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Biomedical subjects

D Miller

Publications and source records attributed to D Miller.

At least 433 records · Page 24Linked to original sources
PubMed1990

Improvement of computer screen viewing in elderly patients.

Patients with early cataracts or cloudy posterior capsules often have problems with the reflected glare from the protective glass surface over the computer screen. This report describes a device which surrounds the computer screen and (a) decreases glare by shading the screen, thus increasing screen contrast, and (b) creates a new image of the computer screen at a lower position. This allows the bifocal wearer to read without tipping his or her head backward.

Aged↗
PubMed1990

Effect of intraocular lens decentration on retinal image contrast.

We describe an optical model of the eye that allowed the effect of intraocular lens (IOL) decentration on retinal image contrast to be photographically studied. Decentrations of varying degrees of severity were modeled to correlate the amount of aphakic pupillary area with the contrast of the resulting images as measured by a digital photometer. Image contrast was found to decrease linearly as the proportion of aphakic pupillary area increased. Human clinical correlates are discussed.

Contrast Sensitivity↗
PubMed1990

A quantitative animal model of traumatic iridodialysis.

The impact velocities and kinetic energies necessary to create a particular form of ocular injury, traumatic iridodialysis, were quantitatively studied by experimentally traumatizing enucleate porcine eyes. Thicknesses and tensile strengths of porcine and human iris tissue were measured in order to allow for predictions of human results to be made from the animal model. Application of blunt trauma at an impact angle of 30-35 degrees with respect to the iris plane with striking of the eye at the corneolimbal junction was found to optimize tearing of the iris from the root. Using this vector, the minimum velocity for the creation of an iridodialysis at least 6 mm in length in the human eye is predicted to be 14 m/sec for impact with a projectile of 13.4 g with a 6 mm diameter tip.

Animals↗
PubMed1990

Influence of age, sex, and concurrent intrathecal methotrexate therapy on intellectual function after cranial irradiation during childhood: a report from the Children's Cancer Study Group.

Standard IQ tests were performed in 70 children and adolescents 3.5-10 years (median 5 yrs) after 24 Gy cranial irradiation, with or without concurrent intrathecal methotrexate, for central nervous system prophylaxis of acute lymphoblastic leukemia. Lower IQ scores correlated with younger age, female gender, and concomitant intrathecal methotrexate therapy. Multivariate analysis identified age as the most important determinant of the three factors. The lowest IQ scores were observed in girls who were less than 5 years old at the time of irradiation and who received concurrent intrathecal methotrexate. The observed adverse contribution of simultaneous intrathecal methotrexate therapy on IQ outcome may have significant implications for school performance, peer relationships, and occupational expectations.

Age Factors↗
PubMed1990

[Subendocardial resection in the surgical treatment of ventricular arrhythmia in patients with ischemic heart disease].

Since 1977 a total of 284 operations were conducted on patients with ventricular tachycardia consequent upon ischemic heart disease. Stimulation mapping was used during the operation as an auxiliary method for locating the arrhythmogenic zone in the ventricles. Demonstration of low-voltage and fragmented activity (delayed potentials) in the sinus rhythm are of diagnostic value in no more than 30% of cases. The results of endocardial preoperative mapping are very important because in 99% of cases the focus of ventricular tachycardia is located endocardially (in the septum of the heart in 2/3 of cases). Dosed endocardial resection is the operation of choice; when the focus is located intramyocardially (or in the region of the base of the papillary muscle) the authors resort to cryodestruction. Operative mortality was 15%. The operations were successful in follow-up periods of up to 10 years in 70% of cases.

Aged↗
PubMed1990

Oxygen-derived free radicals in hepatic ischemia and reperfusion injury in the rat.

We have previously described a chronic, in vivo biochemical and histologic model of ischemia and reperfusion injury and wished to test the ability of superoxide dismutase, catalase and allopurinol to protect against the hepatocellular injury demonstrated by this model. Xanthine oxidase inhibitors given preoperatively produced a significant hepatocellular protective effect when compared with a comparable insult delivered to a cohort of control rats. The protection given seemed greater than that produced by pretreatment with free radical scavengers. Possible mechanisms for this observation are discussed. Investigations combining free radical scavengers with xanthine oxidase inhibitors may further define protection for warm hepatic ischemia and reperfusion injury.

Allopurinol↗
PubMed1989

A covalently constrained congener of the Saccharomyces cerevisiae tridecapeptide mating pheromone is an agonist.

An analog of alpha-factor, the Saccharomyces cerevisiae tridecapeptide mating pheromone (Trp-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr), in which the side chains of Lys7 and Gln10 were covalently linked, was synthesized using solid phase methodologies. The yield of the purified cyclic analog cyclo7,10[Nle12]alpha-factor was 30%, and its structure was verified by amino acid analysis, peptide sequencing, fast atom bombardment-mass spectrometry, and proton nuclear magnetic resonance spectroscopy. Cyclo7,10[Nle12]alpha-factor caused growth arrest and morphological alterations in S. cerevisiae MATa cells qualitatively identical to those induced by linear pheromone and was one-fourth to one-twentieth as active as the linear alpha-factor depending upon the S. cerevisiae strain tested. Consistent with the relative activities of the linear and cyclic peptides, binding competition studies indicated that cyclo7,10[Nle12]alpha-factor had approximately 20-40-fold less affinity for the alpha-factor receptor. Hydrolysis of the cyclic peptide by the target cells did not lead to opening of the ring and was less rapid than that of linear alpha-factor. The alpha-factor antagonist des-Trp1-[Ala3,Nle12]alpha-factor reversed the activity of the cyclic analog, and cyclo7,10[Nle12]alpha-factor was not active at the restrictive temperature in a temperature-sensitive receptor mutant. These results support the conclusion that the cyclic alpha-factor occupies the same binding site within the receptor as is occupied by the natural pheromone. The cyclic alpha-factor represents a rare example of an agonist among covalently constrained congeners of small linear peptide messengers.

