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Biomedical subjects

J R Robinson

Publications and source records attributed to J R Robinson.

At least 19 recordsLinked to original sources

Drug delivery to the posterior segment of the eye: some insights on the penetration pathways after subconjunctival injection.

The aim of this study is to gain an understanding of the penetration pathways for a drug to enter the posterior segment of the eye after subconjunctival injection. 14C-mannitol was injected subconjunctivally, and 14C-mannitol and 14C-inulin were injected intracamerally. The aqueous and vitreous levels were determined at selected time points. The results of subconjunctival injection and intracameral injection were compared. The vitreous level of the dosed eye is much higher than that of the corresponding contralateral eye after subconjunctival injection so that the recirculation pathway is not a dominant penetration pathway. In addition, the results also showed that it is unlikely for significant amounts of drug to move from the aqueous to the vitreous chamber after subconjunctival injection. Therefore, direct penetration is the dominant pathway for a subconjunctivally injected compound to enter the vitreous chamber.

Animals↗

Carrier-enhanced human growth hormone absorption across isolated rabbit intestinal tissue.

Small molecular weight alpha acid derivatives are able to enhance the intestinal absorption of human growth hormone through isolated rabbit intestinal tissue. The enhancement is not through the usual tissue modification associated with traditional penetration enhancers nor is it through an active transport process. Rather these small molecules associate with human growth hormone in solution to make it more transportable through intestinal tissue. It is shown that the enhancer has specificity for a particular protein and the enhancer and human growth hormone must be in solution together to be effective, i.e. pretreating the tissue with enhancer and then adding the protein does not increase tissue permeability. Moreover, the enhancer does not increase the permeability of mannitol or progesterone, thus providing additional evidence of specificity and establishing that these agents are not classical penetration enhancers.

Algorithms↗

Bioadhesive-based dosage forms: the next generation.

Prolonged contact time of a drug with a body tissue, through the use of a bioadhesive polymer, can significantly improve the performance of many drugs. These improvements range from better treatment of local pathologies to improved drug bioavailability and controlled release to enhanced patient compliance. There are abundant examples in the literature over the past 15 years of these improvements using first generation or "off-the-shelf" bioadhesive polymers. The present mini-review will remind us of the success achieved with these first-generation polymers and focus on proposals for the next-generation polymers and attendant benefits likely to occur with these improved polymeric systems.

Adhesives↗

Feeding problems, sleep disturbances, and negative behaviors in a toddler.

Tiffany, a 3-year-old girl, was referred to the developmental and behavioral pediatrics service for evaluation of significant and persistent negative behaviors associated with refusal to eat at meal time and constant snacking during the past 3 months. She lost 2 pounds, but her weight for her height was at the 50th percentile. Her mother indicated that Tiffany had frequent night awakenings (>10) and late sleep onset (between 12:00 and 1:00 a.m.). Her mother described her as being "easily frustrated," getting upset and angry very quickly. Tiffany was identified at an early intervention program as having mild to moderate developmental delays in pragmatic speech, gross and fine motor skills, and social interaction skills. Tiffany was born at 33 weeks gestation and was hospitalized for 10 days without significant perinatal problems. She was readmitted at 2 months of age when she was diagnosed with gastroesophageal reflux, lactose intolerance, sleep apnea, and bradycardia. She was discharged with an apnea monitor. A seizure disorder was diagnosed at 1 year of age and reactive airway disease at 2 years of age. At the time of the referral to the developmental and behavioral pediatrics service, Tiffany was followed by multiple services, including cardiology, neurology, gastroenterology, psychology, and pulmonary. Pharmacologic therapies included albuterol and cromalyn inhalers, phenobarbital, valproic acid, levocarnitine, ranitidine, and an inhaled steroid. She continued to use the apnea monitor each night, although three sleep studies demonstrated a normal sleep pattern with no evidence of apnea or bradycardia. A recent electroencephalogram was normal. Tiffany lives with her mother and maternal grandparents. Her mother is morbidly obese with a history of asthma and depression. She was infertile for a 10-year period, which she attributed to the stress associated with living with an abusive man. Tiffany was the result of a subsequent, brief relationship with another man; she has not had contact with her father. Her mother is a licensed practical nurse who has not worked as a nurse since Tiffany's birth. An interdisciplinary treatment approach to Tiffany's multiple biological and behavioral problems was implemented by admitting her to a collaborative care unit at a children's hospital.

