Biomedical subjects

D Brown

Publications and source records attributed to D Brown.

At least 649 records · Page 36Linked to original sources

PubMed1992

Monoclonal antibodies for the identification of herpesvirus simiae (B virus).

To differentiate between B virus and HSV isolates from monkeys and man monoclonal antibodies (mabs) were produced to herpesvirus simiae (B virus) and herpes simplex type 1 and 2 (HSV-1 and HSV-2). Mabs were tested by indirect immunofluorescence (IFAT) for reactivity against herpesviruses from Asiatic monkeys (B virus), African monkeys (SA 8 virus), and man (HSV-1, HSV-2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus). Mabs could be divided into groups A-E displaying specific reactivity for B virus (A); reactivity with both B virus and SA 8 but not HSV (B); reactivity with B virus, SA 8 virus and HSV strains (C); specific reactivity with HSV-1 (D); and specific reactivity with HSV-2 (E). Two of the B virus specific mabs were able to differentiate between cynomolgus and rhesus strains of B virus. None of the mabs reacted with human varicella-zoster virus, cytomegalovirus, or Epstein-Barr virus. A panel of mabs for the unequivocal identification of B virus isolates from monkey or man is proposed.

Animals↗

PubMed1992

Frozen-thawed human blood monocytes respond reproducibly to activation stimuli: implications for screening of BRMs.

The purpose of this study was to identify the optimal freezing conditions for human blood monocytes to allow their recovery and use for in vitro screening of activation stimuli. Human monocytes separated from buffy coats of healthy blood donors were suspended at a density of 1 x 10(7) cells/ml in freezing medium consisting of 70% medium: 20% fetal bovine serum: 10% DMSO frozen in a stepdown freezer, and stored at -180 degrees C. Monocytes were thawed at different times up to 4 months later. Viability was > 90%. Fresh monocytes from different donors and frozen monocytes thawed at different times were incubated with different concentrations of lipopolysaccharide, muramyl tripeptide, muramyl dipeptide, or lipopeptide. Tumoricidal activity and IL-1 production of fresh monocytes varied greatly among the 5 different preparations. In contrast, the frozen monocytes (thawed at different times) produced uniform levels of antitumor activity and IL-1 production. These results show that monocytes recovered from frozen storage maintain their ability to respond to activation stimuli in a uniform and reproducible manner. Thus, the use of frozen-thawed monocytes is recommended for screening of macrophage-activating agents.

Cryopreservation↗

PubMed1992

Induction of major histocompatibility complex class II glycoproteins by interferon-gamma: attenuation of the effects of restraint stress.

The effect of restraint on the activation of macrophages was evaluated based on the induction of I-A expression following injection of viable Mycobacterium bovis (strain BCG) or treatment in vitro with recombinant interferon-gamma (rIFN-gamma). We found that restraint suppressed the induction of I-A expression when applied just prior to or at the same time as the injection of the microorganisms but had no effect if applied after the injection of the Mycobacteria. The effect of stress was attenuated by increasing the number of microorganisms or by incubating macrophages from stressed mice with higher doses of rIFN-gamma. The suppressive effect of restraint does not appear to be associated with uptake, processing or presentation of antigen but rather to an alteration in the response of the macrophages to rIFN-gamma.

Animals↗

PubMed1992

Characterization of ACTH mediated suppression of MHC class II expression by murine peritoneal macrophages.

The effect of ACTH on the expression of major histocompatibility complex (MHC) class II (I-A) glycoprotein by murine peritoneal macrophages was evaluated. ACTH suppressed the expression of I-A by macrophages in a time- and dose-dependent manner. ACTH mediated its effect by decreasing the level of I-A mRNA. ACTH suppressed the expression of I-A by macrophages from mice that are susceptible to the in vivo growth of mycobacteria but did not affect the expression of I-A by macrophages from Mycobacterium bovis strain (BCG)-resistant mice. The concentrations of ACTH required to suppress I-A expression were greater than that required for an effect on adrenal steroid production and may be related to the localized production of ACTH by lymphocytes and macrophages.

