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Biomedical subjects

T M Cooper

Publications and source records attributed to T M Cooper.

At least 19 recordsLinked to original sources
PubMed1992

Kinetic study of the helix to coil dark reaction of poly(spiropyran-L-glutamate).

An investigation of kinetics of the helix to coil dark reaction of light adapted poly(spiropyran-L-glutamic acid) (PSLG) dissolved in hexafluoroisopropanol was performed. The reaction was associated with the spiropyran (SP) to merocyanine (MC) ring opening. The ring opening reaction monitored with UV/VIS spectroscopy showed first order kinetics. Chromophore and polypeptide backbone circular dichroism data fit to an expression consistent with a single intermediate series mechanism. By FTIR, we monitored the polypeptide alpha-helix amide I, the MC chromophore--C = C--stretch and the protonated unmodified carboxylate C = O stretch bands. During the first step of the series mechanism, changes in the hydrogen bonding of the unmodified carboxylate groups occurred, suggesting breakup of polypeptide aggregates. The second step of the proposed series mechanism was dominated by the helix to coil transition and the ring opening of SP to MC. The CD spectrum of MC in the dark adapted PSLG was red shifted and had a narrower bandwidth than the UV/VIS spectrum. The kinetic and spectroscopic data suggested that a fraction (population I) of the MC chromophores experienced optical activity induced by the chiral polypeptide environment, while the remainder of the MC chromophores (population II) were solvated and enantiomeric.

Benzopyrans↗
PubMed1991

Platelet function in the peri-operative period.

Although platelets have an important role in haemostasis and in thrombosis, what happens to platelet function postoperatively is not well understood. We investigated platelet function in the peri-operative period by measuring total platelet count and several products released by activated platelets, thromboxane, betathromboglobulin and lyso-platelet activating factor (lyso-PAF). The only changes detected were a significant rise in total platelet count between 48 h and 5 days post-operation, and a progressive fall in lyso-PAF up to 48 h post-operation. It is possible that other changes may have occurred, but were an immediate effect and were not apparent at time of the first blood sample 2-3 h post-operation.

Adult↗
PubMed1991

Cloning of a mu-class glutathione S-transferase complementary DNA and characterization of its glucocorticoid inducibility in a smooth muscle tumor cell line.

A cDNA (designated hGSTYBX) encompassing the complete coding sequence of a hamster mu-class glutathione S-transferase (GST) subunit was cloned from a lambda ZAP library constructed with mRNA isolated from triamcinolone acetonide-treated smooth muscle tumor cells (DDT1 MF-2). Analysis of its nucleotide and deduced amino acid sequences demonstrated highest homology to the rat mu-class GST YB2 subunit. In proliferating subconfluent cells, in which constitutive expression of hGSTYBX mRNA was undetectable, glucocorticoid treatment induced hGSTYBX expression after a time lag of 3 h, and maximal induction occurred at 10 h. Nuclear run-on analysis showed that glucocorticoid induction resulted at least in part from an increased rate of transcription. Simultaneous treatment with glucocorticoid and cycloheximide prevented glucocorticoid induction, but had little effect on basal expression in confluent cells. In contrast, cycloheximide treatment 3 h after glucocorticoid treatment resulted in nearly full induction. These results taken together suggest that hGSTYBX induction may be a secondary glucocorticoid response.

Amino Acid Sequence↗
PubMed1990

Drinking coffee and carbonated beverages blocks absorption of nicotine from nicotine polacrilex gum.

Patients failing to obtain benefit from nicotine polacrilex gum in their efforts to quit smoking may be inadvertently blocking nicotine absorption. Effective nicotine absorption depends on the mildly alkaline saliva that is produced when buffering agents in the polacrilex are released along with nicotine as the polacrilex is chewed. We found that intermittent mouth rinsing with coffee or cola, but not distilled water, substantially reduced salivary pH and nicotine absorption. Because many commonly consumed substances were also found to be highly acidic, we recommend that patients do not ingest any substance during or immediately before nicotine polacrilex use.

Absorption↗
PubMed1990

The effect of conformation on the CD of interacting helices: a theoretical study of tropomyosin.

A recent report [M. E. Holtzer, et al. (1988) Biophysics Journal, 53, 96a] of the anomalous CD spectrum of the tropomyosin (TM) fragment 11TM127 motivated us to model the system as two 21-residue alpha-helices distorted to a coiled-coil conformation. We used strong-coupling exciton theory to model the optical properties of the system. Two backbone amide excited states (n pi* and pi pi*) were considered, as well as four excited states (Lb, La, Bb, Ba) for the phenolic side chain. We calculated the effect of superhelix formation on the backbone CD spectrum. The decrease in molar ellipticity of the alpha-helix parallel-polarized transition at 208 nm was found to be a simple function of superhelix tilt angle. We then modeled a coiled coil (radius = 5.5 A, pitch = -140 A) with one aromatic ring per superhelix. Steric interactions between aromatic side chains in a coiled coil were calculated as a function of side-chain conformation and heptet position. Steric interactions between phenolic rings will be significant for heptet positions a and d, but not for positions b, c, e, f, or g. We calculated the phenolic Lb transition rotational strength as a function of position within the heptet repeats, and of all possible side-chain dihedral angles, chi 1 and chi 2. When tyrosines were placed at heptet positions b, c, e, f, or g, the rotational-strength surface was nearly identical to that of a single tyrosine in an undistorted helix. In contrast, the rotational-strength surface for tyrosines in heptet positions a or d showed substantial intertyrosine coupling components. The rotational-strength surfaces for the three types of heptet positions (position a, position d, and the others) allowed an interpretation of the aromatic CD spectra of TM and its fragments. It was predicted that the three types of heptet positions will be spectroscopically distinguishable.

