PubMed Health⌕ Search

Biomedical subjects

D F Anderson

Publications and source records attributed to D F Anderson.

At least 19 recordsLinked to original sources
PubMed2005

Fetal infusions of plasma cause an increase in umbilical vascular resistance in sheep.

Earlier studies suggested that the fetal placental circulation is relatively inert with fetal placental flow increasing or decreasing with perfusion pressure. Subsequent studies have demonstrated that the placenta may not be an unreactive vascular bed. The present study was undertaken to determine if plasma infusion-induced hypertension increased fetal placental flow in proportion to the driving pressure across the fetal placental circulation. Six fetal sheep were operated on at 118-122 days to place intravascular catheters and a flow sensor on the common umbilical artery. Starting 6 days later, the fetuses were infused with adult sheep plasma. During the 7-day-long infusion period, they received a total of 1515+/-217 (SD) ml of fluid and 93.2+/-12.0 g of protein. Fetal plasma protein concentrations increased from 34.2+/-2.3 to 77.0+/-9.7 g/l (P<0.0001). Fetal arterial blood pressures rose from 42+/-3 to 59+/-4 mmHg (P<0.01) and venous pressures rose from 2.2+/-0.5 to 4.8+/-0.8 mmHg (P<0.01). In spite of the large increase in driving pressure, fetal placental blood flow remained (statistically) constant (627+/-299 ml/min and 552+/-221 ml/min) while fetal umbilical resistance increased from 0.077+/-0.038 to 0.115+/-0.053 mmHg min/ml (P<0.01). On day 7, plasma renin activity had fallen from 6.7+/-4.2 ng/(ml/h) at preinfusion control to 0.6+/-0.6 ng/(ml/h) (P<0.05) and plasma angiotensin-II concentration had fallen from 33.2+/-26.6 to 6.2+/-3.9 pg/ml, although this fall was not statistically significant (P=0.07). Fetal placental flow did not increase with increased driving pressure across the fetal placental circulation. The increase in fetal placental resistance may be a response to the increase in arterial pressure since there was no increase in flow.

Animals↗
PubMed2004

Correlation of long term phenotypic and clinical outcomes following limbal epithelial transplantation cultivated on amniotic membrane in rabbits.

AIM: To determine the epithelial phenotype in rabbits with total limbal stem cell deficiency (LSCD) after reconstruction with autologous limbal epithelial stem cells ex vivo expanded on rabbit amniotic membrane (AM). METHODS: Left eyes of 52 rabbits were rendered total LSCD, verified by impression cytology. The fibrovascular pannus of each cornea was removed. Group I (n = 10) received rabbit AM transplantation alone, while groups II-IV (n = 42) underwent transplantation of LSC cultured on rabbit AM (LSC-AM) from a small limbal biopsy taken from the right eye. Clinical outcome was graded as "success," "partial success," or "failure" depending on the corneal smoothness and avascularity. Epithelial phenotype was determined by immunostaining and graded as "corneal (K)," "conjunctival (J)," or "mixed (M)" depending on expression of K3 and Muc5AC. RESULTS: After 1 year follow up, group I showed 100% failure and groups II-IV showed 26% success (p<0.001). Clinical failure correlated with J phenotype p = 0.001), while clinical success correlated with K phenotype p = 0.01). When the phenotypic outcome was used for comparison, J phenotype was significantly high in group I (p = 0.003), while K phenotype was significantly high in groups II-IV (p<0.05). CONCLUSION: There is a strong correlation between clinical success and resultant corneal epithelial phenotype. Ex vivo expanded LSC can successfully reconstruct corneal surfaces with unilateral total LSCD.

Amnion↗
PubMed2001

Nedocromil sodium and levocabastine reduce the symptoms of conjunctival allergen challenge by different mechanisms.

