Stability enhancement for peptide analysis by electrospray using the triple quadrupole mass spectrometer

Electrospray ionization sources, used with triple quadrupole mass spectrometers from PE/Sciex (API III+), Micromass (Quattro II), and Finnigan (TSQ 7000), were modified with a 35-gauge stainless steel needle. The dimensions of the needle were 63 microm i.d. by 145 microm o.d. with variable length, depending on the specific instrument. This modification led to enhanced signal stability, improved signal/noise ratios, and lowered sample consumption for a wide range of peptides. Stable baselines were observed with flow rates in the range of 50 nL/min to 5 microL/min. An alternative design, based on a metal wire housed within a fused silica capillary, led to the most stable signals of all during infusion, but caused excessive peak broadening with capillary chromatography. The Finnigan interface was further modified with an external postcolumn addition tee, used in conjunction with capillary liquid chromatography columns of 30 and 50 microm internal diameter. The best results with the modified Finnigan interface were acquired using the 50-microm column at a flow rate of 150 to 200 nL/min.

Regulation of lipid A modifications by Salmonella typhimurium virulence genes phoP-phoQ

Bacterial pathogenesis requires proteins that sense host microenvironments and respond by regulating virulence gene transcription. For Salmonellae, one such regulatory system is PhoP-PhoQ, which regulates genes required for intracellular survival and resistance to cationic peptides. Analysis by mass spectrometry revealed that Salmonella typhimurium PhoP-PhoQ regulated structural modifications of lipid A, the host signaling portion of lipopolysaccharide (LPS), by the addition of aminoarabinose and 2-hydroxymyristate. Structurally modified lipid A altered LPS-mediated expression of the adhesion molecule E-selectin by endothelial cells and tumor necrosis factor-alpha expression by adherent monocytes. Thus, altered responses to environmentally induced lipid A structural modifications may represent a mechanism for bacteria to gain advantage within host tissues.

Initial studies of a new approach to the design and use of enzyme-based reactor/sensor systems: amperometric system for glucose

This paper describes the development and evaluation of a new approach to the design and use of enzyme-based reactor/sensor systems (so-called "enzyme electrodes"). In the new approach, the reactor/sensor design is such that the measured response corresponds to reaction of all substrate in a fixed volume of solution. The result is that equilibrium-based measurements can be made, which in turn should result in advantages such as extended linear ranges and reduced dependencies on experimental variables such as enzyme activity, temperature, activators, inhibitors, etc. The concept was implemented with a glucose oxidase/electron-mediator reactor system immobilized on a glassy-carbon electrode operated in an amperometric mode. The reactor/sensor system was used in a thin-layer (14 microns) cell such that the mean diffusion time of substrate (glucose) across the cell was very short (< 1 s) and the rate-limiting process was the chemical reaction at the reactor surface. In this way, it was possible to quantify the electrical charge corresponding to reaction of all the substrate in a fixed volume of solution perpendicular to the plane of the reactor system. Because the determined charge is dependent only on the total amount of substrate in the fixed volume, results exhibit linear range up to at least 2-fold the Michaelis constant and reduced dependency on pH relative to results obtained with steady-state responses from the same experimental system. A mathematical treatment is presented which yields equations that are consistent with time-dependent responses for current and charge and which provide a rational basis for several data-processing options evaluated.

Error-compensating kinetic method for enzymatic determination of DNAs

We describe the adaptation and evaluation of an error-compensating method for kinetic determinations of deoxyribonucleic acids (DNAs). The DNA is first reacted with ethidium bromide to produce a fluorescent intercalation complex. Subsequent treatment of the complex with DNase catalyzes hydrolysis of the DNA, causing a time-dependent decrease in fluorescence, which is monitored. A model for two-component parallel first-order processes is fit to the decay curve to predict the total change in fluorescence expected if the process were monitored to equilibrium. The predicted change in fluorescence response varies linearly with DNA concentration with an intercept corresponding to 0.13 mg/L DNA. Results by the predictive method are 47-, 58-, and 250-fold less dependent on DNase activity, temperature, and ethidium bromide concentration, respectively, than are results for an initial-rate method utilizing the same data. Moreover, the predictive method yields a significantly wider linear range than the initial-rate method, and is much less affected by blank fluorescence and RNA interference than is an equilibrium method based on the reaction of DNA with ethidium bromide alone.

