Biomedical subjects

J W Davis

Publications and source records attributed to J W Davis.

At least 109 records · Page 6Linked to original sources

PubMed1995

Iliofemoral venous injuries: an indication for prophylactic caval filter placement.

Prophylactic placement of vena caval filters is recommended in trauma patients at high risk for pulmonary embolism (PE). We present a group of patients with iliofemoral venous trauma, and subsequent complications of deep venous thrombosis (DVT) and PE. Of twelve patients with iliac or common femoral venous injuries, seven underwent primary repair. All received DVT/ PE prophylaxis with mini-dose heparin and/or sequential compression hose. In spite of this, two patients suffered DVT, one patient had DVT and PE and one patient had clinical evidence of PE but did not undergo confirmatory testing. Three patients underwent prophylactic caval filter placement without complication. The DVT/PE complication rate in this small group was at least 43% (3 of 7). Patients with repaired iliofemoral venous injuries represent a high risk subset for DVT/PE and prophylactic caval filter placement is recommended.

Adolescent↗

PubMed1995

Neurogenic pulmonary edema in fatal and nonfatal head injuries.

Impaired pulmonary function is a frequent but poorly understood complication of acute head injury (HI). A potential early contributor to the pulmonary dysfunction seen in HI patients is neurogenic pulmonary edema (NPE). We hypothesized that NPE would occur early after HI and that it would have a continuum of clinical severity depending on the severity of the HI and associated intracranial hypertension. A large autopsy data base and inpatient HI data base were used to search for cases of NPE. Patients in the autopsy data base were stratified according to injury type and whether they died at the scene or within 96 hours of injury. There were significant (p < 0.0001, analysis of variance) elevations in lung weights in patients dying at the scene and within 96 hours from HI, compared with those dying from other noncentral nervous system injuries. No other organs studied showed significant weight increases. The incidence of NPE in isolated HI patients dying at the scene was 32%. In patients with isolated HI dying within 96 hours, the incidence of NPE was 50%. We found an inverse correlation (r = 0.62; p < 0.0014) between the initial cerebral perfusion pressure and the PaO2/FIO2 ratio despite a normal-appearing chest x-ray film. We conclude that NPE occurs frequently in HI patients. The process of edema formation begins early in the clinical course and is isolated to the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Mechanical determinants of myocardial oxygen consumption in conscious dogs.

A new practical descriptor of metabolic to mechanical myocardial energy transfer (MET), termed the virtual work model, was evaluated in 32 conscious dogs and in 8 isolated canine hearts. An index of total mechanical energy expenditure (TME) was calculated as the sum of external energy (stroke work) and an internal energy index of heat (left ventricular end-diastolic volume times left ventricular mean ejection pressure). Physiological comparison of TME (x-axis) and myocardial oxygen consumption (MVO2; y-axis) yielded highly linear MET relationships (mean r = 0.93 +/- 0.07), with an average slope of 0.86 +/- 0.39 (SD) and a y-intercept of 9.1 +/- 6.4 mW/ml myocardium. The linear MVO2-TME relationship did not vary under steady-state vs. dynamic vena caval occlusion, increased heart rate, increased afterload, or increased inotropic state with calcium infusion. Compared with five other indexes of myocardial energetics, the virtual work model of MET was the most linear, the most practical in not requiring determination of the end-systolic pressure-volume relationship, and the most accurate predictor of MVO2 under normal and altered hemodynamic conditions.

Animals↗

PubMed1995

Trampoline-related injuries.

