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Biomedical subjects

P Hoffman

Publications and source records attributed to P Hoffman.

At least 127 records · Page 7Linked to original sources
PubMed1980

Imaging unstained proteoglycan aggregates by soft x-ray contact microscopy.

Soft X-ray contact microscopy is a relatively new form of ultrastructural imaging, having better than 6 nm resolution and being uniquely well suited for the examination of fragile, unstained biological specimens. The biological specimen placed on a layer of photoresist and exposed to soft X-rays (1-10 nm lambda) of a specific wavelength or broad band. After X-ray exposure, the specimen is removed from the photoresist and the latter chemically developed. When the developed replica is examined by high resolution scanning electron microscopy, the fine structure of the original biological specimen is faithfully reproduced. Since the soft X-ray replica is initially formed due to the differential absorption of the incident X-rays by the biological specimen, the resultant contact replica also reveals information about the elemental composition of the sample. This paper presents our application of this new technique for the study of the proteoglycans, the complex polyanionic macromolecules comprising the gel phase in the matrix of mammalian cartilage.

Animals↗
PubMed1980

Ultrastructural and elemental imaging of biological specimens by soft X-ray contact microscopy.

Soft X-ray contact microscopy offers a means of visualizing unstained as well as stained biological materials at better than 6 nm resolution. Unlike light and transmission electron microscopy, which rely on stains to increase specimen contrast, soft X-ray imaging is dependent upon the differential absorption of incident soft (1-10nm wavelength) X-rays by the endogenous elements within the specimen. The advantages of using soft X-rays for imaging are: 1) reduced specimen damage during exposure; 2) ability to image hydrated specimens at atmospheric pressure; 3) ability to image specimens ranging in thickness from less than 40 nm to as much as 10 microns; and 4) ability to map the elemental composition of the specimen through observation of the differential absorption of properly chosen incident x-ray wave lengths. This paper explains the principles of the image formation and demonstrates the use of soft X-ray contact microscopy with biological samples which could not readily be imaged in their natural form using conventional electron microscopy methods.

Animals↗
PubMed1979

Selective aggregation of proteoglycans with hyaluronic acid.

Conditions were established to separate proteoglycan aggregate (AH1) from a bovine nasal septum extract by associative rate zonal sedimentation on a NaCl gradient. The AH1 has a higher protein content than the mixed aggregate-monomer (A1) isolated by conventional associative CsCl density gradient centrifugation from a portion of the same extract. The same associative rate zonal conditions separated the A1 fraction into aggregated AH1 containing hyaluronic acid and nonaggregated proteoglycan monomer (N1) essentially free of hyaluronic acid. The AH1 fraction is richer in protein and keratin sulfate than is N1. Dissociative rate zonal sedimentation of A1 under conditions which totally sedimented most of the disaggregated monomer (AH1-D1) and the nonaggregated monomer N1 separated a less sedimentable protein and keratan sulfate-rich proteoglycan monomer (AH1-D2). Chromatography on Sepharose 2B under dissociative conditions demonstrated that the nonaggregated N1 monomer is intermediate in size between the disaggregated monomers AH1-D1 and AH1-D2. N1 has a buoyant density higher than AH1 and is practically equivalent to AH1-D1. All are dense fractions so that separation by CsCl density gradient equilibration is not feasible.

Amino Acids↗
PubMed1979

A new micro-assay for hyaluronidase activity.

A new micro-method for the assay of hyaluronidase activity is described. The method utilizes chondroitin sulfate as a substrate. The degraded products of chondroitin sulfate by hyaluronidase are determined by modified disc gel electrophoresis. The products are first concentrated into a single band in acrylamide gel, and then the band is stained with cetylpyridinium chloride. The absorbance of the band is proportional to the amount of the degraded products. The hyaluronidase activity is therefore linearly related to the absorbance. This procedure represents a sensitive method for the assay of hyaluronidase activity in the serum and urine.

Animals↗
PubMed1977

Precautions in medical care of, and in handling materials from, patients with transmissible virus dementia (Creutzfeldt-Jakob disease).

We have formulated a series of precautions to be observed in caring for patients with Creutzfeldt-Jakob disease and in handling their tissues. The virus resists inactivation by simple boiling in water. Also ineffective are 10 per cent formalin, 70 per cent alcohol and ionizing and ultraviolet radiation. Autoclaving for one hour at 121 degrees C and 20 psi inactivates the agent completely. Five per cent hypochlorite, 0.03 per cent permanganate, phenolics and iodine solutions are adequate disinfectants inactivating large infective doses of the virus. Special isolation wards for afflicted patients seem unwarranted. Workers exposed to infected saliva, nasopharyngeal secretions, urine or feces need to and should wash thoroughly with ordinary soap. Needles and needle electrodes should be autoclaved or incinerated and discarded. Demented persons should not be used for donations of blood or other tissues. Although precautions are necessary, the epidemiologic evidence does not suggest an unusual risk of Creutzfeldt-Jakob disease for medical workers.

Animals↗
PubMed1977

Neurochemical correlates of ethanol withdrawal: alterations in serotoninergic function.

