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N D Carter

Publications and source records attributed to N D Carter.

At least 73 records · Page 4Linked to original sources
PubMed1993

Localization of acetazolamide-resistant carbonic anhydrase III in human and rat choroid plexus by immunocytochemistry and in situ hybridisation.

Carbonic anhydrase is an essential metabolic enzyme of the central nervous system and has an important role in the production and regulation of cerebrospinal fluid. Although it has been known for over 30 years that inhibition of the enzyme with acetazolamide dramatically but not completely reduces the production of cerebrospinal fluid, the precise mechanism of the inhibitory action has been only recently revealed. In this study we present evidence that apart from carbonic anhydrase II, the catalytically highly active isozyme, carbonic anhydrase III, an acetazolamide-resistant and kinetically different isozyme could be demonstrated in the epithelial cells of the developing and mature rodent and human choroid plexuses. Both isozymes express intense immunostaining revealed with specific antisera, and by using in situ hybridisation histochemistry, carbonic anhydrase III mRNA was also observed. Since the kinetic properties and proportion of brain carbonic anhydrase III in the human choroid plexus are not revealed the function of this isozyme in choroid plexus is still to be determined.

Acetazolamide↗
PubMed1993

Ventricular expression of brain natriuretic peptide gene following orthotopic cardiac transplantation in children--a three year follow up.

OBJECTIVE: The aim was to examine ventricular brain natriuretic peptide (B-type natriuretic peptide, BNP) gene expression and to determine its relationship with ventricular BNP and circulating BNP levels in paediatric cardiac transplant recipients, over a three year period after transplantation. METHODS: Total RNA extracted from endomyocardial right ventricular biopsy tissues (n = 26) of 13 cardiac transplant recipients (age range 5-17 years) and 10 normal hearts obtained at necropsy (age range 19-76 years) as controls was analysed by northern and slot blot hybridisations. Specific radioimmunoassay techniques were used to determine levels of BNP and atrial natriuretic peptide (A-type natriuretic peptide, ANP) in plasma (n = 26) and ventricular biopsy (n = 26) samples. RESULTS: Ventricular BNP messenger ribonucleic acid (mRNA) levels from slot blot hybridisations in the transplanted heart [122(3) arbitrary units, range 97-143] were significantly higher (p < 0.01) than in the normal heart [63(5) arbitrary units, range 37-98]. Northern blot hybridisations confirmed this result and gave a major BNP mRNA transcript of approximately 900 nucleotides. There was no significant relationship between ventricular BNP mRNA levels and ventricular BNP (r = 0.15, p = 0.5, n = 26) or plasma BNP levels (r = 0.16, p = 0.4, n = 26). There was also no significant relationship between ventricular BNP mRNA levels and any of the haemodynamic variables, or immunosuppressive drugs. A ventricular ANP RNA transcript of approximately 900 nucleotides was detected in the transplanted heart but was below the limit of detection in the normal heart. For the long term study, increased levels of BNP and ANP in both plasma and ventricular samples were observed in the first year after transplantation, with a significant reduction (p < 0.01) in levels three years later. CONCLUSIONS: Ventricular BNP gene expression is increased at the mRNA level after heart transplantation in children. Expression of both ventricular BNP mRNA and ANP mRNA in the transplanted heart may be an important response in the modulation of cardiac function after transplantation.

Adolescent↗
PubMed1993

Studies of cardiopulmonary bypass in children: implications for the regulation of brain natriuretic peptide.

