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Biomedical subjects

L Herrero

Publications and source records attributed to L Herrero.

At least 19 recordsLinked to original sources
PubMed2006

Bone remodelling after total hip arthroplasty using an uncemented anatomic femoral stem: a three-year prospective study using bone densitometry.

PURPOSE: To evaluate the clinical, radiological, and densitometric changes in the bone-remodelling patterns of femoral stems aligned in neutral, valgus, or varus positions. METHODS: Between February and October 2000, 70 patients underwent unilateral total hip arthroplasty for primary osteoarthritis using an uncemented Anatomique Benoist Girard (ABG) II stem. 69 patients (30 males and 39 females) with a mean age of 59 years (range, 38-76 years) and a mean body weight of 79.3 kg (range, 29-110 kg) completed 3 years' follow-up on bone remodelling. The clinical, radiological, and densitometric changes of the neutral, valgus, and varus groups were evaluated, and the difference in bone-remodelling patterns between the 3 groups was analysed. RESULTS: 54 patients had neutrally placed stems, while varus and valgus malalignment occurred in 6 and 9 patients, respectively. Clinical and radiological evaluations were very similar among the 3 groups. Only densitometry could detect traceable changes resulting from the differing biomechanics of the neutral, varus, and valgus stem alignments. CONCLUSION: The ABG II stem design made moderate errors in alignment biomechanically tolerable. Alignment defects had no clinical consequences and resulted in minimal differences in bone remodelling.

Absorptiometry, Photon↗
PubMed2005

Eye movements evoked by electrical microstimulation of the mesencephalic reticular formation in goldfish.

Anatomical studies in goldfish show that the tectofugal axons provide a large number of boutons within the mesencephalic reticular formation. Electrical stimulation, reversible inactivation and cell recording in the primate central mesencephalic reticular formation have suggested that it participates in the control of rapid eye movements (saccades). Moreover, the role of this tecto-recipient area in the generation of saccadic eye movements in fish is unknown. In this study we show that the electrical microstimulation of the mesencephalic reticular formation of goldfish evoked short latency saccadic eye movements in any direction (contraversive or ipsiversive, upward or downward). Movements of the eyes were usually disjunctive. Based on the location of the sites from which eye movements were evoked and the preferred saccade direction, eye movements were divided into different groups: pure vertical saccades were mainly elicited from the rostral mesencephalic reticular formation, while oblique and pure horizontal were largely evoked from middle and caudal mesencephalic reticular formation zones. The direction and amplitude of pure vertical and horizontal saccades were unaffected by initial eye position. However the amplitude, but not the direction of most oblique saccades was systematically modified by initial eye position. At the same time, the amplitude of elicited saccades did not vary in any consistent manner along either the anteroposterior, dorsoventral or mediolateral axes (i.e. there was no topographic organization of the mesencephalic reticular formation with respect to amplitude). In addition to these groups of movements, we found convergent and goal-directed saccades evoked primarily from the anterior and posterior mesencephalic reticular formation, respectively. Finally, the metric and kinetic characteristics of saccades could be manipulated by changes in the stimulation parameters. We conclude that the mesencephalic reticular formation in goldfish shares physiological functions that correspond closely with those found in mammals.

Animals↗
PubMed2005

Levels and trends of polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) in Spanish commercial fish and shellfish products, 1995-2003.

