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Biomedical subjects

M Hill

Publications and source records attributed to M Hill.

At least 253 records · Page 14Linked to original sources
PubMed1995

The effect of epitestosterone on spermatogenesis in rats.

The effect of 3-week treatment with increasing doses of endogenous steroid with antiandrogenic properties, epitestosterone (ET), on the spermatogenesis was studied in adult male rats by flow cytometry and correlated with the effect on gonadotropin gene expression and secretion, on testosterone and dihydrotestosterone plasma levels and on the weight of testes and prostates. Epitestosterone was administered to the rats by means of silastic capsules of different lengths filled with the steroid. A decrease of the number of total spermatides in the epitestosterone treated animals was observed. In the group with the lowest dose of ET the number of elongated spermatides was significantly reduced. The number of germ cell types and their relative proportions were correlated with the endocrine parameters reported previously. Significant negative correlation between the pituitary content of LH and total number of germ cells per 1 g of testicular tissue and of the number of spermatides/g and between testosterone level in serum and the number of diploid cells in the animals treated with higher doses of ET was found. In the group with highest ET dose a negative correlation of diploid cells and serum dihydrotestosterone was observed, too. The naturally occurring antiandrogen epitestosterone can be considered as one of the endogenous factors influencing spermatogenesis.

Journal Article↗
PubMed1995

An investigation into the default rate at the Fife colposcopy clinic: implications for target setting.

BACKGROUND: High default rates have been reported from the Fife colposcopy clinic in recent years. However, it was felt that this rate was misleading, as many patients who defaulted initially attended subsequent appointments. It was therefore decided to determine the default rate of a cohort of new patients given appointments at the clinic. The objective of the study was to determine the attendance rates for these new patients, between the dates they were first invited to their various appointments and the dates that their notes were subsequently examined as part of this study in September 1992. METHODS: A retrospective cohort study of new patients invited to the Fife colposcopy clinic was undertaken. The notes of 200 new patients who had been invited during the eight-month period January-August 1991 were selected by systematic sampling. The dates that they had attended for their new patient assessment/treatment, first follow-up and second follow-up appointments were recorded. Attendance rates were then calculated using an incomplete life-table method. Patients were censored if they failed to attend their assessment/treatment or review appointments by 1 October 1992. RESULTS: The study demonstrated that 96 per cent of patients attended their first treatment appointment within six months of their appointment date, 91 per cent of first review patients attended within six months, and 88 per cent of second review patients attended within four months. CONCLUSIONS: These findings suggest that there are two distinct groups of defaulters: those who default initially but subsequently re-attend, and those who default completely. We have named these type A and type B defaulters, respectively. This means that attendance within a certain period of time should also be used to monitor clinic attendance in addition to simple mean attendance rates. As patients who default completely may be more likely to have a severe histological lesion, further work is required to identify factors associated with this type of patient.

Adult↗
PubMed1995

Variability of Doppler microembolic signal counts in patients with prosthetic cardiac valves.

BACKGROUND AND PURPOSE: The purpose of this study was the evaluation of intraobserver, interobserver, and intrasubject variability in the Doppler detection of microembolic signals in patients with mechanical prosthetic valves. Simultaneously, the feasibility of automated embolus detection by means of a neuronal network was investigated. METHODS: From 25 patients with mechanical prosthetic heart valves, single transcranial Doppler monitoring sessions of 30 minutes' duration were recorded on videotape, randomized, and subsequently analyzed by eight independent trained observers from three centers. Three observers evaluated these tapes on three separate occasions, blinded to their previous results. An additional 48 patients with prosthetic heart valves were repetitively monitored with transcranial Doppler ultrasonography for 30 minutes three times within 1 year to examine the long-term variability in the occurrence of microembolic signals. Finally, in an effort to assess the short-term intrasubject variability, 20 patients were examined for 90 minutes, and the results of the three 30-minute periods were compared. The interobserver, intraobserver, and intrasubject (both short- and long-term) variability was evaluated. RESULTS: No significant differences in microembolic signal counts were found among the different observers, between the human observers and the neuronal network, or among the three separate evaluations of stored data by the same observer. The same was true for repeat examinations of the same patient (P > .05, Student's two-paired t test and Friedman's test). CONCLUSIONS: The detection of microembolic signals in patients with prosthetic cardiac valves is a reproducible technique. The reliable performance of the neuronal network argues for a broader use of this device. The intrasubject stability of the microembolic rate over 1 year supports the concept that the underlying emboligenic process is associated with intrinsic mechanical properties of the valve implant and not due to a thromboembolic process in the heart.

