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Biomedical subjects

M Griffin

Publications and source records attributed to M Griffin.

At least 109 records · Page 6Linked to original sources
PubMed1999

Transglutaminase transcription and antigen translocation in experimental renal scarring.

It was recently demonstrated that renal tissue transglutaminase (tTg) protein and its catalytic product the epsilon(gamma-glutamyl) lysine protein cross-link are significantly increased in the subtotal (5/6) nephrectomy model (SNx) of renal fibrosis in rats. It was proposed that the enzyme had two important physiologic functions in disease development; one of stabilizing the increased extracellular matrix (ECM) by protein cross-linking, the other in a novel form of tubular cell death. This study, using the same rat SNx model, demonstrates first by Northern blotting that expression of tTg mRNA when compared with controls is increased by day 15 (+70% increase, P < 0.05), then rises steadily, peaking at day 90 (+391%, P < 0.01), and remains elevated at 120 d (+205%, P < 0.05) when compared with controls. In situ hybridization histochemistry demonstrated that the tubular cells were the major site of the additional tTg synthesis. Immunohistochemistry on cryostat sections revealed a sixfold increase (P < 0.001) in ECM-bound tTg antigen at 90-d post-SNx, whereas in situ transglutaminase activity demonstrated by the incorporation of fluorescein cadaverine into cryostat sections indicated a 750% increase (P < 0.001) on day 90 in SNx animals. This increased activity was extracellular and predominantly found in the peritubular region. These results indicate that increased tTg gene transcription by tubular cells underlies the major changes in renal tTg protein reported previously in SNx rats, and that the presence of the epsilon(gamma-glutamyl) lysine cross-links in the extracellular environment is the result of the extracellular action of tTg. These changes may be in response to tubular cell injury during the scarring process and are likely to contribute to the progressive expansion of the ECM in renal fibrosis.

Animals↗
PubMed1998

Molecular basis of T cell inactivation by CTLA-4.

CTLA-4, a negative regulator of T cell function, was found to associate with the T cell receptor (TCR) complex zeta chain in primary T cells. The association of TCRzeta with CTLA-4, reconstituted in 293 transfectants, was enhanced by p56(lck)-induced tyrosine phosphorylation. Coexpression of the CTLA-4-associated tyrosine phosphatase, SHP-2, resulted in dephosphorylation of TCRzeta bound to CTLA-4 and abolished the p56(lck)-inducible TCRzeta-CTLA-4 interaction. Thus, CTLA-4 inhibits TCR signal transduction by binding to TCRzeta and inhibiting tyrosine phosphorylation after T cell activation. These findings have broad implications for the negative regulation of T cell function and T cell tolerance.

Abatacept↗
PubMed1998

Induction of tissue transglutaminase by dexamethasone: its correlation to receptor number and transglutaminase-mediated cell death in a series of malignant hamster fibrosarcomas.

Treatment of the hamster fibrosarcoma cell lines (Met B, D and E) and BHK-21 hamster fibroblast cells with the glucocorticoid dexamethasone led to a powerful dose-dependent mRNA-synthesis-dependent increase in transglutaminase activity, which can be correlated with dexamethasone-responsive receptor numbers in each cell line. Increasing the number of dexamethasone-responsive receptors by transfection of cells with the HG1 glucocorticoid receptor protein caused an increase in transglutaminase activity that was proportional to the level of transfected receptor. In all experiments the levels of the tissue transglutaminase-mediated detergent-insoluble bodies was found to be comparable with increases in transglutaminase activity. Despite an increase in detergent-insoluble body formation, an increase in apoptosis as measured by DNA fragmentation was not found. Incubation of cells with the non-toxic competitive transglutaminase substrate fluorescein cadaverine led to the incorporation of this fluorescent amine into cellular proteins when cells were damaged after exposure to trypsin during cell passage. These cross-linked proteins containing fluorescein cadaverine were shown to be present in the detergent-insoluble bodies, indicating that the origin of these bodies is via activation of tissue transglutaminase after cell damage by trypsinization rather than apoptosis per se, since Met B cells expressing the bcl-2 cDNA were not protected from detergent-insoluble body formation. We describe a novel mechanism of cell death related to tissue transglutaminase expression and cell damage.

