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At least 1,099 records · Page 61Linked to original sources
PubMed2005

Mechanisms of ensemble failure of the male gonadal axis in aging.

The systemic availability of testosterone (Te) falls by 35-50% after the sixth decade of life in healthy men. Intercurrent illness, trauma, surgery, stress, weight loss, diverse medications and institutionalization reduce Te concentrations further. Impoverishment of anabolic drive probably contributes to physical frailty and diminished quality of life in older individuals. However, the fundamental mechanisms that mediate hypoandrogenemia in the aging male remain unknown. Recent clinical experiments offer new clues to the mechanistic bases of Te depletion in older men. In particular, the following attributes mark aging-related Te withdrawal: (a) high-frequency and low-amplitude LH pulses; (b) disorderly LH-release patterns, consistent with feedback disruption; (c) normal or heightened LH secretion following single or repeated GnRH stimuli; (d) reduced Te secretory-burst mass with normal basal Te secretion; and (e) impaired Leydig-cell Te production in response to secreted LH pulses (stimulated by flutamide, tamoxifen, GnRH or anastrozole) and infused (recombinant human) LH pulses. The foregoing interconnected findings allow us to frame the integrative postulate that androgen deprivation in the older male reflects multisite failure in the GnRH-LH-testosterone axis. The most proximate locus of impairment is not yet known.

Aged↗
PubMed1991

Theoretical considerations on cell ensembles.

Structure-function interdependency must apply at the supracellular level as well as at cellular and molecular levels. The overall structure and the intercellular geometry of the multicellular erythroblastic island, although strongly dependent upon molecular interactions (which determine or modulate recognition, adhesion, and the like), also carry consequences at a more general physical-chemical level. These relate to such factors as local concentrations and gradients, the nature of the forces and the phase-state of the material in the intercellular region, the generalized intercellular transport processes (diffusional, osmotic, electrokinetic, hydrodynamic, etc.), and the dynamic coupling of flows. Such "other-level" phenomena must play a significant role, and therefore must be taken into account, in formulating a comprehensive picture of the ways in which the microenvironment acts in the management and control of the processes of hematopoietic differentiation and development.

Animals↗
PubMed1990

Effects of nerve agent antidote and heat exposure on soldier performance in the BDU and MOPP-IV ensembles.

This study assessed the effects of nerve agent antidote (atropine/2-PAM chloride versus saline placebo) and heat-humidity (95 degrees F/60% RH versus 70 degrees F/30% RH) on repeated performance of militarily relevant psychological tasks while wearing the battle dress uniform (BDU) and while wearing chemical protective clothing (MOPP-IV). All BDU heat sessions (6 hours) were completed, but with some task impairments and a few subjective reactions. MOPP-IV heat sessions could not be continued beyond 2 hours; all tasks were impaired and subjective reactions were numerous and severe. Atropine/2-PAM significantly shortened endurance time for heat sessions in MOPP-IV.

Adolescent↗
PubMedDate not supplied

[Spike transmission in statistical neuronal ensembles. Induced epileptic focus in a model of hippocampal field CA3].

In a spatially heterogeneous model the transition to supercritical phase was investigated as to the parameter characterizing the activation level of the pyramidal cells related to one another assuming the nonuniformity radius to be R0 = const. This is a transition from spontaneous activity to epileptoid bursts. Before the onset of epileptoid bursts the region of stochastic nonequilibrium of solutions is developed likely to produce pathologic dynamic patterns. With further increase of the activation parameter the system comes to epileptoid state. This synchronized firing of pyramidal cells is accompanied with phases of inhibition. A decrease in the nonuniformity radius leads to the formation of an epileptic focus. It is a dissipative structure. The evolution of it is not further followed, since the transport equations do not include its dynamics.

Hippocampus↗
PubMed1990

[Rumpelstilzchen on the couch--an ensemble of shame, identity and father themes].

The fairy-tale "Rumpelstiltsken" is investigated as to its hidden meaning. A method, already described in the literature, is applied which allows conclusions about the hidden meaning to be drawn on the basis of the fairy-tale's place and handling with the history of literature. The hidden meaning found for "Rumpelstiltsken" lies in the question as to how individuation is possible in a symbiotic mother-child relationship. The answer is given in the fairy-tale in that a third person is introduced, who is, however, not involved in the symbiosis. A metapsychological concept of shame is then formulated on the basis of this understanding of "Rumpelstiltsken".

Child↗
PubMedDate not supplied

[Effect of intramolecular energetic barriers on conformation-non-equilibrium states of protein globules in ensemble].

Within the Blumenfeld's model interpretation theoretical investigations of conformation relaxation of the protein globule were carried out. Analytical expressions describing the relaxation time and cyclic frequency of enzymes synchronization by arbitrary number of metastable states and unequal probabilities of transitions between them were found. It was shown that inequality of activation energies affects the frequency and number of cycles of enzymes synchronous work to a considerably greater degree, than the relaxation time of initial disturbance. The number of macromolecules in the definite conformation state was evaluated and conditions of experimental observation of synchronization were discussed.

Biophysical Phenomena↗
PubMed1988

[The role of cAMP in regulating cell ensembles].

Recent studies on the mechanisms of cell regulation have demonstrated that the reactions occurring with participation of secondary messengers, i.e., cyclic adenosine-3',5'-monophosphate (cAMP), Ca2+, 2',5'-oligoadenylate (oligoA), etc., are closely interrelated and the secondary messengers involved therein can thus be regarded as components of the integral regulatory system of the cell. The interaction between these components occurs via at least two pathways. Firstly, some reactions, that are vital for the cell, are under a simultaneous control of several messengers. Secondly, any changes in the intracellular level of one of the messengers inevitably affects the concentrations of other messengers.

Adenine Nucleotides↗