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1.
Br J Cancer ; 115(9): 1147-1155, 2016 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-27727232

RESUMO

BACKGROUND: Cancer incidence and mortality projections are important for understanding the evolving landscape for cancer risk factors as well as anticipating future burden on the health service. METHODS: We used an age-period-cohort model with natural cubic splines to estimate cancer cases and deaths from 2015 to 2035 based on 1979-2014 UK data. This was converted to rates using ONS population projections. Modified data sets were generated for breast and prostate cancers. RESULTS: Cancer incidence rates are projected to decrease by 0.03% in males and increase by 0.11% in females yearly between 2015 and 2035; thyroid, liver, oral and kidney cancer are among the fastest accelerating cancers. 243 690 female and 270 261 male cancer cases are projected for 2035. Breast and prostate cancers are projected to be the most common cancers among females and males, respectively in 2035. Most cancers' mortality rate is decreasing; there are notable increases for liver, oral and anal cancer. For 2035, there are 95 961 female deaths projected and 116 585 male deaths projected. CONCLUSIONS: These findings stress the need to continue efforts to address cancer risk factors. Furthermore, the increased burden of the number of cancer cases and deaths as a result of the growing and ageing population should be taken into consideration by healthcare planners.


Assuntos
Mortalidade/tendências , Neoplasias/epidemiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Causas de Morte , Feminino , Previsões , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Neoplasias/mortalidade , Reino Unido/epidemiologia , Adulto Jovem
2.
J Microsc ; 261(1): 115-26, 2016 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-26575198

RESUMO

BACKGROUND: Spatial characterization of vertical organization of neurons in human cerebral cortex, cortical columnarity or minicolumns, and its possible association with various psychiatric and neurological diseases has been investigated for many years. NEW METHOD: In this study, we obtained 3D coordinates of disector sampled cells from layer III of Brodmann area 4 of the human cerebral cortex using light microscopy and 140-µm-thick glycolmethacrylate sections. A new analytical tool called cylindrical K-function was applied for spatial point pattern analysis of 3D datasets to see whether there is a spatially organized columnar structure. In order to demonstrate the behaviour of the cylindrical K-function, the result from brain tissues was compared with two models: A homogeneous Poisson process exhibiting complete spatial randomness, and a Poisson line cluster point process. The latter is a point process model in 3D space, which exhibits spatial structure of points similar to minicolumns. RESULTS: The data show in three out of four samples nonrandom patterns in the 3D neuronal positions with the direction of minicolumns perpendicular to the pial surface of the brain - without a priori assuming the existence of minicolumns. COMPARISON WITH EXISTING METHODS: Studies on columnarity are difficult and have mainly been based on two-dimensional images analysis of thin sections of the cerebral cortex with the a priori assumption that minicolumns existed. CONCLUSIONS: A clear difference from complete spatial randomness in the data could be detected with the new tool, the cylindrical K-function, although classical functional summary statistics are less useful in this connection.


Assuntos
Córtex Cerebral/anatomia & histologia , Imageamento Tridimensional/métodos , Neurônios/fisiologia , Idoso , Feminino , Humanos , Pessoa de Meia-Idade , Neurônios/citologia
3.
Cephalalgia ; 30(11): 1346-53, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20959429

RESUMO

UNLABELLED: There is a striking similarity between the migraine-provoking effect of the nitric oxide (NO) donor glyceryl trinitrate (GTN) and that of calcitonin gene-related peptide (CGRP). We tested the hypothesis that NO releases CGRP to cause the delayed migraine attack after GTN. METHODS: In a double-blind-cross-over study, 13 migraine without aura (MO) patients were administered GTN 0.5 µg/kg/minute for 20 minutes and subsequently BIBN4096BS (olcegepant) 10 mg or placebo. Headache scores and development of MO were followed for 24 hours. RESULTS: MO developed in seven of 13 with olcegepant and in nine of 13 with placebo (p=0.68). The headache scores were similar after the two treatments (p=0.58). Thus CGRP receptor blockade did not prevent GTN-induced migraine. CONCLUSIONS: The present study indicates that NO does not induce migraine by liberating CGRP. The most likely explanation for our findings is that CGRP has its effect higher than NO in the cascade of events leading to MO attacks.


