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Biomedical subjects

G Benedek

Publications and source records attributed to G Benedek.

At least 91 records · Page 5Linked to original sources
PubMed1992

Visual evoked potentials during the early phase of optic nerve compression in the orbital cavity.

We obtained case histories and electrophysiologic recordings from four patients with transient vision impairment due to acute orbital compression. The visual evoked potentials (VEPs) displayed alterations that depended on the size and consistency of the compressing pathology and also on the duration of the compression. This study provides evidence of the utility of the VEP in the assessment of the severity and reversibility of optic nerve lesions. The case histories also emphasized the necessity to elucidate the pathologic process of compressive lesions of the optic nerve.

Acute Disease↗
PubMed1992

An isobolographic analysis of the hypnotic effects of combinations of dexmedetomidine with fentanyl or diazepam in rats.

The effects of the combinations of dexmedetomidine-fentanyl and dexmedetomidine-diazepam on the righting reflex were studied in rats. The doses that block the righting reflex for the agents given alone and for their combinations were determined with a probit procedure and compared with an isobolographic analysis. The interactions between dexmedetomidine and fentanyl or diazepam were found to be synergistic. In the dexmedetomidine-diazepam combination studies, less than one-fourth of the single drug dose (for each of two agents) was needed to produce the required effect. These data confirm synergistic interactions between dexmedetomidine and fentanyl or diazepam in producing hypnotic-anesthetic action.

Anesthetics↗
PubMed1992

Potentiated hypnotic action with a combination of fentanyl, a calcium channel blocker and an alpha 2-agonist in rats.

An investigation was made of the hypnotic-anaesthetic effects in rats of subcutaneous coadministration of fentanyl (25-100 micrograms.kg-1), clonidine (100-300 micrograms.kg-1) and verapamil (1-5 mg.kg-1). Hypnotic-anaesthetic efficacy was assessed via loss of the righting reflex. In the doses used, none of the three drugs alone was associated with appreciable hypnotic-anaesthetic effects. Coadministration of fentanyl and clonidine resulted in a dose-related enhancement of the anaesthetic potency, without change in the duration of hypnotic action. Verapamil coadministration failed to increase the anaesthetic efficacy of binary combinations of fentanyl and clonidine, but a marked prolongation of the duration of hypnotic action was observed (P less than 0.001). These results suggest the existence of unreported interactions between these three drugs in the production of hypnotic-anaesthetic action in rats.

Adrenergic alpha-Agonists↗
PubMed1992

Calcium channels are involved in the hypnotic-anesthetic action of dexmedetomidine in rats.

Our study examined whether calcium channels are involved in the anesthetic action of dexmedetomidine (100-300 micrograms/kg), a highly selective alpha 2-adrenoceptor agonist. To investigate this, we studied the effects of verapamil (1.25 or 2.5 mg/kg), a calcium channel blocker, and BAY K8644 (0.5 or 1 mg/kg), a calcium channel agonist, on the hypnotic-anesthetic effect of dexmedetomidine in rats. Loss of the righting reflex was used to determine the presence of anesthesia, and its length in minutes was referred to as the duration of hypnosis. Verapamil significantly enhanced the duration of the hypnotic-anesthetic action of dexmedetomidine (P less than 0.05). In contrast, BAY K8644 caused a significantly increased onset of hypnosis (P less than 0.001) and attenuated the anesthetic property of dexmedetomidine. These results suggest that the hypnotic-anesthetic action of dexmedetomidine is influenced by the activation/gating of calcium channels.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Suppression of phase separation in solutions of bovine gamma IV-crystallin by polar modification of the sulfur-containing amino acids.

The calf lens protein gamma IV-crystallin, a strong determinant of the net phase-separation temperature of the lens, was chemically modified with N-bromoacetylethanolamine phosphate. The phase-separation temperatures of solutions of the modified protein were measured and found to be dramatically reduced with respect to those of the native protein. At neutral pH the reagent alkylates only the cysteine and methionine residues and introduces a doubly charged phosphate anion at a maximum distance of 10-12 A from the sulfur atoms. At a protein concentration of 38 g/liter, and with 30% of the cysteines and 40% of the methionines alkylated, the phase-separation temperature is lowered from approximately 25 +/- 2 degrees C to approximately 12 +/- 2 degrees C. The ascending limbs of the coexistence curves for the native and modified proteins were determined at two different degrees of modification. The coexistence curve of the protein with 35% of the cysteines and 40% of the methionines modified shows that as protein concentration approaches the critical concentration of 289 g/liter, there is a much larger suppression of the critical temperature, from approximately 38 +/- 2 degrees C in the native protein to approximately 16 +/- 2 degrees C. Incubation of intact calf lenses in vitro with the reagent results in the suppression of the phase-separation temperature by 3-9 degrees C. These results are consistent with the view that the observed suppression in the critical temperature is due to an increase in the hydrophilicity of the protein in the vicinity of the sulfur-containing residues.

Animals↗
PubMed1991

Organization of cortical and subcortical projections to the feline insular visual area, IVA.

