Photoreversible modulators of Escherichia coli beta-galactosidase. 1-Benzoyl-1-cyano-2-(4,5-dimethoxy-2-nitrophenyl)-ethene and 1,1-dicyano-2-(4,5-dimethoxy-2-nitrophenyl)-ethene

Beta-galactosidase (EC 3.2.1.23) is known to be inhibited by some thiol reagents. 1-Benzoyl-1-cyano-2-(4,5-dimethoxy-2-nitrophenyl)-ethene (1) was shown to be an irreversible inhibitor, while 1, 1-dicyano-2-(4,5-dimethoxy-2-nitrophenyl)-ethene (2) was demonstrated as a positive irreversible modulator causing a rise of up to 186% in beta-galactosidase activity. Compound 2 is, however, an irreversible inhibitor of the cysteine proteinase papain (preceding paper). Kinetic values of beta-galactosidase at pH 8.3 with o-nitrophenyl beta-D-galactopyranoside (ONPG) as the substrate and for compounds 1 and 2 were determined and in view of model experiments, it was assumed that both compounds possibly reacted with the thiol side chain of Cys in the active site inducing allosteric changes in the enzyme. Since the enzyme, modified by compound 1 or 2, was a 2-nitrobenzyl derivative, near-UV irradiation resulted in a recovery of up to 91% and a reduction of the enzyme's activity to 90%, respectively.

Inhibition of Papaya latex papain by photosensitive inhibitors. 1-(4,5-dimethoxy-2-nitrophenyl)-2-nitroethene and 1,1-dicyano-2-(4,5-dimethoxy-2-nitrophenyl)-ethene

1-(4,5-Dimethoxy-2-nitrophenyl)-2-nitroethene (1) was shown to be an irreversible inhibitor of papain (EC 3.4.22.2), causing a complete inhibition (120 min preincubation, pH 8.0), assuming that it attached to Cys-25 at the active site of the enzyme (while a short preincubation time caused activation). Only partial inhibition of papain was achieved, however, with 1,1-dicyano-2-(4,5-dimethoxy-2-nitrophenyl)-ethene (2), a compound synthesized in this work, which is also an irreversible inhibitor of papain. Since both compounds 1 and 2, and in each case of the inhibited enzyme, were 2-nitrobenzyl derivatives, they and the modified enzyme were expected to be photosensitive. Indeed, irradiation of the inhibited enzyme in the presence of mercaptoethanol resulted in a full recovery of the enzyme activity following inactivation with compound 1 (similar to our previous finding with beta-galactosidase) and up to 67% recovery following inhibition with compound 2.

Rapid entry of bitter and sweet tastants into liposomes and taste cells: implications for signal transduction

Some amphipathic bitter tastants and non-sugar sweeteners are direct activators of G proteins and stimulate transduction pathways in cells not related to taste. We demonstrate that the amphipathic bitter tastants quinine and cyclo(Leu-Trp) and the non-sugar sweetener saccharin translocate rapidly through multilamellar liposomes. Furthermore, when rat circumvallate (CV) taste buds were incubated with the above tastants for 30 s, their intracellular concentrations increased by 3.5- to 7-fold relative to their extracellular concentrations. The time course of this dramatic accumulation was also monitored in situ in rat single CV taste buds under a confocal laser-scanning microscope. Tastants were clearly localized to the taste cell cytosol. It is proposed that, due to their rapid permeation into taste cells, these amphipathic tastants may be available for activation of signal transduction components (e. g., G proteins) directly within the time course of taste sensation. Such activation may occur in addition to the action of these tastants on putative G protein-coupled receptors. This phenomenon may be related to the slow taste onset and lingering aftertaste typically produced by many bitter tastants and non-sugar sweeteners.

Sexuality during pregnancy in Pakistani women

OBJECTIVE

We investigated the patterns of sexual activity during pregnancy and explored all beliefs related to coitus during pregnancy in women with the objective of promoting awareness and assisting health care providers in understanding and dispelling fears/misconceptions prevalent in our culture.

