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Biomedical subjects

M L Rivas

Publications and source records attributed to M L Rivas.

At least 19 recordsLinked to original sources
PubMed1999

Interpupillary distance in a normal black population.

This report expands on a study by Pryor [Pryor HB. Objective measurement of interpupillary distance. Pediatrics 1969: 44: 973 977] that related normal values of inner canthal distance (ICD), outer canthal distance (OCD) and interpupillary distance (IPD) for Whites, Asians and Mexican Americans. To date, no similar values have been reported for Blacks. Utilizing a sample (n = 931: 485 males; 446 females) of black people (range, birth 24 years), OCD, ICD, and head circumference (HC) were measured and tabulated. We calculated mean IPD according to Pryor's formulation and report that the general mean OCD and ICD in our sample differed significantly from, and were consistently higher than, Pryor's reported measurements for White males and females at each age level (p < 0.001). However, ICD in our sample was significantly lower at birth in both sexes, appeared to increase at a more rapid rate relative to Whites during the first 3 months of life, and reached and maintained a higher value beyond the age of 3 months, with most age groups showing a significant difference in mean ICD measurements. At each age level, the mean IPD values in Whites and Blacks were significantly higher (p < 0.001). Based upon these findings, we suggest that interpupillary distance of Black children and adults be assessed according to the mean proportions for their race.

Age Factors↗
PubMed1992

Identification of the origin of ring/marker chromosomes in patients with Ullrich-Turner syndrome using X and Y specific alpha satellite DNA probes.

Fluorescent in situ hybridization (FISH) using X and Y chromosome-specific alpha satellite DNA probes hybridizing to loci DXZ1 and DYZ3 was performed to identify the origin of ring/marker chromosomes in 6 patients with Ullrich-Turner syndrome (UTS). All patients had a mosaic karyotype, 5 with 45,X/46,X,r(?) and one with 45,X/46,X,mar. We demonstrated that the marker/ring chromosome in each of these 6 patients originated from the X. A timely knowledge of the X or Y origin of ring and marker chromosomes can be crucial in genetic counseling and medical management since the presence of Y chromosome material in phenotypic females is known to increase the risk for developing gonadoblastoma.

Child↗
PubMed1992

The transmission of vesicoureteral reflux from parent to child.

Vesicoureteral reflux is now recognized to be hereditary and familial. The incidence of reflux in siblings has proved to be significant but less is known about the incidence of reflux in the offspring of known reflux patients. In an ongoing prospective series of reflux screening we identified 23 patients of childbearing age with a known history of reflux and screened their 36 offspring with an awake voiding cystourethrogram. Of these 36 offspring 24 (66%) exhibited vesicoureteral reflux. The literature was also reviewed to determine the incidence of parent/child reflux from reported cases. This review revealed a 65% rate of reflux in the offspring of known patients. Our preliminary results coupled with those in the literature signify a need to screen the offspring of known reflux patients and suggest a rethinking of the genetic transmission for this trait. While vesicoureteral reflux could still be a multifactorial genetic trait with a major gene, consideration must also be given to an autosomal dominant inheritance pattern.

Child↗
PubMed1991

Role for specific complement phenotypes and deficiencies in the clinical expression of IgA nephropathy.