Cerebral Arteries↗
PubMed1994

Na/K competitive transport selectivity of (221) C10-cryptand: effect of temperature.

The kinetics of the competitive transport of Na+ and K+ ions across the membrane of large unilamellar vesicles (LUV) were determined when transport was induced by (221)C10-cryptand at various temperatures in order to quantify the temperature-dependence of the Na/K competitive transport selectivity of this ionizable mobile carrier. At any given temperature, the apparent affinity of (221)C10 for Na+ was higher and less dependent on the concentration of the other competing ion than that for K+. Its enthalpy for Na+ (delta H(KmNa) = 50.6 kJ/mol) was not significantly different from that for K+ (delta H(KmK) = 52.7 kJ/mol). The Na/K competitive transport selectivity (SC(Na/K)) of (221)C10 increased linearly with the Na+ concentrations and decreased hyperbolically with increasing those of K+. When the cation concentrations were equal, this competitive selectivity amounted to about 2 at any given temperature. Equations were established to describe the variations of the competitive transport selectivity (SC) of cryptands, and for comparison of their noncompetitive selectivity (SNC), with the ionic concentrations and the Michaelis parameters of the cations. It is theoretically demonstrated that the ratio between the competitive and noncompetitive transport selectivities, i.e., SC/SNC, of mobile carriers does not depend on the Jmax of the competing ions and that its value amounts to 1 when the specific concentrations (C'S/Km) of the ions are equal. Under these conditions, the transport selectivity of any given mobile carrier has the same value whether determined from competition or separated experiments. The reaction order in Na+ (n(Na)) increased significantly as the temperature rose and decreased significantly as the K+ concentration increased. The results are discussed in terms of the structural, physicochemical and electrical characteristics of carriers and complexes.

Binding, Competitive↗
PubMed1994

Ultrastructural localization of BHRF1: an Epstein-Barr virus gene product which has homology with bcl-2.

BHRF1 is an Epstein-Barr virus encoded protein which has a 38% sequence similarity with bcl-2 over the carboxyl portion. Like bcl-2, BHRF1 has been shown to suppress programmed cell death from apoptosis. Previously BHRF1 has been detected in mitochondrial, microsomal, and nuclear compartments by cell fractionation analysis. In this study we have used the technique of immunoelectron microscopy to define the ultrastructural distribution of the BHRF1 product in the EBV converted cell lines B95.8 and P3HR-1. The BHRF1 product was localized at the periphery of the mitochondria in a pattern similar to that of bcl-2 and by analogy with bcl-2 this is likely to be the functional destination. Sequence analysis of the BHRF1 protein disclosed similarity with the recently described bcl-2 homologues bcl-x (32%) and bax (34%) over the carboxyl portion, with several domains of complete identity. BHRF1 appears to be a member of a gene family involved in the regulation of programmed cell death. The identity between BHRF1 and bcl-2, an apparent shared ability to abrogate apoptosis, and the common ultrastructural localization is compelling and suggests that bcl-2 and BHRF1 are both functionally and mechanistically similar.

Amino Acid Sequence↗
PubMed1994

IL-2-induced expression of TTK, a serine, threonine, tyrosine kinase, correlates with cell cycle progression.

