Biomedical subjects

D S Owens

Publications and source records attributed to D S Owens.

14 recordsLinked to original sources

PubMed2000

Prevention of complications resulting from endovascular carotid sacrifice: a retrospective assessment.

OBJECTIVE: To determine the protective effects of various periprocedural interventions in the prevention of cerebral ischemia as a complication of endovascular carotid sacrifice (ECS). METHODS: Thirty-two cases of ECS performed at our institution, between October 1987 and July 1998, were reviewed. Fifteen patients underwent superficial temporal artery-to-middle cerebral artery bypass surgery. In 21 patients, the carotid artery was occluded proximal to the target lesion; and in 11 patients, a lesion trapping procedure was performed. Six patients were prophylactically anticoagulated, 14 received antiplatelet agents prophylactically, and 12 received no pharmacoprophylaxis. RESULTS: Among the six patients who were anticoagulated, there were no embolic events. Embolic events affected 4 of 14 patients receiving prophylactic antiplatelet agents, 2 of 12 patients receiving no pharmacoprophylaxis, 1 of 11 patients who underwent a trapping procedure, and 5 of 21 patients whose carotid artery was occluded proximal to the target lesion. Postocclusion cerebral ischemia developed in 7 of 15 patients who underwent bypass surgery, and in 1 of the remaining 17. CONCLUSION: Superficial temporal artery-to-middle cerebral artery bypass did not protect against postocclusion cerebral ischemia after ECS in this series (P = 0.01). Although the small number of patients studied precludes statistical validity (P = 0.29), the trends suggest that antiplatelet agents provide no protection against postocclusion cerebral emboli after ECS. Prophylactic anticoagulation (P = 0.32) and lesion trapping (P = 0.12) may reduce the frequency of postocclusion embolic events after ECS; however, because of the small number of patients, statistical significance could not be demonstrated.

Aged↗

PubMed2000

Diurnal variations in the mood and performance of highly practised young women living under strictly controlled conditions.

The diurnal variation in a range of psychological functions and core body temperature were investigated in a series of studies involving a total of 24 highly practised young women who lived in a controlled environment and on a strictly regimented 24-hour routine for 6 or 7 days. Ten participants were exposed to the natural light/dark cycle (L/Dc) through windows, whereas the 14 remaining participants saw no daylight, but all had access to normal clock time. A battery of mood and performance tests was completed every 2 hours whilst awake (08:00-00:00), resulting in nine equally spaced measures per waking day. Average time of day (ToD) functions were calculated from the last 5 or 6 days spent in the controlled environment. Significant ToD effects were found for many of the variables taken although the nature of these effects differed across measures, with a 'post-lunch dip' being observed at 16:00 in some variables. Analysis of the standardized data established that all variables presented reliably different ToD functions to core body temperature, whilst factor analyses indicated possible relationships between the variables. It was concluded that those variables that exhibited diurnal variation showed trends that did not parallel those in core body temperature.

Adult↗

PubMed1998

Time of day effects in, and the relationship between, sleep quality and movement.

The study aimed to measure the effects of a 27-h 'day' sleep-wake regime on actigraphic and subjective sleep variables, and to examine the relationships between these variables. Nine subjects spent 30 days and nights in the laboratory. After sleeping 8 h for each of 8 nights, the subjects had an imposed 27-h 'day', for 18 'days', remaining in bed for 9 h on each sleep period. Sleep periods therefore started 3 h later each day, although subjects' circadian rhythms stayed entrained to 24 h, because subjects were not isolated from the natural light-dark cycle. Time asleep, subjective sleep efficiency and subjective sleep quality, but not movement during sleep, were found to be significantly affected by time of going to bed. There were significant decreases in movement during recovery sleeps following each of two episodes of 26 h sleep deprivation. Over the study there were significant within-subject correlations between subjective sleep quality and subjective sleep efficiency (rav = 0.65), movement during sleep and subjective sleep efficiency (rav = -0.48), and movement during sleep and subjective sleep quality (rav = -0.26). We conclude that sleep movement, despite its low within- and between-subjects variability, is nevertheless a statistically reliable, but weak, indicator of subjective sleep efficiency and quality.