Animals↗
PubMed1998

Regulated expression of tissue transglutaminase in Swiss 3T3 fibroblasts: effects on the processing of fibronectin, cell attachment, and cell death.

Tissue transglutaminase (tTgase) catalyzes the posttranslational modification of proteins by forming Ca2(+)-dependent intermolecular epsilon (gamma-glutamyl) lysine crosslinks; however, its physiological function is unclear despite increasing evidence for its involvement in the extracellular environment. To define where the enzyme is active and characterizes targets of crosslinking we have modulated tTgase expression in stably transformed Swiss 3T3 cell lines, generated by transfecting tTgase cDNA under the control of a tetracycline-regulated inducible promoter. Induced expression of tTgase enabled the detection of two pools of transglutaminase antigen, one intracellular and the other extracellular, which has a cellular distribution comparable to fibronectin. Incubation of cells with the fluorescent tTgase substrate fluorescein cadaverine indicated incorporation only in the extracellular matrix of healthy cells even though the amine was freely permeable to cells. Incorporation paralleled the deposition of fibronectin during fibril assembly when monitored by immunofluorescence. Fibronectin polymerization was confirmed by Western blotting. Cell surface-related tTgase was further demonstrated by preincubation of cells with tTgase antibody which led to inhibition of activity and cell attachment. Activation of the intracellular tTgase by increasing cytosolic Ca2+ using ionomycin resulted in cell death accompanied by extensive crosslinking in the cytoplasm, nucleus, and cell substratum contacts of induced cells. These dead cells were not typical of those undergoing apoptosis or necrosis since they remained adherent, preserved their microtubule network, and showed little DNA fragmentation. Modulation of expression of tTgase has indicated a possible physiological function for the enzyme in cell attachment, the crosslinking of fibronectin during fibril assembly, and the maintenance of cellular integrity in a novel form of cell death.

3T3 Cells↗
PubMed1998

Computer simulation of magnetic resonance spectra employing homotopy.

Multidimensional homotopy provides an efficient method for accurately tracing energy levels and hence transitions in the presence of energy level anticrossings and looping transitions. Herein we describe the application and implementation of homotopy to the analysis of continuous wave electron paramagnetic resonance spectra. The method can also be applied to electron nuclear double resonance, electron spin echo envelope modulation, solid-state nuclear magnetic resonance, and nuclear quadrupole resonance spectra.

Computer Simulation↗
PubMed1998

Peter B. Samuels Award. Restenosis after percutaneous transluminal angioplasty.

BACKGROUND: Determine the feasibility of studying the natural history of the atherosclerotic plaque following percutaneous transluminal angioplasty (PTA), using duplex scanning. METHODS: Twenty-three patients with 40 stenoses (>70% and <5 cm in length) in the iliac and femoro-popliteal segments were studied by duplex scanning before PTA, on day 1, weekly for 8 weeks, and at 3 months, 6 months, and 1 year. The following measurements were made: thickness of the plaque, minimal lumen diameter (MLD), and peak systolic velocity ratio (PSVR). A PSVR >2.0 was used to indicate >50% lumen diameter reduction. RESULTS: Thirty stenoses were available for measurement and analysis. Mean reduction in plaque thickness after angioplasty was greater in echolucent plaques (2.33 +/- 0.9 mm) than echogenic plaques (0.83 +/- 0.6 mm; P < 0.0001). Successful angioplasty (PSVR <2.0) and increase in MLD in echolucent plaques was the result of plaque compression; in echogenic plaques, of wall dilatation. The incidence of restenosis (PSVR >2.0) at 6 months was 12 of 30 (40%) remaining unchanged at 1 year; of the lesions that restenosed, 33% recurred before week 8 and the remainder between weeks 8 and 24, suggesting different mechanisms. During follow-up, all plaques showed "growth"; <2 mm in 17 (57%; group A) and >2 mm in the remaining 13 (43%; group B). The incidence of restenosis (PSVR >2.0) was 4 of 17 (23%) in group A and 8 of 13 (61%) in group B (P <0.05). CONCLUSION: Duplex scanning provides valuable information on both luminal diameter and plaque thickness; it may be used to study the natural history of plaques following angioplasty and also the effects of therapeutic agents aimed at reducing restenosis.

