[Phase â ¡ clinical trial of PD-1 inhibitor combined with chemotherapy for locally advanced resectable oral squamous cell carcinoma].

Objective: To explore the effectiveness and safety of programmed death 1(PD-1) inhibitory combined with chemotherapy as a neoadjuvant therapy for locally advanced resectable oral squamous cell carcinoma. Methods: This study was a randomized controlled phase Ⅱ trial. Patients recruited from Tianjin Medical University Cancer Institute and Hospital from July 2021 to February 2023 were randomly divided into two groups in a 1∶1 ratio: the experimental group (Toripalimab combined with albumin paclitaxel and cisplatin) and the control group (albumin paclitaxel and cisplatin); patients in both groups underwent three cycles of neoadjuvant therapy. After completion of neoadjuvant therapy, patients were evaluated and subsequent surgical treatment was performed. According to the completion of treatment, the analysis was conducted on both the full analysis set and the protocol set. The effectiveness and safety of treatments were evaluated. SPSS 20.0 software was used for statistical analysis. Results: A total of 41 cases with oral cancer were enrolled, including 26 males and 15 females, aged between 34 and 74 years old. There were 23 cases in the experimental group and 18 cases in the control group. A total of 23 cases completed neoadjuvant therapy and surgery according to the protocol. Experimental group and control group showed respectively the complete response rates of 1/19 and 0/17, the partial response rates of 13/19 and 8/17, the stage-down rates of 4/19 and 3/17, the pathologic complete response rate of 8/14 and 2/9, with no statistically significant differences in individual rates between two groups (P>0.05). The major pathological response rate of 13/14 in experimental group was higher than that of 2/9 in control group (P<0.05). The incidence of grade 3-4 adverse reactions related to treatment was low in both groups (4/23 vs. 3/18, χ2=0.13, P=0.72), and the most common serious adverse reactions in the experimental group were granulocyte deficiency and electrolyte disorder. There were no adverse reactions that affected subsequent surgical treatment or caused death, and the safety and tolerability were good. The median follow-up time was 15 months, and the one-year disease-free survival rate of the experimental group was higher than that of control group (92.86% vs. 77.78%, χ2=0.62, P=0.42), with a relative decrease of 87% in the risk of disease progression or death (P=0.029). For patients with programmed death-ligand 1(PD-L1) protein expression combined positive score≥20, the experimental group showed higher major pathological response rate than control group (5/5 vs. 0/4, P=0.03). Conclusion: The neoadjuvant therapy of immunotherapy combined with chemotherapy can improve the pathological remission of oral squamous cell carcinoma and the long-term survival benefits and the prognosis of patients.

LncRNA RPPH1 predicts poor prognosis and regulates cell proliferation and migration by repressing P21 expression in gastric cancer.

OBJECTIVE: The purpose of this study was to explore the expression and biological functions of long non-coding ribonucleic acid (lncRNA) ribonuclease P RNA component H1 (RPPH1) in gastric cancer (GC), and to analyze the correlations of lncRNA expression with the clinical features and prognosis of GC patients. PATIENTS AND METHODS: The relative expression of RPPH1 in tissue specimens from 60 GC patients was measured via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR), and the correlations of RPPH1 expression with tumor-node-metastasis (TNM) stage, lymph node metastasis, etc. in GC patients were analyzed. Then, qRT-PCR was performed to detect the relative expression level of RPPH1 in GC cells. Moreover, colony formation assay, 5-Ethynyl-2'-deoxyuridine (EdU) staining, wound-healing assay, and transwell assay were employed to investigate the influence of RPPH1 on GC cell functions. After interfering in the expression of RPPH1, the changes in p21 (CDKN1A, cyclin dependent kinase inhibitor 1A) expression were determined through qRT-PCR and Western blotting. RESULTS: It was shown in qRT-PCR assay results that the expression of RPPH1 was upregulated in 60 cases of GC tissues. Statistical analysis revealed that RPPH1 expression was positively correlated with the TNM stage, lymph node metastasis, and infiltration depth in GC patients. Besides, highly expressed lncRNA RPPH1 suggested poor prognosis of GC patients. Based on the results of qRT-PCR assay, the expression of RPPH1 in GC cells was upregulated. After interfering in RPPH1 expression, both colony formation assay and EdU staining indicated that the proliferative capacity of GC cells was repressed. Furthermore, it was manifested in the results of wound-healing and transwell assays that the migratory and invasive abilities of GC cells were weakened. Finally, the qRT-PCR and Western blotting assay results demonstrated that p21 expression was upregulated after interfering in the expression of RPPH1 in GC cells. CONCLUSIONS: The expression of lncRNA RPPH1 is upregulated in GC, suggesting that the prognosis of the patients is poor. Highly expressed RPPH1 promotes the proliferation and metastasis of GC cells by regulating p21 expression.

