bluuebunny/crossref_metadata_2025 huggingface dataset:
Restricted expression of Mov13 mutant α1(I) collagen gene in osteoblasts and its consequences for bone development
Authors: Kratochwil Klaus , Ghaffari‐Tabrizi Nassim , Holzinger Ilse , Harbers Klaus
Published: February 2005

Cell type‐specific differences in the transcriptional control of the mouse gene coding for theα1 chain of collagen type I (Col1a1) have been revealed previously with the help of the Mov13 mouse strain which carries a retroviral insert in the first intron of the gene. Transcription of this mutant Col1a1 allele is completely blocked in all mesodermal cell types tested so far, with the exception of the odontoblast where it is expressed at an apparently normal rate (Kratochwil et al.[1989] Cell 57:807–816). To define the tissue specificity of the mutant allele more precisely, we have now studied its expression in osteoblasts, another skeletogenic cell type which, like odontoblasts, produces high amounts of collagen I. Evidence for transcription of the Mov13 allele was obtained by in situ hybridization in homozygous (M/M) and heterozygous (M/+) bone tissue, in grafts as well as in vivo. The presence of mouse collagen I and the development of bone tissue were demonstrated in M/M skeletal elements grown on the chick chorioallantoic membrane (CAM). Further support for expression of the mutant gene was obtained from two 16 day M/M fetuses in vivo. Bone tissue of diverse embryological origin (vertebrae and ribs of somitic origin, long bones derived from lateral plate, calvariae from head paraxial mesoderm, and mandibulae from head neural crest) expresses the mutant allele. However, in situ hybridization experiments indicate that only a subpopulation of osteoblasts is capable of transcribing it at a high rate, resulting in severe impairment of bone development in grafts and in vivo. Therefore, osteoblasts, in comparison to odontoblasts and fibroblast‐like cells, assume an intermediate position with respect to transcription of the Mov13 allele. We suggest that this diversity in the utilization of the mutant collagen gene reflects cell type‐specific differences in the transcriptional regulation of the wild type (wt) Col1a1 gene. © 1993 Wiley‐Liss, Inc.
Developmental regulation of Islet‐1 mRNA expression during neuronal differentiation in embryonic zebrafish
Authors: Inoue Akihiro , Takahashi Mika , Hatta Kohei , Hotta Yoshiki , Okamoto Hitoshi
Published: February 2005

Islet‐1 (Isl‐1) is a LIM domain/homeodomain‐type transcription regulator that has been originally identified as an insulin gene enhancer binding protein. Isl‐1 is also expressed by subsets of neurons in the central nervous system of rat and chick embryos. We have cloned the Isl‐1 cDNA from zebrafish and examined its expression pattern using in situ hybridization to whole‐mount embryos. Isl‐1 mRNA first appears immediately after gastrulation in the polster, the cranial ganglia, and in Rohon‐Beard neurons and ventromedial cells of the spinal cord. The expression by the ventromedial cells is segmentally repeated and becomes restricted to the one or two cells slightly anterior to the segment borders. Double staining by in situ hybridization and an antibody which stains most axons suggested that these segmentally distributed cells may be either the rostral primary motoneuron (RoP) or middle primary motoneuron (MiP). This raises a possibility that Isl‐1 may be involved during determination of subtype identities of the primary motoneurons. Furthermore, the specific Isl‐1 mRNA expression in the spinal cord is under the control of the somites, since mutant embryo with defective somite failed to maintain this pattern. © 1994 Wiley‐Liss, Inc.
Immunolocalization of S‐crystallins in the developing squid (Loligo opalescens) lens
Authors: West Judith A. , Sivak Jacob G. , Pasternak Jack , Piatigorsky Joram
Published: February 2005

S‐crystallins are the predominant soluble proteins of the squid lens. Of these, S‐III crystallin is the major component and S‐I and S‐II crystallin are the minor lens components. The lens has a posterior and anterior segment, each derived from separate groups of ectodermal cells referred to as lentigenic cells. In the present study, the appearance of S‐crystallins during the development of the lens of Loligo opalescens was followed by immuno‐cytochemistry. S‐crystallins of the lens and lentigenic cells were first observed at day 17 (Arnold stage 27) of embryogenesis. S‐crystallins were not confined to a single region, but were present in the middle group (group 2) of lentigenic cells, the posterior lens primordium, and the processes connecting the lentigenic cells and the posterior lens primordium. Two days later (Arnold stage 28), the S‐crystallins were also observed in the anterior group (group 1) of lentigenic cells, the anterior lens primordium, and the processes connecting the cells with the anterior lens primordium. Thus, during development, S‐crystallins accumulate first in the posterior lens primordium and subsequently in the anterior lens primordium and their respective lentigenic cells and connecting lentigenic processes. Incubated sections of the adult lens and lentigenic cells also show specific immuno‐peroxidase staining when compared with controls. This evidence in combination with a recent investigation (West [1993] Ph.D. dissertation), which indicates that the cephalopod lens continues to grow throughout adulthood, suggests that squid lens crystallins are synthesized during adulthood. © 1994 Wiley‐Liss, Inc.
Genetics of nanos localization in Drosophila
Authors: Wang Charlotte , Dickinson Laura K. , Lehmann Ruth
Published: February 2005

