Ligand-activated peroxisome proliferator-activated receptor β/δ modulates human endometrial cancer cell survival

Endometrial cancer is the fourth most common malignancy among women and is a major cause of morbidity contributing to approximately 8,200 annual deaths in the USA. Despite advances to the understanding of endometrial cancer, novel interventions for the disease are necessary given that many tumors become refractory to therapy. As a strategy to identify novel therapies for endometrial carcinoma, in this study, we examined the contribution of the peroxisome proliferator-activated receptor β/δ (PPARβ/δ) to endometrial cancer cell proliferation and apoptosis. We found that when activated with the highly selective PPARβ/δ agonists, GW0742 and GW501516, PPARβ/δ inhibited the proliferation and markedly induced the apoptosis of three endometrial cancer cell lines. The specificity of the PPARβ/δ-induced effects on cell proliferation and apoptosis was demonstrated using PPARβ/δ-selective antagonists and PPARβ/δ small interfering RNA in combination with PPARβ/δ-selective agonists. Furthermore, we showed that PPARβ/δ activation increased phosphatase and tensin homolog expression, which led to protein kinase B (AKT) and glycogen synthase kinase-3β (GSK3β) dephosphorylation, and increased β-catenin phosphorylation associated with its degradation. Overall, our data suggest that the antitumorigenic effect of PPARβ/δ activation in endometrial cancer is mediated through the negative regulation of the AKT/GSK3β/β-catenin pathway. These findings warrant further investigation of PPARβ/δ as a therapeutic target in endometrial cancer.

ESAT-6- and CFP-10-specific Th1, Th22 and Th17 cells in tuberculous pleurisy may contribute to the local immune response against Mycobacterium tuberculosis infection

Th1 cell-mediated adaptive immune response is very important but may not be sufficient to control Mycobacterium tuberculosis (M. tuberculosis) infection. The roles of the various T cell subsets and cytokines in the inflammatory processes are not clearly elucidated. We investigated whether Th1, Th22 and Th17 cells mediated cellular immunity at the local site of M. tuberculosis infection in patients with tuberculous pleurisy (TBP). The results showed that the cytokines IFN-γ and IL-22 but not IL-17 were elevated in tubercular pleural fluid. Following stimulation with immune-dominant peptides of early secreted antigenic target-6 (ESAT-6), culture filtrate protein-10 (CFP-10) or Bacille Calmette-Guerin, pleural fluid mononuclear cells expressed high levels of cytokines IFN-γ, IL-22 and IL-17 as revealed by mRNA and protein measurements. In addition, we showed that cytokines IFN-γ, IL-22 and IL-17 were produced in M. tuberculosis-specific immune response by distinct subsets of CD4+ T cells with the phenotype of CD45RA-CD62L-CCR7+CD27+ . Our results demonstrated for the first time that ESAT-6- and CFP-10-specific Th1, Th22 and Th17 cells existed in the patients with TBP and might play an essential role against M. tuberculosis infection. The findings of this study raised the possibility of unravelling the critical targets for therapeutic intervention in chronic inflammatory diseases such as TBP.

Reversal of the gastric effects of nicotine by nitric oxide donor treatment

Nicotine intensifies experimental gastric ulceration by reducing gastric mucosal blood flow (GMBF) and mucus. As both these parameters can be improved by nitric oxide (NO), we evaluated the impact of a NO donor in ethanol-induced gastric mucosal injury in rats administered nicotine. A nicotine solution or water was administered for 20 days to Sprague-Dawley rats. NO donor (isosorbide dinitrate) was given 60 and 10 min before preparation of ex vivo gastric chambers and exposure to ethanol. Chronic nicotine intake significantly reduced GMBF and gastric mucus content. Nicotine intensifies ethanol-induced gastric injury and short-term administration of NO donor failed to antagonize the ulcerogenic action from either nicotine or alcohol. In another study, rats drank nicotine solution for 20 days, after which the nicotine was withdrawn and replaced by water for 10 additional days. NO donor was provided during these last 10 days. The gastric effects of nicotine persisted for at least 10 days after nicotine was withdrawn but then these effects could be abolished by prolonged NO treatment. Nicotine reduces plasma nitrite level, but gastric mucosal MPO activity remained unchanged. Our data suggest that nicotine cessation plus a longer period of NO donor administration can completely abolish the gastric effects of nicotine.

