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Biomedical subjects

T Perkins

Publications and source records attributed to T Perkins.

16 recordsLinked to original sources
PubMed2001

Renal arteriography using gadolinium enhanced 3D MR angiography--clinical experience with the technique, its limitations and pitfalls.

Gadolinium enhanced 3D MR angiography (MRA) is becoming a widely accepted technique for imaging the vascular system. We set out to evaluate its accuracy and reliability in visualization of renal arteries in the clinical setting. Gadolinium enhanced MRA was performed in 15 potential live renal donors and 26 patients suspected of having renal artery stenosis who were referred for digital subtraction angiography (DSA). MRA was performed on a 1.5 T MR scanner in a single breath hold. Images from each study were prospectively analysed for demonstration of number of main and accessory renal arteries and degree of renal artery stenosis in a double blind fashion. All the main and accessory arteries were visualized on MRA in the renal donor group, but in one case a branch was not identified owing to breathing artefact. In one case, an extrarenal vascular anomaly was not demonstrated on MRA. In the renal artery stenosis group, sensitivity, specificity and negative predictive values of 96%, 93% and 96% were obtained for clinically significant stenosis (>50%). Gadolinium enhanced MRA proved to be a useful technique in demonstration of renal arterial anatomy and grading of renal artery stenosis. However, we encountered some pitfalls and limitations of the technique during the process. It is important to be aware of these before accepting it as the sole technique in clinical practice.

Adult↗
PubMed2000

Morbidity in reflex sympathetic dystrophy.

Reflex sympathetic dystrophy (RSD), an unusual diagnosis in general paediatrics, is well recognised by paediatric rheumatologists. This study reports the presentation and the clinical course of 46 patients (35 female, age range 8-15.2) with RSD. The patients saw professionals from an average of 2.3 specialties (range 1-5). Twenty five (54%) had a history of trauma. Median time to diagnosis was 12 weeks (range 1-130). Many children had multiple investigations and treatments. Once diagnosis was made, treatment followed with physiotherapy and analgesics. Median time to recovery was seven weeks (range 1-140), with 27.5% relapsing. Nine children required assessment by the child and adolescent psychiatry team. This disease, though rare, has significant morbidity and it is therefore important to raise clinicians' awareness of RSD in childhood. Children with the condition may then be recognised and referred for appropriate management earlier, and spared unnecessary investigations and treatments which may exacerbate the condition.

Adolescent↗
PubMed1999

A prospective comparison of brain contrast characteristics and lesion detection using single-shot fast spin-echo and fast spin-echo.

MRI is limited by movement artefact, even with current imagers, when examining a restless or claustrophobic patient. We prospectively analysed the images of 92 patients produced by a single-shot fast spin-echo (SSFSE) pulse sequence and compared them with conventional (FSE) and reduced-time fast spin-echo (RT-FSE) techniques, with regard to lesion detection and movement artefact in brain imaging. Images obtained in each case were independently reviewed and scored for overall diagnosis, number of lesions detected, and movement artefact. FSE showed 1217 lesions, RT-FSE 1137, and SSFSE 1044. This discrepancy arose mainly in patients with multiple sclerosis or small-vessel disease, since with SSFSE we were less able to separate small, adjacent low-contrast lesions than with FSE. Arbitrary movement scores were 36, 25 and zero respectively. There were, however, no clinically significant differences in overall diagnosis between the three techniques. SSFSE thus proved a reliable, fast, accurate method for obtaining T2-weighted images, and may be of particular use in the restless, claustrophobic or obtunded patient.

Algorithms↗
PubMed1998

Intracellular metabolism of a 2'-O-methyl-stabilized ribozyme after uptake by DOTAP transfection or asfree ribozyme. A study by capillary electrophoresis.

The uptake and cellular metabolism of a fluorescein-labelled synthetic ribozyme stabilized by 2'- O -methyl modification and a 3' inverted thymidine have been studied, employing capillary gel electrophoresis as a novel and efficient analytical method. After internalization by DOTAP transfection, electrophoretic peaks of intact ribozyme and different degradation products were easily resolved and the amount of intracellular intact ribozyme was quantified to >10(7) molecules/cell at the peak value after 4 h transfection. On further incubation the amount of intracellular intact ribozyme decreased due to both degradation and efflux from the cell. However, even after 48 h incubation there were still >10(6) intact ribozyme molecules/cell. Clear differences both in uptake and in metabolism were seen when comparing DOTAP transfection with the uptake of free ribozyme. Fluorescence microscopy studies indicated that the ribozyme was mainly localized in intracellular granules, probably not accessible to target mRNA. This implies that agents able to release the intact ribozyme from intracellular vesicles into the cytosol should have a considerable potential for increasing the biological effects of synthetic ribozymes.

