Significant human beta-cell turnover is limited to the first three decades of life as determined by in vivo thymidine analog incorporation and radiocarbon dating

AIMS

Diabetes mellitus results from an absolute or relative deficiency of insulin-producing pancreatic β-cells. The turnover rate of adult human β-cells remains unknown. We employed two techniques to examine adult human islet β-cell turnover and longevity in vivo.

METHODS

Subjects enrolled in National Institutes of Health clinical trials received thymidine analogs [iododeoxyuridine (IdU) or bromodeoxyuridine (BrdU)] 8 d to 4 yr prior to death. Archival autopsy samples from 10 patients (aged 17-74 yr) were employed to assess β-cell turnover by scoring nuclear analog labeling within insulin-staining cells. Human adult β-cell longevity was determined by estimating the cells' genomic DNA integration of atmospheric (14)C. DNA was purified from pancreatic islets isolated from cadaveric donors; whole islet prep DNA was obtained from a 15-yr-old donor, and purified β-cell DNA was obtained from two donors (ages 48 and 80 yr). (14)C levels were then determined using accelerator mass spectrometry. Cellular "birth date" was determined by comparing the subject's DNA (14)C content relative to a well-established (14)C atmospheric prevalence curve.

RESULTS

In the two subjects less than 20 yr of age, 1-2% of the β-cell nuclei costained for BrdU/IdU. No β-cell nuclei costained in the eight patients more than 30 yr old. Consistent with the BrdU/IdU turnover data, β-cell DNA (14)C content indicated that the "birth date" of cells occurred within the subject's first 30 yr of life.

CONCLUSIONS

Under typical circumstances, human β-cells and their cellular precursors are established by young adulthood.

Randomized clinical trial of morbidity after D1 and D3 surgery for gastric cancer

BACKGROUND

A randomized comparison of D1 (level 1 lymphadenectomy) and D3 (levels 1, 2 and 3 lymphadenectomy) dissection was performed to evaluate morbidity and effects on survival from gastric cancer.

METHODS

A total of 221 patients were studied after resection for gastric cancer, 110 after D1 surgery and 111 after D3 surgery.

RESULTS

The morbidity rate was higher after D3 than after D1 resection (17.1 (95 per cent confidence interval (c.i.) 10.1 to 24.1) versus 7.3 (95 per cent c.i. 2.4 to 12.2) per cent respectively; P = 0.012). The difference was largely related to abdominal abscess (8.1 per cent after D3 versus none after D1 resection; P = 0.003). The D3 group had an anastomotic leak rate of 4.5 per cent whereas there was no leakage in the D1 group (P = 0.060). All anastomotic leaks were minor and were managed non-operatively with nutritional support. Patients who had D3 resection had longer operating times, greater blood loss and postoperative drain outputs, and more patients needed blood transfusion. There was no death in either group. The hospital stay was longer after D3 than D1 surgery (mean(s.d.) 19.6(13.9) (range 10-98) versus 15.0(4.0) (range 10-30) days; P = 0.001).

CONCLUSION

Extended lymphadenectomy for gastric cancer is associated with more complications than limited lymphadectomy but this does not lead to significant mortality.

Surgical mortality, survival, and quality of life after resection for gastric cancer in the elderly

Although there were some studies on clinicopathologic characteristics, operative morbidity, and mortality in elderly patients with gastric cancer, no reports have specifically focused on survival and quality of life after resection. A total of 433 patients aged >/= 65 years (1987-1994) who underwent gastric resection for gastric adenocarcinoma were studied. Two groups were considered: patients aged 65 to 74 years and those > 74 years. Most of the patients (78.1%) had advanced diseases, and nearly half (41. 3%) had associated chronic disease(s). Resections with curative intention were performed in 362 patients (83.6%). The overall operative morbidity rate was 21.7% and mortality rate 5.1%. Although operative procedures were similar in both groups, patients aged >74 years had a higher mortality rate than those aged 65 to 74 years (10. 1% vs. 3.5%; p = 0.034). Age and extent of gastric resection were two independent factors negatively affecting mortality. The cumulative survival rates for patients who underwent curative resection were 86.2%, 72.4%, 67.2%, 62.9%, and 60.0% at 1, 2, 3, 4, and 5 years, respectively. Nearly all patients (96%) after surgery had normal work and daily activities. Some patients appeared to lack energy (16%) or experienced a period of anxiety or depression. There was no statistical difference in survival and quality of life assessed by the Spitzer index after curative resection between the two groups. Therefore resection with curative intention can be performed for the elderly with acceptable morbidity and mortality rates, possible long-term survival, and good quality of life, but a limited operation should be considered in the very elderly patients.

