Biomedical subjects

N A Rahman

Publications and source records attributed to N A Rahman.

At least 19 recordsLinked to original sources

PubMed2004

Localization of bovine serum albumin in double-walled microspheres.

Phase separation of binary blends of various combinations of poly (L-lactide) (PLA), and poly (D,L-lactide-co-glycolide) (PLGA), was investigated using differential scanning calorimetry (DSC). Based on this phase separation phenomenon, double-walled microspheres were fabricated. A model agent, bovine serum albumin (BSA) labeled with fluorescein isothiocyanate (FITC-BSA) was localized in each layer. Scanning electron microscopy (SEM) and fluorescence microscopy (FM) were used to assess the formation of double-walled microspheres and the localization of the drug, respectively. When a 1:1 polymer ratio was used, the FITC-BSA was localized in the outer layer. When the relative ratio of PLGA to PLA was increased to 3:1 using the same overall polymer concentration, the FITC-BSA was localized in the inner core. Release studies were carried out to evaluate the advantage of double-walled microspheres compared to single walled microspheres. Microspheres made with FITC-BSA localized in the inner core exhibited a significantly lower initial release rate compared to microspheres where the drug was located in the outer layer, or compared to microspheres made from PLA only. Hence microspheres with a double-walled morphology have the potential for therapeutic use where a high burst might be detrimental.

Animals↗

PubMed2004

Application of the linear interaction energy method (LIE) to estimate the binding free energy values of Escherichia coli wild-type and mutant arginine repressor C-terminal domain (ArgRc)-l-arginine and ArgRc-l-citrulline protein-ligand complexes.

Protein-ligand binding free energy values of wild-type and mutant C-terminal domain of Escherichia coli arginine repressor (ArgRc) protein systems bound to L-arginine or L-citrulline molecules were calculated using the linear interaction energy (LIE) method by molecular dynamics (MD) simulation. The binding behaviour predicted by the dissociation constant (K(d)) calculations from the binding free energy values showed preferences for binding of L-arginine to the wild-type ArgRc but not to the mutant ArgRc(D128N). On the other hand, L-citrulline do not favour binding to wild-type ArgRc but prefer binding to mutant ArgRc(D128N). The dissociation constant for the wild-type ArgRc-L-arginine complex obtained in this study is in agreement with reported experimental results. Our results also support the experimental data for the binding of L-citrulline to the mutant ArgRc(D128N). These showed that LIE method for protein-ligand binding free energy calculation could be applied to the wild-type and the mutant E. coli ArgRc-L-arginine and ArgRc-L-citrulline protein-ligand complexes and possibly to other transcriptional repressor-co-repressor systems as well.

Arginine↗

PubMed2001

Inhibin binding sites and proteins in pituitary, gonadal, adrenal and bone cells.

Activin signals via complexes of type I (50-55 kDa) and II (70-75 kDa) activin receptors, but the mechanism of inhibin action is unclear. Proposed models range from an anti-activin action at the type II activin receptor to independent actions involving putative inhibin receptors. Two membrane-embedded proteoglycans, betaglycan and p120, have recently been implicated in inhibin binding, but neither appears to be a signalling receptor. The present studies on primary cultures of rat pituitary and adrenal cells, and several murine and human cell lines were undertaken to characterise inhibin binding to its physiological targets. High affinity binding of inhibin to the primary cultures and several of the cell lines, like that previously described for ovine pituitary cells, was saturable and reversible. Scatchard analysis revealed two classes of binding sites (K(d) of 40-400 and 500-5000 pM, respectively). Affinity labelling identified [125I]inhibin binding proteins with apparent molecular weights of 41, 74, 114 and >170 kDa in all cell types that displayed high affinity, high capacity binding of inhibin. Additional labelling of a 124 kDa species was evident in gonadal TM3 and TM4 cell lines. In several cases, activin (> or =20 nM) competed poorly or not at all for binding to these proteins. The 74, 114 and >170 kDa inhibin binding proteins in TM3 and TM4 cells were immunoprecipitated by an anti-betaglycan antiserum. These three proteins correspond in size to the activin receptor type II and the core protein and glycosylated forms of betaglycan, respectively, that have been proposed to mediate anti-activin actions of inhibin, but the identity of the 74 kDa species is yet to be confirmed. Studies of [125I]inhibin binding kinetics and competition for affinity labelling of individual binding proteins in several cell lines suggest these three species and the 41 and 124 kDa proteins form a high affinity inhibin binding complex. In summary, common patterns of inhibin binding and affinity labelling were observed in inhibin target cells. Novel inhibin binding proteins of around 41 and 124 kDa were implicated in the high affinity binding of inhibin to cells from several sources.

