Biomedical subjects

J Halász

Publications and source records attributed to J Halász.

At least 19 recordsLinked to original sources

PubMed2005

Neurochemical characterization of hypothalamic neurons involved in attack behavior: glutamatergic dominance and co-expression of thyrotropin-releasing hormone in a subset of glutamatergic neurons.

The electrical stimulation of a specific hypothalamic area rapidly evokes attacks in rats. Noteworthy, attack-related hypothalamic structures were identified in all species studied so far. The area has been extensively mapped in rats, and its anatomical connections have been studied in detail. However, technical difficulties precluded earlier the precise identification of the neural elements mediating the aggressive effects of stimulation. It now appears that a dense and distinct group of glutamatergic cells expressing vesicular glutamate transporter 2 mRNA extends over the entire hypothalamic attack area. Rostral parts overwhelmingly contained glutamatergic neurons. In more caudal parts, glutamatergic and fewer GABAergic neurons were found. The remarkable similarity in the distribution of hypothalamic attack area and glutamatergic cell groups suggests that these cells mediate the aggressive effects of stimulation. Surprisingly, thyrotropin releasing hormone mRNA was co-localized in a subset of glutamatergic neurons. Such neurons were present at all rostro-caudal levels of the hypothalamic attack area, except for that part of the hypothalamic attack area extending into the ventro-lateral part of the ventromedial hypothalamic nucleus. Earlier data on the projections of hypothalamic thyrotropin releasing hormone neurons suggest that this subpopulation plays a specific role in attack behavior. Thus, we identified three neuronal phenotypes in the hypothalamic structure that is involved in the induction of attacks: glutamatergic neurons co-expressing thyrotropin releasing hormone, glutamatergic neurons without thyrotropin releasing hormone, and GABAergic neurons dispersed among the glutamatergic cells. Assessing the specific roles and connections of these neuron subpopulations would contribute to our understanding of the mechanisms underlying attack behavior and aggression.

Aggression↗

PubMed2004

Chronic glucocorticoid deficiency-induced abnormal aggression, autonomic hypoarousal, and social deficit in rats.

Certain aggression-related psychopathologies are associated with decreased glucocorticoid production and autonomic functions in humans. We have previously shown that experimentally-induced chronic glucocorticoid deficiency leads to abnormal forms of attack in rats. Here, we compared the effects of acute and chronic glucocorticoid deficiency on aggressive behaviour, autonomic responses to challenges, and anxiety. Glucocorticoid synthesis was blocked acutely by the glucocorticoid synthesis blocker metyrapone or chronically by adrenalectomy and low glucocorticoid replacement (ADXr). As shown previously, chronic glucocorticoid deficiency facilitated aberrant attacks directed towards the most vulnerable parts of the opponent's body. The acute inhibition of glucocorticoid synthesis lowered aggressive behaviour without affecting attack targeting. In a different experiment, ADXr rats and their sham-operated controls were exposed to different challenges whereas their heart rate and locomotion were telemetrically recorded. Autonomic responses to social challenges were lowered by chronic, but not by acute glucocorticoid deficiency. Autonomic responses to the elevated plus-maze were only slightly affected by chronic glucocorticoid deficiency. Locomotor behaviour was not affected in either challenge; thus, the altered autonomic reactions were not due to interference from workload. The behaviour of ADXr rats was similar to that of sham-operated controls in the elevated plus-maze, but ADXr rats showed reduced social interactions in the social interaction test. Our data demonstrate that, in rats, chronic but not acute glucocorticoid deficiency induces abnormal attack patterns, deviant cardiovascular responses and social deficits that are similar to those seen in abnormally violent humans. Thus, the similar correlations found in humans probably cover a causal relationship. Experimentally-induced glucocorticoid deficiency may be used to assess the mechanisms underlying glucocorticoid deficiency-induced abnormal forms of aggressiveness.

Adrenalectomy↗

PubMed2001

The effect of glucocorticoids on the anxiolytic efficacy of buspirone.

RATIONALE: The serotonergic system and the hypothalamus-hypophysis-adrenocortical axis reciprocally influence each other. Therefore, the interaction between stress and serotonergic anxiolytics should be of major concern for both laboratory investigations and clinical treatment. OBJECTIVES: We have studied the effects of the serotonergic anxiolytic buspirone in rats in which basal levels of glucocorticoids were low and stable, while acute stress reactions were inhibited or exogenously induced. METHODS: Rats were adrenalectomised. Subcutaneous corticosterone pellets maintained basal glucocorticoid concentrations while acute changes were mimicked by corticosterone injections. Anxiety was assessed by the social interaction test. Temporal changes were evaluated by submitting rats to the same manipulations three times at two-day intervals. RESULTS: Buspirone applied to animals with stable and low plasma glucocorticoid concentrations induced a dramatic increase in social interactions. A slight locomotor suppressive effect was also noticed. The effects of buspirone proved to be stable over time in these animals. Acute treatment with corticosterone doubled the locomotor suppressive effects of buspirone and reversed its anxiolytic effects: the buspirone-corticosterone combination was anxiogenic after the first application. During the second and third treatment, the impact of corticosterone on buspirone efficacy gradually decreased, but the combined treatment remained about half as effective in reducing anxiety as buspirone alone.

