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Biomedical subjects

N Carter

Publications and source records attributed to N Carter.

At least 109 records · Page 6Linked to original sources
PubMed1992

Mitochondrial carbonic anhydrase in osteoclasts and two different epithelial acid-secreting cells.

Acid secreting cells are rich in mitochondria and contain high levels of cytoplasmic carbonic anhydrase II. We have studied the ultrastructural distribution of a mitochondrial isoenzyme, carbonic anhydrase V, in two different acid-secreting epithelial cells, gastric parietal cells and kidney intercalated cells as well as in osteoclasts, which are the main bone resorbing cells. The mitochondria differ in carbonic anhydrase V content in these three acid-producing cells: gastric parietal cell mitochondria show strong immunolabelling for this isoenzyme, osteoclast mitochondria faint labelling and kidney intercalated cell mitochondria no labelling. The immunolabelling was located in the mitochondrial matrix, often in close contact with the inner mitochondrial membrane. These results show that mitochondrial carbonic anhydrase levels are not related to acid-transporting activity.

Animals↗
PubMed1992

Atrial natriuretic peptide, cyclic guanosine monophosphate and sodium excretion during postnatal adaptation in male infants below 34 weeks gestation with severe respiratory distress syndrome.

The role of atrial natriuretic peptide (ANP), in the perinatal period, is at present unclear. In adults urinary cyclic guanosine monophosphate (cGMP) is considered an index of the biological activity of plasma ANP. The aim of this study was to determine the relationship between plasma ANP, cGMP excretion (cGMPex) and sodium excretion (Naex) in preterm infants in the first days after birth. Sequential, 4 hourly, measurements of plasma ANP, cGMPex and Naex were made in 12 male neonates of median gestational age 27 weeks (range 25-33) and median birth weight 0.981 kg (range 0.635-2.029) over a median period of 5.2 days (range 2.3-10). The ratios of cGMPex to ANP and of Naex to cGMPex were each plotted against postnatal age. The ratio of cGMPex to ANP increased ten fold in the first 3-4 days after birth but then remained relatively constant; the ratio of Naex to cGMPex showed a steady increase from birth. We conclude that, in extremely immature infants, renal sodium loss in response to cGMP increases rapidly during the first 10 days after birth. In addition, after 3-4 days from birth, plasma ANP ia associated with a constant proportionate rate of cGMP excretion though, as the plateau ratio of cGMPex to ANP varied widely between babies, cGMPex cannot be used to predict plasma ANP in cross sectional studies. These changes may reflect postnatal adaptation and/or maturation of both ANP receptors and cGMP mediated cascades. In the immediate postnatal period, plasma ANP may also have a non-renal role.

Age Factors↗
PubMed1992

Atrial natriuretic peptide in the diagnosis of patent ductus arteriosus.

The aim of this study was to measure plasma atrial natriuretic peptide in preterm infants with a patent ductus arteriosus before and after closure with indomethacin. Atrial natriuretic peptide was measured in 28 preterm infants with clinical and echocardiographic evidence of a patent ductus arteriosus and in eight preterm infants who did not develop clinical evidence of a patent ductus arteriosus. Plasma concentration of atrial natriuretic peptide was measured by radioimmunoassay. In 18 infants the patent ductus arteriosus closed after one course of indomethacin; atrial natriuretic peptide levels decreased from median 1240 pg/ml (range 201-5483 pg/ml) to 266 pg/ml (range 62-1108 pg/ml). In four infants the patent ductus arteriosus closed after two courses of indomethacin and two infants had surgical ligation after indomethacin treatment failed. The patent ductus arteriosus closed spontaneously in four infants (atrial natriuretic peptide median level 152 pg/ml, range 61-495 pg/ml). In the eight infants without patent ductus arteriosus, atrial natriuretic peptide level was median 224 pg/ml (range 38-876 pg/ml). Measurement of plasma atrial natriuretic peptide concentration has a role in predicting when indomethacin treatment is indicated.

Atrial Natriuretic Factor↗
PubMed1992

Influence of cardiopulmonary bypass on water balance hormones in children.