Imaging features of enterohemorrhagic Escherichia coli colitis

OBJECTIVE

The purpose of this article is to define and illustrate the radiologic findings in patients with enterohemorrhagic Escherichia coli colitis.

CONCLUSION

Although not definitive, imaging studies in conjunction with an appropriate clinical history can aid in the early diagnosis of E. coli colitis and exclude surgical conditions. CT is more sensitive than conventional radiography for detection. Contiguous involvement, including the transverse colon, was seen in all patients. Because CT is becoming routine in the initial workup of patients with acute abdominal pain, it is important for the radiologist to suggest E. coli colitis in the proper setting.

Amniotic membrane surgery

Human amniotic membrane (AM) is composed of three layers: a single epithelial layer, a thick basement membrane, and an avascular stroma. Amniotic membrane has anti-adhesive properties and is felt to promote epithelialization and decrease inflammation, neovascularization, and fibrosis. Amniotic membrane transplantation (AMT) is currently being used for a continuously widening spectrum of ophthalmic indications. Amniotic membrane transplantation has been shown to be effective in the reconstruction of the corneal surface in the setting of persistent epithelial defects, sterile corneal ulcerations, and partial limbal stem cell (LSC) deficiency states, including those secondary to chemical or thermal burns. Amniotic membrane transplantation also has been used in conjunction with limbal stem cell transplantation (LSCT) both in a concurrent fashion as well as in preparation for LSCT. Amniotic membrane transplantation also has been used in place of conjunctival autografting after pterygium excision and to reconstruct the conjunctival surface after removal of conjunctival lesions. Most recently, ex vivo cultivation and expansion of limbal epithelial cells has been performed utilizing AM as a matrix. However, the superiority of AMT over other treatment modalities in many of these settings needs to be substantiated by controlled clinical trials.

Susceptibility to cerulein-induced pancreatitis in inducible nitric oxide synthase-deficient mice

Production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) has been proposed as a pathogenic factor in acute pancreatitis, but its role has still not been fully examined. The present study explored the role of iNOS in cerulein-induced acute pancreatitis using iNOS-deficient mice. Twelve- to 14-week-old male mice (C57B1/6 and iNOS-deficient) were administered cerulein by intraperitoneal (i.p.) injection at hourly intervals for 7 hours and killed 24 hours later after the first dose. Pancreatic wet weight, pancreatic myeloperoxidase (MPO) activity, and levels of plasma nitrite and serum amylase were measured. In another experiment isosorbide dinitrate (an NO donor) was given by oral gavage every 6 hours for 24 hours beginning simultaneously with cerulein injections in iNOS-deficient mice. Cerulein administration dose-dependently increased pancreatic wet weight, myeloperoxidase activity, and levels of nitrite and amylase in C57B1/6 mice. These parameters (except nitrite levels) were significantly intensified in iNOS-deficient mice. At the dose employed, cerulein failed to increase nitrite levels in iNOS-deficient mice. The susceptibility to cerulein toxicity in iNOS-deficient mice was abolished by NO donor treatment. NO release from an iNOS source appears to play a protective role in cerulein-induced pancreatitis. At least in part, NO may prevent neutrophil accumulation after cerulein administration.

Total splenic infarct due to Aspergillus and AIDS

Invasive aspergillosis is a rare but important cause of morbidity and mortality in patients with AIDS. In the majority of patients, invasive aspergillosis involves the lungs. Extrapulmonary involvement with total splenic infarction has not been previously described. We illustrate a patient who developed total splenic infarction and septic emboli to the brain from Aspergillus.

