Sequential loss of two neighboring exons of the tropoelastin gene during primate evolution.

Previous evidence has demonstrated the absence of exons 34 and 35 within the 3' end of the human tropoelastin (ELN) gene. These exons encode conserved polypeptide domains within tropoelastin and are found in the ELN gene in vertebrate species ranging from chickens to rats to cows. We have analyzed the ELN gene in a variety of primate species to determine whether the absence of exons 34 and 35 in humans either is due to allelic variation within the human population or is a general characteristic of the Primates order. An analysis of the 3' end of the ELN gene in several nonhuman primates and in 546 chromosomes from humans of varying ethnic background demonstrated a sequential loss of exons 34 and 35 during primate evolution. The loss of exon 35 occurred at least 35-45 million years ago, when Catarrhines diverged from Platyrrhines (New World monkeys). Exon 34 loss, in contrast, occurred only about 6-8 million years ago, when Homo separated from the common ancestor shared with chimpanzees and gorillas. Loss of both exons was probably facilitated by Alu-mediated recombination events and possibly conferred a functional evolutionary advantage in elastic tissue.

Quantitation of tropoelastin mRNA and assessment of alternative splicing in human skin fibroblasts by reverse transcriptase-polymerase chain reaction.

We have developed a reverse transcriptase-polymerase chain reaction (RT-PCR) assay for the quantitative measurement of levels of tropoelastin mRNA in total RNA preparations from skin fibroblasts. This method facilitates the reproducible detection of low abundance tropoelastin mRNA in the range of 10-1000 copies per cell. The procedure is based on a competitive RT-PCR assay where a tropoelastin cDNA-derived internal RNA standard is cotranscribed and coamplified together with the sample derived-endogenous target mRNA. In addition, RT-PCR of several domains of tropoelastin mRNA, followed by DNA sequence analysis of asymmetric PCR products, revealed a previously unknown pattern of alternate exon usage at the 3' end of the tropoelastin gene in human skin fibroblasts.

The substitution of arginine for glycine 85 of the alpha 1(I) procollagen chain results in mild osteogenesis imperfecta. The mutation provides direct evidence for three discrete domains of cooperative melting of intact type I collagen.

We report a case of mild osteogenesis imperfecta in a 56-year-old male undergoing aortic valve replacement surgery. The primary defect in this patient was the substitution of arginine for glycine 85 in one of the two chains of alpha 1(I) procollagen. The thermal stability of the type I collagen synthesized by the patient's cultured skin fibroblasts was examined by enzymatic digestion. Digestion of the mutant type I collagen with trypsin and chymotrypsin at increasing temperatures sequentially generated three discrete collagenous fragments, approximately 90, 170, and 230 amino acids shorter than normal type I collagen. This incremental thermal denaturation is indicative of cooperative melting blocks within the type I collagen. This is the first demonstration of such cooperative blocks of melting in intact, essentially normal post-translationally modified type I collagen. This direct evidence for cooperative melting domains of uncut type I collagen suggests that discrete blocks of amino acids function as core sites stabilizing the collagen helix. The location of mutations of the alpha chains of type I collagen relative to these discrete blocks of amino acids may influence the severity of the disease phenotype.

Psychophysics of muscle tension in psychiatric inpatients.

Twelve psychiatric inpatients and 16 control subjects each took part in a psychophysics experiment in which the method of production was used to study the perception of tension in the frontalis and forearm extensor muscles. Subjects tensed each muscle between 0% and 50% maximum effort, with 25% effort repeated every third trial, and used as a reference stimulus. Patients showed significantly lower correlations between frontalis EMG and percent effort than the control subjects, but no between-groups differences were found for forearm. Correlations were higher for differences between successive trials than for absolute values because of apparent baseline shifts in perception and/or production of muscle tension. The performance among the patients was not correlated with severity of psychiatric symptoms, antipsychotic medication, abnormal movements, or parkinsonian symptoms, although the n was small. Analysis of the regression of EMG on percent effort revealed approximately equal descriptive strength for three functions: a linear relationship, Stevens' power function, and Fechner's law. The implications of these findings for self-regulation therapies are discussed.

Bromocriptine for "negative" schizophrenia.

The hypothesis that the pathophysiology of negative symptoms in schizophrenia may involve relative hypoactivity of central dopaminergic neurotransmission prompts the exploration of dopamine agonist strategies in the treatment of this condition. Although the use of dopamine agonists in otherwise unmedicated schizophrenic patients often leads to the exacerbation of psychosis, trials of dopamine agonists in combination with neuroleptic agents warrant investigation. We therefore report on open clinical experience involving six patients with chronic negative symptoms of schizophrenia, maintained on neuroleptic medication, who appeared to have favorable responses to the addition of moderate doses of bromocriptine (10 to 20 mg/d orally in divided doses). One particular factor that makes these trials potentially informative is that five of the six patients had failed to respond to standard treatments with anticholinergic antiparkinsonian medication before the bromocriptine trial, making it unlikely that the bromocriptine had its effect purely by counteracting neuroleptic-induced akinesia. A trial of bromocriptine under these circumstances has never been reported. A second unique feature of this report concerns the lengthy period of follow-up. Adjunctive bromocriptine was continued for a total of 27 patient-years in the six individuals, with maintenance of favorable course and minimal incidence of psychotic exacerbation.

A somatic gene rearrangement contributing to genetic diversity in maize.

We have discovered a somatic genomic rearrangement that occurs at high frequency at a duplicated zein locus in certain cultures of the maize inbred line A188. The rearranged allele arises from the duplication by a two-step process involving a homologous recombination and a second event, which may be a deletion, inversion, or insertion; both steps always occur together. The frequency of rearrangement is lower in homozygous states of the parental allele than in heterozygotes. In both cases, the rearrangement is shown to be mitotic. The rearranged product can be transmitted through meiosis, providing another mechanism for genome evolution in higher eukaryotes.

The importance of simple coagulation tests (fibrinogen assays and thrombin coagulase clotting time) in the diagnosis of liver cancer.

Dysfibrinogenemia in 36 patients with primary hepatocarcinoma and in 25 patients with cirrhosis of the liver was studied by means of reptilase time, thrombin coagulase time, fibrin polymerization and fibrinogen assays. Both groups of patients were similar in age, sex and incidence of HBs Ag. No electrolyte or fluid imbalances were present. Prolonged reptilase time and prolonged polymerization time were found in both groups; however, thrombin coagulase time was prolonged in 80% of the hepatocarcinoma group, but was normal in almost all patients with cirrhosis (p less than 0.001). In the hepatocarcinoma group, a difference of more than 100 mg per 100 ml was present between the immunologic and coagulative methods of fibrinogen determination in 36.1% of the cases, but in the cirrhotic group this difference was not present in any of the patients (p less than 0.01). We also found that by simply measuring fibrinogen levels by the Mancini method, we could distinguish hepatocarcinoma from cirrhosis in most cases.