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1.
J Dairy Sci ; 98(3): 1634-9, 2015 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-25597969

RESUMEN

Experiments to determine the efficacy of high temperature, short time (HTST) pasteurization of milk in terms of inactivation of pathogenic microorganisms were mainly performed between 1930 and 1960. Among the target organisms were Mycobacterium bovis and Mycobacterium tuberculosis. As a result, the Codex Alimentarius prescribes that HTST treatment of milk should lead to a significant reduction of pathogenic microorganisms during milk pasteurization. Due to the development of improved methods for the detection of survivors and of more advanced heating technology, verification of this requirement seemed to be necessary. To address recent outbreaks of tuberculosis in cattle caused by M. bovis ssp. caprae (M. caprae) in the southern regions of Germany, this organism was tested and compared with M. bovis ssp. bovis (M. bovis). Experiments were performed in a pilot plant for HTST pasteurization of milk with 3 strains of M. caprae and 1 strain of M. bovis. In preliminary trials at a fixed holding time of 25 s, the temperature at which significant inactivation occurred was 62.5°C for all strains. To determine D-values (decimal reduction times) for the inactivation kinetics, the strains were tested at 65, 62.5, and 60°C at holding times of 16.5, 25, and 35 s. At 65°C, the D-values of all strains ranged from 6.8 to 7.8 s, and at 62.5°C, D-values ranged from 14.5 to 18.1 s. Low inactivation was observed at 60°C. When the low slope of the inactivation curve allowed calculation of a D-value, these ranged from 40.8 to 129.9 s. In terms of log10 reductions, the highest values for all strains were 4.1 to 4.9 log at 65°C, with a holding time of 35 s. The tested strains of M. caprae and M. bovis showed similar low resistance to heat. Standard HTST treatment should result in a high reduction of these organisms and thus the requirements of the Codex Alimentarius for inactivation of pathogens by this process are far exceeded.


Asunto(s)
Calor , Viabilidad Microbiana , Leche/microbiología , Mycobacterium bovis/fisiología , Pasteurización , Animales , Cinética
2.
J Hazard Mater ; 436: 129151, 2022 08 15.
Artículo en Inglés | MEDLINE | ID: mdl-35739697

RESUMEN

Long term field studies are required to bridge gaps between research and practical application of arsenic phytoextraction with the arsenic-hyperaccumulating fern Pteris vittata. In a 4-year field study, we investigated the effects of nutrient application (compost, inorganic or organic nitrogen, inorganic or organic phosphorus) and soil texture (13 % and 35 % clay) on arsenic phytoextraction with P. vittata in moderately contaminated soils (74-79 mg As/kg in the 0-15 cm depth interval). We found the highest phytoextraction rates, 5 ± 1 kg As/ha/y, in a coarse-textured compost-amended soil after 2 years of phytoextraction. Phytoextraction rates decreased over time, likely due to decreased root growth in mature stands, indicating plants should be replaced every 2-3 years to maintain phytoextraction efficiency. Across soil textures, nitrogen or phosphorus application led to a 60 % decrease in mean frond arsenic concentrations, leading to mean phytoextraction rates 54 % lower than in control ferns. In the fine-textured soil, frond arsenic concentrations were 54 % lower than in the coarse-textured soil, and fewer ferns survived from year 3 to 4. Across soil textures, compost application increased fern survival. We show that phytoextraction with P. vittata is limited to specific soil and climate conditions, narrower than those under which P. vittata grows in the wild.


Asunto(s)
Arsénico , Helechos , Pteris , Contaminantes del Suelo , Arsénico/análisis , Biodegradación Ambiental , Nitrógeno/farmacología , Fósforo/farmacología , Suelo , Contaminantes del Suelo/análisis
3.
Sci Total Environ ; 818: 151803, 2022 Apr 20.
Artículo en Inglés | MEDLINE | ID: mdl-34808151