Assuntos
Antagonistas do Receptor do Peptídeo Relacionado ao Gene de Calcitonina , Dipeptídeos/farmacologia , Transtornos de Enxaqueca/tratamento farmacológico , Quinazolinas/farmacologia , Adulto , Estudos Cross-Over , Método Duplo-Cego , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Transtornos de Enxaqueca/induzido quimicamente , Transtornos de Enxaqueca/metabolismo , Nitroglicerina/efeitos adversos , Piperazinas , Vasodilatadores/efeitos adversos
4.
Cephalalgia ; 29(1): 23-30, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19126117

RESUMO

Adrenomedullin (ADM) is closely related to calcitonin gene-related peptide, which has a known causative role in migraine. Animal studies have strongly suggested that ADM has a vasodilatory effect within the cerebral circulation. For these reasons, ADM is also likely to be involved in migraine. However, the hypothetical migraine-inducing property and effect on human cerebral circulation of ADM have not previously been investigated. Human ADM (0.08 microg kg(-1) min(-1)) or placebo (saline 0.9%) was administered as a 20-min intravenous infusion to 12 patients suffering from migraine without aura in a crossover double-blind study. The occurrence of headache and associated symptoms were registered regularly 24 h post infusion. Cerebral blood flow (CBF) was measured by (133)Xenon single-photon emission computed tomography, mean blood flow velocity in the middle cerebral artery (V(MCA)) by transcranial Doppler and the diameter of peripheral arteries by transdermal ultrasound (C-scan). ADM did not induce significantly more headache or migraine compared with placebo (P = 0.58). CBF was unaffected by ADM infusion (global CBF, P = 0.32 and rCBF(MCA), P = 0.38) and the same applied for the V(MCA) (P = 0.18). The superficial temporal artery dilated compared with placebo (P < 0.001), and facial flushing was seen after ADM administration (P = 0.001). In conclusion, intravenous ADM is not a mediator of migraine headache and does not dilate intracranial arteries.


Assuntos
Adrenomedulina/metabolismo , Adrenomedulina/farmacocinética , Circulação Cerebrovascular/fisiologia , Transtornos de Enxaqueca/metabolismo , Adulto , Encéfalo/metabolismo , Estudos Cross-Over , Método Duplo-Cego , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ultrassonografia Doppler Transcraniana
5.
Cephalalgia ; 29(3): 384-7, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19220317

RESUMO

Stress is a provoking factor for both tension-type headache and migraine attacks. In the present single-blind study, we investigated if stress induced by norepinephrine (NE) could elicit delayed headache in 10 healthy subjects and recorded the cranial arterial responses. NE at a dose of 0.025 microg kg(-1) min(-1) or placebo was infused for 90 min and the headache was followed for 14 h. Blood flow velocity in the middle cerebral artery (measured with transcranial Doppler) and diameters of the temporal artery and the radial artery (measured with ultrasound) were followed for 2 h. There were no changes in these arterial parameters after NE. In both treatment groups three subjects developed delayed headaches. Thus, stress by NE infusion did not result in delayed headache.


Assuntos
Circulação Cerebrovascular/efeitos dos fármacos , Epinefrina/farmacologia , Cefaleia/etiologia , Hemodinâmica/efeitos dos fármacos , Estresse Fisiológico , Adulto , Encéfalo/irrigação sanguínea , Encéfalo/efeitos dos fármacos , Estudos Cross-Over , Feminino , Humanos , Masculino , Artéria Cerebral Média/efeitos dos fármacos , Artéria Radial/efeitos dos fármacos , Método Simples-Cego , Artérias Temporais/efeitos dos fármacos
6.
Cephalalgia ; 26(11): 1304-9, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17059437

