Regulation of constant cell elongation and Sfm pili synthesis in Escherichia coli via two active forms of FimZ orphan response regulator.

Escherichia coli (E. coli) has multiple copies of the chaperone-usher (CU) pili operon in five fimbria groups: CU pili, curli, type IV pili, type III secretion pili, and type IV secretion pili. Commensal E. coli K-12 contains 12 CU pili operons. Among these operons, Sfm is expressed by the sfmACDHF operon. Transcriptome analyses, reporter assays, and chromatin immunoprecipitation PCR analyses reported that FimZ directly binds to and activates the sfmA promoter, transcribing sfmACDHF. In addition, FimZ regularly induces constant cell elongation in E. coli, which is required for F-type ATPase function. The bacterial two-hybrid system showed a specific interaction between FimZ and the α subunit of the cytoplasmic F1 domain of F-type ATPase. Studies performed using mutated FimZs have revealed two active forms, I and II. Active form I is required for constant cell elongation involving amino acid residues K106 and D109. Active form II additionally required D56, a putative phosphorylation site, to activate the sfmA promoter. The chromosomal fimZ was hardly expressed in parent strain but functioned in phoB and phoP double-gene knockout strains. These insights may help to understand bacterial invasion restricted host environments by the sfm γ-type pili.

Influenza virus replication raises the temperature of cells.

Influenza virus invades the cell by binding sialic acid on the cell membrane through haemagglutinin (HA), and then genome replication and transcription are carried out in the nucleus to produce progeny virus. Multiplication of influenza virus requires metabolites, such as nucleotides and amino acids, as well as cellular machinery to synthesize its genome and proteins, thereby producing viral particles. Influenza virus infection forces the start of several metabolic systems in the cell, which consume or generate large amounts of energy. Thus, the viral multiplication processes involved in both genome replication and transcription are considered to require large numbers of nucleotides. The high-level consumption of nucleotides generates large amounts of energy, some of which is converted into heat, and this heat may increase the temperature of cells. To address this question, we prepared a tool based on rhodamine B fluorescence, which we used to measure the temperatures of influenza virus-infected and uninfected cells. The results indicated that influenza virus multiplication increased the temperature of cells by approximately 4 °C - 5 °C, ATP levels in the cells decreased at 3 h after infection, and mitochondrial membrane potential decreased with multiplication level. Thus, the increase in cellular temperature during influenza virus infection appears to be due to the massive consumption of ATP over a short period.

Cardiac output and other hemodynamic variables in anesthetized dogs undergoing laparotomy because of abdominal neoplasia.

OBJECTIVE: To measure cardiac output and other hemodynamic variables in anesthetized dogs undergoing laparotomy because of abdominal neoplasia. DESIGN: Prospective case series. ANIMALS: 8 dogs with splenic or hepatic tumors. PROCEDURES: Dogs were anesthetized and underwent abdominal laparotomy. End-tidal isoflurane concentration, heart rate, arterial blood pressures, cardiac output, arterial pH, blood gas partial pressures, PCV, and plasma total protein concentration were measured at set intervals before, during, and after surgery. Cardiac index, stroke index, and systemic vascular resistance index were calculated. RESULTS: End-tidal isoflurane concentration was lowest before and after surgery. Heart rate did not change significantly throughout the anesthetic period. Arterial blood pressures and systemic vascular resistance index were highest shortly after surgery began; cardiac index and stroke volume index did not change significantly during surgery but increased significantly after surgery ended. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that in dogs undergoing laparotomy because of abdominal neoplasia, changes in arterial blood pressures were not necessarily indicative of qualitatively similar changes in cardiac index.

Heterotopic implantation of a porcine bioprosthetic heart valve in a dog with aortic valve endocarditis.

CASE DESCRIPTION: A 5-year-old male German Shepherd Dog was evaluated because of a 5-month history of progressive lethargy, weight loss, and heart failure. CLINICAL FINDINGS: On physical examination, bounding femoral pulses and systolic and diastolic murmurs were detected. Echocardiography revealed severe aortic valve insufficiency (AVI) and a large vegetative lesion on the aortic valve consistent with aortic valve endocarditis. The AVI velocity profile half-time was 130 milliseconds; the calculated peak systolic pressure gradient across the aortic valve was 64 mm Hg. Left ventricular diameter during diastole was 63.6 mm (predicted range, 40.2 to 42 mm) and during systole was 42.9 mm (predicted range, 25.4 to 27 mm). Systolic, diastolic, and mean arterial blood pressures were 120, 43, and 65 mm Hg, respectively. TREATMENT AND OUTCOME: To palliate severe AVI, the descending aorta was occluded (duration, 16.75 minutes) and heterotopic implantation of a porcine bioprosthetic heart valve in that vessel was performed. After surgery, systolic, diastolic, and mean arterial blood pressures were 115, 30, and 61 mm Hg, respectively, in the forelimb and 110, 62, and 77 mm Hg, respectively, in the hind limb. Within 6 months, the AVI velocity profile half-time had increased to 210 milliseconds, indicating diminished severity of AVI. After 24 months, the dog was able to engage in vigorous exercise; no pulmonary edema had developed since surgery. CLINICAL RELEVANCE: Heterotopic bioprosthetic heart valve implantation into the descending aorta during brief aortic occlusion appears feasible in dogs and may provide substantial palliation for dogs with severe AVI.

Evaluation of hemodynamic measurements, including lithium dilution cardiac output, in anesthetized dogs undergoing ovariohysterectomy.

OBJECTIVE: To measure cardiac output in healthy female anesthetized dogs by use of lithium dilution cardiac output and determine whether changes in mean arterial pressure were caused by changes in cardiac output or systemic vascular resistance. DESIGN: Prospective clinical study. ANIMALS: 20 healthy female dogs. PROCEDURE: Dogs were anesthetized for ovariohysterectomy. Ten dogs breathed spontaneously throughout anesthesia, and 10 dogs received intermittent positive-pressure ventilation. Cardiovascular and respiratory measurements, including lithium dilution cardiac output, were performed during anesthesia and surgery. RESULTS: Mean arterial pressure and systemic vascular resistance index were low after induction of anesthesia and just prior to surgery and increased significantly after surgery began. Cardiac index (cardiac output indexed to body surface area) did not change significantly throughout anesthesia and surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results provide baseline data for cardiac output and cardiac index measurements during clinical anesthesia and surgery in dogs. Changes in mean arterial pressure do not necessarily reflect corresponding changes in cardiac index.