Fatal dysentery in rural Bangladesh

The purpose of this study was to find out the actual circumstances which lead to dysentery-related deaths in the rural Bangladesh. The Community Health Workers of the International Centre for Diarrhoeal Disease Research, Bangladesh have been collecting records of all deaths at the rural area of Matlab through a surveillance system since 1963. A review of existing data on dysentery-related deaths from this area during 1976-1981 suggests that deaths in children followed a recurring seasonal pattern with an increase during the post-monsoon season of August-November of each year. This seasonal pattern of death was not evident among adults. The overall dysenteric death rate during 1978-1981 was 13.3 per 10,000 population per year. The highest rates were in patients of the two extreme age groups. Deaths reported recently by the health workers were re-investigated. Although the causal agents producing fatal dysentery in most patients in the community remained unidentified, it was likely to be species of Shigella in childhood deaths. To identify clinical determinants of a fatal outcome, a case-control analysis was done with patients hospitalised with dysentery in 1980. The risk factors shown to be significantly associated with deaths were: longer median duration of illness (p = less than 0.001), female sex (p = 0.039), signs of respiratory infection (p = less than 0.001) and severe malnutrition (p = 0.002).

Bile salt-fatty acid mixed micelles as nasal absorption promoters of peptides. I. Effects of ionic strength, adjuvant composition, and lipid structure on the nasal absorption of [D-Arg2]kyotorphin

Bile salts and synthetic surfactants have been used to promote nasal absorption of peptide drugs. Although a marked increase in nasal absorption has been achieved, this may not be adequate and the possibility of adjuvant-induced membrane toxicity exists. The present study employs a rat in situ nasal perfusion technique and mixed micelles between sodium glycocholate (NaGC) and various lipids as potential nasal absorption enhancers of a stable model dipeptide, [D-Arg2]kyotorphin. NaGC alone enhanced the nasal absorption of the dipeptide in a concentration-dependent manner. When linoleic acid was added to form mixed micelles with NaGC, the absorption was further enhanced (P less than 0.01). The effect of mixed micelles was synergistic and much greater than with single adjuvants. Increasing ionic strength was found to increase the adjuvant activity of both NaGC and NaGC-lipid mixed micelles. Structure of the lipid component of the mixed micelles also affected the adjuvant potency. Oleic acid, a cis-unsaturated fatty acid, was more effective than elaidic acid, the trans-isomer, whereas cis-linoleic acid and trans-linolelaidic acid were equally effective (alpha = 0.05). Mixed micelles of mono-glycerides such as monoolein and monolinolein were also more effective than NaGC alone (alpha = 0.05). Micellar solubilization of these polar lipids by NaGC appears to be important for nasal absorption enhancement to occur. Reversal of the membrane permeability was also observed within approximately 20-40 min after removal of the adjuvants from the rat nasal cavity. These observations are similar to the effects of mixed micelles on the rectal mucosa and may involve the same mechanism.

High sensitivity electron diffraction analysis. A study of divalent cation binding to purple membrane

A sensitive high-resolution electron diffraction assay for change in structure is described and harnessed to analyze the binding of divalent cations to the purple membrane (PM) of Halobacterium halobium. Low-dose electron diffraction patterns are subject to a matched filter algorithm (Spencer, S. A., and A. A. Kossiakoff. 1980. J. Appl. Crystallogr. 13:563-571). to extract accurate values of reflection intensities. This, coupled with a scheme to account for twinning and specimen tilt in the microscope, yields results that are sensitive enough to rapidly quantitate any structure change in PM brought about by site-directed mutagenesis to the level of less than two carbon atoms. Removal of tightly bound divalent cations (mainly Ca2+ and Mg2+) from PM causes a color change to blue and is accompanied by a severely altered photocycle of the protein bacteriohodopsin (bR), a light-driven proton pump. We characterize the structural changes that occur upon association of 3:1 divalent cation to PM, versus membranes rendered purple by addition of excess Na+. High resolution, low dose electron diffraction data obtained from glucose-embedded samples of Pb2+ and Na+ reconstituted PM preparations at room temperature identify several sites with total occupancy of 2.01 +/- 0.05 Pb2+ equivalents. The color transition as a function of ion concentration for Ca2+ or Mg2+ and Pb2+ are strictly comparable. A (Pb2(+)-Na+) PM Fourier difference map in projection was synthesized at 5 A using the averaged data from several nominally untilted patches corrected for twinning and specimen tilt. We find six major sites located on helices 7, 5, 4, 3, 2 (nomenclature of Engelman et al. 1980. Proc. Natl. Acad. Sci. USA. 77:2023-2027) in close association with bR. These partially occupied sites (0.55-0.24 Pb2+ equivalents) represent preferential sites of binding for divalent cations and complements our earlier result by x-ray diffraction (Katre et al. 1986. Biophys. J. 50:277-284).

