bluuebunny/crossref_metadata_2025 huggingface dataset:
Concentrator and lens models for calculating the impulse response on IR‐wireless indoor channels using a ray‐tracing algorithm
Authors: Rodríguez Pérez Silvestre , Pérez Jiménez Rafael , González Hernández Oswaldo B. , Rabadán Borges José Alberto , Rodríguez Mendoza Beatriz
Published: January 2003

This paper presents concentrator and lens models for the detector and emitter, respectively, upon which a Monte Carlo ray‐tracing algorithm allows the evaluation of impulse response on infrared (IR) wireless indoor channels. We also present computer simulation results that show the effects of concentrator FOV and reception direction on the impulse response, received optical power, and channel rms delay spread, which allow us to propose structures for angle‐diversity receivers. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 262–267, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10738
Artificial magnetic conductors as reflectors for low sidelobe antenna arrays
Authors: Zhang Ying , Younis Marwan , Fischer Christian , von Hagen Jürgen , Wiesbeck Werner
Published: January 2003

Noticeably lower sidelobe levels in aperture‐coupled patch antenna arrays are achieved by an artificial perfect magnetic conductor (PMC) reflector rather than a traditional reflector. The reduction of parallel‐plate modes is analyzed. The patterns of the antenna array are measured with both a perfect electric conductor (PEC) reflector and a PMC reflector. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 267–270, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10739
Design of LNA at 2.4 GHz using 0.25 μm CMOS technology
Authors: Yang Xiaomin , Wu Thomas X. , McMacken John
Published: January 2003

Two 2.4‐GHz fully integrated CMOS low‐noise amplifiers (LNA) have been designed in a 0.25‐μm CMOS process. Design procedure and simulation results are presented in this paper. In the design of differential LNA, a novel idea is proposed so that the die area can be greatly reduced. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 270–275, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10740
Analysis of rectangular microstrip patch antennas on spherical structures
Authors: Sipus Zvonimir , Burum Niksa , Bartolic Juraj
Published: January 2003

In this paper, the input impedance and radiation pattern of spherical rectangular patch antennas are studied. The electric field integral equation is numerically solved by applying the method of moments where the multilayer spherical structure is rigorously considered, using the spectral‐domain algorithm for calculating Green's functions. In order to avoid numerical problems, a modified vector–Legendre transformation and normalized Legendre polynomials are defined and applied to the solution procedure. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 276–280, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10741
Propagation of a femtosecond laser pulse of a few optical oscillations in a uniaxial crystal
Authors: Hovhannisyan David
Published: January 2003

Using the method of unidirectional waves, we numerically solve a wave equation that describes the vector propagation of a femtosecond laser pulse of few optical cycles in a uniaxial crystal. Propagation of the pulse in the direction normal to the optical axis is studied, taking into account both the second‐ and third‐order nonlinearity of the crystal. Conversion efficiency as a function of crystal length, pump intensity, and pulse duration is studied. As an example, the propagation of a femtosecond laser pulse of τ = 10 fs duration at λ = 810 nm in a 12‐μm thick LiNbO3 crystal is numerically modeled. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 280–285, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10742
Coupling reduction between groove‐backed antennas
Authors: Yang Dong I. , Eom Hyo J. , Ra Jung W.
Published: January 2003

In this paper, the behavior of radiation and coupling reduction between two groove‐backed antennas is investigated. An electric line current is placed inside a rectangular groove in a perfectly conducting plane. Fourier transform and series techniques are employed to express the scattered field. Boundary conditions are enforced to obtain simultaneous equations for the discrete modal coefficients, which are then solved in order to calculate the radiated and coupled fields. The behavior of coupling reduction and radiation is discussed in terms of the antenna geometries. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 285–289, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10743
An nth‐order expression of the frequency domain impulse response of a synthetic aperture system and its applications
Authors: Gimeno‐Nieves E. , Lopez‐Sanchez J. M. , Bara M.
Published: January 2003

A new compact generalized formula of the impulse response of a synthetic aperture system in the frequency domain is presented. This expression affords an improvement of chirped radar and sonar imaging techniques in wide‐band high‐resolution configurations. A new accurate and efficient chirp‐scaling algorithm has been reformulated by including an nth‐order expansion. This new algorithm has been implemented and tested, yielding more accurate images than the conventional CSA. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 289–292, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10744
Capacitively‐loaded CPW shunt stub notch filters
Authors: Singh R. Baliram , Weller T. M. , Smith M. C. , Culver J. W.
Published: January 2003

This paper describes optimal coplanar waveguide (CPW) 2nd harmonic notch filters that utilize metal‐insulator‐metal (MIM) capacitors at each discontinuity, eliminating the need for conventional air‐bridges and significantly reducing the filter footprint. The circuits were fabricated on a high resistivity, 400 μm‐thick silicon substrate. Theoretical and experimental data for 42 GHz notch filters employing straight and bent shunt stubs are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 292–295, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10745
A novel frequency‐reconfigurable patch antenna
Authors: Xiao Shaoqiu , Wang Bing‐Zhong , Yang Xue‐Song
Published: January 2003

A novel frequency‐reconfigurable patch antenna is proposed and analysed using the finite‐difference time‐domain (FDTD) method. The simulated results indicate that the antenna is capable of shifting its operating frequency over a one‐octave bandwidth from 0.6 GHz to 1.2 GHz with the radiation pattern essentially unaffected by the frequency tuning. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 295–297, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10746
An athermal, hitless, tunable add‐drop module with inherently integrated power controller
Authors: Yin Shizhuo , Purwosumarto Purwadi , Su Weihong , Luo Claire , Sheng Yunlong
Published: January 2003

