PubMed Health⌕ Search

Biomedical subjects

B Hecht

Publications and source records attributed to B Hecht.

32 records · Page 2Linked to original sources
PubMed1991

Amino acids determining operator binding specificity in the helix-turn-helix motif of Tn10 Tet repressor.

Each of 22 amino acids in the proposed alpha-helix-turn-alpha-helix operator binding motif of the Tn10 encoded Tet repressor was replaced by alanine and one residue was replaced by valine to determine their role in tet operator recognition by a 'loss of contact' analysis with 16 operator variants. One class of amino acids consisting of T27 and R28 in the first alpha-helix and L41, Y42, W43 and H44 in the recognition alpha-helix are quantitatively most important for wild-type operator binding. These residues are probably involved in the structural architecture of the motif. A second class of residues is quantitatively less important for binding, but determines specificity by forming base pair specific contacts to three positions in tet operator. This property is most clearly demonstrated for Q38 and P39 and to a lesser extent for T40 at the N-terminus of the recognition alpha-helix. The contacted operator base pairs indicate that the N-terminus of the recognition alpha-helix is located towards the palindromic center in the repressor-operator complex. Although the orientation of the recognition alpha-helix in the Tet repressor-tet operator complex is inversed as compared with the lambda- and 434 repressor-operator complexes, the reduced operator binding of the TA27 mutation in the first alpha-helix suggests that the hydrogen bonding networks connecting the two alpha-helices may be similar in these proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1988

Plasma cell karyotype in multiple myeloma.

Karyotypic abnormalities were studied in multiple myeloma and were correlated with clinical features. Among 115 evaluable patients, 46% had an abnormal karyotype. Trisomy 3, 5, 9, and 15 and monosomy 13 and 16 were the most common clonal abnormalities. Translocations described previously in other B cell malignancies occurred in nine patients, including four with t(8;14)(q24;q32) translocations. The association of all t(8;14) abnormalities with IgA protein type suggested a pathogenetic relationship between a specific karyotypic abnormality and myeloma protein type. Hypodiploidy occurred mainly in patients with only Bence Jones protein, was associated with resistance to therapy, and justified the early consideration of investigational therapies.

Chromosome Aberrations↗
PubMed1984

Language intervention: a pragmatic approach.

The approach to language intervention described in this paper provides a means of teaching pragmatically appropriate and effective uses of language in conversational contexts while simultaneously teaching the production and comprehension of specific linguistic forms. The approach, developed in work with seriously language-disabled young children, consists of a series of communication games. These games, which focus and intensify certain characteristics of conversational situations, teach vocabulary, syntax, and articulation as devices for serving the same pragmatic functions these devices serve in ordinary conversation. The games integrate the advantages of the traditional language lessons and those of incidental teaching. Spontaneous speech data collected before and after a 4-month interval from trained and contrast-group children suggest the positive impact of the intervention on the language performance of children with no or moderate cognitive delays, but the results do not suggest a similar impact on children with severe cognitive delays. The results suggest that the intervention merits further application and evaluation, with particular attention to the control of cognitive level.

Child↗
PubMed1978

Micropuncture study on the effects of lithium on proximal and distal tubule function in the rat kidney.

Micropuncture studies were performed in rats infused with LiCl to induce stable plasma lithium concentrations of 2--3 mEq/l, or with an equivalent amount of NaCl. In free flow experiments LiCl reduced proximal tubule fractional reabsorption of sodium and potassium. Reduced reabsorption of bicarbonate, as reflected by a decrease in TF/PCl, was also observed. Proximal fractional reabsorption of chloride, however, was not affected. The TF/PIn at the end proximal tubule was 2.6 +/- 0.2 (mean +/- SEM) in controls and 2.1 +/- 0.1 in the experimental animals (P less than 0.025). In the distal portions of the nephron lithium treatment caused a fall in fractional reabsorption of water and sodium, while potassium secretion was stimulated in the distal tubule. Previous studies have indicated that lithium influences antidiuretic hormone stimulated water transport in the collecting duct. These experiments demonstrate that lithium also affects the transport of water and electrolytes in multiple nephron segments, including the proximal and distal convolution.

Animals↗
PubMed1975

Prognostic significance of DNA-binding capacity patterns in patients with lupus nephritis.

The time course of DNA binding capacity (DNA-bc) was found to correlate with the clinical course in a group of 21 patients who had biopsy-proven lupus glomerulonephritis and were treated with immunosuppressive agents. Eight patients showed a sequential DNA-bc pattern in which a high titre of anti-DNA antibody was present for a prolonged period of time all having an unfavourable clinical course. Persistently high values of DNA-bc preceded by as much as 10 months evidence of renal deterioration obtained by conventional renal function tests. Thirteen patients showed a low titre of anti-DNA antibody throughout most of their course, 12 having a favourable outcome. An initially high value of DNA-bc had no prognostic significance. These results suggest that the persistence of a high titre of anti-DNA antibody in patients with lupus glomerulonephritis is a poor prognostic sign.

Adolescent↗
PubMed1975

Effect of lithium on water and electrolyte metabolism.

Studies were performed in the rat to determine the effect of lithium on electrolyte transport in distal portions of the nephron since steep corticomedullary gradient for lithium has been demonstrated and ionic competition and/or substitution of lithium for sodium and potassium may play a role in inhibition of vasopressin-induced water transport. During the intravenous infusion of LiC1, in the absence of volume expansion and at plasma levels of 2-5 mequiv/liter of Li, maximum urine con-entration was inhibitied. Under the same conditions lithium administration impaired potassium secretion and urinary acidification and resulted in a natriuresis. These results indicate that lithium affects electrolyte transport in the same nephron segments in which the action of vasopressin is inhibitied. In addition, evidence is provided that suggests that during the chronic administration of LiC1, the sustained increase in oral intake of water and urinary flow rate results from an increase in thirst as well as reduced renal concentrating ability.

Animals↗