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Biomedical subjects

H Römer

Publications and source records attributed to H Römer.

At least 19 recordsLinked to original sources
PubMed2005

Chirp rate is independent of male condition in a synchronising bushcricket.

Males of the bushcricket Mecopoda elongata synchronise their chirps with neighbouring males, but because synchrony is imperfect, one male's chirp preceeds the other by some 50-200 ms. Since a male's intrinsic chirp rate is critical for the establishment of the leader role in a duet, and females prefer the leader in a choice situation, we investigated a possible condition dependence of this male trait. In a duet leader males are usually those calling at a higher intrinsic rate; therefore, we investigated whether calling at a higher rate indicates male condition. The calling metabolism was quantified in a respirometer; the factorial slope of males calling at a high rate was three times higher compared to males calling at lower rates. Males produce on average 3.4 singing bouts/per night, and there is a significant increase in chirp periods (CPs) with successive singing bouts. Call properties were investigated throughout a male's life; chirp period increases significantly with age. Two groups of males were reared on either a low- or a high-nutrition diet, and the influence of male condition on different song parameters was investigated. CPs in two feeding regimes did not differ significantly, although males of the low-nutrition diet group were significantly affected by nutrition with respect to mortality, a delayed last moult and reduced weight as adults. We therefore conclude that solo chirp rates do not reflect phenotypic male condition properly.

Age Factors↗
PubMed2000

A gain-control mechanism for processing of chorus sounds in the afferent auditory pathway of the bushcricket Tettigonia viridissima (Orthoptera; Tettigoniidae).

The representation of alternative conspecific acoustic signals in the responses of a pair of local interneurons of the bushcricket Tettigonia viridissima was studied with variation in intensity and the direction of sound signals. The results suggest that the auditory world of the bushcricket is rather sharply divided into two azimuthal hemispheres, with signals arriving from any direction within one hemisphere being predominantly represented in the discharge of neurons of this side of the auditory pathway. In addition, each pathway also selects for the most intense of several alternative sounds. A low-intensity signal at 45 dB sound pressure level is quite effective when presented alone, but completely suppressed when given simultaneously with another signal at 60 dB sound pressure level. In a series of intracellular experiments the synaptic nature of the intensity-dependent suppression of competitive signals was investigated in a number of interneurons. The underlying synaptic mechanism is based on a membrane hyperpolarization with a time-constant in the order of 5-10 s. The significance of this mechanism for hearing in choruses, and for the evolution of acoustic signals and signalling behaviour is discussed.

Acoustic Stimulation↗
PubMed1997

Sexual signalling in bladder grasshoppers: tactical design for maximizing calling range.

Pair formation in the bladder grasshopper (Bullacris membracioides) is by duetting and male phonotaxis. Low-frequency stridulatory signals are emitted by an abdominal resonator in the male and are answered by females using a species-specific time delay. Acoustic transmission in the natural environment was studied using playback of sexual signals over distances of 450m under two atmospheric conditions (day and night). Upward-refracting sound conditions and a sound shadow zone beyond approximately 50m prevailed during the day. Acoustic enhancement was demonstrated at night when downward-refracting temperature inversions created a tunnel effect with sound caught between the ground and zones of different temperatures. Transmission conditions are almost ideal at night when the species actually calls; calling distances of 150m for the male signal in the afternoon increased to 1.5-1.9km at night, arguably the largest calling distance yet reported for insects. In contrast, female calls transmit over a maximum of 50m, signifying a marked discrepancy in the active space of sex-specific signals. Transmission distance may, however, be profoundly affected by levels of masking noise. Adaptations to increase the signal range may variously be found in the signal itself, in behaviour patterns or in the sensory system. Here we demonstrate aspects of the first two types of adaptation in the sexual signalling system of a grasshopper in which maximizing the calling range appears to be the major selection pressure, with lesser effects imposed by inter- and intraspecific pressures and by the transmission channel.

Animals↗
PubMed1995

[Wound drainage with a continuous high vacuum drainage system and a drainage system with variable vacuum].

