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Biomedical subjects

D Richardson

Publications and source records attributed to D Richardson.

At least 127 records · Page 7Linked to original sources
PubMed1996

Establishing a community network for recruitment of African Americans into a clinical trial. The African-American antiplatelet stroke Prevention Study (AAASPS) experience.

A major aspect of a clinical trial is the ability to successfully recruit patients. There is a paucity of information concerning the nuances of recruiting study patients, especially those from minority communities. As minorities generally have been underrepresented in the health-care system, they may be less likely to participate in clinical trials or other studies. Thus, a strategy is needed to overcome this potential shortfall. One of our solutions has been the development of a community network to help disseminate information about our program. We believe that a key aspect has been the involvement of community members during pre-trial planning, community awareness programs, and our Community Advisory Panel. We also believe that it may be a major error to bring a health-care initiative unannounced into a targeted community without extensive pre-program planning in cooperation with that community. As our community awareness scheme suggests (Figure), there are many possible avenues to heighten awareness about a health-care program. While the church remains an important institution for religious and cultural activities in the African-American community, we have found that the news, television, and radio media also can be a powerful source for spreading awareness. Thus, we recommend creating awareness about an initiative through a "grassroots" approach of church and community organizations, along with a global approach through news, television, and radio media. As part of the awareness promotion campaign, it must be emphasized that the study is safe and provides benefits to enrollees. The success of health programs is largely dependent on community acceptance, which must be established in the pre-program planning stages of the initiative. This concept of obtaining community approval and acceptance prior to program initiation is not a new one, nor does it exclusively apply to the African-American community. Community leaders and members need to have a vested interest in such a program and a sense of empowerment. Through this type of communication, patient enrollment and community satisfaction can be substantial. Such success can serve as a springboard for other targeted health-care studies or programs in high-risk communities.

Black or African American↗
PubMed1995

Microsatellite instability in colorectal adenocarcinoma cell lines that have full-length adenomatous polyposis coli protein.

Almost 20% of colon cancers are characterized by genomic instability at simple repeated sequences. This instability is the result of a deficient DNA mismatch repair system. Sporadic, as well as hereditary carcinomas of the proximal colon display this effect. In this study, we examined colorectal adenocarcinoma cell lines, with or without wild-type adenomatous polyposis coli (APC) protein, for the presence of microsatellite instability. The three cell lines that maintained full-length APC protein also displayed the highest level of instability, suggesting a negative correlation between APC mutations and microsatellite instability. This data, in addition to other studies that show a negative correlation between microsatellite instability and mutations in p53 and K-ras, support the idea of a second pathway for colorectal cancer development.

Adenocarcinoma↗
PubMed1995

Mandibular reconstruction and rehabilitation in childhood.

The management of a case of osteosarcoma of the mandible in an 7-year-old girl is presented. A variety of reconstructive techniques were used following surgical ablation of the tumour, including the use of a revascularised free bone flap and osseointegrated endosseous implants.

Child↗
PubMed1995

Cerebral laterality in homosexual males: preliminary communication using magnetoencephalography.

MEG-based auditory M100 source location in the left and right hemispheres of 8 strictly homosexual and 9 strictly heterosexual males were compared to determine if this measure of interhemispheric laterality varies as a function of sexual orientation. MEG fields evoked by auditory tone pips were recorded from left and right hemispheres in response to contralateral ear stimulation. The source of the 100-msec latency component, generated in the superior temporal gyrus, was estimated using a least squares inverse solution algorithm. Auditory sources in heterosexual men were significantly further anterior in the right hemisphere compared to the left hemisphere. Source locations in the homosexual men did not exhibit significant interhemispheric asymmetry, being similarly located in both hemispheres. Findings suggest an anatomic and/or functional difference in the superior temporal gyrus of at least some homosexual men.

Adult↗
PubMed1995

Postoperative symptomatic internal thoracic artery stenosis and successful treatment with PTCA.

