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Biomedical subjects

S K Smith

Publications and source records attributed to S K Smith.

At least 109 records · Page 6Linked to original sources
PubMed1996

Characterization and expression of vascular endothelial growth factor (VEGF) in the ovine corpus luteum.

The corpus luteum undergoes tremendous growth, development and regression each oestrous or menstrual cycle. These changes are reflected by equally impressive growth and regression of the luteal vasculature. We have previously shown that angiogenic factors from corpora lutea are primarily heparin binding and that one of these factors is similar to vascular endothelial growth factor (VEGF). In an effort to identify this factor, and to define its role in luteal vascular development, the cDNA for the coding region of ovine VEGF was sequenced and a sensitive RNase protection assay was developed to quantitate mRNA encoding VEGF in luteal tissues from ewes in the early (days 2-4), mid- (day 8) and late (days 14-15) stages of the oestrous cycle. In addition, an N-terminal peptide was synthesized from the translated ovine cDNA sequence for VEGF and an antiserum was raised against this peptide for use in western immunoblotting procedures. Nested reverse transcriptase (RT)-PCR of RNA from ovine corpora lutea resulted in three products that correspond in size to the alternatively spliced variants of VEGF (VEGF120, VEGF164, and VEGF188) predicted from other species. The RNase protection assay revealed that the proportion of mRNA encoding VEGF was 2- to 3-fold greater on days 2-4 than on day 8 or days 14-15. Densitometric analysis of gels from the RNase protection assay showed that VEGF120 represented approximately one third of the total mRNA encoding VEGF in the corpus luteum and that this proportion did not vary with stage of the oestrous cycle. SDS-PAGE and western immunoblot analysis of a homogenate from corpora lutea showed a single 18 kDa protein. These data demonstrate that VEGF is expressed in luteal tissue throughout the ovine oestrous cycle and that expression of mRNA encoding VEGF is upregulated during the period of rapid luteal development, when luteal vascular growth is at its maximum.

Amino Acid Sequence↗
PubMed1996

Hepatocyte growth factor/scatter factor and its receptor c-met: localisation and expression in the human placenta throughout pregnancy.

Hepatocyte growth factor (HGF), also known as scatter factor, acts via the c-met receptor resulting in pronounced effects on certain epithelial cells. We hypothesised that HGF would be important in placental development where the trophoblast represents a specialised barrier of epithelial origin. In this paper we examine the expression and production of HGF and its receptor in the human placenta throughout pregnancy. In addition, RT-PCR was undertaken on human embryos to ascertain whether pre-implantation embryonic or trophoblast cells were under the influence of this growth factor. In samples from the first trimester of pregnancy in situ hybridisation with a c-met antisense probe detected message expression in villous cytotrophoblast and in decidual glands but not in extravillous trophoblast. Some c-met expression was detected in cytotrophoblast from the second trimester placentae; this declined to negligible levels by term. Staining with an anti c-met antibody largely confirmed these findings but found relatively strong staining of cytotrophoblast at term. HGF was confined to the villous core throughout pregnancy when examined by both in situ hybridisation and immunohistochemistry. Trophoblast was consistently negative for HGF. Pre-implantation embryos examined by RT-PCR were negative for both c-met and HGF mRNA. These results indicate that the HGF may exert an important influence on cytotrophoblast throughout the process of placental formation and growth.

Blastocyst↗
PubMed1996

Demographic effects of natural disasters: a case study of Hurricane Andrew.

Many studies have considered the economic, social, and psychological effects of hurricanes, earthquakes, floods, tornadoes, and other natural disasters, but few have considered their demographic effects. In this paper we describe and evaluate a method for measuring the effects of Hurricane Andrew on the housing stock and population distribution in Dade County, Florida. Using information collected through sample surveys and from other data sources, we investigate the extent of housing damages, the number of people forced out of their homes, where they went, how long they stayed, and whether they returned to their prehurricane residences. We conclude that more than half the housing units in Dade County were damaged by Hurricane Andrew; that more than 353,000 people were forced to leave their homes, at least temporarily; and that almost 40,000 people left the county permanently as a direct result of the hurricane. We believe that this study will provide methodological guidance to analysts studying the demographic effects of other large-scale natural disasters.

