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PubMed2006

Did the lateral enamel of Neandertal anterior teeth grow differently from that of modern humans?

The formation of lateral enamel in Neandertal anterior teeth has been the subject of recent studies. When compared to the anterior teeth of modern humans from diverse regions (Point Hope, Alaska; Newcastle upon Tyne, England; southern Africa), Neandertal anterior teeth appear to fall within the modern human range of variation for lateral enamel formation time. However, the lateral enamel growth curves of Neandertals are more linear than those of these modern human samples. Other researchers have found that the lateral enamel growth curves of Neandertals are more linear than those of Upper Paleolithic and Mesolithic modern humans as well. The statistical significance of this apparent difference between Neandertal and modern human lateral enamel growth curves is analyzed here. The more linear Neandertal enamel growth curves result from the smaller percentage of total perikymata located in the cervical halves of their teeth. The percentage of total perikymata in the cervical halves of teeth is therefore compared between the Neandertal sample (n=56 teeth) and each modern human population sample: Inuit (n=65 teeth), southern African (n=114 teeth), and northern European (n=115 teeth). There are 18 such comparisons (6 tooth types, Neandertals vs. each of the three modern human populations). Eighteen additional comparisons are made among the modern human population samples. Statistically significant differences are found for 16 of the 18 Neandertal vs. modern human comparisons but for only two of the 18 modern human comparisons. Statistical analyses repeated for subsamples of less worn teeth show a similar pattern. Because surface curvature is thought to affect perikymata spacing, we also conducted measurements to assess surface curvature in thirty teeth. Our analysis shows that surface curvature is not a factor in this lateral enamel growth difference between Neandertals and modern humans.

Animals↗

PubMed2004

Laterally elevated wedged insoles in the treatment of medial knee osteoarthritis. A two-year prospective randomized controlled study.

OBJECTIVE: To compare the clinical effects of laterally wedged insoles and neutrally wedged insoles (used as control) in patients with medial femoro-tibial knee osteoarthritis. METHODS STUDY DESIGN: 24-month prospective randomized controlled study. PATIENTS: Outpatients with painful medial femoro-tibial knee osteoarthritis. OUTCOME MEASURES: Patient's overall assessment of disease activity (5 grade scale), WOMAC index subscales and concomitant treatments. STATISTICAL ANALYSIS: Performed as an intention-to-treat analysis, with the last observation carried forward (LOCF). Main symptomatic criterion: Improvement in the patient's assessment of activity (defined as a reduction of one grade or more at the end of the study as compared to baseline, and no intra-articular injection or lavage during the 6 months previous to the last visit). Secondary criteria for assessment: (a) Changes in the WOMAC subscales at month 24, and (b) concomitant therapies (analgesics, NSAIDs and intra-articular injections or lavages). Structural criterion: Joint space width (JSW) at the narrowest point. Non-compliance was defined as intermittent or lack of insole fitting at two consecutive visits. Compliance within groups was compared by using a life table analysis technique (Log-Rank). RESULTS: The baseline characteristics of the 156 recruited patients (41 males, 115 females, mean age 64.8 years) were not different in the 2 treatment groups. At year 2, there was no statistically significant difference between the 2 groups concerning the percentages of patients with improvement in both global assessment of disease activity and in WOMAC subscales (pain, stiffness, function). The number of days with NSAIDs intake was lower in the group with laterally wedged insoles than in the neutrally wedged group (71+/-173 days vs. 127+/-193 days, P=0.003, Mann-Whitney test). The mean joint space narrowing rate did not differ between the two groups: 0.21+/-0.59 mm/year in the laterally wedged group vs 0.12+/-0.32 mm/year in the neutrally wedged group. Compliance and tolerance were satisfactory. Compliance was different between the 2 groups at month 24, with a greater frequency of patients who wore insoles permanently in the laterally wedged insole group than in the other group (85.8% vs 71.9%, P=0.023). CONCLUSION: This study failed to demonstrate a relevant symptomatic and/or structural effect of laterally-wedged insoles in medial femoro-tibial OA. However, the reduced NSAIDs intake and the better compliance in the treatment group are in favor of a beneficial effect of laterally-wedged insoles in medial femoro-tibial OA.

