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Biomedical subjects

L E Perez

Publications and source records attributed to L E Perez.

11 recordsLinked to original sources
PubMed2001

Xenotransplantation of immunodeficient mice with mobilized human blood CD34+ cells provides an in vivo model for human megakaryocytopoiesis and platelet production.

The study of megakaryocytopoiesis has been based largely on in vitro assays. We characterize an in vivo model of megakaryocyte and platelet development in which human peripheral blood stem cells (PBSCs) differentiate along megakaryocytic as well as myeloid/lymphoid lineages in sublethally irradiated nonobese diabetic/severe combined immunodeficient (NOD-SCID) mice. Human hematopoiesis preferentially occurs in the bone marrow of the murine recipients, and engraftment is independent of exogenous cytokines. Human colony-forming units-megakaryocyte (CFU-MK) develop predominantly in the bone marrow, and their presence correlates with the overall degree of human cell engraftment. Using a sensitive and specific flow cytometric assay, human platelets are detected in the peripheral blood from weeks 1 to 8 after transplantation. The number of circulating human platelets peaks at week 3 with a mean of 20 x 10(9)/L. These human platelets are functional as assessed by CD62P expression in response to thrombin stimulation in vitro. Exogenous cytokines have a detrimental effect on CFU-MK production after 2 weeks, and animals treated with these cytokines have no circulating platelets 8 weeks after transplantation. Although cytokine stimulation of human PBSCs ex vivo led to a significant increase in CFU-MK, CD34+/41+, and CD41+ cells, these ex vivo expanded cells provided only delayed and transient platelet production in vivo, and no CFU-MK developed in vivo after transplantation. In conclusion, xenogeneic transplantation of human PBSCs into NOD/SCID mice provides an excellent in vivo model to study human megakaryocytopoiesis and platelet production.

Animals↗
PubMed2001

Mechanical testing of bioresorbable implants for use in metacarpal fracture fixation.

The purpose of this study was to evaluate the mechanical properties of a bioresorbable plate and screw system that was developed for the treatment of unstable metacarpal fractures and to compare the strength and stiffness of this system with those of conventional titanium plates and screws. Using a 4-point bending test, we measured the strength and stiffness of these implants over a 12-week period of in vitro degradation. Our data suggest that these implants provide stable bending strength and stiffness for 8 weeks and gradually lose their strength over a period of 12 weeks. Further research is necessary to determine whether this level of fixation is adequate to stabilize unstable metacarpal fractures.

Absorbable Implants↗
PubMed2001

Malnutrition alters the innate immune response and increases early visceralization following Leishmania donovani infection.

Malnutrition is a risk factor for the development of visceral leishmaniasis. However, the immunological basis for this susceptibility is unknown. We have developed a mouse model to study the effect of malnutrition on innate immunity and early visceralization following Leishmania donovani infection. Three deficient diets were studied, including 6, 3, or 1% protein; these diets were also deficient in iron, zinc, and calories. The control diet contained 17% protein, was zinc and iron sufficient, and was provided ab libitum. Three days after infection with L. donovani promastigotes, the total extradermal (lymph nodes, liver, and spleen) and skin parasite burdens were equivalent in the malnourished (3% protein) and control mice, but in the malnourished group, a greater percentage (39.8 and 4.0%, respectively; P = 0.009) of the extradermal parasite burden was contained in the spleen and liver. The comparable levels of parasites in the footpads in the two diet groups and the higher lymph node parasite burdens in the well-nourished mice indicated that the higher visceral parasite burdens in the malnourished mice were not due to a deficit in local parasite killing but to a failure of lymph node barrier function. Lymph node cells from the malnourished, infected mice produced increased levels of prostaglandin E(2) (PGE(2)) and decreased levels of interleukin-10. Inducible nitric oxide synthase activity was significantly lower in the spleen and liver of the malnourished mice. Thus, malnutrition causes a failure of lymph node barrier function after L. donovani infection, which may be related to excessive production of PGE(2) and decreased levels of IL-10 and nitric oxide.