Data Collection↗
PubMed1996

Patient noncompliance with wearing and replacement schedules of disposable contact lenses.

BACKGROUND: Corneal ulcers related to contact lens wear are four to 15 times more likely to occur with extended wear lenses versus daily wear lenses. The introduction of disposable contact lenses raised hopes that this product would reduce complications related to contact lens wear. Such has proven not to be the case, especially when patients are noncompliant with the prescribed wear and care regimen. METHODS: The ordering patterns of a group of 145 patients wearing disposable contact lenses were monitored for a period of one year, 5 months in an attempt to identify those individuals who were potentially noncompliant in their wearing schedules. RESULTS: Up to 69 percent of the patients studied were identified as potentially noncompliant. A program to counsel and re-educate these patients about proper disposable contact lens wear was proposed. CONCLUSIONS: Eye care professionals have a legal and ethical responsibility to provide appropriate follow-up care for patients. The ability to track ordering patterns of patients who wear disposable contact lenses provides a valuable tool to use in identifying patients who could be putting themselves at risk to develop complications related to contact lens wear.

Contact Lenses↗
PubMed1995

Expression of vascular endothelial growth factor and its receptors flt and KDR in ovarian carcinoma.

BACKGROUND: Two thirds of patients with ovarian carcinoma have advanced disease at diagnosis and have poor prognoses because of the presence of highly invasive carcinoma cells and rapidly accumulating ascitic fluid. Vascular endothelial growth factor (VEGF), a potent mitogen of endothelial cells, is produced in elevated amounts by many tumors, including ovarian carcinomas. The known human receptors for VEGF, flt and KDR, are both cell surface tyrosine kinases and are expressed predominantly on endothelial cells. Acting through these receptors, VEGF may stimulate angiogenesis and promote tumor progression. PURPOSE: We aimed to clarify the function of VEGF in tumor development by identifying the cells in ovarian carcinoma tissue that express VEGF and its receptors. METHODS: VEGF, flt, and KDR expression was localized by in situ hybridization and immunohistochemistry in frozen sections of primary tumors from five patients with ovarian carcinoma and from metastases of ovarian carcinoma from three different patients. Reverse transcription followed by polymerase chain reaction (RT-PCR) and an enzyme-linked immunosorbent assay were used to analyze VEGF, flt, and KDR expression in six epithelial cell lines derived from ovarian carcinoma ascites from five additional patients. RESULTS: Messenger RNAs (mRNAs) encoding VEGF, flt, and KDR were detected in primary ascitic cells and in three of four ovarian carcinoma cell lines examined by RT-PCR. Two novel complementary DNAs that may encode truncated, soluble forms of flt were cloned from one primary source. VEGF levels of 20-120 pM were found in culture media conditioned by the cell lines. Elevated expression of VEGF mRNA was found in all primary tumors and metastases, especially at the margins of tumor acini. VEGF immunoreactivity was concentrated in clusters of tumor cells and patches of stromal matrix. flt immunoreactivity was confined to tumor blood vessels, but flt mRNA was not detected by in situ hybridization. In contrast, KDR mRNA was detected not only in vascular endothelial cells but also in tumor cells at primary malignant sites. CONCLUSIONS: VEGF is expressed by tumor cells in primary and metastatic ovarian carcinoma and accumulates in the stromal matrix. Its receptors, flt and KDR, are expressed by some tumor cells that coexpress VEGF. This is the first localization of KDR expression in nonendothelial cells. IMPLICATIONS: Coexpression of VEGF and KDR by tumor cells in ovarian carcinoma raises the possibility of autocrine stimulation and of therapeutic strategies targeting this receptor-ligand interaction.

Base Sequence↗
PubMed1995

Screening for cytokine mRNA in human villous and extravillous trophoblasts using the reverse-transcriptase polymerase chain reaction (RT-PCR).

