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1.
Contraception ; 2018 Apr 17.
Artículo en Inglés | MEDLINE | ID: mdl-29678366

RESUMEN

PURPOSE: To explore the acceptability of advance provision of emergency contraceptive pills (ECPs) to young men seeking health care. METHODS: For this exploratory study in a clinic setting, we approached young men aged 16-35 to participate in a survey eliciting socio-demographics, sexual and contraceptive history, and knowledge about ECPs. We offered young men advance provision of ECPs and compared characteristics of 126 young men who did and did not accept the ECPs. RESULTS: Most (76%) of the participants accepted advance provision and left with an ECP pack, with even higher proportions among males whose sexual histories were suggestive of increased risk of involvement in an unintended pregnancy. CONCLUSIONS: This study holds promise to inform scale up of advance provision of ECPs among young men.

2.
AJNR Am J Neuroradiol ; 36(7): 1303-9, 2015 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-25857761

RESUMEN

BACKGROUND AND PURPOSE: The advent of modern neuroendovascular techniques has highlighted the need for a simple, effective, and reliable brain arteriovenous malformation endovascular grading scale. A novel scale of this type has recently been described. It incorporates the number of feeding arteries, eloquence, and the presence of an arteriovenous fistula component. Our aim is to assess the validity of this grading scale. MATERIALS AND METHODS: We retrospectively reviewed all suspected brain arteriovenous malformations at Massachusetts General Hospital from 2005 to 2013, identifying 126 patients who met the inclusion criteria. Spearman correlations between endovascular and Spetzler-Martin grading scales and long-term outcomes were performed. Median endovascular grades were compared between treatment modalities and endovascular outcomes. Binary regression analysis was performed with major endovascular complications as a dichotomized dependent variable. Intraclass correlation coefficients were calculated for interobserver reliability of the endovascular grading scale. RESULTS: A significant Spearman correlation between the endovascular grade and the Spetzler-Martin grade was demonstrated (ρ = 0.5, P < .01). Differences in the median endovascular grades between the endovascular cure (median = 2) and endovascular complication groups (median = 4) (P < .05) and between the endovascular cure and successful multimodal treatment groups (median = 3) (P < .05) were demonstrated. The endovascular grade was the only independent predictor of complications (OR = 0.5, P < .01). The intraclass correlation coefficient of the endovascular grade was 0.71 (P < .01). CONCLUSIONS: Validation of a brain arteriovenous malformation endovascular grading scale demonstrated that endovascular grades of ≤II were associated with endovascular cure, while endovascular grades of ≤III were associated with multimodal cure or significant lesion reduction and favorable outcome. The endovascular grade provides useful information to refine risk stratification for endovascular and multimodal treatment.


Asunto(s)
Embolización Terapéutica/métodos , Procedimientos Endovasculares/métodos , Malformaciones Arteriovenosas Intracraneales/patología , Malformaciones Arteriovenosas Intracraneales/cirugía , Adulto , Anciano , Fístula Arteriovenosa/patología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reproducibilidad de los Resultados , Índice de Severidad de la Enfermedad
3.
AJNR Am J Neuroradiol ; 35(11): 2202-6, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-25012675

RESUMEN

BACKGROUND AND PURPOSE: Sacral insufficiency fractures are a common cause of severe low back pain and immobilization in patients with osteoporosis or cancer. Current practice guideline recommendations range from analgesia and physical therapy to resection with surgical fixation. We sought to assess the safety and effectiveness of sacroplasty, an emerging minimally invasive treatment. MATERIALS AND METHODS: We performed a retrospective review of institutional databases for percutaneous sacroplasty performed between January 2004 and September 2013. Demographic and procedural data and pre- and posttreatment Visual Analog Scale, Functional Mobility Scale, and Analgesic Scale scores were reviewed. Overall response was rated by using a 4-point scale (1, complete resolution of pain; 2, improvement of pain; 3, no change; 4, worsened pain) assessed at short-term follow-up. RESULTS: Fifty-three patients were included; most (83%) were female. Fracture etiology was cancer-related (55%), osteoporotic insufficiency (30%), and minor trauma (15%). No major complication or procedure-related morbidity occurred. There were statistically significant decreases in the Visual Analog Scale (P < .001), Functional Mobility Scale (P < .001), and Analgesic Scale scores (P < .01) in 27 patients with recorded data: pretreatment Visual Analog Scale (median [interquartile range], 9.0 [8.0-10.0]); Functional Mobility Scale, 3.0 (2.0-3.0); and Analgesic Scale scores, 3.0 (3.0-4.0) were reduced to 3.0 (0.0-5.8), 1.0 (0.25-2.8), and 3.0 (2.0-3.8) posttreatment. When we used the overall 4-point score at a mean of 27 days, 93% (n = 45) reported complete resolution or improvement in overall pain. CONCLUSIONS: In this single-center cohort, sacroplasty was a safe and effective procedure. There were significant short-term gains in pain relief, increased mobility, and decreased dependence on pain medication.


