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Biomedical subjects

J Arnold

Publications and source records attributed to J Arnold.

At least 163 records · Page 9Linked to original sources
PubMed1990

Urolithiasis in Saudi Arabia.

In a retrospective study, 760 Saudi patients with urolithiasis were epidemiologically and metabolically studied (41% were from the Central region, 32% South, 14% West, 9% North, and 1% East; the remaining 3% were Saudi but of unknown region). The male to female ratio was 5:1; 87 percent of the patients were aged thirty to sixty years and 11 patients were under age fourteen. There was no clear relation of stone formation to occupation. Sixty-nine percent of calculi were renal, 29 percent ureteric, and only 3 percent were bladder calculi. Two hundred seventy-eight operative procedures were done (36.5% of all patients), including pyelolithotomy, nephrolithotomy, ureterolithotomy, ESWL, cystolithotomy, and extractions by basket. Infection was a rarity (6%) and urinary schistosomiasis was found in 33 patients (4.3%), 24 of whom were from a schistosoma-infested region. Raised serum calcium was found in only 5.7 percent and raised serum urate in 13 percent. Increased urinary excretion of urate was found in 60 percent and hypercalciuria in 9 percent. Seventy-six percent of stones analyzed (239) were calcium oxalate, 20.5 percent urate, and 3.3 percent phosphate.

Adolescent↗
PubMed1990

Dopamine beta-hydroxylase inhibition reveals a selective influence of endotoxin on catecholamine content of rat tissues.

Endotoxin is known to affect sympathetic nervous system (SNS) activity. However, it is unknown whether selective activation occurs in different tissues. The present work assessed SNS activity in several tissues of endotoxin-treated rats by measuring the accumulation of dopamine following dopamine beta-hydroxylase inhibition with disulfiram. Twenty-four hours following endotoxin injection (1 mg/kg), body weight and food intake were significantly reduced. The weight of spleen and liver was significantly greater in endotoxin-injected rats compared to either control animals or rats pair-fed the same quantity of food ingested by the endotoxin-treated rats. Norepinephrine (NE) content of heart, liver, and brown adipose tissue (BAT) was significantly lower in endotoxin-injected animals, but it was unchanged in spleen and gastrocnemius muscle. Endotoxin caused a significant elevation in the dopamine content of heart, liver, BAT, and gastrocnemius muscle, whereas it had no effect on spleen. The results suggest that SNS activity is increased in heart, liver, BAT, and gastrocnemius muscle 26 h after endotoxin injection.

Adipose Tissue, Brown↗
PubMed1989

Topical iodine-containing antiseptics and neonatal hypothyroidism in very-low-birthweight infants.

The thyroid function of very-low-birthweight (VLBW; below 1500 g) infants admitted to neonatal intensive-care units was studied at two hospitals; one routinely used topical iodinated antiseptic agents and the other used chlorhexidine-containing antiseptics. Serial monitoring of urinary iodine excretion and serum thyrotropin and thyroxine levels was undertaken from birth for the first 4 weeks of life. Urinary iodine excretion rose dramatically in the 54 iodine-exposed infants and was up to fifty times greater than in the 29 non-exposed infants. Within 14 days, 25% (9 of 36) of the infants exposed to iodine had serum thyrotropin levels above 20 mIU/l, compared with none of the control group. The mean serum thyroxine level in these 9 infants (44.1 nmol/l) was significantly lower than that in exposed infants with normal thyrotropin levels (83.1 nmol/l) and in the non-exposed control group (83.0 nmol/l); thyroxine levels fell before serum thyrotropin rose. These disturbances in thyroid function correlated positively with urinary iodine excretion and hence iodine absorption. Thyroid function had returned to normal by the time of discharge from hospital. It is concluded that iodine absorption, from topical iodine-containing antiseptics, may cause hypothyroidism during a critical period of neurological development in the newborn infant. The routine use of iodine antisepsis in VLBW infants should be avoided because of this effect.

Administration, Topical↗
PubMed1989

Retinal microembolism and neuropsychological deficit following clinical cardiopulmonary bypass: comparison of a membrane and a bubble oxygenator. A preliminary communication.

