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Biomedical subjects

C Hall

Publications and source records attributed to C Hall.

At least 163 records · Page 9Linked to original sources
PubMed1995

Comparison of the effects of losartan and enalapril on clinical status and exercise performance in patients with moderate or severe chronic heart failure.

OBJECTIVES: This study assessed the feasibility of an efficacy trial comparing angiotensin-converting enzyme inhibition and angiotensin II receptor antagonism in heart failure. Patients with moderate or severe heart failure whose condition had previously been stabilized by treatment with a converting enzyme inhibitor were randomly assigned to receive enalapril or losartan. The study was designed to detect any signs of clinical deterioration during double-blind treatment. BACKGROUND: Losartan is a specific, nonpeptide angiotensin II receptor-1 antagonist with a vasodilator hemodynamic profile similar to that of converting enzyme inhibitors. Although therapy with specific receptor blockade has certain theoretic advantages over nonspecific converting enzyme inhibition, demonstration of a comparable therapeutic effect in patients with congestive heart failure will require a major effort comparing two active agents. METHODS: One hundred sixty-six patients with stable heart failure in New York Heart Association functional class III or IV and an ejection fraction < or = 35% were included in a multicenter, double-blind, parallel, enalapril-controlled trial. After a 3-week stabilization period with optimal therapy, including digitalis, diuretic drugs and a converting enzyme inhibitor, patients were randomly assigned to 8 weeks of therapy with losartan, 25 mg/day (n = 52); losartan, 50 mg/day (n = 56); or enalapril, 20 mg/day (n = 58). Patients were assessed with frequent clinical and laboratory evaluation and exercise testing. RESULTS: No significant differences between groups in terms of changes in exercise capacity (6-min walk test), clinical status (dyspnea-fatigue index), neurohumoral activation (norepinephrine, N-terminal atrial natriuretic factor), laboratory evaluation or incidence of adverse experience were observed. CONCLUSIONS: The results suggest that losartan and enalapril are of comparable efficacy and tolerability in the short-term treatment of moderate or severe congestive heart failure. A trial designed to compare the efficacy, tolerability and effect on mortality of long-term angiotensin II receptor blockade with converting enzyme inhibition is both feasible and ethically responsible.

Adult↗
PubMed1995

Atrial natriuretic peptide ANP(1-98) and ANP(99-126) in patients with severe chronic congestive heart failure: relation to echocardiographic measurements. A subgroup analysis from the Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS).

Studies in patients with moderate heart failure have shown a positive relation between atrial size and plasma atrial natriuretic peptide (ANP)(99-126) concentrations; however, the relation of the hormone level and left atrial size and left ventricular function in patients with severe chronic heart failure has not been determined. Fifty-three patients from the Cooperative North Scandinavian Enalapril Survival Study with severe chronic heart failure were evaluated with M-mode echocardiography and determination of plasma concentrations of ANP(99-126). In 35 patients, the plasma level of N-terminal ANP(1-98) was also measured. A significant negative relation was found between ANP(1-98), ANP(99-126), and left atrial diameter (r = -.28, P = .05 and r = -.41, P < .005, respectively). Plasma concentrations of both ANP(1-98) and ANP(99-126) were related to left ventricular systolic function as determined by the systolic time interval index (r = .4, P < .05 and r = .29, P < .05, respectively). A significant improvement of left ventricular systolic function was found in the enalapril group but not in the placebo group. After 6 weeks of therapy, no correlation was found between changes in left atrial size or systolic function or changes in either the ANP(1-98) or ANP(99-126) concentration. The results indicate that high ANP(1-98) or ANP(99-126) plasma concentration is determined by the depressed left ventricular function rather than increased left atrial size in patients with chronic severe heart failure. The findings suggest that the ANP release relation to atrial pressure/atrial size is distorted in severe heart failure.

Aged↗
PubMed1995

Clinical disorders and pressure-pain threshold of the forearm and hand among automobile assembly line workers.

