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N Sitaram

Publications and source records attributed to N Sitaram.

At least 37 records · Page 2Linked to original sources
PubMed1993

Interaction of the 47-residue antibacterial peptide seminalplasmin and its 13-residue fragment which has antibacterial and hemolytic activities with model membranes.

The interaction of seminalplasmin (SPLN), a 47-residue antibacterial peptide, and its 13-residue fragment (SPF), which has antibacterial and hemolytic activities, with model membranes has been investigated. The fluorescence characteristics of the single Trp residue in these peptides indicate strong binding to lipid vesicles. SPLN binds more strongly to dioleoylphosphatidylglycerol vesicles compared to dioleoylphosphatidylcholine and phosphatidylserine vesicles. Localization studies using fluorescence quenchers like NO3-, I-, and acrylamide indicate that the Trp residues in both of the peptides are located away from the head group region and are associated with the hydrophobic core. Both peptides cause release of carboxyfluorescein from zwitterionic as well as anionic vesicles. The biological activities of SPLN and SPF have been rationalized in terms of lipid-peptide interactions. It is proposed that the specificity in biological activity arises due to differences in the manner in which the peptides associate with the bacterial and red blood cell surfaces.

Acrylamide↗
PubMed1992

The antibacterial peptide seminal plasmin alters permeability of the inner membrane of E. coli.

Seminal plasmin (SPLN) a 47-residue peptide, isolated from bovine seminal plasma, exhibits antibacterial activity against Gram-positive and Gram-negative bacteria. Although SPLN strongly inhibits the transcription of various natural and synthetic templates by E. coli RNA polymerase in vitro, it also associates with model membranes of phosphatidylcholine and phosphatidic acid. We have undertaken experiments to ascertain whether SPLN permeabilizes the bacterial inner membrane and thereby exerts its antibacterial activity, as in the case of recently isolated antibacterial peptides from mammalian sources. Our results show that SPLN affects the permeability properties of the bacterial inner membrane which is reflected by increased uptake of ortho-nitrophenylgalactoside (ONPG), which can normally be translocated only by protein transporters. SPLN has also been shown to act on the outer membrane, since divalent cations inhibit antibacterial activity.

Animals↗
PubMed1992

Change of glutamic acid to lysine in a 13-residue antibacterial and hemolytic peptide results in enhanced antibacterial activity without increase in hemolytic activity.

A 13-residue peptide corresponding to a hydrophobic segment of the antimicrobial 47-residue peptide seminalplasmin, PKLLETFLSKWIG (SPF), has been shown to have antibacterial and hemolytic activities (N. Sitaram and R. Nagaraj, J. Biol. Chem. 265:10438-10442, 1990). In an effort to get an insight into the structural and charge requirements for these biological activities, an analog of SPF in which Glu has been replaced with Lys has been synthesized and its antibacterial and hemolytic properties have been examined. It has been demonstrated that the analog, SPFK, exhibits potent antibacterial activity at concentrations at which hemolysis does not occur.

Amino Acid Sequence↗
PubMed1992

Apparent specificity of bovine seminal ribonucleases can depend on the conditions used for the isolation of substrate.

RNAase SPL, a ribonuclease isolated earlier from bovine seminal plasma, was shown to possess the ability to produce large acid-insoluble fragments of Mg(2+)-containing RNA in a limit digest. The factor which could be responsible for this apparent specificity has been identified as polyvinyl sulphate; it has been shown that polyvinyl sulphate inhibits RNAase SPL at much lower concentrations than required for RNAase A. The earlier results are now reinterpreted based on this effect of polyvinyl sulphate, thus providing a plausible explanation for RNAase SPL's apparent specificity. RNAase SPL has been shown to be a mixture of two ribonucleases, RNAase SPL I and RNAase SPL II. RNAase SPL I is like RNAase A in its activity while RNAase SPL II, the major ribonuclease in seminal plasma, appears to be identical to RNAase BS1.

Amino Acid Sequence↗
PubMed1990

A synthetic 13-residue peptide corresponding to the hydrophobic region of bovine seminalplasmin has antibacterial activity and also causes lysis of red blood cells.

Seminalplasmin (SPLN), a 47-residue peptide present in bovine seminal plasma, is one of the few proteins isolated from mammalian sources having potent antibacterial activity. SPLN also interacts with sperm acrosomal and plasma membranes. On the basis of analysis of the primary structure of SPLN with respect to its relative hydrophobicity and hydrophilicity, a region comprising of 13-amino acids, Pro-Lys-Leu-Leu-Glu-Thr-Phe-Leu-Ser-Lys-Trp-Ile-Gly, has been delineated. It is demonstrated that a synthetic peptide corresponding to this 13-residue region inhibits growth of Escherichia coli like SPLN and also has the ability to lyse red blood cells.

Alkaline Phosphatase↗
PubMed1989

Catecholamine depletion produces irrepressible saccadic eye movements in normal humans.

To determine the effect of catecholamine depletion on ocular motor pathways in humans, we studied the eye movements of 3 normal subjects who received the drug metyrosine (alpha-methylparatyrosine). This drug temporarily depleted dopamine and norepinephrine, as measured by a reduction in the metabolite, 3-methoxy-4-hydroxy-phenylethyleneglycol (MHPG). Saccadic, pursuit, and vestibulo-ocular eye movements were recorded using infrared oculography with subjects both on placebo and on metyrosine. The most consistent effect observed with metyrosine was an increase in the amplitude and frequency of saccadic intrusions during fixation and pursuit. Two of the 3 subjects also had shortened time constants for the vestibulo-ocular reflex, attributable in part to the sedative effect of catecholamine depletion. The increase in saccadic intrusions implies that catecholamines modulate the activity of a subpopulation of suppressor motor neurons in the human brainstem.

