Size-dependent exclusion of macromolecules from gel matrices has long been discussed in terms of pore models. An alternate approach is to calculate the partition coefficient of the distributed species between the matrix material and the mobile phase assuming that the gel can be treated as a polymer solution of appropriate concentration and molecular weight. This approach is particularly appealing in attempting to predict the behaviour of 'tentacle' phases in which the matrix contains anchored linear neutral polymers. The mean field theory of polymer solution is used to predict K, the partition coefficient of a polymer molecule distributing between the gel and mobile phases. The reduction in entropy suffered by the macromolecule in the gel phase is sufficient to produce an exponential dependence of K on the molecular weight of the partitioning species. The enthalpy of interaction between the gel polymer and the distributed species provides a parameter which describes the specificity or recognition in the interaction. The predicted linear dependence of in K on protein molecular weight is satisfactorily borne out by a data set on eight standard proteins chromatographed on four separate gel types.

Mathematical Computing↗

PubMedDate not supplied

Reversed genetics: a new approach to the elucidation of structure--function relationship.

Methods for generating point mutations at predetermined sites of RNA or DNA genomes have been developed. With Qbeta RNA as a template, minus strands were synthesized in vitro in a stepwise, substrate-controlled reaction. The nucleotide analogue N4-hydorxyCMP was introduced in the desired position, the minus strands were completed with the four standard triphosphates and used as templates to synthesize plus strands; about 30% of the progeny plus strands showed a base transition at the position corresponding to the nucleotide analogue. Two mutant RNAs with extracistronic nucleotide substitutions have been generated; one of these was viable, albeit with a reduced propagation rate, while the other was non-infectious. Furthermore, mutants with changes at the initiation codon of the coat cistron were prepared. An analysis of ribosome binding to such mutant RNAs revealed the importance of the A-U-G region for the formation of the initiation complex. With a similar approach applied to the beta-globin complementary DNA (CDNA) plasmid PbetaG, point mutations have been introduced at the positions corresponding to amino acids 121 to 123.

Base Sequence↗

PubMedDate not supplied

Quantitative analysis of the active components and the by-products of eight dry extracts of Hypericum perforatum L. (St John's Wort).

The major components of eight different batches of commercially available dry extracts of Hypericum perforatum L. were quantified. Hyperforin (1), hypericin (2) and flavonoids, which are considered to play key roles in the treatment of mild and moderate depressive disorders, were determined by HPLC methods. The contents of 1, 2 and flavonoids were found to be in the range of 1.3-3.9%, 0.19-0.30%, and 4.8-11.4%, respectively. Generally extracts contained, besides the so-called active components, a wide variety of by-products which may act partially as co-effectors and affect the technological properties of the extracts. Water-soluble sugars form one of the main groups of these by-products, and a procedure for the purification and quantification of such sugars in H. perforatum using HPLC with refractive index detection has been established. Native fructose, glucose and sucrose, as well as lactose added during the processing of the extracts, were determined. The total sugar content in the dry herbal extracts varied from 19 to 25% by weight. Further, citric acid (0.9-2.3%) and malic acid (2.3-3.1%) were determined by HPLC, tannins (6.2-9.0%) and total ash (4.9-8.4%) were quantified according to the methods described in the European Pharmacopoeia, and the content of the total protein (3.9-8.3%) was estimated by elemental analysis. Thus, 60-70% of the compounds of the H. perforatum dry extracts have been quantified.

Anthracenes↗

PubMedDate not supplied

Diagnostic implications and treatment of massive spontaneous atelectasis in childhood.

During a 5-month period five children were treated for spontaneously occurring massive lung atelectasis. In three patients the underlying disease was bronchial asthma; in one patient idiopathic plastic bronchitis; and in another patient, infection with anaerobic Corynebacteria may have been a contributing factor. Types I and III hypersensitivity reactions were not considered to be likely causal factors. The clinical manifestations and management of this relatively rare event are described.

Bronchoscopy↗

PubMedDate not supplied

Flecainide alters the cardiac microscopic activation pattern. An in-vitro study using voltage sensitive dyes.

