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Biomedical subjects

C Snyder

Publications and source records attributed to C Snyder.

At least 55 records · Page 3Linked to original sources
PubMed1990

Sensory integrative processing in delinquent-prone and non-delinquent-prone adolescents.

The purposes of this study were to obtain a preliminary description of the sensory integrative and practic abilities of 114 non-delinquent-prone adolescents aged 12 through 18 years and to compare their performances with those of 12 delinquent-prone adolescents with learning problems. Ten of the 17 subtests of the Sensory Integration and Praxis Tests (SIPT) (Ayres, 1989) as well as the Finger Posture Imitation Test (Druker, 1980) and the MacQuarrie Test for Mechanical Ability (MacQuarrie, 1925/1953) were administered to both groups. It was hypothesized that performance on some tests would correlate with age in the non-delinquent-prone adolescents. It was also hypothesized that some delinquent-prone adolescents with learning problems would perform significantly worse on the tests of sensory integrative and practic abilities than would the non-delinquent-prone adolescents. A data analysis indicated that performance on the praxis tests, Manual Form Perception, Graphesthesia, and Bilateral Motor Coordination showed a significant age correlation. The results of this study indicated a difference between the two groups, and it was concluded that the delinquent-prone group performed more poorly on all of the praxis-related tests and on the absolute values of the tests of Postrotary Nystagmus, Standing and Walking Balance, and Bilateral Motor Coordination. Some of the vestibular- and praxis-related tests, therefore, may still provide useful information on children older than 8 years of age.

Adolescent↗
PubMed1990

Rigid contact lens base curve constancy between wet and dry lens storage conditions.

The purpose of this study was to investigate dry storage of rigid gas-permeable contact lenses as an alternative to wet storage. This study evaluated the constancy of lens base curve between the two storage methods for lens materials that spanned the spectrum of oxygen permeability values. The differences found in lens base curve between wet and dry storage for any lens material evaluated did not reach a level considered to be clinically significant, although differences in average base curve constancy did exist among the lens materials. Base curve change did not increase with increasing lens material oxygen permeability value (Dk).

Contact Lenses↗
PubMed1990

Protein levels in nonstimulated and stimulated tears of normal human subjects.

Atraumatically collected nonstimulated (less than 1 microliter/min) and stimulated (greater than 50 microliters/min) tears from 30 clinically normal subjects were fractionated by size exclusion high-performance liquid chromatography (SE-HPLC). Enzyme-linked immunosorbent assay (ELISA) and kinetic assays were applied to relevant HPLC fractions to quantitatively identify 12 tear proteins. Secretory IgA levels were much higher in nonstimulated than in stimulated tears, and a similar disparity was seen also with IgA1 and IgA2 in the HPLC fraction containing secretory IgA. IgM levels were also higher in nonstimulated tears. Levels of the primary lacrimal gland proteins, lactoferrin, tear specific prealbumin, and lysozyme were similar in both types of tears. Significantly higher concentrations of the major serum proteins, IgG, transferrin, and serum albumin were measured in nonstimulated tears. Overall, 8 of the 12 proteins assayed were present at significantly higher concentrations in nonstimulated tears. These results show that tear flow rate strongly influences the protein profile obtained. Therefore, to allow valid comparisons of tear protein profiles within and between studies that use atraumatic collection procedures, an indication of flow rate during collection should be reported.

Adult↗
PubMed1989

Fluid secretion and microvillar ultrastructure in mosquito malpighian tubules.

