Strands Of Tissue Research Articles

Distribution of type-VII collagen in xenografted human carcinomas.

The distribution of type-VII collagen, the main molecular component of the anchoring fibrils (AF) attaching the basal lamina (BL, lamina densa of the basement membrane) to the surrounding connective tissue, was investigated in four xenografted human carcinomas of the hypopharynx (H-Stg 1), the lung (L 261), the sigmoid colon (CA 1), and the rectum (R 85). The studies were performed with a recently prepared, affinity-purified and highly specific antibody to type-VII collagen by using the indirect immunofluorescence and the APAAP (alkaline phosphatase anti-alkaline phosphatase) techniques. For comparison, the localization of the intrinsic BL components laminin and type-IV collagen were additionally analyzed in all four carcinomas. It was shown that type-VII collagen usually colocalized to laminin and type-IV collagen and was deposited at the borderline between carcinoma cell clusters and the surrounding strands of connective tissue in a similar, but more diffuse and less continuous distribution than both intrinsic BL components. In the squamous cell carcinoma H-Stg 1 and the adenocarcinoma L261, type-VII collagen was additionally accumulated in enlarged extracellular spaces between carcinoma cells, away from the contact zone to the connective tissue and again colocalized to laminin and type-IV collagen. Numerous carcinoma cells of both xenografts showed remarkable intracytoplasmic immunoreactivity for the antibody to type-VII collagen. Even in the case of the gastrointestinal carcinomas CA 1 and R 85, faint immunoreactivity for type-VII collagen was found at the contact zone between the mucosal epithelium and the surrounding connective tissue. These results confirm that epithelial carcinoma cells are obviously involved with the synthesis of the main molecular component of AF usually attaching the BL to the adjacent connective tissue and hint at a possible correlation between the localization of type-VII collagen and the observed pattern of the BL. However, it cannot be decided whether there is a direct causal relation between both phenomena or whether they are both the consequence of an independent but common cause, such as abnormal cellular differentiation of carcinoma cells. In no case, can the discontinuities in the distribution of type-VII collagen be explained by active tumor cell invasion since xenografted human carcinomas neither invade nor metastasize.

Cephalic structures in the nemertine Parborlasia corrugatus—Are they really eyes?

The opinion as to whether tiny, approximately 0.1 mm large spots around the innermost margin of the cephalic slits in the Antarctic nemertine worm Parborlasia corrugatus represent photoreceptors or not has fluctuated over the years. This first electron microscope study of the enigmatic spots fails to detect any screening pigment granules, rhabdomeres, or lamellae, but reveals that the structure in question is principally made up of two types of cell, characterized by vesicular and vacuolar material of approximately 80 nm and 0.3 μm in diameter, respectively. Filamentous connective tissue strands with gaps for axons surrounds the ‘eye-spot’ and it is suggested that either exposure to the bright Antarctic summer light has led to a total disintegration of all visual membranes or these structures do not represent eyes at all.

Development of the basal lamina in xenografted human carcinomas: an ultrastructural and immunohistochemical study

The development of the basal lamina (BL), the key structure of the basement membrane (BM), was investigated in three xenografted human carcinomas of the sigmoid colon (CA 1), the lung (L 261), and the hypopharynx (H-Stg 1) following heterotransplantation to athymic mice. The study involved the use of electron microscopy and indirect immunofluorescence techniques employing highly specific antibodies against the intrinsic BL components, heparan sulfate proteoglycan, laminin and type-IV collagen. Following transplantation, the extracellular matrix material of the transplanted tumors decomposed and was phagocytozed by invading macrophages within 1 to 2 days. During this stage, no specific binding of the applied antibodies to BL components could be detected within the xenografts. Following the ingrowth of host-derived connective tissue between days 2 to 6, small fluorescence-positive granules appeared within the cytoplasm and around those tumor cells that were located close to the invaded strands of connective tissue. Ultrastructurally, typical secretory granules were detectable in the cytoplasm of many xenografted carcinoma cells. Thereafter, a tannic acid-positive, patchy material appeared in the extracellular space of CA 1 and L 261 and aggregated to form small fragments of a discontinuous BL. In the H-Stg 1 xenografts, this material assembled to form continuous mono-, bi- and multi-layered structures. Large amounts of excess BL material remained accumulated in the L 261 and H-Stg 1 xenografts until the end of the observation period (day 24). These findings reveal that discontinuities of the BL occur independent of the active invasion processes of tumor cells, since xenografted human carcinomas neither grow invasively nor metastasize in nude mice. Moreover, they confirm that these discontinuities are not caused by a quantitatively insufficient production of BL material, but rather arise from qualitative imbalances of the composition of the synthesized BL material.

