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PubMed1990

Nerve-mediated functions in the circular and longitudinal muscle layers of the proximal female rabbit urethra.

In the present study, nerve mediated functions in the circular and longitudinal muscle layers of the female rabbit urethra were characterized. Based on light microscopic findings, the interest was focused on the proximal third of the organ. A microsurgical dissection technique was developed, allowing separation of the two muscle layers. The following studies were carried out: functional in vitro investigations including exogenous application of drugs and electrical field stimulation, investigations of the release of 3H-noradrenaline (NA), and autoradiography for visualization of muscarinic receptors. The results can be summarized as follows: the adrenergic nervous influence, which was mediated mainly via alpha 1-adrenoceptors, dominated the contractile response of the circular layer and contributed significantly to the contraction of the longitudinal layer. A previously described fast, non-adrenergic, non-cholinergic response was found in the circular muscle layer. This response should probably be ascribed to striated muscle with a different innervation and/or structure than skeletal muscle in general. Muscarinic cholinoceptors were abundant in the outer parts of the urethral wall and decreased in density in luminal direction. A significant cholinergic contractile component was demonstrated in the longitudinal muscle. A non-adrenergic, non-cholinergic nerve-mediated relaxant response was found in both layers, although more pronounced in the circular one. Vasoactive intestinal polypeptide completely relaxed both circular and longitudinal preparations contracted by noradrenaline. A possible basis for an interaction between adrenergic and cholinergic nerve endings was demonstrated in the circular muscle layer. Stimulation of muscarinic receptors on the adrenergic nerve endings markedly reduced the release of 3H-NA. The present results support the findings in previous studies on circularly and longitudinally oriented full-thickness preparations of the female urethra and further underline the differences in structure, innervation and receptor functions between the different muscle layers of the urethral wall.

Adrenergic Fibers↗

PubMed1996

Inhibitory transmission to the longitudinal muscle of the mouse caecum is mediated largely by nitric oxide acting via soluble guanylyl cyclase.

In this work we describe a region of mouse intestine, the caecum, in which inhibitory transmission to the longitudinal muscle is predominantly due to nitric oxide. In the presence of muscarinic receptor blockade, electrical stimulation of intramural nerves in the longitudinal muscle of the mouse caecum evoked a relaxation. The relaxation was reduced to about 25% of the control amplitude by the nitric oxide synthase inhibitor L-NMMA (NG-methyl-L-arginine), but was unaffected by D-NMMA. In the presence of the nitric oxide scavenger oxyhaemoglobin, the relaxation was reduced to less than 10% of the control amplitude. In the circular muscle of the caecum and the longitudinal muscle of the ileum, colon and rectum, electrical field stimulation either evoked only small relaxations, or relaxations that were unaffected by L-NMMA. Nitric oxide synthase-containing neurons in the caecum were localized immunohistochemically using an antibody to neuronal nitric oxide synthase or with NADPH diaphorase histochemistry. Reactive nerve cell bodies were observed in the myenteric plexus, and varicose nerve fibres were present in the longitudinal and circular muscle layers of the caecum. The transduction mechanism of the nitric oxide-mediated relaxation in the longitudinal muscle of the caecum was examined using ODQ (1 H-[1,2,4]oxadiazolo[4,3,-alpha-]quinoxalin-1-one), a selective inhibitor of soluble guanylyl cyclase. ODQ abolished the relaxations induced by applied sodium nitroprusside (0.01-1 mM) and reduced the relaxation induced by electrical stimulation to about 40% of control values. However, ODQ reduced the relaxations induced by electrical stimulation to a lesser extent than L-NMMA. Hence, although the relaxation in this tissue mediated by NO (or an NO-related substance) is largely via soluble guanylyl cyclase, an action of NO on other targets cannot be ruled out.

Animals↗

PubMed1989

Longitudinal melanonychia (melanonychia striata): diagnosis and management.