The polychlorinated dibenzo-p-dioxin (PCDD), dibenzofuran (PCDF), and polychlorinated biphenyl (PCB) contents of 123 Spanish commercial salmon, tuna fish, sardine, oyster, mussel, and clam samples from 1995 to 2003 were investigated. A significant decrease of dioxin and non-ortho PCB concentrations in the studied species was found over the years. The decrease was greater in the case of dioxins than in that of non-ortho PCBs, especially during the early years of the study. PCB and PCDD/F concentrations in the years 2001-2003 were comparable to those reported in the literature for similar species collected after 1999. Mean PCB concentrations ranged from 3.46 ng/g of fresh weight (fw) in clams to 100 ng/g of fw in tuna fish. PCDD/F mean current levels ranged from 0.62 pg/g of fw in clams to 2.89 pg/g of fw in oysters. Toxic equivalent quantities (WHO-TEQ) ranged from 0.05 pg of WHO-TEQ(PCDD/Fs)/g of fw in clams to 0.5 pg of WHO-TEQ(PCDD/Fs)/g of fw in salmon (in the upper bound determination levels). When coplanar PCBs were included, the WHO-TEQ(PCDD/Fs+cop) (PCBs) values increased by a range of 1.7 times in oysters to 14.1 times in tuna fish. The decrease in dioxin concentrations suggests that efforts to control dioxin emissions and to reduce human exposure through foodstuffs are succeeding. The high contribution of PCBs to total WHO-TEQs in the fish and shellfish species investigated suggests that it is important to determine PCBs in foodstuffs, and especially in fish products, and they should be included in further research and future legislation.

Animals↗
PubMed2005

Visual orienting response in goldfish: a multidisciplinary study.

The neural basis underlying the orienting response has been thoroughly studied in frontal-eyed mammals. However, in non-mammalian species, including fish, it remains almost unknown. Therefore, we studied the contribution of the optic tectum and the mesencephalic reticular formation to the performance of the orienting response in goldfish, using behavioural, physiological, and anatomical tracer techniques. The appearance of a visual stimulus (a pellet of food) in the environment of a goldfish evoked a turn of the body to reorient the line of sight. Left-tectal lobe ablation abolished the orienting turn response towards the contralateral hemifield. Electrical microstimulation of the optic tectum suggested the presence of a motor map, which is in correspondence with the overlying visual representation, as previously reported in other vertebrates. The tracer biotin-dextran amine was injected into different functionally identified tectal zones. The results showed that rostral and caudal poles of the mesencephalic reticular formation receive outflow mainly from the rostral and caudal tectal poles, respectively. This suggests that the tectal wiring with downstream structures is site-dependent. Furthermore, the electrical activation of rostral and caudal mesencephalic reticular formation revealed a different contribution to vertical and horizontal orienting eye movements. We conclude that the basic neural system coding the orienting response appears early in phylogenesis, although some specific characteristics are selected by adaptive pressure.

Animals↗
PubMed2005

Differential effects of trans-crotononitrile and 3-acetylpyridine on inferior olive integrity and behavioural performance in the rat.

The inferior olive climbing fibre projection is key to cerebellar contributions to motor control. Here we present evidence for a novel tool, trans-crotononitrile (TCN), to selectively inactivate the olive to study its functions. Anatomical, electrophysiological and behavioural techniques have been used in rats to assess the CNS effects of TCN, with a focus on the olivocerebellar projection. These findings were compared with those obtained with 3-acetylpyridine (plus nicotinamide administered 3.5 h later, 3AP + 3.5 h). Fluoro-Jade B cell labelling showed that TCN and 3AP + 3.5 h induce neurodegeneration primarily within the inferior olive, with no other targets in common. Recordings of evoked field potentials on the cerebellar cortical surface showed that both neurotoxins can reduce transmission in climbing fibre but not mossy fibre pathways. Both histological and electrophysiological differences suggest that TCN and 3AP have distinct mechanisms of action. Estimates of the numbers of surviving cells within individual subdivisions of the olive indicate that TCN and 3AP + 3.5 h cause different patterns of subtotal olivary lesion: most surviving neurons are present in the rostral (TCN) or caudal (3AP + 3.5 h) parts of the medial accessory olive, which are associated with two different cerebellar modules: the C2 and A modules, respectively. In behavioural studies, TCN and 3AP + 3.5 h produced differences in motor deficits consistent with the notion that these cerebellar modules have distinct functional responsibilities. Thus, studies using TCN as compared with 3AP + 3.5 h have the potential to shed light on the contributions of different cerebellar modules in motor control.

Animals↗
PubMed2004

Dietary intakes of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in Spain.

