Synchronous tuning of extended cavity diode lasers: the case for an optimum pivot point.

Diode lasers can be tuned by simultaneous rotation and translation of an external grating. This can be achieved by rotating the grating about a displaced pivot point. We derive the tuning range as a function of pivot point position for various extended cavity geometries. In each case, the geometric problem reduces to the solution of a quadratic equation. For near-infrared wavelengths, placement of the pivot is relatively noncritical for tuning ranges of the order of 10 GHz, but requires millimeter accuracy for a tuning range >100 GHz.

Evidence that spinal interneurons undergo programmed cell death postnatally in the rat.

Programmed cell death has been demonstrated in several specific neuronal populations as a mechanism for modulating the population size following differentiation, but its applicability to all neuronal types is unclear. Evidence for programmed cell death in some populations such as the numerous spinal interneurons has been lacking. We have studied the incidence of apoptosis in the rat spinal cord with three different methods and found a previously undocumented wave of apoptosis occurring in spinal grey matter shortly after birth. The apoptotic morphology was confirmed ultrastructurally. Dying cells were identified as neurons by immunocytochemical labelling for neuronal markers and had an anatomical distribution which indicated that most of the apoptotic cells were interneurons not motoneurons. This wave of apoptosis has the characteristics of a discrete developmental process and occurs later than that of either ventral horn motoneurons or dorsal root ganglion cells, to which most spinal interneurons are connected. These findings indicate that interneurons do undergo programmed cell death, and we suggest that this occurs in response to the earlier reduction in size of their main synaptic targets.

Metabolic response to low- and very-low-calorie diets.

We compared the metabolic effects of 8-wk caloric restrictions with 330 or 780 kcal/d in two groups of eight obese hospitalized subjects; six control subjects were also studied. Loss of weight but not of adipose tissue was significantly greater on the 330-kcal/d diet. It is likely that dehydration rather than protein catabolism was responsible for additional loss of fat-free mass in the 330-kcal/d group because the nitrogen deficit was not excessive. The thermic response to food was blunted only in the 330-kcal/d group whereas resting oxygen uptake decreased by equal amounts in both groups. There was a decrease in 24-h urinary noradrenaline in the 330-kcal/d group but plasma fT4 was sustained when compared with the 780-kcal/d group; fT3 decreased significantly more quickly in the 330-kcal/d group. There was no correlation between plasma hormone levels and changes in oxygen uptake. Hunger scores were greater on the 780-kcal/d diet.

Ulcer healing and relapse prevention by ranitidine in peptic ulcer disease.

Ranitidine, 300 mg daily, was given to 92 patients with duodenal ulcer (DU), 38 with prepyloric ulcer (PPU), and 21 with gastric corporeal ulcer (GCU). The healing rates at 4 weeks differed for the different types of ulcers (P less than 0.01), being 91% for DU, 68% for PPU, and 81% for GCU. After established ulcer healing, maintenance treatment with either ranitidine, 100 mg twice daily or 150 mg at night, or placebo was given for 1 year or until ulcer relapse in a total of 108 patients--71 with DU, 24 with PPU, and 13 with GCU. There were no significant differences in relapse rates between the two groups treated with active drug or between the three ulcer groups. However, the overall relapse rate in the active drug groups was 16%, against 72% in the placebo group (P less than 0.001).

Exposure of hay fever subjects to an indoor environmental grass pollen challenge system.

A new indoor nasal allergen challenge system has been developed which allows subjects with hay fever to be exposed to pre-determined concentration of grass pollen grains in the immediate environment. Thirteen subjects were exposed during the winter months to an atmosphere containing approximately 1000 grains/m3 for 30 min. No changes in nasal airway patency or symptoms of nasal congestion were recorded. It was necessary to increase the pollen concentration to approximately 9000 and 35 000 grains/m3 in two subjects and six subjects respectively, before a positive response was recorded. This response was reproducible in all subjects. Administration of intra-nasal sodium cromoglycate before exposure significantly inhibited the decrease in nasal airway patency and when administered 1 min before exposure totally abolished symptoms of nasal congestion. This new challenge system may therefore be used as an in vivo screen to assess the potential therapeutic value of drugs in hay fever under controlled conditions.

A method for monitoring drug effects on male sexual response: the effect of single dose labetalol.

1 A method for monitoring the effect of drugs on the genital response to stimulation provided by vibration is described. 2 Using this method, the effect on male sexual response of two oral doses (100 mg and 300 mg) labetalol were studied and compared with placebo in six subjects. 3 Labetalol did not affect the attainment or maintenance of erection. 4 Labetalol delayed ejaculation in a dose-related manner. 5 Labetalol treatment resulted in a significant dose-related delay in detumescence.

Slow-release oral salbutamol and aminophylline in nocturnal asthma: relation of overnight changes in lung function and plasma drug levels.

In a double-blind controlled trial 14 chronic asthmatic patients with regular nocturnal exacerbations took 16 mg slow-release oral salbutamol (two Ventolin spandets), 450 mg slow-release aminophylline (two Phyllocontin Continus tablets), or placebo at midnight. Mean peak expiratory flow rates on waking were significantly higher on the active drugs than on placebo (p < 0.01 for salbutamol; p < 0.05 for aminophylline) but neither drug abolished the overnight fall in PEFR. Plasma drug levels at 0600 hr were 17.3 ng/ml (+/- 5.3 ng/ml SD) for salbutamol, and 7.1 micrograms/ml (+/- 3.1 micrograms/ml SD) for theophylline. Steady-state derived from plasma levels of salbutamol during intravenous infusion indicated that the morning salbutamol levels were probably in a therapeutic range for asthma. The morning theophylline levels, however, were suboptimal when aminophylline was given only at night.

Measurement of nasal patency using a Vitalograph.

A standard Vitalograph was used to measure the volume of air inspired through the mouth (M-FIV0.5) and nose (N-FIV0.5) in 0.5 sec. The ratio of these parameters was used as a nasal patency index (NPI) and the characteristics of NPI and N-FIV0.5 investigated in terms of reproducibility and sensitivity. Both indices were significantly reduced by intranasal histamine (100 micrograms and 200 micrograms) and it is concluded that NPI and N-FIV0.5 are reproducible and sensitive indices of nasal patency.

The effect of intravenous and oral salbutamol on fetus and mother in premature labour.

Salbutamol was administered intravenously to 14 patients in premature labour. Inhibition of uterine contractions occurred on 22 out of 23 occasions. The mean increase in maternal and fetal heart rate and blood pressure were within clinically acceptable limits but there were wide individual variations. The mean delay achieved when the intravenous regime was supplemented with oral salbutamol was greater than that achieved by intravenous salbutamol alone, but the difference was not statistically significant.

Evaluation of a breath actuated pressurized aerosol.

Preliminary investigation suggests that some asthmatic patients find it difficult to synchronize the release of a metered dose from a pressurized aerosol with the correct phase of inspiration. An automatic device has been developed to overcome this problem. Information is presented outlining the physical characteristics of the unit and the methods used to establish its performance in patients. It is suggested that the device may have a place in the management of asthma.

Evaluation of tolerance after continuous and prolonged oral administration of salbutamol to asthmatic patients.

Salbutamol (8 mg) was administered twice daily as a sustained release formulation to twenty-four asthmatic patients for up to four weeks under double-blind conditions. 2. The ability of bronchial smooth muscle to respond was determined by monitoring the response to salbutamol (200 mug) administered by aerosol at set intervals three times a week. 3. There was no evidence of diminishing response during the study period. 4. It is concluded that tolerance to salbutamol does not occur at therapeutic dose levels and that clinical observations of tolerance may be due to other factors.