Extracellular recordings with carbon fiber-filled microelectrodes were used to identify the visually responsive area within the insular cortex (referred to hereafter as the insular visual area, IVA) of anaesthetized cats. Broadly speaking, IVA comprises the cortex surrounding the anterior ectosylvian sulcus (AEs) along its ventral bank and the major portion of the anterior sylvian gyrus. Visually sensitive cells were recorded along the whole length of the AEs. In the same animals, the afferent connections of IVA were studied through the use of the retrograde tracers wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) and fluorescent Diamidino yellow (DY), in combination with standard electrophysiological stimulation and recording techniques. The results indicate that: (1) the IVA receives a wide variety of telencephalic inputs, not only from visual, sensorimotor, auditory, limbic and association cortical areas, and from the claustrum, amygdala and basal nucleus of Meynert, as well, but also from the diencephalic projections arising mainly from the lateralis medialis-suprage niculate nuclear complex (LM-Sg) and the ventral medial nucleus (VM). (2) The gyral part of IVA (gIVA) receives afferents mainly from the lateral part of the lateral suprasylvian visual area (LS) throughout almost its entire length, as well as from area 20, the posterior suprasylvian sulcal area (PS), the frontal eye fields, areas 6 and 36, and almost the whole length of the cortical area lying along the anterior ectosylvian sulcus (AEs). (3) By contrast with (2), the sulcal part of IVA (sIVA) which corresponds to the anterior part of the anterior ectosylvian visual area (AEV) of Norita et al. ('86), receives cortical projections mainly from the lateral and medial parts of the anterior half of LS, area 20, PS, the frontal eye fields, area 36, and most parts of the cortical area extending along the AEs. (4) Subcortically, IVA receives thalamic afferents mainly from VM and LM-Sg. The connections between IVA and LM-Sg are organized topographically, with the more anterior part of IVA being related to the more ventral portion of LM-Sg, and with sIVA being related chiefly to the mid-portions of LM-Sg. These results thus suggest that IVA may function as an integrative centre among structures belonging to the extrageniculostriate system, the sensorimotor system, as well as to the limbic system. Furthermore, our electrophysiological and anatomical findings, together with previous reports concerning AEV, suggest that the posterior part of AEV (AEV proper) is distinctive from gIVA, and that the sIVA apparently serves as a transitional region between AEV and gIVA.

Afferent Pathways↗
PubMed1991

CO2 laser in septic surgery.

Authors have performed 29 septic operations by a TLS61 60 W CO2 laser apparatus. In accordance with international experience, favorable results have been obtained in laser surgery of vascularized, hemophilic and bacterium penetrated alterations and infected wounds.

Humans↗
PubMed1990

[Successful use of C02 laser in septic surgery].

The authors have performed 29 septic operations with a TLS61 CO2 surgical laser with 60 Watt output power. They have gained good experiences with the laser excision of the vascularized, bleeding, inflammated, penetrated by bacteries and infected wounds.

Bacterial Infections↗
PubMed1990

[Electrophysiologic signs of macular diseases].

In the past two years, we have treated 80 patients at our clinic for regional changes in the macula lutea. The results of the electrophysiological investigations carried out on these patients are reported: scotopic and photopic whole-field electroretinography (ERG), pattern ERG, and analysis of the visual flash- and pattern-evoked potentials. These different tests are suitable for assessing various types of pathological retinal function. Electrophysiological methods are appropriate for evaluating the degree and progression of the disease. In certain hereditary diseases of the retina, such as in Stargardt macular degeneration and in a few early cases of sex-related retinoschisis, electrophysiological data can also be valuable in making a differential diagnosis.

Adolescent↗
PubMed1990

Effects of alternating 45-min light-dark cycles on sleep in the rat.

We studied the effect of alternating 45-min light-dark (L-D) cycles on sleep in rats. Introduction of short L-D cycles did not abolish the normal circadian rhythm of sleep-wake activity. The amount of non-REM sleep was however increased in the L and decreased in the D 45-min periods. REM was promoted in the D and inhibited in the L 45-min periods. The influence of L-D or D-L transitions depended on the sleep wake activity immediately before the transition.

Animals↗
PubMed1990

Enhancement of fentanyl analgesia by clonidine plus verapamil in rats.

An investigation was made of the analgesic effects of the subcutaneous coadministration of fentanyl, an opioid mu-agonist (15 micrograms/kg), clonidine, an alpha 2-agonist (100 micrograms/kg), and verapamil, a calcium channel blocker (10 mg/kg) in rats. Nociceptive sensitivity was assessed with hot-plate and tail-flick techniques. None of the three drugs alone was associated with appreciable analgesic effects in the doses used. The simultaneous administration of the three drugs resulted in marked analgesia superior to that of all binary combinations of these drugs. Two-way analysis of variance showed statistically significant differences in hot-plate and tail-flick latencies after drug treatments (P less than 0.001). The significant differences in the area under the time-response curve values (P less than 0.001) might indicate not only an increased analgesic effect, but also a prolongation of antinociception. These results suggest the existence of hitherto unreported interactions between drugs involved in the production of analgesia.

Animals↗