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Biomedical subjects

L A Morrow

Publications and source records attributed to L A Morrow.

At least 19 recordsLinked to original sources
PubMed2001

Neuropsychological assessment, depression, and past exposure to organic solvents.

This study assessed neuropsychological performance in persons with a history of exposure to organic solvents and nonexposed healthy controls. Structured clinical interviews were also done to determine current Axis I diagnosis of mood disorder to assess the contribution of mood disorder to neuropsychological performance. Solvent-exposed participants were found to have significantly reduced scores on 3 of 5 neuropsychological clusters (learning and memory, visuospatial, psychomotor speed) compared to controls. No differences were found between the groups on measures of general intelligence. Within the exposed group, 50% met current Axis I criteria for mood disorder. Hierarchical multiple regression, controlling for age and education, revealed that mood disorder was significantly related to performance on only the visuospatial domain. There was no association between mood disorder and measures of learning and memory, attention, motor speed, and general intelligence. Higher ratings of past exposure were associated with poorer scores on learning and memory tests and slower times on speeded tests. These findings are consistent with other research documenting deficits in neuropsychological and psychiatric functioning in exposed workers.

Adult↗
PubMed2000

Mood and behavioral symptoms in individuals with chronic solvent exposure.

Psychiatric symptoms have been reported for individuals who experience chronic exposure to low levels of organic solvents. However, it is not known what proportion of such individuals experience psychiatric disorder; which specific disorders may be characteristic of this population; or whether bioaccumulation of lead contributes to the relationship between solvent exposure and psychiatric symptoms. Twenty-nine male journeymen painters and 32 male non-painter control subjects were administered semi-structured diagnostic interviews for DSM-III-R Axis I and Axis II disorders. Career solvent exposure and blood lead levels were also measured. Painters and control subjects did not differ significantly with respect to age, intelligence, or demographic characteristics. Results showed that the probability of being diagnosed with a mood disorder differed significantly in painters (41%) and control subjects (16%). Painters (66%) and control subjects (50%) did not differ for substance use diagnoses. Groups also did not differ for personality disorders involving an onset before 25 years of age. In contrast, painters exhibited a sub-clinical pattern of personality dysfunction involving symptomatology that was measured allowing for late onset (after age 25). Finally, a significant dose-response relationship was observed between career solvent exposure, blood lead level, and personality symptoms. In summary, these data showed an increased rate of psychological disturbance in a significant and substantial number of painters. However, not all painters were so characterized. This overall pattern raises a question regarding a potential role for differential vulnerability, which requires empirical validation.

Adult↗
PubMed2000

Clinical crown length changes from age 12-19 years: a longitudinal study.

OBJECTIVE: The objective of this study was to investigate the relationship between age, gender and clinical crown length using a longitudinal study design. METHOD: Four hundred and fifty-six sets of study models initially obtained for a large prospective longitudinal cohort study of orthodontic needs were examined. Each set of models corresponded to subjects at three different ages: 11-12, 14-15 and 18-19years old. The clinical crown height of the maxillary right central incisor (11), maxillary right canine (13), maxillary left lateral incisor (22) and mandibular left central incisor (31) was measured from gingival crest to the incisal edge using digital calipers. RESULTS: Analysis revealed a significant (p<0.0001) age effect on crown length for all four teeth investigated. A significant gender effect was found in relation to the maxillary right canine, maxillary right central incisor and maxillary left lateral incisor. Pairwise comparisons of the means for each age group for the maxillary right canine, maxillary right central incisor and maxillary left lateral incisor revealed significant (p<0. 0001) increases in clinical crown length between each assessment period. CONCLUSION: The findings of the present study indicate that, the process of passive eruption, resulting in increased clinical crown length appears to continue throughout the teenage years. This finding is considered to be of importance to the clinician making treatment decisions for teenagers and young adults requiring treatment in the anterior segments of the mouth.

Adolescent↗
PubMed2000

Students' perceptions of seminar and lecture-based teaching in restorative dentistry.

In an era of self-directed learning, it is important to seek the views of dental students regarding their learning experience. Using an anonymous questionnaire, clinical dental students' perceptions of seminar and lecture-based teaching in restorative dentistry were sought. 116 of 136 questionnaires circulated were returned for analysis giving a response rate of 85%. Clinical seminars as opposed to lectures were, in the opinion of the students, a more effective way of learning, more relevant to self-development and more interactive. Seminar-based learning was considered to be more amenable to self-direction than formal didactic lectures. It is concluded that the students included in this study were found to prefer seminar-based learning opportunities as opposed to more traditional styles of learning, specifically, didactic lectures.

