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Biomedical subjects

F Clayton

Publications and source records attributed to F Clayton.

At least 19 recordsLinked to original sources
PubMed2006

Weaning age among foragers at Matjes river rock shelter, South Africa, from stable nitrogen and carbon isotope analyses.

Matjes River Rock Shelter is a large shell midden on the southern coast of South Africa. Stable nitrogen (delta(15)N) and carbon (delta(13)C) isotope ratios were measured in bone collagen and dentine from human skeletons excavated from this site in order to establish a weaning curve in mid-Holocene hunter-gatherers. delta(15)N results show a progressive increase in individuals from birth to 1.5 years old. delta(13)C results are more tightly clustered and mirror the steady progressive change seen for delta(15)N. We deduce that children at Matjes River Rock Shelter were breastfed for at least the first 1.5 years after birth, and were weaned sometime between 2-4 years of age. A similar pattern was documented for historic-era Kalahari foraging people, where the interbirth spacing was approximately 3 years. This study provides the first direct evidence for an extended period of breastfeeding, and thus long interbirth intervals, among prehistoric foragers, even when those foragers lived in an environment with abundant food resources.

Age Factors↗
PubMed2005

Structure and function of the esophagus of the American alligator (Alligator mississippiensis).

Esophageal structure and function were studied in juvenile American alligators (Alligator mississippiensis). The anatomy of alligators differs from humans in several important aspects: the crocodilian esophagus is more muscular and is composed entirely of smooth muscle. Functionally, the crocodilian esophagus is similar to that of mammals, but alligators have peak esophageal peristaltic pressures that are 2-3-fold greater than pressures in the human esophagus. As is found in humans, the incidence of esophageal reflux increased in postprandial animals compared with the fasting state. We observed a large increase in pressure in the lower esophageal sphincter (LES) during ventilation that ranged from 200% to 3000% of the pressures measured during apnea. These pressure changes appear to be intrinsic to the LES. Alligators lack a mammalian-type diaphragm; thus, there is no crural diaphragmatic contribution to LES pressure. These features recommend the alligator as a useful model for the study of regulation of the LES.

Alligators and Crocodiles↗
PubMed2001

Gp120-induced Bob/GPR15 activation: a possible cause of human immunodeficiency virus enteropathy.

Human immunodeficiency virus (HIV)-infected patients often develop malabsorption and increased intestinal permeability with diarrhea, called HIV enteropathy, even without enteric opportunistic infections. HIV gp120-induced calcium signaling, microtubule loss, and physiological changes resembling HIV enteropathy were previously found in the HT-29 intestinal cell line. How gp120 caused these changes was unclear. We show that the HIV co-receptor Bob/GPR15, unlike CCR5 and CXCR4, is abundant at the basal surface of small intestinal epithelium. The gp120-induced effects on HT-29 cells were inhibited by anti-Bob neutralizing antibodies, the selective G protein inhibitor pertussis toxin, and the phospholipase inhibitor U73122, but not neutralizing antibodies to CXCR4. Gp120 strains that induced signaling in HT-29 cells also induced calcium fluxes in Bob-transfected Ghost (3) cells, whereas gp120 strains not activating HT-29 cells also did not activate Bob-transfected cells. Bob is the first HIV co-receptor shown to be abundantly expressed on the basolateral surface of intestinal epithelium. Although Bob is an inefficient infection-inducing co-receptor, it mediates viral strain-specific gp120-induced calcium signaling at low, physiologically reasonable gp120 concentrations, up to 10,000-fold lower gp120 concentrations than the principal co-receptors. Gp120-induced Bob activation is a plausible cause of HIV enteropathy.

Blotting, Western↗
PubMed1999

Pharmacological properties of J-104132 (L-753,037), a potent, orally active, mixed ETA/ETB endothelin receptor antagonist.

