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Biomedical subjects

S S Miller

Publications and source records attributed to S S Miller.

At least 73 records · Page 4Linked to original sources
PubMed1991

Adolescent health care: an assessment of referral activities.

The referral activities of 45 agencies (90% of the sample originally polled) in a moderate-sized midwest community were investigated with respect to agency referral patterns and professionals' appraisal of adolescents' health care status. A combined analysis of qualitative and quantitative data provided valuable insight into the problems of unmet adolescent health care needs and underutilization of adolescent health care services. Referral activity characteristics which may hinder the successful networking of services for adolescents are highlighted.

Adolescent↗
PubMed1990

Zygote intrafallopian transfer as a treatment for nontubal infertility: a 2-year study.

Zygote intrafallopian transfer (ZIFT) was used as a treatment for long-standing nontubal infertility for a 2-year period. The overall clinical pregnancy rate for 114 tubal transfers was 40.4% with a delivery/ongoing rate of 34.2%. Concurrent use of in vitro fertilization and embryo transfer (IVF-ET) for tubal factor infertility gave significantly lower clinical pregnancy and delivery/ongoing rates (21.1% and 15.8%, respectively). The use of gamete intrafallopian transfer (GIFT) for nontubal infertility yielded a 32% clinical pregnancy rate and a 26% delivery rate for 53 transfers. Zygote intrafallopian transfer resulted in an implantation rate per zygote of 17% overall compared with 8.1% per embryo for IVF-ET and 11.2% per oocyte for GIFT. The transfer of three zygotes per patient gave the same clinical pregnancy rate as the transfer of four while reducing the incidence of multiple gestation from 19% to 7.8% per transfer. No significant decline in the clinical pregnancy or delivery rate was seen with ZIFT in women aged 25 through 39.

Adult↗
PubMed1990

Potassium-dependent volume regulation in retinal pigment epithelium is mediated by Na,K,Cl cotransport.

Changes in retinal pigment epithelial (RPE) cell volume were measured by monitoring changes in intracellular tetramethylammonium (TMA) using double-barreled K-resin microelectrodes. Hyperosmotic addition of 25 or 50 mM mannitol to the Ringer of the apical bath resulted in a rapid (approximately 30 s) osmometric cell shrinkage. The initial cell shrinkage was followed by a much slower (minutes) secondary shrinkage that is probably due to loss of cell solute. When apical [K+] was elevated from 2 to 5 mM during or before a hyperosmotic pulse, the RPE cell regulated its volume by reswelling towards control within 3-10 min. This change in apical [K+] is very similar to the increase in subretinal [K+]o that occurs after a transition from light to dark in the intact vertebrate eye. The K-dependent regulatory volume increase (RVI) was inhibited by apical Na removal, Cl reduction, or the presence of bumetanide. These results strongly suggest that a Na(K),Cl cotransport mechanism at the apical membrane mediates RVI in the bullfrog RPE. A unique aspect of this cotransporter is that it also functions at a lower rate under steady-state conditions. The transport requirements for Na, K, and Cl, the inhibition of RVI by bumetanide, and thermodynamic calculations indicate that this mechanism transports Na, K, and Cl in the ratio of 1:1:2.

Animals↗
PubMed1990

The meaning of grandparenthood and its relationship to demographic, relationship, and social participation variables.

The meaning of grandparenthood has been a focus of research, especially during the last decade. Types of meanings and variables differentiating these grandparental meanings have been established. Most recently Kivnick (1981, 1982a, 1982b, 1985) has derived a multidimensional framework representing five aspects of the meaning of grandparenthood. The present study attempted to verify whether these five aspects of meaning were related to unique combinations of demographic, social, personal, and health variables. Zero-order correlations showed high intercorrelations among Kivnick's five subscales, and low correlations among the majority of variables. Regression analyses indicated that no more than 30% of the variance in any one of the dimensions could be explained and that considerable overlap existed in the significant predictors across aspects of meanings.