METHODS

A cross-sectional, KAP (Knowledge, Attitude, Practice) study was conducted using questionnaires to interview 150 healthy pregnant women attending antenatal clinics at Aga Khan University Hospital (AKUH) and Lady Dufferin Hospital, both located in Karachi, Pakistani. Data was analysed using Epi Info 6 statistical package.

RESULTS

The mean frequency of intercourse during pregnancy (1.6 times/week) was less than before pregnancy (3.5 times/week). Husbands were the main initiators of sexual activity (44%) while the wives only rarely did so (0.7%). Some (13.3%) women felt it served to keep husbands around. Coitus during pregnancy was gratifying in 64.7% and painful in 37.3% of respondents. Most (45.4%) believed coitus was harmful for the foetus. Others (28.7%) thought it did not make any difference whereas 4.7% believed that it made a difference if the foetus was female by gender. 22.7% women believed that coitus during pregnancy caused abortions early in pregnancy and 6.7% that it induced pre-term labour. 26% did not know the means by which the harmful effects were produced but still maintained their beliefs. Some (10.7%) thought it could actually help widen the birth canal and facilitate labour. Majority (85.3%) believed that frequency should be lowered during pregnancy, 10% thought that it should be continued as before and 4% that it should be stopped completely.

CONCLUSION

This study suggests a mixed attitude towards sexuality in pregnancy with a tilt towards the belief that it is harmful and should therefore be decreased during pregnancy, specially during the last trimester. It is the responsibility of health care providers to dispel fears and clarify any misconceptions regarding such matters.

The delta-selective opioid peptide dermenkephalin and the mu-selective hybrid peptide dermenkephalin-[1-4]-dermophin-[5-7] display strikingly different conformations despite identical tetrapeptide N-termini. A quantitative 2-D NMR and molecular modeling analysis

The selective recognition of the aminoterminal binding pharmacophore Tyr-D-Xaa-Phe of the opioid heptapeptide dermorphin, Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2 (DRM)1, and of dermenkephalin, Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2 (DREK), by the mu-opioid receptor and delta-opioid receptor, respectively, depends upon the constitution / conformation of the C-terminal tripeptide. The hybrid peptide DREK-[1-4]-DRM-[5-7] is very potent at, and exquisitely selective for the mu-opioid receptor, and differs only from dermenkephalin by its C-terminal tripeptide. Comparison of the structural features of DREK-[1-4]-DRM-[5-7] and dermenkephalin by nmr analysis and molecular modeling revealed striking differences, as well in the trans (Tyr5 - Pro6) isomer (population 75%) than in the cis isomer.. Whereas the folded C-terminal tail of dermenkephalin influenced the tertiary structure of the N-terminal tetrapeptide and placed the Tyr1 and Phe3 aromatic rings in definite orientations that are best suited for the delta-receptor, there were only weak contacts, as shown by NOE data, between the aminoterminal and carboxyterminal parts of the hybrid peptide. This promoted increased flexibility of the whole backbone and relaxed orientations for the side-chains of Tyr1 and Phe3 that are compatible with the mu-receptor but unsuitable for the delta-receptor. The steric hindrance introduced by Pro6 in DREK-[1-4]-DRM-[5-7], plus the absence of large hydrophobic side-chains in positions 5 and 6 may prevent close contacts between the N-terminal and C-terminal domains and reorientation of the main pharmacophoric elements Tyr1 and Phe3.

Prognostic indicators of childhood acute viral encephalitis

OBJECTIVE

To devise a set of clinical signs and laboratory parameters that would help clinicians assess prognosis in patients and plan appropriate management.

METHODS

Medical records of 147 paediatric cases (with a discharge diagnosis of acute viral encephalitis) admitted over a ten year period from 1987 to 1997 were reviewed and relevant information collected on a data extraction form.

