Longitudinal Channels Research Articles

Ultrastructure of the larval compound setae of the polychaete Nereis vexillosa grube.

Larval compound (jointed) setae of the polychaete Nereis vexillosa Grube were examined by scanning and transmission electron microscopy and by polarization microscopy. Long-bladed spinigers and short-bladed falcigers are described. The proximal shaft of each of these types of setae flares distally into a serrated collar and encloses the proximal end of a toothed blade. The collar projects on one side as a boss. The blade and the cortex of the shaft have longitudinal channels. A large excentric cavity in the shaft (the medullary channel) contains a loose meshwork of trabeculae. In the distal part of the shaft these trabeculae are aggregated into diaphragms. The seta is invested with an electron dense layer of enamel. Juvenile setae contain both chitin and protein. With respect to the long axis of the seta, the blade and the cortex of the shaft are positively birefringent and the medullary diaphragms are negatively birefringent. KOH extraction renders the setae negative to a test for protein and reverses the sign of birefringence of the cortical material of the shaft.

Ultrastructural Similarities Between Setae of Brachiopods and Polychaetes

Larvae of the brachiopod Terebratalia transversa Sowerby have 2 bundles of setae on each side of their mantle lobe. Each seta grows out of a follicle of epidermal cells. The cisternae and associated vesicles of the Golgi bodies in lateral follicular cells are filled with electron dense material. The basal follicular cell, or chaetoblast, has apical microvilli projecting into the basal ends of the longitudinal channels of the seta. The channel partitions are composed of fine fibers oriented parallel to the setal axis. The close structural and developmental similarities between polychaete and brachiopod setae are discussed.

Structure of the Malpighian Tubule Muscle of the American Cockroach, Periplaneta americana1,2,3

Two parallel and closely apposed muscles, each about 5 to 10 μ in diameter are wrapped helically around each malpighian tubule in Periplaneta americana (L.) (Dictyoptera: Blattidae). They arise from a network of fibers at the base of the tubule, and extend to its knoblike distal end. The muscles are paralleled and closely accompanied by a trachea. The muscle fibers are striated, with sarcomere units 5 μ long. The Z lines, and A and I bands can be identified, but are somewhat zig-zag in appearance, and not sharply distinct. No H band could be seen. Invaginations of the sarcolemma form a T-system which joins the sarcoplasmic reticulum to form dyads. In cross section, myosin filaments are surrounded by a variable number of irregularly arranged actin filaments. Although the ratio of actin filaments to myofilaments is about 7:1, many of the former are shared among myofilaments so that each of the latter is surrounded by about 12 actin filaments. Mitochondria are confined to longitudinal channels in the central core of the muscle, and to concentrically arranged sarcoplasmic ridges which are on the side of the muscle away from the malpighian tubule epithelium. No evidence of nerves associated with the muscles was found along the distal length of the tubule.

Seismicity of the Solomon and Santa Cruz islands, Southwest pacific

Abstract Seismic data for 1965–68 from stations in the region show two low longitudinal (P) velocity channels at 100–130 km and 400–450 km which correlate with two such channels reported in the Japanese Islands. Spatial distribution of hypocentres for 1963–69 suggests several recognisable surfaces but not a single overall picture, thus neither proving nor disproving the concepts of Isacks et al. (1968). Grover (1967) is not supported.

The Pontomesencephalic Veins

The pontomesencephalic veins have in the past been beautifully demonstrated in roentgenograms of anatomical specimens (2, 3). A few authors have also identified these veins on vertebral angiography performed during life (1, 3–5, 10, 11). The present work is an attempt to investigate the pontomesencephalic venous system in greater detail, using clinical neuroradiological means. The variable roentgenographic appearances of the pontomesencephalic veins, their relationship to the anterior border of the brain stem, and their frequency of visualization on vertebral angiography will be discussed. Anatomy The blood from the major part of the pons and mesencephalon drains in an anterior direction (Fig. 1). Numerous parenchymal veins, on reaching the anterior and anterolateral surfaces of the brain stem, usually empty into larger, longitudinal venous channels which are closely associated with the anterior border of the brain stem (2–4). Occasionally, there may be only a single, midline, longitudinal vein situated between the basilar artery and the brain parenchyma (2). This fact and the frequent impression of seeing only one longitudinal vein in front of the brain stem on lateral roentgenograms of vertebral angiography probably prompted Huang and Wolf (3), for the sake of simplicity, to speak of the “anterior pontomesencephalic vein.” Hassler (2), however, states that anatomically there is generally a plexus of longitudinal veins on each side of the pons, a few millimeters from the midline and fairly parallel to the basilar artery. The venous plexus anterior to the pons is continuous with a similar plexus in the interpeduncular fossa and anterior to the medulla oblongata and spinal cord. The pontomesencephalic veins in most cases drain primarily into (a) the superior petrosal sinuses, mostly through the petrosal veins, and (b) peduncular veins which pass laterally around the upper margins of the cerebral peduncles and empty into the basal veins of Rosenthal or posterior mesencephalic veins. Some drainage also occurs into the inferior petrosal sinuses and through bridging veins into the basilar venous plexus along the clivus (2–4, 6–8, 10, 11). With variation in venous drainage, the pontomesencephalic veins may in part empty into the uncal vein (which usually drains into the cavernous sinus) or the lateral anastomotic mesencephalic vein (3, 11). Material On a review of the 1967–1968 vertebral angiographies performed at Ullevål Hospital, we selected for further study the first 100 examinations encountered with a technically satisfactory demonstration of the posterior cranial fossa veins. Thirty-seven patients were males, and 63 were females. Their ages ranged from five months to seventy-four years (Table I). The lateral views were used as the basis for this screening, which was an inspection of the posterior cranial fossa veins in general.