The Drosophila gene nanos is required for two processes. During oogenesis, nanos function is required for the continued production of egg chambers, and nanos is expressed in the early germarium. During embryogenesis, nanos is required maternally to specify abdominal segmentation. Nanos shares this latter function with nine other genes, collectively known as the posterior group. Of this group, nanos encodes a determinant, and is localized as an RNA to the posterior pole of early embryos. This RNA is translated to form a gradient of nanos protein with highest concentrations at the posterior. Analysis of the distribution of nanos gene products in embryos mutant for posterior group genes shows that eight of these genes are required for localization, but not stability, of the nanos RNA. Embryos mutant for posterior group alleles which produce weak abdominal phenotypes show reduced amounts of localized nanos RNA. This correlation between nanos RNA localization and abdominal phenotype suggests that nanos acts as a localization‐dependent posterior determinant. Localization of nanos is not affected by mutations in bicoid or torso, confirming that the three maternal systems of anterior‐posterior determination initially act independently. © 1994 Wiley‐Liss, Inc.
Dynamic expression patterns of tenascin, proteoglycans, and cell adhesion molecules during human hair follicle morphogenesis
Authors: Kaplan Elizabeth D. , Holbrook Karen A.
Published: February 2005

The development of skin appendages such as hair, feathers, and teeth is brought about by reciprocal interactions between epidermal and mesenchymal tissues and is thought to be influenced in part by cell adhesion molecules and components of the extracellular matrix. The developmental distributions of tenascin, neural cell adhesion molecule (NCAM), E‐cadherin, intercellular adhesion molecule 1 (ICAM‐1), chondroitin sulfate proteoglycan (CSPG), and the heparan sulfate proteoglycan perlecan were studied in relation to hair follicle morphogenesis in fetal human skin. Tenascin first appeared in developing skin in focal concentrations at the epidermal‐mesenchymal interface, just prior to, and presumably correlated with, hair follicle initiation. Tenascin immunostaining remained prominent in the basement membrane zone and extracellular matrix of the follicle sheath during subsequent morphogenetic stages. Two forms of tenascin (Mr 250 × 103 and 280–300 × 103), were revealed by Western blots of skin extracts. NCAM immunolabeling was initially present throughout the dermis, and became progressively restricted to the dermal condensation and the follicle sheath. Western blot analysis revealed an isoform of NCAM (Mr 160 × 103) which lacked polysialic acid. At all stages, E‐cadherin staining was diminished on follicle cells situated adjacent to the basement membrane, relative to cells in the follicle interior. Follicle‐specific immunostaining for ICAM‐1 was transient, appearing only at the pre‐germ and hair germ stages of development. Antibodies to three distinct CSPG determinants revealed unique immunolabeling patterns following follicle initiation: One CSPG epitope co‐distributed with tenascin in the follicle basement membrane and follicle sheath extracellular matrix; one CSPG epitope was similarly expressed, and was also found on follicle epithelial cells; and the third CSPG determinant was noticeably absent from the follicle sheath during elongation of the developing appendage. Perlecan was concentrated in the dermal papilla, in addition to its distribution in all skin basement membranes. A model for how these diverse molecules may inter/act to influence human hair follicle morphogenesis is presented. © 1994 Wiley‐Liss, Inc.
Pattern duplication by retinoic acid treatment in the regenerating limbs of Korean salamander larvae, Hynobius leechii, correlates well with the extent of dedifferentiation
Authors: Ju Bong‐Gun , Kim Won‐Sun
Published: February 2005

In the regenerating limbs of Korean salamanders, Hynobius leechii, retinoic acid (RA) induces duplication of skeletal structures in the proximodistal (PD) axis and often in the transverse axes. In the present study, the stage‐dependent effects of RA for the duplication of limb skeletal structures at two amputation levels, the distal stylopodium and the distal zeugopodium, were studied using larval limbs of Korean salamanders. The results showed that the mean level of proximalization (MLP) by RA treatment increased during the stages of dedifferentiation and early bud formation while the MLP declined thereafter in both amputation levels. The decline of the MLP at the later stages of regeneration was due to the high frequency of hypomorphic regeneration or blocked regeneration. When the effects of RA treatment at two amputation levels were compared, the overall trends were similar but the actual timing was delayed for 2–4 days in the proximal level of amputation. Furthermore, the peak level of proximalization was achieved earlier and the peak level remained longer in the distal stylopodial level of amputation compared to the distal zeugopodial level of amputation. Since the histological observations revealed that the dediferentiation period was also extended up to 2–4 days in the proximal level of amputation, the acid phosphatase activity during the course of regeneration was measured to look for a quantitative relationship between the enzyme activity and the states of dedifferentiation. The results show that the level and the duration of acid phosphatase activity in the upper arm regenerates are both higher and longer than those in the lower arm regenerates. Furthermore, RA treatment caused an increase in acid phosphatase activity. Thus our results suggest that the state of dedifferentiation might be closely linked to the extent of proximalization of regenerating limbs by RA treatment. © 1994 Wiley‐Liss, Inc.
Analysis of the in vivo myogenic status of chick somites by desmin expression in vitro
Authors: Borman William H. , Urlakis Kenneth J. , Yorde Donald E.
Published: February 2005

