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Biomedical subjects

R M Klein

Publications and source records attributed to R M Klein.

At least 127 records · Page 7Linked to original sources
PubMed1987

The effect of epidermal growth factor on neonatal incisor differentiation in the mouse.

The effect of epidermal growth factor (EGF) on cellular differentiation of the neonatal mouse mandibular incisor was examined autoradiographically using tritiated thymidine ([3H]TDR) and tritiated proline ([3H]PRO). On days 0 (day of birth), 1, and 2, EGF was administered (3 micrograms/g body wt) sc to neonates. Mice were killed on Days 1, 4, 7, 10, and 13 after birth and were injected with either [3H]TDR or [3H]PRO 1 hr before death. [3H]TDR was used to analyze cell proliferation in eight cell types in the developing mouse incisor including upper (lingual) and lower (buccal) pulpal fibroblasts, preodontoblasts, inner and outer enamel epithelial cells (IEE and OEE), stratum intermedium (SI), stellate reticulum (SR), and periodontal ligament (PDL) fibroblasts. [3H]PRO was used to analyze protein synthesis in ameloblasts, and their secretion products (enamel and dentin), as well as PDL fibroblasts. The selected EGF injection scheme elicited acceleration of incisor eruption with minimal growth retardation. At Day 1, the upper and lower pulp, preodontoblasts, SI, and SR showed a significant decrease in labeling index (LI) 24 hr after a single EGF injection. After multiple injections (Days 0, 1, 2), two LI patterns were observed. In lower pulp, preodontoblasts, IEE, SI, SR, and OEE, a posteruptive change in LI was observed. In contrast, the upper pulp and PDL regions demonstrated a direct temporal relationship with eruption. Autoradiographic analysis with [3H]PRO indicated that EGF treatment caused significant increases in grain counts per unit area in ameloblast, odontoblast, and PDL regions studied. Significant differences were found in all four regions studied (ameloblasts, enamel, odontoblasts, dentin) at the 45-microns-tall ameloblast level as well as ameloblasts and odontoblasts at the 30-microns level at 13 days of age. The PDL demonstrated significant differences at all locations studied (base, 30 microns, 45 microns,) in 4-, 7-, and 13-day-old mice. Morphologically, EGF-treated groups demonstrated premature differentiation of ameloblasts and odontoblasts at the light microscopic level. The data indicate that EGF alters DNA and protein synthesis as well as differentiation patterns during the eruption process. While EGF affects both DNA and protein synthesis, the alteration of differentiation may be secondary to mitogenic effects on proliferative compartments. In order to determine the cellular target for EGF within the newborn mouse incisor, in vivo 125I-EGF binding was analyzed autoradiographically.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Is Posner's "beam" the same as Treisman's "glue"?: On the relation between visual orienting and feature integration theory.

In the present study we investigated whether the visually allocated "beam" studied by Posner and others is the same visual attentional resource that performs the role of feature integration in Treisman's model. Subjects were cued to attend to a certain spatial location by a visual cue, and performance at expected and unexpected stimulus locations was compared. Subjects searched for a target letter (R) with distractor letters that either could give rise to illusory conjunctions (PQ) or could not (PB). Results from three separate experiments showed that orienting attention in response to central cues (endogenous orienting) showed similar effects for both conjunction and feature search. However, when attention was oriented with peripheral visual cues (exogenous orienting), conjunction search showed larger effects of attention than did feature search. It is suggested that the attentional systems that are oriented in response to central and peripheral cues may not be the same and that only the latter performs a role in feature integration. Possibilities for future research are discussed.

Attention↗
PubMed1987

Kinetics of mast cell, fibroblast, and epidermal cell proliferation during acute graft-versus-host disease in the neonatal rat.

