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Biomedical subjects

M L Robinson

Publications and source records attributed to M L Robinson.

At least 37 records · Page 2Linked to original sources
PubMed1994

The value of duplex sonography after peripheral artery angioplasty in predicting subacute restenosis.

OBJECTIVE: The purpose of this study was to determine if abnormal findings on duplex sonographic examination after peripheral artery angioplasty correlate with the subsequent recurrence of a stenosis. SUBJECTS AND METHODS: We used duplex sonography to examine 35 stenoses in 23 patients within 48 hr after the patients had angioplasty to treat these stenoses. Patients were followed up for 3 years by using one or more of the following: assessment of signs and symptoms, monitoring of peripheral pulses, pulse volume recordings, and angiography. Life tables were constructed to compare long-term patency with the presence of abnormal findings seen on duplex sonograms. Abnormal findings at the dilated segment included a blood-flow velocity greater than 120 cm/sec or a residual elevated velocity ratio greater than 1.4 or 2.0 immediately after angioplasty. RESULTS: Twelve (34%) of 35 angioplasty sites showed recurrent stenosis before 36 months. Patency at 24 months was calculated for velocities less than 120 cm/sec vs velocities of 120 cm/sec or greater (41% vs 68%), for velocity ratios less than 1.4 vs ratios of 1.4 or greater (63% vs 57%), and for velocity ratios less than 2.0 vs ratios of 2.0 or greater (54% vs 74%). We found no significant difference in patency between those patients with normal findings and those with abnormal findings on duplex sonographic examination after angioplasty. CONCLUSION: Abnormal findings on duplex sonograms obtained immediately after peripheral angioplasty cannot be used to predict subacute restenosis.

Angioplasty, Balloon↗
PubMed1993

[125I]Vasoactive intestinal peptide binding in rodent suprachiasmatic nucleus: developmental and circadian studies.

The suprachiasmatic nucleus (SCN) of rat and hamster have been studied extensively and shown to play critical roles in circadian rhythmicity. [125I]Vasoactive intestinal peptide (VIP) binding levels are high in the rat SCN, suggesting that VIP receptors may be an important component of SCN function. In contrast to previously demonstrated diurnal variations in VIP immunoreactivity and VIP mRNA, the present study found [125I]VIP binding to be stable across the light-dark cycle in both rat and hamster SCN. High [125I]VIP labeling appeared to be coextensive with the rat SCN but extended somewhat beyond the cytoarchitectonic boundaries of the hamster SCN. Binding density in hamster SCN was slightly higher than in rat. In the developing rat SCN, [125I]VIP binding levels distinguished the SCN on embryonic day 18, and appeared to increase to postnatal day 10 before declining to adult levels. The early presence of [125I]VIP binding suggests possible involvement of VIP receptors in fetal entrainment of circadian rhythms.

Animals↗
PubMed1993

Genetic control of ocular morphogenesis: defective lens development associated with ocular anomalies in C57BL/6 mice.

Congenital ocular defects, including microphthalmia, anophthalmia and cataracts appear in a small proportion (5-15%) of the C57BL/6 inbred strain of laboratory mice. Previous work from this laboratory utilizing C57BL/6 in equilibrium with DBA/2 allophenic (mosaic) mice suggested that the underlying cause of these defects may be a deficiency in C57BL/6 lens development. In these C57BL/6 in equilibrium with DBA/2 allophenic animals, the major proportion of the lens cells were of the DBA/2 strain, in contrast to the other ocular and non-ocular tissues examined where no strain-specific competition was evident. Results presented here reinforce the notion that C57BL/6 lens cells are developmentally retarded. In allophenic combination with another strain, A/J, cells of the C57BL/6 strain were, again, markedly underrepresented in the mosaic lens, whereas no such genotypic specificity was evident in any of the other ocular and non-ocular tissues. Thus, the previous observation of a C57BL/6 deficiency in mosaic lens is more likely a consequence of low C57BL/6 competitiveness rather than some peculiar hyperactivity of the cells of the partner strains. Histological examination of C57BL/6, DBA/2 and A/J pure strain embryos indicated marked differences in the lens development of C57BL/6 embryos compared to the other two strains. For the first 3 days after lens invagination, the cross-sectional areas of DBA/2 lenses were two- to three-fold larger than those of C57BL/6 lenses at comparable stages of development, whereas no comparable difference was noted in the optic cup development in these two strains. This leads to a much higher lens/optic cup size ratio in DBA/2 embryos than C57BL/6 embryos. Scanning electron microscopy also revealed that lens invagination is much less extensive in the C57BL/6 embryos than the A/J embryos. The smaller C57BL/6 lens vesicle also remains deeper in the optic cup than those of the DBA/2 or A/J embryos of comparable developmental age. This is likely to result in the occasional complete envelopment of the entire lens vesicle by the optic cup and lead to arrested ocular development.

Animals↗
PubMed1993

LC studies on the potential interaction of paraben preservatives with sorbitol and glycerol.

