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L M Collins

Publications and source records attributed to L M Collins.

At least 37 records · Page 2Linked to original sources
PubMed1996

Prenatal cocaine alters dopamine transporter binding in postnatal day 10 rat striatum.

The effect of in utero cocaine exposure on the postnatal binding of the radiolabeled dopamine (DA) uptake inhibitor [3H]GBR 12935 to the DA uptake complex was examined in male rats. One set of pregnant Sprague-Dawley rats was given subcutaneous (s.c.) injections of cocaine (40 mg/kg) or 0.9% saline from gestational day (GD) 8-21. Another set of animals received bilateral s.c. Silastic implants, each containing 60 mg cocaine base dissolved in polyethylene glycol (PEG) or PEG only, from GD 18-21. The density of [3H]GBR 12935 binding to the DA transporter in striatum and mesencephalon was assessed by quantitative autoradiography on postnatal day (PND) 1, 10, 30, and 60. Both treatment methods resulted in a decrease of [3H]GBR 12935 binding in dorsal lateral striatum of cocaine-exposed offspring on PND 10. There were no significant differences in [3H]GBR 12935 binding between offspring of cocaine and vehicle-treated dams at any other time points examined. Thus, prenatal cocaine exposure by either daily injection from GD 8-21 or continuous infusion from GD 18-21 resulted in a transient decrease in DA transporter binding in the dorsal lateral striatum that was apparent on PND 10.

Animals↗
PubMed1996

Monoamine transporters and the neurobehavioral teratology of cocaine.

Prenatal cocaine exposure has been associated with various postnatal behavioral abnormalities in human infants, and also with changes in locomotor activity, learning deficits, and altered responses to drug challenge in nonhuman offspring. Several studies have further demonstrated that cocaine exerts an activating effect on fetal behavior. A variety of mechanisms have been proposed to account for the neurobehavioral teratogenic effects of developmental cocaine treatment, including inhibition of fetal brain neurotransmitter uptake and fetal hypoxemia secondary to constriction of the uteroplacental vascular bed. In support of the hypothesis that cocaine effects may be mediated partly by monoamine uptake inhibition, we and other investigators have recently demonstrated the presence of functional dopamine (DA), serotonin (5-HT), and norepinephrine (NE) transporters in the fetal rat brain. Transporter-related cocaine recognition sites are found in a number of fetal brain areas and could mediate the acute effects of cocaine on these areas as well as developmental changes that are manifested postnatally. For example, DA transporter blockade may underlie the above-mentioned activational effects of cocaine on fetal behavior. Time-dependent changes in DA or 5-HT transporter expression produced by prenatal cocaine exposure could likewise play an important role in some of the behavioral effects observed when offspring are tested postnatally.

Animals↗
PubMed1996

The acquisition and maintenance of safer sexual behaviors among injection drug users.

The current research tests stage-sequential models of safer sexual behavior using a new method for data analysis called Latent Transition Analysis (LTA). Results are presented from data collected on 359 injection drug users participating in a seroconversion study conducted by the UCLA Drug Abuse Research Center. We identified a six-stage model that adequately represented the data. Results indicate that respondents moved back and forth among high, medium, and low risk stages. This finding highlights the need for continual, sustained interventions to help maintain safer sex and drug-using behaviors in high-risk groups.

Adult↗
PubMed1996

Characterization and localization of [125I]RTI-55-labeled cocaine binding sites in fetal and adult rat brain.

The present studies examined the characteristics of fetal (gestational day 20) and adult rat brain cocaine recognition sites labeled with the potent cocaine congener [125I]RTI-55 [3 beta-(4-iodophenyl)-tropane-2 beta-carboxylic acid methyl ester]. Saturation analyses of [125I]RTI-55 binding to membrane fractions from both fetal and adult whole-brain yielded curvilinear Scatchard plots that were resolved by nonlinear curve-fitting into high- and low-affinity components. Mean Kd values were 0.13 nM and 12 nM for fetal brain high- and low-affinity sites, respectively, compared to 0.26 and 18 nM for adult brain. The Kd for high-affinity binding was significantly different between the groups, suggesting a possible developmental change in the properties of [125I]RTI-55 binding sites. Drug displacement studies with various monoamine uptake inhibitors indicated that at a 10 pM concentration of [125I]RTI-55, almost all binding to fetal brain membranes could be accounted for by interaction with the serotonin (5-HT) and (to a lesser extent) dopamine (DA) transporters. This conclusion was supported by autoradiographic studies of both adult and fetal brain, demonstrating a predominance of [125I]RTI-55 binding in areas with high densities of 5-HT and/or DA uptake sites. The present results are in accordance with our previous demonstration of [3H]cocaine binding sites in fetal brain (Meyer et al., 1993) and further suggest that [125I]RTI-55 should be a useful ligand for assessing the effects of prenatal cocaine exposure on the subsequent development of cocaine recognition sites on the DA and 5-HT transporters.

