bluuebunny/crossref_metadata_2025 huggingface dataset:
The MLC1v gene provides a transgenic marker of myocardium formation within developing chambers of the Xenopus heart
Authors: Smith Stuart J. , Ataliotis Paris , Kotecha Surendra , Towers Norma , Sparrow Duncan B. , Mohun Timothy J.
Published: February 2005

Many details of cardiac chamber morphogenesis could be revealed if muscle fiber development could be visualized directly within the hearts of living vertebrate embryos. To achieve this end, we have used the active promoter of the MLC1v gene to drive expression of green fluorescent protein (GFP) in the developing tadpole heart. By using a line of Xenopus laevis frogs transgenic for the MLC1v‐EGFP reporter, we have observed regionalized patterns of muscle formation within the ventricular chamber and maturation of the atrial chambers, from the onset of chamber formation through to the adult frog. In f1 generation MLC1v‐EGFP animals, promoter activity is first detected within the looping heart tube and delineates the forming ventricular chamber and proximal outflow tract throughout their development. The 8‐kb MLC1v promoter faithfully reproduces the embryonic expression of the endogenous MLC1v mRNA. At later larval stages, weak patches of EGFP fluorescence are found on the atrial side of the atrioventricular boundary. Subsequently, an extensive lattice of MLC1v‐expressing fibers extend across the mature atrial chambers of adult frog hearts and the transgene reveals the differing arrangement of muscle fibers in chamber versus outflow myocardium. The complete activity of the promoter resides within the proximal 4.5 kb of the MLC1v DNA fragment, whereas key elements regulating chamber‐specific expression are present in the proximal‐most 1.5 kb. Finally, we demonstrate how cardiac and craniofacial muscle expression of the MLC1v promoter can be used to diagnose mutant phenotypes in living embryos, using the injection of RNA encoding a Tbx1‐engrailed repressor–fusion protein as an example. Development Dynamics 232:1003–1012, 2005. © 2005 Wiley‐Liss, Inc.
Retinoid signaling competence and RARβ‐mediated gene regulation in the developing mammalian telencephalon
Authors: Liao Wen‐Lin , Wang Hsiao‐Fang , Tsai Hsiu‐Chao , Chambon Pierre , Wagner Michael , Kakizuka Akira , Liu Fu‐Chin
Published: February 2005

To study retinoid signaling in the developing telencephalon, we transfected a retinoid reporter gene into different regions of developing telencephalon. We found that the ventral telencephalon was more competent to retinoid signaling than the dorsal telencephalon. Moreover, among all retinoic acid receptors (RARs) and retinoid X receptors (RXRs), RARβ was strongly induced by retinoic acid in the ventral telencephalon, suggesting that RARβ might be involved in retinoid signaling competence. The RT‐PCR analysis indicated that RARβ was selectively expressed in the developing striatum of ventral telencephalon. We then demonstrated that null mutations of RARβ gene resulted in reduction of striatal‐enriched tyrosine phosphatase (STEP) mRNA in the striatum of RARβ−/− mutant mice. Conversely, the gain‐of‐function study showed that ectopic expression of RARβ1 in the cerebral cortex enhanced STEP expression, and the effect was RARβ‐isoform specific. Our study identified RARβ as an important molecule for transducing retinoid signals in developing ventral telencephalon. Developmental Dynamics 232:887–900, 2005. © 2005 Wiley‐Liss, Inc.
Three‐Dimensional Lanthanoid‐Containing Coordination Frameworks: Structure, Magnetic and Fluorescent Properties
Authors: Zhang Hong‐Tao , Song You , Li Yong‐Xiu , Zuo Jing‐Lin , Gao Song , You Xiao‐Zeng
Published: February 2005

Two lanthanoid‐containing 3D coordination polymers, [Gd2L3(H2O)2]n (1) and {[TbL1.5(H2O)]·0.5H2O}n (2) (L = succinate), have been prepared by hydrothermal reaction. The difference in structure between the two 3D coordination polymers is a result of the flexibility of the ligand conformation. The magnetic properties of 1 and 2 have been investigated in the 1.8–300 K range. Both complexes exhibit ferromagnetic interaction between lanthanoid ions. AC magnetic measurements revealed long‐range magnetic order in complex 2. Especially 2 integrates the ferromagnetic, fluorescent and porous properties into a single entity. This motif may be developed to achieve new multifunctional molecular‐based materials. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Porcine small intestine submucosa (SIS) is not an acellular collagenous matrix and contains porcine DNA: Possible implications in human implantation
Authors: Zheng M. H. , Chen J. , Kirilak Y. , Willers C. , Xu J. , Wood D.
Published: February 2005

