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Biomedical subjects

I Schechter

Publications and source records attributed to I Schechter.

At least 55 records · Page 3Linked to original sources
PubMed1985

The Word Retrieval Fluency Test: what does it assess?

The term fluency in aphasia is ambiguous. It can relate to the rate of speech--normal vs. laborious or the ability to retrieve words. In this report, to avoid confusion we refer to fluency in a word retrieval task. Different authors have ascribed defective performance on these tasks to Frontal Lobe Syndrome or Aphasia. Our patient material adds dementia as a causative condition. To determine whether subnormal test performance is due to generalized brain dysfunction or only to left hemisphere disorders, we tested left hemisphere damaged patients, without aphasia as well as right hemisphere damaged patients, obtaining non-significant differences between the two groups. This supports our experience that such a test is highly sensitive to generalized brain dysfunction i.e. to a variety of cerebral disorders and therefore seems not to be highly pathognomonic of aphasia.

Adolescent↗
PubMed1985

The phonemic analysis as a treatment method in dysgraphic aphasic patients.

Two theories have been advanced to explain the underlying process of writing acquisition. The first sees a global registration of whole words in a pictorial (graphic) form; the second is based on an analysis synthesis process of each word into its sound (phonemes), and the translation of each phoneme into its graphic form (grapheme). This paper, derived from the latter theoretical construct, attempts to show that phonemic analysis-synthesis is also an efficient approach in the rehabilitation of dysgraphic aphasics. 51 patients at the Loewenstein Rehabilitation Center--31 post C.V.A. and 20 post C.C.I. were taught to write using this method, and their improvement was tested and analysed within 6 months after the event. It is shown that they all improved significantly, although the various syndrome sub-groups behaved differently. The implications of these differences and the total results are discussed.

Agraphia↗
PubMed1985

Auditory perpetual dysfunction in patients with CCI, with implications for therapy.

Injury to the head, as from impact, can result in damaged function of the auditory receptive (peripheral) or perceptual (central) system, or both. The altered function may be clearly apparent, as in a loss of hearing, or may be exposed only through specially devised tests. At the Loewenstein Rehabilitation Hospital tests were designed or adapted to evaluate processing in the auditory periphery, the brain stem and the cortex. With speech as the the stimulus the tasks explore binaural interaction, cerebral hemisphere dominance and suppression, and cognitive efficiency in understanding degraded speech messages. Other stimuli, such as pure tones and musical patterns are employed to reveal dysfunction on various levels of the system. This report concentrates on tests which require the cerebral hemispheres to listen competitively. Results are given for earphone listening and for two new types of selective listening tasks in the sound field (loudspeaker) mode.

Adult↗
PubMed1982

Somatic DNA rearrangement generates functional rat immunoglobulin kappa chain genes: the J kappa gene cluster is longer in rat than in mouse.

The kappa immunoglobulin (Ig) genes from rat kidney and from rat myeloma cells were cloned and analyzed. In kidney DNA one C kappa species is observed by Southern blotting and cloning in phage vectors; this gene most likely represents the embryonic configuration. In the IR52 myeloma DNA two C kappa species are observed: one in the same configuration seen in kidney and one which has undergone a rearrangement. This somatic rearrangement has brought the expressed V region to within 2.7 kb 5' of the C kappa coding region; the rearrangement site is within the J kappa cluster which we have mapped. The rat somatic Ig rearrangement, therefore, closely resembles that seen in mouse Ig genes. In the rat embryonic fragment two J kappa segments were mapped at 2 and 4.3 kb 5' from the C kappa coding region. Therefore, the rat J kappa cluster extends over about 2.3 kb, a region much longer than the 1.4 kb of the mouse and human J kappa clusters. In the region between C kappa and the expressed J kappa of IR52 myeloma DNA, and XbaI site present in the embryonic kappa gene has been lost. A somatic mutation has therefore occurred in the intervening sequence DNA approx. 0.7 kb 3' from the V/J recombination site. Southern blots of rat kidney DNA hybridized with different rat V kappa probes showed non-overlapping sets of bands which correspond to different subgroups, each composed of 8-10 closely related V kappa genes.

Animals↗
PubMed1982

Recent duplication and germ-line diversification of rat immunoglobulin kappa chain gene joining segments.