2Hz-electroacupuncture attenuates heroin-seeking behaviors via adjusts CB1-Rs and CB2-Rs expression in relapse-relevant brain regions of heroin self-administration rats.

Opiate addiction has a high rate of relapse. The accumulating evidence shows that electroacupuncture (EA) may be effective for the treatment of opiate relapse. However, the change of expression of CB1-Rs and CB2-Rs involve in 2Hz EA anti-relapse pathway is still unclear. To explore the changes of expression of CB1-Rs and CB2-Rs, heroin self-administration (SA) model rats were adopted and treated using 2Hz EA. The expressions of CB1-Rs and CB2-Rs were observed using immunohistochemistry method. The results showed that, compared with the control group, active pokes in the heroin-addicted group increased, while the active pokes decreased significantly in 2Hz EA group compared with heroin-addicted group. Correspondingly, the expression of CB1-Rs in prefrontal cortex (PFC), hippocampus (Hip), nucleus accumbens (NAc) and ventral tegmental area (VTA) all increased significantly while the expression of CB2-Rs in those relapse-relevant brain regions decreased obviously in heroin-addicted group when compared with the control group. In addition, the expression of CB1-Rs obviously decreased in the 2Hz EA group while the expression of CB2-Rs in those relapse-relevant brain regions increased significantly when compared with the heroin-addicted group. It indicated that 2Hz EA could attenuate the heroin-evoked seeking behaviors effectively. The anti-relapse effects of 2Hz EA might be related to the decrease of CB1-Rs and increase of CB2-Rs expression in relapse-relevant brain regions of heroin SA rats.

[Experimental observation of hyperbaric oxygen combined with radioactive seed implantation in the treatment of nude mice bearing esophageal squamous cell carcinoma].

Objective: To investigate the effect and mechanism of hyperbaric oxygen combined with radioactive seed implantation in the treatment of esophageal squamous cell carcinoma. Methods: Subcutaneous tumor model of esophageal squamous cell carcinoma using TE-8 cells was established. Tumor bearing Balb/c(nu/nu) mice (60 mice) were divided into four groups, Cont group that treated with normal oxygen level, HBO group that treated with hyperbaric oxygen, RSI group that treated with radioactive seed implantation, and HBO+ RSI group that treated with hyperbaric oxygen combined with radioactive seed implantation. Tumor volume ratio and mean survival time of tumor bearing mice were observed. Pathological changes of tumor tissue after treatment were observed by hematoxylin eosin (HE) staining. Enzyme linked immunosorbent assay kit was used to detect oxidative stress. Apoptosis related proteins were detected by Western blot. Results: After treatment, the tumor volume ratio of HBO+ RSI group was 3.51±0.80 and was significantly lower than that of Cont group, HBO group, and RSI group (P<0.05). The mean survival time of HBO+ RSI group tumor bearing mice was 62 d and was significantly longer than that in Cont group, HBO group, and RSI group (P<0.05). HE staining showed that the pathological changes of tumor tissues were most obvious in HBO+ RSI group. After treatment, the MDA and Bax levels in nude mice of HBO+ RSI group were significantly higher than those in Cont group, HBO group and RSI group, but the levels of GSH, SOD and Bcl-2 were significantly lower than those of Cont group, HBO group and RSI group (P<0.05). Conclusion: Hyperbaric oxygen combined with radioactive seed implantation could slow tumor growth and increase survival time of tumor bearing mice. The possible mechanism is that hyperbaric oxygen combined with radioactive seed implantation can improve the oxidative stress response and the expression of apoptosis protein in tumor bearing nude mice.