Anxiety↗

Improvement in function after valgus bracing of the knee. An analysis of gait symmetry.

The use of a valgus brace can effectively relieve the symptoms of unicompartmental osteoarthritis of the knee. This study provides an objective measurement of function by analysis of gait symmetry. This was measured in 30 patients on four separate occasions: immediately before and after initial fitting and then again at three months with the brace on and off. All patients reported immediate symptomatic improvement with less pain on walking. After fitting the brace, symmetry indices of stance and the swing phase of gait showed a consistent and immediate improvement at 0 and 3 months, respectively, of 3.92% (p = 0.030) and 3.40% (p = 0.025) in the stance phase and 11.78% (p = 0.020) and 9.58% (p = 0.005) in the swing phase. This was confirmed by a significant improvement at three months in the mean Hospital for Special Surgery (HSS) knee score from 69.9 to 82.0 (p < 0.001). Thus, wearing a valgus brace gives a significant and immediate improvement in the function of patients with unicompartmental osteoarthritis of the knee, as measured by analysis of gait symmetry.

Adult↗

Microbial populations, fermentation end-products, and aerobic stability of corn silage treated with ammonia or a propionic acid-based preservative.

We studied the effects of ammonia treatment on microbial populations during the fermentation of corn silage. We also compared the effects of ammonia to a preservative containing buffered propionic acid and other antifungal compounds on the fermentation and aerobic stability of corn silage. In the first experiment, whole-plant corn was ensiled without treatment or treated with ammonia-N to supply an additional 0.3% N (fresh-forage basis). The addition of ammonia immediately increased silage pH and had no effect on numbers of lactic acid bacteria, but delayed their growth compared with untreated silage. Numbers of enterobacteria declined more slowly, but numbers of yeasts and molds declined more quickly in silage treated with ammonia. During the early stages of ensiling, lactic acid increased more rapidly in untreated than in treated silage. The reverse was true for acetic acid concentrations. When exposed to air, growth of yeasts and molds was delayed in ammonia-treated silage. In a second experiment, various levels (0.1 to 0.3%, fresh weight) of ammonium-N or a preservative with buffered propionic acid were added to whole-plant corn and allowed to ensile for 106 d. Silage treated with ammonia had a greater ratio of L- to D-lactic acid than did other silages. Untreated silage was aerobically stable for 32.3 h, whereas the low (42 h) and moderate (52.7 h) concentrations of both additives numerically improved aerobic stability. High concentrations of ammonia-N (0.3%) or a buffered propionic acid preservative (0.3%), markedly improved the aerobic stability of corn silage (82 and 69 h for ammonia and propionic acid-treated silage, respectively).

Ammonia↗

Transport of human growth hormone across Caco-2 cells with novel delivery agents: evidence for P-glycoprotein involvement.

Emisphere Technologies, Inc. has synthesized a series of small molecules which have been shown to improve protein absorption through mucosal tissue. This enhancement is specific between protein and a particular delivery agent. Despite the specificity of interaction, the mechanism of enhanced tissue penetration is still unclear. The purpose of this work is to understand the enhancement mechanism(s) of these delivery agents by using Caco-2 cells as a model membrane. It was found that the bidirectional transepithelial fluxes of human growth hormone (hGH) in the presence of these delivery agents across human intestinal epithelial Caco-2 cell line showed marked asymmetry. Average permeability coefficient values obtained in the apical (AP) to basolateral (BL) direction were lower than those of the reverse (BL to AP) direction. On the other hand, the fluxes for human growth hormone alone were symmetric. When P-glycoprotein inhibitors were included in the transport medium, the permeability coefficient values of BL to AP direction were significantly decreased while the transport was increased in the reverse direction in the presence of delivery agents. P-glycoprotein inhibitors had no effect on the transport of human growth hormone alone. This study shows that human growth hormone alone can be transported across Caco-2 cells in very limited quantities by passive diffusion, but in the presence of delivery agents, human growth hormone can be effluxed in a P-glycoprotein-mediated fashion. This also indirectly shows that the human growth hormone has become more lipophilic in the presence of delivery agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Transcellular and lipophilic complex-enhanced intestinal absorption of human growth hormone.

