Parietal Position Research Articles

Effect of transducer attachment on vibration transmission and transcranial attenuation for direct drive bone conduction stimulation

Direct drive bone conduction devices (BCDs) are used to rehabilitate patients with conductive or mixed hearing loss by stimulating the skull bone directly, either with an implanted transducer (active transcutaneous BCDs), or through a skin penetrating abutment rigidly coupled to an external vibrating transducer (percutaneous BCDs). Active transcutaneous BCDs have been under development to overcome limitations of the percutaneous bone anchored hearing aid (BAHA), mainly related to the skin penetration. The attachment of a direct drive BCD to the skull bone can differ significantly between devices, and possibly influence the vibrations’ transmission to the cochleae.In this study, four different attachments are considered: (A) small-sized flat surface, (B) extended flat surface, (C) bar with a screw at both ends, and (D) standard bone anchored hearing aid screw. A, B, and C represent three active transcutaneous options, while D is for percutaneous applications. The primary aim of this study was to investigate how the different transcutaneous attachments (A, B, and C) affect the transmission of vibrations to the cochleae to the ipsilateral and the contralateral side. A secondary aim was to evaluate and compare transcranial attenuation (TA, ipsilateral minus contralateral signal level) between transcutaneous (A, B, and C) and percutaneous attachments (D).Measurements were performed on four human heads, measuring cochlear promontory velocity with a LDV (laser Doppler vibrometer) and sound pressure in the ear canal (ECSP) with an inserted microphone. The stimulation signal was a swept sine between 0.1 and 10 kHz. The comparison of ipsilateral transmission between transcutaneous adaptors A, B, and C was in agreement with previous findings, confirming that: (1) Adaptor C seems to give the most effective transmission for frequencies around 6 kHz but somewhat lower in the mid frequency range, and (2) keeping a smaller contact area seems to provide advantages compared to a more extended one. The same trends were seen ipsilaterally and contralaterally. The observed TA was similar for adaptors A, B, and C at the mastoid position, ranging -10-0 dB below 500 Hz, and 10–20 dB above. A lower TA was seen above 500 Hz when using adaptor D at the parietal position.

Association between auditory P300, psychopathology, and memory function in drug-naïve schizophrenia

The aim of this study was to explore memory deficits and psychopathology and their relationships with P300 in drug-naïve patients with schizophrenia. The Positive and Negative Syndrome Scale (PANSS) and the Wechsler Memory Scale—Revised were administered. Auditory event-related potentials elicited by an oddball paradigm were obtained. After controlling for age, sex, the results showed a statistically significant negative correlation between the total PANSS score and P300 amplitude at the parietal position (r = −0.66, p < 0.05). Moreover, visual memory was significantly positively correlated with P300 amplitude at the parietal position (r = 0.67, p < 0.05). After controlling for the duration of illness, the above correlations remained statistically significant. The correlation between P300 and the severity of psychopathology was reconfirmed in drug-naïve patients with schizophrenia. A possible contribution of memory decompensation in P300 among drug-naïve patients with schizophrenia may be considered, and the compensatory or Default Model Network might be a possible explanation of this association.

Tetraflagellochloris mauritanica gen. et sp. nov. (Chlorophyceae), a New Flagellated Alga from the Mauritanian Desert: Morphology, Ultrastructure, and Phylogenetic Framing.

Morphological, ultrastructural, and molecular-sequence data were used to assess the phylogenetic position of a tetraflagellate green alga isolated from soil samples of a saline dry basin near F'derick, Mauritania. This alga can grow as individual cells or form non-coenobial colonies of up to 12 individuals. It has a parietal chloroplast with an embedded pyrenoid covered by a starch sheath and traversed by single parallel thylakoids, and an eyespot located in a parietal position opposite to the flagellar insertion. Lipid vacuoles are present in the cytoplasm. Microspectroscopy indicated the presence of chlorophylls a and b, with lutein as the major carotenoid in the chloroplast, while the eyespot spectrum has a shape typical of green-algal eyespots. The cell has four flagella, two of them long and two considerably shorter. Sequence data from the 18S rRNA gene and ITS2 were obtained and compared with published sequences for green algae. Results from morphological and ultrastructural examinations and sequence analysis support the placement of this alga in the Chlorophyceae, as Tetraflagellochloris mauritanica L. Barsanti et A. Barsanti, gen. et sp. nov.