Adult↗
PubMed1990

Aspartate Aminotransferase in Alfalfa Root Nodules : II. Immunological Distinction between Two Forms of the Enzyme.

Aspartate aminotransferase (AAT), a key enzyme in the biosynthesis of aspartate and asparagine, occurs as two forms in alfalfa (Medicago sativa L.), AAT-1 and AAT-2. Both forms were purified to near homogeneity, and high titer polyclonal antibodies produced to the native proteins. Alfalfa AAT-1 was purified from root suspension culture cells, while AAT-2 was purified from effective root nodules. Antibodies prepared to AAT-1 and used as probes for western blots readily recognized native and SDS forms of AAT-1 but did not recognize either native or SDS forms of AAT-2. Conversely, antibodies to AAT-2 readily recognized native and SDS forms of AAT-2 but did not recognize AAT-1. Immunotitrations further confirmed the immunological distinction between AAT-1 and AAT-2. AAT-1 antibodies immunotitrated 100% of the in vitro activity of purified AAT-1 but had no effect on AAT-2 in vitro activity. Likewise, AAT-2 antibodies removed 100% of the in vitro activity of purified AAT-2 but did not affect AAT-1 in vitro activity. Sequential titration of total AAT activity from roots and nodules showed that AAT-1 comprised the major form (62%) of AAT in roots, while AAT-2 was the predominant form (90%) in nodules. Last, SDS-PAGE western blots showed that the molecular masses of AAT-1 and AAT-2 were 42 and 40 kilodaltons, respectively. These data indicate that AAT is under the control of at least two distinct genes in alfalfa.

Journal Article↗
PubMed1990

Aspartate Aminotransferase in Alfalfa Root Nodules : III. Genotypic and Tissue Expression of Aspartate Aminotransferase in Alfalfa and Other Species.

Aspartate aminotransferase (AAT) plays an important role in nitrogen metabolism in all plants and is particularly important in the assimilation of fixed N derived from the legume-Rhizoblum symbiosis. Two isozymes of AAT (AAT-1 and AAT-2) occur in alfalfa (Medicago sativa L.). Antibodies against alfalfa nodule AAT-2 do not recognize AAT-1, and these antibodies were used to study AAT-2 expression in different tissues and genotypes of alfalfa and also in other legume and nonlegume species. Rocket immunoelectrophoresis indicated that nodules of 38-day-old alfalfa plants contained about eight times more AAT-2 than did nodules of 7-day-old plants, confirming the nodule-enhanced nature of this isozyme. AAT-2 was estimated to make up 16, 15, 5, and 8 milligrams per gram of total soluble protein in mature nodules, roots, stems, and leaves, respectively, of effective N(2)-fixing alfalfa. The concentration of AAT-2 in nodules of ineffective non-N(2)-fixing alafalfa genotypes was about 70% less than that of effective nodules. Western blots of soluble protein from nodules of nine legume species indicated that a 40-kilodalton polypeptide that reacts strongly with AAT-2 antibodies is conserved in legumes. Nodule AAT-2 immunoprecipitation data suggested that amide- and ureide-type legumes may differ in expression and regulation of the enzyme. In addition, Western blotting and immunoprecipitations of AAT activity demonstrated that antibodies against alfalfa AAT-2 are highly cross-reactive with AAT enzyme protein in leaves of soybean (Glycine max L.), wheat (Triticum aestivum L.), and maize (Zea mays L.) and in roots of maize, but not with AAT in soybean and wheat roots. Results from this study indicate that AAT-2 is structurally conserved and localized in similar tissues among diverse species.

Journal Article↗
PubMed1990

Active ion transport pathways in the bovine retinal pigment epithelium.