Enzyme immunoassay (Chlamydiazyme) for the detection of chlamydial antigen in endocervical specimens

Endocervical swabs taken from 86 women were tested by the Chlamydiazyme enzyme immunoassay test to detect chlamydial antigens. Compared to cell culture, Chlamydiazyme was 100% sensitive and 90% specific. This test is suitable as alternative diagnostic method to cell culture and has the potential for automation.

Endocervical chlamydial infection in women with gonorrhoea

Eighty six women attending Middle Road Hospital with endocervical gonococcal infection were evaluated. Chlamydia trachomatis was isolated in 27% of them. Women co-infected with C. trachomatis were similar to those with gonococcal infection alone in terms of demography, type of sexual contact, previous sexually transmitted disease, genitourinary symptoms, and clinical signs.

Comparative double-blinded study between mupirocin and tetracycline ointments for treating skin infections

A double-blinded study was conducted to compare the effects of mupirocin and tetracycline ointments in the treatment of skin infections. 111 patients were available for clinical assessment, of which 53 were treated with mupirocin and 58 treated with tetracycline. Clinically, both groups were improved, and there was no significant difference. Bacteriological assessment however revealed a better response to mupirocin. Staphylococcus aureus and Streptococcus pyogenes were the most common organisms isolated. 99% of Staphylococci were sensitive to mupirocin compared with 61% to tetracycline and 29% to penicillin G. 57% of Group A beta haemolytic Streptococci were resistant to tetracycline compared to 14% to mupirocin. Gram-negative organisms were mostly resistant to both preparations. No side effects were observed in both treatment groups. This study suggests that mupirocin is a safe and effective topical preparation for treating most of our common skin infections.

Chlamydial infection in female prostitutes in Singapore

Three studies conducted in 1982, 1985 and 1988 investigated chlamydial infections in female prostitutes. In 1982, 115 prostitutes with culture-positive gonorrhoea were studied; 8% were coinfected with Chlamydia trachomatis. In 1985, 86 female prostitutes and in 1988, 100 female prostitutes attending for routine tests were examined. Chlamydia trachomatis was isolated in 12% and 9% of the cases, respectively. Gonorrhoea was detected in 10% and 11% of the cases. In the 1988 study, one (9%) of the 11 women with gonorrhoea had concomitant chlamydial infection. Syphilis was diagnosed in 3% of the female prostitutes investigated in 1988. Our findings indicate that concomitant chlamydial infection occurs in about 8-9% of female prostitutes with gonorrhoea and that 9-12% of the female prostitutes screened harboured Chlamydia trachomatis in their endocervices. A chlamydial control programme in prostitutes is desirable.

Epidemiology of acute epididymo-orchitis in Singapore

A prospective study on 55 patients with acute epididymo-orchitis was studied. Their ages ranged from 15 to 65 years. Thirty-three (60%) were within the 20-29 year age group and 9 were above 35 years of age. 69% cited prostitutes as the source of sexual contact. Twenty-six patients did not receive and 29 patients received antibiotic therapy before recruitment. In the former untreated group, 6 patients (23%) had gonococcal urethritis, 3 patients (11%) had chlamydial urethritis and 2 patients (8%) had combined gonococcal and chlamydial urethritis. No pathogens were isolated from the urethra from the remaining 15 (58%) patients, 8 of whom had nonspecific urethritis. In the latter treated group, 4 patients (14%) had gonococcal urethritis and no organisms were isolated from the remaining 25 (86%) of whom 6 had non-specific urethritis. None of the 55 patients had urinary tract infections. Forty-three patients (78%) had unilateral involvement of both the testis and epididymis, and 4 patients (7%) had bilateral epididymo-orchitis. Semen analysis was performed on 13 patients of whom 8 showed pyospermia.

Endocervical chlamydial infection in women attending a sexually transmitted disease clinic in Singapore

Two hundred women attending the sexually transmitted disease (STD) clinic at Middle Road Hospital were investigated. Chlamydia trachomatis was isolated from 32% of women who were contacts of men with nongonococcal urethritis, 15% of contacts of gonococcal urethritis, 27% of contacts of unspecified STD, and 13% of women without any history of STD in their sex partners. Overall, Chlamydia trachomatis was isolated from 17% of 200 women, Neisseria gonorrhoeae from 13% of 199 women, Candida albicans from 34% and Trichomonas vaginalis from 6% of 197 women. Three per cent of the patients had positive VDRL results. A history of bilateral lower abdominal pain and the presence of cervicitis were significantly associated with chlamydial infection. Forty one per cent of the 34 chlamydia-positive women were asymptomatic. The results of this study show that C. trachomatis infection is more common than infection with N. gonorrhoeae in women who attend STD clinics. The need for routine screening and treatment on the basis of epidemiological and clinical markers of infection has to be carefully examined.