RESUMEN

Plant-soil interactions affect arsenic and nutrient availability in arsenic-contaminated soils, with implications for arsenic uptake and tolerance in plants, and leaching from soil. In 22-week column experiments, we grew the arsenic hyperaccumulating fern Pteris vittata in a coarse- and a medium-textured soil to determine the effects of phosphorus fertilization and mycorrhizal fungi inoculation on P. vittata arsenic uptake and arsenic leaching. We investigated soil arsenic speciation using synchrotron-based spectromicroscopy. Greater soil arsenic availability and lower nutrient content in the coarse-textured soil were associated with greater fern arsenic uptake, lower biomass (apparently a metabolic cost of tolerance), and arsenic leaching from soil, due to lower transpiration. P. vittata hyperaccumulated arsenic from coarse- but not medium-textured soil. Mass of plant-accumulated arsenic was 1.2 to 2.4 times greater, but aboveground biomass was 74% smaller, in ferns growing in coarse-textured soil. In the presence of ferns, mean arsenic loss by leaching was 195% greater from coarse- compared to the medium-textured soil, and lower across both soils compared to the absence of ferns. In the medium-textured soil arsenic concentrations in leachate were higher in the presence of ferns. Fern arsenic uptake was always greater than loss by leaching. Most arsenic (>66%) accumulated in P. vittata appeared of rhizosphere origin. In the medium-textured soil with more clay and higher nutrient content, successful iron scavenging increased arsenic release from soil for leaching, but transpiration curtailed leaching.


Asunto(s)
Arsénico , Pteris , Contaminantes del Suelo , Arsénico/análisis , Biodegradación Ambiental , Biomasa , Nutrientes , Pteris/metabolismo , Suelo , Contaminantes del Suelo/análisis
4.
J Phys Condens Matter ; 31(27): 275701, 2019 Jul 10.
Artículo en Inglés | MEDLINE | ID: mdl-30939455

RESUMEN

Epitaxial 200 nm BiFe0.95Mn0.05O3 (BFO) film was grown by pulsed laser deposition (PLD) on (1 1 1) oriented SrTiO3 substrate buffered with a 50 nm thick SrRuO3 electrode. The BFO thin film shows a rhombohedral structure and a large remnant polarization of Pr = 104 µC cm-2. By comparing I(V) characteristics with different conduction models we reveal the presence of both bulk limited Poole-Frenkel and Schottky interface mechanisms and each one dominates in a specific range of temperature. At room temperature (RT) and under 10 mW laser illumination, the as grown BFO film presents short-circuit current density (J sc) and open circuit voltage (V oc) of 2.25 mA cm-2 and -0.55 V respectively. This PV effect can be switched by applying positive voltage pulses higher than the coercive field. For low temperatures a large V oc value of about -4.5 V (-225 kV cm-1) is observed which suggests a bulk non-centrosymmetric origin of the PV response.

5.
Endocrinology ; 126(3): 1430-4, 1990 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-1968380

RESUMEN

The involvement of hypothalamic histaminergic neurons in the stress-induced release of peripheral catecholamines was studied in conscious, freely moving male rats. Blood samples were obtained via a catheter in a femoral artery. Intracerebroventricular infusion of histamine (HA; 30 micrograms) increased the plasma concentrations of norepinephrine (NE) and epinephrine (E) 3- and 9-fold, respectively. The plasma level of dopamine was not affected. The effect of HA was prevented by prior intracerebroventricular infusion of the H1-receptor antagonist mepyramine (100 micrograms) or the H2-receptor antagonist cimetidine (100 micrograms). Restraint stress applied for 5 min caused an immediate but transient increase in the plasma concentrations of NE and E which were increased 5- and 11-fold, respectively. The plasma level of dopamine was not altered significantly by restraint stress. The effect of stress on NE and E was almost prevented by prior icv infusion of mepyramine or cimetidine. The HA receptor antagonists had no effect on the basal plasma catecholamine level. We conclude that neuronal HA is an important mediator of the restraint stress-induced release of peripheral catecholamines by an action on H1- and H2-receptors within the central nervous system.


Asunto(s)
Catecolaminas/metabolismo , Histamina/fisiología , Sistemas Neurosecretores/fisiología , Estrés Fisiológico/metabolismo , Animales , Antagonistas de los Receptores Histamínicos H1/farmacología , Antagonistas de los Receptores H2 de la Histamina/farmacología , Masculino , Ratas , Ratas Endogámicas , Restricción Física , Estrés Fisiológico/etiología
6.
Biotechniques ; 18(6): 1040-7, 1995 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-7546705

RESUMEN

The most frequently altered gene in diverse tumor types is the tumor suppressor gene p53. Typically, normal function is inactivated by point mutation of one allele and deletion of the other. Therefore, loss of heterozygosity (LOH) of intragenic polymorphic markers is a strong indication for p53 involvement in a cancerous lesion. This study shows that a highly polymorphic short tandem repeat (STR) within intron 1 of p53 is an excellent marker for quantitative evaluation of LOH in tumor samples, whose multicolor, fluorescently tagged PCR products are analyzed and quantitated on an automated DNA sequencer. The range of error was analyzed in detail. Discrete allelic profiles were obtained following amplification of DNA from microdissected cell samples of patients with urogenital tumors. By calculating qLOH, the relative allele ratio of a tumor compared with healthy tissue, a quantitative expression for the LOH is obtained. PCR-based tumor DNA typing using fluorescent STR primers and automated analysis provides an enhanced level of accuracy and sensitivity required for routine analysis in clinical practice, where large numbers of tumor samples have to be processed.