Conduction in bullfrog atrial strands: Simulations of the role of disc and extracellular resistance

A number of fundamental properties of intercellular conduction in simulated cylindrical strands of cardiac tissue are examined. The paper is based on recent biophysical information describing the transmembrane ionic currents in bullfrog atrial cells as well as anatomical data on the structures (gap junctions) responsible for the coupling between cells in that tissue. A mathematical model of the single bullfrog atrial cell based on suction microelectrode single-cell voltage clamp data is employed, as well as a modified version of the well-known model of Heppner and Plonsey, to characterize the resistive connections between adjacent cells in a cardiac strand. In addition, the simulated cellular strand is assumed to be encased in a cylindrical, resistive endothelial sheath, thus forming an idealized atrial trabeculum; the trabeculum is immersed in an extensive volume conductor. It is possible to simulate both uniform and discontinuous conduction in this atrial strand model by appropriately changing the resistance of the intercalated discs that occur at cell boundaries. The conduction velocity achieved in the normal or control case is within the range of conduction velocities that have been measured for bullfrog atrial trabeculae using optical methods. Extracellular resistance is shown to have a significant effect on both conduction velocity and the critical value of disc resistance at which discontinuous conduction first occurs. Since the atrial cell model employed in this study is based on experimental data and can accurately simulate the atrial action potential, the transmembrane ionic currents generated by the model are capable of providing detailed information concerning the mechanisms of intercellular current spread, particularly in the region of the intercalated disc.

Healing of the guinea pig incisor after partial pulp removal

A histological and microradiographical study was made of eruption and healing of guinea pig lower incisors after endodontic treatment compared with intact incisors. One incisor per animal was cut perpendicularly at the level of the gingiva. One third to one half of the pulp was removed. The experimental periods were 0, 4, 7, 16, 21 and 31 days. Unstained, HE or Brown and Brenn stained sections were studied microscopically. Some teeth were sectioned undecalcified and studied microradiographically. In intact incisors the dentin matrix deposition and mineralization were described. In the dentin, incisally to the pulp proper, narrow canals, the walls of which consisted of mineralized material, were found opening at the occlusal surface. Histologically, in the treated teeth, a beginning of cell-rich fibrodentin deposition at the original dentin wall was present at Day 4. At Day 7 a substantial walling off of the pulp is achieved by cell-rich and some cell-poor fibrodentin. After 16 days large amounts of cell-rich and cell-poor fibrodentin were covered by some tertiary dentin. After 31 days the amount of tertiary dentin was larger than after 16 days and also covered the incisal part of the root canal walls. Further apically some vasodentin and newly formed normal, secondary, dentin was observed. In course of this period the cells of the cell-rich and cell-poor fibrodentin first showed necrobiosis, then necrosis. The cell-rich fibrodentin appeared not fully mineralized. All blood vessels and strands of soft tissue which ran in canals in the fibrodentin came to a dead end. Thus the root canal was fully obturated. Although the teeth appeared (nearly) normal to the naked eye and radiographically after 31 days, histologically they were not. Large amounts of fibrodentin still being present incisally which showed the dual potential of the guinea pig pulp to produce both fibrodentin and orthodentin.

The arrangement of the heart chambers and associated blood vessels in the Devonian osteostracan Norselaspis glacialis. A reinterpretation based on recent studies of the circulatory system in lampreys

