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Biomedical subjects

D T Allen

Publications and source records attributed to D T Allen.

At least 19 recordsLinked to original sources
PubMed2006

Effects of feeding propionibacteria to dairy cows on milk yield, milk components, and reproduction.

Two weeks before parturition, 38 Holstein primiparous and multiparous cows were assigned to 1 of 3 treatment groups: control animals (n = 13) received regular total mixed rations (TMR), the low-dose group (n = 14) received the control TMR plus 6 x 10(10) cfu/cow of Propionibacterium strain P169 (P169), and the high-dose group (n = 11) received the control TMR plus 6 x 10(11) cfu/cow of P169 from -2 to 30 wk postpartum. Weekly milk samples were analyzed for percentage of milk fat, protein, lactose, and SNF, milk urea nitrogen, and somatic cell counts. Daily milk production expressed as 4% fat-corrected milk was affected by treatment and week x parity. High-dose and low-dose P169-treated cows exhibited 7.1 and 8.5% increases above controls in daily 4% fat-corrected milk, respectively. Treatment x parity and week significantly influenced percentage of milk fat, lactose, and protein, whereas treatment x parity and treatment x week influenced SNF. Ruminal propionate levels were influenced by treatment such that high-dose P169 cows had greater molar percentage of propionate than did low-dose P169 and control cows. Change in body weight postpartum was influenced by week x parity and treatment x parity such that high-dose and low-dose P169 multiparous cows exhibited a more rapid recovery of wk-1 body weight than did control multiparous cows. There was no treatment, parity, or interaction on days to first postpartum ovulation or on estrous behavior at 45 and 90 d postpartum. We concluded that P169 might have potential as an effective direct-fed microorganism to increase milk production in dairy cows.

Acetates↗
PubMed2005

Endocrine disruption of uterine insulin-like growth factor expression in the pregnant gilt.

Early exposure of pregnant gilts to oestrogen, prior to the normal period of porcine conceptus oestrogen secretion, disrupts the uterine environment resulting in complete embryonic mortality during the period of placental attachment to the uterine surface. The current study evaluates the uterine insulin-like growth factor (IGF) system following endocrine disruption of early pregnancy in gilts through exposure to exogenous oestrogen on Days 9 and 10 of gestation. Endometrial IGF gene and protein expression, IGF-I receptor (IGF-IR) gene expression, and uterine lumenal content of IGF binding proteins (IGFBPs) were evaluated in control and oestrogen-treated gilts on Days 10, 12, 13, 15 and 17 of gestation. Oestrogen treatment altered endometrial IGF-I and IGF-IR gene expression on Days 12 and 13 of gestation. Uterine content of IGF-I and IGF-II in control gilts was greatest on Days 10, 12, and 13 followed by a four- to sixfold decrease on Day 15 of gestation. Oestrogen treatment caused a premature proteolysis of IGFBPs within the pregnant pig uterus on Day 10 of gestation, and an earlier decline in uterine lumenal IGF-I content. Results demonstrate that early exposure of pregnant gilts to oestrogen causes premature loss of uterine IGFs during the period of conceptus elongation. Timing for the release of uterine IGFs during early porcine conceptus development may play an important function in the ability of the conceptus to attach and survive during the establishment of pregnancy.

Animals↗
PubMed2004

Insulin-like growth factor-II stimulates steroidogenesis in cultured bovine thecal cells.