The prevalence of forearm and hand disorders was examined by questionnaire and clinical examination in 199 automobile assembly line workers and in 186 controls. The pressure-pain threshold, hand grip force and hand anthropometry were also studied. There was an increased prevalence of de Quervain's disease for male automobile assembly line workers, and of carpal tunnel syndrome in female workers. The prevalence of symptoms in the forearm and hand during the last 7 days were twice as high among automobile assembly line workers than controls for both men and women. The occurrence of symptoms in the last 7 days was associated with de Quervain's disease, carpal tunnel syndrome and sick-leave due to forearm or hand problems, and it also influenced activities of daily living. Hand grip strength and anthropometrics were not associated with findings in the clinical examination or the occurrence of symptoms in the last 7 days. Low pressure-pain threshold was not associated with findings in the clinical examination, except for reported occurrence of symptoms in the last 7 days for women. Pressure-pain threshold as an indicator of tissue damage is discussed.

Adolescent↗
PubMed1995

Failure of oestrogen induced luteinizing hormone surge in women treated with mifepristone (RU 486) every day for 30 days.

It has been demonstrated previously that administration of the antiprogestin mifepristone (RU 486; 1-5 mg daily) inhibits or delays both the pre-ovulatory luteinizing hormone (LH) surge and ovulation. To investigate this mechanism, dynamic tests of pituitary ovarian function were performed in six healthy women before and during the administration of mifepristone (2 mg daily for 30 days). On day 9 of the control and treatment cycles, samples of blood were collected every 15 min over 12 h for measurement of LH concentration. After 10 h, the responsiveness of the pituitary was tested by the i.v. injection of 10 micrograms of gonadotrophin-releasing hormone (GnRH). On day 10 of the control and treatment cycles, two patches releasing 200 micrograms/day of oestradiol were applied to skin on the abdomen for 3 days. Blood was collected at 24, 48, 59, 72, 81 and 96 h after application of the oestrogen patches for the measurement of gonadotrophin and ovarian hormone concentrations. Follicular development continued in all women during their treatment with mifepristone, and ovulation was suppressed (four women) or delayed (two women). There was no significant difference in the basal concentration of LH between the control and treatment cycles (mean +/- SE; 5.5 +/- 0.4 versus 7.7 +/- 0.4 IU/l respectively), or in the frequency (interpulse interval, 101 +/- 12 versus 105 +/- 13 min respectively) and the amplitude (2.1 +/- 0.4 versus 2.6 +/- 0.4 IU/l respectively) of LH pulses. The response to GnRH was similar. On day 10, the basal concentrations of LH, follicle-stimulating hormone (FSH), prolactin, oestradiol and progesterone and the diameter of the dominant follicle (15.7 +/- 1.8 versus 13.3 +/- 1.9 mm) were similar during control and treatment cycles. In control cycles, there were significant increases in the concentrations of LH and FSH within 72 h of application of the oestrogen patches. During treatment cycles, concentrations of FSH and LH remained low, and were significantly lower than the values observed during control cycles (P < 0.006). We conclude that the antiprogestin mifepristone disrupts ovulation by inhibiting the positive feedback effect of oestrogens and, hence, prevents or delays the generation of a pre-ovulatory LH surge.

Administration, Cutaneous↗
PubMed1995

Interference effects of mental imagery on a motor task.