Animals↗
PubMed1996

Latent transition analysis for longitudinal data.

Assessing outcome is a critical problem for the study of addictive behaviors. Traditional approaches often lack power and sensitivity. Latent Transition Analysis is an alternative procedure that is applicable to categorical latent variable models such as stage models. The method involves four different types of parameters, each of which may be relevant to different research questions. Two examples that employ the Stages of Change construct are used to illustrate the method. In the first example, three different models of longitudinal change are compared. In the second example, the effects of an expert system intervention for smoking is compared to a control condition. The method permits the investigation of a series of specific comparisons: (1) the effectiveness of the intervention for individuals in different stages can be assessed; (2) the effectiveness of the intervention can be evaluated for different time intervals; and (3) the effects of intervention on both progression through the stages and regression through the stages or relapse can be assessed. Other potential applications of the method are also discussed.

Alcoholism↗
PubMed1994

Temporal pattern discrimination and speech recognition under electrical stimulation.

Discrimination of temporal patterns has been suggested as a relevant process in speech recognition by subjects with normal hearing [Sorkin, J. Acoust. Soc. Am. 87, 1695-1701 (1990)]. This paper investigates whether performance of Nucleus multichannel cochlear implant subjects on a temporal pattern discrimination task is an efficient and valid psychophysical measure of speech recognition ability. Stimuli consisted of temporal sequences defined by twelve 35-ms tones and eleven randomly generated temporal gaps separating the tones. A fixed-level same/different paradigm was used to measure the discriminability of these sequences as a function of their average correlation across a block of trials. On each trial, the "standard" sequence was generated randomly by drawing gap durations from a Gaussian distribution. The gaps of the comparison sequence were generated in a similar fashion with a specified average correlation with the gaps of the first sequence. Performance of implanted and normal hearing subjects decreased monotonically with increasing average sequence correlation. However, performance across implanted subjects ranged from that observed for acoustically stimulated subjects with audiometrically normal hearing to levels near chance. Comparing these data with measures of speech recognition in the same subjects, we have found that performance on standard speech recognition tests correlates with ability to discriminate among such random temporal patterns.

Adult↗
PubMed1994

Latent transition analysis and how it can address prevention research questions.

The objective of this chapter is to introduce latent transition analysis (LTA) to the substance use prevention research community. LTA is a new methodological technique for testing stage-sequential models, such as models of substance use onset. LTA estimates several different sets of parameters. One of these sets is the transition probability matrix, which contains information about the probability of movement between stages in the model. LTA can be used to evaluate the effectiveness of prevention intervention programs by comparing the transition probability matrices of the program and control groups. If the prevention program is successful, the transition probability matrices will indicate that the probability of moving to a more advanced stage of drug use is lower for the program participants than for the control group. An advantage of taking a stage-sequential approach is that examining the transition probability matrix reveals how effective a program is for individuals entering the program with different levels and types of substance use experience. In this chapter, LTA is used to evaluate a variety of models of the early onset process separately for Anglo, Latino, and Asian-American adolescents, measured in seventh grade and again in eighth grade. Although somewhat different models are found to fit the three ethnic groups best, the differences likely are due to differences in the overall amount of substance use experience. Based on these results, it is suggested that, to be most effective, prevention programs should take place earlier for Anglos and Latinos, and later, followed by boosters, for Asian Americans.

Alcohol Drinking↗
PubMed1994

Seven ways to increase power without increasing N.

