Control of force through feedback in small driven systems.

Controlling a time-dependent force applied to single molecules or colloidal particles is crucial for many types of experiments. Since in optical tweezers the primary controlled variable is the position of the trap, imposing a target force requires an active feedback process. We analyze this feedback process for the paradigmatic case of a nonequilibrium steady state generated by a dichotomous force protocol, first theoretically for a colloidal particle in a harmonic trap and then with both simulations and experiments for a long DNA hairpin. For the first setup, we find there is an optimal feedback gain separating monotonic from oscillatory response, whereas a too strong feedback leads to an instability. For the DNA molecule, reaching the target force requires substantial feedback gain since weak feedback cannot overcome the tendency to relax towards the equilibrium force.

Method-related effects of adenovirus-mediated LacZ and SERCA1 gene transfer on contractile behavior of cultured failing human cardiomyocytes.

INTRODUCTION: Adenovirus-mediated gene transfer into cardiomyocytes has emerged as an interesting tool to study functional effects of single proteins. However, the functional consequences of cell isolation, cell culture per se and adenovirus-mediated transfer of the LacZ or SERCA1 gene in failing human cardiomyocytes warrant further investigation. METHODS: Primary cell culture was performed without or after adenovirus-mediated gene transfer of LacZ or SERCA1. Functional behavior of myocytes was assessed under basal conditions (field stimulation, 0.5 Hz, 37 degrees C), and during inotropic stimulation with isoproterenol (ISO; 10(-9)-10(-5) M), [Ca(2+)](o) (1.5-15 mM) or increasing stimulation rates (0.25-2.5 Hz). Results were compared to trabeculae from the same hearts. RESULTS: Freshly isolated myocytes showed full inotropic competence as compared to multicellular preparations. The response to stimulation with ISO and [Ca(2+)](o), as well as changes in stimulation rate resulted in a maximal increase in fractional cell shortening (FS) to 215+/-24% and 291+/-34%, and a frequency-dependent decline in FS to 46+/-5% of the basal value, respectively. After 48 h of cell culture, basal FS did not change significantly compared to fresh cells but both time to peak shortening and time to 50% relengthening were prolonged. After culture, the concentration-response curve for ISO was significantly shifted to the left (EC(50) 5.16 x 10(-8) vs. 1.12 x 10(-8) M, p<0.05). LacZ gene transfer caused efficient beta-Gal expression without affecting the inotropic responses to ISO or stimulation rate but impaired the contractile amplitude. SERCA1 gene transfer increased FS by 68% vs. LacZ and accelerated relengthening kinetics (+dL/dt 93+/-13 vs. 61+/-8 mum/s, p<0.05 vs. LacZ). DISCUSSION: Contractile responses of isolated human myocytes are comparable to multicellular preparations. The use of primary cell culture and adenovirus infection with CMV-promoter-mediated LacZ expression per se modulates contractile behavior in failing human myocytes. SERCA1 expression markedly improves contractile function. The method-related changes in contractile behavior observed here need to be taken into account in further studies.

Longterm follow-up of childhood epilepsy with absences. I. Epilepsy with absences at onset.

The purpose of the follow-up study was to determine whether modern therapy with ethosuximide and/or valproate with/without phenobarbitone and its derivatives improves the longterm prognosis of absence epilepsy as compared to formerly used treatments. The patient population consisted of 194 cases (88 boys, 106 girls) with spike wave epilepsy starting with absences. In each case the diagnosis was confirmed by clinical observation and the typical EEG pattern. Only those patients were included who could be followed beyond the eighteenth year of life (up to age 45). The sample includes also older patients diagnosed during the fifties, before the present standard therapy was available. Because of the heterogeneity of the material and its selection, the data obtained are not suited to make a general statement about the ultimate prognosis of absences. The results demonstrate the effectiveness of regularly applied modern treatment. 72 out of 194 patients (37%) manifested generalized tonic clonic seizures (gtcs) during the course: 20 of these patients showed only incidental generalized tonic clonic seizures, which were not dependent on therapy. In 52 cases gtcs appeared without relation to precipitating factors. None of these patients received regular standard therapy before onset of gtcs. In 31 cases absence statuses were observed. These patients did not have an unfavourable outcome provided the standard therapy was instituted early and consequently. A change from absence epilepsy into an epilepsy with complex partial seizures sensu strictiori could not be observed. At final investigation 42 of 194 patients still had seizures: 7 with absences, 35 with grand mal with or without absences.(ABSTRACT TRUNCATED AT 250 WORDS)

Longterm follow-up of childhood epilepsy with absences. II. Absence-epilepsy with initial grand mal.

