The paradox of transferrin receptor-mediated drug delivery--intracellular targeting or transcellular transport?
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Animals↗
Biomedical subjects
D Shah
Publications and source records attributed to D Shah.
[3H]bosentan binding to human coronary artery: functional correlates.
The binding characteristics and localization of bosentan, an orally active endothelin-1 (ET-1) antagonist, were studied on sections of human coronary artery by in vitro autoradiography. Competition studies were performed to determine the ability of bosentan to prevent [125I]ET-1 binding to the coronary vasculature. The effects of bosentan on ET-1-induced contraction of the coronary artery were also studied in vitro. [3H]Bosentan bound to the tunica media of the human coronary artery. Unlabeled bosentan prevented [125I]ET-1 binding to this vessel in a concentration-dependent manner, and functional studies indicated that bosentan antagonizes ET-1--induced constriction. These data show that bosentan is able to reduce ET-1 binding to the human coronary artery and ET-1 constrictor effects in vitro. Bosentan is an orally active ET-1 antagonist, and these results suggest that this compound might be used to block the effects of locally released ET-1 in pathologic conditions, such as atherosclerosis, angina, and myocardial ischemia.
Autoradiography↗
Acute coronary occlusion during early post-PTCA exercise testing: a rare but avoidable risk.
We describe here one instance of an acute occlusion of an angioplastied LAD coronary artery occurring during a treadmill stress test performed 2 d after the procedure. The occlusion occurred during the recovery period after a reasonably high level of stress was achieved without evidence of ischaemia. Similar instances described in the literature are summarized and discussed. In the light of these data, it might be prudent to avoid early post-PTCA exercise stress testing.
Acute Disease↗
Natural history of secundum atrial septal defect in adults after medical or surgical treatment: a historical prospective study.
OBJECTIVE: To compare outcome in patients with medically treated secundum atrial septal defect (ASD) first diagnosed after the age of 25 with the long-term outcome in a similar group of patients after surgical closure. DESIGN: A historical, prospective, unrandomised study. SETTING: A tertiary referral centre. PATIENTS: All patients with ASD followed up since 1955 who fulfilled the entry criteria and had reached a current age of over 45 years--that is, 34 medical and 48 surgical patients with a mean follow up of 25 years. MAIN OUTCOME MEASURES: Survival, symptoms, and complications. RESULTS: There was no difference in survival or symptoms between the two groups and no difference in the incidence of new arrhythmias, stroke or other embolic phenomena, or cardiac failure. No patient in either group developed progressive pulmonary vascular disease. CONCLUSION: Outcome in adults with ASD was not improved by surgical closure. Because progressive pulmonary vascular disease did not develop in any of these patients its prevention is not a reason for advising closure of ASD in adults.
Adult↗
The establishment of polarity and enhanced transcytosis of transferrin receptors in enterocyte-like Caco-2 cells.
The effect of enterocyte-like differentiation on the transferrin receptor (TfR) polarity in filter-grown Caco-2 cells was studied. The ratio of apical to basolateral TfRs which was found to be approximately 1:1 on the first day after the cells had reached confluence, changed to 1:40 eight days after reaching confluence. The transepithelial electrical resistance (TEER), transport of horseradish peroxidase (HRP) across the monolayer, and total cellular TfR number remained constant over this period. However, the activity of brush border membrane-associated alkaline phosphatase, an established marker for enterocyte differentiation, increased over this 8-day period concurrent with a decrease in apical TfR number. These results suggest that enterocyte-like differentiation rather than tight junction formation is most likely responsible for the polarized distribution of TfRs in Caco-2 cells. The effects of the fungal metabolite brefeldin A (BFA) on TfR distribution and TfR-mediated transcytosis in Caco-2 cells were also studied. BFA caused a marked decrease in the number of basolateral TfRs along with a slight increase in the number of apical TfR. BFA enhanced the TfR-mediated transcytosis of both 125I-Tf and the horseradish peroxidase-Tf conjugate across Caco-2 cells in both apical-to-basolateral and basolateral-to-apical directions. These findings imply a potential application of BFA as an enhancer for TfR-mediated delivery of protein drugs across the intestinal epithelium.
