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Biomedical subjects

M Miller

Publications and source records attributed to M Miller.

At least 631 records · Page 35Linked to original sources
PubMed1987

Use of one-piece valved tube and variable surface area explant for glaucoma drainage surgery.

The results of glaucoma surgery on 37 eyes of 36 patients after the use of a one-piece valved silicone explant are described. With a follow-up of 6 to 24 months, intraocular pressures (IOPs) averaging 8.0 to 17.3 mmHg were recorded. The maximum number of eyes receiving antiglaucoma medicines at any of the follow-up visits was six. These results were compared with the authors' previous results with the two-piece tube and gutter explant (ACTSEB). It was found that lower IOPs were obtained with fewer complications from overdrainage in the immediate postoperative period. This difference was attributed to the valve reducing but not preventing overdrainage and less chance of "fibrosis" blocking the tube/plate interface.

Adult↗
PubMed1987

Increased vasopressin secretion: an early manifestation of aging in the rat.

Vasopressin release and renal water conserving capacity were measured in normal Long-Evans rats ranging in age from 2 to 17 months. Twenty-four hour urine volume rose and urine osmolality fell as the animals aged, with the first differences evident by age 10 months. Assessment of vasopressin release from isolated hypothalamic-neurohypophysial units by means of an in vitro perifusion system demonstrated that hormone discharge increased as the animals aged, being evident by age 7 months. The increased vasopressin releasability could not be attributed to the greater vasopressin content present in the posterior pituitary of the older rats. The data suggest that increased vasopressin secretion is an early manifestation of aging in the rat and that the consequent hypervasopressinemia may affect the renal tubule with resultant diminished responsiveness to the hormone.

Aging↗
PubMed1987

Effect of history of psychological counseling on selection of applicants for residencies.

The stress of medical education and its consequences are widely recognized and acknowledged. However, many students may be reluctant to seek help for stress-related problems because they are concerned over the ramifications such a decision may have on their career opportunities. The purpose of the present study was to determine the extent to which an applicant's history of having received psychological counseling for stress-related problems influenced residency program directors' perceptions of such applicants seeking admission to residency programs. Five hundred twenty-three residency directors in six medical specialties (pediatrics, internal medicine, family medicine, psychiatry, obstetrics and gynecology, and surgery) rated a hypothetical residency applicant. The student's gender and history of psychological counseling were manipulated, but their basic qualifications remained constant. The directors rated the likelihood that they would invite the student for an interview and accept the applicant for the residency. Analysis of variance showed that the directors in pediatrics, family medicine, and psychiatry viewed the hypothetical applicant more favorably overall than directors in internal medicine, obstetrics and gynecology, and surgery. The program directors rated female applicants more favorably than their male counterparts and had a strong bias against inviting for an interview or accepting into their programs students who had a history of psychological counseling. Implications of these findings are discussed.

Counseling↗
PubMed1987

Arterial blood PO2 and PCO2 in horses during early halothane-oxygen anaesthesia.

Arterial blood was collected from 25 clinically normal horses immediately before and serially throughout the first hour of halothane oxygen anaesthesia. Blood was analysed for oxygen and carbon dioxide partial pressure (PaO2, PaCO2). Measurements of inspired oxygen concentration during anaesthesia permitted direct correlation with blood gases. Horses were divided arbitrarily into two groups based on their age: two to seven years, n = 15; over seven years, n = 10. Average (+/- sd) PaO2 and PaCO2 was 14.1 +/- 1.5 kPa (106 +/- 11 mmHg) and 5.9 +/- 0.6 kPa (44.4 +/- 4.4 mmHg) respectively in conscious, young horses and 14.0 +/- 0.7 and 5.8 +/- 0.5 kPa (105 +/- 5 and 43.3 +/- 3.8 mmHg) respectively in conscious older horses. Arterial oxygen tension decreased to 9.3 +/- 1.0 and 8.5 +/- 1.4 kPa (69.6 +/- 7.8 and 63.7 +/- 10.4 mmHg) in young and older air breathing horses respectively immediately following intravenous anaesthetic induction, recumbency and orotracheal intubation. At this time, PaCO2 was 6.5 +/- 0.5 and 6.0 +/- 0.7 kPa (48.7 +/- 3.5 and 45.1 +/- 4.9 mmHg) respectively. By 30 mins after the start of halothane in oxygen (6 litres/min) anaesthesia PaO2 increased to a maximum in both study groups. Arterial PCO2 increased steadily during anaesthesia and 60 mins after induction PaCO2 was 10.5 +/- 2.4 kPa (78.5 +/- 17.8 mmHg) in the younger horses and 9.2 +/- 1.6 kPa (68.8 +/- 11.8 mmHg) in the older horses. During inhalation anaesthesia PaO2 tended to be greater at comparable time periods in the younger horses despite a slightly greater degree of hypoventilation.

Aging↗
PubMed1987

Naturally occurring methylation inhibitor: DNA hypomethylation and hemoglobin synthesis in human K562 cells.