Expression of the muscle specific intermediate filament protein, desmin, is an early marker for chick somitic myogenesis. Somites are transient, paired, mesodermal structures adjacent to the neural tube which are formed very uniformly in a cranial to caudal fashion. The developmental somitic expression of desmin in vivo has been reported previously (Holtzer et al. [1991] “Frontiers in Muscle Research.” New York: Elsevier Science, pp 187–207; Borman and Yorde [1994] J. Histochem. Cytochem. 42:265–272). Here we explore the ability of those somitic cells which are desmin negative in vivo to successfully carry out a myogenic program of development in the absence of the surrounding embryonic microenvironment. Somites which are known to be overtly desmin negative in the embryo were explanted and cultured on collagen gels for 4 days. Immuno‐detection of desmin identified a population of somites that could support desmin positive cells in vitro as well as a population of somites that could not. The cranially located somites must remain in the embryo for a greater length of time than the caudally positioned somites prior to each being able to express desmin in vitro. In embryos of many ages there is also a population of somites unable to support desmin expression in vitro. The rate at which this ability to support somitic desmin expression in vitro progresses caudally in the embryo is significantly greater than the rate at which somites form. Notably, the detected expression of desmin in somites in vitro is parallel to the rate at which overt expression of desmin in vivo is detected. The implication for these observations with regard to the regulation of somitic myogenesis is discussed. © 1994 Wiley‐Liss, Inc.
Expression pattern of M‐cadherin in normal, denervated, and regenerating mouse muscles
Authors: Irintchev A. , Zeschnigk M. , Starzinski‐Powitz A. , Wernig A.
Published: February 2005

Following muscle damage in adult vertebrates, myofibers can be regenerated from muscle precursor cells (satellite cells). During this process, prenatal myogenesis is recapitulated to a large extent, both morphologically and molecularly. A putative morphoregulatory molecule involved in myogenesis is M‐cadherin (Mcad), a calcium‐dependent cell adhesion protein. The expression of Mcad was studied by immunofluorescence in regenerating, denervated, and normal mouse muscles. Our results demonstrate that Mcad is present in satellite cells in normal muscle. Enhanced staining at sites of contact between satellite cells and the parent muscle fiber suggests an additional, spatially restricted expression of Mcad in muscle fibers. Mcad positive cells in normal and denervated muscles did not incorporate bromodeoxyuridine within 24 hr after injection in vivo, indicating that Mcad is expressed on mitotically quiescent satellite cells. Neural cell adhesion molecule (NCAM) co‐localized with Mcad in nearly all satellite cells in denervated muscles but rarely in intact muscles. At early stages of regeneration, Mcad was exclusively and strongly expressed in myoblasts. After fusion of myoblasts into myotubes, Mcad was down‐regulated and was barely detectable on more mature myotubes surrounded by distinct basal lamina sheaths. These observations are in line with the idea that Mcad plays a crucial role in myogenesis. In intact muscle, Mcad might function as a molecular link between satellite cell and muscle fiber. © 1994 Wiley‐Liss, Inc.
Transient expression of type II collagen and tissue mobilization during development of the scleral ossicle, a membranous bone, in the chick embryo
Authors: Watanabe Kazuo , Bruder Scott P. , Caplan Arnold I.
Published: February 2005

Development of the chick scleral ossicle was studied with respect to expression of various collagen types, cartilage matrix molecules, and osteoblastic cell surface antigens. The extra‐cellular matrix of the scleral ossicle primordium of stage 35.5 chick sclera and the mesenchyme beneath the conjunctival epithelium was immunoreactive with anti‐type II collagen antibody, giving the impression that certain materials and/or cell clusters surrounded by reactive matrix were descending from the epithelial‐mesenchymal interface to the scleral ossicle primordium. In stage 37 embryos, type II collagen immunoreactivity was restricted to the bone matrix of the scleral ossicles, and persisted through stage 39. However, at stage 41, virtually no type II collagen was detected. In contrast, strong immunostaining of type I collagen was first detected in the developing scleral ossicle at stage 37, coinciding with the formation of mineralized bone matrix. Following the extensive accumulation of type I collagen in bone matrix, type XII collagen was detected at the surface of the bone; both type I and type XII collagen immunostainings then remained. By stage 37, immunoreactivity with a pre‐osteoblastic cell surface marker was detected on cells of the scleral ossicle, and typical osteocytes were subsequently identified by both morphological and specific immunostaining techniques. Antibodies other than for type II collagen, specific to chondrogenic mesenchyme or cartilage matrix, never reacted with the scleral ossicle and its primordium during development. Taken together, these observations indicate that the scleral ossicle is a membranous bone, whose development may not require overt chondrogenesis. Implications of type II collagen distribution during the positioning of scleral ossicles and their early bone matrix formation are discussed with respect to the origin and evolution of endoskeletons in vertebrate animals. © 1994 Wiley‐Liss, Inc.
Qualitative cytochemical localization of pyrimidine deoxyribonucleotide residues in fixed tissue sections
Authors: Smith Stuart W. , Anderson Paul N.
Published: February 2005

