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Biomedical subjects

H Falk

Publications and source records attributed to H Falk.

At least 73 records · Page 4Linked to original sources
PubMed1988

Growth requirements, growth factor responsiveness, and growth factor secretion of three human embryonal carcinoma cell lines.

The in vitro growth requirements of three human embryonal carcinoma cell lines (H 12.7, 2102 EP, 1428 A) were investigated. The basal medium DME/F12 supplemented with insulin, transferrin, and low-density and high-density lipoproteins was sufficient to support substantial multiplication of all three lines. The most efficient attachment factor was either fibronectin (for 2102 EP and 1428 A) or collagen type I (H 12.7). In a serum-free system the influence of epidermal growth factor (EGF), insulin-like growth factor I, multiplication stimulating activity (MSA), a platelet extract, and the glucocorticoids dexamethasone and hydrocortisone, as determined by the DNA synthesis rate of the cells, was generally minimal. However, the DNA synthesis rate of cell lines H 12.7 and 2102 EP was increased by MSA, and the line with the highest potential to differentiate (H 12.7) was stimulated by EGF. All three cell lines secreted growth factors in a heterologous stimulation assay. Insulin-like growth factors I and II were not part of the growth promoting activity. The inhibitory effect of a monoclonal anti-EGF antibody on the 3H-thymidine incorporation of cell line 2102 EP might indicate autocrine secretion of EGF or an EGF-like factor by this cell line.

Cell Division↗
PubMed1988

Isolation and characterization of interferon-resistant variants from S49 mouse lymphoma.

S49 mouse lymphoma cells were found to be extremely sensitive to the antiproliferative activity of interferon. These characteristics were studied to select for IFN-resistant cell variants. Some 0.6% of the parental S49 cell population were resistant to the antiproliferative and cytotoxic activities of IFN. The resistant cells were cloned and analyzed for their responses to several of the activities of IFN, namely, inhibition of encephalomyocarditis (EMC) virus, murine leukemia virus (MuLV) replications, and the induction of (2'-5') oligoadenylate synthetase. Among the clones selected some were highly resistant while others demonstrated only partial responsiveness to IFN. S49 cells demonstrate tubular structures in the cytoplasm. These structures were previously reported to be antigenically related to mouse mammary tumor virus (MMTV). We report here that IFN treatment decreases the expression of these cytoplasmic viral structures as revealed by electron microscopy. To correlate this novel antiviral activity to the more established functions of IFN we utilized the above mentioned S49 IFN-resistant variants. The anti-MMTV activity of IFN correlated with the other effects of IFN in both the highly resistant and partially responsive S49 clones. Our findings indicate that a relatively high proportion of S49 cells vary in their response to IFN. The defect in the resistant cells appears to affect a primary response to IFN which is common to its diverse activities. Furthermore, the effect of IFN on MMTV-related structures involves the usual pathway of IFN action.

2',5'-Oligoadenylate Synthetase↗
PubMed1988

Timing of photorefractoriness in the European starling: significance of photoperiod early and late in the reproductive cycle.

In European starlings, as in many other birds inhabiting higher latitudes, gonads develop in response to the increasing daylengths in early spring. Later in the year, however, the hypothalamo-pituitary-gonadal axis becomes refractory to the previously stimulatory long photoperiods and the gonads regress in summer. The present study addresses the question of when during the gonadal growth phase photorefractoriness is determined. A 13-h photoperiod induces testicular development and subsequent testicular regression associated with refractoriness in male starlings. An 11-h photoperiod, in contrast, induces only testicular development, and photorefractoriness never develops. When starlings were transferred to an 11-h photoperiod, either 12 or 25 days following exposure to a 13-h photoperiod, their testes developed to full size, but remained large to the end of the experiment, i.e. refractoriness did not develop. The same was even true of most birds in a third group that were transferred to an 11-h photoperiod after 46 days of the 13-h photoperiod, when gonads had developed to near maximal size. These data show that, in contrast to some other species of passerine birds, the onset of photorefractoriness does not become fixed before the testes have undergone considerable development, and that the photoperiodic conditions experienced at the end of the testicular growth phase are still effective in determining the precise time of onset of photorefractoriness. It is suggested that this peculiarity of the starling is related to the fact that its gonadal development begins rather early in spring and, hence, under much shorter photoperiods than the other species studied.

Animals↗
PubMed1988

[Surgical aortic valve replacement for acute Streptococcus viridans endocarditis with simultaneous moderate hemophilia A].

This is a report of a 25-year-old patient with known aortic valve stenosis since early youth and hemophilia A, showing recurrent joint bleeding. Acute Streptococcus endocarditis induced aortic valve insufficiency resulting in cardiac failure. Aortic valve replacement was performed after substitution of factor VIII, during which intra- and postoperative bleeding was prolonged by pericardial adhesions. Heparin was administered during cardiopulmonary-bypass as usual, but usual postoperative cumarin therapy was not initiated due to prolonged PTT time. One year postoperatively, the patient was in an excellent condition and fully rehabilitated.