Asunto(s)
Procedimientos Ortopédicos/métodos , Sacro/cirugía , Fracturas de la Columna Vertebral/cirugía , Adulto , Anciano , Neoplasias Óseas/complicaciones , Femenino , Humanos , Masculino , Persona de Mediana Edad , Osteoporosis/complicaciones , Estudios Retrospectivos , Sacro/lesiones , Fracturas de la Columna Vertebral/etiología , Resultado del Tratamiento
4.
Int J STD AIDS ; 22(10): 581-4, 2011 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21998179

RESUMEN

Research on management of Chlamydia trachomatis (CT) among men has largely been neglected. Findings from an audit of 284 CT-infected men from 2004 to 2005 attending a young men's clinic primarily serving Latino men in New York City, NY, USA, are presented. Ninety-nine percent received treatment, with 81% treated within 14 days of a positive test. Three percent reported no partner in the last three months, 17% were referred by a CT-positive partner and 24% were missing partner information. Among the rest, 18% received expedited partner therapy, 4% directly observed therapy, 12% partner referral and 65% did not receive documented partner management. Of the 34% who had a post-treatment visit at least three months after their index visit, only 36% received a test for re-infection. Among primarily Latino men in an urban clinic in New York City, a high proportion of CT cases were treated in a timely manner. However, documentation of partner management was often lacking and few CT cases received tests for re-infection.


Asunto(s)
Infecciones por Chlamydia/diagnóstico , Infecciones por Chlamydia/tratamiento farmacológico , Auditoría Médica , Servicio Ambulatorio en Hospital/normas , Adolescente , Adulto , Antibacterianos/uso terapéutico , Infecciones por Chlamydia/epidemiología , Infecciones por Chlamydia/etnología , Chlamydia trachomatis , Trazado de Contacto , Manejo de la Enfermedad , Hispánicos o Latinos , Humanos , Masculino , Salud del Hombre , Ciudad de Nueva York/etnología , Parejas Sexuales , Enfermedades de Transmisión Sexual/diagnóstico , Enfermedades de Transmisión Sexual/tratamiento farmacológico , Adulto Joven
5.
Sex Transm Infect ; 86(5): 400-3, 2010 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-20448100

RESUMEN

BACKGROUND: Condom use is a key part of sexually transmitted infection (STI) prevention for young men. Yet little is known about how younger adolescent boys initially learn about and use condoms. We examined sources of information, attitudes towards, acquisition, practice and early use of condoms among 14-16-year-old boys. METHODS: Thirty 14-16-year-old boys were recruited from a teen clinic serving a community with high STI rates and were asked open-ended questions about condoms, such as, "Where did you learn about condoms?" and "In what situations would you/would you not, use condoms." Interviews were audio recorded, transcribed and coded. Qualitative analysis focused upon key concepts and shared social cognitions related to condom use. RESULTS: Both sexually inexperienced and experienced participants perceived that sex feels or would feel less pleasurable with condoms. For almost all participants, families were the primary source of both information about condoms and of condoms themselves. This information focused on pregnancy prevention, with STIs secondary. Participants' views of condoms fell into three developmental groups: not interested in condoms and equating their use with interest in sex; exploring condoms out of either curiosity or in preparation for sex; and experienced with condom use. Exploring included behaviours such as checking condoms out and trying them on. CONCLUSIONS: Our findings of existing negative perceptions of condoms, the importance of families in learning about condoms and the developmental need to test and try on condoms before use have implications for adolescent STI prevention programmes.