Congener-specific analyses of seventeen 2,3,7,8-substituted PCDD/Fs, three non-ortho and 8 mono-ortho dioxin-like polychlorinated biphenyls (PCBs) were performed on 258 Spanish foodstuff samples, mainly of animal origin, for 2000--03. Daily dietary intakes of PCDD/Fs and PCBs, expressed as toxic equivalents (WHO-TEQs), were estimated by combining food consumption data from the Spanish National Institute Statistics survey and concentration levels measured in individual samples, using upper bound determination values (not detectable = limit of detection). The calculated dietary intake of PCDD/Fs for a person weighing 70 kg was 1.35+/-0.11pg WHO-TEQs kg(-1) bw day(-1), and 3.22+/-0.75 pg WHO-TEQs kg(-1) bw day(-1) if dioxin-like PCBs (non- and mono-ortho PCBs) were included, showing the importance of their inclusion in monitoring studies. Both values were within the range of tolerable daily intake (TDI) proposed by the WHO (1-4pg WHO-TEQs kg(-1) bw day(-1)). The current levels are lower than earlier intakes estimates conducted in Spain. Meat and meat products accounted for more than 35% of the intake, followed by milk and milk products (29%), vegetables oils (19%), fish and seafood (11%) and eggs (4%). Dioxin-like PCBs are an important component in the total WHO-TEQs in foodstuffs. This is particularly true for the fish food group, where the total WHO-TEQs is dominated by dioxin-like PCBs (up to 80% of WHO-TEQs in some cases).

Benzofurans↗
PubMed2003

Knee arthrodesis with the Wichita fusion nail.

We reviewed 32 patients who all had knee arthrodesis performed after failed knee replacement. The minimum clinical follow-up was 1 year. The arthrodesis was performed by means of the Wichita fusion nail in 11, by external fixation in 15 cases, by plating in three and by intramedullary nailing in three. The mean patient age was 68.6 years. When the Wichita nail was used, fusion was achieved in ten out of 11 cases after a mean period of 4.5 (3-7) months. Of the remaining 21 patients, fusion was only achieved in 11 cases after a mean period of 6.5 (4.5-10) months.

Aged↗
PubMed2003

Connectivity of the goldfish optic tectum with the mesencephalic and rhombencephalic reticular formation.

The optic tectum of goldfish, as in other vertebrates, plays a major role in the generation of orienting movements, including eye saccades. To perform these movements, the optic tectum sends a motor command through the mesencephalic and rhombencephalic reticular formation, to the extraocular motoneurons. Furthermore, the tectal command is adjusted by a feedback signal arising from the reticular targets. Since the features of the motor command change with respect to the tectal site, the present work was devoted to determining, quantitatively, the particular reciprocal connectivity between the reticular regions and tectal sites having different motor properties. With this aim, the bidirectional tracer, biotin dextran amine, was injected into anteromedial tectal sites, where eye movements with small horizontal and large vertical components were evoked, or into posteromedial tectal sites, where eye movements with large horizontal and small vertical components were evoked. Labeled boutons and somas were then located and counted in the reticular formation. Both were more numerous in the mesencephalon than in the rhombencephalon, and ipsilaterally than contralaterally, with respect to the injection site. Furthermore, the somas showed a tendency to be located in the area containing the most dense labeling of synaptic endings. In addition, labeled boutons were often observed in close association with retrogradely stained neurons, suggesting the presence of a tectoreticular feedback circuit. Following the injection in the anteromedial tectum, most of the boutons and labeled neurons were found in the reticular formation rostral to the oculomotor nucleus. Conversely, following the injection in the posteromedial tectum, most of the boutons and neurons were also located in the caudal mesencephalic reticular formation. Finally, boutons and neurons were found in the rhombencephalic reticular formation surrounding the abducens nucleus. They were more numerous following the injection in the posteromedial tectum. These results demonstrate characteristic patterns of reciprocal connectivity between physiologically different tectal sites and the mesencephalic and rhombencephalic reticular formation. These patterns are discussed in the framework of the neural substratum that underlies the codification of orienting movements in goldfish.