A brief account is given of the different arrangements of the heart and associated blood vessels of ammocoetes and adult lampreys, the significance of the oesophageal suspension in ammocoetes and the structure of the rigid cartilaginous pericardium which is developed during lamprey metamorphosis. These accounts have then been used, in conjunction with the size, shape and position of the apertures and recesses of the ossified pericardial capsule of the Devonian osteostracan Norselaspis glacialis, to reinterpret the way in which the heart chambers were arranged within this fossil agnathan and to elucidate the vessels responsible for returning blood to its heart. The dorsal aorta of osteostracans undergoes a similar right‐hand curve just behind the postbranchial wall to that exhibited by the dorsal aorta of larval lampreys. This indicates that the dorsal aorta of N. glacialis was likewise shifted to the right by vertical strands of connective tissue which suspend the oesophagus from the under surface of the notochord and between two ducts of Cuvier and the heart. The size and shape of apertures and recesses in the pericardial cavity of Norselaspis glacialis supports the view that, in this osteostracan, two ducts of Cuvier entered the pericardial cavity through a dorsal opening on the posterior part of the capsule and then joined with the sinus venosus. The marginal sinuses/veins in the anterior part of the body of N. glacialis, from which blood passed horizontally into the respective ducts of Cuvier, are now regarded as homologues of the anterior cardinal veins. While there is evidence that, as in ammocoetes, the right duct of Cuvier was larger than the left duct in N. glacialis, the relative size and position of its proposed atrium and ventricle was apparently more like that of adult lampreys. Despite differences in the mode of formation of the ossified pericardium of osteostracans and the cartilagenous pericardium of adult lampreys, these structures presumably had a similar function. This would involve generating negative pressure within the pericardial chamber during ventricular systole, thereby aiding atrial diastole and thus the influx of blood into the heart from the main venous vessels, such as the inferior jugular vein(s) and the ducts of Cuvier. The inner side of the pericardial capsule of osteostracans, like that of adult lampreys, appears to have possessed an extensive vascular network which could thus have likewise played an important role in providing fluid for lubricating the surface of the heart.

The subretinal fluid in retinal detachment

Following retinal detachment, subretinal fluid (SRF) fills the neoformed space. Subsequently subretinal and preretinal strands of proliferative tissue begin to form. We have collected the subretinal fluid withdrawn during retinal detachment surgery. We have studied subretinal fluid cytologically to evaluate the number and the type of cells present in the fluid, and by means of transmission electron microscopy. The first cell type to be present in the fluid represented degenerated aspects of pigmented epithelial cells (PECs). Successively, other cell types appeared in the fluid as nerve cells (rods, cones and glial cells), macrophages and well preserved pigmented epithelial cells.

Aspects of the development and functional morphology of the pericardia, heart and associated blood vessels of lampreys

During the early larval life of lampreys, connective tissue strands develop between the notochord and oesophagus, thereby suspending the oesophagus between the two ducts of Cuvier and above the heart, which, unlike adult lampreys, is not enclosed in a rigid pericardial capsule. Examination of histological sections from proammocoetes and young ammocoetes provides strong evidence that the growth of this suspensory tissue is responsible for the dorsal aorta moving to the right and undergoing a concomitant rotation, which shifts the origin of the anterior mesenteric artery on the dorsal aorta from a right ventro‐lateral to a right dorsolateral position. While the heart initially develops the three major layers found in craniates, i.e. epicardium, myocardium and endocardium, the innermost of these breaks down early in larval life. The myocardium thus becomes bathed in blood, a feature which would help compensate for the lack of a coronary artery. After studying the way in which they are formed early in life, it is proposed that the epicardium is best termed the visceral or splanchnic pericardium and that the thin membrane lining the cavity surrounding the heart should be referred to as the parietal or somitic pericardium. The pericardial capsule of the adult, which is made of non‐compliant walls of cartilage and connective tissue. consists of three main components. The anterior component comprises the anteriorly convex post‐branchial wall. The intermediate component is formed by the posterior part of the seventh branchial arch on each side of the body and their posteriorly‐directed processes. The latter processes expand into the cup‐shaped pericardial cartilage, which constitutes the third and most posterior component of the pericardial capsule. A pear‐shaped opening in the connective tissue formed between the two anteriorly‐directed dorsal extensions of the pericardial cartilage allows the cardinal veins to join the single (right) duct of Cuvier, which in turn enters the sinus venosus. The ventral part of the cartilaginous floor of the pericardial capsule contains a large slit of connective tissue through which the ventral hepatic vein passes upwards to enter the sinus venosus. The inner surface of the pericardial capsule contains an elaborate and very well developed network of venous sinuses and sinusoids, which are supplied by blood from the peripharyngeal sinus and are drained by the inferior jugular vein. It is suggested that this network produces fluid which helps lubricate the heart. A description is given of the way in which the adult pericardial capsule is developed during the seven stages of metamorphosis. This sequence demonstrates that much of the development of the capsule takes place during stage 3 and that by the end of stage 6 the form of the capsule has become essentially the same as that of young adults.

