Showing papers by "University of Texas Health Science Center at Houston published in 1975"
TL;DR: In a population of constant size the expected heterozygosity for a neutral locus when mutation and genetic drift are balanced is given by 4 Nv/(4Nv + 1) under the assumption that new mutations are always different from the pre-existing alleles in the population.
Abstract: In a population of constant size the expected heterozygosity for a neutral locus when mutation and genetic drift are balanced is given by 4 Nv/(4Nv + 1) under the assumption that new mutations are always different from the pre-existing alleles in the population, where N is the effective population size and v the mutation rate per locus per generation (Kimura, 1968). The size of a natural population, however, often changes drastically in the evolutionary process. In an extreme case a single inseminated female from a large population may migrate to an unoccupied geographical or ecological territory and establish a new colony, followed by rapid population growth to form a new species. This process seems to have occurred repeatedly in the evolution of Hawaiian Drosophila species (Carson, 1970; 1971) and also in the establishment of the Bogota, Colombia, population of Drosophila pseudoobscura (Prakash, 1972). When population size is suddenly reduced, the average heterozygosity per locus is expected to decline, the rate of decline depending on the effective population size, while if population size increases the aver-
3,289 citations
TL;DR: Rat electroretinograms were measured as a function of dietary supplements of purified ethyl esters of linolenic Acid, linoleic acid, and oleic acid to investigate the electrical response of photoreceptor cell membranes to polyunsaturated fatty acids derived from precursors.
Abstract: Rat electroretinograms were measured as a function of dietary supplements of purified ethyl esters of linolenic acid, linoleic acid, and oleic acid. Polyunsaturated fatty acids derived from precursors of linolenic and linoleic acids appear to be important functional components of photoreceptor cell membranes, although in equal dietary concentrations, linolenic acid precursors affect electroretinogram amplitudes to a greater extent than linoleic acid precursors. The electrical response of photoreceptor cell membranes appears to be a function of the position of the double bonds as well as a function of the total number of double bonds in fatty acid supplements.
347 citations
TL;DR: Results of this experience show that a combination of conservative surgery and radiation therapy, based upon radical dose levels and sophisticated techniques, is effective: only 13 of 100 patients showed local regrowth during a followup of 2–12 years.
Abstract: Radical dose radiation therapy alone or combined with limited surgery has been employed in the management of 100 patients with primary (71) and recurrent (29) sarcoma of soft tissue. Results of this experience show that a combination of conservative surgery and radiation therapy, based upon radical dose levels and sophisticated techniques, is effective: only 13 of 100 patients showed local regrowth during a followup of 2-12 years. This may be compared with an expected congruent to 25 recurrences had treatment been radical surgery (wide resection or amputation). For lesions located on the distal extremities (elbow-hand, knee-foot) there were local failures in only 3 of 59 (5 percent). Further, 75 percent of patients treated by the improved techniques utilized in the recent 8 years retained a useful limb which is free of pain or edema. Histopathologic grade is demonstrated to be an important indicator of prognosis of local recurrence and of disease-free survival. Local recurrence rates were 0/23, 9/53, and 4/24 for Grades 1, 2, and 3. Disease-free survival rates were 19/23 (86 percent), 27/53 (51 percent), and 4/24 (17 percent) for Grades 1, 2, and 3, respectively. Invasion of skin appeared to be a sign of poor prognosis; 8 of 9 such patients developed distant metastases.
286 citations
TL;DR: This chapter focuses on the four Rs that influence the outcome of fractionated-dose radiotherapy, one or more of which may account for the relative sparing of normal tissues.
Abstract: Publisher Summary Radiotherapy given as multiple doses are effective in sterilizing cancers, but the processes whereby the neoplasm is eradicated and the normal tissues are preserved are not fully understood. The differential between normal tissue and tumor response is enhanced by dose fractionation, single doses resulting in severe normal tissue injury when the dose is sufficient to control a proportion of treated tumors. This chapter focuses on the four Rs that influence the outcome of fractionated-dose radiotherapy, one or more of which may account for the relative sparing of normal tissues. These are repair of sublethal injury in normal and neoplastic cells, reoxygenation of the tumor, redistribution through the division cycle, and regeneration of surviving normal and malignant cells between dose fractions. These have been called the four Rs of fractionated radiotherapy. Other factors are involved in the outcome of multifraction radiotherapy—for example, the maintenance of the architectural integrity of the normal tissues, the volume of tissue irradiated, the tumor bed, and the immunocompetence of the host are some other factors that play a significant role in the differential response.