Asunto(s)
Eliminación de Gen , Genes p53 , Proteína p53 Supresora de Tumor/genética , Alelos , Secuencia de Bases , ADN/análisis , ADN/sangre , Cartilla de ADN , Colorantes Fluorescentes , Geles , Heterocigoto , Humanos , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Reproducibilidad de los Resultados , Volumetría , Neoplasias Urogenitales/sangre , Neoplasias Urogenitales/genética
7.
Eur J Endocrinol ; 132(2): 223-8, 1995 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-7858743

RESUMEN

The neurotransmitter histamine (HA) is involved in central regulation of secretion of prolactin (PRL) and the proopiomelanocortin (POMC)-derived peptides adrenocorticotropin (ACTH), beta-endorphin (beta-END) and alpha-melanocyte-stimulating hormone (alpha-MSH). The effect of HA on POMC-derived peptides and PRL release is, at least in part, indirect and may involve activation of catecholaminergic systems. Therefore, we investigated the effect of beta-adrenergic receptor blockade on HA or HA agonist-induced release of ACTH, beta-END, alpha-MSH and PRL. Central administration of HA, the H1-receptor agonist 2-thiazolylethylamine (2-TEA) or the H2-receptor agonist 4-methylhistamine (4-MeHA) stimulated the secretion of ACTH, beta-END, alpha-MSH and PRL. Pretreatment with the beta-adrenergic antagonist propranolol inhibited secretion of the POMC peptides in response to HA, 2-TEA or 4-MeHA. Propranonol only inhibited the PRL response to HA or 2-TEA, but had no effect on the PRL response to 4-MeHA. Administration of the beta-receptor agonist isoproterenol stimulated ACTH, beta-END, alpha-MSH and PRL two to five-fold. This effect was totally blocked by pretreatment with propranolol. We conclude that HA-induced secretion of POMC-derived peptides from the anterior and intermediate lobe of the pituitary gland and of PRL from the anterior lobe is, at least in part, mediated via catecholamines. beta-Adrenergic receptors are involved in the mediation of the POMC response to H1- as well as H2-receptor activation, whereas beta-receptors are involved only in the mediation of the PRL response to H1-receptor activation.


Asunto(s)
Hormona Adrenocorticotrópica/metabolismo , Histamina/farmacología , Hipófisis/metabolismo , Prolactina/metabolismo , Receptores Adrenérgicos beta/metabolismo , alfa-MSH/metabolismo , betaendorfina/metabolismo , Antagonistas Adrenérgicos beta/farmacología , Animales , Interacciones Farmacológicas , Agonistas de los Receptores Histamínicos/farmacología , Masculino , Ratas , Ratas Wistar
8.
Cancer Genet Cytogenet ; 53(2): 265-70, 1991 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-2065300

RESUMEN

Cultured fibroblasts of 17 first-degree relatives of familial melanoma patients and six first-degree relatives of cutaneous melanoma (CMM) patients with multiple CMM primaries were tested for in vitro sensitivity to UV light. Fibroblasts of nine familial CMM patients with a known UV-sensitivity and 19 healthy probands served as a control. Sister chromatid exchange (SCE) was used as a parameter to detect UV-induced genotoxic damage. We found significantly (p less than 0.001) increased UV-induced SCE levels in familial melanoma patients, as well as in first-degree relatives of familial melanoma patients (p less than 0.001) after UV-A,B irradiation (375 J/m2), compared to the healthy probands without a family history of CMM. A significant (p less than 0.001) increase of UV-induced SCE was also observed in the relatives of CMM patients with multiple CMM primaries. In addition, the spontaneous SCE were significantly increased (p less than 0.05) in familial CMM patients. This study shows that increased UV sensitivity is a familial phenomenon. It is consistent with the concept of a genetic predisposition to CMM, which is based on increased UV sensitivity and may help to define groups with an elevated risk of developing cutaneous malignant melanoma.


