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Biomedical subjects

M Hau

Publications and source records attributed to M Hau.

16 recordsLinked to original sources
PubMed2002

High resolution ultrasound detects a decrease in pannus vascularisation of small finger joints in patients with rheumatoid arthritis receiving treatment with soluble tumour necrosis factor alpha receptor (etanercept).

OBJECTIVE: High resolution ultrasound (HRUS) was used to investigate the effects of tumour necrosis factor alpha (TNFalpha) blockade on pannus formation and vascularisation of small finger joints in patients with active rheumatoid arthritis (RA). METHODS: Five patients with active RA were treated with etanercept, a soluble TNFalpha receptor protein, for one month. Before, during, and after treatment the patients were followed up by clinical rheumatological examination, determination of their subjective pain score, blood chemistry, and by HRUS of the second metacarpophalangeal (MCP) joint of the right hand. RESULTS: One month after treatment with etanercept, rheumatological examination showed a significant decrease in a modified single joint rheumatic disease activity index (from 2.9 (SD 0.2) to 1.2 (0.7); p<0.05) in all patients. Moreover, a significant decrease in the general pain score (from 4.7 (0.4) to 1.8 (0.6); p<0.05) and in C reactive protein (CRP) levels was seen (from 3.02 (0.9) to 0.24 (0.1); p<0.05). Concordantly, HRUS showed a significant reduction in pannus vascularisation of the MCPII joints (from 23,602 (5339) to 2907 (1609) colour signals/region of interest, CS/ROI; p<0.001). Pearson's correlation coefficient between the results obtained by HRUS and the clinical response was 0.85. CONCLUSION: HRUS is promising as an additional useful method in the assessment of RA activity, and probably also in monitoring therapeutic responses.

Aged↗
PubMed2001

Timing of breeding in variable environments: tropical birds as model systems.

Animals need to adjust reproductive decisions to environmental seasonality. In contrast to species from the well-studied temperate zones, little is known for tropical birds about the environmental cues that stimulate reproductive activity and the physiological mechanisms that regulate reproduction. I am investigating the environmental and endocrine mechanisms that underlie the timing of reproduction in spotted antbirds from the near-equatorial Panamanian rainforest and in small ground finches from the equatorial arid Galápagos islands. Spotted antbirds live in a fairly predictable seasonal environment and show regular changes in gonad sizes and some reproductive hormones. Despite the small annual variation in photoperiod close to the equator, these birds can measure slight photoperiodic increases and use it to initiate reproductive activity. Spotted antbirds also respond to seasonal changes in food availability, which allows them to flexibly adjust gonad growth to environmental conditions. Testosterone is involved in regulating song and aggressive behavior in these year-round territorial birds, although it can remain at low plasma levels throughout the year. In contrast, small ground finches exposed to a rather unpredictable climate on Galápagos appear to grow their gonads whenever heavy rains fall and have regressed gonads during other times of the year. The lack of a physiological preparation for the breeding season and their response to short-term cues related to rainfall indicate a striking flexibility in the regulation of breeding in small ground finches. I suggest that tropical birds can serve as model systems to study the physiological adaptations to different environments. Unraveling the neuroendocrine mechanisms behind the flexibility in reproductive timing will clarify whether differences found between temperate and tropical birds represent variations of the same basic mechanism or instead reflect a fundamental divergence in physiological control systems.

Animals↗
PubMed2000

Visual and nutritional food cues fine-tune timing of reproduction in a neotropical rainforest bird.

