Showing papers by "University of Texas Health Science Center at Houston published in 1977"

F-statistics and analysis of gene diversity in subdivided populations.

Abstract: It is show that Wright's F-statistics can be defined as ratios of gene diversities of heterozygosities rather than as the correlations of uniting gametes. This definition is applicable irrespective of the number of alleles involved or whether there is selection or not. The relationship between F-statistics and Nei's gene diversity analysis is discussed.

Bottleneck effects on average heterozygosity and genetic distance with the stepwise mutation model.

Abstract: When a population goes through a small bottleneck, the genetic variability of the population is expected to decline rapidly, but as soon as population size becomes large, it starts to increase owing to new mutations (Wright, 1931; Mayr, 1954). Recently, Nei et al. (1975) studied this problem mathematically and showed that the pattern of change in genetic variability largely depends on the size of bottleneck, rate of population growth, and mutation rate. They provided a general formula for computing the average heterozygosity per locus in a population of changing size. This study is based on the assumption that new mutations occurring in a population are always different from the preexisting ones (Kimura and Crow's (1964) infinite allele model). This assumption seems to be roughly correct if allelic differences are studied at the nucleotide or codon level. In practice, however, the genetic variability of natural populations is usually studied by electrophoretic mobility of proteins. Electrophoretic mobility of a protein is determined mainly by the net charge of the protein, and a positive or negative change in the net charge due to an amino acid substitution may be canceled by the second opposite charge change. Therefore, strictly speaking, the infinite allele model is not appropriate for the study of protein variation detected by electrophoresis. In view of this circumstance, Ohta and Kimura (1973) introduced the so-called stepwise mutation model. In this model each allele is represented as one of the infinite sequence of allelic states and mutation is assumed to produce a one-step change in either the positive or the negative direction. They derived a formula for average heterozygosity in an equilibrium population. Later, Wehrhahn (1975) and Li (1976) extended Ohta and Kimura's work to the case of nonequilibrium populations. On the other hand, Nei and Chakraborty (1973) studied the expected genetic distance between two populations when these are separated for an arbitrary number of generations, using a similar genetic model. The purpose of the present paper is to study the bottleneck effects on average heterozygosity and genetic distance by using the stepwise mutation model. Some studies on the bottleneck effect (the effect of reduction in population size) on genetic distance have been made by Chakraborty and Nei (1974) and Nei (1976), using the infinite allele model. These authors have shown that the reduction in population size results in an accelerated increase in genetic distance in the early generations. In the present paper we shall employ the method of generating function first used by Nei and Chakraborty (1973) in the study of protein variation and extended considerably by Wehrhahn ( 19 7 5).

Immunoglobulin bearing lymphocytes and plasma cells in human periodontal disease

Abstract: Gingival biopsies from areas characterized as clinically normal, mild gingivitis, or periodontitis were examined. Immunoglobulin (IgG, IgA, IgM, IgE and IgD) bearing cells at the sulcular and oral epithelium - lamina propria junctions as well as the central lamina propria areas were quantitated. Normal gingiva (P. I. = 0-0·2) contained few lymphocytes and plasma cells. Biopsies from areas of mild gingivitis (P. I. = 0·2-1) were infiltrated at the sulcular epithelium - lamina propria junction by lymphocytes lacking membrane associated immunoglobulins (94 %). Few plasma cells were evident. In contrast, tissue associated with periodontitis (P. I. = 4·0–8·0) contained significant numbers of immunoglobulin bearing lymphocytes (78 %, IgG; 9 %, IgM; and 4 % IgA) and plasma cells (67 %, IgG; 24 %, IgM; and 8 % IgA) distributed throughout all three major tissue areas. These findings indicated that the nature of cellular infiltrates differed in mild gingivitis and periodontitis. The presence of predominantly IgG and IgM containing cells in periodontitis had important implications for the contribution of nonspecific effector mechanisms to the destruction of periodontal tissue.

