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PubMed2000

The substrate for brain-stimulation reward in the lateral preoptic area. I. Anatomical mapping of its boundaries.

Given the putative role of the lateral preoptic area as a primary contributor of the cell bodies of origin of the descending pathway linking a subset of lateral hypothalamic and ventral tegmental area reward neurons, the distribution of self-stimulation sites in this structure was mapped in 22 animals using moveable electrodes and threshold procedures. Ninety-seven electrode sites were evaluated with placements ranging from just rostral to the midline convergence of the anterior commissure back to the transition zone between the lateral preoptic and lateral hypothalamic areas; of these, roughly 2/3 supported self-stimulation which was widely observed throughout the lateral preoptic area and medial forebrain bundle. In general, self-stimulation thresholds obtained from lateral sites were most stable, and progressively so approaching more caudal regions. Examination of the slopes of the period/current trade-off functions revealed a tendency for higher values in lateral and caudal sites; in contrast, dorsoventral excursions did not influence these estimates. Taken together, these data provide support for the notion that the substrate for brain-stimulation reward in the lateral preoptic area has a relatively homogeneous distribution that is more diffusely organized than that found in reward sites activated further caudally in the medial forebrain bundle.

Animals↗
PubMed2000

Bradycardic and hypotensive responses to microinjection of L-glutamate into the lateral aspect of the commissural NTS are blocked by an NMDA receptor antagonist.

Baroreflex activation by phenylephrine infusion produces a bradycardic response while microinjection of L-glutamate into the most lateral aspect of the commissural nucleus tractus solitarius (NTS, 0.8 mm lateral to the midline) produces bradycardic and hypotensive responses. In the present study we investigated the role of NMDA receptors in the lateral aspect of the commissural NTS (0.8 mm lateral to the midline) in the bradycardic and hypotensive responses to microinjection of L-glutamate as well as in the processing of the bradycardic response to the baroreflex activation. The hypotensive and bradycardic responses to L-glutamate microinjection into the NTS were blocked by methyl-atropine (intravenous, i.v.), indicating that the hypotensive response was secondary to the bradycardia. Microinjection of L-glutamate (1 nmol/50 nl) into the NTS was performed before and after microinjection of increasing doses of phosphonovaleric acid (AP-5, a selective NMDA antagonist) at the same site. The microinjection of AP-5 [0.5 (n = 9), 2.0 (n = 8) and 10.0 nmol/50 nl (n = 7)] into the NTS (0.8 mm lateral to the midline) produced a dose-dependent blockade of the bradycardic and hypotensive responses to L-glutamate. In a specific group of rats the microinjection of 10 nmol/50 nl of AP-5 produced a significant reduction in baroreflex sensitivity 2 min after microinjection into the lateral NTS [gain = -1.48 +/- 0.12 vs. -0.5 +/- 0.2 beats/mmHg, (n = 5)], which was reversible. The data show that the bradycardic responses produced by microinjection of L-glutamate into the most lateral aspect of the commissural NTS or by activation of the baroreflex were blocked by microinjection of AP-5, indicating that the neurotransmission of the parasympathetic component of the baroreflex in the neurons of the lateral aspect of the commissural NTS involves NMDA receptors.

2-Amino-5-phosphonovalerate↗
PubMed1999

The value of inspiratory-expiratory lateral decubitus views in the diagnosis of small pleural effusions.

AIM: To evaluate the usefulness of expiratory lateral decubitus views in the radiological diagnosis of small pleural effusions. MATERIALS AND METHODS: Patients referred for abdominal sonography for various reasons were examined for ultrasonographic features of pleural effusion. From November 1994 until May 1996, 36 patients were found to have pleural effusion not exceeding 15 mm in depth and were included in the study. Erect posteroanterior, lateral, and lateral decubitus (in inspiration and expiration) ragiographs were performed in all patients. RESULTS: The mean thickness of fluid was 4.3 mm on inspiratory lateral decubitus radiographs and 7.9 mm on expiratory lateral decubitus views (P < 0.005). In 31 of 36 patients (86%) there was a difference in the thickness of the fluid layer as measured in expiratory vs. inspiratory lateral decubitus radiographs. In 16% of patients, the fluid was not visible on inspiratory lateral decubitus projections. CONCLUSIONS: Expiratory lateral decubitus views may be useful for demonstrating small pleural effusions.

