Biomedical subjects

M Brooks

Publications and source records attributed to M Brooks.

At least 19 recordsLinked to original sources

PubMed1995

A subgenomic RNA associated with cherry leafroll virus infections.

Cherry leafroll nepovirus (CLRV) genomic RNA 1 (8 kb) and genomic RNA 2 (7 kb) have 3' polyadenylate tracts and, extending 5' from the polyadenylate, nearly identical sequences of 1.6 kb termed the 3' common region. We observed RNAs 1 and 2 and a third RNA of 1.5 kb in nucleic acid extracts of CLRV-infected Nicotiana tabacum suspension cell protoplasts and Chenopodium quinoa plants, using a hybridization probe complementary to 1 kb of the 3' common region. The third RNA was partially purified by preparative gel electrophoresis and chromatography on an oligodeoxythymidylate column. Analyses of transcripts primed by a complementary oligodeoxyribonucleotide and of cDNA clones revealed that the third RNA corresponds to the 3' 1500 nucleotide residues of RNA 1. Hence we designate the newly characterized RNA as RNA 1A. RNA 1A was not detected as encapsidated RNA in extracts of either protoplasts or C. quinoa plants. The amount of accumulated RNA 1A declined between 24 and 48 hr after inoculation of protoplasts with CLRV virions, although CLRV RNAs 1 and 2 continued to accumulate. Other results were not consistent with cleaved RNA 1 being the origin of RNA 1A. RNA 1A has the properties of a subgenomic RNA, presumably synthesized from negative-sense RNA 1 as template.

Base Sequence↗

PubMed1995

Development of degenerative spondylosis of the lumbar spine after partial discectomy. Comparison of laminotomy, discectomy, and posterolateral discectomy.

STUDY DESIGN: The development of degenerative spondylosis after successful operative decompression of the affected nerve root was prospectively evaluated in a comparative case series of 100 patients with a herniated lumbar nucleus pulposus. OBJECTIVES: The objective of this study was to compare the relative incidence of degenerative spondyloarthrosis after successful posterior laminotomy and discectomy and posterolateral extradural discectomy for decompression of a compromised lumbar nerve root. SUMMARY OF BACKGROUND DATA: The relationship between the radiographic appearance of degenerative spondylosis and prior operative procedures has been controversial and at times contradictory. The posterior operative approach with a partial discectomy has been associated with a significant incidence of postoperative degenerative spondylosis and intraneural and perineural fibrosis, complications that may be minimized, or perhaps even eliminated, with the posterolateral evacuation of the offending intervertebral disc fragment. METHODS: Each patient had: 1) not responded favorably to nonoperative treatment, 2) a persistent radiculopathy, 3) correlative imaging studies with no preoperative spondyloarthrosis and 4) minimum 2-year follow-up. Fifty patients were treated by posterior laminotomy and discectomy and fifty were treated by a posterolateral extradural discectomy. Postoperative spondylosis was graded based on the radiographic presence or absence of osteophytes, the intervertebral disc height, the vertebral body alignment and the facet joint changes. RESULTS: At an average postoperative follow-up of 65 months, the incidence of a one grade increase in degenerative spondylosis was 80% of the laminotomy and discectomy patients as compared to 39% of the posterolateral discectomy patients. CONCLUSIONS: The increased incidence of spondyloarthrosis with the posterior approach suggests that minimally invasive posterolateral extradural procedures should be considered for the decompression of a compromised lumbar nerve root.

Diskectomy↗

PubMed1995

Amylase secretion by cultured porcine parotid cells.