Chromatic organization of primate cones

Abstract: The distribution of baboon retinal cones were mapped histochemically by light-stimulated reduction of nitroblue tetrazolium chloride. Blue cones were distributed regularly in the periphery: red and green cones were distributed randomly everywhere. The ordering of cone densities was greeen greater than red greater than blue.

Chemotherapy of malignant fibrous histiocytoma: a Southwest Oncology Group report.

Abstract: Malignant fibrous histiocytoma is a rare tumor, which constitutes 3-4% of the soft tissue sarcomas. It occurs with maximum frequency in the sixth and seventh decades of life and has a distinct male preponderance. In two-thirds of the patients an extremity is the primary site and approximately one-half develop local recurrences and one-half, distant metastases. Response to combination chemotherapy occurred in 33%, a rate similar to that seen in other sarcomas.

Statistical studies on protein polymorphism in natural populations i. distribution of single locus heterozygosity

Abstract: Surveying the literature, the frequency distribution of single-locus heterozygosity among protein loci was examined in 95 vertebrate and 34 invertebrate species with the aim of testing the validity of the mutation-drift hypothesis. This distribution did not differ significantly from that expected under the mutation-drift hypothesis for any of the species examined when tested by the Kolmogorov-Smirnov goodness-of-fit statistic. The agreement between the observed interlocus variance of heterozygosity and its theoretical expectation was also satisfactory. There was an indication that variation in the mutation rate among loci inflates the interlocus variance of heterozygosity. The variance of heterozygosity for a homologous locus among different species was also studied. This variance generally agreed with the theoretical value very well, though in some groups of Drosophila species there was a significant discrepancy. The observed relationship between average heterozygosity and the proportion of polymorphic loci was in good agreement with the theoretical relationship. It was concluded that, with respect to the pattern of distribution of heterozygosity, the majority of data on protein polymorphisms are consistent with the mutation-drift hypothesis. After examining alternative possible explanations involving selection, it was concluded that the present data cannot be explained adequately without considering a large effect of random genetic drift, whether there is selection or not.

Distribution of nucleotide differences between two randomly chosen cistrons in a finite population

Abstract: Watterson's (1975) formula for the steady-state distribution of the number of nucleotide differences between two randomly chosen cistrons in a finite population has been extended to transient states. The rate for the mean of this distribution to approach its equilibrium value is 1/2N and independent of mutation rate, but that for the variance is dependent on mutation rate, where N denotes the effective population size. Numerical computations show that if the heterozygosity (i.e., the probability that two cistrons are different) is low, say of the order of 0.1 or less, the probability that two cistrons differ at two or more nucleotide sites is less than 10 percent of the heterozygosity, whereas this probability may be as high as 50 percent of the heterozygosity if the heterozygosity is 0.5. A simple estimate for the mean number (-d) of site differences between cistrons is d = h/(1 - h) where h is the heterozygosity. At equilibrium, the probability that two cistrons differ by more than one site is equal to h2, the square of heterozygosity.

Oral complications of cancer radiotherapy

Abstract: Injury to surrounding tissues during radiotherapy for oral cancer can have devastating physical and psychologic consequences for the patient. Oral complications include xerostomia, dental decay, mucositis, taste loss, osteoradionecrosis, infection, and trismus. In many instances, these problems can be eradicated or controlled with appropriate treatment.

Thickness of facial gingiva.

Abstract: Gingival thickness was measured in 10 subjects with healthy gingiva on the facial aspect of selected maxillary and mandibular teeth at the depth of the gingival sulcus and midway between the sulcus depth and mucogingival line. Measurement instrumentation, consisting of a differential transformer coupled to an oscillator and digital voltmeter was sensitive to the travel of a probe from the gingival surface to tooth surface or alveolar bone. The probe assembly was accurate to 0.01 mm and the average range of differences in replicate measurements under a variety of conditions never exceeded 0.15 mm. 1. Free gingival thickness averaged 1.56 mm + 0.39, attached gingival thickness averaged 1.25 mm + 0.42 and the total mean thickness for all areas measured was 1.41 mm. 2. Thickness in mandibular free and attached gingiva and maxillary free gingiva increased from anterior to posterior. Thickness in maxillary attached gingiva remained fairly constant. 3. Thickness measured at the depth of the sulcus was directly proportional to the free gingival width. 4. Thickness measured midway between sulcus depth and mucogingival junction was inversely proportional to attached gingival width.

