Biomedical subjects

G Baxter

Publications and source records attributed to G Baxter.

At least 19 recordsLinked to original sources

PubMed2005

Lobar nephronia in a transplanted kidney.

We report a patient who presented with a solid mass in her graft 15 years after renal transplantation. The appearances by ultrasound were consistent with either malignancy or lobar nephronia (focal acute bacterial nephritis). Biopsy confirmed the diagnosis of a lobar nephronia with marked inflammatory infiltrate and frank pus formation. Treatment with antibiotics was associated with resolution of the mass. Lobar nephronia is a diagnosis based upon renal ultrasonography and must be considered in a patient with a solid mass in the kidney.

Acute Disease↗

PubMed2004

Melanoma.

The incidence of malignant melanoma in the UK is still rising despite public health warnings about the risks of excessive sun exposure. This aggressive tumour can metastasize to virtually any organ, even years after resection of the primary lesion and cause a variety of radiological appearances. This review provides examples of both typical and non-specific imaging features of melanoma metastases, as well as examples of primary choroidal melanoma.

Choroid Neoplasms↗

PubMed2002

Lymphoma: pictorial review. I.

Lymphoma is a spectrum of malignant neoplasms of the lymphoid system. The appearances radiologically are diverse with almost all organs susceptible to involvement. The condition is challenging as it can mimic the appearance of almost all other neoplasms. This review highlights in a general way the diversity of the radiological appearances and organs involved.

Americas↗

PubMed2002

Lymphoma: pictorial review. II.

Lymphoma is a spectrum of malignant neoplasms of the lymphoid system. The appearances are radiologically diverse with almost all organs susceptible to involvement. The condition is challenging as it can mimic the appearance of almost all other neoplasms. This review article highlights in a general way the diversity of the radiological appearances and organs.

Diagnostic Imaging↗

PubMed2002

The effect of increased dietary intake on superovulatory response to FSH in heifers.

We have previously shown that the number of ovarian follicles <4 mm in diameter can be increased by enhanced dietary intake in heifers. This study investigated the effect of the same dietary treatment on superovulatory response. The estrous cycles of 24 mature Hereford x Friesian heifers were synchronized by a standard progesterone plus prostaglandin protocol. The animals were fed with either 100% (group M, n = 12) or 200% (group 2M, n = 12) maintenance requirements for a 3-week period. Starting from day 4 of the synchronized estrous cycle, all the animals were superovulated using a standard 4-day FSH regime followed by an injection of GnRH analogue (GnRHa) to induce ovulation. Rectal ultrasound scanning was carried out to assess ovarian follicular populations at the start of FSH treatment and on the day of GnRHa injection, and to determine the number of corpora lutea 5 days after GnRHa injection. The body weight (BW) and body condition score (BCS) were recorded weekly and plasma samples were collected throughout the experimental period. There were no differences in either BW or BCS between two groups at the start of the experiment. The BW and BCS were maintained during the experiment in the group M, whilst animals in the group 2M showed a non-significant (P > 0.05) increase in BW and BCS. Circulating concentrations of insulin were significantly (P < 0.01) higher in heifers from the group 2M throughout the controlled feeding period. The group 2M had significantly (P < 0.05) more follicles 2-4 mm in diameter at the start of FSH treatment and more (P < 0.01) follicles >9 mm in diameter on the day of GnRHa injection, when compared with the group M. Similarly, 5 days after GnRHa injection there were significantly (P < 0.01) more corpora lutea in the group 2M (18.1+/-2.2) than in the group M (10.6+/-3.0). In addition, plasma progesterone concentrations following GnRHa injection were significantly (P < 0.01) higher in heifers from the group 2M. In conclusion, these results confirm that increased dietary intake can enhance the recruitment of ovarian follicles in heifers. This treatment may provide a valuable approach to improving superovulatory response in cattle.

Animals↗

PubMed2002

Steroidogenesis in bovine granulosa cells: the effect of short-term changes in dietary intake.