The similarity of porcine and human physiology and the availability of slaughterhouse tissues suggests the use of porcine parotid cells as a model for amylase secretion. A procedure is described for the isolation of porcine parotid cells by collagenase-P/dispase digestion of the tissue. The preparation consisted of individual cells and small aggregates that were maintained in primary culture, during which the cells formed aggregates that firmly attached to the plastic substrate. The amylase content of the cultured cells remained adequate for assay of secretory activity during culture for one week after isolation. Depending upon variations in experimental treatments, the cultured cells secreted approx. 35-65% of cellular amylase in response to a carbachol challenge. The cells were slightly responsive to long exposures to isoproterenol, and were unresponsive to nicotine, elevated extracellular K+ or substance P. Secretion induced by carbachol required extracellular Ca2+, was inhibited by atropine and occurred with a nearly linear response over a 30-min period. The Ca2+ ionophore A23187 was also a potent secretagogue for amylase secretion, producing levels of secretion equal to that induced by carbachol. The ease of preparation and the retention of amylase during primary culture suggests that the preparation will be useful in studies on muscarinic receptor-mediated control of amylase secretion.

Amylases↗

PubMed1995

Aortic distensibility and stiffness index measured by magnetic resonance imaging in patients with Marfan's syndrome.

OBJECTIVES: To use magnetic resonance imaging to measure the elastic properties of the aorta of adults with Marfan's syndrome and to compare these results with those obtained by echocardiography. PATIENTS AND METHODS: 12 patients with Marfan's syndrome and 12 controls matched for age. Transverse luminal areas of the ascending and descending aorta were measured using electrocardiographic gated magnetic resonance imaging. Echocardiography was used to measure the diameter of the ascending aorta and aortic arch in patients with Marfan's syndrome. Blood pressure was measured during both scans. RESULTS: In diastole, transverse luminal areas of the ascending and descending aorta were significantly greater in patients with Marfan's syndrome when measured by magnetic resonance imaging and corrected for body surface area; P < 0.02 and P < 0.05 respectively. Patients with Marfan's syndrome had a higher stiffness index (112.77 v 5.78, P < 0.05) and a lower distensibility (0.0066 v 0.0105, P < 0.05) than controls. Results produced by MRI and echocardiography were not significantly different. CONCLUSIONS: Magnetic resonance imaging gives good quality reproducible images of the ascending and descending aorta. In patients with Marfan's syndrome, aortic distensibility and stiffness index measured by magnetic resonance imaging were abnormal (but did not always relate directly to the size of the aorta.

Adult↗

PubMed1994

Factor XI deficiency in Kerry Blue Terriers.

A 9-year-old female Kerry Blue Terrier with postoperative hemorrhage and prolonged activated partial thromboplastin and activated clotting times was determined to have factor XI deficiency. Transfusions of fresh-frozen plasma given on 4 consecutive days transiently returned the values for activated clotting time and plasma factor XI activity to within reference range limits and controlled the hemorrhage. Analysis of data from 10 other factor XI-deficient Kerry Blue Terriers with a tendency for mild posttraumatic or postoperative bleeding was suggestive of an autosomal mode of inheritance, with a mild tendency for posttraumatic or postoperative bleeding in homozygous and heterozygous dogs. Factor XI deficiency is the only contact phase protein defect that causes a bleeding disorder in animals, which can be explained by the fact that thrombin is more efficient than factor XIIa in activating factor XI. Factor XIa plays a key role in sustaining coagulation.

Animals↗

PubMed1994

Predictors of outcome after anterior temporal lobectomy: the intracarotid amobarbital test.

The intracarotid amobarbital test (IAT) examines hemispheric memory and language. We set out to determine whether memory performance on the IAT correlated with seizure relief after anterior temporal lobectomy in 117 patients with refractory epilepsy. The IAT assessed recognition memory performance for nine items with correction for false-positive recognitions. We then compared performance of one hemisphere with that of the other, defining a correctly lateralized memory deficit as worse performance when using the hemisphere containing the operated temporal lobe than when using the other hemisphere. The analysis included concurrent factors that might also affect outcome, such as age at first risk for epilepsy, presence or absence of tumor, and Full Scale IQ. A discriminant function analysis demonstrated that patients with a correctly lateralized memory deficit on the IAT had an increased probability of being seizure-free following surgery after controlling for other predictors. The performance of the nonoperated temporal lobe related to outcome, although less strongly. The magnitude of the difference in performance between the two hemispheres and the performance of the operated hemisphere did not relate to outcome. Patients who became seizure-free had an earlier age at first risk than did those with persistent seizures, and tumor presence weakly correlated with postoperative outcome. IQ did not correlate with outcome. We conclude that the IAT predicts seizure relief after anterior temporal lobectomy independent of other known risk factors we examined.

