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Biomedical subjects

J Tamm

Publications and source records attributed to J Tamm.

At least 19 recordsLinked to original sources
PubMed1989

Severe hypoglycemia in children with insulin-dependent diabetes mellitus: frequency and predisposing factors.

We surveyed 311 children with insulin-dependent diabetes mellitus to evaluate the frequency and characteristics of those children experiencing severe hypoglycemia (defined by an episode of coma, convulsion, or both). The children and their parents completed a questionnaire, and we reviewed the hospital records to confirm reported episodes. Ninety-seven (31%) reported severe hypoglycemia, and a further 50 (16%) reported moderate hypoglycemia requiring the assistance of another person but not resulting in coma or convulsion. In 164 children (53%) there was no history of either moderate or severe hypoglycemia. Sixty-nine (22%) reported the occurrence of more than one severe hypoglycemic episode (range 2 to 20); 52 (16%) reported such an event in a single year. A total of 285 episodes were reported, 39% during sleep and 61% while awake. Children reporting such events tended to have diabetes of longer duration and be younger at the time of the first episode. Hemoglobin A1c concentration at the time closest to the severe episode was significantly lower than in children reporting no hypoglycemia. All families had been taught to use glucagon to reverse severe hypoglycemia at home, but it was available in only 80 of the 97 homes and used in only 30. These data suggest that severe hypoglycemia is common in children with insulin-dependent diabetes mellitus who are treated conventionally. Greater vigilance and education are required both to prevent and to treat severe hypoglycemia in children with insulin-dependent diabetes mellitus.

Adolescent↗
PubMed1988

A new type of transforming growth factor-beta, TGF-beta 3.

A new type of TGF-beta, TGF-beta 3, has been identified by cDNA characterization. The amino acid sequence of mature TGF-beta 3 and its precursor has been derived from porcine and human cDNA sequences. The human TGF-beta 3 gene is spread over seven exons as in the case of the TGF-beta 1 gene. Comparison with TGF-beta 1 and -beta 2 indicates a strong conservation of the mature sequences, but a relaxed homology in the precursor segments. TGF-beta 3 mRNA is mainly expressed in cell lines from mesenchymal origin, suggesting a biological role different from the other TGFs-beta.

Amino Acid Sequence↗
PubMed1988

The effect of short term treatment with cyproterone acetate or flutamide on the metabolism of 5 alpha-dihydrotestosterone in human testicular tissue.

Testicular tissue obtained from ten patients orchiectomized for prostatic cancer was incubated with [3H]5 alpha-dihydrotestosterone (DHT) in order to study the metabolic transformation into 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) and 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol). Throughout 5 days before surgery four subjects were treated with cyproterone acetate (CA). To three patients flutamide (F) was administered for the same period of time. Three subjects remained untreated. Compared to the control group the administration of CA decreased the formation of 3 beta-diol whereas that of 3 alpha-diol increased. Treatment with F lead to an elevated formation of both diols. However, the 3 alpha/3 beta ratio did not change. As 3 beta-diol is considered to be an index of tubular function in the human testis it is concluded that CA has a direct inhibitory effect upon this testicular compartment whereas F has none.

Aged↗
PubMed1988

Chromosomal mapping of genes for transforming growth factors beta 2 and beta 3 in man and mouse: dispersion of TGF-beta gene family.

Human cDNA probes for two new types of transforming growth factor-beta, TGF-beta 2 and TGF-beta 3, were used for mapping their cognate genes on human and mouse chromosomes by Southern blot analysis of somatic cell hybrid lines and, for the human loci, also by in situ chromosomal hybridization. For TGF-beta 2, a single site was found on the long arm of human chromosome 1, band 1q41, and on mouse chromosome 1, most likely in the known conserved syntenic region. For TGF-beta 3, the major site of hybridization, both on Southern filters and direct chromosome preparations, was at 14q24 in humans. This region is homologous in part to mouse chromosome 12, to which the murine beta 3 locus was mapped. These results indicate a wide dispersion of the TGF-beta gene family, with genes for TGF-beta 1 previously mapped by us to human chromosome 19q and mouse chromosome 7 and for inhibins alpha, beta B and beta A to human chromosomes 2q33-qter, 2cen-q13 and 7p15-p13, respectively.