J-104132 [(+)-(5S,6R, 7R)-2-butyl-7-[2-((2S)-2-carboxypropyl)-4-methoxyphenyl]-5-(3, 4-methylenedioxyphenyl)cyclopenteno[1,2-b]pyridine-6-carboxylic; also referred to as L-753,037] is a potent, selective inhibitor of ETA and ETB endothelin (ET) receptors (e.g., Ki: cloned human ETA = 0.034 nM; cloned human ETB = 0.104 nM). In both ligand-binding and isolated tissue preparation protocols, the inhibition of ET receptors with J-104132 is reversible and competitive. In vitro, J-104132 is a potent antagonist of ET-1-induced accumulation of [3H]inositol phosphates in Chinese hamster ovary cells stably expressing cloned human ETA receptors (IC50 = 0.059 nM), ET-1-induced contractions in rabbit iliac artery (pA2 = 9.70) and of BQ-3020-induced contractions in pulmonary artery (pA2 = 10.14). J-104132 is selective for ET receptors because it had no effect on contractions elicited by norepinephrine or KCl in the vascular preparations. The in vivo potency of J-104132 was assessed using challenges with exogenous ET-1. In conscious mice, 5 nmol/kg i.v. ET-1 causes death. Pretreatment with J-104132 prevents the lethal response to ET-1 when administered i.v. (ED50 = 0.045 mg/kg) or p.o. in fed animals (ED50 = 0.35 mg/kg). In conscious, normotensive rats, pressor responses to 0.5 nmol/kg i.v. ET-1 are inhibited by J-104132 after i.v. (0.1 mg/kg) or p.o. (1 mg/kg) administration. In anesthetized dogs, ET-1 was administered directly into the renal artery or brachial artery to generate dose-response (blood flow) curves, and the inhibitory potency of J-104132 (i.v. infusion) was quantified. J-104132 produced greater than 10-fold shifts in the ET-1 dose-response curves at 0.03 mg/kg/h (renal) and 0.3 mg/kg/h (brachial). Oral bioavailability of J-104132 in rats was approximately 40%. These studies indicate that J-104132 is a selective, potent, orally active antagonist of both ETA and ETB receptors and is an excellent pharmacological tool to explore the therapeutic use of a mixed ETA/ETB receptor antagonist.

Animals↗
PubMed1998

Effect of combination antiretroviral therapy upon rectal mucosal HIV RNA burden and mononuclear cell apoptosis.

BACKGROUND: Pathogen-negative diarrhea is common in HIV infection and has been associated with clinical symptoms, histopathology, HIV expression, CD4+ lymphocyte depletion, cytokine mRNA expression, and apoptosis of lamina propria mononuclear cells. OBJECTIVES AND METHODS: To examine the short-term (7-day) effects of treatment with combination antiretroviral therapies upon gastrointestinal symptoms and rectal mucosa in 15 HIV-infected subjects. RESULTS: Treatment was associated with significant decreases in the perception of abdominal bloating and cramps. Similar declines in RNA burden and rises in CD4+ lymphocyte counts were found in blood and mucosa. Treatment was also associated with a fall in the number of lamina propria mononuclear cells undergoing apoptosis by in situ labeling, a change that correlated with the change in mucosal viral burden. CONCLUSIONS: Peripheral blood and mucosal compartments are equally responsive to effective antiretroviral therapies. The detection of significant changes within 7 days of starting antiviral therapy implies that intestinal dysfunction may be a direct result of local HIV infection.

Anti-HIV Agents↗
PubMed1998

Pleomorphic lobular carcinoma of the breast: clinicopathologic features of 12 cases.

Pleomorphic lobular carcinoma (PLC) of the breast was recently identified as a histologic variant of infiltrating lobular carcinoma (ILC) with a poor prognosis. Twelve cases identified from a large series of breast carcinomas were studied retrospectively. Of 11 cases with adequate follow up, 9 were fatal. This was significantly worse than either infiltrating ductal carcinoma (IDC) or classical ILC (P < or = .002), even when stratified by axillary lymph node status. Among the fatal cases, the median survival time was 2.1 years, significantly shorter than that for classical lobular, but not ductal, carcinoma A distinctive pattern of in situ carcinoma, which has been described as PLC in situ, was identified in 7 of the 12 patients. This in situ component was composed of tumor cells with nuclear atypia, cytologically similar to the invasive tumor. Most PLCs lacked estrogen and progesterone receptors and stained with BRST-2, an antibody to gross cystic disease fluid protein-15, suggesting the presence of apocrine differentiation. In summary, PLC has many of the histologic features of ILC but has anaplastic nuclei, abundant cytoplasm, and apocrine differentiation. PLC is often aneuploid, usually lacks steroid receptors, and has a significantly poorer prognosis than does classical ILC.