Many readers of this monograph may wonder why a chapter on statistical power was included. After all, by now the issue of statistical power is in many respects mundane. Everyone knows that statistical power is a central research consideration, and certainly most National Institute on Drug Abuse grantees or prospective grantees understand the importance of including a power analysis in research proposals. However, there is ample evidence that, in practice, prevention researchers are not paying sufficient attention to statistical power. If they were, the findings observed by Hansen (1992) in a recent review of the prevention literature would not have emerged. Hansen (1992) examined statistical power based on 46 cohorts followed longitudinally, using nonparametric assumptions given the subjects' age at posttest and the numbers of subjects. Results of this analysis indicated that, in order for a study to attain 80-percent power for detecting differences between treatment and control groups, the difference between groups at posttest would need to be at least 8 percent (in the best studies) and as much as 16 percent (in the weakest studies). In order for a study to attain 80-percent power for detecting group differences in pre-post change, 22 of the 46 cohorts would have needed relative pre-post reductions of greater than 100 percent. Thirty-three of the 46 cohorts had less than 50-percent power to detect a 50-percent relative reduction in substance use. These results are consistent with other review findings (e.g., Lipsey 1990) that have shown a similar lack of power in a broad range of research topics. Thus, it seems that, although researchers are aware of the importance of statistical power (particularly of the necessity for calculating it when proposing research), they somehow are failing to end up with adequate power in their completed studies. This chapter argues that the failure of many prevention studies to maintain adequate statistical power is due to an overemphasis on sample size (N) as the only, or even the best, way to increase statistical power. It is easy to see how this overemphasis has come about. Sample size is easy to manipulate, has the advantage of being related to power in a straight-forward way, and usually is under the direct control of the researcher, except for limitations imposed by finances or subject availability. Another option for increasing power is to increase the alpha used for hypothesis-testing but, as very few researchers seriously consider significance levels much larger than the traditional .05, this strategy seldom is used. Of course, sample size is important, and the authors of this chapter are not recommending that researchers cease choosing sample sizes carefully. Rather, they argue that researchers should not confine themselves to increasing N to enhance power. It is important to take additional measures to maintain and improve power over and above making sure the initial sample size is sufficient. The authors recommend two general strategies. One strategy involves attempting to maintain the effective initial sample size so that power is not lost needlessly. The other strategy is to take measures to maximize the third factor that determines statistical power: effect size.

Data Interpretation, Statistical↗
PubMed1993

Cocaine binding sites in fetal rat brain: implications for prenatal cocaine action.

Binding of [3H]cocaine to membrane preparations from whole fetal rat brain was studied. High-affinity binding (10 nM cocaine) was detected as early as gestational day (GD) 15 and steadily increased across subsequent development. Saturation studies comparing [3H]cocaine binding at GD20 and adulthood yielded similar KD values, and LIGAND analyses favored a two-site model if an extended range of [3H]cocaine concentrations was used. Various monoamine uptake inhibitors displaced labeled cocaine with potencies consistent with the idea that [3H]cocaine labels the dopamine (DA), serotonin (5-HT), and possibly also the norepinephrine (NE) transporters in whole fetal brain preparations. Synaptosomal DA uptake was well developed by GD20, as was the potency of cocaine to inhibit such uptake. The results indicate that functional, monoamine transporter related cocaine binding sites are present in the fetal rat brain. Such sites are likely to play an important role in mediating the direct interactions of prenatally-administered cocaine with developing monoaminergic systems in both animals and humans.

Animals↗
PubMed1991

Modeling transitions in latent stage-sequential processes: a substance use prevention example.

This article illustrates the use of latent transition analysis (LTA), a methodology for testing stage-sequential models of individual growth. LTA is an outgrowth of latent class theory and is a particular type of latent Markov model emphasizing the use of multiple manifest indicators. LTA is used to compare the fit of two models of early adolescent substance use onset and to assess the effects of a school-based substance use prevention program on Ss measured in 7th grade and again in 8th grade. Several interesting findings emerged. First, a model of substance use onset including both alcohol and tobacco use as possible starting points fit better than a model that included alcohol use as the only starting point. Second, Ss who had tried tobacco but not alcohol in in 7th grade seemed to be on an accelerated onset trajectory. Third, the normative education prevention program was generally successful, except for the students who had tried only tobacco in 7th grade.

Age Factors↗
PubMed1991

The measurement of dynamic latent variables in longitudinal aging research: quantifying adult development.

Dynamic latent variables involve systematic intraindividual change over time. Although it seems natural to apply traditional measurement theory to dynamic latent variables, in fact this is often inappropriate. Traditional measurement theory is based on the idea of static latent variables and offers little guidance to the researcher who wishes to measure a dynamic latent variable with a high degree of accuracy and validity. It is the contention of this article that measurement of a dynamic latent variable must start from a clearly defined substantive theory about human development. Two approaches that take this perspective are presented: the longitudinal Guttman simplex (LGS), a measurement model for dynamic latent variables undergoing irreversible cumulative, unitary development; and latent transition analysis (LTA), a more general latent class measurement model.

Aging↗
PubMed1990

Using the longitudinal Guttman simplex as a basis for measuring growth.

Many difficulties inherent in the measurement of growth stem from the use of traditional measurement methodologies. The longitudinal Guttman simplex (LGS), an alternative approach based on a model of growth, is discussed in this article. The LGS has several advantages over traditional methodology. First, interindividual differences in developmental rates are a part of the model. Second, the LGS procedure can easily handle any number of occasions of measurement. Third, the LGS is suited to nonlinear as well as linear monotonic growth. Fourth, a consistency index associated with the LGS methodology, CL, indicates the extent to which cumulative, unitary development characterizes a particular latent variable. Finally, and perhaps most important, because a model of the growth undergone by the latent variable being measured is incorporated in the LGS model the resulting instruments enjoy a high level of construct validity. The LGS is limited to cumulative, unitary development; additional measurement theories are needed for other kinds of development.

