UDP-glucuronosyltransferase in Gilbert's syndrome

The diagnosis of Gilbert's syndrome, a condition characterised by mild jaundice related to chronic unconjugated hyperbilirubinemia, is often presumptive and the pathogenesis is incompletely understood. It would be of interest to develop an immunohistochemical staining method to confirm a diagnosis of Gilbert's syndrome. To this end liver tissues from ten patients with a presumed diagnosis of Gilbert's syndrome and six normal controls were examined by immunohistochemistry with polyclonal antibodies raised to UDP-glucuronosyltransferase (UGT). All subjects had normal liver biopsies by hemotoxylin and eosin staining. In normal human liver specific staining for UGT was seen diffusely in all hepatocytes of the hepatic lobule with zone 3 accentuation. There was a reduction of immunostaining throughout the hepatic lobule in all specimens from patients with Gilbert's syndrome and faint residual staining was seen in zone 3. This thus proved a useful method to confirm a clinical diagnosis of Gilbert's syndrome. Raising monospecific antibodies to UGT may give an insight into polypmorphisms of phase II drug metabolism. Bosma et al.* have recently provided evidence from in vitro studies that subjects with Gilbert's syndrome have a putative defect in the promoter region of the gene encoding UDP-glucuronosyltransferase 1, resulting in reduced transcription. These studies have yet to be confirmed from human biopsy specimens and the possibility of second mutations in intronic sequences affecting the stability of UDP-glucuronosyltransferase 1 m RNA are being explored. *Bosma PJ, Chowdhury JR, Bakker C et al. The genetic basis of the reduced expression of bilirubin UDP-glucuronosyltransferase 1 in Gilbert's syndrome. N Engl J Med 1995; 333: 1171-5.

TGF-alpha immunoreactivity in laryngeal carcinoma: lack of prognostic value and correlation to EGF-receptor expression

BACKGROUND

Transforming growth factor alpha (TGF-alpha) is a polypeptide that is structurally similar to epidermal growth factor (EGF) that binds to the epidermal growth factor receptor (EGFR) and has been implicated in the development of several types of human tumours.

METHODS

The expression of TGF-alpha is examined in laryngeal squamous cell carcinoma (SCC) (n = 24) and non-neoplastic polyps (n = 7) using streptavidin-biotin immunohistochemistry and a monoclonal antibody to the TGF-alpha protein. These cases had been previously characterized for EGFR immunoreactivity. The carcinomas were classified as well differentiated (n = 2), moderately differentiated (n = 16) and poorly differentiated (n = 6). Tissues from metastatic tumour deposits in lymph nodes (n = 5) were also studied.

RESULTS

TGF-alpha overexpression was defined as intense immunoreactivity in more than two-thirds of tumour cells immunostained for TGF-alpha and was present in the majority of the SCC cases (n = 15; 63%) and metastatic tumour deposits (n = 4; 80%). In contrast, although some of the vocal cord polyps showed weak (n = 2) to moderate (n = 5) immunostaining, none had evidence of strong TGF-alpha immunoreactivity. The differences in TGF-alpha immunoreactivity were significant between primary laryngeal SCC and vocal cord polyps (P = 0.013; chi 2 test with continuity correction), and between metastatic laryngeal SCC and vocal cord polyps (P = 0.023; chi 2 test with continuity correction). There was no significant difference in TGF-alpha expression between the different grades of carcinomas (P = 0.92, chi 2 test) or between non-metastatic and metastatic carcinomas (P = 0.82; chi 2 test with continuity correction). No significant correlation was found between TGF-alpha expression and patient survival or tumour recurrence (r = 0.077, r2 = 0.006, P = 0.75; simple regression analysis), or between TGF-alpha expression and EGFR immunoreactivity (r = 0.325, r2 = 0.106, P = 0.0851).

CONCLUSIONS

In conclusion, increased TGF-alpha immunoreactivity is present in most cases of laryngeal SCC with no specific relationship to tumour grade, suggesting that it may be important in the development of laryngeal carcinomas but not in its progression. No significant correlation was found between TGF-alpha and EGFR expression in laryngeal tumours and TGF-alpha immunoreactivity is of no prognostic value.

