Vaginismus and outcome of treatment

Vaginismus is a condition of involuntary spasm of the muscles surrounding the outer third of the vagina that is brought about by real, imagined or anticipated attempts at vaginal penetration and often leads to non-consummation of marriage. It is a classic psychosomatic disorder where phobia of vaginal penetration often stems from sexual ignorance, previous traumatic experiences or religious orthodoxy. Management of vaginismus aims at helping the woman to regain voluntary control of her pelvic floor muscles. The treatment utilises a behavioural method aimed at teaching relaxation of pelvic floor muscles together with a systematic desensitization of the fear of vaginal penetration. There are two approaches to vaginal desensitization. The first is gradual desensitization using vaginal self-dilatation, and the second method utilises rapid desensitization brought about by vaginal mould insertion. Of these, the rapid method is preferred at our institution. Surgical correction is almost never required and may be detrimental to achieving success. Management of these conditions requires a warm, empathetic attitude and demands great patience and understanding on the part of the physician. Between 1985 and 1991, 19 patients with vaginismus were treated at the National University Hospital, with a rapid desensitization programme using vaginal moulds. All 19 women could achieve satisfactory vaginal intercourse within 2 to 6 weeks of commencement of therapy.

Efficacy and safety of oral iron chelating agent deferiprone in beta-thalassemia and hemoglobin E-beta thalassemia

OBJECTIVES

To assess efficacy and safety of oral iron chelating agent deferiprone (DFP) in patients with beta thalassemia and hemoglobin E-beta thalassemia.

DESIGN

Non-randomized study.

SETTING

Hematology Out-Patient Department.

SUBJECTS

Forty-one patients of beta thalassemia and hemoglobin E-beta thalassemia.

INTERVENTIONS

DFP was given to 20 patients, 10 patients of beta thalassemia and 10 with hemoglobin E-beta thalassemia; the rest were taken as controls.

RESULTS

A significant fall in serum ferritin was observed in the study group along with rise in urinary iron excretion (p < 0.05). Adverse effects of DFP were nausea and vomiting (30%), significant arthropathy requiring stopping of the drug (30%), and reversible neutropenia in one patient. All these complications could be managed easily with medical supervision and no death or permanent disability was seen.

CONCLUSIONS

DFP is an effective and fairly well tolerated oral iron chelating agent. The side effects that occur can be tackled easily if monitored properly.

Towards improved perinatal care--perinatal audit

Perinatal audit is a measure of quality of care given in pregnancy and it gives an idea as to how the resources need to be allocated for better outcome. The perinatal mortality data in the National University Hospital over a 7-year period (1986-1992) were compiled and compared with that of the year 1982. The perinatal mortality rate (PNMR) of 14.6/1000 in 1982 declined to 8.9/1000 for the period 1986 to 1992 and the reduction was noticeable in all ethnic groups, particularly in the Malays. When lethal congenital malformations (LCMs) were excluded, the PNMR decreased to 5.7/1000. Such reduction is due to easy availability and acceptance of antenatal care, improvement in antenatal and intrapartum fetal surveillance and advances in neonatal care. Neonatal audit was extended beyond the first 7 days of birth which showed that the majority (65%) of deaths occurred in the first week and 15% occurred after the first month. The fear that intensive neonatal care serves to postpone death is not entirely substantiated. There was nearly a ten-fold rise in PNMR between the non-low birthweight and low birthweight groups. The important causes of perinatal mortality during the review period were LCMs (35.7%), complications of prematurity (17.9%) and asphyxia (15.3%). No cause was identifiable in 28.5%. Detailed analysis revealed that the standard of care could have been improved in a third of the cases (83/235) which could have led to further reduction of perinatal mortality rate.

Risk factors and angiographic profile of coronary artery disease in young

A total of 124 patients of ischaemic heart disease under 40 years of age (96 with myocardial infarction and 28 with angina) were studied for risk factors of coronary artery disease. Electrocardiogram, treadmill test, lipid profile and coronary arteriography were done in all cases. Smoking (56.4%) and hyperlipidaemia (30.6%) emerged as the major risk factors. Further stratification of lipid profile revealed that predictive value of hypercholesterolaemia could be enhanced by considering the different ratios of lipoproteins and indices of atherogenicity. Coronary arteriography revealed a preponderance of single vessel disease (48.4%)-left anterior descending being most commonly involved (71.8%). Increase in low density lipoprotein fraction was related to multivessel involvement.

