Neural modeling in cerebral dynamics

For many years our current conception of neural modeling at cortical level has been marked by three convictions: (i) the representational, explanatory, and predictive capabilities of a model are always limited by the mathematical nature of the formal tools used in its formulation. The external observer in fact injects the additional knowledge, apparently resident in the model. (ii) The analogical and logical languages (and consequently, the neurophysiological data which serves as their basis) are not sufficient to describe, model and predict the most genuine aspects of the cortical determined behavior. (iii) We need new conceptual and formal tools capable of representing cooperative processes (not only physical interactions) in cerebral dynamics. In this paper, we use the neuropsychological findings on the residual function after traumatic and surgical lesions in animals and men, to think about the sort of requirements that are necessary to build these formal tools adequate to model neural information processing at cortical level. If we search for inspiration in the field of computation, we arrive to the conjecture that the cerebral dynamics is a dynamics of neurophysiological symbols and, consequently, we need a set of descriptions at an intermediate level (neural assemblies "programming"), in a similar way as we use programming languages at an intermediate level (the symbol level) between the physical machine and the knowledge level descriptions, in the sense of Newell and Marr.

Structural transformation induced by magnetic field and "colossal-like" magnetoresistance response above 313 K in MnAs

MnAs exhibits a first-order phase transition from a ferromagnetic, high-spin metal hexagonal phase to a paramagnetic, lower-spin insulator orthorhombic phase at T(C)=313 K. Here, we report the results of neutron diffraction experiments showing that an external magnetic field, B, stabilizes the hexagonal phase above T(C). The phase transformation is reversible and constitutes the first demonstration of a bond-breaking transition induced by a magnetic field. The field-induced phase transition is accompanied by an enhanced magnetoresistance of about 17% at 310 K. The phenomenon appears to be similar to that of the colossal magnetoresistance response observed in the Mn [corrected] perovskite family.

Factors related to the chronicity and evolution of hepatitis C infection in patients co-infected by the human immunodeficiency virus

OBJECTIVES

This work analyses the influence of immune status, serum human immunodeficiency virus (HIV) load and hepatitis C virus (HCV) genotypes on the probability of resolution of HCV infection in HIV-co-infected patients, as well as the evolution of HCV viremia after antiretroviral therapy.

PATIENTS AND METHODS

Forty-five patients with anti-HIV and anti-HCV antibodies were classified into two groups as a function of the positivity or persistent negativity of HCV RNA detection (active or recovered HCV infection, respectively). They were treated with highly active antiretroviral therapy (HAART). Serum HCV RNA was quantified by the reverse transcription-polymerase chain reaction. HCV genotypes were detected by line probe assay or by detection of type-specific antibodies.

RESULTS

HCV RNA was detectable in 30 (66.6%) out of 45 HIV-infected patients. CD4+ T-cell counts, HIV viremia, or HCV genotypes were similar in patients with active or recovered HCV infection. Patients with active HCV infection had a non-significant decrease of HCV viremia during a follow-up of 12 months (from 6.15 +/- 6.32 to 5.96 +/- 6.05 log copies/mL). This was not influenced by baseline HCV or HIV viral load, HCV genotype, or CD4+ T-cell count. The non-significant decrease was present in patients with or without an immunological response to HAART.

CONCLUSION

HCV genotypes, immune status, or serum HIV load did not influence the resolution or chronicity of HCV infection in HIV-co-infected individuals. A non-significant decrease of HCV viremia in these patients treated with combinations including antiproteases could be expected.

NasoNet, modeling the spread of nasopharyngeal cancer with networks of probabilistic events in discrete time

The spread of cancer is a non-deterministic dynamic process. As a consequence, the design of an assistant system for the diagnosis and prognosis of the extent of a cancer should be based on a representation method that deals with both uncertainty and time. The ultimate goal is to know the stage of development of a cancer in a patient before selecting the appropriate treatment. A network of probabilistic events in discrete time (NPEDT) is a type of Bayesian network for temporal reasoning that models the causal mechanisms associated with the time evolution of a process. This paper describes NasoNet, a system that applies NPEDTs to the diagnosis and prognosis of nasopharyngeal cancer. We have made use of temporal noisy gates to model the dynamic causal interactions that take place in the domain. The methodology we describe is general enough to be applied to any other type of cancer.