OBJECTIVE: To determine the changes in the endocrine mechanisms of fluid balance after cardiopulmonary bypass in children. DESIGN: Prospective study; analysis of numbered plasma samples performed blind with respect to clinical data. SETTING: Regional paediatric cardiothoracic unit. PATIENTS: Nine patients, median age 4, range 2 to 9 years, five males. Patients under the age of 1 year were excluded because of the frequent blood sampling involved. MAIN OUTCOME MEASURES: Plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin, plasma renin activity, aldosterone, noradrenaline and adrenaline, and urinary concentrations of cyclic guanosine monophosphate (cGMP) as measured by radioimmunoassay. RESULTS: After 30 minutes of cardiopulmonary bypass plasma atrial natriuretic peptide (ANP) decreased from (mean (SEM)) 151 (71) pg/ml to 52 (44) pg/ml (NS), and urinary production of its second messenger cyclic guanosine monophosphate (cGMP) decreased from 1286 (600) pmol/ml to 151 (414) pmol (p < 0.05). Other plasma concentrations of hormones studied did not change significantly although arginine vasopressin, adrenaline, and noradrenaline increased whereas aldosterone and plasma renin activity decreased. After cardiopulmonary bypass stopped there was an immediate and significant rise in plasma ANP, but within the next 24 hours plasma ANP declined significantly (p < 0.05), decreasing from 294 (49) pg/ml to 64 (29) pg/ml at 22 hours. In the postoperative period there was a significant correlation between plasma ANP and both mean fluid balance (r = 0.96, p < 0.001) and mean urine output (r = 0.97, p < 0.001). Plasma aldosterone peaked (p < 0.05) at 22 hours after operation, and argine vasopressin peaked (p < 0.05) at two hours and then declined (p < 0.05) to a trough at 24 hours. Plasma renin activity, adrenaline, noradrenaline, and urinary cGMP concentrations, and mean central venous pressure did not change significantly in the postoperative period. CONCLUSION: The changes documented show the differing pattern of release of water balance hormones invoked by cardiopulmonary bypass. The central role of ANP is shown by its strong correlation with urinary output and its similarly strong relation to fluid balance.

Aldosterone↗
PubMed1990

A proton nuclear magnetic resonance and molecular modeling study of cardiac troponin C. Calcium dependence and aromatic spectral assignments.

Proton (1H) NMR at 360 MHz has been used to characterize calcium-induced spectral changes in bovine cardiac troponin C in more detail than hitherto reported (Hincke, M. T., Sykes, B. D., and Kay, C. M. (1981) Biochemistry 20, 3286-3294). The observed changes are consistent with two equivalents of calcium occupying high affinity sites, with subsequent binding of a single equivalent to a lower affinity site. Two-dimensional J-correlated and nuclear Overhauser effect NOE-correlated and conventional one-dimensional NOE experiments, combined with a consideration of the titration behavior, have allowed all the aromatic signals, and several prominently shifted alpha-CH and methyl group signals, as well as some methionine methyl signals of the calcium-saturated protein, to be assigned. This exercise was facilitated by the construction of a model of the calcium-bound protein based on crystal structure data of the homologous calmodulin and skeletal troponin C, using mutations, energy minimizations, and molecular dynamics simulations, combined with the ring-current shift and NOE prediction program PARSNIP (Reid, D. G., and Saunders, M. R. (1989) J. Biol. Chem. 264, 2003-2012).

Amino Acid Sequence↗
PubMed1990

Chronic stimulation-induced effects point to a coordinated expression of carbonic anhydrase III and slow myosin heavy chain in skeletal muscle.

Chronic low-frequency stimulation of rat fast-twitch muscle induces 3.7-fold elevations in cytochrome c oxidase activity, but remains without effect on carbonic anhydrase III (CAIII) mRNA and protein. This is in contrast with the situation in the rabbit where chronic stimulation elicits more than 10-fold elevations in CAIII activity and mRNA content which coincide with an enhanced expression of the slow myosin heavy chain (HCI). Since chronic stimulation of rat muscle does not enhance the expression of HCI, we conclude that CAIII is expressed in parallel with HCI and, therefore, is present only in type I and C fibers.

Animals↗
PubMed1990

Rehabilitation in chronic back pain: employment status after four years.

Of 129 chronic back pain patients treated consecutively at the Palmerston North hospital rehabilitation unit in 1982-3, 102 responded to a questionnaire in 1987. The 27 nonresponders had had pain for a shorter time and were considered to have a better prognosis. Of the 102 responders, 31 no longer had back pain; 51 (six women) were employed full or part time and 17 (two women) were looking for work. Two men had reversed roles and 17 had retired. Women who no longer had a job outside the home classed themselves as housewives rather than as retired or unemployed. This study provides data for future planning but without controls, confident conclusions cannot be drawn on the efficacy of the rehabilitation programme. There is a need for further controlled studies.