Effects of six carcinogens on SCE frequency and cell kinetics in cultured human lymphocytes

Abstract: The BrdU-differential staining technique has been used in analyzing the effects of six carcinogens on asynchronously dividing cells. Two parameters were used to assess damage: (1) changes in the frequency of sister chromatid exchanges (SCE); and (2) changes in the proportion of fluorescent patterns. Some but not all of these carcinogens produced a statistically significant change in both the distribution of fluorescent patterns (i.e. cell kinetics) and the frequency of SCE. The degree of the effect was dependent on both concentration and length of exposure. It was found that the two parameters, cell fluorescence and SCE frequency, are useful in estimating cumulative damage produced by a chemical over several divisions and could be applied to mutagen and carcinogen screening tests.

On consanguineous marriages and the genetic load

Abstract: It has been reported that studies of the genetic consequences of inbreeding should adopt a different strategy in populations having a relatively old inbreeding history and where inbreeding levels have varied over time. This contention is tested with a series of 39,495 single-birth records from Bombay, India, collected in a World Health Organization survey on congenital malformations. Our analysis reveals that: 1. the incidence of major malformations is significantly higher among the inbred offspring (1.34%) as compared to that among non-inbred ones (0,81%)--a finding at variance with a previous study in the same area; 2. the inbreeding effect on perinatal mortality (stillbirths and mortality during the first few days of life) is also found to be significant. In view of the above findings, the genetic load as disclosed by inbreeding is computed for perinatal mortality, major malformations and pooling these together. A + B, the measure of the number of lethal equivalents per gamete, is found to be at variance with other reports. Such variability can be ascribed to non-genetic factors. Supporting evidence collected from Brazil and Malaysia in the same survey is also presented.

Patterns of loss of enterotoxigenicity by Escherichia coli isolated from adults with diarrhea: suggestive evidence for an interrelationship with serotype.

Abstract: Enterotoxigenic Escherichia coli isolates obtained in Mexico from adult subjects with diarrhea and from healthy controls were examined for the production of heat-stable enterotoxin (ST) and heat-labile enterotoxin (LT) after serial passage in the laboratory. Isolates were found to be either stable for the production of ST and LT or unstable with respect to ST, LT, or both. Unilateral loss of either ST or LT production allowed classification of E. coli isolates into four groups according to stability/instability of enterotoxin production. Fewer serotypes, with more representative isolates, were in group I (stable) than in group IV (completely unstable). Isolates from Dacca, Bangladesh, could be similarly classified into stability groups. There is an apparent relationship between serotype, stability of enterotoxin production, particularly LT, and isolation from diarrhea cases as opposed to isolation from healthy controls.

Effect of apomorphine on schizophrenic symptoms.

Abstract: The effects of apomorphine on psychotic symptoms were evaluated in chronic schizophrenic patients using double-blind placebo controlled procedures. Although on the basis of dopamine theory of schizophrenia, apomorphine was expected to increase schizophrenic symptoms, in this study apomorphine substantially reduced psychotic symptoms in some chronic schizophrenic patients. No patient showed the substantial increase in psychotic symptoms previously demonstrated after the administration of IV methylphenidate. These clinical effects of apomorphine in schizophrenia may be relevant to recent pharmacological research which has indicated that apomorphine also has potent effect on presynaptic dopamine neurons, in addition to its previously described postsynaptic receptor stimulation.

Effect of radiotherapy on whole saliva flow.