Large‐fruited Salicaceae s.l. from the Miocene tuff of the Eichelskopf, northern Hessen, Germany

AbstractReexamination of Saccoglottis kayseri (Schindehütte) Kirchheimer from the Miocene tuff of the Eichelskopf southeast of Homberg an der Efze in northern Hessen, Germany, indicates that the species was incorrectly attributed to Humiriaceae. The large ovoid fruits are 6‐ and 7‐valved capsules bearing numerous seeds in parietal position. The outer surface is hexagonally or heptagonally ridged. Each valve of the capsule bears a broad, ventral longitudinal band that is densely punctate indicating the position of numerous seeds. These characters point to affinities with the Salicaceae s.l. (incl. most former Flacourtiaceae), and match particularly well with Itoa L., which is distributed today in southern China and eastern Malesia. However, the fruit valves appear to separate only from the apical end, rather than both from base and apex which is a feature of fruits in the Itoa‐Carrierea‐Poliothyrsis group. We treat the fruits as a new genus of Salicaceae, Schindehuettea gen. nov. under the binomial Schindehuettea kayseri (Schindehütte) Manchester. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Can sieve-element plastids in Panicum maximum (Poaceae) leaves act in the blockage of injured sieve-tube elements?

The ultrastructural features and the plastid changes caused by sample preparation were studied in sieve elements of Panicum maximum leaves. Samples of expanded leaves, taken near the ligule region, were fixed and processed by common light and transmission electron microscopy methods. In mature sieve-tube elements, the protoplast is electron-translucent and plastids are the most frequent organelles. Mitochondria and smooth endoplasmic reticulum segments are also visible and occupy a parietal position within the cell. The plastids are globular and show electron-dense proteinaceous inclusions in the stroma. The protein crystals are predominantly cuneate, but thin crystalloids and amorphous and/or filamentous proteins also occur. The presence of intact plastids plus others in different phases of plastid envelope rupture were interpreted as evidence that this rupture is a normal event in response to injury. This plastid envelope rupture is possibly activated by the release of pressure in the sieve-tube element. After plastid membrane vesiculation, the stroma and the protein crystals are dispersed within the sieve-element ground cytoplasm. The vesicles originating from the plastid envelope move to one cell pole, while protein crystalloids move to the opposite pole and agglomerate in the sieve-plate region. Our findings indicate that these protein crystalloids, which deposit in the sieve plate, may act in sieve-plate pores occlusion, preventing the release of phloem sap, similar to the role of P-protein in dicotyledons.

Fertilization of Crocus sativus L. ovules and development of seeds after stigmatic pollination with C. thomasii Ten. pollen

Abstract Fertilization and seed development were studied in Crocus sativus L., after pollination with Crocus thomasii Ten. Fertilization was porogamous and resulted in the formation of zygote and primary endosperm nucleus; it was accompanied by degeneration of the receptive synergid and followed by degeneration of the antipodals. The endosperm developed precociously by free nuclear division, occuping a parietal position; subsequently it filled the central vacuole and became cellularized. The zygote divided after a quiescence period by formation of a transversal wall; its division was accompanied by degeneration of the persistent synergid. The embryo developed from the apical cell and, at maturity, was a cylindrical structure showing histological differentiation of the shoot apex. The seed coat was formed from both integuments. Both embryogeny and development of the endosperm and seed coat were entirely similar to those of Crocus thomasii.

Distribution of P-protein in Mature Sieve Elements of Cucurbita maxima Seedlings Subjected to Prolonged Darkness

A study has been made of the structure of the sieve tubes in the phloem of seedlings of Cucurbita maxima kept in total darkness for 2 or 3 days. All cytoplasmic components were found to be parietal in their distribution. The parietal system was closely applied to the cell membrane and appeared to be supported by a continuous framework of endoplasmic reticulum (ER) with which P-protein was intimately associated. The ER-P-protein complex was highly compact in some sieve elements and loosened to various degrees in others. The pores in the sieve plates were either unobstructed or occluded by components of the parietal complex in various ways, occlusion not always being accompanied by noticeable disruption of the parietal system. In visibly undisturbed sieve tubes, in which the ER-P-protein complex was in a highly compact state, occlusion appeared accidental, arbitrary and without any alignment of the components present in the pores. It is suggested that the distribution of the cytoplasmic components in the parietal position represents a true-to-life condition of the sieve tube, preserved due to control of the ‘surge’ artefact to which transporting sieve tubes are susceptible. However, the organization of sieve tube probably changes with the state of transport and the highly compact condition of the ER-P-protein complex as well as unobstructed or arbitrarily obstructed sieve plate pores represent a state of ‘rest’ or low transport.

