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Biomedical subjects

R Morris

Publications and source records attributed to R Morris.

At least 163 records · Page 9Linked to original sources
PubMed1997

Tractional force generation by porcine Müller cells: stimulation by growth factors in human vitreous.

PURPOSE: To examine the levels of Müller cell contraction-stimulating activity in human vitreous, correlate these levels with clinical presentation, and identify, the causative growth factors. METHODS: Human vitreous was collected from patients undergoing pars plana vitrectomy (n = 84). Müller cells were isolated from porcine retina and maintained in tissue culture. Tractional forces generated by cells incubated on three-dimensional collagen gels were measured as changes in gel thickness. Contraction-stimulating activity in vitreous (VA) was calculated from the close-response profiles of gel contraction to vitreous protein. The contributions of individual growth factors to vitreous activity (n = 10) were assessed by inhibition with specific neutralizing antibodies. RESULTS: The mean VA of patients with retinal detachment (3.65) and proliferative vitreoretinopathy stages A, B, and C (2.06) were elevated above that of patients without retinal pathology (vitreous activity = 0.23) or retinal defects alone (0.57). Mean activities in patients with epimacular proliferation (1.22) and vitreous hemorrhage (1.40) were also significantly elevated. The percentage of this activity attributable to insulin-like growth factor 1 (IGF-1) varied from 9.2% to 84.5% with a mean of 61.3%. Similarly, the percent contribution of platelet-derived growth factor (PDGF) ranged from 6.8% to 49.0% with a mean of 26.5%. CONCLUSIONS: The vitreous of patients with retinal detachment, proliferative retinal disease, and vitreous hemorrhage contain varying amounts of growth factors that stimulate tractional force generation by Müller cells. The majority of the activity can be attributed to IGF-1 and a smaller proportion to PDGF.

Animals↗
PubMed1996

Pravastatin and risk factor modification in patients with moderate primary hypercholesterolaemia.

AIM: To evaluate the efficacy and safety of pravastatin 20mg at night, versus placebo, in combination with dietary, smoking cessation, and other lifestyle advice in general practice. METHODS: This was a multicentre, randomised double blind placebo controlled trial carried out in thirty general practices in three New Zealand centres. Patients with moderate primary hypercholesterolaemia (5.2-6.7 mmol/L) and two or more risk factors for coronary heart disease were enrolled. After a minimum of 6 weeks lifestyle changes, 95 patients (aged 18-70 years) were randomised to active or placebo therapy. They continued to receive advice and encouragement in maintaining dietary, exercise or smoking cessation changes. RESULTS: Seventy eight patients, pravastatin (n = 39) and placebo (n = 39), completed the treatment phase of the study. After 6 weeks on 20 mg pravastatin, total cholesterol decreased by 18% (0.9 mmol/L, p < 0.0001), triglycerides decreased by 6% (0.1 mmol/L ns), LDL-cholesterol decreased by 23% (1.1 mmol/L, p < 0.0001), and HDL-cholesterol increased by 8% (0.1 mmol/L, ns). A similar effect was also observed after 26 weeks of therapy. These effects were also significant when compared with the placebo group. In 61% of patients treated with pravastatin there was a reduction in cholesterol to less than 5.2 mmol/L, and no real change in lipid levels in patients receiving placebo. No significant differences were observed between the active and placebo groups with regard to patient withdrawal, compliance, or adverse reactions. CONCLUSIONS: In general practice pravastatin is a well tolerated and safe drug that induces a favourable effect on lipid profile in patients with primary moderate hypercholesterolaemia and two or more other risk factors for coronary artery disease.

Adolescent↗
PubMed1996

Sequence preference of 7,12-dimethylbenz[a]anthracene-syn-diol epoxide-DNA binding in the mouse H-ras gene detected by UvrABC nucleases.