The senior author had the good fortune to begin his medical education at Western Reserve University during Dr. Hoerr's second year as Payne Professor of Anatomy. Dr. Hoerr's warm friendliness and his broad interests and competence in, and enthusiasm for the growing field of cellular biology served as a source of inspiration. It is an honor to dedicate a new finding in cytochemistry, a field central in his interests, to the memory of Dr. Hoerr.
Survival of higher animal cells after the formation and dissolution of intracellular ice
Authors: Sherman J. K.
Published: February 2005

Presence of ice within cells usually is assumed to assure death, while larger ice formations are assumed to induce greater injury. Evidence is presented which questions these assumptions.

MCSA and no. 440 parakeet tumors and C3H mouse skin were studied. Cell structure before freezing (control), while frozen, and after rewarming was correlated with survival on transplantation. Control and rewarmed tissue was fixed in Bouin's fluid and processed routinely. Microscopic sites and appearance of ice artifacts relative to frozen cells were preserved by the author's modified freeze‐drying technique. Tissues were cooled to −75°C and −150°C at rates of from 1°C/min to 40°C/sec and rewarmed at 180°C/min. Tumor transplants were inoculated in and around the pectoralis major muscle of parakeets and followed as to appearance, size and microscopic structure. Using hair color as a marker, ventral to dorsal autografts of 8 mm full thickness circles of skin were made in 4–5 week old female mice.

Data showed that (1) nucleus and cytoplasm were sites of ice formation in cooled cells, (2) little or no structural damage occurred in frozen‐thawed tumors while skin often was altered noticeably, (3) % survival of tumors frozen slowly (1°C/min) was equal to that of controls, (4) 17% of frozen‐thawed skin grafts survived, (5) freezethaw survival was greatest following the formation of the largest ice artifacts which were induced during slow freezing, (6) intracellular ice and structural alteration, therefore, need not be incompatible with survival.
Passage of thyroid hormone across the placenta in intact and hypophysectomized rats
Authors: Hamburgh Max , Sobel Edna H. , Koblin Robert , Rinestone Alan
Published: February 2005

The studies were designed to determine whether thyroid hormone traverses the placenta of the rat.

1. Pregnant rats were hypophysectomized on the twelfth day of the gestation period. The histological appearance and wet weights of the fetal thyroids at term were determined and found to be the same as that of fetuses of intact mothers. These results indicate that maternal TSH is not required for maturation of the fetal thyroid.

2. Intact and hypophysectomized pregnant rats were provided with a diet supplemented with 0.2% propylthiouracil (PTU) added in powdered form starting on the fifteenth day of gestation until term. This treatment led to enlargement of thyroids of fetuses of intact and hypophysectomized mothers.

3. Groups of intact and hypophysectomized pregnant rats given the same goitrogenic treatment as group 2 were injected daily with 100, 50, 25 and 12.5 μg of 1‐thyroxin in suspension. Twenty‐five μg of thyroxin were sufficient to inhibit goiter development in fetuses of hypophysectomized rats, while 50 μg was required to prevent the goiter formation in fetuses obtained from intact non‐hypophysectomized pregnant rats.

These results suggest that maternal thyroid hormone passes the placenta from mother to fetus. The effectiveness with which thyroid hormone passes from the mother to the fetal circulation is probably influenced in some way by the maternal pituitary.
Fine structure of the goblet cell mucous secretory process
Authors: Freeman James A.
Published: February 2005

The Golgi apparatus has been recognized as the initial site of mucigen accumulation. The mucigen is seen forming within the agranular lamellar membranes and vesicles of the Golgi, enlarging and coalescing with loss of individual mucigen droplet membranes, bulging the cell into its characteristic goblet appearance, and subsequent rupturing of the microvilli plasma membrane with discharge of the mucin. The density of the well developed goblet cell is a function of nuclear and cytoplasmic compression by the mass of mucigen. The fine structure of the “resting goblet” cell is indistinguishable from that of the principal columnar absorbing cells. No morphologic evidence of mucigen formation in the endoplasmic reticulum is found, but continuity is demonstrated between the rough‐surfaced endoplasmic reticulum and agranular Golgi membranes. It is possible that the mucigen or its precursors may be synthesized in the endoplasmic reticulum then transported to the Golgi where it is concentrated into the morphologically recognizable mucigen.
Electromyographic study of the extensor apparatus of the forearm
Authors: Travill A. A.
Published: February 2005

An electromyographic study of the extensor apparatus of the forearm, using a multichannel electromyograph and bipolar needle electrodes, was carried out on 12 subjects. Recordings were obtained concurrently from medial, lateral and long heads of the triceps brachii and anconeus.

