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Biomedical subjects

M Kaufman

Publications and source records attributed to M Kaufman.

At least 73 records · Page 4Linked to original sources
PubMed1993

Kinetic evidence for a unique testosterone-receptor complex in 5 alpha-reductase sufficient genital skin fibroblasts and the effects of 5 alpha-reductase deficiency on its formation.

When 5 alpha-reductase-sufficient genital skin fibroblast (GSF) monolayers are incubated with testosterone (T), they first form androgen (A)-receptor (R) complexes that dissociate at a fast rate [k(37 degrees C = 0.024 min-1]. As T is converted to 5 alpha-dihydrotestosterone (DHT), this population of T-R complexes is eventually replaced by one that dissociates much more slowly [k(37 degrees C) = 0.006 min-1], at a rate typical of DHT-R complexes. During the course of T to DHT conversion, one may observe a population of A-R complexes that has a linear (monophasic) intermediate dissociation rate constant [k(37 degrees C) = 0.012 min-1]; this population cannot simply reflect a mixture of T- and DHT-R complexes. The rate at which the complexes are processed from one dissociative form to the next varies with the incubation temperature and the presence or absence of serum in the medium; it also varies within and among GSF strains under apparently constant conditions. To explain these facts, we propose a model that enables the 5 alpha-reductase enzyme to influence the processive dissociative behaviour of T-R complexes by engaging in some sort of coupling with the AR. The proposal is strengthened by a set of observations in cells with constitutive, mendelian or inhibitor-induced 5 alpha-reductase deficiency that preclude a simple quantitative relation between A-R complex processing and the extent of T to DHT conversion.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1993

Reduced transcriptional regulatory competence of the androgen receptor in X-linked spinal and bulbar muscular atrophy.

Expansion of the long (CAG; glutamine)n repeat in the first exon of the X-linked human androgen receptor gene (hAR) causes spinal and bulbar muscular atrophy, frequently in association with mild androgen insensitivity. The relevant normal motor neurons are preferentially stimulated by androgen, however no motor neuron disorder occurs with any other known AR mutation, including those that cause complete androgen insensitivity. We have found that a polyglutamine (Gln) expanded AR transactivates an androgen-responsive reporter gene subnormally. Other groups have reported that a poly Gln-deleted AR transactivates normally. A parsimonious interpretation of all these facts is that poly Gln expansion causes the AR to lose a function that is necessary for full androgen sensitivity and to gain a function that is selectively motor neuronotoxic.

Androgens↗
PubMed1993

Substitution of valine-865 by methionine or leucine in the human androgen receptor causes complete or partial androgen insensitivity, respectively with distinct androgen receptor phenotypes.

We have identified two different single nucleotide missense substitutions at valine-865 in exon 7 of the human androgen receptor (AR) gene in two families with androgen resistance. Val-->methionine is associated with the complete syndrome; Val-->leucine is associated with the partial form. In genital skin fibroblasts, both alterations yield a normal maximum binding capacity, but an increased apparent equilibrium dissociation constant for all androgens tested. In genital skin fibroblasts, Val865-Met A-R complexes have increased rate constants of dissociation with 5 alpha-dihydrotestosterone, and the nonmetabolized ligands methyltrienolone or mibolerone (MB); their Val865-Leu counterparts have increased rates with methyltrienolone and MB, but not with 5 alpha-dihydrotestosterone. In transiently transfected COS-1 or PC-3 cells, Met865 AR is more severely impaired than Leu865 AR in transactivating two different androgen-responsive reporter constructs, thereby correlating with clinical phenotype. In COS-1 cells exposed to MB for 74 h, this relative impairment correlates with the relative instability of the MB-binding activity of each mutant AR, suggesting that their respective intrinsic transcriptional regulatory competence is normal. Notably, these mutant ARs lose significantly more MB-binding activity than immunoreactivity, suggesting that prolonged MB exposure induces them to adopt a nonbinding state. The position homologous to Val865 in the AR is occupied by Leu or Met in the three steroid receptors closely related to the AR. This indicates the structural subtlety that underlies the steroid-binding activity of different steroid receptors.

Amino Acid Sequence↗
PubMed1993

[Use of mechanical suture in anterior resection of the rectum].

Anterior resection of carcinoma of the rectum was carried out in 129 patients. Hand-sutured anastomoses were formed in 73 and stapled anastomoses in 56 patients. There were 7 leaks after sutured anastomoses (9.6%) and 2 leaks after stapled anastomoses (3.57%). No late leaks or strictures were encountered in either group. Stapled anastomoses are advantageous for the following reasons: they are standardized; they can be created at a lower level than those formed by hand sutures, thus avoiding abdominoperineal resection in many patients; the incidence of anastomotic leakage is lower; time is saved. The EEA stapler is recommended for routine use in anastomoses of the rectum.

Aged↗
PubMed1992

Familial intracranial hypertension: report of a case and review of the literature.