Evaluation of coronary artery disease by dipyridamole echocardiography test

Role of oral dipyridamole echocardiography test (DET) was evaluated in 50 patients with effort angina. All patients underwent coronary angiography, the day after oral DET. The echo studies were performed at rest and 65 +/- 15 minutes after 300 mg of oral dipyridamole. Segmental wall motion was analysed in a 16 segment model and a wall motion score index (WMSI) was generated for the entire left ventricle both at rest and following the drug. WMSI was significantly higher after oral dipyridamole, (p < 0.001) compared to resting condition with increased sensitivity (86% vs 74%). When results of DET were compared with coronary angiography, the correlation of WMSI was statistically significant in three vessel disease (p < 0.001), two vessel disease (p < 0.001) as well as for left anterior descending lesions (p < 0.001). However, it was insignificant for single vessel disease, viz, right coronary artery and circumflex artery. Thus we conclude that oral DET is a safe, inexpensive, sensitive and non-exercise dependent method for demonstrating myocardial ischaemia with high diagnostic accuracy.

Disorders of platelets in pregnancy

No significant change in platelet number, function or life-span occurs during pregnancy. However, pregnancy may be complicated by various platelet abnormalities or platelets may be involved in pregnancy pathologies. Thrombocytopenia is the most common platelet disorder to affect pregnancy. It may occur in a number of clinical conditions and both immune and nonimmune mechanisms may be involved. Apart from the risks to the mother, the fetus may be secondarily affected, especially in cases of immunogenic thrombocytopenia. Management of the mother may not necessarily improve fetal prognosis. Improvement in diagnostic techniques like percutaneous umbilical blood sampling (PUBS) has greatly improved in utero diagnosis and management of the affected fetus. The diagnosis and management of the various platelet disorders affecting the pregnant woman and the fetus are discussed in this overview.

Profile of women undergoing medical termination of pregnancy in hospital

The present study was undertaken to find out the profile of women undergoing medical termination of pregnancy (MTP) in Hospital, 1000 consecutive cases undergoing MTP at RG Kar Medical College and Hospital were studied. 95.6% cases were married and 4.4% cases were unmarried. In the whole series, 7.6% cases were teenagers though in unmarried group 90.9% cases were teenagers. In 56% of married group the monthly family income was more than Rs 500/- whereas majority in unmarried group had family income less than Rs 500/- per month. In the whole series, 44.4% cases were illiterate, 48.2% cases were educated up to primary school and only 7.3% cases up to high school and above. In the married group, 204 cases undergoing MTP with one living issue, 388 cases with 2 living issues and 396 cases with 3 living issues. In the whole series, 88% cases were 1st trimester MTP and 12% were 2nd trimester MTP cases, whereas in the unmarried group 72.7% cases were in the 2nd trimester, and 5.7% cases had history of previous MTP. Effective contraception was only 6% before MTP whereas it increased to 90.6% after MTP.

Topography of serotonin neurons in the dorsal raphe nucleus that send axon collaterals to the rat prefrontal cortex and nucleus accumbens

Diverse physiological actions have been reported for 5-hydroxytryptamine (5-HT, serotonin) in the medial prefrontal cortex (MPFC) and the nucleus accumbens (Acb) suggesting that the 5-HT innervation of these forebrain areas may be derived from different populations of neurons. We examined this possibility by mapping the distribution of 5-HT-immunoreactive (ir) and non-5-HT-ir neurons containing retrograde labeling following injections of different tracers into both these target regions. The analysis was focused in the dorsal raphe nucleus (DRN) of the midbrain, since 5-HT pathways to the MPFC and Acb primarily originate from this area. Volume microinjections of the fluorescent retrograde tracer, Fluoro-Gold (FG), were placed into the MPFC and microinjections of cholera toxin B subunit coupled to 15 nm gold particles (CT-Au) were placed into the Acb of the same animal. Sections through the DRN containing retrogradely labeled neurons were further processed for immunofluorescent localization of 5-HT using a rhodamine marker. Neurons retrogradely labeled from the Acb were greater in number overall than those projecting to the MPFC. In addition, Acb-projecting neurons extended into the lateral wings of the DRN, whereas MPFC-projecting neurons were more restricted to the midline. Both groups of retrogradely labeled neurons, however, were more numerous in the caudal aspect of the dorsal raphe nucleus and were scattered amongst 5-HT immunoreactive perikarya. Of 783 +/- 69 CT-Au labeled cells, 15% also contained the FG label and 11% contained FG and 5-HT immunoreactivity. Of 613 +/- 48 FG labeled cells, 24% also contained the CT-Au label and 21% were also immunoreactive to 5-HT. The results suggest a more prominent input to the Acb from both 5-HT-ir and non-5-HT-ir neurons in the caudal aspect of the DRN and further indicate that while most 5-HT-ir and non-5-HT-ir neurons project differentially to both forebrain regions, a few cells also show collateralization to the MPFC and Acb. Such collateralization of single serotonergic neurons to divergent targets may integrate cognitive and motor activities in response to pharmacological manipulations of ascending serotonergic pathways.

