Ingolf Lamprecht

Dielectric properties of yeast cells as determined by electrorotation

Electrorotational spectra of yeast cells, Saccharomyces cerevisiae strain R XII, were measured over a frequency range of nearly 7 decades. The physical properties of distinct cell parts were simultaneously determined for individual cells by comparison with an electrical two-shell model: The conductivity of the cytoplasm, cell wall and cytoplasmic membrane of living cells were found to be 5.5 mS/cm, 0.1 to more than 0.5 mS/cm and less than 0.25 nS/cm to 4.5 microS/cm, respectively. The conductivity of the cytoplasmic membrane was dependent on the conductivity of the medium. Membrane behaviour is interpreted as an opening of membrane channels when the environment becomes more physiological. The specific membrane capacitance was determined to be 1.1 microF/cm2 and the thickness of the cell wall was calculated as 0.11 micron. Heat treated cells showed an increased membrane conductivity of more than 0.1 microS/cm (at 25 microS/cm medium conductivity) and a drop in cytoplasmic conductivity to between 0.1 and 0.8 mS/cm, depending on the length of time the cells were suspended in low conductivity water (25 microS/cm), indicating a perforation of the membrane. A slightly decreased spinning speed scaling factor for dead cells suggests a modification to the cellular surface, while the principal structure of the cell wall appears to be uneffected. It can be demonstrated by these observations, that cellular electrorotation permits the simultaneous investigation of the different cellular compartments of individual cells in vivo under various environmental conditions.

Thermal investigations of a honey bee colony: thermoregulation of the hive during summer and winter and heat production of members of different bee castes

SummaryThe temperature at the centre, the periphery and the entrance of a honey bee colony (Apis mellifera carnica) was continuously determined during the summer season and the broodless time in winter. During the summer season the temperature in the brood nest averages 35.5°C with brief excursions up to 37.0°C and down to 33.8°C. Increasing environmental temperatures resulted in linear increases in the temperature of the hive entrance, its periphery and its centre. The temperature in the centre of an overwintering cluster is maintained at an average value of 21.3°C (min 12.0°C, max 33.5°C). With rising ambient temperatures the central temperature of a winter cluster drops whereas the peripheral temperature increases slightly. With decreasing external temperatures the peripheral temperature is lowered by a small amount while the clusters centre temperature is raised. Linear relationships are observed between the central and the ambient temperature and between the central temperature and the temperature difference of the peripheral and the ambient temperatures. The slopes point to two minimum threshold values for the central (15°C) and the peripheral temperature (5°C) which should not be transgressed in an overwintering cluster. Microcalorimetric determinations of the heat production were performed on the three castes of the honey bee: workers, drones and queens of different ages. Among these groups single adult workers showed the highest heat production rates (209 mW·g−1) with only neglectible fluctuations in the heat production rate. Juvenile workers exhibited a mean heat production rate of 142 mW·g−1. The rate of heat production of adult workers is strongly dependent upon the number of bees together in a group. With more than 10 individuals weight-specific heat dissipation remains constant with increasing group sizes at a level approximately 1/17 that of an isolated bee. Differences are seen between the rates of virgin (117 mW·g−1) and laying (102 mW·g−1) queens. Laying queens showed less thermal fluctuations than virgin queens. High fluctuations in heat production rates are observed for drones. In both groups (fertile, juvenile) phases of high and extremely low activity succeed one another. The heat production of juvenile drones was 68 mW·g−1, that of fertile drones 184 mW·g−1 due to stronger locomotory activities.

Vibrations in Microtubules

Vibrations in microtubules and actin filaments are analysed using amethod similar to that employed for description of lattice vibrationsin solid state physics. The derived dispersion relations show thatvibrations in microtubules can have optical and acoustical branches.The highest frequency of vibrations in microtubules and in actinfilaments is of the order of 108 Hz. Vibrations are polar andinteraction with surroundings is mediated by the generatedelectromagnetic field. Supply of energy from hydrolysis of guanosinetriphosphate (GTP) in microtubules and of adenosine triphosphate(ATP) in actin filaments may excite the vibrations.

