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Biomedical subjects

F Simons

Publications and source records attributed to F Simons.

13 recordsLinked to original sources
PubMed1997

Adjusting to changes in the time of reinforcement: peak-interval transitions in rats.

Thirty rats received training on a peak-interval procedure, where a baseline with a 20-s time of reinforcement was interspersed among cyclic transitions to other reinforcement time values (10, 20, 30, or 40 s), each of which was either in force for only a single session or for 3 sessions. Peak times were close to the time of reinforcement on the 20-s baseline and tracked the new reinforcement times both closely (but not exactly) and very rapidly. Peak time during transitions was affected by the criterion value in force on the previous session, exhibiting a proactive interference effect. Analysis of individual peak times during a session showed that transitions from lower to higher reinforcement time values were usually characterized by abrupt jumps in peak time, whereas descending transitions were mostly smooth but rapid.

Animals↗
PubMed1991

Zinc finger-like structure in U1-specific protein C is essential for specific binding to U1 snRNP.

The U1 small nuclear ribonucleoprotein (snRNP) contains three specific proteins denoted 70K, A and C, in addition to the common proteins. Specific functions of these proteins are not known although recently protein C was shown to be involved in the binding of U1 snRNP to the 5' splice site of a pre-mRNA. Unlike proteins A and 70K, U1-C lacks an RNA binding domain (RNP-80 motif) and does not appear to bind directly to U1 snRNA. However, at the amino terminal end protein C contains a zinc finger-like structure of the CC-HH type found in transcription factor TF IIIA. Several lines of evidence indicate that the zinc finger-like structure is essential for the binding of protein C to U1 snRNP particles: i) deletion analysis of protein C showed that the N-terminal 45 amino acids are sufficient for binding to U1 snRNPs, ii) modification of the cysteine residues in the N-terminal domain with N-ethylmaleimide and iii) single point mutations of the cysteines and histidines contributing to the putative zinc finger abolished binding of protein C to U1 snRNPs. Interestingly, unlike the proteins U1-A and U1-70K the U1-C protein is unable to bind to naked U1 snRNA. On the other hand it is shown that protein C does not bind to the known protein constituents of the U1 particle without the U1 snRNA being present. These data indicate that the binding of protein C to U1 snRNP is dependent on the presence of both the U1 snRNA and one or more of the U1 snRNP proteins.

Amino Acid Sequence↗
PubMed1991

[Cardiac arrest during anesthesia induction with halothane and succinylcholine in an infant. Massive hyperkalemia and rhabdomyolysis in suspected myopathy and/or malignant hyperthermia].

This report describes a cardiac arrest that occurred in a 4-month-old infant during induction of anesthesia. During the administration of N2O/O2 and halothane via a face mask tachycardia was noted and rigor followed the application of succinylcholine for intubation. Shortly thereafter cardiac arrest occurred; 15 min later we found a profound metabolic acidosis as well as signs of rhabdomyolysis with a serum potassium level of 10.3 mmol/l and an increase in serum creatine kinase (CK). While performing cardiopulmonary resuscitation (CPR) and treating the acid-base imbalance and hyperkalemia, we administered--suspecting malignant hyperthermia (MH)--dantrolene. Approximately 60 min post-arrest we achieved stabilization of the vital signs. During the following hours the CK level rose to 99, 600 IU/l and myoglobinuria of 360,000 micrograms/l confirmed the extent of the rhabdomyolysis. The infant was discharged home without detectable sequelae after 2 1/2 weeks. Comparisons with corresponding case reports in the literature lead to the supposition that our patient suffered from a myopathy thus far undiagnosed. To what extent a MH episode may have contributed to the clinical picture cannot be determined at present. The spectrum of adverse reactions to volatile anesthetics and succinylcholine in patients with myopathic disorders is presented and discussed. As in other case reports, the dramatic course described here also demonstrates that in addition to CPR and treatment of the acid-base and electrolyte imbalances, administration of dantrolene should be considered at an early stage.

Anesthesia, Inhalation↗
PubMed1979

[Experimental studies about the origin of the "wedge-blood" in partially atelectatic lungs of mongrel dogs (author's transl)].

We measured in 8 experimental studies the oxygen and carbon dioxide partial pressure in systemic arterial, mixed venous and wedge-blood. The results were: 1. In healthy mongrel dogs with controlled intermittent and continuous positive pressure ventilation (FIO2 0,21 and 1,0) paO2 greater than pwO2 greater than pvO2 and pwCO2 less than paCO2 less than pvCO2. 2. During experimentally produced left-sided atelectasis of the lung and positioning of the catheter in the pulmonary artery a) in the ventilated lung we found pwO2 greater than paO2 greater than pvO2 and pwCO2 less than paCO2 less than pvCO2 b) in the atelectatic lung we found paO2 greater than pwO2 greater than pvO2 and paCO2 less than pwCO2 less than pvCO2. According to these findings the sample of highly saturated mixed venous blood from a catheter in the pulmonary artery should be a hint that pulmonary capillary blood is mixed with central venous blood.

Animals↗
PubMed1978

[Anaesthetic problems during resection of the carina (author's transl)].

Benigne tracheo-bronchial constriction is an infrequent indications for resection of the bifurcation of the trachea. In former times resection and reconstruction of the bifurcation have been performed using extracorporal oxygenation. Nowadays, the method of separate ventilation of both lungs is used more frequently. Pathophysiological variations should be taken into consideration, which may occur during interruption of the ventilation of one side of lung caused by operating procedures. Rapidly developing atelectasis of the non-ventilated but perfused lung endangers the patient, as a result of an increased intrapulmonary right-to-left-shunt. Hypoxaemia can be prevented by temporary occlusion of the pulmonary artery of the nonventilated lung. This procedure is to be recommended in view of the fact that there is no prompt constriction of the vessels. Investigations with dogs show that a slightly developing accommodation of the perfusion can be disturbed by variations of cardiac output or mean pressure of ventilation.

Child↗
PubMed1978

[Cardiovascular effects produced by prophylactic digitalization during introduction of anaesthesia (author's transl)].

The narrow field of non-controversial indications concerning the application of digitalis glycosides is pointed out. Problems of routine digitalization of older patients not suffering from cardiac insuffiency are discussed with special regard to preparing them for operations. Up to now, from the viewpoint of anaesthesiologists no benefits of prophylactic digitalization have been found. In a retrospective computerized study, clinical hemodynamic parameters during introduction of anaesthesia have been investigated by means of anaesthetic data recorded during three years. Nondigitalized patients older than fifty years showed satisfactory cardiac functions, whereas prophylactically digitalized patients--compared with the control group--have been treated with plasma expanders earlier and at a double rate. Furthermore, higher heart frequencies and greater tendency to arrythmias were observed. Consequently, prophylactic digitalization cannot be recommended in general.

Age Factors↗
PubMedDate not supplied

The SS-A/SS-B autoantigenic complex: localization and assembly.

The subcellular distribution of Ro ribonucleoprotein particles (Ro RNPs) and their constituents was determined using mammalian tissue culture cells and Xenopus laevis oocytes. Cell fractionation revealed that Ro RNPs are restricted to the cytoplasm, while the Ro RNP-specific proteins were also present in the nucleus. Transport studies indicated that the protein components of Ro RNPs are actively imported into the nucleus while the RNA component accumulates in the cytoplasm. These results suggest a model for the assembly of Ro RNPs.

Animals↗