Alkaline Phosphatase↗
Determination of biotin in biotin-conjugated protein by measuring fluorescence polarization.
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Binding, Competitive↗
Effect of stress management on blood pressure in mild primary hypertension.
OBJECTIVE: To establish whether stress management had a larger effect than a control treatment on resting blood pressure, ambulatory blood pressure, and left ventricular mass. DESIGN: A 12 week baseline period of habituation to measurement of blood pressure was followed by randomisation to either stress management or mild exercise for six months and follow up six months later. SETTING: General practice, district general hospital, and medical school. PATIENTS: Of the 184 patients aged under 60 with mild primary hypertension who entered the baseline habituation period, 88 were excluded because they failed to meet the entry criteria or they withdrew from the study. The remaining 46 men and 50 women underwent treatment. INTERVENTIONS: 10 clinical sessions and daily practice at home of either stress management based on relaxation or non-aerobic stretching exercises. Mildly stressful 15 minute interviews before and after treatment. MAIN OUTCOME MEASURES: Diastolic and systolic blood pressure in the clinic and during 12 hours of ambulatory recording, and left ventricular mass measured by echocardiography. RESULTS: The patients' blood pressure fell during habituation (systolic pressure from 152 mmHg to 140 mmHg, diastolic pressure from 98 to 93 mm Hg), but neither resting nor ambulatory blood pressure was changed by the treatments. Left ventricular mass was also unchanged. Blood pressure rose during the stressful interview, but this rise was reduced by stress management (systolic pressure rose by 7.4 mmHg before treatment and by 3.7 mmHg after treatment). CONCLUSION: Stress management of a type advocated for treating mild primary hypertension is ineffective in lowering blood pressure in patients who are well habituated to measuring blood pressure.
Adult↗
Prognosis of patients with breast cancer related to the timing of operation.
Whether the timing of mastectomy during the menstrual cycle influences the prognosis of premenopausal women with breast cancer is controversial. We retrospectively reviewed the cases of 97 regularly menstruating women treated for operable stages of breast cancer. At operation, 55 women were in the perimenstrual phase of the menstrual cycle (days 0 through 6 and days 21 through 36) and 42 were in the periovulatory phase (days 7 through 20). No relationship could be identified between the timing of surgical treatment and subsequent recurrence or survival. The timing of biopsy was also not associated with prognosis. We conclude that no delay of surgical treatment for breast cancer need be based on the phase of the menstrual cycle of premenopausal women.
Adult↗
Effect of lymph composition on an in vitro preparation of the alligator lizard cochlea.
The effects of different artificial lymphs on the cochlear duct of the alligator lizard were studied in an in vitro preparation. The duct was dissected and cemented to the glass floor of a chamber that had been filled with an artificial lymph. The vestibular membrane was removed and latex beads (1-5 microns in diameter) were allowed to settle on the endolymphatic surface of the duct. During perfusion with an artificial lymph solution, the positions of beads were measured and video images of the duct were obtained. Artificial lymphs were isosmotic and included artificial endolymph (AE), artificial perilymph (AP), Leibovitz's L-15 culture medium, an AE solution whose calcium concentration was the same as that of AP, and AE and AP solutions in which gluconate was substituted for chloride ions. Results obtained in AE were consistently different from those in other lymphs. The displacements of beads, the projected area of the papilla, the occurrence of blebs, and direct observation of cells in the duct all indicated that the tissue swelled in AE (with or without 2 mmol/l Ca) but showed no consistent shrinking or swelling in any of the other artificial lymphs. Thus for the solutions we used, the presence of both potassium and chloride was required to elicit the swelling response to isosmotic artificial lymphs. There were some regional differences in the swelling response: the swelling of the endolymphatic surface of the tissue in a direction orthogonal to the basilar membrane surface was smaller on the free-standing region of the basilar papilla than either on the tectorial membrane or on the hyaline epithelial cells. The preparation was osmotically stable in AP and in both AE and AP solutions in which gluconate was substituted for chloride ions. After exposure to these solutions for as much as 300 min, the preparation showed no gross signs of deterioration visible with the light microscope, and continued to exhibit a highly specific osmotic response to the composition of the bathing medium.
