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Biomedical subjects

L Rózsa

Publications and source records attributed to L Rózsa.

At least 19 recordsLinked to original sources
PubMed2006

Reduced taxonomic richness of lice (Insecta: Phthiraptera) in diving birds.

Avian lice occupy different habitats in the host plumage that the physical environment outside the host body may affect in several ways. Interactions between host plumage and water may be an important source of such effects. Here, we use a comparative approach to examine the effect of a host's diving behavior on the taxonomic richness of its lice. Louse genera richness was significantly lower in clades of diving birds than on their nondiving sister clades. Species richness of host and body mass did not differ significantly between these clades; thus, these factors did not bias our results. This study suggests that the hosts' diving behavior can effectively influence ectoparasite communities.

Animals↗
PubMed2000

Quantifying parasites in samples of hosts.

Whereas terminological recommendations require authors to use mean intensity or mean abundance to quantify parasites in a sample of hosts, awkward statistical limitations also force them to use either the median or the geometric mean of these measures when making comparisons across different samples. Here, we propose to reconsider this inconsistent practice by giving priority to biological realism in the interpretation of different statistical descriptors and choosing the statistical tools appropriate to our decisions. Prevalence, mean intensity, and indices of parasite distribution (such as median intensity) are suitable descriptors to quantify parasites in a sample of hosts. These measures have different biological interpretations and need different statistical methods to be compared between samples.

Animals↗
PubMed1999

Influencing random transmission is a neutral character in hosts.

This study introduces an individual-based model on a host-parasite assemblage to investigate whether hosts are necessarily selected for obstructing the transmission of virulent parasites to conspecifics. Contrary to the widespread notion, a host's ability to influence parasite transmission within the host population is a neutral character provided that parasite transmission routes are random, with no reference to genetic relatedness. Due to a lack of selection pressure under such circumstances, hosts may fail to evolve counteradaptations against manipulations by parasites to enhance transmission. However, vertically biased transmission (biased toward kin) selects hosts for a decrease of parasite transmission, while it is also known to select parasites to decrease virulence. Horizontally biased transmission routes (biased toward nonrelated conspecifics) select hosts to increase parasite transmission. In this case, their interests coincide with that of their virulent parasites in enhancing transmission to conspecifics. This finding yields the predictions that hosts infected by virulent pathogens, but unable to recover from disease, should be prone to emigrate from their natal territories and also to enhance transmission at a distance from their natal ranges. These results may considerably improve our understanding of the epidemiology of contagious pathogens and the evolution of social and sexual behavior in host species.

Alleles↗
PubMed1998

Host-mediated site segregation of ectoparasites: an individual-based simulation study.

Site segregation of coexisting ectoparasite species may result either from a direct interaction such as resource competition between them or from a host-mediated interaction. Here we present an individual-based model for the coevolution of 1 host and 2 parasite species to study this latter hypothesis. Parasite species are generalists at the start of the simulation and develop site specificities under the following assumptions. Parasite populations are not subject to resource limitations but are limited directly by host defense as predation. Hosts have 2 sites that need different defensive abilities to reduce their parasite burden. Parasites need to exhibit different evasive abilities to survive on different sites. Host grooming selects parasites for an increasing capability for evasion, whereas parasites select hosts for an increasing efficiency of grooming. Two trade-offs are incorporated into the model: one between host defensive abilities on the 2 sites, and another between parasite evasive abilities on the 2 sites. We conclude that, under these assumptions, the optimization of host defense and parasite evasion strategies may select ectoparasites for site segregation and this may stabilize the coexistence of parasite species.