Abstract: Patients with head and neck malignant disease who have received cancerocidal levels of irradiation often develop a highly destructive type of dental caries. There is general agreement that this effect of irradiation on the teeth is indirect and results primarily from the severe depression of salivary gland function associated with such treatment. This study evaluated the effect of such irradiation therapy on the rate of unstimulated whole saliva flow in a series of unselected head and neck cancer patients. Ten white males in the 47 to 67 year age group with primary malignant lesions of the head and neck included in the study only by the criterion of being one of the first 10 patients in the series to complete six full weeks of irradiation (delivered by parallel opposed fields from a Cobalt 60 source and administered at a daily dose level of 225 rads, usually on a Monday through Thursday schedule each week) and saliva sampling. Mean dosage was 4,432 rads (S.D. = 900), ranging from 2,250 to 5,400 rads. The patient receiving 2,250 rads (treatment interrupted due to complications) was an exception; the next lower dosage was 3,825 rads. Unstimulated whole saliva samples were collected from each patient immediately before treatment. Patients were directed to minimize oral movements, and to allow saliva to drool into a calibrated tube. Pretreatment sampling included specimens collected through the morning of the first radiotherapy appointment. Thereafter a saliva sample was collected, as nearly as possible, before each of the four irradiation treatments per week. For each patient, a mean was calculated for flow rate for each week; this figure was used to derive a mean for flow rate for all patients for each week. Before irradiation, 37 samples were collected from these 10 subjects and 159 collections

Angel's Trumpet psychosis: a central nervous system anticholinergic syndrome

Abstract: The authors warn physicians that intoxication by Angel's Trumpet (Datura sauveolens) is becoming more frequent due to its use by adolescents and young adults as a legal, readily available hallucinogen. Ingestion of Angel's Trumpet flowers or a tea brewed from them results in an alkaloid-induced central nervous system anticholinergic syndrome characterized by symptoms such as fever, delirium, hallucinations, agitation, and persistent memory disturbances. Severe intoxication may cause flaccid paralysis, convulsions, and death. Treatment with intravenous physostigmine reverses the toxic effects of Angel's Trumpet.

Occurrence and Distribution of Interdental Gingival Clefts following Orthodontic Movement into Bicuspid Extraction Sites

Abstract: Forty patients in active retention following orthodontic tooth movement into premolar extraction sites were examined for the occurrence and distribution of interdental gingival clefts, defined as an invagination of interproximal tissue with definite mesial and distal peaks having a depth of at least 1 mm. Fourteen of the forty orthodontic patients demonstrated clefts in one or more of the premolar extraction sites. No clefts were observed in premolar areas of orthodontic patients who did not require premolar extraction or in patients without previous orthodontic treatment. Interdental clefts occurred most frequently at the buccal aspect of mandibular first premolar extraction sites. The presence of the cleft appears to have clinical implications, both in terms of orthodontic relapse, and maintenance of gingival health.

Life Stress as a Precursor to Adolescent Drug Dependence

Abstract: Though drug dependence is often characterized as a stress-produced disorder, there seems to be little or no quantitative data relating stress and drug dependence. In this study a recognized instrument for the measurement of stress, Coddington's Life Event Record, was administered to 31 drug-dependent adolescents by estimating levels of life stress during the year preceding their first illicit drug use. The drug-dependent subjects showed significantly higher life stress scores than did a standard normal population of adolescents. The null hypothesis of no difference was rejected at the .005 level. A stress-reduction theory of drug dependence gains support from these results.

Single-dose tolerance to morphine hypothermia in the rat: differentiation of acute from long-term tolerance.

Abstract: The time course for the development and disappearance fo tolerance to the hypothermic effects of morphine was determined after a single subcutaneous injection (10 mg/kg) in rats. Body temperature responses to second injections, given at varying times after the first, were compared with those produced by the initial injections. Tolerance (attenuation of the hypothermic response) induced by a single dose of morphine was found to be biphasic. Acute tolerance was apparent by 4.5 hours and lasted at least 20 hours after morphine administration. Development of long-term tolerance occurred within 24 hours, was maximal at 3 days and persisted up to 11 days. Both acute and long-term tolerance were drug specific since hypothermic responses to pentobarbital were not altered either 4.5 or 72 hours after morphine. Long-term tolerance was attenuated by co-administration of naloxone with initial dose of morphine. Long-term tolerance induced by multiple doses of morphine (300 mg/kg/day) differed from that induced by a single dose in persistence (3-4 weeks) rather than in quality or magnitude. The thermoregulatory response of the rat provides a sensitive measurement system which allows discrimination between acute and long-term opiate effects.