A study of 120 total hip replacements showed the advantages of the variable vacuum drainage system over the continuous high vacuum drainage system. Better wound healing, less severe hematomas and less occlusion of drains confirmed the higher effectiveness of secretion draining. With regard to hygienic aspects, and especially to wound infection, the continuous closed drainage system is an improvement of the intermittent closed drainage system.

Adult↗
PubMed1991

Realimentation of dehydrated children with acute diarrhea: comparison of cow's milk to a chicken-based formula.

A randomized, prospective study was performed on 73 male children between 3 and 14 months of age with mild to moderate dehydration caused by acute diarrhea, and who were rehydrated with WHO-ORS, and then at 4 h after admission were fed either cow's milk or an experimental diet based on chicken, plantain, and coconut oil. There were no statistically significant differences in the admission characteristics. The group of children fed cow's milk had a higher total volume of diarrheic evacuations (p less than 0.05). The average duration of diarrhea was 20 h shorter in the group of infants on the milk-free formula. A significant correlation was observed between the volume of diarrhea and the WHO-ORS consumed during the first 48 h, but not to the volume of diet intake.

Acute Disease↗
PubMed1989

[Complications of Redon drainage following hip joint replacement operations--an analysis of the causes].

After the introduction of Redon high-vacuum drainage, a considerable decrease in post-operative haematomas has been noted. But some of the complications could not be prevented by using the Redon system. They were in fact the result of it. The Redon system cannot be classified as a "closed" wound drainage. During bottle replacement, the system must be disconnected. An effective closed system must remain absolutely tight from application to removal of the drain so no possibility exists of contamination/infection from the outside. After introduction of a continuously absolutely closed system in a prospective study with three different systems the influence after hip joint arthroplasty operations on wound healing was investigated. The wounds were drained with the Redon high-vacuum system or the newly developed, permanently closed drainage system with maximum obtainable low pressure of 80% vacuum and 50% vacuum. Here the maximum obtainable vacuum builds up slowly in relation to the accumulated amount of wound fluids. The loss of low pressure in Redon systems differs between the drains. In the intra-articular drains the mixture of air and blood results in a linear decrease and follows not a hyperbola like in subcutaneous drains. Because of the high suction at the beginning of the Redon drainage necrotic muscle cells adhere to the outside of the drain openings and clogs them up mechanically. The stronger the suction effect on the tissue, the more fatty live cells and small vessels enter the lumen of the drain in the Redon system and 80% vacuum. This mechanisms result in bleeding from the drain canal after removal of the drain and "secondary" haematomas.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗
PubMed1988

Organization of a sensory neuropile in the auditory pathway of two groups of Orthoptera.

The anterior intermediate sensory neuropile (aISN) is a prominent neuropile in the ventral nerve cord of locusts and bushcrickets. Previous studies have shown that it receives its main sensory input from auditory receptors. In this paper we examine the structural and physiological relationship between tympanal receptor terminations and the dendrites of sound-sensitive interneurones in the homologous neuropile of locusts and bushcrickets. Each individual receptor fibre of the bushcricket terminates in a somewhat different target area of the neuropile. The ordering is with respect to the characteristic frequency of the fibres (tonotopic) in the anterior-posterior and dorsoventral axis. In the locust, representatives of the four tympanal receptor groups branch in different areas of the aISN. Most of the dorsal neuropilar region, and the anterior ventral region, do not receive input from tympanal receptors. The dendrites of identified sound-sensitive interneurones were examined in the context of this afferent projection. Local interneurones as well as intersegmental interneurones in bushcrickets have dendritic branches in the whole aISN or part of it and thus overlap with at least some receptors. By recording intracellularly from their main neurites, short-latency synaptic potentials were found in response to receptor spikes indicating monosynaptic input. The tuning of these neurones could be predicted by their dendritic morphology. In contrast, in the locust only local and bisegmental neurones are monosynaptically connected with tympanal receptors, but not the studied intersegmental neurones. This is consistent with the finding that most or all branches of intersegmental neurones lie in the dorsal area of neuropile where no receptors terminate. Anatomical and physiological evidence is presented for identified local neurones providing the excitatory and inhibitory synaptic input for such intersegmental neurones. The difference in the basic wiring diagram in the homologous neuropile of the two orthopteran groups is discussed with respect to the possible different roles that sound plays in their behaviour.

