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Biomedical subjects

M Sander

Publications and source records attributed to M Sander.

At least 19 recordsLinked to original sources
PubMed2006

Effects of ATP-induced leg vasodilation on VO2 peak and leg O2 extraction during maximal exercise in humans.

During maximal whole body exercise VO2 peak is limited by O2 delivery. In turn, it is though that blood flow at near-maximal exercise must be restrained by the sympathetic nervous system to maintain mean arterial pressure. To determine whether enhancing vasodilation across the leg results in higher O2 delivery and leg VO2 during near-maximal and maximal exercise in humans, seven men performed two maximal incremental exercise tests on the cycle ergometer. In random order, one test was performed with and one without (control exercise) infusion of ATP (8 mg in 1 ml of isotonic saline solution) into the right femoral artery at a rate of 80 microg.kg body mass-1.min-1. During near-maximal exercise (92% of VO2 peak), the infusion of ATP increased leg vascular conductance (+43%, P<0.05), leg blood flow (+20%, 1.7 l/min, P<0.05), and leg O2 delivery (+20%, 0.3 l/min, P<0.05). No effects were observed on leg or systemic VO2. Leg O2 fractional extraction was decreased from 85+/-3 (control) to 78+/-4% (ATP) in the infused leg (P<0.05), while it remained unchanged in the left leg (84+/-2 and 83+/-2%; control and ATP; n=3). ATP infusion at maximal exercise increased leg vascular conductance by 17% (P<0.05), while leg blood flow tended to be elevated by 0.8 l/min (P=0.08). However, neither systemic nor leg peak VO2 values where enhanced due to a reduction of O2 extraction from 84+/-4 to 76+/-4%, in the control and ATP conditions, respectively (P<0.05). In summary, the VO2 of the skeletal muscles of the lower extremities is not enhanced by limb vasodilation at near-maximal or maximal exercise in humans. The fact that ATP infusion resulted in a reduction of O2 extraction across the exercising leg suggests a vasodilating effect of ATP on less-active muscle fibers and other noncontracting tissues and that under normal conditions these regions are under high vasoconstrictor influence to ensure the most efficient flow distribution of the available cardiac output to the most active muscle fibers of the exercising limb.

Adenosine Triphosphate↗
PubMed2006

[Alcohol use disorder: risks in anesthesia and intensive care medicine].

Approximately 20% of medical and surgical patients in hospital have an alcohol use disorder (AUD). Diagnosis of chronic alcohol abuse is performed by specific medical history, examination and validated tests. Biomarkers are a means of diagnosing chronic alcoholism in sedated, intubated and emergency patients. Chronic alcohol consumption damages the central nervous and cardiovascular system, the liver and the immune system. In medical ICUs more than 50% of liver injuries and chronic pancreatitis are due to chronic alcohol abuse. The alcohol withdrawal syndrome is emerging in 25% of AUD patients in intensive care after reduction of sedative drugs. Long term alcohol abuse also leads to cardiac arrhythmias, dilatative cardiomyopathy and hypotonic circulatory dysregulation. Bleeding complications are two-fold increased during and after surgery. Immune suppression results in an increased incidence of infectious complications like pneumonia, wound infection and urinary tract infection. In particular, septic encephalopathy is often misinterpreted as alcohol withdrawal syndrome. Due to the fact that AUD patients show a two to five-fold higher rate of postoperative complications they require increased attention to avoid latency of treatment and the development of multiple organ failure. Prophylaxis in terms of drug therapy or abstinence intervals and brief intervention strategies can help to prevent or ease some of these complications and can decrease the rate of long-term injuries.

Alcohol-Induced Disorders↗
PubMed2006

[The influence of intraoperative fluid therapy on the postoperative outcome in "fast track" colon surgery].