RESULTS

Of 147 patients, 24 (16.3%) died and 48 (32.7%) were left with severe neurological deficits. A GCS (Glasgow Coma Scale) score between 6-10 had an association with poor outcome (OR = 2.62, Chi-square = 5.57, p-value = 0.018) and that a GCS score of > or = 5 was even more strongly suggestive of poor outcome (OR = 5.49, Chi-square = 12.08, p-value = 0.0005). A history of having seizures, for more than 3 days, also showed a strong association with poor outcome (OR = 3.66, Chi-square = 5.46, p-value = 0.019).

CONCLUSION

Patients with an increased risk of death and severe disability can be identified using a few guidelines. Of these, a history of seizures of > 3 days and/or impaired consciousness (GCS < or = 10), at the time of presentation to the hospital, constitute high risk. These cases must be identified promptly and aggressive therapy initiated in order to improve long term outcome.

Effects of L-cysteine and N-acetyl-L-cysteine on 4-hydroxy-2, 5-dimethyl-3(2H)-furanone (furaneol), 5-(hydroxymethyl)furfural, and 5-methylfurfural formation and browning in buffer solutions containing either rhamnose or glucose and arginine

Solutions of L-cysteine (Cys) and N-acetyl-L-cysteine (AcCys), containing glucose or rhamnose, with or without arginine, were buffered to pH 3, 5, and 7 and incubated at 70 degrees C for 48 h. Cys and AcCys inhibited the formation of (hydroxymethyl)furfural (HMF) from glucose and methylfurfural (MF) from rhamnose under acidic conditions. AcCys inhibited the accumulation of 4-hydroxy-2, 5-dimethyl- 3(2H)-furanone (DMHF, Furaneol) from rhamnose, but Cys, under our experimental conditions, enhanced Furaneol accumulation from rhamnose. Cys and AcCys reacted directly with Furaneol but not with HMF or MF. Both Cys and AcCys inhibited nonenzymatic browning at pH 7. At pH 3, however, Cys reacted with both glucose and rhamnose to produce unidentified compounds that increased the visible absorbency.

Solution conformations of deltorphin-I obtained from combined use of quantitative 2D-NMR and energy calculations: a comparison with dermenkephalin

Deltorphin-I, Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2 and dermenkephalin, Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2, two highly related opioid peptides from frog skin, display very similar N-termini but strikingly different C-terminal tails. Nevertheless, both peptides are highly potent at, and exquisitely selective for the delta-opioid receptor. To identify common determinants concuring to the remarkably efficient targeting of deltorphin-I and dermenkephalin, combined use of quantitative two-dimensional nuclear magnetic resonance (53 dipolar interactions studied at four temperatures) and energy calculations using simulated annealing generated five groups of deltorphin-I conformers. These groups were pooled into two families whose overall conformation could be described either by a left-handed helix (Family I) or by a big loop (Family II), both stabilized by H-bonds. Proximity of D-Ala2-Phe3-Asp4 and Val5-Val6-Gly7 triads is an obvious structural similarity between almost all groups in both families of structures. Whereas differences between the two families originated mostly from a transition at psi Asp4 backbone dihedral angle, the backbone structures at segment 1-4 are similar and spatial arrangements of Tyr1 (t) and Phe3 (g-) are identical in one group of each family. Moreover, these two groups have a N-terminal tetrapeptide whose conformation most closely resembles that of a well-defined group of structures for dermenkephalin. Altogether, these results suggest that conformational attributes that are common to dermenkephalin and deltorphin-I, i.e., the backbone conformation of the N-terminal tetrapeptide and preferential orientations in the side-chain of Tyr1 (t) and Phe3 (g-) underlie their ability to bind with high selectivity to the delta-opioid receptor.

Impaired responses to sweet taste in vitamin A-deficient rats

In brief-exposure, two-choice preference tests (sucrose solution v water), vitamin A-deficient (VAD) rats exhibited a decreased preference for sucrose relative to control rats. There was no difference in total fluid intake from both choices between the two groups, nor was any significant difference found in circumvallate taste papilla keratin size. It is concluded that the impaired preference for sucrose in VAD rats is due to a specific impairment in taste sensation rather than general malaise.