Adrenocorticotropic Hormone↗

PubMed1992

Relationship between CNV asymmetries and individual differences in cognitive performance, personality and gender.

This study used verbal and spatial variants of a cognitive 'match/mismatch' paradigm to explore relationships between functional brain asymmetries and individual differences in cognitive performance, personality and gender. Contingent negative variation (CNV) elicited in the 'match/mismatch' paradigm was recorded from central (Cz, C3 and C4) derivations in two male and one female samples. Results indicated gender differences in both the degree and direction of CNV asymmetries. Males showed a left hemisphere asymmetry in the verbal task and a right hemisphere asymmetry in the spatial task, with significant laterality (C3-C4) differences between tasks across the foreperiod. Females showed a left hemisphere asymmetry in both tasks with laterality differences between tasks confined to the early part of the foreperiod. CNV amplitude in the verbal task correlated with verbal memory performance and verbal I.Q. CNV amplitude in the spatial task correlated with visuospatial memory performance. Social extraversion was associated with greater left-hemisphere asymmetry in both tasks, while behavioural extraversion was associated with left-hemisphere asymmetry in the verbal task only, and with smaller verbal than spatial CNVs.

Adult↗

PubMed1992

Frequently nebulized beta-agonists for asthma: effects on serum electrolytes.

STUDY OBJECTIVE: To determine the magnitude of the changes in serum potassium, magnesium, and phosphate during the treatment of acute bronchospasm with repeated doses of beta-adrenergic agonists. DESIGN: Prospective study of a convenience sample of asthmatic patients. SETTING: University teaching hospital emergency department. TYPE OF PARTICIPANTS: Twenty-three patients met the inclusion criteria of age of more than 16 years; a history of asthma or chronic obstructive pulmonary disease; and an acute exacerbation. INTERVENTIONS: Baseline peak expiratory flow rate and serum potassium, magnesium, and phosphate levels were measured. Nebulized albuterol (2.5 mg) was administered every 30 minutes until the patient was discharged from the ED. Before each albuterol treatment, repeat serum levels of potassium, magnesium, and phosphate were determined. MEASUREMENTS AND MAIN RESULTS: Baseline peak expiratory flow rate averaged 188 +/- 119 L/min. Serum potassium levels decreased significantly (P = .0001 by repeated-measures analysis of variance) from 4.10 +/- 0.468 (baseline) to 3.55 +/- 0.580 mmol/L (90 minutes) and 3.45 +/- 0.683 mmol/L (180 minutes). Potassium decreased to less than 3.0 mmol/L in 22% of patients at some point during the study. Magnesium decreased from 1.64 +/- 0.133 mmol/L (baseline) to 1.48 +/- 0.184 mmol/L (90 minutes) and 1.40 +/- 0.219 mmol/L (180 minutes) (P = .0001). Phosphate levels also decreased, from 3.74 +/- 1.029 (baseline) to 2.84 +/- 0.957 mmol/L (90 minutes) and 2.55 +/- 0.715 mmol/L (180 minutes) (P = .0001). CONCLUSION: Aggressive administration of nebulized albuterol during the emergency treatment of acute bronchospasm is associated with statistically significant decreases in serum potassium, magnesium, and phosphate. The mechanism and clinical significance of these findings are unknown and warrant further study.

Adolescent↗

PubMed1992

Suggested MRI criteria for surgical decompression in acute spinal cord injury. Preliminary observations.

The effect of spinal cord compression identified with magnetic resonance imaging (MRI), on neurological prognosis, was retrospectively evaluated in 36 patients with acute spinal cord injury. Of the 21 patients without cord compression, 16 had potentially reversible injury (normal spinal cord or cord oedema), all having functional recovery. Of the 15 patients with cord compression, 3 had operative decompression. In the 12 patients who did not undergo surgery, the degree of recovery was directly related to the magnitude of spinal cord compression, only one of the patients with moderate or marked cord compression having useful motor function at follow up. In contrast, the 3 patients with surgical decompression had at least 2 grades of improvement, all having functional recovery. These findings raise the possibility that MRI may be used to identify a patient group who will benefit from surgical decompression. A numerical index is proposed to prospectively identify patients for surgical decompression, and further studies are underway to evaluate this.