During the process of placental implantation, sessile villous trophoblast cells migrate from the villi into the decidua as isolated motile extravillous trophoblast cells. There is differential expression of the epidermal growth factor-receptor (EGF-R) and c-erbB2 proteins on villous and extravillous trophoblast populations. Using monoclonal antibodies to EGF-R and c-erbB2, we have obtained highly purified populations of villous and extravillous trophoblast by fluorescence activated cell sorting. These cells were examined by the reverse transcriptase-polymerase chain reaction (RT-PCR) using nested internal primer pairs for the following cytokines: CSF-1, GM-CSF, TNF-alpha, TGF-beta1, IFN-gamma, IL-2, LIF and also for LIF-receptor. TNF-alpha and TGF-beta 1 were present in all trophoblast populations. GM-CSF and CSF-1 were only found in some samples, with preferential expression of CSF-1 in villous populations. IFN-gamma, IL-2 and LIF mRNA were not found, although all samples contained LIF-receptor mRNA. These cytokines (CSF-1, TGF-beta, TNF-alpha and GM-CSF) are likely to influence trophoblast growth and differentiation in an autocrine manner, since their receptors are also present on trophoblast. These results illustrate a quick and simple method to analyse for the presence of cytokine and other transcripts in trophoblast subpopulations during early pregnancy.

Base Sequence↗
PubMed1995

Validity of major cancer operations in elderly patients.

BACKGROUND: As the population ages, more elderly individuals will be at risk for the development of gastrointestinal malignancies traditionally treated with radical operation. In the past, many major cancer operations were reserved for patients < 65 or 70 years of age, but as the life expectancy for a 70-year-old has improved, this policy has been questioned. METHODS: We examined the records of 124 consecutive patients who underwent one of three major operations (esophagogastrectomy, major liver resection, pancreatoduodenectomy) for gastrointestinal cancer during the past 6 years to determine if preoperative risk factors, operative mortality, length of stay, length of procedure, estimated blood loss, rate of major complication, or Kaplan-Meier survival was different for patients > or = 70 years of age as compared with younger patients. RESULTS: For patients at our institution undergoing esophagogastrectomy, major liver resection, or pancreatoduodenectomy, we found no significant difference in any of the parameters measured. There was no significant difference in any parameter when comparing patients > or = 70 versus < 70 years of age. CONCLUSIONS: We conclude that patients > or = 70 years of age are not necessarily less suitable candidates for major cancer operations than are those < 70 years of age if other risk factors are acceptable. Elderly patients should be included in clinical trials.

Adult↗
PubMed1995

Oestradiol-17 beta modulates PAF-evoked phospholipase D activity but not inositide-lipid hydrolysis in human endometrial cell line, HEC-1B.

Platelet-activating factor (PAF) has been shown to stimulate phospholipase D (PLD) activity in human endometrium. The effect of 17 beta-oestradiol on PAF- and 12-O-tetradecanoylphorbol 13-acetate (TPA)-evoked PLD activity assayed as an accumulation of [3H]phosphatidylbutanol was examined in [3H]myristic acid labelled in a human endometrial epithelial cell line HEC-1B. TPA stimulated PLD activity in a dose-dependent manner whereas PAF had no significant effect on PLD activity. Following 48 h pretreatment with 100 nM 17 beta-oestradiol, PAF evoked PLD activity while leaving inositol trisphosphate accumulation in myo-[2-3H] inositol-labelled HEC-1B cells unaffected. In the 17 beta-oestradiol-treated cells, TPA-stimulated PLD activity was significantly elevated at 100 nM TPA (P < 0.05) and 1 microM TPA (P < 0.05) compared to responses in the untreated cells, suggesting that 17 beta-oestradiol may upregulate PKC activity. Interestingly, following a 30 min pretreatment of HEC-1B cells with a range of 17 beta-oestradiol concentrations. TPA (10 nM) and PAF (100 nM) stimulated PLD activity. However, TPA-stimulated PLD activity levels fell 10-fold while PAF-mediated PLD activity remained elevated at 10 nM and 100 nM concentrations of 17 beta-oestradiol suggesting a different mechanism of activation. These results indicate that 17 beta-oestradiol can upregulate PAF-induced PLD activity in HEC-1B cells.