OBJECTIVE: To evaluate the association between the intraoperative and postoperative application of different quantities of fluids and the incidence of postoperative complications after "fast-track"-colonic surgery. METHODS: We performed a retrospective analysis of 136 patients undergoing elective "fast-track" colonic surgery (sigma resection and right hemicolectomy). Data collection in regard of fluid administration during surgery and in the post anaesthesia care unit (PACU) was based on anaesthesia charts and a prospectively generated surgery database. Classification into three volume groups (up to 3500 ml = group 1, 3500 - 5500 ml = group 2, more than 5500 ml = group 3). Basic patient characteristics, pre-existing conditions, type and duration of surgery and anastomoses were documented. We analysed the incidence of postoperative complications such as wound infections, anastomotic leak, bleeding, bowel obstruction, cardiovascular failure, hypertension, pulmonary failure, pneumonia, renal failure, urinary tract infection, neurological and psychiatric complications in the different volume groups. RESULTS: 115 patients were infused with up to 3500 mLs of fluids, 19 patients received more than 3500 mLs, two patients were infused with 6000 ml and 7500 mLs, respectively. This was in median 36 ml/kg in the restrictive and 53 ml/kg in the higher volume groups (group 2 and 3 together), respectively. The duration of surgery and anaesthesia was significantly different between both fluid groups (p = 0,023). In a logistic regression model only intraoperative blood loss was independently associated with the volume of infused fluid (OR 0,393, 95 % CI 1.028 - 2.306, p < 0.01). The rate of postoperative complications was not different between groups (p = 0,228). CONCLUSION: The incidence of postoperative complications was not different between patients who were infused 36 ml/kg or 53 ml/kg of fluids during surgery and post anaesthesia care unit stay.

Aged↗
PubMed2006

[Bleeding after cardiac surgery: the role of recombinant factor VIIa].

Cardiac surgery carries a remarkable risk of blood loss requiring transfusion of blood products. Moreover, severe bleeding necessitating reoperation occurs in 3-5% of patients according to international studies. These patients face a significantly higher morbidity and mortality. This underscores the need for a safe and effective haemostatic therapy, which may significantly improve the outcome. Recombinant activated factor VII is approved for haemophiliacs with inhibitors and patients with thrombasthenia Glanzmann and factor VII deficiency. In the proceeding years a series of articles has been published reporting the successful and safe therapy of refractory bleeding after cardiac surgery. This review focuses at presenting the pathophysiological alterations of the haemostatic system related to the cardiopulmonary bypass. These alterations are thought to explain the high risk of bleeding after cardiopulmonary bypass. Furthermore, the use of rFVIIa in paediatric and adult cardiac surgery is reviewed and critically discussed.

Blood Coagulation↗
PubMed2005

A hypothesis: autonomic rhythms are reflected in growth lines of teeth in humans and extinct archosaurs.

A major determinant of tooth architecture is the arrangement of lines in dentin and in the enamel following the contour of the surface. Since the original description of these lines in the 19th century, they have been attributed to recurring events during tooth development. They have also attracted the attention of dental scientists and anthropologists; however, to date, studies of these structures have been largely theoretical and microscopic. We show here that the statistical properties of the spacing between the lines are similar in teeth from both ancient and modern humans and from extinct archosaurs, reptiles that lived tens or hundreds of millions of years ago-they also resemble heart rate variability of living humans. We propose that the deposition of these recurring structures is controlled by the autonomic nervous system. This control accounts for their regularity and recurrent nature and implies that the lines are an expression of a biologic rhythm which has been conserved throughout evolution. Details of the rhythms give clues to life styles in ancient civilizations and to the physiology of extinct archosaurs.

Animals↗
PubMed2005

Aspirin and clopidogrel taken until 2 days prior to coronary artery bypass graft surgery is associated with increased postoperative drainage loss.