Aged↗

PubMed2006

Manual fixation versus locking during upper cervical segmental mobilization. Part 2: an in vitro three-dimensional arthrokinematic analysis of manual axial rotation and lateral bending mobilization of the atlanto-axial joint.

BACKGROUND: Three-dimensional kinematic aspects of coupled motion during manual cervical mobilization have not previously been studied. Using an in vitro 3D-motion analysis method, the kinematic effects of two different segmental techniques for axial rotation and lateral bending mobilization of the upper cervical spine were investigated as a second part of the study (in part one, kinematic effects of flexion-extension mobilization have been investigated). METHODS: Axial rotation and lateral bending mobilization of the atlanto-occipital and atlanto-axial segments were analysed in vitro using an electromagnetic tracking device. Local reference frames were defined based on bony reference points that were registered using a 3D-digitizing stylus. Five embalmed and one fresh specimen were analysed. Segmental motion was registered simultaneously in the atlanto-occipital and the atlanto-axial joints during manual mobilization through the full range of axial rotation and lateral bending mobility. The 3D-kinematic aspects during regional mobilization were compared with those during segmental mobilization with manual fixation and during segmental mobilization using a locking technique. RESULTS: During both segmental axial rotation techniques of the atlanto-axial joint, a significant reduction of the coupled lateral bending and flexion-extension motion was observed. The locking technique also induced an increase in the main axial rotation component. During lateral bending mobilization of the atlanto-axial joint, the manual fixation technique reduced the effect on the coupled flexion-extension component significantly. INTERPRETATIONS: These results suggest that for manual segmental axial rotation and lateral bending mobilization of the upper cervical spine segmental manual fixation or locking may be preferred in different situations depending on the desired effects. This study brings additional information to the data provided by part 1 of this study on the 3D-arthrokinematic effects of flexion-extension mobilization.

Atlanto-Axial Joint↗

PubMed2004

Dissociable concurrent activity of lateral and medial frontal lobe during negative feedback processing.

External feedback on results of one's behavior guides flexible adaptation to changing environments. It has been suggested that the lateral and medial parts of the frontal lobe are responsible for cognitive and emotional functions, respectively. In the present fMRI study, multiple mental components evoked by the presentation of negative feedback were dissociated along the cognitive-emotional axis in set-shifting paradigms. The double dissociation of the concurrent feedback-related activity was observed in the right frontal lobe: the lateral frontal lobe was associated with the inferential component, whereas the medial frontal lobe was associated with the emotional component. However, among the multiple right lateral frontal regions, a region of interest (ROI) analysis indicated that the inferential component was not dominant in the region near the inferior frontal junction. The medial frontal activations were observed ventral and anterior to the presupplementary motor area, and dorsal and posterior to the anterior cingulate cortex. The double dissociation in the right frontal lobe suggests that the lateral and medial frontal lobe cooperatively but differentially contributes to the negative feedback processing, demonstrating the lateral-medial dichotomy of the frontal lobe functions suggested by previous neuropsychological studies. At the same time, the functional heterogeneity in the lateral and medial frontal lobe demands modifications of the traditional view of the functional organization of the frontal lobe.

Adult↗

PubMedDate not supplied

A comparison of the lateral and posterior approach for brachial plexus block.