Parenteral nutrition techniques in cancer patients.

Abstract: Summary If a patient is expected to respond optimally to one or more forms of oncologic therapy, he should simultaneously be in the best possible nutritional and metabolic condition. When the alimentary tract cannot be used effectively for feeding cancer patients, parenteral nutrition can be lifesaving. Moreover, patients who are poor candidates or noncandidates for any antineoplastic therapy because of their debility or cachexia can be converted to reasonable candidates following a course of i.v. hyperalimentation. This i.v. hyperalimentation can significantly reduce the morbidity and mortality of cancer patients without stimulating tumor growth when applied conscientiously according to the established principles and techniques and when integrated with specific tumor therapy. With the use of ambulatory or home hyperalimentation techniques, normal nutritional status can be restored or maintained during prolonged periods of antineoplastic therapy on a practical and relatively economical outpatient basis. It is anticipated that specific nutrient substrate formulas and parenteral therapy techniques will be developed to maintain optimal host nutrition while adversely affecting the neoplasm.

The effect of unrecognized drug abuse on diagnosis and therapeutic outcome.

Abstract: One-hundred and ninety-five consecutive psychiatric outpatients had urine sampled for the presence of opiates, cocaine, barbiturates, and amphetamines. All patients had demographic variables, diagnostic information, and treatment course analyzed in a blind fashion using preselected criteria. Patterns of abuse were defined for the 13.3% of the total sample who were covert abusers. An analysis of diagnostic accuracy for abusing and nonabusing populations indicated that covert abuse markedly distorted diagnosis and management. The study indicates that demographic variables and previous history were not reliable predicators of covert abuse. Drug abuse was a major factor in distorting the accuracy of diagnosis. Drug abusers were significantly less likely to improve with therapy than were nonabusers. Barbiturate abusers were most likely to suffer from adverse drug reactions. Urine screening for drugs was the single most valuable diagnostic tool and was felt to be indicated in all cases where diagnostic confusion was present. Therapists saw the covert abuser as sick out of proportion to their social behavior, were perplexed and frightened by these patients' dependency, and perceived them as too brittle for therapy. Therapists behaved very differently with these patients than with diagnostically matched controls. They misdiagnosed them four times more often, missed appointments with them seven times more often, and were ten times more likely to refer them to another therapist or agency. Therapist anxiety and "flight from therapy" with covertly abusing patients are discussed.

Human physiological adaptability through the life sequence.

Abstract: Changes in organ function from birth to old age were investigated from published data. In essence, the observations of Shock and colleagues on maximal breathing capacity, vital capacity, glomerular filtration rate, renal plasma flow, basal metabolic rate (BMR), ulnar nerve conduction velocity, cardiac index, and intracellular water (ICW) for the age period 30 to 85 years were extended to the time of birth. There were two principal findings. First, with the exception of BMR and ICW, these functional indices increased from a low point at birth to a maximum between 3 and 20 years of age and then after 30 years declined progressively to 85 years; BMR declined from a maximum in infancy and ICW peaked at about 30 years and then declinded. Second, the coefficient of variation increased regularly from birth to old age. Because the peak of organ function coincided with the period of minimal mortality, the curve of organ function across the life sequence was considered to represent changes in adaptive capacity. Supporting evidence from studies of physical fitness, thermoregulation, and seasonal change of mortality was considered. It was concluded that these shifts in adaptive capacity between birth and old age were fundamental baselines for investigations of the epidemiology of health.