Determination of the specific heat capacity of healthy and tumorous human tissue

Abstract Specific heat capacities cp of different healthy and tumorous tissues (liver, lung, prostate) were measured using a differential scanning calorimeter (DSC). The obtained values range from 3.6 to 3.9 kJ kg−1 K−1. The influence of thermal coagulation of 100°C and of cooling with liquid nitrogen on the tissue and its specific heat capacity was investigated using animal tissues. Owing to desiccation during freezing, the specific heat of the tissue decreased by about 2%.

Kinetic investigations of microbial metabolism by means of flow calorimeters

Abstract A mathematical model for microbial growth is presented which combines a Michaelis—Menten kinetics for oxygen and a substrate inhibition kinetics of the Haldane-type of phenol. It is applied to flow calorimetric experiments of the growth of Pseudomonas putida on phenol and other aromatic compounds. The model describes features of the growth well and makes unexpected predictions which have been experimentally verified and compared with as yet unexplained observations from the literature. Possible applications to batch and flow calorimetric investigations of microbial growth are discussed with respect to the critical evaluation of the chosen instrumental set-up.

Calorimetric investigations of the different castes of honey bees, Apis mellifera carnica

SummaryHoney bees of different age and castes were investigated calorimetrically at 20, 25 and 30 °C. Experiments were completed by endoscopic observation of the insects in the visible and the near infrared range and by acoustical monitoring and subsequent frequency analysis of various locomotor activities. Direct calorimetric results of this paper are compared with data of indirect calorimetry from the literature using a respiratory quotient of 1.00 and 21.13 J consumed. Agreements between both methods are generally good. The results show that weight-specific heat production rates increase with age of worker bees by a factor of 5.6 at 30 °C, 3.7 at 25 °C and 40.0 at 20 °C. In groups of foragers the heat production decreases with growing group size to around 6% of the value for an isolated bee. The presence of a fertile queen or of brood reduces the heat output of a small worker group significantly. Adult drones exhibit a much higher metabolic rate (up to 19.7-fold at 20 °C) than juveniles with strong fluctuations in the power-time curves. Fertile queens show a less pronounced heat production rate than virgin queens (54% at 30 °C, 87% at 25 °C and 77% at 20 °C). Calorimetric unrest is much higher for young than for adult queens. Heat production is very low in both uncapped and capped brood and less than 30% of that of a newly emerged worker. In most cases temperature showed a significant influence on the metabolic level, although its sign was not homogeneous between the castes or even within them. Locomotor activities are easily recorded by the acoustic frequency spectrum (0–7.5 kHz) and in good agreement with endoscopic observations and calorimetric traces.

Calorimetry and thermodynamics of living systems

Abstract Calorimetry of living systems and classical thermodynamics developed in parallel, from Lavoisier’s early ice calorimeter experiments on guinea pigs, followed by Dubrunfaut’s macrocalorimetric research of fermentation processes and Atwater-Rosa’s whole-body calorimetry on humans and domestic animals, to the introduction of the famous Tian-Calvet instrument that found entrance into so many different fields of biology. In this work, six examples of living-system calorimetry and thermodynamics are presented. These are: (i) glycolytic oscillations far off the thermodynamic equilibrium; (ii) growth and energy balances in fermenting and respiring yeast cultures; (iii) direct and indirect calorimetric monitoring of electrically stimulated reptile metabolism; (iv) biologic and climatic factors influencing the temperature constancy and distribution in the mound of a wood ant colony as an example of a complex ecological system; (v) energetic considerations on the clustering of European honeybees in winter as a means to save energy and stored food as well as for their Japanese counterparts in defending against hornet predators; and (vi) energetic and evolutionary aspects of the mass specific entropy production rate, the so-called bound dissipation or psiu-function. The examples presented here are just a very personal selection of living systems from a broad spectrum at all levels of complexity. Common for all of them is that they were investigated calorimetrically on the background of classical and irreversible thermodynamics.

