Biomedical subjects

T Hall

Publications and source records attributed to T Hall.

At least 19 recordsLinked to original sources

PubMed1992

Development and evaluation of an enzyme-linked immunosorbent assay for Plasmodium vivax-VK247 sporozoites.

An enzyme-linked immunosorbent assay (ELISA) for the Plasmodium vivax-VK247 (variant) circumsporozoite (CS) protein was developed and evaluated using sporozoites produced by feeding mosquitoes on Thai patients with parasitologically confirmed P. vivax infections. The ELISA had a detection threshold of fewer than 50 sporozoites. Using this assay in conjunction with an ELISA for the VK210 polymorph, nearly 16% of the 235 P. vivax cases produced sporozoites positive only for the variant; 69% produced sporozoites positive only in the VK210 assay; and 15% were positive in both assays, indicating mixed infections. Twelve cases (5%) produced sporozoites negative in one assay and with unexpectedly low activity in the other ELISA, indicating the possibility of other CS protein polymorphs.

Amino Acid Sequence↗

PubMed1992

Immunoenzymatic labeling of multiple plasmodial salivary gland sporozoites in a single test.

A direct, double- and triple-staining immunoenzymatic method detected and differentiated sporozoites by color in Anopheles stephensi salivary glands and in mixed sporozoite slide preparations. A double-staining method used beta-galactosidase- and alkaline phosphatase-labeled monoclonal antibodies to the circumsporozoite (CS) proteins of Plasmodium berghei and P. falciparum in mosquito salivary glands. The CS proteins were distinguished clearly by the blue-green and red substrate products of beta-galactosidase and alkaline phosphatase, respectively. A triple-staining method differentiated by color among a mixture of P. falciparum and two strains of P. vivax sporozoites. Monoclonal antibodies to the CS proteins conjugated to beta-galactosidase (P. falciparum), alkaline phosphatase (P. vivax variant), and horseradish peroxidase (P. vivax predominant) readily color differentiated sporozoites by the blue-green, purple-blue, and orange-brown substrate products, respectively. This assay may have potential use in malaria transmission studies, genetic crosses of variant strains of plasmodia to determine assortment of CS antigen alleles, and as a technique to determine the fate of the CS antigen in infected mosquitoes.

Animals↗

PubMed1991

The concentration and temporal relationships of acetaminophen-induced changes in intracellular and extracellular total glutathione in freshly isolated hepatocytes from untreated and 3-methylcholanthrene pretreated Sprague-Dawley and Fischer rats.

Fischer rats are more sensitive to acetaminophen-induced hepatotoxicity than Sprague-Dawley rats, however, the mechanisms for this enhanced sensitivity remain unclear. The susceptibility to hepatotoxicity is determined largely by the balance between acetaminophen toxification and detoxification. Since glutathione plays a critical role in the detoxification process, it would be of interest to compare the effects of acetaminophen on hepatic glutathione homeostasis in the Sprague-Dawley and Fischer rat, and relate these effects to cytotoxicity. To this end, we measured the sequential changes of intracellular and extracellular total glutathione in freshly isolated hepatocytes from untreated and 3-methylcholanthrene pretreated Fischer and Sprague-Dawley rats, both in the absence (basal) and presence of acetaminophen. In the basal state, the intracellular total glutathione content was significantly (P less than 0.01) increased in hepatocytes from untreated Fischer rats. Nevertheless, the sequential release of total glutathione into the medium and the sequential depletion of intracellular total glutathione were quantitatively similar in hepatocytes from untreated Fischer and Sprague-Dawley rats. Following exposure to acetaminophen, there was a striking dose and time associated depletion of intracellular total glutathione in untreated hepatocytes from both rat strains, and quantitatively the depletion was similar in untreated hepatocytes from both rat strains. This degree of depletion of intracellular total glutathione was not associated with acetaminophen-induced cytotoxicity in Sprague-Dawley hepatocytes, whereas significant (P less than 0.05) cytotoxicity was demonstrated in Fischer hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗

PubMed1991

Mechanisms of blood flow during pneumatic vest cardiopulmonary resuscitation.

