Antitumor activity of four macrocyclic ellagitannins from Cuphea hyssopifolia

We evaluated the antitumor activities of four macrocyclic hydrolyzable tannin dimers, cuphiin D1, cuphiin D2, oenothein B and woodfordin C isolated from Cuphea hyssopifolia (Lythraceae). All significantly inhibited the growth of the human carcinoma cell lines KB, HeLa, DU-145, Hep 3B, and the leukemia cell line HL-60, and showed less cytotoxicity than adriamycin against a normal cell line (WISH). All four compounds inhibited the viability of S-180 tumor cells in an in vitro assay and an in vivo S-180 tumor-bearing ICR mice model. Oenothein B demonstrated the greatest cytotoxicity (IC50 = 11.4 microg/ml) against S-180 tumor cells in culture, while cuphiin D1 resulted in the greatest increase in survival on S-180 tumor-bearing mice (%ILS = 84.1%). Our findings suggest that the antitumor effects of these compounds are not only related to their cytotoxicity on carcinoma cell lines, but also depended on a host-mediated mechanism; they may therefore have potential for antitumor applications.

Prevalence of antimicrobial resistance among clinical isolates of Haemophilus influenzae in Taiwan

The purpose of this study was to determine the prevalence of resistance to various antimicrobial drugs among Haemophilus influenzae isolates in Taiwan. Two hundred and ninety-six clinical isolates of H. influenzae were prospectively obtained from nine teaching hospitals throughout Taiwan, from June 1994 to April 1995. All isolates were examined for the presence of type b encapsulation and beta-lactamase production. Antibiotic susceptibility was determined by means of standard broth microdilution procedures. Twenty-three isolates (7.8%) were type b, and the overall rate of beta-lactamase production was 58.1% (172/296). The rates of resistance to antibiotics were 58.1% for ampicillin, 33.8% for trimethoprim-sulfamethoxazole, 20.6% for chloramphenicol, 27% for tetracycline, 6.7% for azithromycin, 3.4% for cefaclor, and 0.3% for cefuroxime. Cefixime, ceftriaxone, and ciprofloxacin were active against all H. influenzae isolates. Thirty (10.1%) of the 296 isolates were resistant to three drugs (ampicillin, chloramphenicol, and tetracycline), 16 of which (5.4%) were resistant to four drugs (ampicillin, chloramphenicol, tetracycline, and trimethoprim-sulfamethoxazole). There was a marked increase in the rates of ampicillin resistance and beta-lactamase production among H. influenzae isolates compared with a previous survey in Taiwan conducted 9 years ago. In addition, isolates with multiple drug resistance were also identified. Continued efforts are needed to monitor antibiotic resistance patterns of H. influenzae in the region.

Risk of HIV infection in oral contraceptive pill users: a meta-analysis

OBJECTIVE

To review the literature and present a summary estimate of the association between HIV-1 acquisition or HIV-1 serostatus and oral contraceptives.

DATA SOURCES

MEDLINE database (January 1986-October 1997), AIDSLINE database (January 1980-October 1997), bibliographies of identified articles, and experts in the field of heterosexual HIV transmission.

STUDY SELECTION

In all, 591 articles were examined. Twenty-eight studies provided adequate data to calculate a risk estimate for the association of HIV-1 serostatus or HIV-1 seroconversion with oral contraceptives and were selected for inclusion.

RESULTS

The overall summary odds ratio (OR) for the association between seroprevalent or seroincident HIV-1 infection and use of oral contraceptives in the 28 studies was 1.19 (95% confidence interval [CI], 0.99-1.42). The summary OR for 21 cross-sectional studies was 1.21 (95% CI, 1.01-1.44), whereas the summary relative risk for seven prospective studies was 1.32 (95% CI, 1.12-1.57). Study quality was assessed by applying a scale reflecting study design, measurement of exposure, ability to assess confounding, and publication status. The summary OR for the eight best studies was 1.60 (95% CI, 1.05-2.44). When analysis was limited to studies conducted in Africa, the summary OR was 1.45 (95% CI, 1.15-1.83) for the 14 studies overall, and 1.65 (95% CI, 1.09-2.52) for the seven best studies.

CONCLUSION

This meta-analysis found a significant association between oral contraceptive use and HIV-1 seroprevalence or seroincidence. For women at risk of HIV-1 infection, oral contraceptive use for prevention of pregnancy should be accompanied by condom use for prevention of HIV-1 infection.