Asunto(s)
Melanoma/etiología , Intercambio de Cromátides Hermanas/efectos de la radiación , Rayos Ultravioleta/efectos adversos , Células Cultivadas , Fibroblastos/citología , Humanos , Técnicas In Vitro , Melanoma/genética , Tolerancia a Radiación
9.
Aviat Space Environ Med ; 64(12): 1128-32, 1993 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8291994

RESUMEN

Changes in immunological competent blood cells were evoked in seven humans during passive head-up tilt (50 degrees anti-Trendelenburg's position maintained until appearance of presyncopal symptoms). Blood samples were collected after 60 min of rest, when presyncopal symptoms appeared during tilt, and 105 min after tilt-down. Natural killer (NK) cell activity increased during head-up tilt due to a three to four-fold increase in CD16+ NK cells in blood. In support NK cell activity boosted with interferon-alpha and interleukin 2 (IL-2) rose in parallel with unboosted NK cell activity. This effect on NK cells disappeared during recovery but was not suppressed when compared to prevalues. Lymphocyte concentration also increased during head-up tilt. Concentrations of CD3+ and CD4+ T cells were almost stable during head-up tilt, whereas the percentage of CD3+ T cells in relation to blood mononuclear cell (BMNC) concentration decreased, due to a diminished percentage of CD4+ T cells and the marked simultaneous increase in the percentage of CD16+ NK cells. Although changes in the BMNC composition occurred, the proliferative responses of BMNC following stimulation with phytohemagglutinin, purified derivative of tuberculin, or IL-2 did not change significantly. We conclude that head-up tilt induced marked changes in subpopulations of BMNC, especially the CD16+ NK cells, as they were recruited to the blood.


Asunto(s)
Volumen Sanguíneo/fisiología , Células Asesinas Naturales/inmunología , Postura/fisiología , Adulto , Antígenos CD , Citotoxicidad Inmunológica , Citometría de Flujo , Humanos , Recuento de Leucocitos , Activación de Linfocitos , Subgrupos Linfocitarios , Masculino
10.
Aviat Space Environ Med ; 69(8): 781-4, 1998 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-9715968

RESUMEN

OBJECTIVE: Orthostatic hypotension is usually a benign event. However, some patients are disabled by frequent syncopal events, and vertical transportation during helicopter rescue, for example, may even be fatal. Normal orthostatic tolerance is poorly defined, so we evaluated the response to 50 degrees head-up tilt. Also, the effect of leg elevation was examined in order to establish the influence of venous return, and a fatal accident associated with orthostasis is reported. METHODS: There were 79 volunteers who were subjected to 50 degrees head-up tilt, and 9 subjects performed 1 h of suspension by double strops placed around the thorax and knee bends, respectively. The time to presyncope and changes in BP, heart rate, thoracic electrical impedance, central venous pressure and central venous and muscle oxygen saturations were measured. RESULTS: Head-up tilt resulted in hypotension, bradycardia and presyncopal symptoms in 69 subjects within 1 h (87%; half time 27 min), but during suspension with elevated legs in only one subject (11%; p < 0.02). In presyncopal subjects the central blood volume was reduced as reflected by an elevated thoracic electrical impedance and reduced central venous and muscle oxygen saturations. CONCLUSIONS: During 50 degrees head-up tilt, half of 79 subjects near-fainted within 27 min, whereas elevation of the legs secured venous return to the heart and prevented presyncopal symptoms. The high rate of near-fainting in normal subjects should be taken into account during evaluation of patients with syncope, and it emphasizes the use of a position that secures venous return during transportation.


Asunto(s)
Hipotensión Ortostática/prevención & control , Hipotensión Ortostática/fisiopatología , Transporte de Pacientes , Adulto , Volumen Sanguíneo , Bradicardia/etiología , Impedancia Eléctrica , Resultado Fatal , Femenino , Humanos , Masculino , Síncope/fisiopatología , Síncope/prevención & control
11.
Scand J Plast Reconstr Surg Hand Surg ; 31(1): 47-50, 1997 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-9075287

RESUMEN

During the period 1984-1994 33 patients were admitted to the department of plastic surgery for the purpose of neovaginal construction. They comprised 22 patients with vaginal agenesis or aplasia and 11 transsexual men. In most cases neovaginal construction was done by blunt dissection and lining with a split thickness skin graft from the thigh, and in the cases of sex-reassignment surgery genital skin was also used. The two groups differed as the patients with vaginal agenesis or aplasia had remarkably few complications compared with the transsexual group. The most common complications were defects in the skin grafts and vaginal stenosis. The transsexuals therefore had an extended recovery period including several admissions and visits to the outpatient clinic. The difference in genotype does not explain the high complication rate in the transsexual group as eight in the vaginal agenesis or aplasia group had Morris syndrome (testicular feminisation (XY)). However, the phenotype may be of importance in vaginal construction as the male (transsexual) pelvis is narrow and the levator muscles are stronger than those in the female pelvis.


