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PubMed1995

The relationship between prevalence of asthma and environmental factors in rural households.

A cross sectional study was conducted among 1007 children aged 1-2 years, from padi farming area. The percentage of male children was 51.4%. The prevalence of at least one of the chronic respiratory symptoms was 12.81%, and the prevalence of chronic cough, chronic sputum, wheezing and bronchial asthma as diagnosed by doctors were 9.33%, 3.87% 5.36% and 3.38% respectively. The overall prevalence of bronchial asthma was 6.26%. The prevalence of asthma was highest among children aged 11-12 years (8.9%) and higher among males (6.95%). No significant relationship was found between the prevalence of either chronic respiratory disease symptoms of bronchial asthma, and selected environmental factors, namely exposure to cigarette smoke, use of mosquito coil and wood stove. However there was a significant relationship between prevalence of asthma in children and history of asthma among parents and grandparents.

Asthma↗

PubMed2025

Repeatable Genomic Outcomes Along the Speciation Continuum: Insights From Pine Hybrid Zones (Genus Pinus).

Hybridization is a widespread evolutionary process and a key source of evolutionary novelty. Despite intensive study, the extent to which hybridization is deterministic and repeatable, particularly in recurrent contact events involving the same species under varying ecological conditions, remains unclear. Here, we investigated three replicated contact zones between Scots pine (Pinus sylvestris) and dwarf mountain pine (Pinus mugo) in Central Europe: two occurring in peatland habitats and one in a contrasting sandstone outcrop. Using genome-wide SNP genotyping of over 1300 individuals, we analysed genomic structure, diversity, and ancestry patterns across these zones. All sites revealed pervasive hybridization, dominated by later-generation hybrids and a notable scarcity of pure P. mugo. Across environments, hybrid populations exhibited strikingly consistent genomic compositions, with asymmetric introgression strongly biased toward P. mugo ancestry, suggesting that hybrid genome structure may follow predictable patterns under similar ecological conditions and could be shaped by cytonuclear incompatibilities. Nonetheless, we also detected site-specific differences in hybrid diversity and phenotype, highlighting the influence of local environmental selection on shared hybrid genomic backgrounds. We provide genomic evidence that Pinus uliginosa, a morphologically distinct peat bog pine traditionally regarded as a relict and endangered species is instead a partially stabilised hybrid lineage. Its genome reflects incomplete hybridization and ecological filtering, yet it lacks sufficient genetic divergence to be recognised as a distinct species. Together, these results provide evidence for the repeatability of hybridization processes, which result in the formation of phenotypes reflecting a species continuum subjected to strong environmental pressures. The findings support the simplification of taxonomic nomenclature within the Pinus mugo complex, informing adaptive conservation strategies and the genetic management of hybrid lineages.

Hybridization, Genetic↗

PubMed1991

Antibiotic availability and use: consequences to man and his environment.

Antibiotics are the cornerstone of therapy for infectious diseases affecting people living worldwide. The ability of these agents to cure infections, with little if any harm to the host, has helped to propagate their designation as "miracle drugs". This idea has continued throughout the past four decades and into the present one. To a large extent, this concept has led to the inappropriate use of these agents. The consequence of this misuse affects not only the individuals taking antibiotics, but indirectly others who may subsequently need antibiotics, but find that the infecting pathogen is resistant. This phenomenon results from the strong selective environmental effect of these drugs for resistant bacteria. Resistant pathogens have emerged and spread worldwide. In response to this global health problem, the Alliance for the Prudent Use of Antibiotics was established. This international network of concerned prescribers and users aims to improve antibiotic use and eliminate inappropriate use worldwide. Prudent use of antibiotics will not only curtail health care costs and the potential side effects to the individual taking these drugs, but also diminish the wide ecologic effects leading to selection of antibiotic resistant forms of common disease-causing agents.

Bacteria↗

PubMed1982

Effects of temperature and salinity on Vibrio cholerae growth.