To observe and quantify cerebrovascular microembolic events in the central nervous system during cardiopulmonary bypass, 40 patients having elective uncomplicated coronary surgery had retinal fluorescein angiograms 5 min before bypass was discontinued. Each patient also had 10 neuropsychological tests before and after surgery. A Harvey H1700 bubble oxygenator was used for 23 patients and a Cobe CML sheet membrane oxygenator was used for 17 patients. All 23 (100%) of patients in the bubble oxygenator group had retinal microvascular occlusions consistent with microembolism compared to 8/17 (47%) in the membrane oxygenator group (P less than 0.001). In those retinas with occlusions, the mean resultant area of non-perfusion was less in the membrane oxygenator group (0.11 mm2; n = 8) than in the bubble oxygenator group (0.29 mm2; P less than 0.01). Arterial PO2 levels during bypass were similar in both groups at moderate hypothermia, but the mean PaO2 during rewarming was higher in the bubble oxygenator group (27 kPa) than in the membrane group (13 kPa; P less than 0.001). Neuropsychological deficits were more common and more severe after bubble oxygenation than after membrane oxygenation, but in this small patient group, the difference was not statistically significant. We conclude that flat sheet membrane oxygenation during cardiopulmonary bypass may confer significant protection against cerebrovascular microembolism.

Cardiopulmonary Bypass↗
PubMed1989

Thermic effect of parenteral nutrition in septic and nonseptic individuals.

This study compared the metabolic responses to parenteral nutrition in five septic and six nonseptic individuals. Oxygen uptake (VO2) was measured for 1 h preinfusion and during the first 2 h of parenteral nutrition infusion. While baseline VO2 was 19% higher in the septic compared with nonseptic patients (p less than 0.01), both groups responded similarly to nutrition: VO2 increased 25% and 27% above baseline in the nonseptic and septic groups, respectively (NS between groups). Respiratory quotient increased 9% in the nonseptic (p less than 0.01) and 5% in the septic (p less than 0.05) patients during infusion. Plasma glucose and insulin increased identically in both groups. Cortisol was consistently higher in the septic patients whereas glucagon decreased similarly in both groups with feeding. Norepinephrine increased 25% in response to the nutrition and remained elevated in the nonseptic group. The results illustrate the effect nutrient-induced thermogenesis may have in the energy balance of parenterally fed patients.

Adult↗
PubMed1989

The effects of assortative mating and migration on cytonuclear associations in hybrid zones.

We examine the influence of nonrandom mating and immigration on the evolutionary dynamics of cytonuclear associations in hybrid zones. Recursion equations for allelic and genotypic cytonuclear disequilibria were generated under models of (1) migration alone, assuming hybrid zone matings are random with respect to cytonuclear genotype; and (2) migration in conjunction with refined epistatic mating, in which females of the pure parental species preferentially mate with conspecific males. Major results are as follows: (a) even the slightest migration removes the dependency of the final outcome on initial conditions, producing a unique equilibrium in which both pure parental genotypes are maintained in the hybrid zone; (b) in contrast to nuclear genes, the dynamics of cytoplasmic allele frequencies appear robust to changes in the assumed mating system, yet are particularly sensitive to gene flow; (c) continued immigration can generate permanent cytonuclear disequilibria, whether mating is random or assortative; and (d) the order of population censusing (before versus after reproduction by immigrants) can have a dramatic effect on the magnitude but not the pattern of cytonuclear disequilibria. Using the maximum likelihood method, the parameter space of migration rates and assortative mating rates was examined for best fit to observed cytonuclear disequilibria data in a hybrid population of Hyla tree frogs. An epistatic mating model with a total immigration rate of about 32% per generation produces equilibrium gene frequencies and cytonuclear disequilibria consistent with the empirical observations.

Animals↗
PubMed1989

Conn's syndrome due to an ectopic adrenal adenoma.

A 31 year old woman presented with resistant hypertension. Investigations revealed that she had Conn's syndrome. Computed tomography showed both adrenals to be normal but an ectopic adenoma was identified posterior to the stomach. Surgical excision of the tumor confirmed benign aldosteronoma and cured her hypertension. We believe this to be the first report of Conn's syndrome caused by an ectopic adrenal adenoma.

Adenoma↗
PubMed1989

Energy balance and brown adipose tissue thermogenesis during chronic endotoxemia in rats.

