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Biomedical subjects

A Irvine

Publications and source records attributed to A Irvine.

At least 37 records · Page 2Linked to original sources
PubMed1991

Haemodynamic significance of incompetent calf perforating veins.

A total of 149 consecutive unselected patients (221 limbs) who presented with signs and symptoms of chronic venous problems (varicose veins with or without ankle oedema, skin changes and leg ulcers) have been studied by clinical examination, ascending deep to superficial venography, Doppler ultrasound and ambulatory venous pressure measurements. Of the limbs, 180 (82 per cent) had varicose veins without obstruction in the deep veins or reflux in the popliteal or femoral veins while 41 (18 per cent) had deep venous disease. Of the 180 limbs with 'primary' varicose veins 110 (60 per cent) did not have incompetent calf perforating veins (group A) while 70 (40 per cent) did (group B). On the basis of the ambulatory venous pressure after calf muscle exercise and the refilling time, the incompetent calf perforating veins of limbs in group B belonged to three subgroups of different haemodynamic significance. In 20 limbs (30 per cent) they were found to be of no haemodynamic significance, in 25 (35 per cent) of moderate haemodynamic significance and in 25 (35 per cent) of major haemodynamic significance. The last were, on clinical examination, indistinguishable from limbs with deep venous disease although they had patent deep veins with competent popliteal valves.

Humans↗
PubMed1991

Focal axonal injury: the early axonal response to stretch.

The development of a model for axonal injury in the optic nerve of the guinea pig has allowed analysis of early morphological changes within damaged axons. We provide evidence that the initial site of damage after stretch is the nodes of Ranvier, some of which develop 'nodal blebs'. The development of nodel blebs is correlated with the loss of subaxolemmal density, disruption of the neurofilament cytoskeleton and aggregation of membranous profiles of smooth endoplasmic reticulum. Nodal blebs are numerous 15 min after injury but less so at later survivals. The glial-axonal junction is intact at early survivals in damaged nodes. Marked accumulation of membranous organelles occurs in the paranodal and internodal regions adjacent to damaged nodes between two and six hours and is correlated with disruption of the myelin sheath. Axotomy and the formation of degeneration bulbs occurs between 24 and 72 h. The area of axonal injury is invaded by phagocytic cells by 72 h and large numbers of myelin figures occur within the neuropil until 14 days. The results are compared with those of other studies of diffuse axonal injury and other neuropathies. The time course of axonal changes is more rapid than during Wallerian degeneration. Our data from longer surviving animals is exactly comparable with published data. We are confident that the principal site of axonal injury is the node of Ranvier. We suggest that damage at the node results in disruption of axonal transport, which in turn leads to a cascade of events, culminating in axotomy between 24 and 72 h after the initial insult.

Animals↗
PubMed1991

The microvascular response to stretch injury in the adult guinea pig visual system.

In a variety of brain injury models, both reactive axonal change and microvascular abnormalities occur. Development of a stretch injury model in the guinea pig optic nerve has allowed for the characterization of the early axonal response to injury. In this same model, we have now attempted to characterize those morphologic changes occurring in the visual system microvasculature after injury. Thirty adult guinea pigs were subjected to axonal stretch injury and killed at posttraumatic survival periods ranging from 10 minutes to 14 days. Twenty animals were examined by scanning electron microscopy (SEM) for the detection of posttraumatic changes in the surface morphology of the microvasculature, and 10 animals were processed for transmission electron microscopy (TEM) analysis. Through this approach, increased pit vesicle activity and formation of endothelial microvilli were recognized within 10 minutes of injury. Pit vesicle activity returned to control levels by 2 hours. The formation of endothelial microvilli was widespread, affecting the microvessels in both the stretched and unstretched optic nerves and in the chiasm. The greatest response developed most slowly in the stretched nerve, and it was faster but less marked in the unstretched nerve and chiasm. Microvilli were more numerous in larger vessels. Related astrocytic swelling/lucency was not apparent until 6 hours after injury. The astrocyte response was less marked than that documented after brain injury. The results of this investigation demonstrate a widespread microvascular response to stretch injury of the guinea pig optic nerve. Comparison with the documented responses to traumatic brain injury indicates different rates of response to different types of insult.

