Possible evidence for shift work schedules in the media workers of the ant species Camponotus compressus

The locomotor activity rhythm of the media workers of the ant species Camponotus compressus was monitored under constant conditions of the laboratory to understand the role of circadian clocks in social organization. The locomotor activity rhythm of most ants entrained to a 24 h light/dark (12:12 h; LD) cycle and free-ran under constant darkness (DD) with circadian periodicities. Under entrained conditions about 75% of media workers displayed nocturnal activity patterns, and the rest showed diurnal activity patterns. In free-running conditions these ants displayed three types of activity patterns (turn-around). The free-running period (τ) of the locomotor activity rhythm of some ants (10 out of 21) showed period lengthening, and those of a few (6 out of 21) showed period shortening, whereas the locomotor activity rhythm of the rest of the ants (5 out of 21) underwent large phase shifts. Interestingly, the pre-turn-around τ of those ants that showed nocturnal activity patterns during earlier LD entrainment was shorter than 24 h, which became greater than 24 h after 6-9 days of free-run in DD. On the other hand, the pre-turn-around τ of those ants, which exhibited diurnal patterns during earlier LD entrainment, was greater than 24 h, which became shorter than 24 h after 6-9 days of free-run in DD. The patterns of activity under LD cycles and the turn-around of activity patterns in DD regime suggest that these ants are shift workers in their respective colonies, and they probably use their circadian clocks for this purpose. Circadian plasticity thus appears to be a general strategy of the media workers of the ant species C. compressus to cope with the challenges arising due to their roles in the colony constantly exposed to a fluctuating environment.     

Some peculiarities of the rotator cuff muscles

The authors studied the origin, course and insertion as well as some peculiarities of RC muscles on 25 cadaverous fixed limbs. They discovered that RC muscles exchange muscle bundles and are secured by synovial sheaths. They described the articular muscles in all of the observed muscles, including the deltoid muscle, which significantly stretch the capsule of the glenohumeral joint. They expressed the opinion that the subscapular bursa enhances motions in the shoulder joint. Due to the possibilities of arthroscopic diagnostic and treatment methods, they are convinced that more attention must directed to this issue from both the morphological and functional perspective.     

Circadian rhythms of physiological functions in men and women as related to shift work

Operators of both sexes employed in the pulp industry were examined during a triple-shift cycle of shift work. Changes in the body temperature, heart rate, blood pressure, and sensorimotor coordination parameters were used as indicators of the circadian rhythms of their physiological functions. Sex-related differences were found with respect to a number of parameters (the muscular strength, critical flicker frequency, duration of the performance of a coordination test and coordination index, blood pressure and autonomic index, and physical general condition and mood scores). Fatigue in this type of operator activity was efficiently detected by the general condition, activity, mood (WAM) test score (especially in women), the number of errors in the test for sensorimotor coordination, and the coordination index.     

A cross-sectional study of the health effects of work schedules on 3212 hospital workers in France: implications for the new French work schedules policy

This study was designed to investigate the effects of work schedules on the health of hospital workers at the Assistance Publique-H?pitaux de Paris (AP-HP). Out of 40 hospitals, 17 volunteered to participate in this study. The Standard Shiftwork Index and a questionnaire concerning physicians' work schedules were used. Ten thousand questionnaires were distributed anonymously to hospital workers between March and April 1999. Professional categories comprised head nurses, nurses, nursing auxiliaries, hospital agents, midwives and full time physicians. Departments included internal and geriatric medicine, general paediatrics, orthopaedic and general surgery, operating and emergency rooms, and anaesthesiology and intensive care units. 3250 questionnaires were returned. Demographics for the respondents were: 79.2% female, average age 38.1 +/- 9.1 years old. Eleven work schedules were identified. One fourth of the personnel had fixed morning work schedules. The highest level of job satisfaction was found in personnel working in paediatrics while dissatisfaction was strongest in the gerontology and, emergency room personnel. General Health Questionnaire (GHQ) scores were high for head nurses, operating room nurses and junior doctors as well as for personnel with rotating and flexible shifts. This study will be used to make recommendations concerning the reduction of working time for French hospital workers.     