Activin Receptors↗

PubMed2001

Ovarian tumorigenesis in mice transgenic for murine inhibin alpha subunit promoter-driven Simian Virus 40 T-antigen: ontogeny, functional characteristics, and endocrine effects.

We previously reported formation of ovarian granulosa cell tumors with 100% penetration in a transgenic mouse model with murine inhibin alpha subunit promoter-driven (inhalpha)/Simian Virus 40 T-antigen (Tag). The tumor-bearing inhalpha/Tag mice showed highly elevated serum levels of immunoreactive inhibin. To investigate the onset of tumorigenesis and related endocrine consequences, 6-8 female mice of two inhalpha/Tag lines and their mating control littermates were killed monthly between 1 and 6 mo of age. We also investigated tumorigenesis-related fertility aspects of these two mouse lines. The ontogeny and progression of tumors could be monitored in both inhalpha/Tag lines by alterations of ovarian weights and serum hormone levels. Serum progesterone levels increased in both inhalpha/Tag lines in an age-dependent manner as ovarian tumorigenesis progressed, and a reciprocal decrease occurred in serum LH and FSH. Neither serum estradiol (E(2)) nor uterine weights were significantly altered during tumorigenesis, suggesting that the ovarian tumors represented late stages of granulosa cell differentiation. In conclusion, the present findings show in the inhalpha/Tag TG mice a relation between endocrine consequences of granulosa cell tumorigenesis, and a connection of onset of tumor formation with aberrant steroidogenesis and gonadotropin secretion. These findings indicate that tumors are endocrinologically active and able to exert enhanced negative feedback effects on pituitary function. The tumors provide a good model for endocrinologically active hormone-dependent tumors.

Adrenal Glands↗

PubMed2001

Gonadal tumors of mice double transgenic for inhibin-alpha promoter-driven simian virus 40 T-antigen and herpes simplex virus thymidine kinase are sensitive to ganciclovir treatment.

We have previously produced transgenic (TG) mice expressing the mouse inhibin alpha-subunit promoter/Simian virus 40 T-antigen (Inhalpha/Tag) fusion gene. The mice develop gonadal somatic cell tumors at the age of 5-7 months; the ovarian tumors originate from granulosa cells, and those of the testes from Leydig cells. In the present study another TG mouse line was produced, expressing under the same inh-alpha promoter the herpes simplex virus thymidine kinase gene (Inhalpha/TK). Crossbreeding of the two TG mouse lines resulted in double TG mice (Inhalpha/TK-Inhalpha/Tag), which also developed gonadal tumors. The single (Inhalpha/Tag) and double TG (Inhalpha/TK-Inhalpha/Tag) mice, both bearing gonadal tumors, were treated at the age of 5.5-6.5 months with ganciclovir (GCV, 150 mg/kg body weight twice daily i.p.) for 14 days, or with aciclovir (ACV, 300-400 mg/kg body weight per day perorally) for 2 months. During GCV treatment, the total gonadal volume including the tumor, decreased in double TG mice by an average of 40% (P<0.05), while in single TG mice, there was a concomitant increase of 60% in gonadal size (P<0.05). GCV was also found to increase apoptosis in gonads of the double TG mice. Peroral treatment with ACV was less effective, it did not reduce significantly the gonadal volume. We also analyzed the in vitro efficacy of ACV and GCV treatments in transiently HSV-TK-transfected KK-1 murine granulosa tumor cells, originating from a single-positive Inhalpha/Tag mouse. GCV proved to be more effective and more specific than ACV in action. These results prove the principle that targeted expression of the HSV-TK gene in gonadal somatic cell tumors is potentially useful for tumor ablation by antiherpes treatment. The findings provide a lead for further development of somatic gene therapy for gonadal tumors.

Acyclovir↗

PubMed2001

Adrenocortical tumorigenesis in transgenic mice: the role of luteinizing hormone receptor and transcription factors GATA-4 and GATA-61.

