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Biomedical subjects

J A Kramer

Publications and source records attributed to J A Kramer.

At least 19 recordsLinked to original sources
PubMed2001

Estrogen protects against hypertension in the spontaneously hypertensive rat, but its protective mechanism is unrelated to impaired arterial muscle relaxation.

OBJECTIVES: To determine if estrogen acutely and directly alters arterial muscle relaxation, if estrogen is responsible for gender dichotomy in hypertension, and if arterial muscle from female spontaneously hypertensive rats (SHR) is slow to relax as is muscle from male SHR compared with arterial muscle of normotensive Wistar-Kyoto rats (WKY). METHODS: Relaxation rates of isometrically contracted arterial muscle from male rats were measured before and after addition of beta-estradiol. Blood pressure (BP) was monitored in intact male and female SHR and WKY and in ovariectomized and estrone-treated ovariectomized SHR and WKY. Relaxation rates of maximum isometric contractions of arterial muscle excised from male SHR and WKY and female SHR and WKY with varying chronic estrogen status were measured. RESULTS: Beta-estradiol had no direct, acute effect on arterial muscle force or relaxation. Intact and estrone-implanted SHR females had significantly lower BP than males. Ovariectomized SHR developed high BP equivalent to that of males. Arterial relaxation was slower in both male and female SHR compared with WKY. CONCLUSIONS: Estrogen lowers BP in female SHR. Strain differences in relaxation rates are independent of gender and estrogen status. Estrogen has no effect on arterial muscle relaxation, suggesting another mechanism for the protective effect of estrogen in hypertension.

Analysis of Variance↗
PubMed2000

Human spermatogenesis as a model to examine gene potentiation.

The first tier of control over the expression of genic domains utilizes chromatin structure. Before the onset of transcription, the chromatin domain that encompasses the gene(s) must assume an open conformation. This renders large segments of the genome available to the tissue-specific and ubiquitous trans-factors necessary for proper expression of the genes present. This process has been termed potentiation. It is a necessary obligate, but alone it is not sufficient for gene expression. Spermatogenesis, the development of a viable fertile male gamete, provides a unique model to begin to address the underlying mechanism(s) governing differentiation and tissue-specific gene expression. Male gametogenesis is typified by the activation of numerous genes whose products have novel functions, as well as testis-specific forms of constitutively expressed somatic genes. We have shown that mouse spermatogenesis represents a selective potentiative process (Kramer et al., 1998: Development 125:4749-4655), but little is known about its human counterpart. To fill this void we have examined the potentiative state of several spermatid-expressed genes during the latter stages of human spermatogenesis. We have shown that spermatidexpressed genes are potentiated by the pachytene stage of differentiation. Furthermore, we establish that a chromatin domain functions as a discrete structural unit during differentiation. Interestingly, some of these open structures are maintained in the mature spermatozoon.

Acrosin↗
PubMed2000

Randomised trial of paclitaxel versus doxorubicin as first-line chemotherapy for advanced breast cancer: quality of life evaluation using the EORTC QLQ-C30 and the Rotterdam symptom checklist.

The aim of the study was to compare the quality of life (QL) of patients treated with single-agent paclitaxel versus doxorubicin as first-line chemotherapy for advanced breast cancer. 331 patients with advanced breast cancer were randomised, with 294 eligible for analysis. Patients completed both the EORTC QLQ-C30 questionnaire and the Rotterdam Symptom Checklist (RSCL) with six additional items, at baseline and after the third, fifth and seventh cycles of chemotherapy. A significant difference in progression-free survival in favour of doxorubicin caused a bias in the data with differences in expected completion rates of questionnaires beyond cycle three. Therefore, statistical comparisons were performed only for the first three cycles. Baseline compliance was 64% and 61% for the QLQ-C30 and RSCL questionnaires, respectively. Doxorubicin was associated with significantly more nausea/vomiting (P=0.001), loss of appetite (P=0.010) and a greater burden of disease and treatment (P=0.044), but with less bone pain (P=0.042) and rash (P=0.045) than paclitaxel. Both treatments were associated with improved emotional function and reduction in psychological distress at cycle 3. Longitudinal data suggested that doxorubicin was associated with less pain, specifically bone pain. Doxorubicin was more active but may have had more side-effects during the first three cycles. Long-term QL outcomes could not be assessed.

