Integral control in accommodation.

Models of the accommodation system available inthe literature may be classified as proportional controller, optimal bang-bang controller and pure integral controller types. Each of these models explains only some aspects of the experimental behavior of the system and conflicts with other experimental observations. Based on two different experiments in which the built-in phyiological feedback loop has been opened, a leaky-integrator element is proposed for the accommodation controller. This element appears to resolve the conflict between the proportional and integral controller models and also explains the experimental observations better than any of the existing models.     

Cardiovascular control in diabetes mellitus.

Heart rate variability and the changes in heart rate and blood pressure which occur on standing were measured in 21 diabetics. These simple measures distinguished four groups of patients, with loss of parasympathetic activity being commoner than loss of sympathetic activity.     

Glycaemic control in diabetic nephropathy.

To investigate the quality of glycaemic control that is achievable in diabetic patients with persistent proteinuria and asymptomatic but declining renal function three matched groups of patients were studied. The first comprised diabetics with proteinuria receiving continuous subcutaneous insulin infusion; the second, diabetics without proteinuria receiving continuous subcutaneous insulin infusion; and the third, diabetics with proteinuria receiving conventional insulin treatment. Glycaemic control in patients receiving continuous subcutaneous insulin infusion was shown to be appreciably worse during the daytime in diabetics with proteinuria than in diabetics without proteinuria, although greatly superior to that in diabetics with proteinuria receiving conventional insulin treatment. The loss of glycaemic control in patients with proteinuria receiving continuous subcutaneous insulin infusion probably occurred as a response to daytime hypoglycaemia and a consequent reduction in the proportion of the total insulin dose given prandially. Difficulty in controlling blood glucose concentrations may be a factor in the failure of intensified insulin regimens to influence the progression of diabetic renal disease.     

Ethical dilemmas in malaria control.

Because the term "malaria control" specifies an anti-malaria activity rather than an outcome of that action, progress has been evaluated in terms of the effort expended. Plans that specify goals and time lines tend to lack irreversible endpoints. Anti-malaria interventions that are stimulated by economic considerations focus on sites in which the residents enjoy some employment advantage, while interventions based on humanitarian objectives serve the neediest residents of broad regions. Site-specific interventions are conducted by industrial or municipal agencies, while regional interventions are conducted by public agencies. Industry contributes an element of sustainability by injecting the possibility of gainful employment into the site. Efforts that distribute assets mainly to the richest-of-the-poor may fail to preserve lives that would otherwise have been preserved, while those that serve the poorest-of-the-poor may fail to create sustainable cycles of health and wealth. Progress in relieving the burden imposed by malaria requires economically motivated as well as humanitarian contributions, and both should specify realistically time-limited goals that ultimately permit deintensification.     

Neuroplasticity in respiratory motor control.

Although recent evidence demonstrates considerable neuroplasticity in the respiratory control system, a comprehensive conceptual framework is lacking. Our goals in this review are to define plasticity (and related neural properties) as it pertains to respiratory control and to discuss potential sites, mechanisms, and known categories of respiratory plasticity. Respiratory plasticity is defined as a persistent change in the neural control system based on prior experience. Plasticity may involve structural and/or functional alterations (most commonly both) and can arise from multiple cellular/synaptic mechanisms at different sites in the respiratory control system. Respiratory neuroplasticity is critically dependent on the establishment of necessary preconditions, the stimulus paradigm, the balance between opposing modulatory systems, age, gender, and genetics. Respiratory plasticity can be induced by hypoxia, hypercapnia, exercise, injury, stress, and pharmacological interventions or conditioning and occurs during development as well as in adults. Developmental plasticity is induced by experiences (e.g., altered respiratory gases) during sensitive developmental periods, thereby altering mature respiratory control. The same experience later in life has little or no effect. In adults, neuromodulation plays a prominent role in several forms of respiratory plasticity. For example, serotonergic modulation is thought to initiate and/or maintain respiratory plasticity following intermittent hypoxia, repeated hypercapnic exercise, spinal sensory denervation, spinal cord injury, and at least some conditioned reflexes. Considerable work is necessary before we fully appreciate the biological significance of respiratory plasticity, its underlying cellular/molecular and network mechanisms, and the potential to harness respiratory plasticity as a therapeutic tool.     

G proteins in cellular control.

In the past year, cDNA cloning has revealed substantial diversity in G protein alpha, beta and gamma subunits. The number of cellular functions recognized to be controlled by G proteins is also increasing. Most G proteins are associated with the cytoplasmic surface of the plasma membrane, and molecular mechanisms for membrane association of certain G protein subunits have been defined recently. Mutations in G protein subunits, both artificially induced and naturally occurring, have provided important insights into G protein structure and function.