Attitude↗
PubMed2000

A chemomechanical method for caries removal.

Over recent years the dental profession has shifted towards practising preventive dentistry and adopting more conservative and tooth-preserving procedures. Such progression is considered to be a response to the decline in the level of dental caries and advances in materials science. This shift in caries management will no doubt continue over the coming decades, based on rational clinical and scientific principles. Chemomechanical caries removal involves the application of a solution that selectively softens the carious dentine, thus facilitating its removal. This limits the removal of sound tooth structure, the cutting of open dentinal tubules, pulpal irritation and pain compared with conventional mechanical methods.

Dental Caries↗
PubMed2000

Case report: restorative maintenance of prostheses stabilised by non-endosseous implants.

For over a century, dentists have looked to dental implants to enhance the stability of dental prostheses. During this time, many approaches and different materials have been used. The purpose of this article is to report on two cases where non-endosseous implant systems were used and to outline how the replacement prostheses were customiZed to comply with the different implant types. Intramucosal inserts and sub-periosteal implants are briefly reviewed in the context of current prosthodontic practise. There are still a small number of patients with clinically acceptable intramucosal and subperiosteal implant retained prostheses, which will continue to need servicing and replacement.

Aged↗
PubMed1999

Neurobehavioral effects of acute exposure to inorganic mercury vapor.

Mercury has well-established toxic effects on the central nervous system. This article describes comprehensive neuropsychological and emotional functioning of a group of 13 workers exposed to inorganic mercury vapor compared to that of a normal control group. The exposed group was exposed over a 2- to 4-week period and had elevated blood mercury levels. The evaluations were conducted between 10 and 15 months after exposure was terminated. Observed cognitive deficits included impairment in the following domains: motor coordination, speeded processing with and without a motor component, cognitive flexibility, verbal fluency, verbal memory, and visual problem solving and conceptualization. Emotional problems included increased focus on physical functioning, depression, anxiety, and social withdrawal. Cognitive deficits were, for the most part, not significantly associated with the degree of depression present.

Acute Disease↗
PubMed1998

PET scan findings in a patient with a remote history of exposure to organic solvents.

This is a single-case study employing positron emission tomography (PET) scanning and neuropsychological assessment on a 47-year-old male with a 15-year history of repeated respiratory and dermal exposure to high levels of organic solvents with at least 750 peak exposures (i.e., solvent "intoxication"). At age 43, he presented with neuropsychological symptoms of a solvent encephalopathy and multiple abnormalities in his peripheral neurological examination but had normal MRI and EEG findings. Four years after cessation of exposure to degreasing and solvent chemicals, the patient produced a grossly abnormal PET scan in which frontal, hippocampal, and parietal hypometabolism were particularly noteworthy. During this same 4-year period of nonexposure, modest improvements in neuropsychological testing were noted, along with substantial improvements in partial seizurelike symptoms. Frontal lobe deficits elicited in testing and from collateral interview, however, did not change. Findings suggest that repeated peak exposures to organic solvents m y result in a neurobehaviorally complex solvent syndrome caused by central nervous system damage that is readily apparent on PET scan, even though it is not evident in either imaging technologies. In addition, the case is the first reported in which functional neuroimaging was employed to study a patient with chronic solvent encephalopathy many years after cessation of solvent exposure.

Journal Article↗
PubMed1998

Predictors of involvement in P300 latency in solvent-exposed adults.

Persons with a history of exposure to organic solvents have been shown to have cognitive and personality changes, as well as abnormalities on measures of neurophysiology (e.g., delays in P300 latency). Studies assessing long-term sequelae in exposed persons have been limited, especially those using neurophysiologic measures. This study assessed cognitive event-related potentials (ERPs) in 16 persons with a history of organic solvent exposure at two testings, separated, on average, by 1.5 years. The sample was divided into persons who showed improvement on P300 latency (e.g., reduction in latency of 1.5 SD of control group) and those who did not. Sixty-three percent showed no improvement, whereas 37% showed significant improvement. Recency of exposure and the interaction of exposure duration and history of peak exposure significantly predicted group membership. That is, persons with shorter duration of exposure coupled with no peak exposures and longer time from exposure to test were more likely to fall in the improved group. Substituting age for duration of exposure in the interaction term improved classification of the two groups. The results support previous findings that most exposed persons do not show significant improvements over time. The results further suggest that there is a need to assess factors, such as aging, which may make one more vulnerable to the neurotoxic effects of solvents.

Adult↗
PubMed1997

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.

Animals↗
PubMed1997

Neuropsychological performance of journeymen painters under acute solvent exposure and exposure-free conditions.