Adult↗
PubMed1997

Spine loading during trunk lateral bending motions.

Increases in lateral trunk velocities have been identified as a mechanism for increasing the risk of low-back disorder. Previous studies have identified an increase in coactivation of the trunk musculature during lateral bends, but no studies have evaluated how spine loading changes as lateral trunk velocity increases. Twelve subjects were asked to lift loads laterally at one static and three dynamic velocities. Ten trunk muscle activities and trunk kinematics were documented and used as input parameters to an EMG-assisted model to evaluate spine loading. Muscle coactivation was observed in all lateral bends. Coactivation significantly increased during dynamic trials compared to the static trials. Coactivity increased spinal loads by as much as 25% compared to values predicted by models that did not consider coactivity. Movements to the right significantly increased spine loadings (252 N increase in compression) compared to movements to the left. Spine compression, A-P shear, and lateral shear all increased in the dynamic trials compared to the static conditions. Peak compression increased by an average of 525 N at 45 degrees s-1 compared to static loading. Compression and lateral shear increased monotonically as trunk velocity increased. It is expected that this combined (compression and lateral shear) loading is the mechanism for increased risk observed in industry.

Adult↗
PubMed1996

Conversion of modified Fontan procedure to lateral atrial tunnel cavopulmonary anastomosis.

After modified Fontan procedures with atriopulmonary anastomoses or right atrium-right ventricle conduits, some patients have progressive exercise intolerance, effusions, arrhythmias, or protein-losing enteropathy. Theoretic advantages of a lateral atrial tunnel cavopulmonary anastomosis and published clinical results suggest that conversion of other Fontan procedures to the lateral atrial tunnel may afford clinical improvement for some patients. Eight patients (8 to 25 years old) with tricuspid atresia (n =4), double-inlet left ventricle (n = 3), and double-outlet right ventricle (n=1) underwent conversion to a lateral tunnel procedure between December 1990 and November 1994. An arbitrary clinical score was assigned before the lateral tunnel procedure and at follow-up. Before conversion, patients had decreased exercise tolerance (n = 8), arrhythmias (n = 6), effusions (n = 4), and protein-losing enteropathy (n = 8). At catheterization, all had a low cardiac index (1.9 +/- 0.7 L x min(-1) x M(-2), five had elevated pulmonary vascular resistance (>3 Wood units), and three had right pulmonary venous return obstruction by compression of an enlarged right atrium. Fenestrated lateral tunnel construction was undertaken 7.3 +/- 3.6 years after atriopulmonary anastomosis, with one early death related to low cardiac output. After the lateral tunnel procedure, two patients had no clinical improvement (no change in clinical score) but five patients had either marked or partial improvement. The right pulmonary vein compression present in three patients was resolved after conversion. The mean clinical scores improved from 4.5 +/- 1 to 3.0 +/- 2 (p < 0.04). In conclusion, conversion to a lateral tunnel procedure led to clinical improvement in five of eight patients at short-term follow-up and may be particularly indicated for patients with giant right atria or pulmonary vein compression who have symptoms. Pulmonary vein compression should be looked for in patients after modified Fontan procedures and can be relieved by conversion to the lateral tunnel procedure.

Adolescent↗
PubMed1997

Cerebral lateral ventricular asymmetry: is this a normal ultrasonographic finding in the fetal brain?

