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Biomedical subjects

J Metz

Publications and source records attributed to J Metz.

At least 199 records · Page 11Linked to original sources
PubMed1978

Studies on the ultrastructure and permeability of the hemotrichorial placenta. I. Intercellular junctions of layer I and tracer administration into the maternal compartment.

The distribution of lanthanum chloride and horseradish peroxidase within the full-term chorioallantoic placenta of the rat was investigated 1 to 20 min after administration of these tracers into the maternal blood circulation. Both tracers rapidly penetrate trophoblastic layer I and diffuse into the interspace between layers I and II. They are localized in extensive infoldings and caveolae of the outer surface of layer II. The syncytial character of layer II is confirmed at this development stage of the placenta. There is no vesicular uptake or penetration beyond layer II until 20 min after tracer administration. Our results indicate that trophoblastic layer II is the main barrier in the chorioallantoic rat placenta preventing the permeation of macromolecules from maternal to fetal compartments. With freeze-fracturing, particulate strutures of variable arrangement and size are found between adjacent cells of layer I. With goniometric analysis small gaps between the appositions of the membrane are observed. These structures are interpreted as tight and/or gap junctions during stages of assembly or disassembly.

Animals↗
PubMed1978

Studies on the ultrastructure and permeability of the hemotrichorial placenta. II. Fetal capillaries and tracer administration into the fetal blood circulation.

The distribution of horseradish peroxidase and lanthanum chloride within the full term chorioallantoic placenta of the rat was examined after administration of these tracers into the umbilical artery. Both tracers rapidly traverse the capillary endothelium. Transendothelial channels, fenestrations and micropinocytotic vesicles provide the main pathways. Intercellular clefts which are either patent or interrupted by leaky intercellular junctions, also contribute to a rapid passage of low and high molecular weight substances. Deep channel-like invaginations, effecting an increase of the exchange area of layer III, are freely accessible to the tracers from the interspace between the capillary endothelium and trophoblastic layer III. The invaginations, however, are not in continuity with the interspace between layers II and III, verifying the syncytial character of layer III. Neither an uptake of the tracers nor a passage across layer III is observed. The main permeability barrier to feto-maternal transfer within the chorioallantoic placenta is localized in the syncytiotrophoblastic layer III. This layer controls the passage of low molecular weight substances and restricts the penetration of high molecular weight substances.

Animals↗
PubMed1978

[Attempts of sensitizing guinea-pigs with five different derivates of para-substituted benzene (author's transl)].

Skin tests with derivatives of para-substituted benzene were carried out at 4 different concentrations on a total of 160 guinea pigs. Results were evaluated macroscopically and histologically. Each substance was tested on 32 animals. Sensitization was obtained with p-aminodiphenylamine in about 50%, with p-toluylenediamine in about 25%, with 1% and 2% p-phenylenediamine in 62% with 5% p-aminoazotoluene in 37%, whereas no sensitization was observed with p-aminobenzoic acid. Thus, p-aminodiphenylamine, p-toluylenediamine and p-phenylenediamine must be regarded as highly sensitizing agents, whereas p-aminozotoluene and p-aminobenzoic acid seem to be less effective respectively non sensitizing.

Animals↗
PubMed1978

Handling of highly infectious material in a clinical pathology laboratory and in a viral diagnostic unit.

The handling of potentially lethal and highly infective material in a routine clinical pathology laboratory and in a viral diagnostic unit is detailed. Extensive precautions were taken at each step of the receiving, processing and disposal cycle. Disposable protective clothing and apparatus were used whenever possible. Laboratory tests were limited to those essential for the clinical management and diagnosis. Technologists who handled infective material were limited to minimal numbers of experienced, non-pregnant, informed volunteers. They wore special protective clothing, including gloves, caps, gowns and masks. When possible, specimens were handled under special protective hoods. Potentially infective material was processed through automated apparatus, and care was taken to prevent contamination of its exterior. The effluent from the machines was collected into viricidal agents (glutaraldehyde, sodium hypochlorite). After processing, the machines were flushed extensively with viricidal solution. This procedure has caused no damage to the automated equipment and has been adopted as a routine laboratory safety measure. The protective procedures adopted were successful in that there was no outbreak of the viral infection among the associated laboratory workers.

Animals↗
PubMed1978

Exocrine pancreas under experimental conditions. IV. Alterations of intercellular junctions between acinar cells following pancreatic duct ligation.

Exocrine pancreatic tissue was investigated during various intervals after pancreatic duct ligation. Concomitant to the increase of the intraluminal pressure, alterations are found in the arrangement of the luminal membrane surface and the zonulae occludentes of the acinar cells. The zonulae occludentes exhibit a disarrangement of their strands. The number of strands diminishes and small interruptions as well as large discontinuities of the strands are observed in most regions of the acinar cells. Furthermore, gap junctions are found very infrequently between acinar cells. The ultrastructural alterations of the zonulae occludentes suggest a gradual adaptation to the increasing unilateral pressure. However, a leakage of the paracellular permeability barrier occurs which contributes to the known shunt between the compartments of the pancreatic juice and the interstitial space following pancreatic duct obstruction. The present investigation is a further example of alterations in the paracellular permeability and intercellular communication of epithelial cells under pathological conditions.

