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Biomedical subjects

P Karli

Publications and source records attributed to P Karli.

At least 37 records · Page 2Linked to original sources
PubMed1984

Discrimination between aversive brain stimulations: effect of stimulation parameters.

Rats placed in a T maze were shown to be able to discriminate between two stimulations applied to one and the same brain site and inducing aversive effects of different magnitude. Discrimination occurred irrespective of whether the two stimulations differed in either intensity or frequency, and irrespective of whether they were applied to a medial hypothalamic or to a mesencephalic central gray site. Generalization experiments were performed in which either the stimulation parameter used to establish the discrimination or another parameter was varied. The results show that the animal's choice cannot be predicted on the sole basis of either the electrical charge/second applied or the escape latency induced.

Animals↗
PubMed1983

Erythrocyte flexibility, ATPase activities and Ca efflux in patients with Duchenne muscular dystrophy, myotonic muscular dystrophy and congenital myotonia.

Erythrocyte flexibility measured by a polycarbonate membrane filtration method showed increased fragility (265 +/- 163 Hb mg/l vs. controls 86 +/- 72 Hb mg/l; mean +/- SD; P less than 0.0025) and increased rigidity (123 +/- 96 mm Hg vs. 79 +/- 19 mm Hg; P less than 0.05) in patients with congenital myotonia, while both parameters were normal in patients with Duchenne muscular dystrophy or with myotonic dystrophy. Erythrocyte ghosts obtained from patients with MyD displayed highly significant increases in both (Na+ + K+)-ATPase and (Ca2+ + Mg2+)-ATPase activities (P less than 0.005) and to a lesser extent in Mg2+-ATPase activity (P less than 0.05), while no difference was seen between patients with DMD and age-matched controls. The efflux of Ca2+ was increased from erythrocytes of patients with DMD as compared to age-matched controls (82 +/- 2% vs. 70 +/- 4%; P less than 0.005), while no difference was detected between patients with MyD and age-matched controls.

Adenosine Triphosphatases↗
PubMed1983

Ambulatory electrocardiographic recording in mild or moderate myotonic dystrophy and myotonia congenita (Thomsen's disease).

Ambulatory electrocardiographic recording (AER) was performed on 27 adult patients with mild or moderate myotonic dystrophy (MD) and in 12 adult patients with mild myotonia congenita (MC) to determine whether characteristic arrhythmias and conduction disturbances occur in the early stages of these myotonic disorders. In MD and MC, AER showed at least one finding regarded as normal in 93% and 0% of cases, respectively. The most common abnormalities in MD were first degree atrioventricular (A-V) block (in 70% of cases) and QTc greater than or equal to 0.46 s (in 33%). Abnormal sinus intervals and frequent second degree A-V block were rare, each occurring in 4% of patients. Ventricular tachycardia did not occur. It is concluded that signs of involvement of cardiac conductive tissue in the MD disease process are very common, even in the early stages. Delayed A-V conduction in the most common single finding. Sinus nodal dysfunction, severe disturbances in A-V conduction, and ventricular arrhythmias are not common in mild disease. Repeated AER is indicated, to evaluate whether conduction disturbances in MD are progressing.

Adolescent↗
PubMed1983

Unilateral injection of GABA agonists in the superior colliculus: asymmetry to tactile stimulation.

A unilateral microinjection of each one of three different GABA agonists (Muscimol: 1.4 nmoles; Baclofen: 0.8 nmole; THIP: 10.7 nmoles) into the superior colliculus was found to result in a reversible asymmetry in the rat's responsiveness to tactile stimulation. The rat was hyporeactive to stimulations applied contralaterally and hyperreactive to stimulations applied ipsilaterally to the infusion site. Furthermore, the rat showed ipsiversive turning in response to tactile stimulation applied either ipsi- or contralaterally to the infusion site. The results are discussed in relation with motor and sensory asymmetry produced by unilateral manipulations affecting the striato-nigro tectal system.

Analgesics↗
PubMed1983

Morphine applied to the mesencephalic central gray suppresses brain stimulation induced escape.

