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Biomedical subjects

M D Marques

Publications and source records attributed to M D Marques.

14 recordsLinked to original sources
PubMed2000

Coupled biological oscillators in a cave insect.

Insects that live in the interior of caves show the basic internal temporal organization of coupled oscillators. An analysis is made of the coupled moulting and oviposition cycles of Folsomia candida, a cave-dwelling Collembolan, with regard to their oscillatory nature, their phase dependent responses to external perturbations, the effect of coupling on these responses, and conjecture about the link of these cycles with circadian clocks in other organisms.

Animals↗
PubMed2000

Prevalence and determinants of periodontal disease in Portuguese adults: results from a multifactorial approach.

The purpose of the present investigation was to study prevalence of periodontal disease among 30 to 39-years-old from Oporto in the north of Portugal. In addition, an attempt was made to elucidate possible periodontal disease determinants in this population. A random sample consisting of a total of 322 individuals was drawn based on electoral lists. The attendance rate was 61%. The CPITN index was used and the results indicate a high prevalence of periodontal disease and a substantial need for periodontal treatment in this population, with 41% of the individuals investigated having one or more sites with a CPITN score 4 (pockets deeper than 5.5 mm). Dental visiting habits, gender (lower CPITN scores for females) and oral hygiene were the determinants most significantly associated with variation in CPITN scores.

Adult↗
PubMed1998

Prevalence of apical periodontitis and results of endodontic treatment in an adult, Portuguese population.

The present epidemiological study is derived from a random sample of 322 residents of the Porto area, aged 30-39 years. Prevalence of apical periodontitis and results of endodontic treatment were evaluated from orthopantomograms, available from 179 of a total of 197 individuals attending for examination. The results indicated a prevalence of apical periodontitis in 27% of this population. The quality of a majority (54%) of the 69 root fillings observed were found to be inadequate, (i.e. short and/or poorly condensed), but only 15 (22%) of the endodontically treated teeth presented with apical periodontitis.

Adult↗
PubMed1996

Dental caries determinants in an adult Portuguese population and a comparison with Norwegian adults.

The present epidemiologic dental caries study indicates a high number of decayed surfaces (mean, 13.5 +/- 11.8 (SD)) in a Portuguese population of 30- to 39-year-olds from Porto. The most influential determinants for variation in carious surfaces were oral hygiene, gender, salivary buffer capacity, and missing teeth. By entering the most influential independent variables in a final multiple classification analysis, the total explained variance in carious surfaces was 27%. A comparison with results from a similar Norwegian dental health study showed that the biologic factors of importance for number of carious surfaces were the same, whereas the sociocultural determinants differed.

Adult↗
PubMed1996

Control of environmental variables in a field study using a chronobiological protocol.

Field work in chronobiology usually is based on observations which differ from those in laboratory studies which are experimental. Non-invasive protocols are recommended in the field in order not to introduce additional variables. We propose an alternative strategy here. The effect of environmental cycles on biological rhythms can be estimated when the observations are made in more than one area. The areas under study must have at least one characteristic in common which is a guarantee that the limits of oscillation of an environmental cycle will be similar. This proposal has been tested using the biological system consisting of an Onagraceae plant, Ludwigia elegans, and its bee visitors, which is found in two localities at the same latitude, but at different altitudes. Under the same photoperiod, but with the mean temperature ranging within known limits, it was possible to determine temporal characteristics of the system in the field by examining the effects of the light/dark and temperature daily cycles.

Animals↗
PubMed1994

Caries prevalence of young adults in Oslo, Norway, and Porto, Portugal. A comparative analysis.

The purpose of the present study was primarily to establish the oral health status of young adults in the area of Porto, Portugal. The assessment is based on a random sample of 30- to 39-year-olds with criteria identical to those of a Norwegian study of 35-year-olds. This makes it possible also to present a comparative analysis of the caries prevalence in Oslo, Norway, and Porto, Portugal. The results indicate lower DMF scores among the Portuguese (DMFS = 46.2) than the Norwegian (DMFS = 85.0) adults. The difference is primarily due to a greater number of filled surfaces among the Norwegians (FS = 59.7) than the Portuguese (FS = 4.4). However, carious surfaces are more prevalent among Portuguese than Norwegian adults (DS = 9.2 versus DS = 3.3). Both among Portuguese and Norwegian adults, oral hygiene and dental visits seem to play an important role with regard to the prevalence of decayed surfaces. Decayed surfaces were more prevalent among men than women, and a correlation between social status and prevalence of decayed surfaces was present in both societies.

Adult↗
PubMed1994

Masking and the evolution of circadian rhythmicity.

In spite of the clear-cut temporal features exhibited by most species, temporal characteristics have merited little attention from evolutionists. However, it is logical to assume that since the environment oscillates cyclically, organisms that adapt to it must also oscillate; that is, cyclic factors have a clear evolutionary role. This article discusses evidence that the timing system is genetically determined; the role of environmental cues such as zeitgebers and masking factors; the temporal basis of mating; and masking as a disorganizing factor.

Animals↗
PubMed1994

From circadians of the fifties to chronomes in vitro as in vivo.

