Biomedical subjects

M Grim

Publications and source records attributed to M Grim.

At least 37 records · Page 2Linked to original sources

PubMed1995

Blood vessel formation in the avian limb bud involves angioblastic and angiotrophic growth.

The vasculature of the avian limb bud takes its origin from the intersomitic vessels as can be shown by ink perfusion of the embryo. While the primitive vessels form a central network in the early limb bud, an area of about 100 microns in width from the ectoderm inward remains free from lumenized vessels. However, this subectodermal avascular zone contains isolated angioblasts, which can be demonstrated by confocal laser scanning microscopy in connection with QH-1-staining. QH-1-positive cells from the avascular zone are capable of giving rise to endothelial cells when grafted ectopically into a "permissive" environment such as the dorso-lateral paraxial mesoderm. Several grafting sites are compared regarding their permissiveness for capillary formation. In order to investigate the origin of the QH-1-positive angioblasts we carried out injections of DiI-Ac-LDL, which is specifically taken up by endothelial cells and macrophages, and found the lumenized vessels and a few isolated cells in the peripheral limb mesoderm stained. In double-labelling studies combining DiI-Ac-LDL and QH-1, it can be shown that there exists a pool of isolated angioblasts that are only QH-1-positive, but have not incorporated DiI-Ac-LDL. In contrast to the lumenized vessels in the core of the limb bud, we found that angioblasts in the avascular zone do not proliferate, as shown by proliferation studies applying the BrdU-method to semithin sections in connection with QH-1-labelled parallel sections. We conclude that the vascularization of the avian limb bud is achieved by a combination of angiotrophic growth (sprouting of vessels) and angioblastic growth (recruitment of angioblasts from the limb mesoderm.

Animals↗

PubMed1994

Early skeletal muscle development proceeds normally in parthenogenetic mouse embryos.

In mouse chimeras with parthenogenetic cell contribution, the skeletal musculature appears to be largely devoid of parthenogenetically derived cells. To analyze the appearance and early distribution of myotomal cells in parthenotes, we determined the expression of the muscle-specific transcription factors myogenin, MYF-5, and MYF-6 by in situ hybridization in somites of Day 10 and 11 embryos. Here, we report that these myogenic regulatory proteins are expressed in parthenogenetic animals together with desmin, one of the early muscle-specific structural proteins. We also show that parthenogenetic cells contribute equally to dermatome, sclerotome, and myotome in Day 10 and 11 chimeras. These results suggest that early myotomal cells expressing the myogenic control proteins develop and allocate normally in parthenogenetic embryos and in parthenogenetic<==>normal chimeras. The underrepresentation in older chimeras may therefore be due to selective elimination. These data also argue against imprinting of the myogenic factor genes myogenin, Myf-5, and Myf-6.

Animals↗

PubMed1994

Emergence of myogenic and endothelial cell lineages in avian embryos.

The roles of cell cycles and of cell-cell interactions in the emergence of myogenic and endothelial cell lineages were studied in avian embryos using the quail-chicken marker system. Quail embryos were treated with drugs preventing either DNA replication or the movement of cells. Portions of drug-treated or untreated quail blastoderms were grafted into chicken wing buds. After an incubation for an additional 4 to 10 days, the embryos were analyzed for the presence of quail muscle or quail endothelial cells by the Feulgen reaction and by immunostaining. Both cell lineages differ in the time of their commitment as well as in the conditions necessary for their emergence. Muscle cells did not differentiate from unincubated blastoderms nor did they develop from drug-treated blastoderms. These results corroborate that the commitment of myogenic cells occurs during gastrulation and indicate that this commitment requires both DNA replication and cellular movements allowing cell-cell and/or cell-matrix interactions. Endothelial cells, on the contrary, developed both from drug-treated and from unincubated blastoderms, indicating that their commitment occurs before and independent of gastrulation and does not require DNA replication during gastrulation.

Adenosine↗

PubMed1994

Principles of ontogenesis of leg and foot in man.

