Identification of the epsilon-subunit of Escherichia coli DNA polymerase III holoenzyme as the dnaQ gene product: a fidelity subunit for DNA replication

Based on extensive genetic and biochemical studies, the multisubunit DNA polymerase III holoenzyme is considered responsible for the chain-elongation stage in replication of the genome of Escherichia coli and is thus expected to be the major determinant of fidelity as well. Previous experiments have shown that two mutations conferring a very high mutation rate on E. coli, mutD5 and dnaQ49, decrease severely the 3' leads to 5' exonucleolytic editing activity of the polymerase III holoenzyme. To identify more precisely the nature of these mutations, we have carried out genetic mapping and complementation experiments. From these studies and experiments by others, we conclude that the most potent general mutator mutations in E. coli occur in a single gene, dnaQ. To define further the role of the dnaQ gene, we have used two-dimensional gel electrophoresis to compare the labeled dnaQ gene product with purified polymerase III holoenzyme. The dnaQ product comigrates with the epsilon-subunit, a 25-kilodalton protein of the polymerase III "core" enzyme. We conclude that the epsilon-subunit of polymerase III holoenzyme has a special role in defining the accuracy of DNA replication, probably through control of the 3' leads to 5' exonuclease activity.

Transoral robotic surgery vs. radiotherapy for management of oropharyngeal squamous cell carcinoma - A systematic review of the literature

BACKGROUND

Intensity-modulated radiation therapy (IMRT) with or without concurrent chemotherapy is widely utilized for the treatment of oropharyngeal squamous cell carcinoma (OPSCC). However, due to significant acute and late toxicities there has been increasing interest in minimally invasive surgical approaches, particularly transoral robotic surgery (TORS) in an attempt to preserve patient quality of life while maintaining oncologic outcomes. The aim of this study was to review the current literature in order to compare primary IMRT versus TORS in the management of OPSCC.

METHODS

A MEDLINE search was conducted to identify studies reporting on the outcomes of TORS or IMRT in the treatment of OPSCC. Reference lists were also reviewed for relevant articles. Oncologic, functional, and quality of life data is summarized and discussed.

RESULTS

One hundred-ninety papers were identified through the MEDLINE search. An additional 52 papers were retrieved by hand searching the reference lists. Ultimately, 44 papers were identified that discussed outcomes after IMRT or TORS for OPSCC. No outcomes from randomized trials were identified.

CONCLUSION

No randomized trials comparing TORS versus IMRT to each other were identified. Uncontrolled reports from the current literature suggest comparable oncologic outcomes with TORS compared to IMRT and functional outcomes may be superior. However, the median follow-up was relatively short and the TORS studies included patients with earlier stage OPSCC on average compared to IMRT studies. Prospective, randomized controlled trials and direct, well-matched comparisons are needed to further elucidate the role for TORS in the treatment of oropharyngeal squamous cell carcinoma.

A randomised controlled trial of nasal continuous positive airway pressure on insulin sensitivity in obstructive sleep apnoea

The effects of treatment of obstructive sleep apnoea (OSA) on glucose metabolism have been investigated previously with conflicting results. This study evaluated the impact of nasal continuous positive airway pressure (nCPAP) treatment of OSA on insulin sensitivity. Males with moderate/severe OSA and no significant comorbidity were randomised to a therapeutic or sham nCPAP treatment group for 1 week and then reassessed. Those who received therapeutic nCPAP were further evaluated at 12 weeks. Insulin sensitivity (K(itt)) was estimated by the short insulin tolerance test. Other evaluations included blood pressure, metabolic profile, urinary catecholamines and intra-abdominal fat. In total, 61 Chinese subjects were randomised. 31 subjects receiving therapeutic nCPAP showed an increase in K(itt) (6.6+/-2.9 to 7.6+/-3.2 % x min(-1); p = 0.017), while the 30 patients on sham CPAP had no significant change, and the changes in K(itt) were different between the two groups (p = 0.022). At 12 weeks, improvement in K(itt) was seen in 20 subjects with BMI >or=25 kg x m(-2) (median (interquartile range) 28.3 (26.6-31.5); p = 0.044), but not in the nine subjects with BMI<25 kg x m(-2), or the entire group. The findings indicate that therapeutic nCPAP treatment of OSA for 1 week improved insulin sensitivity in nondiabetic males, and the improvement appeared to be maintained after 12 weeks of treatment in those with moderate obesity.