Sequence determination of the joining segment gene (J) cluster in the kappa chain (J kappa) in the embryonic context demonstrates that rat genome contains seven J kappa gene segments that expanded from an ancestral cluster of five J kappa genes. The rat J segments are separated by about 300 base pairs (bp) and are flanked 5' by the presumed variable region (V)/J recombination signal sequence and 3' by the RNA splicing signal. Two of the J gene segments designated J2A and J2B and their 5'-flanking spacer DNA bear striking homology to J2 and its 5'-flanking spacer. Thus, the unit of duplication was the entire J kappa coding region and 5' noncoding spacer (345 bp). The duplication probably occurred as two separate unequal crossing-over (UXO) events. The first UXO event can be confined to recombination within an identical stretch (14 bp long) located at the 3' ends of the coding regions of J1 and J2. The second event could involve a longer segment (372 bp) of tight homology generated by the first UXO event, thus increasing the probability of repeated expansion of the same DNA segment. The sequence homology among the rat duplicated segments (98-99%) is larger than the homology between the corresponding rat and mouse segments (89%), showing that the rat J kappa gene expansion must have occurred after rat and mouse divergence 10 X 10(6) yr ago. We estimate that the first and second UXO events occurred 2 X 10(6) and 1 X 10(6) yr ago, respectively. J3 of rat and mouse share the same mutation (G leads to C) in the RNA splicing signal that presumably inactivates J3. This mutation preceded divergence of the two species. A mutation in the first nucleotide of codon 96 has occurred in both duplicated segments, the only position along 345 bp where J2, J2A, and J2B differ from each other. This results in three different amino acids at position 96 not present in any other J kappa. These mutations are physiologically significant because they diversify the third complementarity-determining region (CDR3) and, thus, may reflect selective pressure to increase antibody diversity. The germ-line diversification of CDR3 was exercised within the last 1-2 X 10(6) yr.

Amino Acid Sequence↗
PubMed1981

An experimental approach to enumerate the genes coding for immunoglobulin variable-regions.

Critical to our understanding of the immune system diversity is the determination of the number of germ line V genes. The total number of V genes is given by the product: number of subgroups x number of germ line genes per subgroup. Studies of kappa chains and of embryonic DNA indicate 5-10 V genes per subgroup. Statistical analysis of the limited sequence data of mouse kappa chains suggest about 50 V kappa subgroups. We report here a general approach for direct estimation of the number of VL and VH subgroups expressed in normal spleen, and present data for V kappa. The kappa mRNA of the spleen is a heterogeneous population where different V kappa are linked to the same C kappa, i.e. C kappa equals total V kappa. The ratio C kappa/distinct V kappa approximates the number of subgroups since V kappa of the same subgroup cross hybridize while V kappa of different subgroups do not. This ratio was determined by molecular hybridization of cloned C kappa and V kappa DNA probes with spleen mRNA. The results indicate the expression of 280 V kappa subgroups in mouse. Assuming an average of 7 genes per subgroup, we estimate about 2000 V kappa germ line genes.

Animals↗
PubMed1980

An unusual translocation of immunoglobulin gene segments in variants of the mouse myeloma MPC11.

Immunoglobulin light chain genes of the mouse are composed in germ-line DNA of four separate segments, the leader, V (variable), J (joining) and C (constant) segments. In immunocompetent cells a V and J gene segment are joined by a site-specific recombination event. In variants of the mouse myeloma MPC11 a so-called kappa (k) light chain fragment is expressed which consists of the MOPC321 leader peptide, joined to the kappa constant region peptide. Using the Southern blotting technique we found that the gene coding for the light chain fragment has apkparently been generated by an aberrant translocation of a V gene segment identical or very similar to the MOPC321 V gene segment into the large intervening sequence between the J and the C gene segments. The resulting deletion of the splice signals of the J segments could be the reason for the observed splicing between leader and C region sequences, a phenomenon which may be of general interest for the understanding of the splicing mechanism.

Animals↗
PubMed1980

Synthesis of part of a mouse immunoglobulin light chain in a bacterial clone.