5-Hydroxytryptamine-induced phosphoinositide hydrolysis and Ca2+ mobilisation in canine cultured aorta smooth muscle cells

The effect of 5-hydroxytryptamine (5-HT) on phospholipase C (PLC)-mediated phosphoinositide (PI) hydrolysis and intracellular Ca2+ ([Ca2+]i) changes was investigated in canine cultured aorta smooth muscle cells (ASMCs). 5-HT-stimulated inositol phosphate (IP) accumulation was time and concentration dependent with a half-maximal response (pEC50) and a maximal response at 6.4 and 10 microM, n = 6, respectively. Stimulation of ASMCs by 5-HT produced an initial transient peak followed by a sustained, concentration-dependent elevation in [Ca+]i. The half-maximal response (pEC50) values of 5-HT for the peak and sustained plateau were 7.1 and 6.9, respectively. Ketanserin and mianserin (1 and 3 nM), 5-HT2A antagonists, were equipotent and had high affinity in antagonising the 5-HT-induced IP accumulation and [Ca2+]i change with pK(B) values of 8.6-9.1 and 8.6-9.4, respectively. In contrast, the concentration-effect curves of 5-HT-induced IP and [Ca2+]i responses were not shifted until the concentrations of NAN-190 and metoctopramide (5-HT1A and 5-HT3 receptor antagonists, respectively) were increased to as high as 1 microM with pK(B) values of 5.7-6.3 and 6.1-6.6, respectively, indicating that the 5-HT receptor-mediated responses had low affinity for these antagonists. Pre-treatment of ASMCs with pertussis toxin (100 ng/mL, 24 h) caused a significant inhibition of 5-HT-induced IP accumulation and [Ca2+]i change in ASMCs. Depletion of external Ca2+ or removal of Ca2+ by addition of EGTA led to a significant attenuation of IP accumulation and [Ca2+]i change induced by 5-HT. Influx of external Ca2+ was required for the 5-HT-induced responses, because Ca2+-channel blockers--verapamil, nifedipine and Ni2+--partly inhibited the 5-HT-induced IP accumulation and Ca2+ mobilisation. The sustained elevation of [Ca2+]i response to 5-HT was dependent on the presence of external Ca2+. Removal of external Ca2+ by addition of 5 mM EGTA during the sustained phase caused a rapid decline in [Ca2+]i to lower than the resting level. The sustained elevation of [Ca2+]i could then be evoked by addition of 1.8 mM Ca2+ in the continued presence of 5-HT. These results demonstrate that 5-HT directly stimulates PLC-mediated PI hydrolysis and Ca2+ mobilisation, at least in part, through a pertussis toxin-sensitive G protein in canine ASMCs. 5-HT2A receptors may be predominantly mediating IP accumulation, and subsequently IP-induced Ca2+ mobilisation may function as the transducing mechanism for 5-HT-stimulated contraction of aorta smooth muscle.

"Half of the sites" binding of D-glyceraldehyde-3-phosphate dehydrogenase folding intermediate with GroEL

Two D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) folding intermediate subunits bind with chaperonin 60 (GroEL) to form a stable complex, which can no longer bind with additional GAPDH intermediate subunits, but does bind with one more lysozyme folding intermediate or one chaperonin 10 (GroES) molecule, suggesting that the two GAPDH subunits bind at one end of the GroEL molecule displaying a "half of the sites" binding profile. For lysozyme, GroEL binds with either one or two folding intermediates to form a stable 1:1 or 1:2 complex with one substrate on each end of the GroEL double ring for the latter. The 1:1 complex of GroEL.GroES binds with one lysozyme or one dimeric GAPDH folding intermediate to form a stable ternary complex. Both complexes of GroEL.lysozyme1 and GroEL.GAPDH2 bind with one GroES molecule only at the other end of the GroEL molecule forming a trans ternary complex. According to the stoichiometry of GroEL binding with the GAPDH folding intermediate and the formation of ternary complexes containing GroEL.GAPDH2, it is suggested that the folding intermediate of GAPDH binds, very likely in the dimeric form, with GroEL at one end only.