Animals↗
PubMed1991

A study of patients receiving no billed nursing care.

Although home health care traditionally is conceptualized as nursing care, in today's environment care at home may be delivered by a myriad of professional and nonprofessional practitioners. In fact, many patients who receive home care do not receive billed nursing visits. We studied a group of patients (n = 200) who received no billed nursing care, but rather received billed care from therapists, social workers and home health aides. This cohort of patients differed from patients who received billed nursing care in several ways: they were more frequently referred to home care from the community, their prognoses on admission to home care were significantly better, and their outcomes from home care services were considerably more favorable. Clearly patients not receiving billed nursing care have service and resource needs different from those of the population receiving billed nursing care. Therefore, new perspectives must be used when considering how to assess, deliver and perhaps pay for the requirements of these patients.

Home Care Services↗
PubMed1991

Impact of Medicare payment policy on home health resources utilization.

In this study, the association between Medicare regulations and the provision of public home health care is examined. Medicare clients were compared with non-Medicare groups of those 65 years of age or over and those under 65. Results suggested that both age- and payer-related factors contribute to utilization of services. Older patients showed greater need for chronic illness care relative to younger patients; however, Medicare patients used fewer resources and had poorer outcomes relative to older non-Medicare patients.

Adult↗
PubMed1990

Glycogen accumulation in axons after stretch injury.

Thin-section cytochemistry has been used to demonstrate the formation of glycogen deposits within axons after stretch injury to the optic nerve of adult guinea pigs in a model of focal axonal injury. Glycogen deposits occurred within 17% of structurally normal but, we suggest, damaged fibres within the stretched optic nerve. Adjacent fibres did not stain for glycogen. Small numbers of beta glycogen particles were present 15 min after injury within damaged axons and increasing numbers of particles occurred until 72 h. Degeneration bulbs formed by 72 h, but beta glycogen particles were sparse within these. By 7-14 days after injury there was a marked reduction in the numbers of glycogen particles within axons. Alpha rosettes of glycogen were infrequent within damaged axons. Deposition of glycogen particles within astrocytes after nerve injury was confirmed. Alpha rosettes of glycogen occurred within astrocytes by 6 h and remained until 14 days after injury. Possible mechanisms for the development of glycogen deposits within damaged axons are discussed in relation to a hypothesized influx of Ca2+ at the time of injury into damaged axons. We suggest that glycogen deposition within reactive axons reflects Ca2+ mediated alteration of glycogen synthase activity and compromized axonal transport.

Animals↗
PubMed1990

Nonreimbursed home health care: beyond the bills.

The unprecedented growth in the home care industry over the past decade has produced a highly competitive environment for care delivery. To survive, most agencies are implementing strategies to maximize reimbursable care. This focus, while likely to improve an agency's financial situation, is fraught with potential problems. Reimbursed care represents only a small portion of the care that is required and delivered. Still, aside from anecdotes, little reporting has been done to document such additional service, much less to consider the consequences of reducing or deleting it. We selected a sample of 350 public health home care episodes throughout Virginia, and reviewed billing records to determine the number of billed home visits attached to them. We then reviewed home health records for the matching episodes and recorded all visits and other care-related activities (e.g., telephone calls, conferences, laboratory trips). Total home visits increased, with an average of 1.5 unbilled home visits per episode. In addition, 10 additional care-related activities take place per patient, none of which is billed. These findings represent one of the first attempts to quantify the amounts and types of nonbilled care delivered by nurses. This care consumes significant nursing resources and, as a result, may be destined to be reduced or totally eliminated.

Home Care Services↗
PubMed1989

Number and anatomical distribution of incompetent thigh perforating veins.