Animals↗
PubMed1987

Immunocytochemical detection of Entamoeba histolytica.

Human anti-Entamoeba histolytica immunoglobulin was used to detect Entamoeba histolytica in 74 positive samples from several different sources, using an indirect immunoperoxidase method. In 73 samples, the protozoan was easily identified. Trophozoites and cysts of all cultured Entamoeba strains examined were strongly stained, and as few as 3 trophozoites per microscope slide could be detected. In addition, 51 negative control samples were also tested and non-specific reactions were not observed. These preliminary results show that this method is both sensitive and specific, and can easily detect trophozoites and cysts of different E. histolytica strains.

Amebiasis↗
PubMed1986

Spatial segregation of synaptic inputs and outputs in a locust auditory interneurone.

Using intracellular injection of cobalt, processing for electron microscopy, and using on-section silver intensification, we have investigated the distribution of synapses on the metathoracic arborization of the TN1 intersegmental interneurone in the auditory system of the locust. Previous studies have indicated that inputs to this neurone from tympanal afferents are spatially segregated from its outputs to higher-order inhibitory interneurones. Branches in the area of input are characterised by a smooth appearance in Lucifer Yellow preparations, whereas branches in the main output area appear beaded. Sampling different areas of the TN1 arborization, we have found marked differences in the respective densities of input and output synapses. Labelled profiles in areas of beaded branching have an extremely high density of presynaptic sites, with a much smaller number of synaptic inputs. Smooth branches bear many input synapses, but we have found no output synapses on them. Our results indicate a good correlation between branch beading and presynaptic function and between smooth branches and postsynaptic function. These correlations enable us to predict synapse distribution on other insect neurones with a similar division in branch morphology and also extend our knowledge of the functioning of TN1 itself.

Animals↗
PubMed1985

Spike synchronization of tympanic receptor fibres in a grasshopper (Chorthippus biguttulus L., Acrididae). A possible mechanism for detection of short gaps in model songs.

In recordings from single tympanic receptor fibres in C. biguttulus, the response to synthesized sounds (rectangularly modulated white noise) interrupted by very brief (a few milliseconds) gaps was examined. In behavioral tests, females of the species respond very differently to such 'model syllables' at moderate intensities, depending on the gap width. If the gaps (in a moderate-intensity syllable) are larger than 2 ms, the stimulus fails to elicit a response, whereas stimuli with gaps smaller than 1 ms are as effective as uninterrupted syllables (D. von Helversen 1972; O. von Helversen 1979). Neither the mean spike count nor the interspike-interval distribution of the single receptor response contains the information sufficient to distinguish uninterrupted syllables from syllables with gaps. On the other hand, examination of the temporal distribution of the spikes reveals that gaps (or the pulse onsets following the gaps) cause spike synchronization. An index of synchronization (IS) was defined as a measure of this gap-induced effect. Analysis of the receptor responses based on IS revealed differences that correspond quantitatively to the abrupt abolition of the behavioral response at a gap-width between 1 and 2 ms. From the hypothesis that such brief gaps are detected by the nervous system by way of spike synchronization in the tympanic nerve, one can predict certain features of the behavioral response to high-intensity stimuli. The gap-induced spike synchronization was more pronounced at higher temperatures. This effect was demonstrated in both summated recordings from the tympanic nerve and single fibre recordings. Experiments with primary auditory fibres of Locusta migratoria showed that the receptors in this species respond very similarly to the same stimuli. That is, the receptors of C. biguttulus are not specially adapted for detecting very brief gaps. Synchronization of the spikes in parallel receptor fibres of the tympanal nerve is probably a general feature of acridids; we infer that in C. biguttulus this gap-induced synchronized activity is detected by special processing in higher auditory centres.