From 1988 to 1992, 4,182 coronary bypass grafting procedures were performed at the University of Ottawa Heart Institute. The left internal thoracic artery (ITA) was used in 2,913 patients, the right ITA in 79, and bilateral ITAs in 61 for a total of 3,053 patients with ITAs. This study assessed patients requiring angioplasty for symptomatic ITA stenosis after operation. A total of 29 patients (0.95%) with a mean age of 55.3 +/- 1.9 years underwent angioplasty for ITA stenosis from 4 days to 34 months after operation (mean, 6.5 +/- 1.6 months). Internal thoracic artery stenosis was identified in 18 patients (62.1%) within 3 months after operation. Angina was present in 26 patients (89.7%), a positive stress test in 8 (27.6%), and myocardial infarction in 1 (3.4%). At angiography, a total of 34 stenotic sites were identified in ITA grafts. Angioplasty was successful (< 50% residual stenosis) in 31 sites (91.2%). Follow-up was available for 28 of 29 patients (96.6%) at 24.6 +/- 2.3 months. Four patients (14.3%) returned with restenosis within 3 months, 2 of whom had successful repeat angioplasty, and 1 required reoperation. Canadian Cardiovascular Society anginal class after angioplasty was less than class II in 84.6% of patients. In conclusion, symptomatic postoperative ITA stenosis is uncommon, occurs most frequently at the site of distal anastomosis, and generally presents within 3 months of operation. It may be safely and effectively treated with angioplasty with a low recurrence rate.

Adult↗
PubMed1995

MEG based brain laterality: sex differences in normal adults.

Magnetoencephalographic (MEG) auditory evoked fields produced by short tone pips were recorded from 34 normal adults (17 males, 17 females) and the 100 msec latency component (M100) localized in left and right hemispheres. Absolute M100 location in the antero-posterior dimension was calculated for each subject. M100 sources were significantly further anterior in the right hemisphere of males. Magnetic resonance (MR) based anatomy of the superior temporal gyri (STG) in a subset of 17 subjects showed that in the left STG of both males and females M100 sources were located approximately midway on the STG. In the right hemisphere of males, however, M100 sources were significantly further anterior on the STG than was the case for females. The findings are compatible with a sex based difference in right STG functional anatomy, with evidence of greater hemispheric lateralization in males compared to females based upon a predominantly right hemisphere contribution.

Adult↗
PubMed1995

Suspensory ligament desmitis.

The gross and functional anatomy of the suspensory ligament (SL) and its ultrasonographic variability are described. Injuries of the suspensory apparatus are divided into lesions confined to the proximal one third of the metacarpus or metatarsus (proximal suspensory desmitis and avulsion fractures), lesions of the body, and branch lesions. Complete breakdown injuries are also discussed. In view of the close association of the SL, the second, third, and fourth metacarpal or metatarsal bones, and the proximal sesamoid bones, associated bony lesions are also considered.

Animals↗
PubMed1995

Percutaneous anterior discectomy under ultrasound guidance.

The object of this experiment was to demonstrate that, by using a peritoneal fluid infusion coupled with ultrasound guidance, a safe anterior entry into the L5-S1 disc of the pig could be made. The goal was to develop a procedure with the advantages of a laparoscopic approach to the disc which has been published to allow removal of extruded herniations, that a neurosurgeon could perform without a general surgeon in attendance. The procedure was carried out under general anesthesia and fluoroscopic control. One liter of normal saline was then infused into the abdomen of a pig. Under ultrasound guidance and laparoscopic confirmation, a Nucleotome was placed into the L5-S1 disc and the disc was aspirated. The results showed that the disc was safely entered in all 5 pigs. The disc was successfully removed in 4 of 5 pigs. In all animals the bowel floated out of the pelvis, obviating the need for bowel manipulation. Laparoscopic ultrasound was needed for visualization in 3 pigs, while external ultrasound was used in two. Our conclusion is that peritoneal fluid infusion and ultrasound guidance, when applied to laparoscopic anterior discectomy, eliminates the need for retroperitoneal dissection and bowel manipulation, significantly simplifying the laparoscopic discectomy procedure.

Animals↗
PubMed1995

Posttraumatic stress disorder in peers of adolescent suicide victims: predisposing factors and phenomenology.

OBJECTIVE: To examine the factors predisposing to posttraumatic stress disorder (PTSD) in peers of adolescent suicide victims. METHOD: One hundred forty-six adolescents who were the friends of 26 suicide victims were studied. Five percent (n = 8) developed PTSD after exposure to suicide. These 8 subjects with PTSD were compared to the remainder of the exposed subjects (n = 138). RESULTS: Subjects with PTSD were more likely than those without PTSD to have had a history of substance abuse, agoraphobia, and suicide attempts. Subjects who developed PTSD were more likely to have developed a new-onset depression, to have more severe grief, and to have been closer to the suicide victim. Subjects with PTSD tended to have more severe exposure to suicide and came from discordant households with a history of disruptions in key relationships. The 8 subjects who developed PTSD were compared to 38 subjects who developed new-onset depression but not PTSD. Those with PTSD were more likely to have had past substance abuse, prior suicide attempts, family history of panic disorder, a history of parent-child disruption, and a history of loss. Symptoms of intrusive visual images, hypervigilance, and avoidance of reminders discriminated subjects who had PTSD from new-onset depressives without PTSD. CONCLUSIONS: PTSD is an expectable outcome in youth exposed to suicide. Further work is required to differentiate symptoms of depression from PTSD.