Asunto(s)
Cirugía Plástica , Transexualidad/cirugía , Vagina/anomalías , Vagina/cirugía , Adolescente , Adulto , Constricción Patológica , Femenino , Humanos , Masculino , Complicaciones Posoperatorias , Vagina/patología
12.
Artículo en Inglés | MEDLINE | ID: mdl-10207960

RESUMEN

A randomised controlled study was carried out to compare the effect of a new amorphous hydrocolloid (hydrogel, Coloplast) with that of conventional treatment on the healing time of pressure sores. After initial debridement in the outpatient clinic of pressure sores located in the sacral (n = 21) or trochanteric (n = 11) area the patients were randomised to be treated with either hydrogel (n = 17) or wet saline compresses (n = 15). Once a week the healing was estimated by the same investigator. The relative volumes (from the initial 100%) of hydrogel-treated wounds were significantly less (26 +/- 20%, p < 0.02) than those of saline treated wounds (64 +/- 16%) in the last week of the study. The saline treated wounds needed more frequent weekly debridement than the hydrogel-treated wounds (21% compared with 7% of all weekly dressings, p < 0.03). We conclude that amorphous hydrocolloid increases current healing of pressure sores compared with conventional treatment. It is therefore a better choice for treating patients with pressure sores in their homes.


Asunto(s)
Hidrogeles/administración & dosificación , Úlcera por Presión/tratamiento farmacológico , Anciano , Anciano de 80 o más Años , Vendajes , Coloides/administración & dosificación , Coloides/uso terapéutico , Femenino , Humanos , Hidrogeles/uso terapéutico , Masculino , Factores de Tiempo , Cicatrización de Heridas
13.
Ugeskr Laeger ; 153(5): 361-2, 1991 Jan 28.
Artículo en Danés | MEDLINE | ID: mdl-1994564

RESUMEN

A case of primary aortoduodenal fistula of unknown origin in a 72 year old female is presented. The fistula was successfully treated by excision from the duodenum and direct suture of the aortic wall.


Asunto(s)
Aorta Abdominal/cirugía , Enfermedades Duodenales/cirugía , Fístula Intestinal/cirugía , Anciano , Femenino , Humanos
14.
Ugeskr Laeger ; 153(34): 2359-61, 1991 Aug 19.
Artículo en Danés | MEDLINE | ID: mdl-1897049

RESUMEN

The case records of all patients admitted to one of the hospitals in the County of Frederiksborg with radiologically demonstrated first episodes of urinary calculi during a period of one year in 1983/1984 and 1988/1989 respectively were reviewed retrospectively. Uniform frequencies of calculus incidence and sex distribution were encountered mutually and as compared with the remainder of Denmark during the two periods. In 30% of the cases the calculi were localized to the kidneys and in 58% to the ureter. In approximately 65% of the patients, the greatest diameter of the stones was 100 mm or less. Spontaneous passage of the stones occurred in approximately 40%. Development in the treatment of urinary tract stones has followed the development in the county as a whole. The number of operative interventions during the five year period was reduced by 30% and extracorporeal shock wave treatment was employed in 22% during the second period.


Asunto(s)
Cálculos Urinarios/epidemiología , Adulto , Anciano , Dinamarca/epidemiología , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Cálculos Urinarios/terapia
15.
Nat Commun ; 5: 4415, 2014 Jul 14.
Artículo en Inglés | MEDLINE | ID: mdl-25019998

RESUMEN

With shrinking device sizes, controlling domain formation in nanoferroelectrics becomes crucial. Periodic nanodomains that self-organize into so-called 'superdomains' have been recently observed, mainly at crystal edges or in laterally confined nanoobjects. Here we show that in extended, strain-engineered thin films, superdomains with purely in-plane polarization form to mimic the single-domain ground state, a new insight that allows a priori design of these hierarchical domain architectures. Importantly, superdomains behave like strain-neutral entities whose resultant polarization can be reversibly switched by 90°, offering promising perspectives for novel device geometries.