Food may act as a proximate factor in the regulation of avian seasonal breeding. Food cues could provide particularly important seasonal information to birds living in variable tropical environments, but this has not yet been tested. Spotted antbirds (Hylophylax n. naevioides) inhabiting a humid forest in central Panama (9 degrees N) likely use changes in the tropical photoperiod to time reproduction on a long-term, seasonal basis. We predicted that these insectivorous birds also adjust reproduction to short-term cues such as food availability because the onset of the rainy season and the resulting increase in insect abundance varies considerably between years. To test this prediction, prior to their breeding season (when they had half-maximal gonads), we either exposed captive male spotted antbirds to an ad libitum standard diet only or added live crickets to this diet. Males that received live crickets significantly increased gonad sizes within 3 weeks over controls on the standard diet. Moreover, in six additional experiments cricket availability always increased song rate, usually within a few days. The stimulatory effect of live crickets on song activity may function independent of nutritional aspects: Freshly killed crickets, providing similar nutritional content as live crickets, did not stimulate the birds' song activity. However, song activity increased to intermediate levels when live crickets were shown under a clear plastic wrap, i.e., when birds could see but not eat crickets. We hypothesize that the opportunity to see and handle live insects stimulates song and reproductive activity in these birds. Our data indicate for the first time that a tropical rainforest bird can use food cues to evaluate the suitability of local environmental conditions for breeding. J. Exp. Zool. 286:494-504, 2000.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Ignition of combustible/air mixtures by small radiatively heated surfaces.

Optical radiation as an ignition source in potentially explosive atmospheres was investigated for a number of explosive mixtures with respect to the most important case occurring in practice, i.e., absorption of the radiation by a solid target. Iron oxide was used as the target material. The combustibles were selected in compliance with the well-known temperature classes and apparatus groups to allow a useful graduation of the power limits to be applied.

Absorption↗
PubMed2000

Testosterone and year-round territorial aggression in a tropical bird.

Testosterone (T) regulates avian behaviors such as song and aggression during the breeding season. However, the role of T in year-round territorial birds is still enigmatic, especially in tropical birds. Spotted antbirds (Hylophylax n. naevioides) defend territories in the Panamanian rainforest year-round but have low plasma T levels (0.1-0.2 ng/ml), except during brief periods of social challenges. We manipulated T action in captive male Spotted antbirds to test whether this hormone is involved in the regulation of song and aggression. T-implants increased plasma androgen levels (T and dihydrotestosterone) and enhanced song in nonbreeding males. During a staged male-male encounter, T-implanted males sang more and were more aggressive than controls. In a second experiment, we blocked the two known T actions: its binding to androgen receptors and its conversion into estradiol by the enzyme aromatase. For this, we administered the androgen receptor antagonist flutamide (Flut) in combination with the aromatase inhibitor 1-4-6 androstatrien-3, 17-dione (ATD) to birds in breeding condition. ATD + Flut treatment significantly elevated plasma levels of luteinizing hormone, presumably via the lack of T feedback from its receptors. ATD + Flut-treated birds gave fewer spontaneous songs than control-implanted males. During staged male-male encounters, ATD + Flut-treated males did not sing at all and showed reduced aggressive behavior. Our data indicate that T can regulate aggressive behavior in these tropical birds. Although plasma T levels can be low year-round, Spotted antbirds may use T either by secreting it briefly during social challenges, by having a high sensitivity to T action, or by enzymatically converting circulating T precursors directly at the site of action. We hypothesize that plasma T levels are kept low in these year-round territorial birds to avoid potentially detrimental effects of tonically elevated T. Future treatment of nonbreeding birds with ATD + Flut will reveal whether T is indeed involved year-round in regulating aggressive behavior.

Aggression↗
PubMed2000

Assessment of microvascular changes in Raynaud's phenomenon and connective tissue disease using colour doppler ultrasound.

OBJECTIVE: We used colour Doppler ultrasound (CDU) to differentiate primary from secondary Raynaud's phenomenon (pRP and sRP, respectively) and to assess digital vascular damage in patients with connective tissue disease (CTD). METHODS: Vascularity in the nailbeds of 15 healthy controls and 35 patients with CTD (systemic sclerosis or systemic lupus erythematosus) was quantified using a multi-D array transducer before and after cold and warm challenge, respectively. The results were compared with the clinically evaluated initial skin lesions. Vascularity was compared similarly between 10 pRP and 22 sRP patients. RESULTS: Vascularity at ambient temperature differed between healthy subjects and sRP patients as well as between healthy subjects and CTD patients without initial skin lesions. Patients with pRP had normal vascularity at ambient temperature but differed from healthy controls in response to a dynamic temperature challenge. CDU confirmed the clinical evaluation in 89.4% of the patients with RP and in 78.0% of the skin lesions. CONCLUSION: The novel CDU technique presented here makes it possible to discriminate between pRP and sRP and to quantify vascular changes in CTD patients.