The development of synovial plicae in human knee joints: An embryologic study

An embryologic study about the development of the human knee joint cavity was carried out with special attention to the formation of synovial plicae, using a total of 116 knees of embryos and fetuses. The incidence of synovial plicae in the fetal stage was also investigated. Formation of joint space starts at the middle of the interzone at around 8 weeks of gestation. Multiple small cavitations around the femoral condyle and patella coalesce to form larger cavitations. At around 10 1/2 weeks, the knee joint consists of a single cavity with synovial lining. At certain sites, such as at the medial part of patello-femoral and the infrapatellar regions, mesenchymal tissue strands remain. They may become plica. In the fetal stage from 11 to 20 weeks, an infrapatellar plica was found in 50% of specimens, a suprapatellar plica in 33%, and a mediopatellar plica in 37%. Only the infrapatellar plica showed a decrease in incidence.

Elastin in Alcoholic Liver Disease: An Immunohistochemical and Immunoelectron Microscopic Study

Increased elastic stained material has been described in fibrotic and cirrhotic liver processes. The aim of this work was to follow the development and distribution of elastic fibers from 48 chronic alcoholic patients. Patients were scored for fibrosis as 0, without fibrosis or minimal (n = 5); 1, incipient or early fibrosis (n = 9); 2, fibrosis or incomplete cirrhosis (n = 12); and 3, cirrhosis (n = 22). Elastica staining was performed by orcein, resorcin-fuchsin and iron hematoxylin and confirmed by immunofluorescence staining with an anti-human elastin antibody (Institut Pasteur). Electron microscopy of representative cases of each group and electron microscopy of immunolabelled elastin (n = 5) were also performed. In early alcoholic fibrosis, oxytalan fibers were pointed out in terminal hepatic veins and in Disse space. In fibrous portal extensions and cirrhotic internodular septa, oxytalan and elaunin fibers represented the major elastin components in association with the alcoholic liver fibroplasia. Immunostaining with anti-elastin Ab exhibits the same distribution as with histochemical methods in portal and septal zones. Electron microscopy confirmed abundant microfibrillar bundles between collagen fibers that mesh and are in continuity with elaunin fibers. Immunoelectron microscopy confirmed elastin deposits in the amorphous material and in association with the microfibrillar material in the portal and septal zones and disclosed elastin even in the thin strands of fibrotic tissue. In conclusion, elastogenesis, mainly represented by oxytalan and elaunin fibers, develops in alcoholic disease and takes part, with collagen deposits, in the fibrotic process.

An Electron Microscopic study of the liver in certain marine teleosts

The hepatic parenchyma of five marine teleosts (belonging to five families in the Teleostei) was investiga ted during the summer months by means of light and transmission electron microscopy. The architectural organization of the livers of these teleosts displays remarkable differences with regard to the interrelationship with the pancreatic tissue. In Lates calcarifer and Lutjanus bohar, prominent pancreatic tissue is found in the liver, following the course of portal vein and hepatic artery and surrounding the branches of these vessels. The pancreatic tissue appears less abundant in Mylio macrocephalus than in the preceding species. In Siganus javus and Gymnothorax schismatorhynchus, there are no dispersed intrahepatic pancreas. The liver lobules are defined by the presence of connective tissue strands in Lates and Siganus, but in the other three species there was no precise lobulation of the hepatic tissue.The microstructure of the livers in these teleosts is basically the same in all cases, although there are considerable variations inultrastructure of their parenchymal cells. The plates of hepatocytes which are usually two or more cells thick is in terrupted by sinusoids lined with fenestrated endothelial cells and Kupffer cells (Figs. 1, 2).

