Effects of the presentation of false heart-rate feedback on the performance of two common heartbeat-detection tasks.

Research has indicated that performance on heartbeat counting tasks may be influenced by beliefs about heart rate. Sixty male subjects were administered the Schandry heartbeat counting task after viewing fast, slow, or no heart rate feedback. Subjects were also administered the Whitehead signal-detection type task. Results indicated that subjects who received fast or no heartbeat feedback performed better on the Schandry task than subjects who received slow feedback. Feedback presentation did not affect performance on the Whitehead task. These results suggest that the Schandry task is influenced by external variables (expectations, beliefs) beyond pure awareness of "discrete" visceral sensations and, thus, may not be as powerful a method for determining awareness of individual heartbeats as some other paradigms.

Distribution of coronary arterial capacitance in a canine model.

The capacitative properties of the major left coronary arteries, left main (LM), left anterior descending (LAD), and left circumflex (LCX), were studied in 19 open-chest isolated dog hearts. Capacitance was determined by using ramp perfusion and a left ventricular-to-coronary shunt diastolic decay method; both methods gave similar results, indicating a minimal systolic capacitative component. Increased pericardial pressure (PCP), 25 mmHg, was used to experimentally alter transmural wall pressure. The response to increased PCP was different in the LAD vs. LCX; increasing PCP decreased capacitance in the LCX but increased capacitance in the LAD. This may have been due to the different intramural vs. epicardial volume distribution of these vessels and a decrease in intramural tension during increased PCP. Increased PCP decreased LCX capacitance by approximately 13%, but no changes in conductance or zero flow pressure intercept occurred in any of the three vessels, i. e., evidence against the waterfall theory of vascular collapse at these levels of PCP. Coronary arterial capacitance was also linearly related to perfusion pressure.

Putrescine Aminopropyltransferase Is Responsible for Biosynthesis of Spermidine, Spermine, and Multiple Uncommon Polyamines in Osmotic Stress-Tolerant Alfalfa.

The biosynthesis of polyamines from the diamine putrescine is not fully understood in higher plants. A putrescine aminopropyltransferase (PAPT) enzyme activity was characterized in alfalfa (Medicago sativa L.). This enzyme activity was highly specific for putrescine as the initial substrate and did not recognize another common diamine, 1,3-diaminopropane, or higher-molecular-weight polyamines such as spermidine and spermine as alternative initial substrates. The enzyme activity was inhibited by a general inhibitor of aminopropyltransferases, 5[prime]-methylthioadenosine, and by a specific inhibitor of PAPTs, cyclohexylammonium sulfate. The initial substrate specificity and inhibition characteristics of the enzyme activity suggested that it is a classical example of a PAPT. However, this enzyme activity yielded multiple polyamine products, which is uncharacteristic of PAPTs. The major reaction product of PAPT activity in alfalfa was spermidine. The next most abundant products of the enzyme reaction using putrescine as the initial substrate included the tetramines spermine and thermospermine. These two tetramines were distinguished by thin-layer chromatography to be distinct reaction products exhibiting differential rates of formation. In addition, the uncommon polyamines homocaldopentamine and homocaldohexamine were tentatively identified as minor enzymatic reaction products but only in extracts prepared from osmotic stresstolerant alfalfa cultivars. PAPT activity from alfalfa was highest in meristematic shoot tip and floral bud tissues and was not detected in older, nonmeristematic tissues. Product inhibition of the enzyme activity was observed after spermidine was added into the in vitro assay for alfalfa PAPT activity. A biosynthetic pathway is proposed that accounts for the characteristics of this PAPT activity and accommodates a novel scheme by which certain uncommon polyamines are produced in plants.

Normative data for the personal report of confidence as a speaker.

Normative data for the Personal Report of Confidence as a Speaker (PRCS; Paul, 1966), a measure of public-speaking anxiety, were collected by administering the PRCS to 1109 college students. PRCS scores were examined in relation to gender, race, age, and grade-point average. No significant between-group differences were found. The findings indicate that levels of public-speaking anxiety are generally constant across gender, race, and age. Normative data for all scores across Caucasian and African-American subjects are presented.

Governance challenges for managed care organizations. Interview by Ann C. Bartling.