Adult↗

PubMed1998

Transvenous embolization as the primary therapy for arteriovenous fistulas of the lateral and sigmoid sinuses.

PURPOSE: We report on the evolution in one institution from transarterial embolization for the treatment of dural arteriovenous fistulas of the lateral and sigmoid sinuses to the safer and more durable technique of transvenous endovascular therapy for the majority of these lesions. METHODS: Arterial, venous, and combined embolizations were performed for 24 fistulas of the lateral and sigmoid sinuses between August 1991 and December 1996. The patients were followed up clinically for 2 to 63 months, with a mean follow-up period of 30 months. RESULTS: Nine patients had arterial embolization without transvenous treatment: five of the nine had angiographic and clinical obliteration of their fistulas; two of the nine, with unusual lesions, required surgery; and the remaining two had recurrences and were not retreated. Seven patients had both arterial embolization and coil embolization (packing) of the dural sinuses, four after arterial embolization had failed to cure the lesions; in all seven, the fistulas were obliterated angiographically and clinically. Eight patients had only transvenous coil embolization of the dural sinuses; all eight were cured. One patient had minimal arterial embolization during the primary venous embolization procedure. Complications occurred in two patients, both related to arterial embolization with ethanol. CONCLUSION: Our experience suggests that arterial embolization of dural arteriovenous fistulas of the lateral and sigmoid sinuses is associated with a low cure rate and high rate of recurrence, whereas transvenous endovascular packing of the involved segment of the sinus results in a high cure rate that obviates arterial embolization or surgical excision in most cases.

Adult↗

PubMed1998

Histologic and morphologic comparison of experimental aneurysms with human intracranial aneurysms.

PURPOSE: Vein pouch aneurysms are the most commonly created experimental lesions in neuroendovascular research. We sought to determine whether an experimental aneurysm that is derived from a pancreatic elastase-digested arterial sac (EDASA) models the histology and morphology of human cerebral aneurysms more accurately than the vein pouch aneurysm does. METHODS: EDASAs were created in the common carotid arteries of four rabbits, and vein pouch aneurysms were created in the common carotid arteries of four pigs. Five recently ruptured human cerebral aneurysms were obtained at autopsy. Identical histologic preparations were made for all specimens, and a vascular pathologist performed blinded histologic analyses. Morphologic dimensions were measured with a micrometer at 40-fold magnification. RESULTS: In each human cerebral aneurysm, there was complete absence of internal elastic lamina and tunica media, and none showed evidence of mural inflammation or neointimal proliferation. Average wall thickness was 51 microm. All vein pouch aneurysms had a well-developed internal elastic lamina and tunica media, and all exhibited profound inflammation and neointimal proliferation. Average wall thickness was 290 microm. EDASAs were devoid of internal elastic lamina, their tunica medias were mildly atrophic, and the sac walls contained only mild inflammation and neointimal proliferation. Average wall thickness was 46 microm. CONCLUSIONS: EDASAs model the morphologic and histologic characteristics of human cerebral aneurysms more accurately than vein pouch aneurysms do.

Aneurysm↗

PubMed1998

Diurnal trends in mood and performance do not all parallel alertness.