Aphanomyces cochlioides . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Aphanomyces cochlioides . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Amaranthus blitoides, A. retroflexus, Beta lomatogona, B. patellaris, B. patula, B. trigyna, B. vulgaris, B. vulgaris var. cicla, Celosia argentea, Chenopodium album, Dianthus chinensis, Echinocloa crus-gallii, Escholtzia californica, Gomphrena globosa, Kochia scoparia, K. scoparia var. culta, Lychnis alba, Mollugo verticillata, Papaver rhoeas, Portulaca oleracea, Salsola kali, Saponaria ocymoides, Spinacia oleracea, Tetragonia tetragonioides . DISEASE: Blackroot of sugar beet; the fungus is a facultatively necrotrophic plant pathogen. There is an early acute phase of short duration (causing pre-emergence and post-emergence damping off) and a later chronic phase which may persist throughout the life of the plant. Infection during seed germination is indicated by poor stands with killed seeds remaining in the soil to infect young seedlings emerging elsewhere. Seedling hypocotyls are infected at ground level, a water-soaked area extending up and down the hypocotyl or the upper part of the young taproot from the point of entry. The invaded root or hypocotyl rapidly becomes brownish and then assumes the characteristic jet black discoloration from which the disease derives its name. Soon after, the cortex of the hypocotyl dries, and the stem and hypocotyl shrink, leaving a thin strand of tissue. Oospores are easily seen in the collapsed root and hypocotyl tissue on microscopic examination. The chronic phase first appears on plants in late June to August. A greenish-yellow discoloration of the swollen hypocotyl develops, affected root tissues becoming dark brown, soft, water-soaked, splitting apart and eventually shrivelling. Plants are stunted and lower leaves turn yellow. GEOGRAPHICAL DISTRIBUTION: Asia: Japan. Australasia & Oceania: Australia (Qld). Europe: Austria, Denmark, England, France, Germany (GDR & GFR), Hungary, Ireland, Poland, Sweden, USSR (Russia). North America: Canada (Alberta, NS, Ontario, Quebec), USA (California, Connecticut, Indiana, Michigan, Maine, MT, North Dakota, Ohio, South Dakota, Texas, Washington State, Wisconsin). South America: Chile. See CMI Distribution Maps of Plant Diseases 596. TRANSMISSION: Presumably in soil by oospores originating from sloughed-off root tissues and germinating to produce zoospores. The conditions favouring oospore germination are however largely unknown. Survival may occur on alternative hosts present in the crop, so the disease may be difficult to eliminate. The disease is particularly severe in warm, wet conditions, less so in cool, wet weather.

The influence of fat tissue on neuroma formation.

The proximal stumps of transected sciatic nerves were implanted into an abdominal pedicle flap of fat tissue in rats. Nerve stumps that had been transected without implantation into fat tissue served as control experiments. At 4, 8, or 24 weeks postoperatively, the rats were sacrificed and the neuromas at the transected nerve ends together with the adjacent fat tissue were studied after intra-aortal perfusion fixation. Light microscopy revealed no significant difference in neuroma size between the two groups. In most animals with fat implantation, however, infiltration of fat tissue beyond the margins of the solid neuromatous bulb by regenerating nerve fibers was limited to rare axons growing along blood vessels and connective tissue strands. In only a few instances was the fat tissue itself invaded by minifascicles as was usually seen in the connective tissue surrounding control neuromas. It is concluded that diffuse outgrowth of nerve fibers is limited to some extent by fat tissue, which, however, is not an impermeable barrier for regenerating nerve fibers. Nevertheless, in a fat tissue flap, the neuroma is placed in a "soft pressure-free bed" which might be a prerequisite for permanent diminution of pain sensitivity.

Mobility of the upper esophageal sphincter in relation to the cervical spine: a morphologic study.

If the posterior part of the upper esophageal sphincter (UES) were to lag behind due to the presence of dense tissue strands between the sphincter and the prevertebral ligament, as suggested in the literature, it would be impossible to use the larynx as a radiographic indicator of the location of the UES at intraluminal pressure measurements. The goal of this investigation was to study UES behavior during induced movements in autopsy specimens and to search for dense fibrous strands between the UES and the prevertebral fascia. Histologic studies of frozen sections and paraffin sections showed a loose fatty tissue in the prevertebral space. There were no dense connective tissue strands. Autopsy specimens were used in experiments mimicking the laryngeal/UES elevation during swallowing. The results of this study indicate that the larynx and the UES move as one entity. When one is attempting to register the UES movement during swallowing, the laryngeal skeleton can therefore serve as a radiographic indicator of the UES movements.

