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Biomedical subjects

D Richardson

Publications and source records attributed to D Richardson.

At least 235 records · Page 13Linked to original sources
PubMed1976

Cellular specificity of plasmacytoma-induced immunosuppression.

The pattern of immunodeficiency in plasmacytoma-bearing mice appears to be unique. Mice bearing these tumors exhibit a severe impairment in their ability to mount a primary immune response to thymus-dependent and -independent antigens. However, cell-mediated immune functions in these mice apparently remain intact. Thus, when T cell activity of lymph node cells from plasmacytoma-bearing mice was tested in vivo by sensitization with dinitrofluorobenzene and in vitro by responsiveness to phytohemmagglutinin, allogeneic cells, and dinitrobenzene sulfonate, cell-mediated immunity was found to be normal.

Animals↗
PubMed1975

Early effects of tobacco smoke exposure on vascular dynamics in the microcirculation.

The purpose of these studies is to examine the early effects of chronic tobacco smoke exposure on vascular dynamics in the mesenteric microcirculation. Female rats were exposed daily to tobacco smoke from five reference cigarettes for a period of 2 mo. At the end of this period the smoke-treated rats had gained 12 g less than sham-treated controls, and arterial blood pressure in the smoke-treated animals was slightly less than pressure in the sham-treated animals. These are characteristic effects of tobacco smoke exposure on rats. Following the treatment period, red blood cell (RBC) velocity in single mesenteric capillaries and microvascular pressures in arterioles and venules were measured in accordance to established methods. There was no significant difference in pressure distribution on the arterial side of the mesenteric vascular network, but pressure in the venules of the smoke-treated animals was significantly higher than that of the sham-treated group. In association with the higher venular pressure in the smoke-treated animals, capillary RBC velocity (an index of capillary flow) was significantly lower. The reduction in velocity was in proportion to the decrease in pressure drop (arteriole-venule) across the capillary network.

Animals↗
PubMedDate not supplied

Analysis of human sperm function following exposure to the ionophore A23187. Comparison of normospermic and oligozoospermic men.

Time exposure photomicrography and interspecific in vitro fertilization techniques have been used to compare the responses to the divalent cation ionophore A23187 of spermatozoa from normal fertile and oligozoospermic men. The fertilizing capacity of spermatozoa from the fertile controls produced a bell-shaped dose response curve when assessed in the presence of ionophore. The optimal responses occurred in the presence of 50 and 100 microM A23187. At this concentration, a mean penetration rate of about 75%, in association with multiple polyspermy, was observed without significant changes in motility patterns. At higher doses of A23187, there was a decline in fertilization rates, an independent reduction in sperm motility, and a significant decrease in the amplitude of lateral sperm head displacement. In contrast to the fertile controls, spermatozoa recovered from patients with oligozoospermia failed to exhibit a significant change in their fertilizing potential following exposure to A23187. Calculations based on the Poisson distribution theory indicated that this lack of responsiveness was not related to any differences in the motility of the spermatozoa from the oligozoospermic patients compared to the controls. These results suggest that calcium ionophores may be of value in providing a rapid and sensitive indicator of the functional competence of human spermatozoa, which circumvents problems concerning the rate and efficiency of sperm capacitation encountered with conventional protocols.

Adult↗
PubMedDate not supplied

Missing annual external radiation dosimetry data among Hanford workers.

Epidemiological studies of workers employed at the Hanford Site have been underway for nearly 30 years. Although the external radiation dosimetry program at Hanford has been fairly comprehensive, some workers included in previous epidemiological analyses have periods of employment during which there are missing annual external radiation dosimetry records. In this report, employment history records and annual external dosimetry records have been used to investigate the extent of missing annual external dosimetry records for workers at the Hanford facility. A "nearby" procedure for estimating values for missing annual external dosimetry records was evaluated. Among the 33,459 workers who were employed at least 180 days and had at least one annual external dosimetry record, annual external dosimetry records were missing for 8% of the years of employment (32,323 missing annual external dosimetry records). Missing annual external dosimetry records were more common for female Hanford workers than for male workers, and for workers employed in the early years of Hanford's operation than for workers employed in later years of operation. The nearby procedure provided reliable estimates of values for missing annual external dosimetry records. Using this procedure, 18,937.5 mSv were estimated for missing annual external dosimetry records; this was 2% of the total recorded cumulative external radiation dose for these workers. Missing annual external dosimetry records should be considered as a potential source of bias and uncertainty in investigations of radiation-cancer associations among Hanford workers.