Adult↗
PubMed1997

Gastrointestinal pathology in HIV-infected patients.

Specific pathologic processes, particularly oral, esophageal, and intestinal infections, are common in the alimentary tract of AIDS patients. Many of these diseases are adequately assessed only by biopsy with histologic examination. Most are rare or unreported in immunocompetent hosts and are easily missed by those not familiar with them. This article describes the gross or endoscopic and histologic appearances and the diagnostic criteria for enteric pathologic processes seen in HIV-infected individuals.

AIDS-Related Opportunistic Infections↗
PubMed1997

Selective depletion of rectal lamina propria rather than lymphoid aggregate CD4 lymphocytes in HIV infection.

The goal of this study was to examine the changes in lymphocyte populations in rectal mucosa during HIV infection and to study their relationship to mucosal immunity and to systemic depletion of CD4 lymphocytes. Rectal biopsies from 58 HIV-infected subjects and eight controls were studied. Frozen rectal tissue sections were stained with antibodies to CD4, CD3, CD8, and markers for macrophages. HIV-infected subjects were divided into early stage (no opportunistic infections) and AIDS groups. There was profound depletion of rectal lamina propria CD4 lymphocytes (16% and 6% of normal content in early and AIDS groups, respectively). However, lymphoid aggregate CD4 lymphocytes were far less severely depleted (69% and 40% of normal content, respectively). The extent of lymphoid aggregate CD4 lymphocyte depletion generally parallelled the CD4 lymphocyte depletion in the blood. CD8 lymphocyte content in both the lamina propria and lymphoid aggregates usually were increased, particularly in early-stage patients. Macrophage contents were usually normal in the HIV-infected groups. We conclude that rectal lamina propria and lymphoid aggregates are distinct compartments differing markedly in their CD4 lymphocyte content during HIV infection. In light of this and an increased number of apoptotic cells which were noted in rectal lamina propria in HIV-infected subjects, we hypothesize that intestinal lamina propria could be a site of rapid CD4 lymphocyte destruction during HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1996

bcl-2 is down-regulated in atypical endometrial hyperplasia and adenocarcinoma.

The bcl-2 protein, which protects cells from apoptosis, is normally expressed in a number of adult tissues. Dysregulated bcl-2 expression, secondary to (14;18) chromosomal translocation, seems to promote the development of follicular lymphomas, and recent findings of bcl-2 protein in several solid tumors suggest that it might contribute to the genesis of many other neoplasms. bcl-2 is also highly expressed in normal proliferative endometrium and markedly down-regulated in secretory endometrium, which suggests that its expression is estrogen regulated. Because the development of most endometrial carcinomas is associated with hyperestrogenic states, we began the investigation of the role of bcl-2 in endometrial carcinogenesis by immunohistochemically quantifying its expression in proliferative, hyperplastic, atypically hyperplastic, and carcinomatous endometrium. The results of this study show that bcl-2 is relatively highly expressed in proliferative (n = 11) and hyperplastic (n = 18) endometrium, with respective mean staining scores of 3.59 and 3.47 (scale, 0-4), but is significantly (P < 0.001) down-regulated in atypical hyperplasia (n = 11; score, 0.82), and adenocarcinoma (n = 34; score, 0.86). bcl-2 expression did not correlate with stage, grade, estrogen-receptor, or progesterone-receptor expression. Polymerase chain reaction analyses of DNA isolated from several endometrial carcinomas were negative for (14;18) translocation involving the bcl-2 gene. Thus, bcl-2 apparently plays no role in the progression of atypical hyperplasia to carcinoma or in the development of high-grade or advanced-stage endometrial carcinoma. These results, however, do not rule out the involvement of bcl-2 in very early, preatypical hyperplasia phases of endometrial carcinogenesis. Finally, the marked difference in bcl-2 expression in hyperplastic and atypically hyperplastic glands might prove to be diagnostically useful in the often difficult distinction of these entities.