OBJECTIVE: Platelet aggregation inhibitors, such as aspirin and clopidogrel, are associated with increased bleeding in patients undergoing cardiac surgery with cardiopulmonary bypass. We investigated the impact of time between the last intake of aspirin and clopidogrel before CABG surgery and drainage loss, transfusion requirements and rate of reoperation. PATIENTS AND METHODS: The records of patients who had coronary artery bypass graft surgery (CABG) were reviewed for intake of aspirin and clopidogrel within 7 days prior to surgery. Drainage loss, transfusion requirements and rate of reoperation for bleeding within 5 days after the operation, were recorded. RESULTS: Out of 261 analysed patients, 225 patients (86.2 %) had no anti-platelet medication and 36 patients (13.8 %) were on aspirin and clopidogrel. Aspirin and clopidogrel, taken all until 2 days prior to operation, were associated with a significantly higher postoperative blood loss (1840 mL [1230 - 3710] vs. 280 mL [185 - 765], p = 0.005 for one day and 850 mL [345 - 1725] vs. 277 mL [165 - 778], p = 0.026, for 2 days prior to surgery). The trend showed that patients in the study group received more platelet concentrates (PC: 5.3 % vs. 13.9 %, p = 0.067). The rate of reoperation for bleeding was not different ( p = 0.25). CONCLUSION: Aspirin and clopidogrel up to 2 days prior to CABG were associated with a significantly higher postoperative drainage loss.

Aged↗
PubMed2005

Clopidogrel-related refractory bleeding after coronary artery bypass graft surgery: a rationale for the use of coagulation factor concentrates?

Clopidogrel, an irreversible ADP-receptor antagonist, inhibits platelet aggregation mediated by reduced activation of glycoprotein receptor IIb/IIIa. Clopidogrel in combination with aspirin has been shown to be superior to aspirin alone for treating unstable angina, but clopidogrel recipients have shown increases in blood loss, transfusion requirements, and rate of reoperation after cardiac surgery. We describe a patient who had taken clopidogrel 75 mg daily until the day prior to coronary artery bypass graft surgery. Severe postoperative bleeding developed and was refractory to conventional hemostatic therapy consisting of 19 units of packed red blood cell concentrates, 16 of fresh frozen plasma, 8 of platelet apheresis concentrates plus high-dose treatment with aprotinin (500.000 kallikrein-inhibiting units/h) and administration of 0.3 microg/kg 1-deamino-8-D-arginine vasopressin (DDAVP). Two reoperations were performed, but surgical hemostasis was not achieved, so 100 microg/kg recombinant activated factor VII was applied to generate sufficient thrombin to stop the bleeding. This treatment approach reduced the bleeding. Then, to promote clot formation and firmness, 2 g of fibrinogen and 1250 IU of factor XIII were administered, and the bleeding finally stopped. No further transfusions were required, and the patient was discharged from the hospital on day 10 after the operation. This case suggests that in clopidogrel-related bleeding refractory to conventional hemostatic therapy, hemostasis may be achieved by a stepwise administration of coagulation factor concentrates.

Clopidogrel↗
PubMed2003

Human skeletal muscle and erythrocyte proteins involved in acid-base homeostasis: adaptations to chronic hypoxia.

Chronic hypoxia is accompanied by changes in blood and skeletal muscle acid-base control. We hypothesized that the underlying mechanisms include altered protein expression of transport systems and the enzymes involved in lactate, HCO3- and H+ fluxes in skeletal muscle and erythrocytes. Immunoblotting was used to quantify densities of the transport systems and enzymes. Muscle and erythrocyte samples were obtained from eight Danish lowlanders at sea level and after 2 and 8 weeks at 4100 m (Bolivia). For comparison, samples were obtained from eight Bolivian natives. In muscle membranes there were no changes in fibre-type distribution, lactate dehydrogenase isoforms, Na+,K+-pump subunits or in the lactate-H+ co-transporters MCT1 and MCT4. The Na+-H+ exchanger protein NHE1 was elevated by 39 % in natives compared to lowlanders. The Na+-HCO3- co-transporter density in muscle was elevated by 47-69 % after 2 and 8 weeks at altitude. The membrane-bound carbonic anhydrase (CA) IV in muscle increased in the lowlanders by 39 %, whereas CA XIV decreased by 23-47 %. Levels of cytosolic CA II and III in muscle and CA I and II in erythrocytes were unchanged. The erythrocyte lactate-H+ co-transporter MCT1 increased by 230-405 % in lowlanders and was 324 % higher in natives. The erythrocyte inorganic anion exchanger (Cl--HCO3- exchanger AE1) was increased by 149-228 %. In conclusion, chronic hypoxia induces dramatic changes in erythrocyte proteins, but only moderate changes in muscle proteins involved in acid-base control. Together, these changes suggest a hypoxia-induced increase in the capacity for lactate, HCO3- and H+ fluxes from muscle to blood and from blood to erythrocytes.