Adult↗
PubMed1987

Molecular structure of the bilin binding protein (BBP) from Pieris brassicae after refinement at 2.0 A resolution.

The bilin binding protein (BBP) from the insect Pieris brassicae has been analysed for amino acid sequence, spectral properties and three-dimensional structure. The crystal structure that had been determined by isomorphous replacement has been refined at 2.0 A (1 A = 0.1 nm) resolution to an R-value of 0.20. The asymmetric unit contains four independent subunits of BBP. The co-ordinate differences are 0.25 A, in accord with the estimated error in co-ordinates. The polypeptide chain fold is characterized by an eight-stranded barrel. The connecting loops splay out at the upper end of the barrel and open it, whilst the lower end is closed. The overall shape resembles a calyx. The biliverdin IX gamma chromophore is located in a central cleft at the upper end of the barrel. The bilatriene moiety is in cyclic helical geometry with configuration Z,Z,Z and conformation syn,syn,syn. The geometry is in accord with the spectral properties and permits a correlation between sign of the circular dichroism bands and sense of the bilatriene helices. The fold of BBP is related to retinol binding protein (RBP), as had been recognized in the preliminary analysis, although the amino acid sequences of RBP and BBP show only 10% homology. There are large differences in the loops at the upper end of the barrel, whilst the segments of the centre and the lower end of the barrel superimpose closely. The ligands of BBP and RBP, biliverdin and retinol, respectively, are also similarly located.

Amino Acid Sequence↗
PubMed1987

Occlusal force pattern during mastication in dentitions with mandibular fixed partial dentures supported on osseointegrated implants.

The occlusal force pattern during chewing and biting was studied in eight edentulous patients whose dentitions had been restored with mandibular bilateral posterior two-unit cantilever fixed prostheses supported on osseointegrated titanium fixtures and occluding with complete maxillary dentures. The chewing pattern was comparable to that reported for subjects with complete healthy dentitions or with tooth-supported cross-arch fixed partial dentures. However, during chewing and swallowing the voluntary capacity of the jaw-closing muscles was used to a much greater extent. Contrary to reports for cantilevers in tooth-supported cross-arch unilateral posterior two-unit cantilever fixed partial dentures occluding with natural teeth, the posterior cantilever segments in the present fixture-supported cantilever prostheses occluding with complete dentures regularly exhibited the largest local forces. Despite this, material failures of this type of fixed prostheses are rare, as demonstrated in long-term follow-up studies.

Adult↗
PubMed1987

Lack of therapeutic activity of the lipoidal amine CP-46,665 in rodent tumors and human non-seminomatous germ cell tumors growing in nude mice.

The alkyl-linked lipoidal amine 4-aminomethyl-1-[2,3-(di-n-decyloxy)-n-propyl]-4-phenylpiperidine (CP-46,665) was tested for therapeutic activity in 2 rodent tumor models and 2 human non-seminomatous germ cell tumors growing in nude mice. CP-46,665 failed to show therapeutic efficacy in 3-Lewis lung carcinoma (3-LL) growing in syngeneic C57Bl6-mice, in methylnitrosourea (MNU)-induced rat mammary carcinomas and in 2 human non-seminomatous germ cell tumor cell lines (H 12.1, H 12.7) growing in nu/nu NMRI-mice when given in a dose range including non-toxic doses and doses higher than the lethal dose for 10% of the treated animals (LD10).

Animals↗
PubMed1987

Optimal discrimination of mild hyperparathyroidism with total serum calcium, ionized calcium and parathyroid hormone measurements.

The serum concentrations of calcium, albumin and parathyroid hormone (PTH) and the plasma levels of ionized calcium were determined in 124 healthy subjects, 89 patients with primary hyperparathyroidism (HPT), 23 of whom had the syndrome of multiple endocrine neoplasia type 1 (MEN-1) and 43 patients who had hypercalcaemia of other causes than HPT (non-HPT), in most cases due to widespread malignancies. The total serum calcium was corrected for the serum albumin concentration (CaM). Healthy females over the age of 50 had higher CaM, than younger females and the women of all ages also had, higher serum PTH levels than males. For all study groups both the intra- and inter-diurnal variations were small for all the studied variables. Discriminant function and optimal discriminatory limits were calculated with the help of computer programs. A consideration of all the individuals in the discriminant analysis, revealed that measurements of CaM alone separated most HPT patients both from the healthy subjects and from the non-HPT patients. However, when only those who had borderline values (defined as CaM between 2.45 and 2.75 mmol/l) were included it turned out that measurements of ionized calcium markedly improved the delineation of mild HPT from the healthy subjects and that, in addition, PTH measurements helped to exclude those with non-HPT hypercalcaemia. The optimal discriminatory levels of serum calcium were calculated as the levels which caused the minimum loss in terms of misclassification when attention was paid to the relative importance of false positive to false negative classifications and to the prevalence of HPT. The optimal discriminatory level for serum calcium for a weighting ratio between false positive to false negative of 1:1, and a prevalence of HPT of 1%, was calculated to be 2.68 mmol/l and for a prevalence of 50% 2.56 mmol/l. In the latter situation a weighting ratio of 10:1 for false positive to false negative gave a level of 2.63 mmol/l while a weighting ratio of 1:10 corresponded to an optimal discriminatory level of 2.47 mmol/l.