Air Pollution, Radioactive↗
PubMedDate not supplied

Evaluation of annual external radiation doses at values near minimum detection levels of dosimeters at the Hanford nuclear facility.

In epidemiological studies of workers exposed to ionizing radiation, recognition of the limitations of available radiation dosimetry data is important to interpretation of a study's findings. This paper provides an investigation of external radiation dosimetry data for workers at the Hanford nuclear facility, focusing on changes over time in practices for recording dosimetry measurements that were between zero and the minimum detectable level of a radiation dosimeter. Reported annual external radiation doses for the years 1944-1989 were examined for 33,459 workers; these records are the sum of periodic dosimetry measurements within a calendar year. For each year, the proportion of annual external doses with values in the range of minimum detectable level was examined. Contrary to previous researchers, we conclude that there is evidence that dosimetry measurements with values between zero and the minimum detectable level may have been recorded as zero in some historical periods. This conclusion is supported by evidence drawn from historical documentation about radiation dosimetry practices at the Hanford facility. Although workers at the Hanford facility have relatively complete and detailed external radiation dosimetry data compared to some other nuclear facilities that began operation in the 1940s, these data may suffer limitations related to dosimetry recording practices at the facility.

Adult↗
PubMedDate not supplied

Effects of tobacco smoke inhalation on capillary blood flow in human skin.

To measure the effects of tobacco smoke inhalation on capillary blood flow in human skin, 20 female tobacco smokers consented to smoke three cigarettes with nicotine levels of 0.50, 0.98, and 1.90 mg per cigarette, each on a separate occasion. Measurements of blood flow velocity and vascular diameter were made along the venous limb of capillaries within the nailfold skin of the third finger via videomicroscopy before and for 5 min after the smoking of each cigarette. Capillary blood flow (CBF) was calculated as a product of capillary cross-sectional area and flow velocity. Resting pre-smoke CBF for all experiments combined averaged 4.7 X 10(4) mu 3/sec. All three cigarettes elicited a significant reduction in CBF with the maximal effect within the first 2 min of the post-smoke period (p less than or equal to .05). Respective CBF values during this time averaged 3.6, 3.4, and 2.7 mu 3/sec for the low-, medium-, and high-nicotine cigarettes. Although the data suggested a downward trend in CBF with increasing nicotine levels, the post-smoke values were not significantly different among the three cigarettes. It is concluded that acute tobacco smoke inhalation reduces CBF in human skin, but the effect is not related to the nicotine content of the cigarettes. The changes in cutaneous CBF observed with tobacco smoking are less compared to reported effects of smoke inhalation on total digital blood flow.

Blood Flow Velocity↗
PubMedDate not supplied

Success rates and cost-effectiveness of antibiotic combinations for initial treatment of central-venous-line infections during total parenteral nutrition.

BACKGROUND: Central-venous-line infections can be successfully treated with appropriate antibiotics, thus avoiding the need for catheter removal. Based on our experience, vancomycin, gentamicin, piperacillin, ceftazidime, and amphotericin, alone or in combination, are usually administered, pending sensitivity results. This empirical list, however, has never been verified against actual sensitivity results nor has it been tested for cost or efficacy. METHODS: Medical records of inpatients on hyperalimentation over 1 year were reviewed. Success rate, therapy duration, and drug acquisition cost and charge were assessed for central-venous-line infections. Antibiotics then were paired and evaluated in terms of charge and efficacy against all microorganisms as determined by sensitivity results. RESULTS: In 500 inpatients receiving hyperalimentation for 9,698 patient-days, 8.4 central-venous-line infections/1,000 patient-days occurred. Staphylococcus non-aureus, Candida species, Enterococcus faecium, and Staphylococcus aureus predominantly were isolated. Of the infections, 51 (67%) were sensitive to one or more of the initial antibiotics. A 2-week course of antibiotics successfully treated 50 (66%) catheter infections without line removal. Appropriate initial therapy on average reduced treatment duration by 8 to 10 days and drug charges by $400 to $700. CONCLUSIONS: Amikacin-vancomycin appears to be the most cost-effective selection for presumed central-venous-line infections, pending sensitivity results, followed by valid alternatives. Lower failure rates are well worth the extra cost in pharmaceutical charges.

Adolescent↗