Two hundred and seventeen patients who had sustained an injury during the recreational use of a trampoline were managed in the emergency room of Logan Regional Hospital in Logan, Utah, from January 1991 through December 1992. We retrospectively reviewed the charts and radiographs of these patients to categorize the injuries. Additional details regarding the injuries of seventy-two patients (33 per cent) were obtained by means of a telephone interview with use of a questionnaire. The injuries occurred from February through November, with the peak incidence in July. The patients were eighteen months to forty-five years old (average, ten years old); ninety-four patients (43 per cent) were five to nine years old. Eighty-four patients (39 per cent) sustained a fracture; fifty-four (25 per cent), a sprain or strain; forty-five (21 per cent), a laceration; and thirty-four (16 per cent), a contusion. Fifty-seven injuries (26 per cent) involved the elbow or forearm; forty-six (21 per cent), the head or neck; forty (18 per cent), the ankle or foot; thirty-three (15 per cent), the knee or leg; nineteen (9 per cent), the trunk or back; thirteen (6 per cent), the shoulder or arm; and nine (4 per cent), the wrist or hand. Thirteen patients (6 per cent) had a back injury, but none of them had a permanent neurological deficit. One patient who had an ocular injury was transferred to a tertiary care center. One hundred and fifty-six patients (72 per cent) were evaluated radiographically, fifteen (7 per cent) were admitted to the hospital, and thirteen (6 per cent) had an operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidental Falls↗

PubMed1994

Induction of hepatic acyl-CoA-binding protein and liver fatty acid-binding protein by perfluorodecanoic acid in rats. Lack of correlation with hepatic long-chain acyl-CoA levels.

Liver fatty acid-binding protein (L-FABP) and acyl-CoA-binding protein (ACBP) are involved in the intracellular trafficking and compartmentalization of fatty acids and fatty acyl-CoA esters, respectively, in the liver. Both proteins are induced in rat liver by the potent peroxisome proliferator perfluorodecanoic acid (PFDA). While it is believed that the peroxisome proliferator-activated receptor may mediate the responses to peroxisome proliferators by inducing responsive genes, the ligand(s) of this receptor remains unknown. We hypothesized that induction of L-FABP and ACBP in rat liver by PFDA is secondary to accumulation of long-chain acyl-CoA esters. However, neither dose-response nor time-course effects of PFDA on hepatic long-chain acyl-CoA, L-FABP, or ACBP concentrations confirmed this hypothesis. In a dose-response study, PFDA increased hepatic long-chain acyl-CoA concentrations (7 days after treatment) over the dose range of 20-50 mg/kg, whereas it increased ACBP and L-FABP over the wider dose range of 20-65 mg/kg. In the time-course study, PFDA treatment (50 mg/kg) elevated long-chain acyl-CoA esters in the liver beginning on day 3 post-treatment, yet hepatic L-FABP concentrations were increased earlier beginning on day 2 and ACBP was not induced until day 7. To determine if this dissociation of increases in hepatic long-chain acyl-CoA concentrations from increases in hepatic L-FABP and ACBP concentrations could be demonstrated under other conditions, control rats fasted for 24-48 hr were used. Fasting increased hepatic long-chain acyl-CoA levels to a greater extent than PFDA treatment, yet neither L-FABP nor ACBP was induced. We conclude that elevated concentrations of hepatic long-chain acyl-CoAs in PFDA-treated rats are not a major contributor to the induction of L-FABP or ACBP by peroxisome proliferators. A more plausible mechanism is that PFDA induces L-FABP and ACBP by activating the peroxisome proliferator receptor directly rather than indirectly through long-chain acyl-CoA esters.

Acyl Coenzyme A↗

PubMed1994

Evidence for both generalized and regional low bone mass among elderly women.

The consistency of bone mass measurements across bone sites was examined in a cohort of elderly Japanese-American women. The study included 744 women of mean age 66.6 years (age range 47-82 years) who had bone densitometry measurements at the spine, calcaneus, and distal and proximal radius. The women were classified at the four bone sites as in the lower, middle, or upper bone mass tertile for their age. Slightly more than half (56%) of the women were in the lower tertile at one or more of the bone sites, and such women were usually in the lower category at more than one site. Of the women, 24% were classified in the lower tertile at all four sites. Furthermore, as a group, women classified as in the low bone mass category at any one site had a low average bone mass at all four sites. Prospectively, the number of low bone mass sites predicted the risk of new spine fractures after adjusting for age and the number of spine and nonspine prevalent fractures. The risk increased approximately 1.3-fold for each additional low bone mass site. A subgroup (15%) of the population had marked heterogeneity in bone mass between sites. These women had one or more lower tertile bone mass site(s) and one or more upper tertile bone mass site(s). The results suggest that osteoporosis may occur as either a generalized or as a regional disorder.