Carcinogens↗
PubMed1995

Activation of human endometrial phospholipase D by bradykinin.

Bradykinin may act as a promoter of endometrial regeneration. In [3H]myristate-labelled endometrial stromal cells, bradykinin and tetradecanoylphorbol acetate (TPA) mediated activation of phospholipase D (PLD) as measured by the accumulation of [3H]phosphatidylbutanol ([3H]PtdBut). Kinetics of bradykinin-evoked PLD activation was rapid and transient, whereas the TPA response was relatively slow in onset. Bradykinin induced a dose-dependent (EC50 0.11 nM) [3H]PtdBut accumulation at concentrations at which it stimulated DNA synthesis. In [3H]inositol-labelled cells, bradykinin evoked a rapid increase in inositol phosphates which preceded the increase in [3H]PtdBut formation. Chronic pretreatment with 400 nM TPA abolished PLD activation to subsequent treatment with either TPA and bradykinin. Staurosporine, an inhibitor of protein kinase C, strongly inhibited (IC50 96 nM) TPA-induced [3H]PtdBut formation, but bradykinin-stimulated [3H]PtdBut accumulation was only partially inhibited (IC50 65 microM). The effect of bradykinin and TPA on PLD activity was synergistic, suggesting that the two agents may act via different mechanisms. These results suggest PKC-dependent and independent pathways are involved in bradykinin-induced PLD activation and that the mitogenic activity of this vasoactive peptide on endometrial stromal cells may in part be mediated via the PLD pathway. This may have significance both to implantation and endometrial cancer.

Adult↗
PubMed1995

An evaluation of population projection errors for census tracts.

"In this article we evaluate the accuracy and bias of projections of total population and population by age group for census tracts in three counties in Florida. We use [U.S. census] data from 1970 and 1980 and several simple extrapolation techniques to produce projections for 1990; we then compare these projections with 1990 census counts and evaluate the differences. For the total sample, we find mean absolute errors of 17%-20% for the three most accurate techniques for projecting total population and find no indication of overall bias. For individual age groups, mean absolute errors range from 20%-29%." This is a revised version of a paper presented at the 1993 Annual Meeting of the Population Association of America.

Age Distribution↗
PubMed1995

Human trophoblast adhesion to matrix proteins: inhibition and signal transduction.

At the time of implantation, the extracellular matrix proteins laminin and fibronectin are abundant in the decidua and are distributed pericellularly around each individual stromal cell. First trimester human trophoblast expresses both laminin and fibronectin receptors, specifically the alpha 1 beta 1, alpha 5 beta 1, alpha 6 beta 1 and alpha 6 beta 4 integrin heterodimers. In this study we have demonstrated that in-vitro adhesion of first trimester human trophoblast to purified extracellular matrix proteins and to purified decidual stromal cell monolayers can be inhibited by monoclonal antibodies directed against appropriate integrin subunits and by synthetic peptides containing an arginine-glycine-aspartic acid sequence. Monoclonal antibodies (mAbs) to the alpha 5 and beta 1 integrin subunits and a synthetic peptide significantly inhibited adhesion to fibronectin. Binding of trophoblast to laminin was blocked with mAbs to the alpha 6 and beta 1 but not alpha 1 and beta 4 integrin subunits. Similarly, integrin-mediated adhesion to monolayers of decidual stromal cells could be blocked with mAbs to the alpha 5, alpha 6, beta 1 and beta 4 integrin subunits. Integrin-mediated signal transduction in normal and malignant trophoblast was investigated by Western blotting. A 115 kDa protein was the major tyrosine phosphorylated protein detected in trophoblast after binding to laminin or fibronectin. The profile of tyrosine phosphorylated proteins differed for malignant trophoblast.

3T3 Cells↗
PubMed1995

Stage-specific expression of cytokine and receptor messenger ribonucleic acids in human preimplantation embryos.