Longitudinal melanonychia presents a difficult clinical challenge because subungual melanoma must always be included in the differential diagnosis and because the cause of longitudinal melanonychia is usually not apparent. Accordingly, biopsy is often necessary to establish the cause. This review attempts to expedite management by providing suggestions for the examination of patients with this disorder. The causes of longitudinal melanonychia are enumerated and clues to arrive at the various causes are discussed. Similarities between longitudinal melanonychia and subungual melanoma are discussed in an effort to clarify their differences and similarities; clues to the diagnosis of subungual melanoma are also discussed. Various biopsy techniques applicable to longitudinal melanonychia are considered and the indications for different surgical approaches are emphasized. The importance of the pathologist in interpreting nail biopsy specimens is emphasized.

Biopsy↗

PubMed2003

Evaluation of the longitudinal contraction of the left ventricle in normal subjects by Doppler tissue tracking and strain rate.

BACKGROUND: Tissue tracking (TT) and strain rate (SR) are new echocardiographic modalities on the basis of Doppler tissue imaging, which allow assessment of the systolic longitudinal contraction of the myocardium. OBJECTIVE: The aim of this study was to describe the global and regional longitudinal function of the left ventricle by TT and SR analysis. METHODS: The study population consisted of 55 normal subjects. To assess longitudinal myocardial contraction, TT was performed in the standard apical views and expressed as a score index of the 16 myocardial segments. In addition, SR was performed in each segment. RESULTS: The mean longitudinal contraction was 7.8 +/- 1.8 mm. Longitudinal contraction was significantly decreasing with increasing age and systolic blood pressure (r = -0.46, P <.01 for both measures), but independent of heart rate, left ventricular diameters, ejection fraction, and fractional shortening. SR was found significantly larger in the basal segments than in the middle and apical segments (-1.8 +/- 0.6 s(-1) vs 1.4 +/- 0.3 s(-1) P <.001). CONCLUSION: TT and SR analysis are easily obtained and may complement conventional measures of left ventricular systolic function.

Echocardiography, Doppler↗

PubMed2000

Longitudinal risk of std acquisition in adolescent girls using a generalized estimating equations model

Background: To date, few studies have used a longitudinal approach in examining risk factors for STD acquisition in teenage girls. In the present study, we examined risk of STD acquisition in adolescent girls over a three-year period using longitudinal analyses.Methods: One hundred and seventy-four girls between the ages of 12 and 16 (mean age = 14.5) participated in a longitudinal study of adolescent romantic relationships. The racial composition of the subject pool was 80% African-American and 20% Caucasian. These girls were followed for three years at six-month intervals. By the end of the study, 127 of the girls were sexually experienced, and thus, were included in the analyses regarding risk for STDs. The risk for history of STD was evaluated using a generalized estimating equations (GEE) model, which allows for the inclusion of data from subjects with missing visits. The following independent variables were entered into the model: age, race, screening IQ score, qualitative cognitive functioning, perceptions of STD prevalence among female friends, and whether a condom was used at last intercourse. Additional independent variables included number of lifetime partners (4 or more lifetime partners, 2 to 3 lifetime partners, only one partner) and age of sexual debut (less than 14 years, 14-16 years, and 17 years and older), five factors from the Family Environment Scale, and three types of parental monitoring (direct, direct when with peers, and indirect).Results: The results of the longitudinal (GEE) model indicated that having a history of an STD was significantly related to a younger age of sexual debut (p <.01), having more partners (p <.0001), being African-American (p =. 01), and having a lower screening IQ score (p <.01).Conclusions: These results suggest that risk of STD is associated with both modifiable and non-modifiable variables. Race and intellectual functioning independently contributed to STD risk, stressing the importance of utilizing prevention programs that are culturally and developmentally specific. For example, less intelligent girls may need to have information presented in a more concrete manner, with a focus on the present rather than the future. The targets of these prevention programs should continue to emphasize delaying initiation, as well as partner selection. Finally, the fact that variables for STD acquisition in this longitudinal model are comparable to previous cross-sectional studies of STD acquisition suggests that these are potent predictors of risk.

Journal Article↗

PubMed1998

Longitudinal genetic analysis of menstrual flow, pain, and limitation in a sample of Australian twins.

