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Biomedical subjects

D Stenberg

Publications and source records attributed to D Stenberg.

At least 37 records · Page 2Linked to original sources
PubMed1990

Correlation between salivary and serum melatonin: dependence on serum melatonin levels.

Saliva and serum samples were collected from eight healthy volunteers every two hours during a 26-hour period. Melatonin concentrations were measured by radioimmunoassay after chloroform extraction using radioiodinated melatonin as a tracer. Five of the subjects had high serum melatonin levels at night (peak levels higher than 75 pg/ml); in three subjects the highest serum melatonin concentration was 20-40 pg/ml. All subjects had low levels (less than 10 pg/ml) during the day. The correlations between salivary and serum levels were calculated. The regression line y = 0.33x + 3.7 pg/ml, r = 0.95, P less than 0.001, was obtained for all detectable value pairs (n = 73). The regression and correlation coefficients were almost equal for the peak values of melatonin and during the rising and descending phases of the secretion patterns. However, no significant correlation was found between low daytime salivary and serum concentrations when calculated separately. In the five high-secretors the melatonin levels in saliva reflected reliably the changes in serum, but in the three low-secretors the correlation between salivary and serum melatonin was not significant. The proportion of melatonin found in saliva decreased with increasing serum melatonin levels. Circadian rhythm parameters were estimated by single cosinor analysis. The acrophases did not differ significantly within a subject in the concomitant measurements of serum and salivary melatonin. The measurements of salivary melatonin levels seem valid for studies on melatonin rhythms, but the melatonin concentrations measured in saliva do not always consistently reflect the absolute concentrations in blood.

Adult↗
PubMed1990

Testosterone elevates pituitary prolactin content of long-term castrated rats under constant but not under periodic light.

Intact and castrated male rats were kept for 1 week under constant or periodic light, during which time they received daily injections of either vehicle or testosterone propionate (125 or 250 micrograms day-1). Immediately after the experiment the rats were decapitated and serum and pituitary prolactin were measured radioimmunologically. The pituitary prolactin content was decreased after castration in both lighting conditions. Daily testosterone injections elevated the pituitary prolactin content of the castrated rats to the level of the intact rats in constant-light conditions but were ineffective under periodic light. Serum prolactin concentrations were not affected by constant light. We have previously shown that testosterone decreases the serum luteinizing hormone concentration of castrated rats more effectively under constant than under periodic light. In the present study we showed that serum prolactin was not elevated in constant light and thus could not be the cause of increased testosterone sensitivity. We also showed that testosterone elevates the pituitary prolactin content of castrated rats under constant but not under periodic light. This finding gives further support to the hypothesis that constant light sensitizes the hypothalamo-pituitary axis of castrated male rats to the effects of testosterone.

Animals↗
PubMed1990

Lighting conditions affect serum and pituitary TSH in male rats.

It has been reported that periodicity of lighting plays a role in the regulation of the function of the hypothalamus-anterior pituitary-thyroid axis in the rat. We studied whether other properties of lighting influence the levels of pituitary and serum thyrotropin (TSH) in adult male rats. The animals were reared 7 days under various lighting conditions, then trunk blood and adenohypophyses were collected at different times of the day, and TSH was measured radioimmunologically. In natural lighting conditions the diurnal variation of plasma and pituitary TSH levels was abolished, and the overall levels of plasma TSH were higher and those of pituitary TSH lower than in ordinary laboratory lighting conditions. The intensity of lighting affected the serum TSH levels; daytime serum TSH decreased in the rats under low daytime illuminances and in those under nighttime twilight instead of darkness. Changing the rate of the lighting transition at dawn and dusk had no influence on the TSH patterns. We conclude that, in addition to periodicity, other features of lighting affect the daily secretion patterns of TSH.

Analysis of Variance↗
PubMed1989

alpha-Difluoromethylornithine (DFMO) disturbed the sensorimotor functional recovery from a sciatic lesion.

The effects of inhibition of polyamine synthesis on the motor and sensory functional neural recovery after a sciatic crush lesion was studied by measuring sensory and motor function of a crushed sciatic nerve after daily exposure to alpha-difluoromethylornithine (DFMO). DFMO increased the time needed for functional motor recovery by 13% in the toe-spread test when the lesion was about 20 mm proximal to the target muscle. DFMO reduced the rate of sensory axonal elongation by 24% in the pinch-test.