Human leg and foot anlagen of different developmental stages were studied by means of light and scanning electron microscopy. The findings were compared with principles of human arm and hand development and results obtained experimentally from chicken limbs. The limbs studied have in common the shaping, cell differentiation, and spatial arrangement of different cells as basic processes of development. On the other hand, upper and lower limbs are very different in human and avian embryos with regard to their position, form, and function. We found that the different positions in relation to the dorsal and ventral surfaces and maintenance of the apical ectodermal ridge (AER) are important factors leading to the different orientations and forms of limbs. The unequal length of the fingers and toes might also be explained in this way. Differences in the position of the most distal muscles in the hand and foot could be a consequence of the cranio-caudal sequence of development. The factors controlling the developmental differences between arm and leg are discussed.

Animals↗

PubMed1993

Sensory nerve endings in the beak skin of Japanese quail.

This study is concerned with the distribution and ultrastructure of sensory nerve endings in the beak skin of adult Japanese quail (Coturnix coturnix japonica). The following nerve endings were found: free nerve endings, clusters of dermal Merkel nerve endings, Herbst corpuscles and Ruffini corpuscles. The latter were found only in the dermis of the tip of the upper beak. The remaining endings were present in the skin of all areas of upper and lower beak. Free nerve endings were supplied by either thin myelinated axons or unmyelinated C-fibers and were localized in the dermis close to the basal layer of the epidermis. Merkel cells formed clusters (up to 50) localized below and between the epidermal cones of the beak skin. Disc-shaped thickenings of nerve endings were squeezed between individual Merkel cells. Small Herbst corpuscles were found in the dermis close to the epidermal cones of the beak skin. Large Herbst corpuscles occurred in deep layers of the dermis. The Ruffini corpuscles were cylindrical in shape (80 microns x 400 microns) and arranged in groups of up to ten corpuscles. Each corpuscle was surrounded by an incomplete fibrous capsule.

Animals↗

PubMed1993

The Splotch mutation interferes with muscle development in the limbs.

Homozygosity for the Splotch mutation causes neural tube and neural crest defects in mice. It has been demonstrated that Splotch mutant mice carry mutations in the homeodomain of the Pax-3 gene. Pax-3 is expressed in the neural tube, some neural crest derivatives, the mesenchyme of the limb bud and the somites. We have examined the development of the somite-derived skeletal muscles in homozygotes carrying the Splotch (Sp1H) mutation. Our results suggest that the Splotch mutation affects the development of skeletal muscles in a region-specific way: 1. The expression of the CMZ transgene in homozygotes reveals a disorganisation of the dermomyotome in whole stained embryos. 2. The axial musculature is reduced in size along a rostro-caudal gradient. 3. The muscle anlagen in the limbs develop much more slowly. Muscles of the head and the ventral body wall are normally developed in the mutant on day 13.5 of gestation. Recently, it has been shown that the myogenic precursors of the limbs are derived from the lateral half of the somite. The specific disturbance of muscle development in the limbs of Splotch mutants thus suggests a role for Pax-3 in the organisation of the somite, the production of trophic factors in the limb mesenchyme or an alteration of myogenic and mesenchymal cells.

Animals↗

PubMed1993

Differences in the fibronectin-dependence of migrating cell populations.

In avian embryos, the migration behaviour of several cell populations, melanoblasts, Schwann cells, myogenic cells and axons after application of antibodies directed against the cell-attachment fragment of fibronectin (alpha-CAF) was investigated. The migration of the different cell types was influenced in different ways. 1. Epidermal melanoblasts did not colonize areas into which the antibody had been injected, i.e. distal to the grafting site. They frequently spread proximally to the back and neck, sometimes even as far as to the ipsilateral leg. When grafted to the dorsal side of the wing bud, melanoblasts never spread to the ventral side after injection of the antibody. Non-epidermal melanoblasts continued to migrate distally. 2. Grafted Schwann cells and host axons were not noticeably affected by the antibody injections. Both were found proximally and far distally to the grafting site, i.e. also within the injected area. 3. Myogenic cells were immobilized near the grafting site, where they differentiated biochemically, but sometimes only partially underwent fusion into myotubes. They participated in the formation of host muscle blastemas only immediately adjacent to the non-migratory cell population of the graft such as fibroblasts and cartilage. 4. The injected antibody could be localized up to 5 h after the application in the distal third of the limb bud. We conclude that migrating cell populations show differences in their fibronectin-dependence which probably reflect their use of fibronectin during migration.

