Biomedical subjects

K Holme

Publications and source records attributed to K Holme.

10 recordsLinked to original sources

PubMed1998

Matrix metalloproteinase inhibitors: a structure-activity study.

Modifications around the dipeptide-mimetic core of a hydroxamic acid based matrix metalloproteinase inhibitor were studied. These variations incorporated a variety of natural, unnatural, and synthetic amino acids in addition to modifications of the P1' and P3' substituents. The results of this study indicate the following structural requirements: (1) Two key hydrogen bonds must be present between the enzyme and potent substrates. (2) Potent inhibitors must possess strong zinc-binding functionalities. (3) The potential importance of the hydrophobic group at position R3 as illustrated by its ability to impart greater relative potency against stromelysin when larger hydrophobic groups are used. (4) Requirements surrounding the nature of the amino acid appear to be more restrictive for stromelysin than for neutrophil collagenase, 72 kDa gelatinase, and 92 kDa gelatinase. These requirements may involve planar fused-ring aryl systems and possibly hydrogen-bonding capabilities.

Chromatography, High Pressure Liquid↗

PubMed1996

[Partial or total stripping of the great saphenous vein. 5-year recurrence frequency and 3-year frequency of neural complications after partial and total stripping of the great saphenous vein].

One hundred and sixty-three patients with primary long saphenous vein varices were randomized to either classical (total) stripping of the long saphenous vein (n = 84) or partial stripping, i.e. only of the femoral part of the vein (n = 79). Permanent nerve lesions were evaluated clinically three years and recurrence of varicosities evaluated five years postoperatively. It was found that 24 patients (29%) who had total stripping performed had permanent lesions of the saphenous nerve, whereas only four of the patients (5%) who had partial stripping of the vein had lasting nerve lesions (p < 0.01). Ten percent of patients in both groups had recurrence of varicosities. The present - one and only - long-term, randomized study of different stripping procedures shows that stripping the long saphenous vein below the knee increases the permanent nervedamage six-fold without reducing long-term recurrency. Total stripping of the long saphenous vein should be abandoned as a routine in varicose vein surgery.

Follow-Up Studies↗

PubMed1996

Chemical modifications of heparin that diminish its anticoagulant but preserve its heparanase-inhibitory, angiostatic, anti-tumor and anti-metastatic properties.

Structural features of heparin potentially important for heparanase-inhibitory activity were examined by measuring the ability of heparin derivatives to affect the degradation of [3H]acetylated heparan sulphate by tumor cell heparanases. IC50 values were determined using an assay which distinguished degraded from undegraded substrate by precipitation of the latter with cetylpyridinium chloride (CPC). Removal of heparin's 2-O-sulphate and 3-O-sulphate groups enhanced heparanase-inhibitory activity (50%). Removal of its carboxyl groups slightly lowered the activity (18%), while combining the treatments abolished the activity. At least one negative charge on the iduronic acid/idose moiety, therefore, is necessary for heparanase-inhibitory activity. Replacing heparin's N-sulphate groups with N-acetyl groups reduced its activity (37%). Comparing this heparin derivative with 2,3-O-desulphated heparin, the placement of sulphate groups appears important for activity since the two structures have similar nominal linear charge density. In addition, unsubstituted uronic acids are nonessential for inhibition since their modification (periodate-oxidation/borohydride-reduction) enhanced rather than reduced heparanase-inhibitory activity. The most effective heparanase inhibitors (2,3-O-desulphated heparin, and [periodate-oxidized, borohydride-reduced] heparin) were tested in the chick chorioallantoic membrane (CAM) bioassay for anti-angiogenic activity and found to be at least as efficacious as heparin. 2,3-O-desulphated heparin also significantly decreased the tumor growth of a subcutaneous human pancreatic (Ca-Pan-2) adenocarcinoma in nude mice and prolonged the survival times of C57BL/6N mice in a B16-F10 melanoma experimental lung metastasis assay.

Animals↗

PubMed1995

Identification of structural features of heparin required for inhibition of herpes simplex virus type 1 binding.

