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Biomedical subjects

S Atkinson

Publications and source records attributed to S Atkinson.

At least 37 records · Page 2Linked to original sources
PubMed1988

Inadequate function of corpora lutea following the induction of ovulation with monensin and FSH in seasonally anoestrous ewes.

Sixteen ewes in mid-seasonal anoestrus were stimulated to ovulate using sequential injections of FSH (total dose 10 mg) over a 4-day period. Half of the ewes received a dietary growth promotant (monensin) known to enhance the ovarian response to exogenous gonadotrophins. The ewes were ovariectomized on day 5 or 11 (day 0 = the initiation of FSH treatment). Serial blood samples were taken in half of the ewes to determine peripheral concentrations of LH and a single sample of ovarian venous blood was collected before ovariectomy. All luteal structures were dissected from the ovaries, counted and incubated in vitro to determine progesterone production. The luteal structures were then examined histologically for the abundance of luteal cells. The physical appearance of the ovary, along with plasma concentrations of LH and ovarian venous oestradiol indicated that the monensin-treated ewes ovulated before control ewes. The corpora lutea from control ewes produced significantly (P less than 0.05) more progesterone than did the corpora lutea from the monensin-treated group. Furthermore, only 7% of the remaining luteal structures in the monensin-treated group produced significant amounts of progesterone on day 11, whereas 61% of the luteal structures in the control group were actively secreting progesterone. The mean number of granulosa cells in the follicles was similar at ovulation in the two groups, but the mean numbers of large and small luteal cells were significantly (P less than 0.05) lower in luteal structures from the monensin-treated ewes than in those from the control ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗
PubMed1988

Thyrotrophin-blocking antibodies in goitrous primary hypothyroidism: detection by a highly sensitive bioassay and determination of site of action.

Using a highly sensitive bioassay technique, the presence of antibodies capable of blocking the stimulation of thyrocyte function by TSH has been investigated in the sera of a group of 50 patients with primary hypothyroidism. TSH-blocking activity was detected in immunoglobulin (IgG) preparations from the sera of 13 patients (26%). All 13 IgG preparations blocked both TSH-stimulated iodide uptake and cyclic AMP generation (Spearman's rank correlation = 0.6, p = 0.02). However, only one IgG preparation blocked dibutyryl cyclic AMP-stimulated iodide uptake. The presence of TSH-blocking antibody activity was associated with goitrous (ten out of thirteen patients) as well as atrophic (two out of thirteen patients) primary hypothyroidism. Furthermore, TSH-blocking activity was not associated with other thyroid autoantibodies, as thyrotrophin-binding-inhibiting immunoglobulins and anti-TSH antibodies were undetectable in all cases and there was no correlation between TSH-blocking activity and the presence or titre of anti-thyroglobulin or anti-microsomal antibodies. This study indicates that TSH-blocking antibodies are present in the serum of some patients with primary hypothyroidism and are directed towards a site, presumably adjacent to or contiguous with the TSH receptor, that is not the binding site for TSH. The coexistence of TSH-blocking activity and goitre in the majority of these patients implies that these antibodies, although capable of blocking TSH-stimulated thyroid hormone biosynthesis, do not necessarily inhibit the mitogenic action of TSH in vivo.

Antibodies↗
PubMed1988

Adrenal glands alter the concentration of oestradiol-17 beta and its receptor in the uterus of ovariectomized ewes.

To investigate the effects of adrenal hormones on oestrogen activity in the uterus, ovariectomized ewes were either adrenalectomized, administered glucocorticoid-like preparations (CORT), or remained as controls. The adrenalectomized ewes were maintained with a corticoid-replacement therapy and monitored daily for plasma glucose and Na+/K+ concentrations. Blood samples were collected from all ewes at 15-min intervals for 4 h and assayed for LH and FSH. The adrenalectomized ewes were killed 9 days after adrenalectomy, while the CORT ewes were killed after 3 weeks of drug therapy. The control ewes were killed simultaneously with the CORT ewes. Uterine tissues were homogenized and the numbers of oestradiol receptors and tissue concentrations of oestradiol-17 beta were measured. The adrenalectomized ewes had significantly higher concentrations of cytosolic oestrogen receptors in the uterus than did the control ewes, which had significantly higher concentrations than the CORT ewes (0.95 +/- 0.06, 0.76 +/- 0.02 and 0.60 +/- 0.02 (S.E.M.) mumol/kg protein respectively). The concentrations of oestradiol-17 beta measured in uterine tissues were significantly lower in adrenalectomized and CORT ewes than in control ewes (37.4 +/- 5.5, 61.7 +/- 25.7 and 135.5 +/- 12.8 pmol/kg respectively). There were no significant differences between any groups in the peripheral concentrations of LH or FSH. These results indicate that the adrenal gland affects the concentrations of both oestrogen and its receptor in the uterus of ovariectomized ewes, probably by different mechanisms. These effects are not mediated by gonadotrophins.