There is considerable evidence to suggest that polypeptide growth factors from either the oviduct or the endometrium can control preimplantation development of the mammalian embryo. These act directly through receptors expressed on the embryo. In addition, embryos also produce growth factors. The reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine the pattern of expression of mRNAs encoding several growth factor ligand and receptor genes throughout preimplantation development of cryopreserved human embryos. Transcripts encoding the receptor for c-fms, the receptor for colony-stimulating factor-1 (CSF-1), and c-kit (the receptor for stem cell factor [SCF]) were expressed throughout preimplantation development. Other growth factor ligand and receptor transcripts were expressed in a stage-specific manner: these included receptors for interleukin (IL)-6 (IL-6R), leukemia inhibitory factor (LIFR), tumor necrosis factor alpha (TNF alpha) (TNFRp80 and TNFRp60), and gp130. The transcripts for gp130 and the ligand SCF showed stage-specific splice variants. Blastocysts expressed a novel cDNA encoding gp130, which predicts a truncated form lacking the intracellular signaling domain. No expression of mRNAs encoding LIF, CSF-1, or the cloned receptor for platelet-activating factor was seen in any embryonic stage studied. We have shown that RT-PCR provides a sensitive and powerful method for identifying transcripts encoding growth factors and their receptors in single human embryos. The method is economical, allowing the expression pattern of many genes to be determined from a single embryo. These data are important in defining which cytokines may be involved in regulating human preimplantation development and when they may act.

Amino Acid Sequence↗
PubMed1995

Tumor biology of infiltrating lobular carcinoma. Implications for management.

OBJECTIVE: The purpose of this study was to characterize the biologic determinants that affect the behavior and management of infiltrating lobular cancer. METHODS: A prospectively accrued data base containing 1548 breast cancer cases was queried for specific pathologic and mammographic features. From this data base, 777 patients treated and followed-up at the H. Lee Moffitt Cancer Center were reviewed, and comparisons were made between the following three histologic subgroups: 661 infiltrating ductal (ID), 42 infiltrating ductal plus infiltrating lobular (ID + IL), and 74 infiltrating lobular (IL). RESULTS: Comparisons of the three histologic forms of breast cancer demonstrated the following: 1. At diagnosis tumors with IL components were larger than those with ID components (p < 0.001); in addition, a greater percentage of IL cancers were T3 lesions (14.8%), compared with ID cancers (4.5%). 2. Sizes of IL tumors were underestimated frequently by mammographic examinations when compared with pathologic measurements (p < 0.001). 3. By comparison to ID tumors, increasing IL tumor size is less likely to be associated with an increased number of metastatic lymph nodes per patient (p = 0.09). 4. Infiltrating lobular cancers treated by lumpectomy with cytologic surgical margin analysis more often gave false-negative results than did ID cancers (p < 0.001). 5. Infiltrating lobular cancers treated by lumpectomy required conversion to mastectomy over 2 times more frequently than ID cancers treated by lumpectomy. 6. Mastectomy was performed more frequently than lumpectomy for the treatment of IL versus ID tumors (p = 0.039). CONCLUSIONS: Infiltrating lobular cancers are biologically distinct from ID cancers. Although lumpectomy may be performed safely in selected patients, multiple difficulties exist in the management of IL cancer, particularly when breast conservation is chosen.

Adult↗
PubMed1995

A dose-ranging study of the use of cyclical dydrogesterone with continuous 17 beta oestradiol.

OBJECTIVE: To establish the lowest dose of cyclical dydrogesterone that protects against endometrial hyperplasia induced by continuous 2 mg 17 beta oestradiol, and to study the dose effect on vaginal bleeding and side effects. DESIGN: Double-blind, prospectively randomised dose-ranging study. SETTING: Menopause clinics in the UK and The Netherlands. SUBJECTS: Three hundred and seventy-one postmenopausal women with intact uteri, aged 40 to 60. INTERVENTIONS: Administration of six 28-day treatment cycles of continuous daily micronised 17 beta oestradiol with a randomly allocated dose of 5 to 20 mg of dydrogesterone added for the last 14 days of each. MAIN OUTCOME MEASURES: Histological assessment of adequate progestational endometrial response, bleeding patterns and adverse effects. RESULTS: The study was completed by 320 subjects (86%). Endometrial transformation occurred in over 94% of those taking 5 mg of dydrogesterone, and in over 97% of those on higher doses, without significant differences between the 10, 15 and 20 mg groups. Acceptable bleeding patterns were found at all doses, with the incidence of withdrawal bleeding rising with increasing dose. The day of onset of bleeding was predictable from cycle to cycle, and occurred later in the 20 mg group than in the others. The incidence of noncyclic bleeding was about 6% at all doses. Withdrawal occurred in 3.3% due to unacceptable bleeding and in 5.4% due to side effects. There was no relation with dose. CONCLUSIONS: A dydrogesterone-17 beta oestradiol combination hormone replacement therapy confers endometrial protection with an acceptable bleeding pattern and few side effects At least 10 mg of dydrogesterone for 14 days is required for acceptable endometrial protection.