Human oocyte maturation is dependent on LH-stimulated accumulation of the epidermal growth factor-like growth factor, amphiregulin

BACKGROUND

The LH surge promotes ovulation via activation of multiple signaling networks in the ovarian follicle. Studies in animal models have shown the importance of LH-induced activation of the epidermal growth factor (EGF)signaling network in critical peri-ovulatory events. We investigated the biological significance of regulatory mechanisms mediated by EGF-like growth factors during LH stimulation in humans.

METHODS

We characterized the EGF signaling network in mature human ovarian follicles using in vivo and in vitro approaches. Amphiregulin (AREG) levels were measured in 119 follicular fluid (FF) samples from IVF/ICSI patients. Biological activity of human FF was assessed using in vitro oocyte maturation, cumulus expansion and cell mitogenic assays.

RESULTS

AREG is the most abundant EGF-like growth factor accumulating in the FF of mature follicles of hCG-stimulated patients. No AREG was detected before the LH surge or before hCG stimulation of granulosa cells in vitro, demonstrating that the accumulation of AREG requires gonadotrophin stimulation. Epiregulin and betacellulin mRNA were detected in both human mural and cumulus granulosa cells, although at significantly lower levels than AREG. FF from stimulated follicles causes cumulus expansion and oocyte maturation in a reconstitution assay. Immunodepletion of AREG abolishes the ability of FF to stimulate expansion (P < 0.0001) and oocyte maturation (P < 0.05), confirming the biological activity of AREG. Conversely, mitogenic activity of FF remained after depletion of AREG, indicating that other mitogens accumulate in FF. FF from follicles yielding an immature germinal vesicle oocyte or from an oocyte that develops into an aberrant embryo contains lower AREG levels than that from follicles yielding a healthy oocyte (P = 0.008).

CONCLUSIONS

EGF-like growth factors play a role in critical peri-ovulatory events in humans, and AREG accumulation is a useful marker of gonadotrophin stimulation and oocyte competence.

Synthesis and antiplatelet activity of phenyl quinolones

In our search for novel antiplatelet agents, seven positional phenyl quinolone isomers were synthesized. Preliminary screening confirmed their inhibitory effects against arachidonic acid (AA)-induced platelet aggregation. Varying the substitutional position of the phenyl group had a profound effect on the antiplatelet activity of these isomers. 3-Phenyl-4-quinolone showed the greatest potency and was superior to indomethacin, although the two structures are quite different. The mechanism and pharmacological action of 3-phenyl-4-quinolone are currently under investigation.

Thermodynamic and kinetic characterization of the binding of the TATA binding protein to the adenovirus E4 promoter

A thermodynamic analysis of the binding of the TATA binding protein (TBP) from Saccharomyces cerevisiae to the adenovirus E4 promoter was conducted using quantitative DNase I "footprint" titration techniques. These studies were conducted to provide a foundation for studies of TBP structure-function relations and its assembly into transcription preinitiation complexes. The binding of TBP to the E4 promoter is well described by the Langmuir binding polynomial, suggesting that no linked equilibria contribute to the binding reaction under the conditions examined. Van't Hoff analysis yielded a nonlinear dependence on temperature with the TBP-E4 promoter interaction displaying maximal affinity at 30 degrees C. An unusually negative value of the apparent standard heat capacity change, delta Cp degrees = -3.5 +/- 0.5 kcal/mol.K, was determined from these data. The dependence of the TBP-E4 promoter interaction on [KCl] indicates that 3.6 +/- 0.3 K+ ions are displaced upon complex formation. Within experimental error, no linkage of proton binding with the TBP-E4 promoter interaction is detectable between pH 5.9 and 8.7. Rates of association of TBP for the E4 promoter were obtained using a novel implementation of a quench-flow device and DNase I "footprinting" techniques. The value determined for the second-order rate constant at pH 7.4, 100 mM KCl, 5 mM MgCl2, 1 mM CaCl2, 30 degrees C (ka = 5.2 +/- 0.5) x 10(5) M-1 s-1) confirms the results obtained by Hawley and co-workers [Hoopes, B.C., LeBlanc, J.F., & Hawley, D.K. (1992) J. Biol. Chem. 267, 11539-11547] and extends them through TBP concentrations of 636 nM.(ABSTRACT TRUNCATED AT 250 WORDS)

