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Biomedical subjects

A Novak

Publications and source records attributed to A Novak.

At least 37 records · Page 2Linked to original sources
PubMed1994

GM2 ganglioside activator occurs in multiple forms.

The protein which activates the hydrolysis of GM2 ganglioside by hexosaminidase A was purified from human kidney. The GM2 activator had a molecular mass of 28 kDa by gel filtration and was resolved into three major bands using polyacrylamide gel electrophoresis in the presence of SDS with molecular masses of 23, 22 and 21 kDa. These three bands corresponded respectively to strongly binding, weakly binding and non-binding fractions of GM2 activator chromatographed through concanavalin A-Sepharose, indicating that GM2 activator exists in multiple glycosylated forms.

Carbohydrate Sequence↗
PubMed1994

Classification of disorders of GM2 ganglioside hydrolysis using 3H-GM2 as substrate.

Rates of GM2 ganglioside hydrolysis by fibroblasts from normal controls and patients with GM2 gangliosidosis were measured in situ, with cells growing in tissue culture by assaying the decrease in cell-incorporated 3H-GM2 over time, and in vitro by assaying the rate of 3H-GM2 hydrolysis using fibroblast extracts in the presence of no additives, sodium taurocholate, and GM2 activator protein. In tissue culture, normal cells hydrolyzed cell-incorporated GM2 while fibroblasts from patients with GM2 gangliosidosis did not. The half life of GM2 in normal fibroblasts was 78 hours. In vitro, only normal fibroblast extracts hydrolyzed GM2 in the absence of additives. In the presence of 10 mM sodium taurocholate, rates of GM2 hydrolysis by normal fibroblast extracts were increased 5-16-fold, fibroblast extracts from AB and B1 variant patients hydrolyzed GM2 at normal rates, cell extracts from patients with Tay-Sachs disease hydrolyzed GM2 at nearly normal rates, and cell extracts from Sandhoff disease patients hydrolyzed GM2 at about 10% of normal rates. In the presence of 1 microgram of GM2 activator, rates of GM2 hydrolysis by normal fibroblast extracts were increased 8-25-fold, fibroblast extracts from a patient with the AB variant hydrolyzed GM2 at normal rates, and cell extracts from other variants of GM2 gangliosidosis did not hydrolyze GM2. The results suggest that measuring the persistence of 3H-GM2 in tissue culture over time will detect any variant of GM2 gangliosidosis and may be the ideal way to test for the presence of this disease. Variants can be distinguished by assaying the hydrolysis of 3H-GM2 using cell extracts in the absence of additives, with sodium taurocholate, and with activator.

Carbohydrate Sequence↗
PubMed1994

Rapid method for obtaining high-quality chromosome banding in the study of hematopoietic neoplasia.

The original impetus for this work was the need for a method to analyze chromosome abnormalities in patients with hematopoietic neoplasms immediately after bone marrow (BM) aspiration. We present an easy and reproducible procedure for obtaining G-bands simultaneously with chromosome preparations (utilizing trypsin through hypotonic shock). It provides chromosomes of good quality with satisfactory banding range (450-500) within only 6 hours after BM aspiration. Using this technique, in our series of 560 patients with preleukemia and leukemia, we consistently provided the banding quality that allowed all chromosomes of the karyotype to be identified in 96% of myelodysplastic syndromes (MDS) 91% of acute lymphocytic leukemia (ALL), and 94% of acute myeloid leukemia (AML) cases, and we also identified cytogenetically abnormal clones in 70% of AML patients. With the same success this technique is also applicable to other types of human cells: lymphocytes from peripheral blood (PB) and established cell lines. Furthermore, this technique conserves chromatin structure and permits high hybridization efficiency rate on prebanded chromosomes and identification of chromosome markers within 36 hours after BM aspirations.

Azure Stains↗
PubMed1993

A case of occipital encephalocele combined with right lung aplasia in a twin pregnancy.