Soluble dextran-hemoglobin complex as a potential blood substitute

A complex between soluble dextran and human hemoglobin has been synthesized by two different methods. In the alkylation method, hemoglobin was allowed to react with bromoacetyl groups incorporated into the dextran; the yield of the complex was about 80% in terms of the hemoglobin used. In the dialdehyde method, hemoglobin was allowed to react with dialdehyde groups on the dextran generated by periodate oxidation; the yield of the complex was about 60%. Both soluble dextran-hemoglobin complexes could bind and release oxygen reversibly, but the oxygen-binding curves were shifted to the left relative to that of free hemoglobin. In the rabbit, the complex obtained by the alkylation method was excreted by the kidneys and cleared from the circulation much more slowly than free hemoglobin.

Site-directed PEGylation of trichosanthin retained its anti-HIV activity with reduced potency in vitro

Trichosanthin (TCS) was the first ribosome inactivating protein found to possess anti-HIV-1 activity. Phase I/II clinical trial of this compound had been done. Antigenicity and short plasma half-life were the major side effects preventing further clinical trial. Modification of TCS is therefore necessary to revive the interest to develop this compound as an anti-HIV agent. Three potential antigenic sites (Ser-7, Lys-173, and Gln-219) were identified by computer modeling. Through site-directed mutagenesis, these three antigenic amino acids were mutated to a cysteine residue resulting in 3 TCS mutants, namely S7C, K173C, and Q219C. These mutants were further coupled to polyethylene glycol with a molecular size of 20kDa (PEG) via the cysteine residue. This produced another three TCS derivatives, namely PEG20k-S7C, PEG20k-K173C, and PEG20k-Q219C. PEGylation had been widely used recently to decrease immunogenicity by masking the antigenic sites and prolong plasma half-life by expanding the molecular size. The in vitro anti-HIV-1 activity of these mutants and derivatives was tested. Results showed that the anti-HIV-1 activity of S7C, K173C, and Q219C was decreased by about 1.5- to 5.5-fold with slightly lower cytotoxicity. On the other hand, PEGylation produced larger decrease (20- to 30-fold) in anti-HIV activity. Cytotoxicity was, however, weakened only slightly by about 3-fold. The in vitro study showed that the anti-HIV activity of PEGylated TCS was retained with reduced potency. The in vivo activity is expected to have only slightly changed due to other beneficial effects like prolonged half-life.

Aldose reductase-deficient mice develop nephrogenic diabetes insipidus

Aldose reductase (ALR2) is thought to be involved in the pathogenesis of various diseases associated with diabetes mellitus, such as cataract, retinopathy, neuropathy, and nephropathy. However, its physiological functions are not well understood. We developed mice deficient in this enzyme and found that they had no apparent developmental or reproductive abnormality except that they drank and urinated significantly more than their wild-type littermates. These ALR2-deficient mice exhibited a partially defective urine-concentrating ability, having a phenotype resembling that of nephrogenic diabetes insipidus.

Research communication copper-1,10-phenanthroline induces internucleosomal DNA fragmentation in HepG2 cells, resulting from direct oxidation by the hydroxyl radical

In view of the current speculation regarding the possible role of reactive oxygen species (ROS) in apoptosis, both under physiological conditions and in response to chemicals that promote their intracellular formation, the present investigation was undertaken to examine whether DNA fragmentation during oxidative stress results from endonuclease activity (apoptosis) or from direct attack by ROS. We report that the incubation of HepG2 cells (a human-derived hepatoma cell line) with the copper(II) complex of 1,10-phenanthroline, CuII(OP)2, results in internucleosomal DNA fragmentation, which is widely recognized as being a hallmark of apoptosis. DNA fragmentation did not occur at low temperature, but activity was restored by the addition of ascorbic acid. It is proposed that DNA fragmentation results from the direct attack of hydroxyl radicals upon DNA. Hydroxyl radicals are produced from oxygen by the redox-cycling of CuII(OP)2, which is supported by metabolic processes at normal temperature. At low temperature ascorbic acid provides an artificial cellular reducing environment, thereby restoring hydroxyl radical formation. These findings were confirmed by the detection of internucleosomal DNA fragmentation following the exposure of isolated chromatin to a biomimetic CuII(OP)2 redox-cycling system. We conclude that DNA laddering, the widely employed hallmark of apoptosis, is not unique to endonuclease activity and may also result from direct attack upon DNA by the hydroxyl radical.

