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Biomedical subjects

S Patel

Publications and source records attributed to S Patel.

At least 469 records · Page 26Linked to original sources
PubMed1995

Tear lipid layer structure and stability following expression of the meibomian glands.

In a masked investigation, tear lipid layer structure and non-invasive break-up time (NIBUT) of both eyes of 40 normal subjects were assessed with the Keeler Tearscope after unilateral manual expression of meibomian fluid from the lower lid. The HIRCAL grid (modified keratometer mire) provided the additional measure of tear thinning time (TTT). Twenty untreated normal subjects formed the control group. No difference in lipid layer structure or stability was observed between the right and left eyes of the controls. The NIBUT of the treated eyes was significantly higher than that of the untreated contralateral eyes which was, in turn, greater than that of the control eyes. Lipid layer thickness in the treated eyes was significantly higher than that in the untreated contralateral eyes and the controls but did not differ between the latter two groups. The TTT of the treated eyes was not significantly different from that of the untreated contralateral eyes but both were significantly higher than that of the controls. Unilateral meibomian gland expression results in increased lipid layer thickness and tear stability. A possible reason for the slight increase in tear stability in the untreated contralateral eyes is a complimentary reflex lacrimation induced by mechanical stimulation of the treated eye. Differences between the results of the Tearscope and HIRCAL grid are attributed to differences in the techniques of tear stability measurement.

Adolescent↗
PubMed1995

The isolation and culture of adult mouse colonic epithelium.

A technique is described for the reproducible primary culture of colonic epithelium from adult mice. A collagenase-dispase digestion technique (adapted form Evans et al. 1992) is used to release the epithelium, followed by differential sedimentation to produce a high purity crypt preparation with maintained structural integrity and minimal mesenchymal contamination. The crypt units attach to collagen coated plastic within 24 h and the epithelial cells quickly begin to migrate outwards producing a monolayer surrounding the attached crypts. Electron microscopy revealed that the migrating epithelial cells possessed both desmosomes and microvilli. Proliferation in the colony supports the outward migration of cells until the migratory cells of adjacent colonies connect and a confluent monolayer begins to form. Proliferation is routinely maintained for 10 days (although cultures have now been maintained without subculturing for 35 days) and is demonstrated by increased cell numbers in spite of continuous cell loss into the culture media. Culture growth is enhanced by increasing concentrations of fetal calf and mouse serum and EGF but does not appear to respond significantly to added transferrin. Growth is also stimulated by a murine small intestinal extract thought to contain a potentially novel growth factor or cocktail of factors. This culture model has considerable potential for studies on growth factor control of this carcinoma susceptible tissue and its differentiated function as well as studies into the mechanisms of carinogenesis.

Animals↗
PubMed1995

Craniofacial approaches to sinus malignancy.

Craniofacial approaches to sinonasal malignancies that abut or penetrate the skull base allow isolation of tumor from its vascular supply, identification and preservation of neurovascular structures adjacent to tumor, and en bloc resection with meaningful margins. The transfacial access, and the adjuncts of lateral facial split and mandibular swing, have been presented. An extended frontal craniotomy, which encompasses the superior orbital rims, affords exposure of the nasal, sinus, orbital, and intracranial components of a dissection in one surgical field. The skull base team approach yields a high cure rate for aggressive but benign skull base neoplasms, such as meningiomas, and when combined with external beam irradiation the only nonpalliative regimen for sinonasal malignancies that penetrate the anterior or middle fossa.

Adult↗
PubMed1994

Screening and optimization strategies for macromolecular crystal growth.

Today the determination of successful crystallization conditions for a particular macromolecule remains a highly empirical process. Sparse-matrix and grid-screening procedures are rapid and economical means to determine preliminary crystallization conditions. During optimization the variable set (pH, precipitant type and precipitant concentration) utilized in these procedures is screened in an attempt to determine appropriate conditions for the nucleation and growth of single crystals suitable for X-ray diffraction analysis. Unfortunately, in many cases this strategy will not produce single crystals suitable for X-ray diffraction analysis. We have explored, in an empirical sense, other tools for use during optimization. First, a new screening protocol is evaluated which employs less classical precipitating agents. Second, a set of 24 electrostatic crosslinking agents are evaluated for their ability to promote crystallization. Third, a panel of more than 30 detergents are evaluated for their ability to prevent sample aggregation and influence crystal growth.

Journal Article↗
PubMed1994

Crystallization of macromolecules in silica gels.

