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Biomedical subjects

R K Siegel

Publications and source records attributed to R K Siegel.

At least 19 recordsLinked to original sources
PubMed1999

Maternal factors and the evolution of developmental mode: evolution of oogenesis in Heliocidaris erythrogramma.

Evolutionary change in developmental mode in sea urchins is closely tied to an increase in maternal provisioning. We examined the oogenic modifications involved in production of a large egg by comparison of oogenesis in congeneric sea urchins with markedly different sized oocytes and divergent modes of development. Heliocidaris tuberculata has small eggs (95 microm diameter) and the ancestral mode of development through feeding larvae, whereas H. erythrogramma has large eggs (430 microm diameter) and highly modified non-feeding lecithotrophic larvae. Production of a large egg in H. erythrogramma involved both conserved and divergent mechanisms. The pattern and level of vitellogenin gene expression is similar in the two species. Vitellogenin processing is also similar with the gonads of both species incorporating yolk protein from coelomic and hemal stores into nutritive cells with subsequent transfer of this protein into yolk granules in the developing vitellogenic oocyte. Immunocytology of the eggs of both Heliocidaris species indicates they incorporate similar levels of yolk protein. However, H. erythrogramma has evolved a highly divergent second phase of oogenesis characterised by massive deposition of non-vitellogenic material including additional maternal protein and lipid. Maternal provisioning in H. erythrogramma exhibits recapitulation of the ancestral vitellogenic program followed by a novel oogenic phase with hypertrophy of the lipogenic program being a major contributor to the increase in egg size.

Animals↗
PubMed1985

New patterns of cocaine use: changing doses and routes.

The history of coca and cocaine use is reviewed in terms of medical and nonmedical patterns of use. Use of coca leaves and coca extract products involved daily use of no more than 200 mg to 500 mg of cocaine. When cocaine became available after 1860, daily doses increased to as much as 1,620 mg and the oral route of administration became supplemented by intranasal, injection, topical, and smoking administration. Contemporary patterns of use between 1970 and 1978 involved social-recreational intranasal doses of 1 to 4 grams per month. From 1978 to 1982, doses increased to 1 to 3 grams per week with increased use of smoking cocaine freebase. Between 1982 and 1984, episodes of concentrated binding became more common, as did the development of experimental practices including intranasal cocaine freebase and the smoking of coca paste. These patterns are discussed in terms of several variables, including purity, dosages, dose regimes, routes of administration, paraphernalia, and changing perceptions of cocaine.

Coca↗
PubMed1984

Cocaine and the privileged class: a review of historical and contemporary images.

The belief that cocaine is a drug associated with privilege and the privileged class is frequently cited as a motivating factor for nonmedical use. This association, part myth and part reality, has influenced the perception of cocaine as a glamorous and exotic drug, a drug immune to serious problems, a drug for the successful and wealthy, hence a privileged drug. The origins and development of this myth are examined in terms of both historical and contemporary images. Alternative competing images of cocaine as a drug associated with severe dependency and toxicity are discussed in terms of their past and future trends.

Cocaine↗
PubMed1984

Changing patterns of cocaine use: longitudinal observations, consequences, and treatment.

The literature describing contemporary cocaine use from 1970 to 1983 has been reviewed. Short-term studies published on users observed an initial period of social-recreational use supported by the belief that cocaine was safe. By the end of this period, both dosages and chronicity of cocaine use showed an escalation marked by increased adverse reactions. A longitudinal study tracked 99 social-recreational users from 1975 to 1983. By 1983, 41 users had dropped out of the study while eight others had stopped all use. Of the 50 continuing users still in the study in 1983, 25 remained primarily social users with few negative effects and no toxic physical or psychological crises. The remaining 25 users, while engaged in some social use, were more frequently involved in other patterns. Sixteen users frequently escalated to circumstantial-situational patterns marked by some toxic physical effects but no psychological crises. Four users developed intensified (daily) patterns of use with episodes of both physical and psychological crisis reactions. Five users became compulsive users, smoking cocaine free base, and experienced crisis reactions in approximately 10 percent of their intoxications. The majority of users attempted to treat the hyperexcitability and stimulation of excessive cocaine use with multiple drug use or self-initiated strategies of controlled use or short-term abstinence. It is concluded that many of the social users are capable of controlling use with no escalation to more individual-oriented patterns. Others, by escalating patterns of use, increase the risks of dependency and toxicity.

Adolescent↗
PubMed1984

Hostage hallucinations. Visual imagery induced by isolation and life-threatening stress.

The literature on hallucinatory experiences of hostage victims is reviewed. The phenomenology is examined in 30 case studies involving 31 persons, including ex-prisoners of war and victims of rape, kidnapping, terrorism, robbery, and "UFO abductions." The victims were subjected to conditions of isolation, visual deprivation, restraint on physical movement, physical abuse, and the threat of death. For eight victims, these conditions were sufficient to produce a progression of visual hallucinations from simple geometric images to complex memory images coupled with dissociation. The other 23 victims, subjected to similar conditions but without isolation and life-threatening stress, resulting from the threat of death, did not experience hallucinations. The hostage hallucinations are compared to those resulting from sensory deprivation, near fatal accidents, and other states of isolation and stress. A common mechanism of action based on entoptic phenomena and CNS excitation and arousal is suggested.

Accidents↗
PubMed1979

Cocaine smoking.

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Cocaine↗
PubMed1978

Cocaine hallucinations.

The author reviews the literature on hallucinations that occur as a result of acute and chronic administration of cocaine. He examined the phenomenology of cocaine hallucinations in a group of 85 recreational cocaine users, 15 of whom reported hallucinatory experiences in visual, tactile, olfactory, auditory, and gustatory modalities. He discusses a new phenomenon of "snow lights" in terms of initiating a progression of symptoms leading to the classic "cocaine bugs." He also points out the similarity of cocaine hallucinations to entoptic phenomena and migraine hallucinations, which suggests a common mechanism of action based on CNS excitation and arousal.

Adult↗
PubMed1977

Hallucinations.

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Brain↗
PubMed1977

Stimulus selection and tracking during urination: autoshaping directed behavior with toilet targets.

A simple procedure is described for investigating stimuli selected as targets during urination in the commode. Ten normal males preferred a floating target that could be tracked to a series of stationary targets. This technique was used to bring misdirected urinations in a severely retarded male under rapid stimulus control of a floating target in the commode. The float stimulus was also evaluated with nine institionalized, moderately retarded males and results indicated rapid autoshaping of directed urination without the use of verbal instructions or conventional toilet training. The technique can be applied in training children to control misdirected urinations in institution for the retarded, in psychiatric wards with regressed populations, and in certain male school dormitories.

Adolescent↗