OBJECTIVE: The aim was to examine the influence of cardiopulmonary bypass on brain natriuretic peptide (BNP) and on hormones of importance in the control of sodium and water balance and blood volume. METHODS: Nine patients (mean age 4 years, range 2-9) undergoing cardiac surgery were studied. Blood samples were taken before, during, and up to 24 h after bypass. Plasma levels of BNP, atrial natriuretic peptide (ANP), arginine vasopressin (AVP), plasma renin activity, aldosterone, and catecholamines were measured. RESULTS: Preoperative concentrations of plasma BNP [573(SEM 68) pg.ml-1] and ANP [332(74) pg.ml-1] were greatly increased (p < 0.05) before bypass in all patients when compared to normal levels in children [BNP = 31(4) pg.ml-1; ANP = 27(3) pg.ml-1, n = 28]. With general anaesthetic and sternotomy, there were large reductions (p < 0.05) in both plasma BNP [180(62) pg.ml-1] and plasma ANP [163(59) pg.ml-1]. During bypass, there were no further significant decreases in plasma ANP or BNP concentrations compared with preoperative levels. Postoperatively, plasma BNP gradually increased for 12 h, to 170(28) pg.ml-1, whereas plasma ANP showed a further small decrease, to 107(20) pg.ml-1. However, postoperative plasma levels of both ANP and BNP remained well below preoperative values (p < 0.01). Plasma AVP increased rapidly within 15 min of the onset of bypass, reaching a peak value of 153(5) pg.ml-1 after 45 min. Off bypass, plasma AVP decreased slowly and was still almost 10-fold above preoperative levels 12 h after end of bypass [137(11) pg.ml-1]. Mean central venous pressure decreased during the onset of bypass, from 4.3(1.9) to 0.4(1.1) mm Hg (p < 0.05), and increased again at the end of bypass, to 9.0(3.3) mm Hg (p < 0.05); there was little further change during the postoperative period. CONCLUSIONS: The major source of plasma BNP in patients with congenital heart disease is the cardiac ventricle. The lower plasma ANP and BNP levels and the narrow band of change in central venous pressure following surgical repair of cardiac abnormalities may be a response to improved cardiac function.

Aldosterone↗
PubMed1993

Differentiation-dependent expression of carbonic anhydrase II and III in 3T3 adipocytes.

Carbonic anhydrase (CA) was examined in two adipocyte cell lines, 3T3-L1 and 3T3-F442A. Both CA III and non-CA III activities, measured by 18O mass spectrometry, were present in 3T3-L1 and 3T3-F442A adipocytes; however, no CA activity was detected in 3T3 preadipocytes of either line. These observations were supported by immunoblot experiments employing CA III and CA II isoform-specific antisera. CA III, a major protein in rodent and murine adipocytes, and CA II, another isoform known to be present in adipose tissue, were observed only in the differentiated 3T3 adipocytes. The differentiation-dependent expression of these isozymes may imply an adipocyte-related role for CA. Compared with cultures maintained in the absence of insulin, 3T3 adipocytes maintained in the presence of insulin exhibited 65-90% lower concentrations of CA III. CA II was unaffected. This negative effect of insulin on CA III may explain the metabolic regulation of adipose CA III observed in vivo. After media changes, 3T3 adipocyte cultures rapidly lower media pH, which in turn lowers the bicarbonate/CO2 of bicarbonate/CO2-buffered media. Cultures maintained at low pH displayed 50-90% lower concentrations of CA II and CA III. Similarly, cultures maintained in a low bicarbonate/CO2 media (GibCO2-I medium containing 1 mM bicarbonate under an atmosphere of 100% humidified air) displayed 30-50% lower CA II and CA III concentrations. Thus CA II and CA III concentrations are influenced by pH and bicarbonate/CO2. Neither effect, the pH or the GibCO2-I media effect, was associated with changes in the concentration of pyruvate carboxylase or ATP citrate lyase (2 markers of adipocyte differentiation). Because the regulation by pH and bicarbonate/CO2 may be relatively selective for CA in adipocytes, a simple method for reducing the concentration/activity of CA in 3T3 adipocytes is described that may be a useful tool for studies on the physiological role of the enzyme.

3T3 Cells↗
PubMed1993

Brain and atrial natriuretic peptide plasma concentrations in normal healthy children.