Total splenic infarct due to Aspergillus and AIDS

Invasive aspergillosis is a rare but important cause of morbidity and mortality in patients with AIDS. In the majority of patients, invasive aspergillosis involves the lungs. Extrapulmonary involvement with total splenic infarction has not been previously described. We illustrate a patient who developed total splenic infarction and septic emboli to the brain from Aspergillus.

HLA-DRB1 and tumor necrosis factor gene polymorphisms in Japanese patients with multiple sclerosis

We studied genetic polymorphisms in the tumor necrosis factor (TNF) region as well as HLA-DRB1 of 42 patients with Western-type multiple sclerosis (MS) and 38 with Asian-type MS in Japan. The sex ratio (Female:Male) was significantly higher in Asian than in Western type MS (3.8 vs. 1.3, P = 0.038). The frequency of HLA-DRB1 * 1501 allele in the Western-type MS group increased significantly compared with the control group, while Asian-type MS and control groups showed similar distribution in the frequencies of HLA-DRB1 alleles. No significant differences existed in the TNF region, however, including TNF-a microsatellite alleles. The results suggest that MS in Asians may present two different clinical and immunogenetic manifestations.

Genetic contribution of the tumor necrosis factor region in Guillain-Barré syndrome

We studied genetic polymorphisms in the tumor necrosis factor (TNF) region in 81 Japanese patients with Guillain-Barré syndrome (GBS) and 85 controls. A significantly higher frequency of the 100-base pair (bp) (TNFa2) allele of the TNFa microsatellite marker, which is associated with high TNF alpha production, existed in Campylobacter jejuni-positive (Cj+) GBS patients than in controls, suggesting the involvement of a genetic predisposition to high TNF alpha secretion in the development of C. jejuni-related GBS.

HLA and T-cell receptor gene polymorphisms in Guillain-Barré syndrome

OBJECTIVE

We examined a possible involvement of genetic factors influencing the development of Guillain-Barré syndrome (GBS).

METHODS

We studied T-cell receptor (TCR), alpha-chain constant (AC), and beta-chain variable (BV) gene polymorphisms using microsatellite markers and serologic HLA class I antigens, HLA-DRB1, and HLA-DQB1 alleles in 81 Japanese patients with GBS and 87 controls.

RESULTS

There were no significant differences in these genetic markers between GBS patients and controls. Subgrouping of GBS patients according to recent Campylobacter jejuni infection, the presence of anti-GM1 antibody in the sera, or their combinations also failed to reveal significant associations with these genetic markers. There was, however, a tendency for an increased frequency of HLA-DRB1*0803 in the C. jejuni + GM1 + GBS group, when compared with controls.

CONCLUSIONS

The data suggest that the roles of TCRAC, T-cell receptor beta-chain variable (TCRBV), HLA class I or class II in the development of GBS are not critical, and further research is necessary to clarify other genes encoded within the HLA region for genetic susceptibility to GBS.

Output loss or rehearsal loop? Output-time versus pronunciation-time limits in immediate recall for forgetting-matched materials

Forgetting during recall may be one limit on memory span. Output time and accuracy of immediate serial recall using spoken and keypress responses were measured for digit, letter, and word sets approximately matched in phonemic discriminability and in immediate recognition memory. Nonetheless, the materials differed from one another in recall span, in output time during recall, and in pronunciation time (speech rate). Recall output times accounted precisely and completely for the measured memory span for these matched materials. Pronunciation times are correlated with recall output times, but output time gives a slightly better account of recall accuracy. The output time equivalent to the rule that short-term memory span corresponds to the number of items that can be said in about 1.5-2 s is that span corresponds to the number of items that can be recalled in about 4-6 s. Additional variations in span reflect differential item interference.

