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Biomedical subjects

R Menzel

Publications and source records attributed to R Menzel.

At least 91 records · Page 5Linked to original sources
PubMed1995

Learning and memory in the honeybee.

Insects are favorable subjects for neuroethological studies. Their nervous systems are relatively small and contain many individually identifiable cells. The CNS is highly compartmentalized with clear separations between multisensory higher order neuropiles in the brain and neuropiles serving sensory-motor routines in the ventral cord (Huber, 1974). The rich behavior of insects includes orientation in space and time, visual, chemical, and mechanical communication, and complex motor routines for flying, walking, swimming, nest building, defense, and attack. Learning and memory, though, are not usually considered to be a strong point of insects. Rather, insect behavior is often regarded as highly stereotyped and under tight control of genetically programmed neural circuits. This view, however, does not do justice to the insect order of Hymenoptera (bees, wasps, ants). Most Hymenopteran species care for their brood either as individual females or as a social group of females. Consequently, they regularly return to their nest site to feed, protect, and nurse the larvae, store food, and hide from adverse environmental conditions. Since they search for food (prey; nectar and pollen on flowers) at unpredictable sites, they have to learn the celestial and terrestrial cues that guide their foraging trips over long distances and allow them to find their nest sites (central place foraging; von Frisch, 1967; Seeley, 1985). They learn to relate the sun's position and sky pattern of polarized light to the time of the day (Lindauer, 1959), and landmarks are learned in relationship to the nest site within the framework of the time-compensated sun compass. The honeybee communicates direction and distance of a feeding place to hive mates by performing a ritualized body movement, the waggle dance (von Frisch, 1967). Associative learning is an essential component of the bee's central place foraging behavior and dance communication. Hive mates attending a dance performance learn the odor emanating from the dancing bee and seek it at the indicated food site. The odor, color, and shape of flowers are learned when the bee experiences these stimuli shortly before it finds food (nectar, pollen). This appetitive learning in bees has many characteristics of associative learning well known from mammalian learning studies (Menzel, 1985, 1990; Bitterman, 1988). It follows the rules of classical and operant conditioning, respectively, so that stimuli or behavioral acts are associated with evaluating stimuli. Since associative learning, especially of the classical type, is well described at the phenomenological and operational level (Rescorla, 1988), it provides a favorable approach in the search for the neural substrate underlying learning and memory.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Ultraviolet as a component of flower reflections, and the colour perception of Hymenoptera.

Based on the measurements of 1063 flower reflection spectra, we show that flower colours fall into distinct clusters in the colour space of a bee. It is demonstrated that this clustering is caused by a limited variability in the floral spectral reflectance curves. There are as few as 10 distinct types of such curves, five of which constitute 85% of all measurements. UV reflections are less frequent and always lower in intensity than reflections in other parts of the spectrum. A further cluster of colour loci is formed in the centre of the colour space. It contains the colour loci of green leaves, several other background materials and only very few flowers. We propose a system to classify the reflection functions of flowers, and a set of colour names for bee colours.

Animals↗
PubMed1994

Color learning and memory in honey bees are not affected by protein synthesis inhibition.

The role of protein synthesis was tested for memory formation after color learning in honey bees. Free flying bees were trained to a feeding place. Before the color conditioning started, foragers accustomed to flying to the feeding place received an injection of either cycloheximide in bee ringer or bee ringer alone into the brain. Afterward, the animals were trained appetitively to a specific colored target by three training trials. During the test situation, two targets with different colors and no reward were presented. The choice behavior toward the two targets was evaluated. The first test immediately followed the last trial, the second test 24 h later. A comparison between cycloheximide- and ringer-injected bees showed no significant difference in choice behavior in either test. Although the injection of cycloheximide causes the inhibition of protein synthesis (> 95%) for a period of 3 h, the memory for the learned color signal is not affected. These results corroborate those found for the olfactory conditioning of the proboscis extension reflex in bees (Wittstock, Kaatz, & Menzel, 1993, Menzel, Gaio, Gerberding, Nemrava, & Wittstock, 1993).

Animals↗
PubMed1994

Development and experience lead to increased volume of subcompartments of the honeybee mushroom body.

The mushroom bodies of insects are believed to be involved in higher order sensory integration and learning. In the honeybee, the mushroom body can be separated into three different, modality-specific input compartments and several morphologically inseparable output regions. By means of morphometric analysis we show that the volumes of these subcompartments depend on both the age of the adult bee and its experience. For the most part a significant, age-dependent increase in neuropile volume is observed. Additionally, the olfactory and visual input regions show experience-related differences. Unlike other subcompartments, the visual input region does not change in volume with age, but only with experience. We thus suggest that experience is an important factor in the structural development of higher order brain regions of an insect, the honeybee.

