How well do older persons tolerate moderate altitude?

We studied the physiologic and clinical responses to moderate altitude in 97 older men and women (aged 59 to 83 years) over 5 days in Vail, Colorado, at an elevation of 2,500 m (8,200 ft). The incidence of acute mountain sickness was 16%, which is slightly lower than that reported for younger persons. The occurrence of symptoms of acute mountain sickness did not parallel arterial oxygen saturation or spirometric or blood pressure measurements. Chronic diseases were present in percentages typical for ambulatory elderly persons: 19 (20%) had coronary artery disease, 33 (34%) had hypertension, and 9 (9%) had lung disease. Despite this, no adverse signs or symptoms occurred in our subjects during their stay at this altitude. Our findings suggest that persons with preexisting, generally asymptomatic, cardiovascular or pulmonary disease can safely visit moderate altitudes.     

Production of cell wall hydrolyzing enzymes by barley aleurone layers in response to gibberellic Acid

The cell walls of barley (Hordeum vulgare var. Himalaya) aleurone layers undergo extensive degradation during the tissue's response to gibberellic acid. Previous work had shown that these cell walls consist almost entirely of arabinoxylan. In this study we show that gibberellic acid stimulates endo-β-1,4-xylanase activity in isolated aleurone layers. In addition, gibberellic acid enhances the activity of two glycosidases: β-xylopyranosidase and α-arabinofuranosidase. No gibberellic acid-stimulated cellulase activity was detected. Germination studies showed a similar pattern of enzyme development in intact seeds.     

Role of the cro gene in bacteriophage lambda development

Previous experiments have shown that the product of the cro gene of baeteriophage λ can exert an anti-repression activity, defined by the capacity of certain “cro-constitutive” defective lysogens to channel a superinfecting λ phage toward lytic development. We have used a combination of biological and biochemical assays to draw two main conclusions concerning this anti-repression activity: (1) after infection of a cro-constitutive cell, the superinfecting phage is unable to establish repression because it is unable to commence synthesis of cI protein (λ repressor) at a substantial rate; (2) the cause of this diminished synthesis of cI protein is the capacity of cro product to repress synthesis of the cII and cIII proteins, which normally activate the cI gene to establish repression in an infected cell. From our experiments and those of others, we suggest that cro product possesses a repression activity which is similar to that of the cI protein itself, but normally exerts a very different physiological role: the turnoff of synthesis of replication, recombination and regulation proteins as the virus enters the late stage of lytic development.     

Stochastic emergence of repeating cortical motifs in spontaneous membrane potential fluctuations in vivo

It was recently discovered that subthreshold membrane potential fluctuations of cortical neurons can precisely repeat during spontaneous activity, seconds to minutes apart, both in brain slices and in anesthetized animals. These repeats, also called cortical motifs, were suggested to reflect a replay of sequential neuronal firing patterns. We searched for motifs in spontaneous activity, recorded from the rat barrel cortex and from the cat striate cortex of anesthetized animals, and found numerous repeating patterns of high similarity and repetition rates. To test their significance, various statistics were compared between physiological data and three different types of stochastic surrogate data that preserve dynamical characteristics of the recorded data. We found no evidence for the existence of deterministically generated cortical motifs. Rather, the stochastic properties of cortical motifs suggest that they appear by chance, as a result of the constraints imposed by the coarse dynamics of subthreshold ongoing activity.     

Intracellular expression of a functional short peptide confers resistance to apoptosis

Expression of free short peptides could potentially be used to modulate biochemical cascades and consequently to change cellular phenotypes. Here we demonstrate that expression of a short peptide of 15 amino acids, including the pseudo-substrate site of the baculovirus-apoptosis inhibitor P35, Asp-Gln-Met-Asp (DQMD), leads to abrogation of the apoptotic cascade. Treatment of cells, expressing the DQMD peptide with two apoptosis inducers, etoposide and sodium nitroprusside, (SNP) results in blocking of the apoptotic cascade, indicated by DNA fragmentation and caspase activation. Consequently, stable expression of the DQMD peptide led to protection of cells, following induction of apoptosis and to the outgrowth and enrichment of resistant cell colonies. The results presented in this work demonstrate for the first time the feasibility of expressing in cells functional short peptides that block apoptotic cascade, and to rescue the phenotypically altered cells in a stable fashion. This approach is general and could be applied to the study of other peptides and the respective biochemical cascades.     

Expression of an anti apoptotic recombinant short peptide in mammalian cells

Understanding the mechanisms of the apoptotic and anti apoptotic processes may lead to a better way to control these cascades. Here we demonstrated for the first time the feasibility to express a short functional peptide in mammalian cells that abrogates the apoptosis cascade through interference with the proteolytic activity of the initiator caspase 9 and the executing caspase 3 enzymes. The expression of a short peptide that includes the pseudo-substrate motif of the apoptosis inhibitor protein P35 (Asp-Gln-Met-Asp) leads to the abrogation of cell death induced through either the mitochondrial or the death receptors pathways.Short open reading frames have been detected in several mammalian mRNAs, primarily upstream of the main long reading frame (uORFs), however, direct evidence for de-novo peptides translation has not been provided. Utilizing biochemical and imaging techniques we demonstrate here that the functional recombinant peptide was localized to the cytpoplasmic fraction of the cell.In conclusion, this work demonstrates that ribosomes recognize short ORFs to translate stable short recombinant peptides in mammalian cells. Expression of these intracellular peptides results in the knock down of apoptotic processes to generate apoptosis resistant stable cells.     

Activity-dependent release of tissue plasminogen activator from the dendritic spines of hippocampal neurons revealed by live-cell imaging

Tissue plasminogen activator (tPA) has been implicated in a variety of important cellular functions, including learning-related synaptic plasticity and potentiating N-methyl-D-aspartate (NMDA) receptor-dependent signaling. These findings suggest that tPA may localize to, and undergo activity-dependent secretion from, synapses; however, conclusive data supporting these hypotheses have remained elusive. To elucidate these issues, we studied the distribution, dynamics, and depolarization-induced secretion of tPA in hippocampal neurons, using fluorescent chimeras of tPA. We found that tPA resides in dense-core granules (DCGs) that traffic to postsynaptic dendritic spines and that can remain in spines for extended periods. We also found that depolarization induced by high potassium levels elicits a slow, partial exocytotic release of tPA from DCGs in spines that is dependent on extracellular Ca(+2) concentrations. This slow, partial release demonstrates that exocytosis occurs via a mechanism, such as fuse-pinch-linger, that allows partial release and reuse of DCG cargo and suggests a mechanism that hippocampal neurons may rely upon to avoid depleting tPA at active synapses. Our results also demonstrate release of tPA at a site that facilitates interaction with NMDA-type glutamate receptors, and they provide direct confirmation of fundamental hypotheses about tPA localization and release that bear on its neuromodulatory functions, for example, in learning and memory.