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Biomedical subjects

R Farkas

Publications and source records attributed to R Farkas.

At least 19 recordsLinked to original sources
PubMed2001

Traumatic myiasis of geese in Hungary.

Five geese flocks were surveyed to gather data on the prevalence and clinical manifestation of traumatic myiasis and the fly species involved. Myiasis was recorded in all the flocks and the total number of infested geese was 26 (ca. 0.1% of the total numbers). The first cases were observed at the end of May, the last ones in August. Most birds (16/26) were infested in August. Each affected goose had only one lesion, which was located more frequently on the wings (14/26) than on any other body. In seven geese, Wohlfahrtia magnifica (Diptera: Sarcophagidae) was the only myiasis-causing species. In these cases the detransformed mean number of larvae per wound was 18.1 (range 5-40). Lucilia sericata (Diptera: Calliphoridae) was found to be solely responsible for the lesions of 12 birds, with detransformed mean of 94.0 (range 2-893) larvae per goose. The larvae of this species appeared to be generally less invasive than those of W. magnifica, but in three cases they were also deeply embedded in the wounds. In seven geese larvae of both fly species developed together in and around the wounds. With the exception of one lesion, there were more larvae of W. magnifica (detransformed mean of 21.8 with a range of 1-55) than that of L. sericata (detransformed mean of 11.2 with a range of 2-61) in these mixed infections. Predisposing conditions for development of traumatic myiasis in geese included plucking of feathers, other injuries and bacterial infections (e.g. inflammation of the phallus).

Animals↗
PubMed2001

Traumatic myiasis of horses caused by Wohlfahrtia magnifica.

A survey was carried out in three stud farms with grazing animals, in order to gather data on the prevalence and clinical manifestation of, and the fly species involved in, traumatic myiasis of horses in Hungary. This parasitic disease was recorded in each farm. On the whole, 9.0% (14) of the inspected horses were infested with fly larvae. The affected horses had one infested lesion only, located at the mucosa of the vulva or the vaginal vestibule. The clinical symptoms depended on the age of infestation. Wohlfahrtia magnifica (Diptera: Sarcophagidae) was the only myiasis-causing fly species identified. It was assumed that unknown volatile chemicals might be responsible for the attraction of gravid females to the undamaged vulvar region. These odours are supposed to be produced during different physiological and/or pathological events associated with oestrus, prolonged puerperal period or inflammation of tissues. Daily inspection of grazing horses and early treatment of the affected areas are needed to avert significant damage to the infested horses.

Animals↗
PubMed2000

The timing of drosophila salivary gland apoptosis displays an l(2)gl-dose response.

During Drosophila metamorphosis, larval tissues, such as the salivary glands, are histolysed whereas imaginal tissues differentiate into adult structures forming at eclosion a fly-shaped adult. Inactivation of the lethal(2)giant larvae (l(2)gl) gene encoding the cytoskeletal associated p127 protein, causes malignant transformation of brain neuroblasts and imaginal disc cells with developmental arrest at the larval-pupal transition phase. At this stage, p127 is expressed in wild-type salivary glands which become fully histolysed 12 - 13 h after pupariation. By contrast to wild-type, administration of 20-hydroxyecdsone to l(2)gl-deficient salivary glands is unable to induce histolysis, although it releases stored glue granules and gives rise to a nearly normal pupariation chromosome puffing, indicating that p127 is required for salivary gland apoptosis. To unravel the l(2)gl function in this tissue we used transgenic lines expressing reduced ( approximately 0.1) or increased levels of p127 (3.0). Here we show that the timing of salivary gland histolysis displays an l(2)gl-dose response. Reduced p127 expression delays histolysis whereas overexpression accelerates this process without affecting the duration of third larval instar, prepupal and pupal development. Similar l(2)gl-dependence is noticed in the timing of expression of the cell death genes reaper, head involution defective and grim, supporting the idea that p127 plays a critical role in the implementation of ecdysone-triggered apoptosis. These experiments show also that the timing of salivary gland apoptosis can be manipulated without affecting normal development and provide ways to investigate the nature of the components specifically involved in the apoptotic pathway of the salivary glands.