In this paper, a small‐footprint, athermal, hitless, reconfiguration‐optical add‐drop module with an inherently integrated optical power controller is presented. This unique multiplexer cannot only add‐drop any wavelength among designed wavelength channels without interrupting through traffic, but can also dynamically control the output power of an add‐drop channel. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 297–300, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10747
A 3D posteriori error estimator for FEM solution of electromagnetic problems
Authors: Ezzedine Tahar , Kouki Ammar B. , Bouallegue Ammar
Published: January 2003

We introduce a new method for computing a posteriori error estimator suitable for the finite‐element solution of 3D electromagnetic problems. We take into account both the error due to discontinuity on the elements' faces as well as the volumetric error. We demonstrate the efficiency of the error estimator. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 300–302, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10748
Accurate determination of Q factors of a quasi‐optical resonator
Authors: Kapilevich B. , Faingersh A. , Gover A.
Published: January 2003

This paper presents a novel approach to measuring the Q factors of a quasi‐optical resonator used in a free electron maser (FEM) operating at 100 GHz. Estimation of the Q factors is based on measuring the reflection coefficient in the vicinity of resonance frequencies. The unknown parameters (attenuation constant and coupling inductance) are determined from the numerical solution of a nonlinear system of two equations. As an example, the Q factors of a quasi‐optical resonator, based on the shorted‐line waveguide section, have been determined using the proposed method. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 303–306, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10749
A transmission line model applied to shaped slot dielectric‐filled waveguide antennas
Authors: Chainon S. , Himdi M.
Published: January 2003

This paper presents an extension of the so‐called transmission line model method (TLMM) applied to shaped slot dielectric‐filled waveguide antennas (SDFWAs), especially the L‐shaped slot. This radiating longitudinal slot is fed by a transversal slot used as a coupling element; their association is shaped like the letter L. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 306–310, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10750
Dual‐mode double‐ring resonator for microstrip band‐pass filter design
Authors: Liu Ji‐Chyun , Cheng Chin‐Shen , Yao Leo
Published: January 2003

A novel design of a dual‐mode resonator with double‐ring structure for a band‐pass filter is presented in this paper. Voltage/current couplings between the two rings are proposed based on a mode chart. Because each ring exhibits dual‐mode responses, they determine the range of operation; that is, the inner/outer rings depict the upper/lower frequencies of the pass band, respectively. This is an alternative approach to improve the bandwidth of the conventional dual‐mode ring resonator. Experimental results are presented and discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 310–314, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10751
Analysis of single‐layered multiconductor transmission lines using the Fourier transform and mode‐matching techniques
Authors: Park Hyun H. , Kwon Jong‐Hwa , Lee Jae W. , Eom Hyo J.
Published: January 2003

The Fourier transform and mode‐matching techniques are applied in the analysis of single‐layered multiconductor transmission lines with finite strip thickness. Based on a quasi‐static approach, the problem is formulated to obtain simultaneous equations for the modal coefficients of the potential distributions between transmission lines. Residue calculus is applied to represent the potential distributions in convergent series form. Analytical closed‐form expressions for the self and mutual capacitances are developed. Numerical computations are performed to compare the validity of the proposed with other published data. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 315–317, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10752
Wavelength‐tunable actively mode‐locked fiber‐ring laser using an F‐P LD as a modulator and a tunable comb filter
Authors: Zhao Chun‐Liu , Ma Ning , Yuan Shuzhong , Yang Shiquan , Kai Guiyun , Zhao Qida , Xiaoyi Dong
Published: January 2003

A wavelength‐tunable actively mode‐locked erbium fiber ring laser is demonstrated using an F–P semiconductor as a modulator and a tunable comb filler. Continuous wavelength tuning is enlarged to 6 nm by successively choosing different cavity modes of the F–P LD and tuning the temperature of the LD. The ∼2‐GHz frequency pulse is generated with a side‐mode suppression ratio over 30 dB in the entire tuning range. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 318–320, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10753
Application of CAD load‐pull techniques in mixer design
Authors: Velazquez Arturo , Lazaro Antonio , Pradell Luis , Comeron Adolfo
Published: January 2003

This work describes the application of a commercial CAD software to implement load‐pull techniques in the design of microwave mixers. This method is used to generate conversion‐loss regions when a diode is pumped and operated as a mixer circuit. Emphasis is placed on the inclusion of image and out‐of‐band terminations to optimize the operating conditions required to obtain low conversion loss. An X‐band 5‐dB conversion‐loss mixer is designed and tested using this method. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 320–323, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10754
Spherical bodies present within the germinal vesicle of Podarcis sicula previtellogenic oocyte derive from the temporaneous inactivation of ribosomal genes
Authors: Loredana Ricchiari , Marina Prisco , Stefania Tammaro , Chiara Maria Motta , Isabella Pugliese , Piero Andreuccetti
Published: January 2003