Specific radioimmunoassay techniques were used to measure simultaneously plasma levels of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) in normal healthy children and adults. The concentrations of BNP in plasma of 20 children (mean +/- SEM; 31 +/- 4 pg/ml) were significantly higher (P < 0.05) than concentrations in plasma of 20 adults (12 +/- 1.8 pg/ml). There was no significant difference in levels of plasma ANP between children (27 +/- 3 pg/ml) and adults (36 +/- 2.2 pg/ml). Plasma levels of BNP were positively correlated with plasma ANP levels in children (r = 0.53, P < 0.02, n = 20) and in adults (r = 0.59, P < 0.02, n = 20). These results suggest that plasma levels of BNP in normal children are higher than levels in normal adults; and provide a useful baseline for comparison with levels of BNP and ANP in plasma of children with impaired cardiac function.

Adolescent↗
PubMed1993

Expression of insulin-like growth factor-1 by human ventricular explants in culture.

There is increasing evidence from animal studies for autocrine and paracrine systems in the heart. As the local role of these peptide systems in the human heart is not clear, we assessed cardiac explants in culture as a model for the study of growth factor expression by the heart in humans. Human right ventricular septal biopsies were maintained as explants for up to 9 days in serum-supplemented medium. Insulin-like growth factor-1 (IGF-1) expression was measured by radioimmunoassay and results corrected for tissue protein content. IGF-1 was synthesised by ventricular explants but not secreted into the culture medium. This culture model has the potential to provide insight into the regulation of and response to growth factor expression by the heart in humans.

Culture Techniques↗
PubMed1992

Nucleotide sequence and chromosomal assignment of a cDNA encoding the large isoform of human glutamate decarboxylase.

Glutamic acid decarboxylase (GAD) catalyses the conversion of L-glutamic acid to the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Two forms of human GAD, GAD65 and GAD67, are encoded by two separate genes. A full length human GAD67 cDNA has been isolated from a human frontal cortex cDNA library and the nucleotide sequence determined. The GAD67 gene has been mapped to chromosome 2 using the polymerase chain reaction to amplify specifically the human sequence in rodent/human somatic cell hybrid DNA. This confirms that human GAD67 is not syntenic with the smaller GAD isoform GAD65 which has been assigned to chromosome 10. Production of polyclonal antiserum to a baculovirus-expressed GAD67 enabled immunocytological detection of GAD in the rat brain.

Amino Acid Sequence↗
PubMed1991

Renin and atrial natriuretic peptide restriction fragment length polymorphisms: association with ethnicity and blood pressure.

An investigation of restriction fragment length polymorphisms (RFLPs) and association with blood pressure was carried out for the candidate genes coding for renin (REN) and atrial natriuretic peptide (ANP). The relationship between blood pressure, REN and ANP gene RFLPs was tested in a population of black Afro-Caribbean and white European subjects sampled randomly from family practice registers. Upper and lower quintiles for diastolic blood pressure were selected for analysis. Digests of DNA were prepared from leucocytes and RFLPs were determined using Southern blotting analysis with REN and ANP gene probes. There were highly significant ethnic differences found for BglI, Bg/lI and TaqI polymorphisms with 5'REN probe and for BglI polymorphism with an ANP probe. There was also an association between blood pressure and the BglI/REN polymorphism in Afro-Caribbeans but not with any other polymorphisms studied in either ethnic group. The findings show significant ethnic RFLP differences at the gene loci for both renin and ANP and provide evidence for a possible link between variations within or close to the renin gene and elevated blood pressure in Afro-Caribbeans.

Aged↗
PubMed1991

Immunocytochemical localization of mitochondrial carbonic anhydrase in rat tissues.

We used a monospecific polyclonal antiserum against mitochondrial carbonic anhydrase (CA V) from rat liver to study tissue localization of this new member of the carbonic anhydrase gene family. Strong granular immunostaining reaction of CA V was observed in hepatocytes, myocardium, and in certain populations of skeletal muscle fibers. This is the first time that mitochondrial carbonic anhydrase is described in cardiac tissue of rat or any other species. Different epithelial cells revealed very heterogeneous staining reaction, suggesting that mitochondria are a heterogeneous population with respect to their CA V content. Many cells in different glandular epithelia did not show any CA V, whereas some cells, such as gastric parietal cells, were intensely stained with CA V antibodies. No systematic co-expression of CA V with CA I, CA II, or CA III was observed, although the distribution of CA V in skeletal muscle was somewhat similar to that of CA III. Connective tissue cells such as fibroblasts, chondroblasts, and osteoblasts were negative.