Animals↗
PubMed2000

The LAMMER protein kinase encoded by the Doa locus of Drosophila is required in both somatic and germline cells and is expressed as both nuclear and cytoplasmic isoforms throughout development.

Activity of the Darkener of apricot (Doa) locus of Drosophila melanogaster is required for development of the embryonic nervous system, segmentation, photoreceptor maintenance, normal transcription, and sexual differentiation. The gene encodes a protein kinase, with homologues throughout eukaryotes known as the LAMMER kinases. We show here that DOA is expressed as at least two different protein isoforms of 105 and 55 kD throughout development, which are primarily localized to the cytoplasm and nucleus, respectively. Doa transcripts and protein are expressed in all cell types both during embryogenesis and in imaginal discs. Although it was recently shown that DOA kinase is essential for normal sexual differentiation, levels of both kinase isoforms are equal between the sexes during early pupal development. The presence of the kinase on the cell membrane and in the nuclei of polytene salivary gland cells, as well as exclusion from the nuclei of specific cells, may be indicative of regulated kinase localization. Mosaic analysis in both the soma and germline demonstrates that Doa function is essential for cell viability. Finally, in contrast to results reported in other systems and despite some phenotypic similarities, genetic data demonstrate that the LAMMER kinases do not participate in the ras-MAP kinase signal transduction pathway.

Animals↗
PubMed1999

Uncoupling of sequential heteromorphic developmental programs.

The regulatory basis for differences among species in the developmental rate at which successive life stages are reached ("heterochrony") is a subject of much controversy among vertebrate and invertebrate developmental biologists. The heterochrony in development of different insect species is characterized in part by the intercalcation between the embryo and adult of a (varied) number of heteromorphic larval instars. These heteromorphic larval instars exhibit changes of body form from one larval instar to the next, prior to the final metamorphic molt to the pupal form. The intractability of larval heteromorphosis to experimental dissection is due in part to the lack of suitable experimental probes that can test the nature of the coupling of each heterochronically expressed instar-specific program. The epistatic basis of expression of heteromorphic developmental programs was assessed by two-dimensional electrophoretic analysis of hemolymph proteins during the normal and experimentally manipulated feeding stages of the 3rd, 4th, and 5th (final) instar larvae, and during the prepupal stage, of Trichoplusia ni. Of the several hundred protein spots tracked, some were identified that were uniquely detected during a single stage, while others were observed during combinations of certain stages. The nature of coupling of sequential heterochronic expression of these proteins during successive instars or stages was tested by use of a parasite (Chelonus sp.) that injects regulatory material into the host embryo that later causes the subsequent precocious expression of the final instar larval program. Following the expression of a normal 3rd instar pattern, such larvae were observed to omit expression of the 4th instar program, including omission of the proteins heteromorphically specific to that instar, and instead then express an essentially normal final instar pattern. Thus, normal expression of the final instar feeding stage pattern was not invariantly coupled to prior expression of the penultimate instar-specific proteins or pattern. Also, expression of the full program of the final instar feeding stage was epistatic to teh penultimate instar program, i.e., the protein pattern unique to the penultimate larval instar was not co-expressed with the precociously expressed final instar pattern. Larvae developmentally redirected in this manner failed to fully express the final instar prepupal stage pattern of protein expression, due at least in part to failed expression of prepupal ecdysteroids, but this was shown not to arise from omission of any of the first 4 larval instars per se. The nature of the redirections in host development caused by this parasite finally provides means of probing the coupling of successive expression on heteromorphic programs during larval development.

Animals↗
PubMed1999

Developmental regulation of granule size and numbers in larval salivary glands of drosophila by steroid hormone ecdysone.