Animals↗
PubMed2002

Nosocomial enterococcal endocarditis: a serious hazard for hospitalized patients with enterococcal bacteraemia.

OBJECTIVES: Enterococci are a major leading cause of infectious endocarditis and also a common cause of hospital-acquired bacteraemia, which is not believed to represent a serious hazard for the endocarditis. The incidence and risk factors for infectious endocarditis in patients with hospital-acquired enterococcal bacteraemia is determined. METHODS: Prospective analysis of 116 patients with enterococcal bacteraemia admitted to medical or surgical wards of a tertiary-care, university affiliated hospital during a period of 5 years. Echocardiography was performed when indicated by clinical criteria. RESULTS: Seventy-five (61.4%) episodes were hospital-acquired and 47 (38.5%) were community-acquired. Most patients had one or more underlying chronic diseases and major abdominal (58.6%) or genitourinary (38.6%) surgery. Seventeen patients (14.6%) developed enterococcal endocarditis. By univariate analysis the risk factors associated with endocarditis were community-acquired infection (P 0.012); monomicrobial bacteraemia (P 0.006); three or more positive blood cultures (P < 0.001); underlying valvulopathy (P < 0.001); presence of a prosthetic valve (P < 0.001) and age (P 0.012). Six patients (8%) developed nosocomial endocarditis. In this group of patients, three or more positive blood cultures (P < 0.01), bacteraemia as a result of Enterococcus faecalis (P 0.007); underlying valvulopathy (P < 0.001) and presence of a prosthetic valve (P < 0.001) were associated with endocarditis. By logistic regression, the presence of underlying valvulopathy and three or more positive blood cultures were associated with endocarditis (OR 21.0; CI 95% 1.65-26.9; P 0.019). CONCLUSIONS: The risk of developing infectious endocarditis in patients with hospital-acquired enterococcal bacteraemia is significant. Patients with underlying valvulopathy and three or more positive blood cultures with E. faecalis are prone to nosocomial enterococcal endocarditis.

Adult↗
PubMed2002

Massive scrotal calcinosis.

BACKGROUND: Scrotal calcinosis is a benign entity characterized by the appearance of calcific masses within the dermis of scrotal skin. Its pathogenesis has not been fully elucidated. OBJECTIVE: A 36-year-old man with massive scrotal calcinosis is described. Our aim was to perform a histologic examination of the surgical piece with subsequent closure of the defect achieving satisfactory cosmetic results. METHODS: Case report and literature review. RESULTS: Histologic studies of multiple nodules showed no epithelial lining and one calcified epidermal cyst. Subtotal excision of the scrotal wall was performed with excellent results. CONCLUSION: Even though the pathogenic mechanism of this entity is still unclear, our findings support the theory of dystrophic calcification of epidermoid cysts. Surgical treatment is the only definitive treatment. Subtotal excision of the scrotal wall in cases of massive calcinosis may be performed with good results.

Adult↗
PubMed2001

Hydatidosis of the pelvis and hip.

We report eight cases of osseous hydatidosis involving the pelvis and hip. All patients were treated by curettage and albendazole therapy. In three cases, in which only the ilium was involved, the outcome was satisfactory. The remaining patients required several debridement procedures in combination with chemotherapy and two developed chronic lesions. We conclude that treatment for this condition is difficult and when the osseous involvement is extensive the prognosis is poor.

Aged↗
PubMed2000

Connectivity of the tectal zones coding for upward and downward oblique eye movements in goldfish.

