Biomedical subjects

R Farkas

Publications and source records attributed to R Farkas.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1997

Ecdysone-modulated response of Drosophila cytosolic malate dehydrogenase to juvenile hormone.

Recently, we found that the activity of malate dehydrogenase (MDH), one of the key enzymes in the biosynthesis of lipids, is regulated in Drosophila melanogaster by juvenile hormone (JH) and JH analogues. Here we report that the response of MDH to JH, however, depends on the developmental stage of the animal in relation to its endogenous titre of ecdysteroids. During the interecdysial period of the last instar, when endogenous ecdysteroids are low, MDH rapidly responded to JH by increasing activity, while little or no response was monitored in wandering (post-feeding) larvae, i.e., after a pulse of ecdysteroids. Activity of MDH in ecd1 and su(f)ts67g, two ecdysteroid-deficient mutants of Drosophila, increased during a temperature shift to 29 degrees C as compared to wild-type controls, and was sensitive to administration of JH. In contrast, when ecd1 or su(f)ts67g larvae during restrictive conditions were fed on a 20-hydroxyecdysone diet, JH was unable to increase the activity of the MDH enzyme. However, when JH was applied prior to 20-hydroxyecdysone feeding, the activity of MDH was significantly stimulated. Two phases of MDH response to JH, dependent on ecdysteroids, could be observed. The first phase was short and independent of RNA and protein syntheses. But activation of MDH in later stages of the response was inhibited by actinomycin D and cycloheximide, indicating that MDH might be regulated by JH at the transcriptional and/or translational level.

Animals↗

PubMed1996

Efficacy of ivermectin and moxidectin injection against larvae of Wohlfahrtia magnifica (Diptera: Sarcophagidae) in sheep.

The therapeutic efficacies of ivermectin (Ivomec injection, Merck Sharp & Dohme B.V.) and moxidectin (Cydectin 1% injection, American Cyanamid Company) were evaluated in sheep naturally infested with larvae of Wohlfahrtia magnifica. Sheep were randomly allocated to one of the 2 groups, each consisting of 19 animals. Sheep in one group received ivermectin and those in the other, moxidectin by subcutaneous injection at a dose of 0.2 mg/kg body weight. Evaluation was performed at 19, 24, 28, 39, 43, 48, 52, 63, 67, 72, 87, 96, 120, 144 and 168 h after treatment. At 144 and 168 h post-treatment, late third-instar larvae were collected from wounds of four sheep in both groups and from untreated, infested sheep. These larvae were reared in the laboratory to assess adult emergence. Neither ivermectin nor moxidectin was effective as a rapid acting treatment or as a long-term, or even short-term, prophylactic. Despite the treatment, 30-40% of sheep had live larvae at every evaluation. Although larvae disappeared from the wounds of some sheep in both groups after the treatment, the wounds in these animals failed to recover and were reinfested by larvae of W. magnifica. On day 7 post-treatment the trial had to be finished because the majority of treated sheep were severely infested by Wohlfahrtia maggots. The average number of infested sheep in the two groups and the number of adults that were produced from larvae collected from treated sheep indicate that ivermectin and moxidectin did not differ significantly in efficacy.

Animals↗

PubMed1996

Susceptibility of Hydrotaea aenescens (Wiedemann) (Diptera: Muscidae) to selected insecticides and its importance in integrated fly management.

The doses lethal to 50% of the insects (LD50 values) obtained for a strain of Hydrotaea aenescens (Wiedemann) adults from a layer farm revealed higher sensitivity to 16 insecticides than those recorded for the susceptible WHO/SRS strain of the housefly. Because H. aenescens adults are about half the size of the housefly, the chemical compounds used for adult control may jeopardize the survival of Hydrotaea populations released in animal confinement houses. An efficient and economical combined application of biological and chemical control methods is possible only if the local management conditions and the dissimilar behavior of the adults of the two species are taken into consideration during the use of insecticides. Other suggestions and implications are further discussed.

Animals↗

PubMed1995

Orientation of agents of wound myiasis to hosts and artificial stimuli in Hungary.