The correlation of the weakening effect on gastric mucosal integrity by 5-HT with neutrophil activation

The effects of 5-hydroxytryptamine (5-HT) on ethanol-induced gastric mucosal damage and on epithelial and vascular integrity were investigated. Male Sprague-Dawley rats were administered with 5-HT (5 or 10 mg/kg, IP) 30 min prior to the challenge with ethanol (40% v/v, 10 ml/kg, PO). 5-HT dose dependently aggravated ethanol-induced injury in the gastric mucosa. Both xanthine oxidase (XO) and myeloperoxidase (MPO) activities in the mucosa were significantly increased with the high dose of 5-HT, which also potentiated the elevation of these enzyme activities by ethanol. However, the mucosal superoxide dismutase activity was left unaltered. In neutropenic (antineutrophil serum-treated) animals, the ethanol-induced gastric mucosal injury was significantly ameliorated, with or without the pretreatment of 5-HT (10 mg/kg). In addition, the effect of 5-HT on the activity of MPO, but not of XO, was also attenuated in these animals. In the ex vivo gastric chamber study on pentobarbital-anesthetized animals, volume of gastric secretion was significantly decreased in the 5-HT-treated groups, with further reduction after ethanol incubation. Transmucosal potential difference (PD) was significantly reduced in 5-HT-treated rats, which also potentiated the ethanol-induced drop in PD. Nevertheless, 5-HT dose dependently increased mucosal vascular permeability and further enhanced during ethanol incubation. These findings suggest that 5-HT adversely affects the defense mechanisms of the gastric mucosa by reducing the secretory function of the mucosal cells and to weaken the epithelial and vascular integrity. Neutrophil activation appears to be responsible for the detrimental effects of 5-HT partly through the elevation in MPO activity. The increase in mucosal XO activity by 5-HT may induce free radical production and possibly modulate the ulcerogenic processes.

Output loss or rehearsal loop? Output-time versus pronunciation-time limits in immediate recall for forgetting-matched materials

Forgetting during recall may be one limit on memory span. Output time and accuracy of immediate serial recall using spoken and keypress responses were measured for digit, letter, and word sets approximately matched in phonemic discriminability and in immediate recognition memory. Nonetheless, the materials differed from one another in recall span, in output time during recall, and in pronunciation time (speech rate). Recall output times accounted precisely and completely for the measured memory span for these matched materials. Pronunciation times are correlated with recall output times, but output time gives a slightly better account of recall accuracy. The output time equivalent to the rule that short-term memory span corresponds to the number of items that can be said in about 1.5-2 s is that span corresponds to the number of items that can be recalled in about 4-6 s. Additional variations in span reflect differential item interference.

Characterization of Campylobacter jejuni isolates from patients with Guillain-Barré syndrome

Campylobacter jejuni is a major pathogen preceding Guillain-Barré syndrome (GBS), and most C. jejuni isolates from GBS patients belong to Penner serotype 19 (heat-stable; HS-19). We analyzed sixteen independent clinical isolates from GBS patients, twelve of which belonged to HS-19, three to HS-2, and one to HS-4, using PCR-based RFLP analysis of a flagellin-A (flaA) gene. Two isolates from patients with Miller Fisher syndrome (MFS), and 27 from patients with uncomplicated enteritis were also examined. All HS-19 isolates, regardless of GBS, showed an identical pattern (Cj-1) by RFLP typing and were distinguishable from those of the other Penner serogroups. In contrast, HS-2 and HS-4 isolates were divided into several different RFLP groups, suggesting HS-19 strains are genetically distinctive among C. jejuni isolates. A DNA fingerprinting method also failed to detect any specific band pattern for GBS-related C. jejuni isolates. We examined relationships among anti-GM1 antibody titres in the sera of GBS patients, clinical forms of GBS, serotype of C. jejuni, and the presence of GM1-like structures in lipopolysaccharide (LPS) components from C. jejuni isolates by immunoblotting. HS-19 related GBS was significantly associated with elevated anti-GM1 antibody titers in the sera of the patients, but not associated with any clinical pattern of GBS. No significant correlations were found between anti-GM1 antibody and the pattern of disease, or between GBS-related C. jejuni strains and the presence of GM1-like structures. HS-19 strains seem to be unique among C. jejuni isolates, and HS-19-related GBS may provide an excellent model for clarification of the pathogenesis of GBS.

