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Biomedical subjects

D Singer

Publications and source records attributed to D Singer.

At least 19 recordsLinked to original sources
PubMed2006

[Long-term outcome of preterm neonates: the message behind the statistics].

In view of the current progress in neonatal intensive care, the present outcome of former preterm neonates does not necessarily reflect the future outcome of today's preterm neonates. In spite of this statistical uncertainty, long-term follow-up studies performed in the past few years point to the fact that the sequelae of prematurity may appear well beyond infancy and may be revealed in varying manners with increasing age. Therefore, a chronological account of the consequences of prematurity is given in this paper, ranging from perinatal mortality/morbidity to the problems to be observed during early childhood, preschool age, and adolescence right up to the long-term sequelae arising in later adulthood. Within this context, a two-fold paradigm shift in neonatology becomes apparent in that, first, the outcome of preterm neonates is not a result of immaturity per se, yet is significantly influenced by the factors leading to preterm birth (inflammation, intrauterine growth restriction), and, second, the sequelae of prematurity do not end with the end of neonatal intensive care, but are greatly modulated by familial conditions in their further course. Even though the statistical data are still subject to changes, these insights form the basis of a structured long-term follow-up of preterm neonates which, after the progressive establishment of acute treatment strategies, will become an increasingly important challenge to neonatology within the framework of paediatrics.

Adolescent↗
PubMed2005

Electron microscopy and microcalorimetry of the postnatal rat heart (Rattus norvegicus).

The interplay of ultrastructure and tissue metabolism was examined in neonatal, infant and adult rat hearts by electron microscopy and microcalorimetry. Morphometry was used to determine parameters of oxygen diffusion capacity (distance between capillaries and mitochondria, capillary surface density) and oxidative metabolic capacity (mitochondrial volume fraction). Thin slices and large samples of living tissue were examined calorimetrically to quantify aerobic metabolism and ischemia tolerance, respectively. After birth, rat hearts grow in parallel to body mass and show characteristics of cellular hypertrophy. Capillary surface density increases from neonatal to infant rats, and decreases to an intermediate value in adult rats. The distance between capillaries and mitochondria shows no significant changes throughout postnatal development. Mitochondrial volume fraction increases continuously until adulthood. The specific aerobic tissue metabolic rate is higher in the neonatal than in the infant and adult rat. However, the ischemic decline in metabolic rate is much slower in the neonatal rat, reflecting an elevated hypoxia tolerance. In conclusion, the neonatal rat heart exhibits a high metabolic rate despite a low mitochondrial volume fraction. The subsequent structural rearrangements can be interpreted as long-term adaptations to the increased postnatal workload and may contribute to the progressive loss of hypoxia tolerance.

Aerobiosis↗
PubMed2004

[Aseptic meningitis after intrathecal infusion of a parenteral nutrition solution: examples of rare malpositions of central venous catheters in preterm neonates].

BACKGROUND: Central venous catheters are an indispensable part of intensive care. In the management of preterm neonates, these are introduced after puncture of a peripheral subcutaneous vein. The catheters are supposed to be pushed forward with the venous flow. A chest X-ray is usually performed for verification of the position of the catheter. Localization of the tip of the catheter is often very difficult because of its extremely small diameter. METHODS: A malposition of a central venous catheter resulting in intrathecal infusion of parenteral nutrition and subsequent aseptic meningitis in a preterm neonate is presented. Further cases of catheter malpositions leading to arthrography, arteriography and incorrect position in various parts of the venous system are discussed. DISCUSSION AND CONCLUSION: The case reports demonstrate that wire-guided central venous catheters are not only advanced by the forward blood flow but can also inadvertently end up in undesired sites and may thus induce serious side effects.

Catheterization, Peripheral↗
PubMed2003

Mouse models of human cancer web-based resources.

The Mouse Models of Human Cancers Consortium (MMHCC) is a collaborative program designed to derive and characterize mouse models of human malignancies. To enhance information and resource exchange among the MMHCC investigators and other cancer research scientists, the NCI Center for Bioinformatics (NCICB, http://ncicb.nci.nih.gov/) has developed web-based resources that are freely available to the cancer research community. These resources include a website (http://emice.nci.nih.gov) and databases for cancer models (http://cancermodels.nci.nih.gov) and cancer images (http://cancerimages.nci.nih.gov).