Endocervical chlamydial infection in female contacts of patients with nongonococcal urethritis

Eighty-five female contacts of patients with nongonococcal urethritis attending Middle Road Hospital were examined. Chlamydia trachomatis was isolated from the cervix in 39% of them. Forty-five per cent of the chlamydia-positive patients were asymptomatic and 79% of them showed signs of a cervicitis. None of the patients developed complications. Neisseria gonorrhoeae was not isolated from any of the patients. Clinical markers other than cervicitis are not useful for detecting chlamydial infections in female contacts of NGU. Until such time when cheaper, more convenient and accurate methods of laboratory diagnosis of C. trachomatis are put to routine use, it would seem prudent to treat all female contacts of NGU patients after exclusion of other sexually transmitted diseases.

Dedifferentiated chondrosarcoma metastasizing to the pancreas in pregnancy

Acute abdomen in pregnancy can present difficulties in both diagnosis and treatment. In this patient the presentation of an acute abdomen was due to some intraperitoneal hemorrhage complicating a pancreatic metastasis from a primary dedifferentiated chondrosarcoma arising from the right iliac bone. Neither the primary nor the secondary growths had been suspected previously.

Bacampicillin to treat non-gonococcal urethritis in men: pilot study

Of 84 men with non-gonococcal urethritis (NGU), 24 yielded Chlamydia trachomatis by either cell culture or MicroTrak immunofluorescence test. All 84 were treated with bacampicillin 800 mg twice a day for seven days. Five (one chlamydia positive) defaulted from follow up 10 to 14 days after the start of treatment. Of the 23 chlamydia positive patients who attended follow up, 22 became chlamydia negative; 14 of the 23 patients also became asymptomatic and had normal urethral smears. Of the 56 chlamydia negative patients who attended follow up, 21 were cleared of their urethritis. Two patients reported side effects; one drowsiness and one mild diffuse alopecia. Bacampicillin may therefore be a safe and effective alternative to tetracycline or erythromycin in treating chlamydial urethritis in men.

An immunofluorescence study of lichen planus among Asians in Singapore

Forty-five Asian patients (Indians 35, Chinese 8, Malay 2) with histologically proven lichen planus were studied by immunofluorescence. The most characteristic feature, seen in 93% of the cases, was shaggy deposition of fibrinogen along the basement membrane. Immunoglobulin deposition along the basement membrane was notably, absent. Colloid bodies were observed in 87% of the cases. Fibrinogen was the most common immunoreactant, and its presence in colloid bodies was always associated with fibrinogen deposition along the basement membrane zone. Colloid bodies also contained a variety of other immunoreactants. However, staining for IgM was noted to be the most intense. The combination of shaggy deposition of fibrinogen along the basement membrane, in the absence of immunoglobulins, and the presence of colloid bodies around the basement membrane zone, is highly characteristic of lichen planus. The pattern of immunofluorescence among Asians with lichen planus, conforms to that observed in other races. There did not appear to be any difference in the immunofluorescence staining with pattern in the three racial groups studied.

Lichen planus: a study of 72 cases in Singapore

Seventy-two patients attending this hospital with a diagnosis of lichen planus were examined. There was a striking predominance of Indians (69%) and a surprisingly low incidence of Chinese (24%) and Malays (4%) in the study population, compared to the racial composition of the general clinic population. The age distribution curve of the study population was bimodal with peaks at age groups 21-30 (22%) and 41-60 (33%) years. The most common morphologic variant was lichen planus vulgaris (common type) which we observed in 46 (64%) patients, followed by lichen planus hypertrophicus in 8 (11%) and lichen planus atrophicus in 2 (3%). Lichen planus confined to the skin was observed in 49 (68%) patients. Mucous membrane involvement was seen in 21 (29%)-17 (24%) had oral mucosa membrane involvement and 4 (6%) genital mucous membrane involvement. In 16 (22%) cases, mucous membranes were exclusively involved--12 (17%) had oral mucous membrane involvement and 4 (6%) genital mucous membrane involvement. Nail changes were only observed in 2 (3%) patients. Eight (11%) patients had associated diabetes mellitus. Overall, lichen planus appeared to pursue a protracted course with only 4 (6%) patients clearing completely after a disease duration of 5-12 months.