283 citations
TL;DR: No part of the body reflects the complications of cancer chemotherapy as visibly and vividly as the mouth, and each constitutes a threat that must be kept within manageable limits.
Abstract: No part of the body reflects the complications of cancer chemotherapy as visibly and vividly as the mouth. The hemorrhagic, infectious, nutritional, cytotoxic, and neurologic signs of drug toxicity are registered in the mouth by changes in the color, character, and continuity of the mucosa. Although some of the complications are an inevitable part of the price of treatment, each constitutes a threat that must be kept within manageable limits.
90 citations
TL;DR: A role of dopamine is indicated in the production of the amphetamine state and from the failure of apomorphine to exhibit the stimulus property of d-amphetamine and the antagonism by alpha-methyltyrosine of the d- methamphetamine responding it is further suggested that this amphetamineState is produced via the releasing of newly synthesized dopamine.
Abstract: In two-lever operant chambers, rats were trained in a food-reinforced discrimination task. Reward was contingent upon correct lever choices to the induced differential cue conditions of d-amphetamine (0.8 mg/kg) or saline throughout training on a differential reinforcement of low response rate (DRL-15 sec) schedule. Upon acquisition of discriminative response control the animals were pretreated with various neurochemical agents. Pretreatment with atropine, phentolamine, propranolol, methysergide or cinanserin did not block production of d-amphetamine lever responding. Nicotine and oxotremorine did not produce the amphetamine-like cueing effect. However, pimozide blocked the ability of animals to discriminate d-amphetamine and L-DOPA, in combination with Ro 4-4602 with or without amantadine, generated amphetamine-like responses. These results indicate a role of dopamine in the production of the amphetamine state and from the failure of apomorphine to exhibit the stimulus property of d-amphetamine and the antagonism by α-methyltyrosine of the d-amphetamine responding it is further suggested that this amphetamine state is produced via the releasing of newly synthesized dopamine.
89 citations
TL;DR: Testicular tumors initially diagnosed as pure seminoma were irradiated following orchiectomy in 141 patients and analysis of treatment failures reveals that 2500 rads is adequate for elective irradiation and 3500 rads for small to moderate-size metastases.
Abstract: Testicular tumors initially diagnosed as pure seminoma were irradiated following orchiectomy in 141 patients. Analysis of treatment failures reveals that (a) 2500 rads is adequate for elective irradiation and 3500 rads for small to moderate-size metastases; (b) elective irradiation of the mediastinum and left supraclavicular area is not indicated for Stage I, but is for Stage II; (c) patient with bulky retroperitoneal disease should be treated initially through total abdominal portais followed by additional treatment through reduced fields; and (d) presence of embryonal carcinoma, teratocarcinoma, or choricarconoma should be considered when regression is poor.
76 citations
TL;DR: The survival rates for a selected group of patients with large central lesions managed by combining irradiation and a conservative extrafascial hysterectomy are comparable to those of carcinoma of the cervix in general.
Abstract: The survival rates for a selected group of patients with large central lesions, either squamous cell carcinoma or adenocarcinoma and managed by combining irradiation and a conservative extrafascial hysterectomy, are comparable to those of carcinoma of the cervix in general.Death is caused much more often by distant metastases and intercurrent disease than by failure within the irradiated volume.
68 citations
TL;DR: The contribution of a parental population in the gene pool of a hybrid population which arose by hybridization with one or more other populations is estimated here at the population level from the probability of gene identity.
Abstract: The contribution of a parental population in the gene pool of a hybrid population which arose by hybridization with one or more other populations is estimated here at the population level from the probability of gene identity. The dynamics of accumulation of such admixture is studied incorporating the fluctuations due to finite size of the hybrid population. The method is illustrated with data on admixture in Cherokee Indians.