Animals↗
PubMed1997

Correlation between central somatosensory conduction time, blood flow velocity, and delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

In this retrospective study of 67 aneurysmal patients, the predictive role of central conduction time (CCT) on vasospasm occurrence evaluated by means of transcranial Doppler sonography (TCD) and the correlation of CCT to blood flow velocity measured simultaneously in postoperative course were studied. Data about the clinical state of patients at the time of admission (Hunt Hess scale), severity of subarachnoidal hemorrhage on initial CT scan (Fisher grade), timing of surgery (acute or delayed), outcome (Glasgow Outcome Scale), severity of vasospasm graded by highest mean blood flow velocity (BFV) during the entire clinical course and CCT values measured at admission (preoperatively), then postoperatively (one day after surgery) and simultaneously with later TCD investigations were collected from the files. Interhemispheric difference of CCT was also calculated. The results showed that CCT at admission was not predictive for vasospasm. CCT measured either at admission or on the first postoperative day did not differ significantly in the different grades of vasospasm. Similar results were obtained in the acute and in the late operated group of patients. The results also suggest that increased CCT and interhemispheric difference at the time of admission indicate a worse prognosis, but this can be related to higher surgical risk rather than to a higher incidence of late ischemic deterioration. Simultaneous CCT and TCD examinations demonstrated that coincident and statistically significant (p < 0.01) increase of actual CCT (6.7 msec) was found only in the severe grade of vasospasm (BFV 200 cm/s). The authors discuss the role of CCT and TCD monitoring in the management of aneurysmal subarachnoid hemorrhage.

Adult↗
PubMed1997

Adaptive sex-ratio manipulation in Pediculus humanus capitis: possible interpretations of Buxton's data.

The sex-ratio pattern of an exceptional population of human head lice (collected in the Colombo Prison, Ceylon, in 1934 to 1936) was found to be consistent with a current hypothesis on adaptive sex-ratio manipulation. Data suggest that the louse burdens were isolated and, therefore, small burdens were inbred. Thus, local mate competition favored females that produced offspring with a female bias. This is the first report to suggest that anopluran lice are capable of adaptive sex-ratio manipulation.

Adaptation, Physiological↗
PubMed1997

Comparison of fullfat soybean, sunflower seed and protected fat as fat supplements for their effect on the performance of growing-finishing bulls and carcass fatty acid composition.

One hundred and twelve Holstein bulls (179-203 kg) were allotted to four dietary treatment groups (I: control; II: fullfat soybean diet; III: sunflower seed diet, and IV: protected fat diet) and used in a 120-day comparative feedlot trial to evaluate the effect of toasted fullfat soybean, whole sunflower seed and protected fat (calcium soap) on their weight gain, feed conversion and carcass fatty acid composition. The diets consisted of 45-46% concentrate and 55-54% corn silage. Digestibility, nutritive value as well as degradability were also determined. The apparent digestibility of dry matter, organic matter, N-free extract and crude protein as well as nutritive value were almost similar for the four diets. However, crude fibre, acid detergent fibre (ADF) and neutral detergent fibre (NDF) digestibilities decreased with increasing fat level but the differences were not significant. The inclusion of fullfat soybean or whole sunflower seed significantly (P < 0.05) increased the digestion of fat. Ruminal degradability of protein and dry matter were significantly (P < 0.01) lower for toasted fullfat soybean mixture compared to whole sunflower mixture. The inclusion of toasted fullfat soybean, whole sunflower seed and calcium soap in the diets was not effective in improving the bulls' weight gain or feed conversion in this trial. As both toasted fullfat soybean and whole sunflower seed increased the proportions of C18:1, C18:2 and C18:3 in adipose fat tissue and decreased the proportion of C16:0, they consequently significantly (P < 0.01) increased the ratio of unsaturated fatty acids. Whole sunflower seed was more effective than fullfat soybean. However, inclusion of the calcium soap had no effect on the fatty acid profiles in the present study.

Adipose Tissue↗
PubMed1993

An experimental test of the site specificity of preening to control lice in feral pigeons.

Site specificities of ectoparasites on the host may have evolved due to the selective pressure exerted by host grooming. The present study demonstrates that the efficiency of avian preening varies among sites on the host. The study relies on the simple idea that the effectiveness of preening behavior to control lice can be quantified by the removal rate of dead lice glued onto the feathers of living birds. Two treatments were done to document site-specific differences in the efficiency of preening for louse control. The first treatment showed that lice disappear from the underwing covert feathers significantly more than from the tail feathers. A second treatment showed that preening was responsible for the differential removal of lice. There seems to be some correspondence in the site specificity of the louse species Columbicola columbae and that of the efficiency of preening by the host, which is the feral pigeon (Columba livia).