Base Sequence↗
PubMed1994

On the field inhomogeneity of a birdcage coil.

A mathematical model is developed for the numerical analysis of birdcage coils constructed using capacitors having different capacitance. With the aid of this model, it is shown that the deviation of some capacitance introduced by tune, balance, and drive mechanisms can cause inhomogeneity in the B1 field produced by the coil. Useful curves and formulae are developed to provide a guideline for the design of birdcage coils.

Algorithms↗
PubMed1994

Presentation, diagnosis and treatment of renal abscesses: 1972-1988.

We reviewed 61 consecutive patients with renal abscesses who were treated between 1972 and 1988 to determine whether the patient characteristics and mortality differed from those of patients treated during the preceding 2 decades. The results demonstrate that the predisposing conditions, symptomatology, abnormal physical findings, abnormal laboratory results, abnormal radiographic findings and infecting organisms of patients with renal abscesses have not changed during the last 40 years. Ultrasonography and computerized tomography, which became available in the 1970s, identified 35 of 38 (92%) and 23 of 24 (96%) abscesses, respectively. In 57 cases (97%) the abscess was drained and the patients survived. In 4 cases the abscess escaped clinical detection and contributed to patient death. The marked improvement of survival among patients with renal abscesses during the last 2 decades is attributable to improved diagnostic precision and, probably, improved antimicrobial therapy and supportive care.

Abscess↗
PubMed1990

A regional approach to entry-level critical care education.

The education and training of the novice critical care nurse place a constant financial demand on many Puget Sound area hospitals. Critical care educators from this area, committed to cost-effective, high-quality education, enhanced through precepted clinical experience, assessed the need for a collaborative approach among institutions. Jointly we have successfully planned, implemented, and evaluated a cooperative educational program. To date, the program has served to reduce the costs of preparing the RN entering critical care in the Puget Sound area. Application of principles of adult education, timely application of theory to practice, and expansion of the professional role of critical care clinical nurse specialists and educators have also been recognized as outcomes of the CCEC.

Critical Care↗
PubMed1988

Improvement of dental development in osteopetrotic mice by maternal vitamin D3 sulfate administration.

Utilizing the microphthalamic mouse, (mi/mi) as a model of osteopetrosis, vitamin D3 (cholecalciferol) was administered prenatally and postnatally to study its effects on tooth development and subsequent eruption. It has previously been reported that vitamin D3 crosses the placental barrier and is absorbed into mammary gland milk. Fifteen heterozygotes (+/mi) were used as breeders. There were three study groups: A) 5.0 ng/gm cholecalciferol sulfate; B) 2.5 ng/gm cholecalciferol sulfate; and C) no therapy. Intraperitoneal injections were administered three times per week, beginning when pregnancy was evident, and continuing for 4 additional weeks during lactation. Approximately half of the 59 offspring were sacrificed at age 1 day and the other half at 4 weeks. The former group was studied for crown development, and the latter group was studied for root development and eruption. When the osteopetrotic offspring of group A were compared with osteopetrotic offspring of group C, crown development and tooth eruption were substantially more advanced. Parameters examined were maturity of the ameloblasts and odontoblasts, dentin and enamel formation, root sheath development, status of eruption, and degree of apex closure. It was concluded that cholecalciferol sulfate significantly improves tooth development and subsequent eruption in the osteopetrotic mouse. A genetic disease has had its phenotype modified by vitamin therapy during gestation.

Animals↗
PubMed1987

Early pregnancy factor: large scale isolation of rosette inhibition test-active polypeptides from ovine placental extracts.

Protocols are described for the isolation of substantial (mg) amounts of a rosette inhibition test (RIT)-active polypeptide fraction from ovine placental extracts. The main component of the preparation is a 12K polypeptide which contains a highly reactive thiol group. Oxidation may occur during isolation with the result that the final preparation is a mixture of the 12K polypeptide and a 25K disulphide linked dimer. The highly reactive thiol group was found to be directly involved in activity expression since gentle reduction followed by iodoacetylation resulted in a complete loss of activity. Antisera were prepared and the antibodies removed all the RIT activity from fresh ovine placental extracts, indicating that molecules related to those in the isolated preparation were responsible for all the activity in crude extracts. The antibodies also removed all the RIT activity from ovine and murine pregnancy sera, obtained both before and after implantation. Since EPF is defined as an RIT activity detected in pregnancy serum, these results establish that EPF activity is due to molecules similar to those isolated from the placental extracts. The availability of the preparative protocol and antibodies should hasten the biochemical definition of the EPF phenomenon.

