Biodegradation of topped Kuwait crude

Summary Biodegradation of a topped Kuwait crude by a mixed microbial culture in a stirred tank fermenter was characterised by bursts of respiratory activity. Acinetobacter calcoaceticus var anitratus predominated during the degradation process. n-Alkanes were rapidly and completely removedlosses from other hydrocarbon classes were only partial. The products of the reaction were CO₂, biomass and oxidised hydrocarbon derivatives.     

Site-specific mutagenesis of human apolipoprotein E. Receptor binding activity of variants with single amino acid substitutions

Apolipoprotein (apo) E, an important protein involved in cholesterol transport in the plasma, binds with high specificity and high affinity to the apoB, E (low density lipoprotein) receptor. Several lines of evidence have indicated that key basic residues in the vicinity of residues 140-160 of apoE are important in mediating binding to the receptor. Furthermore, apoE variants exhibiting defective receptor binding are associated with the genetic lipid disorder type III hyperlipoproteinemia. To determine whether other basic amino acids in this region of apoE also affect receptor binding activity, site-specific mutagenesis of apoE in a bacterial expression system was undertaken. This system had been used successfully to produce apoE3 that was structurally and functionally equivalent to human plasma apoE3. Variants of apoE in which neutral amino acids were substituted for basic residues at positions 136, 140, 143, and 150 were produced. The variants all displayed defective binding; their activity ranged from 9 to 52% of normal (a range similar to that seen with naturally occurring variants of human apoE). In addition, to determine whether the conformation of this region is important for receptor binding, we designed variants in which proline was substituted for leucine 144 or alanine 152. Both variants were defective, exhibiting 13 and 27% of normal binding, respectively. In contrast, a double mutant in which arginine was substituted for serine 139 and alanine for leucine 149 displayed slightly enhanced receptor binding activity. These studies confirm that the middle of the apoE molecule is important in receptor binding and indicate that only certain amino acid substitutions in this region interfere with receptor binding activity.     

Growth rate,labeling index,and radiation survival of cells grown in the matrigel threadin vitro tumor model

Summary Six rodent cell lines (36B10 rat glioma cells, 9L rat gliosarcoma cells, V79 Chinese hamster lung fibroblasts, EMT6/UW and EMT6/Ro mouse mammary sarcoma cells, and RIF-1 mouse fibrosarcoma cells) were tested for growth in cylindrical threads of Matrigel. These cells grew in the threads with doubling times of 17–23 h, reaching maximum cell densities on the order of 10⁸ cells/ml. Histological sections of these threads showed a heterogeneous cell distribution: cells grew to confluence at the thread surface and at somewhat lower cell densities in the thread core. [H-3]thymidine labeling index and radiation sensitivity were measured for 9L and EMT6/UW cells in Matrigel threads. For both cell types, the labeling index in Matrigel was lower than observed in cell monolayers, with higher labeling indexes at the thread periphery than in the thread core. When these threads were grown in stirred medium, lower thread diameters, higher cell yields per thread, and higher labeling indices were obtained. EMT6 cell monolayers coated with Matrigel were less radiosensitive than cells in uncoated monolayers. This protective effect was eliminated by irradiating in the presence of 1 mg/ml misonidazole. EMT6 cells consume nearly three times as much oxygen (mole/cm³-sec) as do 9L cells, which are equally radiosensitive in monolayers with or without a Matrigel coating. The radiation sensitivity of EMT6/UW cells in Matrigel threads was similar to that for monolayers of plateau phase cells, whereas for 9L cells, the response in threads was more similar to exponentially growing cells. We conclude that Matrigel threads provide an alternativein vitro model for studying the radiation response of cells in a three-dimensional geometry.     