Cyclin DI amplification is not associated with reduced overall survival in primary breast cancer but may predict early relapse in patients with features of good prognosis

Amplification of chromosome 11q13 is frequently observed in human malignancies, including breast cancers. A candidate oncogene at this locus is the CCND1 gene, which encodes the cell cycle regulatory protein cyclin D1. Because published data on the relationship between 11q13 amplification and prognosis in breast cancer have been controversial, we investigated the clinical significance of CCND1 amplification and its association with established clinicopathological features of prognosis in 1014 primary breast cancer patients. Amplification of the CCND1 gene and the INT-2/FGF-3 gene, which also maps to 11q13, was 10% and 17%, respectively. There were no associations between CCND1 or INT-2 amplification and patient age, tumor size, tumor grade, axillary lymph node status, HER/neu amplification, MIB-1 monoclonal antibody to Ki67 antigen count, or p53 expression. CCND1 amplification was predominantly observed in hormone receptor-positive tumors; at a copy number >/=3, CCND1 amplification was significantly correlated with both estrogen receptor (ER; P = 0.036) and progesterone receptor (P = 0.012) positivity. After a median follow-up period of 66 months, CCND1 or INT-2 amplification was not associated with significant increases in relapse or death from breast cancer. However, in the node-negative and ER-positive subgroups, there was a trend for an increased relapse rate in patients with INT-2 or CCND1 amplification. Thus, in this study, assessment of CCND1 or INT-2 amplification at 11q13 by slot-blot hybridization was of little use in determining phenotype or disease outcome in the whole group of patients but had a potential role in identifying a subset of poor-prognosis patients within the node-negative or ER-positive, good-prognosis groups. Because the prevalence of CCND1 amplification is much lower than the reported prevalence of cyclin D1 overexpression, additional studies are required to determine the true prognostic significance of altered cyclin D1 expression in breast cancer.

Giant aneurysm of main pulmonary artery

Aneurysm of the main pulmonary artery is an extremely rare entity. The first successful repair of an aneurysm of the main pulmonary artery was reported in 1971. Since then, surgical correction of the aneurysm of main pulmonary artery has been undertaken in only 6 cases. A thorough survey of the literature, including autopsy cases, medical cases, and surgical cases, shows the aneurysm in the present case to be one of the largest.

Suppression of interleukin-1 and tumor necrosis factor-alpha production by acanthoic acid, (-)-pimara-9(11),15-dien-19-oic acid, and it antifibrotic effects in vivo

Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) are major proinflammatory cytokines inducing the synthesis and release of many inflammatory mediators. They are involved in immune regulation, autoimmune diseases, and inflammation. Acanthoic acid, (-)-pimara-9(11),15-dien-19-oic acid, is a pimaradiene diterpene isolated from the Korean medicinal plant, Acanthopanax koreanum. When human monocytes/macrophages stimulated with silica were treated with 0.1-10 microg/ml acanthoic acid, the production of IL-1 and TNF-alpha was inhibited up to 90%, but the production of interleukin-6 (IL-6) was not inhibited at all. At these concentrations, it had no cytotoxic effect on human monocytes/macrophages. It also suppressed the production of TNF-alpha by alveolar macrophages and lymphocytes stimulated with silica. In addition, acanthoic acid inhibited the release of superoxide anion and hydrogen peroxide from human monocytes/macrophages and neutrophils. To know the antifibrotic effects of acanthoic acid, its effects on fibroblast proliferation and collagen synthesis were tested. The proliferation of NIH3T3 cells was inhibited almost completely by the addition of the culture supernatants of human monocytes/macrophages treated with acanthoic acid, but not by the addition of acanthoic acid only. In vitro and in vivo treatment with acanthoic acid reduced collagen production by rat lung fibroblasts and lung tissue. Furthermore, acanthoic acid suppressed granuloma formation and fibrosis in the experimental silicosis. Acanthoic acid reduced serum GOT and GPT in the rats with cirrhosis induced by CCl4, and it was effective in reducing hepatic fibrosis and nodular formation. Taken together, these data indicate that acanthoic acid has a potent anti-inflammatory and antifibrosis effect by reducing IL-1 and TNF-alpha production.