A naturally occurring methylation inhibitor isolated from rabbit liver and named methinin inhibits a number of methyltransferases. Methinin is a low-molecular-weight compound (1,400) that has an active amine group. This compound inhibits the DNA methyltransferase of human erythroleukemia cells (K562) in vitro. When the K562 cells were grown in medium containing methinin, fetal hemoglobin was produced. Small but detectable amounts of adult hemoglobin were also produced. Methinin was not toxic to these cells. The overall rate of genomic DNA methylation was reduced by 60% in cells grown in medium containing methinin. Southern blots of genomic DNA from methinin-treated cells and untreated cells hybridized to a 32P-labeled globin gene probe showed that one site in the globin gene region was hypomethylated. Methinin is a naturally occurring compound which inhibits DNA methylation both in vitro and in vivo.

5-Methylcytosine↗
PubMed1987

Lymphoid follicular pattern in the colon: an indicator of barium coating.

A lymphoid follicular pattern was noted more frequently when high-density (100% w/v) replaced low-density (58% w/v) barium in children undergoing double-contrast barium enema examinations. Therefore, a retrospective study was undertaken to compare the presence of follicles seen in 24 consecutive patients under 10 years old given low-density barium with that of 50 patients given high-density barium. The high-density studies revealed follicles in 90% of the children compared with 46% of the children having low-density studies. All follicles were less than 2 mm in diameter. An aphthoid appearance was present in nine of these 50 children. The most common indications for the high-density examination were rectal bleeding and abdominal pain. The final diagnosis was normal bowel in more than two thirds; no child under six years old given high-density barium had inflammatory bowel disease. There was no correlation between final clinical diagnosis and the presence, extent, or severity of the lymphoid follicular pattern.

Barium Sulfate↗
PubMed1987

Prognostic indicators in acute variceal hemorrhage after treatment by schlerotherapy.

The purpose of the study was to evaluate prognostic indicators in patients receiving endoscopic injection sclerosis for bleeding esophageal varices. The results below were obtained from a prospective nonrandomized study in which the patients were subdivided into the following groups (subsets): elective sclerotherapy--10, active variceal bleeding at endoscopy--47, active variceal bleeding with spontaneous resolution at the time of endoscopy--21, and gastric variceal bleeding--nine. The data were analyzed as follows: 14 variables possibly affecting 6-wk survival were evaluated by stepwise logistic regression analysis. Variables examined were subset, age, sex, Child's classification, ascites, comorbid conditions, SGOT, bilirubin, protime, albumin, volume of initial bleed, volume of rebleed, rebleed rate, and Blakemore tube use. Survival curves were also compared using the Kaplan-Meier methodology. The following results were obtained. First, the subsets above had significantly different survival curve patterns with the elective endoscopic injection sclerosis group having the best prognosis and the gastric variceal bleeders a significantly poorer survival. Second, stepwise logistic regression analysis revealed the following four significant variable prognostic indicators: comorbid factors, subset, Child's classification, and serum albumin. Although the latter two variables, Child's class (p = 0.03) and albumin (p = 0.1) had an impact on six week survival, this was no longer seen when subset (p = 0.0124) and comorbid factors (p = 0.003) were taken into account. We conclude that comorbid factors and subsets of variceal bleeding in themselves were the only two prognostic indicators showing a statistically significant association with 6-wk and long-term survival. In contrast, the more usual clinical prognostic parameters, i.e., the physical findings and biochemical test of liver function in patients with cirrhosis and acute variceal bleeding, were of lesser prognostic magnitude.

Acute Disease↗
PubMed1987

Fluid and electrolyte balance in the elderly.

It is increasingly evident that many disorders common in the aging individual may be accompanied by disturbances of fluid and sodium balance, especially hyponatremia. Physiological alterations in water and sodium regulation have been identified as part of the normal aging process which may contribute to the relative frequency of fluid and electrolyte disorders in the elderly. Hyponatremia may present with a wide variety of symptoms and may be a clue to the existence of an underlying major disease process. Treatment involves both acute and long-term management based on identification of the causative disorder and understanding of the pathophysiologic mechanism which has led to development of hyponatremia.

Aged↗
PubMed1987

Pulmonary fibroblasts: a model system for studying elastin synthesis.

Pulmonary interstitial fibroblasts were isolated from 4-day neonatal rat lung and cultured for varying periods of time after first passage. The ability of the cells to synthesize both soluble and insoluble elastin was examined by biochemical, immunological, and ultrastructural techniques. The cells synthesize a tropoelastin of 75,000 daltons which is cross-linked in the extracellular matrix to form sufficient amounts of insoluble elastin to be characterized directly by amino acid analysis. Although the cells produce a soluble form of elastin immediately after confluency and the deposition in the matrix begins shortly thereafter, the actual chemical definition of alkali-resistant elastin does not occur until 4 weeks after confluency. The apparent molecular weight of tropoelastin synthesized by the cells agrees with the molecular size of tropoelastin found in organ culture of neonatal lungs. The pulmonary fibroblast cultures provide an important model system for examining the regulation and response of elastin synthesis in lung interstitium.

