Regulation and expression of human Fabs under the control of the Escherichia coli arabinose promoter,PBAD

Background: The l-arabinose operon from E. coli contains an inducible promoter P_BAD which has been extensively studied for the control of gene expression. P_BAD has a number of potential advantages over P_lac, and has been used successfully to promote high level expression of recombinant proteins. Objectives: The aim of this study was to investigate P_BAD as an alternative system to P_lac for the bacterial expression of recombinant Fabs. Study design: The promoter P_BAD from the E. coli arabinose operon araBAD and the gene encoding the regulator of this promoter, were cloned into the phagemid expression vector MCO1. Expression of human recombinant tetanus toxoid (TT) and c-erb B2 Fabs under the control of P_BAD was compared at two induction temperatures with the same Fabs produced under the control of P_lac. Results: Expression of TT and c-erb B2 Fabs under the control of P_BAD was comparable to Fab expression from P_lac. However, highly expressed TT Fab under the control of P_BAD was localised to the soluble periplasmic fraction whereas under the control of P_lac, there was greater leakage of Fab into the culture supernatant. In addition, Fab expression from P_BAD could be more tightly repressed than from P_lac. Conclusion: P_BAD is a useful and cheaply inducible alternative to the more commonly used P_lac for the rapid expression of soluble recombinant human antibody fragments.     

Anatomic variations of surgical importance in ethmoid labyrinth and sphenoid sinus. A study of radiological anatomy

Summary The present study was performed on axial and coronal CT scans of 100 patients, most of whom were affected by nasal polyposis. Five observers had to analyse the radiograms and answer a questionnaire including the following items: presence of a supraorbital recess; identification of anterior and posterior ethmoidal canals; dehiscences in the lamina papyracea; pneumatized middle turbinate; presence of a spheno-maxillary plate; presence of Haller's cells; presence of Onodi's cells; relationships of the optic canal; relationships of the internal carotid artery; relationships of the maxillary nerve; relationships of the vidian nerve; level difference between the ethmoid roof and nasal vault; depth of the sphenoethmoidal recess. The data obtained were compared with those drawn from anatomical studies. The fair agreement between them proves the value of CT as an alternative method for studying paranasal sinuses anatomy.

---

Anatomie radiologique des variations du labyrinthe ethmoïdal et du sinus sphénoïdal et leurs conséquences chirurgicales

Résumé Cette étude a été réalisée sur 100 patients dont la plupart présentait une polypose nasale étudiée en coupes T D M axiale et coronale. Cinq lecteurs ont revu les clichés et répondu au questionnaire suivant: présence d'un récessus supra orbitaire; identification des canaux ethmoïdaux antérieur et postérieur; déhiscence de la lame papyracée; pneumatisation du cornet moyen; présence d'un plateau sphéno maxillaire; présence de cellules de Haller; présence de cellules d'Onodi; rapports du canal optique; rapports de l'artère carotide interne; rapports du nerf maxillaire; rapports du nerf vidien; dénivelé entre le toit ethmoïdal et le toit nasal; profondeur du récessus sphéno-ethmoïdal. Les données obtenues ont été comparées avec celles provenant de travaux anatomiques. La concordance acceptable entre les deux démontre la valeur du scanner comme méthode d'étude alternative de l'anatomie des sinus para nasaux.

     

In humans the oxygen uptake slow component is reduced by prior exercise of high as well as low intensity

The aim of the study was to examine to what extent prior high- or low-intensity cycling, yielding the same amount of external work, influenced the oxygen uptake (V˙O₂) slow component of subsequent high-intensity cycling. The 12 subjects cycled in two protocols consisting of an initial 3 min period of unloaded cycling followed by two periods of constant-load exercise separated by 3 min of rest and 3 min of unloaded cycling. In protocol 1 both periods of exercise consisted of 6 min cycling at a work rate corresponding to 90% peak oxygen uptake (V˙O_2peak). Protocol 2 differed from protocol 1 in that the first period of exercise consisted of a mean of 12.1 (SD 0.8) min cycling at a work rate corresponding to 50% V˙O_2peak. The difference between the 3rd min V˙O₂ and the end V˙O₂ (ΔV˙O₂₍₆₋₃₎) was used as an index of the V˙O₂ slow component. Prior high-intensity exercise significantly reduced ΔV˙O₂₍₆₋₃₎. The ΔV˙O₂₍₆₋₃₎ was also reduced by prior low-intensity exercise despite an unchanged plasma lactate concentration at the start of the second period of exercise. The reduction was more pronounced after prior high- than after prior low-intensity exercise (59% and 28%, respectively). The results of this study show that prior exercise of high as well as low intensity reduces the V˙O₂ slow component and indicate that a metabolic acidosis is not a necessary condition to elicit a reduction in ΔV˙O₂₍₆₋₃₎. Accepted: 8 July 2000     

The laser flash-initiated polymerization as a tool of evaluating (individual) kinetic constants of free radical polymerization, 1. Outline of method and first results

A method is presented which allows the determination of k_p/k_t-values in free radical polymerization. It is based on measurements of the (average) rate of polymerization under pseudostationary conditions, the polymerization being initiated by laser flashes of short duration. For ρk_t t₀ ? 1 (ρ being the additional polymer radical concentration produced by each laser flash, k_t the bimolecular termination constant between polymer radicals, k_p the rate constant of chain propagation, t₀ the time separating two successive laser flashes) k_p/k_t may be obtained as the slope of a linear plot of the fractional conversion per flash vs. ln t₀. Dividing the intercept by the slope yields ln (pk_t). Thus, if p is accessible, separation of k_p/k_t-data into its individual constituents may be accomplished without making any use of stationary polymerization data. Application of this method to the polymerization of styrene sensitized by benzoin or AIBN at 25°C gives k_p/k_t-values of 1,0 · 10^?6 which are in fair agreement with those obtained by other methods.     

