Phase behavior of ternary blends containing dimethylpolycarbonate,tetramethylpolycarbonate and poly[styrene‐co‐(methyl methacrylate)] copolymers (or polystyrene)

The miscibility and phase behavior of ternary blends containing dimethylpolycarbonate (DMPC), tetramethylpolycarbonate (TMPC) and poly[styrene‐co‐(methyl methacrylate)] copolymer (SMMA) have been explored. Ternary blends containing polystyrene (PS) instead of SMMA were also examined. Blends of DMPC with SMMA copolymers (or PS) did not form miscible blends regardless of methyl methacrylate (MMA) content in copolymers. However, DMPC blends with SMMA (or PS) blends become miscible by adding TMPC. The miscible region of ternary blends is compared with the previously determined miscibility region of binary blends having the same chemical components and compositions. The region where the ternary blends are miscible is much narrower than that of binary blends. Based on lattice fluid theory, the observed phase behavior of ternary blends was analyzed. Even though the term representing the Gibbs free energy change of mixing for certain ternary blends had a negative value, blends were immiscible. It was revealed that a negative value of the Gibbs free energy change of mixing was not a sufficient condition for miscible ternary blends because of the asymmetry in the binary interactions involved in ternary blends. Copyright © 2004 Society of Chemical Industry     

Development of contrast sensitivity and temporal-frequency selectivity in primate lateral geniculate nucleus

We studied the development of spatial contrast-sensitivity and temporal-frequency selectivity for neurons in the monkey lateral geniculate nucleus. During postnatal week 1, the spatial properties of P-cells and M-cells are hardly distinguishable, with low contrast-sensitivity, sluggish responses, and poor spatial resolution. The acuity of P-cells improves progressively until at least 8 months, but there is no obvious increase in their maximum contrast-sensitivity with age. The contrast sensitivity of M-cells is already clearly higher than that of P-cells by 2 months, and at 8 months of age this characteristic difference between M- and P-cells approaches the adult pattern. There is a major increase in responsiveness during the first 2 postnatal months, especially for M-cells, the peak firing rate of which rises fivefold, on average, between birth and 2 months. Many P-cells in the neonatal and 2-month-old animals did not give statistically reliable responses to achromatic gratings, even at the highest contrasts: this unresponsiveness of P-cells might result from low gain and/or chromatic opponency. The upper limit of temporal resolution in the neonate is low--about one-third of that in the adult. Among M-cells, the improvement in temporal resolution, like that in contrast sensitivity, is rapid over the first 2 months, followed by a slower change approaching the adult value by 8 months of age. The development of contrast sensitivity, responsiveness and temporal tuning are little affected, if at all, by binocular deprivation of pattern vision from birth for even a prolonged period.     

The novel inotropic agent CGP 48506 alters force primarily by Ca(2+)-independent mechanisms in porcine skinned trabeculae

OBJECTIVES: The aim was to determine whether, and by what mechanism(s), a novel inotropic agent 5-methyl-6-phenyl-1,3,5,6-tetrahydro-3, 6-methano-1,5-benzodiazocine-2,4-dione (BA 41899) and its enantiomers directly alter the Ca2+ sensitivity of cardiac myofilaments. METHODS: Porcine ventricular trabeculae were permeabilised with Triton X-100. The relationship between force and pCa (-log[Ca2+]) was determined in the presence and absence of ATP. Troponin I was extracted, using vanadate, to produce unregulated maximally activated myofilaments. Force and actomyosin ATPase activity were measured simultaneously to determine tension cost (ATPase activity/tension). The effects of the (+) enantiomer (CGP 48506) on the twitch of intact muscle were demonstrated using rat papillary muscle. RESULTS: 100 microM BA 41899 had a pronounced Ca2+ sensitising effect on force production by porcine skinned cardiac fibres, increasing the pCa required for 50% maximal activation by 0.64 units, while suppressing maximum force by 18.3%. Resting tension was unaffected. These actions were primarily caused by CGP 48506 and were concentration dependent. At concentrations less than 100 microM, CGP 48506 also increased twitch amplitude in intact papillary muscles with no effect on resting tension, whereas 100 microM CGP 48506 increased resting force due to a slowing of relaxation. 100 microM CGP 48506 potentiated Ca(2+)-independent rigor tension in skinned trabeculae, indicating a Ca2+ sensitising mechanism unrelated to Ca2+ binding to troponin C. Tension cost was unaffected by 100 microM CGP 48506 over the entire range of activating Ca2+ concentrations. Suppression of maximum force by CGP 48506 was independent of both Ca2+ concentration and the regulatory troponin complex. CONCLUSIONS: Both the increase in Ca2+ sensitivity during submaximal activation and the depression of maximum force which are induced by CGP 48506 in skinned trabeculae occur at least partly through Ca(2+)-independent mechanisms.     