Adolescent↗
PubMed1987

High sensitivity immunolocalization of double and single-stranded DNA by a monoclonal antibody.

A monoclonal antibody (AK 30-10) is described which specifically reacts with DNA both in double and single-stranded forms but not with other molecules and structures, including deoxyribonucleotides and RNAs. When used in immunocytochemical experiments on tissue sections and permeabilized cultured cells, this antibody detects DNA-containing structures, even when the DNA is present in very small amounts. Examples of high resolution detection include the DNA present in amplified extrachromosomal nucleoli, chromomeres of lampbrush chromosomes, mitochondria, chloroplasts and mycoplasmal particles. In immunoelectron microscopy using the immunogold technique, the DNA was localized in distinct substructures such as the "fibrillar centers" of nucleoli and certain stromal centers in chloroplasts. The antibody also reacts with DNA of chromatin of living cells, as shown by microinjection into cultured mitotic cells and into nuclei of amphibian oocytes. The potential value and the limitations of immunocytochemical DNA detection are discussed.

Animals↗
PubMed1987

Vinyl chloride-induced hepatic angiosarcoma.

In early 1974, an alert plant physician reported the occurrence of several cases of the otherwise rare hepatic angiosarcoma (HAS) at a single polyvinyl chloride (PVC) production facility in Louisville, Kentucky (U.S.A.). Upon further investigation, the relative risk for HAS at this plant appeared to be approximately 5,000, strongly indicating a causal relationship with some factor at the plant. Epidemiologic studies at this and other PVC polymerization plants identified vinyl chloride monomer (VCM) as the causative agent. Experimental studies reported in early 1974 confirmed VCM as a hepatic carcinogen capable of producing HAS and other tumors. Follow-up epidemiologic studies revealed that: 1) HAS is the end stage of a progressive liver disease consisting of hepatocytic and sinusoidal cell hyperplasia, sinusoidal dilatation, and hepatic fibrosis; 2) over 100 cases of VCM-induced HAS have occurred worldwide; and 3) an increased risk of lung cancer has been reported in some cohort studies of PVC polymerization workers, although this outcome may be related to PVC dust or factors other than VCM. A national study of HAS in the United States identified 3 other causes of HAS: Thorotrast, inorganic arsenic, and androgenic-anabolic steroids. Of 168 cases found to occur during 1964 through 1974, 42 cases (25%) were associated with the 4 known etiologic agents, while 126 cases (75%) were of unknown etiology.

Carcinogens↗
PubMed1987

Convulsions caused by endrin poisoning in Pakistan.

From July through September 1984, acute convulsions caused by endrin poisoning occurred in the subdistrict of Talagang, Attock District, Punjab province, Pakistan. Eighteen of the 21 affected villages were surveyed; 70% of the cases for which ages were known (106 of 152) were in children 1 to 9 years of age; 9.8% of all affected persons (19 of 194) died. The outbreak occurred in villages on the main roads of the subdistrict and peaked in early September. Endrin was detected in the blood of 12 of 18 patients with a history of convulsions but was not found in the blood of four hospitalized control patients. One composite sugar sample taken from the homes of three persons had an endrin level of 0.04 ppm. Because of the high toxicity, repeated association with large-scale outbreaks of neurologic illness, and the difficulties of monitoring distribution, endrin should not be used for agricultural purposes.

Child↗
PubMed1986

2,3,7,8-Tetrachlorodibenzo-p-dioxin levels in adipose tissue of exposed and control persons in Missouri. An interim report.

The compound 2,3,7,8-tetrachlorodibenzo-p-dioxin, commonly known as dioxin, was measured in the adipose tissue of 39 persons with a history of residential, recreational, or occupational exposure in Missouri and in 57 persons in a control group. All participants had detectable levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin in their adipose tissue, but the exposed group had significantly higher levels. Levels of six of the exposed persons were more than five times greater than the level of the highest control. Measuring 2,3,7,8-tetrachlorodibenzo-p-dioxin in adipose tissue provides a much improved index of exposure, an important advance for research studies evaluating the possible health effects of this compound.

