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Biomedical subjects

A Whyte

Publications and source records attributed to A Whyte.

At least 19 recordsLinked to original sources
PubMed1999

Reptilian chemistry: characterization of dianeackerone, a secretory product from a crocodile.

The major volatile component in the paracloacal glandular secretion of the adult African dwarf crocodile (Osteolaemus tetraspis) was isolated and characterized as a 19-carbon aromatic ketone, dianeackerone (3,7-diethyl-9-phenyl-2-nonanone). This ketone is absent from the secretion of immatures. Careful examination of dianeackerone samples isolated from individual adults revealed that this ketone occurs as both the (3S, 7S) and (3S, 7R) stereoisomers, with different individuals presenting strikingly different ratios of the isomeric forms. Our initial suspicion that the stereoisomeric dianeackerones might be indicators of gender proved untenable, leaving the role of these glandular constituents a challenge for future study.

Alligators and Crocodiles↗
PubMed1999

Reptilian chemistry: characterization of a family of dianeackerone-related steroidal esters from a crocodile secretion.

The African dwarf crocodile, Osteolaemus tetraspis (Crocodilidae, Reptilia), possesses a pair of skin glands, the paracloacal glands, the secretion of which is thought to be used to mark nest sites or attract mates. Ten aromatic steroidal esters were isolated from this secretion and characterized on the basis of NMR spectroscopic investigations, electrospray ionization-MS analyses, and chemical degradation. These esters, which account for more than 90% of the paracloacal glandular secretion, are derived from either cholesterol or cholestanol, esterified with a C-20 or C-22 acid closely related to dianeackerone, the only significant volatile compound found in this secretion.

Alligators and Crocodiles↗
PubMed1999

Alpha-galactosyl-mediated activation of porcine endothelial cells: studies on CD31 and VE-cadherin in adhesion and signaling.

BACKGROUND: Ligation of alpha-galactosyl epitopes on endothelial cells by naturally occurring human antibodies causes hyperacute rejection in porcine-to-human xenotransplantation. The alpha-galactosyl-specific lectin Bandeiraea simplicifolia isolectin B4 (IB4) has been reported to trigger endothelial "gap" formation and tyrosine phosphorylation of an unidentified 130-kDa protein. We have studied two 130-kDa junctional adhesion molecules, CD31 and VE-cadherin, in porcine aortic endothelial cells (PAECs) during IB4-mediated activation. The cellular distribution of these molecules, their susceptibility to tyrosine phosphorylation, and their capacity to bind IB4 or natural human antibodies have been determined. METHODS: Porcine CD31 and VE-cadherin were cloned. Recombinant proteins and monoclonal antibodies were prepared. The distribution and phosphorylation of CD31 and VE-cadherin in confluent PAECs activated with IB4 or human serum were studied by confocal microscopy and Western blotting, respectively. RESULTS: IB4 caused rapid redistribution of CD31 and VE-cadherin away from cell junctions and tyrosine-phosphorylation of CD31 but not VE-cadherin. A monoclonal antibody to CD31 also triggered tyrosine phosphorylation of this molecule, but brief exposure of PAECs to normal human serum did not. Tyrosine-phosphorylated CD31 complexed with SHP2 and other unidentified phosphoproteins. Both IB4 and natural human antibodies bound to porcine CD31 but not to VE-cadherin. Cell adhesion tests showed that porcine and human CD31 are functionally incompatible. CONCLUSIONS: Endothelial cell retraction during IB4-mediated activation of PAECs is associated with rapid loss of CD31 and VE-cadherin from cell junctions. CD31 becomes strongly tyrosine-phosphorylated and forms a cell signaling complex, which may have a significant role in the response of the xenograft vascular endothelium.

Animals↗
PubMed1999

Phenotypic characterization of histiocytes infiltrating a leiomyofibrosarcoma.