Reducing the immunogenicity and improving the in vivo activity of trichosanthin by site-directed pegylation

PEG modification (PEGylation) has been shown to reduce immunogenicity and prolong circulating half-life of proteins. In the present study, site-directed PEGylation was used to reduce immunogenicity and prolong plasma half-life of trichosanthin (TCS). Four TCS mutants, i.e. S7C, Q219C, K173C and [K173C,Q219C] (KQ), were constructed by site-directed mutagenesis. PEG modifications were done by reacting PEG5k-maleimide or PEG20k-maleimide reagent with the newly introduced cysteine residue of the mutants. The plasma clearance rate of PEGylated TCS mutants decreased up to 100-fold and the decrease was inversely proportional to the effective molecular size. The in vitro activities such as ribosome-inactivating activity and cytotoxicity were also decreased. However, the in vivo abortifacient activity was, slightly decreased, unchanged, or even enhanced in some preparations. PEG5k modification had little effect on immunogenicity. However, PEG20k modification significantly reduced immunogenicity. All PEG20k modified TCS mutants induced lower level IgG and IgE antibodies. In particular, PEG20k-KQ and PEG20k-K173C induced weaker systemic anaphylaxis reaction in guinea pigs. In conclusion, the present results suggest that PEG20k is better than PEG5k for reducing immunogenicity and prolonging plasma half-life. The conjugate can become a better therapeutic agent.

Traditional Chinese medicine causing hepatotoxicity in patients with chronic hepatitis B infection: a 1-year prospective study

BACKGROUND

Safety of traditional Chinese medicine in patients with chronic hepatitis B is unknown.

AIM

To study the clinical outcome of traditional Chinese medicine-induced hepatotoxicity in chronic hepatitis B patients.

PATIENTS AND METHODS

All chronic hepatitis B patients in 2004 with liver dysfunction requiring hospitalization were screened prospectively for traditional Chinese medicine intake. The hepatotoxicity of individual traditional Chinese medicine elements was determined by extensive search of both English and Chinese publications.

RESULTS

Of 45 chronic hepatitis B patients, the liver dysfunction in seven (15.6%) was attributable to traditional Chinese medicine. All had liver dysfunction pattern resembling those of acute exacerbation of chronic hepatitis B. Three patients had adverse outcomes (two deaths, one liver transplantation). One patient had accelerated course of cirrhosis now awaiting liver transplantation. The identified hepatotoxic components were Polygonum multiflorum Thunb, Cassia obtusifolia L, Melia toosendan Sieb., Rheum palmatum L., Scolopendra subspinipes mutilans L, Alisma orientale Juzepe, Glycyrrhiza uralensis Fisch. and Mentha haplocalyx Briq. One traditional Chinese medicine formula was adulterated with a highly hepatotoxic agent, N-nitrosofenfluramine.

CONCLUSIONS

Traditional Chinese medicine-related hepatotoxicity resulted in high mortality in chronic hepatitis B patients. Prospective randomized-controlled trials with the same stringent criteria as western medicine clinical trials are required for Chinese medicines, to document their efficacies and safety before they can be advocated for the treatment of patients.

The anti-HIV-1 effect of scutellarin

Scutellarin was purified from the plant Erigeron breviscapus (Vant.) Hand.-Mazz. The activity against 3 strains of human immunodeficiency virus (HIV) was determined in vitro in this study. These were laboratory-derived virus (HIV-1IIIB), drug-resistant virus (HIV-1(74V)), and low-passage clinical isolated virus (HIV-1(KM018)). From syncytia inhibition study, the EC50 of scutellarin against HIV-1IIIB direct infection in C8166 cells was 26 microM with a therapeutic index of 36. When the mode of infection changed from acute infection to cell-to-cell infection, this compound became even more potent and the EC50 reduced to 15 microM. This suggested that cell fusion might be affected by this compound. By comparing the inhibitory effects on p24 antigen, scutellarin was also found to be active against HIV-1(74V) (EC50 253 microM) and HIV-1KM018 (EC50 136 microM) infection with significant difference in potency. The mechanism of its action was also explored in this study. At a concentration of 433 microM, scutellarin inhibited 48% of the cell free recombinant HIV-1 RT activity. It also caused 82% inhibition of HIV-1 particle attachment and 45% inhibition of fusion at the concentrations of 54 microM. In summary, scutellarin was found to inhibit several strains of HIV-1 replication with different potencies. It appeared to inhibit HIV-1 RT activity, HIV-1 particle attachment and cell fusion. These are essential activities for viral transmission and replication.