Acid-Base Equilibrium↗
PubMed2003

Endogenous NO does not regulate baseline pulmonary pressure, but reduces acute pulmonary hypertension in dogs.

UNLABELLED: It has remained unclear whether endogenous production of nitric oxide (NO) plays an important role in the regulation of physiologically normal pulmonary pressures. Severe alveolar hypoxia is accompanied by decreased pulmonary NO production, which could contribute to the development of hypoxic pulmonary hypertension. On the other hand, pharmacological NO inhibition further augments this hypertensive response. AIMS: The aims of the present study were to test: (a) whether NO contributes importantly in the maintenance of baseline pulmonary pressure; and (b) to which degree NO is involved in the pulmonary haemodynamic adjustments to alveolar hypoxia. METHODS: In anaesthetized dogs (n=37), the systemic and pulmonary haemodynamic effects of the NO synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME, 20 mg kg(-1)) and substrate, L-arginine (200-500 mg kg(-1)), were determined at baseline and during alveolar hypoxia. Constant blood flows were accomplished by biventricular bypass, and systemic normoxaemia was maintained by extracorporeal oxygenation. RESULTS: The primary findings were: (a) L-NAME failed to increase baseline mean pulmonary arterial pressure (10.1 +/- 0.7 vs. 10.5 +/- 0.5 mmHg, P=ns), despite effective NO synthase inhibition as evidenced by robust increases in systemic arterial pressures; (b) L-NAME augmented the pulmonary hypertensive response to alveolar hypoxia (10.2 +/- 0.7 to 19.5 +/- 1.7 with L-NAME vs. 9.9 +/- 1.1 to 15.5 +/- 1.0 mmHg without L-NAME, P<0.05); and (c) L-arginine failed to decrease baseline or elevated pulmonary pressures. Instead, prolonged L-arginine caused increases in pulmonary pressure. CONCLUSION: These findings suggest that NO plays no significant role in the tonic physiological control of pulmonary pressure, but endogenous NO becomes an important vasodilatory modulator during elevated pulmonary pressure.

Acute Disease↗
PubMed2002

Suppression of interleukin-6 to interleukin-10 ratio in chronic alcoholics: association with postoperative infections.

OBJECTIVE: To investigate the interleukin-6 (IL-6) to interleukin-10 (IL-10) ratio and levels of sE-selectin in patients undergoing elective surgery of the upper digestive tract and to define the differences in the perioperative immune response between chronic alcoholic and non-alcoholic patients. DESIGN: Prospective pilot study. SETTING: Single center, interdisciplinary intensive care unit (ICU) at a university hospital. MEASUREMENT AND MAIN RESULTS: The study compared chronic alcoholics ( n=25) and non-alcoholics ( n=20) before and after surgery for resection of upper digestive tract tumors. White blood cell counts, C-reactive protein and circulating levels of sE-selectin, the pro-inflammatory cytokine IL-6 and the inhibitory cytokine IL-10, were obtained at hospital admission, preoperatively, postoperatively at ICU admission and 2 and 4 days later. Rates of postoperative infectious complications including pneumonia and sepsis were determined. sE-selectin only differed between chronic alcoholics and non-alcoholics preoperatively. Compared to non-alcoholics, chronic alcoholic patients showed a fourfold increase in circulating levels of IL-10 ( p<0.01) and a suppression of the IL-6/IL-10 ratio ( p=0.001) immediately after surgery. Coincident with the immune alterations, chronic alcoholics had a prolonged ICU stay ( p<0.01) and a threefold increased rate of wound infections ( p<0.05) and pneumonia ( p<0.01). Lower IL-6/IL-10 ratios were associated with increased rates of infectious complications ( p<0.05). CONCLUSION: Chronic alcoholics had decreased IL-6/IL-10 ratios at ICU admission and increased rates of infectious complications in the postoperative ICU course. This may indicate immediate postoperative immune suppression before the onset of infections and may help to identify chronic alcoholic patients at risk.

