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Biomedical subjects

R L Dennis

Publications and source records attributed to R L Dennis.

16 recordsLinked to original sources
PubMed2001

Developing seasonal ammonia emission estimates with an inverse modeling technique.

Significant uncertainty exists in magnitude and variability of ammonia (NH3) emissions, which are needed for air quality modeling of aerosols and deposition of nitrogen compounds. Approximately 85% of NH3 emissions are estimated to come from agricultural nonpoint sources. We suspect a strong seasonal pattern in NH 3 emissions; however, current NH3 emission inventories lack intra-annual variability. Annually averaged NH 3 emissions could significantly affect model-predicted concentrations and wet and dry deposition of nitrogen-containing compounds. We apply a Kalman filter inverse modeling technique to deduce monthly NH3 emissions for the eastern U.S. Final products of this research will include monthly emissions estimates from each season. Results for January and June 1990 are currently available and are presented here. The U.S. Environmental Protection Agency (USEPA) Community Multiscale Air Quality (CMAQ) model and ammonium (NH4+) wet concentration data from the National Atmospheric Deposition Program (NADP) network are used. The inverse modeling technique estimates the emission adjustments that provide optimal modeled results with respect to wet NH4+ concentrations, observational data error, and emission uncertainty. Our results suggest that annual average NH 3 emissions estimates should be decreased by 64% for January 1990 and increased by 25% for June 1990. These results illustrate the strong differences that are anticipated for NH3 emissions.

Agriculture↗
PubMed1995

Dialysis adequacy indices in high membrane transporters treated with short-dwell peritoneal dialysis.

Treatment of high-membrane transporters with continuous ambulatory peritoneal dialysis (CAPD) is associated with ineffective ultrafiltration, increased dialysate protein loss, lower serum albumin levels, and lower protein catabolic rates, suggesting development of inadequate dialysis. The use of short-dwell nightly intermittent peritoneal dialysis (NIPD) and daytime ambulatory peritoneal dialysis (DAPD) has not been evaluated. Patients with inadequate ultrafiltration secondary to rapid membrane transport [peritoneal equilibration test (PET) confirmation] were managed with NIPD and DAPD (group A, n = 32) and compared to patients on CAPD and continuous cycling peritoneal dialysis (CCPD) (group B, n = 53) after at least 3 months of therapy. Groups A and B were similar in age, gender, diabetic status, prestudy months on peritoneal dialysis (PD), and residual renal function. No significant differences were observed between the groups with respect to serum albumin, daily protein loss, normalized protein catabolic rate (PCRN), or weekly KT/V urea indices. Diabetics demonstrated lower levels of serum albumin and PCRN than nondiabetics while maintaining equivalent KT/V urea indices. Reassessment of patients 6 months later also revealed no differences in outcome measures between group A (n = 20) and group B (n = 36). High transporters treated with NIPD and DAPD appear to have similar dialysate protein loss, adequacy, and nutrition indices when compared to patients on CAPD and CCPD. Future studies will determine if delivery of higher target small-solute clearances benefits patients on NIPD/DAPD as contrasted with continuous PD modalities (CAPD/CCPD), or diabetics compared to nondiabetics.

Biological Transport↗
PubMed1993

Short-dwell peritoneal dialysis: increased use and impact on clinical outcome.

We reviewed 216 patients on peritoneal dialysis over a 3-year period to assess the effects on patient outcome of short-dwell dialysis (SDD), defined as dwell time below 4 hours with a daily dry (empty peritoneum) interval. Forty-nine patients (23%) required SDD for improved management of ultrafiltration failure (82%), effective blood pressure control (8%), abdominal wall hernia (4%), hydrothorax (4%), and patient convenience (2%). Ultrafiltration failure was recognized as the inability to achieve resolution of clinical overhydration, confirmed by the peritoneal equilibration test (PET), demonstrating high membrane glucose transport (absorption) and observed retention of dialysate volume. Daytime ambulatory peritoneal dialysis (DAPD) was used by 69% of patients and nightly peritoneal dialysis (NPD) with cyclers by 31%. Only one patient (hydrothorax) transferred to hemodialysis. Observations include sustained hydration and blood pressure control in all patients with maintenance of biochemical dialysis adequacy, less reliance on very hypertonic solutions, an increase in dry weight in 25% of patients, decreased use of antihypertensive agents, effective management of hernia and hydrothorax in 3 of 4 patients, and satisfactory patient tolerance of DAPD and NPD regimens, and daily dry intervals. Factors promoting SDD include improved understanding of PET studies, use of disconnect systems, and improvement in cycler design. We anticipate increasing use of SDD as recognition of its usefulness and application techniques expands.

Adolescent↗
PubMed1991

Pre-spiking dialysate bags: improved peritonitis prevention in patients on CAPD.

