Biomedical subjects
Publications and source records attributed to M Hammer.
Computerized tomography scans of a ferruginous concretion within the chest region of an ornithischian dinosaur reveal structures that are suggestive of a four-chambered heart and a single systemic aorta. The apparently derived condition of the cardiovascular system in turn suggests the existence of intermediate-to-high metabolic rates among dinosaurs.
BACKGROUND: The aim of this study was to evaluate prospectively whether there are differences in spectrometrically measurable parameters of the fundus between patients with early and late age-related maculopathy (ARM), the children of the ARM patients (F1 generation) and normals. METHOD: Using the "Jenaer Imaging Spectrometer", retinal oxygen saturation, xanthophyll, and intrinsic fluorescence were measured; the spatial distribution of xanthophyll was determined using the Rodenstock SLO 101 model. RESULTS: Xanthophyll is reduced in late ARM as compared to the F1 generation and the control group (alpha < 0.01). The different fluorescence spectra, measured at shortwave and at longwave excitation, suggest the presence of more than one fluorophore. Furthermore, the components of the fluorophores seem to be different between patients with ARM and their F1 generation. The longwave autofluorescence is age-dependent only in late ARM (r2 = 0.81). For the first time, we found an alteration in oxygen saturation in retinal vessels in patients with ARM. CONCLUSIONS: Xanthophyll is reduced only in late ARM. Autofluorescence and oxygen saturation are different between ARM patients, the F1 generation and normals, however, we were not able to identify a genetically based predisposition concerning the parameters studied.
There is a great need for practicing scientists to volunteer their time and expertise in the K-12th grade science classroom. We have found that bioluminescence is a fun and exciting way to teach basic science concepts and is an excellent tool for the volunteering scientist. We have had very positive reactions from both teachers and students. The excitement of the students when they first see bioluminescence is contagious. Bioluminescent dinoflagellates are one of the easiest ways to introduce students to this fascinating topic. Many activities and experiments can be done using the bioluminescent dinoflagellates and many students and teachers could benefit from your knowledge and expertise. See you in the classroom.
The effects of airborne R-(+)- and S-(-)- limonene were studied in conscious BALB/c mice by continuous monitoring respiratory rate (f), tidal volume (VT) and mid-expiratory flow rate (VD) during an exposure period of 30 min. Both enantiomers decreasedf from a trigeminal reflex, i.e., due to sensory irritation. The exposure concentration decreasing f by 50% (RD50) in the first 10 min of the exposure period was estimated to be 1,076 ppm for R-(+)-limonene and 1,467 ppm for S-(-)-limonene. Results for sensory irritation of R-(+)-limonene in BALB/c mice and humans are in close agreement. The reported sensory irritation threshold is above 80 ppm in humans while the no-observed-effect level was estimated to be 100 ppm in mice. The enantiomers were devoid of pulmonary irritation or general anesthetic effects with R-(+)-limonene < or =1,599 ppm and S-(-)-limonene < or =2,421 ppm. R-(+)-limonene did not influence VT below 629 ppm. S-(-)-limonene increased VT above 1,900 ppm. Both enantiomers induced a mild bronchoconstrictive effect above 1,000 ppm.
Sensory preconditioning means that reinforcement of stimulus A after unreinforced exposure to a compound AB also leads to responses to stimulus B. Here, we describe and analyze sensory preconditioning in an insect, the honeybee Apis mellifera. Using two-element odorant compounds in classical conditioning of the proboscis extension reflex, we found (i) that sensory preconditioning is not due to stimulus generalization, (ii) that paired, but not unpaired, presentation of elements supports sensory preconditioning, (iii) that simultaneous, but not sequential, exposure to the elements of the compound supports sensory preconditioning and (iv) that a single presentation of the compound yields maximal sensory preconditioning. The results are discussed with respect to configural and chain-like associative explanations for sensory preconditioning. We suggest an experience-dependent step of compound processing, establishing configural units, as an additional explanation for sensory preconditioning.