Bacteroides fragilis toxin 2 damages human colonic mucosa in vitro

BACKGROUND

Strains of Bacteroides fragilis producing a 20 kDa protein toxin (B fragilis toxin (BFT) or fragilysin) are associated with diarrhoea in animals and humans. Although in vitro results indicate that BFT damages intestinal epithelial cells in culture, the effects of BFT on native human colon are not known.

AIMS

To examine the electrophysiological and morphological effects of purified BFT-2 on human colonic mucosa in vitro.

METHODS

For resistance (R) measurements, colonic mucosa mounted in Ussing chambers was exposed to luminal or serosal BFT-2 (1.25-10 nM) and after four hours morphological damage was measured on haematoxylin and eosin stained sections using morphometry. F actin distribution was assessed using confocal microscopy.

RESULTS

Serosal BFT-2 for four hours was four-, two-, seven-, and threefold more potent than luminal BFT-2 in decreasing resistance, increasing epithelial 3H-mannitol permeability, and damaging crypt and surface colonocytes, respectively (p<0.05). Confocal microscopy showed reduced colonocyte F actin staining intensity after exposure to BFT-2.

CONCLUSIONS

BFT-2 increases human colonic permeability and damages human colonic epithelial cells in vitro. These effects may be important in the development of diarrhoea and intestinal inflammation caused by B fragilis in vivo.

Efficacy of media enriched with nonlactate-generating substrate for organ preservation: in vitro and clinical studies using the cornea model

BACKGROUND

Using a rabbit cornea model, our recent study demonstrated that Chen Medium (CM), an isotonic media enriched with nonlactate-generating high-energy substrates, is very effective for organ preservation. In the present study, the efficacy of CM is further evaluated with human corneas

METHODS

The effectiveness of CM and Optisol for preserving the endothelial integrity of human corneas in vitro was evaluated by scanning electron microscopy. Clinical efficacy was evaluated in a total of 83 patients: 10 patients with keratoconus grafted randomly with either CM- or Optisol-stored cornea of the same donor, and 73 patients with various conditions grafted with CM-stored corneas. After surgery, visual acuity and quality of the graft were monitored for up to 4.6 years.

RESULTS

The scanning electron microscopic study revealed that after 11-day storage at 4 degrees C, the CM-stored cornea had only marginal disruptive changes, 9.4+/-1.1%, in endothelial cells, as opposed to 42.4+/-4.6% of the Optisol-stored cornea. All 78 CM-stored corneas, including 67 with 12.2- to 17.7-hr death-to-storage time, 3-7.6 days of storage time, and initial marginal quality before storage, were successfully transplanted. These grafts were thin and clear, with an excellent epithelial integrity and without significant changes in endothelial cell density. Five Optisol-stored corneas were also successfully grafted; one of them, however, was edematous for about 4 weeks, and all the grafts were slightly thicker with substantial endothelial cell loss.

CONCLUSION

Using a cornea model, present and recent studies show that CM is very effective for preserving tissue viability and endothelial integrity. Previous study revealed that CM-stored tissues maintained high levels of ATP and metabolic function, with suppression of lactate formation and accumulation. Thus, these findings support the concept that preservation of tissue viability is closely associated with the ability of the tissues to retain metabolic activity, to generate ATP efficiently, and to prevent acidosis effectively during storage.

Neurotensin is a proinflammatory neuropeptide in colonic inflammation

The neuropeptide neurotensin mediates several intestinal functions, including chloride secretion, motility, and cellular growth. However, whether this peptide participates in intestinal inflammation is not known. Toxin A, an enterotoxin from Clostridium difficile, mediates pseudomembranous colitis in humans. In animal models, toxin A causes an acute inflammatory response characterized by activation of sensory neurons and intestinal nerves and immune cells of the lamina propria. Here we show that neurotensin and its receptor are elevated in the rat colonic mucosa following toxin A administration. Pretreatment of rats with the neurotensin receptor antagonist SR-48, 692 inhibits toxin A-induced changes in colonic secretion, mucosal permeability, and histologic damage. Exposure of colonic explants to toxin A or neurotensin causes mast cell degranulation, which is inhibited by SR-48,692. Because substance P was previously shown to mediate mast cell activation, we examined whether substance P is involved in neurotensin-induced mast cell degranulation. Our results show that neurotensin-induced mast cell degranulation in colonic explants is inhibited by the substance P (neurokinin-1) receptor antagonist CP-96,345, indicating that colonic mast activation in response to neurotensin involves release of substance P. We conclude that neurotensin plays a key role in the pathogenesis of C. difficile-induced colonic inflammation and mast cell activation.

