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Biomedical subjects

R Hertel

Publications and source records attributed to R Hertel.

At least 73 records · Page 4Linked to original sources
PubMed1978

Structural differences in the mesentery microcirculation between normotensive and spontaneously hypertensive rats.

The mesentery preparation of normotensive rats (NR) (Pcarotis97 +/- 4 mm Hg) and of spontaneously hypertensive rats (SHR) (161 +/- 2 mm Hg) of comparable age (20 +/- 3 weeks) was used to study morphological changes of the microvasculature in established hypertension. The arterioles, classified according to their branching order, had an increased inner diameter in SHR (by 20%). The smooth muscle hypertrophy decreased with smaller vessel size. Pre- and postcapillary vessels were shorter in SHR than in NR by 17 to 35%. The number of these vessels related to the number of the feeding terminal arterioles was found to be reduced by nearly 50% in SHR. The data suggest a lowered arteriolar flow resistance in individual vessels of the hypertensive group concomitant with a gradually disappearing smooth muscle hypertrophy towards the capillary bed. The elevation of the resistance to blood flow in the hypertensive rats is obviously caused by a reduced number of resistance vessels, as seen in the mesentery vascular bed. Similar results were obtained in the true capillaries, which showed greater inner diameters (SHR vs NR:7.2 micron vs 6.4 micron), shortened lengths (141 vs 170 micron) and a reduced number (50 vs 70). Red cell velocity in true capillaries did not differ (0.51 mm/s vs 0.49 mm/s). Arterio-venous shunt vessels were described with an average inner diameter of 11 micron. In SHR these vessels were shorter (424 vs 654 micron) and increased in number. The 'hydraulic hindrance' of AV-shunt vessels and true capillaries together was decreased in SHR; the surface area did not differ between SHR (55.7 . 10(3) micron2) and NR (50.1 . 10(3) micron2) suggesting no major variation in the exchange functions.

Animals↗
PubMed1978

Intravital measurement of arteriolar pressure and tangential wall stress in normotensive and spontaneously hypertensive rats (established hypertension).

Under intravital conditions, intravascular pressures of mesenteric resistance vessels were measured in normotensive (NR, mean blood pressure 92 mm Hg) and spontaneously hypertensive rats (SHR, 161 mm Hg) being elevated over all by about 75%; the tangential wall stress (sigma = p.r/h; p represents the intravascular pressure and r/h the ratio of internal radius to wall thickness) was found to be increased by 120-140% in SHR.

Animals↗
PubMed1977

Characterization of a Membrane Fraction Containing a b-type Cytochrome.

The various components obtained from etiolated corn (Zea mays L.) coleoptiles were fractionated by differential or sucrose gradient centrifugation. The endoplasmic reticulum, proplastids, Golgi, and mitochondria were localized by enzymic or other markers in the various fractions. A fifth fraction was also characterized. It contains glucan synthetase II activity, binding sites for N-naphthylphthalamic acid, NADH dehydrogenase activity which is both antimycin A- and cyanide-insensitive, and a b-type cytochrome. It is possible that this fraction is plasma membrane and that it may contain the blue-ultraviolet photoreceptor for phototropism in corn.

Journal Article↗
PubMed1970

Action of auxin on cell elongation.

The early time course (0-30 min) of the action of auxin (3-indoleacetic acid) on the elongation of segments from corn coleptiles was studied, using a high-resolution continuous recording technique. Two different effects of auxin were observed: (1) After addition of low auxin concentrations (2 x 10(-7)M) to 4-mm sections, a very rapid (2-3 min) enhancement of elongation was found. Similar early responses were seen following the addition of low concentrations of the methyl ester of indoleacetic acid. (2) Following a large step-up in the auxin level (10(-5), 10(-4), or 10(-3)M), a rapid transient decrease was observed one to three minutes after the addition of indoleacetic acid. It lasted 10-15 minutes at which time the steady rate of auxin-promoted elongation became evident. Similar kinetic patterns of auxin effects other than on elongation and the implications of the findings on hypotheses of the primary action of auxin are discussed.

Indoleacetic Acids↗
PubMedDate not supplied

Predictors of humeral head ischemia after intracapsular fracture of the proximal humerus.

The purpose of this study was to evaluate predictors of fracture-induced humeral head ischemia. Between February 1998 and December 2001, 100 intracapsular fractures of the proximal humerus, treated by open surgery, were included in a prospective surgical evaluation protocol (mean age, 60 years; minimum, 21 years; maximum, 88 years; 45 men; 57 right shoulders). Fracture morphology was assessed following a structured questionnaire and based on radiographic and intraoperative findings. Perfusion was assessed intraoperatively by observation of backflow after a borehole was drilled into the central part of the head in all shoulders and by intraosseous laser Doppler flowmetry in 46. Good predictors of ischemia were the length of the metaphyseal head extension (accuracy, 0.84 for calcar segments <8 mm), the integrity of the medial hinge (accuracy, 0.79 for disrupted hinge), and the basic fracture pattern (accuracy, 0.7 for combined types 2, 9, 10, 11, and 12). Moderate and poor predictors of ischemia were fractures consisting of four fragments (accuracy, 0.67), angular displacement of the head (accuracy, 0.62 for angulations over 45 degrees ), the amount of displacement of the tuberosities (accuracy, 0.61 for displacement over 10 mm), glenohumeral dislocation (accuracy, 0.49), head-split components (accuracy, 0.49), and fractures consisting of three fragments (accuracy, 0.38). When the above criteria (anatomic neck, short calcar, disrupted hinge) were combined, positive predictive values of up to 97% could be obtained. The most relevant predictors of ischemia were the length of the dorsomedial metaphyseal extension, the integrity of the medial hinge, and the basic fracture type determined with the binary description system.

Adult↗
PubMedDate not supplied

Factors influencing the results of a modified Bankart procedure.

Forty-two shoulders in 40 patients operated on for anterior instability between 1986 and 1991 were reexamined. The mean follow-up was 47 months. The pathoanatomic findings at surgery were a Bankart lesion in 42 shoulders, a Hill-Sachs lesion in 31 shoulders, and a rounded or defective anterior glenoid rim in 29 shoulders. The surgical technique consisted of an open reinsertion of the anterior capsule-labral complex. Four shoulders had one or more recurrent anterior dislocations, and four shoulders had recurrent anterior subluxations. Three redislocations were caused by severe trauma. The presence and magnitude of a Hill-Sachs lesion did not influence the frequency of recurrence. An osseous defect of the glenoid rim > or = 3 mm was found in three patients, one of whom had redislocation after surgery. In patients with a large Bankart lesion the rate of recurrence was significantly higher.

Adult↗