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Biomedical subjects

P Friedman

Publications and source records attributed to P Friedman.

At least 37 records · Page 2Linked to original sources
PubMed1996

Conversion of lysophospholipids to cyclic lysophosphatidic acid by phospholipase D.

Phospholipase D from Streptomyces chromofuscus hydrolyzes lysophosphatidylcholine or lysophosphatidylethanolamine in aqueous 1% Triton X-100 solution. In situ monitoring of this reaction by 31P NMR revealed the formation of cyclic lysophosphatidic acid (1-acyl 2,3-cyclic glycerophosphate) as an intermediate which was hydrolyzed further by the enzyme at a functionally distinct active site to lysophosphatidic acid (lyso-PA). Synthetic cyclic lyso-PA (1-octanoyl 2,3-cyclic glycerophosphate) was found to be stable in aqueous neutral solutions at room temperature. It was hydrolyzed by the bacterial phospholipase D to lyso-PA at a rate which was approximately 4-fold slower than the rate of formation of cyclic lyso-PA. The addition of 5-10 mM sodium vanadate could partially inhibit the ring opening reaction and thus increase substantially the cyclic lyso-PA accumulation. Cyclic lyso-PA may act as a dormant configuration of the physiologically active lyso-PA or may even possess specific activities which await verification.

Hydrolysis↗
PubMed1996

Cell attachment to frozen sections of injured adult mouse brain: effects of tenascin antibody and lectin perturbation of wound-related extracellular matrix molecules.

Previous studies describing the use of cryoculture methods have focused on the efficacy of the method for studying neuron attachment and neurite outgrowth on intact sections of nerve, and rodent and even human brain. The cryoculture method has shown promise for determining the presence of cell attachment- and neurite-growth-inhibiting molecules in such specimens, and some studies have also attempted to neutralize such molecules with antibodies to myelin inhibitory proteins, nerve growth factor, or factors present in conditioned media that may counteract the repulsiveness of some of these molecules preserved in sections of, for example, myelinated nerves or adult brain white matter. The present study describes the novel use of lesioned central nervous system cryocultures as substrates for investigating the attachment of embryonic neurons and PC12 cells. In addition to demonstrating the use of this novel scar substrate to extend previous 'scar-in-a-dish' models (David et al. (1990) Neuron, 5:463-469; Rudge and Silver (1990) J. Neurosci., 10: 3594-3603; Rudge et al. (1989) Exp. Neurol., 103: 1-16), the present study also describes antibody and lectin perturbations of putative inhibitory molecules that result in an enhanced attachment of cells to cryosection cultures of brain and spinal cord wounds.

Animals↗
PubMed1994

Severe factor VII deficiency caused by mutations abolishing the cleavage site for activation and altering binding to tissue factor.

Factor VII (F.VII) is a vitamin-K-dependent serine protease required in the early stages of blood coagulation. We describe here a patient with severe F.VII deficiency, with a normal plasma F.VII antigen level (452 ng/mL) and F.VII activity less than 1%, who is homozygous for two defects: a G-->A transition at nucleotide 6055 in exon 4, which results in an Arg-->Gln change at amino acid 79 (R79Q); and a G-->A transition at nucleotide 8961 in exon 6, which results in an Arg-->Gln substitution at amino acid 152 (R152Q). The R79Q mutation occurs in the first epidermal growth factor (EGF)-like domain, which has previously been implicated in binding to tissue factor. The R152Q mutation occurs at a site (Arg 152-Ile 153) that is normally cleaved to generate activated F.VII (F.VIIa). Analysis of purified F.VII from patient plasma shows that the material cannot be activated by F.Xa and cofactors. In addition, in an in vitro binding assay using relipidated recombinant tissue factor, patient plasma showed markedly reduced binding to tissue factor at all concentrations tested. In an effort to separate the contributions of the two mutations, three recombinant variants, wild-type, R79Q, and R152Q, were prepared and analyzed. The R152Q variant had markedly reduced activity in a clotting assay, whereas R79Q showed a milder, concentration-dependent reduction. The R152Q variant exhibited nearly normal binding in the tissue factor binding assay, whereas the R79Q variant had markedly reduced binding. The time course of activation of the R79Q variant was slowed compared with wild-type. Our results suggest that the first EGF-like domain is required for binding to tissue factor and that the F.VII zymogen lacks activity and requires activation for expression of biologic activity.