OBJECTIVE: To evaluate the clinical significance of in utero detection of fetal cerebral lateral ventricular asymmetry. METHODS: We used high resolution ultrasonography to study asymmetries of the fetal lateral ventricles in the human brain. A retrospective survey was conducted on 7200 pregnant women who presented at two large district hospitals in Israel. Only fetuses with a difference of greater than 2.4 mm (two standard deviations) in the width of the lateral ventricles, with no known brain pathology, were included in the study. Index cases were evaluated regarding maternal complications, prenatal ultrasound examinations, postnatal imaging studies, and neonatal outcome up to 6 months of age. RESULTS: Lateral ventricular asymmetry was found in 21 subjects, all with available clinical data. In 15 fetuses (71%), the body or the occipital horn of the left lateral ventricle was larger than the right, whereas in six fetuses (29%), the right was larger than the left. In four cases (20%), serial scans noted resolution of asymmetry; in 15 (75%), it was persistent; and in one (5%), asymmetry increased. In one case, termination of pregnancy was performed; however, pathologic examination of the fetal brain failed to detect any structural abnormality. Underlying cerebral pathology was later found only in three fetuses (14%); one had subclinical cytomegalovirus ventriculitis, one had insidious periventricular hemorrhage, and in one fetus with increased asymmetry, trisomy 21 was verified. All the remaining 17 cases had normal neurologic development. CONCLUSIONS: Some degree of asymmetry of the lateral ventricles exists in the human fetal brain and is detectable in utero. Lateral ventricular asymmetry alone is probably not clinically significant, and it may be considered as a normal variant, rather than a pathologic finding.

Adult↗
PubMed2000

Randomised comparison of antero-lateral versus antero-posterior paddle positions for DC cardioversion of persistent atrial fibrillation.

We designed a prospective, randomised, single-blind trial to compare the relative efficacy of antero-lateral versus antero-posterior paddle positions for DC cardioversion of persistent atrial fibrillation. A total of 59 patients were randomised to cardioversion using standard gel pads placed either in the antero-lateral (AL) or antero-posterior (AP) positions. The first synchronised shock was given at 360 J; if this was unsuccessful, a second shock of 360 J was given in the alternative position. We compared cardioversion success rate and energy requirements with each strategy. With the first 360 J DC shock, a significantly greater proportion of patients were restored to sinus rhythm from the antero-lateral position (18/30) compared to the antero-posterior position (10/29) (P=0.048). For those patients remaining in atrial fibrillation, there was no difference in the proportions cardioverted from the antero-lateral position (4/19) compared to the antero-posterior position (5/12) with the second 360 J DC shock (P=0. 22). The total cardioversion success rate was 23/30 (77%) for antero-lateral followed by antero-posterior shocks compared to a success rate of 14/29 (48%) for antero-posterior followed by antero-lateral shocks, and this difference was significant (P=0.024). There was no significant difference in the mean energy delivered for patients randomised to an initial antero-lateral shock (504 J), compared to patients given an initial antero-posterior shock (583 J) (P=0.1). We conclude that the antero-lateral paddle position appears more effective for DC cardioversion of persistent atrial fibrillation.

Aged↗
PubMed1998

Contribution of membrane cholesterol to outer hair cell lateral wall stiffness.

The outer hair cell can be divided into three domains: the apex, the base, and the lateral wall. With the use of filipin, a polyene fluorescent antibiotic that binds to cholesterol, we found under fluorescence microscopy that the lateral wall membranes were less intensely stained than the apical and basal membranes. This difference in filipin fluorescence between the lateral walls and the ends diminished when cells were incubated in water-soluble cholesterol before staining, suggesting that exogenous cholesterol enters the lateral wall. Under confocal microscopy, we studied the incorporation pattern of a fluorescent cholesterol analogue, NBD-cholesterol. NBD-cholesterol did not stain the apical membranes whereas it intensely labeled the lateral wall. The micropipette aspiration technique was used to assess the effect of cholesterol on lateral wall stiffness. The lateral wall stiffness parameter of cells treated with water-soluble cholesterol (n = 23) was significantly higher than that of controls (n = 27): 0.76+/-0.24 (mean +/- SD) versus 0.46+/-0.10 (Student's t-test, p < 0.001). In conclusion, cholesterol has different distributions among outer hair cell membranes, and when water-soluble cholesterol is incorporated into the cells, the outer hair cell lateral wall stiffness parameter increases.

Affinity Labels↗
PubMed1998

Anatomic and mechanical properties of the lateral disc attachment of the temporomandibular joint.

