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Biomedical subjects

J Klein

Publications and source records attributed to J Klein.

At least 415 records · Page 23Linked to original sources
PubMed1993

Multiplication of Mhc-DRB5 loci in the orangutan: implications for the evolution of DRB haplotypes.

The beta chain-encoding (B) class II genes of the primate major histocompatibility complex belong to several families. The DRB family of class II genes is distinguished by the occurrence of haplotype polymorphism--the existence of multiple chromosomal forms differing in length, gene number, and gene combinations, each form occurring at an appreciable frequency in the population. Some of the haplotypes, or fragments thereof, are shared by humans, chimpanzees, and gorillas. In an effort to follow the DRB haplotype polymorphism further back in time, we constructed DRB contig maps of the two chromosomes present in the orangutan cell line CP81. Two types of genes were found in the two haplotypes, Popy-DRB5 and Popy-DRB1*03, the former occurring in two copies and one gene fragment in each haplotype, so that the CP81 cell line contains four complete DRB5 genes and two DRB5 fragments altogether. Since the four genes are more closely related to one another than they are to other DRB5 genes, they must have arisen from a single ancestral copy by multiple duplications. At the same time, however, the two CP81 haplotypes differ considerably in their restriction enzyme sites and in the presence of Alu elements at different positions, indicating that they have been separated for a length of time that exceeds the lifespan of a primate species. Moreover, a segment of about 100 kilobase pairs is shared between the orangutan CP81-1 and the human HLA-DR2 haplotype. These findings indicate that part of the haplotype polymorphism may have persisted for more than 13 million years, which is the estimated time of human-orangutan divergence.

Amino Acid Sequence↗
PubMed1993

Prevalence and functional significance of transient ST-segment depression during daily life activity: comparisons of ambulatory ECG with stress redistribution thallium 201 single-photon emission computed tomographic imaging.

To assess the prevalence and functional significance of ischemic ambulatory ECG responses, we prospectively performed ambulatory ECG monitoring in 244 patients (mean age 61 +/- 10 years) referred for stress redistribution thallium 201 myocardial perfusion scintigraphy. The prevalence of ST-segment depression during ambulatory ECG was 33% among patients with a positive exercise ECG, but prevalence varied in selected patient subgroups. Among three groups with coronary artery disease (CAD), the group with ambulatory ECG ischemia (group 1) had a greater frequency of ischemic thallium responses (p = 0.07), a greater median number of reversible thallium defects (p < 0.05), and a greater summed thallium "reversibility" score (p < 0.05) than did the group with a positive exercise ECG but negative ambulatory ECG response (group 2) or that with negative exercise and ambulatory ECG responses (group 3). Exercise ST depression in group 1 versus group 2 was significantly greater (p = 0.002), occurred at a lower heart rate threshold (p = 0.002), and lasted longer after exercise (p = 0.001). Notably, one third of group 1 patients also manifested evidence of transient ischemic dilation of the left ventricle after exercise (p < 0.01 vs groups 2 and 3), a sign of severe ischemia. However, although functionally less "sick" than group 1 patients, 66% of group 2 patients and 50% of group 3 patients still had an ischemic thallium response, which was sometimes severe. Thus transient ischemia during ambulatory ECG monitoring identifies a functionally sicker cohort of patients with CAD and occurs in approximately one third of CAD patients with positive results of exercise tests. A negative ambulatory ECG response, however, does not exclude functionally significant disease among CAD patients. These results imply that caution should be applied in the interpretation of a negative ambulatory ECG response for the purpose of patient risk stratification.

Activities of Daily Living↗
PubMed1993

Free choline and choline metabolites in rat brain and body fluids: sensitive determination and implications for choline supply to the brain.