BACKGROUND: Brachial plexus block by the posterior approach described by Pippa is not widely used in contrast to the lateral approach of Winnie. We compared the clinical efficacy of both approaches in a randomized prospective study. METHODS: Eighty patients, American Society of Anesthesiologists physical status I or II, scheduled for surgery of the shoulder or upper arm were randomized in 2 groups: lateral (Winnie, n = 40) or posterior approach (Pippa, n = 40). A single injection of ropivacaine 7.5 mg/mL, 0.5 mL/kg, was made after obtaining a motor response in the distribution of the axillary nerve at a current below 0.5 mA (2 Hz, 0.1 millisecond). Onset and distribution of analgesia and motor block were assessed at 5, 10, 15, 20, 30, and 60 minutes after the local anesthetic injection. Complete block was defined as anesthesia in all dermatomes C3-C6 at 60 minutes after injection. RESULTS: The posterior approach provided complete block in 36 patients (90%) and the lateral approach in 33 patients (83%). Corresponding motor block was similar in both approaches, but the block procedure time was faster in the posterior approach (6.2 [5.2-7.2] minutes v 8.4 [7.1-10.2] minutes; P < .001). Surgical success rate (posterior 95% v lateral 93%) and side effects were similar in both approaches. One complication (thoracic epidural block) was seen using the lateral approach, whereas none occurred in the posterior approach. There was no difference in patient satisfaction scores of the 2 approaches, which were equally high in both groups (posterior 98% v lateral 95%). CONCLUSION: Both approaches are comparable regarding clinical efficacy for anesthesia of the shoulder and upper arm.

Adult↗

PubMed2006

A large arachnoid cyst of the lateral ventricle extending from the supracerebellar cistern--case report.

BACKGROUND: The pathogenetic mechanism of intraventricular arachnoid cyst development is still controversial, but is believed to originate from the vascular mesenchyme or as an extension of the arachnoid cyst in the subarachnoid space into the ventricle through the choroidal fissure. We report a case supporting the extension hypothesis and suggest differential points between an intraventricular arachnoid cyst that extended from the supracerebellar space and a lateral ventricular diverticulum that extended into the supracerebellar cistern. CASE DESCRIPTION: A 12-month-old girl presented with macrocephaly and developmental delay. Her magnetic resonance imaging showed an arachnoid cyst that had developed from the supracerebellar space in the posterior fossa, and which extended into the left lateral ventricle resulting in expansion of the left lateral ventricle and displacing the choroids plexus anteriorly and laterally and the midline to the right. We treated an intraventricular arachnoid cyst by endoscopic fenestration resulting in dramatic reduction of the intraventricular arachnoid cyst with large bilateral subdural fluid collection. We performed a subduroperitoneal shunt for subdural fluid collection and subsequent cystoperitoneal shunt for the remnant cyst. CONCLUSION: We suggest that this case supports the extension hypothesis from the subarachnoid space through the choroidal fissure into the lateral ventricle. We also suggest that one of the radiological differential points between an intraventricular arachnoid cyst and a ventricular diverticulum is displacement and compression of the choroid plexus of the lateral ventricle.

Arachnoid Cysts↗

PubMed2004

Optimal combinations for detection of prostate cancer: systematic sextant and laterally directed biopsies versus systematic sextant and color Doppler-targeted biopsies.

OBJECTIVES: To determine the accuracy of different combinations of biopsies in detecting prostate cancer. The standard sextant protocol for obtaining prostate biopsy underestimates the presence of prostate cancer. Conversely, an increased cancer detection rate has been obtained with additional laterally directed biopsies. The results of the studies dedicated to transrectal color Doppler (CD) sonography have shown that it might detect neoplastic lesions with no corresponding gray-scale abnormality. METHODS: A total of 120 consecutive patients underwent sextant biopsy with additional biopsy cores taken from the lateral peripheral zone (four to six cores, depending on the prostate volume) and CD-guided biopsy. The sensitivity of laterally directed, CD-guided, and different combinations of biopsies was compared. Various patient, clinical, and pathologic factors were compared, and multivariate analysis was performed to assess the strongest predictor of cancer detection. RESULTS: Cancer was detected in 43 (35.8%) of 120 patients. The combination of sextant biopsy with laterally directed cores gained sensitivity to 56.6% compared with 67.4% obtained in the regimen that combined sextant and CD-guided biopsy. The CD regimen detected cancer in 11 additional patients. However, the differences in the detection rates of these combinations were not statistically significant (P = 0.797). The results of multivariate analysis showed that sextant biopsy and laterally directed cores were the strongest predictors of cancer detection (odds ratio 8.356 versus 49.282; 95% confidence interval 1.698 to 41.114 versus 10.508 to 231.130). CONCLUSIONS: The regimen that included sextant and CD-guided biopsy was the most sensitive. However, only standard sextant and laterally directed biopsies were statistically significant predictors of cancer detection on biopsy.