Cells in laminae III and IV of the rat spinal cord that possess the neurokinin-1 receptor and have dorsally directed dendrites receive a major synaptic input from tachykinin-containing primary afferents

Many neurons with cell bodies in laminae III or IV of the spinal dorsal horn possess the neurokinin 1 receptor and have dorsal dendrites that arborize in the superficial dorsal horn. We have performed a confocal microscopic study to determine whether these cells receive inputs from substance P-containing primary afferents. All neurons of this type received contacts from substance P-immunoreactive axons, and in most cases the contacts onto dorsal dendrites were very numerous. A great majority (90-100%) of substance P-immunoreactive varicosities in contact with these cells were also immunoreactive with antibody to calcitonin gene-related peptide, indicating that they were of primary afferent origin. The density of contacts from substance P-immunoreactive varicosities onto these cells was significantly higher than that seen on cholinergic neurons in lamina III (which do not possess the receptor). Electron microscopy revealed that synapses were present at points of contact between substance P-immunoreactive boutons and dorsal dendrites of cells with the neurokinin 1 receptor. Some cells of this type belong to the spinothalamic tract, and we therefore examined neurons with cell bodies in laminae III or IV that possessed the neurokinin 1 receptor and were labeled retrogradely after thalamic injection of cholera toxin B subunit. These cells also received contacts from substance P-immunoreactive axons on their dorsal dendrites. The results of this study indicate that neurons of this type are a major target for substance P-containing primary afferents.

Adenylyl cyclase inhibitory pathway is differentially modified in rat white and brown fat by high-energy diets

Incubation of white adipose tissue (WAT) adipocytes from rats fed a high-energy diet (Exp group) with antilipolytic Gi-coupled adenylyl cyclase inhibitory agonists, nicotinic acid (Nic) and N8-(L-2-phenylisopropyl)adenosine (PIA), resulted in lower cellular adenosine 3',5'-cyclic monophosphate (cAMP) levels than in stimulated adipocytes from rats fed a nutritionally balanced diet (Con group). In contrast to WAT, incubation of brown adipose tissue (BAT) adipocytes with Nic yielded higher cAMP levels in the Exp vs. Con rats. In both WAT and BAT adipocytes, pertussis toxin treatment abolished the differences in Nic- and PIA-inhibited cAMP formation between Exp and Con animals. Immunoblotting of adipocyte membranes indicated a lower content of Gi alpha but not Gs alpha in BAT membranes of Exp vs. Con animals after 6 and 10 wk of feeding. No such differences were found in the Gs alpha or Gi alpha contents of WAT membranes. Thus the inhibitory pathway of adenylyl cyclase is proposed to be sensitized in WAT and desensitized in BAT of rats fed high-energy diets. These modifications in sensitivity are in line with reduced cAMP and lipolysis in WAT and increased cAMP and thermogenesis in BAT during obesity.

Folded conformations of the delta-selective opioid dermenkephalin with head-to-tail interactions. A simulated annealing study through NMR restraints

Despite similar tripeptide N-termini, dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2) and dermenkephalin (Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2), naturally occuring opioid peptides from frog skin, exhibit high affinity but contrasting selectivity for the mu- and delta-opioid receptors, respectively. Structure-activity relationship studies have shown that the N-terminal tripeptide, Tyr-D-Xaa-Phe (where Xaa is either Ala or Met), is necessary for binding with both the mu- and delta-receptors while the nature and/or the conformation of the C-terminus His-Leu-Met-Asp-NH2 of dermenkephalin are responsible for addressing the peptide to the delta-receptor. In order to examine the conformational characteristics that are related to the selectivity of dermenkephalin towards the delta-receptor, 50 NOE restraints (10 between non-adjacent residues), and 7 dihedral angles, derived from a two-dimensional 1H-NMR study of dermenkephalin in dimethyl sulfoxide, were used in simulated annealing and energy minimization procedures. Twenty-four resulting conformers (60% of the generated structures) with no severe distance restraint violation were pooled into seven groups and three related families. These 24 conformers show close proximity between the two methionine residues, S-shaped structures, mean planes of N-terminal and C-terminal moieties almost at right angles to each other, a C-terminus region above the plane of the N-terminal region and g- as preferential orientation in the side chain of Phe. Aside these similarities, families of conformers differ by the preferential orientation in the side chain of Tyr (t or g-) and proximity between Tyr and Asp, or Tyr and the C-terminus. In contrast to previous models, practically no beta-turn structures exist for dermenkephalin, most of the NH hydrogen bonds participating to gamma-turns. The possible relationship between the conformational characteristics of dermenkephalin and the delta-opioid receptor selectivity is discussed.

