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Biomedical subjects

D L Brown

Publications and source records attributed to D L Brown.

At least 19 recordsLinked to original sources
PubMed1992

Differential sorting of beta tubulin isotypes into colchicine-stable microtubules during neuronal and muscle differentiation of embryonal carcinoma cells.

Pluripotent P19 embryonal carcinoma (EC) cells were differentiated along the neuronal and muscle pathways. Comparisons of class I, II, III, and IV beta tubulin isotypes in total and colchicine-stable microtubule (MT) arrays from uncommitted EC, neuronal, and muscle cells were made by immunoblotting and by indirect immunofluorescence microscopy. In undifferentiated EC cells the relative amounts of these four isotypes are the same in both the total and stable MT populations. Subcellular sorting of beta tubulin isotypes was demonstrated in both neuronal and muscle differentiated cells. During neuronal differentiation, class II beta tubulin is preferentially incorporated into the colchicine-stable MTs while class III beta tubulin is preferentially found in the colchicine-labile MTs. The subcellular sorting of class II into stable MTs correlates with the increased staining of MAP 1B, and with the expression of MAP 2C and tau. Although muscle differentiated cells express class II beta tubulin, stable MTs in these cells do not preferentially incorporate this isotype but instead show increased incorporation of class IV beta tubulin. Muscle cells do not show high levels of MAP 1B and do not express MAP 2C or tau. These results are consistent with the hypothesis that a subcellular sorting of tubulin isotypes is the result of a complex interaction between tubulin isotypes and MT-associated proteins.

Animals↗
PubMed1992

The topoisomerase II inhibitor teniposide (VM-26) induces apoptosis in unstimulated mature murine lymphocytes.

This study shows that not only concanavalin A-stimulated proliferating lymphocytes but also unstimulated mouse splenic lymphocytes are sensitive to the topoisomerase II (topo II) inhibitor teniposide (VM-26). When unstimulated lymphocytes are pretreated with VM-26 for a 2-h period and are then incubated in drug-free medium, cell viability, as determined by trypan blue exclusion, decreases to 40% of the control by 6 h. The drug-treated cultures show two to three times the level of detergent soluble DNA than the control cultures and agarose gel electrophoresis of the soluble DNA shows the presence of oligonucleosomal-sized fragments, a feature considered to be a hallmark of apoptosis. Phase contrast microscopy, Hoechst staining for DNA, and immunofluorescence microscopy of various nuclear and cytoplasmic antigens (nucleolar fibrillarin, snRNP, ubiquitin, vimentin, tubulin) in the VM-26-treated cells characterize the morphological changes during apoptosis of these cells. The role of topo II as the mediator of the VM-26 effects is supported by pulsed field gel electrophoresis, which shows the typical topo II-induced cleavage of supercoiled DNA into loop-sized 300- and 50-kbp fragments. We conclude that the cancer chemotherapeutic agent VM-26 interacts with topo II and induces apoptosis in unstimulated lymphocytes.

Animals↗
PubMed1992

Incidence and risk factors for side effects of spinal anesthesia.