A case of occipital encephalocele combined with right-sided pulmonary agenesis in one sibling of a twin gestation is presented. Both, encephalocele and lung aplasia, are rare conditions, the former occurring with a frequency of 1:3000-1:30,000, the latter in 1:10,000-1:30,000. Although both conditions may show concomitant malformations, to our knowledge this is the first case of a combination of these two malformations to be reported.

Adult↗
PubMed1992

Four conserved cysteine residues are required for the DNA binding activity of nuclear factor I.

The role of Cys residues in the site-specific DNA binding activity of the nuclear factor I (NFI) family of proteins was assessed by chemical modification and site-specific mutagenesis. Treatment with the thio-specific reagent N-ethylmaleimide abolished site-specific DNA binding of all forms of NFI present in HeLa nuclear extracts. Preincubation of cell extracts with an oligonucleotide containing an NFI-binding site provided partial protection of NFI from N-ethylmaleimide inactivation. Mutations were made in the cDNA encoding a truncated form of the NFI-C/CAAT box transcription factor-1 protein, converting each of the five Cys residues in the DNA-binding domain of the protein into Ser residues. NFI-C proteins containing mutations in any of four conserved Cys residues, expressed in Escherichia coli or in vitro, did not bind to DNA. NFI-C with a mutation in a nonconserved Cys residue had normal DNA binding activity. Both this active mutant and wild-type NFI-C protein were inactivated by modification of their sulfhydryl residues with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), and preincubation with an oligonucleotide containing an NFI-binding site gave partial protection against inactivation. After modification with DTNB, DNA binding activity was partially restored by subsequent incubation with dithiothreitol, indicating that inactivation of NFI by DTNB was reversible. These studies indicate an essential role for free sulfhydryl residues in NFI-DNA binding.

Amino Acid Sequence↗
PubMed1992

Two karyotypically unrelated clones with the t(5;17) and deletion of 5q in myelodysplastic syndrome.

We report a patient with primary myelodysplastic syndrome (MDS) and two coexisting karyotypically independent clones. Cytogenetic investigation of bone marrow (BM) cells at diagnosis showed, besides the cells with normal karyotype, a clone that manifests an interstitial deletion of the long arm of chromosome 5 and a second one with a t(5;17). The rarity of finding a BM mosaicism in myelodysplasia with 5q- in some cells and different chromosomal abnormalities in others may be considered to support the multistep theory of pathogenesis in MDS.

Adult↗
PubMed1992

Diagnostic possibilities of ERA in developmental speech disorders.

The differential diagnosis of developmental speech disorders may be very difficult. We tried to differentiate between the developmental dysphasia and dysarthria by means of CERA, using the different kinds of stimuli--tone bursts, words and white noise. The BERA was performed using the filtered clicks as stimuli. We have found the responses to tone, verbal and noise stimuli in children with developmental dysarthria. The latency times were prolonged to verbal and noise stimuli. We did not find any responses to verbal and noise stimuli in children with developmental dysphasia. At the BERA investigation we did not find the auditory evoked brainstem responses in children with developmental dysarthria on the side of motoric innervation lesion. The latency times of waves N3 and N5 were prolonged in children with developmental dysphasia. The CERA and BERA seems to be a good differential diagnostic tool for differentiation between these two kinds of developmental speech disorders. The results confirmed also that there are the mixed forms of those developmental speech disorders.

Aphasia↗
PubMed1991

[Diagnostic characteristics of the CA-50 and CA 72-4 tumor markers in body fluids. Use in the diagnosis of malignant effusions].