Child↗
PubMed1987

Frequency and adequacy of breast cancer screening among elderly Hispanic women.

Studies have demonstrated that Hispanic (relative to Anglo) women are at greater risk for late-stage breast cancer diagnosis. Screening irregularity may be a factor contributing to late-stage diagnosis, yet virtually nothing is known about the breast cancer-screening behavior of Hispanic women. We interviewed 600 elderly Hispanic women residing in Los Angeles to collect information on frequency of physician breast examinations and mammography and on regularity and competence of breast self-examination. Predictors of screening were also examined. Fifty percent of our sample indicated that they had had a breast exam within the past year; 12.5% had had a mammogram within the past year (74% never had had a mammogram); and 47% reported that they had performed breast self-examination within the past month. Few of the women were able to demonstrate adequate breast self-examination technique on a foam breast model, and only 1% found all five lumps present. Thus, although the observed frequency of screening and self-examination is comparable to national norms, it is unlikely that our subjects' attempts at self-examination would lead to early breast cancer detection. Age, educational level, emotional reactions to screening, and media cues predicted screening behavior. Physician instruction in breast self-examination increased the frequency and adequacy of self-examination. Perceived susceptibility to cancer, perceived benefits of early detection, and level of acculturation were not strong predictors. The extent to which our results generalize to other subpopulations of Hispanic women is discussed.

Aged↗
PubMed1987

The surface area of the adult human mouth and thickness of the salivary film covering the teeth and oral mucosa.

The surface area of the mouth was measured to calculate the average thickness of the salivary film which separates the opposing layers of the oral mucosa and which also overlies the dental plaque. The subjects were 10 adults of each sex, all of whom had essentially a full complement of teeth. Impressions were taken of the upper and lower jaws, the buccal and labial vestibular mucosa, and the ventral surface of the tongue, and stone models were cast. The dorsum of the tongue was assumed to have the same area as the palate plus that of the palatal surfaces of the upper teeth. The six separate areas considered were the teeth, the palate, the buccal and lingual gingival and alveolar mucosa, the buccal and labial vestibular mucosa, the ventral surface of the tongue, including the floor of the mouth, and the dorsum of the tongue. Aluminum foil, of known weight per unit area, was adapted to the models of the different regions of the mouth, and the surface areas were calculated from the weights of the foil. The mean total surface area of the mouth was 214.7 +/- 12.9 cm2, and there was no significant difference due to gender. The teeth, keratinized epithelium, and non-keratinized epithelium occupied about 20%, 50%, and 30% of the total surface area, respectively. Given that the average volumes of saliva present in the mouth before and after swallowing have been estimated to be 0.77 and 1.07 mL, respectively, it can be calculated that the average thickness of the salivary film in the mouth varies between 0.07 and 0.10 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Health behavior of elderly Hispanic women: does cultural assimilation make a difference?

The role of cultural assimilation in Hispanic health behavior has received little empirical examination. Prior studies have operationalized assimilation primarily in terms of language preference and have obtained weak or no effects. We interviewed 603 elderly Hispanic women residing in Los Angeles to evaluate the usefulness of cultural factors as predictors of preventive health behavior (e.g., physical examination, screening for breast cancer) more rigorously. Factor analysis of responses yielded four dimensions of cultural assimilation: "language preference", "country of birth", "contact with homeland", and "attitudes about children's friends." After controlling for education and age, no dimension of assimilation associated strongly or consistently with health behavior. Of the four dimensions, use of English language associated most closely with increased screening, although most of the effects for language were small in magnitude. These findings, coupled with those of other studies, strongly suggest that cultural factors may have little impact on the health behavior of Hispanics. Access to and availability of services, affective reactions toward screening, and sociodemographic factors are stronger determinants of Hispanic health practices.

Aged↗
PubMed1986

High-school smoking prevention: results of a three-year longitudinal study.

This study compared two strategies for preventing cigarette smoking among high-school students. One strategy emphasized social-pressure resistance skills, while the other focused on education about health concerns which are relevant to high-school students. Additionally, the use of same-age peer leaders and the use of familiar models in media presentations were investigated. The results suggest that social-influences resistance training was efficacious in reducing transitions to higher use by those who had previously experimented with cigarettes. Health education was most effective in preventing initial experimentation among those who had not smoked prior to the beginning of the study. Neither program was effective in limiting transitions among those who had gone beyond the experimental stage of smoking, and neither had any effect on encouraging cessation. There were no differences which could be attributed to peer leaders or to familiar media models. During later adolescence, a combined health education and social skills training approach is advocated. It is suggested that while there are some gains by implementing programs during late adolescence, prevention programs targeted at younger students may be more effective generally.

Adolescent↗