Mixed tumors of the skin. A histological and immunohistochemical study

Sixty-four specimens of mixed tumors of the skin were studied by conventional microscopy. Sections from all 64 specimens were stained by hematoxylin and eosin, and sections from 18 of those specimens were stained by immunoperoxidase techniques for the presence of S-100 protein, carcino-embryonic antigen (CEA), keratin, actin, vimentin, epithelial membrane antigen (EMA), and gross cystic disease fluid protein-15 (GCDFP-15). Two distinctive histopathological patterns of mixed tumors of the skin became apparent, namely, apocrine and eccrine. Mixed tumors with apocrine features are by far the most common. Immunoperoxidase techniques, in our experience, do not enable differentiation between apocrine and eccrine types of mixed tumors.

Prevalence and Impact of Vitamin D Insufficiency in Southern Chinese Adults

INTRODUCTION

Vitamin D is a vital element for bone health but the problem of vitamin D deficiency is underestimated in Hong Kong.

METHODS

Serum 25(OH)D and parathyroid hormone (PTH) levels were evaluated in 382 community dwelling Chinese adults >50 years for their relation with bone mineral density (BMD) and risks of osteoporotic fractures and falls.

RESULTS

The mean age of the subjects was 69 +/- 9 years. The mean 25(OH)D level was 28.3 +/- 10.8 ng/ml with 62.8% of the subjects having levels <30 ng/ml. 6.3% of the subjects had elevated PTH levels. A curvilinear relation between serum PTH and 25(OH)D was found, with PTH starting to increase when 25(OH)D level fell below 30 ng/ml (r = -0.233, p < 0.05). Although subjects with vitamin D <30 ng/ml had significantly lower BMD, only sex, age and PTH but not 25(OH)D were predictors of BMD at the spine and hip. Subjects with elevated PTH levels had a 2.92-fold increased risk of falls and 2.94-fold increased risk of fractures at the hip and spine.

CONCLUSIONS

Vitamin D insufficiency and its complication of secondary hyperparathyroidism is common even in subtropical region and is an important risk factor for low bone mass, falls and fractures.

Trichosanthin interacts with and enters cells via LDL receptor family members

The type-I ribosome-inactivating protein trichosanthin displays selective cytotoxicity, suggesting specific mechanisms for entry into cells. Here we show that trichosanthin binds specifically to the endocytic receptors LRP and megalin, and that binding as well as uptake into cells is inhibited by the receptor-associated protein (RAP). The results suggest that the known abortifacient and renotoxic actions of trichosanthin are caused by LRP-mediated uptake in trophoblasts and megalin-mediated uptake in proximal tubule epithelial cells, respectively.

Fish-oil supplement has neutral effects on vascular and metabolic function but improves renal function in patients with Type 2 diabetes mellitus

AIMS

Increased dietary fish-oil consumption is associated with a reduced risk of coronary heart events and has pronounced effects on dyslipidaemia. However, the effects of fish-oil supplement on vascular function and metabolic profile in patients with Type 2 diabetes mellitus (DM) are unclear.

METHODS

In a double-blind placebo-controlled trial, we randomized 97 Type 2 DM patients without prior cardiovascular disease to fish-oil (4 g/day, n = 49) or olive-oil (with equivalent calories, as placebo, n = 48) supplements for 12 weeks. Assessment of vascular function with brachial artery flow-mediated dilation (FMD) and circulating levels of endothelial progenitor cells (EPCs), and metabolic parameters, high-sensitivity C-reactive protein (hsCRP), oxidative stress markers and renal function were examined before and after the supplement.

RESULTS

Despite a significant reduction in serum triglycerides (-0.47 mmol/l, P < 0.01), 12-week supplement of fish oil did not improve vascular function as determined by FMD (+0.16%, P = 0.83) and circulating EPC count (+4 cells/microl, P = 0.78). Furthermore, fish-oil supplement did not have any significant treatment effects on hsCRP, oxidative stress, low- and high-density lipoprotein and glycated haemoglobin (HbA(1c)) (all P > 0.05). In contrast, serum creatinine was lower (-4.5 micromol/l, P = 0.01) in fish-oil-treated patients as compared with control subjects.

CONCLUSIONS

This study demonstrated that 12 weeks of fish-oil supplement had no significant beneficial effect on vascular endothelial function, but improved renal function without changes in endothelial function, metabolic profiles, blood pressure, inflammation or oxidative stress in patients with Type 2 DM.