"C-Pattern" Inferior Vena Cava

THE EMBRYOLOGY of the inferior vena cava is an exceptionally complex mechanism involving phases of development and regression by various segments of three paired longitudinal venous channels draining the lower extremity, trunk, and abdominal viscera. Recognition of the occasional anomalous or accessory inferior vena cava and of the possibility of agenesis has been simplified by development of radiographic techniques and necessitated by progress in vascular surgery, particularly portocaval shunting and prevention of pulmonary embolism. The present report was prompted by the incidental finding at surgery of an exceedingly rare type of anomalous inferior vena cava with subsequent radiographic visualization. <h3>Report of a Case</h3> A 58-year-old white man was referred to the USAF Hospital Andrews because of the incidental finding of an abdominal aortic aneurysm. The patient had been treated for the past four years for hypertension, and recent intravenous pyelography, as part of a definitive reevaluation, demonstrated the presence of

The Problem of Coastal Genesis, with Special Reference to the "Strandflat," the "Banks," or "Grounds," and "Deep Channels" of the Norwegian and Greenland Coasts

The so-called strandflat of the Norwegian coasts has aroused the interest of scientists since an early date. Later other forms, such as banks or grounds and deep channels, were discovered and posed additional problems. But no agreement has ever been reached on these problems in spite of numerous discussions. The formation and processes in the development of the strandflat and adjacent geomorphological forms cannot-according to the author-be separated from the history of the hinterland. Thus, to a major extent, the strandflat forms a part of a polycyclic piedmonttreppe. In the same way the bankflat is stated to be identical with one step of this geomorphological staircase. The banks and grounds off the coasts are explained as galacial-fluviatile-marine deposits of a very complex nature, intersected by longitudinal and transverse channels. These peculiar submarine forms are suggested as having been created by fluvial and glacial erosion and conserved to our day by a system of marine currents. Isostatic and eustatic movements are additional factors to be taken into consideration in the history of the building of the coast forms mentioned.

Comparison of intraosseous vertebral venography and Pantopaque myelography in the diagnosis of surgical conditions of the lumbar spine and nerve roots.

Despite the widespread use and proclaimed safety of Pantopaque myelography (1–7) many still adopt a reluctant attitude toward its indiscriminate and repeated employment or condemn it as a screening procedure. The basis for this hesitancy are reports of occasional adverse reactions of the leptomeninges with early or late sequelae in the spinal canal or intracranial cavity. A method without the disadvantages associated with the introduction of a potentially irritating substance into the subarachnoid space but with comparable accuracy, even if limited to lesions of the lumbar spine, would indeed constitute a valuable addition to our diagnostic armamentarium. It was our feeling that intraosseous vertebral venography might hold such promise. We therefore set out to compare its potentialities with those of Pantopaque myelography in the diagnosis of such surgical lesions of the lumbar spine and nerve roots as disk protrusion, spondylolisthesis, symptomatic spina bifida occulta, tumors of the cauda equina, epidural tumors, and metastatic tumors of the vertebral column. Anatomic Considerations The blood from the medulla spinalis, nerve roots, meninges, vertebral column, and paravertebral muscles is drained by multiple veins constituting a network extending over the entire length of the spine. These venous plexuses are located in part outside and in part inside the spinal canal (Fig. 1). The external vertebral venous plexus surrounds the vertebral column and is best developed in the cervical region, an anatomic peculiarity which has been roentgenographically verified (8, 9). Its posterior division is located along the spinous processes and the posterior surface of the transverse processes, extending also between the posterior paravertebral muscles. The anterior division is situated laterally and anteriorly to the vertebral bodies and is linked to its posterior counterpart as well as to the internal vertebral plexus (Fig. 1). The external vertebral venous plexus assumes important collateral circulatory duties in the presence of some obstruction to the blood flow within the internal vertebral venous plexus. The internal vertebral venous plexus, which we prefer to call the epidural plexus, is located within the spinal canal between the dura and the bony surfaces of the vertebrae. The epidural veins run along the entire length of the spine and their anatomical continuity with the intracranial dural sinuses has been confirmed by Batson (10). The veins of the internal vertebral plexus surround the spinal dura and form two pairs of well developed longitudinal channels connected with each other by a series of venous rings, one opposite each vertebra.

