Exercise training improves lusitropy by isoproterenol in papillary muscles from aged rats

Taffet, George E., Lloyd A. Michael, and Charlotte A. Tate.Exercise training improves lusitropy by isoproterenol in papillarymuscles from aged rats. J. Appl.Physiol. 81(4): 1488-1494, 1996.Aging isassociated with a decreased cardiac responsiveness to -adrenergicstimulation. We examined the effect of endurance exercise training ofold Fischer 344 male rats on -adrenergic stimulation of the functionof isolated left ventricular papillary muscle. Three groups wereexamined: sedentary mature (SM; 12-mo old), sedentary old (SO;23-24 mo old), and exercised old (EO; 23-24 mo old) that weretreadmill trained for 4-8 wk. The isometric contractile propertieswere studied at 0.2 Hz and 0.75 mM calcium. Without -adrenergicstimulation, there were no group differences for peak tension, maximumrate of tension development(+dP/dt), or maximum rateof tension dissipation(dP/dt). The time to peak tension was longer (P < 0.05) forboth EO and SO than for SM rats. Half relaxation time(RT_1/2) was prolonged(P < 0.05) for SO compared with SMand EO (which did not differ). The three groups did not differ in the-adrenergic stimulation by isoproterenol of peak tension,dP/dt, time to peak tension, orcontraction duration. The inotropic response(+dP/dt) of SM was greater(P < 0.05) than that in SO or EOrats (which did not differ); however, the lusitropic response(RT_1/2) was lesser(P < 0.05) in SO than in SM or EO rats (which did not differ). Thus exercise training of old rats improved the lusitropic response to isoproterenol without altering theage-associated impairment in inotropic response.

     

FA1 immunoreactivity in endocrine tumours and during development of the human fetal pancreas; negative correlation with glucagon expression

Fetal antigen 1 (FA1) is a glycoprotein containing six epidermal growth factor (EGF)-like repeats. It is closely similar to the protein translated from the human delta-like (dlk) cDNA and probably constitutes a proteolytically processed form of dlk. dlk is homologous to theDrosophila homeotic proteinsdelta andnotch and to the murine preadipocyte differentiation factor Pref-1. These proteins participate in determining cell fate choices during differentiation. We now report that FA1 immunoreactivity is present in a number of neuroectodermally derived tumours as well as in pancreatic endocrine tumours. A negative correlation between FA1 and glucagon immunoreactants in these tumours prompted a reexamination of FA1 immunoreactants during fetal pancreatic development. At the earliest stages of development, FA1 was expressed by most of the non-endocrine parenchymal cells and, with ensuing development, gradually disappeared from these cells and became restricted to insulin-producing beta cells. Throughout development FA1 was not detected in endocrine glucagon, somatostatin or pancreatic polypeptide cells. Moreover, developing insulin cells that coexpressed glucagon were negative for FA1. Thus, there was a negative correlation between FA1 and glucagon both in tumours and during development. These results, together with FA1/dlk's similarity with homeotic proteins, point to a role of FA1 in islet cell differentiation.     

Drosophilarhythms: from brain to behavior

Theperiod(per) gene and thetimeless(tim) gene are essential components of the circadian clock inDrosophila melanogaster. Both gene products interact in interdependent feedback loops, producing a self-sustained cellular rhythmin situ. Several oscillating cells are combined to discrete pacemaker centers that control rhythmic behavior. This paper reviews the work on localizing the circadian pacemaker neurons controlling activity and eclosion, leading to questions about how these pacemaker cells are synchronized to the external light–dark cycle, and how they impose periodicity on behavior. The circadian system ofDrosophilais also compared with that of other arthropods.     

Novel cyanoguanidines with potent oral antitumour activity

4-Pyridyl cyanoguanidines with hydrophobic aromatic side chains showed potent antiproliferative activity in the human breast and lung cancer cell lines MCF-7, NYH and H460. In vivo, treatment with N-(6-chlorophenoxyhexyl)-N′-cyano-N″-4-pyridylguanidine (18, 20 mg/kg/day po.), gave a complete remission of tumours in a model of NYH inoculated nude mice.     

Neural crest cell migration in relation to extracellular matrix organization in the embryonic axolotl trunk

Temporal and regional aspects of early neural crest cell migration in relation to extracellular matrix (ECM) organization and distribution in the embryonic axolotl trunk were studied by light microscopy, TEM, and SEM. The dominating structure of the interstitial ECM is a complex network of fibrils, which are indicated by ruthenium red staining to consist of collagen in association with ruthenium red-positive components, probably including glycosaminoglycans. The ECM fibrils, which are largely used as substratum for locomotion by the crest cells, have a temporally and regionally specific organization and distribution. Increase in ECM fibrils on the neural tube, ahead of the crest cell front, is correlated with initiation of crest cell emigration, and it is suggested that the fibrils may stimulate this process by providing a suitable substratum for cell locomotion. An increase in ECM fibrils in extracellular spaces surrounding the crest cell population is correlated with an expansion of these spaces and with progressing crest cell migration into them. It is proposed that the spatial organization of the ECM fibrils influences crest cell shape and orientation during early migration.     