The investigation confirms that the three heads contract independently during extension of the forearm, that the medial head and the anconeus are always active, and that the lateral head and, to a lesser extent, the long head act as reinforcing auxiliaries. The anconeus was found to be active also during resisted but not free loaded pronation and supination, contrary to commonly held opinion.
Observations on the innervation of human long bones
Authors: Miller Malcolm R. , Kasahara Michiko
Published: February 2005

The innervation of some of the long bones of the extremities of the human was studied by methylene blue immersion. Small myelinated and amyelinated nerve fibers enter the numerous foramina of the epiphyseal and metaphyseal regions of long bones, traverse the thin cortex, and supply the interior of the bone. Small myelinated fibers wind about the trabeculae of the spongiosa or spread out on the undersurface of the articular cartilage. Small knob‐like terminations end in close relationship to the endosteum.

Other myelinated nerve fibers have branched free fiber endings associated with the walls of intertrabecular marrow arterioles. Amyelinated nerve fibers are usually associated with vascular walls but may also be associated with the connective tissue of the intertrabecular fat or marrow.

Numerous myelinated and amyelinated nerve fibers traverse the nutrient foramen and supply the bone marrow and endosteum of the shaft of the bone.

While the Volkmann's canals of the shaft receive nerve fibers from the overlying periosteum, the disposition of these fibers in the shaft of the bone has not been determined.

No nerve fibers or endings were ever seen between the lamellae in any location.

No function can yet be attributed to any particular type of nerve fiber or nerve ending.
The spinal arachnoid villi of the monkeys Cercopithecus aethiops sabaeus and Macaca irus
Authors: Welch Keasley , Pollay Michael
Published: February 2005

The spinal arachnoid villi have been studied in the monkey by the examination of serial sections of spinal nerve roots, particular attention being paid to the relations of the arachnoid to the dura mater and to the veins which are regularly applied to the emerging roots. Although the roots vary in their content of specialized arachnoid formations, in many, columns and clusters of arachnoidal cells occupy spaces between collagen bundles in the dura mater. In a few, leptomeningeal tissue extends completely through the dura. In approximately one of each six roots examined, arachnoidal tissue formed part of the wall of and projected into a vein associated with the root. This relationship to veins is considered an especially compelling point in dispelling the doubt which has been cast upon the conception of spinal arachnoid villi as specialized structures.
Treatment of nutritional cirrhosis in rats with choline and methionine; with special reference to fibrogenesis and fibroclasia
Authors: Meader Roland D.
Published: February 2005

Early and advanced stages of nutritional cirrhosis were produced in the livers of rats maintained on a choline‐deficient diet for periods of 60 and 150 days respectively. Both cirrhotic groups, i.e., early and advanced, were subdivided into three therapeutic groups and corresponding groups of each cirrhotic stage were treated with comparable supplements of 2% choline, 2% methionine and a combination of both for six months, in order to compare the effectiveness of these therapeutic agents in producing manifestations of progressive repair in both early and advanced stages of nutritional cirrhosis.

The efficacy of the various therapeutic regimens on both early and advanced stages of dietary cirrhosis was assessed by comparing the manifestations of progressive repair observed in serial sections of liver at autopsy, after six months of dietary therapy with those observed in serial sections of the same liver obtained by biopsy preceding therapy.

Under the conditions of this experiment, early and advanced stages of nutritional cirrhosis responded with complete and almost complete recovery respectively, following six months of dietary therapy with choline or a combination of choline and methionine. Dietary supplementation of methionine alone, failed to produce reparative changes comparable to those of choline.

This study does not support the theories of condensation of stroma and attenuation and compression by the expanding nodules of parenchymal cell regeneration for fibrogenesis and fibroclasia.
Microscopy of the response of rodent dentin to injected fluoride
Authors: Yaeger James A.
Published: February 2005

Rats were injected subcutaneously with 50 mg/kg body weight of sodium fluoride. The hypermineralized and hypomineralized components of the response in incisor dentin were identified in ground sections using contact microradiography and analyzed microscopically for matrix alterations. In demineralized sections the hypomineralized component stained weakly for acid polysaccharide (alcian blue, Hale's iron method), was less dense (interference microscopy) and more birefringent than normal matrix. The hypermineralized component stained intensely for acid polysaccharide and was less birefringent than normal matrix. In the electron microscope, the inorganic crystals in the hypomineralized component were less numerous and larger than normal, while those of the hypermineralized component were more numerous but of normal diameters.

These observations indicate that the hypomineralized component results from an inhibition of polysaccharide‐collagen interaction, resulting in a paucity of apatite nucleation sites and a more soluble organic matrix. The hypermineralized component results from an increased period of time for matrix aggregation with the formation of more nucleation sites and therefore more numerous crystals and a less soluble organic matrix. The presence of a hypermineralized component in organic matrix of nearly normal density indicates that mature rodent incisor dentin is less completely mineralized than the bone of mature osteons.
Cellular differentiation in the anuran pronephros
Authors: Jaffee Oscar Charles
Published: February 2005