In the present paper we have investigated the origin of the spherical bodies (SBs) present within the germinal vesicle of about 400 μm previtellogenic oocytes in the lizard Podarcis sicula. In particular, we have attempted to clarify whether they derive from the single, large nucleolus present in early diplotenic oocyte as a consequence of ribosomal gene inactivation. We have, therefore, experimentally induced a decrease in rRNA synthesis by injecting animals with D‐galactosamine or by exposing them to low temperatures. The investigations carried out have demonstrated that both treatments induce significant ultrastructural changes in the nucleolar apparatus and in particular fragmentation and the formation of SBs comparable to those observed in germinal vesicle under physiological conditions. These results indicate that the germinal vesicle of Podarcis sicula has a nucleolar apparatus that significantly changes its aspect according to its functional status and reveal that in this species, the time course of rRNA synthesis is peculiar with respect to any other vertebrate oocyte studies so far. Mol. Reprod. Dev. 64: 321–328, 2003. © 2003 Wiley‐Liss, Inc.
Ultrastructural modifications in bovine oocytes maintained in meiotic arrest in vitro using roscovitine or butyrolactone
Authors: Lonergan Patrick , Faerge Inger , Hyttel Poul Maddox , Boland Maurice , Fair Trudee
Published: January 2003

Butyrolactone‐I (BL‐I) and roscovitine (ROSC) are selective inhibitors of the cyclin‐dependent kinases, and both have been shown to reversibly inhibit meiotic resumption in cattle oocytes for 24 hr without having a negative affect on subsequent development to the blastocyst stage. The aim of the present study was to describe the morphological changes occurring in fully grown immature and in vitro matured bovine oocytes following exposure to either BL‐I or ROSC for 24 hr at concentrations known to be consistent with normal development. Immature bovine cumulus oocyte complexes, recovered from the ovaries of slaughtered heifers, were incubated for 24 hr in the presence of one of the inhibitors. They were then either fixed immediately and processed for transmission electron microscopy (TEM), or cultured for a further 24 hr in the absence of the inhibitor, in conditions permissive to maturation, and subsequently processed for TEM. A control group of oocytes were processed for TEM immediately upon recovery (0 hr) or following in vitro maturation (IVM) for 24 hr. In general, incubation with either inhibitor disrupted the integrity of the surrounding cumulus cells and affected their subsequent expansion during IVM. Within the oocyte cytoplasm, swelling of the mitochondrial cristae was immediately noticeable following meiotic inhibition in the presence of ROSC, while an increased population of pleomorphic mitochondria and mitochondria with electron lucent matrices following BL‐I treatment was not observed until after the subsequent IVM period. Both inhibitors caused degeneration of the cortical granules, effectively reducing the population, most noticeably following IVM. At the level of the nucleus, both inhibitory treatments caused convolution of the nuclear membrane, furthermore, aberrant structures were observed within the nucleoplasm of ROSC‐treated cumulus oocyte complexes (COCs). In conclusion, while it has been shown that inhibition of meiotic resumption using specific cdk inhibitors is possible and that such oocytes are capable of undergoing maturation, fertilization, and early embryo development, there is as yet no definitive proof that oocytes treated in this way can ultimately give rise to normal offspring. We have shown here that some modifications are induced in the oocytes at the ultrastructural level. Whether or not these modifications are compatible with normal gestation and the birth of a live calf remain to be elucidated. Mol. Reprod. Dev. 64: 369–378, 2003. © 2003 Wiley‐Liss, Inc.
Increase in macrophages in the testis of cathepsin a deficient mice suggests an important role for these cells in the interstitial space of this tissue
Authors: Korah Nadine , Smith Charles E. , D'Azzo Alessandra , El‐Alfy Mohammed , Hermo Louis
Published: January 2003

Cathepsin A (PPCA) is a lysosomal carboxypeptidase that functions as a protective protein for α‐neuraminidase and β‐galactosidase in a multienzyme complex. In the present study, the testes of PPCA −/− mice from 2 to 10 months of age were compared with those of their wild type counterparts. While germ and Sertoli cells appeared comparable in appearance and distribution, the mean profile area of seminiferous tubules showed a significant decrease between wild type and PPCA −/− mice, suggesting changes to the seminiferous tubules and their contents. In addition, macrophages in the interstitial space (IS) of PPCA −/− mice were large, spherical, and filled with pale lysosomes, unlike those seen in wild type mice, and a quantitative analysis of their frequency per unit area of IS in PPCA −/− mice revealed a significant increase compared to that of wild type mice; this was also the case for their mean profile area. Absence of mitotic figures, cycling cells, or degenerating figures in the IS suggests that the major recruitment of macrophages appears to be from the circulation. In the IS, Leydig cells also showed an accumulation of large pale lysosomes in PPCA −/− mice, and their frequency also increased significantly as compared to wild type mice. In the electron microscope, a close association of Leydig cell microvilli with the surface of macrophages was pronounced in PPCA −/− mice. Since macrophages and Leydig cells interact by secreting various factors between each other, and considering the fact that Leydig cells show an accumulation of large pale lysosomes in PPCA −/− mice, it is suggested that macrophages accumulate as a result of abnormalities occurring in Leydig cells. Taken together, the data on increase in frequency of macrophages suggests important functions for these cells in both wild type and PPCA −/− mice. Mol. Reprod. Dev. 64: 302–320, 2003. © 2003 Wiley‐Liss, Inc.
Expression of retinol‐binding protein and cellular retinol‐binding protein in the bovine ovary
Authors: Brown J. Alison , Eberhardt Dawn M. , Schrick F. Neal , Roberts Mary P. , Godkin James D.
Published: January 2003