Absorptiometry, Photon↗

PubMed1994

Inhibition of S-(1,2-dichlorovinyl)-L-cysteine-induced lipid peroxidation by antioxidants in rabbit renal cortical slices: dissociation of lipid peroxidation and toxicity.

Precision-cut, rabbit renal slices were used to examine the effects of three novel antioxidants (U-74006, U-74500, and U-78517) on S-(1,2-dichlorovinyl)-L-cysteine (DCVC)-induced lipid peroxidation and toxicity. Slices exposed to DCVC showed a dose- and time-dependent increase in lipid peroxidation (TBARS) and a decrease in cellular viability, as evidenced by the loss of intracellular potassium, during the course of a 3 hour incubation. Subsequent studies employed DCVC concentrations of 100 microM. Microemulsion formulations of U-78517, U-74500, and U-74006 (100 microM) inhibited DCVC-induced lipid peroxidation by 100 +/-, 50 +/-, and < 5% (not significant), respectively. However, none of these antioxidants had a significant effect on DCVC-dependent cytotoxicity, as indicated by intracellular potassium release. The effects of U-78517, the most potent of the three antioxidants, were similar to those observed with two model antioxidants, diphenyl-p-phenylenediamine (DPPD) and the iron chelator, deferoxamine. Aminooxyacetic (AOAA), an inhibitor of renal cysteine conjugate beta-lyase, had only a minimal effect on DCVC-induced lipid peroxidation, and no effect on toxicity. These data represent the first report of DCVC-induced lipid peroxidation in rabbit renal cortical slices, a system which has been widely used to investigate mechanisms of nephrotoxicity, including that induced by DCVC. Our results demonstrate that DCVC-induced lipid peroxidation in renal slices can be inhibited by a variety of antioxidant compounds operating by different mechanisms. Because inhibition of lipid peroxidation had minimal effect on DCVC-dependent cytotoxicity, the data suggest that DCVC-induced lipid peroxidation is not a major mechanism in the cytotoxicity induced by this compound.

Aminooxyacetic Acid↗

PubMed1994

An abundantly expressed hemolymph glycoprotein isolated from newly parasitized Manduca sexta larvae is a polydnavirus gene product.

Cotesia congregata polydnavirus (CcPDV) is essential for successful parasitism of Manduca sexta larvae by the braconid wasp C. congregata. CcPDV virions are present in large numbers in the oviducts of C. congregata and injected with eggs into the hemocoel of M. sexta larvae during parasitization. Injection of sucrose density purified virions into nonparasitized larvae causes several of the parasitism-induced alterations in the physiology of host larvae that occur as a result of natural parasitism, including the synthesis of novel hemolymph proteins and abrogation of the host's immune response against the developing parasites. One of these proteins, early-expressed protein 1 (EP1), is a 190-kDa molecule which constitutes up to 5% of the total hemolymph protein by 24 hr following oviposition by the wasp. Using N-terminal sequence data for EP1 to construct primers for use in the polymerase chain reaction, we amplified and cloned a cDNA corresponding to the gene encoding EP1. This cDNA hybridized to DNA of the CcPDV genome, but not to DNA isolated from M. sexta larvae, suggesting that EP1 is a CcPDV gene product. A cDNA clone was isolated from an expression library generated from RNA extracted from newly parasitized M. sexta larvae. Sequence analysis of the cDNA clone revealed the presence of an open reading frame of 819 bp encoding a protein of 30.7 kDa. In vitro transcription/translation of the cDNA clone produced a protein of approximately 31 kDa, which was immunoprecipitated by EP1-specific polyclonal antiserum generated against purified deglycosylated EP1. EP1-like sequences also were amplified from male wasp genomic DNA, suggestive of integration of EP1-like sequences in the genome. This report constitutes the first evidence that a specific protein isolated from a parasitized host insect is a wasp polydnavirus gene product.

Amino Acid Sequence↗

PubMed1994

When should bone density measurements be repeated?