Converting Escherichia coli RNA polymerase into an enhancer-responsive enzyme: role of an NH2-terminal leucine patch in sigma 54

The protein sigma 54 associates with Escherichia coli core RNA polymerase to form a holoenzyme that binds promoters but is inactive in the absence of enhancer activation. Here, mutants of sigma 54 enabled polymerases to transcribe without enhancer protein and adenosine triphosphate. The mutations are in leucines within the NH2-terminal glutamine-rich domain of sigma 54. Multiple leucine substitutions mimicked the effect of enhancer protein, which suggests that the enhancer protein functions to disrupt a leucine patch. The results indicate that sigma 54 acts both as an inhibitor of polymerase activity and as a receptor that interacts with enhancer protein to overcome this inhibition, and that these two activities jointly confer enhancer responsiveness.

Partial purification and characterization of a soybean beta-glucosidase with high specific activity towards isoflavone conjugates

A beta-glucosidase with high specific activity towards isoflavone conjugates was purified from soybean [Glycine max] roots by high salt extraction from a low speed centrifugal pellet and subsequent anion and cation exchange chromatography. Purification required stabilization throughout fractionation in 10% glycerol. The enzyme is most likely a dimer (approximate M(r) 165 kDa) with potential subunits of M(r) 80 and/or 75 kDa. The pH and temperature optima are pH 6 and 30 degrees C, respectively. The enzyme was highly heat-stable. Of the various potential effectors examined, silver and mercury ions were the most inhibitory. The IC(50) of silver ions was increased from 140 microM to 14 mM in the presence of 250 microM beta-mercaptoethanol. Glucono-delta-lactone was not strongly inhibitory (IC(50) 24 mM). The activity was highly active against isoflavone conjugates, with a specificity constant 160-1000 fold higher for isoflavone conjugates over the generic chromogenic substrate, p-nitrophenyl beta-glucoside. The enzyme was inactive against the flavonol glycosides tested. The partially purified enzyme had similar K(m) and k(cat) towards 7-O-glucosyl- and 7-O-glucosyl-6"-malonyl-isoflavones, suggesting that it may be able to cleave the esterified glucosyl conjugate. We hypothesize that the enzyme is involved in the release of daidzein and genistein, both of which play central roles in soybean defense.

Relation of number of positive lymph nodes to the prognosis of patients with primary gastric adenocarcinoma

BACKGROUND

No nodal grouping category of gastric cancer has been universally accepted for the grading of the effectiveness of therapeutic regimens.

AIMS

To establish an appropriate nodal grouping as a forecaster of distant disease and test its validity as a determinant in survival.

PATIENTS

Five hundred and ten patients who underwent curative resections for gastric cancer were studied.

METHODS

Retrospectively analyse the prognostic significance of the number of metastatic lymph nodes.

RESULTS

A total of 17 176 lymph nodes with an average of 34 per specimen were removed, of which 2811 (16%) showed metastases. Among the 510 patients, 287 (56%) had lymph node metastases, with an average of 9.8 per metastatic case. The survival of all patients was related to their nodal status, an abrupt decrease in survival was seen between 0 and 1 and 4 compared with 5 or more modes while little difference in survival existed among 1, 2, 3, and 4, and among 5, 6, 7, and 8 positive nodes. Multivariate analysis showed that the number of positive nodes (1-4, 5-8 versus > or = 9; relative risk 2.2) and depth of cancer invasion (three levels; relative risk 1.9) were independently correlated with survival. The current nodal stage was not a prognostic factor.

CONCLUSIONS

Gastric cancer patients with 0, 1 to 4, 5 to 8, and > 9 positive nodes may represent four appropriate prognostic groups and should be adopted for classification of nodal stage in gastric cancer.

