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At least 1,513 records · Page 84Linked to original sources
PubMed1993

Intrinsic stability of 'self-sealing' unsutured cataract wounds.

Many operative and postoperative factors can influence cataract wound stability and postoperative astigmatism. The final outcome is fundamentally dependent on the intrinsic biomechanical stability of the corneal dome in the presence of the wound. We determined the stability of the central and peripheral cornea with computer-assisted topographic analysis of six freshly enucleated human globes. Self-sealing, unsutured, scleral tunnel wounds 4.0 mm in length were dissected, with widths varying from 1.4 to 6.0 mm. Intraocular pressure was elevated in 5-mm increments from 15 to 40 mm Hg without measurable topographic change in the visual axis or superior cornea. We conclude that these long scleral tunnel wounds do not necessarily destabilize the cornea within the usual range of intraocular pressure. Postoperative-induced astigmatism is therefore due to other operative and postoperative factors. Some of these factors may be identifiable with this model and controlled or eliminated.

Astigmatism↗
PubMed1995

Long-term stability of blood pressure and pressor reactivity to mental stress in borderline hypertension.

Borderline hypertension is characterized by pressor hyperreactivity to mental stress. However, it has not been shown whether blood pressure hyperresponsiveness is a temporary phenomenon due to situational anxiety or a stable feature of the borderline hypertensive state. We therefore evaluated the long-term stability of invasively assessed blood pressure and central hemodynamic responses to mental stress in 10 young male subjects with borderline hypertension recruited from a population screening. Two identical 10-min mental arithmetic stress tests were performed 50 to 62 months apart (median, 4 years 8 months). Intraarterial blood pressure was monitored continuously before, during, and after stress. Cardiac output was measured by the indocyanine green dye dilution technique and indexed for body surface area. Total peripheral resistance index was computed from cardiac index and mean arterial pressure. During the 4-year follow-up period, none of the central hemodynamic parameters had changed significantly, either with respect to rest or stress levels. Test-retest variability of blood pressure measures was low, and errors of measurement ranged between 4.8 and 8.2 mm Hg for blood pressure levels at rest and during stress. Mental arithmetic induced highly significant blood pressure increments on both occasions (ANOVA, P < .0001 throughout). Pressor responses were somewhat but not significantly lower during the second test. Errors of measurement for absolute blood pressure reactivity ranged between 3.9 and 7.1 mm Hg. Intersession correlation coefficients for blood pressure levels attained during stress were above r = 0.75 throughout (P < or = .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

The densitometric physical fractionator for counting neuronal populations: application to a mouse model of familial amyotrophic lateral sclerosis.

The method of the 'densitometric physical fractionator' presented here realizes an accurate and reproducible stereological quantification, not requiring a motorized or controlled z-axis, of cell populations. It includes a special software for the calibration of the optics alignment of the microscope and a semi-automatic procedure that integrates specific densitometric functions for image analysis, to identify the reference volume and the particle profiles. This improves the identification of the cells significantly, reduces variability in the subjective choice of the particles by the operators, and allows a consistent saving of time during the analysis. The method is proved to be unbiased and the accuracy and reproducibility of the results has been validated through intra- and inter-operator analyses. Furthermore, it has been applied to calculate the loss of spinal motor neurons during pathology progression in transgenic mice for superoxide-dismutase Cu/Zn dependent (SOD1) mutants, a model of amyotrophic lateral sclerosis (ALS).

Amyotrophic Lateral Sclerosis↗
PubMed2000

Non-uniform systematic sampling in stereology.

Non-uniform systematic sampling designs in stereology are studied. Various methods of constructing non-uniform systematic sampling points from prior knowledge of the measurement function are presented. As an example, we consider area estimation from lengths of linear intercepts. The efficiency of two area estimators, based on non-uniform sampling of parallel lines, is compared to that of the classical 2D Cavalieri estimator, based on uniform sampling, in a sample of planar profiles from transverse sections of 41 small myelinated axons. The comparison is based on simulations. It is concluded that for profiles of this type one of the non-uniform sampling schemes is more efficient than the traditional uniform sampling scheme. Other examples where non-uniform systematic sampling may be used are in area estimation from lines emanating from a fixed point, area estimation from concentric circles or spirals and curve length estimation from sweeping lines. It is shown that proportional-to-size sampling is a special case of non-uniform systematic sampling. Finally, the effect of noise in the observations is discussed.

Axons↗
PubMed2000

The corticofugal system for hearing: recent progress.

