Biomedical subjects

S R Grimes

Publications and source records attributed to S R Grimes.

At least 19 recordsLinked to original sources

PubMed1992

Tissue-specific binding of testis nuclear proteins to a sequence element within the promoter of the testis-specific histone H1t gene.

The rat histone H1t gene is transcribed only in testis germinal cells. This testis-specific chromosomal protein is first synthesized during spermatogenesis in pachytene spermatocytes and the entire complement of testis histones is replaced during the midspermatid stage of spermiogenesis by positively charged transition nuclear proteins TP1 and TP2. Mobility shift assays conducted using crude nuclear protein extracts from different tissues and an 18-bp DNA sequence element within the H1t promoter as a probe reveal binding only with nuclear proteins from testis. The binding is specifically competed with an excess of the same unlabeled DNA fragment but not with heterologous competitors. A larger oligonucleotide corresponding to the same sequence element plus 18 bp of the adjacent downstream H1/CCAAT element binds nuclear proteins from all tissues tested, but a unique low mobility band is formed only with testis extracts. Protein-DNA crosslinking experiments reveal that two major polypeptides with molecular weights of approximately 13 and 30 kDa bind to the 18-bp H1t promoter sequence element. This strong correlation between the tissue where the H1t gene is transcribed and the presence of testis-specific nuclear proteins that bind to a sequence element within the testis histone H1t promoter supports the possibility that these DNA-binding proteins may participate in formation of an active transcription initiation complex with the testis H1t promoter.

Animals↗

PubMed1992

Temporal correlation between the appearance of testis-specific DNA-binding proteins and the onset of transcription of the testis-specific histone H1t gene.

The histone H1t gene is transcribed only in testis. Northern blot analyses reveal that transcription of the H1t gene occurs first in pachytene primary spermatocytes. Thus, there is a temporal correlation between onset of transcription of the gene and synthesis of histone H1t in primary spermatocytes during spermatogenesis. Previous studies revealed that replacement of most H1t and core histones occurs during the midspermatid stage of spermiogenesis by transition proteins TP1 and TP2. In this paper we extend our study of the specific binding of testis nuclear proteins to a unique sequence element within the H1t promoter. The relatively tight binding is competed with an excess of homologous DNA but not with a mutated element. Testis proteins from prepubertal animals do not bind to the 18-bp promoter element out proteins from enriched populations of primary spermatocytes do bind. Therefore, the temporal correlation between onset of transcription of the H1t gene and the time when the specific H1t promoter-binding proteins are detected in primary spermatocytes suggests that the DNA-binding proteins might be germinal cell-specific transcription factors that participate in formation of an active H1t transcription initiation complex. These studies present the first analysis of binding sites for testis nuclear proteins from primary spermatocytes within the promoter of a gene expressed only during this stage of spermatogenesis.

Animals↗

PubMed1992

Indolent orbital apex syndrome caused by occult mucormycosis.

The chronic or indolent presentation of rhino-orbital mucormycosis, as defined by the presence of symptoms for more than 1 month before diagnosis, is extremely unusual. A 45-year-old man with stable diabetes presented with a right orbital apex syndrome and minimal ethmoid and sphenoid sinusitis. Progression was indolent, and the diagnosis was not made until 7 weeks after admission, when a third biopsy was prompted by new cavernous sinus and carotid artery thromboses. Mucormycosis was found. The patient improved on amphotericin B (2 g) and strict blood glucose control. A remarkable aberrant regeneration of the right oculomotor nerve was seen following treatment. He remains free of active disease 4 years later. Orbital symptoms in well-controlled diabetics, which may even remain stable for weeks and lack direct signs of tissue invasion, should raise the suspicion of mucormycosis.

Carotid Artery Thrombosis↗

PubMed1992

Effect of povidone-iodine irrigation on the preoperative chemical preparation of the eye.

Preoperative eyes which had been treated with gentamicin for one-half day were subjected to one of two povidone-iodine (PI) preparations. The control eye was prepared using a previously described 5% PI one-drop technique, while the paired eye was irrigated with a 0.02% PI solution. Aerobic and anaerobic bacterial cultures were taken of each eye before and after PI applications. Statistical analysis of the data indicates that both techniques were equally effective in reducing surface colonization of the anaerobic cocci and bacilli, the viridans streptococci and micrococci. Both methods were also equally ineffective in reducing the numbers of coagulase-negative staphylococci from the surface of the eye. With the apparent emergence of gentamicin-resistant coagulase-negative staphylococci the potential for staphylococcal endophthalmitis is increasing.

Colony Count, Microbial↗

PubMed1991

Protein-DNA interactions within the rat histone H4t promoter.