Monitoring Distal Extremity Perfusion with the Pulse Amplitude Monitor during Vascular Reconstruction

One problem in vascular surgery today is the effective monitoring of blood flow to distal extremities before, during, and after a surgical reconstruction. Current methods of blood flow assessment such as periodic pulse palpation, skin signs, Doppler sounds, and capillary refill are neither continuous nor objectively comparable. Because of the qualitative nature of these methods, it is difficult to compare measurements taken by different people at different times, making a quick and appropriate response to changing perfusion requirements difficult. In order to address these problems, a system has been designed to monitor and document pulse amplitudes non-invasively. A pulse amplitude monitor system (Figure 1) consists of a pulse sensor and a waveform monitor (Impra, Tempe, AZ). The sensor (Figure 2) contains a piezoelectric film which is used to detect the slight mechanical oscillations of the arterial wall beneath the skin surface. This film is mounted on a compressible foam block which isolates the vibrations and maintains constant force on the skin. The sensor is taped over a distal pulse, typically that of the dorsalis pedis.

Should assessment of amniotic fluid volume form an integral part of antenatal fetal surveillance of high risk pregnancy?

This study was conducted to evaluate the role of the Amniotic Fluid Index (AFI), used along with nonstress cardiotocography (NST) and fetal acoustic stimulation test (FAST), when required, in prediction of adverse pregnancy outcome. Over a 3-year period 565 pregnant women had antepartum fetal surveillance due to various high risk pregnancy factors and delivered within 7 days of the test. Antepartum fetal surveillance included nonstress cardiotocography together with estimation of AFI. Need for induction of labour, presence of meconium at rupture of membranes, Caesarean section for fetal distress, Apgar score at 5 minutes, need for neonatal endotracheal intubation, admission to neonatal special care unit and perinatal death were the main outcome measures. Nonreactive nonstress tests and Caesarean sections for fetal distress were more common and neonatal outcome was significantly poorer in patients with AFI < 5 cm than in those with higher AFI values. Of the 4 perinatal deaths in the group with AFI < 5 cm, 3 had a reactive NST within 7 days of fetal death. It is concluded that pregnancy outcome is often poor in the presence of very low AFI and in these cases a reactive NST loses its usual reassuring value. It is suggested that AFI estimation should be included as an integral part of antepartum fetal surveillance of high risk pregnancies.

Term breech delivery: does X-ray pelvimetry help?

Over a 3-year period a retrospective audit was performed of all uncomplicated singleton breech presentations at term to assess the role of X-ray pelvimetry. The review included 267 term breech presentations. Seventy-seven women (Group A) delivered in a consultant unit where X-ray pelvimetry was not used for decision making regarding the mode of delivery; 125 women (Group B) delivered in 2 consultant units where X-ray pelvimetry was always used, and 65 women (Group C) delivered in a fourth consultant unit where X-ray pelvimetry was used selectively. Obstetric outcome was measured in terms of mode of delivery. Short-term neonatal outcome was assessed by Apgar score at 5 minutes, evidence of birth trauma and admission to the neonatal special care unit for more than 24 hours. Significantly fewer women (12.9%) had an elective Caesarean section in group A compared with the other 2 groups (27.2% in group B and 33.8% in group C; p < 0.05). The vaginal delivery rates following a trial of labour were not significantly different (79.1% for group A, 65.9% for group B and 65.1% for group C) and neonatal outcome was similar in all groups. It is concluded that fewer Caesarean sections were done, without adversely affecting the neonatal outcome, when X-ray pelvimetry was not used to select the mode of delivery of uncomplicated singleton breech presentation at term. Satisfactory progress in labour is the best indicator of pelvic adequacy.