Age Factors↗
PubMed1994

Mutations in the -10 TATAAT sequence of the gyrA promoter affect both promoter strength and sensitivity to DNA supercoiling.

Transcription of the gyrA and gyrB genes, which encode the subunits of DNA gyrase, increases in response to DNA relaxation. Previous studies have shown that a small segment of DNA extending from the -10 consensus hexamer to the start of transcription encodes the sequence determinants for this response. In this study, we examined the role of the -10 region in relaxation-stimulated transcription (RST). A synthetic derivative of the gyrA promoter was designed to allow the modular replacement of the -10 region, and mixed-oligonucleotide mutagenesis was used to obtain a collection of promoter mutants. Most substitutions result in a reduction of the promoter's RST response, and some mutations abolish it altogether. We also note that a variety of promoter changes can increase basal expression twofold above that seen for the gyrA promoter, despite sequences changes (up to three bases) which diverge from the consensus TATAAT of the wild-type gyrA hexamer. The wild-type gyrA promoter, however, is the strongest promoter in this collection on a relaxed DNA template and appears to be repressed on a supercoiled template in vivo. Our results are consistent with a mechanism for RST that involves a step in transcription initiation.

Base Sequence↗
PubMed1994

Ionic currents of Kenyon cells from the mushroom body of the honeybee.

The mushroom bodies have been suggested to be essentially involved in learning and memory in insects. In the honeybee Apis mellifera they are composed of about 340,000 intrinsic elements, called Kenyon cells, which can be easily separated from all other neurons of the brain. Here we describe a preparation in which we studied ionic currents in the isolated Kenyon cell somata, using tight-seal whole-cell recording. Several outward and inward currents were identified and investigated by the use of pharmacological agents and in ion substitution experiments: a rapidly inactivating A-type potassium current that is completely blocked with 5 mM 4-aminopyridine; a calcium-activated potassium current that is blocked by 1-100 nM charybdotoxin; a delayed rectifier-type potassium current that is only weakly sensitive to tetraethylammonium but is blocked by 100 microM quinidine; a rapidly activating and inactivating, TTX-sensitive sodium current; a persistent sodium current that is both TTX and cadmium sensitive; and a calcium current that is completely blocked at 50 microM cadmium and is affected by verapamil and nifedipine only at high concentrations (100 microM). The currents described here are very similar to currents found in other insect neurons or muscle cells. This preparation will not only facilitate studies concerning the action of transmitters and neuromodulators that are contained within neurons converging onto the Kenyon cells, but will also allow a study of the role of the adenylyl cyclase pathway, elements of which are expressed in Kenyon cells, and are known to be essential for learning in invertebrates.

Animals↗
PubMed1993

Anatomy of the mushroom bodies in the honey bee brain: the neuronal connections of the alpha-lobe.

Neural connections between the mushroom body (MB) and other protocerebral areas of the honeybee's brain were studied with the help of cobalt chloride and Golgi staining methods. Focal injections of cobalt ions into the alpha-lobe neuropil of the MB reveal seven clusters of somata located in the protocerebrum and deutocerebrum of each brain hemisphere. These neurons connect the mushroom body neuropil with protocerebral areas and number approximately 400. They contact the layered organization of the alpha-lobe at different locations. Some project not only into the alpha-lobe, but also into the beta-lobe and pedunculus neuropils. Fifteen cell types which form intraprotocerebral circuits are morphologically described. They can be divided into three categories: 1) unilateral neurons, with projection fields restricted to the ipsilateral protocerebrum; these neurons connect the alpha-lobe with areas in the protocerebral lobe and ramify with densely layered arborisations arranged perpendicularly to the longitudinal axis of the alpha-lobe; 2) recurrent neurons, which interconnect subcompartments of the MB, forming loops at different levels of the neuropil; their arborisations are mainly restricted to the alpha-lobe, beta-lobe, pedunculus, and calyces of the ipsilateral MB; they also ramify sparsely around the neuropil of the alpha-lobe; and 3) bilateral neurons, which either interconnect both alpha-lobes or connect the ipsilateral alpha-lobe and protocerebral lobe with the dorsolateral protocerebral lobe of the contralateral hemisphere. The connections of different compartments of the MB with other parts of the protocerebrum as revealed in this study are discussed in the context of hypotheses about the functional role of MBs in the honeybee brain.

Animals↗
PubMed1993

Primary health care of diabetic patients in a specialized outpatient setting: a DIABCARE-based analysis.