We described previously a unique cutaneous tumour in a young pig, which was characterized by several criteria as a histiocytic leiomyofibrosarcoma. The lipid-laden macrophages (histiocytes) which permeated the tumour were CD2+/CD18+/CD49d+ but MAC387 (L1 antigen) and CD15 negative. The present study compared the phenotypes of histiocytes in tumour metastases in the liver with resident liver macrophages, revealing differential expression of certain macrophage activation markers. After repeated subcutaneous passage of the tumour in athymic (nu/nu) mice, flow cytometry demonstrated a rapid loss of porcine MHC Class II, but a more prolonged expression of porcine MHC Class I, consistent with our immunohistological observations. Mouse macrophages (CD2+/F4.80+) infiltrated the later-passage tumours, suggesting that the histiocytes were not of neoplastic origin.

Animals↗
PubMed1999

[Effects of experimental vasectomy on testicular structure: ultrastructural study].

We have performed experimental vasectomies in dogs in order to study effects of vas deferens ligature with close technique, on the testicular ultrastructure. We point out the existence of alterations: structural changes of the seminiferous epithelium, great extracellular spaces which are generated for the premature exfoliation of germinal cells, degeneration of the germinal shock cells, the appearance of immature germinal cells and multinucleate spermatids in every stages of the spermatogenesis, the fall of mature spermatozoid number, thickening of basal membrane, relative increase in the Sertoli's cells size as well as their phagocytic function, and existence of spermaphagos unfasted into tubular lumen. The Leydig's interstitial islets show an absolutely normal cellular and vascular configuration.

Animals↗
PubMed1999

[Experimental vasectomy: comparison of epididymal structure with various surgical techniques].

OBJECTIVE: To analyze the effects of different surgical techniques of vasectomy on the epididymal structure. METHODS: Experimental vasectomies were performed in dogs using the conventional and open-ended techniques. The animals were orchidectomized 1 to 12 months after vasectomy and the epididymal structure was analyzed. RESULTS: The epididymal structure of dogs submitted to the conventional technique showed marked ectasia, reinforced basement membrane, loss of stereocilia in the principal cells, and formation of spermatic granulomas in interstitial tissue. At 12 months the principal cells showed signs of degenerative changes. In the different time periods analyzed in the study, no changes were observed in the epididymal structure of dogs submitted to the open-ended technique. CONCLUSIONS: The changes observed in the principal cells are ascribable to the increased intraluminal pressure produced by ligation of both ends of the vas deferens (conventional technique), since no changes were found in the epididymal structure of dogs submitted to the open-ended technique, at least in the different time periods analyzed in the study.

Animals↗
PubMed1998

Overview of the Second International Workshop to define swine cluster of differentiation (CD) antigens.

The aim of the Second International Swine Cluster of Differentiation (CD) Workshop, supported by the Veterinary Immunology Committee (VIC) of the International Union of Immunological Societies (IUIS), was to standardize the assignment of monoclonal antibodies (mAb) reactive with porcine leukocyte differentiation antigens and to define new antibody clusters. At the summary meeting of the workshop in July, 1995, revisions in the existing nomenclature for Swine CD were approved, so that the rules are now in accord with those for human and ruminant CD. Swine CD numbers will now be given to clusters of mAb to swine orthologues of human CD molecules when homology is proven by (1) suitable tissue distribution and lymphoid cell subset expression, (2) appropriate molecular mass of the antigen recognized by the mAbs, and (3) reactivity of mAbs with the cloned swine gene products, or cross-reactivity of the mAb on the human gene products. In some cases, this reactivity would not be fully proven, mainly due to the lack of cloned gene products; for these CD antigens, the respective clusters will be assigned by the prefix 'w' which will lead to 'wCD' antigens. As a result of the Second International Swine CD Workshop the assignment of 16 mAb to existing CD groups (CD2a, CD4a, CD5a, wCD6, wCD8, CD14, CD18a, wCD21, wCD25) was confirmed, and 2 mAb to existing swine workshop clusters (SWC). More importantly, for the work on the porcine immune system, was the definition of 5 new swine CD antigens, namely CD3 (recognized by 6 new mAb and 3 epitopes), CD16 (1 new mAb), wCD29 (2 mAb), CD45RA (3 mAb) and CD45RC (1 new mAb). Finally, the demarcation of two new SWC molecules in swine, SWC8 (2 mAb) and SWC9 (2 mAb) was confirmed.