We have recently isolated the cDNA for a unique human 97-kDa kinase, TTK, by expression screening of a cDNA expression library using anti-phosphotyrosine antibodies. When expressed in Escherichia coli, TTK can phosphorylate serine, threonine, and tyrosine residues. Thus TTK appears to belong to a newly described family of kinases able to phosphorylate all three hydroxy amino acids. This family of multispecific kinases includes several other kinases involved in cell cycle progression. In support of a possible role in regulating cell cycle progression, TTK message is readily detected in rapidly proliferating tissues in vivo including testes, thymus, bone marrow, and many malignant tumors, but not in benign tissues with a low proliferative rate in vivo. To determine the effect of cell activation and cell cycle progression on TTK expression, we measured TTK mRNA and protein levels as well as kinase activity in freshly isolated T cells or IL-2-expanded T cell blasts activated to proliferate by the addition of a variety of mitogens. TTK mRNA levels, protein levels, and kinase activity were greatly enhanced when either freshly isolated PBL or T cell blasts were activated by cross-linking the TCR complex by mitogenic lectins or by bypassing the TCR with phorbol esters and cation ionophores. Incubation with IL-2 increased TTK expression in PBL blasts, which proliferate in response to IL-2, but not in fresh PBL, which do not proliferate in response to IL-2. TTK expression was blocked by either cyclosporin A or FK520, which inhibit IL-2 production and could be recovered by the addition of exogenous IL-2. Furthermore, TTK expression was prevented by incubation of the cells with rapamycin, which blocks IL-2 signaling. Thus, TTK expression in T cells appears to be a consequence of IL2-induced cell proliferation. Agonist-induced TTK expression was a delayed event occurring 12 to 24 h after activation of PBL blasts and 48 to 72 h after activation of fresh PBL. TTK protein and mRNA expression increased in both fresh PBL and T cell blasts concurrently with passage of cells through S phase as indicated by [3H]TdR incorporation and cell cycle analysis of propidium iodide-stained cells. TTK mRNA and protein levels reached a maximum as cells entered the G2 phase of the cell cycle. These results were confirmed by cell cycle blockade studies with aphidicolin and nocodazole wherein TTK protein levels are not detected in cells in G1 and are readily detectable in cells in the S and G2 phases of the cell cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

CD3 Complex↗
PubMed1994

Amniotic fluid 17-hydroxyprogesterone in early pregnancy.

The results of measurement of 17-hydroxyprogesterone (17-OH-P) in 125 samples of amniotic fluid (AF) from early amniocenteses are presented. The fetuses from all pregnancies studied were unaffected by congenital adrenal hyperphasia caused by 21-hydroxylase deficiency. The AF 17-OH-P level increases slightly but significantly between the 11th and 15th week of gestation, with a maximum in the 14th week. There is no difference between the values measured in male and female fetuses. The AF 17-OH-P levels from the early gestation were compared with those from the 16th-22nd week of pregnancy (published previously). The overall differences of AF 17-OH-P concentrations when considered in all gestational age groups in the whole period 12-22 weeks were statistically insignificant. Thus, the biochemical prenatal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency and control of its early fetal treatment could be carried out starting from the end of the first trimester in the same way as at the later period of gestation.

17-alpha-Hydroxyprogesterone↗
PubMed1994

Early detection of skin cancer: racial/ethnic differences in behaviors and attitudes.

Data from 384 individuals participating in a worksite skin cancer screening program were used to assess racial/ethnic differences in attitudes toward and practice of prevention and early detection of skin cancer. Caucasians and Hispanics were more likely than African Americans to report having used a sunscreen during the past year. Caucasians performed skin self-examination more frequently than Hispanics, but African Americans did not differ in their frequency of skin self-examination from the other two groups. African Americans and Hispanics reported that they would be less likely than Caucasians to seek immediate follow-up care for suspicious skin lesions. Both similarities and differences were found in a variety of health belief variables across the three groups. These findings suggest a need for intensified efforts at primary and secondary prevention of skin cancer among African Americans.

Adult↗
PubMed1994

Hepatitis C in liver transplantation: preliminary study of prognostic factors.

At the University of Miami liver transplantation for chronic liver disease in HCV-positive patients has shown good results, with a 92% patients survival rate (follow up 8 to 57 months, median 21). None the less, we found that a large number of patients are expected to develop serious histological graft damage and may need retransplantation, which may place a further strain on the already scarce donor resources. We have conducted a preliminary investigation on the importance of parameters which may correlate with the prognosis of HCV grafts. We found no impact of HLA match or typing. An interesting hypothesis, which deserves further investigation, is that some HCV strains could be more virulent than others and play a role as an independent risk factor. We have identified six strains among our patients and the BK serotype shows a trend to be associated with a worse outcome. We have found that patients developing and maintaining higher liver enzyme levels (ALT and GGT) after transplant and those with higher levels of viremia may be at risk to develop serious damage to their grafts.