Adult↗
PubMed1994

Predictors of survival after cerebral infarction: importance of cardiac factors.

BACKGROUND: Stroke is the third leading cause of death in much of the developed world. There are two approaches to lowering mortality from stroke: reducing the incidence of stroke and reducing case fatality rate. AIMS: To determine factors, identified at presentation, that were predictive of mortality in elderly persons with acute cerebral infarction. METHODS: A consecutive series of 215 elderly persons admitted to hospital with acute cerebral infarction, confirmed by computerised tomography, were followed for an average of one year. A proportional hazards model was used to identify predictors of mortality. RESULTS: The following variables were identified on univariate analysis as predictors of death: raised serum creatinine, interstitial oedema on chest radiograph, low score on the Mini-Mental State Examination, atrial fibrillation, advanced age, cardiomegaly, raised leucocyte count, pulmonary venous congestion and homonymous hemianopia. Interstitial oedema was the most powerful predictor of death among the four measures of cardiac status. Two successful multivariate models included: 1) interstitial oedema, serum creatinine, age and homonymous hemianopia; 2) serum creatinine and Mini-Mental State Score. Further studies are required to assess the relationship between elevated serum creatinine and poor survival following stroke.

Aged↗
PubMed1994

Demographic influences on asthma hospital admission rates in New York City.

Surveillance reports describe an increase in asthma prevalence, and cite New York City as an area of excessive asthma mortality. To assess trends and the influence of geography, race, and ethnicity on hospital admission rates for asthma between 1989 and 1991, data of all admissions for asthma to New York City hospitals were reviewed. The average citywide annual hospital admission rate was 681 per 100,000 population, and the racial and ethnic distribution was 1,003 per 100,000 Hispanic patients, 810 per 100,000 for blacks, and 242 per 100,000 for whites (p < 0.0001). Bronx and Manhattan had the highest admissions rates, and contained a few zip codes with very high rates. In these zip codes, admission rates were consistently highest among Hispanics, followed by blacks and whites. New York City asthma admission rates increased 12.7 percent during the study. Very high admission rates among Hispanic patients and high rates in blacks, in specific geographic areas, are responsible for this trend. Targeted education and treatment programs could reduce hospital admissions and mortality in small geographic areas with high asthma morbidity.

Adult↗
PubMed1993

Formation of 1,3-cyclic glycerophosphate by the action of phospholipase C on phosphatidylglycerol.

The action of phospholipase C (PLC) from Bacillus cereus on phosphatidylglycerol (PG), derived from egg yolk phosphatidylcholine (PC), was examined in an ether-water mixture. The PLC cleavage of PG and PC followed a Michaelis-Menten kinetics with apparent Vmax values per 1 microgram enzyme of 0.26 and 0.91 mumol.min-1 and Km values of 10 and 12 mM, respectively. When the same enzymic reaction was carried out in minimally buffered aqueous solution of 1% Triton X-100, the decrease in pH with respect to phospholipid cleavage was as expected with PC but much less pronounced with PG. This could be accounted for by the formation of a cyclic glycerophosphate, rather than alpha-glycerophosphate, in the PLC hydrolysis of PG. Examination of the chemical nature of the water-soluble product of PG by phosphorus nuclear magnetic resonance (31P NMR) revealed a single band at 2.31 ppm, while the bands of alpha-glycerophosphate and beta-glycerophosphate appeared at 5.12 and 4.57 ppm, respectively. Basic hydrolysis of the phospholipase cleavage product of PG (0.1 M NaOH for 1 min at 80 degrees C) followed by neutralization shifted its 31P NMR band to 5.18 ppm, which practically coincided with that of alpha-glycerophosphate. Analogous experiments were carried out with PG labeled with 3H at the carbon 2 of the glycerol headgroup ([3H]PG). Autoradiography of thin layer chromatography (TLC) of the [3H]PG enzymic hydrolyzate displayed a single 3H-labeled compound, which could be converted to alpha-glycerophosphate by basic hydrolysis. These results strongly suggest that the phosphate headgroup of PG is cleaved off by PLC as 1,3-cyclic glycerophosphate. A series of PLC experiments with phosphatidyl dihydroxyacetone and phosphatidyl 1,3-propanediol as model substrates supported this assignment. Two-dimensional homonuclear 1H NMR correlated spectra as well as infrared spectra carried out on the isolated sodium salt of this product could further confirm such a structure. The unique structure and chemical nature of 1,3-cyclic glycerophosphate may bear a distinct physiological function.