The nutritional status of a cow is a key factor in the regulation of both follicle growth and oocyte quality. In this study, the effect of diets designed to increase circulating insulin and insulin-like growth factor I (IGF-I) concentrations on steroid production by granulosa cells in vitro was examined to analyse the mechanisms through which these changes occur. Hereford x Friesian heifers (n = 24) were offered maintenance or twice maintenance diets during the experimental period (17 days). Circulating concentrations of FSH did not differ between the two dietary groups, whereas insulin and IGF-I concentrations showed significant diet x day of oestrous cycle interactions. Ovaries were collected on day 3 of the first follicle wave after synchronization of oestrus. Granulosa cells were isolated from small (1-4 mm) and medium-sized (4-8 mm) follicles and cultured in the presence of long R3-IGF-I or bFSH or both. After 4 days in culture, granulosa cells isolated from small follicles, but not medium-sized follicles, collected from cattle offered the twice maintenance diet secreted significantly higher (P < 0.05) amounts of oestradiol compared with granulosa cells collected from cattle offered the maintenance diet. The effect was apparent in either the presence or absence of FSH and long R3-IGF-I. This nutritional effect on aromatase activity in granulosa cells was not apparent after day 6 of culture. There was no effect of diet on progesterone production by granulosa cells after 4 or 6 days of culture. These results support the hypothesis that dietary-induced changes in circulating insulin and IGF-I concentrations have a direct effect on the steroidogenic potential of bovine granulosa cells from small follicles. The dietary-induced increases in aromatase activity in small follicles combined with the increased concentration of metabolic hormones are possible mechanisms through which short-term changes in nutrition may affect follicle dynamics.

Animal Nutritional Physiological Phenomena↗

PubMed2002

Regulation of expression of ovarian mRNA encoding steroidogenic enzymes and gonadotrophin receptors by FSH and GH in hypogonadotrophic cattle.

A study was conducted to determine the effects of FSH and bovine somatotrophin on the expression of mRNA encoding the gonadotrophin receptors and steroidogenic enzymes in ovarian follicles of cattle rendered hypogonadotrophic by treatment with a GnRH agonist. Hereford x Friesian heifers were allotted into two pretreatment groups: controls (n = 10) and GnRH agonist-treated (n = 20). Ovaries of control cows were removed on day 2 of the first follicular wave after synchronized oestrus. GnRH agonist-treated heifers were given either FSH or no FSH. FSH was infused at 50 microg h(-1) for 48 h. Ovaries in GnRH agonist-treated heifers were removed at the end of exogenous hormone treatment. The control, GnRH agonist and GnRH agonist plus FSH treatment groups were divided further into bovine somatotrophin or no bovine somatotrophin treatments (n = 5 per treatment). Bovine somatotrophin (25 mg day(-1) by s.c. injection) was administered for 3 days. Ovaries were scanned once a day by ultrasonography. Blood samples for hormone measurements were collected three times a day from oestrus until the time of removal of ovaries. Expression of mRNAs for the FSH and LH receptors and cytochrome P450 side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17) and cytochrome P450 aromatase (P450arom) enzymes was localized by in situ hybridization and quantified by image analysis. Ovarian follicular growth was arrested at < or = 4.5 mm in diameter in GnRH agonist-treated heifers. There was no effect of bovine somatotrophin on follicular dynamics, gonadotrophin secretion or expression of mRNA for either the gonadotrophin receptors or steroidogenic enzymes. Infusion of FSH to GnRH agonist-treated heifers increased FSH concentrations in serum to the physiological concentrations observed in controls and stimulated growth of follicles to a size similar (5.5-8.0 mm in diameter) to recruited follicles in control cows. FSH induced mRNA expression of P450scc and P450arom in granulosa cells of follicles at a smaller size (< or = 4.5 mm in diameter) than in controls and increased (P < 0.001) expression in larger (> 4.5 mm in diameter) follicles. Expression of mRNAs for P450scc and P450c17 increased (P < 0.001) with increasing follicle size and was higher (P < 0.01) in theca cells of GnRH agonist plus FSH-treated heifers than in the other groups. There were no treatment differences in expression of FSH receptor in granulosa cells or LH receptor in theca cells, but expression of both receptors increased with follicle size. There was no expression of LH receptor in the granulosa cells of cows from any treatment group. In conclusion, FSH treatment in GnRH agonist-treated heifers induced similar changes in follicular growth to those observed during the first follicular wave, but despite similar peak concentrations, prolonged exposure to high FSH induced precocious expression of mRNAs for P450scc and P450arom in granulosa cells from small follicles and markedly upregulated expression of these enzymes in granulosa cells from recruited follicles. The results of this study demonstrate the key role that FSH plays in the induction of follicular growth and differentiation.