To assure health care quality requires a tool for establishing the feedback between parameters of patient management and related standards. To assess the current situation and to evaluate the DIABCARE system as a potential monitoring instrument, a retrospective study was performed in 85 randomly assigned insulin-treated patients (72% type 2) who were regularly attending the diabetes outpatient unit (total of 3,595 patients) in a township of approximately 90,000 inhabitants. 1,195 records of sequential medical visits during the years 1987 and 1990 were analyzed. -Selected results (averages in 1987 vs. 1990): (1) Visits per year 6.9 vs 7.1; (2) intensified insulin treatment in 14 vs. 27% of all patients, they were on 4.0 vs. 4.5 injections per day applying doses of 0.8 vs. 0.6 IU kg-1 d-1; (3) glycaemic control: random blood glucose 6.0 vs. 5.8 mmol/l on conventional and 6.4 vs. 5.7 mmol/l on intensified regimes, HbA1 regular measurements in 2 vs. 21% of the patients; (4) body mass index 26.4 vs. 26.6 (conventional) and 24.7 vs. 25.9 (intensified) kg/(m)2; (5) retinopathy prevalence 30 vs. 29%, in 4 vs. 29% of the patients no information; (6) nephropathy prevalence 7 vs. 11%, in 75 vs. 68% of the patients no information; (7) foot complications prevalence 6 vs. 9%, in 91 vs. 84% of the patients no pathological findings. -The DIABCARE monitor proved appropriate but too laborious. The general level of care showed a tendency towards improvement between the two investigated periods but dit not yet meet the standards which must be attained to attain the St. Vincent Declaration.

Adult↗
PubMed1993

Inhibition of brain protein synthesis by cycloheximide does not affect formation of long-term memory in honeybees after olfactory conditioning.

The honeybee forms a long-term memory in different training situations that lasts for a lifetime, but the cellular mechanisms of long-term memory formation are not known. We analyzed the dependency of long-term memory on the de novo brain protein synthesis. The protein synthesis inhibitor cycloheximide was injected via the median ocellus directly into the brain. 3H-leucine incorporation into brain proteins was inhibited by > 95% for > 3 hr. The time of protein synthesis inhibition was prolonged by a second injection of the same dose. Worker honeybees were conditioned to an olfactory stimulus at different times before and after injection. The proboscis extension response (PER) of bees restrained in tubes was classically conditioned with sugar water applied first to the antennae followed by feeding (unconditioned stimulus) paired with odor presentation (conditioned stimulus). The bees were tested by presenting the odor alone at different times up to 24 hr after injection. No significant reduction in the probability of the conditioned response in cycloheximide-treated bees was found when compared to the Ringer-injected controls in 4 series of experiments. Since protein synthesis was inhibited between 7 hr pre- and 7 hr postconditioning without affecting the formation of long-term memory, a possible role of de novo protein synthesis in the formation of long-term memory after olfactory conditioning of the PER is not supported by these experiments.

Animals↗
PubMed1992

The spectral input systems of hymenopteran insects and their receptor-based colour vision.

Spectral sensitivity functions S(lambda) of single photoreceptor cells in 43 different hymenopteran species were measured intracellularly with the fast spectral scan method. The distribution of maximal sensitivity values (lambda max) shows 3 major peaks at 340 nm, 430 nm and 535 nm and a small peak at 600 nm. Predictions about the colour vision systems of the different hymenopteran species are derived from the spectral sensitivities by application of a receptor model of colour vision and a model of two colour opponent channels. Most of the species have a trichromatic colour vision system. Although the S(lambda) functions are quite similar, the predicted colour discriminability curves differ in their relative height of best discriminability in the UV-blue or blue-green area of the spectrum, indicating that relatively small differences in the S(lambda) functions may have considerable effects on colour discriminability. Four of the hymenopteran insects tested contain an additional R-receptor with maximal sensitivity around 600 nm. The R-receptor of the solitary bee Callonychium petuniae is based on a pigment (P596) with a long lambda max, whereas in the sawfly Tenthredo campestris the G-receptor appears to act as filter to a pigment (P570), shifting its lambda max value to a longer wavelength and narrowing its bandwidth. Evolutionary and life history constraints (e.g. phylogenetic relatedness, social or solitary life, general or specialized feeding behaviour) appear to have no effect on the S(lambda) functions. The only effect is found in UV receptors, for which lambda max values at longer wavelengths are found in bees flying predominantly within the forest.

Animals↗
PubMed1992

Opponent colour coding is a universal strategy to evaluate the photoreceptor inputs in Hymenoptera.

