Tropical tropospheric ozone and biomass burning.

New methods for retrieving tropospheric ozone column depth and absorbing aerosol (smoke and dust) from the Earth Probe-Total Ozone Mapping Spectrometer (EP/TOMS) are used to follow pollution and to determine interannual variability and trends. During intense fires over Indonesia (August to November 1997), ozone plumes, decoupled from the smoke below, extended as far as India. This ozone overlay a regional ozone increase triggered by atmospheric responses to the El Niño and Indian Ocean Dipole. Tropospheric ozone and smoke aerosol measurements from the Nimbus 7 TOMS instrument show El Niño signals but no tropospheric ozone trend in the 1980s. Offsets between smoke and ozone seasonal maxima point to multiple factors determining tropical tropospheric ozone variability.

Metal-ion assisted, radiation-induced conversion of B- to Z-DNA in poly (dGdC) and two natural DNAs.

Metal-ion assisted, gamma-radiation-induced B-Z conformation changes have been observed with UV and circular dichroism spectroscopy for poly (dGdC), calf thymus and herring testis DNA. These conformational changes are similar to those induced by increasing multivalent metal ion concentrations in DNA containing alternating purine and pyrimidine base sequences. In both the metal-ion-induced and the metal-ion-assisted, radiation-induced conformation changes, the conversions were from the right-handed B-DNA to the left-handed Z-DNA conformation. It is proposed that radiation-induced DNA strand breaks markedly reduce the high activation energy barrier in the metal ion-driven B-Z conformation conversion and allow much smaller metal ion concentrations to induce this conversion than in the absence of strand breaks. The biological importance of such radiation-induced conformational changes is discussed in terms of the potential significance of the Z-DNA conformation in the control of the DNA transcription process.

Ultraviolet difference spectral studies in the gamma radiolysis of DNA and model compounds. I. Aqueous solutions of DNA bases.

Ultraviolet difference spectra of gamma-irradiated, air-saturated aqueous solutions of DNA bases vs. unirradiated solutions of the same bases are shown to be a very sensitive supplemental tool with which to investigate the yields, postirradiation kinetics, and general nature of DNA base radiation products. Irradiated pyrimidines yield difference spectra which are approximately negative mirror-images of the base absorption spectra in the near-UV, indicating loss of ring conjugation. Difference spectra of irradiated purines yield a more complex pattern containing a positive long-wavelength peak, interpreted as radiation-induced extension of conjugation of the pi electron system beyond that of the unirradiated purine. On the basis of the spectroscopic evidence from these studies, 8-hydroxyguanine appears to be the dominant UV-absorbing radiation product in air-saturated guanine solutions with a G-value of 0.3 molec (100 eV)-1. Difference spectral studies provide isosbestic points which can be used in testing proposed radiation products and their yields. Such spectral studies are a rapid, non-invasive, supplemental tool which can be employed in conjunction with other analytical techniques in radiation-chemical studies, and which is one of the few tools able to detect short-lived chemical intermediates observed in oxygenated solutions of irradiated purines.

Exophiala jeanselmei infection in a postrenal transplant patient.

We report a case of Exophiala jeanselmei infection in a postrenal transplant patient. He had verrucous lesions on the thigh and abdomen in which clinical and histologic changes resembled those characteristic of chromoblastomycosis. However, the morphologic features of the fungus seen in the tissue sections made it necessary to diagnose this case as phaeohyphomycosis. The patient was treated successfully by complete excision of the lesion on the abdomen and with oral ketoconazole.

Behçet's syndrome: immune regulation, circulating immune complexes, neutrophil migration, and colchicine therapy.

Immune regulatory dysfunction, circulating immune complexes (CIC), and polymorphonuclear (PMN) cell migration were investigated in patients with Behçet's syndrome. Six patients meeting rigorous clinical criteria were evaluated. Only one patient showed evidence of immune regulatory dysfunction (increased T4/T8 ratio). Although C1q binding and Raji cell assays for CIC yielded positive results in only one of five patients, all five patients had in vivo "histamine trap test" evidence of CIC (all controls had normal results). Sera from all Behçet's syndrome patients increased migration of neutrophils to zymosan-activated serum. Colchicine therapy abolished the enhancing effect of the patient's sera on movement of PMN cells from patients and controls. An immune complex-mediated injury that is followed by an excessive accumulation of PMN cells may lead to the cutaneous lesions and other lesions in Behçet's syndrome. Further evaluation of colchicine therapy is warranted on the basis of these studies.