It can be argued that imaginary practice and physical practice are functionally similar. Evidence in support of this hypothesis comes from several experiments demonstrating that interference effects from imaginary practice in motor learning and motor memory are similar in both direction and size to those resulting from physical practice. The purpose of the present study was to provide additional support for this finding using a retroactive interference paradigm. Sixty participants were required to practise performing a simple motor task that was to be completed in a criterion time of 700 ms. They then were randomly assigned to one of six groups. These groups differed in the amount and type of interpolated practice they experienced. One physical practice group attended one session of interpolated activity involving physical practice of another motor task. The other physical practice group participated in two such sessions. One imagery group attended a single session entailing imaginary practice of the same interpolated motor task, while the other imagery group had two such sessions. A fifth group experienced a combination of physical practice and rest periods for two interpolated sessions. A control group did not experience any interpolated activity sessions. Following the interpolated activity sessions, all groups were given a retention/reacquisition test on the original motor task. Imaginary and physical practice during the interpolated activity sessions caused similar interference effects on retention/reacquisition. All groups showed greater deviation from the criterion movement time (700 ms) during the retention test than the control group, and these deviations were in the expected direction given the nature of the interpolated motor task.

Adolescent↗
PubMed1995

Alagille syndrome: family studies.

Alagille syndrome (AGS) is one of the major forms of chronic liver disease in childhood with severe morbidity and a mortality of 10 to 20%. It is characterised by cholestasis of variable severity with paucity of interlobular bile ducts and anomalies of the cardiovascular system, skeleton, eyes, and face. Previous studies suggest a wide variation in the expression of the disease and a high incidence of new mutations. To determine more accurately the rate of new mutations and to develop criteria for detecting the disorder in parents we systematically investigated parents in 14 families with an affected child. Clinical examination was supplemented by liver function tests, echocardiography, radiographic examination of the spine and forearm, ophthalmological assessment, and chromosome analysis. Six parents had typical anomalies in two or more systems pointing to the presence of autosomal dominant inheritance. Systematic screening of parents for the features defined in this study should improve the accuracy of genetic counselling.

Abortion, Spontaneous↗
PubMed1995

Cerebral blood flow measured with intracerebral laser-Dopplerflow probes and radioactive microspheres.

We have measured cerebral blood flow with intracerebral laser-Doppler microprobes in pentobarbital-anesthetized pigs. We compared the results with measurements from laser-Doppler probes placed on the surface of the brain and with blood flow estimation by the radioactive microsphere method. The cerebral blood flow was varied by alterations in inspired carbon dioxide, hemorrhagic hypotension, and high cerebrospinal fluid pressure. The intracerebral probes and the surface probes showed parallel responses to variations in cerebral blood flow. The correlation was closest between surface probes and the intracerebral probes measuring from the cerebral cortex (r = 0.46; P < 0.005). The r value between laser-Doppler flowmetry and radioactive microspheres was 0.41 (P < 0.0005) for all measurements. The correlation to microspheres was best for the probes located 3 or 10 mm into the brain and poorest for the surface probe. In conclusion, intracerebral laser-Doppler flow measurements reflect changes in blood flow, and the technique appears useful for continuous estimates of cerebral blood flow.

Animals↗
PubMed1995

The use of a computerized method of bone age assessment in clinical practice.

We assessed the reliability and repeatability of a new computerized bone age system, both versions 3.4 and 3.5 (licensed by Discerning System Inc. and Ares Service SA, Serono), able to automatically assess bone age on a left hand and wrist radiograph. This computer system is based upon Tanner and Whitehouse's method (TW2), but there are important differences. Our sample included an initial group of 40 patients who had growth delay/constitutional delay of growth and puberty (n = 10), growth hormone insufficiency/deficiency (n = 15), low birth weight/Silver-Russell syndrome (n = 9), precocious puberty (n = 6), as well as 20 patients with various skeletal dysplasias (multiple epiphyseal dysplasia n = 7, pseudoachondroplasia n = 7, acrodysostosis n = 5, achondroplasia n = 1), 7 girls with Turner syndrome, and 10 boys with nephrotic syndrome on chronic corticosteroid treatment. Multiple anthropometric readings of the same radiographs demonstrated excellent repeatability of the assessment. In addition, the number of times that a manual insertion of a grade was required was similar in four different assessments. The computerized method did not entirely avoid errors in interpretation as the position of the x-ray on the screen was critical. There was a high manual insertion rate in radiographs of children with skeletal dysplasia. However, the computer assessment system, version 3.5, performed adequately for radiographs of children with normal bone morphology and Turner syndrome and had the advantage of a continuous scale of assessment.