In order to evaluate whether flecainide may alter microscopic activation patterns, isolated guinea pig papillary muscles (paced at a rate of 1 Hz or 3 Hz respectively, superfused with saline Tyrode solution at 37 degrees C) were exposed to 1.5 mumol l-1 flecainide. The muscles were stained with the voltage sensitive dye di-4-ANEPPS and excited with argon ion laser light at 514 nm. Fluorescence (F) was measured through a OG 570 filter by a 16*16 photodiode array (spatial resolution 180 microns). Activation times were determined the minimum -dF/dt. From these data on activation sequence could be determined. From the activation times of a given photodiode and of the surrounding diodes, which were activated later, vectors were calculated giving direction and velocity of the local activation wave. The isochrones under control conditions and under treatment were compared directly in a qualitative manner. For quantification the percentage of vectors with similar direction (deviation < 5 degrees) under control conditions and after treatment were determined. Under the influence of flecainide, the percentage of similar vectors decreased from 34% to 24% (1 Hz) or from 27% to 17% (3 Hz) (n = 6). Analysis of the isochrones showed that the propagation velocities were altered inhomogeneously. The total activation time (TAT) of the papillary muscles (calculated from the delay between the end of the stimulus and the activation of the last photodiode) was increased from 10.2 to 11.5 ms at 3 Hz, but was only slightly prolonged at the lower frequency (from 10.9 to 11.1 ms at 1 Hz). These results demonstrate that (a) flecainide can alter the microscopic activation patterns (b) that this effect has a use-dependent component and (c) the total activation time is slowed by flecainide. These effects may be linked to the proarrhythmic and antiarrhythmic activity of the drug.

Action Potentials↗

PubMedDate not supplied

[Mixed connective tissue disease (Sharp's syndrome)].

Explore the source record for details and available documents.

Adult↗

PubMedDate not supplied

Pupil size and the steady-state pattern reversal visual evoked cortical potential.

30 eye-healthy subjects were being examined, with their pupils reacting, mydriatic or miotic. Their pattern reversal visual evoked cortical potentials (PRVECP's) were recorded under steady-state conditions. Test conditions allowed establishing a statistically significant influence of pupil size on the PRVECP.

Cerebral Cortex↗

PubMedDate not supplied

Animal studies on the reduction of aminoglycoside-induced nephrotoxicity by D-glucaro-1,5-lactam.

We studied the effect of D-glucaro-1,5-lactam on aminoglycoside-induced nephrotoxicity in rats. Parameters of nephrotoxicity were urinary excretion of tubule cells and malate dehydrogenase. When given in appropriate doses, either i. m. or via an oral tube, D-glucaro-1,5-lactam significantly reduced the excretion of cells and enzymes during the administration of gentamicin, tobramycin, dibekacin, netilmicin and ribostamycin. It did not impair the therapeutic efficacy of ribostamycin in the experimental treatment of acute pyelonephritis in rats. The protective effect of D-glucaro-1,5-lactam could be ascribed to its inhibition of beta-glucuronidase, an enzyme which is located in renal lysosomes and which is activated by aminoglycosides.

Aminoglycosides↗

PubMedDate not supplied

Characterization of cardiac microsomes from spontaneously hypertonic rats.

Capacity of Ca2+ sequestration was found to be significantly lowered in microsomal preparations of hearts from spontaneously hypertonic rats. A decrease to 40% of the control level was found for basal and extra ATPase. A similar reduction existed in initial and total Ca2+ uptake. These findings are correlated with a lower concentration of the Ca2+ transport ATPase in SDS gel electrophoresis, a lower density of the 7-9 nm intramembraneous particles and higher half-lives of phosphoprotein. Altered contractility of hypertrophied myocardium may thus be partially explained by the dysfunction of the Ca2+ sequestering system.

Adenosine Triphosphatases↗

PubMedDate not supplied

[Sick behavior of patients with rheumatic diseases].

The illness behavior of 119 patients with rheumatic disorders (predominantly nonarticular rheumatism) has been studied. The behavior differed in relation to the rheumatological diagnosis, the personality and the previous stress situations.

Acupuncture Therapy↗

PubMedDate not supplied

Novel applications of fluorescence sensors.

Typically, NAD(P)H-sensitive culture probes have been used to estimate biomass concentrations in suspended-cell cultivations, but these sensors have other uses as well. A number of applications, ranging from biosensors to immobilized-cell metabolic studies, are presented.