Pharmacokinetics of rifabutin

We investigated the pharmacokinetics of rifabutin in 15 male patients as part of a phase I trial of the treatment of early symptomatic human immunodeficiency virus infection. Six or more patients were studied at each of four different oral dosage levels: 300, 600, 900, and 1,200 mg/day. Twelve studies were also conducted with tracer doses of intravenous radiolabeled [14C]rifabutin. Blood and urine samples were collected for at least 72 h after the first (day 1) and last (day 28) doses of rifabutin and analyzed by high-pressure liquid chromatography. The plasma concentration data were best described by a two-compartment open model with a terminal half-life of 36 h. Rifabutin was rapidly absorbed, reaching a peak concentration about 2 to 3 h after an oral dose. Peak and trough concentrations for the 1,200-mg dose were 907 and 194 ng/ml, respectively. Total body clearance was 10 to 18 liters/h. Oral bioavailability was 12 to 20%. The drug was moderately bound to plasma proteins with a free fraction of 29 +/- 2% (mean +/- standard deviation). About 10% of an administered intravenous dose of rifabutin is excreted into the urine unchanged. Renal clearance was 1.5 +/- 0.2 liters/h. The volume of distribution was large (8 to 9 liters/kg), suggesting extensive distribution into the tissues. The area under the curve for the last dose was smaller than that of the first dose, suggesting possible induction of drug-metabolizing enzymes.

Antitumor agents. 174. 2',3',4',5,6,7-Substituted 2-phenyl-1,8-naphthyridin-4-ones: their synthesis, cytotoxicity, and inhibition of tubulin polymerization

Two series of 2',3',4',5,6,7-substituted 2-phenyl-1,8-naphthyridin-4-ones and 2-phenylpyrido[1,2-alpha]pyrimidin-4-ones have been synthesized and evaluated as cytotoxic compounds and as inhibitors of tubulin polymerization. Most 2-phenyl-1,8-naphthyridin-4-ones showed potent cytotoxic and antitubulin activities, whereas 2-phenylpyrido[1,2-alpha]pyrimidin-4-ones showed no activity in either assay. In general, a good correlation was found between cytotoxicity and inhibition of tubulin polymerization in the 2-phenyl-1,8-naphthyridin-4-one series. The 2-phenyl-1,8-naphthyridin-4-ones (44-49) with a methoxy group at the 3'-position showed potent cytotoxicity against most tumor cell lines with GI50 values in the low micromolar to nanomolar concentration range in the National Cancer Institute's 60 human tumor cell line in vitro screen. Introduction of substituents (e.g. F, Cl, CH3, and OCH3) at the 4'-position led to compounds with reduced or little activity and substitution at the 2'-position resulted in inactive compounds. The effects of various A-ring substitutions on activity depend on the substitution in ring C. Compounds 44-50 were potent inhibitors of tubulin polymerization, with activity nearly comparable to that of the potent antimitotic natural products colchicine, podophyllotoxin, and combretastatin A-4. Compounds 44-49 also inhibited the binding of radiolabeled colchicine to tubulin, but the inhibition was less potent than that obtained with the natural products. Further investigation is underway to determine if substitution at the 3'-position and multisubstitutions in ring C will result in compounds with increased activity.

Repeat pediatric visits to a general emergency department

STUDY OBJECTIVE

To determine the rate of repeat visits among children cared for in a general emergency department and associated demographic and clinical variables.

METHODS

We carried out a chart review of patients seen in the ED of a general hospital serving both inner-city and suburban populations. Our subjects were all children younger than 18 years seen in the study ED between July 1, 1992, and June 30, 1993 (N = 4,276).

RESULTS

We found 291 repeat visits (defined as a subsequent visit within 14 days) n 245 children. Among the 242 repeat visits for related complaints, 200 were unanticipated and most without a clear medical need. Mantel-Haenszel adjusted odds ratios (MHORs) showed a significantly increased risk of repeat visit with public insurance (controlled for age: MHOR, 2.57, and 95% confidence interval [CI], 1.93 to 3.43; controlled for race: MHOR, 2.70, and 95% CI, 1.99 to 3.66) and age younger than 2 years (controlled for insurance MHOR, 1.67, and 95% CI, 1.27 to 2.19; controlled for race: MHOR, 1.89, and 95% CI, 1.47 to 2.47.

CONCLUSION

Repeat visits were more likely for respiratory diagnoses and less likely for minor trauma. Both visits and repeat visits were more likely in patients from poorer census tracts than in those from equidistant, more affluent ones.