Adolescent↗

PubMed1992

Responses in tissue protein synthesis to sub- and supra-maintenance intake in young growing sheep: comparison of large-dose and continuous-infusion techniques.

In ten lambs (average live weight 33 kg), five offered 300 g/d (approximately 0.6 x maintenance; L) and five 900 g/d (1.8 x maintenance; H), tissue protein synthesis was measured by three procedures simultaneously. The techniques involved continuous infusion of [U-14C]phenylalanine and [1-13C]leucine over 7-8 h followed by a terminal large dose of [15N]phenylalanine during the last 30 or 60 min. Rates of protein synthesis were then calculated based on the free amino acid or oxo-acid isotopic activity in either arterial, iliac venous blood or tissue homogenate for the continuous-infusion studies, or on plasma or tissue homogenate for the large-dose procedure. For muscle (> 99%), and to a lesser extent skin (85-93%), effective flood conditions were achieved with the [15N]phenylalanine but were either not established or maintained for liver and tissues of the gastrointestinal tract (< 50%). The large dose of phenylalanine also caused changes in the concentration and isotopic activity of blood leucine and 4-methyl-2-oxo-pentanoate. Based on the assumption that the large-dose procedure yields the closest value for the true rate of protein synthesis (L 1.97%/d, H 2.85%/d) then, for muscle, only values based on the homogenate as precursor gave comparable results for both leucine (L 1.83%/d, H 3.01%/d) and phenylalanine (L 1.67%/d, H 2.71%/d) continuous infusion. The values based on the arterial or venous amino or oxo-acid were significantly less, more so at the lower intake. In contrast, for skin, a tissue dominated by export protein synthesis, values from the large-dose procedure (L 6.37%/d, H 10.98%/d) were similar to those derived with arterial or venous metabolites as precursor (L 5.23 and 6.93%/d, H 9.98 and 11.71%/d for leucine), but much less than those based on homogenate data. Based on the large-dose technique, protein synthesis increased with intake in muscle (P < 0.001), skin (P = 0.009) and liver (26.7 v. 30.5%/d; P = 0.029). The contributions of muscle and skin to total protein synthesis were approximately equal. The incremental efficiency of conversion for muscle of synthesized protein into deposition appeared to be similar to values reported for rodents.

Animals↗

PubMed1992

Apical endosomes isolated from kidney collecting duct principal cells lack subunits of the proton pumping ATPase.

Endocytic vesicles that are involved in the vasopressin-stimulated recycling of water channels to and from the apical membrane of kidney collecting duct principal cells were isolated from rat renal papilla by differential and Percoll density gradient centrifugation. Fluorescence quenching measurements showed that the isolated vesicles maintained a high, HgCl2-sensitive water permeability, consistent with the presence of vasopressin-sensitive water channels. They did not, however, exhibit ATP-dependent luminal acidification, nor any N-ethylmaleimide-sensitive ATPase activity, properties that are characteristic of most acidic endosomal compartments. Western blotting with specific antibodies showed that the 31- and 70-kD cytoplasmically oriented subunits of the vacuolar proton pump were not detectable in these apical endosomes from the papilla, whereas they were present in endosomes prepared in parallel from the cortex. In contrast, the 56-kD subunit of the proton pump was abundant in papillary endosomes, and was localized at the apical pole of principal cells by immunocytochemistry. Finally, an antibody that recognizes the 16-kD transmembrane subunit of oat tonoplast ATPase cross-reacted with a distinct 16-kD band in cortical endosomes, but no 16-kD band was detectable in endosomes from the papilla. This antibody also recognized a 16-kD band in affinity-purified H+ ATPase preparations from bovine kidney medulla. Therefore, early endosomes derived from the apical plasma membrane of collecting duct principal cells fail to acidify because they lack functionally important subunits of a vacuolar-type proton pumping ATPase, including the 16-kD transmembrane domain that serves as the proton-conducting channel, and the 70-kD cytoplasmic subunit that contains the ATPase catalytic site. This specialized, non-acidic early endosomal compartment appears to be involved primarily in the hormonally induced recycling of water channels to and from the apical plasma membrane of vasopressin-sensitive cells in the kidney collecting duct.