59 citations
TL;DR: Retinoblastoma should not be considered as the exceptional childhood cancer that shows dominant inheritance, but rather as the typical Childhood cancer that embraces a prezyGotic and postzygotic subgroup.
Abstract: Retinoblastoma should not be considered as the exceptional childhood cancer that shows dominant inheritance, but rather as the typical childhood cancer that embraces a prezygotic and postzygotic subgroup. Postzygotic cases are conceived as involving mutation as a first step too, but with the mutation in somatic rather than germinal cells. In both prezygotic and postzygotic cases a second event, possibly mutational, occurs before the cancer is initiated. The embryonal cancers are all visualized as genetic disease, and their frequencies limited by gene mutability. This mutability can be increased by environmental agents. Prezygotic cases may develop other primary tumors in the same organ and primary tumors in other tissues. They may also have affected family members, the probability of affected offspring approaching 50%. A diagnostic test to identify prezygotic cases among those with a single primary tumor and a negative family history is sorely needed.
56 citations
TL;DR: The results indicate that mescaline produces its discriminative stimulus properties by directly stimulating central serotonergic receptors.
Abstract: Rats were trained to discriminate intraperitoneally administered mescaline from saline in a two-lever operant chamber for food reinforcement. Reward was contingent upon responses made greater than 15 sec apart (DRL-15) on the appropriate lever paired with either drug or saline administration. Following the establishment of discriminative response control by mescaline, the animals were tested for stimulus generalization produced by mescaline after: (a) blockade of periphreral and central serotonin (5-HT) receptors with cinanserin, methysergide, or cyproheptadine; (b) blockade of peripheral 5-HT receptors with xylamidine tosylate; and (c) depletion of brain 5-HT with the tryptophan hydroxylase inhibitor p-chlorophenylalanine (PCPA). The results show that all three central 5-HT antagonists greatly reduced the discriminability of mescaline while the peripheral antagonist, xylamidine tosylate, was without effect. Furthermore, these agents at the doses employed did not effect the discriminability of saline. Depletion of 5-HT with PCPA potentiated the effects of a sub-threshold dose of mescaline and slightly reduced the discriminability of saline. The results indicate that mescaline produces its discriminative stimulus properties by directly stimulating central serotonergic receptors.
TL;DR: An unusual case of tuberous sclerosis with thick sclerotic ribs, thoracic and abdominal aortic aneurysms and sacrococcygeal chordoma is described.
Abstract: An unusual case of tuberous sclerosis with thick sclerotic ribs, thoracic and abdominal aortic aneurysms and sacrococcygeal chordoma is described. The patient has been followed for 17 years and the radiographic features of the ribs and especially the aortic aneurysms are unusual features of this condition.
Journal Article•
TL;DR: Evidence is prisented which shows that the enzymatic defect in mannosidosis, the deficiency of alpha-mannosidase, is expressed in cultured skin fibroblasts from patients with mannosdosis.
TL;DR: The results of the application of this method to Drosophila data do not support Prakash & Lewontin's (1968) contention that the strong association between gene arrangements and alleles at protein loci is evidence of coadaptation of genes in the inverted segment of chromosomes.
Abstract: A mathematical method for evaluating the probability that a locus is monomorphic for the same allele in related species is developed under the neutral mutation hypothesis. A formula for the proportion of identically monomorphic loci in related species is also worked out. The results of the application of this method to Drosophila data do not support Prakash & Lewontin's (1968) contention that the strong association between gene arrangements (inversion chromosomes) and alleles at protein loci is evidence of coadaptation of genes in the inverted segment of chromosomes. Similarly, unlike Haigh & Maynard Smith's (1972) contention, the monomorphism of the haemoglobin a chain locus in man can be accommodated with the neutral mutation hypothesis without invoking the bottleneck effect.
Journal Article•
TL;DR: It is argued that the present prevalence of the sickle cell anemia mutant in Africa may be explained without the necessity of quite so great a heterozygous advantage as .25 or higher as proposed by some workers.