Genetically informative longitudinal data about menstrual disorders allow us to address the extent to which the same genetic risk mechanisms are operating throughout the reproductive life cycle. We investigate the relative contributions of genes and environment to individual differences in menstrual symptomatology reported at two waves, 8 years apart, of a longitudinal Australian twin study. Twins were questioned in 1980-1982 and 1988-1990 about levels of menstrual pain, flow, and perceived limitation by menses. Longitudinal genetic analysis was based on 728 pairs (466 MZ and 262 DZ) who were regularly menstruating at both survey waves. A bivariate Cholesky model was fitted to the two-wave data separately for flow, pain, and limitation variables. The baseline model comprised common genetic and environmental factors influencing responses at both waves and specific effects influencing only the second-wave response. We also included age as a covariate in the model. Proportions of the longitudinally stable variance in menstrual flow, pain, and limitation attributable to genetic and individual environmental effects were calculated for the best-fitting models. Genetic factors accounted for 39% of the longitudinally stable variation in menstrual flow, 55% for pain, and 77% for limitation. The remaining stable variance was due to individual environmental factors (61, 45, and 23%, respectively). Therefore the stable variance over the 8-year interval was largely environmentally influenced for menstrual flow, was approximately equally determined by genetic and by nonshared environmental influences in the case of pain, and was due almost entirely to genetic influences for limitation by periods. We demonstrate for the first time that the same genetic influences are operative throughout the reproductive life span.

Adolescent↗

PubMed2000

Involvement of cyclic AMP - PKA pathway in VIP-induced, charybdotoxin-sensitive relaxation of longitudinal muscle of the distal colon of Wistar-ST rats.

The intracellular mechanism of vasoactive intestinal peptide (VIP)-induced, charybdotoxin (ChTx)-sensitive relaxation of longitudinal muscle of the distal colon of Wistar-ST rats was studied. A single pulse or 100 pulses at 10 Hz of electrical field stimulation (EFS) induced rapid transient relaxation or that with a subsequent contraction of the longitudinal muscle in the presence of atropine and guanethidine, respectively. Rp-8 bromo cAMPS, an inhibitor of cyclic AMP dependent protein kinase (PKA), at 30 microM inhibited the relaxations induced by EFS with a single or 100 pulses maximally by about 80 or 60%, respectively. It also inhibited VIP (300 nM)-induced relaxation by 82%. VIP (100 nM - 1 microM) increased the cyclic AMP content of longitudinal muscle myenteric plexus preparations obtained from the distal colon. ChTx at 100 nM almost completely inhibited 8 bromo cyclic AMP-induced relaxation of the distal segments. EFS with two or three pulses at 10 Hz induced inhibitory junction potentials consisting of two phases, rapid and subsequent slow hyperpolarization in the membrane potential of longitudinal smooth muscle cells. Rp-cAMPS, another inhibitor of PKA, inhibited the delayed slow hyperpolarization. It also inhibited the exogenously added VIP-induced hyperpolarization of the cell membrane. Thus, the present study suggests that activation of PKA via activation of VIP receptors is associated with activation of ChTx-sensitive K(+) channels in relaxation of longitudinal muscle of the distal colon of Wistar-ST rats. British Journal of Pharmacology (2000) 129, 140 - 146

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1999

Limitation of cholangiography in assessing longitudinal spread of extrahepatic bile duct carcinoma to the hepatic side.

BACKGROUND: Preoperative assessment of longitudinal spread of bile duct carcinoma (BDC) to the hepatic side remains a difficult problem for diagnostic imaging. METHODS: We studied the accuracy of cholangiography in assessing BDC. In 54 patients with extrahepatic bile duct cancer, cholangiographic findings were compared retrospectively with the histological findings of the resected specimens. RESULTS: Histological examination of specimens indicated longitudinal spread of the tumour to the hepatic side in 22 of 54 patients. The accuracy of cholangiography in assessing the extent of the longitudinal spread was only 34/54 (63%). When the cholangiographic images showed a main tumour with a collapsed edge, there was a significantly higher frequency of longitudinal spread compared with tumours with sharp edges (P< 0.05). In contrast, the accuracy of mapping biopsy under percutaneous transhepatic cholangioscopy (n=24) was 83%. CONCLUSIONS: Cholangiography cannot accurately assess the extent of the longitudinal spread of bile duct cancer. When cholangiographic images show a tumour with a collapsed edge, preoperative or intraoperative histological examination is essential to determine a suitable surgical line.