Adenocarcinoma↗

PubMed2004

Coding of lateral line stimuli in the goldfish midbrain in still and running water.

We investigated in goldfish, Carassius auratus, how running water affects the responses of toral lateral line units to a stationary vibrating sphere or to a non-vibrating sphere that moves along the side of the fish. Experiments were conducted in the presence of running water (hydrodynamic noise) to further explore the sensory capabilities of the lateral line with special focus on the morphological sub-modalities. Previous recordings from lateral line nerve fibres in various fish species and the first nucleus of the ascending lateral line pathway in goldfish revealed flow-sensitive and flow-insensitive units. These physiological differences represent, at least in part, the differences in morphology of the lateral line, superficial and canal neuromasts. Following up on these findings we recorded flow-sensitive and flow-insensitive units in the Torus semicircularis of goldfish. In still water, both types of units responded to a vibrating or moving sphere. In running water, neural responses were weaker when the sphere was moved with the flow but were comparable or slightly stronger when the sphere was moved against the flow. In running water, responses of flow-sensitive fibres to the vibrating sphere were masked. In contrast, the responses of units insensitive to water flow were not masked. Our data confirm previous findings but also indicate differences when compared to previous reports. We discuss these differences with respect to lateral line morphology, sub-modalities and convergence of different channels of information at higher brain stations.

Journal Article↗

PubMed1997

Blood pressure measurement in pregnant women in the left lateral recumbent position.

To evaluate blood pressure in pregnant women in the left lateral position, we studied indirect blood pressure in 169 patients with normal blood pressure, chronic hypertension, and preeclampsia in the supine and then the lateral recumbent positions. Two additional patients had aortic arch blood pressure compared with indirect measures. For all groups, mean arterial pressure in the lateral position was lower than in the supine position. Regarding direct aortic arch blood pressure, (1) supine blood pressure equaled that in the lateral position and (2) direct blood pressure in the lateral position equaled the mean indirect mean arterial pressure of both arms. Therefore the actual blood pressure in the lateral recumbent position is the combined mean arterial pressure of both arms.

Blood Pressure↗

PubMed1985

The control of condylar growth: an experimental evaluation of the role of the lateral pterygoid muscle.

The present study used 21 male albino rats to test the hypothesis that lateral pterygoid traction regulates the growth of the mandibular condyle. The condyles, the rami, and the top of each glenoid fossa were marked with metallic implants, and, following bilateral section of the condylar neck, one lateral pterygoid muscle was extirpated. On the basis of the literal details of Petrovic's cybernetic model, it was assumed that the continued forward growth of the midface and the backward translation of the glenoid fossa would combine to produce a progressive disturbance in the buccal occlusion that would, in turn, generate a reflex contraction of the remaining lateral pterygoid muscle. Initially, however, growth of the isolated condyles would have little impact on the spatial position of the rest of the mandible. As a result, the condyles on the side with the intact lateral pterygoid should grow for a time at a maximal, open-circuit rate, whereas the experimental condyle, deprived of all muscle traction, should show only a minimal "commanded" rate of growth. The serial change in the position of the condylar and ramal implants was assessed cephalometrically for 6 weeks, and between-sides differences were analyzed by randomized block analysis of variance. The presence or absence of the lateral pterygoid muscle had no significant effect on the anteroposterior position of the condylar implants and only a slight, transitory effect on their vertical position. The translation of the ramal implants, however, was greatly affected by the condylotomy. On both control and experimental sides, the mandible collapsed upward and backward until contact between the growing condyle and ramus had been achieved, whereupon a downward and forward pattern of translatory growth was re-established. Although it could not be shown that lateral pterygoid traction per se is a significant factor in the growth of isolated condyles, it was concluded that the condyle is vitally important to the translatory growth of the mandible as a whole. On the basis of these data and the current literature, a simple hypothesis was advanced for the control of condylar growth by the ongoing pattern of functional loading and for the role of this growth in the normal downward and forward displacement of the rest of the mandible.

