Thermal method for continuous measurement of cerebral perfusion

A new thermal system using constant heating power for continuous measurement of cerebral perfusion is presented. It is designed and implemented for optimal perfusion sensitivity and dynamic response based on heat-transfer analysis of perfused brain tissue with thermistors on the cortical surface. Two matched thermistors are used, one to serve as a perfusion sensor and the other to compensate for the base-line temperature changes. To improve the signal-to-noise ratio of the measurement system, lock-in amplifiers are used to minimise long-term drift and low-frequency noise. Errors in the measurement caused by electrical and thermal fluctuations are tested and analysed. In vitro tests show that the measurement accuracy of temperature change is better than 10(-3) degrees C, and the temperature resolution is even greater. In vivo evaluation confirms that the system is responsive to cerebral perfusion changes associated with sudden changes in mean arterial blood pressure caused by bolus injection of norepinephrine, blood withdrawal and blood infusion. The dynamic response of the system is sufficient to detect the autoregulatory perfusion changes in response to arterial blood pressure alteration and the oscillations of cerebral blood flow.

Mucosal interleukin-6 secretion in ulcerative colitis. Effects of anti-inflammatory drugs and T-cell stimulation

BACKGROUND

We have studied modulation of mucosal interleukin-6 (IL-6) secretion by T-cell activation and by anti-inflammatory agents in inflammatory bowel disease.

METHODS

In vitro secretion of IL-6 by biopsy specimens from patients with active ulcerative colitis was investigated in the presence of cyclosporin-A (CsA) and drugs that have other anti-inflammatory actions. Biopsy specimens from patients with quiescent ulcerative colitis or controls were stimulated with anti-CD3 antibody to activate mucosal T cells.

RESULTS

Stimulation of control specimens increased IL-6 secretion (median increase, 147%; p < 0.003), which was prevented by CsA. In quiescent ulcerative colitis there was enhanced spontaneous secretion of IL-6 but a smaller, non-significant increase after T-cell activation (125%). Dexamethasone inhibited secretion in active ulcerative colitis (p < 0.006). 5-Aminosalicylic acid, 6-mercaptopurine, methotrexate, and indomethacin had no effect. There also tended to be a small reduction with CsA, but this just failed to reach statistical significance.

CONCLUSIONS

In quiescent ulcerative colitis the enhanced spontaneous secretion of IL-6 may be a consequence of mucosal T-cell or macrophage activation: the smaller increase after T-cell stimulation suggests that one or both of these two cell types are already pre-activated.

Magnetic resonance diffusion-weighted imaging: sensitivity and apparent diffusion constant in stroke

Magnetic resonance diffusion-weighted imaging (MR-DWI) is sensitive to the diffusibility of water and may offer characterization and anatomical localization of stroke leading to early tailored therapeutic intervention. We compared DWI, the apparent diffusion constant (ADC), and autoradiographic cerebral blood flow (CBF) in a model of focal cerebral ischemia in the rat. Sprague-Dawley rats were embolized with a single silicone cylinder injected into the internal carotid artery. Both common carotids were permanently ligated. The animals were anesthetized (isoflurane in O2), and paralyzed (gallamine). MR-DWI were obtained with a GE 4.7 T magnet (TE = 3 s, TR = 80 msec, b = 2393.10(-3) mm2/s, slice thickness 3 mm). DWI and CBF autoradiograms were compared visually. ADC was assessed in various regions, including ischemic cortex and a region homologous to ischemic cortex. Imaging times from stroke onset were 50 +/- 6 min (mean +/- SEM) for DWI, 185 +/- 17 min for a second DWI. CBF was determined at 258 +/- 15 min. The specificity was 100% at both 50 min and 185 min, indicating that there were no false positives; in 3 animals ischemia was not present. However, the sensitivity analysis indicated that early DWI yields some false negatives; at 50 min the sensitivity was 60%. We attribute our result of low early sensitivity to small infarcts in relation to the slice thickness. Later, at 185 min, sensitivity was 100%. The first ADCs were higher than the second ADC values in ischemic cortex. For infarcts larger than the slice thickness, early MR-DWI is highly sensitive for imaging evolving ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a cognitive behavioural programme for rehabilitating patients with chronic pain

The aim of this prospective longitudinal study was to evaluate an inpatient cognitive behavioural pain management programme for patients with chronic pain. A physical and psychological assessment of patients was carried out before and after treatment, and at one and six months follow up. A total of 212 patients with disabling chronic pain of mean duration 10.5 years, for whom no further medical or psychiatric treatment was appropriate or available, were admitted; their mean age was 50 years and 65% were women. The four week programme was delivered by a multidisciplinary team of two psychologists, a physiotherapist, nurse, occupational therapist and anaesthetist. The main components of therapy included: education, teaching behavioural and cognitive skills, a stretch and exercise programme, medication reduction, goal setting and pacing, and relaxation training. Outcome measures assessed quality of life, physical performance (for example walking speed), pain intensity and distress, depression severity and confidence. Assessment immediately after treatment revealed significant improvements on all measures. Improvements were well maintained at six month follow up. Cognitive behavioural treatment can be of value in improving the day-to-day functioning and quality of life of patients with chronic pain for whom conventional medical treatments have apparently failed.

Expression of interleukin-6 by intestinal enterocytes

AIMS

To investigate the cellular source of the cytokine interleukin-6 (IL-6) in the small and large intestines of patients with inflammatory bowel disease, coeliac disease, and in controls.

METHODS

IL-6 was detected in frozen sections of bowel by single and double label indirect immunofluorescence using rabbit polyclonal and murine monoclonal anti-IL-6 antibodies. The murine monoclonal antibodies RFDR1 (anti-MHC class II) and UCHT1 (anti-CD3) were used to localise macrophages and T lymphocytes, respectively. Lipopolysaccharide stimulated peripheral blood monocytes were used as positive control cells for IL-6 protein.