Adrenalectomy↗

PubMed2000

Effects of two acute stressors on the anxiolytic efficacy of chlordiazepoxide.

RATIONALE: Limited published data show that drug efficacy can be influenced by stressors. Thus, drug testing in stressed animals may unravel important variables determining drug effects. OBJECTIVES: The experiments tested the anxiolytic efficacy of the benzodiazepine chlordiazepoxide under conditions of acute stress. METHODS: Previously group-housed rats were injected with 0, 3, and 10 mg/kg chlordiazepoxide, thereafter being exposed to two types of stress: novelty (transfer to an individual cage) and social defeat. Controls were group-housed animals. Anxiety was assessed on the plus maze. RESULTS: Speed of locomotion was increased by chlordiazepoxide in both stressed groups but not in controls. Chlordiazepoxide exerted a marked reduction in anxiety in controls and defeated rats but not in novelty exposed animals. The effects of novelty exposure were considerably weaker when drug testing was performed 24 h later. CONCLUSIONS: Stress exposure had an impact on the behavioral effects of chlordiazepoxide. Changes in locomotor activity induced by the drug appear to depend on the presence of a stressor, while anxiolytic efficacy appears to depend on the type of the stressor. Since it has been shown that drug efficacy changes in a variety of behavioral situations and drug classes, it is suggested that experimental background is an important variable in determining behavioral effects of drugs.

Acute Disease↗

PubMed2000

Housing conditions and the anxiolytic efficacy of buspirone: the relationship between main and side effects.

Serotonergic anxiolytics yield contradictory results both in the laboratory and clinically. In an attempt to investigate the cause of discrepancies, the anxiolytic effect of buspirone (0, 3 or 10 mg/kg, single treatment) was tested 1 h and 4 h after injection in rats in different housing conditions. At 1 h after drug administration, buspirone increased corticosterone production and decreased locomotor behaviour in both the elevated plus-maze and the social interaction tests. No anxiolytic-like effect was produced in either test. At 4 h after drug injection, no corticosterone or locomotor effects of buspirone were observed. In contrast, anxiolytic effects emerged in this phase. Open arm exploration and social investigation were increased in the plus-maze and social interaction test, respectively. In the plus-maze, the anxiolytic effect was significant in isolated animals only. In the social interaction test, the anxiolytic effect was stronger in isolated than in group-housed animals. When corticosterone secretion was inhibited by adrenalectomy, a full anxiolytic effect of buspirone was observed 1 h after drug administration. It appears that the side effects of buspirone have a shorter duration than the main anxiolytic effect. The buspirone-induced increase in corticosterone may have abolished the anxiolytic effects of the drug shortly after injection. Individual housing enhanced the anxiolytic efficacy of buspirone 4 h after administration.

Animals↗

PubMed2000

[Biomechanical study on bone grafts harvested from cadavers].

Today the technique of free revascularized bone grafts in reconstruction surgery of the head and neck has been well developed. The grafts can be harvested from different parts of the body. No data have been found regarding biomechanics of different grafts. The authors examined 18 samples of cadaver iliac crest, radius, lateral edge and spine of scapula and fibula, respectively, and 6 samples of mandible. The study pointed out that the stiffness of the fibula approached those of mandible. The stiffness of the other bone grafts were found much smaller.

Biomechanical Phenomena↗

PubMed1999

Defeat is a major stressor in males while social instability is stressful mainly in females: towards the development of a social stress model in female rats.

Social stress models appear useful in elucidating the interrelationship between stress, mood disorders, and drug efficacy. However, reliable social stress models for females are virtually lacking. The aim of this study was to determine stress-related consequences of (a) defeat in aggressive encounters and (b) social instability, in male and female rats. Defeat in male and female subjects was induced by aggressive male residents and female residents made aggressive by surgery (mediobasal hypothalamic lesion [MBHL]), respectively. Aggressiveness of resident males and resident MBHL females was remarkably similar. Alternating isolation and mixed-sex crowding phases with membership rotation were used to induce social instability. Aggression was kept low in the latter paradigm by manipulating crowding group composition. Defeat stress reduced weight gain, and increased both adrenals and plasma corticosterone in males. Only adrenal weight was affected in females. Social instability reduced weight gain, and induced thymus involution, adrenal hypertrophy and elevated plasma corticosterone levels in females. Only weight gain and thymus weights were affected in males. It is concluded that defeat stresses males more than females, while social instability is more stressful for females than for males, if aggressive contacts are low. It is suggested that the social instability model is a good model of social stress in females.