Animals↗

PubMed2001

Lateral thoracic expansion for Jeune's syndrome: midterm results.

BACKGROUND: In 1995, we reported the use of lateral thoracic expansion in a patient with symptomatic Jeune's asphyxiating thoracic dystrophy. We have subsequently used lateral thoracic expansion 16 times on 10 patients during 7 years. This article reports our outcomes and provides surgical details. METHODS: Charts of all patients undergoing lateral thoracic expansion were reviewed. Eight of the 10 patients had symptomatic Jeune's syndrome. The other 2 had similar thoracic deformities limiting thoracic capacity. In half of the patients the procedures were performed bilaterally. RESULTS: All patients older than 1 year of age were symptomatically benefited by lateral thoracic expansion. Functional and anatomic measurements documented thoracic enlargement in several patients who had comparable preoperative and postoperative studies. However, 2 infants with significant underlying airway disease did not improve and went on to succumb to that aspect of their disease despite enlargement of the thorax. Fracture of the titanium ministruts has been a recurrent problem, and we now use larger struts. CONCLUSIONS: Lateral thoracic expansion is a safe and effective procedure in selected patients with Jeune's syndrome older than 1 year of age as judged by short-term and midterm follow-up. More experience and longer follow-up are required to discern the place of the lateral thoracic expansion in the overall management of these patients.

Adolescent↗

PubMed1999

The significance of lateral whole-body vibrations related to separately and simultaneously applied vertical motions. A validation study of ISO 2631.

Sensitivity of lateral motions relative to vertical motions were determined and compared to predictions provided by ISO 2631. Two experiments were executed where lateral and vertical motions were applied consecutively or simultaneously and where the magnitude of a single- or dual-axis test signal was adjusted until it was judged as equivalent to a preceding single-axis reference motion of the same frequency. Experiment 1: References consisted of vertical sinusoidal motions presented with 1.6-12.5 Hz and weighted accelerations of a(zw) = 0.3, 0.6 and 1.2 m s(-2) r.m.s., single-axis test signals were lateral motions of the same frequency. 26 subjects (15 men, 11 women, 20-56 yr) participated in the experiments. Accelerations adjusted for lateral vibrations above 1.6 Hz were considerably lower than predicted suggesting that the weighting factors provided in ISO 2631 are incorrect. Experiment 2: References consisted of single-axis vertical or lateral sinusoidal motions presented with 1.6-12.5 Hz and a weighted acceleration of a(zw) = 1.25 m s(-2) r.m.s. The dual-axis test signals consisted of a constant fraction of the reference acceleration (10, 25, 50, 75, 90%) and a perpendicularly oriented adjustable component. 31 subjects (15 men, 16 women, 19-51 yr) participated in the experiments. Both experiments revealed that ISO 2631 is qualitatively valid, the weighting of lateral motions above 1.6 Hz, however, should be increased in order to meet the actual sensitivity particularly in case of multi-axis vibrations.

Acceleration↗

PubMed1999

Simultaneous recording of mandibular condylar movement and single motor-unit activity at verified sites in the human lateral pterygoid muscle.

In recent years, understanding of normal jaw-muscle function has been enhanced by detailed descriptions of their complex internal architecture and of the functional activity of single motor units (SMUs). The lateral pterygoid muscle, however, has been poorly studied, although it is thought to play an important part in the control of jaw and jaw-joint movement. The present study is the first of a series of SMU studies to clarify the normal function of this muscle. The aims were to demonstrate (a) the unequivocal isolation of SMU activity from one or two verified recording sites within the lateral pterygoid, and (b) that these SMUs can be recorded reliably together with condylar movement during simple command jaw movements. Recordings of SMU activity were made with fine-wire electrodes from sites within the superior and inferior heads of the right lateral pterygoid during biting or command lateral jaw movements and combined with recordings of condylar and mid-incisor point movement. Recording sites were verified by computed tomography. In four young adults, the activities of 17 SMUs were reliably discriminated at seven recording sites within the lateral pterygoid. The units could be recorded during repeated trials of the same movement throughout a recording session with no appreciable change in amplitude or waveform. Units could also be discriminated simultaneously at separate recording sites--one in the superior head and the other in the inferior head. These data demonstrate that SMU activity can be recorded from verified sites within the lateral pterygoid simultaneously with condylar movement during command jaw movements.