RESULTS

IL-6 was demonstrated in the small and large intestine of patients with inflammatory bowel disease, coeliac disease, and in controls. The protein was present predominantly in enterocytes and colocytes in normal and inflamed mucosa, but not in the infiltrating inflammatory cells of the lamina propria. There were no discernable differences between patients with inflammatory bowel disease or coeliac disease and controls, nor between small and large bowel mucosa. Incubation of antibody with recombinant human IL-6 protein abolished the labelling. IL-6 protein was also present in lipopolysaccharide stimulated peripheral blood monocytes.

CONCLUSIONS

The data suggest that enterocytes and colocytes may play an active part in the immune response of the gut. The presence of IL-6 in both inflamed and non-inflamed small and large intestine requires further investigation into the function of this cytokine in the gut.

Serum interleukin-8 in inflammatory bowel disease

To investigate the relationship between serum concentrations of interleukin-8 (IL-8) and disease activity in inflammatory bowel disease, serum IL-8 concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in 93 patients. Interleukin-8 levels were compared with plasma interleukin-6 (IL-6) levels in 80 of these patients. Interleukin-8 levels were also measured in ten patients with active Crohn's disease, before and after treatment with a defined formula polymeric diet. Of these patients, 70 out of 93 IL-8 concentrations were below the detection limit of the assay. Levels were higher in patients with active ulcerative colitis (median < 20 pg/mL, 75th centile value = 190) compared with inactive disease (median and 75th centile value < 20; P < 0.05). Interleukin-8 concentrations correlated with a combined score for disease severity and extent (P = 0.01). Thirty-eight per cent (8/20) of patients with active Crohn's disease also had high levels of IL-8 but there was no significant difference between active and inactive disease. There was no correlation between serum IL-8 and plasma IL-6; on the contrary, very few patients had raised blood levels of both cytokines. In the diet treated group, serum IL-8 fell significantly after treatment (median = 37 pg/mL, range < 20-4615 before treatment, median < 20, range < 20-104 after treatment; P = 0.03). The results suggest that although IL-8 may be involved in the inflammatory process in inflammatory bowel disease, it is a poor marker of disease activity.

Validation of continuous thermal measurement of cerebral blood flow by arterial pressure change

A thermal measurement system to monitor cerebral blood flow (CBF) continuously from the cortical surface is evaluated in vivo. It has a temperature resolution of better than 0.001 degrees C (1 m degrees C) and can compensate for baseline temperature fluctuations in the brain tissue. A new approach has been developed to test the capability of monitoring dynamic CBF response. Transient CBF changes associated with changes in mean arterial blood pressure (MABP) caused by repeated bolus norepinephrine injections are used to examine the response of the measurement system in both the heated mode, sensitive to flow, and the unheated mode, sensitive only to temperature. Experiments on 13 rats demonstrate that changes in the MABP are closely correlated with those of temperature difference in the heated mode. Regression analysis shows a mean slope of 0.9 m degrees C/mm Hg in the heated mode, which is significantly different from zero (p < 0.002) and from the mean slope in the unheated mode (p < 0.002). This indicates that flow signal in the system output can be distinguished from the baseline thermal fluctuations. Thus, the system can be used to detect and study dynamic perfusion changes from the brain surface with minimal tissue damage. Furthermore, analysis of the data shows that the transient flow signal before autoregulation is linearly correlated with changes in MABP.

A patient knowledge questionnaire in inflammatory bowel disease

A multiple choice knowledge questionnaire was developed for patients with inflammatory bowel disease (IBD). Initially, 20 questionnaires were piloted, and then questions of poor discriminatory ability (> 75% patients giving a correct response) were eliminated. A second pilot study proved the internal consistency (coefficient alpha = 0.84) and the stability of the questionnaire using a test-retest method (Spearman R = 0.86, p = 0.002). The questionnaire was then completed by 60 randomly selected patients attending colitis clinic. The mean score was 13 of a total of 36 (range 2-29). Eighty percent of patients wished to know more about their disease. Knowledge score was higher in patients who were members of the National Association of Crohn's Disease and Colitis (NACC) (p < 0.005) and in patients with Crohn's disease (CD) rather than ulcerative colitis (UC) (p < 0.005). Knowledge score correlated with the number of years spent in full-time education (R = 0.48, p < 0.001) and inversely with age (R = -0.33, p < 0.02) but did not correlate with disease duration. The study demonstrated some misunderstandings about IBD although most patients would have liked more information. The questionnaire could be used as a tool to evaluate patient education programs.

Evidence that heterogeneity of cerebral blood flow does not involve vascular recruitment

Recent studies indicate that blood flow to cerebral cortex is not homogeneous but may vary both spatially and temporally. In addition, some investigators have reported that capillaries and arterioles can be recruited to increase cerebral blood flow, an issue that is extremely controversial. The goal of this study was to determine whether recruitment of cerebral blood vessels is an important mechanism in spatial and temporal heterogeneity of cerebral blood flow. In seven anesthetized ventilated rats, different fluorescent tracers were injected 45 and 10 s before decapitation. In addition, [14C]iodoantipyrine also was injected 10 s before decapitation. After the brains were sectioned, fields in the cerebral cortex were examined microscopically for fluorescence and processed for measurement of cerebral blood flow with techniques of quantitative autoradiography and image analysis. With examination of 24 +/- 2 (SE) points in cerebral cortex of each rat, similar numbers of small blood vessels (< or = 10 microns) were counted that contained fluorescent tracers injected 45 and 10 s before decapitation (346 +/- 48 and 355 +/- 42 vessels/mm2, respectively; P > 0.05). Large blood vessels (20-60 microns; 73 +/- 6 vessels in each rat) contained both fluorescent tracers. In addition, adjacent regions of high and low blood flow contained similar numbers of small and large vessels. Our findings indicate that vascular recruitment is not an important mechanism in temporal or spatial heterogeneity of cerebral blood flow.

Cardiovascular changes during focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

Recent studies have suggested that cerebral infarction influences autonomic activity and may contribute to sudden death. The goal of this study was to examine effects of focal cerebral infarction on mean arterial pressure and heart rate.