Animals↗

PubMed2002

Insulin-like growth factor (IGF) system in the oocyte and somatic cells of bovine preantral follicles.

Many studies have highlighted the role of the insulin-like growth factor (IGF) system in the control of antral follicular growth. However, much less is known about the involvement of the IGF system in the regulation of preantral follicular development. In an attempt to address this lack of knowledge, the present study describes the spatial and temporal patterns of expression of mRNA encoding components of the IGF system in bovine follicles during preantral stages of development. mRNA was detected by in situ hybridization using frozen sections (14 microm) of bovine ovarian tissue. Serial sections were probed with 35S-labelled bovine riboprobes. Type 1 IGF receptor mRNA was detected in granulosa cells and in the oocyte of preantral follicles; however, in this study, as in previous studies, it was not possible to detect mRNA encoding either IGF-I or -II. IGF binding protein (IGFBP)-2 mRNA was present in granulosa cells and oocytes of preantral follicles, and immunoreactive IGFBP-2 was detected around granulosa cells during this early stage of development. Occasionally, preantral follicles were identified in which there was no expression of IGFBP-2 in granulosa cells or the oocyte. IGFBP-3 mRNA was detected in the oocyte of preantral follicles and in the surrounding stromal tissue. mRNAs encoding IGFBP-2 and -3, and type 1 IGF receptor were first detected in type 2 follicles. In conclusion, although the IGF ligands are not expressed in preantral follicles, mRNAs encoding the type 1 IGF receptor, and IGFBP-2 and -3 were present and showed unique spatial patterns of expression within preantral follicles.

Animals↗

PubMed2001

Effect of dietary energy and protein on bovine follicular dynamics and embryo production in vitro: associations with the ovarian insulin-like growth factor system.

Heifers were assigned either low or high (HE) levels of energy intake and low or high concentrations of dietary crude protein. The effect of these diets on the plasma concentrations of insulin, insulin-like growth factor (IGF)-I, and urea on follicular growth and early embryo development is described. We propose that the observed dietary-induced changes in the ovarian IGF system increase bioavailability of intrafollicular IGF, thus increasing the sensitivity of follicles to FSH. These changes, in combination with increased peripheral concentrations of insulin and IGF-I in heifers offered the HE diet, contribute to the observed increase in growth rate of the dominant follicle. In contrast to follicular growth, increased nutrient supply decreased oocyte quality, due in part to increased plasma urea concentrations. Clearly a number of mechanisms are involved in mediating the effects of dietary energy and protein on ovarian function, and the formulation of diets designed to optimize cattle fertility must consider the divergent effects of nutrient supply on follicular growth and oocyte quality.

Animals↗

PubMed2000

Randomized trial of graded compression stockings for prevention of deep-vein thrombosis after acute stroke.

Graded compression stockings are commonly used to prevent deep-vein thrombosis (DVT) after stroke, but their efficacy in this setting has not been evaluated. Extrapolation of effectiveness from trials in patients undergoing elective surgery may be inappropriate. We undertook a randomized, controlled trial, with blinded data review, in a University hospital Acute Stroke Unit. Patients were allocated to graded compression stockings or to standard care alone. DVT incidence was determined at baseline and at day 7+/-2 by colour-flow Doppler ultrasound. Ninety-eight patients with acute, immobilizing stroke were randomized; 97 had full outcome data. One patient had clinically manifest DVT, and no patient had pulmonary thromboembolism. DVT was detected in 7/65 patients allocated stockings, and 7/32 controls (odds ratio 0.43, 95% CI 0.14-1.36); DVT involving femoral veins was detected in 3/65 and 2/32. In the first week after stroke, radiologically-detected DVT remains common, but is usually clinically silent. Proximal DVT is less common. Graded compression stockings produced a reduction in DVT incidence comparable to that in other patient groups, but the reduction was not statistically significant, and the magnitude of effect size requires confirmation. There is greater doubt over efficacy in early prevention of proximal DVT.