Action Potentials↗

PubMed2000

Mechanism of lateral movement of filopodia and radial actin bundles across neuronal growth cones.

We investigated the motion of filopodia and actin bundles in lamellipodia of motile cells, using time-lapse sequences of polarized light images. We measured the velocity of retrograde flow of the actin network and the lateral motion of filopodia and actin bundles of the lamellipodium. Upon noting that laterally moving filopodia and actin bundles are always tilted with respect to the direction of retrograde flow, we propose a simple geometric model for the mechanism of lateral motion. The model establishes a relationship between the speed of lateral motion of actin bundles, their tilt angle with respect to the direction of retrograde flow, and the speed of retrograde flow in the lamellipodium. Our experimental results verify the quantitative predictions of the model. Furthermore, our observations support the hypothesis that lateral movement of filopodia is caused by retrograde flow of tilted actin bundles and by their growth through actin polymerization at the tip of the bundles inside the filopodia. Therefore we conclude that the lateral motion of tilted filopodia and actin bundles does not require a separate motile mechanism but is the result of retrograde flow and the assembly of actin filaments and bundles near the leading edge of the lamellipodium.

Actins↗

PubMed2002

Lateral diffusion coefficients in membranes measured by resonance energy transfer and a new algorithm for diffusion in two dimensions.

We describe measurements of lateral diffusion in membranes using resonance energy transfer. The donor was a rhenium (Re) metal-ligand complex lipid, which displays a donor decay time near 3 micros. The long donor lifetime resulted in an ability to measure lateral diffusion coefficient below 10(-8) cm(2)/s. The donor decay data were analyzed using a new numerical algorithm for calculation of resonance energy transfer for donors and acceptors randomly distributed in two dimensions. An analytical solution to the diffusion equation in two dimensions is not known, so the equation was solved by the relaxation method in Laplace space. This algorithm allows the donor decay in the absence of energy transfer to be multiexponential. The simulations show that mutual lateral diffusion coefficients of the donor and acceptor on the order of 10(-8) cm(2)/s are readily recovered from the frequency-domain data with donor decay times on the microsecond timescale. Importantly, the lateral diffusion coefficients and acceptor concentrations can be recovered independently despite correlation between these parameters. This algorithm was tested and verified using the donor decays of a long lifetime rhenium lipid donor and a Texas red-lipid acceptor. Lateral diffusion coefficients ranged from 4.4 x 10(-9) cm(2)/s in 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG) at 10 degrees C to 1.7 x 10(-7) cm(2)/s in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) at 35 degrees C. These results demonstrated the possibility of direct measurements of lateral diffusion coefficients using microsecond decay time luminophores.

Algorithms↗

PubMed1993

Lateral diffusion in model membranes is independent of the size of the hydrophobic region of molecules.