Stratospheric ozone and hydroxyl radical measurements by balloon-borne lidar.

A balloon-borne lidar system for the measurement of ozone and hydroxyl radical in the stratosphere has been constructed and flown by Goddard Space Flight Center. On this flight ozone concentration at altitudes between 20 and 37 km were determined with vertical resolution of approximately 0.5 km. In addition, horizontally resolved ozone measurements with 0.15-km resolution were obtained over a 2-km range. The temporal variation of the hydroxyl radical concentration was measured in the 34-37-km altitude region, ranging from 40 parts/trillion shortly after noon to approximately 5 parts/trillion 2 h after sunset. Improvements in the system are proposed to increase the sensitivity of the instrument below the parts/trillion level, permitting hydroxyl determinations in the 20-30-km altitude range.

The activity of interferon on ultraviolet light-induced squamous cell carcinomas in mice.

The activity of interferons was tested in ultraviolet light-induced skin tumors in mice. After the tumors were well established, they were injected and measured daily for 19 days. Mouse virus type (IF-alpha + IF-beta) and immune (IF-gamma) interferons were injected intralesionally into three groups of test animals and compared with a fourth group which received mock interferon (control). When used separately, virus type and immune interferons did not affect tumor growth; however, we observed regression in tumor size when the two interferons were used in combination.

Central nervous system responses to cigarette smoke inhalation in the cat.

Intact, pentobarbital anesthetized cats (with and without brainstem stimulating electrode implants) and unanesthetized Sherrington (gamma-driven) decerebrate cats "smoked" cigarettes of varying nicotine content (0.2-2.5 mg). Nicotine free lettuce leaf cigarettes were used as controls. "Smoking doses" of nicotine base (10-25 micrograms/kg) were administered i.v. for comparison. Smoke inhalation produced motor reflex depression which paralleled the nicotine content of the cigarettes "smoked". Patellar reflex facilitation due to mesencephalic reticular stimulation was reduced by doses of nicotine and cigarette smoke. Cigarettes (2.5 mg nicotine) and doses of nicotine (25-50 micrograms/kg, i.v.) significantly reduced rigidity and patellar reflex amplitude in the gamma-decerebrate cat. Dihydro-beta-erythroidine reduced the nicotine and cigarette smoke induced patellar reflex depression but not the diminution in the rigidity. Smoking doses of nicotine suppressed pentobarbital-induced EEG spindles in acutely prepared cats. Nicotine (10-25 micrograms/kg) produced EEG and behavioral arousal in cats with chronic deep electrodes. It was concluded that cigarette smoke produces its pharmacological effects via its nicotine content.

Multicentric origin of the atrial depolarization wave: the pacemaker complex. Relation to dynamics of atrial conduction, P-wave changes and heart rate control.

In studies to ascertain the basis of dynamic changes in the P wave, bipolar epicardial potentials were recorded from multiple atrial electrodes in dogs. One hundred to 120 activation times were displayed by a digital computer and used to construct atrial isotemporal activation sequence maps. Changes in heart rate or beat-to-beat cycle length were induced by vagal stimulation or infusion of autonomic mediating drugs. Changes in cycle length were associated with dynamic changes in the atrial activation sequence and surface P-wave. A conspicuous finding was that epicardial atrial depolarization began at three widely separated locations. These three points were consistently present in all animals and were generally located at the 12, 3, and 6 o'clock positions of the superior vena cava-right atrial junction. The dynamic changes in P waves and atrial activation sequence which accompanied the changes in cycle length were due to sudden shifts in the point of earliest activity between the three early sites. Asymmetric atrial depolarization with more rapid conduction along the crista terminalis, superior interatrial band, and pectinate muscles was present in all dogs. Although the anisotropic atrial geometry played an important role in the asymmetric conduction, the widely distributed onset of activity contributed significantly to the uneven spread. The multiple points of origin of the atrial wavefront might be explained by either a trifocal, distributed pacemaker or the epicardial exits of three specialized pathways conducting an impulse emanating from a single focus. These data explain the dynamic variation in P-wave morphology in normal hearts and also imply a relationship between the altered origin of atrial depolarization, atypical P waves, brady- or tachyarrhythmias, and heart rate control.