Mechanisms of blood flow during cardiopulmonary resuscitation (CPR) were studied in a canine model with implanted mitral and aortic flow probes and by use of cineangiography. Intrathoracic pressure (ITP) fluctuations were induced by a circumferential pneumatic vest, with and without simultaneous ventilation, and by use of positive-pressure ventilation alone. Vascular volume and compression rate were altered with each CPR mode. Antegrade mitral flow was interpreted as left ventricular (LV) inflow, and antegrade aortic flow was interpreted as LV outflow. The pneumatic vest was expected to elevate ITP uniformly and thus produce simultaneous LV inflow and LV outflow throughout compression. This pattern, the passive conduit of "thoracic pump" physiology, was unequivocally demonstrated only during ITP elevation with positive-pressure ventilation alone at slow rates. During vest CPR, LV outflow started promptly with the onset of compression, whereas LV inflow was delayed. At compression rates of 50 times/min and normal vascular filling pressures, the delay was sufficiently long that all LV filling occurred with release of compression. This is the pattern that would be expected with direct LV compression or "cardiac pump" physiology. During the early part of the compression phase, catheter tip transducer LV and left atrial pressure measurements demonstrated gradients necessitating mitral valve closure, while cineangiography showed dye droplets moving from the large pulmonary veins retrograde to the small pulmonary veins. When the compression rate was reduced and/or when intravascular pressures were raised with volume infusion, LV inflow was observed at some point during the compressive phase. Thus, under these conditions, features of both thoracic pump and cardiac pump physiology occurred within the same compression. Our findings are not explained by the conventional conceptions of either thoracic pump or cardiac compression CPR mechanisms alone.

Animals↗

PubMed1990

Sequences of three VSG mRNAs expressed in a mixed population of Trypanosoma brucei rhodesiense.

A cDNA library was constructed from a mixed population of bloodstream Trypanosoma brucei rhodesiense expressing at least three different VSGs, one of which is immunologically similar to a VSG present during the metacyclic stage. Complete sequence determinations of three full length VSG cDNAs showed that the 5' spliced leader sequence is located 20-26 nucleotides upstream of the start codons of each of the three VSG mRNAs. Two of the VSGs (472 and 487 aa) are members of one C-terminal isotype group while the other, metacyclic-like, VSG (517 aa) is a member of the other C-terminal group. Since VSGs of different sequences have similar three-dimensional structures, comparison of many different VSGs sequences should lead to a more detailed understanding of the relationship between primary and tertiary structures of proteins in general. GenBank accession numbers: M33823, M33824, and M33825.

Amino Acid Sequence↗

PubMed1990

Dietary intake and changes in body weight in burned children.

Two groups of children were studied. In the first group serial measurements of body weight were made during the child's stay in hospital. In 11 patients, aged 7 months to 13 years, admitted with 10-58 per cent burns, the maximum weight loss was between 6 and 13 per cent of admission weight. Patients had not regained their admission weight at discharge (8-77 days after injury). In the youngest patients, the discharge weight corresponded with the maximum recorded weight loss. In five of the 11 patients dietary intake was calculated by weighing the foods in meals. This was done on average twice per week. Energy and protein intake was below that recommended for children with burns and often lower than that recommended for healthy children. In the second group of 10 patients, 6 months to 7 years had elapsed since the burn. These children were outpatients attending the Burns Aftercare Clinic. Six of the children were at a lower weight centile position when compared to the position at the time of the accident. The children had not 'caught up' to their original centile position.

Adolescent↗

PubMed1990

Inverse relationship between total glutathione S-transferase content and bile acid release in isolated hepatocytes from untreated, phenobarbital pretreated and hypothyroid rats.

The role of cytosolic anion binding proteins (glutathione S-transferases) in the hepatic transport of bile acids remains controversial. To investigate whether increased levels of the hepatocyte total glutathione S-transferase content were associated with changes in the release of bile acids from the hepatocyte, we measured the rate of release of radioactive bile acids in isolated hepatocytes from thyroidectomized, phenobarbital pretreated and untreated rats. The isolated hepatocytes were preincubated with either 14C-cholic acid or 14C-taurocholic acid, and the release rate of radiolabeled bile acids was determined. Hepatocyte total glutathione S-transferase content was measured by rocket immunoelectrophoresis. The release rate of the radiolabeled bile acids was significantly (P less than 0.005) decreased in both hypothyroid and phenobarbital pretreated hepatocytes. The levels of total glutathione S-transferase content were significantly (P less than 0.001) increased in the hepatocytes from both hypothyroid and phenobarbital pretreated animals. Our findings reveal a striking inverse relationship between the total glutathione S-transferase content of the hepatocyte and the release rate of radiolabeled bile acids in isolated hepatocytes from two independent animal models. These observations support the hypothesis that cytosolic anion binding proteins (glutathione S-transferases) may influence the net flux across the hepatocyte plasma membrane largely by limiting efflux.

