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Biomedical subjects

K D Smith

Publications and source records attributed to K D Smith.

At least 91 records · Page 5Linked to original sources
PubMed1993

Use of a porous graphitised carbon column for the high-performance liquid chromatography of oligosaccharides, alditols and glycopeptides with subsequent mass spectrometry analysis.

HPLC using a porous graphitised carbon (PGC) column eluted in acetonitrile-aqueous trifluoroacetic acid has been shown to give complementary chromatography to reversed-phase (ODS) HPLC for separation of peptides and glycopeptides. The PGC column can also be used for separation of oligosaccharides and oligosaccharide alditols released from protein by enzymes (N-linked chains) or base-borohydride degradation (O-linked chains). The advantages are that peptides, glycopeptides, reducing oligosaccharides, sialylated oligosaccharides and oligosaccharide alditols can be chromatographed under the same conditions. The samples can be readily recovered by evaporation for sensitive liquid secondary ion mass spectrometric (LSI-MS) analysis and there is no contamination or deterioration of chromatography from column leakage. LSI-MS analysis revealed that complete peak separation of all of the possible oligosaccharide components of the standard glycoproteins fetuin and bovine submaxillary mucin was not achieved. However, PGC remains as a useful adjunct to other HPLC profiling and separation techniques in particular where subsequent MS analysis is desired.

Amino Acid Sequence↗
PubMed1993

Recognition and destruction of Bacillus Calmette-Guerin-infected human monocytes.

We have established a long-term culture system to study macrophages chronically infected with mycobacteria. Monocytes are infected with Bacillus Calmette-Guerin (BCG) and support exponential intracellular replication without profound perturbation of normal host cell function. We have used this system to investigate lymphokine-activated killer (LAK)-mediated cytolysis. We have found that interleukin 2 stimulation of peripheral blood lymphocytes generates a cytotoxic activity against human monocytes. A CD56- subpopulation of LAK cells specifically recognizes and lyses BCG-infected cells. Lysis of the host cell has no effect on parasite viability and results in the liberation of bacteria capable of infecting more cells.

Animals↗
PubMed1993

HLA-B*0702 antibody epitopes are affected indirectly by distant antigen residues.

We examine the effect of mutations in the HLA-B*0702 alpha 1 domain on the binding of several well-characterized monoclonal antibodies. BB7.1 recognizes the alpha-helix, with a special requirement for residue 67. Combined with an established requirement for the alpha 2 alpha-helix, BB7.1 appears to span the B*0702 peptide-binding groove. Alternatively, BB7.1 epitope conformation may be altered by distant B*0702 sites. ME1 and B27M1 recognize connecting loop residues 41 and 43 and alpha 1 alpha-helical residues 67-71. Instead of contacting residue 67-71 side chains directly, however, ME1 appears to recognizes a B*0702 configuration that depends upon the proper interaction of these and other HLA residues. In addition to solvent-accessible residues 41 and 43, the B27M1 epitope depends on solvent-inaccessible residue 32 at the bottom of the peptide-binding groove. MB40.2, known to require residues 169-182 near the alpha 2-alpha 3 junction, also requires the proper combination of distant residues in the alpha 1 beta-strand and alpha-helix. The effect of mutations near the peptide-binding groove suggests that bound peptides may directly or indirectly affect HLA epitopes. These results illustrate that HLA epitope conformation is very sensitive to changes at distant HLA sites and forecast that epitope models based on sequential amino acid residues will often fail to predict HLA epitopes.

Animals↗
PubMed1993

An association between hypothyroidism and primary open-angle glaucoma.

PURPOSE: To test the hypothesis that there is an association between hypothyroidism and primary open-angle glaucoma. METHODS: The study was conducted in a case-control fashion. Sixty-four patients with primary open-angle glaucoma were evaluated for hypothyroidism by history and by undergoing a thyroid-stimulating hormone immunoradiometric assay. Sixty-four control subjects from the general eye clinic were evaluated in the same manner. Patients found to have elevated thyroid-stimulating hormone immunoradiometric assay were evaluated by an endocrinologist for hypothyroidism. RESULTS: Of the primary open-angle glaucoma group, 23.4% had hypothyroidism. A diagnosis was made previously in 12.5% patients, and 10.9% were newly diagnosed. Of the control subjects, 4.7% had hypothyroidism. A diagnosis had been made previously in 1.6% of the control subjects, and 3.1% were newly diagnosed. The difference between the two groups was found to be statistically significant. CONCLUSION: A statistically significant association between hypothyroidism and primary open-angle glaucoma is demonstrated. There is a large group (10.9%) of patients with primary open-angle glaucoma with undiagnosed hypothyroidism.

Aged↗
PubMed1993

Social desirability of personality items as a predictor of endorsement: a cross-cultural analysis.