Animals↗
PubMed2001

Leishmania donovani p36(LACK) DNA vaccine is highly immunogenic but not protective against experimental visceral leishmaniasis.

The acquisition of immunity following subclinical or resolved infection with the intracellular parasite Leishmania donovani suggests that vaccination could prevent visceral leishmaniasis (VL). The LACK (Leishmania homolog of receptors for activated C kinase) antigen is of interest as a vaccine candidate for the leishmaniases because of its immunopathogenic role in murine L. major infection. Immunization of mice with a truncated (24-kDa) version of the 36-kDa LACK antigen, delivered in either protein or DNA form, was found previously to protect against cutaneous L. major infection by redirecting the early T-cell response away from a pathogenic interleukin-4 (IL-4) response and toward a protective Th1 response. The amino acid sequence of the Leishmania p36(LACK) antigen is highly conserved, but the efficacy of this vaccine antigen in preventing disease caused by strains other than L. major has not been determined. We investigated the efficacy of a p36(LACK) DNA vaccine against VL because of the serious nature of this form of leishmaniasis and because it was unclear whether the LACK vaccine would be effective in a model where there was not a dominant pathogenic IL-4 response. We demonstrate here that although the LACK DNA vaccine induced a robust parasite-specific Th1 immune response (IFN-gamma but not IL-4 production) and primed for an in vivo T-cell response to inoculated parasites, it did not induce protection against cutaneous or systemic L. donovani challenge. Coadministration of IL-12 DNA with the vaccine did not enhance the strong vaccine-induced Th1 response or augment a protective effect.

Animals↗
PubMed1992

Identification of vitellogenin in the little skate (Raja erinacea).

1. Vitellogenin was isolated from mature female skates by selective precipitation with MgCl2/EDTA followed by chromatography on DEAE-cellulose columns. 2. A single monomer of approximately 205 kDa was identified on 6.0% SDS-PAGE gels. 3. In addition, isolation of yolk proteins with ammonium sulfate yielded proteins of 94 and 38 kDa (putative phosvitins) and putative lipovitellins of ca 105, 91 and 67 kDa. 4. In vivo phosphate incorporation in female and male skates implanted with estradiol indicated that vitellogenin was phosphorylated. 5. Total protein phosphate incorporation was significantly higher in females than male skates. 6. In male skates treated with estradiol, phosphate incorporation increased from 2 days after implantation to a maximum at approximately 11 days after implantation. 7. Determination of the rate of disappearance of 32P-labeled protein suggests a half-life of ca 200 hr in normal female skate plasma.

Animals↗
PubMed1992

Putative apolipoprotein B-100 in the freshwater turtle Chrysemys picta: effects of estrogen and progesterone.

1. The isolation and purification of a putative apolipoprotein B-100 in the plasma of the freshwater turtle Chrysemys picta is described. 2. The protein was purified through differential ultracentrifugation and subsequent Sepharose 6B column chromatography. 3. The molecular weight of the protein determined by electrophoresis was approximately 350 kDa. 4. An antibody to chicken apolipoprotein B-100 specifically recognizes this 350 kDa protein in Western blots, suggesting its identity with apolipoprotein B-100. 5. An antibody to the putative Chrysemys apolipoprotein B-100-like protein was developed and used in an ELISA to quantitate protein levels in plasma. 6. Acute estrogen treatment increased levels of apolipoprotein B-100 (7.64 +/- 0.79 mg/ml plasma) over that of control animals (5.07 +/- 1.74 mg/ml plasma). 7. In contrast, chronic estrogen treatment reduced apolipoprotein B-100 significantly to 2.94 +/- 0.53 mg/ml plasma (P < 0.05).

Animals↗
PubMed1991

Vitellogenin--homologs of mammalian apolipoproteins?