Although incompetent thigh perforating veins are considered to be a common cause of recurrence of varicose veins after high saphenous ligation, the number and distribution of such incompetent veins have not been reported. The aim of the study was to determine the number and anatomical distribution of incompetent thigh perforating veins. Sixty-five limbs in 48 patients with varicose veins who were found to have incompetent thigh perforating veins on ascending deep to superficial venography were studied. In 80 per cent of patients one incompetent thigh perforating vein was found and in 20 per cent more than one was found. Concomitant incompetent calf perforating veins were found in 92 per cent of the limbs studied. The incompetent thigh perforating veins were found to occur anywhere in the thigh, from the upper edge of the patella to a few centimetres below the saphenofemoral junction. The majority (71 per cent) were found in the middle third of the thigh. All incompetent thigh perforating veins were communicating with the long saphenous vein, including those in five patients with incomplete stripping. The surgeon should be aware of incompetent thigh perforating veins which may be multiple and occur at any site on the medial aspect of the thigh.

Adult↗
PubMed1989

Intraarterial cisplatin and concurrent radiation for locally advanced bladder cancer.

Between 1983 and 1987 25 patients with invasive bladder cancer (16 stage tumor 3 (T3) and nine stage T4) were treated with intraarterial cisplatin and concurrent radical radiation (20/25) or intraarterial cisplatin, concurrent preoperative radiation, and cystectomy (5/25). One patient died from treatment-related toxicity. Other toxicities have been what one would expect from the individual treatment modalities except for a sensory sacral root neuropathy in 11 of 24 (46%) patients. Twenty-three of 24 (96%) patients achieved a complete response (CR) and the projected actuarial 2-year survival is 90%. Only one of the 23 complete responders has had an invasive local recurrence. The excellent complete local response and survival rates achieved warrant further study of the combination of intraarterial cisplatin and radiation as a bladder-preserving strategy.

Aged↗
PubMed1989

Axonal injury in the optic nerve: a model simulating diffuse axonal injury in the brain.

A new model of traumatic axonal injury has been developed by causing a single, rapid, controlled elongation (tensile strain) in the optic nerve of the albino guinea pig. Electron microscopy demonstrates axonal swelling, axolemmal blebs, and accumulation of organelles identical to those seen in human and experimental brain injury. Quantitative morphometric studies confirm that 17% of the optic nerve axons are injured without vascular disruption, and horseradish peroxidase (HRP) studies confirm alterations in rapid axoplasmic transport at the sites of injury. Since 95% to 98% of the optic nerve fibers are crossed, studies of the cell bodies and terminal fields of injured axons can be performed in this model. Glucose utilization was increased in the retina following injury, confirming electron microscopic changes of central chromatolysis in the ganglion cells and increased metabolic activity in reaction to axonal injury. Decreased activity at the superior colliculus was demonstrated by delayed HRP arrival after injury. The model is unique because it produces axonal damage that is morphologically identical to that seen in human brain injury and does so by delivering tissue strains of the same type and magnitude that cause axonal damage in the human. The model offers the possibility of improving the understanding of traumatic damage of central nervous system (CNS) axons because it creates reproducible axonal injury in a well-defined anatomical system that obviates many of the difficulties associated with studying the complex morphology of the brain.

Animals↗
PubMed1989

Pathogenesis of venous ulceration in relation to the calf muscle pump function.

Air plethysmography has been used to quantitate venous reflux by measuring the average filling rate of the veins (venous filling index; in milliliters per second) on standing from the supine position, the ejection fraction of the calf muscle pump as a result of one tip-toe movement, and the residual volume fraction after 10 tip-toe movements. Thirty normal limbs, 110 limbs with primary varicose veins, 34 limbs with reflux in the deep veins but without occlusion, and 31 limbs with deep venous occlusion, with or without reflux, have been studied. An increase in the incidence of ulceration occurred with increasing values of reflux and decreasing values of the calf muscle pump ejection fraction. A poor ejection fraction was the primary cause of venous ulceration in limbs with minimal reflux. A good ejection fraction, however, significantly reduced the incidence of ulceration in limbs with marked reflux (p less than 0.05). The residual volume fraction, which expresses the combined effect of venous reflux and ejection fraction with rhythmic exercise, showed a good correlation with the incidence of ulceration and the measurements of ambulatory venous pressure (r = 0.81). The air-plethysmographic measurements completely assess the calf muscle pump function and provide an accurate method to identify the predominant hemodynamic factor (ejection fraction, reflux, or both) responsible for the clinical picture of the patient.