When Healthcare Executive asked managed care organization CEOs and board chairs to identify governance challenges, they found the question so easy that it was difficult to limit their responses. while all the healthcare leaders interviewed pointed to the need to--and challenge of--staying ahead of the changes affecting the healthcare field, many identified challenges that were more specific to their organizations, markets, or patient population. Some also pointed out that while their challenges may be shared by hospitals and other provider organizations, there were aspects of each that were particularly relevant to managed care organizations, which often offer a variety of products in a number of different of markets.

Direct action of endotoxin on cardiac muscle.

While the cardiovascular effects of endotoxin include myocardial depression, presumably due to circulating myocardial depressant substances, endotoxin itself is supposed to have no direct effect on the heart. In these experiments, we compared the direct effects of endotoxin on the contractile response of feline papillary muscle to calcium with that seen after administration to the intact animal. The contractile state of the muscle was assessed from developed tension as extracellular calcium concentrations were varied from .5 to 8.0 mM. When endotoxin was administered to the intact animal as well as given to the muscle directly in the bathing solution, endotoxin- exposed muscles showed smaller increases in contractile tension with increasing calcium concentrations than control muscles after 70-85 min. NaOH-inactivated endotoxin produced results similar to the control experiments. Previous experimenters have reported myocardial depression only after endotoxin had circulated in the intact animal for 1-2h; these experiments show a direct depressant effect of endotoxin on cardiac muscle without the release of a substance elsewhere in the body.

Regeneration of shoots from cell suspension-derived protoplasts ofAllium cepa.

Callus from pre-selected regenerating lines ofAllium cepa andA. fistulosum were used to initiate cell suspensions. Small clusters of callus selected for greater friability were placed into BDS liquid medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BA), and were subcultured biweekly. Rapidly growing, finely dispersed lines were used for protoplast isolation. The highest yields came from 3-4 month old cell suspension lines. Protoplasts were cultured in modified K8P liquid medium. Microcalli recovery depended on the number of weeks the cell suspension had been in culture with highest recovery from 4-5 month old cell suspensions. Microcalli were moved to semisolid media when they were approximately 2 mm in diameter. After 4-6 weeks, embryogenic calli thus recovered were moved to variations of standard onion regeneration media containing picloram and BA. Elongating shoots were obtained from up to 88 % of the microcalli of one line, and 40-50 % of the shoots were further multiplied in culture.

Somatic embryogenesis and plant regeneration from zygotic embryo explants in mexican weeping bamboo, Otatea acuminata aztecorum.

An efficient protocol has been developed for the in vitro propagation of Mexican Weeping Bamboo through somatic embryogenesis from zygotic embryo explants. Mature seeds and excised embryos were cultured in the light or in the dark on both Murashige and Skoog's and Gamborg's B5 basal media with various supplements. Optimal somatic embryogenesis and plant regeneration were obtained by culture in the dark on Murashige and Skoog's basal medium supplemented with 3 mg/1 2,4-dichlorophenoxyacetic acid, 0.5 mg/1 6-benzylaminopurine and 2.0% sucrose. More than 95% of the germinating somatic embryos developed shoots and roots, and were transferred to soil with 85% success.

Effects of exogenous auxins on expression of lipoxygenases in cultured soybean embryos.

The expression of lipoxygenases (LOXs) is known to be developmentally regulated in soybeans (Glycine max. [L.] Merr.). Hormones have been firmly established as being involved in the growth and developmental processes of a number of plant species. Correlation between the expression of LOXs and the development and germination of soybean embryos suggests that plant hormones may affect the expression of LOXs. The present studies were conducted to investigate the effects of exogenous auxins on the expression of LOX isozymes and LOX activities in cultured cotyledon tissues of immature soybean seeds. The results revealed that at least one of the more acidic nonembryo LOX isozymes was induced by either alpha-naphthaleneacetic acid or indoleacetic acid but not by 2,4-dichlorophenoxyacetic acid after 4 days' exposure. Levels of LOX-1, -2, and -3 proteins and activities were significantly decreased by 2,4-dichlorophenoxyacetic acid 10 days after explanting. S1 analysis showed that embryo LOX messenger RNAs were detectable in the tissues treated with each of the auxins. The reduced levels of the embryo LOX proteins may, therefore, be regulated at the levels of translation, posttranslational modification, or degradation. The more acidic isozymes induced by alpha-naphthaleneacetic acid showed enzymatic activity and shared the same molecular mass and isoelectric point values as the germination-associated LOX isozymes found in hypocotyls and radicles, suggesting that those LOXs are involved in germination competency of soybean embryos.

