Analysis of 5' flanking regions of the gamma globin genes from major African haplotype backgrounds associated with sickle cell disease.

There are at least three major African haplotype backgrounds on which the beta s mutation arises. Sequence changes in the immediate 5' flanking area of the gamma-globin genes may account for differences in fetal hemoglobin expression among the three haplotypes. We determined the sequence from -350 to 10 bp 5' of the G gamma and A gamma fetal globin genes from one beta s-containing chromosome on each of the three major haplotype backgrounds. The Senegal chromosome had a T at -158 5' to the G gamma gene; the Benin (BEN) chromosome had an A to G change at -309 5' to the G gamma gene; and the Central African Republic (CAR) chromosome had a C to T change at -271 5' to the A gamma gene. Genomic DNA from patients with sickle cell disease was analyzed using the polymerase chain reaction and radiolabeled allele-specific oligonucleotide probes. The -309 G variant 5' to the G gamma gene is associated with BEN chromosomes, and the -271 T variant 5' to A gamma with CAR. The -309 change was also found on beta A-containing chromosomes, while the -271 change was not. The -309 change may have predated the beta s mutation on the BEN chromosome.

Shear wave dispersion behaviors of soft, vascularized tissues from the microchannel flow model.

The frequency dependent behavior of tissue stiffness and the dispersion of shear waves in tissue can be measured in a number of ways, using integrated imaging systems. The microchannel flow model, which considers the effects of fluid flow in the branching vasculature and microchannels of soft tissues, makes specific predictions about the nature of dispersion. In this paper we introduce a more general form of the 4 parameter equation for stress relaxation based on the microchannel flow model, and then derive the general frequency domain equation for the complex modulus. Dispersion measurements in liver (ex vivo) and whole perfused placenta (post-delivery) correspond to the predictions from theory, guided by independent stress relaxation measurements and consideration of the vascular tree structure.

Recruitment of primary care physicians to care for patients with human immunodeficiency virus infection in a large northwestern county.

BACKGROUND: We evaluated an initiative to recruit and to educate physicians to care for persons with human immunodeficiency virus (HIV) infection in King County, Washington, and to refer patients to them through a centralized telephone referral service (the acquired immunodeficiency syndrome [AIDS]/HIV Care Access Project). METHODS: Six physicians trained in AIDS care recruited primary care physicians in clinics throughout King County; the physician cohort was monitored for behavior in accepting referrals during the ensuing year. RESULTS: Of 250 primary care physicians contacted initially, 79 of 120 who met with AIDS-trained physicians were willing to accept patient referrals. Willingness was not related significantly to age, sex, years in practice, or specialty, but was related to level of experience with HIV/AIDS care and current practice. The recruitment initiative increased the physicians available to the telephone referral service by 93% (from 85 to 164). More physicians (41) joined the referral service in the ensuing year, during which 647 patient referrals were made to these 205 physicians (median referral rate of one patient per quarter). Four physicians requested cessation of referrals, however, two later asked for referrals to continue. CONCLUSION: The recruitment initiative was successful in increasing the number of primary care physicians available to accept patients with HIV infection into their practices (thereby reducing the burden of HIV referrals on a small pool of providers), and in establishing a county-wide telephone service to coordinate these referrals. The initiative was self-sustaining, with an ongoing influx of new providers willing to take referrals.

Poverty and HIV seropositivity: the poor are more likely to be infected.

We analyzed demographic and behavioral risk factors for HIV seropositivity using data from 3601 clients of the main HIV counseling and testing clinic for high-risk people in Seattle, Washington, USA. Clients with lower income were found to be more likely to be HIV seropositive, before and after controlling for other demographic and risk factors with logistic regression. This result supports the hypothesis that the impoverished are at increased risk for HIV infection due to the physical and social circumstances in which their poverty places them. These may include poor access to risk-reduction information and less support for implementation of risk-reduction strategies.

Carbon disulfide effects on the visual system. I. Visual thresholds and ophthalmoscopy.