In a recent review of cellular mechanisms of entrainment, an ocular circadian rhythm of Bulla was reported (1). The isolated retina of this marine mollusk is described to contain a circadian oscillator. A glance at the spontaneous impulse frequency from eyes recorded in darkness at 15 degrees C suggests lower-frequency modulations of the about 24-h rhythm and prompts the quantitative assessment of the broader time structure, the chronome, in this extensively used model of a budding neurochronophysiology. The cultured retina of mollusks is interpreted by the original authors as descriptive of similar cellular mechanisms that may underlie mammalian as well as molluscan physiology. We report here the rhythmometric analysis of the original data by Block et al. (2), taken from Figure 2 of the article by Colwell et al. (1), resolved by computer just as the microscope resolves cellular structure. The results are further compared with those obtained on data kindly provided by Stephan Michel on another retina of Bulla. The findings of multiple chronome components (beyond the circadian system) are placed into the broader context of cell biophysics and its implications for biomedicine within the scope of an international chronome endeavor.

Action Potentials↗
PubMed1993

Chronobiologic aspects of a coadaptive process: the interaction of Ludwigia elegans flowers and their more frequent bee visitors.

Field observations spanning 1 year of the visits of two bee species--Tetraglossula bigamica (Hymenoptera: Colletidae) and Pseudagapostemon brasiliensis (Hymenoptera: Halictidae)--to the flowers of Ludwigia elegans (Onagraceae) evinced the existence of circadian and circannual components in the rhythms of activity both of plant and bees. In addition to morphological adaptations to the flower, the bees were temporally adjusted to each other and to the flower's opening and closing mechanisms. At the observation locality (Ribeirão Preto, São Paulo, Brazil--latitude 21 degrees-21 degrees 30S), the plant bloomed year-round. The flowers of the same population open simultaneously at the onset of the photophase, pollen and nectar being available almost immediately. Withering occurs in the afternoon of the same day. Although many bee species visited the flowers, T. bigamica and P. brasiliensis were the most frequent visitors, but their yearly rhythms were phased opposite to one another. Circadian rhythms were detected in pollen and nectar harvest. Comparisons of acrophases showed significant differences for males' and females' nectar collecting rhythm and for females' pollen harvest rhythm. As for the circannual component, acrophases of all rhythms occur at progressively later times from December to July when the migration is reversed until November. These data strongly suggest that the relationship between L. elegans and T. bigamica and P. brasiliensis is in accordance with a clearly temporal pattern and that the two bee species are temporally separated in nature.

Adaptation, Physiological↗
PubMed1987

Chronobiologic view of molt and longevity of Folsomia candida (Collembola) at different ambient temperatures.

A reanalysis of data published earlier indicates that the springtail, Folsomia candida, kept in continuous darkness, lengthens its intermolt interval (stadia) with age. At an environmental temperature of 21 degrees or 26 degrees C, the early stadia show an about-half-weekly or circasemiseptan interval and later stadia an about-weekly or circaseptan intermolt interval. At 15 degrees C, early stadia are about circaseptan, lengthening to nearly circadiseptan with aging. Our own studies of Folsomia candida at 23 degrees C show that the incidence of molting in 24 springtails observed at 3-hr intervals for 17 days is characterized by a prominent circadian rhythmicity and an infradian periodicity with a period of about 3 days. Both components are statistically highly significant (P = 0.001) when assessed concomitantly by least-squares rhythmometry.

Aging↗
PubMed1987

Life span of springtail on 12-hr shifts at varying intervals of 12-hr alternation in ambient temperature.

The effect of shifts at different intervals of a regimen of quasioptimal and nonoptimal ambient temperatures alternating at 12-hr intervals was tested on the springtail, Folsomia candida. Life span data demonstrate that shifts of the temperature regimen can be optimized to prolong life rather than to shorten it or to leave it unaffected. Optimal shift intervals are 7 days apart, in keeping with the results on effects of shifts of a regimen of alternating light and darkness in a giant alga, Acetabularia mediterranea, and in the face fly, Musca autumnalis.

Acetabularia↗
PubMed1983

Sexual behavior elicited in cage-mates of olfactory tubercle stimulated rats.

Fourteen male albino rats kept in pairs were implanted with bipolar electrodes in the olfactory tubercle. Electrical stimulation elicited a behavioral change in the cage-mates of the stimulated rats. This change consisted of increased exploratory activity in six animals. In three of these six rats, sexual behavior with mounting and pelvic thrusting was observed. The changes are described and discussed with special attention to sexual behavior.

Animals↗
PubMedDate not supplied

Experimental models for the study of chronoimmunomodulation (rhythms of the springtail Folsomia candida, Collembola: Isotomidae).

A third-generation cephalosporine, cefodizime, was tested in two experiments on the springtail, Folsomia candida, used as a model of infradian rhythmicity. Any effect on ecdysis (molt), oviposition and oviproduction was sought for 6, 20 or 60 ng of cefodizime administered with brewer's yeast every other day, as compared to controls given only the yeast. Results indicate that a 20-ng dose of cefodizime on alternate days may shorten an infradian period (of molt) in the springtail.

Adjuvants, Immunologic↗