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Biomedical subjects

G Grossman

Publications and source records attributed to G Grossman.

At least 19 recordsLinked to original sources
PubMed2002

Dynamics of testicular germ cell proliferation in normal mice and transgenic mice overexpressing rat androgen-binding protein: a flow cytometric evaluation.

Transgenic mice carrying rat androgen-binding protein (ABP) genomic DNA express high amounts of testicular ABP and develop a progressive impairment of spermatogenesis. To understand the mechanism of these changes, we have studied the pattern of testicular germ cell proliferation from 7 to 360 days of age in wild-type (WT) control and transgenic homozygous (ABP-TG) mice by flow cytometry after labeling DNA in isolated germ cells with propidium iodide. At all ages studied, the body weight of the ABP-TG mice was lower than that of age-matched WT controls. Significantly reduced testicular weight and total germ cell number in the ABP-TG mice were evident from Day 30 and Day 60, respectively. Flow cytometric analysis of isolated germ cells revealed that the number of germ cells undergoing proliferation (S-phase cells) was identical in WT control and ABP-TG mice up to Day 14. Subsequently, the number of germ cells in S-phase was consistently higher in ABP-TG than in WT mice. The number of primary spermatocytes was significantly increased starting from Day 60, and the numbers of round and elongated spermatids were significantly reduced in the ABP-TG animals from Day 21 and Day 60 onwards, respectively. Immunocytometry for intracellular ABP at 90 days of age revealed that the percentage of ABP-containing germ cells was greater in ABP-TG than in WT mice. The continuous presence of ABP in mouse seminiferous tubules at greater than physiological concentrations facilitates the formation of primary spermatocytes but impairs subsequent transformation to round and elongated spermatids. Based on our observations and the analysis of the available literature, the most likely mechanism for production of these effects is sustained reduction in the bioavailability of androgens.

Aging↗
PubMed2001

A three-generational study comparing the families of supportive and unsupportive mothers of sexually abused children.

This three-generational study investigated family histories of attachment relationships and abusive experiences as well as current functioning of family members that differentiate supportive from unsupportive mothers of sexually abused children. Interviews and standardized adult and child measures were administered to a sample, including (a) 99 nonoffending African American mothers and their children aged 4 to 12 years, of whom 61 mothers were classified as supportive and 38 were classified as unsupportive, and (b) 52 grandmothers, of whom 33 were the mothers of supportive mothers and 19 were the mothers of unsupportive mothers. The authors' findings indicate that a history of conflicted and/or disrupted attachment relationships between grandmother and mother, and mother and child, and less support provided by the grandmother to the child characterize families in which sexually abused children do not receive maternal support. Also, nonsupportive mothers showed more substance abuse, criminal behaviors, and problematic relationships with male partners.

Adult↗
PubMed2001

Primate epididymis-specific proteins: characterization of ESC42, a novel protein containing a trefoil-like motif in monkey and human.

Epididymal secreted proteins promote sperm maturation and fertilizing capacity by interacting with sperm during passage through the epididymis. Here we investigate the molecular basis of sperm maturation by isolating cDNA clones for novel epididymis-specific expressed sequences. Thirty-six novel cDNAs were isolated and sequenced from a subtracted Macaca mulatta epididymis library. The clones encode proteins with a range of motifs characteristic of protein-modifying enzymes, protease inhibitors, hydrophobic ligand-binding and transport proteins, extracellular matrix-interacting proteins, and transcription regulatory factors. The full length coding sequences were obtained for 11 clones representing a range of abundance levels. Expression of each is regionally localized and androgen regulated. The most abundant, ESC42, contains a cysteine-rich region similar to the signature binding domain of the trefoil family of motogenic wound repair proteins. The monkey and human proteins are nearly 90% identical. Immunohistochemical staining revealed that the protein is most abundant in the epithelium of the caput and is also present in the lumen and bound to sperm. The ESC42 gene, located on chromosome 20q11, contains two exons encoding two nearly identical predicted signal peptides and a third exon encoding the rest of the protein.

Amino Acid Sequence↗
PubMed2000

HE2beta and HE2gamma, new members of an epididymis-specific family of androgen-regulated proteins in the human.