Porcine small intestinal submucosa (SIS) has been recommended as a cell‐free, biocompatible biomaterial for the repair of rotator cuff tendon tear. However, we have observed noninfectious edema and severe pain in patients who have undergone SIS implantation for tendon repair. The aim of this study was to conduct an independent assessment of the safety and efficacy of Restore™ SIS membrane. The Restore™ orthobiologic implant was examined by histology and the nested PCR technique using porcine immunoreceptor DAP12 gene to examine if SIS membrane contained porcine cells or DNA, respectively. The material was also implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Restore™ SIS was found to contain multiple layers of porcine cells. Chloroacetate esterase staining showed that some of these cells were mast cells. Nested PCR of the DAP12 gene demonstrated that Restore™ SIS contained porcine DNA material. Subcutaneous implantation of Restore™ SIS membrane in mice, and in rabbits for rotator cuff tendon repair, showed that the membrane caused an inflammatory reaction characterized by massive lymphocyte infiltration. In conclusion, Restore™ SIS is not an acellular collagenous matrix, and contains porcine DNA. Our results contradict the current view that Restore™ SIS is a cell‐free biomaterial, and that no inflammatory response is elicited by its implantation. We suggest that further studies should be conducted to evaluate the clinical safety and efficacy of SIS implant biomaterials. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 73B: 61–67, 2005
Effect of porosity on the fluid flow characteristics and mechanical properties of tantalum scaffolds
Authors: Shimko Daniel A. , Shimko Valerie Franz , Sander Edward A. , Dickson Kyle F. , Nauman Eric A.
Published: February 2005

In many cases of traumatic bone injury, bone grafting is required. The primary source of graft material is either autograft or allograft. The use of both material sources are well established, however, both suffer limitations. In response, many grafting alternatives are being explored. This article specifically focuses on a porous tantalum metal grafting material (Trabecular Metal™) marketed by Zimmer. Twenty‐one cylindrical scaffolds were manufactured (66% to 88% porous) and tested for porosity, intrinsic permeability, tangent elastic modulus, and for yield stress and strain behavior. Scaffold microstructural geometries were also measured. Tantalum scaffold intrinsic permeability ranged from 2.1 × 10−10 to 4.8 × 10−10 m2 and tangent elastic modulus ranged from 373 MPa to 2.2 GPa. Both intrinsic permeability and tangent elastic modulus closely matched porosity‐matched cancellous bone specimens from a variety of species and anatomic locations. Scaffold yield stress ranged from 4 to 12.7 MPa and was comparable to bovine and human cancellous bone. Yield strain was unaffected by scaffold porosity (average = 0.010 mm/mm). Understanding these structure–function relationships will help complete the basic physical characterization of this new material and will aid in the development of realistic mathematical models, ultimately enhancing future implant designs utilizing this material. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater
Quantitative studies on colony‐forming units in isogenic radiation chimeras
Authors: Playfair John H. L. , Cole Leonard J.
Published: February 2005

Lethally irradiated LAF1 mice were protected by various numbers of isogenic bone marrow cells. At intervals, cells from femoral bone marrow and spleen were assayed for their content of colony forming units (CFU) by retransplantation into other lethally irradiated mice and counting of spleen nodules at eight days. CFU numbers in femoral marrow were restored to preirradiation levels by about eight weeks. In the spleen, restoration was earlier and more rapid and for several weeks the CFU content exceeded the normal level. Prior splenectomy did not alter the pattern of CFU restoration in the femoral marrow postirradiation. However, splenectomy did appear to slightly improve survival of irradiated marrow‐protected mice. It is argued that the CFU may not be the essential protective cell, and the existence of a precursor “stem” cell in normal marrow is postulated.
Karyology of permanent human cell line, W‐18VA2, originated by SV40 Transformation
Authors: Weinstein David , Moorhead Paul S.
Published: February 2005

The karyology of a permanent human cell line, which retains a viral induced complement‐fixing antigen as a result of its original transformation with simian virus 40, is described. This line, W‐18VA2, is primarily subdiploid after more than two and one‐half years of cultivation in vitro and exhibits high variability of chromosome number and form in the parental line as well as in various clones and sublines.
Taste papillae of the blowfly
Authors: Dethier V. G. , Hanson F. E.
Published: February 2005

Each interpseudotracheal papilla on the oral surface of the labellum of the blowfly contains four bipolar neurons. An electrophysiological analysis has shown that one of these cells is a receptor which responds specifically to carbohydrates. The response consists of a rapid initial discharge which typically adapts to one‐half maximum frequency in 300–400 msec. The response remains normal even in the presence of choline chloride (1.5–2.0 M), NaCl (0.01–2.0 M), and CaCl2 (0.01–1.0 M). The various sugars tested showed the following order of increasing effectiveness: sorbitol < sorbose < inositol < fucose < arabinose < glucose < sucrose < fructose. Mannose, a nutritive sugar, is non‐stimulating. D‐arabinose, an acceptable sugar, is more stimulating than L‐arabinose, an unacceptable sugar. L‐arabinose, in contrast to D‐, also stimulates other neurons in the papilla.

Another cell responds when the electrode contains salt or certain carbohydrates such as L‐arabinose. It is believed that its activity initiates behavioral rejection of compounds. It does not exhibit a high initial discharge or adaptation but waxes and wanes randomly. Its response to monovalent and divalent cations is similar although the latter produces volleys of high frequency.

Mechanical deformation causes an increase in frequency of a third spike. Mechanosensitive units may be classified by their responses into three classes: push, pull, or push‐pull.