We calculated how long to wait before repeating bone mineral density (BMD) measurements to reassess fracture risk. Correlation results from serial measurements of 495 postmenopausal Japanese-American women were used to estimate 95% confidence intervals (CI) for future BMD. After 7 years of follow-up, BMD correlations with the initial measurement ranged between 0.81 and 0.94, depending on age group and measurement site. In this analysis, the period between measurements was defined as the time required for the lower 95% CI to fall below the BMD value corresponding to doubling of fracture risk. Progressive bone loss causes fracture risk to double after 10 years, on average. However, the 95% CIs indicate that a second BMD measurement will detect risk doubling after only 2 or 3 years for some women. For untreated, early postmenopausal women, the period between measurements was approximately 2-5 years for the radius and 4-6 years for the calcaneus, depending on the initial BMD level. The period was approximately 1 year longer for women age 60 and older. Treatments that halve the bone loss rate would increase the period by 1-3 years. In the absence of a second measurement of BMD, the CI will continue to expand with time, corresponding to a wider range in risk between individuals, and a greater proportion of women will be at increased fracture risk. Obtaining a second BMD measurement pinpoints the patient's status within the precision of the measurement. We conclude that repeated BMD measurements will provide a more accurate estimate of fracture risk than a single, baseline measurement.

Age Factors↗

PubMed1994

The peak bone mass of Hawaiian, Filipino, Japanese, and white women living in Hawaii.

Our study compares the bone mass of Hawaiian, Filipino, Japanese, and white women living in Oahu, Hawaii. Eligible women ranged in age from 25 to 34; all had bone mass measurements at the spine, calcaneus, and proximal and distal radius. Their average bone mineral density (BMD) remained stable with age at all four bone sites, indicating that the age range 25-34 may represent the peak bone mass. Bone mass varied, however, between ethnicities; differences in BMD up to 11% were observed. The Hawaiian women had the greatest BMD, and whites had the second greatest BMD at the spine and calcaneus. The Japanese most frequently had the lowest BMD. Differences in body size partly explained the differences; most ethnic differences were reduced or eliminated after adjusting for height and weight. At the spine, the ethnic differences for BMD were also apparent with BMC and with vertebral area. Hawaiian and white women had greater values than Japanese or Filipino women. Differences at the proximal radius resembled the spine, except that whites had the widest proximal widths. The results were more complex for the distal radius. At the distal radius whites had the lowest BMD of the four ethic groups. The difference between whites and Hawaiians derived from the greater bone mineral content (BMC) of the Hawaiian women. By contrast, the difference between whites and the Japanese and Filipinos derived from the wider distal widths of the white women. Compared with the Japanese and Filipino women, the white women appeared to disperse their BMC at the distal radius across a wider bone width.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Spine fracture risk is predicted by non-spine fractures.

A prospective cohort study of 1098 postmenopausal Japanese-American women evaluated the relationship between baseline non-spine fractures and new (incident) spine fractures. At the baseline examination in 1981, prevalent non-spine fractures were ascertained by interview, and prevalent spine fractures by radiograph. Bone mass measurements of the distal radius, proximal radius, calcaneus (1981), the lumbar spine (1984) were obtained and repeated at 1- to 2-year intervals. Women with existing non-spine fractures have a threefold greater risk of subsequent spine fractures, independent of bone mass, and independent of the known association between prevalent spine fractures and subsequent spine fractures. Women with both a prevalent non-spine fracture and low bone mass (50th percentile or lower) have an eightfold greater risk of new spine fractures compared with women above the 50th percentile of bone mass and no prevalent fractures. In addition to low bone mass, both prevalent spine fractures and prevalent non-spine fractures are strong risk factors for subsequent spine fracture. These data suggest that not all osteoporotic risk factors are expressed via bone mass, and that other, unmeasured risk factors, such as bone quality defects, may explain these results. In clinical terms, women with both prevalent fractures and low bone mass should be recognized as being at extremely high risk, and treatment potency should be commensurate with this level of risk.

Adult↗

PubMed1994

Pain and disability associated with new vertebral fractures and other spinal conditions.

