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Biomedical subjects

J J Williams

Publications and source records attributed to J J Williams.

At least 19 recordsLinked to original sources
PubMed1994

Performance characteristics of a whole-body PET scanner.

METHODS: This study characterizes the performance of a newly developed whole-body PET scanner (Advance, General Electric Medical Systems, Milwaukee, WI). The scanner consists of 12,096 bismuth germinate crystals (4.0 mm transaxial by 8.1 mm axial by 30 mm radial) in 18 rings, giving 35 two-dimensional image planes through an axial field of view of 15.2 cm. The rings are separated by retractable tungsten septa. Intrinsic spatial resolution, scatter fraction, sensitivity, high count rate performance and image quality are evaluated. RESULTS: Transaxial resolution (in FWHM) is 3.8 mm at the center and increases to 5.0 mm tangential and 7.3 mm radial at R = 20 cm. Average axial resolution decreases from 4.0 mm FWHM at the center to 6.6 mm at R = 20 cm. Scatter fraction is 9.4% and 10.2% for direct and cross slices, respectively. With septa out, the average scatter fraction is 34%. Total system sensitivity for true events (in kcps/(microCi/cc)) is 223 with septa in and 1200 with septa out. Dead-time losses of 50% correspond to a radioactivity concentration of 4.9 (0.81) microCi/cc and a true event count rate of 489 (480) kcps with septa in (out). Noise-equivalent count rate (NECR) for the system as a whole shows a maximum of 261 (159) kcps at a radioactivity concentration of 4.1 (0.65) microCi/cc with septa in (out). NECR is insensitive to changes in lower gamma-energy discrimination between 250-350 keV. CONCLUSIONS: The results show the performance of the newly designed PET scanner to be well suited for clinical and research applications.

Brain↗
PubMed1990

Respiratory infections caused by Branhamella catarrhalis. Selected epidemiologic features.

PURPOSE: This work reviewed existing literature pertaining to the epidemiologic aspects of respiratory tract infections caused by Branhamella catarrhalis, examined certain epidemiologic features of B. catarrhalis infections occurring at this facility, and identified relevant areas in need of further study. PATIENTS AND METHODS: Literature dealing with the epidemiology of B. catarrhalis infections was reviewed. Records in this Veterans Administration hospital microbiology laboratory were reviewed and all B. catarrhalis isolates and pure cultures of Hemophilus influenzae and Streptococcus pneumoniae were noted for the January 1986 to June 1989 study period. RESULTS: B. catarrhalis is now recognized as a disease-causing pathogen that is particularly noted for its association with acute otitis media in children and lower respiratory tract infections in adults with underlying cardiopulmonary disease. It was recovered from 2.7 percent of all respiratory specimens submitted over a 42-month period at this Veterans hospital. When compared with H. influenzae and S. pneumoniae, B. catarrhalis was found to be the second most commonly isolated respiratory pathogen. It was frequently found in pure culture (53 percent) or in combination with H. influenzae, gram-negative bacilli, or S. pneumoniae. The seasonal recovery of B. catarrhalis was apparent for the November to May period compared with the June to October period (p less than 0.001). CONCLUSION: B. catarrhalis has emerged as a major respiratory pathogen in pediatric and adult patient populations. There is a distinct seasonal pattern associated with its recovery and reasons for this are unclear. Prevalence studies aimed at identifying colonization rates among "low" and "high" risk groups are needed. The availability of restriction endonuclease analysis as a typing system for B. catarrhalis should favorably impact upon future epidemiologic studies. Many B. catarrhalis isolates produce beta-lactamase, and therapeutic options must reflect this.

Adult↗
PubMed1990

Pulmonary endothelial injury and altered fibrinolysis after femur fracture in rabbits.

The pathophysiology of acute lung injury after long bone fracture may be associated with endothelial damage and altered fibrinolysis. Accordingly, we studied metabolic functions of pulmonary endothelial cells: 5-hydroxytryptamine (5-HT) uptake and angiotensin-converting enzyme (ACE) activity in anesthetized rabbits before and every 4 h after long bone fracture (n = 12) or sham (n = 6). To assess changes in fibrinolysis, we studied levels of plasminogen activator inhibitor (PAI), an inhibitor of the fibrinolytic cascade. All animals in the control group and only 6 of 12 animals in the long bone fracture group survived 12 h. 5-HT uptake was depressed after 8 h in both groups. By 12 h, however, 5-HT uptake in the long bone fracture group remained depressed, but returned to baseline in the control group. Conversely, ACE activity was unchanged in both groups. PAI levels were increased in both groups at 4 h. During the next 8 h, levels in the long bone fracture group continued to increase and remained elevated, whereas levels in the control group decreased and were not greater than baseline at 12 h. Initial PAI and 5-HT uptake changes may be related to surgical preparation of the rabbit. Prolonged depression of 5-HT uptake suggests that musculoskeletal trauma is associated with pulmonary endothelial damage. Finally, impaired fibrinolysis due to increased PAI may contribute to the pathogenesis of endothelial injury after long bone fracture.