The study deals with 83 patients with absence epilepsy which had started with generalized tonic clonic seizures. Only those patients were included, who could be followed up to an age older than eighteen years. The patient population is heterogeneous; it includes numerous older patients in whom therapy had been instituted at a time when the present standard medication with ethosuximide and valproate was not available. Therefore the data cannot be used as a basis for global statements concerning the prognosis of absence epilepsy with grand mal onset. About 80% of the patients treated with standard therapy became seizure free. An unfavourable course was mainly preceded by incorrect, irregular and quantitatively inadequate therapy. Standard therapy cannot prevent singular generalised tonic clonic seizures in the late course. The social status of adult patients is mainly favourable if they are seizure free. Sporadic attacks usually will not impair social integration. In all, absence epilepsy starting with grand mal responds not as well to therapy and has a more unfavourable social prognosis than epilepsy starting with absences.

[Polygraphic studies in premature and newborn infants. Conclusions for therapy and prognosis]. / Polygraphische Untersuchungen von Frühund Neugeborenen. Konsequenzen für Therapie und Prognose.

The polygraphic methods currently available for the prognostication of high-risk neonates are time-consuming, almost inaccessible to visual analysis and unsuited for clinical practice. A polygraphic method has been devised using a restricted number of standardized evaluation criteria arranged according to optimalization principles with a reduction of observation time to three sleep cycles corresponding to an average of 90 minutes. Using this type of "compact polygraphy", 135 newborn infants were divided into a "simple" and a "complicated" group. Their follow-up over the first year of life showed that abnormal EEG tracings and/or clinical manifestations of epilepsy occurred only in infants classified as "complicated". No seizures occurred in the "simple" group. 40% of the patients with complicated prognostication showed neurological abnormalities vs. 8% in the simple group, confirming the prognostic value of compact polygraphy. Since the risk of developing epilepsy was 20% in newborns with postnatal seizures and complicated prognostication, preventive treatment with antiepileptic drugs is recommended in these infants. On the other hand, newborns with postnatal seizures and simple prognostication can be spared the long-term exposure to barbiturates or other anticonvulsants. From our data it appears that compact polygraphy is clinically feasible and has a higher predictive accuracy than any of other currently available practical prognostication methods.

[Prognostication of neonates by compact polygraphy (author's transl)]. / Prognostischer Wert einer praktikablen Mehtode zur polygraphischen Schlafuntersuchung von Neugeborenen.

The polygraphic methods currently available for the prognostication of high risk neonates are timeconsuming, almost inaccessible to visual analysis and unsuited for clinical practice. A polygraphic method has been devised using a restricted number of standardized evaluation criteria arranged according to optimalisation principles with a reduction of observation time to three sleep cycles to an average of 90 minutes. Using this type of "compact polygraphy" 135 newborn infants were divided in a "simple" and a "complicated" group. Their follow-up over the first year of life showed that abnormal EEG-tracing and/or clinical manifestations of early epilepsy occurred only in infants classified as complicated. No seizures occurred in the simple group. 40% of the patients with complicated prognostication showed neurological abnormalities vs. 8% in the simple group, confirming the prognostic value of compact polygraphy. Since the risk of developing epilepsy was 20% in newborns with postnatal seizures and complicated prognostication, preventive treatment with antiepileptic drugs is recommended in these infants. On the other hand newborns with postnatal seizures and simple prognostication can be spared the longtime exposure to barbiturates or other anticonvulsants. From our data it appears that compact polygraphy is clinically feasible and has a higher predictive accuracy than any of other currently available practical prognostication methods.

Congenital anomalies in children of epileptic mothers and fathers.

Children of epileptic mothers have a higher risk for major malformations. A similar increase of major malformations is observed in children of epileptic fathers suggesting that the major malformations are related to the parental disease rather than to the antiepileptic drug. No information was available if the pattern of minor acrofacial malformations known as the "hydantoin syndrome" occurs also in children of epileptic fathers. We studied 37 children of treated mothers and 22 children of treated fathers with epilepsy. No major malformations were observed. The typical acrofacial syndrome occurred only in children of epileptic mothers suggesting that this characteristic syndrome is drug-related. Major malformations and the syndrome of minor acrofacial anomalies seem to have a different etiology. Since the pattern of minor acrofacial anomalies occurs after exposure to anticonvulsants other than hydantoin the term "antiepileptica syndrome" should be used for this particular embryopathy.

Familial juvenile nephronophthisis with hepatic fibrosis and neurocutaneous dysplasia.

