The initial synthesis of proteins during development. Phosphoenolpyruvate carboxylase in rat liver at birth

1. A specific antibody, prepared by immunizing rabbits with phosphoenolpyruvate carboxylase (EC 4.1.1.32) purified from adult rat liver, was used to study the appearance of this enzyme in livers from developing rats. 2. Although some inactive precursor of the enzyme may be present in foetal liver, the amount is not sufficient to account for the enzyme appearance at birth. 3. The rate of phosphoenolpyruvate carboxylase synthesis relative to other cytosol proteins increases 20-fold from the foetus to the 1-day-old rat. The high rate of synthesis was maintained at least until 3 days after birth. 4. There was no measurable degradation of phosphoenolpyruvate carboxylase during the first day after birth. During this period the hepatic enzyme content increased 12-fold. 5. When phosphoenolpyruvate carboxylase attained a constant activity in the liver of rats 2 days after birth the half-time of degradation was approx. 13h. 6. We suggest that the pattern of changes occurring during appearance of phosphoenolpyruvate carboxylase is similar to substrate-induced enzyme induction in bacteria.     

Differential effects of furosemide on porcine bronchial arterial and airway smooth muscle.

Furosemide attenuates airway obstruction in asthmatic subjects when administered as an aerosol pretreatment. This protective effect of furosemide could be related to relaxation of bronchial smooth muscle or to increased bronchial blood flow. To determine whether furosemide dilates bronchial smooth muscle, isometric contractile responses in distal bronchi from young pigs were studied. In bronchial smooth muscle rings that were precontracted with 10(-5) M acetylcholine, significant relaxation occurred with 10(-8) to 3 x 10(-6) M isoproterenol but not with 10(-8) to 10(-3) M furosemide. In contrast, bronchial arteries that were precontracted with either 10(-4) M norepinephrine or 10(-8) M vasopressin significantly relaxed in response to 10(-4) to 3 x 10(-3) M and 10(-3) to 3 x 10(-3) M furosemide, respectively. We conclude that furosemide, under the described experimental conditions, relaxes airway vascular smooth muscle but not bronchial smooth muscle. These results are consistent with previous suggestions that inhaled furosemide increases blood flow to airway tissues (Gilbert IA, Lenner KA, Nelson JA, Wolin AD, and Fouke JM. J Appl Physiol 76: 409-415, 1994).     

Sleep, respiratory physiology, and nocturnal asthma.

The nocturnal worsening of asthma is a common feature of this disease that recently has received extensive investigation. Most recent efforts have focused on the role of circadian biorhythms that could promote a nocturnal increase in airway inflammation, leading to a subsequent increase in airflow obstruction and asthma symptoms. However, definitive studies remain lacking. As discussed in this review, there is also substantial evidence that sleep itself may play a direct role in the nocturnal worsening of asthma. Potential mechanisms for such a sleep-related effect could include the supine posture, alterations in sympathetic and parasympathetic "balance," sleep-associated reductions in lung volume, intrapulmonary pooling of blood, and sleep-associated upper airway narrowing, both with and without snoring and obstructive sleep apnea (OSA). These potential contributors to this troublesome phenomenon deserve further consideration when investigating mechanisms of nocturnal asthma.     

Genes that enhance the ecological fitness of Shewanella oneidensis MR-1 in sediments reveal the value of antibiotic resistance

Environmental bacteria persist in various habitats, yet little is known about the genes that contribute to growth and survival in their respective ecological niches. Signature-tagged mutagenesis (STM) of Shewanella oneidensis MR-1 coupled with a screen involving incubations of mutant strains in anoxic aquifer sediments allowed us to identify 47 genes that enhance fitness in sediments. Gene functions inferred from annotations provide us with insight into physiological and ecological processes that environmental bacteria use while growing in sediment ecosystems. Identification of the mexF gene and other potential membrane efflux components by STM demonstrated that homologues of multidrug resistance genes present in pathogens are required for sediment fitness of nonpathogenic bacteria. Further studies with a mexF deletion mutant demonstrated that the multidrug resistance pump encoded by mexF is required for resistance to antibiotics, including chloramphenicol and tetracycline. Chloramphenicol-adapted cultures exhibited mutations in the gene encoding a TetR family regulatory protein, indicating a role for this protein in regulating expression of the mexEF operon. The relative importance of mexF for sediment fitness suggests that antibiotic efflux may be a required process for bacteria living in sediment systems.     