The objective of the present study was to determine the effects of insulin-like growth factor-II (IGF-II) on luteinizing hormone (LH)-induced progesterone and androstenedione production by bovine thecal cells and compare it to that of insulin and IGF-I. Cells from large (>7.9 mm) bovine follicles were collected and cultured for 2 days in the presence of 10% fetal calf serum. Then cells were cultured for an additional 1 or 2 days in serum-free medium with various doses of recombinant human IGF-II, bovine LH (30 ng/ml), IGF-I, and(or) insulin. Cell numbers were determined at the end of treatments via Coulter counting and used to correct steroid production data. In the presence of LH, 1-day treatment with 3-300 ng/ml of IGF-II had no significant effect on progesterone or androstenedione production, whereas 2-day treatment with 30, 100 and 300 ng/ml of IGF-II increased (P < 0.05) both progesterone and androstenedione production by 2-3-fold. The estimated effective dose of IGF-II stimulating 50% of the maximal steroidogenic response was calculated to be 25 ng/ml. In the absence of LH, 2-day treatment of IGF-I or -II had no effect on thecal androstenedione production but increased (P < 0.05) thecal progesterone production. In the presence of LH, 100 ng/ml of IGF-I increased progesterone and androstenedione production to a greater degree than did 100 ng/ml of IGF-II. Maximal effects of IGF-I and insulin on thecal steroidogenesis were similar and were not additive. Anti-IGF type I receptor antibodies attenuated (P < 0.05) the stimulatory effect of both IGF-I and IGF-II on thecal cell steroidogenesis. Use of radioligand assays demonstrated that specific receptors for (125)I-IGF-II existed in thecal cells with a 25 ng/well of IGF-II causing 50% inhibition of binding. IGF-I cross-reactivity with (125)I-IGF-II receptors averaged 3% whereas cross-reactivity of IGF-II with (125)I-IGF-I receptors averaged 114%. These results indicate that the stimulatory effects of IGF-II on thecal cell steroidogenesis is mediated by IGF type I receptors and thus IGF-II, like IGF-I, may play a significant role in thecal cell steroidogenesis during follicular development.

Androstenedione↗
PubMed2003

Separation of fine particulate matter emitted from gasoline and diesel vehicles using chemical mass balancing techniques.

Samples of fine particulate matter were collected in a roadway tunnel near Houston, TX over a period of 4 days during two separate sampling periods: one sampling period from 1200 to 1400 local time and another sampling period from 1600 to 1800 local time. During the two sampling periods, the tunnel traffic contained roughly equivalent numbers of heavy-duty diesel trucks. However, during the late afternoon sampling period, the tunnel contained twice as many light-duty gasoline-powered vehicles. The effect of this shift in the vehicle fleet affects the overall emission index (grams pollutant emitted per kilogram carbon in fuel) for fine particles and fine particulate elemental carbon. Additionally, this shift in the fraction of diesel vehicles in the tunnel is used to determine if the chemical mass balancing techniques used to track emissions from gasoline-powered and diesel-powered emissions accurately separates these two emission categories. The results show that the chemical mass balancing calculations apportion roughly equal amounts of the particulate matter measured to diesel vehicles between the two periods and attribute almost twice as much particulate matter in the late afternoon sampling period to gasoline vehicles. Both of these results are consistent with the traffic volume of gasoline and diesel vehicles in the tunnel in the two separate periods and validate the ability for chemical mass balancing techniques to separate these two primary sources of fine particles.

Air Pollutants↗
PubMed2001

Accounting for spatial variation of ozone productivity in NOx emission trading.

The potential air quality benefits of NO(x) emission-trading programs were compared to the air quality benefits of across-the-board NO(x) reductions for point sources in eastern Texas. The comparison was performed by first determining, using the Comprehensive Air Quality Model with extensions (CAMx), the changes in ozone concentrations associated with NO(x) reductions at more than 50 individual facilities in eastern Texas. These facility-specific changes in ozone concentrations due to NO(x) reductions were then converted into a variety of indices representing ozone reduction benefits. Trading scenarios were then evaluated through Monte Carlo simulations. The results indicate that approximately 20% of all trading scenarios result in ozone reduction benefits that deviate by 25% or more from the ozone reduction benefits achieved by across-the-board reductions. This result was independent of the index used to calculate ozone reduction benefit. This variability in the benefits associated with trading scenarios was comparable to the variability in benefits associated with changes in meteorological conditions over the days that were modeled. Additional Monte Carlo simulations indicated that the average benefit associated with NO(x) trading could be improved and that the variability in benefit was reduced by creating a trading program where a small group of high impact facilities are allowed to sell but may not buy NO(x) allowances.

Air Pollutants↗
PubMed2001

A central giant cell granuloma in a patient seeking orthodontic treatment.

BACKGROUND: This case report illustrates the need to consider central giant cell granuloma, or CGCG, in the differential diagnosis in cases of greatly displaced teeth and facial deformity. The authors review the literature regarding CGCG and emphasize the importance of early diagnosis and treatment. CASE DESCRIPTION: A 9-year-old boy was seen in an orthodontic office with the chief complaint of overlapping front teeth. On radiographic examination, the authors noted a large maxillary midline radiolucency. The child was referred to an oral and maxillofacial surgeon for definitive diagnosis and treatment. CLINICAL IMPLICATIONS: Patients may come to dental offices for treatment of malaligned teeth. The dentist needs to be aware of possible oral pathology when malaligned teeth are present. CGCG should be included in the differential diagnosis for patients with greatly displaced teeth and facial deformity.

