Examining HIV Stigma, Depression, Stress, and Recent Stimulant Use in a Sample of Sexual Minority Men Living with HIV: An Application of the Stigma and Substance Use Process Model.

Sexual minority men (SMM) with HIV are disproportionately impacted by stigma and mental health disorders. Guided by the Stigma and Substance Use Process Model, we evaluated how HIV stigma impacts mental health outcomes among SMM with HIV. Data were drawn from Thrive With Me, an RCT of an mHealth intervention targeting ART adherence among SMM with HIV. Path analyses tested the relationships between HIV stigma, depression, stress, and recent stimulant use. Overall, 49.1% (194/401) had depression symptoms, 68.8% (276/401) had moderate-to-high stress, and 28.1% (111/401) had detectable stimulant use in urine samples at baseline. In path analyses, baseline internalized HIV stigma was associated with depression and stress 5-months post-baseline and enacted stigma was associated with recent stimulant use 11-months post-baseline. We identified internalized and enacted HIV stigma, but not anticipated stigma, as potentially important intervention targets for stimulant use, depression, and stress among SMM with HIV.

Characterizing substance use typologies and their association with HIV viral load outcomes: A latent class analysis among sexual minority men living with HIV.

BACKGROUND: Racially diverse sexual minority men (SMM) are disproportionately impacted by the U.S. HIV epidemic. Substance use, particularly stimulant use, may impact viral suppression for SMM living with HIV. The current study sought to characterize patterns of substance use via latent class analysis (LCA) and test associations between those patterns and future viral load outcomes, among SMM living with HIV. METHODS: Data were drawn from Thrive With Me (TWM), an RCT of an mHealth intervention targeting ART adherence among SMM living with HIV. LCA was performed with six dichotomous indicators of substance use, derived from validated measures and urinalysis results, to determine substance use classes at baseline. Bivariate and multivariable logistic regression models tested associations between baseline substance use classes and HIV viral load 5-months post-baseline. RESULTS: Among 383 SMM living with HIV, we identified a three-class model of substance use fit best: low probability substance use (81.3 %), high probability hazardous alcohol, marijuana, and cocaine use (7.5 %), and high probability methamphetamine and amphetamine use (11.2 %). Additionally, the high probability amphetamine use class was less likely to be virally suppressed at 5-month follow-up compared to the low probability substance use class [Adjusted Odds Ratio = 3.34, 95 % Confidence Interval = 1.39-7.99, p = .0069]. CONCLUSION: We identified that some patterns of substance use (i.e., methamphetamine and amphetamine use), but possibly not others (e.g., alcohol, marijuana, and cocaine use), are potentially important intervention targets for improving HIV-related outcomes among racially diverse SMM living with HIV.

Surface-induced dissociation of molecular ions in a quadrupole ion trap mass spectrometer.

A method is reported by which surface-induced dissociation is used to activate ions stored in a quadrupole ion trap mass spectrometer. The method employs a short (< 5 /-Is), fast-rising (< 20-ns rise time), high voltage direct current (dc) pulse, which is applied to the endcaps of a standard Paul-type quadrupole ion trap. This is in contrast to the application of an alternating current (ac) signal normally used to resonantly excite and dissociate ions in the trap. The effect of the de pulse is to cause the ions rapidly to become unstable in the radial direction and subsequently to collide with the ring electrode. Sufficient internal energy is acquired in this collision to cause high energy fragmentations of relatively intractable molecular ions such as pyrene and benzene. The dissociations of limonene are used to demonstrate that high energy demand processes increase in relative importance in the dc pulse experiment compared with the usual resonance excitation method used to cause activation. The fragments are scanned out of the ion trap using the conventional mass-selective instability scan mode. Simulations of ion motion in the trap provide evidence that surface collisions occur at kinetic energies in the range of tens to several hundred electronvolts. The experiments also demonstrate that production of fragment ions is sensitive to the phase of the main radiofrequency drive voltage at the point when the dc is initiated.