Retinol (vitamin A) is essential for reproduction, and retinoids have been suggested to play a role in ovarian steroidogenesis, oocyte maturation, and early embryonic development. Retinol is transported systemically and intercellularly by retinol‐binding protein (RBP). Within the cell, cellular retinol‐binding protein (CRBP) functions in retinol accumulation and metabolism. Since the actions of retinoids are mediated, in part, by retinoid‐binding proteins, the objective of this study was to investigate cell‐specific expression of RBP and CRBP in the bovine ovary. Immunocytochemical analysis (ICC) localized RBP to the thecal and granulosa cell layers of antral and preantral follicles with the most intense staining in the cells of large, healthy follicles. The tunica adventitia of arterial blood vessels also exhibited RBP staining. Immunostaining of CRBP was most intense in the granulosa cells of preantral follicles and present, but diminished, in thecal and granulosa cells of antral follicles. Within the corpus luteum, both proteins were observed in large luteal cells, but only RBP was observed in small luteal cells. Northern blot analysis demonstrated that thecal and granulosa cells from antral follicles and luteal tissue expressed RBP and CRBP mRNA. Synthesis and secretion of RBP by thecal cells, granulosa cells, and luteal cells were demonstrated by immune‐complex precipitation of radiolabeled RBP from the medium of cultured cells or explants, followed by SDS–PAGE and fluorography. Follicular fluid was collected from small (<5 mm) and large (8–14 mm) follicles, pooled according to follicular size, and analyzed for retinol, RBP, estradiol‐17β, and progesterone. Concentrations of retinol, RBP, and estradiol were greater in the fluid of large follicles. Results demonstrate retinoid‐binding protein expression by bovine ovaries and provide physical evidence that supports the concept that retinoids play a role in ovarian function. Mol. Reprod. Dev. 64: 261–269, 2003. © 2003 Wiley‐Liss, Inc.
Polychlorinated biphenyls affect gene expression in the rabbit preimplantation embryo
Authors: Kietz Silke , Fischer Bernd
Published: January 2003

Polychlorinated biphenyls (PCBs) have been shown to be embryotoxic. The mechanism(s) of action is not clearly understood. The toxic effects could be either direct or indirect. Furthermore, PCB congeners vary in their toxic potential. They can be classified in coplanar PCBs binding to the transcription factor aryl hydrocarbon receptor (AhR), which induce subsequent changes in gene expression, and noncoplanar PCBs exhibiting AhR‐independent effects. In order to investigate possible mechanisms, 5 and 6 days old preimplantation rabbit embryos were exposed in vitro to low levels of coplanar (PCB 77, 126, and 169) or noncoplanar PCBs (PCB 28, 52, 101, 118, 138, 153, and 180). The PCB effects were studied by semiquantitative RT‐PCR analysis of AhR target genes (cytochrome P450 (CYP) 1A1, 1A2, UDP‐glucuronosyl transferase 1, glutathione S‐transferase π1 and aldehyde dehydrogenase) and dioxin‐responsive genes (IL 1β, PAI 2, Cox 2, TGFα, EGF, erbB 1–4, c‐fos, c‐jun, HSP 90, cyclophilin 40), and by differential display (DD) RT‐PCR. CYP 1B1 mRNA and AhR protein were localized by in situ hybridization and immunohistochemistry, respectively. From the AhR target genes studied only CYP 1B1, and cyclooxygenase 2 showed an increase in mRNA levels after coplanar and noncoplanar PCB. Interleukin 1β and plasminogen activator inhibitor 2 were downregulated. CYP 1B1 mRNA showed a stage specific inducibility at day 6, but not at day 5. By DD RT‐PCR we identified six new genes previously not reported to be regulated by PCBs. The mRNAs encoding the subunits 1, 2, 4, and 5 of the NADH ubiquinone oxidoreductase and β‐globin showed a decrease, whereas trichohyalin mRNA was increased after PCB exposure. Coplanar and noncoplanar PCB congeners elicited similar responses on the mRNA levels of the studied genes. Exposure to coplanar PCBs did not result in the AhR being translocated to the nucleus. Our results show that (i) PCBs induce changes in gene expression in rabbit day 5 and 6 preimplantation embryos and imply (ii) that the transcriptional changes observed were not mediated by the nuclear AhR. Mol. Reprod. Dev. 64: 251–260, 2003. © 2003 Wiley‐Liss, Inc.
Acquisition of transcriptional competence in the 1‐cell mouse embryo: Requirement for recruitment of maternal mRNAs
Authors: Aoki Fugaku , Hara Kentaro T. , Schultz Richard M.
Published: January 2003

We previously suggested that the transcriptional machinery is rate‐limiting for genome activation in the preimplantation mouse embryo (Aoki et al., 1997: Dev Biol 181:296‐307), suggesting that genome activation requires the synthesis of some proteins following fertilization. To test this hypothesis, transcriptional activity was measured in 1‐cell embryos in which protein synthesis was inhibited by cycloheximide from the time shortly after insemination. Transcription in both the male and female pronuclei, as assessed by BrUTP incorporation, was markedly inhibited when assayed 14 hr post‐insemination. This result suggested that newly synthesized proteins derived from maternally recruited mRNA, and not maternally derived proteins that were post‐translationally modified following fertilization/egg activation, were critical for the acquisition of transcriptional competence. To test this hypothesis, mobilization of maternally recruited mRNAs was inhibited by treating the embryos with 3′‐deoxyadenosine (3′‐dA), which prevents polyadenylation of mRNA. The results demonstrated that the transcriptional activity was markedly decreased in the embryos cultured with 2 mM 3′‐dA, whereas 3′‐deoxyguanosine had little inhibitory effect, and suggest that recruitment of maternal mRNAs is essential for acquisition of transcriptional competence. Mol. Reprod. Dev. 64: 270–274, 2003. © 2003 Wiley‐Liss, Inc.
Sperm mediated gene transfer in pig: Selection of donor boars and optimization of DNA uptake
Authors: Lavitrano Marialuisa , Forni Monica , Bacci Maria Laura , Di Stefano Carla , Varzi Vincenzo , Wang Hongjun , Seren Eraldo
Published: January 2003