Adolescent↗
PubMed1995

Retinal and choroidal blood flow response to hyperoxemia after severe hypoxemia in the newborn piglet.

To investigate the effect of hyperoxemia on the ocular circulation after a severe hypoxemic insult (8% O2 until base excess reached -20 mmol/l), we randomly reoxygenated newborn piglets with 100% (study group, n = 8) or 21% O2 (control group, n = 10). Retinal (RBF) and choroidal blood flow (ChBF) were measured with radioactive microspheres. The hypoxemic insult did not change RBF, while ChBF significantly decreased. However, a marked reduction in both retinal (RDO2) and choroidal oxygen delivery (ChDO2) was observed, probably resulting in hypoxia both in the inner and outer retina. At 5 and 20 min of reoxygenation a similar hyperemic response in the retina was seen in both groups. RDO2 also increased significantly and no significant differences between the 2 groups could be demonstrated. We found no indication of retinal vasoconstriction during hyperoxemia. We speculate that the vasodilating effect of the preceding hypoxemia overrules the vasoconstrictive effect of the retinal vessels normally found during hyperoxemia.

Animals↗
PubMed1995

The pharmacokinetics of valproic acid in pregnant sheep after maternal and fetal intravenous bolus administration.

The pharmacokinetics and disposition of valproic acid (VPA) have been assessed in pregnant sheep after both maternal and fetal iv bolus administration. The time course of VPA and 16 of its metabolites was followed in maternal and fetal arterial blood, amniotic fluid, and fetal tracheal fluid for 48 hr after administration. Fetal blood gas, acid-base, metabolic, cardiovascular, and fetal breathing activity parameters were also monitored. The disposition of VPA in maternal serum is best described by a biexponential function with a terminal elimination half-life of 2.13 +/- 0.49 hr and volume of distribution of 0.242 +/- 0.036 liter/kg. VPA transfer to fetal serum and other fetal fluids was rapid after drug administration. There was significant fetal exposure to VPA after maternal dosing (mean AUCinfinityFA/AUCinfinityMA = 0.410 +/- 0.118). Similarly, the disposition of VPA in fetal serum after fetal dosing is best described by a biexponential decay with a terminal elimination half-life of 3.37 +/- 1.37 hr. Once again, VPA transfer to other fluids was rapid. However, unlike basic compounds studied previously, VPA did not accumulate extensively in either amniotic or fetal tracheal fluid. The following metabolites were detected after drug administration in these experiments: (E)- and (Z)-2-ene VPA, (E)- and (Z)-3-ene VPA, 4-ene VPA, 3-keto VPA, 4-keto VPA, 3-OH VPA, 4-OH VPA, 5-OH VPA, and 2-PGA. Both maternal and fetal bolus administration of VPA elicited a significant reduction in fetal breathing movements, which may be attributed to the drug's action on gamma-aminobutyric acid dynamics in the central nervous system (CNS). This suggests that the significant fetal exposure to VPA may produce further CNS-related effects in utero.

Amniotic Fluid↗
PubMed1994

The pericardium acts as a restricting factor on the release of ANF (1-98) and ANF (99-126) after volume loading in pigs.

The stimulus for secretion of the atrial peptides from the heart is a mechanical distension of the atria. We studied the changes in plasma levels of immunoreactive ANF (1-98) and ANF (99-126) after volume loading (NaCl 0.9%, 50 ml/kg in 10 min) in pigs that had their pericardium opened (peric-, n = 8) and compared these changes to those of pigs subjected to sham operation (peric+, n = 8). For irANF (99-126), the maximum increase was achieved 10 min after the start of loading: 18.6 +/- 5.5 pmol/l to 31.4 +/- 15.6 pmol/l. (P < 0.05) in peric+ and 23.9 +/- 6.5 pmol/l to 110.2 +/- 46.2 pmol/l (P < 0.05) in peric-. The maximum increase in irANF (1-98) took place after 15 min: 658.8 +/- 223.9 pmol/l to 791.0 +/- 229.4 pmol/l (P < 0.05) in peric+ and 769.9 +/- 228.5 pmol/l to 1136.7 +/- 348.6 pmol/l (P < 0.05) in peric-. For both peptides the maximal increase after loading was significantly greater when the pericardium had been removed. The results demonstrate that the intact pericardium restricts peptide release secondary to volume infusion in closed-chest pigs.