RESUMO

We have previously shown that nitric oxide (NO) and cyclic guanosine monophosphate (GMP) may cause headache and migraine. However, not all findings in previous studies can be explained by an activation of the NO-cGMP pathway. Calcitonin gene-related peptide (CGRP) causes headache and migraine in migraine patients, but CGRP receptor activation causes an increase in cyclic adenosine monophosphate (cAMP). In order to investigate the role of cAMP in vascular headache pathogenesis, we studied the effect of cilostazol, an inhibitor of cAMP degradation, in our human experimental headache model. Twelve healthy volunteers were included in a double-blind, randomized, crossover study. Placebo or cilostazol (200 mg p.o.) was administered on two separate study days. Headache was scored on a verbal rating scale (0-10) and mechanical pain thresholds were measured with von Frey hairs. The median peak headache score 0-16 h postdose was 0 (range 0-2) after placebo and 3.5 (range 0-7) after cilostazol (P = 0.003). The median headache curve peaked at 6-9 h postdose. The headaches induced were usually bilateral and pulsating. Nausea occurred in two volunteers, photo- and phonophobia were not seen. Two volunteers had a headache that fulfilled International Headache Society criteria for migraine without aura after cilostazol. No change in mechanical pain thresholds in the forehead was seen (P = 0.25). The headache after cilostazol was equal to or more severe than headache induced by glyceryl trinitrate in previous experiments. The present study thus indicates that increased levels of cAMP may play a role in headache and migraine pathogenesis.


Assuntos
Cefaleia/induzido quimicamente , Tetrazóis/efeitos adversos , Vasodilatadores/efeitos adversos , Adulto , Área Sob a Curva , Cilostazol , Estudos Cross-Over , AMP Cíclico/metabolismo , Método Duplo-Cego , Feminino , Humanos , Masculino , Medição da Dor , Placebos
7.
J Microsc ; 222(Pt 3): 177-81, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-16872416

RESUMO

Stereological methods for serial sections traditionally assume that the sections are exactly equally spaced. In reality, the spacing and thickness of sections can be quite irregular. This may affect the validity and accuracy of stereological techniques, especially the Cavalieri estimator of volume. We present a new formula for the accuracy of the Cavalieri estimator that includes the effect of random variability in section spacing. A modest amount of variability in section spacing can cause a substantial increase in estimator variance.


Assuntos
Microtomia/estatística & dados numéricos , Análise de Variância , Animais , Interpretação Estatística de Dados , Haplorrinos , Matemática , Microtomia/métodos , Lobo Parietal/anatomia & histologia
8.
Cephalalgia ; 25(6): 424-32, 2005 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15910566

RESUMO

Calcitonin gene-related peptide (CGRP) and related peptides may be involved in migraine pathogenesis. To understand their vasomotor role in the cerebral circulation, we performed two studies, a pressurized arteriography study of the middle cerebral artery (MCA) and a genuine closed cranial window (gCCW) in vivo study. Using the pressurized arteriography model rat MCAs were mounted on micropipettes, pressurized to 85 mmHg and luminally perfused. The diameter responses to luminally and abluminally applied rat-alphaCGRP, rat-betaCGRP, amylin and adrenomedullin were compared with the resting diameter. Only abluminally applied CGRP induced dilation of the cerebral arteries; E(max) for alphaCGRP and betaCGRP were 35 +/- 0.5% and 10.8 +/- 0.2%. These responses were blocked by CGRP(8-37). The gCCW model allowed videomicroscopic visualization of the pial vessels in anaesthetized rats. Changes in vessel diameter to intravenously administered alphaCGRP and betaCGRP were compared with pre-infusion baseline. Intravenous infusion of alphaCGRP and betaCGRP in the highest dose induced dilation of the cerebral cortical pial arteries/arterioles of 40.3 +/- 7.5% and 49.1 +/- 8.4%, respectively. However, this was probably secondary to a decrease in blood pressure of 44.8 +/- 3.3 mmHg and 49.2 +/- 3.3 mmHg. Our results suggest that CGRP receptors are probably functional on the smooth muscle cells and not on the endothelium of rat cerebral arteries.