Effect of floating nest platforms on the breeding performance of Black Terns

ABSTRACT.   In 2003 and 2004, we placed 41 floating nest platforms on Grassy Lake in southeastern Wisconsin (USA) to test the hypothesis that reproductive success of Black Terns ( Chlidonias niger ) is limited by the quality of suitable nesting habitat. Extreme differences in water levels between these 2 yr provided a natural experiment to evaluate the effectiveness of the nest platforms during a drought year (2003) when natural nesting substrate was abundant, and a flood year (2004) when natural substrate was limited during the peak nesting period. Terns nested on 27 of 41 (66%) of the platforms in 2003 and 26 of 41 (63%) in 2004. No difference in the occupancy rate of platforms and natural nests was evident in 2003, but the pattern of clutch initiations early in the season in 2004 indicated that platforms were preferred over natural substrates. In 2003, nest survival rates did not differ between nests placed on platforms and those placed on natural substrates, but platform nests had significantly higher hatching success and nest survival rates in 2004. Both the Kaplan-Meier and Apparent Nest Success methods of calculating nest survival provided similar estimates. In both years, eggs laid on platforms were significantly larger than those laid on natural substrates, suggesting that platforms were occupied by high-quality birds. Our study indicates that floating nest platforms can be an effective management tool to enhance nesting habitat for Black Terns and other aquatic birds that construct floating nests, primarily because platforms provide nest sites when natural sites are not available due to flooding. Nest platforms also may be useful for addressing questions concerning habitat selection and parental quality.     

Some peculiarities of the dynamics of the immunoglobulin M structure

The isotropic mobility of separate regions of the intact molecule of immunoglobulin M (IgM) and its Fab and (Fc)5 fragments was studied using spin-labeling of carbohydrate (2,2,6,6-tetramethyl-4-aminopiperidine-1-oxyl) and peptide (2,2,5,5-tetramethyl-3-dichlorotriazinylaminopyrrolidine-1-oxyl) moieties. The spin-labeled oligosaccharide groups (OGs) in the Fab region are shown to have much more amplitude of anisotropic motion than those in the (Fc)5 region. The spin label in the latter is evidently attached in the C mu 3 domain to one of its OGs which is probably stabilized by ionic contacts between terminal N-acetylneuraminic acid residue and the peptide moiety of the IgM molecule. When the amount of the glycosidase-cleaved carbohydrate does not exceed 10-15%, most OGs affected are of the Fab region. Upon profound splitting (greater than or equal to 50%) the OGs of the (Fc)5 region are also affected; that results evidently in loosening the ionic contacts between the shortened OGs and the peptide moiety of IgM, and consequently in increasing mobility of the former. The structure of the (Fc)5 region of IgM is labile; after detaching this moiety from the intact IgM molecule, its structure is stabilized, but one of its domains (C mu 3) becomes more mobile than it is in the intact IgM molecule; at the same time the amplitude of anisotropic motion of OG bound here is decreased. In the latter case, this decrease depends on the sequence of spin-labeling and fragmentation. The most probable cause of stabilization of the (Fc)5 fragment is the heating of IgM solution to 56 degree C during fragmentation with trypsin. At this temperature the tau value for the (Fc)5 fragment is unusually low, equaling 23 ns. The spin-labeling in the peptide part of IgM occurs mostly in the Fab region which is a rather rigid moiety as expected.     