Evidence for the occurrence of polyamine oxidase in the dicotyledonous plant Medicago sativa L. (alfalfa).

Polyamine oxidase (EC 1.5.3.3) activity has not been detected previously in cells of dicotyledonous plants, although it has been characterized extensively in monocotyledonous plants. Evidence is presented in this report for the occurrence of polyamine oxidase in dialyzed crude extracts of the dicotyledonous plant, Medicago sativa L. (alfalfa). Three enzyme assays were used to quantitate the formation of the three products of the reaction catalyzed by polyamine oxidase. 1-Pyrroline formation was measured colorimetrically as a yellow quinazolinium complex with o-aminobenzaldehyde. Hydrogen peroxide formation was measured spectrophotometrically with a coupled peroxidase assay system by peroxidative oxidation of guaiacol. [(3)H]1,3-Diaminopropane formation was measured by using [1,8-(3)H]spermidine as the substrate and separating the radiolabelled reaction product from the substrate by paper electrophoresis. This latter assay provided evidence that a polyamine oxidase of type [EC 1.5.3.3] catalyzed the cleavage reaction between a secondary nitrogen atom and an adjacent carbon of the butyl moiety of spermidine. Significant polyamine oxidase activity was detected in floral tissues, cortex tissues of the root, young leaves, and young germinated seedlings of alfalfa. The occurrence of polyamine oxidase in alfalfa accounts for the formation of the essential substrate, 1,3-diaminopropane, required for the biosynthesis of the uncommon polyamines, norspermidine and norspermine, which we have recently detected in alfalfa.

Novel occurrence of uncommon polyamines in higher plants.

Diamines and polyamines are ubiquitous components of living cells, and apparently are involved in numerous cellular and physiological processes. Certain "uncommon" polyamines have limited distribution in nature and have been associated primarily with organisms adapted to extreme environments, although the precise function of these polyamines in such organisms is unknown. This article summarizes current knowledge regarding the occurrence in higher plants of the uncommon polyamines related to and including norspermidine and norspermine. A putative biosynthetic pathway to account for the occurrences of these uncommon polyamines in higher plants is presented, with a summary of the supporting evidence indicating the existence of the requisite enzymatic activities in alfalfa, Medicago sativa L.

Detection of Norspermidine and Norspermine in Medicago sativa L. (Alfalfa).

Shoot meristem tissues of alfalfa, Medicago sativa L., were found by high performance liquid chromatography analyses to contain the uncommon polyamines, norspermidine and norspermine. The chemical structures of norspermidine and norspermine, purified from alfalfa, were confirmed by comparison of mass spectra with those from authentic standards. The discovery of norspermidine and norspermine in alfalfa implicates the presence of at least two biosynthetic enzymes, a polyamine oxidase and a previously uncharacterized aminopropyltransferase.

High efficiency Agrobacterium-mediated transformation of Lycopersicon based on conditions favorable for regeneration.

A successful Agrobacterium-mediated transformation system involving a disarmed Ti plasmid is composed of two stages: transformation of cells and recovery of transformed plants. A tissue transformation system with 34% efficiency was developed using stem segments of the interspecific tomato hybrid Lycopersicon esculentum × L. pennellii. This transformation system emphasizes three factors favoring the recovery of transformed plants: 1) promotion of cell division activity at the inoculation site with kinetin in the incubation medium, 2) promotion of adventitious bud initiation by using organized tissue explants in culture, and 3) application of selection at the shoot development stage of adventitious regeneration.

De novo shoot organogenesis of Pinus eldarica Medw. in vitro : I. Reproducible regeneration from long-term callus cultures.

Seedling-derived explants of the Afghan pine, Pinus eldarica, were cultured in a triplicate experiment to produce callus that was serially subcultured for up to three years. Callus was removed at various times and induced to regenerate shoots by de novo organogenesis. The shoot regeneration process involved the identification of four discrete developmental steps, each requiring a separate cultural manipulation. In one case a regenerated shoot was induced to root following an auxin pulse treatment. Induction and limited development of buds in callus derived from mature-tree explants was also achieved. This is the first reproducible system for shoot regeneration from long-term callus cultures of a conifer.