Earlier studies using specialized instruments confirmed a positive relation between a personality item's desirability and its endorsement outside North America, but allowed for few conclusions about the strength of the relationship in non-Western societies and offered no explanations for the observed correlations. In Study 1 of this investigation, university students from Turkey (a country rich in non-Western cultural elements) were found to be as likely as their U.S. counterparts to describe themselves in socially desirable terms. Furthermore, the strength of the relationship between desirability and endorsement did not depend on their level of exposure to the English language or to Western concepts. Study 2 indicated that socially desirable traits were also the most common among students in Turkey (paralleling results with U.S. samples), in support of desirable traits' prevalence as an explanation for the desirability-endorsement correlation.

Adult↗
PubMed1993

The role of the sex-determining region Y gene in the etiology of 46,XX maleness.

The condition of 46,XX maleness is characterized by testicular development in subjects who have two X chromosomes but who lack a normal Y chromosome. Several etiologies have been proposed to explain 46,XX maleness: 1) translocation of the testis-determining factor from the Y to the X chromosome, 2) mutation in an autosomal or X chromosome gene which permits testicular determination in the absence of TDF, and 3) undetected mosaicism with a Y-bearing cell line. We evaluated 10 affected subjects who were ascertained for different reasons and who had several distinct phenotypes. Six subjects had inherited sequences from the short arm of the Y chromosome including the sex-determining region Y gene (SRY). Five of the subjects were pubertal at the time of evaluation and had a phenotype similar to that of Klinefelter syndrome with evidence of Sertoli cell and Leydig cell dysfunction. One subject had evidence from Southern blot analysis and in situ hybridization for the presence of an intact Y chromosome in approximately 1% of cells. Three subjects lacked Y sequences by Southern blot analysis and by polymerase chain reaction amplification of SRY. These subjects were ascertained in the newborn period because of congenital anomalies. One had multiple anomalies including cardiac abnormalities; one had cardiac anomalies alone; and one had ambiguous genitalia. Our data confirm the genetic heterogeneity of 46,XX maleness, in which some subjects have SRY while other subjects lack it. In addition, there is phenotypic heterogeneity among subjects who lack SRY suggesting that there is also genetic heterogeneity within this subgroup.

DNA Restriction Enzymes↗
PubMed1993

Report of a kindred with X-linked (or autosomal dominant sex-limited) 46,XY partial gonadal dysgenesis.

The condition termed 46,XY complete gonadal dysgenesis is characterized by the lack of testicular determination with resulting streak gonads, normal Mullerian structures, and female external genitalia. In the partial form, there is incomplete testicular determination with a wide range in the degree of ambiguous genitalia and sexual duct development. We evaluated a kindred in which a partial form of 46,XY gonadal dysgenesis occurred in four subjects from two generations. Pedigree analysis indicated an X-linked or possibly an autosomal sex-limited mode of inheritance. All affected subjects were ascertained because of ambiguous genitalia with minimal virilization. At 10 days of age, the proband had a subnormal plasma level of testosterone, and at 4 months, there was no rise in plasma T after stimulation with hCG. At laparotomy, a dysgenetic gonad was found on the right side, but no gonad was found on the left side. A vas deferens was present on the right, indicating the presence of functional Leydig cells early in fetal life. In the other affected subjects, gonadal tissue was also limited to one side of the abdomen and showed poorly developed seminiferous tubules. The sex-determining region Y gene, which encodes the testis-determining factor, was present and unaltered in the genomic DNA of all affected subjects. Duplication of the distal short arm of the X-chromosome has been associated with 46,XY complete gonadal dysgenesis in some patients. In our studies, Southern blot analysis revealed that sequences of the distal short arm of the X-chromosome (DXS9 to DXS84) were present in single copy, excluding a large duplication in this area of the X. Several kindreds with familial 46,XY complete gonadal dysgenesis have been reported; five of them had evidence of an X-linked mode of inheritance. Our study of a kindred with 46,XY partial gonadal dysgenesis further supports the role of an X chromosome gene in testicular determination. Evidence of some fetal Leydig cell function in the affected subjects of our report suggests that mutations of the putative X-chromosome gene can result in a partial as well as complete defect in testicular determination.

Blotting, Southern↗
PubMed1992

High-performance liquid chromatography of oligosaccharide alditols and glycopeptides on a graphitized carbon column.

The chromatographic behaviour of oligosaccharide alditols and glycopeptides containing neutral and acetamido sugars and sialic acid has been investigated on a HyperCarb porous graphitised carbon column. The alditols were substantially retained and could be eluted in 0-25% acetonitrile-0.05% trifluoroacetic acid in 0.05% aqueous trifluoroacetic acid between 3-30 min for mono- to hexasaccharides. Elution patterns were based on both size, charge and linkage such that isomeric compounds could be separated from each other.