Fetal hemorrhage: Complication of vacuum extractor after fetal blood sampling

A 28-year-old patient, para 0, gravida 2, was admitted to the hospital in early labor at 39 weeks’ gestation. An epidural anesthetic was administered and a low amniotomy was performed. A spiral scalp electrode was applied to the presenting head to monitor the fetal heart rate. Ninety minutes before delivery fetal tachycardia occurred and scalp blood was taken for pH estimation. The fetal scalp was visualized through an amnioscope, cleaned, and sprayed with ethyl chloride. The surface was then punctured to a depth of 2 mm., with a fetal blood sampling blade,* and the blood drops were drawn into a capillary tube. The site of the wound was compressed for two minutes, with cotton wool attached to an introducer, and finally inspected to ensure that the bleeding had stopped. The pH was normal, but progress of labor had been slow and 22 hours after admission the fetal monitor showed late decelerations. As the cervix was 9 cm. dilated the vacuum extractor was applied to expedite delivery. When the pressure, produced over six minutes, reached 0.6 Kg. per square centimeter, fetal blood began to spurt into the vacuum bottle. The measured blood loss was 45 ml. Light traction rapidly achieved full dilatation, permitting low-forceps delivery of a male infant weighing 3.05 kilograms. There was no asphyxia at birth, and the Apgar scores were 8 and 10 at one and five minutes. Examination showed a small sampling incision and the spiral electrode overlying a cephalhematoma in the right posterior parietal position. The hemoglobin and packed cell volume at birth were 15.6 Cm. per deciliter and 51.8, respectively, and fell to 13.5 Gm. per deciliter and 42.2 by 48 hours, but there was no significant jaundice.

SIEVE‐ELEMENT ONTOGENY IN THE ROOT OF EQUISETUM HYEMALE

Roots of Equisetum hyemale L. var. affine (Engelm.) A. A. Eat. were fixed in glutaraldehyde, postfixed in osmium tetroxide, and sieve elements of various ages were examined with the electron microscope. Young sieve elements are distinguished by their position within the vascular cylinder and by the presence of numerous refractive spherules, which originate within dilated portions of the endoplasmic reticulum (ER). Early in development, the sieve‐element walls undergo a substantial increase in thickness. This is followed by the appearance of massive ER aggregates in the cytoplasm and then by a phase involving stacking and sequestering of the remaining ER. Nuclear degeneration is initiated shortly after the appearance of the ER aggregates. The chromatin condenses into masses of variable size along the inner surface of the nuclear envelope. The envelope then ruptures and chromatin is released into the cytoplasm. During the period of nuclear degeneration, mitochondria and plastids undergo structural modification, while components such as dictyosomes, microtubules, and ribosomes degenerate and disappear. The remaining cytoplasmic components assume a parietal position in the cell, leaving the lumen of the cell clear in appearance. At maturity, the plasmalemma‐lined sieve element contains plastids, mitochondria, some ER, and refractive spherules. At this time many of the refractive spherules are discharged into the region of the wall. Pores between sieve elements occur largely on the end walls. During pore development, tubules of ER apparently traverse the pores, but because of the presence of massive callose deposits in the material examined, the true condition of mature pores could not be determined. The connections between mature sieve elements and pericycle cells are characterized by the presence of massive wall thickenings on the pericycle‐cell side. Plasmodesmata in the wall thickening are matched by pores on the sieve‐element side. Ontogenetic and cytoplasmic factors argue against use of the term “companion cell” for the vascular parenchyma cells associated with the sieve elements.

Development of Intra-Ovarian Ovaries in Carica papaya L.1

Abstract The occurrence of intra-ovarian ovaries in certain strains of Carica papaya L. is not uncommon. Approximately 150 hermaphroditic and 25 female ovaries from a hybrid progeny contained internal ovaries in stages of development ranging from thread-like appendages to round or elongated pistils of various sizes and shapes. A few were large enough to fill the entire seed cavity of the primary fruit and possessed their own cavities with non-viable seeds. Internal ovaries originate either from stimulated growth of rudimentary pistillate structures extending from the central axis of the receptacle or from placentae in positions normally occupied by ovules. The placenta may be in its normal parietal position or a single strand may become free, extended from the base of the primary ovary and support a mal-shaped secondary ovary as well as ovules. The occurrence of internal ovaries supports theories proposed by other investigators on the evolution of floral morphology in the papaya.