No evidence for a water receptor was found.
Amphibian acoustico‐lateralis efferents
Authors: Schmidt Robert S.
Published: February 2005

Efferent spikes were recorded from the nerves supplying the papilla amphibiorum, ampullae, and lateral‐line neuromasts of the mudpuppy (Necturus maculosus). Increased efferent activity was associated with rotatory, vibratory, and tactile stimulation and gill movements. In a single experiment it was possible to record efferents from the nerve to the papilla basilaris of a leopard frog (Rana pipiens). The function of acoustico‐lateralis efferents is not restricted to or closely associated with a single habit, habitat, phylogenetic group, or acoustico lateralis receptor. It seems likely that all acoustico‐lateralis receptors in all vertebrates receive efferent input.
The band forming rhythm of Neurospora mutants
Authors: Berliner Martha D. , Neurath Peter W.
Published: February 2005

The growth rhythm in several strains of “clock” mutants of Neurospora crassa has been observed to have several unusual non‐circadian characteristics. The period may range between 18 and 110 hours, depending upon strain and environmental condition. The phase of the rhythm, even when its period is 24 hours, is not related to a specific time of day, nor is it “set” or phased by light‐dark cycles. Instead, the phase can be set by transfer to fresh medium; moreover, its specific chemical composition influences the length of the period. The period is significantly influenced by temperature; the growth rate is a different function of temperature. All the strains show striking similarities in the functional dependence of period and growth rate on temperature, even though the absolute magnitudes differ widely.
A study of the crustacean axon repetitive response: I. The effect of membrane potential and resistance
Authors: Tomita Tadao , Wright Ernest B.
Published: February 2005

The transmembrane electrical properties of the crustacean axon have been examined by a new technique which allows for quantitative evaluation of the electrical and excitable characteristics across a microscopic area, “patch,” of fiber membrane using external electrodes. Data from repetitive firing and from non‐repetitive firing fibers compare as follows: (1) Membrane potential, resting, 82 mv repetitive; 67 mv non‐repetitive; 70–75 mv transition level repetitive to non‐repetitive. (2) Membrane potential, active, 132 mv, 50 mv overshoot repetitive; 100–120 mv, 30–50 overshoot, non‐repetitive. (3) Membrane resistance, 7.6 × 106 ohms or 2300 ohms cm2 repetitive; 2.8 × 106 ohms or 880 ohms cm2 non‐repetitive. (4) Membrane time constant, 2.5 ms repetitive; 1.5ms non‐repetitive. (5) Membrane capacity 1.0μf repetitive; 1.7 μf non‐repetitive. (6) Repetitive firing property may be restored to non‐repetitive axons by increasing the Vm value with a polarizing inward current. This increases Rm also. (7) Non‐repetitive fibers show considerable inactivation, give rise to “more or less” spikes particularly during refractory period following a spike, and respond to anode‐break stimulation. Repetitive firing axons do not. (8) The action potential has two active components, one to depolarize (sodium) one to repolarize (potassium), both of which drive the membrane potential. toward predetermined levels. (9) The repetitive firing axons show little or nc inactivation with weak prolonged depolarization producing trains of spikes. There is a slow rise in critical firing level which ultimately causes the spike train termination. There is a slow increase in the undershoot (diphasic repolarization) amplitude.
The sodium and potassium activated ATPase of intestinal epithelium. I. Location of enzymatic activity in the cell
Authors: Berg G. G. , Chapman B.
Published: February 2005

The location of sodium and potassium activated Mg‐ATPase (Na‐K ATPase) was studied in columnar epithelial cells of the small intestine of rats. Cell components were segregated in centrifuge fractions by a mild procedure (sucrose medium), which preserved mitochondria and vesicular inclusions, and by a drastic procedure, designed to preserve the striated borders selectively. The contents of fractions were characterized by phase contrast and electron microscopy and by the assay of alkaline phosphatase (E.C.3.1.3.1), cytochome oxidase (E.C.1.9.3.1), invertase (E.C.3.2.1.26) and Mg‐ATPase (E.C.3.6.1.4).

Na‐K ATPase was found to be most concentrated in fractions containing mitochondria on one hand, and striated borders on the other. Its distribution differed from the distributions of the other four enzymes. The physiological implications of finding the “sodium pump” enzyme in the membrane at the apical pole of the epithelial cell were discussed.
Binding of Ca and Mg by lipoprotein and nucleoprotein subfractions of rat liver cell microsomes
Authors: Carvalho Arselio P. , Sanui Hisashi , Pace Nello
Published: February 2005

Rat liver cell microsomes were subfractionated in D2O‐sucrose solutions of various densities into three subfractions with densities > 1.23, 1.18–1.23 and 1.12–1.18. There was an inverse correlation between the nucleic acid and lipid contents of these subfractions; the highest density subfraction had a relatively high nucleic acid (20.9%) and low lipid (15.1%) content and the lowest density subfraction had a low nucleic acid (3.4%) and a high lipid (45.2%) content. Whole microsomes were determined to be composed of 55.0% protein, 8.6% nucleic acid and 36.4% lipid. This composition of microsomes was calculated to reflect a nucleoprotein and lipoprotein content of 28% and 72%, respectively. Investigation of Ca and Mg binding by the three microsome subfractions and by the whole microsome fraction after equilibration for 12 hours in a medium of pH 6.7 containing 8–9 meq Ca or Mg/liter indicated that all fractions retained considerable amounts of the divalent cations (1.5–2.6 meq/g N). The nucleoprotein fraction was calculated to bind 0.35–0.40 meq Ca or Mg/g dry weight of nucleoprotein and the lipoprotein fraction 0.12 meq Ca or Mg/g dry weight of lipoprotein. Nevertheless, the lipoprotein fraction of microsomes is responsible for 45% of the total binding of Ca or Mg by the whole microsome fraction. These observations support the contention that cellular membrane structures, composed essentially of lipoprotein, can bind considerable quantities of the divalent cations.
The accumulation of sodium and calcium in a specific layer of frog skin
Authors: Imamura Akira , Takeda Hitoshi , Sasaki Nagayo
Published: February 2005