The paper presents the results of a comparative investigation of CA-50 and CA 72-4 in the serum and effusions of the control group and a group of patients with various localizations of malignant tumors. The diagnostic applicability of CA-50 in the serum is limited by a substantial extent of falsely positive results, which is not the case with CA 72-4. Malignant cells make a more intensive release of CA 72-4 into effusions than into the blood, and the situation with CA-50 is reverse. It has been established that CA-50 in the serum and that CA 72-4 in effusions are complementary parameters. Markers in effusions have more favorable diagnostic characteristics in relation to serum. Although CA 72-4 is of a more superior diagnostic reliability, the examining of both markers is of help in the differentiation of benign peritoneal and pleural effusions from the malignant ones. The persistence of these markers in body fluids does not indicate the primary origin of malignant tumors.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1990

Chemosensitivity of fine afferents from rat skin in vitro.

1. Properties of sensory receptors with slowly conducting nerve fibers (less than 10 m/s) were studied using a rat skin-saphenous nerve in vitro preparation where receptive fields of identified single units can be isolated and superfused at the corium side with defined chemical solutions. 2. With mechanical search stimuli, 150 slowly adapting units were identified, 88% C-fibers, and the remainder, A delta-fibers. The majority of these units (65%) were categorized as mechano-heat sensitive ("polymodal") with controlled radiant heat stimulation. The remaining units were classified as low- or high-threshold mechanoreceptors according to their von Frey thresholds. 3. Bradykinin (BK), in concentrations of 10(-8) to 10(-4) M, was repeatedly applied for 1 min at 10-min intervals. Fifty-six percent of the polymodal C-fibers responded to BK (up to 10(-5) M), in contrast to 17% of the heat-insensitive units (P less than 0.01). No correlation between BK sensitivity and conduction velocity or von Frey threshold was found. 4. The BK "threshold concentrations" to excite C- and A delta-fibers were about equally distributed over a range from 10(-8) to 10(-5) M. 5. There was a large interindividual variability in pattern and magnitude of the response to BK. Intraindividually, a marked tachyphylaxis upon repeated BK stimulation was observed. 6. In fibers with a slow development of tachyphylaxis, the effects of conditioning application of different chemicals on BK responsiveness were studied. Norepinephrine in 10(-7) M concentration did not produce a significant effect, whereas 10(-5) M and 10(-4) M seemed to increase the BK responses. 7. Prostaglandin E2 (10(-6) M) caused a weak sensitization to BK on average (n.s.), but serotonin (10(-6) M) was clearly effective (P less than 0.05). 8. The strongest sensitization to BK (P = 0.01) resulted from conditioning heat stimulation, which also uncovered a responsiveness in some units initially insensitive to BK. 9. In some experiments the calcium concentration in the superfusate of receptive fields was lowered to 0.3 mM, which induced ongoing activity in C-fibers and markedly increased the BK responses in two polymodal units tested. Increasing the calcium concentration to 3.0 mM reversed these effects. 10. After completing the BK test protocol, polymodal C-fibers were exposed to other chemicals.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1989

Chronic myeloid leukemia associated with pure red cell aplasia and terminating in promyelocytic transformation.

After intermittent treatment with busulphan over a 7-year period for chronic myeloid leukemia (CML) in chronic phase, a 39-year-old female developed leukocytosis in association with pure red cell aplasia (PRCA). Bone marrow examination confirmed erythroid aplasia, and culture revealed a total absence of erythroid progenitor cells. The patient then was treated with azathioprine, corticosteroids, cyclophosphamide, plasma exchange, and cyclosporin A, but she remained erythroblastopenic and transfusion dependent for more than a year, at which time a promyelocytic transformation supervened. The authors propose that this sequence of events, hitherto unreported, is a manifestation of the multistep progression of CML.

Adult↗
PubMed1988

[Septic melioidosis following a visit to India].

A case is reported of lethal septicemic melioidosis due to Pseudomonas pseudomallei in a 40-year-old woman who had been in India. The epidemiology, clinical findings and management of this unusual disease are discussed. The diagnostic value of serological tests and in vitro sensitivity of Pseudomonas pseudomallei to various antibiotics are outlined. Melioidosis should be considered in the differential diagnosis of any febrile condition in a person returning from a tropical country.

Adult↗