Some Remarks on Geomorphology of Continental Shelves off Norway, Labrador, and Southeast Alaska

Studies of the continental shelves off Labrador and the west coast of southeast Alaska suggest that there are marked topographical similarities between these and the Norwegian shelf. A large longitudinal channel or depression is present outside the northeast coast of Labrador, running almost parallel to the coast for more than 400 km., with depths of 300-400 fathoms. Another submarine arcuate channel of smaller dimensions runs parallel to the coast for about 140 km. north of Belle Isle. In the Yakutat Bay region of Alaska and in the Cross Sound area similar, but less significant, channels are present. Both in the Labrador and in the Alaskan area large transverse depressions on the shelf terminate landward in a relatively steep slope which is located along the line of the longitudinal channels. The features are thought to indicate that these present land areas are bordered by major fracture zones along which dislocations took place during the Cenozoic uplift.

A Nolan Amphora of the Kleophrades Painter

MONG the many vases which modern scholarship has attributed to the Kleophrades A Painter' there was until now only one small Nolan amphora.2 Even this is not one of his best works. I believe that a second Nolan amphora can be added to the list, a piece which ranks with his best work. The small neck-amphora with tri-partite handles3 illustrated here on pl. LXIII, belongs to the collection of the Gustav-Ltibcke Museum in Hamm, Westphalia, which was hitherto entirely unknown to scholarship.4 The vase was a gift to the Museum. It was put together from sherds; in addition to minor fractures, a few pieces are unfortunately missing. The brilliant black glaze has flaked off at some of the points of fracture. Nothing has been restored. The glazed foot is profiled, and a low plastic ring, emphasized by incised lines above and below, runs around the vase at the point where the foot joins the body. The handles are black with shallow longitudinal channels. A second thin plastic ring stands at the base of the neck; the latter is slightly concave. The profiled lip with a flat upper surface, left in the natural color of the clay, is marked off from the neck by a groove. Beneath the figures on either side is an interrupted maeander band. On Side A a young warrior strides toward the left, wearing a helmet and greaves and carrying a shield and spear. He wears an armored chiton decorated with stars, and a himation with a band at the border. The device on the shield consists of three stars and a cres-

On Fault Lines Indicated by the Submarine Relief in the Shelf Area West of Spitsbergen

A year ago the writer published in this journal1 an article giving some preliminary results of studies on the continental shelf off the coasts of Norway. In a general map, a system of supposed submarine fault lines was shown — fault lines along which the Scandinavian land-mass is believed to have been lifted up in fairly recent, in Tertiary-Quaternary times. The existence of such lines is indicated by the presence of longitudinal channels, separating the area of banks from that of the rocky land-mass (with the »skjærgård« — skerries — area as its outermost zone) and by the way in which many transverse submarine valleys are abruptly cut off towards the land, along lines lying in the continuation of the said longitudinal channels. It was maintained that the transverse channels represent the outer, peripheral, remnants of old valleys, the inner parts of which cannot generally be traced any longer because of the uplift and

The excretory system of the trematode, Typhlocoelum cucumerinum, with notes on lymph‐like structures in the family Cyclocoelidae

AbstractThe exeretory system of Typhlocoelum cucumerinum consists of three pairs of longitudinal channels communicating by a single ventral vessel with the excretory vesicle. Branches subdivide extensively and anastomose forming a dense network of tubules throughout the body. The vessele possess many of the features characteristic of lymph systems as described in amphistome trematodes. They have cuticular walls, come into intimate association with the intestine and contain a granular coagulum and cellular elements suspended in the lumen. The single system of vessels appears to be functioning as a combined lymph and excretory system. Typhlocoelum americanum Manter and Williams ('28) is regarded as a synonym of Typhlocoelum cucumerinum (Rud. 1809).

On certain Semi-carnivorous Anthomyid Larvae

In previous papers one of us (Keilin, 1915, 1917) has shown that among cyclorrhaphous dipterous larvae there is a remarkable correlation between the anatomical structure of the larvae and their mode of life. Although the mode of life of the larvae is in correlation with such anatomical features as thickness and hardness of the body-wall, the development of sensory organs on the head, and the structure of the alimentary canal, it is in the bucco-pharyngeal armature that the most obvious and important adaptations are to be found. The most important of these adaptations may be mentioned briefly. In certain cyclorrhaphous dipterous larvae the ventral wall of the basal sclerite of the bucco-pharyngeal armature has a number of longitudinal ridges projecting into the lumen of the pharynx. These ridges are usually Y-shaped at their free borders, and form a series of longitudinal channels in the ventral region of the pharynx. In other cyclorrhaphous dipterous larvae such ridges are absent and the ventral wall of the pharynx is smooth. This character allows the larvae to be divided into two groups—“all cyclorrhaphous dipterous larvae parasitic on the most diverse animals or on plants, as well as carnivorous larvae, and larvae which suck the blood of mammals, never have ridges in their pharynx; on the contrary, ridges are always present in saprophagous larvae” (Keilin, 1915). All the larvae which are devoid of ridges and are either parasitic, carnivorous, pass their whole life in the uterus of the female, or are phytophagous, may be united into the group of biontophagous; all larvae which have ridges are saprophagous.