Antineoplastic Agents↗
PubMed2000

Identification and interpretation of clinical and quality of life prognostic factors for survival and response to treatment in first-line chemotherapy in advanced breast cancer.

The aim of the project was to identify clinical and quality of life (QL) factors that together predict survival and response to chemotherapy in advanced breast cancer. Potential prognostic factors were studied in 187 women with baseline QL data from a trial of paclitaxel versus doxorubicin as first-line chemotherapy. Demographic and clinical factors studied were age, performance status, dominant site of disease and preceding disease-free interval (DFI). Factors from the EORTC QLQ-C30 were all function scales, fatigue, nausea/vomiting, pain, dyspnoea, insomnia, loss of appetite and global QL. The proportional hazards regression model with stratification for treatment, and the logistic regression model adjusting for treatment arm were used for univariate and multivariate analyses of survival and response to treatment, respectively. For survival, multiple sites of visceral disease, pain, global QL and fatigue were significant prognostic factors in the univariate analysis. The final multivariate model predicted poor survival with multiple sites of visceral disease (P=0.003), DFI </=2 years (P=0.026) and pain (P=0.003). For response, age, dyspnoea, fatigue and global QL were significant predictive factors in the univariate analysis. The final multivariate model for response selected DFI (P=0.009), multiple sites of visceral disease (P=0.037) and dyspnoea (P=<0.001) using forward selection, but model instability was indicated by the inclusion of fatigue and emotional function in the final model when backward selection was used. In addition to known clinical factors, patient-assessed QL variables appear to be prognostic for survival and response to chemotherapy in women with advanced breast cancer. However, identification of prognostic factors from responses to questionnaires may be unstable, and their reliability and clinical utility should be tested prospectively.

Adolescent↗
PubMed1999

Reprogramming the male gamete genome: a window to successful gene therapy.

Hematopoiesis and spermatogenesis both initiate from a stem cell capable of renewal and differentiation. Each pathway reflects the expression of unique combinations of facultative, i.e. tissue-specific and constitutive, i.e. housekeeping, genes in each cell type. In spermatogenesis, as in hematopoiesis, commitment is mediated by the mechanism of potentiation whereby specific chromatin domains are selectively opened along each chromosome. Within each open chromatin domain, a unique battery of gene(s) is availed to tissue-specific and ubiquitous transacting factors that are necessary to initiate transcription. In the absence of an open domain, trans-factor access is denied, and the initiation of transcription cannot proceed. Cell-fate is thus ultimately defined by the unique series of open-potentiated cell-specific chromatin domains. Defining the mechanism that opens chromatin domains is fundamental in understanding how differentiation from stem cells is controlled and whether cell-fate can be modified. A recent examination of the mammalian spermatogenic pathway [Kramer, J.A., McCarrey, J.M, Djakiew, D., Krawetz, S.A., 1998. Differentiation: the selective potentiation of chromatin domains. Development 125, 4749-4755] supports the view that cell fate is mediated by global changes in chromatin conformation. This stride underscores the possibility of moderating differentiation through chromatin conformation. It is likely that gene therapeutics capable of selectively potentiating individual genic domains in populations of differentiating and/or replicating cells that modify cellular phenotype will be developed in the next millennium.

Animals↗
PubMed1999

Temporal expression of the transgenic human protamine gene cluster.

