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Biomedical subjects

M Weinstein

Publications and source records attributed to M Weinstein.

At least 91 records · Page 5Linked to original sources
PubMed1993

Mutants of the two-component regulatory protein FixJ of Rhizobium meliloti that have increased activity at the nifA promoter.

FixL and FixJ belong to a two-component regulatory system in Rhizobium meliloti that induces the expression of numerous nitrogen-fixation genes during symbiosis with alfalfa. FixJ is a positive activator required for transcription of the regulatory genes nifA and fixK, while FixL is an oxygen-binding hemoprotein capable of regulating the phosphorylation status of both itself and FixJ, in response to oxygen availability. In this study, we isolated four FixJ mutants that display increased activity at the nifA promoter (PnifA) in Escherichia coli. All four mutants possess amino acid changes in a domain of FixJ that is conserved in other response regulator proteins, and all exhibit increased activity at PnifA in R. meliloti that is dependent on the presence of FixL. One of the mutant proteins, while less efficient at accepting phosphate from a truncated derivative of FixL (FixL*), nevertheless has a phosphorylated form that is more stable than the phosphorylated form of wild-type (wt) FixJ and is more resistant to the phosphatase activity of FixL*. The wt FixJ-phosphate was found to have a half-life of approximately 4 h, which makes it an unusually long-lived response regulator protein. The exceptional stability of wt FixJ-phosphate and the altered phosphorylation properties observed for the mutant are discussed in relation to signal transduction in the FixLJ system.

Bacterial Proteins↗
PubMed1993

Autophosphorylation and phosphatase activities of the oxygen-sensing protein FixL of Rhizobium meliloti are coordinately regulated by oxygen.

The FixL and FixJ proteins of Rhizobium meliloti control the expression of other nif and fix genes in response to oxygen levels. FixL is a hemoprotein kinase that senses oxygen availability and responds to the absence of oxygen by activation of its autophosphorylating activity followed by transfer of the phosphate to FixJ. FixJ in turn activates the nifA and fixK promoters. In vitro studies reported here with a soluble truncated version of FixL (FixL*) indicate that, while low oxygen tension specifically increases the autophosphorylating activity of FixL*, the ability of phospho-FixL* to act as a phosphate donor to FixJ is not affected by the presence or absence of oxygen. FixL* is also shown to possess a phosphatase activity that is repressed under anaerobic conditions only when the protein is in the phosphorylated form. A fixL mutant that induces a higher level of nifA promoter activity in the presence of fixJ in vivo displayed both an increased autophosphorylating activity and a decreased phosphatase activity in vitro. These data provide evidence for a role for both autophosphorylation and phosphatase activities of FixL in the mechanism by which oxygen tension within the alfalfa nodule induces expression of bacterial nitrogen fixation genes during symbiosis.

Adenosine Triphosphate↗
PubMed1993

Eye abnormalities in the Smith-Magenis contiguous gene deletion syndrome.

We present the results of ophthalmologic assessment in 10 patients with interstitial chromosome deletions of 17p11.2, otherwise known as the Smith-Magenis syndrome (SMS). The most common abnormalities noted were strabismus, Brushfield spots, high myopia, and retinal detachments. We have previously reported high myopia and retinal detachments in 6 patients with SMS (Finucane et al.: Am J Hum Genet 49:262A, 1991). We present additional details on these individuals, as well as findings in 4 newly reported patients. Ocular pathology appears to be very common in SMS, significantly contributing to disability in people with this syndrome. The combination of high myopia, self-injurious head-banging, aggression, and hyperactivity among these patients makes them particularly susceptible to retinal detachments. Detailed ophthalmologic assessment should be included in the clinical work-up and monitoring of all patients with SMS resulting from deletion 17p11.2.

Adolescent↗
PubMed1993

A missense mutation, S349P, completely inactivates phenylalanine hydroxylase in north African Jews with phenylketonuria.

