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Biomedical subjects

P Gaines

Publications and source records attributed to P Gaines.

43 records · Page 3Linked to original sources
PubMed1992

Clinical demonstration that catheter-delivered ultrasound energy reverses arterial vasoconstriction.

OBJECTIVES: This study was designed to describe the clinical effects of ultrasound energy on guide-wire-induced arterial vasoconstriction. BACKGROUND: We have previously shown that ultrasound energy (20 kHz) delivered by a wire probe produces dose-dependent, endothelium-independent smooth muscle relaxation capable of reversing both receptor-mediated and voltage-dependent vasoconstriction in vitro. METHODS: A high intensity, low frequency ultrasound catheter system was used to recanalize total occlusions in the superficial femoral arteries of two patients. After recanalization, the proximal residual stenoses were each less than 15%. However, distal arterial vasospasm was found angiographically in a popliteal artery of one patient and in an anterior tibial artery of another. Subsequently, the ultrasound catheter probe was advanced to the sites of arterial vasospasm (diffuse in one, focal in one). RESULTS: After 30 and 90 s, respectively, of exposure to ultrasound energy with a frequency of 19.5 kHz, peak tip amplitude of 111 microns and power output at the transducer of 25 W, the vasospasm resolved in each arterial segment. CONCLUSIONS: Our findings are the first reported clinical cases documenting that catheter-delivered low frequency, high intensity ultrasound induces arterial vasodilation at the site of vasoconstriction. These biologic effects appear to be relatively unique for an angioplasty device and may have potential clinical importance.

Aged↗
PubMed1991

The thick common bile duct in pyogenic cholangitis.

The paper describes thickening of the wall of the common bile duct in acute pyogenic cholangitis demonstrated by ultrasound. The abnormality appears as a hypoechoic stripe lying internal to the echogenic line of the normal common bile duct. The clinical features of acute cholangitis may be atypical and this new sign should be of value in these difficult cases.

Cholangitis↗
PubMed1991

Histiocytosis X involving the thyroid and hypothalamus.

A case of histiocytosis X involving the thyroid and hypothalamus is reported. A 16 year old female presented with amenorrhoea and diabetes insipidus. She subsequently developed a painful goitre with biochemical hypothyroidism, and stridor. The stridor and goitre responded to cyclophosphamide. Previous publications on the use of cytotoxics in histiocytosis X involving the thyroid are reviewed. We describe for the first time both the ultrasound appearances of the thyroid in this condition and the use of serial volumetric measurements to monitor therapy.

Adolescent↗
PubMed1989

The pathology of cholesterol embolism arising as a complication of intra-aortic catheterization.

Cholesterol embolism is an unusual but serious complication of intra-arterial procedures such as arteriography and angioplasty. The pathological findings in four cases confirm that this syndrome is due to disseminated micro-emboli composed mainly of cholesterol crystals and that these originate from atheromatous plaques in the aorta which may be traumatized by the catheter used in the intra-arterial procedure. However, angiography is not the sole precipitating cause of this syndrome but is an exacerbating event in a pre-existing process.

Aged↗
PubMedDate not supplied

Retinoids in myelopoiesis.

The vitamin A derivative retinoic acid plays a critical role during the differentiation of myeloid progenitors towards the neutrophil lineage. This role is primarily mediated by binding of retinoic acid to retinoic acid receptor alpha (RARalpha), a nuclear receptor that modulates the expression of multiple downstream targets via retinoic acid response elements. The importance of this signalling pathway in myelopoiesis is evidenced by the recurrent disruption of the RARalpha gene by chromosomal rearrangements in all cases of acute promyelocytic leukemia (APL). Biochemical evidence suggests RARalpha performs two opposing functions, one as a repressor of gene expression in the absence of ligand, the second as a transcriptional activator in the presence of ligand, each controlled by multimeric complexes of transcription corepressors and coactivators, respectively. Here the molecular mechanisms activated by retinoic acid during myelopoiesis in the context of neutrophil development will be reviewed, together with some of the more recently identified targets of the retinoic signalling pathway.

ADP-ribosyl Cyclase↗