Intravenous thrombolytic therapy in unstable angina

One hundred consecutive age and sex-matched patients of 3 different subsets of unstable angina (recent onset angina -65, crescendo angina -20, post-infarct angina-15) were randomized 1:1 after coronary angiography to receive I.V., either 1.5 x 10(6) units of streptokinase (SK) in 200 ml of normal saline or 200 ml of normal saline alone (control) in 1 hour. Repeat angiography was done in those patients having intra-coronary thrombi (37.3%) during the initial angiography. Both groups received optimal doses of heparin followed by warfarin, aspirin and other standard drugs and were followed up for 6 months. Anginal pain subsided significantly in the SK group-41 (82%) vs 25 (50%) (P < 0.005), especially in patients with recent onset angina (92.5% vs 60%, P < 0.005). Incidence of acute myocardial infarction (AMI) was much less in the SKgp (4(8%) vs 17 (34%) (p < 0.05). Four cases of fatal MI and four cases of sudden cardiac death (SCD) occurred in the control group against none in the SKgp. Requirements of mechanical revascularization was significantly less (P < 0.05) in the SK gp. Angiographic evidence of partial or complete clot lysis was noted in 90% of SK gp. vs 4.8% of control (P < 0.01). Echocardiographically assessed LV function improved significantly with SK-therapy in recent onset (P < 0.05) and crescendo angina (P < 0.001) subsets--however, the improvements in post infarct angina subset were not statistically significant. The beneficial outcome with SK therapy was observed in patients irrespective of angiographic evidence of thrombi.(ABSTRACT TRUNCATED AT 250 WORDS)

A case report: vesico-rectal fistula with ano-urethral atresia

Vesico-rectal fistula is a rare congenital abnormality causing severe early second trimester oligohydramnios. Prenatal diagnosis of such a case is reported here. Ultrasound diagnosis could be aided by transabdominal amnio-infusion and, if necessary, fetal intraperitoneal saline installation. In a karyotypically normal fetus with normal somatic growth, demonstration of normal fetal kidneys together with a functioning urinary bladder, in presence of severe oligohydramnios, is very suggestive of the diagnosis. Since pulmonary hypoplasia is the major cause of neonatal mortality in these cases, restoration of normal amniotic fluid volume by serial amnio-infusion was attempted. Although amnio-infusion is an important diagnostic aid in the evaluation of severe midtrimester oligohydramnios, the role of multiple therapeutic amnio-infusion in improving lung growth remains to be evaluated.

Observations of stimulated Raman scattering and laser-induced breakdown in millimeter-sized droplets

We report the first observations, to our knowledge, of nonlinear optical effects in large (millimeter-sized) droplets. Stimulated Raman scattering (SRS) and laser-induced breakdown (LIB) are simultaneously observed in acoustically levitated millimeter-sized glycerol droplets irradiated by either a frequency-doubled (532-nm) or a frequency-tripled (355-nm) Nd:YAG laser. The two processes, which occur above a nearly coincident irradiation threshold, are conjectured to arise from a common initiation mechanism: self-focusing. LIB generates vapor bubbles within the droplet, resulting in the quenching of SRS emission.

Aerosol-induced laser breakdown thresholds: effect of resonant particles

Laser intensity thresholds for the onset of stimulated Raman scattering and the breakdown in resonant micro-meter-sized droplets are reduced to below those for nonresonant droplets by a factor of ~ 3. This reduction is most likely caused by the enhancement of electromagnetic energy (photon) densities within the droplets over and above that in nonresonant droplets. The magnitude of the threshold reduction for breakdown is consistent with the assertion that (1) input (pump) wavelength resonances that initiate plasma have cavity Q's of ~ 10(4) and (2) finite regions of high-electromagnetic-energy density within the droplet, with dimensions of the order of the Debye length, are required to initiate plasma.

Do catechol estrogens participate in the initiation of labor?