Animals↗

PubMed1990

Case management in long-term care: new directions for professional nursing.

Case management can be a highly successful model to deal with issues of cost effectiveness, accountability, and quality care. Continuity of care is a guaranteed benefit of the case management model. Case management is a centralized or structured system whose standard is not set by those performing less effectively. Case management offers autonomy, empowerment, and positive patient care outcomes. These are magnet issues in the retention of staff nurses. The case management method of primary nursing allows for a reduction in the need for professional nurse staff.

Aged↗

PubMed1990

The changing epidemiology of diabetes mellitus among Navajo Indians.

Although early descriptions of diabetes mellitus among Navajo Indians characterized the disease as an infrequent and "benign chemical abnormality," the prevalence of diabetes and its complications among Navajos appears to have increased substantially in this century. We reviewed recent Indian Health Service inpatient and ambulatory care data and compared these data with previous reports. Of the estimated Navajo population aged 45 years or older, 4,331 (16.9%) had an ambulatory care visit for diabetes between October 1, 1986, and September 30, 1987. Diabetes was coded for 1,041 (7.0%) of hospital admissions of persons aged 20 and older. Of 377 lower-extremity amputations done from 1978 to 1987, diabetes was involved in 245 (66%). The 1986 age-adjusted mortality rate from diabetes was 30.3 per 100,000, approximately twice that for the general US population. The explanation for the increased prevalence of diabetes mellitus among Navajos probably relates to an increasing prevalence of obesity.

Adult↗

PubMed1990

Enhancing magnetic resonance images using water bags.

Fascial planes between tissues are separated by connective tissue, fat, and blood vessels. Magnetic resonance imaging displays surface anatomy and soft tissues. Our team has been successful in demonstrating brachial plexus nerves as a model of magnetic resonance anatomy. Radiologists have devised methods to increase the resolution of images by suppressing noise and increasing the sharpness of the image. We added water bags to a 0.3 tesla permanent magnet suppressing the noise and increasing the signal to image our patients. The images proved to be sharper.

Humans↗

PubMed1989

Circumsporozoite protein heterogeneity in the human malaria parasite Plasmodium vivax.

Phenotypic heterogeneity in the repetitive portion of a human malaria circumsporozoite (CS) protein, a major target of candidate vaccines, has been found. Over 14% of clinical cases of uncomplicated Plasmodium vivax malaria at two sites in western Thailand produced sporozoites immunologically distinct from previously characterized examples of the species. Monoclonal antibodies to the CS protein of other P. vivax isolates and to other species of human and simian malarias did not bind to these nonreactive sporozoites, nor did antibodies from monkeys immunized with a candidate vaccine made from the repeat portion of a New World CS protein. The section of the CS protein gene between the conserved regions I and II of a nonreactive isolate contained a nonapeptide repeat, Ala-Asn-Gly-Ala-Gly-Asn-Gln-Pro-Gly, identical at only three amino acid positions with published nonapeptide sequences. This heterogeneity implies that a P. vivax vaccine based on the CS protein repeat of one isolate will not be universally protective.

Amino Acid Sequence↗

PubMed1989

Expression site associated genes of Trypanosoma brucei rhodesiense.

Upstream of at least some telomere-linked genes for the variant surface glycoproteins (VSGs) of African trypanosomes are expression site associated genes (ESAGs) whose transcription is co-ordinated with the transcription of the adjacent VSG gene [Cully et al. (1985) Cell 42, 173-182]. The function of the corresponding ESAG proteins is not known. Here we show the sequences of two members of the ESAG-I family that are upstream of the VSG genes expressed in metacyclic variant antigen types 4 and 7 of Trypanosoma brucei rhodesiense. The corresponding metacyclic ESAG-I proteins of about 330 amino acids display extensive positional identity both with each other and with two other ESAG-I proteins of Trypanosoma brucei brucei. Only about 7% of the positions are occupied by a different amino acid in each of the four putative ESAG proteins while 40% of the positions are identical. Thus, the ESAG-I proteins are much more highly conserved than are the VSGs studied to date.