Abstract: The mean and standard deviation of the first arrival time for a single mutant to reach a certain frequency and the mean age of a mutant persisting in a population have been studied using diffusion methods. These quantities are shown to be highly dependent on both the heterozygous effect and the population size. For partially recessive deleterious mutations, both the mean first arrival time and the mean age decrease with increasing selection coefficient against heterozygotes. For overdominant mutations, the mean age always increases very rapidly with increasing heterozygous advantage, while the mean first arrival time first increases rapidly with increasing heterozygous advantage to a maximum and then decreases rapidly with increasing heterozygous advantage. The standard deviation of the first arrival time is small while that of the age is large. The results of this study have been applied to study the case of the sickle cell anemia mutant in Africa. It is argued that the present prevalence may be explained without the necessity of quite so great a heterozygous advantage as .25 or higher as proposed by some workers. A reasonable range for the heterozygous advantage seems to be from .05 to .18.
TL;DR: A procedure for combining sister chromatid differential staining and G banding in the same metaphase plate is reported, which provides additional information for cytogeneticists.
Abstract: We report a procedure for combining sister chromatid differential staining and G banding in the same metaphase plate. Mammalian cells in culture are grown in medium containing 5-bromodeoxyuridine for two cell cycles, and conventional air-dried preparations are made. The slides are treated with a trypsin or a urea solution the same way as for regular G banding. This method is simple and fast and provides additional information for cytogeneticists.
TL;DR: Life table characteristics did not differ among the cohorts reared in the 2 environments, and significant differences could be shown among strains for the mean lifetimes of both sexes, net reproductive rates and intrinsic rates of increase.
Abstract: Life tables were generated for adults of 5 geographic strains of Aedes aegypti reared in either a fluctuating temperature and humidity regime or a constant regime of temperature and humidity. Significant differences could be shown among strains for the mean lifetimes of both sexes, net reproductive rates and intrinsic rates of increase. However, life table characteristics did not differ among the cohorts reared in the 2 environments.
TL;DR: The history of complete denture impression procefures has been influenced largely by the development of impression materials from which new ideas and techniques arose.
Abstract: The development of various impression materials, and the use of the various techniques associated with them, are chronologically reviewed. The history of complete denture impression procedures has been influenced largely by the development of impression materials from which new ideas and techniques arose. Apparently, some procedures have been devised solely for the promotion of certain impression materials. For the most part, however, impression materials have been developed to accomplish specific goals and, at the time at least, were considered desirable for the purpose.
TL;DR: A pyrimidine nucleoside monophosphate kinase has been purified 2100-fold from rat liver and a NADP+-dependent thioredoxin reductase system from Novikoff ascites rat tumor was found to be the most powerful reducing agent tested.
Abstract: A pyrimidine nucleoside monophosphate kinase has been purified 2100-fold from rat liver. With ATP and dATP as phosphate donors the kinase uses CMP, dCMP, and UMP as phosphate acceptors. Ara-CMP is also phosphorylated by the kinase. In contrast to dCMP and UMP, CMP can be phosphorylated by dCTP. CTP and ara-CTP cannot substitute for dCTP. The stringent specificity of the phosphate donor site for ATP and dATP is lost when CMP serves as acceptor. All nucleoside triphosphates act as donors to a significant extent. No evidence has been found to suggest more than one enzyme. All activities, to different degrees, are strictly dependent upon preincubation at 37 degrees with a sulfhydryl reducing agent. Various reagents (85 mM) are ranked in order of increasing effectiveness of reactivation as follows: dithiothretiol greater than glutathione larger than or equal to 2-mercaptoethanol greater than L-cysteine greater than DL-alpha-lipoic acid. A NADP+-dependent thioredoxin (17 muM)-thioredoxin reductase system from Novikoff ascites rat tumor was found to be the most powerful reducing agent tested. CTP, dCTP, UTP, and dTTP (1 mM) do not affect the kinase activity regardless of the phosphate acceptor.
01 Jan 1975
TL;DR: There are really no new problems in the cultivation of human tumor cells, merely a greater awareness of some of the old ones, an increased understanding of what they are.
Abstract: There are really no new problems in the cultivation of human tumor cells, merely a greater awareness of some of the old ones, an increased understanding of what they are. In general, the difficulties lie in obtaining tumor cells from the patient and growing or maintaining them in vitro without adding any “foreign” living substance. It is equally difficult to separate the tumor cells from extraneous normal cells or tissues and to demonstrate that the cells growing in tissue culture are identical to the neoplastic cells found in the host.