Effects of protein kinase inhibitors on the stimulated neutrophil responses by degraded immunoglobulin G

Effects of protein kinase C inhibitors, staurosporine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine dihydrochloride and protein tyrosine kinase inhibitors, genistein, tyrphostin and 2,5-dimethylcinnamate on the neutrophil responses stimulated by immunoglobulin G (IgG), complement C5a or platelet-activating factor were studied. After receptor binding, the role of protein kinase C and protein tyrosine kinase in the stimulation of neutrophil responses, superoxide production and lysosomal enzyme release in degraded IgG-activated neutrophils may be similar to chemoattractant-stimulated cells. In contrast to complement C5a or platelet-activating factor, protein tyrosine kinase appears to play an important role in the regulation of intracellular Ca2+ mobilization in neutrophils activated by degraded IgG rather than by protein kinase C.

Inverse regulation of oestrogen receptor and epidermal growth factor receptor gene expression in MCF-7 breast cancer cells treated with phorbol ester

In human breast cancer cell lines, an inverse relationship exists between the basal levels of oestrogen receptor (ER) and epidermal growth factor receptor (EGF-R) gene expression. In addition, the tumour-promoting phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibits ER and stimulates EGF-R expression in MCF-7 breast cancer cells. This study aimed to define further the potential mechanisms involved in the modulation of ER and EGF-R gene expression by TPA. ER mRNA levels were reduced after 3 h and declined to 30% of control between 12 and 72 h after exposure to 10 nM TPA. This decrease in mRNA levels was preceded by an apparent fall in ER transcription rate. There was no effect on the stability of ER mRNA following pretreatment for 3-24 h with TPA, supporting the conclusion that the fall in ER mRNA levels was predominantly due to a decrease in ER transcription rate. Levels of EGF-R mRNA increased 10-fold by 12 h due predominantly to an increased transcription rate. The TPA-induced decrease in ER mRNA was unaffected by the simultaneous administration of the protein synthesis inhibitor cycloheximide, whereas the increase in EGF-R mRNA was inhibited by co-incubation with cycloheximide. These data indicate a requirement for continuing protein synthesis for the TPA effect on EGF-R but not on ER mRNA levels. Because the modulation of ER and EGF-R gene expression by TPA is likely to involve the protein kinase C (PKC) signal transduction pathway, the effects of other known activators of PKC were investigated. The non-phorboid tumour promoter mezerein modulated ER (an 80% decrease) and EGF-R (a 20-fold increase) mRNA levels in a similar manner to TPA. In contrast, neither 1,2-dioctanoyl-sn-glycerol (DiC8) nor 1-oleoyl-2-acetyl-sn-glycerol (OAG), both permeant analogues of the endogenous physiological activators of PKC, affected ER and EGF-R mRNA levels. These latter results were not due to a lack of efficacy because a single administration of DiC8 was as effective as TPA in inducing c-fos mRNA at 30 min. However DiC8 was less active in the later induction of c-myc mRNA. These data demonstrate reciprocal regulation of ER and EGF-R gene expression by TPA, involving effects on transcriptional events, which appear to be mediated by sustained activation of PKC.

Dopaminergic neuronal degeneration and motor impairments following axon terminal lesion by instrastriatal 6-hydroxydopamine in the rat

6-Hydroxydopamine-induced nerve terminal lesion of the nigrostriatal system may provide a partial lesion model of Parkinson's disease useful for the assessment of neuroprotective treatments and behavioral recovery after therapeutic intervention. The aim of the present study was to assess the retrograde degenerative changes in the dopaminergic neurons of the substantia nigra and the associated behavioral and neurochemical consequences of intrastriatal injections of 6-hydroxydopamine in young adult rats. Four groups of rats were stereotaxically injected in the right striatum with graded doses of 6-hydroxydopamine ranging from 0 to 20 mu g. Structural and functional deficits were quantified by tyrosine hydroxylase-immunoreactive nigral cell numbers, striatal dopamine content, skilled paw use, and drug-induced rotation. The results show that striatal 6-hydroxydopamine lesions produce dose-dependent decreases in striatal dopamine levels and tyrosine hydroxylase-immunoreactive cell numbers in the ipsilateral substantia nigra, accompanied by a significant long-lasting atrophy of the remaining dopaminergic neurons. Paw reaching test scores on the side contralateral to the lesion were non-linearly correlated with dopaminergic neuronal cell loss and exhibited a clear symptomatic threshold such that impaired paw use appeared only after >50% loss of nigral dopamine neurons or a reduction of 60-80% of striatal dopamine levels. The behavioral, cellular, and neurochemical effects of the nerve terminal lesion thus bear some resemblance to the early stages of Parkinson's disease, where the severity of motor impairment is correlated with the loss of dopamine in the striatum and dopaminergic neuronal loss in the substantia nigra. Rats with intrastriatal 6-hydroxydopamine lesions thus provide a model of progressive dopamine neuron degeneration useful not only for the exploration of neuroprotective therapeutic intervention but also for the study of mechanisms of functional and structural recovery after subtotal damage of the nigrostriatal dopamine system.

