Monoterpene concentrations in fresh, senescent, and decaying foliage of singleleaf pinyon (Pinus monophylla Torr. & Frem.: Pinaceae) from the western Great Basin.

Senescent foliage from pines is potentially a large contributor to the total monoterpene content of the litter layer, and the availability of these compounds as phytotoxins may result from release of these compounds into the vapor phase. In order to determine the fate of several monoterpene hydrocarbons in the natural environment, we examined their concentrations in fresh, senescent, and decaying needles from 32 single-leaf pinyon pine (Pinus monophylla Torr. & Frem.: Pinaceae) trees growing at two different locations. Total monoterpene content was highest in the fresh needles (mean=5.6 ± 2.2 mg/g extracted air dry weight), but also remained relatively high in senescent needles (mean=3.6 ±1.8 mg/g extracted air dry weight), either still attached to the tree or forming the freshest layer of understory litter. Decaying needles within a dark decomposing layer of litter material 5-20 cm from the surface were found to contain much lower amounts of total monoterpenes (average: =0.12 ±0.06 mg/g extracted air dry weight). Further investigation of the fate of these compounds in the pinyon understory is required to determine if these hydrocarbons are indeed exerting phytotoxic characteristics.

Measurement of monoterpene hydrocarbon levels in vapor phase surrounding single-leaf pinyon (Pinus monophylla Torr. & Frem.: Pinaceae) understory litter.

A headspace air-sampling experiment was performed in the laboratory to determine the identity and concentrations of monoterpene hydrocarbons that could be attained in the vapor phase surrounding single-leaf pinyon pine (Pinus monophylla Torr. & Frem.) understory litter using controlled air collection conditions at a simulated field temperature of 37.8°C. The total monoterpene hydrocarbon content in 21 sequential samples of air collected from a sealed glass carboy packed with 1.44 kg of single-leaf pinyon litter equivalent to a bulk density of 0.15 g/cm(3) averaged 3.56 ± 1.04 mg/liter. The monoterpenesα-pinene and camphene were present in the vapor phase at the highest concentrations, averaging 2.40±0.64 and 0.68±0.22 mg/ liter, respectively. Myrcene,ß-pinene, 3-carene,ß-phellandrene, andγ-terpinene were all present at average concentrations below 0.30 mg/liter. The first two traps of the sequential air samples yielded the highest concentrations for the monoterpene hydrocarbons; however, the average total levels were relatively stable throughout the remaining 19 traps. Therefore, the data indicate that these hydrocarbons volatilize from the source pinyon litter and maintain an equilibrium in the vapor phase. Although this analysis was conducted using an artificial system, combined with results from our previous studies, mounting evidence indicates that monoterpene hydrocarbons present in the vapor phase of the single-leaf pinyon understory may be toxic to a variety of native plant species and thus further implicates allelopathy as a significant contributor to the observed patterning of associated vegetation in these forests.

Nutrient dynamics in singleleaf pinyon (Pinus monophylla Torr & Frem.) needles.

Nutrient retranslocation from existing foliage of singleleaf pinyon pine (Pinus monophylla Torr. & Frem.) did not meet the nutrient demands of new needles on the same branch. Singleleaf pinyon pines, with an average age of 177 years, located at an elevation of 2300 m on a ridge in The Sweetwater Range in Nevada, USA retained needles for 18 or more years and increased needle number per branch by 17-18% annually. With age, needles gained weight and accumulated Ca, Mg, Fe, Zn, P, and Mn. The amount of N per needle showed no consistent trend with needle age. Only Cu and K declined in concentrations and amounts with needle age and these differences were not statistically significant. Retranslocation of nutrients at needle abscission could provide only 2 to 13% of the N, P, K, Fe, Cu, and Mg required by new needles. We conclude that nutrient capital in existing foliage constitutes a long-term nutrient reserve for the tree rather than a mobile nutrient pool.

In vitro dissolution profile of water-insoluble drug dosage forms in the presence of surfactants.

The determination of the in vitro release profile of water-insoluble drug products requires dissolution media different from those used for water-soluble drug products. Since the relevance of drug dissolution in organic solvents is questionable, we investigated the use of surfactants to determine the dissolution profiles of water-insoluble drug products. In most cases, the drug dissolution rate and extent increased as the surfactant concentration in the aqueous dissolution medium increased. Suitable dissolution profiles were obtained in the presence of sodium lauryl sulfate (SLS) for water-insoluble drug products, such as griseofulvin, carbamazepine, clofibrate, medroxyprogesterone, and cortisone acetate. These findings recommend the use of surfactants for determining the aqueous dissolution of water-insoluble drug products rather than adding organic solvents to the dissolution medium.