Stimulating effects of modulated 150 MHz electromagnetic fields on the growth of Escherichia coli in a cavity resonator

Abstract A simple and quick screening method is described for investigating the effects of modulated and unmodulated 150 MHz electromagnetic fields on the growth of Escherichia coli . The experiments were performed in a cavity resonator which allowed simultaneous monitoring of the influence of five different field intensities. The impact of temperature fluctuations and the way in which they were taken into account in the experimental set-up are discussed. Screening was performed at modulation frequencies of 72, 217 and 1100 Hz and also with unmodulated electromagnetic fields. Maximum field values of 1.6 kV m −1 for the electrical field and 5.4 μT for the magnetic induction were applied. Cells exhibited identical growth behaviour with the various modulation frequencies and in unmodulated fields. Therefore, the modulation frequency could not be responsible for the observed growth effect. Frequency or intensity windows were not observed. There are hints that the growth stimulation observed at higher field intensities is partly caused by a microthermal effect on the cellular level and not by a general temperature increase of the suspending medium.

Is the indigo molecule perturbed in planarity by matrices

Abstract Raman spectra of pure synthetic indigo and of Maya blue of a Mexican clay sculpture are compared. The Raman spectrum of Maya blue shows extra bands assigned to vibrational modes of Bu symmetry as well as an increasing intensity of some other bands. The partial removal of the mutual exclusion rule for the centrosymmetric indigo molecule is supposed to indicate a loss of its planarity due to strong adsorption at the palygorscite matrix.

Direct and indirect calorimetry of thermogenic flowers of the sacred lotus, Nelumbo nucifera

Abstract Direct and indirect calorimetric experiments were performed on flowers of the sacred lotus, Nelumbo nucifera, and compared with temperature measurements. To this end, a simple, light and cheap heat-flow calorimeter of the twin type was developed to monitor the heat output of lotus flowers in an outdoor pond. Each side of the calorimeter consisted of a water jacket as a heat sink surrounding a 730 ml concentric can as a calorimetric vessel. The vessel and heat sink were thermally connected via a Peltier element but otherwise thermally isolated. Both water jackets were housed in a styrofoam box and connected in parallel to a thermostated water bath. The calorimeter exhibited a mean sensitivity of 25.8 mV W−1, a time constant of 8 min and a 24 h baseline stability better than 1% of the chosen range. This differential calorimeter was placed around lotus flowers ≈ 1 m above the water level. Direct calorimetry was accompanied with indirect calorimetry by measuring oxygen consumption rates of the flowers with open-flow respirometry, and the patterns of temperature change were recorded with thermocouples. Flowers maintained mean temperatures of ca. 30.7° and 34.2°C at mean calorimeter temperatures of 18.4° and 30.4°C, respectively, demonstrating good thermoregulatory ability. Metabolic heat production averaged ca. 0.51 W at the low temperature and 0.25 W at the high temperature. Dry heat loss to the calorimeter averaged −0.62 W and −0.17 W, respectively, which indicated that there was a small condensation of atmospheric water vapor inside the calorimeter at the low temperature, but net evaporation from the flower at a level of ca. 33% of heat production occurred at the high temperature. In a set of laboratory experiments on cut lotus flowers, a heat-flux budget was constructed from measurements of heat production (open-flow respirometry), heat loss (gradient-layer calorimeter of the Benzinger/Kitzinger type), and evaporative heat loss (gravimetric). Heat production rate was ca. 0.3 W and was balanced almost completely by evaporative heat loss into the calorimeter air (25°C; 37% relative humidity). Therefore, total heat flux by convection, conduction and radiation was essentially zero, despite the flowers heat-producing receptacle prevailing ca. 5†C higher than the calorimeter air. Heat from the receptacle was apparently transferred to the petals which, in turn, lost it mainly through evaporation. Equivalence of direct and indirect calorimetry substantiated the assumed caloric equivalent of oxygen consumption of 21.1 J ml−1 and indicated that there was no conservation of energy in metabolic processes during thermogenesis.