Animals↗
PubMed1989

Effect of different nocturnal illuminances on melatonin, prolactin, and gonadotropins in male rats.

We studied the role of nocturnal illuminance as a possible regulatory factor in the production and secretion of reproductive hormones. Adult male rats were kept under artificial lighting conditions (LD 12/12 hours) where the daily illuminance was 520-550 lx and the nocturnal illuminance 0, less than 0.1, or 1-1.5 lx. After a 7 day adaptation period, the pineal contents of melatonin, the serum levels of LH, FSH, and prolactin, and the pituitary contents of these hormones were measured by radioimmunoassay in samples taken 4 and 7 hours after the onset of light and onset of darkness. When the rats were kept in full darkness or under the minimal nocturnal iluminance (less than 0.1 lx), the patterns of pineal melatonin were equal. When nocturnal illuminance was 1-1.5 lx, the pineal melatonin contents at night were lower than in complete darkness. However, this illuminance level did not totally abolish the nocturnal increase of melatonin synthesis. The serum levels of LH, FSH, and prolactin were all affected by the increase of nocturnal illuminance so that the difference between the daytime and nighttime levels increased (higher values during the night). The variation of nocturnal illuminance did not change the pituitary contents of gonadotropins. The effects on pituitary prolactin were negligible as well. The results are interpreted to support the concept that nocturnal illuminance levels may regulate the secretion of the studied hormones in male rats.

Animals↗
PubMed1989

Lighting conditions affect testosterone feedback sensitivity in castrated rats.

It has been shown in the Syrian hamster that a short photoperiod sensitizes the hypothalamo-hypophyseal axis of castrated animals to the negative feedback effect of testosterone. There is some evidence that even the reproductive system of the rat, which is generally considered not to be very sensitive to light, can respond to changes in illumination. Therefore, we found it of interest to examine whether alterations in lighting conditions produce changes of sensitivity in the negative feedback effect of testosterone in the rat. We kept intact, castrated, and castrated testosterone-treated animals either in periodic (L:D 12:12) or constant light for 7 days starting 4 weeks after castration. In all 3 testosterone-injected groups, serum luteinizing hormone (LH) was lower in constant than in periodic light. Exogenous testosterone did not decrease the castration-induced elevations of pituitary LH and follicle-stimulating hormone (FSH). On the contrary, testosterone increased the pituitary contents of LH and FSH, especially in constant light. We conclude that, in constant light, the hypothalamo-hypophyseal axis of the castrated rat becomes more sensitive to the negative feedback action of testosterone.

Animals↗
PubMed1989

Effect of neonatal androgenization on the testosterone feedback sensitivity in adult rats in two lighting conditions.

Neonatally androgenized and intact adult male Wistar rats received daily, during 1 week, either testosterone propionate or sesame oil injections in periodic or constant light. Serum and pituitary gonadotropins and hypothalamic LHRH were measured. In periodic light, neonatal androgenization did not change the serum concentration or pituitary contents of gonadotropins, or the hypothalamic content of LHRH. Testosterone injections decreased serum concentration and pituitary content of gonadotropin of intact rats but failed to decrease the pituitary gonadotropin content of neonatally androgenized rats. In constant light, serum FSH was decreased in neonatally androgenized rats. Testosterone injections decreased both serum LH and FSH concentrations of intact rats but only serum LH of androgenized rats. Pituitary gonadotropin and hypothalamic LHRH contents remained unchanged. We conclude that neonatal androgenization renders the male rat hypothalamo-pituitary axis more resistant to changes of testosterone concentration in adulthood. Constant light did not sensitize the neonatally androgenized rats to testosterone, but on the contrary, testosterone injections were less effective in constant than in periodical light.

Androgens↗
PubMed1989

Daily illuminance levels affect pituitary prolactin in male rats.

The 24-h patterns of melatonin, PRL, and gonadotropins in male rats maintained under natural lighting conditions have been found to differ from the patterns in rats kept under artificial lighting. In the present experiments we studied the role of different daily illuminances as a possible causative factor for the variation of the hormonal patterns. Three groups of male rats were kept under artificial lighting conditions (12 h on/12 h off), where the daily illuminance was 550, 110 or 25 lux. After a 7-day adaptation period the pineal content of melatonin, the serum levels of LH, FSH and PRL, and the pituitary content of these hormones were measured by RIAs in samples taken at 10.00, 13.00, 22.00 and 01.00 h. The patterns of pineal melatonin were equal in all three groups. The variation of daily illuminance did not change the serum levels of LH, FSH and PRL or the pituitary content of the gonadotropins. However, the pituitary content of PRL during the light phase was inversely related to the illuminance. The results suggest that the intensity of daily lighting in the studied range does not affect the patterns of melatonin or gonadotropins, but the synthesis of prolactin may be significantly regulated by the daily illuminance level.

