Chemicomechanical transduction performed by enzymes activated by polymers

Kinetic models for the mode of action of processive and non-processive DNA-helicases are detailed. Fluxes at the steady state are analyzed, and the random walk of the enzymes on the DNA is studied in connection with the rate constants of the chemical reactions involved in the transformation of substrate to products. Finally, the constants of the kinetic model for the processive helicase are related to the parameters of an analogous viscoelastic model.

Preliminary observations on dissolution and bioavailability of triamterene-hydrochlorothiazide combination products

The dissolution profiles of two brands of triamterene-hydrochlorothiazide (TRM-HCT) combination tablets and two brands of TRM-HCT combination capsules were studied using the USP paddle method at 100 rev min-1 in acid medium (0.1N). The tablets represent two products marketed in Germany, whereas the capsules represent the approved innovator's product and an unapproved generic product. The tablets dissolved almost 100 per cent in 15 min whereas the capsules dissolved less than 25 per cent in 60 min. A pilot bioavailability study was carried out in four normal healthy male volunteers. Urine samples were collected over a 48 h period and analysed for TRM, its major metabolite TRM-sulfate, and HCT using HPLC methods. The dissolution characteristics of TRM can be associated with the total drug excretion (absorption) of the product. On the other hand, the excretion (absorption) of HCT was independent of dissolution characteristics of the products. However, in TRM-HCT combination product, there appears to be a 50 per cent reduction in HCT excretion (absorption) when compared to the reported excretion (absorption) from a marketed single-entity product.

Inaccuracy of angiography in the diagnosis of carotid ulceration

It is generally stated that ulceration of the carotid bifurcation plaque may give rise to embolization and symptoms of cerebral ischemia. It has been suggested that prophylactic carotid endarterectomy is indicated in asymptomatic patients if the angiogram is interpreted as showing ulceration. We therefore determined the accuracy of the radiologic diagnosis of ulceration by comparing the radiologic and morphologic findings in 155 carotid endarterectomies. Ulceration was diagnosed in 54% of the angiograms and 47% of the surgical specimens and was not related to the degree of stenosis. Angiography had a sensitivity of 73%, a specificity of 62% and an overall accuracy of 67%. For the non-flow-restrictive lesions these figures were 65%, 66%, and 66%. If surgery were based on the angiographic diagnosis of ulceration in plaques with less than 50% stenosis, 16 out of 42 operations (38%) would have been done unnecessarily. Variability of the angiographic diagnosis of ulceration is also shown by a high interobserver variability; two sets of two authors read the angiograms independently and disagreed in 24% of the cases. The decision to operate should not depend entirely upon the angiographic diagnosis of ulceration.

Prolymphocytic leukemia: postmortem findings after long-term survival

A patient had prolymphocytic leukemia and survived for 44 months. A partial remission for more than 11 months and a short complete remission were induced by agents commonly used for the treatment of acute myelocytic leukemia. However, surface markers identified the disease as of B-cell origin.

Lectin- and ionophore-stimulated Ca2+ influx in murine lymphocytes: inhibition by disialoganglioside

Gangliosides suppress lymphocyte mitogenesis when added exogenously to the cells. On the premise that the mechanism of ganglioside action may be an interference with primary induction events, mitogen-induced 45Ca2+ influx in murine lymphocytes was studied. Disialoganglioside (GD1a) at physiopathological concentrations inhibits concanavalin A-induced 45Ca2+ uptake as well as blast transformation. The suppressive action of GD1a is both concentration dependent (50% suppression at 13 microM) and very rapid (within 1 min). GD1a is not cytotoxic nor does it significantly alter the rate of Ca2+ efflux. The uptake studies were extended to A23187, a compound with mitogenic and specific divalent cation ionophore activities. Ca2+ uptake by lymphoid cells from AKR/J, Swiss, and CBA mice is stimulated by A23187; and GD1a, in a dose-dependent manner, inhibits the ionophore-induced 45Ca2+ influx. Pretreatment of thymocytes with GD1a renders the cells greatly insensitive to the subsequent ionophore activity of A23187. The results suggest that exogenous gangliosides may function as an inhibitor of some of the mitogen-triggered early events, including Ca2+ metabolism, and thus influence the immunological behavior of intact lymphoid cells.

Febrile transfusion reaction following initial transfusion in a man with immunoblastic lymphadenopathy and granulocyte autoantibodies

A 69-year-old man with immunoblastic lymphadenopathy and autoimmune hemolytic anemia who had no previous exposure to blood products developed a severe febrile nonhemolytic transfusion reaction following the initial infusion of packed red blood cells. The reaction recurred with transfusion of packed red blood cells, but not when freeze-thawed red blood cells were used. Immunofluorescence techniques demonstrated granulocyte antibodies in his serum and on the surface of his granulocytes. Circulating immune complex, HLA, and platelet antibodies were not present. The granulocyte antibodies fluctuated in titers with disease activities, and could be completely removed from the serum by autologous granulocyte absorption. We conclude that our patient had granulocyte autoantibodies which probably produced febrile transfusion reactions.