Adrenal Glands↗
PubMed1987

Measurement of urinary and plasma estrone sulphate concentrations from pregnant sows.

The accuracy of urinary estrone sulphate (E1S) concentrations as an indication of pregnancy was compared to that of plasma E1S concentration. Urine and plasma were collected from 145 sows 18 to 30 days after mating. Concentrations of E1S in urine were indexed to creatinine concentration (CR) and specific gravity (SG) to correct for urine dilution. There was no significant difference in E1S concentration between urine corrected for CR or SG and uncorrected urine (UN) from pregnant sows. Urinary E1S concentrations were 20 to 100 times higher than plasma E1S concentrations. The E1S test was accurate in the detection of pregnancy in sows using both plasma and urine (test sensitivity, 98.8% vs. 96.4%, respectively) during the optimal sampling period of 20 to 30 days post mating. The test was slightly more accurate (NS) using plasma than urine in detecting non-pregnant sows (test specificity, 100.0% vs. 91.9%, respectively) 20-30 days after mating. Urinary E1S concentrations could be used to predict litter size, but the precision was poor ( +/- 3 piglets), and thus could only be used to predict small (less than 5 piglets), medium (6-10 piglets) and large (greater than 11 piglets) litters.

Animals↗
PubMed1987

Long-term effect of insulin on glucose transport and insulin binding in cultured adipocytes from normal and obese humans with and without non-insulin-dependent diabetes.

We have tested the hypothesis that in vitro exposure of insulin-resistant adipocytes with insulin results in improved insulin action. A primary culture system of adipocytes from obese subjects with or without non-insulin-dependent diabetes mellitus (NIDDM) and nonobese control subjects has been developed. The adipocytes when cultured in serum-free medium do not lose their original characteristics in regard to insulin binding and glucose transport. The adipocytes from three groups were incubated with insulin (0, 10(-10) M, and 10(-7) M) for 24 h at 37 degrees C, receptor-bound insulin was dissociated, and basal and insulin (1 X 10(-11)-10(-7) M)-stimulated glucose transport and 125I-insulin binding were determined. The 24-h insulin exposure of adipocytes from control subjects decreased basal and insulin-stimulated glucose transport. The effects of 1 X 10(-7) M insulin were more pronounced than 1 X 10(-10) M insulin. Similarly, insulin exposure decreased insulin sensitivity and responsiveness of cultured adipocytes from obese and NIDDM patients. The insulin-induced reduction in insulin sensitivity and responsiveness for glucose transport in three groups were due to alterations at insulin binding and postbinding levels. In conclusion, insulin induces insulin resistance in control adipocytes and further worsens the insulin resistance of adipocytes from obese and NIDDM subjects. For insulin to improve the insulin resistance of adipocytes from NIDDM patients, either more prolonged in vitro insulin exposure and/or other hormonal factors might be required.

Adipose Tissue↗
PubMed1987

The specificity of autoantibodies in Graves' ophthalmopathy.

An autoantibody to orbital antigens is found in patients with Graves' ophthalmopathy. This autoantibody also binds to skeletal muscle antigen. Occasional positive responses have been seen in patients with Hashimoto's disease and with non-organ-specific autoimmune disease. Eye muscle has a higher innervation ratio than skeletal muscle and may be of different embryological origin, but it is nevertheless closely related to skeletal muscle and it is perhaps not surprising that the antibody should interact with both these types of muscle. What remains quite unexplained, is why the disease process apparently affects eye muscle only. The antigen appears to be distinct from thyroidal antigens, but further work with a larger patient population is necessary before one can be certain of this. To date it has been possible to exclude the cytoskeletal proteins, myosin and actin, and also the TSH receptor as possible candidates for the responsible antigens. Further studies are in progress to elucidate the nature of this muscle antigen.