The size and number of secretory granules in late larval salivary glands of Drosophila melanogaster have been related to interecdysial and early metamorphic development represented by well-known puffs in polytene chromosomes. Interecdysial period (puff stage 1 (PS1)) is characterized by presence of numerous small granules (11,000 per cell). The transition from PSI to early metamorphic phase (PS2 and upwards), induced by rapid elevation in endogenous steroid hormone ecdysone, is accompanied by continuous growth of granule diameter with concomitant reduction in their number per cell. In the PS4, just prior to secretion, approximately 3000 mature granules occur per cell. The mature state is associated with the change from hyperbolic to Gaussian distribution of granule number over their size range. Similar changes in secretory granule parameters were observed in interecdysial salivary glands explanted from 3rd instar larvae and cultured in vitro in medium containing 5x10(-6) m ecdysone.

Animals↗
PubMed1999

Effect of bisacylhydrazine ecdysteroid mimics (RH-5849 and RH-5992) on chromosomal puffing, imaginal disc proliferation and pupariation in larvae of Drosophila melanogaster.

Two bisacylhydrazine insecticides with ecdysone-mimetic action, RH-5849 and RH-5992, have been subjected to several bioassay procedures that are prerequisites for ecdysone action in Drosophila larvae: (a) induction of early ecdysone-specific puffs on the polytene chromosomes of the larval salivary glands; (b) secretion of glycoprotein glue into the lumen of the salivary glands; (c) evagination of imaginal discs of adult wings and legs; and (d) partial rescue of wild-type phenotypic expression in ecdysone-deficient mutants (ecdysoneless1 (ecd1) and suppressor of forkedts67g (su(f)ts67g). In all these bioassays on Drosophila larvae, the two purely synthetic hydrazines exhibited similar dose-response relationships as did the natural steroid hormone, 20-hydroxyecdysone. In assays involving induction of early chromosomal puffs (74EF, 75B) or regression of the preexisting puffs (25AC, 68C), the dosages required for induction of standard ED-50 effects were one order of magnitude larger for the hydrazines in comparison with 20-hydroxyecdysone. In the assays related to glycoprotein glue secretion, evagination of imaginal discs, or rescue of phenotypic expression in ecdysone-deficient mutants, 20-hydroxyecdysone was two orders of magnitude more active than RH-5849 and RH-5992. We conclude that, in spite of these quantitative differences, the two hydrazine compounds studied are able to duplicate in Drosophila larvae the complex of qualitative biological effects that are a prerequisite for ecdysteroid hormones. The hormonomimetic stimulus of RH-compounds has been given at very low, intracellular, chromosomal level.

Animals↗
PubMed1999

Changes in plasma catecholamine and corticosterone levels and gene expression of key enzymes of catecholamine biosynthesis in partially hepatectomized rats.

OBJECTIVE: To reexamine the possible role of catecholamines and corticosterone in the early period of liver regeneration after partial hepatectomy (PH)in conscious cannulated rats under carefully controlled conditions which would allow to obtain reliable information about sympathetic-adrenomedullary function after PH in the rat in vivo. METHODS: Plasma levels catecholamines (epinephrine - EPI, norepinephrine - NE) were estimated by radioenzymatic assay and these of corticosterone by competitive protein binding assay. The total RNA was isolated from the adrenals and tyrosine hydroxylase (TH) mRNA expression was estimated by hybridisation with cDNA after Northern blot. The level of immunoreactive protein was measured by using a monoclonal antibody to rat TH, visualized by Western light chemiluminescent detection system and analyzed by densitometry. The level of TH in adrenals was estimated with the aid of 3H-tyrosine and TH cofactor DL-6-methyl-5,6,7,8-tetrahydropterine and the formed radioactive water was measured by scintillation spectometry. RESULTS: The plasma level of norepinephrine (NE), epinephrine (EPI) and corticosterone rapidly increased 20 min. after PH or sham operation (laparotomy). Although the increase of plasma NE was about the same after both PH and laparotomy, that of EPI and corticosterone in PH rats was significantly higher as compared to the laparotomy. One hour after the surgery plasma NE levels in both groups decreased to the basal value and remained still unchanged 4 and 24 h later. At the interval of 4h the plasma level of EPI was higher than in laparotomized controls, but after 24 h the EPI levels returned to basal values. Adrenal tyrosine hydroxylase (TH) mRNA level was significantly elevated in both PH and laparotomized rats, however 24 h after the surgery they returned to the baseline. Adrenal TH immunoprotein levels and TH activity were significantly elevated in both groups 4 h after the surgery, while 24 h later they returned to the baseline in laparotomized rats bur remained elevated in PH rats. Adrenal phenylethanolamine N-methyl-transferase (PNMT) mRNA levels were increased 4 h after both the PH and laparotomy and declined within 24 h. CONCLUSIONS: The first peak of catecholamine and corticosterone levels might result from unspecific stressor associated with the surgery. These levels could be accompanied with the mechanism of the rat liver regeneration. Prolonged elevations of EPI found after PH seems to be specific for liver regeneration indicating that the rise in the adrenal TH mRNA appears to be translated into immunoreactive protein which further leads to the elevation of TH activity. These results contrast markedly with previous studies indicating that the regeneration is modulated predominantly by norepinephrine.