Host-Supplied Connective Tissue as a Guide for Proliferating Tumor Cells in Human Tumor Xenografts

The morphologic alterations of 7 human tumors of different origin and various histologic types, heterotransplanted to athymic nude mice, were investigated in the present study. Constant patterns of histologic and ultrastructural changes were observed in all 7 tumors. Following the initial dying of most inoculated tumor cells, host-supplied inflammatory cells invaded the xenografts and phagocytosed necrotic tumor cells. Fibroblasts which vivaciously produced collagenous material invaded the xenografts and built up solid strands of connective tissue which tightly contacted surviving tumor cells. These stands were used as guide-rails for ingrowing blood vessels. Immediately after their immigration, the first mitoses of tumor cells occurred in close proximity to capillary-conducting strands of connective tissue resulting in a revival of tumor cell proliferation near to the fibrous cords and a spreading of newly formed tumor cells along the strands of connective tissue. These results point to the host-supplied connective tissue as playing an important role for tumor proliferation and local tumor expansion.

Tumour formation and insulin secretion by clonal RINm5F cells following repeated subcutaneous transplantation in NEDH rats

The effects of repeated s.c. transplantation of clonal insulin-secreting RINm5F cells in NEDH rats on tumour morphology, insulin-glucose homeostasis and the function of RINm5F cells re-established in culture were examined after maintenance in vivo for periods of up to 308 days. Transplantation of RINm5F cells for ten consecutive passages consistently produced a single encapsulated vascularized tumour associated with the development in recipient rats of hyperinsulinaemia, hypoglycaemia and eventual neuroglycopenic coma. At the tenth passage, tumour-bearing rats exhibited a markedly enhanced rate of insulin-stimulated glucose uptake by 19 days, with evidence of a large and variable insulin response to i.p. glucose. Survival was 22 +/- 2 days, and resected RINm5F cell tumours exhibited weak immunostaining for insulin in scattered cells, with strands of fibrous tissue separating clusters of tumour cells many of which had distinct polarity. There was no detectable immunostaining for glucagon, somatostatin or pancreatic polypeptide. The insulin content and insulin secretory output of RINm5F cells re-established in culture after 20, 146, 259 or 308 days propagation in vivo were generally enhanced compared with non-passaged RINm5F cells. The magnitude of the effect was not appreciably affected by the duration of maintenance in vivo, but it was critically dependent upon the subsequent period of culture in vitro. Thus, whereas 2-day cultured RINm5F cells from the eighth tumour passage exhibited a greater than 100-fold increment of insulin content and release, with enhanced secretory responsiveness to leucine, arginine, theophylline, K+ (25 mmol/l) or Ca2+ (7.6 mmol/l), RINm5F cells cultured for a further 19 days had almost completely lost the attributes resulting from 259 days of maintenance in vivo. The results indicate substantial enhancement of the functional capabilities of RINm5F cells in vivo, and suggest that the resulting tumours afford a novel model in NEDH rats of responsive trabecular-type insulinomas.

Gap junction uncoupling and discontinuous propagation in the heart. A comparison of experimental data with computer simulations

The effects of octanol on longitudinal propagation in guinea pig papillary muscles were measured by intracellular microelectrodes. These data were compared with alterations in conduction induced by stepwise removal of gap junction channels in computer simulations of propagation based on a discontinuous cable model. Octanol reduced the velocity (theta) of propagating action potentials (APs) from 53.2 +/- 3.5 to less than 6.6 +/- 2.1 cm/s before block occurred. The maximal rate of rise (Vmax) changed in a biphasic manner, increasing from 133.1 +/- 5.4 in controls to 201.7 +/- 11.0 V/s when theta was 20.5 +/- 2.8 cm/s, and then declining to less than 58.6 +/- 15.2 V/s just before block. The input resistance and time constant of the AP foot increased, and the ascending limb of phase-plane loops became increasingly nonlinear and notched during octanol treatment. All effects of octanol reversed upon washout. A strand of cardiac tissue was modeled as a discontinuous cable composed of 40 cells, each with 10 isopotential membrane segments described by Beeler-Reuter kinetics, and coupled by a variable number of gap junction channels (156 pS). Decreasing the number of channels from 40,000 to 400 to 60 slowed conduction from 62.6 to 16.4 to 3.1 cm/s. As noted in the experimental data, Vmax increased from 103 to 130 and then fell to less than 96 V/s. The AP foot increased and became nonexponential. Distinct notches developed during phase 1 of the APs at slower propagation velocities in the experiments and simulations. The close similarities between the experimental and theoretical data obtained in this study supports the applicability of a discontinuous cable model for describing longitudinal propagation in the heart.