Procedures are described for the crystallization of proteins, nucleic acids and viruses in a silica-gel matrix using otherwise standard reagents and conditions. Methods are given based on both vapor diffusion in a sitting drop and liquid-liquid diffusion. Using a variety of macromolecules our results suggest that the gel matrix suppresses nucleation, reduces the rate of growth, and generally leads to larger, higher-quality crystals of enhanced stability. Presumably these effects arise from the decreased mobility of the macromolecules and their flux at the crystal surface during growth.

Journal Article↗
PubMed1994

Characterization of crystals of satellite panicum mosaic virus.

Satellite panicum mosaic virus (SPMV) has been purified from pearl millet and obtained in a variety of different crystal forms, at least two of which appear suitable for high resolution X-ray diffraction analysis. The first is of cubic space group P4(2)32 with a = b = c = 183.1 A and two virus particles in the unit cell. The second is of a primitive orthorhombic space group with a = 166.1 A, b = 266.7 A and c = 269.1 A, with four virus particles in the unit cell. While the cubic crystal has as its asymmetric unit one twelfth of the icosahedron, or five capsid protein subunits, the asymmetric unit of the orthorhombic crystals is an entire particle. The cubic crystals diffract to at least 2.8 A resolution. We have also succeeded in crystallizing, but not yet characterizing the master virus, PMV.

Crystallization↗
PubMed1994

The muscarinic receptor agonist L-658,903 modulates the in vivo accumulation of inositol monophosphates in mouse brain.

In the present study we examined the effects of lithium chloride and the muscarinic receptor agonists pilocarpine hydrochloride and L-658,903 (3-(3-methyl-1,2,4-oxadiazol-5-yl) quinuclidine hydrochloride) upon the accumulation of inositol monophosphates in mouse brain using a radiometric technique. Lithium was able to stimulate dose dependently the accumulation of inositol monophosphates with a minimal effective dose (MED) of 3 mEq/kg s.c. and maximal effect seen at 20 mEq/kg. This corresponded to an increase in the radioactivity in the inositol monophosphate fraction from 1.4 +/- 0.06% to 4.6 +/- 0.60%. The response was time-dependent, with a peak effect observed at 4 h post administration and returning to basal levels by 48 h. The muscarinic receptor agonist pilocarpine (MED 10 mg/kg i.p.) was able to enhance dose dependently the response to 10 mEq/kg lithium, with a maximum response seen at 30 mg/kg (9.3% of the total brain radioactivity present in the inositol monophosphate fraction). The efficacious oxadiazole muscarinic receptor agonist L-658,903 also enhanced the response to lithium, producing a maximal effect of 10.4% of the total brain radioactivity present in the inositol monophosphate fraction at 1 mg/kg i.p. This stimulation was blocked by 1 mg/kg scopolamine i.p. but not by 1 mg/kg N-methylscopolamine. These results demonstrate the linkage of muscarinic receptors to the accumulation of inositol monophosphates in vivo, and confirm that following peripheral administration L-658,903 is a potent efficacious at muscarinic receptors within the central nervous system.

Animals↗
PubMed1994

Characterisation of CCKB receptors on GH3 pituitary cells: receptor activation is linked to Ca2+ mobilisation.

Cholecystokinin receptors on GH3 rat anterior pituitary cells have been characterised using radioligand binding and Ca2+ mobilisation. [125I]Bolton Hunter CCK-8s (BHCCK) bound dose dependently to GH3 cells (Kd 85 pM, Bmax 23 fmol/mg protein). Competition curves with CCK-8s (IC50 2.4 nM), pentagastrin (IC50 25 nM) and devazepide (IC50 820 nM), were consistent with a population predominantly of CCKB receptors. Binding of [125I]BHCCK to lysed cells was inhibited by 10 microM GTP-gamma-S and 10 microM GppNHp, suggesting the receptor was linked to a guanine nucleotide binding protein. Intracellular Ca2+ mobilisation was a functional consequence of CCKB receptor activation in GH3 cells using the fluorescent dye fura-2. CCK-8s (0.1 nM-1 microM) and the selective CCKB receptor agonist, pentagastrin, (0.1 nM-100 microM) dose dependently increased intracellular Ca2+ with a similar maximal increase of 2.85-fold and 2.77-fold respectively. Response to a submaximal dose of the CCKB receptor agonist pentagastrin (100 nM) was dose dependently blocked by the CCKB receptor antagonist L-365,260. GH3 cells may therefore provide a useful model to study CCKB receptor coupling in a pituitary cell line.

Animals↗
PubMed1994

Hypothermia induced by cholinomimetic drugs is blocked by galanin: possible involvement of ATP-sensitive K+ channels.