We prospectively studied 952 patients to identify the incidence of hypotension (systolic blood pressure less than 90 mmHg), bradycardia (heart rate less than 50 beats/min), nausea, vomiting, and dysrhythmia during spinal anesthesia. Historical, clinical, and physiologic data were correlated with the incidence of these side effects by univariate and multivariate analysis. Hypotension developed in 314 patients (33%), bradycardia in 125 (13%), nausea in 175 (18%), vomiting in 65 (7%), and dysrhythmia in 20 (2%). Variables conferring increased odds of developing hypotension include peak block height greater than or equal to T5 (odds ratio 3.8, P less than 0.001), age greater than or equal to 40 yr (2.5, P less than 0.001), baseline systolic blood pressure less than 120 mmHg (2.4, P less than 0.001), combination of spinal and general anesthesia (1.9, P = 0.01), spinal puncture at or above the L2-L3 interspace (1.8, P less than 0.001), and addition of phenylephrine to the local anesthetic (1.6, P = 0.02). Variables conferring increased odds of developing bradycardia include a baseline heart rate less than 60 beats/min (odds ratio 4.9, P less than 0.001), ASA physical status classification of 1 versus 3 or 4 (3.5, P less than 0.001), current therapy with beta-adrenergic blocking drugs (2.9, P less than 0.001), and peak block height greater than or equal to T5 (1.7, P = 0.02). Variables conferring increased odds of developing nausea or vomiting include addition of phenylephrine or epinephrine to the local anesthetic (3.0-6.3, P less than or equal to 0.003), peak block height greater than or equal to T5 (odds ratio 3.9, P less than 0.001), use of procaine (2.6-4.4, P less than or equal to 0.003), baseline heart rate greater than or equal to 60 beats/min (2.3, P = 0.03), history of carsickness (2.0, P = 0.01), and development of hypotension during spinal anesthesia (1.7, P = 0.009). Our results indicate that the incidence of side effects during spinal anesthesia may be reduced by 1) minimizing peak block height; 2) using plain solutions of local anesthetics; 3) performing the spinal puncture at or below the L3-L4 interspace; and 4) avoiding the use of procaine in the subarachnoid space.

Adult↗
PubMed1992

Monoclonal antibodies to Gliocladium roseum, a potential biological control fungus of sap-staining fungi in wood.

Immunological probes were developed to discriminate between a potential biological control fungus and sap-staining fungi present in wood. This paper describes the production of monoclonal antibodies to isolated cell wall fragments of the biological control fungus Gliocladium roseum. Two monoclonals, designated 6A5 and 3F12, were characterized. Their specificity was assessed by ELISA, by immunogold silver staining light microscopy, by immunogold electron microscopy, and by immunoblotting. Monoclonal 6A5 specifically recognized G. roseum and closely related species and did not react with any of 21 sap-staining fungi tested. Monoclonal 3F12 recognized most of the biological control fungi tested and also showed reactivity with two of the 21 sap-staining fungi. Both monoclonals appeared to recognize carbohydrate epitopes of the cell wall in G. roseum. Although the antibodies were produced against the cell wall of fungus grown in liquid culture, they also detected specific fungi in wood and, therefore, can be used for studies of wood colonization by fungi and for investigations of the interactions between different fungi growing on wood.

Antibodies, Fungal↗
PubMed1992

Activation of normal neutrophils by anti-neutrophil cytoplasm antibodies.

Anti-neutrophil cytoplasm antibodies (ANCA) are markers of systemic vasculitis for which a pathogenetic role has been postulated. We have examined the effect of these autoantibodies on the function of normal human neutrophils in vitro. In the presence of ANCA positive sera luminol-amplified chemiluminescence was significantly increased compared to the values seen in the presence of normal or anti-double stranded DNA positive sera (P < 0.01). Five of six ANCA positive F(ab)2 preparations also produced significant neutrophil activation as demonstrated by the chemiluminescence response. This response was totally abrogated by the addition of neutrophil cytoplasm extract, containing the ANCA antigen. Addition of inhibitors to the chemiluminescence system demonstrated that the chemiluminescence response was inhibited by azide and salicylhydroxamic acid and reduced by histidine, suggesting that the chemiluminescence response was due to activation of myeloperoxidase, with generation of singlet oxygen. The chemotactic response to f-Met-Leu-Phe, a bacterial chemotactic peptide, was significantly augmented in the presence of ANCA. Chemotaxis to zymosan-activated serum and chemokinesis was not affected. Phagocytosis was also unaffected. We propose that neutrophil activation and modulation of neutrophil migration by ANCA may be of pathogenetic significance in systemic vasculitis.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1992

Echogenic material in the fetal gallbladder: sonographic and clinical observations.