Neuropeptide Y induced feeding in the rat is mediated by a novel receptor

There are now six recognized neuropeptide Y (NPY) receptor subtypes (Y1-Y4 and two recently cloned distinct receptors labeled Y5), of which Y1 and one of the Y5's have been suggested could mediate the effect of NPY on feeding. The fragments NPY(2-36) and NPY(3-36), which bind Y1 only poorly, were injected intracerebroventricularly (icv) and found to have similar dose-response relationships to NPY in the stimulation of feeding. However NPY (13-36), which stimulates both Y2 and Y5, caused no increase in food intake, even at high doses. Maximal stimulation with the classical Y1 agonist [Pro34]-NPY produced only 50% of the maximum effect of NPY itself despite fully inhibiting adenylyl cyclase activity in vitro in a Y1 system. The novel fragment [Pro34]-NPY(3-36) is as effective at stimulating food intake as the classical Y1 analogue [Pro34]-NPY but bound to the Y1 receptor with only 1/20th of the affinity of NPY and failed to inhibit adenylyl cyclase through this receptor. [Pro34]-NPY(3-36) is therefore a relatively appetite-selective ligand. Coadministration of high dose NPY(13-36) and [Pro34]NPY did not enhance feeding compared with [Pro34]-NPY alone. In addition, the NPY Y1 receptor antagonist BIBP-3226, which does not bind Y2, Y4, or Y5 receptors, significantly reduced NPY induced feeding. These results indicate that the feeding effect of icv NPY involves a novel receptor and that it is functionally distinct from the recognized receptor subtypes.

PCR-based restriction fragment length polymorphism (RFLP) analysis and serotyping of Campylobacter jejuni isolates from diarrheic patients in China and Japan

A molecular typing approach for Campylobacter jejuni was applied with restriction fragment length polymorphism (RFLP) analysis of a 702-bp PCR-amplified portion of the flagellin-A (flaA) gene. We analyzed a total of 179 strains, including 69 independent clinical isolates from diarrheic patients in Japan, 85 isolates in China, and 25 heat-stable (HS) serotype strains by Penner and Hennessy (1980) J. Clin. Microbiol. 12, 732-737). Six AfaI, seven MboI, and five HaeIII RFLPs were found in the 702-bp flaA segment from the 179 strains. Using a combination of these three enzymes, 25 separate RFLP groups were recognized. While 59 of 154 (38.3%) strains obtained in Japan and China were nontypeable by the HS antigenic scheme, all but two of 154 (98.7%) could be typed by RFLP typing. All 11 isolates of HS-19 strains, which are frequently isolated from Guillain-Barré syndrome (GBS) patients, showed an identical RFLP pattern (Cj-1), and Cj-1 consisted only of HS-19 strains. This suggests that the HS-19:Cj-1 strain is distinct among C. jejuni strains. This molecular typing method provides a rapid and reliable typing scheme for epidemiological studies of C. jejuni, and may also be useful for the analysis of C. jejuni subtypes from GBS patients.

Wernicke-Korsakoff syndrome in Sydney hospitals: before and after thiamine enrichment of flour

OBJECTIVE

To estimate the incidence of Wernicke-Korsakoff syndrome (WKS) before and after the introduction of thiamine enrichment of bread flour in 1991.

DESIGN

Retrospective survey of hospital records. Patient records with the diagnostic codes for Wernicke's encephalopathy (WE) or Korsakoff's psychosis (KP) were reviewed and details of acceptable cases were entered onto a data form.

