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Biomedical subjects

M Levin

Publications and source records attributed to M Levin.

At least 127 records · Page 7Linked to original sources
PubMed1996

Reservoir competence of the southeastern five-lined skink (Eumeces inexpectatus) and the green anole (Anolis carolinensis) for Borrelia burgdorferi.

The reservoir competence of two lizard species, the southeastern five-lined skink (Eumeces inexpectatus) and the green anole (Anolis carolinesis), for Borrelia burgdorferi was evaluated. Skinks and anoles were exposed by needle inoculation or tick bite to B. burgdorferi. Xenodiagnosis with larval Ixodes scapularis and culture of tissues were used to asses infection and the ability of infected lizards to infect attached ticks. Both lizard species were susceptible to B. burgdorferi by both routes of exposure. Xenodiagnostic ticks acquired spirochetes while feeding on both species. One tick that dropped from a skink on the ninth day after exposure was infected. The remainder of xenodiagnostic ticks that acquired spirochetes fed three weeks after exposure of the lizards to the spirochete. Lizards remained infectious to attached ticks for at least five weeks. Overall, more than 20% of xenodiagnostic larvae fed on southeastern five-lined skinks acquired spirochetes. Individual skinks infected up to 34% of attached ticks. A smaller proportion of ticks feeding on green anoles became infected. Borrelia burgdorferi recovered from infected lizards retained their infectivity for mammalian hosts. The ability of the lizards to sustain a Borrelia infection and infect attached ticks suggests that they may play a role in the maintenance of spirochete transmission.

Animals↗
PubMed1996

Serological evidence for zoonotic hantaviruses in North Carolina rodents.

In a survey of seven species of wild rodents (n = 423) collected between October 1993 and March 1994 from the three principal ecological biomes of North Carolina (USA), we found hantavirus antibodies in seven (2%) of 301 Peromyscus spp. Hantavirus antibodies were detected in P. leucopus and P. maniculatus captured from mountain and coastal island biomes. Three mice were positive for Sin Nombre virus, while four others had antibodies to Seoul virus or a related agent. Two mice serologically positive for Sin Nombre virus were collected from inside a private mountain domicile. We conclude that the risk of human exposure to hantaviruses in North Carolina resembles that for most other areas of the continental United States.

Animals↗
PubMed1995

Morbidity and severity of illness during interhospital transfer: impact of a specialised paediatric retrieval team.

OBJECTIVE: To evaluate the morbidity and severity of illness during interhospital transfer of critically ill children by a specialised paediatric retrieval team. DESIGN: Prospective, descriptive study. SETTING: Hospitals without paediatric intensive care facilities in and around the London area, and a paediatric intensive care unit at a tertiary centre. SUBJECTS: 51 critically ill children transferred to the paediatric intensive care unit. MAIN OUTCOME MEASURES: Adverse events related to equipment and physiological deterioration during transfer. Paediatric risk of mortality score before and after retrieval. Therapeutic intervention score before and after arrival of retrieval team. RESULTS: Two (4%) patients had preventable physiological deterioration during transport. There were no adverse events related to equipment. Severity of illness decreased during stabilisation and transport by the retrieval team, suggested by the difference between risk of mortality scores before and after retrieval (P < 0.001). The median (range) difference between the two scores was 3.0 (-6 to 17). Interventions during stabilisation by the retrieval team increased, demonstrated by the difference between intervention scores before and after retrieval, median (range) difference between the two scores being 6 (-8 to 38) (P < 0.001). CONCLUSIONS: Our study indicates that a specialised paediatric retrieval team can rapidly deliver intensive care to critically ill children awaiting transfer. Such children can be transferred to a paediatric intensive care unit with minimal morbidity and mortality related to transport. There was no deterioration in the clinical condition of most patients during transfer.

Child↗
PubMed1995

A molecular pathway determining left-right asymmetry in chick embryogenesis.

While significant progress has been made in understanding the molecular events underlying the early specification of the antero-posterior and dorso-ventral axes, little information is available regarding the cellular or molecular basis for left-right (LR) differences in animal morphogenesis. We describe the expression patterns of three genes involved in LR determination in chick embryos: activin receptor IIa, Sonic hedgehog (Shh), and cNR-1 (related to the mouse gene nodal). These genes are expressed asymmetrically during and after gastrulation and regulate the expression of one another in a sequential pathway. Moreover, manipulation of the sidedness of either activin protein or Shh expression alters heart situs. Together, these observations identify a cascade of molecular asymmetry in that determines morphological LR asymmetry in the chick embryo.

Activins↗
PubMed1995

Familial disseminated atypical mycobacterial infection in childhood: a human mycobacterial susceptibility gene?

