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Biomedical subjects

A H Saad

Publications and source records attributed to A H Saad.

At least 37 records · Page 2Linked to original sources
PubMed1990

Immunological changes during pregnancy in the viviparous lizard, Chalcides ocellatus.

Splenic cells from pregnant and non-pregnant viviparous lizards (Chalcides ocellatus) were stimulated in vitro with the mitogens, concanavalin A (Con A), phytohemagglutinin (PHA) and Escherichia coli lipopolysaccharide (LPS). Cell cultures from pregnant animals were significantly less responsive to Con A and PHA than comparable cultures from non-pregnant animals. The response was depressed during the first period of pregnancy and remained low in magnitude until parturition. By contrast, the response of maternal splenic cells to LPS was reduced in pregnant lizards only during advanced pregnancy. The drastic decrease in mitogenic responsiveness was associated with marked involution of the maternal spleen. These findings strongly suggest that pregnancy impairs the immunoreactivity of viviparous lizards. Possible mechanisms for this impairment and the relationship to circulating levels of sex hormones are discussed.

Animals↗
PubMed1990

Blood testosterone level: a season-dependent factor regulating immune reactivity in lizards.

An attempt to study the interaction between testosterone (Ts) and the immune system of the lizard Chalcides ocellatus led to three major findings: 1) Endogenous serum Ts levels in both males and females peak in spring and are minimal during summer; 2) Injection of Ts in either male or female lizards induces significant depletion of lymphoid elements, reduction in serum antibody titers to rat erythrocytes and increase in skin allograft survival; 3) A distinct inverse correlation between endogenous serum Ts levels and lizard immunocompetence is observed from March to September. The data obtained strongly suggested that concentration of circulating Ts is a season-related factor that is critical in defining the immune profile of lizards.

Animals↗
PubMed1989

Ultrasound enhanced drug toxicity on Chinese hamster ovary cells in vitro.

Chinese hamster ovary cells (HA1) were exposed to therapeutic ultrasound (F = 2.025 MHz) in the presence of various drugs at temperatures of 37-43 degrees C. The space averaged intensities used were 0.5-2 W/cm2. The survival of these cells was subsequently tested using the clonogenic assay. Marked enhancement by ultrasound of the cytotoxicity of Adriamycin and amphotericin B was observed. For Adriamycin, the potentiation was dependent upon the intensity of sonication (exposure duration being 30 min). At 0.5 W/cm2, there was enhancement of cytotoxicity above 41 degrees C. At 1 W/cm2, there was a 3-order increase in cytotoxicity at 37 degrees C. Thus an increase in intensity resulted in a decrease in "threshold" temperature. The effect with Adriamycin could be explained in part by an increase in net uptake of drug into the cells. Further, ultrasound was observed to increase the sensitivity of cells to Adriamycin. For amphotericin B, the enhancement was observed only at exposure durations greater than 30 min and at 43 degrees C. There was no enhancement observed for cisplatin and etoposide. From these results, it appears that ultrasound potentiates the cytotoxicity of drugs the mode of action of which (at least in part) involves the plasma membrane.

Amphotericin B↗
PubMed1989

Sex-associated differences in the mitogenic responsiveness of snake blood lymphocytes.

The blastogenic response of male and female snake (Psammophis sibilans) peripheral blood lymphocytes to concanavalin A, phytohaemagglutinin, and E. coli lipopolysaccharide was tested for putative sex-associated differences. Data obtained suggest that normal female blood lymphocytes respond relatively vigorous in comparison to male cells or cells taken from gravid female snakes. The data are discussed in terms of possible correlations with the normal status of the animal.

Animals↗
PubMed1989

Pregnancy-related involution of the thymus in the viviparous lizard, Chalcides ocellatus.

The thymus gland of the adult viviparous lizard, Chalcides ocellatus (Reptilia, Sauria, Scincidae) undergoes conspicuous morphological changes in relation to gestational period. During pregnancy, the thymus is depleted of thymocytes and undergoes changes coming to consist primarily of numerous degenerative cysts. Thymic involution occurs early during pregnancy (starting at phase II) and reaching its highest level at parturition (phase V). These observations correlate with the circulating level of blood progesterone, measured by radioimmunoassay, and suggest a possible relationship between thymic involution and the activity of sex hormones.

