Growth rate and methane affinity of a turbidostatic and oxystatic continuous culture ofMethylococcus capsulatus (Bath)

Summary A turbidostatic and oxystatic fermentation system was used to study the growth kinetic ofMethylococcus capsulatus (Bath). Dissolved oxygen and methane concentrations were measured continuously with membrane inlet mass spectrometry. The specific growth rate was found to increase from 0.25 h^–1 to 0.37 h^–1 and the saturation constant for methane was found to decrease from 71 M to 1.3 M as the copper content of the medium was varied from a very low to a high value.     

Inhibition by ammonia of methane utilization in Methylococcus capsulatus (Bath)

Summary The kinetics of methane uptake by Methylococcus capsulatus (Bath) and its inhibition by ammonia were studied by stopped-flow membrane-inlet mass spectrometry. Measurements were done on suspensions of cells grown in high- and low-copper media. With both types of cells the kinetics of methane uptake are hyperbolic when oxygen is in excess. The apparent K _m and K _max for methane uptake are both higher in low-copper cells than in high-copper cells. Ammonia is a simple competitive inhibitor of methane uptake in high-copper cells when the oxygen concentration is above a few M. The findings agree with the assumption that ammonia is a week alternative substrate for particulate methane monooxygenase. In low-copper cells the effect of ammonia is complicated and cannot be explained in terms of current assumptions on the mechanism of soluble methane monooxygenase. Our data indicate that ammonia inhibition is likely to be a more serious problem in connection with cultivation in low-copper medium than in high-copper medium. Offprint requests to: H. N. Carlsen     

Vaccine Protection against a Heterologous, Non-Syncytium-Inducing, Primary Human Immunodeficiency Virus

Vaccine-induced protection of chimpanzees against laboratory-adapted and syncytium-inducing, multiply passaged primary human immunodeficiency virus type 1 (HIV-1) isolates, but not against non-syncytium-inducing, minimally passaged ones, has been demonstrated. Following challenge with such an isolate, HIV-1₅₀₁₆, we obtained complete protection in one of three chimpanzees previously protected against low- and high-dose HIV-1_SF2 exposures after immunization with an adenovirus-HIV-1_MN gp160 priming–HIV-1_SF2 gp120 boosting regimen. At challenge, the protected chimpanzee exhibited broad humoral immunity, including neutralizing antibody activity. These results demonstrate the potential of this combination vaccine strategy and suggest that vaccine protection against an HIV isolate relevant to infection of people is feasible.     

Arsenate reduction mediated by the plasmid-encoded ArsC protein is coupled to glutathione

Resistance to arsenate conferred on Escherichia coli by the ars operon of plasmid R773 requires both the product of the arsC gene and reduction of arsenate to arsenate. A genetic analysis was performed to identify the source of reducing potential in vivo. in addition to the ars genes, arsenate resistance required the products of the gor gene for glutathione reductase and the gshA and gshB genes for glutathione synthesis. Mutations in the trx and grx genes for thioredoxin and glutaredoxin, respectively, had no effect on arsenate resistance. Although resistance required the arsC gene, the rate of reduction of arsenate to arsenate was nearly the same in cells lacking the ars operon. In strains deficient in glutathione biosynthesis this endogenous reduction was greatly diminished, and cells exhibited increased sensitivity to arsenate. When glutathione was supplied exogenously to such mutants, resistance was restored only to cells expressing the ars operon, and only such cells had detectable arsenate reduction after addition of glutathione. Since ArsC-catalysed reduction of arsenate provides high level resistance, physical coupling of the ArsC reaction to efflux of the resulting arsenite is hypothesised.     

Effects of sex hormone binding globulin (SHBG) on human prostatic carcinoma

The purpose of this study was to determine what effects sex hormone binding globulin (SHBG) might have on the growth and steroid content of human prostate carcinoma. Two human prostate carcinoma cell lines were used for this study, ALVA-41 and ALVA-101. The first part of the study was to determine the effect of SHBG or albumin on the uptake of [³H]DHT in the cells. In this experiment both SHBG and albumin inhibits the uptake of [³H]DHT into each of the cell lines when studied in vitro. The degree of inhibition was dependent on the binding capacity of the protein. When [³H]thymidine uptake was measured in each of the cell lines following either the addition of SHBG or albumin to the culture media, an increase in uptake and presumably DNA synthesis was noted in the ALVA-41 and ALVA-101 cells for SHBG additions but not for albumin. Further, this stimulation was increased when testosterone was added to the media, however, [³H]thymidine uptake was decreased by high concentrations of dihydrotestosterone (DHT) or if the SHBG was saturated with DHT prior to being added to the media. The cells also demonstrate high affinity cell membrane receptors for SHBG. Finally, using a 3′, 550 bp cDNA or SHBG, 1.9 and 2.8 kb mRNAs were detected on Northern analysis of the ALVA-101 and ALVA-41 cells. These data indicate SHBG can inhibit uptake of steroids into the prostrate, but also it may act as a stimulus for growth through a SHBG cell surface receptor. In addition, the growth effect may be through an autocrine effect from SHBG or a SHBG-related peptide.     