Adenocarcinoma↗
PubMed1994

Variation in the enteric distribution of cryptosporidia in acquired immunodeficiency syndrome.

Clinical observation suggests that the natural history of intestinal cryptosporidiosis in patients with acquired immunodeficiency syndrome varies greatly. The relation between clinical, small-bowel functional, and nutritional status and the intestinal distribution of the organism was studied in 41 patients who had acquired immunodeficiency syndrome and cryptosporidiosis and who had undergone both proximal small-bowel and colonic biopsies. Two patterns of enteric cryptosporidiosis were identified: severe clinical disease with malabsorption in patients with cryptosporidia in proximal small-bowel biopsy specimens (61% of cases) and less severe clinical disease in patients with cryptosporidia only in the colon or stool (39% of cases). Patients with cryptosporidia in proximal small-bowel biopsy specimens had small-bowel crypt hyperplastic villous atrophy, lamina propria inflammatory infiltrates, poorer D-xylose absorption, greater weight loss, and shorter survival and more often needed intravenous hydration or hyperalimentation. Patients with cryptosporidia in the small-bowel villi only had less severe disease than those with cryptosporidia in the small-bowel crypts. In conclusion, the anatomic distribution of intestinal cryptosporidia in patients with acquired immunodeficiency syndrome varies, and this variation may explain differences in clinical course. Cryptosporidial infection of the proximal small bowel correlates with mucosal injury, malabsorption, dehydration, weight loss, and shortened survival.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Pathologic correlates of prognosis in lymph node-positive breast carcinomas.

BACKGROUND: Many pathologic features of breast carcinomas have been proposed as prognostic correlates; their interrelationships and their relative value as prognostic indicators were studied. METHODS: A series of 399 axillary lymph node-positive infiltrating ductal breast carcinomas was studied histologically and compared with the patient prognosis. RESULTS: Many pathologic findings fit into two groups of closely related features--those related to the extent of local spread and those related to histologic anaplasia and mitotic count. Both groups correlated with the primary tumor size. The best predictors of long-term survival were measures of the extent of axillary metastasis (the number of axillary metastases, the size of the largest metastasis, and lymph node capsular invasion), which are components of the pathologic node stage. The mitotic count, tumor grade, primary tumor stage, smooth tumor border, tumor necrosis, and multifocal primary tumors were weaker but significant survival correlates. The mitotic count and Bloom-Richardson grade best predicted the survival time of patients with node-positive disease who died. Four years after diagnosis, less than 25% of the patients who would die of breast carcinoma in the low mitotic count and Bloom-Richardson Grade 1 (well differentiated) groups already had died; more than 75% of those in the high mitotic count and Bloom-Richardson Grade 3 (poorly differentiated) groups already had died. Among patients with small tumors (< 1.8 cm in diameter), those with one micrometastasis (1-2 mm) had a worse prognosis than those with uninvolved lymph nodes of similar size. CONCLUSION: The extent of axillary metastasis best predicted the long-term prognosis of patients with infiltrating ductal carcinoma and axillary metastases. The mitotic count and tumor grade best predicted the survival time of those who died.

Breast Neoplasms↗
PubMed1993

Intestinal mucosal inflammation associated with human immunodeficiency virus infection.