Animals↗
PubMed1987

Concentrations of unconjugated 5 alpha-androstane-3 alpha, 17 beta-diol and 5 alpha-androstane-3 beta, 17 beta-diol and their precursor in human testicular tissue. Comparison with testosterone, 5 alpha-dihydrotestosterone, estradiol-17 beta, and with steroid concentrations in human epididymis.

The concentrations of testosterone and its tissular metabolites were determined in testicular and epididymal tissue obtained from eleven male subjects (aged 65-85 years) after orchiectomy for prostatic cancer. The steroids were measured in different tissular compartments, i.e. testis, caput, corpus and cauda epididymis. The values (mean +/- SD; ng/g wet weight) were: Testosterone 724.0 +/- 286.0, 32.08 +/- 2.56, 41.45 +/- 1.77 and 32.24 +/- 2.14; 5 alpha-dihydrotestosterone 6.95 +/- 1.99, 9.76 +/- 2.33, 16.87 +/- 0.21 and 15.79 +/- 2.67; 5 alpha-androstane-3 alpha, 17 beta-diol 6.07 +/- 2.33, 2.17 +/- 0.24, 1.93 +/- 0.02 and 1.17 +/- 0.20; 5 alpha-androstane-3 beta, 17 beta-diol 56.66 +/- 20.97, 3.55 +/- 0.19, 2.21 +/- 0.27 and 3.34 +/- 0.32; estradiol-17 beta 5.36 +/- 3.0, 1.08 +/- 0.014, 1.44 +/- 0.038 and 1.47 +/- 0.03, respectively. Incubation of human testicular tissue with [3H]androst-5-ene-3 beta, 17 beta-diol or [3H]dihydrotestosterone showed that both androstane-diols were exclusively formed from dihydrotestosterone. Since high concentrations of 5 alpha-androstane-3 beta, 17 beta-diol are found in testicular tissue it is suggested that this steroid may be an index of seminiferous tubular function.

Aged↗
PubMed1987

A trans-acting suppressor restores splicing of a yeast intron with a branch point mutation.

Splicing of introns from Saccharomyces cerevisiae pre-mRNA requires the conserved sequence TACTAAC; the 3'-most A residue is utilized as the site of branch formation. We showed previously that the transcript from an actin-HIS4 gene fusion containing the mutation TACTAAC to TACTACC (designated C259) is spliced inefficiently, thereby preventing growth on the histidine precursor histidinol. By selecting for growth on histidinol, we have identified a mutant in which the splicing of the C259 transcript is increased fourfold; splicing of other mutated introns is not significantly improved. The mutant locus encodes a trans-acting suppressor. A single mutation, rna16-1, is sufficient for suppression; however, suppression is maximized in heterozygous diploids containing both rna16-1 and the wild-type allele RNA16. In addition, wild-type pre-mRNAs (and lariat intermediates) accumulate in rna16-1 cells. We propose that the RNA16 locus encodes a component of the splicing machinery.

Genes, Fungal↗
PubMed1986

Mutations in conserved intron sequences affect multiple steps in the yeast splicing pathway, particularly assembly of the spliceosome.

Yeast introns contain three highly conserved sequences which are known to be required for splicing of pre-mRNA. Using in vitro mutagenesis, we have synthesized seven point mutations at five different sites in these signals in the yeast actin intron. The mutant introns were then inserted into each of three constructs, which allowed us to assess the consequences both in vivo and in vitro. In virtually every case, we found the efficiency of splicing to be significantly depressed; mature mRNA levels in vivo ranged from 0 to 47% of wild-type. Surprisingly, the tightest mutations were not necessarily at the sites of nucleolytic cleavage and branch formation; these nucleotides are thus highly preferred, but are not absolutely necessary. Moreover, while particular nucleotides are specifically required for the final step in splicing, i.e. 3' cleavage and exon ligation, the predominant consequence of mutation within the conserved signals appears to be the inhibition of assembly of the splicing complex.

Actins↗
PubMed1985

Isolation and characterization of mutants affecting functional domains of ColE1 RNAI.