A mother and daughter are presented who had intracranial hypertension 5 years apart. Possible contributing factors were the presence of obesity and occasional asthma in both. A review of the literature reveals three other families with intracranial hypertension occurring in successive generations (suggesting autosomal dominant transmission) and four families with intracranial hypertension occurring in siblings (suggesting autosomal recessive transmission). No reported cases of familial intracranial hypertension have revealed a contributing cause.

Adolescent↗
PubMed1992

Suture closure versus stapling of bronchial stump in 304 lung cancer operations.

Suture closure of the bronchial stump was compared with staple closure after 304 operations for bronchogenic carcinoma over an 8-year period. In 154 cases (112 lobectomies and 42 pneumonectomies) the bronchial stump was closed with interrupted sutures of 000 polyester, and in 150 cases (120 lobectomies and 30 pneumonectomies) an autosuture stapler was used. The time for suture closure ranged from 5-15 minutes, whereas stapling was accomplished uniformly in c. 90 seconds. Bronchopleural fistula developed after suture closure in seven cases (4.5%), but in none after stapling closure. Stapling of the bronchial stump after lobectomy or pneumonectomy for lung cancer is safer and quicker than suture closure, and is recommended as the method of choice.

Bronchi↗
PubMed1992

Androgen resistance due to mutation of the androgen receptor.

The androgen receptor (AR) is a 'one-stop' signal transduction system that is the core of the intracellular androgen-response apparatus. It is an androgen-regulated, DNA-binding protein that regulates the expression of certain target genes, primarily at the transcriptional level. Mutations at the X-linked AR locus cause deficient or defective AR activity and, thereby, an extraordinarily wide spectrum of clinical androgen resistance. At one extreme, the affected 46,XY person is an infertile phenotypic female; at the other, he is a phenotypic male who may even be fertile, yet have gynecomastia or other focal signs of postpubertal subvirilization. We have identified 32 proven or putatively pathogenic alterations in the AR gene of 38 androgen-resistant families. This permits heterozygote detection and prenatal diagnosis whenever relevant. Most of the mutations affect the AR's androgen-binding domain, partly because our search has been targetted on those whose genital skin fibroblasts have impaired androgen-binding activities. The AR is a prototypic member of a subfamily that includes the receptors for progesterone, glucocorticoid, and mineralocorticoid. Observations that correlate AR genotype with clinical and receptor phenotypes of androgen resistance will help to generate a fine structure-function map of the AR and its close relatives. Constitutional variation in androgen sensitivity, that may be restricted to an organ (or organ system), could contribute to the pathogenesis of certain diseases whose sex ratio departs significantly from one.

Amino Acid Sequence↗
PubMed1992

Replacement of arginine 773 by cysteine or histidine in the human androgen receptor causes complete androgen insensitivity with different receptor phenotypes.

We have discovered two different point mutations in a single codon of the X-linked androgen-receptor (AR) gene in two pairs of unrelated families who have complete androgen insensitivity (resistance) associated with different AR phenotypes in their genital skin fibroblasts. One mutation is a C-to-T transition at a CpG sequence near the 5' terminus of exon 6; it changes the sense of codon 773 from arginine to cysteine, ablates specific androgen-binding activity at 37 degrees C, and eliminates a unique KpnI site at the intron-exon boundary. The other mutation is a G-to-A transition that changes amino acid 773 to histidine and eliminates an SphI site. This mutant AR has a normal androgen-binding capacity at 37 degrees C but has a reduced affinity for androgens and is thermolabile in their presence. Transient transfection of COS cells with cDNA expression vectors yielded little androgen-binding activity at 37 degrees C from Arg773Cys and abundant activity with abnormal properties from Arg773His, thereby providing the pathogenicity of both sequence alterations. This conclusion coincides with the following facts about evolutionary preservation of the position homologous to Arg773 in the AR: it is occupied by Arg or lysine in the progesterone, glucocorticoid, and mineralocorticoid receptors, and it is within a 14-amino-acid region of their steroid-binding domains that share approximately 85% amino acid identity.

Adolescent↗
PubMed1991

Amber mutation creates a diagnostic MaeI site in the androgen receptor gene of a family with complete androgen insensitivity.

We have discovered in the X-linked androgen receptor gene a single nucleotide substitution that is the putative cause of complete androgen insensitivity (resistance) in a family with affected individuals in 2 generations. Earlier studies on the family indicated co-segregation of mutant phenotype and the RFLPs at the loci DXS1 and DXYS1. The mutation is an adenine-to-thymine transversion in exon 8 that changes the sense of codon 882 from lysine to an amber (UAG) translation termination signal. The substitution creates a recognition sequence for the restriction endonuclease MaeI: this permits ready recognition of hemizygotes and heterozygotes after amplification of genomic exon 8 by the polymerase chain reaction. The mutation predicts the synthesis of a truncated receptor that lacks 36 amino acids at the carboxy terminus of its 252-amino acid androgen-binding domain. The cultured genital skin fibroblasts of the one affected patient examined have normal levels of androgen receptor mRNA, but negligible androgen-receptor binding activity. These results accord with a variety of data from spontaneous and artificial mutations indicating that all portions of the steroid binding domain contribute to normal steroid binding by a steroid receptor.