Adult↗
PubMed1995

Comparative study of tranexamic acid and norethisterone in the treatment of ovulatory menorrhagia.

OBJECTIVE: To compare the efficacy and safety of tranexamic acid and norethisterone in the treatment of ovulatory menorrhagia. DESIGN: A randomised, double-blind, placebo controlled study. SETTING: University Department of Obstetrics and Gynaecology, Addenbrooke's Hospital, Cambridge. SUBJECTS: One hundred and three women complaining of heavy periods with a regular cycle recruited directly from general practitioners within the hospital catchment area and from consultants' gynaecology clinics. INTERVENTIONS: There were forty-six women on placebo with confirmed ovulatory menorrhagia, defined as menstrual blood loss greater than 80 ml/cycle and mid-luteal serum progesterone concentration greater than 9 nmol/l). Twenty-one received norethisterone (5 mg twice a day on days 19 and 26) and 25 received tranexamic acid (1 g four times daily on days 1 to 4) for two cycles. MAIN OUTCOME MEASURES: Menstrual blood loss was measured using the alkaline haematin method. Haematological assessments were made both at the beginning and at the end of the study, questionnaires were given to assess subjective endpoints, and patients were asked to report any adverse events during all cycles. RESULTS: Tranexamic acid reduced mean menstrual blood loss by 45%, from 175 ml to 97 ml (95% CI for the difference in menstrual blood loss 52 to 108, P < 0.0001), norethisterone increased mean blood loss by 20% from 173 ml to 208 ml (95% CI for the difference in menstrual blood loss -64 to 2, P = 0.26). Fourteen (56%) women who received tranexamic acid achieved a mean menstrual loss of less than 80 ml per cycle during treatment, but only two (9.5%) who received norethisterone achieved this mean menstrual loss. There were no serious adverse events reported for either drug. CONCLUSIONS: Tranexamic acid is a safe and effective form of medical therapy in women with menorrhagia and is highly likely to normalise blood loss in women losing 80 to 200 ml prior to treatment. Norethisterone at this dose is not effective therapy for ovulatory menorrhagia.

Adolescent↗
PubMed1995

Muscle growth in response to mechanical stimuli.

The relative merits of the separate and combined uses of stretch and electrical stimulation at 10 Hz in influencing the rates of protein synthesis in vivo, proteolysis, and the growth of the extensor digitorum longus muscle have been investigated after 3 days in the rabbit. Continuous electrical stimulation failed to change muscle protein turnover or growth. Static stretch caused significant adaptive growth, with increases in c-fos, c-jun, and insulin-like growth factor I (IGF-I; 12-fold) mRNA levels, and protein (19%), RNA (128%), and DNA (45%) contents. Both the fractional (138%) and total (191%) rates of protein synthesis increased with stretch, correlating with increased ribosomal capacities. Combining stretch and electrical stimulation increased the mRNA concentration of IGF-I (40-fold). The adaptive growth was greater (35%), with massive increases in the nucleic acids (185 and 300%), ribosomal capacities (230%), and the rates of protein synthesis (345 and 450%). Large increases (i.e., 200-400%) in cathepsins B and L and dipeptidyl aminopeptidase I activities during stretch, with or without stimulation, suggest a role for these enzymes in tissue remodeling during muscle hypertrophy.

Animals↗