22Na‐autoradiography was carried out in frog skin, using the freeze‐drying method. Sodium was found to have accumulated between the papillary and reticular layer in the corium. This region was slightly stained with hematoxylin and metachromatically stained with both toluidine blue and azur‐A, suggesting the presence of mucopolysaccharide. Furthermore the 45Ca‐autoradiogram revealed that calcium was strongly absorbed in this layer. The chemical nature of the substance which retained Na+ and Ca++ in this layer has not yet been identified and awaits further analyses. It can not also be decided whether or not this layer is responsible for the active sodium transport. But from the results obtained in this study, it was suggested that the mucous substance is anyhow related to and plays a role in the ion transport across the frog skin.
On the role of acetylcholine in regulating the rate of the early chick embryo heart
Authors: Roberts Carmel Montgomery , Gimeno Martha A. , Leyden Webb J.
Published: February 2005

A study has been made of the effect of acetylcholine upon the heart rate of the early chick embryo, and it has been noted that under certain experimental conditions acetylcholine stimulates the heart rate during the period of vagal innervation, while depressing the heart rate after the nerve supply is established. Isolated chick embryo hearts freely suspended in a phosphate‐buffered (bicarbonate‐free) medium beat at only about one‐third their in ovo rates, and acetylcholine produces biphasic effects of stimulation and inhibition of the heart rate depending upon the concentration of the drug and the age of the hearts, the maximal stimulation occurring at five days. When suspended in Krebs bicarbonate medium the hearts beat at rates of about 72 to 74% their in ovo rates, and acetylcholine produces only slowing of the heart rate. This effect of acetylcholine can be diminished or reversed when an inhibitor of endogenous acetylcholine, hemicholinium‐3 is added. We have postulated that both inhibitory and stimulatory receptors for acetylcholine exist in the early chick embryo heart and that the response to added acetylcholine depends in part on levels of endogenous acetylcholine already present in the heart. The role of endogenous acetylcholine in regulating heart rate is discussed.
The metabolism of homogenates of the mouse epididymis
Authors: Elliott Paul R.
Published: February 2005

This study has attempted an evaluation of the in vitro metabolic characteristics of the epididymis of the mouse and a definition of areas for further research pursuant to the elucidation of the role of this organ in the process of sperm maturation and storage.

Optimal conditions were ascertained for the manometric measurement of total respiration and for the estimation of glycolytic activity by assay of lactate accumulation and phosphate esterification in fluoride poisoned homogenates. Homogenates of mouse kidney were utilized in all experiments for comparative purposes.

The in vitro data presented indicate the epididymis to be predominantly oriented to a glycolytic metabolism. It is suggested that this metabolic orientation when considered with the results of other investigators is compatible with a hypothesis for the secretion of lactic acid by the epididymal epithelium into the lumen of the epididymal canal for spermatozoan utilization.
Permeability to water and sodium of the crocodilian, Caiman sclerops
Authors: Bentley P. J. , Schmidt‐Nielsen Knut
Published: February 2005

In freshwater the caiman gains water at the rate of 3.5 ml/kg hr or 1.1 μl/cm2 hr. Of this 70% is the result of uptake through the skin, the rest being due to drinking. This gain in water is excreted by the kidneys as a hypotonic urine. Urine sodium losses are reduced by active sodium uptake from the urine during storage for 3 to 4 hours in the cloaca. In vitro and in vivo experiments indicate that the skin is somewhat permeable to sodium, which moves along concentration gradients.

In air the caiman loses water by evaporation (1.2 μl/cm2 hr). About 75% of this takes place from the skin.

In 3.3% NaCl solution caimans show elevated serum sodium concentrations and 20% of them die within 24 hours. The sodium accumulation is mostly due to drinking (4.4% of the body weight/day), and only to a minor extent to osmotic water loss through the skin (2.5% of the body weight/day or 0.6 μl/cm2 hr). The permeability of the caiman is compared to that of fishes, Amphibia and other reptiles.
The effect of volume expansion on the electrophoretic mobility of cells
Authors: Patinkin D. , Doljanski F.
Published: February 2005

Determinations of electrophoretic mobility were made on Landschütz ascites carcinoma cells and mouse leucocytes suspended in a series of solutions of differing hypotonicity. The curves relating volume to the reciprocal of tonicity indicated that both types of cells conform fairly well to the Van't Hoff‐Mariotte Law from a relative tonicity of about two down to 0.325. Beyond this point, leucocyte volumes tended to taper off to a plateau whereas ascites cell volumes first showed an increase in slope and then leveled off. Reversal of hypotonically swollen cells to isotonicity brought about a shrinking of the cells back to their original volume. These expanded and contracted cells were shown to retain other of their normal properties such as impermeability to vital dyes and for ascites, the ability to proliferate upon transplantation. It was concluded from these observations, that throughout their extensive expansion in hypotonic media, the cells remained essentially viable and intact. The possible effects of increase in cell volume on surface area changes were discussed. There was no change in the electrophoretic mobility of the cells in the entire range of hypotonic solutions tested. Enlargement of cell volume without change in mobility may have been produced by an expansion or unfolding of the ultramicroscopic crenations of the membrane and a corresponding exposure of similar surface to the electrokinetic plane of shear.
A histochemical study of intracellular digestion in triclad flatworms
Authors: Willier B. H. , Hyman L. H. , Rifenburgh S. A.
Published: February 2005