Effect of protein rich diet during acute phase of dysentery

Ninety six children upto the age of five years suffering from uncomplicated acute dysentery of less than 3 days' duration were studied to find out the impact of feeding of extra-protein rich diet during their acute phase of illness. These children were randomly allocated to either control group (receiving only hospital diet) and study group (receiving hospital diet and extra milk which constituted 30% of ideal total calorie requirement of patients. Patients in the two groups were comparable on admission. Forty percent reduced food intake was observed among the children of both the groups due to severe anorexia which was reflected by no significant differences in clinical outcome, anthropometrical measurements and haematological parameters between the two groups on day 7 of hospitalisation and on day 15 after discharge.

Deep-vein thrombosis following hip surgery for fracture of the proximal femur

This is a prospective study involving seventy-two consecutive admissions of patients with fractures of the proximal femur over a period of eleven months. It reviews the incidence, pattern and clinical course of deep vein thrombosis in this group of patients. The method of detection of deep vein thrombosis was that of ascending phlebography of the injured limb. Results show that the incidence of deep vein thrombosis is low and complications of thromboembolism and local complications secondary to venous stasis are nil. It appears that prophylaxis and active treatment of deep vein thrombosis in this group of patients may not be essential.

Prodrugs of 5-iodo-2'-deoxyuridine for enhanced ocular transport

Problems associated with the use of 5-iodo-2'-deoxyuridine (IDU) in the treatment of herpes simplex keratitis can be attributed largely to the polar nature of IDU resulting in its poor permeability across the lipoidal epithelial layer of the corneal membrane. Five aliphatic 5'-esters of IDU were synthesized and evaluated as prodrugs for potential use in the treatment of deep ocular infections such as stromal keratitis, iritis, and even retinitis. A parabolic relationship between in vitro corneal membrane permeability and carbon chain length of prodrugs is evident. For a given prodrug, enzymatic hydrolysis proceeded most readily in iris-ciliary body, followed by cornea and aqueous humor. An increase in carbon chain length made the prodrugs more enzymatically labile but more resistant to chemical hydrolysis at pH 7.4 and 34 degrees C. The 5'-butyryl ester of IDU exhibited an approximately fourfold increase in aqueous humor IDU concentration relative to IDU at 25 min following instillation of 25-microliters 5 mM solutions.

Three-dimensional structure of the nicotinic acetylcholine receptor and location of the major associated 43-kD cytoskeletal protein, determined at 22 A by low dose electron microscopy and x-ray diffraction to 12.5 A

The three-dimensional structure of the nicotinic acetylcholine receptor (AChR) from Torpedo californica, crystallized both before and after removal of associated proteins, most notably the main 43-kD cytoskeletal protein that interacts both with AChR and actin, is determined to a resolution of 22 A. This is the first structural analysis where the 43-kD protein has been removed from the sample before crystallization. Thus, it provides the most reliable assessment of what constitutes the structure of the minimal five subunit AChR complex, and, by comparison with the native membrane, of the location of the 43-kD cytoskeletal protein. Image reconstruction of two-dimensional crystals includes information from electron images of up to +/- 52 degrees tilted specimens of latticed AChR. Hybrid density maps that include x-ray diffraction perpendicular to the membrane to 12.5 A resolution were used and eliminate some of the distortions introduced in maps based only on electron microscopic analyses. Comparison of the difference Fourier density maps between AChR with its normal complement of associated proteins, and without them shows that the main density, assigned to the actin-binding 43-kD component is closely associated with the lipid bilayer as well as with the cytoplasmic domain of the AChR. It binds beside the AChR, not beneath it as suggested by others (C. Toyoshima and N. Unwin 1988. Nature [Lond.]. 336:237-240). There is good agreement between the volumes of density for structural components and expected volumes based on their molecular weight. Acetylcholine receptors aggregate in the absence of any cytoskeletal proteins, suggesting that the AChR alone is sufficient to encode and stabilize clustering, and perhaps to do so during synaptogenesis. The main 43-kD component may play a role in location and rate of association of AChR. We show that the disulfide bond that cross-links delta-delta chains of adjacent pentamers in about 80% of AChR, is not required to stabilize the lattice of AChR. Latticed tube structures are stable indefinitely. The lattices described here have 20% less volume of lipid than those originally obtained and characterized by J. Kistler and R. M. Stroud (1981. Proc. Natl. Acad. Sci. USA. 78:3678-3682), or those subsequently characterized by A. Brisson and P. N. T. Unwin (1984. J. Cell Biol. 99:1202-1211) and A. Brisson and P. N. T. Unwin (1985. Nature (Lond.). 315:474-477).