OBJECTIVE: To ascertain the fidelity of expression of the genes from the transgenic human sperm-specific nuclear packaging protamine-1-->protamine-2-->transition protein-2 (PRM1-->PRM2-->TNP2) locus. DESIGN: Controlled human transgene study. SETTING: Basic science laboratory. ANIMAL(S): Age-matched transgenic and nontransgenic mice. INTERVENTION(S): Transgenic mice containing the human protamine locus were mated. One testis from each offspring was frozen at -80 degrees C and the other was preserved in formalin. MAIN OUTCOME MEASURE(S): The temporal expression of the human and mouse protamines was evaluated by Northern blot analysis. Orientation of the transgenic locus was determined by Southern blot analysis. Tissue morphology was assessed histologically. RESULT(S): Conservation of transgenic morphology was confirmed. Head-to-tail integration of the PRM1--> PRM2-->TNP2 locus was shown. Temporal expression of the mouse and human protamine genes was maintained in the transgenic state. CONCLUSION(S): These results show that the head-to-tail concatomer of the PRMI-->PRM2-->TNP2 locus contains all the necessary elements for appropriate temporal expression while maintaining testicular structure and function.

Aging↗
PubMed1998

Genesis of a novel human sequence from the protamine PRM1 gene.

The members of the male haploid expressed protamine 1 (PRM1)-->protamine 2 (PRM2)-->transition protein 2 (TNP2) locus exist as a single, coordinately expressed genic domain. Previous analysis has revealed that the genes within the human PRM1-->PRM2-->TNP2 domain are inter-related, as they share significant sequence similarity at both the nucleotide and amino acid levels. Analysis described here supports the view that a fourth candidate coding region, gene4/Prm3, was derived from PRM1 during the genesis of the PRM1-->PRM2-->TNP2 domain. In some species, gene4 has diverged to a great extent, which can limit its expression.

Animals↗
PubMed1998

A matrix associated region localizes the human SOCS-1 gene to chromosome 16p13.13.

The MarFinder algorithm was applied to a newly sequenced segment of 16p13.13 abutting the 3' end of the human PRM1-->PRM2-->TNP2 locus. A candidate region of matrix attached was identified. Subsequent biophysical analysis showed that this region was attached to the somatic nuclear matrix. Nucleotide sequence analysis also revealed the presence of a CpG island. Data base queries showed that this region contained the SOCS-1 gene. Thus, the SOCS-1 gene is bounded by a somatic MAR and is just 3' of the spermatid-expressed PRM1-->PRM2-->TNP2 domain at position 16p13.13.

Carrier Proteins↗
PubMed1998

Centromere sequences localize to the nuclear halo of human spermatozoa.

Chromatin is organized into a series of discrete nuclear matrix-associated and non-nuclear matrix-associated domains. The non-matrix-associated domains consist of loops of DNA that are attached to the proteinaceous nuclear matrix by matrix-associated regions (MARs). Although this organization is well characterized in somatic cells, comparatively little is known of this mode of organizing the genome in the human sperm nucleus. To define this relationship, the interaction of human sperm chromatin with the nuclear matrix was assessed by fluorescence in situ hybridization using specific alpha satellite probes directed to the centromeric regions of chromosomes 13 plus 21 and 18. Hybridization of the centromeric sequences was visualized as segmented, bundled structures that extended from the nuclear core into the halo.

Cell Nucleus↗
PubMed1998

Differentiation: the selective potentiation of chromatin domains.

Potentiation is requisite for the expression of our genome. It is the mechanism of opening chromatin domains to render genes accessible to tissue-specific and ubiquitous transacting-factors that enables transcription. The results presented in this study demonstrate that modulation of stage- and cell-type-specific gene expression during mammalian spermatogenesis involves selective potentiation of testis-expressed genes that reverses their repressive state when present in the spermatogonial stem cell. This directly contrasts hematopoiesis, which acts to selectively restrict lineage potential during differentiation from its permissive stem cell. These results are key to understanding how differentiative pathways are controlled and cellular phenotypes determined. A window to their modulation is presented.

Aging↗
PubMed1997

Mathematical model to predict regions of chromatin attachment to the nuclear matrix.

