SNARE complexes and neuroexocytosis: how many, how close?

Regulated secretion is an essential process in all eukaryotic cells. The release of molecules contained inside exocytic granules and synaptic vesicles is mediated by the assembly of a SNARE complex formed by the coil-coiling of three proteins: SNAP-25, syntaxin and VAMP/synaptobrevin. It seems that SNARE complexes assemble together in rosette-shaped super-complexes but there is controversy on the actual number (N) of copies of SNARE complexes that are necessary to mediate exocytosis. We discuss attempts to determine the value of N and suggest that N varies with the type of exocytic vesicles. In addition, we propose that the N value in neuroexocytosis can be estimated by the comparative use of different types of botulinum neurotoxins.     

DNA microarrays in the clinic: how soon,how extensively?

Although DNA microarrays are now widely used in research settings, they have been slow to penetrate clinical practice in spite of their apparent advantages. This is due to the very different requirements for a clinical test in contrast to a research tool, and to a strict necessity for demonstrated clinical utility. There is a clear differentiation between two types of DNA array tests: "genomic" diagnostics, developed to ascertain the presence or absence of mutations, deletions or duplications, and for which clinical evidence is already established, and tests using expression profiling for prognosis or predictive purposes, in which case the clinical correlate must be proven. Most array diagnostics currently used belong, understandably, to the "genomic" variety. It is to be expected that future improvements in tailored technology, as well as a logical trend towards measuring an ever-increasing number of parameters, will ensure an important diagnostic role for DNA arrays in the coming decade.     

Oxygen uptake in heart failure: how much,how fast?

Patients with chronic heart failure (CHF) have limited exercise capacity. Exercise intolerance in CHF is associated with increased mortality; 1 moreover, several studies suggest that interventions that increase exercise capacity in CHF improve prognosis. 2–4 Therefore, as Kemps and colleagues state in this issue of the Netherlands Heart Journal, 5 exercise testing is an important tool for evaluating and monitoring heart failure.     

Schistosome monogamy: who,how, and why?

Schistosomes represent a unique animal model for comparative analyses of monogamy. Indeed, schistosomes are classified at the lowest taxonomical level of monogamous species and lack complex social interactions, which could alter our understanding of their unusual mating system. Elements discussed here include the fact that monogamy in schistosomes could be an ancestral state between hermaphroditism and polygyny or polygynandry and the occurrence of mate changes. In addition, hypotheses are proposed to explain monogamy in schistosomes (e.g. female dispersion, the need for paternal care, oviposition site limitation or aggressiveness, and mate guarding). We also propose future experimental and analytical approaches to improve our understanding of the schistosomes' mating system.     

The evolution of noncoding DNA: how much junk, how much func?

Comparative sequence analysis on a genomic scale has opened the door for the systematic analysis of cis-acting regulatory DNA. It is now possible to begin to answer basic questions such as, how much meaningful noncoding sequence is in the genome? How strong is natural selection on functional noncoding sequences in different species? Two recent articles have capitalized on the comparative genomic approach in an attempt to answer these questions with surprising results.     

Signalling sphingomyelinases: which, where, how and why?

A major lipid signalling pathway in mammalian cells implicates the activation of sphingomyelinase (SMase), which upon cell stimulation hydrolyses the ubiquitous sphingophospholipid sphingomyelin to ceramide. This review summarizes our current knowledge on the nature and regulation of signalling SMase(s). Because of the controversy on the identity of this(these) phospholipase(s), the roles of various SMases in cell signalling are discussed. Special attention is also given to the subcellular site of action of signalling SMases and to the cellular factors that positively or negatively control their activity. These regulating agents include lipids (arachidonic acid, diacylglycerol and ceramide), kinases, proteases, glutathione and other proteins.     

Lipid trafficking sans vesicles: where, why, how?