Photovoice: a participatory action research strategy applied to women's health

Photovoice is a participatory action research strategy that may offer unique contributions to women's health. It is a process by which people can identify, represent, and enhance their community through a specific photographic technique. Photovoice has three main goals: to enable people (1) to record and reflect their community's strengths and concerns, (2) to promote critical dialogue and knowledge about personal and community issues through large and small group discussion of their photographs, and (3) to reach policymakers. This report gives an overview of the origins, key concepts, methods, and uses of photovoice as a strategy to enhance women's health.

MRI characteristics of midbrain tumours

We diagnosed 60 cases of midbrain tumours by MRI between 1993 to 1997. There were 39 males and 21 females, aged 2-64 years, mean 25.6 years. We found 38 patients with true intramedullary mid-brain tumours, 11 predominantly in the tectum, 20 in the tegmentum and 7 with a downward extension to the pons; there were 7 within the cerebral aqueduct. There were 22 patients with infiltrating midbrain tumours extending from adjacent structures, 11 cases each from the thalamus and pineal region. All patients received surgical treatment. Gross total resection was achieved in 42 cases, subtotal (> 75 %) resection in 18. Pathological diagnoses included 16 low-grade and 15 high-grade astrocytomas; 5 oligodendroastrocytomas; 2 ependymomas; 11 glioblastomas; and 11 pineal parenchymal or germ-cell tumours. Midbrain tumours are a heterogeneous group of neoplasms, with wide variation in clinical and MRI features, related to the site and type of tumour. MRI not only allows precise analysis of their growth pattern, but also can lead to a correct preoperative diagnosis in the majority of cases.

Effects of losartan on the sexual behavior of male rats

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.

Effects of dexamethasone on antigen expressions and proliferation of amoeboid microglial cells in fetal rat brain

The present study examined the effect of maternal administration of dexamethasone (DEX) on amoeboid microglial cells (AMC) in fetal rats extending from 16 to 20 days postconception (E16 to E20). After an intraperitoneal injection of DEX into pregnant rats at E10, the external morphology and distribution of immunolabelled AMC as detected with OX-42 and ED1 monoclonal antibodies remained unaltered when compared with those of the controls. The major effect of dexamethasone was on microglial cell population. Thus, with OX-42 and ED1, the numbers of immunolabelled AMC in the intermediate zone lateral to the striatum (IZS) of DEX-treated fetuses which remained relatively unchanged at E16 were significantly reduced at E18. However, OX-42 labelled cells showed an unexpected increase in number at E20 following DEX treatment. Microglial response to DEX was also analyzed in sections stained with the isolectin, GSA I-B4, which specifically binds alpha-D-galactosyl glycoproteins on microglia. The number of GSA I-B4 labelled AMC was significantly increased at E16, declined at E18 and remained constant thereafter in DEX-treated rats when compared with that of the controls. A major finding after DEX treatment was the wider occurrence of AMC double labelled with anti-BrdU antibody and GSA I-B4 or OX-42 at E16 compared with those in the controls suggesting that the initial increase of GSA I-B4 labelled AMC may be attributed to their proliferation. The drastic reduction of OX-42 and ED1 positive microglial cells notably at E18 may be due to the downregulation of surface antigens as a result of possible suppressive action of dexamethasone. On the basis of present findings, it is concluded that the antigenic expressions of fetal AMC may be modulated by DEX administrated maternally. Such however appeared to be extremely selective as reflected by the varied expression for certain immune molecules at different stages of brain development. This information would be useful in potential use of glucocorticoids in prenatal therapy of brain pathology via maternal circulation.

Variation of P-QRS relation during atrioventricular node reentry tachycardia

OBJECTIVES

The main objective of this study was to characterize the phenomenon of variation in the P-QRS relation during atrioventricular node reentry tachycardia.

BACKGROUND

Variation of P-QRS relation during tachycardia has been observed occasionally in atrioventricular node reentry tachycardia. However, the incidence, the characteristics and the mechanisms of this phenomenon have not been investigated previously.