Laboratory microecosystems (microcosms) prepared with a chemically defined sea salt solution were used to study effects of selected environmental parameters on growth and activity of Vibrio cholerae. Growth responses under simulated estuarine conditions of 10 strains of V. cholerae, including clinical and environmental isolates as well as serovars O1 and non-O1, were compared, and all strains yielded populations of approximately the same final size. Effects of salinity and temperature on extended survival of V. cholerae demonstrated that, at an estuarine salinity (25%) and a temperature of 10 degrees C, V. cholerae survived (i.e., was culturable) for less than 4 days. Salinity was also found to influence activity, as measured by uptake of 14C-amino acids. Studies on the effect of selected ions on growth and activity of V. cholerae demonstrated that Na+ was required for growth. The results of this study further support the status of V. cholerae as an estuarine bacterium.

Amino Acids↗

PubMed2002

Genetic diversity in the human major histocompatibility complex: lessons for vaccination approaches to HIV infection.

The major histocompatibility complex (MHC) harbours genes that have a primary function of regulating immune responsiveness. Our data on the distribution patterns of molecular subtypes of HLA class I and II extended haplotypes in India suggest that: (1) Asian Indians have extreme diversity in the MHC region, with several novel and unique alleles and disease-associated MHC haplotypes (e.g. the autoimmune-favouring A26-B8-DR3 haplotype); (2) there have been selective environmental and microbial pressures in India that directed either the generation of novel alleles through founder effect or the expansion of other alleles due to geophysical or socio-economic barriers, and (3) Asian Indians have a unique repertoire of peptide-presenting molecules to deal with pathogen-derived autoreactive antigens. This level of polymorphism concentrated within the MHC presents a formidable obstacle to the development of peptide-based vaccines, e.g. for AIDS. Further, studies conducted by us and others have provided a genetic basis for the possible predisposition and fast progression of HIV infections in the Indian population. Since there is selective predominance of different HLA alleles and haplotypes in different populations, a dedicated global screening effort is required to develop MHC-based vaccines against infectious diseases.

Journal Article↗

PubMed2004

Solid-phase microextraction-gas chromatography-mass spectrometry for the analysis of selective serotonin reuptake inhibitors in environmental water.

The continuous contamination of surface waters by pharmaceuticals is of most environmental concern. Selective serotonin reuptake inhibitors (SSRIs) are drugs currently prescribed for the treatment of depressions and other psychiatric disorders and then, they are among the pharmaceuticals that can occur in environmental waters. Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry has been applied to the extraction of five SSRIs--venlafaxine, fluvoxamine, fluoxetine, citalopram and sertraline--from water samples. Some of the analytes were not efficiently extracted as underivatized compounds and so, an in situ acetylation step was introduced in the sample preparation procedure. Different parameters affecting extraction efficiency such as extraction mode, fiber coating and temperature were studied. A mixed-level fractional factorial design was also performed to simultaneously study the influence of other five experimental factors. Finally, a method based on direct SPME at 100 degrees C using polydimethylsiloxane-divinylbenzene fibers is proposed. The performance of the method was evaluated, showing good linearity and precision. The detection limits were in the sub-ng/mL level. Practical applicability was demonstrated through the analysis of real samples. Recoveries obtained for river water and wastewater samples were satisfactory in all cases. An important aspect of the proposed method is that no matrix effects were observed. Two of the target compounds, venlafaxine and citalopram, were detected and quantified in a sewage water sample.

Gas Chromatography-Mass Spectrometry↗

PubMed2006

Uses and issues of biomonitoring.

In the last two decades, an explosion in information and literature on human biomonitoring data has occurred. Symposia, workshops, and workgroups have been formed to discuss all issues surrounding biomonitoring. One such workgroup, formed by the International Life Sciences Institute's Health and Environmental Sciences Institute (HESI), developed a wheel which has biomonitoring at its hub; its spokes depict the uses of biomonitoring. As it rolls and picks up speed, the biomonitoring wheel will no doubt gain additional spokes. In this manuscript, we describe and give examples of these biomonitoring uses and some of their further applications as well as some of the issues surrounding biomonitoring. Special emphasis is placed on the uses and limitations of large-scale representative cross sectional studies such as the National Health and Nutrition Examination Surveys in the United States. Priority setting, improved modeling methods for interpreting the biomonitoring data, and an increase in studies designed to associate health indicators and health risks to selected environmental chemicals are needed to increase the power of biomonitoring.