SETTING

All 17 major public general hospitals in the Sydney area (New South Wales), between 1978 and 1993.

OUTCOME MEASURES

Numbers of confirmed or probable diagnoses of WE, KP or WKS and associated deaths, patient demographic and social characteristics and alcohol intake.

RESULTS

1,267 patients with WKS were found, with 1,012 acute cases. Although numbers of acute cases may have started to fall before 1991, numbers for the last two years were the lowest of all the 16 years (P = 0.004). Cases of KP outnumbered those of WE by about 3:1 and men outnumbered women 4:1. The peak age was 60-64 years (17%) and beer was the most commonly cited alcoholic drink (71%). The red-cell transketolase test was seldom used for diagnosis (3% of acute cases).

CONCLUSIONS

The lower number of "acute" cases in 1992 and 1993 is consistent with a preventive effect of mandatory enrichment of bread with thiamine, but is not conclusive evidence. Longer follow-up of Sydney hospitals, results of postmortem examinations and follow-up in other areas of Australia are required.

Portal hypertension. Its effects on gastric function and ethanol-induced gastric mucosal damage in rats

The time-course effects of portal hypertension on gastric secretory function, mucosal blood flow, vascular permeability, and ethanol-induced gastric mucosal damage were examined in anesthetized rats. Partial ligation of the portal vein effectively produced portal hypertension one to three days later but the raised pressure returned to normal on the sixth day after ligation. This time-course effect coincided with reduced pepsin secretion and mucosal blood flow and also with potentiated ethanol-induced mucosal damage during the first to third days. These effects started to tail off on the sixth day. However, gastric acid output was significantly reduced on the third day, and this was strongest on the sixth day after operation. Portal vein ligation also reduced basal vascular permeability, which was markedly potentiated after ethanol treatment. It is concluded that: (1) portal vein blood pressure changes are a time-dependent process following ligation; (2) changes in gastric mucosal blood flow (GMBF) and lesion formation are closely related to portal hypertension; (3) gastric mucosal injury is associated with vascular damage, as evidenced by increased in vascular permeability; and (4) pepsin but not acid secretion is closely related to the state of the GMBF.

Characteristics, substrate analysis, and intracellular location of Saccharomyces cerevisiae UMP kinase

The yeast Saccharomyces cerevisiae SOC8 DNA fragment was isolated as a wildtype dominant suppressor of the cdc8 mutation. The SOC8 has previously been proved to be allelic with URA6, encoding the UMP kinase in yeast cells. The protein has been purified to homogeneity. In this report, we describe the characteristics of the UMP kinase from yeast. The yeast enzyme requires a divalent cation and is active over the entire range of pH from 6 to 9.5. The enzyme can use UMP and dUMP as phosphate acceptors with high activity; to a lesser extent, it can also use IMP, GMP, dGMP, 5-iodo-dUMP, XMP, and dTMP as substrates. ATP and dATP are the best phosphate donors; the enzyme could use GTP, dGTP, dCTP, and dTTP to some degree (30-50%). CTP and UTP were poor phosphate donors for the UMP kinase reaction (10-14%). Like other monophosphate kinases, UMP kinase contains a conserved nucleotide-binding site at its N-terminus following a cysteine residue, and its enzymatic activity is inhibited by sulfhydryl inhibitors such as 5,5'-dithio-bis(2-nitrobenzoic acid) and N-ethylmaleimide. Subcellular localization studies indicate that the UMP kinase locates primarily in the cytoplasm (approximately 80%) and also in the nucleus (approximately 20%), but not in the mitochondria. These results suggest that it may exert its function in the nucleus, such as in RNA synthesis, as well as in the cytoplasm, but not in the mitochondria. The presence of UMP kinase in the nucleus might facilitate its suppression of cdc8 mutant cells, which are defective in nuclear DNA synthesis.

