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Biomedical subjects

P H Young

Publications and source records attributed to P H Young.

At least 19 recordsLinked to original sources
PubMed1992

A scanning electron microscopic study of arterial endothelial repair under turbulent flow conditions.

In order to study the role of hemodynamic factors on the healing and native morphology of endothelium in vivo, turbulent arterial flow was created using a loop bypass model, with and without occlusion in the recipient vessel. In this model, several different patterns of turbulent arterial blood flow resulted. The scanning electron microscope (SEM) was used to evaluate endothelial morphology in the area of the anastomoses at 3 and 14 days post-operatively. Morphological changes in the native endothelium along the recipient vessel correlated well with the direction of blood flow and predicted patterns of turbulence. The morphology of the native endothelium was altered to reflect the direction and pattern (laminar versus turbulent) of blood flow by 3 days postoperatively. Based on endothelial morphology, very narrow zones of separation could be demonstrated between areas of laminar and turbulent blood flow. The degree of reendothelialization across the suture itself was greatly variable at 3 days and there seemed to be no relationship to the location of turbulent flow.

Anastomosis, Surgical↗
PubMed1992

A comparison of carvedilol with atenolol in the treatment of mild-to-moderate essential hypertension. INT-CAR-07 (U.K.) Study Group.

The efficacy and safety of carvedilol, a beta-blocker with vasodilating properties, were compared at a dosage of 25 to 50 mg once daily with those of atenolol at a dosage of 50-100 mg once daily in a double-blind, randomized, parallel-group, multicenter study. After a single-blind placebo phase of 3 to 6 weeks, 47 patients (median age, 59 years) were randomized to receive carvedilol and 52 patients (median age, 57 years) were randomized to receive atenolol for an 8-week study period. Patients on carvedilol received 12.5 mg for the first 2 days and then 25 mg as a once-daily dosage. The initial dosage of atenolol was 50 mg once daily. The dosage of each treatment could be doubled (to 50 and 100 mg once daily, respectively) at week 4 if the response was inadequate. Sitting and standing blood pressures and heart rates were recorded 24 h after the dose at weeks 4 and 8. Data from 90 of 98 patients who completed the study were eligible for per-protocol analysis. Approximately one-third of the patients in each group required upward dose titration at week 4 because of inadequate response. At week 8, 84% patients receiving carvedilol and 91% receiving atenolol had sitting diastolic blood pressure less than or equal to 90 mm Hg or decreased their blood pressure by greater than or equal to 10 mm Hg (95% confidence intervals for difference between carvedilol and atenolol, +7% and -21%). Safety profiles were similar between treatments. One patient withdrew; a skin rash developed during the fourth week of treatment with atenolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1991

Mural repair following obliteration of aneurysms. Part III: Pathomorphological effects of Nd:YAG laser on aneurysm obliteration.

Twenty-four experimental aneurysms were created in rat carotid arteries using the venous pouch technique. Four to twelve weeks later, these aneurysms were totally obliterated by the external application of Nd:YAG laser. The aneurysmal dome and neck were both exposed to the laser using low amplitude (1-2 W) at continuous or repeat intervals (0.3 sec on/0.1 sec off). Small aneurysms were easily obliterated without external signs of necrosis, whereas aneurysms larger than 2 mm required complete coagulation resulting in a charcoal-like appearance. At varying intervals (30 min, 7 days, 3 weeks, 6 weeks), the obliterated aneurysms were harvested and evaluated using the scanning electron microscope and standard histological techniques. The results indicate that the effects of the laser on the aneurysm and parent vessel are similar to those encountered following the application of bipolar coagulation with massive coagulation necrosis of the aneurysmal neck and dome. Notably, however, the extension of this process onto the parent vessel involving especially the endothelium surrounding the aneurysm orifice (commonly seen with bipolar coagulation) is minimal following laser coagulation. There appears to be a protective effect on the parent vessel endothelium by blood flow through the vessel. On this basis, it appears that the laser may be an alternative method of aneurysmal coagulation; the use of laser entails less manipulation of the aneurysm. The Nd:YAG laser may be a useful adjunct in the surgical obliteration of clinical cerebral artery aneurysms, especially small ones.

Aneurysm↗
PubMed1991

A multicenter comparison of carvedilol with hydrochlorothiazide in the treatment of mild-to-moderate essential hypertension.

The efficacy and safety of carvedilol, a beta-blocker with vasodilatory properties, were compared with that of hydrochlorothiazide (HCTZ) both at a once-daily dose of 25-50 mg in a double-blind, randomized, parallel-group, multicenter study. Following a single-blind placebo phase of 3-6 weeks, 201 eligible patients (aged 27-88 years) were randomized to receive 8 weeks of treatment with either carvedilol or HCTZ, 25 mg doubling to 50 mg at week 4 if the respone was inadequate. Sitting and standing blood pressure and heart rate were recorded 2 h after the first dose and 24 h postdose at weeks 4 and 8. The analysis included 179 patients (11 having withdrawn, including 5 for adverse events, and 11 excluded for protocol violations). There were no statistically or clinically significant differences between treatment groups. Eighty-six percent of patients in the carvedilol group and 88% in the HCTZ group had an 8-week sitting diastolic blood pressure less than or equal to 90 mm Hg or decreased by greater than or equal to 10 mm Hg. Safety profiles were similar for both agents, with a tendency to lower uric acid and total cholesterol levels with carvedilol. Carvedilol and HCTZ at doses compared in this study have similar efficacy and tolerability, with laboratory evidence to suggest a more favorable metabolic profile for carvedilol.

