Glycogen concentrations and endurance capacity of rats with chronic heart failure

The endurance capacities of rats with myocardial infarctions (MI) and of rats having undergone sham operations (SHAM) were tested during a submaximal exercise regimen that consisted of swimming to exhaustion. During this test, a decrement in the endurance capacity of the MI rat was demonstrated as the SHAM rat swam 25% longer than the MI rat (65 +/- 4 vs. 52 +/- 4 min). Glycogen concentrations were measured in the liver and the white gastrocnemius, plantaris, and soleus muscles of SHAM and MI rats that were randomly divided into four subgroups, which consisted of resting control, swim to exhaustion, swim to exhaustion + 24 h recovery, and swim to exhaustion + 24 h recovery + a second swim to exhaustion. The results demonstrated that the glycogen concentrations found in the liver, white gastrocnemius, plantaris, and soleus muscles of the SHAM and MI rats belonging to the resting control groups were similar. After swimming to exhaustion the glycogen concentrations in these tissues were significantly reduced compared with those found in the resting control groups of rats, and after 24 h of recovery the glycogen concentrations in these tissues were again similar to those found in the resting control groups of rats. Since the magnitude of the glycogen depletion in the liver and the white gastrocnemius, plantaris, and soleus muscles was similar in the SHAM and MI rats and because the SHAM rats consistently swam for longer periods of time in each of the experimental groups, it would be logical to assume that the rates of glycogen utilization for the various tissues may have been greater in the MI rat during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Motor control of voluntary arm movements

The motor control of pointing and reaching-to-grasp movements was investigated using two different approaches (kinematic and modelling) in order to establish whether the type of control varies according to modifications of arm kinematics. Kinematic analysis of arm movements was performed on subjects' hand trajectories directed to large and small stimuli located at two different distances. The subjects were required either to grasp and to point to each stimulus. The kinematics of the subsequent movement, during which subject's hand came back to the starting position, were also studied. For both movements, kinematic analysis was performed on hand linear trajectories as well as on joint angular trajectories of shoulder and elbow. The second approach consisted in the parametric identification of the black box (ARMAX) model of the controller driving the arm movement. Such controller is hypothesized to work for the correct execution of the motor act. The order of the controller ARMAX model was analyzed with respect to the different experimental conditions (distal task, stimulus size and distance). Results from kinematic analysis showed that target distance and size influenced kinematic parameters both of angular and linear displacements. Nevertheless, the structure of the motor program was found to remain constant with distane and distal task, while it varied with precision requirements due to stimulus size. The estimated model order of the controller confirmed the invariance of the control law with regard to movement amplitude, whereas it was sensitive to target size.     

Opioid receptor antagonist affinity ligands: 6β-bromoacetamido-6-desoxynaltrexone and 6β-thioglycolamido-6-desoxynaltrexone

The present study, utilizing thioglycolamido as the reactive group, describes the synthesis and pharmacology of a new opioid antagonist affinity ligand, 6-thioglycolamido-6-desoxynaltrexone (TAN) and compares TAN with a related known compound, 6-bromoacetamido-6-desoxynaltrexone (BAN). Both compounds were tested for their reversible and irreversible inhibition of [³H]naloxone binding to calf brain membranes. Reversible binding of BAN and TAN had K_i values of 1×10^–9 and 1×10^–10 M, respectively as determined by log probit plots. Irreversible binding was determined after extensive washing to remove all non-covalently bound ligand. At a concentration of 5×10^–8 and 1×10^–8 M for BAN and TAN irreversible binding was inhibited 50% of the maximum value. A study of the time course of irreversible inhibition of [³H]naloxone binding revealed that maximal inhibition occurred within 5 min with a concentration of 1×10^–7 M of either agent. TAN but not BAN when administered systematically to mice produced an antinociceptive effect as measured by the writhing test. When administered intracerebraventricularly BAN did not block morphine-induced analgesia for more than 2 hr; whereas, with a single ED₅₀ dose of 20 nmoles of TAN i.c.v. morphine-induced analgesia was almost completely blocked for a period of over 24 hr, as determined by the tail flick test. Although the SH group of TAN were required for the covalent interaction with opioid receptors, the site of TAN's interaction appears to involve other than protein SH groups.     

Phylogenetic evidence for the herbaceous origin of angiosperms

The ancestral angiosperm is commonly interpreted as an arborescent to shrubby magnolialean with large, multiparted, complex flowers. We examined this hypothesis using a phylogenetic analysis of new and reevaluated characters polarizabled with outgroup comparison. Our cladistic analysis of basal angiosperms placed the nonmagnolialeanChloranthaceae andPiperaceae at the bottom of the tree. We further inferred the probable ancestral states of characters not polarizable with outgroup comparison by examining their distribution among taxa at the base of our cladogram. The sum of ancestral character states suggests that the protoangiosperm was a diminutive, rhizomatous to scrambling perennial herb, with small, simple flowers.     