Adolescent↗
PubMed1995

Generation of slow wave type action potentials in the mouse small intestine involves a non-L-type calcium channel.

Intrinsic electrical activities in various isolated segments of the mouse small intestine were recorded (i) to characterize action potential generation and (ii) to obtain a profile on the ion channels involved in initiating the slow wave type action potentials (slow waves). Gradients in slow wave frequency, resting membrane potential, and occurrence of spiking activity were found, with the proximal intestine exhibiting the highest frequency, the most hyperpolarized cell membrane, and the greatest occurrence of spikes. The slow waves were only partially sensitive to L-type calcium channel blockers. Nifedipine, verapamil, and pinaverium bromide abolished spikes that occurred on the plateau phase of the slow waves in all tissues. The activity that remained in the presence of L-type calcium channel blockers, the upstroke potential, retained a similar amplitude to the original slow wave and was of identical frequency. The upstroke potential was not sensitive to a reduction in extracellular chloride or to the sodium channel blockers tetrodotoxin and mexiletine. Abolishment of the Na+ gradient by removal of 120 mM extracellular Na+ reduced the upstroke potential frequency by 13 - 18% and its amplitude by 50 - 70% in the ileum. The amplitude was similarly reduced by Ni2+ (up to 5 mM), and by flufenamic acid (100 mu M), a nonspecific cation and chloride channel blocker. Gadolinium, a nonspecific blocker of cation and stretch-activated channels, had no effect. Throughout these pharmacological manipulations, a robust oscillation remained at 5 - 10 mV. This oscillation likely reflects pacemaker activity. It was rapidly abolished by removal of extracellular calcium but not affected by L-type calcium channel blockers. In summary, the mouse small intestine has been established as a model for research into slow wave generation and electrical pacemaker activity. The upstroke part of the slow wave has two components, the pacemaker component involves a non-L-type calcium channel.

Action Potentials↗
PubMed1995

Teaching physiology by combined passive (pedagogical) and active (andragogical) methods.

Pedagogy and andragogy are models of education based, respectively, on passive and active learning. This project compared two balanced sections of an undergraduate course in physiology. Both sections used the pedagogical method of didactic lectures to present basic material. Students in section 01 were given multiple-choice examinations, a pedagogical procedure, over the lecture content for the purpose of performance evaluation. In section 02 the lectures were used as an information source, which students combined with other information researched in the library to draft essays on assigned topics, i.e., an andragogical approach. Grading of the essays constituted 75% of a student's performance evaluation, with participation in class discussions making up the remaining 25%. There was no significant difference in overall performance outcome between the two sections (P > 0.47). Students from both sections valued the lectures, even though they served a different purpose in each section. However, overall the student rating of section 02 was significantly higher than that of section 01 (P < or = 0.05). This reflected different teaching methods rather than different teachers, because the ratings of the two instructors were virtually identical (P > 0.98). These results suggest that a combined pedagogical and andragogical approach is an acceptable model for teaching introductory physiology.

Analysis of Variance↗
PubMed1995

Psychiatric emergencies.

Psychiatric emergencies can arise during pregnancy and the puerperium. When faced with a gravida presenting with the symptoms of an acute psychiatric illness, the obstetrician must consider the possibilities of organic disorders and substance abuse before initiating psychotropic therapy with the consulting psychiatrist. Generally, patients with psychiatric illness have difficulty caring for themselves and hospitalization may be indicated at least initially. Emotional support, a quiet environment, and psychotherapy are often the most important aspects of treatment. Suicide gestures should always be taken seriously. Immediate psychiatric consultation is imperative. Finally, anyone caring for pregnant women should be aware of the possibility of domestic violence. Pregnant women are unlikely to volunteer information about an abusive situation. Detection hinges on willingness of the physician to ask probing questions.

Anxiety Disorders↗
PubMed1995

Reduction in accumulation of plaque, stain, and calculus in dogs by dietary means.