Aged↗

PubMed2000

Expression of mRNA encoding IGF-I, IGF-II and type 1 IGF receptor in bovine ovarian follicles.

IGFs regulate gonadotrophin-stimulated proliferation and differentiation of granulosa and theca cells in vitro. However, the detailed pattern of mRNA expression of IGFs in bovine follicles remains controversial. The objectives of this study were therefore to describe the temporal and spatial pattern of expression of mRNA encoding IGF-I, IGF-II and the type 1 IGF receptor in bovine follicles in vivo. The expression of mRNA encoding IGF-II was detected in theca tissue from around the time of antrum formation up to and during the development of dominance. No IGF-II mRNA expression was detected in granulosa cells. In the majority of follicles we were unable to detect mRNA encoding IGF-I in either granulosa or theca tissue from follicles at any stage of development. Occasionally low amounts of mRNA encoding IGF-I were detected in the theca externa and connective tissue surrounding some follicles. Type 1 IGF receptor mRNA was detected in both granulosa and theca cells of preantral and antral follicles. Expression was greater in granulosa tissue compared with theca tissue. We also measured IGF-I and -II mRNA in total RNA isolated from cultured granulosa and theca cells using reverse transcriptase PCR. In contrast to the in vivo results, IGF-II mRNA was detected in both granulosa and theca tissue. IGF-I mRNA was detected in theca tissue and in very low amounts in granulosa cells. Using a specific IGF-I RIA we were unable to detect IGF-I immunoreactivity in granulosa conditioned cell culture media. Using immunohistochemistry we detected IGF-I immunoreactivity in some blood vessels within the ovarian stroma. We conclude from these results that IGF-II is the principal intrafollicular IGF ligand regulating the growth of bovine antral follicles. In preantral follicles the expression of mRNA encoding type 1 IGF receptor but absence of endogenous IGF-I or -II mRNA expression, highlights a probable endocrine mechanism for the IGF regulation of preantral follicle growth.

Animals↗

PubMed2000

Expression of mRNA encoding insulin-like growth factors I and II and the type 1 IGF receptor in the bovine corpus luteum at defined stages of the oestrous cycle.

Previous studies have implicated insulin-like growth factors I and II (IGF-I and -II), in the regulation of ovarian function. The present study investigated the localization of mRNA encoding IGF-I and -II and the type 1 IGF receptor using in situ hybridization to determine further the roles of the IGFs within the bovine corpus luteum at precise stages of the oestrous cycle. Luteal expression of mRNA encoding IGF-I and -II and the type 1 IGF receptor was detected throughout the oestrous cycle. The expression of IGF-I mRNAvaried significantly during the oestrous cycle. IGF-I mRNA concentrations were significantly higher on day 15 than on day 10, and IGF-I mRNA in the regressing corpus luteum at 48 h after administration of exogenous prostaglandin was significantly greater than in the early or mid-luteal phase (days 5 and 10). In contrast, there was no significant effect of day of the oestrous cycle on expression of mRNA for IGF-II and the type 1 IGF receptor in the corpus luteum. Expression of IGF-II mRNA was localized to a subset of steroidogenic luteal cells and was also associated with cells of the luteal vasculature. mRNA encoding the type 1 IGF receptor was widely expressed in a pattern indicative of expression in large and small luteal cells. These data demonstrate that the bovine corpus luteum is a site of IGF production and reception throughout the luteal phase. Furthermore, this study highlights the potential of IGF-II in addition to IGF-I in the autocrine and paracrine regulation of luteal function.

Analysis of Variance↗

PubMed1998

A phosphatidylcholine phospholipase C inhibitor, D609, blocks interleukin-3 (IL-3)-induced bcl-2 expression but not c-myc expression in human IL-3-dependent cells.