Amino acid substitution analysis of E. coli thymidylate synthase: The study of a highly conserved region at the N-terminus

Amino acid substitution analysis within a highly conserved region of Escherichia coli thymidylate synthase (TS), using suppression of amber mutations by tRNA suppressors, has yielded a bank of 124 new mutationally altered TS proteins. These mutant proteins have been used to study the structure-function relationship of the Escherichia coli TS protein at the N-terminus corresponding to residues 20 through 35. This region contains a block of amino acids whose sequence has been well conserved among other known TS proteins from various organisms. Positions 20 through 25 contain a surface loop structure and positions 26 through 35 encompass a β-strand. We find that residues surrounding a β-bulge structure within the β-strand are particularly sensitive to amino acid substitution, suggesting that this structure is maintained by a highly ordered packing arrangement. Three residues in the surface loop that are present at the base of the substrate binding pocket are also sensitive to amino acid substitution. The remainder of the conserved sites, including those at the dimer interface, are tolerant to most, if not all, of the substitutions tested. © 1992 Wiley-Liss, Inc.     

Production, Distribution, and Kinetic Properties of Inulinase in Continuous Cultures of Kluyveromyces marxianus CBS 6556

From a screening of several Kluyveromyces strains, the yeast Kluyveromyces marxianus CBS 6556 was selected for a study of the parameters relevant to the commercial production of inulinase (EC 3.2.1.7). This yeast exhibited superior properties with respect to growth at elevated temperatures (40 to 45°C), substrate specificity, and inulinase production. In sucrose-limited chemostat cultures growing on mineral medium, the amount of enzyme decreased from 52 U mg of cell dry weight⁻¹ at D = 0.1 h⁻¹ to 2 U mg of cell dry weight⁻¹ at D = 0.8 h⁻¹. Experiments with nitrogen-limited cultures further confirmed that synthesis of the enzyme is negatively controlled by the residual sugar concentration in the culture. High enzyme activities were observed during growth on nonsugar substrates, indicating that synthesis of the enzyme is a result of a derepression/repression mechanism. A substantial part of the inulinase produced by K. marxianus was associated with the cell wall. The enzyme could be released from the cell wall via a simple chemical treatment of cells. Results are presented on the effect of cultivation conditions on the distribution of the enzyme. Inulinase was active with sucrose, raffinose, stachyose, and inulin as substrates and exhibited an S/I ratio (relative activities with sucrose and inulin) of 15 under standard assay conditions. The enzyme activity decreased with increasing chain length of the substrate.     

Identification of monoclonal antibodies specific for the T cell receptor complex by Fc receptor-mediated CTL lysis

Monoclonal antibodies (mAb) directed at the T cell receptor complex (TcR) on cloned T cells have generally been identified by their ability to inhibit the clone's antigen-specific function. Because such inhibition is highly dependent on antibody concentration and affinity, detection of anti-clonotypic antibodies to murine alloreactive T cells has been very difficult. In this report, an alternative method is described on the basis of the ability of antibodies specific for the TcR complex to activate T cells in an antigen-independent manner. The assay is based upon the observation that soluble antibodies to human T3 promote lysis of irrelevant, Fc receptor-positive targets by a human CTL line. By using this approach, an anti-TcR mAb has been identified among a panel of murine mAb generated against an alloreactive CTL clone. Induction of lysis by soluble anti-TcR mAb has been shown to require both the expression of Fc receptors on the target cell and conjugate formation between the effector and the target cell. This assay provides a screening procedure that is much more sensitive than inhibition of function, and it preferentially detects antibodies specific for cell surface molecules involved in T cell activation.     

Stereometry in very close-range stereophotogrammetry with non-metric cameras for human movement analysis

In this paper a stereophotogrammetric algorithm based on a black-box approach to the modelling of object to image spaces relationship is proposed. The algorithm is well suited for 'very close-range photogrammetry', with respect to experiments in which the measurement field is 0.5 X 0.5 X 0.5 m or smaller, as in the analysis of a few or small body segments movements. The attainable accuracy is high, better than 0.1% of the observation distance. Non-professional and even different cameras can be used. Consequently an inexpensive experimental set-up can be realized. A very simple, cheap and easily usable calibration object is needed. Computation time for the reconstruction of object-space co-ordinates of point body landmarks is one order of magnitude lower than in the case of the Direct Linear Transformation (DLT) (Abdel Aziz and Karara, Proceedings of the ASP/U1 Symposium on Close-Range Photogrammetry, pp. 1-18. American Society of Photogrammetry, 1971; Marzan and Karara, Proceedings of the Symposium on close-range Photogrammetric Systems, pp. 420-467. American Society of Photogrammetry, 1975). Computation time for calibration is two-fold in respect of the DLT. An example of application to the recording of the movements of the index finger with respect to the metacarpophalangeal joint is given.