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Biomedical subjects

M Brooks

Publications and source records attributed to M Brooks.

At least 37 records · Page 2Linked to original sources
PubMed1995

Transient gene expression of antisense RNA and coat protein-encoding sequences reduced accumulation of cherry leafroll virus in tobacco protoplasts.

Cherry leafroll nepovirus (CLRV) is the causative agent of blackline disease, which results in a fatal necrosis of the graft union of English walnut scion on certain rootstocks. Tobacco suspension cell protoplasts were electroporated with plasmid constructions, bearing or not bearing RNA-derived sequences, and, subsequently, were electroporated with CLRV virions or virion RNA Replication of CLRV in protoplasts was demonstrated by accumulation of both positive- and negative-sense CLRV genomic RNAs 1 and 2, capsid antigen, and virions. Three plasmids were tested for antiviral action. These have inserts that were derived from the coat protein gene, inserted in both orientations, and from the 3' terminal sequence that is nearly identical in RNA 1 and RNA 2, oriented for expression of antisense RNA. Plasmids were introduced into protoplasts 12 hr prior to introducing the virions or virion RNA. CLRV accumulation was reduced significantly by prior electroporation of plasmids intended to express coat protein or 3' antisense RNA, but not by electroporation of plasmid without insert or plasmid with coat protein encoding sequences in the antisense orientation. These results demonstrate the utility of transient expression in a protoplast system for comparing the efficacy of a variety of virus-derived and other sequences for their potential application in virus control strategies.

Capsid↗
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↗
PubMed1993

Buccal mucosa bleeding time is prolonged in canine models of primary hemostatic disorders.

Bleeding times are reported in many studies using canine models, with a variety of techniques employed to adapt these tests for dogs. We evaluated a canine model of template bleeding time, the buccal mucosa bleeding time (BMBT), by examining the test's sensitivity and specificity for defects of primary hemostasis. We examined thirty-five dogs having defined defects of either primary hemostasis (Types I, II, III von Willebrand's disease, thrombasthenia, thrombopathia) or secondary hemostasis (hemophilia A and B, Factor VII deficiency). Comparisons of BMBT and cuticle bleeding time were made in a subset of these dogs. All dogs having primary hemostatic disorders had long BMBT, and all factor deficient dogs had BMBT within normal range. The BMBT in canine models appears to be a specific and sensitive test of primary hemostasis; suitable for evaluating factors affecting template bleeding time and potential efficacy and thrombogenicity of treatment regimens.

Animals↗
PubMed1993

Intra-arterial streptokinase in acute ischaemic stroke. A pilot study.

AIMS: To assess the safety and efficacy of the intra-arterial administration of streptokinase within 24 hours of acute ischaemic stroke. METHODS: Patients who presented to the Austin Hospital casualty department between 3 and 22 hours after an acute stroke were considered for the study. Eligible patients had pretreatment non-contrast computed tomographic scans of the brain to exclude haemorrhage. Streptokinase (250,000 units) was administered directly into the common carotid artery or the cervical portion of the internal carotid artery. MAIN OUTCOME MEASURES: The incidence of symptomatic and asymptomatic cerebral haemorrhage, haemorrhagic transformation of infarction, angiographic reperfusion, clinical outcome at seven to 10 days and the frequency of other complications. RESULTS: Thirteen patients were treated over a 16-month period. Major clinical improvement occurred in five patients (39%) at 48 hours. This was associated with angiographically demonstrated recanalisation of a middle cerebral artery occlusion in two patients and partial recanalisation in two others. Significant hypotension in two patients required therapy to be stopped. In five other cases mild hypotension developed but the streptokinase infusion was completed. Haemorrhagic transformation of the infarct occurred in four patients without clinical deterioration. CONCLUSION: Intra-arterial administration of streptokinase is safe in selected patients with acute ischaemic stroke. The theoretical benefit of an increased local thrombolytic effect and reduced systemic complications, compared with the use of higher intravenous doses, justifies a randomised clinical trial. If therapies such as this are to be successful, rapid referral to an appropriate centre is necessary.

Aged↗
PubMed1993

Survey of the Anopheles maculatus complex (Diptera: Culicidae) in peninsular Malaysia by analysis of cuticular lipids.

Anopheles maculatus Theobald sensu lato is a species complex now consisting of eight sibling species; An. maculatus is still represented by two cytologically distinct forms; i.e., the widely distributed sensu strictu or B, and E from southern Thailand and adjacent areas in northern Malaysia. Cuticular lipid profiles in conjunction with principal component analysis was used to separate An. maculatus form E from sensu stricto form B in a preliminary survey of the An. maculatus complex at five locations spanning peninsular Malaysia. The relative rank orders, from the areas of the five gas chromatographic peaks used to determine lipid differences for specimens from peninsular Malaysia, matched well with those from cytogenetically identified colony specimens of An. maculatus forms B and E. The two-dimensional principal component pattern of specimens identified as form E was highly clumped, which indicated that very similar cuticular lipids were present within this putative malaria vector. Both forms coexisted in peninsular Malaysia, but form E may be dominant except in the south.

Animals↗
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

Long-range planning for information systems.

While it can appear to be an overwhelming task, developing a long-range plan for information systems (IS) in a community hospital can be a simple exercise. The plan should focus on long-range strategic objectives that best support the hospital's business strategy. The hospital executive management team must work with information systems staff to create a road map for securing the necessary IS technology, applications, and support.

Cost-Benefit Analysis↗
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↗