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Biomedical subjects

D J Lamb

Publications and source records attributed to D J Lamb.

At least 91 records · Page 5Linked to original sources
PubMed1993

Paracrine factors and the regulation of spermatogenesis.

MAIN PROBLEM: Although the gonadotropins and testosterone are required for normal spermatogenesis, it is believed that local control factors regulate spermatogenesis. For many years these regulatory factors had not been identified. Over the past five years, a number of growth factors have been identified in testis or isolated testicular cell types or secretions. Growth factors are key regulatory molecules which affect cell proliferation, meiosis, and differentiated function. These factors usually act in an autocrine (acting upon the cell which secreted it) or paracine (affecting another cell) manner and thus are involved in intercellular communications. METHODS: Growth factor secretion by testicular cell types or testis tissue has been analyzed using a variety of assays measuring cell proliferation in vitro, as well as assays using immunocytochemicals. Growth factor gene expression in testis has been analyzed by Northern blot analysis and in situ hybridization, which gives information concerning the stage and cell specific expression of the gene. Inbred strains of mice with mutations of deletions in a growth factor gene has been used to suggest the function of two specific factors in testicular development and growth. RESULTS: Among the growth factors expressed or secreted by testicular cell types, most are common to some other cell types in the body, such as transforming growth factors alpha and beta, epidermal growth factor, fibroblast-like growth factors, insulin-like growth factors, interleukins, endorphins, inhibin and activin, while others may be more testis specific such as mullerian inhibiting substance (anti-mullerian hormone) and Sertoli cell secreted growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Artificial intelligence in medicine and male infertility.

MAIN PROBLEM: fertility data is inadequately assessed by traditional statistical methods for a variety of reasons. First, the principal test of male fertility potential, the Semen Analysis (SA) is a composite of several dissimilar parameters, and the SA and other laboratory tests of fertility potential reflect physiological mechanisms that interact in complex ways. Second, patient data is often fragmented, obtained from multiple sources. Importantly, 2 patients are required for the final result. METHODS: Novel and powerful computational method, the neural network, was explored to analyze fertility data. An integrated series of programs was written in the C computer language to implement a back propagation algorithm. A model data analysis system was chosen, predicting the penetration of zona-free hamster ova by sperm (Sperm Penetration Assay (SPA)) and the distance travelled by the farthest swimming sperm (Penetrak Assay) from the SA, for these 2 assays are generally believed by the reproductive medical community to be independent of the SA. The classification accuracy of the neural network was compared to 2 standard statistical methods, linear discriminant function analysis (LDFA) and quadratic discriminant function analysis (QDFA). RESULTS: A neural network could be trained to correctly predict the Penetrak result in over 80% of assays it had not previously encountered, and another network could predict the SPA outcome in nearly 70%. The neural network was superior to LDFA and QDFA in predicting both assay outcomes (for Penetrak: LDFA = 64%, QDFA = 69%; for SPA: LDFA = 65%, QDFA = 45%).(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1993

A neural network to analyze fertility data.

OBJECTIVE: To program an artificial intelligence system, a neural network, and use it to predict results of sperm penetration in bovine cervical mucus (Penetrak assay; Serono Laboratories, Norwell, MA) and zona-free hamster egg penetration from the semen analysis. DESIGN: Results of 139 Penetrak assays, 1,416 zona-free hamster egg penetration assays, and the corresponding semen analyses were retrospectively analyzed by an artificial neural network. MAIN OUTCOME MEASURES: Classification errors of the neural network were compared with those of linear and quadratic discriminant function analyses. RESULTS: Data were separated into training and test sets. For the Penetrak result, linear and quadratic discriminant function analysis correctly predicted 58% and 74% of the training set results and only 64.1% and 69.2% of the test data, respectively. The neural network correctly predicted 92% of training set results and 80% of test set results. For the zona-free hamster egg penetration assay outcome, linear and quadratic discriminant function analysis correctly classified 66.3% and 46.0% of the training set and 64.9% and 44.7% of the test set, respectively. The neural network correctly classified 75.7% of the training data and 67.8% of the test data. CONCLUSIONS: Using the semen analysis, the neural network correctly classified 67.8% of zona-free hamster egg penetration assay results and 80% of Penetrak results it had not encountered previously, suggesting that this method of data analysis may be successfully employed to predict fertility potential.

Animals↗
PubMed1993

Growth factors and testicular development.