Asunto(s)
Desarrollo del Adolescente , Actitud Frente a la Salud , Condones/estadística & datos numéricos , Educación del Paciente como Asunto , Adolescente , Salud de la Familia , Humanos , Relaciones Interpersonales , Masculino , Conducta Sexual , Factores de Tiempo
6.
J Antimicrob Chemother ; 45(6): 813-8, 2000 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-10837435

RESUMEN

Melioidosis and glanders are caused by the closely related species Burkholderia pseudomallei and Burkholderia mallei, respectively. Whereas melioidosis is a significant cause of morbidity in south-east Asia, glanders is extremely rare. The efficacies of ciprofloxacin and doxycycline were assessed against a strain of B. pseudomallei and a strain of B. mallei which were susceptible to both antimicrobials in vitro. Porton outbred mice and Syrian hamsters were given 40 mg/kg of either doxycycline or ciprofloxacin twice daily by sc injection according to one of three regimens: dosing starting 48 h before challenge and continuing for 5 days postchallenge; 5 days' therapy starting immediately after challenge; 5 days' therapy starting 24 h after challenge. Mice were challenged ip with B. pseudomallei 4845 and hamsters were challenged ip with B. mallei 23344. Antimicrobial efficacy was determined by the shift in the median lethal dose (MLD). Ciprofloxacin prophylaxis and immediate therapy both raised the MLD of B. pseudomallei to 4 x 10(6) cfu from 19 cfu in untreated animals, but therapeutic ciprofloxacin only raised the MLD to 180 cfu. The results for doxycycline were similar. Ciprofloxacin prophylaxis raised the MLD of B. mallei 23344 to 4.6 x 10(5) cfu compared with 4 cfu in untreated controls. Immediate therapy raised the MLD to 7.0 x 10(4) cfu and therapy raised the MLD to 1.6 x 10(3) cfu. All regimens of doxycycline protected hamsters against challenges of up to 2 x 10(7) cfu. Despite using a susceptible strain of B. pseudomallei, neither antimicrobial was effective when used therapeutically. The timely administration of either antimicrobial, however, was effective in preventing symptomatic infection. Doxycycline was the superior of the two antimicrobials against experimental glanders although relapse did occur in treated animals approximately 4-5 weeks after challenge.


Asunto(s)
Antibacterianos/uso terapéutico , Antiinfecciosos/uso terapéutico , Ciprofloxacina/uso terapéutico , Doxiciclina/uso terapéutico , Muermo/tratamiento farmacológico , Melioidosis/tratamiento farmacológico , Animales , Infecciones por Burkholderia/tratamiento farmacológico , Infecciones por Burkholderia/microbiología , Burkholderia pseudomallei/efectos de los fármacos , Burkholderia pseudomallei/genética , Burkholderia pseudomallei/patogenicidad , Cricetinae , Femenino , Muermo/microbiología , Melioidosis/microbiología , Ratones , Pruebas de Sensibilidad Microbiana , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Análisis de Supervivencia , Factores de Tiempo
7.
Am J Bot ; 86(6): 807-19, 1999 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-10371723

RESUMEN

Species differences in patterns of phenotypic plasticity may be an important aspect of adaptive diversity. Plasticity for functionally important root traits was studied in inbred field lineages of Polygonum persicaria and P. cespitosum (Polygonaceae). Replicate seedlings were grown in plexiglass rhizotrons under a range of constant and temporally variable moisture treatments. Plasticity was determined for final whole-plant biomass, root biomass allocation, and absolute and proportional root length. The dynamic aspect of root plasticity was examined by digitizing weekly tracings of the proportional deployment of each plant's root system to different vertical soil layers. Plants of both species expressed significant functionally adaptive phenotypic plasticity in the relative allocation, length, and vertical deployment of root systems in response to contrasting moisture conditions. Plasticity patterns in these closely related species were in general qualitatively similar, but for most traits differed in the magnitude and/or the timing of the plastic response. Dynamic changes in root deployment were more marked as well as faster in P. persicaria. Species differences in patterns of individual plasticity were generally consistent with the broader ecological distribution of P. persicaria in diverse as well as temporally variable moisture habitats.

8.
Adolesc Med ; 10(1): 57-69, vi, 1999 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-10086166

RESUMEN

The important roles that culture, race, and poverty play in contributing to health beliefs and health behaviors are reviewed in this chapter. It also outlines strategies for working with young people, their parents, and their communities in order to deliver "culturally effective" health care services, with an emphasis on prevention, health promotion, and risk reduction.