Adolescent↗
PubMed1994

Increased acetylcholine release in tracheas from allergen-exposed IgE-immune mice.

Increased release of acetylcholine (ACh) from airway parasympathetic nerve endings is one mechanism that may contribute to increases in airway responsiveness in immunoglobulin E (IgE)-immune allergen-exposed animals. We measured ACh released from murine tracheas following electrical field stimulation in vitro. BALB/c mice were immunized by exposure to an aerosol of 1% ovalbumin in sterile phosphate-buffered saline for 20 min/day for 10 days. At this time, levels of ovalbumin-specific IgE were proportionately higher than ovalbumin-specific IgG. As a control, nonimmune mice were similarly exposed to phosphate-buffered saline alone. Forty-eight hours after the last aerosol, tracheas were removed for assessment of either the contractile responses to electrical field stimulation and a cholinergic agonist (methacholine or ACh) or release of ACh produced by electrical field stimulation. ACh in the bath was measured using high-performance liquid chromatography with electrochemical detection. The stimulation frequencies causing one-half the maximal contractile response to electrical field stimulation were 4.1 +/- 0.2 and 2.8 +/- 0.2 Hz (P = 0.0001) for nonimmune and immune mice, respectively, whereas the molar concentrations of methacholine causing one-half of the maximal contractile response did not significantly differ. In addition, the dose-response curves of immune and nonimmune tracheas to ACh were superimposable. A significant increase in ACh release was demonstrated at both 10 and 20 Hz in tracheas from immune mice. ACh release (pmol.g tissue-1.min-1) from nonimmune and immune murine tracheas, respectively, were 140 +/- 8 and 205 +/- 22 (P = 0.013) at 10 Hz and 147 +/- 13 and 227 +/- 14 (P = 0.008) at 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Fludarabine in lymphoproliferative disorders: the Royal Marsden Hospital experience.

Fludarabine 25 mg/m2 was given on five consecutive days every four weeks to 85 patients with B- and T-cell malignancies. The median number of courses given was five. All patients except one had received previous chemotherapy. The overall response rate in non-Hodgkin's lymphoma (NHL) was 50% (five complete responses (CR) and 19 partial responses (PR)). The response rate in chronic lymphocytic leukemia (CLL) was 43% (four CR and 12 PR). Responses were seen in all groups of B-cell malignancies, but no T-cell malignancies (n = 4) responded. The median duration of CR has not been reached and the median duration of PR was 14 months for NHL and 16 months for CLL. The median survival from starting fludarabine for patients who achieved a CR or PR in NHL has not been reached and the median duration of PR in CLL was 23 months. The median duration of survival in non-responders was five months. Fludarabine was well tolerated and the main toxicity was myelosuppression. Our results suggest that even in patients who have never responded to any chemotherapy, regardless of the number of treatment regimens previously given, there is a 36% chance of response. In addition, this is the first report of fludarabine activity in Franklin's disease.

Adult↗
PubMed1993

Endogenous antioxidant changes in the myocardium in response to acute and chronic stress conditions.

Oxygen is a diradical and because of its unique electronic configuration, it has the potential to form strong oxidants (e.g. superoxide radical, hydrogen peroxide and hydroxyl radical) called oxygen free radicals or partially reduced forms of oxygen (PRFO). These highly reactive oxygen species can cause cellular injury by oxidizing lipids and proteins as well as by causing strand breaks in nucleic acids. PRFO are produced in the cell during normal redox reactions including respiration and there are various antioxidants in the cell which scavenge these radicals. Thus in order to maintain a normal cell structure and function, a proper balance between free radical production and antioxidant levels is absolutely essential. Production of PRFO in the myocardium is increased during various in vivo as well as in vitro pathological conditions and these toxic radicals are responsible for causing functional, biochemical and ultrastructural changes in cardiac myocytes. Indirect evidence of free radical involvement in myocardial injury is provided by studies in which protection against these alterations is seen in the presence of exogenous administration of antioxidants. Endogenous myocardial antioxidants have also been reported to change under various physiological as well as pathophysiological conditions. It appears that endogenous antioxidants respond and adjust to different stress conditions and failure of these compensatory changes may also contribute in cardiac dysfunction. Thus endogenous and/or exogenous increase in antioxidants might have a therapeutic potential in various pathological conditions which result from increased free radical production.

