining was quite homogeneous. The two antibodies also reacted with cultured primary bladder SMC and MF grown in low serum conditions showing a heterogeneous SM22 cell distribution but an identical subcellular localization, i.e., the actin-containing filamentous network, distinguishable in part from that found in vivo. The immunocytochemical, Western blotting and 2D-EF patterns of MF from thickened serosa indicated that the isoform alone is expressed in this tissue. This SM22 variant appeared before the completion of the cellular transition from MF to fully differentiated SMC. This pattern is reminiscent of bladder ontogenesis where SM22 expression in the developing bladder wall precedes that of SM myosin. Taken together these data suggest that: (i) SM22 isoforms are differently assorted in MF vs. SMC; (ii) SM22 is a SMC-lineage marker inasmuch as its expression occurs in an experimental condition characterized by a time-related cell phenotypic transition from MF to SMC, and (iii) cell conversion ability of serosal cells in the adult might take place via the reactivation of a specific foetal gene programme.     

Causal dimensions of college students' perceptions of physical symptoms

According to attribution theory, controllability, locus, and stability are important dimensions underlying causal explanations. The extent to which these theoretical dimensions underlie lay explanations for physical symptoms is unclear. Accordingly, in this study, attributes relevant to the lay public were empirically derived using a multidimensional scaling (MDS) procedure. Undergraduates (N=194) provided similarity judgments for 18 potential causes of physical discomfort. The MDS analysis yielded a three-dimensional solution. The first dimension captured the distinction between physical and nonphysical causes. The second dimension distinguished either variable versus stable causes or those that are controllable versus uncontrollable by health care professionals. The third dimension differentiated causes under low versus high personal control. These findings empirically confirm the theoretically proposed dimensions of personal control and stability and suggest the utility of considering the physical/nonphysical and controllability by health care professional distinctions in future work on attributions in the health domain.