Animals↗
PubMed1989

Histological and carbohydrate histochemical studies of the nasal mucosa of sheep in Saudi Arabia with special reference to its glandular tissue.

The histology and carbohydrate histochemistry of the nasal mucosa with attention to glandular tissue had been studied in 7 heads of sheep. Tissues were taken from vestibular region, septum at level of the alar fold, rostral portion of nasal conchae, caudal portion of nasal conchae, middle portion of septum and ethmoidal conchae region. Stratified squamous nonkeratinized epithelium was observed covering the vestibular region. The propria-submucosa of the nasal vestibule was richly permeated with glands having affinity for PAS and non-alcianophilic. The post-vestibular portion of the nasal cavity was lined by transitional epithelium and caudal to it, stratified columnar nonciliated epithelium was noticed. The respiratory epithelium covered the caudal half of the nasal conchae and the major portion of the septum as well as the recesses of the ethmoidal conchae. The glands associated with the respiratory mucosa were thick, coiled and tubular, containing both nonalcianophilic PAS positive and alcianophilic PAS positive cells. The olfactory mucosa covered the ethmoidal conchae and showed predominant serous glands. The results were discussed with that given for other mammals and in regard to the respiratory functions of the nasal mucosa.

Animals↗
PubMed1989

Histological and histochemical studies on the digestive gland of Bulinus truncatus infected with Schistosoma haematobium.

The structure of the uninfected and infected digestive gland of the fresh-water snail, Bulinus truncatus, was studied histologically and histochemically. The digestive gland consists of two types of cells: digestive and secretory cells clearly differentiated from each other. The pathological effects of infection of the snail with cercariae of Schistosoma haematobium have resulted in considerable structural and histochemical alterations in the digestive gland. Generally, the main effects were reflected by increased cellular vacuolation and marked diminution of carbohydrates, proteins and lipids of the gland cells.

Animals↗
PubMed1988

Primary in vitro stimulation of antibody production by lizard splenocytes.

Single-cell suspensions of adult lizard (Chalcides ocellatus) spleen have been induced, in vitro, to produce a primary immune response. Using rat red cells (RRBC) as antigen and the culture conditions normally used in most vertebrate species but new for reptilia, it has been found that, in vitro at 37 degrees C, lizard spleen cells produce an antibody-forming response optimal at day 10. The response depends on the number of cultured cells and the dose of antigen, and parallels that obtained in vivo. Leibovitz (L-15) medium supplemented with 10% normal adult lizard serum was a satisfactory culture medium. 2-mercaptoethanol (2-ME), an ingredient used in mammalian cell culture, enhanced antibody production in lizard cells.

Animals↗
PubMed1988

Endogenous corticosteroids mediate seasonal cyclic changes in immunity of lizards.

Endogenous corticosteroid (CS) blood levels were radioimmunoassayed in fresh, field-collected lizards Chalcides ocellatus at two week-intervals throughout the four consecutive seasons. These animals were used in parallel to investigate the splenic T and B lymphocyte level, lymphoproliferative responsiveness to concanavalin A and primary antibody production in vitro against rat erythrocytes (RRBC). The recorded data indicated that fully developed splenic lymphoid tissue and powerful immune responsiveness are coincident with a continuously low CS level, and characterize the period from spring through early autumn. On the other hand, the dramatic lymphocytic destruction and impairment of immune reactivity observed in autumn and winter are associated with not only a high, but above all sustained, rise in endogenous CS levels. Apparently, exposure of lizard lymphocytes to comparatively high, yet physiologic, levels of endogenous CS for prolonged periods of time lead to impairment of their immune functions. In support, long-term administration of exogenous hydrocortisone acetate (HC) to "summer" lizards resulted in a high and lasting elevation in blood CS levels that was associated with a considerable depletion of lymphoid elements and abrogation of immune reactivity, exactly as in normal lizards collected from the field in autumn through winter. In addition, pharmacologic inhibition of CS synthesis by administration of metyrapone at the beginning of autumn greatly modulated the lizard lymphocyte response to the autumn-related immunodepression. The study thus strongly suggests that the autumn/winter-dependent immunosuppression in lizards is essentially due to a high and lasting rise in levels of endogenous CS. The results are discussed from the perspective of the role played by CS in mediating the seasonal rhythms that affect reptilian immunity.