Burden of carotid atherosclerosis in patients with stroke: relationships with circulating endothelial progenitor cells and hypertension

Recent studies suggest that reductions in circulating endothelial progenitor cells (EPCs) may contribute to the development of atherosclerosis. However, whether reduced circulating EPCs contribute to cerebrovascular disease remains undefined. We tested the hypothesis that reduced circulating EPCs was associated with an increased burden of carotid atherosclerosis. The level of circulating CD34+/KDR+ EPCs and the extent of carotid atherosclerosis were determined in 30 patients with a history of atherothrombotic ischaemic stroke and 30 age- and sex-matched controls (mean age: 63+/-2 years; 63% men). Stroke patients, compared with controls, had significantly higher carotid mean maximum intima-media thickness (mmIMT) (1.08+/-0.05 versus 0.90+/-0.02 mm, P=0.002), prevalence of carotid plaque (60.0 versus 23.3%, P=0.004) and a lower number of circulating CD34+/KDR+ EPCs (235.7+/-45.5 versus 400.4+/-56.8 cells/mul, P=0.027). The circulating CD34+/KDR+ EPC count correlated negatively with carotid mmIMT (r=-0.50, P<0.001), and was an independent risk factor for increased carotid mmIMT>1 mm (odds ratio (OR): 7.71; 95% confidence interval (CI): 1.62-36.74, P=0.010) and the presence of carotid plaque (OR: 7.04; 95% CI: 1.95-25.43, P=0.003). Furthermore, stroke patients with low (<25th percentile of controls) as compared to those with normal CD34+/KDR+ EPC count had a significantly greater carotid mmIMT (1.21+/-0.07 versus 0.93+/-0.05 mm, P=0.005) and a significantly higher prevalence of carotid plaque (87.5% versus 28.6%; P=0.001). Our observations suggested that reduced circulating EPC may contribute to the progression of carotid atherosclerosis. Circulating EPC count may provide a novel marker for the burden of carotid atherosclerosis.

Iron supplement in pregnancy and development of gestational diabetes--a randomised placebo-controlled trial

OBJECTIVE

To test the hypothesis that iron supplement from early pregnancy would increase the risk of gestational diabetes mellitus (GDM).

DESIGN

Randomised placebo-controlled trial.

SETTING

A university teaching hospital in Hong Kong.

POPULATION

One thousand one hundred sixty-four women with singleton pregnancy at less than 16 weeks of gestation with haemoglobin (Hb) level between 8 and 14 g/dl and no pre-existing diabetes or haemoglobinopathies.

METHODS

Women were randomly allocated to receive 60 mg of iron supplement daily (n= 565) or placebo (n= 599). Oral glucose tolerance tests (OGTTs) were performed at 28 and 36 weeks. Women were followed up until delivery.

OUTCOME MEASURES

The primary outcome was development of GDM at 28 weeks. The secondary outcomes were 2-hour post-OGTT glucose levels, development of GDM at 36 weeks and delivery and infant outcomes.

RESULTS

There was no significant difference in the incidence of GDM in the iron supplement and placebo groups at 28 weeks (OR: 1.04, 95% confidence interval [CI]: 0.7-1.53 at 90% power) or 36 weeks. Maternal Hb and ferritin levels were higher in the iron supplement group at delivery (P < 0.001 and P= 0.003, respectively). Elective caesarean section rate was lower in the iron supplement group (OR: 0.58, 95% CI: 0.37-0.89). Infant birthweight was heavier (P= 0.001), and there were fewer small-for-gestational-age babies in the iron supplement group (OR: 0.46, 95% CI: 0.24-0.85).

CONCLUSION

Iron supplement from early pregnancy does not increase the risk of GDM. It may have benefits in terms of pregnancy outcomes.

Prevalence and extent of subclinical atherosclerosis in patients with psoriasis

OBJECTIVE

Patients with psoriasis are prone to premature atherosclerosis and increased risk of cardiovascular disease events. However, the prevalence and extent of atherosclerosis in patients with psoriasis are unknown.

DESIGN

A cross-sectional study.

SETTING AND SUBJECTS

The prevalence and extent of coronary and carotid atherosclerosis were compared in 70 patients with psoriasis (46 ± 9 years, 71% male) without known cardiovascular disease or joint involvement and 51 age- and gender-matched healthy control subjects (45 ± 7 years, 71% male). Systemic inflammation was assessed by the level of high-sensitivity C-reactive protein (hs-CRP). Coronary atherosclerosis was determined by the coronary calcification score (CCS) measured by multi-detector computed tomography. Carotid atherosclerosis was assessed by high-resolution ultrasound-derived carotid intima-media thickness (cIMT).