Reduction of Visceral Adipose Tissue and Improvement of Metabolic Indices: Effect of Dexfenfluramine in NIDDM

Increased visceral adipose tissue is thought to contribute to impaired glucose tolerance. We studied 10 men with non-insulin dependent diabetes (NIDDM) before and after a 12-week intervention study using dexfenfluramine. Subjects had a mean body mass index (BMI) of 26.4 ± 1.7 kg\m² and had an abdominal distribution of body fatness (waist-to hip ratio >0.9). Anthropometric indices, biochemistry, macronutrient intake from 7-day food records as well as a euglycaemic glucose clamp and magnetic resonance imaging (MRI) were performed at week 0 and week 12. Abdominal adipose tissue area measured by MRI was reduced from 854 ± 270 cm² to 666 ± 231 cm² (p=0.003) due mainly to a selective 32% reduction in visceral fat area from 484 ± 230 cm² to 333 ± 72 cm² (p=0.002). Insulin sensitivity improved from 0.29 ± 0.13 [min^?1 (mU/L)] to 0.54 ± 0.21 [min^?1 (mU/L)] (p=0.01) and C-peptide levels reduced from 0.77 ± 0.24 μmol/L to 0.58 ± 0.15 μmol/L (p=0.002). The reductions in fasting glucose and glycated haemoglobin failed to achieve significance. Fasting total cholesterol and triglyceride levels significantly reduced (p=<0.001 and p=0.021 respectively). There was a reduction in total energy intake (p=0.005) due to a significant reduction in calories obtained from fat (p<0.001). Thus dexfenfluramine was shown to be a useful adjunct therapy for the reduction of visceral fat in abdominally-obese men with NIDDM with an associated improvement in insulin sensitivity.     

Changing patterns of plasma membrane-associated filaments during the initial phases of polymorphonuclear leukocyte adherence

By utilizing a combination of several ultrastructural techniques, we have been able to demonstrate differences in filament organization on the adherent plasma membranes of spreading and mobile PMN as well as within the extending lamellipodia. To follow the subplasmalemmal filaments of this small amoeboid cell during these kinetic events, we sheared off the upper portions of cells onto glass and carbon surfaces for 30 s--5 min. The exposed adherent membranes were immediately fixed and processed for high-resolution SEM or TEM. Whole cells were also examined by phase contrast microscopy, SEM, and oriented thin sections. Observed by SEM, the inner surface of nonadherent PMN membranes is free of filaments, but within 30 s of attachment to the substrate a three-dimensional, interlocking network of globular projections and radiating microfilaments--i.e., a subplasmalemmal filament complex--is consistently demonstrable (with or without postfixation in OsO4). Seen by TEM, extending lamellipodia contain a felt of filamentous and finely granular material, distinct from the golbule/filament complex of the adjacent adherent membrane. In the spread cell, this golbule-filament complex covers the entire lower membrane and increases in filament-density over the next 2--3 min. By 3--5 min after plating, as the PMN rounds up before the initiation of amoeboid movements, another pattern emerges--circumferential bands of anastomosing filament bundles in which thick, short filaments resembling myosin are found. This work provides structural evidence on the organization of polymerized contractile elements associated with the plasma membrane during cellular adherence.     

Lifestyle modifications to prevent and control hypertension. 1. Methods and an overview of the Canadian recommendations. Canadian Hypertension Society,Canadian Coalition for High Blood Pressure Prevention and Control,Laboratory Centre for Disease Control at Health Canada,Heart and Stroke Foundation of Canada