Transgenic animals are produced primarily by microinjecting exogenous DNA into the male pronuclei of a zygote. Microinjection is successful in mice but not efficient in farm animals, limiting its general utility. We have pursued an alternative technology for producing transgenic animals: Sperm Mediated Gene Transfer (SMGT). Based on our finding that sperm cells bind and internalize exogenous DNA, we used sperm as a vector for transmitting, not only their own DNA, but also, the exogenously‐introduced gene of interest to the zygote. SMGT is highly efficient (up to greater than 80%) and relatively inexpensive; it can be used in species refractory to microinjection, whenever reproduction is mediated by gametes. In this report, we describe the procedure for selection of sperm donors and optimization of DNA uptake that are the key steps for the successful outcome of SMGT. We found that the nominal parameters that boar sperm should possess to serve as a good vector for exogenous DNA are the quality of semen based on standard parameters used in conventional animal breeding programs (volume, concentration, presence of abnormal sperm cells, motility at time of collection, and high progressive motility after 2 hr) and the ability of the sperm cells to take up and internalize exogenous DNA. The results described provide significant advances in SMGT technology applied to pigs, so that transgenic pigs can be efficiently obtained. Mol. Reprod. Dev. 64: 284–291, 2003. © 2003 Wiley‐Liss, Inc.
Expression of growth hormone and its transcription factor, Pit‐1, in early bovine development
Authors: Joudrey E.M. , Lechniak D. , Petrik J. , King W.A.
Published: January 2003

During bovine embryogenesis, bovine growth hormone (bGH) contributes to proliferation, differentiation, and modulation of embryo metabolism. Pituitary‐specific transcription factor‐1 (Pit‐1) is a transcription factor that binds to promoters of GH, prolactin (PRL), and thyroid‐stimulating hormone‐beta (TSHβ) encoding genes. A polymorphism in the fifth exon of the bGH gene resulting in a leucine (Leu) to valine (Val) substitution provides an Alu I restriction site when the Leu allele is present. To determine the onset of embryonic expression of the bGH gene, oocytes derived from ovaries homozygous for Leu alleles were fertilized in vitro with spermatozoa obtained from a Val homozygote. For each developmental stage examined, three separate pools of embryos composed of approximately 100 cell samples underwent RNA isolation, reverse transcription to cDNA, and amplification by nested PCR (nPCR). Bovine GH gene transcripts were identified at 2‐ to 4‐cell (n = 162), 8‐ to 16‐cell (n = 73), morulae (n = 51), and blastocyst (n = 15) stages. Likewise, transcripts for Pit‐1 were detected at 2‐cell (n = 125), 4‐cell (n = 114), 8‐cell (n = 56), 12‐to‐32‐cell (n = 32), morulae (n = 68), and blastocyst (n = 14) stages. After digestion with Alu1, bGH cDNA was genotyped by restriction fragment length polymorphism (RFLP) analysis. Bovine GH mRNA was present in all pools of stages examined. Both Leu and Val alleles (maternal and paternal) were only detected in pools of embryos that had reached 8‐ to 16‐cell stage. Results suggest that transcription of the bGH gene begins at the 8‐ to 16‐cell stage in bovine embryos, possibly under control of the transcription factor, Pit‐1, and that RFLP analysis of the bGH gene can be used to determine parental origin of transcripts in early embryonic development. Mol. Reprod. Dev. 64: 275–283, 2003. © 2003 Wiley‐Liss, Inc.
Cleavage stage porcine embryos may have differing developmental requirements for karyopherins α2 and α3
Authors: Cabot Ryan A. , Prather Randall S.
Published: January 2003

Numerous cellular proteins are able to localize to the nucleus due to the fact that they possess a nuclear localization signal (NLS) in their amino acid sequence. Nuclear localization sequences recognized by the importin α/β heterodimer are found in cellular proteins capable of performing many diverse functions, ranging from chromatin remodeling to cell cycle regulation. Evidence has been presented that suggests individual importin α homologues are present at varying levels in different adult tissues. Other data have shown that specific subsets of NLSs found in different cellular proteins are recognized by individual importin α homologues with varying affinities. This evidence led us to hypothesize that due to the specific cargoes they carry, the mammalian embryo has different developmental requirements for individual importin α homologues. The results of the studies presented here indicate that importin α/β‐mediated import occurs throughout early cleavage in the porcine embryo, as determined by a reporter protein microinjection assay, and that multiple importin α homologues are present throughout early cleavage, as determined by immunocytochemical analysis. An RNA interference approach was used in an attempt to determine the developmental requirements for specific importin α homologues during early cleavage in the porcine embryo. Results from this study showed that fertilized porcine embryos injected with double stranded RNA (dsRNA) corresponding to the importin α homologue karyopherin α3 had significantly fewer nuclei following four days of culture than did embryos injected with dsRNA for another importin α homologue, karyopherin α2, or two control groups. This is the first report indicating that mammalian embryos may have differential developmental requirements for specific nuclear trafficking pathways. Mol. Reprod. Dev. 64: 292–301, 2003. © 2003 Wiley‐Liss, Inc.
Instability of crab vitellogenin and its immunological relatedness with mammalian atherogenic lipoproteins
Authors: Warrier Sudha R. , Subramoniam T.
Published: January 2003