METHODS

Retrospective analysis was performed in 311 consecutive patients with slow-fast form and 108 patients with atypical or multiple form of atrioventricular node reentry tachycardia to examine whether variation of P-QRS relation with changes in AH, HA and AH/HA (A = atria; H = His bundle) ratio occurred during tachycardia.

RESULTS

A total of 28 patients, 8 with slow-fast and 20 with atypical or multiple tachycardias, were found to manifest this phenomenon. There were 6 males and 22 females, with an average age of 38+/-16 years. In 10 patients, this phenomenon occurred transiently following electrical induction of the tachycardia. In 15 patients, changes in AH, HA and AH/HA ratio were associated with the occurrence of Wenckebach or 2:1 block proximal to the His bundle (H) recording site without interruption of the tachycardia. In nine patients, three with nonsustained tachycardia and six after administration of adenosine triphosphate, this phenomenon was observed at the termination of the tachycardia. This phenomenon was usually accompanied by a mild lengthening of the tachycardia cycle length.

CONCLUSIONS

Variation of P-QRS relation with or without block may occur during atrioventricular node reentry tachycardia, especially in atypical or multiple-form tachycardias. It was postulated that decremental conduction in the distal common pathway, which exists between the distal link of the reentry circuit and the H, is primarily responsible for this phenomenon.

A Trypanosoma brucei bloodstream form mutant deficient in ornithine decarboxylase can protect against wild-type infection in mice

A Trypanosoma brucei bloodstream mutant in which both copies of the ornithine decarboxylase (ODC) gene were knocked out (ODC mutant) was used to determine the biological functions of ODC in T. brucei. Growth of the mutant cells ceased within 12-24 h in regular culture medium deficient in polyamines, but could be rescued by supplementation with 1 mM putrescine. A mouse model of T. brucei infection was used to determine whether the mutant was still infective and was found to develop either extremely low or undetectable levels of parasitemia, suggesting that in T. brucei, ODC activity is essential for establishing an infection. Furthermore, when these mice were subsequently challenged with wild-type T. brucei cells expressing the same variant surface glycoprotein (VSG), they did not develop any parasitemia, indicating that inoculating the mice with the attenuated ODC mutant had conferred protection against challenge by wild-type cells. These results were reproduced in C57BL/6J mice deficient in alpha-beta and gamma-delta T-cell receptors. However, no protection was observed in rag-2 knockout mice deficient in both B and T lymphocytes or in C57BL/10J mice deficient only in B lymphocytes. The results thus suggest that the ODC mutant could induce a T-lymphocyte-independent but B-lymphocyte-dependent immunity against wild-type cells of the same VSG. Such a mechanism of immunity has been elicited only by live T. brucei cells, but not by isolated VSGs or radiation-killed trypanosomes. This ODC mutant may thus represent a genuinely attenuated T. brucei bloodstream form capable of immunizing mammals against infections by African trypanosomes of the same VSG subtype without causing detectable infection by itself. The observation also raises the interesting likelihood that the in vivo treatment of T. brucei bloodstream forms with alpha-DL-difluoromethylornithine is a de facto attenuation of the parasitic organisms, which may very well result in B-lymphocyte-dependent host immune responses to subsequent infections by parasites of the same VSG subtypes.

Fetal and maternal levels of lipid peroxides in term pregnancies

OBJECTIVE

To examine the relationships between maternal and fetal concentrations of lipid peroxides in term pregnancies before the onset of labor.

METHODS

Umbilical cord arterial and venous blood samples were collected from 114 singleton term pregnancies delivered by elective cesarean section. Base excess, oxygen, carbon dioxide and pH were measured in both samples and compared to identify double venous samples. Maternal venous and umbilical cord arterial and venous concentrations of organic hydroperoxides and malondialdehyde were assayed.

RESULTS

Maternal plasma malondialdehyde was, on average, double that of cord blood, whereas maternal organic hydroperoxide was only 18% higher. Maternal organic hydroperoxide was correlated with cord arterial and venous levels of organic hydroperoxide but not with pH, carbon dioxide, oxygen or base excess. Maternal malondialdehyde concentration was significantly correlated with both umbilical arterial and venous values of malondialdehyde and with arterial oxygen. Multiple regression shows that 70% of the variation in maternal malondialdehyde can be accounted for by variation in arterial and venous malondialdehyde, and arterial oxygen and base excess. A similar regression analysis with maternal organic hydroperoxide as dependant variable incorporated only umbilical arterial organic hydroperoxide concentration.