Ribonucleic acid (RNA) is detectable histochemically by means of methyl green pyronin staining (controlled with ribonuclease) in the cytoplasm of the proximal tubules of the frog (Rana pipiens). This is seen at Shumway stage 23 when the proximal tubules become differentiated from the remainder of the tubular complex. RNA levels remain high during the process of pronephric differentiation, dropping when this process is completed. The onset of specific renal functions (phenol red transport; protein resorption) during the period of high RNA levels raises the question of the role of RNA in the development of renal function as well as cellular differentiation. Histochemical events accompanying differentiation in the pronephros (periodic acid‐Schiff staining of the brush borders and the appearance of protein resorption droplets) are similar to those found in differentiating meso‐ and metanephric kidneys. Mitochondria in the undifferentiated pronephros are found to be granular in form by vital staining with Janus green B and with iron hematoxylin staining. These organelles do not consolidate into rodlets as found in differentiated meso‐ and metanephric kidneys but remain in their original granular form, as demonstrated by the techniques noted above. Granular mitochondria have been demonstrated in the differentiated pronephros of a month old tadpole.
Observations of the ultrastructure of the myocardium of the common lobster (Homarus americanus), especially of the myofibrils
Authors: Smith John R.
Published: February 2005

The ultrastructure of the myocardial cells of the common lobster, Homarus americanus, was examined with the electron microscope. The contractile elements of the cells show the usual A, I and Z band structures in longitudinally cut sections. Sarcomeres in slightly oblique section frequently exhibit distinct H zones at the midportions of the A bands. The fine filaments of the I band may be seen between the larger A band filaments in many areas of the sarcomeres, although in other areas there appears only to be filamentous “bridging” between the filaments of the A bands. Cross sections through the A band do not show a constant “array” of I and A filaments. The H zones, observed in these myocardial cells, appear to result from the separation of the finely filamentous materal between the A rods at the middle of A bands when the sarcomeres are stretched. Notation is also made of the appearance of intercalated disks and the thickening and folding of the basement membranes of the sarcolemma at points of cellular angulation. Mitochondria are numerous in these cells, and there is an extensive sarcotubular system.
Microcirculation in the islets of langerhans of the mouse
Authors: Bunnag Srichitra C. , Bunnag Sirotma , Warner Nancy E.
Published: February 2005

A technique for the study of microcirculation in living islets, using quartz rod and cinephotomicrography, is presented, together with results of a study of insular microcirculation. With this technique, conditions are standard, results are reproducible and the findings are recorded permanently. The pancreas, bathed constantly in Locke‐Ringer's solution at 37°C, is lifted with the spleen from the body, supported on the tip of Knisely's hollow‐tipped fused quartz rod, and the lobules are separated gently. Circulation in the transilluminated islets, which are pale yellow, spherical or ovoid bodies with a distinctive vascular pattern, is studied with the biobjective, binocular microscope. For cinephotomicrography, the camera is aligned over one eyepiece of the microscope and the film is exposed at 64 frames per second, using a 750 watt projection bulb as light source. Direct anastomoses of insular and acinar capillaries are not observed. Blood flow in the islets of the anesthetized mouse is rapid and constant, under these conditions of observation. Intravenous epinephrine and ephedrine cause temporary interruption of blood flow in the islets, whereas nor‐epinephrine slows but does not stop the circulation. Pitressin also causes slowing of insular blood flow. Insulin, glucagon, hydrocortisone, glucose, alloxan and diphenylthiocarbazone have no acute effect upon the insular microcirculation. A possible relation between the circulatory effect and the hyperglycemic effect of epinephrine and ephedrine is suggested.
Cell proliferation and displacement in the adrenal cortex of young rats injected with tritiated thymidine
Authors: Ford Joe K. , Young Richard W.
Published: February 2005

The origin and fate of cells within the growing adrenal cortex have been studied autoradiographycally in young rats injected with thymidine‐H3 and sacrificed at intervals between one hour and ten weeks after injection.

Cell proliferation (DNA synthesis and mitosis) was greatest in the zona glomerulosa, dropped off progressively deeper in the cortex, and was negligible in the inner fasciculata and reticularis. The shorter cell generation times in the glomerulosa, compared to the other zones, were due mainly to a decrease in duration of the G1 period of the cell proliferative cycle, although a slight diminution in the length of G2 + mitosis was also detected. The average duration of DNA synthesis was not appreciably modified.

Growth of the cortex was achieved through peripheral addition of new cells produced by mitosis in the outermost regions of the gland. As the cortex thickened, some labeled cells within these outer layers were gradually displaced to progressively greater distances from the medullary surface. Since these cells remained within the zone of rapid proliferation, they continued to divide, thereby diluting their radioactivity. Other labeled cells were gradually displaced out of the proliferative regions towards the medullary surface, and into zones which did not support cell division (inner fasciculata and reticularis). In consequence, heavily labeled cells were ultimately restricted to the innermost zones.