Journeymen painters were evaluated with a comprehensive battery of neuropsychological tests and compared to demographically similar nonexposed controls. For painters, a cumulative exposure to solvents was estimated from a structured interview that derived an index based on lifetime exposure and exposure in the past year. Painters were tested either shortly after having painted or after an exposure-free interval. Significant between-group differences were found on a cluster of tests measuring learning and memory. Within the painter group, scores on the learning and memory tests were significantly related to the interaction of condition and exposure. That is, those painters who were tested soon after painting and who also had a higher overall lifetime exposure, performed worst on tests of learning and memory. These results are consistent with the view that neuropsychological function--particularly learning and memory--may be compromised in active workers with a history of chronic solvent exposure. Furthermore, both the chronicity of solvent exposure, as well as the acuteness of the exposure, are significant factors in cognitive performance.

Adult↗
PubMed1996

A preliminary neuropsychological study of Persian Gulf veterans.

A neuropsychological investigation of 21 Persian Gulf veterans and 38 demographically matched controls was conducted in order to make a preliminary determination concerning presence of neuropsychological deficits associated with the Persian Gulf War experience. The neuropsychological test battery consisted of measures of complex attention, memory, and motor skills previously shown to be sensitive to exposure to environmental toxins. It was found that the Persian Gulf veteran group did not demonstrate substantial impairment, but an impairment index derived from 14 test variables was statistically significantly different from controls in the direction of poorer performance.

Adult↗
PubMed1996

Comorbid illness is associated with survival and length of hospital stay in patients with chronic disability. A prospective comparison of three comorbidity indices.

OBJECTIVES: This study was designed to determine if comorbidity added more information than knowing only the patient's age in predicting survival and length of hospital stay. METHODS: The authors compared the relative predictive validity of three comorbidity indices: the Cumulative Illness Rating Scale, the Charlson Index, and a count of International Classification of Diseases, 9th Revision, Clinical Modification medical diagnoses in relation to survival and length of hospital stays in patients with spinal cord injury. The sample consisted of 330 longitudinally followed spinal-cord injured patients admitted between January 1989 and December 1990 who were followed for an additional 18 months. RESULTS: During the follow-up, 25 (7.5%) patients died and 249 (75.5%) were readmitted to hospital with a median of one admission (range, 1-8). The corresponding lengths of hospital stay ranged from 0 to 548 days, with a median of 7 days. CONCLUSIONS: Patients who died were not significantly older but had higher comorbidity scores. Using patients alive at the end of the follow-up period, linear regression models were fit to the data to determine if comorbidity added more information regarding length of hospital stay than knowing only the patient's age. In the model that included only age as an independent variable, there was a significant relation between age and length of stay (F(1,303) = 5.2; P = 0.012). The R2 value for this model was 0.017. In further models that included age and each of the three comorbidity scores (separately) as the independent variables, the model that included age and the Cumulative Illness Rating Scale yielded the highest R2 value (R2 = 0.062). This study is among the first to compare three different measures of comorbidity and documents that comorbidity provides more information than knowing only the patient's age in relation to survival and length of hospital stay.

Adult↗
PubMed1996

Differential associations of P300 amplitude and latency with cognitive and psychiatric function in solvent-exposed adults.

Cognitive and mood changes are central components of solvent encephalopathy. This study examined event-related potentials in relation to neuropsychological and psychiatric function in solvent-exposed adults. Results revealed that longer P300 latency was associated with poorer cognitive test scores, whereas reduced P300 amplitude was related to increased psychiatric symptomatology. The findings suggest that the cognitive deficits and the psychiatric disturbance following solvent exposure may have different neurophysiological bases.

Adult↗
PubMed1996

Recombinant human insulin-like growth factor I increases insulin sensitivity and improves glycemic control in type II diabetes.