Extracellular enzymatic activity in 11 Cryptococcus species

The extracellular enzymatic activity of 36 strains of yeast belonging to 11 species of the genus Cryptococcus, has been investigated, using the API-ZYM (BioMérieux, France) commercial system, with the objective of determining the differences in the enzymatic profiles of the various species. The strains studied were: 9 of C. neoformans, 7 of C. albidus, 6 of C. laurentii, 5 of C. uniguttulatus, 3 of C. humicolus, and 1 each of C. ater, C. curvatus, C. dimennae, C. hungaricus, C. infirmo-miniatus and C. magnus. All the strains showed enzymatic activity with positivity to Phosphatase alkaline, Esterase lipase C8, Leucine arylamidase, Phosphatase acid and Naphthol-AS-BI-phosphohydrolase, and negativity to Lipase C14, Trypsin, Chemotrypsin, beta-galactosidase, beta-glucuronidase and alpha-manosidase. Variable enzymatic activity was shown to Esterase C4, Valine arylamidase, Cystine arylamidase, alpha-galactosidase, alpha-glucosidase, beta-glucosidase, N-acetyl-beta-glucosaminidase and alpha-fucosidase. This allowed 11 separate enzymatic patterns to be established. The species C. neoformans and C. laurentii each presented two distinct patterns; C. uniguttulatus, C. hungaricus and C. magnus shared the same pattern; C. albidus, C. ater, C. curvatus, C. dimennae, C. humicolus and C. infirmo-miniatus presented an individual enzymatic pattern. The results obtained suggest that the API-ZYM system could be useful for the identification of species of the genus Cryptococcus and for the differentiation of the enzymotypes for epidemiological purposes.

[Antifungal susceptibility of emerging yeast pathogens]

BACKGROUND

To study the antifungal susceptibility of emerging yeast pathogens to know their possible resistance under the need of applying a treatment.

MATERIAL AND METHODS

We investigated the in vitro susceptibility of 69 yeast strains isolates of clinical samples, belonging to 24 different species, to amphotericin B, fluconazole, itraconazole, ketoconazole and 5-fluorocytosine.

RESULTS

Only 9 species showed susceptibility to all antifungal agents: Candida famata, C. guillermondii, C. holmii, C. kefyr, C. pelliculosa, C. rugosa, C. utilis, C. zeylanoides y Trichosporon cutaneum; the rest of them presented resistance to some antifungal agent. C. haemulonii, Pichia farinosa and Trichosporon mucoides were resistant to amphotericin B; C. haemulonii, C. inconspicua, C. lusitaniae, C. norvegensis, C. pintolepesii, C. valida, P. ohmeri, Rhodotorula glutinis, R. minuta, R. mucilaginosa and Saccharomyces cerevisiae were resistant to azoles; Blastoschizomyces capitatus and C. lipolytica were resistant to 5-fluorocytosine.

CONCLUSIONS

The resistance of emerging yeast pathogens to amphotericin B and 5-fluorocytosine is low, while resistance to azoles is significative, especially to fluconazole (36%). Many of this yeasts present problems of intrinsic resistance. In yeast infections, the correct identification of species and the study of the in vitro susceptibility is important in order to choose the most adequate antifungal treatment.

Neuroblastoma and bronchogenic cyst: a rare association

A few of the known associations between paediatric cancer and congenital anomalies are attributable to contiguous-gene syndromes. Neuroblastoma (NB) has been linked with an excess of gastrointestinal malformations, but there is a significant scarcity of associated respiratory anomalies. We report on two children having an abdominal NB and a bronchogenic cyst diagnosed simultaneously and in different order of appearance. Both masses were removed in separated procedures, taking into account the priority and the time sequence of chemotherapy. Literature is reviewed, checking that the genetic basis for this association is supported by speculations about the oncogene RON.

[Onychomycoses caused by non-dermatophytic filamentous fungi in Cádiz]

BACKGROUND

The incidence and clinical significance of other than dermatophytes fungi or moulds causing onychomycosis is unknown, because they may be colonising organisms rather than pathogen. This report presents the results of a study conducted between 1997 and 1999 to determine the incidence and aetiology of onychomycosis by non-dermatophytic filamentous fungi in the population of Cádiz (Spain).