Analysis of Variance↗
PubMed1991

[Intracranial pressure increase and changes in cerebrovascular circulation, associated with brain death, studied by transcranial Doppler sonography].

Blood flow velocity of 24 patients in state of the brain death were examined by transcranial Doppler sonography. Authors expound the characteristic velocity-pulse graphs recorded in progressively increasing intracranial pressure and their chronology as well. The different forms of the oscillating flow and their successive development are described. The oscillating flow, the systolic spikes and the so called "zero Flow" are the transcranial Doppler signs of the ceased cerebral blood flow, and these signs can be used as one of the evidence of the brain death.

Adolescent↗
PubMed1991

Investigations on oscillating flow spectra as a Doppler ultrasonographic sign of intracranial circulatory arrest.

In a total of 90 patients with intracranial hypertension and subsequent intracranial circulatory arrest, the cerebral basal arteries were examined with transcranial Doppler ultrasonography. In order to explain the development of the various forms of oscillating flow, a blood-pressure cuff was placed on the distal forearm of 25 healthy subjects to investigate the flow spectra in the proximal arteries in the presence of increasing stream resistance. With raising the pressure of the cuff, the changes in the Doppler sonographic flow spectra were simulated as in case of increasing intracranial pressure. As intracranial pressure increases at constant systemic blood pressure values, the flow velocity spectrum changes in a typical manner. At the stage of oscillating flow, characteristic changes in the flow spectra can be observed. Investigations showed that compliance is reduced in a distal to proximal direction. This means that a different frequency spectrum can be recorded in distal branches of the middle cerebral artery than in the proximal carotid artery at the same point in time. By examining the flow velocity spectra from the brachial artery, it was possible to understand better the typical course of an intracranial circulatory arrest resulting from increased stream resistance.

Adolescent↗
PubMed1990

Hemodynamic changes after ruthenium irradiation of Hippel's angiomatosis.

The authors report a case of Hippel's angiomatosis successfully treated with contact beta irradiation. The area of the multiplex retinal angioma and the accompanying retinal detachment was irradiated with a 106Ru/106Rh radioactive applicator. Hemodynamic changes due to irradiation were followed up in the ipsilateral ophthalmic artery with transcranial Doppler sonography. Scarring was also demonstrated by fluorescein angiography and A- and B-scan ultrasonography. Irradiation caused the narrowing and later the occlusion of the precapillaries and capillaries (i.e. the resistance vessels) and that of the shunts inside the angioma; consequently, vascular resistance increased. Transcranial Doppler sonographic recordings showed a decrease in blood flow velocity as compared to pathologically increased blood flow velocity in angiomas, and a gradual increase in vascular resistance which was lower before treatment.

Adult↗
PubMed1989

[Detection of increased intracranial pressure by transcranial Doppler sonography in infants].

The value of transcranial Doppler sonography is demonstrated in two infants with an elevation of intracranial pressure (ICP). One of them suffered from hydrocephalus and ICP increased because of her VP shunt-insufficiency. In the other case status epilepticus caused brain oedema and a rise in intracranial pressure. In both cases, transcranial Doppler sonography showed a decrease in blood flow (CBF) velocity and an increase in the Pourcelot index in the middle cerebral artery. Quick or gradual reduction of the ICP led to an increase in CBF velocity and a decrease in the Pourcelot index. On the basis of experiences of the authors, transcranial Doppler sonography is a valuable method of verifying the elevation of ICP. It is suitable for measuring the effect of treatment necessitated by the elevation of ICP. The method is non-invasive, quick and it can be freely repeated. Therefore it is applicable for monitoring the dynamic of ICP.

Age Factors↗
PubMed1989

[Transcranial Doppler sonography, a new non-invasive method for the study of cerebrovascular circulation].

Transcranial Doppler Sonography. Authors publish the experiences gained by 2300 examinations with Transcranial Doppler Sonography (TDS) which is a new, noninvasive ultrasound method to examine cerebral blood flow velocity in the basal arteries. The theoretical ground and the technique of the investigation is detailed. Mean values of blood flow velocity in the middle cerebral artery of 88 healthy volunteers in different age groups are reported. Authors stress on the numerous advantages of the utilization of this technique. Different pathological alterations of blood flow velocity and characteristic types of velocity-pulse figure are accounted. At last illustrative case reports proving the importance of TDS in different pathological states are presented.