RESULTS

Patients with psoriasis had a higher prevalence of coronary atherosclerosis (CCS > 0; 28.6% vs. 3.9%, P < 0.01), and a higher degree of coronary atherosclerosis estimated by the mean CCS (67.4 ± 349.2 vs. 0.5 ± 3.0, P < 0.05) compared with controls. Similarly, cIMT was significantly greater in patients with psoriasis than in control subjects (0.73 ± 0.11 mm vs. 0.67 ± 0.08 mm, P < 0.01). Multiple logistic regression revealed that psoriasis [odd ratio (OR): 10.54, 95% confidence interval (CI) 1.89-58.67, P < 0.01] and serum total cholesterol level (OR 2.10, 95% CI 1.01-4.37) were associated with the presence of coronary atherosclerosis (CCS > 0). By contrast, only age was independently associated with increased cIMT. Amongst participants with no traditional cardiovascular disease risk factors, hs-CRP level was higher in patients with psoriasis than in controls.

CONCLUSION

The present results demonstrate early-onset, diffuse arterial atherosclerosis in coronary and carotid arteries in patients with psoriasis, but not in age- and gender-matched control subjects. Low-grade inflammation could explain the presence of premature atherosclerosis in patients with psoriasis.

Sifuvirtide, a potent HIV fusion inhibitor peptide

Enfuvirtide (ENF) is currently the only FDA approved HIV fusion inhibitor in clinical use. Searching for more drugs in this category with higher efficacy and lower toxicity seems to be a logical next step. In line with this objective, a synthetic peptide with 36 amino acid residues, called Sifuvirtide (SFT), was designed based on the crystal structure of gp41. In this study, we show that SFT is a potent anti-HIV agent with relatively low cytotoxicity. SFT was found to inhibit replication of all tested HIV strains. The effective concentrations that inhibited 50% viral replication (EC(50)), as determined in all tested strains, were either comparable or lower than benchmark values derived from well-known anti-HIV drugs like ENF or AZT, while the cytotoxic concentrations causing 50% cell death (CC(50)) were relatively high, rendering it an ideal anti-HIV agent. A GST-pull down assay was performed to confirm that SFT is a fusion inhibitor. Furthermore, the activity of SFT on other targets in the HIV life cycle was also investigated, and all assays showed negative results. To further understand the mechanism of action of HIV peptide inhibitors, resistant variants of HIV-1(IIIB) were derived by serial virus passage in the presence of increasing doses of SFT or ENF. The results showed that there was cross-resistance between SFT and ENF. In conclusion, SFT is an ideal anti-HIV agent with high potency and low cytotoxicity, but may exhibit a certain extent of cross-resistance with ENF.

Goitrogenesis during pregnancy and neonatal hypothyroxinaemia in a borderline iodine sufficient area

OBJECTIVE

Severe iodine deficiency disorders (IDDs) may have been eradicated in many parts of the world, but milder forms still exist and may escape detection. We evaluated the impact of pregnancy on the maternal and fetal thyroid axis in Hong Kong, a coastal city in southern China with borderline iodine intake.

DESIGN

A prospective study performed in a maternity hospital.

PATIENTS

Two hundred and thirty pregnant women were prospectively studied and their neonates assessed at birth.

MEASUREMENTS

Urine iodine concentration, thyroid function tests and thyroid volume (TV) by ultrasound were determined in the mothers during pregnancy and up to 3 months postpartum and in the neonates.

RESULTS

Increased urinary iodine concentration was seen from first trimester onwards and the proportion of women having urine iodine concentration of < 0.4 micromol/l decreased from 11.3% in the first trimester to 4.7% in the third trimester. There was progressive reduction in circulating fT4 and fT3 concentrations and free thyroxine index (FTI) with increasing gestation and the percentage of women having subnormal levels at term were 53.2%, 61.1% and 4.8%, respectively. The serum TSH concentration during pregnancy doubled towards term. In the first trimester, multiparous women had significantly larger TV than the nulliparous women (P < 0.001). By the third trimester, TV had increased by 30% (range 3-230%) so that the goitre incidence was 14.1%, 21.8%, 25.9% during the three trimesters of pregnancy, and 24.3% and 21.9% at 6 weeks and 3 months postpartum (ANOVA, P < 0.05). The change in thyroid volume during pregnancy correlated positively with the change in thyroglobulin (r = 0.225, P < 0.002) and negatively with urinary iodine concentration (r = - 0.149, P < 0.02). Fourteen women with excessive thyroidal stimulation in the second trimester (defined as those with thyroglobulin (Tg) concentrations in the highest tertile and FTI in the lowest tertile) were found to have lower urine iodine concentrations and larger TV (both P < 0.005) throughout pregnancy, and their neonates had higher cord TSH (P < 0.05), Tg (P < 0.05) and slightly larger TV (P = 0.06) as compared to the findings in 216 pregnant women without evidence of thyroid stimulation. Seven neonates (50%) born to these women had subnormal fT4 levels at birth.