Determination of ion frequencies in a quadrupole ion trap by using a fast direct current pulse as pump and a laser probe.

A new technique has been developed which allows the direct measurement of frequencies of ions trapped in a quadrupole ion trap mass spectrometer. This pump/probe method employs a fast direct current (DC) pulse (pump) to displace a kinetically cooled ion population from the center of the trap, and a laser (probe) which recognizes when ions reappear at the center of the trap by the formation of photodissociation fragments. The translationally excited ions undergo periodic motion within the confines of the ion trap, and this periodic motion can be followed by recording the intensity of the photodissociation fragment as a function of the delay time between the DC pump and the laser probe. The DC pulse has a rise time of 15 ns; data are taken 1 ms after its application to allow stable ion motion to be sampled. Sampling of the ion cloud is done at 50 ns intervals, and fast Fourier transformation of the time-based data yields the ion frequencies and their relative magnitudes. Data are reported for ions derived from acetophenone (m/z 105) and 1,4-cyclohexadiene (m/z 80) under various trapping conditions corresponding to different Mathieu qz values. The measured fundamental secular frequencies, fz and fr, are found to agree well with those predicted. The presence of higher order multipole contributions to the trapping field is evident from such ion frequencies as the drive frequency, fRF,. The ability to measure ion frequencies under operating conditions provides a new tool for comparing simulated and experimental data. Simulation data from the program ITSIM, modified to account for the effects of collisions, are shown to predict the major frequency components observed in the experimental data.

"Fast excitation" CID in a quadrupole ion trap mass spectrometer.

Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. "Fast excitation" CID deposits (as determined by the intensity ratio of the a(4)/b(4) ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with "fast excitation" CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for "fast excitation" CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M + 17H)(17+) of horse heart myoglobin is also shown to illustrate the application of "fast excitation" CID to proteins.

The chromatographic and GC/MS analysis of organic priority pollutants in water.

This article is an overview of the proposed EPA methods for the analysis of priority pollutants in water by chromatography and gas chromatography/mass spectrometry (GC/MS). It discusses sampling, storage, apparatus, sample preparation, chromatographic and GC/MS analysis, quality control and quality assurance, and data handling as they apply to the proposed methods. Comments on the legal implications are included to underline the importance of understanding the NPDES permit granting and effluent monitoring system, as it applies to the proposed methods.

Cardiac arrhythmias in presidents and other athletes.

We presented examples of both supraventricular and ventricular rhythm disorders which can occur in athletic individuals, even presidents. The vast majority of rhythm problems we deal with in athletes are fortunately benign, entities such as frequent atrial ectopic beats or VPBs. In each patient encountered, we ask ourselves the five questions noted in the discussion pertaining to symptomatology, anatomic source of the arrhythmia, presence or absence of underlying cardiac disease, and precipitating factors. The most common more sustained SVTs we see are AVNRT and atrial fibrillation. Atrial flutter is less common. These are more of a nuisance to patients rather than a threat to their lives, although rarely cerebral embolic events can occur. Therapy includes avoidance of precipitating factors and, when necessary, a sequential trial of available drugs, carefully documenting the response and watching closely for any pro-arrhythmic events. We infrequently see NSVT in athletes, even triplets of VPBs on exercise testing, and rarely see instances of sustained VT. The latter merits a careful search for underlying cardiac disease and usually electrophysiology-guided drug therapy. New techniques such as radiofrequency ablation of the dysrhythmic focus may obviate the need for chronic drug therapy in selected cases.

Thermospray liquid chromatography-mass spectrometry with a quadrupole ion trap mass spectrometer.

A theromospray ion source using corona discharge ionization was interfaced to a quadrupole ion trap mass spectrometer via a multi-element lens system. Ions were injected into the trap periodically where they were stabilized by collisions with helium bath gas. Mass spectra were recorded on the trapped ions using the mass-selective instability scan mode. Data are shown for a peptide and a nucleoside and the effects of some experimental variables on the spectra are explored.