To assess the role of catechol estrogens in the initiation of labor, we compared the levels in amniotic fluid during the second and third trimesters and from women undergoing cesarean section at term not in labor and those with spontaneous labor at term. Catechol estrogen concentrations in amniotic fluid increased significantly with the progress of pregnancy. Further, concentrations (mean +/- SE) were significantly higher in spontaneous labor at term (468.6 +/- 29.5 pg/ml) compared with those obtained during cesarean section (242.6 +/- 22.3 pg/ml) at term not in labor. We suggest that catechol estrogens, through their stimulating effects on prostaglandin synthesis, participate in the initiation of labor.

Identification of 19-norprogesterone in pregnant rat urine

The existence of biosynthetic pathways leading to the formation of 19-nor-androgens and corticoids have been established in animals and humans. The exact biologic function of the products of these pathways in vivo has yet to be established; however, it has been shown that they possess pronounced biologic activity when administered exogenously. This report describes the identification of 19-nor-progesterone isolated from the urine of pregnant rats. The procedures used included isolation as the underivatized material and methoxime derivative by thin-layer and high-performance chromatography. The identity was further confirmed by gas chromatography/mass spectral analysis of the isolated product as the 3,20-bis-methoxime derivative. The spectra obtained from the urinary product and the authentic 19-norprogesterone-3,20-bis-methoxime were identical. A possible biologic role for 19-norprogesterone or its precursors is discussed.

Temporal relationships among the excretory patterns of 2-hydroxyestrone, estrone, estradiol, and progesterone during pregnancy in the rat

The urinary excretion pattern of 2-hydroxyestrone, estradiol, estrone, and progesterone was examined in rats during early, mid, and late pregnancy. Progesterone increased from early to mid pregnancy and declined significantly 2 to 3 days prior to parturition, corresponding to changes observed in blood levels by others. 2-Hydroxyestrone, the major estrogen in rat urine, increased significantly 4 days prior to delivery and remained elevated until it further increased sharply the day of parturition. Urinary estradiol and estrone levels showed little change until the day of parturition, when they increased significantly. Multiple correlation analysis of the data implied that 2-hydroxyestrone and estradiol were negatively correlated at the time of implantation. The results suggest that catechol estrogens, through their effect on prostaglandin synthesis, may participate in the process of implantation as well as in the mechanism involved in the onset of labor.

Lasing and stimulated Raman scattering in spherical liquid droplets: time, irradiance, and wavelength dependence

Measurement of lasing from dye doped micron sized ethanol droplets irradiated by a pulsed Nd:YAG laser shows evidence of lifetime broadening and relaxation oscillations. Observations of stimulated Raman scattering (SRS) and lasing generated by the same laser pulse in a dye doped ethanol droplet and coupled to the same morphology dependent resonance exhibit longer delays in the initiation of SRS than for pure ethanol droplets where lasing is absent. SRS emission above the plasma breakdown threshold is not measurably delayed and is quenched by the developing plasma.

Stimulated Raman-scattering threshold behavior of binary mixture micrometer-sized droplets

Stimulated Raman scattering (SRS) from binary liquid mixture micrometer-sized droplets irradiated by nanosecond laser pulses exhibits previously unreported features. SRS emission at wavelength shifts corresponding to combination frequencies of the individual component Stokes shifts are observed in droplets but not in bulk mixtures. Furthermore, droplet SRS thresholds are determined by component refractive indices and concentrations, in contrast to bulk thresholds, for which self-focusing likely plays a dominant role.

Micron-sized droplets irradiated with a pulsed CO(2) laser: measurement of explosion and breakdown thresholds

Measurements of minimum CO(2) laser fluence required to explode or disintegrate 10-60 microm radius droplets of water, ethanol, diesel (hexadecane), CCl(4), bromoform, and ethyl bromide are reported. Threshold fluences range from 0.4 J cm(-2) for 10-microm radius ethanol drops to 20 J cm(-2) for 30microm bromoform drops. Threshold fluences for water droplets are ~3 J cm(-2) independent of drop size. Comparison of the measurements to calculations of laser fluence required for considered absorbing droplets to reach superheat temperature is in good agreement for cases where liquid material properties are known, suggesting that superheating of droplets is the dominant mechanism causing explosion/disintegration. Measured droplet-induced laser breakdown thresholds are considerably higher than explosion thresholds and have less dependence on droplet size and composition. The highest breakdown threshold values are for water drops, which range from 150 to 280 J cm(-2) (0.9-1.7 x 10(9)W cm(-2)) compared with 670 J cm(-2) (4.0 x 10(9) W cm(-2)) for clean air breakdown for the laser pulse length and spot size.