HE2 is an epididymis-specific sperm-binding secretory protein. We isolated a family of HE2-related complementary DNAs from a human caput/corpus library. The transcripts code for identical 71-amino acid N-termini and different C-termini, and 5'- and 3'-untranslated regions. Compared with the original HE2, HE2beta and HE2gamma proteins have a 25-amino acid deletion near the C-terminus, and HE2gamma isoforms have a second deletion. These frame-shifting deletions result in C-termini differing in length, amino acid sequence, including number of cysteines, and isoelectric point. Identical sequences and deletion start and stop points indicate the HE2 isoforms are derived from alternative splicing of 8 or more exons of a single gene. Northern hybridization revealed that the 0.9-kb messenger RNA (mRNA) is most abundant in human caput; there is much less of it (20%) in corpus and little (<5%) in cauda. In castrated Macaca mulatta, HE2 mRNA decreased to 10% of sham-operated levels. Testosterone replacement maintained HE2 mRNA 3- to 5-fold higher than castrate levels, indicating its androgen dependence. Immunohistochemical staining revealed that the beta1 form is highly expressed in principal cells of the initial segment and caput. It is secreted into the lumen and binds to the sperm surface in the postacrosomal and neck regions. The beta2 form is expressed in principal cells primarily in efferent ducts.

3' Untranslated Regions↗
PubMed2000

Protein inhibitor of activated STAT-1 (signal transducer and activator of transcription-1) is a nuclear receptor coregulator expressed in human testis.

An androgen receptor (AR) interacting protein was isolated from a HeLa cell cDNA library by two-hybrid screening in yeast using the AR DNA+ligand binding domains as bait. The protein has sequence identity with human protein inhibitor of activated signal transducer and activator of transcription (PIAS1) and human Gu RNA helicase II binding protein (GBP). Binding of PIAS1 to human AR DNA+ligand binding domains was androgen dependent in the yeast liquid beta-galactosidase assay. Activation of binding by dihydrotestosterone was greater than testosterone > estradiol > progesterone. PIAS1 binding to full-length human AR in a reversed yeast two hybrid system was also androgen dependent. [35S] PIAS1 bound a glutathione S-transferase-AR-DNA binding domain (amino acids 544-634) fusion protein in affinity matrix assays. In transient cotransfection assays using CV1 cells with full-length human AR and a mouse mammary tumor virus luciferase reporter vector, there was an androgen-dependent 3- to 5-fold greater increase in luciferase activity with PIAS1 over that obtained with an equal amount of control antisense cDNA or mutant PIAS1. Constitutive transcriptional activity of the AR N-terminal+DNA binding domain was increased 6-fold by PIAS1. PIAS1 also enhanced glucocorticoid receptor transactivation in response to dexamethasone but inhibited progesterone-induced progesterone receptor transactivation in the same assay system. mRNA for PIAS1 was highly expressed in testis of human, monkey, rat, and mouse. In rat testis the onset of PIAS1 mRNA expression coincided with the initiation of spermatogenesis between 25-30 days of age. Immunostaining of human and mouse testis with PIAS1-specific antiserum demonstrated coexpression of PIAS1 with AR in Sertoli cells and Leydig cells. In addition, PIAS1 was expressed in spermatogenic cells. The results suggest that PIAS1 functions in testis as a nuclear receptor transcriptional coregulator and may have a role in AR initiation and maintenance of spermatogenesis.

Aged↗
PubMed1999

CREB binding protein coordinates the function of multiple transcription factors including nuclear factor I to regulate phosphoenolpyruvate carboxykinase (GTP) gene transcription.