Animals↗
PubMed1991

Immobilization induces carbonic anhydrase III in type II fibers of rat skeletal muscle.

The amount and fiber distribution of carbonic anhydrase III (CA III), a major soluble protein in Type I muscle fibers, were studied during cast immobilization of rat hindlimb with the ankle in plantar or dorsiflexion. The concentration of CA III increased two- (p less than 0.05) and three- (p less than 0.01) fold in the shortened and lengthened tibialis anterior muscle during a 3-weeks immobilization period, respectively. After 6 weeks of immobilization the increase was even greater (p less than 0.001). Concomitantly, the number of CA III positive fibers in the lengthened muscle increased so that almost all fibers were positive. In the soleus muscle no significant change in the CA III concentration was seen. On the basis of actomyosin ATPase staining, the transition of Type IIb fibers towards Type IIa occurred in the tibialis anterior muscle, whereas in the soleus muscle a transformation of Type I fibers towards Type IIa fibers occurred. Therefore, the increase in the muscle CA III concentration seems to be associated with a cell transformation of the muscle towards a more oxidative type.

Animals↗
PubMed1991

Detection of CAIII mRNA in rat skeletal muscle and liver by in situ hybridization.

We carried out a variety of in situ methods of hybridization on rat liver and rat skeletal muscle using 35S-labeled or biotin-labeled rat carbonic anhydrase III (CAIII) cDNA clone. The methods were compared and evaluated. Use of the biotin system produced defined but nonspecific results which were shown not to be due to the biotinylated cDNA probe binding to the mRNA in the muscle sections. This artifact was shown to persist despite various attempts to eliminate it. Alternatively, using 35S-labeled cDNA gave reproducible results which were shown to be consistent with probe binding specifically to mRNA in the muscle section.

Adenosine Triphosphatases↗
PubMed1990

Expression of hepatic mitochondrial carbonic anhydrase V.

We have raised specific (rabbit anti-rat) polyclonal antibodies to hepatic mitochondrial carbonic anhydrase V (CA V) and used them to assay the amounts of protein expressed in liver mitochondria isolated from term-foetal, control or diabetic adult rats and in perivenous and periportal rat hepatocytes. The levels of CA V expressed in mitochondria isolated from the livers of adult male and female rats are similar and increase (about 2-fold) in mitochondria from adult diabetic rats when compared to those isolated from the livers of control rats. The level of enzyme in adult liver was higher than in the livers of term-foetal rats. CA V is expressed in both perivenous and periportal hepatocytes, but the level of expression is greater (approx. 40%) in perivenous cells. The implications and significance of these findings are discussed with reference to the roles and properties of the other carbonic anhydrase isoenzymes and the metabolic function of the mitochondrial isoenzyme.

Animals↗
PubMed1990

Membrane specific carbonic anhydrase (CAIV) expression in human tissues.

Membrane-bound carbonic anhydrase IV (CAIV) expression has been evaluated in a range of fetal and adult human tissues and in cell culture. All tissues tested showed expression of CAIV, assessed by Western blotting, with a single immunodetected band at 55 kDa. The levels varied in fetal lung and liver during development and in various zones of the fetal brain. CAIV was clearly expressed in lung, pancreatic tumour and skin cell cultures.

Blotting, Western↗
PubMed1990

The episodic secretory pattern of growth hormone regulates liver carbonic anhydrase III. Studies in normal and mutant growth-hormone-deficient dwarf rats.