Animals↗

PubMed1993

Neural crest cell migration into the limb bud of avian embryos.

The colonization of limb buds by neural crest cells was studied in quail-chick chimeras and in chick embryos using HNK-1 and DiI staining and the LD-DOPA reaction. Two populations of neural crest cells were found to colonize the limb bud. They migrate successively and use different routes of migration. The first population migrates within the limb bud subectodermally at stages before the limb is innervated. In the wing bud the migration route is localized postaxially and in the leg bud preaxially. Two cell types were identified differentiating from this first population: melanoblasts and Merkel cells. The second population of crest cells invades the limb bud at a later stage. These cells follow the routes of ingrowing nerves and migrate along a dorsal and a ventral path which correspond to the position of nerves for extensor and flexor muscles. Crest cells were found here also in the absence of nerves. Schwann cells and terminal glial cells develop from this second population of neural crest cells.

Animals↗

PubMed1993

Anatomical interrelation between the phrenic nerve and the internal mammary artery as seen by the surgeon.

Paresis of the diaphragm (especially left-side paresis) is a relatively frequent finding following cardiac surgery. While, usually, it is a rather benign condition, in exceptional cases it may lead to severe impairment to death of the patient. The supposed causes of damage to the phrenic nerve include: local myocardial cooling by ice slush; opening of the pleural cavity in connection with local cooling; cross clamp length; total hypothermia; central venous cannulation; traction-related damage; mammary artery harvesting. Perhaps the commonest cause of damage to the phrenic nerve, i.e., the effect of local myocardial cooling by ice slush, and the mode of phrenic nerve protection have been studied in considerable detail. The authors focused their attention on the interrelation between the phrenic nerve and the proximal segment of the mammary artery. Using anatomical preparations, the authors demonstrate the very intimate relationship of the above entities. The interrelation of the two anatomical structures basically differs depending on whether the left or right side is concerned. 1) On the left: The phrenic nerve, on entering the thorax, runs between the subclavian artery and vein laterally from the mammary artery crossing it medially; it parts the latter and continues in mediastinal adipose tissue to run on the pericardium toward the diaphragm. 2) On the right: The phrenic nerve passes between the subclavian vein and artery medially from the mammary artery. For another 3-4 cm, it runs along the medial and dorsal edges of the mammary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Surgical Procedures↗

PubMed1992

Local signalling in dermomyotomal cell type specification.

The development and differentiation of the avian myotome was studied after removal of the neural tube, including neural crest, and after replacement of dorsal half-somites by ventral half-somites. Results show that in the absence of neural tissue myoblast differentiation within the somites does not take place. Ventral half-somites are able to undergo muscle differentiation if they were grafted in place of dorsal half somites. It is suggested that local signals must be responsible for the dorsalisation of the newly formed somite including myoblast differentiation. Neural crest cells are discussed as possible sources of these signals.

Animals↗

PubMed1992

Schwann cells are not required for guidance of motor nerves in the hindlimb in Splotch mutant mouse embryos.

The topogenesis of the hindlimb nerves of Splotch homozygous mutant mouse embryos was studied using light and electron microscopy. Homozygous mutants show multiple defects of neural crest-derived tissues. The defects increase along a rostro-caudal gradient. The cervical and upper thoracic segments have small spinal ganglia, and Schwann cells are associated with the spinal nerves. In the lumbo-sacral region neurulation is not complete, and the derivatives of the neural crest are missing. The lumbo-sacral nerve trunks are formed by ventral roots only. They are occasionally associated with presumptive glial cells that have migrated from the spinal cord for a short distance. Beyond the vertebral primordia, the spinal nerves are not accompanied by Schwann cells. No compartmentalization of the axons within the lumbo-sacral nerves was visible, whereas Schwann cells did segment the nerve into the fascicles in brachial nerves. The lumbo-sacral plexus develops, and its branches grow into the hindlimb despite the absence of Schwann cells. On day 13.5 of gestation, the lumbo-sacral nerve trunks extend well into the distal calf. They are topographically correctly positioned. Their branches enter the muscle primordia and form contacts with their mesenchymal cells though the cutaneous branches are missing. Generally, the outgrowth of lumbo-sacral nerves is slower than in phenotypically normal littermates, whose nerves reach the foot plate at corresponding stages of development. These results demonstrate that the lumbo-sacral plexus and the topographically correct position of lumbo-sacral nerve trunks develop despite the absence of Schwann cells. Therefore Schwann cells are not necessary for the outgrowth and guidance of axons within the limb.