In recognizing a pattern, honeybees Apis mellifera, may focus either on its ventral frontal part, or on the whole frontal image. We asked whether the conditioning procedure used to train the bees to a pattern determines the recognition strategy employed. Bees were trained with the same patterns presented vertically on the back walls of a Y maze. Conditioning was either absolute, that is, bees should learn to choose a rewarded pattern when there is no alternative, or differential, that is, bees should learn to choose a rewarded pattern that is paired with a different, nonrewarded one. Bees used different pattern recognition strategies depending on the conditioning procedure: absolute conditioning restricted recognition to the lower half whilst differential conditioning extended it to the whole pattern. Bees trained with absolute conditioning saw and learned the features of the upper part of the trained patterns, but assigned more weight to the lower part. Bees trained with differential conditioning learned not only the features of the reinforced stimulus in an excitatory way, but also those of the nonreinforced one in an inhibitory way. Thus, conditioning tasks that involve not only excitatory acquisition of the conditioned stimulus per se, but also discrimination of nonreinforced stimuli, result in an increase in the visual field assigned to the recognition task. Conditioning tasks that involve only excitatory acquisition of the rewarded stimulus result in a higher weighting of the lower pattern half and thus in a more reduced field assigned to the recognition task. This difference may reflect that existing between a conditioned and an incidental behavioural modification. Copyright 1999 The Association for the Study of Animal Behaviour.
UNLABELLED: The accuracy of the spectrometric measurement of the oxygen saturation in retinal vessels is limited by its signal-to-noise ratio. The aim of this study was to investigate the possibility of enhancement of the reflection signal by the use of polarized light. MATERIALS AND METHODS: The Jena ophthalmospectrometer was equipped with two polarizing filters: one in the illumination and the other in front of the detector. Reflection spectra of erythrocytes streaming through a cuvette in the focus of an artificial eye were recorded. The influence of the polarization on the reflection spectra was investigated by rotating the polarizer in front of the detector. Furthermore, the degree of polarization of the light reflected from retinal vessels in vivo was determined. RESULTS: The degree of polarization of the light reflected from the erythrocytes was 0.6-0.8, whereas the polarization of light reflected by a standard white reflectance target was virtually zero. CONCLUSION: Polarized light can be used for the reduction of error in retinal vessel oximetry.
A new method for the spatially resolved measurement of the oxygen saturation of retinal vessels is described. Imaging spectrometry was used for both measurements of transmission and reflectance spectra of whole blood in cuvettes as well as for fundus reflectance spectra. A model was developed for the calculation of the oxygen saturation, valid in the wavelength range between 510 nm and 586 nm, in that the internal reflectance is constant and only the transmitted light depends on layer thickness and hematocrit. Altogether 265 measurements were performed in different number at 30 eyes. In each measurement, the oxygen saturation was simultaneously determined for 193 locations along a line of 1.5 mm at the fundus. The mean oxygen saturation in retinal arteries was (92.2 +/- 4.1)% and (57.9 +/- 9.9)% in retinal veins. The mean retinal arterio-venous difference of the oxygen saturation was (35.1 +/- 9.5)%. The venous oxygen saturation depended on distance from the optic disc. The measured mean of the arterio-venous difference of the oxygen saturation corresponded well to the value of the brain (34%). The utilization of oxygen in the temporal quadrants (inferior: 39.4 +/- 10.4%) is significantly (p = 0.05) higher than in the nasal quadrants (inferior: 31.3 +/- 6.7%).
One of the predictive factors of treatment-resistant depression is the syndrome of relative insulin resistance, i.e. adipositas, mild hypertension and a family history of type-2 diabetes. Such a case is here reported with a good outcome to anti-stress medication, including ketoconazole and lithium.
OBJECTIVE: To optimise sample preparation of synovial fluid for Chlamydia trachomatis (CT) specific polymerase chain reaction (PCR). METHODS: Serial dilutions of purified CT elementary bodies in synovial fluid were prepared. The synovial fluid pellet was processed by eight different methods of sample preparation. Then samples were analysed by CT specific PCR. The sensitivity of PCR was the basis of ranking of the eight different methods. RESULTS: Highest sensitivity was achieved by methods including an additional step of DNA isolation. Additional extraction of protein and polysaccharides by cetyltrimethylammonium bromide (CTAB) increased sensitivity. Addition of hyaluronidase did not increase sensitivity of QIAEX-DNA extraction but was necessary, however, before phenol-chloroform-DNA extraction. CONCLUSIONS: The method of synovial fluid sample preparation significantly influences the sensitivity of subsequent PCR. Additional DNA isolation and extraction of PCR inhibitors by CTAB led to higher sensitivity.