Transgenic (TG) mice, bearing the Simian Virus 40 T-antigen (Tag) under a 6-kb fragment of the murine inhibin alpha-subunit promoter (inhalpha), develop gonadal tumors of granulosa or Leydig cell origin with 100% penetrance by the age of 5-7 months. When these TG mice were gonadectomized prepubertally, between 21-25 days of life, adrenal gland tumors were observed in each mouse by the age of 5-7 months. No adrenal tumors were detected in any intact TG, gonadectomized or intact or control non-TG littermates. The adrenocortical tumors appeared to originate from the X-zone of the adrenal cortex. If functional gonadectomy was induced by GnRH antagonist treatment or by cross-breeding of the TG mice into hypogonadotropic hpg genetic background, neither gonadal nor adrenal tumorigenesis appeared. This prompted a hypothesis that adrenal tumor development in inhalpha/Tag TG mice is related to elevated gonadotropin secretion, which is the most obvious difference between the surgical and functional gonadectomy models. The adrenal tumors and a cell line (Calpha1) derived from them, was found to express luteinizing hormone receptor (LHR), but no FSHR, and hCG treatment stimulated their proliferation. No FSHR was found in the adrenal glands. On the basis of this it was suggested that expression of the potent oncogene T-antigen, allow LH in adrenocortical cells to function as a tumor promoter, and induction of high level functional LHR expression in adrenal tumors. Given the induction of expression and regulation of the GATA-4 and GATA-6 zinc finger family of transcription factors in the gonads by gonadotropins, it was in our interest to explore their expression in the adrenals. We utilized the inalpha/Tag TG mouse model and pathological human adrenal samples to explore the role of GATA-4 and GATA-6 in adrenocortical tumorigenesis. Abundant GATA-6 mRNA expression was found in normal control adrenal cortex during mouse development, whereas GATA-4 mRNA was undetectable. In striking contrast to this, GATA-6 was absent from murine adrenocortical tumors, while GATA-4 mRNA expression was dramatically upregulated in the murine adrenal tumors as well as in human adrenocortical carcinomas. Taken together, these results suggest different roles for GATA-4 and GATA-6 in the adrenal gland, and implicate GATA-4 in adrenal LHR expression and tumorigenesis. Immunohistochemical detection of GATA-4 may serve as a useful marker in differential diagnosis of human adrenal tumors. In addition, the inhalpha/Tag TG model will be helpful for exploring the molecular mechanisms underlying adrenocortical tumorigenesis, ectopic LHR expression in adrenals and the GATA-4/LHR interaction that is related to adrenal tumorigenesis in TG mice.

Adrenal Cortex Neoplasms↗

PubMed1999

Hormonal regulation of proliferation of granulosa and Leydig cell lines derived from gonadal tumors of transgenic mice expressing the inhibin-alpha subunit promoter/simian virus 40 T-antigen fusion gene.

We have produced a transgenic (TG) mouse model expressing the Simian Virus 40 T-antigen (Tag) gene, driven by a 6-kb fragment of the mouse inhibin-alpha subunit promoter (inh-alpha). The mice develop gonadal tumors with 100% penetrance by the age of 5-8 months, of granulosa cell origin in the ovary, and of Leydig cell origin in the testis. In the present study, we characterized the hormonal regulation of proliferation of two immortalized cell lines, BLT-1, originating from a Leydig cell tumor, and NT-1, originating from a granulosa cell tumor. [3H]-thymidine incorporation in both types of cells was stimulated by activin (> or = 10-30 microg/l), while inhibin had no effect. Transforming growth factor (TGF)-beta, at > or = 0.01 microg/l, stimulated proliferation of the granulosa tumor cells, but no effect was found on the Leydig tumor cells. Progesterone inhibited the proliferation of both cell lines, although the granulosa tumor cells were clearly less sensitive than the Leydig cells to this effect ( > or = 3 micromol/l vs. > 10 nmol/l, respectively). hCG had no effect on the Leydig tumor cell DNA synthesis whereas at high concentration (100 microg/l) it stimulated that of the granulosa cells. We also investigated in BLT-1 and NT-1 cells whether the proliferative changes were related to concomitant changes in Tag expression. In BLT-1 cells, this was stimulated by activin, progesterone and hCG, even though the latter substance did not affect cell proliferation. In contrast, TGF-beta inhibited Tag expression. In NT-1 cells, the expression of Tag was stimulated by activin, while hCG had no effect. In contrast, it was reduced by progesterone, inhibin and TGF-beta. In conclusion, our results indicate that the granulosa and Leydig tumor cells, despite similar mechanism of immortalization, respond differently to several mitotic stimuli. The responses in the level of Tag expression in these cells did not always correlate with the changes observed in cell proliferation, indicating the independence of these two phenomena.

