Medial collateral ligament replacement with a partially absorbable tissue scaffold

The medial collateral ligaments and medial capsular structures of canines were resected and replaced with a carbon fiber-polylactic acid polymer tissue scaffold or allowed simply to "scar-in." After 4, 8, 12, and 26 weeks in vivo, the stability of the knees was quantitatively evaluated and the mechanical properties of the regrown structures determined. Histological sections of the regrown structures were examined after 26 weeks in vivo. At all time periods, the knees receiving tissue scaffold ligaments were significantly more stable than those knees allowed to stabilize with scar tissue. Initial strength, rapid ingrowth, and benign tissue reaction suggest this new composite material may be useful in the treatment of joint instability.

Chemically synthesized peptides of hepatitis B surface antigen duplicate the d/y specificities and induce subtype-specific antibodies in chimpanzees

Synthetic peptides, predicted from the nucleotide sequence of the S gene of hepatitis B virus were analyzed in terms of the established specificities of the hepatitis B surface antigen. The analysis indicated that the group-specific alpha antigen is composed of at least three nonoverlapping sequences and that a relatively hydrophilic region of the surface antigen protein, spanning amino acid residues 110-137, specifies the major d and y subtype system. The d/y subtype appears to depend on changes in one or more variable amino acids at positions 127, 131, and 134 of the hepatitis B surface antigen protein. Peptide 49 (consisting of amino acid sequences of the y subtype for the region 110-137), coupled to a carrier protein and mixed with an adjuvant, stimulated a brisk anti-y response in chimpanzees, the relevant model of human response to hepatitis B virus immunization and infection. Experimental challenge with homologous hepatitis B virus resulted in a pattern of partial protection. The results offer promise for the application of chemically synthesized peptides as vaccines in the prophylaxis of hepatitis B virus disease.

Effect of mechanical load in wound healing

This study was designed to investigate the effect of sequentially increasing mechanical load on healing incisions. Full-thickness incisions were made on the back of a young domestic pig. During the period of fibroplasia, one of the incisions was mechanically loaded with a subcutaneous tissue expander. Mechanical and histological evaluations of mechanically loaded and control incision areas indicated that the mechanical stress encouraged healing and remodeling of dermal tissue.

Absorbable polymer-filamentous carbon composites--a new class of tissue scaffolding materials

The utility of filamentous carbon in tendon and ligament repair is limited by its premature mechanical degradation. When filamentous carbon is coated with an absorbable polymer, polylactic acid (PLA), a composite material results which serves as a tissue scaffold, maintaining its integrity long enough for new tissue to grow in and around it before it gradually degrades. Biocompatibility studies showed excellent tissue response to the PLA-carbon composite. Dog patellar tendons and medial collateral ligaments and rabbit Achilles tendons fashioned from the composite were then implanted. The implants allowed almost immediate resumption of activity and encouraged the growth of new structures histologically and mechanically similar to the natural structures. Its high initial strength, rapid ingrowth and benign tissue reaction suggest that this new composite material may be useful in the treatment of tendon and ligament injuries in humans. Consequently, the material was entered into limited clinical trials. To date, thirty patients have had implant surgery for the repair of extensor mechanisms, knee ligaments, Achilles tendons, and rotator cuffs. At this writing, seven month follow-up is available. Early results are encouraging.

Iron deficiency and anemia among Indian women in Fiji

In June 1979, 245 Hindu and 240 Moslem women of childbearing age (14-45 yr) living in a semi-rural area north of Lautoka were tested for anemia and for iron-deficiency. Ninety-six (39%) of the 245 Hindu women and 77 (32%) of the 240 Moslem women were anemic according to World Health Organization criteria. Most of the cases of anemia were due to iron-deficiency. The prevalence of anemia did not change significantly with advancing age or increasing parity. Hookworm ova were found on examination of a single specimen of feces in 27 (14%) of 195 Hindu and 50 (24%) of 209 Moslem women. The presence of hookworm did not correlate with anemia. The red cell folate level was less than 160 micrograms/l in 117 (24%) of 478 women and the serum vitamin B12 level was less than 100 ng/l in 47 (10%) of 476 women. Subnormal levels of these vitamins did not correlate with anemia. The serum ferritin was determined to assess tissue iron stores. Two-hundred-and-twenty-four (46%) of 484 Indian women tested had serum ferritin values of less than 10 microgram/l; 400 (83%) had ferritin values of less than 26 microgram/l. The high prevalence of iron deficiency appears to be due predominantly to dietary factors.

Yersinia enterocolitica in Kansas. Attempted recovery from 1,212 patients

An attempt was made to isolate Yersinia enterocolitica, by cold enrichment, from the stool of 1,212 patients seen at the Wesley Medical Center in Wichita, Kansas. Y. enterocolitica was isolated from 5 (0.4%) of the patients. Shigella was isolated from 36 (3.0%) patients while either Salmonella or Campylobacter were each isolated from 15 (1.2%) patients. Two of our five Yersinia isolates were from patients admitted to the hospital with diarrhea. One was from a patient who developed transient diarrhea while in the hospital, and the other two were from patients without diarrhea. In our opinion, the data do not justify the routine examination of stool specimens for Y. enterocolitica.