Animals↗
PubMed1986

Platelet-activating factor induces the expression of early pregnancy factor activity in female mice.

When synthetic platelet-activating factor (PAF, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) was injected into mature female mice during dioestrus, pro-oestrus or oestrus, it induced the expression of early pregnancy factor (EPF) activity in the sera of these animals within 1 h of injection. The sera of similarly injected males, metoestrous or immature females did not display any EPF activity. The results suggest that embryo-derived PAF may be the ovum factor responsible for triggering the generation of serum EPF activity during the preimplantation stages of pregnancy.

Animals↗
PubMedDate not supplied

Early intervention for human immunodeficiency virus in Baltimore Sexually Transmitted Diseases Clinics. Impact on gonorrhea incidence in patients infected with HIV.

BACKGROUND: High incidences of sexually transmitted diseases (STD) after posttest counseling have been documented in patients diagnosed with human immunodeficiency virus (HIV) in Baltimore STD clinics. In July 1991, the authors instituted an HIV early intervention program providing long-term medical care and social work services. This study compares the incidence of gonorrhea after post-HIV+ test counseling in patients diagnosed with HIV before and after the institution of the early intervention program. METHODS: Medical records of a cohort composed of all patients newly diagnosed with HIV and those who underwent posttest counseling for HIV in 1991 to 1993 in two Baltimore STD clinics were reviewed. Patients were offered early intervention medical and social work services. Gonorrhea incidence in this cohort was compared to a historical cohort diagnosed and counseled for post-HIV+ testing in 1988 to 1989 who were not offered early intervention services. RESULTS: The mean follow-up time was 418 days (range, 26 to 703 days). After post-HIV+ test counseling, gonorrhea developed in 39 of 468 (8.3%) men in the 1989 cohort and 13 of 400 (3.3%) men in the 1991 to 1993 cohort. Controlling for variable length of follow-up, the 1991 to 1993 cohort had a relative risk of 0.442 for the development of gonorrhea during the study period (95% confidence interval, 0.225 to 0.790; P = 0.006). Incident gonorrhea after post-HIV+ test counseling also was associated with a prevalent gonorrhea condition at the time of HIV diagnosis (RR = 3.02; 95% CI, 1.75 to 5.23; P = 0.0001) and failure to return for post-HIV+ test counseling as scheduled (RR = 2.27; 95% CI, 1.17-4.43; P = 0.013). After adjustment for gonorrhea at the time of HIV diagnosis and failure to return for scheduled posttest counseling, the difference in gonorrhea incidence between men in the two cohorts remained statistically significant (RR = 0.494; 95% CI, 0.260 to 0.941; P = 0.032). In comparison, overall gonorrhea rates in Baltimore changed little between 1988 and 1993. No significant difference was found in gonorrhea incidence in women, which may have been the result of active gonorrhea screening during the 1991 to 1993 period, which was not performed in 1988 to 1989. CONCLUSIONS: Providing clinical care to persons with HIV may facilitate the reduction of high-risk behaviors that lead to incident STDs and further HIV transmission.

Adult↗
PubMedDate not supplied

The effects of the child and adolescent trial for cardiovascular health intervention on psychosocial determinants of cardiovascular disease risk behavior among third-grade students.

PURPOSE: The Child and Adolescent Trial for Cardiovascular Health is a multi-site study of a school-based intervention designed to reduce or prevent the development of risk factors for cardiovascular disease. The goal was to change (or prevent) related risk behaviors and the psychosocial variables that theoretically influence those behaviors. DESIGN: A nested design was used in which schools served as the primary unit of analysis. Twenty-four schools participated at each of four sites (Austin, San Diego, Minneapolis, and New Orleans). Each site had 10 control and 14 intervention schools. SETTING AND SUBJECT: Ninety-six schools (with more than 6000 students) in the four sites were randomized to three treatment conditions: control, school-based interventions, and school-plus-family interventions. The sample included approximately equal numbers of males and females and was 67.5% white, 13.9% African-American, 13.9% Hispanic, and 4.7% other. MEASURES: The psychosocial determinants included improvements in dietary knowledge, intentions, self-efficacy, usual behavior, perceived social reinforcement for healthy food choices, and perceived reinforcement and self-efficacy for physical activity. RESULTS: The findings indicated significant improvements in all the psychosocial determinants measured (p < .0001). The results revealed a greater impact in the school-plus-family intervention schools for two determinants, usual dietary behavior and intentions to eat heart-healthy foods. CONCLUSIONS: These findings support theory-based interventions for changing selected psychosocial determinants of cardiovascular disease risk behavior among children.

Cardiovascular Diseases↗