Characterization of Discriminative Response Control by Psychomotor Stimulants

Abstract: Among the drugs which effectively control discriminative responding are the psychomotor stimulants. Despite differences in methodology utilized in different laboratories, the results available to date are quite consistent. Amphetamine, the prototype of this class of drugs, has been most extensively studied. For this reason, our discussion will center on amphetamine, other stimulants being mentioned where data are available.

Genetic and environmental determinants of growth of school-aged children in a rural Colombian population.

Abstract: Parent-offspring correlations and heritabilities of body measurements from midparent-offspring regressions are presented for school-aged children from the village of Tenza, Colombia (N = 403 families). Parent-child correlations and midparent regressions in this subsistence farming sample, are similar in magnitude to those for well nourished, urban industrial samples, suggesting that the environmental component of variability in body size is the same regardless of the environment. Tenza children are significantly shorter and lighter than upper class Bogota children, and Tenza parents have mean heights and weights similar to those of other lower class Colombian samples. Thus, chronic undernutrition has affected the growth of parents and continues to affect the growth of the present generation. Although it has been hypothesized that heritability of growth might be reduced in samples experiencing malnutrition and its sequelae, such a reduction may only be observable where environment of parents during their development is different from that of their offspring, which is not the case here. The pattern of heritabilities with respect to different body measurements in Tenza, is similar to that seen in well nourished samples, except that measurements of breadth (biacromial, bicristal, bicondylar) have heritabilities similar in magnitude to those of linear measurements (height, sitting-height, subischial length) especially in males; and heritabilities of some measurements related to adiposity are significantly higher in daughters than in sons.

Bacterial relationships in stormwaters

Abstract: Data were developed within a three-year period for indicator bacteria and three species of bacterial pathogens following rural storm event hydrographs. The first flush concept was confirmed in all hydrographs. Bacterial density peaking occurred at or before the hydrograph peaks. FC and FS values were higher in more developed areas than the primary rural test site and their numerical ratios followed similar trends. Chlorine demand of storm waters varied between 8 and 16 mg/l and, the ozone requirement was greater than 32 mg/l in the same waters. Aftergrowth of total coliform bacteria occurred following chlorine and ozone doses of 16 mg/l and 32 mg/l respectively. Fecal coliform, fecal streptococci, Salmonella sp., and Pseudomonas sp. all were reduced to near detectable limits by the disinfectants up to 8 days. Staphylococcus sp. demonstrated a propensity to restablish their populations. Multiple regression analysis of the bacterial groups and species in storm waters suggested the fecal streptococci to have been the most useful group in evaluating bacterial storm water quality, with staphylocci have been closely related insofar as their statistical significance was concerned.

Sibling correlations in growth and adult morphology in a rural Colombian population.

Abstract: SummaryCorrelations for body measurements between members of 207 pairs of school-aged and 116 pairs of adult siblings in a mestizo farming community of the Colombian Andes are comparable to those from previous studies of well nourished urban-industrial samples, both in magnitude and pattern of heritabilities. While the genetic potential in physical growth is impeded by undernutrition and disease in childhood in samples such as the present one, hereditary influences on the variability of growth and adult size appear to be as important in such populations as they are in well nourished ones. School-aged sibs have significantly higher correlations than adult sibs and parent-offspring pairs for some measurements, suggesting environmental contributions in physical resemblance of siblings. Fatfold correlations between adult sisters are persistently higher than those of other sib pairings when socio-economic differences, age, and seasonal variation in nutrition are held constant, implying a greater genetic basis ...

Calcifications and the therapeutically irradiated breast.

Abstract: Mammograms of 81 patients who received radiation therapy to the breast were analyzed for patterns of pre- and postirradiation calcifications. Malignant calcifications may remain stable, diminish, or completely disappear following irradiation. The persistence of calcifications need not indicate residual cancer. Calcifications can develop following irradiation which are similar to either intraductal or secretory calcifications. Unusual calcifications may develop at the site of an irradiated cancer. It is important to recognize that benign calcifications can develop so that they will not be confused with recurrent malignancy.