Interactions of small polypeptides with dimyristoylphosphatidylcholine monolayers: effect of size and hydrophobicity

The effects of size and hydrophobicity of small (molecular weights below 2,000) polypeptides on their predominantly hydrophobic interactions with a neutral phospholipid monolayer were studied. The changes in surface pressure were determined when various concentrations of Gly, Gly-Gly-Gly, -Ala, -Ala- -Ala- -Ala, -Ala-Gly-Gly-Gly-Gly, -Phe- -Leu- -Glu- -Glu- -Leu, adrenocorticotropic hormone fragments 1–10 (ACTH-(1–10)), porcine β-lipotropin, -endorphin and human fibrinopeptide A were injected under dimyristoylphosphatidylcholine (DMPC) monolayers at an initial surface pressure of 10 dyne/cm. In all cases, when peptides with the same number of residues are compared, the concentration needed to increase the surface pressure of the film by 1 dyne/cm was inversely related to its hydrophobicity. A reasonably good correlation was found to exist between the calculated free energy of transfer of a polypeptide from ethanol to water (a measure of its hydrophobicity) and its ability to increase the surface pressure of the DMPC film (a measure of the extent of its interaction with the neutral lipid monolayer).     

Augmentation and subsequent attenuation of Ca2+ current due to lipid peroxidation of the membrane caused by t-butyl hydroperoxide in the rabbit sinoatrial node.

Cellular electrophysiological effects of membrane lipid peroxidation by t-butyl hydroperoxide (TBH) were studied in the rabbit sinoatrial (SA) node. Superfusion for 1-5 min with 300 microM TBH caused an initial increase and subsequent decrease in the spontaneous firing frequency of the SA node. Voltage clamp experiments revealed that TBH initially enhanced but later blocked the Ca2+ current. Thus, membrane lipid peroxidation appears to accelerate and then suppress physiological automaticity by causing biphasic changes in the Ca2+ current.     

Choreoacanthocytosis in a Chinese patient--a case report

A 50-year old Chinese woman with the rare neurological disorder of Choreoacanthocytosis is described. Her illness is characterised by seizures, buccolingual dyskinesia, choreiform movements, arreflexia and mild sensorimotor polyneuropathy. Acanthocytes were present in her peripheral blood in large numbers but the serum lipid profile was normal. Her features are consistent with those so far described in Caucasian and Japanese patients. The disease differs from Huntington's chorea in that there are acanthocytes, peripheral neuropathy, and metal function remains relatively intact.     

Periodic oscillation of intracranial pressure in ventricular dilation: a preliminary report

Artificial pressure waves (PWs) were generated by manual inflation of a balloon in the trigonum of the lateral ventricle in seven adult mongrel dogs with normal cerebrospinal fluid (CSF) circulation. In 14 of 16 series of continuous appearances of artificial PWs, local shifts of the brain were successfully monitored using small strain-gauge sensors at the periventricular structures in these animals. Of the 14 series, 13 showed displacements of the periventricular structures, suggesting ventricular dilation. These results did not always correlate with macroscopic findings. They are thought to be due largely to periventricular oedemas and, in part, non-uniform dilations of the ventricles during PWs. We conclude that a water hammer formed by reflection of an increased pulse pressure of PWs at the site of CSF absorption causes a shift of CSF from the ventricle to the periventricular structures through the wall of the ventricle. This phenomenon appears amplified in patients with impaired CSF absorption. Thus, PWs have a pathological role in the progress of ventricular dilation in patients with normal pressure hydrocephalus.     

Immunocytochemical distribution of met-enkephalin-Arg6-Gly7-Leu8 in the rat lower brainstem

The distribution of methionine-enkephalin-Arg6-Gly7-Leu8, a unique peptide derived from proenkephalin A in the rat brainstem, was studied immunocytochemically by using a highly specific antiserum to this octapeptide sequence. Immunoreactive perikarya with various shapes and sizes were detected in many regions of the rat brainstem. Dense accumulation of immunoreactive perikarya and fibers was seen in the nuclei associated with special sensory and visceral functions, such as the interpeduncular nucleus, the parabrachial nucleus, the nucleus of the solitary tract, and the nucleus of the spinal tract of the trigeminal nerve. Clusters of methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactive perikarya and fibers were observed in certain areas considered to play a role in nociception and analgesia, such as the central gray of the midbrain central gray and the raphe magnus nucleus. Some methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactive perikarya were distributed in the lateral reticular nucleus, the nucleus of the solitary tract, and the raphe magnus nucleus, where monoaminergic neurons were also detected. In addition to the previously reported enkephalinergic cells, we found many methionine-enkephalin-Arg6-Gly7-Leu8 containing neurons; the rostral and caudal linear nucleus of raphe, the median raphe nucleus, entire length of the raphe magnus nucleus, the medial longitudinal fasciculus, the cuneate nucleus, the external cuneate nucleus, the gracile nucleus, and the area postrema. The wide distribution of this octapeptide-like immunoreactivity reflected neurons expressing the preproenkephalin A gene distributed more widely than previously reported and that innervated many regions.     

The relationship of scoring systems and mortality in the surgical intensive care unit

To determine the relationship between severity of illness and mortality, therapeutic intervention score (TISS) and acute physiology score (APS) were determined on admission to the Surgical Intensive Care Unit (SICU). Patients were divided into survivors and nonsurvivors and differences were compared by chi-square analysis. The 1524 patients admitted to the SICU during a 12-month period had a mean TISS of 3.03 and a mean APS of 13. The average length of stay (LOS) was 3.75 days. Of the 1524 patients, 97 (6.4%) died. The number of nonsurvivors increased with higher TISS and APS scores (P less than 0.001). There were no deaths in the TISS Category 1 patients or in the APS 0-5 group. Mortality rates dramatically increased with APS greater than 20 (P less than 0.001). There were 1286 patients with APS less than 20, and 24 (2%) of these patients died, whereas 73 (31%) of 238 patients with APS greater than 20 died. Nonsurvivors had a mean TISS of 3.6, mean APS of 27, and LOS of 4.88 days, all of which totals were higher than the survivors' totals. In this study population, risk of death was one in three if the APS was greater than 20. These data indicate that TISS and APS scores are effective means of assessing mortality risk in SICU patients.