Animals↗
PubMed1978

Protein energy malnutrition and nutritional anaemia in preschool children in rural KwaZulu.

The prevalence of protein energy malnutrition (PEM) and nutritional anaemia was investigated in 392 black children, aged 13--60 months, living in a poor rural area. Breast feeding was practised extensively in the population (median duration 14 months). The overall prevalence of PEM was 16,4%, but severe PEM occurred in only 2,7% of the children. Anaemia was present in 6,7% of children, and was almost invariably associated with iron deficiency. Biochemical evidence of iron, folate and vitamin B12 deficiency was detected in 36%, 14,8%, and 0,3% of children respectively. Anaemia was almost confined to the 1-year-old group, but biochemical evidence of iron deficiency, while highest in this age group, continued into the 2-4-year age group. No relationship was found between ecological factors such as income, educational status, etc. and any of the anthropometric, biochemical or haematological variables. The prevalence of PEM and anaemia in these poor rural children is lower than that of a comparable group of underprivileged urban children, thus emphasizing that city slum conditions are producing considerable nutritional problems in their wake. It is of importance to investigate further why some children who are severely deprived in many ways do not necessarily manifest a proportional degree of nutritional deprivation.

Black or African American↗
PubMed1978

[Nevoid hair bundles in man].

Between the different forms of multiple hairs the circumscribed occurence of compound hairs is a rare nevoid hair-abnormality. It is caused by merging of several follicles in the middle or upper corium. The deep parts and the papillae are independent units. The pathogenesis, clinical relevance and therapy of compound hairs are discussed on the basis of an own observation.

Adult↗
PubMed1977

Morphological alterations and functional changes of interhepatocellular junctions induced by bile duct ligation.

The effect of bile duct ligation on the intercellular junctions of hepatocytes was investigated. The features and the arrangement of the bile canaliculi and the zonulae occludentes alter concomitant to the increase of the intracanalicular pressure. The lumen of the bile canaliculi enlarges and the microvilli disappear. The array of the zonulae occludentes becomes irregularly shaped, the number of strands diminishes and interruptions of the strands occur. With peroxidase a leakage in the bile-blood barrier is detected. Furthermore a disappearance of gap junctions between the hepatocytes after bile duct ligation is observed. The present investigation shows that the zonulae occludentes are mobile structures which are changed by increased unilateral pressure. Due to their ultrastructural alterations, a leakage of the permeability barrier between physiological compartments is found.

Animals↗
PubMed1977

The use of ionic lanthanum as a diffusion tracer and as a marker of calcium binding sites.

The distribution of ionic lanthanum (La3+) was studied after perfusion of the isolated rat heart with a buffered salt solution containing lanthanum chloride. We have demonstrated that the localization of lanthanum differed from that shown in previous studies in which hearts were exposed to ionic or colloidal lanthanum during or after fixation. La3+ passed rapidly through the intercellular cleft between endothelial cells. There was relatively little transport by micropinocytosis and no evidence of transendothelial passage through the cytoplasm. Perfusion with a solution containing 1 to 15 mM LaCl3 resulted in localization of La3+ on the entire cytoplasmic membrane system of muscle cells, i.e.: the non-specialized parts of the muscle cell membranes were stained by La3+ as well as the membranes of micropinocytotic vesicles, of the T-system and of the intercalated disc. The cytoplasmic leaflets of gap junctions were especially stained. However, the cell membranes of non-muscle cells were free of lanthanum precipitates. Freeze-fracturing of muscle cells showed concomitant alteration in the distribution of membrane-associated particles. The gap junction membranes also showed changes in particle aggregation. Intracellular binding of La3+ are restricted to muscle cells. Lanthanum was found in the cell nucleus associated with heterochromatin, in the nucleolus, and along the nuclear membrane. The myofibrils were stained mainly over the I-band.

Animals↗
PubMed1977

Exocrine pancreas under experimental conditions. III. Membrane and cell junctions in isolated acinar cells.

The ultrastructure of the cell membrane and intercellular junctions was studied after isolation of exocrine pancreatic cells by tryptic digestion and mechanical treatment. The number and distribution of membrane associated particles does not change significantly when acinar cells in situ are compared to those after the isolation procedure. However, intercellular junctions undergo distinct alterations. Gap junctions in normal pancreatic cells are macular in shape and localized at the lateral parts of the cell membrane. In isolated acinar cells gap junctions are irregularly shaped, more extended, and frequently associated with tight junctions. Tight junctions form belt-like structures which are found to persist after isolation but subsequently become elongated and interrupted. Thus extensive macular areas of tight junctions develop. Further, the strands on the P-face and the grooves on the E-face of freeze-fracture replicas change in array, dissociate, and become loosely packed on large membrane areas. The present investigation shows that the intramembranous proteins of tight and gap junctions are mobile structures within the fluid membrane. The shape of their array is dependent on the form of the intercellular contact zone.

Animals↗