Pharmaceutical formulations often contain one or more paraben preservatives in conjunction with a polyol such as sorbitol or glycerol. In one of these experimental formulations a number of unknown polar peaks have been detected near the solvent front by reversed-phase LC. These degradation products were not attributable to the active drug component or a hydrolysis product. The possibility of an interaction between the polyols and paraben preservatives has been explored using a three-variable, two-level, factorial design to determine the relative significance of the factors involved in the formation of these unknown peaks. The factors examined were pH, temperature and the ratio of polyol to paraben. This study has shown that pH and temperature are key factors affecting the formation of these unknown peaks. On the basis of these results suitable conditions can be suggested for minimizing the production of these unknown peaks. It seems clear that a number of pharmaceutical formulations containing a polyol and a paraben would present potential problems for assay validation on storage owing to the formation of these degradation products, particularly if the drug component is polar and elutes near the solvent front.

Chromatography, Liquid↗
PubMed1992

Duplex sonography of the carotid arteries.

Duplex sonography is the best noninvasive modality for investigation of possible carotid artery stenosis. By using the above described techniques, almost all significant stenoses can be detected and categorized correctly. Knowledge of common pitfalls in the performance and interpretation of the examination is essential to avoid misdiagnosis. Color imaging is a helpful addition to conventional duplex imaging, but is not essential to the performance of high-quality examinations.

Carotid Arteries↗
PubMed1992

Peripheral arterial Doppler ultrasonography: diagnostic criteria.

Fifty-one patients (86 legs) were studied from the aorta to the popliteal artery with both duplex ultrasonography and arteriography with the intention of establishing diagnostic ultrasonographic criteria for degrees of stenosis greater than 50% and determining the effect of multi-segment disease on the accuracy of these criteria. Receiver operator characteristic curves were used to determine diagnostic criteria for greater than 50%, greater than 70%, greater than 90% diameter stenoses or occlusions. A stenosis of greater than 70% was diagnosed either if the peak systolic velocity was more than 160 cm/sec (sensitivity 77%, specificity 90%) of if there was an increase in peak systolic velocity of 100% with respect to the arterial segment above the stenosis (sensitivity 80%, specificity 93%). Sequential stenoses were detected with lesser sensitivities. Ratio criteria were more accurate than peak systolic velocity for all degrees of stenosis. For detection of occlusion, duplex ultrasonography was 92% sensitive and 99% specific.

Arterial Occlusive Diseases↗
PubMed1992

Acute limb ischemia.

Acute ischemia of the extremity may be due to arterial occlusion from spontaneous thrombosis, embolus, arterial bypass graft thrombosis, trauma, or spasm. The presence of occlusion or stenosis can be determined noninvasively with the use of duplex Doppler ultrasonography. Most patients will require arteriography prior to thrombolytic or surgical therapy. New techniques, such as percutaneous aspiration thrombolectomy, expand the role of radiologic percutaneous therapy of the acutely ischemic limb. Prompt diagnosis and therapy are required to avoid limb loss or systemic metabolic complications from reperfusion of a dying limb.

Angioplasty, Balloon↗
PubMed1990

Evaluation of the peripheral arteries with duplex US after angioplasty.

Duplex ultrasound (US) was performed in 22 patients before and immediately after percutaneous transluminal balloon angioplasty (PTA) for peripheral artery stenoses or occlusions. Two patients underwent PTA on two occasions, and one patient underwent PTA of each lower extremity, resulting in 25 duplex US imaging pairs at a total of 40 PTA sites. The criterion for significant stenosis on duplex US studies was an increase in peak systolic velocity of at least 100% compared with the velocity in the arterial segment proximal to the lesion (velocity ratio, greater than or equal to 2.0). For 22 paired duplex US studies, pulse volume recordings or ankle-brachial indexes were obtained before and after PTA. After PTA, eight patients had residual high velocity ratios at 12 PTA sites. Only two of these patients had a residual hemodynamic stenosis as determined with post-PTA arteriography, pulse volume recordings, or ankle-brachial indexes. In this study, duplex US that was performed immediately after PTA for evaluation of residual stenosis was frequently misleading.

Angiography↗
PubMed1989

Report calls for fundamental health care reform.

The Joint Economic Committee in early October issued a report advocating reform of the financing and delivery of health care. Although this committee does not have authority over federal or state health programs, release of the committee's report adds impetus to calls for basic reforms.

Data Collection↗
PubMed1989

Turf battles rock radiology.

CEOs tell Hospitals magazine that imaging is a major area of expansion for their hospitals. But radiology is in a state of transition. Technological advances have made it possible to do more radiological procedures in the physician's office. This situation has created competition--and tension--between physicians in the same community, physicians and hospitals, and physicians on the same medical staff. How can you avoid costly turf wars at your hospital? Health care executives and directors of medical affairs say that the answer to this realignment of specialties is to create integrated teams of medical specialists.

Data Collection↗