Animals↗

PubMed1992

Directional instability of microtubule transport in the presence of kinesin and dynein, two opposite polarity motor proteins.

Kinesin and dynein are motor proteins that move in opposite directions along microtubules. In this study, we examine the consequences of having kinesin and dynein (ciliary outer arm or cytoplasmic) bound to glass surfaces interacting with the same microtubule in vitro. Although one might expect a balance of opposing forces to produce little or no net movement, we find instead that microtubules move unidirectionally for several microns (corresponding to hundreds of ATPase cycles by a motor) but continually switch between kinesin-directed and dynein-directed transport. The velocities in the plus-end (0.2-0.3 microns/s) and minus-end (3.5-4 microns/s) directions were approximately half those produced by kinesin (0.5 microns/s) and ciliary dynein (6.7 microns/s) alone, indicating that the motors not contributing to movement can interact with and impose a drag upon the microtubule. By comparing two dyneins with different duty ratios (percentage of time spent in a strongly bound state during the ATPase cycle) and varying the nucleotide conditions, we show that the microtubule attachment times of the two opposing motors as well as their relative numbers determine which motor predominates in this assay. Together, these findings are consistent with a model in which kinesin-induced movement of a microtubule induces a negative strain in attached dyneins which causes them to dissociate before entering a force-generating state (and vice versa); reversals in the direction of transport may require the temporary dissociation of the transporting motor from the microtubule. The bidirectional movements described here are also remarkably similar to the back-and-forth movements of chromosomes during mitosis and membrane vesicles in fibroblasts. These results suggest that the underlying mechanical properties of motor proteins, at least in part, may be responsible for reversals in microtubule-based transport observed in cells.

Animals↗

PubMed1992

Diagnostic accuracy of exercise thallium-201 scintigraphy in men with asymptomatic essential hypertension.

Coronary artery disease is responsible for much of the morbidity and mortality in patients with essential hypertension, and these complications have proven to be relatively resistant to antihypertensive therapy. However, the diagnosis of coronary disease in the hypertensive population has been considered problematic. In the present study, 30 asymptomatic patients with mild to moderate hypertension with positive exercise electrocardiograms (ECG) or stress thallium-201 scintigrams underwent coronary angiography to determine the accuracy of these tests for coronary artery disease. The exercise ECG was positive in 25 subjects, of whom 15 had significant coronary lesions and 10 did not. Thallium-201 scintigraphy proved more accurate: 17 of 18 patients with reversible abnormalities had significant obstructive coronary disease anatomically corresponding to the defect, one patient with a fixed defect had normal coronary arteries and was found to have an idiopathic cardiomyopathy, and 9 of 11 without defects had no significant lesions. The results were similar in populations with and without echocardiographic criteria for left ventricular hypertrophy. These findings indicate that despite previous suggestions to the contrary, thallium-201 scintigraphy can accurately diagnose coronary artery disease in most patients with asymptomatic essential hypertension, and that most asymptomatic hypertensive patients with physiologic evidence of myocardial ischemia have associated coronary artery disease.

Adult↗

PubMed1992

Allelic diversity of the maize B regulatory gene: different leader and promoter sequences of two B alleles determine distinct tissue specificities of anthocyanin production.

The B gene encodes a transcription factor of the basic helix-loop-helix class, which controls the synthesis of the anthocyanin pigments in maize. This gene, as well as the highly homologous R gene family, displays extensive allelic variation in that different alleles cause distinct distributions of anthocyanin pigments in different tissues and at different developmental times. The analysis of the expression of two B alleles, with distinct tissue-specific patterns of anthocyanin synthesis in plant and seed tissues, demonstrates that the amount of B transcripts correlates with the accumulation of anthocyanins in the various tissues. The comparison of the genomic clones for the two alleles reveals high sequence identity in the coding and 3'-flanking regions (98% and approximately 90%, respectively). In contrast, the most 5' region of their mRNAs and the 5'-flanking sequences share no significant sequence identity. This result suggests that the alleles diverged from each other by complex genome rearrangements rather than by simple base pair substitutions. We have used the high velocity microprojectile transformation assay to demonstrate that the differential expression of the two alleles in the seed is determined by their 5' variant sequences. Thus, the variation in tissue-specific anthocyanin synthesis in plants with these different B alleles is controlled at the level of B gene expression.

