PubMed Health⌕ Search

Biomedical subjects

P A Collins

Publications and source records attributed to P A Collins.

14 recordsLinked to original sources
PubMed1989

Interaction of inhibitin with the human erythrocyte Na+(Li+)i/Nao+ exchanger.

The kinetic interactions of inhibitin, a peptide isolated from cultured leukaemic promyelocytes, with erythrocyte Na+/Na+ and Na+/Li+ exchanges have been investigated. Inhibitin (1 microM) reduced the ouabain- and bumetanide-resistant sodium efflux and influx by equivalent amounts indicating an inhibitin-sensitive exchange component of 0.52 mmol/l per h. This value was not significantly different from that measured as the difference in sodium-rich (140 mM) and sodium-free media (0.49 mmol/l per h). Similarly, the inhibitin-sensitive lithium efflux was equivalent to the sodium/lithium countertransport component (0.36 vs. 0.34 mmol/l per h), indicating that both exchanges were mediated by the same transport process, which is inhibitin-sensitive. The dose-response curve revealed the presence of a single inhibitin binding site per exchanger with a Ki of 2.10(-7) M. In kinetic inhibition studies, inhibitin (0.1 microM) decreased the Vmax of ouabain- and bumetanide-resistant sodium efflux with no effect on the Km for external sodium, i.e., inhibitin displayed a non-competitive mechanism of action. These findings indicate that inhibitin interacts with the Na+(Li+)i/Nao+ exchanger at a site distinct from the sodium binding site.

Biological Transport↗
PubMed1989

Changes in the advertised demand for nurse practitioners in the United States, 1975-1986.

Legislative and reimbursement policies have presented barriers to employment and autonomy for nurse practitioners since the beginning of the nurse practitioner movement in 1965. Greater resistance to NPs in the 1980s was predicted because of a sluggish economy and burgeoning oversupply of physicians. In this study, quantitative content analysis was used to examine 1,022 job advertisements published in The Nurse Practitioner: The American Journal of Primary Health Care from 1975 to 1986. Unstandardized regression analysis was used to compare changes in the demand for nurse practitioners by region, employment setting, job duties, specialty, employment time (full- or part-time), degree required or preferred for the position, and whether the ad specified a joint practice arrangement. Contrary to the predictions of past research, the demand for nurse practitioners increased during this time period, with a greater tendency toward primary care.

Advertising↗
PubMed1987

Musculoskeletal tumors: improved depiction with linear combinations of MR images.

With postprocessing, the authors produced a single hybrid image that combines the complementary information in conventional T1- and T2-weighted magnetic resonance (MR) images. A 1-T MR imager was used to produce T1- and T2-weighted images (repetition time, msec/echo time, msec: 500/30, 1,500/120) of patients with various primary bone tumors. Various weighted sums and differences of these images were then formed. Weighted subtraction allowed formation of hybrid images with high contrast between tumor and all adjacent normal tissues (muscle, fat, bone marrow), unlike the original T1- and T2-weighted images. Certain weighted sums of the acquired images simultaneously display the high signal-to-noise and clear anatomic detail of the T1-weighted technique along with the high contrast between extraosseous tumor and muscle of the T2-weighted image. A single hybrid MR image can contain useful characteristics both of T1- and T2-weighted images, making it easier for one to detect the extent of an abnormality.

Bone Neoplasms↗
PubMed1986

Television viewing at home: age trends in visual attention and time with TV.

The TV-viewing behavior of 99 families with young children was videotaped by automated time-lapse recording equipment placed in homes for 10-day periods. The 99 families comprised 460 individuals from infants to 62 years of age. Time-sample analyses of 4,672 hours of recordings indicated that the TV-viewing room contained no viewers 14.7% of the time that the TV was on. There were no age trends in time spent with television. Percent visual attention to television increased greatly across the preschool years, leveled off at about 70% during the school-age years, and declined in adulthood. Men looked at the TV more than women. There were no significant correlations between time spent with TV and percent of visual attention to TV. The increase in visual attention to television during the preschool years is consistent with the theory that TV program comprehensibility is a major determination of attention in young children.

Adolescent↗
PubMed1985

Characterization and partial purification of the sodium-potassium-ATPase inhibitor released from cultured rat hypothalamic cells.

An inhibitor of sodium-potassium-ATPase has been partially purified from the culture medium obtained from hypothalamic cells maintained in a capillary membrane perfusion system, and some of the properties of this inhibitory factor have been investigated. Gel filtration (Sephadex G-25 Superfine) of heat-treated medium (80 degrees C for 10 min) resulted in elution of inhibitory activity in the post-salt fraction. These fractions inhibited active (i.e. sodium-potassium-ATPase-mediated) sodium transport in intact human erythrocytes, displaced [3H]ouabain from its binding site, and directly inhibited canine kidney sodium-potassium-ATPase as measured by NADH oxidation. High-performance liquid chromatography (on Hypersil ODS) of these fractions after desalting yielded one region which showed inhibitory activity on all three assays. Inhibition of sodium-potassium-ATPase was dose-related and filtered through an Amicon UM10 membrane. Incubation of this material with dispase, carboxypeptidase A, chymotrypsin, and prolidase destroyed inhibitory activity, whereas trypsin and leucine aminopeptidase were ineffective. These studies show that hypothalamic neurones release a low molecular weight heat-stable peptide which inhibits active sodium transport, ouabain binding, and sodium-potassium-ATPase.

Animals↗
PubMed1979

Autologous rectus sheath grafts. V. Growth in aortic grafts.