nm23-H1 protein immunoreactivity in laryngeal carcinoma

BACKGROUND

The nm23-H1 gene encodes a 17-kilodalton cytoplasmic and nuclear protein that has recently been shown to be reduced in a number of human carcinomas including breast, colorectal, lung, gallbladder, and biliary tract carcinomas. This study examines the immunohistochemical staining characteristics of the nm23-H1 protein in human laryngeal carcinomas and nonneoplastic laryngeal polyps, and attempts to determine if there is any relationship between reduction of nm23-H1 protein immunoreactivity and prognosis of patients with laryngeal carcinoma.

METHODS

Routine streptavidin-biotin immunohistochemistry with a polyclonal antibody was employed to study the expression of the nm23-H1 protein in laryngeal squamous cell carcinoma (SCC) (N = 22) and nonneoplastic polyps (N = 8). The carcinomas were classified as well differentiated (N = 2), moderately differentiated (N =15), and poorly differentiated (N = 5). Tissues from metastatic tumor deposits in lymph nodes (N = 5) were also studied. A semiquantitative immunostaining index was derived from the intensity and extent of staining of the cells.

RESULTS

All laryngeal polyps showed intense immunostaining for the nm23-H1 gene product in the squamous epithelium. However, reduced immunoreactivity was found in nearly half of the SCC cases (N = 10; 46%), with the least staining intensity found in tumor metastases in lymph nodes (N = 4; 80%), and were associated with a shorter median survival of 14.3 months. In contrast, tumors that demonstrated moderate to strong nm23-H1 protein immunostaining were associated with a longer median survival period of 20.4 months.

CONCLUSIONS

There is reduced expression of the nm23-H1 gene in human laryngeal SCC compared with nonneoplastic laryngeal polyps. Reduction in the intensity and extent of nm23-H1 protein immunostaining appears to correspond to reduced duration of patients survival.

Mechanical and electrophysiological effects of 8-oxoberberine (JKL1073A) on atrial tissue

The effects of 8-oxoberberine (JKL1073A) on contractions and electrophysiological characteristics of atrial tissues were examined. In driven left atria of the rat JKL1073A (10-100 microM) increased twitch tension dose-dependently. In spontaneously beating right atria, JKL1073A increased twitch tension but decreased beating rate slightly. The positive inotropic and the negative chronotropic effect of 30 microM JKL1073A was not affected by prazosin (1 microM), propranolol (1 microM) and 3-isobutyl-1-methyl-xanthine (10 microM) but significantly suppressed by 4-aminopyridine (2 mM 4-AP). Current-clamp study revealed that JKL1073A prolonged rat atrial action potential duration (APD). This prolongation of APD by JKL1073A was decreased by pretreating the cells with 2 mM 4-AP. Voltage-clamp study showed that JKL1073A inhibited the integral of the transient outward current (I(to)) dose-dependently with a KD value of 3.66 +/- 0.93 microM in rat atrial myocytes. The equilibrium dissociation constant (Kd) for JKL1073A bindings to open state I(to) was 0.50 +/- 0.08 microM. The suppression of I(to) by 3 microM JKL1073A was accompanied by shortening of its inactivation time constant from 52.5 +/- 0.9 ms to 16.8 +/- 0.7 ms. V(0.5) for the steady-state inactivation curve of I(to) was shifted from -25.7 +/- 3.3 mV to -34.8 +/- 3.2 mV. In human atrial cells, similar inhibition of I(to) and prolongation of APD by JKL1073A was found. The KD value of JKL1073A for inhibition of the integral of I(to) in human atrial cells is 4.03 +/- 0.02 microM. The Kd for bindings to open state I(to) is 0.5 microM. Currents through K1 channels of rat and human atrial myocytes were not inhibited by JKL1073A at concentrations up to 10 microM. These results indicate that JKL1073A exerts a positive inotropic effect by inhibition of I(to). JKL1073A inhibit I(to) by binding to open state channels or shifting of the steady-state inactivation curve of I(to).