Obstetric sonograms of 26 fetuses with echogenic material in the gallbladder were reviewed to describe the sonographic findings and clinical significance. Gestational age at the time of diagnosis ranged from 28 to 42 weeks (mean, 36.2 weeks). The echogenic foci were associated with distal shadowing in eight fetuses (30%), comet-tail artifact in nine (35%), and no distal artifact in nine (35%). No hemolytic anemias, other predisposing risk factors, or clinical sequelae associated with biliary tract disease were identified in any of the infants. Postnatal sonographic or pathologic follow-up studies were available in 17 cases. In nine of these 17 infants, the echogenic foci had resolved. In three, the foci have persisted, but none of the children have become symptomatic; the longest period of follow-up with stones still present is 4 1/2 years. Whether all echogenic foci in the fetal gallbladder represent true gallstones remains unknown. Echogenic foci may be seen in the fetal gallbladder during the third trimester. No predisposing fetal risk factors or clinical sequelae were evident in our series. Many echogenic foci, but not all, will resolve.

Anemia, Hemolytic↗
PubMed1992

Cystic testicular mass caused by dilated rete testis: sonographic findings in 31 cases.

We reviewed the scrotal sonograms of 31 patients who had a testicular mass consisting of multiple small spherical or tubular anechoic structures in the region of the mediastinum testis. The median age of the patients was 62 years (range, 31-76 years). The abnormality was unilateral in 22 patients and bilateral in nine. Thirty-four (85%) of the 40 involved testicles had coexisting epididymal abnormalities: 32 with epididymal cysts and two with epididymitis. Follow-up sonograms were available in five patients and showed no change up to 4.5 years after the initial diagnosis. Surgical and histologic findings were available in one other patient and showed dilatation of the rete testis. The sonographic appearance and location of the lesions, the frequent presence of an epididymal abnormality, and the surgical and histologic findings in one case suggest that the lesion is due to dilatation of the rete testis, probably associated with obstruction in the epididymis. Recognition of this entity on sonograms may prevent unnecessary orchiectomy.

Adult↗
PubMed1991

Effects of hyperthermia on microtubule organization and cytolytic activity of murine cytotoxic T lymphocytes.

When murine cytotoxic T lymphocytes (CTL) are heated at 42 degrees C for 30 min their ability to lyse their target cells (TC) is severely impaired. When the CTL are allowed to recover at 37 degrees C, a partial recovery of cytolytic activity that peaks within 6 h is observed. A dye exclusion assay demonstrated that such a heat shock does not affect the viability of the CTL and direct microscopic observations established that their ability to bind to TC is not impaired. Therefore, the step or steps inhibited by hyperthermia are subsequent to TC recognition and binding. Kupfer et al. ((1983) Proc. Natl. Acad. Sci. USA 80, 7224-7228) demonstrated that upon binding to an appropriate TC, a rapid orientation of the Golgi apparatus and the microtubule organizing center (MTOC) occurred within the CTL so that the two organelles face the TC. This orientation is a prerequisite for efficient TC lysis. We have shown by immunofluorescence and confocal microscopy, using a monoclonal antibody to tubulin and a rabbit autoimmune serum that binds a centriole-associated protein, that the organization of the MTOC-microtubule array is disrupted by hyperthermia. EM suggests that this disorganization of the microtubules may result from an aggregation of the pericentriolar material. The recovery of cytolytic activity is coincident with the reorganization of the microtubules about the MTOC. These findings suggest that the initial inhibitory effect of hyperthermia on CTL function results from the disruption of microtubule organization.

Animals↗
PubMed1991

Taxol protects the microtubules of concanavalin A-activated lymphocytes from disassembly by methylmercury, but DNA synthesis is still inhibited.

We have shown previously that there is a good correlation between the degree of microtubule disassembly by methylmercury (MeHg) and the extent of inhibition of DNA replication in Concanavalin A (Con A)-stimulated mouse splenic lymphocytes. The purpose of this study was to determine if these two events are causally related and to examine the effects of MeHg-induced microtubule disassembly on earlier events of the stimulation process. We show that early steps constituting the activation pathway, such as the Con A-induced increase in Ca2+ influx and the expression of interleukin 2 receptor, are not inhibited by concentrations of MeHg that disassemble microtubules. RNA synthesis is not affected by short-term (3 h) treatment with MeHg, but longer treatment (24 h) inhibits RNA synthesis. In contrast, DNA synthesis is effectively inhibited by a 3-h treatment with MeHg. In lymphocytes treated with taxol, microtubules are not disassembled by MeHg; however, the inhibition of RNA and DNA synthesis persists. We conclude that the inhibition of nucleic acid synthesis by MeHg is not causally related to MeHg-induced microtubule disassembly.