Adipose Tissue↗
PubMed1986

The effects of periodontal treatment on mucous membrane thickening in the maxillary sinus.

This study was performed to elucidate the effect of periodontal treatment on the sinus mucosa. 21 patients with periodontal lesions of the upper molars and/or premolars and chronic mucous membrane thickening in the maxillary sinus diagnosed radiographically participated in the study. No teeth in the regions studied showed pulpal or periapical changes. Altogether, the patients exhibited 36 maxillary sinuses with mucous membrane thickening. 15-20 months after the final periodontal treatment, a marked reduction of the plaque index, gingival index and probing depth was recorded. Radiographic examination of the sinus mucosa before and after periodontal treatment showed that successful periodontal treatment in all quadrants resulted in normalisation of the sinus mucosa. Periodontal treatment was not successful in 2 quadrants. In one of these cases the thickness of the mucosa was unchanged and in the other case, further thickening of the mucosa seemed to have occurred. The study shows that severe periodontitis of the upper molars and/or premolars may initiate mucous membrane thickening in the maxillary sinus, and that successful periodontal treatment results in normalisation of the sinus mucosa.

Adult↗
PubMed1986

Contribution of metals to respiratory cancer.

This paper reviews studies on the adverse health effects of exposure to metals, using arsenic and cadmium as examples. The carcinogenic potential of arsenic has been studied in various settings. Inhalation is clearly related to the development of lung cancer in (copper) smelting and arsenical pesticide manufacturing, and also in heavily exposed wine merchants who had an additional source of exposure by ingestion. Animal studies have shown cadmium to be a lung carcinogen, while a study by Thun et al. provides the best evidence to date that cadmium inhaled as CdO particles may be a human lung carcinogen. On the basis of this latter study, EPA estimates the risk due to cadmium at 1.8 X 10(-3) cases/micrograms/m3, which results in more than 100,000 excess lung cancers (lifetime). For arsenic, the risk estimate of 4.29 cases/1,000 micrograms/m3, based on epidemiologic data also results in more than 100,000 lung cancers (lifetime). This paper reviews the bases for these estimates and presents recommendations for further research. Lung cancer risks also exist for other metals such as nickel, chromium, and beryllium. Further study is required before a definitive conclusion can be reached about the significance and magnitude of environmental exposures to metals as a cause of lung cancer.

Air Pollutants↗
PubMed1986

Immediate public health concerns and actions in volcanic eruptions: lessons from the Mount St. Helens eruptions, May 18-October 18, 1980.

A comprehensive epidemiological evaluation of mortality and short-term morbidity associated with explosive volcanic activity was carried out by the Centers for Disease Control in collaboration with affected state and local health departments, clinicians, and private institutions. Following the May 18, 1980 eruption of Mount St. Helens, a series of public health actions were rapidly instituted to develop accurate information about volcanic hazards and to recommend methods for prevention or control of adverse effects on safety and health. These public health actions included: establishing a system of active surveillance of cause-specific emergency room (ER) visits and hospital admissions in affected and unaffected communities for comparison; assessing the causes of death and factors associated with survival or death among persons located near the crater; analyzing the mineralogy and toxicology of sedimented ash and the airborne concentration of resuspended dusts; investigating reported excesses of ash-related adverse respiratory effects by epidemiological methods such as cross-sectional and case-control studies; and controlling rumors and disseminating accurate, timely information about volcanic hazards and recommended preventive or control measures by means of press briefings and health bulletins. Surveillance and observational studies indicated that: excess in morbidity were limited to transient increases in ER visits and hospital admissions for traumatic injuries and respiratory problems (but not for communicable disease or mental health problems) which were associated in time, place, and person with exposures to volcanic ash; excessive mortality due to suffocation (76 per cent), thermal injuries (12 per cent), or trauma (12 per cent) by ash and other volcanic hazards was directly proportional to the degree of environmental damage--that is, it was more pronounced among those persons (48/65, or about 74 per cent) who, at the time of the eruption, were residing, camping, or sightseeing (despite restrictions) or working (with permission) closer to the crater in areas affected by the explosive blast, pyroclastic and mud flows, and heavy ashfall; and de novo appearance of ash-related asthma was not observed, but transient excesses in adverse respiratory effects occurred in two high-risk groups--hypersusceptibles (with preexisting asthma or chronic bronchitis) and heavily exposed workers. Laboratory and field studies indicated that: volcanic ash had mild to moderate fibrogenic potential, consisting of greater than 90 per cent (by count) respirable size particles which contained 4-7 per cent (by weight) crystalline free silica (SiO2).(ABSTRACT TRUNCATED AT 400 WORDS)

Air↗