It was suggested that as cells are displaced within the growing adrenal cortex they encounter changing microenvironments which influence not only proliferative activity, but presumably enzymatic pathways of steroid synthesis as well.
On the presence of valves in the rat cerebral arteries
Authors: Shanklin William M. , Azzam Nabil A.
Published: February 2005

Valves were observed in the muscular cerebral arteries of the rat at the level of the optic chiasm in each of the ten adult animals examined. These paired valves were formed by folds of the intima. They were frequently associated with a branching of the artery. Part of the well formed internal elastic membrane separated the base of the valve from the media, while some very thin elastic fibers spread through the tissue forming the valve. The area of the valve was stained metachromatically by cresyl violet and was sharply differentiated from the remaining non‐metachromatic arterial wall. The internal elastic membrane was intensely stained by fuchsin paraldehyde, PAS, orcein and silver diammine.
Location of anatomic sites in brains of experimental animals based on internal landmarks
Authors: Fry William J. , Fry Francis J.
Published: February 2005

The determination of the spatial positions, with respect to a head holder reference, of anatomic structures within the brains of experimental animals, based on measurements of coordinates of ventricular and internal cranial landmarks, is described. If “appropriate” landmark arrays are employed, the uncertainty in coordinate values for prechosen anatomic sites in cat brain, determined by the methods outlined in the paper, is reduced by a factor of the order of five compared to the deviations experienced when the Horsley‐Clarke landmarks are employed. The instrumentation system developed for implementing the entire procedure, including precision x‐ray contrast ventriculography, and the atlas and roentgenographic data used to obtain the desired coordinate information are illustrated.
Bloodstreams and the formation of the interatrial septum in the anuran heart
Authors: Jaffee Oscar Charles
Published: February 2005

Patterns of blood flow have been observed at several critical stages in the development of the frog heart. Shortly after the onset of circulation (Shumway stage 20) two inflowing streams were noted to cross in the sinus venosus and then continue through the atrium, parallel to each other. With the development of the hepatic return (stage 24) the right stream becomes much larger and its course diverted into the area that will become the definitive right atrium. The smaller left stream is then noted to flow around the right stream with the development of a spiralling of the streams. The left stream now leads into the area which will become the left atrium. This is the hemodynamic situation as the interatrial septum forms; the septum forms between the streams. Experimental and histological evidence indicate that the interatrial septum is formed by a molding action of the bloodstreams on the tissues of the atrial wall.
The pars distalis of the female rabbit hypophysis: An electron microscopic study
Authors: Salazar Hernando
Published: February 2005

New Zealand virgin rabbits were used in this study. Normal males and castrated, thyroidectomized and recently mated females formed the control groups. Correlation with the light microscopical appearance using the method of alternate thin and thick sections, correlation with the control glands, and comparison with the descriptions in the rat, were used as criteria for the identification of five different types of secretory cells in the pars distalis. Two types of “acidophiles” were found, the more numerous and conspicuous having secretory granules of a maximum diameter of 380–400 mm̈ (growth hormone‐producing cell), and a second type with granules of 600–800 mm̈, very seldom seen in the virgin rabbit but increasing in number and granulation after mating (Prolactin‐producing cell). Two types of “basophiles” that correspond to the “thyrotrophes” (angular shape, granules of 150 mm̈ in diameter) and “gonadotrophes” (rounded shape, granules of 280–300 mμ), were also identified. In addition, a peculiar large cell with characteristic mottled cytoplasm and very few granules was tentatively identified as a “basophile” in the process of regranulation. Its functional significance was discussed. A stellate cell having fibrillar material and no secretory granules within its cytoplasmic processes, found between parenchymal cells and approaching basement membranes, was tentatively identified as a supporting element. In addition to the description of the fine structure and possible functional significance of the different cell types, some features as cilia, desmosomes, intranuclear fibrillar material, as well as vacuolization of cells in normal glands were also discussed.
A study of the lateral geniculate body in the diurnal ground squirrel, citellus tridecemlineatus tridecemlineatus and in the nocturnal guinea pig
Authors: Vaidya Prabhakar Gopal
Published: February 2005

The ground squirrel, Citellus tridecemlineatus tridecemlineatus, is a strictly diurnal species and possesses a pure‐cone retina. The present work comprises the results of an investigation of the morphology and the histological structure of the lateral geniculate body of this interesting mammal. The lateral geniculate body of the nocturnal guinea pig was also investigated and a comparison of the two made.

In both species, the lateral geniculate body comprises two nuclei: a smaller ventral and a larger dorsal. These nuclei are devoid of lamination — a feature presumably related to the absence of binocular vision in these animals. Only the dorsal nucleus projects to the cortex in both species.

Measurements on 1,000 neurons in the dorsal nucleus of both species reveal that neuron population is uniform in size and that on the average the neurons of the guinea pig are a little smaller (ground squirrel, nucleus: 12.36 m̈; perikaryon: 16.70 m̈ and guinea pig, nucleus: 12 m̈; perikaryon: 15.82 m̈).