Eukaryotic cells possess a remarkable diversity of lipids, which distribute among cellular membranes by well-characterized vesicle trafficking pathways. However, transport of lipids by alternate, or "nonvesicular," routes is also critical for lipid synthesis, metabolism, and proper membrane partitioning. In the past few years, considerable progress has been made in characterizing the mechanisms of nonvesicular lipid transport and how it may go awry in particular diseases, but many fundamental questions remain for this rising field.     

Biofeedback in medicine: who,when, why and how?

Biofeedback is a mind-body technique in which individuals learn how to modify their physiology for the purpose of improving physical, mental, emotional and spiritual health. Much like physical therapy, biofeedback training requires active participation on the part of patients and often regular practice between training sessions. Clinical biofeedback may be used to manage disease symptoms as well as to improve overall health and wellness through stress management training. Research has shown that biofeedback interventions are efficacious in treating a variety of medical conditions, and many Americans are turning to biofeedback and other less traditional therapies for their routine healthcare.Clinical biofeedback training is growing increasingly popular in the USA, as many people are seeking out relatively new approaches to healthcare. This article provides an overview of clinical biofeedback training, outlines two models of training, details research which has established how effective biofeedback is in patients with a given disease, and describes who should be referred for biofeedback training.     

1998 ISEK Congress Keynote Lecture: Motor units: how many, how large, what kind?

There are now at least nine methods for motor unit number estimation (MUNE) in living human muscles. All methods are based on the comparison of an average single motor unit potential (or twitch) with the response of the whole muscle. Such estimations have been performed for proximal and distal muscles of the arm and leg in healthy subjects and in patients with various neuromuscular disorders. In healthy subjects there is a loss of motor units which is most evident in distal muscles and after the age of 60 years. Substantial losses of motor units have been measured in patients with ALS, post-polio symptoms, and diabetic peripheral neuropathies. In contrast, normal MUNEs have been found in approximately half of patients with persisting obstetric brachial palsies. The sizes of motor units show considerable variations within the same muscle and also between muscles; very large units are usually present in severe partial denervation. Although many motor unit properties are largely governed by motoneurons, some exhibit less plasticity in humans than in other mammals.     

Epigenetic reprogramming: how now, cloned cow?

DNA methylation patterns are dynamic in cleavage-stage embryos of a number of mammalian species. A failure to properly recapitulate preimplantation DNA methylation patterns in embryos derived by nuclear transfer may contribute to the low efficiency of nuclear transfer in producing live offspring.     

FtsZ dynamics in bacterial division: What,how, and why?

Bacterial cell division is orchestrated by the divisome, a protein complex centered on the tubulin homolog FtsZ. FtsZ polymerizes into a dynamic ring that defines the division site, recruits downstream proteins, and directs peptidoglycan synthesis to drive constriction. Recent studies have documented treadmilling of FtsZ polymer clusters both in cells and in vitro. Emerging evidence suggests that FtsZ dynamics are regulated largely by intrinsic properties of FtsZ itself and by the membrane anchoring protein FtsA. Although FtsZ dynamics are broadly required for Z-ring assembly, their role(s) during constriction may vary among bacterial species. These recent advances set the stage for future studies to investigate how FtsZ dynamics are physically and/or functionally coupled to peptidoglycan metabolic enzymes to direct efficient division.     

Reconstituting the kinetochore–microtubule interface: what, why, and how

The kinetochore is the proteinaceous complex that governs the movement of duplicated chromosomes by interacting with spindle microtubules during mitosis and meiosis. Faithful chromosome segregation requires that kinetochores form robust load-bearing attachments to the tips of dynamic spindle microtubules, correct microtubule attachment errors, and delay the onset of anaphase until all chromosomes have made proper attachments. To understand how this macromolecular machine operates to segregate duplicated chromosomes with exquisite accuracy, it is critical to reconstitute and study kinetochore–microtubule interactions in vitro using defined components. Here, we review the current status of reconstitution as well as recent progress in understanding the microtubule-binding functions of kinetochores in vivo.