Constitutive activation of photoreceptor guanylate cyclase by Y99C mutant of GCAP-1. Possible role in causing human autosomal dominant cone degeneration.

Photoreceptor membrane guanylate cyclases (RetGC) are regulated by calcium-binding proteins, GCAP-1 and GCAP-2. At Ca2+ concentrations below 100 nM, characteristic of light-adapted photoreceptors, guanylate cyclase-activating protein (GCAPs) activate RetGC, and at free Ca2+ concentrations above 500 nM, characteristic of dark-adapted photoreceptors, GCAPs inhibit RetGC. A mutation, Y99C, in human GCAP-1 was recently found to be linked to autosomal dominant cone dystrophy in a British family (Payne, A. M., Downes, S. M., Bessant, D. A. R., Taylor, R., Holder, G. E., Warren, M. J., Bird, A. C., and Bhattachraya, S. S. (1998) Hum. Mol. Genet. 7, 273-277). We produced recombinant Y99C GCAP-1 mutant and tested its ability to activate RetGC in vitro at various free Ca2+ concentrations. The Y99C mutation does not decrease the ability of GCAP-1 to activate RetGC. However, RetGC stimulated by the Y99C GCAP-1 remains active even at Ca2+ concentration above 1 microM. Hence, the cyclase becomes constitutively active within the whole physiologically relevant range of free Ca2+ concentrations. We have also found that the Y99C GCAP-1 can activate RetGC even in the presence of Ca2+-loaded nonmutant GCAPs. This is consistent with the fact that cone degeneration was dominant in human patients who carried such mutation (Payne, A. M., Downes, S. M., Bessant, D. A. R. , Taylor, R., Holder, G. E., Warren, M. J., Bird, A. C., and Bhattachraya, S. S. (1998) Hum. Mol. Genet. 7, 273-277). A similar mutation, Y104C, in GCAP-2 results in a different phenotype. This mutation apparently does not affect Ca2+ sensitivity of GCAP-2. Instead, the Y104C GCAP-2 stimulates RetGC less efficiently than the wild-type GCAP-2. Our data indicate that cone degeneration associated with the Y99C mutation in GCAP-1 can be a result of constitutive activation of cGMP synthesis.

Use of electrophoretic karyotyping in the evaluation of Candida infections in a neonatal intensive-care unit.

OBJECTIVE: To evaluate a possible common-source outbreak of Candida infections in the neonatal intensive-care unit. Systemic Candida infections increased from 6 to 11 cases (0.71 to 1.34 per 1,000 patient-days). In addition, Candida parapsilosis infections increased from 1 in 1992 to 10 in 1993. DESIGN AND SETTING: Tertiary-care, teaching, pediatric institution with a 40-bed neonatal intensive-care unit (NICU). Clinical characteristics, associated conditions, and antimicrobial therapy were obtained from the medical records of all NICU patients with positive blood cultures for Candida during 1992 and 1993. Nineteen Candida isolates from 15 infants were studied retrospectively using contour-clamped homogeneous electric-field (CHEF) electrophoresis. RESULTS: CHEF revealed eight karyotypes of C parapsilosis. Five isolates recovered from four patients shared one karyotype. The remaining isolates from seven infants all had distinctly different karyotypes. CONCLUSIONS: The evidence was insufficient to implicate a single source of infection, even though four patients in the same unit had identical strain types. However, identical strains of C parapsilosis were associated geographically, suggesting that nosocomial acquisition of C parapsilosis through indirect patient contact in the NICU was possible. The CHEF technique yields unique patterns that may be used to delineate clinical isolates and to study the molecular epidemiology of candidal infections.

[The incidence of finding and characteristics of Klebsiella pneumoniae strains isolated in neonatal infections]. / Chastota vstrechaemosti i kharakteristika shtammov Klebsiella pneumoniae, vydelennykh pri infektsiiakh novorozhdennykh.

The clinical and laboratory study of 190 hospitalized children revealed that in 122 cases the course of the underlying disease was complicated by Klebsiella infection. From different pathological material obtained from 122 patients 158 K. pneumoniae cultures were isolated. These cultures were mostly isolated from the respiratory organs (69%), from patients with the generalized infection (21.6%), and less frequently from operative wounds and burn surfaces (5.8%), the gastrointestinal tract (1.4%) and the urinary system (1.4%). The isolated clinical strains were multiresistant to antibiotics and contained plasmid DNA with molecular weights of 70 and 105 MD (60.4%). K. pneumoniae were shown to produce an aggravating effect on the course and outcome of the underlying disease, mainly in preterm babies or those born asphyxiated or with congenital defects of development, as well as in patients with immunodeficient states. The probability of infection was directly related to the character and number of medical manipulations on an infant, mainly in connection with artificial ventilation of the lungs and transfusion therapy.

[Use of antibiotics in pediatrics]. / Osobennosti primeneniia antibiotikov v pediatrii.

The problems of an etiotropic approach to the choice of antibiotics in the treatment of infants remain actual and require their solution which is evident from the example of some usual affections: intrahospital pneumonia of newborns, pneumonia of infant outpatients, purulent meningitis, etc. The practice of irrational therapy of some children infections such as streptococcal angina and scarlet fever, whooping cough, intestinal infections, otitis media purulenta, sinusitis is rather common. Attention should be paid to the organization of the bacteriological services and the increase of the physicians qualification in the field of antibiotic therapy and clinical microbiology. It is advisable that chemotherapeutists be included in the staff of certain general hospitals.

[Klebsiella pneumonia today]. / Klebsielleznye pnevmonii v nastoiashchee vremia.

Analysis of incidence and morphology of Klebsiella pneumonia nowadays in the adults (10 observations), children (5 observations) and newborns (23 observations) is presented. The pneumonias account for 11.3% of total number of lobar pneumonias in the adults dying in 1979-1989. Klebsiella infection represent 16.1% of total number of autopsies a year according to the pediatric infection pathology department. Etiological role of Klebsiella is established in 21.5% of total number of autopsies of newborns for 1985-1988, pneumonia being 61% of total Klebsiella infections. Klebsiella pneumonias in the adults correspond in principle to the Friedländer's pneumonia studied in detail by V.D. Zinserling (1891-1960) and his students. Generalized forms of, as a rule, hospital Klebsiellosis with most grave lung damage, unknown up to now, are frequently observed in children. Klebsiellosis was combined practically in all cases both in the adults and children with other bacterial, viral and fungal infections. The degree of clinico-morphological manifestations may considerably vary.

[Pathologic anatomy of Pseudomonas aeruginosa infections in children]. / Patologicheskaia anatomiia sinegnoinoi infektsii u detei.

Examinations of 143 autopsy observations of P. aeruginosa infection in children were performed. Among them, 119 patients had pneumonia, 16 affections of the alimentary tract, 8 sepsis with various localizations of the primary focus. Morphologically the affected organs presented foci of necrosis of different size with tremendous numbers of bacteria, poor leukocyte reaction, and deep circulatory disorders in the periphery. A more manifest leukocyte infiltration in foci of lesions was observed in the cases where other bacterial microflora, in addition to P. aeruginosa, was present. P. aeruginosa isolated from the organs of dead children, as a rule, belonged to immune type 1 or 2 (according to Fisher's scheme). Microbiological studies on these strains showed the most marked necrotic changes to have been caused by microbes having such factors of pathogenicity as protease and plasmocoagulase.