Aggression↗

PubMed1999

Mild social stress abolishes the effects of isolation on anxiety and chlordiazepoxide reactivity.

RATIONALE: Social isolation is anxiogenic and may change the effects of anxiolytic drugs. These effects are generally attributed to "isolation stress". However, isolation does not affect basal corticosterone levels; thus, it cannot be considered stressful. On the contrary, isolation deprives animals of mild daily stressors that are inherent to social life. Since mild stressors were shown to be anxiolytic in rats, it was postulated that short-term, repeated stressors may abolish the effects of isolation. OBJECTIVES: The aim of the present study was to investigate whether short-term, repeated, mild social stress can abolish the consequences of isolation on anxiety and on the effects of chlordiazepoxide. METHODS: Rats were housed in groups or in individual cages for 5 days (isolates). Half of isolates were daily submitted to the attacks of a resident rat for 30 min per day, on 4 consecutive days (stressed isolates). On day 5, rats were treated either with vehicle or with chlordiazepoxide and submitted to the elevated plus-maze test. Endocrinological consequences of experimental manipulations were assessed in a different set of rats. RESULTS: Plasma ACTH and corticosterone levels were similar in the three groups. Weight gain was higher, while plasma growth hormone was lower in stressed isolates, both effects being consistent with a mild stress. Isolation had a clear anxiogenic effect. This effect was completely abolished by the daily experience of social stress. Chlordiazepoxide had a significant anxiolytic effect in all three groups. Its effects on classical plus-maze variables did not differentiate the three groups. However, chlordiazepoxide decreased risk assessment activity only in isolates. CONCLUSIONS: The lack of appropriate endocrinological changes challenges the concept of "isolation stress". However, isolation was anxiogenic in our study and it also induced subtle changes in the effects of chlordiazepoxide. It appears that mild daily stressors have a protective effect against the effects of isolation.

Adrenocorticotropic Hormone↗

PubMed1999

Social stress of variable intensity: physiological and behavioral consequences.

Stress effects in humans depend on stress type, intensity, and duration. Animal models of social stress serve as good ways to mimic stress experienced in humans. However, the available stress paradigms pay little attention to the relationship between the intensity and the type of social stressors. The aim of the present work is to study behavioral and endocrinological consequences of social stress by varying the intensity and type of agonistic social contacts. Subjects were exposed to the attacks of an experienced fighter resident rat once a day for 4 consecutive days. Mild versus strong effects were studied by varying the length of daily confrontations (30 min vs. 4 h). The type of social confrontations was varied by ceasing or maintaining sensory contacts among contestants between encounters. Endocrinological variables were measured on the 5th day. Anxiety was assessed by means of the elevated plus-maze. The stress state depended on the length of daily encounters: 30-min encounters did not, whereas 4-h encounters did result in weight loss and chronic elevation of plasma corticosterone. The type of contacts between subjects and dominants also affected the resulting stress state: adrenal hypertrophy was obtained only when contacts between contestants were maintained between encounters. Although the mildest stress procedure (30-min encounters on 4 consecutive days) did not affect endocrinological variables, it resulted in subtle behavioral modifications that changed the anxiety-related effects of additional acute stressors. Thus, anxiety-related behavioral changes resulting from repeated mild stressors may be hidden factors that can have long-term consequences on the development of anxiety-like behavioral deficits. Results outline the necessity of studying the effects of social stressors of different intensities and different types.

Adrenal Glands↗

PubMed1993

[Epidemiologic study of mid-face fractures in a 14-year (1977-1990) material of the authors' clinic].

The authors made a retrospective study of fractures of the maxilla analyzing the occurrence, localisation and the causal factors of the injury. The treated 223 patients with fracture of the middle face during this period. The most exposed age group was the group of 21-40 years, the most frequent causes were: traffic accident, brawl, and sport accident. The proportion of fracture of middle face and mandible was 1:2. As to the localisation of the fractures, the simple fracture in the lateral area was the most frequent.

Accidents, Traffic↗

PubMed1991

[Use of an osteo-musculo-cutaneous flap from the trapezius muscle for the immediate restoration of a mandibular defect following surgery for cancer of the oral cavity].

The authors state their experiences using trapezius osteomusculocutaneous flaps in 22 clinical patients for primary reconstruction of mandibular defects. The additional investigative study examines the anatomy of 100 osteomusculocutaneous flaps in 50 fresh cadavers. 78 percent of the major vascular pedicle arose form the thyreocervical trunk. The advantages of this method are as follows: 1. This flap provides a well-vascularized bone graft; 2. The operation comparing to other bone grafting methods is simple; 3. After radical neck dissection the trapeziu muscle protects the carotid artery; 4. The vascularized bone graft can be used after irradiation; 5 Good functional and esthetic results can be obtained.

Adult↗

PubMed1990