Phenytoin as a countermeasure for motion sickness in NASA maritime operations

Seasickness is the most prevalent form of motion sickness and is an operational problem during Space Shuttle Solid-fueled Rocket Booster (SRB) retrieval. Phenytoin has been shown to protect against motion sickness induced by Coriolis stress. We exposed SRB recovery personnel to off-vertical rotation and sea motion after phenytoin or placebo. Phenytoin blood levels of at least 9 micrograms/ml were protective against motion sickness at sea. No change in susceptibility to nitrogen narcosis was seen in divers in chamber tests at 460 KPa. Phenytoin was used during performance of critical and hazardous tasks during training and actual SRB recovery operations. Phenytoin is an effective operational countermeasure for motion sickness for selected SRB crewmembers.     

Effects of magnesium sulphate and nitric oxide in pulmonary hypertension induced by hypoxia in newborn piglets

AIM: To examine the haemodynamic effects of intravenous magnesium sulphate on an animal model of neonatal pulmonary hypertension induced by hypoxia. METHODS: The cardiac index (Q), pulmonary arterial pressure (PAP), systemic arterial pressure (SAP), and pulmonary (PVRI) and systemic (SVRI) vascular resistance indices were measured in nine newborn piglets (including three controls). Pulmonary hypertension was induced by lowering the FIO2 to 0.12-0.14, after which there was a significant increase in PAP and PVRI (37% and 142%, respectively; p < 0.01) and a significant fall in SAP and Q (30% and 33%, respectively; p < 0.01). RESULTS: Magnesium sulphate was infused intravenously as four doses of 25 mg/kg, 15 minutes apart, which resulted in a significant mean (SD) increase in serum magnesium (0.83 (0.07) mmol/l to 1.82 (0.19) mmol/l; p < 0.01). After the initial dose SAP, SVRI, PAP and PVRI decreased, but not significantly. Each subsequent dose of (50, 75, 100 mg/kg) was accompanied by further significant reductions in these variables from control baseline (p < 0.05). The PVRI:SVRI ratio remained unchanged throughout. Inhaled nitric oxide (NO) 40 ppm was administered after the last dose of magnesium sulphate. The PVRI:SVRI significantly decreased (p < 0.05), indicating that reversible pulmonary hypertension remained after a maximum dose of magnesium sulphate. CONCLUSIONS: Unlike NO, magnesium sulphate is not a selective pulmonary vasodilator and may lead to deleterious effects on systemic pressures in critically ill newborns.     

Measurement and global analysis of the absorbance changes in the photocycle of the photoactive yellow protein from Ectothiorhodospira halophila

The photocycle of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila was examined by time-resolved difference absorption spectroscopy in the wavelength range of 300-600 nm. Both time-gated spectra and single wavelength traces were measured. Global analysis of the data established that in the time domain between 5 ns and 2 s only two intermediates are involved in the room temperature photocycle of PYP, as has been proposed before (Meyer T.E., E. Yakali, M. A. Cusanovich, and G. Tollin. 1987. Biochemistry. 26:418-423; Meyer, T. E., G. Tollin, T. P. Causgrove, P. Cheng, and R. E. Blankenship. 1991. Biophys. J. 59:988-991). The first, red-shifted intermediate decays biexponentially (60% with tau = 0.25 ms and 40% with tau = 1.2 ms) to a blue-shifted intermediate. The last step of the photocycle is the biexponential (93% with tau = 0.15 s and 7% with tau = 2.0 s) recovery to the ground state of the protein. Reconstruction of the absolute spectra of these photointermediates yielded absorbance maxima of about 465 and 355 nm for the red- and blue-shifted intermediate with an epsilon max at about 50% and 40% relative to the epsilon max of the ground state. The quantitative analysis of the photocycle in PYP described here paves the way to a detailed biophysical analysis of the processes occurring in this photoreceptor molecule.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) accelerates differentiation of murine preimplantation embryos in vitro