CONCLUSION

These findings suggest that there is significant trans-placental transport of malondialdehyde from the fetal circulation.

The effectiveness of single and multiple applications of triple dye on umbilical cord separation time

The effectiveness of single and multiple applications of triple dye for umbilical cord care in the umbilical cord separation time (UCST) was evaluated in 180 neonates. Seven neonates were excluded, three where the cord stump separation time was uncertain and four to whom contact was lost. The participating neonates were randomly assigned to two groups. Group 1, 101 neonates, were treated with a regimen of a single application of triple dye. Group 2, 79 neonates, were treated with multiple applications of triple dye. Complete information was obtained from 97 neonates (96.2%) in group 1 and 76 (96%) in group 2. The UCST was 12.6 +/- 0.45 (mean +/- SE) days in group 1 and 16.68 +/- 0.65 days in group 2 (P < 0.0001) and showed no significant association with infants' gender, mode of delivery, gravidity, gestational age, birth weight, or hospital stay.

CONCLUSION

A single application of triple dye may be a more favourable regimen with a similarly antimicrobial effect, a shorter UCST and may be more cost effective than multiple applications of triple dye in umbilical cord care.

Preparation of Palladium Ultrafine Particles in Reverse Micelles

The preparation of palladium ultrafine particles by the reduction of Pd(NH3)4Cl2 with hydrazine in AOT/isooctane reverse micellar solutions has been studied. By the analyses of high-resolution electron microscope, electron diffraction pattern, and XRD, the resultant particles have been found to be pure fcc palladium. Their sizes were observed to increase first and then approach constant values with increases in the molar ratio of water to AOT (omega0) and in the concentration of Pd(NH3)4Cl2, but were not significantly affected when the concentration ratio of hydrazine to Pd(NH3)4Cl2 was above 10, the AOT concentration increased from 0.1 to 1.0 M, the temperature varied from 15 to 35 degreesC, and the pH of aqueous phase of Pd(NH3)4Cl2 was between 7 and 12. In addition, the kinetic study of particle formation indicated that the nucleation time needed several minutes. After nucleation, the particles grew to their final sizes within several to tens of minutes. The formation rates were found to be faster at larger omega0 values and higher AOT and Pd(NH3)4Cl2 concentrations. Copyright 1999 Academic Press.

The extracellular matrix, interstitial fluid and ions as a mechanical signal transducer in articular cartilage

OBJECTIVE

(1) Provide an overview of the biomechanical factors that are required to analyze and interpret biological data from explant experiments; (2) Present a description of some of the mechano-electrochemical events which occur in cartilage explants during loading.

DESIGN

A thorough and provocative discussion on the effects of loading on articular cartilage will be presented. Five simplest loading cases are considered: hydrostatic pressure, osmotic pressure, permeation (pressure loading), confined compression and unconfined compression. Details of how such surface loadings are converted or transduced by the extracellular matrix (ECM) to pressure, fluid, solute and ion flows, deformation and electrical fields are discussed.

RESULTS

Similarities and differences in these quantities for the five types of loading are specifically noted. For example, it is noted that there is no practical mechanical loading condition that can be achieved in the laboratory to produce effects that are equal to the effects of osmotic pressure loading within the ECM. Some counter-intuitive effects from these loadings are also described. Further, the significance of flow-induced compression of the ECM is emphasized, since this frictional drag effect is likely to be one of the major effects of fluid flow through the porous-permeable ECM. Streaming potentials arising from the flow of ions past the fixed charges of the ECM are discussed in relation to the flow-induced compaction effect as well.

CONCLUSION

Understanding the differences among these explant loading cases is important; it will help to provide greater insights to the mechano-electrochemical events which mediate metabolic responses of chondrocytes in explant loading experiments.

Liver abscess secondary to fish bone penetration of the gastric wall: a case report

An unusual case of liver abscess caused by fish bone perforation of the stomach is presented in this report. A 65-year-old woman was admitted to the Far Eastern Memorial Hospital for abdominal pain, fever and chills. Physical examination revealed anemia and tenderness in the epigastrium. Laboratory data showed leukocytosis and abnormal liver function. Computerized tomography of the abdomen disclosed a huge abscess in the left lobe of the liver. Exploratory laparotomy was performed and a fish bone, 3.7 cm in length, was found perforating the stomach with penetration into the left lobe of the liver, resulting in a hepatic abscess. Drainage of the liver abscess with removal of the fish bone and simple closure of the gastric perforation were performed. The patient recovered uneventfully.