Adolescent↗

PubMed1992

Epidemiologic features of von Willebrand's disease in Doberman pinschers, Scottish terriers, and Shetland sheepdogs: 260 cases (1984-1988)

During a study period from 1985 through 1988, plasma von Willebrand's factor antigen (vWF:Ag) concentration was measured as a marker for prevalence of the von Willebrand's disease (vWD) trait in Doberman Pinschers (doberman, n = 5,554), Scottish Terriers (scottie, n = 1,363), and Shetland Sheepdogs (sheltie, n = 4,279). Significant increase in prevalence of the trait was seen in scotties and shelties during this period. In 1988, 73% of dobermans, 30% of scotties, and 28% of shelties tested had abnormal vWF:Ag concentration (less than 50% vWF:Ag). We found significant differences between breeds with respect to age and vWF:Ag concentration of clinically affected dogs at time of diagnosis. The affected dobermans were older (doberman mean age, 4.6 years; scottie mean age, 1.7 years; sheltie mean age, 1.9 years) and had higher concentration of plasma vWF:Ag (doberman mean vWF:Ag, 15%; scottie mean vWF:Ag, 0%; sheltie mean vWF:Ag, 8%). Bleeding in affected dogs of all 3 breeds was observed predominantly from mucosal surfaces and from cutaneous sites of surgery or trauma. The most common site of mucosal bleeding in scotties and shelties was oral or nasal cavity, and in dobermans was the urogenital tract. Differences in clinical manifestations of vWD in purebred dogs may reflect heterogeneous defects within the vWF gene, causing a variety of abnormalities in production, structure, and function of vWF protein. Analogous to vWD in human beings, acquired deficiencies of vWF may also contribute to the clinical variability of vWD in dogs.

Animals↗

PubMed1992

Induction of apoptosis in fibroblasts by c-myc protein.

Although Rat-1 fibroblasts expressing c-myc constitutively are unable to arrest growth in low serum, their numbers do not increase in culture because of substantial cell death. We show this cell death to be dependent upon expression of c-myc protein and to occur by apoptosis. Regions of the c-myc protein required for induction of apoptosis overlap with regions necessary for cotransformation, autoregulation, and inhibition of differentiation, suggesting that the apoptotic function of c-myc protein is related to its other functions. Moreover, cells with higher levels of c-myc protein are more prone to cell death upon serum deprivation. Finally, we demonstrate that deregulated c-myc expression induces apoptosis in cells growth arrested by a variety of means and at various points in the cell cycle.

Animals↗

PubMed1992

Comparison of thermal injury zones in loop electrical and laser cervical excisional conization.

Thirty cervical conization specimens obtained by thin-loop electric excision were compared with 30 carbon dioxide laser excisional cone specimens. Zones of thermal artifact were measured with a precise stage micrometer technique calibrated to a Zeiss standard. The mean depth of coagulation at the ectocervical margin measured 0.187 and 0.164 mm for thin loop and laser, respectively. Thermal artifact at the endocervical margin was greater with electric loop (0.295 mm) than with superpulsed carbon dioxide laser (0.137 mm). The zones of thermal injury induced by both electric loop and laser made no significant impact on the interpretation of margin adequacy.

Cervix Uteri↗

PubMed1992

How frequent is heteropaternal superfecundation?