Acute graft-versus-host disease (GVHD) was induced in newborn Brown-Norway (BN) and DA rats by i.v. injection of 3 X 10(7) Lewis (L) lymph node cells. Control BN and DA rats received syngeneic cells. Rats were injected i.v. with [methyl-3H]thymidine for 1 h before being killed at 1, 2, 4, 5, 6, 8, 10, 11, 12, 13, and 14 days after the cellular inoculum. A piece of ventral abdominal skin was removed. Autoradiography was used to determine cell proliferative activity (labeling index, LI) in mast cells and fibroblasts of the dermis and basal cells of the epidermis. In addition, the number of mast cells per high-power field was determined for all 4 groups of rats: control DA, GVHD-DA, control BN, and GVHD-BN. Only GVHD-BN rats demonstrated extensive dermatitis. The LI of mast cells, fibroblasts, and basal cells decreased in control rats with increasing age. Although there were differences between DA and BN rats, there was a general pattern of increased proliferation of mast cells at early time points of GVHD followed by a decrease to or below control levels. The number of mast cells per high-power field also increased at early time intervals in both the DA and BN GVHD rats, but decreased significantly at later time points. These data confirm previous studies on chronic GVHD which demonstrated a decrease in the number of mast cells in the skin. Fibroblast LI was decreased at day 1 in both DA and BN GVHD rats. In GVHD-DA, fibroblast LI remained depressed while GVHD-BN demonstrated a second peak in LI at day 10 before declining below control levels. The most prominent basal cell response occurred in GVHD-BN between days 6-14 and is probably indicative of an attempted reparative response associated with GVHD dermatitis in this species. These data demonstrate that the activation of mast cells (proliferation and subsequent degranulation) correlates temporally with cell kinetic alterations occurring in the dermis and epidermis during acute GVHD.

Animals↗
PubMed1986

Human vitreous levels of cefamandole and moxalactam.

We gave 2-g intravenous doses of either cefamandole or moxalactam to 22 patients before vitrectomy. At 1 1/2 to 2 1/2 hours after administration, cefamandole vitreous concentrations varied from 0.36 to 2.05 micrograms/ml (mean, 0.94 micrograms/ml). Individual levels above the minimum inhibitory concentration of cefamandole for 90% (MIC90) of Staphylococcus aureus were found in five of 11 patients. Levels above the MIC90 for S. epidermidis were found in only two of 11 samples. Vitreous concentrations above the MIC90 of cefamandole for common gram-negative pathogens were found in only two patients. Moxalactam concentrations in the vitreous varied from 1.1 to 4 micrograms/ml 30 minutes to six hours after administration. These levels were not above moxalactam's MIC90 for S. aureus or S. epidermidis but were many times higher than the MIC90 of moxalactam for Enterobacteriaceae excluding Pseudomonas.

Cefamandole↗
PubMed1986

Denervation-induced changes in cell proliferation in the rat molar after wounding.

The dental pulp has the capacity to initiate and maintain repair after trauma. The purpose of the present study was to quantitatively analyze the role of the peripheral nervous system in regulation of pulpal cell proliferation in response to wounding. Six groups of ten rats were used in these studies. There was one baseline group (wounded, but innervation intact) and five resection groups. The resection groups included rats with unilateral superior cervical ganglionectomy (SCG), unilateral inferior alveolar nerve resection (IAN), unilateral chorda tympani (CT) resection, IAN + SCG, or a complete unilateral nerve resection (IAN + SCG + CT). One millimeter of enamel and dentin was removed from the first mandibular molar on the experimental (resected) side. Therefore, each rat had an experimental and control molar. Rats were killed at various intervals from day 0 to day 15 after wounding and received 0.5 muCi/g b.wt. 3H-thymidine 1 hour before death. For the baseline (innervation intact) data a peak in 3H-thymidine incorporation occurred at 5 days after wounding. In the resected groups, there was a general increase in the number of labeled cells at the zero time point, and a suppression of the 5-day peak with a delay in the proliferative response to wounding. The SCG + IAN-resected group maintained the lowest number of labeled cells throughout the entire experimental period compared to the experimental baseline data and the two controls. At the initial and termination points the SCG + IAN-resected groups demonstrated the highest number of labeled cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Binding of wheat-germ agglutinin to glycoconjugates in the salivary glands of reserpinized rats.