Anesthesia↗
PubMed1998

Prevalence of traumatic myiasis in Hungary: a questionnaire survey of veterinarians.

Veterinarians in Hungary were asked to complete a questionnaire on traumatic myiasis; of the 664 veterinarians contacted, 247 replied (37.2 per cent) and of these 209 (84.6 per cent) reported myiasis to be a problem among the livestock they treated. Infestation levels of > 10 per cent of animals were reported in sheep, cattle and horses. The myiasis season lasted from March to November with most cases reported in July and August. Significantly more respondents reported that fly larvae were present deep in wounds rather than superficially, consistent with infestations due to the obligate parasite Wohlfahrtia magnifica (Diptera: Sarcophagidae). Frequent inspections and the treatment of infested animals were reported by 64.1 per cent of respondents as contributing to the economic impact of traumatic myiasis, and approximately half of the respondents (51.4 per cent) reported that inspections and treatments were carried out at least weekly during the summer. The most common form of treatment was the manual removal of larvae followed by topical application of insecticides, particularly organophosphates. More than half of the respondents (56.6 per cent) reported that there had been no change in the importance of myiasis over the last five to 10 years, but of those who reported a change, more reported an increase (28.3 per cent) than a decrease (15.2 per cent).

Animals↗
PubMed1998

Preliminary studies on humoral immune response of sheep to wohlfahrtiosis.

The humoral immune response of sheep to wohlfahrtiosis was studied. An enzyme-linked immunosorbent assay was developed to compare four different types of antigens obtained from the third-stage larvae of Wohlfahrtia magnifica. The antigen prepared from salivary glands detected a humoral response in all 35 infested sheep and was more specific in the ELISA than cuticular, intestinal or whole larval antigens. The level of the humoral response in sheep to wohlfahrtiosis differed according to the location of the wounds.

Animals↗
PubMed1998

Use of odour-baited sticky boards to trap tabanid flies and investigate repellents.

Tabanid flies were captured in a sheep pasture in Hungary using black plastic boards (30 x 30 cm), coated with an adhesive sheet, which were either unbaited or baited with ethane-ethiol or Swormlure-4. Five species of tabanid were caught, of which Tabanus tergestinus was caught in the greatest number (87% of 192). The sex ratio of T. tergestinus on unbaited boards was not statistically significantly different to equality. However, on baited boards, males were significantly more numerous, probably due to a repellent effect of the odours on female tabanids. Because of the importance of repellents in tabanid control, this result encourages the exploration of a wider range of compounds as tabanid repellents than are used at present. Sticky boards offer a simple technique for trapping both sexes of tabanids, especially males, which are poorly represented in many tabanid traps.

Animals↗
PubMed1998

Genetic and hormonal control of cytosolic malate dehydrogenase activity in Drosophila melanogaster.

