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Biomedical subjects

H Montenegro

Publications and source records attributed to H Montenegro.

18 recordsLinked to original sources
PubMed2006

Fitness effects of Wolbachia and Spiroplasma in Drosophila melanogaster.

Maternally inherited endosymbionts that manipulate the reproduction of their insect host are very common. Aside from the reproductive manipulation they produce, the fitness of these symbionts depends in part on the direct impact they have on the female host. Although this parameter has commonly been investigated for single infections, it has much more rarely been established in dual infections. We here establish the direct effect of infection with two different symbionts exhibiting different reproductive manipulation phenotypes, both alone and in combination, in the fruit fly Drosophila melanogaster. This species carries a cytoplasmic incompatibility inducing Wolbachia and a male-killing Spiroplasma, occurring as single or double (co-) infections in natural populations. We assessed direct fitness effects of these bacteria on their host, by comparing larval competitiveness and adult fecundity of uninfected, Wolbachia, Spiroplasma and Wolbachia-Spiroplasma co-infected females. We found no effect of infection status on the fitness of females for both estimates, that is, no evidence of any benefits or costs to either single or co-infection. This leads to the conclusion that both bacteria probably have other sources of benefits to persist in D. melanogaster populations, either by means of their reproductive manipulations (fitness compensation from male death in Spiroplasma infection and cytoplasmic incompatibility in Wolbachia infection) or by positive fitness interactions on other fitness components.

Animals↗
PubMed2005

Male-killing Spiroplasma naturally infecting Drosophila melanogaster.

Elucidation of the mechanism of action of selfish genetic elements is difficult outside species with well-defined genetics. Male-killing, the phenomenon whereby inherited bacteria kill male hosts during embryogenesis, is thus uncharacterized in mechanistic terms despite being common and important in insects. We characterized the prevalence, identity and source of the male-killing infection recently discovered in Drosophila melanogaster in Brazil. Male-killing was found to be present in 2.3% of flies from Recife, Brazil, and was uniquely associated with the presence of Spiroplasma infection. The identity of sequences across part of the 16S and across the 16S-23S ITS region indicated that the male-killing infection of D. melanogaster was very closely related to S. poulsonii, the source of the male-killing infection in willistoni group flies also found in South America. The sequences of two further protein-coding genes indicated the D. melanogaster infection to be most closely related to that found in D. nebulosa, from the willistoni group. Our data suggest that the establishment of D. melanogaster in South America was associated with the movement of male-killing bacteria between species.

Animals↗
PubMed2000

Male-killing selfish cytoplasmic element causes sex-ratio distortion in Drosophila melanogaster.

Sex ratio distortion induced by a male-killing agent has been found to affect Drosophila melanogaster. The trait was discovered accidentally in a collection of flies from markets in Campinas, São Paulo State, Brazil. Repeated crosses with Canton-S males (for 15 generations to date) and successful transmission using the injection of macerates of sex ratio flies, have shown that the trait is inherited maternally, is cytoplasmic and is infectious. Crosses with strains marked with the visible mutation white and viability experiments at pre-adult stages of development, indicate that the skewed sex ratio results from male mortality before hatching. Males do not transmit the trait to their progeny.

Animals↗
PubMed2000

Environmental isolation of Cryptococcus neoformans var. gattii and C. neoformans var. neoformans in the city of São Paulo, Brazil.

In order to determine the environmental occurrence of both varieties of Cryptococcus neoformans in the city of São Paulo, pigeon droppings and vegetable material from trees of the genus Eucalyptus were collected at typically crowded places. A total of 38 sites downtown where large heaps of pigeon droppings could be found were selected for sampling. Pigeon droppings from 10 (26.3%) of these sites were positive for C. neoformans var. neoformans in at least one sample. Twelve eucalyptus woods located within four municipal parks were also surveyed; vegetable material from Eucalyptus spp. trees were collected monthly over a 2-year period. C. neoformans var. gattii was recovered from a wood in Ibirapuera Park during the same season on two different occasions (November 1996 and November 1997); this park contained specimens of Eucalyptus camaldulensis, a natural habitat of C. n. var. gattii. C. n. var. neoformans was detected in a wood in Ibirapuera Park and Aclimação Park. The results show that both C. n. var. neoformans and C. n. var. gattii are present in the urban environment of São Paulo city at sites where large numbers of people normally gather.

Animals↗
PubMed2000

[Sex education of children and adolescent].

There is a remarkable ignorance about sexuality among Chilean teenagers, as underscored by the paper by Fernández et al, published in this issue. The authors analyze the biological, psychological and social consequences of the lack of parental and school sexual education. Among them, there is an increasing incidence of unwanted pregnancies, abortions and sexually transmitted diseases in teenagers. Child abuse, neglect, battering, mortality and maternal deprivation are more frequent among the offspring of teenage parents. School desertion caused by unwanted pregnancies will seriously jeopardize the education and training of these teenagers, perpetuating the cycle of poverty.

Adolescent↗
PubMed1995

The cost-effectiveness of a special care unit to care for the chronically critically ill.

To assess the relative value of healthcare programs, technologic innovations, and clinical decisions, policymakers are searching for ways to evaluate cost-effectiveness. What constitutes cost-effectiveness and how should it be measured? The authors discuss ways in which the cost-effectiveness of clinical programs can be measured and describes various methods of assessing both costs and effectiveness. Comparison of the cost-effectiveness of a nurse managed special care unit with that of traditional intensive care units illustrates some of these methods.

Chronic Disease↗
PubMed1987

The impact of age on utilization of intensive care resources.