Nuclear factor I (NFI) binds to a region of the phosphoenolpyruvate carboxykinase (GTP) (PEPCK) gene promoter adjacent to the cAMP regulatory element (CRE) and inhibits the induction of transcription from the gene promoter caused by the catalytic subunit of protein kinase A. In vivo footprinting studies demonstrated that both the CRE and the NFI-binding site are occupied by transcription factors, regardless of the presence of factors that stimulate (dibutyryl cAMP or dexamethasone) or inhibit (insulin) transcription from the PEPCK gene promoter. The NFI effects on transcription from the PEPCK gene promoter were observed even in the absence of the NFI binding site, suggesting the possibility of other weaker binding sites on the promoter or an interaction of NFI with a transcriptional co-activator. A mammalian two-hybrid system was used to demonstrate direct interaction between the transactivation domain of NFI-C and the CREB binding domain of the CREB-binding protein (CBP). Overexpression of a gene fragment encoding the CREB binding domain of CBP stimulates transcription from the PEPCK gene promoter. The inhibitory effect of NFI on transcription of the PEPCK gene induced by the catalytic subunit of protein kinase A appears to be the result of an interaction between NFI and the CREB-binding protein in which NFI competes with CREB for binding to the CREB-binding site on CBP. In contrast, glucocorticoids and thyroid hormone use the steroid hormone receptor binding domain of CBP to stimulate transcription from the PEPCK gene promoter. NFI-A combines with dexamethasone or thyroid hormone in an additive manner to stimulate PEPCK gene transcription. We conclude that CBP coordinates the action of the multiple factors known to control transcription of the PEPCK gene.

Binding Sites↗
PubMed1998

Nuclear factor I regulates expression of the gene for phosphoenolpyruvate carboxykinase (GTP).

Nuclear factor-I (NFI) binds to the phosphoenolpyruvate carboxykinase (GTP) (PEPCK) gene promoter immediately 5' to the cAMP regulatory element (CRE). This suggests an interaction between NFI and factors that bind the CRE. Of the four NFI isoforms expressed in mammalian tissues, NFI-A and -B stimulate basal transcription from the PEPCK gene promoter in HepG2 cells, while NFI-C and -X are slightly inhibitory. All four NFI isoforms abrogate the 20-fold protein kinase Ac (PKAc)-mediated induction of transcription from the PEPCK gene promoter. Normal PKAc-mediated induction was noted when the CRE was moved 10 base pairs 3' of its original location. However if the CRE was moved 5 base pairs 3', placing it out of phase with the other elements in the promoter, or moved 5' to -285 (the P3(I) site in the promoter), some PKA-mediated stimulation was lost. The NFI-C isoform effectively inhibited PKAc induction regardless of the relative positions of the CRE and the NFI binding sites. NFI-C also abrogated cAMP regulatory element-binding protein (CREB)-induced activity of wild type and mutant PEPCK promoters. There was some cooperativity in the binding of CREB and NFI to their respective binding sites but this did not appear to be physiologically important.

Animals↗
PubMed1995

Amino acid exchange activity of the alanine transporter of Giardia intestinalis.

The influx and efflux of alanine and other amino acids was studied in trophozoites of Giardia intestinalis. Transport of L-[2,3-3H]alanine was used as the index of influx. On the basis of the competition of L-[2,3-3H]alanine uptake by analogues of alanine, the substrate specificity of the alanine transporter was determined. The transporter is an antiport. Influx of alanine or those analogues which inhibited alanine influx caused the efflux of intracellular alanine and a number of amino acids structurally related to alanine. Amino acids unrelated to alanine, such as glutamate, effluxed at a slow rate, and the efflux was not stimulated by extracellular alanine or alanine analogues. However, there was a subset of intracellular amino acids, the alanine subset comprising alanine, serine, glycine, and threonine, the efflux of which was stimulated by external alanine or alanine analogues. Direct measurement by amino acid analysis demonstrated intracellular accumulation of alanine analogues concomitant with the efflux of the alanine subset. These data indicate unequivocal evidence of exchange of intracellular alanine with extracellular alanine analogues, with a 1:1 molar stoichiometry. This is the first demonstration in G. intestinalis of the antiport function of an amino acid transporter.

Alanine↗
PubMed1995

Immunocytochemical localization of aspartate and glutamate in the peripheral vestibular system.