Salivary glands from adult rats that had received reserpine for 1, 3 or 7 days and from saline-treated controls were treated with rhodamine-labelled wheat-germ agglutinin conjugates (WGA-TRITC) to localize and characterize the distribution of glycoconjugates. Fluorescent and morphometric analysis of the parotid, submandibular and sublingual glands indicated that each gland responded differently to reserpine treatment. Parotid gland acinar cells and ducts showed no change in pattern or intensity of WGA-TRITC staining after reserpine. Mucous acinar cells of the submandibular gland had increased WGA binding and an accumulation of WGA-positive material in duct lumina after 3-7 days of reserpine. Morphometric analysis showed that the maximal increase in submandibular acinar-cell size occurred after 1 day of reserpine treatment. In sublingual glands, there was no detectable increase in mucous acinar-cell staining, but progressive accumulation of WGA-positive material was seen in duct lumina after 7 days of reserpine. As WGA binds to N-acetyl-glucosamine and N-acetyl-neuraminic acid residues, it may be that the eventual blockage of the duct system is related to increased production and secretion of glycoconjugates that contain these carbohydrates.

Animals↗
PubMed1986

Nitrate reductase of primary roots of red spruce seedlings : effects of acidity and metal ions.

Nitrate reductase activity (NRA) was found in primary roots, but not in foliage of red spruce (Picea rubens Sarg.) seedlings. Nitrate induced NRA:NH(4) (+) did not induce and slightly depressed NRA in older seedlings. Induction required 8 hours and, once induced, NRA decreased slowly in the absence of exogenous NO(3) (-). Seedlings were grown in perlite with a complete nutrient solution containing NH(4) (+) to limit NR induction. Established seedlings were stressed with nutrient solutions at pH 3, 4, or 5 supplemented with Cl(-) salts of Al, Cd, Pb, or Zn each at two concentrations. NRA in primary root tips was measured at 2, 14, 28, and 42 days. NRA induction was greatest at pH 3, and remained high during the period of study. NRA induction at pH 4 was lower. Metal ions suppressed NRA at pH 3 and 5, but enhanced NRA at pH 4. It is concluded that acidity and soluble metals in the root environment of red spruce are unlikely to be important factors in nitrogen transformations in red spruce roots.

Journal Article↗
PubMed1986

Scanning electron microscopy of pulmonary vascular endothelium in rats with hypoxia-induced hypertension.

Scanning electron microscopy was used to study the endothelial surface of the pulmonary trunk, artery, and vein in normobaric control rats as well as in rats exposed to hypobaric hypoxia for 7 and 21 days. The individual endothelial cells of the normobaric pulmonary trunk and hilar artery were flat and slightly elongated with elevated nuclear regions, and those of the intermediate-sized artery were more elongated and had more microvilli than the large arteries studied. Their endothelial cell boundaries were outlined by beaded cytoplasmic projections. The surfaces of the normobaric hilar and intermediate-sized veins were smooth and demonstrated numerous longitudinal streaks. These venous endothelial cells were elongated and their cell boundaries were outlined by low discontinuous marginal folds. Exposure to hypobaric hypoxia caused the following changes on the arterial surface: elevation of the endothelial cells; formation of microvilli-rich cell clusters; formation of hollow defects; and the attachment of leukocytes. Hypobaric hypoxia also caused the disappearance of the longitudinal streaks and the occurrence of microvilli-rich cells in the hilar veins. The endothelial surface modifications in the hypobaric rats could be related to thickening of the endothelium, intimal edema, increased intimal connective tissue, luminal invasion of leukocytes, and increased endothelial cell proliferation, known to occur in systemic arteries of hypertensive animals.

Animals↗
PubMed1986

Alterations in atrial and plasma atrial natriuretic factor (ANF) content during development of hypoxia-induced pulmonary hypertension in the rat.