Human papillomavirus investigation of patients with cervical intraepithelial neoplasia 3, some of whom progressed to invasive cancer

Unstable expansion of the CTG repeats in the 3' untranslated region encoding a member of the protein kinase family in the q13.3 band on chromosome 19 is a mutation specific for myotonic dystrophy. To examine the correlation between clinical expression and CTG trinucleotide repeat length, we carried out Southern blot analysis in a family with myotonic dystrophy. In this pedigree, the expanded CTG repeats were transmitted maternally. The mother had three female children. The mother had about 200 CTG repeats, and the number of repeats for each child was about 800, 1500 and 1600 in birth order. The mother and the patient with 800 repeats were unaware of muscle weakness or myotonia. Symptoms were present from age 3 years in the patient with 1500 repeats and from birth in the one with 1600 repeats. Although the mother menstruated regularly, the patients with 800 and 1500 repeats both menstruated irregularly, and the one with 1600 repeats has never menstruated. The age of onset and severity of the disease were correlated with the size of the expanded repeats. Endocrinological studies revealed that the basal levels of the gonadotropins, PRL and E2 were within normal range, and a pituitary response to LHRH was observed. These data suggest that the amenorrhea and menstrual irregularities were caused by a suprahypophyseal dysfunction. When expanded CTG repeats are transmitted maternally, abnormal products resulting from the metabolic disturbance in the affected mother may harm the fetus in utero. A heterozygous fetus, who has more CTG repeats, may be unable to metabolize the pathologic products sufficiently and therefore may become more severely affected. This may explain the exclusive maternal transmission of congenital myotonic dystrophy.     

Acute aortic dissection: association with patent ductus arteriosus

The Cuban recombinant vaccine against the hepatitis B virus was applied to a group of individuals over 65 from a geriatric home in Havana City. Dose of 20 ìg were administered within a scheme from 0.1 to 6 months in order to study its immunogenicity, which was evaluated at 2, 7, and 12 months after the first dose. 47.1% of protective titres and geometrical mean of 6.04 UI/L were obtained after 60 days. 100% of seroconversion (UI/L) and seroprotection (10 UI/L) and geometric mean of 136.93 UI/L were obtained when the immune response was evaluated on the 7th month. Finally, after a year, seroconversion and seroprotection were also of 100%, and the geometric mean was of 204.61 UI/L. It was proved the high immunogenic power of this vaccine, which makes it recommendable to protect this age group from the hepatitis B virus.     

Dominance--one hundred and fifteen years after Mendel''s paper

Eight conscious chronically instrumented sheep were exposed to 1% inspired carbon monoxide (CO) for 35 min. In all sheep, carboxyhaemoglobin (COHb) levels at the end of the exposure were approximately 65%. Mean arterial blood pressure was unchanged with the exception of 2 sheep in which administration was stopped at 25 min following the sudden onset of hypotension. Oxygen delivery to the brain was sustained throughout the administration of CO due to a significant increase in cerebral blood flow (CBF). There was no evidence of either a metabolic acidosis or of lactate production by the brain suggesting the brain did not become hypoxic during the time-course of this study. Despite the apparent lack of hypoxia, oxygen consumption by the brain fell progressively and the sheep showed behavioural changes which varied from agitation to sedation and narcosis. The mechanism of these changes was therefore probably unrelated to hypoxia, but may have been due to raised intracranial pressure or a direct effect of CO on brain function. It is proposed that the time-course of progressive CO poisoning includes a phase in which CBF is elevated, blood pressure is unchanged and the brain is normoxic despite high COHb levels, but that this situation can rapidly evolve into a phase of haemodynamic collapse and severe hypoxia.     

2-year clinical evaluation of a gallium restorative alloy

PURPOSE: To assess the clinical performance of 2-year old gallium alloy restorations. Parameters evaluated include: (1) fracture at the margins, (2) tarnish, (3) surface roughness, (4) tooth fracture, (5) fracture through the body of the restoration, and (6) any medical or dental conditions arising during the study. MATERIALS AND METHODS: Nine patients received 30 Class I restorations of Galloy gallium alloy. These were placed as conservatively as possible under a rubber dam. Fifteen of the preparations were lined with a Bis-GMA resin to seal the restoration from moisture. The other 15 preparations were sealed with Amalgambond. After placement of the gallium alloy, the exposed surfaces of all restorations were sealed with the Bis-GMA resin, and the occlusion was checked. The restorations were examined at 2 weeks, 3 months, 6 months, 1 year and 2 years. RESULTS: At the 2-year recall, all restorations were intact with the exception of one tooth fracture (cause unknown). Forty-five percent of the restorations exhibited tarnish and 60% had a rough surface. The fracture at the margins of these restorations was minimal, and no significant difference could be found between those using Amalgambond and those sealed with the resin system. No medical problems were reported by the patients, and postoperative sensitivity was minimal.     

Survey of dirofilariasis in Arkansas

A card survey was sent to 340 veterinarians in the Urban, Delta, Highland and Coastal Plain regions of Arkansas. Veterinarians were asked to indicate numbers of dogs tested, confirmed Dirofilaria immitis positive, diagnostic techniques, frequency and period tested. A significantly greater percentage of dogs tested D. immitis positive in the Delta region as compared with the Urban region. There were no significant differences in the percentage of treated dogs on prophylaxis or the types of diagnostic tests among regions.