Animals↗
PubMed1994

Prospective study of central nervous system function in amateur boxers in the United States.

Active amateur boxers from six US cities were studied in 1986-1990 to determine whether changes in central nervous system function over a 2-year interval (as evaluated by tests of perceptual/motor function, attention/concentration, psychomotor speed, memory, visuoconstructional ability, and mental control, measures of ataxia and brain-stem auditory evoked potentials, and electroencephalography) were associated with degree of participation in amateur boxing. A total of 484 participants were examined at baseline; 393 (81.2%) were examined 2 years later. At baseline, 22% of the participants had not yet competed in a bout; 9% had never competed in a bout by the second examination. Exposure was defined by number bouts, sparring-years, and sparring with a professional boxer. Very few statistically significant odds ratios were found between exposure and change in function. Significant tests of trend were found between the total number of bouts incurred before the baseline examination and changes in memory, visuoconstructional ability, and perceptual/motor ability. The significant trends for change in function in the latter two domains were primarily due to performance on the Block Design test, which was common to both test domains. No statistically significant associations were found between more recent bouts (after the baseline visit) and any functional domains, nor between bouts or sparring and any other outcome measures. The significant trends with past bouts, but not more recent bouts, may reflect the need for a long latency period before effects are manifest. Alternatively, given changes in safety practices, the observed association may be related to more severe exposure from bouts that occurred before 1986, when new safety measures were imposed.

Adolescent↗
PubMed1994

The plasma concentration of N-terminal proatrial natriuretic factor ANF(1-98) is related to prognosis in severe heart failure.

Due to its longer halflife, the N-terminal of ANF prohormone, ANF(1-98), has plasma concentrations that exceed those of ANF itself by a factor of 10 or more. It is also less prone to rapid changes secondary to hemodynamic alterations. To evaluate the prognostic significance of ANF(1-98) plasma levels in severe heart failure (NYHA IV), the peptide was measured by radioimmunoassay in plasma samples from patients randomized to additional treatment with enalapril (n = 78) or placebo (n = 61) (CONSENSUS study). In the placebo group there was a positive relation between mortality after 6 months and baseline ANF(1-98) level. Because of a reduced mortality, especially among patients with high ANF(1-98) levels, there was no such relation in the patients treated with enalapril. For both groups there was a positive relationship between increase in ANF(1-98) after 6 weeks of treatment and mortality, while a decrease signaled a favorable prognosis. It is concluded that the magnitude and changes of plasma ANF(1-98) provide information on prognosis and therapeutic effects with respect to mortality in patients with severe heart failure. Plasma ANF(1-98) may serve as a useful clinical biochemical parameter in the treatment of heart failure.

Aged↗
PubMed1994

Developmental expression of poly(A) binding protein mRNAs during spermatogenesis in the mouse.