Adenocarcinoma↗

PubMed2002

MR cholangiography versus cholangioscopy for evaluation of longitudinal extension of hilar cholangiocarcinoma.

BACKGROUND: The utility of magnetic resonance cholangiography for assessment of longitudinal tumor extension of hilar cholangiocarcinoma was investigated with reference to findings by percutaneous transhepatic cholangioscopy. METHODS: Ninety-nine patients with hilar cholangiocarcinoma underwent both magnetic resonance cholangiography and percutaneous transhepatic cholangioscopy. Longitudinal tumor extension was described with the Bismuth-Corlette classification. Hilar cholangiocarcinoma was classified morphologically into stenotic, diffuse sclerosing, and polypoid types based on selective cholangiographic findings obtained during percutaneous transhepatic cholangioscopy. Agreement between percutaneous transhepatic cholangioscopy and magnetic resonance cholangiography according to the Bismuth-Corlette classification was compared. The degree of agreement between magnetic resonance cholangiography and percutaneous transhepatic cholangioscopy according to each morphologic type was also compared in each subgroup without reference to Bismuth-Corlette type. RESULTS: The overall agreement between magnetic resonance cholangiography and percutaneous transhepatic cholangioscopy with regard to Bismuth-Corlette types was 87.9% (kappa = 0.832, p < 0.01). The agreement of magnetic resonance cholangiography for each Bismuth-Corlette type with reference to percutaneous transhepatic cholangioscopy was as follows: type I (n = 18), 16/18 (88.9%); type II (n = 16), 14/16 (87.5%); type IIIa (n = 23), 19/23 (82.6%); type IIIb (n = 14), 14/14 (100%); and type IV (n = 28), 24/28 (85.7%). The overall agreement between magnetic resonance cholangiography and percutaneous transhepatic cholangioscopy for Bismuth-Corlette type according to selective cholangiographic findings was as follows: stenotic type, 58/61 (95.1%, kappa = 0.929, p < 0.01); diffuse sclerosing type, 12/16 (75%, kappa = 0.619, p < 0.01); and polypoid type, 17/22 (77.3%, kappa = 0.696, p < 0.01). CONCLUSION: There is good overall agreement between magnetic resonance cholangiography and percutaneous transhepatic cholangioscopy on longitudinal extension of hilar cholangiocarcinoma. Especially for the stenotic type of hilar cholangiocarcinoma (based on selective cholangiographic findings), magnetic resonance cholangiography may replace percutaneous transhepatic cholangioscopy in the determination of longitudinal tumor extension. For polypoid or diffuse sclerosing types, however, percutaneous transhepatic cholangioscopy is required for accurate evaluation of longitudinal tumor extension.

Adult↗

PubMed2001

Longer longitudinal atrial dimension in patients with idiopathic paroxysmal atrial fibrillation: A possible cause of atrial fibrillation.

BACKGROUND: The ostium of the superior pulmonary veins or superior vena cava has been reported to be an important source of the ectopic beats that initiate paroxysmal atrial fibrillation (PAF). The structural details of the atria in patients with idiopathic PAF, however, remain unknown. METHODS: We studied 113 patients (92 men and 21 women) with idiopathic PAF and 128 normal control subjects (100 men and 28 women). None of the subjects in either group were found to have any evidence of structural cardiac disease. The echocardiographic measurements were performed in the apical 4-chamber view during end-systole of sinus rhythm. RESULTS: The longitudinal dimension of the left and right atria was longer in patients with PAF who were not administered any drugs (non-drug-taking patients) than in the control subjects (P <.001 and P <.01, respectively). However, there were no significant differences in the transverse dimension of either atrium between such patients and control subjects. The longitudinal and transverse dimensions and volume determinations of atria were greater in the patients with idiopathic PAF who were administered class 1 antiarrhythmic drugs than in non-drug-taking patients (P <.05 to.001). In non-drug-taking patients, prolongation of the atrial longitudinal dimension did not depend on either age, the total frequency of PAF, or the interval from the first episode of PAF. The longitudinal dimension of the left and right atria was longer even in the patients with a short history of PAF (<1 month) as compared with control subjects (P <.001 and.05, respectively). CONCLUSIONS: These observations suggest that there is prolongation of the longitudinal dimension in patients with idiopathic PAF independent of PAF frequency and age (and that PAF is probably a consequence of the prolongation).