Biomarkers↗

PubMed2002

Variation in female mate choice within guppy populations: population divergence, multiple ornaments and the maintenance of polymorphism.

The evolutionary significance of variation in mate choice behaviour is currently a subject of some debate and considerable empirical study. Here, I review recent work on variation within and among guppy (Poecilia reticulata) populations in female mate choice and mating preferences. Empirical results demonstrate that there is substantial variation within and among populations in female responsiveness and choosiness, and much of this variation is genetic. Evidence for variation in preference functions also exists, but this appears to be more equivocal and the relative importance of genetic variation is less clear cut. In the second half of this review I discuss the potential significance of this variation to three important evolutionary issues: the presence of multiple male ornaments, the maintenance of polymorphism and divergence in mate recognition among populations. Studies of genetic variation in mate choice within populations indicate that females have complex, multivariate preferences that are able to evolve independently to some extent. These findings suggest that the presence of multiple male ornaments may be due to multiple female mating preferences. The extreme polymorphism in male guppy colour patterns demands explanation, yet no single satisfactory explanation has yet emerged. I review several old ideas and a few new ones in order to identify the most promising potential explanations for future empirical testing. Among these are negative frequency dependent selection, environmental heterogeneity coupled with gene flow, and genetic constraints. Last, I review the relative extent of within and among-population variation in mate choice and mating preferences in order to assess why guppies have not speciated despite a history of isolation and divergence. I argue that variation within guppy populations in mate choice and enhanced mating success of new immigrants to a pool are major impediments to population divergence of the magnitude that would be required for speciation to occur.

Animals↗

PubMed1991

Primary immune responses of selected small mammal species to heterologous erythrocytes.

1. We surveyed the primary humoral immune responsiveness of six small mammal species (Peromyscus leucopus, Microtus pinetorum, Perognathus hispidus, Neotoma floridana, Onychomys leucogaster, Mus musculus) collected from wild populations in central Oklahoma using sheep red blood cells (SRBC) as the immunogen and a splenic plaque-forming cell (PFC) assay. 2. Individuals within each wild species examined produced antibodies to a single intraperitoneal injection of SRBC, however, considerable interspecific and intraspecific variation in responsiveness was indicated. 3. Overall, primary immune responsiveness varied from 0 to 5013 PFC/10(6) cells. Spleen weights, total splenic nucleated cell yields, PFC/spleen, PFC/mg spleen, and PFC/10(6) cells were significantly different among species. 4. Mean cell yield in M. pinetorum was greater than in P. leucopus and CD-1 laboratory mice (included as positive controls). Number of PFC/10(6) cells was greater in CD-1 laboratory mice than P. hispidus and P. leucopus. The coefficient of variation for PFC/10(6) cells in CD-1 laboratory mice was 38% compared to 109, 129, and 56% for M. pinetorum, P. hispidus, and P. leucopus, respectively. 5. Interspecific and intraspecific differences among wild species may be a reflection of disparate life histories and other environmental selection pressures.

Animals↗

PubMed2001

Distribution of Nitrogen-Fixing Microorganisms along the Neuse River Estuary, North Carolina.

Nitrogen fixation genes (nifH) were amplified and sequenced from DNA extracted from surface water samples collected from six stations along the length of the Neuse River Estuary, North Carolina, in order to determine the distribution of nitrogen-fixing organisms in the transition from fresh- to saltwater. Nitrogenase genes were detected in all samples by a nested polymerase chain reaction method, and the amplification products from the upriver, midriver, and downriver stations were cloned, sequenced, and used for phylogenetic analysis. The composition of nifH clone libraries from upriver, midriver, and downriver stations (each composed of 14 randomly selected clones) were very diverse (samples from upriver and midriver stations were composed of 14 unique sequences, downriver station composed of 7 unique sequences) and differed among the stations. Some phylotypes were found at more than one station, but were usually found in the upriver and midriver stations or in the midriver and downriver stations, indicating that the phylotypes were probably transported along the river. Cyanobacterial nifH were not found at the most upriver site, but were a large fraction of sequences (50%) recovered from the downriver station, where nitrate concentration was an order of magnitude lower and salinity was higher. In contrast, g proteobacteria nifH sequences were much more common at the midriver and upriver sites (58% and 64%, respectively), compared to the downriver site (14%). Results indicate that substantially different nitrogen-fixing assemblages are present along the river, reflecting differential watershed hydrological inputs, sedimentation, and environmental selection pressures, along the salinity gradient.