Vitellogenesis is the process of accumulation of vitellogenin (Vg) in rapidly growing oocytes of oviparous animals and its' subsequent transformation into lipovitellin (Lv). Lipovitellin, which forms the major yolk protein, serves as a principal nutrient reserve for the developing embryo. In the present study, Vg and Lv were purified from the hemolymph and ovary, respectively of the crab Scylla serrata by gel filtration followed by preparative gel electrophoresis. It was observed that purified Vg, but not Lv, possessed an intrinsic protease activity with which it underwent autoproteolysis giving rise to several smaller proteins. Furthermore, urea‐mediated unfolding studies by UV‐spectral analysis revealed clearly that Vg was easily disrupted by urea whereas Lv was resistant. Taken together, these results suggest that although Lv had a stable conformation, its precursor Vg was labile and highly sensitive to degradation. Another aspect that was investigated in the present study was the immunological kinship of crab Vg and Lv to mammalian atherogenic lipoproteins, the low density lipoprotein (LDL), very low density lipoprotein (VLDL), and apolipoprotein B (apoB). By Western blot analysis, it was demonstrated that crab Vg and Lv were immunoreactive to antibodies to human LDL, VLDL, and apoB. These observations suggest the existence of common epitope recognition sites in crab Vg and mammalian lipid transferring proteins. This corroborates well with our earlier study on the recognition of crab Vg receptor by mammalian lipoproteins. Mol. Reprod. Dev. 64: 329–340, 2003. © 2003 Wiley‐Liss, Inc.
Apoptosis during spermatogenesis in the spotted ray Torpedo marmorata
Authors: Prisco Marina , Liguoro Annamaria , Comitato Raffaella , Cardone Anna , D'Onghia Barbara , Ricchiari Loredana , Angelini Francesco , Andreuccetti Piero
Published: January 2003

This article is a cytological and molecular investigation on the occurrence of apoptosis during spermatogenesis in Torpedo, a cartilaginous fish characterised by a typical cystic testis. Using DNA fragmentation and Bak gene expression, it demonstrated that germ cells undergo apoptosis only at the stages of spermatocyte and spermatid, and degeneration also involves Sertoli but not Leydig cells. In immature cysts, this cellular process probably occurs when the ratio of germ cells to the only Sertoli cell (SC) forming the spermatoblast changes. Apoptosis also takes place in mature cysts after sperm release to eliminate most of the SCs. Few of them, however, become cytoplasts and probably continue secreting androgens so as to control the final events of spermatogenesis, i.e., passage of spermatozoa through the ductus deferentes. Finally, the present investigation demonstrated that, in Torpedo testis, Bak mRNA is expressed during spermatogenesis, thus suggesting that the mitochondrial pathway might be active. This observation in one of the oldest vertebrate classes indicates that, in all vertebrates, the apoptotic process during spermatogenesis is conserved, contributing to testicular homeostasis. Mol. Reprod. Dev. 64: 341–348, 2003. © 2003 Wiley‐Liss, Inc.
Glucose‐ and fructose‐induced dog‐sperm glycogen synthesis shows specific changes in the location of the sperm glycogen deposition
Authors: Palomo Maria J. , FernÁndez‐Novell Josep M. , Peña Alejandro , Guinovart Joan J. , Rigau Teresa , Rodríguez‐Gil Joan E.
Published: January 2003

Immunocytochemistry of glycogen deposition in dog sperm from fresh ejaculates showed that 53.7% of the population had glycogen at the midpiece, whereas 27.3% of the whole population accumulated glycogen only in the post‐acrosomal region of the head. A similar distribution was observed when glycogen synthase, the enzyme which controls glycogen deposition, was studied. Incubation of spermatozoa with fructose increases the intracellular glycogen levels in a time‐ and concentration‐dependent manner. Moreover, after incubation with 2 mM fructose for 30 min, 47.3% of the spermatozoa had glycogen located in both the midpiece and post‐acrosomal zone, 25.4% of the population showed the polysaccharide only in the midpiece, and 24.7% of the spermatozoa showed a uniform distribution of glycogen all over the cell. Similar results were observed after incubation with 10‐mM fructose. The distribution of glycogen synthase followed a similar pattern to that of glycogen. Incubation with glucose also induced a time‐ and concentration‐dependent increase of glycogen content, whereas incubation with 2 mM glucose for 30 min showed that the majority of the population (81.2%) had the glycogen distributed throughout either the midpiece or the midpiece and the post‐acrosomal zones together. There were practically no cells with a uniform glycogen distribution. Similar results were obtained after incubation with 10‐mM glucose, whereas glycogen synthase suffered a similar glucose‐induced distribution change. These results indicate that dog‐sperm glycogen metabolism is modulated by changes in the activity of their controlling enzymes and also by changes in the specific location places where glycogen synthesis is produced. Mol. Reprod. Dev. 64: 349–359, 2003. © 2003 Wiley‐Liss, Inc.
Developmental failure of hybrid embryos generated by in vitro fertilization of water buffalo (Bubalus bubalis) oocyte with bovine spermatozoa
Authors: Patil Shekhar , Totey Satish
Published: January 2003