BACKGROUND: Nedocromil sodium and levocabastine are widely used for the treatment of ocular allergy, but their mechanisms of action are unclear. OBJECTIVE: We sought to compare the efficacy and mechanisms of action of nedocromil sodium and levocabastine in reducing conjunctival symptoms after ocular allergen challenge. METHODS: We performed a double-blind, placebo-controlled study in which 48 subjects were randomized to 3 groups to receive nedocromil sodium (2%), levocabastine (0.05%), or placebo eye drops twice daily for 2 weeks before ocular challenge with 10 microL of ryegrass extract. Symptoms and tear histamine and PGD(2) concentrations were determined before challenge and at 10, 20, 30, 60, 180, and 360 minutes after challenge. Bulbar biopsy specimens were taken at 6 and 24 hours after challenge to assess conjunctival inflammatory cell numbers, adhesion molecule expression, and mast cell-associated IL-4, IL-5, IL-6, IL-13, and TNF-alpha levels. RESULTS: Both drugs significantly reduced total symptom scores (P <.05) at all times after challenge compared with placebo. Itching, hyperemia, and lacrimation were most affected. Nedocromil sodium treatment reduced tear concentrations of histamine (by 77%) and PGD(2) (by 70%) at 30 minutes after challenge (both P <.05). In biopsy specimens nedocromil sodium reduced the number of 3H4-positive mast cells (purportedly the secreted form of IL-4) by 49% at 6 hours and 59% at 24 hours (both P <.05). Levocabastine reduced intercellular adhesion molecule 1 expression by 52% at 6 hours and 45% at 24 hours (both P <.05). CONCLUSION: Nedocromil sodium and levocabastine both reduced the conjunctival symptoms after ocular allergen challenge but appeared to work by different mechanisms. Nedocromil sodium reduced mast cell function, whereas levocabastine appeared to have primarily antihistaminic actions, although it also reduced the expression of intercellular adhesion molecule 1.

Adult↗
PubMed2001

Amniotic membrane transplantation after the primary surgical management of band keratopathy.

PURPOSE: To determine the safety and efficacy of amniotic membrane transplantation to restore and maintain a stable corneal epithelium and reduce ocular surface pain after surgical removal of band keratopathy arising from ocular causes. METHODS: Fifteen patients (16 eyes) from two centers with band keratopathy secondary to ocular causes underwent amniotic membrane transplantation as a graft after surgical removal of calcific deposits with or without the use of ethylenediaminetetraacetic acid. In a prospective, consecutive, uncontrolled case series, the rate of corneal epithelialization and resultant surface stability were recorded over a mean follow-up period of 14.6 months. RESULTS: Pain from ocular surface instability was the presenting complaint in 14 of 15 (93.3%) patients and resolved in all cases after the procedure even for those who experienced a recurrence of the calcific deposit. Fifteen of 16 eyes (93.7%) achieved epithelialization with a mean time to epithelial healing of 15.2 days. The only eye that failed to heal was subsequently diagnosed with total limbal stem cell deficiency. Visual acuity improved in five of nine (44%) sighted eyes and remained unchanged in four of nine (56%). No patient experienced any major surgical or medical complication after the procedure. CONCLUSION: Amniotic membrane transplantation represents a safe and effective method to restore a stable corneal epithelium in eyes after primary surgical removal of band keratopathy arising from ocular causes.

Adult↗
PubMed2001

Amniotic membrane transplantation for partial limbal stem cell deficiency.

AIM: To examine the efficacy, safety, and long term outcomes of amniotic membrane transplantation for corneal surface reconstruction in cases of partial limbal stem cell deficiency. METHODS: 17 eyes of 15 patients with partial limbal stem cell deficiency underwent superficial keratectomy of the conjunctivalised corneal surface followed by amniotic membrane transplantation. Cases were followed up for at least a year. RESULTS: All eyes exhibited a stable, intact corneal epithelial surface after a mean follow up period of 25.8 months with no eyes developing recurrent erosion or persistent epithelial defect. The mean time to re-epithelialisation was 22.8 days. Overall improvement in visual acuity was observed in 92.9% of 14 eyes with visual potential. Of those, five eyes gained six or more lines, two eyes gained between four and five lines, six eyes gained between one and three lines, and one eye lost three lines of Snellen acuity. Pain and photophobia were abolished in 86% of cases and substantially reduced in 14%, with all eyes exhibiting decreased vascularisation and inflammation at final follow up. CONCLUSIONS: Amniotic membrane transplantation appears to be a safe and effective method of restoring a stable corneal epithelium for cases of partial limbal stem cell deficiency and can be considered as an alternative to limbal autograft or allograft.