Aged↗
PubMed2001

The exercise metaboreflex is maintained in the absence of muscle acidosis: insights from muscle microdialysis in humans with McArdle's disease.

1. In McArdle's disease, muscle glycogenolysis is blocked, which results in absent lactate and enhanced ammonia production in working muscle. Using McArdle patients as an experimental model, we studied whether lactate and ammonia could be mediators of the exercise pressor reflex. 2. Changes in muscle interstitial ammonia and lactate were compared with changes in blood pressure and muscle sympathetic nerve activity (MSNA) during static arm flexor exercise at 30% of maximal contraction force. Muscle interstitial changes in lactate and ammonia were assessed by microdialysis of the biceps muscle, and MSNA by peroneal nerve microneurography, in six McArdle patients and 11 healthy, matched controls. One McArdle patient also had myoadenylate deaminase deficiency, a condition associated with abolished ammonia production in exercise. 3. Exercise-induced increases were higher in McArdle patients vs. controls for MSNA (change of 164 +/- 71 vs. 59 +/- 19%) and blood pressure (change of 47 +/- 7 vs. 38 +/- 4 mmHg). Interstitial lactate increased in controls (peak change 1.3 +/- 0.2 mmol x l(-1)) and decreased in McArdle patients (peak change -0.5 +/- 0.1 mmol x l(-1)) during and after exercise. Interstitial ammonia did not change during exercise in either group, but was higher post-exercise in McArdle patients, except in the patient with myoadenylate deaminase deficiency who had a flat ammonia response. This patient had an increase in MSNA and blood pressure comparable to other patients. MSNA and blood pressure responses were maintained during post-exercise ischaemia in both groups, indicating that sympathetic activation was caused, at least partly, by a metaboreflex. 4. In conclusion, changes in muscle interstitial lactate and ammonia concentrations during and after exercise are temporally dissociated from changes in MSNA and blood pressure in both patients with McArdle's disease and healthy control subjects. This suggests that muscle acidification and changes in interstitial ammonia concentration are not mediators of sympathetic activation during exercise.

Acidosis↗
PubMed2001

Influence of nitric oxide synthase and adrenergic inhibition on adenosine-induced myocardial hyperemia.