PURPOSE: This study measured the strength to failure of the human temporomandibular joint (TMJ) lateral disc attachment (LDA) using a tension-compression machine. These data were correlated with the LDA location and its morphologic aspects, the age and sex of the subjects, and the amount of the lateral pterygoid muscle (LPM) inserted in the disc. METHODS: Forty-two TMJs without any obvious internal damage were carefully dissected to preserve the LDA. The width of insertion of the lateral pterygoid muscle fibers in the anterior band, as well as the width of the disc, were measured. The tension test was performed until the complete failure of the sample using a screw machine. RESULTS: Two types of LDA were recognized. In LDA 1, the anterior and posterior bands lateral disc junction were directly inserted on the lateral pole, whereas in LDA 2 this lateral junction was attached behind and below the pole through a sheet of fibrous tissue. The breaking points for LDA 1 (55.8 N) and LDA 2 (28.8 N) were significantly different (P = .03). No correlation was found between the amount of LPM discal fibers insertion, sex, age, or the LDA breaking strength point. CONCLUSION: The LDA 2 insertion strongly suggests that the lateral joint ligament together with the capsule may act as a substitute for the original disc attachment to the lateral pole of the condyle.

Age Factors↗
PubMed2003

Lateral resolution in elastography.

The factors that control the lateral resolution in elastography were investigated using a simulation study. The lateral resolution was estimated from the simulated axial strain elastograms as the smallest measurable distance between two equally stiff lesions embedded in a homogeneously softer background. The lesions were symmetrically positioned lateral to the center of the target, at the focus of the transducer. Ultrasound (US) systems with different transducer frequencies, bandwidths and f-numbers were simulated. The effects of the ultrasonic parameters, the lateral spacing between adjacent echo signals, the cross-correlation window length, the lesion/background elastic contrast and the lateral motion of scatterers on the estimated lateral resolution were investigated. The results show that the lateral resolution in elastography is proportional to the beam width of the US system used to acquire the data, and is on the same order as the sonographic lateral resolution.

Computer Simulation↗
PubMed2003

Membrane properties of identified lateral and medial perforant pathway projection neurons.

The physiological characteristics of neurons that project to the hippocampus and dentate gyrus via the medial perforant pathway (projection neurons) are well known, but the characteristics of neurons that project to these areas via the lateral perforant pathway (projection neurons) are less well known. We have used retrograde tracing and whole-cell recording in brain slices to compare the membrane and firing properties of medial perforant pathway and lateral perforant pathway projection neurons in layer II of the medial and lateral entorhinal cortex. The properties of medial perforant pathway projection neurons were identical to those reported previously for spiny stellate neurons in the medial entorhinal cortex. In contrast, lateral perforant pathway projection neurons were characterized by a higher input resistance, a lack of time-dependent inward (anomalous) rectification, and a lack of prominent depolarizing spike afterpotentials. Voltage-clamp recordings suggest that the absence of anomalous rectification in lateral perforant pathway projection neurons is due to smaller hyperpolarization activated cation currents in these cells, and the lack of depolarizing afterpotential may be due to smaller low-threshold calcium currents. Persistent sodium current was also smaller in lateral perforant pathway projection neurons, but the difference in persistent sodium current between medial perforant pathway and lateral perforant projection neurons was much less pronounced than the difference in low voltage activated currents. These results underscore the functional differences between the medial entorhinal cortex and lateral entorhinal cortex, and may help to explain the differing abilities of these cortical areas to participate in certain types of network activity.

Action Potentials↗
PubMed1999

Effect of graded spinal cord compression on cardiovascular neurons in the rostro-ventro-lateral medulla.