Peripheral auditory neurons are tuned to single frequencies of sound. In the central auditory system, excitatory (or facilitatory) and inhibitory neural interactions take place at multiple levels and produce neurons with sharp level-tolerant frequency-tuning curves, neurons tuned to parameters other than frequency, cochleotopic (frequency) maps, which are different from the peripheral cochleotopic map, and computational maps. The mechanisms to create the response properties of these neurons have been considered to be solely caused by divergent and convergent projections of neurons in the ascending auditory system. The recent research on the corticofugal (descending) auditory system, however, indicates that the corticofugal system adjusts and improves auditory signal processing by modulating neural responses and maps. The corticofugal function consists of at least the following subfunctions. (i) Egocentric selection for short-term modulation of auditory signal processing according to auditory experience. Egocentric selection, based on focused positive feedback associated with widespread lateral inhibition, is mediated by the cortical neural net working together with the corticofugal system. (ii) Reorganization for long-term modulation of the processing of behaviorally relevant auditory signals. Reorganization is based on egocentric selection working together with nonauditory systems. (iii) Gain control based on overall excitatory, facilitatory, or inhibitory corticofugal modulation. Egocentric selection can be viewed as selective gain control. (iv) Shaping (or even creation) of response properties of neurons. Filter properties of neurons in the frequency, amplitude, time, and spatial domains can be sharpened by the corticofugal system. Sharpening of tuning is one of the functions of egocentric selection.

Animals↗
PubMed2002

Computer-assisted quantitative analysis of immunofluorescence staining of the extracellular matrix in rat dorsal and ventral spinal roots.

The endoneurial extracellular matrix (ECM) is produced by Schwann cells and fibroblasts under the control of axons. Dorsal and ventral spinal roots contain different types of axons, but information is not available on differences in the composition of their ECM. A comparison was made of the intensity of immunofluorescence staining of chondroitin sulfate proteoglycan, fibronectin, tenascin and thrombospondin in the endoneurial ECM of rat dorsal and ventral spinal roots. Sections of dorsal and ventral roots were incubated simultaneously for indirect immunofluorescence detection of the epitopes studied. Brightness of immunofluorescence staining was assessed by computer-assisted image analysis using interactive segmentation of digitized images to select areas to be analyzed. Our results revealed quantitative differences in the composition of endoneurial ECM of spinal dorsal and ventral roots, probably due to the presence of different types of axons. The ECM composition of the endoneurium in dorsal and ventral roots may be related with the creation of extrinsic conditions that support differential regeneration of afferent and motor axons after injury.

Animals↗
PubMed1996

An auditory cortical theory of primitive auditory grouping.

Auditory stream segregation is considered from the point of view of a theory of the central auditory system in which temporal information is spatially coded on three dimensions roughly corresponding to the level of the cochlea, the inferior colliculus and the auditory cortex, respectively. This theory is embodied in the form of a computational model which simulates peripheral and central processing including a cortical cross-channel correlation mechanism.

Journal Article↗
PubMed2002

Flow-rate measurements and models for colloid and crystalloid flows in central and peripheral venous line infusion systems.

The resuscitation fluids, including crystalloids and colloids, were tested in an experimental module with 16-gauge central and peripheral catheters. Infusion pressures were ranged from the gravity driving 10 kPa (75 mmHg) to the pressurized driving 50 kPa (375 mmHg). The experiment results were correlated to obtain the empirical friction factors and the loss factors for the components commonly used in a fluid resuscitation system. The modified Bernoulli equation with the correlated friction factors and loss factors for the components were used to evaluate the pressure and flow relationship in the fluid resuscitation system with peripheral and central catheters. Fair agreements were observed from the comparison of the predictions of the total driving pressure and test results from water, crystalloid and colloid solutions. The modified Bernoulli equation is, therefore, applicable to evaluate the pressure-flow relationship for efficient fluid resuscitations. The coefficients of flow (F) and the square of flow (F2) for the binominal model are varied with the changes of geometry and size of the infusion components, fluid properties and the units of parameters. These coefficients for the fluids and catheters tested in this study were also listed for reference.

Blood Flow Velocity↗
PubMed2004

Spontaneous rupture of adrenal pheochromocytoma with capsular invasion.

A 67-year-old Japanese man developed a sudden onset of severe right-side upper abdominal pain, nausea and vomiting. On hospitalization, physical examination revealed sweating, tachycardia, hypertension and the appearance of peripheral vasoconstriction. An urgent computed tomography scan with contrast demonstrated a large hematoma in the right retroperitoneal space. A phentolamine test and an 131iodine metaiodobenzylguanidine scan suggested pheochromocytoma. An elective right adrenalectomy was successfully performed after pretreatment for sufficient volume replacement with continuous administration of alpha- and beta-adrenergic blocking agents. Pathological diagnosis was an adrenal pheochromocytoma 9.0 x 6.5 cm in diameter with evidence of capsular invasion, which could be associated with a tear in the capsule.