Animals↗
PubMed1990

Radial growth and function of the forearm after excision of the radial head. A study of growing macaque monkeys.

In five immature macaque monkeys, the right radial head was excised and the left forearm served as a control. Growth of each radius, ulna, and proximal and distal physis was followed for eight years. Total radial growth was slightly less on the side that was operated on than it was on the control side. After excision of the radial head, 95 per cent of radial growth came from the distal physis, compared with 71 per cent on the control side. A regenerated radial head, which had an irregular surface of fibrocartilaginous tissue, accounted for the remainder of growth on the side that had been operated on. Incongruous contact of articular surfaces resulted in degenerative changes in the capitellum. The arms that had been operated on were left with a flexion contracture that was an average of 12 degrees greater than that of the normal elbows, and they had a carrying angle that was an average of 6 degrees greater than that on the normal side. The arc of pronation and supination was decreased for the forearms that had been operated on, but motion of the wrist was unaffected. In our study, excision of the radial head in growing monkeys resulted in minimum radial shortening, slight deformity of the elbow, and moderate impairment of rotation of the forearm.

Animals↗
PubMed1989

Bilateral ureteral obstruction secondary to condylomata acuminata of the urinary bladder.

Condyloma acuminatum is a viral infection of near epidemic proportions. Both men and women are affected equally. Most lesions are on the external genitalia and the mucous membranes of the urethra or the vagina. A rare occurrence of condyloma acuminata is involvement of the urinary bladder. To date, only 11 cases have been reported. We describe two additional cases, both with bilateral ureteral obstruction. Current urologic management and review of the literature are presented.

Adult↗
PubMed1989

The effect of ultraviolet B radiation treatments on calcium excretion and vitamin D metabolites in kidney stone formers.

Several factors could explain the effect of warm, sunny weather on kidney stone formation. To determine the role of sun exposure, we used a light box to administer artificial ultraviolet B radiation during the winter months in New York City. Eleven male stone formers and 7 age- and sex-matched controls received 10 UVB light exposures over a two-week period while maintaining a 400 mg calcium diet. 25-OH vitamin D levels increased significantly (p less than 0.001) in both patients (25.9 +/- 9.8 to 51.6 +/- 14.1 ng/ml) and controls (21.3 +/- 7.1 to 49.6 +/- 3.1 ng/ml). However, 1,25 dihydroxyvitamin D levels rose in the patients (50.8 +/- 14.8 to 55.9 +/- 13.1 pg/ml) but fell (60.1 +/- 6.5 to 49.4 +/- 3.1 pg/ml) in the controls. Only 2 of the 11 patients but all of the controls demonstrated this down regulation of 1,25 dihydroxyvitamin D levels (p less than 0.002). 24,25 dihydroxyvitamin D levels tended to rise in both groups but parathyroid hormone levels were unchanged. There was a trend, which did not reach statistical significance, for parameters of calcium excretion to increase after UVB radiation. 24-hour urinary calcium excretion rose 24% from 140 to 173 mg in the patients and 31% from 113 to 148 mg in the controls. The ratio of calcium/creatinine following a one gram calcium load showed a small increase after UVB radiation from 0.17 to 0.20 in patients and 0.118 to 0.124 in the controls. However, no correlation could be discerned between changes in vitamin D metabolite concentrations and changes in urinary calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

New methods of examining gamma camera collimators.

New methods are proposed and described to examine the quality of gamma camera collimators in two special performance categories, namely, uniformity in regional efficiency and regional variations in channel tilt. These two performances are critical areas for SPECT imaging. Results obtained from experimental and commercial collimators illustrate the variability seen for these performance characteristics in currently available collimators.

Quality Control↗
PubMed1988

The effect of pleural pressure on the hypoxic pulmonary vasoconstrictor response in closed chest dogs.