OBJECTIVE: To provide updated, evidence-based recommendations for health care professionals on lifestyle changes to prevent and control hypertension in otherwise healthy adults (except pregnant women). OPTIONS: For people at risk for hypertension, there are a number of lifestyle options that may avert the condition--maintaining a healthy body weight, moderating consumption of alcohol, exercising, reducing sodium intake, altering intake of calcium, magnesium and potassium, and reducing stress. Following these options will maintain or reduce the risk of hypertension. For people who already have hypertension, the options for controlling the condition are lifestyle modification, antihypertensive medications or a combination of these options; with no treatment, these people remain at risk for the complications of hypertension. OUTCOMES: The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the period January 1996 to September 1996 for each of the interventions studied. Reference lists were scanned, experts were polled, and the personal files of the authors were used to identify other studies. All relevant articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Lifestyle modification by means of weight loss (or maintenance of healthy body weight), regular exercise and low alcohol consumption will reduce the blood pressure of appropriately selected normotensive and hypertensive people. Sodium restriction and stress management will reduce the blood pressure of appropriately selected hypertensive patients. The side effects of these therapies are few, and the indirect benefits are well known. There are certainly costs associated with lifestyle modification, but they were not measured in the studies reviewed. Supplementing the diet with potassium, calcium and magnesium has not been associated with a clinically important reduction in blood pressure in people consuming a healthy diet. RECOMMENDATIONS: (1) It is recommended that health care professionals determine the body mass index (weight in kilograms/[height in metres]2) and alcohol consumption of all adult patients and assess sodium consumption and stress levels in all hypertensive patients. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy body mass index. For those who choose to drink alcohol intake should be limited to 2 or fewer standard drinks per day (maximum of 14/week for men and 9/week for women). Adults should exercise regularly. (3) To reduce blood pressure in hypertensive patients, individualized therapy is recommended. This therapy should emphasize weight loss for overweight patients, abstinence from or moderation in alcohol intake, regular exercise, restriction of sodium intake and, in appropriate circumstances, individualized cognitive behaviour modification to reduce the negative effects of stress. VALIDATION: The recommendations were reviewed by all of the sponsoring organizations and by participants in a satellite symposium of the fourth international Conference on Preventive Cardiology. They are similar to those of the World Hypertension League and the Joint National committee, with the exception of the recommendations on stress management, which are based on new information. They have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at health Canada, and the Heart and Stroke Foundation of Canada.     

Lifestyle modifications to prevent and control hypertension. 5. Recommendations on dietary salt. Canadian Hypertension Society,Canadian Coalition for High Blood Pressure Prevention and Control,Laboratory Centre for Disease Control at Health Canada,Heart and Stroke Foundation of Canada

OBJECTIVE: To provide updated, evidence-based recommendations concerning the effects of dietary salt intake on the prevention and control of hypertension in adults (except pregnant women). The guidelines are intended for use in clinical practice and public education campaigns. OPTIONS: Restriction of dietary salt intake may be an alternative to antihypertensive medications or may supplement such medications. Other options include other nonpharmacologic treatments for hypertension and no treatment. OUTCOMES: The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the period 1966-1996 using the terms hypertension, blood pressure, vascular resistance, sodium chloride, sodium, diet, sodium or sodium chloride dietary, sodium restricted/reducing diet, clinical trials, controlled clinical trial, randomized controlled trial and random allocation. Both trials and review articles were obtained, and other relevant evidence was obtained from the reference lists of the articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence. In addition, a systematic review of all published randomized controlled trials relating to dietary salt intake and hypertension was conducted. VALUES: A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: For normotensive people, a marked change in sodium intake is required to achieve a modest reduction in blood pressure (there is a decrease of 1 mm Hg in systolic blood pressure for every 100 mmol decrease in daily sodium intake). For hypertensive patients, the effects of dietary salt restriction are most pronounced if age is greater than 44 years. A decrease of 6.3 mm Hg in systolic blood pressure and 2.2 mm Hg in diastolic blood pressure per 100 mmol decrease in daily sodium intake was observed in people of this age group. For hypertensive patients 44 years of age and younger, the decreases were 2.4 mm Hg for systolic blood pressure and negligible for diastolic blood pressure. A diet in which salt is moderately restricted appears not to be associated with health risks. RECOMMENDATIONS: (1) Restriction of salt intake for the normotensive population is not recommended at present, because of insufficient evidence demonstrating that this would lead to a reduced incidence of hypertension. (2) To avoid excessive intake of salt, people should be counselled to choose foods low in salt (e.g., fresh fruits and vegetables), to avoid foods high in salt (e.g., pre-prepared foods), to refrain from adding salt at the table and minimize the amount of salt used in cooking, and to increase awareness of the salt content of food choices in restaurants. (3) For hypertensive patients, particularly those over the age of 44 years, it is recommended that the intake of dietary sodium be moderately restricted, to a target range of 90-130 mmol per day (which corresponds to 3-7 g of salt per day). (4) The salt consumption of hypertensive patients should be determined by interview. VALIDATION: These recommendations were reviewed by all of the sponsoring organizations and by participants in a satellite symposium of the fourth International Conference on Preventive Cardiology. They have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.