The impact of age on admission practices and pattern of care were examined in 599 admissions to a medical intensive care unit (MICU) and 290 patients on the conventional medical care divisions of the same hospital. Four age groups were compared: under 55, 55 to 64, 65 to 74, and 75 years of age and over. Severity of illness and prior health were assessed using the Acute Physiology Score (APS) and the Chronic Health Evaluation (CHE) instruments. Resource utilization was assessed using the Therapeutic Intervention Scoring System (TISS) and hospital charges. Patients 65 years of age and over comprised 48% of the MICU sample. The distribution of CHE was different among the four groups. Twenty-one percent of patients under 55 years of age had no prior chronic illness, as compared to less than 8% of older patients. The APS at admission was similar for all age groups, as was admission, daily, and total TISS. Hospital survival declined with age from 85% to 70%, while the likelihood of being designated do not resuscitate (DNR) increased from 10% to 24%. Differences in hospital survival disappeared when controlling for severity of illness and prior health, but differences in DNR status did not. Still, elderly DNR patients received as much resources as younger DNR patients and this was more than non-DNR patients. The sample of patients treated on conventional medical divisions had age distribution similar to the MICU sample. There was some evidence that admission APS (median, 5, 5, 6, 6, respectively, P = .055) and maximum APS (median, 5, 5, 7, 8, respectively, P = .023) differed slightly across age groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1987

[Prevalence of mental disorders in the schoolchild population of Santiago de Chile].

A prevalence of approximately 15% of behavioral and emotional problems in children was discovered in a representative sample of Santiago, Chile, primary school population (N = 517). Population's data: boys and girls from three different socio-economic levels, ages 6 to 11. T. Achenbach's Child Behavior Checklist -which was previously standardized in Chile- was the selected instrument. The results show the percentage of children with either high total scores -thus indicating a grossly deviated behavioral profile- or high partial scores in the 9 behavioral categories proposed for both boys and girls. Sex related differences are reported as well as a negative correlation between SES and a percentage of children with deviated profiles. The likeness of an underevaluation of the current prevalence is discussed as well as the impact the child pathology is bound to have on both family mental health and the 'future' adult person.

Age Factors↗
PubMed1984

Conditioning of the diaphragm with phrenic nerve stimulation after prolonged disuse.

We studied the effect of electrical stimulation of the phrenic nerve on the force frequency relationship of the disused diaphragm. A high quadriplegic who had been totally ventilator dependent for 6 months following a C2 fracture received bilateral phrenic nerve stimulators. During a 6-wk period of conditioning by electrical stimulation, the force of diaphragm contraction was assessed by measurement of transdiaphragmatic pressures during stimulation of each nerve over a range of frequencies. Tidal volume as well as rib cage and abdominal motion were studied. There was an upward shift of the force frequency relationship of the diaphragm over the 4-month period of phrenic nerve pacing using repetitive stimulus trains of 14 to 28 Hz. This improvement appeared to plateau at about 11 wk. The increase in contractility was accompanied by a progressive diminution in the stimulus frequency at which fusion of the contraction occurred. The disused diaphragm, like other skeletal muscle, may be conditioned with electrical stimulation.

Aminophylline↗
PubMed1981

Shortening fraction: its dependence on the Starling mechanism.

The influence of increasing muscle length (ML) from L0 to 15 to 20% of L0 and calcium concentration (Ca2+) from 1.34 to 10 mmol . litre-1 on shortening fraction has been analysed in cat papillary muscles. Shortening fraction was calculated by dividing the amount of shortening by the muscle length at which that shortening occurred. When the muscle shortened at contrast total load, increasing muscle length from approximately or equal to L0 to approximately or equal to 15% above L0, increased the shortening fraction from 0.2 +/- 0.1% to 7.1 +/- 0.7% (P less than 0.01) and from 1.0 +/- 0.5% to 12.2 +/- 0.5% (P less than 0.01) at low and high (Ca2+) respectively. The highest shortening fraction values obtained (7 and 12%) correspond to calculated ejection fraction values of 20 and 32% respectively. At a given muscle length, increasing (Ca2+) significantly increased the shortening fraction (P less than 0.01). At constant afterload the shortening fraction increased from 3.5 +/- 1% to 9.1 +/- 1.9% when the muscle length changed from approximately or equal to 5% to approximately or equal to 20% above L0 and from 3,3 +/- 1.6% to 14.3 +/- 0.7% when the muscle was stretched from L0 to approximately or equal to 20% above L0 at low and high calcium respectively. Shortening fraction values of 9 and 14% correspond to calculated ejection fraction values of 25 and 37% respectively. The results indicate that the shortening fraction is altered not only by changes in cardiac contractility but also by the Starling mechanism.

Animals↗
PubMed1978

Papillomas of the tracheobronchial tree with malignant degeneration.

Papillomas are rare tumors of the respiratory tract, which are usually considered benign. We studied a male patient with adult onset of squamous papillomatosis involving both the trachea and the bronchi, with malignant degeneration. When we obtained specimens bronchoscopically, only the bronchial lesions showed carcinomatous changes. Thoracotomy demonstrated carcinoma in the tracheal lesion as well. We conclude that transbronchoscopic biopsy may be inadequate in the evaluation of papillomatosis.

Bronchi↗
PubMedDate not supplied

Low temperature cure of a male killing agent in Drosophila melanogaster.

Environmental factors can affect transmission or phenotype expression of selfish cytoplasmic endosymbionts such as embryonic male killers. Temperature is one factor that usually affects the transmission rate of selfish cytoplasmic endosymbionts. Heat cures have been described for several host-parasite systems, cold cures, however, are rare. We report a temperature cure of the Drosophila melanogaster male-killing agent, which occurs when flies are raised at 16.5 degrees C. Flies grown at 20, 24, and 28 degrees C maintained an extremely female biased sexual proportion.

Animals↗