Activins↗

PubMed1998

Transgenic mouse models for gonadal tumorigenesis.

The versatile transgenic (TG) techniques allow the production of in vivo animal models for a variety of diseases, including malignant tumors, through tissue-specific expression of oncogenes. We have created a TG mouse model for gonadal somatic cell tumors by expressing the powerful viral oncogene, Simian virus 40 T-antigen (Tag) under regulation of the murine inhibin alpha-subunit promoter (inh alpha). Ovarian granulosa and theca cell tumors were formed in the female, and those of testicular Leydig cells, in the male TG mice at the age of 5-6 months, with 100% penetrance. The tumors produced high levels of inhibin peptides, especially the alpha-subunit, and were steroidogenically active, mainly producing progesterone. The gonadal tumorigenesis was gonadotropin-dependent, since TG mice rendered gonadotropin-deficient by crossbreeding them into the hypogonadotropic hpg genetic background, or by treating them with a gonadotropin-releasing hormone (GnRH) antagonist, did not develop tumors. In order to study the possibility of using the tumor mouse model for testing gene therapy, we created another TG mouse model expressing under the same inhibin-alpha promoter the Herpes Simplex virus (HSV) thymidine kinase (TK) transgene. The inh alpha/HSV-TK mice were crossbred with the inh alpha/Tag mice and the double mutant mice also developed gonadal tumors. When they were treated with antiherpes drugs (acyclovir or gancyclovir), further growth of the tumors was blocked. These preliminary findings prove the principle that tumor ablation in our TG mouse model can be achieved by transduction of the HSV-TK gene into the tumor cells. Besides studies of formation, regulation and therapy of the tumors in vivo, immortalized cell lines derived from them provide models for studies of gonadal somatic cell functions in vitro.

Animals↗

PubMed1998

Luteinizing hormone receptors are associated with non-receptor plasma membrane proteins on bovine luteal cell membranes.

Biophysical studies of the bovine luteinizing hormone (LH) receptor on luteal cell membranes suggest that this receptor may be part of a larger molecular weight structure. We have used 5-iodonaphthyl-1-azide (INA) to identify plasma membrane proteins near LH receptors on plasma membranes from bovine corpora lutea. Following binding of eosin isothiocyanate-derivatized ovine LH or human chorionic gonadotropin (hCG), five proteins with molecular weights of 71, 57, 55, 49 and 36 kDa were selectively derivatized with [125I]-INA following 2 h exposure at 22 degreesC to 514 nm light. However, there was no fluorescence energy transfer between LH receptors occupied by ovine LH or hCG indicating that LH receptors were not self-associated in these membrane preparations. Together these results suggest that, following hormone binding, single copies of the LH receptor may exist in large molecular weight structures that include non-receptor proteins.

Animals↗

PubMed1998

Intracranial tuberculoma in Kuwait.

OBJECTIVE: To study the manifestations of intracranial tuberculoma in Kuwait and to provide guidelines for the diagnosis and management of intracranial tuberculoma in developing countries, where the disease is common and facilities are limited. DESIGN: Data were collected from patients with intracranial space-occupying lesions admitted to Adan Hospital Medical Department and the Neurosurgery and Neuromedical Departments at Ibn-Sina Hospital, Kuwait, from January 1987 to December 1995. RESULTS: Intracranial tuberculomas represented 1.4% of all cases with intracranial space-occupying lesions in these hospitals (13/925); 77% of the patients were males, and seizures were the most frequent presenting symptom. Nine patients (66.6%) responded well to medical treatment and four (33.3%) failed to respond. Those who responded to medical treatment showed remarkable improvement of the intracranial lesions within 6 weeks, and almost complete resolution within 12 weeks. Seven patients required surgery, three due to failure of medical treatment. We report a patient who needed emergency shunt operation, a patient with pituitary tuberculoma, and two patients whose lesions recurred several years after surgery. CONCLUSION: Bearing in mind the non-specific nature of computed tomography and magnetic resonance imaging in the diagnosis of intracranial tuberculoma, and the lack of advanced neurosurgical facilities in developing countries where the disease is common, we recommend a 6-week therapeutic test for patients with solitary or multiple enhancing intracranial space-occupying lesions without mass effect. Stereotactic biopsy is recommended in selected cases wherever facilities are available.