16.
J Plast Reconstr Aesthet Surg ; 63(2): 327-31, 2010 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-19064342

RESUMEN

It has previously been questioned if the injection port of soft-tissue expanders is a source of leakage. However, several laboratory studies have concluded that the port is safe. A former quality assessment of our one-stage breast reconstructive procedures showed, that suspicion of leakage led to the removal of the injection port in 12% of the cases. With this level of inconsistency with previous laboratory studies, we found a need to conduct a separate study in order to confirm the true cause of leakage. Thirteen consecutively removed McGhan Style 150 injection ports were examined for leakage by increasing intraluminal pressure. Eight of the 13 ports had been removed because of discomfort due to the subcutaneous placement. Three of these eight ports showed substantial leakage (up to 14.55 ml/hour) at pressures attainable under normal in vivo circumstances. Five of the 13 ports had been removed due to clinical leakage. All five showed substantial leakage in the experimental setting (up to 19.65 ml/hour). Comparing the placement of the leaking puncture holes with the construction of the port, it seems that the leaking puncture holes are the result of peripheral perforations escaping the self-sealing material in the port, while still allowing injection of saline. The study shows clinical and experimental evidence of leakage from the McGhan Style 150 injection port, which is contrary to other similar laboratory studies. However, in those studies the needles were inserted at the apex of the port membrane, while our study shows that this is not in accordance with a clinical setting, where perforation may be all over the port. It is concluded that extreme care should be taken in the clinical setting only to perpendicularly perforate the apex of the injection port membrane. Peripheral perforation of the port may result in leakage of saline.


Asunto(s)
Implantes de Mama/efectos adversos , Análisis de Falla de Equipo , Falla de Prótesis , Implantación de Mama , Humanos , Inyecciones , Agujas , Presión , Diseño de Prótesis , Dispositivos de Expansión Tisular/efectos adversos
17.
Acta Physiol Scand Suppl ; 628: 1-31, 1995.
Artículo en Inglés | MEDLINE | ID: mdl-8801774

RESUMEN

In humans, the head-up tilted position results in central hypovolaemia which mimicks haemorrhage and is associated with cardiovascular changes that can be divided into two stages. 1) One stage with increase in HR and vascular resistance and a slight increase in MAP. 2) Another stage with decrease in HR, vascular resistance and MAP and appearance of presyncopal symptoms (hypovolaemic shock). The first stage is "sympathoexcitatory" as plasma NA originating from postganglionic vasoconstrictory sympathetic neurons increase. Limb vascular resistance contributes to the increase in TPR at this time. The second stage is "sympathoinhibitory" in nature as plasma NA slightly decreases, or remains unchanged, while plasma A, originating from the adrenal medulla, raises. This pattern is a reflection of a differentiated sympathetic response as an increase in the activity of the nerves innervating the adrenals and decrease in renal sympathetic nerves has been reported by others. There is a decrease in limb as well as total vascular resistance. The secretion of potent vasoactive peptides may contribute to the circulatory changes taken place during head-up tilt. The head-up tilted position is associated with central hypovolaemia which is reliably monitored by electrical impedance. There is a close relation between the increase in thoracic electrical impedance and the decrease in plasma ANP which is regulated by atrial stretch. Also, from recording of technetium labeled red blood cells and measurements of haematocrite the decrease in CBV is reflected by thoracic electrical impedance. In contrast, CVP reflects changes in CBV during the initial head-up tilt only, whereafter CVP usually is unchanged or may even increase. After the initial head-up tilt the decrease in the CBV is caused by further reduction in plasma volume as shown by increase in haematocrite and unchanged distribution of labeled red blood cells. This mechanism is reflected by application of regional electrical impedance measurements at a low and high frequency current. The low frequency current, passing extracellular fluid only, changing more than the high frequency current that passes extra as well as intracellular fluid. Central hypovolaemia was found to stimulate the pituitary-adrenal axis, and the development of hypotension strongly increases plasma ACTH, beta-END, cortisol and PRL. Blocking histaminergic receptors did not change the pituitary-adrenal response to central hypovolaemia, while the sympathoadrenal response was affected by histaminergic receptor blockade. The H2-receptor antagonist cimetidine inhibited plasma A, while the H1-receptor antagonist mepyramine attenuated plasma NA and reduced cardiovascular tolerance, and also induced some sedation. A possible effect of sedation and anxiolysis was investigated by administration of the GABAergic drug diazepam. This drug did not change the cardiovascular response to head-up tilt, but reduced the increase in plasma cortisol. This indicates that the appearance of presyncopal symptoms is not related to "stress" but associated with the cardiovascular effects of central hypovolaemia. Another endogenous substance, serotonin (5-HT), may be also involved in cardiovascular as well as endocrine regulation. We investigated the effect of blocking three main receptors on the development and effects of hypovolaemic shock. Methysergide (5-Ht1+2-receptor antagonist) attenuated plasma NA, beta-END, PRL and PRA during tilt with a slight reduction of cardiovascular tolerance. The 5-HT2-receptor antagonist ketanserin reduced cardiovascular tolerance without significant effects on the hormonal responses. The 5-HT3-receptor antagonist ondansetron inhibited the plasma CGRP and adrenalin response to central hypovolaemia without influencing cardiovascular tolerance. It is concluded that the head-up tilted model in humans can be applied to study cardiovascular and endocrine mechanisms until the development of hypovolaemic shock.(ABSTRACT TRUNCATED)