In patients with spinal cord injury, cardiovascular disturbances such as hypotension, bradycardia and autonomic dysreflexia can be directly linked to abnormalities of central autonomic control. To date, the changes in bulbospinal innervation of sympathetic preganglionic neurons after compressive spinal cord injury have not been investigated. Thus, we examined the effect of varying severity of compressive spinal cord injury on neurons of the rostro-ventro-lateral medulla, a nucleus of key importance in cardiovascular control. Adult rats with 20 g, 35 g and 50 g clip compression injuries (n= 18) of the cord at T1 and uninjured controls (n=13) were studied. Neurons in the rostro-ventro-lateral medulla with preserved spinal connections eight weeks after spinal cord injury were identified by retrograde labelling with 4% FluoroGold introduced into the cord at T6. Bulbospinal neurons in the rostro-ventro-lateral medulla were also examined immunocytochemically for the adrenaline-synthesizing enzyme phenylethanolamine-N-methyltransferase. In control rats an average of 451+/-12 rostro-ventrolateral medulla neurons were phenylethanolamine-N-methyltransferase positive. Of these, 213+/-6 projected to the T6 spinal cord. The number of rostro-ventro-lateral medulla neurons retrogradely labelled by FluoroGold decreased as a linear function of severity of spinal cord injury (r= -0.95; P<0.0001). After 50g spinal cord injury at T1, only 7+/-1 rostro-ventro-lateral medulla neurons were labelled by FluoroGold, of which 6+/-1 were phenylethanolamine-N-methyltransferase positive. Moreover, the number of phenylethanolamine-N-methyltransferase positive rostro-ventro-lateral medulla neurons decreased to 361+/-16 after 50 g spinal cord injury. We conclude that compressive spinal cord injury results in disconnection of rostro-ventro-lateral medulla neurons, which project to the thoracic spinal cord, and that these changes vary with the severity of injury. The majority of these axotomized rostro-ventro-lateral medulla neurons maintain their immunopositivity for the adrenaline-synthesizing enzyme phenylethanolamine-N-methyltransferase.

Animals↗
PubMed1997

Effect of low-density lateral interfaces on soft-tissue doses.

PURPOSE: Doses at the interface between tissue and low-density inhomogeneities with the interface positioned perpendicular to the beam direction have been well studied. When the inhomogeneity lies parallel to the beam direction (i.e., a lateral interface), the resulting dose distribution is not as well known. Lateral lung-soft-tissue interfaces are common in many fields used to treat malignancies in the thorax region including tangential breast fields and anteroposterior fields for lung and esophageal cancer. The purpose of this study was to evaluate the dose distribution along lateral interfaces and to determine the implications for treatment. METHODS AND MATERIALS: A polystyrene and cork slab phantom was irradiated from the side to simulate treatment fields with lateral lung-soft-tissue interfaces. The beam was positioned with the isocenter in polystyrene and the field edge in cork. Cork slabs (0.6-2.5 cm) were used to simulate different thicknesses of lung between the field edge and the target volume. Measurements were made using a parallel plate ionization chamber. With the chamber position held constant, polystyrene slabs were added between the cork and the chamber to study the dose distribution in the interface region. Interface doses were studied as a function of the amount of cork in the field, field size, beam energy (6-18 MV), and depth. RESULTS: Doses in the interface region were lower by as much as 10% compared to doses in a homogeneous phantom. For a given cork width and field size, the magnitude of the underdose increased by several percent as the x-ray energy increased from 6 to 18 MV. The underdose at the interface was 5% for 6 MV and 8% for 18 MV X-rays with a 1-cm cork width. For a 2.5-cm cork width, underdoses of 2.5% and 3% at distances up to 2.5 and 4 mm lateral to the interface were observed for 6- and 18-MV X-rays, respectively. However, doses right at the interface were 1% greater for 6 MV and 3% less for 18 MV than doses in a homogeneous phantom. For a given cork width, the interface doses were not significantly dependent on field width but decreased by an additional 2-3% as the length decreased to 4 cm. Additional decreases were also observed when the measurement depth decreased to 3 cm. With a 1-cm width of cork in the field, a lateral distance of 3-4 mm from the interface was necessary to ensure doses of at least 98% of the homogenous dose with 6-MV X-rays. A lateral distance of 6-7 mm was necessary for 10- and 18-MV X-rays. CONCLUSION: Underdosing will occur in the soft tissues adjacent to low-density inhomogeneities. The magnitude depends primarily on the width of the inhomogeneity seen in the treatment field, but also on field size, depth, and beam energy. For treatment fields with a lateral lung interface, a segment of tissue approximately 3-4 mm thick for 6 MV and 6-7 mm thick for higher-energy beams may be underdosed. Lung widths of > or = 1.75 cm as observed on film will generally guarantee doses of at least 96% of those calculated with no inhomogeneity corrections. High-energy beams are often used to treat sites in the thorax or breast to improve dose homogeneity throughout the treatment volume. Potential underdosing due to the presence of lung should be considered and may require a decrease in beam energy or an increase in the margin between the target volume and the field edge to ensure adequate treatment.

