Poly(ethylene glycol)s containing enzymatically degradable bonds

The possibility to use poly(ethylene glycol) (PEG) as a synthetic, water-soluble polymeric carrier of biologically active compounds was investigated. The relationship between structure of oligopeptide (amino acid)-PEG conjugates and their hydrolysis catalyzed by chymotrypsin was studied. Two types of derivatives were synthesized: Derivatives of PEG 2000, containing an oligopeptide sequence terminating in p-nitroaniline (drug model) and higher molecular weight derivatives of PEG 2000 containing in the main chain enzymatically and hydrolytically degradable bonds. The rates of chymotrypsin catalyzed release of p-nitroaniline at pH 8,0 and 25°C were determined over a range of substrate concentrations to derive values for k_cat and K_M. The influence of the length and detailed structure of the oligopeptide sequence on the rate of hydrolysis was demonstrated. Comparison with copolymers of N-(2-hydroxypropyl)methacrylamide and poly(maleic anhydride-co-vinylpyrrolidone) showed that the sterical hindrance of the formation of the enzyme-substrate complex is much less pronounced in the PEG-oligopeptide conjugates. The latter conclusion is also valid in the case of cleavage of PEG derivatives which contain enzymatically degradable bonds in the main chain. The incorporation of a single amino acid residue (phenylalanine) into the main PEG chain is sufficient to make the polymer susceptible to chymotrypsin catalyzed hydrolysis.     

Effect of insulin on sex differences in the intake of glucose solutions in rats

Adult male and female Wistar rats maintained on ad lib diet were given a choice between tap water and a solution of glucose in the concentration of either 5 or 12%. Both sexes exhibited a marked preference for glucose solutions. With the 5% solution the volume intake was similar in both sexes and the total calorie intake was normal. With the 12% solution the volume intake was higher in females than in males, while in both sexes the total calorie intake was increased to a similar (maximum acceptable) level. Treatment with Protamine Zinc Insulin (PZI) in a daily dose of 40 U/kg b.w. markedly increased the intake of the 5% solution in both sexes, but significantly more in females than in males, thus revealing sex differences which were not manifest in untreated rats. PZI treatment had little effect on 12% glucose solution intake, presumably because with this solution the total calorie intake was increased to a maximum already in untreated rats.     

Partial purification and characterization of anhydrotetracycline oxygenase of Streptomyces aureofaciens

Anhydrotetracycline oxygenase was purified both by affinity chromatography and by hydrophobic interaction chromatography. Molecular weight of anhydrotetracycline oxygenase was determined to be 115,000 by Sephadex G-200 gel filtration. Using preparative isoelectric focusing the isoelectric point of the enzyme was estimated to be 5.3. The enzyme showed a sensitivity to thiol-specific inhibitors. During the hydrophobic interaction purification step, the activity dropped considerably. Reactivation occurred when a heat treated crude extract was added to the reaction mixture.     

RPG1: an essential gene of Saccharomyces cerevisiae encoding a 110-kDa protein required for passage through the G1 phase

In Saccharomyces cerevisiae cells a number of genes are required for progression through, or else to pass beyond, the G₁ phase. We characterized a novel gene, RPG1, which is also involved in this phase. RPG1 is an essential gene encoding a 110-kDa evolutionarily conserved protein. Elutriated or α-factor-synchronized cells of the rpg1-1 temperature-sensitive mutant were arrested in the first cell cycle when shifted to a non-permissive temperature. The cells remained unbudded and neither grew nor duplicated DNA. rpg1-1 cells synchronized in S phase completed mitosis and arrested as unseparated G₁ cells after a shift to a non-permissive temperature. Similarly, the asynchronous rpg1-1 cells accumulated in G₁ at the non-permissive temperature, but mother and daughter cells did not separate. A bulk of Calcofluor-stained material was localized in the region adjacent to the cell septum. Our data show that Rpg1p is required for passage through the G₁ phase and may be involved in growth control. Data published recently indicate that Rpg1p exhibits significant sequence similarity to a subunit of the mammalian translation initiation factor 3. Received: 6 October 1997 / 8 November 1997     

The effect of 2,3-dimercaptopropane sodium sulfonate on mercury retention in rats in relation to age

The effectiveness of DMPS (sodium 2,3-dimercaptopropane-1-sulfonate) in reducing inorganic mercury retention was studied in 2-, 6-, and 28-week-old albino rats. ²⁰³Hg was administered IP. The chelating agent DMPS was administered by IP injection at a dose of 250 mol/kg body weight three times, 1 day after ²⁰³Hg administration and at 24 h intervals thereafter. The whole body retention determined 1, 2, 3, and 6 days after ²⁰³Hg administration showed that DMPS decreased the body retention of mercury in all age groups, being about twice as effective in adult compared to suckling rats. The reduced effectiveness was due to the reduced efficacy of DMPS in reducing kidney retention in young animals. In other organs the effectiveness of DMPS was not age dependent. These and previous results obtained with different chelating agents and other metals indicate that age might be an important factor in chelation therapy in general.     