The activity of Drosophila cytosolic malate dehydrogenase (MDH; EC 1.1.1.40), a key enzyme in the biosynthesis of lipids, was found to be regulated by both the sesquiterpenoid juvenile hormone (JH), and the steroid hormone ecdysone. The responsiveness of MDH to JH largely depended on the developmental stage or endogenous titre of ecdysone. During the early through middle period of the last larval instar, when ecdysone levels are low, MDH responded to JH rapidly by increasing activity, while little or no response was measured in mature larvae (postfeeding stage) and fresh pupae when the endogenous pulse of ecdysone is high. Activity of MDH in ecd1 and su(f)ts67g, two ecdysone-deficient mutants of Drosophila, was increased when compared to wild type controls, and was also sensitive to administration of JH. The differences in MDH activity between ecd1 and su(f)ts67g were negligible indicating a substantial role of ecdysone in the enzyme regulation and minimal or no effect of their genetic backgrounds. Accordingly, another Drosophila mutant, ap4 which is naturally deficient in JH production, displayed significantly reduced activity of MDH in heterozygotic combination, and almost undetectable MDH activity in null homozygote adults. The ap4 phenotype was more strongly manifested in the adult stage than in larvae which showed 7-times lower requirements for JH titre. In addition, high/low sucrose diet fed to wild types or mutants affected the activity of larval MDH, but the enzyme remained sensitive to administration of JH. These results corroborate those described for mammals and provide the first evidence that Drosophila MDH might be under differential hormonal and nutritional control. These data will serve as a basis for further molecular characterization of the Drosophila MDH gene and its regulation.

Animals↗
PubMed1998

Bacteriological investigations on wound myiasis of sheep caused by Wohlfahrtia magnifica (Diptera: Sarcophagidae).

The aim of the present investigation was to get further information about obligate aerobic and facultatively anaerobic bacterial communities of the intact and Wohlfahrtia magnifica infested vulval region of sheep. The numbers of aerobic and facultatively anaerobic microorganisms were lower in samples taken from uninfested mucous membrane and myiatic wounds as well as in the wound fluid as compared to samples originating from the uninfested skin surface. Gram-negative bacteria belonging to the family Enterobacteriaceae were isolated only from the skin and mucous membrane of uninfested sheep. Gram-positive microorganisms dominated in all samples. The ratio of facultatively anaerobic bacteria was higher than 80% in the sample taken from a lesion containing third instar Wohlfahrtia larvae and in the wound discharge collected from a vulval wound free of maggots. It is suggested that there is a shift in the composition of the bacterial communities of vulva as staphylococci disappear from the wounds due to the presence of Wohlfahrtia larvae.

Animals↗
PubMed1997

Efficacy of some pyrethroids against a strain of the rabbit ear mite (Psoroptes cuniculi): an unusual cross-resistance pattern.

An in vitro immersion bioassay was used to compare the efficacy of selected pyrethroids against a deltamethrin-resistant strain of rabbit ear mite (Psoroptes cuniculi). A lack of cross-resistance between bromo (deltamethrin) and chloro analogues (cypermethrin) of alpha-cyano-3-phenoxybenzyl-dihalovinyl-dimethylcyclopropane carboxylate was detected. Whereas deltamethrin proved to be inactive (48-h mortality 21.9% at 1000 mg/kg), each cypermethrin isomer mixture tested, including alpha-cypermethrin [IR(cis) alpha S + 1 S (cis) alpha R] and theta-cypermethrin [1R(trans) alpha S + 1 S (trans) alpha R] and their mixture at a ratio of 4/6, beta-cypermethrin, showed high efficiency (48-h mortality > or = 95% at 1000 mg/kg).

Analysis of Variance↗
PubMed1997

Influence of inertia on intersegment moments of the lower extremity joints.