The effect of intrapleural pressure on the hypoxic pulmonary vasoconstrictor (HPV) responses to atelectasis and hypoxia were measured in two groups of anesthetized closed chest dogs. The right lung was continuously ventilated with 100% O2. The left lung was initially ventilated with 100% O2 (hyperoxia) but subsequently underwent either reabsorption atelectasis (atelectasis; group I) or ventilation with a hypoxic gas mixture (hypoxia; group II). The mean intrapleural pressure in the left hemithorax was 5.4 cm H2O during hyperoxia, but with left lung atelectasis decreased significantly to -3.8 cm H2O by 15 minutes and to -4.2 cm H2O by 90 minutes. Venous admixture (% VA) increased significantly from 10.3% during hyperoxia to 33.2% at 15 minutes of left lung atelectasis and to 34.6% at 90 minutes. However, after sternotomy with the left lung still atelectatic, the %VA decreased significantly to 25.4% For the hypoxia group, %VA increased significantly from 9.2% during hyperoxia to 29.9% at 15 minutes of left lung hypoxia and 25.1% at 90 minutes. HPV diverted blood flow away from both atelectatic lung and hypoxic lung. However, due to the negative intrapleural pressure generated during left lung resorption atelectasis when the chest was closed, HPV was less effective during atelectasis than during hypoxia.

Animals↗
PubMed1987

Hypercoagulability produced by treatment with acetohydroxamic acid.

Thrombosis has been observed with unusual frequency in patients receiving acetohydroxamic acid (AHA) for treatment of struvite nephrolithiasis. Because this clinical observation suggests a low-grade state of diffuse intravascular coagulation, standard clinical coagulation assays, platelet counts, and plasma fibrinopeptide A (FPA) levels were measured in patients before and during treatment with AHA. Coagulation assays, fibrinogen, and fibrin-split products were not significantly different when pretreatment and treatment values were compared. FPA levels were significantly elevated and platelet counts were significantly reduced in the treatment period, indicating augmented thrombin activity and consumption of platelets into thrombi or platelet microaggregates. FPA levels were elevated within 24 hours of the initiation of AHA therapy whereas platelet counts did not change significantly within the first 4 days of treatment. The data are consistent with low-grade intravascular coagulation with AHA treatment and suggest that patients treated with this agent should be observed cautiously for signs of thrombosis.

Blood Coagulation↗
PubMed1986

Prostaglandin and complement interaction in clinical acute respiratory failure.

This study investigated the interaction of plasma levels of circulating prostaglandins and activated complement in clinical acute respiratory failure (ARDS). Fifty patients at risk for ARDS were followed up for up to ten days. Arterial blood gases and plasma levels of complement components C3a and C5a, thromboxane B2 (TxB), and prostaglandin 6-keto-F1 alpha (PGI) and granulocyte aggregation (GA) were measured daily. Seventeen patients (34%) developed ARDS, with mortality of 41% vs 23% for patients without ARDS. Compared with patients without ARDS, the ARDS group had significantly increased plasma C3a (1,130 +/- 750 vs 636 +/- 368 ng/mL) and granulocyte aggregation (48 +/- 10 vs 17 +/- 4 percentage of the maximum light transmission [% max T]). Plasma C5a, TxB, or PGI did not change significantly with or without ARDS. No measured variable was significantly associated with mortality. Regression analysis revealed significant correlations between GA, TxB, PGI, and arterial oxygenation. Plasma C3a and GA are increased in ARDS, suggesting systemic complement activation. A complex series of interactions between the prostaglandins, complement, and GA appears to be involved in ARDS.

Acute Disease↗
PubMed1986

Leukocyte aggregation response to quantitative plasma levels of C3a and C5a.

Granulocyte aggregation (GA) response has previously been described as a sensitive assay for complement activation in sepsis. Complement component C5a has been implicated as the plasma factor responsible for GA. The quantitative interaction of complement components C3a and C5a with GA, however, is not clearly defined. This study evaluates the relationship of GA responses to plasma levels of C5a and C3a in zymosan-activated plasma (ZAP). The C3a and C5a levels were measured by radioimmunoassay in serial dilutions of ZAP. Granulocyte aggregation responses of normal human leukocytes were determined for each ZAP dilution. The C5a levels in a 1:16 dilution of ZAP were higher than in normal plasma (22 +/- 7 vs 9 +/- 3 ng/mL), as were GA responses (24 +/- 1 vs 11 +/- 2 percentage of maximum light transmission). The C3a levels in a 1:8 dilution of ZAP are elevated above those of normal plasma (656 +/- 167 vs 411 +/- 29 ng/mL). Correlation coefficients were .9809 for C3a vs GA, .9788 for C5a vs G, and .9860 for C3a vs C5a. Complement components C3a and C5a are involved in GA in vitro. Granulocyte aggregometry can detect low levels of activated complement in ZAP but may not be specific for C5a. The relative contribution of C3a and C5a to observed GA is not clear from the data.