Bacillus cereus↗
PubMed1993

Effects of adenine tracts on the B-Z transition. Fine tuning of DNA conformational transition processes.

The effects exerted by short runs of adenines (A-tracts), alternating (AT)n segments, and single-stranded DNA upon the right- to left-handed DNA transition, as well as upon the energetic and structural parameters of the B/Z junctions, were investigated by using synthetic segments in which these motifs are coupled to a potentially Z-forming core. UV, CD, and 31P NMR studies of the salt-induced B to Z transition occurring in the various segments indicate that the transition is composed of two phases: a slow rate-determining induction of an initial structural deformation followed by a cooperative propagation of this "nucleus" in the form of a left-handed Z-DNA. The first phase is found to be crucially affected by the nature of the sequences coupled to the potentially Z-forming core. Thus, a higher rigidity of the flanking segments, such as that characterizing adenine tracts, is associated with higher energy values required for the induction of the initial conformational deformation, as well as with more defined structural parameters of the ultimate B/Z junctions. The second phase is affected mainly by the composition and sequence of the Z-forming segment. The observations that DNA conformational changes can be finely tuned and modulated by parameters pertaining to both the segment which undergoes the transition and the flanking sequences support the notion that DNA secondary motifs, such as the Z form and A-tracts, might be involved in the regulation of cellular processes.

Adenine↗
PubMed1993

On the metastability of left-handed DNA motifs.

Alternating purine-pyrimidine DNA sequences such as poly [d(C-G)] or poly[d(m5C-G)] undergo a cooperative, salt-induced structural transition from a right-handed B conformation, which prevails at relatively low ionic strength, into a left-handed Z form, generally believed to be stabilized by high salt concentrations. We report here that upon a monotonous increase of the ionic strength, the well-established B to Z transition is followed by a second, hitherto unobserved conformational change leading from Z-DNA back into a right-handed B-like form. This observation indicates that, in contrast with the current convention, the Z motif represents an unstable configuration relative to the B form at both low and high salt concentrations and that the occurrence of a left-handed DNA structure, presently depicted as a step function of the ionic strength, should rather be treated in terms of a pulse. The reported transition underscores the inherent metastability of the Z configuration, and indicates, consequently, that this motif is ideally suited to act as a structural regulatory element, as such an element should be endowed with a large susceptibility to cellular parameters.

Base Sequence↗
PubMed1993

The feasibility of smoking bans on psychiatric units.

We conducted a prospective study of a smoking ban on a general inpatient psychiatry service in response to staff concerns about the feasibility of a proposed hospital-wide ban. Demographic information, smoking history, and DSM III-R diagnoses were obtained for consecutively admitted patients during two study conditions: smoking and nonsmoking. A log of p.r.n. medication, seclusion, restraint, elopement, incident reports, and smoking-related discharges was kept for each patient. Chi-square analysis of 232 patients for whom demographic, smoking, diagnostic, and log data were complete showed no significant differences between study conditions for demographic or diagnostic variables. Two-tailed t-test analysis of the log data for these 232 patients showed no significant difference in disruptive incidents during smoking and nonsmoking conditions (p = 0.183). Fifty staff members answered pre- and post-ban questionnaires. Paired t-test analysis demonstrated a significant change in staff attitude toward supporting the ban. These data indicate that smoking can be stopped on inpatient psychiatry units without increases in unit disruption or adverse effects on staff morale.

Adult↗
PubMed1993

Left ventricular cavity-to-myocardial count ratio: a new parameter for detecting resting left ventricular dysfunction directly from tomographic thallium perfusion scintigraphy.