In the central nervous system, choline is an essential precursor of choline-containing phospholipids in neurons and glial cells and of acetylcholine in cholinergic neurons. In order to study choline transport and metabolism in the brain, we developed a comprehensive methodical procedure for the analysis of choline and its major metabolites which involves a separation step, selective hydrolysis and subsequent determination of free choline by HPLC and electrochemical detection. In the present paper, we report the levels of choline, acetylcholine, phosphocholine, glycerophosphocholine and choline-containing phospholipids in brain tissue, cerebrospinal fluid and blood plasma of the untreated rat. The levels of free choline in blood plasma (11.4 microM), CSF (6.7 microM) and brain intracellular space (64.0 microM) were sufficiently similar to be compatible with an exchange of choline between these compartments. In contrast, the intracellular levels of glycerophosphocholine (1.15 mM) and phosphocholine (0.59 mM) in the brain were considerably higher than their CSF concentrations of 2.83 and 1.70 microM, respectively. In blood plasma, glycerophosphocholine was present in a concentration of 4.58 microM while phosphocholine levels were very low or absent (< 0.1 microM). The levels of phosphatidylcholine and lyso-phosphatidylcholine were high in blood plasma (1267 and 268 microM) but very low in cerebrospinal fluid (< 10 microM). We concluded that the transport of free choline is the only likely mechanism which contributes to the supply of choline to the brain under physiological conditions.

Acetylcholine↗
PubMed1993

Conservative evolution of the Mbc-DP region in anthropoid primates.

To determine the organization of the DP region in the Mbc of anthropoid primates, we constructed contig maps from cosmid clones of the chimpanzee and orangutan, representatives of the infraorder Catarrhini, as well as of the cotton-top tamarin, a representative of the infraorder Platyrrhini. We found the maps to be remarkably similar to each other and to the previously published map of the human DP region. In each of the four species, the DP region consists of four loci arranged in the same order (DPB2 . . . DPA2 . . . DPB1 . . . DPA1) and in the same transcriptional orientation (tail-to-tail). The regions in the four species are of approximately the same length and many of the restriction sites are shared between species. The inserts of most Alu elements, of a ribosomal protein pseudogene, and of an IgC epsilon-like pseudogene are found in corresponding positions in all four species. The data indicate that the human-type organization of the DP region was established before the divergence of the Catarrhini and Platyrrhini lines more than 37 million years ago and that it has remained principally intact since that time. This conservation of the DP region is in striking contrast to the evolutionary instability of certain other Mbc regions, in particular those occupied by the DRB or C4 and CYP21 loci. We interpret the stability of the DP region as an indication that the region is being phased out functionally.

Animals↗
PubMed1993

Quantification, immunoaffinity purification and sequence analysis of a pigment-dispersing hormone of the shore crab, Carcinus maenas (L.).

1. A sensitive sandwich-ELISA for pigment-dispersing hormone (PDH) with a detection limit of approximately 5 fmol per well has been developed using primary IgG and secondary biotinylated IgG fractions from an antiserum against beta-PDH and streptavidin-peroxidase conjugate for detection. 2. ELISA determinations in different parts of the central nervous system of the shore crab Carcinus maenas revealed maximum levels of 15.1 pmol immunoreactive PDH in the two eyestalk ganglia of one crab, 3.6 pmol in the sinus glands, 2.8 pmol in the brain and 0.8 pmol in the thoracic ganglia. 3. Carcinus PDH was purified from whole eyestalk ganglia and sinus glands by use of a simple two-step purification procedure consisting of immunoaffinity-prepurification on an anti-PDH IgG-protein A-Sepharose column and HPLC. 4. Automated gas-phase sequencing of the purified peptide and FAB-mass spectroscopy unambiguously revealed the sequence of Carcinus PDH as NSELINSILGLPKVMNDAamide (M(r) 1927.2 Da), which is identical to the beta-PDH of other brachyuran crustaceans.

Amino Acid Sequence↗
PubMed1993

Up-regulation of beta 2-adrenergic receptors in previously transplanted, denervated nonfailing human hearts.