Asunto(s)
Conducta del Adolescente , Comparación Transcultural , Promoción de la Salud , Medicina Preventiva , Asunción de Riesgos , Adolescente , Servicios de Salud del Adolescente , Actitud Frente a la Salud , Cultura , Atención a la Salud , Etnicidad , Conductas Relacionadas con la Salud , Humanos , Grupos Minoritarios , Pobreza , Grupos Raciales
9.
FEMS Immunol Med Microbiol ; 23(2): 107-13, 1999 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-10076907

RESUMEN

In this study, we have shown that severe combined immunodeficient/beige mice reconstituted with hyperimmune Balb/c lymphocytes can be used as a model to demonstrate adoptive and passive protection against plague infection. Reconstitution of severe combined immunodeficient/beige mice was successful in nine out of ten mice as demonstrated by spleen colonisation and sustained circulating immunoglobulin titres. Furthermore, an increase in antibody titre was evident after a booster immunisation of reconstituted mice. Presence of circulating antibody correlated with protection against a systemic plague challenge and indicated that in reconstituted mice adoptive transfer of a functional immune system had occurred. The severe combined immunodeficient/beige mouse was also used to demonstrate passive protection against inhaled and systemic plague infection. The reconstituted severe combined immunodeficient/beige mouse model demonstrating protective immunity against plague will be further developed to identify the immune cell subsets responsible for this protection.


Asunto(s)
Traslado Adoptivo , Modelos Animales de Enfermedad , Inmunización Pasiva , Linfocitos/inmunología , Peste/inmunología , Peste/prevención & control , Yersinia pestis/inmunología , Animales , Anticuerpos Antibacterianos/biosíntesis , Anticuerpos Antibacterianos/inmunología , Antígenos Bacterianos/inmunología , Femenino , Sueros Inmunes/inmunología , Inmunoglobulinas/biosíntesis , Inmunoglobulinas/inmunología , Péptidos y Proteínas de Señalización Intracelular , Hígado/inmunología , Hígado/microbiología , Pulmón/inmunología , Pulmón/microbiología , Ratones , Ratones Endogámicos BALB C , Ratones SCID , Peste/microbiología , Proteínas/genética , Bazo/inmunología , Bazo/microbiología , Células Th2/inmunología , Proteínas de Transporte Vesicular
10.
J Antimicrob Chemother ; 41(4): 461-5, 1998 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-9598777

RESUMEN

The efficacy of doxycycline and ciprofloxacin against an experimental tularaemia infection was assessed by comparing the median lethal dose (MLD) of Francisella tularensis Schu4 biotype A strain given intraperitoneally to antibiotic-treated and untreated mice. In untreated Porton outbred mice this was <1 cfu. Ciprofloxacin and doxycycline given at 40 mg/kg bd, initiated 48 h before infection and continued for 5 days after infection, afforded protection against intraperitoneal challenges of 3.7 x 10(6) cfu and 6.0 x 10(6) cfu, respectively. Protection was reduced when both antibiotics were given over a similar period at a lower dose regimen (20 mg/kg bd) to 8.8 x 10(5) cfu and 3.5 x 10(2) cfu, respectively. The greater reduction in protection offered by doxycycline was a reflection of the higher in-vitro MIC. Protection also decreased when the antibiotics were initiated 24 h after challenge. The MLD was 3.2 x 10(5) cfu and 1.6 x 10(6) cfu for ciprofloxacin and doxycycline respectively given at 40 mg/kg bd and was reduced further using the lower dose regimen. Overall, 90% of the deaths occurred following the withdrawal of antibiotic, irrespective of the antibiotic dose or type. It was possible to prevent this relapse by extending the antibiotic administration to 10 days after challenge. Ciprofloxacin and doxycycline may be useful for treating tularaemia, although the possibility of relapse should be considered.


Asunto(s)
Antibacterianos/uso terapéutico , Antiinfecciosos/uso terapéutico , Ciprofloxacina/uso terapéutico , Doxiciclina/uso terapéutico , Tularemia/tratamiento farmacológico , Tularemia/prevención & control , Animales , Antibacterianos/administración & dosificación , Antiinfecciosos/administración & dosificación , Profilaxis Antibiótica , Ciprofloxacina/administración & dosificación , Modelos Animales de Enfermedad , Doxiciclina/administración & dosificación , Francisella tularensis/efectos de los fármacos , Ratones , Pruebas de Sensibilidad Microbiana
11.
J Antimicrob Chemother ; 41(2): 301-5, 1998 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-9533478