Patients with reduced left ventricular function or aneurysms have cavities that appear dark on SPECT thallium scintigrams. We hypothesized that a quantitative index, which relates thallium activity in the left ventricular cavity to that in the myocardium (C/M ratio), could provide information on left ventricular function. A group of 80 patients who had both exercise SPECT thallium imaging and cardiac catheterization were studied. The C/M ratio was obtained from the short-axis tomogram on both exercise and rest images. Counts in a 2 x 2 pixel region of interest in the left ventricular cavity were divided by the number of counts in the "hottest" area of the myocardium. Plotting the angiographically determined ejection fraction against the C/M exercise and rest ratios, we observed a linear correlation between ejection fraction and both C/M ratios, r = 0.65 for C/M exercise and r = 0.67 for C/M rest ratio (p < 0.00001). Using data from 12 normal cardiac catheterization patients, we established the lower limit of normal; 50% for ejection fraction and 0.40 for the C/M ratios. A C/M exercise ratio < or = 0.40 identified 26 of 31 patients with an ejection fraction < or = 50%. A C/M exercise ratio > 0.40 identified 39 of 49 patients with an ejection fraction > 50%. These calculations yielded a sensitivity of 83% and specificity of 78% for the C/M exercise ratio. A similar analysis for C/M rest ratio revealed sensitivity of 61% and specificity of 92%. The present study shows that an abnormal C/M ratio correctly distinguishes patients with abnormal from normal ejection fractions with an accuracy of 81%. The C/M ratio is easily obtained, requires minimal processing time and is highly reproducible. These attributes may enable this index to add supplementary information regarding left ventricular function in addition to perfusion from thallium imaging.

Adult↗
PubMed1992

Wild-type p53 activates transcription in vitro.

The p53 protein is an important determinant in human cancer and regulates the growth of cells in culture. It is known to be a sequence-specific DNA-binding protein with a powerful activation domain, but it has not been established whether it regulates transcription directly. Here we show that intact purified wild-type human and murine p53 proteins strongly activate transcription in vitro. This activation depends on the ability of p53 to bind to a template bearing a p53-binding sequence. By contrast, tumour-derived mutant p53 proteins cannot activate transcription from the template at all, and when complexed to wild-type p53, these mutants block transcriptional activation by the wild-type protein. Moreover, the simian virus 40 large T antigen inhibits wild-type p53 from activating transcription. Our results support a model in which p53 directly activates transcription but this activity can be inhibited by mutant p53 and SV40 large T antigen through interaction with wild-type p53.

Animals↗
PubMed1991

Identification of p53 as a sequence-specific DNA-binding protein.

The tumor-suppressor gene p53 is altered by missense mutation in numerous human malignancies. However, the biochemical properties of p53 and the effect of mutation on these properties are unclear. A human DNA sequence was identified that binds specifically to wild-type human p53 protein in vitro. As few as 33 base pairs were sufficient to confer specific binding. Certain guanines within this 33-base pair region were critical, as methylation of these guanines or their substitution with thymine-abrogated binding. Human p53 proteins containing either of two missense mutations commonly found in human tumors were unable to bind significantly to this sequence. These data suggest that a function of p53 may be mediated by its ability to bind to specific DNA sequences in the human genome, and that this activity is altered by mutations that occur in human tumors.

Base Sequence↗
PubMed1991

Mutant p53 proteins bind DNA abnormally in vitro.

The p53 gene encodes a phosphoprotein which binds DNA. Many types of tumors contain mutant p53 genes, but the effects of these mutations on the intrinsic properties of p53 are largely unknown. In the present study, we tested the effect of p53 mutations on DNA-binding. Each of 15 different mutant p53 gene products derived from human tumors or mouse transformants bound calf thymus DNA more weakly than did wild-type products. A significant subset of mutant proteins were also found to be underphosphorylated compared to the wild-type protein when produced in a reticulocyte lysate system, but this did not appear to explain the pattern of alterations of DNA-binding. The tested mutations were dispersed over several regions of the p53 gene and included representatives of all four of the evolutionarily conserved domains that are the known 'hot spots' for p53 mutation. The results suggest common pathways by which these various mutations affect the normal function of p53.

DNA↗