OBJECTIVES: This study examined the hypothesis that alertness can be used to predict time-of-day effects on performance. METHODS: For 6 or 7 days the volunteers (24, highly practiced young women) were required to retire to bed at 0000 and were awakened at 0800. A battery of mood and performance tests was completed every 2 hours while the women were awake; the result was 9 equally spaced measures per day. Measures of mood, serial reaction time, and memory scanning were recorded. Rectal temperature was recorded continuously. RESULTS: After omitting the data from the first day to avoid any carry-over from the "first-night" effect on sleep, average time-of-day functions were calculated for each subject, for each variable, and were then z-transformed. Cross-correlations between the pooled time-of-day trends indicated that, while alertness was a reasonably good "predictor" of the simple perceptual-motor speed measures, it fared less well for some of the other measures. Two-way analyses of variance indicated that the time-of-day trend for all measures differed from that for alertness, although the magnitude of this difference varied substantially and, for some measures, was very largely due to the last reading of the day (0000). CONCLUSION: It is clear from these results that, while alertness may successfully "predict" variations in some measures of performance capability, and especially those of simple perceptual motor speed, care should be exercised in extrapolating to other performance measures.

Adolescent↗

PubMed1997

Blood glucose and subjective energy following cognitive demand.

Previous studies have found a small association between the level of blood glucose and subjective reports of energy in those sitting quietly. Given reports that both memory and attention are influenced by the level of blood glucose it was hypothesised that under conditions of cognitive demand there would be a stronger association between mood and blood glucose levels. In three studies, with three cognitive tasks, the Stroop Task, Rapid Information Processing Task, and a difficult test of hand-eye coordination, falling blood glucose was associated with feeling less energetic.

Adolescent↗

PubMed1997

Traumatic carotid artery dissection and pseudoaneurysm treated with endovascular coils and stent.

PURPOSE: To report a case of post-traumatic internal carotid artery dissection and pseudoaneurysm formation at the C-1 level successfully treated by a percutaneous endovascular technique. METHODS AND RESULTS: A 20-year-old female presented 72 hours after a motor vehicle accident with incomplete occulosympathetic paresis (Horner's syndrome), carotidynia, and leftsided 1.5-cm x 2.5-cm pseudoaneurysm at the C-1 level. Neuroradiologists embolized the pseudoaneurysm with Guglielmi detachable coils and controlled the dissection with placement of a Wallstent. CONCLUSIONS: This report illustrates successful percutaneous endovascular treatment of a carotid dissection and pseudoaneurysm near the base of the skull.

Accidents, Traffic↗

PubMed1996

A preliminary investigation into individual differences in the circadian variation of meal tolerance: effects on mood and hunger.

A forced desynchrony methodology was used to assess postprandial blood glucose in 9 female volunteers during a 3-h period following a mixed meal presented at four times of day (08:00, 14:00, 20:00, 02:00). The influence of time of day on the postmeal glucose responses was evaluated by calculating the area under the curve, largest increase, time taken to reach peak, and fasting level. Circadian variations in meal tolerance were found for the area under the curve and largest increase, responses were greater (indicating poorer meal tolerance) in the evening than the morning. Fasting blood glucose exhibited diurnal variation although in the opposite direction to meal tolerance; levels were higher in the morning than the evening. Time taken to reach peak levels was not modulated by circadian rhythmicity. Estimates of the timing of poorest meal tolerance and the magnitude of this intolerance were computed for each subject. Individual differences in the magnitude of meal intolerance were found to influence hunger and self-reported calmness. Subjects with good tolerance had rhythms in both calmness and hunger, which were not found in those with poor tolerance. Subjects with good tolerance also tended to rate themselves as feeling more calm. These mood and hunger effects may result from differences in insulin resistance, which is hypothesized to underlie the circadian variations in meal tolerance.

Adult↗

PubMed1994

Blood glucose influences memory and attention in young adults.

There is evidence from animal studies that increased blood glucose levels are associated with improved memory and attention. Although previous studies have found human memory to be facilitated by the administration of glucose, attentional measures have been largely ignored. Therefore the impact of a glucose drink, or a placebo, on the Rapid Information Processing Task and the Stroop Task was examined. The reaction times of those taking the Rapid Information Processing Task were faster both during the baseline period and after a glucose drink if the blood glucose values were high. With the Stroop task the ability to perform the most cognitively demanding sub-test was selectively enhanced if blood glucose values were increasing prior to starting the test. The ability to recall words from a word list was greater if a glucose drink had been consumed, although primary and recency were not differentially influenced. The possibility is discussed that higher levels of brain glucose are associated with better memory and attention.