Development of P-protein in sieve elements ofMimosa pudica

The P-protein in sieve elements of leaves ofMimosa pudica L. is first discernible as fine fibrous material which forms homogeneous aggregates. Ribosomes, rough endoplasmic reticulum, and dictyosomes with associated vesicles occur in the cytoplasm surrounding the aggregates. The plastids and mitochondria are in a parietal position in the parts of the cell where the nascent P-protein accumulates. In a later stage, the fibrillar material is organized into a three-dimensional system of five- and six-sided elongated compartments. The corners of the compartments appear solid at first, then they become electron lucent in the center and assume tubular form. Aggregates of mature P-protein tubules usually occur near the compartmentalized system. Tubules in pentagonal or hexagonal arrangements may be present in the aggregates and may be partly interconnected. The conclusion was drawn that the P-protein tubules are assembled at the corners of compartments within a continuous orderly system. The fully formed tubules occur first in aggregates, the P-protein bodies. Later the aggregates become loose and partly dispersed. Many of the dispersed tubules assume a loose, extended, helical form characteristic of P-protein in older sieve elements.

A re-evaluation of the mesangial cells of the renal glomerulus

The topographical localization of the mesangial cells in renal glomeruli of rats, and their relationships with the structures at the hilus of the glomerulus were studied in this investigation. It was observed that the mesangial cells occupy a parietal position in the wall of the glomerular capillaries, and that they are anatomically continuous with the smooth muscle cells of the tunica media of the glomerular arterioles.

ULTRASTRUCTURE OF THE SECONDARY PHLOEM OF TILIA AMERICANA

Summer and winter (July and January) samples of secondary phloem of Tilia americana were studied with the electron microscope. Parenchyma cells contain: nuclei, endoplasmic reticulum, ribosomes, plastids, mitochondria and occasional dictyosomes. Well‐defined tonoplasts separate vacuoles from cytoplasmic ground substance. Vacuoles often contain tannins. Lipid droplets are common in cytoplasm. Endoplasmic reticulum–connected plasmodesmata are aggregated in primary pit fields. Companion cells differ from parenchyma cells in having numerous sieve‐element connections, possibly slime, and in lacking plastids. Mature, enucleate sieve elements possess 1–4 extruded nucleoli. Numerous vesicles occupy a mostly parietal position in association with plasmalemma. The mature sieve element lacks endoplasmic reticulum, organelles (except for few mitochondria) and tonoplast. In OsO4– and glutaraldehyde‐fixed elements, slime has a fine, fibrillar appearance. Normally, these fine fibrils are organized into coarser ones which form strands that traverse the cell and the plasmalemma‐lined pores of sieve plates and lateral sieve areas.

Phloem of White Pine and Other Coniferous Species

1. In Massachusetts, cambial division in white pine starts as early as February in some years, and is rapid during May. Phloem differentiation may lag until late summer or early fall, and daughter cells may remain in various stages of maturity through the winter. 2. Sieve tube differentiation starts with a localization of the nucleus in a protoplasmic bridge in the center of the cell. Rapid turgor expansion follows, bulging the pit areas and enlarging the cell. Protoplasmic streaming and vital stain accumulation indicate a high state of cell activity. As the sieve tube matures the nucleus disintegrates; the cytoplasm ceases streaming, becomes fibroid in consistency, develops an affinity for stains, and assumes a parietal position in the cell. The cell walls thicken, secondary walls are formed, and the connecting protoplasmic threads of the sieve areas stain heavily. Cessation of streaming, loss of the power to accumulate vital stains, and absence of plasmolysis in the presence of hypertonic solutions indicate a low activity state and a high permeability of mature sieve tube cytoplasm. 3. Denaturing of the protoplasm of the connecting threads is attended by callus formation in their immediate vicinity. Starch grains in the sieve tube plastids are released into the lumen and float free in the liquid contained there. 4. Senility of the sieve tube is attended by increase in the volume of callus on the sieve areas, a thinning down and loss of staining affinity by the cytoplasm, and a reduction in the numbers of starch grains. 5. Death of the sieve tube results in loss of the cytoplasm and callus, invasion of the lumen by air from the outer bark, and finally collapse of the elements. 6. White pine phloem contains no fibers; secondary wall thickening occurs in sieve tubes. Other genera of conifers have phloem fibers, and secondary wall thickening is confined to these elements, which are lignified. 7. Protoplasmic connections in the sieve areas of white pine are slender, solid, and fibroid in structure throughout the functioning period. Those of redwood are even more slender, consisting of anastomosing strands. 8. The picture of the functioning sieve tube of the conifers developed during these studies offers little support to theories of phloem transport requiring protoplasmic streaming or a high activity state in the mature sieve tube cytoplasm.