The majority of hyperphenylalaninemias (HPAs) result from mutations at the gene for phenylalanine hydroxylase (PAH). The broad phenotypic variability of these conditions, ranging from phenylketonuria (PKU) to mild benign HPA, is underlain by a wide spectrum of mutations giving rise to various genotypic combinations. Mutant PAH alleles, labeled by specific polymorphic haplotypes and mutations, are becoming useful markers in human population genetics. We report here a mutant PAH allele found in Jews from Morocco and Tunisia, marked by haplotype 4 and a missense mutation, TCASer-->CCAPro, at codon 349 in exon 10 of the gene. In vitro expression of the mutation showed normal levels of mRNA with virtually no enzymatic activity or protein immunoreactivity, pointing to a highly unstable protein. A homozygote for this mutation showed the most severe ("classical") type of PKU, while compound heterozygotes showed two other types of HPA--"atypical" PKU and "high benign" HPA--illustrating the interplay between different mutations that gives rise to various HPAs.

Base Sequence↗
PubMed1993

Various methods of breast reconstruction after mastectomy: an economic comparison.

This study is an economic comparison of various methods of breast reconstruction after mastectomy. The hospital bills of 287 patients undergoing breast reconstruction at three institutions from June of 1988 to March of 1991 were analyzed. The procedures examined included mastectomy, implant and tissue-expander reconstruction, and TRAM and latissimus pedicle flaps, as well as free TRAM and free gluteal flaps. These procedures were subdivided into those which were performed at the time of mastectomy and those performed at a later admission. In addition, auxiliary procedures (i.e., revision, nipple reconstruction, tissue-expander exchange, and contralateral mastopexy/reduction) also were examined. Where appropriate, these procedures were subdivided into those performed under general or local anesthesia and by inpatient or outpatient status. Data from the three institutions were converted to N.Y.U. Medical Center costs for standardization. A table is presented that summarizes the costs of each individual procedure with all the pertinent variations. In addition, a unique and novel method of analyzing the data was developed. This paper describes a menu system whereby other data regarding morbidity, mortality, and revision rates may be superimposed. With this information, the final cost of reconstruction can be extrapolated and the various methods of reconstruction can be compared. This method can be applied to almost any complex series of multiple procedures. The most salient points elucidated by this study are as follows: The savings generated by performing immediate reconstruction varies between $5092 (p < 0.05) for free gluteal flaps and $10,616 (p < 0.05) for pedicled TRAM flaps.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Neoplasms↗
PubMed1993

Rapid prenatal diagnosis of chromosomal aneuploidies by fluorescence in situ hybridization: clinical experience with 4,500 specimens.

Detection of chromosome aneuploidies in uncultured amniocytes is possible using fluorescence in situ hybridization (FISH). We herein describe the results of the first clinical program which utilized FISH for the rapid detection of chromosome aneuploidies in uncultured amniocytes. FISH was performed on physician request, as an adjunct to cytogenetics in 4,500 patients. Region-specific DNA probes to chromosomes 13, 18, 21, X, and Y were used to determine ploidy by analysis of signal number in hybridized nuclei. A sample was considered to be euploid when all autosomal probes generated two hybridization signals and when a normal sex chromosome pattern was observed in greater than or equal to 80% of hybridized nuclei. A sample was considered to be aneuploid when greater than or equal to 70% of hybridized nuclei displayed the same abnormal hybridization pattern for a specific probe. Of the attempted analyses, 90.2% met these criteria and were reported as informative to referring physicians within 2 d of receipt. Based on these reporting parameters, the overall detection rate for aneuploidies was 73.3% (107/146), with an accuracy of informative results for aneuploidies of 93.9% (107/114). Compared to cytogenetics, the accuracy of all informative FISH results, euploid and aneuploid, was 99.8%, and the specificity was 99.9%. In those pregnancies where fetal abnormalities had been observed by ultrasound, referring physicians requested FISH plus cytogenetics at a significantly higher rate than they requested cytogenetics alone. The current prenatal FISH protocol is not designed to detect all chromosome abnormalities and should only be utilized as an adjunctive test to cytogenetics. This experience demonstrates that FISH can provide a rapid and accurate clinical method for prenatal identification of chromosome aneuploidies.

Adult↗
PubMed1992

The FixL protein of Rhizobium meliloti can be separated into a heme-binding oxygen-sensing domain and a functional C-terminal kinase domain.

