Treatment of hypertonicity in muscles of lip retraction.

An EMG biofeedback program was developed for a 56-year-old Parkinsonism patient who exhibited pathological lip hypertonia and retraction. The program was designed to achieve the following goals: (1) to demonstrate a reduction in postural lip hypertonicity and (2) to demonstrate a reduction in lip hypertonicity during a series of increasingly complex speech activities. To achieve the first goal, contrastive tasks of full contraction and relaxation were utilized. Each posture was sustained while voltage measurements were made at specific intervals. Procedures to modify lip retraction during speech included five tasks in which the patient was to monitor the audio feedback signal. The tasks involved: prolongation of a neutral vowel, consonant-vowel combinations, monosyllabic words, sentences, and a paragraph-reading task. Data collected over six biofeedback sessions are presented. Trend analyses showed consistent muscular reduction within each task. The following explanations for the decrease in the patient's hypertonicity were discussed: (1) reduction of anisometric contraction, (2) reduction of isometric contraction, (3) relearning of agonistic-antagonistic muscle balance.     

Pathophysiology of cleft lip muscles following the initial surgical repair.

Muscle biopsy specimens taken from the upper lip and perialar area during the time of secondary lip revision and studied by histochemical techniques demonstrate persistent connective-tissue and muscle abnormalities even at a distance from the cleft margins. Some of these changes are consistent with surgically induced denervation-reinnervation of muscle groups in the surgical field. Increased amounts of connective tissue also were found, most likely secondary to the original deformity and the subsequent surgical procedures. Both these changes may be important factors in subsequent abnormal growth and development of the underlying midfacial structures. This study also demonstrated the resolution of previously noted mitochondrial abnormalities found in the primary cleft lip patient.     

Treatment of the unilateral cleft lip nose.

Unilateral nasal shortening is an essential step in both the primary and the secondary treatment of the unilateral cleft lip nose. Procedures for this are described.     

Electrical changes in isolated rat jejunum induced by hypertonicity

Mucosal hypertonicity produces a drop of transepithelial potential difference in isolated rat jejunum with a half time of about 15 s. The same effect is obtained when the osmorality of both bathing solutions is raised simultaneously. Serosal hypertonicity produces an increase of transepithelial potential difference an order of magnitude lower than the drop produced by mucosal hypertonicity. The change in the short circuit current parallels the one in potential difference.When the transepithelial potential difference is varied by adding different concentrations of glucose to the bathing media, the potential drop induced by mucosal hypertonicity is linearly related to the magnitude of the transepithelial potential difference just before the increase in osmolarity.The drop of potential can be explained by a decrease of the electrical resistance of the extracellular shunt pathway due to opening of the tight junctions. The results can be accounted for in terms of an equivalent electrical circuit proposed for small intestine. Using this equivalent circuit model it is possible to obtain estimates of the values of the diffusion potential and the salt gradient across the tight junction.     

Differential regulation of adenine nucleotide translocators by hypertonicity in the brain

To determine the gene(s) induced by hypertonicity in the brain, we performed a differential display analysis using RNA isolated from isotonic and hypertonic rat astrocytes. One cDNA rapidly up-regulated by hypertonicity was isolated, and the DNA sequence revealed that it was identical to adenine nucleotide translocator (ANT)2. ANT2 protein exchanges intramitochondrial ATP for cytoplasmic ADP. Among three ANT isoforms, only ANT2 mRNA was up-regulated markedly from 1 to 4 h after exposure to hypertonicity. Induction of the mRNA did not require de novo protein synthesis. Furthermore, ADP translocase activity in mitochondria of astrocytes was increased significantly by hypertonicity. To see the localization and regulation of ANT2 mRNA in the brain, we performed in situ hybridization of rat brain after intraperitoneal injection of a high concentration of NaCl. Although there were only weak signals in the control, intense hybridization signals were seen in hypertonic rat whole brain. Microscopic examination showed that ANT2 signals were present in the neurons, as well as glial cells. These results suggest that ANT2 may play a role in brain cells to adapt to the hypertonic environment.     

Effect of hypertonicity on hexose transporter regulation in chicken embryo fibroblasts

The regulation of hexose transporters of cultured fibroblasts was investigated by exposing chicken embryo fibroblasts (CEF) to hypertonic culture medium, a condition known to enhance hexose transport activity. The effects of hypertonicity and the role of protein synthesis were examined with CEF in the basal (glucose fed) and transport enhanced (glucose starved) states. Glucose-fed CEF exposed to hypertonic conditions developed four-fold enhancement of hexose transport activity within 4 hrs; this declined in the following 20 hrs to a level slightly higher than the fed control. Protein synthesis was required in part for this effect, since the presence of cycloheximide during hypertonic exposure of fed CEF blocked the increase in of transport by almost 50%. Although the increased transport produced by glucose starvation was not further enhanced by hypertonicity, hypertonic treatment of starved CEF during glucose refeeding largely prevented the loss of transport activity to the basal, fed state. The hypertonic effects were concentration dependent (240mOsm optimal) and could be elicited with NaCl, KCl, or sucrose. Hypertonic treatment typically led to a greater than 50% decline in the incorporation of [3H]leucine into acid-insoluble fractions. The changes in transport were evident at the plasma membrane level, and studies of membrane vesicles prepared from hypertonically treated fed CEF showed a doubling of both [3H]cytochalasin B binding and the Vmax of D-glucose transport. These findings indicate that exposure of CEF to hypertonic conditions has some effects similar to those produced by glucose starvation and suggest that protein synthesis is to some extent involved in the regulation of hexose transporters in CEF.     

Adaptation to hypertonicity and selection of cell hybrids.

The ability to survive in hypertonic media varies markedly among different cell strains. This property was exploited to set up a selection procedure to isolate cell hybrids, in cell fusion experiments. The results of a cross between two EUE sublines, with a differential sensitivity to hypertonicity, are discussed.     

Weapons of mass retraction

Twitching motility is a unique form of bacterial propulsion on solid surfaces associated with cycles of extension, tethering and retraction of type IV pili (T4P). Although investigations over the last two decades in a number of species have identified the majority of the genes involved in this process, we are still learning how these pili are assembled and the mechanics by which bacteria use T4P to drag themselves from one place to another. Among the puzzles that remain to be solved is the mechanism by which hydrolysis of ATP is coupled to pilus assembly and disassembly, and how the cell envelope structure is modified to accommodate the passage of the pilus through the periplasm. Unravelling of these and other enigmas in the T4P system will not only teach us more about these important colonization and virulence factors, but also help us to understand related processes such as type II secretion, which relies on a set of proteins homologous to those in the T4P system, and bacterial conjugation, involving retractable pili belonging to the F-like subgroup of the type IV secretion family. This review focuses on recent discoveries relating to the assembly and function of T4P in generation of twitching motility.