An unusual case of varicella involving the penis

An unusual case of varicella involving the penis is presented. Herpetiform ulceration of the penis in a person who has had promiscuous sexual contact is not necessarily herpes progenitalis, since varicella may also involve the penis.

Genital herpes in Singapore

As in many parts of the world, the incidence of genital herpes has increased in Singapore, the increase occurring sharply from 1982 onwards, and affecting females to a greater extent than males. Peak incidence in both sexes was found to occur in the 15-34 year age group. Changes in sexual practices, a decreasing prevalence of age-specific antibody to herpes simplex type 1 virus in sexually active adults, and greater interest in the disease following publicity in the media, are factors which have contributed to both a real and an apparent increase in incidence. However, the incidence in Malay males is very low, and neonatal herpes is extremely rare in the local population. Herpes simplex virus type 1 is responsible for about 30% of initial genital infections and an even higher proportion of primary genital herpes infections. Approximately 16% of purulent penile ulcers in Singapore are associated with genital herpes infection.

Newer methods for the detection of Chlamydia trachomatis in genital specimen

Conventional culture isolation methods for detecting Chlamydia trachomatis infections are laborious, expensive, technically demanding and not widely available. Recently, non-culture methods which detect chlamydial antigens have been introduced. These methods utilise immunofluorescence (IF), enzyme immunoassay (EIA) or DNA hybridisation techniques. DNA hybridisation techniques are presently, still experimental. IF and EIA tests are widely available and are suitable alternatives to culture isolation for laboratories who wish to provide a chlamydia-service. The sensitivities and specificities, and advantages and disadvantages of these systems are discussed.

Single dose piperacillin in treating uncomplicated gonococcal urethritis in men

A single intramuscular dose of piperacillin 2 g, with probenecid 1 g orally, was used to treat 82 men with uncomplicated gonococcal urethritis due to penicillinase producing strains of Neisseria gonorrhoeae (PPNG) or non-PPNG. All 49 patients infected with non-PPNG strains were cured, as opposed to only 25 (76%) of 33 patients infected with PPNG strains, giving an overall success rate of 90%. No serious side effects of treatment were observed. Post gonococcal urethritis (PGU) occurred in 18% of the patients treated. Antibiotic susceptibility tests showed that 44 (96%) of the 46 non-PPNG strains tested had MICs of piperacillin of 2 mg/l or less and 26 (76%) of the 34 PPNG strains had MICs of 32 mg/l or more. This regimen is not recommended for use as first line treatment in areas where there is a high incidence of infection with PPNG strains. It is, however, highly effective against non-PPNG strains.

The epidemiology of Malassezia (Pityrosporon) folliculitis in Singapore

Seventy patients with a clinical diagnosis of Malassezia folliculitis were studied, of which 48 were confirmed on finding unipolar budding yeastlike organisms on gramstained microscopy or histology specimens. The epidemiologic and clinical features of these 48 cases (M = 44; F = 4) were analyzed. The typical Singaporean patient with Malassezia folliculitis is a young man of mean age 22.2 years with erythematous follicular papules or pustules on the upper back, shoulders, upper chest, and sides of the back. Aggravating factors include heat and sweating. Excessive sebum production may be an important underlying factor.

Ceftriaxone for treatment of primary syphilis in men: a preliminary study

Eighteen male patients with primary syphilis were randomly assigned to one of the following treatment schedules: ceftriaxone (3 g in a single intramuscular [im] injection), ceftriaxone (2 g im daily for two days), ceftriaxone (2 g im daily for five days), and benzathine penicillin (2.4 X 10(6) units in a single im injection). The single 3-g dose of ceftriaxone cured three men, one had a sustained response, and one failed to be cured. Of the patients given 2 g of ceftriaxone im daily for two days, three were cured and two had a sustained response. All three men treated with 2 g of ceftriaxone daily for five days had a sustained response. In the group given penicillin, three men were cured, one had a sustained response, and one was lost to follow-up.