Adolescent↗

PubMed1997

5-iodonaphthyl-1-azide labeling of plasma membrane proteins adjacent to specific sites via energy transfer.

We have examined conditions optimal for 5-iodonaphthyl-1-azide (INA4) labeling of membrane proteins proximal to known membrane sites. Membrane-bound INA can be indirectly activated by energy transfer from visible chromophores. We demonstrate that the efficiency of this sensitized activation is enhanced by use of triplet-forming chromophores such as eosin and by deoxygenation. Variation of sensitized activation efficiency with INA concentration indicates that the critical distance for eosin-INA energy transfer in solution is 8-14 A. We suggest that photosensitization occurs through triplet exchange and present an improved labeling protocol based on these findings. This protocol was used to examine whether different accessory proteins are associated with isolated and crosslinked Type I Fc epsilon receptors on 2H3 rat basophilic leukemia cells. 2H3 cells were incubated with eosin-conjugated IgE and irradiated at 514 nm yielding [125I]INA derivatized peptides at 53, 38, 34, and 29 kDa. Crosslinking IgE with mouse anti-rat IgE prior to irradiation labeled three additional proteins at 60, 54, and 43 kDa. These results demonstrate the utility of sensitized INA labeling in characterizing protein-protein interactions in membranes of intact cells and indicate the importance of considering photophysical factors when selecting sensitizers and reaction conditions. We discuss estimation of the size of the membrane region surrounding a sensitizing chromophore within which INA labeling of membrane proteins occurs.

Animals↗

PubMed1997

Enlarged spectrum of seminological diagnoses using the resazurin colour reaction; a spectrophotometric application.

Two sets of investigations were carried out in the present study to establish whether, in semen samples processed for the resazurin reaction (RT), the colour change and its intensity were informative for both the quality and quantity of spermatozoa. First, the results of RT were read visually using single semen samples from 42 consecutive men from infertile couples. In the second step, the results were additionally read using a spectrophotometer. Single semen samples obtained from another 87 consecutive men from infertile couples and 12 men from fertile couples were analysed in this step. Visual analysis, which involved grading against and RT colour chart, revealed a significant positive correlation between the RT results and the quantity and quality of spermatozoa. Azoospermia was diagnosed by grade number 1 (dark purple colour), while the highest grades 8-11 (colours dark red to pink) represented a homogeneous group of patients with the highest quality of spermatozoa (> 60% motility) and quantity (> 60 x 10(6)/ml ejaculate). Normal parameters of spermatozoa, according to WHO, appeared with a high predominance (89-100% of cases) in this group and were present in most of the samples. Thus, the grades 8-11 might represent semen samples with optimal fertility potential. Spectrophotometric analysis of RT revealed that visual characteristics corresponded closely to the values for optical density (OD) of the samples. The OD for normozoospermic samples ranged between 1.48 and 1.84; for oligozoospermia between 1.2 and 1.48; for azoospermia between 0.98 and 1.1. The OD for samples with putative optimal fertility potential ranged between 1.6 and 1.84. RT evaluation using a spectrophotometer may therefore provide a tool for obtaining a wider spectrum of seminological diagnoses than classic microscopic examination, especially for distinguishing men with probable optimal fertility potential.

Adult↗

PubMed1997

Expression and hormonal regulation of transcription factors GATA-4 and GATA-6 in the mouse ovary.

Two members of the GATA-binding family of transcription factors, GATA-4 and GATA-6, are expressed in the vertebrate ovary. To gain insight into the role of these factors in ovarian cell differentiation and function, we used in situ hybridization to determine the patterns of expression of GATA-4 and GATA-6 in mouse ovary during development and in response to hormonal stimulation. GATA-4 messenger RNA (mRNA) was first evident in the ovary around the time of birth. In the adult ovary, abundant GATA-4 mRNA was detected in granulosa cells of primary and antral follicles, with lesser amounts of GATA-4 message detected in theca cells, germinal epithelium, and interstitial cells. Little or no GATA-4 mRNA was found in corpus luteum. GATA-6 message exhibited a different distribution in the ovary, with abundant expression evident in both granulosa cells and corpora lutea. Stimulation of 3-week-old females with PMSG or estrogen enhanced follicular expression of GATA-4 and GATA-6 transcripts. Subsequent induction of ovulation with human CG resulted in a decrease in GATA-4 mRNA expression in granulosa cells, whereas GATA-6 mRNA expression persisted in granulosa cells after ovulation and in corpora lutea. Moreover, follicular apoptosis was associated with a decrease in the expression of GATA-4 but not GATA-6 message. Stimulation of cultured gonadal cell lines with FSH resulted in increased expression of GATA-4 message, whereas GATA-6 mRNA expression was not affected. In light of these findings, the established role of other GATA-binding proteins in hematopoetic cell differentiation and apoptosis, and the presence of conserved GATA motifs in the promoters of genes expressed selectively in ovary, we propose that GATA-4 and GATA-6 play distinct roles in follicular development and luteinization.