Controversy exists concerning the identity of the neurotransmitter in the mammalian peripheral vestibular system. Several candidates have been proposed, including the excitatory amino acids glutamate and aspartate and the inhibitory amino acid gamma-aminobutyric acid (GABA). Previous studies have demonstrated vestibuloneural electrophysiological activity associated with glutamate and aspartate. Paraffin sections of rat vestibular ganglia and end-organs were examined for the presence of glutamate-like and aspartate-like immunoreactivity. Our results demonstrate the presence of both aspartate-like and glutamate-like immunoreactivity in vestibular hair cells, peripheral vestibular nerve fibers, and vestibular ganglion cells. Minimal immunoreactivity was noted in the tissues surrounding these cells. These data add support to the hypothesis that the excitatory amino acids glutamate and aspartate are involved in vestibular neurotransmission.

Absorption↗
PubMed1994

Efflux of alanine by Giardia intestinalis.

Giardia intestinalis trophozoites synthesise and then secrete large amounts of alanine into the external medium during growth. This efflux of alanine was studied by preloading cells with L-[2,3-3H]alanine, and determining efflux of radiolabel from intact trophozoites. The efflux of alanine was also determined by measurement of alanine concentration in trophozoites and external medium using high pressure liquid chromatography amino acid analysis. Over the temperature range 4 degrees C to 37 degrees C there was a slow efflux of alanine, but this efflux was greatly stimulated by a number of amino acids structurally similar to alanine, notably glycine, L-serine, L-threonine, L-asparagine and L-glutamine. In contrast, 2-aminoisobutyrate, D-amino acids, and other naturally occurring amino acids had no effect. Those amino acids which stimulated the efflux of intracellular alanine are the same amino acids which inhibited uptake of extracellular alanine. This concordance suggests that an alanine antiport functions for both the influx and efflux of alanine, and acts to maintain a balance between intracellular and extracellular alanine concentrations.

Alanine↗
PubMed1994

Nitric oxide synthase is an active enzyme in the spiral ganglion cells of the rat cochlea.

Nitric oxide (NO) mediates the effects of the excitatory amino acids in the central nervous system. Excitatory amino acids, in particular L-glutamate, are thought to be the neurotransmitter(s) present at the cochlear hair cell-afferent nerve synapse. To our knowledge, no studies to date have documented the presence of NO in the cochlea nor attempted to elucidate the role of NO in hearing. Rat cochlea frozen sections were examined for the presence of nitric oxide synthase (NOS) by NADPH diaphorase histochemistry. Vibratome sections of rat cochlea were examined by immunocytochemistry with an antibody to citrulline, an indication of NOS activity. Spiral ganglion cells in the rat cochlea were positive by NADPH diaphorase histochemistry and by anti-citrulline immunocytochemistry. These results indicate that NOS is present and that the enzyme actively produces nitric oxide in the spiral ganglion cells of the rat cochlea. Given our current understanding of neurotransmission in the cochlea, it is reasonable to postulate that the actions of NO in cochlear neuronal tissue are similar to the actions of NO in the CNS and that NO acts as a neurotransmitter/neuromodulator in the cochlea. In addition, because NO has been implicated as a mediator of excitotoxicity in the CNS, NO may play a role in neurotoxicity in the cochlea.

Amino Acid Oxidoreductases↗
PubMed1987

Effect of right ventricular hypertrophy on cardiac performance and the relation between right ventricular systolic peak pressure and end-systolic volume.

To investigate the role of hypertrophy of the right ventricle upon right heart performance and the significance of the peak systolic pressure/end-systolic volume (P/V) ratio in terms of right ventricular systolic performance, simultaneous measurements of radionuclide ventriculograms and central hemodynamics were done in 32 patients with chronic obstructive pulmonary disease. In 26 of the patients (80%) technically adequate two-dimensional echocardiograms could be performed. In the subset of patients with increased (greater than or equal to 6 mm) right ventricular end-diastolic wall thickness no relationship between pulmonary artery pressure and right ventricular ejection fraction (RVEF) existed in comparison with the remaining patients. P/V indices and cardiac output were not decreased. Considering the patients, whose P/V ratio did not increase from rest to exercise, RVEF decreased highly significantly more than in the remaining patients. The ratio of wall thickness and end-diastolic radius as determinant of peak systolic stress was significantly decreased in these patients compared with the remaining patients. In the patients with right ventricular hypertrophy despite significantly higher values of pulmonary artery pressures and resistances, the afterload in terms of systolic wall stress is markedly reduced. We conclude that in the hypertrophic state, right ventricular performance is not impaired despite decreased RVEF values. In the patients whose P/V ratio does not increase from rest to exercise, an inappropriate high peak systolic wall stress may exist both due to inadequate wall thickness and increased diameter of the right ventricle. The role of P/V in terms of prognosis and development of decompensated right heart failure remains undetermined.