Cultured Kenyon cells from the mushroom body of the honeybee, Apis mellifera, show a voltage-gated, fast transient K+ current that is sensitive to 4-aminopyridine, an A current. The kinetic properties of this A current and its modulation by extracellular K+ ions were investigated in vitro with the whole cell patch-clamp technique. The A current was isolated from other voltage-gated currents either pharmacologically or with suitable voltage-clamp protocols. Hodgkin- and Huxley-style mathematical equations were used for the description of this current and for the simulation of action potentials in a Kenyon cell model. Activation and inactivation of the A current are fast and voltage dependent with time constants of 0.4 +/- 0.1 ms (means +/- SE) at +45 mV and 3.0 +/- 1.6 ms at +45 mV, respectively. The pronounced voltage dependence of the inactivation kinetics indicates that at least a part of this current of the honeybee Kenyon cells is a shaker-like current. Deactivation and recovery from inactivation also show voltage dependency. The time constant of deactivation has a value of 0.4 +/- 0.1 ms at -75 mV. Recovery from inactivation needs a double-exponential function to be fitted adequately; the resulting time constants are 18 +/- 3.1 ms for the fast and 745 +/- 107 ms for the slow process at -75 mV. Half-maximal activation of the A current occurs at -0.7 +/- 2.9 mV, and half-maximal inactivation occurs at -54.7 +/- 2.4 mV. An increase in the extracellular K+ concentration increases the conductance and accelerates the recovery from inactivation of the A current, affecting the slow but not the fast time constant. With respect to these modulations the current under investigation resembles some of the shaker-like currents. The data of the A current were incorporated into a reduced computational model of the voltage-gated currents of Kenyon cells. In addition, the model contained a delayed rectifier K+ current, a Na+ current, and a leakage current. The model is able to generate an action potential on current injection. The model predicts that the A current causes repolarization of the action potential but not a delay in the initiation of the action potential. It further predicts that the activation of the delayed rectifier K+ current is too slow to contribute markedly to repolarization during a single action potential. Because of its fast activation, the A current reduces the amplitude of the net depolarizing current and thus reduces the peak amplitude and the duration of the action potential.
1. Concentration and time-effect relationships of formaldehyde and ozone on the airways were investigated in BALB/c mice. The effects were obtained by continuous monitoring of the respiratory rate, tidal volume, expiratory flow rate, time of inspiration, time of expiration, and respiratory patterns. 2. With concentrations up to 4 p.p.m., formaldehyde showed mainly sensory irritation effects of the upper airways that decrease the respiratory rate from a trigeminal reflex. The no-effect level (NOEL) was about 0.3 p.p.m. This value is close to the human NOEL, which is about 0.08 p.p.m. 3. Ozone caused rapid, shallow breathing in BALB/c mice. Later on, the respiratory rate decreased due to another vagal response that indicated an incipient lung oedema. The NOEL in mice was about 1 p.p.m. during 30 min of ozone exposure. No major effect occurs in resting humans at about 0.4 p.p.m. 4. Thus, the upper airway irritant, formaldehyde, and the deep lung irritant, ozone, showed the same types of respiratory effects in humans and in BALB/c mice. Also, the sensitivity was nearly identical. Continuous monitoring of respiratory effects in BALB/c mice, therefore, may be a valuable method for the study of effects of other environmental pollutants, which, however, should be confirmed in further studies.
Borrelia burgdorferi specific DNA has been detected by polymerase chain reaction (PCR) in different specimens of patients with Lyme disease (LD). The aim of the present study is to evaluate PCR-diagnostic of urine specimens regarding rheumatologic diagnosis of Lyme disease. Urine specimens of 77 patients (LD, n = 34; undifferentiated arthritis (UA), n = 25; arthralgia/myalgia (AM), n = 18) and 15 controls were investigated. Flagellin gene (60 specimens) or OspA-plasmid (32 specimens) were used as targets. Sensitivity of the flagellin-nested-PCR was 27%, by OspA-nested-PCR only one positive PCR result was found. Despite of low sensitivity PCR enabled the correct diagnosis of LD in two patients classified as UA. Therefore, PCR can give valuable hints in single cases if LD is clinically suspected.