Adult↗
PubMed1988

Response of cerebral microvasculature to brain injury.

There is increasing evidence that there is a direct response of the cerebral microvasculature to head injury. We have investigated using SEM and TEM the response of microvessels within the white matter of the baboon brain to lateral head acceleration. There is rapid endothelial disruption and swelling of perivascular astrocytes near the sites of petechial haemorrhage. The formation of microvilli in all vessels reaches a peak at 6 h and extends at least 5 mm from the site of haemorrhage. The astrocyte response suggests a partial recovery by 6 h. The endothelial response is most marked in arterioles and venules and is maintained for 6 days after injury. We suggest there is a biphasic cerebrovascular response to brain injury. First there is rapid astrocytic swelling possibly correlated with transient disruption of the blood-brain barrier. This is followed by morphological changes in the endothelium of all vessels which are most marked in arterioles and venules and extend considerable distances throughout the neuropile. This response is discussed in the light of disruption of the blood-brain barrier.

Animals↗
PubMed1987

Mitomycin-C and metronidazole in the treatment of advanced renal-cell carcinoma.

Fifteen patients with advanced renal-cell carcinoma were treated with the combination of mitomycin-C 14-20 mg/m2 i.v. every 7 weeks and metronidazole 1,500 mg/m2 p.o. 12 and 1 h before and 6 and 24 h after the mitomycin-C. Of 12 patients evaluable for response, three (25%) responded with partial remissions. Myelosuppression did not appear to be increased over that seen with mitomycin-C alone. Pulmonary toxicity occurred in three patients and was fatal in two. The incidence of pulmonary toxicity was probably increased over that seen with mitomycin-C alone. Renal toxicity was also seen. Based on this small study, it was our feeling that this dose-schedule of metronidazole did not appear to result in enough of an augmentation of the efficacy of mitomycin-C against renal-cell carcinoma to justify the incidence of serious toxicity.

Adult↗
PubMed1982

Vitrectomy in ocular toxocariasis.

Subtotal pars plana vitrectomy was performed in four patients with chronic toxocaral endophthalmitis. In two instances, chronic intraocular inflammation proved unresponsive to intensive corticosteroid therapy, but improved dramatically following vitrectomy. In one patient, a dense retrolenticular membrane was removed, and intractable amblyopia was prevented. Vitrectomy relieved vitreoretinal traction involving the macula in two instances and cured a peripheral traction retinal detachment in a third. Information gleaned from these cases suggests new guidelines for the laboratory confirmation of ocular toxocariasis. Patients with toxocaral endophthalmitis may benefit from pars plana vitrectomy when chronic inflammation does not respond to medical measures or when such inflammation causes permanent structural changes that threaten or interfere with central vision.

Adolescent↗
PubMedDate not supplied

Fear of hypoglycemia: quantification, validation, and utilization.

Hypoglycemia can lead to various aversive symptomatic, affective, cognitive, physiological, and social consequences, which in turn can lead to the development of possible phobic avoidance behaviors associated with hypoglycemia. On the other hand, some patients may inappropriately deny or disregard warning signs of hypoglycemia. This study presents preliminary reliability and validity data on a psychometric instrument designed to quantify this fear: the hypoglycemic fear survey. The instrument was found to have internal consistency and test-retest stability, to covary with elevated glycosylated hemoglobin, and to be sensitive to a behavioral treatment program designed to increase awareness of hypoglycemia.

Adolescent↗