The course of digestion of an essentially protein food (beef liver) was followed by histological and histochemical methods in Planaria dorotocephala. After an average fasting period of two weeks, the planarians were fed and examined at close time intervals, ranging from one minute to eighty‐seven days after feeding. Liver particles are engulfed by the phagocytic cells of the intestine into food vacuoles, where a series of digestive changes occur. The liver particles coalesce into a granular spherule which gradually condenses into a homogeneous and chromatophilic spherule. As the spherule transforms from a granular to a homogeneous condition, it exhibits a gradually increasing affinity for stains, an intensified protein reaction, and a gradual diminution in size. These spherules are protein, since they give positive xanthoproteic and Millon reactions.

The homogeneous protein spherules gradually disappear, beginning at about twelve hours after feeding and continuing until the fifth day. During this period fat‐droplets form, gradually increasing at the expense of the protein spherules. The protein spherules apparently dissolve into the cytoplasm, furnishing intermediate chemical compounds (tests indicate that a carbohydrate stage does not intervene) from which fat is synthesized. It thus appears that the fat is formed from the protein spherules. The fat thus formed is stored in the phagocytic cells, and remains unchanged in quantity for a fasting period lasting six weeks, after which it gradually diminishes. During the engulfment of the food, the fat decreases markedly, apparently furnishing energy for phagocytic activities. A few of the protein spherules may persist as «protein reserve».
Correlations of the musculature and the movements of the skull in natrix, with some suggestions of homology in the lacertilians
Authors: Adams L. A.
Published: February 2005

The musculature of the ophidian head is a fairly complex structure, due to the specialization of the skull and the peculiar movements and motions made possible by the high degree of streptostylism.

This musculature has been derived from the lacertilian type by a splitting and a shifting of the original elemental muscle masses of this group. Most of the muscles are clearly homologous with those of the Lacertilia. Some cannot be homologized by a study of the mature forms.

The greatest differences lie in the separation of the muscle masses in the ophidia, as compared with the undivided masses in the Lacertilia. Since the jaw movements of the Lacertilia are rather simple, there is no need for any subdivision or splitting of the jaw muscles, but with the complex movements of the ophidia this becomes necessary.

A few of the ophidian muscles appear to be neomorphs, as no key to their origin could be determined by a comparison with lacertilians.
The growth and chemical composition of three species of turtles fed on rations of pure foods
Authors: Pearse A. S. , Lepkovsky S. , Hintze Laura
Published: February 2005

Painted turtles, gopher tortoises, and terrapins were fed on various mixtures of sand, salts, dextrin, casein, cod‐liver oil, wheat, eggs, lettuce, and meal worms. Each individual was weighted weekly for about a year and then killed for analysis, the water, ash, nitrogen, and fat being determined. Some individuals increased in weight as much as 75 per cent, others lost weight. Judged by growth and chemical analyses, the food requirements of chelonians, as representative poikilothermal vertebrates toward nutritive substances (including vitamines) are similar to those of homoiothermal animals.
Structure, movement, locomotion, and stimulation in amoeba
Authors: Mast S. O.
Published: February 2005

Amoeba proteus contains a central elongated fluid portion (plasmasol), a rigid layer surrounding this (plasmagel), a thin elastic surface layer (plasmalemma), and a hyaline layer between the plasmagel and the plasmalemma which is fluid at the tip of active pseudopods and in certain other regions.

The plasmasol is an emulsion. It consists of a fluid in which various vacuoles and granuoles are suspended. The plasmagel is probably alveolar in structure. It contains the same kinds of substances as the plasmasol, but some of the fluid appears to be gelated so as to form alveoli. The plasmalemma probably consists of interwoven protein fibers and a lipoid which fills the interstices.

The plasmasol is probably hypertonic; the plasmagel and the plasmalemma are probably semipermeable. This and other factors result in an excess inflow of water, stretching the plasmagel and the plasmalemma. When a pseudopod is formed, the inner portion of the plasmagel liquefies locally. This produces a local decrease in elastic strength resulting in the formation of a protuberance, a pseudopod. As this is formed there is contraction at the posterior end, resulting in forward flow of the plasmasol and extension of the pseudopod.

If the pseudopod is attached, the plasmalemma, being attached to the substratum and to the adjoining plasmagel, slides over the plasmagel above and remains stationary below, rolling movement results. If it is free, the plasmalemma is stretched out with movement in it equal on all sides. If the free pseudopods become attached to the substratum at the tip after they are thus formed, walking movement results.

During locomotion of either type, the plasmasol continuously gelates at the tip of the extending pseudopods forming plasmagel, and the plasmagel continuously solates at the posterior end forming plasmasol.

Response is due largely to changes in the elastic strength of the plasmagel in the adhesiveness of the plasmalemma and in turgidity.

