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1

Electronic Resource

The evolution of two west African populations (1992)

Colin Stine, O. ; Dover, G. J. ; Zhu, D. ; [et al.]

Springer

Journal of molecular evolution 34 (1992), S. 336-344

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ISSN: 1432-1432

Keywords: Humans ; Mitochondrial DNA ; Nuclear polymorphisms ; Heteroplasmy ; Genetic differentiation ; Sickle cell ; Rain forest refuges

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The identification of genetically coherent populations is essential for understanding human evolution. Among the culturally uniform ethnic groups of west Africa, there are two geographically distinct populations with high frequencies of sickle-cell hemoglobin (HbS). Although the HbS mutation in each group is found on distinguishable chromosomes 11, these populations have been assumed to be parts of a single population. Analysis of mitochondrial DNA (mtDNA) in these populations demonstrated that the two populations identified by alternative chromosomes 11 bearing HbS have distinct distributions of mitochondrial genotypes, i.e., they are maternally separate. These studies also showed that, contrary to expectation, the mtDNA of some individuals is heteroplasmic. For nuclear loci, a comparison of the frequency of alternative alleles established that these populations are genetically distinct. Both the mitochondrial and nuclear data indicate that these populations have been separate for approximately 50,000 years. Although HbS in the two populations is usually attributed to recent, independent mutations, the duration of the separation and the observed geographic distribution of the population allow for the possibility of an ancient origin of HbS. Assuming an ancient mutation and considering the known biogeography, we suggest that HbS protected selected populations from malaria in rain forest refuges during the most recent ice age.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00160241

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2

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Evolution of human Y-chromosome DNA (1982)

Kunkel, Louis M. ; Smith, Kirby D.

Springer

Chromosoma 86 (1982), S. 209-228

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ISSN: 1432-0886

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract We have used human male-specific 3.4 kb Hae III restriction endonuclease fragments to explore the evolutionary history of man's Y-chromosome. We have identified four sets of reiterated, sequences on the basis of their relative sequence homology with autosomal DNA. The sequences account for approximately 40% of the human Y-chromosome, are interspersed within the same 3.4 kb Hae III fragments, are heterogeneous and contain all reiterated DNA previously demonstrated to be specific for the Y-chromosome (it-Y DNA). Y-specific 3.4 kb Hae III sequences do not reassociate with either human female or ape DNA at standard reassociation criteria. However, approximately half of it-Y DNA (cross reacting it-Y) reassociates with both human female and ape DNA at reduced reassociation criteria. The remaining half (Y-specific it-Y) retains its specificity for the human Y-chromosome. These two sets of it-Y DNA have distinct reiteration frequencies and thermal stabilities with their Y-chromosome homologs. Non-Y-specific 3.4 kb Hae III sequences reassociate with both human female and ape DNA at standard reassociation criteria. The abundance of these non-Y-specific sequences decreases as a function of their evolutionary distance from man. One subset of non-Y-specific 3.4 kb Hae III sequences forms stable duplexes with human Y-chromosome DNA and with human and ape autosomal DNA. No detectable base-mismatch occurs among these homologs suggesting complete conservation of these sequences during primate evolution. The second subset of Non-Y-specific Hae III sequences form stable duplexes with human Y-chromosome DNA but highly mismatched duplexes with human and ape autosomal DNA. The finding that homologs of 3.4 kb Hae III sequences are not found within the Y-chromosome of apes but are only present in autosomes suggests that 3.4 kb Hae III sequences are largely autosomal in origin. Since autosomal homologs of most 3.4 kb Hae III-sequences exhibit a greater degree of divergence than those localized to the Y-chromosome, their evolutionary history seems to be chromosome-dependent. Our findings are not easily correlated with the comparative morphology of primate Y-chromosomes and suggest that sequence rearrangement has been a major event in the evolution of the human Y-chromosome. The significance of the specific interspersion of four sets of reiterated sequences, with distinct evolutionary histories, within a repeating unit specific to the human Y-chromosome is not clear. The apparent conservation of at least some of these reiterated sequences suggests they may be of functional importance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00288677

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3

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The role of the sex-determining region of the Y chromosome (SRY) in the etiology of 46,XX true hermaphroditism (1992)

Berkovitz, Gary D. ; Fechner, Patricia Y. ; Marcantonio, Sandra M. ; [et al.]