Adult↗

PubMed1991

Transverse versus longitudinal arteriotomy: an experimental study in dogs.

An arteriotomy is a commonly used surgical technique. Either a transverse or a longitudinal incision can be made, but no study has been done to determine if one technique results in more stenosis or flow disturbance than the other. Six-millimeter arteriotomies were made on the carotid and femoral arteries of six dogs. Transverse arteriotomies were made on the right, and longitudinal arteriotomies were made on the left. Four weeks later the vessels were reexplored. Duplex scanning was used to assess the amount of turbulence at each arteriotomy. Afterward, latex casts of the arteries were made to determine the percent stenosis caused by each arteriotomy. The mean percent stenosis associated with transverse arteriotomies was 10.5% (+/- 4.4%), versus 22.8% (+/- 9.4%) for the longitudinal arteriotomies, (p = 0.001, matched t test). No difference in the amount of turbulence associated with each technique was demonstrated. A longitudinal arteriotomy results in significantly greater stenosis than does a transverse arteriotomy. Unless there is a specific indication for a longitudinal arteriotomy, a transverse arteriotomy should be used.

Animals↗

PubMedDate not supplied

Career-span analyses of track performance: longitudinal data present a more optimistic view of age-related performance decline.

Sport scientists (Starkes, Weir, Singh, Hodges, & Kerr, 1999; Starkes, Weir, & Young, 2003) have suggested that prolonged training is critical for the maintenance of athletic performance even in the face of predicted age-related decline. This study used polynomial regression analyses to examine the relationship between age and running performance in the 1500 and 10,000 metre events. We compared the age and career-longitudinal performances for 15 male Canadian Masters athletes with a cross-sectional sample of performances at different ages. We hypothesized that the 30 years of uninterrupted training characteristic of this longitudinal sample would moderate the patterns of age-related decline (retention hypothesis); alternatively, the cross-sectional data were expected to demonstrate pronounced age-related decline (quadratic hypothesis). Investigators performed multimodel regression analyses on the age and performance data. Based on the absence (for longitudinal data) or presence (for the cross-sectional data) of significant quadratic components in second-order polynomial models, the authors found support for their respective hypotheses. The longitudinal data showed that running performance declined with age in a more linear fashion than did cross-sectional data. Graphical trends showed that the moderation of age-related decline appeared greater for the longitudinal 10 km performances than for the 1500m event.

Adult↗

PubMed2004

Pressure pulse velocity is related to the longitudinal elastic properties of the artery.

It is known that arteries in their natural position are always subject to a longitudinal stress. However, the effect of this strong longitudinal tension has seldom been addressed. In this paper, we point out that the traditional pulse wave velocity formulae considering only the circumferential elasticity fail to include all the important energies. We present a vigorous derivation of a pressure wave equation, the pressure wave equation with total energy, which considers all the important energies of the whole arterial system by treating the arterial wall and the blood as one system. Our model proposes that the energy transport in the main arterial system is primarily via the transverse vibration motion of the elastic wall. The final equation indicates that the longitudinal stress is essential and the high frequency phase velocity is related to the longitudinal tension along the arterial wall and its Young's shearing modulus. By applying this equation, we suggest that longitudinal elastic property is an important factor in hemodynamics and in the treatment of cardiovascular diseases.

Animals↗

PubMed2003

Statistical significance analysis of longitudinal gene expression data.