Adult↗
PubMed2001

The relative contribution of mast cell subsets to conjunctival TH2-like cytokines.

PURPOSE: To investigate the distribution of the T-helper (TH)2-like cytokines, interleukin (IL)-4, IL-5, IL-6, and IL-13 between mast cell subsets in conjunctival biopsy specimens from normal subjects and those with seasonal allergic conjunctivitis (SAC) during and outside of the grass pollen season. METHODS: Sequential and double in situ hybridization (ISH) and immunohistochemistry (IHC) were performed on thin sections of human conjunctiva to determine the colocalization of the immunoreactivity of IL-4, IL-5, IL-6, and IL-13 to mast cell subsets in normal subjects and subjects with atopy and to detect IL-4 mRNA in conjunctival mast cells. RESULTS: More than 90% of IL-4+-immunoreactive cells were observed to be mast cells in conjunctival biopsy specimens from all patient groups. The majority of IL-5+, IL-6+, and IL-13+ cells were also noted to be mast cells for each group. IL-4 preferentially colocalized to the tryptase+-chymase+ mast cell phenotype (MC(TC)) with MC(TC) cells comprising 93.3% of cytokine+ mast cells in symptomatic SAC (P = 0.0017), 89.2% in asymptomatic SAC (P = 0.0008), and 77.8% in normal subjects (P = 0.0472). IL-13 appeared to colocalize preferentially to the MC(TC) phenotype and IL-5 and IL-6 to the MC(T) phenotype. ISH showed that 75.8% of mast cells in normal subjects, 78.7% in subjects with symptomatic SAC, and 18.7% in subjects with asymptomatic SAC expressed mRNA for IL-4. CONCLUSIONS: Conjunctival mast cells are an important source of IL-4, IL-5, IL-6, and IL-13 immunoreactivity, with preferential colocalization of IL-4 and IL-13 on the MC(TC) subset and IL-5 and IL-6 to the MC(T) subset. This evidence suggests that differences in protease phenotype may also reflect functional differences evidenced by the different patterns of cytokine distribution.

Adult↗
PubMed1999

Regulatory response of intramembranous absorption of amniotic fluid to infusion of exogenous fluid in sheep.

Six fetal sheep were operated on at 118 to 121 days of gestation. The pulmonary end of the trachea was connected to the gastric end of the esophagus with a section of tubing. This left urine as the only source of amniotic fluid and intramembranous absorption as sole exit. Multiple indwelling fetal vascular, intra-amniotic, allantoic, and a fetal bladder catheter were placed. Beginning 5 days after surgery, all urine was drained from the bladder and immediately reinfused into the amniotic sac to monitor urine production rate. After 4 days of urine infusion alone, the urine infusion was augmented for 6 days with an intra-amniotic infusion of Ringer solution. Amniotic and allantoic fluid volumes were measured at autopsy. During the period of Ringer infusion, intramembranous absorption of amniotic fluid increased by more than 1,191 +/- 186 (SE) ml/day (P < 0.002) and the rates of Na(+) and Cl(-) absorption increased to more than five times (P < 0.005) and eight times (P < 0.005) their initial values. Only one of six fetuses had polyhydramnios. It is concluded that intramembranous absorption of amniotic fluid makes a strong regulatory adjustment in response to an abnormal increase in inflow of exogenous fluid.

Absorption↗
PubMed1999

Non-communication between ophthalmologists and optometrists.