The poly(A) binding protein (PABP), a conserved protein that binds to the 3' poly(A) tail on mRNAs in eukaryotic cells, has been implicated in the regulation of mRNA stability and translation. Two PABP cDNAs with different sequences were isolated from mouse testis cDNA libraries. The predicted amino acid sequence of one, PABP1, is nearly identical (98.9%) to human liver PABP, while 80% of the amino acids of the second, PABPt, are identical to mouse and human PABPs. Northern blots reveal that there is one major PABP mRNA species in liver, muscle, kidney, and brain, two in spleen, and at least four in testis. The levels of PABP mRNA in testis are 5-10-fold higher than in these somatic tissues, but surprisingly the vast majority of all PABP mRNA size variants sediment more slowly than single ribosomes, indicating strong translational repression. Reverse transcriptase-polymerase chain reaction assays demonstrate that PABPt mRNAs are abundant only in testis. Northern blots of RNAs purified from highly enriched spermatogenic cells show that the high levels, multiple sizes of PABP mRNAs, and the PABPt mRNA are present in meiotic and early haploid spermatogenic cells, and are sharply reduced in late haploid cells. Comparison of the binding of PABP1 and PABPt to poly(A) Sepharose in vitro revealed subtle differences, even though PABPt contains substitutions for highly conserved aromatic amino acids that are thought to be necessary for binding to poly(A). The existence of two PABP isoforms in mouse spermatogenic cells could influence cytoplasmic gene expression during spermatogenesis.

Amino Acid Sequence↗
PubMed1994

Effect of enalaprilat on splanchnic vascular capacitance during acute ischemic heart failure in dogs.

This study investigates the effect of angiotensin-converting-enzyme inhibition by intravenous enalaprilat (100 micrograms/kg) on splanchnic vascular capacitance during acute left ventricular failure induced by coronary microembolization in alpha-chloralose/urethan anesthetized dogs. Changes in hepatic and splenic vascular volumes were determined from organ diameters (sonomicrometry) at 15, 30, and 45 min after enalaprilat injection. Changes in vascular capacitance were assessed from organ pressure-diameter curves obtained during transient hepatic outflow occlusion. Thirty minutes after enalaprilat, hepatic volume was increased by 52 +/- 14 ml (P < 0.01), and portal and hepatic vein pressures were decreased from 10.2 +/- 0.9 to 8.7 +/- 0.8 mmHg (P < 0.01) and from 3.9 +/- 1.6 to 3.1 +/- 0.7 mmHg (P < 0.05), respectively. Splenic volume did not change. Enalaprilat shifted the hepatic pressure-diameter curve upward, resulting in a larger hepatic volume at any given pressure. Curve intercept was increased, suggesting an increase in unstressed vascular volume. Curve slope was unchanged. In conclusion, enalaprilat increased hepatic vascular volume during acute left ventricular failure in dogs. The pressure-diameter curve shift suggests a reduction in the smooth muscle tone of hepatic capacitance vessels.

Acute Disease↗
PubMed1994

Cerebral blood flow autoregulation after moderate hypoxemia in the newborn piglet.

The isotope-labelled microsphere method was used to study blood flow autoregulation in the brainstem (BS), cerebellum (CBL), cerebrum (CBR) and choroid plexus (ChPl) in 21 newborn piglets exposed to hypoxemia and/or hypovolemia. One group of piglets (n = 7) was made hypoxemic by breathing 10% O2 for 10 min, a second group (n = 8) was studied during hypoxemia (10% O2, 10 min), followed by hypovolemia (bleeding 20% of estimated blood volume). A third group of piglets (n = 6) was made hypovolemic by bleeding 20%. Hypoxemia significantly impaired the autoregulatory capacity in CBL and CBR resulting in a pressure-passive flow pattern. Hypovolemia alone did not produce any significant cerebral vascular response in BS, CBL and CBR, not even when hypovolemia was preceded by hypoxemia, indicating a rapid restoration of the autoregulatory capacity of the cerebral vasculature after hypoxemia of moderate duration. The hypotension seen both during hypoxemia and hypovolemia was gradually compensated for and normalized within 60 min. However, animals exposed to both hypoxemia and hypovolemia were still hypotensive 60 min after the hypoxemic insult. Cardiac output (CO) was not affected by hypoxemia, but was consistently reduced in hypovolemia. We therefore speculate that in the newborn a reduced CO might be a more specific parameter for hypovolemia than a low blood pressure.

Animals↗