RESUMEN

The efficacies of ciprofloxacin and doxycycline prophylaxis and therapy were assessed against experimental pneumonic plague infections induced by two strains of Yersinia pestis in a mouse model. When exposed to an aerosol of Y. pestis strain GB, containing 8.39 x 10(5) +/- 4.17 x 10(4) cfu, the retained dose was 7.3 x 10(3) +/- 2.3 x 10(3) cfu. When exposed to an aerosol of Y. pestis strain CO-92, containing 1.86 x 10(5) +/- 7.4 x 10(3) cfu, the retained dose was 3.4 x 10(4) +/- 2.6 x 10(3) cfu. Both strains resulted in a respiratory and systemic infection closely resembling human pneumonic plague. Ciprofloxacin prophylaxis and therapy was successful against both strains for up to 24 h after challenge, but not after 48 h. Both doxycycline prophylaxis and therapy regimens were ineffective against both strains, although strain CO-92 was more susceptible in vitro to doxycycline than strain GB and supra-MIC levels were achieved in the serum and lungs of the animal.


Asunto(s)
Ciprofloxacina/farmacología , Doxiciclina/farmacología , Peste/tratamiento farmacológico , Yersinia pestis/efectos de los fármacos , Animales , Profilaxis Antibiótica , Modelos Animales de Enfermedad , Pulmón/microbiología , Pulmón/patología , Ratones , Pruebas de Sensibilidad Microbiana , Peste/microbiología , Peste/prevención & control , Resultado del Tratamiento
12.
Oecologia ; 115(4): 564-578, 1998 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-28308277

RESUMEN

Individual physiological response to complex environments is a major factor in the ecological breadth of species. This study compared individual patterns of both long-term and short-term response to controlled, multifactorial environments in four annual Polygonum species that differ in field distribution (P. cespitosum, P. hydropiper, P. lapathifolium, and P. persicaria). To test long-term response, instantaneous net photosynthetic rate and stomatal conductance were measured in situ on one full-sib replicate from five inbred lineages from each of five field populations per species, raised in all possible combinations of low or high light; dry, moist, or flooded soil; and poor or rich nutrient status. Short-term plastic adjustment to changes in light level was examined by switching individual plants of the four species from one of six multifactorial growth environments to the contrasting light environment, and measuring assimilation rates 1 h after transfer. The Polygonum species differed significantly in their patterns of long-term photosynthetic response to particular resources and resource combinations. The species known to have relatively broad ecological distributions (P. persicaria and P. lapathifolium) maintained high photosynthetic performance in a variety of moisture and nutrient environments when grown in high light, while the more narrowly distributed P. hydropiper maintained such functional levels only if given both high light and ample macronutrients. P. cespitosum, a species limited to shaded habitats, maintained low photosynthetic rates across the environmental range. Complex differences among the species in instantaneous water use efficiency (WUE) reflected their highly specific and to some extent independent patterns of photosynthetic and stomatal response to the multifactorial environments. The species also differed significantly in short-term physiological adjustment to changes in light level. Plants of P. persicaria and P. cespitosum reached 78% and 98%, respectively, of their maximum photosynthetic rates 1 h after transfer from low to high light, but P. hydropiper and P. lapathifolium plants reached only c. 60% of their maximum rates. When switched from high to low light, P. persicaria and P. cespitosum plants maintained 64-76% of their maximum rates, while P. hydropiper and P. lapathifolium plants decreased photosynthetic rates sharply to less than 50% of their maximum rates. These results indicate that the latter two species will be less able to maintain effective functional levels in variable light environments, a result consistent with their distributions in the field.

13.
J Antimicrob Chemother ; 37(4): 769-74, 1996 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-8722542

RESUMEN

The efficacy of doxycycline and ciprofloxacin against an experimental plague infection was assessed by comparing the median lethal dose (MLD) of Yersinia pestis in antibiotic-treated and untreated mice. The MLD of Y. pestis GB strain in untreated mice by the intra-peritoneal route was 23 cfu. If ciprofloxacin dosage (20 or 40 mg/kg twice daily) was initiated 48 h before infection, it afforded complete protection against an intra-peritoneal challenge of 5.24 x 10(7) cfu. Ciprofloxacin therapy initiated 24 h post-challenge was less protective, the MLD was raised to 2.0 x 10(5) and 2.2 x 10(5) cfu for 40 and 20 mg/kg respectively. Doxycycline dosage (40 mg/kg twice daily) initiated 48 h prior to infection raised the MLD to 1.6 x 10(4) cfu, but other prophylactic and therapeutic regimes were ineffective against challenges greater than 6.76 x 10(2) cfu. Ciprofloxacin may therefore be a useful antibiotic to consider for the treatment of plague.