Gene expression profiling of human synovial sarcoma cell line (Hs701.T) in response to IL-1beta stimulation.

OBJECTIVE: Synovial sarcoma (SS) is a malignant mesenchymal tumor that accounts for 5-10% of all soft tissue sarcoma. IL-1beta, a pleiotrophic cytokine, has been found in the tumor microenvironment which plays crucial roles in the pathogenesis of tumors. METHODS: In this study, we used Hs701.T as a cellular model to study the short-term (4-h) and long-term (48-h) stimulatory effect of IL-1beta on cell proliferation and differential gene expression. RESULTS: The results showed that IL-1beta can stimulate cell proliferation through activation of NF-kappaB and AP-1 transcription factors; sequentially triggers the expression of genes related to tumor progression. The microarray data indicated that most of the up-regulated genes were related to tumor progression. Five candidate genes which are involved in the mediation of proliferation (IL-6), apoptosis (Hsp27 and Daxx), and angiogenesis (PlGF and SPARC) were further validated by RT-PCR. CONCLUSION: These findings may be useful for understanding the pathogenesis of synovial sarcoma.

Volume-localized two-dimensional correlated magnetic resonance spectroscopy of human breast cancer.

A localized 2D correlation spectroscopic sequence (L-COSY) was implemented and applied in human breast cancer in vivo to evaluate the water to fat (both saturated and unsaturated) ratios and also to identify choline. Being in agreement with the conventional 1D magnetic resonance spectroscopy (MRS) results, elevated water to lipids ratios were found in breast cancers and choline was observed only in a few cancer patients.

The effects of glucose-induced oxidative stress on growth and extracellular matrix gene expression of vascular smooth muscle cells.

Vascular smooth muscle cell (VSMC) dysfunction plays a role in diabetic macrovasculopathy and this may include abnormalities in growth characteristics and the extracellular matrix. As the actual mechanisms by which glucose induces VSMC dysfunction remain unclear, the aim of this study was to assess the potential role of glucose-induced oxidative stress. Porcine aortic VSMCs were cultured for 10 days in either 5 mmol/l normal glucose or 25 mmol/l D-glucose (high glucose). There was evidence of oxidative stress as indicated by a 50% increase in intracellular malondialdehyde (p < 0.05), increased mRNA expression of CuZn superoxide dismutase and Mn superoxide dismutase (by 51% and 37% respectively, p < 0.01) and a 50% decrease in glutathione in 25 mmol/l D-glucose (p < 0.001). Growth was increased by 25.0% (p < 0.01). mRNA expression of extracellular matrix proteins (collagens I, III, IV and fibronectin) was not altered by high glucose in these experimental conditions. Repletion of glutathione with N-acetyl L-cysteine (1 mmol/l) in VSMC grown in high glucose was associated with reduction in malondialdehyde and restored growth to that of normal glucose. The water soluble analogue of vitamin E, Trolox (200 mumol/l), reduced malondialdehyde concentrations, but had no effect on glutathione depletion or the increased growth rate seen with high glucose. The addition of buthionine sulphoximine (10 mumol/l) to VSMC cultured in normal glucose reduced glutathione, increased malondialdehyde and increased growth to a similar extent as that found in high glucose alone. These results suggest that thiol status, rather than lipid peroxides, is a key factor in modulating VSMC growth and that mRNA expression of extracellular matrix proteins is not increased in VSMC under conditions of glucose-induced oxidative stress.

Glucose-induced oxidative stress in vascular contractile cells: comparison of aortic smooth muscle cells and retinal pericytes.