The effects of continuously administered endotoxin on 7-day energy balance were investigated in male rats. Three groups of rats were implanted with osmotic pumps; two groups received saline-filled pumps, whereas the third received endotoxin. One of the saline groups was pair fed to match the food intake of the endotoxemic rats. After 7 days, body energy and protein and fat contents of rats were determined together with the energy content of food and feces. Endotoxin infusion not only induced fever, but it also suppressed appetite and significantly decreased body weight gain. Metabolizable energy intake was reduced by approximately 20% in infected rats. Although protein and fat gains were lowest in the endotoxin group, there appeared to be a selective loss of protein when considered as percent of body weight. Percent body fat was unaltered between the groups. Energy expenditure considered in absolute (kJ) or body weight-independent (kJ/kg0.67) terms yielded similar patterns of results; expenditure (kJ) was 10 and 20% (P less than 0.05, P less than 0.01) lower in the endotoxemic and pair-fed rats, respectively, compared with controls. Hence, compared with pair-fed rats, endotoxin-infused animals had a 10% rise in their expenditure. Brown adipose tissue thermogenesis was assessed by mitochondrial binding of guanosine 5'-diphosphate, and results showed that binding was greatest in endotoxemic rats and lowest in the pair-fed animals. The present results suggest that in this endotoxemic model appetite suppression exacerbates changes in energy balance. However, the reduction in body weight gain is also dependent on a decrease in metabolic efficiency and an increase in total energy expenditure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue, Brown↗
PubMed1989

Acetylcholine in the crayfish optic lobe: concentration profile and cellular localization.

The crayfish optic lobe contains high levels of acetylcholine (ACh) and choline as measured with a chemiluminescent assay in small fragments of optic lobe tissue. The highest concentrations were found in the medulla externa and medulla interna (second and third optic neuromeres), which have ACh concentrations of 270 pmol/mg tissue. This concentration is about 16 times that measured in the photoreceptors and lamina ganglionaris (the first optic neuromere). Immunocytochemistry (based upon antisera to choline-glutaryl-BSA) revealed low levels of ACh-like reactivity in the lamina ganglionaris associated with the terminal arbors of centrifugal and/or tangential neurons. The most intense ACh-like reactivity was observed in monopolar neurons of the medulla externa and medulla interna. One monopolar neuron/medullary column (or about 2500 neurons/medullary neuropile) exhibited reactivity and an estimated cytoplasmic concentration of 8.1 mM.

Acetylcholine↗
PubMed1989

Company sponsored clinical research--it can be trusted.

Clinical research provides the basis for product claims in company literature, in submissions to the Food and Drug Administration (FDA), and in publications. Checks and balances before, during, and after research which safeguard the public are 1) regulatory control of clinical studies by FDA; 2) internal company procedures governing the conduct of clinical studies; and 3) peer and competitor review of published clinical results and product claims.

Clinical Trials as Topic↗
PubMed1989

Passive smoking affects endothelium and platelets.

Blood was obtained before and after ten healthy male nonsmokers sat for 20 minutes in open hospital corridors beside men who were already there smoking by their own initiative. Mean values before and after passive smoking were 0.87 and 0.78 for the platelet aggregate ratio, 2.8 and 3.7 per counting chamber for the endothelial cell count, 0 and 2.8 ng/mL for the plasma nicotine concentration, and 0.9% and 1.3% for the carboxyhemoglobin level. No variable changed significantly during control periods in which the subjects sat in a room where smoking was prohibited. Passive exposure to tobacco smoke affected the endothelial cell count and platelet aggregate ratio in a manner similar to that previously observed with active smoking.

Adult↗
PubMed1988

Mono- through hexanucleotide composition of the sense strand of yeast DNA: a Markov chain analysis.

Here we compare several methods for predicting oligonucleotide frequencies in 392 kb of yeast DNA. As in previous work on E. coli, a relatively simple equation based on tetranucleotide frequencies can be used in predicting the frequencies of longer oligonucleotides. For example, the mean of observed/expected abundances of 4,096 hexamers was 1.00 with a sample standard deviation of .18. This simple predictor arises by considering each base on the sense strand of yeast to depend only on the three bases 5' to it (a 3rd order Markov chain) and is more accurate in estimating oligonucleotide frequencies than other statistical methods examined. This equation is useful in predicting restriction enzyme fragment sizes, selecting restriction enzymes that cut preferentially in coding vs noncoding regions, and in constructing detailed physical maps of whole genomes. When ranked highest to lowest abundance, the observed frequencies of oligomers of a given length (up to 6 bases) are closely tracked by the predicted abundances of a 3rd or 4th order Markov chain. These ordered abundance curves have a power curve shape with a broad linear range with a sharp break at the top end of the curve. There is also a strong disparity between the most and least abundant oligomer with for example a 79-fold variation between the most and least abundant hexamer. The curves reveal a strong dependence of oligomer frequencies on base composition. Unlike E. Coli, there is no sharp downturn at the low end of the curves and hence, no class of oligomers rare relative to other oligomers of the same length.