Animal Communication↗
PubMed1983

Moderate and severe protein energy malnutrition in childhood: effects on jejunal mucosal morphology and disaccharidase activities.

The enzymatic activities of maltase, sucrase, and lactase were determined in jejunal biopsies obtained from 24 children with gastrointestinal symptoms and different degrees of protein energy malnutrition (PEM) to see if these differences were related to the extent of malnutrition or concomitant small intestinal mucosal injury. Even in patients with moderate PEM, lactase activities were significantly lower than control values. The decrease in lactase activity seemed to depend on the severity of malnutrition. In contrast, maltase and sucrase activities were decreased only in second and third degrees of PEM, while no significant changes were observed in first degree and marasmic kwashiorkor. Histologically, all children with PEM had grade I to II mucosal injury which did not correlate with the degree of malnutrition. These results indicate that PEM affects each of the disaccharidases of the jejunal mucosa differently, with lactase being most sensitive to PEM and reflecting most closely the degree of PEM. In contrast, morphological changes showed no correlation with the degree of PEM.

Biopsy↗
PubMed1980

Multiplication of human rotavirus in cultured cells: an electron microscopic study.

Human rotaviruses were capable of efficient multiplication in LLC-MK2 cells when the inoculum was pre-treated with trypsin, centrifuged on to the cell monolayer and the infected cells maintained in a medium containing trypsin. However, not all of the human rotavirus isolates used to infect cells resulted in efficient virus production. The ability of human isolates to multiply in cultured cells was studied by direct observation of virus in the electron microscope, by radioactive labelling with 3H-uridine of the newly synthesized virus and by electron microscopic examination of thin sectioned infected cells. With one of the specimens used (F-617) only 5 to 10% of the cells showed evidence of virus multiplication, with the great majority of the infected cells showing numerous complete (double-capsid) virus particles scattered in the cytoplasm. When cells were inoculated with another human specimen (SIB-I), infected cells were more abundant, reaching a maximum of 60%; however, a variety of particle types, probably representing different subviral structures or different steps of rotavirus morphogenesis, were commonly observed. The presence of these aberrant or incomplete virus structures may represent a manifestation of the defectiveness of this virus and may explain the difficulties encountered in its serial passage.

Animals↗
PubMed1979

Effects of exogenous neuraminidase on unit activity in frog spinal cord and fish optic tectum.

The effect of exogenous neuraminidase on spontaneous and evoked synaptic activity was investigated following injection of the enzyme into frog spinal cord and into cord and into the carp optic tectum. 1. Injection of enzyme into spinal cord segments caused a significant increase of motoneuron activity in the corresponding spinal nerve, which lasted for 7--31 min. 2. The amplitude of postsynaptic evoked potentials in the optic tectum was increased after neuraminidase injection up to 200% of control level for 20--40 min, whereas the amplitude of summed action potentials of retino-tectal afferents remained unchanged. 3. Similar effects were observed in single cell responses of the optic tectum with some differences in the degree of increase in activity, as well as latency and final depression of the stimulus response. 4. The extent of neuraminic acid liberation following neuraminidase treatment was determined biochemically. In both tissues investigated the amount of free neuraminic acid was increased significantly (4--5.5 fold) after enzyme treatment. Whereas after enzyme injection into spinal cord and optic tectum the percentage release of total glycoprotein- and glycolipidbound neuraminic acid was 12% and 15%, respectively, liberation from enzyme incubated tissue homogenates was somewhat higher (20.5% and 24%).

Animals↗
PubMed1971

Behaviour of the rectal juvenile polyp in vitro.

The behaviour of the juvenile polyp in vitro and its cellular development from explants have been studied using cellular dispersion by the trypsinization technique. Only the fibroblastic cells have been found to grow. The significance of this finding suggests that the juvenile polyp is a hamartoma.

Child↗