Abdomen, Acute↗
PubMed1998

An analysis of the effect of basilar membrane nonlinearities on noise suppression.

Computational models of the peripheral auditory system have largely modeled basilar membrane (BM) mechanics as a linear filter-bank-like entity. Recent mathematical work on the nature of auditory system noise suppression allows us to analyze and argue for the incorporation of BM nonlinearities into these models. This analysis shows that vowel perception improves with increasing presence of BM nonlinearities whereas consonant perception degrades with increasing influence of BM nonlinearities. Experimental results on tones and real speech corrupted by noise corroborate the analysis as well as suggest a novel approach to speech processing.

Basilar Membrane↗
PubMed2000

Familial pulmonary Mycobacterium avium complex disease.

We report two Japanese families affected by pulmonary Mycobacterium avium complex (MAC) disease, involving an older brother and younger sister in one family and two brothers in the second family. We investigated whether defects in the natural resistance-associated macrophage protein gene (NRAMP1) underlay susceptibility to MAC in these cases. All of the patients had computed tomographic findings of peripheral nodules and bronchiectasis. Pulse-field gel electrophoresis patterns of mycobacterial genomic DNA restriction fragments revealed that none of the MAC strains isolated from the patients was epidemiologically related to any of the others. Direct sequencing of the complementary DNA of the patients' NRAMP1 revealed a nonconservative missense mutation at codon 419 in one patient, which was heterozygous and was not seen in his affected sibling. No variations similar to those found in mice that show susceptibility to MAC were found. The results suggest an underlying genetic defect in host defense rather than exposure to an unusually virulent strain of MAC as the pathogenetic factor in MAC disease; however, alterations in the coding region of NRAMP1 do not appear to explain the susceptibility to MAC.

Adult↗
PubMed2001

Keynote address.

"Acute strokes are here to stay": this could be the sad conclusion after decades of stroke research. Generalized prevention of ischemic stroke is not fully successful. After the decline in stroke incidence observed by 1970, partly related to better management of vascular risk factors, there has again been an increase in stroke frequency all around the world. This phenomenon may be explained by the lack of educational modalities for modification of lifestyle behavior, the small impact of high-risk individual prevention strategy, and the lack of rationale and guidelines for multiple approaches. In the meantime, the benefits of acute intensive management of stroke have been demonstrated. There is now considerable evidence that careful monitoring and management of general and cerebral functions in a dedicated stroke unit or by a specialized stroke team are superior to management in a neurologic or general ward. Currently, one way of optimizing limited personnel resources is to connect the stroke unit of a main hospital with peripheral hospitals via a computer network. Experts in the central stroke unit can then make on-line evaluations of CT and ultrasound examinations performed in the local hospital and recommend the best course of patient management. This new approach of treating stroke as an emergency will also require educational programs directed at the general public, general practitioners, and primary and emergency department physicians, to teach the recognition of stroke symptoms and the importance of treating stroke with the same urgency as for myocardial infarction (MI).

Brain Ischemia↗
PubMed2003

Neuroleptic-induced acute respiratory distress syndrome.

CONTEXT: A case of neuroleptic malignant syndrome and acute respiratory distress syndrome is presented and discussed with emphasis on the role of muscle relaxation, creatine kinase, and respiratory function tests. CASE REPORT: A 41-year-old man presented right otalgia and peripheral facial paralysis. A computed tomography scan of the skull showed a hyperdense area, 2 cm in diameter, in the pathway of the anterior intercommunicating cerebral artery. Preoperative examination revealed: pH 7.4, PaCO2 40 torr, PaO2 80 torr (room air), Hb 13.8 g/dl, blood urea nitrogen 3.2 mmol/l, and creatinine 90 mmol/l. The chest x-ray was normal. The patient had not eaten during the 12-hour period prior to anesthesia induction. Intravenous halothane, fentanyl 0.5 mg and droperidol 25 mg were used for anesthesia. After the first six hours, the PaO2 was 65 torr (normal PaCO2) with FiO2 50% (PaO2/FiO2 130), and remained at this level until the end of the operation 4 hours later, maintaining PaCO2 at 35 torr. A thrombosed aneurysm was detected and resected, and the ends of the artery were closed with clips. No vasospasm was present. This case illustrates that neuroleptic drugs can cause neuroleptic malignant syndrome associated with acute respiratory distress syndrome. Neuroleptic malignant syndrome is a disease that is difficult to diagnose. Acute respiratory distress syndrome is another manifestation of neuroleptic malignant syndrome that has not been recognized in previous reports: it may be produced by neuroleptic drugs independent of the manifestation of neuroleptic malignant syndrome. Some considerations regarding the cause and effect relationship between acute respiratory distress syndrome and neuroleptic drugs are discussed. Intensive care unit physicians should consider the possibility that patients receiving neuroleptic drugs could develop respiratory failure in the absence of other factors that might explain the syndrome.