Antitumor agents. 178. Synthesis and biological evaluation of substituted 2-aryl-1,8-naphthyridin-4(1H)-ones as antitumor agents that inhibit tubulin polymerization

As part of our continuing search for potential anticancer drug candidates in the 2-aryl-1,8-naphthyridin-4(1H)-one series, we have synthesized two series of 3'-substituted 2-phenyl-1,8-naphthyridin-4(1H)-ones and 2-naphthyl-1,8-naphthyridin-4(1H)-ones. All compounds showed significant cytotoxic effects (log GI50 < -4.0; log molar drug concentration required to cause 50% growth inhibition) against a variety of human tumor cell lines of the National Cancer Institute's in vitro screen, including cells derived from solid tumors such as non-small cell lung, colon, central nervous system, melanoma, ovarian, prostate, and breast cancers. All 3'-substituted compounds demonstrated strong cytotoxic effects in almost all tumor cell lines. Introduction of an aromatic ring at the 2'- and 3'-positions also generated compounds with potent antitumor activity. Incorporation of an aromatic ring at the 3'- and 4'-positions produced compounds with reduced activity. Interestingly, introduction of a halogen at the 3'-position yielded compounds with different selectivity for the tumor cell lines tested. All 3'-halogenated compounds (29-36) and compounds 38 and 42-44 were potent inhibitors of tubulin polymerization with activities nearly comparable to those of the potent antimitotic natural products colchicine, podophyllotoxin, and combretastatin A-4. Active agents also inhibited the binding of [3H]colchicine to tubulin.

Quality of life of patients with gastric adenocarcinoma after curative gastrectomy

Quality of life (QOL) was evaluated in 162 patients having radical gastrectomy for cancer. The results showed that more than half of the patients had a good appetite; they consumed a normal diet and a normal volume of food. Approximately 60% of the patients had weight loss of more than 5 kg. Patients who underwent a total gastrectomy had poor tolerance of normal food and frequent eating and body weight loss versus those who had a subtotal gastrectomy. Patients who underwent Billroth II reconstruction after a distal subtotal gastrectomy lost more body weight than those with a Billroth I anastomosis. The extent of lymphadenectomy did not influence the QOL. Patients under 65 years of age had a better QOL. Nearly all patients had normal work and daily living activities. Some patients appeared to lack energy or had a period of anxiety or depression. These data indicate that radical gastrectomy can be performed with an acceptable QOL for a potentially curable gastric carcinoma.

Virologic factors related to interferon-alpha-induced thyroid dysfunction in patients with chronic hepatitis C

OBJECTIVE

Hepatitis C virus (HCV), being reported to be associated with a high prevalence of serological markers of autoimmunity in HCV-infected patients, and possibly sharing partial sequences in amino acid segments with thyroid tissue antigens, may be associated with interferon-alpha (IFN-alpha)-induced thyroid dysfunction in chronic hepatitis C patients. We conducted this study to clarify the issue.

DESIGN AND METHODS

One hundred and fifty chronic hepatitis C patients with normal baseline thyroid function were treated with IFN-alpha 2a, 2b and n1 (3-6 million Units three times weekly for 24 weeks). Pretreatment sera were tested for HCV genotype and HCV RNA levels. Serum thyrotropin, total thyroxine and free thyroxine index were performed every 4 weeks for 24 weeks followed by every 8 weeks for another 24 weeks.

RESULTS

Twenty-one (14.0%) patients developed early thyroid dysfunction (abnormal thyroid function during the first 3 months of therapy). Female gender, lower HCV RNA levels, IFN-alpha n1 and a lower IFN-alpha dose were significantly associated with early thyroid dysfunction. On multivariate analysis, gender, IFN-alpha preparation and HCV RNA levels were the significant factors associated with early thyroid dysfunction. Seven (4.7%) patients developed thyroid dysfunction during the second 3 months of IFN-alpha therapy. Taken together, 18.7% patients developed thyroid dysfunction. Female, mixed HCV genotype infection and lower HCV RNA levels were significantly associated with thyroid dysfunction. However, only gender remained significantly associated with IFN-alpha-induced thyroid dysfunction in multivariate analysis.

CONCLUSIONS

The virologic features of HCV may be associated with thyroid dysfunction in chronic hepatitis C patients treated with IFN-alpha. Nevertheless, gender still plays the most important role in IFN-alpha-induced thyroid dysfunction.

