Modulation of slow and fast elbow extensor EMG tonic activity by stretch reflexes in man

Reflex EMG responses to sudden passive flexion of the elbow were recorded from anconeus and triceps brachii in 5 human volunteers. While the subjects were required not to resist the flexion movement, they were required to maintain an extension torque of 3.5 or 7.0 Nm prior to its onset. Under these isotonic conditions, the latency and amplitude of the reflex activities from anconeus and triceps brachii did not differ significantly, in contrast to the findings of Le Bozec (1986) in actively relaxed subjects. The myotatic/postmyotatic EMG amplitude ratio did not provide a further quantitative way to distinguish between these muscles. The absence of a difference between the reflex activities of a slow (anconeus) and a fast (triceps brachii) muscle is interpreted as resulting from a strong drive of spindle activity on the whole extensor motoneuron pool, which outweights the differences in recruitment due to the differing relative amounts of type I and type II fibres in the two muscles. Differences like those described between finger and calf muscles by other authors are thought to be due to the relative degree of corticalization of these muscles. All short and long latency responses of the muscles increased in magnitude and decreased in latency with increasing background EMG activity as well as with increasing initial length. The position and tonic activity dependency of these responses is explained in terms of alpha-gamma coactivation.     

A simple method using PCR for direct sequencing of genomic DNA from frozen tumor tissue embedded in optimal cutting temperature compound.

Described here is a three-day protocol that directly yields DNA sequence after isolating and PCR amplifying genomic DNA from a small sample of frozen nasopharyngeal carcinoma tissue embedded in optimal cutting temperature (OCT) compound. The method is consistently successful, reproducible and will facilitate the rapid analysis of DNA sequence from very small samples.     

Natural relationship between bacteroides and flavobacteria.

Comparisons among 16S rRNA sequences from various eubacteria reveal a natural relationship between the bacteroides (represented by the Bacteroides fragilis sequence) and a phylogenetic unit that comprises the flavobacteria, cytophagae, flexibacteria, and others (represented by the Flavobacterium heparinum sequence). Although the relationship is not a close one, it is, nevertheless, specific. rRNAs from these two organisms are not only closer to one another in overall sequence than they are to outgroup species (such as Bacillus subtilis, Escherichia coli, Desulfovibrio desulfuricans, and Agrobacterium tumefaciens), but they show common idiosyncrasies (i.e., derived characteristics) in both rRNA sequences and higher-order structures.     

Enhanced synthesis of type IV collagen in cultured arterial smooth muscle cells associated with phenotypic modulation by dimethyl sulfoxide

The effect of dimethyl sulfoxide (DMSO) on synthesis of basement membrane collagen in cultured smooth muscle cells was evaluated. DMSO promoted phenotypic modulation of cells from the synthetic state to the contractile state accompanied by formation of basement membranes. By immunofluorescence using monospecific antibody against type IV collagen, type IV collagen was identified not only in the cell cytoplasms but intensely along the cell surfaces in the cultures treated with DMSO for 7 days, as compared with untreated cultures. Electron microscopic immunohistochemistry revealed the presence of type IV collagen both in the basement membrane region and in the rough endoplasmic reticulum of DMSO-treated cells. Such an enhancement of type IV collagen synthesis appears to be expressed as a result of the phenotypic changes of smooth muscle cells to the contractile state modulated by DMSO.     

A fast dynamic mode of the EF‐G‐bound ribosome

A key intermediate in translocation is an ‘unlocked state’ of the pre‐translocation ribosome in which the P‐site tRNA adopts the P/E hybrid state, the L1 stalk domain closes and ribosomal subunits adopt a ratcheted configuration. Here, through two‐ and three‐colour smFRET imaging from multiple structural perspectives, EF‐G is shown to accelerate structural and kinetic pathways in the ribosome, leading to this transition. The EF‐G‐bound ribosome remains highly dynamic in nature, wherein, the unlocked state is transiently and reversibly formed. The P/E hybrid state is energetically favoured, but exchange with the classical P/P configuration persists; the L1 stalk adopts a fast dynamic mode characterized by rapid cycles of closure and opening. These data support a model in which P/E hybrid state formation, L1 stalk closure and subunit ratcheting are loosely coupled, independent processes that must converge to achieve the unlocked state. The highly dynamic nature of these motions, and their sensitivity to conformational and compositional changes in the ribosome, suggests that regulating the formation of this intermediate may present an effective avenue for translational control.     

Mise en evidence de l'existence de sensilles chemorecepteurs sur les antennes d'un crustace mysidace cavernicole et de l'intervention de ces sensilles dans la detection d'un extrait de nourriture

The cavernicolous crustacean Antromysis juberthiei showed unexpected behavior when presented with food extract : it avoids the area of odor inflow. This avoidance reaction is reduced by removal of various combinations of antennae and disappears almost with bilateral removal of the first antennae (the aesthetasc-bearing antennules).