NORMALIZED STRESS–STRAIN RELATIONSHIP IN HUMAN HAIR PERTURBATION BY HYPOTHYROIDISM

SUMMARY.— A short review is given of the observations which have been made on the mechanical properties of human hair under axial tension.
Stress–strain curves of dry single fibres of human hair from patients with hypothyroidism and acromegaly revealed a distinctive alteration in the high yield region. The biophysical basis for this anomalous behaviour is not known.
Attention is directed to the potential value of further studies of the physical characteristics of hair with special reference to mass screening programmes for evidence of disease. This aim is furthered by the technique introduced in this paper for distinguishing the abnormal from the normal.     

CONTINUOUS NEGATIVE CHEST-WALL PRESSURE THERAPY FOR ASSISTING VENTILATION IN OLDER CHILDREN WITH PROGRESSIVE RESPIRATORY INSUFFICIENCY1

Abstract. Continuous negative chest-wall pressure (CNP) was used to assist ventilation in 14 children, 6 months to 14 years of age, who had progressive respiratory insufficiency caused by diffuse bilateral alveolar disease. Before the start of CNP therapy, each child had a respiratory rate>50/min, arterial oxygen tension (PaO₂)<70 mmHg (FIO₂≥50%), and arterial carbon dioxide tension (PaCO₂)<45 mmHg. The mean intrapulmonary right-to-left shunt was 28.7±3.8%. Within 6 hours after therapy was started, PaO₂ increased from 55.4±15.9 to 81.6±17.7 mmHg (p<0.005). This improvement was sustained and within 24 hours permitted a decrease in fractional concentration of inspired oxygen (FIO₂) from 51.8±6.2 to 41.0±8.4% (p<0.001) and in respiratory rate from 78.1±23.0 to 56.4±21.3 (p<0.01). There was a concomitant decrease in intrapulmonary right-to-left shunt. Four of the 14 patients developed pneumothorax that was successfully decompressed. Ten patients survived. These observations establish CNP therapy as an effective means of improving arterial oxygenation in spontaneously breathing older children. Of added significance, this mode of therapy eliminates the need for endotracheal intubation and prolonged use of muscle relaxants and sedatives. It also minimizes exposure to high FIO₂, thereby minimizing the hazards of pulmonary oxygen toxicity.     

SUPERIOR SWELLING PROPERTIES OF RESINS OF POLY-N-ACRYLYLDIALKYLAMINES OVER POLYSTYRENE IN SOLVENTS FOR PEPTIDE SYNTHESIS

Three beaded poly-N-acrylyldialkylamine resins have been systematically compared with polystyrene-co-1%-divinylbenzene for their ability to interact with solvents that are useful in peptide synthesis. The three resins have the same cross-linking monomer, N,N¹-bisacrylyl-1,2-diminoethane, and functionalizing monomer, N-acrylyl-1,6-diaminohexane hydrochloride. They differ from one another in the compositions of the base monomer, degree of cross-linking (DC), quantity of functionalizing monomer, or monomer dilution ratio (MDR, ratio of inert solvent to monomers by weight). Resin 1 is poly-N-acrylylpyrrolidine containing 0.75 mmol/g of amino function with DC 4.4 and MDR 4; resin 2 is poly-N-acrylyldimethylamine containing 0.75 mmol/g of amino function with DC 4.4 and MDR 4; resin 3 is poly-N-acrylyldimethylamine with DC 10 and MDR 6.8. Swelling was the property used as the measure of solvation in a given solvent for the macroscopically insoluble polymers. In their protonated or acylated forms resins 1—3 exhibit favorable swelling properties in methanol, ethanol, 2,2,2-trifluoroethanol, 2-propanol, acetic acid, and water, solvents in which polystyrene either swells little or not at all. In addition, the resins swell in methylene chloride, chloroform and dimethylformamide, solvents commonly used in the Merrifield method of solid-phase peptide synthesis, to about the same extent as polystyrene. The favorable swelling properties of the poly-N-acrylyldialkylamine resins should not only allow the use of most of the techniques developed for the solid-phase method, but should allow the invention and application of new techniques that rely on aqueous or other polar solvents.     