Animals↗
PubMed1989

Physiological role of alpha 2-adrenoceptors in the regulation of vigilance and pain: effect of medetomidine.

The sedative action of alpha 2-adrenergic agonists is generally ascribed to inhibition of the locus coeruleus (LC) and its ascending activating projection to the forebrain, although postsynaptic effects in the neocortex may also play a part. The sedative effect of the drugs varies considerably between different species. Systemic application of alpha 2-adrenergic agents have analgesic effects in addition to their sedative actions. Descending noradrenergic projections from the LC area modulate pain transmission at the spinal level. The purpose of this trial was to investigate the sedative properties of medetomidine in the cat. Medetomidine was injected intramuscularly at dose rates of 0.02, 0.06 and 0.18 mg/kg. Xylazine 3.0 mg/kg and saline were used for comparison. Medetomidine increased drowsy waking at the expense of both arousal and sleep. Nociceptive reflexes were suppressed in the case of the smallest dose of medetomidine, and abolished by the others. The 0.18 mg/kg dose of medetomidine had approximately equal effect on vigilance as 3.0 mg/kg of xylazine. The duration of the effect of medetomidine was dose-dependent. The alpha-receptor blocker phentolamine i.m. reversed the heavy sedation produced by medetomidine. Medetomidine also produced significant bradycardia, but the duration of this effect was not dose-dependent.

Adrenergic alpha-Agonists↗
PubMed1988

Putative stimulants for functional recovery after neural trauma: only spermine was effective.

The motor functional recovery after sciatic nerve crush was measured in rats treated with daily injections of (a) thyrotropin-releasing hormone (2.0 mg/kg, (b) alpha-melanocyte-stimulating hormone (0.07 mg/kg/48 h), or (c) testosterone propionate (4.4 mg/kg). The recovery of the motor function of the sciatic nerve was indicated by using the return of the toe-spreading response. None of the treatments differed significantly from saline controls in the time needed for recovery. The same procedure (without injections) was carried out with castrated and noncastrated male rats in order to test the effect of the lack of testosterone on recovery time after sciatic crush. The groups did not differ significantly as to their recovery times. The same method was used to study the effect of spermine (10.0 mg/kg/day) on the recovery of motor function. Spermine seemed to reduce the time needed for recovery from a mean value of 15.7 to 11.0 days (P less than 0.01). We also studied the effect of daily injections of spermine (13.0 mg/kg) on the sensory division of the peripheral nerve using the foot-flick test. The time needed for recovery after crush in the sciatic notch was reduced from 13.7 to 7.7 days (P less than 0.005). These results do not support the hypothesis that alpha-melantocyte-stimulating hormone, thyrotropin-releasing hormone, or testosterone enhance functional recovery of severed motor axons. Our results confirm a previous observation that spermine reduces the time needed for recovery after trauma in peripheral motor neurons. The result of the foot-flick test suggests that spermine enhances both motor and sensory recovery.

Animals↗
PubMed1987

Neonatal desipramine or zimeldine treatment causes long-lasting changes in brain monoaminergic systems and alcohol related behavior in rats.

To study the relationship between neonatal antidepressant administration, active (REM) sleep and adult alcohol-related behavior, rat pups were treated daily with 5 mg/kg desipramine (DMI) or 25 mg/kg zimeldine SC from the 6th to the 19th postnatal days. Movement sensitive mattress ("SCSB") measurements showed that zimeldine treatment suppressed active sleep throughout the whole treatment period, but DMI was more effective during the first 8 days than during the last treatment days. At the age of 70 days, the zimeldine-treated rats expressed a selective increase of some components of activity in the open field test, and the DMI rats had a higher defecation score compared to the controls. Furthermore, the zimeldine-rats responded with a decrease in ambulation in the open field to an alcohol dose which generally stimulates locomotion in rats. At the age of 3 months the DMI and zimeldine rats showed increased voluntary intake of 10% (v/v) alcohol. Measurement of brain monoamines revealed that the neonatal treatment with DMI or zimeldine interfered with the normal development and function of the monoamine neuronal systems: the concentrations of noradrenaline, dopamine and 5-hydroxytryptamine (5-HT), and their metabolites were altered in several brain regions. The results thus suggest that neonatal treatment with DMI or zimeldine suppresses active sleep and has an influence on later alcohol-related behavior, possibly due to a long-lasting defect in brain monoaminergic transmission.