Assuntos
Artérias/efeitos dos fármacos , Circulação Cerebrovascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Pia-Máter/irrigação sanguínea , Receptores de Peptídeo Relacionado com o Gene de Calcitonina/metabolismo , Adrenomedulina , Amiloide/metabolismo , Amiloide/farmacologia , Angiografia , Animais , Artérias/metabolismo , Relação Dose-Resposta a Droga , Técnicas In Vitro , Polipeptídeo Amiloide das Ilhotas Pancreáticas , Masculino , Músculo Liso Vascular/efeitos dos fármacos , Peptídeos/metabolismo , Peptídeos/farmacologia , Pia-Máter/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Vasodilatação , Vasodilatadores/metabolismo , Vasodilatadores/farmacologia
9.
Cephalalgia ; 25(1): 23-9, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15606566

RESUMO

The genuine closed cranial window model, in which the thinned parietal bone constitutes the covering of the preparation, has contributed to a better understanding of the pathophysiological mechanisms in migraine. In its present form, only measurements of the middle meningeal artery (MMA) are performed. The aim of this study was, in addition, to measure pial artery/arteriole (PA) diameter and cortical cerebral blood flux in the same cranial window. The model was evaluated by studying the effects of hypotension and changes in arterial carbon dioxide pressure (PaCO2), because these parameters might influence the interpretation of pharmacological experiments. Out of 23 successful experiments it was possible to measure all three parameters in 19 animals. In four, PA diameter could not be measured, while MMA diameter and local cortical cerebral blood flux (LCBF(Flux)) always could. Haemorrhage-induced hypotension (-64+/-0.8 mmHg) caused an increase of MMA diameter of 11.8+/-8.4%, PA diameter of 61.2+/-7.7% and a decrease in LCBF(Flux) of -36.4+/-2.5%. The decrease in blood pressure did not significantly change the MMA (P=0.38); however, the PA diameter and the LCBF(Flux) were affected (P<0.001). All three parameters were sensitive to hypo- and hypercapnia. In conclusion, we have shown that not only MMA but also PA diameter and LCBF(Flux) can be measured in the same cranial window. Tight control of PaCO2 is essential in pharmacological experiments. If test substances possess hypotensive actions, it may be difficult to interpret whether the PA dilation is caused by the induced hypotension per se or is a direct pharmacological action or a combination. In contrast, the MMA does not autoregulate and MMA diameter changes in pharmacological studies may exclusively be due to direct pharmacological effects.


Assuntos
Dióxido de Carbono/fisiologia , Hipotensão/fisiopatologia , Modelos Animais , Crânio/irrigação sanguínea , Crânio/fisiologia , Animais , Dura-Máter/irrigação sanguínea , Dura-Máter/fisiologia , Masculino , Artérias Meníngeas/fisiologia , Pia-Máter/irrigação sanguínea , Pia-Máter/fisiologia , Ratos , Ratos Sprague-Dawley
10.
Cephalalgia ; 25(4): 249-60, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15773822

RESUMO

The aim of the present study was to examine the effect of K(ATP) channel openers pinacidil and levcromakalim on rat dural and pial arteries as well as their inhibition by glibenclamide. We used an in-vivo genuine closed cranial window model and an in-vitro organ bath. Glibenclamide alone reduced the dural but not the pial artery diameter compared with controls. Intravenous pinacidil and levcromakalim induced dural and pial artery dilation that was significantly attenuated by glibenclamide. In the organ bath pinacidil and levcromakalim induced dural and middle cerebral artery relaxation that was significantly attenuated by glibenclamide. In conclusion, K(ATP) channel openers induce increasing diameter/relaxation of dural and pial arteries after intravenous infusion in vivo and on isolated arteries in vitro. Furthermore, dural arteries were more sensitive to K(ATP) channel openers than pial arteries.