During the last 5 years significant advances have been achieved in defining the endocrine, paracrine and cellular interactions required for normal testicular development. Numerous paracrine factors are likely to regulate spermatogenesis throughout the cycle of the seminiferous epithelium. These factors create the local hormonal milieu required for germ cell proliferation, meiosis and differentiation. The studies of the c-kit oncogene and the stem cell growth factor in the migration and survival of the primordial germ cells to the genital ridge during development have defined at least 1 important role of growth factors in spermatogenesis. 72, 142-146, 148, 149, 154, 159 It is likely that in the next 5 years the role of many of these other paracrine factors in the regulation of testicular development will be determined.

Animals↗
PubMed1993

Tests of sperm function for evaluation of the male: Penetrak and Tru-Trax.

OBJECTIVE: To evaluate the Penetrak (Serono Laboratories, Norwell, MA) and Tru-Trax (Humagen, Charlottesville, VA) bovine cervical mucus (CM) penetration assays and to correlate results to parameters of semen analysis and male factor diagnosis. DESIGN: Prospective, nonrandomized, controlled study. PARTICIPANTS: Two hundred thirty-six males undergoing evaluation for male factor infertility and 37 fertile semen donors. MAIN OUTCOME MEASURES: Human sperm penetration in bovine CM measured by the Penetrak and Tru-Trax assay systems correlated to sperm density, motility, forward progression, and clinical diagnosis. RESULTS: Two parameters of semen analysis, motility and density were correlated to the distance traversed by the vanguard sperm in both Penetrak and Tru-Trax assays. Penetrak results were significantly correlated to male factor infertility diagnosis. CONCLUSIONS: Both assays were reliable and highly reproducible, and the Tru-Trax assay was correlated to its predecessor, Penetrak. Although Penetrak and Tru-Trax were correlated to motility and density, no correlation coefficient was > 0.6, suggesting that these assays measure a facet of sperm function that is independent of semen analysis.

Animals↗
PubMed1992

The effect of EDTA on the oxidation of low density lipoprotein.

Low density lipoprotein (LDL) is routinely isolated and stored in buffers containing ethylene-diaminetetra-acetic acid (EDTA) to inhibit its autoxidation. We have investigated the effect of EDTA on LDL oxidation by both copper ions and macrophages. LDL oxidation by macrophages in Ham's F-10 medium containing 6 microM iron showed a large and concentration-dependent increase when EDTA was added up to about 10 microM. EDTA concentrations above about 10 microM progressively inhibited LDL oxidation as measured by macrophage degradation, thiobarbituric acid-reactive substances and electrophoretic mobility. The oxidation of LDL by 1 microM copper in Ham's F-10 medium, measured by macrophage degradation, also showed a large increase with low concentrations of EDTA (1-3 microM), with higher concentrations (10 microM or above) strongly inhibiting the oxidation. In a simple phosphate buffer, however, EDTA simply inhibited the oxidation of LDL by copper with equimolar amounts of EDTA to copper giving a complete inhibition. The results of this study indicate that when LDL oxidation by cells or by copper in Ham's F-10 medium is investigated, more oxidation may be obtained if the EDTA is not previously removed from the LDL preparation.

Animals↗
PubMed1992

The oxidative modification of low density lipoprotein by human lymphocytes.

Oxidation of low density lipoprotein in atherosclerotic lesions may be involved in converting macrophages into lipid-laden foam cells. Lesions contain endothelial cells, smooth muscle cells, macrophages and lymphocytes. The first three types of cells have been shown previously to modify low density lipoprotein so as to increase its uptake by macrophages. We report here that lymphocytes from human blood are also capable of doing this. The modification process was an oxidative one because there was an increase in the thiobarbituric acid-reactive substances in media containing lymphocyte-modified low density lipoprotein and the modification could be inhibited by the antioxidants butylated hydroxytoluene and probucol. The lymphocyte-modified low density lipoprotein was taken up and degraded by macrophages by their scavenger receptor(s).

Animals↗
PubMed1991

In vitro interaction between primary bone organ cultures, glass-ionomer cements and hydroxyapatite/tricalcium phosphate ceramics.