Alanine Transaminase↗

PubMedDate not supplied

Adaptive feedback-controlled infusion versus repetitive injections of vecuronium in patients during isoflurane anesthesia.

STUDY OBJECTIVE: To compare vecuronium requirements using repetitive injections and a model-based, closed-loop, feedback-controlled infusion during isoflurane anesthesia. DESIGN: Randomized open study. SETTING: Departments of Anesthesiology and Ear, Nose, and Throat Surgery at a university hospital. PATIENTS: Twenty-two patients of ASA physical status I or II undergoing elective otolaryngological surgery requiring general anesthesia. INTERVENTIONS: Vecuronium was used for muscle relaxation. The desired level of neuromuscular transmission was set to 10% of control. All patients received vecuronium 0.08 mg/kg for intubation. Thereafter, vecuronium was injected repetitively in 11 patients (Group 1) whenever spontaneous recovery had reached the 10% level. In the other group of 11 patients (Group 2), relaxation was maintained by an adaptive closed-loop feedback system, which was based on a pharmacokinetic-dynamic model. MEASUREMENTS AND MAIN RESULTS: Neuromuscular transmission was quantified by the evoked electromyogram of the hypothenar muscles. In Group 1, the first repetition of 0.02 mg/kg had to be administered after 27.0 +/- 5.5 minutes, followed by repetitions of the same dose every 16.3 +/- 3.0 minutes. The induced neuromuscular block ranged from 83% to 100%. The mean vecuronium demand was 0.123 +/- 0.018 mg/kg/h. In Group 2, stable relaxation of 90% +/- 2% was achieved within 19.2 +/- 7.5 minutes after a period of damped oscillations. The mean offset from the target value of 90% blockade was 0.65% +/- 0.32%. The average vecuronium requirement was 0.056 +/- 0.021 mg/kg/h during steady state. The difference between the groups in muscle relaxant demand was statistically significant. CONCLUSIONS: The model-based adaptive feedback system proved to be useful in maintaining a stable degree of paralysis, adjusting relaxant input to individual demand, and minimizing drug requirement, as compared with repetitive injections.

Adolescent↗

PubMedDate not supplied

Single-injection inulin clearance--a simple method for measuring glomerular filtration rate in dogs.

The glomerular filtration rates (GFR) of 93 dogs of different breeds with a broad range of bodyweight were determined using an inulin single-injection method. Fifty-two dogs were used as controls, 21 dogs had suspected renal disease but serum creatinine in the normal range, and 20 dogs had elevated serum creatinine levels and a low urine specific gravity due to renal disease. Inulin was injected intravenously at a dosage of 100 mg kg(-1) bodyweight or 3000 mg m(-2) body surface. Blood samples were taken before and three, 20, 40, 80 and 120 minutes after injection. The total clearance was calculated from the decrease in the serum concentration of inulin using a two-compartment model. The range of GFR values was 83.5-144.3 ml min(-1) m(-2) in control dogs, 60.2-96.7 ml min(-1) m(-2) in dogs with suspected renal disease, 50.0-76.2 ml min(-1) m(-2) in dogs with suspected renal disease and polyuria/polydipsia, and 16.3-63.0 ml min(-1) m(-2) in dogs with azotaemic renal disease. The study indicates that single-injection inulin clearance is a cheap and simple tool for GFR measurements in small animal practice.

Animals↗

PubMedDate not supplied

Endemic Tyrolean infantile cirrhosis is not an allelic variant of Wilson's disease.

Recently, 138 cases of infantile cirrhosis originating in several families in the Austrian province of the Tyrol were reported. This endemic Tyrolean infantile cirrhosis (ETIC) is indistinguishable from Indian childhood cirrhosis (ICC), idiopathic copper toxicosis (ICT), and resembles the early forms of Wilson's disease (WND). It has been argued that ETIC might represent an allelic variant of the WND gene, which is a copper transporting P-type ATPase (ATP7B). Assuming that ETIC results from a founder effect, a possible role for ATP7B in ETIC was investigated by association studies and haplotype sharing. Because of its lethality, the mapping of ETIC was focused on obligate gene carriers, i.e. the patients' parents. Our data indicate that ETIC is a separate genetic entity, distinct from WND.

Age of Onset↗