Significance of early morning insomnia for keeping the work continuity of shift workers

Sleep and Biological Rhythms -     

Some peculiarities of the relationships between parasitic copepods and their invertebrate hosts

According to the rule of academican E. N. Pavlovskiy, any organism of host is an environment of inhabit for a parasite (Pavlovskiy, 1934). It was analysed, which "ecological niche" or microbiotop (= microhabitat) is occupied by this or that species of symbiotic (parasitic) copepods in organisms of different groups invertebrate-hosts. The assumption lying in a basis of the given analysis means that each group of hosts may give to cohabitants only certain variants of microbiotopes independently on the general morphological structure and life mode of hosts. Five types of microbiotops offered by various groups of hosts for symbiotic copepods are designated (Ta[symbol: see text] 2). 1. The body surface of benthic invertebrates as a microbiotope is characterized by conditions being little different (concerning any kind of physical and chemical influences on copepods) from those in external environment on any other substrate. Apparently a trophical dependence plays a determining role in this case. There are certain directions in a development of adaptations, which are characteristic in some extent for all water ectoparasitic crustaceans and have one functional task--to help to an ectoparasite to keep itself on a surface of host body. In the first, the maxillules and maxillipeds significantly are developed, they get a form of large claws, with which the dopepods are strongly attached on a surface of host body and have an opportunity to move on it without a danger to be washed off. In the second, the form of the body undergoes a dorso-ventral expression and expansion of prosome, forms a cephalic shield allowing to the symbiont to press itself tightly to the host body surface and to avoid the loss of host (tab. 2). In occasions, some ectoparasites stimulate the formation of galls in skin tissues of the host, that also provides the parasite with constant conditions, without any threat to lose the host. However, this phenomenon has not a wide distribution and is observed in some groups of crustacean and echinoderm hosts. 2. The narrow tubular cavities in the organism of host either they are a part of external environment (as in channel system of spongia) or a part of internal environment of organism (as channels of blood system or thin parts of a digestive system) have always rigidly limited sizes and form. Characteristics of all parasites occupying this microbiotopes are the strong transformations. They are expressed by the reduction of legs or any other appendages (frequently in a significant degree), loss of segmentation to some extent and in eruciform (or vermiform) form of a body (tab. 2). This microbiotope is occupied by an ectoparasite in one case only (Spongicola uncifer from channel system of spongia) and by endoparasites in all other cases. 3. Large cavities connected with external environment. The formations of various genesis, such as mantle cavity of molluscs, gill cavity and marsupium of crustaceans, bursal cavity of ophiuroids and branchial cavity of ascidians, concern this type of microbiotopes. All of them are characterized by the relative difference from the external environment and rather large volume (in comparison to sizes of copepods), that provides the parasites with a sufficient protection from factors of the external environment and constant source of food such as elements of host body or food's particles brought by the water flow. Morphological changes in inhabitants of the microbiotope have two directions. They practically are absent in the overwhelming majority copepods, living in the mantle of cavity of the lamellibranches. On the other hand, the inhabitants of gill cavity and marsupium of crustaceans, bursal cavities of ophiuroids and branchial cavity of ascidians are characterized by the presence of strong transformations. Usually there are expressed in a loss of segmentation to some extent, reduction of appendages and swelling of body, as in species of the genus Sphaeronella (tab. 2). Changes are also observed in the life cycle: the tendency to reduce stages of development (development of nauplii stage, which takes place under the ovarial cover). In this case the copepodid stages hatch from the ova. 4. The internal cavity of organism of host. This type of microbiotopes in different groups of the hosts is represented in a various degree. We recognise it in a coelome of polychaetes, lacunar system of molluscs, mixocoel of crustaceans, coelome of echinoderms and cavity of body in ascidians. Two basic evolutionary directions are observed in copepods occupying this microbiotope. In the first case, the parasite is not exposed to transformations and keeps the initial plan of structure as in ancestral free-living forms. In the second case the parasites are exposed to strong transformations, they either live directly in cavity's liquid, or are surrounded by a cyst (as in Cucumaricolidae). 5. Microbiotope of the last type is most specific. The simultaneous existence in two environments--external environment (environment of the second order) and internal environment (environment of the first order) leads to the complete loss of ancestral type in a structure and level of organisation. At the same time both morphological and functional division of the parasite body into two parts produces a new formation--the ectosome and endosome. In this case we deals with the phenomenon of mesoparasitism.