The potentiation and subsequent initiation of transcription are complex biological phenomena. The region of attachment of the chromatin fiber to the nuclear matrix, known as the matrix attachment region or scaffold attachment region (MAR or SAR), are thought to be requisite for the transcriptional regulation of the eukaryotic genome. As expressed sequences should be contained in these regions, it becomes significant to answer the following question: can these regions be identified from the primary sequence data alone and subsequently used as markers for expressed sequences? This paper represents an effort toward achieving this goal and describes a mathematical model for the detection of MARs. The location of matrix associated regions has been linked to a variety of sequence patterns. Consequently, a list of these patterns is compiled and represented as a set of decision rules using an AND-OR formulation. The DNA sequence was then searched for the presence of these patterns and a statistical significance was associated with the frequency of occurrence of the various patterns. Subsequently, a mathematical potential value,MAR-Potential, was assigned to a sequence region as the inverse proportion to the probability that the observed pattern population occurred at random. Such a MAR detection process was applied to the analysis of a variety of known MAR containing sequences. Regions of matrix association predicted by the software essentially correspond to those determined experimentally. The human T-cell receptor and the DNA sequence from the Drosophila bithorax region were also analyzed. This demonstrates the usefulness of the approach described as a means to direct experimental resources.

Base Sequence↗
PubMed1997

The use of cloned repetitive sequences as hybridization competitors to detect single copy sequences.

To suppress background hybridization due to repetitive sequence elements, competitor Alu containing clones were isolated from a subclone library of human cosmid clone hP3.1. Pre-annealing of the probe-with this competitor increased the signal well above background. In comparison, the addition of the competitor directly to both the prehybridization and hybridization solution was more effective in reducing background. This dramatically increased the signal to noise ratio of the specific hybridization event. Application to fluorescent in situ hybridization (FISH) is readily apparent.

Binding, Competitive↗
PubMed1997

Lysyl oxidase, cellular senescence and tumor suppression.

Replicative senescence may provide a mechanism of tumor suppression and tumor suppressor genes of the extracellular matrix, like lysyl oxidase, may play a role in cellular senescence. To test this hypothesis and determine whether the extracellular matrix may serve as a marker, the steady-state levels of human lysyl oxidase, alpha-I type III collagen and beta-actin transcripts were assessed in various cell lines during in vitro passage. Northern hybridization analysis showed a significant increase in the levels of progeria fibroblast extracellular matrix mRNAs immediately preceding senescence. The levels of these mRNAs were unaffected in age-matched normal fibroblast and fetal fibroblast cell lines.

Actins↗
PubMed1997

Genetic testing for male infertility: a postulated role for mutations in sperm nuclear matrix attachment regions.

Numerous reports have suggested that disturbances in nuclear condensation may result in male infertility. This notion has been supported by the observation of infertile individuals with a decrease or absence of the male sperm-specific chromatin packaging protamine proteins. To date, no correlation between the absence of protamine proteins and a mutation within the coding regions of the protamine genes has been documented. To address this issue, PCR-based mutation scanning analysis has been performed across the human male haploid expressed PRM1-->PRM2-->TNP2 domain in several oligozoospermic infertile individuals. This analysis identified a candidate mutation in a region of contact with the sperm nuclear matrix from 2 of 5 affected individuals. This is the first report of a mutation scan covering the entire PRM1-->PRM2-->TNP2 locus in affected individuals.

Chromosomal Proteins, Non-Histone↗
PubMed1997

RNA in spermatozoa: implications for the alternative haploid genome.

The presence of specific messenger RNAs in the nuclei of mature mammalian spermatozoa has been demonstrated by several independent laboratories. Others have suggested that various polymerases may also be active in mature spermatozoa. This has led to the notion that the 'sleeping' genome may not be so quiescent after all. The alternate use of somatic-like nucleosomal and haploid protamine packaging structures to assemble sperm chromatin and the ordered array of chromosomes within the mature human sperm nucleus support this view. This had led us to address the issue of whether a somatic-like organization of select regions of the paternal genome and the mRNAs present in spermatozoa were correlated. Results from this and other laboratories suggest that this in indeed the case. Potential roles for this novel packaging and the accumulation of transcripts within the mature human nucleus are discussed.

Animals↗