MOTIVATION: Time-course microarray experiments are designed to study biological processes in a temporal fashion. Longitudinal gene expression data arise when biological samples taken from the same subject at different time points are used to measure the gene expression levels. It has been observed that the gene expression patterns of samples of a given tumor measured at different time points are likely to be much more similar to each other than are the expression patterns of tumor samples of the same type taken from different subjects. In statistics, this phenomenon is called the within-subject correlation of repeated measurements on the same subject, and the resulting data are called longitudinal data. It is well known in other applications that valid statistical analyses have to appropriately take account of the possible within-subject correlation in longitudinal data. RESULTS: We apply estimating equation techniques to construct a robust statistic, which is a variant of the robust Wald statistic and accounts for the potential within-subject correlation of longitudinal gene expression data, to detect genes with temporal changes in expression. We associate significance levels to the proposed statistic by either incorporating the idea of the significance analysis of microarrays method or using the mixture model method to identify significant genes. The utility of the statistic is demonstrated by applying it to an important study of osteoblast lineage-specific differentiation. Using simulated data, we also show pitfalls in drawing statistical inference when the within-subject correlation in longitudinal gene expression data is ignored.

Adaptation, Physiological↗

PubMed1992

Longitudinal distribution of pulmonary vascular resistance after endotoxin administration in sheep.

BACKGROUND AND METHODS: Pulmonary hypertension may increase pulmonary capillary pressure and exacerbate pulmonary edema in acute respiratory failure. The effects of pulmonary hypertension on pulmonary capillary pressure depend on the longitudinal distribution of pulmonary vascular resistance. Since pulmonary hypertension occurs during acute respiratory failure, we hypothesized that acute respiratory failure may produce time-dependent changes in the longitudinal distribution of pulmonary vascular resistance. Therefore, we measured pulmonary capillary pressure and the longitudinal distribution of pulmonary vascular resistance in an animal model of acute respiratory failure. Escherichia coli endotoxin (2.5 to 5.0 micrograms/kg) was administered over a 1-hr period in eight anesthetized sheep. Pulmonary and systemic hemodynamics, including pulmonary artery occlusion pressure (PAOP), pulmonary capillary pressure, and the longitudinal distribution of pulmonary vascular resistance, were measured over the next 5 hrs. Pulmonary capillary pressure was estimated by analysis of the pressure decay following pulmonary artery balloon inflation. RESULTS: Endotoxin administration resulted in sustained pulmonary hypertension for the subsequent 5 hrs of the study. Pulmonary capillary pressure was increased 7 mm Hg above baseline at 0.5 and 0.75 hrs during the infusion of endotoxin but returned to baseline values at 1.5 hrs. Despite sustained pulmonary hypertension, pulmonary capillary pressure remained at baseline values for the duration of the study. Similar to pulmonary capillary pressure, pulmonary venous (or postcapillary) resistance was increased approximately four-fold over baseline at 0.5 and 0.75 hrs after initiating endotoxin administration, but returned to baseline values by the end of endotoxin administration and remained at baseline values throughout the remainder of the study. In contrast, pulmonary arterial (or precapillary) resistance remained at values approximately three times baseline during the infusion and throughout the duration of the study. CONCLUSIONS: In this experimental model of acute respiratory failure, the effects of endotoxin on the longitudinal distribution of pulmonary vascular resistance are time-dependent. If these data from animals can be extrapolated to humans, we speculate that the importance of pulmonary venoconstriction in exacerbating pulmonary edema may vary over time in patients with acute respiratory failure.

Animals↗

PubMed1992

Immunohistochemical demonstration of bone morphogenetic protein-2 and transforming growth factor-beta in the ossification of the posterior longitudinal ligament of the cervical spine.

To clarify the mechanism of ossification of the posterior longitudinal ligament, immunohistochemical localization of bone morphogenetic protein-2 and transforming growth factor-beta was examined using surgical specimens of ligament tissues from an affected patient. Two polyclonal antibone morphogenetic protein-2 antibodies and an anti-human transforming growth factor-beta antibody were used as primary antibodies. Bone morphogenetic protein-2 and transforming growth factor-beta were present in ossified matrix and chondrocytes of adjacent cartilaginous areas of ossification of the posterior longitudinal ligament. Although immunostaining with antibone morphogenetic protein-2 antibodies also was observed in mesenchymal cells with fibroblastic features in the immediate vicinity of the cartilaginous areas, no staining could be detected with anti-human transforming growth factor-beta antibody in these cells. The presence of these factors were specific for the ossified ligament because no immunostaining was observed after using antibodies in the posterior longitudinal ligament at unossified levels from the same patient. It is suggested that bone morphogenetic protein-2 and transforming growth factor-beta play important roles in the development of ossification of the posterior longitudinal ligament and that bone morphogenetic protein-2 may act as an initiating factor in the development of ossification of the posterior longitudinal ligament by stimulating differentiation of mesenchymal progenitor cells. Transforming growth factor-beta may stimulate bone formation at a later stage of the process of ectopic ossification.