Experiments were designed to test autologous rectus sheath as a replacement for the thoracic aorta in the growing dog. Adequacy of graft function was determined by angiography at 4 month intervals; stress-strain measurements and microscopic examination were made at the time of autopsy. A 3 cm tubular graft of rectus sheath tissue was employed as an aortic graft in 13 mongrel puppies. Nine puppies (70%) were long-term survivors and were put to death between 6 and 22 months postoperatively. No deaths were due to graft failure. Angiographic studies demonstrated patency of the graft without development of pressure gradients. An increase in diameter of the aorta (21.25%) and the rectus sheath graft %22.87%) were demonstrated in all cases. During the time of observation, the compliance of the growing aorta (93,120 dynes/cm2) decreased to one fourth that of the control aortic tissue (24,800 dynes/cm2), whereas the compliance of the rectus sheath graft (547,1000 dynes/cm2) decreased to only one eighth that of the control rectus sheath (47,400 dynes/cm2). Tensile strength is maintained in both the growing aorta (4.5 x 10(7) dynes/cm2) and the rectus sheath graft (4.7 x 10(7) dynes/cm2; p less than 0.05). Microscopic examination showed no calcification, thinning, or weakness. Vascularization of the graft had occurred, with cellular proliferation and development of more than 30 lamellar-like units in the media and an adventitia-like surface.

Abdominal Muscles↗
PubMed1978

Parallelism between ethanol and imidazole interactions with horse liver alcohol dehydrogenase.

The rate effects of imidazole on the EE isoenzyme of horse liver alcohol dehydrogenase have been analysed in terms of the elucidated kinetic mechanism of the enzyme. These imidazole effects on both directions of the reaction within nonexcess as well as excess ranges of substrate concentrations pointed to the competition between imidazole and ethanol for binding to the same three enzyme species in the kinetic mechanism, namely the free enzyme, the enzyme-NAD+ complex, and the enzyme-NADH complex. Moreover, both imidazole and ethanol brought about an enhancement in the rate of dissociation of NAD+ from its binding site on the enzyme.

1-Propanol↗
PubMed1977

Transhydrogenase activity in the marine bacterium Beneckea natriegens.

The marine bacterium, Beneckea natriegens, which has previously been reported not to form transhydrogenase, has been shown to synthesize a soluble energy-independent transhydrogenase (NADPH:NADP+ oxidoreductase, EC 1.6.1.1), though no energy-linked activity could be detected. The transhydrogenase is induced maximally in stationary phase cells and its formation is 70-90% repressed by raising the medium phosphate level from 0.33 to 3.3 mM. The enzyme is inhibited by arsenate, inorganic ortho- and pyrophosphate and by a range of organic phosphate-containing compounds, including 2'-AMP, which is an activator of several bacterial transhydrogenases.

Bacteria↗
PubMed1977

Adenylate energy charge during batch culture of Beneckea natriegens.

The value of the adenylate energy charge, i.e. ([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP]), during batch culture of Beneckea natriegens remained relatively constant during the exponential and early stationary phases of the growth cycle. During exponential growth the intracellular ATP content remained constant, the amount of ATP in the culture increasing proportionally with growth; these conditions were unaltered during growth in the presence of added cyclic AMP. On cessation of growth, significant variation in bacterial ATP content was observed depending on whether growth of the cultures terminated due to exhaustion of carbon or nitrogen from the medium, and on the presence or absence of added cyclic AMP.

Adenine Nucleotides↗
PubMed1976

Esophago-gastric invagination in patients with sliding hiatus hernia.

Intussusception of the distal esophagus into a reducible hiatus hernia is described in nine female and three male patients. The main radiographic feature is demonstration of a lobulated fundal mass of changeable size and configuration surrounding the narrowed distal esophageal segment. This pseudotumor is produced by inversion of the hiatus hernia into the stomach, and may be mistaken for a neoplasm. Disinvagination invariably occurs when maneuvers directed toward demonstration of a sliding hernia are utilized during upper gastrointestinal fluoroscopy. It is emphasized that esophago-gastric invagination frequently accounts for masses shown in the cardia of older women with intermittent dysphagia and crampy epigastric pain.

Adult↗
PubMed1975

The respiratory system of Chromobacterium violaceum grown under conditions of high and low cyanide evolution.

The particulate fraction of disrupted Chromobacterium violaceum grown under cyanide-evolving conditions was unable to oxidize ascorbate plus N,N,N',N'-tetra-methyl-p-phenylenediamine (TMPD), but oxidized NADH and succinate by a linear respiratory pathway which was very resistant to inhibition by cyanide. When the bacteria were grown under conditions where little cyanide evolution occurred, particulate fractions developed the ability to oxidize ascorbate-TMPD by a pathway highly sensitive to cyanide inhibition; respiratory activity with NADH and succinate proceeded via both the cyanide-sensitive and-resistant pathways. Studies with respiratory inhibitors, and the cytochrome compositions of the fractions derived from cultures grown under both conditions, are presented. A soluble, carbon monoxide-binding cytochrome c was found, and this appears similar to those found recently in Beneckea natiegens, methylotrophic bacteria and the marine pseudomonad B16.

Antimycin A↗
PubMed1975

Matrix calculi.

Matrix calculi are an uncommon form of urinary tract concretion. They must be considered in the differential diagnosis of a radiolucent mass within the renal collecting system or ureter. The clinical and radiographic features of three cases are presented and the literature of matrix calculi is reviewed.

Bacteriuria↗
PubMedDate not supplied

Laryngeal stenosis in acromegaly: a possible cause of airway difficulties associated with anesthesia.

After difficult intubation in an acromegalic patient was encountered, 7 additional acromegalic patients were studied by measuring the cricoid width and anteroposterior diameter. Cricoid width and anteroposterior diameter were generally found to be narrower than in a group of normal patients. Such narrowing may explain airway problems encountered in acromegalic surgical patients.

Acromegaly↗