PURPOSE: To evaluate the transcellular mechanism of novel enhancers absorption enhancement of human growth hormone (hGH), by examining the involvement of a P-glycoprotein-like efflux system, changes in membrane fluidity, and membrane damage. METHODS: Caco-2 cell monolayers were grown on Snapwell filter supports and placed in a side-by-side diffusion apparatus. Transport in both the apical to basolateral (AP to BL) and basolateral to apical (BL to AP) direction was measured at different temperatures and in the presence of potential inhibitors. Fluorescence anisotropy measurement was used to measure membrane fluidity. The fluorescence anisotropy of DPH- and TMA-DPH-labeled cell suspensions was measured at room temperature. LDH (a measure of cytosolic lactate dehydrogenase) leakage assay was used to evaluate cytotoxicity. RESULTS: The bi-directional transepithelial fluxes of hGH in the presence of these novel enhancers across Caco-2 cells showed marked asymmetry. Average permeability coefficient values obtained in the apical to basolateral (AP to BL) direction were lower than those of the reverse (BL to AP) direction. On the other hand, the fluxes for hGH alone were symmetric. When P-gp-like efflux inhibitors were included in the transport medium, the permeability coefficient value of BL to AP direction was significantly decreased while the transport was increased in the reverse direction in the presence of novel enhancers. In addition, lowering the temperature to 25 degrees C completely eliminated the asymmetry of hGH transport in the presence of novel enhancers. It was also shown by fluorescence anisotropy that these novel enhancers alone only slightly increased membrane fluidity. On the other hand, upon addition of hGH to the novel enhancers, the cell membrane showed a dramatic change as compared to treatment with novel enhancers alone. The results from the LDH assay showed that the novel enhancers and/or hGH did not cause cell damage, at least up to 1 hour, and the damage seen at the 2 hour point is also much lower than other known enhancers. CONCLUSIONS: This study shows that human growth hormone alone cannot be transported across Caco-2 cells, except in small quantities, by passive diffusion, but in the presence of novel enhancers, human growth hormone permeation is substantial. In addition, the asymmetry of transport of the complexed hGH appears to be due to a P-gp-like efflux system. Assuming that the present substrate specificity of the P-gp-like efflux system shows the same preference for hydrophobic molecules as p-gp, the present work also indirectly shows that human growth hormone has become more lipophilic in the presence of these novel enhancers. Furthermore, membrane fluidity data also supports the premise that these novel enhancers interact and stabilize hGH, to make them more hydrophobic and easier to be transported through cell membranes.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Partially unfolded proteins efficiently penetrate cell membranes--implications for oral drug delivery.

We have previously reported on the biological activity of members of a library of low molecular weight compounds (carriers) that enable the oral delivery of proteins (Milstein, Proceedings of the 1995 Miami Bio/Technology Winter Symposium on Protein Engineering and Structural Biology, IRL Press at Oxford University Press, 1995, p. 13; Leone-Bay et al., J. Med. Chem. 38 (1995) 4263-4269; Leone-Bay et al., J. Med. Chem. 39 (1996) 2571-2578; [1-3]). When rats or primates are orally administered a solution of carrier and either recombinant human alpha-interferon (rhIFN), insulin or recombinant human growth hormone (rhGH) significant serum concentrations of the proteins are detectable. The transport activity of these compounds is positively correlated with their structural effects on the protein molecules. Direct measurement of the interaction of these carrier molecules with the proteins indicates that they reversibly destabilize the native state of the molecule favoring a partially unfolded conformation. Apparently these intermediate protein conformations are transport competent and are able to be absorbed through the intestinal tissue and into the bloodstream. Since the measured binding of the carriers to the partially unfolded proteins is relatively weak (Kb = 100 M(-1)) and the systemic activity of the proteins appears to be unaffected, the changes in the structure of the proteins are manifestly reversible.

Administration, Oral↗

Differential induction of apoptosis by fludarabine monophosphate in leukemic B and normal T cells in chronic lymphocytic leukemia.