Child↗
PubMed2000

Painful chewing and blindness: signs and symptoms of temporal arteritis.

BACKGROUND: This case report illustrates the need to consider temporal arteritis in the differential diagnosis of jaw or tooth pain. This disease affects the cranial arteries, more frequently in women and usually in those older than age 60 years, causing jaw pain, visual symptoms, headache, scalp pain and sometimes blindness. CASE DESCRIPTION: A 71-year-old man had jaw pain that increased with chewing and speaking, scalp tenderness and dimming vision. A temporal artery biopsy confirmed the diagnosis of temporal arteritis. Treatment with decreasing amounts of oral steroids over 23 months was successful in relieving his signs and symptoms and in saving his vision. CLINICAL IMPLICATIONS: Patients with this disease may seek care from their dentist first. Jaw or tooth pain is the most reliable clinical symptom in the diagnosis of temporal arteritis. Diagnosis and timely referral for treatment with oral steroids can prevent blindness.

Aged↗
PubMed1994

Permeation of proteins from the blood into peripheral nerves and ganglia.

We have attempted to resolve apparently conflicting observations of previous investigators regarding the penetration of proteins into peripheral ganglia and nerves of the rat. Horseradish peroxidase, which is largely cleared from the blood and extracellular fluids in less than 30 min, entered all the extracellular spaces of ganglia, including the clefts between glial cells and neurons, but it did not enter the endoneurium. Rhodamine B-conjugated bovine albumin quickly entered sensory and sympathetic ganglia, but its penetration into avascular enteric nervous tissue was arrested at the outer margin of each myenteric and submucosal ganglion. If injected daily for a week, this fluorescent protein was seen also in the endoneurium, but it was still absent from enteric ganglia. The failure to enter enteric ganglia may have been due to the entrapment of aggregates of dye-labelled albumin molecules in the basal lamina that encloses the enteric nervous system. Extracellular endogenous albumin immunoreactivity was seen in all parts of peripheral nerves and in all types of ganglion. Some neuronal perikarya contained albumin-immunoreactive material; the strongest staining was in enteric neurons. Albumin may reach these cell bodies by retrograde axonal transport from peripheral terminals. We conclude that all the extracellular spaces of the rat's peripheral nervous system are accessible to plasma proteins, though diffusion occurs more slowly into the endoneurium than into ganglia.

Animals↗
PubMed1992

Flow rates and compositions of incinerated waste streams in the United States.

The quantity and composition of RCRA hazardous wastes incinerated during 1986 were examined using the National Hazardous Waste Survey. This Survey, collected for U.S. EPA by the Research Triangle Institute, is the most extensive examination of hazardous waste generation and management available. The survey data show that although a wide variety of hazardous wastes were treated by incineration, more than 75 percent of incinerated waste streams were from chemical manufacturing. The survey data also show that more than 90 percent of the incinerated wastes were treated by incinerators located at the facility generating the waste. Despite the predominance of a single industrial sector in generating incinerated hazardous wastes, the compositional profile of the wastes is far from uniform. To illustrate this variability, the metals and chlorine content of the wastes are reported along with the sources of the metal and chlorine loadings.

Air Pollution↗
PubMed1992

Excluded babies.

Explore the source record for details and available documents.

Adolescent↗
PubMed1990

A circulating exogenous protein can enter enteric nervous tissue in the rat.

Previous studies of the permeation of circulating protein tracers yielded conflicting results in the enteric nervous system. We show that within 5 min of intravenous injection, horseradish peroxidase (HRP) enters all the extracellular spaces of the ganglia and connecting strands of the submucous and myenteric plexuses of the rat's small intestine, including the clefts between neuroglial cells and neurons. The tracer is still there after 10 min, but is nearly all gone 30 min after injection. Enteric neurons, like others with somata in peripheral ganglia, are therefore probably accessible to plasma proteins and to substances with smaller molecules that are protein-bound when circulating in the blood.

Animals↗
PubMed1990

Flow characteristics of bioprosthetic heart valves.