Amino Acid Sequence↗
PubMed1992

Fetal hemoglobin levels in sickle cell disease and normal individuals are partially controlled by an X-linked gene located at Xp22.2.

Fetal hemoglobin (Hb F) production in sickle cell (SS) disease and in normal individuals varies over a 20-fold range and is under genetic control. Previous studies suggested that variant Hb F levels might be controlled by genetic loci separate from the beta-globin complex on chromosome 11. Using microscopic radial immunodiffusion and flow cytometric immunofluorescent assays to determine the percentage of F reticulocytes and F cells in SS and nonanemic individuals, we observed that F-cell levels were significantly higher in nonanemic females than males (mean +/- SD, 3.8% +/- 3.2% v 2.7% +/- 2.3%). F-cell production as determined by F reticulocyte levels in SS females was also higher than in SS males (17% +/- 10% v 13% +/- 8%). We tested the hypothesis that F-cell production in both normal and anemic SS individuals was controlled by an X-linked locus with two alleles, high (H) and low (L). Using an algorithm to determine the 99.8% confidence interval of a normal distribution in nonanemic individuals, we estimated that males and females with at least one H allele had greater than 3.3% F cells. Comparisons of male-male or female-female SS sib pairs with discordant F reticulocyte levels distinguished two phenotypes in SS males (L, less than 12%; H, greater than 12%) and three phenotypes in SS females (LL, less than 12%; HL, 12% to 24%, HH greater than 24%). Linkage analysis using polymorphic restriction sites along the X chromosome in eight SS and one AA family localized the F-cell production (FCP) locus to Xp22.2, with a maximum lod score (logarithm of odds of linkage v independent assortment) of 4.6 at a recombination fraction of 0.04.

Adult↗
PubMed1992

Partial gonadal dysgenesis in a patient with a marker Y chromosome.

We evaluated a patient with partial gonadal dysgenesis including a right dysgenetic testis and a left streak gonad with rudimentary fallopian tube and uterus. She had ambiguous external genitalia and was raised female. Although her height is normal (25th centile at age 12 years), she has some findings of Ullrich-Turner syndrome. Her karyotype was reported to be 46,X,+marker; subsequent molecular investigations showed the marker to be the short arm of the Y chromosome. Genomic DNA, isolated from leukocytes of the patient and her father, was digested with a variety of restriction endonucleases and subjected to Southern blot analysis. A positive hybridization signal was obtained with probes for the short arm of the Y chromosome (pRsY0.55, SRY, ZFY, 47Z, pY-190, and YC-2) in DNA from the patient, indicating the presence of most if not all of the short arm, while long arm probes (HinfA and pY3.4) indicated that at least 75% of the long arm of the Y chromosome was missing. The gene responsible for testicular determination (TDF) is on the distal portion of the short arm of the Y chromosome; Yq has no known influence on sex determination. Hence, the deletion of the long arm of the Y chromosome cannot explain the gonadal dysgenesis in this patient. One explanation for the gonadal dysgenesis and Ullrich-Turner phenotype in the patient could be undetected 45,X/46,X,+marY mosaicism but no such mosaicism was observed in peripheral lymphocytes. Several investigators have suggested the presence of an "anti-Turner" gene near TDF. Hence it is possible that the clinical phenotype in our patient results from a Y chromosomal defect in sequences flanking TDF, which reduces the function of both TDF and the "anti-Turner" genes.

Adult↗
PubMed1992

The evolution of two west African populations.

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.

Africa, Western↗
PubMed1992

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

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.

Base Sequence↗
PubMed1992

Adrenoleukodystrophy: phenotypic variability and implications for therapy.

X-linked adrenoleukodystrophy (ALD) is a relatively common disorder that shows a great deal of phenotypic variability. Approximately half of the patients have the rapidly progressive childhood cerebral form that is associated with an inflammatory response in brain and leads to total disability or death during the first decade. Twenty five per cent or more of the patients have adrenomyeloneuropathy (AMN), a form that progresses slowly, involves the spinal cord mainly, shows little or no inflammatory response, manifests in adulthood, and is compatible with a near-normal life span. The two forms of the disease occur frequently within the same kindreds and nuclear families. Segregation analysis based on 3862 individuals in 89 kindreds points to the existence of an autosomal modifier locus with a likelihood ratio of 20:1. In addition, we present preliminary results of three types of therapy. Two hundred and four patients have received a dietary regimen that combines the administration of oils containing mono-unsaturated fatty acids (oleic and erucic) with the restricted intake of very long-chain fatty acids. This regimen normalizes the levels of satured very long-chain fatty acids in plasma within 4 weeks. It appears to improve peripheral nerve function in patients with AMN, and a large-scale trial is in progress to determine whether it can prevent the onset of neurological involvement in patients who have the biochemical abnormality of ALD but are neurologically intact. We report early results of bone marrow transplantation in 14 patients. There is encouraging but still preliminary evidence that transplantation can arrest the progression of the disease in patients with mild neurological involvement. There is urgent need to develop methods to combat the rapid progression of the cerebral forms of the disease, which so far has resisted therapeutic intervention, including immunosuppression or the administration of immunoglobulin.