Animals↗

PubMed1996

Helicobacter pylori eradication with short-term therapy leads to duodenal ulcer healing without the need for continued acid suppression therapy.

OBJECTIVE: To determine whether duodenal ulcers continue to heal following successful Helicobacter pylori eradication with short-term eradication therapy without further acid suppression therapy. METHODS: Patients with endoscopically proven duodenal ulcers who were H. pylori positive were randomized to receive omeprazole 40 mg each morning and clarithromycin 500 mg three times daily or famotidine 40 mg twice daily and clarithromycin 500 mg three times daily for 2 weeks. No acid-suppressing agents nor ulcerhealing drugs such as bismuth compounds or sucralfate were prescribed after that. Patients were re-examined endoscopically at week 2 at the end of treatment, and at week 6, 4 weeks after the completion of treatment. RESULTS: Thirty of 44 (68.2%) patients from both treatment arms, in whom the bacteria were subsequently noted to have been eradicated, had healed ulcers at week 2; at Week 6, 42 of 44 (95.5%) were noted to have healed ulcers without further acid-suppressing or ulcer-healing treatment. CONCLUSION: Although a short-term acid-suppressing treatment is insufficient to heal ulcers, where an important putative factor such as H. pylori is eliminated, the ulcer healing process continues without further need for acid-suppressing or ulcer-healing agents.

Adult↗

PubMed1995

Rotational dynamics of luteinizing hormone receptors and MHC class I antigens on murine Leydig cells.

We have examined the molecular motions of luteinizing hormone (LH) receptor and the Major Histocompatibility Complex Class I antigen on murine Leydig cells. Using time-resolved phosphorescence anisotropy methods, erythrosin (ErITC)-derivatized ovine luteinizing hormone (oLH) bound to the LH receptor appears rotationally mobile with rotational correlation times of 19.6 +/- 1.3 microseconds, 13.3 +/- 2.4 microseconds, 9.5 +/- 0.7 microseconds and 4.7 +/- 0.5 microseconds at 4 degrees C, 15 degrees C, 25 degrees C and 37 degrees C, respectively. Rotational correlation times for human chorionic gonadotropin (hCG)-occupied LH receptors were similar to those of the ErITC-oLH occupied receptor at each temperature. In addition, both oLH- and hCG-occupied LH receptors were laterally mobile in fluorescence photobleaching recovery experiments with diffusion coefficients at 29 degrees C of (5.8 +/- 0.9) x 10(-10) cm2 s-1 and (2.9 +/- 0.4) x 10(-10) cm2 s-1, respectively. We also measured the rotational correlation time of Class I antigen on murine Leydig cells using ErITC-derivatized 34-12-2S, an anti-Class I monoclonal antibody. Because there was no decay of the anisotropy function at 4 degrees C, 15 degrees C, 25 degrees C or 37 degrees C in the absence of oLH or following preincubation of Leydig cells with 1 nM oLH, it appears that Class I is rotationally immobile on the 1 ms timescale of our experiments. This result is consistent with the presence of Class I antigen in large molecular weight structures and may be the result of Class I self-aggregation. Further, treatment of cells with anti-Class I antibody had no effect on either basal or oLH-stimulated testosterone secretion. Thus, it appears that this anti-Class I antibody is not LH-mimetic on murine Leydig cells.

Animals↗

PubMed1995

Rotational dynamics of luteinizing hormone receptors on bovine and ovine luteal cell plasma membranes.