Dynamic changes in the lymphocyte subpopulations of pig uterine lymph nodes

Cell subpopulations in local lymph nodes draining the uterine tissue of non-pregnant and pregnant pigs were examined by one- and two-colour immunofluorescent staining and flow cytometry using a panel of monoclonal antibodies to pig leucocyte cell surface antigens. Significant changes were observed in the T and B lymphocyte subpopulations and in a subpopulation of non-T or B cells. Activation of lymphocytes in the uterine lymph nodes during cycling in non-pregnant gilts suggests a role for the local immune system in the normal physiology of the uterus. In non-pregnant sows there was evidence of an increase in the CD4/CD8H ratio and in the proportion of B cells in the uterine nodes when compared to gilts with no prior reproductive experience. Pregnancy was shown to induce further dramatic changes in the uterine lymph nodes with an escalation in the proportion of B cells from 48% to 88% and a further increase in the CD4/CD8H ratio. For the first time in swine, low-level CD2 expression is reported on a subpopulation of B cells which are activated during pregnancy. These results provide evidence that the local uterine immune system in pigs plays a role in reproduction and perhaps in the maintenance of normal pregnancy.

Surgical correction of giant patent ductus arteriosus

In reviewing the literature, there was only one report having the ductus over 30 mm in width. Recently, we utilized cardiopulmonary bypass, hypothermia, and low flow through a transpulmonary approach to close 2 cases of giant patent ductus arteriosus. Both cases complicated with systemic pulmonary hypertension. Its outside diameters were 31 mm and 36 mm respectively based on the measurement from magnetic resonance imaging. To our knowledge, its seem the biggest ductus in comparison to previous reports. Both cases survived the operation and doing well for a follow-up time of 5 years and 4 years 10 months respectively.

Abnormalities in type IV collagen immunoreactivity in human laryngeal cancers

Abnormal patterns of expression of the basement membrane type IV collagen are observed in many human cancers. This study examines the immunohistological expression of type IV collagen in the basement membrane in human laryngeal squamous cell carcinomas (SCC) (n = 24). Non-neoplastic vocal cord polyps (n = 4) were used as controls. The formalin-fixed, paraffin-embedded tissues were sectioned and pretreated with protease prior to immunostaining for type IV collagen. There was a statistically significant difference in type IV collagen expression between laryngeal SCC and vocal cord polyps (p = 0.0001; chi 2 test with continuity correction). In laryngeal SCC (n = 24; 100%), type IV collagen distribution was discontinuous and irregular or absent around individual or groups of neoplastic cells. In contrast, all of the cases of vocal cord polyps (n = 4; 100%) displayed a continuous pattern of subepithelial basement membrane type IV collagen. This study has shown that abnormal distribution of type IV collagen occurs in laryngeal squamous cell carcinomas but not in non-neoplastic vocal cord polyps. This may be related to either abnormal synthesis or to the breakdown of the collagen and it may be of use as a potential biological marker in the study of laryngeal carcinogenesis.

Lack of p53 immunoreactivity in pancreatic endocrine tumors

Abnormal expression of the p53 tumor suppressor gene has been implicated in many human epithelial tumors. However recent evidence has revealed the absence of p53 gene abnormalities or overexpression in some human endocrine cancers. This study examines the immunohistological expression of the p53 gene product using the monoclonal antibody DO-7, an antibody directed against both wild and mutant forms of p53 protein, and a streptavidin-biotin-peroxidase method, in pancreatic endocrine tumors (n = 16). None of the cases of pancreatic endocrine tumors showed evidence of p53 immunostaining. This finding is in contrast to that in pancreatic adenocarcinomas in which increased p53 immunoreactivity has been previously observed. These observations suggest that the p53 gene may not be important in the development of endocrine tumors of the pancreas.