Inhibition of Escherichia coli beta-galactosidase by 2-nitro-1-(4,5-dimethoxy-2-nitrophenyl) ethyl, a photoreversible thiol label

1-Nitro-2-phenylethene (beta-nitrostyrene, 1) which is a thiol-protecting reagent (Jung, G., Fouad, H. and Heusel, G. (1975) Angew. Chem. Int. Ed. Engl. 14, 817-818), was demonstrated in this work to be an irreversible inhibitor of beta-galactosidase (EC 3.2.1.23), an enzyme known to be inhibited by some thiol reagents or through modifying a methionine residue at the active site. No reversal of the inhibition was observed upon subsequent incubation with mercaptoethanol or irradiation (350 nm). 1-(4,5-dimethoxy-2-nitrophenyl)-2-Nitroethene 2) was also shown to be an irreversible inhibitor (94% inhibition, pH 8.3) of the enzyme. Kcat values of beta-galactosidase at pH 8.3 with o-nitrophenyl beta-D-galactopyranoside (ONPG) as the substrate and at the highest inhibitor concentrations employed for compound 1 (4.06 x 10(-4) M) ranged from 1.67 x 10(4) S-1 after 30 min of preincubation to <0.07 x 10(4) S-1 after 180 min preincubation. For compound 2 (9.5 x 10(-5) M) Kcat values ranged from 2.70 x 10(4) S-1 following 30 min preincubation to 1.15 x 10(4) S-1 after 180 min of preincubation; the changes in Km(app), however, were small. The activity was not recovered following incubation with mercaptoethanol. Since compound 2 and the inhibited enzyme are 2-nitrobenzyl derivatives, they are expected to be photosensitive and indeed, irradiation of the inhibited enzyme in the presence of mercaptoethanol resulted in recovery (89%, pH 8.3) of the enzyme activity.

Changes in IP3 and cytosolic Ca2+ in response to sugars and non-sugar sweeteners in transduction of sweet taste in the rat

1. The transduction pathways of sweet-sensitive cells in rat circumvallate (CV) taste buds were investigated with assays for inositol 1,4,5-trisphosphate (IP3) and with Ca2+ imaging. Stimulation with the non-sugar sweeteners SC-45647 and saccharin rapidly increased the cellular content of IP3 by 400 pmol (mg protein)-1, while sucrose had a much smaller effect on IP3. As shown previously, sucrose, but not saccharin, increased the content of cyclic adenosine monophosphate (cAMP) of this preparation. 2. Stimulation of isolated CV taste buds with SC-45647 increased the cytosolic Ca2+ concentration ([Ca2+]i) by 56.7 +/- 3.2 nM (n = 181). Due to the non-confocality of the measuring system, these concentrations are underestimates. The increase in [Ca2+]i did not require the presence of extracellular Ca2+, suggesting that the Ca2+ release was from intracellular stores. 3. Individual cells responding to the non-sugar sweeteners with Ca2+ release also responded to sucrose and to forskolin with an increase in [Ca2+]i. Such cells did not respond to the bitter tastant denatonium chloride. 4. Responses to sucrose were abolished by lowering the Ca2+ concentration of the stimulus solution, indicating Ca2+ uptake from the extracellular medium. 5. The responses of sweet-sensitive cells to forskolin were also abolished when Ca2+ ions were omitted from the stimulus solution. They were partially inhibited by the presence of Co2+, Ni2+, D600 (methoxyverapamil) and amiloride, indicating multiple pathways of Ca2+ uptake activated by cAMP. 6. In conclusion, a sweet-sensitive cell of the rat responds to sucrose with an increase in cAMP and Ca2+ uptake, but to non-sugar sweeteners with an increase in IP3 and Ca2+ release. The increase in [Ca2+]i, common to both pathways, is presumably required for synaptic exocytosis and for signal termination.