The control of DNA replication initiation in the plasmid ColE1 is mediated by RNAI, a 108 nucleotide plasmid-encoded RNA that is entirely complementary to the 5'-terminal region of the replication primer RNA. RNAI acts in trans to inhibit primer maturation. Previously, we constructed a plasmid in which the ColE1 RNAI was separated from the primer and placed under transcriptional control of the Serratia marcesens tryptophan promoter. This plasmid provides RNAI in trans in vivo and mediates ColE1-type incompatibility. To determine the critical structural and functional domains of RNAI, we have undertaken a mutational analysis of the RNAI gene carried by this plasmid. We have selected mutants that no longer mediate ColE1-type incompatibility in trans. From the DNA sequences of 18 mutants we have identified mutations at nine new sites in RNAI. In addition, we have determined the secondary structural features of several mutant RNAI species and compared them to wild-type RNAI. Analysis of these mutations has revealed several key features of RNAI secondary structure and function. The domains of RNAI identified in this work which are essential for its function are: the single-stranded loop regions; the integrity of the double-stranded stems; and the single-stranded 5' terminus.

Colicins↗
PubMed1985

Construction of Co1E1 RNA1 mutants and analysis of their function in vivo.

We have carried out experiments designed to investigate the relationship between structure and function for the Co1E1 RNA1 species. RNA1 is a small RNA (108 nucleotides) that has been implicated in copy number control of the multicopy plasmid Co1E1. In vitro, RNA1 inhibits the processing of the primer precursor required for initiation of DNA replication. The RNA1 gene is entirely complementary to the 5'-terminal region of the primer. We have functionally separated these 2 RNA species by cloning the RNA1 gene downstream from the S. marcescens trp promoter. When cloned in a Co1E1-compatible plasmid, a trp-RNA1 fusion has been shown to mediate Co1E1-type incompatibility in vivo. The construction scheme described here also generates mutant RNA1 species with altered sequences at the 5' terminus of RNA1 which have been assayed for function in vivo. These experiments have indicated that sequences at the 5' terminus play a critical role in RNA1 function.

Bacteriocin Plasmids↗
PubMed1985

The effect of infusions of 5 alpha-dihydrotestosterone or estradiol-17 beta on the concentration of some steroids in the human testicular vein and artery.

The concentrations of testosterone, 5 alpha-dihydrotestosterone, 5 alpha-androstan-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol, estradiol-17 beta and testosterone-glucosiduronate were measured in the plasma of the testicular vein and artery simultaneously with the estimation in peripheral venous and arterial plasma 60 min after an infusion of 3000 micrograms dihydrotestosterone (DHT) or estradiol (E2), respectively, in patients undergoing orchiectomy for prostatic cancer. The results were as follows; following infusion of DHT or E2, both steroids were completely metabolized by the testes. After DHT the testicular secretion of E2 was significantly reduced. In peripheral plasma 3 alpha-diol concentration was increased. Following E2 a transient elevation of testosterone in the spermatic vein was observed, whereas a slight decrease of DHT and an increase especially of 3 beta-diol levels occurred. It is assumed that DHT as well as E2 plays a role as intratesticular regulator of steroid synthesis and metabolism.

Aged↗
PubMed1985

Characterization of the ColE1 primer-RNA1 complex: analysis of a domain of ColE1 RNA1 necessary for its interaction with primer RNA.

RNA1 is a small, plasmid-encoded transcript involved in the replication control of the plasmid ColE1. RNA1 blocks replication by preventing processing of the primer RNA necessary for the initiation of replication. It has been proposed that inhibition by RNA1 involves a direct interaction between RNA1 and primer RNA. Here we describe an in vitro system that allows the detection and characterization of the RNA1-primer complex. Using this system, we have demonstrated that the association between ColE1 RNA1 and primer results in the formation of an RNA X RNA hybrid between RNA1 and the 5' end of primer RNA. Furthermore, analysis of mutant RNA1 molecules containing sequence alterations in the 5' single-stranded region of the molecule has revealed that this portion of RNA1 is necessary for the formation of the RNA1-primer complex. These experiments indicate that, in addition to the three single-stranded loops of RNA1, the 5' single-stranded region is a functional domain of the molecule.

DNA Replication↗
PubMed1984

RNA1 is sufficient to mediate plasmid ColE1 incompatibility in vivo.