We review experience with 238 patients over 5.5 years to determine the impact of techniques of spiking dialysis bags in advance of their use (pre-spiking) on peritonitis incidence. Our two units provide peritoneal dialysis therapies only with liberal patient acceptance policies. The Y-set was used almost exclusively over the last 4 years (192/238 patients), peritonitis rate 1:31.5 patient-months (99 episodes/3,122 months). Nineteen patients spiked each exchange, 23 episodes/282 months, 1:12.3; 173 pre-spiked 1-14 days in advance using Y-set and compact exchange device (CXD), 76 episodes/2,840 months, 1:37.4. Peritonitis rates did not worsen with increased pre-spiking intervals: 1 day, 1:16.2; 2-6 days, 1:47.9; 7 days, 1:62.2; 8-14 days, 1:34.3. Similarly, pre-spiking in CCPD patients at 10 day intervals (4 patients) yielded a peritonitis rate of 1:19. We conclude that pre-spiking dialysis bags using the Y-set and CXD promotes significant peritonitis prevention. By spiking at less frequent intervals, technical performance improves, exchanges are simplified and done under more flexible circumstances. Participation by patient-assistants is facilitated. Transfer from CAPD to CCPD is decreased. Low peritonitis rates contribute to excellent patient acceptance and retention. The potential CAPD-eligible population is broadened.

Adolescent↗
PubMed1988

Pharmacological treatment of erectile dysfunction after radical prostatectomy.

The potential for potency after radical retropubic prostatectomy has improved considerably since the anatomical description of the neurovascular bundles to the penis and a technique whereby these nerves may be spared from injury. However, impotence remains an unavoidable complication in some patients. It is in such patients that we have chosen to evaluate the technique of intracavernosal injection of a papaverine/phentolamine mixture to obtain erections. After classical radical prostatectomy potency was restored by the injection technique in 12 of 14 patients (85 per cent). Three patients who failed to attain erections initially had successful results with larger doses. Two patients who failed to achieve erections had the lowest penile brachial index values and 1 in whom priapism developed had the highest value, indicating that this may be a useful technique to determine the initial dosage of the injection.

Drug Combinations↗
PubMed1985

Juxtaglomerular cell tumor of the kidney.

We describe an 11-year-old hypertensive girl who had a 5.0 cm. juxtaglomerular cell tumor. Of the 18 previously reported cases this appears to be the largest such tumor found. The benign nature of the tumor is emphasized, its clinical, radiological and microscopic appearance is illustrated, and appropriate treatment options are discussed.

Child↗
PubMed1984

A dermatoglyphic study of the Gurungs, Mangars and Kirantis of Nepal.

Finger and palm prints were collected from 306 Nepalese males belonging to the Kiranti, Gurung and Mangar tribes of Nepal. The dermatoglyphic characteristics show affinities with other Asiatic Mongoloid populations especially those residing in the southern Himalayas.

Asian People↗
PubMed1978

The hypothenar radial arch and parathenar loop in palmar dermal topology: sex, bimanual and regional variation in samples from the British Isles.

Consideration is given to the regular recording of parathenar distal loops (Pa) and hypothenar radial arches (Ar) in palmar dermal topology. Frequencies are given for four British populations (the North Pennine Dales, the Mid Welsh Borderland, Pembrokeshire and Ireland) and regional variation noted together with sex and bimanual differences. Both Pa and Ar occur infrequently in normal populations, generally in less than 5% of individuals, Pa significantly less than Ar. Both attributes are similar in that they are significantly more common on right than left hands and in females than males. Three out of twelve comparisons between the North Pennine Dales, Welsh Borderland and Pembrokeshire data attained formal significance, in each case in the males. The former two regions were distinguished for both Pa and Ar; the latter two for Ar. This is more than expected by chance at the 5% level.

Dermatoglyphics↗
PubMed1975

Tissue-washing tank for histologic preparations.

A small tank made of plexiglass was designed to wash tissues for histologic preparations. The tank was divided into 16 compartments in 2 rows to wash 16 tissue samples at one time. The compartments in the same row alternately intercommunicated by rows of holes in the upper or lower halves. The arrangement of holes at 2 water levels in the partition appeared to create silent water waves, making the tank more efficient for washing tissues.

Histological Techniques↗
PubMed1975

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: appendix III. evaluation of viscera and other tissues.

Histopathological findings in the lungs, livers, bone marrows, small intestines, gonads, kidneys, and other tissues of the four pocket mice (Perognathus longimembris) that survived the Apollo XVII flight were evaluated in the light of their immediate environment and as targest of HZE cosmic ray particles. Results of this study failed to disclose changes that could be ascribed to the HZE particle radiation. Decreased numbers of erythropoietic cells in the bone marrow of the flight mice were probably related to the increased oxygen pressure. The small intestine showed no changes. Ovaries and tests appeared normal. Two of the three surviving male flight mice displayed early stages of spermatogenesis, just as ground-based controls did at the same season. Abnormalities were also not found in the thyroid, parathyroids, adrenals, or kidneys. The status of the juxtaglomerular apparatus could not be evaluated. The lungs exhibited nonspecific slight rections. A variety of incidental lesions were noted in the livers of both the flight mice and their controls. The heart muscle showed nothing that could be regarded as pathological. Sections of skeletal muscle examined were free from significant change.

Adrenal Cortex↗
PubMed1967

Experimental emphysema. Histologic changes and alterations in pulmonary circulation.

Detailed study of the pathogenesis of bullous emphysema has been hampered by lack of a suitable animal model of this disease. Prolonged exposure of rats and dogs to elevated partial pressures of oxygen produced a chronic obstructive disease in the lungs of these animals which anatomically resembles bullous emphysema in man. The disease was characterized by extensive bullae formation, alveolar septal destruction, airway obstruction and pronounced circulatory changes. It is suggested that this condition in laboratory animals may serve as a model for the study of pulmonary obstructive disease.

Animals↗