Animals↗
PubMed1998

[Experimental vasectomy: comparison of the testicular structure with various surgical techniques].

We have performed experimental vasectomies in dog in order to study different repercussions of various surgical techniques on the testicular structure. The closed technique, with ligature of both cut ends of the sectioned vas deferens caused a severe tubular atrophy, which finally destroyed the architecture of the testis with compensating hypertrophy of the intertubular connective tissue. The technique of the "open cut end", leaving the proximal end free and allowing the normal drainage of the vas deferens into the interstitial space of the spermatic cord, had not any influence on the testicular-structure, at least in the studied period of time, now one year. We can't reject any long-term immunological phenomena. The conclusion of this study is that the peculiarities of the surgical techniques of vasectomy have a decisive influence on the preservation of the testicular structure.

Animals↗
PubMed1998

[A morphological and morphometric study of the testicle in the rat vasectomized by electrocautery technics].

OBJECTIVE: To evaluate the influence of vasectomy by different fulguration methods on the rat testicular structure. METHODS: Experimental vasectomy was performed in Wistar rats by means of the Shapiro and Silber, and the Schmidt cauterization techniques. The animals were orchidectomized between 7 days and 9 months following vasectomy. A morphological and morphometric study of the rat testes was performed. RESULTS: We have observed that both cauterization techniques do not produce sequelae in the rat testicular structure and its morphology is compatible with the normal. The morphometric study showed that both techniques produced a significant decrease (p > 0.05) of the area occupied by seminiferous epithelium within one month post-vasectomy; however, these values returned to normal three months thereafter. CONCLUSIONS: Vasectomy by different fulguration methods does not change the rat testicular structure.

Animals↗
PubMed1997

Pig lymphocytes utilise mouse MAdCAM-1 to enter fetal gut xenografts in SCID mice.

Ileocecal junction (ICJ) and proximal intestine (PI) fragments from CD45(323-) allovariant fetal pigs were grafted subcutaneously into SCID mice. The xenografts were examined 8-12 weeks later using two-color immunohistology and the ICJ, but not PI, xenografts were found to contain three types of vessels. The first (the majority) was lined with mouse endothelium (mAb 9F1+), the second was lined with pig endothelium, and the third was chimeric. The ICJ vessels were specifically lined with mouse endothelium expressing MAdCAM-1, the mucosal addressin. Vessels lined with pig endothelium alone did not express the MAdCAM-1 epitopes. Radiolabeled allovariant pig peripheral blood lymphocytes (PBL) were introduced i.v. into the xenografted SCID mice, and entry into xenografts studied. Pig PBL were occasionally seen in MECA-367+ vessel walls after 4 h and within the ICJ but not PI xenografts after 24 h. This entry was specifically blocked by coinjection of the anti-MAdCAM-1 mAb MECA-367. The results demonstrate reendothelialization of xenografts by host endothelium that expresses its own addressin and is functional for xenogenic PBL.

Animals↗
PubMed1997

[Effects of vasectomy on the testicular structure of the dog].

Study of the effect on testis structure in the dog caused by a vasectomy. Emphasis is made on how in animals undergoing ligature of both ends of the ductus deferens, existence of structural changes, which are consistently present, are proportional to the time elapsed from performance of vasectomy. Such changes are revealed by: degeneration of germinal epithelium, thickening of basal membrane and hypertrophy of interstitial tissue at the expense of unspecific connective tissue. Changes were first seen as from the fourth month, but a full year has to elapse prior to noting a marked germinal hypoplasia. These experimental results cast doubts on the safety of such sterilization approach, although they cannot be entirely extrapolated to humans.

Animals↗
PubMed1996

The role of E-selectin in lymphocyte and polymorphonuclear cell recruitment into cutaneous delayed hypersensitivity reactions in sensitized pigs.