Increased frequency of angiotensin-converting enzyme DD genotype in patients with type 2 diabetes in Taiwan

BACKGROUND

Diabetes is one of the major causes of end-stage renal failure in the Taiwanese population. Previous studies have shown that angiotensin-converting enzyme (ACE) inhibitor can improve glucose utilization and suppress hepatic glucose production and the renin-angiotensin system may play an important role in the initiation and progression of diabetic nephropathy. Thus, ACE gene polymorphism may be associated with type 2 diabetes and diabetic nephropathy.

METHODS

To investigate the distribution of ACE-I/D genotype in type 2 diabetes and diabetic nephropathy, we examined 336 patients with type 2 diabetes (157 without nephropathy and 179 with nephropathy) and 263 age-matched normal controls. The diagnosis of nephropathy was made when daily protein loss exceeded 500 mg. ACE gene polymorphism was analysed by use of polymerase chain reaction.

RESULTS

Our study revealed that the frequency of the D allele of the ACE gene was 29.3% in normal controls. The frequency of ACE DD genotype was significantly higher in type 2 diabetics compared with normal controls (18.2 vs 9.1%, P<0.01). The frequency of ACE DD genotype in patients with diabetic nephropathy was significantly higher than in patients without nephropathy (22.3 vs 13.4%, P<0.05). To determine whether ACE gene polymorphism was associated with the severity of diabetic nephropathy, we divided patients with diabetic nephropathy into dialysis and non-dialysis groups. The frequency of ACE DD genotype in the dialysis group was significantly higher than in non-dialysis group (28.7 vs 15.3%, P<0.05).

CONCLUSION

Our results indicate that the frequency of ACE DD genotype is markedly higher in patients with type 2 diabetes, and the ACE DD genotype is significantly associated with diabetic nephropathy.

Prognostic indicators for survival after curative resection for patients with carcinoma of the stomach

This study aims to determine prognostic indicators among patient-, tumor-, and treatment-related factors of gastric cancer patients. A total of 510 patients who underwent curative gastric resection were studied. Univariate analysis of patient-related factors showed a significantly lower survival in patients with a history of obstruction, hypoalbuminemia, and anemia. Tumor-related factors including gross appearance, location, and size of tumor; depth of cancer invasion; level, number, and frequency of lymph node metastasis; stromal reaction and tumor growth pattern; and histological classification all significantly affected survival. Surgical treatment related factors such as total or distal subtotal gastrectomy, extent of lymphadenectomy, and combined resection of adjacent organ(s) showed a statistically significant adverse influence on survival. Multivariate analysis identified only four tumor-related factors-number of metastatic lymph nodes, depth of cancer invasion, stromal reaction, and gross appearance of the tumor-as independently affecting survival. These findings suggest that only four tumor-related factors were prognostic indicators in patients with gastric cancer.

Neuronal and endothelial nitric oxide synthase expression in outer medulla of streptozotocin-induced diabetic rat kidney

AIMS/HYPOTHESIS

Several investigations have shown that the renal medulla has a greater capacity to generate nitric oxide than the renal cortex. To further evaluate the changes of nitric oxide synthesis in the kidney, particularly in the outer medulla, in disorders involving fluid and electrolyte imbalances, we sought to determine renal nitric oxide synthase expression in the diabetic rats.

METHODS

We determined renal nitric oxide synthase mRNA and urinary nitrite/nitrate excretion in 12 normal and 12 streptozotocin-induced diabetic rats by reverse transcription-polymerase chain reaction with Southern blot hybridization and with Griess reaction, respectively. Nitric oxide synthase immunoreactivity was detected by immunohistochemistry in four normal and four diabetic rats.

RESULTS

Neuronal and endothelial nitric oxide synthase mRNA were 3.5-fold and 1.8-fold increased in the outer medulla of 12 diabetic rats with no difference found in the cortex and inner medulla when compared with 12 normal rats. Urinary nitrite/nitrate excretion was significantly increased from the first week after diabetic induction. In normal rats, immunohistochemical studies showed positive neuronal and endothelial nitric oxide synthase immunostaining in almost all segments of renal tubules. Diabetic rats had the greatest enhancement of immunostaining for neuronal and endothelial nitric oxide synthase in the proximal straight tubule and medullary thick ascending limb.

CONCLUSION/INTERPRETATION

Our results indicate that increases in neuronal and endothelial nitric oxide synthase synthesis in the kidney, particularly in the outer medulla, possibly play an important part in the adaptation of renal function to hyperglycaemia and hyperosmolality in diabetes.