Many patients seen in the British hospital eye service are referred by high-street optometrists; and, if the optometrist is to receive feedback from the ophthalmologist, the patient should consent to disclosure of medical information. On the referral form (revised GOS 18) there is a space for this purpose. We investigated the level of communication by asking optometrists in our hospital catchment area about their use of the GOS 18 form and by examining the medical records of all new patients seen in the eye outpatient department in one month. 79 optometrists (55%) returned the questionnaire. 54 routinely used the GOS 18; and, of these, 10 said they obtained patient consent always, 23 sometimes and 21 never. 158 of 555 sets of medical notes contained an optometrist's referral, 107 of them on the revised GOS 18; and patient consent had been recorded on 17 of these forms. Ophthalmologists responded to the optometrist in 2/17 (12%) cases where consent had been obtained and 15/90 (17%) where it had not. Ophthalmologists could provide much better feedback to optometrists. The GOS 18 form could be used more effectively; and there is no reason why patient consent to disclosure of medical information should not be obtained by ophthalmologists as well as by optometrists.

Communication↗
PubMed1998

Human mast cells express stem cell factor.

Stem cell factor (SCF) is a major cytokine regulator of mast cell growth and function. The present study demonstrates that human mast cells are able to produce SCF. Constitutive synthesis of SCF mRNA was seen in the mast cells isolated from human lung and skin by RT-PCR. This was confirmed by in situ hybridization in conjunctival mast cells of both tryptase-only (MCT) and tryptase/chymase (MCTC) subsets. SCF protein product was found in conjunctival MCT and MCTC mast cells by immunohistochemistry. Soluble SCF protein was detected in the culture supernatant of isolated lung mast cells by ELISA, and cross-linkage of IgE receptor (Fc epsilon-RI) on the lung mast cells in culture did not alter SCF mRNA expression, or the secreted soluble SCF protein. This was consistent with the finding that levels of SCF mRNA expression in conjunctival mast cells were similar between normal subjects and patients with seasonal allergic conjunctivitis (SAC). This study shows that human mast cells themselves are a cellular source of SCF, as well as being target cells for this growth factor. SCF may regulate mast cell growth and function via both paracrine and autocrine mechanisms. The production of SCF by mast cells may be regulated via mechanisms other than IgE receptor-mediated pathways.

Cell Culture Techniques↗
PubMed1998

Direct ophthalmoscopy versus slit lamp biomicroscopy in diagnosis of the acute red eye.

The causes of red eye range from trivial to life-threatening, and many general practitioners are uncertain of their ability to diagnose them with the aid of an ophthalmoscope. We tested the hypothesis that, in the assessment of a patient with red eye, a doctor using a slit lamp biomicroscope would not differ in diagnostic accuracy from a doctor using a direct ophthalmoscope. A cross-over study was conducted in 98 patients newly attending an eye casualty department. 71% of diagnoses agreed exactly, and all potentially sight-threatening lesions were either diagnosed correctly or managed appropriately by doctors using an ophthalmoscope. We conclude that the initial diagnosis and management of patients with an acute red eye is not prejudiced by the lack of a slit lamp biomicroscope.

Acute Disease↗
PubMed1998

Adhesion molecules and relationship to leukocyte levels in allergic eye disease.