In the rat, microinjections of morphine (1.5 to 15 nmoles) into the dorsal part of the mesencephalic central gray (CG) were found to suppress both escape responding induced by electrical stimulations applied to either the medial hypothalamus (MH) or the CG and behavioral responsiveness to peripheral nociceptive stimulations. The time course of these two effects proved quite similar (Experiments 1 and 2). A systemic injection of naloxone reversed--in a dose dependent manner--the effects of morphine on the centrally induced escape responses (Experiment 3). The possibility that microinjections of morphine decrease both responsiveness to peripheral nociceptive stimulation and the reactivity of higher structures involved in the generation of aversive effects is discussed.

Animals↗
PubMed1982

[Implication of gamma-aminobutyric acid (GABA) at the mesencephalic central gray level, in the elaboration of flight responses].

In the rat, a microinjection of bicuculline methiodide (0.03 to 0.065 nmole) into the mesencephalic central gray (GC) provokes a flight response. At a lower dose, it reduces - or increases - the latency with which the rat switches off an electrical stimulation applied to the GC. This latency is regularly increased by a local microinjection of muscimol. These results suggest that a GABAergic link within the GC is involved in the generation of an aversive effect and of the flight response which may express it.

Aggression↗
PubMed1982

Effect of medial hypothalamic stimulation inducing both escape and approach on unit activity in rat mesencephalon.

The activity of central gray (CG) neurons was previously shown to be affected by medial hypothalamic (MH) stimulation, and the discharge rate alterations were found to be often closely correlated with the vigor of the stimulation-induced escape responses. Since MH stimulation induces not only escape responses but also approach responses, this allowed a further investigation of the degree of specificity of the correlation between stimulation-induced neuronal activity and escape responses. Out of 129 CG units studied (in 39 rats), 26 clearly responded to the MH stimulation. When the stimulation parameters were varied, the mean discharge rate alterations of 9 units located in the dorsal part of the mesencephalic CG proved to be closely correlated exclusively with the alterations that affected the stimulation-induced escape responses. Furthermore, the variation of the most frequent interspike interval (modal ISI) proved to be closely correlated with the variation of the escape response in 3 instances in which the mean discharge rate showed no such correlation. In a few instances (2 units located much more ventrally, the spike rate alterations were closely correlated only with the alterations that affected the approach responses. It is suggested that neuronal activity in the dorsal part of the CG is rather specifically implicated in the generation of MH stimulation-induced aversive effects and escape responses.

Animals↗
PubMed1982

Ocular findings in myotonic dystrophy.

Thirty-three patients (20 female and 13 male patients aged 13 to 52 years) with myotonic dystrophy (MyD) were studied. Ophthalmologic examination included tonography, electroretinography (ERG), and fluorescein angiography. Thirty patients had bilateral cataracts of the subcapsular type, two patients had aphakia in both eyes, and one patient had clear lenses. Hypotonia (intraocular pressure, less than or equal to 10 mm Hg) was a common finding in 19 of 66 eyes. The mean IOP was 11.8 mm Hg for the whole series and the mean outflow facility was c = 0.34 cu mm/min. Focal signs of retinouveal affection were present in nine patients. Clinically, they appeared as acquired lesions affecting the retina, pigment epithelium, and choroid. One patient was found to have an outburnt panuveitis. The ERG was normal in 11 patients, subnormal in five patients, and isoelectric in four patients. An extinguished ERG did not correlate to clinical findings of known hereditary retinal or choroidal dystrophies. The ophthalmologic findings may be explained by a primary defect related to the cell membrane.

Adolescent↗
PubMed1981

Distribution of GABA in the periaqueductal gray matter. Effects of medial hypothalamic lesions.

Gas chromatography and chemical ionization mass spectrometry were used in order to measure the GABA (gamma-aminobutyric acid) concentration in a series of successive horizontal slices of the mesencephalic periaqueductal gray (CG) as well as in a series of successive frontal CG slices in the rat. Along the dorso-ventral axis, the GABA concentration (3.5-7 microgram/mg protein) was found first to increase and then to decrease, a maximum concentration being found at the level of the aqueduct. In contrast, no concentration gradient was found along the caudo-rostral axis. In an additional experiment, the medial hypothalamus (MH) was lesioned on one side and the effect of such a unilateral MH lesion on the caudo-rostral distribution of GABA was investigated. Fifteen days after performing the lesion, a graded decrease in GABA concentration--with a maximum in the rostral CG--was found to occur mainly on the lesioned side.

Animals↗
PubMed1981

Influence of rearing conditions on the acquisition of the two-way active avoidance responses by rats septalectomized at an early age.

