Search PubMed⌕ Search

Biomedical subjects

D M Allen

Publications and source records attributed to D M Allen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Thermal control of rod outer segment length and shedding in a fish, Fundulus zebrinus.

The effects of temperature on rod outer segment (ROS) length and membrane shedding were studied in a cyprinodont fish, Fundulus zebrinus. After 30 days in 14L/10D cyclic light and 17 degrees C, ROS length averaged 41.2 microns. Fish were then exposed to 7, 17 or 27 degrees C for 10 and 25 days before being sampled 5 hr before and 1-4 hr after light onset. In 7 degrees C ROS shortened to 83.5% of initial controls within 10 days, then only 4.1% further, to 79.4% by day 25 (34.4, 32.7 microns). ROS length did not change significantly in fish remaining at 17 degrees C (39.7 and 40.7 microns at day 10 and 25) or in fish moved to 27 degrees C (41.7 and 41.6 microns). Phagosomes were most numerous in 7 degrees C and least numerous in 17 degrees C, but varied in overall size among the largest phagosomes being more common after light onset. After light onset at day 25, the estimated volume per phagosome was 1.14, 4.73 and 5.75 microns 3 in 7, 17 and 27 degrees C. Total phagosome volume per 100 microns RPE at 27 degrees C was generally double that at 17 degrees C. Apparently, in F. zebrinus, the number of disks shed from ROS is adjusted during thermal acclimation to stabilize ROS length.

Acclimatization↗
PubMed1995

Pathophysiology and related studies of the no reflow phenomenon in skeletal muscle.

Although the success rate of microvascular replantation and revascularization procedures has increased steadily since the 1960s, some replanted tissues do not reperfuse despite technically adequate arterial anastomoses. This failure of microvascular perfusion is termed no reflow. Much research has been directed toward discovering the etiology of no reflow since it was first described 25 years ago. Three pathophysiologic processes have been identified as playing a central role in the development of no reflow: intracellular calcium overload, oxygen-free radical medicated damage, and altered arachidonic acid metabolism. The first tissue believed to be injured irreversibly by these processes is the endothelium, which leads to dysfunction of the parenchymal cells. All 3 pathways are interrelated extensively, which allows for pharmacologic intervention at many different steps. Agents that have been shown to be beneficial in preventing no reflow include calcium channel blockers, prostaglandin analogs, thromboxane synthesis inhibitors, vasodilators, thrombolytics, and many antioxidants. Although they have been shown to be effective in various laboratory models, additional investigation is necessary before these treatments can be established in clinical use.

Animals↗
PubMed1994

Factitious HIV infection: the importance of documenting infection.

OBJECTIVE: To examine possible causes for factitious human immunodeficiency virus (HIV) infection among patients in an HIV clinic. DESIGN: Retrospective chart review, a case-control study, and a survey of local hospital practices for documenting HIV infection. SETTING: Clinical acquired immunodeficiency syndrome (AIDS) program at a municipal hospital. RESULTS: Seven patients with self-reported, undocumented HIV infection were identified as HIV seronegative after a mean of 9.2 months of care in our clinical AIDS program. The median CD4 count for these patients was 740 cells/mm3; 6 patients had a history of illicit narcotic use and clinical symptoms consistent with HIV disease. Compared with 70 randomly selected controls from HIV clinics, patients with factitious HIV infection had higher CD4 counts (difference, 519 cells/mm3; P < 0.001) and were more likely to have an HIV-infected sexual partner (odds ratio, 15.0; P = 0.005) and a history of a suicide attempt (odds ratio, 9.8; P = 0.02). Known cases of alleged HIV infection have occurred at 8 of the 10 other local hospitals surveyed. However, only 1 of the 10 hospitals routinely documented HIV infection in patients before initiating care. CONCLUSIONS: Limitations of the current serologic tests for HIV, the use of anonymous HIV testing, and recent reports of factitious HIV disease or immune deficiency syndromes that may mimic AIDS underscore the need for clear documentation of HIV infection before medical care is started.

Adult↗
PubMed1994

Behavioural risk factors and HIV infection of injection drug users at detoxification clinics in Puerto Rico.