BACKGROUND: Myocardial perfusion during adenosine-induced hyperemia is used both in clinical diagnosis of coronary heart disease and for scientific investigations of the myocardial microcirculation. The objective of this study was to clarify whether adenosine-induced hyperemia is dependent on endothelial NO production or is influenced by adrenergic mechanisms. METHODS AND RESULTS: In 12 healthy men, myocardial perfusion was measured with PET in 2 protocols performed in random order, each including 3 perfusion measurements. First, perfusion was measured at rest. Second, either saline or the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME, 4 mg/kg) was infused, and perfusion during adenosine-induced hyperemia was determined. Last, in both protocols, the alpha-receptor blocker phentolamine was infused, and perfusion during adenosine-induced hyperemia was determined again. Resting perfusion was similar in the 2 protocols (0.69+/-0.14 and 0.66+/-0.18 mL. min(-1). g(-1)). L-NAME increased mean arterial blood pressure by 12+/-7 mm Hg (P<0.01) and reduced heart rate by 16+/-7 bpm (P<0.01). Adenosine-induced hyperemia (1.90+/-0.33 mL. min(-1). g(-1)) was attenuated by L-NAME (1.50+/-0.55 mL. min(-1). g(-1), P<0.01). The addition of phentolamine had no effect on the adenosine-induced hyperemia (2.10+/-0.34 mL. min(-1). g(-1), P=NS). In the presence of L-NAME, however, when the adenosine response was attenuated, phentolamine was able to increase hyperemic perfusion (2.05+/-0.44 mL. min(-1). g(-1), P<0.05). CONCLUSIONS: Inhibition of endogenous NO synthesis attenuates myocardial perfusion during adenosine-induced hyperemia, indicating that coronary vasodilation by adenosine is partly endothelium dependent. alpha-Adrenergic blockade has no effect on adenosine-induced hyperemia unless NO synthesis is inhibited.

Adenosine↗
PubMed2001

Different levels of repressor activity assign redundant and specific roles to Nkx6 genes in motor neuron and interneuron specification.

Specification of neuronal fate in the vertebrate central nervous system depends on the profile of transcription factor expression by neural progenitor cells, but the precise roles of such factors in neurogenesis remain poorly characterized. Two closely related transcriptional repressors, Nkx6.2 and Nkx6.1, are expressed by progenitors in overlapping domains of the ventral spinal cord. We provide genetic evidence that differences in the level of repressor activity of these homeodomain proteins underlies the diversification of interneuron subtypes, and provides a fail-safe mechanism during motor neuron generation. A reduction in Nkx6 activity further permits V0 neurons to be generated from progenitors that lack homeodomain proteins normally required for their generation, providing direct evidence for a model in which progenitor homeodomain proteins direct specific cell fates by actively suppressing the expression of transcription factors that direct alternative fates.

Animals↗
PubMed2001

Exercise-induced hyperaemia and leg oxygen uptake are not altered during effective inhibition of nitric oxide synthase with N(G)-nitro-L-arginine methyl ester in humans.

1. In the present study the highly potent nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) was intravenously infused and examined for its efficacy in inhibiting NOS activity and in altering blood flow and oxygen uptake in human skeletal muscle. 2. The plasma concentrations of L-NAME and its active metabolite NG-nitro-L-arginine (L-NA), and the activity of NOS in skeletal muscle were measured in healthy male subjects (n = 6) before (control) and after 60 min of intravenous infusion of L-NAME (4 mg kg(-1)). In another group of healthy males (n = 8), the physiological effects of L-NAME were studied at rest, and during submaximal and exhaustive knee extensor exercise before (control) and 30 min after L-NAME infusion (4 mg kg(-1)). 3. The plasma concentrations of L-NAME and L-NA were highest (8.4 +/- 1.6 and 8.3 +/- 0.8 micromol l(-1)) after 60 min of L-NAME infusion. Ninety minutes later mainly L-NA remained in plasma (5.1 +/- 0.4 micromol l(-1)). Thirty minutes after L-NAME infusion, the muscle L-NA content was 38 +/- 4 micromol (kg dry wt)-1 and muscle NOS activity was reduced by 67 +/- 8 % (P < 0.05). 4. Leg blood flow and leg oxygen uptake during submaximal and exhaustive exercise were similar (P > 0.05) following L-NAME infusion and in control. Blood flow during recovery was lower in the L-NAME condition (P < 0.05). 5. In conclusion, the present study shows for the first time that systemic infusion of L-NAME in humans causes a marked reduction in skeletal muscle NOS activity. Despite this attenuated NOS activity, exercise-induced hyperaemia and oxygen uptake were unaltered. Thus, the data strongly suggest that NO is not essential for the regulation of blood flow or oxygen uptake in contracting human skeletal muscle.

Adult↗
PubMed2001

Effects of alcohol on the heart.