Primary organ cultures derived from neonate rat calvaria were maintained for 2 wk and used to study in vitro response of osteoblast and periosteal cells to the component and composite forms of three different glass-ionomer (polyalkenoic) cements, comparing them to densely sintered hydroxyapatite and tricalcium phosphate ceramics. Qualitative analysis by scanning and transmission electron microscopy revealed that osteoblasts colonized all the solid test materials, although there was a less favourable response to materials with a rough surface topography and to unset and fluoride-containing glasses. On solid materials migrated cells maintained their tessellated morphology and exhibited numerous micro-appendages anchoring them to the surface of the test materials. A collagen-containing extracellular matrix was elaborated on to the ceramics and set glass-ionomer cements, except for one (AquaCem). Mineralization of the extracellular matrix was seen adjacent to hydroxyapatite and tricalcium phosphate ceramics, that adjacent to the latter morphologically resembling bone.

Animals↗
PubMed1991

Management of the atrophic anterior maxilla by combined hydroxyapatite augmentation and vestibuloplasty: a pilot study.

A technique is described to overcome the problem of the grossly resorbed maxillary alveolus and improve denture wear, by combining augmentation and increased soft tissue cover of the alveolar ridge. Manipulation and placement of the hydroxyapatite was facilitated by use of a hydroxyapatite/collagen composite (HAC) block. The procedure has been carried out in ten patients where extensive resorption contraindicated the use of permucosal implants. Six cases have been followed up for 2 to 3 years. After some initial compaction of HAC the improvement in ridge height has been maintained and long term improvement in denture function obtained.

Alveolar Bone Loss↗
PubMed1991

Initial in-vivo evaluation of glass-ionomer cements for use as alveolar bone substitutes.

The response of rat femora to implantation of four glass-ionomer (polyalkenoic) cements (GIC) compared to that seen following implantation of densely sintered hydroxyapatite (Ha) ceramic was evaluated for periods up to 12 weeks. Light and transmission electron microscopic analysis of the GIC/bone interface revealed direct bonding of the GIC G338 and Ketac Cem (both based on fluoro-alumino-silicate) glasses to bone, with a mineralized collagen-containing extra-cellular matrix deposited on the surface of the GIC. AquaCem and the fluoride-free GIC based on MP4 glass showed incomplete osseointegration.

Alveolar Ridge Augmentation↗
PubMed1991

Partial characterization of a unique mitogenic activity secreted by rat Sertoli cells.

Sertoli cell conditioned medium (SCCM) contains a potent mitogen, Sertoli cell secreted growth factor (SCSGF). A431 cells, derived from a human epidermoid carcinoma have provided an excellent model cell line for the study of this apparently unique activity secreted by rat Sertoli cells in vitro. Previously, it was shown that SCCM contained an epidermal growth factor (EGF)-like activity which was thought to be the mitogen for A431 cells. The present study showed that these two factors are distinct entities. The secretion of the EGF-like activity decreased with increasing number of culture days, while that of SCSGF and of another Sertoli cell specific protein, transferrin remained constant. The addition of SCCM stimulated whereas 2.5 ng/ml EGF inhibited the A431 cell growth. The proliferative response of A431 cells to a wide variety of growth factors and known Sertoli cell secretions was investigated. SCSGF was the only growth factor of known Sertoli cell secretions tested (transforming growth factors (TGF alpha, TGF beta), EGF, bombesin, fibroblast growth factor (FGF), platelet derived growth factor (PDGF), insulin-like growth factors 1 and 2 (IGF-1 and IGF-2), prostaglandins E-1 and E-2, insulin, transferrin and lactate) which stimulated A431 cell proliferation. SCSGF was mitogenic for A431 cells even in the presence of serum in the culture medium. The partially purified SCSGF was heat- and acid-stable, protease-sensitive with a molecular weight of 14,000. It did not bind to heparin or concanavalin A-Sepharose. The secretion of a mitogenic activity by the Sertoli cell which is different from other previously identified growth factors and which coincides with active spermatogenesis could have important implications in the regulation of spermatogenesis.

Animals↗
PubMed1991

Cyclodextrin sulfates: characterization as polydisperse and amorphous mixtures.

Alpha- and beta-cyclodextrins and their hydroxypropyl derivatives were converted by the reaction with chlorosulfonic acid in pyridine to the corresponding sulfates. Cyclodextrin sulfates were shown by fast-atom bombardment mass spectrometry (negative ion mode, triethanolamine matrix) to be mixtures with nearly symmetrical distributions of degree of substitution by sulfate groups and by powder X-ray diffraction to be amorphous. Thus, in these aspects, cyclodextrin sulfates are similar to the potent drug solubilizers hydroxypropylcyclodextrins.

Cyclodextrins↗