Assuntos
Artérias/citologia , Artérias/fisiologia , Dura-Máter/irrigação sanguínea , Pia-Máter/irrigação sanguínea , Canais de Potássio/fisiologia , Vasodilatação/fisiologia , Animais , Artérias/efeitos dos fármacos , Cromakalim/farmacologia , Dura-Máter/citologia , Dura-Máter/efeitos dos fármacos , Glibureto/farmacologia , Masculino , Pia-Máter/citologia , Pia-Máter/efeitos dos fármacos , Pinacidil/farmacologia , Canais de Potássio/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologia
11.
Cephalalgia ; 25(5): 369-77, 2005 May.
Artigo em Inglês | MEDLINE | ID: mdl-15839852

RESUMO

Adenosine is an endogenous neurotransmitter that is released from the brain during hypoxia and relaxes isolated human cerebral arteries. Many cerebral artery dilators cause migraine attacks. However, the effect of intravenous adenosine on headache and cerebral artery diameter has not previously been investigated in man and reports regarding the effect of intravenous adenosine on cerebral blood flow are conflicting. Twelve healthy participants received adenosine 80, 120 microg kg(-1) min(-1) and placebo intravenously for 20 min, in a double-blind, three-way, crossover, randomized design. Headache was rated on a verbal scale (0-10). Regional cerebral blood flow (rCBF) with 133Xe inhalation and single-photon emission computed tomography (SPECT) and MCA flow velocity (V(MCA)) with transcranial Doppler, were measured in direct sequence. Six participants developed headache during 80 microg kg(-1) min(-1) and six during 120 microg kg(-1) min(-1) compared with none on placebo (P = 0.006). The headache was very mild and predominantly described as a pressing sensation. When correcting data for adenosine-induced hyperventilation, no significant changes in rCBF (P = 0.22) or V(MCA) (P = 0.16) were found between treatments. A significant dilation of the superficial temporal artery (STA) was seen (P < 0.001). These results show that circulating adenosine has no effect on rCBF or V(MCA), while it dilates the STA and causes very mild headache.


Assuntos
Adenosina/administração & dosagem , Adenosina/sangue , Circulação Cerebrovascular/efeitos dos fármacos , Cefaleia/fisiopatologia , Adulto , Velocidade do Fluxo Sanguíneo/efeitos dos fármacos , Velocidade do Fluxo Sanguíneo/fisiologia , Circulação Cerebrovascular/fisiologia , Estudos Cross-Over , Método Duplo-Cego , Feminino , Cefaleia/induzido quimicamente , Humanos , Infusões Intravenosas , Masculino
12.
Cephalalgia ; 25(2): 139-47, 2005 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15658951

RESUMO

BIBN4096BS is a CGRP-antagonist effective in the treatment of migraine. Blocking the receptor of a strong vasodilator involves a theoretical risk of causing cerebral vasoconstriction, a probability not previously investigated with BIBN4096BS. Seven healthy volunteers completed this double-blinded placebo-controlled crossover study. The volunteers received randomly 10 min infusions of either placebo, 2.5 mg or 10 mg of BIBN4096BS on 3 separate days. Transcranial Doppler was used to measure the middle cerebral artery blood flow velocity (V(MCA)); global and regional cerebral blood flow (rCBF(MCA)) was measured by 133-Xenon inhalation SPECT. The diameter of the temporal and radial artery was measured by high-resolution ultrasound. Systemic haemodynamics and partial pressure of CO(2) (P(et)CO(2)), and adverse events were monitored regularly. BIBN4096BS had no influence on global or regional cerebral blood flow, or on the blood flow velocity in the middle cerebral artery. There was no effect on systemic haemodynamics and adverse events were minor. We conclude that there is no effect of CGRP-receptor blockade on the cerebral or systemic circulation in humans. Circulating CGRP is therefore not likely to exert a vasodilatory activity in the resting state and the use of BIBN4096BS for acute migraine seems to be without risk of cerebral vasoactivity. These data suggest that BIBN4096BS is the first specific antimigraine drug without vasoactive effect.


Assuntos
Pressão Sanguínea/efeitos dos fármacos , Encéfalo/irrigação sanguínea , Peptídeo Relacionado com Gene de Calcitonina/antagonistas & inibidores , Circulação Cerebrovascular/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Piperazinas/farmacologia , Quinazolinas/farmacologia , Adulto , Feminino , Humanos , Masculino , Fluxo Sanguíneo Regional/efeitos dos fármacos
13.
Med J Aust ; 160(6): 377-81, 1994 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-8133824

RESUMO

Selective treatment of neonatal infants who are terminally ill or born with profound disabilities is becoming a controversial issue. The potential of medical technology, the practices of doctors and the expectations of parents have moved ahead of the law in this area. The interests of parents, children and medical practitioners would be better served by a clarification of the law. Legal change should be based on an ethical and moral foundation. The application of the "best interests" test should be given further consideration.