The multicopy plasmid ColE1 specifies a small RNA designated RNA1 that has been implicated in copy number control and incompatibility. We have inserted a 148 base-pair ColE1 DNA fragment containing a promoter-less RNA1 gene into a plasmid vector downstream from the tryptophan promoter of Serratia marcesens . The ColE1 RNA1 produced by this plasmid is not functional in vivo due to the presence of 49 nucleotides appended to the 5'-terminus of the wild-type RNA1 sequence. Deletions of these sequences by Bal3l nuclease in vitro and genetic selection for ColE1 incompatibility function in vivo permitted isolation of a plasmid expressing wild-type ColE1 RNA1 initiated properly from the S. marcesens trp promoter. These experiments demonstrate that RNA1 is sufficient to mediate ColE1 incompatibility in vivo. In addition, several plasmids were isolated that contain altered RNA1 genes. These alterations consist of additions or deletions of sequences at the 5'-terminus of RNA1. Analysis of the ability of these altered RNA1 molecules to express incompatibility in vivo suggests that the 5'-terminal region of RNA1 is crucial for its function.

Bacteriocin Plasmids↗
PubMed1984

Spontaneous fractures of the neck of the femur occurring in pregnancy in the absence of pregnancy osteoporosis.

Case report on a patient suffering from spontaneous fractures of the neck of the femur which occured during her first pregnancy at the age of 23 in the left leg and during another pregnancy seven years later in the right leg. Both fractures occured during the eighth month of pregnancy. Special attention is drawn to the fact that local or general osteoporosis which, according to literature, should be obligatory for the occurence of spontaneous necrosis of the femoral head and/or fractures of the neck of the femur, could be demonstrated neither during the first nor the second pregnancy.

Adult↗
PubMed1984

Ultrafiltrable plasma testosterone and 5 alpha-dihydrotestosterone as measured across the human testes.

It has been confirmed that within the human plexus pampiniformis a venous-arterial transfer of testosterone (T) (5.95%) and of dihydrotestosterone (DHT) (16.58%) occurs. It could be established that in the testicular artery the percentage of ultrafiltrable DHT was significantly lower compared with the venous compartment. It is assumed that by this means a biological recycling of the active androgen DHT into the testis is achieved.

Aged↗
PubMed1983

Structural analysis of RNA molecules involved in plasmid copy number control.

DNA replication of the plasmid ColE1 and its relatives is controlled mainly by a small plasmid-encoded transcript known as RNA11. We have studied the conformation of RNA1 molecules from two related but compatible plasmids, ColE1 and RSF1030, using T1 ribonuclease, S1 nuclease, cobra venom nuclease, and diethyl pyrocarbonate modification as probes for secondary structure. Both RNA1 molecules contain three double-stranded stems, three single-stranded loops, and an exposed 5' tail. All loops in both molecules show similar sensitivities to the probes used, as do stems 1 and 3. The region comprising stem 2 of each RNA1 molecule contains the most sequence differences as well as the most structural changes of any region in the two molecules. The structure of the RNA1 molecule encoded by a recessive high copy number mutant of ColE1 was also investigated. Structural alterations involving the first stem and loop of the molecule are proposed to be responsible for the inability of the mutant RNA1 to function in vivo.

Base Sequence↗
PubMed1982

Comparison of steroid concentrations in venous and arterial blood across the human testis. Unconjugated 5 alpha-androstane-3 beta, 17 beta-diol: an important androgen metabolite of the human testicular-epididymal unit.

By means of specific radioimmunoassays unconjugated testosterone, 5 alpha-dihydrotestosterone, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol and estradiol-17 beta as well as testosterone-glucosiduronate were estimated in the plasma of the spermatic vein and artery simultaneously with the determination in peripheral venous and arterial plasma in ten male patients undergoing orchiectomy for prostatic cancer. The following results were obtained: A positive concentration gradient was found for all steroids. The testicular "secretion" of 5 alpha-androstane-3 beta, 17 beta-diol was established for the first time. The venous-arterial transfer of the mentioned steroids within the plexus pampiniformis yielded the following figures: 5.1%; 17.4%; 6.5%; 5.4% 5.1% and 6.5%, respectively. The testicular and/or epididymal origin of the different steroids was calculated to be of the following order of magnitude (mean values): Dihydrotestosterone 28%, 5 alpha-androstane-3 alpha, 17 beta-diol 45%, 5 alpha-androstane-3 beta, 17 beta-diol about 100% estradiol-17 beta 63% and testosterone-glucosiduronate 3%.

Aged↗