Amino Acid Sequence↗

PubMed1989

Specificities of antibodies that inhibit merozoite dispersal from malaria-infected erythrocytes.

When malaria schizont-infected erythrocytes are cultured with immune serum, antibodies prevent dispersal of merozoites, resulting in the formation of immune clusters of merozoites (ICM) and inhibition of parasite growth. Antigens recognized by these antibodies were identified by probing two dimensional immunoblots of Plasmodium falciparum antigens with antibodies dissociated from immune complexes present at the surface of merozoites in ICM. Total immune serum recognized 88 of the 135 protein spots detected by colloidal gold staining, but antibodies dissociated from immune complexes recognized only 15 protein spots attributable to no more than eight distinct antigens. Antigens recognized by antibodies that inhibit merozoite dispersal include the precursor to the major merozoite surface antigens (gp195), a 126-kDa serine-repeat antigen (SERA), the 130-kDa protein that appears to bind to glycophorin (GBP130), and the approx. 45-kDa merozoite surface antigen. One other antigen (230/215-kDa doublet) was identified by using antibodies affinity purified from recombinant expression proteins. The identities of the other three antigens (150 kDa, 127 kDa and less than 30 kDa) were not determined. This approach provides a strategy for identifying epitopes accessible at the merozoite surface which may be important components of a multivalent vaccine against blood stages of P. falciparum.

Amino Acid Sequence↗

PubMed1989

Chlorpromazine, administered in vivo and in vitro, inhibits the efflux of bile acids in freshly isolated rat hepatocytes.

Although it has been speculated that chlorpromazine may alter the transhepatic movement of bile acids from plasma to bile, the effect of chlorpromazine on various determinants of bile acid transport in isolated rat hepatocytes remains incompletely defined. In particular, there is little information about the effect of chlorpromazine on the release of bile acids from freshly isolated hepatocytes. Therefore, we examined the effect of chlorpromazine, administered in vivo and in vitro, on the efflux rate of radiolabeled bile acids in freshly isolated rat hepatocytes. In an isolated haptocyte system, it is not possible to distinguish the sinusoidal plasma membrane function of efflux (back diffusion) from the canalicular plasma membrane function of excretion. Therefore, efflux, as used in this manuscript, reflects both back diffusion and excretion. In vitro, chlorpromazine produced a rapid dose dependent significant (P less than 0.05) decrease of the bile acid efflux rate in freshly isolated hepatocytes. This decrease in bile acid efflux was observed at chlorpromazine concentrations which did not alter hepatocyte plasma membrane permeability (viability), as measured by intracellular potassium content, release of lactate dehydrogenase, and trypan blue exclusion. Moreover, in freshly isolated hepatocytes from chlorpromazine pretreated rats, a significant (P less than 0.05) decrease in the bile acid efflux rate was also observed, and this decrease in efflux was similar in magnitude to the decrease in bile acid efflux observed following exposure of freshly isolated hepatocytes to chlorpromazine in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Cranial arteriovenous malformations in neonates: color Doppler imaging with angiographic correlation.

Five neonates with cranial arteriovenous malformations were studied with color Doppler sonography. Excellent correlation was found between sonography and subsequent angiography. In three patients with vein of Galen aneurysms, sonography showed a cystic structure with rapid or swirling flow. Careful adjustment of the color Doppler system was required to demonstrate flow in another patient with a dural arteriovenous malformation. An arteriovenous fistula in a fifth patient appeared as an area of increased flow. Arterial feeders and major draining veins were visualized in all five patients. Color Doppler imaging also was used to assess the effect of embolic or operative therapy in three of the patients. We conclude that color Doppler sonography is able reliably to characterize flow patterns in neonatal cranial arteriovenous malformations. Color Doppler imaging also is helpful in assessing flow after embolic or surgical therapy.

Cerebral Angiography↗

PubMed1988

Primary structure of a Plasmodium falciparum malaria antigen located at the merozoite surface and within the parasitophorous vacuole.