Although vertebral fractures are common among older women, little is known about associations with pain and disability. In this prospective study, fractures which occurred after the initial radiograph were strong predictors of back pain and disability at the end of followup, with odds ratios (OR) of approximately 4-5. Other, independently significant predictors were self-reported history of (1) disk disease (OR = 3-9), (2) traumatic back injury (OR = 4-7), and (3) spinal arthritis (OR = 3-6). In longitudinal analyses, new fractures were associated (OR = 6.4; 95% CI = 2.6, 15.6) with increases in back pain frequency (relative to pre-fracture levels). The association with prevalent fractures was weaker, and not significant (OR = 1.7; 95% CI = 0.5, 5.6). The pain frequency index increased approximately 3-fold, relative to pre-fracture levels. At the end of followup (mean = 3.5 years), the index was still two times greater than baseline. We conclude that associations with back pain and disability are greater in magnitude for new vertebral fractures than for prevalent fractures.

Adult↗

PubMed1994

Normal ranges for bone loss rates.

We reported previously that the variability in bone loss rates among postmenopausal women decreases dramatically during the first few years of followup. In this paper, we have examined the distributions of bone loss rates measured at the calcaneus, distal radius and proximal radius. The incidence of physical impairment was five times greater among women with bone loss rates faster than 2 S.D. below the mean. Because the rate of change in bone density was skewed at the lower end of the distribution (representing rapid bone loss), the influence of values at the extreme ends of the distribution were statistically removed in order to estimate the normal distribution of bone loss rates. For the convenience of clinicians, the upper and lower limits of the 90 and 70% normal ranges are presented. Because average bone loss rates vary with age, normal ranges are provided separately by age group. The width of each normal range decreased by at least half after 3 or 4 years of followup, compared to less than 1 year. Consequently, measured loss rates which were well within the normal range at 1 year were sometimes far outside the normal range for longer followup times. We conclude that followup duration has a profound effect on estimates of the normal range, and must be considered when interpreting the clinical significance of measured loss rates.

Adult↗

PubMed1994

The relationship of base deficit to lactate in porcine hemorrhagic shock and resuscitation.

This study was undertaken to determine the relationship of arterial and venous base deficit (BD) to lactate levels and SvO2 in shock and resuscitation with the hypothesis that BD is an equally good indicator of the physiologic changes while being more readily accessible. Fifteen mature swine were bled serially of 25% and 40% of their calculated blood volumes, then resuscitated with lactated Ringer's and blood. Serial hemodynamic and metabolic measurements were made. The BD correlated significantly with lactate levels at all increments of shock and resuscitation. Linear regression analysis demonstrated strong associations (p < 0.001) for arterial and venous BD (R = 0.808), for BD and lactate (R = -0.794), and BD and SvO2 (R = 0.538). The BD accurately reflected the hemodynamic and tissue perfusion changes associated with hemorrhagic shock and resuscitation. Base deficit is more readily available than lactate, and is therefore more useful as an index of shock and resuscitation. Venous BD correlates well with arterial BD and can be used when an arterial sample cannot be obtained. The SvO2 correlated well with acute volume changes but the addition of supplemental oxygen made it a less reliable indicator of hemorrhage and resuscitation.

Acidosis↗

PubMed1994

Geriatric home assessment after hospital discharge.

OBJECTIVES: To evaluate the feasibility of an intervention involving post-discharge geriatric home assessment and follow-up and to describe the spectrum of significant clinical problems identified during the home assessment. DESIGN: Prospective observational study nested within a randomized controlled trial. SETTING: Inpatient service of a large academic medical center in Southern California. PATIENTS: There were 152 adults aged 65 or greater who had one or more specific risk factors for functional decline or increased mortality, who were awaiting discharge from the hospital, and who were assigned to the intervention arm of a randomized controlled trial of post-discharge comprehensive geriatric home assessment. MAIN RESULTS: During the home assessment, the gerontologic nurse practitioner (GNP) identified new or worsening problems in 150 patients (99%); 61 problems (eg, serum sodium 125 mg/dL; severe orthostatic hypotension) were considered by a reviewing physician to require urgent medical attention. Older age, non-white race, and new incontinence were associated independently with a greater number of findings (P < 0.05). Based on the findings, an interdisciplinary team made an average of 3.4 recommendations per patient; only two of 111 requests for written approval of recommendations were rejected. CONCLUSIONS: Post-discharge visitation by a GNP to patients at high risk is capable of detecting a high yield of important and potentially reversible clinical problems. This multidisciplinary approach is acceptable to physicians. Research is needed to identify additional links between short hospital stays, impairment or instability at discharge, and adverse outcomes.