To determine whether LH receptor rotational diffusion is similar in closely related species, we compared the rotational correlation times of LH receptors on bovine CL membranes with those of LH receptors on sheep small luteal cells and luteal cell plasma membranes using time-resolved phosphorescence anisotropy techniques. After binding of erythrosin isothiocyanate (ErITC)-derived bovine LH (bLH), ErITC-ovine LH (oLH), or ErITC-hCG, there was no difference in the initial and final anisotropy at 4 degrees C, 15 degrees C, 25 degrees C, and 37 degrees C, indicating that the bLH receptor was rotationally immobile on the time scale of our experiments. On these same membrane preparations, the epidermal growth factor (EGF) receptor occupied by ErITC-murine EGF exhibited temperature-dependent rotational correlation times of 80 +/- 5 microseconds, 111 +/- 7 microseconds, 254 +/- 4 microseconds, and > 1000 microseconds at 4 degrees C, 15 degrees C, 25 degrees C, and 37 degrees C, respectively. Slower rotational times for EGF receptor observed at higher temperatures suggested the occurrence of temperature-dependent receptor aggregation. Like the bLH receptor, the oLH receptor on intact cells and on CL plasma membranes was rotationally immobile on the time scale of our experiments when occupied by ErITC-hCG. However, the oLH-occupied receptors on small luteal cells and on luteal cell membranes had comparable rotational correlation times at 37 degrees C. These results suggest that bLH receptors are present in large, rotationally immobile structures, whereas the receptor-containing structure formed on ovine luteal cells depends on whether that receptor is occupied by hCG or oLH. Also, despite the similarities between reproductive function in these species, the LH-occupied receptor appears to be organized differently in the plasma membranes of these hormone-responsive luteal cells.

Animals↗

PubMed1994

The accumulation and distribution of trace metals in some localized marine species.

Trace elements, such as As, Co, Cr, Hg, Sb, and Zn, were determined by neutron activation analysis (NAA), whereas Cd, Cu, and Pb were determined by graphite furnace atomic absorption spectroscopy (GFAAS) in clam, crab, prawn, swamp cerith, and mussel samples after digestion by microwave heating under controlled conditions before eluting the solutions through a column of a chelating resin, Chelex-100. The standard used in the determination of percentage volatile elements retained by microwave digestion and also in the activation process was Lobster Hepatopancreas TORT-1, whereas known mixed standards were prepared from nitrate salts to determine the efficiency of the separation procedure at a controlled pH. Mercury and lead detected in crabs exceeded the maximum permissible level. Some species also showed a high affinity toward certain elements, and their levels of accumulation in the tissues of these species corresponded with the concentration of these elements in sediments, especially at sites in the vicinity of an industrial zone.

Animals↗

PubMed1993

Class I major histocompatibility complex antigens are not associated with the LH/CG receptor on ovine luteal cells.

We have examined the rotational dynamics of the luteinizing hormone (LH) receptor on day 10 intact ovine small luteal cells and isolated plasma membranes using polarized fluorescence depletion (PFD). This technique measures rotational correlation times which are proportional to the in-membrane volume of a protein and are useful for examining changes in protein size due to receptor aggregation or protein-protein interactions. Eosin isothiocyanate (EITC)-derivatized ovine LH (EITC-oLH) bound to the LH receptor on luteal cell plasma membranes had a rotational correlation time of 20 +/- 6 microseconds, while that for EITC-human chorionic gonadotropin (EITC-hCG)-occupied LH receptors was 46 +/- 13 microseconds. Slower rotational times for EITC-oLH and EITC-hCG, 63 +/- 19 and 87 +/- 20 microseconds, respectively, were obtained on intact ovine luteal cells. These results indicate that the LH receptor exists as a larger molecular mass complex when binding hCG than oLH, a difference which could be attributable to hCG-induced LH-receptor interaction with additional membrane protein(s). One candidate protein for such an interaction is the Major Histocompatibility Complex (MHC) Class-I antigen. However, the rotational correlation time of EITC-anti-MHC Class-I antibody (SBU I) Fab fragments was 247 +/- 34 microseconds, indicating that MHC Class I is located in complexes larger than those identified by EITC-OLH or EITC-hCG. Preincubation of plasma membranes with 1 nM unlabeled oLH or hCG had no significant effect on this rotational correlation time. Further, treatment of cells with SBU I had no affect on either basal or oLH-stimulated progesterone secretion. Thus it appears that the ovine luteal LH-receptor is not associated with MHC Class I and that antibody-induced aggregation of MHC Class I does not cause an LH-mimetic response.

Animals↗