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Biomedical subjects

L Roberts

Publications and source records attributed to L Roberts.

At least 145 records · Page 8Linked to original sources
PubMed1992

Approaches to optimal dosing of hexamethylene bisacetamide.

HMBA is a potent differentiating agent capable of causing > 95% morphological differentiation in cell lines in vitro. The induction of differentiation is dependent on both the concentration of and the duration of exposure to HMBA. However, acute toxicities (neurotoxicity and acidosis) have limited the maximal HMBA css value to < 2 mM, which is at the lower limit of effective in vitro concentrations. When HMBA css values have been maintained at 1-2 mM, thrombocytopenia has limited the duration of HMBA infusion to < or = 10 days. The present studies were performed to determine whether exposure to HMBA could be individualized and maximized without resulting in intolerable toxicity to patients and to determine which factors would predispose a patient to the development of acute toxicity during treatment with HMBA. For these investigations, patients were given HMBA at a target css using an adaptive-feedback-control method rather than at a set dose. Because HMBA administration produces large anion gaps, a simple maneuver such as alkalinization might enable the escalation of plasma HMBA css values to > 2 mM. HMBA was given as a 5-day CI to 14 patients (26 courses) at 2 target HMBA css levels near the maximal tolerated value in the presence or absence of concurrent alkalinization with sodium bicarbonate. Symptomatic acidosis occurred in one patient who did not receive bicarbonate. Neurotoxicity proved to be dose-limiting at the target HMBA css value of 1.5-2.0 mM in the absence of concurrent alkalinization and at a css level of > 2 mM, regardless of alkalinization. No neurotoxicity was seen at target HMBA css values of 1.5-2.0 mM in patients who did receive concurrent alkalinization. Alkalinization was not associated with any detectable changes in plasma HMBA metabolites. With the maximal tolerable 5-day HMBA css having thus been defined at 1.5-2.0 mM, we attempted to maximize exposure to HMBA by defining a tolerable duration of infusion. Individualization of the duration of HMBA infusion to a target nadir PLT was performed in patients who had received an initial 5-day CI of HMBA at a css 1.5-2.0 mM along with concurrent alkalinization. The AUC achieved and the thrombocytopenia produced during this first course were used to predict the duration of infusion that each patient would subsequently tolerate (at an HMBA css of 1-2 mM) to achieve a nadir PLT of 75,000-100,000/microliters.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetamides↗
PubMed1992

Characteristics of heavy smokers.

BACKGROUND: Heavy smokers (those who smoke greater than or equal to 25 or more cigarettes a day) are a subgroup who place themselves and others at risk for harmful health consequences and also are those least likely to achieve cessation. Despite this, heavy smokers are not well described as a segment of the smoking population. METHODS: We used representative population data on 1,048 smokers to examine differences between heavy and lighter smokers (less than or equal to 24 cigarettes per day). RESULTS: Heavy smokers constituted 26.7% of all cigarette smokers. Compared with lighter smokers, heavy smokers were significantly more likely to be male, to be age 30 years or older, to smoke their first cigarette of the day within 30 min of waking, to perceive quitting as very difficult, to have little confidence in their ability to quit, to be less likely to report variation in their rate of smoking between work and leisure days, and to be less likely to be employed. CONCLUSIONS: Public health strategies which may particularly assist heavy smokers include stronger restrictions on smoking in public places, nicotine replacement therapies, and the use of segmentation research to more carefully target campaign messages to influence quit attempts and confidence.

Adult↗
PubMed1992

Glycine-containing terminals in the rat dorsal vagal complex.

The present study examined the distribution of glycine and glycine-receptors in the dorsal vagal complex using pre-embedding immunocytochemistry. Glycine-immunoreactive terminals were present in moderate densities in the medial, intermediate, interstitial, commissural and ventrolateral subnuclei of the nucleus tractus solitarii. The dorsolateral nucleus tractus solitarii and the dorsal vagal motor nucleus contained only very few, scattered glycine-containing terminals. Glycine terminals appeared to be concentrated in regions of the dorsal vagal complex receiving primary vagal afferents, though previous studies have suggested that glycine is not present in these afferents. A conspicuously high concentration of glycine terminals was observed in the medial nucleus tractus solitarii where a population of cholinergic neurons has been identified previously. Ultrastructurally glycine immunoreactivity was principally associated with terminals containing flattened, pleomorphic vesicles and forming symmetrical synaptic contacts, mostly with dendrites. Glycine receptor immunoreactivity was present throughout the dorsal vagal complex with little evidence of subnuclear localization. With electron-microscopic examination, glycine receptor immunoreactivity was associated with dendritic membranes and was associated presynaptically with terminals containing flattened pleomorphic vesicles. Overall, the present data provide evidence consistent with a neurotransmitter role for glycine in the dorsal vagal complex. The presence of glycine in regions of the dorsal vagal complex receiving vagal afferents suggests a prominent role for this neurotransmitter in autonomic regulation.