Carbonic anhydrase III (CAIII) occurs in male rat liver at concentrations twenty times those in the female, and is sensitive to the pattern of growth hormone (GH) release. Males release GH episodically and have high concentrations of CAIII; females produce GH in a more continuous fashion and have lower CAIII levels. In normal female rats, the endogenous GH secretory pattern was masculinized, either by regular injections of GH-releasing factor (GRF) or by intermittent infusions of somatostatin (90 min on/90 min off). Both treatments induced regular GH pulses and stimulated growth, but only intermittent somatostatin infusions raised CAIII levels (controls, 1.5 +/- 0.5; somatostatin-treated, 9.0 +/- 2.9 micrograms/mg; means +/- S.D.). GRF pulses (4 micrograms every 4 h) did not however raise CAIII levels (controls 1.8 +/- 0.5; GRF-treated 1.4 +/- 0.4 micrograms/mg). Surprisingly, hepatic CAIII is also sexually dimorphic (males, 18.8 +/- 3; females, 2.22 +/- 0.4 micrograms/mg) in a GH-deficient dwarf rat strain which has low plasma GH levels without 3-hourly GH peaks. Intermittent somatostatin infusions in female dwarf rats partially masculinized hepatic CAIII, an effect reduced by co-infusion with GRF. This CAIII response was not secondary to growth induction, since neither somatostatin nor GRF stimulated growth in dwarf rats, and pulses of exogenous GH stimulated growth in female dwarfs without masculinizing CAIII levels. Furthermore, continuous GH infusion in male dwarf rats partially feminized hepatic CAIII levels (to 9.1 +/- 2.4 micrograms/mg), whereas infusions of insulin-like growth factor-1, which induced the same body weight gain, did not affect hepatic CAIII (20.8 +/- 6 micrograms/mg). These results show that hepatic CAIII expression is highly sensitive to the endogenous GH secretory pattern, independent of growth. They also implicate the low basal GH levels between pulses, rather than the peak GH levels, as the primary determinant of the sexually dimorphic hepatic CAIII expression in the rat.

Animals↗
PubMed1990

Hormonal manipulation and neonatal imprinting of carbonic anhydrase isozymes in rat liver.

Thyroidectomy has a feminizing effect on the carbonic anhydrase isozymes II and III in male rat liver. These isozymes are known to be sexually differentiated but no treatment so far administered has produced total feminization and this is also true for thyroidectomy. Neonatal castration, however, does produce this result, suggesting the possibility of androgen imprinting for these isozymes during the neonatal period.

Age Factors↗
PubMed1990

Expression of carbonic anhydrase in neisseriae and other heterotrophic bacteria.

A diverse range of heterotrophic bacteria was screened for the presence of carbonic anhydrase (CA) activity, sensitivity to inhibition of growth by acetazolamide (CA inhibitor), and the presence of protein binding monospecific antibody prepared against purified Neisseria sicca CA. CA activity was demonstrated only in strains of N. sicca and N. gonorrhoeae. However, all Neisseria strains, including various isolates of N. meningitidis and N. lactamica, were sensitive to acetazolamide, when grown in air, and showed serological cross-reaction with N. sicca CA. Strains of other genera were resistant to acetazolamide. A number of strains including members of the genera Pseudomonas, Staphylococcus, Streptococcus, Serratia and Proteus also strongly expressed a gene product(s) immunologically related to CA. The presence of CA cross-reacting proteins, which lack hydrase activity, is discussed in relation to the function of the various mammalian CA isoenzymes.

Acetazolamide↗
PubMed1990

Plasma concentration of atrial natriuretic peptide in spontaneous atrioventricular re-entrant tachycardias of childhood.

Plasma atrial natriuretic peptide was measured in 13 children between the ages of 1 week and 2 years 9 months during atrioventricular re-entrant tachycardia and 15 minutes after the restoration of sinus rhythm. There was a significant decline in atrial natriuretic peptide during sinus rhythm. Plasma concentrations of the peptide were significantly higher during tachycardia in seven infants under 1 year than in the six older children. The heart rates and the duration of tachycardia were not significantly different in the two age groups. Cardiac failure was present in five of seven children under 18 weeks of age during tachycardia but in none of the older children. The plasma concentration of atrial natriuretic peptide did not significantly correlate with duration of tachycardia or heart rate. If tachycardia occurs in young infants the low functional reserve capacity of the developing heart leads to cardiac failure more frequently and it is likely that this was the cause of the significantly higher plasma concentration of atrial natriuretic peptide in the younger children.

Adenosine↗