Free radical-mediated damage to vascular cells may be involved in the pathogenesis of diabetic vasculopathy. The aim of this study was to compare the extent of glucose-induced oxidative stress in both vascular smooth muscle cells (VSMCs) and pericytes and the effect on antioxidant enzyme gene expression and activities. Porcine aortic VSMC and retinal pericytes were cultured in either 5 or 25 mmol/l glucose for 10 days. Intracellular malondialdehyde (MDA) was measured as a marker of peroxidative damage, and mRNA expression of CuZn-SOD, MnSOD, catalase, and glutathione peroxidase (GPX) were measured by Northern analysis. Glutathione (GSH) was also measured. There was a significant increase in MDA in VSMCs in 25 mmol/l glucose (1.34 +/- 0.11 vs. 1.88 +/- 0.24 nmol/mg protein, 5 vs. 25 mmol/l D-glucose, mean +/- SE, n = 15, P < 0.01), but not in pericytes (0.38 +/- 0.05 vs. 0.37 +/- 0.05 nmol/mg protein, n = 11). There was a significant decrease in GSH in both cell types (VSMC, 1.40 +/- 0.13 vs. 0.69 +/- 0.12 nmol/mg protein, n = 15, P < 0.001; pericytes, 1.97 +/- 0.17 vs. 0.94 +/- 0.16 nmol/mg protein, n = 11, P < 0.001). mRNA expression of CuZnSOD and MnSOD was increased only in VSMCs (by 58.5 +/- 8.1 and 41.0 +/- 6.9%, respectively, n = 8, P < 0.01). CuZnSOD protein was increased by approximately 120% (P < 0.00001). None of the antioxidant enzyme activities was altered between 5 and 25 mmol/l glucose in either cell type. Both MnSOD activities and GSH concentrations were higher in pericytes compared with VSMC under basal (5 mmol/l) conditions (P < 0.05 and P < 0.02, respectively). These results demonstrate glucose-induced reduction of GSH in both cells, but only in VSMC is there evidence of oxidant damage in the form of lipid peroxidation, implying significant differences in intracellular responses to glucose between contractile cells in the macro- and microvasculature.

Folding proteins with a simple energy function and extensive conformational searching.

We describe a computer algorithm for predicting the three-dimensional structures of proteins using only their amino acid sequences. The method differs from others in two ways: (1) it uses very few energy parameters, representing hydrophobic and polar interactions, and (2) it uses a new "constraint-based exhaustive" searching method, which appears to be among the fastest and most complete search methods yet available for realistic protein models. It finds a relatively small number of low-energy conformations, among which are native-like conformations, for crambin (1CRN), avian pancreatic polypeptide (1PPT), melittin (2MLT), and apamin. Thus, the lowest-energy states of very simple energy functions may predict the native structures of globular proteins.

Resonance Raman study on the iron-sulfur centers of Desulfovibrio gigas aldehyde oxidoreductase.

Resonance Raman spectra of the molybdenum containing aldehyde oxidoreductase from Desulfovibrio gigas were recorded at liquid nitrogen temperature with various excitation wavelengths. The spectra indicate that all the iron atoms are organised in [2Fe-2S] type centers consistent with cysteine ligations. No vibrational modes involving molybdenum could be clearly identified. The features between 280 and 420 cm-1 are similar but different from those of typical plant ferredoxin-like [2Fe-2S] cluster. The data are consistent with the presence of a plant ferredoxin-like cluster (center I) and a unique [2Fe-2S] cluster (center II), as suggested by other spectroscopic studies. The Raman features of center II are different from those of other [2Fe-2S] clusters in proteins. In addition, a strong peak at ca. 683 cm-1, which is not present in other [2Fe-2S] clusters in proteins, was observed with purple excitation (406.7-413.1 nm). The peak is assigned to enhanced cysteinyl C-S stretching in center II, suggesting a novel geometry for this center.

[Serum lipid-associated sialic acid (LSA) in diagnosing and monitoring ovarian cancer].