PURPOSE: To evaluate the conjunctival expression of leukocyte cell adhesion molecules (CAMs) and their relationship to leukocyte patterns on the microvasculature in the different clinical subtypes of allergic eye disease. METHODS: Immunohistochemical analysis, using appropriate monoclonal antibodies, was applied to glycolmethacrylate-embedded biopsies of bulbar and tarsal conjunctival tissue. The proportion of total blood vessels expressing a particular CAM was derived and related to individual cell types identified by cell-specific markers, such as mast cells, eosinophils, neutrophils, T cells, and macrophages. Statistical analysis was used to correlate adhesion molecule expression and, ultimately, cell type. RESULTS: There was a basal expression of intercellular adhesion molecule-1 (ICAM-1) (21% bulbar, 18% tarsal), E-selectin (15% bulbar, 21% tarsal), and vascular cell adhesion molecule-1 (VCAM-1) (13% bulbar and tarsal) in normal controls. In seasonal and perennial (bulbar and tarsal conjunctival) allergic tissue, ICAM-1 and E-selectin were expressed in 40% to 78% of vessels; in chronic disease, they were expressed in 45% to 80% of vessels; and in vernal giant papillae, they were expressed in as many as 90% of vessels. There was also increased expression of endothelial VCAM-1 in all forms of allergic eye disease; the greatest values were found in vernal giant papillae (64%). Biopsies taken in winter from seasonal sufferers demonstrated a marked reduction in levels of all three CAMs compared with those taken in the pollen season. This is almost consistent with values found in normal conjunctiva. Positive correlations were found between the levels of ICAM-1 and E-selectin expression and the degree of granulocyte and lymphocyte infiltration, although VCAM-1 expression correlated most closely with eosinophil numbers. CONCLUSIONS: Increased levels of cell adhesion molecules on the microvasculature and the factors that regulate them are likely to be responsible for the infiltration of cells bearing their ligands and may perpetuate inflammation in the chronic forms of allergic eye disease.

Adult↗
PubMed1997

Coronary heart disease risk factors in employees of Iowa's Department of Public Safety compared to a cohort of the general population.

The prevalence of coronary heart disease (CHD) risk factors in law enforcement personnel compared to that in the general population was studied by determining the predicted 10-year risk for developing CHD (CHD10, expressed as %) in subjects from the Iowa Department of Public Safety and comparing it to the average CHD10 for similarly aged subjects in the Framingham Heart Study cohort. The Iowa data included measures on 388 men from 30 to 64 years old, 246 of whom were measured in 1980-1981 and again in 1992-1993. The CHD10 came from an algorithm developed using the Framingham data; it included measures of age, gender, cholesterol, HDL-C, systolic blood pressure, smoking habit, glucose level, and left ventricular hypertrophy (ECG criteria). For this group, average CHD10 was reported by age in five-year increments [Circulation 83:356, 1991]. The Iowa subjects (n = 388) did not show a statistically significant difference in CHD10 from the reference population (8.9% versus 7.9%). The change with age was very similar in the two groups: for Iowa (n = 388) the estimate was CHD10 = -16.5 + .59 (age); for Framingham it was CHD10 = -17.5 + .60 (age). The change in individual risk factors with time was also similar in both groups; the per year change in CHD10 in the Iowa subjects, which was measured twice (n = 246, 0.63%), did not differ statistically from the 0.60% change predicted by the Framingham model. These results suggest that, for the risk factors considered here, the 10-year probability of developing CHD among Iowa law enforcement personnel is similar to that found in the Framingham population.

Adult↗
PubMed1997

Angiotensin mediated interaction of fetal kidney and placenta in the control of fetal arterial pressure and its role in hydrops fetalis.

Fetal cardiovascular control is effected by an interaction of the fetal somatic and placental circulations. Three primary regulatory mechanisms are involved: transplacental transfer of extracellular fluid, driven by a difference in hydrostatic and oncotic pressures; modulation of fetal placental and somatic vascular resistances by means of blood pressure controlled production of angiotensin; and somatic autoregulation of flow. A systems analysis incorporates these and other fetal cardiovascular functions and this analysis was modelled for computer simulation. Given physiologically plausible values for known cardiovascular parameters in the fetal sheep, the model reproduced in detail a variety of experimental protocols with known outcomes; these included the normal fetus, the fetus after bilateral nephrectomy, the nephrectomized fetus infused with angiotensin, the intact fetus infused with NaCl solutions, the fetus with lymphatic obstruction and the severely anaemic fetus. The systems analysis demonstrated that fetal cardiac failure constituted the strongest stimulus for the formation of fetal oedema of any tested pathological intervention.

Angiotensin II↗