Angioplasty, Balloon↗
PubMed1998

The economic cost of infertility-related services: an examination of the Massachusetts infertility insurance mandate.

OBJECTIVE: To examine the costs and outcomes of infertility-related services in Massachusetts during a time of expanded use of assisted reproductive technology (ART). DESIGN: Cost data were obtained from the Massachusetts Department of Insurance Rate-Setting Commission and 9 large group insurance plans for the period 1986-1993. Utilization and success rates of ART were examined, and the cost per live delivery with the use of ART in 1993 was estimated. SETTING: The state of Massachusetts, in which access to infertility-related services has been mandated by law since 1989. PATIENT(S): The study population consisted of 8 large health maintenance organization plans and the Blue Cross/Blue Shield indemnity plan. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Per capita infertility-related expenditures, infertility-related expenditures as a percentage of total expenditures, live deliveries per initiated ART cycle, and cost per live delivery. RESULT(S): Expenditures for infertility services increased at a rate similar to or slower than inflation during the years 1988-1992. Increases were slowest in health maintenance organizations, probably as a result of provider arrangements. Infertility services accounted for 0.41% of total expenditures within the indemnity plan in 1993 (approximately $1.71 per contract-month). Examination of ART utilization showed no evidence of overutilization by patients with a low chance of success. The cost per live delivery with the use of ART in 1993 was $59,484. CONCLUSION(S): Mandated infertility coverage was associated with increased use of ART but not with excessive increases in consumer cost for infertility insurance coverage.

Adult↗
PubMed1998

Cellular cholesterol synthesis--the relationship to post-prandial glucose and insulin following weight loss.

Hyperinsulinaemia is a risk factor for atherosclerosis. We have previously demonstrated a relationship between hyperinsulinaemia and cellular cholesterol synthesis. In this paper we examine the separate relationship of glucose and insulin to cholesterol synthesis in three groups of obese patients. The first group was a group of non-insulin-dependent diabetic patients with a low post-prandial insulin response (n=8). The second group had non-insulin-dependent diabetes and a high insulin response (n=9). The third group were non-diabetic patients with a high post-prandial insulin (n=12). Six diabetic and seven non-diabetic patients who were hyperinsulinaemic on initial analysis, were re-examined following an 8% body weight reduction. Insulin resistance was defined as the ratio of area under curve for insulin/area under curve for glucose. Cellular cholesterol synthesis was measured in freshly isolated mononuclear leucocytes. Fasting cholesterol synthesis was similar in the three groups. In both diabetic and non-diabetic high insulin subjects cholesterol synthesis rose significantly after the meal (p < 0.05). Both hyperinsulinaemic groups showed a significantly greater change from baseline than did the non-hyperinsulinaemic group. There was a positive correlation between post-prandial cellular cholesterol synthesis and insulin resistance (p < 0.05). Following weight reduction patients were divided into two groups, those who did reduce insulin resistance (group 1) and those who did not reduce insulin resistance (group 2). The significant post-prandial increase in cholesterol synthesis was no longer seen in group 1 after weight loss whereas in group 2 after a similar weight loss the post-prandial cholesterol synthesis remained elevated. These results demonstrate that post-prandial hyperinsulinaemia is associated with increased cellular cholesterol synthesis. This increase in cholesterol synthesis is no longer seen in those patients in whom insulin resistance improved with weight reduction. This study suggests a mechanism for the association between insulin resistance and atherosclerosis.

Blood Glucose↗
PubMed1998

Telomerase activity and human papillomavirus (HPV) infection in human uterine cervical cancers and cervical smears.