BACKGROUND: The ethnic and geographical variations of AIDS prevalence among injection drug users (IDU) have highlighted the need to understand the role of the relevant risk factors in specific subpopulations of IDU. In this study we examine the factors related to seropositivity among IDU entering drug detoxification facilities in metropolitan San Juan, Puerto Rico. METHODS: From October 1990 until August 1991, 390 IDU were interviewed. Four groups of risk factors were examined: sexual practices, drug injection behaviours, risk behaviours while in US Mainland cities, and while incarcerated. A stepwise logistic regression model was used to simultaneously assess the independent effects of the behavioural risk factors on HIV seropositivity. RESULTS: Of the 342 IDU who were tested for HIV antibodies, 29.5% were seropositive. The behaviours found to be associated with seropositivity were: having sex with an IDU in the last 6 months; having injected drugs for over 5 years; and injecting with used needles while incarcerated. DISCUSSION: Public health programmes will need to establish more effective collaborative links with correctional institutions in order to reduce the spread of HIV among IDU in Puerto Rico.

Adult↗
PubMed1994

Malaria: prophylaxis and therapy.

Malaria remains a significant cause of morbidity and mortality in many regions of the world. In Singapore, an average of 200 cases of malaria have been reported annually, the majority of which are imported cases. Malaria eradication is a goal that may not be achieved. A more realistic aim is to educate and protect individual travellers. This paper attempts to summarise various therapeutic options including the use of monotherapy and combination therapy. The decision on therapy depends on several factors, such as the Plasmodium species, risk of transmission of the resistant parasite and the severity of infection. So far, none of the chemoprophylactic regimens available can provide an absolute protection from malaria transmission. Therefore, one needs to assess the risk of transmission against the potential risk of adverse drug reaction. Complications of anti-malaria drugs may range from minor cutaneous manifestations to death. General measures to prevent vector transmission of the disease should be emphasised while awaiting the development of an effective malaria vaccine.

Animals↗
PubMed1994

Advice for the international traveller.

International travel has increased in recent years. The spectrum of disease associated with travel is wide. All travellers should be encouraged to seek pre-travel medical advice which include the need for vaccination and malaria prophylaxis and advice on preventive health measures during travel. The returning traveller with an illness should be advised to seek post-travel treatment.

Antimalarials↗
PubMed1994

Randomised study comparing imipenem/cilastatin to ceftriaxone plus gentamicin in cancer chemotherapy-induced neutropenic fever.

Prompt initiation of empiric antibiotic therapy is the cornerstone in the therapy of chemotherapy-induced neutropenic sepsis in cancer patients. Ceftriaxone plus gentamicin (ceftriaxone/gentamicin) is the most widely used combination of empiric antibiotics in the Department of Medical Oncology, Singapore General Hospital. However, imipenem/cilastatin has been shown to be a practical alternative. To compare the efficacy and cost effectiveness of monotherapy with our usual combination antibiotic therapy, 50 evaluable neutropenic cancer patients admitted for fever were randomised to empiric imipenem/cilastatin or ceftriaxone/gentamicin. Ceftriaxone/gentamicin was started in 24 patients. The initial clinical response rate to ceftriaxone/gentamicin was 62.5% and 84.6% to imipenem/cilastatin (P = 0.075). The average cost of antibiotics per patient started on ceftriaxone/gentamicin including cost of change of antibiotics was S$63 per day of antibiotic use and for imipenem/cilastatin it was S$252 (P < 0.02). In conclusion, although more patients receiving imipenem/cilastatin had an initial clinical response than those receiving ceftriaxone/gentamicin, this difference was not statistically significant. It would appear that imipenem/cilastatin is equivalent to ceftriaxone/gentamicin for the treatment of neutropenic sepsis. However, ceftriaxone/gentamicin was more cost effective.

Antineoplastic Agents↗
PubMed1994

Update of systemic antimicrobials: emphasis on oral agents.

There has been a proliferation of antimicrobial agents in the market and we can expect many more new agents to be available for use in the hospital and community later. In the outpatient setting, the number of oral antimicrobial agents are varied, providing greater flexibility in managing community acquired infections. Unfortunately, the extensive use of antimicrobial agents has contributed to the development of resistance of some bacteria to multiple antimicrobials. This paper will review the basis of activity of antimicrobial agents commonly used in the outpatient clinic. The spectrum of antibacterial activity of these agents is discussed in relation to the common organisms encountered in general practice. Guidelines for the control of the development of bacterial antimicrobial resistance are also given.

Administration, Oral↗
PubMed1994

HIV infection among non-injecting drug users entering drug treatment, United States, 1989-1992. Field Services Branch.