Asunto(s)
Histamina/fisiología , Sistemas Neurosecretores/fisiopatología , Serotonina/fisiología , Choque/fisiopatología , Animales , Fenómenos Fisiológicos Cardiovasculares , Circulación Cerebrovascular , Inclinación de Cabeza , Humanos , Neurotransmisores/fisiología
18.
Neuroendocrinology ; 48(2): 167-73, 1988 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-2975768

RESUMEN

It has been shown that histamine (HA) stimulates prolactin (PRL) secretion via H2 receptors following intra-cerebroventricular infusion and via H1 receptors following systemic (intra-arterial) infusion. Since the effect of HA appears to be exerted at a suprapituitary level, we investigated the involvement of the tuberoinfundibular dopaminergic (TIDA) system in HA-induced PRL secretion in urethane-anesthetized male rats. HA infused intracerebroventricularly (30 micrograms) or intra-arterially (420 micrograms) decreased the dopamine (DA) concentration in pituitary portal blood by 30 and 23%, respectively. Blockade of DA receptors by pimozide did not prevent the stimulation of PRL secretion induced by intracerebroventricular infusion of HA or the H2 receptor agonist dimaprit. Furthermore, during DA receptor blockade intracerebroventricular infusion of the H1 receptor agonist 2-thiazolylethylamine inhibited PRL secretion. In contrast, pimozide prevented the stimulation of PRL secretion induced by intra-arterial infusion of HA and the H1 receptor agonist 2-thiazolylethylamine. In fact, under these conditions intra-arterial infusion of HA or the H2-receptor agonist dimaprit inhibited PRL secretion. During treatment with alpha-methyl-p-tyrosine, which reduced the hypothalamic DA content by 50%, HA infused intracerebroventricularly stimulated PRL secretion, while HA infused intra-arterially inhibited the secretion, which is in accordance with the results obtained during pimozide treatment. Cholinergic blockade by atropine did not prevent the HA-induced PRL release, excluding the possibility that the observed effect of pimozide is due to its anticholinergic property. We suggest that intracerebroventricular infusion of HA by activation of H2 receptors may stimulate PRL secretion partly via inhibition of the TIDA system and partly via other mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Ventrículos Cerebrales/fisiología , Dopamina/fisiología , Histamina/farmacología , Neuronas/fisiología , Prolactina/metabolismo , Receptores Histamínicos H1/fisiología , Receptores Histamínicos H2/fisiología , Tiazoles/farmacología , Tiourea/farmacología , Animales , Ventrículos Cerebrales/efectos de los fármacos , Dimaprit , Histamina/administración & dosificación , Infusiones Intraarteriales , Inyecciones Intraventriculares , Masculino , Ratas , Ratas Endogámicas , Valores de Referencia
19.
Neuroendocrinology ; 47(1): 68-74, 1988 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-3340272