Adolescent↗
PubMed1992

Parenting difficulties among adult survivors of father-daughter incest.

Women with a history of father-daughter incest as children often report difficulty in parenting their own children. This study examined the self-reported parenting experience and practices of women who were incest victims as children. Since many incest victims are also children of alcoholics, we compared their reports of parenting with those of women whose fathers were alcoholic but not sexually abusive, and to women who had no known risk during their childhood. The findigns were that incest survivors reported significantly less confidence and less sense of control as parents than nonrisk mothers. In addition, they reported significantly less support in the parental partnership with their spouses, and reported being less consistent and organized, and making fewer maturity demands on their children. The findings are discussed in terms of the incest survivor's sense of inefficacy and loss of control, the potential of the marital relationship to buffer the adverse effects of growing up in the dysfunctional, incestuous family, and future research directions.

Adolescent↗
PubMed1992

Fluorescent viscoelastic enhancement.

By inserting an Erreger 485 exciter filter into the operating microscope, translucent yellow Healon (sodium hyaluronate) transforms into a brilliant opaque green viscoelastic. We have developed this technique and termed it "fluorescent viscoelastic enhancement." Using the technique, we demonstrated that the time required to remove Healon from the anterior chamber after intraocular lens insertion varies. Healon is usually aspirated quickly, in less than 17 seconds. Otherwise it traps behind the intraocular lens and requires more time for irrigation/aspiration (I/A) and manipulation of the I/A tip. Fluorescent viscoelastic enhancement minimized I/A time, reducing excess turbulence and manipulation in the anterior chamber, and thus may reduce corneal endothelial cell loss. This study also demonstrated that fluorescent viscoelastic enhancement prevented postoperative intraocular pressure rise, compared to the conventional removal of clear Healon. Fluorescent viscoelastic enhancement assures the surgeon that a large amount of Healon is not left behind.

Aged↗
PubMed1992

Cloning and sequencing of an Agrobacterium tumefaciens beta-glucosidase gene involved in modifying a vir-inducing plant signal molecule.

Induction of Agrobacterium tumefaciens virulence genes by plant phenolic compounds is essential for successful T-DNA transfer to a host plant. In Douglas fir needles, the major virulence region inducer is the glycoside coniferin (J. W. Morris and R. O. Morris, Proc. Natl. Acad. Sci. USA 87:3612-3618, 1990). Agrobacterium strains with high beta-glucosidase activity respond to coniferin and infect Douglas fir seedlings, whereas most strains with low beta-glucosidase activity fail to respond to coniferin and are avirulent on this host. We have cloned two beta-glucosidase genes from A. tumefaciens B3/73 and sequenced one of them, cbg1. It appears to be part of a polycistronic unit and shows a high bias for GC-rich codons. When expressed in Escherichia coli, Cbg1 beta-glucosidase hydrolyzes coniferin but not cellobiose. The 88-kDa predicted product of cbg1 is highly similar to one other bacterial beta-glucosidase and several fungal beta-glucosidases. There is little homology between Cbg1 and other bacterial beta-glucosidases, including an Agrobacterium cellobiase.

Agrobacterium tumefaciens↗
PubMed1992

Evidence for increased prevalence of SRY mutations in XY females with complete rather than partial gonadal dysgenesis.

The Y chromosome gene SRY (sex-determining region, Y gene) has been equated with the mammalian testis-determining factor. The SRY gene of five subjects with 46,XY complete gonadal dysgenesis (46,XY karyotype, completely female external genitalia, normal Müllerian ducts, and streak gonads) was evaluated for possible mutations in the coding region by using both single-strand conformation polymorphism (SSCP) assay and DNA sequencing. Mutations were identified in three subjects, of which two gave altered SSCP patterns. Two of them were point mutations causing amino acid substitutions, and the third was a single-base deletion causing a frameshift. All three mutations caused alterations in the putative DNA-binding region of the SRY protein. Genomic DNA was obtained from the fathers of two of the three mutant patients: one mutation was demonstrated to be de novo, and the other was inherited. The presence of SRY mutations in three of five patients suggests that the frequency of SRY mutations in XY females is higher than current estimates.

Base Sequence↗