Cessation of chronic ethanol administration, and elimination of ethanol from the body, results in a withdrawal syndrome in mice characterized by behavioural symptoms and hypothermia. During withdrawal, the accumulation rate of [14C] 5-hydroxytryptamine (5-HT) from [14C]tryptophan, was significantly lower in the brainstem of the ethanol-withdrawn animals than in controls. A similar pattern was seen in forebrain. When the rate of 5-HT accumulation was determined using pargyline, no differences occurred between control and ethanol-treated animals. The endogenous concentrations of tryptophan in plasma, and tryptophan, 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in brain were the same in ethanol-treated and control animals. It is suggested that the changes in accumulation of 14C-5-HT and 14C-5-HIAA in ethanol-withdrawn animals reflected alterations in electrical activity of serotoninergic neurons during withdrawal.

Alcoholism↗
PubMed1976

Influence of fixation and morphometric technics on capillary basement-membrane thickening prevalence data in diabetes.

Muscle tissue obtained by needle biopsy from 20 diabetic subjects and from 20 age-matched control subjects was divided into two portions, one of which was fixed and processed by our routine procedure (primary glutaraldehyde fixation followed by osmium fixation and embedment in araldite) and the other was fixed initially in osmium tetroxide and embedded in maraglas, the procedure employed by Siperstein et al. Basement-membrane width of capillaries was measured by the 20-point method of Siperstein et al. and by the two-minimum-point technic developed in our own laboratory. Contrary to the experience of Siperstein et al., the prevalence of basement-membrane thickening in diabetic subjects based on mean width values and/or standard deviations in excess of 95 per cent tolerance intervals was highest (65 per cent) in minimum measurements of glutaraldehyde-fixed tissues and lowest (30 per cent) in osmium-fixed tissues (X2 = 4.9123, p less than 0.05). Internal discrepancies in the data of Siperstein et al. indicate that (1) their basement-membrane-width values derived from multiple measurements from control subjects are anomalous (low) and (2) the very high prevalence of basement-membrane thickening they reported in diabetic and in prediabetic subjects and considered as strong support for their conclusion that basement-membrane disease is independent of and precedes glucose intolerance is suspect.

Adult↗
PubMed1975

Variable nature of cartilage proteoglycans.

Cartilage proteoglycan aggregates are separated from collagen and other non-proteoglycan protein by preparative rate zonal sedimentation under associative conditions. Dissociative rate zonal sedimentation produces sedimented proteoglycan of lower protein content with a corresponding increase in the amount of less sedimentable protein-rich proteoglycan. An extensive number of sequential rate zonal sedimentations discloses that the proceess of disaggregation involves the separation of proteoglycans varying continuously in composition with no apparent discontinuities in distribution to indicate the presence of distinctively different macromolecules. The variations encompass proteoglycans of low protein content containing less than 2% keratan sulfate and proteoglycans with keratan sulfate as the predominant polysaccharide (present in concentrations greater than 2-fold that of the chondroitin sulfate) and more than a 10-fold increase in protein content.

Amino Acids↗
PubMed1975

Neurologic disorders following surgery for peptic ulcer disease.

The neurologic status of 2,000 veterans who had had surgery for peptic ulcer between 1952 and 1957 was evaluated. In 1970, a total of 156 of these men were examined, 97 of whom had procedures that disrupted the normal continuity of the upper gastrointestinal tract. Twenty-one had neurologic disorders, including 17 patients with peripheral neuropathies. Procedures bypassing the ampulla of Vater were performed in 15 of these. The only detected factor associated with neurologic manifestations was weight loss since surgery. A mortality study of the total population revealed 865 patients had died by the end of 1973. There were seven deaths attributed to neurologic causes, one in a patient with amyotrophic lateral sclerosis and one in another with spinal paralysis. All seven were among the 70% of the deceased who had had surgery that disrupted the continuity of the upper gastrointestinal tract. Thus, we conclude that the type of surgery influenced the likelihood of neurologic complications, but at least for motor neuron disease, the increased risk was not appreciable.

Adult↗
PubMed1975

Distribution studies of proteoglycan aggregates by ultracentrifugation.

The tendency forcartilage proteoglycans to aggregate or disperse in ultracentrifugation at high ionic strength is influenced by cations. Guanidinum, Li+ and Ca++ promote disaggregation and Na+, K+ and Cs+ support aggregation. The process of disaggregation is fundamentally the separation of low density from high density proteoglycans, the density being an inverse function of the protein content. PPL 5 pellet formation is a packing or aggregation phenomenon occurring well below the isopycnic density of proteoglycan which accounts for its difference from the isopycnic density equilibrated complex. Cations which promote disaggregation result in shifts in distribution of the proteoglycans on equilibrated density gradients. Comparisons of the desulfated products of the high density aggregated and disaggregated complexes and of more selective high and low density proteoglycan fractions clearly show the heterogeneity of proteoglycans related to protein content. It is suggested that the nature of the variable population of proteoglycan macromolecules permits its existence as a self aggregating system.

Adhesiveness↗
PubMed1975

[Studies on long-term irradiated rats using clomiphenedihydrogen citrate, LH and LH-RH].

The influence of clomiphene, LH and LH-RH on vaginal cycle and ovarian function in mature rats, which had been exposed to continuous light in order to block the cyclic sexual centre, was examined by different doses. While ovulation was obtained by administration of LH and LH-RH, clomiphene showed no effect. It may be assumed that the central mode of action of the "ovulation inducing effect" of clomiphene is mediated by stimulation of the cyclic sexual centre in the anterior hypothalamus.

Animals↗