METHODS

Halothane-anesthetized rats were assigned to two groups: stroke (n = 10), in which the middle cerebral artery or an adjacent vessel was embolized with a silicone cylinder, and sham (n = 8), in which rats were sham embolized (saline). Arterial pressure and heart rate were measured for 90 minutes and again 24 hours after vascular occlusion. A change in electroencephalographic amplitude of -45% after embolization was used to determine if a significant degree of infarction was present.

RESULTS

Vascular occlusion produced a significant increase in mean arterial pressure at 10, 60, and 90 minutes (p < 0.05). Changes in heart rate were significantly greater (p < 0.05) than in sham-treated rats at 10 and 30 minutes after embolization. In contrast, mean arterial pressure and heart rate measured 24 hours after embolization were similar in both groups. Anatomic analysis of the infarcted areas demonstrated that either insular cortex or amygdala was affected in all embolized rats.

CONCLUSIONS

This study indicates that cerebral infarction produces a transient elevation of mean arterial pressure and heart rate. However, within 24 hours both parameters returned to preinfarcted levels. Our findings are consistent with clinical reports that indicate that mean arterial pressure and heart rate of stroke patients are similar to those of other groups when they are admitted to the hospital, although other cardiovascular parameters are greatly altered.

Transcranial Doppler assessment of cerebral perfusion reserve in patients with carotid occlusive disease and no evidence of cerebral infarction

Using transcranial Doppler ultrasound (TCD), we measured bilateral middle cerebral artery mean blood flow velocities (MCAVs) before and 10 minutes after intravenous infusion of 1 gram of acetazolamide in 20 patients without cerebral infarction. Seven patients had normal carotid arteries (group 1), seven had unilateral internal carotid artery (ICA) stenosis > or = 75% (group 2), and six had unilateral ICA occlusion (group 3). Before acetazolamide infusion, side-to-side differences in MCAV were 0.06 cm/sec in group 1 (p = 0.98), 4.3 cm/sec in group 2 (p = 0.36), and 15.0 cm/sec in group 3 (p = 0.02). Bilateral MCAV increased in all three groups after acetazolamide infusion, and the side-to-side differences in MCAV were 3.2 cm/sec in group 1 (p = 0.40), 11.4 cm/sec in group 2 (p = 0.04), and 27.6 cm/sec in group 3 (p = 0.03). Patients with carotid stenosis or occlusion and ipsilateral transient ischemic attacks (TIAs) had higher side-to-side differences in MCAV before (p = 0.03) and after (p = 0.01) acetazolamide than did asymptomatic patients with carotid disease. The association of impaired cerebral perfusion reserve and TIAs suggests that the TCD-acetazolamide test may enable identification of a subgroup of patients with carotid occlusive disease who are at higher risk for stroke.

Hydroxyethyl starch 200/0.5 reduces infarct volume after embolic stroke in rats

BACKGROUND AND PURPOSE

We evaluated isovolumic hemodilution with hydroxyethyl starch 200/0.5 in a rat model of focal cerebral ischemia. This compound avoids the unfavorable viscosity and erythrocyte aggregation abnormalities of low molecular weight dextran during administration over a period of several days.

METHODS

Sprague-Dawley rats, anesthetized with 0.5-1% halothane and 70% N2O, were subjected to silicon cylinder (treated and control groups) or sham (sham group) embolization of the cerebral circulation. Thirty minutes after embolization, the treated group (n = 5) was infused with 11 ml/kg of 10% hydroxyethyl starch 200/0.5, and the control (n = 5) and sham (n = 4) groups were infused with saline for 1 hour. In the treated group, 7.1 ml/kg of blood was withdrawn. After 24 hours, the animals were reanesthetized, and cerebral blood flow was determined with [14C]iodoantipyrine. Alternative brain slices were either incubated with 2,3,5-triphenyltetrazolium chloride for infarct volume determination or frozen for ischemic volume and cerebral blood flow determination using autoradiography.

RESULTS

The hematocrit in the treated group was reduced from (mean +/- SEM) 46 +/- 1% to 35 +/- 2% at 1.5 hours (p < 0.01). Cortical blood flow was within the normal range of 115-185 ml/min/100 g, except for the ischemic cortex in the embolized groups, treated and control. The ischemic and infarct volume of the treated group was reduced by 74% (p < 0.05) and 89% (p < 0.05), respectively, from the control group. The treated and sham ischemic and infarct volumes were not statistically different.

CONCLUSIONS

These data suggest that hydroxyethyl starch 200/0.5 could be an effective treatment for ischemic stroke when administered early, because it reduces infarct and ischemic volumes from control values to levels indistinguishable from those of the sham group.

Abdominal migraine: a cause of abdominal pain in adults?

Eighty-five patients with non-organic abdominal pain, were interviewed with the help of a questionnaire. Those who responded to a high fibre diet were excluded from the study. Twenty-seven patients had multiple pains and 58 described a single pain, which was intermittent in 39. A detailed analysis of the symptoms and family history of the latter group suggested that in 19 patients the symptoms might have been caused by abdominal migraine. Six of these 19 had typical migraine-associated symptoms during the attack, characteristic abdominal pain and a family or personal history of classical migraine. Abdominal migraine should be considered in patients with non-organic abdominal pain where symptoms are not typical of irritable bowel syndrome and when organic disease has been excluded.

Familial visceral myopathy. A family with involvement of four generations

A family with the autosomal dominant form of familial visceral myopathy is described involving four generations. The members illustrate several different clinical presentations including severe constipation, diarrhea, alternating constipation and diarrhea, volvulus, urinary tract infection, and retention of urine. One patient's history suggested that the uterus may have been involved. Diagnosis of this rare disease requires an awareness of the variable presentation and a careful histological examination of full-thickness sections of bowel. The potential pitfalls in both histological and clinical diagnosis of this condition are demonstrated in this family's history. The extensive involvement of small and large bowel in at least two family members is unusual in the autosomal dominant form of the disease, but their course has so far been favorable, lending further evidence to the impression that prognosis is good. This is of importance for genetic counseling of families who have this very rare disease.