Behavioural tests were carried out with 9 hymenopteran insect species, which ranked certain sets of coloured stimuli according to their subjective similarity to a previously memorized stimulus. Kendall's tau co-efficient is employed for the analysis of correlation between these similarity rankings and the colour distance rankings predicted by various models of neural colour computation. The models are based on the measured spectral sensitivities of photoreceptor colour types and use a variety of simple colour coding systems to derive hypothetical colour distances. The correlation between the predictions of the models and the behavioural results serves as a measure for the likelihood of existence of a colour coding system. In all species, the similarity rankings can be best explained by assuming that colour is coded on a perceptual level by two colour opponent mechanisms. Brightness differences are ignored, indicating that an intensity-coding sub-system is not used in colour discrimination by the insects investigated. The weighting factors of the colour opponent mechanisms differ between species in detail, but not in the principles involved. It is thus possible to employ a standard measure of perceptual colour distance (colour hexagon distance) to predict the capacities of colour discrimination adequately in all the tested insects.

Agonistic Behavior↗
PubMed1990

Inhibition of DNA gyrase activity in an in vitro transcription-translation system stimulates gyrA expression in a DNA concentration dependent manner. Evidence for the involvement of factors which may be titrated.

Stimulation of gyrA expression in an in vitro transcription-translation system by novobiocin, a DNA gyrase inhibitor, depends on the DNA concentration in the extract. At low DNA concentrations (less than 20 micrograms/ml) we note significant stimulation (2 to 25 x) upon the addition of novobiocin; at high DNA concentrations, stimulation is minimal. This observation is not due to the limited capacity of the system to transcribe or relax DNA. Using an extract prepared from a novobiocin-resistant strain of Escherichia coli, we were able to show that DNA gyrase mediates the novobiocin-enhanced expression. In an experiment with a fixed level of a gyrA-lac template, we found that the addition of a second non-Lac template increased expression from the gyrA-lac template, while concomitantly decreasing the extent of novobiocin stimulation. These observations are consistent with an inhibitory factor that can be titrated by increasing the DNA concentration and whose effects are minimized when the DNA template is in a relaxed conformation. The results of a mixed-extract experiment using two extracts that differ in their activities and degrees of novobiocin stimulation are also consistent with an inhibitory factor that mediates the relaxation-induced stimulation of transcription.

DNA↗
PubMed1990

[Nocturnal continuous subcutaneous insulin infusion--a therapeutic possibility in labile type I diabetes under exceptional conditions].

The whole-day continuous subcutaneous insulin infusion (CSII) with portable pumps in daily blood glucose autocontrol guarantees a more stabile and favourable glycaemia than multiple injections in labile type I diabetics. The success is mainly to be traced back to the continuous replacement of the basal secretion, particularly to the nocturnal fasting phase. In this study the effect on the glycaemia is investigated with exclusively nocturnal administration of the CSII under maintenance of multiple insulin injections during this day. In a group of 18 type I diabetics the nocturnal CSII in comparison to intermediate insulin administrations in the evening led to a significant improvement of glycaemia (p less than 0.01), in particular to the decrease of the fasting blood sugars (p less than 0.05). In two casuistic observations in comparison to all the other conventional methods for the compensation of the nocturnal glycaemia (depot insulin, nocturnal injection of normal insulin) the nocturnal CSII proved to be superior. Therefore, the nocturnal CSII is an--though more rarely to be used--alternative, which may be taken into consideration, of a whole-day CSII is temporarily unwished for.

Adult↗
PubMed1990

"Catheter-pens"--an alternative to insulin pump treatment?

Two types of insulin pens MADI and MD, were connected to subcutaneous catheters. These "catheter-pens" were used like hand-driven insulin pumps. Results after 1 year of treatment in 30 type 1 diabetics (HCP-negative; age at onset of diabetes 16.5 +/- 1.7 years; duration of diabetes 18.5 +/- 1.6 years, on multiple insulin injections before catheter-pen application): 1. better quality of life (reduction of frequency of needle pricks, more flexibility, inconspicuous application of insulin in public); 2. daily insulin--increased number of "injections" (4.2 +/- 0.1 vs 5.8 +/- 0.1, p less than 0.01), reduction of units per kg BW (0.70 +/- 0.02 vs 0.60 +/- 0.01, p less than 0.01), reduction of intermediate-acting insulin (14.1 +/- 1.3 vs 9.2 +/- 1.2 U/d, p less than 0.05); 3. no change of HbA1 (10.8 +/- 0.8 vs 10.2 +/- 0.2%, normal range 7.7 to 8.4%), mean blood glucose (MBG) in stress situation (8.4 +/- 0.4 vs 7.7 +/- 0.3 mmol/l), serum cholesterol and body weight, both within normal range; 4. improvement (p less than 0.05) of serum triglycerides, serum HDL-cholesterol, ratio of apolipoprotein A1/B; 5. rare skin reactions at the needle site. Conclusion. Catheter-pens offer a very convenient alternative for insulin administration in intensified conventional insulin treatment with multiple injections in type 1 diabetics.

Apolipoproteins A↗