Connective Tissue↗
PubMed2003

Lateral flagella are required for increased cell adherence, invasion and biofilm formation by Aeromonas spp.

Two types of flagella are responsible for motility in mesophilic Aeromonas strains. A polar unsheathed flagellum is expressed constitutively that allows the bacterium to swim in liquid environments and, in media where the polar flagellum is unable to propel the cell, Aeromonas express peritrichous lateral flagella. Recently, Southern blot analysis using a DNA probe based on the Aeromonas caviae Sch3N lateral flagellin gene sequence showed a good correlation between strains positive for the DNA probe, swarming motility and the presence of lateral flagella by microscopy. Here, we conclude that the easiest method for the detection of the lateral flagellin gene(s) is by PCR (polymerase chain reaction); this showed good correlation with swarming motility and the presence of lateral flagella. This was despite the high degree of DNA heterogeneity found in Aeromonas gene sequences. Furthermore, by reintroducing the laf (lateral flagella) genes into several mesophilic lateral-flagella-negative Aeromonas wild-type strains, we demonstrate that this surface structure enhances the adhesion to and invasion of HEp-2 cells and the capacity for biofilm formation in vitro. These results, together with previous data obtained using Laf- mutants, demonstrate that lateral flagella production is a pathogenic feature due to its enhancement of the interaction with eukaryotic cell surfaces.

Aeromonas↗
PubMed2002

Position of superciliare in relation to the lateral iris: testing a suggested facial approximation guideline.

It has been suggested in the literature that superciliare is located directly above the most lateral point of the iris and that this association may be of use in facial approximation. However, the relationship between the lateral iris and superciliare has not been tested and its accuracy remains unknown. This study aims to determine the accuracy of this relationship using metric and non-metric analysis. The horizontal distance from superciliare to the lateral iris was measured, using photogrammetric methods, in Australians of European extraction (27 males, 48 females), central/south-east Asian extraction (20 males, 19 females) and individuals from other population groups (7 males, 7 females). Results indicate that superciliare position is best approximated by the lateral iris in females. On average, superciliare fell lateral to the lateral iris by 4.8 mm, S.D. 3.4 mm in males, and 1.2 mm, S.D. 5.4mm in females. In approximately 70-80% of the sample, the superciliare fell between the exocanthion and the pupil center on both sides. It is suggested that the proposed guideline that the lateral iris is equal to superciliare is not very accurate, especially for males. Also the large standard deviations indicate that the position of superciliare is highly variable. The above measures should, on average, give a more accurate prediction of superciliare in contrast to the lateral iris border, and therefore, they should be used in facial approximation. However, the large variation in superciliare position should be acknowledged.

Adolescent↗
PubMedDate not supplied

Perinatal exposure to estrogenic compounds and the subsequent effects on the prostate of the adult rat: evaluation of inflammation in the ventral and lateral lobes.

Although the effects of estrogenic compounds administered during the perinatal period on the size and morphology of the prostate have been well documented, the effects of such exposures on inflammatory changes in the prostate have not been well characterized. Since neonatal estradiol exposure has been shown to cause periods of hyperprolactinemia later in life and a relationship exists between high prolactin levels and rat lateral prostate inflammation, we hypothesized that an exposure to environmental compounds with estrogenic activity could result in an increase in lateral prostate inflammation in adulthood. To investigate this possibility and compare differences between estrogen agonists and antagonists, we examined the effect of a perinatal exposure to 17beta-estradiol, the insecticide methoxychlor, the partial estrogen agonist tamoxifen, and the pure antiestrogen ICI 182,780. Dams were dosed from gestation day (GD)18 to parturition and then the pups were dosed from postnatal day (PND) 1 to 5 with 0.1 mL of a solution of 0.355 mM and .0178 mM by sc injection, respectively, of all compounds in sesame oil, except for methoxychlor, which was administered only to the dam by gavage from GD 18 through PND 5 at a dose of 50 mg/kg in sesame oil. At 90 d of age, the weight of the lateral and ventral prostate in the estradiol group was significantly decreased. Tamoxifen caused a decrease in the weight of the lateral prostate, whereas the ventral lobe was not affected. ICI 182,780 did not alter prostate weight. The methoxychlor exposure increased the lateral lobe weight, but the ventral lobe weight was not affected. In the estradiol and tamoxifen groups, an inflammatory infiltrate was observed in the ventral prostates in 45.0 and 27.8% of the animals, respectively. There was a significant increase in the percent and severity of inflammation in the lateral prostate (as determined by a myeloperoxidase or neutrophil quantification assay) in the estradiol, tamoxifen, and methoxychlor groups as compared to controls. The ICI group was comparable to the controls in both ventral and lateral lobes. This study demonstrates that perinatal exposure to estrogenic compounds can result in alterations in the size of the adult prostate and increase the incidence of prostatitis.