1. To determine if a relationship exists between vertebrate vitellogenins and mammalian plasma proteins the EMBL and NBRF computer databases were searched with two partial amino acid sequences from Xenopus laevis and Gallus gallus vitellogenin. 2. A significant relationship was found between vitellogenin and human apolipoprotein B-100 genes, and confirmed using homology-determination programs. 3. Further analysis shows that unique multiple proline consensus regions found in apolipoprotein B-100 are significantly similar to proline dominant regions in vitellogenin. 4. This work suggests that these proteins are functionally and structurally related and should be categorized as a functional group of hepatic lipid transport and metabolism proteins.

Amino Acid Sequence↗
PubMed1990

Prenatal laboratory screening.

Expectations of the clinician are evolving in obstetric practice in regard to standards of performance, cost effectiveness, and outcomes for mother and child. Prenatal laboratory screening is shown to be an area where new developments are evident. The purpose of this article is to update information found in standard obstetrics textbooks.

Clinical Laboratory Techniques↗
PubMed1986

A kinematic study of crawling behavior in the leech, Hirudo medicinalis.

The medicinal leech crawls along a solid substrate by repeated alternating extensions and shortenings of the body. Extension occurs with the posterior sucker attached and the head sucker free. The head sucker then attaches, followed by shortening and release of the tail sucker. The tail sucker is then pulled toward the head, where it reattaches to the substrate. The head sucker then releases, and another crawling cycle begins (Figs. 1, 5). There are two crawling variants: inchworm crawling, in which the head and tail suckers are closely apposed at the end of a cycle and the body forms a loop above the substrate, and vermiform crawling, in which the suckers are placed farther apart and the body remains fairly close to the substrate (Fig. 1). The cycle period and the distance traveled during a cycle are greater in inchworm than in vermiform crawling; however, the velocity of travel is the same for both (Fig. 2). For both variants, the interval between head sucker attachment and tail sucker release is similar at all cycle periods and has a value consistent with direct interneuronal conduction of a signal from head sucker sensory neurons to tail sucker motor neurons. The interval between tail sucker attachment and head sucker release, however, is longer and varies with the cycle period, suggesting a more complex interneuronal circuit in the pathway from tail sucker sensory neurons to head sucker motor neurons (Fig. 4). The onsets of the components of the crawling cycle (extension, post-extension pause, shortening, and post-shortening pause) show an anteroposterior lag (Figs. 5, 7). For both variants, the travel time between segments varies directly with the period (Fig. 8). For both crawl types, the durations of the cycle components vary directly with the period, with several exceptions (Figs. 9, 10). A model is presented that summarizes the coordination of the various motor events in a cycle of leech crawling (Figs. 11 and 12).

Animals↗
PubMed1981

Fertility following fimbriectomy and tubo-ovarian microsurgery in the rabbit.

It is generally believed that tubal fimbriae function as a highly specialized and indispensable component of the ovum pickup mechanism. The present study was undertaken to examine the feasibility of creating a functional tubo-ovarian relationship following fimbriectomy. Fourteen New Zealand White rabbits underwent unilateral microsurgical fimbriectomy followed by creation of a distal ampullary flap which was oversewn to the exposed ovarian cortex. Two weeks after surgery, the animals were inseminated and induced to ovulate with an intravenous injection of 100 IU of human chorionic gonadotropin. Thirteen of fourteen uterine horns on the control side and ten of fourteen on the operated side became pregnant. The ratios of ova ovulated to those which implanted were 73.2% on the control side and 37.8% on the operated side. Morphologic studies revealed a normal complement of ciliated and secretory cells lining the endosalpinx of the juxtaposed ampullary flap. The portion of ovarian cortex covered by the flap similarly exhibited no morphologic abnormalities. These findings indicate that fertility can be maintained in the absence of fimbriae and suggest a surgical technique for restoration of fertility following elective sterilization by fimbriectomy or following pathologically induced destruction of the fimbriae.

Animals↗