The Malpighian tubules of fourth instar larvae, pupae, and female adults of the mosquito Aedes taeniorhynchus were examined with regard to in vitro fluid secretion rate and the ultrastructural features of the microvillar border of the primary cells. In vitro fluid secretion rates were determined after stimulation with 5-hydroxytryptamine. While larval tubules are capable of rapid fluid secretion, the tubules of pupae exhibit very low rates of secretion, indistinguishable from 0 nl/h. The capacity to secrete fluid returns after the pupal-adult molt and is further enhanced after blood feeding. Similar results were obtained in tubules stimulated in vitro with dibutyryl adenosine 3',5'-cyclic monophosphate. Ultrastructural examination of the microvillar border of the primary cells of the Malpighian tubules revealed that the period of reduced secretion capacity in the pupal tubules is correlated with a marked reduction in microvillar volume, microvillar surface area, and mitochondrial content in the microvillar border. The results suggest that microvilli of a certain size and containing extensions of mitochondria are required for rapid fluid transport. The absence of these conditions in pupal tubules cannot be overcome by in vitro stimulation with known secretagogues and therefore represents a physiological limit on transport performance in the pupal tubules of mosquitoes.

Aedes↗
PubMed1989

Masking of astigmatism with selected spherical soft contact lenses.

This observational study investigated the ability of three current brands of spherical soft contact lenses to correct or "mask" low amounts of refractive astigmatism. The lens brands were worn by 16 subjects having at least 0.50 D, but not more than 1.00 D, of refractive astigmatism. Spherocylindrical refraction over the soft lenses was used to determine the amount of astigmatism that was masked by the lenses. Results showed that the wearing of spherical soft contact lenses, such as those used in this study, cannot be expected to predictably mask astigmatism.

Astigmatism↗
PubMed1989

Documenting informed consent for patients wearing disposable lenses.

Disposable contact lenses present new clinical and legal challenges to the contact lens practitioner. Although a frequent lens replacement program should reduce the opportunity for contact lens complications and improve patient compliance with lens care and follow-up procedures, problems still may arise from the manufacturing or packaging of lenses or the failure of the patient to comply with wearing instructions. Because there yet remain significant risks associated with the extended wear of hydrogel lenses, practitioners should use an informed consent agreement to assist in the communication of these risks to patients. Such an agreement also serves as evidence of the practitioner's compliance with legal requirements.

Contact Lenses↗
PubMed1988

Arteriosclerotic plaque development is 'promoted' by polynuclear aromatic hydrocarbons.

In previous work we found that weekly injections of the polynuclear aromatic hydrocarbon (PAH) carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) induced spontaneous aortic plaques in cockerels to grow to a larger size and at a faster rate than plaques in control animals. To determine whether plaque-stimulating ability is related to carcinogenic potency or mutagenicity we have now tested a variety of agents, including PAH carcinogens, non-PAH carcinogens and weakly carcinogenic PAHs. Cockerels were injected weekly (from 4-20 weeks of age) with one of the following compounds: benzo[a]pyrene (B[a]P), benzo[e]pyrene (B[e]P), dibenz[a,h]anthracene (AH), dibenz[a,c]anthracene (AC), 3-methylcholanthrene (MCA), acetylaminofluorene (AAF), N-methyl-N,N'-nitro-nitrosoguanidine (MNNG) or anthracene (ANT). Plaques were present in the abdominal aortas of all animals. Plaque volumes were 8-14 times greater in AC-, B[a]P-, B[e]P-, MCA- and AH-treated cockerels than in controls. Plaques were slightly larger in the AAF-treated group than in control animals, and in the ANT- and MNNG-treated groups were indistinguishable in size from plaques in control animals. The largest plaque volumes were in AH-treated cockerels and were comparable in size to those elicited by DMBA treatment. The accelerated development of plaques is consistent with a 'promotional' role for these agents. There was a poor correlation between mutagenicity or carcinogenicity and plaque 'promotion', which may reflect a role for different metabolites in these processes.

2-Acetylaminofluorene↗
PubMed1987

Mitogenic activity in human atherosclerotic lesions.