Autoantibodies↗
PubMed1987

Effect of thyrotrophin on epidermal growth factor receptors in monolayer cultures of porcine thyroid cells.

Primary cultures of porcine thyroid cells, grown as monolayers, showed saturable binding of epidermal growth factor (EGF). Scatchard analysis resolved the binding to a high-affinity/low-capacity site (dissociation constant = 0.17 nmol/l, maximal binding capacity = 1.67 pmol/10(6) cells) and a low-affinity/high-capacity site. Preincubation of thyroid monolayers with TSH for 3 days caused an increase in binding of 125I-labelled EGF due to an increase in the number of receptors, with the binding affinity unchanged. This effect was dose-dependent within the range of TSH concentrations 0.01-100 mu/l. The same effect was seen with dibutyryl cyclic AMP (10-1000 mumol/l). When the protein synthesis inhibitor cycloheximide was included in the TSH preincubation, the increase in EGF binding was abolished. The TSH effect on EGF binding was not mediated by thyroid hormones, since neither thyroxine (T4) nor tri-iodothyronine (T3) at 0.1 nmol/l-10 mumol/l could mimic the effect of TSH, nor could antisera to T3 or T4 neutralize the effect of TSH. The concentration of extracellular iodide (10 nmol/l-10 mmol/l) had no effect on the binding of 125I-labelled EGF. The results demonstrate that TSH increases the number of receptor sites for binding of EGF to thyroid monolayers in vitro. This effect is dependent upon protein synthesis and is mediated by cyclic AMP but not by thyroid hormones or iodide. This effect on binding of EGF may contribute to the trophic action of TSH.

Animals↗
PubMed1987

Effects of progesterone intravaginal devices on synchronization of estrus in postpartum dairy cows.

Effects of two intravaginal treatments of progesterone on the synchronization of behavioral estrus were compared in three groups of lactating dairy cows at 7 to 8 wk postpartum. Group 1 had progesterone-releasing intravaginal devices with attached estradiol benzoate capsules inserted for 12 d. Groups 2 and 3 had controlled internal drug release devices, containing progesterone alone, inserted for 9 or 12 d. Behavioral estrus was detected as early as 24, 32, and 36 h after removal of the devices in groups 1, 2, and 3, respectively. Estrus was better synchronized and the proportion of cows showing estrus after device removal was greater in group 1 than in groups 2 and 3. After removal of devices, mean milk progesterone of all cows that did not show estrus was higher than that of cows that showed estrus. In groups 1, 2, and 3, 1 of 7, 7 of 12, and 4 of 12 cows not showing estrus had high milk progesterone after removal of the devices, indicating the presence of functional corpora lutea. In cows not displaying estrus milk progesterone concentrations decreased, indicating these cows were cyclic, although behavioral estrus was absent.

Administration, Intravaginal↗
PubMed1986

Steroid production and hCG binding by ram-induced ovarian follicles in seasonally anoestrous ewes.

The introduction of rams to a group of previously isolated anoestrous ewes has been shown to stimulate ovarian follicular development and ovulation. The present experiment was carried out to determine the ability of follicles arising from this ram stimulus to produce steroids and bind hCG. Seasonally anoestrous Southdown ewes were exposed to rams for 24 h, 40 h, 3 days, 10 days or 20 days before ovariectomy. Steroid production and the concentration of hCG binding sites in follicles dissected from the ovaries were measured in vitro. The presence of a ram caused ovulation and enhanced oestradiol production by follicles, but had little effect on total androgen production or the number of hCG binding sites present in the follicles when compared to follicles from anoestrous ewes. The oestradiol concentrations in large follicles were not as high as in preovulatory follicles from cyclic ewes reported in other studies. Follicles continued to develop through the ram contact period and when incubated after 40 h and 10 days of ram contact produced high levels of progesterone, indicating partial luteinization, although the corpora lutea (CL) resulting from the induced ovulations regressed prematurely. We suggest that the lack of hCG binding sites in ram-induced follicles may be the cause of poor luteinization and suboptimal development of luteal tissue after induced ovulation in ewes during seasonal anoestrus.