Physiological changes in hyperactive children following the ingestion of food additives

This study attempted to determine if the ingestion of artificial food additives would produce detectable changes in autonomic and/or central nervous system activity in hyperactive children. A single-case experimental design was used which entailed the comparison of heart rate and electroencephalographic (EEG) measures for hyperactive and control children. The physiological measures were obtained prior to and following the ingestion of drinks containing food additives or placebos, which were administered in a double-blind, randomized, crossover procedure. The hyperactive children exhibited a greater degree of physiological activity following both the placebo and the drink containing food additives than did the control children. However, the magnitude of physiological changes in the hyperactive children were greater in response to ingestion of the additives than to placebo. These physiological findings are consistent with behavioural data indicating that some hyperactive children are adversely affected by food additives.

A phalangeal fracture model--quantitative analysis of rigidity and failure

Nine types of internal fixation techniques were tested in 4-point bending using a pig metacarpal model for phalangeal fractures. Levels of bending rigidity and bending moments at failure were determined, and the modes of failure are described. Plate and screw fixation afforded the greatest rigidity, and epiphyseal fractures occurred, leaving intact the test section. Flexible wire loop fixation failed by wire cutting into bone when a square knot was used. Twisted wire unraveled when placed in tension. Depending on the fracture type and the wire placement. Kirschner wires failed either by slipping in the bone, twisting in the bone cortex, or bending at the bone cortex interface. Rigidity varied widely depending on the way in which the wires were employed.

Herpes simplex virus: a cause for concern

Herpes simplex virus (HSV) is one of several sexually transmitted agents receiving increased attention. HSV infection is a serious problem due to: the increasing number of cases; its ability to remain latent in the host and periodically cause recurrent infection; and lack of effective treatment. HSV may be acquired by infants delivered vaginally to a woman experiencing active infection. Neonatal herpes is a devastating disease, with 60% overall mortality and serious sequelae in many of the survivors. Infection by HSV is detected most reliably by virus culture, but cytology or direct antigen detection may also be useful especially when culture is not available.

Immunogenic structure of the influenza virus hemagglutinin

We chemically synthesized 20 peptides corresponding to 75% of the HA1 molecule of the influenza virus. Antibodies to the majority (18) of these peptides were capable of reacting with the hemagglutinin molecule. These 18 peptides are not confined to the known antigenic determinants of the hemagglutinin molecule, but rather are scattered throughout its three-dimensional structure. In contrast, antibody raised to intact hemagglutinin did not react with any of the 20 peptides. Taken together these results suggest that the immunogenicity of an intact protein molecule is not the sum of the immunogenicity of its pieces.

Soft tissue attachment of a filamentous carbon-absorbable polymer tendon and ligament replacement

Soft tissue structures can be replaced by a filamentous carbon-polylactic acid polymer tissue scaffold. A successful replacement requires a secure bond between the synthetic material and living soft tissue. This attachment has been investigated in a rabbit model. In 23 male, white New Zealand rabbits, the proximal third of the Achilles tendon of the hind leg was resected. Seventeen of these rabbits received composite tendon implants; six received no implants and served as shams. In all cases, the contralateral limb served as a unoperated control. Biological fixation of the synthetic material to the tendinous and myotendinous tissues of the rabbit gastrocnemius system was achieved. This occurred by ingrowth of soft tissue into the 7 mu carbon fiber network. This bond developed rapidly and was mechanically secure under physiologic loading conditions. The anastomoses' strengths were tested in tension over a 12-week period and compared to the breaking strengths of their contralateral, unoperated gastrocnemius systems and the sham systems. After four weeks, the systems with implants had strengths equivalent to those of the unoperated systems. Sham systems were significantly weaker throughout the test period. Histologically, the ingrowth process was associated with little inflammatory response. The ingrown tissue was found to be highly cellular with collagen oriented longitudinally to the tendon. After 12 weeks, the volume of collagenous tissue making up the regrown tendon section appeared nearly normal. Secure biological fixation of the carbon-polylactic acid scaffold to soft tissues may allow it application in repair or replacement of tendon or ligament deficits.

Chemically synthesized peptides predicted from the nucleotide sequence of the hepatitis B virus genome elicit antibodies reactive with the native envelope protein of Dane particles

Thirteen peptides corresponding to amino acid sequences predicted from the nucleotide sequence of the hepatitis B surface antigen were synthesized chemically. The free or carrier-linked synthetic peptides were injected into rabbits, and 7 of the 13 elicited an antipeptide response. Antisera against four of the six soluble peptides longer than 10 amino acids were reactive with native antigen and specifically precipitated the 23,000- and 28,000-dalton forms from Dane particles. As the hepatitis molecule had not been chosen for study because of any structural feature suggesting unique opportunities for success, these results suggest that the strategy is general and should work for any protein as long as enough domains are studied. Peptides such as these could prove to be ideal vaccines.

The role of bioengineering in orthopedics

Orthopedic bioengineering is an example of professionals in distinct disciplines applying their skills to problems that require an interdisciplinary approach. Two current research projects, the development of replacement ligaments and tendons and of an absorbable fracture fixation device, illustrate this integrated approach.

Children and smoking

An experimental educational programme to reduce childhood cigarette smoking in the Hunter health region (NSW) is described. It is an example of the efforts currently being made to tackle childhood cigarette smoking as an increasing problem, particularly among teenage girls. The key factors influencing children to begin smoking are the role of the family, and pressures from the peer group. Preventive strategies need to be implemented in childhood before the smoking habit becomes firmly established in an individual's lifestyle.

Mechanical analysis of Kirschner wire fixation in a phalangeal model

Transverse divisions of the mid-shaft of freshly frozen pig metacarpals were fixed with Kirschner wires of two sizes and using four different configurations. Compared to the usual cross-pin fixation using wires of 0.889 mm. four wires (0.712 mm) eccentrically placed and with their ends hooked provided a 300% improvement in bending rigidity and 170% in bending movement.