EWS/FLI-1 fusion transcript detection and MIC2 immunohistochemical staining in the diagnosis of Ewing's sarcoma

Ewing's sarcoma (ES) and other primitive peripheral neuroectodermal tumors (pPNETs) can present a significant diagnostic problem, as they may morphologically resemble other small round cell tumors (SRCTs) of childhood. However, ES/pPNET is known to carry a characteristic t(11;22)(q24;q12), the detection of which may aid diagnosis. The recent identification of the EWS and FLI-1 genes flanking the translocation break point has enabled reverse transcriptase-polymerase chain reaction (RT-PCR) to be used to detect the putative chimeric transcription factor mRNA produced by the fusion gene. We have assessed the RT-PCR method of detection by examining 40 cases of ES for the presence of EWS/FLI-1 transcripts. Twenty-six (76%) of the 34 cases with intact mRNA yielded fusion transcripts. Four different transcript sizes were detected and two tumors contained two transcripts of different size. No transcripts were detected in a control group of non-ES/pPNET SRCTs. Eight cases with intact mRNA were transcript negative. The MIC2 cell surface antigen, which is reported to be present in over 95% of ES/pPNETs, was present in 32 of 33 tumors (97%), including all 24 EWS/FLI-1 transcript-positive cases examined. Hence MIC2 is a useful screen for ES, with RT-PCR detection of t(11;22) being the optimal method for confirming the diagnosis.

UDP glucuronosyltransferase in the cirrhotic rat liver

In patients with cirrhosis, the elimination of drugs metabolized by glucuronidation is relatively preserved, in comparison with the metabolism of drugs by oxidation. This study explores this phenomenon at a molecular level. In cirrhotic rat livers the content of UDP-glucuronosyltransferase (UGT) was examined by immunohistochemistry and immunoblotting using three antibodies: (i) a polyclonal antibody directed against a broad number of UGT isoforms from both family 1 and family 2; (ii) a family 2-specific antibody; and a (iii) family 1-specific antibody. The steady state mRNA level of UGT of a family 2 isoform was also detected by northern blot analysis. The results demonstrate normal or increased UGT protein by immunohistochemistry and immunoblot in cirrhotic livers compared with controls. This was accompanied by increased steady state mRNA encoding the UGT isoform UGT2B1. In contrast, an isoform of cytochrome P450 (CYP2C11) was reduced markedly in both immunohistochemical staining and immunoblot analysis. These results suggest that in cirrhosis there is a comparative increase or at least a maintenance of UGT enzyme content and that this most likely occurs at a pretranslational level.

Excision of DNA adducts of nitrogen mustards by bacterial and mammalian 3-methyladenine-DNA glycosylases

Nitrogen mustards are among the DNA alkylating agents most widely used in chemotherapy. The homogeneous Escherichia coli AlkA protein (3-methyladenine-DNA glycosylase II) is shown to excise damaged guanine and adenine bases from DNA modified by mechlorethamine, uracil mustard, phenylalanine mustard and chlorambucil, and less efficiently acridine mustard adducts. Homogeneous recombinant human and rat 3-methyladenine-DNA glycosylases excise adducts formed by nitrogen mustards less efficiently than the AlkA protein. In addition to the in vitro excision of adducts, the AlkA protein eliminates cytotoxic mechlorethamine adducts from DNA in vivo.

Pressure distribution near the occluders and impact forces on the outlet struts of Björk-Shiley convexo-concave valves during closing

BACKGROUND AND AIMS OF THE STUDY

An in vitro study of the mechanics of closure of Björk-Shiley convexo-concave (BSCC) valves is presented in order to investigate the mechanics of outlet strut fracture reported in a small fraction of the implanted valves.

MATERIALS AND METHODS

Four BSCC 29 mm valves instrumented with strain gages on the outlet strut legs were mounted in the mitral position of an axisymmetric flow chamber of a mock pulsatile flow loop. Measurements of the pressure field in the vicinity of the occluder, closing velocity of the occluder tip in the major orifice, and the impact force between the occluder and outlet strut at the instant of valve closure were obtained at a range of physiologic flow rates.

RESULTS

The results indicated an uneven pressure distribution on the occluder associated with a tendency for the occluder to over-rotate and induce loads on the outlet struts. The impact loads on the outlet struts were asymmetric with load on one leg being larger than the other by up to 25%. These results are consistent with single leg separation preceding outlet strut fracture in most of the valve failures reported. Orientation of the valve with respect to the mitral orifice (major orifice towards the top or bottom) did not significantly affect the loads on the outlet strut. A significant variation in the impact loads of the four valves was measured for identical experimental conditions suggesting that valve specific factors influence outlet strut loads.