Adult↗
PubMed1989

Traumatic brain swelling studied by computerized tomography and densitometry.

Two-hundred and fifty-two computerized tomography (CT) scans of 107 patients with head injuries were analyzed. The most frequent consequence of trauma was a diffuse swelling of the brain in 91% of the cases. The severity of brain swelling and its course can be estimated by the compression of (or absence of) the intracranial cerebrospinal fluid space. These observations may be of prognostic value as well. By measurement of the Hounsfield units (HU) in 52 cases the blood or water content in the brain tissues was assessed. An increase in blood content of the tissues (hyperaemia) can account for an increase in Hounsfield values. A decrease in HU suggests brain edema. The density measurements showed that in the first hours and days following head injury, the diffuse brain swelling was caused by severe cerebrovascular congestion in the majority (53%) of the cases. Immediate brain edema without a preceding hyperaemic phase occurs less frequently (32%). Between the 1st and 4th day after injury, edema started to prevail, and between the 5th and 8th day the edematous type of brain swelling was present almost exclusively.

Absorptiometry, Photon↗
PubMed1989

Synthesis of dibenzodioxazocines and their effects on cholinesterases and muscarinic cholinergic receptors.

A new family of tricyclic compounds, the dibenzodioxazocines were synthesized. These compounds were the following: 2-chloro-12-(2-piperidino-ethyl)-dibenzo d,g 1,3,6 dioxazocine hydrochloride: EGYT-2347, 2-chloro-12-(3-dimethylamino-2-methyl-propyl)-dibenzo [d,g] [1,3,6]-dibenzodioxazocine hydrochloride: EGYT-2509, 2-chloro-12-(3-dimethylamino-propyl)-dibenzo [d,g] [1,3,6] dioxazocine-maleate: EGYT-2474 and 2-chloro-12-2-(4-methyl-piperazino)-ethyl-dibenzo [d,g] [1,3,6]-dioxazocine-dihydrochloride: EGYT-2541. These compounds are inhibitors of both butyryl- and acetylcholinesterase to and they exhibited relatively good anticholinergic properties in receptor binding experiments. The most selective inhibitor of butyrylcholinesterase is the compound EGYT-2347 (Ki = 1.5 x 10(-7) M) which strongly binds to rat brain muscarinic cholinergic receptor (KD = 4.1 x 10(-8) M).

Animals↗
PubMed1989

Vasospasm after head injury studied by transcranial Doppler sonography.

During the past 2 years cerebral blood flow velocity was measured serially first of all in the middle cerebral arteries and in the bifurcation of the carotid arteries, less frequently in the other basal arteries by transcranial Doppler sonography in 36 head injured patients selected from 87 cerebral contusions and intracranial haematomas. Raised flow velocity referring to cerebral vasospasm was observed in 14 (40%) of 36 cases. Vasospasm developed between the 2nd and 8th days in the basal arteries, never on the first day. It was classified as slight (over 120 cm/sec) and sever (over 160 cm/sec) in the case of vasospasm lasting for several days. Development of vasospasm could be justified in 6 from 14 control angiographies. Authors' observations are compared with some literary data of traumatic vasospasm. The theoretical significance and practical usefulness of transcranial Doppler sonography in the study and follow up of the blood flow of the injured brain, especially in traumatic vasospasm, are emphasized.

Adolescent↗
PubMed1980

Planum sphenoidale meningioma. Attachment and blood supply.

By reviewing clinical and radiological data and surgical findings of 35 so-called "olfactory groove meningioma" cases, the authors conclude that this is not a homogenous group. According to the attachment and blood supply they differentiate two varieties, the planum sphenoidale meningioma (PM) and the olfactory meningioma (OM). It seems possible to distinguish both groups clinically and with regard to the localization of hyperostosis and pneumencephalographic and angiographic findings.

Adult↗