Animals↗
PubMed2002

[Universal newborn hearing screening program in Würzburg. Experience with more than 4000 newborns and the influence of non-pathological factors on the test results].

BACKGROUND: The BERAphon(R) method employing a special headphone and the time-course step-stimulus algorithm offers a quick and reliable tool for universal hearing screening in newborns. An ABR-based universal newborn hearing screening program has been established in Würzburg since August, 1997. Until August 2001, 4115 newborns have undergone primary and/or control-screening with the BERAphon(R). The validity of this method was further examined by testing the effects of non-pathological factors such as gender, age, Apgar score, pH value of the umbilical cord, head circumference and duration of pregnancy on the ABR wave V latency in 415 infants. RESULTS: Out of 3930 infants who were primary screened, 27 infants were diagnosed to have hearing loss. Furthermore, hearing loss was detected in 35 out of 185 infants referred for control screening. Non-pathological factors showed a minor effect on the test results. Apgar score, gender or chronological age did not have any significant effects on the latency of wave V. Duration of pregnancy, pH value of the umbilical cord or head circumference showed a significant but weak correlation with wave V latency. CONCLUSIONS: Only non-pathological factors related to maturation had a minor effect on ABR measurements using the time-course-step-stimulus algorithm. The BERAphon(R) method has proven to be a reliable, robust method giving information related to the hearing threshold and accordingly can be used reliably for hearing screening in newborn infants.

Audiometry, Evoked Response↗
PubMed2002

[Phylogeny of Mammalian metabolism].

Mammals are at the end of a gradual metabolic evolution in the course of which the step from anaerobic to aerobic cellular metabolism and the transition from water to land life formed the basis for an increase in metabolic rate (from brady- to tachymetabolism). The increased metabolic rate and the resulting endogenous heat production were the preconditions for enhanced long-term performance as well as for homeothermy which allowed mammals and birds to invade temperate zones. However, the underlying increase in membrane permeability also results in an increased energy demand (for membrane pump activity) which leads to the reduced hypoxia tolerance of mammals and requires a permanent substrate supply. As an adaptation to a seasonal discrepancy between increased thermoregulatory energy demand and decreased food supply, some small mammals apparently extended the newly evolved non-REM-sleep into hibernation. Mammalian hibernation is characterized by a profound metabolic reduction which is influenced by acidosis and limited to a tolerable degree by maintained thermoregulation. The lower limit of cooling seems to be determined by a critical minimal metabolic rate which is common to all mammals. The higher the normothermic metabolic rate, the lower is the temperature at which this minimal metabolic rate is reached. Since specific (i. e., weight-corrected) basal metabolic rate increases with decreasing body mass, small mammals exhibit a higher hypothermia tolerance than larger ones. On the other hand, the metabolic decrease to a uniform minimal level reflects an inactivation of the overall metabolic size relationship and, thus, forms a counterpart to the metabolic increase from a lower fetomaternal to the higher size-related level, occurring after birth. The postnatal metabolic increase which favours the onset of thermoregulation, parallels the increase in oxygen tension at the transition from fetal to adult circulation and, thus, probably enables mammalian neonates to readjust their metabolic needs in response to hypoxia. There is increasing evidence that, similar to the step from anaerobiosis to aerobiosis, the increase in metabolic rate resulting from any increase in oxygen supply is a general principle of evolution that, apart from its further adaptive benefits, protects tissues from oxygen excess and subsequent oxidative stress.

Animals↗
PubMed2000

Isotopic synovectomy with P-32 in paediatric patients with haemophilia.