Cell Aggregation↗
PubMed1986

Influence of isoflurane on hypoxic pulmonary vasoconstriction in dogs.

The authors studied the influence of locally administered isoflurane anesthesia on the pulmonary vascular response to regional alveolar hypoxia (hypoxic pulmonary vasoconstriction [HPV]) over a range of cardiac outputs (COs) in seven mechanically ventilated, closed-chest dogs. The right lung was ventilated with 100% O2 throughout the study. The left lung was ventilated with either 100% O2 (normoxia) or an hypoxic gas mixture (hypoxia). Different alveolar concentrations of isoflurane (0, 1, and 2.5 MAC) were administered to the left lung in a randomized sequence. The CO was altered by opening and closing surgically produced arteriovenous fistulae, at all isoflurane concentrations, and by hemorrhage at 0 MAC isoflurane. The magnitude of the HPV response was measured by differential CO2 elimination in the absence of isoflurane and by venous admixtures in all phases. During normoxia, the left lung effective flow (QL%) measured from differential CO2 excretion was 39.9 +/- 1.2% of the total blood flow and decreased to 18.8 +/- 2.6% when ventilated with the hypoxic gas mixture. Venous admixture (QVA/QT%) was significantly correlated with QL% during hypoxic ventilation in the absence of isoflurane. QVA/QT% was 22.3 +/- 2.7% during hypoxia with normal CO, and it increased significantly to 27.7 +/- 1.1% when the CO was increased 43%. It was not significantly altered (23.6 +/- 3.6%) when the CO was decreased by 54%. Isoflurane 2.5 MAC significantly increased QVA/QT% during hypoxic ventilation of the left lung to 33.9 +/- 2.6% with low CO and 35.4 +/- 1.7% with normal CO. Isoflurane 1 MAC increased QVA/QT% to 27.2 +/- 2.7% with normal CO and 28.1 +/- 2.6% with high CO.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

CT of fibrous tissues and tumors with sonographic correlation.

Fibrous tissues and tumors may appear hyperdense relative to muscles and solid viscera on CT both before and after IV contrast injection. In addition, fibrous tissues generally have a homogeneously hypoechoic sonographic appearance. The diagnostic value of these criteria is illustrated in a group of 21 fibrous tissue abnormalities that includes retroperitoneal, mediastinal, and perigraft fibrosis, sclerosing pseudotumor of the orbit, generalized fibromatosis, desmoids, malignant fibrous histiocytoma, and normal tendons and ligaments. It is concluded that while hyperdensity on CT and echopenia on sonography are not pathognomonic of fibrous tissue, they occur with sufficient frequency that their presence raises the possibility of a fibrous lesion.

Connective Tissue↗
PubMed1986

Interaction of prostaglandins, activated complement, and granulocytes in clinical sepsis and hypotension.

Activated complement, thromboxane A2, prostacyclin, and activated granulocytes have been implicated in hemodynamic dysfunction after trauma, in sepsis, and in hypovolemic and septic shock. This study evaluated the interaction of plasma concentrations of complement components C3a and C5a, thromboxane B2 (TxB), prostaglandin 6-keto-F1 alpha (PGI), and granulocyte aggregation in clinical sepsis and hypotension. Forty-eight critically ill patients were followed clinically for as long as 10 days. Plasma C3a, C5a, TxB, and PGI were measured daily by the radioimmunoassay method. Granulocyte aggregation, the percentage of maximum aggregation of zymosan-activated plasma standard curves, was performed with patient plasma and normal human leukocytes. Patients were studied in four groups: group I, nonseptic, normotensive; group II, hypovolemic shock, group III, normotensive severe sepsis; and group IV, septic shock. Plasma from 12 normal adults was the control value. PGI, TxB, C3a, C5a, and granulocyte aggregation in patients were greater than that in the control subjects. Granulocyte aggregation was increased in groups III and IV versus groups I and II. C3a was increased in group IV versus groups II and III. C5a and TxB did not vary between groups. PGI was greatly increased in group IV compared with groups I through III. C3a and C5a decreased in nonsurvivors. PaO2/FiO2 ratios correlated directly with PGI and inversely with C3a and TxB/PGI. Plasma PGI and C3a are increased in septic shock. C3a and TxB/PGI imbalances are involved in hypovolemic and septic shock.

Adolescent↗