The lateral geniculate body of the guinea pig is smaller than that of the ground squirrel. The dorsal nucleus in the latter species is estimated to contain 74,900 neurons. This is a large number and undoubtedly is related to the fact that the retina is pure‐cone with numerous ganglion cells and a large optic nerve.
Anatomy of the A–V node of the dog
Authors: James Thomas N.
Published: February 2005

The A‐V node of the dog is composed of closely interwoven fibers which frequently connect with each other within a sparse collagen framework. Fibers from the interatrial septum enter the posterior half of the node along its superior and posterior margins, while the anterior half of the node is isolated from such connections. In addition there are fibers from the interatrial septum which bypass these marginal atrionodal junctions and instead enter the convex surface of the node, which lies beneath the right atrial endocardium. These bypassing fibers circumvent most of the interweaving fibers within the A‐V node. At the posterior margin of the node, lying between it and the coronary sinus, there are ganglia and nerves, with the nerve fibers extending anteriorly through the A‐V node into the A‐V bundle. The only major anatomic difference between the human and canine A‐V nodes is their arterial blood supply, that of man being derived from one source originating from the right coronary artery and that of the dog being from two sources, both of which originate from the left coronary artery.
An apparatus for determination of breaking‐strength of small rodent bones
Authors: Felts William J. L.
Published: February 2005

Analysis of age changes in physical characteristics of mouse limb bones requires a sensitive, consistent and relatively simple apparatus for determination of transverse breaking strength. The developed instrument is essentially a one meter counter‐balanced 4‐to‐1 lever with a tracked, motor‐driven weight on its upper surface. At the beam's short end a loading tool impinges upward on a bone mounted in an adjacent holder; at the opposite end is a mercury switch connected to a relay halting the weight motor when fracture occurs. Bones, with proximal ends embedded in convex securing blocks of impression medium, may be positioned in a standard relationship to the holder, loading tool edge, and the balanced beam.

Repetitive loading of a steel spring indicates instrument error of 1.8%. Preliminary tests with a random series of paired mouse femora show no significant difference between left and right bones. In the long‐term study it will be possible to correlate physical strength with other characteristics of opposite bones.

An air‐gap capacitor across loading tool and bone holder and coupled to a variable frequency oscillator permits monitoring of specimen elasticity on a strip‐chart recorder.
Anatomic considerations for regional intimal changes in the coronary arteries (Dog)
Authors: Boucek Robert J. , Fojaco Rita , Takashita Ruth
Published: February 2005

Intimal proliferation in dog coronary arteries occurred in the vessel having the greatest range of motion. Within an involved segment of the artery, intimal proliferation could be related to the anatomy of the muscle bundles. Arterial muscle bundles originate from the adventitia, spiral around the artery and insert distally into the adventitia. The adventitia and the internal elastic lamina course along the long axis of the artery and are connected by elastin‐collagen fibers. Intimal thickening developed under the muscle insertion sites in regions where the adventitia was apparently placed under tension. In these regions, the net force of a muscle bundle contraction increases and shearing would occur between a muscle bundle at its insertion site and the remaining bundles gliding past it. This local shear force would then be transmitted to the internal elastic lamina through the elastin‐collagen fibers which connect it to the adventitia. Deformation and apparent injury of the internal elastica would follow and cause a fibrous tissue response. In the smaller arteries and arterioles, intimal proliferation occurred most prominently in the vessels supplying a mobile structure, i.e., anterior papillary muscle of the left ventricle.
Microradiography of rat incisor dentin during the development of the response to injected fluoride
Authors: Osmanski C. Paul , Yaeger James A.
Published: February 2005

Fifty day old Sprague‐Dawley rats were given sodium fluoride (50 mg/kg) and killed at times between one half hour and 32 days after injection. Transverse sections of the upper incisor 40 μ thick were radiographed, demineralized and stained with hematoxylin and eosin. The response seen in hematoxylin and eosin stained material agreed with previous descriptions of the “calciotraumatic response” and consisted of three components. However, in the radiogram only two components could be distinguished: an external hypermineralized zone and an adjacent hypomineralized zone. The radiographic response was first recognized four hours after injection as a narrow zone of hypermineralized dentin at the dentin‐predentin junction. When the radiograms were compared to the H and E stained sections in animals killed up to 19 hours after injection, two important features were observed: (1) the width of the predentin had increased markedly, and (2) the hypermineralized zone had increased to its final width. This was interpreted as concurrent formation of both hypermineralized and hypomineralized components. At 24 hours normal dentin formation had resumed. Since both components were forming simultaneously it is believed that sodium fluoride does not cause the response by interfering with the humoral mechanisms of mineralization, but, rather, its effect is most likely on collagen or ground substance.
Autoradiographic and histological investigation of changes in the visual system of rats after unilateral enucleation
Authors: Altman Joseph , Das Gopal D.
Published: February 2005

Following surgical removal of one eye, rats were permitted to survive for three days, one, two and four months, and before killing them they were injected with 2 mc of leucine‐H3 intraperitoneally. The utilization of this radiochemical was investigated in the brain autoradiographically. In all groups of animals the uptake of radioleucine, as determined by microdensitometry, was significantly higher in the “degenerated” optic nerve and tract than in their “normal” counterparts, with the relative difference increasing with longer postoperative survival within the periods tested. This progressive net increase in the utilization of leucine‐H3 was associated with an absolute increase in the number of glia cells. Similar, but attenuated, density differences were also obtained with relatively large‐aperture measurements over the stratum griseum of the superior colliculus in which the optic tract fibers terminate. In contrast, small‐aperture measurements of grain density over single neurons in the lateral geniculate nucleus showed no difference in the utilization of leucine‐H3 between the normal and subtotally deafferented sides. This suggests an absence of transneuronal changes in protein metabolism in the visual system of the rat as long as four months after unilateral enucleation.