When performed in the adult 3-month old rat, septal lesions facilitated the acquisition of a two-way active avoidance (AA) task as compared to animals sham-operated at the same age. When performed in the 7-day-old rat pup, the same lesion also clearly facilitated the 2-way AA acquisition by the rats when adult and, more especially so, when the rats were isolation-reared from weaning. The performances of these early-septal rats reared in isolation did not differ from those of rats septalectomized at adult age, while the performances of the early-septal rats that had been group-reared from weaning proved to be lower than that of adult-operated rats, with regard to both number of shocks avoided and mean response latencies in the initial phase of acquisition. The improvement of the 2-way AA acquisition following septal lesion may result from an increased responsiveness to aversive stimulation and this responsiveness may be enhanced if the early-septal rats are reared in isolation from weaning.

Age Factors↗
PubMed1981

Escape and approach induced by brain stimulation: a parametric analysis.

The study reported pursued two general aims: (a) to find out whether a brain-stimulation-induced escape response results from the bringing into play of similar mechanisms irrespective of whether the stimulation is applied to a site located in the mesencephalic central gray (CG), in the medial hypothalamus (MH) or in the lateral hypothalamus (LH); and (b) to verify whether escape and approach that can be induced by stimulating one and the same hypothalamic site result from a combined activation of two distinct neuronal systems, by means of specifying some of their functional characteristics that would possibly allow differentiation between them. Three experiments were carried out using a situation (shuttle-box) that allowed the measurement, for each given brain site, of both the time for which the rat underwent the stimulation before interrupting it (stimulation time, st., corresponding to an escape latency) and the time for which the animal remained non-stimulated before eventually restarting the stimulation himself (non-stimulation time, nst, corresponding to an approach latency). The following stimulation parameters were varied: the pulse duration (D), the stimulation intensity (I) and the interpulse interval (IPI = 1/stimulation frequency), i.e. the time interval that separated the beginning of a stimulating pulse from the beginning of the next one. The results obtained suggest the following. (1) Some of the mechanisms implicated in the elaboration of an escape response are similar irrespective of whether escape is induced by stimulating a site located in the CG, in the MH or in the LH.

Animals↗
PubMed1981

Acute encephalitis. A survey of epidemiological, clinical and microbiological features covering a twelve-year period.

The 191 adult patients with acute encephalitis who attended the Department of Neurology, University Hospital, Helsinki, during the 12-year period 1967-78, were analyzed for epidemiological, clinical, and microbiological features. Young healthy adults of either sex under 30 years of age were the most susceptible. The duration of symptoms varied from some hours to more than one month (less than or equal to 5 days in half of the patients). Prodromal symptoms were observed in 37.7%, meningeal signs or symptoms in 93.2%, features indicating brain involvement in 84.3% and clear effects on consciousness in 27.7% of the patients. Half (50.8%) recovered, while 43 (22.5%) were left with at least moderate disability after the acute phase. Twelve patients (6.3%) died. Lower socioeconomic status and age over 35 years were associated with increased mortality. The 10 patients with proven or presumptive herpes simplex virus (HSV) etiology had a mortality of 40% and only one recovered satisfactorily. There were 14 further cases suggestive of HSV. Mumps, Coxsackie B, adeno, and measles were the most frequent identifiable causes after HSV. Other etiological factors, including bacteria, appeared occasionally. The etiology remained obscure in 58.6% of the cases.

Adolescent↗
PubMed1980

Herpes simplex virus encephalitis: new diagnostic and clinical features and results of therapy.

Six patients with herpes simplex virus (HSV) encephalitis underwent diagnostic and clinical evaluation. The HSV or its antigenic material was found in three brain biopsy specimens. In the remaining three cases, the diagnosis was supported by detection of HSV antibodies in the CSF. Cell count and total protein concentration in the CSF reached a maximum level at three weeks and two months, respectively. The IgG index and HSV antibody level in the CSF often remained constant after reaching maximal values. In three patients, a transient low serum sodium level was observed. Characteristic EEG changes were present five to 11 days after the onset of symptoms. Computerized tomographic scanning revealed a temporal low-density lesion. Three patients became deeply comatose and had respiratory failure. The patient without vidarabine therapy and one of the five patients treated with vidarabine died.

Antibodies, Viral↗