Asunto(s)
Antibacterianos/uso terapéutico , Antiinfecciosos/uso terapéutico , Ciprofloxacina/uso terapéutico , Doxiciclina/uso terapéutico , Peste/tratamiento farmacológico , Yersinia pestis/efectos de los fármacos , Animales , Ratones
14.
Am J Physiol ; 260(3 Pt 2): H1003-12, 1991 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-2000959

RESUMEN

A technique for studying the real-time effects of arterial wave reflections on the performance of the isolated left ventricle was investigated. Real-time arterial loading of an isolated ferret heart with an asymmetric T-tube wave transmission model was obtained with the use of a multiprocessor computer control system and a volume control linear motor pump. The multiprocessor computer system was programmed to compute the instantaneous aortic flow from the instantaneous ventricular pressure. The time integral of the flow was used as a command to the linear motor pump to control the instantaneous ventricular volume. This loading system allowed the imposition of a wide variety of vascular impedances on the ventricle by changing the parameters of the asymmetric T-tube model.


Asunto(s)
Arterias/fisiología , Modelos Cardiovasculares , Función Ventricular Izquierda/fisiología , Animales , Cardiología/instrumentación , Computadores , Diseño de Equipo , Hurones , Masculino , Ratas , Factores de Tiempo , Resistencia Vascular
15.
Am J Physiol ; 258(6 Pt 2): H1761-74, 1990 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-2360669

RESUMEN

An asymmetric T-tube model of the arterial system with complex terminal loads was formulated in the time domain. The model was formulated to allow it to be fitted to the aortic pressure waveform, the aortic flow waveform, or simultaneously to both the aortic and descending aortic flow waveforms. Pressure and flow measurements were taken in anesthetized open-chest dogs under basal, vasoconstricted, and vasodilated states. It was found that the T-tube model fitted the data well in all formulations and in all vasoactive states. However, all parameters were estimated accurately in all vasoactive states only with the formulation that fitted to both aortic and descending aortic flow simultaneously. The T-tube model was compared with the three-element windkessel model with regard to the respective models' ability to recreate specific aspects of the pressure waveform and with regard to the estimates of global arterial parameters. The T-tube model recremated those features of the pressure waveform, such as diastolic waves, that the windkessel model could not. Also, the T-tube model systematically estimated lower global arterial compliance and higher characteristic impedance than the windkessel. It was argued that the T-tube model accurately represented important wave transmission features of the arterial loading system. The model is recommended for use in characterizing the arterial load and for merging with representations of the left ventricle in studies of left ventricle-systemic arterial interaction.


Asunto(s)
Arterias/fisiología , Modelos Cardiovasculares , Animales , Presión Sanguínea , Perros , Hemodinámica , Flujo Sanguíneo Regional , Factores de Tiempo , Resistencia Vascular , Vasoconstricción , Vasodilatación
16.
Am J Physiol ; 257(1 Pt 2): H38-46, 1989 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-2750948

RESUMEN

Observed pressure responses to quick volume changes in the isolated tetanized heart of ferrets were compared with previously reported tension responses to quick length changes in isolated cardiac muscle. Hearts were isolated from ferrets, perfused with ryanodine solution, and stimulated rapidly (50 ms between stimulations) to produce repeated 4-s intervals of tetanus. During each tetanus interval, volume increments of different amplitudes were rapidly removed and then reinfused into the left ventricular chamber. The pressure responses to these volume changes were evaluated for differences between withdrawals and infusions and for dependence on the amplitude of the volume change. It was found for both withdrawal and infusion that the response could be divided into three phases: 1) an immediate phase coincident with volume change, 2) a fast-recovery phase, and 3) a slow-recovery phase. The amplitude of the immediate phase was linearly dependent on the volume change so that a single regression line fit all the data (withdrawal and infusion). The fast recovery phase was 2.5 times faster for infusion than for withdrawal and generated a rebound effect with the pressure going below the initial pressure in the response to infusion. The pressure never went above the initial pressure in the response to withdrawal. The slow-recovery phases in infusion and withdrawal did not differ. These responses in the isolated heart bear striking similarities to tension responses to quick length changes in isolated constantly activated cardiac muscle. We concluded that muscle fiber dynamics were being faithfully transformed to left ventricular (LV) chamber dynamics without appreciable distortion because of the many intervening factors between the wall muscle fiber and the LV chamber.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Volumen Cardíaco , Contracción Miocárdica , Animales , Hurones , Técnicas In Vitro , Masculino , Presión
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