A novel putative neuropeptide receptor expressed in neural tissue, including sensory epithelia

We have used a homology based approach to identify G protein-coupled receptors preferentially expressed in retinal and taste cells. Rat and bovine sequences encoding a novel G protein-coupled receptor have been isolated. Analysis indicates that while the protein sequence is most similar to the receptors for somatostatin and opiates, it is unlikely to be a subtype of these receptors. Northern and RNase protection analysis indicates that the gene is preferentially expressed in neural and sensory tissues.

Effect of acute occlusion of left renal vein on the kidney: an experimental study in dogs

To study the effects of acute ligation of the left renal vein an experimental study was carried out on 16 Mongrel dogs out of 18 of which 2 had died postoperatively. The right kidney served as control. Changes immediately after ligation were recorded; subsequently the dogs were sacrificed in 4 groups comprising 4 in each at intervals of 24 hours, one week, 4 weeks and 6 weeks. Both the kidneys were removed and gross and microscopic changes were noted. In all cases atrophy of the ligated kidney due to tubular atrophy and fibrosis were seen in spite of good collaterals. It is concluded that left renal vein ligation in dogs is not safe for the kidney, though it is not fatal.

Some taste substances are direct activators of G-proteins

Amphiphilic substances may stimulate cellular events through direct activation of G-proteins. The present experiments indicate that several amphiphilic sweeteners and the bitter tastant, quinine, activate transducin and Gi/Go-proteins. Concentrations of taste substances required to activate G-proteins in vitro correlated with those used to elicit taste. These data support the hypothesis that amphiphilic taste substances may elicit taste through direct activation of G-proteins.

Mechanism of delta-opioid receptor selection by the address domain of dermenkephalin

Dermenkephalin (Tyr-D-Met-Phe-His-Leu-Met-AspNH2) is a highly potent and selective delta-opioid peptide isolated from frog skin. It was recently recognized that the C-terminus His4-Leu5-Met6-Asp7NH2 of dermenkephalin was responsible for the addressing of the peptide towards the delta-opioid receptor. In order to investigate the role played by residues 4, 5 and 6 in this 'delta address', we synthesized and evaluated 20 new analogues for their ability to displace tritiated ligands from mu- and delta-opioid sites. Results showed that position 4 of dermenkephalin contributes to delta selectivity independently of delta-opioid receptor binding by preventing a high affinity mu binding. Position 5 requires a hydrophobic side chain to enhance delta affinity. A high delta affinity was obtained with any amino acids introduced in position 6 suggesting that residue 6 serves as a neutral spacer. Thus, the main features responsible for the high delta-opioid selectivity of dermenkephalin are electrostatic repulsions with the mu-opioid receptor, additional hydrophobic interactions with the delta-opioid receptor and folding of the C-terminal domain.

Quantitative two-dimensional NMR study of dermenkephalin, a highly potent and selective delta-opioid peptide