A review of the in vivo and in vitro fluid dynamic performance of three bioprosthetic heart valves is presented. Data on Hancock porcine valves (standard models 242 aortic and 342 mitral and modified orifice model 250 aortic), Carpentier-Edwards porcine valves (model 2625 aortic and 6625 mitral), and the Ionescu-Shiley pericardial valve are reviewed. These valves were chosen because of their past or present popularity in clinical use and because of the variation in fluid dynamic performance reported by different investigators. The flow parameters that are reported include in vivo and in vitro mean pressure drop, cardiac output or cardiac index, regurgitant volume, effective orifice area, and performance index. These data provide a framework for differentiation of normal and abnormal bioprosthetic valve function.

Animals↗
PubMed1990

A multifocal outbreak of hepatitis A traced to commercially distributed lettuce.

From February 1 through March 20, 1988, 202 cases of hepatitis A were reported in and around Jefferson County, Kentucky. The epidemic curve indicated a common-source exposure. However, there was no apparent single source of exposure from a restaurant, or community gathering; nor was there a geographic clustering by residence. Cases were mainly adults 20-59 years old (89 percent); 51 percent were female. A case-control study using neighborhood controls found that factors associated with hepatitis A were: having eaten downtown (odds ratio [OR] = 4.0) and having dined at any one of three restaurants (OR = 21.0). Case-control studies of patrons of two of these restaurants found that eating green salad was strongly associated with acquiring hepatitis A: OR = 11.6 and OR = 4.4. The three implicated restaurants accounted for 71 percent of the cases. All three restaurants were supplied by the same fresh produce distributor; however, investigation suggested that contamination most likely occurred prior to local distribution. This outbreak of hepatitis A is the first in the United States apparently associated with fresh produce contaminated before distribution to restaurants, and raises important public health issues regarding the regulation of fresh produce.

Adult↗
PubMed1989

In vitro flow dynamics of four prosthetic aortic valves: a comparative analysis.

The velocity fields downstream of four prosthetic heart valves were mapped in vitro over the entire cross-section of a model aortic root using laser Doppler anemometry. THe Björk-Shiley 60 degrees convexo-concave tilting disc valve, the Smeloff-Cutter caged ball valve, the St. Jude Medical bileaflet valve, and the Ionescu-Shiley standard bioprosthesis were examined under both steady and pulsatile flows. Velocity profiles under steady flow conditions were a good approximation for pulsatile profiles only during midsystole. The pulsatile flow characteristics of the four valves showed variation in large scale flow structures. Comparison of the valves according to pressure drop, shear stress and maximum velocities are also provided.

Aortic Valve↗
PubMed1988

An emergency physician's guide to prosthetic heart valves: identification and hemodynamic function.

We describe methods for identifying the type and size of seven commonly used prosthetic heart valves and how these features influence the hemodynamics of flow through the valve. The four mechanical heart valves reviewed are Starr-Edwards silicone rubber ball valves (Models 1200/1260 aortic and 6120 mitral valves), Bjork-Shiley tilting disc valves (60 degrees standard spherical model and the 60 degrees convexo-concave model), Medtronic-Hall (Hall-Kaster) tilting disc valve, and St Jude Medical bileaflet valve. The three bioprostheses reviewed are Hancock porcine valve, Carpentier-Edwards porcine valve, and Ionescu-Shiley bovine pericardial valve. These valves were chosen because of their past or present popularity and therefore are the ones most apt to be implanted in patients seen in the emergency department.

Bioprosthesis↗
PubMed1988

An emergency physician's guide to prosthetic heart valves: valve-related complications.

Serious valve-related complications that occur in patients with prosthetic valves have been discussed. The emergency physician's role primarily is to recognize the high probability that one of these serious complications exists and hospitalize the patient so that rapid definitive diagnoses and therapeutic decisions are not delayed.

Anemia, Hemolytic↗
PubMed1987

Cervical cancer.

This conference concerns economic, psychosocial, preventive, and medical aspects of the care of an indigent, unemployed, 22-year-old mother of three who died of an invasive, large cell, nonkeratinizing cervical cancer 35 months after her last Pap smear, 19 months after the onset of vaginal discharge, 12 months after consulting a physician, 10 months after an exploratory laparotomy, nine months after initiation of radiation therapy, five months after performance of a colostomy, four months after initiation of chemotherapy, and three months after treatment of small bowel obstruction with hyperalimentation and resection. We discuss the cost effectiveness of preventive programs.

Adolescent↗