Sodium valproate: quantitative EEG and serum levels in volunteers and epileptics

Twelve healthy adults and 12 epileptics had quantitative EEG tests while taking valproic acid. The results indicated that the total power of dominant frequency band and the frequency of dominant occipital rhythm were relatively stable in healthy awake adults. A single 400 mg oral dose of sodium valproate had similar influence on the total power of dominant frequency band in both healthy adults and epileptics. The total power of dominant frequency band tended to rise at 2 and 6 hours after medication in subjects with serum VPA concentrations reaching a peak after 2 hours. There was a tendency to rise at 4 and 8 hours in subjects with serum VPA concentrations which peaked after 4 hours. The curve of the total power with time had two peaks. A single oral dose of sodium valproate did not have a marked influence on the frequency of dominant rhythm in the occipital areas in healthy adults or in epileptics.

Protection by moxibustion against experimental hyperbilirubinemia and cholangitis in rats

The effects of moxibustion on experimental hyperbilirubinemia and cholangitis were studied in male rats (n = 33). The experimental group were treated with moxibustion, 18, 12 and 6 hours prior to and 6, 12 and 18 hours after challenge with oral alpha-naphthylisothiocyanate (ANIT, 100 mg per kg). Rats were sacrificed 48 hours after challenge. Serum and liver samples were taken for biochemical and histological analysis, respectively. The results revealed that rats treated with ANIT exhibited elevations in bilirubin, SGOT and SGPT as well as cholangitis. In rats receiving moxibustion and ANIT, biochemical and morphological parameters of liver injury were significantly reduced. Thus, this study shows that moxibustion therapy may be able to prevent ANIT-induced hyperbilirubinemia and cholangitis.

Saccharomyces cerevisiae nucleoside-diphosphate kinase: purification, characterization, and substrate specificity

Nucleoside-diphosphate kinase is an enzyme which catalyzes the phosphorylation of nucleoside diphosphates into the corresponding triphosphates for nucleic acid biosynthesis. In this communication, we describe the purification and characterization of nucleoside-diphosphate kinase from yeast. The purified protein appears to be homogeneous by sodium dodecyl sulfate-polyacrylamide gel analysis, with a molecular weight of about 17,000-18,000. An estimate from the fast protein liquid chromatography Superose 12 gel filtration shows a native molecular weight of about 68,000 to 70,000. The results suggest that yeast nucleoside-diphosphate kinase is composed of four subunits. Substrate specificity studies show that the relative activity of nucleoside diphosphates (NDP) as phosphate acceptors is in the order of dTDP greater than CDP greater than UDP greater than dUDP greater than GDP greater than or equal to dGDP greater than dCDP greater than dADP greater than ADP; and the relative activity of triphosphate donors is in the order of UTP greater than dTTP greater than CTP greater than dCTP greater than dATP greater than ATP greater than or equal to dGTP greater than GTP. The Km and Vm of dTDP, dGDP, dCDP, dUDP, CDP, and UDP have been determined. The rate constant studies indicate that the purified NDP kinase prefers using, to a slight extent, dTDP (approximately 800 min-1) as the substrate rather than other tested deoxyribo- and ribonucleotides (350-450 min-1). The broad substrate specificity and kinetic data suggest that the enzyme is involved in both DNA and RNA metabolism.

The mechanical hypothesis of excitation-contraction (EC) coupling in skeletal muscle

The mechanism of transmission in skeletal muscle EC coupling is still an open question. There is some indirect evidence in favour of the mechanical coupling hypothesis, deriving mostly from consideration of the structure of the Ca2+ release channel protein. A new functional approach is proposed, that consists in comparing the properties of the complete system--EC coupling in a skeletal muscle fibre--with those of the EC coupling molecules in bilayers. In this approach, those properties of the whole system that are not traceable to its constitutive molecules, are ascribed to the physiological interaction, and are expected to yield new information on the nature of this interaction.