The visual effects of carbon disulfide exposure were studied in macaque monkeys with measurements of visual thresholds, fluorescein angiography and fundus photography. Five monkeys were exposed by inhalation for 6 hr a day, 5 days a week to 256 ppm carbon disulfide (CS2). The motor dysfunction observed in these monkeys appeared to be entirely reversible. All five suffered severe reductions in visual acuity and contrast sensitivity although flicker resolution was not affected. Visual loss was found to be irreversible, with degeneration of substantial numbers of retinal ganglion cells (companion paper) in those monkeys permitted to survive after the termination of exposure. None of the monkeys developed retinal microaneurysms or hemorrhages, major accepted signs of visual toxicity in CS2 exposed humans; thus, permanent visual loss may result from carbon disulfide exposure even in the absence of retinal vascular effects.

Carbon disulfide effects on the visual system. II. Retinogeniculate degeneration.

We examined the morphological effects of carbon disulfide exposure on neurons and vasculature of the visual system of macaque monkeys. Five monkeys were exposed to 256 ppm carbon disulfide (CS2) by inhalation for 6 hr a day, 5 days a week. One monkey, sacrificed immediately after exposure, had numerous axonal swellings in the distal optic tract. Four other monkeys survived the exposure period for at least 1 year and were found to have suffered marked degeneration of central retinal ganglion cells, with little or no effect on other neurons in the retina. No evidence was found for arteriosclerotic or aneurysmal changes, suggesting that visual system injury in primates induced by carbon disulfide exposure is not dependent on the occurrence of structural changes in retinal blood vessels.

Effects of calcium chelating agents on corneal permeability.

Corneal penetration studies have been conducted in unanesthetized albino rabbits using various organic compounds representing both polar and nonpolar species. In the presence of calcium chelating agents, polar compounds generally demonstrate an increase in corneal penetration. Evidence that this corneal effect is reversible is presented. Concomitant with an increase in both corneal and aqueous humor drug levels was a decrease in drug concentration in both iris and conjunctival tissues tentatively attributed to chelation effects on vascular permeability of these tissues. EDTA, a known calcium chelator, was shown to penetrate the cornea, conjunctiva, and iris/ciliary body from a topically applied dose. The implications of this observation pertain to both toxicity effects, when EDTA is incorporated into ocular drug products for stability purposes, and novel strategems for improving ocular bioavailability of topically applied drugs.

Stimulus properties of inhaled substances.

Inhaled substances can modify behavior by their toxic action, or because they are discriminable events, or because they can support or suppress behavior. They can be used as discriminative stimuli at concentrations above the olfactory threshold. Inhalants can elicit unconditioned reflexes. As aversive stimuli, they can be studied in respondent conditioning experiments (e.g. conditioned suppression), in punishment paradigms, or as negative reinforcers in escape paradigms. Inhalants can also be positive reinforcers; their intoxicating properties have engendered patterns of chronic self-administration (solvent abuse). Such stimulus properties should be considered in industrial hygiene and environmental quality decisions. Laboratory techniques to study such properties abound.

Behavioral toxicology of carbon disulfide and toluene.

Organic solvents are pervasive in the communal and industrial environments. Although many are potent central nervous system agents, clearly delineated behavioral effects have played only a minor role in the formation of exposure standards. A comprehensive behavioral pharmacology and toxicology of these compounds is one aim of US/USSR collaboration. The current report describes some actions of carbon disulfide and toulene. Earlier data about the actions of carbon disulfide on pigeon operant performance indicated disruption of schedule-controlled key-pecking. Primate data are now described from a situation designed to determine aversive thresholds to electrical stimulation. Effective concentrations of carbon disulfide produced both a rise in the amount of electric shock tolerated and a diminution of the response force exerted by the monkeys. In experiments with toluene, pigeons were shown to elevate key-pecking rate in an operant situation at certain concentrations. Toluene also was studied for its capacity to maintain self-administration in the same way as drugs of abuse. Monkeys worked to gain access to toulene vapor just as they work for opiates or amphetamines. The current experiments demonstrate how comprehensive the range of behavioral toxicology needs to be to deal with environmental health issues.