Serum from 161 patients with ovarian cancer, 28 patients with benign gynecologic disorders and 22 healthy women, was assayed for levels of tumor marker LSA, which were compared with CA125. The results showed that in the patients with ovarian cancer, the sensitivities of LSA and CA125 for the patients prior to surgery were 83.0% and 92.5%, respectively; the sensitivities for the recurrent patients after surgery were 73.7% and 82.5% respectively. A total sensitivity of 89.5% was obtained by combination of both markers. The positive predictive value of LSA and CA125 for the patients with suspected tumor recurrence were 89.4% and 100%, respectively, and their corroborative rate with the postoperative courses were 94.4% and 100%, respectively. Thus serum assay of LSA, can be used in monitoring patients with ovarian cancer. The technique for determination of serum level of LSA is much more simple and less expensive than the radioimmuno-assay of serum level of CA125.

Isolation and identification of a protoheme IX derivative released during autolytic cleavage of human myeloperoxidase.

Myeloperoxidase (MPO) is a functionally important component of the normal human neutrophil host defense system. This enzyme possesses a dimeric structure composed of two heavy-subunit/light-subunit protomers, with a heme-like prosthetic group covalently linked to each heavy subunit. Although MPO exhibits unusual spectral and enzymatic properties, the nature of the prosthetic group and its mode of linkage with the apoenzyme have not been determined. In an earlier report (K.L. Taylor, J. Pohl, and J.M. Kinkade, Jr. (1992) J. Biol. Chem. 267, 25282-25288), characterization of the autolytic cleavage of MPO led to the proposal that the prosthetic group was covalently linked to the apoenzyme via a methionyl sulfonium bond with Met409. In the present study, we have demonstrated that autolytic cleavage of MPO, followed by protease digestion under nonreducing conditions, effects the release of a macrocycle with visible and Raman spectral properties consistent with that of a protoheme IX derivative. Mass spectrometric analysis, in conjunction with metabolic labeling studies and recent X-ray crystallographic data, have led to the structural assignment of this macrocycle as 1,5-dihydroxymethyl-3,8-dimethyl-4-vinyl-2-(2'-methylthio) ethenylporphine-6,7-dipropionic acid-iron complex. Based on the mechanism of methionyl sulfonium bond cleavage, this structure is consistent with our earlier proposal that the MPO prosthetic group is covalently linked to the enzyme via a methionyl sulfonium bond and suggests that this linkage occurs through a peripheral vinyl substituent.

Methoxypsoralen phototherapy of transitional cell carcinoma.

OBJECTIVES: The goal of this research was to assess whether methoxypsoralen compounds in combination with ultraviolet light were effective in preventing cellular proliferation in an in vitro model of human transitional cell carcinoma. METHODS: Three methoxypsoralen compounds, 5-methoxypsoralen (5-MOP), 8-methoxypsoralen (8-MOP), and 4'-aminomethyl 4,5'-8'-trimethylpsoralen (AMT), were added in vitro to T-24 transitional cell carcinoma cells. Psoralens directly bind to DNA, cross-linking the strands when exposed to ultraviolet light and thereby prevent cellular division. RESULTS: In vitro activity was demonstrated utilizing AMT and ultraviolet radiation at 320 to 340 nm, preventing cellular proliferation in T-24 transitional cell carcinoma. CONCLUSIONS: Methoxypsoralen compounds in combination with ultraviolet light are effective in preventing proliferation of bladder carcinoma cells in vitro. This therapy may prove to be effective in clinical early stage transitional cell carcinoma and warrants further assessment.

The bovine desmocollin family: a new gene and expression patterns reflecting epithelial cell proliferation and differentiation.