IgA nephropathy, the most commonly occurring type of chronic glomerulonephritis in individuals of European and Asian descent, exhibits marked heterogeneity of clinical signs and ultimate prognosis. Based upon their studies of regional clustering of the ancestors of related patients in eastern Kentucky, the authors have postulated the existence of an inherited disease susceptibility for IgA nephropathy. They examined serum concentrations of individual complement proteins and phenotypes for C3, C4A, C4B, and factor B (Bf) for related and unrelated patients with IgA nephropathy from Kentucky and for patients from the Mid-South region of Tennessee, Mississippi, and Alabama. In these populations, they have described partial complement deficiencies or specific phenotypes which may be associated with the disease. Their findings include the following: (1) partial deficiencies for C2, beta 1H (H), properdin (P), or C4 binding protein (C4BP) in four patients with end-stage renal disease, (2) an association between the C3*F allele with IgA nephropathy in the combined group of unrelated patients from Kentucky and the Mid-South, (3) the occurrence of C4B deficiency in two siblings with IgA nephropathy, and (4) an association between C4A deficiency and poor outcome in patients with IgA nephropathy diagnosed as adults. In addition, the related patients differ from the unrelated patients from Kentucky with respect to frequencies of Bf*F and the BfF (FF + FS + F1F + F1S) phenotype, suggestive of immunogenetic difference between these groups. Important functional differences exist between C4A and C4B isotypes and functional differences are also possible based upon C3 or Bf phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Carrier Proteins↗
PubMed1990

Infantile hypophosphatasia: autosomal recessive transmission to two related sibships.

Hypophosphatasia, a rare heritable form of rickets/osteomalacia, is characterized by deficient activity of the tissue nonspecific (liver/bone/kidney) isoenzyme of alkaline phosphatase (ALP). Signs may be present prenatally or not until late adult life. Although the infantile form of hypophosphatasia has usually been categorized as an autosomal recessive (AR) disorder, several studies suggest that childhood cases are the consequence of either AR or autosomal dominant (AD) inheritance and adult cases are primarily AD. Eastman and Bixler (J Craniofac Genet Dev Biol 3:213-234, 1983) propose that all cases of hypophosphatasia may reflect AD inheritance with 85% penetrance and homozygous lethality. We report on 3 patients with hypophosphatasia in a black family, first manifested clinically during infancy, where the pattern of inheritance for each is consistent with AR transmission. Two were brothers who died from the disorder. The other patient, a cousin, presented with classic stigmata of hypophosphatasia during infancy, but is now age 5 1/2 years and has had a much milder clinical course. Although consanguinity is absent, the maternal grandmothers are sibs as are the maternal grandfathers and the paternal grandmothers. The family history is otherwise negative for skeletal or dental disease. Laboratory and radiographic results are consistent with heterozygosity in each parent. Fibroblast ALP activity is less than 1% normal in all 3 patients with no complementation observed in heterokaryon analysis. Accordingly, the genetic defects appear to be identical in all 3 patients. Our findings show that infantile hypophosphatasia may be inherited as an AR condition where there is variable expressivity and that homozygosity or compound heterozygosity, as may be the case in this family, is not necessarily lethal.

Black People↗
PubMed1990

Regional variation in C4 phenotype in patients with IgA nephropathy.

The relationship between complete deficiency for either isotype of the fourth component of complement, C4A or C4B, and glomerulonephritis was initially examined in white patients from Kentucky with either IgA nephropathy or Schönlein-Henoch purpura. Subsequently, C4B deficiency was found to be associated with IgA nephropathy for pediatric patients followed in Cincinnati, Ohio. We later reported that at least 60% of the original patients from Kentucky were related to at least one other patient with the disease. This finding raised the possibility that the C4 phenotype frequencies for these patients may have been biased by the fact that they were based on a sample of related patients. In our study, C4 phenotyping was performed for 52 related and 63 unrelated patients from Kentucky, 81 unrelated patients from the Mid-South region of the United States, and 39 unrelated patients from the Puglia region of southeastern Italy. In addition, data from patients with IgA nephropathy from Spain were available for comparative studies. Neither C4A deficiency nor C4B deficiency was significantly increased for groups of unrelated patients from the Mid-South, Italy, Spain, or Kentucky in comparison with regional control subjects. In fact, C4A and C4B deficiencies did not occur in any of the Italian patients. With the exception of C4A.6, frequencies for the most common C4A and C4B alleles did not differ among the unrelated patient and control groups from Kentucky and the Mid-South. In addition, no significant differences in C4A and C4B allelic frequencies were observed in comparisons of pediatric patients (diagnostic biopsy before age 18 years) and adult patients with IgA nephropathy in either U.S. population. Italian control subjects had a significantly lower frequency for C4A null alleles in comparison with control subjects from both Kentucky and the Mid-South; a significantly higher frequency of C4B null alleles was found among Kentucky control subjects than in Mid-South, Italian, and Spanish control samples. The importance of recognizing the ethnic background of study subjects and of eliciting a good family history to minimize unsuspected sampling of related patients should be considered in future disease association studies.

