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Biomedical subjects

J P Harris

Publications and source records attributed to J P Harris.

At least 19 recordsLinked to original sources
PubMed1992

Modified anastomotic technique for 1 millimeter internal diameter polytetrafluoroethylene arterial grafts in the rat.

Reported patency rates after standard end-to-end anastomoses for microvascular prosthetic grafts have been inconsistent and usually disappointing. A modified anastomotic technique is described in which the prosthetic graft is invaginated inside the arterial lumen. In this study of 6 cm lengths of 1 mm internal diameter polytetrafluoroethylene femoro-femoral bypass grafts in the rat, 6 (40%) of 15 grafts with standard anastomoses were patent at 6 months compared to 28 (90%) of 31 grafts using the modified anastomotic technique (P < 0.001). With invagination of the prosthetic graft inside the arterial lumen, reliable high patency rates can be achieved with microvascular prostheses long enough for potential clinical applications.

Anastomosis, Surgical↗
PubMed1992

Visual memory for vernier offsets.

Human ability to perceive and remember precise spatial relationships was investigated in a vernier acuity task. An initial ("standard") vernier stimulus with a variable offset was presented for 100 msec. After a delay of 1, 4, or 8 sec, another vernier target (the "variable" stimulus) followed, also for 100 msec. Observers compared the offsets of the two stimuli with each other. For very small offsets, discrimination between smaller and larger offsets was very precise, in the hyperacuity range. Thresholds increased linearly with the spatial offset of the standard stimulus, suggesting that the precision of the mechanism solving this spatial task scales with offset size. Control experiments suggested that this effect was not due to variations in retinal eccentricity. Thresholds also increased with increasing delay between the presentations of the two stimuli. By varying the delay, we directly measured the fading of the spatial memory trace.

Humans↗
PubMed1992

Bilateral mycotic axillary artery false aneurysms in an intravenous drug user: unsuspected broken needle-tips pose a risk to the treating personnel.

Mycotic false aneurysms due to local arterial injury from attempted intravenous injections in drug addicts are increasing in frequency. The high incidence of HIV and hepatitis B virus in parenteral drug users may present a considerable risk to the treating personnel. This paper reports the unsuspected presence of broken needle-tips in the subcutaneous tissues of an intravenous drug abuser, in association with bilateral mycotic aneurysms of the axillary arteries. Broken needle-tips have the potential to cause needlestick injury to the operating team and the nursing staff, with the associated risk of transmission of HIV and hepatitis B virus infection. The presence of broken needle-tips should be suspected in drug users presenting with false aneurysms associated with local arterial injection injury and a specific history of needle-breakage should be sought. Preoperative plain radiographs should be performed of the planned operative field to exclude the presence of such needle-tips. Any soft tissue swelling in the vicinity of a major artery in an intravenous drug abuser should be suspected of being a false aneurysm until proven otherwise and should prompt immediate referral to a vascular surgeon for investigation and management.

Adult↗
PubMed1992

Processing of spatial contrast in peripheral vision in Parkinson's disease.

Two experiments were carried out to test the hypothesis, based on anatomical evidence, that contrast gain might be reduced in the retinal periphery in Parkinson's disease. In the first experiment, subjects set contrast thresholds before and after adaptation to a vertical grating of 2 cycles per degree (c/deg), either stationary or oscillating sideways through its spatial period at 8 Hz, presented either in central vision or 7 degrees peripherally. Threshold elevations were similar for central viewing in both patients and controls. However, for peripheral viewing, elevations were greater in the controls, but smaller in the patients, than for central viewing. In the second experiment, a staircase procedure was used to find the contrast of a peripherally viewed grating of either 4 or 1.2 c/deg which apparently matched that of a centrally viewed grating of the same spatial frequency. Patients needed more contrast (about 1.6 times, at both spatial frequencies) than controls for a match. These results suggest that contrast gain may be lowered in the peripheral retina in Parkinson's disease, perhaps because of an abnormality of dopamine amacrine cells, whose density peaks in the peripheral retina.

Contrast Sensitivity↗
PubMed1992

Spontaneous remission in experimental autoimmune labyrinthitis.

