Variability of sediment-contact tests in freshwater sediments with low-level anthropogenic contamination--determination of toxicity thresholds.

Freshwater sediments with low levels of anthropogenic contamination and a broad range of geochemical properties were investigated using various sediment-contact tests in order to study the natural variability and to define toxicity thresholds for the various toxicity endpoints. Tests were performed with bacteria (Arthrobacter globiformis), yeast (Saccharomyces cerevisiae), nematodes (Caenorhabditis elegans), oligochaetes (Lumbriculus variegatus), higher plants (Myriophyllum aquaticum), and the eggs of zebrafish (Danio rerio). The variability in the response of some of the contact tests could be explained by particle size distribution and organic content. Only for two native sediments could a pollution effect not be excluded. Based on the minimal detectable difference (MDD) and the maximal tolerable inhibition (MTI), toxicity thresholds (% inhibition compared to the control) were derived for each toxicity parameter: >20% for plant growth and fish-egg survival, >25% for nematode growth and oligochaete reproduction, >50% for nematode reproduction and >60% for bacterial enzyme activity.

Next generation 1.5 microm terahertz antennas: mesa-structuring of InGaAs/InAlAs photoconductive layers.

Mesa-structuring of InGaAs/InAlAs photoconductive layers is performed employing a chemical assisted ion beam etching (CAIBE) process. Terahertz photoconductive antennas for 1.5 microm operation are fabricated and evaluated in a time domain spectrometer. Order-of-magnitude improvements versus planar antennas are demonstrated in terms of emitter power, dark current and receiver sensitivity.

[Herpes simplex digitalis--an important differential diagnosis of paronychia]. / Herpes simplex digitalis--eine wichtige Differentialdiagnose des Panaritiums.

Herpes simplex infection of the hand is often falsely diagnosed as a pyogenic paronychia or felon and treated as such, because the clinical picture is not known and pathogen isolation is difficult. However, the surgical treatment of herpes digitalis is contraindicated, since it promotes the development of superinfections and triggers recurrence. The pathogen can be isolated in cell cultures prepared from the vesicle contents or a smear from the vesicle base. Serological antibody testing is unreliable. Topical application of Acyclovir cream (Zovirax) is the treatment of choice.

Adaptive changes in cats after long-term exposure to various temperatures.

Two groups of cats were exposed to 5 and 30 degrees C, respectively for 24 mo in climatic chambers under artificial illumination. Then the ambient temperatures were reversed for both groups for another 36 mo. The group adapted to cold for 36 mo showed an increase in fur growth (+35%), an increase in resting metabolism (+20%), and a shift in threshold of the cold-induced metabolic response to 8 degrees C lower ambient temperatures. Norepinephrine (0.4 mg . kg-1) elicited nonshivering thermogenesis (+37%) in the cold-adapted animals but was ineffective in the warm-adapted ones. Fur insulation at thermoneutrality was 55% higher in the cold-adapted cats. During acute exposure to -5 degrees C, tissue insulation decreased in both groups; fur insulation increased by 34% in the warm-adapted cats but remained nearly constant in the cold-adapted animals. At all ambient temperatures cold-adapted cats had higher (+0.4 degrees C) rectal temperatures. Body weight was not significantly different in both groups, although the cats living in the cold had a 45% higher metabolism. This was compensated by an increased food consumption.

Static an dynamic activity of cold receptors in cats after long-term exposure to various temperatures.

Ten cats were adapted for 4.7 years in a climatic chamber to an ambient temperature of 5 degree C an 8 cats to 30 degree C under artificial illumination and food ad libitum., Cats living at 5 degree C had 15.2 +/- 0.5 mean nasal and 38.0 +/- 0.3 degree C mean rectal temperature; the corresponding values for cats living at 30 degree C were 31.0 +/- 0.4 degree an 38.3 +/- 0.1 degree C. Static and dynamic activities of single specific cold fibers from the nose were recorded when applying static temperature of 40, 35, 30, 25, 20, 15 and 10 degree C and dynamic cooling steps of 5 degree C starting from static temperature between 40 and 15 degree C. In each group, a population of 100 cold fibers was examined. The average static frequencies between 35 and 20 degree C slightly but not significantly lower in the cold adapted group, the respective values for both groups at 30 degree C being 5.6 and 5.6s-1. The average dynamic maxima were considerably lower in the cold adapted group throughout the whole temperature range, the values at 30 degree C being 44 and 61s-1, respectively. The difference between the dynamic frequency-temperature curves of both fiber populations was highly significant (P less than 0.001). The distribution of static maxima of individual cold fibers as well as the distribution of fibers with static bursts was nearly identical for both groups, whereas the distribution of dynamic maxima and dynamic bursts was significantly shifted lower temperatures in the could adapted group. Seven sub-groups of cold fibers were formed according to their static maximum at temperatures between 40 and 10 degree C. The most pronounced adaptive modification was a significantly lower dynamic peak frequency of the sub-groups with static maxima at 15, 20, 25, 35 and 40 degree C in the cold adapted animals.

Neural processes in long-term thermal adaptation.