Circular Dichroism↗
PubMed1990

The relationships of concentrations of insulin, intact proinsulin and 32-33 split proinsulin with cardiovascular risk factors in type 2 (non-insulin-dependent) diabetic subjects.

Standard radioimmunoassay for insulin may substantially overestimate levels of insulin because of cross-reaction with other insulin-like molecules. We have measured concentrations of insulin, intact proinsulin and 32-33 split proinsulin using two-site monoclonal antibody based immunoradiometric assays, and of insulin by a standard radioimmunoassay ("immunoreactive insulin") in 51 Type 2 (non-insulin-dependent) diabetic subjects in the fasting state. The relationships of these concentrations were sought with those of total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglyceride, plasminogen activator inhibitor, blood pressure, and indices of body fat distribution. Significant relationships were apparent between concentrations of "immunoreactive insulin" as measured by standard radioimmunoassay and triglyceride (rs = 0.42, p less than 0.001), total cholesterol (rs = 0.25, p = 0.038), high density lipoprotein cholesterol (rs = -0.30, p = 0.018) and body mass index (rs = 0.30, p = 0.017), but only the relationships with triglyceride (rs = 0.36, p = 0.006) and body mass index (rs = 0.26, p = 0.34) remained significant when concentrations of immunoradiometrically measured insulin were employed. Concentrations of 32-33 split proinsulin, which comprises the major insulin-like molecule in these subjects, correlated positively with triglyceride (rs = 0.33, p = 0.009), total cholesterol (rs = 0.23, p = 0.050), and plasminogen activator inhibitor (rs = 0.26, p = 0.049), and negatively with high density lipoprotein cholesterol (rs = -0.29, p = 0.021).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Influence of energy and nitrogen contents of enteral diets on nitrogen balance: a double blind prospective controlled clinical trial.

Results of recent controlled studies show that because of difficulties in administering adequate quantities of enteral diet, positive nitrogen balance is not consistently achieved during enteral feeding. In order to determine whether nitrogen balance can be improved in routine clinical practice by prescribing enteral diets containing higher concentrations of nutrients, 118 patients with normal gastrointestinal function needing enteral nutrition were randomised to receive daily 21 of one of three polymeric diets: Standard diet (1.0 kcal/ml; 6.3 gN/l), Energy Dense diet (1.5 kcal/ml; 7.8 gN/l), and Energy-Nitrogen Dense diet (1.5 kcal/ml; 9.4 gN/l. The three diets, administered by continuous nasogastric infusion, were equally well tolerated. Results were analysed only for patients fed five or more days and who received at least 60% of prescribed enteral diet (n = 42). Positive nitrogen balance was achieved only in the patients receiving the Energy-Nitrogen Dense diet (n = 16; + 1.6 (SE) 0.6 gN/d, compared with the Standard diet (n = 12; -3.8 (1.1) gN/d; p less than 0.001), and the Energy Dense diet (m = 14; -1.9 (0.8) gN/d; p less than 0.005). As the findings of this prospective controlled trial show that positive nitrogen balance was not consistently achieved by administering 21 enteral diet containing up to 15.6 gN, consideration could, therefore, be given to routinely using enteral diets containing up to 9.4 gN/l.

Adolescent↗
PubMed1989

Stop-smoking program using nicotine reduction therapy and behavior modification for heavy smokers.

One hundred eighteen volunteers were studied in a hospital-based smoking cessation program in which nicotine polacrilex (Nicorette) was used as an adjunct to behavioral modification (group support). The "success" rate of 40% to 47% at 1 year was chemically verified. The regimen for using the nicotine polacrilex was "within labeling" but decidedly different from the regimen used in most smoking cessation programs involving this product.

Adult↗
PubMed1988

Gloved and ungloved: performance time for two dental procedures.

This study examines the time required to perform two routine dental procedures requiring fine hand manipulative skills--a pin placement procedure and an endodontic procedure. No significant time difference was noted in performing the procedures while wearing gloves or not wearing gloves. Twelve dentists who had routinely worn gloves for the past 6 months participated, each performing four procedures.

Dental Pins↗
PubMed1988

Maintaining vitality in the mature dental practice.

The dentists interviewed for this third article in the series report this is a satisfying time; they are private practitioners aged 40 to 54. These dentists are enthusiastic about their profession and enjoy using the new technological advances for better treatment of their patients. For these active practitioners, the practice does not need to be revitalized: they're enjoying fulfillment in what they do.

Adult↗
PubMed1987

Energy storage in the primary photochemical events of rhodopsin and isorhodopsin.

The energetics associated with the photoequilibrium (Formula: see text) are measured at 77 K by using pulsed-laser photocalorimetry and a range of excitation wavelengths and relative starting concentrations. Enthalpies for the photochemical transformations R hv----B and I hv----B are measured to be delta HRB = 32.2 +/- 0.9 kcal mol-1 and delta HIB = 27.1 +/- 3.2 kcal mol-1, respectively. Although the value of delta HRB is slightly lower than that reported previously by Cooper of 34.7 +/- 2.2 kcal mol-1 [Cooper, A. (1979) Nature (London) 282, 531-533], the two values are in agreement within experimental error. The energy difference delta HRB - delta HIB = 5.1 +/- 3.3 kcal mol-1 is identical within experimental error with the difference in enthalpies of isorhodopsin and rhodopsin [5.2 +/- 2.3; Cooper, A. (1979) FEBS Lett. 100, 382-384]. We suggest that this result is consistent with the theory that bathorhodopsin is a single, common photochemical intermediate connecting rhodopsin and isorhodopsin.

Animals↗