Journal Article↗

PubMed1975

[Metabolism of rat liver in the electrostatic field and in the faraday cage before and after hepatectomy (author's transl)].

Investigations were performed with the aim of establishing the influence of various environmental conditions (such as steady field conditions, climatized laboratories, Faraday's cage) on a number of enzymic activities in the rat (including glutamic oxaloacetic tic transaminase, glutamic pyruvic transaminase, lactic dehydrogenase, gamma-glutamyl transpeptidase, acid phosphatase), as well as the serum concentrations of triglycerides, the oxygen consumption of hepatic parenchyma cells, and the influence on the incorporation of 3H-thymidine (following partial hepatectomy). In the steady field, the activities of the cytoplasmic enzymes (GOT, GPT, LDH) were higher then under Faraday conditions. The same applies both to the hepatic oxygen consumption and to the neutral fat serum levels. The control values always remained within the range of the results obtained under steady field or Faraday conditions. In the structure-linked enzymes (gamma-glutamyl transpeptidase, acid phosphatase) the results were not uniform. Following partial hepatectomy, and under steady field conditions, the serum triglyceride concentrations showed a less pronounced drop than they did in the controls. Under selected environmental conditions, the results obtained lie within the physiological range. The present findings, therefore, do not permit definite conclusions to be drawn on favourable or unfavourable effects exerted by the different types of electroclimates.

Acid Phosphatase↗

PubMed2006

Synthetic musk fragrances in environmental Standard Reference Materials.

Synthetic musk fragrances have been measured in water, air, sediments, sewage sludge, and biota worldwide. As the study of the environmental fate and impacts of these compounds progresses, the need for Standard Reference Materials (SRMs) for these compounds to facilitate analytical method improvement and interlaboratory comparisons becomes increasingly important. The National Institute of Standards and Technology (NIST) issues environmental matrix SRMs with certified concentrations for a variety of persistent organic pollutants including polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides, and polychlorinated biphenyl congeners (PCBs). Until now synthetic musk fragrance concentrations have not been reported in NIST SRMs. The objective of this study was to provide reference values for several commonly detected synthetic musk fragrances in several NIST natural matrix SRMs. In this study five polycyclic musk fragrances [HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-gamma-2-benzopyran), AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene), ADBI (4-acetyl-1,1-dimethyl-6-tert-butylindane), AHMI (6-acetyl-1,1,2,3,3,5-hexamethylindane), and ATII (5-acetyl-1,1,2,6-tetramethyl-3-isopropylindane] and two nitro musk fragrances [musk xylene (1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene) and musk ketone (4-tert-butyl-3,5-dinitro-2,6-dimethylacetophenone)] were measured in selected environmental SRMs. Gas chromatography-electron impact mass spectrometry (GC/EI-MS) was used for all analyses. HHCB was the most frequently detected synthetic musk fragrance and was detected in SRM 2585 Organic Contaminants in House Dust, SRM 2781 Domestic Sludge, SRM 1974b Organics in Mussel Tissue (Mytilus edulis), and SRM 1947 Lake Michigan Fish Tissue. It was not detected in SRM 1946 Lake Superior Fish Tissue or SRM 1945 Organics in Whale Blubber. Concentrations of HHCB in these SRMs ranged from 1.12 ng/g in SRM 1947 to 92,901 ng/g in SRM 2781. All of the polycyclic musk fragrances were detected in SRM 2781 and all of the target compounds were detected in SRM 2585.

Animals↗

PubMedDate not supplied

[Anopheline population genetics].