The developmental potential of inter‐species hybrid embryos produced by in vitro fertilization of in vitro matured buffalo oocytes with bovine spermatozoa was studied with a view to investigate pre‐implantation embryo development and its gross morphology, early embryonic gene expression, and embryonic genome activation. Fertilization events with both buffalo and cattle spermatozoa were almost similar. Overall fertilization rate with cattle spermatozoa was 78.4% was not significantly different from that of buffalo spermatozoa (80.2%). Initial cleavage rate between buffalo and hybrid embryo was also similar, and there was no significant difference in their developmental rate till 8‐cell stage (26.0 ± 4.1 vs. 24.3 ± 4.8). However, only 5.3% of hybrid embryos developed into blastocyst stage compared to 21.7% in buffalo. mRNA phenotyping of insulin‐like growth factor family (Insulin, insulin receptor, IGF‐I, IGF‐I receptor, IGF‐II, and IGF‐II receptor) and glucose transporter isoforms (GLUT‐I, II, III, IV) in hybrid embryos clearly showed that these molecules were not expressed after 8‐cell stage onward. Similarly, as observed in buffalo embryos, incorporation of 35S‐methionine and 3H‐uridine could not be observed in hybrid embryos from 8‐cell stage onward. This suggests that the maternal‐zygotic genome activation did not occur in hybrid embryos. Differential staining also showed that the blastomere stopped dividing after 8‐cell stage. Collectively, these parameters clearly showed that there was developmental failure of hybrid embryos. Mol. Reprod. Dev. 64: 360–368, 2003. © 2003 Wiley‐Liss, Inc.
Improved perfusion‐weighted MRI by a novel double inversion with proximal labeling of both tagged and control acquisitions
Authors: Jahng Geon‐Ho , Zhu Xiao‐Ping , Matson Gerald B. , Weiner Michael W. , Schuff Norbert
Published: January 2003

A novel pulsed arterial spin labeling (PASL) technique for multislice perfusion‐weighted imaging is proposed that compensates for magnetization transfer (MT) effects without sacrificing tag efficiency, and balances transient magnetic field effects (eddy currents) induced by pulsed field gradients. Improved compensation for MT is demonstrated using a phantom. Improvement in perfusion measurement was compared to other PASL techniques by acquiring perfusion images from 13 healthy volunteers (nine women and four men; age range 29–64 years; mean age 45 ± 14 years) and second‐order image texture analysis. The main improvements with the new method were significantly higher image contrast, higher mean signal intensity, and better signal uniformity across slices. In conclusion, this new PASL method should provide improved accuracy in measuring brain perfusion. Magn Reson Med 49:307–314, 2003. © 2003 Wiley‐Liss, Inc.
In vivo time‐resolved quantitative motion mapping of the murine myocardium with phase contrast MRI
Authors: Streif Jörg U.G. , Herold Volker , Szimtenings Michael , Lanz Titus E. , Nahrendorf Matthias , Wiesmann Frank , Rommel Eberhard , Haase Axel
Published: January 2003

Myocardial motion of healthy mice and mice with myocardial infarction was assessed in vivo by phase contrast (PC) cine MRI. The imaging module was a segmented fast low angle shot (FLASH) sequence with velocity compensation in all three gradient directions. To accomplish additional motion encoding, the spin phase was prepared using bipolar gradient pulses, which resulted in a linear dependence between the voxel velocity and spin phase. This method provided accurate quantification of the velocity magnitude and direction of the murine myocardium at a spatial resolution of 234 μm and a temporal resolution of about 10 ms. The acquisition was EKG‐gated and the mice were anesthetized by inhalation of 1.5–4.0 vol.% isoflurane at 1.5 l/min oxygen flow. To validate the MRI measurements, an experiment with a calibrated rotating phantom was performed. Deviations between MR velocity measurements and optical assessment by a light detector were lower than 1.6%. During our study, myocardial motion velocities between 0.4 cm/s and 1.7 cm/s were determined for the healthy murine myocardium across the heart cycle. Areas with myocardial infarction were clearly segmented and showed a motion velocity which was significantly reduced. In conclusion, the method is an accurate technique for the assessment of murine myocardial motion in vivo. Magn Reson Med 49:315–321, 2003. © 2003 Wiley‐Liss, Inc.
Dynamic MRI reveals that the magnitude of the ischemia‐related enhancement in skeletal muscle is age‐dependent
Authors: Sbarbati Andrea , Marzola Pasquina , Nicolato Elena , Farace Paolo , Asperio Roberto M. , Lunati Ernesto , Fabene Paolo F. , Marzioni Daniela , Castellucci Mario , Capogrossi Maurizio C. , Osculati Francesco
Published: January 2003