The nucleotide sequence of the cloned rpoD gene for the RNA polymerase sigma subunit from E coli K12

We have determined the nucleotide sequence of the rpoD gene which codes for the sigma subunit of RNA polymerase from E. coli K12. The gene, which we formerly cloned as a HindIII restriction fragment in the transducing phage, charon 25, was recloned into several plasmids. We have determined a 2600 base pair DNA sequence which includes the entire structural gene for sigma. The resulting amino acid sequence agrees with previous information obtained about sigma including the amino acid composition, partial sequence data for the N-terminus, the highly acidic nature of the polypeptide, and the cleavage pattern at cysteines. The molecular weight of 70,263 daltons calculated for the 613 amino acid polypeptides is significantly lower than had been determined previously by SDS polyacrylamide gel analysis.

Influence of pancreatic duct ligation on gastric acid secretion

The influence of pancreatic duct ligation (PDL) on gastric secretion was investigated in dogs with a Heidenhain pouch. A test meal was given to the dogs before PDL, and following PDL the dogs were administered with the test meal mixed with pancreatic enzymes and with the test meal alone in succession. The responses to the test meal were examined in the control period and every one week for a period of 1 to 6 weeks following PDL to identify the changes in gastric acid secretion, serum gastrin levels, immunoreactive glucagon (IRG) levels and immunoreactive insulin (IRI) levels. Gastric acid secretion in response to food stimulations markedly increased after PDL. However, the acid secretion was significantly inhibited by the administration of pancreatic enzymes. Serum gastrin levels began to increase from the second week and continued to increase until the sixth week after PDL, revealing no effect of pancreatic enzymes. IRG levels also increased following PDL, particularly in cases administered with pancreatic enzymes. IRI levels were higher at the first week of PDL than before PDL, but tended to decrease thereafter. It is assumed that gastric hypersecretion after PDL would have complicated relations with IRG, gastric inhibitory polypeptide (GIP) as well as with antral gastrin.

Effect of human plasma apolipoproteins on the activity of purified lecithin: cholesterol acyltransferase

An active preparation of lecithin: cholesterol acyltransferase (LCAT, EC 2.3.1.43) was isolated from human plasma by density ultracentrifugation, high-density lipoprotein affinity chromatography, DEAE-Sepharose and hydroxylapatite chromatography. This enzyme preparation gave a single band on polyacrylamide gel electrophoresis in 8 M urea and on sodium dodecyl sulfate gel electrophoresis. Upon analytical isoelectric focusing the enzyme separated into at least five isoforms with isoelectric points ranging from 5.1 to 5.5. The enzyme with an apparent molecular weight of 66,000 +/- 2,000 was characterized by a high content of glutamic acid, aspartic acid, leucine and glycine and contained approximately 31 moles of glucosamine/10(3) moles of protein and no galactosamine. The purified enzyme, stored at 20-40 microgram/ml at 4 degrees C, had a half-life of 26 +/- 4 days. The effect of purified human plasma apolipoproteins A-I, A-II, C-I, C-II, C-III and D on the activity of purified LCAT was studied, using egg-yolk lecithin (40 microM): cholesterol (10 microM) vesicles prepared in 1.25% ethanol in the absence or presence of 0.5% albumin. Addition of albumin to the incubation mixture nearly doubled the esterification rate of LCAT with A-I as activator (n=4), whereas it inhibited esterification by approximately 35% (n=3) if C-I was the activator. Maximum activation by C-I yielded only 13 +/- 6% (vesicles with albumin) or 42 +/- 5% (vesicles without albumin) of the LCAT activity obtained with A-I. Each of the apoproteins A-II, C-II, C-III and D inhibited the LCAT reaction in the presence of A-I or C-I at concentrations needed for maximal activation. Contrary to previous work, apolipoprotein D does not appear to be an activator of LCAT. LCAT activity is significantly affected by albumin and the apolipoproteins A-II, C-II, C-III, and D.

CT contrast enhancement in cerebral infarction

Computed tomography was used to study 100 patients with ischemic cerebral infarcts. All cases were documented by autopsy, radionuclide imaging, cerebral angiography, or clinical course. Vascular distribution of infarcts was varied and included infarcts of cerebral hemispheres, basal ganglia, and cerebellum. Distinct patterns of enhancement are seen following administration of intravenous contrast material: predominantly peripheral, central, homogeneous, or heterogeneous. Enhancement of the infarcted area usually occurs 1-4 weeks after the onset of clinical symptoms, but was seen as early as the first day or as late as several months after the onset of symptoms. Infarcts showing contrast enhancement may or may not revert to a nonenhanced pattern on follow-up examination for several months. Lesions demonstrating contrast enhancement in cerebrovascular disease may at times be indistinguishable from tumor. Contrast enhancement was the only manifestation of infarction in some instances, and an infarcted area may be completely missed if a postcontrast examination is not performed.

An analytical approach to the determination of optimal phasing for external counterpulsation

An inhomogeneous linear one-dimensional mathematical model is constructed as a conceptual approach to the study of the effects of External Counterpulsation (ECP) on the pressure and flow at the root of the aorta. The optimal operation of ECP is defined by two conditions: (1) minimization of the mean systolic pressure; and (b) maximization of the ratio of diastolic area over systolic area under the total pressure curve. The phase shift of the external pressure is determined so as to satisfy these two requirements. It is demonstrated within our approximation that with a given magnitude of external pressure, the phase shifts that satisfy these two requirements are the same. These phase shifts are linear functions of the systolic fraction of the total cardiac period, and depend on the time for the external wave to travel from the site of application up the vascular bed to the root of the aorta, plus the reflection contributions. Even though these results are derived from a simple model far from the complexity of the actual vasculature, the basic concepts would remain valid even if more complex mathematical treatments would have been used.