Adult↗
PubMed1999

Evaluation of pannus and vascularization of the metacarpophalangeal and proximal interphalangeal joints in rheumatoid arthritis by high-resolution ultrasound (multidimensional linear array).

OBJECTIVE: To evaluate the extent of intraarticular vascularization and pannus formation in metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of patients with rheumatoid arthritis (RA) by high-resolution ultrasound (US). METHODS: A newly developed, high-resolution multidimensional linear array US was utilized to obtain longitudinal and transverse scans of joints with active RA (n = 21), moderately active RA (n = 39), or inactive RA (n = 93), and of joints from healthy controls (n = 120). RESULTS: Healthy joints had no detectable pannus, whereas pannus could be detected in 52% of the joints with active RA, 82% of the joints with moderately active RA, and 67% of the joints with inactive RA. There was a significant difference in vascularization in the joints of all subgroups of RA patients and those of healthy subjects (P < 0.001). Moreover, vascularization differed significantly among the RA subgroups: inactive versus moderately active RA (P < 0.02) and inactive versus active RA (P < 0.05). Both pannus and vascularization appeared to be localized preferentially on the radial side of the joints. CONCLUSION: Evaluation of pannus and the extent of vascularization within the joints of patients with RA by high-resolution US might be helpful in the assessment of disease activity, and thus influence therapeutic strategies.

Adult↗
PubMed1999

Gender and aesthetic norms in popular hygienic culture in Germany from 1900 to 1914.

The paper concerns the construction of gender norms in popular hygienic literature at the turn of the century. It argues that the formulation of aesthetic gender norms for women's and men's bodies was a response to social developments which were perceived as a threat to the middle-class ideology of separate spheres for the sexes. Concerns about the blurring of gender distinctions were expressed in the aesthetic idiom of the educated middle class. Aesthetic norms for each sex were established and contrasted with the degenerate body forms of contemporaries. The spectre of masculinized women and feminized men was raised, reflecting a deep-seated uneasiness about changing gender roles and identities. The increasing assertiveness of women as expressed in feminist activism was interpreted by anti-feminist authors as a sign of degeneracy. For these authors any articulation of self-interest by women was suspect. Strong sexual desires of women which could serve as the basis for the independent articulation of female sexual interests were denied or declared as abnormal. Feminist critics argued that it was the lack of economic and social independence of women which was the reason for the declining health and beauty of the female sex.

Esthetics↗
PubMed1997

Adjustment of house sparrow circadian rhythms to a simultaneously applied light and food zeitgeber.

Periodic food availability has been shown to be an effective circadian zeitgeber in many vertebrates. It is still unclear, however, i) whether light-active species like most birds can synchronize with food cycles in the presence of a strong light-dark (LD) cycle and ii) whether it is common among non-mammalian vertebrates to use a separate circadian oscillator to synchronize with food cycles as most mammals do. We investigated these questions experimentally by exposing house sparrows simultaneously to two zeitgebers: light and food. The LD cycle was set at 1410 h; food was always available for 12 hour per day, but at different phases of the LD cycle. The effects of the two zeitgebers were analyzed by observing two behavioral outputs of the birds' circadian system, the rhythms of locomotion and feeding. The data revealed that light acted as the dominant zeitgeber in most conditions. Food cycles affected the phase of the behavioral rhythms of the birds only when the food was presented no later than 3 h after the onset of light. Apart from their synchronizing actions both light and food cycles also exerted direct (masking) effects on the behavioral rhythms of the birds. The results suggest that the circadian system of house sparrows can indeed adjust to two simultaneous environmental periodicities, i.e. light and food. We propose that light is the stronger zeitgeber and plays a 'permissive' role in determining the phases at which synchronization with food cycles comes into effect. We did not find evidence that the house sparrows' behavioral rhythms are controlled by a food-entrainable circadian oscillator that is distinct from the light-entrainable system as is the case in most mammals. The differences in the patterns of food synchronization and organization of the circadian system that appear to exist between different species can be interpreted in two ways: i) species of different phylogenetic origin (e.g., mammals versus birds) evolved different circadian system or ii) regardless of phylogeny, species with different ecological requirements show a specialization in their circadian organization which is adjusted to the importance of zeitgebers in nature.

