Peroxide crosslinking of rigid poly(vinyl chloride)

Peroxide crosslinking of unplasticized poly(vinyl chloride) with trimethylolpropane trimethacrylate was investigated. Formulations used in this work contained a nontoxic lead‐free stabilizer and showed good color and heat stability. The samples were examined by differential scanning calorimetry, and their tensile properties were measured at room temperature and at 130°C. Gel content or tetrahydrofuran‐insoluble material was measured as an indication of crosslinking. It was shown that premature crosslinking could be avoided during processing and that 190°C was the optimum processing temperature for maximum gel content. The residual unsaturation was monitored by using FTIR spectroscopy. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers     

Dependence of muscle VO2 on blood flow dynamics at onset of forearm exercise

The hypothesis that the rate of increase in muscle O2 uptake (VO2mus) at the onset of exercise is influenced by muscle blood flow was tested during forearm exercise with the arm either above or below heart level to modify perfusion pressure. Ten young men exercised at a power of approximately 2.2 W, and five of these subjects also worked at 1.4 W. Blood flow to the forearm was calculated from the product of blood velocity and cross-sectional area obtained with Doppler techniques. Venous blood was sampled from a deep forearm vein to determine O2 extraction. The rate of increase in VO2mus and blood flow was assessed from the mean response time (MRT), which is the time to achieve approximately 63% increase from baseline to steady state. In the arm below heart position during the 2.2-W exercise, blood flow and VO2mus both increased, with a MRT of approximately 30 s. With the arm above the heart at this power, the MRTs for blood flow [79.8 +/- 15.7 (SE)s] and VO2mus (50.2 +/- 4.0 s) were both significantly slower. Consistent with these findings were the greater increases in venous plasma lactate concentration over resting valued in the above heart position (2.8 +/- 0.4 mmol/l) than in the below heart position (0.9 +/- mmol/l). At the lower power, both blood flow and VO2mus also increased more rapidly with the arm below compared with above the heart. These data support the hypothesis that changes in blood flow at the onset of exercise have a direct effect on oxidative metabolism through alterations in O2 transport.     

Effect of profound hearing loss on a central auditory nucleus

The present study was designed to investigate the type and extent of degeneration occurring in the human central auditory system subsequent to profound hearing loss. The authors have examined the size of one population of neurons in the ventral cochlear nucleus in seven subjects with profound hearing loss (audiometric responses poorer than 90-100 dB HL). Six normal subjects, ages 35-78, were used as controls. Cell size in the hearing-impaired subjects ranged from normal to reduced by more than 50 percent. Two factors appear to contribute to the variability in cell size reduction. The correlation coefficient (Spearman rs) of cell size with duration of profound deafness was -0.48, indicating a moderate tendency for neurons to become smaller with longer periods of deafness. The correlation coefficient of cell size with number of surviving cochlear ganglion cells was 0.73, indicating a stronger tendency for neurons to be larger with greater eighth nerve innervation of the cochlear nucleus. Two cases of Scheibe degeneration showed the most severe degenerative change in the central auditory system.     

A longitudinal study of green-liver osteomyelitis complex in commercial turkeys

Two flocks of Nicholas tom turkeys from separate farms with histories of above-average condemnations for turkey green-liver osteomyelitis complex (TOC) were studied throughout a 16-week growout. Fifty birds from each farm were necropsied each week for 15 weeks, and birds that had green livers, osteomyelitis in the proximal tibia, or swollen joints were cultured for aerobic bacteria along with an equal number of control birds. At processing, TOC lesions and green livers were obtained for bacterial culture and histopathology. Green-liver-associated TOC was not observed until the turkeys were 9 or 10 weeks of age. The incidence of TOC was higher on one farm, which also had a higher incidence of airsacculitis, higher early and weekly mortality, seroconversion to Newcastle disease virus and Mycoplasma meleagridis, and significantly higher average body weights, relative spleen weights, and relative liver weights. Both farms had a high incidence of intestinal lesions and infestation with Ascaridia dissimilis. Histological evaluation of green livers revealed hyperplasia of bile ducts, dilation of sinusoids, and pigment-containing Kupffer's cells, some of which stained positive for iron. The bacterial isolates most frequently cultured from bones and livers were pleomorphic gram-variable coccobacilli, which grew visible colonies only after a series of subcultures and extended incubation.     