Homeostatic regulation of h‐conductance controls intrinsic excitability and stabilizes the threshold for synaptic modification in CA1 neurons

Key points

• We determined the contribution of the hyperpolarization‐activated cationic (h) current (I _h) to the homeostatic regulation of CA1 pyramidal cells in vitro using chronic treatments (48 h) that either increase (picrotoxin) or decrease (kynurenate) neuronal activity.
• The h‐conductance was found to be up‐ or down‐regulated following chronic activity enhancement or activity deprivation, respectively. This bidirectional plasticity of I _h was found to subsequently alter both apparent input resistance and intrinsic neuronal excitability.
• Bidirectional homeostatic plasticity of I _h also determined EPSP waveform and EPSP summation tested at 5–30 Hz.
• Long‐term synaptic modification induced by repetitive stimulation of the Schaffer collaterals was found to be constant across treatments in the presence of I _h but not when I _h was blocked pharmacologically. Thus, bidirectional homeostatic regulation of I _h stabilizes induction of long‐term synaptic modification in CA1 pyramidal neurons that depends on EPSP summation.

Abstract

The hyperpolarization‐activated cationic (h) current is a voltage‐shock absorber, highly expressed in the dendrites of CA1 pyramidal neurons. Up‐regulation of I _h has been reported following episodes of intense network activity but the effect of activity deprivation on I _h and the functional consequence of homeostatic regulation of I _h remain unclear. We determined here the contribution of I _h to the homeostatic regulation of CA1 pyramidal cell excitability. Intrinsic neuronal excitability was decreased in neurons treated for 2–3 days with the GABA_A channel blocker picrotoxin (PiTx) but increased in neurons treated (2–3 days) with the glutamate receptor antagonist kynurenate (Kyn). Membrane capacitance remained unchanged after treatment but the apparent input resistance was reduced for PiTx‐treated neurons and enhanced for Kyn‐treated neurons. Maximal I _h conductance was up‐regulated after chronic hyperactivity but down‐regulated following chronic hypoactivity. Up‐regulation of I _h in PiTx‐treated cultures was found to accelerate EPSP kinetics and reduce temporal summation of EPSPs whereas opposite effects were observed in Kyn‐treated cultures, indicating that homeostatic regulation of I _h may control the induction of synaptic modification depending on EPSP summation. In fact, stimulation of the Schaffer collaterals at 3–10 Hz induced differential levels of plasticity in PiTx‐treated and Kyn‐treated neurons when I _h was blocked pharmacologically but not in control conditions. These data indicate that homeostatic regulation of I _h normalizes the threshold for long‐term synaptic modification that depends on EPSP summation. In conclusion, bidirectional homeostatic regulation of I _h not only controls spiking activity but also stabilizes the threshold for long‐term potentiation induced in CA1 pyramidal neurons by repetitive stimulation.

Abbreviations

BCM

Bienenstock–Cooper–Monroe rule

fEPSP

field EPSP

I_h

hyperpolarization‐activated cationic current

Kyn

kynurenate

LTD

long‐term depression

LTP

long‐term potentiation; PiTx, picrotoxin

     

Caffeine increases maximal anaerobic power and blood lactate concentration

Summary The aim of this study was to specify the effects of caffeine on maximal anaerobic power (W _max). A group of 14 subjects ingested caffeine (250 mg) or placebo in random double-blind order. TheW _max was determined using a force-velocity exercise test. In addition, we measured blood lactate concentration for each load at the end of pedalling and after 5 min of recovery. We observed that caffeine increasedW _max [964 (SEM 65.77) W with caffeine vs 903.7 (SEM 52.62) W with placebo;P<0.02] and blood lactate concentration both at the end of pedalling [8.36 (SEM 0.95) mmol · l^–1 with caffeine vs 7.17 (SEM 0.53) mmol · l^–1 with placebo;P<0.011 and after 5 min of recovery [10.23 (SEM 0.97) mmol · l^–1 with caffeine vs 8.35 (SEM 0.66) mmol · l^–1 with placebo;P<0.04]. The quotient lactate concentration/power (mmol · l^–1 · W^–1) also increased with caffeine at the end of pedalling [7.6 · 10^–3 (SEM 3.82 · 10^–5) vs 6.85 · 10^–3 (SEM 3.01 · 10^–5);P<0.01] and after 5 min of recovery [9.82·10^–3 (SEM 4.28 · 10^–5) vs 8.84 · 10^–3 (SEM 3.58 · 10^–5);P<0.02]. We concluded that caffeine increased bothW _max and blood lactate concentration.     

3. Quality and Performance Measures in Bone Densitometry

3.3.1 Conceptual Definition of Osteoporosis 3.3.2 Diagnostic Criteria for the Individual Patient 3.3.2.1 Fracture Status 3.3.2.2 Low Bone Mineral Density Absolute Values Percent Decrements T-score and Z-score 3.3.2.3 Clinical Limitations of the WHO Definition of Osteoporosis 3.3.3 Diagnostic Performance of Techniques 3.3.3.1 Concepts of Diagnostic Performance Diagnostic Response and Diagnostic Power Standardized Bias Sensitivity–Specificity Analysis Analysis of the Area Under the Receiver Operator Curve 3.3.4 Reference Data 3.3.5 Clinical Limitations of Bone Mineral Density as Diagnostic Criterion 3.4 Performance Measures to Assess Fracture Risk3.4.1 Relevance of Fracture Risk Assessment 3.4.2 Basic Definitions 3.4.3 Risk Factors and Fracture Risk