Academic Medical Centers↗

PubMed1994

Measurement of left ventricular volume in normal and volume-overloaded canine hearts.

Serial studies of adaptation to aortic regurgitation (AR) were undertaken to determine whether sonomicrometry and echocardiography could be combined to measure changes in left ventricular (LV) cavitary volume (Vlv) and wall mass using the geometric formula [Vlv = K pi b2 alpha--wall volume], where K is a constant depending on the geometric model and a and be are epicardial major- and minor-axis diameters, respectively. Postmortem studies were performed in six normal dogs and in nine with AR; ultrasonic ventricular dimensions were measured as Vlv was varied with an intracavitary balloon. Three models were tested: 1) ellipsoid (model I; K = 1/6), 2) cylinder-ellipsoid (model II; K = 5/24), and 3) cylinder (model III; K = 1/4). The slope of the relationship between calculated Vlv and balloon volume varied between models (I, 0.71 +/- 0.11; II, 0.89 +/- 0.14; III, 1.07 +/- 0.17), and empiric determination of K to produce a slope of 1.0 resulted in a value of 0.26 +/- 0.04, not significantly different from the cylindrical model. Serial measurements of LV dimensions in 10 chronically instrumented conscious dogs revealed no significant change in end-diastolic or end-ejection LV shape after up to 16 wk of AR. Sonomicrometry and echocardiography can be integrated using a cylindrical geometric model to accurately estimate changes in end-diastolic or end-ejection Vlv during chronic volume overload.

Animals↗

PubMed1994

Prevention of exercise-induced endothelemia by isradipine in men with angina pectoris.

The primary purpose of this study was to determine whether treatment with isradipine would prevent an exercise-induced increase in the concentration of anuclear carcasses of endothelial cells in the blood of men with angina pectoris. Endothelial cells were prepared for microscopic counting by a method involving differential centrifugation of venous blood. The endothelial cell count of 20 men increased from 0.78 +/- (SD) 0.41 per counting chamber approximately 2 h before exercise to 1.28 +/- 0.54 three minutes after moderate angina was induced by treadmill exercise (p = 0.003). After treatment with isradipine, the endothelial cell count decreased with or without treadmill exercise. These results suggest that exercise caused an increase in the endothelial cell count of men with coronary artery disease and that isradipine caused an acute decrease and prevented the exercise-induced increase in the endothelial cell count.

Adult↗

PubMed1994

Randomized study of algorithms for discontinuing tube thoracostomy drainage.

BACKGROUND: The optimal method for removal of chest tubes has not been determined and opinion remains divided. The purpose of this study was to determine the difference between two algorithms for the removal of chest tubes: one with continuous negative intrathoracic pressure (suction group) and the other with a trial of water seal (water-seal group). STUDY DESIGN: This study was a prospective randomized trial of 80 trauma patients requiring tube thoracostomies. RESULTS: Both methods of chest tube removal had similar incidences of recurrent pneumothorax (2.5 percent). The suction group had a shorter total chest tube time (72.2 hours versus 92.5 hours, p = 0.013) and shorter time required to remove the chest tube following air leak resolution (25.2 hours versus 35.6 hours, p = 0.034). Additionally, there were more patients requiring prolonged (greater than 36 hours) removal times in the water-seal group (p = 0.009). CONCLUSIONS: Both suction and water-seal methods for chest tube removal are effective and have similar incidences of recurrent pneumothorax. The use of the suction algorithm significantly decreased both chest tube duration and the time taken for chest tube removal. In patients hospitalized for isolated pneumo- or hemothorax, the use of the suction algorithm potentially could lead to shorter length of stay.

Algorithms↗