Springer

Human genetics 〈Berlin〉 88 (1992), S. 411-416

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ISSN: 1432-1203

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The syndrome of 46,XX true hermaphroditism is a clinical condition in which both ovarian and testicular tissue are found in one individual. Both Mullerian and Wolffian structures are usually present, and external genitalia are often ambiguous. Two alternative mechanisms have been proposed to explain the development of testicular tissue in these subjects: (1) translocation of chromosomal material encoding the testicular determination factor (TDF) from the Y to the X chromosome or to an autosome, or (2) an autosomal dominant mutation that permits testicular determination in the absence of TDF. We have investigated five subjects with 46,XX true hermaphroditism. Four individuals had a normal 46,XX karyotype; one subject (307) had an apparent terminal deletion of the short arm of one X chromosome. Genomic DNA was isolated from these individuals and subjected to Southern blot analysis. Only subject 307 had Y chromosomal sequences that included the pseudoautosomal boundary, SRY (sex-determining region of Y), ZFY (Y gene encoding a zinc finger protein), and DXYS5 (an anonymous locus on the distal short arm of Y) but lacked sequences for DYZ5 (proximal short arm of Y) and for the long arm probes DYZ1 and DYZ2. The genomic DNA of the other four subjects lacked detectable Y chromosomal sequences when assayed either by Southern blotting or after polymerase chain reaction amplification. Our data demonstrate that 46,XX true hermaphroditism is a genetically heterogeneous condition, some subjects having TDF sequences but most not. The 46,XX subjects without SRY may have a mutation of an autosomal gene that permits testicular determination in the absence of TDF.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00215675

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4

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Organization and chromosomal specificity of autosomal homologs of human Y chromosome repeated DNA (1985)

Burk, Robert D. ; Szabo, Paul ; O'Brien, Steve ; [et al.]

Springer

Chromosoma 92 (1985), S. 225-233

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ISSN: 1432-0886

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract The human Y chromosome contains a group of repeated DNA elements, identified as 3.4-kilobase pair (kb) fragments in Hae III digests of male genomic DNA, which contain both Y-specific and non-Y-specific sequences. We have used these 3.4-kb Hae III Y fragments to explore the organizational properties and chromosomal distribution of the autosomal homologs of the non-Y-specific (NYS) 3.4-kb Hae III Y elements. Three distinct organizations, termed domains, have been identified and shown to have major concentrations on separate chromosomes. We have established that domain K is located on chromosome 15 and domain D on chromosome 16 and suggested that domain R is on chromosome 1. Our findings suggest that each domain is composed of a tandemly arrayed cluster of a regularly repeating unit containing two sets of repeated sequences: one that is homologous to the NYS 3.4-kb Hae III Y sequences and one that does not cross-react with the 3.4-kb Hae III Y repeats. Thus, these autosomal repeated DNA domains, like their Y chromosome counterparts, consist of a complex mixture of repeated DNA elements interspersed among each other in ways that lead to defined periodicities. Although each of the three identified autosomal domains cross-reacts with 3.4-kb Hae III Y fragments purified from genomic DNA, the length periodicities and sequence content of the autosomal domains are chromosome specific. The organizational properties and chromosomal distribution of these NYS 3.4-kb Hae III homologs seem inconsistent with stochastic mechanisms of sequence diffusion between chromosomes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00348698

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5

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Histochemical characterization of the surface mucoprotein of normal and abnormal human trophoblast (1970)

Bradbury, S. ; Billington, W. D. ; Kirby, D. R. S. ; [et al.]

Springer

Journal of molecular histology 2 (1970), S. 263-274

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ISSN: 1573-6865

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Synopsis The surface coating of normal and abnormal trophoblast has been studied histochemically. It has been found to contain a highly sulphated mucosaccharide which is probably present together with an acidic non-sulphated mucosaccharide; there are suggestions that the accompanying protein is highly basic. The only difference noted between the coat on the normal trophoblast and that of the hydatidiform mole and ectopic trophoblast was the presence ofvis-glycol groups in the normal which were not found in the abnormal. It is suggested that the presence of the sulphated mucoprotein on the surface of the trophoblast is involved in the protection of the trophoblast from immunological attack.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01004995

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6

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Effects of naloxone on renal responses to noxious stimuli in the cynomolgus monkey (1986)

Kirby, D. A. ; Herd, J. A.