The role of the human immunodeficiency virus type-1 (HIV) in producing intestinal disease was studied prospectively in 74 HIV-infected individuals with (43) or without (31) the acquired immunodeficiency syndrome (AIDS). Thirty-one subjects had enteric infections; all but one had AIDS. Alteration in bowel habits was the most common symptom and occurred independently of enteric infections. Abnormal histopathology was present in 69% of cases, and the finding was associated with altered bowel habits. An HIV-associated protein, p24, was detected in 71% of biopsies by ELISA assay. Tissue p24 contents varied with disease stage and were highest in HIV-infected individuals without AIDS (Walter Reed classes 3 and 4). Tissue p24 detection was associated with both altered bowel habits and histologic mucosal abnormalities. Tissue contents of the cytokines, tumor necrosis factor-alpha and interleukin-1 beta, were higher in HIV-infected individuals than in controls and their elevations were independent of enteric infection. We conclude that HIV reactivation in the intestinal mucosa may be associated with an inflammatory bowel syndrome in the absence of other enteric pathogens.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Passive transfer of adjuvant-induced arthritis into irradiated DA recipient rats.

Adjuvant-induced arthritis (AIA) can be passively transferred in Dark Agouti (DA) rats by spleen and lymph node cells after culture with Concanavalin A (Con A). A model not requiring in vitro Con A expansion and activation would be important in investigations of anti-rheumatic drugs in AIA. A new model using irradiated recipients fills this need. Donor DA rats treated with 0.1 ml complete Freund's adjuvant (CFA) containing 7.5 mg M. butyricum/ml were sacrificed 11 days after CFA injection, donor spleen cells harvested, and donor spleen cells injected intravenously into recipient DA rats previously irradiated with 5 Gy. Recipient rats developed arthritis 4-14 days after spleen cell transfer. This model can now be used to further define the effects of anti-rheumatic drugs in the passive transfer of AIA by eliminating the need for the in vitro Con A-induced expansion and/or activation of donor cells.

Animals↗
PubMed1993

Induction of arthritis in DA rats by incomplete Freund's adjuvant.

OBJECTIVE: To define the arthritogenic effects of incomplete Freund's adjuvant (ICFA) injections in DA rats. METHODS: ICFA was injected into DA rats and other inbred rat strains. The severity of arthritis was scored and associated changes in weight recorded. RESULTS: After ICFA injection a mild transient symmetric arthritis developed in 15/22 (68%) of the DA rats observed for greater than 4 weeks. Histologic examination of the observed arthritis showed edema and neutrophil infiltrates with some lymphocytes and plasma cells. No arthritis developed in DA rats given normal saline injections nor in Lewis, DA.1N and WF.1N rats given ICFA. CONCLUSIONS: Injection of DA rats with ICFA alone can produce arthritis.

Animals↗
PubMed1992

Rectal mucosal pathology varies with human immunodeficiency virus antigen content and disease stage.

Rectal mucosal biopsy specimens from 75 human immunodeficiency virus (HIV)-seropositive and 16 HIV-seronegative subjects were examined. The histopathologic changes were correlated with immunoperoxidase staining for UCHL-1 and HIV core protein p24, quantitative p24 enzyme-linked immunosorbent assay (ELISA) assay in homogenized rectal tissue and serum, and a modified Walter Reed clinical stage. Four phases were seen in the HIV-infected subjects: (1) early phase, in Walter Reed stage 1-2 subjects, with nearly normal histology and low p24; (2) inflammatory phase, typically in Walter Reed stage 3-4 subjects, with a superficial lamina propria infiltrate of lymphocytes, plasma cells, and eosinophils with degranulation, abundant UCHL-1 staining, and maximal p24 by both immunoperoxidase staining and ELISA; (3) transitional phase, in many Walter Reed 5 and some Walter Reed 6 subjects, with normal lymphocyte population density but with subtle inflammatory changes; and (4) lymphoid depletion phase, mainly in Walter Reed stage 6 subjects, with decreased lymphocytes but often with endothelial cell activation and apoptosis. These phases presumably result from effective HIV suppression by a relatively intact immune system, followed by maximal HIV infection and lymphocyte activation, then progressive lymphocyte depletion. The inflammation correlated with the presence and amount of HIV in rectal tissue determined by immunohistochemistry and ELISA and was maximal before overt immunodeficiency developed. Intestinal mucosa could be a preferred site of HIV proliferation and T-cell destruction.

Antibodies, Monoclonal↗