The histone H4t gene is actively transcribed in rat testis germinal cells and in several non-testis cell types including cells from liver. This histone H4 gene is expressed most actively in testis premeiotic pachytene spermatocytes, and its expression is down-regulated in postmeiotic early spermatids. The histone H4 gene promoter is functional as demonstrated by finding significant levels of chloramphenicol acetyltransferase (CAT) mRNA in mammalian cells transiently transfected with a histone H4-promoted CAT expression vector compared to cells transfected with an expression vector lacking of the promoter. Examination of the proximal promoter of the histone H4 gene by electrophoretic mobility shift assays indicates that specific protein-DNA interactions occur when pachytene spermatocyte nuclear proteins are mixed with promoter fragments containing regions designated site I and site II, consensus sequence elements essential for regulating transcription of the histone H4 gene. These specific protein-DNA interactions are eliminated by competition with identical DNA fragments, but are not eliminated by competition with nonhomologous DNA fragments. Significant differences are found in mobility shift patterns upon comparison of nuclear proteins from germinal cell populations enriched in pachytene spermatocytes where the gene is actively expressed and early spermatids where the gene is not expressed.

Amino Acid Sequence↗

PubMed1991

Preoperative antibiotic and povidone-iodine preparation of the eye.

We compared gentamicin 0.3% one drop every three hours the night before and the morning of surgery ("half-day regimen") with the same drug one drop qid for three days ("three-day regimen") in 15 eyes undergoing intraocular surgery. Conjunctival cultures of both groups taken before povidone-iodine preparation showed mean colony counts of 3.67 +/- 0.82 in the half-day regimen versus 1.0 +/- 0.43 in the three-day regimen. Conjunctival cultures taken after the administration of a povidone-iodine 5% preparation showed 7.17 +/- 3.52 and 2.75 +/- 0.88, respectively, in the two groups. Although there was a statistical difference in colony counts, topical gentamicin 0.3% given the night before and day of surgery had comparable low colony counts with the three-day course. The 5% povidone-iodine solution was not effective in reducing bacterial flora although it did eliminate all fungal colonies.

Bacteria↗

PubMed1990

Structural and functional analysis of the rat testis-specific histone H1t gene.

A 6.86 kb rat genomic DNA fragment containing the testis-specific histone H1t gene and the histone H4t gene has been sequenced. S1-nuclease protection analyses of total cellular RNA from rat liver and testis showed that histone H1t mRNA was present only in testis. Examination of various highly enriched populations of rat testis cell types revealed that H1t mRNA was found exclusively in a fraction enriched in pachytene spermatocytes. When protein, DNA interactions within the proximal promoter region of the histone H1t gene were examined by electrophoretic mobility shift assays, only minor differences were found in mobility shift patterns of the H1t promoter in assays comparing binding of nuclear proteins from pachytene spermatocytes and early spermatids. However, major differences in binding were observed upon comparing nuclear proteins from rat pachytene spermatocytes to liver. Comparison of binding patterns of rat testis, rat hepatoma H4 cells, HeLa cells, and COS-1 cells also revealed dramatic differences. Transcriptional activity of the histone H1t promoter was examined by measuring H1t promoted chloramphenicol acetyltransferase (CAT) mRNA levels in transient expression assays in transfected rat hepatoma H4 cells, HeLa cells, and COS-1 cells. These assays revealed that the histone H1t promoted CAT gene functioned poorly in HeLa cells and COS-1 cells compared to expression with the parent SV40 promoted vector pSV2CAT. The H1t promoted CAT gene apparently did not work at all in transfected rat hepatoma H4 cells, which is consistent with testis germinal cell specific expression of the histone H1t gene.

Animals↗

PubMed1990

Modifications of protein-DNA interactions in the proximal promoter of a cell-growth-regulated histone gene during onset and progression of osteoblast differentiation.

A temporal sequence of interrelated cellular, biochemical, and molecular events which occurs during the progressive expression of the differentiated osteoblast phenotype in primary cultures of fetal rat calvarial cells results in the development of a bone-tissue-like organization. This ordered developmental sequence encompasses three periods: proliferation, matrix maturation, and mineralization. Initially, the cells actively proliferate and synthesize type I collagen. This is followed by a period of matrix organization and maturation and then by a period of extracellular matrix mineralization. At the completion of proliferation, when expression of osteoblast phenotype markers such as alkaline phosphatase is observed, the cell-cycle-related histone genes are down-regulated transcriptionally, suggesting that a key signaling mechanism at this transition point involves modifications of protein-DNA interactions in the regulatory elements of these growth-regulated genes. Our results demonstrate that there is a selective loss of interaction of the promoter binding factor HiNF-D with the site II region of an H4 histone gene proximal promoter that regulates the specificity and level of transcription only when the down-regulation of proliferation is accompanied by modifications in the extracellular matrix that contribute to progression of osteoblast differentiation. Thus, this specific loss of protein-DNA interaction serves as a marker for a key transition point in the osteoblast developmental sequence, where the down-regulation of proliferation is functionally coupled to the appearance of osteoblast phenotypic properties associated with the organization and maturation of an extracellular matrix that becomes competent to mineralize.

Animals↗

PubMed1989

Comparison of the structural organization and expression of germinal and somatic rat histone H4 genes.