1. Radioactive tracer flux measurements demonstrate that active ion transport across the isolated bovine retinal pigment epithelium (RPE)-choroid preparation can be maintained for hours after the eye is enucleated and the tissue removed from the eye. 2. It has been shown that 86Rb tracer fluxes can be used to monitor potassium (K+) transport across bull-frog RPE. In bovine RPE, net 86Rb (K+) absorption is zero. Apical barium (Ba2+) elevated active K+ absorption from zero to approximately 0.3 mu equiv cm-2 h-1. This Ba2(+)-induced increase in active K+ absorption was inhibited either by ouabain or bumetanide in the apical bath. 3. In control Ringer solution, buffered with bicarbonate and CO2, the RPE-choroid actively absorbs chloride (Cl-) at a rate of approximately 0.5 mu equiv cm-2 h-1. In contrast, sodium (Na+) is secreted at a rate of approximately 0.5 mu equiv cm-2 h-1. Chloride absorption was inhibited by apical bumetanide, and Na+ secretion was inhibited by apical ouabain. These drugs were only effective when placed in the solution bathing the apical or retinal side of the tissue. 4. Net Cl- absorption requires an exit mechanism at the basolateral membrane. DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid) in the basal bath completely inhibited net Cl- absorption in bicarbonate-free Ringer solution. 5. These experiments show that the chloride transport pathway contains at least two components: (1) a bumetanide-sensitive uptake mechanism at the apical membrane; and (2) an efflux mechanism at the basolateral membrane that is blocked by DIDS. 6. Three apical membrane mechanisms were identified that could help modulate [K+]o in the subretinal or extracellular space that separates the distal retina and the RPE apical membrane. They are: (1) an ouabain-sensitive Na(+)-K+ pump; (2) a bumetanide-sensitive mechanism, the putative Na(+)-K(+)-Cl- co-transporter; (3) a barium-sensitive K+ channel that recycles, to the apical bath, most or all of the potassium that is actively taken up by the Na(+)-K+ pump and the co-transporter. 7. These data suggest that light-induced alterations in subretinal potassium that occur in vivo can activate the chloride transport pathway and help modulate RPE intracellular Cl- during transitions between the light and dark.

Animals↗
PubMed1990

Isolation and provisional identification of plasma membrane populations from cultured human retinal pigment epithelium.

We have attempted to isolate samples of apical and basal-lateral plasma membranes from cultured fetal human RPE. Cells from confluent, dome-forming cultures were disrupted with a Dounce apparatus. Nuclei and melanin granules were sedimented by centrifugation at 2600 g for 10 min. The supernates were layered over gradients of 17.5-65% sorbitol and centrifuged at 122,000 g for 5 hr. Fractions were grouped into "density windows" on the basis of their biochemical marker contents. Na,K-ATPase and alkaline phosphatase overlapped but did not precisely parallel one another, suggesting associations with two partially separated membrane populations; in density window I, alkaline phosphatase was enriched 4.3-fold, and Na,K-ATPase was enriched 1.7-fold, whereas in window II the corresponding enrichment factors were 7.7 and 6.7. These markers were well resolved from a mitochondrial marker, but they were overlapped by endoplasmic reticulum and Golgi markers. Additional density gradient centrifugations, performed after samples had been suspended in 55% sorbitol, further separated alkaline phosphatase- and Na,K-ATPase-containing membranes from endoplasmic reticulum and Golgi membranes, yielding alkaline phosphatase and Na,K-ATPase cumulative enrichment factors of 6.8 and 2.5 for the sample from window I and 9.3 and 10.9 for the sample from window II. Subsequent phase partitioning analysis of the sample from window I further enriched an alkaline-phosphatase-rich membrane population, which is believed to represent the RPE basal-lateral membranes. The sample from density window II contained two membrane populations, both enriched in Na,K-ATPase, alkaline phosphatase, and galactosyltransferase, and both of which appear to be derived from the apical plasma membrane. SDS-PAGE and Western blotting confirmed a correlation between Na,K-ATPase catalytic activity and Na,K-ATPase alpha subunit immunoreactivity.

