Twenty-four-hour patterns of pineal melatonin and pituitary and plasma prolactin in male rats under 'natural' and artificial lighting conditions

Natural lighting differs from usual artificial lighting mainly as follows: it has larger spectral composition, fluctuations of intensity during the day, higher intensity levels during the night (moonlight, starlight), and gradual changes of illuminance at dawn and dusk. The present experiment was performed in order to study whether these features of lighting affect the 24-hour patterns of melatonin and prolactin in male rats. The rats were kept 7 days in 'natural' lighting (sunlight through windows) or in artificial lighting (cool white fluorescent lamps) of similar periodicities (13/11 h light/dark). The samples were collected at 3-hour intervals during a 24-hour period. Pineal melatonin contents, pituitary prolactin contents, and plasma prolactin concentrations were measured radioimmunologically. The nocturnal pineal melatonin contents were higher and the daytime contents lower in natural than in artificial lighting conditions. A corresponding 'strengthening of rhythm' of prolactin was found in natural lighting. A reason for the higher amplitude variation of melatonin in the natural lighting conditions may be the gradual changes of illuminance at dawn and dusk. The different pituitary and plasma prolactin patterns of the rats kept in the two lighting conditions might partly be explained by a stimulatory effect of melatonin on the production and secretion of prolactin, but other regulatory factors had to be involved, too.     

Using adiabatic inversion pulses for long-T2 suppression in ultrashort echo time (UTE) imaging.

Ultrashort echo time (UTE) imaging is a technique that can visualize tissues with sub-millisecond T(2) values that have little or no signal in conventional MRI techniques. The short-T(2) tissues, which include tendons, menisci, calcifications, and cortical bone, are often obscured by long-T(2) tissues. This paper introduces a new method of long-T(2) component suppression based on adiabatic inversion pulses that significantly improves the contrast of short-T(2) tissues. Narrow bandwidth inversion pulses are used to selectively invert only long-T(2) components. These components are then suppressed by combining images prepared with and without inversion pulses. Fat suppression can be incorporated by combining images with the pulses applied on the fat and water resonances. Scaling factors must be used in the combination to compensate for relaxation during the preparation pulses. The suppression is insensitive to RF inhomogeneities because it uses adiabatic inversion pulses. Simulations and phantom experiments demonstrate the adiabatic pulse contrast and how the scaling factors are chosen. In vivo 2D UTE images in the ankle and lower leg show excellent, robust long-T(2) suppression for visualization of cortical bone and tendons.     

Effect of a Single Nighttime Dose of Oxazepam on Seizure Duration in Electroconvulsive Therapy

In a double-blind crossover study, 12 depressed inpatients receiving bilateral electroconvulsive therapy (ECT) were given 22.5 mg oxazepam or placebo (identical tablets, randomized order) the night before treatment. Seizure duration was measured using the cuff method and a total of 20 pairs of measurements were made. Mean duration after oxazepam administration was 0.9 s longer than after placebo; this difference was not statistically significant. The relevant lower one-sided 95% confidence limit was -4.1 s. Single administration of oxazepam, 22.5 mg, has little average effect on seizure duration in ECT.     

Examination stress affects plasma levels of TSH and thyroid hormones differently in females and males

Plasma levels of TSH and thyroid hormones in 22 male and 27 female medical students were determined by radioimmunoassay before and after an academic examination. The plasma values of TSH were slightly higher in both sexes on the examination day than on the control days. The values were lower after the examination than before it in females but not in males. Plasma levels of T3 were higher in males than in females on the examination day. In contrast, the plasma rT3 values were higher for females on the examination day than on control days. The plasma levels of T4 were similar in both sexes. The results suggest that during psychic stress, the pituitary-thyroid endocrine system of the female reacts differently from that of the male.     

Mechanics of porcine coronary arteries<Emphasis Type="Italic">ex vivo</Emphasis> employing impedance planimetry: A new intravascular technique

Our objective was to evaluate methodological aspects of impedance planimetry, a new balloon catheter-based technique, for the investigation of coronary artery mechanical wall properties. We used a four ring-electrode electrical impedance measuring system that was located inside a balloon. Two of the electrodes were used for excitation and connected to a generator producing a constant alternating current of 250 mA at 5 kHz. The other two electrodes for detection were placed midway between the excitation electrodes. The balloon was distended with electrically conducting fluid through an infusion channel. The vessel cross-sectional area (CSA) was measured according to the field gradient principle by measuring the impedance of the fluid inside the balloon. Impedance planimetry was applied in the three major branches of the coronary arteries of seven extracted porcine hearts to assess luminal CSAs in response to internal pressurization. The biomechanical wall properties were evaluated by computing the strain [(r?r ₀)·r ₀ ^?1, wherer is the vessels inner radius computed as (CSA · π^?1)^½ andr ₀ is the radius of the vessel at a minimal distension pressure], the tension [(r·dP), wheredP is the transmural pressure difference], and the pressure elastic modulus (ΔP·r·Δr ^?1). We found thatin vitro testing demonstrated that impedance planimetry was accurate and reproducible. The technique has controllable sources of crror. Measurements were performed with consecutively increasing pressures in the range 1–25 kPa (8–188 mmHg, 0.01–0.25 atm). The CSAs increased nonlinearly and were significantly larger in the left anterior descendent coronary artery (LAD) (1 kPa, mean 5.0 mm²; 25 kPa, mean 21.8 mm²) than in both the left circumflex (Cx) (4.5–16.0 mm²) and the right coronary artery (RCA) (2.8–15.6 mm²) (analysis of variance,P<0.001 for both). The circumferential wall tension-strain relation showed exponential behavior. For a given strain, tension values for LAD were significantly lower than those of Cx (P<0.01). The pressure elastic modulus-strain relation also was exponential, and values for Cx were significantly lower than values for LAD (P<0.001) and RCA (P<0.05). Impedance planimetry was applied to the study of coronary artery biomechanicsex vivo. The LAD had the largest CSA, and the Cx was the least compliant. Methodological aspects of anin vivo introduction of the method require additional evaluation.