Locomotion in Amoeba verrucosa is in principle the same as it is in Amoeba proteus.
The cheek pouches of Richardson's groundsquirrel, citellus richardsonii, sabine
Authors: Sleggs George F.
Published: February 2005

The lips of the animal are modified in relation to the act of passing seeds into the sac. The cheek‐sacs are invaginations of the buccal mucosa, and their development as diverticula of the vestibulum oris is associated with the establishment of extrinsic muscles, derived from the platysma. The sac is invested by a coat of striated muscle. The epithelial lining of the sac attains a degree of complexity comparable to the epidermis of the skin, except that a stratum lucidum and stratum granulosum are not developed. No glands are developed in the mucous membrane of the sac.
Autotomy in Arachnida
Authors: Wood Florence Dowden
Published: February 2005

On the basis of experimental study and observations on the morphology of the legs of spiders, P. Friedrich described a cutting device within the trochanter which would sever that appendage from the body when the leg was stimulated by injury.

A reinvestigation of the problem yielded entirely contrary results. Experiments calculated to induce spontaneous amputation through an automatic reflex in the leg were negative on scorpions, harvestmen, and more than a dozen species of spiders. A detailed morphological study of the skeleton and musculature of the arachnid leg showed that no autotomizing device exists, either in the skeleton or in the arrangement of muscles (as is usually supposed). In all species studied, except the scorpion, severance of the leg from the body occurs most readily at some given point. The point at which severance readily occurs is directly correlated with a definite structural weakness in the skeleton and musculature. The spider itself removes an injured leg by grasping the stump with its mouth‐parts. No such injured stump falls off spontaneously or without the application of tension. Scorpions do not autotomize appendages under any stimulation, nor do they show any anatomical weakness in the leg skeleton or musculature.

Autotomy as an automatic reflex does not exist in the Arachnida.
The comparative morphology of the secondary sexual characters of elasmobranch fishes. The claspers, clasper siphons, and clasper glands. Memoir X
Authors: Leigh‐Sharpe W. Harold
Published: February 2005

A summary is given of the previous memoirs, and an attempt has been made, upon the three characters of this investigation, to arrange the genera into families, which agree, with two exceptions (Mitsukurina and Dicerobatis), with preexisting families. Some deductions are drawn as to relationships and attention is drawn to Cestracion galeatus and Triakis as connecting links. Separate families are erected for Dicerobatis and Mitsukurina, and the latter is placed near to Notidanus. Resemblances are shown between Chlamydoselachus and the Holocephali. The Trygonidae, Torpedinidae, and Rhinobatidae are singularly uniform families. An index is added both general and specific.
The effects of mechanical shock on locomotion in Amoeba proteus
Authors: Folger Harry T.
Published: February 2005

Amoeba responds to a mechanical shock by a cessation of movement which occurs shortly after the application of the stimulus. The length of the reaction time, the period intervening between application of stimulus and the response, varies inversely with the magnitude of the shock. After stopping Amoeba remains quiescent for a short time, and the length of this period of quiescence varies directly with the magnitude of the shock. A certain amount of time must elapse after a reaction before another can be obtained; during this time the animal reverts to the physiological state which existed prior to the first shock.

Partial recovery from the effects of a shock is manifested by a reaction time that is longer than after complete recovery, and a period of quiescence which is shorter. A shock which in itself is too slight to cause a cessation of movement may result in the lack of a response to a heavier one which follows immediately after it, although under other conditions the second shock would have called forth a reaction. If the second shock, however, is made sufficiently heavy, it will bring about a response, despite the effects of the first. This is what would be expected if the reactions take place in accordance with the Weber‐Foechner law.
A new dorsal gland in the ground‐squirrel, Callospermophilus, with a note on its anal gland
Authors: Hatt Robert Torrens
Published: February 2005

In the golden‐mantled ground‐squirrel, Callospermophilus, a spatulate glandular area has been noted in the skin of the back. It has been found in the following species: C. l. lateralis, C. l. arizonensis, C. l. caryi, C. l. saturatus, C. l. tescorum, C. c. chrysodeirus, and C. bernardinus. Probably it is common to the genus.

The individual glands making up this area are modified and enlarged sudoriparous glands. They are divided into a tightly coiled and branched fundus, a large sinus, and a duct which passes caudad and outward to its exit at the surface.

The glands secrete a strongly smelling oil, which is probably left on vegetation and other objects in the animal's environment and serves as a source of information to other members of the species. The glands are more active in spring and summer than in winter. They are stimulated by excitement. While present in both sexes, both adult and juvenile, they are best developed in adult males.

Callospermophilus has three anal glands. These have flat‐topped, straight‐sided nipples which are protruded from the anus if the animal is frightened. A milky substance with a very weak odor can be extruded.
The chromosomes of the house mouse
Authors: Cox Elizabeth K.
Published: February 2005

The spermatogenesis of the domestic mouse has been studied. There are forty chromosomes in spermatogonia and twenty in primary spermatocytes. The sex chromosomes are of the usual X‐Y type. Especial attention has been devoted to the study of chromosome morphology, both in spermatogonia and in primary spermatocytes.
Studies of hyperthyroidism IV. The behavior of the epidermal mitochondria and the pigment in frog tadpoles under conditions of thyroid‐accelerated metamorphosis and of regeneration following wound infliction
Authors: Speidel C. C.
Published: February 2005

In the epidermal cells of green‐frog tadpoles (Rana clamitans) there are present coarse, conspicuous mitochondrial threads. In the dorsal body regions, epidermal cells of the middle layers also contain pigment granules, grouped in crescentic masses in the distal portions of the cells.