The calculation of three-dimensional intersegment moments of the lower extremity modelled as a system of rigid bodies-during human locomotion with the help of an inverse dynamics approach is one of the main strategies to describe the local kinetics of a human motion. From the numerical point of view, the resultant intersegment moment consists of different contributions; the moment of ground reaction force, the moment dependent on the weights of the segments and two inertia dependent parts, the moment of inertia force and the rate of change of angular momentum (with respect to the segments centre of gravity). For running with a horizontal velocity of 5 m s(-1), the calculation of the moment of inertia force can be neglected for the ankle but is important for the hip. Looking at the knee, this contribution is needed if the touch down phase is of special interest. The rate of change of angular momentum-with respect to the segments centre of gravity-can be neglected for all joints of the lower extremity.

Adult↗
PubMed1997

On the mechanical effects of knee bandages in the therapy of patellar chondropathy.

OBJECTIVE: The study aimed to clarify whether the therapeutic success of an infrapatellar bandage placed above the tibial tubercle in the treatment of patellar chondropathy is based on altered knee joint loads during specific movements. DESIGN: In a clinical trial the influence of the bandage on kinetic and EMG variables is investigated. BACKGROUND: Although the used bandage is not a supporting device, the patients report an instant improvement. Thus neurological mechanisms are hypothesized as capable of pain reduction by changing the neuromuscular movement coordination or sensation thresholds. METHODS: Ten patients performed three different movements (running, drop jump, walking downstairs), before and after attaching the bandage, while kinematic, dynamic, and EMG data were acquired. After calculating the intersegment moment of the knee joint, different kinetic and EMG parameters were combined to the dependent MANOVA procedure. RESULTS: The neuromuscular activity during drop jump was reduced significantly (P < 0.01) wearing the bandage while, apart from individual changes, no general alteration of the knee joint loads could be statistically confirmed. CONCLUSIONS: The effect of the examined infrapatellar bandage is not a consequence of a decreased joint load due to a general movement adaptation, but is probably due to a neural influence on the nociception.

Journal Article↗
PubMed1997

Wound myiasis of sheep in Hungary.

In Hungary, 4388 sheep in six flocks were surveyed in June-August of 1992-1995 to gather basic data on wound myiasis, its incidence, the predominant fly species involved and the clinical manifestations of infestation. The pathogenesis and economic significance of wound myiasis, as well as the interrelation of breed and sex with infestation levels, were evaluated. Active wound myiasis was recorded in all flocks, in 17.6% (774/4388) of the inspected sheep. The incidence varied among flocks and inspections from 4.7% to 38.9%, but it was significantly greater in imported breeds (28.8%, 651/2257) than in indigenous breeds (5.8%, 123/2131). Lesions of wound myiasis were located more frequently on the external genital organs (in 87%, 673/774 of all cases) than on other body regions. Overall, significantly more males (74.3%, 61/82) than females (16.5%, 713/4306) were infested. With the exception of five cases (0.06% of the total), when larvae of Lucilia sericata (Diptera: Calliphoridae) were also found, Wohlfahrtia magnifica (Diptera: Sarcophagidae) was the only species identified in wounds in this study. Despite the fact that larvae of L. sericata were so rarely encountered in wounds, adults of L. sericata were much the more common of the two species observed around wounds, even those infested by W. magnifica. The vast majority of animals inspected had only one myiasis wound. Clinical signs depended on the body part affected. The most severe infestations, in terms of extent of wounds and numbers of visible larvae, were usually those of the vulva and prepuce. Wound consisted of from one up to six foci, each completely filled by larvae of W. magnifica. These foci were either isolated from each other or they merged into a large lesion. Larvae in any focus tended to be at the same stage of development, but, were wounds were very severe, a range of developmental stages was observed together, indicating that frequent restrikes of wounds occurred. The most common signs were restlessness, anxiety and reluctance to graze. The animals were obviously depressed when they suffered from severe infestations causing lameness or blindness. Some of the most severely affected animals displayed obvious loss of condition. However, overall, there was no significant difference between the mean bodyweights of a sample of infested (59.2 kg) and uninfested (60.9 kg) animals.

Animals↗