Dermenkephalin, H-Tyr-(D)Met-Phe-His-Leu-Met-Asp-NH2, a highly potent and selective delta-opioid peptide isolated from frog skin, was studied in DMSO-d6 solution by two-dimensional nmr spectroscopy, including the determination of NH temperature coefficients, the evaluation of 3J coupling constants from phase-sensitive correlated spectroscopy (COSY) and the volumes of nuclear Overhauser effect (NOE) correlations. The two-dimensional NOE spectroscopy (NOESY) spectrum of dermenkephalin revealed sequential, medium-, and long-range effects. To put this information on a quantitative basis, special attention was devoted to J cross-peak suppression, quantification of the NOE volumes and analysis of the overlaps, normalization of the NOEs against diagonal peaks and H beta beta' geminal interactions. Although most of the dihedral angles deduced from the 3JN alpha coupling constants together with several Ni alpha i and alpha iNi+1 NOEs pointed to a partially extended peptide backbone, several NiNi+1 NOEs and beta iNi+1 interactions argued in favor of a folded structure. Moreover, several long-range correlations of strong intensities were found that supported a close spatial proximity between the side chains of D-Met2 and Met6, Tyr1 and His4, Tyr1 and Asp7, and His4 and the C-terminal amide group. In Phe, the g- rotamer in the side chain is deduced from the 3J alpha beta coupling constants and alpha beta and N beta NOE correlations. Whereas the amide proton dependency was not indicative of stable hydrogen bonds, the nonuniform values of the temperature coefficient may reflect an equilibrium mixture of folded and extended conformers. The overall data should provide realistic starting models for energy minimization and modelization studies.

Folding trends in a flexible peptide: two-dimensional NMR study of deltorphin-I, a delta selective opioid heptapeptide

Deltorphin-I, H-Tyr-(D)ala-Phe-Asp-Val-Val-Gly-NH2 and dermenkephalin, H-Tyr-(D)met-Phe-His-Leu-Met-Asp-NH2 are 2 members of small but growing family of D-amino acid containing opioid peptides isolated from the frog skin. Both peptides exhibit high affinity and selectivity for the delta-opioid receptor. Two-dimensional NMR study of deltorphin-I in DMSO-d6 revealed a close conformational homology with dermenkephalin. However, the temperature dependency of NOE correlations issued from Val5 and Val6 of deltorphin-I reflects a high intrinsic flexibility of the carboxyend. Whereas most of the JN alpha coupling constants and interresidue alpha N NOE effects were compatible with an extended structure, some sequential NOEs together with several medium and long range correlations involving Tyr1, Val6 and Asp4 may reflect an equilibrium mixture of extended and folded conformers in which the C- and the N-terminal parts of deltorphin-I are in close proximity. Finally, g- is the preferential conformer in the side chain of Phe3 in both deltorphin-I and dermenkephalin.

Synthesis and antifungal activity of medicagenic acid saponins on plant pathogens: modification of the saccharide moiety and the 23 alpha substitution

The study of structure-antifungal activity relationships of medicagenic acid saponins was widened to include synthetic glycosides of mannose, galactose, cellobiose, and lactose as well as a 23 alpha-hydroxymethyl analog of medicagenic acid, namely, methyl 2 beta,3 beta-dihydroxy-23 alpha-hydroxymethyl-delta (12)-oleanene-28 beta-carboxylate, against Sclerotium rolfsii, Rhizoctonia solani, Trichoderma viride, Aspergillus niger, and Fusarium oxysporum. The native glucose-containing saponin was a more effective antifungal agent than the aforementioned saponins, except in the case of the cellobiose-containing derivative and F. oxysporum. A carboxyl substituent at the 23 alpha position of the sapogenin brought about higher fungistatic activity than a methyl carboxylate which, in turn, was more effective than an hydroxymethyl group at the same position.

Differential post-receptor responses of adenylate cyclase in white and brown adipose tissue membranes of rats fed high-energy diets

1. Adenylate cyclase activity was determined in membranes of white and brown adipose tissue (WAT and BAT, respectively) from rats fed a high-energy diet (EXP group) vs those fed a nutritionally balanced one (CON group). 2. The isoproterenol- and guanine nucleotide-induced adenylate cyclase activity in WAT membranes of EXP rats was lower than that in CON rats. 3. Relative adenylate cyclase activity in like treated BAT membranes was higher in EXP than in CON rats. 4. It is concluded that feeding high-energy diets to rats induces similar post-receptor modifications of adenylate cyclase as found in genetic obese rodents.