Adult↗

PubMed1994

The impact of raising blood glucose on reaction times.

Although previous studies have demonstrated enhanced mood and memory in humans following the consumption of glucose drinks, the effect of increasing blood glucose levels on other tasks has not received the same attention. In the present study, inspection time was unaffected by glucose drinks and blood glucose levels. However, increasing blood glucose levels resulted in faster decision times when reaction time was measured. It is concluded that speed of processing is faster when the availability of glucose to the brain is increased. The possibility that the glucose-induced improvements in reaction time reflect an increased synthesis of acetylcholine is discussed.

Adolescent↗

PubMed1993

Blood glucose and human memory.

As it has been suggested that blood glucose might play a role in the action of some cognitive enhancing drugs, the influence of glucose containing drinks on human memory was examined. In a double-blind study the influence was examined of a drink containing 50 g glucose, or a placebo, on the ability to recall a word list. There was a significant correlation between blood glucose values and the number of words recalled. Those whose blood glucose levels were increasing remembered significantly more words than those whose blood glucose levels were falling. No relationship was found between blood glucose and performance on a test of spatial memory. In a second study blood glucose levels were raised for 2 h by taking a series of glucose-containing drinks. The number of words recalled from a word list correlated significantly with blood glucose levels but not with recall of a Wechsler story. The glucose-induced improvement in memory did not occur only in those whose blood glucose levels were initially low; rather it occurred irrespective of initial blood glucose level.

Adult↗

PubMedDate not supplied

Cryptosporidium andersoni n. sp. (Apicomplexa: Cryptosporiidae) from cattle, Bos taurus.

A new species of Cryptosporidium is described from the feces of domestic cattle, Bos taurus. Oocysts are structurally similar to those of Cryptosporidium muris described from mice but are larger than those of Cryptosporidium parvum. Oocysts of the new species are ellipsoidal, lack sporocysts, and measure 7.4 x 5.5 microm (range, 6.0-8.1 by 5.0-6.5 microm). The length to width ratio is 1.35 (range, 1.07-1.50). The colorless oocyst wall is < 1 microm thick, lacks a micropyle, and possesses a longitudinal suture at one pole. A polar granule is absent, whereas an oocyst residuum is present. Oocysts were passed fully sporulated and are not infectious to outbred, inbred immunocompetent or immunodeficient mice, chickens or goats. Recent molecular analyses of the rDNA 18S and ITS1 regions and heat-shock protein 70 (HSP-70) genes demonstrate this species to be distinct from C. muris infecting rodents. Based on transmission studies and molecular data, we consider the large form of Cryptosporidium infecting the abomasum of cattle to be a new species and have proposed the name Cryptosporidium andersoni n. sp. for this parasite.

Animals↗

PubMedDate not supplied

Thromboembolic complications after inferior petrosal sinus sampling in patients with cushing's syndrome.

OBJECTIVE: To heighten the awareness of treating physicians of the potential for serious and fatal thromboembolic complications after inferior petrosal sinus sampling in patients with Cushing's syndrome. METHODS: We retrospectively reviewed inpatient and outpatient medical records for a 12-year period to identify patients with Cushing's syndrome who had thromboembolic complications after inferior petrosal sinus sampling at a single institution. Case reports of affected patients are presented. RESULTS: Of 34 patients with corticotropin-dependent Cushing's syndrome who underwent inferior petrosal sinus sampling, 2 had deep venous thrombosis. One of these patients succumbed to pulmonary thromboembolism. CONCLUSION: Serious and potentially fatal thromboembolic disorders may complicate inferior petrosal sinus sampling. Prospective studies should be undertaken to determine the true incidence of deep venous thrombosis after this procedure in patients with Cushing's syndrome.

Journal Article↗