Activation of the interleukin-3 (IL-3) receptor is required for the induction of cell proliferation and suppression of apoptosis in primitive hematopoietic progenitor cells. A rapid activation of tyrosine kinases and a phosphatidylcholine-specific phospholipase C has been observed in these cells in response to IL-3. The signal transduction cascades regulating cell proliferation and the suppression of apoptosis are poorly understood. Using human IL-3-dependent TF-1 cells, we have found that the tyrosine kinase inhibitor genistein blocks both the IL-3 suppression of apoptosis and the expression of the cell survival gene bcl-2. In addition, we have found that D609, a specific inhibitor of phosphatidylcholine-specific phospholipase C, also inhibits IL-3-induced expression of the bcl-2 gene without affecting IL-3-induced tyrosine phosphorylation. D609 also drove these cells into apoptosis even in the presence of IL-3. Significantly, genistein inhibited the IL-3 induction of both bcl-2 and c-myc gene. The latter gene is related to the induction of cell proliferation. D609, however, blocked the induction only of the cell survival gene bcl-2. Thus, phosphatidylcholine hydrolysis appears linked to the induction of genes related to cell survival. These data fit with the hypothesis that there is a bifurcation in the signaling pathways downstream of IL-3 receptor-induced tyrosine phosphorylation.

Apoptosis↗

PubMed1998

Expression of monocyte chemoattractant protein-1 in the bovine corpus luteum around the time of natural luteolysis.

Monocyte chemoattractant protein (MCP-1) is a specific chemoattractant for monocytes/macrophages that could have a role in the influx of macrophages into the corpus luteum (CL) during structural luteolysis. In this study, reverse transcription-polymerase chain reaction and in situ hybridization were used to investigate MCP-1 mRNA expression in CL collected from 18 heifers between Days 15 and 20 of the estrous cycle. There was expression of mRNA encoding MCP-1 in luteal tissue from all cows; however, expression was greater in animals that had undergone luteolysis at the time of CL collection as compared to animals in which the CL was still functional. Similarly, in situ hybridization showed greater expression of mRNA encoding MCP-1 in CL after functional luteolysis. There was also evidence of increased MCP-1 mRNA expression in an animal with a functional CL where the systemic concentration of prostaglandin F2alpha metabolite was high at the time of tissue collection. T lymphocyte populations, identified by immunohistochemistry, had a distribution similar to that of cells expressing MCP-1 mRNA within the CL, but other cell types were also involved. These results demonstrate an increase in MCP-1 mRNA after functional luteolysis in the cow, which may be related to the influx of macrophages that occurs at this time.

Animals↗

PubMed1998

Insulin-like growth factor binding protein -2 and -4 messenger ribonucleic acid expression in bovine ovarian follicles: effect of gonadotropins and developmental status.

This work is concerned with the role of insulin-like growth factor binding protein (IGFBP)-2 and -4 in the regulation of IGF bioactivity in bovine follicles during the development of dominance. We measured the expression of IGFBP-2 and -4 messenger RNA (mRNA) in small (1-4 mm) gonadotropin-sensitive follicles and medium (4-8 mm) and large (>8 mm) gonadotropin-dependent follicles using in situ hybridization. In healthy nonatretic bovine follicles, IGFBP-2 and -4 mRNA expression was confined to granulosa and theca tissue, respectively. Moreover, during the development of follicular atresia, there were distinct changes in the temporal and spatial expression of these genes. IGFBP-2 immunoactivity was localized in granulosa tissue and the basement membrane of healthy preantral follicles, whereas IGFBP-4 immunoactivity was localized in both theca and granulosa tissue. Of particular interest was the lack of IGFBP-2 mRNA expression in large (>8 mm) gonadotropin-dependent follicles, an observation that was confirmed by the lack of immunoreactive IGFBP-2 in these follicles. The regulation of IGFBP-2 and -4 mRNA expression in granulosa and theca cells was analyzed using a serum-free cell culture system. FSH inhibited the expression of IGFBP-2 mRNA in granulosa cells, whereas LH stimulated IGFBP-4 mRNA expression in theca cells. Our results provide evidence for the existence of different roles for IGFBP-2 and -4 in the developing follicle.

Animals↗

PubMed1997

Survey of diplomates of the American College of Veterinary Internal Medicine and the American College of Veterinary Surgeons regarding clinical aspects and treatment of endotoxemia in horses.