Animals↗

PubMed1992

Effect of a novel series of macrocyclic hypolipidemic agents on plasma lipid and lipoprotein levels of four non-primate species.

The ansamycins are structurally novel hypolipidemic agents derived from rifampicin, but lacking antibacterial activity. Oral or intravenous administration resulted in rapid lowering of plasma cholesterol in rats, hamsters, guinea pigs and dogs. In the chow-fed rat, three related compounds (CGP 43371, CGS 23810 and CGS 24565) exhibited ED50 values of 13.7, 3.1 and 0.18 mg/kg, respectively. A feature common to the lipid lowering documented in these four species was the concomitant reduction of low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol. In the chow-fed rat, however, apolipoprotein AI (apo AI) levels were much less affected than were those of HDL cholesterol. CGP 43371 at 3 and 10 mg/kg, lowered HDL cholesterol by 20% and 39%, respectively, whereas plasma apo AI was reduced by only 1% and 12%. Similarly, in lipoprotein fractions separated by ultracentrifugation, apo AI was unchanged in the d = 1.019-1.21 g/ml fraction after treatment with 3 or 10 mg/kg of CGP 43371, but HDL cholesterol was reduced 12% and 26% in this fraction at the two dose levels. Plasma and lipoprotein apo B levels, on the other hand, were reduced to a level equivalent to that of the reduction in cholesterol. The ansamycins thus represent a new structural series which may possess a novel mechanism of action as well, involving differential effects on HDL cholesterol and protein.

Animals↗

PubMed1992

Processing the telephone speech signal for the hearing impaired.

Speech intelligibility scores from 16 subjects with sensorineural hearing loss were evaluated using a digitized version of the California Consonant Test that was presented via headphones through a 300 to 3000 Hz bandpass filter to simulate the telephone band. Each subject was tested with an unprocessed signal that was frequency-equalized to compensate for the individual's hearing loss, and a signal that was equalized and compressed by the use of a compressor compression technique. Subjects were tested at three sound pressure levels above a pure-tone average threshold for frequencies 1 and 2 kHz. Two digital signal processing techniques designed to compensate for high-frequency hearing loss were examined: frequency domain processing and time domain processing. Frequency domain involved modification of the short-term spectrum obtained through a fast Fourier transform, whereas time domain processing involved passing the signal through a bank of finite impulse response filters. Both techniques showed significant intelligibility improvements (15-30%). In a second experiment, 16 additional subjects with high-frequency hearing loss compared an amplified telephone signal to three processed signals: (1) 6 dB per octave emphasis; (2) a signal frequency equalized for their hearing loss; and (3) a signal that was equalized for their hearing loss and was compressed according to their uncomfortable loudness levels. Most subjects preferred the signal with the 6 dB per octave emphasis.

Adult↗

PubMed1991

Muscle morphogenesis in the absence of myogenic cells.

Experimental evidence indicates, that the myogenic cells themselves are not responsible for the muscle pattern formation. We report on a chance observation that reveals that muscle pattern formation can occur even in the absence of myogenic cells. Epiblastic cells from a quail embryo in the primitive streak stage were implanted into the wing bud of a chick embryo. The grafted quail cells developed into mononucleate, fibroblast-like cells that formed the muscle belly of the extensor medius longus muscle. This showed essentially normal form and topography as revealed by computer-aided 3D-reconstruction. This finding shows, that the formation of muscles does not depend on the presence of myogenic cells.

Animals↗

PubMed1991

Differentiation of endothelial cells in avian embryos does not depend on gastrulation.