DNA sequence-specific recognition by the Saccharomyces cerevisiae "TATA" binding protein: promoter-dependent differences in the thermodynamics and kinetics of binding

The equilibrium binding and association kinetics of the Saccharomyces cerevisiae TATA Binding Protein (TBP) to the E4 and Major Late promoters of adenovirus (TATATATA and TATAAAAG, respectively), have been directly compared by quantitative DNase I titration and quench-flow "footprinting". The equilibrium binding of TBP to both promoters is described by the equilibrium TBP + DNA"TATA" left and right arrow TBP-DNA"TATA". The salt dependence of TBP binding to both promoters is identical within experimental error while the temperature dependence differs significantly. The observed rate of association follows simple second-order kinetics over the TBP concentration ranges investigated. The salt and temperature dependencies of the second-order association rate constants for TBP binding the two promoters reflect the dependencies determined by equilibrium binding. The TBP-E4 promoter interaction is entropically driven at low temperature and enthalpically driven at high temperature while the TBP-Major Late promoter reaction is entropically driven over virtually the entire temperature range investigated. These data suggest that the reaction mechanisms of TBP-promoter interactions are TATA sequence-specific and provide for differential regulation of promoters as a function of environmental variables.

Comparison of the DNA association kinetics of the Lac repressor tetramer, its dimeric mutant LacIadi, and the native dimeric Gal repressor

The rates of association of the tetrameric Lac repressor (LacI), dimeric LacIadi (a deletion mutant of LacI), and the native dimeric Gal repressor (GalR) to DNA restriction fragments containing a single specific site were investigated using a quench-flow DNase I "footprinting" technique. The dimeric proteins, LacIadi and GalR, and tetrameric LacI possess one and two DNA binding sites, respectively. The nanomolar protein concentrations used in these studies ensured that the state of oligomerization of each protein was predominantly either dimeric or tetrameric, respectively. The bimolecular association rate constants (ka) determined for the LacI tetramer exceed those of the dimeric proteins. The values of ka obtained for LacI, LacIadi, and GalR display different dependences on [KCl]. For LacIadi and GalR, they diminish as [KCl] increases from 25 mM to 200 mM, approaching rates predicted for three-dimensional diffusion. In contrast, the ka values determined for the tetrameric LacI remain constant up to 300 mM [KCl], the highest salt concentration that could be investigated by quench-flow footprinting. The enhanced rate of association of the tetramer relative to the dimeric proteins can be modeled by enhanced "sliding" (Berg, O. G., Winter, R. B., and von Hippel, P. H. (1981) Biochemistry 20, 6929-6948) of the LacI tetramer relative to the LacIadi dimer or a combination of enhanced sliding and the superimposition of "direct transfer" mediated by the bidentate DNA interactions of the tetramer.

Analysis of trinucleotide repeats in different SCA loci in spinocerebellar ataxia patients and in normal population of Taiwan

OBJECTIVE

To identify various subtypes of spinocerebellar ataxias (SCAs) among autosomal dominant cerebellar ataxia (ADCA) patients referred to our research center, SCA1, SCA2, SCA3/MJD (Machado-Joseph disease), SCA6, SCA7, SCA8 and SCA12 loci were assessed for expansion of trinucleotide repeats.

PATIENTS AND METHODS

A total of 211 ADCA patients, including 202 patients with dominantly inherited ataxia from 81 Taiwanese families and nine patients with sporadic ataxia, were included in this study and subjected to polymerase chain reaction (PCR) analysis. The amplified products of all loci were analyzed on both 3% agarose gels and 6% denaturing urea-polyacrylamide gels. PCR-based Southern blots were also applied for the detection of SCA7 locus.

RESULTS

The SCA1 mutation was detected in six affected individuals from one family (1.2%) with expanded alleles of 50-53 CAG repeats. Fourteen individuals from nine families (11%) had a CAG trinucleotide repeat expansion at the SCA2 locus, while affected SCA2 alleles have 34-49 CAG repeats. The SCA3/MJD CAG trinucleotide repeat expansion in 60 affected individuals from 26 families (32%) was expanded to 71-85 CAG repeats. As for the SCA7 locus, there were two affected individuals from one family (1.2%) possessed 41 and 100 CAG repeats, respectively. However, we did not detect expansion in the SCA6, SCA8 and SCA12 loci in any patient.