CONCLUSION

In a borderline iodine sufficient area, pregnancy posed an important stress resulting in higher rates of maternal goitrogenesis as well as neonatal hypothyroxinaemia and hyperthyro- trophinaemia. An adequate iodization program is necessary to eliminate iodine deficiency disorders during pregnancy.

Rapamycin prevents the development of nephritis in lupus-prone NZB/W F1 mice

Rapamycin is a potent immunosuppressive drug currently used mainly for rejection prophylaxis in renal transplantation. The aim of this study was to determine the effect of rapamycin treatment on the development of nephritis in lupus-prone New Zealand Black/White F1 (NZB/W F1) mice. Twelve-week-old female NZB/W F1 mice were treated with rapamycin (3 mg/kg body weight) or saline once daily by oral gavage for 20 weeks. The severity of nephritis was assessed by clinical and biochemical parameters, renal histology, immunohistochemistry and gene expression studies. Rapamycin treatment markedly reduced proteinuria, improved renal function, decreased serum anti-double stranded DNA antibody levels and diminished splenomegaly. Kidney sections from saline-treated mice showed marked mesangial proliferation, tubular dilation with protein cast deposition and interstitial inflammatory cell infiltration. Rapamycin-treated mice had near normal renal histology, with marked reduction in glomerular immune deposition and the infiltration by T cells, B cells and macrophages. Rapamycin treatment was associated with down-regulation of intra-renal expression of monocyte chemoattractant protein-1 (MCP-1) mRNA and protein. We conclude that rapamycin is highly effective in preventing the development of nephritis in NZB/W F1 mice. The beneficial effects of rapamycin are mediated through inhibition of lymphoproliferation and reduced MCP-1 expression.

Value of intra-arterial calcium stimulated venous sampling for regionalization of pancreatic insulinomas

BACKGROUND

Intra-arterial calcium stimulation with hepatic venous sampling (ASVS) for insulin gradients has been reported to be the most sensitive preoperative localizing technique for insulinomas. We reviewed our experience with ASVS to localize and guide the treatment of insulinomas over the past decade.

METHODS

Eighteen patients who underwent ASVS before surgical exploration for insulinoma were studied. The accuracy of ASVS was compared with intraoperative findings and other localizing studies.

RESULTS

There were no complications arising from the procedures. A more than 2-fold step-up in insulin level 30 to 60 seconds after injection to at least 1 feeding artery was observed in 16 patients. Fourteen of the 16 solitary tumors (87.5%) were correctly located; 100% (6/6 tumors) at the head and 80% (8/10 tumors) at the body/tail. The overall accuracy of this test was 89%, compared with 11%, 33%, 38%, and 63% of ultrasonography, computed tomography, magnetic resonance imaging, and endoscopic ultrasonography, respectively. Six enucleations and 10 distal resections were performed, which included 2 laparoscopic procedures. The combination of intraoperative ultrasonography with preoperative ASVS identified all tumors.

CONCLUSIONS

ASVS is the most accurate preoperative localization tool for the localization of insulinomas and, in combination with intraoperative ultrasonography, can enhance surgical success.

Parathyroid autotransplantation during thyroidectomy: documentation of graft function

HYPOTHESIS

Biochemical function of normal parathyroid tissue grafted during thyroidectomy can be documented.

DESIGN

An intervention study in which devascularized or inadvertently removed parathyroid glands are reimplanted in forearm muscle pockets during thyroidectomy. Postoperative serum parathyroid hormone levels were evaluated by venous sampling from both forearms on postoperative days 1, 3, 14, 28, 56, and 84.

SETTING

Tertiary care teaching hospital.

PATIENTS

Seven patients undergoing thyroidectomy at risk for postoperative hypocalcemia.

RESULTS

A 1.5-fold gradient of parathyroid hormone measurements between grafted and nongrafted arms was demonstrated in all patients on postoperative day 28. A maximal parathyroid hormone gradient was reached on day 56, and biochemical function persisted in 6 patients on day 84.

CONCLUSIONS

Biochemical function of parathyroid glands reimplanted during thyroidectomy can be demonstrated objectively. The application of parathyroid autotransplantation may preserve parathyroid function for inadvertently removed or devascularized parathyroid glands during thyroid surgery.