Adrenergic beta-Antagonists↗
PubMed1990

In search of the "perfect" anastomosis.

Forty-five end-to-side microvascular anastomoses were completed in rat carotid arteries of 0.7-0.8 mm diameter (anastomosing the distal end of the left common carotid to the side of the right common carotid). For comparison both 10-0 and 11-0 sutures were utilized in different anastomotic techniques: interrupted, direct-continuous, and diagonal-continuous sutures, plus total mural thickness vs. partial mural thickness (piercing only the adventitia and outer media, excluding the intima). Anastomoses were evaluated for patency and scanning electron microscopic appearance after 10 to 12 weeks. The results indicate complete patency in all anastomoses. Ultrastructural observations revealed nearly normal intimal appearance in the partial medial technique and only minimal evidence of intimal injury in the other techniques. It is concluded that 100% patency can be obtained regardless of suture size or anastomotic technique. The most important factor in anastomotic patency is the operator's technical skill.

Anastomosis, Surgical↗
PubMed1990

A new technique for closure of the dura following transsphenoidal and transclival operations. Technical note.

Watertight closure of the dura following transsphenoidal operations for pituitary adenoma or hypophysectomy and following transclival operations for paraclival tumors has been technically very difficult. This is true both immediately after the initial approach and later for the treatment of delayed cerebrospinal fluid leakage. An innovative practical technique and special suture-tying instruments and needle designed by the principal author for this purpose have greatly facilitated this procedure. This technique has been applied to both direct dural closure and dural patching with watertight dural closure. The technique is also widely applicable for closing (or suturing) the dura following any procedure through a small opening, such as the dural tears occasionally encountered during lumbar or cervical discectomy, or tacking the tentorium during a craniotomy. The technique and suture-tying instruments are described in detail.

Dura Mater↗
PubMed1988

Mural repair following obliteration of aneurysms: II. Pathomorphology of treated aneurysms.

Mural vascular repair following experimental and clinical aneurysm obliteration was studied using the scanning electron microscope and standard histological techniques. Two of the more frequently utilized clinical obliteration techniques, clipping and coagulation, were examined. A chronological description of the mural reparative process reveals that clipping is superior to coagulation in most instances, that coagulation results in satisfactory obliteration of the aneurysmal orifice only in very selected circumstances, and that a combination of coagulation and clipping may be the best overall obliteration technique.

Aneurysm↗
PubMed1987

Mural repair following obliteration of aneurysms: production of experimental aneurysms.

One hundred thirty-two experimental rat carotid artery aneurysms were produced using a variety of methods, in order to determine which of these approaches should be employed in the development of a satisfactory laboratory model. The gross appearance and pathomorphology of aneurysms created by vein pouch and partial arteriotomy methods most closely resembled those features reported in clinical intracranial aneurysms.

Aneurysm↗
PubMed1986

Effects of long-term preservation of frankia strains on infectivity, effectivity, and in vitro nitrogenase activity.

Frankia strain HFP ArI3 which had been preserved for 27 months by being lyophilized, frozen in glycerol, or stored in complex medium was successfully used as an inoculum after being subcultured for inducing nodulation and nitrogen fixation of Alnus rubra. Glycerol-preserved HFP ArI3 produced significantly lower rates of nitrogenase activity than did lyophilized or complex-medium-preserved inocula. Bacteria that had been preserved by all three methods were successfully induced to fix atmospheric nitrogen by being cultured in nitrogen-free medium. Subculturing of these cells in nitrogen-free medium a second and third time yielded increasing rates of nitrogenase activity. Initial nitrogenase activity was detected on days 5, 4, and 3 during the first, second, and third subcultures after preservation, respectively. Maximum activity was observed on days 11, 10, and 8 during the first, second, and third subcultures, respectively. A description is given of standard culture techniques used in our laboratory for Frankia isolates, and methods used to distribute Frankia cultures by mail are described.

Journal Article↗
PubMed1984

Ventriculo-peritoneal shunt pseudocyst causing ureteropelvic junction obstruction in a child with myelomeningocele and retrocaval ureter.

We report on a boy with myelomeningocele and a ventriculo-peritoneal shunt, who presented with progressive ureteropelvic junction obstruction and an enlarging right upper quadrant mass. Exploration revealed a large pseudocyst around the distal portion of the shunt, causing obstruction of an unsuspected retrocaval ureter. To our knowledge this is the first reported case of an upper urinary tract complication due to a ventriculo-peritoneal shunt as well as the first case of a retrocaval ureter associated with myelomeningocele.

Abnormalities, Multiple↗
PubMed1984

The effect of cimetidine on the maintenance of healing of gastric ulceration.

The rate of endoscopically confirmed gastric ulcer relapse was compared in two groups of patients with newly healed benign gastric ulcers, receiving either cimetidine 400 mg nocte or matching placebo, over a period of 1 year. Six of 24 (25%) patients on cimetidine and 16 of 27 (59%) patients on placebo had endoscopically confirmed relapse. These included two patients in each group with asymptomatic relapses. The difference in the rate of relapse between the two groups was statistically significant (P = 0.01).

Adult↗