Adult↗
PubMed2004

Clinical features and management of intracranial hemorrhage in patients undergoing maintenance dialysis therapy.

The management and outcome were retrospectively investigated in patients with chronic renal failure receiving maintenance blood purification who suffered intracranial hemorrhage. Patients with intracerebral hemorrhage (ICH, n = 36) or subarachnoid hemorrhage (SAH, n = 5) were evaluated. Both groups were initially managed using continuous hemofiltration (HF) after admission, except for two patients with SAH receiving maintenance peritoneal dialysis. Patients with ICH were managed with HF three times a week after computed tomography showed decreased peripheral edema. Nafamostat mesilate was used as the anticoagulant for both continuous HF and HF. Hemodialysis (HD) three times a week was initiated after confirming the absence of neurological deterioration using HF. Craniotomy was not performed in any patient with ICH, but if necessary, the hematoma was aspirated using burr-hole surgery. Angiography was performed on the day of admission in patients with SAH. Delayed neck-clipping surgery was performed after continuous HF for 2 weeks with lumbar cerebrospinal fluid drainage. In patients with ICH, continuous HF was continued for 2-9 days after admission (mean 5.2 +/- 2.2 days), followed by 2-9 courses of HF (mean 4.7 +/- 2.1 courses). HD was initiated 9-26 days after admission (mean 15.5 +/- 4.6 days). Favorable outcomes were achieved by 13 of the 36 patients with ICH and two of the five patients with SAH, whereas 22 patients with ICH and three patients with SAH died. Death occurred in 12 of 16 patients with ICH and diabetic nephropathy. In contrast, 10 of 20 non-diabetic patients with ICH had favorable outcomes. Ten of the 16 patients with initial GCS < or = 8 and six of the 20 with GCS > or = 9 were diabetic. Therefore, there were significant differences between diabetic and non-diabetic patients (p = 0.05). Poor outcomes in diabetic patients with ICH are caused by primary brain damage, reflected in the initial disturbance of consciousness.

Adult↗
PubMed1994

Arginine-induced insulin release in glucokinase-deficient subjects.

OBJECTIVE: In eight glucokinase (GCK)-deficient subjects, we have investigated insulin secretion rates (ISRs) in response to intravenous arginine. Impairment in the enzymatic activity of mutant GCK leads to a reduced glycolytic flux in beta-cells. This defect translates in vivo as a right shift in the glucose/SR dose-response curve. Insulin secretion in response to other secretagogues has not been reported. RESEARCH DESIGN AND METHODS: The arginine test was performed immediately after a 2-h hyperglycemic (10 mM) clamp. ISR was computed by deconvolution of peripheral C-peptide levels. Linear regression analyses were performed to assess correlations between the beta-cell secretory responses to the arginine test, an intravenous glucose tolerance test (IVGTT), and a hyperglycemic clamp (areas under the C-peptide curves), and between these parameters and the glucose tolerance status (area under the glucose curve during an oral glucose tolerance test). RESULTS: Two minutes after the injection of arginine, the increment in ISR was 30.17 +/- 10.01 pmol insulin.kg-1.min-1 in patients and 36.25 +/- 15.46 pmol insulin.kg-1.min-1 in control subjects (P = 0.38). Throughout the experiment, increments in ISR were comparable in both groups. The amount of insulin secreted in response to arginine (0-5 min) was similar in patients and control subjects: 81 +/- 28 vs. 119 +/- 55 pmol/kg (P = 0.16), respectively. The arginine test C-peptide response was not correlated with the IVGTT or hyperglycemic clamp responses. The arginine test and hyperglycemic clamp responses were not correlated to the glucose tolerance status. The best predictor of the glucose tolerance was the C-peptide response to the IVGTT (r2 = 0.78; P = 0.002). CONCLUSIONS: beta-cell secretory increment in response to arginine was found to be in the normal range in GCK-deficient subjects. The arginine test does not seem to reflect either the beta-cell secretory defect or the glucose tolerance status of these subjects. IVGTT seems to be the best predictor of the latter parameter in this population.

Adolescent↗