Population genetic studies of vectors are essential for (i) the determination of their taxonomic status and consequently the definition of their vectorial role in the transmission of pathogenic agents; (ii) the evaluation of the species genetic variability and the estimation of their capacities of adaptation to selection pressure; (iii) an estimation of gene flow among populations in order to evaluate their degree of isolation and gene circulation, especially resistance genes. Among the malaria vectors taken as examples on three continents, Africa, South-East Asia and Latin America, the large majority of the species showed an important polymorphism. The Gambiae Complex, which is by far the most studied one, includes at present 7 species with the recent description of An. quadriannulatus A and B from Ethiopia. An. gambiae s.s. includes itself 5 chromosomal forms. One of them, the Mopti form, should be considered as a species unto itself. For An. arabiensis, a strong differentiation has been observed among the populations from Senegal and the Indian Ocean Islands. The kdr mutation, which confers resistance to pyrethroid knockdown effect, has never been found either in the Mopti form, or An. arabiensis, indicating a restricted gene flow between these latter two and An. gambiae s.s. The speciation process of the Gambiae Complex seems to be a recent phenomenon due to environmental selection pressure. Species of the Funestus Group are distinguishable by morphological characters. The genetic study of An. funestus s.s. did not show the presence of a complex, in spite of high polymorphism and population structure. Anophelines from eastern areas present an important biodiversity. The Minimus Complex includes two species, A and C, which are widely distributed in South-East Asia. Species A is strongly endophilic, on the contrary species C is at once more exophilic and zoophilic. The latter species might have been selected by DDT indoor house spraying. After numerous taxonomic investigations, the Dirus Complex includes now 7 species. In Latin America, An. pseudopunctipennis clustered into three geographic populations which are under a speciation process. One covers North America and Guatemala, the other South America and Belize, whilst the last one is restricted to Grenada Island. On the contrary, An. darlingi showed little morphologic and genetic variability throughout the species geographic range suggesting the existence of a single species. The main objective of these studies is to implement a more selective approach of vector control programs in relation to the incriminated species, their bioecology and their role in malaria transmission. The improvement of efficiency and selectivity of vector control is becoming a major goal in order to make the best out of the available tools and control the impact of interventions on the environment.

Africa↗

PubMed2002

Distribution of environmentally regulated genes of Streptococcus suis serotype 2 among S. suis serotypes and other organisms.

The occurrence of 36 environmentally regulated genes of Streptococcus suis strain 10 among all 35 S. suis serotypes was determined by using hybridization with the amplified genes as probes. In addition, the distribution of these genes among the virulence phenotypes of serotypes 1 and 2 was assessed. Hybridization was also performed with various other streptococcal species and nonstreptococcal bacterial species which may be present in pigs. Interestingly, probe ivs-25/iri-1, similar to agrA and sapR, hybridized only with S. suis serotype 1 and 2 strains with virulent phenotypes and is therefore suitable as a diagnostic parameter. Only one probe was specific for S. suis. This probe's sequence was identical to the epf gene, a putative virulence factor of S. suis. Probe ivs-31 was similar to a virulence factor of S. suis, namely, a gene encoding a fibronectin- and fibrinogen-binding protein. This probe hybridized only with oral streptococci. Nearly half of the probes (45%) hybridized with the oral streptococci (S. oralis, S. milleri, S. sanguis, S. gordonii, and S. mitis) and with Streptococcus pneumoniae. This indicates a close relationship between S. suis, the oral streptococci, and S. pneumoniae with respect to the selected environmentally regulated genes. One probe only hybridized with gram-negative species and therefore seems to be obtained by S. suis from a gram-negative organism by horizontal transfer.

Animals↗

PubMed1998

Thermoregulatory responses to variations of photoperiod and ambient temperature in the male lesser mouse lemur: a primitive or an advanced adaptive character?

The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in ambient temperature, evaporative water loss (EWL), body temperature (Tb) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging from 5 degrees C to 35 degrees C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions. In both photoperiods, EWL, Tb and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 degrees C was associated with a decrease in Tb and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in Tb and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed according to daylength. Daily variations in Tb and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of Tb decrease with or without the occurrence of torpor (Tb < 33 degrees C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations.

Adaptation, Physiological↗

PubMed2005

Multilocus sequence analysis and comparative evolution of virulence-associated genes and housekeeping genes of Clostridium difficile.