PATIENTS AND METHODS

Diagnosis of onychomycosis was performed by direct microscopic examination, culture and, some times, by histologic examination, on samples from 610 patients with clinical suspected fungal nail infections.

RESULTS

Among 196 (32%) cases of ungual mycosis detected, 29 (15%) of them were caused by non-dermatophytic filamentous fungi, presenting positive direct microscopy and repeated cultures. Superficial and distal onychomycosis were the most frequent clinical types. Twenty two patients had onychomycosis of toenails. The highest incidence was found in women and subjects over the age 40. Scopulariopsis spp. (n = 11), Aspergillus spp. (n = 6), Alternaria spp. (n = 5) and Fusarium spp. (n = 4) were the most common fungi. Occasionally, Acremonium spp. and Scedosporium spp. were isolated.

CONCLUSION

The incidence of onychomycosis caused by opportunistic fungi is not well known. For their diagnosis, it is important to select correctly the appropriate site for specimen collection, as well as direct microscopy and fungal cultures. The incidence of onychomycosis is high in Cádiz (Spain), being higher in women and older people. Predispondent factors are not always identified in the patients. Toenails were infected more than fingernails in both sexes. The results of our study suggest that Scopulariopsis spp. is an important agent of onychomycosis. Epidemiological investigations should be performed in every country in order to determine the fungal species responsible of onychomycosis.

A problem-solving method for 'unprotocolised' therapy administration task in medicine

This paper describes a problem-solving method for modelling the 'unprotocolised' treatment administration task in medicine. We argue that there are medical domains in which no well-established standard treatment protocols exist, and the physician has to decide on the therapy that is to be applied to each patient, in function of a set of therapeutic objectives to be fulfilled. For this reason, we propose the modelling of this type of task adapting the generic class of problem resolution methods for design task, labelled as Propose-Critique-Modify (PCM). In this paper, we are presenting a model of expertise which has been developed using the basic modelling components of the CommonKADS methodology.

[Congenital hydronephrosis. An evolutionary study of renal function]

Between 1986 and 1995, 24 newborn and young infants underwent to surgical repair of 32 renal units affected by congenital hydronephrosis in spite of their levels of renal function and dilation. 22 renal units were pelviureteral junction obstruction and 10 were vesico-ureteral obstruction. Isotopic studies were made pre- and post-operatively, resulting in a high percentage of kidneys with the highest values of relative renal function showing a downward after surgery, and a general improvement among the renal units with previously moderate function. Drainage slope curves showed an improvement of its partial obstruction, and no change when dilation without obstruction. The clearance half-time showed a reduction in the slower renal units. We conclude that the natural evolution of these age-group kidneys is a counterbalance with the healthy contralateral renal unit.

Isolation of Hanseniaspora uvarum (Kloeckera apiculata) in humans

Isolation of Hanseniaspora uvarum, a yeast of the ascomycetes group, whose anamorph corresponds to Kloeckera apiculata, obtained from stool and two ungual specimens from three patients, is reported. This yeast has been found in soil, water, various fruits, bivalve molluscs, crabs, prawns and fruit flies; in Spain, it has been described in the fermentation processes of some wines. In our region, it has also been found in the intestine of mackerel (Scomber scombrus). Its finding in humans constitutes a clinical rarity.

Multilobated large B-cell lymphoma diagnosed cytologically. A case report

BACKGROUND

Fine needle aspiration (FNA) biopsy can be used to reliably classify most conditions involving lymph nodes or, at least, significantly reduce the differential diagnosis.

CASE

A 70-year-old male presented with an ulcerated mass arising from the left tonsillar fossa and involving the anterior and posterior pillars. A biopsy of the tonsillar mass performed at an outside hospital was interpreted as a large cell undifferentiated carcinoma. Subsequently the patient developed systemic lymphadenopathy. A bone scan showed intense uptake within the medial tibial plateau of the left knee. FNA biopsy of the right axillary mass was interpreted at University of Cincinnati Medical College as a large cell lymphoma, multilobated type. Histologic and immunohistochemical studies of the lymph node confirmed the presence of multilobated B-cell lymphoma. Lymphoma chemotherapy was initially successful but was discontinued due to toxicity. The patient died two months after the initial cytologic diagnosis of lymphoma.