Alleles↗

PubMed1992

Pharmacological characterization of a receptor for calcitonin gene-related peptide on rat, L6 myocytes.

1 The L6 myocyte cell line expresses high affinity receptors for calcitonin gene-related peptide (CGRP) which are coupled to activation of adenylyl cyclase. The biochemical pharmacology of these receptors has been examined by radioligand binding or adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation. 2 In intact cells at 37 degrees C, human and rat alpha- and beta-CGRP all activated adenylyl cyclase with EC50s of about 1.5 nM. A number of CGRP analogues containing up to five amino acid substitutions showed similar potencies. In membrane binding studies at 22 degrees C in 1 mM Mg2+, the above all bound to a single site with IC50s of 0.1-0.4 nM. 3 The fragment CGRP(8-37) acted as a competitive antagonist of CGRP stimulation of adenylyl cyclase with a calculated Kd of 5 nM. The Kd determined in membrane binding assays was lower (0.5 nM). 4 The N-terminal extended human alpha-CGRP analogue Tyro-CGRP activated adenylyl cyclase and inhibited [125I]-iodohistidyl-CGRP binding less potently than human alpha-CGRP (EC50 for cyclase = 12 nM, IC50 for binding = 4 nM). 5 The pharmacological profile of the L6 CGRP receptor suggests that it most closely resembles sites on skeletal muscle, cardiac myocytes and hepatocytes. The L6 cell line should be a stable homogeneous model system in which to study CGRP mechanisms and pharmacology.

Animals↗

PubMed1992

A comparison of external rate responsive pacemakers with identical implanted units.

Seven patients with previously implanted accelerometer-based DDDR pacemakers had an identically programmed external pacemaker taped onto their chest. Both units underwent a simultaneous test to set the sensitivity of the accelerometer. The units were then programmed to record the pacing rates for a 15-minute period. The patients underwent an exercise course that included walking and stairs. After the exercise, the patients sat for 3 minutes and the pacing rates from the test were telemetered. The pacing rate was compared at 2 minutes, 4 minutes, peak, and 3 minutes postexercise. The mean standard deviation (SED) for the external pacemaker was 97.9 at 3.53 ppm, 102 at 10.6 ppm, 106 at 8.94 ppm, and 71.3 at 2.29 ppm at 2, 4, peak, and decay, respectively. The mean SED for the implanted pacemaker was 98.1 at 5.76 ppm, 100 at 10.2 ppm, 104 8.24 ppm, 72.4 at 2.88 ppm at 2, 4, peak, and decay, respectively. Difference between pacemakers in ppm was 0.286, 2.0, 2.71, and 1.14 at 2, 4, peak, and decay, respectively. A 95% confidence interval in ppm was -5.28 to 5.85, -10.1 to 14.1, -7.30 to 12.7, and -1.89 to 4.17 at 2, 4, peak, and decay, respectively. In all patients there was a high confidence correlation between the implanted and external unit. An external unit can be used to predict the rate response of an accelerometer-based pacemaker without any adjustments to the pacing parameters.

Acceleration↗

PubMed1992

Increased steady-state levels of alpha-fetoprotein mRNA in hepatocellular carcinoma: an analysis by in situ hybridization.