Focal smooth muscle cell proliferation is a key event in atherogenesis, but the stimulating factors are unknown, and there is little information on the occurrence of growth promoting factors in the arterial wall. We have tested extracts of human aortic intima for stimulation of DNA synthesis, using the chick chorioallantoic membrane (CAM) assay in an attempt to avoid artifacts arising with cultured cells. Consistently high levels of stimulation were obtained with early proliferative (gelatinous) lesions (mean DNA synthesis 188% of control, n = 6) and slightly more advanced transitional lesions (mean 160%, n = 4); results with mature fibrous plaques were variable (range 120-182%, n = 3). Significant stimulation was also given by four of eleven samples of apparently lesion-free intima. Intima contains fibrinogen and a range of fibrinogen and fibrin degradation products (FRA) and preliminary fractionation experiments suggest that activity may reside in the FRA fraction. Serum does not stimulate DNA synthesis in the CAM; extract activity was retained in FRA-containing fractions after removal of most serum proteins by affinity chromatography, but was mainly lost from serum protein-containing fractions after removal of FRA.

Adult↗
PubMed1986

The impact of parental life change on the early development of children.

The effect of parental life change on children's mental and social development was explored in a longitudinal study of 193 families. Data on life changes, social supports, home environment, child development and interactions were obtained in a series of nine interviews from before the child's birth to 48 months after birth. For the sample as a whole, significant negative correlations were obtained between maternal life change in the first year of the child's life, and the child's IQ and receptive language at 4 years. An examination of subgroups revealed, however, that this relationship was strongest for mothers low in both personal coping resources and in social support. Findings suggest that both direct and indirect effects of maternal life change on the child contribute to the observed relationship.

Adult↗
PubMed1984

Supportive measures for high-risk infants and families.

The experience of providing a 3-month nursing program of care to infants and their families with physical, health, and social-environmental risks is presented. An individualized case approach was used which first involved a nursing assessment of the family, infant, and environmental needs and then was followed by subsequent appropriate nursing intervention. Brammer's conceptual model about the helping process was used to assist the analysis of the success or failure experienced in assisting these high-risk families. The differences that emerged were in the mothers' involvement in the exploration phase which involves goal setting. Families with incomplete progression through the helping process not only participated in less mutual decision making, but they were also less open to the initial assessment phase and had higher social risk. The nurses had less total contact with the uninvolved families. A brief description of a subsequent approach to provide effective nursing to a socially high-risk group of pregnant women is given. The approach involves a more extended period of intervention and emphasizes the development of a therapeutic relationship.

Adaptation, Psychological↗
PubMed1983

Cigarette smoke and carbon monoxide do not have equivalent effects upon development of arteriosclerotic lesions.

Experiments were performed to test whether exposure to mainstream cigarette smoke, without any diet modification, was sufficient to exacerbate arteriosclerotic lesion development in cockerels. Additionally, the experiments were designed to test whether any such effect could be attributed solely to carbon monoxide (CO) in the smoke. Three groups of cockerels (7/group) were exposed 5 days/week in standard inhalation chambers. Each day, one group (smoke) was exposed to smoke produced from the combustion of two packs of cigarettes. A second group (CO) was exposed to CO at levels equivalent to those produced during the combustion of two packs of cigarettes. A third group was sham-exposed. Following sacrifice, the abdominal aorta of each animal was cut into 5 mm segments and the extent of arteriosclerotic lesion development was measured. In smoke animals, compared to those in either of the other two groups, there were more aortic segments with measurable lesions present and the cross-sectional areas of these segments were greater. On a comparative basis, the smoke lesions were three times larger than in either of the other two groups, despite the fact that blood carboxyhemoglobin levels were the same in CO and smoke animals. The location of the lesions and their histological appearance were very similar to those previously described for spontaneous and carcinogen-associated lesions in the cockerel. These results demonstrate that as little as four months of daily exposure to cigarette smoke, in the absence of a cholesterol supplemented diet, can help accelerate arteriosclerotic lesion development. Further, this accelerated development cannot be attributed solely to CO in the smoke.

Animals↗