Testing the neural sensitization and kindling hypothesis for illness from low levels of environmental chemicals.

Sensitization in the neuroscience and pharmacology literatures is defined as progressive increase in the size of a response over repeated presentations of a stimulus. Types of sensitization include stimulant drug-induced time-dependent sensitization (TDS), an animal model related to substance abuse, and limbic kindling, an animal model for temporal lobe epilepsy. Neural sensitization (primarily nonconvulsive or subconvulsive) to the adverse properties of substances has been hypothesized to underlie the initiation and subsequent elicitation of heightened sensitivity to low levels of environmental chemicals. A corollary of the sensitization model is that individuals with illness from low-level chemicals are among the more sensitizable members of the population. The Working Group on Sensitization and Kindling identified two primary goals for a research approach to this problem: to perform controlled experiments to determine whether or not sensitization to low-level chemical exposures occurs in multiple chemical sensitivity (MCS) patients; and to use animal preparations for kindling and TDS as nonhomologous models for the initiation and elicitation of MCS.

Stimulus control and the effects of d-amphetamine in the rat.

External discriminative stimuli can modify the behavioral effects of d-amphetamine. Previous work with the pigeon has demonstrated that some aspects of performance on the fixed consecutive number schedule are changed less if a discriminative stimulus indicates when reinforcement is available. This effect has now been replicated with the rat using both simple and multiple schedules. Moderate doses of d-amphetamine (0.56--1.0 mg/kg) usually produced large decreases in reinforced runs when no external cue indicated the possibility of reinforcement. Adding discriminative stimuli when the number requirement was met decreased the drug effect. As was true in the pigeon, response rate measures did not differ between the two stimulus control conditions. Thus, external stimulus control diminishes the drug effect in both species, despite the fact that key pecking was studied in the pigeon and lever pressing in the rat. Evidence was also seen of a possible increase in discriminative stimulus control by d-amphetamine.

Acquired immunodeficiency syndrome.

Acquired immunodeficiency syndrome (AIDS) is the lethal end stage of a sexually transmitted disease caused by a virus that is producing the major epidemic of our century. In this article we describe the history and epidemiology of AIDS and the disease states associated with infection with the human immunodeficiency virus (HIV), the apparent cause of AIDS. We review what is known about disease pathogenesis and present an overview of clinical management issues. In the absence of vaccine or therapy to prevent and eradicate this viral infection, we present formative educational approaches for its control.

Effects of methylecgonidine on acetylcholine-induced bronchoconstriction and indicators of lung injury in guinea pigs.

The fumarate salt of methylecgonidine (MEG; anhydroecgonine methylester), a pyrolysis product of cocaine, has previously been shown to antagonize contractions of guinea pig isolated trachea induced by acetylcholine (ACh) and other spasmogenics. We determined the effects of MEG fumarate on ACh-induced bronchoconstriction in vivo. Specific airway conductance (SGaw) was measured in guinea pigs receiving 30-300 mg/kg s.c. MEG fumarate and exposed one hour later to nebulized ACh (0.2-3.2%; by inhalation). MEG fumarate did not induce any changes in SGaw; neither did it antagonize dose-dependent decreases in SGaw induced by ACh. However, tremors, salivation, startle and increased numbers of fecal boli were observed after MEG administration. Thus, unlike antagonism of ACh-induced contractions of guinea pig isolated trachea observed in vitro, MEG fumarate does not antagonize ACh-induced bronchoconstriction in vivo, even at doses which induced changes in grossly-observable behavior. Inhalation of a condensation aerosol of MEG base induced lung damage as evidenced by the presence of blood and higher levels of protein and lactate dehydrogenase in the lung lavage fluid of MEG-treated animals than of control animals. Aerosols of MEG fumarate, on the other hand, did not induce lung damage when inhaled. These results extend previous observations that MEG base may contribute to detrimental pulmonary effects of crack smoking.