We have cloned double stranded cDNA sequences encoding a mouse immunoglobulin light chain (L-321) into the PstI site of the beta-lactamase gene of plasmid pBR322 by the oligo (dG)-oligo (dC) tailing procedure. Escherichia coli X1776 transformed by the recombinant plasmids were screened for the expression of L-321 antigenic determinants by a newly developed in situ radio-immunoassay. One out of seven transformants screened was found to synthesize an L-chain like protein. Each bacterial cell produces about 550 molecules of the L-chain sequence. Preferential segregation of the L-chain sequence to the periplasmic space suggest covalent attachment of the L-chain sequence to the N-terminal portion of beta-lactamase. Restriction mapping of the plasmid DNA isolated from the positive clone indicated the presence of a DNA sequence coding for the entire constant region and extending into the variable region for a length corresponding to about 40 amino acid residues. The orientation of the cloned cDNA with respect to the plasmid DNA is compatible with the formation of a fused beta-lactamase-L-321 peptide.

Animals↗
PubMed1980

The use of biological dressings in radical vulvectomy.

The use of biological dressing techniques accelerates recovery from radical vulvectomy combined with lymphadenectomy. Our earliest interest in the field arose as a result of the morbidity rate which ensued subsequent to surgical therapy of cancer of the vulva. The technique involved in 8 such procedures is described, and its applicability illustrated with photographic plates and review of the literature.

Aged↗
PubMed1979

Messenger RNA of opsin from bovine retina: isolation and partial sequence of the in vitro translation product.

Opsin, the apoprotein of the visual pigment rhodopsin, is synthesized on membranes of the rough endoplasmic reticulum and subsequently passes through the Golgi apparatus to the rod outer segment. This pathway parallels the early stages of biosynthesis of some secretory proteins and viral membrane glycoproteins. Most of these proteins are initially synthesized as precursor molecules with a short-lived hydrophobic extra peptide segment at the NH(2) terminus. Therefore we investigated whether or not the immediate translation product of opsin mRNA contains a similar short-lived NH(2)-terminal extra peptide. The mRNA coding for opsin was isolated from bovine retina polysomes precipitated by antibodies to opsin. The mRNA directed the cell-free synthesis of a protein comparable in size to opsin that was specifically precipitated by anti-opsin antibodies. Sequence analyses of the immunoprecipitated protein labeled with six radioactive amino acids (Met, Asn, Pro, Phe, Tyr, Val) provided the following result: [Formula: see text] (X is unknown). This partial sequence of the cell-free product corresponds exactly to the published NH(2)-terminal segment of native opsin (21 residues long) and extends beyond this region. Met-1 was shown to be the initiator methionine residue, because only the initiator [(35)S]Met-tRNA(1) (Met)-not the internal [(35)S]Met-tRNA(2) (Met)-donated the NH(2)-terminal methionine. This finding essentially rules out the possibility that Met-1 was preceded by a peptide that was rapidly cleaved. Thus opsin, and not a precursor, is the immediate product of opsin mRNA translation.

Amino Acid Sequence↗
PubMed1979

Primary structure of the NH2-terminal extra piece of the precursor to human placental lactogen.

The cell-free translation product of human placental lactogen mRNA is a precursor molecule larger than the mature hormone that circulates in plasma. To determine the structure of pre-placental lactogen, the poly(A)-rich RNA fraction of term placenta was isolated and translated in a wheat germ cell-free system. The mRNA programmed the synthesis of a major protein, 3000 daltons larger than placental lactogen, that was specifically precipitated by hormone antibodies. The immunoprecipitated protein was labeled separately with 20 radioactive amino acids and subjected to sequence analysis. The results showed the synthesis of pre-placental lactogen in which an extra piece 25 residues long preceded the NH2 terminus of the mature protein. The structure of the extra piece is as follows: Met-Pro-Gly-Ser-Arg-Thr-Ser-Leu-Leu-Ala-Phe-Ala-Leu-Leu-Cys-Leu-Pro-Trp-Leu-Gln-Glu-Ala-Gly-Ala-. Met1 is the initiator residue because only initiator [35S]Met-tRNAMet1, but not internal [35S]Met-tRNA2Met, donated NH2-terminal methionine. The structure of the extra piece showed little homology with that of unrelated hormones but striking homology (64%) with the extra piece of rat pre-growth hormone. Most amino acid substitutions involved a single base change in the codon. Mature human placental lactogen and rat growth hormone have 59% homology in sequence. Thus, our findings provide additional evidence to support the common evolutionary origin of these hormones, not only of the mature proteins but also of the extra piece segments.

Amino Acid Sequence↗