A newly discovered case of heteropaternal superfecundation (HS) is reported. Three HS cases were found in a parentage test database of 39,000 records. The frequency of HS among dizygotic twins whose parents were involved in paternity suits is 2.4%. Although the study population appears similar to the general population with respect to twinning data, inferences about the frequency of HS in other populations should be drawn with caution.

Adolescent↗

PubMed1992

Two-man and two-sibling paternity cases.

Traditional genetic marker systems rarely fail to resolve paternity disputes when two or more men are accused, except when men are brothers. A sibling of the biologic father may not be excluded by these laboratory tests and sometimes yields calculated odds of paternity that are equal to or higher than the true male parent. Resolved two-brother cases were compared with resolved cases involving two unrelated men. In each case, the residual odds of paternity were determined for each man and the greater was divided by the lesser to produce a paternity fraction. The paternity fraction is a useful indicator of biologic parentage when it exceeds a value of 10 (log10 of-the-odds score greater than or equal to 1). Tests for alleles at highly heterozygous loci are indicated in initial laboratory evaluations of cases involving brothers. Human leukocyte antigen and variable number of tandem repeat polymorphisms appear suitable.

Alleles↗

PubMed1992

Effects of verapamil and Bay K 8644 on defibrillation energy requirements in dogs.

Antiarrhythmic drugs are often required in patients with implantable cardioverter-defibrillator devices. Prior evidence suggests that drugs modulate defibrillation energy requirements by altering ion channel activity. To evaluate the effects of calcium ion channel activity on internal defibrillation energy requirements, the calcium antagonist verapamil and Bay K 8644, a calcium channel activator, were investigated in 30 open-chest, pentobarbital-anesthetized dogs. Defibrillation energies were applied across two epicardial patch electrodes. The likelihood of successful defibrillation was determined at various shock energy levels, and the 50 and 90% effective energy doses were calculated using nonlinear regression. In saline control experiments (n = 10), the stability of the preparation throughout the 6-h duration of the experiments could be demonstrated. Verapamil administration (n = 10) infused to a mean plasma concentration of 69 ng/ml increased the 50 and 90% effective defibrillation energies by 41 and 43% (p less than 0.05), respectively, and to a mean plasma verapamil concentration of 170 ng/ml by 95 and 75% (p less than 0.01), respectively. The mean cycle length during ventricular fibrillation decreased with verapamil and was inversely related to the change in defibrillation energy requirement. Administration of Bay K 8644 (n = 10) produced a slight increase in the 50% effective defibrillation energy (25%; p less than 0.05) and 90% effective defibrillation energy (17%; n.s.). The electrophysiologic effects of verapamil were neither prevented nor reversed by Bay K 8644. In conclusion, intravenous verapamil administration caused an increase in defibrillation energy requirements, but the mechanism by which verapamil exerted this effect remains unclear. These experimental data suggest that verapamil should be used in patients with automatic implantable cardioverter-defibrillator devices only after individual testing.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

Management of canine von Willebrand's disease.

Canine von Willebrand's disease (vWD) is the most common inherited bleeding disorder of purebred dogs. Optimum treatment of affected dogs is influenced by the presence of concurrent disorders, especially thyroid insufficiency, and the nature of hemostatic stress encountered. Blood component therapy, most specifically the use of cryoprecipitate, provides the most effective transfusion support for severely affected dogs.

Animals↗

PubMed1991

Bleeding disorder (von Willebrand disease) in a quarter horse.

Bleeding diathesis in a Quarter Horse filly was caused by von Willebrand disease. Hemorrhage occurred mainly from mucosal surfaces and after trauma. Quantitative and qualitative measurements of plasma von Willebrand factor (vWF) documented a specific deficiency of vWF high molecular weight multimers, and concurrently greater than expected deficiency of vWF activity relative to vWF concentration. These findings are characteristic of type-II von Willebrand disease in human beings. Application of vWF assays used in human and small animal medicine now permits evaluation of vWF and diagnosis of von Willebrand disease in horses with bleeding disorders.

Animals↗

PubMed1991

Cystourethrometric findings in patients with detubularized right colonic segment for bladder replacement.