Fludarabine (F-ara-A), an adenine nucleoside analog with efficacy in B-cell chronic lymphocytic leukemia (B-CLL), has also been shown to have a long-lasting suppressive effect on T lymphocytes. In heterogeneous clinical samples, apoptosis cannot be detected by standard methods in small cellular subsets. We developed, therefore, a combined assay of in situ end-labeling of nicked DNA by terminal deoxynucleotide transferase, with measurements of cellular DNA content and surface antigens (CD3, CD4, CD8, and CD19) by multiparametric flow cytometry. This assay was used to determine F-ara-A-induced apoptosis in different lymphocyte subsets from CLL patients and normal controls treated with F-ara-A in vitro. Apoptosis was also correlated to bcl-2 protein levels. We observed a direct effect of F-ara-A on both B-CLL and T lymphocytes. The response to F-ara-A in B-CLL lymphocytes in vitro was Rai stage-dependent, the early-stages being more responsive (P = .01). Higher levels of spontaneous apoptosis were observed in B-CLL lymphocytes from early stage patients (P = .02). No difference was observed in spontaneous apoptosis of normal T cells in B-CLL, although T lymphocytes in late-stage disease were more sensitive to F-ara-A-induced apoptosis. Incubation with cyclosporin A did not affect B-CLL and T-lymphocyte survival compared with control cultures. Results suggested a direct apoptotic effect of F-ara-A on B-CLL lymphocytes that decreases with increasing clinical stage. No correlation was found between bcl-2 and spontaneous or F-ara-A-induced apoptosis. Apoptosis occurred at all cell-cycle stages and was not restricted to cells in S phase. The mechanisms of this stage-dependent apoptosis in CLL remain to be elucidated.

Antigens, CD19↗

The natural history of mental disorder in old age: Alzheimer's disease and depressive illness compared.

BACKGROUND: Depressive illness (DI) and Alzheimer's disease (AD) are important causes of morbidity in old age and the relationships between these two disorders are uncertain. METHOD: In a prospective, descriptive, comparative study of consecutive referrals aged over 65 years to one consultant, 218 patients with AD and 280 patients with DI were followed up for 15 years. RESULTS: The prognosis of DI uncomplicated by physical illness at referral was reasonably good and 5-year survival was double that of AD. The rate of occurrence of AD in DI is no greater than in the general population. The higher mortality from cancer in DI than in AD is unexplained but may relate to differences in aetiology of these two disorders. CONCLUSION: Although their symptoms frequently overlap, AD and DI are distinct disorders with very different prognoses and accurate diagnosis may have important implications for appropriate treatment.

Aged↗

Mechanistic studies on effervescent-induced permeability enhancement.

PURPOSE: To determine the mechanism(s) by which effervescence induces penetration enhancement of a broad range of compounds ranging in size, structure, and other physiocochemical properties across rat and rabbit small intestinal epithelium. METHODS: Effervescent induced penetration enhancement was investigated in vitro by utilization of a modified Ussing chamber diffusion cell apparatus and in vivo by single-pass intestinal perfusion. RESULTS: Carbon dioxide (CO2) bubbling directly onto rabbit ileum epithelium induced an increase in drug permeability. Mechanistic studies indicated that effects due to CO2 bubble evolution, such as increased drug dissolution rates, mucus thinning/stripping, and pH buffer effects did not contribute to increases in drug flux. Cellular enzyme (5'-ND and LDH) and total protein release assays did not indicate cell membrane perturbation and/or damage. CO2 bubbling induced a reduction in transepithelial electrical resistance (TEER) indicating epithelial disruption due to a structural change of the paracellular pathway. This was further substantiated by a MW dependence on paracellular marker flux. In addition, tissue recovery was relatively rapid, approximately 20 min. CONCLUSIONS: CO2 bubbling directly onto the intestinal epithelium induced enhanced drug permeability due to an alteration of the paracellular pathway. This, in addition to fluid flow and membrane hydrophobicity concepts, may account for observed increases in drug flux.

Animals↗

Scleral permeability to hydrocortisone and mannitol in the albino rabbit eye.

To further explore barrier properties of the sclera, the diffusion of 3H-hydrocortisone and 14C-mannitol was measured across isolated rabbit scleral membrane. In vitro permeability studies were performed using side by side diffusion cells. Bicarbonated Ringer Solution with oxidized glutathione (GBR) at pH 7.4 was the perfusion medium, and the temperature was kept at 37 degrees C. Diffusion of hydrocortisone through the cornea was also measured to compare scleral and corneal permeation. Scleral permeability was found to be five times greater than corneal permeability. Drug analyses were performed by radionuclide counting (LSC), and permeability coefficients were obtained. In vitro metabolism of hydrocortisone was examined by incubation of tissue in hydrocortisone solution in GBR for 5 hours and 37 degrees C. Permeability coefficients of hydrocortisone diffusion through the sclera were also obtained at 25 degrees C, 15 degrees C, and 5 degrees C. Activation energy of scleral transport of hydrocortisone was calculated from an Arrhenius plot. The low activation energy suggests an aqueous pore pathway unlike permeation of the drug across the cornea which uses a transcellular pathway.