Anestrus↗
PubMed1986

Demonstration of significant epidermal growth factor activity in murine thyroid tissue.

Epidermal growth factor (EGF) was first isolated from the mouse submaxillary gland (SMG) which remains its only known site of synthesis. Earlier work suggests that EGF may be implicated in the regulation of thyroid cell growth and proliferation. Moreover, thyroid hormones increase the EGF content of mouse SMG and mimic the maturational effects associated with EGF. The aim of this study was therefore to determine whether the mouse thyroid gland is a site of EGF production. Thyroid and submaxillary glands were homogenized in Tris-HCl, the EGF content was measured by a homologous radioimmunoassay (RIA) and receptor-binding activity assessed in a radioreceptor assay. Epidermal growth factor was readily detectable in each thyroid extract. Dilution curves were parallel to the standard curve. Values obtained for right and left lobes of thyroid were in excellent agreement (r = 0.997, P less than 0.001). The intrathyroidal EGF concentration obtained by RIA was 26.1 +/- 6.0 (S.E.M.) ng/mg protein (n = 40); values obtained by the receptor assay were slightly lower but correlated closely (r = 0.828, P less than 0.01). Assay of homogenates prepared at the same time from the submaxillary glands of these mice showed that thyroidal EGF was not correlated with EGF content in the SMG. These findings indicate that EGF, both biologically active and immunoreactive, is readily detectable in the mouse thyroid and that the thyroid gland is a probable site of EGF synthesis. The methodology provides a model for further studies of the regulation of EGF production and its significance in relation to thyroid disease.

Animals↗
PubMed1985

Homologous radioimmunoassay for epidermal growth factor in human saliva.

Epidermal growth factor (EGF) is a small polypeptide with potent mitogenic activity. Its synthesis by mouse submaxillary gland is stimulated by certain hormones. To assess its physiological significance in man, we have developed a homologous radioimmunoassay for human epidermal growth factor (hEGF) in saliva. A satisfactory standard curve was readily obtained using either buffer or peptide-free saliva. The mean IC50 was 436 +/- 200 pM (mean +/- SD) and sensitivity approximately 35 pM. The mean normal salivary hEGF in 63 males was 314.6 +/- 21.7 pM (+/- SEM) and 354 +/- 27.8 pM in 48 females. The difference between the means of the sexes was not significant. Assays of aliquots stored under different conditions showed hEGF in saliva to be stable and the method reproducible. Salivary hEGF secretion did not suggest diurnal rhythmicity and was unrelated to meals.

Adult↗
PubMed1985

Ram-induced growth of ovarian follicles and gonadotrophin inhibition in anoestrous ewes.

Southdown ewes in mid-seasonal anoestrus were exposed to rams for 0 h (control group), 2 h, 24 h, 40 h, 3 days, 10 days or 20 days. Serial blood samples were then taken to determine LH and FSH levels. Ewes with greater than 24 h ram exposure were ovariectomized immediately after bleeding, and all follicles greater than 1 mm diameter were dissected from the ovaries and measured. LH basal concentrations and pulse frequency increased significantly within 2 h of ram introduction, but by 24 h fell, and then remained low. FSH concentrations fell within 2 h of ram introduction and remained low. Control group ewes (isolated) had no follicles greater than 4 mm diameter, whereas all ewes exposed to rams had large follicles, with CL or preovulatory follicles present at 40 h after ram introduction. Ram introduction was also associated with follicle recruitment (antrum formation to less than 2 mm). Follicular recruitment and development to the large follicle stage therefore occurred during a period of low plasma gonadotrophin levels and suppressed LH pulsing.

Anestrus↗
PubMed1984

Ophthalmopathic immunoglobulin in patients with Graves' ophthalmopathy.