We have discovered a third bovine desmocollin gene, DSC3, and studied expression of all three desmocollin genes, DSC1, 2, and 3, by Northern blotting, RT-PCR and in situ hybridization. DSC1 is strongly expressed in epidermis and tongue papillae, showing a "skin"-type pattern resembling that previously described for keratins 1 and 10. Expression is absent from the epidermal basal layer but appears in the immediate suprabasal layers and continues uniformly to the lower granular layer. In tongue epithelium, expression is suprabasal and strictly localized to papillae, being absent from interpapillary regions. In other epithelial low level DSC1 expression is detectable only by RT-PCR. The distribution of Dsc1 glycoproteins, detected by an isoform-specific monoclonal antibody, closely reflects mRNA distribution in epidermis and tongue. DSC2 is ubiquitously expressed in epithelia and cardiac muscle. In stratified epithelia, expression appears immediately suprabasal, continuing weakly to the lower granular layer in epidermis and to just above half epithelial thickness in interpapillary tongue, oesophageal, and rumenal epithelia. DSC3 expression is restricted to the basal and immediately suprabasal layers in stratified epithelia. In deep rete ridges DSC expression strikingly resembles the distribution of stem, transit-amplifying, and terminally differentiating cells described by others. DSC3 expression is strongly basal, DSC2 is strong in 5-10 suprabasal layers, and then weakens to be superseded by strong DSC1. These results suggest that desmocollin isoform expression has important functional consequences in epithelial proliferation, stratification, and differentiation. The data also provide a standard for nomenclature of the desmocollins.

A Raman study of the binding of Fe(III) to ATP and AMP.

ATP-Fe and AMP-Fe complexes in water (H2O and 2H2O) at pH 7.5 were studied using Raman spectroscopy. Parallel and perpendicular polarization spectra were recorded in the spectral range 200-1650 cm-1, and the depolarization ratios for most of the bands were calculated. The changes in the frequencies, intensities and depolarization ratios of the ATP and AMP bands after the addition of FeCl3 showed that the adenine moiety, in addition to the phosphate(s), was involved in the binding of Fe to both ATP and AMP. Direct interactions of Fe(III) with the phosphate chain and the N-7 nitrogen and indirect interaction (via water molecules) with the amide group were proposed for the ATP-Fe complex. In contrast, direct interaction with the phosphate group and indirect interaction with the amide group were observed for the AMP-Fe complex. The different interactions of the two complexes suggest an 'anti' conformation for the ATP-Fe complex and a 'syn' conformation for the AMP-Fe complex. The strong binding of Fe to ATP compared with AMP and the difference in the conformation of the ATP-Fe and the AMP-Fe complexes may be significant in the pathway of Fe release in mitochondria.

Effect of N-alkyl substituents on the DNA binding properties of meso-tetrakis (4-N-alkylpyridinium-4-yl)porphyrins and their nickel derivatives.

Resonance Raman, NMR, and visible spectroscopies, as well as viscosity and equilibrium dialysis studies were used to assess the effect of the N-alkyl substituent of meso-tetrakis(4-N-alkylpyridinium-4-yl)porphyrin cations on DNA binding. The DNAs studied include the native DNA, calf thymus DNA (CT DNA), the synthetic polynucleotides [poly(dGdC)]2 and [poly(dAdT)]2, and the oligonucleotide d(TATACGTATA)2. Both the porphyrins and the metalloporphyrins containing Ni(II) were examined with the N-alkyl = propyl (TPrpyP(4) and NiTPrpyP(4)) and 2-hydroxyethyl (TEtOHpyP(4) and NiTEtOHpyP(4)). The results were compared to those from the parent porphyrins with the N-methyl substituent (TMpyP(4) and NiTMpyP(4)). For almost all the comparisons made, the new porphyrin cations gave results very similar to those for the TMpyP(4) species. The resonance Raman study indicated that for the three DNA polymers all the Ni species were in the four-coordinate form when bound to all three polymers. It is suggested that both TPrpyP(4) and TEtOHpyP(4) bind to GC regions of DNA in the same intercalative manner as TMpyP(4) with the N-alkyl substituent extended into the solvent. For AT regions of DNA, the binding of TPrpyP(4) and TEtOHpyP(4) is nonintercalative, as found previously for TMpyP(4). The NiPrpy(4) and NiTEtOHpyP(4) cations bind to these polymers in a similar manner to the apo-porphyrins. The similar Raman spectral changes for the three Ni porphyrins upon addition of [poly(dAdT)]2 suggest that partial intercalation is not occurring because models indicate that it would be difficult to accommodate the bulkier N-alkyl substituents.

Classical Raman spectroscopic studies of NADH and NAD+ bound to liver alcohol dehydrogenase by difference techniques.