Aging↗
PubMed1994

The aetiology of lateral cervical (branchial) cysts: past and present theories.

Four theories have been suggested to explain the aetiology of lateral cervical cysts. Ascherson (1832) suggested that the cysts arose due to incomplete obliteration of branchial cleft mucosa, which remained dormant until stimulated to grow later in life. His (1886) suggested these cysts were vestiges of the precervical sinus. Wenglowski (1912) believed lateral cervical cysts developed from the third pharyngeal pouch (thymopharyngeal duct). A number of investigators during the 19th century noted the close relationship between lateral cervical cysts and lymphoid tissue (Lucke, 1861). Luschka (1848) suggested that cystic degeneration of cervical lymph nodes was the mechanism by which lateral cervical cysts were formed. This theory received little support until King (1949) studied the histology of a large number of lateral cervical cysts and concluded that these cysts resulted from cystic transformation of cervical lymph nodes. The evidence for and against these theories of aetiology is discussed. The debate is centred on a study of 20 patients with lateral cervical cysts operated on in the Department of Otolaryngology, Bedford Hospital, between January 1986 and December 1991. In all twenty cases the wall of the cyst was found to be composed of lymphoid tissue, histologically identical to the present in lymph nodes. The mean age of presentation was 31 years, and in no case was a tract or cord found which connected the cyst to the skin or pharynx. The evidence strongly suggests that lateral cervical cysts develop from the cystic transformation of cervical lymph nodes. Mechanisms by which this may occur are discussed.

Adolescent↗
PubMedDate not supplied

Regulation of arrestin mRNA levels in Limulus lateral eye: separate and combined influences of circadian efferent input and light.

Most animals experience daily changes in light and darkness. The retinas of many of these animals show concomitant rhythmic changes in the levels of mRNAs that encode proteins involved in the photoresponse. These changes may be circadian and independent of light, independent of circadian clocks and regulated by light, or regulated by a circadian clock and light. We have taken advantage of the organization of the Limulus visual system to examine the separate and combined effects of signals from a circadian clock and light on arrestin mRNA levels in photoreceptors. The clock that regulates photoreceptors in the lateral eye of Limulus is in the brain, and signals from the clock reach the lateral eye via activation of a well-characterized efferent projection in the lateral optic nerve. In the experiments described, clock-driven efferent input to the lateral eye was eliminated by cutting the lateral optic nerve, and light input to the lateral eye was eliminated by placing an opaque patch over the eye. Arrestin mRNA levels were quantified relative to 18s rRNA with a ribonuclease protection assay. We observed the following. In lateral eyes exposed to natural diurnal light and endogenous efferent nerve activity, the level of arrestin mRNA was higher during the day in the light than during the night in the dark. Circadian efferent nerve activity was necessary and sufficient to produce normal daily fluctuations in the level of arrestin mRNA. Light influenced arrestin mRNA levels only in eyes with intact and active efferent projections. We conclude that arrestin mRNA levels in lateral eye photoreceptors are controlled entirely by efferent nerve activity, and that light exerts its effects by modulating this output from the circadian clock. Light-stimulated changes in arrestin mRNA in the vertebrate retina may likewise require interactions between light-driven biochemical cascades and clock output.

Animals↗