The effects of antioxidant-rich foods as adjuncts to a prudent diet were compared for 12 weeks in a randomized, single-blind and controlled trial in 204 (group A) and 202 (group B) patients with acute myocardial infarction. There was a significant decrease in cardiac end points in group A compared to group B (37 vs 58, p < 0.01) after 12 weeks. Within intervention group A, those 108 patients with greater adherence to the intervention program showed a greater reduction in cardiac end points (14 vs 58, p < 0.001), and a significant decrease in total mortality (6 vs 28, p < 0.001), including cardiac mortality (6 vs 25, p < 0.01) compared to group B. Underlying these beneficial effects, antioxidant-rich foods caused a significantly smaller rise in lactate dehydrogenase (LDH) cardiac enzyme in group A than in group B (427.8 vs 561.6 IU/dL), indicating that the protective influence of such a diet may be observed within 1 week. The subset of group A patients showing reduction in mortality also had a lesser rise in LDH and greater reduction in blood lipids, blood glucose and blood pressures. Antioxidant-rich foods also caused a significant decrease in blood lipids with a lower decrease in high-density lipoprotein cholesterol in group A than in group B. Assay of serum level of antioxidants and long-term follow-up may confirm our observations.     

Modified technique of blunt cannula retrobulbar anesthesia for vitreoretinal surgery

We prospectively evaluated a modified version of a previously reported technique of retrobulbar anesthesia for vitreoretinal surgery involving the use of a blunt 19-gauge cannula to directly infuse anesthetic into the retrobulbar space. Using this method, 60 consecutive patients undergoing scleral buckling surgery had effective anesthesia and akinesia, with no complications.     

No association between Parkinson's disease and low-activity alleles of catechol O-methyltransferase

Idiopathic Parkinson's disease (IPD) is characterised by the loss of pigmented neurones in the substantia nigra, leading to reduced tyrosine hydroxylase activity and depletion of dopamine. Treatments attempt to correct this deficit by the use of levodopa and inhibitors of dopamine metabolising enzymes such as catechol-O-methytransferase (COMT). A common amino-acid polymorphism in COMT, valine-108-methionine, results in a low activity form of the enzyme which we hypothesised may influence susceptibility to IPD. We examined this polymorphism in 139 Caucasian subjects with IPD and 173 control subjects, using a PCR-RFLP and a novel Amplification Refractory Mutation System (ARMS) assay. Allele and genotype frequencies were similar in the affected and control subjects, indicating that variation of COMT activity is not an aetiological factor in IPD. We have also characterised a new polymorphism, 256C/G, which is not associated with IPD. However it remains possible that allelic variation in COMT influences severity, type of pathology or treatment response to levodopa or COMT inhibitors.     

Adenosine receptor antagonism affects regional resting vascular resistance during rat peritoneal sepsis

We examined sequential changes of bone-resorbing cytokines and bone metabolic markers and the effect of ovarian hormones on bone metabolism during the menstrual cycle in 10 healthy Japanese women, aged 22-43 yr, with normal ovarian function. Serum soluble interleukin-6 receptor (sIL-6R) showed a significant variation; a rise during the early and late follicular periods followed by a fall during the early luteal period (P = 0.0423, P = 0.0334) and an increase during the mid and late luteal periods. There were significant changes in the levels of markers of bone formation: a rise in serum bone-specific alkaline phosphatase (ALP) during the mid and late follicular (P = 0.0265) periods and a fall in serum carboxyl-terminal propeptide of type I procollagen (PICP) during the midluteal period (P = 0.0161). As for the levels of bone resorption markers, urinary type I collagen C-telopeptide breakdown products (CTx) and free deoxypyridinoline (D-Pyr) decreased significantly during the early and midfollicular periods, urinary free D-Pyr and serum pyridinoline cross-linked carboxyl-terminal telopeptide of type I collagen (ICTP) (P = 0.0440) increased significantly during the early luteal period, and urinary CTx, free D-Pyr, and serum ICTP decreased significantly during the late luteal period (P = 0.0170-0.0008). The serum PTH level was significantly higher during the follicular than the luteal period (P = 0.0132). Serum sIL-6R significantly correlated with urinary CTx (r = 0.190, P < 0.05) and serum ALP (r = 0.209, P < 0.05) and serum estradiol with intact osteocalcin (r = 0.309, P < 0.0005) and serum ALP (r = 0.181, P < 0.05). These observations strongly suggest that cyclic variations in the levels of bone formation and resorption markers and of a bone-resorbing cytokine may be modulated by cyclic changes in serum steroid hormones during the menstrual period. In addition, the specific days of biochemical events in the menstrual cycle are crucial for evaluating osteoclastic and osteoblastic activities in pre- and perimenopausal women or in women starting GnRH agonist therapy.     