Neurologic complications related to cardiac surgery

Neurologic complications are a major cause of morbidity, complicating open heart surgery, cardiac catheterization, and interventional techniques. Global or focal brain ischemia related to embolism or hypoperfusion predominates. Breakthrough cerebral hemorrhage and infection can complicate cardiac transplantation. Identifying individuals at risk for cerebrovascular complications may lead to more effective preventative and treatment measures.

Plasma viscosity in inflammatory bowel disease

AIMS

To assess the relation of plasma viscosity to disease activity in patients with inflammatory bowel disease.

METHODS

Crohn's disease (n = 60) and ulcerative colitis (n = 71) were diagnosed on the basis of typical histological or radiological features. Active Crohn's disease was defined as a Crohn's disease activity index of 150 or over. Active ulcerative colitis was defined as a liquid stool passed three times a day or more with blood. Blood samples were assessed for haemoglobin concentration, total white cell count, platelets, plasma viscosity, erythrocyte sedimentation rate, serum albumin, and C-reactive protein.

RESULTS

Plasma viscosity was higher in those with active Crohn's disease compared with those with inactive Crohn's disease or active ulcerative colitis. Plasma viscosity correlated significantly with erythrocyte sedimentation rate, C-reactive protein, and platelet count in patients with Crohn's disease. In ulcerative colitis plasma viscosity correlated only with serum C-reactive protein. Plasma viscosity showed a low sensitivity for detecting active Crohn's disease, with 48% of those with active disease having a plasma viscosity within the laboratory reference range.

CONCLUSIONS

Plasma viscosity is related to disease activity in Crohn's disease, but is insufficiently sensitive for it to replace erythrocyte sedimentation rate as a measure of the acute phase response in Crohn's disease.

Abdominal migraine: does it exist?

Abdominal migraine is well recognised in children, but in spite of anecdotal reports migraine is not well established as a cause of abdominal pain in adults. Functional abdominal pain is usually classified as either irritable bowel syndrome or nonulcer dyspepsia, but some patients have intermittent abdominal pain associated with headache or other migraine accompaniments and, in these, a diagnosis of abdominal migraine should be considered. It is possible that some patients with functional abdominal pain have migraine presenting with few or even no migraine accompaniments. There is no nonclinical objective standard for diagnosing migraine, and research in this area is therefore very difficult. Nevertheless, some patients with functional abdominal pain may respond to antimigraine medication and, if their symptoms are suggestive, a trial of therapy may be desirable.

Effect of topical recombinant TGF-beta on healing of partial thickness injuries

Peptide growth factors produced by platelets, macrophages, epidermal, and dermal cells may play key roles in regulating healing of partial-thickness skin wounds. We examined the effects of recombinant transforming growth factor beta (TGF-beta) on cultures of epidermal and dermal cells in vitro and on healing of partial-thickness injuries in vivo. Increasing concentrations of TGF-beta (0.1, 1, and 10 ng/ml) progressively inhibited serum-stimulated DNA synthesis by up to 95% in cultures of adult human keratinocytes during 48 hr of exposure to TGF-beta. In contrast, TGF-beta (10 and 100 ng/ml) in serum-free media stimulated DNA synthesis by up to 80% compared to serum-free control cultures of adult human dermal fibroblasts. To evaluate the effects of TGF-beta on healing of partial-thickness injuries in vivo, wounds (20 x 20 x 0.6 mm) were created on the dorsal thoracolumbar region of adult pigs by an electrokeratome and were treated daily for 5 days after injury with vehicle or vehicle containing 0.1 or 1 microgram/ml TGF-beta and covered with occlusive dressing. Computerized planimetry of wound photographs demonstrated that TGF-beta treatment stimulated statistically significantly increases in the area of regenerated epidermis compared to wounds treated with saline vehicle on Days 3, 4, 5, and 7 after injury probably due to TGF-beta increasing the rate of epidermal cell migration. In addition, morphometry of biopsy specimens showed that TGF-beta treatment stimulated statistically significant increases in the cross-sectional depths of regenerated dermis compared to wounds treated with saline or Silvadene vehicles on Days 5, 6, and 8 after injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of freezing time when iodoantipyrine is used for measurement of cerebral blood flow

The goal of the present study was to determine effects of delay of freezing of the brain on distribution of [14C]iodoantipyrine in the brain. Blood flow to parietal cerebral cortex (CBF) and choroid plexus was measured with the indicator fractionation technique and quantitative autoradiography. After injection of iodoantipyrine, each rat was decapitated, and the head was immersed in chlorodifluoromethane (-40 degrees C). The brain was removed from the skull after it was frozen. In some rats, heads were immersed immediately after decapitation, and CBF was markedly heterogeneous. In another group, heads were frozen 3 min after decapitation. In this case, CBF was uniform in its distribution. Average CBF was similar in groups with immediate and delayed freezing (90-104 ml.min-1 x 100 g-1). In contrast, delays in freezing decreased blood flow to choroid plexus from 551 +/- 115 to 261 +/- 48 ml.min-1 x 100 g-1. Our findings indicate that immediate freezing of the brain after decapitation is necessary to prevent diffusion of iodoantipyrine from regions of high blood flow to regions of lower blood flow and underestimations of blood flow in regions with high blood flow.

Vascular responses of choroid plexus during hypercapnia in rats

The response of blood flow to choroid plexus (CPBF) during hypercapnia is controversial. The goal of this study was to determine the effect of hypercapnia on CPBF in unanesthetized rats. Rats breathed air or a mixture of 5-8% CO2 in air, and CPBF was measured with [14C]isopropyliodoamphetamine and quantitative autoradiography. In hypercapnic rats [arterial PCO2 61.6 +/- 1.6 (SE) mmHg; n = 7] CPBF was similar to that of normocapnic control rats (525 +/- 39 ml.min-1.100 g-1; arterial PCO2 42.7 +/- 0.6 mmHg; n = 5). In contrast, blood flow to cerebral cortex increased 67% during hypercapnia. CPBF in normocapnic rats that were treated with phentolamine was similar to untreated normocapnic and hypercapnic rat CPBF. However, during hypercapnia, CPBF in phentolamine-treated rats increased 29%. Responses were similar in blood flow to choroid plexus of lateral, third, and fourth ventricles. Our findings indicate that hypercapnia has no effect on CPBF when alpha-adrenergic receptors are intact. In contrast, after blockade of alpha-adrenergic receptors, hypercapnia increases CPBF. These findings suggest that, during hypercapnia, levels of sympathetic activity or blood-borne catecholamines are increased that prevent increases in CPBF.