Alkaloids↗
PubMed1991

Assessing dairy potential of western white-faced ewes.

Two experiments were conducted to examine the milk producing ability of Western White-Faced sheep and to identify traits that correlate well with milk production. In Exp. 1, 31 Targhee ewes were milked and five samples were taken during 107-d lactations in which the ewes nursed twin lambs. Milk yield and composition, lamb weights, ewe weights, wool growth, and udder size also were measured. In Exp. 2, 24 ewes (Rambouillet x Finn-Dorset) were separated from their lambs at 7 wk and milked twice per day for eight more weeks, during which milk yield and composition, feed consumption, udder width, and ewe weights were measured. Results from Exp. 1 showed that lamb 30-d weights, ewe weights at breeding time, and udder width at peak lactation were highly correlated with suckled milk yield (r = .81, .75 and .66, respectively). Results from Exp. 2 indicated that lamb weights and ewe weights were not useful for predicting milk yield in dairy ewes, but feed intake and udder width were (r = .74 and .86, respectively). Single-day milk yield measurements were excellent estimators of total lactation yield in both experiments. Milk yields averaged 1,714 g/d in the suckled ewes and 477 g/d in the dairy ewes.

Animals↗
PubMed1991

Serial endovaginal sonography of ectopic pregnancies treated with methotrexate.

Methotrexate therapy is a newly established treatment modality for ectopic pregnancy. We performed this study to determine the time frame for resolution of the sonographically identifiable mass during such therapy and to determine the role of sonography in the management of these patients. Eighteen patients treated with methotrexate for laparoscopically proven ectopic pregnancy consented to long-term follow-up with endovaginal sonography. These 18 patients constitute the study group. The time required for sonographic resolution of the mass was variable, although poor patient compliance with sonographic follow-up affected the conclusions regarding resolution time. One hundred eight days was the longest period accurately known for resolution of a mass. In seven patients, the mass persisted after a negative hCG titer. Enlargement of the adnexal mass during therapy did not necessarily predict treatment failure, as only two of ten such patients required surgery for rupture. Serial sonography did not alter the management of most patients and appears not to be warranted on a routine basis. Follow-up sonography was most useful when complications were suspected. All patients considered for methotrexate therapy should first have an endovaginal sonogram, as cardiac activity remains a relative contraindication to this treatment. We have determined that the mass of an ectopic pregnancy may remain after the hCG is negative. Therefore, a persistent mass should not be interpreted as treatment failure.

Female↗
PubMed1990

Body composition of adult cystic fibrosis patients and control subjects as determined by densitometry, bioelectrical impedance, total-body electrical conductivity, skinfold measurements, and deuterium oxide dilution.

This study contrasts body compositions (by six methods) of eight cystic fibrosis (CF) subjects with those of eight control subjects matched for age, height, and sex. CF subjects weighed 84% as much as control subjects. Densitometry and two bioelectrical impedance-analysis methods suggested that reduced CF weights were due to less lean tissue (10.7, 9.5, and 10.4 kg). Total-body electrical conductivity (TOBEC) and skinfold-thickness measurements indicated that CF subjects were leaner than control subjects and had less fat (5.4 and 3.6 kg) and less lean (5.2 and 7 kg) tissue. D2O dilution showed a pattern similar to TOBEC (8.3 kg less lean, 2.7 kg less fat tissue). Densitometry estimates of fat (mass and percent) were not correlated (r less than 0.74, p greater than 0.05) with any other method for CF subjects but were correlated with all other methods for control subjects. CF subjects contained less fat and lean tissue than did control subjects. Densitometry by underwater weighing is unsuitable for assessing body composition of CF patients.

Adipose Tissue↗