OBJECTIVES: The purpose of this study was to examine beta-adrenergic receptor signal transduction in denervated, previously transplanted human ventricular myocardium. BACKGROUND: In model systems, surgical denervation typically results in both presynaptic and postsynaptic supersensitivity in beta-adrenergic receptor pathways and alteration in G protein-mediated signal transduction. METHODS: We examined beta-adrenergic receptor signal transduction in the left and right ventricles removed from nine subjects with a previous transplant and surgical denervation 25 +/- 4 months after their first transplantation. Twenty-six hearts removed from organ donors served as control hearts. RESULTS: Total beta-adrenergic receptor density and stimulation of muscle contraction in isolated right ventricular trabeculae by the nonselective agonist isoproterenol were similar in the transplant and donor groups. Beta 1-receptor density was not different in the left ventricles of the two groups but tended to be reduced (by 29%, p = 0.09) in transplant right ventricles. By contrast, beta 2-receptor density was higher in transplant left and right ventricles relative to the respective values in donor ventricles by 33% in left ventricles and 97% in right ventricles (both p < 0.05). Isoproterenol, which in particulate fractions of human heart stimulates adenylyl cyclase primarily via beta 2-receptors, produced a greater increase in cyclic adenosine monophosphate generation in membranes prepared from transplant left ventricles and right ventricles compared with donors. In contrast, guanosine 5'-[beta,gamma-imido]triphosphate, sodium fluoride and forskolin, which stimulate adenylyl cyclase through nonreceptor/G protein-sensitive mechanisms, yielded similar degrees of adenylyl cyclase stimulation in the two groups, and both pertussis toxin- and cholera toxin-catalyzed adenosine diphosphate ribosylation were not altered in transplanted left ventricles. CONCLUSIONS: These data indicate that the transplanted human heart exhibits an up-regulation of functional beta 2-adrenergic receptors.

Adenylyl Cyclases↗
PubMed1993

Composite origin of major histocompatibility complex genes.

Major histocompatibility complex (MHC) genes have now been cloned from representatives of all vertebrate classes except Agnatha. The recent accumulation of sequence data has given great insight into the course of evolution of these genes. Although the primary structure of the MHC genes varies greatly from class to class and also within the individual classes, the general features of the tertiary and quaternary structure have been conserved remarkably well during more than 400 million years of evolution. The ancestral MHC genes may have been assembled from at least three structural elements derived from different gene families. Class II MHC genes appear to have been assembled first, and then to have given rise to class I genes.

Amino Acid Sequence↗
PubMed1993

Morphine pharmacokinetics in children following cardiac surgery: effects of disease and inotropic support.

The pharmacokinetics of morphine have not been previously studied in children following cardiac surgery for tetralogy of Fallot (TOF) or transposition of the great arteries (TGA). Morphine steady-state pharmacokinetics were studied in 21 children undergoing repair of TOF, TGA, or atrio-ventricular septal defects (AVSD). Children with TOF or TGA had increased right-sided pressures with no differences between the groups. Children with TOF had significantly faster clearance rates of morphine (1.39 +/- 0.37 L/kg/h) than children following the Fontan procedure (0.86 +/- 0.31 L/kg/h, P < 0.01). When stratifying children by their postsurgical needs for inotropic support, those needing epinephrine, dopamine, or dobutamine at more than 10 micrograms/kg/min had significantly slower clearance rates (0.73 +/- 0.3 L/kg/h) when compared to the rest of the patients (1.5 +/- 0.41 L/kg/h, P < 0.05). Because most children needing inotropic support underwent the Fontan procedure, it is conceivable that their cardiovascular status had a major impact on morphine metabolism. These results suggest a 50% reduction in morphine dosage in children requiring inotropic support following cardiac surgery.

Blood Pressure↗
PubMed1993

Comparison between colposcopic, cytologic, and histologic findings in women positive and negative for human papillomavirus DNA.