Some evidence suggests that light to moderate alcohol consumption protects against cardiovascular diseases. However, this cardioprotective effect of alcohol consumption in adults is absent at the population level. Approximately 20 to 30% of patients admitted to a hospital are alcohol abusers. In medical practice, it is essential that patients' levels of consumption are known because of the many adverse effects that might result in the course of routine care. Ethanol damage to the heart is evident if alcohol consumption exceeds 90 to 100 g/d. Heavy ethanol consumption leads to increased risk for sudden cardiac death and cardiac arrhythmias. In patients with coronary heart disease, alcohol use was associated with increased mortality. An early response to drinking was an increased ventricular wall thickness to diameter ratio, possibly proceeding with continuous drinking to alcoholic cardiomyopathy, which had a worse outcome compared with idiopathic dilative cardiomyopathy if drinking was not stopped or at least reduced (< 60 g/d). In the ICU, patients with chronic alcoholism have more cardiac complications postoperatively. These complications probably are caused by biventricular dysfunction, particularly with the occurrence of severe infections or septic shock, events that are three to four times more frequent among chronic alcoholics than occasional drinkers or nondrinkers. To prevent further complications from drinking and for long-term management of drinking, patients with alcohol abuse and heart failure should be treated in brief intervention and follow-up programs. Prognosis is good even in patients with New York Heart Association class IV heart failure caused by cardiomyopathy if complete abstinence is accomplished. Noncompliance to smoking and alcohol restrictions, which are amenable to change, dramatically increases the risk for hospital readmissions among patients with heart failure.

Alcohol Drinking↗
PubMed2001

Method for host-independent detection of generalized transducing bacteriophages in natural habitats.

Despite an increasing interest in horizontal gene transfer in bacteria, the role of generalized transduction in this process has not been well investigated yet. Certainly one of the reasons is that only a small fraction of general transducing bacteriophages have been characterized, because many bacterial hosts needed for propagation and identification are not culturable or are simply unknown. A method for host-independent detection of transducing bacteriophages was developed. Phage-encapsulated DNA was used as a template for PCR amplification of 16S ribosomal DNA using primers specific for the 16S rRNA genes of most eubacteria. Sequencing of the cloned amplification products permits the identification of the host bacteria. The Salmonella phage P22 was used as an example. Applying this method to a sample of the supernatant of the mixed liquor in the aeration tank of an activated sludge treatment works revealed the presence of transducing phages infecting several bacterial species for which such phages have not yet been described. This method is suitable for estimating the contribution of generalized transduction to horizontal gene transfer in different habitats.

Bacteriophages↗
PubMed2001

Arterial baroreflex control of sympathetic nerve activity during acute hypotension: effect of fitness.

We examined arterial baroreflex control of muscle sympathetic nerve activity (MSNA) during abrupt decreases in mean arterial pressure (MAP) and evaluated whether endurance training alters baroreflex function. Acute hypotension was induced nonpharmacologically in 14 healthy subjects, of which 7 were of high fitness (HF) and 7 were of average fitness (AF), by releasing a unilateral arterial thigh cuff after 9 min of resting ischemia under two conditions: control, which used aortic and carotid baroreflex (ABR and CBR, respectively) deactivation; and suction, which used ABR deactivation alone. The application of neck suction to counteract changes in carotid sinus transmural pressure during cuff release significantly attenuated the MSNA response (which increased 134 +/- 32 U/14 s) compared with control (which increased 195 +/- 43 U/14 s) and caused a greater decrease in MAP (19 +/- 2 vs. 15 +/- 2 mmHg; P < 0.05). Furthermore, during both trials, the HF subjects exhibited a greater decrease in MAP compared with AF subjects despite an augmented baroreflex control of MSNA. These data indicate that the CBR contributes importantly to the MSNA response during acute systemic hypotension. Additionally, we suggest that an impaired control of vascular reactivity hinders blood pressure regulation in HF subjects.

Adult↗