The Adult G?ttingen Minipig as a Model for Chronic Heart Failure After Myocardial Infarction: Focus on Cardiovascular Imaging and Regenerative Therapies

Porcine models have become increasingly popular in cardiovascular research. The standard farm pig rapidly increases in body weight and size, potentially confounding serial measurements of cardiac function and morphology. We developed an adult porcine model that does not show physiologic increases in heart mass during the study period and is suitable for long-term study. We compared adult minipigs with the commonly used adolescent Yorkshire swine. Myocardial infarction was induced in adult Göttingen minipigs and adolescent Yorkshire swine by occlusion of the left anterior descending coronary artery followed by reperfusion. At 8 wk after infarction, the left ventricular ejection fraction was 34.1 ± 2.3% in minipigs and 30.7 ± 2.0% in Yorkshire swine. The left ventricular end-diastolic mass in Yorkshire pigs assessed by magnetic resonance imaging increased 17 ± 5 g, from 42.6 ± 4.3 g at week 1 after infarction to 52.8 ± 6.6 g at week 8, whereas it remained unchanged in minipigs. Cardiac anatomy and physiology in adult minipigs were evaluated invasively by angiography and noninvasively by Multidetector Computed Tomography and by Magnetic Resonance Imaging at 1.5 T and 3 T prior to myocardial infarction and during folow-up. This porcine heart failure model is reproducible, mimics the pathophysiology in patients who have experienced myocardial infarction, and is suitable for imaging studies. New heart failure therapies and devices can be tested preclinically in this adult animal model of chronic heart failure.Abbreviations: CEMRA, contrast-enhanced magnetic resonance angiography; CI, confidence interval; ECG, electrocardiogram; LAD, left anterior descending artery; LV, left ventricle; LVEF, left ventricular ejection fraction; MDCT, multidetector computed tomography; MI, myocardial infarction; MRI, magnetic resonance imagingIn the United States alone, 7.1 million people are survivors of myocardial infarction (MI) and 4.9 million people live with congestive heart failure.⁴ New medical therapies, surgical procedures and devices for heart failure all rely heavily on preclinical testing in animal models. Porcine models of MI are used because of the similarities between porcine and human hearts.^29,38 However, the commonly employed farm pigs are utilized at a young age, grow rapidly and continue to gain in mass during use, thereby complicating long-term follow-up. The utilization of farm pigs at a young age, while their hearts are still growing does not accurately reflect the remodeling that occurs in adult patients after MI and can limit accurate assessment of chronic remodeling processes. This inaccuracy can confound evaluation of devices and pharmacologic therapies.Noninvasive imaging techniques for determining anatomic and functional manifestations of congestive heart failure are accurate and reliable, and are used as surrogate markers of outcome and safety in phase I/II trials.^15,34 Cardiovascular imaging improves evaluation of the effects of new therapies and devices during preclinical assessment. Animal models of congestive heart failure should allow noninvasive imaging during a long-term follow-up period.The Göttingen minipig was developed in the early 1960s at the Institute of Animal Breeding and Genetics (University of Göttingen, Germany) to reduce space requirements and housing costs for preclinical porcine studies.⁹ They were created by crossbreeding the Minnesota minipig with Vietnamese potbelly and German Landrace pigs.¹⁹ Göttingen minipigs are white miniature pigs with good fertility and stable genetics.Göttingen minipigs have a characteristic growth curve that avoids the dramatic increase in weight in adulthood seen in farm pigs.^25,26 A newborn Göttingen minipig has a body mass of 350 to 450 g. Boars become sexually mature at 3 to 4 mo of age, weighing 6 to 8 kg, whereas sows become sexually mature at 4 to 5 mo and 7 to 9 kg. The gestational period is 112 to 114 d, and the average litter size is 5 to 6 animals. Closure of the growth plates is complete at 18 to 22 mo and 30 to 35 kg. Göttingen minipigs have a mature body weight of 35 to 45 kg,¹⁰ and they achieve 40% of the maximal body weight at approximately 10 mo (310 d) with a body weight of 21 kg. In comparison intensively fed farm pigs reach 88 kg at the same time point, with a mature weight of 220 kg, and restrictively fed farm pigs, like Yorkshire swine, typically weigh about 64 kg at 10 mo of age and 160 kg at maturity.²⁶ Characteristics of Yorkshire swine are reported in the literature.¹¹Adult Göttingen minipigs are large enough to allow testing of human equipment and devices. Until now cardiovascular parameters have only been reported in juvenile Göttingen minipigs.^9,13 Here, we demonstrate the unique value of Göttingen minipigs as a novel adult porcine heart failure model for cardiac research in the fields of regenerative medicine, electrophysiology, and noninvasive imaging.     

Landscape genetics and the spatial distribution of chronic wasting disease

Predicting the spread of wildlife disease is critical for identifying populations at risk, targeting surveillance and designing proactive management programmes. We used a landscape genetics approach to identify landscape features that influenced gene flow and the distribution of chronic wasting disease (CWD) in Wisconsin white-tailed deer. CWD prevalence was negatively correlated with genetic differentiation of study area deer from deer in the area of disease origin (core-area). Genetic differentiation was greatest, and CWD prevalence lowest, in areas separated from the core-area by the Wisconsin River, indicating that this river reduced deer gene flow and probably disease spread. Features of the landscape that influence host dispersal and spatial patterns of disease can be identified based on host spatial genetic structure. Landscape genetics may be used to predict high-risk populations based on their genetic connection to infected populations and to target disease surveillance, control and preventative activities.