Deep layers of the goldfish tectum code movements in a topographically ordered motor map. This work studies the relationship between tectal sites (coding eye movements with different vertical directions) and the distributions of boutons (left by their projections), within rostral mesencephalic structures and rhombencephalic reticular formations. These regions have been involved in the generation of the vertical and horizontal components of eye movement, respectively, as suggested by the Cartesian hypothesis of de-codification of tectal signal. With this aim, discrete injections of biotinylated dextran amine (BDA) and Fluoro-Ruby (FR) were made into functionally identified tectal sites, coding oblique eye movements with similar amplitude of the horizontal component but opposite upward and downward vertical directions, and the distribution of synaptic endings was determined. The main findings of the present work were as follows: 1) within the tectal descending tract, axons were organized according to the location of injected sites within the tectum; 2) BDA and FR boutons were distributed in separate clusters within the medial longitudinal fasciculus and oculomotor nuclei, as well as in the nearby mesencephalic reticular formation; and 3) the regions containing both types of bouton overlapped moderately within the mesencephalic reticular formation at the isthmus level. Overlapping was more extended at the different levels of the rhombencephalic reticular formation, although a shift in the distribution of both types of bouton was always observed. These results suggest that, within the vertical generator, the endings were separated to contact the different neuronal population that codes the upward and downward components of movements. In contrast, in the horizontal generator, tectal endings more likely converge on the same neuronal population to code the horizontal component of movements, irrespective of whether the oblique movements were directed upward or downward.

Animals↗
PubMed1999

Tectotectal connectivity in goldfish.

The vertebrate optic tectum is a functionally coupled bilateral structure which plays a major role in the generation of motor commands for orienting responses. However, the characteristics of the tectotectal connectivity are unknown in fish, and have been reported only to a limited extent in other vertebrates. The purpose of the present study was to determine the anatomical basis underlying the functional coupling between tecta in goldfish, and to identify both similarities and differences to those features reported in other vertebrate species. The present experiments used the bidirectional tracer biotinylated dextran amine to map the distribution of labeled cells and synaptic boutons in the contralateral tectum following injections into identified tectal sites. Fibers that interconnect both tecta coursed through the tectal commissure. The cells of origin of these fibers, the tectotectal cells, and their synaptic endings were located in the deep layers, mainly in the strata periventricular and griseum central, respectively. Corresponding sites throughout the two tecta were interconnected in a symmetrical point-to-point fashion. The tectal commissure was composed of at least two distinct bundles of axons, which differed in their dorsoventral location, fiber diameter, and projection targets. The dorsal axons were tectotectal axons, they were thinner in diameter and profusely branched, and gave off en passant and terminal boutons in the deep layers of the contralateral tectum. The ventral axons were thicker in diameter, and formed the contralateral tectofugal-descending tract. Such fibers had few axon collaterals and boutons in the contralateral tectum. Boutons adjacent to retrogradely labeled tectotectal cells were very scarce. The data are discussed in terms of the coupling between tecta generating the motor commands required for orienting movements.

Animals↗
PubMed1998

Influence of the tectal zone on the distribution of synaptic boutons in the brainstem of goldfish.

This study investigated whether the topographic differences in the functional properties of the tectal motor map of goldfish are related to particular patterns of connections with downstream structures. With this aim, the distribution of synaptic boutons in the mesencephalic and rhombencephalic structures was studied after discrete injections of the tracer biotinylated dextran amine were placed at separate sites along the tectal anteroposterior axis. Irrespective of the location of the injection site, the boutons were more abundant in the mesencephalon than in the rhombencephalon, and they were located chiefly ipsilaterally all throughout the brainstem. In the mesencephalon, the boutons were found in its ventrolateral reticular formation and, to a lesser extent, in the nucleus of the medial longitudinal fasciculus, the oculomotor and isthmi nuclei, and the torus semicircularis. In the mesencephalic reticular formation, the bouton location was distributed topographically with respect to the injection site. Terminals were also observed in the nucleus of the medial longitudinal fasciculus after injections into anteromedial or middle tectal zones. In the oculomotor nucleus, boutons were present exclusively in the case of the anteromedial injection. In the rhombencephalon, most boutons were found in the superior reticular formation, and their number decreased in the medial and inferior reticular formations. A topographic distribution could be observed within the superior reticular formation, although its density was attenuated compared with that observed in the mesencephalic reticular formation. The domains of synaptic endings on the ipsilateral side were different from those on the contralateral side: The ipsilateral synaptic endings were located more medially. Finally, a few boutons were also found in the vestibulocerebellar area on either the ipsilateral or the contralateral side, depending on the injection site. From these data, the authors conclude that, in goldfish, irrespective of the tectal injection site, the endings are in similar nuclei in the brainstem; however, the distribution of synaptic boutons within such nuclei can be related to the functional properties of each tectal zone.