Animals↗
PubMed1992

Stages of readiness to quit smoking: population prevalence and correlates.

We examined the population prevalence and correlates of stages in smokers' readiness to quit, using data from 1,048 smokers recruited in a self-weighting, multistage, systematic clustered area sample from 0.44% of South Australian dwellings, with an 89% response rate. Smokers in the precontemplation stage comprised 24.1% of the sample, smokers in the contemplation stage comprised 47.2%, and smokers in the preparation stage comprised 28.7%. No sociodemographic variables (i.e., age, sex, marital status, educational level) were found to be significant independent predictors of membership in the different stages. The five significant independent predictors of being in the precontemplation stage (vs. the contemplation stage) were (a) having a higher confidence of quitting, (b) seeing fewer health risks associated with smoking, (c) not having made an attempt to quit, (d) seeing quitting as more difficult, and (e) smoking 25 or more cigarettes a day. The two significant independent predictors of being in the contemplation stage (vs. the preparation stage) were (a) having lower confidence of quitting and (b) not having tried to quit. We discuss implications for the understanding of smoking behavior in populations and also consider how cessation campaigns might address the factors associated with different stages of readiness to quit.

Adaptation, Psychological↗
PubMed1992

Renal acidosis, thyroiditis, hemolytic anemia: an autoimmune link?

Distal renal tubular acidosis (DRTA) is characterized by a urine of inappropriately high pH in the presence of a metabolic acidosis. Female patients with DRTA may have associated autoimmune disorders. We have described a patient with DRTA, followed by acute thyroiditis and autoimmune hemolytic anemia within 2 years. This combination of autoimmune diseases has not been described previously. These conditions are likely linked by an autoimmune pathogenesis. Clinicians are advised that some patients with DRTA may subsequently have features of any autoimmune disorder as the natural history of the disease.

Acidosis, Renal Tubular↗
PubMed1992

Workplace smoking restrictions, occupational status, and reduced cigarette consumption.

Reductions in workday cigarette consumption among indoor workers subject to different levels of smoking restriction were examined using representative population data for both blue-collar and white-collar workers. Regardless of whether workplace smoking bans were total or applied only to the usual work station, reported workday cigarette consumption was reduced by approximately five cigarettes per day compared with leisure-day consumption. This was in contrast to there being no difference between workday and leisure-day consumption among those who had no ban on smoking at their usual work station. This pattern of findings applied to all occupational-status groups, after controlling for sex and number of cigarettes smoked on a leisure day. These results are discussed with reference to potential public-health benefits and to implications for reduced retail sales of cigarettes.

Adult↗
PubMed1992

Making the burned hand functional.

The goal of treatment of the burned hand is to make the hand functional at the conclusion of treatment. Function should ideally include both fine pinch and power grip but will ultimately be determined by the individual patient's needs. At no time, however, can the care of the burned hand be performed in a vacuum, losing sight of the patient as a whole. It must also be remembered that the hand functions as part of the upper extremity. Full hand motion is useless if significant contractures of the elbow or axilla prevent the patient from positioning the hand so that this motion can be utilized. Rehabilitation must render the entire extremity functional. Thus, it becomes obvious that a team effort is mandatory. This usually will include the following individuals: physician, nurse, occupational therapist, physical therapist, vocational rehabilitation counselor, and social worker. A functional upper extremity means that the goal must be to return patients to their preburn vocations and avocations. A clear understanding of job requirements and work habits will allow realistic goals to be established. However, when the goal of optimal function cannot be reached, early retraining will help to obtain optimal rehabilitation.

Acute Disease↗