Adult↗
PubMed1989

C4 and Bf phenotypes in black and Caucasian patients with childhood onset insulin dependent diabetes mellitus.

Certain alleles for the complement proteins, C4 and Bf, have been shown to be markers for insulin-dependent diabetes mellitus (IDDM) in samples of different racial and geographic composition. However, the same markers are not demonstrable in each group studied. Phenotyping for the complement alleles, C4 and Bf was performed on 168 Caucasian and 49 Black patients with IDDM. All of the patients were followed in Memphis, Tennessee and had onset of disease prior to age 18. The Bf*F1 allelic frequency was significantly increased for the Caucasian patients as compared to 93 healthy Caucasian controls (0.063 vs. 0.016) and for the Black IDDM patients as compared to 43 healthy Black controls (0.102 vs. 0.035). C4 phenotype frequencies showed a significant increase of the C4AQ0 (rr = 2.13) and C4A4 (rr = 2.91) phenotypes for the Caucasian IDDM patients as compared to controls, but the frequency of homozygous null C4A was not significantly increased. In addition significant negative associations of IDDM with C4A3 and C4A6 phenotypes and no association with any C4B phenotype were observed in our Caucasian patient population. Our data for Mild-South Blacks with IDDM suggest a similar positive association of IDDM with the BfF1 phenotype (rr = 3.4). However, there was no evidence among Black IDDM patients of the C4AQ0 and C4A4 associations observed in the Caucasian sample. The data support a possible association of IDDM with the C4A2 (rr = 5.86) and C4B2 (rr = 5.26) phenotypes. The hypothesis that racial admixture may account for the higher frequency of IDDM in US Blacks as compared with African Blacks has been forwarded by others.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1987

Regionalization in hereditary IgA nephropathy.

The genealogies of 80 patients with IgA nephropathy who were born in central or eastern Kentucky or whose parents were born in this region were researched. At a minimum, 48 of these patients were related to at least one other patient. On the basis of presence or absence of established kinships, the patients were divided into three groups. Twenty-nine patients in group 1 belonged to one large pedigree. Their birthplaces and those of their parents, grandparents, and great-grandparents clustered in the extreme eastern portion of the state. Seventeen other patients, group 2, were related to at least one other patient but not to a patient in group 1. Their birthplaces and those of their ancestors did not show significant clustering. With the exception of two siblings, the 34 patients of group 3 had no family members with IgA nephropathy. The birthplaces for these patients and ancestors were widely scattered. These data suggest that one or more genetically determined factors are important in the pathogenesis of IgA nephropathy in some patients. A founder effect, whereby a gene(s) conveying susceptibility to IgA nephropathy was carried into eastern Kentucky by one or more of the early settlers, would explain the geographic clustering of the birthplaces of the patients in group 1 and their ancestors. The characteristic immunopathology of IgA nephropathy may represent the histologic result of separate disease processes, one or more of which could be genetically influenced.

Consanguinity↗
PubMed1980

Population distribution of human salivary amylases: differential inhibition by wheat protein.

Based upon response to an inhibitor from wheat gliadin, 80 random samples of human salivary amylase were separated into three phenotypic groups. Each phenotype occurred with a high frequency rendering this a polymorphinc locus. The susceptibility to the inhibitor may be a useful marker for studies of tendency to caries and periodontal disease as well as for studies of genetic variation and linkage.

Adolescent↗