Short-term habituation of cats to repeated cold stimuli includes a peripheral component owing to the dynamic response of cutaneous cold receptors. Long-term cold adaptation of up to 4 years causes significant changes in the static and dynamic cold fiber afferents from the cat's nose. These changes, however, do not seem to be essential for the adaptive changes of the thermoregulatory system. Fur growth of cats living for 2 years at 5 C ambient temperature was 30-40% higher than that of controls living at 30 C, and the metabolic response curve was shifted to lower ambient temperatures in the cold-adapted animals. These adaptations are maintained by thermal afferents from the periphery rather than from central thermosensors. Repeated local hypothalamic or spinal cooling in unanesthetized rats for 130 h increased nonshivering thermogenesis after noradrenaline and operant work for warmth in cold environments but did not change general cold resistance. Local cold thresholds of the hand in human subjects were practically independent of the general thermoregulatory state at 10 and 50 C ambient temperature, respectively, whereas thermal comfort elicited by cooling or warming the hand changed considerably with thermoregulation. It is thus assumed that temperature sensation and thermal comfort are mediated by different neural pathways. Repeated exposure to warm or cold environments for 5 days led to a nonspecific increase of affective responses to heating as well as to cooling the hand.

Activity of warm receptors in Boa constrictor raised at various temperatures.

Nine young specimens of Boa constrictor were raised for 4 years in a climatic chamber at an ambient temperature of 30 degrees C under artificial illumination. Seven boas were raised at 23 degrees C under the same conditions. At the end of the adaptation period, mean body weight of the warm adapted boas was 9.6 +/- 0.8 kg and that of the cold adapted ones 5.9 +/- 0.3 kg. Static and dynamic activities of single specific trigeminal warm fibers were recorded when applying static temperatures of 20, 23, 26, 29, 32, 35 and 38 degrees C and dynamic warming steps of 3 degrees C, the initial temperatures being 20, 23, 26, 29, 32 and 35 degrees C. Eighty-nine warm fibers were examined in the warm adapted and 62 fibers in the cold adapted group. The average static frequencies between 29 and 35 degrees C were higher in the warm adapted animals, the respective values for both groups at 32 degrees C being 16.5 and 12 s-1. The average peak frequencies for dynamic warming were 80 s-1 for both groups, but the temperature of the dynamic maximum was shifted from 32 degrees C in the warm adapted to 26 degrees C in the cold adapted boas. At 32 and 35 degrees C the average peak frequencies were higher in the warm adapted animals. The whole fiber population contained various groups with static maxima between 23 and 35 degrees C. Long-term adaptation modified mainly the static and dynamic discharge of the low-temperature fibers. The fiber group with a static maximum at 29 degrees C showed a crossing of the static and dynamic frequency-temperature curves. In the higher temperature range the warm adapted animals had a higher and in the lower temperature range a lower static and dynamic frequency.

Influence of cold adaptation on the activity of thermoresponsive neurons in thalamus and midbrain of the rat.

A group of 25 rats was adapted to cold by housing for five weeks at +3 degrees C. Using thermal stimuli of the scrotal skin, 53 recordings of warm-responsive thalamic and midbrain neurons were analyzed and compared with 84 control recordings from non-adapted rats. The activity of the analyzed neurons is characterized by a steep increase of firing rate above a certain temperature threshold zone. Between scrotal skin temperatures of 36 degrees and 38 degrees C the percentage of neurons with firing rates above the basal rate is higher, both in the thalamic and midbrain population of the cold adapted rats. It is concluded that after cold-adaptation the increase of firing rate starts on average at a lower temperature. The results are discussed in the context of findings of other authors on peripheral structures and on effector behaviour.

The effect of whole body heat exposure and of cooling the hypothalamus on antibody titre in the rat.

In rats implanted with chronic hypothalamic thermodes and immunized with sheep erythrocytes, body temperature was increased, 4 h per day for 2 weeks, either by exposing the animals to external heat or by cooling the preoptic area. The titre of antibodies against sheep erythrocytes was nearly tripled by preoptic cooling but was drastically decreased by heat exposure. These opposing effects of active and passive increases in body temperature indicate that factors other than the change in body temperature must also have played a significant role in modifying the humoral immune response.

Sensory experiences in man evoked by intraneural electrical stimulation of intact cutaneous afferent fibers.

The response of slowly conducting myelinated and unmyelinated afferent units to natural types of cutaneous stimuli was recorded extracellularly with tungsten microelectrodes from intact human skin nerves. Seven fibers had characteristics of C-polymodal units (conduction velocity: 0.75-1.2 m/s) and two fit descriptions of myelinated high- threshold mechanoreceptors (conduction velocity of one: 19 m/s). Attempts were made to evoke a sensation in a subject by stimulating the impaled fascicles directly with electrical pulses of controlled amplitude, duration and frequency so as to try to correlate responsive properties of the sensory units and sensory experience. The subjective sensations evoked by natural stimuli to the skin surface were used as criteria for comparison.

Extra-auditory responses to long-term intermittent noise stimulation in humans.

Respiration, heart rate, cutaneous blood flow, and electroencephalogram (EEG) reactions to long-term intermittent noise exposure were recorded from 13 volunteers (20-29 yr) with normal hearing and vegetative reactivity. They received daily within 1 h 12 noise stimuli (16 s 100 dB (A) white noise) for 10 or 21 days, respectively. Most subjects reported partial subjective adaptation to the noise. Heart rate adapted within a session but did not change considerably during successive days. Vascular responses did not change during one session but diminished mainly during the first 10 days. Noise responses in the EEG remained constant, but a decrease in vigilance occurred during the whole experimental series. Respiration responses were unpredictable and showed no trend within the sessions. It was concluded that certain physiological responses adapt to loud noise but that the time course of adaptation is different. Therefore a general statement about physiological noise adaptation is not possible.