Insulin resistance is a major factor in the pathophysiology of type II diabetes and a major impediment to successful therapy. The identification of treatments that specifically target insulin resistance could improve diabetes management significantly. Since IGFs exert insulin-like actions and increase insulin sensitivity when administered at supraphysiological doses, we determined the effect of 6 weeks of recombinant human IGF-I (rhIGF-I) administration on insulin resistance and glycemic control in obese insulin-resistant patients with type II diabetes. A total of 12 patients with type II diabetes were recruited for the study. Subcutaneous administration of rhIGF-I (100 micrograms/kg b.i.d.) significantly lowered blood glucose. Fructosamine declined from 369 to 299 mumol/l by 3 weeks of administration and then declined further to 271 at the end of 5 weeks. Glycosylated hemoglobin, which was 10.4% pretreatment, declined to 8.1% at the end of therapy. Mean 24-h blood glucose during a modal day was 14.71 +/- 4.5 mmol/l pretreatment and declined to 9.1 +/- 3.21 mmol/l by the end of treatment. These improvements in glycemia were associated with a decrease in serum insulin levels. Mean insulin concentrations declined from 108.0 to 57.0 pmol/l during the modal day measurements and from 97.2 to 72.0 pmol/l during the mixed-meal tolerance test. Changes in glycemia were accompanied by a marked increase in insulin sensitivity. The insulin sensitivity index (SI) calculated from a frequently sampled intravenous glucose tolerance test (FSIVGTT) after the method of Bergman et al. (Bergman RN, Finegold DT, Ader M: Assessment of insulin sensitivity in vivo. Endocr Rev 6:45-86, 1985) increased 3.4-fold. Furthermore, the improvement in glycemic control was accompanied by a change in body composition with a 2.1% loss in body fat as calculated by dual energy x-ray absorptiometry without change in total body weight. Significant side effects were present in some subjects, although nine subjects were able to complete at least 4.5 weeks of the protocol and six subjects completed the entire 6 weeks. Supraphysiological IGF-I concentrations were maintained throughout the study, increasing from 206 micrograms/l in the control period to 849 micrograms/l at the end of 6 weeks of rhIGF-I treatment. The increase in IGF-I levels was accompanied by a significant increase in IGF binding protein-2 levels, a slight reduction in IGF binding protein-3 levels, and an increase in levels of IGF binding protein-1. In summary, IGF-I significantly lowered blood glucose as reflected by short-term and long-term indexes of glycemic control and increased insulin sensitivity. It remains to be determined whether a dosage can be administered that avoids significant side effects and still achieves reasonable glycemic control.

Adult↗
PubMed1995

Alterations in heart rate and pupillary response in persons with organic solvent exposure.

Cardiac and pupillary reactivity were examined in 25 persons with a history of exposure to organic solvents and 19 nonexposed controls during performance of a counting and a choice reaction task. The solvent-exposed group demonstrated an atypical pattern of responding across tasks. While control subjects showed a decline in heart rate across the two conditions (e.g., habituation), exposed persons had an increase in heart rate. Initial pupil diameter was similar for both groups, but only the control subjects exhibited habituation across the two tasks. In the exposed group, higher heart rate was not associated with higher levels of self-reported anxiety. Anticipatory cardiac deceleration preceding unpredictable events was significantly less in the exposed group, but there were no significant group differences on poststimulus acceleration. The results suggest that persons with solvent exposure have a deficiency in the allocation of attention (reduced anticipatory deceleration and decreased pupillary dilation). It is further suggested that difficulty in the allocation of attention produces an increase in tonic sympathetic levels when confronted with a cognitively challenging task. In this experiment, in which the choice reaction task was purposely presented last, and was apparently more challenging for exposed persons, a failure to exhibit autonomic habituation over the course of the session characterized the solvent-exposed group.

Adult↗
PubMed1995

Insulin-like growth factor I (rhIGF-I) as a therapeutic agent for hyperinsulinemic insulin-resistant diabetes mellitus.

Insulin resistance is one of the major underlying abnormalities in NIDDM, however, its pathophysiologic mechanisms are not well understood. Many clues about the mechanisms of insulin action have come from patients with the most severe forms of insulin resistance, including those with genetic abnormalities in the insulin signal transduction cascade. We used rhIGF-I as a probe to differentiate insulin and IGF-I action and to study the therapeutic potential of IGF in states of insulin resistance. To date, we have studied six subjects with varying phenotypes of severe insulin resistance but without mutations in the insulin receptor itself. All subjects underwent baseline physiologic monitoring to quantitate carbohydrate tolerance, insulin secretion, and insulin action prior to receiving rhIGF-I at 100 micrograms/kg body wt s.c. bid for 1 month with interval testing of glycemic control and insulin sensitivity. None of the six subjects noted significant side effects from the rhIGF-I. Four of the six subjects had overt diabetes during control testing; three of these subjects demonstrated normalization of fasting and postprandial blood glucose concentrations during rhIGF-I administration on no other therapy. In the fourth patient, insulin requirements and fasting hypertriglyceridemia decreased without improvement in glycemic control. The two subjects with normal glucose tolerance (two sisters with congenital lipodystrophy) maintained normal glucose tolerance at dramatically lower insulin levels and had a dramatic reduction in triglyceride levels. The efficacy of IGF-I continued to increase over the duration of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