Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

BACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly(3‐hydroxyalkanoate) films in an accelerated in vitro biodegradation system. RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R² = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R² = 0.95), rather than the strongly attached biofilm (R² = 0.78). During biodegradation the surface rugosity of poly(3‐hydroxybutyrate) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3‐hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity. CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. Copyright © 2008 Society of Chemical Industry     

A nonlinear least-squares method for determining cerebrospinal fluid formation and absorption kinetics in pseudotumor cerebri

Data from 14 patients with benign intracranial hypertension (pseudotumor cerebri) have been analyzed using a nonlinear least-squares regression model which was developed and programmed from in-hospital microcomputer use. The method of analysis permits rapid estimation of cerebrospinal fluid (CSF) formation and absorption rates as functions of pressure in individual patients using data from constant-rate infusion manometrics. The analysis predicts that prednisone therapy in pseudotumor cerebri reduces resting CSF pressure by increasing CSF absorption at all intracranial pressures studied, and decreasing CSF formation at high pressures. This result is in accordance with evidence suggesting that impaired CSF absorption plays a major role in the pathogenesis of increased intracranial pressure in pseudotumor cerebri.     

Glutathione synthetase is dispensable for growth under both normal and oxidative stress conditions in the yeast Saccharomyces cerevisiae due to an accumulation of the dipeptide gamma-glutamylcysteine

Glutathione (GSH) synthetase (Gsh2) catalyzes the ATP-dependent synthesis of GSH from gamma-glutamylcysteine (gamma-Glu-Cys) and glycine. GSH2, encoding the Saccharomyces cerevisiae enzyme, was isolated and used to construct strains that either lack or overproduce Gsh2. The identity of GSH2 was confirmed by the following criteria: 1) the predicted Gsh2 protein shared 37-39% identity and 58-60% similarity with GSH synthetases from other eukaryotes, 2) increased gene dosage of GSH2 resulted in elevated Gsh2 enzyme activity, 3) a strain deleted for GSH2 was dependent on exogenous GSH for wild-type growth rates, and 4) the gsh2 mutant lacked GSH and accumulated the dipeptide gamma-Glu-Cys intermediate in GSH biosynthesis. Overexpression of GSH2 had no effect on cellular GSH levels, whereas overexpression of GSH1, encoding the enzyme for the first step in GSH biosynthesis, lead to an approximately twofold increase in GSH levels, consistent with Gsh1 catalyzing the rate-limiting step in GSH biosynthesis. In contrast to a strain deleted for GSH1, which lacks both GSH and gamma-Glu-Cys, the strain deleted for GSH2 was found to be unaffected in mitochondrial function as well as resistance to oxidative stress induced by hydrogen peroxide, tert-butyl hydroperoxide, and the superoxide anion. Furthermore, gamma-Glu-Cys was at least as good as GSH in protecting yeast cells against an oxidant challenge, providing the first evidence that gamma-Glu-Cys can act as an antioxidant and substitute for GSH in a eukaryotic cell. However, the dipeptide could not fully substitute for the essential function of GSH in the cell as shown by the poor growth of the gsh2 mutant on minimal medium. We suggest that this function may be the detoxification of harmful intermediates that are generated during normal cellular metabolism.     

Anxiety-performance relationships in cricketers: testing the zone of optimal functioning hypothesis

This study extended Hanin's 1980 Zone of Optimal Functioning hypothesis by assessing both intensity and direction components of competitive state anxiety. 20 volunteer semiprofessional cricketers responded to the modified Competitive State Anxiety Inventory-2 prior to ten matches. For each game, players' performances were intraindividually evaluated by three qualified cricket coaches using subjective criteria. Separate Cognitive Anxiety and Somatic Anxiety 'below,' 'in,' and 'above' zones for Intensity and Direction of state anxiety were identified via repeated empirical assessments. Two two-way analyses of variance were computed for Intensity and Direction of anxiety (Cognitive Anxiety Zone Level x Somatic Anxiety Zone Level) with standardized performance scores as the dependent variable. A significant interaction was found between the zone levels for Cognitive and Somatic Anxiety Direction and performance scores. Examination of the Zone of Optimal Functioning hypothesis that focuses on the interactions between Cognitive and Somatic Anxiety and in particular the directional elements of the modified inventory seems warranted.     

Relation between encapsulation and various properties of Streptococcus suis

Encapsulation is thought to be a critical virulence factor for Streptococcus suis. In this study, encapsulation of a selected S. suis culture could be stimulated by cultivation conditions. After cultivation of the S. suis culture in fluid media supplemented with serum, the culture grew with short chains and a uniform turbidity of the growth medium. Autoclave extracts of this culture reacted with capsular type-1-specific antiserum. After cultivation of the S. suis culture in fluid media without serum, the bacteria generally formed longer chains, grew in fluid medium as granular sediment with clear supernatant, and were non-typeable. In addition, the unencapsulated variant appeared to have a more hydrophobic surface and adhered significantly more to HeLa cells. In contrast to the unencapsulated variant, the encapsulated S. suis was phagocytosed to a lesser extent by polymorphonuclear leucocytes. These findings might help to elucidate the role of encapsulation in infections with this bacterial organism.     

The effects of L-dopa on the activity of methionine adenosyltransferase: relevance to L-dopa therapy and tolerance

L-dopa, the major treatment for Parkinson's disease (PD), depletes S-adenosyl-L-methionine (SAM). Since SAM causes PD-like symptoms in rodents, the decreased efficacy of chronic L-dopa administered to PD patients may result from a rebound increase in SAM via methionine adenosyl transferase (MAT), which produces SAM from methionine and ATP. This was tested by administering intraperitoneally saline, or L-dopa to mice and assaying for brain MAT activity. As compared to controls, L-dopa (100 mg/kg) treatments of 1 and 2 times per day for 4 days did not significantly increase MAT activity. However, treatments of 3 times per day for 4 and 8 days did significantly increase the activity of MAT by 21.38% and 28.37%, respectively. These results show that short interval, chronic L-dopa treatments significantly increases MAT activity, which increases the production of SAM. SAM may physiologically antagonize the effects of L-dopa and biochemically decrease the concentrations of L-dopa and dopamine. Thus, an increase in MAT may be related to the decreased efficacy of chronic L-dopa therapy in PD.