Isovolumic hemodilution with dextran 40 in the rat: effect on the development of peripheral edema and various physiologic parameters

Low molecular weight dextran 40 (D40), 40,000 daltons, is a potential therapeutic agent for cerebral ischemia because it increases local cerebral blood flow. However, the evaluation of D40 in the rat has been difficult due to systemic effects. We evaluated the effects of isovolumic hemodilution with D40 on the development of peripheral edema, mean arterial pressure, hematocrit (Hct) and total blood volume in 18 rats, during 30 min or 4 hr i.v. infusions, in animals with and without previous challenge with D40. Reduction of Hct without peripheral edema to a mean of approximately 31% was only achieved in the animals challenged with i.p. D40 24 hr before hemodilution and who received D40 over a period of 4 hr. Infusion of D40 over a period of 30 min was associated with shorter survival time, compared to the 4-hr infusion group (P less than .005). In the pretreated, rapidly infused group, total blood volume per body weight decreased significantly over time (P less than .005) and the mean arterial blood pressure dropped, but not significantly (P less than .07), whereas no change in Hct was detected and there was a trend toward increased peripheral edema, relative to the slowly infused groups. We conclude that reduction of Hct can be achieved successfully with i.p. administration of D40 24 hr before the study combined with infusion of the agent during a 4-hr period, without significant peripheral edema and early hypotension. This procedure should be used to avoid allergic reactions when evaluating hemodilution with D40 in rats.

Cerebral blood flow with the indicator fractionation of [14C]iodoantipyrine: effect of PaCO2 on cerebral venous appearance time

The indicator fractionation technique using a diffusible indicator as a tracer for the determination of CBF has been used for numerous investigations of the cerebral circulation and its pathophysiology. The diffusible tracer is "trapped" in the brain based on the proper delay between tracer injection and cessation of the cerebral circulation by decapitation before the appearance of the tracer in the cerebral venous circulation. If this delay is too long, the quantitative assumption of the indicator fractionation technique will not be met, and CBF values will be underestimated. In 13 Sprague-Dawley rats anesthetized with pentobarbital, the appearance of [14C]iodoantipyrine at the torcular was assessed as a function of PaCO2. An inverse linear relationship between PaCO2 (in millimeters of mercury) and cerebral venous appearance, Ta (in seconds), was established with the regression equation Ta = -0.0842.PaCO2 + 12.3 (R2 = 0.70, slope significantly different from zero, p less than 0.001). Ta varied between 5 and 12 s and PaCO2 varied between 84 and 18 mm Hg, respectively. Thus, in low-flow states, the decapitation time may be lengthened to 12 s, whereas in high-flow states, the time must be 5 s to eliminate the possibility of backflux of tracer out of the brain.

The role of unemployment in parasuicide

Sixty-four in-patient cases of deliberate non-fatal self-poisoning were compared for psychosocial problems in a case-control study with a similar number of individually matched community controls. A strongly significant association was found between unemployment and self-poisoning. Further analysis revealed no firm evidence to support the hypotheses that unemployment was causally related to self-poisoning in an indirect manner or that it increased the vulnerability of individuals who self-poison to other stressful life events and difficulties. It is concluded that a possible explanation is that some third factor independently increases the risk of both unemployment and self-poisoning, giving rise to a non-causal relationship between these last two variables.

Prevalence and follow-up of abnormal thyrotrophin (TSH) concentrations in the elderly in the United Kingdom

Increasing use of assays for TSH with improved sensitivity as a first-line test of thyroid function has raised questions regarding prevalence and clinical significance of abnormal results, especially values below normal. We have assessed the thyroid status of 1210 patients aged over 60 registered with a single general practice by measurement of serum TSH using a sensitive assay. High TSH values were more common in females (11.6%) than males (2.9%). TSH values below normal were present in 6.3% of females and 5.5% of males, with values below the limit of detection of the assay present in 1.5% of females and 1.4% of males. Anti-thyroid antibodies were found in 60% of those with high TSH but only 5.6% of those with subnormal TSH. Eighteen patients were hypothyroid (high TSH, low free thyroxine) and one thyrotoxic (low TSH, raised free thyroxine) at initial testing. Seventy-three patients with elevated TSH but normal free T4 were followed for 12 months; 13 (17.8%) developed low free T4 levels and commenced thyroxine, TSH returned to normal in four (5.5%) and 56 (76.7%) continued to have high TSH values. Sixty-six patients with TSH results below normal were followed. Of the 50 subjects with low but detectable TSH at initial testing, 38 (76%) returned to normal at 12 months; of those 16 with undetectable TSH followed, 14 (87.5%) remained low at 12 months. Only one subject (who had an undetectable TSH) developed thyrotoxicosis. In view of the marked prevalence of thyroid dysfunction in the elderly, we suggest that screening of all patients over 60 should be considered.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimal design of a thermistor probe for surface measurement of cerebral blood flow

Microthermistors are put on the surface of cerebral cortex to monitor local cerebral blood flow (CBF) continuously with minimal tissue damage and disturbance to the normal physiological state. Using a distributed, dynamic model of the measurement system, we simulated the effects of this flow measurement method under isothermal and adiabatic boundary conditions. Numerical results show that the adiabatic boundary condition can provide maximal sensitivity to perfusion changes at physiological perfusion levels. The constant power and constant temperature operating modes are compared in terms of output relation, sensitivity, and frequency response through analytical and numerical solutions. While the steady-state relations between thermistor measurements and perfusion for the two modes do not differ significantly, the constant temperature mode has better frequency response. Analytical results show that the relative sensitivity is the same for the two modes and is approximately proportional to the radius of thermistor. If there is an unperfused layer surrounding the thermistor, the sensitivity will decrease as the thickness of the layer increases. Simulations predict that the thermal measurement has a low-pass frequency response and the cutoff frequency is inversely proportional to the probe surface area. The results provide a theoretical foundation to the optimal design of thermistor probe for continuous CBF measurement from tissue surface.