RESUMEN

Histamine (HA) is likely to participate in the neuroendocrine regulation of prolactin (PRL) secretion. We, therefore, studied the possible involvement of HA in the stress-induced release of PRL in conscious male rats. HA (30 micrograms) infused intracerebroventricularly 15 min before decapitation elevated PRL plasma levels from 5 +/- 1 to 54 +/- 6 ng/ml (p less than 0.01). Intracerebroventricular infusion of the H2 receptor antagonists cimetidine (CIM: 100 micrograms) or ranitidine (RAN: 125 micrograms) abolished the PRL response to HA (p less than 0.01), while intracerebroventricular infusion of the H1 receptor antagonist mepyramine (MEP; 100 micrograms) inhibited the response only 40% (p less than 0.05). Intra-arterial infusion of CIM (2,000 micrograms) or RAN (2,500 micrograms) inhibited the HA-stimulated PRL secretion 52% (p less than 0.01) or 63% (p less than 0.01), respectively. The H1 receptor antagonists MEP (1,000 micrograms) and SKF-93944 (1,500 micrograms) had no effect following intra-arterial administration. Restraint stress increased the PRL level to 84 +/- 6 ng/ml (p less than 0.01 vs. control). This effect was prevented by intracerebroventricular infusion of CIM or RAN (p less than 0.01) and inhibited 75% by MEP (p less than 0.01). Intra-arterial infusion of CIM, MEP, and SKF-93944 inhibited the stress response about 50% (p less than 0.01), while RAN decreased the response only 25% (p less than 0.05). Ether stress elevated the plasma PRL concentration to 46 +/- 5 ng/ml (p less than 0.01 vs. control). When infused intracerebroventricularly CIM or RAN prevented the response (p less than 0.01), while MEP had no effect.(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Histamina/fisiología , Prolactina/sangre , Estrés Fisiológico/metabolismo , Animales , Cimetidina/administración & dosificación , Cimetidina/farmacología , Éter , Histamina/administración & dosificación , Inyecciones Intravenosas , Inyecciones Intraventriculares , Masculino , Pirilamina/administración & dosificación , Pirilamina/farmacología , Pirimidinonas/administración & dosificación , Pirimidinonas/farmacología , Ranitidina/administración & dosificación , Ranitidina/farmacología , Ratas , Ratas Endogámicas , Receptores Histamínicos/efectos de los fármacos , Restricción Física
20.
Acta Endocrinol (Copenh) ; 115(4): 461-8, 1987 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-2888250

RESUMEN

The effects on prolactin secretion of histamine H2-receptor antagonists infused intracerebroventricularly were studied in urethane anaesthetized male rats. A dose of 1.6 mumol cimetidine stimulated basal prolactin secretion and did not affect the histamine-induced release, whereas 0.4 mumol cimetidine inhibited basal and histamine-stimulated prolactin secretion. 0.1 mumol cimetidine had no effect. The more potent H2-receptor antagonist ranitidine at doses of 0.1, 0.4, 1.6 mumol had no effect on basal prolactin secretion, whereas 0.4 and 1.6 mumol inhibited the histamine-stimulated secretion completely. SKF-92408, a compound resembling cimetidine in chemical structure but devoid of H2-receptor antagonist activity, stimulated basal prolactin secretion at a dose of 1.6 mumol, but had no effect on the histamine-induced release or at a dose of 0.4 mumol. The H2-receptor antagonists metiamide and oxmetidine (1.6 mumol) stimulated basal prolactin secretion and did not prevent the response to histamine. A dose of 0.4 or 1.6 mumol imidazole (the ring structure contained in cimetidine, SKF-92408, metiamide, and oxmetidine) had no effect on basal or histamine-stimulated prolactin secretion. The findings indicate that cimetidine stimulates prolactin secretion by a non-specific action when infused centrally at high doses. In contrast, when infused at lower doses cimetidine inhibits the basal and histamine-stimulated secretion by blockade of H2-receptors. The prolactin-stimulatory action of cimetidine was not due to an H2-agonist effect, since ranitidine did not prevent the response. Cimetidine did not stimulate prolactin secretion via an effect on the dopaminergic system, since the drug had no effect on the dopamine concentration in hypophysial portal blood or in hypothalamic tissue and since inhibition of the dopamine synthesis by alpha-methyl-p-tyrosine did not prevent the cimetidine-induced prolactin release.


Asunto(s)
Cimetidina/administración & dosificación , Antagonistas de los Receptores H2 de la Histamina/administración & dosificación , Prolactina/metabolismo , Animales , Dopamina/metabolismo , Relación Dosis-Respuesta a Droga , Guanidinas/farmacología , Imidazoles/administración & dosificación , Imidazoles/farmacología , Inyecciones Intraventriculares , Masculino , Metiamida/administración & dosificación , Prolactina/sangre , Ranitidina/administración & dosificación , Ratas , Ratas Endogámicas
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