Alkaline Phosphatase↗
PubMed1989

Apical electrogenic NaHCO3 cotransport. A mechanism for HCO3 absorption across the retinal pigment epithelium.

Intracellular microelectrode techniques and intracellular pH (pHi) measurements using the fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) were employed to characterize an electrogenic bicarbonate transport mechanism at the apical membrane of the frog retinal pigment epithelium (RPE). Reductions in apical concentrations of both [HCO3]o (at constant Pco2 or pHo) or [Na]o caused rapid depolarization of the apical membrane potential (Vap). Both of these voltage responses were inhibited when the concentration of the other ion was reduced or when 1 mM diisothiocyano-2-2 disulfonic acid stilbene (DIDS) was present in the apical bath. Reductions in apical [HCO3]o or [Na]o also produced a rapid acidification of the cell interior that was inhibited by apical DIDS. Elevating pHi at constant Pco2 (and consequently [HCO3]i) by the addition of apical NH4 (20 mM) produced an immediate depolarization of Vap. This response was much smaller when either apical [HCO3]o or [Na]o was reduced or when DIDS was added apically. These results strongly suggest the presence of an electrogenic NaHCO3 cotransporter at the apical membrane. Apical DIDS rapidly depolarized Vap by 2-3 mV and decreased pHi (and [HCO3]i), indicating that the transporter moves NaHCO3 and net negative charge into the cell. The voltage dependence of the transporter was assessed by altering Vap with transepithelial current and then measuring the DIDS-induced change in Vap. Depolarization of Vap increased the magnitude of the DIDS-induced depolarization, whereas hyperpolarization decreased it. Hyperpolarizing Vap beyond -114 mV caused the DIDS-induced voltage change to reverse direction. Based on this reversal potential, we calculate that the stoichiometry of the transporter is 1.6-2.4 (HCO3/Na).

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1989

Purification and Characterization of NADH-Glutamate Synthase from Alfalfa Root Nodules.

Glutamate synthase (GOGAT), a key enzyme in the pathway for the assimilation of symbiotically fixed dinitrogen (N(2)) into amino acids in alfalfa (Medicago sativa L.) root nodules, was purified and used to produce high titer polyclonal antibodies. Purification resulted in a 208-fold increase in specific activity to 13 micromole per minute per milligram of protein and an activity yield of 37%. Further purification to near homogeneity was achieved by fast protein liquid chromatography, but with substantial loss of activity. Enzymic activity was highly labile, losing 3% per hour even when substrates, stabilizers, and reducing agents were included in buffers. However, activity could be partially stabilized for up to 1 month by storing GOGAT at -80 degrees C in 50% glycerol. The subunit molecular weight of GOGAT was estimated at 200 +/- 7 kilodaltons with a native molecular weight of 235 +/- 16 kilodaltons, which suggested that GOGAT is a monomer of unusually high molecular weight. The pl was estimated to be 6.6. The K(m) values for glutamine, alpha-ketoglutarate, and NADH were 466, 33, and 4.2 micromolar, respectively. Antibodies were produced to NADH-GOGAT. Specificity of the antibodies was shown by immunotitration of GOGAT activity. Alfalfa nodule NADH-GOGAT antibodies cross-reacted with polypeptides of a similar molecular weight in a number of legume species. Western blots probed with anti-GOGAT showed that the high GOGAT activity of nodules as compared to roots was associated with increased levels of GOGAT polypeptides. Nodule NADH-GOGAT appeared to be highly expressed in effective nodules and little if any in other organs.

Journal Article↗
PubMed1989

Nitrogen Assimilating Enzyme Activities and Enzyme Protein during Development and Senescence of Effective and Plant Gene-Controlled Ineffective Alfalfa Nodules.