Anatomy, Artistic↗
PubMed1998

Tail and eye movements evoked by electrical microstimulation of the optic tectum in goldfish.

This work studies the tail and eye co-ordinated movements evoked by the focal electrical stimulation of the tectum in goldfish. The aim of the study is to understand better those tectal sites and mechanisms that either remain functionally unaltered or are adaptively modified across vertebrates. Stimulation was applied in various tectal zones, and the characteristics of evoked tail and eye movements were examined as a function of the stimulation site over tectal surface and the stimulus parameters. Two types of response were electrically evoked: the former turned the body and the eyes contraversively towards the source of natural stimulus; the second produced initial ipsiversive turning of the body and eyes, followed by several tail beats. Evoking one or other response depended on both the site and parameters of stimulation, and responses were interpreted as orienting- and escape-like, respectively. Depending on the stimulation site, four different zones in the tectum were distinguished: in the medial zone the stimulus elicited eye and tail movements whose size increased with the distance to the rostral pole. The stimulation of the antero-medial zone evoked contraversive or ipsiversive eye saccades but tail movements were similar, irrespective of eye movements. Stimulation within the extreme antero-medial zone evoked convergent eye movements, and tail displacements turning the body either ipsiversively or contraversively. Stimulation of the posterior zone often evoked complex tail movements and pure horizontal eye saccades. Both orienting- and escape-like responses were also dependent on the stimulus parameters. The relationships between stimulus parameters and tail- and eye-orienting movement characteristics suggest that the velocity and duration might be encoded in different aspects of the tectal activity. Current strength also modified the number of tail beats that appeared during escape-like response. In conclusion, the present data suggest the involvement of the optic tectum not only in orienting but also in escape responses and that movements of eye and tail mediating such responses depend on the tectal active locus together with its level of activity.

Animals↗
PubMed1997

Tectal codification of eye movements in goldfish studied by electrical microstimulation. f.

This work compares the tectal codification of eye movements in goldfish with those reported for other vertebrate groups. Focal electrical stimulation was applied in various tectal zones and the characteristics of evoked eye movements were examined as a function of (i) the position of the stimulation over the tectal surface, (ii) the initial position of the eyes and (iii) the parameters (pulse rate, current strength, duration) of the stimulus. In a large medial zone, stimulation within the intermediate and deep layers of the tectum evoked contraversive saccades of both eyes, whose direction and amplitude were roughly congruent with the retinotopic representation of the visual world within overlying layers. These saccades were minimally influenced by the initial position of the eye in the orbit. The topographical arrangement of evoked saccades and body movements suggests that this tectal zone triggers orienting responses in a similar way to those described in other vertebrates. Stimulations applied within the caudal tectum also evoked contraversive saccades, but in disagreement with the overlying retinotopic map--the vertical component was absent. Taken together with electrically evoked body movements reported in free-swimming fish, these saccades could reveal that this zone is involved in escape responses. When stimulations were applied within the anteromedial zone of the tectum, contraversive movements of both eyes appeared much more dependent on initial eye position. Saccades elicited from this area displayed characteristics of "goal-directed saccades" which were similar to those described in the cat. The generation of goal-directed movements from the anteromedial zone suggests that this portion of the goldfish optic tectum has a different intrinsic organization or is connected with the brainstem saccade generator in a different fashion than the medial zone. Finally, stimulation of the extreme anteromedial zone evoked convergent eye movements. These movements and those reported in free-swimming fish following electrical stimulation of this tectal area suggest that this zone could be involved in feeding responses. The relationships between the parameters of electrical stimulation and the characteristics of elicited saccades suggest that the stimulated location within the tectum determines a constant direction in the evoked saccade, whereas the amount and duration of tectal activity, as mimicked by changes in stimulus parameters, together with the tectal locus, determine the velocity and amplitude of the evoked saccade.

Animals↗