Recent observations on the neurobehavioral toxicity of carbon disulfide.

Visual thresholds, fluorescein angiography, color fundus photography and tests of motor function were used to examine the effects of carbon disulfide (CS2) on macaque monkeys. After reliable baseline measures were obtained, two monkeys were exposed to 256 ppm CS2, 6 hours a day, 5 days each week for 7 weeks. A third monkey was tested similarly but received a sham exposure over the same period. Visual acuity of the exposed monkeys dropped more than 5 fold during exposure and showed a partial subsequent recovery only in one monkey. Flicker resolution, on the other hand, was only slightly and transiently impaired. Tests of motor function also showed only brief and partial disruption. No evidence was seen in either exposed monkey of the retinal vascular changes that are currently the major diagnostic signs in human carbon disulfide poisoning.

Pulmonary effects of the cocaine pyrolysis product, methylecgonidine, in guinea pigs.

The pulmonary effects of the cocaine pyrolysis product, methylecgonidine (MEG; anhydroecgonine methyl ester), were assessed in guinea pigs. Specific airway conductance (SGaw), which decreases during bronchoconstriction, was measured in guinea pigs exposed to atmospheres containing a condensation aerosol of MEG free base (13 +/- 1 mg/liter of air), nebulized MEG fumarate (3 and 12% in phosphate buffered saline) or nebulized acetylcholine chloride (0.2 and 0.4% in phosphate buffered saline). A decrease in SGaw to 24.0 +/- 4.2% (mean +/- 2 S.E.M.) of baseline levels was observed in guinea pigs breathing MEG free base. A decrease to 28.4 +/- 4.5% of baseline was observed following administration of 0.4% acetylcholine. No change in SGaw was measured in guinea pigs exposed to 3% MEG fumarate but SGaw was reduced to 69.3 +/- 5.3% of baseline after exposure to 12% MEG fumarate. MEG free base poses an alkaline challenge to the lung, 3% MEG fumarate is neutral (pH approximately 7.4) and 12% MEG fumarate is acidic (pH approximately 4.3); thus, MEG free-base and 12% MEG fumarate might provoke a reflex bronchoconstriction due to direct pulmonary irritant effects. These results suggest that MEG free base produced during crack pyrolysis may play a role in bronchoconstriction observed in crack smokers.

Gunshot wounds of the spine: the effects of laminectomy.

In a review of 185 patients with gunshot wounds of the spine from low-velocity missiles, 106 were found to have a complete lesion and seventy-nine, an incomplete lesion. Fifty-six patients with complete lesions underwent laminectomy and only one had a partial (sensory) return of function. The fifty patients with complete lesions who had no laminectomy also had no spontaneous improvement. There were forty-five patients with incomplete lesions who had laminectomy and thirty-two (71 per cent) of them showed measurable improvement. For comparison, thirty-four patients with incomplete lesions had no operative treatment and in twenty-six (76.5 per cent) there was some spontaneous return of neural function. Four wound infections and six spinal fistulae developed in the operative group (a complication rate of 10 per cent). Spinal instability developed in six patients because of the laminectomies.

Two studies of good clinical judgment.

There is a continuing controversy about the quality of unaided clinical judgment. This paper reports two studies that show that experienced medical providers made accurate probability assessments and applied those assessments to patient care in a manner consistent with principles of optimal decision making. In the first study, experienced clinicians and physician assistants accurately judged the relative frequency of three cough-related diagnoses in an outpatient population, suggesting that their encounter with several "unrelated" diagnostic problems does not interfere with their ability to judge accurately the frequency of any single diagnostic problem. In the second study, a group of clinicians assessed the probability that each patient seen in an outpatient clinic had pneumonia. Physicians were more likely to assign a pneumonia diagnosis and to order a radiograph for patients with a greater assessed probability of pneumonia (p less than 0.05). Most of the physicians appeared to use cutoff probabilities or "thresholds" above which they acted as though the patient had the disease and below which they acted as though the patient did not have the disease, consistent with rational decision-making principles. However, the threshold probabilities being used were quite different from physician to physician, implying that the physicians managed the patient population in a nonuniform manner. Thus it may be desirable to supplement "good" clinical judgment with decision aids to ensure standardized medical care.