Biomechanical Phenomena↗
PubMed1985

Physiological activity of pulmonary surfactant with low protein content: effect of enrichment with synthetic phospholipids.

A natural surfactant with low protein content (1%) was prepared by a sequence of cold centrifugation, heating to 90 degrees C, sucrose-gradient centrifugation, and extraction with chloroform:methanol. Some of the material was enriched with dipalmitoylphosphatidylcholine (DPPC) and unsaturated phosphatidylglycerol (PG) to relative concentrations of 56% and 10%, respectively. The in vitro physical properties of these preparations were evaluated with pulsating bubble and Wilhelmy balance and their in vivo activity with experiments on artificially ventilated premature newborn rabbits, delivered on day 27 of gestation. The animals were kept in body plethysmographs at 37 degrees C and ventilated artificially with a standardized sequence of insufflation pressures: 25, 20, and 15 cm H2O. The lungs were fixed by vascular perfusion and the alveolar expansion evaluated morphometrically in histologic sections. Enrichment of surfactant with DPPC and PG resulted in lower minimal surface tension during surface compression but did not further improve lung compliance or the alveolar expansion pattern. Treatment with nonenriched surfactant at a phospholipid concentration of 100 mg/ml (individual dose = 200 mg/kg) caused a markedly increased lung compliance at all insufflation pressure levels (p vs. controls less than .01). Our data indicate that pulmonary surfactant remains physiologically active after removal of most of its protein components and that enrichment with DPPC and PG reduces the in vitro minimal surface tension without adding to the in vivo efficacy.

Animals↗
PubMed1985

Bioenergetic studies in adult patients recovering from semi-starvation.

A model of energy-nitrogen balance developed in animals was adapted to the study of human bioenergetics. By creating balance conditions and steady-state formula infusion rates, each of the needed components of energy and nitrogen balance can now be measured with a high level of accuracy. A comprehensive description of energetic efficiency at the whole body level is possible using appropriate mathematical modeling. Key questions in human bioenergetics await these results, and our laboratory is currently undertaking these studies.

Adult↗
PubMed1984

The use of viscoelastometry to determine survival curves for intact genomes.

Viscoelastometry enables one to determine both size (Mr) and number concentration (L1) of intact genome molecules in solution. Comparison of four parameters, corrected for shear stress, as functions of 60Co gamma-ray dose showed that (1) the principal retardation time (tau 11,0) remained constant, indicating that intact genomes (bacteriophage T4c) were being measured; (2) the principal recoil (gamma 11,r,0) decreased with dose directly proportionately to (and determining) L1; (3) both the total recoil (gamma r,0) and the recoil area (Ar,0), under conditions of high solvent viscosity decreased with dose almost as sensitively as gamma 11,r,0. The DNAD37 was 540 +/- 25 Gy and the biological PFUD37 was 410.1 +/- 4.5 Gy yielding 75.9 +/- 3.6% of inactivating events explicable by one double-strand break (DSB) per genome. This value is comparable to Freifelder's [Virology 36, 613-619 (1981)] value of 86% for phage T4r48+, and the Frankenberg-Schwager et al. (Br. J. Cancer, in press) value of 0.84 DSB/cell/lethal event in diploid mutant rad54-3 yeast under conditions restrictive for DSB repair. Therefore, T4c may be an excellent model system for DNA damage repair studies with relevance to pro- and eukaryotes. Viscoelastometry, working near its lower size limit, provided precise estimates of the proportion of genomes lacking DSBs. It is not subject to the molecular deformation upper size limitations of the other biophysically understood size measurement methods (e.g., sedimentation rotor speed dependence). Therefore, it should be the method of choice for the study of genomes larger than those of the T even bacteriophages.

Aerobiosis↗