Animals↗

Estimating the burden of disease. Comparing administrative data and self-reports.

OBJECTIVES: A cardiovascular health survey of a representative sample of the adult population of Manitoba, Canada was combined with the provincial health insurance claims database to determine the accuracy of survey questions in detecting cases of diabetes, hypertension, ischemic heart disease, stroke, and hypercholesterolemia. METHODS: Of 2,792 subjects in the survey, 97.7% were linked successfully using a scrambled personal health insurance number. Hospital and physician claims were extracted for these individuals for the 3-year period before the survey. RESULTS: The authors found no benefits to using restrictive criteria for entrance into the study (ie, requiring more than one diagnosis to define a case). Using additional years of data increased agreement between data sources. Kappa values indicated high levels of agreement between administrative data and self-reports for diabetes (0.72) and hypertension (0.59); kappa values were approximately 0.4 for the other conditions. Using administrative data as the "gold standard," specificity was generally very high, although cases with hypertension and hypercholesterolemia (diagnosed primarily by laboratory or physical measurement) were associated with a lower specificity than the other conditions. Sensitivity varied markedly and was lowest for "other heart disease" and "stroke". For diabetes and hypertension, inclusion criteria calling for more than one diagnosis reduced the accuracy of case identification, whereas increasing the number of years of data increased accuracy of identification. For diabetes and hypertension, self-reports were fairly accurate in detecting "true" past history of the illness based on physician diagnosis recorded on insurance claims. CONCLUSIONS: This study demonstrates the feasibility of linking a large health survey with administrative data and the validity of self-reports in estimating the prevalence of chronic diseases, especially diabetes and hypertension. A linked data set offers unusual opportunities for epidemiologic and health services research in a defined population.

Adolescent↗

Reliability of the Manitoba Mental Health Management Information System for Research.

OBJECTIVES: To determine the accuracy of data contained in Manitoba's Mental Health Management Information System (MHMIS) as compared with client charts and to determine which factors influence completeness and accuracy. METHODS: Data on diagnosis, open date and close date, demographic information, and contact information were obtained from client charts and compared with data extracted from the MHMIS. Semistructured interviews were conducted with individuals who contribute data to the MHMIS. RESULTS: Data on required demographic variables, primary diagnosis, and open and close dates are highly similar in the 2 sources. The correlation between data sources on the number of client contacts is also good. CONCLUSION: This study establishes the reliability of MHMIS data. MHMIS data, in combination with hospital abstracts and physician claims data, provide the information needed to serve as a psychiatric case register (PCR) and can be used for psychiatric epidemiology as well as for planning, monitoring, and evaluating mental health services.

Cross-Sectional Studies↗

Vaginal permeability and enzymatic activity studies in normal and ovariectomized rabbits.

PURPOSE: This study was initiated to develop an animal model, using ovariectomized rabbits, for the post-menopausal human, based on in vitro vaginal tissue permeability and aminopeptidase activity. METHODS: An enkephalin derivative [D-ala(2),N-methyl-phe(4)-glycol(5)][tyrosyl-3,5-(3)H] enkephalin {[(3)H] RX 783006), which has relative enzymatic stability to aminopeptidases and dipeptidyl peptidase, was used as a model peptide drug for permeability experiments. Aminopeptidase activity in vaginal homogenates, as well as in tissue pieces, was determined using 4-methoxy-2-naphthylamides of leucine, alanine, arginine, and glutamic acid as specific substrates. In addition, histological examination of normal and ovariectomized vaginal tissues was performed. RESULTS: Vaginal permeability of the drug was significantly increased in the ovariectomized compared to the intact animal. The full vaginal tissue became thinner and mucosal epithelial thickness was reduced about two-fold after ovariectomization and vaginal cells from the castrated rabbit were typically immature. Aminopeptidase activity, leucine aminopeptidase, aminopeptidase B and A, was the same in vaginal tissue homogenates and whole-tissue specimens in both normal and ovariectomized rabbits whereas the activity of aminopeptidase N was significantly decreased in ovariectomized as compared to normal rabbits. CONCLUSIONS: Based on the present data, the ovariectomized rabbit may be useful as an animal model for postmenopausal vaginal studies.

Aminopeptidases↗