Telomerase activity and human papillomavirus (HPV) infection were investigated in uterine cervical samples using molecular biology techniques. Thirteen cervical carcinomas and corresponding normal tissue from the same patient, and 102 cervical swabs were examined. Telomerase activity was detected in 12 of 13 cervical cancer tissues (92%). Of the 12 cases that showed telomerase activity, all were HPV positive, and the one case that did not show telomerase activity was HPV negative. A telomeric repeat amplification protocol assay detected telomerase activity in one out of seven normal cervical tissues (14%), and this one case was HPV positive. In cervical smear samples, telomerase activity was detected in two out of 36 normal smears (6%; both HPV positive), in 10 of 32 (31%) CIN1 (cervical intra-epithelial neoplasia) cases (three HPV positive), in four of five (80%) CIN2 cases (two HPV positive), in 15 of 21 (71%) CIN3 cases, (seven HPV positive) and in seven of eight (88%) squamous cell carcinoma cases (six HPV positive). These results suggest that telomerase activity may play some role in cervical carcinogenesis, and telomerase activity is associated with HPV infection in uterine cervical lesions.

Carcinoma, Squamous Cell↗
PubMed1998

The objective characterisation of ultrasonic carotid plaque features.

OBJECTIVE: To determine the influence of ultrasonic carotid plaque morphology on the incidence of ipsilateral hemispheric symptoms (IHS). DESIGN: Cross-sectional study. MATERIALS: A consecutive series of 80 patients (96 plaques) with more than 50% ICA stenosis was studied. METHODS: B mode ultrasonic images were captured and transferred to a computer on magneto-optic disk and standardised using linear scaling so that adventitia would have a grey scale median (GSM) value of 185-195 and blood 0-5. The GSM and the percentage of echolucent pixels (PEP) in plaques were determined to measure echodensity. Homogeneity, entropy, and contrast were also determined to measure spatial distribution (heterogeneity) of grey shades in each plaque. Each measurement was correlated to presence or absence of IHS. RESULTS: Twenty-five plaques were associated with IHS and 71 plaques were asymptomatic. In symptomatic plaques the mean of GSM was 23 and the mean of PEP was 70%, compared to 38 and 55% respectively in asymptomatic plaques (p = 0.02; Wilcoxon test). Sixty per cent of symptomatic plaques were associated with a homogeneity, entropy, and contrast values of > 0.2, < 2.95, < 150 respectively as compared to 40% in asymptomatic plaques. Multiple regression analysis revealed that the GSM and the PEP were the most significant variables (p = 0.001) that are related to presence or absence of IHS. CONCLUSION: This study indicates that computer aided analysis of ultrasonic B mode features of carotid plaques could identify a potentially high-risk subgroup (patients with IHS). A GSM less than 40 or PEP greater than 50% is a good predictor of IHS related to carotid plaques. The fact that these measurements are operator independent and performed after image standardisation should encourage their use in multicenter clinical trials where different operators and equipment are used.

Carotid Artery, Internal↗
PubMed1998

General anaesthesia for thyroplasty.

A new anaesthetic technique is described for thyroplasty. Thyroplasty was performed to restore the voice in unilateral vocal cord paralysis. After skin incision and dissection down to the larynx, a window was cut in the thyroid ala and a silastic wedge used to displace the vocal cord medially. The required size of this wedge was determined by pre-operative computerized tomography scanning of the larynx. At this point the patient had to be awake and cooperative to allow repeated phonation to facilitate correct displacement of the vocal cord.