Amniotic septostomy for the treatment of twin oligohydramnios-polyhydramnios sequence

A mass balance for lead for the year 1989 in the South Coast Air Basin has inputs to the atmosphere of 600 +/- 190 kg/day and outputs of 580 +/- 160 kg/day, showing rough agreement. Stationary sources are responsible for only about 5% of the total lead emissions. The bulk of the lead is emitted from vehicles using leaded gasoline (37%) and unleaded gasoline (15%), as well as from resuspension of previously deposited lead on roads (43%). Over half of the total emitted lead deposits on roads and nearby soil, while about one-third is carried out the basin by wind. A small amount, less than 10%, is deposited on surfaces throughout the basin. These percentages are approximately the same as those in a mass balance for the same region calculated for 1972, when lead emissions from leaded gasoline were about a factor of 70 greater than leaded gas emissions in 1989. When the lead emissions are used as inputs to a simple continuously stirred flow reactor model for the basin, reasonable agreement is obtained between calculated and measured concentrations.     

Gas bubbles in the hip joint on CT: an indication of recent dislocation

OBJECTIVE: The purpose of this study was to determine if gas bubbles in the hip joint seen on CT scans after trauma are reliable indicators of recent (< 48 hr) hip dislocation. We believe that the gas seen in the hip joint represents intracapsular nitrogen bubbles that result from the vacuum created by forcible distraction associated with traumatic dislocation. MATERIALS AND METHODS: CT scans of 79 consecutive patients with pelvic injury were reviewed retrospectively. We noted the number and position of intracapsular gas bubbles, presence of joint effusion, soft-tissue injury, and associated fractures or dislocations. Intracapsular gas bubbles were defined as round areas of low attenuation, in an intracapsular position, that on visual inspection were equivalent to air. Seventy-three of 79 patients were imaged within 48 hr of injury. Most patients had been involved in a motor vehicle collision or were pedestrians struck by a motor vehicle. Fifteen patients had hip dislocation, including one patient with bilateral dislocation. Fifty-five patients had pelvic fractures without hip dislocation, and nine patients had soft-tissue injury without fracture or dislocation. Fourteen of 16 dislocations had been reduced at the time of scanning. RESULTS: Gas bubbles were seen in the hip joint on CT scans in 13 (81%) of the 16 dislocated hips, including 12 (92%) of 13 dislocations in patients scanned within 4 hr of admission. Bubbles were present in 11 (79%) of 14 hip joints that had dislocations reduced at the time of scanning and in both hip joints that remained dislocated. Most bubbles were located anterior to the femoral neck; however, bubbles were also seen posteriorly. Bubble size (1-3 mm) and number (1-7) varied. Only two (3%) of 64 patients without dislocation had intracapsular gas bubbles; one had been shot and the other had extensive soft-tissue emphysema. CONCLUSION: In the absence of penetrating trauma, intracapsular gas bubbles on CT are reliable indicators of recent hip dislocation and may be the only objective finding of this injury.