Animals↗
New aspects of brain oxidative stress induced by tert-butylhydroperoxide.
Many diseases and aging may be associated with oxidative stress in the brain. However, the effects of oxidative stress in the brain should be more clearly described, especially in terms of effects on brain reduced glutathione (GSH). This issue was addressed by intracerebroventricular injection of a direct-acting oxidative stress inducing agent, tert-butylhydroperoxide. Oxidized glutathione (GSSG) levels in the brain increased by as much as 90-fold during tert-butylhydroperoxide-induced oxidative stress. At the same time, brain GSH levels decreased. The brain appears to retain GSSG and not reduce it or export it efficiently. Vitamin E levels in the striatum increased during tert-butylhydroperoxide-induced oxidative stress. Aging alters the ability of the brain to detoxify an oxidative stress, in that 8-month-old mice retain GSSG in their brains much more than 2-month-old mice. Eight-month-old mice were much more susceptible to tert-butylhydroperoxide-induced toxicity than 2-month-old mice. This may indicate that aging makes the brain more susceptible to oxidative damage.
Aging↗
Effects of lisinopril on cardiorespiratory, neuroendocrine, and renal function in patients with asymptomatic left ventricular dysfunction.
OBJECTIVE: To determine the cardiac, renal, and neuroendocrine effects of lisinopril in men with untreated, symptom free left ventricular systolic dysfunction. DESIGN: A randomised, double blind cross over trial with six week treatment periods to compare lisinopril (10 mg/day) and matching placebo. SETTING: Hospital outpatient department. PATIENTS: Patients with pronounced systolic dysfunction on cross sectional echocardiography due to myocardial infarction at least six months previously, without angina and with no or minimal breathlessness. Eighteen men were identified of whom 15 completed the study. INTERVENTIONS: Lisinopril (10 mg) or placebo given once daily by mouth. MAIN OUTCOME MEASURES: Primary: oxygen consumption at peak exercise. Secondary: resting cardiac function as measured by radionuclide ventriculography and echocardiography, renal function estimated radioisotopically, and plasma indices of neuroendocrine activity. RESULTS: Compared with placebo, lisinopril increased (mean (SD)) peak oxygen consumption during exercise (19.8(3.1) ml/kg/min v 21.4(3.2) ml/kg/min; p < 0.003). Lisinopril did not improve indices of cardiac function at rest. It reduced plasma concentrations of angiotensin II (median values 7 pg/ml to 5 pg/ml; p < 0.02), aldosterone (median values 113 pg/ml to 66 pg/ml; p < 0.05) and atrial natriuretic peptide (median values 69 pg/ml to 40 pg/ml; p < 0.04), but noradrenaline and antidiuretic hormone concentrations did not change. Renal blood flow increased and glomerular filtration rate declined. CONCLUSIONS: Even before the onset of heart failure lisinopril improves the cardiopulmonary response to exercise in patients with systolic ventricular dysfunction.
Angiotensin-Converting Enzyme Inhibitors↗
Cloning, nucleotide sequence, and chromosome localization of the human pleiotrophin gene.