We report the Raman spectra of reduced and oxidized nicotinamide adenine dinucleotide (NADH and NAD+, respectively) and adenosine 5'-diphosphate ribose (ADPR) when bound to the coenzyme site of liver alcohol dehydrogenase (LADH). The bound NADH spectrum is calculated by taking the classical Raman difference spectrum of the binary complex, LADH/NADH, with that of LADH. We have investigated how the bound NADH spectrum is affected when the ternary complexes with inhibitors are formed with dimethyl sulfoxide (Me2SO) or isobutyramide (IBA), i.e., LADH/NADH/Me2SO or LADH/NADH/IBA. Similarly, the difference spectra of LADH/NAD+/pyrazole or LADH/ADPR with LADH are calculated. The magnitude of these difference spectra is on the order of a few percent of the protein Raman spectrum. We report and discuss the experimental configuration and control procedures we use in reliably calculating such small difference signals. These sensitive difference techniques could be applied to a large number of problems where the classical Raman spectrum of a "small" molecule, like adenine, bound to the active site of a protein is of interest. The spectrum of bound ADPR allows an assignment of the bands of the bound NADH and NAD+ spectra to normal coordinates located primarily on either the nicotinamide or the adenine moiety. By comparing the spectra of the bound coenzymes with model compound data and through the use of deuterated compounds, we confirm and characterize how the adenine moiety is involved in coenzyme binding and discuss the validity of the suggestion that the adenine ring is protonated upon binding. The nicotinamide moiety of NADH shows significant molecular changes upon binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of low temperature to arrest degradation of 14C-adenosine 5'-diphosphate by human plasma in the presence of EDTA.

Degradation of 14C-ADP in human platelet-rich and platelet-poor plasmas was studied. Three procedures were tested to determine which method was most effective in "stopping" enzyme reactions. One involved the immediate addition of perchloric acid to the reaction mixture at the end of the incubation period. Another involved "stopping" enzyme reactions at 0 degree C for about 20 min before the addition of perchloric acid. The third involved adding EDTA (10 mM final concentration) to "stop" the reactions at the end of incubation. The protein-free extracts from the plasmas were processed for adenine nucleotide assays by thin-layer chromatography. Addition of perchoric acid was most effective. Low temperature did not stop degradation of 14C-ADP in plasma even in the presence of EDTA. 14C-ADP was converted primarily to 14C-AMP. ADPase activity was the same in platelet-rich and platelet-poor plasmas. We conclude that the addition of EDTA and the cooling of plasma did not completely stop the enzymic degradation of ADP.

Effect of oral aspirin on "ecto-ATPase" activity of washed human platelets.

Aspirin is a potent inhibitor of the platelet release reaction and the accompanying second phase of platelet aggregation. The platelet release reaction is an active, energy-dependent process which appears to require ATP. Eight men ingested 0.32 gm of aspirin daily for 7 days. Although the second phase of 1.7 micron ADP-induced platelet aggregation was absent after aspirin ingestion, the "ecto-ATPase" activities of washed human platelet suspensions were not significantly different before and after ingestion of aspirin. This suggests that the effect of aspirin on the second phase of platelet aggregation is not mediated through inhibition of "ecto-ATPase".

Effect of aspirin on exercise-induced angina.

Suspecting that platelet thromboemboli could play a role in the pathogenesis of myocardial ischemia, we did a random-order, double-blind, crossover study of the effect of the platelet aggregation inhibitor, aspirin, on treadmill exercise-induced angina in 13 men with coronary artery disease. Although collagen-induced platelet aggregation and the second phase of adenosine diphosphate (ADP)-induced platelet aggregation were significantly decreased and the rate of disaggregation of ADP-induced platelet aggregates was significantly increased after 650 mg aspirin in buffered solution, there was no delay in onset of exercise-induced angina, change in heart rate-blood pressure product at onset of angina, or change in S-T segment depression at onset of angina. Regardless of whether the patients had received placebo or aspirin on the preceding day, treadmill exercise until angina was followed by no changes in platelet aggregation or disaggregation, platelet count in blood or platelet-rich plasma, or of the plasma concentration of nonesterified fatty acids.