Vascular pressures and cortical blood flow in cavernous angioma of the brain

This study was designed to investigate the hemodynamic characteristics of cavernous angiomas of the brain. Five adult patients with a cavernous angioma underwent local cortical blood flow studies and vascular pressure measurements during surgery for the excision of the cavernous angioma. Clinical presentation included headache in four patients, seizures in four patients, and recurring diplopia in one patient. Magnetic resonance imaging demonstrated the cavernous angiomas in all patients and revealed an associated small hematoma in two. Four patients with a cerebral cavernous angioma were operated on in the supine position and the remaining patient, whose lesion involved the brain stem, was operated on in the sitting position. Mean local cortical blood flow (+/- standard error of the mean) in the cerebral cortex adjacent to the lesion was 60.5 +/- 8.3 ml/100 gm/min at a mean PaCO2 of 35.0 +/- 0.6 torr. Mean CO2 reactivity was 1.1 +/- 0.2 ml/100 gm/min/torr. The local cortical blood flow results were similar to established normal control findings. Mean pressure within the lesion in the patients undergoing surgery while supine was 38.2 +/- 0.5 mm Hg; a slight decline in cavernous angioma pressure occurred with a drop in mean systemic arterial blood pressure and PaCO2. Mean pressure in the cavernous angioma in the patient operated on in the sitting position was 7 mm Hg. Jugular compression resulted in a 9-mm Hg rise in cavernous angioma pressure in one supine patient but no change in the patient in the sitting position. Direct microscopic observation revealed slow circulation within the lesions. The hemodynamic features demonstrated in this study indicate that cavernous angiomas are relatively passive vascular anomalies that are unlikely to produce ischemia in adjacent brain. Frank hemorrhage would be expected to be self-limiting because of relatively low driving pressures.

Epidermal growth factor binding and action on tympanic membranes

A significant percentage of tympanic membrane (TM) perforations require some form of therapy to heal. Topical application of epidermal growth factor (EGF), a potent mitogen for epidermal and mesodermal cells, promotes healing of injuries in tissues histologically similar to TM, such as cornea and skin. We evaluated TM as a target tissue for EGF action. Specific, high affinity receptors for EGF were detected in TM (Kd = 3.1 nM, 150 fmol receptor/mg protein). Autoradiography of iodine 125-EGF binding to intact TMs revealed that EGF receptors were present on cells in the stratified squamous epithelial layer and in the stromal/mucoepithelial layer. Repetitive treatment of perforated cat TMs with 20 micrograms of EGF formulated in saline induced substantial hyperplasia of epithelial and stromal layers compared to paired TMs treated with saline. A single treatment of perforated cat TMs with 50 micrograms of EGF formulated in a hydrogel or in shredded Gelfoam produced significantly (p less than .05) smaller perforations at 6 days following the operation compared to paired TMs treated with vehicles. These results demonstrate that TM is a target tissue for EGF and that topical treatment with EGF stimulates healing of TM perforations.

Bimodal treatment with nimodipine and low-molecular-weight dextran for focal cerebral ischemia in the rat

We compared the effects of intravenous treatment with combined low-molecular-weight dextran and nimodipine (n = 9), or placebo (n = 10), on local cerebral blood flow after occlusion of the left middle cerebral and common carotid artery in the rat. Treatment for a total of 4 hours with low-molecular-weight dextran (5 mg/kg/min) and nimodipine (0.25 microgram/kg/min) produced a decrease in hematocrit from 46 +/- 1 to 33 +/- 1% at the end of the study and a statistically significant increase in local cerebral blood flow, when compared to the control group, in 6 regions of interest: the territories of the right middle (p = 0.01), right anterior (p = 0.007), and left anterior cerebral arteries (p = 0.001); the superior (p = 0.03) and inferior border zone (p = 0.003); and white matter in the right hemisphere (p = 0.04). The ischemic volume, defined as brain volume with a cerebral blood flow of less than the critical level of 25 ml/min/100 gm was determined as a percentage of total brain volume for the control and treatment groups. The group treated with low-molecular-weight dextran and nimodipine showed a 31% decrease in ischemic volume (p = 0.03). These results indicate that a bimodal approach with low-molecular-weight dextran and nimodipine can be safely used in a model of acute stroke and has a beneficial effect on local cerebral blood flow and ischemic volume when compared with control subjects. After 4 hours, the potential exists that this treatment is therapeutic, assuming that the ischemic volume progresses to infarction.

Local cortical blood flow and oxygen consumption during isoflurane-induced hypotension. Results in patients undergoing intracranial aneurysm clipping

Cerebral cortical blood flow (lCoBF) and metabolic rate for oxygen (lCoMRO2) were studied in eight patients undergoing intracranial aneurysm clipping. The patients were anesthetized with fentanyl 10 micrograms/kg and 70% nitrous oxide combined with 30% oxygen. Hypotension was induced with isoflurane. A thermal diffusion probe was used to measure lCoBF, and arterial and cerebral venous blood samples were obtained for measurement of arterio-cerebral venous O2 content difference. Measurements were made prior to hypotension, during hypotension (to mean arterial pressure approximately 50 mmHg), and posthypotension. Mean lCoBF decreased from 69 +/- 20 mL/100 g/min at normotension to 59 +/- 13 mL/100 g/min during hypotension (P less than .03, NS) and was 61 +/- 18 mL/100 g/min upon return to normotension (all values mean +/- 1 SD). The lCoMRO2 averaged 3.9 +/- 1.6 mL/100 g/min and 3.1 +/- 1.5 mL/100 g/min, respectively (P less than .03, NS) for normotension upsilon hypotension. Values for cerebral venous PO2 and O2 saturation also did not differ significantly between study periods. These results indicate that isoflurane-induced hypotension during fentanyl-nitrous oxide anesthesia allows maintenance of a constant lCoBF and oxygen delivery.