Preparation and characterization of methotrexate-immunoglobulin conjugates

In the targeting of chemotherapeutic agents to specific cells via covalent conjugation of the agent to monoclonal antibodies, conjugation methods which lead to maximum binding capacity with minimum loss of activity (for both drug and antibody) are essential. A model system for evaluation of various conjugation procedures is described. Rabbit anti-bovine serum albumin immunoglobulin (IgG) was used to represent the antibody, and methotrexate (MTX) was used as the targeting agent. The procedures evaluated were coupling via water soluble 1-ethyl-3 (3'-dimethylaminopropyl) carbodiimide (EDCI), or via prior activation of MTX's carboxyl groups involving active ester (N-hydroxysuccinimide) or mixed anhydride (isobutylchloroformate) formation. The formation of covalent conjugates in all three cases was verified by (a) the lack of incorporation of MTX into IgG when the reactions were performed in the absence of EDCI, or when MTX was reacted without prior activation, and (b) the presence of a constant amount of MTX in the conjugates after exhaustive dialysis of gel-filtration through Sephadex G-50. High incorporation of MTX and high retention of antifolate activity resulted from the EDCI coupling reaction, but there was very low recovery of protein (conjugate) and antibody activity. The biological and physicochemical properties of the conjugates prepared by the two pre-activation methods did not show any significant difference, but the conjugates prepared by the active ester method had a longer shelf-life. Therefore, of the three reactions investigated, the active ester method is our method of choice for conjugating MTX to IgG.

Synthesis, physicochemical properties, and cytotoxicity of a series of 5'-ester prodrugs of 5-iodo-2'-deoxyuridine

Five aliphatic 5'-esters of 5-iodo-2'deoxyuridine (IDU) were synthesized via an acid chloride alcoholysis reaction. The solubility in pH 7.4 phosphate buffer, lipophilicity as determined by partition experiments in octanol/pH 7.4 buffer, and cytotoxicity of these potential prodrugs were evaluated. The esters showed a 43- to 250-fold increase in lipophilicity and a 1.6- to 14-fold decrease in aqueous solubility relative to IDU. At a concentration of 50 microM, all esters showed reduced cytotoxicity toward uninfected Vero cells relative to IDU.

Mechanism of transcorneal permeation of pilocarpine

The mechanism of transcorneal permeation of pilocarpine has been investigated in relation to the physicochemical properties of the permeating species and its interaction with the membrane biophase. In vitro corneal transport experiments suggested the transport of un-ionized as well as ionized pilocarpine species across the corneal membrane. However, the permeability of the ionized pilocarpine species was 4.818 x 10(-6) cm s-1, a value only one-half of that obtained for the un-ionized pilocarpine species (9.744 x 10(-6) cm s-1). Further evidence of ion transport across the cornea was obtained by examining the transport of the quaternized pilocarpine compound (i.e., pilocarpinium methyl iodide). The quaternized compound had a corneal permeability of 4.66 x 10(-6) cm s-1, similar to that obtained for the ionized pilocarpine species. The lipoidal epithelial layer of the corneal membrane appears to be the predominant barrier to the transport of polar species. Therefore, the transport of pilocarpinium cations across the lipoidal epithelium might have occurred as tightly bound ion pairs with dihydrogen phosphate and/or nitrate counter ions. Excellent linear correlation has been obtained between pilocarpine corneal permeability and the 1-octanol-water partition coefficient as a function of the state of ionization of pilocarpine. The ratio of un-ionized to ionized drug permeability across the cornea is expected to be much higher for drugs with higher 1-octanol-water partition coefficients.