We investigated the time course of hearing impairment and cellular infiltration into the inner ear after systemic sensitization of guinea pigs with a single intradermal injection of bovine inner ear antigen (IEAg) in complete Freund's adjuvant (CFA). Lymphocytes and polymorphonucleocytes appeared mainly in the scala tympani on days 7 to 14, and in addition there was thickening and cellular infiltration of the round window membrane at day 14. These cellular infiltrations resolved after day 28. The auditory brain stem response thresholds from IEAg-sensitized animals were significantly elevated after day 7. Some sensitized animals (n = 5) had spontaneous remissions after day 28; however, the hearing thresholds did not completely recover. These results demonstrate that experimental autoimmune labyrinthitis can be induced by a single inoculation of IEAg-CFA and that remission, as evidenced by clearing of the cochlear cellular infiltration and improved hearing thresholds, can occur spontaneously.

Animals↗
PubMed1992

Spiral modiolar vein: its importance in viral load of the inner ear.

Guinea pig-specific cytomegalovirus and Sendai virus were inoculated into the cochleas of seronegative guinea pigs to study the route of entry of cells participating in inner ear inflammation. Inflammatory cells accumulated around the spiral modiolar vein and appeared to be streaming from this vein into the scala tympani via a collecting venule. Inactivated virus inoculated into the cochlea and normal control cochlea failed to show inflammatory cell infiltrates. The spiral modiolar vein appears to play an important role in the movement of cells from the systemic circulation into the inner ear as part of the host's normal defense against invading pathogens such as viruses.

Animals↗
PubMed1992

Effects of bacterial endotoxin applied to the guinea pig cochlea.

The ototoxic potential of bacterial endotoxin present in middle ear effusions was evaluated by inoculating endotoxin solutions of 10 micrograms/mL or 1000 micrograms/mL directly into the scala tympani of the guinea pig cochlea. Median auditory brainstem response threshold shifts of 12.5 and 20 dB were observed in the experimental ears exposed to the higher dose at days 2 and 4, respectively, with gradual improvement to near baseline by day 28. Histologic examination revealed inflammatory infiltrates in the scala tympani and scala vestibuli of several of these cochleas. The lower concentration, closer to that found in human effusions, elicited no significant loss of hearing and a milder inflammatory response. It is concluded that brief exposure of the cochlea to endotoxin from middle ear effusions is insufficient to cause hearing loss. Under chronic conditions, however, persistent inflammation within the cochlea may result in a sensorineural deficit.

Animals↗
PubMed1992

Electrical promontory stimulation in patients with intact cochlear nerve and anacusis following acoustic neuroma surgery.

Anacusis following hearing preservation surgery for acoustic neuroma removal in which the cochlear nerve was preserved has been explained on the basis of neural or vascular compromise. In the absence of pathologic evidence for either theory, a physiologic model was chosen. Electrical promontory stimulation with monitoring of subjective and electrically evoked auditory brainstem responses was undertaken. A positive response to stimulation suggests a vascular impairment of the cochlea sparing the cochlear nerve and spiral ganglion. The absence of response suggests loss of neural integrity at the level of the spiral ganglion or cochlear nerve. Six patients who suffered anacusis following hearing preservation surgery for acoustic neuroma were studied. Data regarding electrical promontory stimulation, auditory brainstem responses, and implications of the possible role of cochlear implantation are discussed.

California↗
PubMed1992

Audiologic profiles of children with Kawasaki disease.

Kawasaki disease (KD) is an idiopathic vasculitis associated with systemic inflammation and profound immunoregulatory changes. Recent reports from Japan and the United States have documented the association of sensorineural hearing loss (SNHL) with acute KD. To further characterize the nature and prevalence of this complication, we prospectively evaluated the hearing of 40 consecutive patients with acute KD at a single institution. Standard audiometric procedures were used, including visual reinforcement audiometry and play audiometry. Auditory brainstem response (ABR) testing using clicks and tone pips (1000-4000 Hz) was performed in patients with abnormal or unreliable results on behavioral audiometry. Acoustic immittance measurements were obtained on all patients. Of the 23 males and 17 females (mean age 3.2 +/- 2.3 years, range 0.6-11.1 years), all but three were evaluated and treated with aspirin and intravenous gama globulin within 1 month of onset of fever. Seven children had test results suggesting sensorineural threshold shifts, 16 had normal hearing, and 14 had inconclusive hearing evaluations. Laboratory data in patients with hearing threshold shifts revealed significantly longer duration of fever (4.1 +/- 1.0 versus 1.9 +/- 0.5 days), and a tendency for higher temperatures and white blood cell counts at diagnosis compared to those with normal hearing. Results suggest that transient as well as persistent SNHL may be associated with the acute vasculitis of KD, and may be associated with laboratory markers indicating more severe systemic inflammation. Audiologic screening should be considered for all patients following KD.