Base Composition↗
PubMed1988

Shivering and nonshivering thermogenesis in exercised cold-deacclimated rats.

Norepinephrine (NE)-induced increase in oxygen consumption (VO2) and colonic temperature (Tc) was greater in cold-acclimated rats housed at 4 degrees C for 4 weeks (CA) than warm-acclimated controls housed at 24 degrees C for 4 weeks (WA). On the other hand, shivering activity measured at 4 degrees C was less in CA than in WA, while propranolol administration eliminated the difference between these two groups by enhancing shivering in CA. Wet weight and protein content of interscapular brown adipose tissue (IBAT) were greater in CA than in WA. Following cold acclimation, CA were deacclimated at 24 degrees C for 5 weeks. During deacclimation, half of this latter group were forced to run (15 m.min-1 for 1 h) every day (CD-T) while the remaining rats remained sedentary (CD-S). Shivering activity assessed at 4 degrees C 4 weeks after commencing cold deacclimation was significantly less in CD-T than in CD-S and the difference disappeared following propranolol injection. VO2 and Tc responses to NE injection measured 1, 2 and 5 weeks after commencing cold deacclimation did not differ between CD-S and CD-T. Although IBAT weight was lighter in CD-T than in CD-S, its total protein content was not different between the latter two groups of rats. These results suggest that a greater degree of NE-independent nonshivering thermogenesis (NST) is retained in rats that are exercised during the process of deacclimation as compared with animals that are sedentary. This difference in NST would not seem to be directly related to BAT thermogenic capacity.

Acclimatization↗
PubMed1988

An epistatic mating system model can produce permanent cytonuclear disequilibria in a hybrid zone.

We examine the evolutionary dynamics of gametic and genotypic disequilibria between a cytoplasmic gene and a nuclear gene under two mating system models relevant to hybrid zones. In the first model, in which female mating preference is determined by an epistatic interaction between the two loci, permanent nonzero cytonuclear disequilibria are possible for a variety of initial genotype frequencies, particularly when rates of assortative mating for the two parental species are high. In contrast, when mating preference is effectively determined by interaction between a cytoplasmic gene and the multilocus nuclear genotypes characteristic of the parental species, all cytonuclear disequilibria, as well as frequencies of pure parentals, rapidly decay to zero unless assortative mating is nearly perfect. Results of the models are applied to the interpretation of observed cytonuclear associations in a hybrid population of Hyla tree frogs.

Algorithms↗
PubMed1988

Recombination within a subclass of restriction fragment length polymorphisms may help link classical and molecular genetics.

Restriction fragment length polymorphisms (RFLPs) are being used to construct complete linkage maps for many eukaryotic genomes. These RFLP maps can be used to predict the inheritance of important phenotypic loci and will assist in the molecular cloning of linked gene(s) which affect phenotypes of scientific, medical and agronomic importance. However, genetic linkage implies very little about the actual physical distances between loci. An assay is described which uses genetic recombinants to measure physical distance from a DNA probe to linked phenotypic loci. We have defined the subset of all RFLPs which have polymorphic restriction sites at both ends as class II RFLPs. The frequency of class II RFLPs is computed as a function of sequence divergence and total RFLP frequency for highly divergent genomes. Useful frequencies exist between organisms which differ by more than 7% in DNA sequence. Recombination within class II RFLPs will produce fragments of novel sizes which can be assayed by pulsed field electrophoresis to estimate physical distance in kilobase pairs between linked RFLP and phenotypic loci. This proposed assay should have particular applications to crop plants where highly divergent and polymorphic species are often genetically compatible and thus, where class II RFLPs will be most frequent.

Chromosome Mapping↗