CONCLUSION

Multilobated lymphomas are an unusual variant of non-Hodgkin's lymphomas (mostly B-cell type). Cytology and immunocytochemistry are useful diagnostic procedures that can help to diagnose this relatively uncommon type of lymphoma and significantly reduce the possibility of misdiagnosis.

Case of onychomycosis caused by Microsporum racemosum

We report the case of a Spanish 60-year-old female who presented in 1997 with onychomycosis of the left thumbnail following an injury caused by a fresh fish bone. Microsporum racemosum was repeatedly cultured from nail scrapings, and its identity was confirmed by sequencing the isolate's ITS1/ITS2 and 5.8S rRNA regions. The patient was successfully treated with itraconazole, which was administered for 12 weeks. This represents the first case of onychomycosis due to M. racemosum and the first time that this species has been isolated from a human in Europe.

Thyroid transcription factor-1 and cytokeratins 7 and 20 in pulmonary and breast carcinoma

OBJECTIVE

To evaluate the immunohistochemical expression of a lung epithelial gene transcription factor, thyroid transcription factor-1 (TTF-1), in lung and breast carcinoma in pulmonary cytologic preparations and to correlate the results with the expression of cytokeratin 7 (CK7) and 20 (CK20).

STUDY DESIGN

Cell blocks of cytologic specimens were immunostained with antibodies to TTF-1, CK7 and CK20. Specimens included 41 primary lung carcinomas (21 adenocarcinomas, 8 squamous cell carcinomas and 12 small cell undifferentiated carcinomas) and 6 metastatic breast adenocarcinomas.

RESULTS

The lung adenocarcinomas showed nuclear reactivity for TTF-1 in 76% (16/21) of the cases and a staining combination of CK7+/CK20- in 95% (20/21) of the cases. Only one case was CK7+/CK20+. All the breast carcinomas were nonreactive to TTF-1, and all were CK7+/CK20-. The squamous cell carcinomas and small cell undifferentiated carcinomas showed TTF-1 positivity in 38% (3/8) and 83% (10/12), respectively.

[Identification of yeasts of clinical interest on CHROMagar Candida culture medium.]

The efficiency of CHROMagar Candida was evaluated as a medium for the presumptive identification of yeasts. We tested 36 different yeast species, pertaining to 9 genera: one Blastoschizomyces, 20 Candida, five Cryptococcus, two Geotrichum, one Kloeckera, two Pichia, three Rhodotorula, one Saccharomyces and one Trichosporon, to determine the colony colors and characteristics on this medium. Afterwards, we identified 2,230 strains isolated directly on CHROMagar Candida from clinical samples by specific colouration and morphology of the colonies after 72 hours. Their results were compared with standard methods for the identification of yeasts. The sensitivity and specificity were both superior to 97% for all strains, 100% and 100% for Candida albicans, 97.3% and 99.9% for Candida glabrata, 92.3% and 99.6% for Candida krusei, 90.3% and 99.6% for Candida parapsilosis, and 100% and 100% for Candida tropicalis. CHROMagar Candida is a very useful medium for the culture of clinical samples; its use for identification of yeasts has an accuracy of 97.5%, close to 100% of conventional methods.

Towards the unification of inference structures in medical diagnostic tasks

The central purpose of artificial intelligence applied to medicine is to develop models for diagnosis and therapy planning at the knowledge level, in the Newell sense, and software environments to facilitate the reduction of these models to the symbol level. The usual methodology (KADS, Common-KADS, GAMES, HELIOS, Protégé, etc) has been to develop libraries of generic tasks and reusable problem-solving methods with explicit ontologies. The principal problem which clinicians have with these methodological developments concerns the diversity and complexity of new terms whose meaning is not sufficiently clear, precise, unambiguous and consensual for them to be accessible in the daily clinical environment. As a contribution to the solution of this problem, we develop in this article the conjecture that one inference structure is enough to describe the set of analysis tasks associated with medical diagnoses. To this end, we first propose a modification of the systematic diagnostic inference scheme to obtain an analysis generic task and then compare it with the monitoring and the heuristic classification task inference schemes using as comparison criteria the compatibility of domain roles (data structures), the similarity in the inferences, and the commonality in the set of assumptions which underlie the functionally equivalent models. The equivalences proposed are illustrated with several examples. Note that though our ongoing work aims to simplify the methodology and to increase the precision of the terms used, the proposal presented here should be viewed more in the nature of a conjecture.