We conducted 215 evaluations for plaque, stain, and calculus in 120 dogs at two research sites. Dogs were balanced in groups of five according to baseline plaque index scores; groups were randomly assigned to treatment or control dietary regimens. Dental cleanings were done on Day 0. Dogs in the treatment group were fed a food formulated to reduce accumulation of plaque, stain, and calculus. Control group dogs were fed a commercially available dry dog food. No other foods, treats, or snacks were given to either group. We graded 22 teeth for plaque accumulation on Day 7 and for stain and calculus accumulation on Day 21. Six trials were conducted and the results reported as a combined mean for all treatment and control groups. Dogs fed the treatment food had significantly less plaque, stain, and calculus accumulation (p = 0.001) than dogs fed the control food. Plaque, stain, and calculus accumulation can be reduced by dietary means.

Analysis of Variance↗
PubMed1994

The effect of the iron(III) chelator, desferrioxamine, on iron and transferrin uptake by the human malignant melanoma cell.

The mechanism of action of the clinically used iron(III) chelator, desferrioxamine (DFO), on preventing iron (Fe) uptake from transferrin (Tf) has been investigated using the human melanoma cell line SK-MEL-28. This investigation was initiated due to the paucity of information on the mechanisms of action of DFO in neoplastic cells and because recent studies have suggested that DFO may be a useful antitumor agent. The effect of DFO was dependent on incubation time. After a 2-h incubation, DFO acted like the extracellular chelators, EDTA and diethylenetriaminepentaacetic acid, because there was little inhibition of 59Fe uptake from Tf. In contrast, after a 24-h incubation, DFO (0.5 mM) efficiently reduced internalized 59Fe uptake from Tf to 18% of the control value. These observations suggested the existence of a kinetic block to the entry of the apochelator to intracellular Fe pools and/or to the exit of the DFO-59Fe complex. Indeed, cellular fractionation demonstrated that, in contrast to the decrease in the percentage of 59Fe in the ferritin and membrane fractions, a marked increase in the percentage of 59Fe present in the ferritin-free cytosol occurred. These observations suggested an accumulation of the DFO-59Fe complex within the cell. The highly lipophilic Fe chelator, pyridoxal isonicotinoyl hydrazone, was far more effective than DFO at preventing 59Fe uptake from Tf, illustrating the importance of membrane permeability for effective Fe chelation. Desferrioxamine at a concentration of 1 mM decreased internalized 125I-Tf uptake to 70% of the control. However, the decrease in 59Fe uptake observed could only be partially accounted for by a decrease in Tf uptake, and it appeared that DFO was chelating 59Fe at an intracellular site consistent with the transit Fe pool. The results are discussed in the context of the use of Fe chelators as effective antineoplastic agents.

Cell Division↗
PubMed1994

Role of nitric oxide in the response of capillary blood flow in the rat tail to body heating.

This study tested whether or not nitric oxide (NO) is involved in mediating the response of cutaneous capillary blood flow to an indirect heat stress. Blood cell velocity (BCV) in capillaries within the subepidermal plexus of the tail of anesthetized Sprague-Dawley rats was measured by videomicroscopy while the animals' trunk was exposed to a 35 degrees environment. Vascular conductance, estimated as the ratio of BCV to mean arterial pressure (MAP), increased by 259% in saline (placebo)-treated rats. Intravenous administration of 32 mg/Kg of the NO synthesis inhibitor NG-nitro-L-arginine (NNA) attenuated the response of vascular conductance (BCV/MAP) to body heating regardless of whether NNA was given before or during the heat stress procedure. In a subset of NNA-treated animals, infusion of the NO substrate L-arginine restored the BCV/MAP response to heat stress. In summary, the results of this study support the hypothesis that NO is involved in the response of cutaneous capillary blood flow to heat stress. Possible mechanisms mediating the local release of NO are discussed.

Animals↗
PubMed1994

Estrogen antibodies reduce vulnerability to stress-induced failure of intrauterine implantation in inseminated mice.

In Experiment 1, inseminated mice were randomly assigned to either an undisturbed control condition or four conditions involving exposure to restraint stress on days 1 through 5 of pregnancy. Restrained animals received one of three doses of estrogen antibodies or just vehicle injections on each day of restraint. Restrained animals receiving vehicle only showed significantly fewer uterine implantation sites than did unrestrained controls, while restrained animals given estrogen antibodies showed more implantation sites than did vehicle-treated restrained animals. In Experiment 2, varied dosages of refined estrogen antibodies were administered to inseminated females concurrent to restraint-stress on days 1 through 5 of pregnancy. More females receiving the higher dosages of antibodies produced litters than did restrained females with just vehicle injections, and at the highest dose the number of litters was similar to that produced by undisturbed control females. These results converge with other evidence to suggest that stress-induced pregnancy blocks are mediated by estrogens.

Animals↗