Urodynamic evaluation was performed in 13 men 4 to 18 months after cystoprostatectomy and bladder replacement using a detubularized right colonic segment. All patients are continent by day and only 3 are incontinent during the night to a degree that necessitates use of a condom catheter. Two patients awaken every 2 to 3 hours to void and the remainder have nocturia comparable to normal men of their age. The residual volume was 0 to 70 ml. The urethral closure pressure was normal, and in 3 patients studied preoperatively and postoperatively no significant change was observed other than shortening of the profile length. Maximal flow rates were normal although the pattern was intermittent. In 2 patients no cystoplasty contractions were recorded and in all but 2 patients the amplitude of the contractions was less than 40 cm. water. Simultaneous bladder and urethral pressure recordings during bladder filling demonstrated no change in urethral pressure in 10 patients. Although creation of a reservoir with a low pressure and careful preservation of the infraprostatic urethra are important for continence in these patients, we believe that the absence of normal sacral route reflexes after cystoprostatectomy is an important contributing cause to nocturnal incontinence.

Colon↗

PubMed1991

A sensitive immunoassay for von Willebrand factor.

We have developed an ELISA specific for canine von Willebrand factor antigen (vWF:Ag) that also strongly reacts with the VWF:Ag of humans and many other vertebrates. This assay was designed to avoid the use of immunoreagents of human origin, however, commercially available antibodies to human vWF:Ag may also be used. von Willebrand factor (vWF) was quantitated using a modified double-sandwich ELISA with polyclonal antibodies specific for canine vWF:Ag. The assay was as sensitive for measuring canine vWF:Ag as previously published immuno-radiometric assays and the most sensitive ELISA for human vWF:Ag. Employing commercially available antibodies to human vWF:Ag in the same double-sandwich configuration, the lower limit of detection for human vWF:Ag was 4.8 x 10(-6) units/ml, lower by a factor of ten than previously reported ELISAs. In addition, a wide range of vWF:Ag levels can be determined with just a single plasma dilution. The assay readily distinguishes type III von Willebrand disease from other types of von Willebrand disease having very low levels of vWF. This vWF ELISA can be used to evaluate large numbers of plasma samples simultaneously and is therefore well-suited for large-scale screening programs.

Animals↗

PubMed1991

Imaging of the orthopaedic patient: implications for primary care.

Pain in the skeleton is the foundation on which this article is based. Patients with musculoskeletal pain are frequently seen in primary care. There are many diagnostic imaging studies available to aid the practitioner in formulating and confirming a working diagnosis. This article offers specific guidelines for ordering imaging studies for common orthopaedic problems. The authors take into consideration costs and reliability of tests with each recommendation. The trend in many cases is to order magnetic resonance imaging scans rather than traditional radiographs. The indications for the commonly requested studies are reviewed.

Bone Diseases↗

PubMed1990

Cuticular lipid differences between the malaria vector and non-vector forms of the Anopheles maculatus complex.

Two chromosomal forms (E and F) of the Anopheles maculatus Theobald complex were distinguished by gas-liquid chromatographic (GC) analysis of cuticular lipids in association with a multivariate principal component analysis. The GC chromatogram obtained from n-hexane extracts of individual specimens showed no consistent qualitative differences in normalized peak areas between forms. Of the seventeen consistent peaks, five were found to be quantitatively different between forms at a high (99.5-99.95%) level of statistical confidence. Relative ratios of these five quantitatively different GC peaks were used as criteria to distinguish single specimens as either form E or form F. Chemical structures of the five GC peaks were assigned by both electron impact and chemical ionization gas chromatography/mass spectrometry analysis. The first three peaks, which were always doublets, were partially resolved saturated and mono-unsaturated free fatty acids; the other two peaks were n-alkanes. Principal component analysis substantiated that the vector form E has very similar cuticular lipid profiles and is well separated from the non-vector form F.

Animals↗