Aspirin↗
PubMed1991

Occult surgical glove perforations in otolaryngology-head and neck surgery.

With the advent of the acquired immunodeficiency syndrome crisis, it has become imperative that all surgeons minimize their risk of direct contact with the patient's body fluids. In the course of performing surgery, perforations are frequently created in surgical gloves, which often go unnoticed. This study determined the frequency with which occult glove perforations occurred in 134 consecutive head and neck surgical procedures. One thousand fifty gloves (650 gloves used in surgery, 400 unused control gloves) were analyzed for the presence of perforations large enough to permit the passage of fluid. An unrecognized glove perforation was detected in 25% of surgical cases. The duration of surgery correlated strongly and positively with the incidence of perforation. Perforation rates varied widely for specific types of procedures, and are reported for each of the five subdivisions within otolaryngology-head and neck surgery. The implications of these results are described, and recommendations for the use of protective measures, especially in reference to the use of double-gloving, are made.

Equipment Failure↗
PubMed1991

Bench repair of complex renal arterial lesions.

Between 1968 and 1989, 160 patients underwent aortorenal bypass for renovascular hypertension. During the same interval, 13 patients had ex-vivo bench repair of complex renal arterial pathology. There were eight men and five women, with a mean age of 36 years. Twelve of the 13 patients had fibromuscular disease; one had atherosclerosis. Twelve patients had renovascular hypertension with complex stenotic disease beyond the main renal artery. Seven of these also had an associated renal aneurysm as did the sole normotensive patient. Saphenous vein patch or bypass were used to correct stenotic segments in four patients, while the remaining nine patients had excision of stenotic or aneurysmal segments with primary arterial anastomosis. There were no deaths in the series. One kidney was lost because of arterial thrombosis. One patient required reoperation to control postoperative bleeding. Nine of the 12 patients with renovascular hypertension were normotensive off medication, and three were improved, with reduced medication controlling their blood pressure. Ureteric obstruction occurred in two patients; this settled spontaneously in one patient and was corrected by reoperation in the other. From this experience, we conclude that bench repair is a safe and effective way to maximize salvage of kidneys affected by complex arterial pathology.

Adult↗
PubMed1991

Does division of the left renal vein during aortic surgery adversely affect renal function?

Between July 1980 and July 1988, 478 consecutive patients underwent aortic aneurysm operations at Royal Prince Alfred Hospital. Renal function was assessed by measurement of serum creatinine levels. The left renal vein was divided in 28 (8%) of the 355 patients undergoing elective aneurysm resection. The mean immediate postoperative creatinine values were significantly higher after left renal vein division, 193 +/- 174 mumol/L, compared to 133 +/- 93 mumol/l for those whose left renal vein remained intact (p less than 0.05 by Mann-Whitney U test). After one month, serum creatinine levels had decreased but were still significantly higher in those patients in whom the left renal vein had been divided, 170 +/- 166 mumol/l, compared to those in whom it was left intact 109 +/- 49 mumol/l (p less than 0.05 by Mann-Whitney U test). The suprarenal aorta was cross-clamped in seven (25%) of the 28 patients in whom the left renal vein was divided, compared to 21 (6%) of the 327 with the left renal vein intact. A rise in creatinine level was observed after suprarenal aortic cross-clamping. The left renal vein was divided in 17 (14%) of the 123 patients having emergency surgery for ruptured aortic aneurysm, 61 (49%) of whom survived more than 30 days. The mean immediate postoperative creatinine values were significantly higher after left renal vein division, 426 +/- 277 mumol/l, compared to those in whom the vein was left intact, 178 +/- 136 mumol/l (p less than 0.05 by Mann-Whitney U test). After one month, serum creatinine levels were still significantly higher in those patients in whom the left renal vein had been divided. Although division of the left renal vein is a useful way to improve exposure of the juxtarenal aorta, the maneuver is associated with an adverse effect on renal function.

