An electrogenetic toggle switch model

Synthetic biology uses molecular biology to implement genetic circuits that perform computations. These circuits can process inputs and deliver outputs according to predefined rules that are encoded, often entirely, into genetic parts. However, the field has recently begun to focus on using mechanisms beyond the realm of genetic parts for engineering biological circuits. We analyse the use of electrogenic processes for circuit design and present a model for a merged genetic and electrogenetic toggle switch operating in a biofilm attached to an electrode. Computational simulations explore conditions under which bistability emerges in order to identify the circuit design principles for best switch performance. The results provide a basis for the rational design and implementation of hybrid devices that can be measured and controlled both genetically and electronically.     

Evaluation of investigations to diagnose the cause of dizziness in elderly people: a community based controlled study.

OBJECTIVE: To compare the findings in dizzy elderly people with those in controls of a similar age to identify which investigations differentiate dizzy from non-dizzy patients and to design an investigational algorithm. DESIGN: Community based study of clinical and laboratory findings in dizzy and control elderly people. SETTING: Research outpatient clinic at a teaching hospital. SUBJECTS: 149 dizzy and 97 control subjects aged over 65 years recruited from a community survey and articles in the local press. MAIN OUTCOME MEASURES: Findings on physical examination, blood testing, electrocardiography (at rest and over 24 hours), electronystagmography, posturography, and magnetic resonance imaging of head and neck (125 (84%) dizzy subjects and 86 (89%) controls); hospital anxiety and depression score; responses to hyperventilation, carotid sinus massage, and the Hallpike manoeuvre. RESULTS: Blood profile, electrocardiography, electronystagmography, and magnetic resonance imaging failed to distinguish dizzy from control subjects because of the frequency of asymptomatic abnormalities in controls. Posturography and clinical assessment (physical examination, dizziness provocation, and psychological assessment) showed significant differences between the groups. A cause of the dizziness was identified from clinical diagnostic criteria based on accepted definitions in 143 subjects, with 126 having more than one cause. The most common diagnoses were central vascular disease (105) and cervical spondylosis (98), often accompanied by poor vision and anxiety. CONCLUSION: Expensive investigations are rarely helpful in dizzy elderly people. The cause of the dizziness can be diagnosed in most cases on the basis of a thorough clinical examination without recourse to hospital referral.     

Transformation of carbon tetrachloride via sulfur and oxygen substitution by Pseudomonas sp. strain KC.

Pseudomonas sp. strain KC transforms carbon tetrachloride into carbon dioxide and nonvolatile products, without chloroform as an intermediate. To define the pathway for hydrolysis, nonvolatile products were analyzed. Condensation products containing the carbon atom of carbon tetrachloride as carbonyl and thioxo moieties were identified, indicating the intermediacy of phosgene and thiophosgene in the pathway.     

Vasomotor instability preceding tilt-induced syncope: does respiration play a role?

Lipsitz, Lewis A., Raymond Morin, Margaret Gagnon, DanKiely, and Aharon Medina. Vasomotor instability precedingtilt-induced syncope: does respiration play a role? J. Appl. Physiol. 83(2): 383-390, 1997.This studyaimed to determine whether alterations in cardiovascular dynamicsbefore syncope are related to changes in spontaneous respiration.Fifty-two healthy subjects underwent continuous heart rate (HR),arterial blood pressure (BP), and respiratory measurements during10-min periods of spontaneous and paced breathing (0.25 Hz) in thesupine and 60° head-up tilt positions. Data were evaluated by powerspectrum and transfer function analyses. During tilt, 27 subjectsdeveloped syncope or presyncope and 25 remained asymptomatic. Subjectswith tilt-induced syncope had significantly greater increases inlow-frequency (0.04-0.15 Hz) systolic BP, diastolic BP, and HRpower during tilt than the asymptomatic subjects(P  0.01). This difference waspresent during spontaneous but not paced breathing. However, averagetidal volume, respiratory rate, minute ventilation, proportion ofbreaths below 0.15 Hz, and low-frequency respiratory power during tilt did not differ between syncopal and nonsyncopal subjects. Transfer magnitudes between low-frequency respiration and BP, and between BP andinterbeat interval, were also similar between groups. Thus vasomotorinstability before syncope is not related to alterations in respirationor the cardiovagal baroreflex but may reflect oscillating centralsympathetic outflow to the vasculature.

     

Geometry and energetics of DNA basepairs and triplets from first principles quantum molecular relaxations.

A first principles model for calculating hydrogen bonding interactions, previously applied to water, is here applied to the more difficult problem of interactions between DNA bases. We first consider the energetics and geometry for the A-T and the G-C basepairs, comparing our results to other calculated results as well as to experiment. Next, we study the interactions of isomorphic DNA base triplet structures, which are important because of their suggested role in the recombination process. We find that energetically the third base in the triplet tends to favor a position along the dyadic axis, where it is hydrogen bonded to both bases in the duplex.     

Surgical Treatment of Constipation

A 30-year retrospective review of 544,354 Seattle area hospital admissions yielded 25 patients who underwent surgical therapy for the relief of intractable idiopathic constipation. All patients were refractory to conventional medical treatment consisting of the daily use of laxatives, cathartics, emollients or enemas. Long-term follow-up was available for 13 of the 25 patients. All 13 patients had clinical improvement as a result of the operation. This confirms results reported by other authors. Subtotal colectomy and left hemicolectomy are the procedures generally favored.     

Blood chemistry of the common marmoset (Callithrix jacchus) maintained in an indoor-outdoor environment: Primate comparisons

Blood chemistry values were collected over a three-year period from at least 10 colony-born and 24 wild-born apparently normal common marmosets. BUN, SGOT, creatinine, calcium, phosphorus, alkaline phosphatase, protein, albumin, cholesterol, triglycerides, uric and glucose values were determined. A statistical comparison of baseline values was made between wild-born, colony-born, male and female marmosets. Also the same comparison was made between common marmosets and cotton-top tamarins, white lipped tamarins and human subjects.