Acute Disease↗
PubMed1993

Identification of novel sequences in the repertoire of hypervariable TRE17 genes from immortalized nonmalignant and malignant human keratinocytes.

The TRE17 oncogene, originally cloned from transfected DNA of Ewing's sarcoma cells, maps to chromosome 17q and is expressed in a wide variety of human cancer cells. We recently detected the variants of this gene by using the polymerase chain reaction (PCR) and sequencing from the first exon to the third intron. Based on sequence homology scores, the variants could be grouped into three families, denoted alpha, beta, and gamma. Here, we used human keratinocytes from healthy skin which had been spontaneously immortalized and then rendered malignant by serum privation in vitro. Both immortalized and malignant cells expressed TRE17 sequences to the same extent, and, according to the restriction site analysis of cloned PCR products, both contained common and rare TRE17 variants in similar proportions. These variants, one of each from both cell types, were then sequenced and compared with those from the previous study. In the phylogenetic tree, they clustered with alpha and gamma at the most distant tree positions. The overall fraction of conserved sites in the whole TRE17 repertoire was 80%. An unexpected feature of the observed variability was that intronic sites were significantly better conserved than exonic sites. Members of TRE17 gamma detected in immortalized and malignant keratinocytes differed one from another, and both differed from the TRE17 gamma already identified in Ewing's sarcoma. No TRE17 gamma has been found so far in healthy tissues, thus leaving open the possibility of its origin from TRE17 beta by somatic changes during tumor progression.

Base Sequence↗
PubMed1993

Identification, cloning, and characterization of a novel human T-cell-specific tyrosine kinase located at the hematopoietin complex on chromosome 5q.

Signal transduction through the T-cell receptor and cytokine receptors on the surface of T lymphocytes occurs largely via tyrosine phosphorylation of intracellular substrates. Because neither the T-cell receptor nor cytokine receptors contain intrinsic kinase domains, signal transduction is thought to occur via association of these receptors with intracellular protein tyrosine kinases. Although several members of the SRC and SYK families of tyrosine kinases have been implicated in signal transduction in lymphocytes, it seems likely that additional tyrosine kinases involved in signal transduction remain to be identified. To identify unique T-cell tyrosine kinases, we used polymerase chain reaction-based cloning with degenerate oligonucleotides directed at highly conserved motifs of tyrosine kinase domains. We have cloned the complete cDNA for a unique human tyrosine kinase that is expressed mainly in T lymphocytes (EMT) and natural killer (NK) cells. The cDNA of EMT predicts an open reading frame of 1866 bp encoding a protein with a predicted size of 72 Kd, which is in keeping with its size on Western blotting. A single 6.2-kb EMT mRNA and 72-Kd protein were detected in T lymphocytes and NK-like cell lines, but were not detected in other cell lineages. EMT contains both SH2 and SH3 domains, as do many other intracellular kinases. EMT does not contain the N-terminal myristylation site or the negative regulatory tyrosine phosphorylation site in its carboxyterminus that are found in the SRC family of tyrosine kinases. EMT is related to the B-cell progenitor kinase (BPK), which has recently been implicated in X-linked hypogammaglobulinemia, to the TECI mammalian kinase, which has been implicated in liver neoplasia, to the more widely expressed TECII mammalian kinase, and to the Drosophila melanogaster Dsrc28 kinase. Sequence comparison suggests that EMT is likely the human homologue of a recently identified murine interleukin-2 (IL-2)-inducible T cell kinase (ITK). However, unlike ITK, EMT message and protein levels do not vary markedly on stimulation of human IL-2-responsive T cells with IL-2. Taken together, it seems that EMT is a member of a new family of intracellular kinases that includes BPK, TECI, and TECII. EMT was localized to chromosome 5q31-32, a region that contains the genes for several growth factors and receptors as well as early activation genes, particularly those involved in the hematopoietic system. Furthermore, the 5q31-32 region is implicated in the genesis of the 5q- syndrome associated with myelodysplasia and development of leukemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