Adolescent↗
PubMed1990

Prenatal diagnosis of a double bisatellited marker with an unusual copy number ratio.

Prenatal diagnosis, by amniocentesis, revealed mosaicism with respect to a bisatellited, apparently dicentric, DA/DAPI positive, de novo marker. The following cell lines were observed in decreasing order of frequency: 46,XX greater than 48,XX,+mar,+mar much greater than 47,XX,+mar. The pregnancy was terminated and post-mortem examination revealed an apparently normal fetus. Cytogenetic studies of fetal and placental tissues revealed approximately the same level of mosaicism together with the unusual copy number ratio seen in the amniotic fluid cultures. Non-disjunction at the first post-zygotic mitotic division giving rise to a mosaic: 46,XX/48,XX,+mar,+mar followed by subsequent mitotic instability of the marker could account for the unusual copy number ratio.

Adult↗
PubMed1990

Plasma atrial natriuretic peptide after the Fontan procedure and total cavopulmonary connexion.

Plasma atrial natriuretic peptide was measured in 10 children undergoing the Fontan procedure and 3 children undergoing total cavopulmonary connexion. There was no significant difference in pre-operative plasma levels, but post-operative levels were significantly higher 48 hours after cardiopulmonary bypass in the Fontan group. There was no significant difference in plasma arginine vasopressin levels either pre- or post-operatively. Post-operative pleural effusions occurred in only 2 of the 10 patients undergoing the Fontan procedure, but were present in all 3 of those undergoing total cavopulmonary connexion. The release of atrial natriuretic peptide is an appropriate homeostatic response to volume loading and the impairment of this response in the early post-operative period may be of clinical importance.

Arginine Vasopressin↗
PubMed1990

The relationship between fecal fat and water in very-low-birth-weight infants.

Metabolic balances were carried out in nine preterm very-low-birth-weight (VLBW) infants, five of whom were fed on expressed breast milk and four on a preterm formula. In 39 stool samples from these infants, there was a very close relationship between the fecal fat and the fecal water (r = -0.95; p less than 0.001), independent of the type of feed. This relationship was present over a very wide range of fat and water contents. Validation experiments confirmed the reproducibility and reliability of this relationship. The correlation is clinically and experimentally so close that measurement of stool water by freeze-drying a sample is an accurate indirect measure of fecal fat in VLBW infants when the daily stool weight was known.

Enteral Nutrition↗
PubMed1990

Human trophoblast cells in culture express an unusual major histocompatibility complex class I-like antigen.

We present evidence that the trophoblast cells obtained from first trimester placentae by a culture method developed in our laboratory express a class I-like HLA antigen that is only sparsely distributed on the cell surface, lacks classical polymorphic determinants, and consists of heavy chains of lower molecular weight than those of classical HLA in association with beta 2-microglobulin (beta 2M). The latter two features are in general agreement with a previous report describing the nature of the HLA molecule on trophoblast disaggregated from term amniochorion. These cultured trophoblast cells could be useful for molecular studies of the unusual class I antigen, as well as for other in vitro experiments designed to mimic the in vivo local trophoblast-uterine interactions.

Antibodies, Monoclonal↗
PubMed1989

Carbonic anhydrase localization to perivenous hepatocytes.

It was shown by immunohistochemical methods, using antisera against highly purified carbonic anhydrases CA I, II and III, that CA II and CA III are specifically located in hepatocytes around central veins of adult rat livers. CA II was found in these perivenous hepatocytes of both male and female rats. Its physiological role is probably to facilitate the secretion of bicarbonate ions by these cells into canalicular bile. CA III and CA I were found in the same hepatocytes but only in the livers of male rats. The function of CA I and CA II exclusively in these cells of male rats cannot be simply explained.

Animals↗
PubMed1989

Separation of pancreatic islets by fluorescence-activated sorting.