Amino Acid Sequence↗
PubMed1989

Interaction of permanently charged chlorpromazine and dopamine analogs with the striatal D-1 dopaminergic receptor.

Although a structural feature common to all dopaminergic agonists and antagonists is a side-chain basic amino group, it is unclear whether this moiety binds to the D-1 dopamine (DA) receptor in the charged or uncharged form. To obtain information on this point, we synthesized permanently charged dimethylsulfonium and quaternary ammonium analogs of chlorpromazine and DA and determined whether these compounds can bind to the D-1 receptor by measuring their abilities to inhibit the binding of SCH 23390, a D-1 receptor antagonist. Chlorpromazine and the dimethylsulfonium and trimethylammonium analogs of chlorpromazine were found to inhibit the binding of [3H]SCH 22390, which was maximally inhibited to the same extent by all three compounds. In addition, inhibition curves for the compounds fit a one-site binding model, indicating binding to a single class of sites. However, while the permanently charged chlorpromazine analogs were able to inhibit [3H]SCH-23390 binding, they were considerably less potent than chlorpromazine. DA and dimethyl DA were also able to inhibit [3H]SCH 23390 binding. However, the permanently charged dimethylsulfonium and trimethylammonium analogs of DA were ineffective in inhibiting [3H]SCH 23390 binding. In addition, the permanently uncharged methylsulfide analog did not inhibit binding. These studies show that permanently charged analogs of chlorpromazine can bind to the striatal D-1 receptor, which is consistent with an anionic recognition site on the D-1 receptor that interacts with antagonists in the cationic form. In addition, it appears that a nitrogen atom is not required for binding to the D-1 receptor, since the sulfonium analog of chlorpromazine bound to the receptor to the same extent as chlorpromazine. However, since the permanently charged or uncharged analogs of DA did not bind to the D-1 receptor, it is still unclear as to whether the charged form of a dopaminergic agonist can bind. The lower potency or ineffectiveness of the permanently charged analogs compared to the parent amines (chlorpromazine, DA, dimethyl DA) in binding to the D-1 receptor may reflect the inability of the permanently charged analogs to undergo hydrogen binding with the anionic site of the receptor.

Animals↗
PubMed1989

A new culture method for infectious endophthalmitis.

We studied the use of blood culture bottles for culturing vitreous specimens obtained during vitrectomy for infectious endophthalmitis. In a retrospective review of 83 cases, blood culture bottles yielded a 91% incidence of positive cultures. A laboratory comparison of direct media inoculation, a membrane filter system, and three blood culture systems was undertaken using inocula of nine organisms in three different concentrations. The blood culture bottle systems became positive at the same time as, or within 24 hours of, the membrane filter system for nearly every organism tested. A prospective clinical comparison was also performed in 14 cases of endophthalmitis, confirming our laboratory findings. The direct inoculation of blood culture bottles may be an acceptable adjunct or alternative to more sophisticated laboratory techniques for vitreous cultures in infectious endophthalmitis.

Adolescent↗
PubMed1989

Lactase deficiency in Singapore-born and Canadian-born Chinese.

Seventy-three of 77 adult Singapore-born Chinese (95%) and 48 of 49 Canadian-born adult Chinese (98%) were demonstrated to be lactase deficient using the lactose breath hydrogen test. The similar prevalence of lactase deficiency in the Singapore- and the Canadian-born Chinese despite a larger estimated amount of daily milk ingestion in the Canadian-born Chinese (430 ml vs 157 ml) supports the concept that lactase deficiency, which is transmitted genetically, does not have an adaptable component related to the quantity of lactose ingested. When the lactose breath hydrogen test performed with a dose of 0.5 g/kg of lactose was compared with the test using a standard dose of 50 g of lactose, there was very little loss of sensitivity. In spite of the presence of lactase deficiency, only 32% of the Singapore subjects and 23% of the Canadian subjects had gastrointestinal symptoms when milk was ingested in the daily diet. Peak breath H2 was higher in females than males, but the difference was more significant in the Canadian cohort.

Adolescent↗
PubMed1989

Interview assessment of critically Ill patients regarding resuscitation decisions. A case study in ethics research.

To examine how patients perceive and decide their resuscitation status, we monitored 113 admissions to a coronary care unit. We review the research process, including Institutional Review Board concerns, sampling bias and permission by physicians, informed consent, and the patient interview. In-depth psychiatric interviews on 16 patients demonstrated marked misperceptions about resuscitation procedures. Although standardized psychologic measures indicated distress in some of these critically ill patients, the interview itself induced no detected untoward physiologic or emotional reactions. This pilot study demonstrates the feasibility of assessing patients regarding resuscitation status and also identifies relevant methodologic problems to guide future research of resuscitation decision-making.

Behavioral Research↗