A rat somatic histone H4 gene was isolated by screening a rat genomic library using a cloned cell-cycle-regulated human histone H4 gene as a probe. The somatic histone H4 gene was subcloned and the nucleotide sequence was determined. The structural organization and expression of the somatic histone H4 gene and the rat germinal histone H4t gene were compared. Although the predicted amino-acid sequences of the two histones were identical, 49 out of 102 codons differed. The leader sequence of the germinal histone H4t mRNA was 17 bases compared to 40 bases for the somatic histone H4 mRNA, and the 3' terminal sequence of the germinal histone H4t mRNA was 52 bases compared to 75 bases for the somatic histone H4 mRNA. The germinal histone H4 gene also lacked a consensus purine-rich motif which was present in the 5' noncoding region of the somatic histone H4 gene. Northern blot analyses and S1-nuclease protection analyses revealed that the germinal histone H4t and H1t genes were expressed during spermatogenesis in rat pachytene spermatocytes, and the somatic histone H4 gene was expressed only in nongerminal rat cells and tissues. The histone H4t gene was also expressed in some other rat cell types. The differences in expression of the histone H4t and H1t genes may reflect differences in transcription, differences in turnover rates of the mRNAs, or a combination of these factors.

Amino Acid Sequence↗

PubMed1987

Gut-associated lymphoid tissue as source of an IgA immune response in respiratory tissues after oral immunization and intrabronchial challenge.

Most IgA plasma cells in the digestive tract are thought to derive from gut-associated lymphoid tissue, whereas IgA plasma cells in the respiratory mucosa are thought to originate largely in bronchus-associated lymphoid tissue. However, previous work has also shown that IgA antibodies to gut antigens can be detected in immunocytes of the bronchial mucosa and in bronchial secretions after appropriate stimulation via the gut. To analyze the cellular origin of such respiratory antibodies, mice were orally immunized with ferritin for 40 days and then segregated for intrabronchial challenge as follows: one group was given saline, another group Formalin-fixed Escherichia coli as a nonspecific challenge, and a third group ferritin. Lungs and intestines from these animals were then examined by immunofluorescence for the presence of plasma cells containing particular isotypes of antibody to ferritin. Animals fed ferritin and given saline or E. coli intrabronchially showed a greater than 6-fold increment in IgA antiferritin plasma cells in the bronchial mucosa, compared to animals which had not received ferritin, whereas orally immunized animals challenged intrabronchially with ferritin showed a greater than 15-fold increase. In other experiments, ferritin-naive animals transfused with mesenteric node cells that were obtained from donors that had been orally immunized with ferritin and were already committed to IgA production showed a 4-fold or greater increase in IgA antiferritin plasma cells in respiratory mucosa after intrabronchial challenge with ferritin when compared to recipients of peripheral node cells from the same donors or to recipients of mesenteric node cells that had not been specifically boosted intrabronchially. These results suggest that immunologically specific IgA immunocytes from gut-associated lymphoid tissue can migrate to the respiratory mucosa after oral immunization, and that migration and/or local cell division are enhanced by subsequent intrabronchial challenge. In providing further evidence for interrelations between gut-associated and bronchus-associated lymphoid tissue, the findings lend added support to the overall concept of a generalized secretory immune system.

Administration, Oral↗

PubMed1986

Nuclear proteins in spermatogenesis.

Mammalian somatic type histone variants are replaced or supplemented in early primary spermatocytes and possibly spermatogonia by testis specific and testis enriched histone variants. The testis complement of histones is replaced entirely by transition basic proteins in mid-spermatids. This transition is accompanied by a dramatic reduction of thermal stability of mid-spermatid chromatin which may be due in part to hyperacetylation of histone H4. The transition basic proteins are replaced by protamines which are arginine-rich and contain cysteine.

Animals↗

PubMed1985

Changes in the structural organization of chromatin during spermatogenesis in the rat.

In this study, histone H4 was shown to be extensively hyperacetylated in mid-spermatids of the rat during the time period when the entire complement of histones is replaced by basic spermatidal transition proteins. The degree of hyperacetylation of histone H4 was minimal in pachytene spermatocytes. Therefore, the hyperacetylation appears to be directly involved in the histone replacement process late in spermatogenesis in mid-spermatids. In order to investigate further the possible effects of histone H4 hyperacetylation and the other dramatic changes in the nuclear proteins on the structure of chromatin in germinal cells, we examined the thermal denaturation profiles of chromatin from various purified germinal cell types. Our analyses revealed that chromatins from pachytene spermatocytes and early spermatids have similar thermal denaturation profiles, with their major thermal transitions slightly lower than those for rat liver. However, the major thermal transitions for chromatin from mid-spermatids are much lower than those from pachytene spermatocytes and early-spermatids. We propose that the greatly lowered thermal stability of mid-spermatid chromatin represents a dramatic relaxation or decondensation of the chromatin in this cell type in preparation for the replacement of histone by the basic spermatidal transition proteins and that the decondensation is due in large part to the extensive histones hyperacetylation which occurs in these cells.

Acetylation↗

PubMed1978