A questionnaire designed to elicit information concerning prevalence, underlying causes, diagnosis, prevention, treatment, and complications of endotoxemia in horses was mailed to diplomates of the American College of Veterinary Internal Medicine and the American College of Veterinary Surgeons who identified themselves as equine practitioners. Gastrointestinal tract compromise, conditions associated with foaling, and grain overload were reported to be the most common clinical conditions that led to endotoxemia. Most of the respondents diagnosed endotoxemia on the basis of the following clinical and laboratory findings: neutropenia, leukopenia, hyperemic mucous membranes, tachycardia, and fever. Treatments used to attempt to prevent development of endotoxemia or to treat horses with endotoxemia included i.v. fluids and administration of broad-spectrum antimicrobials and flunixin meglumine.

Animals↗

PubMed1997

Lansoprazole 30 mg daily versus ranitidine 150 mg b.d. in the treatment of acid-related dyspepsia in general practice.

AIM: To compare lansoprazole 30 mg daily with ranitidine 150 mg b.d. in the treatment of acid-related dyspepsia in general practice. METHODS: In a double-blind, parallel group, randomized, mutlicentre study conducted in 32 general practices in the UK, 213 patients were randomized to receive lansoprazole 30 mg daily, and 219 to receive ranitidine 150 mg b.d., for 4 weeks. All patients had experienced symptoms of reflux-like or ulcer-like dyspepsia on at least 4 of the 7 days prior to the study; 75% had experienced dyspepsia in the past, and 74 of the lansoprazole patients and 77 of the ranitidine patients had documented histories of acid-related disorders, investigating by either radiology or endoscopy. RESULTS: After 2 weeks 55% of the lansoprazole patients and 33% of the ranitidine group were symptom-free (P = 0.001, chi 2 = 7.12) with corresponding 4-week figures of 69% and 44%, respectively (P = 0.001, chi 2 = 18.03). Similar figures were found at both 2 and 4 weeks for daytime and night-time heartburn and epigastric pain scores; in the lansoprazole group, at 4 weeks, 80% of patients were free of daytime heartburn and 81% of night-time epigastric pain, compared with 55% (P = 0.001, chi 2 = 15.44) and 65% (P = 0.01, chi 2 = 6.10) in the ranitidine group. CONCLUSION: Superior symptom relief for patients presenting with ulcer-like and reflux-like symptoms in general practice is provided by lansoprazole 30 mg daily compared with ranitidine 150 mg twice daily.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1997

Enhancement of ovarian follicle development in heifers by treatment with recombinant bovine somatotrophin: a dose-response study.

Treatment with recombinant bovine somatotrophin (bST) can enhance the development of ovarian antral follicles in cattle. The underlying mechanism was examined further by performing a dose-response study to investigate the effects of bST on peripheral concentrations of somatotrophin, insulin-like growth factor I (IGF-I), insulin, FSH and LH, and ovarian follicle development. Twenty mature heifers were randomly divided into five groups and injected s.c. at 6 h intervals for 7 days with 25% of one of the following daily doses of bST: 0, 3.13, 6.25, 12.5 or 25.0 mg. Ovarian follicular dynamics were monitored by real-time ultrasonography. Blood samples were collected daily during the experiment, and every 15 min for 8 h on days 1 and 5 of bST treatment. Treatment with bST increased (P < 0.01) peripheral concentrations of somatotrophin in a dose-dependent manner. Serum concentrations of both IGF-I and insulin were significantly (P < 0.01) increased in all heifers given 12.5 or 25.0 mg bST per day. Peripheral concentrations of IGF-I and insulin in all animals in the group given 3.13 mg bST and two heifers in the group given 6.25 mg bST were not different from those in the control group, while concentrations in the other two heifers given 6.25 mg bST were significantly (P < 0.01) higher. The number of ovarian follicles < 5 mm in diameter was increased (P < 0.05) in response to bST, but only in heifers (n = 10) with significantly increased serum concentrations of IGF-I and insulin. There were no effects of treatment on peripheral concentrations of FSH, LH and progesterone, and on the numbers of follicles > 5 mm in diameter. In conclusion, this study has demonstrated in vivo that the effect of treatment with bST on ovarian follicle development appears to be mediated through an increase in circulating IGF-I or insulin concentrations, rather than via an alteration in the secretion of pituitary gonadotrophins or a direct effect of bST on ovarian follicles.

Animals↗