De novo shoot organogenesis of Pinus eldarica Medw. in vitro : II. Macro- and micro-photographic evidence of de novo regeneration.

Semi-thin section microscopy was used to evaluate callus formation and subsequent shoot regeneration in the Afghan pine, Pinus eldarica, as correlated to macro-photography of the same processes. Evidence showed the development of unorganized callus required three to six months. Observations over the following two years of culture revealed that regeneration of buds involved induction of subsurface reorganization in the tissues. Buds emerged through the surface of the callus later during development. Evidence indicated regeneration was de novo in origin and proceeded by the mode of shoot organogenesis. A single shoot was adventitiously rooted with continuous vascular connection between shoot and root.

Orientation bandwidths of spatial mechanisms measured by masking.

Orientation tuning curves were measured at 10 spatial frequencies ranging from 0.5 to 11.3 cycles per degree (cpd) using a masking paradigm. The stimuli were spatially localized test patterns of 1.0 octave bandwidth superimposed upon cosine grating masks. By using a model that corrects for the nonlinearity inherent in the masking process, we obtain the half-amplitude half-bandwidths (theta 1/2) of Cartesian-separable receptive fields that may underlie orientation selectivity. Additional experiments show that the data are not compatible with separability in polar coordinates (spatial frequency and orientation). The orientation half-bandwidths have been found to decrease somewhat with increasing spatial frequency, going from about 30 degrees at 0.5 cpd to 15 degrees at 11.3 cpd, for both sustained and transient forms of temporal modulation. Similar bandwidths are obtained from data where the test is oriented along 45 degrees. These bandwidth estimates are shown to be consistent with subthreshold summation data as well as physiological data from monkey striate cortex.

Spatial frequency tuning of orientation selective units estimated by oblique masking.

Threshold elevations were measured as a function of the spatial frequency of high contrast cosine masks using spatially localized test stimuli with a 1.0 octave bandwidth. The cosine masks were oriented at 14.5 degrees relative to the vertical test patterns in order to average out spatial phase effects. The experiment was repeated for each of 14 test frequencies spanning the range 0.25-22.0 c/deg in 0.5 octave steps. The resulting threshold elevation curves fell into a small number of distinct groups, suggesting the existence of discrete spatial frequency mechanisms in human central vision. The data are shown to be consistent with a model having just six distinct classes of spatial frequency mechanisms in the fovea. Spatial frequency bandwidths of these mechanisms ranged from 2.5 octaves at low frequencies to as narrow as 1.25 octaves at high spatial frequencies. These results require revision of the Wilson and Bergen (1979) [Vision Res. 19, 19-32] model for spatial vision.

Interspecific hybridization of red clover (Trifolium pratense L.) with T. sarosiense Hazsl. Using in vitro embryo rescue.

Interspecific hybrid clover plants from the cross Trifolium sarosiense Hazsl. X T. pratense L. were obtained in the present investigation. Immature hybrid embryos were excised aseptically from the pistillate parent, T. sarosiense (2 n = 48), and cultured in vitro prior to in situ abortion. Agar-solidified nutrient media modified from that developed previously for tissue and cell cultures of red clover (2 n = 14) were used for embryo rescue.The heart shaped embryos obtained were cultured for 8 to 14 days on a medium containing a high level of sucrose, a moderate level of auxin, and low cytokinin activity. Viable embryos were then transferred to a standard medium with low auxin and moderate cytokinin levels for the direct germination of shoots. Some embryos produced only callus. Plants were regenerated from callus using an alternate culture scheme. Hybrid shoot numbers were increased on a low auxin, high cytokinin medium and subsequently rooted before transfer to soil in the greenhouse.About 10% of the hybrid embryos were rescued using the optimal culture sequence. Five full-sib families of the F1 hybrid were successfully grown to maturity. Root-tip cells of hybrid plants possessed the expected somatic chromosome number of 31. The genetically determined leaf-mark trait carried by the staminate parent and the rhizomatous root habit of the pistillate parent were expressed in hybrid plants.