Aged↗
PubMed1991

Combined percutaneous transluminal angioplasty and extraanatomic bypass for symptomatic unilateral iliac artery occlusion with contralateral iliac artery stenosis.

We have reviewed our experience with percutaneous transluminal angioplasty of contralateral iliac stenosis and extraanatomic bypass of the occluded iliac artery. Twenty-two men and nine women with a mean age of 65 years (range 46 to 84) presented with symptomatic iliac occlusive disease. Twenty-four (77%) had disabling claudication, four (13%) rest pain, and three (10%) ischemic tissue loss. Six (19%) had undergone previous vascular reconstructive procedures. All had an occluded iliac artery on the symptomatic side and greater than 50% stenosis of the contralateral iliac artery. Percutaneous transluminal angioplasty of the iliac stenosis was done prior to extraanatomic bypass, using polytetrafluoroethylene. There were six late deaths after discharge. The only significant complication was a femoral artery thrombosis which was corrected when the bypass graft was performed. Cumulative primary graft patency was 89% at one year and 81% at three years. The crossover graft occluded in six patients, five within 48 months of surgery, and one after nine years. One of these occluded grafts was salvaged by thrombectomy, for a secondary patency rate of 85% at three years. Two patients required aortobifemoral bypass, one an iliobifemoral bypass and one an ilioprofunda bypass. One patient operated upon for rest pain came to below-knee amputation. Mean resting ankle/brachial systolic pressure index increased significantly on the side of the iliac occlusion from 0.35 +/- 0.21 to 0.70 +/- 0.20 (p less than 0.05, paired t test) after the combined procedure. There was no significant difference in the mean resting ankle/brachial systolic pressure index on the contralateral side (0.60 +/- 0.22 to 0.65 +/- 0.27, ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

The time course of adaptation to spatial contrast.

We explored the buildup and decay of threshold elevation during and after adaptation to sinewave gratings in a series of experiments investigating the effects of adapting time, adapting contrast, spatial frequency and retinal eccentricity. Contrast thresholds for vertical sinewave gratings truncated in space by a one-dimensional Gaussian envelope were measured before and after adaptation to a full-field suprathreshold grating of the same spatial frequency and orientation. Thresholds were measured intermittently after adaptation in a "seen/not-seen" single presentation procedure until these thresholds returned to baseline values. The first test grating was presented 300 msec after the offset of the adapting stimulus, and thereafter at regular intervals. At different times after adaptation, contrast thresholds were estimated by off-line analysis of the data using the QUEST algorithm. Adapting time was either 1, 10, 100 or 1000 sec and adapting contrast was either 9, 19, 29 or 39 dB (re. 1%). The test gratings were presented centered either at the fixation point or at 5 and 10 deg eccentricity along the horizontal meridian. The results suggest that up to the saturation level the buildup and the decay of adaptation to contrast is well described by a power function of time. The slope of the best fitting line on log-log axes is fairly constant for the adaptation times tested. As reported earlier, thresholds increased with adapting contrast and these contrast-dependent differences were evident 300 msec after the termination of adaptation. Adaptation at 10 deg eccentricity yielded slightly higher threshold elevations than for central vision. Based on these results, a description is given of the dynamic response of the underlying neural mechanisms.

Adaptation, Ocular↗
PubMed1991

Laser angioplasty of the iliac arteries.

Laser-assisted balloon angioplasty has the potential to reduce mortality and morbidity by replacing aorto-femoral bypass operations in patients with occlusion of the iliac arteries. We present our early experience with 16 patients undergoing this procedure, using a Cardiolase neodymium:yttrium aluminum garnet (Nd:YAG) laser in the operating room. Initial recanalization was achieved in 14 of the 16 patients. Early re-occlusion occurred in 4 patients, one of whom had a successful repeat laser angioplasty. This patient, together with the remaining 10 patients with successful initial recanalization remain patent at a mean follow-up period of 10 months. There were no deaths or chest complications. Angiographically demonstrated arterial perforation occurred in 2 patients, neither of whom required operation on the perforated segment. We conclude that recanalization of the iliac arteries is possible and safe. The procedure is unlikely to replace aorto-femoral bypass until the proportion of early failures is reduced. This may require larger probes or the immediate placement of intra-arterial stents following laser angioplasty.

Aged↗