Isotopic synovectomy is being proposed as an option in the treatment of patients with haemophilic arthropathy. We present our experience with 11 paediatric patients who underwent 17, P-32 isotopic synovectomies for chronic haemophilic arthropathy. P-32 was injected into the joint per protocol, approved by the institutional review board. All our patients were male. Nine were factor VIII and two were factor IX deficient. The following joints were treated: ankle (n=10 procedures), elbow (n=5) and knee (n=2). The first procedure was performed on December 1993. None were human immunodeficiency virus positive. Mean age at the first procedure was 10.8 years (range, 5.2-15.2 years). Mean pretreatment joint clinical scores using the World Federation of Hemophilia guidelines for the ankle was 5.5 (SD +/- 2.3), the elbow 4.2 (+/-2.5), and knee 5.5 (+/-3.5); the corresponding post-treatment scores were 2.6 (+/-2.0), 1.4 (+/-0.5) and 2.5 (+/-3.5) respectively. Presynovectomy mean radiological scores using the Pettersson method were: ankle 1.8, elbow 1.8, and knee 1.5. A scoring system used in our centre for evaluating joints using magnetic resonance imaging (MRI) gave the following mean pretreatment scores: ankle 9.5, elbow 8.4, and knee 5.0. A marked decrease (an 80-100% decrease) in bleeding was seen in 13 of 17 procedures, and a moderate decrease (51-79% decrease) in two procedures, accounting for 85% reduction in bleeding into the target joints. The procedure was well tolerated and no untoward side-effects were noted as of May 1999, with a median follow-up of 40 months (range 19-65 months). None had any clinical evidence of cancer. Three patients had their joints retreated [elbow (one), ankle (two)]. These procedures were also well tolerated. In conclusion, in our study, isotopic synovectomy using P-32 appears to be feasible, safe and efficacious in the treatment of haemophilic arthropathy in paediatric patients who have been followed for a median of 40 months. As previously shown, MRI appears to give more detailed information about joint arthropathy than plain radiographs.

Adolescent↗
PubMed2000

Azithromycin eruption in infectious mononucleosis: a proposed mechanism of interaction.

The penicillin family of antibiotics may induce drug eruptions when prescribed to patients with infectious mononucleosis. Very similar phenomena have also been cited with other antibiotic families. We report the first case of a cutaneous reaction in a patient with infectious mononucleosis treated with azithromycin. We propose an immune-based hypothesis to explain the transient sensitivity resulting in this secondary cutaneous eruption.

Adult↗
PubMed1999

Determination of airway humidification in high-frequency oscillatory ventilation using an artificial neonatal lung model. Comparison of a heated humidifier and a heat and moisture exchanger.

OBJECTIVE: Thus far only few data are available on airway humidification during high-frequency oscillatory ventilation (HFOV). Therefore, we studied the performance and efficiency of a heated humidifier (HH) and a heat and moisture exchanger (HME) in HFOV using an artificial lung model. METHODS: Experiments were performed with a pediatric high-frequency oscillatory ventilator. The artificial lung contained a sponge saturated with water to simulate evaporation and was placed in an incubator heated to 37 degrees C to prevent condensation. The airway humidity was measured using a capacitive humidity sensor. The water loss of the lung model was determined gravimetrically. RESULTS: The water loss of the lung model varied between 2.14 and 3.1 g/h during active humidification; it was 2.85 g/h with passive humidification and 7.56 g/h without humidification. The humidity at the tube connector varied between 34. 2 and 42.5 mg/l, depending on the temperature of the HH and the ventilator setting during active humidification, and between 37 and 39.9 mg/l with passive humidification. CONCLUSION: In general, HH and HME are suitable devices for airway humidification in HFOV. The performance of the ventilator was not significantly influenced by the mode of humidification. However, the adequacy of humidification and safety of the HME remains to be demonstrated in clinical practice.

Artificial Organs↗
PubMed1999

Neonatal tolerance to hypoxia: a comparative-physiological approach.