Unincubated quail eggs were treated with Cytochalasin B. By this means, gastrulation of the blastodiscs was inhibited. Fragments of these blastodiscs were grafted into wings buds of chick embryos, and the differentiation fate of graft-derived cells was studied. Results show that only endothelial cells differentiate from the grafts. They were even found outside the graft site in vessels made up of a chimeric endothelium. It can be concluded that determination, differentiation and migration of endothelial cells does not depend on gastrulation.

Animals↗

PubMed1990

Origin of spinal cord meninges, sheaths of peripheral nerves, and cutaneous receptors including Merkel cells. An experimental and ultrastructural study with avian chimeras.

The origin of cells covering the nervous system and the cutaneous receptors was studied using the quail-chick marking technique and light and electron microscopy. In the first experimental series the brachial neural tube of the quail was grafted in place of a corresponding neural tube segment of the chick embryo at HH-stages 10 to 14. In the second series the leg bud of quail embryos at HH-stages 18-20 was grafted in place of the leg bud of the chick embryos of the same stages and vice versa. It was found that all meningeal layers of the spinal cord, the perineurium and the endoneurium of peripheral nerves, as well as the capsular and inner space cells of Herbst sensory corpuscles, develop from the local mesenchymal cells. Schwann cells and cells of the inner core of sensory corpuscles are of neural crest origin. The precursors of Merkel cells migrate similarly to the Schwann cells into the limb bud where they later differentiate. This means that in addition to the Schwann cells and the melanocytes a further neural crest-derived subpopulation of cells enters the limb.

Animals↗

PubMed1990

Localization of dipeptidylpeptidase IV and alkaline phosphatase in developing spinal cord meninges and peripheral nerve coverings of the rat.

Localization of dipeptidylpeptidase IV was studied in the spinal cord meninges and peripheral nerve coverings of fetal and postnatal rats. In the same sections, the localization of alkaline phosphatase was monitored. In the prenatal period, dipeptidylpeptidase (DPP) IV activity in the differentiating meninges appeared at the time of cerebrospinal fluid spaces formation (on day 16 in the cervical region and on day 18 in the lumbar region). In adult animals DPP IV was found in cells of those meningeal lamellae which delineated the cerebrospinal fluid spaces (the outer, intermediate and inner lamellae), in the perineurium, in Schwann cells and in some fibroblasts of the bulk of dura mater. It is suggested that DPP IV plays a role in the metabolism of neuropeptides by their interaction with cerebrospinal fluid. Alkaline phosphatase activity was detectable earlier than DPP IV activity. Positivity was first observed in some cells of the meninx primitiva and, later on, in the ectomeninx and also in the differentiating endomeninx where it disappeared postnatally. The developing ectomeninx exhibited activities of both enzymes. Alkaline phosphatase occupied its external layers, while DPP IV was localized in its inner layers. This enzymatic heterogeneity of the ectomeningeal layers suggests that the ectomeninx gives rise not only to dura mater (which in adult animals exhibits alkaline phosphatase activity) but also to the outer arachnoid layer (positive for DPP IV in adult rats).

Aging↗

PubMed1990

Alkaline phosphatase and dipeptidylpeptidase IV staining of tissue components of skeletal muscle: a comparative study.

A combined alkaline phosphatase (AP) and dipeptidlypeptidase IV (DPP IV) staining reaction has demonstrated enzymatic heterogeneity of the arterial and venous segments of capillaries in rat skeletal muscle. This study compared the staining reactions of skeletal muscles in many commonly used laboratory animals, including the axolotl, chick, quail, Monodelphys, rat, mouse, hamster, guinea pig, rabbit, dog, monkey, and human. DPP IV activity was found in the venous ends of the capillaries and in the endothelium of some larger veins in many of the species but was never demonstrated in the arterial side of the circulation. AP was found in the arterial ends of capillaries in all species except the axolotl, and it was also found in the endothelium of larger arteries of most species. AP activity was absent in venous endothelium of all species except for birds and Monodelphys. DPP IV activity was found in the perineurium of intramuscular nerves of most species, and AP activity was commonly seen in tendons and intramuscular connective tissue. The interspecies variability found in this study shows that care must be taken in comparing experimental data involving this technique from one species to another, but within a species the technique allows a fine level of discrimination between functionally distinct compounds of skeletal muscle tissue.

Alkaline Phosphatase↗