Transcription of nitrogen fixation (nif and fix) genes in Rhizobium meliloti is induced by a decrease in oxygen concentration. The products of two genes, fixL and fixJ, are responsible for sensing and transmitting the low-oxygen signal. The proteins encoded by fixL and fixJ (FixL and FixJ, respectively) are homologous to a family of bacterial proteins that transduce environmental signals through a common phosphotransfer mechanism [David, M., Daveran, M., Batut, J., Dedieu, A., Domergue, O., Ghai, J., Hertig, C., Boistard, P. & Khan, D. (1988) Cell 54, 671-683]. FixL, the oxygen sensor, is a membrane protein. It has previously been shown that a soluble derivative of FixL, FixL*, is an oxygen-binding hemoprotein and a kinase that autophosphorylates and also phosphorylates FixJ [Gilles-Gonzalez, M. A., Ditta, G. S. & Helinski, D. R. (1991) Nature (London) 350, 170-172]. In this work, deletion derivatives of fixL* were constructed and overexpressed in Escherichia coli, and the truncated proteins were purified. We show that a fragment of FixL from amino acid residue 127 to residue 260 binds heme, retains the ability to bind oxygen, and has no detectable kinase activity. A C-terminal fragment of FixL, beginning at residue 260, fails to bind heme but is active as a kinase. We also demonstrate that anaerobiosis results in an enhancement of FixL* autophosphorylation and FixJ phosphorylation activities in vitro. Finally, we show that the heme-binding region of FixL is required in vitro for oxygen regulation of its kinase activities.

Bacterial Proteins↗
PubMed1992

Glycosaminoglycan patterns in gingival proteoglycans of rat with age.

Among the potential biochemical indices that are closely associated with craniofacial development are the proteoglycans. Gingival segments from the palate of 4-, 6-, 8-, 12- and 18-week-old rats were incubated for 4 h in medium containing [3H]-glucosamine and [35S]-Na2SO4, and subjected to proteoglycan isolation and glycosaminoglycan analysis. Two distinct proteoglycan fractions differing in the degree of sulphation were obtained by ion-exchange chromatography. The incorporation of both labels in the undersulphated fraction increased with age; there was a pronounced decrease with age in the sulphated proteoglycan fraction. The undersulphated proteoglycans showed an age-dependent decrease in hyaluronic acid, and increase in dermatan sulphate and chondroitin 4- and 6-sulphates. Gel filtration of the sulphated proteoglycan fraction yielded high and low molecular-weight proteoglycans, the glycosaminoglycans of which were particularly rich (61-76%) in dermatan sulphate. Smaller quantities of chondroitin 4- and 6-sulphates, and heparan sulphate were also present. All glycosaminoglycans showed a decrease in content with age. The findings suggest a possible correlation between gingival proteoglycan/glycosaminoglycan patterns and development.

Aging↗
PubMed1992

Cytogenetic studies of bone marrow fibroblasts cultured from patients with myelofibrosis and myeloid metaplasia.

Cytogenetic studies of bone marrow fibroblasts and blood cells from peripheral blood or bone marrow were performed in 19 patients with myelofibrosis with myeloid metaplasia (group 1), nine patients with other myeloproliferative syndromes without myelofibrosis (group 2), and 12 patients with anaemia secondary to iron deficiency or chronic inflammatory disease (group 3). Clonal cell populations with abnormal karyotypes were seen in the bone marrow or blood in five of 14 (36%) group 1 patients, one of nine (11%) group 2 patients and none (0%) of the group 3 patients. Abnormal karyotypes of bone marrow fibroblasts were found in three of 16 (19%) of patients of group 1, and in two of nine (22%) and two of 12 (17%) patients each of groups 2 and 3, respectively. Since abnormal karyotypes can be found in bone marrow fibroblasts cultured from normal subjects, and since the abnormalities seen in the bone marrow fibroblasts differed from those found in bone marrow or blood cells, it is suggested that abnormal karyotypes found in bone marrow fibroblasts cultured from patients with primary myelofibrosis do not necessarily reflect neoplasia. The results of this study are compatible with the widely accepted hypothesis that in patients presenting with 'primary' myelofibrosis, the fibrosis is a secondary reactive process.

Aged↗
PubMed1992

Isolation of phosphorylation-deficient mutants of the Rhizobium meliloti two-component regulatory protein, FixJ.