Delay of explosive vaporization in pulsed laser-heated droplets

Measurements of time delays for explosion of pulsed CO(2) laser-heated droplets are presented. A simple model based on classical nucleation theory in superheated liquids, which neglects heat and mass transport, is used to interpret the data. The model shows good agreement with the experimental observations.

Cationic antiprotozoal drugs. Trypanocidal activity of 2-(4'-formylphenyl)imidazo[1,2-a]pyridinium guanylhydrazones and related derivatives of quaternary heteroaromatic compounds

A series of quaternary 2-phenylimidazo[1,2-a]pyridinum salts has been prepared and evaluated for antiparasitic activity. Primary attention was focused on derivatives with amido, substituted hydrazone, and heterocyclic functionality at the para position of the phenyl substituent. Guanylhydrazones and N-substituted guanylhydrazones of the 4'-formyl-substituted compounds are very active against the blood state Trypanosoma rhodesiense in mice by subcutaneous or oral administration. The most potent compounds attain 100% survival for 30 days at doses of less than 1.0 mg/kg (sc) and greater than 5.0 mg/kg (po). Weaker activity is noted for certain other 4'-substituents such as carboxamidines and carboxamide oximes. Considerable variation in structure, including replacing of the imidazo [1,2-a]pyridinium ring by other cationic heterocyclic rings and insertion of linking groups between the heterocyclic ring and phenyl group, can be done, and a high level of activity is maintained. Relationships between these structural changes and biological activity are discussed.

Time-resolved spectroscopy of laser emission from dye-doped droplets

Micrometer-sized droplets of Rhodamine 6G solution in water and ethanol are irradiated by high-intensity nanosecond pulses from a frequency-doubled Nd:YAG laser. Coupling of the spontaneous fluorescence emission with natural resonant modes of the spherical droplets results in stimulated emission, with each droplet behaving like a laser cavity. Spectral observations suggest that droplet lasing emission is supported by resonances of a single mode order. The emission exhibits faster rise times and is shorter lived than corresponding bulk-liquid fluorescence. Lasing in droplets is generally initiated almost simultaneously with elastic scattering, unlike stimulated Raman scattering, which is significantly delayed.

Stimulated Raman scattering in micrometer-sized droplets: measurements of angular scattering characteristics

Measurements of the angular scattering characteristics of elastic and stimulated Raman scattering (SRS) in single (nominal 20-microm-radius) water, ethanol, and CC1(4) droplets irradiated with 0.532-microm-wavelength radiation from a pulsed laser demonstrate that SRS is more isotropic than elastic scattering yet qualitatively mimics angularly smoothed elastic scattering patterns. The angular fine structure characteristic of the coherent elastic scattering process is lacking in SRS, regardless of whether the SRS derives from multiple orders of Stokes shifts, multiple resonances within a single Stokes shift, or single resonances within a single Stokes shift.

Omega-conotoxin GVIA binding to a high-affinity receptor in brain: characterization, calcium sensitivity, and solubilization

We describe unique, high-affinity binding sites for omega[125I]conotoxin GVIA in membranes from rat brain and rabbit sympathetic ganglia which appear to be primarily associated with N-type voltage-dependent calcium channels. The dissociation constant (KD) for the toxin in rat brain membranes is 60 pM. Physiologic extracellular concentrations of calcium inhibit toxin binding noncompetitively (IC50 = 0.2 mM). The regional distribution of the binding sites in rat brain differs markedly from that of dihydropyridine calcium antagonist receptors associated with L-type calcium channels. In detergent-solubilized brain membranes, toxin binding retains the same affinity, specificity, and ionic sensitivity as in particulate preparations.

Irradiance and laser wavelength dependence of plasma spectra from single levitated aerosol droplets

Plasma spectra initiated on single, optically levitated, micron-sized droplets of a glycerine-saturated brine solution are presented. The temporal development of the droplet plasma is monitored by observing neutral and once-ionized carbon and neutral sodium emission, and that of the air plasma by once-ionized nitrogen emission. The dependence of the plasma on laser parameters, such as wavelength and irradiance, is discussed.