Protein disulfide isomerase assists protein folding as both an isomerase and a chaperone

Protein disulfide isomerase (PDI) is the physiological catalyst of native disulfide bond formation of nascent peptides in the cells. As a foldase, PDI has both isomerase and chaperone activities. The chaperone activity is intrinsic and independent of its isomerase activity. Both chaperone and isomerase activities are required for PDI to assist folding of denatured and reduced disulfide-containing proteins. PDI may have great applications in protein production by bioengineering for its function as a foldase.

Altering the purine specificity of hypoxanthine-guanine-xanthine phosphoribosyltransferase from Tritrichomonas foetus by structure-based point mutations in the enzyme protein

The hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRTase) from Tritrichomonas foetus has been proven to be a target for potential anti-tritrichomonial chemotherapy. Using a structure-based approach, the base-binding region of the active site of this enzyme, which confers unique purine base specificity, was characterized using site-directed mutagenesis. Determining the roles of different active-site residues in purine specificity would form the basis for designing specific inhibitors toward the parasitic enzyme. A D163N mutant converts the HGXPRTase into a HGPRTase, which no longer recognizes xanthine as a substrate, whereas specificities toward guanine and hypoxanthine are unaffected. Apparently, the side-chain carboxyl of Asp163 forms a hydrogen bond through a water molecule with the C2-carbonyl of xanthine, which constitutes the critical force enabling the enzyme to recognize xanthine as a substrate. Mutations of Arg155, which orients and stacks the neighboring Tyr156 onto the bound purine base by forming a salt bridge between itself and Glu11, result in drastic increases in the Kms for GMP and XMP (but not IMP). This change leads to increased kcats for the forward reactions with guanine and xanthine as substrates without affecting the conversion of hypoxanthine to IMP. Thus, the apparent dislocation of Tyr156, resulted from mutations of Arg155, bring little effect on the hydrophobic interactions between Tyr156 and the purine ring. But the forces involved in recognizing the exocyclic C2-substituents of the purine ring, which involve the Tyr156 hydroxyl, Ile157 backbone carbonyl, and Asp163 side-chain carboxyl, may be weakened by the shifted conformation of the peptide backbone resulted from loss of the Glu11-Arg155 salt bridge. The conserved Lys134 was proven to be the primary determinant in conferring the specificity of the enzyme toward 6-oxopurines. By substituting the lysine residue for a serine, which can potentially hydrogen bond to either an amino or an oxo-group, we have successfully augmented the purine specificity of the enzyme. The K134S mutant recognizes adenine in addition to hypoxanthine, guanine, and xanthine as its substrates. Adenine and hypoxanthine are equivalent substrates for the mutant enzyme with similar Kms of 34.6 and 38.0 microM, respectively. The catalysis of an adenine phosphoribosyltransferase reaction by this mutant enzyme was further demonstrated by the competitive inhibition of AMP with an estimated Kis of 25.4 microM against alpha-D-5-phosphoribosyl-pyrophosphate (PRPP) in converting hypoxanthine to IMP. We have thus succeeded in using site-directed mutagenesis to convert T. foetusHGXPRTase into either a HGPRTase or a genuine AHGXPRTase.

Ocular neovascularization: an epidemiologic review

Neovascularization occurs in many eye diseases, and its epidemiologic impact is significant. However, data on the prevalence and incidence of ocular neovascularization have never been compiled to demonstrate its pervasiveness. This overview of ocular angiogenesis provides a review of the epidemiologic literature for neovascularization in various parts of the eye, including the cornea, iris, retina, and choroid. Relevant disease states are reviewed, as are their risk factors, so that their pathogenesis can be better understood. Data on the prevalence and incidence of the major diseases involving angiogenesis are synthesized to provide statistical evidence of the span and magnitude of ocular neovascularization. These prevalence and incidence data on ocular neovascularization are extrapolated to USA population data where possible, and "worst-case" estimates are calculated as well. Information was gathered with a search of the MEDLINE database, published monographs and volumes, and consultation with a number of primary authors. This study attempts to unify much of past and present epidemiologic research, and the information is presented in sections divided according to the anatomy of the eye.