Semen analysis and treatment risk factors in long-term survivors of childhood cancer

The objective of this study was to compare semen quality (sperm density, progressive motility and spermia) between long-term childhood cancer survivors and a control group of males. The second objective was to correlate the semen analysis of the survivors with cancer treatment and endocrine status. The semen quality of 143 survivors (median age, 23.6 years) was compared to 200 men (median age, 27.9 years) who had not been diagnosed with cancer. The cancer-related risk factors and gonadotrophin levels were compared. Overall, 65% of the survivors had abnormal semen analysis compared to 26.5% of the controls (p < 0.0001). Survivors with nonaspermia had lower sperm density than the controls (p < 0.001). Other observed correlations were not significant. Survivors who were treated with alkylating agents were more likely to have abnormal semen analysis (p < 0.008). Follicle-stimulating hormone and luteinising hormone levels were significantly elevated (p < 0.0001) in survivors with abnormal semen analysis. The semen quality parameters, except for low sperm density, did not differ in survivors with nonaspermia compared to the controls. The risk factors included treatment with alkylating agents. Elevated gonadotrophin levels correlated with abnormal semen analysis. All cancer survivors should be made aware of the possibility of suffering from cancer treatment-related infertility.     

Radiological and clinical comparisons of the patients with rheumatoid arthritis operated with rigid and dynamic instrumentation systems due to lumbar degenerative spinal diseases

BackgroundIt is extremely difficult to treat spine disorders with stabilization in patients with rheumatoid arthritis. Because revision rates are significantly higher in rigid stabilization. To date, there is no data about patients with rheumatoid arthritis treated with dynamic stabilization. Our aim was to compare the radiological and clinical results of patients with rheumatoid arthritis who underwent lumbar rigid stabilization or dynamic stabilization with Polyetheretherketone rod (PEEK).MethodsPatients with degenerative lumbar spine disease with rheumatoid arthritis who underwent dynamic stabilization between 2013 and 2015 and rigid stabilization between 2010 and 2012 were evaluated radiologically for adjacent segment disease, proximal junctional kyphosis, system problem (nonunion, screw loosening, instrumentation failure, pull out). It was also compared according to both the revision rates and the Visual Analog Scale and Oswestry Disability Index scores at the 12th month and 24th month.ResultsThe difference of decrease in Visual Analog Scale and Oswestry Disability Index scores from preoperative to 12th month between patients who underwent dynamic stabilization and rigid stabilization was statistically insignificant. However, there was a significant difference of increase in Visual Analog Scale and Oswestry Disability Index scores between the 12th month and 24th month of patients who underwent rigid stabilization, compared with patients with dynamic stabilization. In patients with dynamic stabilization, the problems of instrumentation were seen less frequently. Revision rates were high in patients with rigid stabilization when compared the patients with dynamic stabilization.ConclusionRadiological and clinical outcomes in patients with rheumatoid arthritis operated with dynamic stabilization are more significant when compared to rigid stabilization. These patients have lower pain and disability scores in their follow up periods. Revision rates are lower in patients with dynamic stabilization.     

The impact of the health-care sector on national economies in selected European countries

Policy-makers face pressures to improve lives and safeguard public finances sustainably. In this analysis, we estimate the economic importance of the health-care sector in 19 European national economies.We use input–output tables for the year 2010 and sectoral data to estimate a set of multipliers: simple, total, truncated, type I and type II multipliers for output, income, value-added, employment and import multiplier.The analysis reveals similarities in the economic importance of the health-care sector for the national economies of the observed countries. Results suggest prevailing positive effects on national economies (value-added, employment and household income) when spending on health-care sector products and services increases, especially in comparison to the effects of increases in spending in other sectors. The importance of the health-care sector is connected to countries’ levels of development; the benefits are especially promising in countries with lower levels of gross domestic product (GDP) per capita, where changes in the health-care sector have a larger impact on employment in the national economy than similar changes in more developed countries. The health-care sector therefore can play an important role as an instrument of economic policy.     

Voltage clamp of a small muscle membrane area by means of a circular sucrose gap arrangement

Summary A new method is described which permits the measurement of membrane currents of thick muscle fibres (diameter 300 m or more) ofAstacus fluviatilis orBalanus balanus under voltage clamp conditions.The potential difference across a small patch of membrane (60–100 m in diameter) is controlled by connecting a voltage source across it with two external electrodes. One of them is connected to the fluid bathing the muscle fibre. The other, tubular one is in touch with the test area. The current flowing through the electrodes represents the sum of the membrane current flowing across the test area and the leak current flowing in the external fluid between the electrodes. In the first version of the method the leak current is limited by a circular sucrose gap around the test area. In the second, more elaborate method, the leak current is eliminated by a system of two concentric sucrose rings with a guard ring electrode between them. This method permits in addition the measurement of full sized action potentials in the test area.This work has been briefly reported in Cs. fysiol.17, 48 (1968).