Administration of thyroid extract results in permanent disappearance of the mitochondrial threads and disappearance to a large extent of the epidermal pigment granules. Processes of cellular dedifferentiation and proliferation occur rapidly over widespread areas, the mitochondria undergoing intracellular resorption. A new type of epidermis is developed containing many cutaneous glands, adapted for the approaching terrestrial life.

Wound infliction induces similar processes of cellular dedifferentiation and proliferation in the epidermis in the immediate vicinity of the wound. Cells in this region lose their mitochondrial threads by intracellular resorption, and there is also some disappearance of pigment granules. The new epidermal cells in the early stages of regeneration produce neither mitochondrial threads nor pigment. This condition is not permanent, however, and in the later stages the larval characteristics appear again, both mitochondrial threads and pigment being redifferentiated.

In the hyperthyroid animals there is also a significant mobilization of mesenchymal chromatophores, correlated to some extent with the loss of epidermal pigment.

The significance of epidermal changes is discussed with reference to cutaneous abnormalities associated with hyperthyroid and hypothyroid conditions.
The prenatal skull of the Canadian porcupine (Erethizon dorsatus)
Authors: Struthers P. H.
Published: February 2005

This study represents the first critical investigation on the development of the embryonic skull of the porcupine. A complete series of stages makes it possible to trace the developing chondrocranium from its first formation in precartilage to its later transformation into cartilage bone. Concurrent with this growth is the investment of the cartilaginous cranium by membrane bone.

The very primitive nature of the chondrocranium offers an excellent opportunity to discuss the existing problems of the embryonic skull from a new angle. Evidence is presented in support of the assumption that the ala temporalis is the homologue of the cynodont epipterygoid. The lamina parietalis develops from a single chondrifying center, thus producing a different arrangement of parietal elements from that found in most mammals. New evidence as to the relationship of the dens epistrophei and basal plate is presented. The position of the internal carotid artery on entering the cranium is different from the condition found in most mammals and throws new light on the interpretation of surrounding structures. The presence of a structure comparable with the crista longitudinalis of Lacerta shows close affinity to the solum nasi of more primitive forms.

The great specialization of the face is seen in the early and rapid growth of the membrane bones. The chondrocranium is long persistent and cartilage bone appears late in embryonic life.
The formation of contractile vacuoles in Amoeba proteus
Authors: Day Howard Calvin
Published: February 2005

The history of investigations on the contractile vacuole is reviewed briefly and brought up to date.

The study of the contractile vacuole in Amoeba proteus is considered from standpoints of origin, structure, behavior, and function. The results are obtained from a prolonged study of normal organisms and from their reactions when introduced into conductivity water.

The origin of vacuoles is studied by means of dark‐field illumination which reveals the vacuole to be formed from a fusion and coalescence of extremely minute droplets.

The retaining ‘wall’ of the contractile vacuole is not a permanent structure, but is in the nature of a condensation membrane, totally disappearing with each contraction.

The loci of the contractile vacuoles are not permanent, but vacuoles are formed more or less at random. It is unlikely that they are supported in gelated areas, for amoebae with a dozen vacuoles are quite active and there is no interference with amoeboid movement.

Conductivity water increases the size, number, and rate of contraction of contractile vacuoles, which suggests that they may function in maintaining an osmotic gradient as well as in the elimination of metabolic waste.
A study of the tonsillar developments in the lingual region of anurans
Authors: Myers Mabel A.
Published: February 2005

In this study the problem of the tonsil is considered in anurans. The common toad (family Bufonidae) is used as the type, and representative species of the other families are compared.

In each species representative stages beginning before transformation were selected, and the lingual region of each was sectioned. Some thyroid‐fed toad tadpoles which had prematurely transformed were examined. The investigations led to the following conclusions:

Accumulations of lymphocytes occur in all the families except Hylidae.

A pair of tonsils located on either side of the tongue appear before transformation in Bufo, and persist, increasing in size through old age.

This pair has its developmental origin at or near the cephalic end of pouch II. In no other species examined do the tonsils appear as early; in almost all forms the accumulations are inconstant in occurrence, as are also some in Bufo.

The cells of the ‘tonsils’ are lymphocytes of varying sizes. They arise from the mesenchyme; later their accumulations become sites of lymphopoiesis.

This type of lympho‐epithelial mass is simple in structure and has a greatly thickened epithelium, due to extensive infiltration by lymphocytes. In the connective tissue the vascular supply is abundant.

The differentiation of lymphocytes may be due to a factor of strain, arising through adjustments made during metamorphosis.

Thyroid‐fed toad tadpoles transform, apparently without developing tonsils.
Reactions of immature monkeys (Macacus rhesus) to injections of ovarian hormone
Authors: Allen Edgar
Published: February 2005

Series of injections of ovarian hormone have been made into normal and ovariectomized immature animals. Injections were made twice daily for twenty‐two days. The total dose exceeded 1000 rat units per animal.