Liquid chromatographic determination of chlorpropamide in tablet dosage forms: collaborative study.

A reverse-phase liquid chromatographic method was developed for determining chlorpropamide in tablet dosage forms. Linearity was established over the range 0.2-2.0 micrograms at a wavelength of 240 nm. The Associate Referee obtained a mean recovery for a synthetic tablet mixture of 99.2%, with a relative standard deviation (RSD) of 1.41. For an authentic tablet mixture, collaborators obtained a mean recovery of 99.6% with an RSD of 0.60%. RSDs were 1.24% for 250 mg/tablet commercial product and also for 100 mg/tablet commercial product. The method has been adopted official first action.

Liquid chromatographic determination of methocarbamol in injection and tablet dosage forms: collaborative study.

A reverse phase liquid chromatographic method was developed for determining methocarbamol in injection and tablet dosage forms. The injections require dilution only; the tablets require a filtration step before introduction into the chromatograph. Response for methocarbamol was linear over the range 0-18 micrograms, using an ultraviolet detector at 274 nm. Recoveries by the author ranged from 96.1 to 101.9% for authentic injection formulations and 98.0 to 101.0% for authentic tablet formulations. A collaborative study of the method by 6 laboratories resulted in standard deviations of 1.70 and 2.22 for injection and tablet dosage forms, respectively. The method has been adopted official first action.

Digital system for P-wave detection and synchronization of the artificial heart.

This paper describes the implementation of a microcomputer based P-wave synchronization system for the artificial heart. This system provides for synchronization of the cardiac prosthesis pump with P-wave signals from electrodes implanted in the remnant of the natural atrium. The device carries out the functions of P-wave detection and determines the duration of systole based upon a moving average of the time intervals between successive pulses. The system has been tested both on a mock circulatory system and in vivo on calves. The purpose of the paper is to provide details of the circuitry and algorithms used.

High pressure liquid chromatographic method for indole in shrimp: development of method and collaborative study.

A collaborative study on the determination of indole in shrimp was conducted in which a high pressure liquid chromatographic (HPLC) method and a spectrofluorometric method were compared with the AOAC gas-liquid chromatographic (GLC) method (18.075-18.078, 13th ed.). In the HPLC method, 10 g shrimp was blended with methanol, an internal standard was added, and the extract was filtered. Indole was separated on an octadecylsilane reverse phase column, using 60% MeOH-H2O, and quantitated with a fluorescence detector (excitation 280 nm, emission 330 nm) by comparing the indole peak height with that of an internal standard, 2-methyl-indole. Recoveries at a 25 micrograms/100 g level averaged 104% with a range of 90-127%, and at a level of 35 micrograms/100 g averaged 102% with a range of 93-112%. In the spectrofluorometric method, 25 g shrimp was extracted with 2% EtOAc-hexane. After several washes, indole was partitioned into a saturated NaCl-MeOH solution and its fluorescence was measured (excitation 280 nm, emission 332 nm). Recoveries at a 25 micrograms/100 g level averaged 93% with a range of 0-255% and at a level of 35 micrograms/100 g averaged 64% with a range of 0-107%. Recoveries obtained by the AOAC-GLC method at a level of 25 micrograms/100 g averaged 96% with a range of 81-116% and at a level of 35 micrograms/100 g averaged 101% with a range of 81-119%. The coefficients of variation were 20, 10, and 64% at a 25 micrograms/100 g level for the GLC method, the HPLC method, and the spectrofluorometric method, respectively. The HPLC method was adopted as official first action for indole levels in shrimp exceeding 1 microgram/100 g.

Automated detection of EEG artifacts during sleep: preprocessing for all-night spectral analysis.

This paper describes a simple artifact detection algorithm which can be used when large amounts of EEG data are to be automatically processed via spectral analysis techniques in a general purpose digital computer, and visual inspection of each EEG epoch becomes an impossible task. The technique is based on a chi-square (chi(2)) goodness-of-fit test to a Gaussian distribution (CSQ), and it was applied to EEG epochs each 30 sec long. This test proved to be very sensitive to non-stationarities in the EEG amplitude distribution for a particular epoch, and it produced a large value for the chi(2) coefficient when an artifact was present. EEG epochs that gave rise to chi(2) coefficients of value larger than a heuristically determined minimum were discarded from further analysis. The above technique enabled efficient data reduction and reliable automatic off-line processing of 50 nights of sleep EEG via spectral techniques.