The significance of an increased RQ after sucrose ingestion during prolonged aerobic exercise

Summary Four well-trained male subjects worked for periods of 6 h on bicycle ergometers at work loads requiring about 47% of their maximal aerobic capacity. In one series of studies they received only water; in a second series they received 100 g of sucrose containing 100 c U-C¹⁴-labelled sucrose at the beginning of the fourth hour of work. In a third series of experiments, the same subjects received 100 g of non-labelled sucrose at the beginning of the fourth hour. During the experiment without U-C¹⁴-labelled sucrose, blood samples were withdrawn and analysed for glucose, lactate and pyruvate content. Data from C¹⁴O₂ recovery in expired air showed a good correlation with the amount of carbohydrate oxidized during the sucrose experiment. Peak values for the respiratory exchange ratio showed the same time response as those observed for the C¹⁴O₂ in the expired air. It is concluded that the observed rise in RQ after sucrose ingestion, under the conditions studied, is of metabolic origin, resulting from a complete conversion of pyruvate to CO₂.     

Influence of deposition parameters on chemical properties of calcium phosphate coatings prepared by using electrostatic spray deposition

The electrostatic spray deposition (ESD) technique offers the possibility of depositing calcium phosphate (CaP) coatings onto various substrate materials with defined chemical and morphological properties. The relationship between physical, apparatus-related deposition parameters, and the chemical characteristics of ESD coatings was investigated by means of X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy to be able to deposit CaP coatings with tailored chemical properties. The results showed that the chemical characteristics of CaP coatings, deposited with use of the ESD technique, were strongly dependent on the deposition temperature, the nozzle-to-substrate distance, the liquid flow rate, and the geometry of the spraying nozzle. By investigating the influence of the deposition temperature, information could be obtained on the formation mechanism of CaP coatings-and specifically the biologically interesting carbonate apatite phase-using the ESD technique. CaP coatings were not formed merely because of solvent evaporation; a chemical reaction was needed to synthesize the coatings. This reaction involved thermal decomposition of the organic solvent butyl carbitol into carbonate ions via formation of intermediate oxalate ions. The amount of carbonate incorporation, and consequently, the Ca/P ratios of the deposited coatings, was shown 1) to decrease with increasing nozzle-to-substrate distance, 2) to decrease with increasing liquid flow rate, and 3) to decrease by making use of a novel two-component nozzle geometry.     

In vivo magnetic resonance imaging explorative study of ectopic bone formation in the rat

In animal studies of tissue engineering of bone, histology remains the standard for assessing bone formation. As longitudinal studies with this method are feasible only at the cost of large numbers of animals, we looked for an alternative. Therefore, demineralized bone matrix (DBM) and inactivated demineralized bone matrix (iDBM) implants were subcutaneously implanted in a rat. At 1, 3, 5, and 7 weeks postimplantation soft X-ray and magnetic resonance imaging (MRI) were done to monitor bone formation in the implants. At 7 weeks, the animal was killed and the implants were retrieved for histology. Our results showed that in vivo MRI is well suited to assess bone formation larger than 0.5 mm in diameter and to monitor the complete three-dimensional shape of the newly formed bone noninvasively and longitudinally. The MRI results matched well with the histology results obtained at 7 weeks. In contrast, X-ray imaging appeared inappropriate to monitor the bone formation process in DBM.     

Autoradiographic localisation of NMDA, quisqualate and kainic acid receptors in human spinal cord.

The phencyclidine (PCP) binding site of the N-methyl-D-aspartate receptor, the kainic acid (KA) receptor and the quisqualate (QA) receptor were visualised, using autoradiography in the human spinal cord and the distributions compared with that of benzodiazepine (BDZ) receptors and substance P (SP). All of the receptor types, and SP, were concentrated in lamina II of the dorsal horn, consistent with physiological data indicating that glutamate is a neurotransmitter of primary afferent terminals in the spinal cord.     