Newborn mammals exhibit a number of physiological reactions which differ from normal adult physiology and are often regarded as signs of immaturity. However, when looked upon from a comparative point of view, it becomes obvious that some of these 'physiological peculiarities' bear striking similarity to adaptation mechanisms known from hypoxia-tolerant animals and may thus contribute to the well-established, yet poorly understood, phenomenon of neonatal hypoxia tolerance. As the mammalian fetus lives at oxygen partial pressures corresponding to 8000 m altitude, the first line of perinatal hypoxia defense consists of long-term adaptations to limited intrauterine oxygen supply: (1) improved O2 transport by fetal acclimatization to high altitude, (2) reduced metabolic rate by hibernation-like deviation from metabolic size allometry, (3) diminished cerebral vulnerability by functional analogies to diving turtle brain, and (4) enhanced metabolic flexibility by optional repartitioning of energy supply from growth to maintenance metabolism. In the case of birth asphyxia, these background mechanisms are complemented by short-term responses to acute oxygen lack: (1) reduction of body temperature as in natural torpor, (2) reduction of heart rate and redistribution of circulation as in diving mammals, (3) reduction of respiration rate typical of 'hypoxic hypometabolism', and (4) reduction of blood pH according to the concept of 'acidotic torpidity'. Although anaerobic metabolism is improved in neonatal mammals by increased glycogen stores, reduced metabolic demands, and sustained wash-out of acid metabolites, neonatal hypoxia tolerance seems to be primarily based on the ability to maintain tissue aerobiosis as long as possible. This is even reflected by isoenzyme patterns which do not consistently favour anaerobic glycolysis and, thus, are reminiscent of the 'lactate paradox' found in high altitude adaptation. Altogether, from a biological point of view, the perinatal period appears as a source of adaptive mechanisms that can be refound, in varying combinations, in many survival strategies. From a clinical point of view, the interplay of long- and short-term mechanisms offers a novel approach to estimation of the newborn's ability to withstand temporary oxygen lack. However, most of these mechanisms are not unambiguous and, above all, not unlimited in their protective effect so that they do not release obstetricians or neonatologists from their obligation to counteract fetal or neonatal hypoxia without delay.

Adaptation, Physiological↗
PubMed1999

Comparison between a short and a conventional blade periodontal curet: an in vitro study.

This in vitro study was done to compare a short-blade, long-shank (test) curet designed for deeper pockets of incisors and a conventional Gracey 1/2 curet regarding (a) their ability to remove root surface material at different pocket depths, and (b) their effect on root surface roughness. 2 groups of 12 senior dental hygiene students used either the randomly assigned test or conventional curet for a defined period on maxillary and mandibular incisors in a cross-over experimental design. Extent of root debridement was determined by assessing the removal of black enamel paint on root surfaces within pockets using a computerized video routine and root surface roughness measured using a profilometer. When each surface of the root was analyzed separately at 2-mm increments, the test instrument exhibited superior material removal on all surfaces at the 4-6 mm CAL (p-values<0.001). However, the test curet caused a rougher surface than the conventional curet on all surfaces (p<0.001), with a mean difference of 0.27 microm. While it is assumed that the ability of the test instrument to debride the root surface of deeper pockets more thoroughly is clinically more important than the rougher root surfaces it produces, this can only be assessed by further studies in vivo.

Analysis of Variance↗
PubMed1999

Detection of Helicobacter pylori in oral aphthous ulcers.

A causative role for Helicobacter pylori (H. pylori) in the pathogenesis of oral mucosal ulcerations has been suggested previously. We have adopted the polymerase chain reaction (PCR) as a rapid and sensitive means to detect H. pylori in swabs of recurrent oral aphthous ulcers and in samples of other oral sites. Of the oral aphthous ulcer samples, 32 (71.8%) were found to be positive, while the saliva and plaque samples (most of them taken from the patients with aphthous ulcers) were consistently negative for H. pylori DNA, as detected by the PCR assay. Only two of the swab samples from the tongue (collected at the time of concurrent, H. pylori-positive oral aphthous ulcers) were found to be positive. The data suggest that H. pylori may be associated frequently with recurrent oral aphthous ulcers, and are consistent with previous studies indicating that saliva and plaque are not likely sources of contamination with this microorganism. There was no apparent correlation with HIV status (infection with human immunodeficiency virus). The possible pathogenic significance of Helicobacter pylori in oral ulcerations is discussed.

Adult↗