We have found that 7,12-dimethylbenz[a]anthracene-syn-diol epoxide (syn-DMBADE)-modified DNA fragments are sensitive to UvrABC incision. The incisions occur mainly seven bases 5' and four bases 3' of a syn-DMBADE-modified adenine or guanine residue. The kinetics of UvrABC incision at different sequences in a DNA fragment are the same, and the extent of UvrABC incision is proportional to the syn-DMBADE concentration. On the basis of these results, we have concluded that UvrABC incision on syn-DMBADE-DNA adducts is independent of DNA sequence and is quantitative. Using the UvrABC incision method, we have analyzed the syn-DMBADE-DNA binding spectrum in several defined DNA fragments, including the first two exons of the mouse H-ras gene. We have found that both guanine and adenine residues in codons 12, 13, and 61 of the H-ras gene are strong syn-DMBADE binding sites. These results suggest that the initial binding of DMBADE may greatly contribute to the frequency of H-ras mutations. Results from dinucleotide binding analysis indicate that the 5'-nearest neighbor displays a greater effect on syn-DMBADE-DNA binding than the 3'-nearest neighbor.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Cognitive correlates of long-term cannabis use in Costa Rican men.

BACKGROUND: Cognitive correlates of long-term cannabis use have been elusive. We tested the hypothesis that long-term cannabis use is associated with deficits in short term memory, working memory, and attention in a literate, westernized culture (Costa Rica) in which the effects of cannabis use can be isolated. METHODS: Two cohorts of long-term cannabis users and nonusers were studied. Within each cohort, users and nonusers were comparable in age and socioeconomic status. Polydrug users and users who tested positive for the use of cannabis at the time of cognitive assessment after a 72-hour abstention period were excluded. The older cohort (whose age was approximately 45 years) had consumed cannabis for an average of 34 years, and comprised 17 users and 30 nonusers, who had been recruited in San José, Costa Rica, and had been observed since 1973. The younger cohort (whose age was approximately 28 years) had consumed cannabis for an average of 8 years, and comprised 37 users and 49 nonusers. Short-term memory, working memory, and attentional skills were measured in each subject. RESULTS: Older long-term users performed worse than older nonusers on 2 short-term memory tests involving learning lists of words. In addition, older long-term users performed worse than older nonusers on selective and divided attention tasks associated with working memory. No notable differences were apparent between younger users and nonusers. CONCLUSION: Long-term cannabis use was associated with disruption of short-term memory, working memory, and attentional skills in older long-term cannabis users.

Adult↗
PubMed1996

A standardized classification of ocular trauma.

BACKGROUND: No internationally standardized classification of ocular trauma terminology has existed heretofore. Despite a growing interest in eye injuries, the absence of a common language continues to impede both clinical care and research. METHODS: A classification was initially developed based on the authors' extensive personal experience. It then under-went repeated reviews over a 3-year period by international ophthalmic specialists. Written and oral suggestions from respondents in 19 countries and from selected ocular trauma experts were considered and incorporated. RESULTS: By always using the entire globe as the tissue of reference, the new classification is unambiguous, consistent, simple, and comprehensive. It provides definitions for the terms commonly used in eye trauma and creates a logical system of injury types. CONCLUSION: In addition to widespread international acceptance by professionals, the new classification has been endorsed by the International Society of Ocular Trauma, the United States Eye Injury Registry, the American Academy of Ophthalmology, the Hungarian Eye injury Registry, the Vetreous Society, and the Retina Society. It can be reasonably expected that the system will ultimately become the standardized international language of ocular trauma.

Eye Injuries↗
PubMed1996

Diagnosis and classification in autism.

This study compared four systems for the diagnosis of autism (DSM-III, DSM-III-R, DSM-IV, and ICD-10) with two empirically derived taxa of autism, and with three social subgroups of autism (Aloof, Passive, and Active-but-Odd) in 194 preschool children with salient social impairment. There were significant behavior and IQ differences between autistic and other-PDD groups for all four diagnostic systems, and a significant association was found (a) for Taxon B, diagnoses of autism, and the Aloof subgroup, and (b) for Taxon A, other-PDD, and the Active-but-Odd subgroup. Findings offer support for two major overlapping continua within idiopathic Pervasive Developmental Disorder.

Algorithms↗
PubMed1996

Infertility treatment dropout and insurance coverage.