Role of Na+-K+-Cl- cotransport and Na+/Ca2+ exchange in mitochondrial dysfunction in astrocytes following in vitro ischemia

Na⁺-K⁺-Cl^– cotransporter isoform 1 (NKCC1) and reverse mode operation of the Na⁺/Ca²⁺ exchanger (NCX) contribute to intracellular Na⁺ and Ca²⁺ overload in astrocytes following oxygen-glucose deprivation (OGD) and reoxygenation (REOX). Here, we further investigated whether NKCC1 and NCX play a role in mitochondrial Ca²⁺ (Ca_m²⁺) overload and dysfunction. OGD/REOX caused a doubling of mitochondrial-releasable Ca²⁺ (P < 0.05). When NKCC1 was inhibited with bumetanide, the mitochondrial-releasable Ca²⁺ was reduced by 42% (P < 0.05). Genetic ablation of NKCC1 also reduced Ca_m²⁺ accumulation. Moreover, OGD/REOX in NKCC1^+/+ astrocytes caused dissipation of the mitochondrial membrane potential (_m) to 42 ± 3% of controls. In contrast, when NKCC1 was inhibited with bumetanide, depolarization of _m was attenuated significantly (66 ± 10% of controls, P < 0.05). Cells were also subjected to severe in vitro hypoxia by superfusion with a hypoxic, acidic, ion-shifted Ringer buffer (HAIR). HAIR/REOX triggered a secondary, sustained rise in intracellular Ca²⁺ that was attenuated by reversal NCX inhibitor KB-R7943. The hypoxia-mediated increase in Ca_m²⁺ was accompanied by loss of _m and cytochrome c release in NKCC1^+/+ astrocytes. Bumetanide or genetic ablation of NKCC1 attenuated mitochondrial dysfunction and astrocyte death following ischemia. Our study suggests that NKCC1 acting in concert with NCX causes a perturbation of Ca_m²⁺ homeostasis and mitochondrial dysfunction and cell death following in vitro ischemia. intracellular calcium ion; mitochondrial membrane potential; sodium ion influx; bumetanide; cytochrome c; glial cell death     

Atrial electrophysiological and molecular remodelling induced by obstructive sleep apnoea

Obstructive sleep apnoea (OSA) affects 9–24% of the adult population. OSA is associated with atrial disease, including atrial enlargement, fibrosis and arrhythmias. Despite the link between OSA and cardiac disease, the molecular changes in the heart which occur with OSA remain elusive. To study OSA‐induced cardiac changes, we utilized a recently developed rat model which closely recapitulates the characteristics of OSA. Male Sprague Dawley rats, aged 50–70 days, received surgically implanted tracheal balloons which were inflated to cause transient airway obstructions. Rats were given 60 apnoeas per hour of either 13 sec. (moderate apnoea) or 23 sec. (severe apnoea), 8 hrs per day for 2 weeks. Controls received implants, but no inflations were made. Pulse oximetry measurements were taken at regular intervals, and post‐apnoea ECGs were recorded. Rats had longer P wave durations and increased T wave amplitudes following chronic OSA. Proteomic analysis of the atrial tissue homogenates revealed that three of the nine enzymes in glycolysis, and two proteins related to oxidative phosphorylation, were down regulated in the severe apnoea group. Several sarcomeric and pro‐hypertrophic proteins were also up regulated with OSA. Chronic OSA causes proteins changes in the atria which suggest impairment of energy metabolism and enhancement of hypertrophy.     

Wild turkey (<Emphasis Type="Italic">Meleagris gallopavo</Emphasis>) detectability from helicopters and ramifications for estimating abundance

Aerial surveys have been used to estimate abundance for several wild bird species but its application for wild turkey (Meleagris gallopavo) populations has been limited. We surveyed Rio Grande wild turkey (M. gallopavo intermedia) populations during March 2006 using an R44 helicopter. We used flocks with radio-tagged birds to estimate flock detectability. We also used simulations to evaluate accuracy and precision and examine power to detect trends in population change. We observed that wild turkey flock detectability was 94.7% (74.0–99.9%; 95% CI). Our simulations suggested helicopter surveys would underestimate abundance by about 5.6% (4.6% CV). Surveying 980 to 1,960 km² (requiring 27 to 55 h of flight time) can provide sufficient power (≥0.80) to detect a 10 to 25% change in abundance over a 4- to 5-year period.     

The mitochondrial genome: mutation, selection and recombination

Within an individual, mitochondria must function in a range of tissue specific environments that are largely governed by expression of a particular suite of nuclear genes. Furthermore, mitochondrial proteins form large complexes with nuclear-encoded proteins to form the electron-transport system. These dynamics between mitochondrial and nuclear genomes have important implications in studies of within and among species genetic variation, and interpretation of disease phenotypes. Experimentally disrupting naturally occurring combinations of nuclear and mitochondrial genomes should provide insights into the coevolutionary dynamics among genomes.