The molecular basis for the augmented production of alpha-fetoprotein is unknown. We have used in situ hybridization of alpha-fetoprotein cDNA to malignant hepatocytes to establish if increased serum alpha-fetoprotein concentrations are related to detectable steady-state levels of alpha-fetoprotein mRNA in hepatocytes. Tumor tissue from four patients with histologically confirmed hepatocellular carcinoma were examined, and the results compared to fetal liver. Northern blot hybridization for alpha-fetoprotein mRNA in tumor tissue was also analyzed. As expected a high number of grains was observed in fetal liver tissue, indicative of high levels of alpha-fetoprotein mRNA physiologically present during pre-natal development. Sections from all patients with high serum concentrations of alpha fetoprotein showed appreciable hybrid formation, which correlated semi-quantitatively with the serum concentrations. However, hybrids were not detected in a patient with a normal serum alpha-fetoprotein. The high alpha-fetoprotein mRNA levels in fetal and neoplastic liver suggest that gene transcription is the mechanism of alpha-fetoprotein production in malignancy, although the control of this mechanism remains speculative.

Adult↗

PubMed1992

A plasma membrane proton ATPase in specialized cells of rat epididymis.

Acidification of the luminal fluid in the epididymis is believed to play an important role in sperm maturation. Previous studies have shown that specialized cells in the epithelium lining the epididymis contain high levels of carbonic anhydrase and that these cells have rod-shaped intramembraneous particles when examined by freeze fracture. Both of these features are characteristic of proton-transporting intercalated cells in the kidney collecting duct. We now show that apical cells in the head of the epididymis and clear cells in the body and tail of the epididymis express high levels of a vacuolar proton-pumping adenosinetriphosphatase on their apical plasma membranes and on intracellular vesicles. By analogy with kidney intercalated cells, these cell types may be specialized for acid secretion in the epididymis.

Animals↗

PubMed1992

Localization of the CHIP28 water channel in rat kidney.

CHIP28 is an integral membrane protein that has been identified as the erythrocyte water channel and that is also expressed in the kidney. Antibodies against erythrocyte CHIP28 were used to localize this protein along the rat urinary tubule. By Western blotting, CHIP28 was detected in kidney plasma membrane and endosome fractions. With the use of immunocytochemistry, CHIP28 was located in brush-border and basolateral plasma membranes of the proximal tubule. The initial S1 segment was weakly stained, but the S2 and S3 segments were heavily labeled. Subapical vesicles were also positive. Apical and basolateral membranes of the long thin descending limb were strongly labeled, but ascending thin and thick limbs of Henle and distal convoluted tubules were negative. Some vasa recta profiles in the medulla were positive. CHIP28 is, therefore, present in membranes with a high constitutive water permeability, where it probably acts as a transmembrane water-conducting channel. Finally, a weak staining of apical and basolateral membranes of cortical collecting duct principal cells was detectable, suggesting a potential relationship of CHIP28 to the vasopressin-sensitive water channel.

Animals↗

PubMed1992

Differential collagen and fibronectin production by Thy 1+ and Thy 1- lung fibroblast subpopulations.

Pulmonary fibrosis resulting from diverse etiologies is characterized by proliferation of fibroblasts and excessive accumulation of interstitial collagen. Whether fibrosis is associated with selective expansion of fibroblast subpopulations differing in amounts or types of collagens synthesized is unknown. We have previously isolated lines and clones of normal murine lung fibroblasts based on the presence of the Thy 1 surface antigen. These subpopulations differ in morphology, growth characteristics, and display of class II major histocompatibility complex antigens (R.P. Phipps, D.P. Penney, P. Keng, H. Quill, A. Paxhia, S. Derdak, and M. E. Felch. Am. J. Respir. Cell Mol. Biol. 1: 65-74, 1989). We evaluated the amounts and types of collagen and fibronectin synthesized by Thy 1+ (Fib2-T-3+) and Thy 1- (Fib2-T-4-) lung fibroblast lines and clones. Thy 1+ fibroblast line synthesized two- to threefold more collagen and noncollagen protein than the Thy 1- line. In contrast, both the Thy 1+ and Thy 1- lines synthesized similar amounts of fibronectin. Thy 1+ and Thy 1- lines and clones expressed mRNA for alpha 1(I)-and alpha 1(III)-procollagen and synthesized both types (predominantly type I and lesser amounts of type III) of collagen, protein, and mRNA. The fibroblast clones varied significantly in total collagen and fibronectin production, with one Thy 1- clone (D3) synthesizing the largest amount of collagen but relatively little fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