Effects noted in the living animals were the appearance of reddening and swelling of the ‘sexual skin’ and change of the cell content of the vaginal smear to the interval type of the mature animal. Measurements made at operation, before and after injections, indicated considerable enlargement of both the cervix and body of the uterus. The thymus glands of the injected animals weighed significantly less than those of the controls. Histologic study of the genital tract showed extreme thickening of the vaginal walls, considerable growth of the uterine epithelium and glands, hypertrophy of the muscle layers of the uterus, and advanced differentiation of the epithelium of the uterine tubes.

The ovaries of the injected normal animal were smaller and contained fewer primordial and medium‐sized follicles than those of the controls. The presence of large numbers of atretic follicles, especially large flattened scars from former relatively well‐developed follicles also suggests a harmful effect of this amount of ovarian hormone upon follicular development. Several stages of elimination of ova from polyovular follicles were also observed. There was marked growth in the ducts and an increase in the number of alveoli of the mammary glands.
Chromosomal variations correlated with geographical distribution in circotettix verruculatus (Orthoptera)
Authors: Helwig Edwin R.
Published: February 2005

The first spermatocytes of Circotettix verruculatus have eleven chromosomes. Five of these are regularly atelomitic and three are telomitic. The other three are variable and may have both diads telomitic, both atelomitic, or one diad telomitic while the other is atelomitic. The locus of fiber attachment and, consequently, the form of the chromosome are constant for the individual. The point of fiber insertion is known to be inherited according to mendelian principles, and is, therefore, a measure of the frequencies of the telomitic and atelomitic diads in a group of individuals.

Samples of five geographically different populations were studied with respect to the proportion of atelomitic to telomitic diads in the three variable tetrads. The proportion for each of the three chromosomes was compared with that for the corresponding tetrads from the other localities. The data were subjected to statistical analysis, and significant differences between some of the groups were found in the proportion of atelomitic to telomitic diads in corresponding chromosomes.

A possible correlation between these cytological differences among the various localities and the formation of geographical races or subspecies are discussed. An inversion of the portion of a chromosome, which causes an apparent, although not a real, change in the locus of fiber attachment, is suggested as the origin of atelomitic chromosomes. The effect which heteromorphism of synaptic mates may have on crossing‐over is considered.
A histological study of the parathyroids in the Anura
Authors: Waggener Roy A.
Published: February 2005

The parenchymal cells in the parathyroids of Rana catesbeiana (Shaw) are found to undergo a very curious cyclic change. The cytoplasm is broken down by a process of cytolysis. The nuclei are decomposed by chromatolysis and pycnosis. The entire parenchyma is finally liquefied, except for a layer of cells lining the capsule.

The parathyroid body is reconstructed by young cells which are produced from rather definite growth centers. The process of regeneration begins some time before cytolysis is completed and continues until the entire organ is restored.

The cytolytic and regenerative processes transpire in such sequence that the amount of apparently healthy tissue present at any one time is a rather large portion of the total mass normally present.

The relationship between the parenchymal tissue and the stroma of the parathyroid is described.
The influence of thyroid deficiency on the structure and epinephrin content of the adrenal gland of the albino rat (Mus norvegicus albinus)
Authors: Sun Tson Pen
Published: February 2005

It was found that thyroid deficiency in the albino rat (Mus norvegicus albinus) is followed by a trend to increased concentration of epinephrin in the suprarenals. The basis of this lies in the relatively greater retrogression of the cortex as contrasted with the medulla which becomes a relatively greater proportion of the organ as a whole. Confirmatory evidence is found in cell counts per unit area and the part of the disappearance of lipoid from the cortical cells of the suprarenals of thyroidless animals.
Maturation of the male germ cells in the rat
Authors: Swezy Olive
Published: February 2005

Maturation of the male germ cells in the rat shows some slight modifications of the typical procedure in sex cells, a distinct and rather prolonged synapsis occurring before synizesis and a confused stage immediately after it. The clumping in synizesis is not extreme. In the mixed strain of rats both twenty‐one and thirty‐one tetrads appear in the late diakinesis. This procedure in the male resembles the maturation of the oocytes in only two points, the beginning of the process, the deutobroch nuclei, and the end of it when the haploid number of chromosomes take their places on the spindle.
The parietal fossa and related structures in the plagiostome fishes
Authors: Norris H. W.
Published: February 2005

The parietal fossa or pit is situated in the middorsal line between the ear capsules. From its floor four (sometimes only two) apertures lead into the ear capsules. The anterior apertures are the foramina of the endolymphatic ducts; the posterior ones are the fenestrae. Through the fossa each endolymphatic duct passes from its formen to its external aperture in the dorsal integument, describing in its course a loop with the convexity directed anteriorly. The part of the duct involving the loop is enlarged into an endolymphatic pouch. Into the angle of this loop a small muscle is inserted which is a continuation of the anterior trunk muscles, or one taking a more lateral origin from the edge of the fossa. The fenestra may or may not be closed by a definite fenestral membrane. The posterior semicircular canal (posterior utriculus) bears a peculiar relation to the fenestra. The endolymphatic pouch, like the sacculus, contains otoconia, and sometimes siliceous sand grains. Various functions have been assigned to the endolymphatic organ. There is no convincing experimental evidence as to its significance.