Familial juvenile nephronophthisis (FJN) is an autosomal-recessive disease which may exist as an isolated nephropathy or in combination with degenerative involvement of certain oran systems. The case reported describes a new variant of this lethal syndrome consisting of FJN, hepatic fibrosis, and neurocutaneous dysplasia (hypoplastic vermis of the cerebellum, choroid coloboma, and naevus flammeus). The same condition was probably present in the patient's sister who had also died at 6 years of age.

[A practicable method of polygraphic investigations in preterm and fullterm neonates (author's transl)]. / Eine praktikable Methode zur polygraphischen Untersuchung von Früh- und Neugeborenen.

Polygraphic recording techniques (simultaneous recording of several physiological variables) have been used earlier in investigations of normal newborn and preterm infants. The clinical value of prolonged polygraphic recordings in highrisk neonates is well-known. The main-purpose of this paper is to demonstrate a clinically practicable method of polygraphic recording technique, needing no more than two hours recording-time and its interpretation by means of visual analysis.

[Electroencephalographic findings in the late stage after CNS-irradiation for malignant neoplasms in children (author's transl)]. / Elektroenzephalographische Befunde im Spätstatus nach ZNS-Bestrahlung wegen maligner Neoplasien im Kindesalter.

Of forty children having undergone two or more years ago an irradiation of the brain case with cobalt-60 delivering doses between 1800 and 2400 R TD (n = 20) or a dose above 3500 R TD (n = 20), as a matter of fact ten presented pathological EEG findings which, however, may be interpreted as genetically determined characteristics, or instead in connection with a recurrence of the tumor just manifesting itself, or else as the consequence of a residual tumor or of the surgery performed. Pathological EEG findings on the account of radiation therapy apparently are much less frequent than morphological changes of the brain after radiation therapy. It is not necessary to assume that the latter need always have an effect upon the function of the infantine brain.

[Risk of a second malignant neoplasm after successful treatment of a malignant tumour in children (author's transl)]. / Risiko zweiter maligner Neoplasien nach erfolgreicher Tumorbehandlung im Kindesalter.

One boy, given radiotherapy and cytostatic drugs for a rhabdomyosarcoma died nine years later of acute leukaemia. A girl, who had received radiotherapy for an inoperable suprasellar tumour and also given cytostatic drugs, fell ill seven years later with a glioblastoma. Among a total of 750 children with malignant neoplasm observed by the authors, a permanent cure rate of about 50% is to be expected among about 300 children treated recently. If this rate applies to the entire Federal Republic of Germany, about 1,000 children are likely to be cured annually. In these circumstances it is likely that 80-160 children treated in any one year will develop a second neoplasm or leukaemia 20 years later, most commonly as a late sequela of the treatment.

[Encephalopathy due to vincristine sulfate (author's transl)]. / Zur Frage der Encephalotoxizität des Vincristin (EEG-Befunde bei Langzeitüberlebenden nach Leukämien und soliden Tumoren im Kindesalter, die mit Vincristin behandelt wurden).

A cytotoxic effect by vincristine sulfate on the cerebral cortex is claimed in literature. In 188 children treated with vincristine we saw no so called "Vincristine-induced Encephalopathy". The proportional risk of vincristin-induced cerebral complications amount to 1%, as demonstrated by various authors. In 67 children investigated 5 weeks up to 2 years after last vincristine-injection we found no EEG-tracing, which could be discussed as a vincristine-induced finding.

[Electroencephalographic observations after therapy with vincristine (author's transl)]. / EEG-Befunde nach Vincristinbehandlung.

A direct cytotoxic effect of vincristine on the neurons, especially the cerebral cortex is discussed in the literature. In 188 patients treated with vincristine we saw no so called "Vincristine-induced Encephalopathy". In 67 children investigated 5 weeks up to 2 years after the last vincristine-injection we found no changes in EEG-tracings which could be discussed as vincristine-induced.

[Photosensitivity in children with malign tumors (author's transl)]. / Photosensibilität bei Kindern mit malignen Tumoren.

Photosensitivity (photoconvulsive reaction = PCR) has to be regarded as a genetically determined EEG-symptom, which is seen with markedly age dependent in up to 15% of healthy individuals. Correlations with epileptic and nonepileptic diseases (migraine, anorexia nervosa, psychovegetativ instability) are known. 157 children with malign tumors (Tab 1) were investigated. Children with Wilms' tumors showed significant more PCR than all other children with malign tumors (Tab. 2, 3). That finding may corroborate the hypothesis, that Wilms' tumor may be the most important clinical symptom of syndroms with congenital malformations (aniridy, hamartom, hemihypertrophy).