Binding of HSV-1 to cells is mediated by interactions of virion glycoproteins gC and/or gB with heparin sulfate (HS) glycosaminoglycans on cell surface proteoglycans. HS and the related glycosaminoglycan, heparin, comprise a family of heterogeneous carbohydrates composed of long, unbranched polysaccharides modified, for example, by sulfations and acetylations. To define the specific features of HS important for viral binding, we took advantage of the structural similarities between heparin and cell surface HS and compared the ability of chemically modified heparin compounds to inhibit the binding of viral particles to the cell surface and subsequent plaque formation. Because binding presumably involves multiple, complex interactions between both known heparin-binding glycoproteins, gC and gB, and cell surface HS, we compared the effects of modified heparin compounds on the binding and subsequent plaque formation of wild-type and gC-negative strains of HSV-1 and, in select cases, the binding of gB-negative virus to cells. We identified specific structural features of heparin essential for the inhibition of viral binding. For example, both N-sulfation and 6-O-sulfation must be important determinants since desulfation of heparin at these sites abolished or decreased the antiviral activity of heparin. Moreover, we found that the antiviral activity of heparin was independent of its anticoagulant activity. Carboxyl-reduced and 2,3-O-desulfated heparin selectively inhibited binding of gC-positive viruses (wild-type or a gB-negative strain) to cells, but had little or no inhibitory effect on binding and subsequent plaque formation for a gC-deletion virus. These results suggest that gC and gB interact with different structural features of HS.

Animals↗

PubMed1994

Structural features in heparin which modulate specific biological activities mediated by basic fibroblast growth factor.

The biological activity of basic fibroblast growth factor (bFGF) is influenced greatly by direct binding to heparin and heparan sulphate (HS). Heparin-derived oligosaccharides have been utilized to determine the structural requirements present in the polymer that account for binding to bFGF. We had previously demonstrated that fragments > 6 mer can inhibit the interaction between cell surface heparan sulphate proteoglycan (HSPG) and bFGF, and bFGF-induced proliferation of adrenocortical endothelial (ACE) cells. In contrast, oligosaccharides > 10 mer can enhance the binding of bFGF to its high-affinity receptor or support bFGF-induced mitogenesis in ACE cells (Ishihara et al., J. Biol. Chem., 268, 4675-4683, 1993). We have extended these studies to size- and structure-defined oligosaccharides from heparin, 2-O-desulphated (2-O-DS-) heparin, 6-O-desulphated (6-O-DS-) heparin, carboxy-reduced (CR-) heparin and carboxy-amidomethylsulphonated (AMS-) heparin. Oligosaccharides from these polymers were fractionated on a bFGF-affinity column and were assessed as inhibitors or enhancers of specific bFGF-derived biological activities. The results of these studies indicate that both 2-O-sulphate and the negative charge of the carboxy group [L-iduronic acid (IdoA) residues] are required for specific interactions of heparin-derived oligosaccharides with bFGF and for modulation of bFGF mitogenic activity. In addition, the charge of the carboxy groups in uronic acids can be replaced by other functional groups with a negative charge, such as the amidomethyl sulphonate moiety described here.

Animals↗

PubMed1991

Biologically meaningful determinants of the in vitro strength of lumbar vertebrae.

Applying unbiased stereological methods and a new stereological parameter, star volume of cancellous bone, the bone structure of the first vertebral body was examined and compared with the compressive strength of the second lumbar vertebra. The material came from eight males, aged 33-69 years (mean 49 years) and seven women, aged 22-87 years (mean 52 years) without malignant or metabolic bone disease. From these individuals, first and second lumbar vertebral body were obtained at autopsy. The heights and weights of the individuals were recorded. The following structural parameters were estimated on undecalcified, seven-microns, Goldner-Trichrome stained vertical sections: fractional volume of trabecular bone (BV/TV%), mean trabecular thickness (Tb.Th.l1 microns), trabecular star volume (V*tr mm3), marrow space star volume (V* m.space mm3), and mean thickness of the lateral cortical ring (microns). The compressive strength of whole vertebral body, mean cross sectional area (cm2), and ash density (g/cm3) were estimated and the data were compared to bone histomorphometric estimates. A significant decrease with age for all parameters was found except for marrow space star volume, which increased. With compressive strength as the dependent variable and all other parameters as independent variables, it was shown by standard multiple regression analysis that the in vitro tested compressive strength could be predicted from mean cortical thickness, mean cross sectional area, and marrow space star volume or ash density with a multiple, squared coefficient of regression (r2) of 0.95 when the height and sex of the individual were known.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

An oligosaccharide-tetanus toxoid conjugate vaccine against type III group B Streptococcus.