We have systematically investigated the probe size and shape dependence of lateral diffusion in model dimyristoyl phosphatidylcholine membranes. Linear hydrophobic polymers, which differ in length by an order of magnitude, were used to explore the effect on the lateral diffusion coefficient of hydrodynamic restrictions in the bilayer interior. The polymers employed are isoprenoid alcohols--citronellol, solanesol, and dolichol. Tracer lateral diffusion coefficients were measured by fluorescence photobleaching recovery. Despite the large difference in lengths, the nitrobenzoxadiazole labelled alcohols all diffuse at the rate of lipid self-diffusion (5.0 x 10(-12) m2 s-1, 29 degrees C) in the liquid crystal phase. Companion measurements in isotropic polymer solution, in gel phase lipid membranes and with nonpolar fluorescent polyaromatic hydrocarbons, show a marked dependence of the lateral diffusion coefficient on the probe molecule size. Our results in the liquid crystal phase are in accord with free area theory which asserts that lateral diffusion in the membrane is restricted by the surface-free area. Probe molecules which are significantly longer than the host phospholipid, seven times longer in the case of dolichol, are still restricted in their lateral motion by the surface properties of the bilayer in the liquid crystal phase. Fluorescence quenching experiments indicate that the nitrobenzoxadiazole label does not reside at the aqueous interface, although it must reside in close proximity according to the diffusion measurements.

Diffusion↗

PubMed1995

Intracellular mediators regulate CD2 lateral diffusion and cytoplasmic Ca2+ mobilization upon CD2-mediated T cell activation.

CD2 is a T cell surface glycoprotein that participates in T cell adhesion and activation. These processes are dynamically interrelated, in that T cell activation regulates the strength of CD2-mediated T cell adhesion. The lateral redistribution of CD2 and its ligand CD58 (LFA-3) in T cell and target membranes, respectively, has also been shown to affect cellular adhesion strength. We have used the fluorescence photobleaching recovery technique to measure the lateral mobility of CD2 in plasma membranes of resting and activated Jurkat T leukemia cells. CD2-mediated T cell activation caused lateral immobilization of 90% of cell surface CD2 molecules. Depleting cells of cytoplasmic Ca2+, loading cells with dibutyric cAMP, and disrupting cellular microfilaments each partially reversed the effect of CD2-mediated activation on the lateral mobility of CD2. These intracellular mediators apparently influence the same signal transduction pathways, because the effects of the mediators on CD2 lateral mobility were not additive. In separate experiments, activation-associated cytoplasmic Ca2+ mobilization was found to require microfilament integrity and to be negatively regulated by cAMP. By directly or indirectly controlling CD2 lateral diffusion and cell surface distribution, cytoplasmic Ca2+ mobilization may have an important regulatory role in CD2 mediated T cell adhesion.

Actin Cytoskeleton↗

PubMed1996

Lateral diffusion of small compounds in human stratum corneum and model lipid bilayer systems.

An image-based technique of fluorescence recovery after photobleaching (video-FRAP) was used to measure the lateral diffusion coefficients of a series of nine fluorescent probes in two model lipid bilayer systems, dimyristoylphosphatidylcholine (DMPC) and DMPC/cholesterol (40 mol%), as well as in human stratum corneum-extracted lipids. The probes were all lipophilic, varied in molecular weight from 223 to 854 Da, and were chosen to characterize the lateral diffusion of small compounds in these bilayer systems. A clear molecular weight dependence of the lateral diffusion coefficients in DMPC bilayers was observed. Values ranged from 6.72 x 10(-8) to 16.2 x 10(-8) cm2/s, with the smaller probes diffusing faster than the larger ones. Measurements in DMPC/cholesterol bilayers, which represent the most thorough characterization of small-solute diffusion in this system, exhibited a similar molecular weight dependence, although the diffusion coefficients were lower, ranging from 1.62 x 10(-8) to 5.60 x 10(-8) cm2/s. Lateral diffusion measurements in stratum corneum-extracted lipids, which represent a novel examination of diffusion in this unique lipid system, also exhibited a molecular weight dependence, with values ranging from 0.306 x 10(-8) to 2.34 x 10(-8) cm2/s. Literature data showed that these strong molecular weight dependencies extend to even smaller compounds than those examined in this study. A two-parameter empirical expression is presented that describes the lateral diffusion coefficient in terms of the solute's molecular weight and captures the size dependence over the range examined. This study illustrates the degree to which small-molecule lateral diffusion in stratum corneum-extracted lipids can be represented by diffusion in DMPC and DMPC/cholesterol bilayer systems, and may lead to a better understanding of small-solute transport across human stratum corneum.

Cholesterol↗