Transport of tyrosine and phenylalanine across the rat nasal mucosa

Transport of tyrosine (Tyr) and phenylalanine (Phe) across the rat nasal mucosa was studied using an in situ perfusion technique. It was found that both amino acids were absorbed by active, saturable transport processes. The Km and Vmax values were calculated to be 0.68 mM and 0.44 mM/hr for L-Tyr, and 0.40 mM and 0.39 mM/hr for L-Phe, respectively. The values for L-Tyr agreed well with the results previously reported. When D-Tyr and D-Phe were used as substrates, the extent of nasal absorption was significantly reduced indicating the specific affinity of the carrier for the L-amino acids. When mixtures of L-Tyr and L-Phe were used as perfusates, both amino acids were found to be concomitantly absorbed in a competitive manner. This implied that at least one common carrier system was present in the nasal mucosa. In addition the transport appears to be Na+-dependent and may require metabolic energy as a driving force as seen from the inhibition of the L-Phe uptake by ouabain and 2,4-dinitrophenol.

Host preference of Phlebotomus argentipes in different biotopes

A study on host preference of P. argentipes in two different biotopes was conducted by capturing the flies from cowsheds and human dwellings. The human blood index of P. argentipes collected from cowsheds was 21.5% and 69.6% when collected from human dwellings; this indicates that host preference of P. argentipes varies widely in different biotopes.

Hyaluronic acid double helix

The hyaluronic acid double helix, contrary to an earlier visualization, probably incorporates extensively hydrogen-bonded chains and is pinned together by carboxyl-carboxylate hydrogen bonds and water bridges. Transient interactions between stiffened chain segments provided by the formation of double-helical loops could give rise to the characteristic viscoelastic properties of hyaluronic acid solutions.

Dermatan sulfate: molecular conformations and interactions in the condensed state

The molecular conformations and manner of aggregation has been determined for three allomorphs of the connective tissue polysaccharide dermatan sulfate by analysis of X-ray diffraction from oriented, polycrystalline fibers of sodium salts. One allomorph is unique among glycosaminoglycans in having right-handed (8(3)) helical chains. Two such chains pack antiparallel in a tetragonal unit cell (a = b = 1.267 nm, c = 7.353 nm) with P4(3)2(1)2 space group symmetry. The 3(2) chains of the second allomorph are organized in a trigonal unit cell (a = b = 1.460 nm, c = 2.823 nm, space group symmetry P3(2)21) containing two left-handed antiparallel polysaccharide molecules. (The chirality of this allomorph has been assumed to be the same as in other 3-fold glycosaminoglycan helices, since discrimination between 3(1) and 3(2) symmetries was found not to be possible.) The archiral 2(1) helices of the third allomorph, pack probably in an orthorhombic unit cell (a = 1.151 nm, b = 1.065 nm, c = 1.878 nm, space group symmetry P2(1)2(1)2(1)) that contains again two antiparallel polymer molecules. Each dermatan sulfate chain is stabilized intramolecularly by O3-O5 hydrogen bonds across the beta (1 leads to 4) linkage. There are two intermolecular hydrogen bonds per tetrasaccharide repeat in the tetragonal structure and two per disaccharide in the trigonal structure. Fourier difference syntheses indicated equivalents of four sodium ions per tetrasaccharide and two sodium ions per disaccharide in the tetragonal and trigonal structures, respectively. The cations are either partially or fully hydrated and link dermatan sulfate chains either intra- or intermolecularly by involving besides other polyanion oxygen atoms, carboxylate and sulfate oxygen atoms. The probable mode of packing in the orthorhombic structure indicates a pair of hydrogen bonds between adjacent antiparallel polysaccharide chains and suggests plausible cationic sites in the unit cell.

Hyaluronic acid: molecular conformation and interactions in the tetragonal form of the potassium salt containing extended chains

X-ray diffraction data were used to determine the detailed crystal structure of a tetragonal form of potassium hyaluronate containing relatively extended 4-fold helical chains (rise per disaccharide h = 0.95 nm). The polysaccharide chains are left-handed (4(3] helices. Two antiparallel chains pack in a tetragonal unit cell (a = b = 0.996 nm, c = 3.788 nm) with P4(3)2(1)2 space group symmetry. The chain conformations are stabilized intramolecularly by O4-O5 hydrogen bonds across the beta(1 leads to 3) linkage and by a pair of intermolecular hydrogen bonds per disaccharide between adjacent antiparallel chains. Fourier difference synthesis revealed one potassium ion and two water molecules per disaccharide. Six polyanion oxygen atoms from three neighboring chains together with one of these water molecules form the co-ordination polyhedra. Further stability is brought about through inter- and intrachain water bridges involving both water molecules. The probable reason for the stability of this extended allomorph is discussed in terms of the preferred co-ordination geometry of the potassium ion.