We have developed an oligosaccharide-tetanus toxoid conjugate vaccine against type III group B Streptococcus. Purified group B streptococcal type III capsular polysaccharide was depolymerized by enzymatic digestion using endo-beta-galactosidase produced by Citrobacter freundii. Following enzymatic digestion, oligosaccharides were fractionated by gel filtration chromatography on Sephadex G-75. An oligosaccharide pool of average Mr = 14,500 (corresponding to 13.6 repeating units of the type III polysaccharide) was used for conjugation to tetanus toxoid. Tetanus toxoid was covalently coupled via a synthetic spacer molecule to the reducing end of the oligosaccharide by reductive amination. The oligosaccharide-tetanus toxoid conjugate elicited type III-specific anticapsular antibodies (measured in enzyme-linked immunosorbent assay) in three out of three rabbits whereas the unconjugated native type III polysaccharide was nonimmunogenic. Antiserum from rabbits vaccinated with the oligosaccharide-protein conjugate protected mice against lethal challenge with live group B streptococci (16 out of 16 mice survived) and opsonized group B streptococci for phagocytosis in vitro. No protection was conferred by preimmune serum nor by serum from rabbits vaccinated with unconjugated native type III polysaccharide. An oligosaccharide-protein conjugate vaccine of this design may prove to be an effective immunogen for protection against group B streptococcal infection in humans. In addition, the approach to vaccine design utilized in these studies will facilitate further definition of the structural parameters that determine immune response to glycoconjugate vaccines.

Animals↗

PubMed1990

Immunogenicity in animals of a polysaccharide-protein conjugate vaccine against type III group B Streptococcus.

The native capsular polysaccharide of type III group B Streptococcus elicits a specific antibody response in only 60% of nonimmune human subjects. To enhance the immunogenicity of this polysaccharide, we coupled the type III polysaccharide to tetanus toxoid. Prior to coupling, aldehyde groups were introduced on the polysaccharide by controlled periodate oxidation, resulting in the conversion of 25% of the sialic acid residues of the polysaccharide to residues of the 8-carbon analogue of sialic acid, 5-acetamido-3,5-dideoxy-D-galactosyloctulosonic acid. Tetanus toxoid was conjugated to the polysaccharide by reductive amination, via the free aldehyde groups present on the partially oxidized sialic acid residues. Rabbits vaccinated with the conjugate vaccine produced IgG antibodies that reacted with the native type III group B streptococcal polysaccharide (3/3 rabbits), while rabbits immunized with the unconjugated type III polysaccharide failed to respond (0/3 rabbits). Sera from animals receiving conjugate vaccine opsonized type III group B streptococci for phagocytic killing by human peripheral blood leukocytes, and protected mice against lethal challenge with live type III group B streptococci. The results suggest that this method of conjugation to a carrier protein may be a useful strategy to improve the immunogenicity of the type III group B Streptococcus polysaccharide in human subjects.

Animals↗

PubMed1990

Incidence of lesions of the saphenous nerve after partial or complete stripping of the long saphenous vein.

To find out whether the usual total stripping of the long saphenous vein in operations for varicose veins could be replaced by a less traumatic removal of only the femoral part of the vein, a randomised prospective study was carried out in 163 consecutive patients, of whom 157 were evaluable. Group A (n = 80) had total stripping and group B (n = 77) had partial stripping (extraction of the long saphenous vein from the groin to immediately below the knee). The two groups, which were comparable, were assessed three months after operation when 75 in group A (94%) and 75 in group B (97%) had excellent or good relief of symptoms and comparable absence of residual varicosities. Lesions of the saphenous nerve were found in 31 in group A (39%) and 5 in group B (7%) (p less than 0.001). There were few other complications. We conclude that preservation of the distal long saphenous vein not only reduces nerve damage, but also retains enough vein for use should coronary artery bypass or peripheral vascular grafting be necessary in future.

Adult↗

PubMedDate not supplied

The anatomic relationship between the long saphenous vein and the saphenous nerve. Relevance for radical varicose vein surgery.

Radical surgery for varicose veins often includes total stripping of the long saphenous vein. Some surgeons now claim, however, that stripping of the distal part of that vein can be avoided, thereby reducing the risk of damage to the saphenous nerve. Dissection of 60 cadaver legs to demonstrate the relationship between the long saphenous vein and the saphenous nerve indicated that stripping performed from the groin to immediately below the knee would minimize the risk of nerve damage.

Female↗