Administration, Oral↗
PubMed1989

Elevated sleep and waking heart rates in anxious depressions.

Autonomic functioning, as measured by baseline heart rates during daytime (DHR) and during sleep (SLHR), was examined in 28 patients with major depressive disorder (MDD), 13 patients with panic disorder (PD), 28 patients with MDD and coexisting PD (MDD + PD), and 19 controls. DHR and SLHR in patients with PD or MDD did not differ from normals. Only the MDD + PD group showed significantly higher heart rates than controls. This pattern of results suggests a combined effect of MDD and PD, providing psychophysiological support for clinical findings of poorer prognosis in this group.

Adult↗
PubMed1989

The effect of clonidine on auditory P300.

Auditory evoked potential recordings were done on 14 normal subjects during baseline conditions as well as after oral administration of 0.2 mg of clonidine or placebo. P300 amplitude and latency measurements were obtained from 28 electrodes and analyzed. Clonidine resulted in a decrease in P300 amplitude, which was most marked in the occipital and left parieto-temporal regions. This effect was significant even after controlling for the sedative side effect of clonidine. P300 was unaffected by clonidine. These data suggest the possible use of clonidine-induced changes in P300 amplitude as an index of central noradrenergic responsiveness.

Adult↗
PubMed1988

Cholinergic REM sleep induction by arecoline in normal subjects: relation to thyroid function.

Serum thyroid hormones and the speed of rapid eye movement (REM) sleep induction by the central muscarinic agonist arecoline were measured in 21 normal volunteers. The arecoline-REM induction latencies had a modestly significant negative correlation with free thyroxine index. This finding is discussed in the light of observations in animal studies that thyroid hormones stimulate central cholinergic neuronal function.

Adult↗
PubMed1988

The effects of field inversion electrophoresis on small DNA fragment mobility and its relevance to DNA polymorphism research.

The electrophoretic mobility of several DNA size markers of molecular lengths from 1.23 x 10(2) to 2.36 x 10(4) base pairs has been investigated in gels of 1% and 1.3% agarose (w/v) by field inversion gel electrophoresis (FIGE), in vertical slabs. Pulsing times studied were in the range of 0.3/0.1 ms to 300/100 ms. (Pulsing times are given in milliseconds, as X/Y, where X is the forward pulsing time and Y is the reverse time.) FIGE differentially retards DNA migration: this effect is more marked for shorter pulsing times, and varies as a function of molecular length of the DNA fragment, down to fragments as small as about 1.7 kb, with the pulsing times we used. Several FIGE conditions were found which generate improved resolution of DNA fragments in different size ranges. DNA separation improves by more than a factor of two for fragments of 23.1-9.4 kb (with 300/100 ms pulsing) and for fragments of 4.4-2.0 kb (3/1 ms). FIGE does not seem to have a marked resolution enhancing effect on DNA sized from 9.4-4.4 kb. An example of improved detection of closely spaced bands on Southern blots is shown.

Blotting, Southern↗
PubMed1987

The association of supersensitive cholinergic REM-induction and affective illness within pedigrees.

Based on the Rieder and Gershon (1978) biological genetic study paradigm we compared the prevalence of a putative vulnerability factor (rapid cholinergic REM sleep induction) between 35 affectively ill and 31 well first-degree relatives of 34 probands chosen on the basis of presence of primary affective illness and positive marker status. A significantly higher percentage of ill relatives (63%, 22 out of 35 subjects) had a supersensitive REM-induction response as compared to well relatives (22%, 7 out of 31 subjects). Since the current study does not rule out the effects of prior depressive episodes or treatment on cholinergic sensitivity, caution must be exercised in the interpretation of our findings.

Acetylcholine↗
PubMed1987

Sleep and depression.

Manifestations of sleep disturbances can potentially serve as external criteria for the diagnosis of specific subtypes of major depressive disorder (MDD). Depressed patients generally experience disturbances of sleep continuity and rapid eye movement (REM) sleep. Disturbances in nonrapid eye movement (NREM) sleep (stages III and IV) also occur. Characteristic of primary sleep disturbance in many depressed patients are shortened REM latency periods and instabilities in NREM sleep identified by increases in the number of stage shifts, decreases in the duration of stage III and IV sleep, and a shift towards lighter sleep stages (sleep efficiency disturbances). Treatment modalities for these sleep disturbances include sleep deprivation therapy and antidepressant therapy. Sleep deprivation alone has been only moderately successful, while antidepressant therapy usually results in symptomatic improvement. To restore normative sleep, REM sleep periods and stage III and IV sleep must be returned to normal. Trazodone therapy has been shown to reduce the frequency of arousals, the severity of drowsiness, and the duration of REM sleep, and increase restorative slow wave sleep and stage III and IV NREM sleep.

Depressive Disorder↗
PubMed1986

Seminalplasmin and caltrin are the same protein.

The sequence of seminalplasmin, a basic antimicrobial and transcription-inhibitory protein from bovine seminal plasma, has been determined using an automated sequenator. This sequence is slightly different from that reported earlier by Theil and Scheit [(1983) EMBO J. 2, 1159-1163] and identical with that of caltrin, a Ca2+-transport-inhibitory protein of bovine seminal plasma. Caltrin and seminalplasmin are, therefore, the same protein.

Amino Acid Sequence↗