Inherited defects in specific components of the immune system have provided many clues to the immunological mechanisms underlying resistance to microbial infection. We report a familial immune defect predisposing to disseminated atypical mycobacterial infection in childhood. 6 children with disseminated atypical mycobacterial infection and no recognised form of immunodeficency were identified. Four, including two brothers, come from a village in Malta, and two are brothers of Greek Cypriot origin. They presented with fever, weight loss, lymphadenopathy, and hepatosplenomegaly. They had anaemia and an acute phase response. A range of different mycobacteria (Mycobacterium fortuitum, M chelonei, and four strains of M avium intracellulare complex) were isolated. Treatment with multiple antibiotics failed to eradicate the infection, although treatment with gamma interferon was associated with improvement. Three have died and the surviving children have chronic infection. Tumour necrosis factor-alpha production in response to endotoxin and gamma-interferon was found to be defective in affected patients and their parents. T-cell proliferative responses to mycobacterial and recall antigens were reduced in parents of affected children and gamma-interferon production was diminished in the affected patients and their parents. Clinical and immunological features suggest that these patients are phenotypically similar to Lsh/Ity/Bcg susceptible mice. Understanding of this defect may provide insights into the mechanisms responsible for susceptibility to mycobacteria.

Adult↗
PubMed1995

Applied AC and DC magnetic fields cause alterations in the mitotic cycle of early sea urchin embryos.

This study demonstrates that exposure to 60 Hz magnetic fields (3.4-8.8 mT) and magnetic fields over the range DC-600 kHz (2.5-6.5 mT) can alter the early embryonic development of sea urchin embryos by inducing alterations in the timing of the cell cycle. Batches of fertilized eggs were exposed to the fields produced by a coil system. Samples of the continuous cultures were taken and scored for cell division. The times of both the first and second cell divisions were advanced by ELF AC fields and by static fields. The magnitude of the 60 Hz effect appears proportional to the field strength over the range tested. The relationship to field frequency was nonlinear and complex. For certain frequencies above the ELF range, the exposure resulted in a delay of the onset of mitosis. The advance of mitosis was also dependent on the duration of exposure and on the timing of exposure relative to fertilization.

Animals↗
PubMed1995

Primary breast carcinoma of the vulva: a case report and review of the literature.

We present a case of primary carcinoma of the vulva successfully treated with local excision and ipsilateral groin dissection. Eleven cases of this entity have been reported in the world literature since 1936. We review the literature and offer guidelines regarding morphologic and immunohistochemical criteria for diagnosis and primary and adjuvant treatment for this rare condition.

Adenocarcinoma↗
PubMed1995

Modulation of the endothelial procoagulant response to lipopolysaccharide and tumour necrosis factor-alpha in-vitro: the effects of dexamethasone, pentoxifylline, iloprost and a polyclonal anti-human IL-1 alpha antibody.

Endothelial expression of tissue factor (TF), a potent procoagulant molecule, is increased in response to inflammatory mediators such as lipopolysaccharide (LPS), tumour necrosis factor (TNF) and interleukin-1 (IL-1). We have examined the effects of three antiinflammatory agents and a polyclonal anti-human IL-1 alpha antibody on the human endothelial TF response to E. coli 0111:B4 LPS and recombinant TNF alpha (rTNF alpha) in vitro. In contrast to the expected inhibitory effect, dexamethasone, pentoxyfilline and iloprost failed to block TF expression when administered simultaneously or 30 minutes prior to stimulation with either LPS or rTNF alpha. Inhibition of procoagulant activity was demonstrated with the anti-IL-1 alpha antibody, suggesting that endothelial derived IL-1 alpha is partially responsible for the TF response to the agonists employed. The failure of the antiinflammatory agents to inhibit endothelial TF expression highlights the possibility that therapeutic agents that modulate the circulating monocyte response to LPS and TNF alpha may not ameliorate the endothelial dysfunction that is also induced by these inflammatory mediators.

Adjuvants, Immunologic↗
PubMed1995

The evolution of understanding: a genetic algorithm model of the evolution of communication.

Much animal communication takes place via symbolic codes, where each symbol's meaning is fixed by convention only and not by intrinsic meaning. It is unclear how understanding can arise among individuals utilizing such arbitrary codes, and specifically, whether evolution unaided by individual learning is sufficient to produce such understanding. Using a genetic algorithm implemented on a computer, I demonstrate that a significant though imperfect level of understanding can be achieved by organisms through evolution alone. The population as a whole settles on one particular scheme of coding/decoding information (there are no separate dialects). Several features of such evolving systems are explored and it is shown that the system as a whole is stable against perturbation along many different kinds of ecological parameters.

Algorithms↗
PubMed1995

Postinfectious purpura fulminans caused by an autoantibody directed against protein S.

