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Biomedical subjects

R F Davis

Publications and source records attributed to R F Davis.

82 records · Page 5Linked to original sources
PubMed1969

Effects of external cations and respiratory inhibitors on electrical potential of the xylem exudate of excised corn roots.

Glass capillary microelectrodes were used to study the electrical potential difference (PD) between the xylem exudate of excised corn roots, Zea mays L. Golden Bantam hybrid, and the external solution. A survey of the effects of various ions on the PD was made. With 1 mm single salt solutions, the PD was between 25 and 50 mv, exudate negative. The PD responded to concentration differences in single salt solutions of K(+), Na(+), and Ca(2+) in a manner suggestive of cation selectivity and cation diffusion potentials. With Ca(2+) present, the PD was insensitive to concentration changes of other cations. Substitution of NO(3) (-) for Cl(-) in K(+) solutions increased the PD by 2 to 5 mv, although in general the PD showed little response to anion concentration changes. The PD was partially abolished by cyanide. The remaining fraction of the PD was sensitive to concentration changes in external K(+), and we postulate that the PD is the result of both a diffusion potential and an electrogenic pump.

Journal Article↗
PubMedDate not supplied

Acute effect of tobacco cigarette smoking on the platelet aggregate ratio.

The purpose of this study was to determine whether cigarette smoking acutely increased circulating platelet aggregates as detected by lowering of the platelet aggregate ratio. Eighteen (11 male and 7 female) volunteers ranging from 16 to 47 years of age rested during a 20-minute control period and smoked two unfiltered tobacco cigarettes during another 20-minute period. Platelet aggregate ratios (mean +/- SD) before and after the control period were 0.86 +/- 13 and 0.82 +/- 0.12 respectively (p greater than 0.05) and before and after smoking were 0.84 +/- 0.14 and 0.66 +/- 0.18 respectively (p less than 0.01). The mean plasma nonesterified fatty acid concentration was not significantly different before and after smoking suggesting that the decrease in platelet aggregate ratio was not mediated through elevation of the plasma nonesterified fatty acid concentration. Our results are consistent with the theory that platelet aggregates contribute to the increased incidence of myocardial infarction and sudden death from coronary artery disease observed among cigarette smokers.

Adolescent↗
PubMedDate not supplied

Racial differences in newborn intensive care morbidity in Alaska.

Birthweight-specific neonatal mortality for Alaska Natives is higher than for non-natives for the years 1987-1996. We investigated the reasons for this based on Level III Neonatal Intensive Care Unit information available from 1991-1996. We also investigated whether differences in mortality extended to measures of morbidity. There were less Native patients born at the tertiary care center for babies with birthweight < 1500 grams and 1500-2499 grams (64% for Natives and 87% for non-natives, p = .000). Differences in antenatal referral were only apparent for the population residing within the Anchorage/Mat-Su area. There were also less cesarean deliveries for Native infants that were born outside of the tertiary care center for both birthweight categories (25% for Native vs. 53% for non-native infants < 1500 grams, p = .01; 27% for Native vs. 48% for non-native infants 1500-2499 grams, p = .01). For Alaska Native babies < 1500 grams there was more necrotizing enterocolitis (13% in Native vs. 4.9% in non-native, p = .01), more severe retinopathy of prematurity (12% in Native vs. 4.6% in non-native, p = .01), and more bronchopulmonary dysplasia (49% in Native vs. 34% in non-native, p = .04). For Alaska Native babies 1500-2499 grams that needed ventilatory assistance there was more intraventricular hemorrhage (19% in Native vs. 7.4% in non-native, p = .003), more severe (grade 3-4) intraventricular hemorrhage (9.5% in Native vs. 0.9% in nonnative, p = .001), and more acquired sepsis (7.1% in Native vs. 1.7% in non-native, p = .02). Differences in access to Level III perinatal care and intrapartum care (cesarean delivery rates) are likely factors that contribute to the worse outcomes in the Alaska Native population.