Ammonia clearance by peritoneal dialysis and continuous arteriovenous hemodiafiltration

We report the use of continuous arteriovenous hemodiafiltration (CAVHD) in a neonate with severe hyperammonemia due to a urea cycle disorder. We compared the ammonia clearance (C(NH3)) for peritoneal dialysis (PD) and CAVHD. C(NH3) for CAVHD was 7.45 ml/min per m2 at a dialysate flow of 300 ml/h and was 10.55 ml/min per m2 at a dialysate flow rate of 600 ml/h. The mean PD clearance was 2.15 ml/min per m2. Our data suggest that CAVHD is superior to PD for the removal of plasma ammonia. We conclude that CAVHD should be considered a reasonable alternative in the treatment of neonatal hyperammonemia in urea cycle disorders when medical treatment fails.

Thyroxine suppressive therapy decreases bone mineral density in post-menopausal women

OBJECTIVE

Hyperthyroidism is associated with increased bone turnover and decreased bone mass. This study aimed to evaluate the bone mineral density (BMD) of post-menopausal women on long-term thyroxine suppressive therapy.

DESIGN

An age and sex-matched cross-sectional study.

PATIENTS

Thirty-four post-menopausal women with carcinoma of thyroid, post total thyroidectomy and 131I ablation, on L-T4 for 12.2 +/- 6.6 years (mean +/- SD). Controls were 34 age-matched healthy Southern Chinese women.

MEASUREMENTS

Total body and regional BMDs were determined by dual-energy X-ray absorptiometry. Bone turnover was assessed by biochemical markers.

RESULTS

In the thyroxine treated group, total body mineral content was significantly lower than the controls (1652 +/- 356 vs 1994 +/- 270 g mean +/- SD, P < 0.005). They also had lower BMDs in the lumbar spine, femoral neck, trochanter and Ward's triangle (0.75 +/- 0.15 vs 0.92 +/- 0.16 g/cm2, P < 0.005; 0.62 +/- 0.12 vs 0.70 +/- 0.12 g/cm2, P < 0.01; 0.55 +/- 0.14 vs 0.63 +/- 0.15 g/cm2, P < 0.001; 0.55 +/- 0.14 vs 0.63 +/- 0.14 g/cm2, P < 0.005 respectively.) The thyroxine treated group also had higher serum alkaline phosphatase and osteocalcin levels as well as urinary hydroxyproline excretion, suggesting that they had high turnover bone loss. However, the Z-scores of the various regional BMDs were correlated only with the serum osteocalcin level and showed no correlation with the serum thyroxine level or with the dosage or duration of thyroxine treatment.

CONCLUSION

Long-term thyroxine suppressive therapy was associated with bone loss and preventive therapy may be indicated in these post-menopausal women at risk of osteoporosis.

Receptor-mediated endocytosis of trichosanthin in choriocarcinoma cells

Trichosanthin (TCS) is a ribosome inactivating protein (RIP). It is generally believed that its many biological activities act through inhibition of ribosomes resulting in a decrease in protein synthesis. It has been hypothesized that the rate of entry of TCS into cells to reach ribosomes is an important factor in determining its biological activity. To prove this hypothesis, we have mapped out and compared the intracellular routing of TCS in two cell lines, namely the choriocarcinoma JAR cell line, which is known to be highly sensitive to the toxic effects of TCS, and the hepatoma H35 cell line, to which TCS shows minimal toxicity. Results from laser scanning confocal microscopy indicated that fluorescein isothiocyanate labeled TCS quickly accumulated inside JAR cells within 4 h of incubation while only a low level of fluorescent signals was detected in H35 cells during the same period of time. When TCS was conjugated with gold particles (Au) and its intracellular locations were traced with a transmission electron microscope, it was found that most of TCS were bound to coated pits on the JAR cell surface and were rapidly internalized within an hour. By 4 h, TCS reached almost every cytoplasmic region including ribosomes, and the JAR cell began to degenerate. In H35 cells, however, the binding of TCS to coated pits was not observed, but instead, a small amount of TCS was found to penetrate the cell non-specifically by direct diffusion across the cell membrane. Our observations suggest that most of TCS enter JAR cells via a specific receptor mediated pathway, which allows a swift transport of TCS across the membrane and a rapid accumulation of intracellular TCS, while in H35 cells, TCS takes a slow and non-specific route. The receptor-mediated uptake together with the specific intracellular routing of TCS may partly account for the differential vulnerability of the choriocarcinoma cell line towards the toxicity of TCS.