An IgG which binds specifically to retro-orbital antigen has been detected in patients with Graves' ophthalmopathy. By means of an assay which detects ophthalmopathic immunoglobulin (OIg) in patients' serum with an antigen prepared from porcine retro-orbital muscle, levels of OIg above the normal reference range were found in 21 of 33 (64%) patients with active untreated ophthalmopathy, in 3 of 12 (25%) with active disease already receiving steroid treatment, and in 3 of 18 (16%) with longstanding inactive eye disease. OIg was found in only 1 of 22 thyroid patients without eye disease. There was no correlation of OIg with thyrotropin-binding-inhibiting immunoglobulin nor with thyroid microsomal antibody, and there was no clear association with thyroglobulin antibody. Ophthalmopathy seems to be distinct from Graves' hyperthyroidism and the autoimmune response is directed to retro-orbital antigens.

Animals↗
PubMed1984

A specific IgG in Graves' ophthalmopathy and its relation to retro-orbital and thyroid autoimmunity.

An IgG (ophthalmopathic immunoglobulin) that binds to retro-orbital antigen was identified in serum from patients with active Graves' ophthalmopathy, and its nature and specificity were investigated. Dose related binding of this immunoglobulin to retro-orbital antigens prepared from guinea pig harderian gland or porcine eye muscle was found, which could be abolished by prior incubation with antigen. The immunoglobulin did not bind to thyroid membranes, thyroid microsomes, or thyroglobulin or interact with liver, skeletal muscle, or fat membranes. Serum with high activity of thyrotrophin binding inhibiting immunoglobulin did not react with retro-orbital antigen, and this activity was not affected by preincubation of the serum with retro-orbital antigen. Thyroid stimulating hormone was also without effect on retro-orbital antigen. It is concluded that Graves' ophthalmopathy is associated with a specific ophthalmopathic immunoglobulin that reacts with retro-orbital antigen as distinct from thyroid antigens, and that the autoimmune response is directed towards retro-orbital antigens. This suggests that the ophthalmopathy is an entity distinct from autoimmune thyroid disease.

Adult↗
PubMed1984

Evidence that thyroid-stimulating antibody is produced in the thyroid gland.

The hyperthyroidism in Graves' disease results from the action of thyroid-stimulating antibodies (TSAb). The thyroid gland in Graves' disease shows diffuse lymphocytic infiltration, and after removal of the gland antibody titres usually decline and patients go into remission. It is postulated that the lymphocytes in the thyroid may be an important site of TSAb production. 10 patients with Graves' disease and 8 patients with other thyroid disorders were studied. Blood was taken during operation, but before thyroid mobilisation, from the thyroid vein and simultaneously from a peripheral vein. In patients with Graves' disease the concentration of TSAb activity in the thyroid vein was much greater than that in the peripheral vein. TSAb was not detected in either peripheral vein or thyroid vein samples in the other patients. The increase in TSAb concentration in the thyroid vein indicates production of antibodies by lymphocytes within the thyroid and could explain why removal of the thyroid results in disappearance of TSAb from the circulation.

Adult↗
PubMed1984

Screening for refractive errors in 6-9 month old infants by photorefraction.

The method of isotropic photorefraction has been used in a trial of refractive screening of 6-9 month old infants. Data are presented on the calibration of the method against retinoscopic measurements and its reliability. In photorefractive screening of 1096 infants under cyclopentolate cycloplegia 5% were found to be hypermetropic (over +3.5 D), 4.5% myopic, and 1.3% anisometropic (over 1 D). These refractive errors were confirmed on retinoscopic follow-up (with the exception of a few anisometropes). Follow-up of controls shows that one small refractive error was missed in 52 infants. We conclude that photorefraction is a valid and practical screening technique. Longitudinal study of infants with refractive errors will assess the value of early detection, in particular for prediction and prevention of strabismus.

Adult↗
PubMed1983

Specific epidermal growth factor receptors on porcine thyroid cell membranes.

Specific saturable receptors for epidermal growth factor (EGF) of high affinity (Ka 1.7 X 10(9) M-1) have been demonstrated on porcine thyroid membranes. Optimal conditions for EGF binding have been determined. TSH and other peptide hormones do not inhibit the binding of 125I-EGF and EGF does not inhibit 125I-TSH binding to thyroid membranes. The results suggest that EGF may be involved in the regulation of thyroid follicular cell growth and function.

Animals↗