Amino Acid Sequence↗
PubMed1991

The 56 kDa androgen binding protein is an aldehyde dehydrogenase.

We have described a 56 kDa protein from genital skin fibroblasts that specifically binds androgen and that is generally not expressed in genital skin fibroblasts from patients with androgen insensitivity due to genetic defects of the androgen receptor. We have isolated a partial cDNA clone for the 56 kDa protein from an expression library of genital skin fibroblasts. In vitro translation of message selected with this clone faithfully produces the 56 kDa protein which can be immuneprecipitated with an anti-56 kDa antiserum. Northern blots probed with this clone show a 2.2 kb message, which parallels the expression of the 56 kDa protein. The sequence of this 998bp clone is identical to human liver aldehyde dehydrogenase 1, the cytoplasmic isoenzyme. On activity gels of genital skin fibroblast cytosol covalently labelled with androgen, aldehyde dehydrogenase activity comigrates with the single band labelled specifically with androgen. Thus, the 56 kDa androgen binding protein is an aldehyde dehydrogenase, which is prominently expressed in normal genital skin fibroblasts, but not in non-genital skin fibroblasts.

Alcohol Dehydrogenase↗
PubMed1991

The 56/58 kDa androgen-binding protein in male genital skin fibroblasts with a deleted androgen receptor gene.

Human genital skin fibroblasts (GSF) make a relatively abundant 56/58 kDa protein that binds androgens. The protein shares many properties with the approximately 100 kDa androgen receptor that is encoded by a locus in the q12 region of the X chromosome. It does not appear to be androgen-induced, yet is absent in GSF of most patients with complete androgen insensitivity (CAI). A precursor-product relation with the androgen receptor (AR) protein has been largely excluded; that it may be an unorthodox product of the AR gene has not. The 56/58 kDa protein is made by the GSF of a mentally retarded subject who has CAI because of a complete deletion of the coding portion of the AR gene. Hence, the strong constitutional and statistical correlations that have been demonstrated between the two proteins cannot arise because they share the same gene. The subject's genomic DNA hybridizes normally with 11 single-copy probes from Xq11-Xq13. Therefore, we cannot attribute her mental retardation to a contiguous gene syndrome.

Androgen-Binding Protein↗
PubMed1991

A cryoglobulin with cold agglutinin and erythroid stem cell suppressant properties.

A 93-year-old woman presented with profound anemia (hematocrit 23% [0.23]); there was clumping of her red cells in test tubes and on peripheral blood smears. There was also a marked decrease in erythroid precursors in the bone marrow and reticulocytopenia in the peripheral blood. An IgM kappa monoclonal gammopathy was found in low concentration (approximately 1%) in her serum, and the cold agglutinins had a titer of 2560. However, the cold agglutinin titer of the supernatant after cryoglobulin precipitation was 40. Redissolving the cryoglobulin in the supernatant resulted in a cold agglutinin titer of 1280. Moreover, the addition of the patient's whole serum inhibited erythroid colony formation in culture. The inhibition was removed by cryoprecipitation of the cryoglobulin. The patient was given steroid therapy, to which she responded with reticulocytosis and an elevation of hematocrit. By 3 months, the cold agglutinin titer had fallen to 10. She remained well 4 years later. Whereas reports of cryoprecipitable cold agglutinins are rare, this case is unique because there have been no previous reports that these cold active proteins also have erythroid stem cell-suppressant properties.

Aged↗
PubMed1991

Induction of long-term but reversible unresponsiveness after activation of murine T cell hybridomas.

T cell receptor (TCR)-mediated stimulation of murine T cell hybridomas induces cell activation and lymphokine production. We have observed that following productive activation, T cell hybridomas become refractory to a subsequent stimulation. Hyporesponsiveness is long-lasting but reversible, and is not due to reduced receptor expression. It is noteworthy that hyporesponsiveness is cell autonomous, persists in spite of cell division and does not require continuous exposure to ligands. Hyporesponsive cells retain the ability to produce lymphokines in response to pharmacological agents bypassing receptor triggering, indicating that they possess a functional enzymatic machinery for interleukin 2 synthesis and secretion. Reduced phosphatidylinositol hydrolysis was observed in these cells in response to TCR stimulation, suggesting that hyporesponsiveness result from defective transduction of activation signals. The development of unresponsiveness following receptor stimulation resembles desensitization, and may thus play an important role in the regulation of an immune response and in the induction of immune tolerance.

Animals↗