Springer

Primates 27 (1986), S. 507-515

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ISSN: 0032-8332

Keywords: Renal function ; Na+ and H2O excretion ; Naloxone ; Non-human primates ; Noxious stimuli

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Behavioral influences on excretion of Na+ and H2O were studied during saline diuresis in three unanesthetized adult female cynomolgus monkeys. During control infusions of isotonic saline, the average rates of urine and Na+ excretion were 210µl/kg/min and 36.1µl/kg/min, respectively, and the average rate of inulin clearance was 4.6 ml/kg/min. Intermittent exposure to an electrical stimulus applied to the monkey's tail for a 30-min period modestly reduced rates of excretion of Na+ and H2O; these reductions were 58% and 56% of baseline values respectively during the first 10 min, but excretion rates returned to baseline values or exceeded them by the end of the 30-min period. The effects of naloxone hydrochloride (10 mg/kg), an opiate antagonist, were studied by administering the drug immediately before the period of electrical-stimulus delivery. After naloxone, the electrical-stimulus markedly reduced the rates of Na+ and H2O excretion to 29% and 31% of baseline values during the first 10 min, and delayed the return to baseline values. Inulin clearance was not altered significantly by the electrical stimulus in the absence of naloxone, but was decreased to 32% of the baseline rate during the first 10 min of exposure to the electric stimulus in the presence of naloxone. Naloxone had similar effects on rates of Na+ and urine excretion in response to 30 min of 108 dBA noise. These results show that renal responses to noxious environmental stimuli (electrical stimulus or noise) can be altered by naloxone.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02381895

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7

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Hilbert polynomials and powers of an ideal (1974)

Kirby, D.

Springer

Annali di matematica pura ed applicata 101 (1974), S. 185-213

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ISSN: 1618-1891

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Sunto Nel n1. viene definito il complesso generalizzato di Koszul K(A; E; t) di R-moduli associato ad una matrice A sopra un anello R e un R-modulo E. Si studia poi K(A; E; t) nel caso particolare in cui A sia una matrice della forma B(m, s) data nel n.3. Si dimostra infine che, sotto certe condizioni di finitezza, la lunghezza di ogni modulo d'omologia à una funzione polinomiale in m per m grande, e che per ogni m ≥1 la caratteristica di Euler-Poincaré è il prodotto di un coefficiente binomiale per la caratteristica del complesso di Koszul K(B(1, s); E;0).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02417104

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8

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Ductile-to-brittle transition of rubber-modified polypropylene (1988)

Chou, C. J. ; Vijayan, K. ; Kirby, D. ; [et al.]

Springer

Journal of materials science 23 (1988), S. 2521-2532

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ISSN: 1573-4803

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The irreversible deformation mechanisms of polypropylene (PP) blended with an ethylenepropylene rubber (EPR) were investigated in the region of the ductile-to-brittle (D-B) transition. The nature of the D-B transition over the composition range of 0 to 25% EPR was studied as a function of temperature and strain rate. Optical microscopy and scanning electron microscopy were used to examine the irreversible microdeformation processes in the fractured specimens. At −40° C, the controlling irreversible deformation process in PP was crazing. In the blends, two kinds of damage zones were observed: a diffuse zone due to voiding at rubber particles and an intense damage zone due to craze-like damage and deformation bands. In general, the size and density of the damage zones increase in a gradual manner through the D-B transition whether examined as a function of temperature, strain rate or blend composition.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01111912

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9

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Ductile-to-brittle transition of rubber-modified polypropylene (1988)

Chou, C. J. ; Vijayan, K. ; Kirby, D. ; [et al.]

Springer

Journal of materials science 23 (1988), S. 2533-2545

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ISSN: 1573-4803

Source: Springer Online Journal Archives 1860-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The deformation behaviour of blends of polypropylene (PP) with ethylene-propylene rubber was studied as a function of temperature and composition under tension. The damage ahead of the deliberately introduced defect was traced quantitatively as a function of external load with the aid of intensity analysis. In unmodified PP or in rubber-modified blends, no stable crack growth was obtained up to 99% of the maximum stress. However, a hierarchy of failure events was observed. First, there was a gradual occurrence of a fan-shaped damage zone. Then an intense damage zone initiated. Finally, a slow tearing mode of crack growth occurred at the maximum stress and the sample failed. The size and shape of the damage zone were influenced by temperature, composition and the artificially introduced stress-raiser. Voids were dominant in the fan zone with some crazes close to the intense damage zone. In the intense damage zone, the crazes coalesced to form a network of deformation bands. The description of the fan zone was achieved by a non-linear or elastoplastic failure approach, analogous to the Hilton-Hutchinson formalism, and the analysis of the intense zone by a critical stress instability criterion. There was also a fair correlation with the Dugdale model for the growth of a wedge-like intense damage zone in the specific case of unmodified PP at −40° C.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01111913

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