OBJECTIVE: To assess early patient dropout rates during infertility treatment as a potential measure of wasted resources. METHODS: The study involved multifaceted population cohorts, including a prospectively observed captive health maintenance organization (HMO) population and retrospectively selected preferred provider organization (PPO) patients. One hundred twenty-eight HMO couples were followed prospectively for 6 months. The insurance carrier retroactively selected 96 couples from their PPO population who were believed to be infertility patients. They were matched by date, age, and time of hysterosalpingography to infertility patients in the carrier's HMO population. Patients were considered treatment dropouts if they either requested their provider to abandon further work-up or treatment, or if they failed to return for an appointment for 3 months. RESULTS: Forty-six of 128 (36%) HMO patients followed prospectively discontinued care within 180 days, with only eight (6.3%) providing defined reasons. Preferred provider organization patients uniformly demonstrated significantly higher dropout rates than HMO patients, a finding already apparent at 60 days (P < .002; odds ratio [OR] 3.67, 95% confidence interval [CI] 1.47-9.97) and 120 days of treatment (P = .002; OR 2.87, 95% CI 1.39-6.06). Among PPO patients, dropout rates were especially pronounced if infertility care was provided by generalists. At billing levels of at least $2000, HMO patients also demonstrated less dropout than PPO patients (P < .001; OR 6.14, 95% CI 2.72-14.79), with generalists again demonstrating a significantly larger patient loss than infertility specialists (P < .001; OR 0.18, 95% CI 0.66-0.49). CONCLUSION: Infertility patients demonstrate a surprisingly large early dropout rate, which is significantly larger if patients receive infertility care from generalists rather than specialists. Newly presenting infertility patients should be carefully evaluated, especially in indemnity situations, before expensive diagnostic and therapeutic interventions are ordered.

Adult↗
PubMed1996

Malignant schwannoma in a burn scar.

The malignant potential of a burn scar is well recognized. Epidermal malignancies predominate and sarcomas are a rare finding. The first case of a malignant schwannoma developing in a burn scar is reported, and the management discussed.

Burns↗
PubMed1996

A standardized classification of ocular trauma.

BACKGROUND: No internationally standardized classification of ocular trauma terminology has existed previously. Despite a growing interest in eye injuries, the absence of a common language continues to impede both clinical care and research. METHODS: A classification has been developed initially based on the authors' extensive personal experience. It then has undergone repeated reviews over a 3-year period by international ophthalmic audiences, incorporating suggestions from respondents in 13 countries and selected ocular trauma experts. RESULTS: By always using the entire globe as the tissue of reference, the new classification is unambiguous, consistent, and simple. It provides definitions for the commonly used eye trauma terms within the framework of a comprehensive system. CONCLUSION: The new classification has been endorse by the Board of Directors of the International Society of Ocular Trauma, the United States Eye Injury Registry, the Hungarian Eye Injury Registry, the Vitreous Society, the Retina Society, and the American Academy of Ophthalmology. It can be reasonable expected that the system eventually will become the standardized international language of ocular trauma. The authors urge ophthalmologists to begin using this terminology in both clinical practice and research.

Eye Injuries↗
PubMed1996

The culture of female circumcision.

The issue of female circumcision takes on special significance as more women migrate to the United States from countries where the practice has religious and traditional underpinnings. Female circumcision is a problem unfamiliar to most Western health care practitioners. This article describes an ethnographic study of the types of female circumcision, the reasons for and against the practice, the health implications of this practice, and cultural attitudes of circumcised women both in Western Africa and as migrant refugees living in the United States. Ethical dilemmas in dealing with this practice and implications for nurses and health care providers are discussed.

Adolescent↗
PubMed1996

Thrombin receptor expression in rheumatoid and osteoarthritic synovial tissue.