Little is known about the role of detection of human papillomavirus (HPV) DNA in exfoliated cells of the cervix in aiding the colposcopic diagnosis of cervical lesions. The purpose of our study was to compare the colposcopic findings of young women who were positive and negative for HPV DNA. Eighty-four women aged 13-22 years attending family planning clinics were examined colposcopically with the aide of acetic acid and Lugol's solution and without knowledge of HPV DNA status. Lesions identified were given scores based on the severity of observed colposcopic changes. Samples for cytology and HPV DNA testing, which included types 6, 11, 16, 18, 31, 33, and 35, were obtained at the time of the examination. Biopsies were performed on women with significant lesions identified on examination or with cytology suggestive of neoplasia. Students t-test and chi 2 analysis were performed to compare colposcopic variables and HPV DNA type. Of the 84 women examined, 17 were positive for HPV DNA; 9 had type 16/18. The average length of sexual activity was 2.7 years. Women with HPV 16/18 had a mean of 1.7 lesions visible at colposcopy compared to 0.7 lesions visible in those negative for HPV 16/18 (this included HPV DNA negative women and women positive for HPV types 6, 11, 31, 33, and 35) (p < 0.001). Women who were positive for HPV 16/18 also had higher lesional scores than the HPV 16/18-negative group (3.4 versus 1.0, respectively, p < 0.001). All four women who had dysplasia either on cytology or histology were positive for type 16/18.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Surgical treatment of the Wolff-Parkinson-White syndrome--experiences in 120 patients.

Since January 1984, 120 patients (78 male, 42 female; aged 3 to 66 years) with the Wolff-Parkinson-White (WPW) syndrome have been operated upon. The indication for surgery was documented recurrent, paroxysmal tachycardia refractory to medical treatment in 118 cases. Twenty-two patients (18%) had additional heart disease. One hundred and twenty patients had a total of 140 accessory pathways (AP). AP were localized at the left free wall in 63% (87 AP), at the right free wall in 24% (35 AP), and septally in 13% (18 AP). Sixteen patients (13%) had multiple AP (12 patients had two and four patients had three AP), 124 AP were known pre-operatively (88%), 133 were localized intra-operatively (94%) and seven were diagnosed during re-operation (6%). Surgery in 28 patients with left lateral AP was via the epicardial approach and the endocardial approach in 59. Of 15 patients with right lateral AP, the surgical approach was epicardial in two and transmural in 13. A cryosurgery was also used in 117 patients. Fifteen patients suffered recurrences, in 12 of whom repeat surgery was required. One hundred and thirty-six AP (97%) were dissected successfully, of which 14 (10%) were ablated during re-operation. All patients survived the initial operation, but two patients died after re-operation. One patient is pacer-dependent due to persisting postoperative atrioventricular (AV) block. We conclude that surgical dissection of accessory pathways can be offered as an alternative to non-surgical treatment modes, at a low risk and with a high success rate.

Adolescent↗
PubMed1993

Dating the primigenial C4-CYP21 duplication in primates.

C4 and CYP21 are two adjacent, but functionally unrelated genes residing in the middle of the mammalian major histocompatibility complex (Mhc). The C4 gene codes for the fourth component of the complement cascade, whereas the CYP21 gene specifies an enzyme (cytochrome P450c21) of the glucocorticoid and mineralocorticoid pathways. The genes occur frequently in multiple copies on a single chromosome arranged in the order C4 ... CYP21 ... C4 ... CYP21. The unit of duplication (a module) is the C4-CYP21 gene pair. We sequenced the flanking regions of the C4-CYP21 modules and the intermodular regions of the chimpanzee, gorilla, and orangutan, as well as the intermodular region of an Old World monkey, the pigtail macaque. By aligning the sequences, we could identify the duplication breakpoints in these species. The breakpoint turned out to be at exactly the same position as that found previously in humans. The sequences flanking paralogous genes in the same species were found to be more similar to one another than sequences flanking orthologous genes in different species. We interpret these results as indicating that the original (primigenial) duplication occurred before the separation of apes from Old World monkeys more than 23 million years ago. The nature of the sequence at the breakpoint suggests that the duplication occurred by nonhomologous recombination. Since then, the C4-CYP21 haplotypes have been expanding and contracting by homologous crossing over which has homogenized the sequences in each species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Different modes of Mhc evolution in primates.