CONCLUSIONS

This study provided an understanding of the cause-effect relationship between valve dynamics and outlet strut fracture.

An efficient expression of human growth hormone (hGH) in the milk of transgenic mice using rat beta-casein/hGH fusion genes

In order to produce human growth hormone (hGH) in the milk of transgenic mice, two expression vectors for hGH differing in their 3' flanking sequences were constructed by placing the genomic sequences of hGH gene under the control of the rat beta-casein gene promotor. The 3' flanking sequences of the expression constructs were derived from either the hGH gene (pBCN1GH) or the rat beta-casein gene (pBCN2GH). Transgenic lines bearing pBCN1GH expressed hGH more efficiently than those bearing pBCN2GH in the milk (19-5500 micrograms/mL vs 0.7-2 micrograms/mL). In particular, one of the BCN1GH lines expressed hGH as much as 5500 +/- 620 micrograms/mL. Northern blot analysis showed that the transgene expression was specifically confined to the mammary gland and developmentally regulated like the endogenous mouse beta-casein gene in the mammary gland. However, a low level of nonmammary expression was also detected with more sensitive assay methods. In conclusion, the rat beta-casein/hGH fusion gene could direct an efficient production of hGH in a highly tissue-and stage-specific manner in the transgenic mice and the 3' flanking sequences of hGH gene had an important role for the efficient expression.

Long-term outcome after surgery for asymptomatic small hepatocellular carcinoma

The subjects of this study were 48 asymptomatic patients who had surgery for small hepatocellar carcinoma (HCC). There were 42 men and six women with mean (s.d.) tumour size of 3.31 (1.46) cm and age 55.0 (7.4) years. Follow-up was for a minimum of 10 years. The main concern of this study was a univariate analysis of factors that might affect long-term survival after surgery, which was 50 per cent at 5 years and 31 per cent at 10 years. A high incidence of recurrent HCC (37 of 48 patients) was observed but reoperation further prolonged life in some cases. The significant prognostic factors detected by multivariate analysis were: histological classification, functional liver reserve and histology of the resection margin. Tumour size, gross appearance of tumour, presence of liver cirrhosis, serum alpha-fetoprotein level, age or sex did not affect the prognosis.

Cavitation dynamics of medtronic hall mechanical heart valve prosthesis: fluid squeezing effect

The cause of cavitation in mechanical heart valves is investigated with Medtronic Hall tilting disk valves in an in vitro flow system simulating the closing event in the mitral position. Recordings of pressure wave forms and photographs in the vicinity of the inflow surface of the valve are attempted under controlled transvalvular loading rates averaged during valve closing period. The results revealed presence of a local flow field with a very high velocity around the seat stop of mechanical heart valves that could induce pressure reduction below liquid vapor pressure and a cloud of cavitation bubbles. The analysis of the results indicates that the "fluid squeezing" between the stop and occluder as the main cause of cavitation in Medtronic Hall valves. The threshold loading rate for cavitation initiation around the stop was found to be very low (300 and 400 mmHg/s; half the predicted normal human loading rate that was estimated to be 750 mmHg/s) because even a mild impact created a high speed local flow field on the occluder surface that could induce pressure reduction below vapor pressure. The present study suggests that mechanical heart valves with stops at the edge of major orifice region are more vulnerable to cavitation, and hence, have higher potential for damage on valve components and formed elements in blood.

Spermine binding to GC-rich DNA: experimental and theoretical studies

The DNA binding of spermine has been studied using experimental and computational approaches. Spermine blocks 5'-GC interstrand crosslinking by 2,5-diaziridinylbenzoquinone in the oligonucleotide duplex 5'-CTTCCAAGATGCATCAGATG 5'-CATCTGATGCATCTTGGAAG (where the underlined nucleotide bases represent the crosslinking site). Molecular dynamics simulations suggest that this is a result of preferential spermine binding at the 5'-GC major groove site of the oligonucleotide. A further simulation with a GC-alternating sequence shows a similar preference for the 5'-GC step. In a simulation including multiple spermine molecules, occupation of alternate 5'-GC steps occurred. From this, we deduced a mechanism for the experimentally observed cooperativity of spermine binding to poly(dGdC)2.