Alaska↗
PubMedDate not supplied

Racial differences in birthweight-specific neonatal mortality in Alaska: 1987-1996.

OBJECTIVES: This study compared the neonatal mortality in the Alaska Native and non-native (primarily white) population in Alaska for a 10-year period (1987-1996). METHODS: Natality, mortality, and cause of death data were obtained from the State of Alaska's Bureau of Vital Statistics (BVS). Birthweight-specific and preventable birthweight-specific mortality were analyzed for babies < 1500 grams, 1500-2499 grams, and > or = 2500 grams birthweight. RESULTS: The low birthweight (LBW) and very low birthweight (VLBW) rates were similar for the Alaska Native and non-native populations. The neonatal mortality rate for the Alaska Native population was higher than for the non-native population (6.4 per 1,000 live births for Alaska Native vs. 4.1 for non-native for 1987-1991; 5.5 for Alaska Native vs. 3.5 for non-native for 1992-1996). Birthweight-specific mortality was higher in the Alaska Native population for all birthweight groups. The exclusion of non-preventable conditions accentuated the differences in mortality rates between the Alaska Native and non-native population for infants < 2500 grams birthweight. CONCLUSION: The higher neonatal mortality in the Alaska Native population is associated with a higher overall and preventable birthweight-specific neonatal mortality. The differences are therefore likely to reflect differences in access to and quality of perinatal care.

Alaska↗
PubMedDate not supplied

Nonconstrained total elbow arthroplasty.

Thirty capitellocondylar unhinged implant arthroplasties were performed on 27 patients during the period from October 1976 through June 1981. The average patient age was 59.4 years, with a preoperative diagnosis of rheumatoid arthritis in 28 elbows and osteoarthritis in two elbows. Follow-up periods averaged 39.9 months (range, 10-62 months). The indication for elbow arthroplasty were intractable pain, joint instability, failed synovectomy, or bilateral limitation of motion. Ranged of motion evaluations showed moderate increases in flexion, pronation and supination after operation, although there was no significant improvement in extension. Ewald functional evaluation scores improved significantly from the mean of eight points prior to operation to the postoperative mean of 85 points. The significant complications occurring were deep wound infections, necessitating removal of the prosthesis (6.6%), and subluxation (13.2%), which responded to conservative treatment by long-arm casting. One patient required reconstruction of the medial collateral ligament for subluxation. Ulnar nerve paresthesia developed in 10% of the patients. One patient required neurolysis and transposition of the nerve for relief of symptoms. The posterolateral approach was adopted to reduce the incidence of ulnar nerve complications.

Adult↗
PubMedDate not supplied

The next challenge for newborn intensive care in Alaska: improving the survival of the larger neonate.

Using information from our database, a review of mortality for the Newborn Intensive Care Unit at Providence Alaska Medical Center was conducted for 1987-1996. There has been a significant decline in mortality over the last decade (p = 0.003). An analysis of mortality by birthweight and gestational age groups demonstrated a decline in mortality (p = 0.005) for infants with birthweight < 2 kg and infants < or = 34 weeks gestation, but no change for infants > or = 2 kg and > or = 35 weeks gestation. As a result, larger and more mature babies now account for an increasing proportion of NICU deaths. For 1995 and 1996 the major contributors to mortality for the smaller neonates were respiratory distress syndrome and congenital and nosocomial sepsis/pneumonia. The major contributors to mortality for larger neonates were persistent pulmonary hypertension of the newborn, congenital heart disease, congenital diaphragmatic hernia, and primary birth asphyxia. A majority of deaths in the larger neonates were due to non-lethal causes. We contend that improved survival in the larger neonate is an important and achievable goal. The introduction of ECMO (Extracorporeal Membrane Oxygenation) for the NICU and a focused review of the neonatal cardiac program offers the best possible potential for achieving this goal.

Alaska↗