Developing, implementing, and evaluating a condom promotion program targeting sexually active adolescents.

This article describes the development, implementation, and evaluation of the Condom Campaign, a 1995 HIV prevention program promoting condom use among sexually active adolescents in three King County, Washington, urban communities. This program employed three main strategies: (a) mobilizing all levels of the target communities to support and guide program development and implementation; (b) creating and implementing a mass media campaign targeting sexually active teenagers that promoted correct condom use and favorable attitudes toward condoms; and (c) recruiting public agencies, community organizations, and businesses to distribute condoms from bins and vending machines. We evaluated the program through a series of cross-sectional interviews conducted in the three communities chosen for their elevated levels of adolescent sexual risk behavior. Overall, 73% of target youth reported exposure to the Condom Campaign; exposure did not differ by age, gender, race, or level of sexual experience. Levels of sexual activity remained stable throughout the media campaign.

PIP: This paper describes the development, implementation, and evaluation of the Condom Campaign, a 1995 HIV prevention program promoting condom use among sexually active adolescents in three King County, Washington, urban communities. The three main strategies employed by the program were: 1) mobilizing all levels of the target communities to support and guide program development and implementation; 2) creating and implementing a mass media campaign targeting sexually active teenagers that promoted correct condom use and favorable attitudes toward condoms; and 3) recruiting public agencies, community organizations, and businesses to distribute condoms from bins and vending machines. The program was evaluated through a series of cross-sectional interviews conducted in the three communities chosen for their elevated levels of adolescent sexual risk behavior. Overall, 73% of target youths reported exposure to the Condom Campaign. The exposure did not differ by age, gender, race, or level of sexual experience. The proportion of youths currently sexually active did not increase in conjunction with the Condom Campaign.

Determination of phenylmercuric nitrate by potentiometric titration.

A procedure was developed for measuring small amounts of phenylmercuric nitrate in aqueous solutions. The method depends on the formation of insoluble phenylmercuric iodide upon titration of phenylmercuric nitrate with potassium iodide. The end-point can be detected using an iodide-sensitive electrode. The method is able to measure down to 0.000125% aqueous solution of phenylmercuric nitrate with a 1% accuracy. Procedural details and dexcriptions of excipient effects on the assay are presented. Naphazoline hydrochloride, phenylephrine hydrochloride, fluroescein sodium, and antipyrine interfered with the method, while the common buffer systems, polyvinyl alcohol, sodium thiosulfate, edetate sodium, and chloramphenicol had no effect.

In vitro dissolution and in vivo bioavailability of commercial levothyroxine sodium tablets in the hypothyroid dog model.

The objective of this study was to determine whether a correlation exists between the rate of in vitro dissolution and bioavailability of levothyroxine sodium (T4) tablets. Dissolution versus time profiles for Synthroid, the Flint brand of levothyroxine sodium, and two competitors' tablets (brands A and B) were generated using an official dissolution apparatus (USP), and 0.05 M phosphate buffer (pH 7.4) as the medium. These tablets were also utilized in single-dose crossover bioavailability studies in the hypothyroid dog model (n = 6). The average areas under the serum T4 concentration versus time curve from 0 to 8 h (AUC) for Synthroid, brand A, and brand B were 8.22, 6.32, and 8.70 ng-h/mL per dose (micrograms per kg body weight), respectively. Respective peak serum concentrations (Cmax) for each tablet formulation were 1.26, 1.07, and 1.36 ng/mL per dose. The corresponding dissolution rates, expressed as t50%, were 20.5, 3.06, and 14.1 min, respectively. Data analysis indicated no correlation between dissolution kinetic parameters and the bioavailability parameters AUC and Cmax. However, a linear relationship was observed between dissolution kinetics and both the time to reach maximal serum concentration (tmax) and the observed absorption rate constant (ka).