Distension of the atrial wall has been proposed as a signal for the increased release of atrial natriuretic factor (ANF) from atrial myocytes in response to perceived volume overload. To determine whether pressure changes resulting from hypertension in the pulmonary circulation may stimulate release of ANF, rats were exposed to chronic hypobaric hypoxia for 3 or 21 days and the ANF concentration in the atria and plasma were determined by specific radioimmunoassay. Exposure to chronic hypoxia resulted in significant increases in hematocrit at both 3 (p less than 0.025) and 21 days (p less than 0.005) and in the development of right ventricular hypertrophy (RVH) expressed as the ratio of the weight of the right ventricle to the weight of the left ventricle and septum (RV/LV+S) at both 3 (RV/LV+S = 0.278 +/- 0.005) and 21 days (RV/LV+S = 0.536 +/- 0.021). After 21 days, left atrial (LA) ANF content was significantly increased in hypoxic rats compared to controls (508 +/- 70 ng/mg tissue vs 302 +/- 37 ng/mg), while right atrial (RA) ANF content was significantly reduced (440 +/- 45 vs 601 +/- 58 ng/mg). At this time, plasma ANF concentration was significantly elevated compared to controls (238 +/- 107 pg/ml vs 101 +/- 10 pg/ml). These results suggest that the development of pulmonary hypertension following chronic hypobaric exposure induces altered atrial ANF content and increased plasma ANF concentration as a result of altered distension of the atrial wall.

Animals↗
PubMed1985

Human vitreous levels of selected antistaphylococcal antibiotics.

Staphylococcus epidermidis and S. aureus are the most common causes of bacterial endophthalmitis. A study of the penetration of selected antistaphylococcal antibiotics into human vitreous was undertaken in 58 patients. After 2-g intravenous doses of cephalothin, cefazolin, methicillin, oxacillin, or nafcillin were given to patients about to undergo vitreous surgery, mean vitreous levels for each antibiotic were as follows: cephalothin, 0.97 microgram/ml in diabetics and 0.69 microgram/ml in nondiabetics; cefazolin, 0.84 microgram/ml in diabetics and 1.6 microgram/ml in nondiabetics; methicillin, 2.56 micrograms/ml in diabetics and 2.64 micrograms/ml in nondiabetics; oxacillin, 0.62 microgram/ml in diabetics and 0.34 microgram/ml in nondiabetics; and nafcillin, 0.73 microgram/ml in diabetics and 0.75 microgram/ml in nondiabetics. Only cefazolin produced vitreous concentrations consistently above its minimum inhibitory concentration for 90% of S. epidermidis isolates. Staphylococcus aureus isolates were not similarly covered. There was a trend toward higher vitreous antibiotic concentrations in patients with proliferative vitreoretinopathy and rubeosis.

Anti-Bacterial Agents↗
PubMed1984

Beta-adrenergic drug induced hyperplasia in the immature rat parotid and submandibular glands.

In this study the proliferative response of rat parotid (PRG) and submandibular (SMG) gland acinar cells to beta-adrenergic stimulation with Isoproterenol (a non-selective beta-agonist) or terbutaline (a relatively selective beta 2-agonist) was determined during the 4th-5th postnatal weeks in intact and guanethidine-sympathectomized (Sx) rats. Rats were divided into 2 age groups (21 and 28 days) and 6 experimental groups (control-intact (C), guanethidine-treated (Sx), intact + TER (C + TER), intact + Isoproterenol (C + IPR), guanethidine-treated + TER (Sx + TER), and guanethidine-treated + isoproterenol (Sx + IPR]. Intact and Sx rats were treated with either IPR or TER for 3 days (days 21, 22, and 23 or days 28, 29 and 30). On day 24 or 31 all rats were injected with [3H]-thymidine and killed 1 h later. PRG of Sx and C + TER rats showed no significant differences from controls in wet weight while SMG from Sx rats demonstrated a reduced wet weight compared to C rats. [3H]Thymidine labelling index and mitotic index were not significantly different in Sx and C + TER rats in either PRG or SMG. C + IPR rats showed increased wet weight, labelling and mitotic index compared to controls (P less than 0.01). Sx + IPR increased values over controls (P less than 0.01) and above C + IPR values (P less than 0.01). Sx + TER values were significantly higher than controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