Stimulated Raman scattering in micrometer-sized droplets: time-resolved measurements

Time-resolved measurements of elastic scattering and stimulated Raman scattering (SRS) in micrometer-sized water and carbon tetrachloride droplets irradiated with a pulsed, frequency-doubled Nd:YAG laser (pulse width 8 nsec, lambda = 532 nm, peak intensity ~1 GW cm(-2)) are reported. Elastic scattering of light is instantaneous within our measurement error, estimated to be <+/-3 nsec. On the other hand, the first Stokes shift in water and multiple-order (through ninth-order) Stokes shifts in carbon tetrachloride are delayed from the elastically scattered light by 5-7 nsec. The delay in SRS is apparently a consequence of structure resonances within the droplet, which acts as an optical cavity with relatively high Q. Quasi-periodic peaks in SRS spectra of water droplets are shown to be associated with elastic-scattering structure resonances having the same mode order.

Aerosol-induced laser breakdown thresholds: wavelength dependence

Aerosol-induced loser breakdown thresholds have been measured for liquid droplets at wavelengths lambda= 1.064, 0.532, 0.355, 0.266 microm using a Nd:YAG laser with 5-10-ns pulse duration. Breakdown thresholds are 2-3 orders of magnitude below those for clean air and range from 4 x 10(7) to 3 x 10(9) W cm(-2) for nominal 50-microm diam droplets, depending on laser wavelength and droplet composition. Thresholds decrease with decreasing wavelength; they also decrease for droplets having a higher real refractive index. For water droplets the breakdown threshold intensity varies approximately as lambda(0.5). The wavelength dependence of breakdown thresholds can be qualitatively explained by considering (1) the effect of enhancement of internal fields and energy density within and near droplets and (2) the increasing importance of multiphoton absorption processes at shorter wavelengths. Laser transmission losses through the breakdown plasma and observations of the suppression of stimulated Raman scattering by the addition of small quantitites of absorbing material to water and carbon tetrachloride droplets are also reported.

Time-resolved spectroscopy of plasmas initiated on single, levitated aerosol droplets

Plasma spectra resulting from the irradiation of single, optically levitated glycerine droplets by an intense pulse from a Nd:YAG laser are presented. The temporal development of the plasma is studied by observing emission lines of neutral and once-ionized carbon and of once-ionized nitrogen. Stark shifts of the neutral-carbon lines are used to compute the plasma electron density. The droplet data are compared with similar data for laser-induced breakdown on a graphite surface.

Enzymatic reactions on thin-layer chromatographic plates. II. Phospholipase A2 hydrolysis of phosphatidylcholine and separation of the products on a single plate

A procedure for the phospholipase A2 hydrolysis of phosphatidylcholine on a thin-layer chromatographic plate and subsequent separation of the products on the same plate is described. A 0.2-0.8-mg amount of Russell's viper venom (phospholipase A2) in 0.2 ml of 0.005 M calcium chloride solution was applied on a 0.5-mm silica gel G plate as a band over which 2-5 mg of egg phosphatidylcholine in 0.2 ml of diethyl ether containing 5% of methanol was evenly applied. After the reaction had proceeded for 15-20 min in a diethyl ether-saturated chamber at 25 degrees, the plate was developed with chloroform-methanol-water (65:25:4). The bands were identified and their contents extracted. The extent of hydrolysis under different reaction conditions was evaluated from the amount of lysophosphatidylcholine formed. Approximately 74.6% (maximum) conversion was obtained within 15 min at 25 degrees using a substrate to enzyme ratio of 4:1. The acyl group distributions in the 1- and 2-positions of hen egg phosphatidylcholine obtained from the gas-liquid chromatographic analysis of the methyl ester corresponding to the lyso and free fatty acid band agreed with those obtained by the method of Wells and Hanahan. The method is also applicable to phosphatidylethanolamine.

A method for the estimation of free and esterified cholesterol involving thin-layer chromatography

A method for the estimation of both free and bound cholesterol in serum and plasma involving thin-layer chromatography has been developed. The serum or plasma is applied as a band directly on the plate. Extraction of lipid material from this band and the chromatographic separation of the above components are carried out on the same plate. The components are extracted from the adsorbent directly with acetic acid and measured colorimetrically using iron(III) chloride-sulphuric acid reagent.