Long-term reduction of vasopressin excretion induced by the central injection of an immunoconjugate (antibody to vasopressin linked to ricin a chain)

We have previously demonstrated that vasopressin-producing neurons are the target of monoclonal antibodies to vasopressin microinjected into the brain tissue. At the same time, this central microinjection of vasopressin-monoclonal antibody into the supraoptic nuclei produced hydro-osmotic disorders mimicking the effects of a central diabetes insipidus. In order to investigate the increase in both duration and amplitude of the biological effects seen after the injection of vasopressin-monoclonal antibody, an immunoconjugate was constructed with the vasopressin-monoclonal antibody IgG1k isotype and the cytotoxic part of the ricin molecule, the ricin A chain. The biological parameters, such as diuresis and urine osmolality which are directly regulated by vasopressin, and vasopressin excretion, were measured after the central injection of this immunotoxin/immunoconjugate. The consequences of immunotoxin injection were also studied when immunotoxin was co-injected with monensin (50 nM) which has been shown to decrease the intracellular degradation of immunotoxin, and plasma complement, which has been shown to increase the neuronal uptake of immunotoxin. Single injection of immunotoxin near the hypothalamic supraoptic nuclei significantly increased diuresis and decreased vasopressin excretion. However, these effects were only transient and disappeared 24 h later. Four successive injections of immunotoxin (one per day) with monensin induced a decrease of vasopressin excretion which was still observed after a resting period of four days after the fourth injection. The long-term reduction of vasopressin excretion was induced in rats receiving four successive injections of a mixture consisting of immunotoxin with monensin and plasma complement. In such experiments, the vasopressin content of urine remained low (55% under the baseline value), two weeks after the fourth injection of immunotoxin. At the same time, the diuresis was increased (80% above the baseline value) and urine osmolality lowered (45% under the baseline value). When non-specific IgG replaced specific antibody, vasopressin excretion, diuresis as well as urine osmolality were unchanged.

The results of this study demonstrated that the use of a specific immunotoxin results in a local interference with the vasopressinergic neurons and induces a long-term reduction of vasopressin secretion.     

Functional and phenotypical studies of the Leu-4 (CD3)+, Leu-1 (CD5)- T lymphocyte.

A small T cell subpopulation expressing the phenotype Leu-5(CD2)+, Leu-4(CD3)+, Leu-1 (CD5)- can be found in peripheral blood and bone marrow of normal individuals. When these cells were sorted out by three colour immunofluorescence cell sorting and tested in limiting dilution assays, they were found to have lower frequencies of proliferating (9.0 +/- 5.6 times, n = 7) and of IL-2 producing cells (11.5 +/- 5.0 times n = 5), and a higher frequency of cytotoxic cells (3.1 +/- 2.6 times, n = 2) than T lymphocytes expressing the three markers. In peripheral blood lymphocytes, 1/3 of the CD3+, CD5- cells were positive for Leu-2a (CD8) while virtually all were negative for Leu-3a (CD4). Four colour flow cytometric analysis revealed a small subset of T cells positive for CD3 and negative for CD5, CD4 and CD8. Approximately 75% of the CD3+, CD5- cells were negative for Leu-7 and CD16 simultaneously. These results shed a light on the phenotype of T cells that escape killing by CD5 and complement in T cell depleted bone marrow and may explain why fewer residual T cells in the depleted marrow are detected by limiting dilution assays than by flow cytometric analysis.     

Transforming growth factor-beta3-loaded microtextured membranes for skin regeneration in dermal wounds

Adverse effects of wound healing, such as excessive scar tissue formation, wound contraction, or nonhealing wounds represent a major clinical issue in today's healthcare. Transforming growth factor (TGF)-beta3 has specifically been implicated in wound healing. Our hypothesis was that local administration of TGF-beta3 to excisional dermal wounds would diminish wound contraction and scar formation. Microtextured wound covers, containing different concentrations of TGF-beta3, were placed onto full-thickness excisional skin wounds in guinea pigs. Tattooed reference marks were used to quantify wound contraction. Sixty-four male guinea pigs in four study groups (5 ng TGF-beta3, 50 ng TGF-beta3, no growth factor, sham wound) were followed for up to 6 weeks. We analyzed 19 different parameters of wound healing. Results showed that, in some instances, the 50-ng TGF-beta3 group gave less contraction, whereas the 5-ng TGF-beta3 group gave more contraction. These differences confirm that TGF-beta3 has an optimum working concentration, and suggest this concentration to be closer to 50 ng than to 5 ng TGF-beta3. However, only very few significant differences occurred, and thus we conclude that the clinical relevance of our findings is negligible. Earlier studies, reporting clinically improved wound healing by TGF-beta3, could therefore not be confirmed by this study.