Reentry as a cause of ventricular tachycardia in patients with chronic ischemic heart disease: electrophysiologic and anatomic correlation.

In this report we describe electrophysiologic and histologic findings in hearts and endocardially resected preparations from patients with sustained ventricular tachycardias in the chronic phase of myocardial infarction. We recorded simultaneously from 64 endocardial sites during tachycardia in 72 patients that were operated on for medically intractable ventricular tachycardias. Two other patients underwent heart transplantation, and mapping was performed on the explanted isolated heart connected to a Langendorff perfusion set-up. During operation 139 tachycardias with different morphologies could be induced. Although the majority of evidence supports the concept of a reentrant mechanism for these tachycardias, we found that 105 tachycardias appeared to arise at a focal area of less than 1.4 cm2. In only three cases macroreentry around the infarction scar could be detected. Of 21 tachycardias in which the "origin" appeared to be focal, earliest subendocardial activation was preceded by discrete electrograms of low amplitude (presystolic activity). In three tachycardias presystolic activity was detected at several sites, permitting reconstruction of its route. Histology of the endocardial resected preparation in one of these cases revealed separate zones of viable myocardial fibers in areas in which presystolic activity was recorded. These zones were located intramurally and subendocardially, supporting the concept that reentry occurred via isolated bundles of surviving myocytes at the border of the infarct and the larger subendocardial muscle mass. Conduction velocity through the isolated tracts was on the order of 25 cm/sec. Similar reentrant pathways were found in the two isolated hearts. Extracellular and intracellular recordings were made from 20 endocardial preparations that were excised from areas in which tachycardia originated. Preparations were superfused in a tissue bath. These experiments showed that action potentials were usually close to normal, but occasionally action potentials with reduced amplitude and slow upstrokes were found. In addition, there were cells that exhibited both fast and slow upstrokes, depending on the direction of the wavefront. Histology of seven resected preparations and the isolated hearts showed subendocardially as well as intramurally located zones of viable myocardium. Fractionation of extracellular electrograms and slow conduction were found in areas where surviving muscle fibers and strands of fibrous tissue were interwoven, and in zones where muscle fibers were oriented in parallel but isolated by strands of connective tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Glyphosate effects on Canada thistle (Cirsium arvense) roots, root buds, and shoots

SummaryGlyphosate† was sprayed at 0009–1·12 kg a.i. ha−1 on the foliage of large potted glasshouse‐grown Canada thistle [Cirsium arvense (L.) Scop.], which had extensive, well‐developed roots. Increasing the glyphosate rate progressively reduced the total number of visible adventitious root buds plus emerged secondary shoots per plant proportionately more than root biomass, 10 days after treatment. Cortical tissue of thickened propagative roots became soft, water‐soaked, darkened, and some regions decomposed, exposing strands of vascular tissue. Lateral roots completely decomposed. When thickened roots were segmented to stimulate secondary shoot emergence from root buds 10 days after foliar treatment, Fewer secondary shoots emerged than expected from the number of visible adventitious root buds present on both control and herbicide‐treated plants. Increasing the rate of glyphosate also reduced the regrowth potential of root buds proportionately more than root biomass. Regrowth potential was measured as the number of emerged secondary shoots 35 days after segmenting unearthed roots from plants that had been sprayed 10 days earlier. When foliar‐applied at 0·28 kg ha−1, glyphosate decreased the regrowth potential of root buds to zero in 2 and 3 days, as measured by secondary shoot dry weight and number, respectively, even though root fresh weight was unchanged 3 days after foliar treatment. These dose‐response and time‐course experiments demonstrate that glyphosate did not reduce root biomass as much as it decreased root bud numbers and secondary shoot regrowth potential from root buds.

Source of Increased Serum Beta-Hexosaminidase in Rat Liver Cirrhosis

Lysosomal enzymes were studied by histo- and biochemical methods in cirrhotic rat livers in order to explain the serum increase of lysosomal enzymes in cirrhosis. Biochemically, the most evident increase was found in isolated hepatocytes. Histochemically, the lysosomal enzymes were increased mainly in rows of macrophages and necrotic or atrophic hepatocytes adjacent to strands of connective tissue at the periphery of the cirrhotic nodules. The results were compared to similar studies in cholestatic rats. It is concluded that most of the increased serum activities of the lysosomal enzymes derive from the hepatocytes.