The effect of glucagon on the kinetics of hepatic mitochondrial calcium uptake

Summary Previous work by this and other laboratories has shown that glucagon administration stimulates calcium uptake by subsequently isolated hepatic mitochondria. This stimulation of hepatic mitochondrial Ca²⁺ uptake byin vivo administration of glucagon was further characterized in the present report. Maximal stimulation of mitochondrial Ca²⁺ accumulation was achieved between 6–10 min after the intravenous injection of glucagon into intact rats. Under control conditions, Ca²⁺ uptake was inhibited by the presence of Mg²⁺ in the incubation medium. Glucagon treatment, however, appeared to obliterate the observed inhibition by Mg²⁺ of mitochondrial Ca²⁺ uptake. Kinetic experiments revealed the usual sigmoidicity associated with initial velocity curves for mitochondrial calcium uptake. Glucagon treatment did not alter this sigmoidal relationship. Glucagon treatment significantly increased the V_max for Ca²⁺ uptake from 292±22 to 377±34 nmoles Ca²⁺ /min per mg protein (n=8) but did not affect the K_0.5, (6.5–8.6 μM). Since the major kinetic change in mitochondrial Ca²⁺ uptake evoked by glucagon is an increase in V_max, the enhancement mechanism is likely to be an increase either in the number of active transport sites available to Ca²⁺ or in the rate of Ca²⁺ carrier movement across the mitochondrial membranes.     

Vitreous Carbon: A New Material for Making Microtome Knives

The quality of sections obtained by microtomy depends to a large extent on the quality and characteristics of the microtome knife itself. Despite the need for improved microtomy techniques, there have been few significant developments since the introduction of glass and diamond knives in the 1950's. The manufacture of microtome knives from vitreous carbon provides new possibilities for developing both improved methods and improved equipment for specimen sectioning. Vitreous carbon has unique physical properties that lend themselves to the generation of precision cutting edges. Such an edge can be obtained either by breaking a piece of vitreous carbon or by using lapidary techniques. The resultant edge seems well adapted to both thick and thin sectioning. The introduction of vitreous carbon as a sectioning tool offers a significant alternative to metal, glass and diamond knives.     

Settlement of the diazotrophic,phytoeffective bacterial strain Pantoea agglomerans on and within winter wheat: An investigation using ELISA and transmission electron microscopy

The aim of this study was to investigate the ability of Pantoea agglomerans, a plant growth-promoting bacterium, to colonize various regions and tissues of the wheat plant (Triticum aestivum L.) by using different inoculation methods and inoculum concentrations. In addition, the enzyme-linked immunosorbent assay (ELISA) and transmission electron microscopy (TEM) were used to determine: (a) the ability of the bacterial cells to grow and survive both on the surface and within internal tissue of the plant and (b) the response of the plant to bacterial infection. After inoculation, cells of the diazotrophic bacterial strain P. agglomerans were found to be located in roots, stems and leaves. Colony development of bacterial cells was only detected within intercellular spaces of the root and on the root surface. However, single bacterial cells were observed in leaves and stems on the surface of the epidermis, in the vicinity to stomatal cells, within intercellular spaces of the mesophyll and within xylem vessels. Inoculated bacterial cells were found to be able to enter host tissues, to multiply in the plant and to maintain a delicate relationship between endophyte and host. The density of bacterial settlement in the plant in all experiments was about 10⁶ to 10⁷ cells per mL root or shoot sap. Establishment was confirmed by a low coefficient of variation of ELISA means at these concentrations.     

Screening of insect cell lines for the production of recombinant proteins and infectious virus in the baculovirus expression system.

Eight cell lines derived from the insects Spodoptera frugiperda, Trichoplusia ni, Mamestra brassicae, and Estigmene acrea were evaluated for recombinant beta-galactosidase and infectious virus production following infection with the baculovirus Autographa californica multiple nuclear polyhedrosis virus (AcMNPV). Production was assessed on a specific (per cell and per microgram of uninfected cellular protein) and on a volumetric (per milliliter) basis. Cell density was found to be an important factor in comparing the cell lines due to a density-dependent inhibition of specific protein and virus production that appeared to result from cell-cell contact. After infection of cells at low-density specific beta-galactosidase production per cell would drop between 3- and 6-fold in five of the eight cell lines when plated on tissue culture plates at near-confluent and confluent cell densities. The cell lines Sf 21 and Sf 9 were least sensitive to cell density. After accounting for cell density effects and differences in cell size, two cell lines, BTI Tn 5B1-4 and BTI TnM, were identified that were superior to the other cell lines, including Sf 21 and Sf 9, in beta-galactosidase production. Optimal volumetric and specific beta-galactosidase production from Tn 5B1-4 and TnM cells was 2-fold and 5-fold higher, respectively, in both cell lines than the optimal production from Sf 9 or Sf 21 cells. The Tn 5B1-4 cell line also had the highest viability of all the cell lines at 3 days postinfection and could be adapted to serum-free media.(ABSTRACT TRUNCATED AT 250 WORDS)