The orientation of adults of the myiasis species Wohlfahrtia magnifica and Lucilia sericata to artificial visual stimuli (cloth targets) and olfactory stimuli ('swormlure-4', a potent screwworm attractant), was studied in sheep pastures near to Sárbogard in Hungary. Experiments with odour-baited cloth targets, enclosed in electrocuting grids, demonstrated that colour was an important factor influencing catches on targets: a black target caught most flies of both species, with other colours in the following order of effectiveness, blue > white > yellow. Wohlfahrtia magnifica did not respond to swormlure-4 in the strong manner that L.sericata did. The sex ratios of W.magnifica caught on targets (67.2% males) and hand-netted from fence posts (68.8% males) were similar and biased towards males, whereas that of L.sericata on targets was strongly biased towards females (15.6% males), indicating a fundamental difference in the response of these two myiasis species towards the swormlure-baited targets. The orientation of these two species towards hosts was also recorded together with that of a third species, Phormia regina. Electric nets placed beside infested sheep caught significantly more flies of all three species than those placed beside uninfested sheep or in the absence of sheep. The sex ratio of W.magnifica caught around infested sheep was the reverse of that on targets, with 68.5% females. Wohlfahrtia magnifica responded more strongly to healthy, uninfested sheep than did L. sericata and P.regina. The potential for use of targets both for population monitoring and control is discussed.

Animals↗

PubMed1995

Ecdysone Regulated RNA synthesis in Drosophila larval salivary glands.

The changes in total and ribosomal RNA (rRNA) synthesis in cultured larval salivary glands of Drosophila in response to steroid hormone ecdysone have been studied. By using the incorporation of [3H]-uridine or [32P]-UTP into salivary gland cells, followed by RNA extraction and electrophoretic or sucrose gradient fractionation it was found that physiological concentrations of ecdysone stimulate the synthesis of rRNA. Administration of selective transcription inhibitors (actinomycin D, alpha-amanitin, cordycepin, DRB, and 5- fluorouridine) as well as protein synthesis inhibitors (cycloheximide, puromycin) showed that early response to ecdysone involved a direct stimulation of rDNA transcription, probably by ecdysone-ecdysone receptor complex, and is independent of protein synthesis. In later stages of the response to ecdysone, as revealed again using transcription and protein synthesis inhibitors, the synthesis of rRNA is dependent on the factor(s) produced during early stages of the response, in the manner which is very similar to sequential gene activation in chromosomal puffs. Experiments with the withdrawal of ecdysone from culture medium in early stages of its action show similar negative effects on rRNA synthesis as inhibitors of RNA polymerase II, thus proving the existence of parallel mechanism controlling induction of specific chromosomal puffs and transcription of rDNA. The data presented suggest that, in addition to the expression of tissue and developmentally-specific genes, the regulation of rDNA transcription, along with the production of ribosomes, might be required for Drosophila metamorphosis. The results are discussed in the light of vertebrate's steroid hormone action on ribosomal genes.

Journal Article↗

PubMed1994

The Doa locus encodes a member of a new protein kinase family and is essential for eye and embryonic development in Drosophila melanogaster.

Mutations at the Darkener of apricot (Doa) locus of Drosophila cause roughened eyes and increase transcript accumulation from the retrotransposon copia up to fourfold. Cloning of the gene and sequencing of cDNAs reveals that it encodes a putative serine/threonine protein kinase. Sequence data base searches identify it is a member of a novel highly conserved protein kinase family, with homologs in humans, mice, and Saccharomyces cerevisiae, not related to each other previously. Family members are characterized by a peptide motif reading EHLAMMERILG at kinase subdomain X, which is virtually 100% identical in all homologs. We therefore refer to this new family as the LAMMER protein kinases. As predicted from its primary sequence, Doa protein possess intrinsic protein kinase activity when expressed in bacteria, as assayed via autophosphorylation. The gene is expressed throughout development, and both stage and tissue-specific RNAs are found. Its function is essential, because maternally deposited or zygotically transcribed mRNA is required for development to larval stages, and defects in segmentation and development of the nervous system are observed in embryos derived from heteroallelic mothers. Doa function is also critical to Drosophila eye development, because the organization and development of pigment cells, bristles, and photoreceptors are affected in various mutant classes. In the most extreme cases that survive to adulthood, retinal photoreceptors degenerate prior to eclosion. These results demonstrate that the kinase encoded by Doa is required at multiple stages of development, for both differentiation and maintenance of specific cell types.

Amino Acid Sequence↗

PubMed1992

[Stress on the upper ankle joint in tennis-specific forms of movement].

The permanently increasing number of injuries in tennis, which are mainly located at the lower extremity, indicates that the internal load e.g. applicated to the ankle during certain movements might be a critical factor. In the present study the relationship between calculated ankle load and muscle forces appearing during tennis techniques performed in a laboratorial setup and some varying parameters such as playing surface, footwear and individual differences in movement structure were investigated. It could be shown that on a felt tennis floor due to its frictional characteristics the midfootstriking subject produced the highest ankle load, while the heelstriking technique reduces the load as well as the change of the playing surface to a floor with loose granulate. In addition it should be considered that external forces (e.g. gained from a force plate) must not be used as predictors for internal load. The presented data show that the model-aided load calculation (MALC) from two trials with similar ground reaction forces leads to completely different values of e.g. the ankle-joint force.

Ankle Injuries↗