CONCLUSIONS

The SCA3/MJD CAG expansion was the most frequent mutation among the SCA patients. The relative prevalence of SCA3/MJD in Taiwan was higher than that of SCA2, SCA1 and SCA7.

Increased nitric oxide synthase mRNA expression in the renal medulla of water-deprived rats

Increased nitric oxide synthase mRNA expression in the renal medulla of water-deprived rats.

BACKGROUND

Experiments were performed to investigate whether renal nitric oxide synthase (NOS) mRNA and protein expression are responsive to the alteration of body volume.

METHODS

Four days of water deprivation (WD) was initiated in 16 male Wistar rats, and 16 normal rats (NC) served as the control group. Neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS) mRNAs and immunoreactivity were measured by reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern blot hybridization and immunohistochemistry, respectively. Plasma angiotensin II, vasopressin, and atrial natriuretic peptide (ANP) concentrations were measured by radioimmunoassay.

RESULTS

The four-day WD increased plasma sodium and osmolality levels, but severely decreased daily urine sodium excretion and urine volume. Plasma angiotensin II and vasopressin concentrations were increased, but the plasma ANP level was significantly decreased in WD rats. nNOS, eNOS, and iNOS mRNA levels were increased by 5.2-, 3.3-, and 3. 4-fold in the outer medulla and 1.7-, 1.5-, and 1.8-fold in the inner medulla, whereas no significant difference was found in the renal cortex of WD rats as compared with NC rats. Additionally, immunohistochemistry revealed that the immunostaining intensity of nNOS, eNOS, and iNOS was clearly enhanced in the medullary thick ascending limb, proximal straight tubule, inner medullary collecting duct, and proximal convoluted tubule in WD rats. Kidney angiotensin II content as well as renin mRNA levels in renal cortex, outer medulla, and inner medulla in WD rats were apparently increased.

CONCLUSIONS

Our results indicate that the increases of nNOS, eNOS, and iNOS synthesis in the kidney, particularly in the renal medulla, may have a role in the adaptation of renal function to volume depletion in the face of an increase of systemic and intrarenal vasoconstrictive substances.

Analysis of the N-terminal leucine heptad and hexad repeats of sigma 54

In order to assess the role of leucine repeat motifs within bacterial protein sigma 54, a series of point mutants were introduced into the many leucine residues near the N terminus. Functional assays in vivo showed that the leucine residues that comprise the previously identified heptad repeat motif are selectively important for function. These heptad leucine residues are critical for mRNA production and also for recognition of the -12 promoter element. An internal proline substitution destroys the function of the heptad repeat region, suggesting a possible alpha-helical structure. Mutants with changes in the distal part of this N-terminal region show the interesting property of allowing nearly full levels of open complex formation, while nonetheless reducing the level of mRNA transcripts produced. All of the above-mentioned properties differ from those exhibited by mutating the interdigitated glutamine residues, which were previously found to be closely involved in the DNA melting reaction. The collection of data suggests that the N-terminal region contains overlapping functional motifs, hydrophobic heptad and glutamine-rich, which together appear to constitute the activation domain of sigma 54.

Surrogate consent by family members for out-of-hospital cardiac arrest research

OBJECTIVES

To evaluate the availability of family members of potential subjects to provide consent for participation in out-of-hospital cardiac arrest (OOHCA) research and to estimate the time required to contact a family member.

METHODS

This study was a prospective observational study of adult patients (>18 years old) with nontraumatic OOHCA treated by an urban emergency medical service. Emergency medicine resident physicians responded to each scene and noted the presence of family members. A subsequent convenience sample of family members answered standardized questions about their ability to provide consent for research participation on behalf of the patient.

RESULTS

Physicians were present at 100 of the 112 adult medical cardiac arrests during the study period. A family member was present at 57% of the scenes (95% CI = 47% to 67%). Patients with family present were older and were less likely to have bystander cardiopulmonary resuscitation (CPR) or live in a nursing home. The mean time (+/-SE) from emergency dispatch to family contact was 24.40 (+/-2.60) minutes and from physician arrival to family contact was 2.45 (+/-0.87) minutes (n = 20). Eight of 13 family members were willing to enroll the patient into a resuscitation study, but five family members were unable to understand the explanation of informed consent.

CONCLUSIONS

Family members were present for an unrepresentative subset of OOHCA cases, and were contacted after the therapeutic window for many interventions. The emotional nature of the emergency situation also limited the reliability of surrogate consent for OOHCA research.