TL;DR: Although the materials used in this paper form probably only a non-random sample of structural genome, intralocus variance (sampling) is found to contribute only a little in the variabilities of heterozygosity or genetic distance.
Abstract: Extent of genic variability among 22 tribal groups of South American Indians in terms of net codon differences per locus has been studied on the basis of determinations on ten genetic systems. The possibility of more than one (other than the north-south route, considered by others) migrational pattern is discussed in the light of the existing genetic variability among the Andean highland and the jungle populations. Genic similarities (as measured by gene identity) are related with geographic proximities which reflect the importance of random genetic drift in creating the present genic divergence among these population groups. Although the materials used in this paper form probably only a non-random sample of structural genome, intralocus variance (sampling) is found to contribute only a little in the variabilities of heterozygosity or genetic distance.
TL;DR: A case of central neurofibroma of the maxilla withpacinian corpuscle histodifferentiation with pacinian corpuscles histod differentiation is presented and a possible cause is cited.
01 Apr 1975
TL;DR: The Acquisition, Maintenance and Treatment of Polydrug Dependence: A Public Health Model as discussed by the authors is a public health model for polydrug dependence. But it does not consider the effects of polydrug dependency on mental health.
Abstract: (1975). The Acquisition, Maintenance and Treatment of Polydrug Dependence: A Public Health Model. Journal of Psychedelic Drugs: Vol. 7, No. 2, pp. 209-213.
TL;DR: The lipid composition has been determined for rhabdomeric photoreceptor membranes of Limulus, and these data are compared with those from photorecept membranes of albino rats, and the major differences are a greater percentage of sphingomyelin in Limulus and a great percentage of phosphatidylethanolamine in the rat.
TL;DR: The agents used in cancer chemotherapy are highly potent and have only a slight margin of safety between the tumoricidal and toxic doses, so the skin is a frequent target for the side effects of these drugs.
Abstract: The agents used in cancer chemotherapy are highly potent and have only a slight margin of safety between the tumoricidal and toxic doses. The skin is a frequent target for the side effects of these drugs. Major cutaneous manifestations of toxicity include alopecia, cellulitis, hyperpigmentation, hemorrhage, and infection.
TL;DR: The authors believe that the observed skin reaction in the axilla for the Clinac 4 linear accelerator is due to a combination of increased dose at Dmax from the anterior mantle field and an increase in exit dose from the posterior mantle field when compared to similar treatments for 60Co.
Abstract: To determine the cause of increased skin reactions near the edges of the field the authors measured doses at and near the surface of the skin with an extrapolation chamber for the gamma-ray beam of an AECL Eldorado 8 60Co irradiator and the x-ray beams of a Varian Clinac 4 linear accelerator, a Varian Clinac 6 linear accelerator, and an ARCO Mevatron 8 linear accelerator. Buildup curves were measured on each machine to locate the depth of the maximum dose (Dmax). The surface dose of the central axis was measured as a function of field size. Off-axis surface doses were measured on the Clinac 4 linear accelerator and on the Eldorado 8 60Co therapy unit. No measurable increase in surface dose was found leading the authors to believe that the observed skin reaction in the axilla for the Clinac 4 linear accelerator is due to a combination of increased dose at Dmax from the anterior mantle field and an increase in exit dose from the posterior mantle field when compared to similar treatments for 60Co.
TL;DR: Using gene frequency data for 14 genetic loci, genetic distances between 13 tribes of Mexican Indians belonging to 12 language groups were determined and a dendrogram was constructed.
Abstract: Using gene frequency data for 14 genetic loci, genetic distances between 13 tribes of Mexican Indians belonging to 12 language groups were determined and a dendrogram was constructed. The genetic distance between tribes is correlated more with geographic proximity than with language affinity. The gene diversity (heterozygosity) of the total population was decomposed into the three components, i.e., the gene diversity between three main linguistic groups, the gene diversity between tribes within the main linguistic groups and the gene diversity within tribes. About 95% of the total gene diversity exists within tribes, the intergroup and intertribe components being only about 5%.