Rhizobium meliloti FixL and FixJ are members of a symbiotically essential two-component system that regulates nitrogen-fixation genes in response to environmental oxygen concentrations. FixL is a membrane protein that is thought to relay information about oxygen availability to FixJ via a phosphotransfer mechanism. FixJ increases expression of the nifA and fixK genes by activating transcription of the nifA and fixK promoters (p-nifA and p-fixK, respectively). In this study, we examined the relationship between the in vivo activity of FixJ as a transcriptional regulator and its ability to be phosphorylated in vitro by the sensor FixL. FixJ mutants were isolated that showed decreased activity on p-nifA in Escherichia coli. Most of the FixJ mutant proteins also showed decreased activity on the fixK promoter. These mutants were analysed in R. meliloti for activity on p-nifA during vegetative growth, where similarities and differences were observed when compared with their phenotypes in E. coli. Three mutants showing significantly less activity in R. meliloti were examined for symbiotic activity in planta and were found to be ineffective. When these three mutant FixJ proteins were examined in vitro for their ability to be phosphorylated by FixL, two mutants were found to have a significantly decreased ability to accept phosphate from FixL. These findings are discussed in relation to signal transduction in the FixLJ system.

Bacterial Proteins↗
PubMed1992

A region of the broad-host-range plasmid RK2 causes stable in planta inheritance of plasmids in Rhizobium meliloti cells isolated from alfalfa root nodules.

We demonstrate for the first time that the broad-host-range stabilization loci from plasmid RK2 cause total retention of plasmids in cells of Rhizobium meliloti during symbiosis with alfalfa. Two derivatives of plasmid RK2, pRK290 and a 7.3-kb mini-RK2 plasmid, were stabilized in R. meliloti cells isolated from root nodules by the insertion of a 3.2-kb DNA fragment or a smaller 0.8-kb DNA fragment derived from the RK2 stabilization region.

Aerobiosis↗
PubMed1992

Isometric squeeze relaxation (progressive relaxation) vs meditation: absorption and focusing as predictors of state effects.

We taught isometric squeeze relaxation (a variant of progressive relaxation) or meditation to 52 anxious subjects (16 men, 36 women). For meditation, pretreatment high absorption correlated with reductions in state cognitive and somatic anxiety as well as increments in state focusing. For isometric squeeze relaxation, pretreatment low state focusing correlated with reductions in somatic anxiety and increments in focusing. Results suggest that isometric squeeze relaxation (and progressive relaxation) may be more appropriate for individuals who have difficulty focusing, and meditation for those who already possess well-developed relaxation skills at a trait level. The results appear more consistent with Smith's cognitive-behavioral model of relaxation than with Benson's relaxation response or Davidson and Schwartz's specific effects models.

Adult↗
PubMed1992

Managed care strategies for the '90s.

With the proportion of patient care activity controlled by managed care organizations skyrocketing, providers need to study managed care trends, understand their strategic implications, and devise a response to them. Tremendous opportunities exist for hospitals that offer their own managed care programs, as long as they can avoid making costly mistakes. A critical tool is an overall strategy that includes collaboration with physicians, internal organization to manage risk, and direct contracting.

Contract Services↗
PubMed1992

Does desmopressin acetate prophylaxis reduce blood loss after valvular heart operations? A randomized, double-blind study.

The effectiveness of prophylactic desmopressin acetate in reducing hemorrhage after cardiopulmonary bypass operations is controversial. We conducted a prospective, randomized, placebo-controlled, double-blind trial to determine its effectiveness and safety in such patients. Eighty-three evaluable patients undergoing valvular heart operations were randomized to receive desmopressin (0.3 microgram/kg) (41) or placebo (42) after cardiac bypass. Demographic characteristics were similar in both groups. There was no significant difference in total 24-hour blood loss between groups (desmopressin 1064.8 +/- 647.1 ml versus placebo 844.4 +/- 507.6 ml; p greater than 0.05), or in the requirement for red blood cell, platelet, or fresh frozen plasma transfusion, or for reexploration for control of hemorrhage. Neither was there a difference in the occurrence of thrombotic complications between groups. Analysis of factor VIII activity, von Willebrand factor, or von Willebrand factor multimers failed to show significant correlations with blood loss or differences between groups except for factor VIII activity, which was significantly higher in the desmopressin group 1 hour after operation than in the placebo group. A detailed comparative analysis of similar trials to determine the reasons for different outcomes suggests that desmopressin should not be used routinely as a prophylactic agent to reduce postsurgical hemorrhage, but that it may be beneficial when used in patients who already manifest excessive bleeding postoperatively.

Blood Loss, Surgical↗