This study was designed to evaluate the influence of age on the dynamic contrast‐enhanced MRI of ischemic tissue. A well‐established model of peripheral arterial insufficiency (i.e., the rat hindlimb ischemia after removal of femoral artery) in different age groups (i.e., young, presenescent, and senescent rats) was studied. The analysis of the MR signal demonstrated a marked accumulation of a contrast agent (Gd‐DTPA) in the ischemic leg (ischemia‐related enhancement, IRE). IRE was an age‐related event: 4‐month‐old rats showed a strong IRE while 12‐month‐old rats and 20‐month old rats showed a significantly reduced IRE in comparison to young animals. Histological analysis of the ischemic muscles revealed that there was no evidence of significant necrosis of the muscle tissue but only a weak interstitial fibrosis; CD31‐immunostaining revealed a preserved microcirculatory bed. Magn Reson Med 49:386–390, 2003. © 2003 Wiley‐Liss, Inc.
Detection of eye movements from fMRI data
Authors: Beauchamp Michael S.
Published: January 2003

Awake humans make eye movements with amplitudes and frequencies that depend on behavioral state and task. This poses two problems for functional magnetic resonance imaging (fMRI) studies that compare brain activity across tasks. First, motion of the eye in the orbit increases the variance of the MR signal in adjacent regions of the orbitofrontal cortex, hampering activation detection. Second, eye movements are associated with activity in a distributed network of brain areas, confounding comparisons of task activation. Direct measurement of eye movements in the scanner bore is possible with expensive and technically demanding equipment. A method is described that detects eye movements directly from MR data without the use of additional equipment. Changes in the MR time series from the vitreous of the eye were observed that correlated with eye movements, as measured directly with an infrared pupil tracking system. In each of 10 subjects, the variance of the MR time series from the eye vitreous was greater when the subject made eye movements than when the subject fixated centrally (average standard deviation (SD) 99.7 vs. 75.6, P = 0.001). The assessment of eye movements directly from fMRI data may be especially useful for retrospective and meta‐analyses. Magn Reson Med 49:376–380, 2003. Published 2003 Wiley‐Liss, Inc.
Visualization of myocardial microstructure using high‐resolution T imaging at high magnetic field
Authors: Köhler Sascha , Hiller Karl‐Heinz , Waller Christiane , Jakob Peter M. , Bauer Wolfgang R. , Haase Axel
Published: January 2003

The analysis of myocardial microstructure in vivo is important for the determination of myocardial contractility and function. The purpose of the present study was to demonstrate that high‐resolution T imaging has the potential to visualize the microstructure of beating, isolated rat hearts. To perform T imaging, a multiple gradient‐echo sequence was implemented on an 11.75 Tesla microscopy system. An in‐plane resolution of 78 μm and a slice thickness of 250 μm were achieved in 24 min. In comparison to histological sections, the T maps showed an excellent spatial correspondence to the myocardial fiber structure. To demonstrate the utility of this technique, morphologic alterations in myocardial microstructure were investigated in hearts with chronic myocardial infarction. Scar tissue and the extent of the infarcted region were clearly visualized and quantified using high‐resolution T imaging. Magn Reson Med 49:371–375, 2003. © 2003 Wiley‐Liss, Inc.
Renal and systemic pH imaging by contrast‐enhanced MRI
Authors: Raghunand Natarajan , Howison Christine , Sherry A. Dean , Zhang Shanrong , Gillies Robert J.
Published: January 2003

Perturbations of renal and systemic pH accompany diseases of the kidney, such as renal tubular acidosis, and the ability to image tissue pH would be helpful to assess the extent and severity of such conditions. A dual‐contrast‐agent strategy using two gadolinium agents, the pH‐insensitive GdDOTP5− and the pH‐sensitive GdDOTA‐4AmP5−, has been developed to generate pH maps by MRI. The renal pharmacokinetics of the structurally dissimilar pH‐insensitive contrast agents GdDTPA2− and GdDOTP5− were found to be similar. On that basis, and on the basis of similarity of structure and charge, the renal pharmacokinetics of GdDOTP5− and GdDOTA‐4AmP5− were assumed to be identical. Dynamic T1‐weighted images of mice were acquired for 1 hr each following boluses of GdDOTP5− and GdDOTA‐4AmP5−. The time‐varying apparent concentration of GdDOTP5− and the time‐varying enhancement in longitudinal relaxation rate following GdDOTA‐4AmP5− were calculated for each pixel and used to compute pH images of the kidneys and surrounding tissues. MRI pH maps of control mice show acidic regions corresponding to the renal papilla, calyx, and ureter. Pretreatment of mice with the carbonic anhydrase inhibitor acetazolamide resulted in systemic metabolic acidosis and accompanying urine alkalinization that was readily detected by this dual‐contrast‐agent approach. Magn Reson Med 49:249–257, 2003. © 2003 Wiley‐Liss, Inc.
Resolution enhancement in lung 1H imaging using parallel imaging methods
Authors: Heidemann R.M. , Griswold M.A. , Kiefer B. , Nittka M. , Wang J. , Jellus V. , Jakob P.M.
Published: January 2003

Resolution in 1H lung imaging is limited mainly by the acquisition time. Today, half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) sequences, with short echo time (TE) and short interecho spacing (Tinter) have found increased use in lung imaging. In this study, a HASTE sequence was used in combination with a partially parallel acquisition (PPA) strategy to increase the spatial resolution in single‐shot 1H lung imaging. To investigate the benefits of using a combination of single‐shot sequences and PPA, five healthy volunteers were examined. Compared to conventional imaging methods, substantially increased resolution is obtained using the PPA approach. Representative in vivo 1H lung images acquired with a HASTE sequence in combination with the generalized autocalibrating partially parallel acquisition (GRAPPA) method, up to an acceleration factor of three, are presented. Magn Reson Med 49:391–394, 2003. © 2003 Wiley‐Liss, Inc.