Conditioning of skin conductance levels through a combined instrumental-classical conditioning procedure

A paucity of studies and inconsistent results characterize attempts to instrumentally condition tonic electrodermal activity. The present study was conducted to further explore the classical and instrumental conditioning of skin conductance levels (SCLs) through auditory analogue feedback. Fifty undergraduates were randomly assigned to one of five groups of equal size: instrumental conditioning alone, classical conditioning alone, instrumental and classical conditioning combined, and two control groups. The combined training group achieved significantly higher SCLs relative to the group receiving instrumental conditioning alone.     

Immunocytochemical visualization of coated pits and vesicles in human fibroblasts: relation to low density lipoprotein receptor distribution.

The coated pit-coated vesicle system has a key role in the uptake of plasma low density lipoprotein (LDL) and other receptor-bound proteins in human fibroblasts. To study the distribution of coated pits and coated vesicles in fibroblasts by immunochemical techniques at both the light and electron microscopic levels, we immunized rabbits with coat protein extracted from bovine brain-coated vesicles. The resulting anti-coat protein antibody was directed predominantly against clathrin, the 180,ooo dalton protein that constitutes the major component of coat protein. By indirect immunoperoxidase electron microscopy, the anti-coat protein antibody was observed to bind specifically to coated pits on the surface of human fibroblasts and to coated vesicles within the cell. Indirect immunofluorescence and immunoperoxidase staining techniques at the light microscopic level revealed that the coat protein was distributed in fibroblasts in two distinctive patterns: as discrete foci on or near the cell surface that were linearly aligned in association with phase-dense cellular fibers (first pattern), and as intracellular foci that were randomly arranged around the cell nucleus (second pattern). The distribution of coat protein in fibroblasts was compared with the distribution of ferritin-labeled LDL, which was studied with the use of similar electron microscopic and immunofluorescence techniques. As previously reported, electron microscopic studies revealed that the LDL-ferritin binding sites at 4 degrees C were clustered in coated pits. By immunofluorescence microscopy, the LDL-ferritin that was bound to receptors within coated pits was shown to be arranged linearly over the cell surface in a pattern that was similar to the linear arrangement of coat protein (first pattern). Considered together, the current data indicate that coated pits in human fibroblasts contain a protein analogous to clathrin, and that those coated pits which contain receptors for LDL are located over intracellular fibers most likely corresponding to stress fibers. These observationa may have relevance to the mechanisms by which the coated pit-coated vesicle system efficiently delivers recptor-bound ligands to lysosomes.     

Sensitivity to low-dose/low-LET ionizing radiation in mammalian cells harboring mutations in succinate dehydrogenase subunit C is governed by mitochondria-derived reactive oxygen species

It has been hypothesized that ionizing radiation-induced disruptions in mitochondrial O? metabolism lead to persistent heritable increases in steady-state levels of intracellular superoxide (O?(?U+2212)) and hydrogen peroxide (H?O?) that contribute to the biological effects of radiation. Hamster fibroblasts (B9 cells) expressing a mutation in the gene coding for the mitochondrial electron transport chain protein succinate dehydrogenase subunit C (SDHC) demonstrate increases in steady-state levels of O??- and H?O?. When B9 cells were exposed to low-dose/low-LET radiation (5-50 cGy), they displayed significantly increased clonogenic cell killing compared with parental cells. Clones derived from B9 cells overexpressing a wild-type human SDHC (T4, T8) demonstrated significantly increased surviving fractions after exposure to 5-50 cGy relative to B9 vector controls. In addition, pretreatment with polyethylene glycol-conjugated CuZn superoxide dismutase and catalase as well as adenoviral-mediated overexpression of MnSOD and/or mitochondria-targeted catalase resulted in significantly increased survival of B9 cells exposed to 10 cGy ionizing radiation relative to vector controls. Adenoviral-mediated overexpression of either MnSOD or mitochondria-targeted catalase alone was equally as effective as when both were combined. These results show that mammalian cells over expressing mutations in SDHC demonstrate low-dose/low-LET radiation sensitization that is mediated by increased levels of O??- and H?O?. These results also support the hypothesis that mitochondrial O??- and H?O? originating from SDH are capable of playing a role in low-dose ionizing radiation-induced biological responses.     