OBJECTIVE: To describe HIV seroprevalence among non-injecting drug users (non-IDU) entering sentinel drug treatment centers in the United States. DESIGN: Anonymous, blinded (unlinked) HIV seroprevalence surveys. SETTING: Sixty-eight sentinel drug treatment centers in 37 United States metropolitan areas. PARTICIPANTS: Consecutive sample of clients admitted to sentinel drug treatment centers from January 1989 through December 1992. Of 84,617 clients, 37,633 (44.5%) had used illicit drugs but reported no injecting drug use since 1978. MAIN OUTCOME MEASURES: Center-specific, metropolitan area-specific, and national median HIV seroprevalence rates. RESULTS: National median center-specific HIV seroprevalence among non-IDU was 3.2% (range, 0-15.2%). Rates varied widely by geographic area. Median rates were highest in the northeast (5.6%; range, 0-15.2%), intermediate in the south (3.4%; range, 0.6-8.0%), and generally lower throughout the rest of the country: midwest (1.3%; range, 0-3.1%) and west (1.8%; range, 0-14.5%). When stratified by treatment center, there were few statistically significant differences in seroprevalence among African Americans, Hispanics and whites. The median rate was 3.4% among men and 2.7% among women. Rates among non-IDU were lower than among IDU attending the same drug treatment centers, but consistently higher than among heterosexual patients attending sexually transmitted disease clinics in the same metropolitan areas. CONCLUSIONS: HIV seroprevalence among non-IDU entering drug treatment is high in many metropolitan areas. HIV prevention and education efforts in drug treatment centers should target sexual as well as drug-use risk reduction for all clients.

Adolescent↗
PubMed1994

HIV infection among homeless adults and runaway youth, United States, 1989-1992. Field Services Branch.

OBJECTIVES: Homeless persons have an increased risk of HIV infection because of a high prevalence of HIV-related risk behaviors. These include drug use, sexual contact with persons at risk for HIV infection, and the exchange of sex for drugs. The objectives of this investigation were to describe HIV seroprevalence rates in homeless adults and runaway youth. METHODS: In 1989, the Centers for Disease Control and Prevention began collaboration with state and local health departments to conduct HIV seroprevalence surveys in homeless populations. Unlinked HIV seroprevalence surveys were conducted in 16 sites; 11 provided medical services primarily to homeless adults, and five to runaway youth aged < 25 years. RESULTS: From January 1989 through December 1992, annual surveys were conducted in 16 sites in 14 cities. Site-specific seroprevalence rates ranged from 0-21.1% (median, 3.3%). Among homeless adults in three sites, rates were higher among men who had sex with other men and those who injected drugs than among persons with other risk exposures (28.9 versus 5.3%). In general, rates were higher for heterosexual men than for women and higher among African Americans than whites. In sites providing services to homeless youth, HIV seroprevalence rates ranged from 0-7.3% (median, 2.3%). CONCLUSIONS: These data indicate that HIV infection among homeless adults and runaway youth is an important public health problem. HIV prevention and treatment should be integrated into comprehensive health and medical programs serving homeless populations.

Adolescent↗
PubMed1994

Acquired immunodeficiency syndrome and Cryptosporidium infection.

A child suffering from the acquired immunodeficiency syndrome (AIDS) with intestinal cryptosporidiosis is reported. The child presented with profuse diarrhoea up to 15 episodes a day over a period of one week. Management was with intravenous rehydration and oral spiramycin. Diagnosis of intestinal cryptosporidiosis requires examination of multiple stool specimens by several concentration and staining procedures which aid in the visualisation of the oocysts. In the absence of an effective treatment for cryptosporidiosis, the cornerstone of management is mainly supportive therapy.

AIDS-Related Opportunistic Infections↗
PubMed1993

Disseminated Mycobacterium flavescens in a probable case of chronic granulomatous disease.

We report the case of a diabetic Chinese male with no previous history of recurrent infections. His course was at first notable for relapsing Salmonella blockley infections, following which he developed repeated soft-tissue infections and Cryptococcus neoformans pneumonia. He was diagnosed as having chronic granulomatous disease and was treated with gamma interferon. During the latter stages of his illness he developed Mycobacterium flavescens infection in soft tissues, joints, bones and lung. This is the first report of disseminated M. flavescens infection.