Pleiotrophin (PTN), midkine (MK), and retinoic acid-induced heparin-binding (RI-HB) protein are members of a recently discovered family of developmentally regulated cytokines. We report here the cloning, sequencing, chromosomal localization, and structural organization of the genomic version of the human PTN gene and its comparison to the mouse MK gene. The PTN gene was found to be arranged in five exons and four introns, in a fashion similar to that of the mouse MK gene. Exon 1, as for MK, does not appear to encode amino acid sequence. As in the case of the MK gene, exon 2 encodes the hydrophobic leader sequence of PTN, which constitutes the beginning of gene translation. The signal peptide cleavage site of both genes lies toward the 3' end of exon 2. Exons 3 and 4 of PTN were most closely related to exons 3 and 4 of the MK gene; in particular, six of the ten cysteine residues were coded for in exon 3 and the remaining 4 in exon 4. The intron-exon splice junctions of both genes occurred through the same residues. The two genes were found to be less closely related in the fifth exon which encodes the highly basic C-terminal domains, the translation termination codon, and the polyadenylation signal of both cDNAs. We also report approximately 2000 bp of the 5' untranslated sequence of the PTN gene and the site of initiation of transcription in human placenta. PTN was localized to human chromosome 7q33-34 by fluorescence in situ hybridization. These data confirm the existence of a new gene family of developmentally regulated cytokines.
Amino Acid Sequence↗
Angiotensin-converting enzyme inhibitors, left ventricular dysfunction, and early heart failure.
A study was undertaken to examine the effects of the angiotensin-converting enzyme inhibitor lisinopril on exercise performance in 18 patients with major impairment of left ventricular systolic function. The study was a randomized, double-blind, crossover design, and patients received treatment with either once-daily lisinopril (2.5-10 mg) or placebo for a period of 6 weeks. A total of 15 patients completed the study. Compared with placebo, lisinopril had no significant effect on supine or standing blood pressure or heart rate. Although lisinopril had no effect on exercise duration during a low-intensity exercise protocol, in patients undergoing a high-intensity exercise protocol, there was a trend toward improved exercise time and peak oxygen consumption improved significantly. In addition, treatment with lisinopril resulted in an increase in renal blood flow and a reduction in glomerular filtration rate. Moreover, administration of once-daily lisinopril 10 mg resulted in a decrease in plasma concentrations of angiotensin II, aldosterone, and atrial natriuretic peptide, and an increase in plasma concentrations of active renin.
Aldosterone↗
Brefeldin A enhances receptor-mediated transcytosis of transferrin in filter-grown Madin-Darby canine kidney cells.
The effects of brefeldin A (BFA) on transferrin (Tf) transcellular transport, Tf receptor (TfR) distribution, and TfR-mediated endocytosis in filter-grown Madin-Darby canine kidney (MDCK) cells were studied. BFA (1.6 micrograms/ml) markedly enhanced the transcytosis of 125I-labeled Tf (125I-Tf) in both apical-to-basal and basal-to-apical directions; yet, BFA did not enhance the transcytosis of either native horseradish peroxidase (HRP) or membrane-bound HRP-poly(L-lysine) conjugates. Furthermore, this enhanced transcytosis of 125I-Tf was abolished either by competition with excess unlabeled Tf or by incubation at temperatures less than or equal to 25 degrees C. In addition, BFA treatment to MDCK cells: (a) increased 125I-Tf specific binding to the apical membrane and decreased 125I-Tf specific binding to the basal membrane; (b) decreased TfR recycling at the basolateral membrane; (c) altered the apical/basolateral distribution of TfRs in favor of the apical side; and (d) markedly increased 59Fe extraction, but not transcytosis, from apically endocytosed 59Fe-loaded Tf. These effects are consistent with a model in which BFA alters the traffic pattern of internalized Tf by decreasing basolateral TfR recycling, while diverting the nonrecycled fraction to the apical side of the cell. Our results indicate that, unlike the reported inhibition of polymeric IgA transcytosis (Hunziker, W., Whitney, J. A., and Mellman, I. (1991) Cell 67, 617-627), BFA can enhance the transcytosis of Tf in MDCK cells. Thus, by altering the intracellular traffic of ligand-receptor complexes, BFA can elicit either a decrease or an increase in transcytosis depending on the nature of the intracellular receptor processing.