Seventy-seven Ethiopians were investigated for mtDNA and Y chromosome-specific variations, in order to (1) define the different maternal and paternal components of the Ethiopian gene pool, (2) infer the origins of these maternal and paternal lineages and estimate their relative contributions, and (3) obtain information about ancient populations living in Ethiopia. The mtDNA was studied for the RFLPs relative to the six classical enzymes (HpaI, BamHI, HaeII, MspI, AvaII, and HincII) that identify the African haplogroup L and the Caucasoid haplogroups I and T. The sample was also examined at restriction sites that define the other Caucasoid haplogroups (H, U, V, W, X, J, and K) and for the simultaneous presence of the DdeI10394 and AluI10397 sites, which defines the Asian haplogroup M. Four polymorphic systems were examined on the Y chromosome: the TaqI/12f2 and the 49a,f RFLPs, the Y Alu polymorphic element (DYS287), and the sY81-A/G (DYS271) polymorphism. For comparison, the last two Y polymorphisms were also examined in 87 Senegalese previously classified for the two TaqI RFLPs. Results from these markers led to the hypothesis that the Ethiopian population (1) experienced Caucasoid gene flow mainly through males, (2) contains African components ascribable to Bantu migrations and to an in situ differentiation process from an ancestral African gene pool, and (3) exhibits some Y-chromosome affinities with the Tsumkwe San (a very ancient African group). Our finding of a high (20%) frequency of the "Asian" DdeI10394AluI10397 (++) mtDNA haplotype in Ethiopia is discussed in terms of the "out of Africa" model.
A developing tool in ophthalmological research and practice is the study of the oxygen saturation in retinal vessels because this measurement contains important diagnostic information about the metabolism at the human ocular fundus. Imaging spectrometry enables locally resolved measurements of the oxygen saturation simultaneously in arteries and veins. The vessel reflex, imaging errors of the detection system and the noise of the signal result in substantial uncertainties in the calculated data. We present a data processing method for the improvement of the primary information leading to a reduction of the uncertainties of the derived oxygen saturation.
Stachybotrys chartarum, a mycotoxin producing mould found in some damp buildings, was grown in aluminum dishes in closed exposure chambers. The loading factor, 5.12 m2/m3, corresponded to 2.8 times the loading in a normal room with all surfaces covered by mould. Sensory irritation, bronchoconstriction and pulmonary irritation effects were investigated using a sensitive mouse bioassay in which the airway reactions were measured plethysmographically. Little effect was seen from the vapours in agreement with the predicted effects of the low concentrations of volatile organic compounds measured. Even under the influence of an airflow about four times that measured in normal buildings, the concentration of liberated spores and other particles was very low, corresponding to the biological effects observed, and probably reflecting the high water content of the substrate. These results demonstrate that many factors are important for the transport of biologically active mould metabolites from building material to occupants and that no direct relationship may exist between immediate biological effects and surface area covered with mould. Therefore, risk assessments should be based on estimated effects of emitted vapours, effects of liberated particles, e.g. sensitization potentials of the mould spores and effects of the generated metabolites (mycotoxins).
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The 5' flanking region of the mouse calretinin gene was cloned and a 1.8 kbp region adjacent to exon 1 was sequenced. Putative upstream promoter and enhancer elements were identified, including appropriately positioned TATA and CAAT boxes (positions -50 and -68, respectively). There was considerable sequence and structural homology between mouse and human upstream elements. Neuron-restrictive activity was demonstrated via transfection of calretinin promoter-reporter constructs into primary embryonic mouse brain cultures expressing calretinin. In promoterless reporter constructs, the proximal upstream 1.5 kbp of the mouse calretinin gene boosted luciferase activity (up to 100-fold) exclusively in the neuronal population. Deletion analysis revealed the minimal promoter to be within the 95-bp proximal to the transcription start site. Transfections with SV40 promoter constructs in these cultures resulted in reporter gene expression predominantly in non-neuronal cells. Inserting the proximal 1.5 kbp of mouse calretinin upstream in SV40 promoter-reporter constructs reduced luciferase activity. Thus, calretinin upstream sequences increased reporter expression in cultured neurons and decreased expression from the SV40 promoter in non-neuronal cultured brain cells. The calretinin promoter contained relevant regulatory element consensus motifs and demonstrated in vitro neuron-restrictive bioactivity.