Chondroitin 4-sulfate: comparison of the structures of the potassium and sodium salts

Analysis of the X-ray diffraction pattern from an oriented, polycrystalline fiber of a potassium chondroitin 4-sulfate proteoglycan shows that the polysaccharide chains have a left-handed 3-fold helical secondary structure stabilized by intra- and intermolecular hydrogen bonds. Two antiparallel chains pass through each trigonal unit cell, which has dimensions a = b = 1.385 nm, c = 2.776 nm and space group symmetry P3(2)21. The cations and water molecules in the crystals are not all periodic and only one potassium ion and four water molecules per disaccharide were located by difference Fourier methods. Sodium chondroitin 4-sulfate forms an analogous structure with polyanions of similar geometry. However, the packing arrangements in the two salts are quite different, presumably because of the different co-ordination preference of K+ and Na+. Thus the relatively small differences between these two cations are greatly amplified by the idiosyncratic polymer networks they promote.

Hyaluronic acid: molecular conformations and interactions in the orthorhombic and tetragonal forms containing sinuous chains

The conformation, packing and probable mode of cation binding have been determined for compact potassium hyaluronate chains (average rise per disaccharide h = 0.89 nm) organized in an orthorhombic unit cell (a = 1.173 nm, b = 0.925 nm, c = 3.542 nm). The space group symmetry is P2(1)2(1)2(1) and the unit cell contains two antiparallel polysaccharide chains that are disturbed 4(3) helices. Each chain is stabilized intramolecularly by four hydrogen bonds and between adjacent antiparallel chains there are two intermolecular hydrogen bonds per crystallographic tetrasaccharide repeat. Fourier difference synthesis revealed two potassium ions and two water molecules in each asymmetric unit. Both potassium ions show octahedral co-ordination geometries and link adjacent antiparallel polysaccharide chains. The water molecules provide further intermolecular association through water bridges. A comparison of this potassium hyaluronate structure with the orthorhombic and tetragonal sodium hyaluronate structures containing similar compact hyaluronate chains revealed that the apparently isomorphous orthorhombic sodium and potassium salts did not have the same packing arrangements. The relative orientations of the sinuous hyaluronate chains in the sodium and potassium salts are about 90 degrees apart. The locations of the cations and hence the coordination schemes of K+ and Na+ are therefore very different. These analyses have delineated, for the first time, how hyaluronate chains can respond differentially to two different monovalent cations.

Synthesis and 19F spectra of tetra-L-alanine analogs containing selectively incorporated 3-fluoro-L-alanine residues

The synthesis of analogs of tetra-L-alanine containing 3-fluoro-L-alanine selectively incorporated at each position is described. The standard procedures in the literature used to couple L-alanine peptides together were often found to lead to undesired products, or elimination reactions when corresponding 3-fluoro-L-alanine peptide analogs were used. Several modified procedures have thus been developed for the synthesis of fluorine-substituted analogs. In addition, the pH-dependence of 19F n.m.r. spectra of 3-fluoro-L-alanine and the tetrapeptide analogs is presented.

13C n.m.r. study of L-alanine peptides

The di-, tri-, and tetrapeptides of L-alanine have been studied in aqueous solution by 13C n.m.r. spectroscopy at 25 and 50 MHz. By using selectively 13C enriched analogs containing either 90% 13C methyl or carbonyl carbons and measurements as a function of pH, assignment of the chemical shifts of the peptides has been made. T1 and NOE measurements of the peptides in their cationic, anionic, and zwitterionic states have been recorded as a function of concentration. The results show considerable segmental motion along the backbone carbons of the peptides, with only small changes occurring in the dynamic motions of the peptides as their charge states are altered. The lack of concentration dependence of the chemical shift and T1 values, as well as the similarity of T1 values for individual peptides in the three charge states, indicate that the peptides do not self-associate in aqueous solution.

High-performance liquid chromatographic determination of pilocarpine in aqueous humor: derivatization by quaternization of methylimidazole tertiary amine group

A derivatization procedure and a high-performance liquid chromatographic (HPLC) method of analysis for pilocarpine are described. The method is based on the quaternization of the 3'-tertiary amino group of the methylimidazole ring of pilocarpine with p-nitrobenzyl bromide. The HPLC system employs and RP-ODS column with a methanol-water mobile phase containing octanesulfonate as an ion-pairing agent. The sensitivity of the method permits the analysis of pilocarpine in biological fluids such as aqueous humor. The method is selective for pilocarpine in the presence of isopilocarpine. Its applicability to the analysis of aromatic heterocyclic and alkyl tertiary amines is demonstrated.