To allow clinical pancreatic islet transplantation, the yield and purity of islets must be improved. Intravital staining of islets with neutral red is a specific, nontoxic technique for labeling islets of various species. Using neutral red-stained rat islets, we investigated the known fluorescence absorbance and emission spectra in comparison with unstained exocrine tissue and have shown that stimulation with light of wavelength between 500 and 560 nm produces detectable emission greater than 610 nm, which is absent from unstained exocrine tissue. The PARTEC cell sorter is an inexpensive alternative to currently available fluorescence-activated cell sorters and has a sorting mechanism based on a piezoelectric valve. We made extensive modifications to this machine to allow passage of particles up to 300 micron diam. Using rat pancreas stained intravitally with neutral red and dispersed by intraductal collagenase technique, we have shown that islets can be accurately identified in a high-speed flow system and sorted to a purity of greater than 90% islet tissue. The islets remain intact and viable as determined by supravital staining and isogeneic transplantation to the kidney capsule site. These studies prove the feasibility of separating intact islets by fluorescence-activated sorting.

Animals↗
PubMed1988

L-myo-inositol 1,4,5,6-tetrakisphosphate is present in both mammalian and avian cells.

When myo-[3H]inositol-prelabelled primary-cultured murine bone-marrow-derived macrophages were challenged with platelet-activating factor (PAF; 200 ng/ml), there was a rapid (2.5-fold at 10 s) rise in the intracellular concentration of D-myo-[3H]inositol 1,4,5-trisphosphate, followed by a rise in myo-[3H]inositol tetrakisphosphate. myo-[3H]Inositol tetrakisphosphate fractions were isolated by high-performance anion-exchange chromatography from myo-[3H]inositol-prelabelled chick erythrocytes and primary-cultured macrophages. In both cases [3H]iditol and [3H]inositol were the only significant products (greater than 90% of recovered radioactivity) after oxidation to completion with periodic acid, reduction with NaBH4 and dephosphorylation with alkaline phosphatase. The presence of [3H]inositol after this procedure is consistent with the occurrence of [3H]inositol 1,3,4,5-tetrakisphosphate in the cell extracts, whereas [3H]iditol could only be derived from D- or L-inositol 1,4,5,6-tetrakisphosphate. When [3H]inositol tetrakisphosphate fractions obtained from (A) unstimulated macrophages, (B) macrophages that had been stimulated with PAF for 40s or (C) chick erythrocytes were subjected to the above procedure, radioactivity was recovered in these polyols in the following proportions: A, 60-90% in iditol, with 10-40% in inositol; B, total radioactivity increased by a factor of 9.8, 94% being recovered in inositol and 8% in iditol; C, 70-80% in iditol and 20-30% in inositol. [3H]Iditol derived from myo-[3H]inositol tetrakisphosphate fractions from macrophages and chick erythrocytes was oxidized to sorbose by L-iditol dehydrogenase (L-iditol:NAD+2-oxidoreductase, 1.1.1.14) at the same rate as authentic L-iditol. D-[14C]Iditol, derived from D-myo-inositol 1,4,5-trisphosphate, was not oxidized by L-iditol dehydrogenase. This result indicates that the [3H]iditol was derived from L-myo-inositol inositol 1,4,5,6-tetrakisphosphate. The data are consistent with rapid PAF-sensitive synthesis of D-myo-[3H]inositol 1,3,4,5-tetrakisphosphate in macrophages, and demonstrate that L-myo-inositol 1,4,5,6-tetrakisphosphate is synthesized in both mammalian and avian cells. The levels of L-myo-[3H]inositol 1,4,5,6-tetrakisphosphate in primary-cultured macrophages are not acutely sensitive to PAF.

Animals↗
PubMed1988

Theft reduction in a grocery store through product identification and graphing of losses for employees.

Shoplifting and employee theft constitute a major problem for retailers. Previous research has described techniques for effectively reducing either type of theft but has not addressed the problem of thefts of unspecified origin. In a grocery store we evaluated the effect of identifying for employees frequently stolen products from three groups of items and graphing, twice weekly in the lunchroom, losses for the separate groups. After the products were identified and losses graphed, thefts from the three groups dropped from eight per day to two per day.

Journal Article↗
PubMed1987

Increased ATPase acid stability in type 1 fibers of rat soleus.

Type 1 fibers in skeletal muscle have been considered homogeneous on the basis of their acid-resistant ATPase activity. We have found that the Type 1 fibers in rat soleus are more resistant to prolonged acid pre-incubation than are those in other muscles.

Acids↗