A multilocus sequence analysis of ten virulence-associated genes was performed to study the genetic relationships between 29 Clostridium difficile isolates of various origins, hosts and clinical presentations, and selected from the main lineages previously defined by multilocus sequence typing (MLST) of housekeeping genes. Colonization-factor-encoding genes (cwp66, cwp84, fbp68, fliC, fliD, groEL and slpA), toxin A and B genes (tcdA and tcdB), and the toxin A and B positive regulator gene (tcdD) were investigated. Binary toxin genes (cdtA and cdtB) were also detected, and internal fragments were sequenced for positive isolates. Virulence-associated genes exhibited a moderate polymorphism, comparable to the polymorphism of housekeeping genes, whereas cwp66 and slpA genes appeared highly polymorphic. Isolates recovered from human pseudomembranous colitis cases did not define a specific lineage. The presence of binary toxin genes, detected in five of the 29 isolates (17 %), was also not linked to clinical presentation. Conversely, toxigenic A-B+ isolates defined a very homogeneous lineage, which is distantly related to other isolates. By clustering analysis, animal isolates were intermixed with human isolates. Multilocus sequence analysis of virulence-associated genes is consistent with a clonal population structure for C. difficile and with the lack of host specificity. The data suggest a co-evolution of several of the virulence-associated genes studied (including toxins A and B and the binary toxin genes) with housekeeping genes, reflecting the genetic background of C. difficile, whereas flagellin, cwp66 and slpA genes may undergo recombination events and/or environmental selective pressure.

Alleles↗

PubMed1994

Possible nosocomial transmission of Pseudomonas cepacia in patients with cystic fibrosis.

OBJECTIVE: To determine whether nosocomial transmission of Pseudomonas cepacia occurred at a hospital with endemic P cepacia infection of patients with cystic fibrosis. DESIGN: Two retrospective case-control studies. SETTING: A large pediatric cystic fibrosis center. PARTICIPANTS: To assess risk factors for acquisition of P cepacia, 18 cases, defined as any patient with cystic fibrosis with first documented isolation of P cepacia in 1988 or 1989, were compared with 18 matched P cepacia-negative controls with cystic fibrosis. To assess potential modes of nosocomial P cepacia transmission, 14 cases with a hospitalization(s) between their last P cepacia-negative culture and first P cepacia-positive culture were compared with 14 hospitalized P cepacia-negative controls with cystic fibrosis. METHODS: Handwiping cultures (N = 68) and selective environmental cultures were performed. MAIN RESULTS: Cases tended to be more likely than controls to have been hospitalized at the cystic fibrosis center in the 3 months before their first P cepacia-positive culture (P = .08). In addition, cases tended to be more likely than hospitalized controls with cystic fibrosis to have had a P cepacia-positive roommate (P = .06) before becoming colonized with P cepacia organisms. Pseudomonas cepacia was cultured from the hands of two individuals: a P cepacia-colonized patient who had just undergone chest physiotherapy and consequent coughing and the investigator who shook the P cepacia-positive patient's hand after the patient's procedure. CONCLUSIONS: These results suggest that in this cystic fibrosis center, hospitalization is a risk factor for P cepacia acquisition and that person-to-person transmission of P cepacia may occur in the hospital via hand contact.

Adolescent↗

PubMed1977

Differences in the collagen types synthesized by lapine articular chondrocytes in spinner and monolayer culture.

In five different secondary monolayer cultures of rabbit articular chondrocytes, 72-89% of the the collagen synthesized was Type 1, as determined by alpha chain separation and CNBr-cleavage peptide analysis. When sister cells were transferred to spinner bottles after primary monolayer culture growth, 88% of the collagen formed in four separate experiments was Type II. A reversion to Type I collagen synthesis occurred when the spinner-cultured cells were returned to monolayer flasks. The change in the species of collagen depended on the suspension condition and not on the low Ca2+ content (0.33 mM) of the spinner medium. These findings parallel the switch to phenotypic glycosaminoglycan synthesis that also occurs when monolayer-cultured cells are transferred to spinner bottles. Whether this phenomenon arises through a genetic control mechanism rather than environmental selection for particular cohorts of cells has not yet been determined.

Animals↗