Central administration of galanin in the mouse dose-dependently blocked the hypothermia induced by the muscarinic receptor agonist, 2-ethyl 8-methyl-2,8-diazospiro[4,5]decan-1,3-dion hydrobromide, RS86 (minimum effective dose, MED = 3 nmol) and the acetylcholinesterase inhibitor tetrahydroaminoacridine, (MED = 3 nmol). This inhibitory effect was reversed over the dose range (0.1, 0.3, 1, 3 nmol) by the galanin receptor antagonist galantide (MED = 0.3 nmol). Furthermore, the ATP-sensitive K+ channel blockers glibenclamide (MED = 1 nmol) and gliquidone (10 nmol) both prevented the inhibitory effects of galanin on RS86 induced hypothermia. Glibenclamide (10 nmol) also reversed the inhibitory effects of galanin on tetrahydroaminoacridine induced hypothermia. Preincubation of rat cortical membranes with galanin (10 nM, 1000 nM) in vitro had no effect on binding affinity, receptor number or pharmacology of the rat cortical muscarinic receptor. In contrast to the high affinity of glibenclamide, galanin only weakly displaced [3H]glibenclamide binding in mouse whole brain homogenates (36% at 10 microM). These studies suggest that the inhibitory effect of galanin on cholinergically mediated hypothermia induced by RS86 and tetrahydroaminoacridine may be exerted via an action at ATP-sensitive K+ channels but is unlikely to be acting directly at the site labelled by [3H]glibenclamide.

Adenosine Triphosphate↗
PubMed1994

A second generation of non-peptide cholecystokinin receptor antagonists and their possible therapeutic potential.

The profile of an acidic series of benzodiazepine CCK-B receptor antagonists is described. The tetrazolyl urea derivative L-368,935 had high affinity (CCK-B IC50 0.1 nM) and was one of the most selective (CCK-B/CCK-A 10,000) CCK-B antagonists known. L-368,935 was a CCK-B antagonist with high affinity on the rat ventromedial hypothalamic slice preparation (Kb 0.6 nM) and also blocked pentagastrin-induced calcium mobilization in GH3 cells. L-368,935 had potent in vivo activity and antagonized pentagastrin-induced gastric acid secretion in the anesthetized rat and CCK-8S-induced aspartate release using microdialysis in the striatum of conscious rats. Activity within the central nervous system was confirmed by a mouse ex vivo binding assay and by direct measurement of the compound within the central nervous system using an HPLC assay. A second generation of CCK-B receptor antagonists such as L-368,935 will be important in determining the therapeutic potential of this class of compound in man.

Animals↗
PubMed1994

Measurement of central nervous system activity of systemically administered CCKB receptor antagonists by ex vivo binding.

In the present study we have described an ex vivo binding assay in mice to measure the central nervous system (CNS) activity of systemically administered CCKB receptor antagonists. This assay incorporated a transcardiac perfusion step to remove the residual blood from the brain, which otherwise may result in an overestimation of CNS activity. The benzodiazepine CCKB receptor antagonist L-365,260 had marked CNS activity in this assay following i.v. (ED50 12.0 mg/kg) and p.o. (ED50 20.0 mg/kg) administration, whereas the dipeptoid CCKB receptor antagonist, CI988 exhibited relatively weak CNS activity following i.v. injection (ED50 > 30.0 mg/kg). In contrast, following i.c.v. administration, CI988 potently inhibited ex vivo binding of [125I]Bolton Hunter-CCK-8S to mouse brain. The recently described acidic tetrazole CCKB receptor antagonist, L-368,935 had potent CNS activity with an ED50 of 5.6 mg/kg i.v. and an ED50 of 1.9 micrograms/kg i.c.v. These studies suggest that the weak CNS activity of CI988 following systemic injection may, in part, be due to poor brain penetration and that the ex vivo binding assay is a useful way of assessing the brain penetration of CCKB receptor antagonists.

Analysis of Variance↗
PubMed1994

Crystallographic characterization and molecular symmetry of edestin, a legumin from hemp.

Edestin, a legumin class reserve protein from hemp seeds having six identical subunits was crystallized from ammonium phosphate at pH 5 and subsequently characterized by X-ray diffraction. The crystals are of space group R32 with a = 127 A and gamma = 116 degrees having an equivalent triply centered hexagonal cell of a = b = 215 A, c = 80 A. There is one hexameric protein in the rhombohedral unit cell, hence the subunits of the Edestin molecule must be arranged with 32 point group symmetry.

Cannabis↗