The human major histocompatibility complex (Mhc) is a chromosomal segment approximately 4 million bp long that contains > or = 84 genes. Some of these genes code for the class I and class II molecules, while the remaining genes code for complement components, cytochrome P450, tumor necrosis factor, and many other, unrelated proteins. We demonstrate on three examples (DP, C4-CYP21, and DRB) that different regions of the Mhc have different evolutionary histories. The organization of the DP region, which in humans contains four genes, was established in the ancestral Anthropoidea or earlier and has not changed since. The duplication that generated the two C4-CYP21 modules occurred in the ancestral Catarrhini or earlier, but the region has been undergoing periodic homogenizations via unequal crossing-over, which make paralogous genes in the same species more similar to each other than to orthologous genes of different species. The eight or nine genes of the DRB region were also generated in the ancestral Catarrhini, but the region has since been subject to frequent rearrangements, which generated various DRB haplotypes. Not only the alleles but, in part, also the haplotype polymorphism is evolving transspecifically. The DRB region of the Platyrrhini has an origin different from that of the Catarrhini. The picture emerging from these studies is that of both stability in some regions of the Mhc and tremendous evolutionary instability in other regions.

Animals↗
PubMed1993

Major-histocompatibility-complex variation in two species of cichlid fishes from Lake Malawi.

Lake Malawi in eastern Africa harbors > 500 endemic species of cichlid fishes, all of which are believed to have emerged from a single founding population in the past 2 Myr. Molecular characterization of differences among the species could provide important information about the nature of speciation in the period of adaptive radiation. Because of the close relationship, however, molecular variation among the species has been difficult to ascertain. In this communication, we provide evidence for extensive differences, in major-histocompatibility-complex (Mhc) class II genes, between two related species, Pseudotropheus zebra and Melanochromis auratus. We used specific primers to amplify and sequence intron 1 and exon 2 of the class II genes from 18 individuals. Although we found 20 different sequences among the 42 that we produced, there was not a single sequence shared by the two species. Thus the study suggests that different cichlid species of Lake Malawi have different profiles of class II alleles, presumably because the polymorphism present in the ancestral founding population segregated differentially into the various species. These results make Mhc genes an important tool for elucidating speciation.

Amino Acid Sequence↗
PubMed1993

Preliminary studies of the effects of extracorporeal membrane oxygenator on the disposition of common pediatric drugs.

There is an increased use of extracorporeal membrane oxygenation (ECMO) in the last 15 years for critically ill neonates. While receiving ECMO therapy, the critically ill infant needs various medications. We performed an in vitro study to evaluate the potential effect of the membrane oxygenator on drug extraction. Two closed ECMO circuits were set up at rates of 320 ml/min. One circuit was new and the other was used clinically for 5 days. Morphine at 8 ng/ml, gentamicin 10 micrograms/ml, vancomycin 40 micrograms/ml, phenobarbital 20 micrograms/ml, and phenytoin 20 micrograms/ml were injected into the circuit at 1-h intervals. Blood samples were drawn from the circuit at 10, 30, 60, and 240 minutes after injection. In the new circuit, drugs were eliminated as follows: vancomycin 36%, gentamicin 10%, phenobarbital 17%, phenytoin 43%, morphine 36%. In the used system, levels fell to a much smaller extent: vancomycin 11%, phenobarbital 6%, gentamicin 0%, phenytoin 0%, and morphine 16%. In a child receiving 20 micrograms/kg/h infusion of morphine, steady-state concentrations of 68.2 ng/ml fell to 11.6 ng/ml after changing the membrane. Our data indicate that the ECMO is associated with lowering of the concentrations of commonly used medications and that this process may depend partially on how new the membrane is. Before these changes may lead to new dosing guidelines for small children receiving ECMO, more experiments with new and used systems are warranted, as well as with different types of ECMO.

Anti-Bacterial Agents↗
PubMed1993

Implicit memory during balanced anaesthesia. Lack of evidence.

The effect of the number of presentations on implicit memory for words was studied in anaesthetised patients. During standardised, balanced anaesthesia, 81 surgical patients were presented with less common specimens of familiar word categories. For each of three word categories the number of word presentations varied between the patients (0 (control), 5, or 30 presentations). Postoperatively, repetition priming was tested by asking patients to generate exemplars for each of the word categories. No implicit memory for the words presented during anaesthesia was found and consequently no effect of number of word presentations could be demonstrated. It is suggested that this finding, which contradicts previous results, may be caused by the relatively low familiarity of the words used.

Adult↗