Myostatin-deficient mice lose more skeletal muscle mass than wild-type controls during hindlimb suspension

Myostatin inhibits myogenesis. Therefore, we sought to determine if mice lacking the myostatin gene [Mstn(-/-)] would lose less muscle mass than wild-type mice during 7 days of hindlimb suspension (HS). Male Mstn(-/-) and wild-type (C57) mice were subjected to HS or served as ground-based controls (n = 6/group). Wild-type mice lost 8% of body mass and approximately 13% of wet mass from biceps femoris, quadriceps femoris, and soleus, whereas the mass of extensor digitorum longus (EDL) was unchanged after HS. Unexpectedly, Mstn(-/-) mice lost more body (13%, P < 0.05) and quadriceps femoris (17%, P < 0.05) mass than wild-type mice and lost 33% of EDL mass (P < 0.01) after HS. Protein expression of myostatin in biceps femoris and quadriceps femoris was not altered, whereas expression of MyoD, Myf-5, and myogenin increased in wild-type mice and tended to decrease in muscles of Mstn(-/-) mice. These data suggest that HS induced myogenesis in wild-type mice to counter atrophy, whereas myogenesis was not induced in Mstn(-/-) mice, thereby resulting in a greater loss of muscle mass.     

Ca2+ binding by Myxicola neurofilament proteins

Titrimetric, 45Ca dialysis, and autoradiographic methods were used to examine how axoplasmic proteins from the giant neuron of the marine annelid Myxicola infundibulum bind calcium. Following the autoradiographic method of Maruyama et al., the 150-160 kD neurofilament subunits were identified as prominent intracellular Ca-binding peptides. Using equilibrium dialysis, extracts of axoplasmic proteins (greater than 50% neurofilament subunits) were examined in 300 mM KCl at different concentrations of free Ca and Mg, and at different pH. Axoplasmic proteins showed a high affinity Ca binding site (K1/2 3-6 microM, capacity 3-7 mumole g-1 protein) at pH 6.8 or pH 7.5. Changing the Mg concentration from 0 to 5 mM had no effect on the Ca binding. Elevating the dialysis pH from 7.0 to 9.0 reduced the apparent number of binding sites for Ca. Using microelectrodes to record the free Ca, microtitrations of axoplasmic proteins were completed by adding small amounts of CaCl2 to 100 microliters volumes of protein solutions. In a medium containing ionic constituents closely resembling those of the Myxicola axon, a Ca binding capacity of 5.0 mumole g-1 protein and a K1/2 of approximately 1 microM were measured.     

Direct sequencing of mitochondrial DNA detects highly divergent haplotypes in blue marlin (Makaira nigricans).

We were able to differentiate between species of billfish (Istiophoridae family) and to detect considerable intraspecific variation in the blue marlin (Makaira nigricans) by directly sequencing a polymerase chain reaction (PCR)-amplified, 612-bp fragment of the mitochondrial cytochrome b gene. Thirteen variable nucleotide sites separated blue marlin (n = 26) into 7 genotypes. On average, these genotypes differed by 5.7 base substitutions. A smaller sample of swordfish from an equally broad geographic distribution displayed relatively little intraspecific variation, with an average of 1.3 substitutions separating different genotypes. A cladistic analysis of blue marlin cytochrome b variants indicates two major divergent evolutionary lines within the species. The frequencies of these two major evolutionary lines differ significantly between Atlantic and Pacific ocean basins. This finding is important given that the Atlantic stocks of blue marlin are considered endangered. Migration from the Pacific can help replenish the numbers of blue marlin in the Atlantic, but the loss of certain mitochondrial DNA haplotypes in the Atlantic due to overfishing probably could not be remedied by an influx of Pacific fish because of their absence in the Pacific population. Fishery management strategies should attempt to preserve the genetic diversity within the species. The detection of DNA sequence polymorphism indicates the utility of PCR technology in pelagic fishery genetics.     

Pyramiding transgenes for multiple resistance in rice against bacterial blight,yellow stem borer and sheath blight

The present investigation revealed that the alk and gel(t) genes, which cause the differences between a japonica rice variety Nipponbare and an indica rice variety Kasalath in terms of the disintegration of endosperm starch granules in alkali solution and their gelatinisation in a 4 M urea solution, respectively, cosegregated in backcross inbred lines derived from a cross between the two varieties. The segregation pattern of the profile for amylopectin chain-length, which was distinguished by enrichment in short chains of DP≦11 and depletion in intermediate-size chains of 12≦DP≦24 in japonica as compared with indica, was exactly the same as those of the above physico-chemical properties of starch granules, and the gene was designated as acl(t). Gene-mapping analysis showed that the starch synthase IIa (SSIIa) gene is located at the alk locus on chromosome 6 in the rice genome. These results lead us to the possibility that different alleles of the SSIIa gene are responsible for differences in amylopectin structure between the two varieties, in that SSIIa plays a distinct role in the elongation of short chains within clusters (A+B₁ chains) of amylopectin. It is proposed that the activity of SSIIa in japonica rice is reduced in amount or functional capacity relative to the activity of this enzyme in indica rice. This, in turn, would explain why starch from japonica rice has a lower gelatinisation temperature than starch from indica rice and is more susceptible to disintegration in alkali or urea. The evidence for this hypothesis is that the alk(t), gel(t), acl(t) and SSIIa genes all map to the same locus. Received: 29 January 2001 / Accepted: 12 April 2001