Bronchopneumonia↗
PubMed1993

Sequence of the gtfK gene of Streptococcus salivarius ATCC 25975 and evolution of the gtf genes of oral streptococci.

Many strains of oral streptococci secrete glucosyltransferases (GTFs) that polymerize sucrose into glucans that form an integral part of the plaque matrix on the tooth surface. Recently, we reported the cloning of two closely linked GTF-encoding genes (gtfJ and gtfK) from Streptococcus salivarius ATCC 25975 as well as the sequence of gtfJ, which encodes a primer-dependent GTF that synthesizes an insoluble product (a GTF-I). In this communication we report the sequence of gtfK, which encodes a primer-dependent GTF that synthesizes a soluble product (a GTF-S), as well as the sequence of a small downstream open reading frame of unknown function. The deduced sequence of GtfK was compared with those of seven other streptococcal Gtfs and an unrooted phylogenetic tree constructed. This analysis suggested that Gtfs with similar product specificities do not form phylogenetic clusters and was consistent with currently accepted phylogenetic schemes. The tree was tested by constructing a series of 'sub-trees' from different blocks of the alignment. Evidence was obtained for recombination events involving gtfB and gtfC from S. mutans GS-5, gtfJ and gtfK from S. salivarius, as well as the gtfI genes from S. downei and S. sobrinus. The recombination events between gtfB and gtfC, and between the two gtfI genes, were confirmed by examining divergences at silent sites.

Algorithms↗
PubMed1993

Fatal varicella infections in Singapore.

Varicella (chickenpox) is common in Singapore. The annual incidence of reported cases for the period 1977-1990 ranged from 790 to 18,934, with a mean of 4,747. Mortality from chickenpox is rare. However, failure to recognise the severity and the potential complications of the disease, especially in immunocompetent patients, exists because of the common knowledge that chickenpox is a mild and self-limiting illness. We report six cases of fatal varicella in immunocompetent patients during the period 1988 to 1990.

Adolescent↗
PubMed1992

Youth at risk. Sex, drugs, and human immunodeficiency virus.

Adolescents and young adults are at risk for human immunodeficiency virus type 1 infection due to unprotected sexual intercourse and drug use. In 1988 and 1989, blinded surveys were conducted in 84 sexually transmitted disease clinics, 115 women's health clinics, and 19 drug treatment centers in 38 metropolitan areas. Blood specimens from 153,242 clients, aged 15 to 24 years, were tested for human immunodeficiency virus type 1 antibodies after all client identifiers were removed. In sexually transmitted disease clinics, the median rate was 0.4% among 15- to 19-year-olds, compared with 1.4% among 20- to 24-year-olds. Among heterosexual adolescents, rates in females were significantly higher than in males (Wilcoxon signed rank test). Rates in heterosexuals were highest in the northeastern and southeastern United States and in Puerto Rico. In 20- to 24-year-old male clients in sexually transmitted disease clinics who had sex with males, rates ranged from 9.7% to 55.6%. In drug treatment centers, the median rate among 20- to 24-year-old men and women was 8.3% (range, 0% to 33.3%). Rates in women's health clinics were much lower (median, 0.1%). The high rates of infection in certain groups of adolescents and young adults indicate the need for improved care, education, and outreach targeted toward those at high risk.

Adolescent↗
PubMed1992

A 7-day course of ciprofloxacin for enteric fever.

A prospective, open and non-randomised clinical trial using a 7-day short course of oral ciprofloxacin 500 mg twice daily was conducted on 25 adult patients with bacteraemic enteric fever. Twenty-four patients (96%) were cured and there was one treatment failure. Two patients with typhoid fever relapsed 6 weeks after finishing treatment. Defervescence of fever was rapid (median: 4 days) and the duration of hospitalisation was short (median: 8 days). Both factors resulted in patient satisfaction. A short-course regime of ciprofloxacin for the treatment of enteric fever, is therefore, highly promising.

Administration, Oral↗
PubMed1992

Transmission of disseminated histoplasmosis via cadaveric renal transplantation: case report.

A 30-year-old woman received a cadaveric renal allograft from a donor who was subsequently found to have renal infection due to Histoplasma capsulatum. The recipient had funguria in the early postoperative period and later developed cutaneous manifestations of disseminated histoplasmosis. We report a case of histoplasmosis transmitted via renal transplantation and describe the subsequent 20-year clinical course.

Adult↗