Multiple forms of epileptic attack secondary to a small chronic subdural haematoma

Images

CO2 reactivity and heterogeneity of cerebral blood flow in ischemic, border zone, and normal cortex

Regional arterial CO2 tension (PaCO2) reactivity of cerebral blood flow (CBF) and the effect of PaCO2 on the spatial and temporal heterogeneity of CBF were investigated by using autoradiographically determined CBF in the rat middle cerebral artery occlusion model after a 2-h period under pentobarbital anesthesia to clarify the relation between PaCO2 reactivity, CBF heterogeneity, and the temporal cycling of CBF. PaCO2 was adjusted to one of four levels. CBF was determined in four cortical areas and white matter using the tissue fractionation of [14C]iodoantipyrine [( 14C]IAP) in combination with vessel mapping using in vivo 4% thioflavine S. Specific PaCO2 reactivity and CBF were normal in the nonischemic cortex, normal, although slightly depressed, in the border zone far from the ischemic core area, and depressed in the border zone adjacent to the ischemic core area (P less than 0.001) and the ischemic core (P less than 0.001). In normocapnic and hypocapnic animals, CBF heterogeneity in the form of regularly spaced CBF columns perpendicular to the cortical surface was observed in the nonischemic hemisphere but was absent in the ischemic core area. In hypercapnic rats, flow columns were present in the ischemic core areas and border zones but were absent on the nonischemic side. There was a highly significant interaction (P less than 0.0001) in observer-determined heterogeneity grades between PaCO2 level and each of three areas, normal, border zone, and ischemic core. In normal cortex, comparison of the thioflavine S-stained vessels with the flow columns provided evidence supporting the concept of capillary recruitment and cycling as a mode of normal cerebral blood flow control. The presence of flow columns in severely ischemic areas in hypercapnic animals indicates that a short period of high PaCO2 transiently augments microregional flow and could enhance the delivery of a therapeutic agent to these microregions of the ischemic core. The regional analysis of PaCO2 reactivity suggests an index of future tissue viability.

Kinetic independence between red cell anion exchange and urea transport

Urea equilibrium exchange fluxes were measured in human red cells under conditions which recruit the anion transporter into an outward-facing or an inward-facing state (with respect to the anion transport site). Regardless of these conditions, urea transport always occurred at the same rate: 41 +/- 2 mol.(kg cell solids.min)-1 with 1.5 M urea at 0 degrees C. These data suggest that the pathway on the band-3 protein which mediates anion transport is kinetically uncoupled from urea transport and is probably not involved in the transport of urea across the red cell membrane.

Altered cerebral autoregulation and CO2 reactivity after aneurysmal subarachnoid hemorrhage

Disruption of local cortical blood flow (CBF) autoregulation and CO2 reactivity, or vasoparalysis, has been documented in humans after aneurysmal subarachnoid hemorrhage (SAH). Generally, the degree of vasoparalysis is related to the patient's clinical grade. Using intraoperative measurement of local CBF, we evaluated pressure autoregulation and CO2 reactivity in patients after SAH. Fourteen patients with SAH and 10 patients with asymptomatic aneurysm underwent craniotomy for clipping of their aneurysms. During operation, local CBF was recorded with thermal conductivity probes placed on the middle frontal gyrus, 4 to 6 cm from the nearest point of retraction. Before retractor placement, CBF was measured with the PCO2 at 25 and 35 mm Hg and the mean arterial blood pressure (MABP) between 70 and 80 mm Hg. After aneurysm clipping, flows were again measured. With the PCO2 at 25 mm Hg, the MABP was raised from 65 to 85 mm Hg. The PCO2 was then allowed to rise to 35 mm Hg, after which the MABP was lowered from 85 to 65 mm Hg. Six patients underwent operation within the 1st week after SAH (Grade I, n = 3; Grade II, n = 3). The remainder (n = 8) were operated on 9 days to 3 months after SAH. After aneurysm clipping, significant CBF changes (P less than 0.001) with PCO2 alteration occurred in control patients and those operated on more than 7 days after SAH. There was no significant change in CBF in patients operated on within 7 days after SAH. Changes in CBF reactivity to alteration of MABP were significantly larger in early operation patients than in other groups (P less than 0.008).(ABSTRACT TRUNCATED AT 250 WORDS)

The evaluation of quantitative autoradiogram processing systems for cerebrovascular research

The development of an image processing system for quantitative autoradiography (QAR) is described, with emphasis on the evaluation of image digitization systems independent of hardware or software design. Each step of converting the autoradiographic image to a functional image of a physiological variable such as local cerebral blood flow (LCBF) or local cerebral glucose utilization rate (LCGU) is evaluated. The autoradiograms are digitized, aligned, transformed to a tissue tracer concentrations image based on the gray value (GV) of calibrated 14C standards, subtracted from each other as required in double tracer QAR, and converted to an LCBF or LCGU image using the proper tracer kinetic model. Geometric size, mean and standard deviation of the LCBF, LCGU, and tracer concentration can be measured in regions of interest. These steps are evaluated separately for their contribution to the accuracy and precision of the final, functional image. The qualities important in the final image are spatial resolution, intensity linearity, and intensity sensitivity, as well as the noise level. Techniques for evaluating the LCBF image include: (1) optimization of the input linearity and dynamic range of the video camera to maximize relative intensity sensitivity of the final functional image; (2) visual inspection of the curves used to fit various functions that are important in the conversion of the GV image to an image of physiological interest; (3) consideration of the noise introduced by the input devices and during the image conversion; and (4) above all, the integration of the various parts of the system to produce an accurate image useful in cerebrovascular research.