Adaptation, Psychological↗
PubMed1997

Melatonin: generation and modulation of avian circadian rhythms.

The pineal organ and its hormone melatonin are significant components of avian circadian pacemaking systems. In songbirds, pinealectomy results in the abolition or destabilization of overt circadian rhythms such as the rhythm of locomotor activity, feeding, or body temperature. A stable rhythmicity can be restored either by reimplanting a pineal organ, by periodic injections or infusions of melatonin, or by applying melatonin rhythmically through the drinking water. Several results suggest that the pineal melatonin rhythm acts on at least one other oscillator within the circadian pacemaking system, presumably the SCN, which in turn, feeds back to the pineal. As described by the "Neuroendocrine Loop" and "Internal Resonance" models, overall pacemaker output thus depends on the relative strengths of the oscillations in the pineal and the SCN. Investigations on migratory birds have shown that the amplitude of the 24-h plasma melatonin rhythm is reduced during the migratory seasons compared with the nonmigratory seasons. According to the models mentioned above, such a reduced melatonin amplitude should result in a reduction in the degree of self-sustainment of the pacemaker as a whole. This, in turn, should facilitate adjustment to the altered Zeitgeber conditions encountered by these birds as a result of their own migratory flights. A seasonal reduction in melatonin amplitude also occurs in some high-latitude birds during midsummer and midwinter. Under such conditions a less self-sustained circadian pacemaker may enhance entrainability to weak zeitgeber conditions. These examples suggest that the properties of the circadian system may be adjusted to match the changing requirements for synchronization, and that this is achieved by altering the melatonin amplitude.

Animals↗
PubMed1996

Food as a circadian Zeitgeber for house sparrows: the effect of different food access durations.

House sparrows (Passer domesticus) can synchronize their circadian rhythms of locomotion and feeding with times of periodic food availability. In contrast to most mammals, which synchronize only a specific part of their circadian system with feeding cycles and thus express two distinct activity components, house sparrows synchronize their circadian activity rhythms as a whole with the food zeitgeber. Previous results had indicated that feeding cycles act as comparatively weak zeitgebers for house sparrows. In the present study, therefore, we investigate whether feeding schedules are weak zeitgebers in general or whether their impact on the circadian system of the birds depends on the degree of food restriction. A detailed analysis of the synchronization pattern under the different experimental conditions should help to clarify whether house sparrows use a different mechanism for food-synchronization than mammals. House sparrows were kept in continuous dim light and exposed to different feeding schedules with daily food access durations ranging from 8 to 20 h. Many birds lost synchronization and exhibited free-running rhythms in locomotor and feeding activity when the daily food access duration was lengthened but became synchronized when the feeding duration was shortened. The interpretation that short food access durations represent stronger zeitgebers than long food access durations was supported by the occurrence of large negative phase-angle differences during long daily feeding schedules, contrasting with small and sometimes positive phase-angle differences under short food access durations. There were no indications that house sparrows possess a specific food-entrainable circadian oscillator as mammals do. Rather, periodic food availability seems to be a zeitgeber for the whole circadian system, which, hence, can be synchronized both by light and food. An explanation for such different mechanisms of food-synchronization is offered in the feeding ecology of these animals. Birds may evaluate the importance of a specific feeding schedule as a zeitgeber either from temporal information on the duration of the daily food access time or from energetic considerations. The phase-angle differences associated with the different feeding schedules and the maintenance of daily activity times may ensure an appropriate temporal integration of behavior with specific conditions. Non-synchronized birds exhibited masking-induced feeding activity, which might represent an alternative means of adjusting to feeding cycles when synchronization cannot occur.