We have studied the role of E-selectin in leukocyte accumulation into Ag-specific cutaneous delayed-type hypersensitivity reactions in pigs sensitized to the topical application of 2,4-dinitro-1-fluorobenzene or to the intradermal injection of bacillus Calmette-Guérin. The delayed-type hypersensitivity reactions were shown to be specific for the sensitizing Ag and characterized by the up-regulation of E-selectin, as demonstrated by the uptake of tracer 99mTc-labeled monoclonal anti-E-selectin mAb and entry of 51Cr-labeled PBL and (111)In-labeled polymorphonuclear cells (PMN). Intravenous injection of 5 mg/kg of a F(ab')2 preparation of a monoclonal anti-E-selectin Ab at peak times of leukocyte entry resulted in a significant inhibition of entry of both PMN and lymphocytes. The anti-E-selectin Ab inhibited PMN recruitment by 70 to 90% and lymphocyte recruitment by 50 to 60%. In comparison, an anti-CD18 treatment reduced PMN recruitment by 70 to 90% and lymphocyte recruitment by 60 to 70% in this model. These data confirm an important role for E-selectin in the recruitment of both PMN and lymphocytes to sites of immune-based dermal inflammation.

Age Factors↗
PubMed1996

Complete gene map of the plastid-like DNA of the malaria parasite Plasmodium falciparum.

Malaria parasites, and other parasitic protists of the Phylum Apicomplexa, carry a plastid-like genome with greatly reduced sequence complexity. This 35 kb DNA circle resembles the plastid DNA of non-photosynthetic plants, encoding almost exclusively components involved in gene expression. The complete gene map described here includes genes for duplicated large and small subunit rRNAs, 25 species of tRNA, three subunits of a eubacterial RNA polymerase, 17 ribosomal proteins, and a translation elongation factor. In addition, it codes for an unusual member of the Clp family of chaperones, as well as an open reading frame of unknown function found in red algal plastids. Transcription is polycistronic. This plastid-like DNA molecule is conserved in several genera of apicomplexans and is conjectured to have been acquired by an early progenitor of the Phylum by secondary endosymbiosis. The function of the organelle (plastid) carrying this DNA remains obscure, but appears to be specified by genes transferred to the nucleus.

Amino Acid Sequence↗
PubMed1996

Anti-CD4 monoclonal antibodies suppress murine collagen-induced arthritis only at the time of primary immunisation.

We have examined the ability of a mixture of two anti-CD4 mAbs to protect against collagen-induced arthritis. Anti-CD4 mAbs, administered around the time of primary immunisation with type II collagen in adjuvant, reduced the subsequent incidence of arthritis from 67 to 16% (P < 0.01 by Fisher exact test). However, anti-CD4 treatment 3 weeks after the primary immunisation did not significantly affect the incidence of arthritis. This result extends earlier findings concerning the lack of efficacy of anti-CD4 treatment in established collagen-induced arthritis. Next, the ability of anti-CD4 treatment to induce tolerance to bovine type II collagen (and hence protect against arthritis) was evaluated using a regime known to be capable of inducing tolerance to human gamma-globulin. Anti-CD4 treatment completely failed to induce tolerance to type II collagen, as judged by levels of anti-collagen antibody, or protect against collagen-induced arthritis. These findings highlight the potential limitations of anti-CD4 mAb depleting treatment in immunotherapy.

Animals↗
PubMed1996

Expression of CD44 isoforms during bleomycin-or radiation-induced pulmonary fibrosis in rats and mini-pigs.

The distribution of CD44s and CD44v molecules in normal and injured lung tissue of rats and mini-pigs was studied by examining the immunohistochemical binding of monoclonal antibodies against CD44 isoforms. We showed that the expression of CD44v and CD44s varies greatly among different pulmonary fibrosis samples and that some tissues express either enhanced expression of CD44s, particularly in the interstitium and on alveolar macrophages, or very low levels of CD44v in the alveolar epithelium. Normal type II pneumocytes expressed the CD44s and CD44v molecules at the basolateral aspect of the cell. Such localisation favours a role for CD44 in epithelial cell-fibroblast interaction during lung development and repair.

Animals↗