Animals↗
Stability of the recombinant hepatitis B core antigen.
The recombinant gene for hepatitis B core antigen (HBcAg) was cloned and expressed, and the protein was purified from Escherichia coli cultures. Purified HBcAg was tested for the effects of various physical and chemical agents on its immunoreactivity by a paramagnetic particle-based enzyme immunoassay. Recombinant HBcAg retained its immunoreactivity when heated at 70 degrees C for 60 min but was inactivated at 85 degrees C in 10 min. It was stable between pHs 5 and 10.5 but not at pHs 2 and 13.5. Treatment with sodium dodecyl sulfate (SDS), ethanol, and methanol caused a significant loss in HBcAg reactivity. The proteolytic enzymes papain and bacterial protease (type VIII from Bacillus licheniformis) degraded HBcAg significantly, but trypsin and chymotrypsin did not. The effect of combined SDS and 2-mercaptoethanol on recombinant HBcAg was an immediate loss in immunoreactivity, followed by rapid recovery to about 50% of the initial level. This level was maintained for 24 to 48 h and was followed by an almost total loss of HBcAg in about 120 h.
Base Sequence↗
Reliability of ultrasound in the prenatal diagnosis of urinary tract abnormalities.
To investigate the ability of ultrasonography to detect urinary tract abnormalities prenatally, we reviewed the records of 26 pregnancies diagnosed by prenatal ultrasound to have urinary tract anomalies. We compared the prenatal diagnoses with postnatal renal and urinary tract pathology. This comparison showed different degrees of agreement for different prenatal diagnoses (2 individuals had more than one diagnosis): 4 of 8 for multicystic kidneys, 1 of 1 for polycystic kidney disease, 1 of 2 for renal agenesis, 6 of 7 for ureteropelvic junction obstruction, 1 of 3 for posterior urethral valves, 4 of 5 for no pathology noted, and 2 of 2 for other abnormalities. Prenatal diagnosis and postnatal findings were in agreement in 68% of cases. Varying levels of diagnostic reliability should be considered when managing pregnancies complicated by fetal urinary tract abnormalities and subsequent postnatal evaluation and diagnosis. Further efforts are needed to improve on the techniques and reliability of prenatal diagnosis of urinary tract abnormalities.
Female↗
Palliative radiotherapy--counting the costs of changing practice.
"Working for Patients', the government's review of the National Health Service (NHS) advocates reforms which have led inevitably to pressure for medical specialities to review both the outcomes of their services and the resources used in achieving these outcomes. This paper considers these issues in the context of provision of palliative radiotherapy for patients with incurable cancers and presents the results of a study which evaluated the costs of radiotherapy. In addition to producing some of the first detailed cost estimates for the delivery of radiotherapy, this exercise highlighted the methodological and practical difficulties of undertaking such studies. As increasing pressure to evaluate cancer therapy is a prominent feature of a 'post-NHS Review' world, lessons learnt from this study may also be applicable to the audit of other cancer therapies. Efficient audit practices will, of course, have to evaluate the benefits (in terms of enhancements to length and quality of life) as well as the costs of cancer therapies.
Capital Expenditures↗
Prenatal diagnosis of fetal cephalocele: a sonographic spectrum.
We present the findings in a series of 15 fetuses diagnosed as having a cephalocele. Eleven cephaloceles were located in the occipital region and two each at the vertex and the frontonasal region. Eleven fetuses were diagnosed before 24 week's gestation. Nine families opted for an interruption. Of the two fetuses that went to term, one had a benign meningocele and is growing normally at 18 months, the other died in the neonatal period of associated cardiac anomalies. Of the four fetuses diagnosed after 24 weeks, one is normal (after surgery) at 9 months, two are severely handicapped, and one died in the immediate postpartum period.
Diagnosis, Differential↗