Animals↗
PubMed1986

Effects of SMS 201-995 on intermediary metabolism and endocrine status in normal and diabetic humans.

The hormonal and metabolic effects of the somatostatin analogue SMS 201-995 have been examined in normal and diabetic humans. When 50 micrograms of analogue was administered subcutaneously at 8 A.M. and 5:30 P.M., growth hormone secretion over 24 hours was not significantly affected, and the nocturnal growth hormone surge persisted in normal subjects and in type II diabetic patients. Insulin secretion was suppressed in both groups, but glucose tolerance deteriorated only in the normal subjects. Gastrointestinal side effects developed in both groups. Subcutaneous administration of 50 micrograms of SMS 201-995 at 11 P.M. decreased nocturnal growth hormone secretion (peak, 5 +/- 2 milliunits/liter versus 23 +/- 6 milliunits/liter; p less than 0.01) in normal subjects. Postprandial circulating glucose and insulin levels the following day were unaffected by SMS 201-995, and no side effects were observed. In type I diabetic patients receiving a variable rate insulin infusion overnight to maintain normoglycemia, SMS 201-995 (50 micrograms) administered at 11 P.M. decreased insulin requirements for two to three hours after injection. Insulin sensitivity thereafter was unaffected despite suppression of growth hormone secretion. Alternative dosage regimens are necessary to suppress growth hormone release over 24 hours and to minimize side effects in type II diabetes. Administration of the analogue in the late evening suppresses growth hormone secretion overnight, but the "dawn phenomenon" persists in type I diabetic patients.

Blood Glucose↗
PubMed1986

Mechanism of oligonucleotide loop formation in solution.

We have studied the tridecadeoxynucleotide CGCGAATTACGCG (I), which contains an additional A at position 9 compared to the dodecanucleotide of which the crystal structure has been determined. Sequence I exhibits no distinct melting curve and also has a concentration-dependent pattern of peaks on reverse-phase chromatography. This behavior is explained by a slow equilibration between loop and duplex forms in solution. We have characterized this equilibrium by proton NMR spectroscopy and shown that it is fully reversible by monitoring the two thymine methyl resonances, each of which occurs in two environments. Lower temperature and higher concentration favor the duplex; the midpoint of the transition is such that the loop predominates at room temperature. We have measured the van't Hoff enthalpy of formation of the duplex and the activation energy by temperature-jump and saturation-transfer experiments. The results are compared with those for the 17-mer sequence CGCGCGAATTACGCGCG (II), which contains two additional base pairs in the stem of the loop. The thermodynamic parameters and the effect of increasing salt concentration on the rate of conversion of the loop and duplex forms lead us to presume that the mechanism of interconversion involves complete strand separation and re-formation rather than cruciform formation and branch migration.

Base Sequence↗
PubMed1986

Crystal structure analysis and refinement at 2.5 A of hexameric C-phycocyanin from the cyanobacterium Agmenellum quadruplicatum. The molecular model and its implications for light-harvesting.

The crystal structure of the light-harvesting protein-pigment complex C-phycocyanin from the cyanobacterium Agmenellum quadruplicatum has been determined by Patterson search techniques on the basis of the molecular model of C-phycocyanin from Mastigocladus laminosus. The crystal unit cell (space group P321) contains three (alpha beta)6 hexamers centred on the crystallographic triads. The hexamer at the origin of the unit cell exhibits crystallographic 32 point symmetry. The other two hexamers (independent of the former) show crystallographic 3-fold and local 2-fold symmetry. The 3-fold redundancy of the asymmetric unit of the crystal cell was used in the refinement process, which proceeded by cyclic averaging, model building and energy-restrained crystallographic refinement. Refinement was terminated with a conventional crystallographic R-value of 0.20 with data to 2.5 A resolution. The two independent hexamers of the unit cell are identical within the limits of error at all levels of aggregation. Two trimers, which closely resemble the M. laminosus C-phycocyanin, are aggregated head-to-head to form the hexamer. Both trimers fit complementarily and are held together by polar and ionic interactions. Conservation of the amino acid residues involved in protein-chromophore and intermonomer interactions suggests common structural features for all biliproteins. Most probably, the hexameric aggregation form present in the crystals is closely related to the discs of native phycobilisome rods. All tetrapyrrole chromophores are extended but with different geometries enforced by different protein surroundings. In particular, interactions of the propionic side-chains with arginine residues and of the pyrrole nitrogen atoms with aspartate residues define configuration and conformation of the chromophores. Relative chromophore distances and orientations have been determined and a preferential pathway for the energy transfer suggested. Accordingly, within a hexamer the absorbed energy is funneled to chromophore B84 and then transduced via B84 chromophores along the phycobilisome rods.

Amino Acid Sequence↗