OBJECTIVE: To determine the mechanism responsible for idiopathic purpura fulminans, we investigated the procoagulant and anticoagulant pathways in five consecutive patients, four after varicella, and the fifth after a nonspecific infection. METHODS: Procoagulant and anticoagulant factors, including protein C, protein S, and antithrombin III, were measured by quantitative or functional assays. Anti-protein S autoantibodies were identified by dot blotting and Western blotting, and quantified serially by enzyme-linked immunosorbent assay. Clinical and laboratory data were collated retrospectively. RESULTS: In each case the disease began 7 to 10 days after the onset of the precipitating infection, with rapidly progressive purpura leading to extensive areas of skin necrosis. The illness was complicated by impaired perfusion of limbs or digits (two patients), peripheral gangrene resulting in an above-knee amputation (one patient), and major organ dysfunction caused by thromboembolic phenomena involving the lungs (two patients), the heart (one patient), or the kidneys (one patient). Protein S levels were virtually undetectable at the time of admission and failed to respond to infusions of fresh frozen plasma, despite correction of other procoagulant and anticoagulant factors. All five children had anti-protein S IgM and IgG autoantibodies, which persisted for less than 3 months after admission. Decline in the anti-protein S IgG antibody concentration was associated with normalization of the plasma protein S levels. CONCLUSIONS: Autoimmune protein S deficiency may be a common mechanism causing postinfectious idiopathic purpura fulminans. Recognition of the pathophysiologic mechanism may provide a rational basis for treatment. Immediate heparinization, infusions of fresh frozen plasma, and, in cases complicated by major vessel thrombosis, the use of tissue-type plasminogen activator may limit thromboembolic complications.

Acute Disease↗
PubMed1995

Whole blood model of meningococcal bacteraemia--a method for exploring host-bacterial interactions.

An ex vivo whole blood model of meningococcal bacteraemia was developed to examine the total bactericidal activity of blood. Using a single defined donor and strains belonging to serogroups A, B and C and an unencapsulated strain, we demonstrated that the bactericidal mechanisms operating in whole blood varied with anticoagulant, serogroup and bacterial growth conditions. The choice of anticoagulant had a major effect on the survival of the serogroup A strain with 94% (SEM 7.6) survival in citrated blood compared to 19.7% (SEM 19.6) survival in heparinised blood after 60 min incubation. The serogroup C strain showed enhanced survival when grown in liquid medium compared to growth on solid medium (73.5%, SEM 7.5, and 8.2%, SEM 3.1, respectively, in citrated blood after 60 min). The pattern of survival of serogroup B and the unencapsulated strain were largely unaffected by these variables. Comparison with cell free conditions allowed the contribution of cellular components in meningococcal killing to be determined. Secreted levels of tumour necrosis factor and neutrophil elastase secreted during whole blood assays did not correlate with bacterial growth or viability indicating a lack of relationship between killing and activation of phagocytes.

Anticoagulants↗
PubMed1995

Neonatal intussusception misdiagnosed as necrotizing enterocolitis.

Two premature infants with abdominal distension, respiratory distress syndrome, and sepsis were initially diagnosed and treated for necrotizing enterocolitis (NEC). After failure of conservative measures, a diagnosis of intussusception was contemplated. This pitfall in the management of NEC, with medical treatment and a poor response, has been increasingly reported.

Diagnosis, Differential↗
PubMed1995

Reservoir competence of the rice rat (Rodentia: Cricetidae) for Borrelia burgdorferi.

The reservoir competence of the rice rat, Oryzomys palustris, for Borrelia burgdorferi is described. Infected Ixodes scapularis Say (I. dammini, Spielman, Clifford, Piesman & Corwin) nymphs were used to infect animals. Borrelia infection was diagnosed by xenodiagnostic feeding of noninfected I. scapularis larvae and by reisolation of the spirochetes from blood and other tissues. Rice rats acquired B. burgdorferi and maintained spirochete infection for 5-9 wk. B. burgdorferi were cultured from samples of skin and urinary bladders from all animals killed on day 21 (three rats), 35 (three rats), or 56 (three rats) after infection. The spirochetes were also detected in blood samples obtained 1 and 2 wk after exposure. Spirochetes that persisted for 5 wk in rice rats did not lose their infectivity for golden Syrian hamsters. The prepatent period for infecting xenodiagnostic ticks was 1 wk. Overall, 75.6% of I. scapularis larvae (n = 694) that fed on infected rice rats acquired B. burgdorferi. Prevalence of infection reached 83% in ticks that fed on tick-exposed animals during the 2nd-4th wk, 68% during the 5th wk, and 17.4% during the 9th wk. The duration of rice rat infectivity for ticks exceeded 2 mo. I. scapularis nymphs infected as larvae on rice rats transmitted B. burgdorferi. Taken together, these studies confirm the reservoir competence of the rice rat for B. burgdorferi.

Animals↗