Esterified estrogens with and without methyltestosterone decrease arterial LDL metabolism in cynomolgus monkeys

OBJECTIVES: To assess retinal complications and to identify risk factors for retinal complications following aqueous shunt procedures. MATERIALS AND METHODS: Records of 38 consecutive aqueous shunt procedures that were performed on 36 patients at the Eye Institute of the Medical College of Wisconsin, Milwaukee, from June 1993 to March 1995 (minimum follow-up, 6 months) were reviewed. The mean +/- SD follow-up was 11.4 +/- 5.2 months (median, 10.5 months). RESULTS: Twelve patients (32%) had the following retinal complications: 4 serous choroidal effusions (10%) that required drainage, 3 suprachoroidal hemorrhages (8%), 2 vitreous hemorrhages (5%), 1 rhegmatogenous retinal detachment (3%), 1 endophthalmitis (3%), and 1 scleral buckling extrusion (3%). Surgical procedures for retinal complications were required in 8 (67%) of these 12 patients. Visual acuity decreased 2 lines or more in 9 (75%) of these 12 patients. The median onset of a postoperative retinal complication was 12.5 days, with 10 patients (83%) experiencing complications within 35 days. Serous choroidal effusions developed in 10 other patients (26%), and these effusions resolved spontaneously. Visual acuity decreased 2 lines or more in 2 (20%) of these additional 10 patients. Patients who experienced serious retinal complications were significantly older, had a higher rate of hypertension, and postoperative ocular hypotony. Serious retinal complications were distributed evenly among patients with Krupin valves with discs and Molteno and Baerveldt devices. Experience with the Ahmed glaucoma valve implant was limited. CONCLUSION: Aqueous shunt procedures may be associated with significant retinal complications and subsequent visual loss.     

The Xcad-2 gene can provide a ventral signal independent of BMP-4

Patterning of the marginal zone in the Xenopus embryo has been attributed to interactions between dorsal genes expressed in the organizer and ventral-specific genes. In this antagonistic interplay of activities, BMP-4, a gene that is not expressed in the organizer, provides a strong ventralizing signal. The Xenopus caudal type homeobox gene, Xcad-2, which is expressed around the blastopore with a gap over the dorsal lip, was analyzed as part of the ventral signal. Xcad-2 was shown to efficiently repress during early gastrula stages the dorsal genes gsc, Xnot-2, Otx-2, XFKH1 and Xlim-1, while it positively regulates the ventral genes, Xvent-1 and Xvent-2, with Xpo exhibiting a strong positive response to Xcad-2 overexpression. Xcad-2 was also capable of inducing BMP-4 expression in the organizer region. Support for a ventralizing role for Xcad-2 was obtained from co-injection experiments with the dominant negative BMP receptor which was used to block BMP-4 signaling. Under lack-of-BMP-signaling conditions Xcad-2 could still regulate dorsal and ventral gene expression and restore normal development, suggesting that it can act downstream of BMP-4 signaling or independently of it. Xcad-2 could also inhibit secondary axis formation and dorsalization induced by the dominant negative BMP receptor. Xcad-2 was also shown to efficiently reverse the dorsalizing effects of LiCl. These results place Xcad-2 as part of the ventralizing gene program which acts during early gastrula stages and can execute its ventralizing function in the absence of BMP signaling.     

Fractures of the patella in children and adolescents

Renal scarring is considered a criterion of reflux nephropathy and the end stage of pyelonephritis. Prednisolone, a strong anti-inflammatory drug, at doses of 1 or 2 mg/kg prevented renal scarring in rats following infection with Serratia marcescens. Four or 8 mg/kg of prednisolone, however, did not inhibit renal scar formation. In a time course experiment, renal scarring was prevented when 4-day treatment with prednisolone was initiated 2, 5, or 13 days after infection. These results show that prednisolone is effective in preventing such scarring and suggest the clinical use of this drug for preventing renal scar formation after pyelonephritis and reflux nephropathy.