Aged↗

PubMed1993

Relationship of the dura, Hofmann's ligaments, Batson's plexus, and a fibrovascular membrane lying on the posterior surface of the vertebral bodies and attaching to the deep layer of the posterior longitudinal ligament. An anatomical, radiologic, and clinical study.

With the advent of computed tomography (CT) and magnetic resonance imaging (MRI), visualization of soft tissue structures in the spinal canal, which were previously undetectable, is possible. This study was undertaken to more accurately identify these soft tissue layers and to determine factors such as when is a disc contained and when is it not; in discography, when the disc leaks, into what layer is the contrast going; or when a nuclear fragment creeps upward or downward, just where is it. The works of Fick, Dommisse, Kikuchi, Schellinger, Hofmann, Batson, and Parke were studied. The professors of anatomy of four major medical schools were consulted along with several neuroradiologists and embryologists. Forty lumbar spines were dissected (20 fresh, 20 preserved). Magnetic resonance imaging scans were taken. Photographs and photomicrographs were made. A fibrous membrane, first mentioned by Fick, can be identified lying anterior to the posterior longitudinal ligament and attaching to the deep layer of the posterior longitudinal ligament. It has been given relatively little attention in the past. This membrane has about one fourth the toughness of the dura and is made up largely of fibrous tissue. The veins of Batson lie on its dorsal surface and pierce it to go ventral to this membrane and enter the vertebral body. Batson's plexus crosses the disc space. The peridural membrane extends from one side to the other, spanning the width of the vertebral body and encircling the bony canal around the outside of the dura. There is a potential space between it and the dura. It does not cross the disc space. A probe can easily be passed posterior or anterior to it, between it and the posterior longitudinal ligament or between it and the vertebral body. We also identified Hofmann's ligament anterior to the dura, attaching the dura to the posterior longitudinal ligament. Laterally, tiny attachments between this fibrovascular membrane and the circumneural sheaths of the spinal nerves can be observed as the nerves enter the foramina. The posterior longitudinal ligament (PLL) is very tough and strong and seldom ruptures. The annulus frequently ruptures. Fragments of nucleus pulposus can creep out at the vertebral rim and get under the PLL and the peridural membrane. Hematoma can form by the same route and have the exact appearance as a sequestrated disc. There is no periosteum inside the vertebral canal. With MRI, hematomas can be differentiated from an extruded fragment. They may cause symptoms similar to an extruded disc but will probably heal with time.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗

PubMed2000

Prediction of pattern selection due to an interaction between longitudinal rolls and transverse modes in a flow through a rectangular channel heated from below

Convection patterns in a flow through a horizontal channel that is heated from below are predicted on the basis of a weakly nonlinear theory. At a certain value of the Reynolds number and the Rayleigh number, the conduction state with steady shear flow becomes linearly unstable to both longitudinal rolls and transverse modes, simultaneously. The longitudinal rolls align along the streamwise direction whereas the transverse modes are periodic in the streamwise direction. Amplitude equations for the interaction between the longitudinal rolls and the transverse modes are derived in a consistent manner. Coefficients in the equations are determined numerically for a wide range of parameters. The longitudinal rolls are found to bifurcate supercritically. On the other hand, the transverse modes bifurcate subcritically or supercritically, depending on the Prandtl number, the aspect ratio of the channel, and the boundary conditions on the sidewalls. Stable convection patterns are classified in a parameter space. A mixed mode pattern, which is a mixture of the components of the longitudinal rolls and the transverse modes, is found to be stable for some sets of parameters.

Journal Article↗