Effective (N(2)-fixing) alfalfa (Medicago sativa L.) and plant-controlled ineffective (non-N(2)-fixing) alfalfa recessive for the in(1) gene were compared to determine the effects of the in(1) gene on nodule development, acetylene reduction activity (ARA), and nodule enzymes associated with N assimilation and disease resistance. Effective nodule ARA reached a maximum before activities of glutamine synthetase (GS), glutamate synthase (GOGAT), aspartate aminotransferase (AAT), asparagine synthetase (AS), and phosphoenolpyruvate carboxylase (PEPC) peaked. Ineffective nodule ARA was only 5% of effective nodule ARA. Developmental profiles of GS, GOGAT, AAT, and PEPC activities were similar for effective and ineffective nodules, but activities in ineffective nodules were lower and declined earlier. Little AS activity was detected in developing ineffective nodules. Changes in GS, GOGAT, AAT, and PEPC activities in developing and senescent effective and ineffective nodules generally paralleled amounts of immunologically detectable enzyme polypeptides. Effective nodule GS, GOGAT, AAT, AS, and PEPC activities declined after defoliation. Activities of glutamate dehydrogenase, malate dehydrogenase, phenylalanine ammonia lyase, and caffeic acid-o-methyltransferase were unrelated to nodule effectiveness. Maximum expression of nodule N-assimilating enzymes appeared to require the continued presence of a product associated with effective bacteroids that was lacking in in(1) effective nodules.

Journal Article↗
PubMed1988

Surgical treatment of necrotizing enterocolitis: a population-based study in the Grampian region, Scotland.

Ninety-two cases of necrotizing enterocolitis (NEC) were diagnosed in the Grampian Region of Scotland between 1978 and 1984, for a regional incidence of 2.2/1,000 live births. Twenty-seven cases (29.3%) required surgery, 19 acutely and eight for delayed stricture. Acute operative mortality was 10.5%. Disease-related mortality was 3.3%, and overall mortality was 8.7%. Follow-up ranged from 15 to 77 months for surgical patients, with only three of 23 survivors having increased bowel frequency.

Enterocolitis, Pseudomembranous↗
PubMed1988

cAMP stimulates the Na+-K+ pump in frog retinal pigment epithelium.

Adenosine 3', 5'-cyclic monophosphate (cAMP) induced increases in active Na+ secretion and K+ absorption that were blocked by apical ouabain (10(-4) M), suggesting stimulation of the Na+-K+ pump. cAMP also produced rapid membrane voltage and resistance changes that could be divided chronologically into three phases. In phase 1, the basolateral membrane depolarized at a faster rate than the apical membrane, probably as a result of an increase in basolateral membrane conductance. In phase 2, the apical membrane repolarized toward control faster than the basal membrane, whereas in phase 3 the basolateral membrane repolarized faster than the apical membrane. Apical ouabain completely inhibited the cAMP-induced repolarization of the apical membrane during phase 2. Thus the stimulation of the Na+-K+ pump occurs within minutes of cAMP elevation. Na+ removal from the basal side did not block the cAMP-induced voltage changes, indicating that the initial conductance increase is not due to Na+. In contrast, Na+ removal from the apical bath inhibited all phases of the cAMP response. This suggests that apical membrane Na+-dependent transport mechanisms mediate the stimulation of the Na+-K+ pump. cAMP also caused a significant drop in intracellular K+ activity (approximately 5 mM) that preceded phase 2. This drop could stimulate the Na+-K+ pump, as suggested by previous experiments.

Animals↗
PubMed1987

Antibiotic prophylaxis in non-perforated appendicitis of childhood: tetracycline lavage compared with peroperative intravenous cefuroxime and metronidazole.

Eighty-four cases of non-perforated appendicitis in children were randomly allocated to receive either oxytetracycline lavage alone or oxytetracycline lavage plus peroperative intravenous metronidazole and cefuroxime. The wound infection rate with the oxytetracycline lavage alone was 4.4% compared with 7.7% when metronidazole and cefuroxime were added. These rates were not significantly different. This study supports the use of oxytetracycline lavage alone as effective prophylaxis against wound infection in non-perforated appendicitis of childhood.

Adolescent↗