Alcohol Drinking↗
PubMed1987

Sedative action of the alpha 2-agonist medetomidine in cats.

Medetomidine, a novel alpha 2-agonist drug intended for small animal sedation, was injected intramuscularly at dose rates of 0.02, 0.06 and 0.18 mg/kg. Xylazine (3.0 mg/kg) and saline were used for comparison. The five treatments were tested in a Latin square design in five cats. Treatments differed significantly in three-way analysis of variance, medetomidine inducing an increase in drowsiness with a corresponding decrease in both aroused waking and sleep determined by polygraphical criteria. The duration of effect was dose-dependent. The effect of 0.18 mg/kg medetomidine was comparable to 3.0 mg/kg of xylazine. The drugs also induced bradycardia.

Adrenergic alpha-Agonists↗
PubMed1986

Sleep in Macaca arctoides and the effects of prazosin.

Polygraphic (EEG, EOG, EMG) 12-hr recordings were made in 3 adult monkeys (Macaca arctoides) to document their normal sleep pattern and to examine the effects of prazosin, an alpha-1-adrenoceptor antagonist. In comparison to man, REM episodes appeared at shorter intervals (50 min) and they always ended in movement arousal or waking up. As in man the proportion of deep sleep decreased and the proportion of REM sleep increased towards morning. During eight hours after parenteral administration of prazosin, at doses without any noticeable behavioral side effects, the number of REM episodes and the amount of REM sleep was 30 to 80 percent greater than during the control nights. The changes were statistically nonsignificant. However, since the results were similar in all three monkeys, it can be suggested that prazosin had some effect on the cyclicity of sleep. Dose 1 mg/kg resulted in behavioral side effects and disturbed sleep.

Animals↗
PubMed1983

Visual and spectral EEG analysis in the evaluation of the outcome in patients with ischemic brain infarction.

Serial EEGs were recorded in 15 patients with acute cerebral infarctions in order to study clinical and prognostic correlations. The EEG was recorded within 48 h from the first symptoms and thereafter weekly for 4 weeks. The EEGs were analyzed both visually and with a computerized spectral analysis. Eight of the patients recovered fully and seven had permanent neurological deficits. On admission, 87% of the patients had an abnormal EEG by visual analysis. The spectral parameters correlated well with visual findings, especially the delta and alpha bands. The spectral analysis was superior to visual in predicting the correct laterality of the lesion. It showed the correct side of the lesion in 87%, while the visual did it in only 54% of the cases. The first EEG records reliably predicted the outcome of the patients. The degree of background abnormality was most important in visual EEG analysis. In spectral analysis, parameters from single derivations were superior to the average of all derivations. A high proportion of delta or low proportion of alpha power were reliable indicators of poor outcome.

Adult↗
PubMed1980

EEG and end-tidal carbon dioxide concentration in the hyperventilation syndrome.

The hyperventilation syndrome (HVS) is a functional disorder with repeated involuntary hyperventilation attacks together with symptoms of respiratory alkalosis. We have studied the EEG and end-tibial pCO2 in the resting state and during hyperventilation activation in 12 HVS patients in order to find out whether there is a greater susceptibility to cerebral vasoconstriction in HVS patients than in controls, as indicated by slowing of the EEG. A surprisingly high proportion (58%) of abnormal resting EEGs was found in HVS patients, although the patients were neurologically normal. More theta and beta background activity was usually revealed in a quantitative computer analysis, especially frontally. Although the hyperventilation activation caused the same degree of hypocapnia in HVS patients and in controls, peripheral symptoms like tingling and numbness of fingers, as well as carpopedal spasms, occurred much more often in HVS patients. However, the EEG changes due to hyperventilation were similar in both HVS patients and normal controls, and it thus seems that the reason for cerebral symptoms in HVS patients is not a greater susceptibility to cerebral vasoconstriction.

Adult↗