OBJECTIVE: To investigate the possibility that synovial cells might respond to thrombin in the inflamed human joint, using immunohistochemical detection of thrombin receptors. METHODS: Frozen sections of synovial membrane from 20 patients with rheumatoid arthritis, 16 with osteoarthritis, and four normal controls were stained using a monoclonal antibody to the human thrombin receptor. Sections were also double stained for both receptors and non-specific esterase. RESULTS: Receptor positive cells were present in rheumatoid synovia, with some cells also staining positively for non-specific esterase. In contrast, both osteoarthritic and normal synovia contained very few cells expressing receptors. CONCLUSIONS: Thrombin may mediate important pathological changes during chronic inflammatory joint disease.

Arthritis, Rheumatoid↗
PubMed1996

Cognitive functioning and posttraumatic stress disorder.

OBJECTIVE: The authors examined the association of cognitive impairment with posttraumatic stress disorder (PTSD) and other psychiatric diagnoses known to affect cognitive functioning. METHOD: The results of standardized neuropsychological tests were compared in four groups of Vietnam veterans: veterans with both a lifetime history of PTSD and a current diagnosis of depression, anxiety, or substance abuse; veterans with only a PTSD diagnosis; veterans with only a current diagnosis of depression, anxiety, or substance abuse; and veterans with none of these diagnoses. RESULTS: Veterans with both PTSD and concurrent diagnoses. exhibited more impairment in cognitive functioning than did veterans without these diagnoses. CONCLUSIONS: Cognitive deficits seen among persons diagnosed with PTSD may be associated with their concomitant diagnoses.

Adult↗
PubMed1996

An assessment of tonometry and regional splanchnic blood flow during aortic cross-clamping in the pig.

We aimed to evaluate the tonometer in the assessment of gastrointestinal ischaemia induced by an infrarenal aortic cross-clamp. Nine anaesthetized pigs were cannulated for haemodynamic monitoring and radionuclide labelled microsphere (RLM) injection. Gastric and sigmoid tonometers were positioned. After haemodynamic stabilization an infrarenal aortic cross-clamp was applied. Animals were sacrificed at the completion of the study and tissue sampled from the stomach and sigmoid colon for regional blood flow measurements. Measurements were made pre-clamp, post-clamp, pre-release and post-release. Haemodynamic parameters, gastric intramucosal pH (pHi) and blood flow did not change throughout the experiment. Arterial pH increased during cross-clamp and returned to baseline post-release. Arterial bicarbonate fell post release. Sigmoid blood flow fell during cross-clamp. The sigmoid pHi fall, delayed until pre-release, remained low post-release. Although there was a consistent fall in sigmoid pHi, 63% of post-clamp values remained within the baseline range. We conclude that maintaining haemodynamic parameters around baseline values resulted in maintenance of gastric mucosal perfusion as indicated by a steady gastric pHi. However, below the aortic cross-clamp, delay between change in sigmoid colon blood flow and change in pHi and wide variation in sigmoid pHi limits the value of an individual pHi measurement in detecting ischaemia.

Animals↗
PubMed1996

Landmark stability: studies exploring whether the perceived stability of the environment influences spatial representation.

To investigate whether spatial learning complies with associative learning theories or with theories of cognitive mapping, rats were trained in three experiments exploring the effect of variations in spatial predictive relationships. In experiment 1, it was found that making one of two landmarks the sole spatial predictor of reward, by varying the spatial relationship between reward and other cues, reduced the control over search exerted by that landmark compared with that observed when the landmark and context cues were both reliable predictors of reward location. This requirement for landmark stability rather than predictive power appears to contradict results obtained in conventional conditioning paradigms. Discrimination learning was unaffected, suggesting a dissociation between discrimination and spatial learning with respect to the influence of geometric stability. Further experiments used arrays of both single and multiple landmarks. Experiment 2 revealed that the stability of a single landmark improved accuracy of search, but also showed that local stability between a pair of landmarks that moved around the arena together was sufficient to support spatial learning. Experiment 3 examined landmark stability using fixed directional cues in the absence of vestibular disorientation. This also revealed a relative advantage of stable landmarks, but animals presented with a landmark that moved from trial to trial did show some evidence of learning. Parametric manipulation of landmark stability offers an intriguing way of influencing the process of spatial representation and thus understanding better the processes through which egocentric representations of perceived space are transformed into allocentric representations of the real world.

Journal Article↗