The fitness of human translocation carriers

A simple method to estimate the mean fitness of human translocation carriers is described. The method is based on information about the inheritance pattern of the translocations. This kind of data can be obtained from the surveys of the chromosome constitutions of new-born babies. The following fitness estimates are obtained: D/D translocation carriers, 0-94; D/G translocation carriers, 0-83; and reciprocal translocation carriers, 0-67. The estimates are rather uncertain due to the scarcity of information, but they are consistent with the expected results. More accurate estimates will be obtained in the future when more data on translocation carriers are available and the cytological classification of the different translocations becomes more exact.     

Epitopic characterization of the human wild-type and mutant ras proteins using membrane-bound peptides

Overlapping octapeptides encompassing the entire sequences of the human oncogene products Ha-ras, K-ras and N-ras protein were synthesized as spots on polypropylene membrane sheets. The binding of anti-row protein monoclonal antibodies (mAbs) to the membrane-bound peptides was assessed using an enzyme-linked immunosorbent assay. Epitopes of 10 of 18 mAbs to the human ras proteins were mapped and identified by this procedure. The epitopes of nine of the mAbs are within residues 28-39 in the constant domain common to the three ras proteins, whereas the epitope of the tenth (mAb 21) spans residues 136-144 in Ha-ras. The minimal lengths of epitopes of all ten of the mAbs were further precisely mapped using peptides of varying length, and the tolerance for mAb binding of mutated epitopes was determined by systematically replacing each residue in the epitope with each of the 20 common amino acids. The results show that most of these mAbs have essentially the same binding specificity, namely for the sequence YDPT (residues 32–35) or for slightly longer sequences containing these residues. This site is in the switch 1 region (residues 32-38) in the ras effector loop, indicating that some of the same residues important for the interaction of ras with other proteins (GTPase-activating protein, neurofibromin or raf) are highly antigenic. In addition, we investigated epitopes and specificity of five mAbs against the activated human ras proteins by the same procedure. The information gained from this study should be useful both for study of the complicated functions of ras proteins and for clinical detection of ras oncogenes in human tumor cells.     

Working memory and preparation elicit different patterns of slow wave event-related brain potentials

Some event-related brain potential (ERP) studies of working memory have used delayed match-to-sample designs in which a stimulus (S1) is held in memory for comparison with a subsequent stimulus (S2). During the S1-S2 interval, ERP slow negativities varied with both the type and amount of material held in working memory. One interpretation is that these slow waves index working memory operations. An alternative explanation is that they only reflect general preparatory processing for the response to S2. To decide between these explanations, we used two visual processing tasks that required similar preparation for S2. In one task, visual memory rehearsal operations were required. During the S1-S2 interval, there were clear differences between the amplitudes, topographies, and the effect of information load on the slow waves in the two tasks, thus ruling out preparation only as an explanation.     

A New Electrohydraulic Energy Converter for a Left Ventricular Assist Device

Abstract: An energy converting system that can function for years without maintenance is required for the drive of a left ventricular assist device (LVAD). To meet the requirements of safety, the energy converter should have a simple design with few moving elements. The design applied herein has only one moving part and thus has greater inherent safety than competing systems. The only moving part is the rotor unit, comprised of the impeller of a centrifugal pump, the rotor of an electric motor, and the rotor of an electric axial actuator. A reversal of flow of the transmitter fluid can be achieved with an axial shift of this rotor unit. This fluid acts on the outer surface of a blood chamber and enables it to draw in blood and to expel it. Valves direct the flow of blood. The energy converter performs a flow of 12 L/min at a motor speed of 6, 000 rpm against a pressure head of 115 mm Hg according to an output of the pulsatile blood pump of 5 L/min.