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Biomedical subjects

B L Carter

Publications and source records attributed to B L Carter.

At least 181 records · Page 10Linked to original sources
PubMedDate not supplied

Hypertension and left ventricular hypertrophy: is drug therapy beneficial?

Left ventricular hypertrophy (LVH) is a consequence of long-standing hypertension and is considered to be an independent risk factor for cardiovascular morbidity and mortality. Several antihypertensive agents are capable of inducing regression of LVH, but it is not known which class of drugs is most effective. The impact of drug-induced reversal of hypertrophy on ventricular function remains a controversial issue. Furthermore, the long-term clinical benefits of LVH regression have yet to be documented. Controversies also exist regarding the clinical outcomes associated with drug-induced LVH regression.

Adult↗
PubMedDate not supplied

5'-secondary structure formation, in contrast to a short string of non-preferred codons, inhibits the translation of the pyruvate kinase mRNA in yeast.

The effects of poor codon bias and secondary structure formation upon the translation of the pyruvate kinase (PYK1) mRNA have been investigated in Saccharomyces cerevisiae. Following insertion mutagenesis at the 5'-end of the PYK1 coding region, the gene was transformed into yeast, and translation assessed directly in vivo by determining the distribution of the modified PYK1 mRNAs across polysomes fractionated by sucrose density gradient centrifugation. The chromosomally-encoded (wild-type) PYK1 mRNA, and the actin, ribosomal protein L3 and glyceraldehyde-3-phosphate dehydrogenase mRNAs were used to control for minor differences between polysome preparations. An insertion containing 13 non-preferred codons at the 5'-end of the coding region was found to have no significant effect upon PYK1 mRNA translation. In contrast, translation was inhibited by an insertion which increased the formation of secondary structures at the 5'-end of the mRNA (overall delta G = -36.6 kcal/mol). Control insertions were also analysed to exclude the possibility that alterations to the amino acid sequence of pyruvate kinase affect the translation of its mRNA. These insertions, which introduced preferred codons or restored wild-type levels of secondary structure formation, did not significantly influence PYK1 mRNA translation.

Amino Acid Sequence↗
PubMedDate not supplied

Computed tomography in Caroli's disease.

Two cases of Caroli's disease are presented in which the diagnosis could be made by computed tomography without the use of invasive modalities. The findings in computed tomography in Caroli's disease are outlined.

Biliary Dyskinesia↗
PubMedDate not supplied

CT scanning in septic sacroiliac arthritis or periarticular osteomyelitis.

Two cases are presented which demonstrate the utility of CT scanning in the evaluation of patients with septic sacroiliitis. The importance of making an early diagnosis in such patients is noted and the roles of various other modalities are related to that of CT scanning.

Arthritis, Infectious↗
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Computed tomographic demonstration of gas collections simulating infection.

Two cases of computed tomographic demonstration of gas collections simulating gas forming organism infection are presented in patients shown subsequently not to be infected--the air resulting from tissue necrosis. These observations are helpful in guiding conservative management of certain patients in the appropriate clinical setting.

Abscess↗
PubMedDate not supplied

Bullous change by CT heralding metastatic sarcoma.

The association of spontaneous pneumothorax with metastatic osteosarcoma is well known. Small blebs and bullous change can be easily detected in the lungs by computed tomography. In patients with known sarcomas, blebs and bullae may appear as the first or early manifestation of metastatic disease (or concurrent with the disease) as illustrated by the three patients presented here with three different types of sarcomas. The literature has been reviewed as to the etiology of spontaneous pneumothoraces occurring in metastatic sarcomas and the relationship of bleb and bullae formation to these spontaneous pneumothoraces is discussed.

Adolescent↗
PubMedDate not supplied

Bronchogenic cyst causing superior vena cava obstruction: CT appearance.

The CT appearance of bronchogenic cysts is well known. In addition, CT is useful in evaluating cases of suspected superior vena cava (SVC) syndrome. Although most cases of SVC syndrome are caused by malignant diseases, certain benign disorders such as granulomatous infections may be the underlying cause. A case of a bronchogenic cyst causing SVC occlusion is presented here.

Adult↗
PubMedDate not supplied

Variable CT appearance of plasma cell granuloma of the lung.

Plasma cell granuloma of the lung is an uncommon benign inflammatory pseudotumor. Although it typically presents as a solitary mass on chest radiography, several chest film appearances have been described. Three cases are presented that illustrate the variable range and nonspecificity of CT appearances of plasma cell granuloma of the lung. Computed tomography is useful in the evaluation of these lesions primarily to establish important anatomic relationships associated with each of the various manifestations.

Adult↗
PubMedDate not supplied

Esophageal pseudomass at the thoracic inlet on barium swallow: CT findings.

PURPOSE: Our goal was to describe the CT findings in patients with an apparent mass at the thoracic inlet on barium swallow and to further explore its etiology by making appropriate measurements on CT. METHOD: Barium swallows and CT scans of five patients with esophageal pseudomass were reviewed and compared with CT scans of 65 controls. Anteroposterior (AP) diameters of the thoracic inlet were measured, and the relationships of the esophagus to the trachea were determined on CT. RESULTS: Absence of a demonstrable mass on CT in patients with an extrinsic impression on barium swallow was associated with narrowed AP diameter of the thoracic inlet (< 5 cm) and the esophagus to the left of the trachea. A significant correlation was observed between the AP diameter of the inlet and the position of the esophagus in relation to the trachea in control subjects (r = 0.52, p < 0.001); with diminished diameter, the esophagus is more frequently located to the left side of the trachea. CONCLUSION: An apparent mass is simulated by lateral deviation of the lower cervical esophagus, due to diminished available space between the trachea and the esophagus in subjects with a narrow (< 5 cm) AP diameter of the thoracic inlet.