Animals↗
PubMed1995

Continuous melatonin administration accelerates resynchronization following phase shifts of a light-dark cycle.

Circadian rhythms of most passerine birds and some reptiles depend to a considerable extent on the presence of periodic melatonin, which is considered to be part of the central pacemaking system. Recent results on house sparrows have suggested that melatonin, apart from its periodic effects on the circadian system, may also exert effects derived from a constant action: Continuous melatonin applied through subcutaneously implanted silastic tubing enhanced the synchronization response to a low-amplitude light-dark zeitgeber, indicating some kind of sensitization to zeitgeber stimuli. In the present study we tested the prediction derived from these results, that speed of resynchronization after a phase shift of a light-cycle should be enhanced if melatonin is continuously administered. We found that, indeed, house sparrows required less time to resynchronize to an 8 h advance or delay phase shift of a low-amplitude light-dark cycle while carrying a silastic implant filled with melatonin than while carrying an empty implant. The effect is suggested to result from either one or a combination of the following mechanisms: (i) An increased circadian visual sensitivity, (ii) a diminished amplitude of the circadian oscillation, iii) an altered feedback of the locomotor activity to the oscillatory system.

Animals↗
PubMed1995

Is there an endogenous tidal foraging rhythm in marine iguanas?

As strictly herbivorous reptiles, Galápagos marine iguanas graze on algae in the intertidal areas during low tide. Daily foraging rhythms were observed on two islands during 3 years to determine the proximate factors underlying behavioral synchrony with the tides. Marine iguanas walked to their intertidal foraging grounds from far-off resting areas in anticipation of the time of low tide. Foraging activity was restricted to daytime, resulting in a complex bitidal rhythm including conspicuous switches from afternoon foraging to foraging during the subsequent morning when low tide occurred after dusk. The animals anticipated the daily low tide by a maximum of 4 h. The degree of anticipation depended on environmental parameters such as wave action and food supply. "Early foragers" survived in greater numbers than did animals arriving later at foraging sites, a result indicating selection pressure on the timing of anticipation. The timing of foraging trips was better predicted by the daily changes in tabulated low tide than it was by the daily changes in actual exposure of the intertidal foraging flats, suggesting an endogenous nature of the foraging rhythms. Endogenous rhythmicity would also explain why iguanas that had spontaneously fasted for several days nevertheless went foraging at the "right" time of day. A potential lunar component of the foraging rhythmicity of marine iguanas showed up in their assemblage on intertidal rocks during neap tide nights. This may indicate that iguanas possessed information on the semi-monthly rhythms in tide heights. Enclosure experiments showed that bitidal foraging rhythms of iguanas may free run in the absence of direct cues from the intertidal areas and operate independent of the light:dark cycle and social stimuli. Therefore, the existence of a circatidal oscillator in marine iguanas is proposed. The bitidal foraging pattern may result from an interaction of a circadian system with a circatidal system. Food intake or related stimuli may be used as tidal zeitgebers in synchronizing the foraging rhythms of these reptiles under natural conditions.

Animals↗
PubMed1992

Circadian entrainment by feeding cycles in house sparrows, Passer domesticus.

We studied the potential zeitgeber qualities of periodic food availability on the circadian rhythms of locomotor and feeding activity of house sparrows. The birds were initially held in a LD-cycle of 12:12 h, with food restricted to the light phase. After transfer to constant dim light, the birds remained entrained by the restricted feeding schedule. Following an exposure to food ad libitum conditions, the rhythms could be resynchronized by the feeding cycle. Shortening of the zeitgeber period to 23.5 h resulted in the loss of entrainment in most birds, whereas a longer zeitgeber period of 25 h re-entrained the rhythms of most birds. Although these results prove that periodic food availability can act as a zeitgeber for the circadian rhythms of house sparrows, several features of our data indicate that restricted feeding is only a weak zeitgeber. The pattern of feeding activity prior to the daily time of food access shown under some experimental conditions suggests that anticipation is due to a positive phase-angle difference of the birds' normal circadian system rather than being caused by a separate pacemaker.

Animals↗