DNA encoding an antigen of 101,000 apparent molecular weight from the human malaria parasite Plasmodium falciparum was cloned and sequenced. Genomic DNA from the Camp strain covering the complete coding region along with cDNA from the FCR3 strain covering 81% of the coding region were obtained. The cloned DNA specified a full-length protein of 743 amino acids which included two tandemly repeated regions, one near the amino terminus containing eight hexapeptide repeats of sequence TVNDEDED, and the second near the carboxyl terminus containing primarily KE and KEE repeats. The latter repeated region is encoded by a 174-base stretch of mRNA containing only a single pyrimidine. Except for a putative leader sequence located at the amino terminus of the protein, the protein is hydrophilic and highly charged with a calculated isoelectric point of 5.6. Sequences from the Camp and FCR3 strains are very close and are also nearly identical to the partial cDNA sequence of the acidic basic repeated antigen (ABRA) protein from the FC27 strain (Stahl, H.D., Bianco, A.E., Crewther, R.F., Anders, R.F., Kyne, A.P., Coppel, R. L., Mitchell, G.F., Kemp, D.J., and Brown, G.V. (1986) Mol. Biol. Med. 3, 351-368). ABRA was previously shown to be located at the merozoite surface and in the parasitophorous vacuole. Because of its location and because it becomes complexed to merozoites when schizonts rupture in the presence of immune serum, ABRA is a candidate component of a malaria vaccine.

Amino Acid Sequence↗

PubMed1988

Oxmetidine (H2 receptor antagonist) induced cytotoxicity in isolated rat hepatocytes.

Oxmetidine, a new and more potent analogue of the H2 receptor antagonist, cimetidine, was recently withdrawn from clinical trials because of associated hepatotoxicity. We investigated the potential hepatotoxicity of the drug in vitro and in vivo in the rat. In addition, we investigated, in in vitro experiments, the potential hepatoxicity of other gastric acid inhibitory drugs (cimetidine, ranitidine, omeprazole and nolinium bromide). In in vitro experiments, oxmetidine, at various concentrations, was added to isolated hepatocyte incubations and cytotoxicity was assayed by trypan blue exclusion. In in vivo experiments, oxmetidine was administered both i.p. and orally, and hepatotoxicity was assessed by serum biochemical measures (transaminases, alkaline phosphatase, 5' nucleotidase, gamma glutamyl transpeptidase) and liver histopathology. In the in vitro studies, the addition of oxmetidine to the hepatocyte incubations was associated with significant (P less than 0.001) dose and time dependent cytotoxicity. However, the in vivo experiments revealed no significant changes in serum biochemistry and no significant alterations in liver histopathology up to 72 h following the administration three different dosages of oxmetidine. Of the other gastric acid inhibitory drugs, only nolinium bromide was associated with significant (P less than 0.001) in vitro cytotoxicity. Our in vitro observations establish that oxmetidine is cytotoxic to isolated rat hepatocytes and suggest that nolinium bromide be further evaluated for potential hepatotoxicity.

Aniline Compounds↗

PubMed1988

Radionuclide evaluation of liver transplants.

Orthotopic liver transplantation is now an established technique for treating patients with various forms of end stage liver disease. The number of centers performing the procedure is increasing and, as the number of transplant recipients in the population increases, many institutions performing nuclear medicine studies will be confronted with requests to evaluate these patients. While a variety of radionuclides are proving useful in this evaluation, the 99mTc iminodiacetic acid (IDA) compounds, particularly 99mTc diisopropyl IDA (DISIDA), will probably account for the majority of radionuclide evaluations of these patients because they are well suited to monitor both structural and functional changes of the graft. The primary application of radionuclide studies is focused in the postoperative period, when problems with the vascular and biliary anastomoses, rejection, infections, and bile leaks all produce alterations in radionuclide hepatobiliary studies. Abnormalities such as rejection and infection produce primarily functional, rather than structural changes and are not easily differentiated based upon the kinetics of 99mTc-DISIDA extraction and excretion by the liver, serial imaging and correlation with clinical data is necessary in such situations. Quantitative analyses of kinetic 99mTc IDA (DISIDA) studies and quantitative approaches with other compounds such as 99mTc galactosyl-neoglycoalbumin (NGA) may permit better assessments of relatively subtle changes in liver function in the posttransplant period.

Bile Duct Diseases↗