Adrenal Cortex Hormones↗
PubMed1988

Sexual dimorphism on the immune responses of the snake, Psammophis sibilans.

Recent trends in research have documented the influence of sex factors on the immune response of higher vertebrates. The present study is the first to indicate the existence of sex-dependent differences in the immune potentiality in reptiles. In optimal seasonal conditions, kinetics of the primary anti-rat erythrocytes (RRBC) antibody response were compared in individual male and female snakes, Psammophis sibilans. Antigen specific rosette forming cells (RFC) were enumerated in the spleen after in vivo primary immunization with 0.5 ml of 10% RRBC. A greater RFC activity as well as highest antibody titers were noted in females as compared to males. In addition, the peak of primary antibody response to RRBC in males was somewhat delayed in comparison with females. A similar pattern of sex-dependent differences was also observed regarding mitogen responsiveness to Con A, PHA and LPS with female lymphocytes being always the highest responders. In conclusion, female snakes demonstrated an elevated response in almost all comparative tests. Thereafter, at least under physiological conditions, our observations suggest a possible influence of sex hormones as immunoenhancers/immunosuppressors in reptiles.

Animals↗
PubMed1988

Detection of Thy-1+ cells in the developing thymus of the lizard, Chalcides ocellatus.

The ontogenic appearance of Thy-1+ cells was studied in the thymus of the lizard, Chalcides ocellatus, by indirect immunofluorescence using a rabbit antibrain antiserum produced against surface determinants shared by both the thymus and the brain lizards. Thymic Thy-1+ cells were first detected at stage 37. They increased rapidly reaching adult numbers by stage 41. Apparently Thy-1+ cells differentiate from lymphoid precursors arriving at the thymus analage before stage 37. The results are compared to those found during the differentiation of Thy-1+ thymocyte in murine thymus and agree with former reports on the thymic development in Chalcides using rabbit antisera against adult thymocyte marker(s).

Animals↗
PubMed1987

Ontogeny of con A responsiveness and mixed leucocyte reactivity in the lizard, Chalcides ocellatus.

The immune system of phylogenetically key animals will contribute significantly to our understanding of the evolution of immune response in higher vertebrates. Reptiles, being evolutionary precursors of both birds and mammals, represent a pivotal group and thus a study of their immune system is of special significance. Here we described the emergence of T-cell immune capability in the viviparous lizard (Chalcides ocellatus) throughout embryonic development (stages 36-41 of Zada and El Deeb, 1984) and in newborns. The response of embryonic thymocytes (5 X 10(5) cells/ml) to Con A (5 micrograms/ml in culture) was first detected at stages 36-37, increased gradually during successive stages and then declined at birth to yield low responses in newborn lizards. In addition, embryonic thymocytes cultured in two-way MLR, using several combination sets, were significantly responsive at all stages. Our results reveal a degree of immunological T-cell maturation during reptitilian embryonic life which is similar to results in amphibians and mammals, but not clear with respect to fish and birds where comparative information still somewhat limited.

Animals↗
PubMed1987

Concanavalin A responsiveness and interleukin 2 production in the snake Spalerosophis diadema.

Thymocytes and splenocytes (SC) of adult snakes, Spalerosophis diadema, responded to concanavalin A (Con A) in vitro by strong proliferation during the spring and autumn seasons. Con A-mediated mitogenesis was, however, abrogated in summer and winter. Conditioned medium (CM) collected from snake SC cultures stimulated with Con A in spring or autumn could enhance the Con A summer and winter responses and support the proliferation of splenic lymphoblasts. Gel filtration of native CM on Sephadex G-100 revealed the presence of two biologically active peaks of molecular weight 39-42 and 15 KD. However, only one peak of activity corresponding to molecular weight (m.w.) of 14-15 KD was observed when CM was subjected to analysis by sodium dodecyl sulphate gel electrophoresis (SDS-PAGE). The active molecular forms exhibited isoelectric points of 5.5-5.8 and 6.4-6.6. The findings suggest that Con A activation of snake lymphocytes in optimal seasonal conditions is associated with the secretion of a lymphokine analogous to the interleukin 2 (IL 2) of endothermic vertebrates.

Animals↗