Evolving focal cerebral ischemia in cats: spatial correlation of nuclear magnetic resonance imaging, cerebral blood flow, tetrazolium staining, and histopathology

The spatial correlation of nuclear magnetic resonance imaging (NMRI) and cerebral blood flow (CBF) may improve our ability to identify ischemic brain lesions and may provide further insight into the pathophysiology of early cerebral ischemia. Eleven pentobarbital-anesthetized adult cats underwent exposure of the common carotid arteries bilaterally and the right middle cerebral artery through a transorbital approach. Baseline NMRI images were obtained with a single spin-echo, multislice technique using a 0.6-T field, 0.4-cm slice thickness, and a surface coil. Focal ischemia was produced with right middle cerebral artery occlusion and potentiated with bilateral common carotid artery ligation. Sequential NMRI studies were then performed at 1, 2, 4, 6, and 12 hours or until CBF was determined in the same cats using [14C]iodoantipyrine at either 2 (n = 2), 4 (n = 2), 6 (n = 2), or 12 (n = 1) hours after the time of occlusion. This protocol allowed temporal and spatial correlation of NMRI and CBF. Alternate 5-mm brain slices were incubated with 1% 2,3,5-triphenyltetrazolium chloride (TTC) for 45 minutes at 37-41 degrees C and frozen in liquid Freon for later autoradiographic CBF determination. Four cats were studied only with NMRI and TTC (not CBF). The correlation between areas of increased NMRI signal intensity observed in T2-weighted images (repetition time 2,000 msec, echo time 120 msec), vital staining with TTC, low CBF, and routine histology was evaluated. During the early phase (less than 6 hours), T2-weighted NMRI changes were localized to the central ischemic gray matter areas, as defined in the later CBF images, with no involvement of the white matter. By the twelfth hour the NMRI changes involved the entire ischemic area including gray and white matter. The initial visible changes seen on T2-weighted NMRI are suggestive of cellular edema, and the later changes are characteristic of vasogenic edema. The spread of NMRI changes compared with the ischemic area determined from autoradiographic CBF is consistent with the previously described biphasic evolution of ischemic injury. These data suggest that T2-weighted NMRI could be used clinically to delineate areas of acute ischemic stroke.

[14C]iodoantipyrine and microsphere blood flow estimates in cat brain

A comparison of local cerebral blood flow estimates with the microsphere and the 4-[N-methyl-14C]iodoantipyrine ([14C]IAP) techniques has been performed in cats. Good correlation of [14C]IAP with microsphere flow estimates in the gray matter was found. In the white matter, however, [14C]IAP flow estimates were consistently lower than microsphere flow estimates. Error analysis of both techniques and comparison with previous studies suggest that peculiarities of white matter arterial vasculature with preferential microsphere accumulation may lead to this discrepancy. Microspheres did not interfere with flow as shown by the normal appearance of subsequent [14C]IAP autoradiograms. The number of microspheres seen on autoradiograms was used for an estimate of microvessels blocked by spheres and found to be negligible. The study also demonstrates that [14C]IAP is not diffusion limited up to the observed flow values of 2 ml.g-1.min-1. Both techniques might be used together for a combination of their respective advantages, which are temporal and spatial resolution for microsphere and [14C]IAP, respectively.

Cerebral circulation during arteriovenous malformation operation

The circulatory changes in the cortex around a cerebral arteriovenous malformation (AVM) were studied in 18 patients. The AVMs had rapid circulation times with early draining veins on angiography. Local cortical blood flow (lCoBF) was measured with cortically applied thermister/Peltier stack arrays. The AVMs had a more pronounced effect on lCoBF at a 2- to 4-cm distance from the AVM margin than in the adjacent cortex. Mean preexcision lCoBF was 62.9 +/- 6.7 (SE) ml/100 g/minute (i.e., similar to normal controls) near the AVM margin and 43.0 +/- 4.2 ml/100 g/minute far (i.e., greater than 2 cm) from the AVM. CO2 reactivity (COR) before excision was 1.1 +/- 0.3 ml/100 g/minute/torr of CO2 (i.e., similar to normal controls) at near sites and 0.6 +/- 0.3 ml/100 g/minute/torr of CO2 at far sites. The mean postexcision near lCoBF remained stable at 55.8 +/- 5.1 ml/100 g/minute at near sites, but the far lCoBF significantly increased (P less than 0.05) to 57.2 +/- 6.8 ml/100 g/minute. The cortical feeding artery pressure was substantially below the normal cortical artery pressure in 50% of the cases studied. Pressure in these arteries normalized after occlusion and AVM excision, resulting in a rapid increase in cortical artery perfusion pressure. Draining red vein pressure, which was elevated before AVM excision, also dropped after excision, contributing to the increase in perfusion pressure. Two patients who developed the normal perfusion pressure breakthrough syndrome (PBS) after operation had low lCoBF and disturbed COR before AVM excision and marked increase of lCoBF after excision.(ABSTRACT TRUNCATED AT 250 WORDS)

Denaturation of a membrane transport protein by urea: the erythrocyte anion exchanger

Chloride equilibrium exchange was measured in the presence of intracellular and extracellular urea, several different alkylureas and thiourea. Urea half-inhibited Cl exchange at about 2.5 M, but the other, less polar analogs had significantly higher potencies; e.g., butylurea half-inhibited at about 60 mM. Onset and reversal of inhibition occurred within less than 2 sec. The inhibition exhibited no obvious sigmoidal dependence on urea concentration, and at low concentrations dimethylurea was a noncompetitive inhibitor of Cl exchange. However, at higher concentrations the Dixon plots were curved upward and a Hill analysis of the dimethylurea data yielded a Hill coefficient of at least 1.5. When present on only one side of the membrane, the slowly penetrating thiourea inhibited Cl exchange with a higher potency from the outside of the cell. Cl/Br exchange was inhibited less under conditions of self-inhibition of anion exchange than in the absence of self-inhibition. These data indicate that the ureas inactivate the anion transporter by a reversible denaturation process, and that the function of the anion transport mechanism may be more sensitive to small perturbations of protein structure than are spectroscopically derived structural parameters.