Adult↗
PubMed1998

Detection of Ca2+-dependent transglutaminase activity in root and leaf tissue of monocotyledonous and dicotyledonous plants

Protein extracted from root and leaf tissue of the dicotyledonous plants pea (Pisum sativum) and broad bean (Vicia faba) and the monocotyledonous plants wheat (Triticum aestivum) and barley (Hordeum vulgare) were shown to catalyze the incorporation of biotin-labeled cadaverine into microtiter-plate-bound N', N'-dimethylcasein and the cross-linking of biotin-labeled casein to microtiter-plate-bound casein in a Ca2+-dependent manner. The cross-linking of biotinylated casein and the incorporation of biotin-labeled cadaverine into N',N'-dimethylcasein were time-dependent reactions with a pH optimum of 7.9. Transglutaminase activity was shown to increase over a 2-week growth period in both the roots and leaves of pea. The product of transglutaminase's protein-cross-linking activity, epsilon-(gamma-glutamyl)-lysine isodipeptide, was detected in root and shoot protein from pea, broad bean, wheat, and barley by cation-exchange chromatography. The presence of the isodipeptide was confirmed by reversed-phase chromatography. Hydrolysis of the isodipeptide after cation-exchange chromatography confirmed the presence of glutamate and lysine.

Journal Article↗
PubMed1998

Diabetic retinopathy in Down's syndrome.

AIM: To determine the prevalence of diabetic retinopathy in patients with Down's syndrome and diabetes mellitus. METHODS: Nine patients with Down's syndrome and diabetes mellitus were assessed. Factors recorded included type and duration of diabetes, level of diabetic control, blood pressure, urinalysis, and results of ophthalmological examination. RESULTS: The duration of diabetes ranged from 8 to 41 years (mean 17.6 years). All had satisfactory glycaemic control and blood pressure measurements on the low side of normal (mean 106.6/70 mm Hg). One patient had early background diabetic retinopathy. The remainder had no evidence of diabetic retinopathy. CONCLUSION: The low prevalence of diabetic retinopathy in these Down's syndrome patients, despite the long duration, is an interesting finding. It suggests some inherent protective factor against the development of diabetic retinopathy in this patient subgroup.

Adult↗
PubMed1998

Shock waves in vascular diseases: an in-vitro study.

UNLABELLED: Three human aortic specimens were used for this in-vitro study on the effects of shock waves on the arterial wall. Specimen one was from a normal (for age) healthy aorta. The full abdominal length was used (including mesenteric and renal arteries and the aortoiliac bifurcation), divided into six pieces (3 cm). The pieces were placed and fixed into degassed water. Shock waves (SW) were focused onto the aortic wall by means of a B-mode ultrasound imager. An SW generator (Minilith SL1, Storz Medical AG, Kreuzlingen, Switzerland) was used for setting of energy flux density between 0.03 and 0.5 mJ/mm2. The six aortic pieces (excluding piece 1, placed in water and left untreated as control) were treated with SW at increasing energy levels. A second aortic specimen of a man with arteriosclerotic plaques was also used and the experiment repeated at energy levels 1, 5, and 8. Another specimen of normal thoracic aorta was exposed at energy levels 1 and 8 only. Energy levels delivered onto the aortic walls were selected from theoretically destructive levels to minimal levels known not to alter vascular tissues. High-resolution ultrasounds of the aortic segments were performed with a 10 MHz high-resolution, broad-band (ATL 3000, USA) probe in water before and after SW application to detect structural changes in the wall after SW. Histology was performed with a standard hematoxylin-eosin staining. RESULTS: The aortic pieces did not show macroscopic damages at visual examination, and at the ultrasound examination no visible changes were observed even at higher levels of SW energy. Also no effects were seen by histology. In conclusion, no damaging effects were observed, visually, by ultrasound, or by histology. At these energy levels SW appear to be safe and do not produce any damage to the aortic wall. Therefore, SW could be considered a safe, nondamaging procedure for potential treatment (ie, thrombolysis) in which vessel walls could be involved. Theoretically it is possible that functional changes could be observed in vivo including cell permeability modifications and other alterations (including changes in the potential of the cells in SW fields to modify themselves and to divide). At the energy levels described in this study SW could, theoretically be, safely used for vascular applications (ie, treating venous and arterial thrombi or in arterial plaques modification) without altering major, structural, arterial wall characteristics. Lesions or alterations that have a different density from the normal wall (thrombi or plaques) could be differently sensitive to the same dosage of SW. These differences in acoustic impedance characteristics could be used for potential treatments with SW without damaging the arterial wall.

Aorta↗