Adult↗
PubMedDate not supplied

Dual calcium-channel blocker therapy in the treatment of hypertension.

OBJECTIVE: To review the in vitro receptor binding data of calcium-channel blockers (CCBs) and in vivo studies in humans regarding the use of dual calcium-channel blocker therapy, with a focus on the use of this therapy for hypertension. DATA SOURCE: A MEDLINE search was conducted to identify literature pertaining to CCBs. STUDY SELECTION: In vitro studies and investigations that evaluated CCB receptor binding and the interactions between subclasses of CCBs were chosen. All studies in humans and clinical trials that evaluated the use of dual CCB therapy in the treatment of cardiovascular diseases were selected for review. Also, case reports describing the use of dual CCB therapy were included in this article. DATA EXTRACTION: The methodology, results, and conclusions of the selected data were evaluated. Data regarding the in vitro receptor binding kinetics of CCBs, as well as interactions, were reported. Because there is limited information on dual CCB therapy for hypertension, clinical studies using this treatment for ischemic heart disease were also reviewed. They were summarized and compared on the basis of the degree of disease control (e.g., blood pressure, exercise tolerance), adverse effects, and other clinical endpoints of pharmacologic therapy. DATA SYNTHESIS: In vitro studies have identified binding sites for the dihydropyridine (nifedipine), diphenylalkylamine (verapamil), and benzothiazepine (diltiazem) subclasses of CCBs, and indicate that they are allosterically related to each other within the voltage-sensitive calcium-channel receptor. Dihydropyridine binding affinity is decreased with concomitant verapamil binding, but is enhanced by concomitant diltiazem binding. Dual CCB therapy has been shown to be efficacious in patients with ischemic heart disease. Although this therapy is limited by dose-related adverse effects, it appears to have an important role in patients with ischemia that is refractory to conventional therapy, or for those whose therapeutic options are limited by contraindications. Theoretically, many patients with hypertension may benefit similarly from dual CCB therapy. Because data evaluating this treatment option are sparse, recommendations regarding safety, efficacy, and the role of dual CCB therapy for hypertension would be premature. CONCLUSIONS: Controlled data evaluating dual CCB therapy for the treatment of hypertension are lacking. This treatment modality may be beneficial in the future, but requires further investigation to determine safety and efficacy.

Calcium Channel Blockers↗
PubMedDate not supplied

Pathophysiology and treatment of deep-vein thrombosis and pulmonary embolism.

The pathophysiology of deep-vein thrombosis (DVT) and pulmonary embolism (PE) is briefly discussed, and the efficacy, dosage and administration, laboratory monitoring, and adverse effects of thrombolytic agents, heparin, and warfarin are reviewed. Acute therapy of DVT and PE is usually initiated with intravenous heparin; however, thrombolytic agents such as streptokinase and urokinase may be preferred in patients with massive PE or severe DVT when clot lysis rather than clot stabilization is deemed necessary. For DVT or PE, an intravenous loading dose of streptokinase or urokinase is given, followed by a continuous infusion of the drug. Therapy with streptokinase is continued for 24 hours in patients with PE and for 72 hours in those with DVT; urokinase is continued for 12 hours in patients with PE. Monitoring of blood coagulation tests during thrombolytic therapy is recommended primarily for ensuring that a lytic state is achieved. Intravenous heparin is preferred for acute treatment of DVT or PE; controversy exists regarding whether administration by continuous infusion or intermittent bolus injection is superior. Heparin dosage is usually adjusted to maintain the activated partial-thromboplastin time (APTT) ratio between 1.5 and 2.5; however, the ideal therapeutic range has never been firmly established. After acute treatment with heparin, most patients should continue to receive either warfarin or subcutaneous heparin for several months to prevent recurrent thromboembolism. Bleeding is the major adverse effect of thrombolytic agents and anticoagulants. The risk of bleeding with heparin and warfarin therapy increases with excessive prolongation of the APTT and prothrombin time (PT), respectively. Future clinical trials should further define the role of thrombolytic agents in the treatment of DVT and PE and the efficacy of less-intense warfarin therapy for pulmonary embolism or arterial thromboembolic events.

Acute Disease↗
PubMedDate not supplied

Update on acyclovir: oral therapy for herpesvirus infections.

The results of the major human clinical trials on oral acyclovir are reviewed, and the pharmacokinetics, adverse effects, and role of oral acyclovir in the management of herpes simplex virus (HSV) infections are discussed. Clinical studies have demonstrated the effectiveness of oral acyclovir in causing significant reductions in the duration of viral shedding, development of new lesions, and time to crusting and healing in several clinical situations. The drug appears to achieve the most dramatic results in the treatment of initial primary genital herpes infections. Oral acyclovir also has a potential role in suppressing reactivations of HSV infections in immunocompromised patients or patients experiencing greater than 10-12 recurrences of genital herpes per year. Most trials have used 200-mg capsules administered five times daily for 5-10 days for treating acute infections. Reduced doses have been successful for suppressive therapy. Acyclovir does not alter the frequency of recurrence once treatment has been discontinued. The absolute bioavailability of oral acyclovir is approximately 20%, and plasma concentrations are about one tenth of those achieved after a typical i.v. infusion. The relationship between plasma concentration and clinical response has not been established. The half-life is 3-4 hours, and the predominant route of elimination is via renal excretion and tubular secretion. Clinical studies have consistently reported minimal adverse effects with oral acyclovir. Conservative use is justified by the potential development of resistant viral strains. The extent and clinical importance of resistant viral selection remain to be determined. Oral acyclovir represents an advance in the development of a nontoxic antiviral agent suitable for both hospitalized and ambulatory patients that should be recommended for formulary inclusion.

Acyclovir↗