Assuntos
Defesa da Criança e do Adolescente/legislação & jurisprudência , Anormalidades Congênitas/terapia , Eutanásia Passiva/legislação & jurisprudência , Recém-Nascido , Austrália , Encefalopatias , Inglaterra , Ética Médica , Feminino , Homicídio/legislação & jurisprudência , Humanos , Bem-Estar do Lactente/legislação & jurisprudência , Masculino , Consentimento dos Pais , Pais , Poder Psicológico , Valor da Vida , Suspensão de Tratamento
14.
Acta Neurol Scand ; 97(3): 160-3, 1998 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9531431

RESUMO

We aimed to characterize the clinical profile and EEG features of 43 patients with juvenile myoclonic epilepsy. In a retrospective design we studied the records of, and re-interviewed, 43 patients diagnosed with JME from the epilepsy clinic data base. Furthermore, available EEGs were re-evaluated. Of the patients 72% were female and 28% male. Average age of onset was 13 (5.5-22) years for absences, 16 (5.2-25) years for myoclonic seizures, and 16 (8-29) years for generalized tonic-clonic seizures. Forty-two percent reported asymmetric or unilateral myoclonic jerks. Commonly reported precipitating factors were sleep deprivation (84%), stress (70%), and alcohol consumption (51%). EEG findings included rapid spike-wave and polyspike-wave.


Assuntos
Epilepsias Mioclônicas/fisiopatologia , Adulto , Idade de Início , Eletroencefalografia , Epilepsias Mioclônicas/tratamento farmacológico , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fatores Desencadeantes , Estudos Retrospectivos , Convulsões/classificação , Convulsões/fisiopatologia , Resultado do Tratamento
15.
J Microsc ; 195(Pt 1): 79-86, 1999 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10444304

RESUMO

A method designed for stereological estimation in a very complex tissue using vertical sections is presented. In some tissues, the random rotation of the tissue for vertical sections may obscure recognition of the anatomical structures of interest. The present method overcomes this problem by generating sections with both a particular orientation, 'mapping sections', and ordinary random vertical sections usable for the required observations. A map describing the positions of the vertical sections is produced to make the complex reference space recognizable. The method is illustrated by estimating the number and size of neurones in the dorsal raphe nucleus of the human brainstem with its dense packing of roughly 100 nuclei within a volume less than 50 cm3.


Assuntos
Anatomia Transversal/métodos , Tronco Encefálico/anatomia & histologia , Humanos , Masculino , Núcleos da Rafe/anatomia & histologia
16.
J Microsc ; 204(Pt 3): 232-46, 2001 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11903800

RESUMO

This paper is a review of the stereological problems related to the unbiased estimation of particle number and size when tissue deformation is present. The deformation may occur during the histological processing of the tissue. It is especially noted that the widely used optical disector may be biased by dimensional changes in the z-axis, i.e. the direction perpendicular to the section plane. This is often the case when frozen sections or vibratome sections are used for the stereological measurements. The present paper introduces new estimators to be used in optical fractionator and optical disector designs; the first is, as usual, the simplest and most robust. Finally, it is stated that when tissue deformation only occurs in the z-direction, unbiased estimation of particle size with several estimators is possible.


Assuntos
Encéfalo/citologia , Microscopia/métodos , Humanos , Masculino , Microtomia , Tamanho da Partícula , Inclusão do Tecido , Fixação de Tecidos
17.
J Microsc ; 200(Pt 2): 148-57, 2000 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11106955

RESUMO

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.


Assuntos
Axônios/ultraestrutura , Processamento de Imagem Assistida por Computador/métodos , Nervos Periféricos/ultraestrutura
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